The role of the pharmacist in the selection and use of over-the-counter proton-pump inhibitors.

PubMed

Boardman, Helen F; Heeley, Gordon

2015-10-01

Heartburn and other symptoms of gastro-oesophageal reflux occur in ~30% of survey respondents in multiple countries worldwide. Heartburn and acid regurgitation are common complaints in the pharmacy, where patients frequently seek relief through medication and advice. The growing number of proton-pump inhibitors available in the over-the-counter setting provides an efficacious choice to patients experiencing frequent heartburn. Pharmacists can assist patients in their treatment decisions whilst inquiring about alarm symptoms that should prompt a physician referral. Aim of the review Provide pharmacists with a review of current clinical research and expert guidelines on use of over-the-counter proton-pump inhibitors. This narrative review was conducted to identify publications relevant to the following themes: overview of available treatments for frequent episodes of heartburn/acid regurgitation; treatment algorithms providing guidance on when to use over-the-counter proton-pump inhibitors; and the role of the pharmacist in the use of over-the-counter proton-pump inhibitors. Frequent symptoms of acid reflux, such as heartburn and acid regurgitation, can interfere substantially with daily life activities. Proton-pump inhibitors are the most efficacious treatment for frequent reflux symptoms and are recommended as an appropriate initial treatment in uncomplicated cases. Proton-pump inhibitors have varying pharmacokinetics and pharmacodynamics across the class; 20 mg esomeprazole has higher bioavailability and exposure than over-the-counter omeprazole, for example. However, differences in clinical efficacy for symptom relief have not been demonstrated. The safety and tolerability of proton-pump inhibitors have been well established in clinical trial and post-marketing settings, and use of a short regimen is associated with a very low likelihood of missing a more serious condition. Pharmacists can assist patients with accurate self-diagnosis by asking short, simple questions to characterize the nature, severity, and frequency of symptoms. Additionally, pharmacists can inquire about alarm symptoms that should prompt referral to a physician. Pharmacists should inform those patients for whom over-the-counter proton-pump inhibitors are appropriate on their proper use. Over-the-counter proton-pump inhibitors have a valuable role in the treatment of frequent heartburn. Pharmacists have the opportunity to guide patients through selection of the best treatment option for their symptoms.

Molecular basis of proton uptake in single and double mutants of cytochrome c oxidase

NASA Astrophysics Data System (ADS)

Henry, Rowan M.; Caplan, David; Fadda, Elisa; Pomès, Régis

2011-06-01

Cytochrome c oxidase, the terminal enzyme of the respiratory chain, utilizes the reduction of dioxygen into water to pump protons across the mitochondrial inner membrane. The principal pathway of proton uptake into the enzyme, the D channel, is a 2.5 nm long channel-like cavity named after a conserved, negatively charged aspartic acid (D) residue thought to help recruiting protons to its entrance (D132 in the first subunit of the S. sphaeroides enzyme). The single-point mutation of D132 to asparagine (N), a neutral residue, abolishes enzyme activity. Conversely, replacing conserved N139, one-third into the D channel, by D, induces a decoupled phenotype, whereby oxygen reduction proceeds but not proton pumping. Intriguingly, the double mutant D132N/N139D, which conserves the charge of the D channel, restores the wild-type phenotype. We use molecular dynamics simulations and electrostatic calculations to examine the structural and physical basis for the coupling of proton pumping and oxygen chemistry in single and double N139D mutants. The potential of mean force for the conformational isomerization of N139 and N139D side chains reveals the presence of three rotamers, one of which faces the channel entrance. This out-facing conformer is metastable in the wild-type and in the N139D single mutant, but predominant in the double mutant thanks to the loss of electrostatic repulsion with the carboxylate group of D132. The effects of mutations and conformational isomerization on the pKa of E286, an essential proton-shuttling residue located at the top of the D channel, are shown to be consistent with the electrostatic control of proton pumping proposed recently (Fadda et al 2008 Biochim. Biophys. Acta 1777 277-84). Taken together, these results suggest that preserving the spatial distribution of charges at the entrance of the D channel is necessary to guarantee both the uptake and the relay of protons to the active site of the enzyme. These findings highlight the interplay of long-range electrostatic forces and local structural fluctuations in the control of proton movement and provide a physical explanation for the restoration of proton pumping activity in the double mutant.

Cyanobacterial Light-Driven Proton Pump, Gloeobacter Rhodopsin: Complementarity between Rhodopsin-Based Energy Production and Photosynthesis

PubMed Central

Choi, Ah Reum; Shi, Lichi; Brown, Leonid S.; Jung, Kwang-Hwan

2014-01-01

A homologue of type I rhodopsin was found in the unicellular Gloeobacter violaceus PCC7421, which is believed to be primitive because of the lack of thylakoids and peculiar morphology of phycobilisomes. The Gloeobacter rhodopsin (GR) gene encodes a polypeptide of 298 amino acids. This gene is localized alone in the genome unlike cyanobacterium Anabaena opsin, which is clustered together with 14 kDa transducer gene. Amino acid sequence comparison of GR with other type I rhodopsin shows several conserved residues important for retinal binding and H+ pumping. In this study, the gene was expressed in Escherichia coli and bound all-trans retinal to form a pigment (λmax  = 544 nm at pH 7). The pKa of proton acceptor (Asp121) for the Schiff base, is approximately 5.9, so GR can translocate H+ under physiological conditions (pH 7.4). In order to prove the functional activity in the cell, pumping activity was measured in the sphaeroplast membranes of E. coli and one of Gloeobacter whole cell. The efficient proton pumping and rapid photocycle of GR strongly suggests that Gloeobacter rhodopsin functions as a proton pumping in its natural environment, probably compensating the shortage of energy generated by chlorophyll-based photosynthesis without thylakoids. PMID:25347537

Low-dose or standard-dose proton pump inhibitors for maintenance therapy of gastro-oesophageal reflux disease: a cost-effectiveness analysis.

PubMed

You, J H S; Lee, A C M; Wong, S C Y; Chan, F K L

2003-03-15

Studies on the use of low-dose proton pump inhibitor for the maintenance therapy of gastro-oesophageal reflux disease have shown that it might be comparable with standard-dose proton pump inhibitor treatment and superior to standard-dose histamine-2 receptor antagonist therapy. To compare the impact of standard-dose histamine-2 receptor antagonist, low-dose proton pump inhibitor and standard-dose proton pump inhibitor treatment for the maintenance therapy of gastro-oesophageal reflux disease on symptom control and health care resource utilization from the perspective of a public health organization in Hong Kong. A Markov model was designed to simulate, over 12 months, the economic and clinical outcomes of gastro-oesophageal reflux disease patients treated with standard-dose histamine-2 receptor antagonist, low-dose proton pump inhibitor and standard-dose proton pump inhibitor. The transition probabilities were derived from the literature. Resource utilization was retrieved from a group of gastro-oesophageal reflux disease patients in Hong Kong. Sensitivity analysis was conducted to examine the robustness of the model. The standard-dose proton pump inhibitor strategy was associated with the highest numbers of symptom-free patient-years (0.954 years) and quality-adjusted life-years gained (0.999 years), followed by low-dose proton pump inhibitor and standard-dose histamine-2 receptor antagonist. The direct medical cost per patient in the standard-dose proton pump inhibitor group (904 US dollars) was lower than those of the low-dose proton pump inhibitor and standard-dose histamine-2 receptor antagonist groups. The standard-dose proton pump inhibitor strategy appears to be the most effective and least costly for the maintenance management of patients with gastro-oesophageal reflux disease in Hong Kong.

Measuring H(+) Pumping and Membrane Potential Formation in Sealed Membrane Vesicle Systems.

PubMed

Wielandt, Alex Green; Palmgren, Michael G; Fuglsang, Anja Thoe; Günther-Pomorski, Thomas; Justesen, Bo Højen

2016-01-01

The activity of enzymes involved in active transport of matter across lipid bilayers can conveniently be assayed by measuring their consumption of energy, such as ATP hydrolysis, while it is more challenging to directly measure their transport activities as the transported substrate is not converted into a product and only moves a few nanometers in space. Here, we describe two methods for the measurement of active proton pumping across lipid bilayers and the concomitant formation of a membrane potential, applying the dyes 9-amino-6-chloro-2-methoxyacridine (ACMA) and oxonol VI. The methods are exemplified by assaying transport of the Arabidopsis thaliana plasma membrane H(+)-ATPase (proton pump), which after heterologous expression in Saccharomyces cerevisiae and subsequent purification has been reconstituted in proteoliposomes.

[Pharmacogenic osteoporosis beyond cortisone. Proton pump inhibitors, glitazones and diuretics].

PubMed

Kann, P H; Hadji, P; Bergmann, R S

2014-05-01

[corrected] There are many drugs which can cause osteoporosis or at least favor its initiation. The effect of hormones and drugs with antihormonal activity, such as glucocorticoids and aromatase inhibitors, on initiation of osteoporosis is well known. In addition, proton pump inhibitors, glitazones and diuretics also influence the formation of osteoporosis. The results of currently available studies on the correlation between proton pump inhibitors, glitazones and diuretics on formation of osteoporosis were evaluated and summarized. Proton pump inhibitors and glitazones increase the risk for osteoporotic fractures. Loop diuretics may slightly increase fracture risk, whereas thiazides were shown to be osteoprotective by reducing fracture probability on a relevant scale. Proton pump inhibitors should not be prescribed without serious consideration and then only as long as necessary. Alternatively, the administration of the less effective H2 antagonists should be considered when possible due to the reduction of acid secretion. Because the long-term intake of thiazides is associated with a clinically relevant reduction in the risk of fractures and they are economic and well-tolerated, prescription can be thoroughly recommended within the framework of differential diagnostic considerations in an appropriate clinical context. The briefly increased risk of falling immediately after starting diuretic therapy is the only point which needs to be considered.

The nitric-oxide reductase from Paracoccus denitrificans uses a single specific proton pathway.

PubMed

ter Beek, Josy; Krause, Nils; Reimann, Joachim; Lachmann, Peter; Ädelroth, Pia

2013-10-18

The NO reductase from Paracoccus denitrificans reduces NO to N2O (2NO + 2H(+) + 2e(-) → N2O + H2O) with electrons donated by periplasmic cytochrome c (cytochrome c-dependent NO reductase; cNOR). cNORs are members of the heme-copper oxidase superfamily of integral membrane proteins, comprising the O2-reducing, proton-pumping respiratory enzymes. In contrast, although NO reduction is as exergonic as O2 reduction, there are no protons pumped in cNOR, and in addition, protons needed for NO reduction are derived from the periplasmic solution (no contribution to the electrochemical gradient is made). cNOR thus only needs to transport protons from the periplasm into the active site without the requirement to control the timing of opening and closing (gating) of proton pathways as is needed in a proton pump. Based on the crystal structure of a closely related cNOR and molecular dynamics simulations, several proton transfer pathways were suggested, and in principle, these could all be functional. In this work, we show that residues in one of the suggested pathways (denoted pathway 1) are sensitive to site-directed mutation, whereas residues in the other proposed pathways (pathways 2 and 3) could be exchanged without severe effects on turnover activity with either NO or O2. We further show that electron transfer during single-turnover reduction of O2 is limited by proton transfer and can thus be used to study alterations in proton transfer rates. The exchange of residues along pathway 1 showed specific slowing of this proton-coupled electron transfer as well as changes in its pH dependence. Our results indicate that only pathway 1 is used to transfer protons in cNOR.

Identification of proton-pump inhibitor drugs that inhibit Trichomonas vaginalis uridine nucleoside ribohydrolase.

PubMed

Shea, Tara A; Burburan, Paola J; Matubia, Vivian N; Ramcharan, Sandy S; Rosario, Irving; Parkin, David W; Stockman, Brian J

2014-02-15

Trichomonas vaginalis continues to be a major health problem with drug-resistant strains increasing in prevalence. Novel antitrichomonal agents that are mechanistically distinct from current therapies are needed. The NIH Clinical Compound Collection was screened to find inhibitors of the uridine ribohydrolase enzyme required by the parasite to scavenge uracil for its growth. The proton-pump inhibitors omeprazole, pantoprazole, and rabeprazole were identified as inhibitors of this enzyme, with IC50 values ranging from 0.3 to 14.5 μM. This suggests a molecular mechanism for the in vitro antitrichomonal activity of these proton-pump inhibitors, and may provide important insights toward structure-based drug design. Copyright © 2014 Elsevier Ltd. All rights reserved.

A rationale for the use of proton pump inhibitors as antineoplastic agents.

PubMed

De Milito, Angelo; Marino, Maria Lucia; Fais, Stefano

2012-01-01

It is becoming increasingly acknowledged that tumorigenesis is not simply characterized by the accumulation of rapidly proliferating, genetically mutated cells. Microenvironmental biophysical factors like hypoxia and acidity dramatically condition cancer cells and act as selective forces for malignant cells, adapting through metabolic reprogramming towards aerobic glycolysis. Avoiding intracellular accumulation of lactic acid and protons, otherwise detrimental to cell survival is crucial for malignant cells to maintain cellular pH homeostasis. As a consequence of the upregulated expression and/or function of several pH-regulating systems, cancer cells display an alkaline intracellular pH (pHi) and an acidic extracellular pH (pHe). Among the pH-regulating proteins, proton pumps play an important role in both drug-resistance and metastatic spread, thus representing a suitable therapeutic target. Proton pump inhibitors (PPI) have been reported as cytotoxic drugs active against several human tumor cells and preclinical data have prompted the investigation of PPI as anticancer agents in humans. This review will update the current knowledge on the antitumor activities of PPI and their potential applications.

Correlation between proton pump inhibitors and risk of pyogenic liver abscess.

PubMed

Lin, Hsien-Feng; Liao, Kuan-Fu; Chang, Ching-Mei; Lin, Cheng-Li; Lai, Shih-Wei

2017-08-01

Little is known about the relationship between proton pump inhibitors use and pyogenic liver abscess. The objective of this study was to evaluate the correlation between proton pump inhibitors use and pyogenic liver abscess in Taiwan. This was a population-based case-control study using the database of the Taiwan National Health Insurance Program since 2000 to 2011. Subjects aged 20 to 84 who experienced their first episode of pyogenic liver abscess were enrolled as the case group (n = 1372). Randomly selected subjects aged 20 to 84 without pyogenic liver abscess were enrolled as the control group (n = 1372). Current use, early use, and late use of proton pump inhibitors was defined as subjects whose last one tablet for proton pump inhibitors was noted ≤30 days, between 31 to 90 days and ≥91 days before the date of admission for pyogenic liver abscess. Subjects who never received a prescription for proton pump inhibitors were defined as nonusers of proton pump inhibitors. A multivariable unconditional logistic regression model was used to measure the odds ratio and 95% confidence interval to evaluate the correlation between proton pump inhibitors use and pyogenic liver abscess. After adjusting for confounders, the adjusted odds ratio of pyogenic liver abscess was 7.59 for subjects with current use of proton pump inhibitors (95% confidence interval 5.05, 11.4), when compared with nonusers. Current use of proton pump inhibitors is associated with a greater risk of pyogenic liver abscess.

In Vitro Activities of Rabeprazole, a Novel Proton Pump Inhibitor, and Its Thioether Derivative Alone and in Combination with Other Antimicrobials against Recent Clinical Isolates of Helicobacter pylori

PubMed Central

Kawakami, Yoshiyuki; Akahane, Takayuki; Yamaguchi, Masaru; Oana, Kozue; Takahashi, Yuko; Okimura, Yukie; Okabe, Tadashi; Gotoh, Akira; Katsuyama, Tsutomu

2000-01-01

The MICs of rabeprazole sodium (RPZ), a newly developed benzimidazole proton pump inhibitor (PPI), against 133 clinical Helicobacter pylori strains revealed a higher degree of activity than the another two PPIs, lansoprazole and omeprazole. Time-kill curve assays of RPZ, when combined with amoxicillin, clarithromycin, or metronidazole, disclosed that synergistic effects were demonstrated in combination with each antibiotic examined. Moreover, no apparent antagonistic effect appeared among all of the strains tested. PMID:10639386

Protons and how they are transported by proton pumps.

PubMed

Buch-Pedersen, M J; Pedersen, B P; Veierskov, B; Nissen, P; Palmgren, M G

2009-01-01

The very high mobility of protons in aqueous solutions demands special features of membrane proton transporters to sustain efficient yet regulated proton transport across biological membranes. By the use of the chemical energy of ATP, plasma-membrane-embedded ATPases extrude protons from cells of plants and fungi to generate electrochemical proton gradients. The recently published crystal structure of a plasma membrane H(+)-ATPase contributes to our knowledge about the mechanism of these essential enzymes. Taking the biochemical and structural data together, we are now able to describe the basic molecular components that allow the plasma membrane proton H(+)-ATPase to carry out proton transport against large membrane potentials. When divergent proton pumps such as the plasma membrane H(+)-ATPase, bacteriorhodopsin, and F(O)F(1) ATP synthase are compared, unifying mechanistic premises for biological proton pumps emerge. Most notably, the minimal pumping apparatus of all pumps consists of a central proton acceptor/donor, a positively charged residue to control pK(a) changes of the proton acceptor/donor, and bound water molecules to facilitate rapid proton transport along proton wires.

Root bacterial endophytes confer drought resistance and enhance expression and activity of a vacuolar H+ -pumping pyrophosphatase in pepper plants.

PubMed

Vigani, Gianpiero; Rolli, Eleonora; Marasco, Ramona; Dell'Orto, Marta; Michoud, Grégoire; Soussi, Asma; Raddadi, Noura; Borin, Sara; Sorlini, Claudia; Zocchi, Graziano; Daffonchio, Daniele

2018-05-22

It has been previously shown that the transgenic overexpression of the plant root vacuolar proton pumps H + -ATPase (V-ATPase) and H + -PPase (V-PPase) confer tolerance to drought. Since plant-root endophytic bacteria can also promote drought tolerance, we hypothesize that such promotion can be associated to the enhancement of the host vacuolar proton pumps expression and activity. To test this hypothesis, we selected two endophytic bacteria endowed with an array of in vitro plant growth promoting traits. Their genome sequences confirmed the presence of traits previously shown to confer drought resistance to plants, such as the synthesis of nitric oxide and of organic volatile organic compounds. We used the two strains on pepper (Capsicuum annuum L.) because of its high sensitivity to drought. Under drought conditions, both strains stimulated a larger root system and enhanced the leaves' photosynthetic activity. By testing the expression and activity of the vacuolar proton pumps, H + -ATPase (V-ATPase) and H + -PPase (V-PPase), we found that bacterial colonization enhanced V-PPase only. We conclude that the enhanced expression and activity of V-PPase can be favoured by the colonization of drought-tolerance-inducing bacterial endophytes. This article is protected by copyright. All rights reserved. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Mammalian complex I pumps 4 protons per 2 electrons at high and physiological proton motive force in living cells.

PubMed

Ripple, Maureen O; Kim, Namjoon; Springett, Roger

2013-02-22

Mitochondrial complex I couples electron transfer between matrix NADH and inner-membrane ubiquinone to the pumping of protons against a proton motive force. The accepted proton pumping stoichiometry was 4 protons per 2 electrons transferred (4H(+)/2e(-)) but it has been suggested that stoichiometry may be 3H(+)/2e(-) based on the identification of only 3 proton pumping units in the crystal structure and a revision of the previous experimental data. Measurement of proton pumping stoichiometry is challenging because, even in isolated mitochondria, it is difficult to measure the proton motive force while simultaneously measuring the redox potentials of the NADH/NAD(+) and ubiquinol/ubiquinone pools. Here we employ a new method to quantify the proton motive force in living cells from the redox poise of the bc(1) complex measured using multiwavelength cell spectroscopy and show that the correct stoichiometry for complex I is 4H(+)/2e(-) in mouse and human cells at high and physiological proton motive force.

Inward H+ pump xenorhodopsin: Mechanism and alternative optogenetic approach.

PubMed

Shevchenko, Vitaly; Mager, Thomas; Kovalev, Kirill; Polovinkin, Vitaly; Alekseev, Alexey; Juettner, Josephine; Chizhov, Igor; Bamann, Christian; Vavourakis, Charlotte; Ghai, Rohit; Gushchin, Ivan; Borshchevskiy, Valentin; Rogachev, Andrey; Melnikov, Igor; Popov, Alexander; Balandin, Taras; Rodriguez-Valera, Francisco; Manstein, Dietmar J; Bueldt, Georg; Bamberg, Ernst; Gordeliy, Valentin

2017-09-01

Generation of an electrochemical proton gradient is the first step of cell bioenergetics. In prokaryotes, the gradient is created by outward membrane protein proton pumps. Inward plasma membrane native proton pumps are yet unknown. We describe comprehensive functional studies of the representatives of the yet noncharacterized xenorhodopsins from Nanohaloarchaea family of microbial rhodopsins. They are inward proton pumps as we demonstrate in model membrane systems, Escherichia coli cells, human embryonic kidney cells, neuroblastoma cells, and rat hippocampal neuronal cells. We also solved the structure of a xenorhodopsin from the nanohalosarchaeon Nanosalina ( Ns XeR) and suggest a mechanism of inward proton pumping. We demonstrate that the Ns XeR is a powerful pump, which is able to elicit action potentials in rat hippocampal neuronal cells up to their maximal intrinsic firing frequency. Hence, inwardly directed proton pumps are suitable for light-induced remote control of neurons, and they are an alternative to the well-known cation-selective channelrhodopsins.

Insights into proton translocation in cbb3 oxidase from MD simulations.

PubMed

Carvalheda, Catarina A; Pisliakov, Andrei V

2017-05-01

Heme-copper oxidases are membrane protein complexes that catalyse the final step of the aerobic respiration, namely the reduction of oxygen to water. The energy released during catalysis is coupled to the active translocation of protons across the membrane, which contributes to the establishment of an electrochemical gradient that is used for ATP synthesis. The distinctive C-type (or cbb 3 ) cytochrome c oxidases, which are mostly present in proteobacteria, exhibit a number of unique structural and functional features, including high catalytic activity at low oxygen concentrations. At the moment, the functioning mechanism of C-type oxidases, in particular the proton transfer/pumping mechanism presumably via a single proton channel, is still poorly understood. In this work we used all-atom molecular dynamics simulations and continuum electrostatics calculations to obtain atomic-level insights into the hydration and dynamics of a cbb 3 oxidase. We provide the details of the water dynamics and proton transfer pathways for both the "chemical" and "pumped" protons, and show that formation of protonic connections is strongly affected by the protonation state of key residues, namely H243, E323 and H337. Copyright © 2017 Elsevier B.V. All rights reserved.

A population-based study of the drug interaction between proton pump inhibitors and clopidogrel

PubMed Central

Juurlink, David N.; Gomes, Tara; Ko, Dennis T.; Szmitko, Paul E.; Austin, Peter C.; Tu, Jack V.; Henry, David A.; Kopp, Alex; Mamdani, Muhammad M.

2009-01-01

Background Most proton pump inhibitors inhibit the bioactivation of clopidogrel to its active metabolite. The clinical significance of this drug interaction is unknown. Methods We conducted a population-based nested case–control study among patients aged 66 years or older who commenced clopidogrel between Apr. 1, 2002, and Dec. 31, 2007, following hospital discharge after treatment of acute myocardial infarction. The cases in our study were those readmitted with acute myocardial infarction within 90 days after discharge. We performed a secondary analysis considering events within 1 year. Event-free controls (at a ratio of 3:1) were matched to cases on age, percutaneous coronary intervention and a validated risk score. We categorized exposure to proton pump inhibitors before the index date as current (within 30 days), previous (31–90 days) or remote (91–180 days). Results Among 13 636 patients prescribed clopidogrel following acute myocardial infarction, we identified 734 cases readmitted with myocardial infarction and 2057 controls. After extensive multivariable adjustment, current use of proton pump inhibitors was associated with an increased risk of reinfarction (adjusted odds ratio [OR] 1.27, 95% confidence interval [CI] 1.03–1.57). We found no association with more distant exposure to proton pump inhibitors or in multiple sensitivity analyses. In a stratified analysis, pantoprazole, which does not inhibit cytochrome P450 2C19, had no association with readmission for myocardial infarction (adjusted OR 1.02, 95% CI 0.70–1.47). Interpretation Among patients receiving clopidogrel following acute myocardial infarction, concomitant therapy with proton pump inhibitors other than pantoprazole was associated with a loss of the beneficial effects of clopidogrel and an increased risk of reinfarction. PMID:19176635

Structural and Functional Studies of a Newly Grouped Haloquadratum walsbyi Bacteriorhodopsin Reveal the Acid-resistant Light-driven Proton Pumping Activity.

PubMed

Hsu, Min-Feng; Fu, Hsu-Yuan; Cai, Chun-Jie; Yi, Hsiu-Pin; Yang, Chii-Shen; Wang, Andrew H-J

2015-12-04

Retinal bound light-driven proton pumps are widespread in eukaryotic and prokaryotic organisms. Among these pumps, bacteriorhodopsin (BR) proteins cooperate with ATP synthase to convert captured solar energy into a biologically consumable form, ATP. In an acidic environment or when pumped-out protons accumulate in the extracellular region, the maximum absorbance of BR proteins shifts markedly to the longer wavelengths. These conditions affect the light-driven proton pumping functional exertion as well. In this study, wild-type crystal structure of a BR with optical stability under wide pH range from a square halophilic archaeon, Haloquadratum walsbyi (HwBR), was solved in two crystal forms. One crystal form, refined to 1.85 Å resolution, contains a trimer in the asymmetric unit, whereas another contains an antiparallel dimer was refined at 2.58 Å. HwBR could not be classified into any existing subgroup of archaeal BR proteins based on the protein sequence phylogenetic tree, and it showed unique absorption spectral stability when exposed to low pH values. All structures showed a unique hydrogen-bonding network between Arg(82) and Thr(201), linking the BC and FG loops to shield the retinal-binding pocket in the interior from the extracellular environment. This result was supported by R82E mutation that attenuated the optical stability. The negatively charged cytoplasmic side and the Arg(82)-Thr(201) hydrogen bond may play an important role in the proton translocation trend in HwBR under acidic conditions. Our findings have unveiled a strategy adopted by BR proteins to solidify their defenses against unfavorable environments and maintain their optical properties associated with proton pumping. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Structural and Functional Studies of a Newly Grouped Haloquadratum walsbyi Bacteriorhodopsin Reveal the Acid-resistant Light-driven Proton Pumping Activity*

PubMed Central

Hsu, Min-Feng; Fu, Hsu-Yuan; Cai, Chun-Jie; Yi, Hsiu-Pin; Yang, Chii-Shen; Wang, Andrew H.-J.

2015-01-01

Retinal bound light-driven proton pumps are widespread in eukaryotic and prokaryotic organisms. Among these pumps, bacteriorhodopsin (BR) proteins cooperate with ATP synthase to convert captured solar energy into a biologically consumable form, ATP. In an acidic environment or when pumped-out protons accumulate in the extracellular region, the maximum absorbance of BR proteins shifts markedly to the longer wavelengths. These conditions affect the light-driven proton pumping functional exertion as well. In this study, wild-type crystal structure of a BR with optical stability under wide pH range from a square halophilic archaeon, Haloquadratum walsbyi (HwBR), was solved in two crystal forms. One crystal form, refined to 1.85 Å resolution, contains a trimer in the asymmetric unit, whereas another contains an antiparallel dimer was refined at 2.58 Å. HwBR could not be classified into any existing subgroup of archaeal BR proteins based on the protein sequence phylogenetic tree, and it showed unique absorption spectral stability when exposed to low pH values. All structures showed a unique hydrogen-bonding network between Arg82 and Thr201, linking the BC and FG loops to shield the retinal-binding pocket in the interior from the extracellular environment. This result was supported by R82E mutation that attenuated the optical stability. The negatively charged cytoplasmic side and the Arg82–Thr201 hydrogen bond may play an important role in the proton translocation trend in HwBR under acidic conditions. Our findings have unveiled a strategy adopted by BR proteins to solidify their defenses against unfavorable environments and maintain their optical properties associated with proton pumping. PMID:26483542

TOR complex 1 regulates the yeast plasma membrane proton pump and pH and potassium homeostasis.

PubMed

Mahmoud, Shima; Planes, María Dolores; Cabedo, Marc; Trujillo, Cristina; Rienzo, Alessandro; Caballero-Molada, Marcos; Sharma, Sukesh C; Montesinos, Consuelo; Mulet, José Miguel; Serrano, Ramón

2017-07-01

We have identified in yeast a connection between two master regulators of cell growth: a biochemical connection involving the TORC1 protein kinase (which activates protein synthesis, nutrient uptake, and anabolism) and a biophysical connection involving the plasma membrane proton-pumping H + -ATPase Pma1 (which drives nutrient and K + uptake and regulates pH homeostasis). Raising the temperature to nonpermissive values in a TOR thermosensitive mutant decreases Pma1 activity. Rapamycin, a TORC1 inhibitor, inhibits Pma1 dependent on its receptor Fpr1 and on the protein phosphatase Sit4, a TORC1 effector. Mutation of either Sit4 or Tco89, a nonessential subunit of TORC1, decreases proton efflux, K + uptake, intracellular pH, cell growth, and tolerance to weak organic acids. Tco89 does not affect Pma1 activity but activates K + transport. © 2017 Federation of European Biochemical Societies.

Proton pump inhibitors and the risk of severe adverse events - a cardiovascular bomb?

PubMed

Cunha, Nelson; Machado, António Pedro

2018-05-24

Proton pump inhibitors are currently one of the most prescribed pharmacological classes in developed countries, given their effectiveness and safety profile previously considered favourable. However, over the last few years, several papers have been published that associate prolonged use of these drugs with a wide range of adverse effects, posing doubts about their safety. Among the adverse effects described, one should emphasize the increased risk of cardiovascular events. This relationship was first described in subjects after acute coronary syndrome by the interference of proton pump inhibitors in cytochrome P450 2C19 and the conversion of clopidogrel to active metabolite. However, more recent studies describe this relationship also with the use of antiplatelet agents that do not depend on cytochrome P450 2C19 activation. The proposed mechanism is by inhibiting dimethylarginine dimethylaminohydrolase, a physiological inhibitor of asymmetric dimethylarginine, thus increasing the plasma concentrations of the latter enzyme and in turn translating into lower levels of nitric oxide. The authors reviewing in this article the relationship between the use of proton pump inhibitors and the increased risk of cardio and cerebrovascular events, are intended to alert the scientific community to the potentially harmful effects of these drugs and recommend the setting of a moratorium on their prolonged use. Copyright © 2018 Sociedade Portuguesa de Cardiologia. Publicado por Elsevier España, S.L.U. All rights reserved.

Mammalian Complex I Pumps 4 Protons per 2 Electrons at High and Physiological Proton Motive Force in Living Cells*

PubMed Central

Ripple, Maureen O.; Kim, Namjoon; Springett, Roger

2013-01-01

Mitochondrial complex I couples electron transfer between matrix NADH and inner-membrane ubiquinone to the pumping of protons against a proton motive force. The accepted proton pumping stoichiometry was 4 protons per 2 electrons transferred (4H+/2e−) but it has been suggested that stoichiometry may be 3H+/2e− based on the identification of only 3 proton pumping units in the crystal structure and a revision of the previous experimental data. Measurement of proton pumping stoichiometry is challenging because, even in isolated mitochondria, it is difficult to measure the proton motive force while simultaneously measuring the redox potentials of the NADH/NAD+ and ubiquinol/ubiquinone pools. Here we employ a new method to quantify the proton motive force in living cells from the redox poise of the bc1 complex measured using multiwavelength cell spectroscopy and show that the correct stoichiometry for complex I is 4H+/2e− in mouse and human cells at high and physiological proton motive force. PMID:23306206

Multimorbidities and Overprescription of Proton Pump Inhibitors in Older Patients.

PubMed

Delcher, Anne; Hily, Sylvie; Boureau, Anne Sophie; Chapelet, Guillaume; Berrut, Gilles; de Decker, Laure

2015-01-01

To determine whether there is an association between overprescription of proton pump inhibitors (PPIs) and multimorbidities in older patients. Multicenter prospective study. Acute geriatric medicine at the University Hospital of Nantes and the Hospital of Saint-Nazaire. Older patients aged 75 and over hospitalized in acute geriatric medicine. Older patients in acute geriatric medicine who received proton pump inhibitors. Variables studied were individual multimorbidities, the burden of multimorbidity evaluated by the Cumulative Illness Rating Scale, age, sex, type of residence (living in nursing home or not), functional abilities (Lawton and Katz scales), nutritional status (Body Mass Index), and the type of concomitant medications (antiaggregant, corticosteroids', or anticoagulants). Overprescription of proton pump inhibitors was found in 73.9% older patients. In the full model, cardiac diseases (odds ratio [OR] = 4.17, p = 0.010), metabolic diseases (OR = 2.14, p = 0.042) and corticosteroids (OR = 5.39, p = 0.028) were significantly associated with overprescription of proton pump inhibitors. Esogastric diseases (OR = 0.49, p = 0.033) were negatively associated with overprescription of proton pump inhibitors. Cardiac diseases and metabolic diseases were significantly associated with overprescription of proton pump inhibitors.

Timing of electron and proton transfer in the ba(3) cytochrome c oxidase from Thermus thermophilus.

PubMed

von Ballmoos, Christoph; Lachmann, Peter; Gennis, Robert B; Ädelroth, Pia; Brzezinski, Peter

2012-06-05

Heme-copper oxidases are membrane-bound proteins that catalyze the reduction of O(2) to H(2)O, a highly exergonic reaction. Part of the free energy of this reaction is used for pumping of protons across the membrane. The ba(3) oxidase from Thermus thermophilus presumably uses a single proton pathway for the transfer of substrate protons used during O(2) reduction as well as for the transfer of the protons that are pumped across the membrane. The pumping stoichiometry (0.5 H(+)/electron) is lower than that of most other (mitochondrial-like) oxidases characterized to date (1 H(+)/electron). We studied the pH dependence and deuterium isotope effect of the kinetics of electron and proton transfer reactions in the ba(3) oxidase. The results from these studies suggest that the movement of protons to the catalytic site and movement to a site located some distance from the catalytic site [proposed to be a "proton-loading site" (PLS) for pumped protons] are separated in time, which allows individual investigation of these reactions. A scenario in which the uptake and release of a pumped proton occurs upon every second transfer of an electron to the catalytic site would explain the decreased proton pumping stoichiometry compared to that of mitochondrial-like oxidases.

Metal Fluoride Inhibition of a P-type H+ Pump

PubMed Central

Pedersen, Jesper Torbøl; Falhof, Janus; Ekberg, Kira; Buch-Pedersen, Morten Jeppe; Palmgren, Michael

2015-01-01

The plasma membrane H+-ATPase is a P-type ATPase responsible for establishing electrochemical gradients across the plasma membrane in fungi and plants. This essential proton pump exists in two activity states: an autoinhibited basal state with a low turnover rate and a low H+/ATP coupling ratio and an activated state in which ATP hydrolysis is tightly coupled to proton transport. Here we characterize metal fluorides as inhibitors of the fungal enzyme in both states. In contrast to findings for other P-type ATPases, inhibition of the plasma membrane H+-ATPase by metal fluorides was partly reversible, and the stability of the inhibition varied with the activation state. Thus, the stability of the ATPase inhibitor complex decreased significantly when the pump transitioned from the activated to the basal state, particularly when using beryllium fluoride, which mimics the bound phosphate in the E2P conformational state. Taken together, our results indicate that the phosphate bond of the phosphoenzyme intermediate of H+-ATPases is labile in the basal state, which may provide an explanation for the low H+/ATP coupling ratio of these pumps in the basal state. PMID:26134563

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca exchangers.

PubMed

Barkla, Bronwyn J; Hirschi, Kendal D; Pittman, Jon K

2008-05-01

Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+)exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant's stress response. A common feature of these mutants was the perturbation of H(+)-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca(2+)/H(+) exchangers and H(+) pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca(2+) flux. These results suggest cautious interpretation of mutant Ca(2+)/H(+) exchanger phenotypes that may be due to either perturbed Ca(2+) or H(+) transport.

Head-to-head comparison of H2-receptor antagonists and proton pump inhibitors in the treatment of erosive esophagitis: A meta-analysis

PubMed Central

Wang, Wei-Hong; Huang, Jia-Qing; Zheng, Ge-Fan; Xia, Harry Hua-Xiang; Wong, Wai-Man; Lam, Shiu-Kum; Wong, Benjamin Chun-Yu

2005-01-01

AIM: To systematically evaluate the efficacy of H2-receptor antagonists (H2RAs) and proton pump inhibitors in healing erosive esophagitis (EE). METHODS: A meta-analysis was performed. A literature search was conducted in PubMed, Medline, Embase, and Cochrane databases to include randomized controlled head-to-head comparative trials evaluating the efficacy of H2RAs or proton pump inhibitors in healing EE. Relative risk (RR) and 95% confidence interval (CI) were calculated under a random-effects model. RESULTS: RRs of cumulative healing rates for each comparison at 8 wk were: high dose vs standard dose H2RAs, 1.17 (95%CI, 1.02-1.33); standard dose proton pump inhibitors vs standard dose H2RAs, 1.59 (95%CI, 1.44-1.75); standard dose other proton pump inhibitors vs standard dose omeprazole, 1.06 (95%CI, 0.98-1.06). Proton pump inhibitors produced consistently greater healing rates than H2RAs of all doses across all grades of esophagitis, including patients refractory to H2RAs. Healing rates achieved with standard dose omeprazole were similar to those with other proton pump inhibitors in all grades of esophagitis. CONCLUSION: H2RAs are less effective for treating patients with erosive esophagitis, especially in those with severe forms of esophagitis. Standard dose proton pump inhibitors are significantly more effective than H2RAs in healing esophagitis of all grades. Proton pump inhibitors given at the recommended dose are equally effective for healing esophagitis. PMID:15996033

Activation of acid-sensing ion channels by localized proton transient reveals their role in proton signaling.

PubMed

Zeng, Wei-Zheng; Liu, Di-Shi; Liu, Lu; She, Liang; Wu, Long-Jun; Xu, Tian-Le

2015-09-15

Extracellular transients of pH alterations likely mediate signal transduction in the nervous system. Neuronal acid-sensing ion channels (ASICs) act as sensors for extracellular protons, but the mechanism underlying ASIC activation remains largely unknown. Here, we show that, following activation of a light-activated proton pump, Archaerhodopsin-3 (Arch), proton transients induced ASIC currents in both neurons and HEK293T cells co-expressing ASIC1a channels. Using chimera proteins that bridge Arch and ASIC1a by a glycine/serine linker, we found that successful coupling occurred within 15 nm distance. Furthermore, two-cell sniffer patch recording revealed that regulated release of protons through either Arch or voltage-gated proton channel Hv1 activated neighbouring cells expressing ASIC1a channels. Finally, computational modelling predicted the peak proton concentration at the intercellular interface to be at pH 6.7, which is acidic enough to activate ASICs in vivo. Our results highlight the pathophysiological role of proton signalling in the nervous system.

[Influence of proton pump inhibitors on intestinal fermentative profile: a case-control study].

PubMed

Senderovky, Melisa; Lasa, Juan; Dima, Guillermo; Peralta, Daniel; Argüello, Mariano; Soifer, Luis

2014-01-01

Proton pump inhibitors could have an impact on the results of breath tests performed in patients with irritable bowel syndrome. This impact could be due to the development of small intestine bacterial overgrowth. To compare the prevalence of fermentative profile alterations of irritable bowel syndrome patients exposed and not-exposed to proton pump inhibitor therapy. Subjects with irritable bowel syndrome were enrolled. A validated questionnaire assessing symptom severity as well as proton pump inhibitor treatment was delivered. A lactulose breath test was undertaken by each enrolled subject. Fermentative profile (area under the curve of hydrogen excretion/time) was compared between proton pump inhibitors consumers and non-consumers. Furthermore, small intestine bacterial overgrowth prevalence was compared. Two hundred and twenty five patients were enrolled. No significant differences were found on the fermentative profile between groups [AUC mediana 3,776 (rango 2,124-5,571) vs 4,347 (rango 2,038-5,481), P = 0.3]. Small intestine bacterial overgrowth prevalence was similar as well [33% vs 27.5%]. These differences remained non-significant after adjusting for proton pump inhibitor dose and treatment time. Surprisingly, symptom score was significantly higher in those patients under proton pump inhibitor therapy [28.5 (23-26) vs 23 (15-29), P = 0.01]. Proton pump inhibitors have no significant influence on lactulose breath tests, regardless of the dosage and time of administration.

Multimorbidities and Overprescription of Proton Pump Inhibitors in Older Patients

PubMed Central

Delcher, Anne; Hily, Sylvie; Boureau, Anne Sophie; Chapelet, Guillaume; Berrut, Gilles; de Decker, Laure

2015-01-01

Objectives To determine whether there is an association between overprescription of proton pump inhibitors (PPIs) and multimorbidities in older patients. Design Multicenter prospective study. Setting Acute geriatric medicine at the University Hospital of Nantes and the Hospital of Saint-Nazaire. Participants Older patients aged 75 and over hospitalized in acute geriatric medicine. Measurements Older patients in acute geriatric medicine who received proton pump inhibitors. Variables studied were individual multimorbidities, the burden of multimorbidity evaluated by the Cumulative Illness Rating Scale, age, sex, type of residence (living in nursing home or not), functional abilities (Lawton and Katz scales), nutritional status (Body Mass Index), and the type of concomitant medications (antiaggregant, corticosteroids’, or anticoagulants). Results Overprescription of proton pump inhibitors was found in 73.9% older patients. In the full model, cardiac diseases (odds ratio [OR] = 4.17, p = 0.010), metabolic diseases (OR = 2.14, p = 0.042) and corticosteroids (OR = 5.39, p = 0.028) were significantly associated with overprescription of proton pump inhibitors. Esogastric diseases (OR = 0.49, p = 0.033) were negatively associated with overprescription of proton pump inhibitors. Conclusion Cardiac diseases and metabolic diseases were significantly associated with overprescription of proton pump inhibitors. PMID:26535585

Endoscopic and histopathologic gastric changes in chronic users of proton-pump inhibitors.

PubMed

Camilo, Sílvia Maria Perrone; Almeida, Élia Cláudia de Souza; Miranzi, Benito André Silveira; Silva, Juliano Carvalho; Nomelini, Rosemary Simões; Etchebehere, Renata Margarida

2015-01-01

Proton-pump inhibitors have been used for at least two decades. They are among the most commonly sold drugs in the world. However, some controversy remains about the indications for their use and the consequences of their prolonged use. To evaluate and compare the endoscopic and histopathologic gastric changes in chronic users of proton-pump inhibitors to changes in non-users. A prospective study performed at a tertiary Public Hospital involving 105 patients undergoing upper-gastrointestinal endoscopy. Subjects included 81 proton-pump inhibitor users and 24 non-users (control group). Biopsies of the antral-type mucosa, the antral-fundic transition, and the fundus were evaluated by the Sydney System. The presence of erosion or ulceration, lymphatic follicles, reactive gastropathy, and polypoid or epithelial hyperplasia was also determined. Serum levels of gastrin were measured. We found two polyps, one in each group, both of which were negative for Helicobacter pylori. There were two cases of parietal cell hyperplasia in users of proton-pump inhibitors. Gastrin was elevated in 28 users of proton-pump inhibitors and in four members of the control group. We did not find statistically significant differences in the endoscopic or histopathologic findings between the two groups. Chronic use of proton-pump inhibitors for the duration examined was not associated with significant gastric changes. An interesting finding was that the 4 chronic users of proton-pump inhibitors who had serum gastrin levels above 500 pg/mL also had positive serology for Chagas disease.

Value of pH regulators in the diagnosis, prognosis and treatment of cancer.

PubMed

Granja, Sara; Tavares-Valente, Diana; Queirós, Odília; Baltazar, Fátima

2017-04-01

Altered metabolism, associated with acidification of the extracellular milieu, is one of the major features of cancer. As pH regulation is crucial for the maintenance of all biological functions, cancer cells rely on the activity of lactate exporters and proton transporters to regulate their intracellular pH. The major players in cancer pH regulation are proton pump ATPases, sodium-proton exchangers (NHEs), monocarboxylate transporters (MCTs), carbonic anhydrases (CAs) and anion exchangers (AEs), which have been shown to be upregulated in several human malignancies. Thanks to the activity of the proton pumps and transporters, tumours acidify their microenvironment, becoming more aggressive and resistant to therapy. Thus, targeting tumour pH may contribute to more effective anticancer strategies for controlling tumour progression and therapeutic resistance. In the present study, we review the role of the main pH regulators expressed in human cancer cells, including their diagnostic and prognostic value, as well as their usefulness as therapeutic targets. Copyright © 2017 Elsevier Ltd. All rights reserved.

F"orster-type mechanism of the redox-driven proton pump

NASA Astrophysics Data System (ADS)

Mourokh, Lev; Smirnov, Anatoly; Nori, Franco

2007-03-01

We propose a model to describe an electronically-driven proton pump in the cytochrome c oxidase (CcO). We examine the situation when the electron transport between the two sites embedded into the inner membrane of the mitochondrion occurs in parallel with the proton transfer from the protonable site that is close to the negative (inner) side of the membrane to the other protonable site located nearby the positive (outer) surface of the membrane. In addition to the conventional electron and proton tunnelings between the sites, the Coulomb interaction between electrons and protons localized on the corresponding sites leads to so-called F"orster transfer, i.e. to the process when the simultaneous electron and proton tunnelings are accompanied by the resonant energy transfer between the electrons and protons. Our calculations based on reasonable parameters have demonstrated that the F"orster process facilitates the proton pump at physiological temperatures. We have examined the effects of an electron voltage build-up, external temperature, and molecular electrostatics driving the electron and proton energies to the resonant conditions, and have shown that these parameters can control the proton pump operation.

Activation of acid-sensing ion channels by localized proton transient reveals their role in proton signaling

PubMed Central

Zeng, Wei-Zheng; Liu, Di-Shi; Liu, Lu; She, Liang; Wu, Long-Jun; Xu, Tian-Le

2015-01-01

Extracellular transients of pH alterations likely mediate signal transduction in the nervous system. Neuronal acid-sensing ion channels (ASICs) act as sensors for extracellular protons, but the mechanism underlying ASIC activation remains largely unknown. Here, we show that, following activation of a light-activated proton pump, Archaerhodopsin-3 (Arch), proton transients induced ASIC currents in both neurons and HEK293T cells co-expressing ASIC1a channels. Using chimera proteins that bridge Arch and ASIC1a by a glycine/serine linker, we found that successful coupling occurred within 15 nm distance. Furthermore, two-cell sniffer patch recording revealed that regulated release of protons through either Arch or voltage-gated proton channel Hv1 activated neighbouring cells expressing ASIC1a channels. Finally, computational modelling predicted the peak proton concentration at the intercellular interface to be at pH 6.7, which is acidic enough to activate ASICs in vivo. Our results highlight the pathophysiological role of proton signalling in the nervous system. PMID:26370138

Citrate Accumulation-Related Gene Expression and/or Enzyme Activity Analysis Combined With Metabolomics Provide a Novel Insight for an Orange Mutant

PubMed Central

Guo, Ling-Xia; Shi, Cai-Yun; Liu, Xiao; Ning, Dong-Yuan; Jing, Long-Fei; Yang, Huan; Liu, Yong-Zhong

2016-01-01

‘Hong Anliu’ (HAL, Citrus sinensis cv. Hong Anliu) is a bud mutant of ‘Anliu’ (AL), characterized by a comprehensive metabolite alteration, such as lower accumulation of citrate, high accumulation of lycopene and soluble sugars in fruit juice sacs. Due to carboxylic acid metabolism connects other metabolite biosynthesis and/or catabolism networks, we therefore focused analyzing citrate accumulation-related gene expression profiles and/or enzyme activities, along with metabolic fingerprinting between ‘HAL’ and ‘AL’. Compared with ‘AL’, the transcript levels of citrate biosynthesis- and utilization-related genes and/or the activities of their respective enzymes such as citrate synthase, cytosol aconitase and ATP-citrate lyase were significantly higher in ‘HAL’. Nevertheless, the mitochondrial aconitase activity, the gene transcript levels of proton pumps, including vacuolar H+-ATPase, vacuolar H+-PPase, and the juice sac-predominant p-type proton pump gene (CsPH8) were significantly lower in ‘HAL’. These results implied that ‘HAL’ has higher abilities for citrate biosynthesis and utilization, but lower ability for the citrate uptake into vacuole compared with ‘AL’. Combined with the metabolites-analyzing results, a model was then established and suggested that the reduction in proton pump activity is the key factor for the low citrate accumulation and the comprehensive metabolite alterations as well in ‘HAL’. PMID:27385485

Squeezing at Entrance of Proton Transport Pathway in Proton-translocating Pyrophosphatase upon Substrate Binding*

PubMed Central

Huang, Yun-Tzu; Liu, Tseng-Huang; Lin, Shih-Ming; Chen, Yen-Wei; Pan, Yih-Jiuan; Lee, Ching-Hung; Sun, Yuh-Ju; Tseng, Fan-Gang; Pan, Rong-Long

2013-01-01

Homodimeric proton-translocating pyrophosphatase (H+-PPase; EC 3.6.1.1) is indispensable for many organisms in maintaining organellar pH homeostasis. This unique proton pump couples the hydrolysis of PPi to proton translocation across the membrane. H+-PPase consists of 14–16 relatively hydrophobic transmembrane domains presumably for proton translocation and hydrophilic loops primarily embedding a catalytic site. Several highly conserved polar residues located at or near the entrance of the transport pathway in H+-PPase are essential for proton pumping activity. In this investigation single molecule FRET was employed to dissect the action at the pathway entrance in homodimeric Clostridium tetani H+-PPase upon ligand binding. The presence of the substrate analog, imidodiphosphate mediated two sites at the pathway entrance moving toward each other. Moreover, single molecule FRET analyses after the mutation at the first proton-carrying residue (Arg-169) demonstrated that conformational changes at the entrance are conceivably essential for the initial step of H+-PPase proton translocation. A working model is accordingly proposed to illustrate the squeeze at the entrance of the transport pathway in H+-PPase upon substrate binding. PMID:23720778

Effect of proton pump inhibitors on markers of risk for high-grade dysplasia and oesophageal cancer in Barrett's oesophagus.

PubMed

Hillman, L C; Chiragakis, L; Shadbolt, B; Kaye, G L; Clarke, A C

2008-02-15

It has been shown that the presence on diagnosis of endoscopic macroscopic markers indicates a high-risk group for Barrett's oesophagus. To determine whether proton pump inhibitor therapy prior to diagnosis of Barrett's oesophagus influences markers for risk development of subsequent high-grade dysplasia/adenocarcinoma. A review of all patients with Barrett's oesophagus entering a surveillance programme was undertaken. Five hundred and two patients diagnosed with Barrett's oesophagus were assessed on diagnosis for endoscopic macroscopic markers or low-grade dysplasia. Subsequent development of high-grade dysplasia/adenocarcinoma was documented. The relationship between the initiation of proton pump inhibitor therapy prior to the diagnosis of BE and the presence of macroscopic markers or low-grade dysplasia at entry was determined. Fourteen patients developed high-grade dysplasia/adenocarcinoma during surveillance. Patients who entered without prior proton pump inhibitor therapy were 3.4 times (95% CI: 1.98-5.85) more likely to have a macroscopic marker or low-grade dysplasia than those patients already on a proton pump inhibitor. Use of proton pump inhibitor therapy prior to diagnosis of Barrett's oesophagus significantly reduced the presence of markers used to stratify patient risk. Widespread use of proton pump inhibitors will confound surveillance strategies for patients with Barrett's oesophagus based on entry characteristics but is justified because of the lower risk of neoplastic progression.

Single mutations that redirect internal proton transfer in the ba3 oxidase from Thermus thermophilus

PubMed Central

Smirnova, Irina; Chang, Hsin-Yang; von Ballmoos, Christoph; Ädelroth, Pia; Gennis, Robert B.; Brzezinski, Peter

2014-01-01

The ba3-type cytochrome c oxidase from Thermus thermophilus is a membrane-bound proton pump. Results from earlier studies have shown that with the aa3-type oxidases proton uptake to the catalytic site and “pump site” occur simultaneously. However, with the ba3 oxidase the pump site is loaded before proton transfer to the catalytic site because the proton transfer to the latter is slower than with the aa3 oxidases. In addition, the timing of formation and decay of catalytic intermediates is different in the two types of oxidases. In the present study, we have investigated two mutant ba3 CytcOs in which residues of the proton pathway leading to the catalytic site as well as the pump site were exchanged, Thr312Val and Tyr244Phe. Even though the ba3 CytcO uses only a single proton pathway for transfer of the substrate and “pumped” protons, the amino-acid residue substitutions had distinctly different effects on the kinetics of proton transfer to the catalytic site and the pump site, respectively. The results indicate that the rates of these reactions can be modified independently by replacement of single residues within the proton pathway. Furthermore, the data suggest that the Thr312Val and Tyr244Phe mutations interfere with a structural rearrangement in the proton pathway that is rate limiting for proton transfer to the catalytic site. PMID:24004023

Investigating the Proton Donor in the NO Reductase from Paracoccus denitrificans

PubMed Central

ter Beek, Josy; Krause, Nils; Ädelroth, Pia

2016-01-01

Variant nomenclature: the variants were made in the NorB subunit if not indicated by the superscript c, which are variants in the NorC subunit (e.g. E122A = exchange of Glu-122 in NorB for an Ala, E71cD; exchange of Glu-71 in NorC for an Asp). Bacterial NO reductases (NORs) are integral membrane proteins from the heme-copper oxidase superfamily. Most heme-copper oxidases are proton-pumping enzymes that reduce O2 as the last step in the respiratory chain. With electrons from cytochrome c, NO reductase (cNOR) from Paracoccus (P.) denitrificans reduces NO to N2O via the following reaction: 2NO+2e-+2H+→N2O+H2O. Although this reaction is as exergonic as O2-reduction, cNOR does not contribute to the electrochemical gradient over the membrane. This means that cNOR does not pump protons and that the protons needed for the reaction are taken from the periplasmic side of the membrane (since the electrons are donated from this side). We previously showed that the P. denitrificans cNOR uses a single defined proton pathway with residues Glu-58 and Lys-54 from the NorC subunit at the entrance. Here we further strengthened the evidence in support of this pathway. Our further aim was to define the continuation of the pathway and the immediate proton donor for the active site. To this end, we investigated the region around the calcium-binding site and both propionates of heme b3 by site directed mutagenesis. Changing single amino acids in these areas often had severe effects on cNOR function, with many variants having a perturbed active site, making detailed analysis of proton transfer properties difficult. Our data does however indicate that the calcium ligation sphere and the region around the heme b3 propionates are important for proton transfer and presumably contain the proton donor. The possible evolutionary link between the area for the immediate donor in cNOR and the proton loading site (PLS) for pumped protons in oxygen-reducing heme-copper oxidases is discussed. PMID:27030968

Investigating the Proton Donor in the NO Reductase from Paracoccus denitrificans.

PubMed

ter Beek, Josy; Krause, Nils; Ädelroth, Pia

2016-01-01

Variant nomenclature: the variants were made in the NorB subunit if not indicated by the superscript c, which are variants in the NorC subunit (e.g. E122A = exchange of Glu-122 in NorB for an Ala, E71cD; exchange of Glu-71 in NorC for an Asp). Bacterial NO reductases (NORs) are integral membrane proteins from the heme-copper oxidase superfamily. Most heme-copper oxidases are proton-pumping enzymes that reduce O2 as the last step in the respiratory chain. With electrons from cytochrome c, NO reductase (cNOR) from Paracoccus (P.) denitrificans reduces NO to N2O via the following reaction: 2NO+2e-+2H+→N2O+H2O. Although this reaction is as exergonic as O2-reduction, cNOR does not contribute to the electrochemical gradient over the membrane. This means that cNOR does not pump protons and that the protons needed for the reaction are taken from the periplasmic side of the membrane (since the electrons are donated from this side). We previously showed that the P. denitrificans cNOR uses a single defined proton pathway with residues Glu-58 and Lys-54 from the NorC subunit at the entrance. Here we further strengthened the evidence in support of this pathway. Our further aim was to define the continuation of the pathway and the immediate proton donor for the active site. To this end, we investigated the region around the calcium-binding site and both propionates of heme b3 by site directed mutagenesis. Changing single amino acids in these areas often had severe effects on cNOR function, with many variants having a perturbed active site, making detailed analysis of proton transfer properties difficult. Our data does however indicate that the calcium ligation sphere and the region around the heme b3 propionates are important for proton transfer and presumably contain the proton donor. The possible evolutionary link between the area for the immediate donor in cNOR and the proton loading site (PLS) for pumped protons in oxygen-reducing heme-copper oxidases is discussed.

Proton pump inhibitors are associated with accelerated development of cirrhosis, hepatic decompensation and hepatocellular carcinoma in noncirrhotic patients with chronic hepatitis C infection: results from ERCHIVES.

PubMed

Li, D K; Yan, P; Abou-Samra, A-B; Chung, R T; Butt, A A

2018-01-01

Proton pump inhibitors are among the most commonly prescribed medications in the United States. Their safety in cirrhosis has recently been questioned, but their overall effect on disease progression in noncirrhotic patients with chronic liver disease remains unclear. To determine the impact of proton pump inhibitors on the progression of liver disease in noncirrhotic patients with hepatitis C virus (HCV) infection. Using the electronically retrieved cohort of HCV-infected veterans (ERCHIVES) database, we identified all subjects who received HCV treatment and all incident cases of cirrhosis, hepatic decompensation and hepatocellular carcinoma. Proton pump inhibitor use was measured using cumulative defined daily dose. Multivariate Cox regression analysis was performed after adjusting univariate predictors of cirrhosis and various indications for proton pump inhibitor use. Among 11 526 eligible individuals, we found that exposure to proton pump inhibitors was independently associated with an increased risk of developing cirrhosis (hazard ratio [HR]: 1.32; 95% confidence interval: [1.17, 1.49]). This association remained robust to sensitivity analysis in which only patients who achieved sustained virologic response were analysed as well as analysis excluding those with alcohol abuse/dependence. Proton pump inhibitor exposure was also independently associated with an increased risk of hepatic decompensation (HR: 3.79 [2.58, 5.57]) and hepatocellular carcinoma (HR: 2.01 [1.50, 2.70]). In patients with chronic HCV infection, increasing proton pump inhibitor use is associated with a dose-dependent risk of progression of chronic liver disease to cirrhosis, as well as an increased risk of hepatic decompensation and hepatocellular carcinoma. © 2017 John Wiley & Sons Ltd.

Review article: relationship between the metabolism and efficacy of proton pump inhibitors--focus on rabeprazole.

PubMed

Horn, J

2004-11-01

Proton pump inhibitors are now considered the mainstay of treatment for acid-related disease. Although all proton pump inhibitors are highly effective, the antisecretory effects of different drugs in this class are not completely consistent across patients. One reason for this is the acid-suppressing effect of Helicobacter pylori infection, which may augment the actions of proton pump inhibitors. A second important reason for interpatient variability of the effects of proton pump inhibitors on acid secretion involves genetically determined differences in the metabolism of these drugs. This article focuses on the impact of genetic polymorphism of cytochrome P450 (CYP)2C19 on the pharmacokinetics and pharmacodynamics of proton pump inhibitors, particularly rabeprazole. Results reviewed indicate that the metabolism and pharmacokinetics of rabeprazole differ significantly from those of other proton pump inhibitors. Most importantly, the clearance of rabeprazole is largely nonenzymatic and less dependent on CYP2C19 than other drugs in its class. This results in greater consistency of pharmacokinetics for rabeprazole across a wide range of patients with acid-related disease, particularly those with different CYP2C19 genotypes. The pharmacodynamic profile for rabeprazole is also characterized by more rapid suppression of gastric acid secretion than with other proton pump inhibitors, which is also independent of CYP2C19 genotype. The favourable pharmacokinetic/pharmacodynamic profile for rabeprazole has been shown to result in high eradication rates for H. pylori in both normal and poor metabolizers. Pharmacodynamic results have also suggested that rabeprazole may be better suited than omeprazole as on-demand therapy for symptomatic gastro-oesophageal reflux disease. Finally, the use of rabeprazole is not complicated by clinically significant drug-drug interactions of the type that have been reported for omeprazole.

Biological proton pumping in an oscillating electric field.

PubMed

Kim, Young C; Furchtgott, Leon A; Hummer, Gerhard

2009-12-31

Time-dependent external perturbations provide powerful probes of the function of molecular machines. Here we study biological proton pumping in an oscillating electric field. The protein cytochrome c oxidase is the main energy transducer in aerobic life, converting chemical energy into an electric potential by pumping protons across a membrane. With the help of master-equation descriptions that recover the key thermodynamic and kinetic properties of this biological "fuel cell," we show that the proton pumping efficiency and the electronic currents in steady state depend significantly on the frequency and amplitude of the applied field, allowing us to distinguish between different microscopic mechanisms of the machine. A spectral analysis reveals dominant reaction steps consistent with an electron-gated pumping mechanism.

Job Sharing in the Endomembrane System: Vacuolar Acidification Requires the Combined Activity of V-ATPase and V-PPase.

PubMed

Kriegel, Anne; Andrés, Zaida; Medzihradszky, Anna; Krüger, Falco; Scholl, Stefan; Delang, Simon; Patir-Nebioglu, M Görkem; Gute, Gezahegn; Yang, Haibing; Murphy, Angus S; Peer, Wendy Ann; Pfeiffer, Anne; Krebs, Melanie; Lohmann, Jan U; Schumacher, Karin

2015-12-01

The presence of a large central vacuole is one of the hallmarks of a prototypical plant cell, and the multiple functions of this compartment require massive fluxes of molecules across its limiting membrane, the tonoplast. Transport is assumed to be energized by the membrane potential and the proton gradient established by the combined activity of two proton pumps, the vacuolar H(+)-pyrophosphatase (V-PPase) and the vacuolar H(+)-ATPase (V-ATPase). Exactly how labor is divided between these two enzymes has remained elusive. Here, we provide evidence using gain- and loss-of-function approaches that lack of the V-ATPase cannot be compensated for by increased V-PPase activity. Moreover, we show that increased V-ATPase activity during cold acclimation requires the presence of the V-PPase. Most importantly, we demonstrate that a mutant lacking both of these proton pumps is conditionally viable and retains significant vacuolar acidification, pointing to a so far undetected contribution of the trans-Golgi network/early endosome-localized V-ATPase to vacuolar pH. © 2015 American Society of Plant Biologists. All rights reserved.

Selective production of sealed plasma membrane vesicles from red beet (Beta vulgaris L.) storage tissue.

PubMed

Giannini, J L; Gildensoph, L H; Briskin, D P

1987-05-01

Modification of our previous procedure for the isolation of microsomal membrane vesicles from red beet (Beta vulgaris L.) storage tissue allowed the recovery of sealed membrane vesicles displaying proton transport activity sensitive to both nitrate and orthovanadate. In the absence of a high salt concentration in the homogenization medium, contributions of nitrate-sensitive (tonoplast) and vanadate-sensitive (plasma membrane) proton transport were roughly equal. The addition of 0.25 M KCl to the homogenization medium increased the relative amount of nitrate-inhibited proton transport activity while the addition of 0.25 M KI resulted in proton pumping vesicles displaying inhibition by vanadate but stimulation by nitrate. These effects appeared to result from selective sealing of either plasma membrane or tonoplast membrane vesicles during homogenization in the presence of the two salts. Following centrifugation on linear sucrose gradients it was shown that the nitrate-sensitive, proton-transporting vesicles banded at low density and comigrated with nitrate-sensitive ATPase activity while the vanadate-sensitive, proton-transporting vesicles banded at a much higher density and comigrated with vanadate-sensitive ATPase. The properties of the vanadate-sensitive proton pumping vesicles were further characterized in microsomal membrane fractions produced by homogenization in the presence of 0.25 M KI and centrifugation on discontinuous sucrose density gradients. Proton transport was substrate specific for ATP, displayed a sharp pH optimum at 6.5, and was insensitive to azide but inhibited by N'-N-dicyclohexylcarbodiimide, diethylstilbestrol, and fluoride. The Km of proton transport for Mg:ATP was 0.67 mM and the K0.5 for vanadate inhibition was at about 50 microM. These properties are identical to those displayed by the plasma membrane ATPase and confirm a plasma membrane origin for the vesicles.

Physiological uncoupling of mitochondrial oxidative phosphorylation. Studies in different yeast species.

PubMed

Guerrero-Castillo, Sergio; Araiza-Olivera, Daniela; Cabrera-Orefice, Alfredo; Espinasa-Jaramillo, Juan; Gutiérrez-Aguilar, Manuel; Luévano-Martínez, Luís A; Zepeda-Bastida, Armando; Uribe-Carvajal, Salvador

2011-06-01

Under non-phosphorylating conditions a high proton transmembrane gradient inhibits the rate of oxygen consumption mediated by the mitochondrial respiratory chain (state IV). Slow electron transit leads to production of reactive oxygen species (ROS) capable of participating in deleterious side reactions. In order to avoid overproducing ROS, mitochondria maintain a high rate of O(2) consumption by activating different exquisitely controlled uncoupling pathways. Different yeast species possess one or more uncoupling systems that work through one of two possible mechanisms: i) Proton sinks and ii) Non-pumping redox enzymes. Proton sinks are exemplified by mitochondrial unspecific channels (MUC) and by uncoupling proteins (UCP). Saccharomyces. cerevisiae and Debaryomyces hansenii express highly regulated MUCs. Also, a UCP was described in Yarrowia lipolytica which promotes uncoupled O(2) consumption. Non-pumping alternative oxido-reductases may substitute for a pump, as in S. cerevisiae or may coexist with a complete set of pumps as in the branched respiratory chains from Y. lipolytica or D. hansenii. In addition, pumps may suffer intrinsic uncoupling (slipping). Promising models for study are unicellular parasites which can turn off their aerobic metabolism completely. The variety of energy dissipating systems in eukaryote species is probably designed to control ROS production in the different environments where each species lives.

Route, mechanism, and implications of proton import during Na+/K+ exchange by native Na+/K+-ATPase pumps

PubMed Central

Vedovato, Natascia

2014-01-01

A single Na+/K+-ATPase pumps three Na+ outwards and two K+ inwards by alternately exposing ion-binding sites to opposite sides of the membrane in a conformational sequence coupled to pump autophosphorylation from ATP and auto-dephosphorylation. The larger flow of Na+ than K+ generates outward current across the cell membrane. Less well understood is the ability of Na+/K+ pumps to generate an inward current of protons. Originally noted in pumps deprived of external K+ and Na+ ions, as inward current at negative membrane potentials that becomes amplified when external pH is lowered, this proton current is generally viewed as an artifact of those unnatural conditions. We demonstrate here that this inward current also flows at physiological K+ and Na+ concentrations. We show that protons exploit ready reversibility of conformational changes associated with extracellular Na+ release from phosphorylated Na+/K+ pumps. Reversal of a subset of these transitions allows an extracellular proton to bind an acidic side chain and to be subsequently released to the cytoplasm. This back-step of phosphorylated Na+/K+ pumps that enables proton import is not required for completion of the 3 Na+/2 K+ transport cycle. However, the back-step occurs readily during Na+/K+ transport when external K+ ion binding and occlusion are delayed, and it occurs more frequently when lowered extracellular pH raises the probability of protonation of the externally accessible carboxylate side chain. The proton route passes through the Na+-selective binding site III and is distinct from the principal pathway traversed by the majority of transported Na+ and K+ ions that passes through binding site II. The inferred occurrence of Na+/K+ exchange and H+ import during the same conformational cycle of a single molecule identifies the Na+/K+ pump as a hybrid transporter. Whether Na+/K+ pump–mediated proton inflow may have any physiological or pathophysiological significance remains to be clarified. PMID:24688018

Effect of the Prophylactic Use of Proton-Pump Inhibitors on the Pattern of Gastrointestinal Symptoms in Patients Late After Kidney Transplant.

PubMed

Królikowski, Jerzy; Pawłowicz, Ewa; Budzisz, Ewa; Nowicki, Michał

2016-10-01

Although immunosuppressive drugs have been recognized as leading causes of gastrointestinal symptoms after kidney transplant, other widely used medications such as proton-pump inhibitors recently have been implicated. Our aim was to study the effects of chronic proton-pump inhibitor therapy on gastrointestinal symptoms in clinically stable patients late after kidney transplant. The study comprised 100 kidney transplant recipients (66 men and 34 women, mean age of 49 ± 12 y, mean time after transplant of 56 ± 46 mo). All patients completed the Gastrointestinal Symptoms Rating Scale and the Quality of Life Questionnaire SF-8 surveys. The most commonly reported symptoms included borborygmus (27%), flatulence (23%), abdominal distension (18%), urgent need of defecation (17%), and heartburn, acid reflux, and eructation (13%). Proton-pump inhibitors were chronically used by 50% of patients and sporadically by 33%. Gastrointestinal Symptoms Rating Scale scores were higher in patients who used proton-pump inhibitors (mean score of 7.8 ± 5.5 vs 4.6 ± 3.0; P = .013). Total score of items representing diarrhea in the Gastrointestinal Symptoms Rating Scale (increased passage of stools, loose stools, urgent need of defecation, incomplete evacuation) was higher in patients treated with proton-pump inhibitors than in those not treated (2.3 ± 2.2 vs 1.3 ± 1.9; P = .04). Chronic use of proton-pump inhibitors may increase the prevalence of gastrointestinal symptoms, particularly diarrhea, in patients late after kidney transplant.

Biological proton pumping in an oscillating electric field

PubMed Central

Kim, Young C.; Furchtgott, Leon A.; Hummer, Gerhard

2010-01-01

Time-dependent external perturbations provide powerful probes of the function of molecular machines. Here we study biological proton pumping in an oscillating electric field. The protein cytochrome c oxidase is the main energy transducer in aerobic life, converting chemical energy into an electric potential by pumping protons across a membrane. With the help of master-equation descriptions that recover the key thermodynamic and kinetic properties of this biological “fuel cell,” we show that the proton pumping efficiency and the electronic currents in steady state both depend significantly and distinctly on the frequency and amplitude of the applied field, allowing us to distinguish between different microscopic mechanisms of the machine. A spectral analysis reveals dominant kinetic modes that show reaction steps consistent with an electron-gated pumping mechanism. PMID:20366348

Respiratory Complex I in Bos taurus and Paracoccus denitrificans Pumps Four Protons across the Membrane for Every NADH Oxidized.

PubMed

Jones, Andrew J Y; Blaza, James N; Varghese, Febin; Hirst, Judy

2017-03-24

Respiratory complex I couples electron transfer between NADH and ubiquinone to proton translocation across an energy-transducing membrane to support the proton-motive force that drives ATP synthesis. The proton-pumping stoichiometry of complex I ( i.e. the number of protons pumped for each two electrons transferred) underpins all mechanistic proposals. However, it remains controversial and has not been determined for any of the bacterial enzymes that are exploited as model systems for the mammalian enzyme. Here, we describe a simple method for determining the proton-pumping stoichiometry of complex I in inverted membrane vesicles under steady-state ADP-phosphorylating conditions. Our method exploits the rate of ATP synthesis, driven by oxidation of NADH or succinate with different sections of the respiratory chain engaged in catalysis as a proxy for the rate of proton translocation and determines the stoichiometry of complex I by reference to the known stoichiometries of complexes III and IV. Using vesicles prepared from mammalian mitochondria (from Bos taurus ) and from the bacterium Paracoccus denitrificans , we show that four protons are pumped for every two electrons transferred in both cases. By confirming the four-proton stoichiometry for mammalian complex I and, for the first time, demonstrating the same value for a bacterial complex, we establish the utility of P. denitrificans complex I as a model system for the mammalian enzyme. P. denitrificans is the first system described in which mutagenesis in any complex I core subunit may be combined with quantitative proton-pumping measurements for mechanistic studies. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Enhancement of survival and electricity production in an engineered bacterium by light-driven proton pumping.

PubMed

Johnson, Ethan T; Baron, Daniel B; Naranjo, Belén; Bond, Daniel R; Schmidt-Dannert, Claudia; Gralnick, Jeffrey A

2010-07-01

Microorganisms can use complex photosystems or light-dependent proton pumps to generate membrane potential and/or reduce electron carriers to support growth. The discovery that proteorhodopsin is a light-dependent proton pump that can be expressed readily in recombinant bacteria enables development of new strategies to probe microbial physiology and to engineer microbes with new light-driven properties. Here, we describe functional expression of proteorhodopsin and light-induced changes in membrane potential in the bacterium Shewanella oneidensis strain MR-1. We report that there were significant increases in electrical current generation during illumination of electrochemical chambers containing S. oneidensis expressing proteorhodopsin. We present evidence that an engineered strain is able to consume lactate at an increased rate when it is illuminated, which is consistent with the hypothesis that proteorhodopsin activity enhances lactate uptake by increasing the proton motive force. Our results demonstrate that there is coupling of a light-driven process to electricity generation in a nonphotosynthetic engineered bacterium. Expression of proteorhodopsin also preserved the viability of the bacterium under nutrient-limited conditions, providing evidence that fulfillment of basic energy needs of organisms may explain the widespread distribution of proteorhodopsin in marine environments.

Trypanosoma cruzi H+-ATPase 1 (TcHA1) and 2 (TcHA2) genes complement yeast mutants defective in H+ pumps and encode plasma membrane P-type H+-ATPases with different enzymatic properties.

PubMed

Luo, Shuhong; Scott, David A; Docampo, Roberto

2002-11-15

Previous studies in Trypanosoma cruzi have shown that intracellular pH homeostasis requires ATP and is affected by H(+)-ATPase inhibitors, indicating a major role for ATP-driven proton pumps in intracellular pH control. In the present study, we report the cloning and sequencing of a pair of genes linked in tandem (TcHA1 and TcHA2) in T. cruzi which encode proteins with homology to fungal and plant P-type proton-pumping ATPases. The genes are expressed at the mRNA level in different developmental stages of T. cruzi: TcHA1 is expressed maximally in epimastigotes, whereas TcHA2 is expressed predominantly in trypomastigotes. The proteins predicted from the nucleotide sequence of the genes have 875 and 917 amino acids and molecular masses of 96.3 and 101.2 kDa, respectively. Full-length TcHA1 and an N-terminal truncated version of TcHA2 complemented a Saccharomyces cerevisiae strain deficient in P-type H(+)-ATPase activity, the proteins localized to the yeast plasma membrane, and ATP-driven proton pumping could be detected in proteoliposomes reconstituted from plasma membrane purified from transfected yeast. The reconstituted proton transport activity was reduced by inhibitors of P-type H(+)-ATPases. C-terminal truncation did not affect complementation of mutant yeast, suggesting the lack of C-terminal autoinhibitory domains in these proteins. ATPase activity in plasma membrane from TcHA1- and (N-terminal truncated) TcHA2-transfected yeast was inhibited to different extents by vanadate, whereas the latter yeast strain was more resistant to extremes of pH, suggesting that the native proteins may serve different functions at different stages in the T. cruzi life cycle.

Design and modeling of a light powered biomimicry micropump

NASA Astrophysics Data System (ADS)

Sze, Tsun-kay Jackie; Liu, Jin; Dutta, Prashanta

2015-06-01

The design of compact micropumps to provide steady flow has been an on-going challenge in the field of microfluidics. In this work, a novel micropump concept is introduced utilizing bacteriorhodopsin and sugar transporter proteins. The micropump utilizes light energy to activate the transporter proteins, which create an osmotic pressure gradient and drive the fluid flow. The capability of the bio inspired micropump is demonstrated using a quasi 1D numerical model, where the contributions of bacteriorhodopsin and sugar transporter proteins are taken care of by appropriate flux boundary conditions in the flow channel. Proton flux created by the bacteriorhodopsin proteins is compared with experimental results to obtain the appropriate working conditions of the proteins. To identify the pumping capability, we also investigate the influences of several key parameters, such as the membrane fraction of transporter proteins, membrane proton permeability and the presence of light. Our results show that there is a wide bacteriorhodopsin membrane fraction range (from 0.2 to 10%) at which fluid flow stays nearly at its maximum value. Numerical results also indicate that lipid membranes with low proton permeability can effectively control the light source as a method to turn on/off fluid flow. This capability allows the micropump to be activated and shut off remotely without bulky support equipment. In comparison with existing micropumps, this pump generates higher pressures than mechanical pumps. It can produce peak fluid flow and shutoff head comparable to other non-mechanical pumps.

Hypomagnesaemia associated with long-term use of proton pump inhibitors

PubMed Central

Toh, James Wei Tatt; Ong, Evonne; Wilson, Robert

2015-01-01

Hypomagnesaemia and associated hypocalcaemia and hypoparathyroidism have been increasingly recognised as rare long-term side-effects of proton pump inhibitors (PPIs). The PPIs may inhibit active magnesium (Mg) absorption by interfering with transcellular transient receptor potential melastatin-6 and -7 (TRPM 6 and 7) channels. More recent cell culture studies have suggested concomitant inhibition of passive Mg absorption by omeprazole. After being treated with a range of PPIs, the four patients in our case series developed hypomagnesaemia, which responded to withdrawal of therapy and initiation of Mg replacement. Their clinical course and management demonstrate key aspects of hypomagnesaemia associated with long-term use of PPIs. PMID:25138239

Proton-pump inhibitors in patients requiring antiplatelet therapy: new FDA labeling.

PubMed

Johnson, David A; Chilton, Robert; Liker, Harley R

2014-05-01

Proton-pump inhibitors (PPIs) are recommended for patients who require antiplatelet therapy and have a history of upper gastrointestinal bleeding. Proton-pump inhibitors should also be considered for patients receiving antiplatelet therapy who have other risk factors for gastrointestinal bleeding, including use of aspirin. Thus, evidence of pharmacokinetic and pharmacodynamic interactions between PPIs and consequent impaired effectiveness of the antiplatelet agent clopidogrel has caused concern. Here, we discuss comparative studies suggesting that the extent to which a PPI reduces exposure to the active metabolite of clopidogrel and attenuates its antithrombotic effect differs among PPIs. Although a clinically meaningful effect of the interaction between PPIs and clopidogrel on cardiovascular outcomes has not been established, these studies provided the basis for recent changes in US Food and Drug Administration (FDA) labeling for several PPIs and clopidogrel. New labeling suggests that PPI use among patients taking clopidogrel be limited to pantoprazole, rabeprazole, lansoprazole, or dexlansoprazole. Because comparative studies indicate that omeprazole and esomeprazole have a greater effect on the CYP2C19-mediated conversion of clopidogrel to its active metabolite and, consequently, clopidogrel's effect on platelet reactivity, FDA labeling recommends avoiding omeprazole and esomeprazole in patients taking clopidogrel. Even a 12-hour separation of dosing does not appear to prevent drug interactions between omeprazole and clopidogrel.

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle*

PubMed Central

Yano, Naomine; Muramoto, Kazumasa; Shimada, Atsuhiro; Takemura, Shuhei; Baba, Junpei; Fujisawa, Hidenori; Mochizuki, Masao; Shinzawa-Itoh, Kyoko; Yamashita, Eiki; Tsukihara, Tomitake; Yoshikawa, Shinya

2016-01-01

Bovine heart cytochrome c oxidase (CcO) pumps four proton equivalents per catalytic cycle through the H-pathway, a proton-conducting pathway, which includes a hydrogen bond network and a water channel operating in tandem. Protons are transferred by H3O+ through the water channel from the N-side into the hydrogen bond network, where they are pumped to the P-side by electrostatic repulsion between protons and net positive charges created at heme a as a result of electron donation to O2 bound to heme a3. To block backward proton movement, the water channel remains closed after O2 binding until the sequential four-proton pumping process is complete. Thus, the hydrogen bond network must collect four proton equivalents before O2 binding. However, a region with the capacity to accept four proton equivalents was not discernable in the x-ray structures of the hydrogen bond network. The present x-ray structures of oxidized/reduced bovine CcO are improved from 1.8/1.9 to 1.5/1.6 Å resolution, increasing the structural information by 1.7/1.6 times and revealing that a large water cluster, which includes a Mg2+ ion, is linked to the H-pathway. The cluster contains enough proton acceptor groups to retain four proton equivalents. The redox-coupled x-ray structural changes in Glu198, which bridges the Mg2+ and CuA (the initial electron acceptor from cytochrome c) sites, suggest that the CuA-Glu198-Mg2+ system drives redox-coupled transfer of protons pooled in the water cluster to the H-pathway. Thus, these x-ray structures indicate that the Mg2+-containing water cluster is the crucial structural element providing the effective proton pumping in bovine CcO. PMID:27605664

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle.

PubMed

Yano, Naomine; Muramoto, Kazumasa; Shimada, Atsuhiro; Takemura, Shuhei; Baba, Junpei; Fujisawa, Hidenori; Mochizuki, Masao; Shinzawa-Itoh, Kyoko; Yamashita, Eiki; Tsukihara, Tomitake; Yoshikawa, Shinya

2016-11-11

Bovine heart cytochrome c oxidase (CcO) pumps four proton equivalents per catalytic cycle through the H-pathway, a proton-conducting pathway, which includes a hydrogen bond network and a water channel operating in tandem. Protons are transferred by H 3 O + through the water channel from the N-side into the hydrogen bond network, where they are pumped to the P-side by electrostatic repulsion between protons and net positive charges created at heme a as a result of electron donation to O 2 bound to heme a 3 To block backward proton movement, the water channel remains closed after O 2 binding until the sequential four-proton pumping process is complete. Thus, the hydrogen bond network must collect four proton equivalents before O 2 binding. However, a region with the capacity to accept four proton equivalents was not discernable in the x-ray structures of the hydrogen bond network. The present x-ray structures of oxidized/reduced bovine CcO are improved from 1.8/1.9 to 1.5/1.6 Å resolution, increasing the structural information by 1.7/1.6 times and revealing that a large water cluster, which includes a Mg 2+ ion, is linked to the H-pathway. The cluster contains enough proton acceptor groups to retain four proton equivalents. The redox-coupled x-ray structural changes in Glu 198 , which bridges the Mg 2+ and Cu A (the initial electron acceptor from cytochrome c) sites, suggest that the Cu A -Glu 198 -Mg 2+ system drives redox-coupled transfer of protons pooled in the water cluster to the H-pathway. Thus, these x-ray structures indicate that the Mg 2+ -containing water cluster is the crucial structural element providing the effective proton pumping in bovine CcO. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

FTIR Studies of Internal Water Molecules of Bacteriorhodopsin: Structural Analysis of Halide-bound D85S and D212N Mutants in the Schiff Base Region

NASA Astrophysics Data System (ADS)

Shibata, Mikihiro; Kandori, Hideki

2007-12-01

Bacteriorhodopsin (BR), a membrane protein found in Halobacterium salinarum, functions as a light-driven proton pump. The Schiff base region has a quadropolar structure with positive charges located at the protonated Schiff base and Arg82, and counterbalancing negative charges located at Asp85 and Asp212 (Figure 1A). It is known that BR lacks a proton-pumping activity if Asp85 or Asp212 is neutralized by mutation. On the other hand, binding of C1- brings different effects for pumping functions in mutants at D85 and D212 position. While C1--bound D85T and D85S pump C1-, photovoltage measurements suggested that C1--bound D212N pumps protons at low pH. In this study, we measured low-temperature FTIR spectra of D85S and D212N containing various halides to compare the halide binding site of both proteins. In the case of D85S, the N-D stretching vibrations of the Schiff base were halide-dependent. This result suggests that the halide is a hydrogen-bond acceptor of the Schiff base, being consistent with the X-ray crystal structure. On the other hand, no halide dependence was observed for vibrational bands of the retinal skeleton and the Schiff base in the D212N mutant. This result suggests that the halide does not form a hydrogen bond with the Schiff base directly, unlike the mutation at D85 position. Halide-dependent water bands in the Schiff base region also differ between D85S and D212N. From these results, halide binding site of both proteins and role of two negative charges in BR will be discussed.

Biosolar energy generation and harvesting from biomolecule-copolymer hybrid systems

NASA Astrophysics Data System (ADS)

Chu, Bong-Chieh Benjamin

Alternative energy sources have become an increasingly important topic as energy needs outpace supply. Furthermore, as the world moves into the digital age of portable electronics, highly efficient and lightweight energy sources will need to be developed. Current technology, such as lithium ion batteries, provide enough power to run portable electronics for hours or days, but can still allow for improvement in their power density (W/kg). Utilizing energy-transducing membrane proteins, which are by nature highly efficient, it is possible to engineer biological-based energy sources with energy densities far greater than any solid-state systems. Furthermore, solar powered membrane proteins have the added benefit of a virtually unlimited supply of energy. This work has developed protein-polymer hybrid films and nanoscale vesicles for a variety of applications from fuel-cell technology to biological-based photovoltaics. Bacteriorhodopsin (BR), a light-activated proton pump, and Cytochrome C Oxidase (COX), a protein involved in the electron transport chain in mitochondria, were reconstituted into biomimetic triblock copolymer membranes. Block copolymer membranes mimic the amphiphilic nature of a natural lipid bilayer but exhibit greater mechanical stability due to UV-polymerizable endgroups. In BR/COX functionalized nanovesicles, proton gradients generated by the light-activated proton pumping of BR are used to drive COX in reverse to generate electrons, providing a hybrid biologically-active polymer to convert solar energy to chemical energy, and finally to electrical energy. This work has found protein activity in planar membranes through the photoelectric current generation by BR and the proton pumping activity of BR-functionalized polymer membranes deposited onto proton exchange membranes, as well as the coupled functionality of BR and COX through current generation in cyclic voltammetry and direct current measurements. Current switching between light and dark environments of composite BR/COX polymer vesicles show a light-dependent current generation with current changes as high as 10muA. Furthermore, electrode modifications were made using polymer and polymer/carbon nanotube (CNT) coatings as anti-absorbent and conductive anti-absorbent layers for the purpose of a more robust electrode. These findings have shown that biological functionality can be engineered into synthetic polymers to make hybrid devices.

Molecular mechanisms for generating transmembrane proton gradients

PubMed Central

Gunner, M.R.; Amin, Muhamed; Zhu, Xuyu; Lu, Jianxun

2013-01-01

Membrane proteins use the energy of light or high energy substrates to build a transmembrane proton gradient through a series of reactions leading to proton release into the lower pH compartment (P-side) and proton uptake from the higher pH compartment (N-side). This review considers how the proton affinity of the substrates, cofactors and amino acids are modified in four proteins to drive proton transfers. Bacterial reaction centers (RCs) and photosystem II (PSII) carry out redox chemistry with the species to be oxidized on the P-side while reduction occurs on the N-side of the membrane. Terminal redox cofactors are used which have pKas that are strongly dependent on their redox state, so that protons are lost on oxidation and gained on reduction. Bacteriorhodopsin is a true proton pump. Light activation triggers trans to cis isomerization of a bound retinal. Strong electrostatic interactions within clusters of amino acids are modified by the conformational changes initiated by retinal motion leading to changes in proton affinity, driving transmembrane proton transfer. Cytochrome c oxidase (CcO) catalyzes the reduction of O2 to water. The protons needed for chemistry are bound from the N-side. The reduction chemistry also drives proton pumping from N- to P-side. Overall, in CcO the uptake of 4 electrons to reduce O2 transports 8 charges across the membrane, with each reduction fully coupled to removal of two protons from the N-side, the delivery of one for chemistry and transport of the other to the P-side. PMID:23507617

Inhibitors of Proton Pumping

PubMed Central

Bisson, Mary A.

1986-01-01

Reported inhibitors of the Characean plasmalemma proton pump were tested for their ability to inhibit the passive H+ conductance which develops in Chara corallina Klein ex Willd. at high pH. Diethylstilbestrol inhibits the proton pump and the passive H+ conductance with about the same time course, at concentrations that have no effect on cytoplasmic streaming. N-Ethylmaleimide, a sulfhydryl reagent which is small and relatively nonpolar, also inhibits both pumping and passive conductance of H+. However, it also inhibits cytoplasmic streaming with about the same time course, and therefore could not be considered a specific ATPase inhibitor. p-Chloromercuribenzene sulfonate (PCMBS), a sulfhydryl reagent which is large and charged and hence less able to penetrate the membrane, does not inhibit pumping or conductance at low concentration. At high concentration, PCMBS sometimes inhibits pumping without affecting H+ conductance, but since streaming is also inhibited, the effect on the pump cannot be said to be specific. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide, a water soluble carbodiimide, weakly inhibits both pump and conductance, apparently specifically. PMID:16664807

Calcium Modulation of Plant Plasma Membrane-Bound Atpase Activities

NASA Technical Reports Server (NTRS)

Caldwell, C.

1983-01-01

The kinetic properties of barley enzyme are discussed and compared with those of other plants. Possibilities for calcium transport in the plasma membrane by proton pump and ATPase-dependent calcium pumps are explored. Topics covered include the ph phase of the enzyme; high affinity of barley for calcium; temperature dependence, activation enthalpy, and the types of ATPase catalytic sites. Attention is given to lipids which are both screened and bound by calcium. Studies show that barley has a calmodulin activated ATPase that is found in the presence of magnesium and calcium.

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca(2+) exchangers

USDA-ARS?s Scientific Manuscript database

Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+) exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recen...

1-Arylsulfonyl-2-(Pyridylmethylsulfinyl) Benzimidazoles as New Proton Pump Inhibitor Prodrugs

PubMed Central

Shin, Jai Moo; Sachs, George; Cho, Young-moon; Garst, Michael

2010-01-01

New arylsulfonyl proton pump inhibitor (PPI) prodrug forms were synthesized. These prodrugs provided longer residence time of an effective PPI plasma concentration, resulting in better gastric acid inhibition. PMID:20032890

Proton pump inhibitors and the risk of pneumonia: a comparison of cohort and self-controlled case series designs

PubMed Central

2013-01-01

Background To compare the results of a new-user cohort study design and the self-controlled case series (SCCS) design using the risk of hospitalisation for pneumonia in those dispensed proton pump inhibitors compared to those unexposed as a case study. Methods The Australian Government Department of Veterans’ Affairs administrative claims database was used. Exposure to proton pump inhibitors and hospitalisations for pneumonia were identified over a 4 year study period 01 Jul 2007 -30 Jun 2011. The same inclusion and exclusion criteria were applied to both studies, however, the SCCS study included subjects with a least one hospitalisation for pneumonia. Results There were 105,467 subjects included in the cohort study and 6775 in the SCCS. Both studies showed an increased risk of hospitalisations for pneumonia in the three defined risk periods following initiation of proton pump inhibitors compared to baseline. With the highest risk in the first 1 to 7 days (Cohort RR, 3.24; 95% CI (2.50, 4.19): SCCS: RR, 3.07; 95% CI (2.69, 3.50)). Conclusions This study has shown that the self-controlled case series method produces similar risk estimates to a new-users cohort study design when applied to the association of proton pump inhibitors and pneumonia. Exposure to a proton pump inhibitor increases the likelihood of being admitted to hospital for pneumonia, with the risk highest in the first week of treatment. PMID:23800078

PEP3 overexpression shortens lag phase but does not alter growth rate in Saccharomyces cerevisiae exposed to acetic acid stress

PubMed Central

Ding, Jun; Holzwarth, Garrett; Bradford, C. Samuel; Cooley, Ben; Yoshinaga, Allen S.; Patton-Vogt, Jana; Abeliovich, Hagai; Penner, Michael H.; Bakalinsky, Alan T.

2017-01-01

In fungi, two recognized mechanisms contribute to pH homeostasis: the plasma membrane proton-pumping ATPase that exports excess protons and the vacuolar proton-pumping ATPase (V-ATPase) that mediates vacuolar proton uptake. Here, we report that overexpression of PEP3 which encodes a component of the HOPS and CORVET complexes involved in vacuolar biogenesis, shortened lag phase in Saccharomyces cerevisiae exposed to acetic acid stress. By confocal microscopy, PEP3-overexpressing cells stained with the vacuolar membrane-specific dye, FM4-64 had more fragmented vacuoles than the wild-type control. The stained overexpression mutant was also found to exhibit about 3.6-fold more FM4-64 fluorescence than the wild-type control as determined by flow cytometry. While the vacuolar pH of the wild-type strain grown in the presence of 80 mM acetic acid was significantly higher than in the absence of added acid, no significant difference was observed in vacuolar pH of the overexpression strain grown either in the presence or absence of 80 mM acetic acid. Based on an indirect growth assay, the PEP3-overexpression strain exhibited higher V-ATPase activity. We hypothesize that PEP3 overexpression provides protection from acid stress by increasing vacuolar surface area and V-ATPase activity and, hence, proton-sequestering capacity. PMID:26051671

Recent advances in chirally pure proton pump inhibitors.

PubMed

Pai, Vikas; Pai, Nitin

2007-08-01

Chirality is a ubiquitous natural phenomenon resulting because of a differential spatial orientation of molecules around its chiral centre. This leads to the existence of two or more spatially dissimilar forms, known as stereoisomers or enantiomers, which are non-superimposable images of each other and may significantly differ from each other with respect to pharmacokinetic and pharmacodynamic properties and molecular interaction. Thus one isomer may offer significant pharmacokinetic and therapeutic advantages as compared to the other isomer or the racemic mixture (mixture containing both enantiomers). Proton pump inhibitors are a class of drugs which have been very effective in the management of acid-related disorders. The proton pumps currently available in the market including omeprazole, pantoprazole, rabeprazole and lansoprazole are racemic mixtures of the S and R isomers. Chirally pure forms of proton pump inhibitors show a superior metabolic and pharmacokinetic profile as compared to their racemates. The therapeutic efficacy is also superior to the parent racemate. This has been clearly demonstrated with the development of esomeprazole- the S-isomer of omeprazole. S-pantoprazole and dexrabeprazole also offer therapeutic advantages as compared to racemic pantoprazole and racemic rabeprazole respectively. This article reviews the chiral developments in the proton pump inhibitors and their clinical applications.

Aspirin and omeprazole for secondary prevention of cardiovascular disease in patients at risk for aspirin-associated gastric ulcers.

PubMed

García-Rayado, Guillermo; Sostres, Carlos; Lanas, Angel

2017-08-01

Cardiovascular disease is the most important cause of morbidity and mortality in the world and low-dose aspirin is considered the cornerstone of the cardiovascular disease prevention. However, low-dose aspirin use is associated with gastrointestinal adverse effects in the whole gastrointestinal tract. In this setting, co-therapy with a proton pump inhibitor is the most accepted strategy to reduce aspirin related upper gastrointestinal damage. In addition, some adverse effects have been described with proton pump inhibitors long term use. Areas covered: Low-dose aspirin related beneficial and adverse effects in cardiovascular system and gastrointestinal tract are reviewed. In addition, this manuscript summarizes current data on upper gastrointestinal damage prevention and adverse events with proton pump inhibition. Finally, we discuss the benefit/risk ratio of proton pump inhibitor use in patients at risk of gastrointestinal damage taking low-dose aspirin. Expert commentary: Nowadays, with the current available evidence, the combination of low-dose aspirin with proton pump inhibitor is the most effective therapy for cardiovascular prevention in patients at high gastrointestinal risk. However, further studies are needed to discover new effective strategies with less related adverse events.

Peptic ulcer disease - discharge

MedlinePlus

... will take two types of antibiotics and a proton pump inhibitor (PPI). These medicines may cause nausea, diarrhea, and ... NSAIDs, you will likely need to take a proton pump inhibitor for 8 weeks. Taking antacids as needed between ...

[Proton pump inhibitors in gastro-oesophageal reflux disease: what is the further step?].

PubMed

Simon, Mireille; Zerbib, Frank

2013-01-01

Optimisation of proton pump inhibitors use may improve reflux symptoms in 20-25% of the patients. Pathological gastro-oesophageal reflux should be documented in a patient with refractory reflux symptoms using upper endoscopy and/or pH testing. While on proton pump inhibitors twice daily, persistent symptoms are not related to gastro-oesophageal refluxdisease(GERD) in 50% of the patients. The new anti-reflux compounds have yet a limited efficacy and side effects that currently limit their development. Copyright © 2012. Published by Elsevier Masson SAS.

Qualitative analysis of anatomopathological changes of gastric mucosa due to long term therapy with proton pump inhibitors: experimental studies x clinical studies.

PubMed

de Souza, Iure Kalinine Ferraz; da Silva, Alcino Lázaro; de Araújo, Alex; Santos, Fernanda Carolina Barbosa; Mendonça, Bernardo Pinto Coelho Keuffer

2013-01-01

For a few decades the long-term use of proton pump inhibitors has had wide application in the treatment of several gastrointestinal diseases. Since then, however, several studies have called attention to the possible development of anatomical and pathological changes of gastric mucosa, resulting from the long term use of this therapeutic modality. Recent experimental and clinical studies suggest that these changes have connection not only to the development of precancerous lesions, but also of gastric tumors. To present a qualitative analysis of anatomical and pathological changes of gastric mucosa resulting from the long-term use of proton pump inhibitors. The headings used were: proton pump inhibitors, precancerous lesions and gastric neoplasms for a non systematic review of the literature, based on Medline, Lillacs and Scielo. Twelve articles were selected from clinical (9) and experimental (3) studies, for qualitative analysis of the results. The gastric acid suppression by high doses of proton pump inhibitors induces hypergastrinemia and the consequent emergence of neuroendocrine tumors in animal models. Morphological changes most often found in these experimental studies were: enterochromaffin-like cell hyperplasia, neuroendocrine tumor, atrophy, metaplasia and adenocarcinoma. In the studies in humans, however, despite enterochromaffin-like cell hyperplasia, the other effects, neuroendocrine tumor and gastric atrophy, gastric metaplasia and or adenocarcinoma, were not identified. Although it is not possible to say that the long-term treatment with proton pump inhibitors induces the appearance or accelerates the development of gastric cancer in humans, several authors have suggested that prolonged administration of this drug could provoke the development of gastric cancer. Thus, the evidence demonstrated in the animal model as well as the large number of patients who do or will do a long-term treatment with proton pump inhibitors, justifies the maintenance of this important line of research.

EFFECT OF CYP2C19 GENETIC POLYMORPHISMS ON THE EFFICACY OF PROTON PUMP INHIBITOR-BASED TRIPLE ERADICATION THERAPY IN SLAVIC PATIENTS WITH PEPTIC ULCERS: A META-ANALYSIS.

PubMed

Denisenko, N P; Sychev, D A; Sizova, Zh M; Rozhkov, A V; Kondrashov, A V

Several meta-analyzes reported the effect of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple therapy for Helicobacter pylori eradication. Most of the studies which were included in these meta-analyzes were held on Asian population. Thus, there is lack of information about the effect of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple eradication therapy in Slavic patients with peptic ulcers. The aim of the study - to determine whether CYP2C19 affect the efficacy of proton pump inhibitor-based triple eradica- tion therapy in Slavic patients with peptic ulcers. Data search was performed using Russian index of scientific citation database, Google Scholar and MEDLINE PubMed. Statistics was held in Review Manager v 5.3. The odds ratio (OR) and 95% confidence interval (95% Cl) for eradication of H.pylori was estimated in a fixed-effect model when no heterogeneity across the studies was indicated. Four articles published between 2008 and 2015 were included in meta-analysis (three Russian studies, one Polish study). Eradication rates were significantly lower in CYP2C19 extensive metabolizers of proton pump inhibitors than in a combined group of intermediate and poor metabolizers (OR = 1,90, CI-95% 1,08-3,34, p = 0,03; heterogeneity: 12= 0%, p = 0,74). We also found that proton pump inhibitor-based triple eradication therapy achieved higher rates in poor metabolizers than in a combined group of intermediate and extensive metabolizers of CYP2C19 (OR= 5,48 CI-95% 1,51-19,93, p = 0,01; heterogeneity: F= 0%, p = 0,66). The impact of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple eradication therapy in Slavic patients appears significant.

The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium[OPEN

PubMed Central

Pacheco-Villalobos, David; Tamaki, Takayuki; Gujas, Bojan; Jaspert, Nina; Oecking, Claudia; Bulone, Vincent; Hardtke, Christian S.

2016-01-01

The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463

Water exit pathways and proton pumping mechanism in B-type cytochrome c oxidase from molecular dynamics simulations.

PubMed

Yang, Longhua; Skjevik, Åge A; Han Du, Wen-Ge; Noodleman, Louis; Walker, Ross C; Götz, Andreas W

2016-09-01

Cytochrome c oxidase (CcO) is a vital enzyme that catalyzes the reduction of molecular oxygen to water and pumps protons across mitochondrial and bacterial membranes. While proton uptake channels as well as water exit channels have been identified for A-type CcOs, the means by which water and protons exit B-type CcOs remain unclear. In this work, we investigate potential mechanisms for proton transport above the dinuclear center (DNC) in ba3-type CcO of Thermus thermophilus. Using long-time scale, all-atom molecular dynamics (MD) simulations for several relevant protonation states, we identify a potential mechanism for proton transport that involves propionate A of the active site heme a3 and residues Asp372, His376 and Glu126(II), with residue His376 acting as the proton-loading site. The proposed proton transport process involves a rotation of residue His376 and is in line with experimental findings. We also demonstrate how the strength of the salt bridge between residues Arg225 and Asp287 depends on the protonation state and that this salt bridge is unlikely to act as a simple electrostatic gate that prevents proton backflow. We identify two water exit pathways that connect the water pool above the DNC to the outer P-side of the membrane, which can potentially also act as proton exit transport pathways. Importantly, these water exit pathways can be blocked by narrowing the entrance channel between residues Gln151(II) and Arg449/Arg450 or by obstructing the entrance through a conformational change of residue Tyr136, respectively, both of which seem to be affected by protonation of residue His376. Copyright © 2016 Elsevier B.V. All rights reserved.

Possible roles of two quinone molecules in direct and indirect proton pumps of bovine heart NADH-quinone oxidoreductase (complex I).

PubMed

Ohnishi, S Tsuyoshi; Salerno, John C; Ohnishi, Tomoko

2010-12-01

In many energy transducing systems which couple electron and proton transport, for example, bacterial photosynthetic reaction center, cytochrome bc(1)-complex (complex III) and E. coli quinol oxidase (cytochrome bo(3) complex), two protein-associated quinone molecules are known to work together. T. Ohnishi and her collaborators reported that two distinct semiquinone species also play important roles in NADH-ubiquinone oxidoreductase (complex I). They were called SQ(Nf) (fast relaxing semiquinone) and SQ(Ns) (slow relaxing semiquinone). It was proposed that Q(Nf) serves as a "direct" proton carrier in the semiquinone-gated proton pump (Ohnishi and Salerno, FEBS Letters 579 (2005) 4555), while Q(Ns) works as a converter between one-electron and two-electron transport processes. This communication presents a revised hypothesis in which Q(Nf) plays a role in a "direct" redox-driven proton pump, while Q(Ns) triggers an "indirect" conformation-driven proton pump. Q(Nf) and Q(Ns) together serve as (1e(-)/2e(-)) converter, for the transfer of reducing equivalent to the Q-pool. Copyright © 2010 Elsevier B.V. All rights reserved.

25 Years of Proton Pump Inhibitors: A Comprehensive Review.

PubMed

Strand, Daniel S; Kim, Daejin; Peura, David A

2017-01-15

Proton pump inhibitors (PPIs) were clinically introduced more than 25 years ago and have since proven to be invaluable, safe, and effective agents for the management of a variety of acid-related disorders. Although all members in this class act in a similar fashion, inhibiting active parietal cell acid secretion, there are slight differences among PPIs relating to their pharmacokinetic properties, metabolism, and Food and Drug Administration (FDA)-approved clinical indications. Nevertheless, each is effective in managing gastroesophageal reflux disease and uncomplicated or complicated peptic ulcer disease. Despite their overall efficacy, PPIs do have some limitations related to their short plasma half-lives and requirement for meal-associated dosing, which can lead to breakthrough symptoms in some individuals, especially at night. Longer-acting PPIs and technology to prolong conventional PPI activity have been developed to specifically address these limitations and may improve clinical outcomes.

25 Years of Proton Pump Inhibitors: A Comprehensive Review

PubMed Central

Strand, Daniel S.; Kim, Daejin; Peura, David A.

2017-01-01

Proton pump inhibitors (PPIs) were clinically introduced more than 25 years ago and have since proven to be invaluable, safe, and effective agents for the management of a variety of acid-related disorders. Although all members in this class act in a similar fashion, inhibiting active parietal cell acid secretion, there are slight differences among PPIs relating to their pharmacokinetic properties, metabolism, and Food and Drug Administration (FDA)-approved clinical indications. Nevertheless, each is effective in managing gastroesophageal reflux disease and uncomplicated or complicated peptic ulcer disease. Despite their overall efficacy, PPIs do have some limitations related to their short plasma half-lives and requirement for meal-associated dosing, which can lead to breakthrough symptoms in some individuals, especially at night. Longer-acting PPIs and technology to prolong conventional PPI activity have been developed to specifically address these limitations and may improve clinical outcomes. PMID:27840364

Characterizing the proton loading site in cytochrome c oxidase.

PubMed

Lu, Jianxun; Gunner, M R

2014-08-26

Cytochrome c oxidase (CcO) uses the energy released by reduction of O2 to H2O to drive eight charges from the high pH to low pH side of the membrane, increasing the electrochemical gradient. Four electrons and protons are used for chemistry, while four more protons are pumped. Proton pumping requires that residues on a pathway change proton affinity through the reaction cycle to load and then release protons. The protonation states of all residues in CcO are determined in MultiConformational Continuum Electrostatics simulations with the protonation and redox states of heme a, a3, Cu(B), Y288, and E286 used to define the catalytic cycle. One proton is found to be loaded and released from residues identified as the proton loading site (PLS) on the P-side of the protein in each of the four CcO redox states. Thus, the same proton pumping mechanism can be used each time CcO is reduced. Calculations with structures of Rhodobacter sphaeroides, Paracoccus denitrificans, and bovine CcO derived by crystallography and molecular dynamics show the PLS functions similarly in different CcO species. The PLS is a cluster rather than a single residue, as different structures show 1-4 residues load and release protons. However, the proton affinity of the heme a3 propionic acids primarily determines the number of protons loaded into the PLS; if their proton affinity is too low, less than one proton is loaded.

Characterizing the proton loading site in cytochrome c oxidase

PubMed Central

Lu, Jianxun; Gunner, M. R.

2014-01-01

Cytochrome c oxidase (CcO) uses the energy released by reduction of O2 to H2O to drive eight charges from the high pH to low pH side of the membrane, increasing the electrochemical gradient. Four electrons and protons are used for chemistry, while four more protons are pumped. Proton pumping requires that residues on a pathway change proton affinity through the reaction cycle to load and then release protons. The protonation states of all residues in CcO are determined in MultiConformational Continuum Electrostatics simulations with the protonation and redox states of heme a, a3, CuB, Y288, and E286 used to define the catalytic cycle. One proton is found to be loaded and released from residues identified as the proton loading site (PLS) on the P-side of the protein in each of the four CcO redox states. Thus, the same proton pumping mechanism can be used each time CcO is reduced. Calculations with structures of Rhodobacter sphaeroides, Paracoccus denitrificans, and bovine CcO derived by crystallography and molecular dynamics show the PLS functions similarly in different CcO species. The PLS is a cluster rather than a single residue, as different structures show 1–4 residues load and release protons. However, the proton affinity of the heme a3 propionic acids primarily determines the number of protons loaded into the PLS; if their proton affinity is too low, less than one proton is loaded. PMID:25114210

Coherent evolution of parahydrogen induced polarisation using laser pump, NMR probe spectroscopy: Theoretical framework and experimental observation.

PubMed

Halse, Meghan E; Procacci, Barbara; Henshaw, Sarah-Louise; Perutz, Robin N; Duckett, Simon B

2017-05-01

We recently reported a pump-probe method that uses a single laser pulse to introduce parahydrogen (p-H 2 ) into a metal dihydride complex and then follows the time-evolution of the p-H 2 -derived nuclear spin states by NMR. We present here a theoretical framework to describe the oscillatory behaviour of the resultant hyperpolarised NMR signals using a product operator formalism. We consider the cases where the p-H 2 -derived protons form part of an AX, AXY, AXYZ or AA'XX' spin system in the product molecule. We use this framework to predict the patterns for 2D pump-probe NMR spectra, where the indirect dimension represents the evolution during the pump-probe delay and the positions of the cross-peaks depend on the difference in chemical shift of the p-H 2 -derived protons and the difference in their couplings to other nuclei. The evolution of the NMR signals of the p-H 2 -derived protons, as well as the transfer of hyperpolarisation to other NMR-active nuclei in the product, is described. The theoretical framework is tested experimentally for a set of ruthenium dihydride complexes representing the different spin systems. Theoretical predictions and experimental results agree to within experimental error for all features of the hyperpolarised 1 H and 31 P pump-probe NMR spectra. Thus we establish the laser pump, NMR probe approach as a robust way to directly observe and quantitatively analyse the coherent evolution of p-H 2 -derived spin order over micro-to-millisecond timescales. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Pathways of proton transfer in the light-driven pump bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lanyi, J. K.

1993-01-01

The mechanism of proton transport in the light-driven pump bacteriorhodopsin is beginning to be understood. Light causes the all-trans to 13-cis isomerization of the retinal chromophore. This sets off a sequential and directed series of transient decreases in the pKa's of a) the retinal Schiff base, b) an extracellular proton release complex which includes asp-85, and c) a cytoplasmic proton uptake complex which includes asp-96. The timing of these pKa changes during the photoreaction cycle causes sequential proton transfers which result in the net movement of a proton across the protein, from the cytoplasmic to the extracellular surface.

Are higher doses of proton pump inhibitors better in acute peptic bleeding?

PubMed

Villalón, Alejandro; Olmos, Roberto; Rada, Gabriel

2016-06-24

Although there is broad consensus about the benefits of proton pump inhibitors in acute upper peptic bleeding, there is still controversy over their optimal dosing. Searching in Epistemonikos database, which is maintained by screening 30 databases, we identified six systematic reviews including 27 randomized trials addressing this question. We combined the evidence using meta-analysis and generated a summary of findings table following the GRADE approach. We concluded high-dose proton pump inhibitors probably result in little or no difference in re-bleeding rate or mortality. The risk/benefit and cost/benefit balance probably favor use of low-doses.

Persistent reflux symptoms cause anxiety, depression, and mental health and sleep disorders in gastroesophageal reflux disease patients

PubMed Central

Kimura, Yoshihide; Kamiya, Takeshi; Senoo, Kyouji; Tsuchida, Kenji; Hirano, Atsuyuki; Kojima, Hisayo; Yamashita, Hiroaki; Yamakawa, Yoshihiro; Nishigaki, Nobuhiro; Ozeki, Tomonori; Endo, Masatsugu; Nakanishi, Kazuhisa; Sando, Motoki; Inagaki, Yusuke; Shikano, Michiko; Mizoshita, Tsutomu; Kubota, Eiji; Tanida, Satoshi; Kataoka, Hiromi; Katsumi, Kohei; Joh, Takashi

2016-01-01

Some patients with gastroesophageal reflux disease experience persistent reflux symptoms despite proton pump inhibitor therapy. These symptoms reduce their health-related quality of life. Our aims were to evaluate the relationship between proton pump inhibitor efficacy and health-related quality of life and to evaluate predictive factors affecting treatment response in Japanese patients. Using the gastroesophageal reflux disease questionnaire, 145 gastroesophageal reflux disease patients undergoing proton pump inhibitor therapy were evaluated and classified as responders or partial-responders. Their health-related quality of life was then evaluated using the 8-item Short Form Health Survey, the Pittsburgh Sleep Quality Index, and the Hospital Anxiety and Depression Scale questionnaires. Sixty-nine patients (47.6%) were partial responders. These patients had significantly lower scores than responders in 5/8 subscales and in the mental health component summary of the 8-item Short Form Health Survey. Partial responders had significantly higher Pittsburgh Sleep Quality Index and Hospital Anxiety and Depression Scale scores, including anxiety and depression scores, than those of responders. Non-erosive reflux disease and double proton pump inhibitor doses were predictive factors of partial responders. Persistent reflux symptoms, despite proton pump inhibitor therapy, caused mental health disorders, sleep disorders, and psychological distress in Japanese gastroesophageal reflux disease patients. PMID:27499583

Persistent reflux symptoms cause anxiety, depression, and mental health and sleep disorders in gastroesophageal reflux disease patients.

PubMed

Kimura, Yoshihide; Kamiya, Takeshi; Senoo, Kyouji; Tsuchida, Kenji; Hirano, Atsuyuki; Kojima, Hisayo; Yamashita, Hiroaki; Yamakawa, Yoshihiro; Nishigaki, Nobuhiro; Ozeki, Tomonori; Endo, Masatsugu; Nakanishi, Kazuhisa; Sando, Motoki; Inagaki, Yusuke; Shikano, Michiko; Mizoshita, Tsutomu; Kubota, Eiji; Tanida, Satoshi; Kataoka, Hiromi; Katsumi, Kohei; Joh, Takashi

2016-07-01

Some patients with gastroesophageal reflux disease experience persistent reflux symptoms despite proton pump inhibitor therapy. These symptoms reduce their health-related quality of life. Our aims were to evaluate the relationship between proton pump inhibitor efficacy and health-related quality of life and to evaluate predictive factors affecting treatment response in Japanese patients. Using the gastroesophageal reflux disease questionnaire, 145 gastroesophageal reflux disease patients undergoing proton pump inhibitor therapy were evaluated and classified as responders or partial-responders. Their health-related quality of life was then evaluated using the 8-item Short Form Health Survey, the Pittsburgh Sleep Quality Index, and the Hospital Anxiety and Depression Scale questionnaires. Sixty-nine patients (47.6%) were partial responders. These patients had significantly lower scores than responders in 5/8 subscales and in the mental health component summary of the 8-item Short Form Health Survey. Partial responders had significantly higher Pittsburgh Sleep Quality Index and Hospital Anxiety and Depression Scale scores, including anxiety and depression scores, than those of responders. Non-erosive reflux disease and double proton pump inhibitor doses were predictive factors of partial responders. Persistent reflux symptoms, despite proton pump inhibitor therapy, caused mental health disorders, sleep disorders, and psychological distress in Japanese gastroesophageal reflux disease patients.

What is heartburn worth? A cost-utility analysis of management strategies.

PubMed

Heudebert, G R; Centor, R M; Klapow, J C; Marks, R; Johnson, L; Wilcox, C M

2000-03-01

To determine the best treatment strategy for the management of patients presenting with symptoms consistent with uncomplicated heartburn. We performed a cost-utility analysis of 4 alternatives: empirical proton pump inhibitor, empirical histamine2-receptor antagonist, and diagnostic strategies consisting of either esophagogastroduodenoscopy (EGD) or an upper gastrointestinal series before treatment. The time horizon of the model was 1 year. The base case analysis assumed a cohort of otherwise healthy 45-year-old individuals in a primary care practice. Empirical treatment with a proton pump inhibitor was projected to provide the greatest quality-adjusted survival for the cohort. Empirical treatment with a histamine2 receptor antagonist was projected to be the least costly of the alternatives. The marginal cost-effectiveness of using a proton pump inhibitor over a histamine2-receptor antagonist was approximately $10,400 per quality-adjusted life year (QALY) gained in the base case analysis and was less than $50,000 per QALY as long as the utility for heartburn was less than 0.95. Both diagnostic strategies were dominated by proton pump inhibitor alternative. Empirical treatment seems to be the optimal initial management strategy for patients with heartburn, but the choice between a proton pump inhibitor or histamine2-receptor antagonist depends on the impact of heartburn on quality of life.

What Is Heartburn Worth?

PubMed Central

Heudebert, Gustavo R; Centor, Robert M; Klapow, Joshua C; Marks, Robert; Johnson, Lawrence; Wilcox, C Mel

2000-01-01

OBJECTIVE T o determine the best treatment strategy for the management of patients presenting with symptoms consistent with uncomplicated heartburn. METHODS We performed a cost-utility analysis of 4 alternatives: empirical proton pump inhibitor, empirical histamine2-receptor antagonist, and diagnostic strategies consisting of either esophagogastroduodenoscopy (EGD) or an upper gastrointestinal series before treatment. The time horizon of the model was 1 year. The base case analysis assumed a cohort of otherwise healthy 45-year-old individuals in a primary care practice. MAIN RESULTS Empirical treatment with a proton pump inhibitor was projected to provide the greatest quality-adjusted survival for the cohort. Empirical treatment with a histamine2receptor antagonist was projected to be the least costly of the alternatives. The marginal cost-effectiveness of using a proton pump inhibitor over a histamine2-receptor antagonist was approximately $10,400 per quality-adjusted life year (QALY) gained in the base case analysis and was less than $50,000 per QALY as long as the utility for heartburn was less than 0.95. Both diagnostic strategies were dominated by proton pump inhibitor alternative. CONCLUSIONS Empirical treatment seems to be the optimal initial management strategy for patients with heartburn, but the choice between a proton pump inhibitor or histamine2-receptor antagonist depends on the impact of heartburn on quality of life. PMID:10718898

A spectroscopic investigation of the Schiff base reprotonation mechanism of bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Russell, Terence Stephen

This thesis reports time-resolved visible spectroscopy experiments performed on the light-driven proton pumping protein, bacteriorhodopsin (bR), and a number of artificially produced analogs. These analogs comprise a variety of single and double amino acid substitutions produced in several of the residues previously implicated in proton transport in bR. Also addressed are the results of resonance Raman and FTIR difference spectroscopy which provide information about the vibrational modes of the protein. The results from these experiments confirm aspects of both structural and functional models of bR based on previous electron diffraction and spectroscopic data. During a phase of the proton pumping photocycle in bR known as Schiff base reprotonation (also referred to as M intermediate decay), a proton is transferred over a 12 A distance from a proton donor residue (Asp-96) to the light-absorbing active site. The behavior of the M intermediate was monitored by time-resolved visible spectroscopy. In the single substitution known as D96N, the Asp-96 residue was replaced with a less efficient proton donor, asparagine. This mutant exhibited an M intermediate which decayed slowly in comparison to that of wild-type bR. However, this effect was reversed with the double substitution, T46D/D96N. This result indicates that the proton donor group can be moved to another nearby location and still yield a system functionally similar to the native protein. Replacement of the donor group with a histidine, His-96, resulted in a photocycle similar to D96N above pH 7. However, below this pH, the M intermediate is not detected. FTIR difference spectroscopy indicates that the protonation state of the substituted His-96 residue influences the structure of the active site of bR which suggests that a proton that is associated with His-96 may move towards the active site and thereby block M intermediate formation. Finally, the residue Thr-89 was replaced with an asparagine. This substitution altered not only the vibrational modes of the protein but also its visible absorption, which indicates that Thr-89 interacts directly with the active site of bR. These results are used to correct and extend an overall molecular model of the proton transport mechanism in bacteriorhodopsin.

Proton pump inhibitors induce apoptosis of human B-cell tumors through a caspase-independent mechanism involving reactive oxygen species.

PubMed

De Milito, Angelo; Iessi, Elisabetta; Logozzi, Mariantonia; Lozupone, Francesco; Spada, Massimo; Marino, Maria Lucia; Federici, Cristina; Perdicchio, Maurizio; Matarrese, Paola; Lugini, Luana; Nilsson, Anna; Fais, Stefano

2007-06-01

Proton pumps like the vacuolar-type H+ ATPase (V-ATPase) are involved in the control of cellular pH in normal and tumor cells. Treatment with proton pump inhibitors (PPI) induces sensitization of cancer cells to chemotherapeutics via modifications of cellular pH gradients. It is also known that low pH is the most suitable condition for a full PPI activation. Here, we tested whether PPI treatment in unbuffered culture conditions could affect survival and proliferation of human B-cell tumors. First, we showed that PPI treatment increased the sensitivity to vinblastine of a pre-B acute lymphoblastic leukemia (ALL) cell line. PPI, per se, induced a dose-dependent inhibition of proliferation of tumor B cells, which was associated with a dose- and time-dependent apoptotic-like cytotoxicity in B-cell lines and leukemic cells from patients with pre-B ALL. The effect of PPI was mediated by a very early production of reactive oxygen species (ROS), that preceded alkalinization of lysosomal pH, lysosomal membrane permeabilization, and cytosol acidification, suggesting an early destabilization of the acidic vesicular compartment. Lysosomal alterations were followed by mitochondrial membrane depolarization, release of cytochrome c, chromatin condensation, and caspase activation. However, inhibition of caspase activity did not affect PPI-induced cell death, whereas specific inhibition of ROS by an antioxidant (N-acetylcysteine) significantly delayed cell death and protected both lysosomal and mitochondrial membranes. The proapoptotic activity of PPI was consistent with a clear inhibition of tumor growth following PPI treatment of B-cell lymphoma in severe combined immunodeficient mice. This study further supports the importance of acidity and pH gradients in tumor cell homeostasis and suggests new therapeutic approaches for human B-cell tumors based on PPI.

[New-generation proton pump inhibitors: progress in the treatment of peptic acid diseases?].

PubMed

de Korwin, Jean-Dominique; Ducrotté, Philippe; Vallot, Thierry

2004-06-19

EFFECTS AND INCONVENIENCIES OF THE OLDER PRODUCTS: The proton pump inhibitors (PPIs) are now universally considered the treatment of choice for management of gastric-acid-related diseases, mainly gastro-oesophageal reflux disease (GERD). These drugs share similar properties: general structure, acid-activation step, covalent binding to the proton pump of the gastric parietal cell via the production of covalent disulphide bonds, relatively stable inhibition of H+,K+-ATPase. However, the older PPIs (omeprazole, lansoprazole et pantoprazole) have notable limitations. These drugs exhibit substantial interpatient variability and may have significant interactions with other drugs. These first-generation PPIs also do not achieve a rapid and sustained suppression of gastric acid, leading to the development of new acid-pump antagonists. The new-generation PPIs, esomeprazole and rabeprazole, offer several pharmacokinetic advantages: lower oxidative hepatic metabolism rate via the CYP 2C19 reducing the activity variations due to genetic polymorphisms and decreasing the risk of significant drug-drug interactions (advantages mainly for rabeprazole), lower metabolic clearance of esomeprazole (S-enantiomer of omeprazole) increasing plasma concentrations and acid suppression of this new PPI, higher accumulation of rabeprazole in the parietal cell due to its higher pKa. Gastric pH studies and therapeutic trials have demonstrated significant advantages of esomeprazole and rabeprazole compared with the older PPIs, which omeprazole is the prototype: a greater inhibition of acid secretion, a more rapid onset of action to provide reflux symptoms relief over 24 hours with lower GERD-related cost for rabeprazole, a sustained acid suppression, cost-effectiveness advantages for esomeprazole in the healing and maintenance of erosive esophagitis compared with lansoprazole, reduced potential for clinically significant drug-drug interactions with rabeprazole compared with omeprazole and esomeprazole. Due to their properties, esomeprazole and rabeprazole are the best candidates for "on demand" treatment of GERD.

The added value of impedance-pH monitoring to Rome III criteria in distinguishing functional heartburn from non-erosive reflux disease.

PubMed

Savarino, Edoardo; Marabotto, Elisa; Zentilin, Patrizia; Frazzoni, Marzio; Sammito, Giorgio; Bonfanti, Daria; Sconfienza, Luca; Assandri, Lorenzo; Gemignani, Lorenzo; Malesci, Alberto; Savarino, Vincenzo

2011-07-01

Functional heartburn is defined by Rome III criteria as an endoscopy-negative condition with normal oesophageal acid exposure time, negative symptom association to acid reflux and unsatisfactory response to proton pump inhibitors. These criteria underestimated the role of non-acid reflux. To assess the contribution of impedance-pH with symptom association probability (SAP) analysis in identifying endoscopy-negative patients with reflux disease and separating them from functional heartburn. Consecutive endoscopy-negative patients treated with proton pump inhibitors (n=219) undergoing impedance-pH monitoring off-therapy were analysed. Distal acid exposure time, reflux episodes, SAP and symptomatic response to proton pump inhibitors were measured. Based on impedance-pH/SAP, 67 (31%) patients were pH+/SAP+, 6 (2%) pH+/SAP-, 83 (38%) hypersensitive oesophagus and 63 (29%) functional heartburn. According to pH-metry alone/response to proton pump inhibitors, 62 (28%) were pH+/SAP+, 11 (5%) pH+/SAP-, 61 (28%) hypersensitive oesophagus and 85 (39%) functional heartburn. In the normal-acid exposure population the contribution of impedance-pH/SAP compared to pH-metry alone/response to proton pump inhibitors in identifying patients with reflux disease and functional heartburn resulted to be 10%. In patients with abnormal-acid exposure, the contribution of impedance-pH/SAP increased by 3%. Comparing impedance-pH testing with pH-metry alone plus the response to proton pump inhibitor therapy demonstrated that the latter ones cause underestimation of reflux disease patients and overestimation of functional heartburn patients. Copyright © 2011 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

MdMYB1 Regulates Anthocyanin and Malate Accumulation by Directly Facilitating Their Transport into Vacuoles in Apples1[OPEN

PubMed Central

Hu, Da-Gang; Sun, Cui-Hui; Ma, Qi-Jun; You, Chun-Xiang; Hao, Yu-Jin

2016-01-01

Tonoplast transporters, including proton pumps and secondary transporters, are essential for plant cell function and for quality formation of fleshy fruits and ornamentals. Vacuolar transport of anthocyanins, malate, and other metabolites is directly or indirectly dependent on the H+-pumping activities of vacuolar H+-ATPase (VHA) and/or vacuolar H+-pyrophosphatase, but how these proton pumps are regulated in modulating vacuolar transport is largely unknown. Here, we report a transcription factor, MdMYB1, in apples that binds to the promoters of two genes encoding the B subunits of VHA, MdVHA-B1 and MdVHA-B2, to transcriptionally activate its expression, thereby enhancing VHA activity. A series of transgenic analyses in apples demonstrates that MdMYB1/10 controls cell pH and anthocyanin accumulation partially by regulating MdVHA-B1 and MdVHA-B2. Furthermore, several other direct target genes of MdMYB10 are identified, including MdVHA-E2, MdVHP1, MdMATE-LIKE1, and MdtDT, which are involved in H+-pumping or in the transport of anthocyanins and malates into vacuoles. Finally, we show that the mechanism by which MYB controls malate and anthocyanin accumulation in apples also operates in Arabidopsis (Arabidopsis thaliana). These findings provide novel insights into how MYB transcription factors directly modulate the vacuolar transport system in addition to anthocyanin biosynthesis, consequently controlling organ coloration and cell pH in plants. PMID:26637549

MdMYB1 Regulates Anthocyanin and Malate Accumulation by Directly Facilitating Their Transport into Vacuoles in Apples.

PubMed

Hu, Da-Gang; Sun, Cui-Hui; Ma, Qi-Jun; You, Chun-Xiang; Cheng, Lailiang; Hao, Yu-Jin

2016-03-01

Tonoplast transporters, including proton pumps and secondary transporters, are essential for plant cell function and for quality formation of fleshy fruits and ornamentals. Vacuolar transport of anthocyanins, malate, and other metabolites is directly or indirectly dependent on the H(+)-pumping activities of vacuolar H(+)-ATPase (VHA) and/or vacuolar H(+)-pyrophosphatase, but how these proton pumps are regulated in modulating vacuolar transport is largely unknown. Here, we report a transcription factor, MdMYB1, in apples that binds to the promoters of two genes encoding the B subunits of VHA, MdVHA-B1 and MdVHA-B2, to transcriptionally activate its expression, thereby enhancing VHA activity. A series of transgenic analyses in apples demonstrates that MdMYB1/10 controls cell pH and anthocyanin accumulation partially by regulating MdVHA-B1 and MdVHA-B2. Furthermore, several other direct target genes of MdMYB10 are identified, including MdVHA-E2, MdVHP1, MdMATE-LIKE1, and MdtDT, which are involved in H(+)-pumping or in the transport of anthocyanins and malates into vacuoles. Finally, we show that the mechanism by which MYB controls malate and anthocyanin accumulation in apples also operates in Arabidopsis (Arabidopsis thaliana). These findings provide novel insights into how MYB transcription factors directly modulate the vacuolar transport system in addition to anthocyanin biosynthesis, consequently controlling organ coloration and cell pH in plants. © 2016 American Society of Plant Biologists. All Rights Reserved.

Salinity Tolerance of Two Potato Cultivars (Solanum tuberosum) Correlates With Differences in Vacuolar Transport Activity

PubMed Central

Jaarsma, Rinse; de Boer, Albertus H.

2018-01-01

Potato is an important cultivated crop species and since it is moderately salt sensitive there is a need to develop more salt tolerant cultivars. A high activity of Na+ transport across the tonoplast in exchange for H+ is essential to reduce Na+ toxicity. The proton motive force (PMF) generated by the V-H+-ATPase and the V-H+-PPase energizes the Na+(K+)/H+ antiport. We compared the activity, gene expression, and protein levels of the vacuolar proton pumps and the Na+/H+ antiporters in two potato cultivars (Solanum tuberosum) contrasting in their salt tolerance (cv. Desiree; tolerant and Mozart; sensitive) grown at 0 and 60 mM NaCl. Tonoplast-enriched vesicles were used to study the pump activity and protein levels of the V-H+-ATPase and the V-H+-PPase and the activity of the Na+/H+ antiporter. Although salt stress reduced the V-H+-ATPase and the V-H+-PPase activity in both cultivars, the decline in H+ pump activity was more severe in the salt-sensitive cultivar Mozart. After salt treatment, protein amounts of the vacuolar H+ pumps decreased in Mozart but remained unchanged in the cultivar Desiree. Decreased protein amounts of the V-H+-PPase found in Mozart may explain the reduced V-H+-PPase activity found for Mozart after salt stress. Under non-stress conditions, protein amounts of V-H+-PPase were equal in both cultivars while the V-H+-PPase activity was already twice as high and remained higher after salt treatment in the cultivar Desiree as compared to Mozart. This cultivar-dependent V-H+-PPase activity may explain the higher salt tolerance of Desiree. Moreover, combined with reduced vacuolar H+ pump activity, Mozart showed a lower Na+/H+ exchange activity and the Km for Na+ is at least twofold lower in tonoplast vesicles from Desiree, what suggests that NHXs from Desiree have a higher affinity for Na+ as compared to Mozart. From these results, we conclude that the higher capacity in combination with the higher affinity for Na+ uptake can be an important factor to explain the differences in salt tolerance of these two potato cultivars. PMID:29922314

Salinity Tolerance of Two Potato Cultivars (Solanum tuberosum) Correlates With Differences in Vacuolar Transport Activity.

PubMed

Jaarsma, Rinse; de Boer, Albertus H

2018-01-01

Potato is an important cultivated crop species and since it is moderately salt sensitive there is a need to develop more salt tolerant cultivars. A high activity of Na + transport across the tonoplast in exchange for H + is essential to reduce Na + toxicity. The proton motive force (PMF) generated by the V-H + -ATPase and the V-H + -PPase energizes the Na + (K + )/H + antiport. We compared the activity, gene expression, and protein levels of the vacuolar proton pumps and the Na + /H + antiporters in two potato cultivars ( Solanum tuberosum ) contrasting in their salt tolerance (cv. Desiree; tolerant and Mozart; sensitive) grown at 0 and 60 mM NaCl. Tonoplast-enriched vesicles were used to study the pump activity and protein levels of the V-H + -ATPase and the V-H + -PPase and the activity of the Na + /H + antiporter. Although salt stress reduced the V-H + -ATPase and the V-H + -PPase activity in both cultivars, the decline in H + pump activity was more severe in the salt-sensitive cultivar Mozart. After salt treatment, protein amounts of the vacuolar H + pumps decreased in Mozart but remained unchanged in the cultivar Desiree. Decreased protein amounts of the V-H + -PPase found in Mozart may explain the reduced V-H + -PPase activity found for Mozart after salt stress. Under non-stress conditions, protein amounts of V-H + -PPase were equal in both cultivars while the V-H + -PPase activity was already twice as high and remained higher after salt treatment in the cultivar Desiree as compared to Mozart. This cultivar-dependent V-H + -PPase activity may explain the higher salt tolerance of Desiree. Moreover, combined with reduced vacuolar H + pump activity, Mozart showed a lower Na + /H + exchange activity and the K m for Na + is at least twofold lower in tonoplast vesicles from Desiree, what suggests that NHXs from Desiree have a higher affinity for Na + as compared to Mozart. From these results, we conclude that the higher capacity in combination with the higher affinity for Na + uptake can be an important factor to explain the differences in salt tolerance of these two potato cultivars.

Crystal structure of Escherichia coli-expressed Haloarcula marismortui bacteriorhodopsin I in the trimeric form.

PubMed

Shevchenko, Vitaly; Gushchin, Ivan; Polovinkin, Vitaly; Round, Ekaterina; Borshchevskiy, Valentin; Utrobin, Petr; Popov, Alexander; Balandin, Taras; Büldt, Georg; Gordeliy, Valentin

2014-01-01

Bacteriorhodopsins are a large family of seven-helical transmembrane proteins that function as light-driven proton pumps. Here, we present the crystal structure of a new member of the family, Haloarcula marismortui bacteriorhodopsin I (HmBRI) D94N mutant, at the resolution of 2.5 Å. While the HmBRI retinal-binding pocket and proton donor site are similar to those of other archaeal proton pumps, its proton release region is extended and contains additional water molecules. The protein's fold is reinforced by three novel inter-helical hydrogen bonds, two of which result from double substitutions relative to Halobacterium salinarum bacteriorhodopsin and other similar proteins. Despite the expression in Escherichia coli and consequent absence of native lipids, the protein assembles as a trimer in crystals. The unique extended loop between the helices D and E of HmBRI makes contacts with the adjacent protomer and appears to stabilize the interface. Many lipidic hydrophobic tail groups are discernible in the membrane region, and their positions are similar to those of archaeal isoprenoid lipids in the crystals of other proton pumps, isolated from native or native-like sources. All these features might explain the HmBRI properties and establish the protein as a novel model for the microbial rhodopsin proton pumping studies.

A randomized controlled trial of laparoscopic nissen fundoplication versus proton pump inhibitors for treatment of patients with chronic gastroesophageal reflux disease: One-year follow-up.

PubMed

Anvari, Mehran; Allen, Christopher; Marshall, John; Armstrong, David; Goeree, Ron; Ungar, Wendy; Goldsmith, Charles

2006-12-01

A randomized controlled trial conducted in patients with gastroesophageal reflux disease compared optimized medical therapy using proton pump inhibitor (n = 52) with laparoscopic Nissen fundoplication (n = 52). Patients were monitored for 1 year. The primary end point was frequency of gastroesophageal reflux dis-ease symptoms. Surgical patients had improved symptoms, pH control, and overall quality of life health index after surgery at 1 year compared with the medical group. The overall gastroesophageal reflux disease symptom score at 1 year was unchanged in the medical patients, but improved in the surgical patients. Fourteen patients in the medical arm experienced symptom relapse requiring titration of the proton pump inhibitor dose, but 6 had satisfactory symptom remission. No surgical patients required additional treatment for symptom control. Patients controlled on long-term proton pump inhibitor therapy for chronic gastroesophageal reflux disease are excellent surgical candidates and should experience improved symptom control after surgery at 1 year.

Chimeric Proton-Pumping Rhodopsins Containing the Cytoplasmic Loop of Bovine Rhodopsin

PubMed Central

Sasaki, Kengo; Yamashita, Takahiro; Yoshida, Kazuho; Inoue, Keiichi; Shichida, Yoshinori; Kandori, Hideki

2014-01-01

G-protein-coupled receptors (GPCRs) transmit stimuli to intracellular signaling systems. Rhodopsin (Rh), which is a prototypical GPCR, possesses an 11-cis retinal. Photoisomerization of 11-cis to all-trans leads to structural changes in the protein of cytoplasmic loops, activating G-protein. Microbial rhodopsins are similar heptahelical membrane proteins that function as bacterial sensors, light-driven ion-pumps, or light-gated channels. They possess an all-trans retinal, and photoisomerization to 13-cis triggers structural changes in protein. Despite these similarities, there is no sequence homology between visual and microbial rhodopsins, and microbial rhodopsins do not activate G-proteins. In this study, new chimeric proton-pumping rhodopsins, proteorhodopsin (PR) and Gloeobacter rhodopsin (GR) were designed by replacing cytoplasmic loops with bovine Rh loops. Although G-protein was not activated by the PR chimeras, all 12 GR chimeras activated G-protein. The GR chimera containing the second cytoplasmic loop of bovine Rh did not activate G-protein. However, the chimera with a second and third double-loop further enhanced G-protein activation. Introduction of an E132Q mutation slowed the photocycle 30-fold and enhanced activation. The highest catalytic activity of the GR chimera was still 3,200 times lower than bovine Rh but only 64 times lower than amphioxus Go-rhodopsin. This GR chimera showed a strong absorption change of the amide-I band on a light-minus-dark difference FTIR spectrum which could represent a larger helical opening, important for G-protein activation. The light-dependent catalytic activity of this GR chimera makes it a potential optogenetic tool for enzymatic activation by light. PMID:24621599

Cost-effectiveness of histamine receptor-2 antagonist versus proton pump inhibitor for stress ulcer prophylaxis in critically ill patients*.

PubMed

MacLaren, Robert; Campbell, Jon

2014-04-01

To examine the cost-effectiveness of using histamine receptor-2 antagonist or proton pump inhibitor for stress ulcer prophylaxis. Decision analysis model examining costs and effectiveness of using histamine receptor-2 antagonist or proton pump inhibitor for stress ulcer prophylaxis. Costs were expressed in 2012 U.S. dollars from the perspective of the institution and included drug regimens and the following outcomes: clinically significant stress-related mucosal bleed, ventilator-associated pneumonia, and Clostridium difficile infection. Effectiveness was the mortality risk associated with these outcomes and represented by survival. Costs, occurrence rates, and mortality probabilities were extracted from published data. A simulation model. A mixed adult ICU population. Histamine receptor-2 antagonist or proton pump inhibitor for 9 days of stress ulcer prophylaxis therapy. Output variables were expected costs, expected survival rates, incremental cost, and incremental survival rate. Univariate sensitivity analyses were conducted to determine the drivers of incremental cost and incremental survival. Probabilistic sensitivity analysis was conducted using second-order Monte Carlo simulation. For the base case analysis, the expected cost of providing stress ulcer prophylaxis was $6,707 with histamine receptor-2 antagonist and $7,802 with proton pump inhibitor, resulting in a cost saving of $1,095 with histamine receptor-2 antagonist. The associated mortality probabilities were 3.819% and 3.825%, respectively, resulting in an absolute survival benefit of 0.006% with histamine receptor-2 antagonist. The primary drivers of incremental cost and survival were the assumptions surrounding ventilator-associated pneumonia and bleed. The probabilities that histamine receptor-2 antagonist was less costly and provided favorable survival were 89.4% and 55.7%, respectively. A secondary analysis assuming equal rates of C. difficile infection showed a cost saving of $908 with histamine receptor-2 antagonists, but the survival benefit of 0.0167% favored proton pump inhibitors. Histamine receptor-2 antagonist therapy appears to reduce costs with survival benefit comparable to proton pump inhibitor therapy for stress ulcer prophylaxis. Ventilator-associated pneumonia and bleed are the variables most affecting these outcomes. The uncertainty in the findings justifies a prospective trial.

Regulatory assembly of the vacuolar proton pump VoV1-ATPase in yeast cells by FLIM-FRET

NASA Astrophysics Data System (ADS)

Ernst, Stefan; Batisse, Claire; Zarrabi, Nawid; Böttcher, Bettina; Börsch, Michael

2010-02-01

We investigate the reversible disassembly of VOV1-ATPase in life yeast cells by time resolved confocal FRET imaging. VOV1-ATPase in the vacuolar membrane pumps protons from the cytosol into the vacuole. VOV1-ATPase is a rotary biological nanomotor driven by ATP hydrolysis. The emerging proton gradient is used for secondary transport processes as well as for pH and Ca2+ homoeostasis in the cell. The activity of the VOV1-ATPase is regulated through assembly / disassembly processes. During starvation the two parts of VOV1-ATPase start to disassemble. This process is reversed after addition of glucose. The exact mechanisms are unknown. To follow the disassembly / reassembly in vivo we tagged two subunits C and E with different fluorescent proteins. Cellular distributions of C and E were monitored using a duty cycle-optimized alternating laser excitation scheme (DCO-ALEX) for time resolved confocal FRET-FLIM measurements.

Micromotor-enabled active drug delivery for in vivo treatment of stomach infection.

PubMed

de Ávila, Berta Esteban-Fernández; Angsantikul, Pavimol; Li, Jinxing; Angel Lopez-Ramirez, Miguel; Ramírez-Herrera, Doris E; Thamphiwatana, Soracha; Chen, Chuanrui; Delezuk, Jorge; Samakapiruk, Richard; Ramez, Valentin; Obonyo, Marygorret; Zhang, Liangfang; Wang, Joseph

2017-08-16

Advances in bioinspired design principles and nanomaterials have led to tremendous progress in autonomously moving synthetic nano/micromotors with diverse functionalities in different environments. However, a significant gap remains in moving nano/micromotors from test tubes to living organisms for treating diseases with high efficacy. Here we present the first, to our knowledge, in vivo therapeutic micromotors application for active drug delivery to treat gastric bacterial infection in a mouse model using clarithromycin as a model antibiotic and Helicobacter pylori infection as a model disease. The propulsion of drug-loaded magnesium micromotors in gastric media enables effective antibiotic delivery, leading to significant bacteria burden reduction in the mouse stomach compared with passive drug carriers, with no apparent toxicity. Moreover, while the drug-loaded micromotors reach similar therapeutic efficacy as the positive control of free drug plus proton pump inhibitor, the micromotors can function without proton pump inhibitors because of their built-in proton depletion function associated with their locomotion.Nano- and micromotors have been demonstrated in vitro for a range of applications. Here the authors demonstrate the in-vivo therapeutic use of micromotors to treat H. pylori infection.

Piston-assisted proton pumping in Complex I of mitochondria membranes

NASA Astrophysics Data System (ADS)

Mourokh, Lev; Filonenko, Ilan

2014-03-01

Proton-pumping mechanism of Complex I remains mysterious because its electron and proton paths are well separated and the direct Coulomb interaction seems to be negligible. The structure of this enzyme was resolved very recently and its functionality was connected the shift of the helix HL. We model the helix as a piston oscillating between the protons and electrons. We assume that positive charges are accumulated near the edges of the helix. In the oxidized state, the piston is attracted to electrons, so its distance to the proton sites increases, the energy of these sites decreases and the sites can be populated. When electrons proceed to the drain, elastic forces return the piston to the original position and the energies of populated proton sites increase, so the protons can be transferred to the positive site of the membrane. In this work, we explore a simplified model when the interaction of the piston with electrons is replaced by a periodic force. We derive quantum Heisenberg equations for the proton operators and solve them jointly with the Langevin equation for the piston position. We show that the proton pumping is possible in such structure with parameters closely resembling the real system. We also address the feasibility of using such mechanism in nanoelectronics.

Proton Pumps: Mechanism of Action and Applications

NASA Technical Reports Server (NTRS)

Lanyi, Janos K.; Pohorille, Andrew; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

Recent progress in understanding molecular structures and mechanisms of action of proton pumps has paved the way to their novel applications in biotechnology. Proton pumps, in particular bacteriorhodopsin and ATP synthases, are capable of continuous, renewable conversion of light to chemical, mechanical or electrical energy, which can be used in macro- or nano-scale devices. The capability of protein systems incorporated into liposomes to generate ATP, which can be further used to drive chemical reactions, and to act as molecular motors has been already demonstrated. Other possible applications of such biochemical devices include targeted drug delivery and biocatalytic re actors. All these devices might prove superior to their inorganic alternatives.

Pharmacokinetics and pharmacodynamics of the proton pump inhibitors.

PubMed

Shin, Jai Moo; Kim, Nayoung

2013-01-01

Proton pump inhibitor (PPI) is a prodrug which is activated by acid. Activated PPI binds covalently to the gastric H(+), K(+)-ATPase via disulfide bond. Cys813 is the primary site responsible for the inhibition of acid pump enzyme, where PPIs bind. Omeprazole was the first PPI introduced in market, followed by pantoprazole, lansoprazole and rabeprazole. Though these PPIs share the core structures benzimidazole and pyridine, their pharmacokinetics and pharmacodynamics are a little different. Several factors must be considered in understanding the pharmacodynamics of PPIs, including: accumulation of PPI in the parietal cell, the proportion of the pump enzyme located at the canaliculus, de novo synthesis of new pump enzyme, metabolism of PPI, amounts of covalent binding of PPI in the parietal cell, and the stability of PPI binding. PPIs have about 1hour of elimination half-life. Area under the plasmic concentration curve and the intragastric pH profile are very good indicators for evaluating PPI efficacy. Though CYP2C19 and CYP3A4 polymorphism are major components of PPI metabolism, the pharmacokinetics and pharmacodynamics of racemic mixture of PPIs depend on the CYP2C19 genotype status. S-omeprazole is relatively insensitive to CYP2C19, so better control of the intragastric pH is achieved. Similarly, R-lansoprazole was developed in order to increase the drug activity. Delayed-release formulation resulted in a longer duration of effective concentration of R-lansoprazole in blood, in addition to metabolic advantage. Thus, dexlansoprazole showed best control of the intragastric pH among the present PPIs. Overall, PPIs made significant progress in the management of acid-related diseases and improved health-related quality of life.

Meta-analysis: comparative efficacy of different proton-pump inhibitors in triple therapy for Helicobacter pylori eradication.

PubMed

Vergara, M; Vallve, M; Gisbert, J P; Calvet, X

2003-09-15

It is not known whether certain proton-pump inhibitors are more efficacious than others when used in triple therapy for Helicobacter pylori eradication. To compare the efficacy of different proton-pump inhibitors in triple therapy by performing a meta-analysis. A MEDLINE search was performed. Abstracts of the European Helicobacter pylori Study Group and the American Gastroenterological Association congresses from 1996 to 2002 were also examined. Randomized studies with at least two branches of triple therapy that differed only in terms of type of proton-pump inhibitor were included in a meta-analysis using Review Manager 4.1. Fourteen studies were included. Intention-to-treat cure rates were similar for omeprazole and lansoprazole: 74.7% vs. 76%, odds ratio (OR) 0.91 [95% confidence interval (CI) 0.69-1.21] in a total of 1085 patients; for omeprazole and rabeprazole: 77.9% vs. 81.2%, OR 0.81 (95% CI 0.58-1.15) in a total of 825 patients; for omeprazole and esomeprazole: 87.7% vs. 89%, OR 0.89 (95% CI 0.58-1.35) in 833 patients; and for lansoprazole and rabeprazole: 81% vs. 85.7%, OR 0.77 (95% CI 0.48-1.22) in 550 patients. The efficacy of various proton-pump inhibitors seems to be similar when used for H. pylori eradication in standard triple therapy.

Optical silencing of body wall muscles induces pumping inhibition in Caenorhabditis elegans

PubMed Central

Takahashi, Megumi

2017-01-01

Feeding, a vital behavior in animals, is modulated depending on internal and external factors. In the nematode Caenorhabditis elegans, the feeding organ called the pharynx ingests food by pumping driven by the pharyngeal muscles. Here we report that optical silencing of the body wall muscles, which drive the locomotory movement of worms, affects pumping. In worms expressing the Arch proton pump or the ACR2 anion channel in the body wall muscle cells, the pumping rate decreases after activation of Arch or ACR2 with light illumination, and recovers gradually after terminating illumination. Pumping was similarly inhibited by illumination in locomotion-defective mutants carrying Arch, suggesting that perturbation of locomotory movement is not critical for pumping inhibition. Analysis of mutants and cell ablation experiments showed that the signals mediating the pumping inhibition response triggered by activation of Arch with weak light are transferred mainly through two pathways: one involving gap junction-dependent mechanisms through pharyngeal I1 neurons, which mediate fast signals, and the other involving dense-core vesicle-dependent mechanisms, which mediate slow signals. Activation of Arch with strong light inhibited pumping strongly in a manner that does not rely on either gap junction-dependent or dense-core vesicle-dependent mechanisms. Our study revealed a new aspect of the neural and neuroendocrine controls of pumping initiated from the body wall muscles. PMID:29281635

Optogenetic Acidification of Synaptic Vesicles and Lysosomes

PubMed Central

Grauel, M. Katharina; Wozny, Christian; Bentz, Claudia; Blessing, Anja; Rosenmund, Tanja; Jentsch, Thomas J.; Schmitz, Dietmar; Hegemann, Peter; Rosenmund, Christian

2016-01-01

Acidification is required for the function of many intracellular organelles, but methods to acutely manipulate their intraluminal pH have not been available. Here we present a targeting strategy to selectively express the light-driven proton pump Arch3 on synaptic vesicles. Our new tool, pHoenix, can functionally replace endogenous proton pumps, enabling optogenetic control of vesicular acidification and neurotransmitter accumulation. Under physiological conditions, glutamatergic vesicles are nearly full, as additional vesicle acidification with pHoenix only slightly increased the quantal size. By contrast, we found that incompletely filled vesicles exhibited a lower release probability than full vesicles, suggesting preferential exocytosis of vesicles with high transmitter content. Our subcellular targeting approach can be transferred to other organelles, as demonstrated for a pHoenix variant that allows light-activated acidification of lysosomes. PMID:26551543

Optogenetic acidification of synaptic vesicles and lysosomes.

PubMed

Rost, Benjamin R; Schneider, Franziska; Grauel, M Katharina; Wozny, Christian; Bentz, Claudia; Blessing, Anja; Rosenmund, Tanja; Jentsch, Thomas J; Schmitz, Dietmar; Hegemann, Peter; Rosenmund, Christian

2015-12-01

Acidification is required for the function of many intracellular organelles, but methods to acutely manipulate their intraluminal pH have not been available. Here we present a targeting strategy to selectively express the light-driven proton pump Arch3 on synaptic vesicles. Our new tool, pHoenix, can functionally replace endogenous proton pumps, enabling optogenetic control of vesicular acidification and neurotransmitter accumulation. Under physiological conditions, glutamatergic vesicles are nearly full, as additional vesicle acidification with pHoenix only slightly increased the quantal size. By contrast, we found that incompletely filled vesicles exhibited a lower release probability than full vesicles, suggesting preferential exocytosis of vesicles with high transmitter content. Our subcellular targeting approach can be transferred to other organelles, as demonstrated for a pHoenix variant that allows light-activated acidification of lysosomes.

Probing the mechanistic role of the long α-helix in subunit L of respiratory Complex I from Escherichia coli by site-directed mutagenesis

PubMed Central

Belevich, Galina; Knuuti, Juho; Verkhovsky, Michael I; Wikström, Mårten; Verkhovskaya, Marina

2011-01-01

The C-terminus of the NuoL subunit of Complex I includes a long amphipathic α-helix positioned parallel to the membrane, which has been considered to function as a piston in the proton pumping machinery. Here, we have introduced three types of mutations into the nuoL gene to test the piston-like function. First, NuoL was truncated at its C- and N-termini, which resulted in low production of a fragile Complex I with negligible activity. Second, we mutated three partially conserved residues of the amphipathic α-helix: Asp and Lys residues and a Pro were substituted for acidic, basic or neutral residues. All these variants exhibited almost a wild-type phenotype. Third, several substitutions and insertions were made to reduce rigidity of the amphipathic α-helix, and/or to change its geometry. Most insertions/substitutions resulted in a normal growth phenotype, albeit often with reduced stability of Complex I. In contrast, insertion of six to seven amino acids at a site of the long α-helix between NuoL and M resulted in substantial loss of proton pumping efficiency. The implications of these results for the proton pumping mechanism of Complex I are discussed. PMID:22060017

A light-driven proton pump from Haloterrigena turkmenica: Functional expression in Escherichia coli membrane and coupling with a H{sup +} co-transporter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamo, Naoki; Hashiba, Tsuyoshi; Kikukawa, Takashi

2006-03-10

A gene encoding putative retinal protein was cloned from Haloterrigena turkmenica (JCM9743). The deduced amino acid sequence was most closely related to that of deltarhodopsin, which functions as a light-driven H{sup +} pump and was identified in a novel strain Haloterrigena sp. arg-4 (K. Ihara, T. Uemura, I. Katagiri, T. Kitajima-Ihara, Y. Sugiyama, Y. Kimura, Y. Mukohata, Evolution of the archaeal rhodopsins: Evolution rate changes by gene duplication and functional differentiation, J. Mol. Biol. 285 (1999) 163-174. GenBank Accession No. AB009620). Thus, we called the present protein H. turkmenica deltarhodopsin (HtdR) in this report. Differing from the Halobacterium salinarum bacteriorhodopsinmore » (bR), functional expression of HtdR was achieved in Escherichia coli membrane with a high yield of 10-15mg protein/L culture. The photocycle of purified HtdR was similar to that of bR. The photo-induced electrogenic proton pumping activity of HtdR was verified. We co-expressed both HtdR and EmrE, a proton-coupled multi-drug efflux transporter in E. coli, and the cells successfully extruded ethidium, a substrate of EmrE, on illumination.« less

Review article: pH, healing and symptom relief with rabeprazole treatment in acid-related disorders.

PubMed

Robinson, M

2004-11-01

Control of gastric acid secretion by antisecretory agents has been the cornerstone of therapy in the successful management of all acid-related disorders, including gastro-oesophageal reflux disease (GERD), and duodenal and gastric ulcer. Treatment efficacy has been strongly correlated with degree and duration of acid suppression within the 24-h period and with total duration of therapy. All proton pump inhibitors are highly effective for the healing of ulcers and erosive oesophagitis. All have closely similar mechanisms of action, yet important pharmacological differences exist, which can significantly impact certain aspects of their clinical efficacy. Rabeprazole's rapid activation over a wide pH range may be the explanation for its early onset of effective acid inhibition compared with other proton pump inhibitors such as omeprazole, lansoprazole and pantoprazole. Like rabeprazole, esomeprazole is also a potent inhibitor of gastric acid at steady state, although it is thought that rabeprazole may provide enhanced first-day acid suppression compared with esomeprazole. First-day antisecretory efficacy should produce faster symptom relief, a hypothesis supported by clinical data. Moreover, drugs with pharmacological profiles that include both rapid onset and potent antisecretory effects should help control healthcare costs by reducing the need for otherwise commonly used twice-daily proton pump inhibitor administration.

A quantum chemical study of the mechanism for proton-coupled electron transfer leading to proton pumping in cytochrome c oxidase

NASA Astrophysics Data System (ADS)

Blomberg, Margareta R. A.; Siegbahn, Per E. M.

2010-10-01

The proton pumping mechanism in cytochrome c oxidase, the terminal enzyme in the respiratory chain, has been investigated using hybrid DFT with large chemical models. In previous studies, a gating mechanism was suggested based on electrostatic interpretations of kinetic experiments. The predictions from that analysis are tested here. The main result is that the suggestion of a positively charged transition state for proton transfer is confirmed, while some other suggestions for the gating are not supported. It is shown that a few critical relative energy values from the earlier studies are reproduced with quite high accuracy using the present model calculations. Examples are the forward barrier for proton transfer from the N-side of the membrane to the pump-loading site when the heme a cofactor is reduced, and the corresponding back leakage barrier when heme a is oxidised. An interesting new finding is an unexpected double-well potential for proton transfer from the N-side to the pump-loading site. In the intermediate between the two transition states found, the proton is bound to PropD on heme a. A possible purpose of this type of potential surface is suggested here. The accuracy of the present values are discussed in terms of their sensitivity to the choice of dielectric constant. Only one energy value, which is not critical for the present mechanism, varies significantly with this choice and is therefore less certain.

Development of a tritium monitor combined with an electrochemical tritium pump using a proton conducting oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, M.; Sugiyama, T.

2015-03-15

The detection of low level tritium is one of the key issues for tritium management in tritium handling facilities. Such a detection can be performed by tritium monitors based on proton conducting oxide technique. We tested a tritium monitoring system composed of a commercial proportional counter combined with an electrochemical hydrogen pump equipped with CaZr{sub 0.9}In{sub 0.1}O{sub 3-α} as proton conducting oxide. The hydrogen pump operated at 973 K under electrolysis conditions using tritiated water vapor (HTO). The proton conducting oxide extracts tritium molecules (HT) from HTO and tritium concentration is measured by the proportional counter. The advantage of themore » proposed tritium monitoring system is that it is able to convert HTO into molecular hydrogen.« less

Enhancement of Survival and Electricity Production in an Engineered Bacterium by Light-Driven Proton Pumping▿ †

PubMed Central

Johnson, Ethan T.; Baron, Daniel B.; Naranjo, Belén; Bond, Daniel R.; Schmidt-Dannert, Claudia; Gralnick, Jeffrey A.

2010-01-01

Microorganisms can use complex photosystems or light-dependent proton pumps to generate membrane potential and/or reduce electron carriers to support growth. The discovery that proteorhodopsin is a light-dependent proton pump that can be expressed readily in recombinant bacteria enables development of new strategies to probe microbial physiology and to engineer microbes with new light-driven properties. Here, we describe functional expression of proteorhodopsin and light-induced changes in membrane potential in the bacterium Shewanella oneidensis strain MR-1. We report that there were significant increases in electrical current generation during illumination of electrochemical chambers containing S. oneidensis expressing proteorhodopsin. We present evidence that an engineered strain is able to consume lactate at an increased rate when it is illuminated, which is consistent with the hypothesis that proteorhodopsin activity enhances lactate uptake by increasing the proton motive force. Our results demonstrate that there is coupling of a light-driven process to electricity generation in a nonphotosynthetic engineered bacterium. Expression of proteorhodopsin also preserved the viability of the bacterium under nutrient-limited conditions, providing evidence that fulfillment of basic energy needs of organisms may explain the widespread distribution of proteorhodopsin in marine environments. PMID:20453141

The Evolution of Ion Pumps.

ERIC Educational Resources Information Center

Maloney, Peter C.; Wilson, T. Hastings

1985-01-01

Constructs an evolutionary sequence to account for the diversity of ion pumps found today. Explanations include primary ion pumps in bacteria, features and distribution of ATP-driven pumps, preference for cation transport, and proton pump reversal. The integrated evolutionary hypothesis should encourage new experimental approaches. (DH)

Acidic digestion in a teleost: postprandial and circadian pattern of gastric pH, pepsin activity, and pepsinogen and proton pump mRNAs expression.

PubMed

Yúfera, Manuel; Moyano, Francisco J; Astola, Antonio; Pousão-Ferreira, Pedro; Martínez-Rodríguez, Gonzalo

2012-01-01

Two different modes for regulation of stomach acid secretion have been described in vertebrates. Some species exhibit a continuous acid secretion maintaining a low gastric pH during fasting. Others, as some teleosts, maintain a neutral gastric pH during fasting while the hydrochloric acid is released only after the ingestion of a meal. Those different patterns seem to be closely related to specific feeding habits. However, our recent observations suggest that this acidification pattern could be modified by changes in daily feeding frequency and time schedule. The aim of this study was to advance in understanding the regulation mechanisms of stomach digestion and pattern of acid secretion in teleost fish. We have examined the postprandial pattern of gastric pH, pepsin activity, and mRNA expression for pepsinogen and proton pump in white seabream juveniles maintained under a light/dark 12/12 hours cycle and receiving only one morning meal. The pepsin activity was analyzed according to the standard protocol buffering at pH 2 and using the actual pH measured in the stomach. The results show how the enzyme precursor is permanently available while the hydrochloric acid, which activates the zymogen fraction, is secreted just after the ingestion of food. Results also reveal that analytical protocol at pH 2 notably overestimates true pepsin activity in fish stomach. The expression of the mRNA encoding pepsinogen and proton pump exhibited almost parallel patterns, with notable increases during the darkness period and sharp decreases just before the morning meal. These results indicate that white seabream uses the resting hours for recovering the mRNA stock that will be quickly used during the feeding process. Our data clearly shows that both daily illumination pattern and feeding time are involved at different level in the regulation of the secretion of digestive juices.

Conjecture regarding posttranslational modifications to the arabidopsis type I proton-pumping pyrophosphatase (AVP1)

USDA-ARS?s Scientific Manuscript database

Agbiotechnology uses genetic engineering to improve the output and value of crops. Altering the expression of the plant Type I Proton-pumping Pyrophosphatase (H+-PPase) has already proven to be a useful tool to enhance crop productivity. Despite the effective use of this gene in translational resear...

Surgery and proton pump inhibitors for treatment of vocal process granulomas.

PubMed

Hong-Gang, Duan; He-Juan, Jin; Chun-Quan, Zheng; Guo-Kang, Fan

2013-11-01

The aim of this study was to analyze the outcomes of vocal process granulomas treated with surgery and proton pump inhibitors and to specify related factors of recurrence. The medical records of patients with diagnosis of vocal process granuloma between 2000 and 2012 were reviewed. All patients were treated with surgery and proton pump inhibitors for at least 1 month. Forty-one patients were reviewed; mean follow-up time was 45 months. There was no recurrence among the patients who had a recent history of intubation. The recurrence rates of contact granuloma was 38.7 %, and significantly related to the frequency of surgery (P = 0.042), but was not significantly associated with the history of acid reflux (P = 0.676) and vocal abuse (P = 0.447), lesion size (P = 0.203) or surgical techniques (P = 0.331). Surgery combined with proton pump inhibitors was partially effective for the vocal process granulomas, especially with intubated patients. However, repeat surgery for recurrent contact granuloma should be preceded with caution due to high recurrence rates.

Proton pump inhibitors as anti vacuolar-ATPases drugs: a novel anticancer strategy.

PubMed

Spugnini, Enrico P; Citro, Gennaro; Fais, Stefano

2010-05-08

The vacuolar ATPases are ATP-dependent proton pumps whose functions include the acidification of intracellular compartments and the extrusion of protons through the cell cytoplasmic membrane. These pumps play a pivotal role in the regulation of cell pH in normal cells and, to a much greater extent, in tumor cells. In fact, the glucose metabolism in hypoxic conditions by the neoplasms leads to an intercellular pH drift towards acidity. The acid microenvironment is modulated through the over-expression of H+ transporters that are also involved in tumor progression, invasiveness, distant spread and chemoresistance. Several strategies to block/downmodulate the efficiency of these transporters are currently being investigated. Among them, proton pump inhibitors have shown to successfully block the H+ transporters in vitro and in vivo, leading to apoptotic death. Furthermore, their action seems to synergize with conventional chemotherapy protocols, leading to chemosensitization and reversal of chemoresistance. Aim of this article is to critically revise the current knowledge of this cellular machinery and to summarize the therapeutic strategies developed to counter this mechanism.

Decrease in Switches to 'Unsafe' Proton Pump Inhibitors After Communications About Interactions with Clopidogrel.

PubMed

Kruik-Kollöffel, Willemien J; van der Palen, Job; van Herk-Sukel, Myrthe P P; Kruik, H Joost; Movig, Kris L L

2017-08-01

In 2009 and 2010 medicines regulatory agencies published official safety statements regarding the concomitant use of proton pump inhibitors and clopidogrel. We wanted to investigate a change in prescription behaviour in prevalent gastroprotective drug users (2008-2011). Data on drug use were retrieved from the Out-patient Pharmacy Database of the PHARMO Database Network. We used interrupted time series analyses (ITS) to estimate the impact of each safety statement on the number of gastroprotective drug switches around the start of clopidogrel and during clopidogrel use. After the first statement (June 2009), significantly fewer patients switched from another proton pump inhibitor to (es)omeprazole (-14.9%; 95% CI -22.6 to -7.3) at the moment they started clopidogrel compared to the period prior to this statement. After the adjusted statement in February 2010, the switch percentage to (es)omeprazole decreased further (-4.5%; 95% CI -8.1 to -0.9). We observed a temporary increase in switches from proton pump inhibitors to histamine 2-receptor antagonists after the first statement; the decrease in the reverse switch was statistically significant (-23.0%; 95% CI -43.1 to -2.9). With ITS, we were able to demonstrate a decrease in switches from other proton pump inhibitors to (es)omeprazole and an increase of the reverse switch to almost 100%. We observed a partial and temporary switch to histamine 2-receptor antagonists. This effect of safety statements was shown for gastroprotective drug switches around the start of clopidogrel treatment.

Proton pump inhibitor use and risk of adverse cardiovascular events in aspirin treated patients with first time myocardial infarction: nationwide propensity score matched study

PubMed Central

Grove, Erik L; Hansen, Peter Riis; Olesen, Jonas B; Ahlehoff, Ole; Selmer, Christian; Lindhardsen, Jesper; Madsen, Jan Kyst; Køber, Lars; Torp-Pedersen, Christian; Gislason, Gunnar H

2011-01-01

Objective To examine the effect of proton pump inhibitors on adverse cardiovascular events in aspirin treated patients with first time myocardial infarction. Design Retrospective nationwide propensity score matched study based on administrative data. Setting All hospitals in Denmark. Participants All aspirin treated patients surviving 30 days after a first myocardial infarction from 1997 to 2006, with follow-up for one year. Patients treated with clopidogrel were excluded. Main outcome measures The risk of the combined end point of cardiovascular death, myocardial infarction, or stroke associated with use of proton pump inhibitors was analysed using Kaplan-Meier analysis, Cox proportional hazard models, and propensity score matched Cox proportional hazard models. Results 3366 of 19 925 (16.9%) aspirin treated patients experienced recurrent myocardial infarction, stroke, or cardiovascular death. The hazard ratio for the combined end point in patients receiving proton pump inhibitors based on the time dependent Cox proportional hazard model was 1.46 (1.33 to 1.61; P<0.001) and for the propensity score matched model based on 8318 patients it was 1.61 (1.45 to 1.79; P<0.001). A sensitivity analysis showed no increase in risk related to use of H2 receptor blockers (1.04, 0.79 to 1.38; P=0.78). Conclusion In aspirin treated patients with first time myocardial infarction, treatment with proton pump inhibitors was associated with an increased risk of adverse cardiovascular events. PMID:21562004

Systematic review: proton pump inhibitors (PPIs) for the healing of reflux oesophagitis - a comparison of esomeprazole with other PPIs.

PubMed

Edwards, S J; Lind, T; Lundell, L

2006-09-01

No randomized controlled trial has compared all the licensed standard dose proton pump inhibitors in the healing of reflux oesophagitis. To compare the effectiveness of esomeprazole with licensed standard dose proton pump inhibitors for healing of reflux oesophagitis (i.e. lansoprazole 30 mg, omeprazole 20 mg, pantoprazole 40 mg and rabeprazole 20 mg). Systematic review of CENTRAL, BIOSIS, EMBASE and MEDLINE for randomized controlled trials in patients with reflux oesophagitis. Searching was completed in February 2005. Data on endoscopic healing rates at 4 and 8 weeks were extracted and re-analysed if not analysed by intention-to-treat. Meta-analysis was conducted using a fixed effects model. Of 133 papers identified in the literature search, six were of sufficient quality to be included in the analysis. No studies were identified comparing rabeprazole with esomeprazole. A meta-analysis of healing rates of esomeprazole 40 mg compared with standard dose proton pump inhibitors gave the following results: at 4 weeks [relative risk (RR) 0.92; 95% CI: 0.90, 0.94; P < 0.00001], and 8 weeks (RR 0.95; 95% CI: 0.94, 0.97; P < 0.00001). Publication bias did not have a significant impact on the results. The results were robust to changes in the inclusion/exclusion criteria and using a random effects model. Esomeprazole consistently demonstrates higher healing rates when compared with standard dose proton pump inhibitors.

Prolonged utilization of proton pump inhibitors in patients with ischemic and valvular heart disease is associated with surgical treatments, weight loss and aggravates anemia.

PubMed

Boban, Marko; Zulj, Marinko; Persic, Viktor; Medved, Igor; Zekanovic, Drazen; Vcev, Aleksandar

2016-09-15

Proton pump inhibitors (PPIs) are among the commonest drugs used nowadays. The aim of our study was to analyze prolonged utilization of proton pump inhibitors in medical therapy of patients with ischemic and valvular heart disease. Secondly, profile of utilization was scrutinized to patient characteristics and type of cardiovascular treatments. The study included consecutive patients scheduled for cardiovascular rehabilitation 2-6months after index cardiovascular treatment. Two hundred ninety-four patients (n=294/604; 48.7%) have been using proton pump inhibitor in their therapy after index cardiovascular treatment. Cardiovascular treatments were powerfully connected with utilization of PPIs; surgery 5.77 (95%-confidence intervals [CI]: 4.05-8.22; p<0.001) and PCI 0.15 (CI: 0.10-0.22; p<0.001). The odds for having proton pump inhibitor in their chronic therapy were increased for atrial fibrillation 1.87 (CI: 1.08-3.23; p=0.025) and decreased for obesity 0.65 (CI: 0.45-0.96; p=0.035); surviving myocardial infarction 0.49 (CI: 0.29-0.83; p=0.035). Multinomial logistic regression controlled for existence of chronic renal disease found no significant association of renal dysfunction and PPI therapy. The existence of anemia was significantly increased in patients taking PPIs than controls; 6.00 (CI: 3.85-9.33; p<0.001). The use of PPI was also associated with worsening of metabolic profile, in part due to decreased utilization of ACE-inhibitors and statins. PPI consumption correlated with age of patients (Rho=0.216; p<0.001). High proportion of cardiovascular, particularly surgical patients with ischemic and valvular heart disease utilized proton pump inhibitor in prolonged courses. Prolonged courses of PPIs were connected with existence and worsening of red blood count indexes, older age, lesser weight of patients and underutilization of cardioprotective drugs. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Mechanism and energetics by which glutamic acid 242 prevents leaks in cytochrome c oxidase.

PubMed

Kaila, Ville R I; Verkhovsky, Michael I; Hummer, Gerhard; Wikström, Mårten

2009-10-01

Cytochrome c oxidase (CcO) is the terminal enzyme of aerobic respiration. The energy released from the reduction of molecular oxygen to water is used to pump protons across the mitochondrial or bacterial membrane. The pump function introduces a mechanistic requirement of a valve that prevents protons from flowing backwards during the process. It was recently found that Glu-242, a key amino acid in transferring protons to be pumped across the membrane and to the site of oxygen reduction, fulfils the function of such a valve by preventing simultaneous contact to the pump site and to the proton-conducting D-channel (Kaila V.R.I. et al. Proc. Natl. Acad. Sci. USA 105, 2008). Here we have incorporated the valve model into the framework of the reaction mechanism. The function of the Glu valve is studied by exploring how the redox state of the surrounding metal centers, dielectric effects, and membrane potential, affects the energetics and leaks of this valve. Parallels are drawn between the dynamics of Glu-242 and the long-standing obscure difference between the metastable O(H) and stable O states of the binuclear center. Our model provides a suggestion for why reduction of the former state is coupled to proton translocation while reduction of the latter is not.

ANTISECRETORY TREATMENT FOR PEDIATRIC GASTROESOPHAGEAL REFLUX DISEASE - A SYSTEMATIC REVIEW.

PubMed

Mattos, Ângelo Zambam de; Marchese, Gabriela Meirelles; Fonseca, Bárbara Brum; Kupski, Carlos; Machado, Marta Brenner

2017-12-01

Proton pump inhibitors and histamine H2 receptor antagonists are two of the most commonly prescribed drug classes for pediatric gastroesophageal reflux disease, but their efficacy is controversial. Many patients are treated with these drugs for atypical manifestations attributed to gastroesophageal reflux, even that causal relation is not proven. To evaluate the use of proton pump inhibitors and histamine H2 receptor antagonists in pediatric gastroesophageal reflux disease through a systematic review. A systematic review was performed, using MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials databases. The search was limited to studies published in English, Portuguese or Spanish. There was no limitation regarding date of publication. Studies were considered eligible if they were randomized-controlled trials, evaluating proton pump inhibitors and/or histamine H2 receptor antagonists for the treatment of pediatric gastroesophageal reflux disease. Studies published only as abstracts, studies evaluating only non-clinical outcomes and studies exclusively comparing different doses of the same drug were excluded. Data extraction was performed by independent investigators. The study protocol was registered at PROSPERO platform (CRD42016040156). After analyzing 735 retrieved references, 23 studies (1598 randomized patients) were included in the systematic review. Eight studies demonstrated that both proton pump inhibitors and histamine H2 receptor antagonists were effective against typical manifestations of gastroesophageal reflux disease, and that there was no evidence of benefit in combining the latter to the former or in routinely prescribing long-term maintenance treatments. Three studies evaluated the effect of treatments on children with asthma, and neither proton pump inhibitors nor histamine H2 receptor antagonists proved to be significantly better than placebo. One study compared different combinations of omeprazole, bethanechol and placebo for the treatment of children with cough, and there is no clear definition on the best strategy. Another study demonstrated that omeprazole performed better than ranitidine for the treatment of extraesophageal reflux manifestations. Ten studies failed to demonstrate significant benefits of proton pump inhibitors or histamine H2 receptor antagonists for the treatment of unspecific manifestations attributed to gastroesophageal reflux in infants. Proton pump inhibitors or histamine H2 receptor antagonists may be used to treat children with gastroesophageal reflux disease, but not to treat asthma or unspecific symptoms.

A bioenergetic basis for membrane divergence in archaea and bacteria.

PubMed

Sojo, Víctor; Pomiankowski, Andrew; Lane, Nick

2014-08-01

Membrane bioenergetics are universal, yet the phospholipid membranes of archaea and bacteria-the deepest branches in the tree of life-are fundamentally different. This deep divergence in membrane chemistry is reflected in other stark differences between the two domains, including ion pumping and DNA replication. We resolve this paradox by considering the energy requirements of the last universal common ancestor (LUCA). We develop a mathematical model based on the premise that LUCA depended on natural proton gradients. Our analysis shows that such gradients can power carbon and energy metabolism, but only in leaky cells with a proton permeability equivalent to fatty acid vesicles. Membranes with lower permeability (equivalent to modern phospholipids) collapse free-energy availability, precluding exploitation of natural gradients. Pumping protons across leaky membranes offers no advantage, even when permeability is decreased 1,000-fold. We hypothesize that a sodium-proton antiporter (SPAP) provided the first step towards modern membranes. SPAP increases the free energy available from natural proton gradients by ∼60%, enabling survival in 50-fold lower gradients, thereby facilitating ecological spread and divergence. Critically, SPAP also provides a steadily amplifying advantage to proton pumping as membrane permeability falls, for the first time favoring the evolution of ion-tight phospholipid membranes. The phospholipids of archaea and bacteria incorporate different stereoisomers of glycerol phosphate. We conclude that the enzymes involved took these alternatives by chance in independent populations that had already evolved distinct ion pumps. Our model offers a quantitatively robust explanation for why membrane bioenergetics are universal, yet ion pumps and phospholipid membranes arose later and independently in separate populations. Our findings elucidate the paradox that archaea and bacteria share DNA transcription, ribosomal translation, and ATP synthase, yet differ in equally fundamental traits that depend on the membrane, including DNA replication.

Duodenal ulcer and gastroesophageal reflux disease today: long-term therapy--a sideways glance.

PubMed Central

Bardhan, K. D.

1996-01-01

Acid-peptic disease is widely considered conquered or controlled, future advances being refinements of existing treatments rather than radical new developments. Yet controversies remain and developments have yet to be made. DUODENAL ULCER: Daily maintenance treatment with the anti-secretory drugs, histamine H2 receptor antagonists and proton pump blockers, controls duodenal ulcer effectively, markedly reducing relapse rate at one year after treatment from about 75 percent to 15 to 20 percent (and to about 10 percent on proton pump blockers). In contrast, Helicobacter pylori eradication with a one to two week course of treatment yields prolonged remission or cure. The consequent reduction in drug costs in individual patients, however, has been exceeded by increasing community use on the more expensive proton pump blockers for the treatment of gastroesophageal reflux disease. The marked decline in elective surgery since the introduction of histamine H2 receptor antagonists is commonly attributed to the power of these drugs. The fall, however, had started much earlier, indicating that the decline is due to changing natural history. In contrast, complication rates remain unaltered. An increasing proportion of newly diagnosed duodenal ulcer patients are elderly, and more of them now present for the first time with complications (in this center, about 40 percent), which consequently cannot be forestalled. Thus, duodenal ulcer disease is likely to remain a problem and in many will be a serious illness. GASTROESOPHAGEAL REFLUX DISEASE: The proton pump blockers have revolutionized the treatment of gastroesophageal reflux disease. In clinical trials they have proven markedly superior to the histamine H2 receptor antagonists in healing (at eight weeks, 80 to 90 percent vs. 50 to 60 percent), symptom relief, prevention of relapse on maintenance therapy and cost-effectiveness. However, several issues remain. The prevalence of gastroesophageal reflux disease seems to be rising and is now probably the commonest acid-peptic disease encountered in the West. Most clinical trials comparing proton pump blockers vs. histamine H2 receptor antagonists have been done in patients with erosive esophagitis, whereas the majority (50 to 60 percent) of patients with gastroesophageal reflux disease have milder, generally non-erosive, disease. The therapeutic gain of proton pump blockers diminishes in mild disease so may not be worth the higher drug costs. This is an important area for investigation. The majority of patients with erosive esophagitis relapse when treatment is stopped (about 75 percent at one year). Relapse is markedly reduced (to 20 to 25 percent) by daily maintenance treatment with proton pump blockers. Mild disease relapses less often, so longterm therapy by intermittent treatment may prove acceptable and more cost-effective than maintenance treatment. This strategy remains unexplored in trials. The ideal profile of an anti-secretory drug for intermittent treatment would combine rapid onset of action (similar to histamine H2 receptor antagonists) with powerful effect (as with proton pump blockers). The new class of drug, the reversible proton pump blocker (e.g., BY841) approaches this requirement. PMID:9165690

[Interaction of surface-active base with fraction of membrane-bound Williams's protons].

PubMed

Iaguzhinskiĭ, L S; Motovilov, K A; Volkov, E M; Eremeev, S A

2013-01-01

In the process of mitochondrial respiratory H(+)-pumps functioning, the fraction membrane-bound protons (R-protons), which have an excess of free energy is formed. According to R.J. Williams this fraction is included as energy source in the reaction of ATP synthesis. Previously, in our laboratory was found the formation of this fraction was found in the mitochondria and on the outer surface of mitoplast. On the mitoslast model we strictly shown that non-equilibrium R-proton fraction is localized on the surface of the inner mitochondrial membrane. In this paper a surface-active compound--anion of 2,4,6-trichloro-3-pentadecylphenol (TCP-C15) is described, which selectively interacts with the R-protons fraction in mitochondria. A detailed description of the specific interaction of the TCP-C15 with R-protons fraction in mitochondria is presented. Moreover, in this work it was found that phosphate transport system reacts with the R-protons fraction in mitochondria and plays the role of the endogenous volume regulation system of this fraction. The results of experiments are discussed in the terms of a local coupling model of the phosphorylation mechanism.

Excited state proton transfer in strongly enhanced GFP (sGFP2).

PubMed

van Oort, Bart; ter Veer, Mirelle J T; Groot, Marie Louise; van Stokkum, Ivo H M

2012-07-07

Proton transfer is an elementary process in biology. Green fluorescent protein (GFP) has served as an important model system to elucidate the mechanistic details of this reaction, because in GFP proton transfer can be induced by light absorption. We have used pump-dump-probe spectroscopy to study how proton transfer through the 'proton-wire' around the chromophore is affected by a combination of mutations in a modern GFP variety (sGFP2). The results indicate that in H(2)O, after absorption of a photon, a proton is transferred (A* → I*) in 5 ps, and back-transferred from a ground state intermediate (I → A) in 0.3 ns, similar to time constants found with GFPuv, although sGFP2 shows less heterogeneous proton transfer. This suggests that the mutations left the proton-transfer largely unchanged, indicating the robustness of the proton-wire. We used pump-dump-probe spectroscopy in combination with target analysis to probe suitability of the sGFP2 fluorophore for super-resolution microscopy.

FTIR spectroscopic study on individual amino acid residues in the proton pumping process of bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Liu, Xiaomei

1998-05-01

My thesis project has concentrated on clarifying the role of individual amino acids such as tyrosine, arginine and threonine in the active proton transferring process of Bacteriorhodopsin(bR). BR is a protein found in the purple membrane of Halobacteria salinarium. The main function of bR is to transfer a proton from the interior side of the cell to the external medium upon illumination by visible light. BR belongs to a family of retinal- containing membrane proteins which includes rhodopsin, a visual receptor found in the eye, and sensory rhodopsin I, a light receptor for phototaxis found in H. salinarium. Complete understanding of the proton transferring mechanism of bR can help explain the energy transduction and active ion transport in biological systems. This information also provides insight into other members of the retinal-containing protein family. To study the behavior of a single amino acid in a protein which consists of 248 amino acids, I employed the Fourier transform infrared (FTIR) difference spectroscopy technique. This was combined with the recently developed genetic engineering method of site directed isotope labeling (SDIL). As complementary work, I also characterized the vibrational properties of individual amino acids in various environments. Because of the high resolution and sensitivity of FTIR difference spectroscopy, along with the ability of SDIL to detect structural changes at the single amino acid level, we are able to determine changes in the structure of specific amino acids at different steps in bR photocycle. My research results provide strong evidence for a proton pump model. This model predicts the participation of tyrosine 185 and one or more threonines in a hydrogen bonded chain which can transfer proton across the membrane. My data also suggest a more accurate model for the proton release step which involves arginine 82.

The management of gastro-oesophageal reflux disease.

PubMed

Keung, Charlotte; Hebbard, Geoffrey

2016-02-01

If there are no features of serious disease, suspected gastro-oesophageal reflux disease can be initially managed with a trial of a proton pump inhibitor for 4-8 weeks. This should be taken 30-60 minutes before food for optimal effect. Once symptoms are controlled, attempt to withdraw acid suppression therapy. If symptoms recur, use the minimum dose that controls symptoms. Patients who have severe erosive oesophagitis, scleroderma oesophagus or Barrett's oesophagus require long-term treatment with a proton pump inhibitor. Lifestyle modification strategies can help gastro-oesophageal reflux disease. Weight loss has the strongest evidence for efficacy. Further investigation and a specialist referral are required if there is no response to proton pump inhibitor therapy. Atypical symptoms or signs of serious disease also need investigation.

Proton transfer mediated by the vibronic coupling in oxygen core ionized states of glyoxalmonoxime studied by infrared-X-ray pump-probe spectroscopy.

PubMed

Felicíssimo, V C; Guimarães, F F; Cesar, A; Gel'mukhanov, F; Agren, H

2006-11-30

The theory of IR-X-ray pump-probe spectroscopy beyond the Born-Oppenheimer approximation is developed and applied to the study of the dynamics of intramolecular proton transfer in glyoxalmonoxime leading to the formation of the tautomer 2-nitrosoethenol. Due to the IR pump pulses the molecule gains sufficient energy to promote a proton to a weakly bound well. A femtosecond X-ray pulse snapshots the wave packet route and, hence, the dynamics of the proton transfer. The glyoxalmonoxime molecule contains two chemically nonequivalent oxygen atoms that possess distinct roles in the hydrogen bond, a hydrogen donor and an acceptor. Core ionizations of these form two intersecting core-ionized states, the vibronic coupling between which along the OH stretching mode partially delocalizes the core hole, resulting in a hopping of the core hole from one site to another. This, in turn, affects the dynamics of the proton transfer in the core-ionized state. The quantum dynamical simulations of X-ray photoelectron spectra of glyoxalmonoxime driven by strong IR pulses demonstrate the general applicability of the technique for studies of intramolecular proton transfer in systems with vibronic coupling.

The controlled relay of multiple protons required at the active site of nitrogenase.

PubMed

Dance, Ian

2012-07-07

The enzyme nitrogenase, when reducing natural and unnatural substrates, requires large numbers of protons per chemical catalytic cycle. The active face of the catalytic site (the FeMo-cofactor, FeMo-co) is situated in a protein domain which is largely hydrophobic and anhydrous, and incapable of serial provision of multiple protons. Through detailed analysis of the high quality protein crystal structures available the characteristics of a chain of water molecules leading from the protein surface to a key sulfur atom (S3B) of FeMo-co are described. The first half of the water chain from the surface inwards is branched, slightly variable, and able to accommodate exogenous small molecules: this is dubbed the proton bay. The second half, from the proton bay to S3B, is comprised of a single chain of eight hydrogen bonded water molecules. This section is strictly conserved, and is intimately involved in hydrogen bonds with homocitrate, an essential component that chelates Mo. This is the proton wire, and a detailed Grotthuss mechanism for serial translocation of protons through this proton wire to S3B is proposed. This controlled serial proton relay from the protein surface to S3B is an essential component of the intramolecular hydrogenation paradigm for the complete chemical mechanisms of nitrogenase. Each proton reaching S3B, instigated by electron transfer to FeMo-co, becomes a hydrogen atom that migrates to other components of the active face of FeMo-co and to bound substrates and intermediates, allowing subsequent multiple proton transfers along the proton wire. Experiments to test the proposed mechanism of proton supply are suggested. The water chain in nitrogenase is comparable with the purported proton pumping pathway of cytochrome c oxidase.

Lansoprazole as a rescue agent in chemoresistant tumors: a phase I/II study in companion animals with spontaneously occurring tumors.

PubMed

Spugnini, Enrico P; Baldi, Alfonso; Buglioni, Sabrina; Carocci, Francesca; de Bazzichini, Giulia Milesi; Betti, Gianluca; Pantaleo, Ilaria; Menicagli, Francesco; Citro, Gennaro; Fais, Stefano

2011-12-28

The treatment of human cancer has been seriously hampered for decades by resistance to chemotherapeutic drugs. Mechanisms underlying this resistance are far from being entirely known. A very efficient mechanism of tumor resistance to drugs is related to the modification of tumour microenvironment through changes in the extracellular and intracellular pH. The acidification of tumor microenvironment depends on proton pumps that actively pump protons outside the cells, mostly to avoid intracellular acidification. In fact, we have shown in pre-clinical settings as pre-treatment with proton-pumps inhibitors (PPI) increase tumor cell and tumor responsiveness to chemotherapeutics. In this study pet with spontaneously occurring cancer proven refractory to conventional chemotherapy have been recruited in a compassionate study. Thirty-four companion animals (27 dogs and 7 cats) were treated adding to their chemotherapy protocols the pump inhibitor lansoprazole at high dose, as suggested by pre-clinical experiments. Their responses have been compared to those of seventeen pets (10 dogs and 7 cats) whose owners did not pursue any other therapy than continuing the currently ongoing chemotherapy protocols. The drug was overall well tolerated, with only four dogs experiencing side effects due to gastric hypochlorhydria consisting with vomiting and or diarrhea. In terms of overall response twenty-three pets out of 34 had partial or complete responses (67.6%) the remaining patients experienced no response or progressive disease however most owners reported improved quality of life in most of the non responders. On the other hand, only three animals in the control group (17%) experienced short lived partial responses (1-3 months duration) while all the others died of progressive disease within two months. high dose proton pump inhibitors have been shown to induce reversal of tumor chemoresistance as well as improvement of the quality of life in pets with down staged cancer and in the majority of the treated animals PPI were well tolerated. Further studies are warranted to assess the efficacy of this strategy in patients with advanced cancers in companion animals as well as in humans.

Imaging an optogenetic pH sensor reveals that protons mediate lateral inhibition in the retina.

PubMed

Wang, Tzu-Ming; Holzhausen, Lars C; Kramer, Richard H

2014-02-01

The reciprocal synapse between photoreceptors and horizontal cells underlies lateral inhibition and establishes the antagonistic center-surround receptive fields of retinal neurons to enhance visual contrast. Despite decades of study, the signal mediating the negative feedback from horizontal cells to cones has remained under debate because the small, invaginated synaptic cleft has precluded measurement. Using zebrafish retinas, we show that light elicits a change in synaptic proton concentration with the correct magnitude, kinetics and spatial dependence to account for lateral inhibition. Light, which hyperpolarizes horizontal cells, causes synaptic alkalinization, whereas activating an exogenously expressed ligand-gated Na(+) channel, which depolarizes horizontal cells, causes synaptic acidification. Whereas acidification was prevented by blocking a proton pump, re-alkalinization was prevented by blocking proton-permeant ion channels, suggesting that distinct mechanisms underlie proton efflux and influx. These findings reveal that protons mediate lateral inhibition in the retina, raising the possibility that protons are unrecognized retrograde messengers elsewhere in the nervous system.

A nonmainstream approach against cancer.

PubMed

Fais, Stefano

2016-12-01

The discovery of antibiotics as specific and effective drugs against infectious agents has generated the belief that the famous Paul Erlich theory on magic bullet should be applied to cancer as well. However, after around 60 years of failures in finding a magic bullet against cancer, a question appears mandatory: does the magic bullet against cancer really exist? In trying to understand more on the issue, we propose three discoveries are coming from a nonmainstream approach against cancer. Tumor is acidic, and tumor acidity impairs drugs entering within tumor cells and isolates tumors from the rest of the body. Proton pumps are key in allowing tumor cells to live in the acidic microenvironment. A class of antiacidic drugs, proton pump inhibitors (PPIs), were shown to have a potent anti-tumor effect, through inhibition of proton pumps in tumor cells. PPIs are indeed prodrugs needing acidity to be activated into the active molecule. So they use protonation by H+ as an activating mechanism, while the vast majority of drugs are totally neutralized by protonation. An anti-tumor therapy based on PPI showed to be effective both in vitro and in vivo. Differently from normal cells, cancer cells meet their energy needs in great part by fermentation, and it appears conceivable that hypoxia and low nutrient transform tumor cells into fermenting anaerobes. This suggests that cancer cells are more similar to unicellular organisms, aimed at surviving in a continuous fighting, rather than cooperating, with other cells, as it occurs in the normal homeostasis of our body. We have shown that cancer cells take their fuel by "cannibalizing" other cells, either dead or alive, especially when starved and in acidic condition. This finding led to the discovery of a new oncogene TM9SF4 that human malignant cell shares with amoebas. The evidence is accumulating that almost all the cells release extracellular vehicles (EVs), from micro- to nanosize, which shuttle a variety of molecules. Tumor cells, particularly when stressed in their hostile microenvironment, release high levels of EVs, able to interact with target cells in various ways, within an organ or at a distance. They may represent both valuable tumor biomarker and shuttles for drugs with anti-tumor properties. This article wants to burst a real change in future anti-cancer strategies, based on the idea that tumors are much more common features than specific molecular targets.

Proton transfer in the K-channel analog of B-type Cytochrome c oxidase from Thermus thermophilus.

PubMed

Woelke, Anna Lena; Wagner, Anke; Galstyan, Gegham; Meyer, Tim; Knapp, Ernst-Walter

2014-11-04

A key enzyme in aerobic metabolism is cytochrome c oxidase (CcO), which catalyzes the reduction of molecular oxygen to water in the mitochondrial and bacterial membranes. Substrate electrons and protons are taken up from different sides of the membrane and protons are pumped across the membrane, thereby generating an electrochemical gradient. The well-studied A-type CcO uses two different entry channels for protons: the D-channel for all pumped and two consumed protons, and the K-channel for the other two consumed protons. In contrast, the B-type CcO uses only a single proton input channel for all consumed and pumped protons. It has the same location as the A-type K-channel (and thus is named the K-channel analog) without sharing any significant sequence homology. In this study, we performed molecular-dynamics simulations and electrostatic calculations to characterize the K-channel analog in terms of its energetic requirements and functionalities. The function of Glu-15B as a proton sink at the channel entrance is demonstrated by its rotational movement out of the channel when it is deprotonated and by its high pKA value when it points inside the channel. Tyr-244 in the middle of the channel is identified as the valve that ensures unidirectional proton transfer, as it moves inside the hydrogen-bond gap of the K-channel analog only while being deprotonated. The electrostatic energy landscape was calculated for all proton-transfer steps in the K-channel analog, which functions via proton-hole transfer. Overall, the K-channel analog has a very stable geometry without large energy barriers.

Proton Transfer in the K-Channel Analog of B-Type Cytochrome c Oxidase from Thermus thermophilus

PubMed Central

Woelke, Anna Lena; Wagner, Anke; Galstyan, Gegham; Meyer, Tim; Knapp, Ernst-Walter

2014-01-01

A key enzyme in aerobic metabolism is cytochrome c oxidase (CcO), which catalyzes the reduction of molecular oxygen to water in the mitochondrial and bacterial membranes. Substrate electrons and protons are taken up from different sides of the membrane and protons are pumped across the membrane, thereby generating an electrochemical gradient. The well-studied A-type CcO uses two different entry channels for protons: the D-channel for all pumped and two consumed protons, and the K-channel for the other two consumed protons. In contrast, the B-type CcO uses only a single proton input channel for all consumed and pumped protons. It has the same location as the A-type K-channel (and thus is named the K-channel analog) without sharing any significant sequence homology. In this study, we performed molecular-dynamics simulations and electrostatic calculations to characterize the K-channel analog in terms of its energetic requirements and functionalities. The function of Glu-15B as a proton sink at the channel entrance is demonstrated by its rotational movement out of the channel when it is deprotonated and by its high pKA value when it points inside the channel. Tyr-244 in the middle of the channel is identified as the valve that ensures unidirectional proton transfer, as it moves inside the hydrogen-bond gap of the K-channel analog only while being deprotonated. The electrostatic energy landscape was calculated for all proton-transfer steps in the K-channel analog, which functions via proton-hole transfer. Overall, the K-channel analog has a very stable geometry without large energy barriers. PMID:25418102

Intrinsic uncoupling of mitochondrial proton pumps. 2. Modeling studies.

PubMed

Pietrobon, D; Zoratti, M; Azzone, G F; Caplan, S R

1986-02-25

The thermodynamic and kinetic properties associated with intrinsic uncoupling in a six-state model of a redox proton pump have been studied by computing the flow-force relations for different degrees of coupling. Analysis of these relations shows the regulatory influence of the thermodynamic forces on the extent and relative contributions of redox slip and proton slip. Inhibition has been introduced into the model in two different ways, corresponding to possible modes of action of experimental inhibitors. Experiments relating the rate of electron transfer to delta microH at static head upon progressive inhibition of the pumps have been simulated considering (1) the limiting case that the nonzero rate of electron transfer at static head is only due to intrinsic uncoupling (no leaks) and (2) the experimentally observed case that about 30% of the nonzero rate of electron transfer at static head is due to a constant proton leakage conductance in parallel with the pumps, the rest being due to intrinsic uncoupling. The same simulations have been performed for experiments in which the rate of electron transfer is varied by varying the substrate concentration rather than by using an inhibitor. The corresponding experimental results obtained by measuring delta microH and the rate of electron transfer at different succinate concentrations in rat liver mitochondria are presented. Comparison between simulated behavior and experimental results leads to the general conclusion that the typical relationship between rate of electron transfer and delta microH found in mitochondria at static head could certainly be a manifestation of some degree of intrinsic uncoupling in the redox proton pumps.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and Functional Reconstitution of a Seven-Subunit Mrp-Type Na+/H+ Antiporter

PubMed Central

Morino, Masato; Suzuki, Toshiharu; Ito, Masahiro

2014-01-01

Mrp antiporters and their homologues in the cation/proton antiporter 3 family of the Membrane Transporter Database are widely distributed in bacteria. They have major roles in supporting cation and cytoplasmic pH homeostasis in many environmental, extremophilic, and pathogenic bacteria. These antiporters require six or seven hydrophobic proteins that form hetero-oligomeric complexes, while most other cation/proton antiporters require only one membrane protein for their activity. The resemblance of three Mrp subunits to membrane-embedded subunits of the NADH:quinone oxidoreductase of respiratory chains and to subunits of several hydrogenases has raised interest in the evolutionary path and commonalities of their proton-translocating domains. In order to move toward a greater mechanistic understanding of these unusual antiporters and to rigorously demonstrate that they function as secondary antiporters, powered by an imposed proton motive force, we established a method for purification and functional reconstitution of the seven-subunit Mrp antiporter from alkaliphilic Bacillus pseudofirmus OF4. Na+/H+ antiporter activity was demonstrated by a fluorescence-based assay with proteoliposomes in which the Mrp complex was coreconstituted with a bacterial FoF1-ATPase. Proton pumping by the ATPase upon addition of ATP generated a proton motive force across the membranes that powered antiporter activity upon subsequent addition of Na+. PMID:24142251

Purification and functional reconstitution of a seven-subunit mrp-type na+/h+ antiporter.

PubMed

Morino, Masato; Suzuki, Toshiharu; Ito, Masahiro; Krulwich, Terry Ann

2014-01-01

Mrp antiporters and their homologues in the cation/proton antiporter 3 family of the Membrane Transporter Database are widely distributed in bacteria. They have major roles in supporting cation and cytoplasmic pH homeostasis in many environmental, extremophilic, and pathogenic bacteria. These antiporters require six or seven hydrophobic proteins that form hetero-oligomeric complexes, while most other cation/proton antiporters require only one membrane protein for their activity. The resemblance of three Mrp subunits to membrane-embedded subunits of the NADH:quinone oxidoreductase of respiratory chains and to subunits of several hydrogenases has raised interest in the evolutionary path and commonalities of their proton-translocating domains. In order to move toward a greater mechanistic understanding of these unusual antiporters and to rigorously demonstrate that they function as secondary antiporters, powered by an imposed proton motive force, we established a method for purification and functional reconstitution of the seven-subunit Mrp antiporter from alkaliphilic Bacillus pseudofirmus OF4. Na(+)/H(+) antiporter activity was demonstrated by a fluorescence-based assay with proteoliposomes in which the Mrp complex was coreconstituted with a bacterial FoF1-ATPase. Proton pumping by the ATPase upon addition of ATP generated a proton motive force across the membranes that powered antiporter activity upon subsequent addition of Na(+).

Teaching the Fundamentals of Biological Research with Primary Literature: Learning from the Discovery of the Gastric Proton Pump

ERIC Educational Resources Information Center

Zhu, Lixin

2011-01-01

For the purpose of teaching collegians the fundamentals of biological research, literature explaining the discovery of the gastric proton pump was presented in a 50-min lecture. The presentation included detailed information pertaining to the discovery process. This study was chosen because it demonstrates the importance of having a broad range of…

A thermo-physical analysis of the proton pump vacuolar-ATPase: the constructal approach.

PubMed

Lucia, Umberto; Ponzetto, Antonio; Deisboeck, Thomas S

2014-10-24

Pumping protons across a membrane was a critical step at the origin of life on earth, and it is still performed in all living organisms, including in human cells. Proton pumping is paramount to keep normal cells alive, e.g. for lysosomal digestion and for preparing peptides for immune recognition, but it goes awry in cancer cells. They acidify their microenvironment hence membrane voltage is lowered, which in turn induces cell proliferation, a hallmark of cancer. Proton pumping is achieved by means of rotary motors, namely vacuolar ATPases (V-ATPase), which are present at many of the multiple cellular interfaces. Therefore, we undertook an examination of the thermodynamic properties of V-ATPases. The principal result is that the V-ATPase-mediated control of the cell membrane potential and the related and consequent environmental pH can potentially represent a valuable support strategy for anticancer therapies. A constructal theory approach is used as a new viewpoint to study how V-ATPase can be modulated for therapeutic purposes. In particular, V-ATPase can be regulated by using external fields, such as electromagnetic fields, and a theoretical approach has been introduced to quantify the appropriate field strength and frequency for this new adjuvant therapeutic strategy.

Conformational change during photocycle of bacteriorhodopsin and its proton-pumping mechanism.

PubMed

Chou, K C

1993-06-01

Based on the recent finding on the structural difference of seven helix bundles in the all-trans and 13-cis bacteriorhodopsins, the distances among the key groups performing the function of proton translocation as well as their microenvironments have been investigated. Consequently, a pore-gated model was proposed for the light-driven proton-pumping mechanism of bacteriorhodopsin. According to this model, the five double-bounded polyene chain in retinal chromophore can be phenomenologically likened to a molecular "lever," whose one end links to a "piston" (the beta-ionone ring) and the other end to a pump "relay station" (the Schiff base). During the photocycle of bacteriorhodopsin, the molecular "lever" is moving up and down as marked by the position change of the "piston," so as to trigger the gate of pore to open and close alternately. When the "piston" is up, the pore-controlled gate is open so that the water channel from Asp-96 to the Schiff base and that from the Schiff base to Asp-85 is established; when the "piston" is down, the pore-controlled gate is closed and the water channels for proton transportation in both the cytoplasmic half and extracellular half are blocked. The current model allows a consistent interpretation of a great deal of experimental data and also provides a useful basis for further investigating the mechanism of proton pumping by bacteriorhodopsin.

Conformational coupling between the active site and residues within the K(C)-channel of the Vibrio cholerae cbb3-type (C-family) oxygen reductase.

PubMed

Ahn, Young O; Mahinthichaichan, Paween; Lee, Hyun Ju; Ouyang, Hanlin; Kaluka, Daniel; Yeh, Syun-Ru; Arjona, Davinia; Rousseau, Denis L; Tajkhorshid, Emad; Adelroth, Pia; Gennis, Robert B

2014-10-21

The respiratory chains of nearly all aerobic organisms are terminated by proton-pumping heme-copper oxygen reductases (HCOs). Previous studies have established that C-family HCOs contain a single channel for uptake from the bacterial cytoplasm of all chemical and pumped protons, and that the entrance of the K(C)-channel is a conserved glutamate in subunit III. However, the majority of the K(C)-channel is within subunit I, and the pathway from this conserved glutamate to subunit I is not evident. In the present study, molecular dynamics simulations were used to characterize a chain of water molecules leading from the cytoplasmic solution, passing the conserved glutamate in subunit III and extending into subunit I. Formation of the water chain, which controls the delivery of protons to the K(C)-channel, was found to depend on the conformation of Y241(Vc), located in subunit I at the interface with subunit III. Mutations of Y241(Vc) (to A/F/H/S) in the Vibrio cholerae cbb3 eliminate catalytic activity, but also cause perturbations that propagate over a 28-Å distance to the active site heme b3. The data suggest a linkage between residues lining the K(C)-channel and the active site of the enzyme, possibly mediated by transmembrane helix α7, which contains both Y241(Vc) and the active site cross-linked Y255(Vc), as well as two CuB histidine ligands. Other mutations of residues within or near helix α7 also perturb the active site, indicating that this helix is involved in modulation of the active site of the enzyme.

Proteorhodopsins: an array of physiological roles?

PubMed

Fuhrman, Jed A; Schwalbach, Michael S; Stingl, Ulrich

2008-06-01

Metagenomic analyses have revealed widespread and diverse retinal-binding rhodopsin proteins (named proteorhodopsins) among numerous marine bacteria and archaea, which has challenged the notion that solar energy can only enter marine ecosystems by chlorophyll-based photosynthesis. Most marine proteorhodopsins share structural and functional similarities with archaeal bacteriorhodopsins, which generate proton motive force via light-activated proton pumping, thereby ultimately powering ATP production. This suggests an energetic role for proteorhodopsins. However, results from a growing number of investigations do not readily fit this model, which indicates that proteorhodopsins could have a range of physiological functions.

MitoQ regulates autophagy by inducing a pseudo-mitochondrial membrane potential

PubMed Central

Sun, Chao; Liu, Xiongxiong; Di, Cuixia; Wang, Zhenhua; Mi, Xiangquan; Liu, Yang; Zhao, Qiuyue; Mao, Aihong; Chen, Weiqiang; Gan, Lu; Zhang, Hong

2017-01-01

ABSTRACT During the process of oxidative phosphorylation, protons are pumped into the mitochondrial intermembrane space to establish a mitochondrial membrane potential (MMP). The electrochemical gradient generated allows protons to return to the matrix through the ATP synthase complex and generates ATP in the process. MitoQ is a lipophilic cationic drug that is adsorbed to the inner mitochondrial membrane; however, the cationic moiety of MitoQ remains in the intermembrane space. We found that the positive charges in MitoQ inhibited the activity of respiratory chain complexes I, III, and IV, reduced proton production, and decreased oxygen consumption. Therefore, a pseudo-MMP (PMMP) was formed via maintenance of exogenous positive charges. Proton backflow was severely impaired, leading to a decrease in ATP production and an increase in AMP production. Excess AMP activates AMP kinase, which inhibits the MTOR (mechanistic target of rapamycin) pathway and induces macroautophagy/autophagy. Therefore, we conclude that MitoQ increases PMMP via proton displacement with exogenous positive charges. In addition, PMMP triggered autophagy in hepatocellular carcinoma HepG2 cells via modification of mitochondrial bioenergetics pathways. PMID:28121478

MitoQ regulates autophagy by inducing a pseudo-mitochondrial membrane potential.

PubMed

Sun, Chao; Liu, Xiongxiong; Di, Cuixia; Wang, Zhenhua; Mi, Xiangquan; Liu, Yang; Zhao, Qiuyue; Mao, Aihong; Chen, Weiqiang; Gan, Lu; Zhang, Hong

2017-04-03

During the process of oxidative phosphorylation, protons are pumped into the mitochondrial intermembrane space to establish a mitochondrial membrane potential (MMP). The electrochemical gradient generated allows protons to return to the matrix through the ATP synthase complex and generates ATP in the process. MitoQ is a lipophilic cationic drug that is adsorbed to the inner mitochondrial membrane; however, the cationic moiety of MitoQ remains in the intermembrane space. We found that the positive charges in MitoQ inhibited the activity of respiratory chain complexes I, III, and IV, reduced proton production, and decreased oxygen consumption. Therefore, a pseudo-MMP (PMMP) was formed via maintenance of exogenous positive charges. Proton backflow was severely impaired, leading to a decrease in ATP production and an increase in AMP production. Excess AMP activates AMP kinase, which inhibits the MTOR (mechanistic target of rapamycin) pathway and induces macroautophagy/autophagy. Therefore, we conclude that MitoQ increases PMMP via proton displacement with exogenous positive charges. In addition, PMMP triggered autophagy in hepatocellular carcinoma HepG2 cells via modification of mitochondrial bioenergetics pathways.

The management of gastro-oesophageal reflux disease

PubMed Central

Keung, Charlotte; Hebbard, Geoffrey

2016-01-01

SUMMARY If there are no features of serious disease, suspected gastro-oesophageal reflux disease can be initially managed with a trial of a proton pump inhibitor for 4–8 weeks. This should be taken 30–60 minutes before food for optimal effect. Once symptoms are controlled, attempt to withdraw acid suppression therapy. If symptoms recur, use the minimum dose that controls symptoms. Patients who have severe erosive oesophagitis, scleroderma oesophagus or Barrett’s oesophagus require long-term treatment with a proton pump inhibitor. Lifestyle modification strategies can help gastro-oesophageal reflux disease. Weight loss has the strongest evidence for efficacy. Further investigation and a specialist referral are required if there is no response to proton pump inhibitor therapy. Atypical symptoms or signs of serious disease also need investigation. PMID:27041798

Proton storage site in bacteriorhodopsin: new insights from QM/MM simulations of microscopic pKa and infrared spectra

PubMed Central

Goyal, Puja; Ghosh, Nilanjan; Phatak, Prasad; Clemens, Maike; Gaus, Michael; Elstner, Marcus; Cui, Qiang

2011-01-01

Identifying the group that acts as the proton storage/loading site is a challenging but important problem for understanding the mechanism of proton pumping in biomolecular proton pumps, such as bacteriorhodopsin (bR) and cytochrome c oxidase. Recent experimental studies of bR propelled the idea that the proton storage/release group (PRG) in bR is not an amino acid but a water cluster embedded in the protein. We argue that this idea is at odds with our knowledge of protein electrostatics, since invoking the water cluster as PRG would require the protein to raise the pKa of a hydronium by almost 11 pKa units, which is difficult considering known cases of pKa shifts in proteins. Our recent QM/MM simulations suggested an alternative “intermolecular proton bond” model in which the stored proton is shared between two conserved Glu residues (194 and 204). Here we show that this model leads to microscopic pKa values consistent with available experimental data and the functional requirement of a PRG. Extensive QM/MM simulations also show that, independent of a number of technical issues, such as the influence of QM region size, starting x-ray structure and nuclear quantum effects, the “intermolecular proton bond” model is qualitatively consistent with available spectroscopic data. Potential of mean force calculations show explicitly that the stored proton strongly prefers the pair of Glu residues over the water cluster. The results and analyses help highlight the importance of considering protein electrostatics and provide arguments for why the “intermolecular proton bond” model is likely applicable to PRG in biomolecular proton pumps in general. PMID:21761868

Aspartate-Histidine Interaction in the Retinal Schiff Base Counterion of the Light-Driven Proton Pump of Exiguobacterium sibiricum†

PubMed Central

Balashov, S.P.; Petrovskaya, L.E.; Lukashev, E.P.; Imasheva, E.S.; Dioumaev, A.K.; Wang, J.M.; Sychev, S.V.; Dolgikh, D.A.; Rubin, A.B.; Kirpichnikov, M.P.; Lanyi, J.K.

2012-01-01

One of the distinctive features of eubacterial retinal based proton pumps, proteorhodopsins, xanthorhodopsin and others, is hydrogen bonding of the key aspartate residue, the counterion to the retinal Schiff base, to a histidine. We describe properties of the recently found eubacterium proton pump from Exiguobacterium sibiricum (named ESR) expressed in E. coli, especially features that depend on Asp-His interaction, the protonation state of the key aspartate, Asp85, and its ability to accept proton from the Schiff base during the photocycle. Proton pumping by liposomes and E. coli cells containing ESR occurs in a broad pH range above pH 4.5. Large light-induced pH changes indicate that ESR is a potent proton pump. Replacement of His57 with methionine or asparagine strongly affects the pH dependent properties of ESR. In the H57M mutant a dramatic decrease in the quantum yield of chromophore fluorescence emission and a 45 nm blue shift of the absorption maximum upon raising the pH from 5 to 8 indicates deprotonation of the counterion with a pKa of 6.3, which is also the pKa at which the M intermediate is observed in the photocycle of the protein solubilized in detergent (DDM). This is in contrast with the wild type protein, in which the same experiments show that the major fraction of Asp85 is deprotonated at pH > 3 and that it protonates only at low pH, with a pKa of 2.3. The M intermediate in the wild type photocycle accumulates only at high pH, with an apparent pKa of 9 from deprotonation of a residue interacting with Asp85, presumably His57. In liposomes reconstituted with ESR the pKas for M formation and spectral shifts are 2–3 pH units lower than in DDM. The distinctively different pH dependencies of the protonation of Asp85 and the accumulation of the M intermediate in the wild type protein vs. the H57M mutant indicate that there is strong Asp-His interaction, which substantially lowers the pKa of Asp85 by stabilizing its deprotonated state. PMID:22738070

Why are patients prescribed proton pump inhibitors? Retrospective analysis of link between morbidity and prescribing in the General Practice Research Database

PubMed Central

Bashford, James N R; Norwood, Jeff; Chapman, Stephen R

1998-01-01

Objectives: To establish the relation between new prescriptions for proton pump inhibitors and recorded upper gastrointestinal morbidity within a large computerised general practitioner database. Design: Retrospective survey of morbidity and prescribing data linked to new prescriptions for proton pump inhibitors and comparison with licensed indications between 1991 and 1995. Setting: General Practice Research Database and prescribing analysis and cost (PACT) data for the former West Midlands region. Subjects: Information for 612 700 patients in the General Practice Research Database. Anonymous PACT data for all general practitioners in West Midlands region. Main outcome measures: Diagnostic codes linked to the first prescriptions issued for proton pump inhibitors; relation between new prescriptions and licensed indications; yearly change in ratio of new to repeat prescriptions and prescribing volumes measured as defined daily doses. Results: Oesophagitis was the commonest recorded indication in 1991, accounting for 31% of new prescriptions, but was third in 1995 (14%). During the study new prescriptions increased substantially, especially for duodenal disease (780%) and non-ulcer dyspepsia (690%). In 1995 non-specific morbidity accounted for 46% of new prescriptions. The total volume of prescribing rose 10-fold between 1991 and 1995, when repeat prescribing accounted for 77% of the total. Conclusions: Changes in recorded morbidity associated with new prescriptions of proton pump inhibitors did not necessarily reflect changes in licensed indications. Although general practitioners seemed to respond to changes in licensing, particularly for duodenal and gastric disease, prescribing for unlicensed indications non-ulcer dyspepsia and non-specific abdominal pain increased. Key messages There has been much speculation about the reasons behind the substantial rise in prescribing of proton pump inhibitors, especially their use for minor symptoms. We used the General Practitioner Research Database for the former West Midlands region to show that the volume of proton pump inhibitor prescribing rose 10-fold between 1992 and 1995 and repeat prescribing had risen to 77% of the volume by 1995 Prescribing for uncomplicated dyspepsia and non-specific abdominal symptoms, which were outside the licensed indications, accounted for 46% of new prescribing by 1995 The proportion of prescribing for the licensed indication of oesophagitis fell during the study, but that for duodenal ulceration increased in line with the expansion of licensed indications Analysis of PACT data showed similar prescribing trends to those found with the General Practitioner Research Database PMID:9703528

Proton pump inhibitors versus histamine 2 receptor antagonists for stress ulcer prophylaxis in critically ill patients: a systematic review and meta-analysis.

PubMed

Alhazzani, Waleed; Alenezi, Farhan; Jaeschke, Roman Z; Moayyedi, Paul; Cook, Deborah J

2013-03-01

Critically ill patients may develop bleeding caused by stress ulceration. Acid suppression is commonly prescribed for patients at risk of stress ulcer bleeding. Whether proton pump inhibitors are more effective than histamine 2 receptor antagonists is unclear. To determine the efficacy and safety of proton pump inhibitors vs. histamine 2 receptor antagonists for the prevention of upper gastrointestinal bleeding in the ICU. We searched Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, ACPJC, CINHAL, online trials registries (clinicaltrials.gov, ISRCTN Register, WHO ICTRP), conference proceedings databases, and reference lists of relevant articles. Randomized controlled parallel group trials comparing proton pump inhibitors to histamine 2 receptor antagonists for the prevention of upper gastrointestinal bleeding in critically ill patients, published before March 2012. Two reviewers independently applied eligibility criteria, assessed quality, and extracted data. The primary outcomes were clinically important upper gastrointestinal bleeding and overt upper gastrointestinal bleeding; secondary outcomes were nosocomial pneumonia, ICU mortality, ICU length of stay, and Clostridium difficile infection. Trial authors were contacted for additional or clarifying information. Fourteen trials enrolling a total of 1,720 patients were included. Proton pump inhibitors were more effective than histamine 2 receptor antagonists at reducing clinically important upper gastrointestinal bleeding (relative risk 0.36; 95% confidence interval 0.19-0.68; p = 0.002; I = 0%) and overt upper gastrointestinal bleeding (relative risk 0.35; 95% confidence interval 0.21-0.59; p < 0.0001; I = 15%). There were no differences between proton pump inhibitors and histamine 2 receptor antagonists in the risk of nosocomial pneumonia (relative risk 1.06; 95% confidence interval 0.73-1.52; p = 0.76; I = 0%), ICU mortality (relative risk 1.01; 95% confidence interval 0.83-1.24; p = 0.91; I = 0%), or ICU length of stay (mean difference -0.54 days; 95% confidence interval -2.20 to 1.13; p = 0.53; I = 39%). No trials reported on C. difficile infection. In critically ill patients, proton pump inhibitors seem to be more effective than histamine 2 receptor antagonists in preventing clinically important and overt upper gastrointestinal bleeding. The robustness of this conclusion is limited by the trial methodology, differences between lower and higher quality trials, sparse data, and possible publication bias. We observed no differences between drugs in the risk of pneumonia, death, or ICU length of stay.

Formation of M-Like Intermediates in Proteorhodopsin in Alkali Solutions (pH ≥ ∼8.5) Where the Proton Release Occurs First in Contrast to the Sequence at Lower pH.

PubMed

Tamogami, Jun; Sato, Keitaro; Kurokawa, Sukuna; Yamada, Takumi; Nara, Toshifumi; Demura, Makoto; Miyauchi, Seiji; Kikukawa, Takashi; Muneyuki, Eiro; Kamo, Naoki

2016-02-23

Proteorhodopsin (PR) is an outward light-driven proton pump observed in marine eubacteria. Despite many structural and functional similarities to bacteriorhodopsin (BR) in archaea, which also acts as an outward proton pump, the mechanism of the photoinduced proton release and uptake is different between two H(+)-pumps. In this study, we investigated the pH dependence of the photocycle and proton transfer in PR reconstituted with the phospholipid membrane under alkaline conditions. Under these conditions, as the medium pH increased, a blue-shifted photoproduct (defined as Ma), which is different from M, with a pKa of ca. 9.2 was produced. The sequence of the photoinduced proton uptake and release during the photocycle was inverted with the increase in pH. A pKa value of ca. 9.5 was estimated for this inversion and was in good agreement with the pKa value of the formation of Ma (∼ 9.2). In addition, we measured the photoelectric current generated by PRs attached to a thin polymer film at varying pH. Interestingly, increases in the medium pH evoked bidirectional photocurrents, which may imply a possible reversal of the direction of the proton movement at alkaline pH. On the basis of these findings, a putative photocycle and proton transfer scheme in PR under alkaline pH conditions was proposed.

Proteorhodopsin-Like Genes Present in Thermoacidophilic High-Mountain Microbial Communities

PubMed Central

Bohorquez, Laura C.; Ruiz-Pérez, Carlos A.

2012-01-01

Proteorhodopsin (PR) sequences were PCR amplified from three Andean acidic hot spring samples. These sequences were similar to freshwater and marine PRs and they contained residues indicative of proton-pumping activity and of proteins that absorb green light; these findings suggest that PRs might contribute to cellular metabolism in these habitats. PMID:22941077

The Mechanism of Guard Cell Movement

ERIC Educational Resources Information Center

Marques, M.; Arrabaca, J.; Chagas, I.

2005-01-01

Leaves of higher terrestrial plants have small pores--stomata--responsible for gas exchange. The opening of each stoma results from the osmotic uptake of water by two specialised cells--the guard cells. Because of the involvement in this mechanism of ATPase-proton pumps and active transport of ions across membranes, we have designed an Exploring…

Molecular cloning of the plasma membrane H(+)-ATPase from Kluyveromyces lactis: a single nucleotide substitution in the gene confers ethidium bromide resistance and deficiency in K+ uptake.

PubMed Central

Miranda, M; Ramírez, J; Peña, A; Coria, R

1995-01-01

A Kluyveromyces lactis strain resistant to ethidium bromide and deficient in potassium uptake was isolated. Studies on the proton-pumping activity of the mutant strain showed that a decreased H(+)-ATPase specific activity was responsible for the observed phenotypes. The putative K. lactis PMA1 gene encoding the plasma membrane H(+)-ATPase was cloned by its ability to relieve the potassium transport defect of this mutant and by reversing its resistance to ethidium bromide. Its deduced amino acid sequence predicts a protein 899 residues long that is structurally colinear in its full length to H(+)-ATPases cloned from different yeasts, except for the presence of a variable N-terminal domain. By PCR-mediated amplification, we identified a transition from G to A that rendered the substitution of the fully conserved methionine at position 699 by isoleucine. We attribute to this amino acid change the low capacity of the mutant H(+)-ATPase to pump out protons. PMID:7730265

Time-resolved generation of membrane potential by ba3 cytochrome c oxidase from Thermus thermophilus coupled to single electron injection into the O and OH states.

PubMed

Siletsky, Sergey A; Belevich, Ilya; Belevich, Nikolai P; Soulimane, Tewfik; Wikström, Mårten

2017-11-01

Two electrogenic phases with characteristic times of ~14μs and ~290μs are resolved in the kinetics of membrane potential generation coupled to single-electron reduction of the oxidized "relaxed" O state of ba 3 oxidase from T. thermophilus (O→E transition). The rapid phase reflects electron redistribution between Cu A and heme b. The slow phase includes electron redistribution from both Cu A and heme b to heme a 3 , and electrogenic proton transfer coupled to reduction of heme a 3 . The distance of proton translocation corresponds to uptake of a proton from the inner water phase into the binuclear center where heme a 3 is reduced, but there is no proton pumping and no reduction of Cu B . Single-electron reduction of the oxidized "unrelaxed" state (O H →E H transition) is accompanied by electrogenic reduction of the heme b/heme a 3 pair by Cu A in a "fast" phase (~22μs) and transfer of protons in "middle" and "slow" electrogenic phases (~0.185ms and ~0.78ms) coupled to electron redistribution from the heme b/heme a 3 pair to the Cu B site. The "middle" and "slow" electrogenic phases seem to be associated with transfer of protons to the proton-loading site (PLS) of the proton pump, but when all injected electrons reach Cu B the electronic charge appears to be compensated by back-leakage of the protons from the PLS into the binuclear site. Thus proton pumping occurs only to the extent of ~0.1 H + /e - , probably due to the formed membrane potential in the experiment. Copyright © 2017 Elsevier B.V. All rights reserved.

Pancreatic bicarbonate secretion involves two proton pumps.

PubMed

Novak, Ivana; Wang, Jing; Henriksen, Katrine L; Haanes, Kristian A; Krabbe, Simon; Nitschke, Roland; Hede, Susanne E

2011-01-07

Pancreas secretes fluid rich in digestive enzymes and bicarbonate. The alkaline secretion is important in buffering of acid chyme entering duodenum and for activation of enzymes. This secretion is formed in pancreatic ducts, and studies to date show that plasma membranes of duct epithelium express H(+)/HCO(3)(-) transporters, which depend on gradients created by the Na(+)/K(+)-ATPase. However, the model cannot fully account for high-bicarbonate concentrations, and other active transporters, i.e. pumps, have not been explored. Here we show that pancreatic ducts express functional gastric and non-gastric H(+)-K(+)-ATPases. We measured intracellular pH and secretion in small ducts isolated from rat pancreas and showed their sensitivity to H(+)-K(+) pump inhibitors and ion substitutions. Gastric and non-gastric H(+)-K(+) pumps were demonstrated on RNA and protein levels, and pumps were localized to the plasma membranes of pancreatic ducts. Quantitative analysis of H(+)/HCO(3)(-) and fluid transport shows that the H(+)-K(+) pumps can contribute to pancreatic secretion in several species. Our results call for revision of the bicarbonate transport physiology in pancreas, and most likely other epithelia. Furthermore, because pancreatic ducts play a central role in several pancreatic diseases, it is of high relevance to understand the role of H(+)-K(+) pumps in pathophysiology.

A new hypothesis on the simultaneous direct and indirect proton pump mechanisms in NADH-quinone oxidoreductase (complex I)

PubMed Central

Ohnishi, Tomoko; Nakamaru-Ogiso, Eiko; Ohnishi, S. Tsuyoshi

2010-01-01

Recently, Sazanov’s group reported the X-ray structure of whole complex I [Nature, 465, 441 (2010)], which presented a strong clue for a “piston-like” structure as a key element in an “indirect” proton pump. We have studied the NuoL subunit which has a high sequence similarity to Na+/H+ antiporters, as do the NuoM and N subunits. We constructed 27 site-directed NuoL mutants. Our data suggest that the H+/e− stoichiometry seems to have decreased from (4H+/2e−) in the wild-type to approximately (3H+/2e−) in NuoL mutants. We propose a revised hypothesis that each of the “direct” and the “indirect” proton pumps transports 2H+ per 2e−. PMID:20816962

[Proton pump inhibitor - side effects and complications of long-term proton pump inhibitor administration].

PubMed

Ueberschaer, Hendrik; Allescher, Hans-Dieter

2017-01-01

Proton Pump Inhibitors are among the most common drugs taken. The indication is for treatment of heartburn, reflux disease, prophylaxis and treatment of peptic ulcers, in combination with NSAIDs and steroids as well as H. pylori-eradication. PPI's are widely used, even with non-specific symptoms. This certainly has to do with good tolerability and a previously considered low side effect profile. At the moment, there is growing evidence that the long-term intake of PPI's may not be as safe as assumed. In addition to interactions with some drugs, including platelet aggregation inhibitors, recent studies have shown an increased risk of myocardial infarction, interstitial nephritis, chronic renal injury, infections, vitamin deficiencies and electrolyte shifts as well developing dementia. © Georg Thieme Verlag KG Stuttgart · New York.

Voltage Dependence of Proton Pumping by Bacteriorhodopsin Mutants with Altered Lifetime of the M Intermediate

PubMed Central

Geibel, Sven; Lörinczi, Èva; Bamberg, Ernst; Friedrich, Thomas

2013-01-01

The light-driven proton pump bacteriorhodopsin (BR) from Halobacterium salinarum is tightly regulated by the [H+] gradient and transmembrane potential. BR exhibits optoelectric properties, since spectral changes during the photocycle are kinetically controlled by voltage, which predestines BR for optical storage or processing devices. BR mutants with prolonged lifetime of the blue-shifted M intermediate would be advantageous, but the optoelectric properties of such mutants are still elusive. Using expression in Xenopus oocytes and two-electrode voltage-clamping, we analyzed photocurrents of BR mutants with kinetically destabilized (F171C, F219L) or stabilized (D96N, D96G) M intermediate in response to green light (to probe H+ pumping) and blue laser flashes (to probe accumulation/decay of M). These mutants have divergent M lifetimes. As for BR-WT, this strictly correlates with the voltage dependence of H+ pumping. BR-F171C and BR-F219L showed photocurrents similar to BR-WT. Yet, BR-F171C showed a weaker voltage dependence of proton pumping. For both mutants, blue laser flashes applied during and after green-light illumination showed reduced M accumulation and shorter M lifetime. In contrast, BR-D96G and BR-D96N exhibited small photocurrents, with nonlinear current-voltage curves, which increased strongly in the presence of azide. Blue laser flashes showed heavy M accumulation and prolonged M lifetime, which accounts for the strongly reduced H+ pumping rate. Hyperpolarizing potentials augmented these effects. The combination of M-stabilizing and -destabilizing mutations in BR-D96G/F171C/F219L (BR-tri) shows that disruption of the primary proton donor Asp-96 is fatal for BR as a proton pump. Mechanistically, M destabilizing mutations cannot compensate for the disruption of Asp-96. Accordingly, BR-tri and BR-D96G photocurrents were similar. However, BR-tri showed negative blue laser flash-induced currents even without actinic green light, indicating that Schiff base deprotonation in BR-tri exists in the dark, in line with previous spectroscopic investigations. Thus, M-stabilizing mutations, including the triple mutation, drastically interfere with electrochemical H+ gradient generation. PMID:24019918

Potential of proton-pumping rhodopsins: engineering photosystems into microorganisms.

PubMed

Claassens, Nico J; Volpers, Michael; dos Santos, Vitor A P Martins; van der Oost, John; de Vos, Willem M

2013-11-01

A wide range of proton-pumping rhodopsins (PPRs) have been discovered in recent years. Using a synthetic biology approach, PPR photosystems with different features can be easily introduced in nonphotosynthetic microbial hosts. PPRs can provide hosts with the ability to harvest light and drive the sustainable production of biochemicals or biofuels. PPRs use light energy to generate an outward proton flux, and the resulting proton motive force can subsequently power cellular processes. Recently, the introduction of PPRs in microbial production hosts has successfully led to light-driven biotechnological conversions. In this review, we discuss relevant features of natural PPRs, evaluate reported biotechnological applications of microbial production hosts equipped with PPRs, and provide an outlook on future developments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Recent effectiveness of proton pump inhibitors for severe reflux esophagitis: the first multicenter prospective study in Japan.

PubMed

Mizuno, Hideki; Matsuhashi, Nobuyuki; Sakaguchi, Masahiro; Inoue, Syuji; Nakada, Koji; Higuchi, Kazuhide; Haruma, Ken; Joh, Takashi

2015-11-01

Proton pump inhibitors are the first-line treatment for reflux esophagitis. Because severe reflux esophagitis has very low prevalence in Japan, little is known about the effectiveness of proton pump inhibitors in these patients. This prospective multicenter study assessed the effectiveness of proton pump inhibitors for severe reflux esophagitis in Japan. Patients with modified Los Angeles grade C or D reflux esophagitis were treated with daily omeprazole (10 or 20 mg), lansoprazole (15 or 30 mg), or rabeprazole (10, 20, or 40 mg) for 8 weeks. Healing was assessed endoscopically, with questionnaires administered before and after treatment to measure the extent of reflux and dyspepsia symptoms. Factors affecting healing rates, including patient characteristics and endoscopic findings, were analyzed. Of the 115 patients enrolled, 64 with grade C and 19 with grade D reflux esophagitis completed the study. The healing rate was 67.5% (56/83), with 15 of the other 27 patients (55.6%) improving to grade A or B. No patient characteristic or endoscopic comorbidity was significantly associated with healing rate. Reflux and dyspepsia symptoms improved significantly with treatment. The low healing rate suggests the need of endoscopic examination to assess healing of reflux esophagitis at the end of therapy. (UMIN000005271).

Proton Pump Inhibition Increases Rapid Eye Movement Sleep in the Rat

PubMed Central

Jha, Sushil K.

2014-01-01

Increased bodily CO2 concentration alters cellular pH as well as sleep. The proton pump, which plays an important role in the homeostatic regulation of cellular pH, therefore, may modulate sleep. We investigated the effects of the proton pump inhibitor “lansoprazole” on sleep-wakefulness. Male Wistar rats were surgically prepared for chronic polysomnographic recordings. Two different doses of lansoprazole (low: 1 mg/kg; high: 10 mg/kg) were injected intraperitoneally in the same animal (n = 7) and sleep-wakefulness was recorded for 6 hrs. The changes in sleep-wakefulness were compared statistically. Percent REM sleep amount in the vehicle and lansoprazole low dose groups was 9.26 ± 1.03 and 9.09 ± 0.54, respectively, which increased significantly in the lansoprazole high dose group by 31.75% (from vehicle) and 34.21% (from low dose). Also, REM sleep episode numbers significantly increased in lansoprazole high dose group. Further, the sodium-hydrogen exchanger blocker “amiloride” (10 mg/kg; i.p.) (n = 5) did not alter sleep-wake architecture. Our results suggest that the proton pump plays an important role in REM sleep modulation and supports our view that REM sleep might act as a sentinel to help maintain normal CO2 level for unperturbed sleep. PMID:24701564

ATP4A gene regulatory network for fine-tuning of proton pump and ion channels.

PubMed

Singh, Vijai; Mani, Indra; Chaudhary, Dharmendra Kumar

2013-06-01

The ATP4A encodes α subunit of H(+), K(+)-ATPase that contains catalytic sites of the enzyme forming pores through cell membrane which allows the ion transport. H(+), K(+)-ATPase is a membrane bound P-type ATPase enzyme which is found on the surface of parietal cells and uses the energy derived from each cycle of ATP hydrolysis that can help in exchanging ions (H(+), K(+) and Cl(-)) across the cell membrane secreting acid into the gastric lumen. The 3-D model of α-subunit of H(+), K(+)-ATPase was generated by homology modeling. It was evaluated and validated on the basis of free energies and amino acid residues. The inhibitor binding amino acid active pockets were identified in the 3-D model by molecular docking. The two drugs Omeprazole and Rabeprazole were found more potent interactions with generated model of α-subunit of H(+), K(+)-ATPase on the basis of their affinity between drug-protein interactions. We have generated ATP4A gene regulatory networks for interactions with other proteins which involved in regulation that can help in fine-tuning of proton pump and ion channels. These findings provide a new dimension for discovery and development of proton pump inhibitors and gene regulation of the ATPase. It can be helpful in better understanding of human physiology and also using synthetic biology strategy for reprogramming of parietal cells for control of gastric ulcers.

The therapeutic journey of benzimidazoles: a review.

PubMed

Bansal, Yogita; Silakari, Om

2012-11-01

Presence of benzimidazole nucleus in numerous categories of therapeutic agents such as antimicrobials, antivirals, antiparasites, anticancer, anti-inflammatory, antioxidants, proton pump inhibitors, antihypertensives, anticoagulants, immunomodulators, hormone modulators, CNS stimulants as well as depressants, lipid level modulators, antidiabetics, etc. has made it an indispensable anchor for development of new therapeutic agents. Varied substitutents around the benzimidazole nucleus have provided a wide spectrum of biological activities. Importance of this nucleus in some activities like, Angiotensin I (AT(1)) receptor antagonism and proton-pump inhibition is reviewed separately in literature. Even some very short reviews on biological importance of this nucleus are also known in literature. However, owing to fast development of new drugs possessing benzimidazole nucleus many research reports are generated in short span of time. So, there is a need to couple the latest information with the earlier information to understand the current status of benzimidazole nucleus in medicinal chemistry research. In the present review, various derivatives of benzimidazole with different pharmacological activities are described on the basis of substitution pattern around the nucleus with an aim to help medicinal chemists for developing an SAR on benzimidazole derived compounds for each activity. This discussion will further help in the development of novel benzimidazole compounds. Copyright © 2012 Elsevier Ltd. All rights reserved.

Photoluminescence of radiation-induced color centers in lithium fluoride thin films for advanced diagnostics of proton beams

NASA Astrophysics Data System (ADS)

Piccinini, M.; Ambrosini, F.; Ampollini, A.; Picardi, L.; Ronsivalle, C.; Bonfigli, F.; Libera, S.; Nichelatti, E.; Vincenti, M. A.; Montereali, R. M.

2015-06-01

Systematic irradiation of thermally evaporated 0.8 μm thick polycrystalline lithium fluoride films on glass was performed by proton beams of 3 and 7 MeV energies, produced by a linear accelerator, in a fluence range from 1011 to 1015 protons/cm2. The visible photoluminescence spectra of radiation-induced F2 and F3+ laser active color centers, which possess almost overlapping absorption bands at about 450 nm, were measured under laser pumping at 458 nm. On the basis of simulations of the linear energy transfer with proton penetration depth in LiF, it was possible to obtain the behavior of the measured integrated photoluminescence intensity of proton irradiated LiF films as a function of the deposited dose. The photoluminescence signal is linearly dependent on the deposited dose in the interval from 103 to about 106 Gy, independently from the used proton energies. This behavior is very encouraging for the development of advanced solid state radiation detectors based on optically transparent LiF thin films for proton beam diagnostics and two-dimensional dose mapping.

pH-dependent antitumor activity of proton pump inhibitors against human melanoma is mediated by inhibition of tumor acidity.

PubMed

De Milito, Angelo; Canese, Rossella; Marino, Maria Lucia; Borghi, Martina; Iero, Manuela; Villa, Antonello; Venturi, Giulietta; Lozupone, Francesco; Iessi, Elisabetta; Logozzi, Mariantonia; Della Mina, Pamela; Santinami, Mario; Rodolfo, Monica; Podo, Franca; Rivoltini, Licia; Fais, Stefano

2010-07-01

Metastatic melanoma is associated with poor prognosis and still limited therapeutic options. An innovative treatment approach for this disease is represented by targeting acidosis, a feature characterizing tumor microenvironment and playing an important role in cancer malignancy. Proton pump inhibitors (PPI), such as esomeprazole (ESOM) are prodrugs functionally activated by acidic environment, fostering pH neutralization by inhibiting proton extrusion. We used human melanoma cell lines and xeno-transplated SCID mice to provide preclinical evidence of ESOM antineoplastic activity. Human melanoma cell lines, characterized by different mutation and signaling profiles, were treated with ESOM in different pH conditions and evaluated for proliferation, viability and cell death. SCID mice engrafted with human melanoma were used to study ESOM administration effects on tumor growth and tumor pH by magnetic resonance spectroscopy (MRS). ESOM inhibited proliferation of melanoma cells in vitro and induced a cytotoxicity strongly boosted by low pH culture conditions. ESOM-induced tumor cell death occurred via rapid intracellular acidification and activation of several caspases. Inhibition of caspases activity by pan-caspase inhibitor z-vad-fmk completely abrogated the ESOM-induced cell death. ESOM administration (2.5 mg kg(-1)) to SCID mice engrafted with human melanoma reduced tumor growth, consistent with decrease of proliferating cells and clear reduction of pH gradients in tumor tissue. Moreover, systemic ESOM administration dramatically increased survival of human melanoma-bearing animals, in absence of any relevant toxicity. These data show preclinical evidence supporting the use of PPI as novel therapeutic strategy for melanoma, providing the proof of concept that PPI target human melanoma modifying tumor pH gradients.

Amino Acid Availability Modulates Vacuolar H+-ATPase Assembly*

PubMed Central

Stransky, Laura A.; Forgac, Michael

2015-01-01

The vacuolar H+-ATPase (V-ATPase) is an ATP-dependent proton pump composed of a peripheral ATPase domain (V1) and a membrane-integral proton-translocating domain (V0) and is involved in many normal and disease processes. An important mechanism of regulating V-ATPase activity is reversible assembly of the V1 and V0 domains. Increased assembly in mammalian cells occurs under various conditions and has been shown to involve PI3K. The V-ATPase is necessary for amino acid-induced activation of mechanistic target of rapamycin complex 1 (mTORC1), which is important in controlling cell growth in response to nutrient availability and growth signals. The V-ATPase undergoes amino acid-dependent interactions with the Ragulator complex, which is involved in recruitment of mTORC1 to the lysosomal membrane during amino acid sensing. We hypothesized that changes in the V-ATPase/Ragulator interaction might involve amino acid-dependent changes in V-ATPase assembly. To test this, we measured V-ATPase assembly by cell fractionation in HEK293T cells treated with and without amino acids. V-ATPase assembly increases upon amino acid starvation, and this effect is reversed upon readdition of amino acids. Lysosomes from amino acid-starved cells possess greater V-ATPase-dependent proton transport, indicating that assembled pumps are catalytically active. Amino acid-dependent changes in both V-ATPase assembly and activity are independent of PI3K and mTORC1 activity, indicating the involvement of signaling pathways distinct from those implicated previously in controlling assembly. By contrast, lysosomal neutralization blocks the amino acid-dependent change in assembly and reactivation of mTORC1 after amino acid starvation. These results identify an important new stimulus for controlling V-ATPase assembly. PMID:26378229

Modeling and design of light powered biomimicry micropump utilizing transporter proteins

NASA Astrophysics Data System (ADS)

Liu, Jin; Sze, Tsun-Kay Jackie; Dutta, Prashanta

2014-11-01

The creation of compact micropumps to provide steady flow has been an on-going challenge in the field of microfluidics. We present a mathematical model for a micropump utilizing Bacteriorhodopsin and sugar transporter proteins. This micropump utilizes transporter proteins as method to drive fluid flow by converting light energy into chemical potential. The fluid flow through a microchannel is simulated using the Nernst-Planck, Navier-Stokes, and continuity equations. Numerical results show that the micropump is capable of generating usable pressure. Designing parameters influencing the performance of the micropump are investigated including membrane fraction, lipid proton permeability, illumination, and channel height. The results show that there is a substantial membrane fraction region at which fluid flow is maximized. The use of lipids with low membrane proton permeability allows illumination to be used as a method to turn the pump on and off. This capability allows the micropump to be activated and shut off remotely without bulky support equipment. This modeling work provides new insights on mechanisms potentially useful for fluidic pumping in self-sustained bio-mimic microfluidic pumps. This work is supported in part by the National Science Fundation Grant CBET-1250107.

Halorhodopsin pumps Cl– and bacteriorhodopsin pumps protons by a common mechanism that uses conserved electrostatic interactions

PubMed Central

Gunner, M. R.

2014-01-01

Key mutations differentiate the functions of homologous proteins. One example compares the inward ion pump halorhodopsin (HR) and the outward proton pump bacteriorhodopsin (BR). Of the nine essential buried ionizable residues in BR, six are conserved in HR. However, HR changes three BR acids, D85 in a central cluster of ionizable residues, D96, nearer the intracellular, and E204, nearer the extracellular side of the membrane to the small, neutral amino acids T111, V122, and T230, respectively. In BR, acidic amino acids are stationary anions whose proton affinity is modulated by conformational changes, establishing a sequence of directed binding and release of protons. Multiconformation continuum electrostatics calculations of chloride affinity and residue protonation show that, in reaction intermediates where an acid is ionized in BR, a Cl– is bound to HR in a position near the deleted acid. In the HR ground state, Cl– binds tightly to the central cluster T111 site and weakly to the extracellular T230 site, recovering the charges on ionized BR-D85 and neutral E204 in BR. Imposing key conformational changes from the BR M intermediate into the HR structure results in the loss of Cl– from the central T111 site and the tight binding of Cl– to the extracellular T230 site, mirroring the changes that protonate BR-D85 and ionize E204 in BR. The use of a mobile chloride in place of D85 and E204 makes HR more susceptible to the environmental pH and salt concentrations than BR. These studies shed light on how ion transfer mechanisms are controlled through the interplay of protein and ion electrostatics. PMID:25362051

Nuclear-Pumped Lasers. [efficient conversion of energy liberated in nuclear reactions to coherent radiation

NASA Technical Reports Server (NTRS)

1979-01-01

The state of the art in nuclear pumped lasers is reviewed. Nuclear pumped laser modeling, nuclear volume and foil excitation of laser plasmas, proton beam simulations, nuclear flashlamp excitation, and reactor laser systems studies are covered.

Circulating aldosterone induces the apical accumulation of the proton pumping V-ATPase and increases proton secretion in clear cells in the caput epididymis.

PubMed

Roy, Jeremy W; Hill, Eric; Ruan, Ye Chun; Vedovelli, Luca; Păunescu, Teodor G; Brown, Dennis; Breton, Sylvie

2013-08-15

Clear cells express the vacuolar proton-pumping H(+)-ATPase (V-ATPase) and acidify the lumen of the epididymis, a process that is essential for male fertility. The renin-angiotensin-aldosterone system (RAAS) regulates fluid and electrolyte balance in the epididymis, and a previous study showed binding of aldosterone exclusively to epididymal clear cells (Hinton BT, Keefer DA. Steroid Biochem 23: 231-233, 1985). We examined here the role of aldosterone in the regulation of V-ATPase in the epididymis. RT-PCR showed expression of the mineralocorticoid receptor [MR; nuclear receptor subfamily 3, group C member 2 (NR3C2)] and 11-β-dehydrogenase isozyme 2 (HSD11β2) mRNAs specifically in clear cells, isolated by fluorescence-activated cell sorting from B1-enhanced green fluorescent protein (EGFP) mice. Tail vein injection of adult rats with aldosterone, 1,2-dioctanoyl-sn-glycerol (DOG), or 8-(4-chlorophenylthio)-cAMP (cpt-cAMP) induced V-ATPase apical membrane accumulation and extension of V-ATPase-labeled microvilli in clear cells in the caput epididymis but not in the cauda. V-ATPase activity was measured in EGFP-expressing clear cells using the intracellular pH (pHi)-sensing dye seminaphthorhodafluor-5F-5-(and 6)-carboxylic acid, acetoxymethyl ester acetate (SNARF-5F). Aldosterone induced a rapid increase in the rate of Na(+)- and bicarbonate-independent pHi recovery following an NH4Cl-induced acid load in clear cells isolated from the caput but not the cauda. This effect was abolished by concanamycin A, spironolactone, and chelerythrine but not myristoylated-protein kinase inhibitor (mPKI) or mifepristone. Thus aldosterone increases V-ATPase-dependent proton secretion in clear cells in the caput epididymis via MR/NR3C2 and PKC activation. This study, therefore, identifies aldosterone as an active member of the RAAS for the regulation of luminal acidification in the proximal epididymis.

A Conserved Asparagine in a P-type Proton Pump Is Required for Efficient Gating of Protons*

PubMed Central

Ekberg, Kira; Wielandt, Alex G.; Buch-Pedersen, Morten J.; Palmgren, Michael G.

2013-01-01

The minimal proton pumping machinery of the Arabidopsis thaliana P-type plasma membrane H+-ATPase isoform 2 (AHA2) consists of an aspartate residue serving as key proton donor/acceptor (Asp-684) and an arginine residue controlling the pKa of the aspartate. However, other important aspects of the proton transport mechanism such as gating, and the ability to occlude protons, are still unclear. An asparagine residue (Asn-106) in transmembrane segment 2 of AHA2 is conserved in all P-type plasma membrane H+-ATPases. In the crystal structure of the plant plasma membrane H+-ATPase, this residue is located in the putative ligand entrance pathway, in close proximity to the central proton donor/acceptor Asp-684. Substitution of Asn-106 resulted in mutant enzymes with significantly reduced ability to transport protons against a membrane potential. Sensitivity toward orthovanadate was increased when Asn-106 was substituted with an aspartate residue, but decreased in mutants with alanine, lysine, glutamine, or threonine replacement of Asn-106. The apparent proton affinity was decreased for all mutants, most likely due to a perturbation of the local environment of Asp-684. Altogether, our results demonstrate that Asn-106 is important for closure of the proton entrance pathway prior to proton translocation across the membrane. PMID:23420846

A conserved asparagine in a P-type proton pump is required for efficient gating of protons.

PubMed

Ekberg, Kira; Wielandt, Alex G; Buch-Pedersen, Morten J; Palmgren, Michael G

2013-04-05

The minimal proton pumping machinery of the Arabidopsis thaliana P-type plasma membrane H(+)-ATPase isoform 2 (AHA2) consists of an aspartate residue serving as key proton donor/acceptor (Asp-684) and an arginine residue controlling the pKa of the aspartate. However, other important aspects of the proton transport mechanism such as gating, and the ability to occlude protons, are still unclear. An asparagine residue (Asn-106) in transmembrane segment 2 of AHA2 is conserved in all P-type plasma membrane H(+)-ATPases. In the crystal structure of the plant plasma membrane H(+)-ATPase, this residue is located in the putative ligand entrance pathway, in close proximity to the central proton donor/acceptor Asp-684. Substitution of Asn-106 resulted in mutant enzymes with significantly reduced ability to transport protons against a membrane potential. Sensitivity toward orthovanadate was increased when Asn-106 was substituted with an aspartate residue, but decreased in mutants with alanine, lysine, glutamine, or threonine replacement of Asn-106. The apparent proton affinity was decreased for all mutants, most likely due to a perturbation of the local environment of Asp-684. Altogether, our results demonstrate that Asn-106 is important for closure of the proton entrance pathway prior to proton translocation across the membrane.

Light energy conservation processes in Halobacterium halobium cells

NASA Technical Reports Server (NTRS)

Bogomolni, R. A.

1977-01-01

Proton pumping driven by light or by respiration generates an electrochemical potential difference across the membrane in Halobacterium halobium. The pH changes induced by light or by respiration in cell suspensions are complicated by proton flows associated with the functioning of the cellular energy transducers. A proton-per-ATP ratio of about 3 is calculated from simultaneous measurements of phosphorylation and the proton inflow. This value is compatible with the chemiosmotic coupling hypothesis. The time course of the light-induced changes in membrane potential indicates that light-driven pumping increases a dark pre-existing potential of about 130 mV only by a small amount (20 to 30 mV). The complex kinetic features of the membrane potential changes do not closely follow those of the pH changes, which suggests that flows of ions other than protons are involved. A qualitative model consistent with the available data is presented.

A new hypothesis on the simultaneous direct and indirect proton pump mechanisms in NADH-quinone oxidoreductase (complex I).

PubMed

Ohnishi, Tomoko; Nakamaru-Ogiso, Eiko; Ohnishi, S Tsuyoshi

2010-10-08

Recently, Sazanov's group reported the X-ray structure of whole complex I [Nature, 465, 441 (2010)], which presented a strong clue for a "piston-like" structure as a key element in an "indirect" proton pump. We have studied the NuoL subunit which has a high sequence similarity to Na(+)/H(+) antiporters, as do the NuoM and N subunits. We constructed 27 site-directed NuoL mutants. Our data suggest that the H(+)/e(-) stoichiometry seems to have decreased from (4H(+)/2e(-)) in the wild-type to approximately (3H(+)/2e(-)) in NuoL mutants. We propose a revised hypothesis that each of the "direct" and the "indirect" proton pumps transports 2H(+) per 2e(-). Copyright © 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Fatal spontaneous Clostridium septicum gas gangrene: a possible association with iatrogenic gastric acid suppression.

PubMed

Wu, Yiru E; Baras, Alexander; Cornish, Toby; Riedel, Stefan; Burton, Elizabeth C

2014-06-01

The long-term use of proton pump inhibitors has been linked to an increased risk for the development of gastric polyps, hip fractures, pneumonia, and Clostridium difficile colitis. There is evidence that chronic acid suppression from long-term use of proton pump inhibitors poses some risk for the development of C difficile-associated diarrhea by decreasing the elimination of pathogenic microbes before reaching the lower gastrointestinal tract. Here we present a case of a 51-year-old woman with a recent history of abdominal pain and fever who presented to the emergency department with rapidly progressive spontaneous necrotizing fasciitis and gas gangrene and died within hours of presentation. Postmortem examination confirmed spreading tissue gas gangrene and myonecrosis. In addition, multiple intestinal ulcers containing Clostridium septicum were present at autopsy. This case illustrates a possible association between proton pump inhibitor therapy and fatal C septicum infection.

ZmPUMP encodes a fully functional monocot plant uncoupling mitochondrial protein whose affinity to fatty acid is increased with the introduction of a His pair at the second matrix loop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favaro, Regiane Degan; Borecky, Jiri; Colombi, Debora

Uncoupling proteins (UCPs) are specialized mitochondrial transporter proteins that uncouple respiration from ATP synthesis. In this study, cDNA encoding maize uncoupling protein (ZmPUMP) was expressed in Escherichia coli and recombinant ZmPUMP reconstituted in liposomes. ZmPUMP activity was associated with a linoleic acid (LA)-mediated H{sup +} efflux with K {sub m} of 56.36 {+-} 0.27 {mu}M and V {sub max} of 66.9 {mu}mol H{sup +} min{sup -1} (mg prot){sup -1}. LA-mediated H{sup +} fluxes were sensitive to ATP inhibition with K {sub i} of 2.61 {+-} 0.36 mM (at pH 7.2), a value similar to those for dicot UCPs. ZmPUMP wasmore » also used to investigate the importance of a histidine pair present in the second matrix loop of mammalian UCP1 and absent in plant UCPs. ZmPUMP with introduced His pair (Lys155His and Ala157His) displayed a 1.55-fold increase in LA-affinity while its activity remained unchanged. Our data indicate conserved properties of plant UCPs and suggest an enhancing but not essential role of the histidine pair in proton transport mechanism.« less

Physiological characterisation of the efflux pump system of antibiotic-susceptible and multidrug-resistant Enterobacter aerogenes.

PubMed

Martins, A; Spengler, G; Martins, M; Rodrigues, L; Viveiros, M; Davin-Regli, A; Chevalier, J; Couto, I; Pagès, J M; Amaral, L

2010-10-01

Enterobacter aerogenes predominates amongst Enterobacteriaceae species that are increasingly reported as producers of extended-spectrum beta-lactamases. Although this mechanism of resistance to beta-lactams is important, other mechanisms bestowing a multidrug-resistant (MDR) phenotype in this species are now well documented. Amongst these mechanisms is the overexpression of efflux pumps that extrude structurally unrelated antibiotics prior to their reaching their targets. Interestingly, although knowledge of the genetic background behind efflux pumps is rapidly advancing, few studies assess the physiological nature of the overall efflux pump system of this, or for that matter any other, bacterium. The study reported here evaluates physiologically the efflux pump system of an E. aerogenes ATCC reference as well as two strains whose MDR phenotypes are mediated by overexpressed efflux pumps. The activities of the efflux pumps in these strains are modulated by pH and glucose, although the effects of the latter are essentially restricted to pH 8, suggesting the presence of two general efflux pump systems, i.e. proton-motive force-dependent and ABC transporter types, respectively. Copyright 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

Proton Transport and pH Control in Fungi.

PubMed

Kane, Patricia M

2016-01-01

Despite diverse and changing extracellular environments, fungi maintain a relatively constant cytosolic pH and numerous organelles of distinct lumenal pH. Key players in fungal pH control are V-ATPases and the P-type proton pump Pma1. These two proton pumps act in concert with a large array of other transporters and are highly regulated. The activities of Pma1 and the V-ATPase are coordinated under some conditions, suggesting that pH in the cytosol and organelles is not controlled independently. Genomic studies, particularly in the highly tractable S. cerevisiae, are beginning to provide a systems-level view of pH control, including transcriptional responses to acid or alkaline ambient pH and definition of the full set of regulators required to maintain pH homeostasis. Genetically encoded pH sensors have provided new insights into localized mechanisms of pH control, as well as highlighting the dynamic nature of pH responses to the extracellular environment. Recent studies indicate that cellular pH plays a genuine signaling role that connects nutrient availability and growth rate through a number of mechanisms. Many of the pH control mechanisms found in S. cerevisiae are shared with other fungi, with adaptations for their individual physiological contexts. Fungi deploy certain proton transport and pH control mechanisms not shared with other eukaryotes; these regulators of cellular pH are potential antifungal targets. This review describes current and emerging knowledge proton transport and pH control mechanisms in S. cerevisiae and briefly discusses how these mechanisms vary among fungi.

Proton Transport and pH Control in Fungi

PubMed Central

Kane, Patricia M.

2018-01-01

Despite diverse and changing extracellular environments, fungi maintain a relatively constant cytosolic pH and numerous organelles of distinct lumenal pH. Key players in fungal pH control are V-ATPases and the P-type proton pump Pma1. These two proton pumps act in concert with a large array of other transporters and are highly regulated. The activities of Pma1 and the V-ATPaseare coordinated under some conditions, suggesting that pH in the cytosol and organelles is not controlled independently. Genomic studies, particularly in the highly tractable S. cerevisiae, are beginning to provide a systems-level view of pH control, including transcriptional responses to acid or alkaline ambient pH and definition of the full set of regulators required to maintain pH homeostasis. Genetically encoded pH sensors have provided new insights into localized mechanisms of pH control, as well as highlighting the dynamic nature of pH responses to the extracellular environment. Recent studies indicate that cellular pH plays a genuine signaling role that connects nutrient availability and growth rate through a number of mechanisms. Many of the pH control mechanisms found in S. cerevisiae are shared with other fungi, with adaptations for their individual physiological contexts. Fungi deploy certain proton transport and pH control mechanisms not shared with other eukaryotes; these regulators of cellular pH are potential antifungal targets. This re view describes current and emerging knowledge proton transport and pH control mechanisms in S. cerevisiae and briefly discusses how these mechanisms vary among fungi. PMID:26721270

Small Bowel Bacterial Overgrowth Associated with Persistence of Abdominal Symptoms in Children Treated with a Proton Pump Inhibitor.

PubMed

Sieczkowska, Agnieszka; Landowski, Piotr; Zagozdzon, Pawel; Kaminska, Barbara; Lifschitz, Carlos

2015-05-01

Small bowel bacterial overgrowth (SBBO) was diagnosed in 22.5% of 40 children treated for 3 months with a proton pump inhibitor (PPI). Compared with those without SBBO, children with SBBO had higher frequency of abdominal pain, bloating, eructation, and flatulence. Patients with gastrointestinal symptoms after PPI treatment should be evaluated for SBBO rather than empirically prolonging PPI therapy. Copyright © 2015 Elsevier Inc. All rights reserved.

The acidity of the tumor microenvironment is a mechanism of immune escape that can be overcome by proton pump inhibitors

PubMed Central

Bellone, Matteo; Calcinotto, Arianna; Filipazzi, Paola; De Milito, Angelo; Fais, Stefano; Rivoltini, Licia

2013-01-01

We have recently reported that lowering the pH to values that are frequently detected in tumors causes reversible anergy in both human and mouse CD8+ T lymphocytes in vitro. The same occurs in vivo, in the tumor microenvironment and the administration of proton pump inhibitors, which buffer tumor acidity, can revert T-cell anergy and increase the efficacy of immunotherapy. PMID:23483769

The relationship between long-term proton pump inhibitor therapy and skeletal frailty.

PubMed

Lau, Arthur N; Tomizza, Michael; Wong-Pack, Matthew; Papaioannou, Alexandra; Adachi, Jonathan D

2015-08-01

Proton pump inhibitors (PPIs) are a commonly prescribed class of medications. Their use has been associated with an increased rate of fractures, most notably hip fractures. However, there does not seem to be a clear association between PPI use and bone mineral density measurements, assessed by dual X-ray absorptiometry. The mechanism by which PPI use increases the risk of fractures remains unclear. This review will summarize the current evidence on this topic.

Proton-pumping rhodopsins are abundantly expressed by microbial eukaryotes in a high-Arctic fjord.

PubMed

Vader, Anna; Laughinghouse, Haywood D; Griffiths, Colin; Jakobsen, Kjetill S; Gabrielsen, Tove M

2018-02-01

Proton-pumping rhodopsins provide an alternative pathway to photosynthesis by which solar energy can enter the marine food web. Rhodopsin genes are widely found in marine bacteria, also in the Arctic, and were recently reported from several eukaryotic lineages. So far, little is known about rhodopsin expression in Arctic eukaryotes. In this study, we used metatranscriptomics and 18S rDNA tag sequencing to examine the mid-summer function and composition of marine protists (size 0.45-10 µm) in the high-Arctic Billefjorden (Spitsbergen), especially focussing on the expression of microbial proton-pumping rhodopsins. Rhodopsin transcripts were highly abundant, at a level similar to that of genes involved in photosynthesis. Phylogenetic analyses placed the environmental rhodopsins within disparate eukaryotic lineages, including dinoflagellates, stramenopiles, haptophytes and cryptophytes. Sequence comparison indicated the presence of several functional types, including xanthorhodopsins and a eukaryotic clade of proteorhodopsin. Transcripts belonging to the proteorhodopsin clade were also abundant in published metatranscriptomes from other oceanic regions, suggesting a global distribution. The diversity and abundance of rhodopsins show that these light-driven proton pumps play an important role in Arctic microbial eukaryotes. Understanding this role is imperative to predicting the future of the Arctic marine ecosystem faced by a changing light climate due to diminishing sea-ice. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Formation and dissociation of proteasome storage granules are regulated by cytosolic pH.

PubMed

Peters, Lee Zeev; Hazan, Rotem; Breker, Michal; Schuldiner, Maya; Ben-Aroya, Shay

2013-05-27

The 26S proteasome is the major protein degradation machinery of the cell and is regulated at many levels. One mode of regulation involves accumulation of proteasomes in proteasome storage granules (PSGs) upon glucose depletion. Using a systematic robotic screening approach in yeast, we identify trans-acting proteins that regulate the accumulation of proteasomes in PSGs. Our dataset was enriched for subunits of the vacuolar adenosine triphosphatase (V-ATPase) complex, a proton pump required for vacuole acidification. We show that the impaired ability of V-ATPase mutants to properly govern intracellular pH affects the kinetics of PSG formation. We further show that formation of other protein aggregates upon carbon depletion also is triggered in mutants with impaired activity of the plasma membrane proton pump and the V-ATPase complex. We thus identify cytosolic pH as a specific cellular signal involved both in the glucose sensing that mediates PSG formation and in a more general mechanism for signaling carbon source exhaustion.

The Chemically Elegant Proton Pump Inhibitors

PubMed Central

Roche, Victoria F.

2006-01-01

Medicinal chemistry instruction at Creighton University is designed to provide an in-depth scientifically grounded and clinically relevant learning experience for pharmacy students. Each topic covered in the 2-semester required course sequence is selected based on the general utility of the compounds in question and/or the therapeutic importance of the drugs in treating life-threatening diseases. All lessons provided to campus- and Web-based students by the author are in the form of a descriptive and conversational narrative and course requirements are in place to assure that students read the lesson prior to the class period in which it is discussed. Learning tools and aids are provided to help students more readily discern the most critical aspects of each lesson, to practice required critical thinking and structure analysis skills, and to self-assess competency in meeting specific learning objectives. This manuscript illustrates this approach by sharing a lesson on the chemistry and clinically relevant structure-activity relationships of proton pump inhibitors. PMID:17149430

Exchangers man the pumps

PubMed Central

Barkla, Bronwyn J; Hirschi, Kendal D

2008-01-01

Tonoplast-localised proton-coupled Ca2+ transporters encoded by cation/H+ exchanger (CAX) genes play a critical role in sequestering Ca2+ into the vacuole. These transporters may function in coordination with Ca2+ release channels, to shape stimulus-induced cytosolic Ca2+ elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant's stress response. A common feature of these mutants was the perturbation of H+-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca2+/H+ exchangers and H+ pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca2+ flux. These results suggest cautious interpretation of mutant Ca2+/H+ exchanger phenotypes that may be due to either perturbed Ca2+ or H+ transport. PMID:19841670

Beyond gastric acid reduction: Proton pump inhibitors induce heme oxygenase-1 in gastric and endothelial cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becker, Jan C.; Grosser, Nina; Waltke, Christian

2006-07-07

Proton pump inhibitors (PPIs) have been demonstrated to prevent gastric mucosal injury by mechanisms independent of acid inhibition. Here we demonstrate that both omeprazole and lansoprazole protect human gastric epithelial and endothelial cells against oxidative stress. This effect was abrogated in the presence of the heme oxygenase-1 (HO-1) inhibitor ZnBG. Exposure to either PPI resulted in a strong induction of HO-1 expression on mRNA and protein level, and led to an increased activity of this enzyme. Expression of cyclooxygenase isoforms 1 and 2 remained unaffected, and COX-inhibitors did not antagonize HO-1 induction by PPIs. Our results suggest that the antioxidantmore » defense protein HO-1 is a target of PPIs in both endothelial and gastric epithelial cells. HO-1 induction might account for the gastroprotective effects of PPIs independently of acid inhibition, especially in NSAID gastropathy. Moreover, our findings provide additional perspectives for a possible but yet unexplored use of PPIs in vasoprotection.« less

Repositioning Proton Pump Inhibitors as Anticancer Drugs by Targeting the Thioesterase Domain of Human Fatty Acid Synthase

PubMed Central

2015-01-01

Fatty acid synthase (FASN), the enzyme responsible for de novo synthesis of free fatty acids, is up-regulated in many cancers. FASN is essential for cancer cell survival and contributes to drug resistance and poor prognosis. However, it is not expressed in most nonlipogenic normal tissues. Thus, FASN is a desirable target for drug discovery. Although different FASN inhibitors have been identified, none has successfully moved into clinical use. In this study, using in silico screening of an FDA-approved drug database, we identified proton pump inhibitors (PPIs) as effective inhibitors of the thioesterase activity of human FASN. Further investigation showed that PPIs inhibited proliferation and induced apoptosis of cancer cells. Supplementation of palmitate, the end product of FASN catalysis, rescued cancer cells from PPI-induced cell death. These findings provide new evidence for the mechanism by which this FDA-approved class of compounds may be acting on cancer cells. PMID:25513712

Analogies between respiration and a light-driven proton pump as sources of energy for active glutamate transport in Halobacterium halobium

NASA Technical Reports Server (NTRS)

Belliveau, J. W.; Lanyi, J. K.

1977-01-01

Halobacterium halobium is known to contain sheets of bacteriorhodopsin, a pigment which upon exposure to light undergoes cyclic protonation and deprotonation, resulting in net H(+) translocation. In this paper, experiments were conducted to test H. halobium cell envelope vesicles for respiration-induced glutamate uptake. It is shown that glutamate transport in H. halobium cell envelope vesicles can occur as a result of respiration, as well as light acting on bacteriorhodopsin. Glutamate transport can be energized by the oxidation of dimethyl phenylenediamine, and the properties of the transport system are entirely analogous to those observed with illumination as the source of energy. In the case of respiration-dependent glutamate transport, the transportation is also driven by a Na(+) gradient, thereby confirming the existence of a single glutamate transport system independent of the source of energy. The analogy observed is indirect evidence that the cytochrome oxidase of H. halobium functions as a H(+) pump.

The proton pump inhibitor pantoprazole disrupts protein degradation systems and sensitizes cancer cells to death under various stresses.

PubMed

Cao, Yu; Chen, Min; Tang, Dehua; Yan, Hongli; Ding, Xiwei; Zhou, Fan; Zhang, Mingming; Xu, Guifang; Zhang, Weijie; Zhang, Shu; Zhuge, Yuzheng; Wang, Lei; Zou, Xiaoping

2018-05-22

Proton pump inhibitors (PPIs) play a role in antitumor activity, with studies showing specialized impacts of PPIs on cancer cell apoptosis, metastasis, and autophagy. In this study, we demonstrated that pantoprazole (PPI) increased autophagosomes formation and affected autophagic flux depending on the pH conditions. PPI specifically elevated SQSTM1 protein levels by increasing SQSTM1 transcription via NFE2L2 activation independent of the specific effect of PPI on autophagic flux. Via decreasing proteasome subunits expression, PPI significantly impaired the function of the proteasome, accompanied by the accumulation of undegraded poly-ubiquitinated proteins. Notably, PPI-induced autophagy functioned as a downstream response of proteasome inhibition by PPI, while suppressing protein synthesis abrogated autophagy. Blocking autophagic flux in neutral pH condition or further impairing proteasome function with proteasome inhibitors, significantly aggravated PPI cytotoxicity by worsening protein degradation ability. Interestingly, under conditions of mitochondrial stress, PPI showed significant synergism when combined with Bcl-2 inhibitors. Taken together, these findings provide a new understanding of the impact of PPIs on cancer cells' biological processes and highlight the potential to develop more efficient and effective combination therapies.

Comparison of p.o. or i.v. proton pump inhibitors on 72-h intragastric pH in bleeding peptic ulcer.

PubMed

Javid, Gul; Zargar, Showkat Ali; U-Saif, Riyaz-; Khan, Bashir Ahmad; Yatoo, Ghulam Nabi; Shah, Altaf Hussain; Gulzar, Ghulam Mohammad; Sodhi, Jaswinder Singh; Khan, Mushtaq Ahmad

2009-07-01

After successful endoscopic hemostasis in bleeding peptic ulcer, addition of proton pump inhibitors reduce the rate of recurrent bleeding by maintaining intragastric pH at neutral level. The aim of the present study was to evaluate the effect of various proton pump inhibitors given through different routes on intragastric pH over 72 h after endoscopic hemostasis in bleeding peptic ulcer. Ninety consecutive patients who had successful endoscopic therapy of bleeding peptic ulcer underwent 72-h continuous ambulatory intragastric pH study, were randomly assigned to receive p.o. omeprazole 80 mg bolus followed by 40 mg every 12 h for 72 h or i.v. 80 mg omeprazole followed by infusion 8 mg/h for 72 h. Oral pantoprazole 80 mg bolus followed by 80 mg every 12 h for 72 h or i.v. 80 mg pantoprazole followed by infusion of 8 mg/h for 72 h. Oral rabeprazole 80 mg bolus followed by 40 mg every 12 h for 72 h or i.v. 80 mg rabeprazole followed by infusion 8 mg/h for 72 h. Five patients received no treatment after successful endoscopic therapy and underwent 72-h pH study. Mean 72-h intragastric pH for p.o. omeprazole was 6.56 versus 6.93 for omeprazole infusion (P = 0.48). Mean 72-h intragastric pH for p.o. pantoprazole was 6.34 versus 6.32 for pantoprazole infusion (P = 0.62). Mean 72-h intragastric pH for rabeprazole p.o. was 6.11 versus 6.18 rabeprazole i.v. (P = 0.55). Mean 72-h pH for the no proton pump inhibitor group was 2.04. There was no significant difference among various proton pump inhibitors given through different routes on raising intragastric pH above 6 for 72 h after successful endoscopic hemostasis in bleeding peptic ulcer.

The Ca2+-ATPase pump facilitates bidirectional proton transport across the sarco/endoplasmic reticulum.

PubMed

Espinoza-Fonseca, L Michel

2017-03-28

Ca 2+ transport across the sarco/endoplasmic reticulum (SR) plays an essential role in intracellular Ca 2+ homeostasis, signalling, cell differentiation and muscle contractility. During SR Ca 2+ uptake and release, proton fluxes are required to balance the charge deficit generated by the exchange of Ca 2+ and other ions across the SR. During Ca 2+ uptake by the SR Ca 2+ -ATPase (SERCA), two protons are countertransported from the SR lumen to the cytosol, thus partially compensating for the charge moved by Ca 2+ transport. Studies have shown that protons are also transported from the cytosol to the lumen during Ca 2+ release, but a transporter that facilitates proton transport into the SR lumen has not been described. In this article we propose that SERCA forms pores that facilitate bidirectional proton transport across the SR. We describe the location and structure of water-filled pores in SERCA that form cytosolic and luminal pathways for protons to cross the SR membrane. Based on this structural information, we suggest mechanistic models for proton translocation to the cytosol during active Ca 2+ transport, and into the SR lumen during SERCA inhibition by endogenous regulatory proteins. Finally, we discuss the physiological consequences of SERCA-mediated bidirectional proton transport across the SR membrane of muscle and non-muscle cells.

HOW MAY PROTON PUMP INHIBITORS IMPAIR CARDIOVASCULAR HEALTH?

PubMed Central

Sukhovershin, Roman A.; Cooke, John P.

2016-01-01

Proton pump inhibitors (PPIs) are among the most widely used drugs worldwide. They are used to treat a number of gastro-esophageal disorders and usually prescribed as a long-term medication or even taken without a prescription. There are a number of clinical studies that associate PPI use with an increased cardiovascular risk. In this article we review the clinical evidence for adverse cardiovascular effects of PPIs, and we discuss possible biological mechanisms by which PPIs can impair cardiovascular health. PMID:26817947

Association of Proton Pump Inhibitor (PPI) Use with Energy Intake, Physical Activity, and Weight Gain

PubMed Central

Czwornog, Jennifer L.; Austin, Gregory L.

2015-01-01

Studies suggest proton pump inhibitor (PPI) use impacts body weight regulation, though the effect of PPIs on energy intake, energy extraction, and energy expenditure is unknown. We used data on 3073 eligible adults from the National Health and Nutrition Examination Survey (NHANES). Medication use, energy intake, diet composition, and physical activity were extracted from NHANES. Multivariate regression models included confounding variables. Daily energy intake was similar between PPI users and non-users (p = 0.41). Diet composition was similar between the two groups, except that PPI users consumed a slightly greater proportion of calories from fat (34.5% vs. 33.2%; p = 0.02). PPI users rated themselves as being as physically active as their age/gender-matched peers and reported similar frequencies of walking or biking. However, PPI users were less likely to have participated in muscle-strengthening activities (OR: 0.53; 95% CI: 0.30–0.95). PPI users reported similar sedentary behaviors to non-users. Male PPI users had an increase in weight (of 1.52 ± 0.59 kg; p = 0.021) over the previous year compared to non-users, while female PPI users had a non-significant increase in weight. The potential mechanisms for PPI-associated weight gain are unclear as we did not find evidence for significant differences in energy intake or markers of energy expenditure. PMID:26492268

Linking Chemical Electron–Proton Transfer to Proton Pumping in Cytochrome c Oxidase: Broken-Symmetry DFT Exploration of Intermediates along the Catalytic Reaction Pathway of the Iron–Copper Dinuclear Complex

PubMed Central

2015-01-01

After a summary of the problem of coupling electron and proton transfer to proton pumping in cytochrome c oxidase, we present the results of our earlier and recent density functional theory calculations for the dinuclear Fe-a3–CuB reaction center in this enzyme. A specific catalytic reaction wheel diagram is constructed from the calculations, based on the structures and relative energies of the intermediate states of the reaction cycle. A larger family of tautomers/protonation states is generated compared to our earlier work, and a new lowest-energy pathway is proposed. The entire reaction cycle is calculated for the new smaller model (about 185–190 atoms), and two selected arcs of the wheel are chosen for calculations using a larger model (about 205 atoms). We compare the structural and redox energetics and protonation calculations with available experimental data. The reaction cycle map that we have built is positioned for further improvement and testing against experiment. PMID:24960612

Thermal and Spectroscopic Characterization of a Proton Pumping Rhodopsin from an Extreme Thermophile*

PubMed Central

Tsukamoto, Takashi; Inoue, Keiichi; Kandori, Hideki; Sudo, Yuki

2013-01-01

So far retinylidene proteins (∼rhodopsin) have not been discovered in thermophilic organisms. In this study we investigated and characterized a microbial rhodopsin derived from the extreme thermophilic bacterium Thermus thermophilus, which lives in a hot spring at around 75 °C. The gene for the retinylidene protein, named thermophilic rhodopsin (TR), was chemically synthesized with codon optimization. The codon optimized TR protein was functionally expressed in the cell membranes of Escherichia coli cells and showed active proton transport upon photoillumination. Spectroscopic measurements revealed that the purified TR bound only all-trans-retinal as a chromophore and showed an absorption maximum at 530 nm. In addition, TR exhibited both photocycle kinetics and pH-dependent absorption changes, which are characteristic of rhodopsins. Of note, time-dependent thermal denaturation experiments revealed that TR maintained its absorption even at 75 °C, and the denaturation rate constant of TR was much lower than those of other proton pumping rhodopsins such as archaerhodopsin-3 (200 ×), Haloquadratum walsbyi bacteriorhodopsin (by 10-times), and Gloeobacter rhodopsin (100 ×). Thus, these results suggest that microbial rhodopsins are also distributed among thermophilic organisms and have high stability. TR should allow the investigation of the molecular mechanisms of ion transport and protein folding. PMID:23740255

Thermal and spectroscopic characterization of a proton pumping rhodopsin from an extreme thermophile.

PubMed

Tsukamoto, Takashi; Inoue, Keiichi; Kandori, Hideki; Sudo, Yuki

2013-07-26

So far retinylidene proteins (∼rhodopsin) have not been discovered in thermophilic organisms. In this study we investigated and characterized a microbial rhodopsin derived from the extreme thermophilic bacterium Thermus thermophilus, which lives in a hot spring at around 75 °C. The gene for the retinylidene protein, named thermophilic rhodopsin (TR), was chemically synthesized with codon optimization. The codon optimized TR protein was functionally expressed in the cell membranes of Escherichia coli cells and showed active proton transport upon photoillumination. Spectroscopic measurements revealed that the purified TR bound only all-trans-retinal as a chromophore and showed an absorption maximum at 530 nm. In addition, TR exhibited both photocycle kinetics and pH-dependent absorption changes, which are characteristic of rhodopsins. Of note, time-dependent thermal denaturation experiments revealed that TR maintained its absorption even at 75 °C, and the denaturation rate constant of TR was much lower than those of other proton pumping rhodopsins such as archaerhodopsin-3 (200 ×), Haloquadratum walsbyi bacteriorhodopsin (by 10-times), and Gloeobacter rhodopsin (100 ×). Thus, these results suggest that microbial rhodopsins are also distributed among thermophilic organisms and have high stability. TR should allow the investigation of the molecular mechanisms of ion transport and protein folding.

Coarse-grained Simulations of Substrate Export through Multidrug Efflux Transporter AcrB

NASA Astrophysics Data System (ADS)

Jewel, Yead; Dutta, Prashanta; Liu, Jin

2017-11-01

The treatment of bacterial infectious diseases hampered by the overexpression of multidrug resistance (MDR) systems. The MDR system actively pumps the antibiotic drugs as well as other toxic compounds out of the cells. During the pumping, AcrB (one of the key MDR components) undergoes a series of large-scale proton/substrate dependent conformational changes. In this work, we implement a hybrid coarse-grained PACE force field that couples the united-atom protein model with the coarse-grained MARTINI water/lipid, to investigate the conformational changes of AcrB. We first develop the substrate force field which is compatible with PACE, then we implement the force field to explore large scale structural changes of AcrB in microsecond simulations. The effects of the substrate and the protonation states of two key residues: Asp407 and Asp408, are investigated. Our results show that the drug export through AcrB is proton as well as substrate dependent. Our simulations explain molecular mechanisms of substrate transport through AcrB complex, as well as provide valuable insights for designing proper antibiotic drugs. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R01GM122081.

Natural Arabidopsis brx loss-of-function alleles confer root adaptation to acidic soil.

PubMed

Gujas, Bojan; Alonso-Blanco, Carlos; Hardtke, Christian S

2012-10-23

Soil acidification is a major agricultural problem that negatively affects crop yield. Root systems counteract detrimental passive proton influx from acidic soil through increased proton pumping into the apoplast, which is presumably also required for cell elongation and stimulated by auxin. Here, we found an unexpected impact of extracellular pH on auxin activity and cell proliferation rate in the root meristem of two Arabidopsis mutants with impaired auxin perception, axr3 and brx. Surprisingly, neutral to slightly alkaline media rescued their severely reduced root (meristem) growth by stimulating auxin signaling, independent of auxin uptake. The finding that proton pumps are hyperactive in brx roots could explain this phenomenon and is consistent with more robust growth and increased fitness of brx mutants on overly acidic media or soil. Interestingly, the original brx allele was isolated from a natural stock center accession collected from acidic soil. Our discovery of a novel brx allele in accessions recently collected from another acidic sampling site demonstrates the existence of independently maintained brx loss-of-function alleles in nature and supports the notion that they are advantageous in acidic soil pH conditions, a finding that might be exploited for crop breeding. Copyright © 2012 Elsevier Ltd. All rights reserved.

How cytochrome c oxidase can pump four protons per oxygen molecule at high electrochemical gradient.

PubMed

Blomberg, Margareta R A; Siegbahn, Per E M

2015-03-01

Experiments have shown that the A-family cytochrome c oxidases pump four protons per oxygen molecule, also at a high electrochemical gradient. This has been considered a puzzle, since two of the reduction potentials involved, Cu(II) and Fe(III), were estimated from experiments to be too low to afford proton pumping at a high gradient. The present quantum mechanical study (using hybrid density functional theory) suggests a solution to this puzzle. First, the calculations show that the charge compensated Cu(II) potential for CuB is actually much higher than estimated from experiment, of the same order as the reduction potentials for the tyrosyl radical and the ferryl group, which are also involved in the catalytic cycle. The reason for the discrepancy between theory and experiment is the very large uncertainty in the experimental observations used to estimate the equilibrium potentials, mainly caused by the lack of methods for direct determination of reduced CuB. Second, the calculations show that a high energy metastable state, labeled EH, is involved during catalytic turnover. The EH state mixes the low reduction potential of Fe(III) in heme a3 with another, higher potential, here suggested to be that of the tyrosyl radical, resulting in enough exergonicity to allow proton pumping at a high gradient. In contrast, the corresponding metastable oxidized state, OH, is not significantly higher in energy than the resting state, O. Finally, to secure the involvement of the high energy EH state it is suggested that only one proton is taken up via the K-channel during catalytic turnover. Copyright © 2014 Elsevier B.V. All rights reserved.

Protonation of key acidic residues is critical for the K+-selectivity of the Na/K pump

PubMed Central

Yu, Haibo; Ratheal, Ian; Artigas, Pablo; Roux, Benoît

2011-01-01

The sodium-potassium (Na/K) pump is a P-type ATPase that generates Na+ and K+ concentration gradients across the cell membrane. For each ATP molecule, the pump extrudes three Na+ and imports two K+ by alternating between outward- and inward-facing conformations that preferentially bind K+ or Na+, respectively. Remarkably, the selective K+ and Na+ binding sites share several residues, and how the pump is able to achieve the selectivity required for the functional cycle is unclear. Here, free energy perturbation molecular dynamics (FEP/MD) simulations based on the crystal structures of the Na/K pump in a K+-loaded state (E2·Pi) reveal that protonation of the high-field acidic side-chains involved in the binding sites is critical to achieve the proper K+ selectivity. This prediction is tested with electrophysiological experiments showing that the selectivity of the E2P state for K+ over Na+ is affected by extracellular pH. PMID:21909093

Acid suppression and surgical therapy for Barrett's oesophagus.

PubMed

de Jonge, Pieter J F; Spaander, Manon C; Bruno, Marco J; Kuipers, Ernst J

2015-02-01

Gastro-oesophageal reflux disease is a common medical problem in developed countries, and is a risk factor for the development of Barrett's oesophagus and oesophageal adenocarcinoma. Both proton pump inhibitor therapy and antireflux surgery are effective at controlling endoscopic signs and symptoms of gastro-oesophageal reflux in patients with Barrett's oesophagus, but often fail to eliminate pathological oesophageal acid exposure. The current available studies strongly suggest that acid suppressive therapy, both pharmacological as well as surgical acid suppression, can reduce the risk the development and progression in patients with Barrett's oesophagus, but are not capable of complete prevention. No significant differences have been found between pharmacological and surgical therapy. For clinical practice, patients should be prescribed a proton pump inhibitor once daily as maintenance therapy, with the dose guided by symptoms. Antireflux surgery can be a good alternative to proton pump inhibitor therapy, but should be primarily offered to patients with symptomatic reflux, and not to asymptomatic patients with the rationale to protect against cancer. Copyright © 2014 Elsevier Ltd. All rights reserved.

Unraveling the mechanism of proton translocation in the extracellular half-channel of bacteriorhodopsin.

PubMed

Ge, Xiaoxia; Gunner, M R

2016-05-01

Bacteriorhodopsin, a light activated protein that creates a proton gradient in halobacteria, has long served as a simple model of proton pumps. Within bacteriorhodopsin, several key sites undergo protonation changes during the photocycle, moving protons from the higher pH cytoplasm to the lower pH extracellular side. The mechanism underlying the long-range proton translocation between the central (the retinal Schiff base SB216, D85, and D212) and exit clusters (E194 and E204) remains elusive. To obtain a dynamic view of the key factors controlling proton translocation, a systematic study using molecular dynamics simulation was performed for eight bacteriorhodopsin models varying in retinal isomer and protonation states of the SB216, D85, D212, and E204. The side-chain orientation of R82 is determined primarily by the protonation states of the residues in the EC. The side-chain reorientation of R82 modulates the hydrogen-bond network and consequently possible pathways of proton transfer. Quantum mechanical intrinsic reaction coordinate calculations of proton-transfer in the methyl guanidinium-hydronium-hydroxide model system show that proton transfer via a guanidinium group requires an initial geometry permitting proton donation and acceptance by the same amine. In all the bacteriorhodopsin models, R82 can form proton wires with both the CC and the EC connected by the same amine. Alternatively, rare proton wires for proton transfer from the CC to the EC without involving R82 were found in an O' state where the proton on D85 is transferred to D212. © 2016 Wiley Periodicals, Inc.

Changing hydration level in an internal cavity modulates the proton affinity of a key glutamate in cytochrome c oxidase.

PubMed

Goyal, Puja; Lu, Jianxun; Yang, Shuo; Gunner, M R; Cui, Qiang

2013-11-19

Cytochrome c oxidase contributes to the transmembrane proton gradient by removing two protons from the high-pH side of the membrane each time the binuclear center active site is reduced. One proton goes to the binuclear center, whereas the other is pumped to the low-pH periplasmic space. Glutamate 286 (Glu286) has been proposed to serve as a transiently deprotonated proton donor. Using unrestrained atomistic molecular dynamics simulations, we show that the size of and water distribution in the hydrophobic cavity that holds Glu286 is controlled by the protonation state of the propionic acid of heme a3, a group on the proton outlet pathway. Protonation of the propionate disrupts hydrogen bonding to two side chains, allowing a loop to swing open. Continuum electrostatics and atomistic free-energy perturbation calculations show that the resultant changes in hydration and electrostatic interactions lower the Glu proton affinity by at least 5 kcal/mol. These changes in the internal hydration level occur in the absence of major conformational transitions and serve to stabilize needed transient intermediates in proton transport. The trigger is not the protonation of the Glu of interest, but rather the protonation of a residue ∼10 Å away. Thus, unlike local water penetration to stabilize a new charge, this finding represents a specific role for water molecules in the protein interior, mediating proton transfers and facilitating ion transport.

Proton pump inhibitors are associated with lower gastrointestinal tract bleeding in low-dose aspirin users with ischaemic heart disease.

PubMed

Miyake, Kazumasa; Akimoto, Teppei; Hanada, Yuriko; Nagoya, Hiroyuki; Kodaka, Yasuhiro; Ueki, Nobue; Kusunoki, Masafumi; Kawagoe, Tetsuro; Futagami, Seiji; Takahashi, Yasuhiro; Takano, Hitoshi; Sakamoto, Choitsu

2015-09-01

Impact of acid suppressants on lower gastrointestinal bleeding remains unclear in low-dose aspirin users; we aimed to investigate this relationship. Retrospective cohort study of low-dose aspirin users who underwent coronary angiography for ischaemic heart disease in our institution between October 2005 and December 2006; patients were evaluated for upper or lower gastrointestinal bleedings within 3 years post-angiography. 538 patients were enrolled (males, 74.4%; mean age 67.4±10.6 years). Risk for upper gastrointestinal bleeding decreased with concomitant use of statins (HR, 0.37; 95% CI, 0.15-0.89), calcium channel blockers (HR, 0.29; 95% CI, 0.10-0.85), and histamine-2 receptor antagonists (HR, 0.26; 95% CI, 0.08-0.89). Concomitant use of proton pump inhibitors tended to decrease risk of upper gastrointestinal bleeding (HR, 0.27; 95% CI, 0.06-1.18). Risk for lower gastrointestinal bleeding increased with both concomitant use of warfarin (HR, 15.68; 95% CI, 4.43-55.53) and proton pump inhibitors (HR, 6.55; 95% CI, 2.01-21.32), but not with histamine-2 receptor antagonists. Hyperuricemia lowered risk for lower gastrointestinal bleeding (HR, 0.12; 95% CI, 0.02-0.88). In low-dose aspirin users, concomitant use of proton pump inhibitors increased lower gastrointestinal bleeding risk, independent from effects on upper gastrointestinal bleeding. Copyright © 2015 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Proton electrochemical gradient: Driving and regulating neurotransmitter uptake.

PubMed

Farsi, Zohreh; Jahn, Reinhard; Woehler, Andrew

2017-05-01

Accumulation of neurotransmitters in the lumen of synaptic vesicles (SVs) relies on the activity of the vacuolar-type H + -ATPase. This pump drives protons into the lumen, generating a proton electrochemical gradient (Δμ H+ ) across the membrane. Recent work has demonstrated that the balance between the chemical (ΔpH) and electrical (ΔΨ) components of Δμ H+ is regulated differently by some distinct vesicle types. As different neurotransmitter transporters use ΔpH and ΔΨ with different relative efficiencies, regulation of this gradient balance has the potential to influence neurotransmitter uptake. Nevertheless, the underlying mechanisms responsible for this regulation remain poorly understood. In this review, we provide an overview of current neurotransmitter uptake models, with a particular emphasis on the distinct roles of the electrical and chemical gradients and current hypotheses for regulatory mechanisms. © 2017 WILEY Periodicals, Inc.

The frequency of CYP2C19 genetic polymorphisms in Russian patients with peptic ulcers treated with proton pump inhibitors.

PubMed

Sychev, D A; Denisenko, N P; Sizova, Z M; Grachev, A V; Velikolug, K A

2015-01-01

Proton pump inhibitors, which are widely used as acid-inhibitory agents for the treatment of peptic ulcers, are mainly metabolized by 2C19 isoenzyme of cytochrome P450 (CYP2C19). CYP2C19 has genetic polymorphisms, associated with extensive, poor, intermediate or ultra-rapid metabolism of proton pump inhibitors. Genetic polymorphisms of CYP2C19 could be of clinical concern in the treatment of peptic ulcers with proton pump inhibitors. To investigate the frequencies of CYP2C19*2, CYP2C19*3, and CYP2C19*17 alleles and genotypes in Russian patients with peptic ulcers. We retrospectively reviewed the cases of 971 patients of Caucasian origin with Russian nationality from Moscow region with endoscopically and histologically proven ulcers, 428 males (44%) and 543 females (56%). The mean age was 44.6±11.9 years (range: 15-88 years). DNA was extracted from ethylenediaminetetraacetic acid whole blood samples (10 mL). The polymorphisms CYP2C19 681G.A (CYP2C19*2, rs4244285), CYP2C19 636 G.A (CYP2C19*3, rs4986893) and CYP2C19 -806 C.T (CYP2C19*17, rs12248560) were evaluated using real-time polymerase chain reaction. Regarding CYP2C19 genotype, 317 patients (32.65%) out of 971 were CYP2C19*1/*1 carriers classified as extensive metabolizers. Three hundred and eighty-six (39.75%) with CYP2C19*1/*17 or CYP2C19*17/*17 genotype were ultra-rapid metabolizers. Two hundred and fifty-one people (25.85%) were intermediate metabolizers with CYP2C19*1/*2, CYP2C19*2/*17, CYP2C19*1/*3, CYP2C19*3/*17 genotypes. Seventeen patients (1.75%) with CYP2C19*2/*2, CYP2C19*3/*3, CYP2C19*2/*3 genotypes were poor metabolizers. The allele frequencies were the following: CYP2C19*2 - 0.140, CYP2C19*3 - 0.006, CYP2C19*17 - 0.274. There is a high frequency of CYP2C19 genotypes associated with modified response to proton pump inhibitors in Russian patients with peptic ulcers. Genotyping for CYP2C19 polymorphisms is suggested to be a useful tool for personalized dosing of proton pump inhibitors.

Role of protons in the pump cycle of KdpFABC investigated by time-resolved kinetic experiments.

PubMed

Damnjanovic, Bojana; Apell, Hans-Jürgen

2014-05-20

The time-resolved kinetics of the KdpFABC complex solubilized in Aminoxide WS-35 was investigated by ATP concentration jump experiments. ATP was photoreleased from its inactive precursor, caged ATP, and charge movements in the membrane domain of the KdpFABC were detected by the electrochromic dye RH421. At low ATP concentrations, the ATP binding step became rate-limiting with an apparent, pH-independent ATP binding affinity of ~70 μM. At saturating ATP concentrations, the rate-limiting step is the conformational transition (E1-P → P-E2) with a rate constant of ~1.7 s(-1) at 20 °C that was independent of K(+) concentration. This observation together with the detected fluorescence decrease indicates that K(+) (or another positive ion) is bound in the membrane domain after enzyme phosphorylation and the conformational transition to the P-E2 state. pH dependence experiments revealed different roles of H(+) in the transport mechanism. Two different functions of protons for the ion pump must be distinguished. On one hand, there are electrogenically bound "functional" protons, which are not transported but prerequisite for the performance of the ATP-driven half-cycle. On the other hand, protons bind to the transport sites, acting as weak congeners of K(+). There possibly are noncompetitively bound protons, affecting the enzyme activity and/or coupling between KdpA and KdpB subunits. Finally, the recently proposed Post-Albers model for the KdpFABC complex was supplemented with stoichiometry factors of 2 for K(+) and 3 for H(+), and additional inhibitory side reactions controlled by H(+) were introduced, which are relevant at pH <6.5 and/or in the absence of K(+).

Proton Transfer Dynamics at the Membrane/Water Interface: Dependence on the Fixed and Mobile pH Buffers, on the Size and Form of Membrane Particles, and on the Interfacial Potential Barrier

PubMed Central

Cherepanov, Dmitry A.; Junge, Wolfgang; Mulkidjanian, Armen Y.

2004-01-01

Crossing the membrane/water interface is an indispensable step in the transmembrane proton transfer. Elsewhere we have shown that the low dielectric permittivity of the surface water gives rise to a potential barrier for ions, so that the surface pH can deviate from that in the bulk water at steady operation of proton pumps. Here we addressed the retardation in the pulsed proton transfer across the interface as observed when light-triggered membrane proton pumps ejected or captured protons. By solving the system of diffusion equations we analyzed how the proton relaxation depends on the concentration of mobile pH buffers, on the surface buffer capacity, on the form and size of membrane particles, and on the height of the potential barrier. The fit of experimental data on proton relaxation in chromatophore vesicles from phototropic bacteria and in bacteriorhodopsin-containing membranes yielded estimates for the interfacial potential barrier for H+/OH− ions of ∼120 meV. We analyzed published data on the acceleration of proton equilibration by anionic pH buffers and found that the height of the interfacial barrier correlated with their electric charge ranging from 90 to 120 meV for the singly charged species to >360 meV for the tetra-charged pyranine. PMID:14747306

V-ATPase as an effective therapeutic target for sarcomas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perut, Francesca, E-mail: francesca.perut@ior.it; Avnet, Sofia; Fotia, Caterina

2014-01-01

Malignant tumors show intense glycolysis and, as a consequence, high lactate production and proton efflux activity. We investigated proton dynamics in osteosarcoma, rhabdomyosarcoma, and chondrosarcoma, and evaluated the effects of esomeprazole as a therapeutic agent interfering with tumor acidic microenvironment. All sarcomas were able to survive in an acidic microenvironment (up to 5.9–6.0 pH) and abundant acidic lysosomes were found in all sarcoma subtypes. V-ATPase, a proton pump that acidifies intracellular compartments and transports protons across the plasma membrane, was detected in all cell types with a histotype-specific expression pattern. Esomeprazole administration interfered with proton compartmentalization in acidic organelles andmore » induced a significant dose-dependent toxicity. Among the different histotypes, rhabdomyosarcoma, expressing the highest levels of V-ATPase and whose lysosomes are most acidic, was mostly susceptible to ESOM treatment. - Highlights: • Osteosarcoma, rhabdomyosarcoma, and chondrosarcoma survive in acidic microenvironment. • At acidic extracellular pH, sarcoma survival is dependent on V-ATPase expression. • Esomeprazole administration induce a significant dose-dependent toxicity.« less

The impact of metabolic state on Cd adsorption onto bacterial cells

USGS Publications Warehouse

Johnson, K.J.; Ams, D.A.; Wedel, A.N.; Szymanowski, J.E.S.; Weber, D.L.; Schneegurt, M.A.; Fein, J.B.

2007-01-01

This study examines the effect of bacterial metabolism on the adsorption of Cd onto Gram-positive and Gram-negative bacterial cells. Metabolically active Gram-positive cells adsorbed significantly less Cd than non-metabolizing cells. Gram-negative cells, however, showed no systematic difference in Cd adsorption between metabolizing and non-metabolizing cells. The effect of metabolism on Cd adsorption to Gram-positive cells was likely due to an influx of protons in and around the cell wall from the metabolic proton motive force, promoting competition between Cd and protons for adsorption sites on the cell wall. The relative lack of a metabolic effect on Cd adsorption onto Gram-negative compared to Gram-positive cells suggests that Cd binding in Gram-negative cells is focused in a region of the cell wall that is not reached, or is unaffected by this proton flux. Thermodynamic modeling was used to estimate that proton pumping causes the pH in the cell wall of metabolizing Gram-positive bacteria to decrease from the bulk solution value of 7.0 to approximately 5.7. ?? 2007 The Authors.

Epididymal expression of the forkhead transcription factor Foxi1 is required for male fertility.

PubMed

Blomqvist, Sandra Rodrigo; Vidarsson, Hilmar; Söder, Olle; Enerbäck, Sven

2006-09-06

An essential aspect of male reproductive capacity is the immediate availability of fertilization-ready spermatozoa. To ensure this, most mammals rely on post-testicular sperm maturation. In epididymis, germ cells are matured and stored in a quiescent state that readily can be altered to produce active spermatozoa. This depends on active proton secretion into the epididymal lumen. We have identified Foxi1 as an important regulator of gene expression in narrow and clear cells-the major proton secretory cells of epididymal epithelia. Foxi1 appears to be required for the expression of the B1-subunit of the vacuolar H+ -ATPase proton pump and for carbonic anhydrase II as well as the chloride/bicarbonate transporter pendrin. Using transfection experiments, we have identified a Foxi1 binding cis-element in the ATP6V1B1 (encoding the B1-subunit) promoter that is critical for reporter gene activation. When this site is mutated to eliminate Foxi1 binding, activation is also abolished. As a consequence of defect Foxi1-dependent epididymal sperm maturation, we demonstrate that spermatozoa from Foxi1 null males fail to reach the female genital tract in sufficient number to allow fertilization.

Epididymal expression of the forkhead transcription factor Foxi1 is required for male fertility

PubMed Central

Blomqvist, Sandra Rodrigo; Vidarsson, Hilmar; Söder, Olle; Enerbäck, Sven

2006-01-01

An essential aspect of male reproductive capacity is the immediate availability of fertilization-ready spermatozoa. To ensure this, most mammals rely on post-testicular sperm maturation. In epididymis, germ cells are matured and stored in a quiescent state that readily can be altered to produce active spermatozoa. This depends on active proton secretion into the epididymal lumen. We have identified Foxi1 as an important regulator of gene expression in narrow and clear cells—the major proton secretory cells of epididymal epithelia. Foxi1 appears to be required for the expression of the B1-subunit of the vacuolar H+-ATPase proton pump and for carbonic anhydrase II as well as the chloride/bicarbonate transporter pendrin. Using transfection experiments, we have identified a Foxi1 binding cis-element in the ATP6V1B1 (encoding the B1-subunit) promoter that is critical for reporter gene activation. When this site is mutated to eliminate Foxi1 binding, activation is also abolished. As a consequence of defect Foxi1-dependent epididymal sperm maturation, we demonstrate that spermatozoa from Foxi1 null males fail to reach the female genital tract in sufficient number to allow fertilization. PMID:16932748

The role of Rnf in ion gradient formation in Desulfovibrio alaskensis

DOE PAGES

Wang, Luyao; Bradstock, Peter; Li, Chuang; ...

2016-04-14

Rnf is a membrane protein complex that has been shown to be important in energy conservation. Here, Desulfovibrio alaskensis G20 and Rnf mutants of G20 were grown with different electron donor and acceptor combinations to determine the importance of Rnf in energy conservation and the type of ion gradient generated. The addition of the protonophore TCS strongly inhibited lactate-sulfate dependent growth whereas the sodium ionophore ETH2120 had no effect, indicating a role for the proton gradient during growth. Mutants in rnfA and rnfD were more sensitive to the protonophore at 5 µM than the parental strain, suggesting the importance ofmore » Rnf in the generation of a proton gradient. The electrical potential (ΔΨ), ΔpH and proton motive force were lower in thernfAmutant than in the parental strain of D.alaskensis G20. In conclusion, these results provide evidence that the Rnf complex in D. alaskensis functions as a primary proton pump whose activity is important for growth.« less

Electromagnetic ion cyclotron waves stimulated by modest magnetospheric compressions

NASA Technical Reports Server (NTRS)

Anderson, B. J.; Hamilton, D. C.

1993-01-01

AMPTE/CCE magnetic field and particle data are used to test the suggestion that increased hot proton temperature anisotropy resulting from convection during magnetospheric compression is responsible for the enhancement in Pc 1 emission via generation of electromagnetic ion cyclotron (EMIC) waves in the dayside outer equatorial magnetosphere. The relative increase in magnetic field is used to gauge the strength of the compression, and an image dipole model is used to estimate the motion of the plasma during compression. Proton data are used to analyze the evolution of the proton distribution and the corresponding changes in EMIC wave activity expected during the compression. It is suggested that enhancements in dynamic pressure pump the energetic proton distributions in the outer magnetosphere, driving EMIC waves. Waves are expected to be generated most readily close to the magnetopause, and transient pressure pulses may be associated with bursts of EMIC waves, which would be observed on the ground in association with ionospheric transient signatures.

Is the Ca2+-ATPase from sarcoplasmic reticulum also a heat pump?

PubMed

Kjelstrup, Signe; de Meis, Leopoldo; Bedeaux, Dick; Simon, Jean-Marc

2008-11-01

We calculate, using the first law of thermodynamics, the membrane heat fluxes during active transport of Ca(2+) in the Ca(2+)-ATPase in leaky and intact vesicles, during ATP hydrolysis or synthesis conditions. The results show that the vesicle interior may cool down during hydrolysis and Ca(2+)-uptake, and heat up during ATP synthesis and Ca(2+)-efflux. The heat flux varies with the SERCA isoform. Electroneutral processes and rapid equilibration of water were assumed. The results are consistent with the second law of thermodynamics for the overall processes. The expression for the heat flux and experimental data, show that important contributions come from the enthalpy of hydrolysis for the medium in question, and from proton transport between the vesicle interior and exterior. The analysis give quantitative support to earlier proposals that certain, but not all, Ca(2+)-ATPases, not only act as Ca(2+)-pumps, but also as heat pumps. It can thus help explain why SERCA 1 type enzymes dominate in tissues where thermal regulation is important, while SERCA 2 type enzymes, with their lower activity and better ability to use the energy from the reaction to pump ions, dominate in tissues where this is not an issue.

Association Between Proton Pump Inhibitors and Metronomic Capecitabine as Salvage Treatment for Patients With Advanced Gastrointestinal Tumors: A Randomized Phase II Trial.

PubMed

Marchetti, Paolo; Milano, Annalisa; D'Antonio, Chiara; Romiti, Adriana; Falcone, Rosa; Roberto, Michela; Fais, Stefano

2016-12-01

The acidification of extracellular compartment represents a conceivable mechanism of drug resistance in malignant cells. In addition, it has been reported to drive proliferation and promote invasion and metastasis. Experimental evidence has shown that proton pump inhibitors can counteract tumor acidification and restore sensitivity to anticancer drugs. Moreover, early clinical data have supported the role of proton pump inhibitors in anticancer treatments. Metronomic capecitabine has demonstrated beneficial effects as salvage chemotherapy for heavily pretreated or frail patients with gastrointestinal cancer. The present study (EudraCT Number: 2013-001096-20) was aimed at investigating the activity and safety of high-dose rabeprazole in combination with metronomic capecitabine in patients with advanced gastrointestinal cancer refractory to standard treatment. A total of 66 patients will be randomized 1:1 to receive capecitabine 1500 mg/daily, continuously with or without rabeprazole 1.5 mg/kg twice a day, 3 days a week until disease progression, undue toxicity, or withdrawal of informed consent. The primary endpoint is progression-free survival. The secondary endpoints are clinical benefit, which reflects the proportion of patients with complete response, partial response, and stable disease, and overall survival. Progression-free and overall survival will be evaluated using a log-rank test to determine the effect of rabeprazole independently at the 2-sided α-level of 0.05. Other assessments will include the frequency and severity of adverse events and changes in laboratory parameters to measure the safety, and the pharmacokinetics of capecitabine. The results are expected in 2016. Copyright © 2016 Elsevier Inc. All rights reserved.

Defining Appropriate Use of Proton-Pump Inhibitors Among Medical Inpatients.

PubMed

Pappas, Matt; Jolly, Sanjay; Vijan, Sandeep

2016-04-01

Proton-pump inhibitors (PPIs) are commonly used among medical inpatients, both for prophylaxis against upper gastrointestinal bleeding (UGIB) and continuation of outpatient use. While PPIs reduce the risk of UGIB, they also appear to increase the risk of hospital-acquired pneumonia (HAP) and Clostridium difficile infection (CDI). Depending upon the underlying risks of these conditions and the changes in those risks with PPIs, use of proton-pump inhibitors may lead to a net benefit or net harm among medical inpatients. We aimed to determine the net impact of PPIs on hospital mortality among medical inpatients. A microsimulation model, using literature-derived estimates of the risks of UGIB, HAP, and CDI among medical inpatients, along with the changes in risk associated with PPI use for each of these outcomes. The primary outcome was change in inpatient mortality. Simulated general medical inpatients outside the intensive care unit (ICU). Change in overall mortality during hospitalization. New initiation of PPI therapy led to an increase in hospital mortality in about 90% of simulated patients. Continuation of outpatient PPI therapy on admission led to net increase in hospital mortality in 79% of simulated patients. Results were robust to both one-way and multivariate sensitivity analyses, with net harm occurring in at least two-thirds of patients in all scenarios. For the majority of medical inpatients outside the ICU, use of PPIs likely leads to a net increase in hospital mortality. Even in patients at particularly high risk of UGIB, only those at the very lowest risk of HCAP and CDI should be considered for prophylactic PPI use. Continuation of outpatient PPIs may also increase expected hospital mortality. Apart from patients with active UGIB, use of PPIs in hospitalized patients should be discouraged.

Clopidogrel and proton pump inhibitors - where do we stand in 2012?

PubMed Central

Drepper, Michael D; Spahr, Laurent; Frossard, Jean Louis

2012-01-01

Clopidogrel in association with aspirine is considered state of the art of medical treatment for acute coronary syndrome by reducing the risk of new ischemic events. Concomitant treatment with proton pump inhibitors in order to prevent gastrointestinal side effects is recommended by clinical guidelines. Clopidogrel needs metabolic activation predominantly by the hepatic cytochrome P450 isoenzyme Cytochrome 2C19 (CYP2C19) and proton pump inhibitors (PPIs) are extensively metabolized by the CYP2C19 isoenzyme as well. Several pharmacodynamic studies investigating a potential clopidogrel-PPI interaction found a significant decrease of the clopidogrel platelet antiaggregation effect for omeprazole, but not for pantoprazole. Initial clinical cohort studies in 2009 reported an increased risk for adverse cardiovascular events, when under clopidogrel and PPI treatment at the same time. These observations led the United States Food and Drug Administration and the European Medecines Agency to discourage the combination of clopidogrel and PPI (especially omeprazole) in the same year. In contrast, more recent retrospective cohort studies including propensity score matching and the only existing randomized trial have not shown any difference concerning adverse cardiovascular events when concomitantly on clopidogrel and PPI or only on clopidogrel. Three meta-analyses report an inverse correlation between clopidogrel-PPI interaction and study quality, with high and moderate quality studies not reporting any association, rising concern about unmeasured confounders biasing the low quality studies. Thus, no definite evidence exists for an effect on mortality. Because PPI induced risk reduction clearly overweighs the possible adverse cardiovascular risk in patients with high risk of gastrointestinal bleeding, combination of clopidogrel with the less CYP2C19 inhibiting pantoprazole should be recommended. PMID:22611308

Polyamines cause plasma membrane depolarization, activate Ca2+-, and modulate H+-ATPase pump activity in pea roots.

PubMed

Pottosin, Igor; Velarde-Buendía, Ana María; Bose, Jayakumar; Fuglsang, Anja T; Shabala, Sergey

2014-06-01

Polyamines regulate a variety of cation and K(+) channels, but their potential effects on cation-transporting ATPases are underexplored. In this work, noninvasive microelectrode ion flux estimation and conventional microelectrode techniques were applied to study the effects of polyamines on Ca(2+) and H(+) transport and membrane potential in pea roots. Externally applied spermine or putrescine (1mM) equally activated eosin yellow (EY)-sensitive Ca(2+) pumping across the root epidermis and caused net H(+) influx or efflux. Proton influx induced by spermine was suppressed by EY, supporting the mechanism in which Ca(2+) pump imports 2 H(+) per each exported Ca(2+). Suppression of the Ca(2+) pump by EY diminished putrescine-induced net H(+) efflux instead of increasing it. Thus, activities of Ca(2+) and H(+) pumps were coupled, likely due to the H(+)-pump inhibition by intracellular Ca(2+). Additionally, spermine but not putrescine caused a direct inhibition of H(+) pumping in isolated plasma membrane vesicles. Spermine, spermidine, and putrescine (1mM) induced membrane depolarization by 70, 50, and 35 mV, respectively. Spermine-induced depolarization was abolished by cation transport blocker Gd(3+), was insensitive to anion channels' blocker niflumate, and was dependent on external Ca(2+). Further analysis showed that uptake of polyamines but not polyamine-induced cationic (K(+)+Ca(2+)+H(+)) fluxes were a main cause of membrane depolarization. Polyamine increase is a common component of plant stress responses. Activation of Ca(2+) efflux by polyamines and contrasting effects of polyamines on net H(+) fluxes and membrane potential can contribute to Ca(2+) signalling and modulate a variety of transport processes across the plasma membrane under stress. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Practical considerations in the management of proton-pump inhibitors.

PubMed

Aguilera-Castro, Lara; Martín-de-Argila-dePrados, Carlos; Albillos-Martínez, Agustín

2016-03-01

Proton-pump inhibitors (PPIs) are one of the most active ingredients prescribed in Spain. In recent decades there has been an overuse of these drugs in both outpatient clinics and hospitals that has lead to a significant increase in healthcare spending and to an increase in the risk of possible side effects. It is important for health professionals to know the accepted indications and the correct doses for the use of these drugs. On the market there are different types of PPI: omeprazole, pantoprazole, lansoprazole, rabeprazole and esomeprazole. Omeprazole is the oldest and most used PPI, being also the cheapest. Although there are no important differences between PPIs in curing diseases, esomeprazole, a new-generation PPI, has proved to be more effective in eradicating H. pylori and in healing severe esophagitis compared to other PPIs. In recent years the use of generic drugs has spread; these drugs have the same bioavailability than the original drugs. In the case of PPIs, the few comparative studies available in the literature between original and generic drugs have shown no significant differences in clinical efficacy.

Influence of proton-pump inhibitors on stomach wall uptake of 99mTc-tetrofosmin in cadmium-zinc-telluride SPECT myocardial perfusion imaging.

PubMed

Mouden, Mohamed; Rijkee, Karlijn S; Schreuder, Nanno; Timmer, Jorik R; Jager, Pieter L

2015-02-01

Proton-pump inhibitors (PPIs) induce potentially interfering stomach wall activity in single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) with technetium-99m ((99m)Tc)-sestamibi. However, no data are available for (99m)Tc-tetrofosmin. We assessed the influence of prolonged (>2 weeks) PPI use on the stomach wall uptake of (99m)Tc-tetrofosmin in patients referred for stress MPI with a cadmium-zinc-telluride-based SPECT camera and its relation with dyspepsia symptoms. Consecutive patients (n=127) underwent a 1-day adenosine stress-first SPECT-MPI with (99m)Tc-tetrofosmin, of whom 54 (43%) patients had been on PPIs for more than 2 weeks. Stomach wall activity was identified on stress SPECT using computed tomographic attenuation maps and was scored using a four-point grading scale into clinically relevant (scores 2 or 3) or nonrelevant (scores 0 or 1).Patients on PPIs had stomach wall uptake more frequently as compared with patients not using PPIs (22 vs. 7%, P=0.017). Dyspepsia was similar in both groups. Prolonged use of PPIs is associated with stomach wall uptake of (99m)Tc-tetrofosmin in stress cadmium-zinc-telluride-SPECT images. Gastric symptoms were not associated with stomach wall uptake.

Is the required therapeutic effect always achieved by racemic switch of proton-pump inhibitors?

PubMed Central

Zhou, Quan; Yan, Xiao-Feng; Pan, Wen-Sheng; Zeng, Su

2008-01-01

Many of the drugs currently used in medical practice are racemates. The enantiomers of a racemic drug differ in pharmacodynamics and/or pharmacokinetics, thus in some cases it is preferable to develop pure enantiomers by racemic switch. In a recent study by Pai et al, dexrabeprazole [R(+)-rabeprazole] (10 mg) was found to be more effective than rabeprazole (20 mg) in the treatment of gastroesophageal reflux disease. We read with great interest in this study and discussed whether such racemic switch would be applicable to other proton-pump inhibitors (PPIs). A literature review indicates that stereoselective pharmacokinetics, rather than stereoselective pharmacological activity, is the main cause of differences in clinical efficacy between pure enantiomer and racemic PPI. Racemic switches of PPI provide the therapeutic advantages such as reducing metabolic load on the body, simplifying pharmacokinetics, providing benefit to the non-responders to standard dose of racemate, more homogenous response to treatment and better efficacy with equal safety. Further studies in quantitative structure-activity relationships (QSARs) are needed to address the fact that the preferred enantiomer of PPI is not always in the same absolute configuration, i.e., S-form is for omeprazole, pantoprazole and tenatoprazole whereas R-form is for lansoprazole and rabeprazole. PMID:18442220

Pantoprazole: a new proton pump inhibitor.

PubMed

Jungnickel, P W

2000-11-01

This paper reviews the pharmacology, clinical efficacy, and tolerability of pantoprazole in comparison with those of other available proton pump inhibitors (PPIs). Relevant English-language research and review articles were identified by database searches of MEDLINE, International Pharmaceutical Abstracts, and UnCover, and by examining the reference lists of the articles so identified. In selecting data for inclusion, the author gave preference to full-length articles published in peer-reviewed journals. Like other PPIs, pantoprazole exerts its pharmacodynamic actions by binding to the proton pump (H+,K+ -adenosine triphosphatase) in the parietal cells, but, compared with other PPIs, its binding may be more specific for the proton pump. Pantoprazole is well absorbed when administered as an enteric-coated, delayed-release tablet, with an oral bioavailability of approximately 77%. It is hepatically metabolized via cytochrome P2C19 to hydroxypantoprazole, an inactive metabolite that subsequently undergoes sulfate conjugation. The elimination half-life ranges from 0.9 to 1.9 hours and is independent of dose. Pantoprazole has similar efficacy to other PPIs in the healing of gastric and duodenal ulcers, as well as erosive esophagitis, and as part of triple-drug regimens for the eradication of Helicobacter pylori from the gastric mucosa. It is well tolerated, with the most common adverse effects being headache, diarrhea, flatulence, and abdominal pain. In clinical studies, it has been shown to have no interactions with various other agents, including carbamazepine, cisapride, cyclosporine, digoxin, phenytoin, theophylline, and warfarin. Pantoprazole appears to be as effective as other PPIs. Its low potential for drug interactions may give it an advantage in patients taking other drugs.

Risk factors and prescription patterns of gastroesophageal reflux disease: HEAL study in Pakistan.

PubMed

Butt, Arshad Kamal; Hashemy, Irfan

2014-07-01

To determine the frequency of the use of proton-pump inhibitor therapy in patients with typical symptoms of gastroesophageal reflux disease and evaluate its risk factors. The cross-sectional study was conducted between June 2010 and February 2011 across 10 cities of Pakistan. Adult patients giving a current history of typical gastroesophageal reflux disease symptoms were included. Information on patient demography, medical history, family history, prescription patterns, lifestyle factors and dietary habits were collected. SPSS 18 was used for statistical analysis and descriptive statistics were used for the analysis of categorical and continuous variables. Of the 1010 patients enrolled, 954 (94.45%) formed the study population. Of them, 520 (54.5%) were men. The overall mean age was 41.9 +/- 12.5 years, and 439 (46%) had body mass index > or = 25 kg/m2. Further, 805 (84.4%) reported history of dyspepsia while 692 (72.5%) had gastroesophageal reflux disease during the preceding year. Family history of acid peptic disease was reported by 231 (24.2%) patients. Prior to consultation, 505 (52.9%) patients were on proton-pump inhibitors. Following consultation, 923 (96.8%) patients were prescribed proton-pump inhibitors, with omeprazole being the preferred choice in 577 (60.5%). Associated risk factors included regular use of nonsteroidal anti-inflammatory drugs in 355 (37.2%) and current smoking in 210 (22.0%). Consuming spicy meals was reported by 666 (70.0%). Nearly half the patients with typical gastroesophageal reflux disease symptoms were overweight, and a majority consumed spicy meals. Proton-pump inhibitors were widely prescribed, and omeprazole was the preferred choice of drug.

Prescribing patterns and economic costs of proton pump inhibitors in Colombia

PubMed Central

Fernández, Alejandra; Castrillón, Juan Daniel; Campo, Carlos Felipe; Echeverri, Luis Felipe; Gaviria, Andrés; Londoño, Manuel José; Ochoa, Sergio Andrés; Ruíz, Joaquín Octavio

2013-01-01

Objective: To determine the prescribing patterns for proton pump inhibitors and to estimate the economic cost of their use in a group of patients affiliated with the Colombian Health System. Methods: This is a descriptive observational study. Data for analysis consisted of prescriptions dispensed between October 1st, 2010 and October 31st, 2010 and were collected from a systematic database of 4.2 million members. Socio-demographic variables were considered along with the defined daily dose,comedication, convenience of the indication for proton pump inhibitor use and costs. Results: In this study, 113,560 prescriptions were dispensed in 89 cities, mostly to women (57.6%) with a mean age of 54.4 ± 18.7 years; the drugs were omeprazole (n= 111.294; 97.81%),esomeprazole (n= 1.378; 1.2%), lansoprazole (n= 524; 0.4%), pantoprazole and rabeprazole. The indication for 87.349 of the formulas (76.9%) was justified and statistically associated with the use of NSAIDs, antithrombotics, corticosteroids, anti-ulcer, antibiotics and prokinetics. No justification was found for 26.211 (23.1%) of the prescriptions, which were associated with antidiabetics, antihypertensives, hypolipidemics and others (p <0.001).The annual justified cost was estimated to be US$ 1,654,701 and the unjustified cost was estimated to be U.S. $2,202,590, as calculated using the minimum reference prices. Discussion: Each month, the Colombian health system is overloaded by unjustified costs that include payments for non-approved indications of proton pump inhibitors and for drugs outside the list of essential medications. This issue is contributing to rising costs of healthcare in Colombia. PMID:24892316

NSAID gastropathy and enteropathy: distinct pathogenesis likely necessitates distinct prevention strategies

PubMed Central

Wallace, John L

2012-01-01

The mechanisms underlying the ability of nonsteroidal anti-inflammatory drugs (NSAIDs) to cause ulceration in the stomach and proximal duodenum are well understood, and this injury can largely be prevented through suppression of gastric acid secretion (mainly with proton pump inhibitors). In contrast, the pathogenesis of small intestinal injury induced by NSAIDs is less well understood, involving more complex mechanisms than those in the stomach and proximal duodenum. There is clear evidence for important contributions to NSAID enteropathy of enteric bacteria, bile and enterohepatic recirculation of the NSAID. There is no evidence that suppression of gastric acid secretion will reduce the incidence or severity of NSAID enteropathy. Indeed, clinical data suggest little, if any, benefit. Animal studies suggest a significant exacerbation of NSAID enteropathy when proton pump inhibitors are co-administered with the NSAID. This worsening of damage appears to be linked to changes in the number and types of bacteria in the small intestine during proton pump inhibitor therapy. The distinct mechanisms of NSAID-induced injury in the stomach/proximal duodenum versus the more distal small intestine likely dictate distinct strategies for prevention. PMID:21627632

A rapid Fourier transform infrared spectroscopic method for analysis of certain proton pump inhibitors in binary and ternary mixtures

NASA Astrophysics Data System (ADS)

Khashaba, Pakinaz Y.; Ali, Hassan Refat H.; El-Wekil, Mohamed M.

2018-02-01

A simple and non-destructive FTIR method was used to determine certain proton pump inhibitors (PPIs) in binary and ternary mixtures. Proton pump inhibitors (PPIs); omeprazole (OMZ), esomeprazole (EZM), lansoprazole (LAN), pantoprazole sodium (PAN sodium) and rabeprazole sodium (RAB sodium) in binary mixture with domperidone (DOM) and ternary mixture of OMZ, clarithromycin (CLM) and tinidazole (TNZ) were determined in the solid-state by FTIR spectroscopy for the first time. The method was validated according to ICH-guidelines where linearity was ranged from 20 to 850 μg/g and 20-360 μg/g for PPIs and DOM, respectively in binary mixtures and 10-400, 100-8000 and 150-14,000 μg/g for OMZ, CLM and TNZ, respectively. Limits of detection were found to be 6-100 and 9-100 μg/g for PPIs and DOM, respectively and 4, 40 and 50 μg/g for OMZ, CLM and TNZ, respectively. The method was applied successfully for determination of the cited drugs in their respective pharmaceutical dosage forms.

Properties of the anion-binding site of pharaonis Halorhodopsin studied by ultrafast pump-probe spectroscopy and low-temperature FTIR spectroscopy.

PubMed

Nakashima, Keisuke; Nakamura, Takumi; Takeuchi, Satoshi; Shibata, Mikihiro; Demura, Makoto; Tahara, Tahei; Kandori, Hideki

2009-06-18

Halorhodopsin (HR) is a light-driven chloride pump. Cl(-) is bound in the Schiff base region of the retinal chromophore, and unidirectional Cl(-) transport is probably enforced by the specific hydrogen-bonding interaction with the protonated Schiff base and internal water molecules. It is known that HR from Natronobacterium pharaonis (pHR) also pumps NO(3)(-) with similar efficiency, suggesting that NO(3)(-) binds to the Cl(-)-binding site. In the present study, we investigated the properties of the anion-binding site by means of ultrafast pump-probe spectroscopy and low-temperature FTIR spectroscopy. The obtained data were surprisingly similar between pHR-NO(3)(-) and pHR-Cl(-), even though the shapes and sizes of the two anions are quite different. Femtosecond pump-probe spectroscopy showed very similar excited-state dynamics between pHR-NO(3)(-) and pHR-Cl(-). Low-temperature FTIR spectroscopy of unlabeled and [zeta-(15)N]Lys-labeled pHR revealed almost identical hydrogen-bonding strengths of the protonated retinal Schiff base between pHR-NO(3)(-) and pHR-Cl(-), which is similarly strengthened after retinal isomerization. There were spectral variations for water stretching vibrations between pHR-NO(3)(-) and pHR-Cl(-), suggesting that the water molecules hydrate each anion. Nevertheless, the overall spectral features were similar for the two species. These observations strongly suggest that the anion-binding site has a flexible structure and that the interaction between retinal and the anions is weak, despite the presence of an electrostatic interaction. Such a flexible hydrogen-bonding network in the Schiff base region in HR appears to be in remarkable contrast to that in light-driven proton-pumping proteins.

Electrogenic steps of light-driven proton transport in ESR, a retinal protein from Exiguobacterium sibiricum.

PubMed

Siletsky, Sergey A; Mamedov, Mahir D; Lukashev, Evgeniy P; Balashov, Sergei P; Dolgikh, Dmitriy A; Rubin, Andrei B; Kirpichnikov, Mikhail P; Petrovskaya, Lada E

2016-11-01

A retinal protein from Exiguobacterium sibiricum (ESR) functions as a light-driven proton pump. Unlike other proton pumps, it contains Lys96 instead of a usual carboxylic residue in the internal proton donor site. Nevertheless, the reprotonation of the Schiff base occurs fast, indicating that Lys96 facilitates proton transfer from the bulk. In this study we examined kinetics of light-induced transmembrane electrical potential difference, ΔΨ, generated in proteoliposomes reconstituted with ESR. We show that total magnitude of ΔΨ is comparable to that produced by bacteriorhodopsin but its kinetic components and their pH dependence are substantially different. The results are in agreement with the earlier finding that proton uptake precedes reprotonation of the Schiff base in ESR, suggesting that Lys96 is unprotonated in the initial state and gains a proton transiently in the photocycle. The electrogenic phases and the photocycle transitions related to proton transfer from the bulk to the Schiff base are pH dependent. At neutral pH, they occur with τ 0.5ms and 4.5ms. At alkaline pH, the fast component ceases and Schiff base reprotonation slows. At pH8.4, a spectrally silent electrogenic component with τ 0.25ms is detected, which can be attributed to proton transfer from the bulk to Lys96. At pH5.1, the amplitude of ΔΨ decreases 10 fold, reflecting a decreased yield and rate of proton transfer, apparently from protonation of the acceptor (Asp85-His57 pair) in the initial state. The features of the photoelectric potential generation correlate with the ESR structure and proposed mechanism of proton transfer. Copyright © 2016 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subramaniam, S.; Marti, T.; Khorana, H.G.

Previous studies with site-specific mutants of bacteriorhodopsin have demonstrated that replacement of Asp-85 or Arg-82 affects the absorption spectrum. Between pH 5.5 and 7, the Asp-85----Glu and Arg-82----Ala mutants exist in a pH-dependent equilibrium between purple (lambda max approximately 550/540 nm) and blue (lambda max approximately 600/590 nm) forms of the pigment. Measurement of proton transport as a function of wavelength in reconstituted vesicles shows that proton-pumping activities for the above mutants reside exclusively in their respective purple species. For both mutants, formation of the blue form with decreasing pH is accompanied by loss of proton transport activity. The Asp-85----Asnmore » mutant displays a blue chromophore (lambda max approximately 588 nm), is inactive in proton translocation from pH 5 to 7.5, and shows no transition to the purple form. In contrast, the Asp-212----Asn mutant is purple (lambda max approximately 555 nm) and shows no transition to a blue chromophore with decreasing pH. The experiments suggest that (i) the pKa of the purple-to-blue transition is directly influenced by the pKa of the carboxylate at residue 85 and (ii) the relative strengths of interaction between the protonated Schiff base, Asp-85, Asp-212, and Arg-82 make a major contribution to the regulation of color and function of bacteriorhodopsin.« less

Occupational Airborne Contact Dermatitis From Proton Pump Inhibitors.

PubMed

DeKoven, Joel G; Yu, Ashley M

2015-01-01

Few published reports have described occupational contact dermatitis from proton pump inhibitor (PPI) exposure in the literature. We present an additional case of a 58-year-old male pharmaceutical worker with an occupational airborne allergic contact dermatitis to PPIs confirmed by patch testing. This is a novel report of workplace exposure to dexlansoprazole and esomeprazole PPIs with resultant clinical contact allergy and relevant positive patch test results to these 2 agents. A literature review of all previously reported cases of occupational contact dermatitis to PPI is summarized. The case also emphasizes the importance of even minute exposures when considering workplace accommodation.

Coprescribing proton-pump inhibitors with nonsteroidal anti-inflammatory drugs: risks versus benefits

PubMed Central

Gwee, Kok Ann; Goh, Vernadine; Lima, Graca

2018-01-01

Nonsteroidal anti-inflammatory drugs (NSAIDs) are often coadministered with proton-pump inhibitors (PPIs) to reduce NSAID-induced gastrointestinal (GI) adverse events. This coadministration is generally regarded as safe, and is included in many of the guidelines on NSAID prescription. However, recent evidence indicates that the GI risks associated with NSAIDs can be potentiated when they are combined with PPIs. This review discusses the GI effects and complications of NSAIDs and how PPIs may potentiate these effects, options for prevention of GI side effects, and appropriate use of PPIs in combination with NSAIDs. PMID:29491719

Coprescribing proton-pump inhibitors with nonsteroidal anti-inflammatory drugs: risks versus benefits.

PubMed

Gwee, Kok Ann; Goh, Vernadine; Lima, Graca; Setia, Sajita

2018-01-01

Nonsteroidal anti-inflammatory drugs (NSAIDs) are often coadministered with proton-pump inhibitors (PPIs) to reduce NSAID-induced gastrointestinal (GI) adverse events. This coadministration is generally regarded as safe, and is included in many of the guidelines on NSAID prescription. However, recent evidence indicates that the GI risks associated with NSAIDs can be potentiated when they are combined with PPIs. This review discusses the GI effects and complications of NSAIDs and how PPIs may potentiate these effects, options for prevention of GI side effects, and appropriate use of PPIs in combination with NSAIDs.

[Development of a perforated peptic ulcer in a child during high dose prednisolone treatment].

PubMed

Moll Harboe, Kirstine; Midtgaard, Helle; Wewer, Vibeke; Cortes, Dina

2012-09-24

Since perforated peptic ulcer is uncommon in children proton pump inhibitor prophylaxis is not routinely recommended when children are treated with high dose steroids. We describe a case of perforated ulcer in a six-year-old patient with nephrotic syndrome treated with high dose prednisolone. Initially, ulcer was not suspected due to uncharacteristic symptoms. The child developed peritoneal signs and surgery revealed a perforated peptic ulcer in the stomach. We recommend treatment with proton pump inhibitors if children, who are treated with high dose steroids develop abdominal symptoms, which can be caused by an ulcus.

Antiprotozoal activity of proton-pump inhibitors.

PubMed

Pérez-Villanueva, Jaime; Romo-Mancillas, Antonio; Hernández-Campos, Alicia; Yépez-Mulia, Lilián; Hernández-Luis, Francisco; Castillo, Rafael

2011-12-15

Parasitic diseases are still a major health problem in developing countries. In our effort to find new antiparasitic agents, in this Letter we report the in vitro antiprotozoal activity of omeprazole, lansoprazole, rabeprazole and pantoprazole against Trichomonas vaginalis, Giardia intestinalis and Entamoeba histolytica. Molecular modeling studies were an important tool to highlight the potential antiprotozoal activity of these drugs. Experimental evaluations revealed a strong activity for all compounds tested. Rabeprazole and pantoprazole were the most active compounds, having IC(50) values in the nanomolar range, which were even better than metronidazole, the drug of choice for these parasites. Copyright © 2011 Elsevier Ltd. All rights reserved.

Presence of a plant-like proton-pumping pyrophosphatase in acidocalcisomes of Trypanosoma cruzi.

PubMed

Scott, D A; de Souza, W; Benchimol, M; Zhong, L; Lu, H G; Moreno, S N; Docampo, R

1998-08-21

The vacuolar-type proton-translocating pyrophosphatase (V-H+-PPase) is an enzyme previously described in detail only in plants. This paper demonstrates its presence in the trypanosomatid Trypanosoma cruzi. Pyrophosphate promoted organellar acidification in permeabilized amastigotes, epimastigotes, and trypomastigotes of T. cruzi. This activity was stimulated by K+ ions and was inhibited by Na+ ions and pyrophosphate analogs, as is the plant activity. Separation of epimastigote extracts on Percoll gradients yielded a dense fraction that contained H+-PPase activity measured both by proton uptake and phosphate release but lacked markers for mitochondria, lysosomes, glycosomes, cytosol, and plasma membrane. Antiserum raised against specific sequences of the plant V-H+-PPase cross-reacted with a T. cruzi protein, which was also detectable in the dense Percoll fraction. The organelles in this fraction appeared by electron microscopy to consist mainly of acidocalcisomes (acidic calcium storage organelles). This identification was confirmed by x-ray microanalysis. Immunofluorescence and immunoelectron microscopy indicated that the V-H+-PPase was located in the plasma membrane and acidocalcisomes of the three different forms of the parasite. Pyrophosphate was able to drive calcium uptake in permeabilized T. cruzi. This uptake depended upon a proton gradient and was reversed by a specific V-H+-PPase inhibitor. Our results imply that the phylogenetic distribution of V-H+-PPases is much wider than previously perceived but that the enzyme has a unique subcellular location in trypanosomes.

Numerical Modeling of Flow through Phloem Considering Active Loading

NASA Astrophysics Data System (ADS)

Liu, Jin; Sze, Tsun-Kay Jackie; Dutta, Prashanta

2013-11-01

Transport through phloem is of significant interest in engineering applications including self-powered microfluidic pumps. We present a phloem model, combining protein level mechanics with cellular level fluid transport. Fluid flow and sucrose transport through a petiole sieve tube are simulated using the Nernst-Planck, Navier-Stokes, and continuity equations. Governing equations are solved using the finite volume method with dynamically calculated boundary conditions. Sieve tube cell structure consisting of sieve plates is included in a two dimensional model by computational cell blocking. Sucrose transport is incorporated as a boundary condition through a six-state model, bringing in active loading mechanisms with consideration of physical plant properties. The effects of reaction rates and leaf sucrose concentration are investigated to understand the transport mechanism in petiole sieve tubes. Numerical results show that increasing forward reactions of the proton sucrose transporter significantly promotes the pumping ability. A lower leaf sieve sucrose concentration results in a lower wall inflow velocity, but yields a higher inflow of water due to the active loading mechanism. The overall effect is higher outflow velocity for lower leaf sieve sucrose concentration because the increase in inflow velocity outweighs wall velocity. This new phloem model provides new insights on mechanisms potentially useful for fluidic pumping in self-powered microfluidic pumps. This work is supported in part by the National Science Fundation grant CBET-1250107.

Protein Activity of the Fusarium fujikuroi Rhodopsins CarO and OpsA and Their Relation to Fungus–Plant Interaction

PubMed Central

Adam, Alexander; Deimel, Stephan; Pardo-Medina, Javier; García-Martínez, Jorge; Konte, Tilen; Limón, M. Carmen; Avalos, Javier

2018-01-01

Fungi possess diverse photosensory proteins that allow them to perceive different light wavelengths and to adapt to changing light conditions in their environment. The biological and physiological roles of the green light-sensing rhodopsins in fungi are not yet resolved. The rice plant pathogen Fusarium fujikuroi exhibits two different rhodopsins, CarO and OpsA. CarO was previously characterized as a light-driven proton pump. We further analyzed the pumping behavior of CarO by patch-clamp experiments. Our data show that CarO pumping activity is strongly augmented in the presence of the plant hormone indole-3-acetic acid and in sodium acetate, in a dose-dependent manner under slightly acidic conditions. By contrast, under these and other tested conditions, the Neurospora rhodopsin (NR)-like rhodopsin OpsA did not exhibit any pump activity. Basic local alignment search tool (BLAST) searches in the genomes of ascomycetes revealed the occurrence of rhodopsin-encoding genes mainly in phyto-associated or phytopathogenic fungi, suggesting a possible correlation of the presence of rhodopsins with fungal ecology. In accordance, rice plants infected with a CarO-deficient F. fujikuroi strain showed more severe bakanae symptoms than the reference strain, indicating a potential role of the CarO rhodopsin in the regulation of plant infection by this fungus. PMID:29324661

Fluoroquinolone resistance of Serratia marcescens: involvement of a proton gradient-dependent efflux pump.

PubMed

Kumar, Ayush; Worobec, Elizabeth A

2002-10-01

To determine the presence of a proton gradient-dependent efflux of fluoroquinolone drugs in Serratia marcescens. Thirteen clinical isolates of S. marcescens were screened for resistance to four fluoroquinolones: ofloxacin, ciprofloxacin, norfloxacin and nalidixic acid by determining MICs. The presence of a proton gradient-dependent efflux mechanism was assessed using ethidium bromide accumulation assays. Drug accumulation studies for norfloxacin, ciprofloxacin and ofloxacin were performed to determine the drug specificity of efflux. Western transfer of cellular proteins, followed by immunodetection using anti-AcrA (Escherichia coli) antibodies were used to demonstrate the presence of a resistance-nodulation-cell division (RND) pump protein. PCR was used to identify a RND pump-encoding gene using primers for two conserved motifs within inner membrane components of RND proteins. A mutant strain of S. marcescens, UOC-67WL, was isolated by culturing the wild-type strain in the presence of ciprofloxacin in T-soy media and was subjected to the same studies as described above for the clinical isolates. Ethidium bromide accumulation assays confirmed the presence of a proton gradient-dependent efflux mechanism in S. marcescens. One clinical isolate, T-861, and the mutant strain, UOC-67WL, were found to efflux ciprofloxacin and ofloxacin. Western immunoblot results confirmed overexpression of an AcrA-like protein in T-861 and UOC-67WL. Sequencing of the PCR product showed the presence of a mexF-like gene, which is overexpressed in nfxC mutants of Pseudomonas aeruginosa. This study reports the presence of a proton gradient-dependent efflux mechanism in S. marcescens.

The emerging structure of vacuolar ATPases.

PubMed

Drory, Omri; Nelson, Nathan

2006-10-01

Bioenergetics and physiology of primary pumps have been revitalized by new insights into the mechanism of energizing biomembranes. Structural information is becoming available, and the three-dimensional structure of F-ATPase is being resolved. The growing understanding of the fundamental mechanism of energy coupling may revolutionize our view of biological processes. The F- and V-ATPases (vacuolar-type ATPase) exhibit a common mechanical design in which nucleotide-binding on the catalytic sector, through a cycle of conformation changes, drives the transmembrane passage of protons by turning a membrane-embedded rotor. This motor can run in forward or reverse directions, hydrolyzing ATP as it pumps protons uphill or creating ATP as protons flow downhill. In contrast to F-ATPases, whose primary function in eukaryotic cells is to form ATP at the expense of the proton-motive force (pmf), V-ATPases function exclusively as an ATP-dependent proton pump. The pmf generated by V-ATPases in organelles and membranes of eukaryotic cells is utilized as a driving force for numerous secondary transport processes. V- and F-ATPases have similar structure and mechanism of action, and several of their subunits evolved from common ancestors. Electron microscopy studies of V-ATPase revealed its general structure at low resolution. Recently, several structures of V-ATPase subunits, solved by X-ray crystallography with atomic resolution, were published. This, together with electron microscopy low-resolution maps of the whole complex, and biochemistry cross-linking experiments, allows construction of a structural model for a part of the complex that may be used as a working hypothesis for future research.

Lactobacillus paracasei F19 versus placebo for the prevention of proton pump inhibitor-induced bowel symptoms: a randomized clinical trial.

PubMed

Compare, Debora; Rocco, Alba; Sgamato, Costantino; Coccoli, Pietro; Campo, Salvatore Maria Antonio; Nazionale, Immacolata; Larussa, Tiziana; Luzza, Francesco; Chiodini, Paolo; Nardone, Gerardo

2015-04-01

Proton pump inhibitors may foster intestinal dysbiosis and related bowel symptoms. To evaluate the effect of Lactobacillus paracasei F19 on bowel symptom onset in patients on long-term proton pump inhibitors. In this randomized, double-blind, placebo-controlled study, patients with typical gastroesophageal reflux disease symptoms receiving pantoprazole 40 mg/d for six months were randomly assigned to receive: (A) Lactobacillus paracasei F19 bid for three days/week for six months; (B) placebo bid for three days/week for six months; (C) Lactobacillus paracasei F19 bid for three days/week for three months and placebo bid for three days/week for the following three months; (D) placebo bid for three days/week for three months and Lactobacillus paracasei F19 bid for three days/week for the following three months. Bloating, flatulence, abdominal pain and bowel habit were assessed monthly. 100/312 patients were enrolled. In the parallel groups, the treatment-by-time interaction affected bloating (p = 0.015), while Lactobacillus paracasei F19 treatment alone affected flatulence (p = 0.011). Moreover, the treatment-by-time interaction significantly affected the mean score of bloating (p = 0.01) and flatulence (p < 0.0001), the mean stool form (p = 0.03) and mean stool frequency/week (p = 0.016). Analysis of the cross-over groups, limited to the first three months because of carry-over effect, confirmed these results. Lactobacillus paracasei F19 supplementation prevents bowel symptom onset in patients on long-term proton pump inhibitors. Copyright © 2015 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Proton-pump inhibitors are associated with a reduced risk for bleeding and perforated gastroduodenal ulcers attributable to non-steroidal anti-inflammatory drugs: a nested case-control study

PubMed Central

Vonkeman, Harald E; Fernandes, Robert W; van der Palen, Job; van Roon, Eric N; van de Laar, Mart AFJ

2007-01-01

Treatment with non-steroidal anti-inflammatory drugs (NSAIDs) is hampered by gastrointestinal ulcer complications, such as ulcer bleeding and perforation. The efficacy of proton-pump inhibitors in the primary prevention of ulcer complications arising from the use of NSAIDs remains unproven. Selective cyclooxygenase-2 (COX-2) inhibitors reduce the risk for ulcer complications, but not completely in high-risk patients. This study determines which patients are especially at risk for NSAID ulcer complications and investigates the effectiveness of different preventive strategies in daily clinical practice. With the use of a nested case-control design, a large cohort of NSAID users was followed for 26 months. Cases were patients with NSAID ulcer complications necessitating hospitalisation; matched controls were selected from the remaining cohort of NSAID users who did not have NSAID ulcer complications. During the observational period, 104 incident cases were identified from a cohort of 51,903 NSAID users with 10,402 patient years of NSAID exposure (incidence 1% per year of NSAID use, age at diagnosis 70.4 ± 16.7 years (mean ± SD), 55.8% women), and 284 matched controls. Cases were characterised by serious, especially cardiovascular, co-morbidity. In-hospital mortality associated with NSAID ulcer complications was 10.6% (incidence 21.2 per 100,000 NSAID users). Concomitant proton-pump inhibitors (but not selective COX-2 inhibitors) were associated with a reduced risk for NSAID ulcer complications (the adjusted odds ratio 0.33; 95% confidence interval 0.17 to 0.67; p = 0.002). Especially at risk for NSAID ulcer complications are elderly patients with cardiovascular co-morbidity. Proton-pump inhibitors are associated with a reduced risk for NSAID ulcer complications. PMID:17521422

Proton pump inhibitors are associated with increased risk of development of chronic kidney disease.

PubMed

Arora, Pradeep; Gupta, Anu; Golzy, Mojgan; Patel, Nilang; Carter, Randolph L; Jalal, Kabir; Lohr, James W

2016-08-03

Acute interstitial nephritis secondary to proton pump inhibitors (PPIs) frequently goes undiagnosed due to its subacute clinical presentation, which may later present as chronic kidney disease (CKD). We investigated the association of PPI use with the development of CKD and death. Two separate retrospective case-control study designs were employed with a prospective logistic regression analysis of data to evaluate the association of development of CKD and death with PPI use. The population included 99,269 patients who were seen in primary care VISN2 clinics from 4/2001 until 4/2008. For evaluation of the CKD outcome, 22,807 with preexisting CKD at the first observation in Veterans Affairs Health Care Upstate New York (VISN2) network data system were excluded. Data obtained included use of PPI (Yes/No), demographics, laboratory data, pre-PPI comorbidity variables. A total of 19,311/76,462 patients developed CKD. Of those who developed CKD 24.4 % were on PPI. Patients receiving PPI were less likely to have vascular disease, COPD, cancer and diabetes. Of the total of 99,269 patients analyzed for mortality outcome, 11,758 died. A prospective logistic analysis of case-control data showed higher odds for development of CKD (OR 1.10 95 % CI 1.05-1.16) and mortality (OR 1.76, 95 % CI 1.67-1.84) among patients taking PPIs versus those not on PPIs. Use of proton pump inhibitors is associated with increased risk of development of CKD and death. With the large number of patients being treated with proton pump inhibitors, healthcare providers need to be better educated about the potential side effects of these medications.

The effect of charged lipids on bacteriorhodopsin membrane reconstitution and its photochemical activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Zhen; Bai Jing; Xu Yuhong

2008-07-11

Bacteriorhodopsin (BR) was reconstituted into artificial lipid membrane containing various charged lipid compositions. The proton pumping activity of BR under flash and continuous illumination, proton permeability across membrane, as well as the decay kinetics of the photocycle intermediate M{sub 412} were studied. The results showed that lipid charges would significantly affect the orientation of BR inserted into lipid membranes. In liposomes containing anionic lipids, BRs were more likely to take natural orientation as in living cells. In neutral or positively charged liposomes, most BRs were reversely assembled, assuming an inside out orientation. Moreover, the lipids charges also affect BR's Mmore » intermediate kinetics, especially the slow component in M intermediate decay. The half-life M{sub 412s} increased significantly in BRs in liposomes containing cationic lipids, while decreased in those in anionic liposomes.« less

PHYSIOLOGY OF ION TRANSPORT ACROSS THE TONOPLAST OF HIGHER PLANTS.

PubMed

Barkla, Bronwyn J.; Pantoja, Omar

1996-06-01

The vacuole of plant cells plays an important role in the homeostasis of the cell. It is involved in the regulation of cytoplasmic pH, sequestration of toxic ions and xenobiotics, regulation of cell turgor, storage of amino acids, sugars and CO2 in the form of malate, and possibly as a source for elevating cytoplasmic calcium. All these activities are driven by two primary active transport mechanisms present in the vacuolar membrane (tonoplast). These two mechanisms employ high-energy metabolites to pump protons into the vacuole, establishing a proton electrochemical potential that mediates the transport of a diverse range of solutes. Within the past few years, great advances at the molecular and functional levels have been made on the characterization and identification of these mechanisms. The aim of this review is to summarize these studies in the context of the physiology of the plant cell.

Sensory Transduction and Electrical Signaling in Guard Cells

PubMed Central

Serrano, Elba E.; Zeiger, Eduardo

1989-01-01

Guard cells are a valuable model system for the study of photoreception, ion transport, and osmoregulation in plant cells. Changes in stomatal apertures occur when sensing mechanisms within the guard cells transduce environmental stimull into the ion fluxes and biosynthesis of organic solutes that regulate turgor. The electrical events mediating sensory transduction in guard cells can be characterized with a variety of electrophysiological recording techniques. Recent experiments applying the patch clamp method to guard cell protoplasts have demonstrated activation of electrogenic pumps by blue and red light as well as the presence of potassium channels in guard cell plasmalemma. Light activation of electrogenic proton pumping and the ensuing gating of voltage-dependent ion channels appear to be components of sensory transduction of the stomatal response to light. Mechanisms underlying stomatal control by environmental signals can be understood by studying electrical events associated with ion transport. PMID:16667138

Enhanced Proton Translocating Pyrophosphatase Activity Improves Nitrogen Use Efficiency in Romaine Lettuce1[C][W][OA

PubMed Central

Paez-Valencia, Julio; Sanchez-Lares, Jonathan; Marsh, Ellen; Dorneles, Liane T.; Santos, Mirella P.; Sanchez, Diego; Winter, Alexander; Murphy, Sean; Cox, Jennifer; Trzaska, Marcin; Metler, Jason; Kozic, Alex; Facanha, Arnoldo R.; Schachtman, Daniel; Sanchez, Charles A.; Gaxiola, Roberto A.

2013-01-01

Plant nitrate (NO3−) acquisition depends on the combined activities of root high- and low-affinity NO3− transporters and the proton gradient generated by the plasma membrane H+-ATPase. These processes are coordinated with photosynthesis and the carbon status of the plant. Here, we present the characterization of romaine lettuce (Lactuca sativa ‘Conquistador’) plants engineered to overexpress an intragenic gain-of-function allele of the type I proton translocating pyrophosphatase (H+-PPase) of Arabidopsis (Arabidopsis thaliana). The proton-pumping and inorganic pyrophosphate hydrolytic activities of these plants are augmented compared with control plants. Immunohistochemical data show a conspicuous increase in H+-PPase protein abundance at the vasculature of the transgenic plants. Transgenic plants displayed an enhanced rhizosphere acidification capacity consistent with the augmented plasma membrane H+-ATPase proton transport values, and ATP hydrolytic capacities evaluated in vitro. These transgenic lines outperform control plants when challenged with NO3− limitations in laboratory, greenhouse, and field scenarios. Furthermore, we report the characterization of a lettuce LsNRT2.1 gene that is constitutive up-regulated in the transgenic plants. Of note, the expression of the LsNRT2.1 gene in control plants is regulated by NO3− and sugars. Enhanced accumulation of 15N-labeled fertilizer by transgenic lettuce compared with control plants was observed in greenhouse experiments. A negative correlation between the level of root soluble sugars and biomass is consistent with the strong root growth that characterizes these transgenic plants. PMID:23307651

Chemoelectrical energy conversion of adenosine triphosphate

NASA Astrophysics Data System (ADS)

Sundaresan, Vishnu Baba; Sarles, Stephen Andrew; Leo, Donald J.

2007-04-01

Plant and animal cell membranes transport charged species, neutral molecules and water through ion pumps and channels. The energy required for moving species against established concentration and charge gradients is provided by the biological fuel - adenosine triphosphate (ATP) -synthesized within the cell. The adenosine triphosphatase (ATPases) in a plant cell membrane hydrolyze ATP in the cell cytoplasm to pump protons across the cell membrane. This establishes a proton gradient across the membrane from the cell exterior into the cell cytoplasm. This proton motive force stimulates ion channels that transport nutrients and other species into the cell. This article discusses a device that converts the chemical energy stored in adenosine triphosphate into electrical power using a transporter protein, ATPase. The V-type ATPase proteins used in our prototype are extracted from red beet(Beta vulgaris) tonoplast membranes and reconstituted in a bilayer lipid membrane or BLM formed from POPC and POPS lipids. A pH7 medium that can support ATP hydrolysis is provided on both sides of the membrane and ATP is dissolved in the pH7 buffer on one side of the membrane. Hydrolysis of ATP results in the formation of a phosphate ion and adenosine diphosphate. The energy from the reaction activates ATPase in the BLM and moves a proton across the membrane. The charge gradient established across the BLM due to the reaction and ion transport is converted into electrical current by half-cell reference electrodes. The prototype ATPase cell with an effective BLM area of 4.15 mm2 carrying 15 μl of ATPase proteins was observed to develop a steady state peak power output of 70 nW, which corresponds to a specific power of 1.69 μW/cm2 and a current density of 43.4 μA/cm2 of membrane area.

The impact of proton pump inhibitors on the human gastrointestinal microbiome.

PubMed

Freedberg, Daniel E; Lebwohl, Benjamin; Abrams, Julian A

2014-12-01

Potent gastric acid suppression using proton pump inhibitors (PPIs) is common in clinical practice but may have important effects on human health that are mediated through changes in the gastrointestinal microbiome. In the esophagus, PPIs change the normal bacterial milieu to decrease distal esophageal exposure to inflammatory gram-negative bacteria. In the stomach, PPIs alter the abundance and location of gastric Helicobacter pylori and other bacteria. In the small bowel, PPIs cause polymicrobial small bowel bacterial overgrowth and have been associated with the diagnosis of celiac disease. In the colon, PPIs associate with incident but not recurrent Clostridium difficile infection. Copyright © 2014 Elsevier Inc. All rights reserved.

Evidence-based assessment of proton-pump inhibitors in Helicobacter pylori eradication: a systematic review.

PubMed

Nagaraja, Vinayak; Eslick, Guy D

2014-10-28

Peptic ulcer disease continues to be issue especially due to its high prevalence in the developing world. Helicobacter pylori (H. pylori) infection associated duodenal ulcers should undergo eradication therapy. There are many regimens offered for H. pylori eradication which include triple, quadruple, or sequential therapy regimens. The central aim of this systematic review is to evaluate the evidence for H. pylori therapy from a meta-analytical outlook. The consequence of the dose, type of proton-pump inhibitor, and the length of the treatment will be debated. The most important risk factor for eradication failure is resistance to clarithromycin and metronidazole.

The Proton Pump Inhibitor Non-Responder: A Clinical Conundrum

PubMed Central

Hussain, Zilla H; Henderson, Emily E; Maradey-Romerao, Carla; George, Nina; Fass, Ronnie; Lacy, Brian E

2015-01-01

Gastroesophageal reflux disease (GERD) is a highly prevalent chronic condition where in stomach contents reflux into the esophagus causing symptoms, esophageal injury, and subsequent complications. Proton pump inhibitors (PPI) remain the mainstay of therapy for acid suppression. Despite their efficacy, significant proportions of GERD patients are either partial or non-responders to PPI therapy. Patients should be assessed for mechanisms that can lead to PPI failure and may require further evaluation to investigate for alternative causes. This monograph will outline a diagnostic approach to the PPI non-responder, review mechanisms associated with PPI failure, and discuss therapeutic options for those who fail to respond to PPI therapy. PMID:26270485

Proton Pump Inhibitor use in Hospitalized Patients: Is Overutilization Becoming a Problem?

PubMed Central

Durand, Cheryl; Willett, Kristine C.; Desilets, Alicia R.

2012-01-01

Proton pump inhibitors (PPIs) are among the most common classes of medications prescribed. Though they were previously thought of as safe, recent literature has shown risks associated with their use including increased risk for Clostridium difficile infection, pneumonia, and fractures. Due to these risks, it is important to determine if PPIs are being used appropriately. This review evaluates seven studies in hospitalized patients. Additionally, this review evaluates literature pertaining to recently discovered adverse reactions; all studies found PPIs are being overutilized. Findings highlight the importance of evaluating appropriate therapy with these agents and recommending discontinuation if a proper indication does not exist. PMID:24833936

NSAID gastropathy and enteropathy: distinct pathogenesis likely necessitates distinct prevention strategies.

PubMed

Wallace, John L

2012-01-01

The mechanisms underlying the ability of nonsteroidal anti-inflammatory drugs (NSAIDs) to cause ulceration in the stomach and proximal duodenum are well understood, and this injury can largely be prevented through suppression of gastric acid secretion (mainly with proton pump inhibitors). In contrast, the pathogenesis of small intestinal injury induced by NSAIDs is less well understood, involving more complex mechanisms than those in the stomach and proximal duodenum. There is clear evidence for important contributions to NSAID enteropathy of enteric bacteria, bile and enterohepatic recirculation of the NSAID. There is no evidence that suppression of gastric acid secretion will reduce the incidence or severity of NSAID enteropathy. Indeed, clinical data suggest little, if any, benefit. Animal studies suggest a significant exacerbation of NSAID enteropathy when proton pump inhibitors are co-administered with the NSAID. This worsening of damage appears to be linked to changes in the number and types of bacteria in the small intestine during proton pump inhibitor therapy. The distinct mechanisms of NSAID-induced injury in the stomach/proximal duodenum versus the more distal small intestine likely dictate distinct strategies for prevention. © 2011 The Author. British Journal of Pharmacology © 2011 The British Pharmacological Society.

Antitumor effect of combination of the inhibitors of two new oncotargets: proton pumps and reverse transcriptase.

PubMed

Lugini, Luana; Sciamanna, Ilaria; Federici, Cristina; Iessi, Elisabetta; Spugnini, Enrico Pierluigi; Fais, Stefano

2017-01-17

Tumor therapy needs new approaches in order to improve efficacy and reduce toxicity of the current treatments. The acidic microenvironment and the expression of high levels of endogenous non-telomerase reverse transcriptase (RT) are common features of malignant tumor cells. The anti-acidic proton pump inhibitor Lansoprazole (LAN) and the non-nucleoside RT inhibitor Efavirenz (EFV) have shown independent antitumor efficacy. LAN has shown to counteract drug tumor resistance. We tested the hypothesis that combination of LAN and EFV may improve the overall antitumor effects. We thus pretreated human metastatic melanoma cells with LAN and then with EFV, both in 2D and 3D spheroid models. We evaluated the treatment effect by proliferation and cell death/apoptosis assays in classical and in pulse administration experiments. The action of EFV was negatively affected by the tumor microenvironmental acidity, and LAN pretreatment overcame the problem. LAN potentiated the cytotoxicity of EFV to melanoma cells and, when administered during the drug interruption period, prevented the replacement of tumor cell growth.This study supports the implementation of the current therapies with combination of Proton Pumps and Reverse Transcriptase inhibitors.

Antitumor effect of combination of the inhibitors of two new oncotargets: proton pumps and reverse transcriptase

PubMed Central

Lugini, Luana; Sciamanna, Ilaria; Federici, Cristina; Iessi, Elisabetta; Spugnini, Enrico Pierluigi; Fais, Stefano

2017-01-01

Tumor therapy needs new approaches in order to improve efficacy and reduce toxicity of the current treatments. The acidic microenvironment and the expression of high levels of endogenous non-telomerase reverse transcriptase (RT) are common features of malignant tumor cells. The anti-acidic proton pump inhibitor Lansoprazole (LAN) and the non-nucleoside RT inhibitor Efavirenz (EFV) have shown independent antitumor efficacy. LAN has shown to counteract drug tumor resistance. We tested the hypothesis that combination of LAN and EFV may improve the overall antitumor effects. We thus pretreated human metastatic melanoma cells with LAN and then with EFV, both in 2D and 3D spheroid models. We evaluated the treatment effect by proliferation and cell death/apoptosis assays in classical and in pulse administration experiments. The action of EFV was negatively affected by the tumor microenvironmental acidity, and LAN pretreatment overcame the problem. LAN potentiated the cytotoxicity of EFV to melanoma cells and, when administered during the drug interruption period, prevented the replacement of tumor cell growth. This study supports the implementation of the current therapies with combination of Proton Pumps and Reverse Transcriptase inhibitors. PMID:27926505

Air swallowing can be responsible for non-response of heartburn to high-dose proton pump inhibitor.

PubMed

Zentilin, P; Accornero, L; Dulbecco, P; Savarino, E; Savarino, V

2005-06-01

Intraluminal electrical impedance is a novel technique, which is able for the first time to provide a qualitative assessment of refluxed material moving from the stomach to the oesophagus. In other words, the presence of air can be differentiated from that of liquid, because the former is characterised by high and the latter by low impedance compared with baseline. Moreover, the combined measurement of electrical impedance and pH-metry permits to distinguish acid from non-acid liquid reflux. One of the most important clinical applications of this method is to assess the reasons for poor response of GORD patients to high-dose proton pump inhibitors. This case report describes the results of impedance in the evaluation of a young woman, who did not respond to twice-daily doses of rabeprazole. She continued to complain of heartburn as major symptom and impedance allowed us to clarify that it was not related to acid or non-acid reflux, but to air swallowing. Therefore, this technique identified aerophagia to be responsible for persistent heartburn despite high-dose proton pump inhibitor and prevented the adoption of more aggressive, but probably unuseful therapies, such as the surgical one.

General pharmacological properties of YJA 20379-1, a novel proton pump inhibitor with antiulcer activities.

PubMed

Lee, E B; Cho, S I; Cheon, S A; Chang, M S; Kim, K B; Sohn, S K; Chung, Y K

1999-12-01

The general pharmacological properties of YJA 20379-1 (2-amino-4,5-dihydro-8-phenylimidazo[2,1-b]thiazolo[4,5-g]benzo thi azole), a novel proton pump inhibitor with antiulcer activities, were investigated in mice, rats, guinea pig and rabbits. YJA 20379-1 at oral doses of 50, 100 and 200 mg/kg did not affect the general behaviour, hexobarbital hypnosis, motor coordination and body temperature in mice. The drug does not have analgesic and anticonvulsant action at 200 mg/kg p.o. The locomotor activity was not affected at 100 mg/kg p.o., but at 200 mg/kg, the activity was suppressed. YJA 20379-1 (at 2 x 10(-4) g/ml) did neither produce any contraction nor relaxation of isolated organs such as rat fundus, rat uterus, guinea pig ileum and guinea pig vas deferens, and the drug did not antagonize the contractile response to several spasmogens, such as histamine, acetylcholine, serotonin and oxytocin, and the drug up to 200 mg/kg p.o. did not affect pupil size of mice. The intestinal propulsion in mice was not affected up to 200 mg/kg p.o. The gastric emptying in rats was not affected at 100 mg/kg p.o., even if retardation in gastric emptying occurred at 200 mg/kg. YJA 20379-1 did not show anti-inflammatory action nor did it affect urinary excretion up to 200 mg/kg p.o. From these results, it is suggested that YJA 20379-1 at the high dose of 100 mg/kg p.o. may not exert any adverse effects.

Designed inhibitors with hetero linkers for gastric proton pump H+,K+-ATPase: Steered molecular dynamics and metadynamics studies.

PubMed

Jana, Kalyanashis; Bandyopadhyay, Tusar; Ganguly, Bishwajit

2017-11-01

Acid suppressant SCH28080 and its derivatives reversibly reduce acid secretion activity of the H + ,K + -ATPase in a K + competitive manner. The results on homologation of the SCH28080 by varying the linker chain length suggested the improvement in efficacy. However, the pharmacokinetic studies reveal that the hydrophobic nature of the CH 2 linker units may not help it to function as a better acid suppressant. We have exploited the role of linker unit to enhance the efficacy of such reversible acid suppressant drug molecules using hetero linker, i.e., disulfide and peroxy linkers. The logarithm of partition coefficient defined for a drug molecule relates to the partition coefficient, which allows the optimum solubility characteristics to reach the active site. The logarithm of partition coefficient calculated for the designed inhibitors suggests that inhibitors would possibly reach the active site in sufficient concentration like in the case of SCH28080. The steered molecular dynamics studies have revealed that the Inhibitor-1 with disulfide linker unit is more stable at the active site due to greater noncovalent interactions compared to the SCH28080. Centre of mass distance analysis suggests that the Cysteine-813 amino acid residue selectively plays an important role in the inhibition of H + ,K + -ATPase for Inhibitor-1. Furthermore, the quantum chemical calculations with M11L/6-31+G(d,p) level of theory have been performed to account the noncovalent interactions responsible for the stabilization of inhibitor molecules in the active site gorge of the gastric proton pump at different time scale. The hydrogen bonding and hydrophobic interaction studies corroborate the center of mass distance analysis as well. Well-tempered metadynamics free energy surface and center of mass separation analysis for the Inhibitor-1 is in good agreement with the steered molecular dynamics results. The torsional angle of the linker units seems to be crucial for better efficacy of drug molecules. The torsional angle of linker units of SCH28080 (COCH 2 C) and of Inhibitor 1 (CSSC) prefers to lie within ∼60°-90° for a longer time during the simulations, whereas, the peroxy linker (COOC) of Inhibitor 2 prefers to adopt ∼120-160°. Therefore, it appears that the smaller torsion angle of linker units can achieve better interactions with the active site residues of H + ,K + -ATPase to inhibit the acid secretion activity. The reversible drug molecules with disulfide linker unit would be a promising candidate as proton pump antagonist to H + ,K + -ATPase. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of proton pump inhibitors on magnesium balance: is there a link to cardiovascular risk?

PubMed

Pisani, Laura Francesca; Filippi, Elisabetta; Vavassori, Sara; Munizio, Nadia; Vecchi, Maurizio; Pastorelli, Luca

2016-03-01

Magnesium (Mg(2+)) is the second most copious element inside human cells and the fourth most abundant positively charged ion in the human body. It is of central importance for a broad variety of physiological processes, including intracellular signaling, neuronal excitability, muscle contraction, bone formation and enzyme activation. Its overall balance is tightly regulated by the concerted actions of the intestine, bones and kidneys. Disturbance of this balance can have serious consequences. Symptoms of hypomagnesaemia include tetany, seizures and cardiac arrhythmias, whereas hypermagnesaemia may cause cardiovascular and neuromuscular abnormalities. Drugs can interfere with Mg(2+) homoeostasis in several ways, and proton-pump inhibitors (PPIs) have been associated with hypomagnesaemia. A better understanding of the molecular mechanisms underlying the adverse effects of these medications on Mg(2+) balance will isuggest ideas for prevention and treatment, and might provide greater insight into Mg(2+) homoeostasis. This review gives an overview of the influence of PPIs on Mg(2+) homoeostasis and provides some understanding of the underlying physiological mechanisms. Moreover, we will discuss the potential link between PPI-induced changes in Mg(2+) homeostasis, and the reported cardiovascular risk observed in long-term PPI users.

pH sensing and regulation in cancer.

PubMed

Damaghi, Mehdi; Wojtkowiak, Jonathan W; Gillies, Robert J

2013-12-17

Cells maintain intracellular pH (pHi) within a narrow range (7.1-7.2) by controlling membrane proton pumps and transporters whose activity is set by intra-cytoplasmic pH sensors. These sensors have the ability to recognize and induce cellular responses to maintain the pHi, often at the expense of acidifying the extracellular pH. In turn, extracellular acidification impacts cells via specific acid-sensing ion channels (ASICs) and proton-sensing G-protein coupled receptors (GPCRs). In this review, we will discuss some of the major players in proton sensing at the plasma membrane and their downstream consequences in cancer cells and how these pH-mediated changes affect processes such as migration and metastasis. The complex mechanisms by which they transduce acid pH signals to the cytoplasm and nucleus are not well understood. However, there is evidence that expression of proton-sensing GPCRs such as GPR4, TDAG8, and OGR1 can regulate aspects of tumorigenesis and invasion, including cofilin and talin regulated actin (de-)polymerization. Major mechanisms for maintenance of pHi homeostasis include monocarboxylate, bicarbonate, and proton transporters. Notably, there is little evidence suggesting a link between their activities and those of the extracellular H(+)-sensors, suggesting a mechanistic disconnect between intra- and extracellular pH. Understanding the mechanisms of pH sensing and regulation may lead to novel and informed therapeutic strategies that can target acidosis, a common physical hallmark of solid tumors.

The selectivity of the Na+/K+-pump is controlled by binding site protonation and self-correcting occlusion

PubMed Central

Rui, Huan; Artigas, Pablo; Roux, Benoît

2016-01-01

The Na+/K+-pump maintains the physiological K+ and Na+ electrochemical gradients across the cell membrane. It operates via an 'alternating-access' mechanism, making iterative transitions between inward-facing (E1) and outward-facing (E2) conformations. Although the general features of the transport cycle are known, the detailed physicochemical factors governing the binding site selectivity remain mysterious. Free energy molecular dynamics simulations show that the ion binding sites switch their binding specificity in E1 and E2. This is accompanied by small structural arrangements and changes in protonation states of the coordinating residues. Additional computations on structural models of the intermediate states along the conformational transition pathway reveal that the free energy barrier toward the occlusion step is considerably increased when the wrong type of ion is loaded into the binding pocket, prohibiting the pump cycle from proceeding forward. This self-correcting mechanism strengthens the overall transport selectivity and protects the stoichiometry of the pump cycle. DOI: http://dx.doi.org/10.7554/eLife.16616.001 PMID:27490484

Essential arginine in subunit a and aspartate in subunit c of FoF1 ATP synthase: effect of repositioning within helix 4 of subunit a and helix 2 of subunit c.

PubMed

Langemeyer, Lars; Engelbrecht, Siegfried

2007-07-01

FoF1 ATP synthase couples proton flow through the integral membrane portion Fo (ab2c10) to ATP-synthesis in the extrinsic F1-part ((alphabeta)3gammadeltaepsilon) (Escherichia coli nomenclature and stoichiometry). Coupling occurs by mechanical rotation of subunits c10gammaepsilon relative to (alphabeta)3deltaab2. Two residues were found to be essential for proton flow through ab2c10, namely Arg210 in subunit a (aR210) and Asp61 in subunits c (cD61). Their deletion abolishes proton flow, but "horizontal" repositioning, by anchoring them in adjacent transmembrane helices, restores function. Here, we investigated the effects of "vertical" repositioning aR210, cD61, or both by one helical turn towards the N- or C-termini of their original helices. Other than in the horizontal the vertical displacement changes the positions of the side chains within the depth of the membrane. Mutant aR210A/aN214R appeared to be short-circuited in that it supported proton conduction only through EF1-depleted EFo, but not in EFoEF1, nor ATP-driven proton pumping. Mutant cD61N/cM65D grew on succinate, retained the ability to synthesize ATP and supported passive proton conduction but apparently not ATP hydrolysis-driven proton pumping.

The effect of proton pump inhibitors on the CYP2C19 enzyme activity evaluated by the pantoprazole-13C breath test in GERD patients: clinical relevance for personalized medicine.

PubMed

Modak, Anil S; Klyarytska, Iryna; Kriviy, Valerij; Tsapyak, Tatjana; Rabotyagova, Yliya

2016-12-17

Patients with gastroesophageal reflux disease (GERD) are routinely prescribed one of the six FDA approved proton pump inhibitors (PPI). All of these PPI are inhibitors of CYP2C19 enzyme to varying degrees. The phenotype pantoprazole- 13 C breath test (Ptz-BT) was used to identify patients who are poor metabolizers (PM) and the extent of phenoconversion of CYP2C19 enzyme activity caused by four PPI (omeprazole, esomprazole pantoprazole and rabeprazole) in 54 newly diagnosed GERD patients prior to initiating randomly selected PPI therapy and 30 d after PPI therapy. The phenoconversion after 30 d of PPI therapy in GERD patients was statistically significant (p  =0.001) with omeprazole/esomeprazole (n  =  27) strong CYP2C19 inhibitors, while there was no change in CYP2C19 enzyme activity (p  =  0.8) with pantoprazole/ rabeprazole (n  =  27), weak CYP2C19 inhibitors. The concommitant use of omeprazole/esomeprazole, therefore, could have critical clinical relevance in individualizing medications metabolized primarily by CYP2C19 such as PPI, clopidogrel, phenytoin, cyclophosphamide, thalidomide, citalopram, clonazepam, diazepam, proguanil, tivantinib etc. The rapid (30 min), in vivo, and non-invasive phenotype Ptz-BT can evaluate CYP2C19 enzyme activity. More importantly, it can identify GERD patients with low CYP2C19 enzyme activity (PM), caused by PPI or other concomitant medications, who would benefit from dose adjustments to maintain efficacy and avoid toxicity. The existing CYP2C19 genotype tests cannot predict the phenotype nor can it detect phenoconversion due to non genetic factors.

Proton Pump Inhibitors Inhibit Pancreatic Secretion: Role of Gastric and Non-Gastric H+/K+-ATPases

PubMed Central

Tozzi, Marco; Giannuzzo, Andrea; Sørensen, Christiane E.; Novak, Ivana

2015-01-01

The mechanism by which pancreas secretes high HCO3 - has not been fully resolved. This alkaline secretion, formed in pancreatic ducts, can be achieved by transporting HCO3 - from serosa to mucosa or by moving H+ in the opposite direction. The aim of the present study was to determine whether H+/K+-ATPases are expressed and functional in human pancreatic ducts and whether proton pump inhibitors (PPIs) have effect on those. Here we show that the gastric HKα1 and HKβ subunits (ATP4A; ATP4B) and non-gastric HKα2 subunits (ATP12A) of H+/K+-ATPases are expressed in human pancreatic cells. Pumps have similar localizations in duct cell monolayers (Capan-1) and human pancreas, and notably the gastric pumps are localized on the luminal membranes. In Capan-1 cells, PPIs inhibited recovery of intracellular pH from acidosis. Furthermore, in rats treated with PPIs, pancreatic secretion was inhibited but concentrations of major ions in secretion follow similar excretory curves in control and PPI treated animals. In addition to HCO3 -, pancreas also secretes K+. In conclusion, this study calls for a revision of the basic model for HCO3 - secretion. We propose that proton transport is driving secretion, and that in addition it may provide a protective pH buffer zone and K+ recirculation. Furthermore, it seems relevant to re-evaluate whether PPIs should be used in treatment therapies where pancreatic functions are already compromised. PMID:25993003

Effect of a pH Gradient on the Protonation States of Cytochrome c Oxidase: A Continuum Electrostatics Study.

PubMed

Magalhães, Pedro R; Oliveira, A Sofia F; Campos, Sara R R; Soares, Cláudio M; Baptista, António M

2017-02-27

Cytochrome c oxidase (CcO) couples the reduction of dioxygen to water with transmembrane proton pumping, which leads to the generation of an electrochemical gradient. In this study we analyze how one of the components of the electrochemical gradient, the difference in pH across the membrane, or ΔpH, influences the protonation states of residues in CcO. We modified our continuum electrostatics/Monte Carlo (CE/MC) method in order to include the ΔpH and applied it to the study of CcO, in what is, to our best knowledge, the first CE/MC study of CcO in the presence of a pH gradient. The inclusion of a transmembrane pH gradient allows for the identification of residues whose titration behavior depends on the pH on both sides of the membrane. Among the several residues with unusual titration profiles, three are well-known key residues in the proton transfer process of CcO: E286 I , Y288 I , and K362 I . All three residues have been previously identified as being critical for the catalytic or proton pumping functions of CcO. Our results suggest that when the pH gradient increases, these residues may be part of a regulatory mechanism to stem the proton flow.

Pharmacokinetics and Pharmacodynamics of Azeloprazole Sodium, a Novel Proton Pump Inhibitor, in Healthy Japanese Volunteers.

PubMed

Toda, Ryoko; Shiramoto, Masanari; Komai, Emi; Yoshii, Kazuyoshi; Hirayama, Masamichi; Kawabata, Yoshihiro

2018-04-01

The pharmacokinetics (PK) and pharmacodynamics (PD) of proton pump inhibitors differ among cytochrome P450 (CYP) 2C19 genotypes. Therefore, we developed azeloprazole sodium (Z-215), a novel proton pump inhibitor, whose metabolism is not affected by CYP2C19 activity in vitro. However, the PK and PD of azeloprazole sodium have not been evaluated in Japanese subjects. We conducted an open-label, crossover study in healthy Japanese male volunteers to evaluate the plasma concentration and intragastric pH with respect to CYP2C19 genotype after repeated administration of 10, 20, and 40 mg azeloprazole sodium and 10 and 20 mg rabeprazole sodium (rabeprazole). The plasma concentration profile of azeloprazole sodium was similar among genotypes, whereas that of rabeprazole differed. The 24-hour intragastric pH ≥ 4 holding time ratio (pH ≥ 4 HTR) of azeloprazole sodium was similar among genotypes. The pH ≥ 4 HTR was 52.5%-60.3%, 55.1%-65.8%, and 69.4%-77.1% after administration of 10, 20, and 40 mg azeloprazole sodium, respectively, and 59.2%-72.3% and 64.4%-91.2% after administration of 10 and 20 mg rabeprazole, respectively, on the fifth day of dosing. The maximum plasma concentration (C max ), area under the plasma concentration-time curve (AUC), and pH ≥ 4 HTR of azeloprazole sodium were proportional to dose. The C max , AUC, and pH ≥ 4 HTR on day 5 were slightly higher following administration of 20 mg azeloprazole sodium before comparison with after a meal. No serious adverse events were observed. These results suggest that azeloprazole sodium is useful for treating gastroesophageal reflux disease in all CYP2C19 genotypes. © 2017, The American College of Clinical Pharmacology.

V-ATPase proton pumping activity is required for adult zebrafish appendage regeneration.

PubMed

Monteiro, Joana; Aires, Rita; Becker, Jörg D; Jacinto, António; Certal, Ana C; Rodríguez-León, Joaquín

2014-01-01

The activity of ion channels and transporters generates ion-specific fluxes that encode electrical and/or chemical signals with biological significance. Even though it is long known that some of those signals are crucial for regeneration, only in recent years the corresponding molecular sources started to be identified using mainly invertebrate or larval vertebrate models. We used adult zebrafish caudal fin as a model to investigate which and how ion transporters affect regeneration in an adult vertebrate model. Through the combined use of biophysical and molecular approaches, we show that V-ATPase activity contributes to a regeneration-specific H+ ef`flux. The onset and intensity of both V-ATPase expression and H+ efflux correlate with the different regeneration rate along the proximal-distal axis. Moreover, we show that V-ATPase inhibition impairs regeneration in adult vertebrate. Notably, the activity of this H+ pump is necessary for aldh1a2 and mkp3 expression, blastema cell proliferation and fin innervation. To the best of our knowledge, this is the first report on the role of V-ATPase during adult vertebrate regeneration.

V-ATPase Proton Pumping Activity Is Required for Adult Zebrafish Appendage Regeneration

PubMed Central

Monteiro, Joana; Aires, Rita; Becker, Jörg D.; Jacinto, António; Certal, Ana C.; Rodríguez-León, Joaquín

2014-01-01

The activity of ion channels and transporters generates ion-specific fluxes that encode electrical and/or chemical signals with biological significance. Even though it is long known that some of those signals are crucial for regeneration, only in recent years the corresponding molecular sources started to be identified using mainly invertebrate or larval vertebrate models. We used adult zebrafish caudal fin as a model to investigate which and how ion transporters affect regeneration in an adult vertebrate model. Through the combined use of biophysical and molecular approaches, we show that V-ATPase activity contributes to a regeneration-specific H+ ef`flux. The onset and intensity of both V-ATPase expression and H+ efflux correlate with the different regeneration rate along the proximal-distal axis. Moreover, we show that V-ATPase inhibition impairs regeneration in adult vertebrate. Notably, the activity of this H+ pump is necessary for aldh1a2 and mkp3 expression, blastema cell proliferation and fin innervation. To the best of our knowledge, this is the first report on the role of V-ATPase during adult vertebrate regeneration. PMID:24671205

Persistent gastro-oesophageal reflux symptoms despite proton pump inhibitor therapy

PubMed Central

Ang, Daphne; How, Choon How; Ang, Tiing Leong

2016-01-01

About one-third of patients with suspected gastro-oesophageal reflux disease (GERD) do not respond symptomatically to proton pump inhibitors (PPIs). Many of these patients do not suffer from GERD, but may have underlying functional heartburn or atypical chest pain. Other causes of failure to respond to PPIs include inadequate acid suppression, non-acid reflux, oesophageal hypersensitivity, oesophageal dysmotility and psychological comorbidities. Functional oesophageal tests can exclude cardiac and structural causes, as well as help to confi rm or exclude GERD. The use of PPIs should only be continued in the presence of acid reflux or oesophageal hypersensitivity for acid reflux-related events that is proven on functional oesophageal tests. PMID:27779277

Persistent gastro-oesophageal reflux symptoms despite proton pump inhibitor therapy.

PubMed

Ang, Daphne; How, Choon How; Ang, Tiing Leong

2016-10-01

About one-third of patients with suspected gastro-oesophageal reflux disease (GERD) do not respond symptomatically to proton pump inhibitors (PPIs). Many of these patients do not suffer from GERD, but may have underlying functional heartburn or atypical chest pain. Other causes of failure to respond to PPIs include inadequate acid suppression, non-acid reflux, oesophageal hypersensitivity, oesophageal dysmotility and psychological comorbidities. Functional oesophageal tests can exclude cardiac and structural causes, as well as help to confi rm or exclude GERD. The use of PPIs should only be continued in the presence of acid reflux or oesophageal hypersensitivity for acid reflux-related events that is proven on functional oesophageal tests. Copyright: © Singapore Medical Association.

Development of a Compact, Efficient Cooling Pump for Space Suit Life Support Systems

NASA Technical Reports Server (NTRS)

van Boeyen, Roger; Reeh, Jonathan; Trevino, Luis

2009-01-01

A compact, low-power electrochemically-driven fluid cooling pump is currently being developed by Lynntech, Inc. With no electric motor and minimal lightweight components, the pump is significantly lighter than conventional rotodynamic and displacement pumps. Reliability and robustness is achieved with the absence of rotating or moving components (apart from the bellows). By employing sulfonated polystyrene-based proton exchange membranes, rather than conventional Nafion membranes, a significant reduction in the actuator power consumption was demonstrated. Lynntech also demonstrated that these membranes possess the necessary mechanical strength, durability, and temperature range for long life space operation. The preliminary design for a Phase II prototype pump compares very favorably to the fluid cooling pumps currently used in space suit primary life support systems (PLSSs). Characteristics of the electrochemically-driven pump are described and the benefits of the technology as a replacement for electric motor pumps in mechanically pumped single-phase fluid loops is discussed.

Patient acceptability and experiences of therapeutic switching of proton pump inhibitors within the National Preferred Drugs initiative in Ireland.

PubMed

O'Connor, G; O'Keeffe, D; Darker, C; O'Shea, B

2017-08-01

A 'Preferred Drugs' initiative was introduced into Ireland in 2013. This identified a single recommended drug to be prescribed to patients requiring treatment from a particular class of drugs. This study investigates how patients on established proton pump inhibitor (PPI) therapy experienced the therapeutic switching of their medication to the 'preferred drug', and the extent to which they regarded it as an acceptable practice. The experiences of 61 patients on established proton pump inhibitor (PPI) therapy were sought before and after their drug was switched to the 'preferred drug'. Eighty per cent of patients were happy to switch medications. When asked for their opinions on medications in general, 71% felt doctors should prescribe the least expensive medication, 84% agreed that all licensed medications were safe while 67% felt their GP changing medication for cost reasons was safe. After 8 weeks, 20% of patients had switched back to their old PPI. When asked how they felt about their medication change, 74% felt happy or pleased. The majority of patients in our study were satisfied to have their medication switched. However, prescribers should be mindful that 1 in 5 patients encountered problems as a result of the switching process.

Key parameters controlling the performance of catalytic motors.

PubMed

Esplandiu, Maria J; Afshar Farniya, Ali; Reguera, David

2016-03-28

The development of autonomous micro/nanomotors driven by self-generated chemical gradients is a topic of high interest given their potential impact in medicine and environmental remediation. Although impressive functionalities of these devices have been demonstrated, a detailed understanding of the propulsion mechanism is still lacking. In this work, we perform a comprehensive numerical analysis of the key parameters governing the actuation of bimetallic catalytic micropumps. We show that the fluid motion is driven by self-generated electro-osmosis where the electric field originates by a proton current rather than by a lateral charge asymmetry inside the double layer. Hence, the surface potential and the electric field are the key parameters for setting the pumping strength and directionality. The proton flux that generates the electric field stems from the proton gradient induced by the electrochemical reactions taken place at the pump. Surprisingly the electric field and consequently the fluid flow are mainly controlled by the ionic strength and not by the conductivity of the solution, as one could have expected. We have also analyzed the influence of the chemical fuel concentration, electrochemical reaction rates, and size of the metallic structures for an optimized pump performance. Our findings cast light on the complex chemomechanical actuation of catalytic motors and provide important clues for the search, design, and optimization of novel catalytic actuators.

Stress ulcer prophylaxis with a proton pump inhibitor versus placebo in critically ill patients (SUP-ICU trial): study protocol for a randomised controlled trial.

PubMed

Krag, Mette; Perner, Anders; Wetterslev, Jørn; Wise, Matt P; Borthwick, Mark; Bendel, Stepani; Pelosi, Paolo; Keus, Frederik; Guttormsen, Anne Berit; Schefold, Joerg C; Møller, Morten Hylander

2016-04-19

Critically ill patients in the intensive care unit (ICU) are at risk of clinically important gastrointestinal bleeding, and acid suppressants are frequently used prophylactically. However, stress ulcer prophylaxis may increase the risk of serious adverse events and, additionally, the quantity and quality of evidence supporting the use of stress ulcer prophylaxis is low. The aim of the SUP-ICU trial is to assess the benefits and harms of stress ulcer prophylaxis with a proton pump inhibitor in adult patients in the ICU. We hypothesise that stress ulcer prophylaxis reduces the rate of gastrointestinal bleeding, but increases rates of nosocomial infections and myocardial ischaemia. The overall effect on mortality is unpredictable. The SUP-ICU trial is an investigator-initiated, pragmatic, international, multicentre, randomised, blinded, parallel-group trial of stress ulcer prophylaxis with a proton pump inhibitor versus placebo (saline) in 3350 acutely ill ICU patients at risk of gastrointestinal bleeding. The primary outcome measure is 90-day mortality. Secondary outcomes include the proportion of patients with clinically important gastrointestinal bleeding, pneumonia, Clostridium difficile infection or myocardial ischaemia, days alive without life support in the 90-day period, serious adverse reactions, 1-year mortality, and health economic analyses. The sample size will enable us to detect a 20 % relative risk difference (5 % absolute risk difference) in 90-day mortality assuming a 25 % event rate with a risk of type I error of 5 % and power of 90 %. The trial will be externally monitored according to Good Clinical Practice standards. Interim analyses will be performed after 1650 and 2500 patients. The SUP-ICU trial will provide high-quality data on the benefits and harms of stress ulcer prophylaxis with a proton pump inhibitor in critically ill adult patients admitted in the ICU. ClinicalTrials.gov Identifier: NCT02467621 .

TOPPITS: Trial Of Proton Pump Inhibitors in Throat Symptoms. Study protocol for a randomised controlled trial.

PubMed

Watson, Gillian; O'Hara, James; Carding, Paul; Lecouturier, Jan; Stocken, Deborah; Fouweather, Tony; Wilson, Janet

2016-04-01

Persistent throat symptoms and Extra Oesophageal Reflux (EOR) are among the commonest reasons for attendance at a secondary care throat or voice clinic. There is a growing trend to treat throat symptom patients with proton pump inhibitors (PPIs) to suppress stomach acid, but most controlled studies fail to demonstrate a significant benefit of PPI over placebo. In addition, patient views on PPI use vary widely. A UK multi-centre, randomised, controlled trial for adults with persistent throat symptoms to compare the effectiveness of treatment with the proton pump inhibitor (PPI) lansoprazole versus placebo. The trial includes a six-month internal pilot, during which three sites will recruit 30 participants in total, to assess the practicality of the trial and assess the study procedures and willingness of the patient population to participate. If the pilot is successful, three additional sites will be opened to recruitment, and a further 302 participants recruited across the six main trial sites. Further trial sites may be opened, as necessary. The main trial will continue for a further 18 months. Participants will be followed up for 12 months from randomisation, throughout which both primary and secondary outcome data will be collected. The primary outcome is change in Reflux Symptom Index (RSI) score, the 'area standard' for this type of assessment, after 16 weeks (four months) of treatment. Secondary outcomes are RSI changes at 12 months after randomisation, Quality of Life assessment at four and 12 months, laryngeal mucosal changes, assessments of compliance and side effects, and patient-reported satisfaction. TOPPITS is designed to evaluate the relative effectiveness of treatment with a proton pump inhibitor versus placebo in patients with persistent throat symptoms. This will provide valuable information to clinicians and GPs regarding the treatment and management of care for these patients, on changes in symptoms, and in Quality of Life, over time. ISRCTN38578686 . Registered 17 April 2014.

Compensatory Internalization of Pma1 in V-ATPase Mutants in Saccharomyces cerevisiae Requires Calcium- and Glucose-Sensitive Phosphatases.

PubMed

Velivela, Swetha Devi; Kane, Patricia M

2018-02-01

Loss of V-ATPase activity in organelles, whether through V-ATPase inhibition or V-ATPase ( vma ) mutations, triggers a compensatory downregulation of the essential plasma membrane proton pump Pma1 in Saccharomyces cerevisiae We have previously determined that the α-arrestin Rim8 and ubiquitin ligase Rsp5 are essential for Pma1 ubiquination and endocytosis in response to loss of V-ATPase activity. Here, we show that Pma1 endocytosis in V-ATPase mutants does not require Rim101 pathway components upstream and downstream of Rim8, indicating that Rim8 is acting independently in Pma1 internalization. We find that two phosphatases, the calcium-responsive phosphatase calcineurin and the glucose-sensitive phosphatase Glc7 (PP1), and one of the Glc7 regulatory subunits Reg1, exhibit negative synthetic genetic interactions with vma mutants, and demonstrate that both phosphatases are essential for ubiquitination and endocytic downregulation of Pma1 in these mutants. Although both acute and chronic loss of V-ATPase activity trigger the internalization of ∼50% of surface Pma1, a comparable reduction in Pma1 expression in a pma1-007 mutant neither compensates for loss of V-ATPase activity nor stops further Pma1 endocytosis. The results indicate that the cell surface level of Pma1 is not directly sensed and that internalized Pma1 may play a role in compensating for loss of V-ATPase-dependent acidification. Taken together, these results provide new insights into cross talk between two major proton pumps central to cellular pH control. Copyright © 2018 by the Genetics Society of America.

Vibrational Spectroscopy of Cation and Anion Channelrhodopsins

NASA Astrophysics Data System (ADS)

Yi, Adrian S.

Optogenetics is a technique to control and monitor cell activity with light by expression of specific microbial rhodopsins. Cation channelrhodopsins (CCRs) and anion channelrhodopsins (ACRs) have been demonstrated to activate and silence cell activity, respectively. In this dissertation, the molecular mechanisms of two channelrhodopsins are studied: a CCR from Chlamydomonas augustae (CaChR1) and an ACR from Guillardia theta (GtACR1). The recently discovered GtACR1is especially interesting, as it achieves neural silencing with 1/1000th of the light intensity compared to previous microbial rhodopsin silencing ion pumps. Static and time-resolved resonance Raman, FTIR difference, and UV-visible spectroscopies were utilized in addition to various biochemical and genetic techniques to explore the molecular mechanisms of these channelrhodopsins. In CaChR1, Glu169 and Asp299 residues are located nearby the Schiff base (SB) similar to the homologous residues Asp85 and Asp212, which exist in an ionized state in unphotolyzed bacteriorhodopsin (BR) and play a key role in proton pumping. We observe significant changes in the protonation states of the SB, Glu169, and Asp299 of CaChR1 leading up to the open-channel P2 state, where all three groups exist in a charge neutral state. This unusual charge neutrality along with the position of these groups in the CaChR1 ion channel suggests that charge neutrality plays an important role in cation gating and selectivity in these low efficiency CCRs. Significant differences exist in the photocycle and protonation/hydrogen bonding states of key residues inGtACR1compared to BR and CaChR1. Resonance Raman studies reveal that in the unphotolyzed state of GtACR1, residues Glu68, Ser97 (BR Asp85 homolog), and Asp234 (BR Asp212 homolog) located near the SB exist in charge neutral states. Furthermore, upon K formation, these residues do not change their protonation states. At room temperature, a slow decay of the red-shifted K intermediate is observed, which exists in equilibrium with the L intermediate. At 80 K, a lower thermal barrier for K → L transition is observed compared to BR and CaChR1. This effect may be due to substitution of a Met residue at position 105 for the highly conserved Leu or Ile residue.

H+-type and OH--type biological protonic semiconductors and complementary devices

NASA Astrophysics Data System (ADS)

Deng, Yingxin; Josberger, Erik; Jin, Jungho; Rousdari, Anita Fadavi; Helms, Brett A.; Zhong, Chao; Anantram, M. P.; Rolandi, Marco

2013-10-01

Proton conduction is essential in biological systems. Oxidative phosphorylation in mitochondria, proton pumping in bacteriorhodopsin, and uncoupling membrane potentials by the antibiotic Gramicidin are examples. In these systems, H+ hop along chains of hydrogen bonds between water molecules and hydrophilic residues - proton wires. These wires also support the transport of OH- as proton holes. Discriminating between H+ and OH- transport has been elusive. Here, H+ and OH- transport is achieved in polysaccharide- based proton wires and devices. A H+- OH- junction with rectifying behaviour and H+-type and OH--type complementary field effect transistors are demonstrated. We describe these devices with a model that relates H+ and OH- to electron and hole transport in semiconductors. In turn, the model developed for these devices may provide additional insights into proton conduction in biological systems.

H+-type and OH−-type biological protonic semiconductors and complementary devices

PubMed Central

Deng, Yingxin; Josberger, Erik; Jin, Jungho; Rousdari, Anita Fadavi; Helms, Brett A.; Zhong, Chao; Anantram, M. P.; Rolandi, Marco

2013-01-01

Proton conduction is essential in biological systems. Oxidative phosphorylation in mitochondria, proton pumping in bacteriorhodopsin, and uncoupling membrane potentials by the antibiotic Gramicidin are examples. In these systems, H+ hop along chains of hydrogen bonds between water molecules and hydrophilic residues – proton wires. These wires also support the transport of OH− as proton holes. Discriminating between H+ and OH− transport has been elusive. Here, H+ and OH− transport is achieved in polysaccharide- based proton wires and devices. A H+- OH− junction with rectifying behaviour and H+-type and OH−-type complementary field effect transistors are demonstrated. We describe these devices with a model that relates H+ and OH− to electron and hole transport in semiconductors. In turn, the model developed for these devices may provide additional insights into proton conduction in biological systems. PMID:24089083

The role of endomembrane-localized VHA-c in plant growth.

PubMed

Zhou, Aimin; Takano, Tetsuo; Liu, Shenkui

2018-01-02

In plant cells, the vacuolar-type H + -ATPase (V-ATPase), a large multis`ubunit endomembrane proton pump, plays an important role in acidification of subcellular organelles, pH and ion homeostasis, and endocytic and secretory trafficking. V-ATPase subunit c (VHA-c) is essential for V-ATPase assembly, and is directly responsible for binding and transmembrane transport of protons. In previous studies, we identified a PutVHA-c gene from Puccinellia tenuiflora, and investigated its function in plant growth. Subcellular localization revealed that PutVHA-c is mainly localized in endosomal compartments. Overexpression of PutVHA-c enhanced V-ATPase activity and promoted plant growth in transgenic Arabidopsis. Furthermore, the activity of V-ATPase affected intracellular transport of the Golgi-derived endosomes. Our results showed that endomembrane localized-VHA-c contributes to plant growth by influencing V-ATPase-dependent endosomal trafficking. Here, we discuss these recent findings and speculate on the VHA-c mediated molecular mechanisms involved in plant growth, providing a better understanding of the functions of VHA-c and V-ATPase.

Time-resolved absorbance changes induced by fast acidification of bacteriorhodopsin in vesicle systems.

PubMed Central

Druckmann, S; Ottolenghi, M; Korenstein, R

1985-01-01

The direction of the accessibility to protons of the binding site in bacteriorhodopsin is of primary importance in elucidating the proton-pump mechanism. The problem is approached via the pH-dependent equilibrium bR560 in equilibrium bR605 in vesicles with preferentially oriented purple membranes. Fast acidification (stopped-flow) experiments with inside-out, monomeric, bR vesicles were carried out with and without a buffer enclosed in the vesicle interior. The results, showing a buffer-induced delay in the formation of bR605, indicate that the binding site is accessible to protons from the inside of the vesicles. We arrive at this conclusion also by working with inside-out trimeric vesicles in the presence and in the absence of H+ (and K+) ionophores. The results suggest that in Halobacterium halobium, the binding site and thus the retinal Schiff base are exposed to the outside of the cell. This conclusion is consistent with a pumping mechanism based on a light-induced pK change. PMID:3978185

Real-time observation of intramolecular proton transfer in the electronic ground state of chloromalonaldehyde: an ab initio study of time-resolved photoelectron spectra.

PubMed

do N Varella, Márcio T; Arasaki, Yasuki; Ushiyama, Hiroshi; Takatsuka, Kazuo; Wang, Kwanghsi; McKoy, Vincent

2007-02-07

The authors report on studies of time-resolved photoelectron spectra of intramolecular proton transfer in the ground state of chloromalonaldehyde, employing ab initio photoionization matrix elements and effective potential surfaces of reduced dimensionality, wherein the couplings of proton motion to the other molecular vibrational modes are embedded by averaging over classical trajectories. In the simulations, population is transferred from the vibrational ground state to vibrationally hot wave packets by pumping to an excited electronic state and dumping with a time-delayed pulse. These pump-dump-probe simulations demonstrate that the time-resolved photoelectron spectra track proton transfer in the electronic ground state well and, furthermore, that the geometry dependence of the matrix elements enhances the tracking compared with signals obtained with the Condon approximation. Photoelectron kinetic energy distributions arising from wave packets localized in different basins are also distinguishable and could be understood, as expected, on the basis of the strength of the optical couplings in different regions of the ground state potential surface and the Franck-Condon overlaps of the ground state wave packets with the vibrational eigenstates of the ion potential surface.

Proton pump inhibition and cancer therapeutics: A specific tumor targeting or it is a phenomenon secondary to a systemic buffering?

PubMed

Spugnini, Enrico; Fais, Stefano

2017-04-01

One of the unsolved mysteries in oncology includes the strategies that cancer cells adopt to cope with an adverse microenvironment. However, we knew, from the Warburg's discovery that through their metabolism based on sugar fermentation, cancer cells acidify their microenvironment and this progressive acidification induces a selective pressure, leading to the development of very malignant cells entirely armed to survive in the hostile microenvironment generated by their own metabolism. In the last decades a primordial role for proton exchangers has been supported as a key tumor advantage in facing off the acidic milieu. Proton exchangers do not allow intracellular acidification through a continuous elimination of H+ either outside the cells or within the internal vacuoles. This article wants to comment a translational process through that led to the preclinical demonstration that a class of proton pump inhibitors (PPI) exploited worldwide for peptic ulcer treatment and gastroprotection are indeed powerful chemosensitizers as well. In this process we achieved the clinical proof of concept that PPI may well be included in new anti-cancer strategies with a solid background and rationale. Copyright © 2017 Elsevier Ltd. All rights reserved.

Crystallization and preliminary X-ray analysis of membrane-bound pyrophosphatases.

PubMed

Kellosalo, Juho; Kajander, Tommi; Honkanen, Riina; Goldman, Adrian

2013-02-01

Membrane-bound pyrophosphatases (M-PPases) are enzymes that enhance the survival of plants, protozoans and prokaryotes in energy constraining stress conditions. These proteins use pyrophosphate, a waste product of cellular metabolism, as an energy source for sodium or proton pumping. To study the structure and function of these enzymes we have crystallized two membrane-bound pyrophosphatases recombinantly produced in Saccharomyces cerevisae: the sodium pumping enzyme of Thermotoga maritima (TmPPase) and the proton pumping enzyme of Pyrobaculum aerophilum (PaPPase). Extensive crystal optimization has allowed us to grow crystals of TmPPase that diffract to a resolution of 2.6 Å. The decisive step in this optimization was in-column detergent exchange during the two-step purification procedure. Dodecyl maltoside was used for high temperature solubilization of TmPPase and then exchanged to a series of different detergents. After extensive screening, the new detergent, octyl glucose neopentyl glycol, was found to be the optimal for TmPPase but not PaPPase.

A Genetic Screen for Pathogenicity Genes in the Hemibiotrophic Fungus Colletotrichum higginsianum Identifies the Plasma Membrane Proton Pump Pma2 Required for Host Penetration

PubMed Central

Dahl, Marlis; Müller, Susanne; Voll, Lars M.; Koch, Christian

2015-01-01

We used insertional mutagenesis by Agrobacterium tumefaciens mediated transformation (ATMT) to isolate pathogenicity mutants of Colletotrichum higginsianum. From a collection of 7200 insertion mutants we isolated 75 mutants with reduced symptoms. 19 of these were affected in host penetration, while 17 were affected in later stages of infection, like switching to necrotrophic growth. For 16 mutants the location of T-DNA insertions could be identified by PCR. A potential plasma membrane H+-ATPase Pma2 was targeted in five independent insertion mutants. We genetically inactivated the Ku80 component of the non-homologous end-joining pathway in C. higginsianum to establish an efficient gene knockout protocol. Chpma2 deletion mutants generated by homologous recombination in the ΔChku80 background form fully melanized appressoria but entirely fail to penetrate the host tissue and are non-pathogenic. The ChPMA2 gene is induced upon appressoria formation and infection of A. thaliana. Pma2 activity is not important for vegetative growth of saprophytically growing mycelium, since the mutant shows no growth penalty under these conditions. Colletotrichum higginsianum codes for a closely related gene (ChPMA1), which is highly expressed under most growth conditions. ChPMA1 is more similar to the homologous yeast genes for plasma membrane pumps. We propose that expression of a specific proton pump early during infection may be common to many appressoria forming fungal pathogens as we found ChPMA2 orthologs in several plant pathogenic fungi. PMID:25992547

Development of a Compact Efficient Cooling Pump for Space Suit Life Support Systems

NASA Technical Reports Server (NTRS)

vanBoeyen, Roger W.; Reeh, Jonathan A.; Trevino, Luis

2008-01-01

With the increasing demands placed on extravehicular activity (EVA) for the International Space Station (ISS) assembly and maintenance, along with planned lunar and Martian missions, the need for increased human productivity and capability becomes ever more critical. This is most readily achieved by reduction in space suit weight and volume, and increased hardware reliability, durability, and operating lifetime. Considerable progress has been made with each successive generation of space suit design; from the Apollo A7L suit, to the current Shuttle Extravehicular Mobile Unit (EMU) suit, and the next generation Constellation Space Suit Element (CSSE). However, one area of space suit design which has continued to lag is the fluid pump used to drive the water cooling loop of the Primary Life Support System (PLSS). The two main types of fluid pumps typically used in space applications are rotodynamic pumps (pumping is achieved through a rotary vaned impeller) and displacement pumps (which includes rotary and diaphragm pumps). The rotating and moving parts found in the pumps and electric motor add significantly to the susceptibility to wear and friction, thermal mismatch, and complexity of the pumps. Electric motor-driven pumps capable of achieving high operational reliability are necessarily large, heavy, and energy inefficient. This report describes a development effort conducted for NASA by Lynntech, Inc., who recently demonstrated the feasibility of an electrochemically-driven fluid cooling pump. With no electric motor and minimal lightweight components, an electrochemically-driven pump is expected to be significantly smaller, lighter and achieve a longer life time than conventional rotodynamic and displacement pumps. By employing sulfonated polystyrene-based proton exchange membranes, rather than conventional Nafion membranes, a significant reduction in the actuator power consumption was demonstrated. It was also demonstrated that these membranes possess the necessary mechanical strength, durability, and temperature range for long life space operation. The preliminary design for a Phase II prototype pump compares very favorably to the fluid cooling pumps currently used in space suit portable life support systems (PLSS). Characteristics of the electrochemically-driven pump are described and the benefits of the technology as a replacement for electric motor pumps in mechanically pumped single-phase fluid loops (MPFLs) is discussed.

Ultrafast dynamics of isolated model photoactive yellow protein chromophores: "Chemical perturbation theory" in the laboratory.

PubMed

Vengris, Mikas; Larsen, Delmar S; van der Horst, Michael A; Larsen, Olaf F A; Hellingwerf, Klaas J; van Grondelle, Rienk

2005-03-10

Pump-probe and pump-dump probe experiments have been performed on several isolated model chromophores of the photoactive yellow protein (PYP). The observed transient absorption spectra are discussed in terms of the spectral signatures ascribed to solvation, excited-state twisting, and vibrational relaxation. It is observed that the protonation state has a profound effect on the excited-state lifetime of p-coumaric acid. Pigments with ester groups on the coumaryl tail end and charged phenolic moieties show dynamics that are significantly different from those of other pigments. Here, an unrelaxed ground-state intermediate could be observed in pump-probe signals. A similar intermediate could be identified in the sinapinic acid and in isomerization-locked chromophores by means of pump-dump probe spectroscopy; however, in these compounds it is less pronounced and could be due to ground-state solvation and/or vibrational relaxation. Because of strong protonation-state dependencies and the effect of electron donor groups, it is argued that charge redistribution upon excitation determines the twisting reaction pathway, possibly through interaction with the environment. It is suggested that the same pathway may be responsible for the initiation of the photocycle in native PYP.

New Observation of Wave Excitation and Inverse Cascade in the Foreshock Region

NASA Astrophysics Data System (ADS)

He, Jiansen; Duan, Die; Yan, Limei; Huang, Shiyong; Tu, Chuanyi; Marsch, Eckart; Wang, Linghua; Tian, Hui

2016-04-01

Foreshock with nascent plasma turbulence is regarded as a fascinating region to understand the basic plasma physical processes, e.g., wave-particle interactions as well as wave-wave couplings. Although there have been a bunch of intensive studies on this topic, some key clues about the chain of the physical processes still lacks from observations, e.g., the co-existence of upstream energetic particles as the free energy source, excited pump waves as the wave seed, inverse cascaded daughter waves, and scattered energetic particles as the end of nonlinear processes. A relatively comprehensive case study with some new observations is presented in this work. In our case, upstream energetic protons drifting at tens of Alfvén speed with respect to the background plasma protons is observed from 3DP/PESA-High onboard the WIND spacecraft. When looking at the wave magnetic activities, we are surprised to find the co-existence of high-frequency (0.1-0.5 Hz) large-amplitude right-hand polarized (RHP) waves and low-frequency (0.02-0.1 Hz) small-amplitude left-hand polarized (LHP) waves in the spacecraft (SC) frame. The anti-correlation between magnetic and velocity fluctuations along with the sunward magnetic field direction indicates the low-frequency LHP waves in the SC frame is in fact the sunward upstream RHP waves in the solar wind frame. This new observation lays solid foundation for the applicability of plasma non-resonance instability theory and inverse cascade theory to the foreshock region, in which the downstream high-frequency RHP pump waves are excited by the upstream reflected energetic protons through non-resonance instability and low-frequency RHP daughter waves are generated by the pump waves due to nonlinear parametric decay. The weak signal of alpha particle flux in the foreshock region concerned is also favorable to the occurrence of nonlinear decay process. Furthermore, enhanced downstream energetic proton fluxes are found and inferred to be scattered by the nascent turbulent fluctuations. Therefore, some key clues about the newborn turbulence in the foreshock are supplemented in this work. Nevertheless, the more complete scenario about the fundamental plasma physical processes in the foreshock is left for the newly launched MMS project and the proposed THOR mission.

Anti-ulcer agents: chemical aspect of solving the problem

NASA Astrophysics Data System (ADS)

Rogoza, L. N.; Salakhutdinov, N. F.

2015-01-01

The data on chemical structures and specific activities of compounds functioning as histamine H2-receptor antagonists, H+/K+-ATPase inhibitors at the exchange sites of hydrogen ions (proton pump inhibitors) and potassium ions (K+-competitive acid blockers) published from 1990 to 2013 are surveyed. The antisecretory agents with studied cytoprotective activity or with additional therapeutic properties compensating for disorders of internal defence mechanisms are presented. A separate section is devoted to the drugs that prevent or mitigate the NSAID-induced intestinal damage. All of the considered structures are classified according to the type of biological mechanism of action. Some aspects of the structure-activity relationships for such compounds are considered. The bibliography includes 83 references.

Review of pharmacokinetic and pharmacodynamic modeling and safety of proton pump inhibitors and aspirin.

PubMed

Gesheff, Martin G; Franzese, Christopher J; Bliden, Kevin P; Contino, Chase J; Rafeedheen, Rahil; Tantry, Udaya S; Gurbel, Paul A

2014-09-01

The efficacy of aspirin in primary and secondary prevention of cardiovascular diseases has been convincingly demonstrated. Gastrointestinal (GI) adverse effects with aspirin may lead to poor adherence and/or discontinuation of treatment. Proton pump inhibitors (PPIs) have been used for more than 20 years as the first choice for treating peptic ulcers and their bleeding complications, gastroesophageal reflux disease, non-steroidal anti-inflammatory drug-induced GI lesions and dyspepsia. Adherence becomes a major concern when aspirin is co-prescribed with PPIs to prevent GI adverse effects. Combining aspirin and PPIs into one tablet is an effective approach to address aspirin-related GI adverse effects and increase adherence to aspirin therapy for the prevention of cardiovascular diseases.

Proton pump inhibitors suppress iNOS-dependent DNA damage in Barrett's esophagus by increasing Mn-SOD expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thanan, Raynoo; Department of Environmental and Molecular Medicine, Mie University Graduate School of Medicine, Tsu, Mie 514-8507; Ma, Ning

2012-05-04

Highlights: Black-Right-Pointing-Pointer Inflammation by Barrett's esophagus (BE) is a risk factor of its adenocarcinoma (BEA). Black-Right-Pointing-Pointer 8-Nitroguanine and 8-oxodG are inflammation-related DNA lesions. Black-Right-Pointing-Pointer DNA lesions and iNOS expression were higher in the order, BEA > BE > normal tissues. Black-Right-Pointing-Pointer Proton pump inhibitors suppress DNA damage by increasing Mn-SOD via Nrf2 activation. Black-Right-Pointing-Pointer DNA lesions can be useful biomarkers to predict risk of BEA in BE patients. -- Abstract: Barrett's esophagus (BE), an inflammatory disease, is a risk factor for Barrett's esophageal adenocarcinoma (BEA). Treatment of BE patients with proton pump inhibitors (PPIs) is expected to reduce the riskmore » of BEA. We performed an immunohistochemical study to examine the formation of nitrative and oxidative DNA lesions, 8-nitroguanine and 8-oxo-7,8-dihydro-2 Prime -deoxygaunosine (8-oxodG), in normal esophageal, BE with pre- and post-treatment by PPIs and BEA tissues. We also observed the expression of an oxidant-generating enzyme (iNOS) and its transcription factor NF-{kappa}B, an antioxidant enzyme (Mn-SOD), its transcription factor (Nrf2) and an Nrf2 inhibitor (Keap1). The immunoreactivity of DNA lesions was significantly higher in the order of BEA > BE > normal tissues. iNOS expression was significantly higher in the order of BEA > BE > normal tissues, while Mn-SOD expression was significantly lower in the order of BEA < BE < normal tissues. Interestingly, Mn-SOD expression and the nuclear localization of Nrf2 were significantly increased, and the formation of DNA lesions was significantly decreased in BE tissues after PPIs treatment for 3-6 months. Keap1 and iNOS expression was not significantly changed by the PPIs treatment in BE tissues. These results indicate that 8-nitroguanine and 8-oxodG play a role in BE-derived BEA. Additionally, PPIs treatment may trigger the activation and nuclear translocation of Nrf2 resulting in the expression of antioxidant genes, leading to DNA damage suppression. These DNA lesions can be useful biomarkers to predict both the risk of BEA and the efficacy of PPIs treatment to prevent BEA in BE patients.« less

Pharmacological and Safety Profile of Dexlansoprazole: A New Proton Pump Inhibitor - Implications for Treatment of Gastroesophageal Reflux Disease in the Asia Pacific Region.

PubMed

Goh, Khean Lee; Choi, Myung Gyu; Hsu, Ping I; Chun, Hoon Jai; Mahachai, Varocha; Kachintorn, Udom; Leelakusolvong, Somchai; Kim, Nayoung; Rani, Abdul Aziz; Wong, Benjamin C Y; Wu, Justin; Chiu, Cheng Tang; Shetty, Vikram; Bocobo, Joseph C; Chan, Melchor M; Lin, Jaw-Town

2016-07-30

Although gastroesophageal reflux disease is not as common in Asia as in western countries, the prevalence has increased substantially during the past decade. Gastroesophageal reflux disease is associated with considerable reductions in subjective well-being and work productivity, as well as increased healthcare use. Proton pump inhibitors (PPIs) are currently the most effective treatment for gastroesophageal reflux disease. However, there are limitations associated with these drugs in terms of partial and non-response. Dexlansoprazole is the first PPI with a dual delayed release formulation designed to provide 2 separate releases of medication to extend the duration of effective plasma drug concentration. Dexlansoprazole has been shown to be effective for healing of erosive esophagitis, and to improve subjective well-being by controlling 24-hour symptoms. Dexlansoprazole has also been shown to achieve good plasma concentration regardless of administration with food, providing flexible dosing. Studies in healthy volunteers showed no clinically important effects on exposure to the active metabolite of clopidogrel or clopidogrel-induced platelet inhibition, with no dose adjustment of clopidogrel necessary when coprescribed. This review discusses the role of the new generation PPI, dexlansoprazole, in the treatment of gastroesophageal reflux disease in Asia.

Partial response to proton pump inhibitor therapy for GERD: observational study of patient characteristics, burden of disease, and costs in the USA.

PubMed

Stålhammar, Nils-Olov; Spiegel, Brennan M; Granstedt Löfman, Helena; Karlsson, Maria; Wahlqvist, Peter; Næsdal, Jørgen; Nelson, M Todd; Despiégel, Nicolas

2012-01-01

Disease burden and associated costs are not well understood among patients with gastroesophageal reflux disease (GERD) who have persistent symptoms despite optimized proton pump inhibitor (PPI) therapy. The aim of this study was to investigate disease burden and costs of GERD in partial responders to PPI therapy. The Partial Response to PPI treatment: the Cost to Society and the Burden to the Patient in the US (REMAIN US) study was a 12-month, multicenter, noninterventional, observational study of 552 partial PPI responders in the USA. Participating sites were comprised of family practice (n = 30), internal medicine (n = 8), and specialist (gastroenterologist) centers (n = 15). GERD symptoms, health-related quality of life (HRQL), and impact on productivity were evaluated from patient-reported outcome instruments. Resource utilization data were also collected. Patients had a high symptom burden, impaired HRQL, and reduced productivity while at work and in daily activities, despite optimized PPI therapy. Mean annual GERD-related costs were US$9944 per patient, comprising total direct costs and mean productivity loss costs of US$4068 and US$5876 per patient, respectively. Patients with GERD and a partial response to PPI therapy have considerable direct and indirect costs, along with substantial impairments in HRQL and productivity.

Repositioning of proton pump inhibitors in cancer therapy.

PubMed

Lu, Zhen-Ning; Tian, Bing; Guo, Xiu-Li

2017-11-01

Drug repositioning, as a smart way to exploit new molecular targets of a known drug, has been gaining increasing attention in the discovery of anti-cancer drugs. Proton pump inhibitors (PPIs) as benzimidazole derivatives, which are essentially H + -K + -ATPases inhibitors, are commonly used in the treatment of acid-related diseases such as gastric ulcer. In recent years, exploring the new application of PPIs in anti-cancer field has become a hot research topic. Interestingly, cancer cells display an alkaline intracellular pH and an acidic extracellular pH. The extracellular acidity of tumors can be corrected by PPIs that are selectively activated in an acid milieu. It is generally believed that PPIs might provoke disruption of pH homeostasis by targeting V-ATPase on cancer cells, which is the theoretical basis for PPIs to play an anti-cancer role. Numerous studies have shown specialized effects of the PPIs on tumor cell growth, metastasis, chemoresistance, and autophagy. PPIs may really represent new anti-cancer drugs due to better safety and tolerance, the potential selectivity in targeting tumor acidity, and the ability to inhibit mechanism pivotal for cancer homeostasis. In this review, we focus on the new therapeutic applications of PPIs in multiple cancers, explaining the rationale behind this approach and providing practical evidence.

Antiplatelet drug interactions with proton pump inhibitors

PubMed Central

Scott, Stuart A; Obeng, Aniwaa Owusu; Hulot, Jean-Sébastien

2014-01-01

Introduction Non-aspirin antiplatelet agents (e.g., clopidogrel, prasugrel, ticagrelor) are commonly prescribed for the prevention of recurrent cardiovascular events among patients with acute coronary syndromes (ACS) and/or those undergoing percutaneous coronary intervention (PCI). In addition, combination therapy with proton pump inhibitors (PPIs) is often recommended to attenuate gastrointestinal bleeding risk, particularly during dual antiplatelet therapy (DAPT) with clopidogrel and aspirin. Importantly, a pharmacological interaction between clopidogrel and some PPIs has been proposed based on mutual CYP450-dependent metabolism, but available evidence is inconsistent. Areas covered This article provides an overview of the currently approved antiplatelet agents and PPIs, including their metabolic pathways. Additionally, the CYP450 isoenzyme at the center of the drug interaction, CYP2C19, is described in detail, and the available evidence on both the potential pharmacological interaction and influence on clinical outcomes are summarized and evaluated. Expert opinion Although concomitant DAPT and PPI use reduces clopidogrel active metabolite levels and ex vivo-measured platelet inhibition, the influence of the drug interaction on clinical outcomes has been conflicting and largely reported from non-randomized observational studies. Despite this inconsistency, a clinically important interaction cannot be definitively excluded, particularly among patient subgroups with higher overall cardiovascular risk and potentially among CYP2C19 loss-of-function allele carriers. PMID:24205916

Adverse drug reactions due to drug-drug interactions with proton pump inhibitors: assessment of systematic reviews with AMSTAR method.

PubMed

Yucel, Emre; Sancar, Mesut; Yucel, Aylin; Okuyan, Betul

2016-01-01

Many systematic reviews resulted in claims on drug-drug interactions (DDIs) with proton pump inhibitors (PPIs). Such a large number begs for consensus on the clinical significance of findings. We critically evaluated the safety of PPI use with respect to DDIs with a meta-review of systematic reviews published between 1978 and 2015. We assessed the evidence by their reliability, repeatability, transparency, and objectivity according to the Assessment of Multiple Systematic Reviews (AMSTAR) criteria. Clinicians must assess risks for each PPI for certain comorbid conditions. DDIs don't substantiate class effect for PPIs; each PPI could induce unique DDIs. Concomitant use of PPIs with thienopyridines (e.g. clopidogrel) could be justified in patients without strong affinity to cytochrome CYP2C19 and with high risk of bleeding (e.g. patients with prior upper gastrointestinal bleeding, Helicobacter pylori infection, advanced age, steroid treatment, and nonsteroidal anti-inflammatory drug use). DDIs could occur in an AIDS subpopulation treated with highly active antiretroviral therapy (HAART). DDIs exist for cancer patients undergoing targeted therapy. Hypomagnesemia could increase in the setting of advanced age and polypharmacy. Omeprazole poses high risks owing to its pharmacokinetic DDI profile. Future systematic reviews should incorporate these additional risks for better clinical guidance.

Pharmacological and Safety Profile of Dexlansoprazole: A New Proton Pump Inhibitor – Implications for Treatment of Gastroesophageal Reflux Disease in the Asia Pacific Region

PubMed Central

Goh, Khean Lee; Choi, Myung Gyu; Hsu, Ping I; Chun, Hoon Jai; Mahachai, Varocha; Kachintorn, Udom; Leelakusolvong, Somchai; Kim, Nayoung; Rani, Abdul Aziz; Wong, Benjamin C Y; Wu, Justin; Chiu, Cheng Tang; Shetty, Vikram; Bocobo, Joseph C; Chan, Melchor M; Lin, Jaw-Town

2016-01-01

Although gastroesophageal reflux disease is not as common in Asia as in western countries, the prevalence has increased substantially during the past decade. Gastroesophageal reflux disease is associated with considerable reductions in subjective well-being and work productivity, as well as increased healthcare use. Proton pump inhibitors (PPIs) are currently the most effective treatment for gastroesophageal reflux disease. However, there are limitations associated with these drugs in terms of partial and non-response. Dexlansoprazole is the first PPI with a dual delayed release formulation designed to provide 2 separate releases of medication to extend the duration of effective plasma drug concentration. Dexlansoprazole has been shown to be effective for healing of erosive esophagitis, and to improve subjective well-being by controlling 24-hour symptoms. Dexlansoprazole has also been shown to achieve good plasma concentration regardless of administration with food, providing flexible dosing. Studies in healthy volunteers showed no clinically important effects on exposure to the active metabolite of clopidogrel or clopidogrel-induced platelet inhibition, with no dose adjustment of clopidogrel necessary when coprescribed. This review discusses the role of the new generation PPI, dexlansoprazole, in the treatment of gastroesophageal reflux disease in Asia. PMID:26932927

Proton Probing using the T-Cubed Laser

NASA Astrophysics Data System (ADS)

Kordell, Peter; Campbell, Paul; Willingale, Louise; Maksimchuk, Anatoly; Krushelnick, Karl; Tubman, Eleanor; Woolsey, Nigel

2015-11-01

The University of Michigan's 20 TW, 400 fs pulse T-cubed laser can produce proton beams of up to 7.2 MeV through target normal sheeth acceleration. The proton flux at 4 MeV produces sufficient signal on Radiochromic Film for use as an ultrafast, electromagnetic field diagnostic. A two beam experiment has been set-up to enable co-timed, pump-probe relativistic intensity interactions. We present an evaluation of the flux, uniformity, energy and laminar flow of the proton probe for future use in imaging of a simple wire target interaction. This work was supported by the DOE (Grant No. DE-SC0012327).

Molecular Dynamics Simulations Reveal Proton Transfer Pathways in Cytochrome C-Dependent Nitric Oxide Reductase

PubMed Central

Pisliakov, Andrei V.; Hino, Tomoya; Shiro, Yoshitsugu; Sugita, Yuji

2012-01-01

Nitric oxide reductases (NORs) are membrane proteins that catalyze the reduction of nitric oxide (NO) to nitrous oxide (N2O), which is a critical step of the nitrate respiration process in denitrifying bacteria. Using the recently determined first crystal structure of the cytochrome c-dependent NOR (cNOR) [Hino T, Matsumoto Y, Nagano S, Sugimoto H, Fukumori Y, et al. (2010) Structural basis of biological N2O generation by bacterial nitric oxide reductase. Science 330: 1666–70.], we performed extensive all-atom molecular dynamics (MD) simulations of cNOR within an explicit membrane/solvent environment to fully characterize water distribution and dynamics as well as hydrogen-bonded networks inside the protein, yielding the atomic details of functionally important proton channels. Simulations reveal two possible proton transfer pathways leading from the periplasm to the active site, while no pathways from the cytoplasmic side were found, consistently with the experimental observations that cNOR is not a proton pump. One of the pathways, which was newly identified in the MD simulation, is blocked in the crystal structure and requires small structural rearrangements to allow for water channel formation. That pathway is equivalent to the functional periplasmic cavity postulated in cbb 3 oxidase, which illustrates that the two enzymes share some elements of the proton transfer mechanisms and confirms a close evolutionary relation between NORs and C-type oxidases. Several mechanisms of the critical proton transfer steps near the catalytic center are proposed. PMID:22956904

Proton pumping in the bc1 complex: a new gating mechanism that prevents short circuits.

PubMed

Crofts, Antony R; Lhee, Sangmoon; Crofts, Stephanie B; Cheng, Jerry; Rose, Stuart

2006-08-01

The Q-cycle mechanism of the bc1 complex explains how the electron transfer from ubihydroquinone (quinol, QH2) to cytochrome (cyt) c (or c2 in bacteria) is coupled to the pumping of protons across the membrane. The efficiency of proton pumping depends on the effectiveness of the bifurcated reaction at the Q(o)-site of the complex. This directs the two electrons from QH2 down two different pathways, one to the high potential chain for delivery to an electron acceptor, and the other across the membrane through a chain containing heme bL and bH to the Qi-site, to provide the vectorial charge transfer contributing to the proton gradient. In this review, we discuss problems associated with the turnover of the bc1 complex that center around rates calculated for the normal forward and reverse reactions, and for bypass (or short-circuit) reactions. Based on rate constants given by distances between redox centers in known structures, these appeared to preclude conventional electron transfer mechanisms involving an intermediate semiquinone (SQ) in the Q(o)-site reaction. However, previous research has strongly suggested that SQ is the reductant for O2 in generation of superoxide at the Q(o)-site, introducing an apparent paradox. A simple gating mechanism, in which an intermediate SQ mobile in the volume of the Q(o)-site is a necessary component, can readily account for the observed data through a coulombic interaction that prevents SQ anion from close approach to heme bL when the latter is reduced. This allows rapid and reversible QH2 oxidation, but prevents rapid bypass reactions. The mechanism is quite natural, and is well supported by experiments in which the role of a key residue, Glu-295, which facilitates proton transfer from the site through a rotational displacement, has been tested by mutation.

A Research and Development Strategy for Unexploded Ordnance Sensing

DTIC Science & Technology

1996-04-01

Each lane was carefully traversed with the MK-26 Ordnance Detector (dual fluxgate magnetometer hand-held unit) and the operator hand-excavated any...proton-precessing magnetometers , optically pumped magnetometers , fluxgates magnetometers , and magnetometers based on superconducting quantum...sensitivity better than 0.05 nT, and the optically-pumped magnetometers have sensitivity better than 0.005 nT. Fluxgate magnetometers are based on solid

Upper gastrointestinal bleeding - state of the art.

PubMed

Szura, Mirosław; Pasternak, Artur

2014-01-01

Upper gastrointestinal (GI) bleeding is a condition requiring immediate medical intervention, with high associated mortality exceeding 10%. The most common cause of upper GI bleeding is peptic ulcer disease, which largely corresponds to the intake of NSAIDs and Helicobacter pylori infection. Endoscopy is the essential tool for the diagnosis and treatment of active upper GI hemorrhage. Endoscopic therapy together with proton pump inhibitors and eradication of Helicobacter pylori significantly reduces rebleeding rates, mortality and number of emergency surgical interventions. This paper presents contemporary data on the diagnosis and treatment of upper gastrointestinal bleeding.

Effect of long-term proton pump inhibitor administration on gastric mucosal atrophy: A meta-analysis

PubMed Central

Li, Zhong; Wu, Cong; Li, Ling; Wang, Zhaoming; Xie, Haibin; He, Xiaozhou; Feng, Jin

2017-01-01

Background/Aims: Proton pump inhibitors (PPIs) are widely used for the treatment of acid-related gastrointestinal diseases. Recently, some studies have reported that PPIs can alter the gastric mucosal architecture; however, the relationship remains controversial. This meta-analysis study was designed to quantify the association between long-term PPI administration and gastric atrophy. Materials and Methods: A PubMed search was conducted to identify studies using the keywords proton pump inhibitors or PPI and gastric atrophy or atrophic gastritis; the timeframe of publication searched was up to May 2016. Heterogeneity among studies was tested with the Q test; odds ratios (OR) and 95% confidence intervals (CI) were calculated. P values were calculated by I2 tests and regarded as statistically significant when <0.05. Results: We identified 13 studies that included 1465 patients under long-term PPI therapy and 1603 controls, with a total gastric atrophy rate of 14.50%. There was a higher presence of gastric atrophy (15.84%; statistically significant) in PPI group compared to the control group (13.29%) (OR: 1.55, 95% CI: 1.00–2.41). Conclusions: The pooled data suggest that long-term PPI use is associated with increased rates of gastric atrophy. Large-scale multicenter studies should be conducted to further investigate the relationship between acid suppressants and precancerous diseases. PMID:28721975

Structure of a prokaryotic virtual proton pump at 3.2 Å resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Yiling; Jayaram, Hariharan; Shane, Tania

2009-09-15

To reach the mammalian gut, enteric bacteria must pass through the stomach. Many such organisms survive exposure to the harsh gastric environment (pH 1.5-4) by mounting extreme acid-resistance responses, one of which, the arginine-dependent system of Escherichia coli, has been studied at levels of cellular physiology, molecular genetics and protein biochemistry. This multiprotein system keeps the cytoplasm above pH 5 during acid challenge by continually pumping protons out of the cell using the free energy of arginine decarboxylation. At the heart of the process is a 'virtual proton pump' in the inner membrane, called AdiC, that imports L-arginine from themore » gastric juice and exports its decarboxylation product agmatine. AdiC belongs to the APC superfamily of membrane proteins, which transports amino acids, polyamines and organic cations in a multitude of biological roles, including delivery of arginine for nitric oxide synthesis, facilitation of insulin release from pancreatic {beta}-cells, and, when inappropriately overexpressed, provisioning of certain fast-growing neoplastic cells with amino acids. High-resolution structures and detailed transport mechanisms of APC transporters are currently unknown. Here we describe a crystal structure of AdiC at 3.2 {angstrom} resolution. The protein is captured in an outward-open, substrate-free conformation with transmembrane architecture remarkably similar to that seen in four other families of apparently unrelated transport proteins.« less

Prevalence and characteristics of acid gastro-oesophageal reflux disease in Jackhammer oesophagus.

PubMed

Mallet, Anne-Laure; Ropert, Alain; Bouguen, Guillaume; Siproudhis, Laurent; Boutroux, Dominique; Bretagne, Jean-François; Brochard, Charlène

2016-10-01

An association between acid gastro-oesophageal reflux disease (GERD) and Jackhammer oesophagus has been suggested. To assess the prevalence and characteristics of acid-GERD in Jackhammer oesophagus and the efficacy of proton pump inhibitors. Data and outcomes of patients with Jackhammer oesophagus were assessed. Two groups were compared: (i) GERD, defined by endoscopic oesophagitis or by an increase in acid exposure time or by an acid-hypersensitive oesophagus and (ii) non-GERD defined by normal oesophageal acid exposure without acid-hypersensitive oesophagus. Among the 1994 high-resolution manometries performed, 44 Jackhammer oesophagus (2.2%) were included (sex ratio M/F: 19/25; median age: 66 [61-75] years). Nineteen patients (43.2%) had GERD, 16 (36.4%) had no GERD and 9 patients (20.4%) were undetermined. Dysphagia was the predominant symptom (37/43 (86%)). After a median follow-up of 25.3 months [9.6-31.4], dysphagia was improved in 22/36 (61.1%) patients. Dysphagia improvement as well as other symptoms improvement was not associated with GERD status or proton-pump inhibitors use. The prevalence of GERD is high among patients with Jackhammer oesophagus. The rates of symptom improvement in Jackhammer oesophagus were high regardless of the use of proton-pump inhibitors treatment or of the presence of GERD. Copyright © 2016 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Key parameters controlling the performance of catalytic motors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esplandiu, Maria J.; Afshar Farniya, Ali; Reguera, David, E-mail: dreguera@ub.edu

2016-03-28

The development of autonomous micro/nanomotors driven by self-generated chemical gradients is a topic of high interest given their potential impact in medicine and environmental remediation. Although impressive functionalities of these devices have been demonstrated, a detailed understanding of the propulsion mechanism is still lacking. In this work, we perform a comprehensive numerical analysis of the key parameters governing the actuation of bimetallic catalytic micropumps. We show that the fluid motion is driven by self-generated electro-osmosis where the electric field originates by a proton current rather than by a lateral charge asymmetry inside the double layer. Hence, the surface potential andmore » the electric field are the key parameters for setting the pumping strength and directionality. The proton flux that generates the electric field stems from the proton gradient induced by the electrochemical reactions taken place at the pump. Surprisingly the electric field and consequently the fluid flow are mainly controlled by the ionic strength and not by the conductivity of the solution, as one could have expected. We have also analyzed the influence of the chemical fuel concentration, electrochemical reaction rates, and size of the metallic structures for an optimized pump performance. Our findings cast light on the complex chemomechanical actuation of catalytic motors and provide important clues for the search, design, and optimization of novel catalytic actuators.« less

Clinical trial: factors associated with freedom from relapse of heartburn in patients with healed reflux oesophagitis--results from the maintenance phase of the EXPO study.

PubMed

Labenz, J; Armstrong, D; Zetterstrand, S; Eklund, S; Leodolter, A

2009-06-01

Ability to predict freedom from heartburn relapse during maintenance therapy for healed reflux oesophagitis may facilitate optimal treatment choices for individual patients. To determine factors predicting freedom from heartburn relapse during maintenance proton pump inhibitor therapy in patients with healed reflux oesophagitis. This post-hoc analysis used data from the maintenance phase of the EXPO study (AstraZeneca study code: SH-NEG-0008); 2766 patients with healed reflux oesophagitis and resolved heartburn received once-daily esomeprazole 20 mg or pantoprazole 20 mg for 6 months. Multiple logistic regression analysis determined factors associated with freedom from heartburn relapse. Heartburn relapse rates were lower with esomeprazole than pantoprazole in all subgroups analysed. Esomeprazole treatment was the factor most strongly associated with freedom from heartburn relapse (odds ratio 2.08; P < 0.0001). Other factors significantly associated with freedom from heartburn relapse were Helicobacter pylori infection, greater age, non-obesity, absence of epigastric pain at baseline, pre-treatment nonsevere heartburn and GERD symptom duration < or =5 years. Several factors predict freedom from heartburn relapse during maintenance proton pump inhibitor therapy for healed reflux oesophagitis, the strongest being choice of proton pump inhibitor. These findings outline the importance of optimizing acid control and identifying predictors of relapse for effective long-term symptom management in reflux oesophagitis patients.

Imaging and controlling proton motion in molecules

NASA Astrophysics Data System (ADS)

Ibrahim, H.; Beaulieu, S.; Wanie, V.; Endo, T.; Wales, B.; Tong, X.-M.; Schuurman, M. S.; Sanderson, J.; Légaré, F.

2017-11-01

How do atoms move within a molecule? What are the paths they take? Coulomb Explosion Imaging combined with a multi-color pump probe scheme allows us to address these questions with a table top setup. Since the momentum information of molecular fragments is preserved at the moment of explosion, we can deduce the fragment's momentary position, representing the structure of the molecule. We have studied isomerization and dissociation events through the movement of protons, deuterons and electrons, taking advantage of the rich statistics this technique provides. In the case of proton migration in the acetylene cation, we were able to identify an isotope dependent to- and fro isomerization behavior [1]. Presently, we are expanding our studies on more complex processes. Aside from passively studying dynamics, we have also actively controlled the electron localization in small molecules [2] using two-color mid-infrared asymmetric laser fields. The manipulation of protons, the lightest atomic fragments in molecules, is of great interest due to the tremendous diversity of molecules containing them, in combination with the generality of how protons behave within molecules. Their detection involves certain challenges since they move extremely fast compared to heavier atoms. Here, we focus on two different proton motions which are triggered by excitation with ultrashort laser pulses and imaged with the Coulomb explosion imaging (CEI) technique. First, we will discuss proton migration dynamics in the acetylene cation launched due to strong field multiphoton ionization with UV pulses in a rather simple table top approach. Second, we will concentrate on controlling electron localization - and thus proton localization - in the cation of the hydrogen molecule by using an asymmetric two color field in the mid-infrared (MIR).

Lysosomal ROS formation.

PubMed

Nohl, Hans; Gille, Lars

2005-01-01

Ubiquinone is inhomogenously distributed in subcellular biomembranes. Apart from mitochondria, where ubiquinone has bioenergetic and pathophysiological functions, unusually high levels of ubiquinone have also been reported in Golgi vesicles and lysosomes. In lysosomes, the interior differs from other organelles in its low pH value which is important to ensure optimal activity of hydrolytic enzymes. Since redox-cycling of ubiquinone is associated with the acceptance and release of protons, we assumed that ubiquinone is part of a redox chain contributing to unilateral proton distribution. A similar function of ubiquinone was earlier suggested by Crane to operate in Golgi vesicles. Support for the involvement of ubiquinone in a presumed couple of redox carriers came from our observation that almost 70% of total lysosomal ubiquinone was in the divalently reduced state. Further reduction was seen in the presence of external NADH. Analysis of the components involved in the transfer of reducing equivalents from cytosolic NADH to ubiquinone revealed the existence of an FAD-containing NADH dehydrogenase. The latter was found to reduce ubiquinone by means of a b-type cytochrome. Proton translocation into the interior was linked to the activity of the novel lysosomal redox chain. Oxygen was found to be the terminal electron acceptor, thereby also regulating acidification of the lysosomal matrix. In contrast to mitochondrial respiration, oxygen was only trivalently reduced giving rise to the release of HO radicals. The role of this novel proton-pumping redox chain and the significance of the associated ROS formation has to be elucidated.

Contrasting phagosome pH regulation and maturation in human M1 and M2 macrophages

PubMed Central

Canton, Johnathan; Khezri, Rojyar; Glogauer, Michael; Grinstein, Sergio

2014-01-01

Macrophages respond to changes in environmental stimuli by assuming distinct functional phenotypes, a phenomenon referred to as macrophage polarization. We generated classically (M1) and alternatively (M2) polarized macrophages—two extremes of the polarization spectrum—to compare the properties of their phagosomes. Specifically, we analyzed the regulation of the luminal pH after particle engulfment. The phagosomes of M1 macrophages had a similar buffering power and proton (equivalent) leakage permeability but significantly reduced proton-pumping activity compared with M2 phagosomes. As a result, only the latter underwent a rapid and profound acidification. By contrast, M1 phagosomes displayed alkaline pH oscillations, which were caused by proton consumption upon dismutation of superoxide, followed by activation of a voltage- and Zn2+-sensitive permeation pathway, likely HV1 channels. The paucity of V-ATPases in M1 phagosomes was associated with, and likely caused by, delayed fusion with late endosomes and lysosomes. The delayed kinetics of maturation was, in turn, promoted by the failure of M1 phagosomes to acidify. Thus, in M1 cells, elimination of pathogens through deployment of the microbicidal NADPH oxidase is given priority at the expense of delayed acidification. By contrast, M2 phagosomes proceed to acidify immediately in order to clear apoptotic bodies rapidly and effectively. PMID:25165138

Dexlansoprazole

MedlinePlus

... is in a class of medications called proton pump inhibitors. It works by decreasing the amount of ... symptoms are severe or do not go away: gas nausea vomiting Some side effects can be serious. ...

Esomeprazole

MedlinePlus

... is in a class of medications called proton pump inhibitors. It works by decreasing the amount of ... severe or do not go away: headache nausea gas constipation dry mouth Some side effects can be ...

Coupling of remote alternating-access transport mechanisms for protons and substrates in the multidrug efflux pump AcrB

PubMed Central

Eicher, Thomas; Seeger, Markus A; Anselmi, Claudio; Zhou, Wenchang; Brandstätter, Lorenz; Verrey, François; Diederichs, Kay; Faraldo-Gómez, José D; Pos, Klaas M

2014-01-01

Membrane transporters of the RND superfamily confer multidrug resistance to pathogenic bacteria, and are essential for cholesterol metabolism and embryonic development in humans. We use high-resolution X-ray crystallography and computational methods to delineate the mechanism of the homotrimeric RND-type proton/drug antiporter AcrB, the active component of the major efflux system AcrAB-TolC in Escherichia coli, and one most complex and intriguing membrane transporters known to date. Analysis of wildtype AcrB and four functionally-inactive variants reveals an unprecedented mechanism that involves two remote alternating-access conformational cycles within each protomer, namely one for protons in the transmembrane region and another for drugs in the periplasmic domain, 50 Å apart. Each of these cycles entails two distinct types of collective motions of two structural repeats, coupled by flanking α-helices that project from the membrane. Moreover, we rationalize how the cross-talk among protomers across the trimerization interface might lead to a more kinetically efficient efflux system. DOI: http://dx.doi.org/10.7554/eLife.03145.001 PMID:25248080

Constitutive activation of a plasma membrane H(+)-ATPase prevents abscisic acid-mediated stomatal closure.

PubMed

Merlot, Sylvain; Leonhardt, Nathalie; Fenzi, Francesca; Valon, Christiane; Costa, Miguel; Piette, Laurie; Vavasseur, Alain; Genty, Bernard; Boivin, Karine; Müller, Axel; Giraudat, Jérôme; Leung, Jeffrey

2007-07-11

Light activates proton (H(+))-ATPases in guard cells, to drive hyperpolarization of the plasma membrane to initiate stomatal opening, allowing diffusion of ambient CO(2) to photosynthetic tissues. Light to darkness transition, high CO(2) levels and the stress hormone abscisic acid (ABA) promote stomatal closing. The overall H(+)-ATPase activity is diminished by ABA treatments, but the significance of this phenomenon in relationship to stomatal closure is still debated. We report two dominant mutations in the OPEN STOMATA2 (OST2) locus of Arabidopsis that completely abolish stomatal response to ABA, but importantly, to a much lesser extent the responses to CO(2) and darkness. The OST2 gene encodes the major plasma membrane H(+)-ATPase AHA1, and both mutations cause constitutive activity of this pump, leading to necrotic lesions. H(+)-ATPases have been traditionally assumed to be general endpoints of all signaling pathways affecting membrane polarization and transport. Our results provide evidence that AHA1 is a distinct component of an ABA-directed signaling pathway, and that dynamic downregulation of this pump during drought is an essential step in membrane depolarization to initiate stomatal closure.

The VPH1 gene encodes a 95-kDa integral membrane polypeptide required for in vivo assembly and activity of the yeast vacuolar H(+)-ATPase.

PubMed

Manolson, M F; Proteau, D; Preston, R A; Stenbit, A; Roberts, B T; Hoyt, M A; Preuss, D; Mulholland, J; Botstein, D; Jones, E W

1992-07-15

Yeast vacuolar acidification-defective (vph) mutants were identified using the pH-sensitive fluorescence of 6-carboxyfluorescein diacetate (Preston, R. A., Murphy, R. F., and Jones, E. W. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 7027-7031). Vacuoles purified from yeast bearing the vph1-1 mutation had no detectable bafilomycin-sensitive ATPase activity or ATP-dependent proton pumping. The peripherally bound nucleotide-binding subunits of the vacuolar H(+)-ATPase (60 and 69 kDa) were no longer associated with vacuolar membranes yet were present in wild type levels in yeast whole cell extracts. The VPH1 gene was cloned by complementation of the vph1-1 mutation and independently cloned by screening a lambda gt11 expression library with antibodies directed against a 95-kDa vacuolar integral membrane protein. Deletion disruption of the VPH1 gene revealed that the VPH1 gene is not essential for viability but is required for vacuolar H(+)-ATPase assembly and vacuolar acidification. VPH1 encodes a predicted polypeptide of 840 amino acid residues (molecular mass 95.6 kDa) and contains six putative membrane-spanning regions. Cell fractionation and immunodetection demonstrate that Vph1p is a vacuolar integral membrane protein that co-purifies with vacuolar H(+)-ATPase activity. Multiple sequence alignments show extensive homology over the entire lengths of the following four polypeptides: Vph1p, the 116-kDa polypeptide of the rat clathrin-coated vesicles/synaptic vesicle proton pump, the predicted polypeptide encoded by the yeast gene STV1 (Similar To VPH1, identified as an open reading frame next to the BUB2 gene), and the TJ6 mouse immune suppressor factor.

Ulcers

MedlinePlus

... These include both regular and decaffeinated coffee, tea, chocolate, meat extracts, alcohol, black pepper, chili powder, mustard ... Disease, peptic ulcers, proton pump inhibitor, sucralfate, triple therapy January 1, 1996 Copyright © American Academy of Family ...

Vismodegib

MedlinePlus

... cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac); and proton-pump inhibitors such as dexlansoprazole (Dexilant), lansoprazole (Prevacid, in Prevpac), omeprazole (Prilosec, Zegerid), pantoprazole (Protonix), and rabeprazole (AcipHex). Your doctor may need to change the ...

Proton pump inhibitors and symptomatic hypomagnesemic hypoparathyroidism.

PubMed

Fatuzzo, P; Portale, G; Scollo, V; Zanoli, L; Granata, Antonio

2017-04-01

Hypomagnesemia is a common but often overlooked problem in hospitalized patients. Unrecognized hypomagnesemia can cause serious complications. The association of hypokalemia and hypocalcemia is strongly evocative of a magnesium deficiency. Research into the causes of hypomagnesemia is imperative, as it will definitely change the approach, treatment and prognosis. We report the case of a 65-year-old man with chronic hypocalcemia and hypokalemia associated with cerebellar syndrome, a solitary seizure and cerebellar hyperintensities on magnetic resonance imaging. After the detection and treatment of hypomagnesemia with oral supplements of magnesium and the replacement of pantoprazole with ranitidine, we observed immediate relief of the symptoms. In conclusion, in clinical practice, magnesium depletion should be investigated in elderly patients with hypocalcemia treated with proton pump inhibitors for many years, in particular in the presence of neurological disorders.

Proton pump inhibitor-refractory gastroesophageal reflux disease: challenges and solutions

PubMed Central

Mermelstein, Joseph; Chait Mermelstein, Alanna; Chait, Maxwell M

2018-01-01

A significant percentage of patients with gastroesophageal reflux disease (GERD) will not respond to proton pump inhibitor (PPI) therapy. The causes of PPI-refractory GERD are numerous and diverse, and include adherence, persistent acid, functional disorders, nonacid reflux, and PPI bioavailability. The evaluation should start with a symptom assessment and may progress to imaging, endoscopy, and monitoring of esophageal pH, impedance, and bilirubin. There are a variety of pharmacologic and procedural interventions that should be selected based on the underlying mechanism of PPI failure. Pharmacologic treatments can include antacids, prokinetics, alginates, bile acid binders, reflux inhibitors, and antidepressants. Procedural options include laparoscopic fundoplication and LINX as well as endoscopic procedures, such as transoral incisionless fundoplication and Stretta. Several alternative and complementary treatments of possible benefit also exist. PMID:29606884

Proton pump inhibitor failure in gastro-oesophageal reflux disease: a perspective aided by the Gartner hype cycle.

PubMed

Heading, Robert C

2017-04-01

Some patients with gastro-oesophageal reflux disease (GORD) experience symptoms despite proton pump inhibitor (PPI) treatment. In the early years of their availability, these drugs were thought to be a highly effective treatment for GORD and realisation that symptom relief was often incomplete came as a disappointment. This review considers the evolution of thinking with the aid of the Gartner hype cycle - a graphical depiction of the process of innovation, evolution and adoption of new technologies. Acknowledging that over-simplistic concepts of GORD have been largely responsible for inflated expectations of PPI therapy is an important step forward in establishing how patients with persistent symptoms, despite PPIs, should be assessed and treated. © Royal College of Physicians 2017. All rights reserved.

Roles of histidine residues in plant vacuolar H(+)-pyrophosphatase.

PubMed

Hsiao, Yi Y; Van, Ru C; Hung, Shu H; Lin, Hsin H; Pan, Rong L

2004-02-15

Vacuolar proton pumping pyrophosphatase (H(+)-PPase; EC 3.6.1.1) plays a pivotal role in electrogenic translocation of protons from cytosol to the vacuolar lumen at the expense of PP(i) hydrolysis. Alignment analysis on amino acid sequence demonstrates that vacuolar H(+)-PPase of mung bean contains six highly conserved histidine residues. Previous evidence indicated possible involvement of histidine residue(s) in enzymatic activity and H(+)-translocation of vacuolar H(+)-PPase as determined by using histidine specific modifier, diethylpyrocarbonate [J. Protein Chem. 21 (2002) 51]. In this study, we further attempted to identify the roles of histidine residues in mung bean vacuolar H(+)-PPase by site-directed mutagenesis. A line of mutants with histidine residues singly replaced by alanine was constructed, over-expressed in Saccharomyces cerevisiae, and then used to determine their enzymatic activities and proton translocations. Among the mutants scrutinized, only the mutation of H716 significantly decreased the enzymatic activity, the proton transport, and the coupling ratio of vacuolar H(+)-PPase. The enzymatic activity of H716A is relatively resistant to inhibition by diethylpyrocarbonate as compared to wild-type and other mutants, indicating that H716 is probably the target residue for the attack by this modifier. The mutation at H716 of V-PPase shifted the optimum pH value but not the T(1/2) (pretreatment temperature at which half enzymatic activity is observed) for PP(i) hydrolytic activity. Mutation of histidine residues obviously induced conformational changes of vacuolar H(+)-PPase as determined by immunoblotting analysis after limited trypsin digestion. Furthermore, mutation of these histidine residues modified the inhibitory effects of F(-) and Na(+), but not that of Ca(2+). Single substitution of H704, H716 and H758 by alanine partially released the effect of K(+) stimulation, indicating possible location of K(+) binding in the vicinity of domains surrounding these residues.

Cobicistat

MedlinePlus

... taking a medication for indigestion, heartburn, or ulcers (proton pump inhibitors) such as esomeprazole (Nexium, in Vimovo), lansoprazole (Prevacid), omeprazole (Prilosec, in Zegerid), pantoprazole (Protonix), or rabeprazole (AcipHex) take them at least 12 hours after ...

Assay of Plasma Membrane H+-ATPase in Plant Tissues under Abiotic Stresses.

PubMed

Janicka, Małgorzata; Wdowikowska, Anna; Kłobus, Grażyna

2018-01-01

Plasma membrane (PM) H + -ATPase, which generates the proton gradient across the outer membrane of plant cells, plays a fundamental role in the regulation of many physiological processes fundamental for growth and development of plants. It is involved in the uptake of nutrients from external solutions, their loading into phloem and long-distance transport, stomata aperture and gas exchange, pH homeostasis in cytosol, cell wall loosening, and cell expansion. The crucial role of the enzyme in resistance of plants to abiotic and biotic stress factors has also been well documented. Such great diversity of physiological functions linked to the activity of one enzyme requires a suitable and complex regulation of H + -ATPase. This regulation comprises the transcriptional as well as post-transcriptional levels. Herein, we describe the techniques that can be useful for the analysis of the plasma membrane proton pump modifications at genetic and protein levels under environmental factors.

Nafion-coating of the electrodes improves the flow-stability of the Ag/SiO2/Ag2O electroosmotic pump.

PubMed

Shin, Woonsup; Zhu, Enhua; Nagarale, Rajaram Krishna; Kim, Chang Hwan; Lee, Jong Myung; Shin, Samuel Jaeho; Heller, Adam

2011-06-15

When a current or a voltage is applied across the ceramic membrane of the nongassing Ag/Ag(2)O-SiO(2)-Ag/Ag(2)O pump, protons produced in the anodic reaction 2Ag(s) + H(2)O → Ag(2)O(s) + 2H(+) + 2e(-) are driven to the cathode, where they are consumed by the reaction Ag(2)O(s) + H(2)O + 2e(-) → 2Ag(s) + 2 OH(-). The flow of water is induced by momentum transfer from the electric field-driven proton-sheet at the surface of the ceramic membrane. About 10(4) water molecules flowed per reacted electron. Because dissolved ions decrease the field at the membrane surface, the flow decreases upon increasing the ionic strength. For this reason Ag(+) ions introduced through the anodic reaction and by dissolution of Ag(2)O decrease the flow. Their accumulation is reduced by applying Nafion-films to the electrodes. The 20 μL min(-1) flow rate of 6 mm i.d. pumps with Nafion coated electrodes operate daily for 5 min at 1 V for 1 month, for 70 h when the pump is pulsed for 30 s every 30 min, and for 2 h when operating continuously.

An intelligent displacement pumping film system: a new concept for enhancing heavy metal ion removal efficiency from liquid waste.

PubMed

Wang, Zhongde; Feng, Yanting; Hao, Xiaogang; Huang, Wei; Guan, Guoqing; Abudula, Abuliti

2014-06-15

A concept of electrochemically switched ion exchange (ESIX) hybrid film system with piston-like proton pumping effect for the removal of heavy metal ions was proposed. Based on this concept, a novel ESIX hybrid film composed of layered alpha zirconium phosphate (α-Zr(HPO4)2; α-ZrP) nanosheets intercalated with a potential-responsive conducting polyaniline (PANI) was developed for the removal of Ni(2+) ions from wastewater. It is expected that the space between α-ZrP nanosheets acts as the reservoir for the functional ions while the intercalated PANI works as the potential-sensitive function element for piston-like proton pumping in such ESIX hybrid films. The prepared ESIX hybrid film showed an excellent property of rapid removal of Ni(2+) ions from wastewater with a high selectivity. The used film was simply regenerated by only altering the applied potential. The ion pumping effect for the ESIX of Ni(2+) ions using this kind of film was proved via XPS analysis. The proposed ESIX hybrid film should have high potential for the removal of Ni(2+) ions and/or other heavy metal ions from wastewater in various industrial processes. Copyright © 2014 Elsevier B.V. All rights reserved.

Deletion of a unique loop in the mycobacterial F-ATP synthase γ subunit sheds light on its inhibitory role in ATP hydrolysis-driven H(+) pumping.

PubMed

Hotra, Adam; Suter, Manuel; Biuković, Goran; Ragunathan, Priya; Kundu, Subhashri; Dick, Thomas; Grüber, Gerhard

2016-05-01

The F1 FO -ATP synthase is one of the enzymes that is essential to meet the energy requirement of both the proliferating aerobic and hypoxic dormant stages of the life cycle of mycobacteria. Most F-ATP synthases consume ATP in the α3 :β3 headpiece to drive the γ subunit, which couples ATP cleavage with proton pumping in the c ring of FO via the bottom of the γ subunit. ATPase-driven H(+) pumping is latent in mycobacteria. The presence of a unique 14 amino acid residue loop of the mycobacterial γ subunit has been described and aligned in close vicinity to the c-ring loop Priya R et al. (2013) J Bioenerg Biomembr 45, 121-129 Here, we used inverted membrane vesicles (IMVs) of fast-growing Mycobacterium smegmatis and a variety of covalent and non-covalent inhibitors to characterize the ATP hydrolysis activity of the F-ATP synthase inside IMVs. These vesicles formed a platform to investigate the function of the unique mycobaterial γ loop by deleting the respective loop-encoding sequence (γ166-179 ) in the genome of M. smegmatis. ATP hydrolysis-driven H(+) pumping was observed in IMVs containing the Δγ166-179 mutant protein but not for IMVs containing the wild-type F-ATP synthase. In addition, when compared to the wild-type enzyme, IMVs containing the Δγ166-179 mutant protein showed increased ATP cleavage and lower levels of ATP synthesis, demonstrating that the loop affects ATPase activity, ATPase-driven H(+) pumping and ATP synthesis. These results further indicate that the loop may affect coupling of ATP hydrolysis and synthesis in a different mode. © 2016 Federation of European Biochemical Societies.

Roles of the Sodium-Translocating NADH:Quinone Oxidoreductase (Na+-NQR) on Vibrio cholerae Metabolism, Motility and Osmotic Stress Resistance

PubMed Central

Minato, Yusuke; Halang, Petra; Quinn, Matthew J.; Faulkner, Wyatt J.; Aagesen, Alisha M.; Steuber, Julia; Stevens, Jan F.; Häse, Claudia C.

2014-01-01

The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ΔnqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ΔnqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ΔnqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology. PMID:24811312

Cleistanthus collinus induces type I distal renal tubular acidosis and type II respiratory failure in rats.

PubMed

Maneksh, Delinda; Sidharthan, Anita; Kettimuthu, Kavithapriya; Kanthakumar, Praghalathan; Lourthuraj, Amala A; Ramachandran, Anup; Subramani, Sathya

2010-06-01

A water decoction of the poisonous shrub Cleistanthus collinus is used for suicidal purposes. The mortality rate is 28%. The clinical profile includes distal renal tubular acidosis (DRTA) and respiratory failure. The mechanism of toxicity is unclear. To demonstrate features of C. collinus toxicity in a rat model and to identify its mechanism(s) of action. Rats were anesthetized and the carotid artery was cannulated. Electrocardiogram and respiratory movements were recorded. Either aqueous extract of C. collinus or control solution was administered intraperitoneally. Serial measurements of blood gases, electrolytes and urinary pH were made. Isolated brush border and basolateral membranes from rat kidney were incubated with C. collinus extract and reduction in ATPase activity was assessed. Venous blood samples from human volunteers and rats were incubated with an acetone extract of C. collinus and plasma potassium was estimated as an assay for sodium-potassium pump activity. The mortality was 100% in tests and 17% in controls. Terminal event in test animals was respiratory arrest. Controls had metabolic acidosis, respiratory compensation acidic urine and hyperkalemia. Test animals showed respiratory acidosis, alkaline urine and low blood potassium as compared to controls. C. collinus extract inhibited ATPase activity in rat kidney. Plasma K(+) did not increase in human blood incubated with C. collinus extract. Active principles of C. collinus inhibit proton pumps in the renal brush border, resulting in type I DRTA in rats. There is no inhibition of sodium-potassium pump activity. Test animals develop respiratory acidosis, and the immediate cause of death is respiratory arrest.

Proton pump inhibitor chemosensitization in human osteosarcoma: from the bench to the patients’ bed

PubMed Central

2013-01-01

Background Major goals in translational oncology are to reduce systemic toxicity of current anticancer strategies and improve effectiveness. An extremely efficient cancer cell mechanism to avoid and/or reduce the effects of highly cytotoxic drugs is the establishment of an acidic microenvironment, an hallmark of all malignant tumors. The H + −rich milieu that anticancer drugs meet once they get inside the tumor leads to their protonation and neutralization, therefore hindering their access into tumor cells. We have previously shown that proton pump inhibitors (PPI) may efficiently counterattack this tumor advantage leading to a consistent chemosensitization of tumors. In this study, we investigated the effects of PPI in chemosensitizing osteosarcoma. Method MG-63 and Saos-2 cell lines were used as human osteosarcoma models. Cell proliferation after pretreatment with PPI and subsequent treatment with cisplatin was evaluated by using erythrosin B dye vital staining. Tumour growth was evaluated in xenograft treated with cisplatin after PPI pretreatment. Subsequently, a multi-centre historically controlled trial, was performed to evaluate the activity of a pre-treatment administration of PPIs as chemosensitizers during neoadjuvant chemotherapy based on methotrexate, cisplatin, and adriamycin. Results Preclinical experiments showed that PPI sensitize both human osteosarcoma cell lines and xenografts to cisplatin. A clinical study subsequently showed that pretreatment with PPI drug esomeprazole leads to an increase in the local effect of chemotherapy, as expressed by percentage of tumor necrosis. This was particularly evident in chondroblastic osteosarcoma, an histological subtype that normally shows a poor histological response. Notably, no significant increase in toxicity was recorded in PPI treated patients. Conclusion This study provides the first evidence that PPI may be beneficially added to standard regimens in combination to conventional chemotherapy. PMID:24156349

Proton pump inhibitor chemosensitization in human osteosarcoma: from the bench to the patients' bed.

PubMed

Ferrari, Stefano; Perut, Francesca; Fagioli, Franca; Brach Del Prever, Adalberto; Meazza, Cristina; Parafioriti, Antonina; Picci, Piero; Gambarotti, Marco; Avnet, Sofia; Baldini, Nicola; Fais, Stefano

2013-10-24

Major goals in translational oncology are to reduce systemic toxicity of current anticancer strategies and improve effectiveness. An extremely efficient cancer cell mechanism to avoid and/or reduce the effects of highly cytotoxic drugs is the establishment of an acidic microenvironment, an hallmark of all malignant tumors. The H +-rich milieu that anticancer drugs meet once they get inside the tumor leads to their protonation and neutralization, therefore hindering their access into tumor cells. We have previously shown that proton pump inhibitors (PPI) may efficiently counterattack this tumor advantage leading to a consistent chemosensitization of tumors. In this study, we investigated the effects of PPI in chemosensitizing osteosarcoma. MG-63 and Saos-2 cell lines were used as human osteosarcoma models. Cell proliferation after pretreatment with PPI and subsequent treatment with cisplatin was evaluated by using erythrosin B dye vital staining. Tumour growth was evaluated in xenograft treated with cisplatin after PPI pretreatment. Subsequently, a multi-centre historically controlled trial, was performed to evaluate the activity of a pre-treatment administration of PPIs as chemosensitizers during neoadjuvant chemotherapy based on methotrexate, cisplatin, and adriamycin. Preclinical experiments showed that PPI sensitize both human osteosarcoma cell lines and xenografts to cisplatin. A clinical study subsequently showed that pretreatment with PPI drug esomeprazole leads to an increase in the local effect of chemotherapy, as expressed by percentage of tumor necrosis. This was particularly evident in chondroblastic osteosarcoma, an histological subtype that normally shows a poor histological response. Notably, no significant increase in toxicity was recorded in PPI treated patients. This study provides the first evidence that PPI may be beneficially added to standard regimens in combination to conventional chemotherapy.

Proton transfer events in GFP.

PubMed

Di Donato, Mariangela; van Wilderen, Luuk J G W; Van Stokkum, Ivo H M; Stuart, Thomas Cohen; Kennis, John T M; Hellingwerf, Klaas J; van Grondelle, Rienk; Groot, Marie Louise

2011-09-28

Proton transfer is one of the most important elementary processes in biology. Green fluorescent protein (GFP) serves as an important model system to elucidate the mechanistic details of this reaction, because in GFP proton transfer can be induced by light absorption. Illumination initiates proton transfer through a 'proton-wire', formed by the chromophore (the proton donor), water molecule W22, Ser205 and Glu222 (the acceptor), on a picosecond time scale. To obtain a more refined view of this process, we have used a combined approach of time resolved mid-infrared spectroscopy and visible pump-dump-probe spectroscopy to resolve with atomic resolution how and how fast protons move through this wire. Our results indicate that absorption of light by GFP induces in 3 ps (10 ps in D(2)O) a shift of the equilibrium positions of all protons in the H-bonded network, leading to a partial protonation of Glu222 and to a so-called low barrier hydrogen bond (LBHB) for the chromophore's proton, giving rise to dual emission at 475 and 508 nm. This state is followed by a repositioning of the protons on the wire in 10 ps (80 ps in D(2)O), ultimately forming the fully deprotonated chromophore and protonated Glu222.

Synergy of 2-deoxy-D-glucose combined with berberine in inducing the lysosome/autophagy and transglutaminase activation-facilitated apoptosis.

PubMed

Halicka, H Dorota; Garcia, Jorge; Li, Jiangwei; Zhao, Hong; Darzynkiewicz, Zbigniew

2017-02-01

Utilizing a variety of flow cytometric methods evidence was obtained indicating that a combination of the glucose analog 2-deoxy-D-glucose (2-dG) and the plant alkaloid berberine (BRB) produces synergistic effect in the induction of apoptosis in human lymphoblastoid TK6 cells. The synergistic effect is seen at concentrations of the drugs at which each of them alone shows no cytotoxicity at all. The data suggest that the combination of these drugs, which are known in terms of their overall toxicity, side effects and pharmacokinetics may be considered for further studies as chemopreventive and cancer treatment modalities. Of interest are results indicating that rapamycin, which similarly to BRB, suppresses mTOR signaling, when combined with 2-dG shows no synergistic properties. Metformin, on other hand, requires much higher concentration to show the synergy with 2-dG. Also of interest are the findings pertaining to the methodology of the present study. Specifically, dynamic assessment of cellular viability was performed by using the DRAQ7 cell exclusion fluorochrome present in cultures from 0 to 72 h. Concurrent measurement of lysosomal proton pump using acridine orange as the probe shows activation of lysosomes in the cells treated with 2-dG or BRB alone as well as with the drugs combined. Apoptosis was assessed by measuring DNA fragmentation, cell cycle, activation of caspase-3 and tissue transglutaminase (Tgase). A novel cytometric method was developed based on analysis of lysosomal (acidic vesicles) proton pump in live cells followed by cell lysis with detergent and fluorochrome labeling of proteins and DNA to analyze Tgase activation concurrently with cell cycle, in same population of cells. The data show that the cell subpopulation undergoing apoptosis has increased side (right-angle) light scatter likely due to the presence of the crosslinked (solid state) proteins, the consequence Tgase activation.

Flexibility within the rotor and stators of the vacuolar H+-ATPase.

PubMed

Song, Chun Feng; Papachristos, Kostas; Rawson, Shaun; Huss, Markus; Wieczorek, Helmut; Paci, Emanuele; Trinick, John; Harrison, Michael A; Muench, Stephen P

2013-01-01

The V-ATPase is a membrane-bound protein complex which pumps protons across the membrane to generate a large proton motive force through the coupling of an ATP-driven 3-stroke rotary motor (V1) to a multistroke proton pump (Vo). This is done with near 100% efficiency, which is achieved in part by flexibility within the central rotor axle and stator connections, allowing the system to flex to minimise the free energy loss of conformational changes during catalysis. We have used electron microscopy to reveal distinctive bending along the V-ATPase complex, leading to angular displacement of the V1 domain relative to the Vo domain to a maximum of ~30°. This has been complemented by elastic network normal mode analysis that shows both flexing and twisting with the compliance being located in the rotor axle, stator filaments, or both. This study provides direct evidence of flexibility within the V-ATPase and by implication in related rotary ATPases, a feature predicted to be important for regulation and their high energetic efficiencies.

Hypoalbuminemia is a predictor of mortality and rebleeding in peptic ulcer bleeding under proton pump inhibitor use.

PubMed

Cheng, Hsiu-Chi; Yang, Er-Hsiang; Wu, Chung-Tai; Wang, Wen-Lun; Chen, Po-Jun; Lin, Meng-Ying; Sheu, Bor-Shyang

2018-04-01

Peptic ulcer bleeding remains a deadly disease, and a simple indicator of long-term outcomes is crucial. This study validated whether hypoalbuminemia and its related factors in patients with peptic ulcer bleeding can indicate long-term mortality and rebleeding under proton pump inhibitor use. The prospective cohort study enrolled 426 patients with peptic ulcer bleeding who had high risk stigmata at endoscopy and had received endoscopic hemostasis. They were divided into 79 patients in the hypoalbuminemia group (Hypo-AG, serum albumin <28 g/L), 135 in the marginal hypoalbuminemia group (Margin-AG, serum albumin 28-34.9 g/L), and 212 in the normal albuminemia group (Normal-AG, serum albumin ≥35 g/L). Each subject received 72-h of intravenous infusion and then the oral form of proton pump inhibitors and were monitored for 84 days to assess all-cause mortality and recurrent bleeding. The primary outcome of all-cause mortality rates were increased in a stepwise fashion in a trend from Normal-AG, Margin-AG, to Hypo-AG (0-28th day: 1.9%, 2.2%, 12.8%, p < 0.001; 29th-84th day: 2.5%, 8.0%, 10.6%, p < 0.01). The secondary outcome of recurrent bleeding rates were also increased in the same fashion (0-28th day: 6.4%, 15.4%, 24.6%, p < 0.001; 29th-84th day: 0%, 3.0%, 4.2%, p = 0.01). Abnormal albuminemia was <30 g/L related to hemoglobin levels <70 g/L, nosocomial bleeding, cirrhosis, age ≥70 years, shock, and ulcer size ≥1.0 cm independently (p < 0.05). Hypoalbuminemia in patients with peptic ulcer bleeding can be an alarm indicator of all-cause mortality and recurrent bleeding in a long-term follow-up situation under proton pump inhibitor use (NCT01591083). Copyright © 2017. Published by Elsevier B.V.

A non-equilibrium thermodynamics model of reconstituted Ca(2+)-ATPase.

PubMed

Waldeck, A R; van Dam, K; Berden, J; Kuchel, P W

1998-01-01

A non-equilibrium thermodynamics (NET) model describing the action of completely coupled or 'slipping' reconstituted Ca(2+)-ATPase is presented. Variation of the coupling stoichiometries with the magnitude of the electrochemical gradients, as the ATPase hydrolyzes ATP, is an indication of molecular slip. However, the Ca2+ and H+ membrane-leak conductances may also be a function of their respective gradients. Such non-ohmic leak typically yields 'flow-force' relationships that are similar to those that are obtained when the pump slips; hence, caution needs to be exercised when interpreting data of Ca(2+)-ATPase-mediated fluxes that display a non-linear dependence on the electrochemical proton (delta mu H) and/or calcium gradients (delta mu Ca). To address this issue, three experimentally verifiable relationships differentiating between membrane leak and enzymic slip were derived. First, by measuring delta mu H as a function of the rate of ATP hydrolysis by the enzyme. Second, by measuring the overall 'efficiency' of the pump as a function of delta mu H. Third, by measuring the proton ejection rate by the pump as a function of its ATP hydrolysis rate.

Tunneling induced electron transfer between separated protons

NASA Astrophysics Data System (ADS)

Vindel-Zandbergen, Patricia; Meier, Christoph; Sola, Ignacio R.

2018-04-01

We study electron transfer between two separated protons using local control theory. In this symmetric system one can favour a slow transfer by biasing the algorithm, achieving high efficiencies for fixed nuclei. The solution can be parametrized using a sequence of a pump followed by a dump pulse that lead to tunneling-induced electron transfer. Finally, we study the effect of the nuclear kinetic energy on the efficiency. Even in the absence of relative motion between the protons, the spreading of the nuclear wave function is enough to reduce the yield of electronic transfer to less than one half.

Comparison of proton-specific ATPase activities in plume and root tissues of two co-occurring hydrocarbon seep tubeworm species Lamellibrachia luymesi and Seepiophila jonesi.

PubMed

Dattagupta, Sharmishtha; Redding, Meredith; Luley, Kathryn; Fisher, Charles

2009-01-01

Lamellibrachia luymesi and Seepiophila jonesi are co-occurring species of vestimentiferan tubeworms found at hydrocarbon seepage sites on the upper Louisiana slope of the Gulf of Mexico. Like all vestimentiferans, they rely on internal sulfide-oxidizing symbiotic bacteria for nutrition. These symbionts produce hydrogen ions as a byproduct of sulfide oxidation, which the host tubeworm needs to eliminate to prevent acidosis. The hydrothermal vent tubeworm Riftia pachyptila uses a high activity of P- and V-type H + -ATPases located in its plume epithelium to excrete protons. Unlike R. pachyptila , the seep species grow a posterior root, which they can use in addition to their plumes as a nutrient exchange surface. In this study we measured the ATPase activities of plume and root tissues collected from L. luymesi and S. jonesi , and used a combination of inhibitors to determine the relative activities of P- and V-type H + -ATPases. We found that the total H + -ATPase activity of their plumes was approximately 14 μmol h -1  g -1 wet weight, and that of their roots was between 5 and 7 μmol h -1  g -1 wet weight. These activities were more than ten times lower than those measured in R. pachyptila . We suggest that seep tubeworms might use passive channels to eliminate protons across their roots, in addition to ATP-dependant proton pumps located in their plumes and roots. In addition, we found strong differences between the types of ATPase activities in the plumes of L. luymesi and S. jonesi . While the H + -ATPase activity of L. luymesi plumes is dominated by P-type ATPases, S. jonesi has an unusually high activity of V-type H + -ATPases. We suggest that S. jonesi relies on its high V-type H + -ATPase activity to drive carbon dioxide uptake across its plume surface. L. luymesi , on the other hand, might rely partially on bicarbonate uptake across its root.

Proton pump inhibitors

MedlinePlus

... used to: Relieve symptoms of acid reflux, or gastroesophageal reflux disease (GERD). This is a condition in which ... MF. Guidelines for the diagnosis and management of gastroesophageal reflux disease. Am J Gastroenterol . 2013;108(3):308- ...

Gastroesophageal Reflux (For Parents)

MedlinePlus

... with caffeine fatty and fried foods garlic and onions spicy foods tomato-based foods and sauces peppermint ... as H2 blockers, which can help block the production of stomach acid, or proton pump inhibitors, which ...

Modifications of the chemical structure of phenolics differentially affect physiological activities in pulvinar cells of Mimosa pudica L. I. Multimode effect on early membrane events.

PubMed

Rocher, Françoise; Dédaldéchamp, Fabienne; Saeedi, Saed; Fleurat-Lessard, Pierrette; Chollet, Jean-Francois; Roblin, Gabriel

2014-11-01

A study of the structure-activity relationship carried out on several benzoic acid-related phenolics indicates that this type of compounds hinders the osmocontractile reaction of pulvinar cells in the range of 0-100%. Tentatively, we tried to find a way that could explain this differential action. With this aim, the relationship between the inhibitory effect and important molecular physico-chemical parameters (namely lipophilicity and degree of dissociation) was drawn. In addition, the effect of a variety of these compounds was investigated on their capacity to modify the electrical transmembrane potential and induce modifications in proton fluxes. Finally, using plasma membrane vesicles purified from pulvinar tissues, we examined the effects of some selected compounds on the proton pump activity and catalytic activity of the plasma membrane H(+)-ATPase. Taken together, the results indicate that a modification of the molecular structure of phenolics may induce important variation in the activity of the compound on these early membrane events. Among the tested phenolics, salicylic acid (SA) and acetylsalicylic acid (ASA, aspirin) are of particuler note, as they showed atypical effects on the physiological processes studied. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

In vivo inhibition of gastric acid secretion by the aqueous extract of Scoparia dulcis L. in rodents.

PubMed

Mesía-Vela, Sonia; Bielavsky, Monica; Torres, Luce Maria Brandão; Freire, Sonia Maria; Lima-Landman, Maria Teresa R; Souccar, Caden; Lapa, Antonio José

2007-05-04

The freeze-dried aqueous extract (AE) from the aerial parts of Scoparia dulcis was tested for its effects on experimental gastric hypersecretion and ulcer in rodents. Administration of AE to animals with 4h pylorus ligature potently reduced the gastric secretion with ED(50)s of 195 mg/kg (rats) and 306 mg/kg (mice). The AE also inhibited the histamine- or bethanechol-stimulated gastric secretion in pylorus-ligated mice with similar potency suggesting inhibition of the proton pump. Bio-guided purification of the AE yielded a flavonoid-rich fraction (BuF), with a specific activity 4-8 times higher than the AE in the pylorus ligature model. BuF also inhibited the hydrolysis of ATP by H(+),K(+)-ATPase with an IC(50) of 500 microg/ml, indicating that the inhibition of gastric acid secretion of Scoparia dulcis is related to the inhibition of the proton pump. Furthermore, the AE inhibited the establishment of acute gastric lesions induced in rats by indomethacin (ED(50)=313 mg/kg, p.o.) and ethanol (ED(50)=490 mg/kg, p.o.). No influence of the AE on gastrointestinal transit allowed discarding a possible CNS or a cholinergic interaction in the inhibition of gastric secretion by the AE. Collectively, the present data pharmacologically validates the popular use of Scoparia dulcis in gastric disturbances.

Proton pump inhibitors and functional decline in older adults discharged from acute care hospitals.

PubMed

Corsonello, Andrea; Maggio, Marcello; Fusco, Sergio; Adamo, Bakhita; Amantea, Diana; Pedone, Claudio; Garasto, Sabrina; Ceda, Gian Paolo; Corica, Francesco; Lattanzio, Fabrizia; Antonelli Incalzi, Raffaele

2014-06-01

To investigate the relationship between use of proton pump inhibitors (PPIs) and incident dependency in older adults discharged from acute care hospitals. Prospective observational study. Eleven geriatric and internal medicine acute care wards located throughout Italy. Individuals (mean age 79.2 ± 5.5) who were not completely dependent at the time of discharge from participating wards (N = 401). The outcome of interest was the loss of at least one basic activity of daily living (ADL) from discharge to the end of follow-up (12 months). The relationship between PPI use and functional decline was investigated using logistic regression analysis before and after propensity score matching. Use of PPIs was significantly associated with functional decline before (odds ratio (OR) = 1.75, 95% confidence interval (CI) = 1.17-2.60) and after propensity score matching (OR = 2.44; 95% CI = 1.36-4.41). Other predictors of functional decline were hypoalbuminemia (OR = 3.10, 95% CI = 1.36-7.10 before matching, OR = 2.81, 95% CI = 1.09-7.77 after matching) and cognitive impairment (OR = 4.08, 95% CI = 1.63-10.2 before matching, OR = 6.35, 95% CI = 1.70-24.0 after matching). Use of PPIs is associated with functional decline during 12 months of follow-up in older adults discharged from acute care hospitals. © 2014, Copyright the Authors Journal compilation © 2014, The American Geriatrics Society.

Clopidogrel and proton pump inhibitor (PPI) interaction: separate intake and a non-omeprazole PPI the solution?

PubMed

Kenngott, S; Olze, R; Kollmer, M; Bottheim, H; Laner, A; Holinski-Feder, E; Gross, M

2010-05-18

Dual therapy with aspirin and clopidogrel increases the risk of gastrointestinal bleeding. Therefore, co-therapy with a proton pump inhibitor (PPI) is recommended by most guidelines. However, there are warnings against combining PPIs with clopidogrel because of their interactions with cytochrome P450 isoenzyme 2C19 (CYP2C19). The effects of the combined or separate intake of 20 mg of omeprazole and 75 mg of clopidogrel on the clopidogrel-induced inhibition of platelet aggregation were measured in four healthy subjects whose CYP2C19 exon sequences were determined. The effects of co-therapy with 10 mg of rabeprazole were also examined. Two subjects showed the wild-type CYP2C19 sequence. The concurrent intake of omeprazole had no effect on clopidogrel-induced platelet inhibition in these subjects. Two subjects were heterozygous for the *2 allele, with predicted reduced CYP2C19 activity. One of them was a clopidogrel non-responder. In the second heterozygous subject, omeprazole co-therapy reduced the clopidogrel anti-platelet effect when taken simultaneously or separately. However, the simultaneous intake of rabeprazole did not reduce the clopidogrel effect. The clopidogrel-PPI interaction does not seem to be a PPI class effect. Rabeprazole did not affect the clopidogrel effect in a subject with a clear omeprazole-clopidogrel interaction. The separate intake of PPI and clopidogrel may not be sufficient to prevent their interaction.

Impact of active geomagnetic conditions on stimulated radiation during ionospheric second electron gyroharmonic heating

NASA Astrophysics Data System (ADS)

Bordikar, M. R.; Scales, W. A.; Mahmoudian, A.; Kim, H.; Bernhardt, P. A.; Redmon, R.; Samimi, A. R.; Brizcinski, S.; McCarrick, M. J.

2014-01-01

Recently, narrowband emissions ordered near the H+ (proton) gyrofrequency (fcH) were reported in the stimulated electromagnetic emission (SEE) spectrum during active geomagnetic conditions. This work presents new observations and theoretical analysis of these recently discovered emissions. These emission lines are observed in the stimulated electromagnetic emission (SEE) spectrum when the transmitter is tuned near the second electron gyroharmonic frequency (2fce) during recent ionospheric modification experiments at the High Frequency Active Auroral Research (HAARP) facility near Gakona, Alaska. The spectral lines are typically shifted below and above the pump wave frequency by harmonics of a frequency roughly 10% less than fcH (≈ 800 Hz) with a narrow emission bandwidth less than the O+ gyrofrequency (≈ 50 Hz). However, new observations and analysis of emission lines ordered by a frequency approximately 10% greater than fcH are presented here for the first time as well. The interaction altitude for the heating for all the observations is in the range of 160 km up to 200 km. As described previously, proton precipitation due to active geomagnetic conditions is considered as the reason for the presence of H+ ions known to be a minor background constituent in this altitude region. DMSP satellite observations over HAARP during the heating experiments and ground-based magnetometer and riometer data validate active geomagnetic conditions. The theory of parametric decay instability in multi-ion component plasma including H+ ions as a minority species described in previous work is expanded in light of simultaneously observed preexisting SEE features to interpret the newly reported observations. Impact of active geomagnetic conditions on the SEE spectrum as a diagnostic tool for proton precipitation event characterization is discussed.

Positive Darwinian Selection in the Piston That Powers Proton Pumps in Complex I of the Mitochondria of Pacific Salmon

PubMed Central

Garvin, Michael R.; Bielawski, Joseph P.; Gharrett, Anthony J.

2011-01-01

The mechanism of oxidative phosphorylation is well understood, but evolution of the proteins involved is not. We combined phylogenetic, genomic, and structural biology analyses to examine the evolution of twelve mitochondrial encoded proteins of closely related, yet phenotypically diverse, Pacific salmon. Two separate analyses identified the same seven positively selected sites in ND5. A strong signal was also detected at three sites of ND2. An energetic coupling analysis revealed several structures in the ND5 protein that may have co-evolved with the selected sites. These data implicate Complex I, specifically the piston arm of ND5 where it connects the proton pumps, as important in the evolution of Pacific salmon. Lastly, the lineage to Chinook experienced rapid evolution at the piston arm. PMID:21969854

Positive Darwinian selection in the piston that powers proton pumps in complex I of the mitochondria of Pacific salmon.

PubMed

Garvin, Michael R; Bielawski, Joseph P; Gharrett, Anthony J

2011-01-01

The mechanism of oxidative phosphorylation is well understood, but evolution of the proteins involved is not. We combined phylogenetic, genomic, and structural biology analyses to examine the evolution of twelve mitochondrial encoded proteins of closely related, yet phenotypically diverse, Pacific salmon. Two separate analyses identified the same seven positively selected sites in ND5. A strong signal was also detected at three sites of ND2. An energetic coupling analysis revealed several structures in the ND5 protein that may have co-evolved with the selected sites. These data implicate Complex I, specifically the piston arm of ND5 where it connects the proton pumps, as important in the evolution of Pacific salmon. Lastly, the lineage to Chinook experienced rapid evolution at the piston arm.

Long-term safety concerns with proton pump inhibitors.

PubMed

Ali, Tauseef; Roberts, David Neil; Tierney, William M

2009-10-01

Proton pump inhibitors (PPIs) are among the most widely prescribed medications worldwide. Their use has resulted in dramatic improvements in treatment of peptic ulcer disease and gastroesophageal reflux disease. Despite an acceptable safety profile, mounting data demonstrate concerns about the long-term use of PPIs. To provide a comprehensive review regarding the concerns of long-term PPI use, a literature search was performed to identify pertinent original and review articles. Despite study shortcomings, the collective body of information overwhelmingly suggests an increased risk of infectious complications and nutritional deficiencies. Data regarding any increased risk in gastric or colon malignancy are less convincing. PPIs have revolutionized the management and complications of acid-related disorders with a high margin of safety; however, with the data available, efforts to reduce the dosing of or discontinue the use of PPIs must be reassessed frequently.

Scopadulcic acid B, a new tetracyclic diterpenoid from Scoparia dulcis L. Its structure, H+, K(+)-adenosine triphosphatase inhibitory activity and pharmacokinetic behaviour in rats.

PubMed

Hayashi, T; Okamura, K; Kakemi, M; Asano, S; Mizutani, M; Takeguchi, N; Kawasaki, M; Tezuka, Y; Kikuchi, T; Morita, N

1990-10-01

The structure of scopadulcic acid B (2, SDB), a major ingredient of the Paraguayan herb "Typychá kuratũ" (Scoparia dulcis L.), was elucidated mainly by comparison of its spectral data with that of scopadulcic acid A (1). SDB inhibited both the K(+)-dependent adenosine triphosphatase (ATPase) activity of a hog gastric proton pump (H+, K(+)-ATPase) with a value of 20-30 microM for IC50 and proton transport into gastric vesicles. Pharmacokinetic studies of SDB in rats indicated that plasma SDB concentrations after i.v. injection of the sodium salt of SDB (SDB-Na) were described reasonably well by a two-compartment open model with Michaelis-Menten elimination kinetics. Plasma concentrations after oral administration of SDB-Na or SDB showed a much slower decline than what was expected following the i. v. study. It was suggested that the sustained plasma level of SDB after oral administration of SDB-Na or SDB was accounted for by relatively slow but efficient gastro-intestinal absorption in rats.

Proton Pump Inhibitors: Risk for Myopathy?

PubMed

Colmenares, Evan W; Pappas, Ashley L

2017-01-01

The purpose of this article is to describe the relationship between proton pump inhibitors (PPIs) and symptoms of myopathy based on case reports. A literature search was conducted in PubMed (1946 to June 2016) using MeSH terms proton pump inhibitors, omeprazole, esomeprazole, lansoprazole, dexlansoprazole, rabeprazole, pantoprazole, and muscular diseases. Additionally, a search was conducted in ToxNet and EMBASE using similar search criteria. The resulting articles were scanned to assess relevance to the review. Bibliographies of all relevant articles were evaluated for additional sources; 26 articles resulted from the search of PubMed, ToxNet, and EMBASE; articles that involved medications typically considered to have myalgia-like side effects (eg, statins), or included patients who presented with a confounding disease state (eg, Guillain-Barré) were excluded. In total, 11 case reports as well as a review of an adverse event reporting database that included 292 cases were evaluated. Association of PPI use and myopathy symptoms does not have a clear etiology. Overall, the available published data do not show a high risk of myopathy with PPI use but should be considered if a patient presents with myopathy symptoms and concurrent PPI use. A limited body of published data suggests that PPI use has been associated with myopathy-like symptoms without long-term effects following discontinuation. Although myopathy is a rare adverse effect observed with PPIs, it can be a serious side effect to be considered when starting a patient on acid suppression therapy.

Association Between Proton Pump Inhibitors and Microscopic Colitis.

PubMed

Law, Ernest H; Badowski, Melissa; Hung, Yu-Ting; Weems, Kimberly; Sanchez, Angelica; Lee, Todd A

2017-03-01

Microscopic colitis (MC) is a chronic inflammatory disease of the colon that is characterized by chronic, watery, nonbloody diarrhea. Concern regarding a potential association between proton-pump inhibitors (PPIs) and MC has recently emerged. We sought to systematically review and summarize the evidence for the potential association between PPIs and MC. We systematically searched EMBASE, MEDLINE, Cochrane Database of Systematic Reviews, International Pharmaceutical Abstracts, and Google Scholar using the terms proton-pump inhibitors (omeprazole, lansoprazole, dexlansoprazole, rabeprazole, pantoprazole, or esomeprazole), microscopic colitis, collagenous colitis, and lymphocytic colitis. Full-text, English-language reports of case reports/series, observational studies, experimental studies, and systematic reviews/meta-analyses published between January 2000 to August 2016 were included. Bibliographies from pertinent publications were reviewed for additional references. Outcome was defined as the development of biopsy-confirmed MC. A total of 19 publications were identified: 5 case control studies and 14 case reports/series (encompassing a total of 32 cases). All studies were limited by small sample sizes. Risk of MC by dose or specific PPI agent was not investigated in any of the studies. A review of the current body of evidence reveals a possible association between PPIs and MC. There is a need for large observational studies of high quality to examine the differential effect of specific PPIs and whether the magnitude of association is dose dependent. Given their widespread use, clinicians should routinely question whether patients are receiving unnecessary treatment with PPIs and discontinue therapy where appropriate.

Lansoprazole induces sensitivity to suboptimal doses of paclitaxel in human melanoma.

PubMed

Azzarito, Tommaso; Venturi, Giulietta; Cesolini, Albino; Fais, Stefano

2015-01-28

Tumor acidity is now considered an important determinant of drug-resistance and tumor progression, and anti-acidic approaches, such as Proton Pump inhibitors (PPIs), have demonstrated promising antitumor and chemo-sensitizing efficacy. The main purpose of the present study was to evaluate the possible PPI-induced sensitization of human melanoma cells to Paclitaxel (PTX). Our results show that PTX and the PPI Lansoprazole (LAN) combination was extremely efficient against metastatic melanoma cells, as compared to the single treatments, both in vitro and in vivo. We also showed that acidity plays an important role on the anti-tumor activity of these drugs, being detrimental for PTX activity, while crucial for the synergistic effect of PTX following pretreatment with LAN, due to its nature of pro-drug needing protonation for a full activation. We obtained straightforward results in a human melanoma xenograft model combining well tolerated LAN doses with suboptimal and poorly toxic doses of PTX. With this study we provide a clear evidence that the PPI LAN may be included in new combined therapy of human melanoma together with low doses of PTX. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Proton Pump Inhibitor Use and the Risk of Chronic Kidney Disease.

PubMed

Lazarus, Benjamin; Chen, Yuan; Wilson, Francis P; Sang, Yingying; Chang, Alex R; Coresh, Josef; Grams, Morgan E

2016-02-01

Proton pump inhibitors (PPIs) are among the most commonly used drugs worldwide and have been linked to acute interstitial nephritis. Less is known about the association between PPI use and chronic kidney disease (CKD). To quantify the association between PPI use and incident CKD in a population-based cohort. In total, 10,482 participants in the Atherosclerosis Risk in Communities study with an estimated glomerular filtration rate of at least 60 mL/min/1.73 m(2) were followed from a baseline visit between February 1, 1996, and January 30, 1999, to December 31, 2011. The data was analyzed from May 2015 to October 2015. The findings were replicated in an administrative cohort of 248,751 patients with an estimated glomerular filtration rate of at least 60 mL/min/1.73 m(2) from the Geisinger Health System. Self-reported PPI use in the Atherosclerosis Risk in Communities study or an outpatient PPI prescription in the Geisinger Health System replication cohort. Histamine2 (H2) receptor antagonist use was considered a negative control and active comparator. Incident CKD was defined using diagnostic codes at hospital discharge or death in the Atherosclerosis Risk in Communities Study, and by a sustained outpatient estimated glomerular filtration rate of less than 60 mL/min/1.73 m(2) in the Geisinger Health System replication cohort. Among 10,482 participants in the Atherosclerosis Risk in Communities study, the mean (SD) age was 63.0 (5.6) years, and 43.9% were male. Compared with nonusers, PPI users were more often of white race, obese, and taking antihypertensive medication. Proton pump inhibitor use was associated with incident CKD in unadjusted analysis (hazard ratio [HR], 1.45; 95% CI, 1.11-1.90); in analysis adjusted for demographic, socioeconomic, and clinical variables (HR, 1.50; 95% CI, 1.14-1.96); and in analysis with PPI ever use modeled as a time-varying variable (adjusted HR, 1.35; 95% CI, 1.17-1.55). The association persisted when baseline PPI users were compared directly with H2 receptor antagonist users (adjusted HR, 1.39; 95% CI, 1.01-1.91) and with propensity score-matched nonusers (HR, 1.76; 95% CI, 1.13-2.74). In the Geisinger Health System replication cohort, PPI use was associated with CKD in all analyses, including a time-varying new-user design (adjusted HR, 1.24; 95% CI, 1.20-1.28). Twice-daily PPI dosing (adjusted HR, 1.46; 95% CI, 1.28-1.67) was associated with a higher risk than once-daily dosing (adjusted HR, 1.15; 95% CI, 1.09-1.21). Proton pump inhibitor use is associated with a higher risk of incident CKD. Future research should evaluate whether limiting PPI use reduces the incidence of CKD.

Membrane Electrical Noise in Chara corallina1

PubMed Central

Ross, Stephen; Dainty, Jack

1986-01-01

Certain inhibitors have been found to affect the low frequency spectral component of the electrical noise power spectrum in Chara corallina. Application of the ATPase inhibitor N,N′-dicyclohexylcarbodiimide removed the low frequency spectral component, strengthening the case that the component is produced by active proton pumping. Cytocholasin B, which inhibits cyclosis in internodes of C. corallina, removed the low frequency spectral component in a time-dependent fashion which was correlated with the cessation of streaming. The protonophore carbonyl cyanide m-chlorophenylhydrazone did not produce consistent effects on the low frequency spectral component in these cells. PMID:16664898

Marine Bacterial and Archaeal Ion-Pumping Rhodopsins: Genetic Diversity, Physiology, and Ecology

PubMed Central

DeLong, Edward F.; Béjà, Oded; González, José M.; Pedrós-Alió, Carlos

2016-01-01

SUMMARY The recognition of a new family of rhodopsins in marine planktonic bacteria, proton-pumping proteorhodopsin, expanded the known phylogenetic range, environmental distribution, and sequence diversity of retinylidene photoproteins. At the time of this discovery, microbial ion-pumping rhodopsins were known solely in haloarchaea inhabiting extreme hypersaline environments. Shortly thereafter, proteorhodopsins and other light-activated energy-generating rhodopsins were recognized to be widespread among marine bacteria. The ubiquity of marine rhodopsin photosystems now challenges prior understanding of the nature and contributions of “heterotrophic” bacteria to biogeochemical carbon cycling and energy fluxes. Subsequent investigations have focused on the biophysics and biochemistry of these novel microbial rhodopsins, their distribution across the tree of life, evolutionary trajectories, and functional expression in nature. Later discoveries included the identification of proteorhodopsin genes in all three domains of life, the spectral tuning of rhodopsin variants to wavelengths prevailing in the sea, variable light-activated ion-pumping specificities among bacterial rhodopsin variants, and the widespread lateral gene transfer of biosynthetic genes for bacterial rhodopsins and their associated photopigments. Heterologous expression experiments with marine rhodopsin genes (and associated retinal chromophore genes) provided early evidence that light energy harvested by rhodopsins could be harnessed to provide biochemical energy. Importantly, some studies with native marine bacteria show that rhodopsin-containing bacteria use light to enhance growth or promote survival during starvation. We infer from the distribution of rhodopsin genes in diverse genomic contexts that different marine bacteria probably use rhodopsins to support light-dependent fitness strategies somewhere between these two extremes. PMID:27630250

Gastroesophageal Reflux Disease (GERD) (and Asthma)

MedlinePlus

... examines the inside of the esophagus) • Ambulatory acid (pH) test (monitors the amount of acid in the ... H2 blockers may help decrease the effects of stomach acid. Proton pump inhibitors block acid production and ...

Coping with low pH: molecular strategies in neutralophilic bacteria.

PubMed

Lund, Peter; Tramonti, Angela; De Biase, Daniela

2014-11-01

As part of their life cycle, neutralophilic bacteria are often exposed to varying environmental stresses, among which fluctuations in pH are the most frequent. In particular, acid environments can be encountered in many situations from fermented food to the gastric compartment of the animal host. Herein, we review the current knowledge of the molecular mechanisms adopted by a range of Gram-positive and Gram-negative bacteria, mostly those affecting human health, for coping with acid stress. Because organic and inorganic acids have deleterious effects on the activity of the biological macromolecules to the point of significantly reducing growth and even threatening their viability, it is not unexpected that neutralophilic bacteria have evolved a number of different protective mechanisms, which provide them with an advantage in otherwise life-threatening conditions. The overall logic of these is to protect the cell from the deleterious effects of a harmful level of protons. Among the most favoured mechanisms are the pumping out of protons, production of ammonia and proton-consuming decarboxylation reactions, as well as modifications of the lipid content in the membrane. Several examples are provided to describe mechanisms adopted to sense the external acidic pH. Particular attention is paid to Escherichia coli extreme acid resistance mechanisms, the activity of which ensure survival and may be directly linked to virulence. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Forecast of Remote Underwater Sensing Technology.

DTIC Science & Technology

1980-07-01

hr T. MAGNETICS (2 Replies) Q. What will be sensitivities of fluxgate , proton, optical pump, SQUID (superconducting) magnetometers ? A. Fluxgate 0.1...ft Oujtpuit Analog, digital and B3CD Cost $65.K 227 Manu factu rer EG&G Geometric Unit G-806M System Marine Search Proton Magnetometer Sensitivity...optional) Depth Range 0 to 100 m or 6000 m Precision +0.15% FS Time Constant 60 ms Output Digital display, analog and digital BCD output Cost $13.K 243

Proton-transfer lasers based on solid copolymers of modified 2-(2'-hydroxyphenyl)benzimidazoles with methacrylate monomers

NASA Astrophysics Data System (ADS)

Costela, A.; García-Moreno, I.; Mallavia, Ricardo; Amat-Guerri, F.; Barroso, J.; Sastre, R.

1998-06-01

We report on the lasing action of two newly synthesized 2-(2'-hydroxyphenyl) benzimidazole derivatives copolymerized with methyl methacrylate. The laser samples were transversely pumped with a N 2 laser at 337 nm. The influence on the proton-transfer laser performance of the distance between the chromophore group and the polymeric main chain and of the rigidity of the polymeric host matrix, were studied. Significant increases in lasing efficiency and photostability are demonstrated for some of the new materials, as compared to those previously obtained with related proton-transfer dyes also covalently bound to methacrylic monomers.

A light-powered bio-capacitor with nanochannel modulation.

PubMed

Rao, Siyuan; Lu, Shanfu; Guo, Zhibin; Li, Yuan; Chen, Deliang; Xiang, Yan

2014-09-03

An artificial bio-capacitor system is established, consisting of the proton-pump protein proteorhodopsin and a modified alumina nanochannel, inspired by the capacitor-like behavior of plasma membranes realized through the cooperation of ion-pump and ion-channel proteins. Capacitor-like features of this simplified system are realized and identified, and the photocurrent duration time can be modulated by nanochannel modification to obtain favorable square-wave currents. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CCCP activation of the reconstituted NaK-pump.

PubMed

Yoda, A; Yoda, S

1990-08-01

In the NaK-ATPase proteoliposomes (PLs), the NaK-pump activity, Na+ uptake, and ATP hydrolysis were apparently enhanced by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and other ionophores without ion gradients. These ionophore effects were not cation specific. Without ionophores, the PL's ATPase activity fell to its steady-state value within 3 sec at 15 degrees C. This decrease in activity disappeared in the presence of CCCP. Since CCCP is believed to enhance proton mobility across the lipid bilayer and dissipate membrane potential (Vm), we postulated that a Vm build-up partially inhibits the PLs by changing the conformation of the NaK-pump, and that CCCP eliminated this partial inhibition. Since this activation required extracellular K+ and high ATP concentration in the PLs, CCCP must affect the conversion between the phosphorylated forms of NaK-ATPase (EP); this step has been suggested by Goldschlegger et al. (1987) to be the voltage-sensitive step (J. Physiol. (London) 387:331-355). Although cytoplasmic K+ accelerated the change of ADP- and K(+)-sensitive EP (E*P) to K(+)-sensitive ADP-insensitive EP (E2P), CCCP did not complete with cytoplasmic K+ when cytoplasmic Na+ was saturated. When the PLs were phosphorylated with 20 microM ATP and 20 microM palmitoyl CoA instead of with high concentration of ATP, CCCP increased the E*P content and decreased the ADP-sensitive K(+)-insensitive EP (E1P). The results described above suggest that CCCP affects the E1P to E*P change in the E1P----E*P----E2P conversion and that this reaction step is inhibited by Vm.

Development of a MeV proton beam irradiation system.

PubMed

Park, Bum-Sik; Cho, Yong-Sub; Hong, In-Seok

2008-02-01

A proton beam irradiation system for the application of the MeV class proton beam, such as an implantation for a power semiconductor device and a smart-cut technology for a semiconductor production process, has been developed. This system consists of a negative ion source, an Einzel lens for a low energy beam transport, accelerating tubes, a gas stripper, a Cockroft-Walton high voltage power supply with 1 MV, a vacuum pumping system, and a high pressure insulating gas system. The negative hydrogen ion source is based on TRIUMF's design. Following the tandem accelerator, a pair of magnets is installed for raster scanning of the MeV proton beam to obtain a uniform irradiation pattern on the target. The system is 7 m long from the ion source to the target and is optimized for the proton beam irradiation. The details of the system development will be described.

Sulfate-reducing bacteria: Microbiology and physiology

NASA Technical Reports Server (NTRS)

Peck, H. D.

1985-01-01

The sulfate reducing bacteria, the first nonphotosynthetic anaerobic bacteria demonstrated to contain c type cytochromes, perform electron transfer coupled to phosphorylation. A new bioenergetic scheme for the formation of a proton gradient for growth of Desulfovibrio on organic substrates and sulfate involving vectors electron transfer and consistent with the cellular localization of enzymes and electron transfer components was proposed. Hydrogen is produced in the cytoplasm from organic substrates and, as a permease molecule diffuses rapidly across the cytoplasmic membrane, it is oxidized to protons and electrons by the periplasmic hydrogenase. The electrons only are transferred across the cytoplasmic membrane to the cytoplasm where they are used to reduce sulfate to sulfide. The protons are used for transport or to drive a reversible ATPOSE. The net effect is the transfer of protons across the cytoplasmic membrane with the intervention of a proton pump. This type of H2 cycling is relevant to the bioenergetics of other types of anaerobic microorganisms.

Acid Reflux

MedlinePlus

... term maintenance therapy is generally required. Occasionally, a health care plan seeks to limit use of proton pump ... and not the medication. Please consult with your care provider if you have any questions. ... Health Centers Colorectal Cancer Hepatitis C Inflammatory Bowel Disease ...

Comparison of TAK-438 (Vonoprazan) to Lansoprazole in the Treatment of Gastric Ulcer Participants With or Without Helicobacter Pylori Infection

ClinicalTrials.gov

2017-05-24

Gastric Ulcer; Peptic Ulcer; Gastrointestinal Diseases; Digestive System Diseases; Lansoprazole; Anti-Ulcer Agents; Gastrointestinal Agents; Proton Pump Inhibitors; Enzyme Inhibitors; Molecular Mechanisms of Pharmacological Action

Photonic Potential of Haloarchaeal Pigment Bacteriorhodopsin for Future Electronics: A Review.

PubMed

Ashwini, Ravi; Vijayanand, S; Hemapriya, J

2017-08-01

Haloarchaea are known for its adaptation in extreme saline environment. Halophilic archaea produces carotenoid pigments and proton pumps to protect them from extremes of salinity. Bacteriorhodopsin (bR) is a light-driven proton pump that resides in the membrane of haloarchaea Halobacterium salinarum. The photocycle of Bacteriorhodopsin passes through several states from K to O, finally liberating ATP for host's survival. Extensive studies on Bacteriorhodopsin photocycle has provided in depth knowledge on their sequential mechanism of converting solar energy into chemical energy inside the cell. This ability of Bacteriorhodopsin to harvest sunlight has now been experimented to exploit the unexplored and extensively available solar energy in various biotechnological applications. Currently, bacteriorhodopsin finds its importance in dye-sensitized solar cell (DSSC), logic gates (integrated circuits, IC's), optical switching, optical memories, storage devices (random access memory, RAM), biosensors, electronic sensors and optical microcavities. This review deals with the optical and electrical applications of the purple pigment Bacteriorhodopsin.

Development of a beam line for radio-isotope production at the KOMAC

NASA Astrophysics Data System (ADS)

Kim, Han-Sung

2016-09-01

A new beam line of the 100-MeV proton linac at the KOMAC (Korea Multi-purpose Accelerator Complex), aiming for RI (radioisotope) production has been constructed reflecting the increasing demands for various RIs (radioisotopes), such as Sr-82 and Cu-67 for medical applications. Proton beam with beam energy of 100 MeV and an average current of 0.6 mA is directed to the 100-mm-diameter production target through a beam window made of aluminum-beryllium alloy. Major components of the newly-installed beam line include electromagnets for bending and focusing, beam diagnostic systems such as a BPM (beam position monitor) and a BCM (beam current monitor), and a vacuum pumping system based on an ion pump. In this paper, the design features and the installation of the RI-production beam line at the KOMAC are given.

Proton pump inhibitors while belonging to the same family of generic drugs show different anti-tumor effect.

PubMed

Lugini, Luana; Federici, Cristina; Borghi, Martina; Azzarito, Tommaso; Marino, Maria Lucia; Cesolini, Albino; Spugnini, Enrico Pierluigi; Fais, Stefano

2016-08-01

Tumor acidity represents a major cause of chemoresistance. Proton pump inhibitors (PPIs) can neutralize tumor acidity, sensitizing cancer cells to chemotherapy. To compare the anti-tumor efficacy of different PPIs in vitro and in vivo. In vitro experiments PPIs anti-tumor efficacy in terms of cell proliferation and cell death/apoptosis/necrosis evaluation were performed. In vivo PPIs efficacy experiments were carried out using melanoma xenograft model in SCID mice. Lansoprazole showed higher anti-tumor effect when compared to the other PPIs. The lansoprazole effect lasted even upon drug removal from the cell culture medium and it was independent from the lipophilicity of the PPIs formulation. These PPIs have shown different anti-tumoral efficacy, and the most effective at low dose was lansoprazole. The possibility to contrast tumor acidity by off-label using PPIs opens a new field of oncology investigation.

The Proton Pump Inhibitor Nonresponder: a Behavioral Approach to Improvement and Wellness.

PubMed

Riehl, Megan E; Chen, Joan W

2018-06-09

Gastroesophageal reflux disease (GERD) is a difficult to treat medical condition, where nearly 40% of patients are refractory to standard medical intervention, which typically begins with a proton pump inhibitor (PPI). These PPI nonresponders represent a population of patients, where treatment planning must be individualized; multidisciplinary and psychiatric comorbidities should be considered. This review highlights treatment options that include neuromodulators, lifestyle, and psychological interventions for the PPI nonresponder. Mental health specialists in the field of psychogastroenterology can aid in the management of esophageal hypersensitivity, which can drive the symptom experience of a PPI nonresponder. Considerations for comorbid anxiety and depression in this population require careful assessment and treatment. Physicians are encouraged to create realistic expectations for symptom management and offer multidisciplinary options for treatment early in care. Patients will frequently benefit from working with a GI psychologist and find value in behavioral interventions.

Proton Pump Inhibitors Decrease Phlebotomy Need in HFE Hemochromatosis: Double-Blind Randomized Placebo-Controlled Trial.

PubMed

Vanclooster, Annick; van Deursen, Cees; Jaspers, Reggy; Cassiman, David; Koek, Ger

2017-09-01

Phlebotomy constitutes the established treatment for HFE-related hemochromatosis. Retrospective studies have suggested proton pump inhibitors (PPIs) reduce the need for phlebotomy in this population. We conducted a randomized controlled trial to prove this. Thirty p.C282Y homozygous patients were randomly allocated to PPI (pantoprazole 40 mg/day) or placebo for 12 months. Phlebotomies were performed when serum ferritin was > 100 μg/L. Phlebotomy need turned out to be significantly lower in patients taking PPI (P = .0052). PPI treatment significantly reduces the need for phlebotomies in p.C282Y homozygous patients. In view of the known long-term safety profile of PPI, they can be a valuable addition to standard therapy. Clinicaltrials.gov: NCT01524757. Copyright © 2017 AGA Institute. Published by Elsevier Inc. All rights reserved.

Proton Pump Inhibitors in Gastroesophageal Reflux Disease: Friend or Foe.

PubMed

Gyawali, C Prakash

2017-09-01

Proton pump inhibitor (PPI) use in gastroesophageal reflux disease (GERD) has been redefined, in light of recent advances highlighting GERD phenotypes that respond to PPIs, and fresh revelations of potential risks of long-term PPI therapy. Erosive esophagitis predicts excellent response to PPI therapy, but non-erosive reflux disease (NERD) with abnormal reflux parameters on ambulatory reflux monitoring also demonstrates a similar response. In contrast, response is suboptimal in the absence of abnormal reflux parameters. In this setting, if an alternate appropriate indication for PPI therapy does not coexist, risks may outweigh benefits of PPI therapy. Adverse events from long-term PPI therapy continue to be reported, most based on association rather than cause-and-effect. Appropriate indications need to be established before embarking on long-term PPI therapy. Future research will define true risks of long-term PPI therapy, and develop alternate management options for acid peptic diseases.

Harmonic generation by yeast cells in response to low-frequency electric fields

NASA Astrophysics Data System (ADS)

Nawarathna, D.; Claycomb, J. R.; Cardenas, G.; Gardner, J.; Warmflash, D.; Miller, J. H., Jr.; Widger, W. R.

2006-05-01

We report on harmonic generation by budding yeast cells (Saccharomyces cerevisiae, 108cells/ml ) in response to sinusoidal electric fields with amplitudes ranging from zero to 5V/cm in the frequency range 10-300Hz . The cell-generated harmonics are found to exhibit strong amplitude and frequency dependence. Sodium metavanadate, an inhibitor of the proton pump known as H+ -ATPase, and glucose, a substrate of H+ -ATPase, are found to increase harmonic production at low amplitudes while reducing it at large amplitudes. This P-type proton pump can be driven by an oscillatory transmembrane potential, and its nonlinear response is believed to be largely responsible for harmonic production at low frequencies in yeast cells. We find that the observed harmonics show dramatic changes with time and in their field and frequency dependence after perturbing the system by adding an inhibitor, substrate, or membrane depolarizer to the cell suspension.

Transient proton inflows during illumination of anaerobic Halobacterium halobium cells

NASA Technical Reports Server (NTRS)

Helgerson, S. L.; Stoeckenius, W.

1985-01-01

The roles of bacteriorhodopsin (bR), halorhodopsin (hR), and the H(+)-ATPase in the proton uptake in intact cells are examined. The Halobacterium halobium strains and solutions utilized in the experiment, and the techniques for measuring extracellular pH changes and intracellular K(+) concentrations are described. It is observed that in Halobacterium halobium strain R1, containing bR and hR, the light-driven proton uptake is divided into three transient inflows superimposed on the larger proton outflow. Under anaerobic conditions early proton uptake consists of an inflow which can be blocked with Dio-9 and a second inflow that can be eliminated by low concentrations (less than 125 nm) of triphenyltin chloride (TPT). The effects of Dio-9 and TPT on the passive proton-hydroxyl permeability of the cell membrane are investigated. A third transient light-driven proton flow observed at later times of illumination is studied. The data reveal that the first proton inflow correlates with proton dependent ATP synthesis; the second inflow is a passive uptake through an unidentified channel in response to electrogenic chloride pumping by bR and/or hR; and the third inflow correlates with the Na(+)/H(+) antiporter function.

The design features cells use to build their transmembrane proton gradient

NASA Astrophysics Data System (ADS)

Gunner, M. R.; Koder, Ronald

2017-02-01

Organisms store energy from food and sunlight as an electrochemical gradient across the membranes of mitochondria, chloroplasts and bacteria. The gradient arises from differences in the concentration of protons and ions on the negative (N) and positive (P) sides of these membranes. This perspective describes how the proton gradient is formed. One strategy is the movement of electrons but not protons across a membrane-embedded protein from a site of proton-releasing oxidative chemistry on the P-side of the protein to a site of proton-binding reductive chemistry on the N-side. Alternately, protons are directly pumped across membrane-embedded proteins, which have gated proton transfer pathways that are opened and closed, as well as internal sites where the proton affinity varies as the protein goes through the reaction cycle. The molecules that carry out these roles are complex, utilizing non-amino acid cofactors and earth-abundant metals. However, these are also potential sources of high-energy toxic byproducts. Understanding these reactions can open the door to their rational redesign, with possible beneficial effects as far-reaching as improving the global food supply, preventing neurodegenerative diseases, and better understanding the role of metabolism in aging.

The design features cells use to build their transmembrane proton gradient.

PubMed

Gunner, M R; Koder, Ronald

2017-02-07

Organisms store energy from food and sunlight as an electrochemical gradient across the membranes of mitochondria, chloroplasts and bacteria. The gradient arises from differences in the concentration of protons and ions on the negative (N) and positive (P) sides of these membranes. This perspective describes how the proton gradient is formed. One strategy is the movement of electrons but not protons across a membrane-embedded protein from a site of proton-releasing oxidative chemistry on the P-side of the protein to a site of proton-binding reductive chemistry on the N-side. Alternately, protons are directly pumped across membrane-embedded proteins, which have gated proton transfer pathways that are opened and closed, as well as internal sites where the proton affinity varies as the protein goes through the reaction cycle. The molecules that carry out these roles are complex, utilizing non-amino acid cofactors and earth-abundant metals. However, these are also potential sources of high-energy toxic byproducts. Understanding these reactions can open the door to their rational redesign, with possible beneficial effects as far-reaching as improving the global food supply, preventing neurodegenerative diseases, and better understanding the role of metabolism in aging.

Intraorganellar acidification by V-ATPases: a target in cell proliferation and cancer therapy.

PubMed

Hernández, Agustín; Serrano, Gloria; Herrera-Palau, Rosana; Pérez-Castiñeira, José R; Serrano, Aurelio

2010-06-01

Vacuolar-type ATPases are multicomponent proton pumps involved in the acidification of single membrane intracellular compartments such as endosomes and lysosomes. They couple the hydrolysis of ATP to the translocation of one to two protons across the membrane. Acidification of the lumen of single membrane organelles is a necessary factor for the correct traffic of membranes and cargo to and from the different internal compartments of a cell. Also, V-ATPases are involved in regulation of pH at the cytosol and, possibly, extracellular milieu. The inhibition of V-ATPases has been shown to induce apoptosis and cell cycle arrest in tumour cells and, therefore, chemicals that behave as inhibitors of this kind of proton pumps have been proposed as putative treatment agents against cancer and many have been patented as such. The compounds filed in patents fall into five major types: plecomacrolides, benzolactone enamides, archazolids, chondropsins and indoles. All these have proved to be apoptosis inducers in cell culture and many to be able to reduce xenograft tumor growth in murine models. The present review will summarize their general structure, origin and mechanisms of action and put them in relation to the patents registered so far for the treatment of cancer.

Evidence-based support for the use of proton pump inhibitors in cancer therapy.

PubMed

Fais, Stefano

2015-11-24

'We can only cure what we can understand first', said Otto H. Warburg, the 1931 Nobel laureate for his discovery on tumor metabolism. Unfortunately, we still don't know too much the mechanisms underlying of cancer development and progression. One of the unsolved mystery includes the strategies that cancer cells adopt to cope with an adverse microenvironment. However, we knew, from the Warburg's discovery, that through their metabolism based on sugar fermentation, cancer cells acidify their microenvironment and this progressive acidification induces a selective pressure, leading to development of very malignant cells entirely armed to survive in the hostile microenvironment generated by their own metabolism. One of the most mechanism to survive to the acidic tumor microenvironment are proton exchangers not allowing intracellular acidification through a continuous elimination of H(+) either outside the cells or within the internal vacuoles. This article wants to comment a translational process through which from the preclinical demonstration that a class of proton pump inhibitors (PPI) exploited worldwide for peptic ulcer treatment and gastroprotection are indeed chemosensitizers as well, we have got to the clinical proof of concept that PPI may well be included in new anti-cancer strategies, and with a solid background and rationale.

Preferential Heating of Oxygen 5+ Ions by Finite-Amplitude Oblique Alfven Waves

NASA Technical Reports Server (NTRS)

Maneva, Yana G.; Vinas, Adolfo; Araneda, Jamie; Poedts, Stefaan

2016-01-01

Minor ions in the fast solar wind are known to have higher temperatures and to flow faster than protons in the interplanetary space. In this study we combine previous research on parametric instability theory and 2.5D hybrid simulations to study the onset of preferential heating of Oxygen 5+ ions by large-scale finite-amplitude Alfven waves in the collisionless fast solar wind. We consider initially non-drifting isotropic multi-species plasma, consisting of isothermal massless fluid electrons, kinetic protons and kinetic Oxygen 5+ ions. The external energy source for the plasma heating and energization are oblique monochromatic Alfven-cyclotron waves. The waves have been created by rotating the direction of initial parallel pump, which is a solution of the multi-fluid plasma dispersion relation. We consider propagation angles theta less than or equal to 30 deg. The obliquely propagating Alfven pump waves lead to strong diffusion in the ion phase space, resulting in highly anisotropic heavy ion velocity distribution functions and proton beams. We discuss the application of the model to the problems of preferential heating of minor ions in the solar corona and the fast solar wind.

The novel, peripherally restricted GABAB receptor agonist lesogaberan (AZD3355) inhibits acid reflux and reduces esophageal acid exposure as measured with 24-h pHmetry in dogs.

PubMed

Brändén, Lena; Fredriksson, Anita; Harring, Emelie; Jensen, Jörgen; Lehmann, Anders

2010-05-25

While patients with symptoms of gastroesophageal reflux disease generally respond well to proton pump inhibitors, 20-30% continue to experience troublesome symptoms. In such cases, agents that target transient lower esophageal sphincter (LES) relaxation may be useful as add-on therapy to proton pump inhibitors. The GABAB receptor agonist baclofen inhibits transient LES relaxation but it is not an ideal agent due to central nervous system activity. Lesogaberan (AZD3355) is a peripherally restricted GABAB receptor agonist with limited central nervous system activity that inhibits transient LES relaxation in dogs. In the present study, the comparative effects of lesogaberan (7 micromol/kg) and baclofen (2.8 micromol/kg) on reflux were studied in dogs using 24-h pHmetry. Drugs (or vehicle control) were administered orally prior to the first meal of the day, and the number of reflux episodes (pH<4 for > or = 5 s) and acid exposure time were computed for the 24-h monitoring period. The mean (S.E.M.) number of reflux episodes/24 h was 4.6 (0.4) and 6.4 (0.6) for lesogaberan and baclofen, respectively, versus 10.7 (0.5) for control (P<0.0001 for both). Acid exposure time was 51.2 (4.5) min for control versus 23.6 (3.8) min for lesogaberan (P<0.0001) and 35.4 (6.5) min with baclofen (P=0.05). It is concluded that lesogaberan significantly reduces acid reflux in dogs, with comparable efficacy to baclofen. Copyright 2010 Elsevier B.V. All rights reserved.

Regulation of thermogenesis in plants: the interaction of alternative oxidase and plant uncoupling mitochondrial protein.

PubMed

Zhu, Yan; Lu, Jianfei; Wang, Jing; Chen, Fu; Leng, Feifan; Li, Hongyu

2011-01-01

Thermogenesis is a process of heat production in living organisms. It is rare in plants, but it does occur in some species of angiosperm. The heat is generated via plant mitochondrial respiration. As possible involvement in thermogenesis of mitochondrial factors, alternative oxidases (AOXs) and plant uncoupling mitochondrial proteins (PUMPs) have been well studied. AOXs and PUMPs are ubiquitously present in the inner membrane of plant mitochondria. They serve as two major energy dissipation systems that balance mitochondrial respiration and uncoupled phosphorylation by dissipating the H+ redox energy and proton electrochemical gradient (ΔμH+) as heat, respectively. AOXs and PUMPs exert similar physiological functions during homeothermic heat production in thermogenic plants. AOXs have five isoforms, while PUMPs have six. Both AOXs and PUMPs are encoded by small nuclear multigene families. Multiple isoforms are expressed in different tissues or organs. Extensive studies have been done in the area of thermogenesis in higher plants. In this review, we focus on the involvement and regulation of AOXs and PUMPs in thermogenesis.

[The participation of the transport-barrier functions of the plasma membrane in the development of fluoroquinolone (ciprofloxacin) resistance in Acholeplasma laidlawii].

PubMed

Abramycheva, N Iu; Govorun, V M

2000-01-01

The role of transport activity of Acholeplasma laidlawii plasmatic membrane in the development of resistance to ciprofloxacin was investigated. It was shown that ethidium bromide used as fluoroquinolone analogue in plasmatic membrane efflux pump was accumulated in ciprofloxacin-resistant cells in much less amount. It was estimated that ethidium bromide efflux depended on temperature, glucose and transmembrane electro-chemical proton potential. Inhibitors of efflux systems--reserpine and verapamil enhanced the ethidium bromide accumulation much more intensively in ciprofloxacin resistant cells. The results of investigation allowed to consider the existence of active efflux system for toxic agents in acholeplasma; in the case of ciprofloxacin-resistant strain these systems are inducible.

Sulfide-dependent photosynthetic electron flow coupled to proton translocation in thylakoids of the cyanobacterium Oscillatoria limnetica.

PubMed

Shahak, Y; Arieli, B; Binder, B; Padan, E

1987-12-01

Light-induced proton translocation coupled to sulfide-dependent electron transport has been studied in isolated thylakoids of the cyanobacterium Oscillatoria limnetica. The thylakoids are obtained by osmotic shock of washed spheroplasts, prepared with glycine-betaine as the osmotic stabilizer. 13C NMR studies suggests that betaine is the major osmoregulator in O. limnetica. Thylakoid preparations obtained from both sulfide-induced anoxygenic cells and noninduced oxygenic cells are capable of proton pumping coupled to phenazinemethosulfate-mediated cyclic electron flow. However, only in the induced thylakoids can sulfide-dependent proton gradient (delta pH) formation be measured, using either NADP or methyl viologen as the terminal acceptor. Sulfide-dependent delta pH formation correlates with a high-affinity electron donation site (apparent Km 44 microM at pH 7.9). This site is not lost upon washing of the thylakoids. In addition, both sulfide-dependent electron transport and delta pH formation are sensitive to inhibitors of the cytochrome b6f complex such as 2-n-nonyl-4-hydroxyquinoline-N-oxide, 2,4-dinitrophenyl ether of 2-iodo-4-nitrothymol, or stigmatellin. Sulfide-dependent NADP photoreduction of low affinity (which does not saturate by as much as 7 mM sulfide) is detected in both induced and noninduced thylakoids, but this activity is insensitive to the inhibitors and is not coupled to proton transport. It is suggested that the adaptation of O. limnetica to anoxygenic photosynthesis involves the induction of a thylakoid factor(s) which creates a high-affinity site for sulfide, and the transfer of its electrons via the cytochrome b6f complex, coupled to proton translocation.

Ion Fluxes in Giant Excised Cardiac Membrane Patches Detected and Quantified with Ion-selective Microelectrodes

PubMed Central

Kang, Tong Mook; Markin, Vladislav S.; Hilgemann, Donald W.

2003-01-01

We have used ion-selective electrodes (ISEs) to quantify ion fluxes across giant membrane patches by measuring and simulating ion gradients on both membrane sides. Experimental conditions are selected with low concentrations of the ions detected on the membrane side being monitored. For detection from the cytoplasmic (bath) side, the patch pipette is oscillated laterally in front of an ISE. For detection on the extracellular (pipette) side, ISEs are fabricated from flexible quartz capillary tubing (tip diameters, 2–3 microns), and an ISE is positioned carefully within the patch pipette with the tip at a controlled distance from the mouth of the patch pipette. Transport activity is then manipulated by solution changes on the cytoplasmic side. Ion fluxes can be quantified by simulating the ion gradients with appropriate diffusion models. For extracellular (intrapatch pipette) recordings, ion diffusion coefficients can be determined from the time courses of concentration changes. The sensitivity and utility of the methods are demonstrated with cardiac membrane patches by measuring (a) potassium fluxes via ion channels, valinomycin, and Na/K pumps; (b) calcium fluxes mediated by Na/Ca exchangers; (c) sodium fluxes mediated by gramicidin and Na/K pumps; and (d) proton fluxes mediated by an unknown electrogenic mechanism. The potassium flux-to-current ratio for the Na/K pump is approximately twice that determined for potassium channels and valinomycin, as expected for a 3Na/2K pump stoichiometery (i.e., 2K/charge moved). For valinomycin-mediated potassium currents and gramicidin-mediated sodium currents, the ion fluxes calculated from diffusion models are typically 10–15% smaller than expected from the membrane currents. As presently implemented, the ISE methods allow reliable detection of calcium and proton fluxes equivalent to monovalent cation currents <1 pA in magnitude, and they allow detection of sodium and potassium fluxes equivalent to <5 pA currents. The capability to monitor ion fluxes, independent of membrane currents, should facilitate studies of both electrogenic and electroneutral ion–coupled transporters in giant patches. PMID:12668735

The influence of prophylactic proton pump inhibitor treatment on the development of symptomatic marginal ulceration in Roux-en-Y gastric bypass patients: a historic cohort study.

PubMed

Coblijn, Usha K; Lagarde, Sjoerd M; de Castro, Steve M M; Kuiken, Sjoerd D; van Tets, Willem F; van Wagensveld, Bart A

2016-02-01

Marginal ulceration at the gastrojejunostomy is a serious complication after laparoscopic Roux-en-Y gastric bypass surgery (LRYGB) and occurs in 1%-16% of patients. Proton pump inhibitors (PPIs) might lower the occurrence of these ulcers. The aim of the present study was to evaluate the effect of 6 months prophylactic usage of PPIs on the development of marginal ulceration and compare this with a historic patient control group. A single institution cohort at a bariatric center of excellence, The Sint Lucas Andreas Zienkenhuis, Amsterdam A consecutive database of patients who underwent LRYGB from November 2007 to September 2012 in a single institution was retrospectively reviewed. From August 2011, patients received a standard dose of pantozol 40 mg once daily directly postoperatively for 6 months. No standard PPI prophylaxis was administered before August 2011, and the patients not using PPIs in this historic cohort served as the control group. A total of 610 patients underwent LRYGB, of which 128 patients (21.0%) underwent revisional surgery. Postoperative PPIs were administered in the intervention group of 337 patients, compared with the historic control group consisting of 273 patients. Six patients (1.2%) who received postoperative PPIs versus 20 patients (7.3 %) in the historic control group developed marginal ulceration (P = .001). Patients using proton pump inhibitors developed fewer gastrointestinal complaints postoperatively (P< .001). Routine usage of PPIs reduced the occurrence of marginal ulceration after LRYGB. Copyright © 2016 American Society for Bariatric Surgery. Published by Elsevier Inc. All rights reserved.

H+/K+-ATPase-Inhibition Causes Left-Right Aortic Arch Inversion in Mouse Development.

PubMed

Miyachi, Yukihisa

2017-09-01

An organ known as a "node" forms during embryogenesis and plays a vital role in determining laterality in vertebrates. However, according to some reports in vertebrates, left-right patterning may be determined long before the node has developed. In this study, we analyzed left-right asymmetry formation in mammals based on ion-signaling factors, which has never been attempted before. First, a proton pump inhibitor was injected into pregnant mice to investigate whether H + /K + -ATPase is involved in the differentiation of pharyngeal arch arteries during embryonic development. Injection of 30 mg/kg of lansoprazole early in the organogenesis period increased the penetrance of right aortic arch formation by 34% compared to a saline injection. Furthermore, administration of a proton pump inhibitor resulted in strong expression of PI3K/phosphor-AKT, which led to potent inhibition of apoptosis induction factors such as BAD. This could relate to why the right pharyngeal arch arteries, which should have disappeared during differentiation, remained intact. The other important point is that proton pump inhibitors suppressed calcineurin signaling, and Wnt5a expression was significantly higher than in the controls. This research is particularly notable for demonstrating that administration of an H + /K + -ATPase inhibitor could cause dextroposition of the fetal vasculature. Moreover, since previous publications have reported that H + /K + -ATPase plays a role in asymmetry in other species, this article adds important information for developmental biology in that the role of H + /K + -ATPase in asymmetry is conserved in the mouse model, suggesting that rodents are not unique and that a common mechanism may function across vertebrates.

Prescription drugs associated with false-positive results when using faecal immunochemical tests for colorectal cancer screening.

PubMed

Ibáñez-Sanz, Gemma; Garcia, Montse; Rodríguez-Moranta, Francisco; Binefa, Gemma; Gómez-Matas, Javier; Domènech, Xènia; Vidal, Carmen; Soriano, Antonio; Moreno, Víctor

2016-10-01

The most common side effect in population screening programmes is a false-positive result which leads to unnecessary risks and costs. To identify factors associated with false-positive results in a colorectal cancer screening programme with the faecal immunochemical test (FIT). Cross-sectional study of 472 participants with a positive FIT who underwent colonoscopy for confirmation of diagnosis between 2013 and 2014. A false-positive result was defined as having a positive FIT (≥20μg haemoglobin per gram of faeces) and follow-up colonoscopy without intermediate/high-risk lesions or cancer. Women showed a two-fold increased likelihood of a false-positive result compared with men (adjusted OR, 2.3; 95%CI, 1.5-3.4), but no female-specific factor was identified. The other variables associated with a false-positive result were successive screening (adjusted OR, 1.5; 95%CI, 1.0-2.2), anal disorders (adjusted OR, 3.1; 95%CI, 2.1-4.5) and the use of proton pump inhibitors (adjusted OR, 1.8; 95%CI, 1.1-2.9). Successive screening and proton pump inhibitor use were associated with FP in men. None of the other drugs were related to a false-positive FIT. Concurrent use of proton pump inhibitors at the time of FIT might increase the likelihood of a false-positive result. Further investigation is needed to determine whether discontinuing them could decrease the false-positive rate. Copyright © 2016 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

The fourth Mexican consensus on Helicobacter pylori.

PubMed

Bosques-Padilla, F J; Remes-Troche, J M; González-Huezo, M S; Pérez-Pérez, G; Torres-López, J; Abdo-Francis, J M; Bielsa-Fernandez, M V; Camargo, M Constanza; Esquivel-Ayanegui, F; Garza-González, E; Hernández-Guerrero, A I; Herrera-Goepfert, R; Huerta-Iga, F M; Leal-Herrera, Y; Lopéz-Colombo, A; Ortiz-Olvera, N X; Riquelme-Pérez, A; Sampieri, C L; Uscanga-Domínguez, L F; Velasco, J A Velarde-Ruiz

2018-06-22

Important advances have been made since the last Mexican consensus on the diagnosis and treatment of Helicobacter pylori (H. pylori) infection was published in 2007. Therefore, the Asociación Mexicana de Gastroenterología summoned 20 experts to produce "The Fourth Mexican Consensus on Helicobacter pylori". From February to June 2017, 4 working groups were organized, a literature review was performed, and 3 voting rounds were carried out, resulting in the formulation of 32 statements for discussion and consensus. From the ensuing recommendations, it was striking that Mexico is a country with a low-to-intermediate risk for gastric cancer, despite having a high prevalence of H. pylori infection. It was also corroborated that peptic ulcer disease, premalignant lesions, and histories of gastric cancer and mucosa-associated lymphoid tissue lymphoma should be considered clear indications for eradication. The relation of H. pylori to dyspeptic symptoms continues to be controversial. Eradication triple therapy with amoxicillin, clarithromycin, and a proton pump inhibitor should no longer be considered first-line treatment, with the following 2 options proposed to take its place: quadruple therapy with bismuth (proton pump inhibitor, bismuth subcitrate, tetracycline, and metronidazole) and quadruple therapy without bismuth (proton pump inhibitor, amoxicillin, clarithromycin, and metronidazole). The need for antimicrobial sensitivity testing when 2 eradication treatments have failed was also established. Finally, the promotion of educational campaigns on the diagnosis and treatment of H. pylori for both primary care physicians and the general population were proposed. Copyright © 2018 Asociación Mexicana de Gastroenterología. Publicado por Masson Doyma México S.A. All rights reserved.

Delirium in the geriatric unit: proton-pump inhibitors and other risk factors.

PubMed

Otremba, Iwona; Wilczyński, Krzysztof; Szewieczek, Jan

2016-01-01

Delirium remains a major nosocomial complication of hospitalized elderly. Predictive models for delirium may be useful for identification of high-risk patients for implementation of preventive strategies. Evaluate specific factors for development of delirium in a geriatric ward setting. Prospective cross-sectional study comprised 675 consecutive patients aged 79.2±7.7 years (66% women and 34% men), admitted to the subacute geriatric ward of a multiprofile university hospital after exclusion of 113 patients treated with antipsychotic medication because of behavioral disorders before admission. Comprehensive geriatric assessments including a structured interview, physical examination, geriatric functional assessment, blood sampling, ECG, abdominal ultrasound, chest X-ray, Confusion Assessment Method for diagnosis of delirium, Delirium-O-Meter to assess delirium severity, Richmond Agitation-Sedation Scale to assess sedation or agitation, visual analog scale and Doloplus-2 scale to assess pain level were performed. Multivariate logistic regression analysis revealed five independent factors associated with development of delirium in geriatric inpatients: transfer between hospital wards (odds ratio [OR] =2.78; confidence interval [CI] =1.54-5.01; P=0.001), preexisting dementia (OR =2.29; CI =1.44-3.65; P<0.001), previous delirium incidents (OR =2.23; CI =1.47-3.38; P<0.001), previous fall incidents (OR =1.76; CI =1.17-2.64; P=0.006), and use of proton-pump inhibitors (OR =1.67; CI =1.11-2.53; P=0.014). Transfer between hospital wards, preexisting dementia, previous delirium incidents, previous fall incidents, and use of proton-pump inhibitors are predictive of development of delirium in the geriatric inpatient setting.

Temporal trends of Barrett's oesophagus and gastro-oesophageal reflux and related oesophageal cancer over a 10-year period in England and Wales and associated proton pump inhibitor and H2RA prescriptions: a GPRD study.

PubMed

Alexandropoulou, Kalliopi; van Vlymen, Jeremy; Reid, Fiona; Poullis, Andrew; Kang, Jin-Yong

2013-01-01

There is an increasing burden of gastro-oesophageal reflux disease (GORD) and Barrett's oesophagus (BO), paralleled by an increasing incidence of oesophageal adenocarcinoma. Using the General Practice Research Database, we derived the incidence GORD and BO and incidence of oesophageal cancer (OC) populations, between 1996 and 2005. Acid suppression treatment over the study period was also studied. There were 5860 patients with BO and 1 25 519 with GORD. The incidence of BO increased from 0.11 to 0.24/1000 men and from 0.06 to 0.11/1000 women. The incidence of GORD diagnosed in general practice remained stable. There were 69 incident OCs in patients with BOs and 183 incident OCs in patients with GORD occurring more than a year after the GORD diagnosis. The cumulative incidence of OC was 3.00/1000 BO patient years and 0.30/1000 GORD patient years. There was a progressive decrease in H2RA prescriptions from 39 to 14.5% and an increase in proton pump inhibitor prescriptions from 52 to 79% in patients with a new diagnosis of GORD. The incidence of BO has doubled from 1996 to 2005, whereas the incidence of GORD has remained stable. OC occurred 10 times more commonly in patients with BO than those with GORD. Proton pump inhibitor prescribing increased gradually over the study period. These trends have significant implications for healthcare planning and financing in the UK and other countries.

Drug substitution associated with a hospital stay in Belgium: a retrospective analysis of a claims database.

PubMed

Simoens, Steven; Dubois, Cécile; Spinewine, Anne; Foulon, Veerle; Paulus, Dominique

2014-04-01

This study measures the extent of drug substitution associated with a hospital stay in Belgium. Data were extracted from the 2006-2007 dataset of the Belgian Agency of Health Insurance Funds on drug use of patients hospitalized in acute hospitals. Reimbursed drugs received in ambulatory care during the 3 months prior to hospitalization were compared with drugs received during the 3 months following hospital discharge. Both a narrow definition and a broad definition were used for drug substitution. Narrow substitution (switches between generic and originator drugs) was computed for 14 drug classes for chronic conditions with the highest public expenditure. Broad substitution (changes between chemical substances within the drug class at ATC level 4, changes in brand name) was calculated for statins and proton-pump inhibitors only. The database included 17 764 patients (mean age 66 ± 17 years; 60% female). In 71% of cases an originator drug was received prior to and following hospitalization. A generic drug was received prior to and following hospitalization in 25% of cases. Some form of narrow substitution occurred in 4% of cases: a generic drug was replaced by an originator drug in 2% of cases and an originator drug was replaced by a generic drug in 2% of cases. Some form of broad substitution occurred in 25% of cases for proton-pump inhibitors and 13% of cases for statins. Hospitalization was not a trigger for changes between originator and generic versions of a drug. Broad substitution associated with a hospital stay was relatively limited for statins and proton-pump inhibitors. © 2013 Royal Pharmaceutical Society.

Fe deficiency differentially affects the vacuolar proton pumps in cucumber and soybean roots

PubMed Central

Dell’Orto, Marta; Nisi, Patrizia De; Vigani, Gianpiero; Zocchi, Graziano

2013-01-01

Iron uptake in dicots depends on their ability to induce a set of responses in root cells including rhizosphere acidification through H+ extrusion and apoplastic Fe(III) reduction by Fe(III)-chelate reductase. These responses must be sustained by metabolic rearrangements aimed at providing the required NAD(P)H, ATP and H+. Previous results in Fe-deficient cucumber roots showed that high H+ extrusion is accompanied by increased phosphoenolpyruvate carboxylase (PEPC) activity, involved in the cytosol pH-stat; moreover 31P-NMR analysis revealed increased vacuolar pH and decreased vacuolar [inorganic phosphate (Pi)]. The opposite was found in soybean: low rhizosphere acidification, decreased PEPC activity, vacuole acidification, and increased vacuolar [Pi]. These findings, highlighting a different impact of the Fe deficiency responses on cytosolic pH in the two species, lead to hypothesize different roles for H+ and Pi movements across the tonoplast in pH homeostasis. The role of vacuole in cytosolic pH-stat involves the vacuolar H+-ATPase (V-ATPase) and vacuolar H+-pyrophosphatase (V-PPase) activities, which generating the ΔpH and ΔΨ, mediate the transport of solutes, among which Pi, across the tonoplast. Fluxes of Pi itself in its two ionic forms, H2PO4- predominating in the vacuole and HPO42- in the cytosol, may be involved in pH homeostasis owing to its pH-dependent protonation/deprotonation reactions. Tonoplast enriched fractions were obtained from cucumber and soybean roots grown with or without Fe. Both V-ATPase and V-PPase activities were analyzed and the enrichment and localization of the corresponding proteins in root tissues were determined by Western blot and immunolocalization. V-ATPase did not change its activity and expression level in response to Fe starvation in both species. V-PPase showed a different behavior: in cucumber roots its activity and abundance were decreased, while in Fe-deficient soybean roots they were increased. The distinct role of the two H+ pumps in Pi fluxes between cytoplasm and vacuole in Fe-deficient cucumber and soybean root cells is discussed. PMID:23986768

Ion Source Development for a Compact Proton Beam Writing System III

DTIC Science & Technology

2013-06-28

to yield ion beam with energies up to 3 keV. The electrical power required to operate multiple components (like RF Valve , Probe and Extraction...they are powered through an isolation transformer. The required gas, to be ionized in the RF ion source, is fed through a coarse needle valve ...connector, the system can be pumped down to 3×10-2 mbar using an oil roughing pump. Nitrogen gas is feed in by adjusting the gas regulating valve

Helicobacter Pylori Infections

MedlinePlus

... sure he takes the full course of these antibiotics as directed by your pediatrician. They are usually prescribed in combination with drugs called proton pump inhibitors or histamine receptor blockers that interfere with the production of acid in the stomach. What Is the ...

A pathway for protons in nitric oxide reductase from Paracoccus denitrificans.

PubMed

Reimann, Joachim; Flock, Ulrika; Lepp, Håkan; Honigmann, Alf; Adelroth, Pia

2007-05-01

Nitric oxide reductase (NOR) from P. denitrificans is a membrane-bound protein complex that catalyses the reduction of NO to N(2)O (2NO+2e(-)+2H(+)-->N(2)O+H(2)O) as part of the denitrification process. Even though NO reduction is a highly exergonic reaction, and NOR belongs to the superfamily of O(2)-reducing, proton-pumping heme-copper oxidases (HCuOs), previous measurements have indicated that the reaction catalyzed by NOR is non-electrogenic, i.e. not contributing to the proton electrochemical gradient. Since electrons are provided by donors in the periplasm, this non-electrogenicity implies that the substrate protons are also taken up from the periplasm. Here, using direct measurements in liposome-reconstituted NOR during reduction of both NO and the alternative substrate O(2), we demonstrate that protons are indeed consumed from the 'outside'. First, multiple turnover reduction of O(2) resulted in an increase in pH on the outside of the NOR-vesicles. Second, comparison of electrical potential generation in NOR-liposomes during oxidation of the reduced enzyme by either NO or O(2) shows that the proton transfer signals are very similar for the two substrates proving the usefulness of O(2) as a model substrate for these studies. Last, optical measurements during single-turnover oxidation by O(2) show electron transfer coupled to proton uptake from outside the NOR-liposomes with a tau=15 ms, similar to results obtained for net proton uptake in solubilised NOR [U. Flock, N.J. Watmough, P. Adelroth, Electron/proton coupling in bacterial nitric oxide reductase during reduction of oxygen, Biochemistry 44 (2005) 10711-10719]. NOR must thus contain a proton transfer pathway leading from the periplasmic surface into the active site. Using homology modeling with the structures of HCuOs as templates, we constructed a 3D model of the NorB catalytic subunit from P. denitrificans in order to search for such a pathway. A plausible pathway, consisting of conserved protonatable residues, is suggested.

Inhibition of ATP Hydrolysis by Thermoalkaliphilic F1Fo-ATP Synthase Is Controlled by the C Terminus of the ɛ Subunit

PubMed Central

Keis, Stefanie; Stocker, Achim; Dimroth, Peter; Cook, Gregory M.

2006-01-01

The F1Fo-ATP synthases of alkaliphilic bacteria exhibit latent ATPase activity, and for the thermoalkaliphile Bacillus sp. strain TA2.A1, this activity is intrinsic to the F1 moiety. To study the mechanism of ATPase inhibition, we developed a heterologous expression system in Escherichia coli to produce TA2F1 complexes from this thermoalkaliphile. Like the native F1Fo-ATP synthase, the recombinant TA2F1 was blocked in ATP hydrolysis activity, and this activity was stimulated by the detergent lauryldimethylamine oxide. To determine if the C-terminal domain of the ɛ subunit acts as an inhibitor of ATPase activity and if an electrostatic interaction plays a role, a TA2F1 mutant with either a truncated ɛ subunit [i.e., TA2F1(ɛΔC)] or substitution of basic residues in the second α-helix of ɛ with nonpolar alanines [i.e., TA2F1(ɛ6A)] was constructed. Both mutants showed ATP hydrolysis activity at low and high concentrations of ATP. Treatment of the purified F1Fo-ATP synthase and TA2F1(ɛWT) complex with proteases revealed that the ɛ subunit was resistant to proteolytic digestion. In contrast, the ɛ subunit of TA2F1(ɛ6A) was completely degraded by trypsin, indicating that the C-terminal arm was in a conformation where it was no longer protected from proteolytic digestion. In addition, ATPase activity was not further activated by protease treatment when compared to the untreated control, supporting the observation that ɛ was responsible for inhibition of ATPase activity. To study the effect of the alanine substitutions in the ɛ subunit in the entire holoenzyme, we reconstituted recombinant TA2F1 complexes with F1-stripped native membranes of strain TA2.A1. The reconstituted TA2FoF1(ɛWT) was blocked in ATP hydrolysis and exhibited low levels of ATP-driven proton pumping consistent with the F1Fo-ATP synthase in native membranes. Reconstituted TA2FoF1(ɛ6A) exhibited ATPase activity that correlated with increased ATP-driven proton pumping, confirming that the ɛ subunit also inhibits ATPase activity of TA2FoF1. PMID:16707672

Lambda Red-mediated mutagenesis and efficient large scale affinity purification of the Escherichia coli NADH:ubiquinone oxidoreductase (complex I).

PubMed

Pohl, Thomas; Uhlmann, Mareike; Kaufenstein, Miriam; Friedrich, Thorsten

2007-09-18

The proton-pumping NADH:ubiquinone oxidoreductase, the respiratory complex I, couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. The Escherichia coli complex I consists of 13 different subunits named NuoA-N (from NADH:ubiquinone oxidoreductase), that are coded by the genes of the nuo-operon. Genetic manipulation of the operon is difficult due to its enormous size. The enzymatic activity of variants is obscured by an alternative NADH dehydrogenase, and purification of the variants is hampered by their instability. To overcome these problems the entire E. coli nuo-operon was cloned and placed under control of the l-arabinose inducible promoter ParaBAD. The exposed N-terminus of subunit NuoF was chosen for engineering the complex with a hexahistidine-tag by lambda-Red-mediated recombineering. Overproduction of the complex from this construct in a strain which is devoid of any membrane-bound NADH dehydrogenase led to the assembly of a catalytically active complex causing the entire NADH oxidase activity of the cytoplasmic membranes. After solubilization with dodecyl maltoside the engineered complex binds to a Ni2+-iminodiacetic acid matrix allowing the purification of approximately 11 mg of complex I from 25 g of cells. The preparation is pure and monodisperse and comprises all known subunits and cofactors. It contains more lipids than earlier preparations due to the gentle and fast purification procedure. After reconstitution in proteoliposomes it couples the electron transfer with proton translocation in an inhibitor sensitive manner, thus meeting all prerequisites for structural and functional studies.

The V0-ATPase mediates apical secretion of exosomes containing Hedgehog-related proteins in Caenorhabditis elegans

PubMed Central

Liégeois, Samuel; Benedetto, Alexandre; Garnier, Jean-Marie; Schwab, Yannick; Labouesse, Michel

2006-01-01

Polarized intracellular trafficking in epithelia is critical in development, immunity, and physiology to deliver morphogens, defensins, or ion pumps to the appropriate membrane domain. The mechanisms that control apical trafficking remain poorly defined. Using Caenorhabditis elegans, we characterize a novel apical secretion pathway involving multivesicularbodies and the release of exosomes at the apical plasma membrane. By means of two different genetic approaches, we show that the membrane-bound V0 sector of the vacuolar H+-ATPase (V-ATPase) acts in this pathway, independent of its contribution to the V-ATPase proton pump activity. Specifically, we identified mutations in the V0 “a” subunit VHA-5 that affect either the V0-specific function or the V0+V1 function of the V-ATPase. These mutations allowed us to establish that the V0 sector mediates secretion of Hedgehog-related proteins. Our data raise the possibility that the V0 sector mediates exosome and morphogen release in mammals. PMID:16785323

Relationship between use of proton pump inhibitors and IGF system in older subjects.

PubMed

Maggio, M; Lauretani, F; De Vita, F; Buttò, V; Cattabiani, C; Masoni, S; Sutti, E; Bondi, G; Dall'aglio, E; Bandinelli, S; Corsonello, A; Abbatecola, A M; Lattanzio, F; Ferrucci, L; Ceda, G P

2014-04-01

to investigate the effects of proton pump inhibitors (PPIs) on the insulin-like-growth factor 1(IGF-1) system in the elderly. cross-sectional. InCHIANTI study. 938 older subjects (536 women, 402 men, mean age 75.7±7.4 years). complete data on age, sex, BMI, liver function, medications, dietary intake, IGF-1, IGF-binding protein-1 and -3 (IGFBP-1, IGFBP-3). Participants were categorized by PPI use, identifying 903 PPI non users and 35 users. After adjusting for age, male PPI users (107.0 ± 69.6 vs. 127.1 ± 55.8, p<0.001) and female PPI users (87.6 ± 29.1 vs. 107.6 ± 52.3, p=0.03) had lower IGF-1 levels than non-users. IGFBP-1 levels were similar in the two groups in both sexes. In whole population, after adjustment for age and sex, PPI users had lower IGF-1 levels 81.9 [61.1-113.8] than non-users 110 [77.8-148.6], p=0.02. After further adjustment for BMI, albumin, liver function, C-reactive protein, Interleukin-6, number of medications, ACE-inhibitors use, caloric intake, protein intake, physical activity, glycemia, and IGFBP-1, the use of PPIs remained significantly and negatively associated with IGF-1 levels (β±SE = -19.60±9.83, p=0.045). Use of PPIs was independently and negatively associated with IGF-1 levels.

RELATIONSHIP BETWEEN USE OF PROTON PUMP INHIBITORS AND IGF SYSTEM IN OLDER SUBJECTS

PubMed Central

MAGGIO, M.; LAURETANI, F.; DE VITA, F.; BUTTO, V.; CATTABIANI, C.; MASONI, S.; SUTTI, E.; BONDI, G.; DALL’AGLIO, E.; BANDINELLI, S.; CORSONELLO, A.; ABBATECOLA, A.M.; LATTANZIO, F.; FERRUCCI, L.; CEDA, G.P.

2016-01-01

Objectives to investigate the effects of proton pump inhibitors (PPIs) on the insulin-like-growth factor 1(IGF-1) system in the elderly. Design cross-sectional. Setting InCHIANTI study. Participants 938 older subjects (536 women, 402 men, mean age 75.7±7.4 years). Measurements complete data on age, sex, BMI, liver function, medications, dietary intake, IGF-1, IGF-binding protein-1 and -3 (IGFBP-1, IGFBP-3). Results Participants were categorized by PPI use, identifying 903 PPI non users and 35 users. After adjusting for age, male PPI users (107.0 ± 69.6 vs 127.1 ± 55.8, p<0.001) and female PPI users (87.6 ± 29.1 vs 107.6 ± 52.3, p=0.03) had lower IGF-1 levels than non-users. IGFBP-1 levels were similar in the two groups in both sexes. In whole population, after adjustment for age and sex, PPI users had lower IGF-1 levels 81.9 [61.1–113.8] than non-users 110 [77.8–148.6], p=0.02. After further adjustment for BMI, albumin, liver function, C-reactive protein, Interleukin-6, number of medications, ACE-inhibitors use, caloric intake, protein intake, physical activity, glycemia, and IGFBP-1, the use of PPIs remained significantly and negatively associated with IGF-1 levels (β±SE=−19.60±9.83, p=0.045). Conclusion Use of PPIs was independently and negatively associated with IGF-1 levels. PMID:24676324

Proton pump inhibitors protect mice from acute systemic inflammation and induce long-term cross-tolerance

PubMed Central

Balza, E; Piccioli, P; Carta, S; Lavieri, R; Gattorno, M; Semino, C; Castellani, P; Rubartelli, A

2016-01-01

Incidence of sepsis is increasing, representing a tremendous burden for health-care systems. Death in acute sepsis is attributed to hyperinflammatory responses, but the underlying mechanisms are still unclear. We report here that proton pump inhibitors (PPIs), which block gastric acid secretion, selectively inhibited tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) secretion by Toll-like receptor (TLR)-activated human monocytes in vitro, in the absence of toxic effects. Remarkably, the oversecretion of IL-1β that represents a hallmark of monocytes from patients affected by cryopyrin-associated periodic syndrome is also blocked. Based on these propaedeutic experiments, we tested the effects of high doses of PPIs in vivo in the mouse model of endotoxic shock. Our data show that a single administration of PPI protected mice from death (60% survival versus 5% of untreated mice) and decreased TNF-α and IL-1β systemic production. PPIs were efficacious even when administered after lipopolysaccharide (LPS) injection. PPI-treated mice that survived developed a long-term cross-tolerance, becoming resistant to LPS- and zymosan-induced sepsis. In vitro, their macrophages displayed impaired TNF-α and IL-1β to different TLR ligands. PPIs also prevented sodium thioglycollate-induced peritoneal inflammation, indicating their efficacy also in a non-infectious setting independent of TLR stimulation. Lack of toxicity and therapeutic effectiveness make PPIs promising new drugs against sepsis and other severe inflammatory conditions. PMID:27441656

Clopidogrel and proton pump inhibitor (PPI) interaction: separate intake and a non-omeprazole PPI the solution?

PubMed Central

2010-01-01

Background Dual therapy with aspirin and clopidogrel increases the risk of gastrointestinal bleeding. Therefore, co-therapy with a proton pump inhibitor (PPI) is recommended by most guidelines. However, there are warnings against combining PPIs with clopidogrel because of their interactions with cytochrome P450 isoenzyme 2C19 (CYP2C19). Methods The effects of the combined or separate intake of 20 mg of omeprazole and 75 mg of clopidogrel on the clopidogrel-induced inhibition of platelet aggregation were measured in four healthy subjects whose CYP2C19 exon sequences were determined. The effects of co-therapy with 10 mg of rabeprazole were also examined. Results Two subjects showed the wild-type CYP2C19 sequence. The concurrent intake of omeprazole had no effect on clopidogrel-induced platelet inhibition in these subjects. Two subjects were heterozygous for the *2 allele, with predicted reduced CYP2C19 activity. One of them was a clopidogrel non-responder. In the second heterozygous subject, omeprazole co-therapy reduced the clopidogrel anti-platelet effect when taken simultaneously or separately. However, the simultaneous intake of rabeprazole did not reduce the clopidogrel effect. Conclusion The clopidogrel-PPI interaction does not seem to be a PPI class effect. Rabeprazole did not affect the clopidogrel effect in a subject with a clear omeprazole-clopidogrel interaction. The separate intake of PPI and clopidogrel may not be sufficient to prevent their interaction. PMID:20562062

New insights into the dynamic regulation of water and acid-base balance by renal epithelial cells.

PubMed

Brown, Dennis; Bouley, Richard; Păunescu, Teodor G; Breton, Sylvie; Lu, Hua A J

2012-05-15

Maintaining tight control over body fluid and acid-base homeostasis is essential for human health and is a major function of the kidney. The collecting duct is a mosaic of two cell populations that are highly specialized to perform these two distinct processes. The antidiuretic hormone vasopressin (VP) and its receptor, the V2R, play a central role in regulating the urinary concentrating mechanism by stimulating accumulation of the aquaporin 2 (AQP2) water channel in the apical membrane of collecting duct principal cells. This increases epithelial water permeability and allows osmotic water reabsorption to occur. An understanding of the basic cell biology/physiology of AQP2 regulation and trafficking has informed the development of new potential treatments for diseases such as nephrogenic diabetes insipidus, in which the VP/V2R/AQP2 signaling axis is defective. Tubule acidification due to the activation of intercalated cells is also critical to organ function, and defects lead to several pathological conditions in humans. Therefore, it is important to understand how these "professional" proton-secreting cells respond to environmental and cellular cues. Using epididymal proton-secreting cells as a model system, we identified the soluble adenylate cyclase (sAC) as a sensor that detects luminal bicarbonate and activates the vacuolar proton-pumping ATPase (V-ATPase) via cAMP to regulate tubular pH. Renal intercalated cells also express sAC and respond to cAMP by increasing proton secretion, supporting the hypothesis that sAC could function as a luminal sensor in renal tubules to regulate acid-base balance. This review summarizes recent advances in our understanding of these fundamental processes.

New insights into the dynamic regulation of water and acid-base balance by renal epithelial cells

PubMed Central

Bouley, Richard; Pǎunescu, Teodor G.; Breton, Sylvie; Lu, Hua A. J.

2012-01-01

Maintaining tight control over body fluid and acid-base homeostasis is essential for human health and is a major function of the kidney. The collecting duct is a mosaic of two cell populations that are highly specialized to perform these two distinct processes. The antidiuretic hormone vasopressin (VP) and its receptor, the V2R, play a central role in regulating the urinary concentrating mechanism by stimulating accumulation of the aquaporin 2 (AQP2) water channel in the apical membrane of collecting duct principal cells. This increases epithelial water permeability and allows osmotic water reabsorption to occur. An understanding of the basic cell biology/physiology of AQP2 regulation and trafficking has informed the development of new potential treatments for diseases such as nephrogenic diabetes insipidus, in which the VP/V2R/AQP2 signaling axis is defective. Tubule acidification due to the activation of intercalated cells is also critical to organ function, and defects lead to several pathological conditions in humans. Therefore, it is important to understand how these “professional” proton-secreting cells respond to environmental and cellular cues. Using epididymal proton-secreting cells as a model system, we identified the soluble adenylate cyclase (sAC) as a sensor that detects luminal bicarbonate and activates the vacuolar proton-pumping ATPase (V-ATPase) via cAMP to regulate tubular pH. Renal intercalated cells also express sAC and respond to cAMP by increasing proton secretion, supporting the hypothesis that sAC could function as a luminal sensor in renal tubules to regulate acid-base balance. This review summarizes recent advances in our understanding of these fundamental processes. PMID:22460710

Therapy with proton-pump inhibitors for gastroesophageal reflux disease does not reduce the risk for severe exacerbations in COPD.

PubMed

Baumeler, Luzia; Papakonstantinou, Eleni; Milenkovic, Branislava; Lacoma, Alicia; Louis, Renaud; Aerts, Joachim G; Welte, Tobias; Kostikas, Konstantinos; Blasi, Francesco; Boersma, Wim; Torres, Antoni; Rohde, Gernot G U; Boeck, Lucas; Rakic, Janko; Scherr, Andreas; Tamm, Michael; Stolz, Daiana

2016-07-01

Gastroesophageal reflux disease (GERD) symptoms are associated with a higher risk of chronic obstructive pulmonary disease (COPD) exacerbation. We hypothesize that treatment with proton pump inhibitors reduces the risk of exacerbation in patients with stable COPD. A total of 638 patients with stable COPD for ≥6 weeks, ≥10 pack-years of smoking and Global Initiative for Chronic Obstructive Lung Disease II-IV seeking care in tertiary hospitals in eight European countries in the Predicting Outcome using Systemic Markers in Severe Exacerbations-COPD cohort was prospectively evaluated by us. Comorbidities including associated medical treatment were assessed at baseline, at exacerbation and at biannual visits. Median observation time was 24 months. The primary study outcomes were exacerbation and/or death. A total of 85 (13.3%) of COPD patients were on anti-GERD therapy. These patients had higher annual and higher severe exacerbation rates (P = 0.009 and P = 0.002), decreased quality of life (SF-36: activity score P = 0.004, St. George's Respiratory Questionnaire: physical functioning P = 0.013 and social functioning P = 0.007), higher body mass airflow obstruction, dyspnea and exercise capacity index (P = 0.033) and Modified Medical Research Council scores (P = 0.002), shorter 6-min walking distance (P = 0.0004) and a higher adjusted Charlson score (P < 0.0001). Anti-GERD therapy was associated with a shorter time to severe exacerbation (HR 2.05 95% CI 1.37-3.08). Using three multivariable Cox-regression models, this association was independent of the following: (i) adjusted Charlson score and FEV1% predicted (HR 1.91 95% CI 1.26-2.90); (ii) adjusted Charlson score, body mass, airflow obstruction, dyspnea and exercise capacity index and Modified Medical Research Council (HR 1.62 95% CI 1.04-2.54); and (iii) adjusted Charlson score, FEV1% predicted and nine classes of medication for comorbidities (HR 1.63 95% CI 1.04-2.53). These findings suggest that patients with stable COPD receiving acid-suppressive therapy with proton pump inhibitors remain at high risk of frequent and severe exacerbations. © 2016 Asian Pacific Society of Respirology.

Tabletop Imaging of Structural Evolutions in Chemical Reactions

NASA Astrophysics Data System (ADS)

Ibrahim, Heide; Wales, Benji; Beaulieu, Samuel; Schmidt, Bruno E.; Thiré, Nicolas; Fowe, Emmanuel P.; Bisson, Éric; Hebeisen, Christoph T.; Wanie, Vincent; Giguére, Mathieu; Kieffer, Jean-Claude; Spanner, Michael; Bandrauk, André D.; Sanderson, Joseph; Schuurman, Michael S.; Légaré, François

The first high-resolution molecular movie of proton migration in the acetylene cation is obtained using a tabletop multiphoton pump-probe approach—an alternative to demanding free-electron-lasers and other VUV light sources when ionizing from the HOMO-1.

Effects of rabeprazole on the antiplatelet effects and pharmacokinetics of clopidogrel in healthy volunteers.

PubMed

Funck-Brentano, Christian; Szymezak, Jean; Steichen, Olivier; Ducint, Dominique; Molimard, Mathieu; Remones, Véronique; Azizi, Michel; Gaussem, Pascale

2013-12-01

Several studies have suggested that proton-pump inhibitors (PPIs), mostly omeprazole, interact with clopidogrel efficacy by inhibiting the formation of its active metabolite via CYP2C19 inhibition. Whether this occurs with all PPIs is a matter of debate. As rabeprazole is a less potent CYP2C19 inhibitor than other PPIs, we studied the interaction between rabeprazole and the antiplatelet actions and pharmacokinetics of clopidogrel. To demonstrate the non-inferiority of rabeprazole over placebo using change in platelet reactivity index (PRI; vasodilator-stimulated phosphoprotein [VASP] assay) in a predefined population of good clopidogrel responders. Omeprazole was used as the positive control. In this randomized three-period crossover study in healthy volunteers, 36 healthy men received clopidogrel (75 mg/day for 7 days) with placebo, omeprazole (20mg/day) or rabeprazole (20mg/day). Clopidogrel antiplatelet effects and disposition kinetics were assessed on day 7 of combination therapy. Non-inferiority threshold was predefined as an upper limit of the 90% confidence interval for the difference in change in PRI between placebo and rabeprazole of<10% in good clopidogrel responders. In good clopidogrel responders (inhibition of VASP index>30%), the clopidogrel antiplatelet effect remained non-inferior to placebo during rabeprazole (difference 3.4% [-1.7; 8.5]) but not omeprazole (difference 7.5% [2.5; 12.6]) co-administration. The AUC0-24 and Cmax of active clopidogrel metabolite decreased with both omeprazole and rabeprazole, and conditions of bioequivalence were not met, except for AUC0-24 with rabeprazole. Rabeprazole does not interact with clopidogrel to the same extent as omeprazole. However, under our experimental conditions and proton-pump inhibitor doses, there was no significant pharmacodynamic interaction between rabeprazole or omeprazole and clopidogrel, despite a significant decrease in the formation of clopidogrel active metabolite. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Demonstration of a sensory rhodopsin in eubacteria.

PubMed

Jung, Kwang-Hwan; Trivedi, Vishwa D; Spudich, John L

2003-03-01

We report the first sensory rhodopsin observed in the eubacterial domain, a green light-activated photoreceptor in Anabaena (Nostoc) sp. PCC7120, a freshwater cyanobacterium. The gene encoding the membrane opsin protein of 261 residues (26 kDa) and a smaller gene encoding a soluble protein of 125 residues (14 kDa) are under the same promoter in a single operon. The opsin expressed heterologously in Escherichia coli membranes bound all-trans retinal to form a pink pigment (lambda max 543 nm) with a photochemical reaction cycle of 110 ms half-life (pH 6.8, 18 degrees C). Co-expression with the 14 kDa protein increased the rate of the photocycle, indicating physical interaction with the membrane-embedded rhodopsin, which we confirmed in vitro by affinity enrichment chromatography and Biacore interaction. The pigment lacks the proton donor carboxylate residue in helix C conserved in known retinylidene proton pumps and did not exhibit detectable proton ejection activity. We detected retinal binding to the protein in Anabaena membranes by SDS-PAGE and autofluorography of 3H-labelled all-trans retinal of reduced membranes from the organism. We conclude that Anabaena rhodopsin functions as a photosensory receptor in its natural environment, and suggest that the soluble 14 kDa protein transduces a signal from the receptor. Therefore, unlike the archaeal sensory rhodopsins, which transmit signals by transmembrane helix-helix interactions with membrane-embedded transducers, the Anabaena sensory rhodopsin may signal through a soluble cytoplasmic protein, analogous to higher animal visual pigments.

Determination of retinal chromophore structure in bacteriorhodopsin with resonance Raman spectroscopy.

PubMed

Smith, S O; Lugtenburg, J; Mathies, R A

1985-01-01

The analysis of the vibrational spectrum of the retinal chromophore in bacteriorhodopsin with isotopic derivatives provides a powerful "structural dictionary" for the translation of vibrational frequencies and intensities into structural information. Of importance for the proton-pumping mechanism is the unambiguous determination of the configuration about the C13=C14 and C=N bonds, and the protonation state of the Schiff base nitrogen. Vibrational studies have shown that in light-adapted BR568 the Schiff base nitrogen is protonated and both the C13=C14 and C=N bonds are in a trans geometry. The formation of K625 involves the photochemical isomerization about only the C13=C14 bond which displaces the Schiff base proton into a different protein environment. Subsequent Schiff base deprotonation produces the M412 intermediate. Thermal reisomerization of the C13=C14 bond and reprotonation of the Schiff base occur in the M412------O640 transition, resetting the proton-pumping mechanism. The vibrational spectra can also be used to examine the conformation about the C--C single bonds. The frequency of the C14--C15 stretching vibration in BR568, K625, L550 and O640 argues that the C14--C15 conformation in these intermediates is s-trans. Conformational distortions of the chromophore have been identified in K625 and O640 through the observation of intense hydrogen out-of-plane wagging vibrations in the Raman spectra (see Fig. 2). These two intermediates are the direct products of chromophore isomerization. Thus it appears that following isomerization in a tight protein binding pocket, the chromophore cannot easily relax to a planar geometry. The analogous observation of intense hydrogen out-of-plane modes in the primary photoproduct in vision (Eyring et al., 1982) suggests that this may be a general phenomenon in protein-bound isomerizations. Future resonance Raman studies should provide even more details on how bacterio-opsin and retinal act in concert to produce an efficient light-energy convertor. Important unresolved questions involve the mechanism by which the protein catalyzes deprotonation of the L550 intermediate and the mechanism of the thermal conversion of M412 back to BR568. Also, it has been shown that under conditions of high ionic strength and/or low light intensity two protons are pumped per photocycle (Kuschmitz & Hess, 1981). How might this be accomplished?(ABSTRACT TRUNCATED AT 400 WORDS)

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9.

PubMed

Köhler, Thomas; Weber, Ingrid; Glaubitz, Clemens; Wachtveitl, Josef

2017-05-01

The retinal protein proteorhodopsin is a homolog of the well-characterized light-driven proton pump bacteriorhodopsin. Basic mechanisms of proton transport seem to be conserved, but there are noticeable differences in the pH ranges of proton transport. Proton transport and protonation state of a carboxylic acid side chain, the primary proton acceptor, are correlated. In case of proteorhodopsin, the pK a of the primary proton acceptor Asp-97 (pK a  ≈ 7.5) is unexpectedly close to environmental pH (pH ≈ 8). A significant fraction of proteorhodopsin is possibly inactive at natural pH, in contrast to bacteriorhodopsin. We investigated photoinduced kinetics of proteorhodopsin between pH 5 and pH 9 by time resolved UV/vis absorption spectroscopy. Kinetics is inhomogeneous within that pH region and can be considered as a superposition of two fractions. These fractions are correlated with the Asp-97 titration curve. Beside Asp-97, protonation equilibria of other groups influence kinetics, but the observations do not point toward major differences of primary proton acceptor function in proteorhodopsin and bacteriorhodopsin. The pK a of proteorhodopsin and some of its variants is suspected to be an example of molecular adaptation to the physiology of the original organisms. © 2017 The American Society of Photobiology.

Acidity of a Cu-bound histidine in the binuclear center of cytochrome C oxidase.

PubMed

Fadda, Elisa; Chakrabarti, Nilmadhab; Pomès, Régis

2005-12-01

Cytochrome c oxidase (CcO) is a crucial enzyme in the respiratory chain. Its function is to couple the reduction of molecular oxygen, which takes place in the Fea3-CuB binuclear center, to proton translocation across the mitochondrial membrane. Although several high-resolution structures of the enzyme are known, the molecular basis of proton pumping activation and its mechanism remain to be elucidated. We examine a recently proposed scheme (J. Am. Chem. Soc. 2004, 126, 1858; FEBS Lett. 2004, 566, 126) that involves the deprotonation of the CuB-bound imidazole ring of a histidine (H291 in mammalian CcO) as a key element in the proton pumping mechanism. The central feature of that proposed mechanism is that the pKa values of the imidazole vary significantly depending on the redox state of the metals in the binuclear center. We use density functional theory in combination with continuum electrostatics to calculate the pKa values, successively in bulk water and within the protein, of the Cu-bound imidazole in various Cu- and Cu-Fe complexes. From pKas in bulk water, we derived a value of -266.34 kcal.mol(-1) for the proton solvation free energy (Delta). This estimate is in close agreement with the experimental value of -264.61 kcal.mol(-1) (J. Am. Chem. Soc. 2001, 123, 7314), which reinforces the conclusion that Delta is more negative than previous values used for pKa calculations. Our approach, on the basis of the study of increasingly more detailed models of the CcO binuclear center at different stages of the catalysis, allows us to examine successively the effect of each of the two metals' redox states and of solvation on the acidity of imidazole, whose pKa is approximately 14 in bulk water. This analysis leads to the following conclusions: first, the effect of Cu ligation on the imidazole acidity is negligible regardless of the redox state of the metal. Second, results obtained for Cu-Fe complexes in bulk water indicate that Cu-bound imidazole pKa values lie within the range of 14.8-16.6 throughout binuclear redox states corresponding to the catalytic cycle, demonstrating that the effect of the Fe oxidation states is also negligible. Finally, the low-dielectric CcO proteic environment shifts the acid-base equilibrium toward a neutral imidazole, further increasing the corresponding pKa values. These results are inconsistent with the proposed role of the Cu-bound histidine as a key element in the pumping mechanism. Limitations of continuum solvation models in pKa calculations are discussed.

Two different forms of metarhodopsin II: Schiff base deprotonation precedes proton uptake and signaling state.

PubMed

Arnis, S; Hofmann, K P

1993-08-15

Rhodopsin is a retinal protein and a G-protein-coupled receptor; it shares with both of these families the seven helix structure. To generate the G-interacting helix-loop conformation, generally identified with the 380-nm absorbing metarhodopsin II (MII) photoproduct, the retinal Schiff base bond to the apoprotein must be deprotonated. This occurs as a key event also in the related retinal proteins, sensory rhodopsins, and the proton pump bacteriorhodopsin. In MII, proton uptake from the aqueous phase must be involved as well, since its formation increases the pH of the aqueous medium and is accelerated under acidic conditions. In the native membrane, the pH effect matches MII formation kinetically, suggesting that intramolecular and aqueous protonation changes contribute in concert to the protein transformation. We show here, however, that proton uptake, as indicated by bromocresol purple, and Schiff base deprotonation (380-nm absorption change) show different kinetics when the protein is solubilized in suitable detergents. Our data are consistent with a two-step reaction:

Persistence of dysphagia and odynophagia after mediastinal radiation and chemotherapy in patients with lung cancer or lymphoma.

PubMed

Shields, Helen; Li, Justin; Pelletier, Stephen; Wang, Helen; Freedman, Rachel; Mamon, Harvey; Ng, Andrea; Freedman, Arnold; Come, Steven; Avigan, David; Huberman, Mark; Recht, Abram

2017-02-01

Esophageal symptoms are common during radiation and chemotherapy. It is unclear how often these symptoms persist after therapy. We retrospectively reviewed medical records of 320 adults treated for nonmetastatic breast cancer (84), lung cancer (109), or Hodgkin and non-Hodgkin lymphoma (127) who were disease-free at 10-14 months after therapy. Treatment included chemotherapy with or without nonmediastinal radiation therapy (150 patients), chemotherapy plus sequential mediastinal radiation therapy (MRT) (48 patients), chemotherapy plus concurrent MRT (61 patients), or non-MRT only (61 patients). Proton pump inhibitor use was documented. All treatment groups had similar prevalence of the esophageal symptom of heartburn before therapy. Rates were higher during treatment in those who received MRT with or without chemotherapy, but declined by 10-14 months after treatment. However, low baseline rates of dysphagia (4%) and odynophagia (2%) increased significantly after combined chemotherapy and MRT to 72% for dysphagia and 62% for odynophagia (P < 0.01) during treatment and stayed significantly elevated over baseline with 27% of the patients having dysphagia and 11% having odynophagia at 10-14 months after treatment. The use of proton pump inhibitors by patients who had MRT with chemotherapy was significantly increased during and after treatment (P = 0.002). Dysphagia, odynophagia and the use of proton pump inhibitors were significantly more common both during and after treatment than before treatment in patients who received both chemotherapy and mediastinal radiation. Our data highlight the important challenge for clinicians of managing patients with lung cancer and lymphoma who have persistent esophageal problems, particularly dysphagia and odynophagia, at approximately 1 year after treatment. © 2016 International Society for Diseases of the Esophagus.

Regulation of Organelle Acidity

PubMed Central

Grabe, Michael; Oster, George

2001-01-01

Intracellular organelles have characteristic pH ranges that are set and maintained by a balance between ion pumps, leaks, and internal ionic equilibria. Previously, a thermodynamic study by Rybak et al. (Rybak, S., F. Lanni, and R. Murphy. 1997. Biophys. J. 73:674–687) identified the key elements involved in pH regulation; however, recent experiments show that cellular compartments are not in thermodynamic equilibrium. We present here a nonequilibrium model of lumenal acidification based on the interplay of ion pumps and channels, the physical properties of the lumenal matrix, and the organelle geometry. The model successfully predicts experimentally measured steady-state and transient pH values and membrane potentials. We conclude that morphological differences among organelles are insufficient to explain the wide range of pHs present in the cell. Using sensitivity analysis, we quantified the influence of pH regulatory elements on the dynamics of acidification. We found that V-ATPase proton pump and proton leak densities are the two parameters that most strongly influence resting pH. Additionally, we modeled the pH response of the Golgi complex to varying external solutions, and our findings suggest that the membrane is permeable to more than one dominant counter ion. From this data, we determined a Golgi complex proton permeability of 8.1 × 10−6 cm/s. Furthermore, we analyzed the early-to-late transition in the endosomal pathway where Na,K-ATPases have been shown to limit acidification by an entire pH unit. Our model supports the role of the Na,K-ATPase in regulating endosomal pH by affecting the membrane potential. However, experimental data can only be reproduced by (1) positing the existence of a hypothetical voltage-gated chloride channel or (2) that newly formed vesicles have especially high potassium concentrations and small chloride conductance. PMID:11279253

Proton pump inhibitor medication is associated with colonisation of gut flora in the oropharynx.

PubMed

Tranberg, A; Thorarinsdottir, H R; Holmberg, A; Schött, U; Klarin, B

2018-03-08

The normal body exists in mutualistic balance with a large range of microbiota. The primary goal of this study was to establish whether there is an imbalance in the oropharyngeal flora early after hospital or ICU admittance, and whether flora differs between control, ward and critically ill patients. The secondary goal was to explore whether there are patient characteristics that can be associated with a disturbed oropharyngeal flora. Oropharyngeal cultures were obtained from three different study groups: (1) controls from the community, (2) ward patients and (3) critically ill patients, the two latter within 24 h after admittance. Cultures were obtained from 487 individuals: 77 controls, 193 ward patients and 217 critically ill patients. Abnormal pharyngeal flora was more frequent in critically ill and ward patients compared with controls (62.2% and 10.4% vs. 1.3%, P < 0.001 and P = 0.010, respectively). Colonisation of gut flora in the oropharynx was more frequent in critically ill patients compared with ward patients or controls (26.3% vs. 4.7% and 1.3%, P < 0.001 and P < 0.001, respectively). Proton pump inhibitor medication was the strongest independent factor associated with the presence of gut flora in the oropharynx in both ward and critically ill patients (P = 0.030 and P = 0.044, respectively). This study indicates that abnormal oropharyngeal flora is an early and frequent event in hospitalised patients and more so in the critically ill, compared to controls. Proton pump inhibitor medication is associated with colonisation of gut flora in the oropharynx. © 2018 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Increase of weakly acidic gas esophagopharyngeal reflux (EPR) and swallowing-induced acidic/weakly acidic EPR in patients with chronic cough responding to proton pump inhibitors.

PubMed

Kawamura, O; Shimoyama, Y; Hosaka, H; Kuribayashi, S; Maeda, M; Nagoshi, A; Zai, H; Kusano, M

2011-05-01

Gastro-esophageal reflux disease (GERD)-related chronic cough (CC) may have multifactorial causes. To clarify the characteristics of esophagopharyngeal reflux (EPR) events in CC patients whose cough was apparently influenced by gastro-esophageal reflux (GER), we studied patients with CC clearly responding to full-dose proton pump inhibitor (PPI) therapy (CC patients). Ten CC patients, 10 GERD patients, and 10 healthy controls underwent 24-h ambulatory pharyngo-esophageal impedance and pH monitoring. Weakly acidic reflux was defined as a decrease of pH by >1 unit with a nadir pH >4. In six CC patients, monitoring was repeated after 8 weeks of PPI therapy. The number of each EPR event and the symptom association probability (SAP) were calculated. Symptoms were evaluated by a validated GERD symptom questionnaire. Weakly acidic gas EPR and swallowing-induced acidic/weakly acidic EPR only occurred in CC patients, and the numbers of such events was significantly higher in the CC group than in the other two groups (P < 0.05, respectively). Symptom association probability analysis revealed a positive association between GER and cough in three CC patients. Proton pump inhibitor therapy abolished swallowing-induced acidic/weakly acidic EPR, reduced weakly acidic gas EPR, and improved symptoms (all P < 0.05). Most patients with CC responding to PPI therapy had weakly acidic gas EPR and swallowing-induced acidic/weakly acidic EPR. A direct effect of acidic mist or liquid refluxing into the pharynx may contribute to chronic cough, while cough may also arise indirectly from reflux via a vago-vagal reflex in some patients. © 2011 Blackwell Publishing Ltd.

Proton Pump Inhibitors and Risk of Mild Cognitive Impairment and Dementia.

PubMed

Goldstein, Felicia C; Steenland, Kyle; Zhao, Liping; Wharton, Whitney; Levey, Allan I; Hajjar, Ihab

2017-09-01

To examine the risk associated with the use of proton pump inhibitors (PPIs) of conversion to mild cognitive impairment (MCI), dementia, and specifically Alzheimer's disease (AD). Observational, longitudinal study. Tertiary academic Alzheimer's Disease Centers funded by the National Institute on Aging. Research volunteers aged 50 and older with two to six annual visits; 884 were taking PPIs at every visit, 1,925 took PPIs intermittently, and 7,677 never reported taking PPIs. All had baseline normal cognition or MCI. Multivariable Cox regression analyses evaluated the association between PPI use and annual conversion of baseline normal cognition to MCI or dementia or annual conversion of baseline MCI to dementia, controlling for demographic characteristics, vascular comorbidities, mood, and use of anticholinergics and histamine-2 receptor antagonists. Continuous (always vs never) PPI use was associated with lower risk of decline in cognitive function (hazard ratio (HR) = 0.78, 95% confidence interval (CI) =0.66-0.93, P = .005) and lower risk of conversion to MCI or AD (HR = 0.82, 95% CI = 0.69-0.98, P = .03). Intermittent use was also associated with lower risk of decline in cognitive function (HR = 0.84, 95% CI = 0.76-0.93, P = .001) and risk of conversion to MCI or AD (HR = 0.82, 95% CI = 0.74-0.91, P = .001). This lower risk was found for persons with normal cognition or MCI. Proton pump inhibitors were not associated with greater risk of dementia or of AD, in contrast to recent reports. Study limitations include reliance on self-reported PPI use and lack of dispensing data. Prospective studies are needed to confirm these results to guide empirically based clinical treatment recommendations. © 2017, Copyright the Authors Journal compilation © 2017, The American Geriatrics Society.

Use of proton pump inhibitors and mortality after hip fracture in a nationwide study.

PubMed

Brozek, W; Reichardt, B; Zwerina, J; Dimai, H P; Klaushofer, K; Zwettler, E

2017-05-01

We analyzed the association of proton pump inhibitors (PPIs) with mortality after osteoporosis-related hip fracture in Austria. PPIs were associated with reduced 90-day mortality but elevated mortality after half a year when initiated pre-fracture. Inpatients and discharged patients on PPIs showed lowered in-hospital and 90-day mortality, respectively. We herein investigated use of proton pump inhibitors (PPIs) and mortality among hip fracture patients in a nationwide study in Austria. In this retrospective cohort study, data on use of PPIs were obtained from 31,668 Austrian patients ≥50 years with a hip fracture between July 2008 and December 2010. All-cause mortality in patients without anti-osteoporotic drug treatment who had received their first recorded PPI prescription in the study period either before or after fracture was compared with hip fracture patients on neither PPIs nor anti-osteoporotic medication using logistic and Cox regression analysis. With PPI use, 90-day mortality was significantly reduced, both at initiation before (OR 0.66; p < 0.0001) and after hip fracture (OR 0.23; p < 0.0001). 90-day mortality was also reduced when PPIs were prescribed not until after discharge from the last recorded hip fracture-related hospital stay (OR 0.49; p < 0.0001) except for patients aged <70 years. In a sub-cohort of patients beginning PPIs during hospital stay, in-hospital mortality (0.2%) was substantially reduced relative to matched control patients (3.5%) (p < 0.0001). Longer-term mortality significantly increased after half a year post-fracture only among those who started PPI prescription before fracture. PPI use during and after hospital stay due to hip fracture is associated with a considerable decrease in mortality. These findings could have implications for hip fracture treatment.

[Do opioids, sedatives and proton-pump inhibitors increase the risk of fractures?

PubMed

Thorsdottir, Gudlaug; Benedikz, Elisabet; Thorgeirsdottir, Sigridur A; Johannsson, Magnus

2017-01-01

A pharmacoepidemiological study was conducted to analyse the relationship between bone fracture and the use of certain drugs. The study includes patients 40 years and older, diagnosed with bone fractures in the Emergency Department of Landspitali University Hospital in Reykjavik, Iceland, during a 10-year period (2002-2011). Also were included those who picked up from a pharmacy 90 DDD or more per year of the drugs included in the study in the capital region of Iceland during same period. Opiates, benzodiazepines/hypnotics (sedatives) were compared with HMG-CoA reductase inhibitors (statins), non-steroid anti-inflammatory drugs (NSAID) and beta blockers. Proton-pump inhibitors (PPI) and histamine H2-antagonists were also examined. To examine the association between above drugs and fractures the data from electronic hospital database were matched to the prescription database run by the Directorate of Health. A total of 29,056 fractures in 22,891 individuals were identified. The females with fractures were significantly older and twice as many, compared to males. The odds ratio (OR) for fractures was not significantly different between the NSAID, statins and beta blockers. OR for opiates showed almost double increased risk of fractures, 40% increased risk for sedatives and 30% increased risk for PPIs compared to beta blockers. No increased fracture-risk was noted in patients taking H2 antagonists. This study shows a relationship between the use of opiates, sedatives and bone fractures. The incidence of fractures was also increased in patients taking PPIs which is interesting in the light of the wide-spread use of PPIs in the community. Key words: Opiates, sedatives, proton- pump inhibitors, fractures. Correspondence: Magnus Johannsson, magjoh@hi.is.

A study with pharyngeal and esophageal 24-hour pH-impedance monitoring in patients with laryngopharyngeal symptoms refractory to proton pump inhibitors.

PubMed

Dulery, C; Lechot, A; Roman, S; Bastier, P-L; Stoll, D; de Gabory, L; Zerbib, F

2017-01-01

The role of gastroesophageal reflux in chronic laryngeal symptoms is difficult to establish. The aim of this study was to characterize pharyngeal and esophageal pH-impedance reflux patterns in a group of patients with suspected laryngopharyngeal reflux and to determine predictive factors of response to proton pump inhibitors. Patients with chronic pharyngolaryngeal symptoms were evaluated with a symptom score questionnaire, laryngoscopy, and 24-hour pharyngeal and esophageal pH-impedance monitoring at baseline and after 8-week treatment with esomeprazole 40 mg b.i.d. Response to treatment was defined by a diminution of more than 50% of the score for the primary symptom. Reflux patterns and baseline impedance values were compared to those obtained in 46 healthy subjects. Twenty-four patients were included (17 women, median age 54 years), all previously refractory to antisecretory therapy. Symptom scores were 46 (32-62) and 40 (27-76) off and on therapy, respectively (P=.1). There was no significant difference between patients and controls for pH-impedance reflux parameters and baseline values off and on therapy in distal and proximal esophagus and in the pharynx. Median numbers of pharyngeal reflux were 0 and 0 off and on therapy, respectively. Only two patients were responders to treatment, both with excessive distal reflux but no pharyngeal reflux. Only one patient had abnormal pharyngeal reflux but did not respond to proton pump inhibitors. Patients with suspected laryngopharyngeal reflux refractory to therapy do not exhibit abnormal pharyngeal or esophageal pH-impedance reflux. In these patients, laryngopharyngeal reflux is unlikely. © 2016 John Wiley & Sons Ltd.

Proton-pump inhibitors and risk of fractures: an update meta-analysis.

PubMed

Zhou, B; Huang, Y; Li, H; Sun, W; Liu, J

2016-01-01

To identify the relationship between proton-pump inhibitors (PPIs) and the risk of fracture, we conducted an update meta-analysis of observational studies. Results showed that PPI use was associated with a modestly increased risk of hip, spine, and any-site fracture. Many studies have investigated the association of proton-pump inhibitors (PPIs) with fracture risk, but the results have been inconsistent. To evaluate this question, we performed a meta-analysis of relevant observational studies. A systematic literature search up to February 2015 was performed in PubMed. We combined relative risks (RRs) for fractures using random-effects models and conducted subgroup and stratified analyses. Eighteen studies involving a total of 244,109 fracture cases were included in this meta-analysis. Pooled analysis showed that PPI use could moderately increase the risk of hip fracture [RR = 1.26, 95 % confidence intervals (CIs) 1.16–1.36]. There was statistically significant heterogeneity among studies (p < 0.001; I 2 = 71.9 %). After limiting to cohort studies, there was also a moderate increase in hip fracture risk without evidence of study heterogeneity. Pooling revealed that short-term use (<1 year) and longer use (>1 year) were similarly associated with increased risk of hip fracture. Furthermore, a moderately increased risk of spine (RR = 1.58, 95 % CI 1.38–1.82) and any-site fracture (RR = 1.33, 95 % CI 1.15–1.54) was also found among PPI users. In this update meta-analysis of observational studies, PPI use modestly increased the risk of hip, spine, and any-site fracture, but no evidence of duration effect in subgroup analysis.

Clinical value of wireless pH-monitoring of gastro-esophageal reflux in children before and after proton pump inhibitors.

PubMed

Boström, Michaela; Thorsson, Ola; Toth, Ervin; Agardh, Daniel

2014-12-24

Wireless pH-monitoring is an accurate method for diagnosing adults with gastroesophageal reflux disease (GERD). The aim of this study was to evaluate the use of the Bravo capsule on children investigated for GERD in terms of safety, tolerability and feasibility before and after administration of proton pump inhibitors. A Bravo capsule was inserted during upper endoscopy under general anaesthesia or deep sedation with propofol. 48-hour pH-metry was performed in 106 children (50 males, 56 females) at the median age of 11 years (range 17 months-18 years). On the second day of investigation, proton pump inhibitor (PPI) was given at a mean dose of 1.6 mg/kg (SD ±0.6 mg). The definition of GERD was set to a reflux index (RI) of ≥5% and DeMeester score (DMS) ≥14.7. Application of the capsule was successful in 103 of the 106 children (97.2%) and interpretable in 99 of these 103 (96.1%). 49 of the children with interpretable results (49.5%) had GERD according to RI, while 51 (56.7%) had GERD according to DMS. After PPI was given on day 2, RI decreased from a median of 4.9% (range 0.3-63.4%) to 2.2% (0-58.0%), while DMS decreased from a median of 17.6 (range 2.2-207.6) to 8.2 (0.3-178.6), respectively (p < 0.0001). No severe adverse events were reported. Wireless pH-metry is a safe and tolerable method when investigating children for GERD. PPI given on the second day of assessment provides additional information on response to treatment suggesting that pH-metry preferably should be extended to 48 hours.

A Review of New Surgical and Endoscopic Therapies for Gastroesophageal Reflux Disease.

PubMed

Ganz, Robert A

2016-07-01

Treatment of gastroesophageal reflux disease in the United States today is binary, with the majority of patients with gastroesophageal reflux disease being treated with antisecre-tory medications and a minority of patients, typically those with volume regurgitation, undergoing Nissen fundoplication. However, there has been increasing dissatisfaction with proton pump inhibitor therapy among a significant number of patients with gastroesophageal reflux disease owing to cost, side effects, and refractory symptoms, and there has been a general reluctance to undergo surgical fundoplication due to its attendant side-effect profile. As a result, a therapy gap exists for many patients with gastroesophageal reflux disease. Alternative techniques are available for these gap patients, including 2 endoscopic fundoplication techniques, an endoscopic radiofrequency energy delivery technique, and 2 minimally invasive surgical procedures. These alternative techniques have been extensively evaluated; however, there are limitations to published studies, including arbitrary definitions of success, variable efficacy measurements, deficient reporting tools, inconsistent study designs, inconsistent lengths of follow-up postintervention, and lack of comparison data across techniques. Although all of the techniques appear to be safe, the endoscopic techniques lack demonstrable reflux control and show variable symptom improvement and variable decreases in proton pump inhibitor use. The surgical techniques are more robust, with evidence for adequate reflux control, symptom improvement, and decreased proton pump inhibitor use; however, these techniques are more difficult to perform and are more intrusive. Additionally, these alternative techniques have only been studied in patients with relatively normal anatomy. The field of gastroesophageal reflux disease treatment is in need of consistent definitions of efficacy, standardized study design and outcome measurements, and improved reporting tools before the role of these techniques can be fully ascertained.

Constitutive and Companion Cell-Specific Overexpression of AVP1, Encoding a Proton-Pumping Pyrophosphatase, Enhances Biomass Accumulation, Phloem Loading, and Long-Distance Transport1[OPEN

PubMed Central

Shulaev, Vladimir; Paez-Valencia, Julio

2016-01-01

Plant productivity is determined in large part by the partitioning of assimilates between the sites of production and the sites of utilization. Proton-pumping pyrophosphatases (H+-PPases) are shown to participate in many energetic plant processes, including general growth and biomass accumulation, CO2 fixation, nutrient acquisition, and stress responses. H+-PPases have a well-documented role in hydrolyzing pyrophosphate (PPi) and capturing the released energy to pump H+ across the tonoplast and endomembranes to create proton motive force (pmf). Recently, an additional role for H+-PPases in phloem loading and biomass partitioning was proposed. In companion cells (CCs) of the phloem, H+-PPases localize to the plasma membrane rather than endomembranes, and rather than hydrolyzing PPi to create pmf, pmf is utilized to synthesize PPi. Additional PPi in the CCs promotes sucrose oxidation and ATP synthesis, which the plasma membrane P-type ATPase in turn uses to create more pmf for phloem loading of sucrose via sucrose-H+ symporters. To test this model, transgenic Arabidopsis (Arabidopsis thaliana) plants were generated with constitutive and CC-specific overexpression of AVP1, encoding type 1 ARABIDOPSIS VACUOLAR PYROPHOSPHATASE1. Plants with both constitutive and CC-specific overexpression accumulated more biomass in shoot and root systems. 14C-labeling experiments showed enhanced photosynthesis, phloem loading, phloem transport, and delivery to sink organs. The results obtained with constitutive and CC-specific promoters were very similar, such that the growth enhancement mediated by AVP1 overexpression can be attributed to its role in phloem CCs. This supports the model for H+-PPases functioning as PPi synthases in the phloem by arguing that the increases in biomass observed with AVP1 overexpression stem from improved phloem loading and transport. PMID:26530315

Utilization of nonsteroidal anti-inflammatory drugs and antisecretory agents: a managed care claims analysis.

PubMed

Ofman, Joshua J; Badamgarav, Enkhe; Henning, James M; Knight, Kevin; Laine, Loren

2004-06-15

To describe patients initiating nonsteroidal anti-inflammatory drug (NSAID) therapy with regard to gastrointestinal and cardiac risks and patterns of antisecretory agent use, and to explore the relation between therapy type and subsequent outcomes. We studied patients aged 18 years or older who had continuous coverage from 1998 to 2001 and who had initiated treatment with cyclooxygenase-2 (COX-2) selective inhibitors or nonselective NSAIDs. Patients were categorized with respect to gastrointestinal and cardiac risk profiles. Proton pump inhibitor use within 15 days of initiating NSAID therapy was considered prophylactic. Logistic regression analysis was used to evaluate associations between treatment and hospitalization events, cardiac events, and health care costs. We identified 106,564 eligible NSAID initiators: 65.2% used COX-2 inhibitors and 34.8% used traditional NSAIDs. Users of COX-2 inhibitors were more likely to be at higher risk of gastrointestinal bleeding and cardiac events than were NSAID users. Proton pump inhibitor prophylaxis was most common among users of COX-2 inhibitors, but was only 11% in patients at high risk of gastrointestinal bleeding. There were no differences among treatment groups in terms of gastrointestinal or cardiac events. Initiation of COX-2 inhibitor therapy was associated with greater total health care costs. Although we found that COX-2 inhibitors were used more frequently than were traditional NSAIDs in certain groups of patients with varying cardiac or gastrointestinal risk, we did not find that their use resulted in reductions in clinical events, cotherapy with proton pump inhibitors, or costs, suggesting that a better understanding of the relation between NSAID treatment strategies and outcomes in patients with differing risk characteristics is needed.

Nitric oxide contributes to minerals absorption, proton pumps and hormone equilibrium under cadmium excess in Trifolium repens L. plants.

PubMed

Liu, Shiliang; Yang, Rongjie; Pan, Yuanzhi; Ma, Mingdong; Pan, Jiang; Zhao, Yan; Cheng, Qingsu; Wu, Mengxi; Wang, Maohua; Zhang, Lin

2015-09-01

Nitric oxide (NO) is a stress-signaling molecule in plants that mediates a wide range of physiological processes and responses to metal toxicity. In this work, various NO modulators (NO donor: SNP; NO scavenger: cPTIO; NO synthase inhibitor: l-NAME; and SNP analogs: sodium nitrite/nitrate and sodium ferrocyanide) were investigated to determine the role of NO in Trifolium repens L. plants exposed to Cd. Cd (100μM) markedly reduced biomass, NO production and chlorophyll (Chl a, Chl b and total Chl) concentration but stimulated reactive oxygen species (ROS) and Cd accumulation in plants. SNP (50μM) substantially attenuated growth inhibition, reduced hydrogen peroxide (H2O2) and malonyldialdehyde (MDA) levels, stimulated ROS-scavenging enzymes/agents, and mitigated the H(+)-ATPase inhibition in proton pumps. Interestingly, SNP considerably up-regulated the levels of jasmonic acid (JA) and proline in plant tissues but down-regulated the levels of ethylene (ET) in both shoots and roots and the level of salicylic acid (SA) in roots only, which might be related to the elevated NO synthesis. Additionally, SNP (25-200μM) regulated mineral absorption and, particularly at 50μM, significantly enhanced the uptake of shoot magnesium (Mg) and copper (Cu) and of root calcium (Ca), Mg and iron (Fe). Nevertheless, the effects of SNP on plant growth were reversed by cPTIO and l-NAME, suggesting that the protective effect of SNP might be associated with NO synthesis in vivo. Moreover, SNP analogs did not display roles similar to that of SNP. These results indicated that NO depleted Cd toxicity by eliminating oxidative damage, enhancing minerals absorption, regulating proton pumps, and maintaining hormone equilibrium. Copyright © 2015 Elsevier Inc. All rights reserved.

The association between the use of proton pump inhibitors and the risk of hypomagnesemia: a systematic review and meta-analysis.

PubMed

Park, Chan Hyuk; Kim, Eun Hye; Roh, Yun Ho; Kim, Ha Yan; Lee, Sang Kil

2014-01-01

Although many case reports have described patients with proton pump inhibitor (PPI)-induced hypomagnesemia, the impact of PPI use on hypomagnesemia has not been fully clarified through comparative studies. We aimed to evaluate the association between the use of PPI and the risk of developing hypomagnesemia by conducting a systematic review with meta-analysis. We conducted a systematic search of MEDLINE, EMBASE, and the Cochrane Library using the primary keywords "proton pump," "dexlansoprazole," "esomeprazole," "ilaprazole," "lansoprazole," "omeprazole," "pantoprazole," "rabeprazole," "hypomagnesemia," "hypomagnesaemia," and "magnesium." Studies were included if they evaluated the association between PPI use and hypomagnesemia and reported relative risks or odds ratios or provided data for their estimation. Pooled odds ratios with 95% confidence intervals were calculated using the random effects model. Statistical heterogeneity was assessed with Cochran's Q test and I2 statistics. Nine studies including 115,455 patients were analyzed. The median Newcastle-Ottawa quality score for the included studies was seven (range, 6-9). Among patients taking PPIs, the median proportion of patients with hypomagnesemia was 27.1% (range, 11.3-55.2%) across all included studies. Among patients not taking PPIs, the median proportion of patients with hypomagnesemia was 18.4% (range, 4.3-52.7%). On meta-analysis, pooled odds ratio for PPI use was found to be 1.775 (95% confidence interval 1.077-2.924). Significant heterogeneity was identified using Cochran's Q test (df = 7, P<0.001, I2 = 98.0%). PPI use may increase the risk of hypomagnesemia. However, significant heterogeneity among the included studies prevented us from reaching a definitive conclusion.

Blood Pressure-Lowering Effect of Orally Ingested Nitrite Is Abolished by a Proton Pump Inhibitor.

PubMed

Montenegro, Marcelo F; Sundqvist, Michaela L; Larsen, Filip J; Zhuge, Zhengbing; Carlström, Mattias; Weitzberg, Eddie; Lundberg, Jon O

2017-01-01

Inorganic nitrate and nitrite from dietary and endogenous sources are metabolized to NO and other bioactive nitrogen oxides that affect blood pressure. The mechanisms for nitrite bioactivation are unclear, but recent studies in rodents suggest that gastric acidity may influence the systemic effects of this anion. In a randomized, double-blind, placebo-controlled crossover study, we tested the effects of a proton pump inhibitor on the acute cardiovascular effects of nitrite. Fifteen healthy nonsmoking, normotensive subjects, aged 19 to 39 years, were pretreated with placebo or esomeprazole (3×40 mg) before ingesting sodium nitrite (0.3 mg kg -1 ), followed by blood pressure monitoring. Nitrite reduced systolic blood pressure by a maximum of 6±1.3 mm Hg when taken after placebo, whereas pretreatment with esomeprazole blunted this effect. Peak plasma nitrite, nitrate, and nitroso species levels after nitrite ingestion were similar in both interventions. In 8 healthy volunteers, we then infused increasing doses of sodium nitrite (1, 10, and 30 nmol kg -1 min -1 ) intravenously. Interestingly, although plasma nitrite peaked at similar levels as with orally ingested nitrite (≈1.8 µmol/L), no changes in blood pressure were observed. In rodents, esomeprazole did not affect the blood pressure response to the NO donor, DEA NONOate, or vascular relaxation to nitroprusside and acetylcholine, demonstrating an intact downstream NO-signaling pathway. We conclude that the acute blood pressure-lowering effect of nitrite requires an acidic gastric environment. Future studies will reveal if the cardiovascular complications associated with the use of proton pump inhibitors are linked to interference with the nitrate-nitrite-NO pathway. © 2016 American Heart Association, Inc.

Progress toward an explicit mechanistic model for the light-driven pump, bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lanyi, J. K.

1999-01-01

Recent crystallographic information about the structure of bacteriorhodopsin and some of its photointermediates, together with a large amount of spectroscopic and mutational data, suggest a mechanistic model for how this protein couples light energy to the translocation of protons across the membrane. Now nearing completion, this detailed molecular model will describe the nature of the steric and electrostatic conflicts at the photoisomerized retinal, as well as the means by which it induces proton transfers in the two half-channels leading to the two membrane surfaces, thereby causing unidirectional, uphill transport.

Study of Xanthorhodopsin, the Retinal-Protein Proton Pump of Salinibacter ruber with Light-Harvesting Carotenoid Antenna

DTIC Science & Technology

2009-03-19

including suggesstions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215...gen-bonded to the c=o and the NHz of the amide side-chain of Asn19t, as well as NHI ofArg184. The dependence of the carotenoid spectrum on the retinal...protonation of ASp85 [22]. This is unlikely to occur in the xan- thorhodopsin photocyc1e, because NHI and NH2 of Arg93 are both hydrogen-bonded to the peptide

The photochemical cycle of bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lozier, R. H.; Niederberger, W.

1977-01-01

The reaction cycle of bacteriorhodopsin in the purple membrane isolated from Halobacterium halobium has been studied by optical absorption spectroscopy using low-temperature and flash kinetic techniques. After absorption of light, bacteriorhodopsin passes through at least five distinct intermediates. The temperature and pH dependence of the absorbance changes suggests that branch points and/or reversible steps exist in this cycle. Flash spectroscopy in the presence of a pH-indicating dye shows that the transient release of a proton accompanies the photoreaction cycle. The proton release occurs from the exterior and the uptake is on the cytoplasmic side of the membrane, as required by the function of bacteriorhodopsin as a light-driven proton pump. Proton translocating steps connecting release and uptake are indicated by deuterium isotope effects on the kinetics of the cycle. The rapid decay of a light-induced linear dichroism shows that a chromophore orientation change occurs during the reaction cycle.

The efficiency of cellular energy transduction and its implications for obesity.

PubMed

Harper, Mary-Ellen; Green, Katherine; Brand, Martin D

2008-01-01

We assess the existence, mechanism, and functions of less-than-maximal coupling efficiency of mitochondrial oxidative phosphorylation and its potential as a target for future antiobesity interventions. Coupling efficiency is the proportion of oxygen consumption used to make adenosine triphosphate (ATP) and do useful work. High coupling efficiency may lead to fat deposition; low coupling efficiency to a decrease in fat stores. We review obligatory and facultative energy expenditure and the role of a futile cycle of proton pumping and proton leak across the mitochondrial inner membrane in dissipating energy. Basal proton conductance is catalyzed primarily by the adenine nucleotide translocase but can be mimicked by chemical uncouplers. Inducible proton conductance is catalyzed by specific uncoupling proteins. We discuss the opportunities and pitfalls of targeting these processes as a treatment for obesity by decreasing coupling efficiency and increasing energy expenditure, either directly or through central mechanisms of energy homeostasis.

Intermittent and on-demand use of proton pump inhibitors in the management of symptomatic gastroesophageal reflux disease.

PubMed

Bardhan, Karna Dev

2003-03-01

The epidemic of gastroesophageal reflux disease (GERD) in industrialized nations is currently spreading to less-developed ones, with more than half of the patients having symptomatic or mild erosive GERD. The long-term management of GERD has been dominated by daily maintenance treatment with proton pump inhibitors (PPI) to prevent relapse. It is common, however, for many patients with mild disease and infrequent symptom relapses to use a PPI only when symptoms demand. Patients with symptomatic or mild erosive GERD are therefore ideal for on-demand or intermittent treatment. The efficacy of such a strategy of intermittent treatment, or treatment of symptoms on demand, has recently been evaluated in four randomized controlled studies. These trials demonstrate that such therapeutic strategies reduce symptoms, improve quality of life, and are cost effective. In clinical practice, the author has found these treatment strategies suitable for approximately 60% of newly diagnosed patients with GERD for the long-term management of symptomatic GERD of mild or moderate severity.

What are the effects of proton pump inhibitors on the small intestine?

PubMed Central

Fujimori, Shunji

2015-01-01

Generally, proton-pump inhibitors (PPIs) have great benefit for patients with acid related disease with less frequently occurring side effects. According to a recent report, PPIs provoke dysbiosis of the small intestinal bacterial flora, exacerbating nonsteroidal anti-inflammatory drug-induced small intestinal injury. Several meta-analyses and systematic reviews have reported that patients treated with PPIs, as well as post-gastrectomy patients, have a higher frequency of small intestinal bacterial overgrowth (SIBO) compared to patients who lack the aforementioned conditions. Furthermore, there is insufficient evidence that these conditions induce Clostridium difficile infection. At this time, PPI-induced dysbiosis is considered a type of SIBO. It now seems likely that intestinal bacterial flora influence many diseases, such as inflammatory bowel disease, diabetes mellitus, obesity, non-alcoholic fatty liver disease, and autoimmune diseases. When attempting to control intestinal bacterial flora with probiotics, prebiotics, and fecal microbiota transplantation, etc., the influence of acid suppression therapy, especially PPIs, should not be overlooked. PMID:26078557

Structure of the vacuolar H+-ATPase rotary motor reveals new mechanistic insights.

PubMed

Rawson, Shaun; Phillips, Clair; Huss, Markus; Tiburcy, Felix; Wieczorek, Helmut; Trinick, John; Harrison, Michael A; Muench, Stephen P

2015-03-03

Vacuolar H(+)-ATPases are multisubunit complexes that operate with rotary mechanics and are essential for membrane proton transport throughout eukaryotes. Here we report a ∼ 1 nm resolution reconstruction of a V-ATPase in a different conformational state from that previously reported for a lower-resolution yeast model. The stator network of the V-ATPase (and by implication that of other rotary ATPases) does not change conformation in different catalytic states, and hence must be relatively rigid. We also demonstrate that a conserved bearing in the catalytic domain is electrostatic, contributing to the extraordinarily high efficiency of rotary ATPases. Analysis of the rotor axle/membrane pump interface suggests how rotary ATPases accommodate different c ring stoichiometries while maintaining high efficiency. The model provides evidence for a half channel in the proton pump, supporting theoretical models of ion translocation. Our refined model therefore provides new insights into the structure and mechanics of the V-ATPases. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Proton Pump Inhibitors in cancer patients: How useful they are? A review of the most common indications for their use.

PubMed

Numico, Gianmauro; Fusco, Vittorio; Franco, Pierfrancesco; Roila, Fausto

2017-03-01

Proton-Pump Inhibitors (PPIs) are commonly prescribed in the general population and in cancer patients. A supposed role in the prevention of gastric mucosal damage apparently justify their use in patients undergoing cytotoxic chemotherapy, steroids and radiotherapy on the gastro-duodenal region. They are frequently given also to patients admitted to Intensive Care Units, for the prevention of stress-related gastric ulcers. The evidence about these use of gastroprotection is reviewed. In the majority of the cases the prescription of PPIs is not justified. In two circumstances (chemotherapy and stress-related gastric disease) randomized studies have shown a protective action of PPIs although this effect did not translate into the reduction of serious clinical consequences. PPIs are not free of toxic effects that are acknowledged by an expanding literature. Also the interaction with anticancer drugs is a potential source of unwanted consequences. Copyright © 2017 Elsevier B.V. All rights reserved.

The impact of proton pump inhibitors on the human gastrointestinal microbiome

PubMed Central

Freedberg, Daniel E.; Lebwohl, Benjamin; Abrams, Julian A.

2014-01-01

Potent gastric acid suppression using proton pump inhibitors (PPIs) is common in clinical practice yet may have important effects on human health that are mediated through changes in the gastrointestinal microbiome. Acting through pH-dependent or pH-independent mechanisms, PPIs have the potential to alter the normal microbiota throughout the human gastrointestinal lumen. In the esophagus, PPIs change the normal bacterial milieu to decrease distal esophageal exposure to inflammatory Gram-negative bacteria which may lower the risk of Barrett's esophagus. In the stomach, PPIs alter the abundance and location of gastric Helicobacter pylori and other bacteria, which has implications for peptic ulcer disease and gastric malignancy. In the small bowel, PPIs cause polymicrobial small bowel bacterial overgrowth and have been associated with the diagnosis of celiac disease. In the colon, PPIs associate with incident but not recurrent Clostridium difficile infection, putatively through alterations in commensal colonic anaerobes. Our understanding of the effect of gastric acid suppression on the human gastrointestinal microbiome is incomplete but is rapidly advancing. PMID:25439276

What are the effects of proton pump inhibitors on the small intestine?

PubMed

Fujimori, Shunji

2015-06-14

Generally, proton-pump inhibitors (PPIs) have great benefit for patients with acid related disease with less frequently occurring side effects. According to a recent report, PPIs provoke dysbiosis of the small intestinal bacterial flora, exacerbating nonsteroidal anti-inflammatory drug-induced small intestinal injury. Several meta-analyses and systematic reviews have reported that patients treated with PPIs, as well as post-gastrectomy patients, have a higher frequency of small intestinal bacterial overgrowth (SIBO) compared to patients who lack the aforementioned conditions. Furthermore, there is insufficient evidence that these conditions induce Clostridium difficile infection. At this time, PPI-induced dysbiosis is considered a type of SIBO. It now seems likely that intestinal bacterial flora influence many diseases, such as inflammatory bowel disease, diabetes mellitus, obesity, non-alcoholic fatty liver disease, and autoimmune diseases. When attempting to control intestinal bacterial flora with probiotics, prebiotics, and fecal microbiota transplantation, etc., the influence of acid suppression therapy, especially PPIs, should not be overlooked.

The influence of proton pump inhibitors and other commonly used medication on the gut microbiota.

PubMed

Imhann, Floris; Vich Vila, Arnau; Bonder, Marc Jan; Lopez Manosalva, Ailine G; Koonen, Debby P Y; Fu, Jingyuan; Wijmenga, Cisca; Zhernakova, Alexandra; Weersma, Rinse K

2017-07-04

Proton pump inhibitors (PPIs), used to treat gastro-esophageal reflux and prevent gastric ulcers, are among the most widely used drugs in the world. The use of PPIs is associated with an increased risk of enteric infections. Since the gut microbiota can, depending on composition, increase or decrease the risk of enteric infections, we investigated the effect of PPI-use on the gut microbiota. We discovered profound differences in the gut microbiota of PPI users: 20% of their bacterial taxa were statistically significantly altered compared with those of non-users. Moreover, we found that it is not only PPIs, but also antibiotics, antidepressants, statins and other commonly used medication were associated with distinct gut microbiota signatures. As a consequence, commonly used medications could affect how the gut microbiota resist enteric infections, promote or ameliorate gut inflammation, or change the host's metabolism. More studies are clearly needed to understand the role of commonly used medication in altering the gut microbiota as well as the subsequent health consequences.

Proton-pump inhibitors: understanding the complications and risks.

PubMed

Malfertheiner, Peter; Kandulski, Arne; Venerito, Marino

2017-12-01

Proton-pump inhibitors (PPIs) are the most effective therapy for the full spectrum of gastric-acid-related diseases. However, in the past decade, a steadily increasing list of complications following long-term use of PPIs has been reported. Their potent acid-suppressive action induces several structural and functional changes within the gastric mucosa, including fundic gland polyps, enterochromaffin-like cell hyperplasia and hypergastrinaemia, which can be exaggerated in the presence of Helicobacter pylori infection. As discussed in this Review, most associations of PPIs with severe adverse events are not based on sufficient evidence because of confounding factors and a lack of plausible mechanisms. Thus, a causal relationship remains unproven in most associations, and further studies are needed. Awareness of PPI-associated risks should not lead to anxiety in patients but rather should induce the physician to consider the appropriate dosing and duration of PPI therapy, including long-term monitoring strategies in selected groups of patients because of their individual comorbidities and risk factors.

[Gastro-esophageal reflux and chronic respiratory diseases].

PubMed

Dirou, S; Germaud, P; Bruley des Varannes, S; Magnan, A; Blanc, F-X

2015-12-01

Gastroesophageal reflux disease (GERD) frequently occurs in association with chronic respiratory diseases although the casual link is not always clear. Several pathophysiological and experimental factors are considered to support a role for GERD in respiratory disease. Conversely, respiratory diseases and bronchodilator treatment can themselves exacerbate GERD. When cough or severe asthma is being investigated, GERD does not need to be systematically looked for and a therapeutic test with proton pump inhibitors is not always recommended. pH impedance monitoring is now the reference diagnostic tool to detect non acid reflux, a form of reflux for which proton pump inhibitor treatment is ineffective. Recent data have shown a potential role of GERD in idiopathic pulmonary fibrosis and bronchiolitis obliterans following lung transplantation, leading to discussions about the place of surgery in this context. However, studies using pH impedance monitoring are still needed to better understand and manage the association between GERD and chronic respiratory diseases. Copyright © 2015 SPLF. Published by Elsevier Masson SAS. All rights reserved.

Proton pump inhibitor resistance, the real challenge in gastro-esophageal reflux disease.

PubMed

Cicala, Michele; Emerenziani, Sara; Guarino, Michele Pier Luca; Ribolsi, Mentore

2013-10-21

Gastro-esophageal reflux disease (GERD) is one of the most prevalent chronic diseases. Although proton pump inhibitors (PPIs) represent the mainstay of treatment both for healing erosive esophagitis and for symptom relief, several studies have shown that up to 40% of GERD patients reported either partial or complete lack of response of their symptoms to a standard PPI dose once daily. Several mechanisms have been proposed as involved in PPIs resistance, including ineffective control of gastric acid secretion, esophageal hypersensitivity, ultrastructural and functional changes in the esophageal epithelium. The diagnostic evaluation of a refractory GERD patients should include an accurate clinical evaluation, upper endoscopy, esophageal manometry and ambulatory pH-impedance monitoring, which allows to discriminate non-erosive reflux disease patients from those presenting esophageal hypersensitivity or functional heartburn. Treatment has been primarily based on doubling the PPI dose or switching to another PPI. Patients with proven disease, not responding to PPI twice daily, are eligible for anti-reflux surgery.

Gastrointestinal symptoms associated with gastroesophageal reflux disease, and their relapses after treatment with proton pump inhibitors: A systematic review

PubMed Central

Hosseini, Mousalreza; Salari, Roshanak; Shariatmaghani, Somayeh; Birjandi, Batul; Salari, Masoumeh

2017-01-01

Gastroesophageal reflux disease (GERD) is a common functional gastrointestinal disorder with significant effects on the quality of life. The burden of GERD is soaring in Asia. Preventing symptom relapse is a therapeutic goal in GERD patients. Since proton pump inhibitors (PPI) are the first-line treatment of GERD, drug failure has become a major problem in the treatment procedure. We reviewed the literature in order to find articles related to comorbidities and symptoms affecting GERD from 1980 to 2015 via PubMed and Google Scholar using keywords such as ‘Gastroesophageal reflux disease’, ‘Gastrointestinal symptoms’ and Boolean operators (such as AND, OR, NOT). Due to the cost of PPI therapy and the high rate of GERD relapse after PPI therapy, demand for continuing this type of treatment is decreasing. Thus, we need to discover new approaches to treat the disease and also investigate the relationship between the treatment of GERD and its comorbidities and symptoms such as functional constipation. PMID:28848636

An Evidence-Based Approach to the Treatment of Gastroesophageal Reflux Disease.

PubMed

Patti, Marco G

2016-01-01

Gastroesophageal reflux disease (GERD) is prevalent worldwide, particularly in developed countries. It is estimated that the prevalence of GERD in the United States is approximately 20% and that it is increasing because of the epidemic of obesity. To review the pathophysiology, clinical presentation, diagnostic evaluation, and treatment of GERD. A search of PubMed was conducted for the years spanning 1985 to 2015 and included the following terms: heartburn, regurgitation, dysphagia, gastroesophageal reflux disease, cough, aspiration, laryngitis, GERD, GORD, endoscopy, manometry, pH monitoring, proton pump inhibitors, open fundoplication, and laparoscopic fundoplication. Only articles in English were included. Lifestyle modifications, proton pump inhibitors, and laparoscopic fundoplication are proven treatment modalities for GERD. Endoscopic procedures have not been proven as effective. A Roux-en-Y gastric bypass is the procedure of choice when GERD and morbid obesity coexist. Gastroesophageal reflux disease is a highly prevalent disease. Once the diagnosis has been established, the best results are obtained by a multidisciplinary team with the goal of individualizing treatment for patients.

In silico design of novel proton-pump inhibitors with reduced adverse effects.

PubMed

Li, Xiaoyi; Kang, Hong; Liu, Wensheng; Singhal, Sarita; Jiao, Na; Wang, Yong; Zhu, Lixin; Zhu, Ruixin

2018-05-30

The development of new proton-pump inhibitors (PPIs) with less adverse effects by lowering the pKa values of nitrogen atoms in pyrimidine rings has been previously suggested by our group. In this work, we proposed that new PPIs should have the following features: (1) number of ring II = number of ring I + 1; (2) preferably five, six, or seven-membered heteroatomic ring for stability; and (3) 1 < pKa1 < 4. Six molecular scaffolds based on the aforementioned criteria were constructed, and R groups were extracted from compounds in extensive data sources. A virtual molecule dataset was established, and the pKa values of specific atoms on the molecules in the dataset were calculated to select the molecules with required pKa values. Drug-likeness screening was further conducted to obtain the candidates that significantly reduced the adverse effects of long-term PPI use. This study provided insights and tools for designing targeted molecules in silico that are suitable for practical applications.

Chloride transport in functionally active phagosomes isolated from Human neutrophils

PubMed Central

Aiken, Martha L.; Painter, Richard G.; Zhou, Yun; Wang, Guoshun

2012-01-01

Chloride anion is critical for hypochlorous acid (HOCl) production and microbial killing in neutrophil phagosomes. However, the molecular mechanism by which this anion is transported to the organelle is poorly understood. In this report, membrane-enclosed and functionally active phagosomes were isolated from human neutrophils by using opsonized paramagnetic latex microspheres and a rapid magnetic separation method. The phagosomes recovered were highly enriched for specific protein markers associated with this organelle such as lysosomal-associated membrane protein-1, myeloperoxidase (MPO), lactoferrin, and NADPH oxidase. When FITC–dextran was included in the phagocytosis medium, the majority of the isolated phagosomes retained the fluorescent label after isolation, indicative of intact membrane structure. Flow cytometric measurement of acridine orange, a fluorescent pH indicator, in the purified phagosomes demonstrated that the organelle in its isolated state was capable of transporting protons to the phagosomal lumen via the vacuolar-type ATPase proton pump (V-ATPase). When NADPH was supplied, the isolated phagosomes constitutively oxidized dihydrorhodamine 123, indicating their ability to produce hydrogen peroxide. The preparations also showed a robust production of HOCl within the phagosomal lumen when assayed with the HOCl-specific fluorescent probe R19-S by flow cytometry. MPO-mediated iodination of the proteins covalently conjugated to the phagocytosed beads was quantitatively measured. Phagosomal uptake of iodide and protein iodination were significantly blocked by chloride channel inhibitors, including CFTRinh-172 and NPPB. Further experiments determined that the V-ATPase-driving proton flux into the isolated phagosomes required chloride cotransport, and the cAMP-activated CFTR chloride channel was a major contributor to the chloride transport. Taken together, the data suggest that the phagosomal preparation described herein retains ion transport properties, and multiple chloride channels including CFTR are responsible for chloride supply to neutrophil phagosomes. PMID:23089227

Chloride transport in functionally active phagosomes isolated from Human neutrophils.

PubMed

Aiken, Martha L; Painter, Richard G; Zhou, Yun; Wang, Guoshun

2012-12-15

Chloride anion is critical for hypochlorous acid (HOCl) production and microbial killing in neutrophil phagosomes. However, the molecular mechanism by which this anion is transported to the organelle is poorly understood. In this report, membrane-enclosed and functionally active phagosomes were isolated from human neutrophils by using opsonized paramagnetic latex microspheres and a rapid magnetic separation method. The phagosomes recovered were highly enriched for specific protein markers associated with this organelle such as lysosomal-associated membrane protein-1, myeloperoxidase (MPO), lactoferrin, and NADPH oxidase. When FITC-dextran was included in the phagocytosis medium, the majority of the isolated phagosomes retained the fluorescent label after isolation, indicative of intact membrane structure. Flow cytometric measurement of acridine orange, a fluorescent pH indicator, in the purified phagosomes demonstrated that the organelle in its isolated state was capable of transporting protons to the phagosomal lumen via the vacuolar-type ATPase proton pump (V-ATPase). When NADPH was supplied, the isolated phagosomes constitutively oxidized dihydrorhodamine 123, indicating their ability to produce hydrogen peroxide. The preparations also showed a robust production of HOCl within the phagosomal lumen when assayed with the HOCl-specific fluorescent probe R19-S by flow cytometry. MPO-mediated iodination of the proteins covalently conjugated to the phagocytosed beads was quantitatively measured. Phagosomal uptake of iodide and protein iodination were significantly blocked by chloride channel inhibitors, including CFTRinh-172 and NPPB. Further experiments determined that the V-ATPase-driving proton flux into the isolated phagosomes required chloride cotransport, and the cAMP-activated CFTR chloride channel was a major contributor to the chloride transport. Taken together, the data suggest that the phagosomal preparation described herein retains ion transport properties, and multiple chloride channels including CFTR are responsible for chloride supply to neutrophil phagosomes. Copyright © 2012 Elsevier Inc. All rights reserved.

Changes in cellular distribution regulate SKD1 ATPase activity in response to a sudden increase in environmental salinity in halophyte ice plant

PubMed Central

Jou, Yingtzy; Chiang, Chih-Pin; Yen, Hungchen Emilie

2013-01-01

Halophyte Mesembryanthemum crystallinum L. (ice plant) rapidly responds to sudden increases in salinity in its environment by activating specific salt-tolerant mechanisms. One major strategy is to regulate a series of ion transporters and proton pumps to maintain cellular Na+/K+ homeostasis. Plant SKD1 (suppressor of K+ transport growth defect 1) proteins accumulate in cells actively engaged in the secretory processes, and play a critical role in intracellular protein trafficking. Ice plant SKD1 redistributes from the cytosol to the plasma membrane hours after salt stressed. In combination with present knowledge of this protein, we suggest that stress facilitates SKD1 movement to the plasma membrane where ADP/ATP exchange occurs, and functions in the regulation of membrane components such as ion transporters to avoid ion toxicity. PMID:24390077

Modeling the detailed kinetics of mitochondrial cytochrome c oxidase: Catalytic mechanism and nitric oxide inhibition

PubMed Central

Pannala, Venkat R.; Camara, Amadou K. S.

2016-01-01

Cytochrome c oxidase (CcO) catalyzes the exothermic reduction of O2 to H2O by using electrons from cytochrome c, and hence plays a crucial role in ATP production. Although details on the enzyme structure and redox centers involved in O2 reduction have been known, there still remains a considerable ambiguity on its mechanism of action, e.g., the number of sequential electrons donated to O2 in each catalytic step, the sites of protonation and proton pumping, and nitric oxide (NO) inhibition mechanism. In this work, we developed a thermodynamically constrained mechanistic mathematical model for the catalytic action of CcO based on available kinetic data. The model considers a minimal number of redox centers on CcO and couples electron transfer and proton pumping driven by proton motive force (PMF), and accounts for the inhibitory effects of NO on the reaction kinetics. The model is able to fit well all the available kinetic data under diverse experimental conditions with a physiologically realistic unique parameter set. The model predictions show that: 1) the apparent Km of O2 varies considerably and increases from fully reduced to fully oxidized cytochrome c depending on pH and the energy state of mitochondria, and 2) the intermediate enzyme states depend on pH and cytochrome c redox fraction and play a central role in coupling mitochondrial respiration to PMF. The developed CcO model can easily be integrated into existing mitochondrial bioenergetics models to understand the role of the enzyme in controlling oxidative phosphorylation in normal and disease conditions. PMID:27633738

Self-consistent model of the interstellar pickup protons, Alfvenic turbulence, and core solar wind in the outer heliosphere

DOE PAGES

Gamayunov, Konstantin V.; Zhang, Ming; Pogorelov, Nikolai V.; ...

2012-09-05

In this study, a self-consistent model of the interstellar pickup protons, the slab component of the Alfvénic turbulence, and core solar wind (SW) protons is presented for r ≥ 1 along with the initial results of and comparison with the Voyager 2 (V2) observations. Two kinetic equations are used for the pickup proton distribution and Alfvénic power spectral density, and a third equation governs SW temperature including source due to the Alfvén wave energy dissipation. A fraction of the pickup proton free energy, fD , which is actually released in the waveform during isotropization, is taken from the quasi-linear considerationmore » without preexisting turbulence, whereas we use observations to specify the strength of the large-scale driving, C sh, for turbulence. The main conclusions of our study can be summarized as follows. (1) For C sh ≈ 1-1.5 and f D ≈ 0.7-1, the model slab component agrees well with the V2 observations of the total transverse magnetic fluctuations starting from ~8 AU. This indicates that the slab component at low-latitudes makes up a majority of the transverse magnetic fluctuations beyond 8-10 AU. (2) The model core SW temperature agrees well with the V2 observations for r ≳ 20 AU if f D ≈ 0.7-1. (3) A combined effect of the Wentzel-Kramers-Brillouin attenuation, large-scale driving, and pickup proton generated waves results in the energy sink in the region r ≲ 10 AU, while wave energy is pumped in the turbulence beyond 10 AU. Without energy pumping, the nonlinear energy cascade is suppressed for r ≲ 10 AU, supplying only a small energy fraction into the k-region of dissipation by the core SW protons. A similar situation takes place for the two-dimensional turbulence. (4) The energy source due to the resonant Alfvén wave damping by the core SW protons is small at heliocentric distances r ≲ 10 AU for both the slab and the two-dimensional turbulent components. As a result, adiabatic cooling mostly controls the model SW temperature in this region, and the model temperature disagrees with the V2 observations in the region r ≲ 20 AU.« less

Consequences of the pathogenic T9176C mutation of human mitochondrial DNA on yeast mitochondrial ATP synthase

PubMed Central

Kucharczyk, Roza; Ezkurdia, Nahia; Couplan, Elodie; Procaccio, Vincent; Ackerman, Sharon H.; Blondel, Marc; di Rago, Jean-Paul

2010-01-01

Summary Several human neurological disorders have been associated with various mutations affecting mitochondrial enzymes involved in cellular ATP production. One of these mutations, T9176C in the mitochondrial DNA (mtDNA), changes a highly conserved leucine residue into proline at position 217 of the mitochondrially encoded Atp6p (or a) subunit of the F1FO-ATP synthase. The consequences of this mutation on the mitochondrial ATP synthase are still poorly defined. To gain insight into the primary pathogenic mechanisms induced by T9176C, we have investigated the consequences of this mutation on the ATP synthase of yeast where Atp6p is also encoded by the mtDNA. In vitro, yeast atp6-T9176C mitochondria showed a 30% decrease in the rate of ATP synthesis. When forcing the F1FO complex to work in the reverse mode, i.e. F1-catalyzed hydrolysis of ATP coupled to proton transport out of the mitochondrial matrix, the mutant showed a normal proton-pumping activity and this activity was fully sensitive to oligomycin, an inhibitor of the ATP synthase proton channel. However, under conditions of maximal ATP hydrolytic activity, using non-osmotically protected mitochondria, the mutant ATPase activity was less efficiently inhibited by oligomycin (60% inhibition versus 85% for the wild type control). BN-PAGE analyses revealed that atp6-T9176C yeast accumulated rather good levels of fully assembled ATP synthase complexes. However, a number of subcomplexes (F1, Atp9p-ring, unassembled α-F1 subunits) could be detected as well, presumably because of a decreased stability of Atp6p within the ATP synthase. Although the oxidative phosphorylation capacity was reduced in atp6-T9176C yeast, the number of ATP molecules synthesized per electron transferred to oxygen was similar compared with wild type yeast. It can therefore be inferred that the coupling efficiency within the ATP synthase was mostly unaffected and that the T9176C mutation did not increase the proton permeability of the mitochondrial inner membrane. PMID:20056103

Proton Pump Inhibitors Inhibit Metformin Uptake by Organic Cation Transporters (OCTs)

PubMed Central

Nies, Anne T.; Hofmann, Ute; Resch, Claudia; Schaeffeler, Elke; Rius, Maria; Schwab, Matthias

2011-01-01

Metformin, an oral insulin-sensitizing drug, is actively transported into cells by organic cation transporters (OCT) 1, 2, and 3 (encoded by SLC22A1, SLC22A2, or SLC22A3), which are tissue specifically expressed at significant levels in various organs such as liver, muscle, and kidney. Because metformin does not undergo hepatic metabolism, drug-drug interaction by inhibition of OCT transporters may be important. So far, comprehensive data on the interaction of proton pump inhibitors (PPIs) with OCTs are missing although PPIs are frequently used in metformin-treated patients. Using in silico modeling and computational analyses, we derived pharmacophore models indicating that PPIs (i.e. omeprazole, pantoprazole, lansoprazole, rabeprazole, and tenatoprazole) are potent OCT inhibitors. We then established stably transfected cell lines expressing the human uptake transporters OCT1, OCT2, or OCT3 and tested whether these PPIs inhibit OCT-mediated metformin uptake in vitro. All tested PPIs significantly inhibited metformin uptake by OCT1, OCT2, and OCT3 in a concentration-dependent manner. Half-maximal inhibitory concentration values (IC50) were in the low micromolar range (3–36 µM) and thereby in the range of IC50 values of other potent OCT drug inhibitors. Finally, we tested whether the PPIs are also transported by OCTs, but did not identify PPIs as OCT substrates. In conclusion, PPIs are potent inhibitors of the OCT-mediated metformin transport in vitro. Further studies are needed to elucidate the clinical relevance of this drug-drug interaction with potential consequences on metformin disposition and/or efficacy. PMID:21779389

Bringing GERD Management up to PAR-2.

PubMed

Souza, Rhonda F

2010-09-01

Proton pump inhibitors (PPIs) are extremely effective for mucosal healing of reflux esophagitis, but less so for relieving the symptom of heartburn. PPIs block the secretion of gastric acid, the caustic effects of which have been assumed to be the primary culprit in the pathogenesis of reflux esophagitis. However, mounting data suggest that reflux-stimulated, immune-mediated mechanisms may underlie the development of esophagitis in patients with gastroesophageal reflux disease (GERD). Thus, the future of GERD therapy, particularly for patients who are refractory to PPIs, may be the targeting of proteins such as proteinase-activated receptor-2, which have central roles in the generation of immune-mediated esophageal mucosal damage and in eliciting the symptom of heartburn.

Glycolytic control of vacuolar-type ATPase activity: A mechanism to regulate influenza viral infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohio, Hinissan P.; Adamson, Amy L., E-mail: aladamso@uncg.edu

As new influenza virus strains emerge, finding new mechanisms to control infection is imperative. In this study, we found that we could control influenza infection of mammalian cells by altering the level of glucose given to cells. Higher glucose concentrations induced a dose-specific increase in influenza infection. Linking influenza virus infection with glycolysis, we found that viral replication was significantly reduced after cells were treated with glycolytic inhibitors. Addition of extracellular ATP after glycolytic inhibition restored influenza infection. We also determined that higher levels of glucose promoted the assembly of the vacuolar-type ATPase within cells, and increased vacuolar-type ATPase proton-transportmore » activity. The increase of viral infection via high glucose levels could be reversed by inhibition of the proton pump, linking glucose metabolism, vacuolar-type ATPase activity, and influenza viral infection. Taken together, we propose that altering glucose metabolism may be a potential new approach to inhibit influenza viral infection. - Highlights: • Increased glucose levels increase Influenza A viral infection of MDCK cells. • Inhibition of the glycolytic enzyme hexokinase inhibited Influenza A viral infection. • Inhibition of hexokinase induced disassembly the V-ATPase. • Disassembly of the V-ATPase and Influenza A infection was bypassed with ATP. • The state of V-ATPase assembly correlated with Influenza A infection of cells.« less

Intracellular Requirements for Passive Proton Transport through the Na+,K+-ATPase.

PubMed

Stanley, Kevin S; Meyer, Dylan J; Gatto, Craig; Artigas, Pablo

2016-12-06

The Na + ,K + -ATPase (NKA or Na/K pump) hydrolyzes one ATP to exchange three intracellular Na+ (Na + i ) for two extracellular K+ (K + o ) across the plasma membrane by cycling through a set of reversible transitions between phosphorylated and dephosphorylated conformations, alternately opening ion-binding sites externally (E2) or internally (E1). With subsaturating [Na + ] o and [K + ] o , the phosphorylated E2P conformation passively imports protons generating an inward current (I H ), which may be exacerbated in NKA-subunit mutations associated with human disease. To elucidate the mechanisms of I H , we studied the effects of intracellular ligands (transported ions, nucleotides, and beryllium fluoride) on I H and, for comparison, on transient currents measured at normal Na + o (Q Na ). Utilizing inside-out patches from Xenopus oocytes heterologously expressing NKA, we observed that 1) in the presence of Na + i , I H and Q Na were both activated by ATP, but not ADP; 2) the [Na + ] i dependence of I H in saturating ATP showed K 0.5,Na  = 1.8 ± 0.2 mM and the [ATP] dependence at saturating [Na + ] i yielded K 0.5,ATP  = 48 ± 11 μM (in comparison, Na + i -dependent Q Na yields K 0.5,Na  = 0.8 ± 0.2 mM and K 0.5,ATP  = 0.43 ± 0.03 μM; 3) ATP activated I H in the presence of K + i (∼15% of the I H observed in Na + i ) only when Mg 2+ i was also present; and 4) beryllium fluoride induced maximal I H  even in the absence of nucleotide. These data indicate that I H occurs when NKA is in an externally open E2P state with nucleotide bound, a conformation that can be reached through forward Na/K pump phosphorylation of E1, with Na + i and ATP, or by backward binding of K + i to E1, which drives the pump to the occluded E2(2K), where free P i (at the micromolar levels found in millimolar ATP solutions) promotes external release of occluded K + by backdoor NKA phosphorylation. Maximal I H through beryllium-fluorinated NKA indicates that this complex mimics ATP-bound E2P states. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

The role of the Serratia marcescens SdeAB multidrug efflux pump and TolC homologue in fluoroquinolone resistance studied via gene-knockout mutagenesis.

PubMed

Begic, Sanela; Worobec, Elizabeth A

2008-02-01

Serratia marcescens is a prominent opportunistic nosocomial pathogen resistant to several classes of antibiotics. The major mechanism for fluoroquinolone resistance in various Gram-negative pathogens is active efflux. Our group previously identified SdeAB, a resistance-nodulation-cell division (RND) efflux pump complex, and a TolC-like outer-membrane protein (HasF), which together mediate energy-dependent fluoroquinolone efflux. In addition, a regulatory protein-encoding gene in the upstream region of sdeAB was identified (sdeR) and found to be 40 % homologous to MarA, an Escherichia coli transcriptional regulator. To provide conclusive evidence as to the role of these components in S. marcescens, sdeB, hasF and sdeR deletion mutants were constructed. Suicide vectors were created and introduced via triparental mating into S. marcescens UOC-67 (wild-type) and, for sdeB and hasF, T-861 (clinical isolate). We have analysed these genetically altered strains using minimal inhibitory concentration (MIC) assays for a wide range of compounds (fluoroquinolones, SDS, novobiocin, ethidium bromide and chloramphenicol). Intracellular accumulation of a variety of fluoroquinolones was measured fluorospectroscopically. The sdeB, hasF and sdeR knockout strains were consistently more susceptible to antibiotics than the parent strains, with the sdeB/hasF double knockout strain showing the highest susceptibility. A marked increase in fluoroquinolone (ciprofloxacin) accumulation was observed for strains deficient in either the sdeB or hasF genes when compared to the parental strains, with the highest ciprofloxacin accumulation observed for the sdeB/hasF double knockout. Antibiotic accumulation assays for the sdeB knockout mutant strains performed in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP), a proton-motive-force inhibitor, demonstrated that SdeAB-mediated efflux is proton-motive-force dependent. Due to the comparable susceptibility of the sdeB and the hasF individual knockouts, we conclude that S. marcescens HasF is the sole outer-membrane component of the SdeAB pump. In addition, MIC data for sdeR-deficient and overexpressing strains confirm that SdeR is an activator of sdeAB and acts to enhance the overall multidrug resistance of S. marcescens.

Auxin effects on ion transport in Chara corallina.

PubMed

Zhang, Suyun; de Boer, Albertus H; van Duijn, Bert

2016-04-01

The plant hormone auxin has been widely studied with regard to synthesis, transport, signaling and functions among the land plants while there is still a lack of knowledge about the possible role for auxin regulation mechanisms in algae with "plant-like" structures. Here we use the alga Chara corallina as a model to study aspects of auxin signaling. In this respect we measured auxin on membrane potential changes and different ion fluxes (K(+), H(+)) through the plasma membrane. Results showed that auxin, mainly IAA, could hyperpolarize the membrane potential of C. corallina internodal cells. Ion flux measurements showed that the auxin-induced membrane potential change may be based on the change of K(+) permeability and/or channel activity rather than through the activation of proton pumps as known in land plants. Copyright © 2016 Elsevier GmbH. All rights reserved.

Potentiation of the gastric antisecretory activity of histamine H2-receptor antagonists by clebopride.

PubMed

Fernández, A G; Massingham, R; Roberts, D J

1988-05-01

The substituted benzamide, clebopride, at doses (0.03-3 mg kg-1 i.p.) that were without effect per se on the secretion of gastric acid in pylorus ligated (Shay) rats, potentiated the antisecretory effects of the histamine H2 receptor antagonists cimetidine and ranitidine in this model but not those of the muscarine receptor antagonist pirenzepine nor those of the proton pump inhibitor omeprazole. By contrast, clebopride was without influence on the inhibitory effects of cimetidine on pentagastrin-induced secretion in perfused stomach (Ghosh and Schild) preparations in anaesthetized rats. The significance of these findings is discussed in relation to the previously described potentiating effects of clebopride on the anti-ulcer activity of cimetidine in various experimental models, and the potential beneficial effects of such combined therapy in the clinic.

Investigation of evolution-related aspects of bacterial rhodopsins

NASA Technical Reports Server (NTRS)

1994-01-01

We have investigated evolution-related aspects of bacterial rhodopsins, the unique retinal-based energy transducing systems of halophilic archae. The approach was to describe both structural and functional aspects: the structure by sequencing genes to explore which regions are conserved, and the function by comparing proton and chloride transport in the closely related systems, bacteriorhodopsin and halorhodopsin, respectively. In the latter, we have made a good start toward the ultimate goal of separating the attributes of the general principles of retinal-based ionic pumps from those of the specific ion specificities, by determining the thermodynamics of the internal steps of the protein-mediated active transport process, as well as some of the intraprotein ion-transfer steps. Our present emphasis is on continuing to acquire the tools for studying what distinguishes proton transport from chloride transport. We consider it important, therefore, that we have been able to provide firm mathematical grounds for the kinetics analyses which underlies these studies. Our molecular biological studies have received a great boost from the expression vector for the bop gene based on a halobacterial plasmid, that we recently developed.

Unmet Needs in the Treatment of Gastroesophageal Reflux Disease

PubMed Central

Dickman, Ram; Maradey-Romero, Carla; Gingold-Belfer, Rachel; Fass, Ronnie

2015-01-01

Gastroesophageal reflux disease (GERD) is a highly prevalent gastrointestinal disorder. Proton pump inhibitors have profoundly revolutionized the treatment of GERD. However, several areas of unmet need persist despite marked improvements in the therapeutic management of GERD. These include the advanced grades of erosive esophagitis, nonerosive reflux disease, maintenance treatment of erosive esophagitis, refractory GERD, postprandial heartburn, atypical and extraesophageal manifestations of GERD, Barrett’s esophagus, chronic protein pump inhibitor treatment, and post-bariatric surgery GERD. Consequently, any future development of novel therapeutic modalities for GERD (medical, endoscopic, or surgical), would likely focus on the aforementioned areas of unmet need. PMID:26130628

ETFE polymer bombarded with 1 MeV proton

NASA Astrophysics Data System (ADS)

Parada, M. A.; de Almeida, A.; Muntele, I.; Muntele, C.; Delalez, N.; Ila, D.

2005-12-01

The ethylenetetrafluoroethylene (ETFE) is a polymer formed by alternating ethylene and tetrafluoroethylene segments. It has high impact resistance and useful mechanical properties. ETFE can be used as components of pumps, valves, tie wraps, and electrical components. It can also be applied in the field of medical physics as intra venous catheters and as radiation dosimeter. When a material is exposed to the ionizing radiation, it suffers damage that depends on the type, energy and intensity of the radiation. In order to determine the radiation damage mechanism, ETFE films were bombarded with 1 MeV protons to the fluence between 1 × 1011 and 1 × 1016 protons/cm2 and the chemical species emitted during the bombardment were measured with residual gas analysis (RGA) and show that HF gas is the entity preferentially emitted. Optical absorption photospectrometry (OAP) and attenuated total reflectometry fourier transform infrared (ATR-FTIR) shows quantitative chemical evidence of the damage. Our results show that damage is detectable at low proton fluence, but damage that can compromise the application in dosimetry occurs only for fluence greater than 1014 protons/cm2.

Two different forms of metarhodopsin II: Schiff base deprotonation precedes proton uptake and signaling state.

PubMed Central

Arnis, S; Hofmann, K P

1993-01-01

Rhodopsin is a retinal protein and a G-protein-coupled receptor; it shares with both of these families the seven helix structure. To generate the G-interacting helix-loop conformation, generally identified with the 380-nm absorbing metarhodopsin II (MII) photoproduct, the retinal Schiff base bond to the apoprotein must be deprotonated. This occurs as a key event also in the related retinal proteins, sensory rhodopsins, and the proton pump bacteriorhodopsin. In MII, proton uptake from the aqueous phase must be involved as well, since its formation increases the pH of the aqueous medium and is accelerated under acidic conditions. In the native membrane, the pH effect matches MII formation kinetically, suggesting that intramolecular and aqueous protonation changes contribute in concert to the protein transformation. We show here, however, that proton uptake, as indicated by bromocresol purple, and Schiff base deprotonation (380-nm absorption change) show different kinetics when the protein is solubilized in suitable detergents. Our data are consistent with a two-step reaction: Images Fig. 6 PMID:8356093

SNAPIN is critical for lysosomal acidification and autophagosome maturation in macrophages

PubMed Central

Shi, Bo; Huang, Qi-Quan; Birkett, Robert; Doyle, Renee; Dorfleutner, Andrea; Stehlik, Christian; He, Congcong; Pope, Richard M.

2017-01-01

ABSTRACT We previously observed that SNAPIN, which is an adaptor protein in the SNARE core complex, was highly expressed in rheumatoid arthritis synovial tissue macrophages, but its role in macrophages and autoimmunity is unknown. To identify SNAPIN's role in these cells, we employed siRNA to silence the expression of SNAPIN in primary human macrophages. Silencing SNAPIN resulted in swollen lysosomes with impaired CTSD (cathepsin D) activation, although total CTSD was not reduced. Neither endosome cargo delivery nor lysosomal fusion with endosomes or autophagosomes was inhibited following the forced silencing of SNAPIN. The acidification of lysosomes and accumulation of autolysosomes in SNAPIN-silenced cells was inhibited, resulting in incomplete lysosomal hydrolysis and impaired macroautophagy/autophagy flux. Mechanistic studies employing ratiometric color fluorescence on living cells demonstrated that the reduction of SNAPIN resulted in a modest reduction of H+ pump activity; however, the more critical mechanism was a lysosomal proton leak. Overall, our results demonstrate that SNAPIN is critical in the maintenance of healthy lysosomes and autophagy through its role in lysosome acidification and autophagosome maturation in macrophages largely through preventing proton leak. These observations suggest an important role for SNAPIN and autophagy in the homeostasis of macrophages, particularly long-lived tissue resident macrophages. PMID:27929705

A proton pump ATPase with testis-specific E1-subunit isoform required for acrosome acidification.

PubMed

Sun-Wada, Ge-Hong; Imai-Senga, Yoko; Yamamoto, Akitsugu; Murata, Yoshiko; Hirata, Tomoyuki; Wada, Yoh; Futai, Masamitsu

2002-05-17

The vacuolar-type H(+)-ATPases (V-ATPases) are a family of multimeric proton pumps involved in a wide variety of physiological processes. We have identified two novel mouse genes, Atp6e1 and Atp6e2, encoding testis-specific (E1) and ubiquitous (E2) V-ATPase subunit E isoforms, respectively. The E1 transcript appears about 3 weeks after birth, corresponding to the start of meiosis, and is expressed specifically in round spermatids in seminiferous tubules. Immunohistochemistry with isoform-specific antibodies revealed that the V-ATPase with E1 and a2 isoforms is located specifically in developing acrosomes of spermatids and acrosomes in mature sperm. In contrast, the E2 isoform was expressed in all tissues examined and present in the perinuclear compartments of spermatocytes. The E1 isoform exhibits 70% identity with the E2, and both isoforms functionally complemented a null mutation of the yeast counterpart VMA4, indicating that they are bona fide V-ATPase subunits. The chimeric enzymes showed slightly lower K(m)(ATP) than yeast V-ATPase. Consistent with the temperature-sensitive growth of Deltavma4-expressing E1 isoform, vacuolar membrane vesicles exhibited temperature-sensitive coupling between ATP hydrolysis and proton transport. These results suggest that E1 isoform is essential for energy coupling involved in acidification of acrosome.

Probing of high density plasmas using the multi-beam, high power TiSa laser system ARCTURUS

NASA Astrophysics Data System (ADS)

Willi, Oswald; Aktan, Esin; Brauckmann, Stephannie; Aurand, Bastian; Cerchez, Mirela; Prasad, Rajendra; Schroer, Anna Marie

2017-10-01

The understanding of relativistic laser plasma interaction at ultra-high intensities has advanced considerably during the last decade with the availability of multi-beam, high power TiSa laser systems. These laser systems allow pump-probe experiments to be carried out. The ARCTURUS laser at the University of Duesseldorf is ideally suited for various kinds of pump-probe experiments as it consists of two identical, high power beams with energies of 5J in 30 fs and a third beam for optical probing with energy of 30mJ in a 30fs pulse. All three beams are synchronised and have flexible time delays with respect to each other. Several different processes were studied where one of the beams was used as an interaction beam and the second one was incident on a thin solid gold foil to generate a proton beam. For example, thin foil targets were irradiated either with a linear or circular polarized pulse and probed with protons at different times. The expansion of foils for the two cases was clearly different consistent with numerical simulations. In addition, the interaction of gas targets was probed with protons and separately with an optical probe. With both diagnostics the formation of a channel was observed. In the presentation various two beam measurements will be discussed.

Transient Resonance Raman Spectroscopy of a Light-Driven Sodium-Ion-Pump Rhodopsin from Indibacter alkaliphilus.

PubMed

Kajimoto, Kousuke; Kikukawa, Takashi; Nakashima, Hiroki; Yamaryo, Haruki; Saito, Yuta; Fujisawa, Tomotsumi; Demura, Makoto; Unno, Masashi

2017-05-04

Sodium-ion-pump rhodopsin (NaR) is a microbial rhodopsin that transports Na + during its photocycle. Here we explore the photocycle mechanism of NaR from Indibacter alkaliphilus with transient absorption and transient resonance Raman spectroscopy. The transient absorption data indicate that the photocycle of NaR is K (545 nm) → L (490 nm)/M (420 nm) → O 1 (590 nm) → O 2 (560 nm) → NaR, where the L and M are formed as equilibrium states. The presence of K, L, M, and O intermediates was confirmed by the resonance Raman spectra with 442 and 532 nm excitation. The main component of the transient resonance Raman spectra was due to L which contains a 13-cis retinal protonated Schiff base. The presence of an enhanced hydrogen out-of-plane band as well as its sensitivity to the H/D exchange indicate that the retinal chromophore is distorted near the Schiff base region in L. Moreover, the retinal Schiff base of the L state forms a hydrogen bond that is stronger than that of the dark state. These observations are consistent with a Na + pumping mechanism that involves a proton transfer from the retinal Schiff base to a key aspartate residue (Asp116 in Krokinobacter eikastus rhodopsin 2) in the L/M states.

Evaluation of a Proton Pump Inhibitor for Sleep Bruxism: A Randomized Clinical Trial.

PubMed

Ohmure, H; Kanematsu-Hashimoto, K; Nagayama, K; Taguchi, H; Ido, A; Tominaga, K; Arakawa, T; Miyawaki, S

2016-12-01

Bruxism is a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or bracing or thrusting of the mandible. Recent advances have clarified the relationship between gastroesophageal reflux and sleep bruxism (SB). However, the influence of pharmacological elimination of gastric acid secretion on SB has not been confirmed. The authors aimed to assess the efficacy of a proton pump inhibitor (PPI) on SB and to examine the gastrointestinal (GI) symptoms and endoscopic findings of the upper GI tract in SB patients. The authors performed a randomized double-blind placebo-controlled crossover study at Kagoshima University Hospital. Twelve patients with polysomnography (PSG)-diagnosed SB underwent an assessment of GI symptoms using the frequency scale for the symptoms of gastroesophageal reflux disease (FSSG) and esophagogastroduodenoscopy. At baseline (i.e., before interventions), the mean frequencies of electromyography (EMG) bursts and rhythmic masticatory muscle activity (RMMA) episodes were 65.4 ± 49.0 bursts/h and 7.0 ± 4.8 episodes/h, respectively, and at least 1 RMMA episode with grinding noise was confirmed in all participants. The mean FSSG score was 8.4 ± 5.6, and 41.7% of patients were diagnosed with gastroesophageal reflux disease. Mild reflux esophagitis was confirmed in 6 patients. PSG, including EMG of the left masseter muscle and audio-video recording, was performed on days 4 and 5 of administration of 10 mg of the PPI (rabeprazole) or placebo. PPI administration yielded a significant reduction in the frequency of EMG bursts, RMMA episodes, and grinding noise. No significant differences were observed regarding the swallowing events and sleep variables. Since the clinical application of PPI for SB treatment should remain on hold at present, the results of this trial highlight the potential application of pharmacological gastroesophageal reflux disease treatment for SB patients. Larger scale studies are warranted to corroborate these findings. (UMIN Clinical Trials Registry: UMIN000004577). © International & American Associations for Dental Research 2016.

Genome-Guided Analysis of Clostridium ultunense and Comparative Genomics Reveal Different Strategies for Acetate Oxidation and Energy Conservation in Syntrophic Acetate-Oxidising Bacteria

PubMed Central

Manzoor, Shahid; Schnürer, Anna; Müller, Bettina

2018-01-01

Syntrophic acetate oxidation operates close to the thermodynamic equilibrium and very little is known about the participating organisms and their metabolism. Clostridium ultunense is one of the most abundant syntrophic acetate-oxidising bacteria (SAOB) that are found in engineered biogas processes operating with high ammonia concentrations. It has been proven to oxidise acetate in cooperation with hydrogenotrophic methanogens. There is evidence that the Wood-Ljungdahl (WL) pathway plays an important role in acetate oxidation. In this study, we analysed the physiological and metabolic capacities of C. ultunense strain Esp and strain BST on genome scale and conducted a comparative study of all the known characterised SAOB, namely Syntrophaceticus schinkii, Thermacetogenium phaeum, Tepidanaerobacter acetatoxydans, and Pseudothermotoga lettingae. The results clearly indicated physiological robustness to be beneficial for anaerobic digestion environments and revealed unexpected metabolic diversity with respect to acetate oxidation and energy conservation systems. Unlike S. schinkii and Th. phaeum, C. ultunense clearly does not employ the oxidative WL pathway for acetate oxidation, as its genome (and that of P. lettingae) lack important key genes. In both of those species, a proton motive force is likely formed by chemical protons involving putative electron-bifurcating [Fe-Fe] hydrogenases rather than proton pumps. No genes encoding a respiratory Ech (energy-converting hydrogenase), as involved in energy conservation in Th. phaeum and S. schinkii, were identified in C. ultunense and P. lettingae. Moreover, two respiratory complexes sharing similarities to the proton-translocating ferredoxin:NAD+ oxidoreductase (Rnf) and the Na+ pumping NADH:quinone hydrogenase (NQR) were predicted. These might form a respiratory chain that is involved in the reduction of electron acceptors rather than protons. However, involvement of these complexes in acetate oxidation in C. ultunense and P. lettingae needs further study. This genome-based comparison provides a solid platform for future meta-proteomics and meta-transcriptomics studies and for metabolic engineering, control, and monitoring of SAOB. PMID:29690652

Genome-Guided Analysis of Clostridium ultunense and Comparative Genomics Reveal Different Strategies for Acetate Oxidation and Energy Conservation in Syntrophic Acetate-Oxidising Bacteria.

PubMed

Manzoor, Shahid; Schnürer, Anna; Bongcam-Rudloff, Erik; Müller, Bettina

2018-04-23

Syntrophic acetate oxidation operates close to the thermodynamic equilibrium and very little is known about the participating organisms and their metabolism. Clostridium ultunense is one of the most abundant syntrophic acetate-oxidising bacteria (SAOB) that are found in engineered biogas processes operating with high ammonia concentrations. It has been proven to oxidise acetate in cooperation with hydrogenotrophic methanogens. There is evidence that the Wood-Ljungdahl (WL) pathway plays an important role in acetate oxidation. In this study, we analysed the physiological and metabolic capacities of C. ultunense strain Esp and strain BS T on genome scale and conducted a comparative study of all the known characterised SAOB, namely Syntrophaceticus schinkii , Thermacetogenium phaeum , Tepidanaerobacter acetatoxydans , and Pseudothermotoga lettingae . The results clearly indicated physiological robustness to be beneficial for anaerobic digestion environments and revealed unexpected metabolic diversity with respect to acetate oxidation and energy conservation systems. Unlike S. schinkii and Th. phaeum , C. ultunense clearly does not employ the oxidative WL pathway for acetate oxidation, as its genome (and that of P. lettingae ) lack important key genes. In both of those species, a proton motive force is likely formed by chemical protons involving putative electron-bifurcating [Fe-Fe] hydrogenases rather than proton pumps. No genes encoding a respiratory Ech (energy-converting hydrogenase), as involved in energy conservation in Th. phaeum and S. schinkii, were identified in C. ultunense and P. lettingae . Moreover, two respiratory complexes sharing similarities to the proton-translocating ferredoxin:NAD⁺ oxidoreductase (Rnf) and the Na⁺ pumping NADH:quinone hydrogenase (NQR) were predicted. These might form a respiratory chain that is involved in the reduction of electron acceptors rather than protons. However, involvement of these complexes in acetate oxidation in C. ultunense and P. lettingae needs further study. This genome-based comparison provides a solid platform for future meta-proteomics and meta-transcriptomics studies and for metabolic engineering, control, and monitoring of SAOB.

Evidence for a role in growth and salt resistance of a plasma membrane H+-ATPase in the root endodermis

NASA Technical Reports Server (NTRS)

Vitart, V.; Baxter, I.; Doerner, P.; Harper, J. F.; Evans, M. L. (Principal Investigator)

2001-01-01

The plasma membrane of plant cells is energized by an electrochemical gradient produced by P-type H+-ATPases (proton pumps). These pumps are encoded by at least 12 genes in Arabidopsis. Here we provide evidence that isoform AHA4 contributes to solute transport through the root endodermis. AHA4 is expressed most strongly in the root endodermis and flowers, as suggested by promoter-GUS reporter assays. A disruption of this pump (aha4-1) was identified as a T-DNA insertion in the middle of the gene (after VFP(574)). Truncated aha4-1 transcripts accumulate to approximately 50% of the level observed for AHA4 mRNA in wild-type plants. Plants homozygous for aha4-1 (-/-) show a subtle reduction in root and shoot growth compared with wild-type plants when grown under normal conditions. However, a mutant phenotype is very clear in plants grown under salt stress (e.g., 75 or 110 mM NaCl). In leaves of mutant plants subjected to Na stress, the ratio of Na to K increased 4-5-fold. Interestingly, the aha4-1 mutation appears to be semidominant and was only partially complemented by the introduction of additional wild-type copies of AHA4. These results are consistent with the hypothesis that aha4-1 may produce a dominant negative protein or RNA that partially disrupts the activity of other pumps or functions in the root endodermal tissue, thereby compromising the function of this cell layer in controlling ion homeostasis and nutrient transport.

Electrostatic coupling of ion pumps.

PubMed

Nieto-Frausto, J; Lüger, P; Apell, H J

1992-01-01

In this paper the electrostatic interactions between membrane-embedded ion-pumps and their consequences for the kinetics of pump-mediated transport processes have been examined. We show that the time course of an intrinsically monomolecular transport reaction can become distinctly nonexponential, if the reaction is associated with charge translocation and takes place in an aggregate of pump molecules. First we consider the electrostatic coupling of a single dimer of ion-pumps embedded in the membrane. Then we apply the treatment to the kinetic analysis of light-driven proton transport by bacteriorhodopsin which forms two-dimensional hexagonal lattices. Finally, for the case of nonordered molecules, we also consider a model in which the pumps are randomly distributed over the nodes of a lattice. Here the average distance is equal to that deduced experimentally and the elemental size of the lattice is the effective diameter of one single pump. This latter model is applied to an aggregate of membrane-embedded Na, K- and Ca-pumps. In all these cases the electrostatic potential considered is the exact solution calculated from the method of electrical images for a plane membrane of finite thickness immersed in an infinite aqueous solution environment. The distributions of charges (ions or charged binding sites) are considered homogeneous or discrete in the membrane and/or in the external solution. In the case of discrete distributions we compare the results from a mean field approximation and a stochastic simulation.

The energetics of the primary proton transfer in bacteriorhodopsin revisited: it is a sequential light-induced charge separation after all.

PubMed

Braun-Sand, Sonja; Sharma, Pankaz K; Chu, Zhen T; Pisliakov, Andrei V; Warshel, Arieh

2008-05-01

The light-induced proton transport in bacteriorhodopsin has been considered as a model for other light-induced proton pumps. However, the exact nature of this process is still unclear. For example, it is not entirely clear what the driving force of the initial proton transfer is and, in particular, whether it reflects electrostatic forces or other effects. The present work simulates the primary proton transfer (PT) by a specialized combination of the EVB and the QCFF/PI methods. This combination allows us to obtain sufficient sampling and a quantitative free energy profile for the PT at different protein configurations. The calculated profiles provide new insight about energetics of the primary PT and its coupling to the protein conformational changes. Our finding confirms the tentative analysis of an earlier work (A. Warshel, Conversion of light energy to electrostatic energy in the proton pump of Halobacterium halobium, Photochem. Photobiol. 30 (1979) 285-290) and determines that the overall PT process is driven by the energetics of the charge separation between the Schiff base and its counterion Asp85. Apparently, the light-induced relaxation of the steric energy of the chromophore leads to an increase in the ion-pair distance, and this drives the PT process. Our use of the linear response approximation allows us to estimate the change in the protein conformational energy and provides the first computational description of the coupling between the protein structural changes and the PT process. It is also found that the PT is not driven by twist-modulated changes of the Schiff base's pKa, changes in the hydrogen bond directionality, or other non-electrostatic effects. Overall, based on a consistent use of structural information as the starting point for converging free energy calculations, we conclude that the primary event should be described as a light-induced formation of an unstable ground state, whose relaxation leads to charge separation and to the destabilization of the ion-pair state. This provides the driving force for the subsequent PT steps.

Alpha-helical hydrophobic polypeptides form proton-selective channels in lipid bilayers

NASA Technical Reports Server (NTRS)

Oliver, A. E.; Deamer, D. W.

1994-01-01

Proton translocation is important in membrane-mediated processes such as ATP-dependent proton pumps, ATP synthesis, bacteriorhodopsin, and cytochrome oxidase function. The fundamental mechanism, however, is poorly understood. To test the theoretical possibility that bundles of hydrophobic alpha-helices could provide a low energy pathway for ion translocation through the lipid bilayer, polyamino acids were incorporated into extruded liposomes and planar lipid membranes, and proton translocation was measured. Liposomes with incorporated long-chain poly-L-alanine or poly-L-leucine were found to have proton permeability coefficients 5 to 7 times greater than control liposomes, whereas short-chain polyamino acids had relatively little effect. Potassium permeability was not increased markedly by any of the polyamino acids tested. Analytical thin layer chromatography measurements of lipid content and a fluorescamine assay for amino acids showed that there were approximately 135 polyleucine or 65 polyalanine molecules associated with each liposome. Fourier transform infrared spectroscopy indicated that a major fraction of the long-chain hydrophobic peptides existed in an alpha-helical conformation. Single-channel recording in both 0.1 N HCl and 0.1 M KCl was also used to determine whether proton-conducting channels formed in planar lipid membranes (phosphatidylcholine/phosphatidylethanolamine, 1:1). Poly-L-leucine and poly-L-alanine in HCl caused a 10- to 30-fold increase in frequency of conductive events compared to that seen in KCl or by the other polyamino acids in either solution. This finding correlates well with the liposome observations in which these two polyamino acids caused the largest increase in membrane proton permeability but had little effect on potassium permeability. Poly-L-leucine was considerably more conductive than poly-L-alanine due primarily to larger event amplitudes and, to a lesser extent, a higher event frequency. Poly-L-leucine caused two populations of conductive events, one in the 0.1-0.5 pA range, and one in the 1.0-5.0 pA range, whereas nearly all events caused by poly-L-alanine were in the 0.1-0.5 pA range at an applied voltage of +60 mV. The channel-like activity appeared to switch between conductive and nonconductive states, with most open-times in the range of 50-200 ms. We conclude that hydrophobic polyamino acids produce proton-conducting defects in lipid bilayers that may be used to model functional proton channels in biological membranes.

Cooperation through Competition-Dynamics and Microeconomics of a Minimal Nutrient Trade System in Arbuscular Mycorrhizal Symbiosis.

PubMed

Schott, Stephan; Valdebenito, Braulio; Bustos, Daniel; Gomez-Porras, Judith L; Sharma, Tripti; Dreyer, Ingo

2016-01-01

In arbuscular mycorrhizal (AM) symbiosis, fungi and plants exchange nutrients (sugars and phosphate, for instance) for reciprocal benefit. Until now it is not clear how this nutrient exchange system works. Here, we used computational cell biology to simulate the dynamics of a network of proton pumps and proton-coupled transporters that are upregulated during AM formation. We show that this minimal network is sufficient to describe accurately and realistically the nutrient trade system. By applying basic principles of microeconomics, we link the biophysics of transmembrane nutrient transport with the ecology of organismic interactions and straightforwardly explain macroscopic scenarios of the relations between plant and AM fungus. This computational cell biology study allows drawing far reaching hypotheses about the mechanism and the regulation of nutrient exchange and proposes that the "cooperation" between plant and fungus can be in fact the result of a competition between both for the same resources in the tiny periarbuscular space. The minimal model presented here may serve as benchmark to evaluate in future the performance of more complex models of AM nutrient exchange. As a first step toward this goal, we included SWEET sugar transporters in the model and show that their co-occurrence with proton-coupled sugar transporters results in a futile carbon cycle at the plant plasma membrane proposing that two different pathways for the same substrate should not be active at the same time.

Differences in the phenotypic effects of mutations in homologous MrpA and MrpD subunits of the multi-subunit Mrp-type Na+/H+ antiporter.

PubMed

Morino, Masato; Ogoda, Shinichiro; Krulwich, Terry Ann; Ito, Masahiro

2017-01-01

Mrp antiporters are the sole antiporters in the Cation/Proton Antiporter 3 family of transporter databases because of their unusual structural complexity, 6-7 hydrophobic proteins that function as a hetero-oligomeric complex. The two largest and homologous subunits, MrpA and MrpD, are essential for antiport activity and have direct roles in ion transport. They also show striking homology with proton-conducting, membrane-embedded Nuo subunits of respiratory chain complex I of bacteria, e.g., Escherichia coli. MrpA has the closest homology to the complex I NuoL subunit and MrpD has the closest homology to the complex I NuoM and N subunits. Here, introduction of mutations in MrpD, in residues that are also present in MrpA, led to defects in antiport function and/or complex formation. No significant phenotypes were detected in strains with mutations in corresponding residues of MrpA, but site-directed changes in the C-terminal region of MrpA had profound effects, showing that the MrpA C-terminal region has indispensable roles in antiport function. The results are consistent with a divergence in adaptations that support the roles of MrpA and MrpD in secondary antiport, as compared to later adaptations supporting homologs in primary proton pumping by the respiratory chain complex I.

Inhibitory action of lansoprazole and its analogs against Helicobacter pylori: inhibition of growth is not related to inhibition of urease.

PubMed Central

Nagata, K; Takagi, E; Tsuda, M; Nakazawa, T; Satoh, H; Nakao, M; Okamura, H; Tamura, T

1995-01-01

The proton pump inhibitors omeprazole and lansoprazole and its acid-activated derivative AG-2000, which are potent and specific inhibitors of urease of Helicobacter pylori (K. Nagata, H. Satoh, T. Iwahi, T. Shimoyama, and T. Tamura, Antimicrob. Agents Chemother. 37:769-774, 1993), inhibited the growth of H. pylori. The growth was inhibited not only in urease-positive clinical isolates but also in their urease-negative derivatives which had no urease polypeptides. AG-1789, a derivative of lansoprazole with no inhibitory activity against H. pylori urease, also inhibited the growth of both strains even more strongly than the urease inhibitors lansoprazole and AG-2000. Furthermore, the antibacterial activity of omeprazole and lansoprazole was not affected by glutathione or dithiothreitol, which completely abolished the inhibitory activity of lansoprazole against H. pylori urease. These results indicated that the inhibitory action of these compounds against the growth of H. pylori was independent from the inhibitory action against urease. PMID:7726537

The effect of a genetically reduced plasma membrane protonmotive force on vegetative growth of Arabidopsis.

PubMed

Haruta, Miyoshi; Sussman, Michael R

2012-03-01

The plasma membrane proton gradient is an essential feature of plant cells. In Arabidopsis (Arabidopsis thaliana), this gradient is generated by the plasma membrane proton pump encoded by a family of 11 genes (abbreviated as AHA, for Arabidopsis H(+)-ATPase), of which AHA1 and AHA2 are the two most predominantly expressed in seedlings and adult plants. Although double knockdown mutant plants containing T-DNA insertions in both genes are embryonic lethal, under ideal laboratory growth conditions, single knockdown mutant plants with a 50% reduction in proton pump concentration complete their life cycle without any observable growth alteration. However, when grown under conditions that induce stress on the plasma membrane protonmotive force (PMF), such as high external potassium to reduce the electrical gradient or high external pH to reduce the proton chemical gradient, aha2 mutant plants show a growth retardation compared with wild-type plants. In this report, we describe the results of studies that examine in greater detail AHA2's specific role in maintaining the PMF during seedling growth. By comparing the wild type and aha2 mutants, we have measured the effects of a reduced PMF on root and hypocotyl growth, ATP-induced skewed root growth, and rapid cytoplasmic calcium spiking. In addition, genome-wide gene expression profiling revealed the up-regulation of potassium transporters in aha2 mutants, indicating, as predicted, a close link between the PMF and potassium uptake at the plasma membrane. Overall, this characterization of aha2 mutants provides an experimental and theoretical framework for investigating growth and signaling processes that are mediated by PMF-coupled energetics at the cell membrane.

Cariporide and other new and powerful NHE1 inhibitors as potentially selective anticancer drugs – an integral molecular/biochemical/metabolic/clinical approach after one hundred years of cancer research

PubMed Central

2013-01-01

In recent years an increasing number of publications have emphasized the growing importance of hydrogen ion dynamics in modern cancer research, from etiopathogenesis and treatment. A proton [H+]-related mechanism underlying the initiation and progression of the neoplastic process has been recently described by different research groups as a new paradigm in which all cancer cells and tissues, regardless of their origin and genetic background, have a pivotal energetic and homeostatic disturbance of their metabolism that is completely different from all normal tissues: an aberrant regulation of hydrogen ion dynamics leading to a reversal of the pH gradient in cancer cells and tissues (↑pHi/↓pHe, or “proton reversal”). Tumor cells survive their hostile microenvironment due to membrane-bound proton pumps and transporters, and their main defensive strategy is to never allow internal acidification because that could lead to their death through apoptosis. In this context, one of the primary and best studied regulators of both pHi and pHe in tumors is the Na+/H+ exchanger isoform 1 (NHE1). An elevated NHE1 activity can be correlated with both an increase in cell pH and a decrease in the extracellular pH of tumors, and such proton reversal is associated with the origin, local growth, activation and further progression of the metastatic process. Consequently, NHE1 pharmaceutical inhibition by new and potent NHE1 inhibitors represents a potential and highly selective target in anticancer therapy. Cariporide, being one of the better studied specific and powerful NHE1 inhibitors, has proven to be well tolerated by humans in the cardiological context, however some side-effects, mainly related to drug accumulation and cerebrovascular complications were reported. Thus, cariporide could become a new, slightly toxic and effective anticancer agent in different human malignancies. PMID:24195657