Skeletal muscle expresses the extracellular cyclic AMP–adenosine pathway

PubMed Central

Chiavegatti, T; Costa, V L; Araújo, M S; Godinho, R O

2007-01-01

Background and purpose: cAMP is a key intracellular signalling molecule that regulates multiple processes of the vertebrate skeletal muscle. We have shown that cAMP can be actively pumped out from the skeletal muscle cell. Since in other tissues, cAMP efflux had been associated with extracellular generation of adenosine, in the present study we have assessed the fate of interstitial cAMP and the existence of an extracellular cAMP-adenosine signalling pathway in skeletal muscle. Experimental approach: cAMP efflux and/or its extracellular degradation were analysed by incubating rat cultured skeletal muscle with exogenous cAMP, forskolin or isoprenaline. cAMP and its metabolites were quantified by radioassay or HPLC, respectively. Key results: Incubation of cells with exogenous cAMP was followed by interstitial accumulation of 5′-AMP and adenosine, a phenomenon inhibited by selective inhibitors of ecto-phosphodiesterase (DPSPX) and ecto-nucleotidase (AMPCP). Activation of adenylyl cyclase (AC) in cultured cells with forskolin or isoprenaline increased cAMP efflux and extracellular generation of 5′-AMP and adenosine. Extracellular cAMP-adenosine pathway was also observed after direct and receptor-dependent stimulation of AC in rat extensor muscle ex vivo. These events were attenuated by probenecid, an inhibitor of ATP binding cassette family transporters. Conclusions and implications: Our results show the existence of an extracellular biochemical cascade that converts cAMP into adenosine. The functional relevance of this extracellular signalling system may involve a feedback modulation of cellular response initiated by several G protein-coupled receptor ligands, amplifying cAMP influence to a paracrine mode, through its metabolite, adenosine. PMID:18157164

Dibutyryl Adenosine Cyclic 3′:5′-Monophosphate Effects on Goldfish Behavior and Brain RNA Metabolism

PubMed Central

Shashoua, Victor E.

1971-01-01

Intraventricular administration of dibutyryl adenosine cyclic 3′:5′-monophosphate into goldfish brains produced hyperactive animals. A study of the effects of the drug (25-50 mg/kg) on the incorporation of [5-3H] orotic acid, as a precursor of labeled uridine and cytidine, into newly synthesized RNA showed the formation of an RNA with a uridine to cytidine ratio 20-50% higher than that of the control. In double-labeling experiments with uridine as the labeled precursor, the synthesis of a nuclear RNA fraction (not produced in the absence of drug) was demonstrated. Some of this RNA was found to migrate into the cytoplasmic fraction and to become associated with polysomes. The results suggest that cyclic AMP might function as a “metabolic demand signal” for eliciting new RNA synthesis in goldfish brain. PMID:4330944

Activation of Cyclic Adenosine Monophosphate Pathway Increases the Sensitivity of Cancer Cells to the Oncolytic Virus M1.

PubMed

Li, Kai; Zhang, Haipeng; Qiu, Jianguang; Lin, Yuan; Liang, Jiankai; Xiao, Xiao; Fu, Liwu; Wang, Fang; Cai, Jing; Tan, Yaqian; Zhu, Wenbo; Yin, Wei; Lu, Bingzheng; Xing, Fan; Tang, Lipeng; Yan, Min; Mai, Jialuo; Li, Yuan; Chen, Wenli; Qiu, Pengxin; Su, Xingwen; Gao, Guangping; Tai, Phillip W L; Hu, Jun; Yan, Guangmei

2016-02-01

Oncolytic virotherapy is a novel and emerging treatment modality that uses replication-competent viruses to destroy cancer cells. Although diverse cancer cell types are sensitive to oncolytic viruses, one of the major challenges of oncolytic virotherapy is that the sensitivity to oncolysis ranges among different cancer cell types. Furthermore, the underlying mechanism of action is not fully understood. Here, we report that activation of cyclic adenosine monophosphate (cAMP) signaling significantly sensitizes refractory cancer cells to alphavirus M1 in vitro, in vivo, and ex vivo. We find that activation of the cAMP signaling pathway inhibits M1-induced expression of antiviral factors in refractory cancer cells, leading to prolonged and severe endoplasmic reticulum (ER) stress, and cell apoptosis. We also demonstrate that M1-mediated oncolysis, which is enhanced by cAMP signaling, involves the factor, exchange protein directly activated by cAMP 1 (Epac1), but not the classical cAMP-dependent protein kinase A (PKA). Taken together, cAMP/Epac1 signaling pathway activation inhibits antiviral factors and improves responsiveness of refractory cancer cells to M1-mediated virotherapy.

A short review on structure and role of cyclic-3',5'-adenosine monophosphate-specific phosphodiesterase 4 as a treatment tool.

PubMed

Eskandari, Nahid; Mirmosayyeb, Omid; Bordbari, Gazaleh; Bastan, Reza; Yousefi, Zahra; Andalib, Alireza

2015-01-01

Cyclic nucleotide phosphodiesterases (PDEs) are known as a super-family of enzymes which catalyze the metabolism of the intracellular cyclic nucleotides, cyclic-3',5'-adenosine monophosphate (cAMP), and cyclic-3',5'-guanosine monophosphate that are expressed in a variety of cell types that can exert various functions based on their cells distribution. The PDE4 family has been the focus of vast research efforts over recent years because this family is considered as a prime target for therapeutic intervention in a number of inflammatory diseases such as asthma, chronic obstructive pulmonary disease, and rheumatoid arthritis, and it should be used and researched by pharmacists. This is because the major isoform of PDE that regulates inflammatory cell activity is the cAMP-specific PDE, PDE4. This review discusses the relationship between PDE4 and its inhibitor drugs based on structures, cells distribution, and pharmacological properties of PDE4 which can be informative for all pharmacy specialists.

Role of 2',3'-cyclic nucleotide 3'-phosphodiesterase in the renal 2',3'-cAMP-adenosine pathway.

PubMed

Jackson, Edwin K; Gillespie, Delbert G; Mi, Zaichuan; Cheng, Dongmei; Bansal, Rashmi; Janesko-Feldman, Keri; Kochanek, Patrick M

2014-07-01

Energy depletion increases the renal production of 2',3'-cAMP (a positional isomer of 3',5'-cAMP that opens mitochondrial permeability transition pores) and 2',3'-cAMP is converted to 2'-AMP and 3'-AMP, which in turn are metabolized to adenosine. Because the enzymes involved in this "2',3'-cAMP-adenosine pathway" are unknown, we examined whether 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) participates in the renal metabolism of 2',3'-cAMP. Western blotting and real-time PCR demonstrated expression of CNPase in rat glomerular mesangial, preglomerular vascular smooth muscle and endothelial, proximal tubular, thick ascending limb and collecting duct cells. Real-time PCR established the expression of CNPase in human glomerular mesangial, proximal tubular and vascular smooth muscle cells; and the level of expression of CNPase was greater than that for phosphodiesterase 4 (major enzyme for the metabolism of 3',5'-cAMP). Overexpression of CNPase in rat preglomerular vascular smooth muscle cells increased the metabolism of exogenous 2',3'-cAMP to 2'-AMP. Infusions of 2',3'-cAMP into isolated CNPase wild-type (+/+) kidneys increased renal venous 2'-AMP, and this response was diminished by 63% in CNPase knockout (-/-) kidneys, whereas the conversion of 3',5'-cAMP to 5'-AMP was similar in CNPase +/+ vs. -/- kidneys. In CNPase +/+ kidneys, energy depletion (metabolic poisons) increased kidney tissue levels of adenosine and its metabolites (inosine, hypoxanthine, xanthine, and uric acid) without accumulation of 2',3'-cAMP. In contrast, in CNPase -/- kidneys, energy depletion increased kidney tissue levels of 2',3'-cAMP and abolished the increase in adenosine and its metabolites. In conclusion, kidneys express CNPase, and renal CNPase mediates in part the renal 2',3'-cAMP-adenosine pathway. Copyright © 2014 the American Physiological Society.

A conjugate of decyltriphenylphosphonium with plastoquinone can carry cyclic adenosine monophosphate, but not cyclic guanosine monophosphate, across artificial and natural membranes.

PubMed

Firsov, Alexander M; Rybalkina, Irina G; Kotova, Elena A; Rokitskaya, Tatyana I; Tashlitsky, Vadim N; Korshunova, Galina A; Rybalkin, Sergei D; Antonenko, Yuri N

2018-02-01

The present study demonstrated for the first time the interaction between adenosine 3',5'-cyclic monophosphate (cAMP), one of the most important signaling compounds in living organisms, and the mitochondria-targeted antioxidant plastoquinonyl-decyltriphenylphosphonium (SkQ1). The data obtained on model liquid membranes and human platelets revealed the ability of SkQ1 to selectively transport cAMP, but not guanosine 3',5'-cyclic monophosphate (cGMP), across both artificial and natural membranes. In particular, SkQ1 elicited translocation of cAMP from the source to the receiving phase of a Pressman-type cell, while showing low activity with cGMP. Importantly, only conjugate with plastoquinone, but not dodecyl-triphenylphosphonium, was effective in carrying cAMP. In human platelets, SkQ1 also appeared to serve as a carrier of cAMP, but not cGMP, from outside to inside the cell, as measured by phosphorylation of the vasodilator stimulated phosphoprotein. The SkQ1-induced transfer of cAMP across the plasma membrane found here can be tentatively suggested to interfere with cAMP signaling pathways in living cells. Copyright © 2017 Elsevier B.V. All rights reserved.

Regulation of cyclic adenosine monophosphate response element binding protein on renin expression in kidney via complex cyclic adenosine monophosphate response element-binding-protein-binding protein/P300 recruitment.

PubMed

Li, Pei; Zhang, Jing; Zhu, Yuanfang; Liu, Ming; Xuan, Jin

2015-11-01

Renin synthesis and release is the rate-limiting step in the renin-angiotensin system, because cyclic adenosine monophosphate (cAMP) has been identified as dominant pathway for renin gene expression, and cAMP response element-binding protein (CREB) is found in the human and mouse renin promoter. This study aimed to evaluate the role of CREB in expression of the renin gene. We created conditional deletion of CREB in mice with low-sodium diet, specifically in renin cells of the kidney. To assess the effect of CREB on renin expression, immunostaining of renin was used in samples from wild-type mice and mice with gene knock-down of CREB. Cyclic AMP response element-binding-protein-binding protein (CBP) and p300 were measured in cultured renin cells of the mice, and RNA detection was done with real-time polymerase chain reaction. With low-sodium diet, renin was expressed along the whole wall of the afferent glomerular arterioles in wild-type mice, while there was no increase or even decrease in renin expression in CREB-specific deletion mice; RNA level of renin in cultured cells decreased by 50% with single knock-down of CREB, CBP, or p300, and decreased 70% with triple knock-down of CREB, CBP, and p300. This study found that CREB was important for renin synthesis and the role of CREB can be achieved through the recruitment of co-activators CBP and p300.

Synthesis and Release of Cyclic Adenosine 3′:5′-Monophosphate by Ochromonas malhamensis1

PubMed Central

Bressan, Ray A.; Handa, Avtar K.; Quader, Hartmut; Filner, Philip

1980-01-01

The chrysophycean alga, Ochromonas malhamensis Pringsheim, was shown to synthesize cyclic adenosine 3′:5′-monophosphate (cAMP) and to release it into the culture medium. Cells contained 3 to 3,000 picomoles per gram fresh weight; medium contained up to 20 times the amount in the cells. Putative [32P]cAMP was purified from cultures supplied [32P]phosphate. The compound was identified as [32P]cAMP by co-chromatography with authentic cAMP through 10 serial steps; by chemical deamination at the same rate as authentic cAMP, to a 32P compound with the chromatographic behavior of cIMP; and by its conversion through the action of cyclic nucleotide phosphodiesterase to a 32P compound with the chromatographic behavior of 5′-AMP. A two-step procedure involving chromatography on alumina and on Dowex 50 purified the unlabeled compound from cells or medium sufficiently for it to be assayable by competitive inhibition of binding of [3H]cAMP to cAMP-binding protein (Gilman assay) or by stimulation of cAMP-dependent protein kinase. The activity was destroyed by cyclic nucleotide phosphodiesterase with the same kinetics as authentic cAMP, provided that an endogenous inhibitor of the phosphodiesterase was first removed by an additional purification step. Images PMID:16661154

Cyclic Adenosine Monophosphate Regulation of Ion Transport in Porcine Vocal Fold Mucosae

PubMed Central

Sivasankar, Mahalakshmi; Nofziger, Charity; Blazer-Yost, Bonnie

2012-01-01

Objectives/Hypothesis Cyclic adenosine monophosphate (cAMP) is an important biological molecule that regulates ion transport and inflammatory responses in epithelial tissue. The present study examined whether the adenylyl cyclase activator, forskolin, would increase cAMP concentration in porcine vocal fold mucosa and whether the effects of increased cAMP would be manifested as a functional increase in transepithelial ion transport. Additionally, changes in cAMP concentrations following exposure to an inflammatory mediator, tumor necrosis factor-α (TNFα) were investigated. Study Design In vitro experimental design with matched treatment and control groups. Methods Porcine vocal fold mucosae (N = 30) and tracheal mucosae (N = 20) were exposed to forskolin, TNFα, or vehicle (dimethyl sulfoxide) treatment. cAMP concentrations were determined with enzyme-linked immunosorbent assay. Ion transport was measured using electrophysiological techniques. Results Thirty minute exposure to forskolin significantly increased cAMP concentration and ion transport in porcine vocal fold and tracheal mucosae. However, 30-minute and 2-hour exposure to TNFα did not significantly alter cAMP concentration. Conclusions We demonstrate that forskolin-sensitive adenylyl cyclase is present in vocal fold mucosa, and further, that the product, cAMP increases vocal fold ion transport. The results presented here contribute to our understanding of the intracellular mechanisms underlying vocal fold ion transport. As ion transport is important for maintaining superficial vocal fold hydration, data demonstrating forskolin-stimulated ion transport in vocal fold mucosa suggest opportunities for developing pharmacological treatments that increase surface hydration. PMID:18596479

Cyclic 3',5'-adenosine monophosphate (cAMP) signaling in the anterior pituitary gland in health and disease.

PubMed

Hernández-Ramírez, Laura C; Trivellin, Giampaolo; Stratakis, Constantine A

2018-03-05

The cyclic 3',5'-adenosine monophosphate (cAMP) was the first among the so-called "second messengers" to be described. It is conserved in most organisms and functions as a signal transducer by mediating the intracellular effects of multiple hormones and neurotransmitters. In this review, we first delineate how different members of the cAMP pathway ensure its correct compartmentalization and activity, mediate the terminal intracellular effects, and allow the crosstalk with other signaling pathways. We then focus on the pituitary gland, where cAMP exerts a crucial function by controlling the responsiveness of the cells to hypothalamic hormones, neurotransmitters and peripheral factors. We discuss the most relevant physiological functions mediated by cAMP in the different pituitary cell types, and summarize the defects affecting this pathway that have been reported in the literature. We finally discuss how a deregulated cAMP pathway is involved in the pathogenesis of pituitary disorders and how it affects the response to therapy. Copyright © 2017. Published by Elsevier B.V.

Benzodiazepines modulate the A2 adenosine binding sites on 108CC15 neuroblastoma X glioma hybrid cells.

PubMed Central

Snell, C. R.; Snell, P. H.

1984-01-01

We have demonstrated high affinity diazepam binding sites of the Ro5-4864 benzodiazepine receptor subtype on 108CC15 neuroblastoma X glioma hybrid cells. These cells were previously shown to have purinoceptors of the A2 adenosine subtype and we have now found that [3H]-adenosine can be displaced from this binding site by the benzodiazepines and related compounds that can also bind to the Ro5-4864 site. Diazepam was found to have no intrinsic activity at the A2-receptor as measured by the stimulation of adenosine 3':5'-cyclic monophosphate (cyclic AMP) production in this cell line. At concentrations sufficient to compete for the A2-receptor, diazepam was shown to facilitate, by approximately 2 fold, the stimulation of cyclic AMP by adenosine. These effects are not due to inhibition of adenosine uptake or phosphodiesterase activity, but are probably a consequence of modulation of the coupling of the A2-receptor to cyclic AMP production in this hybrid cell line. PMID:6150742

Metabolic control mechanisms in mammalian systems. Involvement of adenosine 3′:5′-cyclic monophosphate in androgen action

PubMed Central

Singhal, Radhey L.; Parulekar, M. R.; Vijayvargiya, R.; Robison, G. Alan

1971-01-01

1. The ability of exogenously administered cyclic AMP (adenosine 3′:5′-monophosphate) to exert andromimetic action on certain carbohydrate-metabolizing enzymes was investigated in the rat prostate gland and seminal vesicles. 2. Cyclic AMP, when injected concurrently with theophylline, produced marked increases in hexokinase, phosphofructokinase, glyceraldehyde phosphate dehydrogenase, pyruvate kinase, and two hexose monophosphate-shunt enzymes, as well as α-glycerophosphate dehydrogenase activity in accessory sexual tissues of castrated rats. The 6-N,2′-O-dibutyryl analogue of cyclic AMP caused increases of enzyme activity that were greater than those induced by the parent compound. 3. Time-course studies demonstrated that, whereas significant increases in the activities of most enzymes occurred within 4h after the injection of cyclic AMP, maximal increases were attained at 16–24h. 4. Increase in the activity of the various prostatic and vesicular enzymes was dependent on the dose of cyclic AMP; in most instances, 2.5mg of the cyclic nucleotide/rat was sufficient to elicit a statistically significant response. 5. Administration of cyclic AMP and theophylline also produced stimulation of enzyme activities in secondary sexual tissues of immature rats. 6. Cyclic AMP and theophylline did not affect significantly any of the enzymes studied in hepatic tissue. 7. Stimulation of various carbohydrate-metabolizing enzymes in the prostate gland and seminal vesicles by cyclic AMP was independent of adrenal function. 8. Concurrent treatment with actinomycin or cycloheximide prevented the cyclic AMP- and theophylline-induced increases in enzyme activities in both castrated and adrenalectomized–castrated animals. 9. Administration of a single dose of testosterone propionate (5.0mg/100g) to castrated rats caused a significant increase in cyclic AMP concentration in both accessory sexual tissues. 10. In addition, treatment with theophylline potentiated the effects of a

Cyclic adenosine monophosphate modulates cell morphology and behavior of a cultured renal epithelial.

PubMed

Amsler, K

1990-07-01

The role of cyclic adenosine monophosphate (cAMP) dependent protein kinase (PKA) in modulating functions of differentiated renal cells is well established. Its importance in controlling their growth and differentiation is less clear. We have used somatic cell genetic techniques to probe the role of PKA in controlling morphology and behavior of a renal epithelial cell line, LLC-PK1, which acquires many properties characteristic of the renal proximal tubular cell. Mutants of this line altered in PKA activity have been isolated and their behavior compared to that of the parent line. The results indicate that PKA is involved, either directly or indirectly, in maintenance of cell morphology, cell-cell and cell-substratum interactions, density-dependent growth regulation, and expression of one function characteristic of the renal proximal tubular cell, Na-hexose symport. The relevance of these results to the role of PKA in controlling growth and differentiation of renal epithelial cells in vivo is discussed.

Effect of dibutyryl cyclic adenosine monophosphate on the gene expression of plasminogen activator inhibitor-1 and tissue factor in adipocytes.

PubMed

Taniguchi, Makoto; Ono, Naoko; Hayashi, Akira; Yakura, Yuwna; Takeya, Hiroyuki

2011-10-01

Hypertrophic adipocytes in obese states express the elevated levels of plasminogen activator inhibitor-1 (PAI-1) and tissue factor (TF). An increase in the intracellular concentration of cyclic adenosine monophosphate (cAMP) promotes triglyceride hydrolysis and may improve dysregulation of adipocyte metabolism. Here, we investigate the effect of dibutyryl-cAMP (a phosphodiesterase-resistant analog of cAMP) on the gene expression of PAI-1 and TF in adipocytes. Differentiated 3T3-L1 adipocytes were treated with dibutyryl-cAMP and agents that would be expected to elevate intracellular cAMP, including cilostazol (a phosphodiesterase inhibitor with anti-platelet and vasodilatory properties), isoproterenol (a beta adrenergic agonist) and forskolin (an adenylyl cyclase activator). The levels of PAI-1 and TF mRNAs were measured using real-time quantitative reverse transcription-PCR. The treatment of adipocytes with dibutyryl-cAMP resulted in the inhibition of both lipid accumulation and TF gene expression. However, PAI-1 gene expression was slightly but significantly increased by dibutyryl-cAMP. On the other hand, cilostazol inhibited the expression of PAI-1 without affecting lipid accumulation. When the adipocytes were treated with cilostazol in combination with isoproterenol or forskolin, the inhibitory effect of cilostazol on PAI-1 gene expression was counteracted, thus suggesting that inhibition by cilostazol may not be the result of intracellular cAMP accumulation by phosphodiesterase inhibition. These results suggest the implication of cAMP in regulation of the gene expression of TF and PAI-1 in adipocytes. Our findings will serve as a useful basis for further research in therapy for obesity-associated thrombosis. Copyright © 2011 Elsevier Ltd. All rights reserved.

Gonadotropin stimulation of cyclic adenosine monophosphate and testosterone production without detectable high-affinity binding sites in purified Leydig cells from rat testis

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

Browne, E.S.; Bhalla, V.K.

1991-02-01

Rat testicular interstitial cells were separated by three different gradient-density procedures and, with each, two biochemically and morphologically distinct cell fractions were isolated. The lighter density cells in fraction-I bound iodine 125-labeled human chorionic gonadotropin (hCG) with high-affinity (apparent equilibrium dissociation constant, Kd, approximately 10{sup {minus} 10} M) without producing either cyclic adenosine monophosphate or testosterone in response to hormone action. The heavier-density cells displayed morphologic features typical of Leydig cells and produced cyclic adenosine monophosphate and testosterone in the presence of hCG without detectable {sup 125}I-labeled hCG high-affinity binding. These cell fractions were further characterized by studies using deglycosylatedmore » hCG, a known antagonist to hCG action. Cell concentration-dependent studies with purified Leydig cells revealed that maximal testosterone production was achieved when lower cell concentrations (0.5 x 10(6) cells/250 microliters) were used for in vitro hCG stimulation assays. Under these conditions, the {sup 125}I-labeled hCG binding was barely detectable (2.24 fmol; 2,698 sites/cell). Furthermore, these studies revealed that the hCG-specific binding in Leydig cells is overestimated by the classic method for nonspecific binding correction using excess unlabeled hormone. An alternate method is presented.« less

Further studies on the effect of adenosine cyclic monophosphate derivatives on cell proliferation in the jejunal crypts of rat.

PubMed

Tutton, P J; Barkla, D H

1982-01-01

1. Cell proliferation in the jejunal crypt epithelium of rat was measured using a stathmokinetic technique. 2. Sodium butyrate was found to promote jejunal crypt cell proliferation. 3. N6, O2'-Dibutyryl cyclic adenosine monophosphate (cAMP), N6-monobutyryl-cAMP and N6-monobutyryl-8-bromo-cAMP were found to inhibit cell proliferation when compared to sodium butyrate treated tissues. 4. 8-Chlorophenylthio-cAMP was found to inhibit cell division when compared to untreated animals. 5. O2'-Monobutyryl cAMP and 8-bromo-cAMP were not found to inhibit cell proliferation.

Cyclic nucleotide content of tobacco BY-2 cells.

PubMed

Richards, Helen; Das, Swadipa; Smith, Christopher J; Pereira, Louisa; Geisbrecht, Alan; Devitt, Nicola J; Games, David E; van Geyschem, Jan; Gareth Brenton, A; Newton, Russell P

2002-11-01

The cyclic nucleotide content of cultured tobacco bright yellow-2 (BY-2) cells was determined, after freeze-killing, perchlorate extraction and sequential chromatography, by radioimmunoassay. The identities of the putative cyclic nucleotides, adenosine 3',5'-cyclic monophosphate (cyclic AMP), guanosine 3',5'-cyclic monophosphate (cyclic GMP) and cytidine 3',5'-cyclic monophosphate (cyclic CMP) were unambiguously confirmed by tandem mass spectrometry. The potential of BY-2 cell cultures as a model system for future investigations of cyclic nucleotide function in higher plants is discussed.

Adenosine receptors regulate gap junction coupling of the human cerebral microvascular endothelial cells hCMEC/D3 by Ca2+ influx through cyclic nucleotide‐gated channels

PubMed Central

Bader, Almke; Bintig, Willem; Begandt, Daniela; Klett, Anne; Siller, Ina G.; Gregor, Carola; Schaarschmidt, Frank; Weksler, Babette; Romero, Ignacio; Couraud, Pierre‐Olivier; Hell, Stefan W.

2017-01-01

Key points Gap junction channels are essential for the formation and regulation of physiological units in tissues by allowing the lateral cell‐to‐cell diffusion of ions, metabolites and second messengers.Stimulation of the adenosine receptor subtype A2B increases the gap junction coupling in the human blood–brain barrier endothelial cell line hCMEC/D3.Although the increased gap junction coupling is cAMP‐dependent, neither the protein kinase A nor the exchange protein directly activated by cAMP were involved in this increase.We found that cAMP activates cyclic nucleotide‐gated (CNG) channels and thereby induces a Ca2+ influx, which leads to the increase in gap junction coupling.The report identifies CNG channels as a possible physiological link between adenosine receptors and the regulation of gap junction channels in endothelial cells of the blood–brain barrier. Abstract The human cerebral microvascular endothelial cell line hCMEC/D3 was used to characterize the physiological link between adenosine receptors and the gap junction coupling in endothelial cells of the blood–brain barrier. Expressed adenosine receptor subtypes and connexin (Cx) isoforms were identified by RT‐PCR. Scrape loading/dye transfer was used to evaluate the impact of the A2A and A2B adenosine receptor subtype agonist 2‐phenylaminoadenosine (2‐PAA) on the gap junction coupling. We found that 2‐PAA stimulated cAMP synthesis and enhanced gap junction coupling in a concentration‐dependent manner. This enhancement was accompanied by an increase in gap junction plaques formed by Cx43. Inhibition of protein kinase A did not affect the 2‐PAA‐related enhancement of gap junction coupling. In contrast, the cyclic nucleotide‐gated (CNG) channel inhibitor l‐cis‐diltiazem, as well as the chelation of intracellular Ca2+ with BAPTA, or the absence of external Ca2+, suppressed the 2‐PAA‐related enhancement of gap junction coupling. Moreover, we observed a 2�

Adenosine receptors regulate gap junction coupling of the human cerebral microvascular endothelial cells hCMEC/D3 by Ca2+ influx through cyclic nucleotide-gated channels.

PubMed

Bader, Almke; Bintig, Willem; Begandt, Daniela; Klett, Anne; Siller, Ina G; Gregor, Carola; Schaarschmidt, Frank; Weksler, Babette; Romero, Ignacio; Couraud, Pierre-Olivier; Hell, Stefan W; Ngezahayo, Anaclet

2017-04-15

Gap junction channels are essential for the formation and regulation of physiological units in tissues by allowing the lateral cell-to-cell diffusion of ions, metabolites and second messengers. Stimulation of the adenosine receptor subtype A 2B increases the gap junction coupling in the human blood-brain barrier endothelial cell line hCMEC/D3. Although the increased gap junction coupling is cAMP-dependent, neither the protein kinase A nor the exchange protein directly activated by cAMP were involved in this increase. We found that cAMP activates cyclic nucleotide-gated (CNG) channels and thereby induces a Ca 2+ influx, which leads to the increase in gap junction coupling. The report identifies CNG channels as a possible physiological link between adenosine receptors and the regulation of gap junction channels in endothelial cells of the blood-brain barrier. The human cerebral microvascular endothelial cell line hCMEC/D3 was used to characterize the physiological link between adenosine receptors and the gap junction coupling in endothelial cells of the blood-brain barrier. Expressed adenosine receptor subtypes and connexin (Cx) isoforms were identified by RT-PCR. Scrape loading/dye transfer was used to evaluate the impact of the A 2A and A 2B adenosine receptor subtype agonist 2-phenylaminoadenosine (2-PAA) on the gap junction coupling. We found that 2-PAA stimulated cAMP synthesis and enhanced gap junction coupling in a concentration-dependent manner. This enhancement was accompanied by an increase in gap junction plaques formed by Cx43. Inhibition of protein kinase A did not affect the 2-PAA-related enhancement of gap junction coupling. In contrast, the cyclic nucleotide-gated (CNG) channel inhibitor l-cis-diltiazem, as well as the chelation of intracellular Ca 2+ with BAPTA, or the absence of external Ca 2+ , suppressed the 2-PAA-related enhancement of gap junction coupling. Moreover, we observed a 2-PAA-dependent activation of CNG channels by a combination of

Inhibition of Cyclic Adenosine Monophosphate-Specific Phosphodiesterase by Various Food Plant-Derived Phytotherapeutic Agents

PubMed Central

Pacjuk, Olga; Hernández-Huguet, Silvia; Körner, Johanna; Scherer, Katharina; Richling, Elke

2017-01-01

Background: Phosphodiesterases (PDEs) play a major role in the regulation of cyclic adenosine monophosphate (cAMP)- and cyclic guanosine monophosphate (cGMP)-mediated pathways. Their inhibitors exhibit anti-inflammatory, vasodilatory and antithrombotic effects. Therefore, consumption of foods with PDE-inhibiting potential may possess beneficial influence on the risk of cardiovascular diseases. Methods: Four plant extracts (Arbutus unedo, Camellia sinensis, Cynara scolymus, Zingiber officinale) with promising ingredient profiles and physiological effects were tested for their ability to inhibit cAMP-specific PDE in vitro in a radioactive assay. Results: Strawberry tree fruit (Arbutus unedo) and tea (Camellia sinensis) extracts did not inhibit PDE markedly. Alternatively, artichoke (Cynara scolymus) extract had a significant inhibitory influence on PDE activity (IC50 = 0.9 ± 0.1 mg/mL) as well as its flavone luteolin (IC50 = 41 ± 10 μM) and 3,4-dicaffeoylquinic acid (IC50 > 1.0 mM). Additionally, the ginger (Zingiber officinale) extract and one of its constituents, [6]-gingerol, significantly inhibited PDE (IC50 = 1.7 ± 0.2 mg/mL and IC50 > 1.7 mM, respectively). Crude fractionation of ginger extract showed that substances responsible for PDE inhibition were in the lipoid fraction (IC50 = 455 ± 19 μg/mL). Conclusions: A PDE-inhibitory effect was shown for artichoke and ginger extract. Whether PDE inhibition in vivo can be achieved through ingestion of artichoke or ginger extracts leading to physiological effects concerning cardiovascular health should be addressed in future research. PMID:29113064

Cyclic adenosine monophosphate levels and the function of skin microvascular endothelial cells.

PubMed

Tuder, R M; Karasek, M A; Bensch, K G

1990-02-01

The maintenance of the normal epithelioid morphology of human dermal microvascular endothelial cells (MEC) grown in vitro depends strongly on the presence of factors that increase intracellular levels of cyclic AMP. Complete removal of dibutyryl cAMP and isobutylmethylxanthine (IMX) from the growth medium results in a progressive transition from an epithelioid to a spindle-shaped cell line. This transition cannot be reversed by the readdition of dibutyryl cAMP and IMX to the growth medium or by addition of agonists that increase cAMP levels. Spindle-shaped MEC lose the ability to express Factor VIII rAG and DR antigens and to bind peripheral blood mononuclear leukocyte (PBML). Ultrastructural analyses of transitional cells and spindle-shaped cells show decreased numbers of Weibel-Palade bodies in transitional cells and their complete absence in spindle-shaped cells. Interferon-gamma alters several functional properties of both epithelioid and spindle-shaped cells. In the absence of dibutyryl cAMP it accelerates the transition from epithelial to spindle-shaped cells, whereas in the presence of cyclic AMP interferon-gamma increases the binding of PBMLs to both epithelioid and spindle-shaped MEC and the endocytic activity of the endothelial cells. These results suggest that cyclic AMP is an important second messenger in the maintenance of several key functions of microvascular endothelial cells. Factors that influence the levels of this messenger in vivo can be expected to influence the angiogenic and immunologic functions of the microvasculature.

Role of 2′,3′-cyclic nucleotide 3′-phosphodiesterase in the renal 2′,3′-cAMP-adenosine pathway

PubMed Central

Gillespie, Delbert G.; Mi, Zaichuan; Cheng, Dongmei; Bansal, Rashmi; Janesko-Feldman, Keri; Kochanek, Patrick M.

2014-01-01

Energy depletion increases the renal production of 2′,3′-cAMP (a positional isomer of 3′,5′-cAMP that opens mitochondrial permeability transition pores) and 2′,3′-cAMP is converted to 2′-AMP and 3′-AMP, which in turn are metabolized to adenosine. Because the enzymes involved in this “2′,3′-cAMP-adenosine pathway” are unknown, we examined whether 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) participates in the renal metabolism of 2′,3′-cAMP. Western blotting and real-time PCR demonstrated expression of CNPase in rat glomerular mesangial, preglomerular vascular smooth muscle and endothelial, proximal tubular, thick ascending limb and collecting duct cells. Real-time PCR established the expression of CNPase in human glomerular mesangial, proximal tubular and vascular smooth muscle cells; and the level of expression of CNPase was greater than that for phosphodiesterase 4 (major enzyme for the metabolism of 3′,5′-cAMP). Overexpression of CNPase in rat preglomerular vascular smooth muscle cells increased the metabolism of exogenous 2′,3′-cAMP to 2′-AMP. Infusions of 2′,3′-cAMP into isolated CNPase wild-type (+/+) kidneys increased renal venous 2′-AMP, and this response was diminished by 63% in CNPase knockout (−/−) kidneys, whereas the conversion of 3′,5′-cAMP to 5′-AMP was similar in CNPase +/+ vs. −/− kidneys. In CNPase +/+ kidneys, energy depletion (metabolic poisons) increased kidney tissue levels of adenosine and its metabolites (inosine, hypoxanthine, xanthine, and uric acid) without accumulation of 2′,3′-cAMP. In contrast, in CNPase −/− kidneys, energy depletion increased kidney tissue levels of 2′,3′-cAMP and abolished the increase in adenosine and its metabolites. In conclusion, kidneys express CNPase, and renal CNPase mediates in part the renal 2′,3′-cAMP-adenosine pathway. PMID:24808540

Involvement of a cyclic adenosine monophosphate-dependent signal in the diet-induced canalicular trafficking of adenosine triphosphate-binding cassette transporter g5/g8.

PubMed

Yamazaki, Yasuhiro; Yasui, Kenta; Hashizume, Takahiro; Suto, Arisa; Mori, Ayaka; Murata, Yuzuki; Yamaguchi, Masahiko; Ikari, Akira; Sugatani, Junko

2015-10-01

The adenosine triphosphate-binding cassette (ABC) half-transporters Abcg5 and Abcg8 promote the secretion of neutral sterol into bile. Studies have demonstrated the diet-induced gene expression of these transporters, but the regulation of their trafficking when the nutritional status changes in the liver remains to be elucidated. Here, we generated a novel in vivo kinetic analysis that can monitor the intracellular trafficking of Abcg5/Abcg8 in living mouse liver by in vivo transfection of the genes of fluorescent protein-tagged transporters and investigated how hypernutrition affects the canalicular trafficking of these transporters. The kinetic analysis showed that lithogenic diet consumption accelerated the translocation of newly synthesized fluorescent-tagged transporters to intracellular pools in an endosomal compartment and enhanced the recruitment of these pooled gene products into the bile canalicular membrane in mouse liver. Because some ABC transporters are reported to be recruited from intracellular pools to the bile canaliculi by cyclic adenosine monophosphate (cAMP) signaling, we next evaluated the involvement of this machinery in a diet-induced event. Administration of a protein kinase A inhibitor, N-(2-{[3-(4-bromophenyl)-2-propenyl]amino}ethyl)-5-isoquinolinesulfonamide, decreased the canalicular expression of native Abcg5/Abcg8 in lithogenic diet-fed mice, and injection of a cAMP analog, dibutyryl cAMP, transiently increased their levels in standard diet-fed mice, indicating the involvement of cAMP signaling. Indeed, canalicular trafficking of the fluorescent-tagged Abcg5/Abcg8 was enhanced by dibutyryl cAMP administration. These observations suggest that diet-induced lipid loading into liver accelerates the trafficking of Abcg5/Abcg8 to the bile canalicular membrane through cAMP signaling machinery. © 2015 by the American Association for the Study of Liver Diseases.

21 CFR 862.1230 - Cyclic AMP test system.

Code of Federal Regulations, 2014 CFR

2014-04-01

...) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862... measure the level of adenosine 3′, 5′-monophosphate (cyclic AMP) in plasma, urine, and other body fluids...

Regulatory actions of 3',5'-cyclic adenosine monophosphate on osteoclast function: possible roles of Epac-mediated signaling.

PubMed

Jeevaratnam, Kamalan; Salvage, Samantha C; Li, Mengye; Huang, Christopher L-H

2018-05-30

Alterations in cellular levels of the second messenger 3',5'-cyclic adenosine monophosphate ([cAMP] i ) regulate a wide range of physiologically important cellular signaling processes in numerous cell types. Osteoclasts are terminally differentiated, multinucleated cells specialized for bone resorption. Their systemic regulator, calcitonin, triggers morphometrically and pharmacologically distinct retraction (R) and quiescence (Q) effects on cell-spread area and protrusion-retraction motility, respectively, paralleling its inhibition of bone resorption. Q effects were reproduced by cholera toxin-mediated G s -protein activation known to increase [cAMP] i , unaccompanied by the [Ca 2+ ] i changes contrastingly associated with R effects. We explore a hypothesis implicating cAMP signaling involving guanine nucleotide-exchange activation of the small GTPase Ras-proximate-1 (Rap1) by exchange proteins directly activated by cAMP (Epac). Rap1 activates integrin clustering, cell adhesion to bone matrix, associated cytoskeletal modifications and signaling processes, and transmembrane transduction functions. Epac activation enhanced, whereas Epac inhibition or shRNA-mediated knockdown compromised, the appearance of markers for osteoclast differentiation and motility following stimulation by receptor activator of nuclear factor kappa-Β ligand (RANKL). Deficiencies in talin and Rap1 compromised in vivo bone resorption, producing osteopetrotic phenotypes in genetically modified murine models. Translational implications of an Epac-Rap1 signaling hypothesis in relationship to N-bisphosphonate actions on prenylation and membrane localization of small GTPases are discussed. © 2018 New York Academy of Sciences.

Abnormal regulation of adenosine 3′,5′-monophosphate and corticosterone formation in an adrenocortical carcinoma

PubMed Central

Ney, R. L.; Hochella, N. J.; Grahame-Smith, D. G.; Dexter, R. N.; Butcher, R. W.

1969-01-01

A spontaneously occurring rat adrenocortical carcinoma which produces corticosterone was maintained by transplantation. The carcinoma appeared to utilize corticosterone biosynthetic steps similar to those of the normal adrenal, but the tumor produced only about 1-10% as much corticosterone per unit tissue weight as nontumorous adrenal glands. The tumor demonstrated little or no increase in corticosterone production in response to adrenocorticotropic hormone (ACTH) either in vivo or in vitro. In normal adrenals, ACTH increases the activity of adenyl cyclase which catalyzes the conversion of adenosine triphosphate (ATP) to adenosine-3′,5′-monophosphate (cyclic AMP), the latter then serving as an intracellular regulator of steroidogenesis. ACTH failed to increase cyclic AMP levels in the tumor in vivo or in slices in vitro, conditions under which there were 50- and 20-fold increases in nontumorous adrenals. However, in homogenates fortified with exogenous ATP, adenyl cyclase activity was comparable in the tumor and adrenals, and cyclic AMP formation was increased 3-fold by ACTH in each. As measured in homogenates, the tumor did not possess a greater ability to destroy cyclic AMP than did normal adrenals. Although ATP levels in the carcinoma were found to be considerably lower than those in normal adrenals, it was not clear that this finding can explain the inability of ACTH to increase cyclic AMP levels in intact tumor cells. While the failure to normally influence cyclic AMP levels in the carcinoma cells could be an important factor in the lack of a steroid response to ACTH, several lines of evidence suggest that the tumor possesses one or more additional abnormalities in the regulation of steroidogenesis. First, in the absence of ACTH stimulation, the tissue concentrations of cyclic AMP were comparable in the tumor and in nontumorous adrenals, but these cyclic AMP levels were associated with a lower level of steroidogenesis in the tumor. Second, tumor slices

Increased cortical extracellular adenosine correlates with seizure termination.

PubMed

Van Gompel, Jamie J; Bower, Mark R; Worrell, Gregory A; Stead, Matt; Chang, Su-Youne; Goerss, Stephan J; Kim, Inyong; Bennet, Kevin E; Meyer, Fredric B; Marsh, W Richard; Blaha, Charles D; Lee, Kendall H

2014-02-01

Seizures are currently defined by their electrographic features. However, neuronal networks are intrinsically dependent on neurotransmitters of which little is known regarding their periictal dynamics. Evidence supports adenosine as having a prominent role in seizure termination, as its administration can terminate and reduce seizures in animal models. Furthermore, microdialysis studies in humans suggest that adenosine is elevated periictally, but the relationship to the seizure is obscured by its temporal measurement limitations. Because electrochemical techniques can provide vastly superior temporal resolution, we test the hypothesis that extracellular adenosine concentrations rise during seizure termination in an animal model and humans using electrochemistry. White farm swine (n = 45) were used in an acute cortical model of epilepsy, and 10 human epilepsy patients were studied during intraoperative electrocorticography (ECoG). Wireless Instantaneous Neurotransmitter Concentration Sensor (WINCS)-based fast scan cyclic voltammetry (FSCV) and fixed potential amperometry were obtained utilizing an adenosine-specific triangular waveform or biosensors, respectively. Simultaneous ECoG and electrochemistry demonstrated an average adenosine increase of 260% compared to baseline, at 7.5 ± 16.9 s with amperometry (n = 75 events) and 2.6 ± 11.2 s with FSCV (n = 15 events) prior to electrographic seizure termination. In agreement with these animal data, adenosine elevation prior to seizure termination in a human patient utilizing FSCV was also seen. Simultaneous ECoG and electrochemical recording supports the hypothesis that adenosine rises prior to seizure termination, suggesting that adenosine itself may be responsible for seizure termination. Future work using intraoperative WINCS-based FSCV recording may help to elucidate the precise relationship between adenosine and seizure termination. Wiley Periodicals, Inc. © 2014 International League Against

Roles of p300 and cyclic adenosine monophosphate response element binding protein in high glucose-induced hypoxia-inducible factor 1α inactivation under hypoxic conditions.

PubMed

Ding, Lingtao; Yang, Minlie; Zhao, Tianlan; Lv, Guozhong

2017-05-01

Given the high prevalence of diabetes and burn injuries worldwide, it is essential to dissect the underlying mechanism of delayed burn wound healing in diabetes patients, especially the high glucose-induced hypoxia-inducible factor 1 (HIF-1)-mediated transcription defects. Human umbilical vein endothelial cells were cultured with low or high concentrations of glucose. HIF-1α-induced vascular endothelial growth factor (VEGF) transcription was measured by luciferase assay. Immunofluorescence staining was carried out to visualize cyclic adenosine monophosphate response element binding protein (CREB) localization. Immunoprecipitation was carried out to characterize the association between HIF-1α/p300/CREB. To test whether p300, CREB or p300+CREB co-overexpression was sufficient to rescue the HIF-1-mediated transcription defect after high glucose exposure, p300, CREB or p300+CREB co-overexpression were engineered, and VEGF expression was quantified. Finally, in vitro angiogenesis assay was carried out to test whether the high glucose-induced angiogenesis defect is rescuable by p300 and CREB co-overexpression. Chronic high glucose treatment resulted in impaired HIF-1-induced VEGF transcription and CREB exclusion from the nucleus. P300 or CREB overexpression alone cannot rescue high glucose-induced HIF-1α transcription defects. In contrast, co-overexpression of p300 and CREB dramatically ameliorated high glucose-induced impairment of HIF-1-mediated VEGF transcription, as well as in vitro angiogenesis. Finally, we showed that co-overexpression of p300 and CREB rectifies the dissociation of HIF-1α-p300-CREB protein complex in chronic high glucose-treated cells. Both p300 and CREB are required for the function integrity of HIF-1α transcription machinery and subsequent angiogenesis, suggesting future studies to improve burn wound healing might be directed to optimization of the interaction between p300, CREB and HIF-1α. © 2016 The Authors. Journal of Diabetes

Effect of electromagnetic field on cyclic adenosine monophosphate (cAMP) in a human mu-opioid receptor cell model.

PubMed

Ross, Christina L; Teli, Thaleia; Harrison, Benjamin S

2016-01-01

During the cell communication process, endogenous and exogenous signaling affect normal as well as pathological developmental conditions. Exogenous influences such as extra-low-frequency electromagnetic field (EMF) have been shown to effect pain and inflammation by modulating G-protein receptors, down-regulating cyclooxygenase-2 activity, and affecting the calcium/calmodulin/nitric oxide pathway. Investigators have reported changes in opioid receptors and second messengers, such as cyclic adenosine monophosphate (cAMP), in opiate tolerance and dependence by showing how repeated exposure to morphine decreases adenylate cyclase activity causing cAMP to return to control levels in the tolerant state, and increase above control levels during withdrawal. Resonance responses to biological systems using exogenous EMF signals suggest that frequency response characteristics of the target can determine the EMF biological response. In our past research we found significant down regulation of inflammatory markers tumor necrosis factor alpha (TNF-α) and nuclear factor kappa B (NFκB) using 5 Hz EMF frequency. In this study cAMP was stimulated in Chinese Hamster Ovary (CHO) cells transfected with human mu-opioid receptors, then exposed to 5 Hz EMF, and outcomes were compared with morphine treatment. Results showed a 23% greater inhibition of cAMP-treating cells with EMF than with morphine. In order to test our results for frequency specific effects, we ran identical experiments using 13 Hz EMF, which produced results similar to controls. This study suggests the use of EMF as a complementary or alternative treatment to morphine that could both reduce pain and enhance patient quality of life without the side-effects of opiates.

Requirement of the cyclic adenosine monophosphate response element-binding protein for hepatitis B virus replication.

PubMed

Kim, Bo Kyung; Lim, Seoung Ok; Park, Yun Gyu

2008-08-01

The cyclic adenosine monophosphate-response element (CRE)-transcription factor complex participates in the regulation of viral gene expression and pathologic processes caused by various viruses. The hepatitis B virus (HBV) enhancer I directs liver-specific transcription of viral genes and contains a CRE sequence (HBV-CRE); however, whether the HBV-CRE and CRE-binding protein (CREB) are required for the HBV life cycle remains to be determined. This study was designed to investigate the role of CREB in HBV replication and gene expression. Sequence-comparison analysis of 984 HBVs reported worldwide showed that the HBV-CRE sequence is highly conserved, indicating the possibility that it plays an important role in the HBV life cycle. The binding of CREB to the HBV-CRE site was markedly inhibited by oligonucleotides containing HBV-CRE and consensus CRE sequences in vitro and in vivo. The HBV promoter activity was demonstrated to be dependent upon the transactivation activity of CREB. Treatment with CRE decoy oligonucleotides reduced HBV promoter activity, and this was reversed by CREB overexpression. The levels of viral transcripts, DNA, and antigens were remarkably decreased in response to the overexpression of CREB mutants or treatment with the CRE decoy oligonucleotides, whereas enhancing CREB activity increased the levels of viral transcripts. In addition, introduction of a three-base mutation into the HBV-CRE led to a marked reduction in HBV messenger RNA synthesis. Taken together, our results demonstrate that both replication and gene expression of HBV require a functional CREB and HBV-CRE. We have also demonstrated that CRE decoy oligonucleotides and the overexpression of CREB mutants can effectively block the HBV life cycle, suggesting that interventions against CREB activity could provide a new avenue to treat HBV infection.

Adenosine transiently modulates stimulated dopamine release in the caudate putamen via A1 receptors

PubMed Central

Ross, Ashley E.; Venton, B. Jill

2014-01-01

Adenosine modulates dopamine in the brain via A1 and A2A receptors, but that modulation has only been characterized on a slow time scale. Recent studies have characterized a rapid signaling mode of adenosine that suggests a possible rapid modulatory role. Here, fast-scan cyclic voltammetry was used to characterize the extent to which transient adenosine changes modulate stimulated dopamine release (5 pulses at 60 Hz) in rat caudate putamen brain slices. Exogenous adenosine was applied and dopamine concentration monitored. Adenosine only modulated dopamine when it was applied 2 or 5 s before stimulation. Longer time intervals and bath application of 5 µM adenosine did not decrease dopamine release. Mechanical stimulation of endogenous adenosine 2s before dopamine stimulation also decreased stimulated dopamine release by 41 ± 7 %, similar to the 54 ± 6 % decrease in dopamine after exogenous adenosine application. Dopamine inhibition by transient adenosine was recovered within 10 minutes. The A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) blocked the dopamine modulation, whereas dopamine modulation was unaffected by the A2A receptor antagonist SCH 442416. Thus, transient adenosine changes can transiently modulate phasic dopamine release via A1 receptors. These data demonstrate that adenosine has a rapid, but transient, modulatory role in the brain. PMID:25219576

Correlation of transient adenosine release and oxygen changes in the caudate-putamen

PubMed Central

Wang, Ying; Venton, B. Jill

2016-01-01

Adenosine is an endogenous nucleoside that modulates important physiological processes, such as vasodilation, in the central nervous system. A rapid, 2–4 seconds, mode of adenosine signaling has been recently discovered, but the relationship between this type of adenosine and blood flow change has not been characterized. In this study, adenosine and oxygen changes were simultaneously measured using fast-scan cyclic voltammetry. Oxygen changes occur when there is an increase in local cerebral blood flow and thus are a measure of vasodilation. About 34% of adenosine transients in the rat caudate-putamen are correlated with a subsequent transient change in oxygen. The amount of oxygen was correlated with the concentration of adenosine release and larger adenosine transients (over 0.4 μM) always had subsequent oxygen changes. The average duration of adenosine and oxygen transients were 3.2 seconds and 3.5 seconds, respectively. On average, the adenosine release starts and peaks 0.2 seconds prior to the oxygen. The A2a antagonist, SCH442416, decreased the number of both adenosine and oxygen transient events by about 32%. However, the A1 antagonist, DPCPX, did not significantly affect simultaneous adenosine and oxygen release. The nitric oxide (NO) synthase inhibitor L-NAME also did not affect the concentration or number of adenosine and oxygen release events. These results demonstrate that both adenosine and oxygen release are modulated via A2a receptors. The correlation of transient concentrations, time delay between adenosine and oxygen peaks, and effect of A2a receptors suggests adenosine modulates blood flow on a rapid, sub-second time scale. PMID:27314215

Effect of parathyroid hormone and insulin on extracellular cyclic adenosine-3',5'-monophosphate in patients with benign and malignant breast tumors.

PubMed

Berstein, L M; Semiglazov, V F; Vishnevski, A S; Dilman, V M

1978-01-01

Basal excretion of cyclic adenosine monophosphate (cAMP) and its basal level in blood plasma in breast cancer (BC) patients and those with fibroadenomatosis did not differ essentially. However, intravenous injection of parathyroid hormone (100 U) and insulin (0.08 U/kg body weight) was followed by a much less rise in urine-cAMP excretion and blood-cAMP levels in BC patients than in benign process in mammary gland. A substantial correlation between changes in plasma cAMP level and the degree of insulin-induced hypoglycemia was not observed. There was a negative correlation between reponse to parathyroid hormone and insulin and body overweight in BC patients. It was suggested that body fat content may influence the peculiarities of metabolism of extracellular cAMP in cancer patients considerably.

Role of CNPase in the Oligodendrocytic Extracellular 2′,3′-cAMP-Adenosine Pathway

PubMed Central

Verrier, Jonathan D.; Jackson, Travis C.; Gillespie, Delbert G.; Janesko-Feldman, Keri; Bansal, Rashmi; Goebbels, Sandra; Nave, Klaus-Armin; Kochanek, Patrick M.; Jackson, Edwin K.

2014-01-01

Extracellular adenosine 3′,5′-cyclic monophosphate (3′,5′-cAMP) is an endogenous source of localized adenosine production in many organs. Recent studies suggest that extracellular 2′,3′-cAMP (positional isomer of 3′,5′-cAMP) is also a source of adenosine, particularly in the brain in vivo post-injury. Moreover, in vitro studies show that both microglia and astrocytes can convert extracellular 2′,3′-cAMP to adenosine. Here we examined the ability of primary mouse oligodendrocytes and neurons to metabolize extracellular 2′,3′-cAMP and their respective adenosine monophosphates (2′-AMP and 3′-AMP). Cells were also isolated from mice deficient in 2′,3′-cyclic nucleotide-3′-phosphodiesterase (CNPase). Oligodendrocytes metabolized 2′,3′-cAMP to 2′-AMP with 10-fold greater efficiency than did neurons (and also more than previously examined microglia and astrocytes); whereas, the production of 3′-AMP was minimal in both oligodendrocytes and neurons. The production of 2′-AMP from 2′,3′-cAMP was reduced by 65% in CNPase -/- versus CNPase +/+ oligodendrocytes. Oligodendrocytes also converted 2′-AMP to adenosine, and this was also attenuated in CNPase -/- oligodendrocytes. Inhibition of classic 3′,5′-cAMP-3′-phosphodiesterases with 3-isobutyl-1-methylxanthine did not block metabolism of 2′,3′-cAMP to 2′-AMP and inhibition of classic ecto-5′-nucleotidase (CD73) with α,β-methylene-adenosine-5′-diphosphate did not attenuate the conversion of 2′-AMP to adenosine. These studies demonstrate that oligodendrocytes express the extracellular 2′,3′-cAMP-adenosine pathway (2′,3′-cAMP → 2′-AMP → adenosine). This pathway is more robustly expressed in oligodendrocytes than in all other CNS cell types because CNPase is the predominant enzyme that metabolizes 2′,3′-cAMP to 2-AMP in CNS cells. By reducing levels of 2′,3′-cAMP (a mitochondrial toxin) and increasing levels of adenosine (a neuroprotectant

Adenosine 5'-monophosphate ameliorates D-galactosamine/lipopolysaccharide-induced liver injury through an adenosine receptor-independent mechanism in mice.

PubMed

Zhan, Y; Wang, Z; Yang, P; Wang, T; Xia, L; Zhou, M; Wang, Y; Wang, S; Hua, Z; Zhang, J

2014-01-09

D-galactosamine (GalN)/lipopolysaccharide (LPS)-induced lethality and acute liver failure is dependent on endogenously produced inflammatory cytokines. Adenosine has been proven to be a central role in the regulation of inflammatory response. It is not entirely clear that which adenosine action is actually crucial to limiting inflammatory tissue destruction. Here we showed that GalN/LPS challenge elevated hepatic adenosine and induced lethality in adenosine receptor-deficient mice with equal efficiency as wild-type mice. In GalN/LPS-treated mice, pretreatment with adenosine 5'-monophosphate (5'-AMP) significantly elevated hepatic adenosine level and reduced mortality through decreasing cytokine and chemokine production. In RAW264.7 cells, 5'-AMP treatment inhibited the production of inflammatory cytokines, which is not mediated through adenosine receptors. 5'-AMP failed to attenuate LPS-induced nuclear factor-κB (NF-κB) p65 nuclear translocation, but reduced LPS-induced recruitment of NF-κB p65 to inflammatory gene promoters and decreased LPS-induced enrichment of H3K4 dimethylation at the tumor necrosis factor-α (TNF-α) promoter, which was involved in 5'-AMP-induced elevation of cellular adenosine and a decline of methylation potential. In vitro biochemical analysis revealed that adenosine directly attenuated recruitment of NF-κB to the TNF-α and interleukin-6 promoters. Our findings demonstrate that 5'-AMP-inhibiting inflammatory response is not mediated by adenosine receptors and it may represent a potential protective agent for amelioration of LPS-induced liver injury.

Scale factor duality for conformal cyclic cosmologies

NASA Astrophysics Data System (ADS)

Camara da Silva, U.; Alves Lima, A. L.; Sotkov, G. M.

2016-11-01

The scale factor duality is a symmetry of dilaton gravity which is known to lead to pre-big-bang cosmologies. A conformal time version of the scale factor duality (SFD) was recently implemented as a UV/IR symmetry between decelerated and accelerated phases of the post-big-bang evolution within Einstein gravity coupled to a scalar field. The problem investigated in the present paper concerns the employment of the conformal time SFD methods to the construction of pre-big-bang and cyclic extensions of these models. We demonstrate that each big-bang model gives rise to two qualitatively different pre-big-bang evolutions: a contraction/expansion SFD model and Penrose's Conformal Cyclic Cosmology (CCC). A few examples of SFD symmetric cyclic universes involving certain gauged Kähler sigma models minimally coupled to Einstein gravity are studied. We also describe the specific SFD features of the thermodynamics and the conditions for validity of the generalized second law in the case of Gauss-Bonnet (GB) extension of these selected CCC models.

Effect of nitrogen starvation on the level of adenosine 3',5'-monophosphate in Anabaena variabilis.

PubMed

Hood, E E; Armour, S; Ownby, J D; Handa, A K; Bressan, R A

1979-12-03

Low levels of adenosine 3',5'-monophosphate (cyclic AMP) were detected in the cyanobacterium Anabaena variabilis using a protein binding assay and two radioisotopic labelling methods. The basal concentration of intracellular cyclic AMP ranged from 0.27 pmol/mg protein in A. variabilis Kutz grown under heterotrophic conditions to 1.0--2.7 pmol/mg protein in A. variabilis strain 377 grown autotrophically. Extracellular cyclic AMP was found to comprise as much as 90% of the total cyclic AMP in rapidly growing cultures. When A. variabilis strain 377 was starved of nitrogen, a 3--4-fold increase in intracellular cyclic AMP was observed during the 24 h period coincident with early heterocyst development.

Adenosine 5′-monophosphate ameliorates D-galactosamine/lipopolysaccharide-induced liver injury through an adenosine receptor-independent mechanism in mice

PubMed Central

Zhan, Y; Wang, Z; Yang, P; Wang, T; Xia, L; Zhou, M; Wang, Y; Wang, S; Hua, Z; Zhang, J

2014-01-01

D-galactosamine (GalN)/lipopolysaccharide (LPS)-induced lethality and acute liver failure is dependent on endogenously produced inflammatory cytokines. Adenosine has been proven to be a central role in the regulation of inflammatory response. It is not entirely clear that which adenosine action is actually crucial to limiting inflammatory tissue destruction. Here we showed that GalN/LPS challenge elevated hepatic adenosine and induced lethality in adenosine receptor-deficient mice with equal efficiency as wild-type mice. In GalN/LPS-treated mice, pretreatment with adenosine 5′-monophosphate (5′-AMP) significantly elevated hepatic adenosine level and reduced mortality through decreasing cytokine and chemokine production. In RAW264.7 cells, 5′-AMP treatment inhibited the production of inflammatory cytokines, which is not mediated through adenosine receptors. 5′-AMP failed to attenuate LPS-induced nuclear factor-κB (NF-κB) p65 nuclear translocation, but reduced LPS-induced recruitment of NF-κB p65 to inflammatory gene promoters and decreased LPS-induced enrichment of H3K4 dimethylation at the tumor necrosis factor-α (TNF-α) promoter, which was involved in 5′-AMP-induced elevation of cellular adenosine and a decline of methylation potential. In vitro biochemical analysis revealed that adenosine directly attenuated recruitment of NF-κB to the TNF-α and interleukin-6 promoters. Our findings demonstrate that 5′-AMP-inhibiting inflammatory response is not mediated by adenosine receptors and it may represent a potential protective agent for amelioration of LPS-induced liver injury. PMID:24407238

Adenine formation from adenosine by mycoplasmas: adenosine phosphorylase activity.

PubMed Central

Hatanaka, M; Del Giudice, R; Long, C

1975-01-01

Mammalian cells have enzymes to convert adenosine to inosine by deamination and inosine to hypoxanthine by phosphorolysis, but they do not possess the enzymes necessary to form the free base, adenine, from adenosine. Mycoplasmas grown in broth or in cell cultures can produce adenine from adenosine. This activity was detected in a variety of mycoplasmatales, and the enzyme was shown to be adenosine phosphorylase. Adenosine formation from adenine and ribose 1-phosphate, the reverse reaction of adenine formation from adenosine, was also observed with the mycoplasma enzyme. Adenosine phosphorylase is apparently common to the mycoplasmatales but it is not universal, and the organisms can be divided into three groups on the basis of their use of adenosine as substrate. Thirteen of 16 Mycoplasma, Acholeplasma, and Siroplasma species tested exhibit adenosine phosphorylase activity. M. lipophilium differed from the other mycoplasmas and shared with mammalian cells the ability to convert adenosine to inosine by deamination. M. pneumoniae and the unclassified M. sp. 70-159 showed no reaction with adenosine. Adenosine phosphorylase activity offers an additional method for the detection of mycoplasma contamination of cells. The patterns of nucleoside metabolism will provide additional characteristics for identification of mycoplasmas and also may provide new insight into the classification of mycoplasmas. PMID:236559

Lipopolysaccharide-induced endothelial barrier breakdown is cyclic adenosine monophosphate dependent in vivo and in vitro.

PubMed

Schlegel, Nicolas; Baumer, Yvonne; Drenckhahn, Detlev; Waschke, Jens

2009-05-01

To determine whether cyclic adenosine monophosphate (cAMP) is critically involved in lipopolysaccharide (LPS)-induced breakdown of endothelial barrier functions in vivo and in vitro. Experimental laboratory research. Research laboratory. Wistar rats and cultured human microvascular endothelial cells. Permeability measurements in single postcapillary venules in vivo and permeability measurements and cell biology techniques in vitro. We demonstrate that within 120 minutes LPS increased endothelial permeability in rat mesenteric postcapillary venules in vivo and caused a barrier breakdown in human dermal microvascular endothelial cells in vitro. This was associated with the formation of large intercellular gaps and fragmentation of vascular endothelial cadherin immunostaining. Furthermore, claudin 5 immunostaining at cell borders was drastically reduced after LPS treatment. Interestingly, activity of the small GTPase Rho A, which has previously been suggested to mediate the LPS-induced endothelial barrier breakdown, was not increased after 2 hours. However, activity of Rac 1, which is known to be important for maintenance of endothelial barrier functions, was significantly reduced to 64 +/- 8% after 2 hours. All LPS-induced changes of endothelial cells were blocked by a forskolin-mediated or rolipram-mediated increase of cAMP. Consistently, enzyme-linked immunosorbent assay-based measurements demonstrated that LPS significantly decreased intracellular cAMP. In summary, our data demonstrate that LPS disrupts endothelial barrier properties by decreasing intracellular cAMP. This mechanism may involve inactivation of Rac 1 rather than activation of Rho A.

PAP and NT5E inhibit nociceptive neurotransmission by rapidly hydrolyzing nucleotides to adenosine

PubMed Central

2011-01-01

Background Prostatic acid phosphatase (PAP) and ecto-5'-nucleotidase (NT5E, CD73) produce extracellular adenosine from the nucleotide AMP in spinal nociceptive (pain-sensing) circuits; however, it is currently unknown if these are the main ectonucleotidases that generate adenosine or how rapidly they generate adenosine. Results We found that AMP hydrolysis, when measured histochemically, was nearly abolished in dorsal root ganglia (DRG) neurons and lamina II of spinal cord from Pap/Nt5e double knockout (dKO) mice. Likewise, the antinociceptive effects of AMP, when combined with nucleoside transport inhibitors (dipyridamole or 5-iodotubericidin), were reduced by 80-100% in dKO mice. In addition, we used fast scan cyclic voltammetry (FSCV) to measure adenosine production at subsecond resolution within lamina II. Adenosine was maximally produced within seconds from AMP in wild-type (WT) mice but production was reduced >50% in dKO mice, indicating PAP and NT5E rapidly generate adenosine in lamina II. Unexpectedly, we also detected spontaneous low frequency adenosine transients in lamina II with FSCV. Adenosine transients were of short duration (<2 s) and were reduced (>60%) in frequency in Pap-/-, Nt5e-/- and dKO mice, suggesting these ectonucleotidases rapidly hydrolyze endogenously released nucleotides to adenosine. Field potential recordings in lamina II and behavioral studies indicate that adenosine made by these enzymes acts through the adenosine A1 receptor to inhibit excitatory neurotransmission and nociception. Conclusions Collectively, our experiments indicate that PAP and NT5E are the main ectonucleotidases that generate adenosine in nociceptive circuits and indicate these enzymes transform pulsatile or sustained nucleotide release into an inhibitory adenosinergic signal. PMID:22011440

Discovery of a cAMP Deaminase That Quenches Cyclic AMP-Dependent Regulation

PubMed Central

Goble, Alissa M.; Feng, Youjun; Raushel, Frank M.; Cronan, John E.

2013-01-01

An enzyme of unknown function within the amidohydrolase superfamily was discovered to catalyze the hydrolysis of the universal second messenger, cyclic-3’, 5’-adenosine monophosphate (cAMP). The enzyme, which we have named CadD, is encoded by the human pathogenic bacterium Leptospira interrogans. Although CadD is annotated as an adenosine deaminase, the protein specifically deaminates cAMP to cyclic-3’, 5’-inosine monophosphate (cIMP) with a kcat/Km of 2.7 ± 0.4 × 105 M−1 s−1 and has no activity on adenosine, adenine, or 5’-adenosine monophosphate (AMP). This is the first identification of a deaminase specific for cAMP. Expression of CadD in Escherichia coli mimics the loss of adenylate cyclase in that it blocks growth on carbon sources that require the cAMP-CRP transcriptional activator complex for expression of the cognate genes. The cIMP reaction product cannot replace cAMP as the ligand for CRP binding to DNA in vitro and cIMP is a very poor competitor of cAMP activation of CRP for DNA binding. Transcriptional analyses indicate that CadD expression represses expression of several cAMP-CRP dependent genes. CadD adds a new activity to the cAMP metabolic network and may be a useful tool in intracellular study of cAMP-dependent processes. PMID:24074367

Cyclic phosphatidic acid and lysophosphatidic acid induce hyaluronic acid synthesis via CREB transcription factor regulation in human skin fibroblasts.

PubMed

Maeda-Sano, Katsura; Gotoh, Mari; Morohoshi, Toshiro; Someya, Takao; Murofushi, Hiromu; Murakami-Murofushi, Kimiko

2014-09-01

Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator and an analog of the growth factor-like phospholipid lysophosphatidic acid (LPA). cPA has a unique cyclic phosphate ring at the sn-2 and sn-3 positions of its glycerol backbone. We showed before that a metabolically stabilized cPA derivative, 2-carba-cPA, relieved osteoarthritis pathogenesis in vivo and induced hyaluronic acid synthesis in human osteoarthritis synoviocytes in vitro. This study focused on hyaluronic acid synthesis in human fibroblasts, which retain moisture and maintain health in the dermis. We investigated the effects of cPA and LPA on hyaluronic acid synthesis in human fibroblasts (NB1RGB cells). Using particle exclusion and enzyme-linked immunosorbent assays, we found that both cPA and LPA dose-dependently induced hyaluronic acid synthesis. We revealed that the expression of hyaluronan synthase 2 messenger RNA and protein is up-regulated by cPA and LPA treatment time dependently. We then characterized the signaling pathways up-regulating hyaluronic acid synthesis mediated by cPA and LPA in NB1RGB cells. Pharmacological inhibition and reporter gene assays revealed that the activation of the LPA receptor LPAR1, Gi/o protein, phosphatidylinositol-3 kinase (PI3K), extracellular-signal-regulated kinase (ERK), and cyclic adenosine monophosphate response element-binding protein (CREB) but not nuclear factor κB induced hyaluronic acid synthesis by the treatment with cPA and LPA in NB1RGB cells. These results demonstrate for the first time that cPA and LPA induce hyaluronic acid synthesis in human skin fibroblasts mainly through the activation of LPAR1-Gi/o followed by the PI3K, ERK, and CREB signaling pathway. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Cyclic AMP system in muscle tissue during prolonged hypokinesia

NASA Technical Reports Server (NTRS)

Antipenko, Y. A.; Bubeyev, Y. A.; Korovkin, B. F.; Mikhaleva, N. P.

1980-01-01

Components of the cyclic Adenosine-cyclic-35-monophosphate (AMP) system in the muscle tissue of white rats were studied during 70-75 days of hypokinesia, created by placing the animals in small booths which restricted their movements, and during the readaptation period. In the initial period, cyclic AMP levels and the activities of phosphodiesterase and adenylate cyclase in muscle tissue were increased. The values for these indices were roughly equal for controls and experimental animals during the adaptation period, but on the 70th day of the experiment cAMP levels dropped, phosphodiesterase activity increased, and the stimulative effect of epinephrine on the activity of adenylate cyclase decreased. The indices under study normalized during the readaptation period.

New Insights into the Cyclic Di-adenosine Monophosphate (c-di-AMP) Degradation Pathway and the Requirement of the Cyclic Dinucleotide for Acid Stress Resistance in Staphylococcus aureus.

PubMed

Bowman, Lisa; Zeden, Merve S; Schuster, Christopher F; Kaever, Volkhard; Gründling, Angelika

2016-12-30

Nucleotide signaling networks are key to facilitate alterations in gene expression, protein function, and enzyme activity in response to diverse stimuli. Cyclic di-adenosine monophosphate (c-di-AMP) is an important secondary messenger molecule produced by the human pathogen Staphylococcus aureus and is involved in regulating a number of physiological processes including potassium transport. S. aureus must ensure tight control over its cellular levels as both high levels of the dinucleotide and its absence result in a number of detrimental phenotypes. Here we show that in addition to the membrane-bound Asp-His-His and Asp-His-His-associated (DHH/DHHA1) domain-containing phosphodiesterase (PDE) GdpP, S. aureus produces a second cytoplasmic DHH/DHHA1 PDE Pde2. Although capable of hydrolyzing c-di-AMP, Pde2 preferentially converts linear 5'-phosphadenylyl-adenosine (pApA) to AMP. Using a pde2 mutant strain, pApA was detected for the first time in S. aureus, leading us to speculate that this dinucleotide may have a regulatory role under certain conditions. Moreover, pApA is involved in a feedback inhibition loop that limits GdpP-dependent c-di-AMP hydrolysis. Another protein linked to the regulation of c-di-AMP levels in bacteria is the predicted regulator protein YbbR. Here, it is shown that a ybbR mutant S. aureus strain has increased acid sensitivity that can be bypassed by the acquisition of mutations in a number of genes, including the gene coding for the diadenylate cyclase DacA. We further show that c-di-AMP levels are slightly elevated in the ybbR suppressor strains tested as compared with the wild-type strain. With this, we not only identified a new role for YbbR in acid stress resistance in S. aureus but also provide further insight into how c-di-AMP levels impact acid tolerance in this organism. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

New Insights into the Cyclic Di-adenosine Monophosphate (c-di-AMP) Degradation Pathway and the Requirement of the Cyclic Dinucleotide for Acid Stress Resistance in Staphylococcus aureus*

PubMed Central

Bowman, Lisa; Zeden, Merve S.; Kaever, Volkhard

2016-01-01

Nucleotide signaling networks are key to facilitate alterations in gene expression, protein function, and enzyme activity in response to diverse stimuli. Cyclic di-adenosine monophosphate (c-di-AMP) is an important secondary messenger molecule produced by the human pathogen Staphylococcus aureus and is involved in regulating a number of physiological processes including potassium transport. S. aureus must ensure tight control over its cellular levels as both high levels of the dinucleotide and its absence result in a number of detrimental phenotypes. Here we show that in addition to the membrane-bound Asp-His-His and Asp-His-His-associated (DHH/DHHA1) domain-containing phosphodiesterase (PDE) GdpP, S. aureus produces a second cytoplasmic DHH/DHHA1 PDE Pde2. Although capable of hydrolyzing c-di-AMP, Pde2 preferentially converts linear 5′-phosphadenylyl-adenosine (pApA) to AMP. Using a pde2 mutant strain, pApA was detected for the first time in S. aureus, leading us to speculate that this dinucleotide may have a regulatory role under certain conditions. Moreover, pApA is involved in a feedback inhibition loop that limits GdpP-dependent c-di-AMP hydrolysis. Another protein linked to the regulation of c-di-AMP levels in bacteria is the predicted regulator protein YbbR. Here, it is shown that a ybbR mutant S. aureus strain has increased acid sensitivity that can be bypassed by the acquisition of mutations in a number of genes, including the gene coding for the diadenylate cyclase DacA. We further show that c-di-AMP levels are slightly elevated in the ybbR suppressor strains tested as compared with the wild-type strain. With this, we not only identified a new role for YbbR in acid stress resistance in S. aureus but also provide further insight into how c-di-AMP levels impact acid tolerance in this organism. PMID:27834680

Adenosine and Hypoxia-Inducible Factor Signaling in Intestinal Injury and Recovery

PubMed Central

Eltzschig, Holger K.

2013-01-01

The gastrointestinal mucosa has proven to be an interesting tissue in which to investigate disease-related metabolism. In this review, we outline some of the evidence that implicates hypoxia-mediated adenosine signaling as an important signature within both healthy and diseased mucosa. Studies derived from cultured cell systems, animal models, and human patients have revealed that hypoxia is a significant component of the inflammatory microenvironment. These studies have revealed a prominent role for hypoxia-induced factor (HIF) and hypoxia signaling at several steps along the adenine nucleotide metabolism and adenosine receptor signaling pathways. Likewise, studies to date in animal models of intestinal inflammation have demonstrated an almost uniformly beneficial influence of HIF stabilization on disease outcomes. Ongoing studies to define potential similarities with and differences between innate and adaptive immune responses will continue to teach us important lessons about the complexity of the gastrointestinal tract. Such information has provided new insights into disease pathogenesis and, importantly, will provide insights into new therapeutic targets. PMID:21942704

cGMP and cyclic nucleotide-gated channels participate in mouse sperm capacitation.

PubMed

Cisneros-Mejorado, Abraham; Sánchez Herrera, Daniel P

2012-01-20

During capacitation of mammalian sperm intracellular [Ca(2+)] and cyclic nucleotides increase, suggesting that CNG channels play a role in the physiology of sperm. Here we study the effect of capacitation, 8Br-cAMP (8-bromoadenosine 3',5'-cyclic monophosphate) and 8Br-cGMP (8-bromoguanosine 3',5'-cyclic monophosphate) on the macroscopic ionic currents of mouse sperm, finding the existence of different populations of sperm, in terms of the recorded current and its response to cyclic nucleotides. Our results show that capacitation and cyclic nucleotides increase the ionic current, having a differential sensitivity to cGMP (cyclic guanosine monophosphate) and cAMP (cyclic adenosine monophosphate). Using a specific inhibitor we determine the contribution of CNG channels to macroscopic current and capacitation. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Alterations in phosphorylated cyclic adenosine monophosphate response element of binding protein activity: a pathway for fetal alcohol syndrome-related neurotoxicity.

PubMed

Roberson, Robin; Cameroni, Irene; Toso, Laura; Abebe, Daniel; Bissel, Stephanie; Spong, Catherine Y

2009-02-01

Fetal alcohol syndrome (FAS) is the leading cause of a spectrum of preventable nongenetic learning and behavioral disorders. In adult (FAS) mice, we measured phosphorylated cyclic adenosine monophosphate response element of binding protein (pCREB) staining in hippocampal subregions to evaluate a possible mechanism underlying FAS learning deficits. Pregnant C57BL6/J mice were treated on gestational day 8 with alcohol or control (saline). After learning assessment, the offspring were perfused for immunohistochemistry and brain sections probed using SER 133 pCREB antibody. Relative staining density was assessed using National Institutes of Health Image software. Statistical analysis included analysis of variance with P < .05 considered significant. In all hippocampal subregions, pCREB staining was greater in the control animals than in the alcohol-treated group (P < or = .0001). In utero alcohol exposure decreased pCREB activity in hippocampal subregions of adult mice. The dentate gyrus had the most robust cumulative decrease in pCREB staining, suggesting FAS adult learning deficits may correlate to enhanced dentate gyrus neurodegeneration.

Increasing plasma fibrinogen, but unchanged levels of intraplatelet cyclic nucleotides, plasma endothelin-1, factor VII, and neopterin during cholesterol lowering with fluvastatin.

PubMed

Gottsäter, A; Anwaar, I; Lind, P; Mattiasson, I; Lindgärde, F

1999-04-01

Lipid-lowering statin treatment reduces cardiovascular morbidity and mortality and improves endothelial function in patients with hypercholesterolemia. The aim of the present study was to evaluate plasma levels of fibrinogen, factor VII, and the macrophage-derived inflammatory mediator neopterin during lipid lowering. In addition, the endothelial production of platelet antiaggregatory and vasodilatory factors such as nitric oxide and prostacyclin, and vasoconstrictive factors such as endothelin-1, was assessed. Plasma fibrinogen, factor VII, endothelin-1, and the neopterin and intraplatelet nitric oxide and prostacyclin mediators cyclic 3'-5'guanosine monophosphate (cGMP) and cyclic 3'-5'adenosine monophosphate (cAMP) were measured before and 6 months after the institution of treatment with fluvastatin in 17 patients (eight men and nine women, median age 60 years) with vascular disease and previously untreated hypercholesterolemia. After 6 months, a decrease of 1.62 mmol/l [1.26-2.18 (19%); P < 0.01] was noted in levels of total cholesterol, and a decrease of 1.70 mmol/l [1.52-2.30 (28%); P < 0.01] in levels of low-density lipoprotein cholesterol. Plasma levels of fibrinogen had increased [from 4.81 g/l (4.26-5.27) to 5.17 g/l (4.81-5.67); P < 0.05], whereas no significant changes had occurred in intraplatelet levels of cGMP [decrease by 0.05 pmol/10(9) platelets (-0.17 to 0.24); NS], cAMP [decrease by 0.13 pmol/10(9) platelets (-0.37 to 0.86); NS], plasma endothelin-1 [decrease by 0.05 pg/ml (-0.60 to 0.70); NS], plasma factor VII [from 1.14 IE/ml (0.58-1.38) to 1.22 IE/ml (0.96-1.46); NS], or plasma neopterin [from 8.6 nmol/l (7.1-11.5) to 8.7 nmol/l (7.9-11.3); NS]. In conclusion, during cholesterol-lowering treatment with fluvastatin, plasma levels of fibrinogen increased whereas intraplatelet cyclic nucleotide levels and plasma endothelin-1, factor VII and neopterin levels were unchanged.

The Brain In Vivo Expresses the 2′,3′-cAMP-Adenosine Pathway

PubMed Central

Verrier, Jonathan D.; Jackson, Travis C.; Bansal, Rashmi; Kochanek, Patrick M.; Puccio, Ava M.; Okonkwo, David O.; Jackson, Edwin K.

2012-01-01

Although multiple biochemical pathways produce adenosine, studies suggest that the 2′,3′-cAMP-adenosine pathway (2′,3′-cAMP → 2′-AMP/3′-AMP → adenosine) contributes to adenosine production in some cells/tissues/organs. To determine whether the 2′,3′-cAMP-adenosine pathway exists in vivo in the brain, we delivered to the brain (gray matter and white matter separately) via the inflow perfusate of a microdialysis probe either 2′,3′-cAMP, 3′,5′-cAMP, 2′-AMP, 3′-AMP, or 5′-AMP and measured the recovered metabolites in the microdialysis outflow perfusate with mass spectrometry. In both gray and white matter, 2′,3′-cAMP increased 2′-AMP, 3′-AMP and adenosine, and 3′,5′-cAMP increased 5′-AMP and adenosine. In both brain regions, 2′-AMP, 3-AMP and 5′-AMP were converted to adenosine. Microdialysis experiments in 2′,3′-cyclic nucleotide-3′-phosphodiesterase (CNPase) wild-type mice demonstrated that traumatic brain injury (TBI; controlled cortical impact model) activated the brain 2,3′-cAMP-adenosine pathway; similar experiments in CNPase knockout mice indicated that CNPase was involved in the metabolism of endogenous 2′,3′-cAMP to 2′-AMP and to adenosine. In CSF from TBI patients, 2′,3′-cAMP was significantly increased in the initial 12 hours after injury and strongly correlated with CSF levels of 2′-AMP, 3′-AMP, adenosine and inosine. We conclude that in vivo, 2′,3′-cAMP is converted to 2′-AMP/3′-AMP, and these AMPs are metabolized to adenosine. This pathway exists endogenously in both mice and humans. PMID:22360621

The Clinical Correlation of Regulatory T Cells and Cyclic Adenosine Monophosphate in Enterovirus 71 Infection

PubMed Central

Wang, Shih-Min; Chen, I-Chun; Liao, Yu-Ting; Liu, Ching-Chuan

2014-01-01

Background Brainstem encephalitis (BE) and pulmonary edema (PE) are notable complications of enterovirus 71 (EV71) infection. Objective This study investigated the immunoregulatory characterizations of EV71 neurological complications by disease severity and milrinone treatment. Study Design Patients <18 years with virologically confirmed EV71 infections were enrolled and divided into 2 groups: the hand, foot, and mouth disease (HFMD) or BE group, and the autonomic nervous system (ANS) dysregulation or PE group. Cytokine and cyclic adenosine monophosphate (cAMP) levels, and the regulatory T cell (Tregs) profiles of the patients were determined. Results Patients with ANS dysregulation or PE exhibited significantly low frequency of CD4+CD25+Foxp3+ and CD4+Foxp3+ T cells compared with patients with HFMD or BE. The expression frequency of CD4−CD8− was also significantly decreased in patients with ANS dysregulation or PE. Among patients with ANS dysregulation or PE, the expression frequency of CD4+Foxp3+ increased markedly after milrinone treatment, and was associated with reduction of plasma levels IL-6, IL-8 and IL-10. Plasma concentrations of cAMP were significantly decreased in patients with ANS dysregulation or PE compared with patients with HFMD or BE; however, cAMP levels increased after milrinone treatment. Conclusions These findings suggested decreased different regulatory T populations and cAMP expression correlate with increased EV71 disease severity. Improved outcome after milrinone treatment may associate with increased regulatory T populations, cAMP expression and modulation of cytokines levels. PMID:25010330

Cyclic Adenosine Monophosphate Accumulation and beta-Adrenergic Binding in Unweighted and Denervated Rat Soleus Muscle

NASA Technical Reports Server (NTRS)

Kirby, Christopher R.; Woodman, Christopher R.; Woolridge, Dale; Tischler, Marc E.

1992-01-01

Unweighting, but not denervation, of muscle reportedly "spares" insulin receptors, increasing insulin sensitivity. Unweighting also increases beta-adrenergic responses of carbohydrate metabolism. These differential characteristics were studied further by comparing cyclic adenosine monophosphate (cAMP) accumulation and beta-adrenergic binding in normal and 3-day unweighted or denervated soleus muscle. Submaximal amounts of isoproterenol, a p-agonist, increased cAMP accumulation in vitro and in vivo (by intramuscular (IM) injection) to a greater degree (P less than .05) in unweighted muscles. Forskolin or maximal isoproterenol had similar in vitro effects in all muscles, suggesting increased beta-adrenergic sensitivity following unweighting. Increased sensitivity was confirmed by a greater receptor density (B(sub max)) for iodo-125(-)-pindolol in particulate preparations of unweighted (420 x 10(exp -18) mol/mg muscle) than of control or denervated muscles (285 x 10(exp-18) mol/mg muscle). The three dissociation constant (Kd) values were similar (20.3 to 25.8 pmol/L). Total binding capacity (11.4 fmol/muscle) did not change during 3 days of unweighting, but diminished by 30% with denervation. This result illustrates the "sparing" and loss of receptors, respectively, in these two atrophy models. In diabetic animals, IM injection of insulin diminished CAMP accumulation in the presence of theophylline in unweighted muscle (-66% +/- 2%) more than in controls (-42% +'- 6%, P less than .001). These results show that insulin affects CAMP formation in muscle, and support a greater in vivo insulin response following unweighting atrophy. These various data support a role for lysosomal proteolysis in denervation, but not in unweighting, atrophy.

Endogenous Production of Extracellular Adenosine by Trabecular Meshwork Cells: Potential Role in Outflow Regulation

PubMed Central

Wu, Jing; Li, Guorong; Luna, Coralia; Spasojevic, Ivan; Epstein, David L.; Gonzalez, Pedro

2012-01-01

Purpose. To investigate the mechanisms for endogenous production of extracellular adenosine in trabecular meshwork (TM) cells and evaluate its physiological relevance to the regulation of aqueous humor outflow facility. Methods. Extra-cellular levels of adenosine monophosphate (AMP) and adenosine in porcine trabecular meshwork (PTM) cells treated with adenosine triphosphate (ATP), AMP, cAMP or forskolin with or without specific inhibitors of phosphodiesterases (IBMX) and CD73 (AMPCP) were determined by high-pressure liquid chromatography fluorometry. Extracellular adenosine was also evaluated in cell cultures subjected to cyclic mechanical stress (CMS) (20% stretching; 1 Hz) and after disruption of lipid rafts with methyl-β-cyclodextrin. Expression of CD39 and CD73 in porcine TM cells and tissue were examined by Q-PCR and Western blot. The effect of inhibition of CD73 on outflow facility was evaluated in perfused living mouse eyes. Results. PTM cells generated extracellular adenosine from extracellular ATP and AMP but not from extracellular cAMP. Increased intracellular cAMP mediated by forskolin led to a significant increase in extracellular adenosine production that was not prevented by IBMX. Inhibition of CD73 resulted, in all cases, in a significant decrease in extracellular adenosine. CMS induced a significant activation of extracellular adenosine production. Inhibition of CD73 activity with AMPCP in living mouse eyes resulted in a significant decrease in outflow facility. Conclusions. These results support the concept that the extracellular adenosine pathway might play an important role in the homeostatic regulation of outflow resistance in the TM, and suggest a novel mechanism by which pathologic alteration of the TM, such as increased tissue rigidity, could lead to abnormal elevation of IOP in glaucoma. PMID:22997289

Smoke Extract Impairs Adenosine Wound Healing. Implications of Smoke-Generated Reactive Oxygen Species

PubMed Central

Zimmerman, Matthew C.; Zhang, Hui; Castellanos, Glenda; O’Malley, Jennifer K.; Alvarez-Ramirez, Horacio; Kharbanda, Kusum; Sisson, Joseph H.; Wyatt, Todd A.

2013-01-01

Adenosine concentrations are elevated in the lungs of patients with asthma and chronic obstructive pulmonary disease, where it balances between tissue repair and excessive airway remodeling. We previously demonstrated that the activation of the adenosine A2A receptor promotes epithelial wound closure. However, the mechanism by which adenosine-mediated wound healing occurs after cigarette smoke exposure has not been investigated. The present study investigates whether cigarette smoke exposure alters adenosine-mediated reparative properties via its ability to induce a shift in the oxidant/antioxidant balance. Using an in vitro wounding model, bronchial epithelial cells were exposed to 5% cigarette smoke extract, were wounded, and were then stimulated with either 10 μM adenosine or the specific A2A receptor agonist, 5′-(N-cyclopropyl)–carboxamido–adenosine (CPCA; 10 μM), and assessed for wound closure. In a subset of experiments, bronchial epithelial cells were infected with adenovirus vectors encoding human superoxide dismutase and/or catalase or control vector. In the presence of 5% smoke extract, significant delay was evident in both adenosine-mediated and CPCA-mediated wound closure. However, cells pretreated with N-acetylcysteine (NAC), a nonspecific antioxidant, reversed smoke extract–mediated inhibition. We found that cells overexpressing mitochondrial catalase repealed the smoke extract inhibition of CPCA-stimulated wound closure, whereas superoxide dismutase overexpression exerted no effect. Kinase experiments revealed that smoke extract significantly reduced the A2A-mediated activation of cyclic adenosine monophosphate–dependent protein kinase. However, pretreatment with NAC reversed this effect. In conclusion, our data suggest that cigarette smoke exposure impairs A2A-stimulated wound repair via a reactive oxygen species–dependent mechanism, thereby providing a better understanding of adenosine signaling that may direct the development of

Effects of cyclic-nucleotide derivatives on the growth of human colonic carcinoma xenografts and on cell production in the rat colonic crypt epithelium.

PubMed Central

Tutton, P. J.; Barkla, D. H.

1981-01-01

Previous studies have shown that various amine hormones are able to influence the growth rate of human colorectal carcinomas propagated as xenografts in immune-deprived mice, and it is now well known that the effects of many amine and other hormones are mediated by cyclic nucleotides, acting as second messengers within cells. In the present study the influence of various derivatives of cyclic adenosine monophosphate and cyclic guanosine monophosphate on the growth of two different lines of colorectal cancer growing in immune-deprived mice, and on the cell production rate in the colonic crypt epithelium of the rat, was assessed. Growth of each tumour line, as well as crypt-cell production, was suppressed by treatment wit N6O2' dibutyryl and N6 monobutyryl derivatives of cyclic adenosine monophosphate. Dibutyryl cyclic guanosine monophosphate, on the other hand, was found to promote the growth of Tumour HXK4 and to promote crypt cell production, but to have no significant effect on Tumour HXM2. PMID:6268136

Effects of cyclic-nucleotide derivatives on the growth of human colonic carcinoma xenografts and on cell production in the rat colonic crypt epithelium.

PubMed

Tutton, P J; Barkla, D H

1981-08-01

Previous studies have shown that various amine hormones are able to influence the growth rate of human colorectal carcinomas propagated as xenografts in immune-deprived mice, and it is now well known that the effects of many amine and other hormones are mediated by cyclic nucleotides, acting as second messengers within cells. In the present study the influence of various derivatives of cyclic adenosine monophosphate and cyclic guanosine monophosphate on the growth of two different lines of colorectal cancer growing in immune-deprived mice, and on the cell production rate in the colonic crypt epithelium of the rat, was assessed. Growth of each tumour line, as well as crypt-cell production, was suppressed by treatment wit N6O2' dibutyryl and N6 monobutyryl derivatives of cyclic adenosine monophosphate. Dibutyryl cyclic guanosine monophosphate, on the other hand, was found to promote the growth of Tumour HXK4 and to promote crypt cell production, but to have no significant effect on Tumour HXM2.

Regulatory factors governing adenosine-to-inosine (A-to-I) RNA editing.

PubMed

Hong, HuiQi; Lin, Jaymie Siqi; Chen, Leilei

2015-03-31

Adenosine-to-inosine (A-to-I) RNA editing, the most prevalent mode of transcript modification in higher eukaryotes, is catalysed by the adenosine deaminases acting on RNA (ADARs). A-to-I editing imposes an additional layer of gene regulation as it dictates various aspects of RNA metabolism, including RNA folding, processing, localization and degradation. Furthermore, editing events in exonic regions contribute to proteome diversity as translational machinery decodes inosine as guanosine. Although it has been demonstrated that dysregulated A-to-I editing contributes to various diseases, the precise regulatory mechanisms governing this critical cellular process have yet to be fully elucidated. However, integration of previous studies revealed that regulation of A-to-I editing is multifaceted, weaving an intricate network of auto- and transregulations, including the involvement of virus-originated factors like adenovirus-associated RNA. Taken together, it is apparent that tipping of any regulatory components will have profound effects on A-to-I editing, which in turn contributes to both normal and aberrant physiological conditions. A complete understanding of this intricate regulatory network may ultimately be translated into new therapeutic strategies against diseases driven by perturbed RNA editing events. Herein, we review the current state of knowledge on the regulatory mechanisms governing A-to-I editing and propose the role of other co-factors that may be involved in this complex regulatory process.

Circadian variations of adenosine and of its metabolism. Could adenosine be a molecular oscillator for circadian rhythms?

PubMed

Chagoya de Sánchez, V

1995-03-01

The present review describes the biological implications of the periodic changes of adenosine concentrations in different tissues of the rat. Adenosine is a purine molecule that could have been formed in the prebiotic chemical evolution and has been preserved. The rhythmicity of this molecule, as well as its metabolism and even the presence of specific receptors, suggests a regulatory role in eukaryotic cells and in multicellular organisms. Adenosine may be considered a chemical messenger and its action could take place at the level of the same cell (autocrine), the same tissue (paracrine), or on separate organs (endocrine). Exploration of the circadian variations of adenosine was planned considering the liver as an important tissue for purine formation, the blood as a vehicle among tissues, and the brain as the possible acceptor for hepatic adenosine or its metabolites. The rats used in these studies were adapted to a dark-light cycle of 12 h with an unrestrained feeding and drinking schedule. The metabolic control of adenosine concentration in the different tissues studied through the 24-h cycle is related to the activity of adenosine-metabolizing enzyme: 5'-nucleotidase adenosine deaminase, adenosine kinase, and S-adenosylhomocysteine hydrolase. Some possibilities of the factors modulating the activity of these enzymes are commented upon. The multiphysiological action of adenosine could be mediated by several actions: (i) by interaction with extracellular and intracellular receptors and (ii) through its metabolism modulating the methylation pathway, possibly inducing physiological lipoperoxidation, or participating in the energetic homeostasis of the cell. The physiological meaning of the circadian variations of adenosine and its metabolism was focused on: maintenance of the energetic homeostasis of the tissues, modulation of membrane structure and function, regulation of fasting and feeding metabolic pattern, and its participation in the sleep-wake cycle. From

Difference in protective effects of GIP and GLP-1 on endothelial cells according to cyclic adenosine monophosphate response.

PubMed

Lim, Dong-Mee; Park, Keun-Young; Hwang, Won-Min; Kim, Ju-Young; Kim, Byung-Joon

2017-05-01

Receptors for glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are present in vascular endothelial cells. Previous studies investigating euglycemic status have demonstrated that GIP is directly involved in the physiology of blood vessels by controlling the blood flow rate of portal veins and that GLP-1 has a protective effect on blood vessels by acting on endothelial cells. However, to the best of our knowledge, the effects of GIP and GLP-1 on endothelial cells in patients with hyperglycemia remain unknown. Therefore, the present study investigated whether the effect of the incretin hormones GLP-1 and GIP differed with regards to the reversal of endothelial cell dysfunction caused by hyperglycemia. The production of nitric oxide (NO) was measured using the Griess reagent system kit and the expression of cyclic adenosine monophosphate (cAMP) in the cell was measured at a wavelength of 405 nm with the ELISA reader using the cyclic AMP EIA kit. Exposure of human umbilical vein endothelial cells (HUVEC) to a high glucose concentration decreased NO and endothelial nitric oxide synthase (eNOS) levels but increased inducible NOS (iNOS) levels. However, when HUVECs were pretreated with GLP-1, a reduction of iNOS expression was observed and the expression of eNOS and NO were increased, as opposed to pretreatment with GIP. The results differed according to the response of cAMP, the second messenger of incretin hormones: The GIP pretreatment group did not exhibit an increase in cAMP levels while the GLP-1 pretreatment group did. The results of the present study provide evidence that GLP-1, but not GIP, has a protective effect on endothelial function associated with cardiovascular disease, as it is associated with increased eNOS expression and the levels of NO. This effect may be due to an increase in the cAMP concentration during hyperglycemic events.

Amp Synthesis in Aqueous Solution of Adenosine and Phosphorus Pentoxide

NASA Astrophysics Data System (ADS)

Yamagata, Y.; Kojima, H.; Ejiri, K.; Inomata, K.

1982-12-01

Possible formation of a P4O10 molecule in magma, the stability of the molecule in hydrous volcanic gas at high temperatures and a possible prebiotic phosphate cycle were discussed in relation to chemical evolution. To demonstrate the utility of phosphorus pentoxide as a phosphorylating agent, aqueous solutions of adenosine (0.02M) and phosphorus pentoxide (0.2M) were incubated at 37°C for 5 months. The pH of the solutions was adjusted every day or every few days to each fixed value (9.0, 10.5, 11.5, 12.5) with 10 N NaOH. The HPLC analysis showed the formation of 2'-AMP, 3'-AMP, 5'-AMP, cyclic (2' 3')-AMP and cyclic (3' 5')-AMP. The main components of the products were 2'- and 3'-AMP, though cyclic (2' 3')-AMP was the main component in the early period of the incubation at pH 9.0. The yields (conversion rate of adenosine to AMPs) were increased almost linearly with the incubation time for 5 months in the case of pH 9.0. The final yields were about 3% (pH 9.0), 6% (pH 9.0, 1 M NaCl), 5% (pH 9.0, 0.01 M CaCl2, 0.01 M MgCl2), 7% (pH 9.0, 0.5 M NaCl, 0.01 M CaCl2, 0.01 M MgCl2), 9% (pH 9.0, 1 M NaCl, 0.01 M CaCl2, 0.01 M MgCl2), 32% (pH 10.5), 43% (pH 11.5), 35% (pH 12.5).

[Prognostic significance of the cyclic AMP concentration in acute leukemias].

PubMed

Paietta, E; Mittermayer, K; Schwarzmeier, J D

1979-01-01

In patients with acute leukemia (myeloblastic, lymphoblastic, undifferentiated) proliferation kinetics and cyclic adenosine-3', 5'-monophosphate (cAMP) concentration of the leukemic cells were studied for their significance in the prediction of responsiveness to cytostatic therapy. Patients with good clinical response had significantly faster turnover and lower cAMP-levels than those who failed to respond to treatment.

Proliferation kinetics and cyclic AMP as prognostic factors in adult acute leukemia.

PubMed

Paietta, E; Mittermayer, K; Schwarzmeier, J

1980-07-01

In 41 adult patients with acute leukemia (myeloblastic, lymphoblastic, and undifferentiated), proliferation kinetics (as determined by double-label autoradiography) and cyclic adenosine 3',5'-monophosphate (cAMP) concentration were studied for their significance in the prediction of responsiveness to cytostatic therapy. Patients with good clinical response had significantly shorter turnover times and higher labeling indices in the bone marrow than did those who failed to respond to treatment. Cases for which cell kinetics did not correlate with clinical response were explained by variance in the distribution of leukemic blasts between the proliferative cell cycle and the resting pool. Good clinical response was also found to be associated with low levels of cAMP in leukemic cells prior to therapy, whereas high cAMP contents predicted failure. Low cAMP concentrations, however, did not necessarily correlate with short turnover times and vice versa. This might be due to fluctuations of the cAMP concentrations during the cell cycle.

Staphylococcus aureus synthesizes adenosine to escape host immune responses

PubMed Central

Thammavongsa, Vilasack; Kern, Justin W.; Missiakas, Dominique M.

2009-01-01

Staphylococcus aureus infects hospitalized or healthy individuals and represents the most frequent cause of bacteremia, treatment of which is complicated by the emergence of methicillin-resistant S. aureus. We examined the ability of S. aureus to escape phagocytic clearance in blood and identified adenosine synthase A (AdsA), a cell wall–anchored enzyme that converts adenosine monophosphate to adenosine, as a critical virulence factor. Staphylococcal synthesis of adenosine in blood, escape from phagocytic clearance, and subsequent formation of organ abscesses were all dependent on adsA and could be rescued by an exogenous supply of adenosine. An AdsA homologue was identified in the anthrax pathogen, and adenosine synthesis also enabled escape of Bacillus anthracis from phagocytic clearance. Collectively, these results suggest that staphylococci and other bacterial pathogens exploit the immunomodulatory attributes of adenosine to escape host immune responses. PMID:19808256

Is adenosine associated with sudden death in schizophrenia? A new framework linking the adenosine pathway to risk of sudden death.

PubMed

Gadelha, Ary; Zugman, André; Calzavara, Mariana Bendlin; de Mendonça Furtado, Remo Holanda; Scorza, Fulvio Alexandre; Bressan, Rodrigo Afonsecca

2018-01-01

Schizophrenia is associated with an increased mortality from cardiovascular disease. Relatively few studies have assessed the putative association of schizophrenia pathophysiology with sudden death. Low adenosine levels have been associated with schizophrenia. In cardiology, increased mortality among patients with congestive heart failure has been associated with genetic polymorphisms that potentially lead to lower adenosine levels. Thus, we hypothesize that adenosine could link schizophrenia and cardiovascular mortality, with decreased adenosine levels leading to increased vulnerability to hyperexcitability following hypoxic insults, increasing the odds of fatal arrhythmias. Low adenosine levels might also lead to a small increase in overall mortality rates and a major increase in the sudden death rate. This hypothesis paves the way for further investigation of the increased cardiac mortality associated with schizophrenia. Potentially, a better characterization of adenosine-related mechanisms of sudden death in schizophrenia could lead to new evidence of factors leading to sudden death in the general population. Copyright © 2017. Published by Elsevier Ltd.

Elevated placental adenosine signaling contributes to the pathogenesis of preeclampsia.

PubMed

Iriyama, Takayuki; Sun, Kaiqi; Parchim, Nicholas F; Li, Jessica; Zhao, Cheng; Song, Anren; Hart, Laura A; Blackwell, Sean C; Sibai, Baha M; Chan, Lee-Nien L; Chan, Teh-Sheng; Hicks, M John; Blackburn, Michael R; Kellems, Rodney E; Xia, Yang

2015-02-24

Preeclampsia is a prevalent hypertensive disorder of pregnancy and a leading cause of maternal and neonatal morbidity and mortality worldwide. This pathogenic condition is speculated to be caused by placental abnormalities that contribute to the maternal syndrome. However, the specific factors and signaling pathways that lead to impaired placentas and maternal disease development remain elusive. Using 2 independent animal models of preeclampsia (genetically engineered pregnant mice with elevated adenosine exclusively in placentas and a pathogenic autoantibody-induced preeclampsia mouse model), we demonstrated that chronically elevated placental adenosine was sufficient to induce hallmark features of preeclampsia, including hypertension, proteinuria, small fetuses, and impaired placental vasculature. Genetic and pharmacological approaches revealed that elevated placental adenosine coupled with excessive A₂B adenosine receptor (ADORA2B) signaling contributed to the development of these features of preeclampsia. Mechanistically, we provided both human and mouse evidence that elevated placental CD73 is a key enzyme causing increased placental adenosine, thereby contributing to preeclampsia. We determined that elevated placental adenosine signaling is a previously unrecognized pathogenic factor for preeclampsia. Moreover, our findings revealed the molecular basis underlying the elevation of placental adenosine and the detrimental role of excess placental adenosine in the pathophysiology of preeclampsia, and thereby, we highlight novel therapeutic targets. © 2014 American Heart Association, Inc.

Adenosine and adenosine receptors in the pathogenesis and treatment of rheumatic diseases.

PubMed

Cronstein, Bruce N; Sitkovsky, Michail

2017-01-01

Adenosine, a nucleoside derived primarily from the extracellular hydrolysis of adenine nucleotides, is a potent regulator of inflammation. Adenosine mediates its effects on inflammatory cells by engaging one or more cell-surface receptors. The expression and function of adenosine receptors on different cell types change during the course of rheumatic diseases, such as rheumatoid arthritis (RA). Targeting adenosine receptors directly for the treatment of rheumatic diseases is currently under study; however, indirect targeting of adenosine receptors by enhancing adenosine levels at inflamed sites accounts for most of the anti-inflammatory effects of methotrexate, the anchor drug for the treatment of RA. In this Review, we discuss the regulation of extracellular adenosine levels and the role of adenosine in regulating the inflammatory and immune responses in rheumatic diseases such as RA, psoriasis and other types of inflammatory arthritis. In addition, adenosine and its receptors are involved in promoting fibrous matrix production in the skin and other organs, and the role of adenosine in fibrosis and fibrosing diseases is also discussed.

Adenosine and preeclampsia.

PubMed

Salsoso, Rocío; Farías, Marcelo; Gutiérrez, Jaime; Pardo, Fabián; Chiarello, Delia I; Toledo, Fernando; Leiva, Andrea; Mate, Alfonso; Vázquez, Carmen M; Sobrevia, Luis

2017-06-01

Adenosine is an endogenous nucleoside with pleiotropic effects in different physiological processes including circulation, renal blood flow, immune function, or glucose homeostasis. Changes in adenosine membrane transporters, adenosine receptors, and corresponding intracellular signalling network associate with development of pathologies of pregnancy, including preeclampsia. Preeclampsia is a cause of maternal and perinatal morbidity and mortality affecting 3-5% of pregnancies. Since the proposed mechanisms of preeclampsia development include adenosine-dependent biological effects, adenosine membrane transporters and receptors, and the associated signalling mechanisms might play a role in the pathophysiology of preeclampsia. Preeclampsia associates with increased adenosine concentration in the maternal blood and placental tissue, likely due to local hypoxia and ischemia (although not directly demonstrated), microthrombosis, increased catecholamine release, and platelet activation. In addition, abnormal expression and function of equilibrative nucleoside transporters is described in foetoplacental tissues from preeclampsia; however, the role of adenosine receptors in the aetiology of this disease is not well understood. Adenosine receptors activation may be related to abnormal trophoblast invasion, angiogenesis, and ischemia/reperfusion mechanisms in the placenta from preeclampsia. These mechanisms may explain only a low fraction of the associated abnormal transformation of spiral arteries in preeclampsia, triggering cellular stress and inflammatory mediators release from the placenta to the maternal circulation. Although increased adenosine concentration in preeclampsia may be a compensatory or adaptive mechanism favouring placental angiogenesis, a poor angiogenic state is found in preeclampsia. Thus, preeclampsia-associated complications might affect the cell response to adenosine due to altered expression and activity of adenosine receptors, membrane transporters

Coupling to protein kinases A and C of adenosine A2B receptors involved in the facilitation of noradrenaline release in the prostatic portion of rat vas deferens.

PubMed

Queiroz, Glória; Quintas, Clara; Talaia, Carlos; Gonçalves, Jorge

2004-08-01

In the prostatic portion of rat vas deferens, the non-selective adenosine receptor agonist NECA (0.1-30 microM), but not the A(2A) agonist CGS 21680 (0.001-10 microM), caused a facilitation of electrically evoked noradrenaline release (up to 43 +/- 4%), when inhibitory adenosine A(1) receptors were blocked. NECA-elicited facilitation of noradrenaline release was prevented by the A(2B) receptor-antagonist MRS 1754, enhanced by preventing cyclic-AMP degradation with rolipram, abolished by the protein kinase A inhibitors H-89, KT 5720 and cyclic-AMPS-Rp and attenuated by the protein kinase C inhibitors Ro 32-0432 and calphostin C. The adenosine uptake inhibitor NBTI also elicited a facilitation of noradrenaline release; an effect that was abolished by adenosine deaminase and attenuated by MRS 1754, by inhibitors of the extracellular nucleotide metabolism and by blockade of alpha(1)-adrenoceptors and P2X receptors with prazosin and NF023, respectively. It was concluded that adenosine A(2B) receptors are involved in a facilitation of noradrenaline release in the prostatic portion of rat vas deferens that can be activated by adenosine formed by extracellular catabolism of nucleotides. The receptors seem to be coupled to the adenylyl cyclase-protein kinase A pathway but activation of the protein kinase C by protein kinase A, may also contribute to the adenosine A(2B) receptor-mediated facilitation of noradrenaline release.

Effects of cyclic adenosine monophosphate response element binding protein overexpression in the basolateral amygdala on behavioral models of depression and anxiety.

PubMed

Wallace, Tanya L; Stellitano, Kathryn E; Neve, Rachael L; Duman, Ronald S

2004-08-01

Chronic antidepressant administration increases the cyclic adenosine monophosphate response element binding protein (CREB) in the amygdala, a critical neural substrate involved in the physiologic responses to stress, fear, and anxiety. To determine the role of CREB in the amygdala in animal models of depression and anxiety, a viral gene transfer approach was used to selectively express CREB in this region of the rat brain. In the learned helplessness model of depression, induction of CREB in the basolateral amygdala after training decreased the number of escape failures, an antidepressant response. However, expression of CREB before training increased escape failures, and increased immobility in the forced swim test, depressive effects. Expression of CREB in the basolateral amygdala also increased behavioral measures of anxiety in both the open field test and the elevated plus maze, and enhanced cued fear conditioning. Taken together, these data demonstrate that CREB expression in the basolateral amygdala influences behavior in models of depression, anxiety, and fear. Moreover, in the basolateral amygdala, the temporal expression of CREB in relation to learned helplessness training, determines the qualitative outcome in this animal model of depression.

Effects of drugs affecting endogenous amines or cyclic nucleotides on ethanol withdrawal head twitches in mice.

PubMed Central

Collier, H O; Hammond, M D; Schneider, C

1976-01-01

1 Twenty-four hours after ethanol withdrawal, dependent mice exhibited frequent head twitching. Naive mice exhibited similar twitching 15 min after treatment with 5-hydroxytryptophan (5-HTP) or 6 h after alpha-methyl-p-tyrosine (AMPT). Ethanol lessened the incidence of head twitches induced by any of these treatments. 5-HTP and AMPT each increased the incidence of head twitches induced by withdrawal of ethanol from dependent mice. 2 Drugs that affect the amount or activity of endogenous amines or cyclic nucleotides modified the incidence of head twitches. Nearly all drugs acted in the same direction on twitching elicited by any of these three treatments. 3 The incidence was lessened by: (a) methysergide, methergoline, MA 1420, p-chlorophenylalanine and p-chloroamphetamine; (b) dopamine, noradrenaline, L-DOPA, amphetamine and apomorphine; (c) hyoscine and nicotine; and (d) adenosine triphosphate, dibutyryl cyclic adenosine-3',5'-monophosphate (db cyclic AMP) and prostaglandins E1 and E2. 4 The incidence was increased by: (a) acetylcholine, carbachol and physostigmine; and (b) guanosine triphosphate, dibutyryl cyclic guanosine monophosphate (db cyclic GMP), theophylline and 3-isobutyl-1-methyl-xanthine. 5 These findings suggest that head twitching induced by these three treatments arises from a common biochemical mechanism, which may ultimately be a change in favour of cyclic GMP of the balance between this nucleotide and cyclic AMP within appropriate neurones. This imbalance appears to be elicited or increased by 5-hydroxytryptamine and acetylcholine and to be decreased by dopamine, noradrenaline and E prostaglandins. 6 Neither actinomycin D nor cycloheximide, given during the induction of ethanol dependence, altered the incidence of head twitches after ethanol withdrawal. PMID:987821

Low-power laser irradiation promotes the proliferation and osteogenic differentiation of human periodontal ligament cells via cyclic adenosine monophosphate

PubMed Central

Wu, Jyun-Yi; Chen, Chia-Hsin; Yeh, Li-Yin; Yeh, Ming-Long; Ting, Chun-Chan; Wang, Yan-Hsiung

2013-01-01

Retaining or improving periodontal ligament (PDL) function is crucial for restoring periodontal defects. The aim of this study was to evaluate the physiological effects of low-power laser irradiation (LPLI) on the proliferation and osteogenic differentiation of human PDL (hPDL) cells. Cultured hPDL cells were irradiated (660 nm) daily with doses of 0, 1, 2 or 4 J⋅cm−2. Cell proliferation was evaluated by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and the effect of LPLI on osteogenic differentiation was assessed by Alizarin Red S staining and alkaline phosphatase (ALP) activity. Additionally, osteogenic marker gene expression was confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR). Our data showed that LPLI at a dose of 2 J⋅cm−2 significantly promoted hPDL cell proliferation at days 3 and 5. In addition, LPLI at energy doses of 2 and 4 J⋅cm−2 showed potential osteogenic capacity, as it stimulated ALP activity, calcium deposition, and osteogenic gene expression. We also showed that cyclic adenosine monophosphate (cAMP) is a critical regulator of the LPLI-mediated effects on hPDL cells. This study shows that LPLI can promote the proliferation and osteogenic differentiation of hPDL cells. These results suggest the potential use of LPLI in clinical applications for periodontal tissue regeneration. PMID:23788285

Prostaglandin E2 Stimulates EP2, Adenylate Cyclase, Phospholipase C, and Intracellular Calcium Release to Mediate Cyclic Adenosine Monophosphate Production in Dental Pulp Cells.

PubMed

Chang, Mei-Chi; Lin, Szu-I; Lin, Li-Deh; Chan, Chiu-Po; Lee, Ming-Shu; Wang, Tong-Mei; Jeng, Po-Yuan; Yeung, Sin-Yuet; Jeng, Jiiang-Huei

2016-04-01

Prostaglandin E2 (PGE2) plays a crucial role in pulpal inflammation and repair. However, its induction of signal transduction pathways is not clear but is crucial for future control of pulpal inflammation. Primary dental pulp cells were exposed to PGE2 and 19R-OH PGE2 (EP2 agonist) or sulprostone (EP1/EP3 agonist) for 5 to 40 minutes. Cellular cyclic adenosine monophosphate (cAMP) levels were measured using the enzyme-linked immunosorbent assay. In some experiments, cells were pretreated with SQ22536 (adenylate cyclase inhibitor), H89 (protein kinase A inhibitor), dorsomorphin (adenosine monophosphate-activated protein kinase inhibitor), U73122 (phospholipase C inhibitor), thapsigargin (inhibitor of intracellular calcium release), W7 (calmodulin antagonist), verapamil (L-type calcium channel blocker), and EGTA (extracellular calcium chelator) for 20 minutes before the addition of PGE2. PGE2 and 19R-OH PGE2 (EP2 agonist) stimulated cAMP production, whereas sulprostone (EP1/EP3 agonist) shows little effect. PGE2-induced cAMP production was attenuated by SQ22536 and U73122 but not H89 and dorsomorphin. Intriguingly, thapsigargin and W7 prevented PGE2-induced cAMP production, but verapamil and EGTA showed little effect. These results indicate that PGE2-induced cAMP production is associated with EP2 receptor and adenylate cyclase activation. These events are mediated by phospholipase C, intracellular calcium release, and calcium-calmodulin signaling. These results are helpful for understanding the role of PGE2 in pulpal inflammation and repair and possible future drug intervention. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Adenosine and Ischemic Preconditioning

PubMed Central

Liang, Bruce T.; Swierkosz, Tomasz A.; Herrmann, Howard C.; Kimmel, Stephen; Jacobson, Kenneth A.

2012-01-01

Adenosine is released in large amounts during myocardial ischemia and is capable of exerting potent cardioprotective effects in the heart. Although these observations on adenosine have been known for a long time, how adenosine acts to achieve its anti-ischemic effect remains incompletely understood. However, recent advances on the chemistry and pharmacology of adenosine receptor ligands have provided important and novel information on the function of adenosine receptor subtypes in the cardiovascular system. The development of model systems for the cardiac actions of adenosine has yielded important insights into its mechanism of action and have begun to elucidate the sequence of signalling events from receptor activation to the actual exertion of its cardioprotective effect. The present review will focus on the adenosine receptors that mediate the potent anti-ischemic effect of adenosine, new ligands at the receptors, potential molecular signalling mechanisms downstream of the receptor, mediators for cardioprotection, and possible clinical applications in cardiovascular disorders. PMID:10607860

Nephrogenous Cyclic Adenosine Monophosphate as a Parathyroid Function Test

PubMed Central

Broadus, Arthur E.; Mahaffey, Jane E.; Bartter, Frederic C.; Neer, Robert M.

1977-01-01

Nephrogenous cyclic AMP (NcAMP), total cyclic AMP excretion (UcAMP), and plasma immunoreactive parathyroid hormone (iPTH), determined with a multivalent antiserum, were prospectively measured in 55 control subjects, 57 patients with primary hyperparathyroidism (1°HPT), and 10 patients with chronic hypoparathyroidism. In the group with 1° HPT, NcAMP was elevated in 52 patients (91%), and similar elevations were noted in subgroups of 26 patients with mild (serum calcium ≤10.7 mg/dl) or intermittent hypercalcemia, 19 patients with mild renal insufficiency (mean glomerular filtration rate, 64 ml/min), and 10 patients with moderate renal insufficiency (mean glomerular filtration rate, 43 ml/min). Plasma iPTH was increased in 41 patients (73%). The development of a parametric expression for UcAMP was found to be critically important in the clinical interpretation of results for total cAMP excretion. Because of renal impairment in a large number of patients, the absolute excretion rate of cAMP correlated poorly with the hyperparathyroid state. Expressed as a function of creatinine excretion, UcAMP was elevated in 81% of patients with 1° HPT, but the nonparametric nature of the expression led to a number of interpretive difficulties. The expression of cAMP excretion as a function of glomerular filtration rate was developed on the basis of the unique features of cAMP clearance in man, and this expression, which provided elevated values in 51 (89%) of the patients with 1° HPT, avoided entirely the inadequacies of alternative expressions. Results for NcAMP and UcAMP in nonazotemic and azotemic patients with hypoparathyroidism confirmed the validity of the measurements and the expressions employed. PMID:197123

Determination of cyclic guanosine- and cyclic adenosine monophosphate (cGMP and cAMP) in human plasma and animal tissues by solid phase extraction on silica and liquid chromatography-triple quadrupole mass spectrometry.

PubMed

Van Damme, Thomas; Zhang, Yanhua; Lynen, Frédéric; Sandra, Pat

2012-11-15

3',5'-Cyclic guanosine monophosphate (cGMP) and 3',5'-cyclic adenosine monophosphate (cAMP) are essential second messenger molecules. They are involved in signal transduction within cells, in physiological functions such as neurotransmission and in the modulation of cell growth and differentiation of organisms, respectively. A quantitative solid phase extraction method (SPE) based on hydrophilic interaction on silica was developed and applied to both plasma and tissue samples. The stable isotope-labeled internal standards ²D₁, ¹⁵N₃-3',5'-cGMP and ¹³C₁₀, ¹⁵N₅-3',5'-cAMP were added prior to the sample preparation to ensure high precision and accuracy. The samples were analyzed by reversed-phase liquid chromatography (RP-LC). Negative electrospray (ESI)-MS/MS was used to selectively monitor several transitions of each metabolite. The method for the analysis of 3',5'-cAMP and 3',5'-cGMP in plasma was validated in the range of 0.15-20 ng/mL (R²=0.9996 and 0.9994 for 3',5'-cAMP and 3',5'-cGMP, respectively). Basal plasma concentrations for fifteen healthy human patients determined with this method varied between 4.66-9.20 ng/mL for 3',5'-cAMP and between 0.30-1.20 ng/mL for 3',5'-cGMP, with precisions better than 9.1%. 3',5'-cGMP and 3',5'-cAMP together with their 2',3'-isomers were also determined in a semi quantitative way in animal tissues. The structures of the isomers were confirmed by analysis with LC-high resolution time-of-flight MS and subsequently by comparison of retention times with standards. Copyright © 2012 Elsevier B.V. All rights reserved.

[Qualitative analysis of bis-(3'-5')-cyclic dimeric adenosine monophosphate of Porphyromonas gingivalis by high performance liquid chromatography coupled with mass spectrometry].

PubMed

Yongmei, Tan; Xiaojun, Yang; Juan, Du; Wanghong, Zhao; Xiaodan, Chen; Jin, Hou

2016-06-01

To test whether Porphyromonas gingivalis (P. gingivalis) could produce bacterial signal molecule, bis-(3'-5')-cyclic dimeric adenosine monophosphate (c-di-AMP) and lay the foundation for explorations of its roles in life metabolism and periodontitis immunity of P. gingivalis. P. gingivalis standard strain ATCC33277 was used as the experimental strain to extract nucleic acids from the bacteria. Then, c-di-AMP was detected using high performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS). Subsequently, HPLC was used to validate the sample further. Based on the signal/noise (S/N) for 3 : 1, the limit of determination of HPLC-MS/MS for peak time of c-di-AMP standard substances was 7.49 min and nucleic acid extractions from P. gingivalis was 8.82 min (S/N > 3). Further confirmation of HPLC showed that nucleic acid extractions from both P. gingivalis and c-di-AMP standard substances pre- sented goal absorbent peaks at 15.7 min, with the same ultraviolet absorbent spectrum. The nucleic acid extrac- tions from P. gingivalis contained c-di-AMP, which shows that P. gingivalis could produce c-di-AMP.

A Role for Adenosine Deaminase in Drosophila Larval Development

PubMed Central

Dolezal, Tomas; Dolezelova, Eva; Zurovec, Michal

2005-01-01

Adenosine deaminase (ADA) is an enzyme present in all organisms that catalyzes the irreversible deamination of adenosine and deoxyadenosine to inosine and deoxyinosine. Both adenosine and deoxyadenosine are biologically active purines that can have a deep impact on cellular physiology; notably, ADA deficiency in humans causes severe combined immunodeficiency. We have established a Drosophila model to study the effects of altered adenosine levels in vivo by genetic elimination of adenosine deaminase-related growth factor-A (ADGF-A), which has ADA activity and is expressed in the gut and hematopoietic organ. Here we show that the hemocytes (blood cells) are the main regulator of adenosine in the Drosophila larva, as was speculated previously for mammals. The elevated level of adenosine in the hemolymph due to lack of ADGF-A leads to apparently inconsistent phenotypic effects: precocious metamorphic changes including differentiation of macrophage-like cells and fat body disintegration on one hand, and delay of development with block of pupariation on the other. The block of pupariation appears to involve signaling through the adenosine receptor (AdoR), but fat body disintegration, which is promoted by action of the hemocytes, seems to be independent of the AdoR. The existence of such an independent mechanism has also been suggested in mammals. PMID:15907156

Adenosine receptors and caffeine in retinopathy of prematurity.

PubMed

Chen, Jiang-Fan; Zhang, Shuya; Zhou, Rong; Lin, Zhenlang; Cai, Xiaohong; Lin, Jing; Huo, Yuqing; Liu, Xiaoling

2017-06-01

Retinopathy of prematurity (ROP) is a major cause of childhood blindness in the world and is caused by oxygen-induced damage to the developing retinal vasculature, resulting in hyperoxia-induced vaso-obliteration and subsequent delayed retinal vascularization and hypoxia-induced pathological neovascularization driven by vascular endothelial growth factor (VEGF) signaling pathway in retina. Current anti-VEGF therapy has shown some effective in a clinical trial, but is associated with the unintended effects on delayed eye growth and retinal vasculature development of preterm infants. Notably, cellular responses to hypoxia are characterized by robust increases in extracellular adenosine production and the markedly induced adenosine receptors, which provide a novel target for preferential control of pathological angiogenesis without affecting normal vascular development. Here, we review the experimental evidence in support of adenosine receptor-based therapeutic strategy for ROP, including the aberrant adenosine signaling in oxygen-induced retinopathy and the role of three adenosine receptor subtypes (A 1 R, A 2A R, A 2B R) in development and treatment of ROP using oxygen-induced retinopathy models. The clinical and initial animal evidence that implicate the therapeutic effect of caffeine (a non-selective adenosine receptor antagonist) in treatment of ROP are highlighted. Lastly, we discussed the translational potential as well therapeutic advantage of adenosine receptor- and caffeine-based therapy for ROR and possibly other proliferative retinopathy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adenosine receptors and caffeine in retinopathy of prematurity

PubMed Central

Chen, Jiang-Fan; Zhang, Shuya; Zhou, Rong; Lin, Zhenlang; Cai, Xiaohong; Lin, Jing; Huo, Yuqing; Liu, Xiaoling

2017-01-01

Retinopathy of prematurity (ROP) is a major cause of childhood blindness in the world and is caused by oxygen-induced damage to the developing retinal vasculature, resulting in hyperoxia-induced vaso-obliteration and subsequent delayed retinal vascularization and hypoxia-induced pathological neovascularization driven by vascular endothelial growth factor (VEGF) signaling pathway in retina. Current anti-VEGF therapy has shown some effective in a clinical trial, but is associated with the unintended effects on delayed eye growth and retinal vasculature development of preterm infants. Notably, cellular responses to hypoxia are characterized by robust increases in extracellular adenosine production and the markedly induced adenosine receptors, which provide a novel target for preferential control of pathological angiogenesis without affecting normal vascular development. Here, we review the experimental evidence in support of adenosine receptor-based therapeutic strategy for ROP, including the aberrant adenosine signaling in oxygen-induced retinopathy and the role of three adenosine receptor subtypes (A1R, A2AR, A2BR) in development and treatment of ROP using oxygen-induced retinopathy models. The clinical and initial animal evidence that implicate the therapeutic effect of caffeine (a non-selective adenosine receptor antagonist) in treatment of ROP are highlighted. Lastly, we discussed the translational potential as well therapeutic advantage of adenosine receptor- and caffeine-based therapy for ROR and possibly other proliferative retinopathy. PMID:28088487

Adenosine and the Auditory System

PubMed Central

Vlajkovic, Srdjan M; Housley, Gary D; Thorne, Peter R

2009-01-01

Adenosine is a signalling molecule that modulates cellular activity in the central nervous system and peripheral organs via four G protein-coupled receptors designated A1, A2A, A2B, and A3. This review surveys the literature on the role of adenosine in auditory function, particularly cochlear function and its protection from oxidative stress. The specific tissue distribution of adenosine receptors in the mammalian cochlea implicates adenosine signalling in sensory transduction and auditory neurotransmission although functional studies have demonstrated that adenosine stimulates cochlear blood flow, but does not alter the resting and sound-evoked auditory potentials. An interest in a potential otoprotective role for adenosine has recently evolved, fuelled by the capacity of A1 adenosine receptors to prevent cochlear injury caused by acoustic trauma and ototoxic drugs. The balance between A1 and A2A receptors is conceived as critical for cochlear response to oxidative stress, which is an underlying mechanism of the most common inner ear pathologies (e.g. noise-induced and age-related hearing loss, drug ototoxicity). Enzymes involved in adenosine metabolism, adenosine kinase and adenosine deaminase, are also emerging as attractive targets for controlling oxidative stress in the cochlea. Other possible targets include ectonucleotidases that generate adenosine from extracellular ATP, and nucleoside transporters, which regulate adenosine concentrations on both sides of the plasma membrane. Developments of selective adenosine receptor agonists and antagonists that can cross the blood-cochlea barrier are bolstering efforts to develop therapeutic interventions aimed at ameliorating cochlear injury. Manipulations of the adenosine signalling system thus hold significant promise in the therapeutic management of oxidative stress in the cochlea. PMID:20190966

Detrimental effects of adenosine signaling in sickle cell disease

PubMed Central

Zhang, Yujin; Dai, Yingbo; Wen, Jiaming; Zhang, Weiru; Grenz, Almut; Sun, Hong; Tao, Lijian; Lu, Guangxiu; Alexander, Danny C; Milburn, Michael V; Carter-Dawson, Louvenia; Lewis, Dorothy E; Zhang, Wenzheng; Eltzschig, Holger K; Kellems, Rodney E; Blackburn, Michael R; Juneja, Harinder S; Xia, Yang

2016-01-01

Hypoxia can act as an initial trigger to induce erythrocyte sickling and eventual end organ damage in sickle cell disease (SCD). Many factors and metabolites are altered in response to hypoxia and may contribute to the pathogenesis of the disease. Using metabolomic profiling, we found that the steady-state concentration of adenosine in the blood was elevated in a transgenic mouse model of SCD. Adenosine concentrations were similarly elevated in the blood of humans with SCD. Increased adenosine levels promoted sickling, hemolysis and damage to multiple tissues in SCD transgenic mice and promoted sickling of human erythrocytes. Using biochemical, genetic and pharmacological approaches, we showed that adenosine A2B receptor (A2BR)-mediated induction of 2,3-diphosphoglycerate, an erythrocyte-specific metabolite that decreases the oxygen binding affinity of hemoglobin, underlies the induction of erythrocyte sickling by excess adenosine both in cultured human red blood cells and in SCD transgenic mice. Thus, excessive adenosine signaling through the A2BR has a pathological role in SCD. These findings may provide new therapeutic possibilities for this disease. PMID:21170046

Detrimental effects of adenosine signaling in sickle cell disease.

PubMed

Zhang, Yujin; Dai, Yingbo; Wen, Jiaming; Zhang, Weiru; Grenz, Almut; Sun, Hong; Tao, Lijian; Lu, Guangxiu; Alexander, Danny C; Milburn, Michael V; Carter-Dawson, Louvenia; Lewis, Dorothy E; Zhang, Wenzheng; Eltzschig, Holger K; Kellems, Rodney E; Blackburn, Michael R; Juneja, Harinder S; Xia, Yang

2011-01-01

Hypoxia can act as an initial trigger to induce erythrocyte sickling and eventual end organ damage in sickle cell disease (SCD). Many factors and metabolites are altered in response to hypoxia and may contribute to the pathogenesis of the disease. Using metabolomic profiling, we found that the steady-state concentration of adenosine in the blood was elevated in a transgenic mouse model of SCD. Adenosine concentrations were similarly elevated in the blood of humans with SCD. Increased adenosine levels promoted sickling, hemolysis and damage to multiple tissues in SCD transgenic mice and promoted sickling of human erythrocytes. Using biochemical, genetic and pharmacological approaches, we showed that adenosine A(2B) receptor (A(2B)R)-mediated induction of 2,3-diphosphoglycerate, an erythrocyte-specific metabolite that decreases the oxygen binding affinity of hemoglobin, underlies the induction of erythrocyte sickling by excess adenosine both in cultured human red blood cells and in SCD transgenic mice. Thus, excessive adenosine signaling through the A(2B)R has a pathological role in SCD. These findings may provide new therapeutic possibilities for this disease.

Retinal Cyclic Nucleotide-Gated Channels: From Pathophysiology to Therapy.

PubMed

Michalakis, Stylianos; Becirovic, Elvir; Biel, Martin

2018-03-07

The first step in vision is the absorption of photons by the photopigments in cone and rod photoreceptors. After initial amplification within the phototransduction cascade the signal is translated into an electrical signal by the action of cyclic nucleotide-gated (CNG) channels. CNG channels are ligand-gated ion channels that are activated by the binding of cyclic guanosine monophosphate (cGMP) or cyclic adenosine monophosphate (cAMP). Retinal CNG channels transduce changes in intracellular concentrations of cGMP into changes of the membrane potential and the Ca 2+ concentration. Structurally, the CNG channels belong to the superfamily of pore-loop cation channels and share a common gross structure with hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and voltage-gated potassium channels (KCN). In this review, we provide an overview on the molecular properties of CNG channels and describe their physiological role in the phototransduction pathways. We also discuss insights into the pathophysiological role of CNG channel proteins that have emerged from the analysis of CNG channel-deficient animal models and human CNG channelopathies. Finally, we summarize recent gene therapy activities and provide an outlook for future clinical application.

Retinal Cyclic Nucleotide-Gated Channels: From Pathophysiology to Therapy

PubMed Central

Biel, Martin

2018-01-01

The first step in vision is the absorption of photons by the photopigments in cone and rod photoreceptors. After initial amplification within the phototransduction cascade the signal is translated into an electrical signal by the action of cyclic nucleotide-gated (CNG) channels. CNG channels are ligand-gated ion channels that are activated by the binding of cyclic guanosine monophosphate (cGMP) or cyclic adenosine monophosphate (cAMP). Retinal CNG channels transduce changes in intracellular concentrations of cGMP into changes of the membrane potential and the Ca2+ concentration. Structurally, the CNG channels belong to the superfamily of pore-loop cation channels and share a common gross structure with hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and voltage-gated potassium channels (KCN). In this review, we provide an overview on the molecular properties of CNG channels and describe their physiological role in the phototransduction pathways. We also discuss insights into the pathophysiological role of CNG channel proteins that have emerged from the analysis of CNG channel-deficient animal models and human CNG channelopathies. Finally, we summarize recent gene therapy activities and provide an outlook for future clinical application. PMID:29518895

A combined variable temperature 600 MHz NMR/MD study of the calcium release agent cyclic adenosine diphosphate ribose (cADPR): Structure, conformational analysis, and thermodynamics of the conformational equilibria.

PubMed

Javornik, Uroš; Plavec, Janez; Wang, Baifan; Graham, Steven M

2018-01-02

A combined variable temperature 600 MHz NMR/molecular dynamics study of the Ca 2+ -release agent cyclic adenosine 5'-diphosphate ribose (cADPR) was conducted. In addition to elucidating the major and minor orientations of the conformationally flexible furanose rings, γ- (C4'-C5'), and β- (C5'-O5') bonds, the thermodynamics (ΔH o , ΔS o ) associated with each of these conformational equilibria were determined. Both furanose rings were biased towards a south conformation (64-74%) and both β-bonds heavily favored trans conformations. The R-ring γ-bond was found to exist almost exclusively as the γ + conformer, whereas the A-ring γ-bond was a mixture of the γ + and γ t conformers, with the trans conformer being slightly favored. Enthalpic factors accounted for most of the observed conformational preferences, although the R-ring furanose exists as its major conformation based solely on entropic factors. There was excellent agreement between the NMR and MD results, particularly with regard to the conformer identities, but the MD showed a bias towards γ + conformers. The MD results showed that both N-glycosidic χ-bonds are exclusively syn. Collectively the data allowed for the construction of a model for cADPR in which many of the conformationally flexible units in fact effectively adopt single orientations and where most of the conformational diversity resides in its A-ring furanose and γ-bond. Copyright © 2017 Elsevier Ltd. All rights reserved.

5'-adenosine monophosphate is the neutrophil-derived paracrine factor that elicits chloride secretion from T84 intestinal epithelial cell monolayers.

PubMed Central

Madara, J L; Patapoff, T W; Gillece-Castro, B; Colgan, S P; Parkos, C A; Delp, C; Mrsny, R J

1993-01-01

Neutrophil transmigration across intestinal epithelia is thought to contribute to epithelial dysfunction and characterizes many inflammatory intestinal diseases. Neutrophils activated by factors, normally present in the lumen, release a neutrophil-derived secretagogue activity to which intestinal epithelia respond with an electrogenic chloride secretion, the transport event which underlies secretory diarrhea. Using sequential ultrafiltration, column chromatographic, and mass and Raman spectroscopic techniques, neutrophil-derived secretagogue was identified as 5'-AMP. Additional studies suggested that neutrophil-derived 5'-AMP is subsequently converted to adenosine at the epithelial cell surface by ecto-5'-nucleotidase and that adenosine subsequently activates intestinal secretion through adenosine receptors on the apical membrane of target intestinal epithelial cells. These findings suggest that this ATP metabolite may serve as a neutrophil-derived paracrine mediator that contributes to secretory diarrhea in states of intestinal inflammation. PMID:8486793

Effect of bucladesine, pentoxifylline, and H-89 as cyclic adenosine monophosphate analog, phosphodiesterase, and protein kinase A inhibitor on acute pain.

PubMed

Salehi, Forouz; Hosseini-Zare, Mahshid S; Aghajani, Haleh; Seyedi, Seyedeh Yalda; Hosseini-Zare, Maryam S; Sharifzadeh, Mohammad

2017-08-01

The aim of this study was to determine the effects of cyclic adenosine monophosphate (cAMP) and its dependent pathway on thermal nociception in a mouse model of acute pain. Here, we studied the effect of H-89 (protein kinase A inhibitor), bucladesine (Db-cAMP) (membrane-permeable analog of cAMP), and pentoxifylline (PTX; nonspecific phosphodiesterase (PDE) inhibitor) on pain sensation. Different doses of H-89 (0.05, 0.1, and 0.5 mg/100 g), PTX (5, 10, and 20 mg/100 g), and Db-cAMP (50, 100, and 300 nm/mouse) were administered intraperitoneally (I.p.) 15 min before a tail-flick test. In combination groups, we injected the first and the second compounds 30 and 15 min before the tail-flick test, respectively. I.p. administration of H-89 and PTX significantly decreased the thermal-induced pain sensation in their low applied doses. Db-cAMP, however, decreased the pain sensation in a dose-dependent manner. The highest applied dose of H-89 (0.5 mg/100 g) attenuated the antinociceptive effect of Db-cAMP in doses of 50 and 100 nm/mouse. Surprisingly, Db-cAMP decreased the antinociceptive effect of the lowest dose of H-89 (0.05 mg/100 g). All applied doses of PTX reduced the effect of 0.05 mg/100 g H-89 on pain sensation; however, the highest dose of H-89 compromised the antinociceptive effect of 20 mg/100 g dose of PTX. Co-administration of Db-cAMP and PTX increased the antinociceptive effect of each compound on thermal-induced pain. In conclusion, PTX, H-89, and Db-cAMP affect the thermal-induced pain by probably interacting with intracellular cAMP and cGMP signaling pathways and cyclic nucleotide-dependent protein kinases. © 2017 Société Française de Pharmacologie et de Thérapeutique.

Adenosine receptor desensitization and trafficking.

PubMed

Mundell, Stuart; Kelly, Eamonn

2011-05-01

As with the majority of G-protein-coupled receptors, all four of the adenosine receptor subtypes are known to undergo agonist-induced regulation in the form of desensitization and trafficking. These processes can limit the ability of adenosine receptors to couple to intracellular signalling pathways and thus reduce the ability of adenosine receptor agonists as well as endogenous adenosine to produce cellular responses. In addition, since adenosine receptors couple to multiple signalling pathways, these pathways may desensitize differentially, while the desensitization of one pathway could even trigger signalling via another. Thus, the overall picture of adenosine receptor regulation can be complex. For all adenosine receptor subtypes, there is evidence to implicate arrestins in agonist-induced desensitization and trafficking, but there is also evidence for other possible forms of regulation, including second messenger-dependent kinase regulation, heterologous effects involving G proteins, and the involvement of non-clathrin trafficking pathways such as caveolae. In this review, the evidence implicating these mechanisms is summarized for each adenosine receptor subtype, and we also discuss those issues of adenosine receptor regulation that remain to be resolved as well as likely directions for future research in this field. Copyright © 2010 Elsevier B.V. All rights reserved.

Factors associated with early cyclicity in postpartum dairy cows.

PubMed

Vercouteren, M M A A; Bittar, J H J; Pinedo, P J; Risco, C A; Santos, J E P; Vieira-Neto, A; Galvão, K N

2015-01-01

The objective of this study was to evaluate factors associated with resumption of ovarian cyclicity within 21 days in milk (DIM) in dairy cows. Cows (n=768) from 2 herds in north Florida had their ovaries scanned at 17±3, 21±3, and 24±3 DIM. Cows that had a corpus luteum ≥20mm at 17±3 or at 21±3 DIM or that had a corpus luteum <20mm in 2 consecutive examinations were determined to be cyclic by 21±3 DIM. The following information was collected for up to 14 DIM: calving season, parity, calving problems, metabolic problems, metritis, mastitis, digestive problems, lameness, body weight loss, dry period length, and average daily milk yield. Body condition was scored at 17±3 DIM. Multivariable mixed logistic regression analysis was performed using the GLIMMIX procedure of SAS. Variables with P≤0.2 were considered in each model. Herd was included as a random variable. Three models were constructed: model 1 included all cows, model 2 included only cows from dairy 1 that had daily body weights available, and model 3 included only multiparous cows with a previous dry period length recorded. In model 1, variables associated with greater cyclicity by 21±3 DIM were calving in the summer and fall rather than in the winter or spring, being multiparous rather than primiparous, and not having metabolic or digestive problems. In model 2, variables associated with greater cyclicity by 21±3 DIM were calving in the summer and fall, not having metritis or digestive problems and not losing >28 kg of BW within 14 DIM. In model 3, variables associated with greater cyclicity by 21±3 DIM were absence of metabolic problems and dry period ≤76 d. In summary, cyclicity by 21±3 DIM was negatively associated with calving in winter or spring, primiparity, metritis, metabolic or digestive problems, loss of >28 kg of body weight, and a dry period >76d. Strategies preventing extended dry period length and loss of BW, together with reductions in the incidence of metritis as well as

AMP and adenosine are both ligands for adenosine 2B receptor signaling.

PubMed

Holien, Jessica K; Seibt, Benjamin; Roberts, Veena; Salvaris, Evelyn; Parker, Michael W; Cowan, Peter J; Dwyer, Karen M

2018-01-15

Adenosine is considered the canonical ligand for the adenosine 2B receptor (A 2B R). A 2B R is upregulated following kidney ischemia augmenting post ischemic blood flow and limiting tubular injury. In this context the beneficial effect of A 2B R signaling has been attributed to an increase in the pericellular concentration of adenosine. However, following renal ischemia both kidney adenosine monophosphate (AMP) and adenosine levels are substantially increased. Using computational modeling and calcium mobilization assays, we investigated whether AMP could also be a ligand for A 2B R. The computational modeling suggested that AMP interacts with more favorable energy to A 2B R compared with adenosine. Furthermore, AMPαS, a non-hydrolyzable form of AMP, increased calcium uptake by Chinese hamster ovary (CHO) cells expressing the human A 2B R, indicating preferential signaling via the G q pathway. Therefore, a putative AMP-A 2B R interaction is supported by the computational modeling data and the biological results suggest this interaction involves preferential G q activation. These data provide further insights into the role of purinergic signaling in the pathophysiology of renal IRI. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extracellular formation and uptake of adenosine during skeletal muscle contraction in the rat: role of adenosine transporters

PubMed Central

Lynge, J; Juel, C; Hellsten, Y

2001-01-01

The existence of adenosine transporters in plasma membrane giant vesicles from rat skeletal muscles and in primary skeletal muscle cell cultures was investigated. In addition, the contribution of intracellularly or extracellularly formed adenosine to the overall extracellular adenosine concentration during muscle contraction was determined in primary skeletal muscle cell cultures. In plasma membrane giant vesicles, the carrier-mediated adenosine transport demonstrated saturation kinetics with Km= 177 ± 36 μm and Vmax= 1.9 ± 0.2 nmol ml−1 s−1 (0.7 nmol (mg protein)−1 s−1). The existence of an adenosine transporter was further evidenced by the inhibition of the carrier-mediated adenosine transport in the presence of NBMPR (nitrobenzylthioinosine; 72 % inhibition) or dipyridamol (64 % inhibition; P < 0.05). In primary skeletal muscle cells, the rate of extracellular adenosine accumulation was 5-fold greater (P < 0.05) with electrical stimulation than without electrical stimulation. Addition of the adenosine transporter inhibitor NBMPR led to a 57 % larger (P < 0.05) rate of extracellular adenosine accumulation in the electro-stimulated muscle cells compared with control cells, demonstrating that adenosine is taken up by the skeletal muscle cells during contractions. Inhibition of ecto-5′-nucleotidase with AOPCP in electro-stimulated cells resulted in a 70 % lower (P < 0.05) rate of extracellular adenosine accumulation compared with control cells, indicating that adenosine to a large extent is formed in the extracellular space during contraction. The present study provides evidence for the existence of an NBMPR-sensitive adenosine transporter in rat skeletal muscle. Our data furthermore demonstrate that the increase in extracellular adenosine observed during electro-stimulation of skeletal muscle is due to production of adenosine in the extracellular space of skeletal muscle and that adenosine is taken up rather than released by the skeletal muscle cells

Cyclic strain alters the expression and release of angiogenic factors by human tendon cells.

PubMed

Mousavizadeh, Rouhollah; Khosravi, Shahram; Behzad, Hayedeh; McCormack, Robert G; Duronio, Vincent; Scott, Alex

2014-01-01

Angiogenesis is associated with the tissue changes underlying chronic overuse tendinopathy. We hypothesized that repetitive, cyclic loading of human tendon cells would lead to increased expression and activity of angiogenic factors. We subjected isolated human tendon cells to overuse tensile loading using an in vitro model (1 Hz, 10% equibiaxial strain). We found that mechanically stimulated human tendon cells released factors that promoted in vitro proliferation and tube formation by human umbilical vein endothelial cells (HUVEC). In response to cyclic strain, there was a transient increase in the expression of several angiogenic genes including ANGPTL4, FGF-2, COX-2, SPHK1, TGF-alpha, VEGF-A and VEGF-C, with no change in anti-angiogenic genes (BAI1, SERPINF1, THBS1 and 2, TIMP1-3). Cyclic strain also resulted in the extracellular release of ANGPTL4 protein by tendon cells. Our study is the first report demonstrating the induction of ANGPTL4 mRNA and release of ANGPTL4 protein in response to cyclic strain. Tenocytes may contribute to the upregulation of angiogenesis during the development of overuse tendinopathy.

Cyclic Strain Alters the Expression and Release of Angiogenic Factors by Human Tendon Cells

PubMed Central

Mousavizadeh, Rouhollah; Khosravi, Shahram; Behzad, Hayedeh; McCormack, Robert G.; Duronio, Vincent; Scott, Alex

2014-01-01

Angiogenesis is associated with the tissue changes underlying chronic overuse tendinopathy. We hypothesized that repetitive, cyclic loading of human tendon cells would lead to increased expression and activity of angiogenic factors. We subjected isolated human tendon cells to overuse tensile loading using an in vitro model (1 Hz, 10% equibiaxial strain). We found that mechanically stimulated human tendon cells released factors that promoted in vitro proliferation and tube formation by human umbilical vein endothelial cells (HUVEC). In response to cyclic strain, there was a transient increase in the expression of several angiogenic genes including ANGPTL4, FGF-2, COX-2, SPHK1, TGF-alpha, VEGF-A and VEGF-C, with no change in anti-angiogenic genes (BAI1, SERPINF1, THBS1 and 2, TIMP1-3). Cyclic strain also resulted in the extracellular release of ANGPTL4 protein by tendon cells. Our study is the first report demonstrating the induction of ANGPTL4 mRNA and release of ANGPTL4 protein in response to cyclic strain. Tenocytes may contribute to the upregulation of angiogenesis during the development of overuse tendinopathy. PMID:24824595

Kinetic parameters and renal clearances of plasma adenosine 3′,5′-monophosphate and guanosine 3′,5′-monophosphate in man

PubMed Central

Broadus, Arthur E.; Kaminsky, Neil I.; Hardman, Joel G.; Sutherland, Earl W.; Liddle, Grant W.

1970-01-01

Kinetic parameters and the renal clearances of plasma adenosine 3′,5′-monophosphate (cyclic AMP) and guanosine 3′,5′-monophosphate (cyclic GMP) were evaluated in normal subjects using tritium-labeled cyclic nucleotides. Each tracer was administered both by single, rapid intravenous injection and by constant intravenous infusion, and the specific activities of the cyclic nucleotides in plasma and urine were determined. Both cyclic AMP and cyclic GMP were cleared from plasma by glomerular filtration. The kidney was found to add a variable quantity of endogenous cyclic AMP to the tubular urine, amounting to an average of approximately one-third of the total level of cyclic AMP excreted. Plasma was the source of virtually all of the cyclic GMP excreted. Plasma levels of the cyclic nucleotides appeared to be in dynamic steady state. The apparent volumes of distribution of both nucleotides exceeded extracellular fluid volume, averaging 27 and 38% of body weight for cyclic AMP and cyclic GMP, respectively. Plasma production rates ranged from 9 to 17 nmoles/min for cyclic AMP and from 7 to 13 nmoles/min for cyclic GMP. Plasma clearance rates averaged 668 ml/min for cyclic AMP and 855 ml/min for cyclic GMP. Approximately 85% of the elimination of the cyclic nucleotides from the circulation was due to extrarenal clearance. PMID:5480849

Purine 3':5'-cyclic nucleotides with the nucleobase in a syn orientation: cAMP, cGMP and cIMP.

PubMed

Řlepokura, Katarzyna Anna

2016-06-01

Purine 3':5'-cyclic nucleotides are very well known for their role as the secondary messengers in hormone action and cellular signal transduction. Nonetheless, their solid-state conformational details still require investigation. Five crystals containing purine 3':5'-cyclic nucleotides have been obtained and structurally characterized, namely adenosine 3':5'-cyclic phosphate dihydrate, C10H12N5O6P·2H2O or cAMP·2H2O, (I), adenosine 3':5'-cyclic phosphate 0.3-hydrate, C10H12N5O6P·0.3H2O or cAMP·0.3H2O, (II), guanosine 3':5'-cyclic phosphate pentahydrate, C10H12N5O7P·5H2O or cGMP·5H2O, (III), sodium guanosine 3':5'-cyclic phosphate tetrahydrate, Na(+)·C10H11N5O7P(-)·4H2O or Na(cGMP)·4H2O, (IV), and sodium inosine 3':5'-cyclic phosphate tetrahydrate, Na(+)·C10H10N4O7P(-)·4H2O or Na(cIMP)·4H2O, (V). Most of the cyclic nucleotide zwitterions/anions [two from four cAMP present in total in (I) and (II), cGMP in (III), cGMP(-) in (IV) and cIMP(-) in (V)] are syn conformers about the N-glycosidic bond, and this nucleobase arrangement is accompanied by Crib-H...Npur hydrogen bonds (rib = ribose and pur = purine). The base orientation is tuned by the ribose pucker. An analysis of data obtained from the Cambridge Structural Database made in the context of syn-anti conformational preferences has revealed that among the syn conformers of various purine nucleotides, cyclic nucleotides and dinucleotides predominate significantly. The interactions stabilizing the syn conformation have been indicated. The inter-nucleotide contacts in (I)-(V) have been systematized in terms of the chemical groups involved. All five structures display three-dimensional hydrogen-bonded networks.

A continuous spectrophotometric assay for monitoring adenosine 5'-monophosphate production.

PubMed

First, Eric A

2015-08-15

A number of biologically important enzymes release adenosine 5'-monophosphate (AMP) as a product, including aminoacyl-tRNA synthetases, cyclic AMP (cAMP) phosphodiesterases, ubiquitin and ubiquitin-like ligases, DNA ligases, coenzyme A (CoA) ligases, polyA deadenylases, and ribonucleases. In contrast to the abundance of assays available for monitoring the conversion of adenosine 5'-triphosphate (ATP) to ADP, there are relatively few assays for monitoring the conversion of ATP (or cAMP) to AMP. In this article, we describe a homogeneous assay that continuously monitors the production of AMP. Specifically, we have coupled the conversion of AMP to inosine 5'-monophosphate (IMP) (by AMP deaminase) to the oxidation of IMP (by IMP dehydrogenase). This results in the reduction of oxidized nicotine adenine dinucleotide (NAD(+)) to reduced nicotine adenine dinucleotide (NADH), allowing AMP formation to be monitored by the change in the absorbance at 340 nm. Changes in AMP concentrations of 5 μM or more can be reliably detected. The ease of use and relatively low expense make the AMP assay suitable for both high-throughput screening and kinetic analyses. Copyright © 2015 Elsevier Inc. All rights reserved.

Regulation of theta-antigen expression by agents altering cyclic AMP level and by thymic factor.

PubMed

Bach, M A; Fournier, C; Bach, J F

1975-02-28

Thymic factor, cyclic AMP, and products increasing its cellular level, such as Prostaglandin E1, induce the appearance of the theta-antigen on T-cell precursors whether assessed by a rossette-inhibition assay or a cytotoxic assay after cell fractionation on BSA discontinuous gradiet. Synergism has been demonstrated between cyclic AMPT and TF for that effect. Conversely, decrease of theta expression has been obtained by altering cyclic AMP level in theta-positive cells either increasing it by dibutyryl cAMP treatment or decreasing it by indomethacin treatment. Finally, these data suggest the involvement of cyclic AMP in the regulation of theta expression under thymic hormone control.

Bacillus anthracis Edema Factor Substrate Specificity: Evidence for New Modes of Action

PubMed Central

Göttle, Martin; Dove, Stefan; Seifert, Roland

2012-01-01

Since the isolation of Bacillus anthracis exotoxins in the 1960s, the detrimental activity of edema factor (EF) was considered as adenylyl cyclase activity only. Yet the catalytic site of EF was recently shown to accomplish cyclization of cytidine 5′-triphosphate, uridine 5′-triphosphate and inosine 5′-triphosphate, in addition to adenosine 5′-triphosphate. This review discusses the broad EF substrate specificity and possible implications of intracellular accumulation of cyclic cytidine 3′:5′-monophosphate, cyclic uridine 3′:5′-monophosphate and cyclic inosine 3′:5′-monophosphate on cellular functions vital for host defense. In particular, cAMP-independent mechanisms of action of EF on host cell signaling via protein kinase A, protein kinase G, phosphodiesterases and CNG channels are discussed. PMID:22852066

Potentiation of adenosine triphosphate-induced contractile responses of the guinea-pig isolated vas deferens by adenosine monophosphate and adenosine 5'-monophosphorothioate.

PubMed Central

Fedan, J. S.

1987-01-01

The effects of incubating the guinea-pig isolated vas deferens in the presence of adenine nucleotides (adenosine triphosphate, ATP; adenosine diphosphate, ADP; and adenosine monophosphate, AMP), or in the presence of their phosphorothioate analogues (adenosine 5'-O-(3-thiotriphosphate), ATP gamma S; adenosine 5'-O-(2-thiodiphosphate), ADP beta S; and adenosine 5'-monophosphorothioate, AMP alpha S), on contractile responses to ATP were compared. After challenge with a low (1 microM) or high (300 microM) concentration of ATP to obtain control responses, one vas deferens of a pair was incubated for 5 min with one of the adenine nucleotides, while the contralateral preparation was incubated with the corresponding phosphorothioate analogue. At the conclusion of the incubation the preparations were challenged again with ATP. Incubation with AMP or AMP alpha S resulted in a transient potentiation of responses to 1 microM and 300 microM ATP. The potentiation following incubation with AMP alpha S was larger than that produced by AMP. After incubation with ADP, ADP beta S, ATP and ATP gamma S, responses to 1 microM ATP were decreased, while those to 300 microM ATP were unaffected. Thus, incubation with AMP and AMP alpha S results in potentiation, rather than inhibition, of ATP-induced responses. On the other hand, 5'-diphosphate, 5'-triphosphate, 5'-O-(2-thiodiphosphate) and 5'-O-(3-thiotriphosphate) moieties on adenosine have no effect or cause autoinhibition. These results indicate that AMP exerts a potentiating effect on reactivity to exogenous ATP. AMP arising from the enzymatic degradation of ATP might modulate the level of response to ATP released endogenously as a cotransmitter. PMID:3038248

Medicinal Chemistry of the Noncanonical Cyclic Nucleotides cCMP and cUMP.

PubMed

Schwede, Frank; Rentsch, Andreas; Genieser, Hans-Gottfried

2017-01-01

After decades of intensive research on adenosine-3',5'-cyclic monophosphate (cAMP)- and guanosine-3',5'-cyclic monophosphate (cGMP)-related second messenger systems, also the noncanonical congeners cyclic cytidine-3',5'-monophosphate (cCMP) and cyclic uridine-3',5'-monophosphate (cUMP) gained more and more interest. Until the late 1980s, only a small number of cCMP and cUMP analogs with sometimes undefined purities had been described. Moreover, most of these compounds had been rather synthesized as precursors of antitumor and antiviral nucleoside-5'-monophosphates and hence had not been tested for any second messenger activity. Along with the recurring interest in cCMP- and cUMP-related signaling in the early 2000s, it became evident that well-characterized small molecule analogs with reliable purities would serve as highly valuable tools for the evaluation of a putative second messenger role of cyclic pyrimidine nucleotides. Meanwhile, for this purpose new cCMP and cUMP derivatives have been developed, and already known analogs have been resynthesized and highly purified. This chapter summarizes early medicinal chemistry work on cCMP and cUMP and analogs thereof, followed by a description of recent synthetic developments and an outlook on potential future directions.

Adenosine-Associated Delivery Systems

PubMed Central

Kazemzadeh-Narbat, Mehdi; Annabi, Nasim; Tamayol, Ali; Oklu, Rahmi; Ghanem, Amyl; Khademhosseini, Ali

2016-01-01

Adenosine is a naturally occurring purine nucleoside in every cell. Many critical treatments such as modulating irregular heartbeat (arrhythmias), regulation of central nervous system (CNS) activity, and inhibiting seizural episodes can be carried out using adenosine. Despite the significant potential therapeutic impact of adenosine and its derivatives, the severe side effects caused by their systemic administration have significantly limited their clinical use. In addition, due to adenosine’s extremely short half-life in human blood (less than 10 s), there is an unmet need for sustained delivery systems to enhance efficacy and reduce side effects. In this paper, various adenosine delivery techniques, including encapsulation into biodegradable polymers, cell-based delivery, implantable biomaterials, and mechanical-based delivery systems, are critically reviewed and the existing challenges are highlighted. PMID:26453156

[Role of cyclic adenosine monophosphate(cAMP) in the regulation of intestinal epithelial barrier function under hypoxia].

PubMed

Yang, Yang; Wang, Wen-Sheng; Qiu, Yuan; Sun, Li-Hua; Yang, Hua

2013-05-01

To investigate the role of cyclic adenosine monophosphate(cAMP) in the regulation of intestinal epithelial barrier function under hypoxia. Intestinal epithelial barrier was established by Caco-2 monolayers. Cells were divided into four groups: normoxia (Nx), normoxia plus Forskolin(Nx+FSK), hypoxia(Hx), hypoxia plus SQ22536(Hx+SQ22536). cAMP concentrations of different groups were assessed by cAMP enzyme immunoassay kit. RT-PCR and Western blotting were used to detect the mRNA and protein expressions of claudin-1 and occludin under normoxic and hypoxic condition. Caco-2 monolayers were grown on Millicell filters, and transepithelial electrical resistance(TER) was measured using a Millipore electric resistance system. The concentration of cAMP under hypoxic conditions(Hx group) was higher compared with Nx group [(6.30±0.50) pmol/L vs. (2.38±0.18) pmol/L, P<0.01]. At the same time, both mRNA and protein expressions of claudin-1 and occluding were lower in Hx group than those in Nx group(all P<0.05). TER decreased by 76.30±0.64(P<0.01). When the monolayers were exposed to hypoxia plus SQ22536 (Hx+SQ22536 group), the concentration of cAMP was(2.12±0.23) pmol/L, which was lower than that under hypoxic conditions(Hx group, P<0.01). Both mRNA and protein expressions of claudin-1 and occludin were higher compared to Hx group (all P<0.01). TER increased by 32.96±2.16 (P<0.05). When Caco-2 cells are exposed to hypoxia, barrier function, claudin-1 and occludin expression are diminished in parallel with a high level of intracellular cAMP compared with the normoxic condition. Inhibition of the intracellular cAMP level under hypoxia can maintain the intestinal epithelial function through regulating the claudin-1 and occludin expression and attenuate the permeability of intestinal mucosa.

A metabolomic, geographic, and seasonal analysis of the contribution of pollen-derived adenosine to allergic sensitization.

PubMed

Mueller, Geoffrey A; Thompson, Peter M; DeRose, Eugene F; O'Connell, Thomas M; London, Robert E

2016-12-01

Studies on ragweed and birch pollen extracts suggested that the adenosine content is an important factor in allergic sensitization. However, exposure levels from other pollens and considerations of geographic and seasonal factors have not been evaluated. This study compared the metabolite profile of pollen species important for allergic disease, specifically measured the adenosine content, and evaluated exposure to pollen-derived adenosine. An NMR metabolomics approach was used to measure metabolite concentrations in twenty-six pollen extracts. Pollen count data was analyzed from five cities to model exposure. A principal component analysis of the various metabolites identified by NMR showed that pollen extracts could be differentiated primarily by sugar content: glucose, fructose, sucrose, and myo-inositol. In extracts of 10 mg of pollen/ml, the adenosine was highest for grasses (45 μM) followed by trees (23 μM) and weeds (19 μM). Pollen count data showed that tree pollen was typically 5-10 times the amount of other pollens. At the daily peaks of tree, grass, and weed season the pollen-derived adenosine exposure per day is likely to only be 1.1, 0.11, and 0.12 μg, respectively. Seasonal models of pollen exposure and respiration suggest that it would be a rare event limited to tree pollen season for concentrations of pollen-derived adenosine to approach physiological levels. Sugar content and other metabolites may be useful in classifying pollens. Unless other factors create localized exposures that are very different from these models, pollen-derived adenosine is unlikely to be a major factor in allergic sensitization.

Time-resolved photoelectron spectroscopy of adenosine and adenosine monophosphate photodeactivation dynamics in water microjets

NASA Astrophysics Data System (ADS)

Williams, Holly L.; Erickson, Blake A.; Neumark, Daniel M.

2018-05-01

The excited state relaxation dynamics of adenosine and adenosine monophosphate were studied at multiple excitation energies using femtosecond time-resolved photoelectron spectroscopy in a liquid water microjet. At pump energies of 4.69-4.97 eV, the lowest ππ* excited state, S1, was accessed and its decay dynamics were probed via ionization at 6.20 eV. By reversing the role of the pump and probe lasers, a higher-lying ππ* state was excited at 6.20 eV and its time-evolving photoelectron spectrum was monitored at probe energies of 4.69-4.97 eV. The S1 ππ* excited state was found to decay with a lifetime ranging from ˜210 to 250 fs in adenosine and ˜220 to 250 fs in adenosine monophosphate. This lifetime drops with increasing pump photon energy. Signal from the higher-lying ππ* excited state decayed on a time scale of ˜320 fs and was measureable only in adenosine monophosphate.

Short-term hyperthyroidism modulates adenosine receptors and catalytic activity of adenylate cyclase in adipocytes.

PubMed Central

Rapiejko, P J; Malbon, C C

1987-01-01

The effects of short-term hyperthyroidism in vivo on the status of the components of the fat-cell hormone-sensitive adenylate cyclase were investigated. The number of beta-adrenergic receptors was elevated by about 25% in membranes of fat-cells isolated from hyperthyroid rats as compared with euthyroid rats, but their affinity for radioligand was unchanged. Membranes of hyperthyroid-rat fat-cells displayed less than 65% of the normal complement of receptors for [3H]cyclohexyladenosine. The affinity of the receptors for this ligand was normal. In contrast with the marked increase in the amounts of the alpha-subunits of the guanine nucleotide-binding proteins Gi (Mr 41,000) and Go (Mr 39,000) observed in the hypothyroid state [Malbon, Rapiejko & Mangano (1985) J. Biol. Chem. 260, 2558-2564], the amounts of alpha-Gi, alpha-Go as well as alpha-Gs subunits [Mr 42,000 (major) and 46,000/48,000 (minor)] were not changed by hyperthyroidism. Adenylate cyclase activity in response to forskolin, guanosine 5'-[gamma-thio]triphosphate or isoprenaline, in contrast, was decreased by 30-50% in fat-cell membranes from hyperthyroid rats. Fat-cells isolated from hyperthyroid rats accumulated cyclic AMP to less than 50% of the extent in their euthyroid counterparts in the presence of adenosine deaminase and either adrenaline or forskolin, suggesting a decrease in the amount or activity of the catalytic subunit of adenylate cyclase. In the absence of exogenous adenosine deaminase, cyclic AMP accumulation in response to adrenaline was elevated rather than decreased in fat-cells from hyperthyroid rats. The inhibitory influence of adenosine is apparently limited in the hyperthyroid state by the decreased complement of inhibitory R-site purinergic receptors in these fat-cells. Short-term hyperthyroidism modulates the fat-cell adenylate cyclase system at the receptor level (beta-receptor number increased, R-site purinergic-receptor number decreased) and the catalytic subunit of adenylate

A calmodulin inhibitor, W-7 influences the effect of cyclic adenosine 3', 5'-monophosphate signaling on ligninolytic enzyme gene expression in Phanerochaete chrysosporium

PubMed Central

2012-01-01

The capacity of white-rot fungi to degrade wood lignin may be highly applicable to the development of novel bioreactor systems, but the mechanisms underlying this function are not yet fully understood. Lignin peroxidase (LiP) and manganese peroxidase (MnP), which are thought to be very important for the ligninolytic property, demonstrated increased activity in Phanerochaete chrysosporium RP-78 (FGSC #9002, ATCC MYA-4764™) cultures following exposure to 5 mM cyclic adenosine 3', 5'-monophosphate (cAMP) and 500 μM 3'-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that transcription of most LiP and MnP isozyme genes was statistically significantly upregulated in the presence of the cAMP and IBMX compared to the untreated condition. However, 100 μM calmodulin (CaM) inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), which had insignificant effects on fungal growth and intracellular cAMP concentration, not only offset the increased activity and transcription induced by the drugs, but also decreased them to below basal levels. Like the isozyme genes, transcription of the CaM gene (cam) was also upregulated by cAMP and IBMX. These results suggest that cAMP signaling functions to increase the transcription of LiP and MnP through the induction of cam transcription. PMID:22273182

Cyclic adenosine monophosphate metabolism in synaptic growth, strength, and precision: neural and behavioral phenotype-specific counterbalancing effects between dnc phosphodiesterase and rut adenylyl cyclase mutations.

PubMed

Ueda, Atsushi; Wu, Chun-Fang

2012-03-01

Two classic learning mutants in Drosophila, rutabaga (rut) and dunce (dnc), are defective in cyclic adenosine monophosphate (cAMP) synthesis and degradation, respectively, exhibiting a variety of neuronal and behavioral defects. We ask how the opposing effects of these mutations on cAMP levels modify subsets of phenotypes, and whether any specific phenotypes could be ameliorated by biochemical counter balancing effects in dnc rut double mutants. Our study at larval neuromuscular junctions (NMJs) demonstrates that dnc mutations caused severe defects in nerve terminal morphology, characterized by unusually large synaptic boutons and aberrant innervation patterns. Interestingly, a counterbalancing effect led to rescue of the aberrant innervation patterns but the enlarged boutons in dnc rut double mutant remained as extreme as those in dnc. In contrast to dnc, rut mutations strongly affect synaptic transmission. Focal loose-patch recording data accumulated over 4 years suggest that synaptic currents in rut boutons were characterized by unusually large temporal dispersion and a seasonal variation in the amount of transmitter release, with diminished synaptic currents in summer months. Experiments with different rearing temperatures revealed that high temperature (29-30°C) decreased synaptic transmission in rut, but did not alter dnc and wild-type (WT). Importantly, the large temporal dispersion and abnormal temperature dependence of synaptic transmission, characteristic of rut, still persisted in dnc rut double mutants. To interpret these results in a proper perspective, we reviewed previously documented differential effects of dnc and rut mutations and their genetic interactions in double mutants on a variety of physiological and behavioral phenotypes. The cases of rescue in double mutants are associated with gradual developmental and maintenance processes whereas many behavioral and physiological manifestations on faster time scales could not be rescued. We discuss

Downregulation of adenosine and adenosine 1 receptor contributes to neuropathic pain in resiniferatoxin neuropathy.

PubMed

Kan, Hung-Wei; Chang, Chin-Hong; Lin, Chih-Lung; Lee, Yi-Chen; Hsieh, Sung-Tsang; Hsieh, Yu-Lin

2018-04-16

The neurochemical effects of adenosine signaling in small-fiber neuropathy leading to neuropathic pain are yet to be explored in a direct manner. This study examined this system at the level of ligand (via the ectonucleotidase activity of prostatic acid phosphatase, PAP) and adenosine A1 receptors (A1Rs) in resiniferatoxin (RTX) neuropathy, a peripheral neurodegenerative disorder which specifically affects nociceptive nerves expressing transient receptor potential vanilloid type 1 (TRPV1). We conducted immunohistochemistry on dorsal root ganglion neurons (DRG), high-performance liquid chromatography (HPLC) for functional assays, and pharmacological interventions to alter PAP and A1Rs in mice with RTX neuropathy. In DRG of RTX neuropathy, PAP(+) neurons were reduced compared with vehicle-treated mice (P = 0.002) . Functionally, PAP ectonucleotidase activity was consequently reduced (i.e., the content of adenosine in DRG, P = 0.012). PAP(+) neuronal density was correlated with the degree of mechanical allodynia, which was reversed by intrathecal lumbar puncture (i.t.) injection of recombinant PAP with a dose-dependent effect. Furthermore, A1Rs were downregulated (P = 0.002), and this downregulation was colocalized with the TRPV1 receptor (31.0% ± 2.8%). Mechanical allodynia was attenuated in a dose-dependent response by i.t. injection of the A1R ligand, adenosine; however, no analgesia was evident when an exogenous adenosine was blocked by A1R antagonist. This study demonstrated dual mechanisms of neuropathic pain in TRPV1-induced neuropathy, involving a reduced adenosine system at both the ligand (adenosine) and receptor (A1Rs) levels.

Adenosine and sleep

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

Yanik, G.M. Jr.

Behavioral and biochemical approaches have been used to determine the relative contribution of endogenous adenosine and adenosine receptors to the sleep-wake cycle in the rat. Adenosine concentrations in specific areas of the rat brain were not affected by 24 hours of total sleep deprivation, or by 24 or 48 hours of REM sleep deprivation. In order to assess the effect of REM sleep deprivation on adenosine A/sub 1/ receptors, /sup 3/H-L-PIA binding was measured. The Bmax values for /sup 3/H-L-PIA binding to membrane preparations of the cortices and corpus striata from 48 hour REM sleep-deprived animals were increased 14.8% andmore » 23%, respectively. These increases were not maintained following the cessation of sleep deprivation and recovered within 2 hours. The results of a 96 hour REM deprivation experiment were similar to those of the 48 hour REM sleep deprivation experiment. However, these increases were not evident in similar structures taken from stress control animals, and conclusively demonstrated that the changes in /sup 3/H-L-PIA binding resulted from REM sleep deprivation and not from stress.« less

Balanol analogues probe specificity determinants and the conformational malleability of the cyclic 3',5'-adenosine monophosphate-dependent protein kinase catalytic subunit.

PubMed

Akamine, Pearl; Madhusudan; Brunton, Laurence L; Ou, Horng D; Canaves, Jaume M; Xuong, Nguyen-huu; Taylor, Susan S

2004-01-13

The protein kinase family is a prime target for therapeutic agents, since unregulated protein kinase activities are linked to myriad diseases. Balanol, a fungal metabolite consisting of four rings, potently inhibits Ser/Thr protein kinases and can be modified to yield potent inhibitors that are selective-characteristics of a desirable pharmaceutical compound. Here, we characterize three balanol analogues that inhibit cyclic 3',5'-adenosine monophosphate-dependent protein kinase (PKA) more specifically and potently than calcium- and phospholipid-dependent protein kinase (PKC). Correlation of thermostability and inhibition potency suggests that better inhibitors confer enhanced protection against thermal denaturation. Crystal structures of the PKA catalytic (C) subunit complexed to each analogue show the Gly-rich loop stabilized in an "intermediate" conformation, disengaged from important phosphoryl transfer residues. An analogue that perturbs the PKA C-terminal tail has slightly weaker inhibition potency. The malleability of the PKA C subunit is illustrated by active site residues that adopt alternate rotamers depending on the ligand bound. On the basis of sequence homology to PKA, a preliminary model of the PKC active site is described. The balanol analogues serve to test the model and to highlight differences in the active site local environment of PKA and PKC. The PKA C subunit appears to tolerate balanol analogues with D-ring modifications; PKC does not. We attribute this difference in preference to the variable B helix and C-terminal tail. By understanding the details of ligand binding, more specific and potent inhibitors may be designed that differentiate among closely related AGC protein kinase family members.

Adenosine Kinase: Exploitation for Therapeutic Gain

PubMed Central

2013-01-01

Adenosine kinase (ADK; EC 2.7.1.20) is an evolutionarily conserved phosphotransferase that converts the purine ribonucleoside adenosine into 5′-adenosine-monophosphate. This enzymatic reaction plays a fundamental role in determining the tone of adenosine, which fulfills essential functions as a homeostatic and metabolic regulator in all living systems. Adenosine not only activates specific signaling pathways by activation of four types of adenosine receptors but it is also a primordial metabolite and regulator of biochemical enzyme reactions that couple to bioenergetic and epigenetic functions. By regulating adenosine, ADK can thus be identified as an upstream regulator of complex homeostatic and metabolic networks. Not surprisingly, ADK dysfunction is involved in several pathologies, including diabetes, epilepsy, and cancer. Consequently, ADK emerges as a rational therapeutic target, and adenosine-regulating drugs have been tested extensively. In recent attempts to improve specificity of treatment, localized therapies have been developed to augment adenosine signaling at sites of injury or pathology; those approaches include transplantation of stem cells with deletions of ADK or the use of gene therapy vectors to downregulate ADK expression. More recently, the first human mutations in ADK have been described, and novel findings suggest an unexpected role of ADK in a wider range of pathologies. ADK-regulating strategies thus represent innovative therapeutic opportunities to reconstruct network homeostasis in a multitude of conditions. This review will provide a comprehensive overview of the genetics, biochemistry, and pharmacology of ADK and will then focus on pathologies and therapeutic interventions. Challenges to translate ADK-based therapies into clinical use will be discussed critically. PMID:23592612

Pain-relieving prospects for adenosine receptors and ectonucleotidases

PubMed Central

Zylka, Mark J.

2010-01-01

Adenosine receptor agonists have potent antinociceptive effects in diverse preclinical models of chronic pain. In contrast, the efficacy of adenosine or adenosine receptor agonists at treating pain in humans is unclear. Two ectonucleotidases that generate adenosine in nociceptive neurons were recently identified. When injected spinally, these enzymes have long-lasting adenosine A1 receptor (A1R)-dependent antinociceptive effects in inflammatory and neuropathic pain models. Furthermore, recent findings indicate that spinal adenosine A2A receptor activation can enduringly inhibit neuropathic pain symptoms. Collectively, these studies suggest the possibility of treating chronic pain in humans by targeting specific adenosine receptor subtypes in anatomically defined regions with agonists or with ectonucleotidases that generate adenosine. PMID:21236731

Minoxidil-induced hair growth is mediated by adenosine in cultured dermal papilla cells: possible involvement of sulfonylurea receptor 2B as a target of minoxidil.

PubMed

Li, M; Marubayashi, A; Nakaya, Y; Fukui, K; Arase, S

2001-12-01

The mechanism by which minoxidil, an adenosine-triphosphate-sensitive potassium channel opener, induces hypertrichosis remains to be elucidated. Minoxidil has been reported to stimulate the production of vascular endothelial growth factor, a possible promoter of hair growth, in cultured dermal papilla cells. The mechanism of production of vascular endothelial growth factor remains unclear, however. We hypothesize that adenosine serves as a mediator of vascular endothelial growth factor production. Minoxidil-induced increases in levels of intracellular Ca(2+) and vascular endothelial growth factor production in cultured dermal papilla cells were found to be inhibited by 8-sulfophenyl theophylline, a specific antagonist for adenosine receptors, suggesting that dermal papilla cells possess adenosine receptors and sulfonylurea receptors, the latter of which is a well-known target receptor for adenosine-triphosphate-sensitive potassium channel openers. The expression of sulfonylurea receptor 2B and of the adenosine A1, A2A, and A2B receptors was detected in dermal papilla cells by means of reverse transcription polymerase chain reaction analysis. In order to determine which of the adenosine receptor subtypes contribute to minoxidil-induced hair growth, the effects of subtype-specific antagonists for adenosine receptors were investigated. Significant inhibition in increase in intracellular calcium level by minoxidil or adenosine was observed as the result of pretreatment with 8-cyclopentyl-1,3-dipropylxanthine, an antagonist for adenosine A1 receptor, but not by 3,7-dimethyl-1-propargyl-xanthine, an antagonist for adenosine A2 receptor, whereas vascular endothelial growth factor production was blocked by both adenosine A1 and A2 receptor antagonists. These results indicate that the effect of minoxidil is mediated by adenosine, which triggers intracellular signal transduction via both adenosine A1 and A2 receptors, and that the expression of sulfonylurea receptor 2B in

Adenosine kinase regulation of cardiomyocyte hypertrophy

PubMed Central

Fassett, John T.; Hu, Xinli; Xu, Xin; Lu, Zhongbing; Zhang, Ping; Chen, Yingjie

2011-01-01

There is evidence that extracellular adenosine can attenuate cardiac hypertrophy, but the mechanism by which this occurs is not clear. Here we investigated the role of adenosine receptors and adenosine metabolism in attenuation of cardiomyocyte hypertrophy. Phenylephrine (PE) caused hypertrophy of neonatal rat cardiomyocytes with increases of cell surface area, protein synthesis, and atrial natriuretic peptide (ANP) expression. These responses were attenuated by 5 μM 2-chloroadenosine (CADO; adenosine deaminase resistant adenosine analog) or 10 μM adenosine. While antagonism of adenosine receptors partially blocked the reduction of ANP expression produced by CADO, it did not restore cell size or protein synthesis. In support of a role for intracellular adenosine metabolism in regulating hypertrophy, the adenosine kinase (AK) inhibitors iodotubercidin and ABT-702 completely reversed the attenuation of cell size, protein synthesis, and expression of ANP by CADO or ADO. Examination of PE-induced phosphosignaling pathways revealed that CADO treatment did not reduce AKTSer473 phosphorylation but did attenuate sustained phosphorylation of RafSer338 (24–48 h), mTORSer2448 (24–48 h), p70S6kThr389 (2.5–48 h), and ERKThr202/Tyr204 (48 h). Inhibition of AK restored activation of these enzymes in the presence of CADO. Using dominant negative and constitutively active Raf adenoviruses, we found that Raf activation is necessary and sufficient for PE-induced mTORC1 signaling and cardiomyocyte hypertrophy. CADO treatment still blocked p70S6kThr389 phosphorylation and hypertrophy downstream of constitutively active Raf, however, despite a high level phosphorylation of ERKThr202/Tyr204 and AKTSer473. Reduction of Raf-induced p70S6kThr389 phosphorylation and hypertrophy by CADO was reversed by inhibiting AK. Together, these results identify AK as an important mediator of adenosine attenuation of cardiomyocyte hypertrophy, which acts, at least in part, through inhibition of

Adenosine kinase regulation of cardiomyocyte hypertrophy.

PubMed

Fassett, John T; Hu, Xinli; Xu, Xin; Lu, Zhongbing; Zhang, Ping; Chen, Yingjie; Bache, Robert J

2011-05-01

There is evidence that extracellular adenosine can attenuate cardiac hypertrophy, but the mechanism by which this occurs is not clear. Here we investigated the role of adenosine receptors and adenosine metabolism in attenuation of cardiomyocyte hypertrophy. Phenylephrine (PE) caused hypertrophy of neonatal rat cardiomyocytes with increases of cell surface area, protein synthesis, and atrial natriuretic peptide (ANP) expression. These responses were attenuated by 5 μM 2-chloroadenosine (CADO; adenosine deaminase resistant adenosine analog) or 10 μM adenosine. While antagonism of adenosine receptors partially blocked the reduction of ANP expression produced by CADO, it did not restore cell size or protein synthesis. In support of a role for intracellular adenosine metabolism in regulating hypertrophy, the adenosine kinase (AK) inhibitors iodotubercidin and ABT-702 completely reversed the attenuation of cell size, protein synthesis, and expression of ANP by CADO or ADO. Examination of PE-induced phosphosignaling pathways revealed that CADO treatment did not reduce AKT(Ser⁴⁷³) phosphorylation but did attenuate sustained phosphorylation of Raf(Ser³³⁸) (24-48 h), mTOR(Ser²⁴⁴⁸) (24-48 h), p70S6k(Thr³⁸⁹) (2.5-48 h), and ERK(Thr²⁰²/Tyr²⁰⁴) (48 h). Inhibition of AK restored activation of these enzymes in the presence of CADO. Using dominant negative and constitutively active Raf adenoviruses, we found that Raf activation is necessary and sufficient for PE-induced mTORC1 signaling and cardiomyocyte hypertrophy. CADO treatment still blocked p70S6k(Thr³⁸⁹) phosphorylation and hypertrophy downstream of constitutively active Raf, however, despite a high level phosphorylation of ERK(Thr202/Tyr204) and AKT(Ser⁴⁷³). Reduction of Raf-induced p70S6k(Thr³⁸⁹) phosphorylation and hypertrophy by CADO was reversed by inhibiting AK. Together, these results identify AK as an important mediator of adenosine attenuation of cardiomyocyte

Cyclic load magnitude is a risk factor for a cumulative lower back disorder.

PubMed

Le, Peter; Solomonow, Moshe; Zhou, Bing-He; Lu, Yun; Patel, Vikas

2007-04-01

Epidemiological data suggest that high loads lifted by workers engaged in static and cyclic daily activities may be a risk factor for low back disorder. Our previous research provided physiological and biomechanical validation of the epidemiological data for static load conditions. The objective of this report was to provide physiological and biomechanical experimental validation to the epidemiological data in cyclic (repetitive) load conditions. Three groups of in vivo feline models were subjected to 3 cyclic load levels in a series of 6 periods of 10 minutes of work spaced by 10 minutes of rest followed by 7 hours of rest. Multifidus electromyography (EMG) and lumbar displacement were statistically analyzed after processing. Delayed muscular hyperexcitability was observed only in moderate (40 N) and high (60 N) loads (P<0.0001) but was absent in low (20 N) loads. The magnitude of the delayed hyperexcitability was found to be higher (P<0.0001) in the high (60 N) loads compared with the moderate (40 N) loads. Exposure to moderate and high loads in cyclic (repetitive) work results in an acute neuromuscular disorder indicative of soft tissue inflammation that may become chronic with further exposure.

FRET-based binding assay between a fluorescent cAMP analogue and a cyclic nucleotide-binding domain tagged with a CFP.

PubMed

Romero, Francisco; Santana-Calvo, Carmen; Sánchez-Guevara, Yoloxochitl; Nishigaki, Takuya

2017-09-01

The cyclic nucleotide-binding domain (CNBD) functions as a regulatory domain of many proteins involved in cyclic nucleotide signalling. We developed a straightforward and reliable binding assay based on intermolecular fluorescence resonance energy transfer (FRET) between an adenosine-3', 5'-cyclic monophosphate analogue labelled with fluorescein and a recombinant CNBD of human EPAC1 tagged with a cyan fluorescence protein (CFP). The high FRET efficiency of this method (~ 80%) allowed us to perform several types of binding experiments with nanomolar range of sample using conventional equipment. In addition, the CFP tag on the CNBD enabled us to perform a specific binding experiment using an unpurified protein. Considering these advantages, this technique is useful to study poorly characterized CNBDs. © 2017 Federation of European Biochemical Societies.

Neuroprotective effects of adenosine deaminase in the striatum

PubMed Central

Tamura, Risa; Satoh, Yasushi; Nonoyama, Shigeaki; Nishida, Yasuhiro; Nibuya, Masashi

2016-01-01

Adenosine deaminase (ADA) is a ubiquitous enzyme that catabolizes adenosine and deoxyadenosine. During cerebral ischemia, extracellular adenosine levels increase acutely and adenosine deaminase catabolizes the increased levels of adenosine. Since adenosine is a known neuroprotective agent, adenosine deaminase was thought to have a negative effect during ischemia. In this study, however, we demonstrate that adenosine deaminase has substantial neuroprotective effects in the striatum, which is especially vulnerable during cerebral ischemia. We used temporary oxygen/glucose deprivation (OGD) to simulate ischemia in rat corticostriatal brain slices. We used field potentials as the primary measure of neuronal damage. For stable and efficient electrophysiological assessment, we used transgenic rats expressing channelrhodopsin-2, which depolarizes neurons in response to blue light. Time courses of electrically evoked striatal field potential (eFP) and optogenetically evoked striatal field potential (optFP) were recorded during and after oxygen/glucose deprivation. The levels of both eFP and optFP decreased after 10 min of oxygen/glucose deprivation. Bath-application of 10 µg/ml adenosine deaminase during oxygen/glucose deprivation significantly attenuated the oxygen/glucose deprivation-induced reduction in levels of eFP and optFP. The number of injured cells decreased significantly, and western blot analysis indicated a significant decrease of autophagic signaling in the adenosine deaminase-treated oxygen/glucose deprivation slices. These results indicate that adenosine deaminase has protective effects in the striatum. PMID:26746865

Exogenous adenosine 5'-phosphoramidate behaves as a signal molecule in plants; it augments metabolism of phenylpropanoids and salicylic acid in Arabidopsis thaliana seedlings.

PubMed

Pietrowska-Borek, Małgorzata; Nuc, Katarzyna; Guranowski, Andrzej

2015-09-01

Cells contain various congeners of the canonical nucleotides. Some of these accumulate in cells under stress and may function as signal molecules. Their cellular levels are enzymatically controlled. Previously, we demonstrated a signaling function for diadenosine polyphosphates and cyclic nucleotides in Arabidopsis thaliana and grape, Vitis vinifera. These compounds increased the expression of genes for and the specific activity of enzymes of phenylpropanoid pathways resulting in the accumulation of certain products of these pathways. Here, we show that adenosine 5'-phosphoramidate, whose level can be controlled by HIT-family proteins, induced similar effects. This natural nucleotide, when added to A. thaliana seedlings, activated the genes for phenylalanine:ammonia lyase, 4-coumarate:coenzyme A ligase, cinnamate-4-hydroxylase, chalcone synthase, cinnamoyl-coenzyme A:NADP oxidoreductase and isochorismate synthase, which encode proteins catalyzing key reactions of phenylpropanoid pathways, and caused accumulation of lignins, anthocyanins and salicylic acid. Adenosine 5'-phosphofluoridate, a synthetic congener of adenosine 5'-phosphoramidate, behaved similarly. The results allow us to postulate that adenosine 5'-phosphoramidate should be considered as a novel signaling molecule. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

High-repetition cyclic loading is a risk factor for a lumbar disorder.

PubMed

Navar, Daniel; Zhou, Bing-He; Lu, Yun; Solomonow, Moshe

2006-11-01

Epidemiological data suggest that prolonged exposure to cyclic lumbar flexion elicits a chronic neuromuscular disorder and disability in workers. This study provides a physiological and biomechanical assessment of various repetitions of cyclic lumbar flexion sessions as a risk factor for development of an acute neuromuscular disorder. An in vivo feline model was subjected to 10 minutes of cyclic (0.25-HZ) loading, followed by a 10-minute rest period, repeated three times in one experimental group, six times in a second group, and nine times in the third group, followed by rest for 7 hours. Displacement of the lumbar viscoelastic tissue and reflex electromyographic (EMG) activity from the lumbar multifidus muscle were monitored. Creep developed and accumulated during each load/rest period and partially recovered during the subsequent rest. Loading periods were characterized by a decrease in reflex EMG activity with superimposed spasms. In the 7-hour recovery period, initial hyperexcitability was present in all groups, whereas only the six- and nine-repetition groups displayed significant delayed hyperexcitability, indicating the presence of acute inflammation. The mathematical model developed fit the data reasonably well, as the R2 values were generally near 0.90. It was concluded that the resulting delayed muscular hyperexcitability constitutes an acute neuromuscular disorder associated with exposure to many repetitions of cyclic lumbar flexion. The acute disorder can become chronic if not allowed sufficient rest to resolve itself. Workers engaged in cyclic lumbar flexion (e.g., loading/unloading, assembly workers) should avoid long-term exposure in order to prevent the development of a chronic neuromuscular condition known as cumulative trauma disorder.

Aquaporin 3 expression in human fetal membranes and its up-regulation by cyclic adenosine monophosphate in amnion epithelial cell culture.

PubMed

Wang, Shengbiao; Amidi, Fataneh; Beall, Marie; Gui, Lizhen; Ross, Michael G

2006-04-01

The cell membrane water channel protein aquaporins (AQPs) may be important in regulating the intramembranous (IM) pathway of amniotic fluid (AF) resorption. The objective of the present study was to determine whether aquaporin 3 (AQP3) is expressed in human fetal membranes and to further determine if AQP3 expression in primary human amnion cell culture is regulated by second-messenger cyclic adenosine monophosphate (cAMP). AQP3 expression in human fetal membranes of normal term pregnancy was studied by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). To determine the effect of cAMP on AQP3 expression, primary human amnion cell cultures were treated in either heat-inactivated medium alone (control), or heat-inactivated medium containing: (1) SP-cAMP, a membrane-permeable and phosphodiesterase resistant cAMP agonist, or (2) forskolin, an adenylate cyclase stimulator. Total RNA was isolated and multiplex real-time RT-PCR employed for relative quantitation of AQP3 expression. We detected AQP3 expression in placenta, chorion, and amnion using RT-PCR. Using IHC, we identified AQP3 protein expression in placenta syncytiotrophoblasts and cytotrophoblasts, chorion cytotrophoblasts, and amnion epithelia. In primary amnion epithelial cell culture, AQP3 mRNA significantly increased at 2 hours following forskolin or SP-cAMP, remained elevated at 10 hours following forskolin, and returned to baseline levels by 20 hours following treatment. This study provides evidence of AQP3 expression in human fetal membranes and demonstrates that AQP3 expression in primary human amnion cell culture is up-regulated by second-messenger cAMP. As AQP3 is permeable to water, urea, and glycerol, modulation of its expression in fetal membranes may contribute to AF homeostasis.

AMP is an adenosine A1 receptor agonist.

PubMed

Rittiner, Joseph E; Korboukh, Ilia; Hull-Ryde, Emily A; Jin, Jian; Janzen, William P; Frye, Stephen V; Zylka, Mark J

2012-02-17

Numerous receptors for ATP, ADP, and adenosine exist; however, it is currently unknown whether a receptor for the related nucleotide adenosine 5'-monophosphate (AMP) exists. Using a novel cell-based assay to visualize adenosine receptor activation in real time, we found that AMP and a non-hydrolyzable AMP analog (deoxyadenosine 5'-monophosphonate, ACP) directly activated the adenosine A(1) receptor (A(1)R). In contrast, AMP only activated the adenosine A(2B) receptor (A(2B)R) after hydrolysis to adenosine by ecto-5'-nucleotidase (NT5E, CD73) or prostatic acid phosphatase (PAP, ACPP). Adenosine and AMP were equipotent human A(1)R agonists in our real-time assay and in a cAMP accumulation assay. ACP also depressed cAMP levels in mouse cortical neurons through activation of endogenous A(1)R. Non-selective purinergic receptor antagonists (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid and suramin) did not block adenosine- or AMP-evoked activation. Moreover, mutation of His-251 in the human A(1)R ligand binding pocket reduced AMP potency without affecting adenosine potency. In contrast, mutation of a different binding pocket residue (His-278) eliminated responses to AMP and to adenosine. Taken together, our study indicates that the physiologically relevant nucleotide AMP is a full agonist of A(1)R. In addition, our study suggests that some of the physiological effects of AMP may be direct, and not indirect through ectonucleotidases that hydrolyze this nucleotide to adenosine.

Excess adenosine in murine penile erectile tissues contributes to priapism via A2B adenosine receptor signaling

PubMed Central

Mi, Tiejuan; Abbasi, Shahrzad; Zhang, Hong; Uray, Karen; Chunn, Janci L.; Xia, Ling Wei; Molina, Jose G.; Weisbrodt, Norman W.; Kellems, Rodney E.; Blackburn, Michael R.; Xia, Yang

2008-01-01

Priapism, abnormally prolonged penile erection in the absence of sexual excitation, is associated with ischemia-mediated erectile tissue damage and subsequent erectile dysfunction. It is common among males with sickle cell disease (SCD), and SCD transgenic mice are an accepted model of the disorder. Current strategies to manage priapism suffer from a poor fundamental understanding of the molecular mechanisms underlying the disorder. Here we report that mice lacking adenosine deaminase (ADA), an enzyme necessary for the breakdown of adenosine, displayed unexpected priapic activity. ADA enzyme therapy successfully corrected the priapic activity both in vivo and in vitro, suggesting that it was dependent on elevated adenosine levels. Further genetic and pharmacologic evidence demonstrated that A2B adenosine receptor–mediated (A2BR-mediated) cAMP and cGMP induction was required for elevated adenosine–induced prolonged penile erection. Finally, priapic activity in SCD transgenic mice was also caused by elevated adenosine levels and A2BR activation. Thus, we have shown that excessive adenosine accumulation in the penis contributes to priapism through increased A2BR signaling in both Ada–/– and SCD transgenic mice. These findings provide insight regarding the molecular basis of priapism and suggest that strategies to either reduce adenosine or block A2BR activation may prove beneficial in the treatment of this disorder. PMID:18340377

Caffeine and adenosine.

PubMed

Ribeiro, Joaquim A; Sebastião, Ana M

2010-01-01

Caffeine causes most of its biological effects via antagonizing all types of adenosine receptors (ARs): A1, A2A, A3, and A2B and, as does adenosine, exerts effects on neurons and glial cells of all brain areas. In consequence, caffeine, when acting as an AR antagonist, is doing the opposite of activation of adenosine receptors due to removal of endogenous adenosinergic tonus. Besides AR antagonism, xanthines, including caffeine, have other biological actions: they inhibit phosphodiesterases (PDEs) (e.g., PDE1, PDE4, PDE5), promote calcium release from intracellular stores, and interfere with GABA-A receptors. Caffeine, through antagonism of ARs, affects brain functions such as sleep, cognition, learning, and memory, and modifies brain dysfunctions and diseases: Alzheimer's disease, Parkinson's disease, Huntington's disease, Epilepsy, Pain/Migraine, Depression, Schizophrenia. In conclusion, targeting approaches that involve ARs will enhance the possibilities to correct brain dysfunctions, via the universally consumed substance that is caffeine.

AMP Is an Adenosine A1 Receptor Agonist*

PubMed Central

Rittiner, Joseph E.; Korboukh, Ilia; Hull-Ryde, Emily A.; Jin, Jian; Janzen, William P.; Frye, Stephen V.; Zylka, Mark J.

2012-01-01

Numerous receptors for ATP, ADP, and adenosine exist; however, it is currently unknown whether a receptor for the related nucleotide adenosine 5′-monophosphate (AMP) exists. Using a novel cell-based assay to visualize adenosine receptor activation in real time, we found that AMP and a non-hydrolyzable AMP analog (deoxyadenosine 5′-monophosphonate, ACP) directly activated the adenosine A1 receptor (A1R). In contrast, AMP only activated the adenosine A2B receptor (A2BR) after hydrolysis to adenosine by ecto-5′-nucleotidase (NT5E, CD73) or prostatic acid phosphatase (PAP, ACPP). Adenosine and AMP were equipotent human A1R agonists in our real-time assay and in a cAMP accumulation assay. ACP also depressed cAMP levels in mouse cortical neurons through activation of endogenous A1R. Non-selective purinergic receptor antagonists (pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid and suramin) did not block adenosine- or AMP-evoked activation. Moreover, mutation of His-251 in the human A1R ligand binding pocket reduced AMP potency without affecting adenosine potency. In contrast, mutation of a different binding pocket residue (His-278) eliminated responses to AMP and to adenosine. Taken together, our study indicates that the physiologically relevant nucleotide AMP is a full agonist of A1R. In addition, our study suggests that some of the physiological effects of AMP may be direct, and not indirect through ectonucleotidases that hydrolyze this nucleotide to adenosine. PMID:22215671

A defect in KCa3.1 channel activity limits the ability of CD8+ T cells from cancer patients to infiltrate an adenosine-rich microenvironment.

PubMed

Chimote, Ameet A; Balajthy, Andras; Arnold, Michael J; Newton, Hannah S; Hajdu, Peter; Qualtieri, Julianne; Wise-Draper, Trisha; Conforti, Laura

2018-04-24

The limited ability of cytotoxic T cells to infiltrate solid tumors hampers immune surveillance and the efficacy of immunotherapies in cancer. Adenosine accumulates in solid tumors and inhibits tumor-specific T cells. Adenosine inhibits T cell motility through the A 2A receptor (A 2A R) and suppression of KCa3.1 channels. We conducted three-dimensional chemotaxis experiments to elucidate the effect of adenosine on the migration of peripheral blood CD8 + T cells from head and neck squamous cell carcinoma (HNSCC) patients. The chemotaxis of HNSCC CD8 + T cells was reduced in the presence of adenosine, and the effect was greater on HNSCC CD8 + T cells than on healthy donor (HD) CD8 + T cells. This response correlated with the inability of CD8 + T cells to infiltrate tumors. The effect of adenosine was mimicked by an A 2A R agonist and prevented by an A 2A R antagonist. We found no differences in A 2A R expression, 3',5'-cyclic adenosine monophosphate abundance, or protein kinase A type 1 activity between HNSCC and HD CD8 + T cells. We instead detected a decrease in KCa3.1 channel activity, but not expression, in HNSCC CD8 + T cells. Activation of KCa3.1 channels by 1-EBIO restored the ability of HNSCC CD8 + T cells to chemotax in the presence of adenosine. Our data highlight the mechanism underlying the increased sensitivity of HNSCC CD8 + T cells to adenosine and the potential therapeutic benefit of KCa3.1 channel activators, which could increase infiltration of these T cells into tumors. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Adenosine and inflammation: what's new on the horizon?

PubMed

Antonioli, Luca; Csóka, Balázs; Fornai, Matteo; Colucci, Rocchina; Kókai, Endre; Blandizzi, Corrado; Haskó, György

2014-08-01

Adenosine contributes to the maintenance of tissue integrity by modulating the immune system. Encouraging results have emerged with adenosine receptor ligands for the management of several inflammatory conditions in preclinical and clinical settings. However, therapeutic applications of these drugs are sometimes complicated by the occurrence of serious adverse effects. The scientific community is making intensive efforts to design novel adenosine receptor ligands endowed with greater selectivity or to develop innovative compounds acting as allosteric receptor modulators. In parallel, research is focusing on novel pharmacological entities (designated as adenosine-regulating agents) that can increase, in a site- and event-specific manner, adenosine concentrations at the inflammatory site, thereby minimizing the adverse systemic effects of adenosine. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cultured astrocytes do not release adenosine during hypoxic conditions

PubMed Central

Fujita, Takumi; Williams, Erika K; Jensen, Tina K; Smith, Nathan A; Takano, Takahiro; Tieu, Kim; Nedergaard, Maiken

2012-01-01

Recent reports based on a chemiluminescent enzymatic assay for detection of adenosine conclude that cultured astrocytes release adenosine during mildly hypoxic conditions. If so, astrocytes may suppress neural activity in early stages of hypoxia. The aim of this study was to reevaluate the observation using high-performance liquid chromatography (HPLC). The HPLC analysis showed that exposure to 20 or 120 minutes of mild hypoxia failed to increase release of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine from cultured astrocytes. Similar results were obtained using a chemiluminescent enzymatic assay. Moreover, since the chemiluminescent enzymatic assay relies on hydrogen peroxide generation, release of free-radical scavengers from hypoxic cells can interfere with the assay. Accordingly, adenosine added to samples collected from hypoxic cultures could not be detected using the chemiluminescent enzymatic assay. Furthermore, addition of free-radical scavengers sharply reduced the sensitivity of adenosine detection. Conversely, use of a single-step assay inflated measured values due to the inability of the assay to distinguish adenosine and its metabolite inosine. These results show that cultured astrocytes do not release adenosine during mild hypoxia, an observation consistent with their high resistance to hypoxia. PMID:21989480

Activation of adenosine A(3) receptors supports hematopoiesis-stimulating effects of granulocyte colony-stimulating factor in sublethally irradiated mice.

PubMed

Hofer, Michal; Pospísil, Milan; Sefc, Ludek; Dusek, Ladislav; Vacek, Antonín; Holá, Jirina; Hoferová, Zuzana; Streitová, Denisa

2010-08-01

Research areas of 'post-exposure treatment' and 'cytokines and growth factors' have top priority among studies aimed at radiological nuclear threat countermeasures. The experiments were aimed at testing the ability of N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA), an adenosine A(3) receptor agonist, to modulate hematopoiesis in sublethally irradiated mice, when administered alone or in a combination with granulocyte colony-stimulating factor (G-CSF) in a two-day post-irradiation treatment regimen. A complete analysis of hematopoiesis including determination of numbers of bone marrow hematopoietic progenitor and precursor cells, as well as of numbers of peripheral blood cells, was performed. The outcomes of the treatment were assessed at days 3 to 22 after irradiation. IB-MECA alone has been found to induce a significant elevation of numbers of bone marrow granulocyte-macrophage progenitor cells (GM-CFC) and peripheral blood neutrophils. IB-MECA given concomitantly with G-CSF increased significantly bone marrow GM-CFC and erythroid progenitor cells (BFU-E) in comparison with the controls and with animals administered each of the drugs alone. The findings suggest the ability of IB-MECA to stimulate hematopoiesis and to support the hematopoiesis-stimulating effects of G-CSF in sublethally irradiated mice.

N6-(2-Hydroxyethyl)-Adenosine Exhibits Insecticidal Activity against Plutella xylostella via Adenosine Receptors.

PubMed

Fang, Ming; Chai, Yiqiu; Chen, Guanjv; Wang, Huidong; Huang, Bo

The diamondback moth, Plutella xylostella, is one of the most important pests of cruciferous crops. We have earlier shown that N6-(2-hydroxyethyl)-adenosine (HEA) exhibits insecticidal activity against P. xylostella. In the present study we investigated the possible mechanism of insecticidal action of HEA on P. xylostella. HEA is a derivative of adenosine, therefore, we speculated whether it acts via P. xylostella adenosine receptor (PxAdoR). We used RNAi approach to silence PxAdoR gene and used antagonist of denosine receptor (AdoR) to study the insecticidal effect of HEA. We cloned the whole sequence of PxAdoR gene. A BLAST search using NCBI protein database showed a 61% identity with the Drosophila adenosine receptor (DmAdoR) and a 32-35% identity with human AdoR. Though the amino acids sequence of PxAdoR was different compared to other adenosine receptors, most of the amino acids that are known to be important for adenosine receptor ligand binding and signaling were present. However, only 30% binding sites key residues was similar between PxAdoR and A1R. HEA, at a dose of 1 mg/mL, was found to be lethal to the second-instar larvae of P. xylostella, and a significant reduction of mortality and growth inhibition ratio were obtained when HEA was administered to the larvae along with PxAdoR-dsRNA or antagonist of AdoR (SCH58261) for 36, 48, or 60 h. Especially at 48 h, the rate of growth inhibition of the PxAdoR knockdown group was 3.5-fold less than that of the HEA group, and the corrected mortality of SCH58261 group was reduced almost 2-fold compared with the HEA group. Our findings show that HEA may exert its insecticidal activity against P. xylostella larvae via acting on PxAdoR.

A2A adenosine receptor ligand binding and signalling is allosterically modulated by adenosine deaminase.

PubMed

Gracia, Eduard; Pérez-Capote, Kamil; Moreno, Estefanía; Barkešová, Jana; Mallol, Josefa; Lluís, Carme; Franco, Rafael; Cortés, Antoni; Casadó, Vicent; Canela, Enric I

2011-05-01

A2ARs (adenosine A2A receptors) are highly enriched in the striatum, which is the main motor control CNS (central nervous system) area. BRET (bioluminescence resonance energy transfer) assays showed that A2AR homomers may act as cell-surface ADA (adenosine deaminase; EC 3.5.4.4)-binding proteins. ADA binding affected the quaternary structure of A2ARs present on the cell surface. ADA binding to adenosine A2ARs increased both agonist and antagonist affinity on ligand binding to striatal membranes where these proteins are co-expressed. ADA also increased receptor-mediated ERK1/2 (extracellular-signal-regulated kinase 1/2) phosphorylation. Collectively, the results of the present study show that ADA, apart from regulating the concentration of extracellular adenosine, may behave as an allosteric modulator that markedly enhances ligand affinity and receptor function. This powerful regulation may have implications for the physiology and pharmacology of neuronal A2ARs.

Tween 20-stabilized gold nanoparticles combined with adenosine triphosphate-BODIPY conjugates for the fluorescence detection of adenosine with more than 1000-fold selectivity.

PubMed

Hung, Szu-Ying; Shih, Ya-Chen; Tseng, Wei-Lung

2015-02-01

This study describes the development of a simple, enzyme-free, label-free, sensitive, and selective system for detecting adenosine based on the use of Tween 20-stabilized gold nanoparticles (Tween 20-AuNPs) as an efficient fluorescence quencher for boron dipyrromethene-conjugated adenosine 5'-triphosphate (BODIPY-ATP) and as a recognition element for adenosine. BODIPY-ATP can interact with Tween 20-AuNPs through the coordination between the adenine group of BODIPY-ATP and Au atoms on the NP surface, thereby causing the fluorescence quenching of BODIPY-ATP through the nanometal surface energy transfer (NSET) effect. When adenosine attaches to the NP surface, the attached adenosine exhibits additional electrostatic attraction to BODIPY-ATP. As a result, the presence of adenosine enhances the efficiency of AuNPs in fluorescence quenching of BODIPY-ATP. The AuNP-induced fluorescence quenching of BODIPY-ATP progressively increased with an increase in the concentration of adenosine; the detection limit at a signal-to-noise ratio of 3 for adenosine was determined to be 60nM. The selectivity of the proposed system was more than 1000-fold for adenosine over any adenosine analogs and other nucleotides. The proposed system combined with a phenylboronic acid-containing column was successfully applied to the determination of adenosine in urine. Copyright © 2014 Elsevier B.V. All rights reserved.

Short rest between cyclic flexion periods is a risk factor for a lumbar disorder.

PubMed

Hoops, Heather; Zhou, Bing-He; Lu, Yun; Solomonow, Moshe; Patel, Vikas

2007-08-01

The epidemiology identifies cyclic lumbar loading as a risk factor for cumulative trauma disorder. Experimental biomechanical and physiological confirmation is lacking. The objective of this study was to asses the impact of different rest durations applied between periods of cyclic loading on the development of an acute lumbar disorder which, if continued to be subjected to loading, may develop into a cumulative disorder. Three groups of in vivo feline preparations were subjected to six sequential 10 min loading periods of cyclic lumbar flexion at 40 N with a frequency of 0.25 Hz applied to the L-4/5 level. The rest durations varied from 5 min in the first group, to 10 min in the second and to 20 min in the third. Reflexive EMG from the multifidi and lumbar displacement were used to identify significant (P<0.001) effects of time and rest duration for post-load EMG and displacement. Single-cycle test were performed hourly for 7 h post-loading to assess recovery. A model developed earlier was applied to represent the experimental data. The groups allowed 5 and 10 min rest exhibited an acute neuromuscular disorder expressed by a significant (P<0.001) delayed hyperexcitability 2-3 h into the 7 h recovery period with the intensity of the hyperexcitability significantly higher (P<0.001) for the group allowed only 5 min rest. The group allowed 20 min rest had a slow, uneventful recovery, free of delayed hyperexcitability. Occupational and sports activities requiring repetitive (cyclic) loading of the lumbar spine may be a risk factor for the development of a cumulative lumbar disorder and may require sufficient rest, as much as twice as long as the loading period, for prevention. Comparison to similar data for static lumbar loading shows that cyclic loading is more deleterious than static loading, requiring more rest to offset the negative effect of the repeated acts of stretch.

Cyclic di-adenosine monophosphate (c-di-AMP) is required for osmotic regulation in Staphylococcus aureus but dispensable for viability in anaerobic conditions.

PubMed

Zeden, Merve S; Schuster, Christopher F; Bowman, Lisa; Zhong, Qiyun; Williams, Huw D; Gründling, Angelika

2018-03-02

Cyclic di-adenosine monophosphate (c-di-AMP) is a recently discovered signaling molecule important for the survival of Firmicutes, a large bacterial group that includes notable pathogens such as Staphylococcus aureus However, the exact role of this molecule has not been identified. dacA , the S. aureus gene encoding the diadenylate cyclase enzyme required for c-di-AMP production, cannot be deleted when bacterial cells are grown in rich medium, indicating that c-di-AMP is required for growth in this condition. Here, we report that an S. aureus dacA mutant can be generated in chemically defined medium. Consistent with previous findings, this mutant had a severe growth defect when cultured in rich medium. Using this growth defect in rich medium, we selected for suppressor strains with improved growth to identify c-di-AMP-requiring pathways. Mutations bypassing the essentiality of dacA were identified in alsT and opuD, encoding a predicted amino acid and osmolyte transporter, the latter of which we show here to be the main glycine betaine-uptake system in S. aureus. Inactivation of these transporters likely prevents the excessive osmolyte and amino acid accumulation in the cell, providing further evidence for a key role of c-di-AMP in osmotic regulation. Suppressor mutations were also obtained in hepS, hemB, ctaA, and qoxB, coding proteins required for respiration. Furthermore, we show that dacA is dispensable for growth in anaerobic conditions. Together, these findings reveal an essential role for the c-di-AMP signaling network in aerobic, but not anaerobic, respiration in S. aureus . © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Adenosine through the A2A adenosine receptor increases IL-1β in the brain contributing to anxiety

PubMed Central

Chiu, Gabriel S.; Darmody, Patrick T.; Walsh, John P.; Moon, Morgan L.; Kwakwa, Kristin A.; Bray, Julie K.; McCusker, Robert H.; Freund, Gregory G.

2014-01-01

Anxiety is one of the most commonly reported psychiatric conditions, but its pathogenesis is poorly understood. Ailments associated with activation of the innate immune system, however, are increasingly linked to anxiety disorders. In adult male mice, we found that adenosine doubled caspase-1 activity in brain by a pathway reliant on ATP-sensitive potassium (KATP) channels, protein kinase A (PKA) and the A2A adenosine receptor (AR). In addition, adenosine-dependent activation of caspase-1 increased interleukin (IL)-1β in the brain by two-fold. Peripheral administration of adenosine in wild-type (WT) mice led to a 2.3-fold increase in caspase-1 activity in the amygdala and to a 33% and 42% reduction in spontaneous locomotor activity and food intake, respectively, that were not observed in caspase-1 knockout (KO), IL-1 receptor type 1 (IL-1R1) KO and A2A AR KO mice or in mice administered a caspase-1 inhibitor centrally. Finally, adenosine administration increased anxiety-like behaviors in WT mice by 28% in the open field test and by 55% in the elevated zero-maze. Caspase-1 KO mice, IL-1R1 KO mice, A2A AR KO mice and WT mice treated with the KATP channel blocker, glyburide, were resistant to adenosine-induced anxiety-like behaviors. Thus, our results indicate that adenosine can act as an anxiogenic by activating caspase-1 and increasing IL-1β in the brain. PMID:24907587

Adenosine signaling promotes hematopoietic stem and progenitor cell emergence

PubMed Central

Jing, Lili; Tamplin, Owen J.; Chen, Michael J.; Deng, Qing; Patterson, Shenia; Kim, Peter G.; Durand, Ellen M.; McNeil, Ashley; Green, Julie M.; Matsuura, Shinobu; Ablain, Julien; Brandt, Margot K.; Schlaeger, Thorsten M.; Huttenlocher, Anna; Daley, George Q.; Ravid, Katya

2015-01-01

Hematopoietic stem cells (HSCs) emerge from aortic endothelium via the endothelial-to-hematopoietic transition (EHT). The molecular mechanisms that initiate and regulate EHT remain poorly understood. Here, we show that adenosine signaling regulates hematopoietic stem and progenitor cell (HSPC) development in zebrafish embryos. The adenosine receptor A2b is expressed in the vascular endothelium before HSPC emergence. Elevated adenosine levels increased runx1+/cmyb+ HSPCs in the dorsal aorta, whereas blocking the adenosine pathway decreased HSPCs. Knockdown of A2b adenosine receptor disrupted scl+ hemogenic vascular endothelium and the subsequent EHT process. A2b adenosine receptor activation induced CXCL8 via cAMP–protein kinase A (PKA) and mediated hematopoiesis. We further show that adenosine increased multipotent progenitors in a mouse embryonic stem cell colony-forming assay and in embryonic day 10.5 aorta-gonad-mesonephros explants. Our results demonstrate that adenosine signaling plays an evolutionary conserved role in the first steps of HSPC formation in vertebrates. PMID:25870200

A High Affinity Adenosine Kinase from Anopheles gambiae

PubMed Central

Cassera, María B.; Ho, Meng-Chiao; Merino, Emilio F.; Burgos, Emmanuel S.; Rinaldo-Matthis, Agnes; Almo, Steven C.; Schramm, Vern L.

2011-01-01

Genome analysis revealed a mosquito orthologue of adenosine kinase in Anopheles gambiae (AgAK; the most important vector for the transmission of Plasmodium falciparum in Africa). P. falciparum are purine auxotrophs and do not express an adenosine kinase but rely on their hosts for purines. AgAK was kinetically characterized and found to have the highest affinity for adenosine (Km 8.1 nM) of any known adenosine kinase. AgAK is specific for adenosine at the nucleoside site but several nucleotide triphosphate phosphoryl donors are tolerated. The AgAK crystal structure with a bound bisubstrate analogue Ap4A (2.0 Å resolution) reveals interactions for adenosine, ATP and the geometry for phosphoryl transfer. The polyphosphate charge is partly neutralized by a bound Mg2+ ion and an ion pair to a catalytic site Arg. The AgAK structure consists of a large catalytic core in a three-layered α/β/α sandwich, and a small cap domain in contact with adenosine. The specificity and tight-binding for adenosine arises from hydrogen bond interactions of Asn14, Leu16, Leu40, Leu133, Leu168, Phe168 and Thr171 and the backbone of Ile39 and Phe168 with the adenine ring as well as through hydrogen bond interactions between Asp18, Gly64 and Asn68 and the ribosyl 2′- and 3′-hydroxyl groups. The structure is more similar to human adenosine kinase (48% identity) than to AK from Toxoplasma gondii (31% identity). With this extraordinary affinity for AgAK, adenosine is efficiently captured and converted to AMP at near the diffusion limit, suggesting an important role of this enzyme to maintain the adenine nucleotide pool. mRNA analysis verifies that AgAK transcripts are produced in the adult insects. PMID:21247194

A High-Affinity Adenosine Kinase from Anopheles Gambiae

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

M Cassera; M Ho; E Merino

2011-12-31

Genome analysis revealed a mosquito orthologue of adenosine kinase in Anopheles gambiae (AgAK; the most important vector for the transmission of Plasmodium falciparum in Africa). P. falciparum are purine auxotrophs and do not express an adenosine kinase but rely on their hosts for purines. AgAK was kinetically characterized and found to have the highest affinity for adenosine (K{sub m} = 8.1 nM) of any known adenosine kinase. AgAK is specific for adenosine at the nucleoside site, but several nucleotide triphosphate phosphoryl donors are tolerated. The AgAK crystal structure with a bound bisubstrate analogue Ap{sub 4}A (2.0 {angstrom} resolution) reveals interactionsmore » for adenosine and ATP and the geometry for phosphoryl transfer. The polyphosphate charge is partly neutralized by a bound Mg{sup 2+} ion and an ion pair to a catalytic site Arg. The AgAK structure consists of a large catalytic core in a three-layer {alpha}/{beta}/{alpha} sandwich, and a small cap domain in contact with adenosine. The specificity and tight binding for adenosine arise from hydrogen bond interactions of Asn14, Leu16, Leu40, Leu133, Leu168, Phe168, and Thr171 and the backbone of Ile39 and Phe168 with the adenine ring as well as through hydrogen bond interactions between Asp18, Gly64, and Asn68 and the ribosyl 2'- and 3'-hydroxyl groups. The structure is more similar to that of human adenosine kinase (48% identical) than to that of AK from Toxoplasma gondii (31% identical). With this extraordinary affinity for AgAK, adenosine is efficiently captured and converted to AMP at near the diffusion limit, suggesting an important role for this enzyme in the maintenance of the adenine nucleotide pool. mRNA analysis verifies that AgAK transcripts are produced in the adult insects.« less

Comparative Transcriptome Analysis of Bacillus subtilis Responding to Dissolved Oxygen in Adenosine Fermentation

PubMed Central

Yin, Chun-Yun; Zhou, Ying; Ye, Bang-Ce

2011-01-01

Dissolved oxygen (DO) is an important factor for adenosine fermentation. Our previous experiments have shown that low oxygen supply in the growth period was optimal for high adenosine yield. Herein, to better understand the link between oxygen supply and adenosine productivity in B. subtilis (ATCC21616), we sought to systematically explore the effect of DO on genetic regulation and metabolism through transcriptome analysis. The microarrays representing 4,106 genes were used to study temporal transcript profiles of B. subtilis fermentation in response to high oxygen supply (agitation 700 r/min) and low oxygen supply (agitation 450 r/min). The transcriptome data analysis revealed that low oxygen supply has three major effects on metabolism: enhance carbon metabolism (glucose metabolism, pyruvate metabolism and carbon overflow), inhibit degradation of nitrogen sources (glutamate family amino acids and xanthine) and purine synthesis. Inhibition of xanthine degradation was the reason that low oxygen supply enhanced adenosine production. These provide us with potential targets, which can be modified to achieve higher adenosine yield. Expression of genes involved in energy, cell type differentiation, protein synthesis was also influenced by oxygen supply. These results provided new insights into the relationship between oxygen supply and metabolism. PMID:21625606

Ischaemic tolerance in aged mouse myocardium: the role of adenosine and effects of A1 adenosine receptor overexpression

PubMed Central

Headrick, John P; Willems, Laura; Ashton, Kevin J; Holmgren, Kirsten; Peart, Jason; Matherne, G Paul

2003-01-01

The genesis of the ischaemia intolerant phenotype in aged myocardium is poorly understood. We tested the hypothesis that impaired adenosine-mediated protection contributes to ischaemic intolerance, and examined whether this is countered by A1 adenosine receptor (A1AR) overexpression. Responses to 20 min ischaemia and 45 min reperfusion were assessed in perfused hearts from young (2–4 months) and moderately aged (16–18 months) mice. Post-ischaemic contractility was impaired by ageing with elevated ventricular diastolic (32 ± 2 vs. 18 ± 2 mmHg in young) and reduced developed (37 ± 3 vs. 83 ± 6 mmHg in young) pressures. Lactate dehydrogenase (LDH) loss was exaggerated (27 ± 2 vs. 16 ± 2 IU g−1in young) whereas the incidence of tachyarrhythmias was similar in young (15 ± 1 %) and aged hearts (16 ± 1 %). Functional analysis confirmed equipotent effects of 50 μm adenosine at A1 and A2 receptors in young and aged hearts. Nonetheless, while 50 μm adenosine improved diastolic (5 ± 1 mmHg) and developed pressures (134 ± 7 mmHg) and LDH loss (6 ± 2 IU g−1) in young hearts, it did not alter these variables in the aged group. Adenosine did attenuate arrhythmogenesis for both ages (to ∼10 %). In contrast to adenosine, 50 μm diazoxide reduced ischaemic damage and arrhythmogenesis for both ages. Contractile and anti-necrotic effects of adenosine were limited by 100 μm 5-hydroxydecanoate (5-HD) and 3 μm chelerythrine. Anti-arrhythmic effects were limited by 5-HD but not chelerythrine. Non-selective (100 μm 8-sulfophenyltheophylline) and A1-selective (150 nm 8-cyclopentyl-1,3-dipropylxanthine) adenosine receptor antagonism impaired ischaemic tolerance in young but not aged hearts. Quantitative real-time PCR and radioligand analysis indicated that impaired protection is unrelated to changes in A1AR mRNA transcription, or receptor density (∼8 fmol mg−1 protein in both age groups). However, A1AR overexpression improved tolerance for both ages, restoring

Adenosine regulation of microtubule dynamics in cardiac hypertrophy.

PubMed

Fassett, John T; Xu, Xin; Hu, Xinli; Zhu, Guangshuo; French, Joel; Chen, Yingjie; Bache, Robert J

2009-08-01

There is evidence that endogenous extracellular adenosine reduces cardiac hypertrophy and heart failure in mice subjected to chronic pressure overload, but the mechanism by which adenosine exerts these protective effects is unknown. Here, we identified a novel role for adenosine in regulation of the cardiac microtubule cytoskeleton that may contribute to its beneficial effects in the overloaded heart. In neonatal cardiomyocytes, phenylephrine promoted hypertrophy and reorganization of the cytoskeleton, which included accumulation of sarcomeric proteins, microtubules, and desmin. Treatment with adenosine or the stable adenosine analog 2-chloroadenosine, which decreased hypertrophy, specifically reduced accumulation of microtubules. In hypertrophied cardiomyocytes, 2-chloroadenosine or adenosine treatment preferentially targeted stabilized microtubules (containing detyrosinated alpha-tubulin). Consistent with a role for endogenous adenosine in reducing microtubule stability, levels of detyrosinated microtubules were elevated in hearts of CD73 knockout mice (deficient in extracellular adenosine production) compared with wild-type mice (195%, P < 0.05). In response to aortic banding, microtubules increased in hearts of wild-type mice; this increase was exaggerated in CD73 knockout mice, with significantly greater amounts of tubulin partitioning into the cold-stable Triton-insoluble fractions. The levels of this stable cytoskeletal fraction of tubulin correlated strongly with the degree of heart failure. In agreement with a role for microtubule stabilization in promoting cardiac dysfunction, colchicine treatment of aortic-banded mice reduced hypertrophy and improved cardiac function compared with saline-treated controls. These results indicate that microtubules contribute to cardiac dysfunction and identify, for the first time, a role for adenosine in regulating cardiomyocyte microtubule dynamics.

Differential distribution of adenosine receptors in rat cochlea.

PubMed

Vlajkovic, Srdjan M; Abi, Shukri; Wang, Carol J H; Housley, Gary D; Thorne, Peter R

2007-06-01

Adenosine is a constitutive cell metabolite that can be released from cells via specific bi-directional transporters and is an end-point for nucleotide hydrolysis. In the extracellular space, adenosine becomes a signalling molecule for P1 (adenosine) receptors that modulate physiological responses in a wide range of mammalian tissues. Whereas adenosine signalling has been implicated in the regulation of cochlear blood flow and in cochlear protection from oxidative damage, the potential roles for adenosine signalling in the modulation of sound transduction and auditory neurotransmission have not been established. We have characterised the expression and distribution of adenosine receptors in the rat cochlea. mRNA transcripts for all four subtypes of adenosine receptors (A(1), A(2A), A(2B) and A(3)) were detected in dissected cochlear tissue by using reverse transcription/polymerase chain reaction analysis. The protein distribution for the A(1), A(2A) and A(3) receptor subtypes was identified by immunoperoxidase histochemistry and confocal immunofluorescence labelling. These receptors were differentially expressed in the organ of Corti, spiral ganglion neurones, lateral wall tissues and cochlear blood vessels. The distribution of adenosine receptors in sensory and neural tissues and in the vasculature coincided with other elements of purinergic signalling (P2X and P2Y receptors, ectonucleotidases), consistent with the integrative regulation of many physiological processes in the cochlea by extracellular nucleotides and nucleosides. Our study provides a framework for further investigation of adenosine signalling in the inner ear, including putative roles in oxidative stress responses.

Mechanism-specific effects of adenosine on ventricular tachycardia.

PubMed

Lerman, Bruce B; Ip, James E; Shah, Bindi K; Thomas, George; Liu, Christopher F; Ciaccio, Edward J; Wit, Andrew L; Cheung, Jim W; Markowitz, Steven M

2014-12-01

There is no universally accepted method by which to diagnose clinical ventricular tachycardia (VT) due to cAMP-mediated triggered activity. Based on cellular and clinical data, adenosine termination of VT is thought to be consistent with a diagnosis of triggered activity. However, a major gap in evidence mitigates the validity of this proposal, namely, defining the specificity of adenosine response in well-delineated reentrant VT circuits. To this end, we systematically studied the effects of adenosine in a model of canine reentrant VT and in human reentrant VT, confirmed by 3-dimensional, pace- and substrate mapping. Adenosine (12 mg [IQR 12-24]) failed to terminate VT in 31 of 31 patients with reentrant VT due to structural heart disease, and had no effect on VT cycle length (age, 67 years [IQR 53-74]); ejection fraction, 35% [IQR 20-55]). In contrast, adenosine terminated VT in 45 of 50 (90%) patients with sustained focal right or left outflow tract tachycardia. The sensitivity of adenosine for identifying VT due to triggered activity was 90% (95% CI, 0.78-0.97) and its specificity was 100% (95% CI, 0.89-1.0). Additionally, reentrant circuits were mapped in the epicardial border zone of 4-day-old infarcts in mongrel dogs. Adenosine (300-400 μg/kg) did not terminate sustained VT or have any effect on VT cycle length. These data support the concept that adenosine's effects on ventricular myocardium are mechanism specific, such that termination of VT in response to adenosine is diagnostic of cAMP-mediated triggered activity. © 2014 Wiley Periodicals, Inc.

N6-(2-Hydroxyethyl)-Adenosine Exhibits Insecticidal Activity against Plutella xylostella via Adenosine Receptors

PubMed Central

Fang, Ming; Chai, Yiqiu; Chen, Guanjv; Wang, Huidong; Huang, Bo

2016-01-01

The diamondback moth, Plutella xylostella, is one of the most important pests of cruciferous crops. We have earlier shown that N6-(2-hydroxyethyl)-adenosine (HEA) exhibits insecticidal activity against P. xylostella. In the present study we investigated the possible mechanism of insecticidal action of HEA on P. xylostella. HEA is a derivative of adenosine, therefore, we speculated whether it acts via P. xylostella adenosine receptor (PxAdoR). We used RNAi approach to silence PxAdoR gene and used antagonist of denosine receptor (AdoR) to study the insecticidal effect of HEA. We cloned the whole sequence of PxAdoR gene. A BLAST search using NCBI protein database showed a 61% identity with the Drosophila adenosine receptor (DmAdoR) and a 32–35% identity with human AdoR. Though the amino acids sequence of PxAdoR was different compared to other adenosine receptors, most of the amino acids that are known to be important for adenosine receptor ligand binding and signaling were present. However, only 30% binding sites key residues was similar between PxAdoR and A1R. HEA, at a dose of 1 mg/mL, was found to be lethal to the second-instar larvae of P. xylostella, and a significant reduction of mortality and growth inhibition ratio were obtained when HEA was administered to the larvae along with PxAdoR-dsRNA or antagonist of AdoR (SCH58261) for 36, 48, or 60 h. Especially at 48 h, the rate of growth inhibition of the PxAdoR knockdown group was 3.5-fold less than that of the HEA group, and the corrected mortality of SCH58261 group was reduced almost 2-fold compared with the HEA group. Our findings show that HEA may exert its insecticidal activity against P. xylostella larvae via acting on PxAdoR. PMID:27668428

Role of nitric oxide in adenosine-induced vasodilation in humans

NASA Technical Reports Server (NTRS)

Costa, F.; Biaggioni, I.; Robertson, D. (Principal Investigator)

1998-01-01

Vasodilation is one of the most prominent effects of adenosine and one of the first to be recognized, but its mechanism of action is not completely understood. In particular, there is conflicting information about the potential contribution of endothelial factors. The purpose of this study was to explore the role of nitric oxide in the vasodilatory effect of adenosine. Forearm blood flow responses to intrabrachial adenosine infusion (125 microg/min) were assessed with venous occlusion plethysmography during intrabrachial infusion of saline or the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) (12.5 mg/min). Intrabrachial infusions of acetylcholine (50 microg/min) and nitroprusside (3 microg/min) were used as a positive and negative control, respectively. These doses were chosen to produce comparable levels of vasodilation. In a separate study, a second saline infusion was administered instead of L-NMMA to rule out time-related effects. As expected, pretreatment with L-NMMA reduced acetylcholine-induced vasodilation; 50 microg/min acetylcholine increased forearm blood flow by 150+/-43% and 51+/-12% during saline and L-NMMA infusion, respectively (P<.01, n=6). In contrast, L-NMMA did not affect the increase in forearm blood flow produced by 3 microg/min nitroprusside (165+/-30% and 248+/-41% during saline and L-NMMA, respectively) or adenosine (173+/-48% and 270+/-75% during saline and L-NMMA, respectively). On the basis of our observations, we conclude that adenosine-induced vasodilation is not mediated by nitric oxide in the human forearm.

Enzymatic regeneration of adenosine triphosphate cofactor

NASA Technical Reports Server (NTRS)

Marshall, D. L.

1974-01-01

Regenerating adenosine triphosphate (ATP) from adenosine diphosphate (ADP) by enzymatic process which utilizes carbamyl phosphate as phosphoryl donor is technique used to regenerate expensive cofactors. Process allows complex enzymatic reactions to be considered as candidates for large-scale continuous processes.

Pretreatment with the nitric oxide donor SNAP or nerve transection blocks humoral preconditioning by remote limb ischemia or intra-arterial adenosine.

PubMed

Steensrud, Tor; Li, Jing; Dai, Xiaojing; Manlhiot, Cedric; Kharbanda, Rajesh K; Tropak, Michael; Redington, Andrew

2010-11-01

We have previously shown that remote ischemic preconditioning (rIPC) by transient limb ischemia leads to the release of a circulating factor(s) that induces potent myocardial protection. Intra-arterial injection of adenosine into a limb also leads to cardioprotection, but the mechanism of its signal transduction is poorly understood. Eleven groups of rabbits received saline control or rIPC or adenosine administration with additional pretreatment with the nitric oxide (NO) synthase blocker N(G)-nitro-l-arginine methyl ester, the NO donor S-nitroso-N-acetylpenicillamine, its non-NO-donating derivative N-acetylpenicillamine, or femoral nerve section. Blood was then drawn from each animal, and the dialysate of the plasma was used to perfuse a naïve heart from an untreated donor. Infarct size was measured after 30 min of global ischemia and 120 min reperfusion. When compared with that of the control, mean infarct size was significantly smaller in groups treated with rIPC alone (P < 0.01) and intra-arterial adenosine (P < 0.01). Pretreatment with N(G)-nitro-l-arginine methyl ester or N-acetylpenicillamine did not affect the level of protection induced by rIPC (P = not significant, compared with rIPC alone) or intra-arterial adenosine (P = not significant, compared with intra-arterial adenosine alone), but prior femoral nerve transection or pretreatment with S-nitroso-N-acetylpenicillamine abolished the cardioprotective effect of intra-arterial adenosine and rIPC. Intra-arterial adenosine, like rIPC, releases a blood-borne cardioprotective factor(s) that is dependent on an intact femoral nerve and is inhibited by pretreatment with a NO donor. These results may be important when designing or assessing the results of clinical trials of adenosine or rIPC cardioprotection, where NO donors are used as part of therapy.

A surrogate analyte-based liquid chromatography-tandem mass spectrometry method for the determination of endogenous cyclic nucleotides in rat brain.

PubMed

Chen, Jie; Tabatabaei, Ali; Zook, Doug; Wang, Yan; Danks, Anne; Stauber, Kathe

2017-11-30

A robust high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS) assay was developed and qualified for the measurement of cyclic nucleotides (cNTs) in rat brain tissue. Stable isotopically labeled 3',5'-cyclic adenosine- 13 C 5 monophosphate ( 13 C 5 -cAMP) and 3',5'-cyclic guanosine- 13 C, 15 N 2 monophosphate ( 13 C 15 N 2 -cGMP) were used as surrogate analytes to measure endogenous 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP). Pre-weighed frozen rat brain samples were rapidly homogenized in 0.4M perchloric acid at a ratio of 1:4 (w/v). Following internal standard addition and dilution, the resulting extracts were analyzed using negative ion mode electrospray ionization LC-MS/MS. The calibration curves for both analytes ranged from 5 to 2000ng/g and showed excellent linearity (r 2 >0.996). Relative surrogate analyte-to-analyte LC-MS/MS responses were determined to correct concentrations derived from the surrogate curves. The intra-run precision (CV%) for 13 C 5 -cAMP and 13 C 15 N 2 -cGMP was below 6.6% and 7.4%, respectively, while the inter-run precision (CV%) was 8.5% and 5.8%, respectively. The intra-run accuracy (Dev%) for 13 C 5 -cAMP and 13 C 15 N 2 -cGMP was <11.9% and 10.3%, respectively, and the inter-run Dev% was <6.8% and 5.5%, respectively. Qualification experiments demonstrated high analyte recoveries, minimal matrix effects and low autosampler carryover. Acceptable frozen storage, freeze/thaw, benchtop, processed sample and autosampler stability were shown in brain sample homogenates as well as post-processed samples. The method was found to be suitable for the analysis of rat brain tissue cAMP and cGMP levels in preclinical biomarker development studies. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Adenosine increases anagen hair growth and thick hairs in Japanese women with female pattern hair loss: a pilot, double-blind, randomized, placebo-controlled trial.

PubMed

Oura, Hajimu; Iino, Masato; Nakazawa, Yosuke; Tajima, Masahiro; Ideta, Ritsuro; Nakaya, Yutaka; Arase, Seiji; Kishimoto, Jiro

2008-12-01

Adenosine upregulates the expression of vascular endothelial growth factor and fibroblast growth factor-7 in cultured dermal papilla cells. It has been shown that, in Japanese men, adenosine improves androgenetic alopecia due to the thickening of thin hair due to hair follicle miniaturization. To investigate the efficacy and safety of adenosine treatment to improve hair loss in women, 30 Japanese women with female pattern hair loss were recruited for this double-blind, randomized, placebo-controlled study. Volunteers used either 0.75% adenosine lotion or a placebo lotion topically twice daily for 12 months. Efficacy was evaluated by dermatologists and by investigators and in phototrichograms. As a result, adenosine was significantly superior to the placebo according to assessments by dermatologists and investigators and by self-assessments. Adenosine significantly increased the anagen hair growth rate and the thick hair rate. No side-effects were encountered during the trial. Adenosine improved hair loss in Japanese women by stimulating hair growth and by thickening hair shafts. Adenosine is useful for treating female pattern hair loss in women as well as androgenetic alopecia in men.

Role of adenosine receptors in caffeine tolerance

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

Holtzman, S.G.; Mante, S.; Minneman, K.P.

1991-01-01

Caffeine is a competitive antagonist at adenosine receptors. Receptor up-regulation during chronic drug treatment has been proposed to be the mechanism of tolerance to the behavioral stimulant effects of caffeine. This study reassessed the role of adenosine receptors in caffeine tolerance. Separate groups of rats were given scheduled access to drinking bottles containing plain tap water or a 0.1% solution of caffeine. Daily drug intake averaged 60-75 mg/kg and resulted in complete tolerance to caffeine-induced stimulation of locomotor activity, which could not be surmounted by increasing the dose of caffeine. 5'-N-ethylcarboxamidoadenosine (0.001-1.0 mg/kg) dose dependently decreased the locomotor activity ofmore » caffeine-tolerant rats and their water-treated controls but was 8-fold more potent in the latter group. Caffeine (1.0-10 mg/kg) injected concurrently with 5-N-ethylcarboxamidoadenosine antagonized the decreases in locomotor activity comparably in both groups. Apparent pA2 values for tolerant and control rats also were comparable: 5.05 and 5.11. Thus, the adenosine-antagonist activity of caffeine was undiminished in tolerant rats. The effects of chronic caffeine administration on parameters of adenosine receptor binding and function were measured in cerebral cortex. There were no differences between brain tissue from control and caffeine-treated rats in number and affinity of adenosine binding sites or in receptor-mediated increases (A2 adenosine receptor) and decreases (A1 adenosine receptor) in cAMP accumulation. These results are consistent with theoretical arguments that changes in receptor density should not affect the potency of a competitive antagonist. Experimental evidence and theoretical considerations indicate that up-regulation of adenosine receptors is not the mechanism of tolerance to caffeine-induced stimulation of locomotor activity.« less

Administration of exogenous adenosine triphosphate to ischemic skeletal muscle induces an energy-sparing effect: role of adenosine receptors.

PubMed

Maldonado, Claudio; Pushpakumar, Sathnur B; Perez-Abadia, Gustavo; Arumugam, Sengodagounder; Lane, Andrew N

2013-05-01

Ischemia-reperfusion injury is a devastating complication that occurs in allotransplantation and replantation of limbs. Over the years, several preservation strategies have been used to conserve the critical levels of intracellular adenosine triphosphate (ATP) during ischemia to sustain the ion gradients across the membranes and thus the tissue viability. The administration of exogenous ATP to ischemic tissues is known to provide beneficial effects during reperfusion, but it is unclear whether it provides protection during ischemia. The purpose of the present study was to determine the effect of ATP administration on high-energy phosphate levels in ischemic skeletal muscle and to examine the role of purinergic and adenosine receptors in mediating the response to exogenous ATP. The extensor digitorum longus muscles of Fischer rats were subjected to ischemia and treated with different concentrations of ATP with or without purinergic and adenosine receptor blockers. Phosphorus-31 nuclear magnetic resonance spectroscopy was used to measure the rate of decay of ATP, phosphocreatine (PCr), and the formation of adenosine monophosphate and acidification. Phosphorylated compounds were analyzed using a simple model of energy metabolism, and the PCr half-life was used as an index of internal depletion of ATP to distinguish between intracellular and extracellular ATP. PCr decay was rapid in all muscle groups and was followed by gradual ATP decay. The half-life of PCr was significantly longer in the ATP-treated muscles than in the vehicle controls and was maximally prolonged by treating with slow hydrolyzing adenosine 5'-O-(3-thio)triphosphate. Purinoceptor (P2X) blockade with ATP treatment significantly increased the half-life of PCr, and adenosine receptor blockers blunted the response. Administration of adenosine to ischemic muscles significantly increased the half-life of PCr compared with that in the vehicle controls. Exogenous ATP administration to ischemic skeletal

Immunosuppression via adenosine receptor activation by adenosine monophosphate released from apoptotic cells.

PubMed

Yamaguchi, Hiroshi; Maruyama, Toshihiko; Urade, Yoshihiro; Nagata, Shigekazu

2014-03-25

Apoptosis is coupled with recruitment of macrophages for engulfment of dead cells, and with compensatory proliferation of neighboring cells. Yet, this death process is silent, and it does not cause inflammation. The molecular mechanisms underlying anti-inflammatory nature of the apoptotic process remains poorly understood. In this study, we found that the culture supernatant of apoptotic cells activated the macrophages to express anti-inflammatory genes such as Nr4a and Thbs1. A high level of AMP accumulated in the apoptotic cell supernatant in a Pannexin1-dependent manner. A nucleotidase inhibitor and A2a adenosine receptor antagonist inhibited the apoptotic supernatant-induced gene expression, suggesting AMP was metabolized to adenosine by an ecto-5'-nucleotidase expressed on macrophages, to activate the macrophage A2a adenosine receptor. Intraperitoneal injection of zymosan into Adora2a- or Panx1-deficient mice produced high, sustained levels of inflammatory mediators in the peritoneal lavage. These results indicated that AMP from apoptotic cells suppresses inflammation as a 'calm down' signal. DOI: http://dx.doi.org/10.7554/eLife.02172.001.

An Adenosine-Mediated Glial-Neuronal Circuit for Homeostatic Sleep.

PubMed

Bjorness, Theresa E; Dale, Nicholas; Mettlach, Gabriel; Sonneborn, Alex; Sahin, Bogachan; Fienberg, Allen A; Yanagisawa, Masashi; Bibb, James A; Greene, Robert W

2016-03-30

Sleep homeostasis reflects a centrally mediated drive for sleep, which increases during waking and resolves during subsequent sleep. Here we demonstrate that mice deficient for glial adenosine kinase (AdK), the primary metabolizing enzyme for adenosine (Ado), exhibit enhanced expression of this homeostatic drive by three independent measures: (1) increased rebound of slow-wave activity; (2) increased consolidation of slow-wave sleep; and (3) increased time constant of slow-wave activity decay during an average slow-wave sleep episode, proposed and validated here as a new index for homeostatic sleep drive. Conversely, mice deficient for the neuronal adenosine A1 receptor exhibit significantly decreased sleep drive as judged by these same indices. Neuronal knock-out of AdK did not influence homeostatic sleep need. Together, these findings implicate a glial-neuronal circuit mediated by intercellular Ado, controlling expression of homeostatic sleep drive. Because AdK is tightly regulated by glial metabolic state, our findings suggest a functional link between cellular metabolism and sleep homeostasis. The work presented here provides evidence for an adenosine-mediated regulation of sleep in response to waking (i.e., homeostatic sleep need), requiring activation of neuronal adenosine A1 receptors and controlled by glial adenosine kinase. Adenosine kinase acts as a highly sensitive and important metabolic sensor of the glial ATP/ADP and AMP ratio directly controlling intracellular adenosine concentration. Glial equilibrative adenosine transporters reflect the intracellular concentration to the extracellular milieu to activate neuronal adenosine receptors. Thus, adenosine mediates a glial-neuronal circuit linking glial metabolic state to neural-expressed sleep homeostasis. This indicates a metabolically related function(s) for this glial-neuronal circuit in the buildup and resolution of our need to sleep and suggests potential therapeutic targets more directly related to

Parallel effect of 4-octylphenol and cyclic adenosine monophosphate (cAMP) alters steroidogenesis, cell viability and ROS production in mice Leydig cells.

PubMed

Jambor, Tomas; Greifova, Hana; Kovacik, Anton; Kovacikova, Eva; Tvrda, Eva; Forgacs, Zsolt; Massanyi, Peter; Lukac, Norbert

2018-05-01

Over the last decade, there is growing incidence of male reproductive malfunctions. It has been documented that numerous environmental contaminants, such as endocrine disruptors (EDs) may adversely affect the reproductive functions of humans as well as wildlife species. The aim of this in vitro study was to examine the effects of 4-octylphenol (4-OP) on the steroidogenesis in mice Leydig cells. We evaluated the impact of this endocrine disruptor on the cholesterol levels and hormone secretion in a primary culture. Subsequently, we determined the cell viability and generation of reactive oxygen species (ROS) following 4-OP treatment. Isolated mice Leydig cells were cultured in the presence of different 4-OP concentrations (0.04-5.0 μg/mL) and 1 mM cyclic adenosine-monophosphate during 44 h. Cholesterol levels were determined from the culture medium using photometry. Quantification of steroid secretion was performed by enzyme-linked immunosorbent assay. The cell viability was assessed using the metabolic activity assay, while ROS production was assessed by the chemiluminescence technique. Slightly increased cholesterol levels were recorded following exposure to the whole applied range of 4-OP, without significant changes (P>0.05). In contrast, the secretion of steroid hormones, specifically dehydroepiandrosterone, androstenedione, and testosterone was decreased following exposure to 4-OP. Experimental doses of 4-OP did not affect cell viability significantly; however a moderate decrease was recorded following the higher doses (2.5 and 5.0 μg/mL) of 4-OP. Furthermore, relative treatment of 4-OP (5.0 μg/mL) caused a significant (P < 0.001) ROS overproduction in the exposed cells. Copyright © 2018 Elsevier Ltd. All rights reserved.

Characterization of the swine adipocyte A1 adenosine receptor using an optimized assay system.

PubMed

Dong, Q; Schuchman, J; Carey, G B

1994-07-01

The radioligand binding assay of A1 adenosine receptors in adipocyte crude plasma membrane from Yucatan miniature swine was optimized by evaluating 17 factors involved in the assay. Significant effects of CHAPS, adenosine deaminase, EDTA, pre-rinsing glass fiber filters and pH were found for the binding measurements. Using the optimized procedure, [3H]8-cyclopentyl-1,3-dipropylxanthine, ([3H]-DPCPX) binding to A1 adenosine receptors in swine subcutaneous adipocyte crude plasma membrane was measured; Bmax and Kd values were 479 +/- 77 fmol/mg protein and 0.87 +/- 0.10 nM, respectively. Values for mesenteric adipose tissue from sedentary swine and subcutaneous adipose tissue from exercise-trained swine were also measured.

Activation of adenosine low-affinity A3 receptors inhibits the enteric short interplexus neural circuit triggered by histamine.

PubMed

Bozarov, Andrey; Wang, Yu-Zhong; Yu, Jun Ge; Wunderlich, Jacqueline; Hassanain, Hamdy H; Alhaj, Mazin; Cooke, Helen J; Grants, Iveta; Ren, Tianhua; Christofi, Fievos L

2009-12-01

We tested the novel hypothesis that endogenous adenosine (eADO) activates low-affinity A3 receptors in a model of neurogenic diarrhea in the guinea pig colon. Dimaprit activation of H2 receptors was used to trigger a cyclic coordinated response of contraction and Cl(-) secretion. Contraction-relaxation was monitored by sonomicrometry (via intracrystal distance) simultaneously with short-circuit current (I(sc), Cl(-) secretion). The short interplexus reflex coordinated response was attenuated or abolished by antagonists at H2 (cimetidine), 5-hydroxytryptamine 4 receptor (RS39604), neurokinin-1 receptor (GR82334), or nicotinic (mecamylamine) receptors. The A1 agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) abolished coordinated responses, and A1 antagonists could restore normal responses. A1-selective antagonists alone [8-cyclopentyltheophylline (CPT), 1,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine (PACPX), or 8-cyclopentyl-N(3)-[3-(4-(fluorosulfonyl)benzoyloxy)propyl]-xanthine (FSCPX)] caused a concentration-dependent augmentation of crypt cell secretion or contraction and acted at nanomolar concentrations. The A3 agonist N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) abolished coordinated responses and the A3 antagonist 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS1191) could restore and further augment responses. The IB-MECA effect was resistant to knockdown of adenosine A1 receptor with the irreversible antagonist FSCPX; the IC(50) for IB-MECA was 0.8 microM. MRS1191 alone could augment or unmask coordinated responses to dimaprit, and IB-MECA suppressed them. MRS1191 augmented distension-evoked reflex I(sc) responses. Adenosine deaminase mimicked actions of adenosine receptor antagonists. A3 receptor immunoreactivity was differentially expressed in enteric neurons of different parts of colon. After tetrodotoxin, IB-MECA caused circular muscle relaxation. The data support the novel concept that

Activation of adenosine low-affinity A3 receptors inhibits the enteric short interplexus neural circuit triggered by histamine

PubMed Central

Bozarov, Andrey; Wang, Yu-Zhong; Yu, Jun Ge; Wunderlich, Jacqueline; Hassanain, Hamdy H.; Alhaj, Mazin; Cooke, Helen J.; Grants, Iveta; Ren, Tianhua

2009-01-01

We tested the novel hypothesis that endogenous adenosine (eADO) activates low-affinity A3 receptors in a model of neurogenic diarrhea in the guinea pig colon. Dimaprit activation of H2 receptors was used to trigger a cyclic coordinated response of contraction and Cl− secretion. Contraction-relaxation was monitored by sonomicrometry (via intracrystal distance) simultaneously with short-circuit current (Isc, Cl− secretion). The short interplexus reflex coordinated response was attenuated or abolished by antagonists at H2 (cimetidine), 5-hydroxytryptamine 4 receptor (RS39604), neurokinin-1 receptor (GR82334), or nicotinic (mecamylamine) receptors. The A1 agonist 2-chloro-N6-cyclopentyladenosine (CCPA) abolished coordinated responses, and A1 antagonists could restore normal responses. A1-selective antagonists alone [8-cyclopentyltheophylline (CPT), 1,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine (PACPX), or 8-cyclopentyl-N3-[3-(4-(fluorosulfonyl)benzoyloxy)propyl]-xanthine (FSCPX)] caused a concentration-dependent augmentation of crypt cell secretion or contraction and acted at nanomolar concentrations. The A3 agonist N6-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (IB-MECA) abolished coordinated responses and the A3 antagonist 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(±)-dihydropyridine-3,5-dicarboxylate (MRS1191) could restore and further augment responses. The IB-MECA effect was resistant to knockdown of adenosine A1 receptor with the irreversible antagonist FSCPX; the IC50 for IB-MECA was 0.8 μM. MRS1191 alone could augment or unmask coordinated responses to dimaprit, and IB-MECA suppressed them. MRS1191 augmented distension-evoked reflex Isc responses. Adenosine deaminase mimicked actions of adenosine receptor antagonists. A3 receptor immunoreactivity was differentially expressed in enteric neurons of different parts of colon. After tetrodotoxin, IB-MECA caused circular muscle relaxation. The data support the novel concept that eADO acts at

Autophagy occurs within an hour of adenosine triphosphate treatment after nerve cell damage: the neuroprotective effects of adenosine triphosphate against apoptosis

PubMed Central

Lu, Na; Wang, Baoying; Deng, Xiaohui; Zhao, Honggang; Wang, Yong; Li, Dongliang

2014-01-01

After hypoxia, ischemia, or inflammatory injuries to the central nervous system, the damaged cells release a large amount of adenosine triphosphate, which may cause secondary neuronal death. Autophagy is a form of cell death that also has neuroprotective effects. Cell Counting Kit assay, monodansylcadaverine staining, flow cytometry, western blotting, and real-time PCR were used to determine the effects of exogenous adenosine triphosphate treatment at different concentrations (2, 4, 6, 8, 10 mmol/L) over time (1, 2, 3, and 6 hours) on the apoptosis and autophagy of SH-SY5Y cells. High concentrations of extracellular adenosine triphosphate induced autophagy and apoptosis of SH-SY5Y cells. The enhanced autophagy first appeared, and peaked at 1 hour after treatment with adenosine triphosphate. Cell apoptosis peaked at 3 hours, and persisted through 6 hours. With prolonged exposure to the adenosine triphosphate treatment, the fraction of apoptotic cells increased. These data suggest that the SH-SY5Y neural cells initiated autophagy against apoptosis within an hour of adenosine triphosphate treatment to protect themselves against injury. PMID:25368646

Utility of Adenosine Monophosphate Detection System for Monitoring the Activities of Diverse Enzyme Reactions.

PubMed

Mondal, Subhanjan; Hsiao, Kevin; Goueli, Said A

Adenosine monophosphate (AMP) is a key cellular metabolite regulating energy homeostasis and signal transduction. AMP is also a product of various enzymatic reactions, many of which are dysregulated during disease conditions. Thus, monitoring the activities of these enzymes is a primary goal for developing modulators for these enzymes. In this study, we demonstrate the versatility of an enzyme-coupled assay that quantifies the amount of AMP produced by any enzymatic reaction regardless of its substrates. We successfully implemented it to enzyme reactions that use adenosine triphosphate (ATP) as a substrate (aminoacyl tRNA synthetase and DNA ligase) by an elaborate strategy of removing residual ATP and converting AMP produced into ATP; so it can be detected using luciferase/luciferin and generating light. We also tested this assay to measure the activities of AMP-generating enzymes that do not require ATP as substrate, including phosphodiesterases (cyclic adenosine monophosphate) and Escherichia coli DNA ligases (nicotinamide adenine dinucleotide [NAD + ]). In a further elaboration of the AMP-Glo platform, we coupled it to E. coli DNA ligase, enabling measurement of NAD + and enzymes that use NAD + like monoadenosine and polyadenosine diphosphate-ribosyltransferases. Sulfotransferases use 3'-phosphoadenosine-5'-phosphosulfate as the universal sulfo-group donor and phosphoadenosine-5'-phosphate (PAP) is the universal product. PAP can be quantified by converting PAP to AMP by a Golgi-resident PAP-specific phosphatase, IMPAD1. By coupling IMPAD1 to the AMP-Glo system, we can measure the activities of sulfotransferases. Thus, by utilizing the combinations of biochemical enzymatic conversion of various cellular metabolites to AMP, we were able to demonstrate the versatility of the AMP-Glo assay.

Application of the newly developed Japanese adenosine normal database for adenosine stress myocardial scintigraphy.

PubMed

Harata, Shingo; Isobe, Satoshi; Morishima, Itsuro; Suzuki, Susumu; Tsuboi, Hideyuki; Sone, Takahito; Ishii, Hideki; Murohara, Toyoaki

2015-10-01

The currently available Japanese normal database (NDB) in stress myocardial perfusion scintigraphy recommended by the Japanese Society of Nuclear Medicine (JSNM-NDB) is created based on the data from exercise tests. The newly developed adenosine normal database (ADS-NDB) remains to be validated for patients undergoing adenosine stress test. We tested whether the diagnostic accuracy of adenosine stress test is improved by the use of ADS-NDB (Kanazawa University). Of 233 consecutive patients undergoing (99m)Tc-MIBI adenosine stress test, 112 patients were tested. The stress/rest myocardial (99m)Tc-MIBI single-photon emission computed tomography (SPECT) images were analyzed by AutoQUANT 7.2 with both ADS-NDB and JSNM-NDB. The summed stress score (SSS) and summed difference score (SDS) were calculated. The agreements of the post-stress defect severity between ADS-NDB and JSNM-NDB were assessed using a weighted kappa statistic. In all patients, mean SSSs of all, right coronary artery (RCA), left anterior descending (LAD), and left circumflex (LCx) territories were significantly lower with ADS-NDB than those with JSNM-NDB. Mean SDSs in all, RCA, and LAD territories were significantly lower with ADS-NDB than those with JSNM-NDB. In 28 patients with significant coronary stenosis, the mean SSS in the RCA territory was significantly lower with ADS-NDB than that with JSNM-NDB. In 84 patients without ischemia, both mean SSSs and SDSs in all, RCA, LAD, and LCx territories were significantly lower with ADS-NDB than those with JSNM-NDB. Weighted kappa values of all patients, patients with significant stenosis, and patients without ischemia were 0.89, 0.83, and 0.92, respectively. Differences were observed between results from ADS-NDB and JSNM-NDB. The diagnostic accuracy of adenosine stress myocardial perfusion scintigraphy may be improved by reducing false-positive results.

Adenosine signaling contributes to ethanol-induced fatty liver in mice

PubMed Central

Peng, Zhongsheng; Borea, Pier Andrea; Wilder, Tuere; Yee, Herman; Chiriboga, Luis; Blackburn, Michael R.; Azzena, Gianfranco; Resta, Giuseppe; Cronstein, Bruce N.

2009-01-01

Fatty liver is commonly associated with alcohol ingestion and abuse. While the molecular pathogenesis of these fatty changes is well understood, the biochemical and pharmacological mechanisms by which ethanol stimulates these molecular changes remain unknown. During ethanol metabolism, adenosine is generated by the enzyme ecto-5′-nucleotidase, and adenosine production and adenosine receptor activation are known to play critical roles in the development of hepatic fibrosis. We therefore investigated whether adenosine and its receptors play a role in the development of alcohol-induced fatty liver. WT mice fed ethanol on the Lieber-DeCarli diet developed hepatic steatosis, including increased hepatic triglyceride content, while mice lacking ecto-5′-nucleotidase or adenosine A1 or A2B receptors were protected from developing fatty liver. Similar protection was also seen in WT mice treated with either an adenosine A1 or A2B receptor antagonist. Steatotic livers demonstrated increased expression of genes involved in fatty acid synthesis, which was prevented by blockade of adenosine A1 receptors, and decreased expression of genes involved in fatty acid metabolism, which was prevented by blockade of adenosine A2B receptors. In vitro studies supported roles for adenosine A1 receptors in promoting fatty acid synthesis and for A2B receptors in decreasing fatty acid metabolism. These results indicate that adenosine generated by ethanol metabolism plays an important role in ethanol-induced hepatic steatosis via both A1 and A2B receptors and suggest that targeting adenosine receptors may be effective in the prevention of alcohol-induced fatty liver. PMID:19221436

The adenosine salvage pathway as an alternative to mitochondrial production of ATP in maturing mammalian oocytes.

PubMed

Scantland, Sara; Tessaro, Irene; Macabelli, Carolina H; Macaulay, Angus D; Cagnone, Gaël; Fournier, Éric; Luciano, Alberto M; Robert, Claude

2014-09-01

Although the oocyte is the largest cell in the body and an unavoidable phase in life, its physiology is still poorly understood, and other cell types provide little insight into its unique nature. Even basic cellular functions in the oocyte such as energy metabolism are not yet fully understood. It is known that the mitochondria of the female gamete exhibit an immature form characterized by limited energy production from glucose and oxidative phosphorylation. We show that the bovine oocyte uses alternative means to maintain ATP production during maturation, namely, the adenosine salvage pathway. Meiosis resumption is triggered by destruction of cyclic AMP by phosphodiesterases producing adenosine monophosphate that is converted into ATP by adenylate kinases and creatine kinases. Inhibition of these enzymes decreased ATP production, and addition of their substrates restored ATP production in denuded oocytes. Addition of phosphocreatine to the oocyte maturation medium influenced the phenotype of the resulting blastocysts. We propose a model in which adenylate kinases and creatine kinases act as drivers of ATP production from added AMP during oocyte maturation. © 2014 by the Society for the Study of Reproduction, Inc.

Cyclic Mechanical Stretch Up-regulates Hepatoma-Derived Growth Factor Expression in Cultured Rat Aortic Smooth Muscle Cells.

PubMed

Kao, Ying-Hsien; Chen, Po-Han; Sun, Cheuk-Kwan; Chang, Yo-Chen; Lin, Yu-Chun; Tsai, Ming-Shian; Lee, Po-Huang; Cheng, Cheng-I

2018-02-21

Hepatoma-derived growth factor (HDGF) is a potent mitogen for vascular smooth muscle cells (SMCs) during embryogenesis and injury repair of vessel walls. Whether mechanical stimuli modulate HDGF expression remains unknown. This study aimed at investigating whether cyclic mechanical stretch plays a regulatory role in HDGF expression and regenerative cytokine production in aortic SMCs. A SMC cell line was grown on a silicone-based elastomer chamber with extracellular matrix coatings (either type I collagen or fibronectin) and received cyclic and uni-axial mechanical stretches with 10% deformation at frequency 1 Hz. Morphological observation showed that fibronectin coating provided better cell adhesion and spreading and that consecutive 6 hours of cyclic mechanical stretch remarkably induced reorientation and realignment of SMCs. Western blotting detection demonstrated that continuous mechanical stimuli elicited up-regulation of HDGF and PCNA, a cell proliferative marker. Signal kinetic profiling study indicated that cyclic mechanical stretch induced signaling activity in RhoA/ROCK and PI3K/Akt cascades. Kinase inhibition study further showed that blockade of PI3K activity suppressed the stretch-induced TNF-a, whereas RhoA/ROCK inhibition significantly blunted the IL-6 production and HDGF over-expression. Moreover, siRNA-mediated HDGF gene silencing significantly suppressed constitutive expression of IL-6, but not TNF-α, in SMCs. These findings support the role of HDGF in maintaining vascular expression of IL-6, which has been regarded a crucial regenerative factor for acute vascular injury. In conclusion, cyclic mechanical stretch may maintain constitutive expression of HDGF in vascular walls and be regarded an important biophysical regulator in vascular regeneration. ©2018 The Author(s).

Adenosine signaling in normal and sickle erythrocytes and beyond.

PubMed

Zhang, Yujin; Xia, Yang

2012-08-01

Sickle cell disease (SCD) is a debilitating hemolytic genetic disorder with high morbidity and mortality affecting millions of individuals worldwide. Although SCD was discovered more than a century ago, no effective mechanism-based prevention and treatment are available due to poorly understood molecular basis of sickling, the fundamental pathogenic process of the disease. SCD patients constantly face hypoxia. One of the best-known signaling molecules to be induced under hypoxic conditions is adenosine. Recent studies demonstrate that hypoxia-mediated elevated adenosine signaling plays an important role in normal erythrocyte physiology. In contrast, elevated adenosine signaling contributes to sickling and multiple life threatening complications including tissue damage, pulmonary dysfunction and priapism. Here, we summarize recent research on the role of adenosine signaling in normal and sickle erythrocytes, progression of the disease and therapeutic implications. In normal erythrocytes, both genetic and pharmacological studies demonstrate that adenosine can enhance 2,3-bisphosphoglycerate (2,3-BPG) production via A(2B) receptor (ADORA2B) activation, suggesting that elevated adenosine has an unrecognized role in normal erythrocytes to promote O(2) release and prevent acute ischemic tissue injury. However, in sickle erythrocytes, the beneficial role of excessive adenosine-mediated 2,3-BPG induction becomes detrimental by promoting deoxygenation, polymerization of sickle hemoglobin and subsequent sickling. Additionally, adenosine signaling via the A(2A) receptor (ADORA2A) on invariant natural killer T (iNKT) cells inhibits iNKT cell activation and attenuates pulmonary dysfunction in SCD mice. Finally, elevated adenosine coupled with ADORA2BR activation is responsible for priapism, a dangerous complication seen in SCD. Overall, the research reviewed here reveals a differential role of elevated adenosine in normal erythrocytes, sickle erythrocytes, iNK cells and

Immunosuppression via adenosine receptor activation by adenosine monophosphate released from apoptotic cells

PubMed Central

Yamaguchi, Hiroshi; Maruyama, Toshihiko; Urade, Yoshihiro; Nagata, Shigekazu

2014-01-01

Apoptosis is coupled with recruitment of macrophages for engulfment of dead cells, and with compensatory proliferation of neighboring cells. Yet, this death process is silent, and it does not cause inflammation. The molecular mechanisms underlying anti-inflammatory nature of the apoptotic process remains poorly understood. In this study, we found that the culture supernatant of apoptotic cells activated the macrophages to express anti-inflammatory genes such as Nr4a and Thbs1. A high level of AMP accumulated in the apoptotic cell supernatant in a Pannexin1-dependent manner. A nucleotidase inhibitor and A2a adenosine receptor antagonist inhibited the apoptotic supernatant-induced gene expression, suggesting AMP was metabolized to adenosine by an ecto-5’-nucleotidase expressed on macrophages, to activate the macrophage A2a adenosine receptor. Intraperitoneal injection of zymosan into Adora2a- or Panx1-deficient mice produced high, sustained levels of inflammatory mediators in the peritoneal lavage. These results indicated that AMP from apoptotic cells suppresses inflammation as a ‘calm down’ signal. DOI: http://dx.doi.org/10.7554/eLife.02172.001 PMID:24668173

Reaction kinetics and inhibition of adenosine kinase from Leishmania donovani.

PubMed

Bhaumik, D; Datta, A K

1988-04-01

The reaction kinetics and the inhibitor specificity of adenosine kinase (ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20) from Leishmania donovani, have been analysed using homogeneous preparation of the enzyme. The reaction proceeds with equimolar stoichiometry of each reactant. Double reciprocal plots of initial velocity studies in the absence of products yielded intersecting lines for both adenosine and Mg2+-ATP. AMP is a competitive inhibitor of the enzyme with respect to adenosine and noncompetitive inhibitor with respect to ATP. In contrast, ADP was a noncompetitive inhibitor with respect to both adenosine and ATP, with inhibition by ADP becoming uncompetitive at very high concentration of ATP. Parallel equilibrium dialysis experiments against [3H]adenosine and [gamma-32P]ATP resulted in binding of adenosine to fre enzyme. Tubercidin (7-deazaadenosine) and 6-methyl-mercaptopurine riboside acted as substrates for the enzyme and were found to inhibit adenosine phosphorylation competitively in vitro. 'Substrate efficiency (Vmax/Km)' and 'turnover numbers (Kcat)' of the enzyme with respect to specific analogs were determined. Taken together the results suggest that (a) the kinetic mechanism of adenosine kinase is sequential Bi-Bi, (b) AMP and ADP may regulate enzyme activity in vivo and (c) tubercidin and 6-methylmercaptopurine riboside are monophosphorylated by the parasite enzyme.

A cup product structure for cyclic cohomology

NASA Astrophysics Data System (ADS)

Espinosa Tintos, Jose Eduardo

In this work we construct a cup product structure for cyclic cohomology of a cyclic set X. introduced by Comics. We make use of a categorical construction of cyclic homology by Fiedorowicz and Loday to define our cup product structure by using a large resolution of the cyclic category. We also provide a way to construct a chain map from a smaller resolution where the action of the finite groups is clear. and in the process of constructing this map we learn the large complex can be viewed as all factorizations in the category DeltaC using the cyclic structure of X.

Magnesium Lithospermate B Implicates 3'-5'-Cyclic Adenosine Monophosphate/Protein Kinase A Pathway and N-Methyl-d-Aspartate Receptors in an Experimental Traumatic Brain Injury.

PubMed

Chang, Chih-Zen; Wu, Shu-Chuan; Kwan, Aij-Lie; Lin, Chih-Lung

2015-10-01

Decreased 3'-5'-cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), and increased N-methyl-d-aspartate (NMDA) related apoptosis were observed in traumatic brain injury (TBI). It is of interest to examine the effect of magnesium lithospermate B (MLB) on cAMP/PKA pathway and NMDAR in TBI. A rodent weight-drop TBI model was used. Administration of MLB was initiated 1 week before (precondition) and 24 hours later (reversal). Cortical homogenates were harvested to measure cAMP (enzyme-linked immunosorbent assay), soluble guanylyl cyclases, PKA and NMDA receptor-2β (Western blot). In addition, cAMP kinase antagonist and H-89 dihydrochloride hydrate were used to test MLB's effect on the cytoplasm cAMP/PKA pathway after TBI. Morphologically, vacuolated neuron and activated microglia were observed in the TBI groups but absent in the MLB preconditioning and healthy controls. Induced cAMP, soluble guanylyl cyclase α1, and PKA were observed in the MLB groups, when compared with the TBI group (P < 0.01) Administration of H-89 dihydrochloride hydrate reversed the effect of MLB on cortical PKA and NMDA-2β expression after TBI. This study showed that MLB exerted an antioxidant effect on the enhancement of cytoplasm cAMP and PKA. This compound also decreased NMDA-2β levels, which may correspond to its neuroprotective effects. This finding lends credence to the presumption that MLB modulates the NMDA-2β neurotoxicity through a cAMP-dependent mechanism in the pathogenesis of TBI. Copyright © 2015 Elsevier Inc. All rights reserved.

Role of central and peripheral adenosine receptors in the cardiovascular responses to intraperitoneal injections of adenosine A1 and A2A subtype receptor agonists.

PubMed

Schindler, Charles W; Karcz-Kubicha, Marzena; Thorndike, Eric B; Müller, Christa E; Tella, Srihari R; Ferré, Sergi; Goldberg, Steven R

2005-03-01

1. The cardiovascular effects of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and the adenosine A2A receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680) were investigated in rats implanted with telemetry transmitters for the measurement of blood pressure and heart rate. 2. Intraperitoneal (i.p.) injections of the adenosine A1 receptor agonist CPA led to dose-dependent decreases in both blood pressure and heart rate. These effects of 0.3 mg kg(-1) CPA were antagonized by i.p. injections of the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dimethyl-xanthine (CPT), but not by i.p. injections of the adenosine A2A receptor antagonist 3-(3-hydroxypropyl)-8-(m-methoxystyryl)-7-methyl-1-propargylxanthine phosphate disodium salt (MSX-3). Injections (i.p.) of the peripherally acting nonselective adenosine antagonist 8-sulfophenyltheophylline (8-SPT) and the purported nonselective adenosine antagonist caffeine also antagonized the cardiovascular effects of CPA. 3. The adenosine A2A agonist CGS 21680 given i.p. produced a dose-dependent decrease in blood pressure and an increase in heart rate. These effects of 0.5 mg kg(-1) CGS 21680 were antagonized by i.p. injections of the adenosine A2A receptor antagonist MSX-3, but not by i.p. injections of the antagonists CPT, 8-SPT or caffeine. 4. Central administration (intracerebral ventricular) of CGS 21680 produced an increase in heart rate, but no change in blood pressure. MSX-3 given i.p. antagonized the effects of the central injection of CGS 21680. 5. These results suggest that adenosine A1 receptor agonists produce decreases in blood pressure and heart rate that are mediated by A1 receptors in the periphery, with little or no contribution of central adenosine A1 receptors to those effects. 6. The heart rate increasing effect of adenosine A2A agonists appears to be mediated by adenosine A2A receptors in the central nervous system. The blood pressure decreasing

Adenosine up-regulates cyclooxygenase-2 in human granulocytes: impact on the balance of eicosanoid generation.

PubMed

Pouliot, Marc; Fiset, Marie-Elaine; Massé, Mireille; Naccache, Paul H; Borgeat, Pierre

2002-11-01

Polymorphonuclear neutrophils (granulocytes; PMNs) are often the first blood cells to migrate toward inflammatory lesions to perform host defense functions. PMNs respond to specific stimuli by releasing several factors and generate lipid mediators of inflammation from the 5-lipoxygenase and the inducible cyclooxygenase (COX)-2 pathways. In view of adenosine's anti-inflammatory properties and suppressive impact on the 5-lipoxygenase pathway, we addressed in this study the impact of this autacoid on the COX-2 pathway. We observed that adenosine up-regulates the expression of the COX-2 enzyme and mRNA. Production of PGE(2) in response to exogenous arachidonic acid was also increased by adenosine and correlated with COX-2 protein levels. The potentiating effect of adenosine on COX-2 could be mimicked by pharmacological increases of intracellular cAMP levels, involving the latter as a putative second messenger for the up-regulation of COX-2 by adenosine. Specific COX-2 inhibitors were used to confirm the predominant role of the COX-2 isoform in the formation of prostanoids by stimulated PMNs. Withdrawal of extracellular adenosine strikingly emphasized the inhibitory potential of PGE(2) on leukotriene B(4) formation and involved the EP(2) receptor subtype in this process. Thus, adenosine may promote a self-limiting regulatory process through the increase of PGE(2) generation, which may result in the inhibition of PMN functions. This study identifies a new aspect of the anti-inflammatory properties of adenosine in leukocytes, introducing the concept that this autacoid may exert its immunomodulatory activities in part by modifying the balance of lipid mediators generated by PMNs.

Regulation of aggregate size and pattern by adenosine and caffeine in cellular slime molds

PubMed Central

2012-01-01

Background Multicellularity in cellular slime molds is achieved by aggregation of several hundreds to thousands of cells. In the model slime mold Dictyostelium discoideum, adenosine is known to increase the aggregate size and its antagonist caffeine reduces the aggregate size. However, it is not clear if the actions of adenosine and caffeine are evolutionarily conserved among other slime molds known to use structurally unrelated chemoattractants. We have examined how the known factors affecting aggregate size are modulated by adenosine and caffeine. Result Adenosine and caffeine induced the formation of large and small aggregates respectively, in evolutionarily distinct slime molds known to use diverse chemoattractants for their aggregation. Due to its genetic tractability, we chose D. discoideum to further investigate the factors affecting aggregate size. The changes in aggregate size are caused by the effect of the compounds on several parameters such as cell number and size, cell-cell adhesion, cAMP signal relay and cell counting mechanisms. While some of the effects of these two compounds are opposite to each other, interestingly, both compounds increase the intracellular glucose level and strengthen cell-cell adhesion. These compounds also inhibit the synthesis of cAMP phosphodiesterase (PdsA), weakening the relay of extracellular cAMP signal. Adenosine as well as caffeine rescue mutants impaired in stream formation (pde4- and pdiA-) and colony size (smlA- and ctnA-) and restore their parental aggregate size. Conclusion Adenosine increased the cell division timings thereby making large number of cells available for aggregation and also it marginally increased the cell size contributing to large aggregate size. Reduced cell division rates and decreased cell size in the presence of caffeine makes the aggregates smaller than controls. Both the compounds altered the speed of the chemotactic amoebae causing a variation in aggregate size. Our data strongly suggests

Regulation of aggregate size and pattern by adenosine and caffeine in cellular slime molds.

PubMed

Jaiswal, Pundrik; Soldati, Thierry; Thewes, Sascha; Baskar, Ramamurthy

2012-01-23

Multicellularity in cellular slime molds is achieved by aggregation of several hundreds to thousands of cells. In the model slime mold Dictyostelium discoideum, adenosine is known to increase the aggregate size and its antagonist caffeine reduces the aggregate size. However, it is not clear if the actions of adenosine and caffeine are evolutionarily conserved among other slime molds known to use structurally unrelated chemoattractants. We have examined how the known factors affecting aggregate size are modulated by adenosine and caffeine. Adenosine and caffeine induced the formation of large and small aggregates respectively, in evolutionarily distinct slime molds known to use diverse chemoattractants for their aggregation. Due to its genetic tractability, we chose D. discoideum to further investigate the factors affecting aggregate size. The changes in aggregate size are caused by the effect of the compounds on several parameters such as cell number and size, cell-cell adhesion, cAMP signal relay and cell counting mechanisms. While some of the effects of these two compounds are opposite to each other, interestingly, both compounds increase the intracellular glucose level and strengthen cell-cell adhesion. These compounds also inhibit the synthesis of cAMP phosphodiesterase (PdsA), weakening the relay of extracellular cAMP signal. Adenosine as well as caffeine rescue mutants impaired in stream formation (pde4- and pdiA-) and colony size (smlA- and ctnA-) and restore their parental aggregate size. Adenosine increased the cell division timings thereby making large number of cells available for aggregation and also it marginally increased the cell size contributing to large aggregate size. Reduced cell division rates and decreased cell size in the presence of caffeine makes the aggregates smaller than controls. Both the compounds altered the speed of the chemotactic amoebae causing a variation in aggregate size. Our data strongly suggests that cytosolic glucose and

Ticagrelor and Rosuvastatin Have Additive Cardioprotective Effects via Adenosine.

PubMed

Birnbaum, Yochai; Birnbaum, Gilad D; Birnbaum, Itamar; Nylander, Sven; Ye, Yumei

2016-12-01

Ticagrelor inhibits the equilibrative-nucleoside-transporter-1 and thereby, adenosine cell re-uptake. Ticagrelor limits infarct size (IS) in non-diabetic rats and the effect is adenosine-dependent. Statins, via ecto-5'-nucleotidase activation, also increase adenosine levels and limit IS. Ticagrelor and rosuvastatin have additive effects on myocardial adenosine levels, and therefore, on IS and post-reperfusion activation of the NLRP3-inflammasome. Diabetic ZDF rats received via oral gavage; water (control), ticagrelor (150 mg/kg/d), prasugrel (7.5 mg/kg/d), rosuvastatin (5 mg/kg/d), ticagrelor + rosuvastatin and prasugrel + rosuvastatin for 3d. On day 4, rats underwent 30 min coronary artery occlusion and 24 h of reperfusion. Two additional groups received, ticagrelor + rosuvastatin or water in combination with CGS15943 (CGS, an adenosine receptor antagonist, 10 mg/kg i.p. 1 h before ischemia). Both ticagrelor and rosuvastatin increased myocardial adenosine levels with an additive effect of the combination whereas prasugrel had no effect. Similarly, both ticagrelor and rosuvastatin significantly reduced IS with an additive effect of the combination whereas prasugrel had no effect. The effect on IS was adenosine dependent as CGS15943 reversed the effect of ticagrelor + rosuvastatin. The ischemia-reperfusion injury increased myocardial mRNA levels of NLRP3, ASC, IL-1β and IL-6. Ticagrelor and rosuvastatin, but not prasugrel, significantly decreased these pro-inflammatory mediators with a trend to an additive effect of the combination. The combination also increased the levels of anti-inflammatory 15-epilipoxin A 4 . Ticagrelor and rosuvastatin when given in combination have an additive effect on local myocardial adenosine levels in the setting of ischemia reperfusion. This translates into an additive cardioprotective effect mediated by adenosine-induced effects including downregulation of pro- but upregulation of anti-inflammatory mediators.

Adenosine uptake by the isolated epithelium of guine pig jejunum.

PubMed

Kolassa, N; Stengg, R; Turnheim, K

1977-10-01

The uptake of [8-14C]adenosine by the isolated epithelium of guinea pig jejunum was faster than that of inosine, hypoxanthine, or adenine. The initial velocity of adenosine uptake from both the luminal and the antiluminal side of the epithelium exhibited saturation kinetics. The apparent Km, V, and passive permeability of luminal adenosine uptake were all lower than the corresponding values of antiluminal uptake. p-Nitrobenzyl-thioguanosine inhibited adenosine uptake from both the luminal and the antiluminal side, whilst hexobendine decreased the uptake only from the antiluminal side of the epithelium. The results suggest that adenosine enters the intestinal epithelium by a carrier-mediated process in addition to passive diffusion. The antiluminal transport system for adenosine seems similar to that of other tissues with respect to hexobendine inhibition; the luminal transport mechanism, however, exhibits different properties, being insensitive to hexobendine.

Reentry Tachycardia in Children: Adenosine Can Make It Worse.

PubMed

Hien, Maximilian D; Benito Castro, Fernando; Fournier, Philippe; Filleron, Anne; Tran, Tu-Anh

2016-10-08

We report on a rare but severe complication of adenosine use in a child with reentry tachycardia. Treatment with adenosine, which is the standard medical therapy of atrioventricular reentry tachycardia, led to the development of an irregular wide complex tachycardia, caused by rapid ventricular response to atrial fibrillation. The girl was finally stabilized with electrical cardioversion. We analyze the pathomechanism and discuss possible treatment options. Atrial fibrillation, as well as its conduction to the ventricles, can be caused by adenosine. Rapid ventricular response in children with Wolff-Parkinson-White syndrome is more frequent than previously believed. A patient history of atrial fibrillation is a contraindication for cardioversion with adenosine and needs to be assessed in children with reentry tachycardia. High-risk patients may potentially profit from prophylactic comedication with antiarrhythmic agents, such as flecainide, ibutilide, or vernakalant, before adenosine administration.

Sweet taste transduction in hamster: sweeteners and cyclic nucleotides depolarize taste cells by reducing a K+ current.

PubMed

Cummings, T A; Daniels, C; Kinnamon, S C

1996-03-01

1. The gigaseal voltage-clamp technique was used to record responses of hamster taste receptor cells to synthetic sweeteners and cyclic nucleotides. Voltage-dependent currents and steady-state currents were monitored during bath exchanges of saccharin, two high-potency sweeteners, 8-chlorophenylthio-adenosine 3',5'-cyclic monophosphate (8cpt-cAMP), and dibutyryl-guanosine 3',5'-cyclic monophosphate (db-cGMP). 2. Of the 237 fungiform taste cells studied, only one in eight was sweet responsive. Outward currents, both voltage-dependent and resting, were reduced by all of the sweeteners tested in sweet-responsive taste cells, whereas these currents were unaffected by sweeteners in sweet-unresponsive taste cells. 3. In every sweet-responsive cell tested, 8cpt-cAMP and db-cGMP mimicked the response to the sweeteners, but neither nucleotide elicited responses in sweet-unresponsive cells. Thus there was a one-to-one correlation between sweet responsivity and cyclic nucleotide responsivity. 4. Sweet responses showed cross adaptation with cyclic nucleotide responses. This indicates that the same ion channel is modulated by sweeteners and cyclic nucleotides. 5. The sweetener- and cyclic nucleotide-blocked current had an apparent reversal potential of -50 mV, which was close to the potassium reversal potential in these experiments. In addition, there was no effect of sweeteners and cyclic nucleotides in the presence of the K+ channel blocker tetraethylammonium bromide (TEA). These data suggest that block of a resting, TEA-sensitive K+ current is the final common step leading to taste cell depolarization during sweet transduction. 6. These data, together with data from a previous study (Cummings et al. 1993), suggest that both synthetic sweeteners and sucrose utilize second-messenger pathways that block a resting K+ conductance to depolarize the taste cell membrane.

LDL-cholesterol reduction in patients with hypercholesterolemia by modulation of adenosine triphosphate-citrate lyase and adenosine monophosphate-activated protein kinase.

PubMed

Filippov, Sergey; Pinkosky, Stephen L; Newton, Roger S

2014-08-01

To review the profile of ETC-1002, as shown in preclinical and clinical studies, including LDL-cholesterol (LDL-C)-lowering activity and beneficial effects on other cardiometabolic risk markers as they relate to the inhibition of adenosine triphosphate-citrate lyase and the activation of adenosine monophosphate-activated protein kinase. ETC-1002 is an adenosine triphosphate-citrate lyase inhibitor/adenosine monophosphate-activated protein kinase activator currently in Phase 2b clinical development. In seven Phase 1 and Phase 2a clinical studies, ETC-1002 dosed once daily for 2-12 weeks has lowered LDL-C and reduced high-sensitivity C-reactive protein by up to 40%, with neutral to positive effects on glucose levels, blood pressure, and body weight. Importantly, use of ETC-1002 in statin-intolerant patients has shown statin-like lowering of LDL-C without the muscle pain and weakness responsible for discontinuation of statin use by many patients. ETC-1002 has also been shown to produce an incremental benefit, lowering LDL-C as an add-on therapy to a low-dose statin. In over 300 individuals in studies of up to 12 weeks, ETC-1002 has been well tolerated with no serious adverse effects. Because adenosine triphosphate-citrate lyase and adenosine monophosphate-activated protein kinase play central roles in regulating lipid and glucose metabolism, pharmacological modulation of these two enzymes could provide an important therapeutic alternative for statin-intolerant patients with hypercholesterolemia.

TOR-induced resistance to toxic adenosine analogs in Leishmania brought about by the internalization and degradation of the adenosine permease.

PubMed

Detke, Siegfried

2007-05-15

TOR is an atypical multidrug resistance protein present in the human protozoan parasite, Leishmania. Resistance to the toxic adenosine analog tubercidin was brought about by redirecting the adenosine permease from the plasma membrane to the multivesicular tubule lysosome. The cells became resistant to tubercidin because they were unable to take up and accumulate this toxic purine. The domain, which was recognized by TOR in this internalization pathway, was identified by expressing portions of this transporter in Leishmania and assessing whether they were capable of hindering the multidrug resistance capability of TOR. This approach identified the adenosine permease region spanning Met289 to Trp305. This region was also the epitope recognized by the internalization mechanism. An internal deletion mutant lacking Met289-Trp305 was functionally active but could no longer be internalized in cells with high TOR levels. The internalization and altered trafficking of the adenosine permease by TOR was observed in yeast and human embryonic kidney cells co-expressing these two Leishmania proteins indicating that the internalization process was conserved in evolutionary diverse organisms. The inability of Saccharomyces with a temperature-sensitive ubiquitin ligase to internalize adenosine permease suggested that ubiquitination was involved in this altered trafficking.

Beneficial and detrimental role of adenosine signaling in diseases and therapy

PubMed Central

Liu, Hong

2015-01-01

Adenosine is a major signaling nucleoside that orchestrates cellular and tissue adaptation under energy depletion and ischemic/hypoxic conditions by activation of four G protein-coupled receptors (GPCR). The regulation and generation of extracellular adenosine in response to stress are critical in tissue protection. Both mouse and human studies reported that extracellular adenosine signaling plays a beneficial role during acute states. However, prolonged excess extracellular adenosine is detrimental and contributes to the development and progression of various chronic diseases. In recent years, substantial progress has been made to understand the role of adenosine signaling in different conditions and to clarify its significance during the course of disease progression in various organs. These efforts have and will identify potential therapeutic possibilities for protection of tissue injury at acute stage by upregulation of adenosine signaling or attenuation of chronic disease progression by downregulation of adenosine signaling. This review is to summarize current progress and the importance of adenosine signaling in different disease stages and its potential therapeutic effects. PMID:26316513

Insulin and adenosine regulate the phosphatidylcholine concentration in isolated rat adipocyte plasma membranes.

PubMed

Kiechle, F L; Sykes, E; Artiss, J D

1995-01-01

Blockade of adenosine receptors by 3-isobutyl-1-methylxanthine or degradation of endogenous adenosine with adenosine deaminase increased the phosphatidylcholine concentration in isolated rat adipocyte plasma membranes, an effect which was suppressed by the phosphatidylethanolamine methyltransferase inhibitor, S-adenosyl-L-homocysteine, and reversed by the adenosine analogue, N6-(L-phenylisopropyl)-adenosine. For example, the addition of N6-(L-phenylisopropyl)-adenosine to adenosine deaminase pretreated plasma membranes rapidly lowered the concentration of phosphatidylcholine by 171 nmol/mg at 30 seconds compared to control. Insulin-induced stimulation of phospholipid methylation in membranes treated with 3-isobutyl-1-methylxanthine or adenosine deaminase was achieved only after the addition of N6-(L-phenylisopropyl)-adenosine. These results suggest that adenosine receptor occupancy inhibits phospholipid methylation, is required for insulin stimulation of phospholipid methylation, and may perhaps activate a phosphatidylcholine-specific phospholipase C or phospholipase D.

Low-dose adenosine stress echocardiography: detection of myocardial viability.

PubMed

Djordjevic-Dikic, Ana; Ostojic, Miodrag; Beleslin, Branko; Nedeljkovic, Ivana; Stepanovic, Jelena; Stojkovic, Sinisa; Petrasinovic, Zorica; Nedeljkovic, Milan; Saponjski, Jovica; Giga, Vojislav

2003-06-03

The aim of this study was to evaluate the diagnostic potential of low-dose adenosine stress echocardiography in detection of myocardial viability. Vasodilation through low dose dipyridamole infusion may recruit contractile reserve by increasing coronary flow or by increasing levels of endogenous adenosine. Forty-three patients with resting dyssynergy, due to previous myocardial infarction, underwent low-dose adenosine (80, 100, 110 mcg/kg/min in 3 minutes intervals) echocardiography test. Gold standard for myocardial viability was improvement in systolic thickening of dyssinergic segments of >or= 1 grade at follow-up. Coronary angiography was done in 41 pts. Twenty-seven patients were revascularized and 16 were medically treated. Echocardiographic follow up data (12 +/- 2 months) were available in 24 revascularized patients. Wall motion score index improved from rest 1.55 +/- 0.30 to 1.33 +/- 0.26 at low-dose adenosine (p < 0.001). Of the 257 segments with baseline dyssynergy, adenosine echocardiography identified 122 segments as positive for viability, and 135 as necrotic since no improvement of systolic thickening was observed. Follow-up wall motion score index was 1.31 +/- 0.30 (p < 0.001 vs. rest). The sensitivity of adenosine echo test for identification of viable segments was 87%, while specificity was 95%, and diagnostic accuracy 90%. Positive and negative predictive values were 97% and 80%, respectively. Low-dose adenosine stress echocardiography test has high diagnostic potential for detection of myocardial viability in the group of patients with left ventricle dysfunction due to previous myocardial infarction. Low dose adenosine stress echocardiography may be adequate alternative to low-dose dobutamine test for evaluation of myocardial viability.

Low-dose adenosine stress echocardiography: Detection of myocardial viability

PubMed Central

Djordjevic-Dikic, Ana; Ostojic, Miodrag; Beleslin, Branko; Nedeljkovic, Ivana; Stepanovic, Jelena; Stojkovic, Sinisa; Petrasinovic, Zorica; Nedeljkovic, Milan; Saponjski, Jovica; Giga, Vojislav

2003-01-01

Objective The aim of this study was to evaluate the diagnostic potential of low-dose adenosine stress echocardiography in detection of myocardial viability. Background Vasodilation through low dose dipyridamole infusion may recruit contractile reserve by increasing coronary flow or by increasing levels of endogenous adenosine. Methods Forty-three patients with resting dyssynergy, due to previous myocardial infarction, underwent low-dose adenosine (80, 100, 110 mcg/kg/min in 3 minutes intervals) echocardiography test. Gold standard for myocardial viability was improvement in systolic thickening of dyssinergic segments of ≥ 1 grade at follow-up. Coronary angiography was done in 41 pts. Twenty-seven patients were revascularized and 16 were medically treated. Echocardiographic follow up data (12 ± 2 months) were available in 24 revascularized patients. Results Wall motion score index improved from rest 1.55 ± 0.30 to 1.33 ± 0.26 at low-dose adenosine (p < 0.001). Of the 257 segments with baseline dyssynergy, adenosine echocardiography identified 122 segments as positive for viability, and 135 as necrotic since no improvement of systolic thickening was observed. Follow-up wall motion score index was 1.31 ± 0.30 (p < 0.001 vs. rest). The sensitivity of adenosine echo test for identification of viable segments was 87%, while specificity was 95%, and diagnostic accuracy 90%. Positive and negative predictive values were 97% and 80%, respectively. Conclusion Low-dose adenosine stress echocardiography test has high diagnostic potential for detection of myocardial viability in the group of patients with left ventricle dysfunction due to previous myocardial infarction. Low dose adenosine stress echocardiography may be adequate alternative to low-dose dobutamine test for evaluation of myocardial viability. PMID:12812523

Release of prostaglandins from the isolated frog ventricle and associated changes in endogenous cyclic nucleotide levels.

PubMed Central

Flitney, F W; Singh, J

1980-01-01

1. A study has been made of the decline in contractility and some associated metabolic changes which occur in the isolated frog ventricle during the development of hypodynamic depression. 2. The release of two identified prostaglandins (PG), E1 and E2, together with several as yet unknown prostaglandin-related substances (PRS), accompanies the development of hypodynamic depression. There is a close correlation between the extent to which the isometric twitch is depressed and the quantity of prostaglandin released into the superfusate. 3. Fractionation of extracts of 'used' superfusates, using preparative-scale thin-layer chromatography, revealed the presence of six major components, four of which (PGE1 and PGE2 and two unidentified components) were found to be cardioactive and potentiated contraction when tested subsequently on hypodynamic preparations. 4. Two agents which influence prostaglandin biosynthesis, arachidonic acid and indomethacin, are found to affect both the rate at which the hypodynamic state develops and the extent to which the 'steady-state' twitch tension is depressed, in a dose-dependent manner. Indomethacin, a PG-synthetase inhibitor, accelerates the decay and depresses the final 'steady-state' tension attained, whereas arachidonic acid, the principal precursor for prostaglandin biosynthesis, has the converse effects. 5. Measurements of endogenous 3'5'-cyclic nucleotide levels reveal a time-dependent decrease in intracellular adenosine 3'5'-cyclic monophosphate (3'5'-cyclic AMP) and a concomitant increase in guanosine 3'5' cyclic monophosphate (3'5'-cyclic GMP). The decline in isometric twitch tension is paralleled almost exactly by an equivalent reduction in the ratio 3'5'-cyclic AMP: 3'5'-cyclic GMP. 6. Superfusion of isolated ventricles with Ringer solution containing exogenous, lipid-soluble derivatives of 3'5'-cyclic AMP and 3'5'-cyclic GMP affects both the rate of decline of the isometric twitch and the steady-state tension ultimately

Enzymatic properties of Staphylococcus aureus adenosine synthase (AdsA)

PubMed Central

2011-01-01

Background Staphylococcus aureus is a human pathogen that produces extracellular adenosine to evade clearance by the host immune system, an activity attributed to the 5'-nucleotidase activity of adenosine synthase (AdsA). In mammals, conversion of adenosine triphosphate to adenosine is catalyzed in a two-step process: ecto-nucleoside triphosphate diphosphohydrolases (ecto-NTDPases) hydrolyze ATP and ADP to AMP, whereas 5'-nucleotidases hydrolyze AMP to adenosine. NTPDases harbor apyrase conserved regions (ACRs) that are critical for activity. Results NTPDase ACR motifs are absent in AdsA, yet we report here that recombinant AdsA hydrolyzes ADP and ATP in addition to AMP. Competition assays suggest that hydrolysis occurs following binding of all three substrates at a unique site. Alanine substitution of two amino acids, aspartic acid 127 and histidine 196 within the 5'-nucleotidase signature sequence, leads to reduced AMP or ADP hydrolysis but does not affect the binding of these substrates. Conclusion Collectively, these results provide insight into the unique ability of AdsA to produce adenosine through the consecutive hydrolysis of ATP, ADP and AMP, thereby endowing S. aureus with the ability to modulate host immune responses. PMID:22035583

Metabolic changes of cultured DRG neurons induced by adenosine using confocal microscopy imaging

NASA Astrophysics Data System (ADS)

Zheng, Liqin; Huang, Yimei; Chen, Jiangxu; Wang, Yuhua; Yang, Hongqin; Zhang, Yanding; Xie, Shusen

2012-12-01

Adenosine exerts multiple effects on pain transmission in the peripheral nervous system. This study was performed to use confocal microscopy to evaluate whether adenosine could affect dorsal root ganglia (DRG) neurons in vitro and test which adenosine receptor mediates the effect of adenosine on DRG neurons. After adding adenosine with different concentration, we compared the metabolic changes by the real time imaging of calcium and mitochondria membrane potential using confocal microscopy. The results showed that the effect of 500 μM adenosine on the metabolic changes of DRG neurons was more significant than others. Furthermore, four different adenosine receptor antagonists were used to study which receptor mediated the influences of adenosine on the cultured DRG neurons. All adenosine receptor antagonists especially A1 receptor antagonist (DPCPX) had effect on the Ca2+ and mitochondria membrane potential dynamics of DRG neurons. The above studies demonstrated that the effect of adenosine which may be involved in the signal transmission on the sensory neurons was dose-dependent, and all the four adenosine receptors especially the A1R may mediate the transmission.

Adenosine uptake is the major effector of extracellular ATP toxicity in human cervical cancer cells

PubMed Central

Mello, Paola de Andrade; Filippi-Chiela, Eduardo Cremonese; Nascimento, Jéssica; Beckenkamp, Aline; Santana, Danielle Bertodo; Kipper, Franciele; Casali, Emerson André; Nejar Bruno, Alessandra; Paccez, Juliano Domiraci; Zerbini, Luiz Fernando; Wink, Marcia Rosângela; Lenz, Guido; Buffon, Andréia

2014-01-01

In cervical cancer, HPV infection and disruption of mechanisms involving cell growth, differentiation, and apoptosis are strictly linked with tumor progression and invasion. Tumor microenvironment is ATP and adenosine rich, suggesting a role for purinergic signaling in cancer cell growth and death. Here we investigate the effect of extracellular ATP on human cervical cancer cells. We find that extracellular ATP itself has a small cytotoxic effect, whereas adenosine formed from ATP degradation by ectonucleotidases is the main factor responsible for apoptosis induction. The level of P2×7 receptor seemed to define the main cytotoxic mechanism triggered by ATP, since ATP itself eliminated a small subpopulation of cells that express high P2×7 levels, probably through its activation. Corroborating these data, blockage or knockdown of P2×7 only slightly reduced ATP cytotoxicity. On the other hand, cell viability was almost totally recovered with dipyridamole, an adenosine transporter inhibitor. Moreover, ATP-induced apoptosis and signaling—p53 increase, AMPK activation, and PARP cleavage—as well as autophagy induction were also inhibited by dipyridamole. In addition, inhibition of adenosine conversion into AMP also blocked cell death, indicating that metabolization of intracellular adenosine originating from extracellular ATP is responsible for the main effects of the latter in human cervical cancer cells. PMID:25103241

Adenosine signaling promotes regeneration of pancreatic β-cells in vivo

PubMed Central

Andersson, Olov; Adams, Bruce A.; Yoo, Daniel; Ellis, Gregory C.; Gut, Philipp; Anderson, Ryan M.; German, Michael S.; Stainier, Didier Y. R.

2012-01-01

Diabetes can be controlled with insulin injections, but a curative approach that restores the number of insulin-producing β-cells is still needed. Using a zebrafish model of diabetes, we screened ~7000 small molecules to identify enhancers of β-cell regeneration. The compounds we identified converge on the adenosine signaling pathway and include exogenous agonists and compounds that inhibit degradation of endogenously produced adenosine. The most potent enhancer of β-cell regeneration was the adenosine agonist 5′-N-Ethylcarboxamidoadenosine (NECA), which acting through the adenosine receptor A2aa increased β-cell proliferation and accelerated restoration of normoglycemia in zebrafish. Despite markedly stimulating β-cell proliferation during regeneration, NECA had only a modest effect during development. The proliferative and glucose-lowering effect of NECA was confirmed in diabetic mice, suggesting an evolutionarily conserved role for adenosine in β-cell regeneration. With this whole-organism screen, we identified components of the adenosine pathway that could be therapeutically targeted for the treatment of diabetes. PMID:22608007

A rapid enzymatic assay for high-throughput screening of adenosine-producing strains

PubMed Central

Dong, Huina; Zu, Xin; Zheng, Ping; Zhang, Dawei

2015-01-01

Adenosine is a major local regulator of tissue function and industrially useful as precursor for the production of medicinal nucleoside substances. High-throughput screening of adenosine overproducers is important for industrial microorganism breeding. An enzymatic assay of adenosine was developed by combined adenosine deaminase (ADA) with indophenol method. The ADA catalyzes the cleavage of adenosine to inosine and NH3, the latter can be accurately determined by indophenol method. The assay system was optimized to deliver a good performance and could tolerate the addition of inorganic salts and many nutrition components to the assay mixtures. Adenosine could be accurately determined by this assay using 96-well microplates. Spike and recovery tests showed that this assay can accurately and reproducibly determine increases in adenosine in fermentation broth without any pretreatment to remove proteins and potentially interfering low-molecular-weight molecules. This assay was also applied to high-throughput screening for high adenosine-producing strains. The high selectivity and accuracy of the ADA assay provides rapid and high-throughput analysis of adenosine in large numbers of samples. PMID:25580842

Cyclic tensile strain and cyclic hydrostatic pressure differentially regulate expression of hypertrophic markers in primary chondrocytes.

PubMed

Wong, Marcy; Siegrist, Mark; Goodwin, Kelly

2003-10-01

Endochondral ossification is regulated by many factors, including mechanical stimuli, which can suppress or accelerate chondrocyte maturation. Mathematical models of endochondral ossification have suggested that tension (or shear stress) can accelerate the formation of endochondral bone, while hydrostatic stress preserves the cartilage phenotype. The goal of this study was to test this hypothesis by examining the expression of hypertrophic chondrocyte markers (transcription factor Cbfa1, MMP-13, type X collagen, VEGF, CTGF) and cartilage matrix proteins under cyclic tension and cyclic hydrostatic pressure. Chondrocyte-seeded alginate constructs were exposed to one of the two loading modes for a period of 3 h per day for 3 days. Gene expression was analyzed using real-time RT-PCR. Cyclic tension upregulated the expression of Cbfa1, MMP-13, CTGF, type X collagen and VEGF and downregulated the expression of TIMP-1. Cyclic tension also upregulated the expression of type 2 collagen, COMP and lubricin, but did not change the expression of SOX9 and aggrecan. Cyclic hydrostatic pressure downregulated the expression of MMP-13 and type I collagen and upregulated expression of TIMP-1 compared to the unloaded controls. Hydrostatic pressure may slow chondrocyte differentiation and have a chondroprotective, anti-angiogenic influence on cartilage tissue. Our results suggest that cyclic tension activates the Cbfa1/MMP-13 pathway and increases the expression of terminal differentiation hypertrophic markers. Mammalian chondrocytes appear to have evolved complex mechanoresponsive mechanisms, the effects of which can be observed in the histomorphologic establishment of the cartilaginous skeleton during development and maturation.

Mediation of tubuloglomerular feedback by adenosine: evidence from mice lacking adenosine 1 receptors.

PubMed

Sun, D; Samuelson, L C; Yang, T; Huang, Y; Paliege, A; Saunders, T; Briggs, J; Schnermann, J

2001-08-14

Adenosine is a determinant of metabolic control of organ function increasing oxygen supply through the A2 class of adenosine receptors and reducing oxygen demand through A1 adenosine receptors (A1AR). In the kidney, activation of A1AR in afferent glomerular arterioles has been suggested to contribute to tubuloglomerular feedback (TGF), the vasoconstriction elicited by elevations in [NaCl] in the macula densa region of the nephron. To further elucidate the role of A1AR in TGF, we have generated mice in which the entire A1AR coding sequence was deleted by homologous recombination. Homozygous A1AR mutants that do not express A1AR mRNA transcripts and do not respond to A1AR agonists are viable and without gross anatomical abnormalities. Plasma and urinary electrolytes were not different between genotypes. Likewise, arterial blood pressure, heart rates, and glomerular filtration rates were indistinguishable between A1AR(+/+), A1AR(+/-), and A1AR(-/-) mice. TGF responses to an increase in loop of Henle flow rate from 0 to 30 nl/min, whether determined as change of stop flow pressure or early proximal flow rate, were completely abolished in A1AR(-/-) mice (stop flow pressure response, -6.8 +/- 0.55 mmHg and -0.4 +/- 0.2 in A1AR(+/+) and A1AR(-/-) mice; early proximal flow rate response, -3.4 +/- 0.4 nl/min and +0.02 +/- 0.3 nl/min in A1AR(+/+) and A1AR(-/-) mice). Absence of TGF responses in A1AR-deficient mice suggests that adenosine is a required constituent of the juxtaglomerular signaling pathway. A1AR null mutant mice are a promising tool to study the functional role of A1AR in different target tissues.

Ethanol Tolerance Affects Endogenous Adenosine Signaling in Mouse Hippocampus

PubMed Central

Zhang, Dali; Xiong, Wei; Jackson, Michael F.

2016-01-01

Ethanol has many pharmacological effects, including increases in endogenous adenosine levels and adenosine receptor activity in brain. Ethanol consumption is associated with both positive and negative health outcomes, but tolerance to the behavioral effects of ethanol can lead to increased consumption, which increases the risk of negative health outcomes. The present study was performed to test whether a 7-day treatment with ethanol is linked to reduced adenosine signaling and whether this is a consequence of reduced ecto-5′-nucleotidase activity. Wild-type (CD73+/+) and ecto-5′-nucleotidase-deficient (CD73−/−) mice were treated with ethanol (2 g/kg) or saline for 7 days. In CD73+/+ mice, repeated ethanol treatment reduced the hypothermic and ataxic effects of acute ethanol, indicating the development of tolerance to the acute effects of ethanol. In CD73+/+ mice, this 7-day ethanol treatment led to increased hippocampal synaptic activity and reduced adenosine A1 receptor activity under both basal and low Mg2+ conditions. These effects of ethanol tolerance were associated with an 18% decrease in activity of ecto-5′-nucleotidase activity in hippocampal cell membranes. In contrast, ethanol treatment was not associated with changes in synaptic activity or adenosine signaling in hippocampus from CD73−/− mice. These data indicate that ethanol treatment is associated with a reduction in adenosine signaling through adenosine A1 receptors in hippocampus, mediated, at least in part, via reduced ecto-5′-nucleotidase activity. PMID:27189965

Ethanol Tolerance Affects Endogenous Adenosine Signaling in Mouse Hippocampus.

PubMed

Zhang, Dali; Xiong, Wei; Jackson, Michael F; Parkinson, Fiona E

2016-07-01

Ethanol has many pharmacological effects, including increases in endogenous adenosine levels and adenosine receptor activity in brain. Ethanol consumption is associated with both positive and negative health outcomes, but tolerance to the behavioral effects of ethanol can lead to increased consumption, which increases the risk of negative health outcomes. The present study was performed to test whether a 7-day treatment with ethanol is linked to reduced adenosine signaling and whether this is a consequence of reduced ecto-5'-nucleotidase activity. Wild-type (CD73(+/+)) and ecto-5'-nucleotidase-deficient (CD73(-/-)) mice were treated with ethanol (2 g/kg) or saline for 7 days. In CD73(+/+) mice, repeated ethanol treatment reduced the hypothermic and ataxic effects of acute ethanol, indicating the development of tolerance to the acute effects of ethanol. In CD73(+/+) mice, this 7-day ethanol treatment led to increased hippocampal synaptic activity and reduced adenosine A1 receptor activity under both basal and low Mg(2+) conditions. These effects of ethanol tolerance were associated with an 18% decrease in activity of ecto-5'-nucleotidase activity in hippocampal cell membranes. In contrast, ethanol treatment was not associated with changes in synaptic activity or adenosine signaling in hippocampus from CD73(-/-) mice. These data indicate that ethanol treatment is associated with a reduction in adenosine signaling through adenosine A1 receptors in hippocampus, mediated, at least in part, via reduced ecto-5'-nucleotidase activity. Copyright © 2016 The Author(s).

Estimation of skeletal muscle interstitial adenosine during forearm dynamic exercise in humans

NASA Technical Reports Server (NTRS)

Costa, F.; Heusinkveld, J.; Ballog, R.; Davis, S.; Biaggioni, I.

2000-01-01

It has been proposed that adenosine is a metabolic signal that triggers activation of muscle afferents involved in the exercise pressor reflex. Furthermore, exogenous adenosine induces sympathetic activation that mimics the exercise pressor reflex, and blockade of adenosine receptors inhibits sympathetic activation induced by exercise. Thus, we hypothesize that adenosine is released locally by the muscle during exercise. We used microdialysis probes, placed in the flexor digitorium superficialis muscle, to estimate muscle interstitial adenosine levels in humans. We estimated resting in vivo muscle interstitial adenosine concentrations (0.292+/-0.058 micromol/L, n=4) by perfusing increasing concentrations of adenosine to determine the gradient produced in the dialysate. Muscle interstitial adenosine concentrations increased from 0.23+/-0.04 to 0.82+/-0.14 micromol/L (n=14, P<0.001) during intermittent dynamic exercise at 50% of maximal voluntary contraction. Lactate increased from 0.8+/-0.1 to 2.3+/-0.3 mmol/L (P<0.001). Lower intensity (15% maximal voluntary contraction) intermittent dynamic exercise increased adenosine concentrations from 0.104+/-0.02 to 0.42+/-0.16 micromol/L (n=7). The addition of ischemia to this low level of exercise produced a greater increase in adenosine (from 0.095+/-0.02 to 0.48+/-0.2 micromol/L) compared with nonischemic exercise (0. 095+/-0.02 to 0.25+/-0.12 micromol/L). These results indicate that microdialysis is useful in estimating adenosine concentrations and in reflecting changes in muscle interstitial adenosine during dynamic exercise in humans.

Effect of Electrical Stimulation on Beta-Adrenergic Receptor Population and Cyclic AMP Production in Chicken and Rat Skeletal Muscle Cell Cultures

NASA Technical Reports Server (NTRS)

Young, Ronald B.; Bridge, Kristin Y.; Strietzel, Catherine J.

2000-01-01

Expression of the beta-adrenergic receptor (PAR) and its coupling to Adenosine 3'5' Cyclic Monophosphate (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the PAR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for 7 d in culture, were subjected to electrical stimulation for an additional 2 d at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the PAR population was not significantly affected by electrical stimulation; however, the ability, of these cells to synthesize cyclic AMP was reduced by approximately one-half. In contrast, the PAR population in rat muscle cells was increased slightly but not significantly by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was increased by almost twofold. The basal levels of intracellular cyclic AMP in neither rat muscle cells nor chicken muscle cells were affected by electrical stimulation.

CD73-Generated Adenosine Is Critical for Immune Regulation during Toxoplasma gondii Infection

PubMed Central

Mahamed, Deeqa A.; Toussaint, Leon E.

2014-01-01

As an obligate intracellular pathogen, the apicomplexan parasite Toxoplasma gondii evades immune system-mediated clearance by undergoing stage differentiation to persist indefinitely in susceptible hosts. Previously, we found that mice deficient in the ectoenzyme CD73, which generates adenosine in the extracellular matrix, were resistant to chronic toxoplasmosis after oral infection with T. gondii. Resistance in CD73 knockout mice was due to a delay in parasite differentiation in the central nervous system (CNS). To further clarify the role of CD73 and extracellular adenosine in T. gondii pathogenesis, we infected wild-type (WT) and CD73−/− mice with T. gondii cysts systemically by the intraperitoneal (i.p.) route. In contrast to oral infection, i.p. infected CD73−/− mice were highly susceptible to immune-mediated pathology, with significantly increased infiltration of neutrophils and T cells into the peritoneal cavity. Administration of the broad-spectrum adenosine receptor agonist 5′-N-ethylcarboxamidoadenosine (NECA) protected CD73−/− mice against T. gondii-induced immunopathology, suggesting that the absence of CD73-generated adenosine led to the increased susceptibility in these mice. Peritoneal exudate cells from infected CD73−/− mice produced higher levels of the inflammatory mediators nitric oxide, tumor necrosis factor alpha (TNF-α), and interleukin-1β (IL-1β), without enhanced parasite killing or clearance. Bone marrow chimeras established that CD73 expression in both hematopoietic and nonhematopoietic compartments contributes to limiting T. gondii-induced immunopathology. In addition, mice deficient in the adenosine receptor A2A were more susceptible to immunopathology during intraperitoneal infection with T. gondii than WT mice. Thus, extracellular adenosine is a key immune regulator that limits collateral tissue damage due to an intracellular pathogen and promotes host survival. PMID:25452548

TOR induced resistance to toxic adenosine analogs in Leishmania brought about by the internalization and degradation of the adenosine permease

PubMed Central

Detke, Siegfried

2007-01-01

TOR is an atypical multidrug resistance protein present in the human protozoan parasite, Leishmania. Resistance to the toxic adenosine analog tubercidin was brought about by redirecting the adenosine permease from the plasma membrane to the multivesicular tubule lysosome. The cells became resistant to tubercidin because they were unable to take up and accumulate this toxic purine. The domain which was recognized by TOR in this internalization pathway was identified by expressing portions of this transporter in Leishmania and assessing whether they were capable of hindering the multidrug resistance capability of TOR. This approach identified the adenosine permease region spanning Met289 to Trp305. This region was also the epitope recognized by the internalization mechanism. An internal deletion mutant lacking Met289-Trp305 was functionally active but could no longer be internalized in cells with high TOR levels. The internalization and altered trafficking of the adenosine permease by TOR was observed in yeast and human embryonic kidney cells co-expressing these two Leishmania proteins indicating that the internalization process was conserved in evolutionary diverse organisms. The inability of Saccharomyces with a temperature sensitive ubiquitin ligase to internalize adenosine permease suggested that ubiquitination was involved in this altered trafficking. PMID:17428463

Sitagliptin attenuates sympathetic innervation via modulating reactive oxygen species and interstitial adenosine in infarcted rat hearts.

PubMed

Lee, Tsung-Ming; Chen, Wei-Ting; Yang, Chen-Chia; Lin, Shinn-Zong; Chang, Nen-Chung

2015-02-01

We investigated whether sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, attenuates arrhythmias through inhibiting nerve growth factor (NGF) expression in post-infarcted normoglycemic rats, focusing on adenosine and reactive oxygen species production. DPP-4 bound adenosine deaminase has been shown to catalyse extracellular adenosine to inosine. DPP-4 inhibitors increased adenosine levels by inhibiting the complex formation. Normoglycemic male Wistar rats were subjected to coronary ligation and then randomized to either saline or sitagliptin in in vivo and ex vivo studies. Post-infarction was associated with increased oxidative stress, as measured by myocardial superoxide, nitrotyrosine and dihydroethidium fluorescent staining. Measurement of myocardial norepinephrine levels revealed a significant elevation in vehicle-treated infarcted rats compared with sham. Compared with vehicle, infarcted rats treated with sitagliptin significantly increased interstitial adenosine levels and attenuated oxidative stress. Sympathetic hyperinnervation was blunted after administering sitagliptin, as assessed by immunofluorescent analysis and western blotting and real-time quantitative RT-PCR of NGF. Arrhythmic scores in the sitagliptin-treated infarcted rats were significantly lower than those in vehicle. Ex vivo studies showed a similar effect of erythro-9-(2-hydroxy-3-nonyl) adenine (an adenosine deaminase inhibitor) to sitagliptin on attenuated levels of superoxide and NGF. Furthermore, the beneficial effects of sitagliptin on superoxide anion production and NGF levels can be reversed by 8-cyclopentyl-1,3-dipropulxanthine (adenosine A1 receptor antagonist) and exogenous hypoxanthine. Sitagliptin protects ventricular arrhythmias by attenuating sympathetic innervation via adenosine A1 receptor and xanthine oxidase-dependent pathways, which converge through the attenuated formation of superoxide in the non-diabetic infarcted rats. © 2014 The Authors. Journal of Cellular and

Endogenous adenosine produced during hypoxia attenuates neutrophil accumulation: coordination by extracellular nucleotide metabolism.

PubMed

Eltzschig, Holger K; Thompson, Linda F; Karhausen, Jorn; Cotta, Richard J; Ibla, Juan C; Robson, Simon C; Colgan, Sean P

2004-12-15

Hypoxia is a well-documented inflammatory stimulus and results in tissue polymorphonuclear leukocyte (PMN) accumulation. Likewise, increased tissue adenosine levels are commonly associated with hypoxia, and given the anti-inflammatory properties of adenosine, we hypothesized that adenosine production via adenine nucleotide metabolism at the vascular surface triggers an endogenous anti-inflammatory response during hypoxia. Initial in vitro studies indicated that endogenously generated adenosine, through activation of PMN adenosine A(2A) and A(2B) receptors, functions as an antiadhesive signal for PMN binding to microvascular endothelia. Intravascular nucleotides released by inflammatory cells undergo phosphohydrolysis via hypoxia-induced CD39 ectoapyrase (CD39 converts adenosine triphosphate/adenosine diphosphate [ATP/ADP] to adenosine monophosphate [AMP]) and CD73 ecto-5'-nucleotidase (CD73 converts AMP to adenosine). Extensions of our in vitro findings using cd39- and cd73-null animals revealed that extracellular adenosine produced through adenine nucleotide metabolism during hypoxia is a potent anti-inflammatory signal for PMNs in vivo. These findings identify CD39 and CD73 as critical control points for endogenous adenosine generation and implicate this pathway as an innate mechanism to attenuate excessive tissue PMN accumulation.

Adenosine for postoperative analgesia: A systematic review and meta-analysis

PubMed Central

2017-01-01

Purpose Perioperative infusion of adenosine has been suggested to reduce the requirement for inhalation anesthetics, without causing serious adverse effects in humans. We conducted a meta-analysis of randomized controlled trials evaluating the effect of adenosine on postoperative analgesia. Methods We retrieved articles in computerized searches of Scopus, Web of Science, PubMed, EMBASE, and Cochrane Library databases, up to July 2016. We used adenosine, postoperative analgesia, and postoperative pain(s) as key words, with humans, RCT, and CCT as filters. Data of eligible studies were extracted, which included pain scores, cumulative opioid consumption, adverse reactions, and vital signs. Overall incidence rates, relative risk (RR), and 95% confidence intervals (CI) were calculated employing fixed-effects or random-effects models, depending on the heterogeneity of the included trials. Results In total, 757 patients from 9 studies were included. The overall effect of adenosine on postoperative VAS/VRS scores and postoperative opioid consumption was not significantly different from that of controls (P >0.1). The occurrence of PONV and pruritus was not statistically significantly different between an adenosine and nonremifentanil subgroup (P >0.1), but the rate of PONV occurrence was greater in the remifentanil subgroup (P <0.01). Time to first postoperative analgesic requirement in the adenosine group was not significantly difference from that of the saline group (SMD = 0.07, 95%CI: −0.28 to 0.41, P = 0.71); but this occurred significantly later than with remifentanil (SMD = 1.10, 95%CI: 2.48 to 4.06, P < 0.01). Time to hospital discharge was not significantly different between the control and adenosine groups (P = 0.78). The perioperative systolic blood pressure was significantly lower in the adenosine than in the control group in the mannitol subgroup (P < 0.01). The incidence of bradycardia, transient first- degree atrioventricular block, and tachycardia was not

Adenosine-Induced Atrial Fibrillation: Localized Reentrant Drivers in Lateral Right Atria due to Heterogeneous Expression of Adenosine A1 Receptors and GIRK4 Subunits in the Human Heart.

PubMed

Li, Ning; Csepe, Thomas A; Hansen, Brian J; Sul, Lidiya V; Kalyanasundaram, Anuradha; Zakharkin, Stanislav O; Zhao, Jichao; Guha, Avirup; Van Wagoner, David R; Kilic, Ahmet; Mohler, Peter J; Janssen, Paul M L; Biesiadecki, Brandon J; Hummel, John D; Weiss, Raul; Fedorov, Vadim V

2016-08-09

Adenosine provokes atrial fibrillation (AF) with a higher activation frequency in right atria (RA) versus left atria (LA) in patients, but the underlying molecular and functional substrates are unclear. We tested the hypothesis that adenosine-induced AF is driven by localized reentry in RA areas with highest expression of adenosine A1 receptor and its downstream GIRK (G protein-coupled inwardly rectifying potassium channels) channels (IK,Ado). We applied biatrial optical mapping and immunoblot mapping of various atrial regions to reveal the mechanism of adenosine-induced AF in explanted failing and nonfailing human hearts (n=37). Optical mapping of coronary-perfused atria (n=24) revealed that adenosine perfusion (10-100 µmol/L) produced more significant shortening of action potential durations in RA (from 290±45 to 239±41 ms, 17.3±10.4%; P<0.01) than LA (from 307±24 to 286±23 ms, 6.7±6.6%; P<0.01). In 10 hearts, adenosine induced AF (317±116 s) that, when sustained (≥2 minutes), was primarily maintained by 1 to 2 localized reentrant drivers in lateral RA. Tertiapin (10-100 nmol/L), a selective GIRK channel blocker, counteracted adenosine-induced action potential duration shortening and prevented AF induction. Immunoblotting showed that the superior/middle lateral RA had significantly higher adenosine A1 receptor (2.7±1.7-fold; P<0.01) and GIRK4 (1.7±0.8-fold; P<0.05) protein expression than lateral/posterior LA. This study revealed a 3-fold RA-to-LA adenosine A1 receptor protein expression gradient in the human heart, leading to significantly greater RA versus LA repolarization sensitivity in response to adenosine. Sustained adenosine-induced AF is maintained by reentrant drivers localized in lateral RA regions with the highest adenosine A1 receptor/GIRK4 expression. Selective atrial GIRK channel blockade may effectively treat AF during conditions with increased endogenous adenosine. © 2016 American Heart Association, Inc.

ST 1535: a preferential A2A adenosine receptor antagonist.

PubMed

Stasi, Maria Antonietta; Borsini, Franco; Varani, Katia; Vincenzi, Fabrizio; Di Cesare, Maria Assunta; Minetti, Patrizia; Ghirardi, Orlando; Carminati, Paolo

2006-10-01

Antagonism of the A2A adenosine function has proved beneficial in the treatment of Parkinson's disease, in that it increases L-dopa therapeutical effects without concomitant worsening of its side-effects. In this paper we describe a preferential A2A adenosine antagonist, ST 1535, with long-lasting pharmacodynamic effects. It competitively antagonizes the effects of the A2A adenosine agonist NECA on cAMP in cells cloned with the human A2A adenosine receptor (IC50=353+/-30 nM), and the effects of the A1 adenosine agonist CHA on cAMP in cells cloned with the human A1 adenosine receptor (IC50=510+/-38 nM). ST 1535, at oral doses of 5 and 10 mg/kg, antagonizes catalepsy induced by intracerebroventricular administration of the A2A adenosine agonist CGS 21680 (10 microg/5 microl) in mice. At oral doses ranging between 5 and 20 mg/kg, ST 1535 induces hypermotility and antagonizes haloperidol-induced catalepsy in mice up to 7 h. Oral ST 1535, at 1.25 and 2.5 mg/kg, potentiates L-dopa effects in reducing haloperidol-induced catalepsy. ST 1535 represents a potential new compound, with long-lasting activity, for the treatment of Parkinson's disease.

Wireless Instantaneous Neurotransmitter Concentration System–based amperometric detection of dopamine, adenosine, and glutamate for intraoperative neurochemical monitoring

PubMed Central

Agnesi, Filippo; Tye, Susannah J.; Bledsoe, Jonathan M.; Griessenauer, Christoph J.; Kimble, Christopher J.; Sieck, Gary C.; Bennet, Kevin E.; Garris, Paul A.; Blaha, Charles D.; Lee, Kendall H.

2009-01-01

Object In a companion study, the authors describe the development of a new instrument named the Wireless Instantaneous Neurotransmitter Concentration System (WINCS), which couples digital telemetry with fast-scan cyclic voltammetry (FSCV) to measure extracellular concentrations of dopamine. In the present study, the authors describe the extended capability of the WINCS to use fixed potential amperometry (FPA) to measure extracellular concentrations of dopamine, as well as glutamate and adenosine. Compared with other electrochemical techniques such as FSCV or high-speed chronoamperometry, FPA offers superior temporal resolution and, in combination with enzyme-linked biosensors, the potential to monitor nonelectroactive analytes in real time. Methods The WINCS design incorporated a transimpedance amplifier with associated analog circuitry for FPA; a microprocessor; a Bluetooth transceiver; and a single, battery-powered, multilayer, printed circuit board. The WINCS was tested with 3 distinct recording electrodes: 1) a carbon-fiber microelectrode (CFM) to measure dopamine; 2) a glutamate oxidase enzyme-linked electrode to measure glutamate; and 3) a multiple enzyme-linked electrode (adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase) to measure adenosine. Proof-of-principle analyses included noise assessments and in vitro and in vivo measurements that were compared with similar analyses by using a commercial hardwired electrochemical system (EA161 Picostat, eDAQ; Pty Ltd). In urethane-anesthetized rats, dopamine release was monitored in the striatum following deep brain stimulation (DBS) of ascending dopaminergic fibers in the medial forebrain bundle (MFB). In separate rat experiments, DBS-evoked adenosine release was monitored in the ventrolateral thalamus. To test the WINCS in an operating room setting resembling human neurosurgery, cortical glutamate release in response to motor cortex stimulation (MCS) was monitored using a large-mammal animal

Wireless Instantaneous Neurotransmitter Concentration System-based amperometric detection of dopamine, adenosine, and glutamate for intraoperative neurochemical monitoring.

PubMed

Agnesi, Filippo; Tye, Susannah J; Bledsoe, Jonathan M; Griessenauer, Christoph J; Kimble, Christopher J; Sieck, Gary C; Bennet, Kevin E; Garris, Paul A; Blaha, Charles D; Lee, Kendall H

2009-10-01

In a companion study, the authors describe the development of a new instrument named the Wireless Instantaneous Neurotransmitter Concentration System (WINCS), which couples digital telemetry with fast-scan cyclic voltammetry (FSCV) to measure extracellular concentrations of dopamine. In the present study, the authors describe the extended capability of the WINCS to use fixed potential amperometry (FPA) to measure extracellular concentrations of dopamine, as well as glutamate and adenosine. Compared with other electrochemical techniques such as FSCV or high-speed chronoamperometry, FPA offers superior temporal resolution and, in combination with enzyme-linked biosensors, the potential to monitor nonelectroactive analytes in real time. The WINCS design incorporated a transimpedance amplifier with associated analog circuitry for FPA; a microprocessor; a Bluetooth transceiver; and a single, battery-powered, multilayer, printed circuit board. The WINCS was tested with 3 distinct recording electrodes: 1) a carbon-fiber microelectrode (CFM) to measure dopamine; 2) a glutamate oxidase enzyme-linked electrode to measure glutamate; and 3) a multiple enzyme-linked electrode (adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase) to measure adenosine. Proof-of-principle analyses included noise assessments and in vitro and in vivo measurements that were compared with similar analyses by using a commercial hardwired electrochemical system (EA161 Picostat, eDAQ; Pty Ltd). In urethane-anesthetized rats, dopamine release was monitored in the striatum following deep brain stimulation (DBS) of ascending dopaminergic fibers in the medial forebrain bundle (MFB). In separate rat experiments, DBS-evoked adenosine release was monitored in the ventrolateral thalamus. To test the WINCS in an operating room setting resembling human neurosurgery, cortical glutamate release in response to motor cortex stimulation (MCS) was monitored using a large-mammal animal model, the pig. The

Adenosine formation and release from neonatal-rat heart cells in culture.

PubMed Central

Meghji, P; Holmquist, C A; Newby, A C

1985-01-01

The incorporation of [3H]adenosine (10 microM) into neonatal-rat heart cell nucleotides was inhibited in a concentration-dependent manner, such that 50% inhibition was obtained with 0.75 microM-dipyridamole, 0.26 microM-hexobendine or 0.22 microM-dilazep. Adenosine formation was accelerated 2.5-fold to 2.1 +/- 0.3 nmol/10(7) cells in 10 min when cells were incubated with a combination of 30 mM-2-deoxyglucose and 2 micrograms of oligomycin/ml. Of the newly formed adenosine, 6 +/- 2% was in the cells. Dipyridamole, hexobendine or dilazep (10 microM) increased the amount of adenosine in the cells and decreased that in the medium such that 45-50% of the newly formed adenosine was in the cells. Antibodies which inhibited ecto-5'-nucleotidase by 98.7 +/- 0.3% did not alter the rate of adenosine formation or its distribution between cells and medium. We conclude that adenosine was formed in the cytoplasm during catabolism of cellular ATP and was released via the dipyridamole-sensitive symmetric nucleoside transporter. PMID:2996488

Acetate supplementation modulates brain adenosine metabolizing enzymes and adenosine A₂A receptor levels in rats subjected to neuroinflammation.

PubMed

Smith, Mark D; Bhatt, Dhaval P; Geiger, Jonathan D; Rosenberger, Thad A

2014-06-04

Acetate supplementation reduces neuroglia activation and pro-inflammatory cytokine expression in rat models of neuroinflammation and Lyme neuroborreliosis. Because single-dose glyceryl triacetate (GTA) treatment increases brain phosphocreatine and reduces brain AMP levels, we postulate that GTA modulates adenosine metabolizing enzymes and receptors, which may be a possible mechanism to reduce neuroinflammation. To test this hypothesis, we quantified the ability of GTA to alter brain levels of ecto-5'-nucleotidase (CD73), adenosine kinase (AK), and adenosine A2A receptor using western blot analysis and CD73 activity by measuring the rate of AMP hydrolysis. Neuroinflammation was induced by continuous bacterial lipopolysaccharide (LPS) infusion in the fourth ventricle of the brain for 14 and 28 days. Three treatment strategies were employed, one and two where rats received prophylactic GTA through oral gavage with LPS infusion for 14 or 28 days. In the third treatment regimen, an interventional strategy was used where rats were subjected to 28 days of neuroinflammation, and GTA treatment was started on day 14 following the start of the LPS infusion. We found that rats subjected to neuroinflammation for 28 days had a 28% reduction in CD73 levels and a 43% increase in AK levels that was reversed with prophylactic acetate supplementation. CD73 activity in these rats was increased by 46% with the 28-day GTA treatment compared to the water-treated rats. Rats subjected to neuroinflammation for 14 days showed a 50% increase in levels of the adenosine A2A receptor, which was prevented with prophylactic acetate supplementation. Interventional GTA therapy, beginning on day 14 following the induction of neuroinflammation, resulted in a 67% increase in CD73 levels and a 155% increase in adenosine A2A receptor levels. These results support the hypothesis that acetate supplementation can modulate brain CD73, AK and adenosine A2A receptor levels, and possibly influence purinergic

Characterization of adenosine receptors in guinea-pig isolated left atria.

PubMed Central

Jahnel, U.; Nawrath, H.

1989-01-01

1. The effects of purinergic stimulation on action potential, force of contraction, 86Rb efflux and 45Ca uptake were investigated in guinea-pig left atria. 2. Adenosine exerted a negative inotropic effect which was antagonized by adenosine deaminase but enhanced by dipyridamole. 3. The negative inotropic effect of adenosine was mimicked by 5'-(N-ethyl)-carboxamido-adenosine (NECA) and the isomers of N6-(phenyl-isopropyl)-adenosine, R-PIA and S-PIA. NECA and R-PIA were about 100 times more potent than adenosine, whereas R-PIA was about 100 times more potent than S-PIA. 4. The inotropic effects of adenosine (in the presence of dipyridamole), NECA, R-PIA and S-PIA were competitively antagonized either by theophylline (pA2 about 4.5) or 8-phenyltheophylline (pA2 about 6.3). 5. NECA and R-PIA shortened the action potential duration and increased the rate constant of the efflux of 86Rb in a concentration-dependent manner with no differences in potency; the effects were competitively antagonized by 8-phenyltheophylline. 6. Barium ions reduced the efflux of 86Rb under control conditions and antagonized the increase induced by NECA and R-PIA. 7. NECA and R-PIA significantly reduced 45Ca uptake in beating preparations. 8. It is concluded that adenosine, NECA and R-PIA activate a common receptor population (P1 or A3) on the outside of the cell membrane of atrial heart muscle to increase the potassium conductance and to reduce the action potential and, thereby, calcium influx and force of contraction. PMID:2790380

A cyclic peptide derived from alpha-fetoprotein inhibits the proliferative effects of the epidermal growth factor and estradiol in MCF7 cells.

PubMed

Torres, Cristian; Antileo, Elmer; Epuñán, Maráa José; Pino, Ana María; Valladares, Luis Emilio; Sierralta, Walter Daniel

2008-06-01

A cyclic peptide derived from the active domain of alpha-fetoprotein (AFP) significantly inhibited the proliferation of MCF7 cells stimulated with the epidermal growth factor (EGF) or estradiol (E2). The action of these three agents on cell growth was independent of the presence of calf serum in the culture medium. Our results demonstrated that the cyclic peptide interfered markedly with the regulation of MAPK by activated c-erbB2. The cyclic peptide showed no effect on the E2-stimulated release of matrix metalloproteinases 2 and 9 nor on the shedding of heparin-binding EGF into the culture medium. We propose that the AFP-derived cyclic peptide represents a valuable novel antiproliferative agent for treating breast cancer.

Translocation of arrestin induced by human A(3) adenosine receptor ligands in an engineered cell line: comparison with G protein-dependent pathways.

PubMed

Gao, Zhan-Guo; Jacobson, Kenneth A

2008-04-01

Structurally diverse ligands were studied in A(3) adenosine receptor (AR)-mediated beta-arrestin translocation in engineered CHO cells. The agonist potency and efficacy were similar, although not identical, to their G protein signaling. However, differences have also been found. MRS542, MRS1760, and other adenosine derivatives, A(3)AR antagonists in cyclic AMP assays, were partial agonists in beta-arrestin translocation, indicating possible biased agonism. The xanthine 7-riboside DBXRM, a full agonist, was only partially efficacious in beta-arrestin translocation. DBXRM was shown to induce a lesser extent of desensitization compared with IB-MECA. In kinetic studies, MRS3558, a potent and selective A(3)AR agonist, induced beta-arrestin translocation significantly faster than IB-MECA and Cl-IB-MECA. Non-nucleoside antagonists showed similar inhibitory potencies as previously reported. PTX pretreatment completely abolished ERK1/2 activation, but not arrestin translocation. Thus, lead candidates for biased agonists at the A(3)AR have been identified with this arrestin-translocation assay, which promises to be an effective tool for ligand screening.

Conservation and divergence of the cyclic adenosine monophosphate-protein kinase A (cAMP-PKA) pathway in two plant-pathogenic fungi: Fusarium graminearum and F. verticillioides.

PubMed

Guo, Li; Breakspear, Andrew; Zhao, Guoyi; Gao, Lixin; Kistler, H Corby; Xu, Jin-Rong; Ma, Li-Jun

2016-02-01

The cyclic adenosine monophosphate-protein kinase A (cAMP-PKA) pathway is a central signalling cascade that transmits extracellular stimuli and governs cell responses through the second messenger cAMP. The importance of cAMP signalling in fungal biology has been well documented and the key conserved components, adenylate cyclase (AC) and the catalytic subunit of PKA (CPKA), have been functionally characterized. However, other genes involved in this signalling pathway and their regulation are not well understood in filamentous fungi. Here, we performed a comparative transcriptomics analysis of AC and CPKA mutants in two closely related fungi: Fusarium graminearum (Fg) and F. verticillioides (Fv). Combining available Fg transcriptomics and phenomics data, we reconstructed the Fg cAMP signalling pathway. We developed a computational program that combines sequence conservation and patterns of orthologous gene expression to facilitate global transcriptomics comparisons between different organisms. We observed highly correlated expression patterns for most orthologues (80%) between Fg and Fv. We also identified a subset of 482 (6%) diverged orthologues, whose expression under all conditions was at least 50% higher in one genome than in the other. This enabled us to dissect the conserved and unique portions of the cAMP-PKA pathway. Although the conserved portions controlled essential functions, such as metabolism, the cell cycle, chromatin remodelling and the oxidative stress response, the diverged portions had species-specific roles, such as the production and detoxification of secondary metabolites unique to each species. The evolution of the cAMP-PKA signalling pathway seems to have contributed directly to fungal divergence and niche adaptation. © 2015 The Authors. Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.

Secreted adenosine triphosphate from Aggregatibacter actinomycetemcomitans triggers chemokine response.

PubMed

Ding, Q; Quah, S Y; Tan, K S

2016-10-01

Extracellular ATP (eATP) is an important intercellular signaling molecule secreted by activated immune cells or released by damaged cells. In mammalian cells, a rapid increase of ATP concentration in the extracellular space sends a danger signal, which alerts the immune system of an impending danger, resulting in recruitment and priming of phagocytes. Recent studies show that bacteria also release ATP into the extracellular milieu, suggesting a potential role for eATP in host-microbe interactions. It is currently unknown if any oral bacteria release eATP. As eATP triggers and amplifies innate immunity and inflammation, we hypothesized that eATP secreted from periodontal bacteria may contribute to inflammation in periodontitis. The aims of this study were to determine if periodontal bacteria secrete ATP, and to determine the function of bacterially derived eATP as an inducer of inflammation. Our results showed that Aggregatibacter actinomycetemcomitans, but not Porphyromonas gingivalis, Prevotella intermedia, or Fusobacterium nucleatum, secreted ATP into the culture supernatant. Exposure of periodontal fibroblasts to filter sterilized culture supernatant of A. actinomycetemcomitans induced chemokine expression in an eATP-dependent manner. This occurred independently of cyclic adenosine monophosphate and phospholipase C, suggesting that ionotrophic P2X receptor is involved in sensing of bacterial eATP. Silencing of P2X7 receptor in periodontal fibroblasts led to a significant reduction in bacterial eATP-induced chemokine response. Furthermore, bacterial eATP served as a potent chemoattractant for neutrophils and monocytes. Collectively, our findings provide evidence for secreted ATP of A. actinomycetemcomitans as a novel virulence factor contributing to inflammation during periodontal disease. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Adenosine receptor subtypes in the airways responses to 5'-adenosine monophosphate inhalation of sensitized guinea-pigs.

PubMed

Smith, N; Broadley, K J

2008-09-01

Endogenous adenosine levels are raised in the lungs during asthma attacks. 5'-adenosine monophosphate (5'-AMP) inhalation in asthmatics causes bronchoconstriction and in sensitized guinea-pigs induces early (EAR) and late asthmatic responses (LAR), airway hyper-reactivity (AHR) and inflammatory cell recruitment to the lungs. The aim of this study was to investigate the roles of A(1), A(2A), A(2B) and A(3) adenosine receptors in these responses to inhaled 5'-AMP in sensitized guinea-pigs. Comparisons were made with the effect of dexamethasone treatment on 5'-AMP-induced responses. Functional airways responses to inhaled 5'-AMP (3 and 300 mM) of actively sensitized, conscious guinea-pigs were determined by whole-body plethysmography following administration of selective adenosine receptor antagonists or their vehicles. AHR to inhaled histamine (1 mM) and inflammatory cell influx in bronchoalveolar lavage fluid were determined. 5'-AMP at 3 mM caused an immediate bronchoconstriction (EAR), whereas 300 mM caused bronchodilatation. Both responses were followed at 6 h by a LAR, together with inflammatory cell influx and AHR to histamine. The A(2A) receptor antagonist, ZM241385, further enhanced cell influx after 5'-AMP inhalation (3 and 300 mM), and blocked the immediate bronchodilator response to 300 mM 5'-AMP, exposing an EAR. The A(2B) receptor antagonist, MRS1706 (in the presence of ZM241385), inhibited the LAR, AHR and cell influx, following inhalation of 5'-AMP (300 mM). The A(3) receptor antagonist, MRS1220, inhibited 5'-AMP-induced inflammatory cell influx. The A(1) receptor antagonist, DPCPX (in the presence of ZM241385), inhibited the EAR following 5'-AMP inhalation (300 mM). Dexamethasone inhibited the LAR, AHR and cell influx following inhalation of 5'-AMP (300 mM). All four adenosine receptor subtypes play various roles in the airways responses to inhaled 5'-AMP in sensitized guinea-pigs.

Intracoronary Adenosine: Dose-Response Relationship With Hyperemia.

PubMed

Adjedj, Julien; Toth, Gabor G; Johnson, Nils P; Pellicano, Mariano; Ferrara, Angela; Floré, Vincent; Di Gioia, Giuseppe; Barbato, Emanuele; Muller, Olivier; De Bruyne, Bernard

2015-09-01

The present study sought to establish the dosage of intracoronary (IC) adenosine associated with minimal side effects and above which no further increase in flow can be expected. Despite the widespread adoption of IC adenosine in clinical practice, no wide-ranging, dose-response study has been conducted. A recurring debate still exists regarding its optimal dose. In 30 patients, Doppler-derived flow velocity measurements were obtained in 10 right coronary arteries (RCAs) and 20 left coronary arteries (LCAs) free of stenoses >20% in diameter. Flow velocity was measured at baseline and after 8 ml bolus administrations of arterial blood, saline, contrast medium, and 9 escalating doses of adenosine (4 to 500 μg). The hyperemic value was expressed in percent of the maximum flow velocity reached in a given artery (Q/Qmax, %). Q/Qmax did not increase significantly beyond dosages of 60 μg for the RCA and 160 μg for LCA. Heart rate did not change, whereas mean arterial blood pressure decreased by a maximum of 7% (p < 0.05) after bolus injections of IC adenosine. The incidence of transient A-V blocks was 40% after injection of 100 μg in the RCA and was 15% after injection of 200 μg in the LCA. The duration of the plateau reached 12 ± 13 s after injection of 100 μg in the RCA and 21 ± 6 s after the injection of 200 μg in the LCA. A progressive prolongation of the time needed to return to baseline was observed. Hyperemic response after injection of 8 ml of contrast medium reached 65 ± 36% of that achieved after injection of 200 μg of adenosine. This wide-ranging, dose-response study indicates that an IC adenosine bolus injection of 100 μg in the RCA and 200 μg in the LCA induces maximum hyperemia while being associated with minimal side effects. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

The opposing effects of calmodulin, adenosine 5 prime -triphosphate, and pertussis toxin on phorbol ester induced inhibition of atrial natriuretic factor stimulated guanylate cyclase in SK-NEP-1 cells

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

Sekiya, M.; Frohlich, E.D.; Cole, F.E.

1991-01-01

In the present study, we investigated the effects of calmodulin, adenosine 5{prime}-triphosphate (ATP) and pertussis toxin (PT) on phorbol ester (PMA) induced inhibition of ANF-stimulated cyclic GMP formation in cells from the human renal cell line, SK-NEP-1. PMA inhibited ANF-stimulated guanylate cyclase activity in particulate membranes by about 65%. Calmodulin reversed this inhibition in a dose dependent manner. ATP potentiated Mg++ but not Mn++ supported guanylate cyclase activity. In PMA treated membranes, ATP potentiating effects were abolished. PMA also inhibited ANF-stimulated cGMP accumulation, but pretreatment with PT prevented this PMA inhibition. PT did not affect basal or ANF-stimulated cGMP accumulation.more » In conclusion, these results demonstrated that PMA inhibited ANF stimulation of particulate guanylate cyclase in opposition to the activating effects of calmodulin or ATP in SK-NEP-1 cells. The protein kinase C inhibitory effects appeared to be mediated via a PT-sensitive G protein.« less

Primary adenosine monophosphate (AMP) deaminase deficiency in a hypotonic infant.

PubMed

Castro-Gago, Manuel; Gómez-Lado, Carmen; Pérez-Gay, Laura; Eirís-Puñal, Jesús; Martínez, Elena Pintos; García-Consuegra, Inés; Martín, Miguel Angel

2011-06-01

The spectrum of the adenosine monophosphate (AMP) deaminase deficiency ranges from asymptomatic carriers to patients who manifest exercise-induced muscle pain, occasionally rhabdomyolysis, and idiopathic hyperCKemia. However, previous to the introduction of molecular techniques, rare cases with congenital weakness and hypotonia have also been reported. We report a 6-month-old girl with the association of congenital muscle weakness and hypotonia, muscle deficiency of adenosine monophosphate deaminase, and the homozygous C to T mutation at nucleotide 34 of the adenosine monophosphate deaminase-1 gene. This observation indicates the possible existence of a primary adenosine monophosphate deaminase deficiency manifested by congenital muscle weakness and hypotonia.

SYNERGISTIC EFFECTS of CYCLIC TENSION and TRANSFORMING GROWTH FACTOR-β1 on the AORTIC VALVE MYOFIBROBLAST

PubMed Central

Merryman, W. David; Lukoff, Howard D.; Long, Rebecca A.; Engelmayr, George C.; Hopkins, Richard A.; Sacks, Michael S.

2007-01-01

Background Phenotypically, the aortic valve interstitial cell (AVIC) is a dynamic myofibroblast, appearing contractile and activated in times of development, disease, and remodeling. The precise mechanism of phenotypic modulation is unclear, but it is speculated that both biomechanical and biochemical factors are influential. Therefore, we hypothesized that isolated and combined treatments of cyclic tension and TGF-β1 would alter the phenotype and subsequent collagen biosynthesis of AVICs in situ. Methods and Results Porcine aortic valve leaflets received 7 and 14 day treatments of 15% cyclic stretch (Tension), 0.5 ng/ml TGF-β1 (TGF), 15% cyclic stretch and 0.5 ng/ml TGF-β1 (Tension+TGF), or neither mechanical nor cytokine stimuli (Null). Tissues were homogenized and assayed for AVIC phenotype (smooth muscle α-actin (SMA)) and collagen biosynthesis (via heat shock protein 47 (Hsp47) which was further verified with type I collagen C-terminal propeptide (CICP)). At both 7 and 14 days, SMA, Hsp47, and CICP quantities were significantly greater (p<0.001) in the Tension+TGF group compared to all other groups. Additionally, Tension alone appeared to maintain SMA and Hsp47 levels that were measured at day 0, while TGF alone elicited an increase in SMA and Hsp47 compared to day 0 levels. Null treatment revealed diminished proteins at both time points. Conclusions Elevated TGF-β1 levels, in the presence of cyclic mechanical tension, resulted in synergistic increases in the contractile and biosynthetic proteins in AVICs. Since cyclic mechanical stimuli can never be relieved in vivo, the presence of TGF-β1 (possibly from infiltrating macrophages) may result in overly biosynthetic AVICs, leading to altered ECM architecture, compromised valve function, and ultimately degenerative valvular disease. PMID:17868877

Delayed production of adenosine underlies temporal modulation of swimming in frog embryo

PubMed Central

Dale, Nicholas

1998-01-01

To investigate the dynamics of adenosine production in the spinal cord during motor activity, and its possible contribution to the temporal modulation of motor patterns, a sensor sensitive to adenosine at concentrations as low as 10 nm was devised.When pressed against the outside of the spinal cord, the sensor detected slow changes in the levels of adenosine during fictive swimming that ranged from 10 to 650 nm. In four embryos where particularly large signals were recorded due to favourable probe placement, the adenosine levels continued to rise for up to a minute following cessation of activity before slowly returning to baseline. In the remaining thirteen embryos, levels of adenosine started to return slowly to baseline almost immediately after activity had stopped.Inhibitors of adenosine uptake increased the magnitude of the signal recorded and slowed the recovery following cessation of activity.A realistic computational model of the spinal circuitry was combined with models of extracellular breakdown of ATP to adenosine. ATP and adenosine inhibited, as in the real embryo, the voltage-gated K+ and Ca2+ currents, respectively. The model reproduced the temporal run-down of motor activity seen in the real embryo suggesting that synaptic release of ATP together with its extracellular breakdown to adenosine is sufficient to exert time-dependent control over motor pattern generation.The computational analysis also suggested that the delay in the rise of adenosine levels is likely to result from feed-forward inhibition of the 5′-ectonucleotidase in the spinal cord. This inhibition is a key determinant of the rate of run-down. PMID:9679180

Adenosine Kinase Deficiency in the Brain Results in Maladaptive Synaptic Plasticity.

PubMed

Sandau, Ursula S; Colino-Oliveira, Mariana; Jones, Abbie; Saleumvong, Bounmy; Coffman, Shayla Q; Liu, Long; Miranda-Lourenço, Catarina; Palminha, Cátia; Batalha, Vânia L; Xu, Yiming; Huo, Yuqing; Diógenes, Maria J; Sebastião, Ana M; Boison, Detlev

2016-11-30

Adenosine kinase (ADK) deficiency in human patients (OMIM:614300) disrupts the methionine cycle and triggers hypermethioninemia, hepatic encephalopathy, cognitive impairment, and seizures. To identify whether this neurological phenotype is intrinsically based on ADK deficiency in the brain or if it is secondary to liver dysfunction, we generated a mouse model with a brain-wide deletion of ADK by introducing a Nestin-Cre transgene into a line of conditional ADK deficient Adk fl/fl mice. These Adk Δbrain mice developed a progressive stress-induced seizure phenotype associated with spontaneous convulsive seizures and profound deficits in hippocampus-dependent learning and memory. Pharmacological, biochemical, and electrophysiological studies suggest enhanced adenosine levels around synapses resulting in an enhanced adenosine A 1 receptor (A 1 R)-dependent protective tone despite lower expression levels of the receptor. Theta-burst-induced LTP was enhanced in the mutants and this was dependent on adenosine A 2A receptor (A 2A R) and tropomyosin-related kinase B signaling, suggesting increased activation of these receptors in synaptic plasticity phenomena. Accordingly, reducing adenosine A 2A receptor activity in Adk Δbrain mice restored normal associative learning and contextual memory and attenuated seizure risk. We conclude that ADK deficiency in the brain triggers neuronal adaptation processes that lead to dysregulated synaptic plasticity, cognitive deficits, and increased seizure risk. Therefore, ADK mutations have an intrinsic effect on brain physiology and may present a genetic risk factor for the development of seizures and learning impairments. Furthermore, our data show that blocking A 2A R activity therapeutically can attenuate neurological symptoms in ADK deficiency. A novel human genetic condition (OMIM #614300) that is based on mutations in the adenosine kinase (Adk) gene has been discovered recently. Affected patients develop hepatic encephalopathy

Neutrophil-derived 5′-Adenosine Monophosphate Promotes Endothelial Barrier Function via CD73-mediated Conversion to Adenosine and Endothelial A2B Receptor Activation

PubMed Central

Lennon, Paul F.; Taylor, Cormac T.; Stahl, Gregory L.; Colgan, Sean P.

1998-01-01

During episodes of inflammation, polymorphonuclear leukocyte (PMN) transendothelial migration has the potential to disturb vascular barrier function and give rise to intravascular fluid extravasation and edema. However, little is known regarding innate mechanisms that dampen fluid loss during PMN-endothelial interactions. Using an in vitro endothelial paracellular permeability model, we observed a PMN-mediated decrease in endothelial paracellular permeability. A similar decrease was elicited by cell-free supernatants from activated PMN (FMLP 10−6 M), suggesting the presence of a PMN-derived soluble mediator(s). Biophysical and biochemical analysis of PMN supernatants revealed a role for PMN-derived 5′-adenosine monophosphate (AMP) and its metabolite, adenosine, in modulation of endothelial paracellular permeability. Supernatants from activated PMN contained micromolar concentrations of bioactive 5′-AMP and adenosine. Furthermore, exposure of endothelial monolayers to authentic 5′-AMP and adenosine increased endothelial barrier function more than twofold in both human umbilical vein endothelial cells and human microvascular endothelial cells. 5′-AMP bioactivity required endothelial CD73-mediated conversion of 5′-AMP to adenosine via its 5′-ectonucleotidase activity. Decreased endothelial paracellular permeability occurred through adenosine A2B receptor activation and was accompanied by a parallel increase in intracellular cAMP. We conclude that activated PMN release soluble mediators, such as 5′-AMP and adenosine, that promote endothelial barrier function. During inflammation, this pathway may limit potentially deleterious increases in endothelial paracellular permeability and could serve as a basic mechanism of endothelial resealing during PMN transendothelial migration. PMID:9782120

[Role of cyclic adenosine monophosphate response element binding protein in ventricular pacing induced cardiac electrical remodeling in a canine model].

PubMed

Chen, Xuesi; Chen, Xingxing; Cheng, Junhua; Hong, Jun; Zheng, Cheng; Zhao, Jinglin; Li, Jin; Lin, Jiafeng

2015-04-01

This project is designed to explore the potential role of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) in cardiac electrical remodeling induced by pacing at different ventricular positions in dogs. An animal model by implanting the pacemakers in beagles was established. According to the different pacing positions, the animals were divided into 4 groups:conditional control group (n=6), left ventricle pacing group (n=6), right ventricle pacing group (n=6) and bi-ventricle pacing group (n=6). Cardiac and electrical remodeling were observed by echocardiography, electrocardiogram and plasma BNP. Myocardial pathology and protein expression of extracellular regulated protein kinases1/2 (ERK1/2), P38 mitogen activated protein kinases (P38 MAPK) and CREB were examined at 4 weeks post pacing. Cardiac structure and plasma BNP level were similar among 4 groups (all P>0.05). Electrocardiogram derived Tp-Te interval was significantly prolonged post pacing (92±11, 91±10, and 79±13 ms vs. 60±12 ms), and the Tp-Te interval in bi-ventricle pacing group was shorter than in left or right ventricle pacing group (P < 0.05). Western blot results showed that the expression of p-ERK1/2 in left ventricular myocardium of left ventricle pacing group, right ventricular myocardium of right ventricle pacing group and bi-ventricular myocardium of bi-ventricle pacing group was 2.7±0.4, 2.4±0.2, 1.7±0.1 and 1.9±0.2, respectively, the expression of p-P38 MAPK was 1.9±0.3, 1.7±0.2, 0.8±0.1 and 1.1±0.1, respectively, and the expression of p-CREB was 2.1±0.2, 2.0±0.2, 2.7±0.4 and 2.6±0.3, respectively. The p-ERK1/2 and p-P38 MAPK expression of bi-ventricle pacing group was lower,but the p-CREB expression was higher compared to the other pacing groups (P < 0.05). Ventricular pacing could induce electrical remodeling evidenced by prolonged Tp-Te interval and increased phosphorylation of ERK1/2 and p38 MAPK and reduced phosphorylation of CREB. Compared with

Neuronal transporter and astrocytic ATP exocytosis underlie activity-dependent adenosine release in the hippocampus

PubMed Central

Wall, Mark J; Dale, Nicholas

2013-01-01

The neuromodulator adenosine plays an important role in many physiological and pathological processes within the mammalian CNS. However, the precise mechanisms of how the concentration of extracellular adenosine increases following neural activity remain contentious. Here we have used microelectrode biosensors to directly measure adenosine release induced by focal stimulation in stratum radiatum of area CA1 in mouse hippocampal slices. Adenosine release was both action potential and Ca2+ dependent and could be evoked with low stimulation frequencies and small numbers of stimuli. Adenosine release required the activation of ionotropic glutamate receptors and could be evoked by local application of glutamate receptor agonists. Approximately 40% of stimulated-adenosine release occurred by translocation of adenosine via equilibrative nucleoside transporters (ENTs). This component of release persisted in the presence of the gliotoxin fluoroacetate and thus results from the direct release of adenosine from neurons. A reduction of adenosine release in the presence of NTPDase blockers, in slices from CD73−/− and dn-SNARE mice, provides evidence that a component of adenosine release arises from the extracellular metabolism of ATP released from astrocytes. This component of release appeared to have slower kinetics than the direct ENT-mediated release of adenosine. These data suggest that activity-dependent adenosine release is surprisingly complex and, in the hippocampus, arises from at least two distinct mechanisms with different cellular sources. PMID:23713028

Alkaline Phosphatase, Soluble Extracellular Adenine Nucleotides, and Adenosine Production after Infant Cardiopulmonary Bypass

PubMed Central

Davidson, Jesse A.; Urban, Tracy; Tong, Suhong; Twite, Mark; Woodruff, Alan

2016-01-01

Rationale Decreased alkaline phosphatase activity after infant cardiac surgery is associated with increased post-operative cardiovascular support requirements. In adults undergoing coronary artery bypass grafting, alkaline phosphatase infusion may reduce inflammation. Mechanisms underlying these effects have not been explored but may include decreased conversion of extracellular adenine nucleotides to adenosine. Objectives 1) Evaluate the association between alkaline phosphatase activity and serum conversion of adenosine monophosphate to adenosine after infant cardiac surgery; 2) assess if inhibition/supplementation of serum alkaline phosphatase modulates this conversion. Methods and Research Pre/post-bypass serum samples were obtained from 75 infants <4 months of age. Serum conversion of 13C5-adenosine monophosphate to 13C5-adenosine was assessed with/without selective inhibition of alkaline phosphatase and CD73. Low and high concentration 13C5-adenosine monophosphate (simulating normal/stress concentrations) were used. Effects of alkaline phosphatase supplementation on adenosine monophosphate clearance were also assessed. Changes in serum alkaline phosphatase activity were strongly correlated with changes in 13C5-adenosine production with or without CD73 inhibition (r = 0.83; p<0.0001). Serum with low alkaline phosphatase activity (≤80 U/L) generated significantly less 13C5-adenosine, particularly in the presence of high concentration 13C5-adenosine monophosphate (10.4μmol/L vs 12.9μmol/L; p = 0.0004). Inhibition of alkaline phosphatase led to a marked decrease in 13C5-adenosine production (11.9μmol/L vs 2.7μmol/L; p<0.0001). Supplementation with physiologic dose human tissue non-specific alkaline phosphatase or high dose bovine intestinal alkaline phosphatase doubled 13C5-adenosine monophosphate conversion to 13C5-adenosine (p<0.0001). Conclusions Alkaline phosphatase represents the primary serum ectonucleotidase after infant cardiac surgery and low post

Alkaline Phosphatase, Soluble Extracellular Adenine Nucleotides, and Adenosine Production after Infant Cardiopulmonary Bypass.

PubMed

Davidson, Jesse A; Urban, Tracy; Tong, Suhong; Twite, Mark; Woodruff, Alan; Wischmeyer, Paul E; Klawitter, Jelena

2016-01-01

Decreased alkaline phosphatase activity after infant cardiac surgery is associated with increased post-operative cardiovascular support requirements. In adults undergoing coronary artery bypass grafting, alkaline phosphatase infusion may reduce inflammation. Mechanisms underlying these effects have not been explored but may include decreased conversion of extracellular adenine nucleotides to adenosine. 1) Evaluate the association between alkaline phosphatase activity and serum conversion of adenosine monophosphate to adenosine after infant cardiac surgery; 2) assess if inhibition/supplementation of serum alkaline phosphatase modulates this conversion. Pre/post-bypass serum samples were obtained from 75 infants <4 months of age. Serum conversion of 13C5-adenosine monophosphate to 13C5-adenosine was assessed with/without selective inhibition of alkaline phosphatase and CD73. Low and high concentration 13C5-adenosine monophosphate (simulating normal/stress concentrations) were used. Effects of alkaline phosphatase supplementation on adenosine monophosphate clearance were also assessed. Changes in serum alkaline phosphatase activity were strongly correlated with changes in 13C5-adenosine production with or without CD73 inhibition (r = 0.83; p<0.0001). Serum with low alkaline phosphatase activity (≤80 U/L) generated significantly less 13C5-adenosine, particularly in the presence of high concentration 13C5-adenosine monophosphate (10.4μmol/L vs 12.9μmol/L; p = 0.0004). Inhibition of alkaline phosphatase led to a marked decrease in 13C5-adenosine production (11.9μmol/L vs 2.7μmol/L; p<0.0001). Supplementation with physiologic dose human tissue non-specific alkaline phosphatase or high dose bovine intestinal alkaline phosphatase doubled 13C5-adenosine monophosphate conversion to 13C5-adenosine (p<0.0001). Alkaline phosphatase represents the primary serum ectonucleotidase after infant cardiac surgery and low post-operative alkaline phosphatase activity leads to

Insulin Restores Gestational Diabetes Mellitus–Reduced Adenosine Transport Involving Differential Expression of Insulin Receptor Isoforms in Human Umbilical Vein Endothelium

PubMed Central

Westermeier, Francisco; Salomón, Carlos; González, Marcelo; Puebla, Carlos; Guzmán-Gutiérrez, Enrique; Cifuentes, Fredi; Leiva, Andrea; Casanello, Paola; Sobrevia, Luis

2011-01-01

OBJECTIVE To determine whether insulin reverses gestational diabetes mellitus (GDM)–reduced expression and activity of human equilibrative nucleoside transporters 1 (hENT1) in human umbilical vein endothelium cells (HUVECs). RESEARCH DESIGN AND METHODS Primary cultured HUVECs from full-term normal (n = 44) and diet-treated GDM (n = 44) pregnancies were used. Insulin effect was assayed on hENT1 expression (protein, mRNA, SLC29A1 promoter activity) and activity (initial rates of adenosine transport) as well as endothelial nitric oxide (NO) synthase activity (serine1177 phosphorylation, l-citrulline formation). Adenosine concentration in culture medium and umbilical vein blood (high-performance liquid chromatography) as well as insulin receptor A and B expression (quantitative PCR) were determined. Reactivity of umbilical vein rings to adenosine and insulin was assayed by wire myography. Experiments were in the absence or presence of l-NG-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) or ZM-241385 (an A2A-adenosine receptor antagonist). RESULTS Umbilical vein blood adenosine concentration was higher, and the adenosine- and insulin-induced NO/endothelium-dependent umbilical vein relaxation was lower in GDM. Cells from GDM exhibited increased insulin receptor A isoform expression in addition to the reported NO–dependent inhibition of hENT1-adenosine transport and SLC29A1 reporter repression, and increased extracellular concentration of adenosine and NO synthase activity. Insulin reversed all these parameters to values in normal pregnancies, an effect blocked by ZM-241385 and l-NAME. CONCLUSIONS GDM and normal pregnancy HUVEC phenotypes are differentially responsive to insulin, a phenomenon where insulin acts as protecting factor for endothelial dysfunction characteristic of this syndrome. Abnormal adenosine plasma levels, and potentially A2A-adenosine receptors and insulin receptor A, will play crucial roles in this phenomenon in GDM. PMID:21515851

Insulin restores gestational diabetes mellitus-reduced adenosine transport involving differential expression of insulin receptor isoforms in human umbilical vein endothelium.

PubMed

Westermeier, Francisco; Salomón, Carlos; González, Marcelo; Puebla, Carlos; Guzmán-Gutiérrez, Enrique; Cifuentes, Fredi; Leiva, Andrea; Casanello, Paola; Sobrevia, Luis

2011-06-01

To determine whether insulin reverses gestational diabetes mellitus (GDM)-reduced expression and activity of human equilibrative nucleoside transporters 1 (hENT1) in human umbilical vein endothelium cells (HUVECs). Primary cultured HUVECs from full-term normal (n = 44) and diet-treated GDM (n = 44) pregnancies were used. Insulin effect was assayed on hENT1 expression (protein, mRNA, SLC29A1 promoter activity) and activity (initial rates of adenosine transport) as well as endothelial nitric oxide (NO) synthase activity (serine(1177) phosphorylation, l-citrulline formation). Adenosine concentration in culture medium and umbilical vein blood (high-performance liquid chromatography) as well as insulin receptor A and B expression (quantitative PCR) were determined. Reactivity of umbilical vein rings to adenosine and insulin was assayed by wire myography. Experiments were in the absence or presence of l-N(G)-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) or ZM-241385 (an A(2A)-adenosine receptor antagonist). Umbilical vein blood adenosine concentration was higher, and the adenosine- and insulin-induced NO/endothelium-dependent umbilical vein relaxation was lower in GDM. Cells from GDM exhibited increased insulin receptor A isoform expression in addition to the reported NO-dependent inhibition of hENT1-adenosine transport and SLC29A1 reporter repression, and increased extracellular concentration of adenosine and NO synthase activity. Insulin reversed all these parameters to values in normal pregnancies, an effect blocked by ZM-241385 and l-NAME. GDM and normal pregnancy HUVEC phenotypes are differentially responsive to insulin, a phenomenon where insulin acts as protecting factor for endothelial dysfunction characteristic of this syndrome. Abnormal adenosine plasma levels, and potentially A(2A)-adenosine receptors and insulin receptor A, will play crucial roles in this phenomenon in GDM.

The Role of Extracellular Adenosine Triphosphate in Ischemic Organ Injury.

PubMed

Zhao, Hailin; Kilgas, Susan; Alam, Azeem; Eguchi, Shiori; Ma, Daqing

2016-05-01

Ischemic tissue injury contributes to significant morbidity and mortality and is implicated in a range of pathologic conditions, including but not limited to myocardial infarction, ischemic stroke, and acute kidney injury. The associated reperfusion phase is responsible for the activation of the innate and adaptive immune system, further accentuating inflammation. Adenosine triphosphate molecule has been implicated in various ischemic conditions, including stroke and myocardial infarction. Adenosine triphosphate is a well-defined intracellular energy transfer and is commonly referred to as the body's "energy currency." However, Laboratory studies have demonstrated that extracellular adenosine triphosphate has the ability to initiate inflammation and is therefore referred to as a damage-associated molecular pattern. Purinergic receptors-dependent signaling, proinflammatory cytokine release, increased Ca influx into cells, and subsequent apoptosis have been shown to form a common underlying extracellular adenosine triphosphate molecular mechanism in ischemic organ injury. In this review, we aim to discuss the molecular mechanisms behind adenosine triphosphate-mediated ischemic tissue injury and evaluate the role of extracellular adenosine triphosphate in ischemic injury in specific organs, in order to provide a greater understanding of the pathophysiology of this complex process. We also appraise potential future therapeutic strategies to limit damage in various organs, including the heart, brain, kidneys, and lungs.

Evidence for an A2/Ra adenosine receptor in the guinea-pig trachea

PubMed Central

Brown, C.M.; Collis, M.G.

1982-01-01

1 An attempt was made to determine whether the extracellular adenosine receptor that mediates relaxation in the guinea-pig trachea is of the A1/Ri or A2/Ra subtype. 2 Dose-response curves to adenosine and a number of 5′- and N6-substituted analogues were constructed for the isolated guinea-pig trachea, contracted with carbachol. 3 The 5′-substituted analogues of adenosine were the most potent compounds tested, the order of potency being 5′-N-cyclopropylcarboxamide adenosine (NCPCA) > 5′-N-ethylcarboxamide adenosine (NECA) > 2-chloroadenosine > L-N6-phenylisopropyladenosine (L-PIA) > adenosine > D-N6-phenylisopropyladenosine (D-PIA). 4 The difference in potency between the stereoisomers D- and L-PIA on the isolated trachea was at the most five fold. 5 Responses to low doses of adenosine and its analogues were attenuated after treatment with either theophylline or 8-phenyltheophylline. The responses to 2-chloroadenosine were affected to a lesser extent than were those to the other purines. 6 Adenosine transport inhibitors, dipyridamole and dilazep, potentiated responses to adenosine, did not affect those to NCPCA, NECA, L-PIA and D-PIA but significantly reduced the responses to high doses of 2-chloroadenosine. 7 Relaxations evoked by 9-β-D-xylofuranosyladenosine which can activate intracellular but not extracellular adenosine receptors, were attenuated by dipyridamole but unaffected by 8-phenyltheophylline. 8 The results support the existence of an extracellular A2/Ra subtype of adenosine receptor and an intracellular purine-sensitive site, both of which mediate relaxation. PMID:6286021

The 2′,3′-cAMP-adenosine pathway

PubMed Central

2011-01-01

Our recent studies employing HPLC-tandem mass spectrometry to analyze venous perfusate from isolated, perfused kidneys demonstrate that intact kidneys produce and release into the extracellular compartment 2′,3′-cAMP, a positional isomer of the second messenger 3′,5′-cAMP. To our knowledge, this represents the first detection of 2′,3′-cAMP in any cell/tissue/organ/organism. Nuclear magnetic resonance experiments with isolated RNases and experiments in isolated, perfused kidneys suggest that 2′,3′-cAMP likely arises from RNase-mediated transphosphorylation of mRNA. Both in vitro and in vivo kidney experiments demonstrate that extracellular 2′,3′-cAMP is efficiently metabolized to 2′-AMP and 3′-AMP, both of which can be further metabolized to adenosine. This sequence of reactions is called the 2′,3′-cAMP-adenosine pathway (2′,3′-cAMP → 2′-AMP/3′-AMP → adenosine). Experiments in rat and mouse kidneys show that metabolic poisons increase extracellular levels of 2′,3′-cAMP, 2′-AMP, 3′-AMP, and adenosine; however, little is known regarding the pharmacology of 2′,3′-cAMP, 2′-AMP, and 3′-AMP. What is known is that 2′,3′-cAMP facilitates activation of mitochondrial permeability transition pores, a process that can lead to apoptosis and necrosis, and inhibits proliferation of vascular smooth muscle cells and glomerular mesangial cells. In summary, there is mounting evidence that at least some types of cellular injury, by triggering mRNA degradation, engage the 2′,3′-cAMP-adenosine pathway, and therefore this pathway should be added to the list of biochemical pathways that produce adenosine. Although speculative, it is possible that the 2′,3′-cAMP-adenosine pathway may protect against some forms of acute organ injury, for example acute kidney injury, by both removing an intracellular toxin (2′,3′-cAMP) and increasing an extracellular renoprotectant (adenosine). PMID:21937608

Molecular Evidence of Adenosine Deaminase Linking Adenosine A2A Receptor and CD26 Proteins

PubMed Central

Moreno, Estefanía; Canet, Júlia; Gracia, Eduard; Lluís, Carme; Mallol, Josefa; Canela, Enric I.; Cortés, Antoni; Casadó, Vicent

2018-01-01

Adenosine is an endogenous purine nucleoside that acts in all living systems as a homeostatic network regulator through many pathways, which are adenosine receptor (AR)-dependent and -independent. From a metabolic point of view, adenosine deaminase (ADA) is an essential protein in the regulation of the total intracellular and extracellular adenosine in a tissue. In addition to its cytosolic localization, ADA is also expressed as an ecto-enzyme on the surface of different cells. Dipeptidyl peptidase IV (CD26) and some ARs act as binding proteins for extracellular ADA in humans. Since CD26 and ARs interact with ADA at opposite sites, we have investigated if ADA can function as a cell-to-cell communication molecule by bridging the anchoring molecules CD26 and A2AR present on the surfaces of the interacting cells. By combining site-directed mutagenesis of ADA amino acids involved in binding to A2AR and a modification of the bioluminescence resonance energy transfer (BRET) technique that allows detection of interactions between two proteins expressed in different cell populations with low steric hindrance (NanoBRET), we show direct evidence of the specific formation of trimeric complexes CD26-ADA-A2AR involving two cells. By dynamic mass redistribution assays and ligand binding experiments, we also demonstrate that A2AR-NanoLuc fusion proteins are functional. The existence of this ternary complex is in good agreement with the hypothesis that ADA could bridge T-cells (expressing CD26) and dendritic cells (expressing A2AR). This is a new metabolic function for ecto-ADA that, being a single chain protein, it has been considered as an example of moonlighting protein, because it performs more than one functional role (as a catalyst, a costimulator, an allosteric modulator and a cell-to-cell connector) without partitioning these functions in different subunits. PMID:29497379

Molecular Evidence of Adenosine Deaminase Linking Adenosine A2A Receptor and CD26 Proteins.

PubMed

Moreno, Estefanía; Canet, Júlia; Gracia, Eduard; Lluís, Carme; Mallol, Josefa; Canela, Enric I; Cortés, Antoni; Casadó, Vicent

2018-01-01

Adenosine is an endogenous purine nucleoside that acts in all living systems as a homeostatic network regulator through many pathways, which are adenosine receptor (AR)-dependent and -independent. From a metabolic point of view, adenosine deaminase (ADA) is an essential protein in the regulation of the total intracellular and extracellular adenosine in a tissue. In addition to its cytosolic localization, ADA is also expressed as an ecto-enzyme on the surface of different cells. Dipeptidyl peptidase IV (CD26) and some ARs act as binding proteins for extracellular ADA in humans. Since CD26 and ARs interact with ADA at opposite sites, we have investigated if ADA can function as a cell-to-cell communication molecule by bridging the anchoring molecules CD26 and A 2A R present on the surfaces of the interacting cells. By combining site-directed mutagenesis of ADA amino acids involved in binding to A 2A R and a modification of the bioluminescence resonance energy transfer (BRET) technique that allows detection of interactions between two proteins expressed in different cell populations with low steric hindrance (NanoBRET), we show direct evidence of the specific formation of trimeric complexes CD26-ADA-A 2A R involving two cells. By dynamic mass redistribution assays and ligand binding experiments, we also demonstrate that A 2A R-NanoLuc fusion proteins are functional. The existence of this ternary complex is in good agreement with the hypothesis that ADA could bridge T-cells (expressing CD26) and dendritic cells (expressing A 2A R). This is a new metabolic function for ecto-ADA that, being a single chain protein, it has been considered as an example of moonlighting protein, because it performs more than one functional role (as a catalyst, a costimulator, an allosteric modulator and a cell-to-cell connector) without partitioning these functions in different subunits.

Cloning and Immunocytochemical Localization of a Cyclic Nucleotide–Gated Channel α-Subunit to All Cone Photoreceptors in the Mouse Retina

PubMed Central

HIRANO, ARLENE A.; HACK, IRIS; WÄSSLE, HEINZ; DUVOISIN, ROBERT M.

2010-01-01

Cyclic nucleotide–gated channels (CNGC) are ligand-gated ion channels that open and close in response to changes in the intracellular concentration of the second messengers, 3′,5′-cyclic adenosine monophosphate and 3′,5′-cyclic guanosine monophosphate. Most notably, they transduce the chemical signal produced by the absorption of light in photoreceptors into a membrane potential change, which is then transmitted to the ascending visual pathway. CNGCs have also been implicated in the signal transduction of other neurons downstream of the photoreceptors, in particular the ON-bipolar cells, as well as in other areas of the central nervous system. We therefore undertook a search for additional cyclic nucleotide–gated channels expressed in the retina. Following a degenerate reverse transcription polymerase chain reaction approach to amplify low-copy number messages, a cDNA encoding a new splice variant of CNGC α-subunit was isolated from mouse retina and classified as mCNG3. An antiserum raised against the carboxy-terminal sequence identified the retinal cell type expressing mCNG3 as cone photoreceptors. Preembedding immunoelectron microscopy demonstrated its membrane localization in the outer segments, consistent with its role in phototransduction. Double-labeling experiments with cone-specific markers indicated that all cone photoreceptors in the murid retina use the same or a highly conserved cyclic nucleotide–gated channel. Therefore, defects in this channel would be predicted to severely impair photopic vision. PMID:10813773

Opiate-induced Changes in Brain Adenosine Levels and Narcotic Drug Responses

PubMed Central

Wu, Manhong; Sahbaie, Peyman; Zheng, Ming; Lobato, Robert; Boison, Detlev; Clark, J. David; Peltz, Gary

2012-01-01

We have very little information about the metabolomic changes that mediate neurobehavioral responses, including addiction. It was possible that opioid-induced metabolomic changes in brain could mediate some of the pharmacodynamic effects of opioids. To investigate this, opiate-induced brain metabolomic responses were profiled using a semi-targeted method in C57BL/6 and 129Sv1 mice, which exhibit extreme differences in their tendency to become opiate dependent. Escalating morphine doses (10–40 mg/kg) administered over a 4-day period selectively induced a two-fold decrease (p<0.00005) in adenosine abundance in the brainstem of C57BL/6 mice, which exhibited symptoms of narcotic drug dependence; but did not decrease adenosine abundance in 129Sv1 mice, which do not exhibit symptoms of dependence. Based on this finding, the effect of adenosine on dependence was investigated in genetically engineered mice with alterations in adenosine tone in the brain and in pharmacologic experiments. Morphine withdrawal behaviors were significantly diminished (P<0.0004) in genetically engineered mice with reduced adenosine tone in the brainstem, and by treatment with an adenosine receptor1 (A1) agonist (2-chloro-N6-cyclopentyladenosine, 0.5 mg/kg) or an A2a receptor (A2a) antagonist (SCH 58261 1 mg/kg). These results indicate that adenosine homeostasis plays a crucial role in narcotic drug responses. Opiate-induced changes in brain adenosine levels may explain many important neurobehavioral features associated with opiate addiction and withdrawal. PMID:23098802

Systemic Adenosine Triphosphate Impairs Neutrophil Chemotaxis and Host Defense in Sepsis.

PubMed

Li, Xiaoou; Kondo, Yutaka; Bao, Yi; Staudenmaier, Laura; Lee, Albert; Zhang, Jingping; Ledderose, Carola; Junger, Wolfgang G

2017-01-01

Sepsis remains an unresolved clinical problem. Therapeutic strategies focusing on inhibition of neutrophils (polymorphonuclear neutrophils) have failed, which indicates that a more detailed understanding of the underlying pathophysiology of sepsis is required. Polymorphonuclear neutrophil activation and chemotaxis require cellular adenosine triphosphate release via pannexin-1 channels that fuel autocrine feedback via purinergic receptors. In the current study, we examined the roles of endogenous and systemic adenosine triphosphate on polymorphonuclear neutrophil activation and host defense in sepsis. Prospective randomized animal investigation and in vitro studies. Preclinical academic research laboratory. Wild-type C57BL/6 mice, pannexin-1 knockout mice, and healthy human subjects used to obtain polymorphonuclear neutrophils for in vitro studies. Wild-type and pannexin-1 knockout mice were treated with suramin or apyrase to block the endogenous or systemic effects of adenosine triphosphate. Mice were subjected to cecal ligation and puncture and polymorphonuclear neutrophil activation (CD11b integrin expression), organ (liver) injury (plasma aspartate aminotransferase), bacterial spread, and survival were monitored. Human polymorphonuclear neutrophils were used to study the effect of systemic adenosine triphosphate and apyrase on chemotaxis. Inhibiting endogenous adenosine triphosphate reduced polymorphonuclear neutrophil activation and organ injury, but increased the spread of bacteria and mortality in sepsis. By contrast, removal of systemic adenosine triphosphate improved bacterial clearance and survival in sepsis by improving polymorphonuclear neutrophil chemotaxis. Systemic adenosine triphosphate impairs polymorphonuclear neutrophil functions by disrupting the endogenous purinergic signaling mechanisms that regulate cell activation and chemotaxis. Removal of systemic adenosine triphosphate improves polymorphonuclear neutrophil function and host defenses

Erythrocytic Adenosine Monophosphate as an Alternative Purine Source in Plasmodium falciparum*

PubMed Central

Cassera, María B.; Hazleton, Keith Z.; Riegelhaupt, Paul M.; Merino, Emilio F.; Luo, Minkui; Akabas, Myles H.; Schramm, Vern L.

2008-01-01

Plasmodium falciparum is a purine auxotroph, salvaging purines from erythrocytes for synthesis of RNA and DNA. Hypoxanthine is the key precursor for purine metabolism in Plasmodium. Inhibition of hypoxanthine-forming reactions in both erythrocytes and parasites is lethal to cultured P. falciparum. We observed that high concentrations of adenosine can rescue cultured parasites from purine nucleoside phosphorylase and adenosine deaminase blockade but not when erythrocyte adenosine kinase is also inhibited. P. falciparum lacks adenosine kinase but can salvage AMP synthesized in the erythrocyte cytoplasm to provide purines when both human and Plasmodium purine nucleoside phosphorylases and adenosine deaminases are inhibited. Transport studies in Xenopus laevis oocytes expressing the P. falciparum nucleoside transporter PfNT1 established that this transporter does not transport AMP. These metabolic patterns establish the existence of a novel nucleoside monophosphate transport pathway in P. falciparum. PMID:18799466

Erythrocytic adenosine monophosphate as an alternative purine source in Plasmodium falciparum.

PubMed

Cassera, María B; Hazleton, Keith Z; Riegelhaupt, Paul M; Merino, Emilio F; Luo, Minkui; Akabas, Myles H; Schramm, Vern L

2008-11-21

Plasmodium falciparum is a purine auxotroph, salvaging purines from erythrocytes for synthesis of RNA and DNA. Hypoxanthine is the key precursor for purine metabolism in Plasmodium. Inhibition of hypoxanthine-forming reactions in both erythrocytes and parasites is lethal to cultured P. falciparum. We observed that high concentrations of adenosine can rescue cultured parasites from purine nucleoside phosphorylase and adenosine deaminase blockade but not when erythrocyte adenosine kinase is also inhibited. P. falciparum lacks adenosine kinase but can salvage AMP synthesized in the erythrocyte cytoplasm to provide purines when both human and Plasmodium purine nucleoside phosphorylases and adenosine deaminases are inhibited. Transport studies in Xenopus laevis oocytes expressing the P. falciparum nucleoside transporter PfNT1 established that this transporter does not transport AMP. These metabolic patterns establish the existence of a novel nucleoside monophosphate transport pathway in P. falciparum.

Purification and properties of adenosine kinase from rat brain.

PubMed

Yamada, Y; Goto, H; Ogasawara, N

1980-12-04

Adenosine kinase (ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20) has been purified to apparent homogeneity from rat brain by (NH4)2SO4 fractionation, affinity chromatography on AMP-Sepharose 4B, gel filtration with Sephadex G-100, and DE-52 cellulose column chromatography. The yield was 56% of the initial activity with a final specific activity of 7.8 mumol/min per mg protein. The molecular weight was estimated as 38 000 by gel filtration with Sephadex G-100 and 41 000 by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS). The enzyme catalyzed the phosphorylation of adenosine, deoxyadenosine, arabinoadenosine, inosine and ribavirin. The activity of deoxyadenosine phosphorylation was 20% that of adenosine phosphorylation. The pH optimum profile was biphasic; a sharp pH optimum at pH 5.5 and a broad pH optimum at pH 7.5-8.5. The Km value for adenosine was 0.2 microM and the maximum activity was observed at 0.5 microM. At higher concentrations of adenosine, the activity was strongly inhibited. The Km value for ATP was 0.02 mM and that for Mg2+ was 0.1 mM. GTP, dGTP, dATP and UTP were also proved to be effective phosphate donors. Co2+ was as effective as Mg2+, and Ca2+, Mn2+ or Ni2+ showed about 50% of the activity for Mg2+. The kinase is quite unstable, but stable in the presence of a high concentration of salt; e.g., 0.15 M KCl.

[High performance liquid chromatogram (HPLC) determination of adenosine phosphates in rat myocardium].

PubMed

Miao, Yu; Wang, Cheng-long; Yin, Hui-jun; Shi, Da-zhuo; Chen, Ke-ji

2005-04-18

To establish method for the quantitative determination of adenosine phosphates in rat myocardium by optimized high performance liquid chromatogram (HPLC). ODS HYPERSIL C(18) column and a mobile phase of 50 mmol/L tribasic potassium phosphate buffer solution (pH 6.5), with UV detector at 254 nm were used. The average recovery rates of myocardial adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) were 99%-107%, 96%-104% and 95%-119%, respectively; relative standard deviations (RSDs) of within-day and between-days were less than 1.5% and 5.1%, respectively. The method is simple, rapid and accurate, and can be used to analyse the adenosine phosphates in myocardium.

Factors influencing breeding success, ovarian cyclicity, and cub survival in zoo-managed tigers (Panthera tigris).

PubMed

Saunders, Sarah P; Harris, Tara; Traylor-Holzer, Kathy; Beck, Karen Goodrowe

2014-01-10

Understanding factors that influence reproduction and offspring survival in zoo populations is critical for management of threatened and endangered species. Examination of long-term data (1989-2011) compiled from the Association of Zoos and Aquarium's zoo-managed tiger breeding program provides the basis for a more thorough understanding of reproduction and scientifically based decisions for effective population management in this endangered felid. Biological and management-related factors that could influence tiger breeding success and cub survival were evaluated using logistic mixed models. Breeding success improved with female age until approximately age five, then declined thereafter. Experienced female breeders had greater breeding success than inexperienced females. Litter size was most predictive of cub survival, with average-sized litters (3-4 cubs) experiencing the highest proportional survival. Management-related factors, such as whether the breeding institution had a recent tiger litter and whether both animals were already located at the same institution, also influenced breeding success and cub survival. These results highlight the importance of institutional husbandry experience and the need to retain knowledge through staff turnovers to achieve optimal reproductive success. Using fecal estrogen data, frequency of ovarian cyclicity and mean cycle length did not differ by female age or parity; thus, lack of cyclicity and/or increased cycle duration are not likely explanations for declining breeding success with age. These results provide valuable reproductive information that should improve scientific management of zoo-based tiger populations. Copyright © 2013 Elsevier B.V. All rights reserved.

Adenosine-Induced Atrial Fibrillation: Localized Reentrant Drivers in Lateral Right Atria due to Heterogeneous Expression of Adenosine A1 Receptors and GIRK4 Subunits in the Human Heart

PubMed Central

Li, Ning; Csepe, Thomas A.; Hansen, Brian J.; Sul, Lidiya V.; Kalyanasundaram, Anuradha; Zakharkin, Stanislav O.; Zhao, Jichao; Guha, Avirup; Van Wagoner, David R.; Kilic, Ahmet; Mohler, Peter J; Janssen, Paul ML; Biesiadecki, Brandon; Hummel, John D; Weiss, Raul; Fedorov, Vadim V.

2016-01-01

Background Adenosine provokes atrial fibrillation (AF) with a higher activation frequency in right atria (RA) versus left atria (LA) in patients, but the underlying molecular and functional substrates are unclear. We tested the hypothesis that adenosine-induced AF is driven by localized reentry in RA areas with highest expression of adenosine A1 receptor (A1R) and its downstream GIRK channels (IK,Ado). Methods We applied bi-atrial optical mapping and immunoblot mapping of various atrial regions to reveal the mechanism of adenosine-induced AF in explanted failing and non-failing human hearts (n=37). Results Optical mapping of coronary-perfused atria (n=24) revealed that adenosine perfusion (10–100μM) produced more significant shortening of action potential durations (APD80) in RA (from 290±45ms to 239±41ms, 17.3±10.4%; p<0.01) than LA (from 307±24ms to 286±23ms, 6.7±6.6%; p<0.01). In ten hearts, adenosine induced AF (317±116 sec) that, when sustained (≥2 min), was primarily maintained by one/two localized reentrant drivers in lateral RA. Tertiapin (10–100nM), a selective GIRK channel blocker, counteracted adenosine-induced APD shortening and prevented AF induction. Immunoblotting showed that the superior/middle lateral RA had significantly higher A1R (2.7±1.7 fold; p<0.01) and GIRK4 (1.7±0.8 fold; p<0.05) protein expression than lateral/posterior LA. Conclusions This study revealed a three-fold RA-to-LA A1R protein expression gradient in the human heart, leading to significantly greater RA vs. LA repolarization sensitivity in response to adenosine. Sustained adenosine-induced AF is maintained by reentrant drivers localized in lateral RA regions with the highest A1R/GIRK4 expression. Selective atrial GIRK channel blockade may effectively treat AF during conditions with increased endogenous adenosine. PMID:27462069

Treatment of out-of-hospital supraventricular tachycardia: adenosine vs verapamil.

PubMed

Brady, W J; DeBehnke, D J; Wickman, L L; Lindbeck, G

1996-06-01

To compare the use of adenosine and the use of verapamil as out-of-hospital therapy for supraventricular tachycardia (SVT). A period of prospective adenosine use (March 1993 to February 1994) was compared with a historical control period of verapamil use (March 1990 to February 1991) for SVT. Data were obtained for SVT patients treated in a metropolitan, fire-department-based paramedic system serving a population of approximately 1 million persons. Standard drug protocols were used and patient outcomes (i.e., conversion rates, complications, and recurrences) were monitored. During the adenosine treatment period, 105 patients had SVT; 87 (83%) received adenosine, of whom 60 (69%) converted to a sinus rhythm (SR). Vagal maneuvers (VM) resulted in restoration of SR in 8 patients (7.6%). Some patients received adenosine for non-SVT rhythms: 7 sinus tachycardia, 18 atrial fibrilation, 7 wide-complex tachycardia (WCT), and 2 ventricular tachycardia; no non-SVT rhythm converted to SR and none of these patients experienced an adverse effect. Twenty-five patients were hemodynamically unstable (systolic blood pressure < 90 mm Hg), with 20 receiving drug and 13 converting to SR; 8 patients required electrical cardioversion. Four patients experienced adverse effects related to adenosine (chest pain dyspnea, prolonged bradycardia, and ventricular tachycardia). In the verapamil period, 106 patients had SVT: 52 (49%) received verapamil (p < 0.001, compared with the adenosine period), of whom 43 (88%) converted to SR (p = 0.11). Two patients received verapamil for WCT; neither converted to SR and both experienced cardiovascular collapse. VM resulted in restoration of SR in 12 patients (11.0%) (p = 0.52). Sixteen patients were hemodynamically unstable, with 5 receiving drug (p = 0.005) and 5 converting to SR; 9 patients required electrical cardioversion (p = 0.48). Four patients experienced adverse effects related to verapamil (hypotension ventricular tachycardia, ventricular

Chronic hypoxia up-regulates expression of adenosine A1 receptors in DDT1-MF2 cells.

PubMed

Hammond, Lucy C; Bonnet, Claire; Kemp, Paul J; Yates, Michael S; Bowmer, Christopher J

2004-02-01

As the first step to understand how chronic hypoxia might regulate smooth muscle function in health and disease, we have employed an established immortalised cell model of smooth muscle, DDT1-MF2 cells, to address the hypothesis that adenosine A1 receptor density is modulated by O2 availability. Maximal specific binding (Bmax) of the selective adenosine A1 receptor antagonist, [3H]-DPCPX, to cell membranes increased 3.5-fold from 0.48 +/- 0.02 pmol/mg to 1.7 +/- 0.5 pmol/mg protein after 16 hr of hypoxia and this effect was not accompanied by any statistically significant changes in either binding affinity (0.84 +/- 0.2 nM vs. 1.2 +/- 0.3 nM) or Hill coefficient (1.1 +/- 0.1 vs. 0.99 +/- 0.03). Hypoxia-evoked increases in membrane receptor density were paralleled in intact DDT1-MF2 cells. In addition, the increase in [3H]-DPCPX binding to intact cells was inhibited by co-incubation during hypoxia with the translational inhibitor cycloheximide, the transcriptional blocker actinomycin D and the NFkappaB inhibitor sulphasalazine. Together, these data show that adenosine A1 receptor density is modulated, at least in part, by O2-dependent activation of the transcription factor NFkappaB and adds to the list of processes dynamically regulated by ambient oxygen availability. Since hypoxia is an initiating factor in acute renal failure, similar changes in transcription may account for up-regulation of adenosine A1 receptors noted previously in the renal vasculature of rats with acute renal failure.

Astrocyte-derived adenosine is central to the hypnogenic effect of glucose

PubMed Central

Scharbarg, Emeric; Daenens, Marion; Lemaître, Frédéric; Geoffroy, Hélène; Guille-Collignon, Manon; Gallopin, Thierry; Rancillac, Armelle

2016-01-01

Sleep has been hypothesised to maintain a close relationship with metabolism. Here we focus on the brain structure that triggers slow-wave sleep, the ventrolateral preoptic nucleus (VLPO), to explore the cellular and molecular signalling pathways recruited by an increase in glucose concentration. We used infrared videomicroscopy on ex vivo brain slices to establish that glucose induces vasodilations specifically in the VLPO via the astrocytic release of adenosine. Real-time detection by in situ purine biosensors further revealed that the adenosine level doubles in response to glucose, and triples during the wakefulness period. Finally, patch-clamp recordings uncovered the depolarizing effect of adenosine and its A2A receptor agonist, CGS-21680, on sleep-promoting VLPO neurons. Altogether, our results provide new insights into the metabolically driven release of adenosine. We hypothesise that adenosine adjusts the local energy supply to local neuronal activity in response to glucose. This pathway could contribute to sleep-wake transition and sleep intensity. PMID:26755200

Adenosine deaminase from Streptomyces coelicolor: recombinant expression, purification and characterization.

PubMed

Pornbanlualap, Somchai; Chalopagorn, Pornchanok

2011-08-01

The sequencing of the genome of Streptomyces coelicolor A3(2) identified seven putative adenine/adenosine deaminases and adenosine deaminase-like proteins, none of which have been biochemically characterized. This report describes recombinant expression, purification and characterization of SCO4901 which had been annotated in data bases as a putative adenosine deaminase. The purified putative adenosine deaminase gives a subunit Mr=48,400 on denaturing gel electrophoresis and an oligomer molecular weight of approximately 182,000 by comparative gel filtration. These values are consistent with the active enzyme being composed of four subunits with identical molecular weights. The turnover rate of adenosine is 11.5 s⁻¹ at 30 °C. Since adenine is deaminated ∼10³ slower by the enzyme when compared to that of adenosine, these data strongly show that the purified enzyme is an adenosine deaminase (ADA) and not an adenine deaminase (ADE). Other adenine nucleosides/nucleotides, including 9-β-D-arabinofuranosyl-adenine (ara-A), 5'-AMP, 5'-ADP and 5'-ATP, are not substrates for the enzyme. Coformycin and 2'-deoxycoformycin are potent competitive inhibitors of the enzyme with inhibition constants of 0.25 and 3.4 nM, respectively. Amino acid sequence alignment of ScADA with ADAs from other organisms reveals that eight of the nine highly conserved catalytic site residues in other ADAs are also conserved in ScADA. The only non-conserved residue is Asn317, which replaces Asp296 in the murine enzyme. Based on these data, it is suggested here that ADA and ADE proteins are divergently related enzymes that have evolved from a common α/β barrel scaffold to catalyze the deamination of different substrates, using a similar catalytic mechanism. Copyright © 2011 Elsevier Inc. All rights reserved.

Oral tremor induced by the muscarinic agonist pilocarpine is suppressed by the adenosine A2A antagonists MSX-3 and SCH58261, but not the adenosine A1 antagonist DPCPX.

PubMed

Collins, Lyndsey E; Galtieri, Daniel J; Brennum, Lise T; Sager, Thomas N; Hockemeyer, Jörg; Müller, Christa E; Hinman, James R; Chrobak, James J; Salamone, John D

2010-02-01

Tremulous jaw movements in rats, which can be induced by dopamine (DA) antagonists, DA depletion, and cholinomimetics, have served as a useful model for studies of tremor. Although adenosine A(2A) antagonists can reduce the tremulous jaw movements induced by DA antagonists and DA depletion, there are conflicting reports about the interaction between adenosine antagonists and cholinomimetic drugs. The present studies investigated the ability of adenosine antagonists to reverse the tremorogenic effect of the muscarinic agonist pilocarpine. While the adenosine A(2A) antagonist MSX-3 was incapable of reversing the tremulous jaw movements induced by the 4.0mg/kg dose of pilocarpine, both MSX-3 and the adenosine A(2A) antagonist SCH58261 reversed the tremulous jaw movements elicited by 0.5mg/kg pilocarpine. Systemic administration of the adenosine A(1) antagonist DPCPX failed to reverse the tremulous jaw movements induced by either an acute 0.5mg/kg dose of the cholinomimetic pilocarpine or the DA D2 antagonist pimozide, indicating that the tremorolytic effects of adenosine antagonists may be receptor subtype specific. Behaviorally active doses of MSX-3 and SCH 58261 showed substantial in vivo occupancy of A(2A) receptors, but DPCPX did not. The results of these studies support the use of adenosine A(2A) antagonists for the treatment of tremor. Copyright 2009 Elsevier Inc. All rights reserved.

[Effects of dopamine and adenosine on regulation of water-electrolyte exchange in Amoeba proteus].

PubMed

Bagrov, Ia Iu; Manusova, N B

2014-01-01

Dopamine and adenosine both regulate transport of sodium chloride in the renal tubules in mammals. We have studied the effect of dopamine and adenosine on spontaneous activity of contractile vacuole of Amoeba proteous. Both substances stimulated contractile vacuole. The effect of dopamine was suppressed by D2 receptor antagonist, haloperidol, but not by D1 antagonist, SCH 39166. Adenylate cyclase inhibitor, 2.5-dideoxyadenosine, suppressed the effect of dopamine, but not of adenosine. Inhibitor of protein kinase C, staurosporine, in contrast, blocked the effect of adenosine, but not dopamine. Notably, dopamine opposed effect of adenosine and vice versa. These results suggest that similar effects of dopamine and adenosine could be mediated by different intracellulare mechanisms.

A novel mouse model for sudden unexpected death in epilepsy (SUDEP): role of impaired adenosine clearance.

PubMed

Shen, Hai-Ying; Li, Tianfu; Boison, Detlev

2010-03-01

Sudden unexpected death in epilepsy (SUDEP) is a significant cause of mortality in people with epilepsy. Two postulated causes for SUDEP, cardiac and respiratory depression, can both be explained by overstimulation of adenosine receptors. We hypothesized that SUDEP is a consequence of a surge in adenosine as a result of prolonged seizures combined with deficient adenosine clearance; consequently, blockade of adenosine receptors should prevent SUDEP. Here we induced impaired adenosine clearance in adult mice by pharmacologic inhibition of the adenosine-removing enzymes, adenosine kinase and deaminase. Combination of impaired adenosine clearance with kainic acid-induced seizures triggered sudden death in all animals. Most importantly, the adenosine receptor antagonist caffeine, when given after seizure onset, increased survival from 23.75 +/- 1.35 min to 54.86 +/- 6.59 min (p < 0.01). Our data indicate that SUDEP is due to overactivation of adenosine receptors and that caffeine treatment after seizure onset might be beneficial.

A2B Adenosine Receptor–Mediated Induction of IL-6 Promotes CKD

PubMed Central

Dai, Yingbo; Zhang, Weiru; Wen, Jiaming; Zhang, Yujin; Kellems, Rodney E.

2011-01-01

Chronic elevation of adenosine, which occurs in the setting of repeated or prolonged tissue injury, can exacerbate cellular dysfunction, suggesting that it may contribute to the pathogenesis of CKD. Here, mice with chronically elevated levels of adenosine, resulting from a deficiency in adenosine deaminase (ADA), developed renal dysfunction and fibrosis. Both the administration of polyethylene glycol–modified ADA to reduce adenosine levels and the inhibition of the A2B adenosine receptor (A2BR) attenuated renal fibrosis and dysfunction. Furthermore, activation of A2BR promoted renal fibrosis in both mice infused with angiotensin II (Ang II) and mice subjected to unilateral ureteral obstruction (UUO). These three mouse models shared a similar profile of profibrotic gene expression in kidney tissue, suggesting that they share similar signaling pathways that lead to renal fibrosis. Finally, both genetic and pharmacologic approaches showed that the inflammatory cytokine IL-6 mediates adenosine-induced renal fibrosis downstream of A2BR. Taken together, these data suggest that A2BR-mediated induction of IL-6 contributes to renal fibrogenesis and shows potential therapeutic targets for CKD. PMID:21511827

Modulation of bicarbonate secretion in rabbit duodenum: the role of calcium.

PubMed

Hogan, D L; Yao, B; Isenberg, J I

1998-01-01

Surface epithelial bicarbonate secretion protects the proximal duodenum from acid peptic injury. Cyclic adenosine monophosphate and calcium serve as intracellular mediators of intestinal transport. Experiments were performed to examine whether calcium participates in duodenal bicarbonate transport. Stripped duodenal mucosa from rabbits was studied in Ussing chambers. HCO3- transport was stimulated by the calcium ionophore A23187, carbachol, vasoactive intestinal peptide, prostaglandin E2, dibutyryl-cyclic adenosine monophosphate, and electrical field stimulation. A23187 stimulated HCO3- secretion and Isc; tetrodotoxin failed to inhibit this effect. The calcium-channel blocker verapamil abolished HCO3- secretion stimulated by carbachol, vasoactive intestinal peptide, and electrical field stimulation, but failed to alter basal, prostaglandin E2- or dibutyryl-cyclic adenosine monophosphate-stimulated HCO3- secretion. Therefore, calcium is likely required during stimulation of duodenal epithelial HCO3- transport by carbachol, vasoactive intestinal peptide, and electrical field stimulation. Prostaglandin E2 and dibutyryl-cyclic adenosine monophosphate appear to activate duodenal HCO3- secretion by a calcium-independent pathway(s).

Elevated Adenosine Induces Placental DNA Hypomethylation Independent of A2B Receptor Signaling in Preeclampsia.

PubMed

Huang, Aji; Wu, Hongyu; Iriyama, Takayuki; Zhang, Yujin; Sun, Kaiqi; Song, Anren; Liu, Hong; Peng, Zhangzhe; Tang, Lili; Lee, Minjung; Huang, Yun; Ni, Xin; Kellems, Rodney E; Xia, Yang

2017-07-01

Preeclampsia is a prevalent pregnancy hypertensive disease with both maternal and fetal morbidity and mortality. Emerging evidence indicates that global placental DNA hypomethylation is observed in patients with preeclampsia and is linked to altered gene expression and disease development. However, the molecular basis underlying placental epigenetic changes in preeclampsia remains unclear. Using 2 independent experimental models of preeclampsia, adenosine deaminase-deficient mice and a pathogenic autoantibody-induced mouse model of preeclampsia, we demonstrate that elevated placental adenosine not only induces hallmark features of preeclampsia but also causes placental DNA hypomethylation. The use of genetic approaches to express an adenosine deaminase minigene specifically in placentas, or adenosine deaminase enzyme replacement therapy, restored placental adenosine to normal levels, attenuated preeclampsia features, and abolished placental DNA hypomethylation in adenosine deaminase-deficient mice. Genetic deletion of CD73 (an ectonucleotidase that converts AMP to adenosine) prevented the elevation of placental adenosine in the autoantibody-induced preeclampsia mouse model and ameliorated preeclampsia features and placental DNA hypomethylation. Immunohistochemical studies revealed that elevated placental adenosine-mediated DNA hypomethylation predominantly occurs in spongiotrophoblasts and labyrinthine trophoblasts and that this effect is independent of A2B adenosine receptor activation in both preeclampsia models. Extending our mouse findings to humans, we used cultured human trophoblasts to demonstrate that adenosine functions intracellularly and induces DNA hypomethylation without A2B adenosine receptor activation. Altogether, both mouse and human studies reveal novel mechanisms underlying placental DNA hypomethylation and potential therapeutic approaches for preeclampsia. © 2017 American Heart Association, Inc.

Why do premature newborn infants display elevated blood adenosine levels?

PubMed

Panfoli, Isabella; Cassanello, Michela; Bruschettini, Matteo; Colella, Marina; Cerone, Roberto; Ravera, Silvia; Calzia, Daniela; Candiano, Giovanni; Ramenghi, Luca

2016-05-01

Our preliminary data show high levels of adenosine in the blood of very low birth weight (VLBW) infants, positively correlating to their prematurity (i.e. body weight class). This prompted us to look for a mechanism promoting such impressive adenosine increase. We hypothesized a correlation with oxygen challenge. In fact, it is recognized that either oxygen lack or its excess contribute to the pathogenesis of the injuries of prematurity, such as retinopathy (ROP) and periventricular white matter lesions (PWMI). The optimal concentration of oxygen for resuscitation of VLBW infants is currently under revision. We propose that the elevated adenosine blood concentrations of VLBW infants recognizes two sources. The first could be its activity-dependent release from unmyelinated brain axons. Adenosine in this respect would be an end-product of the hypometabolic VLBW newborn unmyelinated axon intensely firing in response to the environmental stimuli consequent to premature birth. Adenosine would be eventually found in the blood due to blood-brain barrier immaturity. In fact, adenosine is the primary activity-dependent signal promoting differentiation of premyelinating oligodendrocyte progenitor cells (OPC) into myelinating cells in the Central Nervous System, while inhibiting their proliferation and inhibiting synaptic function. The second, would be the ecto-cellular ATP synthesized by the endothelial cell plasmalemma exposed to ambient oxygen concentrations due to premature breathing, especially in lung. ATP would be rapidly transformed into adenosine by the ectonucleotidase activities such as NTPDase I (CD39), and NT5E (CD73). An ectopic extra-mitochondrial aerobic ATP synthetic ability was reported in many cell plasma-membranes, among which endothelial cells. The potential implications of the cited hypotheses for the neonatology area would be great. The amount of oxygen administration for reviving of newborns would find a molecular basis for its assessment. VLBW

Effect of adenosine on the growth of human T-lymphocyte leukemia cell line MOLT-4.

PubMed

Streitová, Denisa; Weiterová, Lenka; Hofer, Michal; Holá, Jirina; Horváth, Viktor; Kozubík, Alois; Znojil, Vladimír

2007-09-01

Adenosine has been observed to suppress the growth of MOLT-4 human leukemia cells in vitro. Changes in the cell cycle, especially increased percentage of cells in S phase, prolonged generation time, and induction of apoptosis at higher adenosine concentrations have been found to be responsible for the growth suppression. Dipyridamole, a drug inhibiting the cellular uptake of adenosine, reversed partially but significantly the adenosine-induced growth suppression. It follows from these results that the action of adenosine on the MOLT-4 cells comprises its cellular uptake and intracellular operation. These findings present new data on anticancer efficacy of adenosine.

Impact of Hyperpolarization-activated, Cyclic Nucleotide-gated Cation Channel Type 2 for the Xenon-mediated Anesthetic Effect: Evidence from In Vitro and In Vivo Experiments.

PubMed

Mattusch, Corinna; Kratzer, Stephan; Buerge, Martina; Kreuzer, Matthias; Engel, Tatiana; Kopp, Claudia; Biel, Martin; Hammelmann, Verena; Ying, Shui-Wang; Goldstein, Peter A; Kochs, Eberhard; Haseneder, Rainer; Rammes, Gerhard

2015-05-01

The thalamus is thought to be crucially involved in the anesthetic state. Here, we investigated the effect of the inhaled anesthetic xenon on stimulus-evoked thalamocortical network activity and on excitability of thalamocortical neurons. Because hyperpolarization-activated, cyclic nucleotide-gated cation (HCN) channels are key regulators of neuronal excitability in the thalamus, the effect of xenon on HCN channels was examined. The effects of xenon on thalamocortical network activity were investigated in acutely prepared brain slices from adult wild-type and HCN2 knockout mice by means of voltage-sensitive dye imaging. The influence of xenon on single-cell excitability in brain slices was investigated using the whole-cell patch-clamp technique. Effects of xenon on HCN channels were verified in human embryonic kidney cells expressing HCN2 channels. Xenon concentration-dependently diminished thalamocortical signal propagation. In neurons, xenon reduced HCN channel-mediated Ih current amplitude by 33.4 ± 12.2% (at -133 mV; n = 7; P = 0.041) and caused a left-shift in the voltage of half-maximum activation (V1/2) from -98.8 ± 1.6 to -108.0 ± 4.2 mV (n = 8; P = 0.035). Similar effects were seen in human embryonic kidney cells. The impairment of HCN channel function was negligible when intracellular cyclic adenosine monophosphate level was increased. Using HCN2 mice, we could demonstrate that xenon did neither attenuate in vitro thalamocortical signal propagation nor did it show sedating effects in vivo. Here, we clearly showed that xenon impairs HCN2 channel function, and this impairment is dependent on intracellular cyclic adenosine monophosphate levels. We provide evidence that this effect reduces thalamocortical signal propagation and probably contributes to the hypnotic properties of xenon.

Neuronal adenosine release, and not astrocytic ATP release, mediates feedback inhibition of excitatory activity

PubMed Central

Lovatt, Ditte; Xu, Qiwu; Liu, Wei; Takano, Takahiro; Smith, Nathan A.; Schnermann, Jurgen; Tieu, Kim; Nedergaard, Maiken

2012-01-01

Adenosine is a potent anticonvulsant acting on excitatory synapses through A1 receptors. Cellular release of ATP, and its subsequent extracellular enzymatic degradation to adenosine, could provide a powerful mechanism for astrocytes to control the activity of neural networks during high-intensity activity. Despite adenosine's importance, the cellular source of adenosine remains unclear. We report here that multiple enzymes degrade extracellular ATP in brain tissue, whereas only Nt5e degrades AMP to adenosine. However, endogenous A1 receptor activation during cortical seizures in vivo or heterosynaptic depression in situ is independent of Nt5e activity, and activation of astrocytic ATP release via Ca2+ photolysis does not trigger synaptic depression. In contrast, selective activation of postsynaptic CA1 neurons leads to release of adenosine and synaptic depression. This study shows that adenosine-mediated synaptic depression is not a consequence of astrocytic ATP release, but is instead an autonomic feedback mechanism that suppresses excitatory transmission during prolonged activity. PMID:22421436

Topical adenosine increases the proportion of thick hair in Caucasian men with androgenetic alopecia.

PubMed

Iwabuchi, Tokuro; Ideta, Ritsuro; Ehama, Ritsuko; Yamanishi, Haruyo; Iino, Masato; Nakazawa, Yosuke; Kobayashi, Takashi; Ohyama, Manabu; Kishimoto, Jiro

2016-05-01

Adenosine is an effective treatment for androgenetic alopecia (AGA) in Japanese men and women. Adenosine exerts its effects by significantly increasing the proportion of thick hair. In this study, we assessed the clinical outcome of adenosine treatment for 6 months in 38 Caucasian men. The change in proportion of thick hair (≥60 μm) compared with baseline in the adenosine group was significantly higher than that in the placebo group (P < 0.0001). The change in vellus hair proportion (<40 μm) was significantly lower in the adenosine group than that in the placebo group (P = 0.0154). The change in hair density compared with baseline of the adenosine group was also significantly higher compared with that of the placebo group (P = 0.0470). No adverse effects due to treatment were noted during this study by dermatological evaluation. Adenosine is effective in increasing the proportion of thick hair in Caucasian men with AGA as well as in Japanese men and women. © 2015 Japanese Dermatological Association.

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.

Squalenoyl adenosine nanoparticles provide neuroprotection after stroke and spinal cord injury

NASA Astrophysics Data System (ADS)

Gaudin, Alice; Yemisci, Müge; Eroglu, Hakan; Lepetre-Mouelhi, Sinda; Turkoglu, Omer Faruk; Dönmez-Demir, Buket; Caban, Seçil; Sargon, Mustafa Fevzi; Garcia-Argote, Sébastien; Pieters, Grégory; Loreau, Olivier; Rousseau, Bernard; Tagit, Oya; Hildebrandt, Niko; Le Dantec, Yannick; Mougin, Julie; Valetti, Sabrina; Chacun, Hélène; Nicolas, Valérie; Desmaële, Didier; Andrieux, Karine; Capan, Yilmaz; Dalkara, Turgay; Couvreur, Patrick

2014-12-01

There is an urgent need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. However, many drugs with potential neuropharmacological activity, such as adenosine, are inefficient upon systemic administration because of their fast metabolization and rapid clearance from the bloodstream. Here, we show that conjugation of adenosine to the lipid squalene and the subsequent formation of nanoassemblies allows prolonged circulation of this nucleoside, providing neuroprotection in mouse stroke and rat spinal cord injury models. The animals receiving systemic administration of squalenoyl adenosine nanoassemblies showed a significant improvement of their neurologic deficit score in the case of cerebral ischaemia, and an early motor recovery of the hindlimbs in the case of spinal cord injury. Moreover, in vitro and in vivo studies demonstrated that the nanoassemblies were able to extend adenosine circulation and its interaction with the neurovascular unit. This Article shows, for the first time, that a hydrophilic and rapidly metabolized molecule such as adenosine may become pharmacologically efficient owing to a single conjugation with the lipid squalene.

Adenosine uptake is the major effector of extracellular ATP toxicity in human cervical cancer cells.

PubMed

Mello, Paola de Andrade; Filippi-Chiela, Eduardo Cremonese; Nascimento, Jéssica; Beckenkamp, Aline; Santana, Danielle Bertodo; Kipper, Franciele; Casali, Emerson André; Nejar Bruno, Alessandra; Paccez, Juliano Domiraci; Zerbini, Luiz Fernando; Wink, Marcia Rosângela; Lenz, Guido; Buffon, Andréia

2014-10-01

In cervical cancer, HPV infection and disruption of mechanisms involving cell growth, differentiation, and apoptosis are strictly linked with tumor progression and invasion. Tumor microenvironment is ATP and adenosine rich, suggesting a role for purinergic signaling in cancer cell growth and death. Here we investigate the effect of extracellular ATP on human cervical cancer cells. We find that extracellular ATP itself has a small cytotoxic effect, whereas adenosine formed from ATP degradation by ectonucleotidases is the main factor responsible for apoptosis induction. The level of P2 × 7 receptor seemed to define the main cytotoxic mechanism triggered by ATP, since ATP itself eliminated a small subpopulation of cells that express high P2 × 7 levels, probably through its activation. Corroborating these data, blockage or knockdown of P2 × 7 only slightly reduced ATP cytotoxicity. On the other hand, cell viability was almost totally recovered with dipyridamole, an adenosine transporter inhibitor. Moreover, ATP-induced apoptosis and signaling-p53 increase, AMPK activation, and PARP cleavage-as well as autophagy induction were also inhibited by dipyridamole. In addition, inhibition of adenosine conversion into AMP also blocked cell death, indicating that metabolization of intracellular adenosine originating from extracellular ATP is responsible for the main effects of the latter in human cervical cancer cells. © 2014 Mello et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Suppression of Adenosine-Activated Chloride Transport by Ethanol in Airway Epithelia

PubMed Central

Raju, Sammeta V.; Wang, Guoshun

2012-01-01

Alcohol abuse is associated with increased lung infections. Molecular understanding of the underlying mechanisms is not complete. Airway epithelial ion transport regulates the homeostasis of airway surface liquid, essential for airway mucosal immunity and lung host defense. Here, air-liquid interface cultures of Calu-3 epithelial cells were basolaterally exposed to physiologically relevant concentrations of ethanol (0, 25, 50 and 100 mM) for 24 hours and adenosine-stimulated ion transport was measured by Ussing chamber. The ethanol exposure reduced the epithelial short-circuit currents (ISC) in a dose-dependent manner. The ion currents activated by adenosine were chloride conductance mediated by cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated chloride channel. Alloxazine, a specific inhibitor for A2B adenosine receptor (A2BAR), largely abolished the adenosine-stimulated chloride transport, suggesting that A2BAR is a major receptor responsible for regulating the chloride transport of the cells. Ethanol significantly reduced intracellular cAMP production upon adenosine stimulation. Moreover, ethanol-suppression of the chloride secretion was able to be restored by cAMP analogs or by inhibitors to block cAMP degradation. These results imply that ethanol exposure dysregulates CFTR-mediated chloride transport in airways by suppression of adenosine-A2BAR-cAMP signaling pathway, which might contribute to alcohol-associated lung infections. PMID:22442662

A Genomic Response to Trace Fear Conditioning in the Amygdala of Female Rats After Developmental Exposure to Manganese

EPA Science Inventory

Increases in brain-derived neurotrophic factor (Bdnf), Ca2+/calmodulin-dependent protein kinase II alpha (Camk2a), and cyclic adenosine monophosphate (cAMP) response element binding (Creb1) gene expression have been associated with learning in a variety of different rodent studie...

Genome Editing in Neuroepithelial Stem Cells to Generate Human Neurons with High Adenosine-Releasing Capacity.

PubMed

Poppe, Daniel; Doerr, Jonas; Schneider, Marion; Wilkens, Ruven; Steinbeck, Julius A; Ladewig, Julia; Tam, Allison; Paschon, David E; Gregory, Philip D; Reik, Andreas; Müller, Christa E; Koch, Philipp; Brüstle, Oliver

2018-06-01

As a powerful regulator of cellular homeostasis and metabolism, adenosine is involved in diverse neurological processes including pain, cognition, and memory. Altered adenosine homeostasis has also been associated with several diseases such as depression, schizophrenia, or epilepsy. Based on its protective properties, adenosine has been considered as a potential therapeutic agent for various brain disorders. Since systemic application of adenosine is hampered by serious side effects such as vasodilatation and cardiac suppression, recent studies aim at improving local delivery by depots, pumps, or cell-based applications. Here, we report on the characterization of adenosine-releasing human embryonic stem cell-derived neuroepithelial stem cells (long-term self-renewing neuroepithelial stem [lt-NES] cells) generated by zinc finger nuclease (ZFN)-mediated knockout of the adenosine kinase (ADK) gene. ADK-deficient lt-NES cells and their differentiated neuronal and astroglial progeny exhibit substantially elevated release of adenosine compared to control cells. Importantly, extensive adenosine release could be triggered by excitation of differentiated neuronal cultures, suggesting a potential activity-dependent regulation of adenosine supply. Thus, ZFN-modified neural stem cells might serve as a useful vehicle for the activity-dependent local therapeutic delivery of adenosine into the central nervous system. Stem Cells Translational Medicine 2018;7:477-486. © 2018 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.

Adenosine-dependent phrenic motor facilitation is inflammation resistant

PubMed Central

Agosto-Marlin, Ibis M.; Nichols, Nicole L.

2016-01-01

Phrenic motor facilitation (pMF), a form of respiratory plasticity, can be elicited by acute intermittent hypoxia (i.e., phrenic long-term facilitation, pLTF) or direct application of drugs to the cervical spinal cord. Moderate acute intermittent hypoxia (mAIH; 3 × 5-min episodes of 35–50 mmHg arterial Po2, 5-min normoxic intervals) induces pLTF by a serotonin-dependent mechanism; mAIH-induced pLTF is abolished by mild systemic inflammation induced by a low dose of lipopolysaccharide (LPS; 100 μg/kg ip). In contrast, severe acute intermittent hypoxia (sAIH; 3 × 5-min episodes of 25–30 mmHg arterial Po2, 5-min normoxic intervals) elicits pLTF by a distinct, adenosine-dependent mechanism. Since it is not known if systemic LPS blocks the mechanism giving rise to sAIH-induced pLTF, we tested the hypothesis that sAIH-induced pLTF and adenosine 2A (A2A) receptor-induced pMF are insensitive to mild systemic inflammation elicited by the same low dose of LPS. In agreement with our hypothesis, neither sAIH-induced pLTF nor cervical intrathecal A2A receptor agonist (CGS-21680; 200 μM, 10 μl × 3)-induced pMF were affected 24 h post-LPS. Pretreatment with intrathecal A2A receptor antagonist injections (MSX-3; 10 μM, 12 μl) blocked sAIH-induced pLTF 24 h post LPS, confirming that pLTF was adenosine dependent. Our results give insights concerning the differential impact of systemic inflammation and the functional significance of multiple cascades capable of giving rise to phrenic motor plasticity. The relative resistance of adenosine-dependent pMF to inflammation suggests that it provides a “backup” system in animals lacking serotonin-dependent pMF due to ongoing inflammation associated with systemic infections and/or neural injury. NEW & NOTEWORTHY This study gives novel insights concerning how a mild systemic inflammation impacts phrenic motor plasticity (pMF), particularly adenosine-dependent pMF. We suggest that since this adenosine-dependent pathway is

cCMP, cUMP, cTMP, cIMP and cXMP as possible second messengers: development of a hypothesis based on studies with soluble guanylyl cyclase α(1)β(1).

PubMed

Beste, Kerstin Y; Seifert, Roland

2013-02-01

Adenosine 3',5'-cyclic monophosphate and guanosine 3',5'-cyclic monophosphate are second messengers that regulate multiple physiological functions. The existence of additional cyclic nucleotides in mammalian cells was postulated many years ago, but technical problems hampered development of the field. Using highly specific and sensitive mass spectrometry methods, soluble guanylyl cyclase has recently been shown to catalyze the formation of several cyclic nucleotides in vitro. This minireview discusses the broad substrate-specificity of soluble guanylyl cyclase and the possible second messenger roles of cyclic nucleotides other than adenosine 3',5'-cyclic monophosphate and guanosine 3',5'-cyclic monophosphate. We hope that this article stimulates productive and critical research in an area that has been neglected for many years.

Cyclic AMP is a key regulator of M1 to M2a phenotypic conversion of microglia in the presence of Th2 cytokines.

PubMed

Ghosh, Mousumi; Xu, Yong; Pearse, Damien D

2016-01-13

Microglia and macrophages play a central role in neuroinflammation. Pro-inflammatory cytokines trigger their conversion to a classically activated (M1) phenotype, sustaining inflammation and producing a cytotoxic environment. Conversely, anti-inflammatory cytokines polarize the cells towards an alternatively activated (M2), tissue reparative phenotype. Elucidation of the signal transduction pathways involved in M1 to M2 phenotypic conversion may provide insight into how the innate immune response can be harnessed during distinct phases of disease or injury to mediate neuroprotection and neurorepair. Microglial cells (cell line and primary) were subjected to combined cyclic adenosine monophosphate (cyclic AMP) and IL-4, or either alone, in the presence of pro-inflammatory mediators, lipopolysaccharide (LPS), or tumor necrosis factor-α (TNF-α). Their effects on the expression of characteristic markers for M1 and M2 microglia were assessed. Similarly, the M1 and M2 phenotypes of microglia and macrophages within the lesion site were then evaluated following a contusive spinal cord injury (SCI) to the thoracic (T8) spinal cord of rats and mice when the agents were administered systemically. It was demonstrated that cyclic AMP functions synergistically with IL-4 to promote M1 to M2 conversion of microglia in culture. The combination of cyclic AMP and IL-4, but neither alone, induced an Arg-1(+)/iNOS(-)cell phenotype with concomitant expression of other M2-specific markers including TG2 and RELM-α. M2-converted microglia showed ameliorated production of pro-inflammatory cytokines (TNF-α and IP-10) and reactive oxygen species, with no alteration in phagocytic properties. M2a conversion required protein kinase A (PKA), but not the exchange protein directly activated by cyclic AMP (EPAC). Systemic delivery of cyclic AMP and IL-4 after experimental SCI also promoted a significant M1 to M2a phenotypic change in microglia and macrophage population dynamics in the lesion

Temporal and mechanistic dissociation of ATP and adenosine release during ischaemia in the mammalian hippocampus1

PubMed Central

Frenguelli, Bruno G; Wigmore, Geoffrey; Llaudet, Enrique; Dale, Nicholas

2007-01-01

Abstract Adenosine is well known to be released during cerebral metabolic stress and is believed to be neuroprotective. ATP release under similar circumstances has been much less studied. We have now used biosensors to measure and compare in real time the release of ATP and adenosine during in vitro ischaemia in hippocampal slices. ATP release only occurred following the anoxic depolarisation, whereas adenosine release was apparent almost immediately after the onset of ischaemia. ATP release required extracellular Ca2+. By contrast adenosine release was enhanced by removal of extracellular Ca2+, whilst TTX had no effect on either ATP release or adenosine release. Blockade of ionotropic glutamate receptors substantially enhanced ATP release, but had only a modest effect on adenosine release. Carbenoxolone, an inhibitor of gap junction hemichannels, also greatly enhanced ischaemic ATP release, but had little effect on adenosine release. The ecto-ATPase inhibitor ARL 67156, whilst modestly enhancing the ATP signal detected during ischaemia, had no effect on adenosine release. Adenosine release during ischaemia was reduced by pre-treament with homosysteine thiolactone suggesting an intracellular origin. Adenosine transport inhibitors did not inhibit adenosine release, but instead they caused a twofold increase of release. Our data suggest that ATP and adenosine release during ischaemia are for the most part independent processes with distinct underlying mechanisms. These two purines will consequently confer temporally distinct influences on neuronal and glial function in the ischaemic brain. PMID:17459147

Amyotrophic Lateral Sclerosis (ALS) and Adenosine Receptors.

PubMed

Sebastião, Ana M; Rei, Nádia; Ribeiro, Joaquim A

2018-01-01

In the present review we discuss the potential involvement of adenosinergic signaling, in particular the role of adenosine receptors, in amyotrophic lateral sclerosis (ALS). Though the literature on this topic is not abundant, the information so far available on adenosine receptors in animal models of ALS highlights the interest to continue to explore the role of these receptors in this neurodegenerative disease. Indeed, all motor neurons affected in ALS are responsive to adenosine receptor ligands but interestingly, there are alterations in pre-symptomatic or early symptomatic stages that mirror those in advanced disease stages. Information starts to emerge pointing toward a beneficial role of A 2A receptors (A 2A R), most probably at early disease states, and a detrimental role of caffeine, in clear contrast with what occurs in other neurodegenerative diseases. However, some evidence also exists on a beneficial action of A 2A R antagonists. It may happen that there are time windows where A 2A R prove beneficial and others where their blockade is required. Furthermore, the same changes may not occur simultaneously at the different synapses. In line with this, it is not fully understood if ALS is a dying back disease or if it propagates in a centrifugal way. It thus seems crucial to understand how motor neuron dysfunction occurs, how adenosine receptors are involved in those dysfunctions and whether the early changes in purinergic signaling are compensatory or triggers for the disease. Getting this information is crucial before starting the design of purinergic based strategies to halt or delay disease progression.

Lack of endogenous adenosine tonus on sympathetic neurotransmission in spontaneously hypertensive rat mesenteric artery.

PubMed

Sousa, Joana Beatriz; Vieira-Rocha, Maria Sofia; Sá, Carlos; Ferreirinha, Fátima; Correia-de-Sá, Paulo; Fresco, Paula; Diniz, Carmen

2014-01-01

Increased sympathetic activity has been implicated in hypertension. Adenosine has been shown to play a role in blood flow regulation. In the present study, the endogenous adenosine neuromodulatory role, in mesenteric arteries from normotensive and spontaneously hypertensive rats, was investigated. The role of endogenous adenosine in sympathetic neurotransmission was studied using electrically-evoked [3H]-noradrenaline release experiments. Purine content was determined by HPLC with fluorescence detection. Localization of adenosine A1 or A2A receptors in adventitia of mesenteric arteries was investigated by Laser Scanning Confocal Microscopy. Results indicate a higher electrically-evoked noradrenaline release from hypertensive mesenteric arteries. The tonic inhibitory modulation of noradrenaline release is mediated by adenosine A1 receptors and is lacking in arteries from hypertensive animals, despite their purine levels being higher comparatively to those determined in normotensive ones. Tonic facilitatory adenosine A2A receptor-mediated effects were absent in arteries from both strains. Immunohistochemistry revealed an adenosine A1 receptors redistribution from sympathetic fibers to Schwann cells, in adventitia of hypertensive mesenteric arteries which can explain, at least in part, the absence of effects observed for these receptors. Data highlight the role of purines in hypertension revealing that an increase in sympathetic activity in hypertensive arteries is occurring due to a higher noradrenaline/ATP release from sympathetic nerves and the loss of endogenous adenosine inhibitory tonus. The observed nerve-to-glial redistribution of inhibitory adenosine A1 receptors in hypertensive arteries may explain the latter effect.

High Concordance Between Mental Stress-Induced and Adenosine-Induced Myocardial Ischemia Assessed Using SPECT in Heart Failure Patients: Hemodynamic and Biomarker Correlates.

PubMed

Wawrzyniak, Andrew J; Dilsizian, Vasken; Krantz, David S; Harris, Kristie M; Smith, Mark F; Shankovich, Anthony; Whittaker, Kerry S; Rodriguez, Gabriel A; Gottdiener, John; Li, Shuying; Kop, Willem; Gottlieb, Stephen S

2015-10-01

Mental stress can trigger myocardial ischemia, but the prevalence of mental stress-induced ischemia in congestive heart failure (CHF) patients is unknown. We characterized mental stress-induced and adenosine-induced changes in myocardial perfusion and neurohormonal activation in CHF patients with reduced left-ventricular function using SPECT to precisely quantify segment-level myocardial perfusion. Thirty-four coronary artery disease patients (mean age±SD, 62±10 y) with CHF longer than 3 mo and ejection fraction less than 40% underwent both adenosine and mental stress myocardial perfusion SPECT on consecutive days. Mental stress consisted of anger recall (anger-provoking speech) followed by subtraction of serial sevens. The presence and extent of myocardial ischemia was quantified using the conventional 17-segment model. Sixty-eight percent of patients had 1 ischemic segment or more during mental stress and 81% during adenosine. On segment-by-segment analysis, perfusion with mental stress and adenosine were highly correlated. No significant differences were found between any 2 time points for B-type natriuretic peptide, tumor necrosis factor-α, IL-1b, troponin, vascular endothelin growth factor, IL-17a, matrix metallopeptidase-9, or C-reactive protein. However, endothelin-1 and IL-6 increased, and IL-10 decreased, between the stressor and 30 min after stress. Left-ventricular end diastolic dimension was 179±65 mL at rest and increased to 217±71 after mental stress and 229±86 after adenosine (P<0.01 for both). Resting end systolic volume was 129±60 mL at rest and increased to 158±66 after mental stress (P<0.05) and 171±87 after adenosine (P<0.07), with no significant differences between adenosine and mental stress. Ejection fraction was 30±12 at baseline, 29±11 with mental stress, and 28±10 with adenosine (P=not significant). There was high concordance between ischemic perfusion defects induced by adenosine and mental stress, suggesting that mental

The rate of the AMP/adenosine substrate cycle in concanavalin-A-stimulated rat lymphocytes.

PubMed Central

Szondy, Z; Newsholme, E A

1989-01-01

The effect of adenosine on the metabolism of prelabelled adenine nucleotides was investigated in concanavalin-A-stimulated rat lymphocytes. Adenosine in the presence of the adenosine deaminase inhibitor, deoxycoformycin, caused a 2-fold increase in the ATP concentration. This effect was, in part, countereacted by an increased rate of adenine nucleotide catabolism, which could be explained by a stimulation of AMP deaminase (EC 3.5.4.6). At the same time a continuous rate of labelled adenosine production was found, which was not affected by the increased ATP concentration and which could only be detected by the trapping effect of a high concentration of added unlabelled adenosine. It is concluded that the rate of the substrate cycle between AMP and adenosine is low (1.9 +/- 0.2 nmol/h per 10(7) cells) in comparison to the rate of AMP deamination. PMID:2552990

Role of adenosine as adjunctive therapy in acute myocardial infarction.

PubMed

Forman, Mervyn B; Stone, Gregg W; Jackson, Edwin K

2006-01-01

Although early reperfusion and maintained patency is the mainstay therapy for ST elevation myocardial infarction, experimental studies demonstrate that reperfusion per se induces deleterious effects on viable ischemic cells. Thus "myocardial reperfusion injury" may compromise the full potential of reperfusion therapy and may account for unfavorable outcomes in high-risk patients. Although the mechanisms of reperfusion injury are complex and multifactorial, neutrophil-mediated microvascular injury resulting in a progressive decrease in blood flow ("no-reflow" phenomenon) likely plays an important role. Adenosine is an endogenous nucleoside found in large quantities in myocardial and endothelial cells. It activates four well-characterized receptors producing various physiological effects that attenuate many of the proposed mechanisms of reperfusion injury. The cardio-protective effects of adenosine are supported by its role as a mediator of pre- and post-conditioning. In experimental models, administration of adenosine in the peri-reperfusion period results in a marked reduction in infarct size and improvement in ventricular function. The cardioprotective effects in the canine model have a narrow time window with the drug losing its effect following three hours of ischemia. Several small clinical studies have demonstrated that administration of adenosine with reperfusion therapy reduces infarct size and improves ventricular function. In the larger AMISTAD and AMISTAD II trials a 3-h infusion of adenosine as an adjunct to reperfusion resulted in a striking reduction in infarct size (55-65%). Post hoc analysis of AMISTAD II showed that this was associated with significantly improved early and late mortality in patients treated within 3.17 h of symptoms. An intravenous infusion of adenosine for 3 h should be considered as adjunctive therapy in high risk-patients undergoing reperfusion therapy.

Creep crack growth by grain boundary cavitation under monotonic and cyclic loading

NASA Astrophysics Data System (ADS)

Wen, Jian-Feng; Srivastava, Ankit; Benzerga, Amine; Tu, Shan-Tung; Needleman, Alan

2017-11-01

Plane strain finite deformation finite element calculations of mode I crack growth under small scale creep conditions are carried out. Attention is confined to isothermal conditions and two time histories of the applied stress intensity factor: (i) a monononic increase to a plateau value subsequently held fixed; and (ii) a cyclic time variation. The crack growth calculations are based on a micromechanics constitutive relation that couples creep deformation and damage due to grain boundary cavitation. Grain boundary cavitation, with cavity growth due to both creep and diffusion, is taken as the sole failure mechanism contributing to crack growth. The influence on the crack growth rate of loading history parameters, such as the magnitude of the applied stress intensity factor, the ratio of the applied minimum to maximum stress intensity factors, the loading rate, the hold time and the cyclic loading frequency, are explored. The crack growth rate under cyclic loading conditions is found to be greater than under monotonic creep loading with the plateau applied stress intensity factor equal to its maximum value under cyclic loading conditions. Several features of the crack growth behavior observed in creep-fatigue tests naturally emerge, for example, a Paris law type relation is obtained for cyclic loading.

The NLRP3 inflammasome is activated by nanoparticles through ATP, ADP and adenosine

PubMed Central

Baron, L; Gombault, A; Fanny, M; Villeret, B; Savigny, F; Guillou, N; Panek, C; Le Bert, M; Lagente, V; Rassendren, F; Riteau, N; Couillin, I

2015-01-01

The NLR pyrin domain containing 3 (NLRP3) inflammasome is a major component of the innate immune system, but its mechanism of activation by a wide range of molecules remains largely unknown. Widely used nano-sized inorganic metal oxides such as silica dioxide (nano-SiO2) and titanium dioxide (nano-TiO2) activate the NLRP3 inflammasome in macrophages similarly to silica or asbestos micro-sized particles. By investigating towards the molecular mechanisms of inflammasome activation in response to nanoparticles, we show here that active adenosine triphosphate (ATP) release and subsequent ATP, adenosine diphosphate (ADP) and adenosine receptor signalling are required for inflammasome activation. Nano-SiO2 or nano-TiO2 caused a significant increase in P2Y1, P2Y2, A2A and/or A2B receptor expression, whereas the P2X7 receptor was downregulated. Interestingly, IL-1β secretion in response to nanoparticles is increased by enhanced ATP and ADP hydrolysis, whereas it is decreased by adenosine degradation or selective A2A or A2B receptor inhibition. Downstream of these receptors, our results show that nanoparticles activate the NLRP3 inflammasome via activation of PLC-InsP3 and/or inhibition of adenylate cyclase (ADCY)-cAMP pathways. Finally, a high dose of adenosine triggers inflammasome activation and IL-1β secretion through adenosine cellular uptake by nucleotide transporters and by its subsequent transformation in ATP by adenosine kinase. In summary, we show for the first time that extracellular adenosine activates the NLRP3 inflammasome by two ways: by interacting with adenosine receptors at nanomolar/micromolar concentrations and through cellular uptake by equilibrative nucleoside transporters at millimolar concentrations. These findings provide new molecular insights on the mechanisms of NLRP3 inflammasome activation and new therapeutic strategies to control inflammation. PMID:25654762

Effects of adenosine on pressure-flow relationships in an in vitro model of compartment syndrome.

PubMed

Shrier, I; Baratz, A; Magder, S

1997-03-01

Blood flow through skeletal muscle is best modeled with a vascular waterfall at the arteriolar level. Under these conditions, flow is determined by the difference between perfusion pressure (Pper) and the waterfall pressure (Pcrit), divided by the arterial resistance (Ra). By pump perfusing an isolated canine gastrocnemius muscle (n = 6) after it was placed within an airtight box, with and without adenosine infusion, we observed an interaction between the pressure surrounding a muscle (as occurs in compartment syndrome) and baseline vascular tone. We titrated adenosine concentration to double baseline flow. We measured Pcrit and Ra at box pressures (Pbox), which resulted in 100 (Pbox = 0), 90, 75, and 50% flow without adenosine; and 200, 180, 150, 100, and 50% flow with adenosine. Without adenosine, each 10% decline in flow was associated with a 5.7 mmHg increase in Pcrit (P < 0.01). With adenosine, the same decrease in flow was associated with a 2.6-mmHg increase in Pcrit (P < 0.01). Values of Pcrit at 50% of flow were almost identical. Each 10% decrease in flow was also associated with 2.2% increase in Ra with or without adenosine (P < 0.001). Ra decreased with adenosine infusion (P < 0.05), and there was no interaction between adenosine and flow (P > 0.9). We conclude that increases in pressure surrounding a muscle limit flow primarily through changes in Pcrit with and without adenosine-induced vasodilation. The interaction between Pbox and adenosine with respect to Pcrit but not Ra suggests that Pbox affects the tone of the vessels responsible for Pcrit but not Ra.

Nitric oxide - an activating factor of adenosine deaminase 2 in vitro.

PubMed

Sargisova, Ye G; Andreasyan, N A; Hayrapetyan, H L; Harutyunyan, H A

2012-01-01

In this study we have investigated the effect of reactive oxygen species produced by some chemicals in aqueous solutions on activity of adenosine deaminase 2 (ADA2) purified from human blood plasma. An activating effect on ADA2 was observed in vitro with sodium nitroprusside (SNP), the source of NO (nitrosonium ions NO(-) in aqueous solutions). Not SH-groups of cysteine but other amino acid residues sensitive to NO were responsible for ADA2 activation. The SNP-derived activation was more pronounced when purified ADA2 was preincubated with heparin and different proteins as an experimental model of the protein environment in vivo. The most effective was heparin, which is known for its ability to regulate enzyme and protein functions in extracellular matrix. We conclude that ADA2 is a protein with flexible conformation that is affected by the protein environment, and it changes its activity under oxidative (nitrosative) stress.

Methotrexate inhibits neutrophil function by stimulating adenosine release from connective tissue cells

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

Cronstein, B.N.; Eberle, M.A.; Levin, R.I.

1991-03-15

Although commonly used to control a variety of inflammatory diseases, the mechanism of action of a low dose of methotrexate remains a mystery. Methotrexate accumulates intracellularly where it may interfere with purine metabolism. Therefore, the authors determined whether a 48-hr pretreatment with methotrexate affected adenosine release from ({sup 14}C)adenine-labeled human fibroblasts and umbilical vein endothelial cells. Methotrexate significantly increased adenosine release by fibroblasts. The effect of methotrexate on adenosine release was not due to cytotoxicity since cells treated with maximal concentrations of methotrexate took up ({sup 14}C)adenine and released {sup 14}C-labeled purine (a measure of cell injury) in a mannermore » identical to control cells. Methotrexate treatment of fibroblasts dramatically inhibited adherence to fibroblasts by both unstimulated neutrophils and stimulated neutrophils. One hypothesis that explains the effect of methotrexate on adenosine release is that, by inhibition of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase, methotrexate induces the accumulation of AICAR, the nucleoside precursor of which has previously been shown to cause adenosine release from ischemic cardiac tissue. The observation that the antiinflammatory actions of methotrexate are due to the capacity of methotrexate to induce adenosine release may form the basis for the development of an additional class of antiinflammatory drugs.« less

Adenosine monophosphate as a mediator of ATP effects at P1 purinoceptors

PubMed Central

Ross, Fiona M; Brodie, Martin J; Stone, Trevor W

1998-01-01

When perfused with a medium containing no added magnesium and 4-aminopyridine (4AP) (50 μM) hippocampal slices generated epileptiform bursts of an interictal nature. We have shown in a previous study that adenosine 5′-triphosphate (ATP) depressed epileptiform activity and that this effect was blocked by the adenosine A1 receptor antagonist cyclopentyltheophylline but was not affected by adenosine deaminase. This implied that ATP might act indirectly at P1 receptors or at a xanthine-sensitive P2 receptor. The aim of the present study was to investigate further the action of ATP on epileptiform activity.ATP can be metabolized by ecto-nucleotidases to adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP) and adenosine, respectively. Each of these metabolites can activate receptors in its own right: P2 receptors for ADP and P1 receptors for AMP and adenosine.We now show that both AMP and ATP (50 μM) significantly decrease epileptiform discharge rate in a rapid and reversible manner. 5′Adenylic acid deaminase (AMP deaminase, AMPase) (0.2 u ml−1), when perfused alone did not significantly alter the discharge rate over the 10 min superfusion period used for drug application. When perfused concurrently with AMP (50 μM), AMP deaminase prevented the depressant effect of AMP on discharge rate.AMP deaminase, at a concentration of 0.2 u ml−1 which annulled the effect of AMP (50 μM), prevented the inhibitory activity of ATP (50 μM). A higher concentration of ATP (200 μM) depressed the frequency of spontaneous bursts to approximately 30% control and this response was also prevented by AMP deaminase.Superfusion of the slices with 5′-nucleotidase also prevented the inhibitory activity of ATP on epileptiform discharges.The results suggest that AMP mediates the inhibitory effects of ATP on epileptiform activity, a conclusion which can explain the earlier finding that cyclopentyltheophylline but not adenosine deaminase inhibited the

Protective effect of preconditioning and adenosine pretreatment in experimental skeletal muscle reperfusion injury.

PubMed

Papanastasiou, S; Estdale, S E; Homer-Vanniasinkam, S; Mathie, R T

1999-07-01

Prolonged ischaemia followed by reperfusion (I/R) of skeletal muscle results in significant tissue injury. Ischaemic preconditioning (IPC), achieved by repeated brief periods of I/R before prolonged ischaemia or adenosine pretreatment, can prevent I/R injury in cardiac muscle. The aim of this study was to ascertain in a rodent model if damage to skeletal muscle due to global hindlimb tourniquet-induced I/R could be similarly attenuated. Anaesthetized rats were randomized (n = 6-10 per group) to five groups: sham-operated controls; I/R (4 h of ischaemia, 2 h of reperfusion); IPC (three cycles of 10 min of ischaemia/10 min of reperfusion) alone; IPC immediately preceding I/R; or adenosine 1000 microg/kg immediately before I/R. At the end of reperfusion, biopsies were taken from the left gastrocnemius muscle for measurement of myeloperoxidase (MPO) and reduced glutathione (GSH). Before ischaemia and at the end of reperfusion, blood samples were taken for measurement of nitric oxide metabolites, tumour necrosis factor (TNF) alpha and macrophage inflammatory protein (MIP) 2. IPC before I/R resulted in lower levels of MPO (P < 0.001) and TNF-alpha (P = 0.004), and higher levels of GSH (P < 0.001) and nitric oxide metabolites (P = 0.002) than I/R alone. Adenosine had effects comparable to IPC pretreatment (P < 0.001 for MPO, P = 0.002 for GSH, P = 0.02 for nitric oxide metabolites and P = 0.001 for TNF-alpha). There was no difference in the blood pressure or the MIP-2 concentration among the groups. IPC or pretreatment with adenosine ameliorates the I/R injury of skeletal muscle.

Adenosine as an adjunct to thrombolytic therapy for acute myocardial infarction: results of a multicenter, randomized, placebo-controlled trial: the Acute Myocardial Infarction STudy of ADenosine (AMISTAD) trial.

PubMed

Mahaffey, K W; Puma, J A; Barbagelata, N A; DiCarli, M F; Leesar, M A; Browne, K F; Eisenberg, P R; Bolli, R; Casas, A C; Molina-Viamonte, V; Orlandi, C; Blevins, R; Gibbons, R J; Califf, R M; Granger, C B

1999-11-15

The Acute Myocardial Infarction STudy of ADenosine (AMISTAD) trial was designed to test the hypothesis that adenosine as an adjunct to thrombolysis would reduce myocardial infarct size. Reperfusion therapy for acute myocardial infarction (MI) has been shown to reduce mortality, but reperfusion itself also may have deleterious effects. The AMISTAD trial was a prospective, open-label trial of thrombolysis with randomization to adenosine or placebo in 236 patients within 6 h of infarction onset. The primary end point was infarct size as determined by Tc-99 m sestamibi single-photon emission computed tomography (SPECT) imaging 6+/-1 days after enrollment based on multivariable regression modeling to adjust for covariates. Secondary end points were myocardial salvage index and a composite of in-hospital clinical outcomes (death, reinfarction, shock, congestive heart failure or stroke). In all, 236 patients were enrolled. Final infarct size was assessed in 197 (83%) patients. There was a 33% relative reduction in infarct size (p = 0.03) with adenosine. There was a 67% relative reduction in infarct size in patients with anterior infarction (15% in the adenosine group vs. 45.5% in the placebo group) but no reduction in patients with infarcts located elsewhere (11.5% for both groups). Patients randomized to adenosine tended to reach the composite clinical end point more often than those assigned to placebo (22% vs. 16%; odds ratio, 1.43; 95% confidence interval, 0.71 to 2.89). Many agents thought to attenuate reperfusion injury have been unsuccessful in clinical investigation. In this study, adenosine resulted in a significant reduction in infarct size. These data support the need for a large clinical outcome trial.

Pharmacological prevention of reperfusion injury in acute myocardial infarction. A potential role for adenosine as a therapeutic agent.

PubMed

Quintana, Miguel; Kahan, Thomas; Hjemdahl, Paul

2004-01-01

The concept of reperfusion injury, although first recognized from animal studies, is now recognized as a clinical phenomenon that may result in microvascular damage, no-reflow phenomenon, myocardial stunning, myocardial hibernation and ischemic preconditioning. The final consequence of this event is left ventricular (LV) systolic dysfunction leading to increased morbidity and mortality. The typical clinical case of reperfusion injury occurs in acute myocardial infarction (MI) with ST segment elevation in which an occlusion of a major epicardial coronary artery is followed by recanalization of the artery. This may occur either spontaneously or by means of thrombolysis and/or by primary percutaneous coronary intervention (PCI) with efficient platelet inhibition by aspirin (acetylsalicylic acid), clopidogrel and glycoprotein IIb/IIIa inhibitors. Although the pathophysiology of reperfusion injury is complex, the major role that neutrophils play in this process is well known. Neutrophils generate free radicals, degranulation products, arachidonic acid metabolites and platelet-activating factors that interact with endothelial cells, inducing endothelial injury and neutralization of nitrous oxide vasodilator capacity. Adenosine, through its multi-targeted pharmacological actions, is able to inhibit some of the above-mentioned detrimental effects. The net protective of adenosine in in vivo models of reperfusion injury is the reduction of the infarct size, the improvement of the regional myocardial blood flow and of the regional function of the ischemic area. Additionally, adenosine preserves the post-ischemic coronary flow reserve, coronary blood flow and the post-ischemic regional contractility. In small-scale studies in patients with acute MI, treatment with adenosine has been associated with smaller infarcts, less no-reflow phenomenon and improved LV function. During elective PCI adenosine reduced ST segment shifts, lactate production and ischemic symptoms. During the

(S)-α-Chlorohydrin Inhibits Protein Tyrosine Phosphorylation through Blocking Cyclic AMP - Protein Kinase A Pathway in Spermatozoa

PubMed Central

Zheng, Weiwei; Yang, Bei; Pi, Jingbo; He, Gengsheng; Qu, Weidong

2012-01-01

α-Chlorohydrin is a common contaminant in food. Its (S)-isomer, (S)-α-chlorohydrin (SACH), is known for causing infertility in animals by inhibiting glycolysis of spermatozoa. The aim of present work was to examine the relationship between SACH and protein tyrosine phosphorylation (PTP), which plays a critical role in regulating mammalian sperm capacitation. In vitro exposure of SACH 50 µM to isolated rat epididymal sperm inhibited PTP. Sperm-specific glyceraldehyde 3-phosphate dehydrogenase (GAPDS) activities, the intracellular adenosine 5′-triphosphate (ATP) levels, 3′-5′-cyclic adenosine monophosphate (cAMP) levels and phosphorylation of protein kinase A (PKA) substrates in rat sperm were diminished dramatically, indicating that both glycolysis and the cAMP/PKA signaling pathway were impaired by SACH. The inhibition of both PTP and phosphorylation of PKA substrates by SACH could be restored by addition of cAMP analog dibutyryl-cAMP (dbcAMP) and phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). Moreover, addition of glycerol protected glycolysis, ATP levels, phosphorylation of PKA substrates and PTP against the influence of SACH. These results suggested SACH inhibited PTP through blocking cAMP/PKA pathway in sperm, and PTP inhibition may play a role in infertility associated with SACH. PMID:22916194

(S)-α-chlorohydrin inhibits protein tyrosine phosphorylation through blocking cyclic AMP - protein kinase A pathway in spermatozoa.

PubMed

Zhang, Hao; Yu, Huan; Wang, Xia; Zheng, Weiwei; Yang, Bei; Pi, Jingbo; He, Gengsheng; Qu, Weidong

2012-01-01

α-Chlorohydrin is a common contaminant in food. Its (S)-isomer, (S)-α-chlorohydrin (SACH), is known for causing infertility in animals by inhibiting glycolysis of spermatozoa. The aim of present work was to examine the relationship between SACH and protein tyrosine phosphorylation (PTP), which plays a critical role in regulating mammalian sperm capacitation. In vitro exposure of SACH 50 µM to isolated rat epididymal sperm inhibited PTP. Sperm-specific glyceraldehyde 3-phosphate dehydrogenase (GAPDS) activities, the intracellular adenosine 5'-triphosphate (ATP) levels, 3'-5'-cyclic adenosine monophosphate (cAMP) levels and phosphorylation of protein kinase A (PKA) substrates in rat sperm were diminished dramatically, indicating that both glycolysis and the cAMP/PKA signaling pathway were impaired by SACH. The inhibition of both PTP and phosphorylation of PKA substrates by SACH could be restored by addition of cAMP analog dibutyryl-cAMP (dbcAMP) and phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). Moreover, addition of glycerol protected glycolysis, ATP levels, phosphorylation of PKA substrates and PTP against the influence of SACH. These results suggested SACH inhibited PTP through blocking cAMP/PKA pathway in sperm, and PTP inhibition may play a role in infertility associated with SACH.

Importance of tissue perfusion in ST segment elevation myocardial infarction patients undergoing reperfusion strategies: role of adenosine.

PubMed

Forman, Mervyn B; Jackson, Edwin K

2007-11-01

High risk ST segment elevation myocardial infarction (STEMI) patients undergoing reperfusion therapy continue to exhibit significant morbidity and mortality due in part to myocardial reperfusion injury. Importantly, preclinical studies demonstrate that progressive microcirculatory failure (the "no-reflow" phenomenon) contributes significantly to myocardial reperfusion injury. Diagnostic techniques to measure tissue perfusion have validated this concept in humans, and it is now clear that abnormal tissue perfusion occurs frequently in STEMI patients undergoing reperfusion therapy. Moreover, because tissue perfusion correlates poorly with epicardial blood flow (TIMI flow grade), clinical studies show that tissue perfusion is an independent predictor of early and late mortality in STEMI patients and is associated with infarct size, ventricular function, CHF and ventricular arrhythmias. The mechanisms responsible for abnormal tissue perfusion are multifactorial and include both mechanical obstruction and vasoconstrictor humoral factors. Adenosine, an endogenous nucleoside, maintains microcirculatory flow following reperfusion by activating four well-characterized extracellular receptors. Because activation of adenosine receptors attenuates the mechanical and functional mechanisms leading to the "no reflow" phenomenon and activates other cardioprotective pathways as well, it is not surprising that both experimental and clinical studies show striking myocardial salvage with intravenous infusions of adenosine administered in the peri-reperfusion period. For example, a post hoc analysis of the AMISTAD II trial indicates a significant reduction in 1 and 6-month mortality in STEMI patients undergoing reperfusion therapy who are treated with adenosine within 3 hours of symptoms. In conclusion, adenosine's numerous cardioprotective effects, including attenuation of the "no-reflow" phenomenon, support its use in high risk STEMI undergoing reperfusion.

Age-dependent changes of presynaptic neuromodulation via A1-adenosine receptors in rat hippocampal slices.

PubMed

Sperlágh, B; Zsilla, G; Baranyi, M; Kékes-Szabó, A; Vizi, E S

1997-10-01

The presynaptic neuromodulation of stimulation-evoked release of [3H]-acetylcholine by endogenous adenosine, via A1-adenosine receptors, was studied in superfused hippocampal slices taken from 4-, 12- and 24-month-old rats. 8-Cyclopentyl-1,3-dimethylxanthine (0.25 microM), a selective A1-receptor antagonist, increased significantly the electrical field stimulation-induced release of [3H]-acetylcholine in slices prepared from 4- and 12-month-old rats, showing a tonic inhibitory action of endogenous adenosine via stimulation of presynaptic A1-adenosine receptors. In contrast, 8-cyclopentyl-1,3-dimethylxanthine had no effect in 24-month-old rats. 2-Chloroadenosine (10 microM), an adenosine receptor agonist decreased the release of [3H]-acetylcholine in slices taken from 4- and 12-month-old rats, and no significant change was observed in slices taken from 24-month-old rats. In order to show whether the number/or affinity of the A1-receptors was affected in aged rats, [3H]-8-cyclopentyl-1,3-dimethylxanthine binding was studied in hippocampal membranes prepared from rats of different ages. Whereas the Bmax value was significantly lower in 2-year-old rats than in younger counterparts, the dissociation constant (Kd) was not affected by aging, indicating that the density rather than the affinity of adenosine receptors was altered. Endogenous adenosine levels present in the extracellular space were also measured in the superfusate by high performance liquid chromatography (HPLC) coupled with ultraviolet detection, and an age-related increase in the adenosine level was found. In summary, our results indicate that during aging the level of adenosine in the extracellular fluid is increased in the hippocampus. There is a downregulation and reduced responsiveness of presynaptic adenosine A1-receptors, and it seems likely that these changes are due to the enhanced adenosine level in the extracellular space.

Cyclic strain increases protease-activated receptor-1 expression in vascular smooth muscle cells

NASA Technical Reports Server (NTRS)

Nguyen, K. T.; Frye, S. R.; Eskin, S. G.; Patterson, C.; Runge, M. S.; McIntire, L. V.

2001-01-01

Cyclic strain regulates many vascular smooth muscle cell (VSMC) functions through changing gene expression. This study investigated the effects of cyclic strain on protease-activated receptor-1 (PAR-1) expression in VSMCs and the possible signaling pathways involved, on the basis of the hypothesis that cyclic strain would enhance PAR-1 expression, reflecting increased thrombin activity. Uniaxial cyclic strain (1 Hz, 20%) of cells cultured on elastic membranes induced a 2-fold increase in both PAR-1 mRNA and protein levels. Functional activity of PAR-1, as assessed by cell proliferation in response to thrombin, was also increased by cyclic strain. In addition, treatment of cells with antioxidants or an NADPH oxidase inhibitor blocked strain-induced PAR-1 expression. Preincubation of cells with protein kinase inhibitors (staurosporine or Ro 31-8220) enhanced strain-increased PAR-1 expression, whereas inhibitors of NO synthase, tyrosine kinase, and mitogen-activated protein kinases had no effect. Cyclic strain in the presence of basic fibroblast growth factor induced PAR-1 mRNA levels beyond the effect of cyclic strain alone, whereas no additive effect was observed between cyclic strain and platelet-derived growth factor-AB. Our findings that cyclic strain upregulates PAR-1 mRNA expression but that shear stress downregulates this gene in VSMCs provide an opportunity to elucidate signaling differences by which VSMCs respond to different mechanical forces.

Genetics Home Reference: adenosine deaminase deficiency

MedlinePlus

... to eliminate a molecule called deoxyadenosine, which is generated when DNA is broken down. Adenosine deaminase converts ... a substitute for professional medical care or advice. Users with questions about a personal health condition should ...

Cyclic multiverses

NASA Astrophysics Data System (ADS)

Marosek, Konrad; Dąbrowski, Mariusz P.; Balcerzak, Adam

2016-09-01

Using the idea of regularization of singularities due to the variability of the fundamental constants in cosmology we study the cyclic universe models. We find two models of oscillating and non-singular mass density and pressure (`non-singular' bounce) regularized by varying gravitational constant G despite the scale factor evolution is oscillating and having sharp turning points (`singular' bounce). Both violating (big-bang) and non-violating (phantom) null energy condition models appear. Then, we extend this idea on to the multiverse containing cyclic individual universes with either growing or decreasing entropy though leaving the net entropy constant. In order to get an insight into the key idea, we consider the doubleverse with the same geometrical evolution of the two `parallel' universes with their physical evolution [physical coupling constants c(t) and G(t)] being different. An interesting point is that there is a possibility to exchange the universes at the point of maximum expansion - the fact which was already noticed in quantum cosmology. Similar scenario is also possible within the framework of Brans-Dicke theory where varying G(t) is replaced by the dynamical Brans-Dicke field φ(t) though these theories are slightly different.

Optimal Adenosine Stress for Maximum Stress Perfusion, Coronary Flow Reserve, and Pixel Distribution of Coronary Flow Capacity by Kolmogorov-Smirnov Analysis.

PubMed

Kitkungvan, Danai; Lai, Dejian; Zhu, Hongjian; Roby, Amanda E; Johnson, Nils P; Steptoe, Derek D; Patel, Monica B; Kirkeeide, Richard; Gould, K Lance

2017-02-01

Different adenosine stress imaging protocols have not been systemically validated for absolute myocardial perfusion and coronary flow reserve (CFR) by positron emission tomography, where submaximal stress precludes assessing physiological severity of coronary artery disease. In 127 volunteers, serial rest-stress positron emission tomography scans using rubidium-82 with various adenosine infusion protocols identified (1) the protocol with maximum stress perfusion and CFR, (2) test-retest precision in same subject, (3) stress perfusion and CFR after adenosine compared with dipyridamole, (4) heterogeneity of coronary flow capacity combining stress perfusion and CFR, and (5) potential relevance for patients with risk factors or coronary artery disease. The adenosine 6-minute infusion with rubidium-82 injection at 3 minutes caused CFR that was significantly 15.7% higher than the 4-minute adenosine infusion with rubidium-82 injection at 2 minutes and significantly more homogeneous by Kolmogorov-Smirnov analysis for histograms of 1344 pixel range of perfusion in paired positron emission tomographies. In a coronary artery disease cohort separate from volunteers of this study, compared with the 3/6-minute protocol, the 2/4-minute adenosine protocol would potentially have changed 332 of 1732 (19%) positron emission tomographies at low-risk physiological severity CFR ≥2.3 to CFR <2.0, thereby implying high-risk quantitative severity potentially appropriate for interventions but because of suboptimal stress of the 2/4 protocol in some patients. The 6-minute adenosine infusion with rubidium-82 activation at 3 minutes produced CFR that averaged 15.7% higher than that in the 2/4-minute protocol, thereby potentially providing essential information for personalized management in some patients. © 2017 American Heart Association, Inc.

Adenosine A2A receptor agonists with potent antiplatelet activity.

PubMed

Fuentes, Eduardo; Fuentes, Manuel; Caballero, Julio; Palomo, Iván; Hinz, Sonja; El-Tayeb, Ali; Müller, Christa E

2018-05-01

Selected adenosine A 2A receptor agonists (PSB-15826, PSB-12404, and PSB-16301) have been evaluated as new antiplatelet agents. In addition, radioligand-binding studies and receptor-docking experiments were performed in order to explain their differential biological effects on a molecular level. Among the tested adenosine derivatives, PSB-15826 was the most potent compound to inhibit platelet aggregation (EC 50 0.32 ± 0.05 µmol/L) and platelet P-selectin cell-surface localization (EC 50 0.062 ± 0.2 µmol/L), and to increase intraplatelets cAMP levels (EC 50 0.24 ± 0.01 µmol/L). The compound was more active than CGS21680 (EC 50 0.97±0.07 µmol/L) and equipotent to NECA (EC 50 0.31 ± 0.05 µmol/L) in platelet aggregation induced by ADP. In contrast to the results from cAMP assays, K i values determined in radioligand-binding studies were not predictive of the A 2A agonists' antiplatelet activity. Docking studies revealed the key molecular determinants of this new family of adenosine A 2A receptor agonists: differences in activities are related to π-stacking interactions between the ligands and the residue His264 in the extracellular loop of the adenosine A 2A receptor which may result in increased residence times. In conclusion, these results provide an improved understanding of the requirements of antiplatelet adenosine A 2A receptor agonists.

Cyclic Peptidic Mimetics of Apollo Peptides Targeting Telomeric Repeat Binding Factor 2 (TRF2) and Apollo Interaction.

PubMed

Chen, Xia; Liu, Liu; Chen, Yong; Yang, Yuting; Yang, Chao-Yie; Guo, Tianyue; Lei, Ming; Sun, Haiying; Wang, Shaomeng

2018-05-10

Telomeric repeat binding factor 2 (TRF2) is a telomere-associated protein that plays an important role in the formation of the 3' single strand DNA overhang and the "T loop", two structures critical for the stability of the telomeres. Apollo is a 5'-exonuclease recruited by TRF2 to the telomere and contributes to the formation of the 3' single strand DNA overhang. Knocking down of Apollo can induce DNA damage response similar to that caused by the knocking down of TRF2. In this Letter, we report the design and synthesis of a class of cyclic peptidic mimetics of the TRFH binding motif of Apollo (Apollo TBM ). We found conformational control of the C terminal residues of Apollo TBM can effectively improve the binding affinity. We have obtained a crystal structure of a cyclic peptidic Apollo peptide mimetic ( 34 ) complexed with TRF2, which provides valuable guidance to the future design of TRF2 inhibitors.

Regulation of Nutrient Transport in Quiescent, Lactating, and Neoplastic Mammary Epithelia.

DTIC Science & Technology

1996-10-01

cells after addition of serum, peptide growth factors, and agents which increase intracellular cAMP concentration( Hiraki , et al., 1989). The two...Histol. 14:433-445. Hiraki , Y., I. M. McMorrow and M. J. Birnbaum. 1989. The regulation of glucose transporter gene expression by cyclic adenosine

Polymorphisms in adenosine receptor genes are associated with infarct size in patients with ischemic cardiomyopathy.

PubMed

Tang, Z; Diamond, M A; Chen, J-M; Holly, T A; Bonow, R O; Dasgupta, A; Hyslop, T; Purzycki, A; Wagner, J; McNamara, D M; Kukulski, T; Wos, S; Velazquez, E J; Ardlie, K; Feldman, A M

2007-10-01

The goal of this experiment was to identify the presence of genetic variants in the adenosine receptor genes and assess their relationship to infarct size in a population of patients with ischemic cardiomyopathy. Adenosine receptors play an important role in protecting the heart during ischemia and in mediating the effects of ischemic preconditioning. We sequenced DNA samples from 273 individuals with ischemic cardiomyopathy and from 203 normal controls to identify the presence of genetic variants in the adenosine receptor genes. Subsequently, we analyzed the relationship between the identified genetic variants and infarct size, left ventricular size, and left ventricular function. Three variants in the 3'-untranslated region of the A(1)-adenosine gene (nt 1689 C/A, nt 2206 Tdel, nt 2683del36) and an informative polymorphism in the coding region of the A3-adenosine gene (nt 1509 A/C I248L) were associated with changes in infarct size. These results suggest that genetic variants in the adenosine receptor genes may predict the heart's response to ischemia or injury and might also influence an individual's response to adenosine therapy.

Erythrocytes retain hypoxic adenosine response for faster acclimatization upon re-ascent

PubMed Central

Song, Anren; Zhang, Yujin; Han, Leng; Yegutkin, Gennady G.; Liu, Hong; Sun, Kaiqi; D'Alessandro, Angelo; Li, Jessica; Karmouty-Quintana, Harry; Iriyama, Takayuki; Weng, Tingting; Zhao, Shushan; Wang, Wei; Wu, Hongyu; Nemkov, Travis; Subudhi, Andrew W.; Jameson-Van Houten, Sonja; Julian, Colleen G.; Lovering, Andrew T.; Hansen, Kirk C.; Zhang, Hong; Bogdanov, Mikhail; Dowhan, William; Jin, Jianping; Kellems, Rodney E.; Eltzschig, Holger K.; Blackburn, Michael; Roach, Robert C.; Xia, Yang

2017-01-01

Faster acclimatization to high altitude upon re-ascent is seen in humans; however, the molecular basis for this enhanced adaptive response is unknown. We report that in healthy lowlanders, plasma adenosine levels are rapidly induced by initial ascent to high altitude and achieved even higher levels upon re-ascent, a feature that is positively associated with quicker acclimatization. Erythrocyte equilibrative nucleoside transporter 1 (eENT1) levels are reduced in humans at high altitude and in mice under hypoxia. eENT1 deletion allows rapid accumulation of plasma adenosine to counteract hypoxic tissue damage in mice. Adenosine signalling via erythrocyte ADORA2B induces PKA phosphorylation, ubiquitination and proteasomal degradation of eENT1. Reduced eENT1 resulting from initial hypoxia is maintained upon re-ascent in humans or re-exposure to hypoxia in mice and accounts for erythrocyte hypoxic memory and faster acclimatization. Our findings suggest that targeting identified purinergic-signalling network would enhance the hypoxia adenosine response to counteract hypoxia-induced maladaptation. PMID:28169986

Does adenosine triphosphate released into voided urodynamic fluid contribute to urgency signaling in women with bladder dysfunction?

PubMed

Cheng, Ying; Mansfield, Kylie J; Allen, Wendy; Walsh, Colin A; Burcher, Elizabeth; Moore, Kate H

2010-03-01

Adenosine triphosphate released from urothelium during stretch stimulates afferent nerves and conveys information on bladder fullness. We measured adenosine triphosphate released during cystometric bladder filling in women with idiopathic detrusor overactivity and stress incontinence (controls), and assessed whether the level of released adenosine triphosphate is related to cystometric parameters. Routine cystometry was done in 51 controls and 48 women with detrusor overactivity who were 28 to 87 years old. Voided urodynamic fluid was collected and stored at -30 C. Adenosine triphosphate was measured by a bioluminescence assay. Adenosine triphosphate levels were similar in voided urodynamic fluid of controls and patients with detrusor overactivity (p = 0.79). A significant inverse correlation was seen between adenosine triphosphate and maximal cystometric capacity in controls (p = 0.013), and between voided volume and adenosine triphosphate in controls (p = 0.015) and detrusor overactivity cases (p = 0.019). A significant correlation between first desire to void and adenosine triphosphate was also noted in detrusor overactivity cases (p = 0.033) but not in controls (p = 0.58). No correlation was seen between adenosine triphosphate and detrusor pressure during filling or voiding. Adenosine triphosphate measurement in voided urodynamic fluid is a novel approach to understanding signals that may contribute to the urgency sensation (a sudden compelling desire to pass urine). The inverse correlation between adenosine triphosphate in voided urodynamic fluid and first desire to void suggests that adenosine triphosphate has a role in modulating the early filling sensation in patients with detrusor overactivity. 2010 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Cyclic mechanical stretch promotes energy metabolism in osteoblast-like cells through an mTOR signaling-associated mechanism.

PubMed

Zeng, Zhaobin; Jing, Da; Zhang, Xiaodong; Duan, Yinzhong; Xue, Feng

2015-10-01

Energy metabolism is essential for maintaining function and substance metabolism in osteoblasts. However, the role of cyclic stretch in regulating osteoblastic energy metabolism and the underlying mechanisms remain poorly understood. In this study, we found that cyclic stretch (10% elongation at 0.1 Hz) significantly enhanced glucose consumption, lactate levels (determined using a glucose/lactate assay kit), intracellular adenosine triphosphate (ATP) levels (quantified using rLuciferase/Luciferin reagent) and the mRNA expression of energy metabolism-related enzymes [mitochondrial ATP synthase, L-lactate dehydrogenase A (LDHA) and enolase 1; measured by RT-qPCR], and increased the phosphorylation levels of Akt, mammalian target of rapamycin (mTOR) and p70s6k (measured by western blot analysis) in human osteoblast‑like MG‑63 cells. Furthermore, the inhibition of Akt or mTOR with an antagonist (wortmannin or rapamycin) suppressed the stretch-induced increase in glucose consumption, lactate levels, intracellular ATP levels and the expression of mitochondrial ATP synthase and LDHA, indicating the significance of the Akt/mTOR/p70s6k pathway in regulating osteoblastic energy metabolism in response to mechanical stretch. Thus, we concluded that cyclic stretch regulates energy metabolism in MG‑63 cells partially through the Akt/mTOR/p70s6k signaling pathway. The present findings provide novel insight into osteoblastic mechanobiology from the perspective of energy metabolism.

Mechanism of repression of the inhibin alpha-subunit gene by inducible 3',5'-cyclic adenosine monophosphate early repressor.

PubMed

Burkart, Anna D; Mukherjee, Abir; Mayo, Kelly E

2006-03-01

The rodent ovary is regulated throughout the reproductive cycle to maintain normal cyclicity. Ovarian follicular development is controlled by changes in gene expression in response to the gonadotropins FSH and LH. The inhibin alpha-subunit gene belongs to a group of genes that is positively regulated by FSH and negatively regulated by LH. Previous studies established an important role for inducible cAMP early repressor (ICER) in repression of alpha-inhibin. These current studies investigate the mechanisms of repression by ICER. It is not clear whether all four ICER isoforms expressed in the ovary can act as repressors of the inhibin alpha-subunit gene. EMSAs demonstrate binding of all isoforms to the inhibin alpha-subunit CRE (cAMP response element), and transfection studies demonstrate that all isoforms can repress the inhibin alpha-subunit gene. Repression by ICER is dependent on its binding to DNA as demonstrated by mutations to ICER's DNA-binding domain. These mutational studies also demonstrate that repression by ICER is not dependent on heterodimerization with CREB (CRE-binding protein). Competitive EMSAs show that ICER effectively competes with CREB for binding to the inhibin alpha CRE in vitro. Chromatin immunoprecipitation assays demonstrate a replacement of CREB dimers bound to the inhibin alpha CRE by ICER dimers in ovarian granulosa cells in response to LH signaling. Thus, there is a temporal association of transcription factors bound to the inhibin alpha-CRE controlling inhibin alpha-subunit gene expression.

Cyclic AMP- and (Rp)-cAMPS-induced Conformational Changes in a Complex of the Catalytic and Regulatory (RIα) Subunits of Cyclic AMP-dependent Protein Kinase*

PubMed Central

Anand, Ganesh S.; Krishnamurthy, Srinath; Bishnoi, Tanushree; Kornev, Alexandr; Taylor, Susan S.; Johnson, David A.

2010-01-01

We took a discovery approach to explore the actions of cAMP and two of its analogs, one a cAMP mimic ((Sp)-adenosine cyclic 3′:5′-monophosphorothioate ((Sp)-cAMPS)) and the other a diastereoisomeric antagonist ((Rp)-cAMPS), on a model system of the type Iα cyclic AMP-dependent protein kinase holoenzyme, RIα(91–244)·C-subunit, by using fluorescence spectroscopy and amide H/2H exchange mass spectrometry. Specifically, for the fluorescence experiments, fluorescein maleimide was conjugated to three cysteine single residue substitution mutants, R92C, T104C, and R239C, of RIα(91–244), and the effects of cAMP, (Sp)-cAMPS, and (Rp)-cAMPS on the kinetics of R-C binding and the time-resolved anisotropy of the reporter group at each conjugation site were measured. For the amide exchange experiments, ESI-TOF mass spectrometry with pepsin proteolytic fragmentation was used to assess the effects of (Rp)-cAMPS on amide exchange of the RIα(91–244)·C-subunit complex. We found that cAMP and its mimic perturbed at least parts of the C-subunit interaction Sites 2 and 3 but probably not Site 1 via reduced interactions of the linker region and αC of RIα(91–244). Surprisingly, (Rp)-cAMPS not only increased the affinity of RIα(91–244) toward the C-subunit by 5-fold but also produced long range effects that propagated through both the C- and R-subunits to produce limited unfolding and/or enhanced conformational flexibility. This combination of effects is consistent with (Rp)-cAMPS acting by enhancing the internal entropy of the R·C complex. Finally, the (Rp)-cAMPS-induced increase in affinity of RIα(91–244) toward the C-subunit indicates that (Rp)-cAMPS is better described as an inverse agonist because it decreases the fractional dissociation of the cyclic AMP-dependent protein kinase holoenzyme and in turn its basal activity. PMID:20167947

K+ depolarization evokes ATP, adenosine and glutamate release from glia in rat hippocampus: a microelectrode biosensor study

PubMed Central

Heinrich, A; Andó, RD; Túri, G; Rózsa, B; Sperlágh, B

2012-01-01

BACKGROUND AND PURPOSE This study was undertaken to characterize the ATP, adenosine and glutamate outflow evoked by depolarization with high K+ concentrations, in slices of rat hippocampus. EXPERIMENTAL APPROACH We utilized the microelectrode biosensor technique and extracellular electrophysiological recording for the real-time monitoring of the efflux of ATP, adenosine and glutamate. KEY RESULTS ATP, adenosine and glutamate sensors exhibited transient and reversible current during depolarization with 25 mM K+, with distinct kinetics. The ecto-ATPase inhibitor ARL67156 enhanced the extracellular level of ATP and inhibited the prolonged adenosine efflux, suggesting that generation of adenosine may derive from the extracellular breakdown of ATP. Stimulation-evoked ATP, adenosine and glutamate efflux was inhibited by tetrodotoxin, while exposure to Ca2+-free medium abolished ATP and adenosine efflux from hippocampal slices. Extracellular elevation of ATP and adenosine were decreased in the presence of NMDA receptor antagonists, D-AP-5 and ifenprodil, whereas non-NMDA receptor blockade by CNQX inhibited glutamate but not ATP and adenosine efflux. The gliotoxin fluoroacetate and P2X7 receptor antagonists inhibited the K+-evoked ATP, adenosine and glutamate efflux, while carbenoxolone in low concentration and probenecid decreased only the adenosine efflux. CONCLUSIONS AND IMPLICATIONS Our results demonstrated activity-dependent gliotransmitter release in the hippocampus in response to ongoing neuronal activity. ATP and glutamate were released by P2X7 receptor activation into extracellular space. Although the increased extracellular levels of adenosine did derive from released ATP, adenosine might also be released directly via pannexin hemichannels. LINKED ARTICLE This article is commented on by Sershen, pp. 1000–1002 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.02072.x PMID:22394324

Altered sarco(endo)plasmic reticulum calcium adenosine triphosphatase 2a content: Targets for heart failure therapy.

PubMed

Liu, Gang; Li, Si Qi; Hu, Ping Ping; Tong, Xiao Yong

2018-05-01

Sarco(endo)plasmic reticulum calcium adenosine triphosphatase is responsible for transporting cytosolic calcium into the sarcoplasmic reticulum and endoplasmic reticulum to maintain calcium homeostasis. Sarco(endo)plasmic reticulum calcium adenosine triphosphatase is the dominant isoform expressed in cardiac tissue, which is regulated by endogenous protein inhibitors, post-translational modifications, hormones as well as microRNAs. Dysfunction of sarco(endo)plasmic reticulum calcium adenosine triphosphatase is associated with heart failure, which makes sarco(endo)plasmic reticulum calcium adenosine triphosphatase a promising target for heart failure therapy. This review summarizes current approaches to ameliorate sarco(endo)plasmic reticulum calcium adenosine triphosphatase function and focuses on phospholamban, an endogenous inhibitor of sarco(endo)plasmic reticulum calcium adenosine triphosphatase, pharmacological tools and gene therapies.

Caffeine's Attenuation of Cocaine-Induced Dopamine Release by Inhibition of Adenosine.

PubMed

Malave, Lauren B; Broderick, Patricia A

2014-06-01

Background: It is well known that the reinforcing properties of cocaine addiction are caused by the sharp increase of dopamine (DA) in the reward areas of the brain. However, other mechanisms have been speculated to contribute to the increase. Adenosine is one system that is associated with the sleep-wake cycle and is most important in regulating neuronal activity. Thus, more and more evidence is pointing to its involvement in regulating DA release. The current study set out to examine the role of adenosine in cocaine-induced DA release. Methods: Increasing doses of cocaine, caffeine, and their combination, as well as, 8-cyclopentyltheophylline (CPT), an adenosine A1 antagonist (alone and in combination with cocaine) were used to denote a response curve. A novel biosensor, the BRODERICK PROBE ® was implanted in the nucleus accumbens to image the drug-induced surge of DA release in vivo , in the freely moving animal in real time. Results: Combinations of cocaine and caffeine were observed to block the increased release of DA moderately after administration of the low dose (2.5 mg/kg cocaine and 12.5 mg/kg caffeine) and dramatically after administration of the high dose (10 mg/kg cocaine and 50 mg/kg caffeine), suggesting neuroprotection. Similarly, CPT and cocaine showed a decreased DA surge when administered in combination. Thus, the low and high dose of a nonselective adenosine antagonist, caffeine, and a moderate dose of a selective adenosine antagonist, CPT, protected against the cocaine-induced DA release. Conclusions: These results show a significant interaction between adenosine and DA release and suggest therapeutic options for cocaine addiction and disorders associated with DA dysfunction.

Caffeine's Attenuation of Cocaine-Induced Dopamine Release by Inhibition of Adenosine

PubMed Central

Malave, Lauren B.

2014-01-01

Background: It is well known that the reinforcing properties of cocaine addiction are caused by the sharp increase of dopamine (DA) in the reward areas of the brain. However, other mechanisms have been speculated to contribute to the increase. Adenosine is one system that is associated with the sleep-wake cycle and is most important in regulating neuronal activity. Thus, more and more evidence is pointing to its involvement in regulating DA release. The current study set out to examine the role of adenosine in cocaine-induced DA release. Methods: Increasing doses of cocaine, caffeine, and their combination, as well as, 8-cyclopentyltheophylline (CPT), an adenosine A1 antagonist (alone and in combination with cocaine) were used to denote a response curve. A novel biosensor, the BRODERICK PROBE® was implanted in the nucleus accumbens to image the drug-induced surge of DA release in vivo, in the freely moving animal in real time. Results: Combinations of cocaine and caffeine were observed to block the increased release of DA moderately after administration of the low dose (2.5 mg/kg cocaine and 12.5 mg/kg caffeine) and dramatically after administration of the high dose (10 mg/kg cocaine and 50 mg/kg caffeine), suggesting neuroprotection. Similarly, CPT and cocaine showed a decreased DA surge when administered in combination. Thus, the low and high dose of a nonselective adenosine antagonist, caffeine, and a moderate dose of a selective adenosine antagonist, CPT, protected against the cocaine-induced DA release. Conclusions: These results show a significant interaction between adenosine and DA release and suggest therapeutic options for cocaine addiction and disorders associated with DA dysfunction. PMID:25054079

G-quadruplex based Exo III-assisted signal amplification aptasensor for the colorimetric detection of adenosine.

PubMed

Xu, Lei; Shen, Xin; Li, Bingzhi; Zhu, Chunhong; Zhou, Xuemin

2017-08-08

Adenosine is an endogenous nucleotide pivotally involved in nucleic acid and energy metabolism. Its excessive existence may indicate tumorigenesis, typically lung cancer. Encouraged by its significance as the clinical biomarker, sensitive assay methods towards adenosine have been popularized, with high cost and tedious procedures as the inevitable defects. Herein, we report a label-free aptamer-based exonuclease III (Exo III) amplification colorimetric aptasensor for the highly sensitive and cost-effective detection of adenosine. The strategy employed two unlabeled hairpin DNA oligonucleotides (HP1 and HP2), where HP1 contained the aptamer towards adenosine and HP2 embedded the guanine-rich sequence (GRS). In the presence of adenosine, hairpin HP1 could form specific binding with adenosine and trigger the unfolding of HP1's hairpin structure. The resulting adenosine-HP1 complex could hybridize with HP2, generating the Exo III recognition site. After Exo III-assisted degradation, the GRS was released from HP2, and the adenosine-HP1 was released back to the solution to combine another HP2, inducing the cycling amplification. After multiple circulations, the released ample GRSs were induced to form G-quadruplex, further catalyzing the oxidation of TMB, yielding a color change which was finally mirrored in the absorbance change. On the contrary, the absence of adenosine failed to unfold HP1, remaining color unchanged eventually. Thanks to the amplification strategy, the limit of detection was lowered to 17 nM with a broad linear range from 50 nM to 6 μM. The proposed method was successfully applied to the detection of adenosine in biological samples and satisfying recoveries were acquired. Copyright © 2017 Elsevier B.V. All rights reserved.

Cyclical cell stretching of skin-derived fibroblasts downregulates connective tissue growth factor (CTGF) production.

PubMed

Kanazawa, Yuichiro; Nomura, Jun; Yoshimoto, Shinya; Suzuki, Toshikazu; Kita, Kazuko; Suzuki, Nobuo; Ichinose, Masaharu

2009-01-01

Delayed healing of skin wounds can be caused by wound instability, whereas appropriate massage or exercise prevents sclerosis and scar contracture. However, the mechanism by which wound healing is related to mechanical stress has not been fully elucidated. The present study aimed to identify whether mechanical stretching of fibroblasts reduces their production of extracellular matrix. We transferred skin fibroblasts into collagen-coated elastic silicone chambers, cultured them on a stretching apparatus, and used RT-PCR to examine the effects of mechanical stretching on the expression levels of 17 genes related to extracellular matrix production and growth factor secretion. We found that connective tissue growth factor (CTGF) was downregulated after 24 hr of cell stretching. Specifically, the CTGF mRNA and protein levels were 50% and 48% of the control levels, respectively. These findings suggest that cyclic stretching of fibroblasts contributes to anti-fibrotic processes by reducing CTGF production.

Adenosine metabolism in Toxoplasma gondii: potential targets for chemotherapy.

PubMed

el Kouni, Mahmoud H

2007-01-01

Toxoplasma gondii is an intracellular parasitic protozoan that infects approximately a billion people worldwide. Infection with T. gondii represents a major health problem for immunocompromised individuals, such as AIDS patients, organ transplant recipients, and the unborn children of infected mothers. Currently available drugs usually do not eradicate infection and as many as 50% of the patients do not respond to this therapy. Furthermore, they are ineffective against T. gondii tissue cysts. In addition, prolonged exposure to these drugs induces serious host toxicity forcing the discontinuation of the therapy. Finally, there is no effective vaccine currently available for the treatment of toxoplasmosis. Therefore, it is necessary to develop new and effective drugs for the treatment and management of toxoplasmosis. The rational design of a drug depends on the exploitation of fundamental biochemical or physiological differences between pathogens and their host. Some of the most striking differences between T. gondii and their mammalian host are found in purine metabolism. T. gondii, like most parasites studied, lack the ability to synthesize purines do novo and depend on the salvage of purines from their host to satisfy their requirements of purines. In this respect, the salvage of adenosine is the major source of purines in T. gondii. Therefore, interference with adenosine uptake and metabolism in T. gondii can be selectively detrimental to the parasite. The host cells, on the other hand, can still obtain their purine requirements by their de novo pathways. This review will focus on the broad aspects of the adenosine transport and the enzyme adenosine kinase (EC 2.7.1.20) which are the two primary routes for adenosine utilization in T. gondii, in an attempt to illustrate their potentials as targets for chemotherapy against this parasite.

Protection against methamphetamine-induced neurotoxicity to neostriatal dopaminergic neurons by adenosine receptor activation.

PubMed

Delle Donne, K T; Sonsalla, P K

1994-12-01

Methamphetamine (METH)-induced neurotoxicity to nigrostriatal dopaminergic neurons in experimental animals appears to have a glutamatergic component because blockade of N-methyl-D-aspartate receptors prevents the neuropathologic consequences. Because adenosine affords neuroprotection against various forms of glutamate-mediated neuronal damage, the present studies were performed to investigate whether adenosine plays a protective role in METH-induced toxicity. METH-induced decrements in neostriatal dopamine content and tyrosine hydroxylase activity in mice were potentiated by concurrent treatment with caffeine, a nonselective adenosine antagonist that blocks both A1 and A2 adenosine receptors. In contrast, chronic treatment of mice with caffeine through their drinking water for 4 weeks, which increased the number of adenosine A1 receptors in the neostriatum and frontal cortex, followed by drug washout, prevented the neurochemical changes produced by the treatment of mice with METH treatment. In contrast, this treatment did not prevent 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine-induced dopaminergic neurotoxicity. Furthermore, concurrent administration of cyclopentyladenosine, an adenosine A1 receptor agonist, attenuated the METH-induced neurochemical changes. This protection by cyclopentyladenosine was blocked by cyclopentyltheophylline, an A1 receptor antagonist. These results indicate that activation of A1 receptors can protect against METH-induced neurotoxicity in mice.

An enzyme-linked immuno-mass spectrometric assay with the substrate adenosine monophosphate.

PubMed

Florentinus-Mefailoski, Angelique; Soosaipillai, Antonius; Dufresne, Jaimie; Diamandis, Eleftherios P; Marshall, John G

2015-02-01

An enzyme-linked immuno-mass spectrometric assay (ELIMSA) with the specific detection probe streptavidin conjugated to alkaline phosphatase catalyzed the production of adenosine from the substrate adenosine monophosphate (AMP) for sensitive quantification of prostate-specific antigen (PSA) by mass spectrometry. Adenosine ionized efficiently and was measured to the femtomole range by dilution and direct analysis with micro-liquid chromatography, electrospray ionization, and mass spectrometry (LC-ESI-MS). The LC-ESI-MS assay for adenosine production was shown to be linear and accurate using internal (13)C(15)N adenosine isotope dilution, internal (13)C(15)N adenosine one-point calibration, and external adenosine standard curves with close agreement. The detection limits of LC-ESI-MS for alkaline phosphatase-streptavidin (AP-SA, ∼190,000 Da) was tested by injecting 0.1 μl of a 1 pg/ml solution, i.e., 100 attograms or 526 yoctomole (5.26E-22) of the alkaline-phosphatase labeled probe on column (about 315 AP-SA molecules). The ELIMSA for PSA was linear and showed strong signals across the picogram per milliliter range and could robustly detect PSA from all of the prostatectomy patients and all of the female plasma samples that ranged as low as 70 pg/ml with strong signals well separated from the background and well within the limit of quantification of the AP-SA probe. The results of the ELIMSA assay for PSA are normal and homogenous when independently replicated with a fresh standard over multiple days, and intra and inter diem assay variation was less than 10 % of the mean. In a blind comparison, ELIMSA showed excellent agreement with, but was more sensitive than, the present gold standard commercial fluorescent ELISA, or ECL-based detection, of PSA from normal and prostatectomy samples, respectively.

The role of anti-cyclic citrullinated peptide antibodies in predicting rheumatoid arthritis.

PubMed

Rexhepi, Sylejman; Rexhepi, Mjellma; Sahatçiu-Meka, Vjollca; Tafaj, Argjend; Izairi, Remzi; Rexhepi, Blerta

2011-01-01

The study presents the results of predicting role of anti-cyclic citrullinated peptide antibodies in rheumatoid arthritis, compared to rheumatoid factor. 32 patients with rheumatoid arthritis were identified from a retrospective chart review. The results of our study show that presence of the rheumatoid factor has less diagnostic and prognostic significance than the anti-cyclic citrullinated peptide, and suggests its superiority in predicting an erosive disease course.

Predictors and Diagnostic Significance of the Adenosine Related Side Effects on Myocardial Perfusion SPECT/CT Imaging

PubMed Central

Yıldırım Poyraz, Nilüfer; Özdemir, Elif; Poyraz, Barış Mustafa; Kandemir, Zuhal; Keskin, Mutlay; Türkölmez, Şeyda

2014-01-01

Objective: The aim of this study was to investigate the relationship between patient characteristics and adenosine-related side-effects during stress myocard perfusion imaging (MPI). The effect of presence of adenosine-related side-effects on the diagnostic value of MPI with integrated SPECT/CT system for coronary artery disease (CAD), was also assessed in this study. Methods: Total of 281 patients (109 M, 172 F; mean age:62.6±10) who underwent standard adenosine stress protocol for MPI, were included in this study. All symptoms during adenosine infusion were scored according to the severity and duration. For the estimation of diagnostic value of adenosine MPI with integrated SPECT/CT system, coronary angiography (CAG) or clinical follow-up were used as gold standard. Results: Total of 173 patients (61.6%) experienced adenosine-related side-effects (group 1); flushing, dyspnea, and chest pain were the most common. Other 108 patients completed pharmacologic stress (PS) test without any side-effects (group 2). Test tolerability were similar in the patients with cardiovascular or airway disease to others, however dyspnea were observed significantly more common in patients with mild airway disease. Body mass index (BMI) ≥30 kg/m2 and age ≤45 years were independent predictors of side-effects. The diagnostic value of MPI was similar in both groups. Sensitivity of adenosine MPI SPECT/CT was calculated to be 86%, specificity was 94% and diagnostic accuracy was 92% for diagnosis of CAD. Conclusion: Adenosine MPI is a feasible and well tolerated method in patients who are not suitable for exercise stress test as well as patients with cardiopulmonary disease. However age ≤45 years and BMI ≥30 kg/m2 are the positive predictors of adenosine-related side-effects, the diagnostic value of adenosine MPI SPECT/CT is not affected by the presence of adenosine related side-effects. PMID:25541932

Hyperpolarisation of cultured human chondrocytes following cyclical pressure-induced strain: evidence of a role for alpha 5 beta 1 integrin as a chondrocyte mechanoreceptor.

PubMed

Wright, M O; Nishida, K; Bavington, C; Godolphin, J L; Dunne, E; Walmsley, S; Jobanputra, P; Nuki, G; Salter, D M

1997-09-01

Mechanical stimuli influence chondrocyte metabolism, inducing changes in intracellular cyclic adenosine monophosphate and proteoglycan production. We have previously demonstrated that primary monolayer cultures of human chondrocytes have an electrophysiological response after intermittent pressure-induced strain characterised by a membrane hyperpolarisation of approximately 40%. The mechanisms responsible for these changes are not fully understood but potentially involve signalling molecules such as integrins that link extracellular matrix with cytoplasmic components. The results reported in this paper demonstrate that the transduction pathways involved in the hyperpolarisation response of human articular chondrocytes in vitro after cyclical pressure-induced strain involve alpha 5 beta 1 integrin. We have demonstrated, using pharmacological inhibitors of a variety of intracellular signalling pathways, that the actin cytoskeleton, the phospholipase C calmodulin pathway, and both tyrosine protein kinase and protein kinase C activities are important in the transduction of the electrophysiological response. These results suggest that alpha 5 beta 1 is an important chondrocyte mechanoreceptor and a potential regulator of chondrocyte function.

Adenosine decreases oxidative stress and protects H2O2-treated neural stem cells against apoptosis through decreasing Mst1 expression.

PubMed

Gholinejad, Masoumeh; Jafari Anarkooli, Iraj; Taromchi, Amirhossein; Abdanipour, Alireza

2018-05-01

Overproduction of free radicals during oxidative stress induces damage to key biomolecules and activates programed cell death pathways. Neuronal cell death in the nervous system leads to a number of neurodegenerative diseases. The aim of the present study was to evaluate the neuroprotective effect of adenosine on inhibition of apoptosis induced by hydrogen peroxide (H 2 O 2 ) in bone marrow-derived neural stem cells (B-dNSCs), with focus on its regulatory effect on the expression of mammalian sterile 20-like kinase 1 ( Mst1 ), as a novel proapoptotic kinase. B-dNSCs were exposed to adenosine at different doses (2, 4, 6, 8 and 10 µM) for 48 h followed by 125 µM H 2 O 2 for 30 min. Using MTT, terminal deoxynucleotidyl transferase dUTP nick-end labeling and real-time reverse transcription polymerase chain reaction assays, the effects of adenosine on cell survival, apoptosis and Mst1 , nuclear factor (erythroid-derived 2)-like 2 and B-cell lymphoma 2 and adenosine A1 receptor expression were evaluated in pretreated B-dNSCs compared with controls (cells treated with H 2 O 2 only). Firstly, results of the MTT assay indicated 6 µM adenosine to be the most protective dose in terms of promotion of cell viability. Subsequent assays using this dosage indicated that apoptosis rate and Mst1 expression in B-dNSCs pretreated with 6 µM adenosine were significantly decreased compared with the control group. These findings suggest that adenosine protects B-dNSCs against oxidative stress-induced cell death, and therefore, that it may be used to promote the survival rate of B-dNSCs and as a candidate for the treatment of oxidative stress-mediated neurological diseases.

The amphiphilic peptide adenoregulin enhances agonist binding to A1-adenosine receptors and [35S]GTP gamma S to brain membranes.

PubMed

Moni, R W; Romero, F S; Daly, J W

1995-08-01

1. Adenoregulin is an amphilic peptide isolated from skin mucus of the tree frog, Phyllomedusa bicolor. Synthetic adenoregulin enhanced the binding of agonists to several G-protein-coupled receptors in rat brain membranes. 2. The maximal enhancement of agonist binding, and in parentheses, the concentration of adenoregulin affording maximal enhancement were as follows: 60% (20 microM) for A1-adenosine receptors, 30% (100 microM) for A2a-adenosine receptors, 20% (2 microM) for alpha 2-adrenergic receptors, and 30% (10 microM) for 5HT1A receptors. High affinity agonist binding for A1-, alpha 2-, and 5HT1A-receptors was virtually abolished by GTP gamma S in the presence of adenoregulin, but was only partially abolished in its absence. Magnesium ions increased the binding of agonists to receptors and reduced the enhancement elicited by adenoregulin. 3. The effect of adenoregulin on binding of N6-cyclohexyladenosine ([3H]CHA) to A1-receptors was relatively slow and was irreversible. Adenoregulin increased the Bmax value for [3H]CHA binding sites, and the proportion of high affinity states, and slowed the rate of [3H]CHA dissociation. Binding of the A1-selective antagonist, [3H]DPCPX, was maximally enhanced by only 13% at 2 microM adenoregulin. Basal and A1-adenosine receptor-stimulated binding of [35S]GTP gamma S were maximally enhanced 45% and 23%, respectively, by 50 microM adenoregulin. In CHAPS-solubilized membranes from rat cortex, the binding of both [3H]CHA and [3H]DPCPX were enhanced by adenoregulin. Binding of [3H]CHA to membranes from DDT1 MF-2 cells was maximally enhanced 17% at 20 microM adenoregulin. In intact DDT1 MF-2 cells, 20 microM adenoregulin did not potentiate the inhibition of cyclic AMP accumulation mediated via the adenosine A1 receptor. 4. It is proposed that adenoregulin enhances agonist binding through a mechanism involving enhancement of guanyl nucleotide exchange at G-proteins, resulting in a conversion of receptors into a high affinity state

Crystal Structure of Schistosoma mansoni Adenosine Phosphorylase/5’-Methylthioadenosine Phosphorylase and Its Importance on Adenosine Salvage Pathway

PubMed Central

Torini, Juliana Roberta; Brandão-Neto, José; DeMarco, Ricardo; Pereira, Humberto D'Muniz

2016-01-01

Schistosoma mansoni do not have de novo purine pathways and rely on purine salvage for their purine supply. It has been demonstrated that, unlike humans, the S. mansoni is able to produce adenine directly from adenosine, although the enzyme responsible for this activity was unknown. In the present work we show that S. mansoni 5´-deoxy-5´-methylthioadenosine phosphorylase (MTAP, E.C. 2.4.2.28) is capable of use adenosine as a substrate to the production of adenine. Through kinetics assays, we show that the Schistosoma mansoni MTAP (SmMTAP), unlike the mammalian MTAP, uses adenosine substrate with the same efficiency as MTA phosphorolysis, which suggests that this enzyme is part of the purine pathway salvage in S. mansoni and could be a promising target for anti-schistosoma therapies. Here, we present 13 SmMTAP structures from the wild type (WT), including three single and one double mutant, and generate a solid structural framework for structure description. These crystal structures of SmMTAP reveal that the active site contains three substitutions within and near the active site when compared to it mammalian counterpart, thus opening up the possibility of developing specific inhibitors to the parasite MTAP. The structural and kinetic data for 5 substrates reveal the structural basis for this interaction, providing substract for inteligent design of new compounds for block this enzyme activity. PMID:27935959

The regulation of ATP release from the urothelium by adenosine and transepithelial potential.

PubMed

Dunning-Davies, Bryony M; Fry, Christopher H; Mansour, Dina; Ferguson, Douglas R

2013-03-01

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Stretch of the urothelium, as occurs during bladder filling, is associated with a release of ATP that is postulated to act as a sensory neurotransmitter. The regulation of ATP release is poorly understood and in particular if there is a feedback mechanism provided by ATP itself. Adenosine, a breakdown product of ATP, is a potent inhibitor of stretch-induced ATP release, acting through and A1 receptor; endogenous levels are about 0.6μM. Data are consistent with ATP release relying on the rise of intracellular Ca2+. Transepithelial potential also controls ATP release, also acting via an A1 receptor-dependent pathway. To test the hypothesis that distension-induced ATP release from the bladder urothelium is regulated by adenosine as well as changes to transurothelial potential (TEP). To examine the role of changes to intracellular [Ca(2+) ] in ATP release. Rabbit urothelium/suburothelium membranes were used in an Ussing chamber system. Distension was induced by fluid removal from the chamber bathing the serosal (basolateral) membrane face. The TEP and short-circuit current were measured. ATP was measured in samples aspirated from the serosal chamber by a luciferin-luciferase assay. Intracellular [Ca(2+) ] was measured in isolated urothelial cells using the fluorochrome Fura-2. All experiments were performed at 37°C. Distension-induced ATP release was decreased by adenosine (1-10 μm) and enhanced by adenosine deaminase and A1- (but not A2-) receptor antagonists. Distension-induced ATP release was reduced by 2-APB, nifedipine and capsazepine; capsaicin induced ATP release in the absence of distension. ATP and capsaicin, but not adenosine, generated intracellular Ca(2+) transients; adenosine did not affect the ATP-generated Ca(2+) transient. ATP release was dependent on a finite transepithelial potential. Changes to TEP, in the absence of distension, generated ATP release that was in turn reduced by adenosine

Adenosine-loaded dissolving microneedle patches to improve skin wrinkles, dermal density, elasticity and hydration.

PubMed

Kang, G; Tu, T N T; Kim, S; Yang, H; Jang, M; Jo, D; Ryu, J; Baek, J; Jung, H

2018-04-01

Although dissolving microneedle patches have been widely studied in the cosmetics field, no comparisons have been drawn with the topical applications available for routine use. In this study, two wrinkle-improving products, adenosine-loaded dissolving microneedle patches and an adenosine cream, were evaluated for efficacy, with respect to skin wrinkling, dermal density, elasticity, and hydration, and safety in a clinical test on the crow's feet area. Clinical efficacy and safety tests were performed for 10 weeks on 22 female subjects with wrinkles around their eyes. The adenosine-loaded dissolving microneedle patch was applied once every 3 days, in the evening, for 8 weeks to the designated crow's feet area. The adenosine cream was applied two times per day, in the morning and evening, for 8 weeks to the other crow's feet area. Skin wrinkling, dermal density, elasticity, and hydration were measured by using PRIMOS ® premium, Dermascan ® C, Cutometer ® MPA580, and Corneometer ® CM 825, respectively. In addition, subjective skin irritation was evaluated by self-observation, and objective skin irritation was assessed through expert interviews. The adenosine-loaded dissolving microneedle patches had a similar or better efficacy than the adenosine cream. Both groups showed statistically significant efficacy for almost all parameters (P < 0.05). The dissolving microneedle patches had a long-lasting effect on the average wrinkle depth (P < 0.05), only showed efficacy in dermal density (P < 0.05), had an early improving effect on elasticity (P < 0.05), and demonstrated better hydration efficacy (P < 0.001). No adverse effects were observed in either group during the test period. In the clinical efficacy test of four skin-improvement parameters, adenosine-loaded dissolving microneedle patches showed the same or better effect than the adenosine cream, although the weekly adenosine dose was 140 times lower. The dissolving microneedle patches caused no

Adenosine regulates CD8 T-cell priming by inhibition of membrane-proximal T-cell receptor signalling

PubMed Central

Linnemann, Carsten; Schildberg, Frank A; Schurich, Anna; Diehl, Linda; Hegenbarth, Silke I; Endl, Elmar; Lacher, Svenja; Müller, Christa E; Frey, Jürgen; Simeoni, Luca; Schraven, Burkhart; Stabenow, Dirk; Knolle, Percy A

2009-01-01

Adenosine is a well-described anti-inflammatory modulator of immune responses within peripheral tissues. Extracellular adenosine accumulates in inflamed and damaged tissues and inhibits the effector functions of various immune cell populations, including CD8 T cells. However, it remains unclear whether extracellular adenosine also regulates the initial activation of naïve CD8 T cells by professional and semi-professional antigen-presenting cells, which determines their differentiation into effector or tolerant CD8 T cells, respectively. We show that adenosine inhibited the initial activation of murine naïve CD8 T cells after αCD3/CD28-mediated stimulation. Adenosine caused inhibition of activation, cytokine production, metabolic activity, proliferation and ultimately effector differentiation of naïve CD8 T cells. Remarkably, adenosine interfered efficiently with CD8 T-cell priming by professional antigen-presenting cells (dendritic cells) and semi-professional antigen-presenting cells (liver sinusoidal endothelial cells). Further analysis of the underlying mechanisms demonstrated that adenosine prevented rapid tyrosine phosphorylation of the key kinase ZAP-70 as well as Akt and ERK1/2 in naïve αCD3/CD28-stimulated CD8 cells. Consequently, αCD3/CD28-induced calcium-influx into CD8 cells was reduced by exposure to adenosine. Our results support the notion that extracellular adenosine controls membrane-proximal T-cell receptor signalling and thereby also differentiation of naïve CD8 T cells. These data raise the possibility that extracellular adenosine has a physiological role in the regulation of CD8 T-cell priming and differentiation in peripheral organs. PMID:19740334

Adenosine regulates CD8 T-cell priming by inhibition of membrane-proximal T-cell receptor signalling.

PubMed

Linnemann, Carsten; Schildberg, Frank A; Schurich, Anna; Diehl, Linda; Hegenbarth, Silke I; Endl, Elmar; Lacher, Svenja; Müller, Christa E; Frey, Jürgen; Simeoni, Luca; Schraven, Burkhart; Stabenow, Dirk; Knolle, Percy A

2009-09-01

Adenosine is a well-described anti-inflammatory modulator of immune responses within peripheral tissues. Extracellular adenosine accumulates in inflamed and damaged tissues and inhibits the effector functions of various immune cell populations, including CD8 T cells. However, it remains unclear whether extracellular adenosine also regulates the initial activation of naïve CD8 T cells by professional and semi-professional antigen-presenting cells, which determines their differentiation into effector or tolerant CD8 T cells, respectively. We show that adenosine inhibited the initial activation of murine naïve CD8 T cells after alphaCD3/CD28-mediated stimulation. Adenosine caused inhibition of activation, cytokine production, metabolic activity, proliferation and ultimately effector differentiation of naïve CD8 T cells. Remarkably, adenosine interfered efficiently with CD8 T-cell priming by professional antigen-presenting cells (dendritic cells) and semi-professional antigen-presenting cells (liver sinusoidal endothelial cells). Further analysis of the underlying mechanisms demonstrated that adenosine prevented rapid tyrosine phosphorylation of the key kinase ZAP-70 as well as Akt and ERK1/2 in naïve alphaCD3/CD28-stimulated CD8 cells. Consequently, alphaCD3/CD28-induced calcium-influx into CD8 cells was reduced by exposure to adenosine. Our results support the notion that extracellular adenosine controls membrane-proximal T-cell receptor signalling and thereby also differentiation of naïve CD8 T cells. These data raise the possibility that extracellular adenosine has a physiological role in the regulation of CD8 T-cell priming and differentiation in peripheral organs.

Adenosine deaminase deficiency: a review.

PubMed

Flinn, Aisling M; Gennery, Andrew R

2018-04-24

Adenosine deaminase (ADA) deficiency leads to an accumulation of toxic purine degradation by-products, most potently affecting lymphocytes, leading to adenosine deaminase-deficient severe combined immunodeficiency. Whilst most notable affects are on lymphocytes, other manifestations include skeletal abnormalities, neurodevelopmental affects and pulmonary manifestations associated with pulmonary-alveolar proteinosis. Affected patients present in early infancy, usually with persistent infection, or with pulmonary insufficiency. Three treatment options are currently available. Initial treatment with enzyme replacement therapy may alleviate acute symptoms and enable partial immunological reconstitution, but treatment is life-long, immune reconstitution is incomplete, and the reconstituted immune system may nullify the effects of the enzyme replacement. Hematopoietic stem cell transplant has long been established as the treatment of choice, particularly where a matched sibling or well matched unrelated donor is available. More recently, the use of gene addition techniques to correct the genetic defect in autologous haematopoietic stem cells treatment has demonstrated immunological and clinical efficacy. This article reviews the biology, clinical presentation, diagnosis and treatment of ADA-deficiency.

Adenosine enhances sweet taste through A2B receptors in the taste bud

PubMed Central

Dando, Robin; Dvoryanchikov, Gennady; Pereira, Elizabeth; Chaudhari, Nirupa; Roper, Stephen D.

2012-01-01

Mammalian taste buds use ATP as a neurotransmitter. Taste Receptor (Type II) cells secrete ATP via gap junction hemichannels into the narrow extracellular spaces within a taste bud. This ATP excites primary sensory afferent fibers and also stimulates neighboring taste bud cells. Here we show that extracellular ATP is enzymatically degraded to adenosine within mouse vallate taste buds and that this nucleoside acts as an autocrine neuromodulator to selectively enhance sweet taste. In Receptor cells in a lingual slice preparation, Ca2+ mobilization evoked by focally applied artificial sweeteners was significantly enhanced by adenosine (50 µM). Adenosine had no effect on bitter or umami taste responses, and the nucleoside did not affect Presynaptic (Type III) taste cells. We also used biosensor cells to measure transmitter release from isolated taste buds. Adenosine (5 µM) enhanced ATP release evoked by sweet but not bitter taste stimuli. Using single-cell RT-PCR on isolated vallate taste cells, we show that many Receptor cells express adenosine receptors, Adora2b, while Presynaptic (Type III) and Glial-like (Type I) cells seldom do. Furthermore, Adora2b receptors are significantly associated with expression of the sweet taste receptor subunit, Tas1r2. Adenosine is generated during taste stimulation mainly by the action of the ecto-5′-nucleotidase, NT5E, and to a lesser extent, prostatic acid phosphatase (ACPP). Both these ecto-nucleotidases are expressed by Presynaptic cells, as shown by single-cell RT-PCR, enzyme histochemistry and immunofluorescence. Our findings suggest that ATP released during taste reception is degraded to adenosine to exert positive modulation particularly on sweet taste. PMID:22219293

Adenosine enhances sweet taste through A2B receptors in the taste bud.

PubMed

Dando, Robin; Dvoryanchikov, Gennady; Pereira, Elizabeth; Chaudhari, Nirupa; Roper, Stephen D

2012-01-04

Mammalian taste buds use ATP as a neurotransmitter. Taste Receptor (type II) cells secrete ATP via gap junction hemichannels into the narrow extracellular spaces within a taste bud. This ATP excites primary sensory afferent fibers and also stimulates neighboring taste bud cells. Here we show that extracellular ATP is enzymatically degraded to adenosine within mouse vallate taste buds and that this nucleoside acts as an autocrine neuromodulator to selectively enhance sweet taste. In Receptor cells in a lingual slice preparation, Ca(2+) mobilization evoked by focally applied artificial sweeteners was significantly enhanced by adenosine (50 μM). Adenosine had no effect on bitter or umami taste responses, and the nucleoside did not affect Presynaptic (type III) taste cells. We also used biosensor cells to measure transmitter release from isolated taste buds. Adenosine (5 μM) enhanced ATP release evoked by sweet but not bitter taste stimuli. Using single-cell reverse transcriptase (RT)-PCR on isolated vallate taste cells, we show that many Receptor cells express the adenosine receptor, Adora2b, while Presynaptic (type III) and Glial-like (type I) cells seldom do. Furthermore, Adora2b receptors are significantly associated with expression of the sweet taste receptor subunit, Tas1r2. Adenosine is generated during taste stimulation mainly by the action of the ecto-5'-nucleotidase, NT5E, and to a lesser extent, prostatic acid phosphatase. Both these ecto-nucleotidases are expressed by Presynaptic cells, as shown by single-cell RT-PCR, enzyme histochemistry, and immunofluorescence. Our findings suggest that ATP released during taste reception is degraded to adenosine to exert positive modulation particularly on sweet taste.

Interleukin-6 Contributes to Inflammation and Remodeling in a Model of Adenosine Mediated Lung Injury

PubMed Central

Pedroza, Mesias; Schneider, Daniel J.; Karmouty-Quintana, Harry; Coote, Julie; Shaw, Stevan; Corrigan, Rebecca; Molina, Jose G.; Alcorn, Joseph L.; Galas, David; Gelinas, Richard; Blackburn, Michael R.

2011-01-01

Background Chronic lung diseases are the third leading cause of death in the United States due in part to an incomplete understanding of pathways that govern the progressive tissue remodeling that occurs in these disorders. Adenosine is elevated in the lungs of animal models and humans with chronic lung disease where it promotes air-space destruction and fibrosis. Adenosine signaling increases the production of the pro-fibrotic cytokine interleukin-6 (IL-6). Based on these observations, we hypothesized that IL-6 signaling contributes to tissue destruction and remodeling in a model of chronic lung disease where adenosine levels are elevated. Methodology/Principal Findings We tested this hypothesis by neutralizing or genetically removing IL-6 in adenosine deaminase (ADA)-deficient mice that develop adenosine dependent pulmonary inflammation and remodeling. Results demonstrated that both pharmacologic blockade and genetic removal of IL-6 attenuated pulmonary inflammation, remodeling and fibrosis in this model. The pursuit of mechanisms involved revealed adenosine and IL-6 dependent activation of STAT-3 in airway epithelial cells. Conclusions/Significance These findings demonstrate that adenosine enhances IL-6 signaling pathways to promote aspects of chronic lung disease. This suggests that blocking IL-6 signaling during chronic stages of disease may provide benefit in halting remodeling processes such as fibrosis and air-space destruction. PMID:21799929

The role of adenosine challenge in catheter ablation for atrial fibrillation: A systematic review and meta-analysis.

PubMed

McLellan, Alex J A; Kumar, Saurabh; Smith, Catherine; Ling, Liang-Han; Prabhu, Sandeep; Kalman, Jonathan M; Kistler, Peter M

2017-06-01

Adenosine may unmask dormant PV conduction and facilitate consolidation of PV isolation. We performed a meta-analysis to determine the impact of adenosine administration on clinical outcomes in patients undergoing PVI. References and electronic databases reporting AF ablation and adenosine following PVI were searched through to 22nd November 2015. The impact of adenosine on freedom from AF was assessed in twenty publications after radiofrequency ablation (RFA), and in four publications after cryoablation to achieve PVI. Relative risks were calculated and combined in a meta-analysis using random effects modeling. In patients undergoing RFA with adenosine challenge, there was a significant reduction in freedom from AF in patients with versus without adenosine induced reconnection (RR 0.86; 95%CI 0.77-0.98; p=0.02) particularly if no further ablation was performed (RR 0.66; 95%CI 0.50-0.87; p<0.01). There was no difference when comparing outcomes in studies of routine adenosine challenge vs no adenosine (RR 1.07; 95%CI 0.93-1.22; p=0.36). There was a non-significant trend to an increase in freedom from AF in patients receiving routine adenosine challenge (RR 1.18 95%CI 0.99-1.42; p=0.07) in non-randomized studies using cryoablation. Adenosine induced PV reconnection following PVI is associated with a significant increase in AF recurrence, particularly if the reconnection sites are not targeted for ablation. The routine use of adenosine may be beneficial in AF ablation if given early post-PVI, at sufficient dose and reconnection is ablated. Copyright © 2017 Elsevier B.V. All rights reserved.

New parasite inhibitors encompassing novel conformationally-locked 5'-acyl sulfamoyl adenosines.

PubMed

Dixit, Shailesh S; Upadhayaya, Ram Shankar; Chattopadhyaya, Jyoti

2012-08-14

We describe the design, synthesis and biological evaluation of conformationally-locked 5'-acyl sulfamoyl adenosine derivatives as new parasitic inhibitors against Trypanosoma and Leishmania. The conformationally-locked (3'-endo, North-type) nucleosides have been synthesized by covalently attaching a 4'-CH(2)-O-2' bridge () across C2'-C4' of adenosine in order to reduce the conformational flexibility of the pentose ring. This is designed to decrease the entropic penalty for complex formation with the target protein, which may improve free-energy of stabilization of the complex leading to improved potency. Conformationally-locked 5'-acyl sulfamoyl adenosine derivatives (16-22) were tested against parasitic protozoans for the first time in this work, and showed potent inhibition of Trypanosoma cruzi, Trypanosoma brucei, Trypanosoma rhodesiense and Leishmania infantum with IC(50) = 0.25-0.51 μM. In particular, the potent 5'-pentanyl acyl sulfamoyl adenosine derivative 17 (IC(50) = 0.25 μM) against intracellular L. infantum amastigotes and Trypanosoma subspecies is interesting in view of its almost insignificant cytotoxicity in murine macrophage host cells (CC(50) >4 μM) and in diploid human fibroblasts MRC-5 cell lines (CC(50) 4 μM). This work also suggests that variable alkyl chain length of the acyl group on the acylsulfamoyl side chain at 5' can modulate the toxicity of 5'-O-sulfamoylnucleoside analogues. This conformationally-locked sulfamoyl adenosine scaffold presents some interesting possibilities for further drug design and lead optimization.

Potentiation of the depression by adenosine of rat cerebral cortical neurones by progestational agents.

PubMed Central

Phillis, J. W.

1986-01-01

The effects of four progestational agents pregnenolone sulphate, cyproterone acetate, norethindrone acetate and progesterone, on adenosine-evoked depression of the firing of rat cerebral cortical neurones have been studied. When applied iontophoretically, pregnenolone sulphate, cyproterone, and norethindrone enhanced the actions of iontophoretically applied adenosine and failed to potentiate the depressant effects of adenosine 5'-N-ethylcarboxamide and gamma-aminobutyric acid. Cyproterone acetate (50 micrograms kg-1) and progesterone (200 micrograms kg-1) administered intravenously enhanced the depressant actions of iontophoretically applied adenosine. When applied by large currents, cyproterone, and less frequently norethindrone, depressed the firing of cerebral cortical neurones. The depressant effects of cyproterone were antagonized by caffeine. Pregnenolone sulphate tended to excite cortical neurones but neither this action, nor its potentiation of adenosine were reproduced by application of sulphate ions. It is hypothesized that some of the psychotropic actions of progestational agents may involve an enhancement of 'purinergic' tone in the central nervous system. PMID:3814905

Cyclic GMP-AMP Synthase Is an Innate Immune DNA Sensor for Mycobacterium tuberculosis.

PubMed

Collins, Angela C; Cai, Haocheng; Li, Tuo; Franco, Luis H; Li, Xiao-Dong; Nair, Vidhya R; Scharn, Caitlyn R; Stamm, Chelsea E; Levine, Beth; Chen, Zhijian J; Shiloh, Michael U

2015-06-10

Activation of the DNA-dependent cytosolic surveillance pathway in response to Mycobacterium tuberculosis infection stimulates ubiquitin-dependent autophagy and inflammatory cytokine production, and plays an important role in host defense against M. tuberculosis. However, the identity of the host sensor for M. tuberculosis DNA is unknown. Here we show that M. tuberculosis activated cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) in macrophages to produce cGAMP, a second messenger that activates the adaptor protein stimulator of interferon genes (STING) to induce type I interferons and other cytokines. cGAS localized with M. tuberculosis in mouse and human cells and in human tuberculosis lesions. Knockdown or knockout of cGAS in human or mouse macrophages blocked cytokine production and induction of autophagy. Mice deficient in cGAS were more susceptible to lethality caused by infection with M. tuberculosis. These results demonstrate that cGAS is a vital innate immune sensor of M. tuberculosis infection. Copyright © 2015 Elsevier Inc. All rights reserved.

Protein kinase C is involved in cyclic adenosine monophosphate formation due to PGF2 alpha desensitization in bovine iris sphincter.

PubMed

Tachado, S D; Zhang, Y; Abdel-Latif, A A

1993-05-01

To examine the mechanisms underlying the effects of PGF2 alpha receptor desensitization on agonist-induced second messenger formation and contraction in bovine iris sphincter. Short-term PGF2 alpha receptor desensitization of the bovine iris sphincter was carried out by incubating the tissue in Krebs-Ringer bicarbonate buffer containing 25 microM PGF2 alpha for 45 min at 37 degrees C. The effects of PGF2 alpha and other pharmacologic agents on inositol 1,4,5-triphosphate (IP3) production and cyclic adenosine monophosphate (cAMP) formation in desensitized and nondesensitized tissues were monitored by anion-exchange chromatography and radioimmunoassay. In the isolated bovine iris sphincter, protein kinase C (PKC) is involved in the activation of adenylate cyclase and the desensitization of prostaglandin F2 alpha receptor-mediated responses supported by these findings. (A) Exposure of the tissue to phorbol 12,13-dibutyrate, used to activate PKC, enhanced basal cAMP formation in a dose (EC50 = 8.8 x 10(-8) M) and time (t1/2 = 7.5 min) dependent manner. Phorbol 12,13-dibutyrate increased cAMP levels by twofold and it potentiated the isoproterenol-induced cAMP formation. The biologically inactive phorbol ester, 4 alpha-phorbol had no effect. Staurosporine, a potent PKC inhibitor, inhibited phorbol 12,13-dibutyrate-induced cAMP formation in a dose-dependent manner (IC50 of 0.25 microM). The increase in cAMP levels by phorbol 12,13-dibutyrate results from stimulation of adenylate cyclase, rather than from inhibition of cAMP phosphodiesterase, and it is not mediated through Ca2+ mobilization. Pretreatment of the tissue with phorbol 12,13-dibutyrate inhibited IP3 production in response to PGF2 alpha. (B) Desensitization of the sphincter with PGF2 alpha for 45 min increased cAMP formation and attenuated IP3 production and contraction. The effects of PGF2 alpha desensitization were reversed by pretreatment of the tissue with staurosporine. Down-regulation of PKC prevented the

Ability of γδ T cells to modulate the Foxp3 T cell response is dependent on adenosine.

PubMed

Liang, Dongchun; Woo, Jeong-Im; Shao, Hui; Born, Willi K; O'Brien, Rebecca L; Kaplan, Henry J; Sun, Deming

2018-01-01

Whether γδ T cells inhibit or enhance the Foxp3 T cell response depends upon their activation status. The critical enhancing effector in the supernatant is adenosine. Activated γδ T cells express adenosine receptors at high levels, which enables them to deprive Foxp3+ T cells of adenosine, and to inhibit their expansion. Meanwhile, cell-free supernatants of γδ T cell cultures enhance Foxp3 T cell expansion. Thus, inhibition and enhancement by γδ T cells of Foxp3 T cell response are a reflection of the balance between adenosine production and absorption by γδ T cells. Non-activated γδ T cells produce adenosine but bind little, and thus enhance the Foxp3 T cell response. Activated γδ T cells express high density of adenosine receptors and have a greatly increased ability to bind adenosine. Extracellular adenosine metabolism and expression of adenosine receptor A2ARs by γδ T cells played a major role in the outcome of γδ and Foxp3 T cell interactions. A better understanding of the functional conversion of γδ T cells could lead to γδ T cell-targeted immunotherapies for related diseases.

Phenotype overlap in Xylella fastidiosa is controlled by the cyclic di-GMP phosphodiesterase Eal in response to antibiotic exposure and diffusible signal factor-mediated cell-cell signaling.

PubMed

de Souza, Alessandra A; Ionescu, Michael; Baccari, Clelia; da Silva, Aline M; Lindow, Steven E

2013-06-01

Eal is an EAL domain protein in Xylella fastidiosa homologous to one involved in resistance to tobramycin in Pseudomonas aeruginosa. EAL and HD-GYP domain proteins are implicated in the hydrolysis of the secondary messenger bis-(3'-5')-cyclic dimeric GMP (cyclic di-GMP). Cell density-dependent communication mediated by a Diffusible Signal Factor (DSF) also modulates cyclic di-GMP levels in X. fastidiosa, thereby controlling the expression of virulence genes and genes involved in insect transmission. The possible linkage of Eal to both extrinsic factors such as antibiotics and intrinsic factors such as quorum sensing, and whether both affect virulence, was thus addressed. Expression of eal was induced by subinhibitory concentrations of tobramycin, and an eal deletion mutant was more susceptible to this antibiotic than the wild-type strain and exhibited phenotypes similar to those of an rpfF deletion mutant blocked in DSF production, such as hypermotility, reduced biofilm formation, and hypervirulence to grape. Consistent with that, the rpfF mutant was more susceptible than the wild-type strain to tobramycin. Therefore, we propose that cell-cell communication and antibiotic stress can apparently lead to similar modulations of cyclic di-GMP in X. fastidiosa, resulting in similar phenotypes. However, the effect of cell density is dominant compared to that of antibiotic stress, since eal is suppressed by RpfF, which may prevent inappropriate behavioral changes in response to antibiotic stress when DSF accumulates.

Phenotype Overlap in Xylella fastidiosa Is Controlled by the Cyclic Di-GMP Phosphodiesterase Eal in Response to Antibiotic Exposure and Diffusible Signal Factor-Mediated Cell-Cell Signaling

PubMed Central

de Souza, Alessandra A.; Ionescu, Michael; Baccari, Clelia; da Silva, Aline M.

2013-01-01

Eal is an EAL domain protein in Xylella fastidiosa homologous to one involved in resistance to tobramycin in Pseudomonas aeruginosa. EAL and HD-GYP domain proteins are implicated in the hydrolysis of the secondary messenger bis-(3′-5′)-cyclic dimeric GMP (cyclic di-GMP). Cell density-dependent communication mediated by a Diffusible Signal Factor (DSF) also modulates cyclic di-GMP levels in X. fastidiosa, thereby controlling the expression of virulence genes and genes involved in insect transmission. The possible linkage of Eal to both extrinsic factors such as antibiotics and intrinsic factors such as quorum sensing, and whether both affect virulence, was thus addressed. Expression of eal was induced by subinhibitory concentrations of tobramycin, and an eal deletion mutant was more susceptible to this antibiotic than the wild-type strain and exhibited phenotypes similar to those of an rpfF deletion mutant blocked in DSF production, such as hypermotility, reduced biofilm formation, and hypervirulence to grape. Consistent with that, the rpfF mutant was more susceptible than the wild-type strain to tobramycin. Therefore, we propose that cell-cell communication and antibiotic stress can apparently lead to similar modulations of cyclic di-GMP in X. fastidiosa, resulting in similar phenotypes. However, the effect of cell density is dominant compared to that of antibiotic stress, since eal is suppressed by RpfF, which may prevent inappropriate behavioral changes in response to antibiotic stress when DSF accumulates. PMID:23542613

Selective inhibition of KCa3.1 channels mediates adenosine regulation of the motility of human T cells.

PubMed

Chimote, Ameet A; Hajdu, Peter; Kucher, Vladimir; Boiko, Nina; Kuras, Zerrin; Szilagyi, Orsolya; Yun, Yeo-Heung; Conforti, Laura

2013-12-15

Adenosine, a purine nucleoside, is present at high concentrations in tumors, where it contributes to the failure of immune cells to eliminate cancer cells. The mechanisms responsible for the immunosuppressive properties of adenosine are not fully understood. We tested the hypothesis that adenosine's immunosuppressive functions in human T lymphocytes are in part mediated via modulation of ion channels. The activity of T lymphocytes relies on ion channels. KCa3.1 and Kv1.3 channels control cytokine release and, together with TRPM7, regulate T cell motility. Adenosine selectively inhibited KCa3.1, but not Kv1.3 and TRPM7, in activated human T cells. This effect of adenosine was mainly mediated by A2A receptors, as KCa3.1 inhibition was reversed by SCH58261 (selective A2A receptor antagonist), but not by MRS1754 (A2B receptor antagonist), and it was mimicked by the A2A receptor agonist CGS21680. Furthermore, it was mediated by the cAMP/protein kinase A isoform (PKAI) signaling pathway, as adenylyl-cyclase and PKAI inhibition prevented adenosine effect on KCa3.1. The functional implication of the effect of adenosine on KCa3.1 was determined by measuring T cell motility on ICAM-1 surfaces. Adenosine and CGS21680 inhibited T cell migration. Comparable effects were obtained by KCa3.1 blockade with TRAM-34. Furthermore, the effect of adenosine on cell migration was abolished by pre-exposure to TRAM-34. Additionally, adenosine suppresses IL-2 secretion via KCa3.1 inhibition. Our data indicate that adenosine inhibits KCa3.1 in human T cells via A2A receptor and PKAI, thereby resulting in decreased T cell motility and cytokine release. This mechanism is likely to contribute to decreased immune surveillance in solid tumors.

Inhibition of Transient Receptor Potential Channel Mucolipin-1 (TRPML1) by Lysosomal Adenosine Involved in Severe Combined Immunodeficiency Diseases*

PubMed Central

Zhong, Xi Zoë; Zou, Yuanjie; Sun, Xue; Dong, Gaofeng; Cao, Qi; Pandey, Aditya; Rainey, Jan K.; Zhu, Xiaojuan; Dong, Xian-Ping

2017-01-01

Impaired adenosine homeostasis has been associated with numerous human diseases. Lysosomes are referred to as the cellular recycling centers that generate adenosine by breaking down nucleic acids or ATP. Recent studies have suggested that lysosomal adenosine overload causes lysosome defects that phenocopy patients with mutations in transient receptor potential channel mucolipin-1 (TRPML1), a lysosomal Ca2+ channel, suggesting that lysosomal adenosine overload may impair TRPML1 and then lead to subsequent lysosomal dysfunction. In this study, we demonstrate that lysosomal adenosine is elevated by deleting adenosine deaminase (ADA), an enzyme responsible for adenosine degradation. We also show that lysosomal adenosine accumulation inhibits TRPML1, which is rescued by overexpressing ENT3, the adenosine transporter situated in the lysosome membrane. Moreover, ADA deficiency results in lysosome enlargement, alkalinization, and dysfunction. These are rescued by activating TRPML1. Importantly, ADA-deficient B-lymphocytes are more vulnerable to oxidative stress, and this was rescued by TRPML1 activation. Our data suggest that lysosomal adenosine accumulation impairs lysosome function by inhibiting TRPML1 and subsequently leads to cell death in B-lymphocytes. Activating TRPML1 could be a new therapeutic strategy for those diseases. PMID:28087698

Genetics Home Reference: adenosine monophosphate deaminase deficiency

MedlinePlus

... view the expand/collapse boxes. Description Adenosine monophosphate (AMP) deaminase deficiency is a condition that can affect ... for movement ( skeletal muscles ). In many affected individuals, AMP deaminase deficiency does not cause any symptoms. People ...

Adenosine transport systems on dissociated brain cells from mouse, guinea-pig, and rat

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

Johnston, M.E.; Geiger, J.D.

1990-09-01

The kinetics and sodium dependence of adenosine transport were determined using an inhibitor-stop method on dissociated cell body preparations obtained from mouse, guinea-pig and rat brain. Transport affinity (KT) values for the high affinity adenosine transport systems KT(H) were significantly different between these three species; mean +/- SEM values were 0.34 +/- 0.1 in mouse, 0.9 +/- 0.2 in rat, and 1.5 +/- 0.5 microM in guinea-pig. The KT values for the low affinity transport system KT(L) were not different between the three species. Brain cells from rat displayed a significantly greater maximal capacity to accumulate (3H)adenosine (Vmax) than didmore » mouse or guinea-pig for the high affinity system, or than did mouse for the low affinity system. When sodium chloride was replaced in the transport medium with choline chloride, the KT(H) values for guinea-pig and rat were both increased by approximately 100%; only in rat did the change reach statistical significance. The sodium-dependence of adenosine transport in mouse brain was clearly absent. The differences between KT(H) values in mouse and those in guinea-pig or rat were accentuated in the absence of sodium. The differences in kinetic values, ionic requirements, and pharmacological characteristics between adenosine transporters in CNS tissues of mouse, guinea-pig and rat may help account for some of the variability noted among species in terms of their physiological responses to adenosine.« less

Investigations into the origin of the molecular recognition of several adenosine deaminase inhibitors.

PubMed

Gillerman, Irina; Fischer, Bilha

2011-01-13

Inhibitors of adenosine deaminase (ADA, EC 3.5.4.4) are potential therapeutic agents for the treatment of various health disorders. Several highly potent inhibitors were previously identified, yet they exhibit unacceptable toxicities. We performed a SAR study involving a series of C2 or C8 substituted purine-riboside analogues with a view to discover less potent inhibitors with a lesser toxicity. We found that any substitution at C8 position of nebularine resulted in total loss of activity toward calf intestinal ADA. However, several 2-substituted-adenosine, 8-aza-adenosine, and nebularine analogues exhibited inhibitory activity. Specifically, 2-Cl-purine riboside, 8-aza-2-thiohexyl adenosine, 2-thiohexyl adenosine, and 2-MeS-purine riboside were found to be competitive inhibitors of ADA with K(i) values of 25, 22, 6, and 3 μM, respectively. We concluded that electronic parameters are not major recognition determinants of ADA but rather steric parameters. A C2 substituent which fits ADA hydrophobic pocket and improves H-bonding with the enzyme makes a good inhibitor. In addition, a gg rotamer about C4'-C5' bond is apparently an important recognition determinant.

Adenosine and adenine nucleotides as regulators of cerebral blood flow: roles of acidosis, cell swelling, and KATP channels.

PubMed

Phillis, John W

2004-01-01

A considerable volume of evidence implicates the purine adenosine in the regulation of cerebral blood flow during states such as hypotension, neural activation, hypoxia/ischemia, and hypercapnia/acidosis. The aim of this review is to describe developments in our understanding of the roles that adenosine and the adenine nucleotides play in cerebral blood flow control, with some comparisons to coronary blood flow. The first part of the review focuses on the categorization of receptors for adenosine (A1, A2A, A2B, and A3) and the adenine nucleotides, ATP and ADP (P2X and P2Y). Frequently used agonists and antagonists for these different receptors are mentioned. A description follows of the distribution of these different receptors in cerebral arterioles. The second part of the review initially deals with the literature on the release of adenosine and adenine nucleotides into the extracellular space of the brain, describing the various techniques used to make these measurements and assessing the pitfalls associated with their use. This is followed by a discussion of the factors affecting purine release, which include cell swelling and acidosis. The third section evaluates the role of smooth muscle potassium channels in controlling arteriolar diameter. There is evidence for an important role of KATP and KCa channels, but less is known about the contributions of voltage-dependent (KV) and inwardly rectifying (KIR) channels. This section ends with a discussion on the reported inhibitory effect of nitric oxide synthase inhibitors on the KATP channel and the consequences of such an action for the interpretation of much of the published work on nitric oxide as a regulator of cerebral blood flow. The fourth section evaluates the data supporting a role of adenosine and ATP in the regulation of cerebral blood flow during autoregulation, hypotension, neural activity, hypoxia/ ischemia, and hypercapnia. Studies using antagonists and potentiators of adenosine's actions have led to

Effects of targeted deletion of A1 adenosine receptors on postischemic cardiac function and expression of adenosine receptor subtypes.

PubMed

Morrison, R Ray; Teng, Bunyen; Oldenburg, Peter J; Katwa, Laxmansa C; Schnermann, Jurgen B; Mustafa, S Jamal

2006-10-01

To examine ischemic tolerance in the absence of A(1) adenosine receptors (A(1)ARs), isolated wild-type (WT) and A(1)AR knockout (A(1)KO) murine hearts underwent global ischemia-reperfusion, and injury was measured in terms of functional recovery and efflux of lactate dehydrogenase (LDH). Hearts were analyzed by real-time RT-PCR both at baseline and at intervals during ischemia-reperfusion to determine whether compensatory expression of other adenosine receptor subtypes occurs with either A(1)AR deletion and/or ischemia-reperfusion. A(1)KO hearts had higher baseline coronary flow (CF) and left ventricular developed pressure (LVDP) than WT hearts, whereas heart rate was unchanged by A(1)AR deletion. After 20 min of ischemia, CF was attenuated in A(1)KO compared with WT hearts, and this reduction persisted throughout reperfusion. Final recovery of LVDP was decreased in A(1)KO hearts (54.4 +/- 5.1 vs. WT 81.1 +/- 3.4% preischemic baseline) and correlated with higher diastolic pressure during reperfusion. Postischemic efflux of LDH was greater in A(1)KO compared with WT hearts. Real-time RT-PCR demonstrated the absence of A(1)AR transcript in A(1)KO hearts, and the message for A(2A), A(2B), and A(3) adenosine receptors was similar in uninstrumented A(1)KO and WT hearts. Ischemia-reperfusion increased A(2B) mRNA expression 2.5-fold in both WT and A(1)KO hearts without changing A(1) or A(3) expression. In WT hearts, ischemia transiently doubled A(2A) mRNA, which returned to preischemic level upon reperfusion, a pattern not observed in A(1)KO hearts. Together, these data affirm the cardioprotective role of A(1)ARs and suggest that induced expression of other adenosine receptor subtypes may participate in the response to ischemia-reperfusion in isolated murine hearts.

Aberrant Bone Density in Aging Mice Lacking the Adenosine Transporter ENT1

PubMed Central

Hinton, David J.; McGee-Lawrence, Meghan E.; Lee, Moonnoh R.; Kwong, Hoi K.; Westendorf, Jennifer J.; Choi, Doo-Sup

2014-01-01

Adenosine is known to regulate bone production and resorption in humans and mice. Type 1 equilibrative nucleoside transporter (ENT1) is responsible for the majority of adenosine transport across the plasma membrane and is ubiquitously expressed in both humans and mice. However, the contribution of ENT1-mediated adenosine levels has not been studied in bone remodeling. With the recent identification of the importance of adenosine signaling in bone homeostasis, it is essential to understand the role of ENT1 to develop novel therapeutic compounds for bone disorders. Here we examined the effect of ENT1 deletion on bone density using X-ray, dual energy X-ray absorptiometry and micro-computerized tomography analysis. Our results show that bone density and bone mineral density is reduced in the lower thoracic and lumbar spine as well as the femur of old ENT1 null mice (>7 months) compared to wild-type littermates. Furthermore, we found increased mRNA expression of tartrate-resistant acid phosphatase (TRAP), an osteoclast marker, in isolated long bones from 10 month old ENT1 null mice compared to wild-type mice. In addition, aged ENT1 null mice displayed severe deficit in motor coordination and locomotor activity, which might be attributed to dysregulated bone density. Overall, our study suggests that ENT1-regulated adenosine signaling plays an essential role in lumbar spine and femur bone density. PMID:24586402

Metformin augments doxorubicin cytotoxicity in mammary carcinoma through activation of adenosine monophosphate protein kinase pathway.

PubMed

El-Ashmawy, Nahla E; Khedr, Naglaa F; El-Bahrawy, Hoda A; Abo Mansour, Hend E

2017-05-01

Since the incidence of breast cancer increases dramatically all over the world, the search for effective treatment is an urgent need. Metformin has demonstrated anti-tumorigenic effect both in vivo and in vitro in different cancer types. This work was designed to examine on molecular level the mode of action of metformin in mice bearing solid Ehrlich carcinoma and to evaluate the use of metformin in conjunction with doxorubicin as a combined therapy against solid Ehrlich carcinoma. Ehrlich ascites carcinoma cells were inoculated in 60 female mice as a model of breast cancer. The mice were divided into four equal groups: Control tumor, metformin, doxorubicin, and co-treatment. Metformin (15 mg/kg) and doxorubicin (4 mg/kg) were given intraperitoneally (i.p.) for four cycles every 5 days starting on day 12 of inoculation. The anti-tumorigenic effect of metformin was mediated by enhancement of adenosine monophosphate protein kinase activity and elevation of P53 protein as well as the suppression of nuclear factor-kappa B, DNA contents, and cyclin D1 gene expression. Metformin and doxorubicin mono-treatments exhibited opposing action regarding cyclin D1 gene expression, phosphorylated adenosine monophosphate protein kinase, and nuclear factor-kappa B levels. Co-treatment markedly decreased tumor volume, increased survival rate, and improved other parameters compared to doxorubicin group. In parallel, the histopathological findings demonstrated enhanced apoptosis and absence of necrosis in tumor tissue of co-treatment group. Metformin proved chemotherapeutic effect which could be mediated by the activation of adenosine monophosphate protein kinase and related pathways. Combining metformin and doxorubicin, which exhibited different mechanisms of action, produced greater efficacy as anticancer therapeutic regimen.

Cyclic control stick

DOEpatents

Whitaker, Charles N.; Zimmermann, Richard E.

1989-01-01

A cyclic control stick of the type used in helicopters for reducing the safety hazards associated with such a mechanism in the event of a crewman being thrown violently into contact with the cyclic control stick resulting from a crash or the like. The cyclic control stick is configured to break away upon the exertion of an impact force which exceeds a predetermined value and/or is exerted for more than a momentary time duration. The cyclic control stick is also configured to be adjustable so as to locate the grip thereof as far away from the crewman as possible for safety reasons without comprising the comfort of the crewman or the use of the control stick, and a crushable pad is provided on the top of the grip for impact energy absorbing purposes.

Mechanical annealing under low-amplitude cyclic loading in micropillars

NASA Astrophysics Data System (ADS)

Cui, Yi-nan; Liu, Zhan-li; Wang, Zhang-jie; Zhuang, Zhuo

2016-04-01

Mechanical annealing has been demonstrated to be an effective method for decreasing the overall dislocation density in submicron single crystal. However, simultaneously significant shape change always unexpectedly happens under extremely high monotonic loading to drive the pre-existing dislocations out of the free surfaces. In the present work, through in situ TEM experiments it is found that cyclic loading with low stress amplitude can drive most dislocations out of the submicron sample with virtually little change of the shape. The underlying dislocation mechanism is revealed by carrying out discrete dislocation dynamic (DDD) simulations. The simulation results indicate that the dislocation density decreases within cycles, while the accumulated plastic strain is small. By comparing the evolution of dislocation junction under monotonic, cyclic and relaxation deformation, the cumulative irreversible slip is found to be the key factor of promoting junction destruction and dislocation annihilation at free surface under low-amplitude cyclic loading condition. By introducing this mechanics into dislocation density evolution equations, the critical conditions for mechanical annealing under cyclic and monotonic loadings are discussed. Low-amplitude cyclic loading which strengthens the single crystal without seriously disturbing the structure has the potential applications in the manufacture of defect-free nano-devices.

Compressed sensing with cyclic-S Hadamard matrix for terahertz imaging applications

NASA Astrophysics Data System (ADS)

Ermeydan, Esra Şengün; ćankaya, Ilyas

2018-01-01

Compressed Sensing (CS) with Cyclic-S Hadamard matrix is proposed for single pixel imaging applications in this study. In single pixel imaging scheme, N = r . c samples should be taken for r×c pixel image where . denotes multiplication. CS is a popular technique claiming that the sparse signals can be reconstructed with samples under Nyquist rate. Therefore to solve the slow data acquisition problem in Terahertz (THz) single pixel imaging, CS is a good candidate. However, changing mask for each measurement is a challenging problem since there is no commercial Spatial Light Modulators (SLM) for THz band yet, therefore circular masks are suggested so that for each measurement one or two column shifting will be enough to change the mask. The CS masks are designed using cyclic-S matrices based on Hadamard transform for 9 × 7 and 15 × 17 pixel images within the framework of this study. The %50 compressed images are reconstructed using total variation based TVAL3 algorithm. Matlab simulations demonstrates that cyclic-S matrices can be used for single pixel imaging based on CS. The circular masks have the advantage to reduce the mechanical SLMs to a single sliding strip, whereas the CS helps to reduce acquisition time and energy since it allows to reconstruct the image from fewer samples.

Adenosine signaling in striatal circuits and alcohol use disorders.

PubMed

Nam, Hyung Wook; Bruner, Robert C; Choi, Doo-Sup

2013-09-01

Adenosine signaling has been implicated in the pathophysiology of alcohol use disorders and other psychiatric disorders such as anxiety and depression. Numerous studies have indicated a role for A1 receptors (A1R) in acute ethanol-induced motor incoordination, while A2A receptors (A2AR) mainly regulate the rewarding effect of ethanol in mice. Recent findings have demonstrated that dampened A2AR-mediated signaling in the dorsomedial striatum (DMS) promotes ethanol-seeking behaviors. Moreover, decreased A2AR function is associated with decreased CREB activity in the DMS, which enhances goal-oriented behaviors and contributes to excessive ethanol drinking in mice. Interestingly, caffeine, the most commonly used psychoactive substance, is known to inhibit both the A1R and A2AR. This dampened adenosine receptor function may mask some of the acute intoxicating effects of ethanol. Furthermore, based on the fact that A2AR activity plays a role in goal-directed behavior, caffeine may also promote ethanol-seeking behavior. The A2AR is enriched in the striatum and exclusively expressed in striatopallidal neurons, which may be responsible for the regulation of inhibitory behavioral control over drug rewarding processes through the indirect pathway of the basal ganglia circuit. Furthermore, the antagonistic interactions between adenosine and dopamine receptors in the striatum also play an integral role in alcoholism and addiction-related disorders. This review focuses on regulation of adenosine signaling in striatal circuits and the possible implication of caffeine in goal-directed behaviors and addiction.

Neurochemical Measurement of Adenosine in Discrete Brain Regions of Five Strains of Inbred Mice

PubMed Central

Pani, Amar K.; Jiao, Yun; Sample, Kenneth J.; Smeyne, Richard J.

2014-01-01

Adenosine (ADO), a non-classical neurotransmitter and neuromodulator, and its metabolites adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP), have been shown to play an important role in a number of biochemical processes. Although their signaling is well described, it has been difficult to directly, accurately and simultaneously quantitate these purines in tissue or fluids. Here, we describe a novel method for measuring adenosine (ADO) and its metabolites using high performance liquid chromatography with electrochemical detection (HPLC-ECD). Using this chromatographic technique, we examined baseline levels of ADO and ATP, ADP and AMP in 6 different brain regions of the C57BL/6J mouse: stratum, cortex, hippocampus, olfactory bulb, substantia nigra and cerebellum and compared ADO levels in 5 different strains of mice (C57BL/6J, Swiss-Webster, FVB/NJ, 129P/J, and BALB/c). These studies demonstrate that baseline levels of purines vary significantly among the brain regions as well as between different mouse strains. These dissimilarities in purine concentrations may explain the variable phenotypes among background strains described in neurological disease models. PMID:24642754

8-(2-Furyl)adenine derivatives as A₂A adenosine receptor ligands.

PubMed

Dal Ben, Diego; Buccioni, Michela; Lambertucci, Catia; Thomas, Ajiroghene; Klotz, Karl-Norbert; Federico, Stephanie; Cacciari, Barbara; Spalluto, Giampiero; Volpini, Rosaria

2013-01-01

Selective adenosine receptor modulators are potential tools for numerous therapeutic applications, including cardiovascular, inflammatory, and neurodegenerative diseases. In this work, the synthesis and biological evaluation at the four human adenosine receptor subtypes of a series of 9-substituted 8-(2-furyl)adenine derivatives are reported. Results show that 8-(2-furyl)-9-methyladenine is endowed with high affinity at the A₂A subtype. Further modification of this compound with introduction of arylacetyl or arylcarbamoyl groups in N(6)-position takes to different effects on the A₂A affinity and in particular on the selectivity versus the other three adenosine receptor subtypes. A molecular modelling analysis at three different A₂A receptor crystal structures provides an interpretation of the obtained biological results. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Use of antibody to membrane adenosine triphosphatase in the study of bacterial relatioships.

PubMed

Whiteside, T L; De Siervo, A J; Salton, M R

1971-03-01

An antiserum to Ca(2+)-activated adenosine triphosphatase from membranes of Micrococcus lysodeikticus cross-reacted in agar gels with membrane adenosine triphosphatases from other pigmented micrococci and related species. Species of Micrococcus and Sarcina showed different levels of inhibition of adenosine triphosphatase activities in heterologous reactions with antiserum. Inter- and intraspecific relationships based on the inhibition reaction were compared with an independent parameter, namely the quantitative and qualitative composition of the bacterial membrane phospholipids and fatty acids. The guanine plus cytosine contents in the deoxyribonucleic acid of the species studied correlated well with the serological cross-reactivity of adenosine triphosphatases from their membranes. The types of cross-bridges found in the peptidoglycans of these cocci were also compared with the other properties. The results suggest that an antiserum specific for a major membrane protein may be a reliable and most useful adjunct in studying bacterial serotaxonomy.

Small-animal PET study of adenosine A(1) receptors in rat brain: blocking receptors and raising extracellular adenosine.

PubMed

Paul, Soumen; Khanapur, Shivashankar; Rybczynska, Anna A; Kwizera, Chantal; Sijbesma, Jurgen W A; Ishiwata, Kiichi; Willemsen, Antoon T M; Elsinga, Philip H; Dierckx, Rudi A J O; van Waarde, Aren

2011-08-01

Activation of adenosine A(1) receptors (A(1)R) in the brain causes sedation, reduces anxiety, inhibits seizures, and promotes neuroprotection. Cerebral A(1)R can be visualized using 8-dicyclopropylmethyl-1-(11)C-methyl-3-propyl-xanthine ((11)C-MPDX) and PET. This study aims to test whether (11)C-MPDX can be used for quantitative studies of cerebral A(1)R in rodents. (11)C-MPDX was injected (intravenously) into isoflurane-anesthetized male Wistar rats (300 g). A dynamic scan of the central nervous system was obtained, using a small-animal PET camera. A cannula in a femoral artery was used for blood sampling. Three groups of animals were studied: group 1, controls (saline-treated); group 2, animals pretreated with the A(1)R antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 1 mg, intraperitoneally); and group 3, animals pretreated (intraperitoneally) with a 20% solution of ethanol in saline (2 mL) plus the adenosine kinase inhibitor 4-amino-5-(3-bromophenyl)-7-(6-morpholino-pyridin-3-yl)pyrido[2,3-d] pyrimidine dihydrochloride (ABT-702) (1 mg). DPCPX is known to occupy cerebral A(1)R, whereas ethanol and ABT-702 increase extracellular adenosine. In groups 1 and 3, the brain was clearly visualized. High uptake of (11)C-MPDX was noted in striatum, hippocampus, and cerebellum. In group 2, tracer uptake was strongly suppressed and regional differences were abolished. The treatment of group 3 resulted in an unexpected 40%-45% increase of the cerebral uptake of radioactivity as indicated by increases of PET standardized uptake value, distribution volume from Logan plot, nondisplaceable binding potential from 2-tissue-compartment model fit, and standardized uptake value from a biodistribution study performed after the PET scan. The partition coefficient of the tracer (K(1)/k(2) from the model fit) was not altered under the study conditions. (11)C-MPDX shows a regional distribution in rat brain consistent with binding to A(1)R. Tracer binding is blocked by the selective A

BCYCLIC: A parallel block tridiagonal matrix cyclic solver

NASA Astrophysics Data System (ADS)

Hirshman, S. P.; Perumalla, K. S.; Lynch, V. E.; Sanchez, R.

2010-09-01

A block tridiagonal matrix is factored with minimal fill-in using a cyclic reduction algorithm that is easily parallelized. Storage of the factored blocks allows the application of the inverse to multiple right-hand sides which may not be known at factorization time. Scalability with the number of block rows is achieved with cyclic reduction, while scalability with the block size is achieved using multithreaded routines (OpenMP, GotoBLAS) for block matrix manipulation. This dual scalability is a noteworthy feature of this new solver, as well as its ability to efficiently handle arbitrary (non-powers-of-2) block row and processor numbers. Comparison with a state-of-the art parallel sparse solver is presented. It is expected that this new solver will allow many physical applications to optimally use the parallel resources on current supercomputers. Example usage of the solver in magneto-hydrodynamic (MHD), three-dimensional equilibrium solvers for high-temperature fusion plasmas is cited.

The cyclic AMP cascade is altered in the fragile X nervous system.

PubMed

Kelley, Daniel J; Davidson, Richard J; Elliott, Jamie L; Lahvis, Garet P; Yin, Jerry C P; Bhattacharyya, Anita

2007-09-26

Fragile X syndrome (FX), the most common heritable cause of mental retardation and autism, is a developmental disorder characterized by physical, cognitive, and behavioral deficits. FX results from a trinucleotide expansion mutation in the fmr1 gene that reduces levels of fragile X mental retardation protein (FMRP). Although research efforts have focused on FMRP's impact on mGluR signaling, how the loss of FMRP leads to the individual symptoms of FX is not known. Previous studies on human FX blood cells revealed alterations in the cyclic adenosine 3', 5'-monophosphate (cAMP) cascade. We tested the hypothesis that cAMP signaling is altered in the FX nervous system using three different model systems. Induced levels of cAMP in platelets and in brains of fmr1 knockout mice are substantially reduced. Cyclic AMP induction is also significantly reduced in human FX neural cells. Furthermore, cAMP production is decreased in the heads of FX Drosophila and this defect can be rescued by reintroduction of the dfmr gene. Our results indicate that a robust defect in cAMP production in FX is conserved across species and suggest that cAMP metabolism may serve as a useful biomarker in the human disease population. Reduced cAMP induction has implications for the underlying causes of FX and autism spectrum disorders. Pharmacological agents known to modulate the cAMP cascade may be therapeutic in FX patients and can be tested in these models, thus supplementing current efforts centered on mGluR signaling.

Regulation of renal adenosine A(1) receptors: effect of dietary sodium chloride.

PubMed

Smith, J A; Whitaker, E M; Yaktubay, N; Morton, M J; Bowmer, C J; Yates, M S

1999-11-12

The influence of dietary NaCl on the regulation of renal adenosine A(1) receptors was investigated in the rat. Renal membranes from rats fed on a diet low (0.04%) in NaCl showed a 46% increase in B(max) for the binding of [3H]-1,3-dipropyl-8-cyclopentylxanthine ([3H]DPCPX), a selective adenosine A(1) receptor antagonist, compared to membranes from rats fed on a normal diet (0.4% NaCl). Conversely, a high NaCl diet (4.0%) resulted in a 37% decrease in B(max). Levels of renal adenosine A(1) receptor mRNA were 65% lower in rats on a high salt diet. Autoradiographic studies showed that, for the inner medullary collecting ducts, a low NaCl diet resulted in a 30% increase in [3H]DPCPX binding with a 39% decrease noted in rats maintained on a high salt diet. The results indicate that changes in adenosine A(1) receptor density may represent a novel mechanism whereby the kidneys adapt to changes in salt load.

The impact of posture and prolonged cyclic compressive loading on vertebral joint mechanics.

PubMed

Gooyers, Chad E; McMillan, Robert D; Howarth, Samuel J; Callaghan, Jack P

2012-08-01

An in vitro biomechanics investigation exposing porcine functional spinal units (FSUs) to submaximal cyclic or static compressive forces while in a flexed, neutral, or extended posture. To investigate the combined effect of cyclically applied compressive force (e.g., vibration) and postural deviation on intervertebral joint mechanics. Independently, prolonged vibration exposure and non-neutral postures are known risk factors for development of low back pain and injury. However, there is limited basic scientific evidence to explain how the risk of low back injury from vibration exposure is modified by other mechanical factors. This work examined the influence of static postural deviation on vertebral joint height loss and compressive stiffness under cyclically applied compressive force. Forty-eight FSUs, consisting of 2 adjacent vertebrae, ligaments, and the intervening intervertebral disc were included in the study. Each specimen was randomized to 1 of 3 experimental posture conditions (neutral, flexed, or extended) and assigned to 1 of 2 loading protocols, consisting of (1) cyclic (1500 ± 1200 N applied at 5 Hz using a sinusoidal waveform, resulting in 0.2 g rms acceleration) or (2) 1500 N of static compressive force. RESULTS.: As expected, FSU height loss followed a typical first-order response in both the static and cyclic loading protocols, with the majority (~50%) of the loss occurring in the first 20 minutes of testing. A significant interaction between posture and loading protocol (P < 0.001) was noted in the magnitude of FSU height loss. Subsequent analysis of simple effects revealed significant differences between cyclic and static loading protocols in both a neutral (P = 0.016) and a flexed posture (P < 0.0001). No significant differences (P = 0.320) were noted between pre/postmeasurements of FSU compressive stiffness. Posture is an important mechanical factor to consider when assessing the risk of injury from cyclic loading to the lumbar spine.

Limitation of Infarct Size and No-Reflow by Intracoronary Adenosine Depends Critically on Dose and Duration.

PubMed

Yetgin, Tuncay; Uitterdijk, André; Te Lintel Hekkert, Maaike; Merkus, Daphne; Krabbendam-Peters, Ilona; van Beusekom, Heleen M M; Falotico, Robert; Serruys, Patrick W; Manintveld, Olivier C; van Geuns, Robert-Jan M; Zijlstra, Felix; Duncker, Dirk J

2015-12-28

In the absence of effective clinical pharmacotherapy for prevention of reperfusion-mediated injury, this study re-evaluated the effects of intracoronary adenosine on infarct size and no-reflow in a porcine model of acute myocardial infarction using clinical bolus and experimental high-dose infusion regimens. Despite the clear cardioprotective effects of adenosine, when administered prior to ischemia, studies on cardioprotection by adenosine when administered at reperfusion have yielded contradictory results in both pre-clinical and clinical settings. Swine (54 ± 1 kg) were subjected to a 45-min mid-left anterior descending artery occlusion followed by 2 h of reperfusion. In protocol A, an intracoronary bolus of 3 mg adenosine injected over 1 min (n = 5) or saline (n = 10) was administered at reperfusion. In protocol B, an intracoronary infusion of 50 μg/kg/min adenosine (n = 15) or saline (n = 21) was administered starting 5 min prior to reperfusion and continued throughout the 2-h reperfusion period. In protocol A, area-at-risk, infarct size, and no-reflow were similar between groups. In protocol B, risk zones were similar, but administration of adenosine resulted in significant reductions in infarct size from 59 ± 3% of the area-at-risk in control swine to 46 ± 4% (p = 0.02), and no-reflow from 49 ± 6% of the infarct area to 26 ± 6% (p = 0.03). During reperfusion, intracoronary adenosine can limit infarct size and no-reflow in a porcine model of acute myocardial infarction. However, protection was only observed when adenosine was administered via prolonged high-dose infusion, and not via short-acting bolus injection. These findings warrant reconsideration of adenosine as an adjuvant therapy during early reperfusion. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Content of Adenosine Phosphates and Adenylate Energy Charge in Germinating Ponderosa Pine Seeds

PubMed Central

Ching, Te May; Ching, Kim K.

1972-01-01

An average of 540 picomoles of total adenosine phosphates was found in the embryo of mature seeds of ponderosa pine (Pinus ponderosa Laws.) and 1140 picomoles in the gametophyte. Adenylate energy charges were 0.44 and 0.26, respectively. After stratification, total adenosine phosphates increased 7-fold and 6-fold in embryo and gametophyte, respectively, and energy charges rose to 0.85 and 0.75. During germination, total adenosine phosphates increased to a 20-fold peak on the 9th day in gametophytic tissue, parallel with the peak of reserve regradation and organellar synthesis, and then decreased. In embryo and seedling, total adenosine phosphates elevated 80-fold with two distinct oscillating increases of AMP and ADP. The oscillating increases occurred before the emergence of radicle and cotyledons during which the highest mitotic index prevailed in all tissues. Energy charges fluctuated between 0.65 at the rapid cell dividing stage to 0.85 at the fully differentiated stage of the seedling, while energy charges remained around 0.75 in the gametophyte. These data indicated that the content of adenosine phosphates of germinating seeds reflects growth, organogenesis, and morphogenesis, and that a compartmentalized energy metabolism must exist in dividing and growing plant cells. PMID:16658212

A2B Adenosine Receptor Agonist Improves Erectile Function in Diabetic Rats.

PubMed

Wen, Jiaming; Wang, Bohan; Du, Chuanjun; Xu, Gang; Zhang, Zhewei; Li, Yi; Zhang, Nan

2015-10-01

Diabetes is an important risk factor for erectile dysfunction (ED). Recent studies have indicated that A2B adenosine receptor (ADORA2B) signaling is essential for penile erection. Thus, we hypothesize that diabetic ED may be attributed to impaired A2B adenosine signaling. To test this hypothesis, we generated diabetic rats by injecting streptozocin as animal model. After 12 weeks, immunohistochemistry staining was used to localize the expression of ADORA2B. Western Blot and quantitative PCR were employed to determine ADORA2B expression level. Intracavernosal pressure (ICP) measurement was used to evaluate erectile function. Diabetic rats received a single intravenous injection of BAY 60-6583, an ADORA2B agonist, or vehicle solution, at 60 min before the ICP measurement. The results showed that ADORA2B expressed in the nerve bundle, smooth muscle, and endothelium in penile tissue of control mice. Western Blot and quantitative PCR results indicated that the expression levels of ADORA2B protein and mRNA were significantly reduced in penile tissues of diabetic rats. Functional studies showed that the erectile response induced by electrical stimulation was remarkably decreased in diabetic rats, compared with age-matched control rats. However, at 60 min after BAY 60-6583 treatment, the erectile function was improved in diabetic rats, suggesting that enhancement of ADORA2B signaling may improve erectile function in diabetic ED. This preclinical study has revealed a previously unrecognized therapeutic possibility of BAY 60-6583 as an effective and mechanism-based drug to treat diabetic ED. In conclusion, we propose that impaired A2B adenosine signaling is one of the pathological mechanisms of diabetic ED.

Intrinsic A(1) adenosine receptor activation during ischemia or reperfusion improves recovery in mouse hearts.

PubMed

Peart, J; Headrick, J P

2000-11-01

We assessed the role of A(1) adenosine receptor (A(1)AR) activation by endogenous adenosine in the modulation of ischemic contracture and postischemic recovery in Langendorff-perfused mouse hearts subjected to 20 min of total ischemia and 30 min of reperfusion. In control hearts, the rate-pressure product (RPP) and first derivative of pressure development over time (+dP/dt) recovered to 57 +/- 3 and 58 +/- 3% of preischemia, respectively. Diastolic pressure remained elevated at 20 +/- 2 mmHg (compared with 3 +/- 1 mmHg preischemia). Interstitial adenosine, assessed by microdialysis, rose from approximately 0.3 to 1.9 microM during ischemia compared with approximately 15 microM in rat heart. Nonetheless, these levels will near maximally activate A(1)ARs on the basis of effects of exogenous adenosine and 2-chloroadenosine. Neither A(1)AR blockade with 200 nM 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) during the ischemic period alone nor A(1)AR activation with 50 nM N(6)-cyclopentyladenosine altered rapidity or extent of ischemic contracture. However, ischemic DPCPX treatment significantly depressed postischemic recovery of RPP and +dP/dt (44 +/- 3 and 40 +/- 4% of preischemia, respectively). DPCPX treatment during the reperfusion period alone also reduced recovery of RPP and +dP/dt (to 44 +/- 2 and 47 +/- 2% of preischemia, respectively). These data indicate that 1) interstitial adenosine is lower in mouse versus rat myocardium during ischemia, 2) A(1)AR activation by endogenous adenosine or exogenous agonists does not modify ischemic contracture in murine myocardium, 3) A(1)AR activation by endogenous adenosine during ischemia attenuates postischemic stunning, and 4) A(1)AR activation by endogenous adenosine during the reperfusion period also improves postischemic contractile recovery.

A Novel Ras-interacting Protein Required for Chemotaxis and Cyclic Adenosine Monophosphate Signal Relay in Dictyostelium

PubMed Central

Lee, Susan; Parent, Carole A.; Insall, Robert; Firtel, Richard A.

1999-01-01

We have identified a novel Ras-interacting protein from Dictyostelium, RIP3, whose function is required for both chemotaxis and the synthesis and relay of the cyclic AMP (cAMP) chemoattractant signal. rip3 null cells are unable to aggregate and lack receptor activation of adenylyl cyclase but are able, in response to cAMP, to induce aggregation-stage, postaggregative, and cell-type-specific gene expression in suspension culture. In addition, rip3 null cells are unable to properly polarize in a cAMP gradient and chemotaxis is highly impaired. We demonstrate that cAMP stimulation of guanylyl cyclase, which is required for chemotaxis, is reduced ∼60% in rip3 null cells. This reduced activation of guanylyl cyclase may account, in part, for the defect in chemotaxis. When cells are pulsed with cAMP for 5 h to mimic the endogenous cAMP oscillations that occur in wild-type strains, the cells will form aggregates, most of which, however, arrest at the mound stage. Unlike the response seen in wild-type strains, the rip3 null cell aggregates that form under these experimental conditions are very small, which is probably due to the rip3 null cell chemotaxis defect. Many of the phenotypes of the rip3 null cell, including the inability to activate adenylyl cyclase in response to cAMP and defects in chemotaxis, are very similar to those of strains carrying a disruption of the gene encoding the putative Ras exchange factor AleA. We demonstrate that aleA null cells also exhibit a defect in cAMP-mediated activation of guanylyl cyclase similar to that of rip3 null cells. A double-knockout mutant (rip3/aleA null cells) exhibits a further reduction in receptor activation of guanylyl cyclase, and these cells display almost no cell polarization or movement in cAMP gradients. As RIP3 preferentially interacts with an activated form of the Dictyostelium Ras protein RasG, which itself is important for cell movement, we propose that RIP3 and AleA are components of a Ras-regulated pathway

A novel Ras-interacting protein required for chemotaxis and cyclic adenosine monophosphate signal relay in Dictyostelium.

PubMed

Lee, S; Parent, C A; Insall, R; Firtel, R A

1999-09-01

We have identified a novel Ras-interacting protein from Dictyostelium, RIP3, whose function is required for both chemotaxis and the synthesis and relay of the cyclic AMP (cAMP) chemoattractant signal. rip3 null cells are unable to aggregate and lack receptor activation of adenylyl cyclase but are able, in response to cAMP, to induce aggregation-stage, postaggregative, and cell-type-specific gene expression in suspension culture. In addition, rip3 null cells are unable to properly polarize in a cAMP gradient and chemotaxis is highly impaired. We demonstrate that cAMP stimulation of guanylyl cyclase, which is required for chemotaxis, is reduced approximately 60% in rip3 null cells. This reduced activation of guanylyl cyclase may account, in part, for the defect in chemotaxis. When cells are pulsed with cAMP for 5 h to mimic the endogenous cAMP oscillations that occur in wild-type strains, the cells will form aggregates, most of which, however, arrest at the mound stage. Unlike the response seen in wild-type strains, the rip3 null cell aggregates that form under these experimental conditions are very small, which is probably due to the rip3 null cell chemotaxis defect. Many of the phenotypes of the rip3 null cell, including the inability to activate adenylyl cyclase in response to cAMP and defects in chemotaxis, are very similar to those of strains carrying a disruption of the gene encoding the putative Ras exchange factor AleA. We demonstrate that aleA null cells also exhibit a defect in cAMP-mediated activation of guanylyl cyclase similar to that of rip3 null cells. A double-knockout mutant (rip3/aleA null cells) exhibits a further reduction in receptor activation of guanylyl cyclase, and these cells display almost no cell polarization or movement in cAMP gradients. As RIP3 preferentially interacts with an activated form of the Dictyostelium Ras protein RasG, which itself is important for cell movement, we propose that RIP3 and AleA are components of a Ras

Genetics Home Reference: cyclic neutropenia

MedlinePlus

... Facebook Twitter Home Health Conditions Cyclic neutropenia Cyclic neutropenia Printable PDF Open All Close All Enable Javascript to view the expand/collapse boxes. Description Cyclic neutropenia is a disorder that causes frequent infections and ...

Rapid adenosine release in the nucleus tractus solitarii during defence response in rats: real-time measurement in vivo

PubMed Central

Dale, Nicholas; Gourine, Alexander V; Llaudet, Enrique; Bulmer, David; Thomas, Teresa; Spyer, K Michael

2002-01-01

We have measured the release of adenosine and inosine from the dorsal surface of the brainstem and from within the nucleus tractus solitarii (NTS) during the defence response evoked by hypothalamic stimulation in the anaesthetised rat. At the surface of the brainstem, only release of inosine was detected on hypothalamic defence area stimulation. This inosine signal was greatly reduced by addition of the ecto-5′-nucleotidase inhibitor α,β-methylene ADP (200 μM), suggesting that the inosine arose from adenosine that was produced in the extracellular space by the prior release of ATP. By placing a microelectrode biosensor into the NTS under stereotaxic control we have recorded release of adenosine within this nucleus. By contrast to the brainstem surface, a fast increase in adenosine, accompanied only by a much smaller change in inosine levels, was seen following stimulation of the hypothalamic defence area. The release of adenosine following hypothalamic stimulation was mainly confined to a narrow region of the NTS some 500 μm in length around the level of the obex. Interestingly the release of adenosine was depletable: when the defence reaction was evoked at short time intervals, much less adenosine was released on the second stimulus. Our novel techniques have given unprecedented real-time measurement and localisation of adenosine release in vivo and demonstrate that adenosine is released at the right time and in sufficient quantities to contribute to the cardiovascular components of the defence reaction. PMID:12356888

5' adenosine monophosphate-activated protein kinase, metabolism and exercise.

PubMed

Aschenbach, William G; Sakamoto, Kei; Goodyear, Laurie J

2004-01-01

The 5' adenosine monophosphate-activated protein kinase (AMPK) is a member of a metabolite-sensing protein kinase family that functions as a metabolic 'fuel gauge' in skeletal muscle. AMPK is a ubiquitous heterotrimeric protein, consisting of an alpha catalytic, and beta and gamma regulatory subunits that exist in multiple isoforms and are all required for full enzymatic activity. During exercise, AMPK becomes activated in skeletal muscle in response to changes in cellular energy status (e.g. increased adenosine monophosphate [AMP]/adenosine triphosphate [ATP] and creatine/phosphocreatine ratios) in an intensity-dependent manner, and serves to inhibit ATP-consuming pathways, and activate pathways involved in carbohydrate and fatty-acid metabolism to restore ATP levels. Recent evidence shows that although AMPK plays this key metabolic role during acute bouts of exercise, it is also an important component of the adaptive response of skeletal muscles to endurance exercise training because of its ability to alter muscle fuel reserves and expression of several exercise-responsive genes. This review discusses the putative roles of AMPK in acute and chronic exercise responses, and suggests avenues for future AMPK research in exercise physiology and biochemistry.

Affordable Cyclic Voltammetry

ERIC Educational Resources Information Center

Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.

2009-01-01

Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

Adenosine and inosine exert cytoprotective effects in an in vitro model of liver ischemia-reperfusion injury

PubMed Central

MÓDIS, KATALIN; GERŐ, DOMOKOS; STANGL, RITA; ROSERO, OLIVÉR; SZIJÁRTÓ, ATTILA; LOTZ, GÁBOR; MOHÁCSIK, PETRA; SZOLECZKY, PETRA; COLETTA, CIRO; SZABÓ, CSABA

2013-01-01

Liver ischemia represents a common clinical problem. In the present study, using an in vitro model of hepatic ischemia-reperfusion injury, we evaluated the potential cytoprotective effect of the purine metabolites, such as adenosine and inosine, and studied the mode of their pharmacological actions. The human hepatocellular carcinoma-derived cell line HepG2 was subjected to combined oxygen-glucose deprivation (COGD; 0-14-24 h), followed by re-oxygenation (0-4-24 h). Adenosine or inosine (300–1,000 μM) were applied in pretreatment. Cell viability and cytotoxicity were measured by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and lactate dehydrogenase methods, respectively. The results showed that both adenosine and inosine exerted cytoprotective effects, and these effects were not related to receptor-mediated actions, since they were not prevented by selective adenosine receptor antagonists. On the other hand, the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA, 10 μM) markedly and almost fully reversed the protective effect of adenosine during COGD, while it did not influence the cytoprotective effect of inosine in the same assay conditions. These results suggest that the cytoprotective effects are related to intracellular actions, and, in the case of adenosine also involve intracellular conversion to inosine. The likely interpretation of these findings is that inosine serves as an alternative source of energy to produce ATP during hypoxic conditions. The protective effects are also partially dependent on adenosine kinase, as the inhibitor 4-amino-5-(3-bromophenyl)-7-(6-morpholino-pyridin-3-yl)pyrido[2,3-d]pyrimidine, 2HCl (ABT 702, 30 μM) significantly reversed the protective effect of both adenosine and inosine during hypoxia and re-oxygenation. Collectively, the current results support the view that during hypoxia, adenosine and inosine exert cytoprotective effects via receptor

Adenosine and inosine exert cytoprotective effects in an in vitro model of liver ischemia-reperfusion injury.

PubMed

Módis, Katalin; Gerő, Domokos; Stangl, Rita; Rosero, Olivér; Szijártó, Attila; Lotz, Gábor; Mohácsik, Petra; Szoleczky, Petra; Coletta, Ciro; Szabó, Csaba

2013-02-01

Liver ischemia represents a common clinical problem. In the present study, using an in vitro model of hepatic ischemia-reperfusion injury, we evaluated the potential cytoprotective effect of the purine metabolites, such as adenosine and inosine, and studied the mode of their pharmacological actions. The human hepatocellular carcinoma-derived cell line HepG2 was subjected to combined oxygen-glucose deprivation (COGD; 0-14-24 h), followed by re-oxygenation (0-4-24 h). Adenosine or inosine (300-1,000 µM) were applied in pretreatment. Cell viability and cytotoxicity were measured by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and lactate dehydrogenase methods, respectively. The results showed that both adenosine and inosine exerted cytoprotective effects, and these effects were not related to receptor-mediated actions, since they were not prevented by selective adenosine receptor antagonists. On the other hand, the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA, 10 µM) markedly and almost fully reversed the protective effect of adenosine during COGD, while it did not influence the cytoprotective effect of inosine in the same assay conditions. These results suggest that the cytoprotective effects are related to intracellular actions, and, in the case of adenosine also involve intracellular conversion to inosine. The likely interpretation of these findings is that inosine serves as an alternative source of energy to produce ATP during hypoxic conditions. The protective effects are also partially dependent on adenosine kinase, as the inhibitor 4-amino-5-(3-bromophenyl)-7-(6‑morpholino-pyridin-3-yl)pyrido[2,3-d]pyrimidine, 2HCl (ABT 702, 30 µM) significantly reversed the protective effect of both adenosine and inosine during hypoxia and re-oxygenation. Collectively, the current results support the view that during hypoxia, adenosine and inosine exert cytoprotective effects via receptor

Determination of adenosine phosphates in rat gastrocnemius at various postmortem intervals using high performance liquid chromatography.

PubMed

Huang, Hong; Yan, Youyi; Zuo, Zhong; Yang, Lin; Li, Bin; Song, Yu; Liao, Linchuan

2010-09-01

Although the change in adenosine phosphate levels in muscles may contribute to the development of rigor mortis, the relationship between their levels and the onset and development of rigor mortis has not been well elucidated. In the current study, levels of the adenosine phosphates including adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) in gastrocnemius at various postmortem intervals of 180 rats from different death modes were detected by high performance liquid chromatography. The results showed that the levels of ATP and ADP significantly decreased along with the postmortem period of rats from different death mode whereas the AMP level remained the same. In addition, it was found that changes in the ATP levels in muscles after death correlated well with the development of rigor mortis. Therefore, the ATP level could serve as a reference parameter for the deduction of rigor mortis in forensic science.

Immune monitoring with a lymphocyte adenosine triphosphate assay in kidney transplant recipients treated with a calcineurin inhibitor.

PubMed

Sugiyama, Kentaro; Tsukaguchi, Mahoto; Toyama, Akira; Satoh, Hiroshi; Saito, Kazuhide; Nakagawa, Yuki; Takahashi, Kota; Tanaka, Sachiko; Onda, Kenji; Hirano, Toshihiko

2014-06-01

The adenosine triphosphate assay using peripheral lymphocytes may be useful to evaluate the risks of acute rejection and infection in kidney transplant patients. We used the adenosine triphosphate assay to evaluate differences between recipients who were treated with cyclosporine- or tacrolimus-based immunosuppressive therapy. Adenosine triphosphate levels were measured in peripheral CD4+ cells before and after transplant and were correlated with clinical outcomes in 45 kidney transplant recipients. These recipients received immunosuppressive therapy with either cyclosporine (23 patients) or tacrolimus (22 patients). Adenosine triphosphate levels were significantly lower in the cyclosporine- than tacrolimus-based therapy groups from 2 to 6 weeks after transplant. Adenosine triphosphate levels were similar between these groups before and 1 week after transplant. The frequency of cytomegalovirus infection was greater in the recipients who received cyclosporine (17 patients [74%]) than tacrolimus (6 patients [27%]; P ≦ .003). The frequency of acute rejection episodes was similar between the cyclosporine and tacrolimus groups. These observations suggest that cyclosporine-based immunosuppressive therapy causes excessive immunosuppression compared with tacrolimus-based therapy, evidenced by the lymphocyte adenosine triphosphate levels. The adenosine triphosphate assay using peripheral CD4+ cells may be a useful method for predicting the occurrence of cytomegalovirus infections in kidney transplant recipients.

Structure-activity relationship studies and pharmacological characterization of N5-heteroarylalkyl-substituted-2-(2-furanyl)thiazolo[5,4-d]pyrimidine-5,7-diamine-based derivatives as inverse agonists at human A2A adenosine receptor.

PubMed

Varano, Flavia; Catarzi, Daniela; Vincenzi, Fabrizio; Falsini, Matteo; Pasquini, Silvia; Borea, Pier Andrea; Colotta, Vittoria; Varani, Katia

2018-06-09

This paper describes the synthesis and characterization of N 5 -(hetero)arylalkyl-substituted-thiazolo [5,4-d]pyrimidine-5,7-diamine derivatives (4-19) as novel human (h) A 2A adenosine receptor (AR) inverse agonists. Competition binding and cyclic AMP assays indicate that the examined compounds behave as hA 2A AR inverse agonists showing binding affinity values in the nanomolar or subnanomolar range. Notably, compounds 4, 5, 6 and 11 showed two affinity values for the hA 2A ARs with the highest (KH) falling in the femtomolar range and the lowest (KL) of the nanomolar order. In addition, in cyclic AMP assays, compounds 4, 5, 6 and 11 exhibited potency (IC 50 ) values in the picomolar range. This study has confirmed that 2-(2-furanyl)thiazolo [5,4-d]pyrimidine-5,7-diamine-based derivatives represent a unique new class of hA 2A AR inverse agonists. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Bidirectional regulation of adenosine-to-inosine (A-to-I) RNA editing by DEAH box helicase 9 (DHX9) in cancer.

PubMed

Hong, HuiQi; An, Omer; Chan, Tim H M; Ng, Vanessa H E; Kwok, Hui Si; Lin, Jaymie S; Qi, Lihua; Han, Jian; Tay, Daryl J T; Tang, Sze Jing; Yang, Henry; Song, Yangyang; Bellido Molias, Fernando; Tenen, Daniel G; Chen, Leilei

2018-05-18

Adenosine-to-inosine (A-to-I) RNA editing entails the enzymatic deamination of adenosines to inosines by adenosine deaminases acting on RNA (ADARs). Dysregulated A-to-I editing has been implicated in various diseases, including cancers. However, the precise factors governing the A-to-I editing and their physiopathological implications remain as a long-standing question. Herein, we unravel that DEAH box helicase 9 (DHX9), at least partially dependent of its helicase activity, functions as a bidirectional regulator of A-to-I editing in cancer cells. Intriguingly, the ADAR substrate specificity determines the opposing effects of DHX9 on editing as DHX9 silencing preferentially represses editing of ADAR1-specific substrates, whereas augments ADAR2-specific substrate editing. Analysis of 11 cancer types from The Cancer Genome Atlas (TCGA) reveals a striking overexpression of DHX9 in tumors. Further, tumorigenicity studies demonstrate a helicase-dependent oncogenic role of DHX9 in cancer development. In sum, DHX9 constitutes a bidirectional regulatory mode in A-to-I editing, which is in part responsible for the dysregulated editome profile in cancer.

Dielectric spectra broadening as a signature for dipole-matrix interaction. III. Water in adenosine monophosphate/adenosine-5'-triphosphate solutions.

PubMed

Puzenko, Alexander; Levy, Evgeniya; Shendrik, Andrey; Talary, Mark S; Caduff, Andreas; Feldman, Yuri

2012-11-21

In this, the third part of our series on the dielectric spectrum symmetrical broadening of water, we consider the nucleotide aqueous solutions. Where in Parts I [E. Levy et al., J. Chem. Phys. 136, 114502 (2012)] and II [E. Levy et al., J. Chem. Phys. 136, 114503 (2012)], the dipole-dipole or ion-dipole interaction had a dominant feature, now the interplay between these two types of dipole-matrix interactions will be considered. We present the results of high frequency dielectric measurements of different concentrations of adenosine monophosphate/adenosine-5'-triphosphate aqueous solutions. We observed the Cole-Cole broadening of the main relaxation peak of the solvent in the solutions. Moreover, depending on the nucleotide concentration, we observed both types of dipole-matrix interaction. The 3D trajectory approach (described in detail in Part I) is applied in order to highlight the differences between the two types of interaction.

Coronary effects of diadenosine tetraphosphate resemble those of adenosine in anesthetized pigs: involvement of ATP-sensitive potassium channels.

PubMed

Nakae, I; Takahashi, M; Takaoka, A; Liu, Q; Matsumoto, T; Amano, M; Sekine, A; Nakajima, H; Kinoshita, M

1996-07-01

Diadenosine tetraphosphate (Ap4A) is an adenine nucleotide with vasodilatory properties. We examined the effects of Ap4A on coronary circulation in comparison with those of adenosine, its metabolite, in anesthetized pigs. Left atrial (LA) infusion of Ap4A at increasing doses of 100, 200, and 300 micrograms/kg/min increased coronary blood flow (CBF) and decreased systemic blood pressure (BP) and coronary vascular resistance (CVR). Ap4A had no effect on large epicardial coronary artery diameter (CoD). Likewise, LA infusion of adenosine at doses of 150 and 300 micrograms/kg/min increased CBF and decreased BP and coronary vascular resistance (CVR) but did not affect CoD. Therefore, the vasodilatory effects of Ap4A and adenosine were predominant in small coronary resistance vessels and negligible in large coronary arteries. Pretreatment with glibenclamide (2 mg/kg, intravenously, i.v.), a specific blocker of ATP-sensitive potassium channels (KATP), attenuated alterations of CBF, BP, and CVR induced by Ap4A and by adenosine. In contrast, treatment with cromakalim (0.5 microgram/kg/min i.v.), an activator of KATP, enhanced the coronary effects of Ap4A and adenosine. Therefore, the opening of KATP in the pig coronary circulation is involved in the in vivo vasodilatory effects of Ap4A and adenosine. Treatment with 8-phenyltheophylline (8-PT, 4 mg/kg i.v.), an adenosine receptor antagonist, suppressed CBF increases induced by Ap4A (20 micrograms/kg/min, intracoronarily, i.c.) and adenosine (5 micrograms/kg/min i.c.) by 68 and 90%, respectively. These findings suggest that the in vivo coronary effects of Ap4A are largely caused by the opening of KATP through rapid degradation to adenosine to activate adenosine receptors.

Prospective Study of Adenosine on Atrioventricular Nodal Conduction in Pediatric and Young Adult Patients After Heart Transplantation.

PubMed

Flyer, Jonathan N; Zuckerman, Warren A; Richmond, Marc E; Anderson, Brett R; Mendelsberg, Tamar G; McAllister, Jennie M; Liberman, Leonardo; Addonizio, Linda J; Silver, Eric S

2017-06-20

Supraventricular tachycardia is common after heart transplantation. Adenosine, the standard therapy for treating supraventricular tachycardia in children and adults without transplantation, is relatively contraindicated after transplantation because of a presumed risk of prolonged atrioventricular block in denervated hearts. This study tested whether adenosine caused prolonged asystole after transplantation and if it was effective in blocking atrioventricular nodal conduction in these patients. This was a single-center prospective clinical study including healthy heart transplant recipients 6 months to 25 years of age presenting for routine cardiac catheterization during 2015 to 2016. After catheterization, a transvenous pacing catheter was placed and adenosine was given following a dose-escalation protocol until atrioventricular block was achieved. The incidence of clinically significant asystole (≥12 seconds after adenosine) was quantified. The effects of patient characteristics on adenosine dose required to produce atrioventricular block and duration of effect were also measured. Eighty patients completed adenosine testing. No patient (0%; 95% confidence interval, 0-3) required rescue ventricular pacing. Atrioventricular block was observed in 77 patients (96%; 95% confidence interval, 89-99). The median longest atrioventricular block was 1.9 seconds (interquartile range, 1.4-3.2 seconds), with a mean duration of adenosine effect of 4.3±2.0 seconds. No patient characteristic significantly predicted the adenosine dose to produce atrioventricular block or duration of effect. Results were similar across patient weight categories. Adenosine induces atrioventricular block in healthy pediatric and young adult heart transplant recipients with minimal risk when low initial doses are used (25 μg/kg; 1.5 mg if ≥60 kg) and therapy is gradually escalated. URL: http://www.clinicaltrials.gov. Unique identifier: NCT02462941. © 2017 American Heart Association, Inc.

Use of Antibody to Membrane Adenosine Triphosphatase in the Study of Bacterial Relationships1

PubMed Central

Whiteside, Theresa L.; De Siervo, August J.; Salton, Milton R. J.

1971-01-01

An antiserum to Ca2+-activated adenosine triphosphatase from membranes of Micrococcus lysodeikticus cross-reacted in agar gels with membrane adenosine triphosphatases from other pigmented micrococci and related species. Species of Micrococcus and Sarcina showed different levels of inhibition of adenosine triphosphatase activities in heterologous reactions with antiserum. Inter- and intraspecific relationships based on the inhibition reaction were compared with an independent parameter, namely the quantitative and qualitative composition of the bacterial membrane phospholipids and fatty acids. The guanine plus cytosine contents in the deoxyribonucleic acid of the species studied correlated well with the serological cross-reactivity of adenosine triphosphatases from their membranes. The types of cross-bridges found in the peptidoglycans of these cocci were also compared with the other properties. The results suggest that an antiserum specific for a major membrane protein may be a reliable and most useful adjunct in studying bacterial serotaxonomy. Images PMID:4323299

2′-O Methylation of Internal Adenosine by Flavivirus NS5 Methyltransferase

PubMed Central

Dong, Hongping; Chang, David C.; Hua, Maggie Ho Chia; Lim, Siew Pheng; Chionh, Yok Hian; Hia, Fabian; Lee, Yie Hou; Kukkaro, Petra; Lok, Shee-Mei; Dedon, Peter C.; Shi, Pei-Yong

2012-01-01

RNA modification plays an important role in modulating host-pathogen interaction. Flavivirus NS5 protein encodes N-7 and 2′-O methyltransferase activities that are required for the formation of 5′ type I cap (m7GpppAm) of viral RNA genome. Here we reported, for the first time, that flavivirus NS5 has a novel internal RNA methylation activity. Recombinant NS5 proteins of West Nile virus and Dengue virus (serotype 4; DENV-4) specifically methylates polyA, but not polyG, polyC, or polyU, indicating that the methylation occurs at adenosine residue. RNAs with internal adenosines substituted with 2′-O-methyladenosines are not active substrates for internal methylation, whereas RNAs with adenosines substituted with N6-methyladenosines can be efficiently methylated, suggesting that the internal methylation occurs at the 2′-OH position of adenosine. Mass spectroscopic analysis further demonstrated that the internal methylation product is 2′-O-methyladenosine. Importantly, genomic RNA purified from DENV virion contains 2′-O-methyladenosine. The 2′-O methylation of internal adenosine does not require specific RNA sequence since recombinant methyltransferase of DENV-4 can efficiently methylate RNAs spanning different regions of viral genome, host ribosomal RNAs, and polyA. Structure-based mutagenesis results indicate that K61-D146-K181-E217 tetrad of DENV-4 methyltransferase forms the active site of internal methylation activity; in addition, distinct residues within the methyl donor (S-adenosyl-L-methionine) pocket, GTP pocket, and RNA-binding site are critical for the internal methylation activity. Functional analysis using flavivirus replicon and genome-length RNAs showed that internal methylation attenuated viral RNA translation and replication. Polymerase assay revealed that internal 2′-O-methyladenosine reduces the efficiency of RNA elongation. Collectively, our results demonstrate that flavivirus NS5 performs 2′-O methylation of internal adenosine of

A comparison of N-methyl-D-aspartate-evoked release of adenosine and ( sup 3 H)norepinephrine from rat cortical slices

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

Hoehn, K.; Craig, C.G.; White, T.D.

1990-10-01

Tetrodotoxin reduced N-methyl-D-aspartate (NMDA)-evoked release of adenosine by 35% but virtually abolished (3H)norepinephrine release. Although (3H)norepinephrine release from rat cortical slices evoked by 500 microM NMDA was abolished by 1.2 mM Mg++, which produces a voltage-sensitive, uncompetitive block of NMDA-channels, adenosine release was increased in the presence of Mg++. Partial depolarization with 12 mM K+ relieved the Mg++ block of 500 microM NMDA-evoked (3H)norepinephrine release but did not affect adenosine release, indicating that a Mg++ requirement for the adenosine release process per se cannot account for this discrepancy. NMDA was 33 times more potent in releasing adenosine than (3H)norepinephrine. Atmore » submaximal concentrations of NMDA (10 and 20 microM), adenosine release was augmented in Mg+(+)-free medium. Although a high concentration of the uncompetitive NMDA antagonist MK-801 ((+)-5-methyl-10,11,dihydro-5H-dibenzo(a,d)cyclohepten-5-10-imine maleate) (3 microM) blocked NMDA-evoked release of (3H)norepinephrine and adenosine, a lower concentration (300 nM) decreased NMDA-evoked (3H)norepinephrine release by 66% without affecting adenosine release. These findings suggest that maximal adenosine release occurs when relatively few NMDA receptors are activated, raising the possibility that spare receptors exist for NMDA-evoked adenosine release. Rather than acting as a protectant against excessive NMDA excitation, released adenosine might provide an inhibitory threshold which must be overcome for NMDA-mediated neurotransmission to proceed.« less

OPC-13013, a cyclic nucleotide phosphodiesterase type III, inhibitor, inhibits cell proliferation and transdifferentiation of cultured rat hepatic stellate cells.

PubMed

Shimizu, E; Kobayashi, Y; Oki, Y; Kawasaki, T; Yoshimi, T; Nakamura, H

1999-01-01

Activated hepatic stellate cells (HSC; lipocytes; Ito cells) proliferate and are responsible for extracellular matrix synthesis during hepatic fibrogenesis. During activation, HSC undergo transdifferentiation into myofibroblasts expressing alpha-smooth muscle actin (alpha-SMA). Adenosine 3', 5'-cyclic monophosphate (cyclic AMP) is an ubiquitous intracellular signaling molecule, and is upregulated by the activation of adenylate cyclase and downregulated via hydrolysis by cyclic nucleotide phosphodiesterases (PDEs). Recently, increased intracellular cyclic AMP has been shown to inhibit HSC activation. The aim of the current study was to determine the effects of inhibition of PDEs on cell proliferation and transdifferentiation in cultured rat HSC. Cell proliferation was determined by [3H]thymidine incorporation, and Western blot analysis was performed for detection of alpha-SMA, a phenotypic marker of transdifferentiation into myofibroblast. When the cells were exposed to 3-isobutyl-1-methylxanthine (IBMX; 50-1000 microM), a nonselective PDE inhibitor, serum-stimulated [3H]thymidine incorporation was suppressed in a dose-dependent manner with a maximum inhibition of 66% at a concentration of 500 microM OPC-13013 (1-60 microM), a selective PDE III isoenzyme inhibitor, induced a dose-dependent inhibitory effect on serum-stimulated DNA synthesis that reached a maximum inhibition of 95% at a concentration of 60 microM, while neither 8-methoxymethyl-3-isobutyl-1-methylxanthine (8-MMX), a PDE I isoenzyme inhibitor, nor Ro-20-1724, a PDE IV isoenzyme inhibitor, had an inhibitory effect. Western blot analysis revealed that IBMX or OPC-13013 decreased alpha-SMA expression, while other selective PDE isoenzyme inhibitors did not have a suppressive effect. IBMX, OPC-13013 or Ro-20-1724, but not 8-MMX augmented forskolin-induced increase in intracellular cyclic AMP levels although cyclic AMP levels were not affected by treatment with any of these PDE inhibitors alone. These data

Regulation of adenosine deaminase (ADA) on induced mouse experimental autoimmune uveitis (EAU) ‡

PubMed Central

Liang, Dongchun; Zuo, Aijun; Zhao, Ronglan; Shao, Hui; Kaplan, Henry J.; Sun, Deming

2016-01-01

Adenosine is an important regulator of the immune response and adenosine deaminase (ADA) inhibits this regulatory effect by converting adenosine into functionally inactive molecules. Studies have shown that adenosine receptor (AR) agonists can be either anti- or pro-inflammatory. Clarification of the mechanisms that cause these opposing effects should provide a better guide for therapeutic intervention. In this study, we investigated the effect of ADA on the development of experimental autoimmune uveitis (EAU) induced by immunizing EAU-prone mice with a known uveitogenic peptide, IRBP1–20. Our results showed that the effective time to administer a single dose of ADA to suppress induction of EAU was 8–14 days post-immunization, shortly before EAU expression, but ADA treatment at other time points exacerbated disease. ADA preferentially inhibited Th17 responses and this effect was γδ T cell-dependent. Our results demonstrated that the existing immune status strongly influences the anti- or proinflammatory effects of ADA. Our observations should help improve the design of ADA- and AR-targeted therapies. PMID:26856700

Adenosine receptor antagonist and augmented vasodilation during hypoxic exercise

PubMed Central

Madery, Brandon D.; Pike, Tasha L.; Eisenach, John H.; Dietz, Niki M.; Joyner, Michael J.; Wilkins, Brad W.

2009-01-01

We tested the hypothesis that adenosine contributes to augmented skeletal muscle vasodilation during hypoxic exercise. In separate protocols, subjects performed incremental rhythmic forearm exercise (10% and 20% of maximum) during normoxia and normocapnic hypoxia (80% arterial O2 saturation). In protocol 1 (n = 8), subjects received an intra-arterial administration of saline (control) and aminophylline (adenosine receptor antagonist). In protocol 2 (n = 10), subjects received intra-arterial phentolamine (α-adrenoceptor antagonist) and combined phentolamine and aminophylline administration. Forearm vascular conductance (FVC; in ml·min−1·100 mmHg−1) was calculated from forearm blood flow (in ml/min) and blood pressure (in mmHg). In protocol 1, the change in FVC (ΔFVC; change from normoxic baseline) during hypoxic exercise with saline was 172 ± 29 and 314 ± 34 ml·min−1·100 mmHg−1 (10% and 20%, respectively). Aminophylline administration did not affect ΔFVC during hypoxic exercise at 10% (190 ± 29 ml·min−1·100 mmHg−1, P = 0.4) or 20% (287 ± 48 ml·min−1·100 mmHg−1, P = 0.3). In protocol 2, ΔFVC due to hypoxic exercise with phentolamine infusion was 313 ± 30 and 453 ± 41 ml·min−1·100 mmHg−1 (10% and 20% respectively). ΔFVC was similar at 10% (352 ± 39 ml·min−1·100 mmHg−1, P = 0.8) and 20% (528 ± 45 ml·min−1·100 mmHg−1, P = 0.2) hypoxic exercise with combined phentolamine and aminophylline. In contrast, ΔFVC to exogenous adenosine was reduced by aminophylline administration in both protocols (P < 0.05 for both). These observations suggest that adenosine receptor activation is not obligatory for the augmented hyperemia during hypoxic exercise in humans. PMID:19661449

Adenosine A1 receptors (A1Rs) play a critical role in osteoclast formation and function

PubMed Central

Kara, Firas M.; Chitu, Violeta; Sloane, Jennifer; Axelrod, Matthew; Fredholm, Bertil B.; Stanley, E. Richard; Cronstein, Bruce N.

2010-01-01

Adenosine regulates a wide variety of physiological processes via interaction with one or more G-protein-coupled receptors (A1R, A2AR, A2BR, and A3R). Because A1R occupancy promotes fusion of human monocytes to form giant cells in vitro, we determined whether A1R occupancy similarly promotes osteoclast function and formation. Bone marrow cells (BMCs) were harvested from C57Bl/6 female mice or A1R-knockout mice and their wild-type (WT) littermates and differentiated into osteoclasts in the presence of colony stimulating factor-1 and receptor activator of NF-κB ligand in the presence or absence of the A1R antagonist 1,3-dipropyl-8-cyclopentyl xanthine (DPCPX). Osteoclast morphology was analyzed in tartrate-resistant acid phosphatase or F-actin-stained samples, and bone resorption was evaluated by toluidine blue staining of dentin. BMCs from A1R-knockout mice form fewer osteoclasts than BMCs from WT mice, and the A1R antagonist DPCPX inhibits osteoclast formation (IC50=1 nM), with altered morphology and reduced ability to resorb bone. A1R blockade increased ubiquitination and degradation of TRAF6 in RAW264.7 cells induced to differentiate into osteoclasts. These studies suggest a critical role for adenosine in bone homeostasis via interaction with adenosine A1R and further suggest that A1R may be a novel pharmacologic target to prevent the bone loss associated with inflammatory diseases and menopause.—Kara, F. M., Chitu, V., Sloane, J., Axelrod, M., Fredholm, B. B., Stanley, R., Cronstein, B. N. Adenosine A1 receptors (A1Rs) play a critical role in osteoclast formation and function. PMID:20181934

Cyclic GMP-mediated memory enhancement in the object recognition test by inhibitors of phosphodiesterase-2 in mice.

PubMed

Lueptow, Lindsay M; Zhan, Chang-Guo; O'Donnell, James M

2016-02-01

Cyclic nucleotide phosphodiesterase-2 (PDE2) is a potential therapeutic target for the treatment of cognitive dysfunction. Using the object recognition test (ORT), this study assessed the effects of two PDE2 inhibitors, Bay 60-7550 and ND7001, on learning and memory, and examined underlying mechanisms. To assess the role of PDE2 inhibition on phases of memory, Bay 60-7550 (3 mg/kg) was administered: 30 min prior to training; 0, 1, or 3 h after training; or 30 min prior to recall testing. To assess cyclic nucleotide involvement in PDE2 inhibitor-enhanced memory consolidation, either the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg; intraperitoneal (IP)), soluble guanylyl cyclase inhibitor 1H-[-1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ; 20 mg/kg; IP), protein kinase G inhibitor KT5823 (2.5 μg; intracerebroventricular (ICV)), or protein kinase A inhibitor H89 (1 μg; ICV) was administered 30 min prior to the PDE2 inhibitor Bay 60-7550 (3 mg/kg) or ND7001 (3 mg/kg). Changes in the phosphorylation of 3'5'-cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) at Ser-133 and vasodilator-stimulated phosphoprotein (VASP) at Ser-239 were determined to confirm activation of cAMP and 3'5'-cyclic guanosine monophosphate (cGMP) signaling. Bay 60-7550 (3 mg/kg) enhanced memory of mice in the ORT when given 30 min prior to training, immediately after training, or 30 min prior to recall. Inhibitors of the cGMP pathway blocked the memory-enhancing effects of both Bay 60-7550 (3 mg/kg) and ND7001 (3 mg/kg) on early consolidation processes. Bay 60-7550 (3 mg/kg) enhanced phosphorylation of CREB and VASP, both targets of cGMP-dependent protein kinase (PKG). These results confirm a potential of PDE2, or components of its signaling pathway, as a therapeutic target for drug discovery focused on restoring memory function.

Elevated synovial fluid concentration of adenosine triphosphate in dogs with osteoarthritis or sodium urate-induced synovitis of the stifle.

PubMed

Torres, Bryan T; Jimenez, David A; Budsberg, Steven C

2016-07-19

Adenosine triphosphate has been shown to stimulate nociceptive nerve terminals in joints. Elevated synovial fluid adenosine triphosphate concentrations as well as a correlation between synovial fluid adenosine triphosphate concentrations and osteoarthritic knee pain has been demonstrated in humans, but not yet in dogs. This study documented elevated synovial fluid adenosine triphosphate concentrations in the stifles of dogs with secondary osteoarthritis and urate-induced synovitis, as compared to normal stifles.

A new s-adenosylhomocysteine hydrolase-linked method for adenosine detection based on DNA-templated fluorescent Cu/Ag nanoclusters.

PubMed

Ahn, Jun Ki; Kim, Hyo Yong; Baek, Songyi; Park, Hyun Gyu

2017-07-15

We herein describe a novel fluorescent method for the rapid and selective detection of adenosine by utilizing DNA-templated Cu/Ag nanoclusters (NCs) and employing s-adenosylhomocysteine hydrolase (SAHH). SAHH is allowed to promote hydrolysis reaction of s-adenosylhomocysteine (SAH) and consequently produces homocysteine, which would quench the fluorescence signal from DNA-templated Cu/Ag nanoclusters employed as a signaling probe in this study. On the other hand, adenosine significantly inhibits the hydrolysis reaction and prevent the formation of homocysteine. Consequently, highly enhanced fluorescence signal from DNA-Cu/Ag NCs is retained, which could be used to identify the presence of adenosine. By employing this design principle, adenosine was sensitively detected down to 19nM with high specificity over other adenosine analogs such as AMP, ADP, ATP, cAMP, guanosine, cytidine, and urine. Finally, the diagnostic capability of this method was successfully verified by reliably detecting adenosine present in a real human serum sample. Copyright © 2016 Elsevier B.V. All rights reserved.

An improved Armstrong-Frederick-Type Plasticity Model for Stable Cyclic Stress-Strain Responses Considering Nonproportional Hardening

NASA Astrophysics Data System (ADS)

Li, Jing; Zhang, Zhong-ping; Li, Chun-wang

2018-03-01

This paper modified an Armstrong-Frederick-type plasticity model for investigating the stable cyclic deformation behavior of metallic materials with different sensitivity to nonproportional loadings. In the modified model, the nonproportionality factor and nonproportional cyclic hardening coefficient coupled with the Jiang-Sehitoglu incremental plasticity model were used to estimate the stable stress-strain responses of the two materials (1045HR steel and 304 stainless steel) under various tension-torsion strain paths. A new equation was proposed to calculate the nonproportionality factor on the basis of the minimum normal strain range. Procedures to determine the minimum normal strain range were presented for general multiaxial loadings. Then, the modified model requires only the cyclic strain hardening exponent and cyclic strength coefficient to determine the material constants. It is convenient for predicting the stable stress-strain responses of materials in engineering application. Comparisons showed that the modified model can reflect the effect of nonproportional cyclic hardening well.

Adenosine signalling mediates the anti-inflammatory effects of the COX-2 inhibitor nimesulide.

PubMed

Caiazzo, Elisabetta; Maione, Francesco; Morello, Silvana; Lapucci, Andrea; Paccosi, Sara; Steckel, Bodo; Lavecchia, Antonio; Parenti, Astrid; Iuvone, Teresa; Schrader, Jürgen; Ialenti, Armando; Cicala, Carla

2016-07-15

Extracellular adenosine formation from ATP is controlled by ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase/CD39) and ecto-5'-nucleotidase (e-5NT/CD73); the latter converts AMP to adenosine and inorganic phosphate, representing the rate limiting step controlling the ratio between extracellular ATP and adenosine. Evidence that cellular expression and activity of CD39 and CD73 may be subject to changes under pathophysiological conditions has identified this pathway as an endogenous modulator in several diseases and was shown to be involved in the molecular mechanism of drugs, such as methotrexate, salicylates , interferon-β. We evaluated whether CD73/adenosine/A2A signalling pathway is involved in nimesulide anti-inflammatory effect, in vivo and in vitro. We found that the adenosine A2A agonist, 4-[2-[[6-amino-9-(N-ethyl-β-d-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid hydrochloride (CGS21680, 2mg/kg ip.), inhibited carrageenan-induced rat paw oedema and the effect was reversed by co-administration of the A2A antagonist -(2-[7-amino-2-[2-furyl][1,2,4]triazolo[2,3-a][1,3,5]triazin-5-yl-amino]ethyl)phenol (ZM241385; 3mg/kg i.p.). Nimesulide (5mg/kg i.p.) anti-inflammatory effect was inhibited by pre-treatment with ZM241385 (3mg/kg i.p.) and by local administration of the CD73 inhibitor, adenosine 5'-(α,β-methylene)diphosphate (APCP; 400μg/paw). Furthermore, we found increased activity of 5'-nucleotidase/CD73 in paws and plasma of nimesulide treated rats, 4h following oedema induction. In vitro, the inhibitory effect of nimesulide on nitrite and prostaglandin E2 production by lipopolysaccharide-activated J774 cell line was reversed by ZM241385 and APCP. Furthermore, nimesulide increased CD73 activity in J774 macrophages while it did not inhibit nitrite accumulation by lipopolysaccharide-activated SiRNA CD73 silenced J774 macrophages. Our data demonstrate that the anti-inflammatory effect of nimesulide in part is mediated by CD73

Adenosine receptors as markers of brain iron deficiency: Implications for Restless Legs Syndrome.

PubMed

Quiroz, César; Gulyani, Seema; Ruiqian, Wan; Bonaventura, Jordi; Cutler, Roy; Pearson, Virginia; Allen, Richard P; Earley, Christopher J; Mattson, Mark P; Ferré, Sergi

2016-12-01

Deficits of sensorimotor integration with periodic limb movements during sleep (PLMS) and hyperarousal and sleep disturbances in Restless Legs Syndrome (RLS) constitute two pathophysiologically distinct but interrelated clinical phenomena, which seem to depend mostly on alterations in dopaminergic and glutamatergic neurotransmission, respectively. Brain iron deficiency is considered as a main pathogenetic mechanism in RLS. Rodents with brain iron deficiency represent a valuable pathophysiological model of RLS, although they do not display motor disturbances. Nevertheless, they develop the main neurochemical dopaminergic changes found in RLS, such as decrease in striatal dopamine D 2 receptor density. On the other hand, brain iron deficient mice exhibit the characteristic pattern of hyperarousal in RLS, providing a tool to find the link between brain iron deficiency and sleep disturbances in RLS. The present study provides evidence for a role of the endogenous sleep-promoting factor adenosine. Three different experimental preparations, long-term (22 weeks) severe or moderate iron-deficient (ID) diets (3- or 7-ppm iron diet) in mice and short-term (3 weeks) severe ID diet (3-ppm iron diet) in rats, demonstrated a significant downregulation (Western blotting in mouse and radioligand binding saturation experiments in rat brain tissue) of adenosine A 1 receptors (A1R) in the cortex and striatum, concomitant to striatal D2R downregulation. On the other hand, the previously reported upregulation of adenosine A 2A receptors (A2AR) was only observed with severe ID in both mice and rats. The results suggest a key role for A1R downregulation in the PLMS and hyperarousal in RLS. Published by Elsevier Ltd.

Comparison of the efficacy of topical minoxidil 5% and adenosine 0.75% solutions on male androgenetic alopecia and measuring patient satisfaction rate.

PubMed

Faghihi, Gita; Iraji, Fariba; Rajaee Harandi, Manijeh; Nilforoushzadeh, Mohammad-Ali; Askari, Gholamreza

2013-01-01

According to the hypothesis on the stimulating effect of adenosine on increasing fibroblast growth factor 7 in dermal papilla cells and its vasorelaxant effect, we performed this study to compare the effect of topical minoxidil 5% and adenosine 0.75% on male pattern androgenetic alopecia. This prospective-randomized study recruited 110 male patients suffering from grade II-V Hamilton androgenetic alopecia. Fifty-five patients received minoxidil 5% (group 1) and adenosine 0.75% (group 2) each. Later, 16 patients were excluded due to allergic reactions or loss to follow up. After 3 and 6 months of treatment, complete and relative recovery rates alongside patient satisfaction rate (faster prevention of primary hair loss and appearance of newly grown hair) were compared between the groups. After 3 months of treatment, relative recovery was achieved in 2.4% and 1.9% of patients in group 1 and group 2, respectively, which was not significantly different (p=0.17). During 6 months, the relative recovery rate did not change either within or between the groups (p=0.99) and after 6 months none of the patients achieved complete recovery. However, the patient satisfaction rate was significantly higher in group 2 (p=0.003). In the light of the results, adenosine has no statistically superiority to minoxidil in the treatment of androgenetic alopecia according to recovery rates. However, the patients were significantly more satisfied with adenosine because of faster prevention of hair loss and appearance of the newly grown hairs. It seems further studies with larger sample size or different drug dosages are required to clarify the findings.

Endogenous and exogenous cyclicity and temperament in bipolar disorder: review, new data and hypotheses.

PubMed

Koukopoulos, Athanasios; Sani, Gabriele; Koukopoulos, Alexia E; Albert, Matthew J; Girardi, Paolo; Tatarelli, Roberto

2006-12-01

In this special issue dedicated to Falret and the French contributions to the concept of cyclicity in manic depressive illness, we begin with a historical overview of the development of the concept of cyclicity and its fundamental significance in manic-depressive illness and we underscore how the concept fell into neglect only to reemerge in recent years. We then look at the intimate relationship between mania and depression. The hypothesis of the primacy of mania is discussed. The thesis is presented, supported by the examination of 100 consecutive index manias, that in most cases mania is triggered by external factors acting upon hyperthymic patients, determining an exogenous cyclicity. On the other hand, in BPII patients the temperamental mood instability (cyclothymia) is an inherent and decisive factor in determining the cyclic autonomous course of the disorder. Finally, a new distinction of Bipolar Disorders, based on premorbid temperament and course of the illness, is considered.

Visual search of cyclic spatio-temporal events

NASA Astrophysics Data System (ADS)

Gautier, Jacques; Davoine, Paule-Annick; Cunty, Claire

2018-05-01

The analysis of spatio-temporal events, and especially of relationships between their different dimensions (space-time-thematic attributes), can be done with geovisualization interfaces. But few geovisualization tools integrate the cyclic dimension of spatio-temporal event series (natural events or social events). Time Coil and Time Wave diagrams represent both the linear time and the cyclic time. By introducing a cyclic temporal scale, these diagrams may highlight the cyclic characteristics of spatio-temporal events. However, the settable cyclic temporal scales are limited to usual durations like days or months. Because of that, these diagrams cannot be used to visualize cyclic events, which reappear with an unusual period, and don't allow to make a visual search of cyclic events. Also, they don't give the possibility to identify the relationships between the cyclic behavior of the events and their spatial features, and more especially to identify localised cyclic events. The lack of possibilities to represent the cyclic time, outside of the temporal diagram of multi-view geovisualization interfaces, limits the analysis of relationships between the cyclic reappearance of events and their other dimensions. In this paper, we propose a method and a geovisualization tool, based on the extension of Time Coil and Time Wave, to provide a visual search of cyclic events, by allowing to set any possible duration to the diagram's cyclic temporal scale. We also propose a symbology approach to push the representation of the cyclic time into the map, in order to improve the analysis of relationships between space and the cyclic behavior of events.

Adenosine-to-inosine RNA editing by ADAR1 is essential for normal murine erythropoiesis

PubMed Central

Liddicoat, Brian J.; Hartner, Jochen C.; Piskol, Robert; Ramaswami, Gokul; Chalk, Alistair M.; Kingsley, Paul D.; Sankaran, Vijay G.; Wall, Meaghan; Purton, Louise E.; Seeburg, Peter H.; Palis, James; Orkin, Stuart H.; Lu, Jun; Li, Jin Billy; Walkley, Carl R.

2016-01-01

Adenosine deaminases that act on RNA (ADARs) convert adenosine residues to inosine in double-stranded RNA. In vivo, ADAR1 is essential for the maintenance of hematopoietic stem/progenitors. Whether other hematopoietic cell types also require ADAR1 has not been assessed. Using erythroid- and myeloid-restricted deletion of Adar1, we demonstrate that ADAR1 is dispensable for myelopoiesis but is essential for normal erythropoiesis. Adar1-deficient erythroid cells display a profound activation of innate immune signaling and high levels of cell death. No changes in microRNA levels were found in ADAR1-deficient erythroid cells. Using an editing-deficient allele, we demonstrate that RNA editing is the essential function of ADAR1 during erythropoiesis. Mapping of adenosine-to-inosine editing in purified erythroid cells identified clusters of hyperedited adenosines located in long 3’-untranslated regions of erythroid-specific transcripts and these are ADAR1-specific editing events. ADAR1-mediated RNA editing is essential for normal erythropoiesis. PMID:27373493

Suitability of the adenosine antagonist istradefylline for the treatment of Parkinson's disease: pharmacokinetic and clinical considerations.

PubMed

Müller, Thomas

2013-08-01

Recent experimental and clinical research has shown that A2A adenosine receptor antagonism can bring about an improvement in the motor behavior of patients with Parkinson's disease. Istradefylline , a xanthine derivative, has the longest half-life of all the currently available A2A adenosine receptor antagonists; it can successfully permeate through the blood-brain barrier and has a high human A2A adenosine receptor affinity. In this article, the author discusses the potential role of A2A adenosine receptor antagonists in the treatment of Parkinson's disease through the evaluation of istradefylline. Specifically, the article reviews the clinical and pharmacokinetic information available to elucidate its therapeutic potential. A2A adenosine receptor antagonists are efficacious in combination with l-dopa. l-dopa has a complex pharmacokinetic behavior and causes long-term behavioral and metabolic side effects. Future research on A2A adenosine receptor antagonism should consider compounds like istradefylline as l-dopa and/or dopamine agonist-sparing treatment alternatives, since their clinical handling, safety and side-effect profile are superior to l-dopa and/or dopamine agonists. The current focus to demonstrate a specific dyskinesia-ameliorating efficacy of A2A adenosine receptor antagonism in clinical trials is risky, since the presentation of dyskinesia varies on a day-to-day basis and is considerably influenced by peripheral l-dopa metabolism. The demonstration of an antidyskinetic effect may convince authorities, but this is far less relevant in clinical practice as patients generally better tolerate dyskinesia than other phenomena and dopaminergic side effects.

Adenosine, caffeine, and performance: from cognitive neuroscience of sleep to sleep pharmacogenetics.

PubMed

Urry, Emily; Landolt, Hans-Peter

2015-01-01

An intricate interplay between circadian and sleep-wake homeostatic processes regulate cognitive performance on specific tasks, and individual differences in circadian preference and sleep pressure may contribute to individual differences in distinct neurocognitive functions. Attentional performance appears to be particularly sensitive to time of day modulations and the effects of sleep deprivation. Consistent with the notion that the neuromodulator, adenosine , plays an important role in regulating sleep pressure, pharmacologic and genetic data in animals and humans demonstrate that differences in adenosinergic tone affect sleepiness, arousal and vigilant attention in rested and sleep-deprived states. Caffeine--the most often consumed stimulant in the world--blocks adenosine receptors and normally attenuates the consequences of sleep deprivation on arousal, vigilance, and attention. Nevertheless, caffeine cannot substitute for sleep, and is virtually ineffective in mitigating the impact of severe sleep loss on higher-order cognitive functions. Thus, the available evidence suggests that adenosinergic mechanisms, in particular adenosine A2A receptor-mediated signal transduction, contribute to waking-induced impairments of attentional processes, whereas additional mechanisms must be involved in higher-order cognitive consequences of sleep deprivation. Future investigations should further clarify the exact types of cognitive processes affected by inappropriate sleep. This research will aid in the quest to better understand the role of different brain systems (e.g., adenosine and adenosine receptors) in regulating sleep, and sleep-related subjective state, and cognitive processes. Furthermore, it will provide more detail on the underlying mechanisms of the detrimental effects of extended wakefulness, as well as lead to the development of effective, evidence-based countermeasures against the health consequences of circadian misalignment and chronic sleep restriction.

Extracellular adenosine production by ecto-5′-nucleotidase (CD73) enhances radiation-induced lung fibrosis

PubMed Central

Wirsdörfer, Florian; de Leve, Simone; Cappuccini, Federica; Eldh, Therese; Meyer, Alina V.; Gau, Eva; Thompson, Linda F.; Chen, Ning-Yuan; Karmouty-Quintana, Harry; Fischer, Ute; Kasper, Michael; Klein, Diana; Ritchey, Jerry W.; Blackburn, Michael R.; Westendorf, Astrid M.; Stuschke, Martin; Jendrossek, Verena

2016-01-01

Radiation-induced pulmonary fibrosis is a severe side effect of thoracic irradiation, but its pathogenesis remains poorly understood and no effective treatment is available. In this study, we investigated the role of the extracellular adenosine as generated by the ecto-5'-nucleotidase CD73 in fibrosis development after thoracic irradiation. Exposure of wild-type C57BL/6 mice to a single dose (15 Gray) of whole thorax irradiation triggered a progressive increase in CD73 activity in the lung between 3 and 30 weeks post-irradiation. In parallel, adenosine levels in bronchoalveolar lavage fluid (BALF) were increased by approximately three-fold. Histological evidence of lung fibrosis was observed by 25 weeks after irradiation. Conversely, CD73-deficient mice failed to accumulate adenosine in BALF and exhibited significantly less radiation-induced lung fibrosis (P<0.010). Furthermore, treatment of wild-type mice with pegylated adenosine deaminase (PEG-ADA) or CD73 antibodies also significantly reduced radiation-induced lung fibrosis. Taken together, our findings demonstrate that CD73 potentiates radiation-induced lung fibrosis, suggesting that existing pharmacological strategies for modulating adenosine may be effective in limiting lung toxicities associated with the treatment of thoracic malignancies. PMID:26921334

Adenosine A2A receptors and depression.

PubMed

El Yacoubi, Malika; Costentin, Jean; Vaugeois, Jean-Marie

2003-12-09

Adenosine and its analogues have been shown to induce "behavioral despair" in animal models believed to be relevant to depression. Recent data have shown that selective adenosine A2A receptor antagonists (e.g., SCH 58261, ZM241385, and KW6002) or genetic inactivation of the receptor was effective in reversing signs of behavioral despair in the tail suspension and forced swim tests, two screening procedures predictive of antidepressant activity. A2A antagonists were active in the tail suspension test using either mice previously screened for having high immobility scores or mice that were selectively bred for their spontaneous "helplessness" in this test. At stimulant doses, caffeine, a nonselective A1/A2A receptor antagonist, was effective in the forced swim test. The authors have hypothesized that the antidepressant-like effect of selective A2A antagonists is linked to an interaction with dopaminergic transmission, possibly in the frontal cortex. In support of this idea, administration of the dopamine D2 receptor antagonist haloperidol prevented antidepressant-like effects elicited by SCH 58261 in the forced swim test (putatively involving cortex), whereas it had no effect on stimulant motor effects of SCH 58261 (putatively linked to ventral striatum). The interaction profile of caffeine with haloperidol differed markedly from that of SCH 58261 in the forced swim and motor activity tests. Therefore, a clear-cut antidepressant-like effect could not be ascribed to caffeine. In conclusion, available data support the proposition that a selective blockade of the adenosine A2A receptor may be an interesting target for the development of effective antidepressant agents.

Adenosine Monophosphate (AMP)-Activated Protein Kinase: A New Target for Nutraceutical Compounds.

PubMed

Marín-Aguilar, Fabiola; Pavillard, Luis E; Giampieri, Francesca; Bullón, Pedro; Cordero, Mario D

2017-01-29

Adenosine monophosphate-activated protein kinase (AMPK) is an important energy sensor which is activated by increases in adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratio and/or adenosine diphosphate (ADP)/ATP ratio, and increases different metabolic pathways such as fatty acid oxidation, glucose transport and mitochondrial biogenesis. In this sense, AMPK maintains cellular energy homeostasis by induction of catabolism and inhibition of ATP-consuming biosynthetic pathways to preserve ATP levels. Several studies indicate a reduction of AMPK sensitivity to cellular stress during aging and this could impair the downstream signaling and the maintenance of the cellular energy balance and the stress resistance. However, several diseases have been related with an AMPK dysfunction. Alterations in AMPK signaling decrease mitochondrial biogenesis, increase cellular stress and induce inflammation, which are typical events of the aging process and have been associated to several pathological processes. In this sense, in the last few years AMPK has been identified as a very interesting target and different nutraceutical compounds are being studied for an interesting potential effect on AMPK induction. In this review, we will evaluate the interaction of the different nutraceutical compounds to induce the AMPK phosphorylation and the applications in diseases such as cancer, type II diabetes, neurodegenerative diseases or cardiovascular diseases.

Adenosine Monophosphate (AMP)-Activated Protein Kinase: A New Target for Nutraceutical Compounds

PubMed Central

Marín-Aguilar, Fabiola; Pavillard, Luis E.; Giampieri, Francesca; Bullón, Pedro; Cordero, Mario D.

2017-01-01

Adenosine monophosphate-activated protein kinase (AMPK) is an important energy sensor which is activated by increases in adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratio and/or adenosine diphosphate (ADP)/ATP ratio, and increases different metabolic pathways such as fatty acid oxidation, glucose transport and mitochondrial biogenesis. In this sense, AMPK maintains cellular energy homeostasis by induction of catabolism and inhibition of ATP-consuming biosynthetic pathways to preserve ATP levels. Several studies indicate a reduction of AMPK sensitivity to cellular stress during aging and this could impair the downstream signaling and the maintenance of the cellular energy balance and the stress resistance. However, several diseases have been related with an AMPK dysfunction. Alterations in AMPK signaling decrease mitochondrial biogenesis, increase cellular stress and induce inflammation, which are typical events of the aging process and have been associated to several pathological processes. In this sense, in the last few years AMPK has been identified as a very interesting target and different nutraceutical compounds are being studied for an interesting potential effect on AMPK induction. In this review, we will evaluate the interaction of the different nutraceutical compounds to induce the AMPK phosphorylation and the applications in diseases such as cancer, type II diabetes, neurodegenerative diseases or cardiovascular diseases. PMID:28146060

Use of tailored loading-dose clopidogrel in patients undergoing selected percutaneous coronary intervention based on adenosine diphosphate-mediated platelet aggregation.

PubMed

Meng, Kang; Lü, Shu-Zheng; Zhu, Hua-Gang; Chen, Xin; Ge, Chang-Jiang; Song, Xian-Tao

2010-12-01

Adenosine phosphate-mediated platelet aggregation is a prognostic factor for major adverse cardiac events in patients who have undergone selective percutaneous coronary interventions. This study aimed to assess whether an adjusted loading dose of clopidogrel could more effectively inhibit platelet aggregation in patients undergoing selected percutaneous coronary intervention. A total of 205 patients undergoing selected percutaneous coronary intervention were enrolled in this multicenter, prospective, randomized study. Patients receiving domestic clopidogrel (n = 104) served as the Talcom (Taijia) group; others (n = 101) received Plavix, the Plavix group. Patients received up to 3 additional 300-mg loading doses of clopidogrel to decrease the adenosine phosphate-mediated platelet aggregation index by more than 50% (the primary endpoint) compared with the baseline. The secondary endpoint was major adverse cardiovascular events at 12 months. Compared with the rational loading dosage, the tailored loading dosage better inhibited platelet aggregation based on a > 50% decrease in adenosine phosphate-mediated platelet aggregation (rational loading dosage vs. tailored loading dosage, 48% vs. 73%, P = 0.028). There was no significant difference in the eligible index between the Talcom and Plavix groups (47% vs. 49% at 300 mg; 62% vs. 59% at 600 mg; 74% vs. 72% at 900 mg; P > 0.05) based on a standard adenosine diphosphate-mediated platelet aggregation decrease of > 50%. After 12 months of follow-up, there were no significant differences in major adverse cardiac events (2.5% vs. 2.9%, P = 5.43). No acute or subacute stent thrombosis events occurred. An adjusted loading dose of clopidogrel could have significant effects on antiplatelet aggregation compared with a rational dose, decreasing 1-year major adverse cardiac events in patients undergoing percutaneous coronary interventions based on adenosine phosphate-mediated platelet aggregation with no increase in bleeding.

Restoring auditory cortex plasticity in adult mice by restricting thalamic adenosine signaling

DOE PAGES

Blundon, Jay A.; Roy, Noah C.; Teubner, Brett J. W.; ...

2017-06-30

Circuits in the auditory cortex are highly susceptible to acoustic influences during an early postnatal critical period. The auditory cortex selectively expands neural representations of enriched acoustic stimuli, a process important for human language acquisition. Adults lack this plasticity. We show in the murine auditory cortex that juvenile plasticity can be reestablished in adulthood if acoustic stimuli are paired with disruption of ecto-5'-nucleotidase–dependent adenosine production or A1–adenosine receptor signaling in the auditory thalamus. This plasticity occurs at the level of cortical maps and individual neurons in the auditory cortex of awake adult mice and is associated with long-term improvement ofmore » tone-discrimination abilities. We determined that, in adult mice, disrupting adenosine signaling in the thalamus rejuvenates plasticity in the auditory cortex and improves auditory perception.« less

Restoring auditory cortex plasticity in adult mice by restricting thalamic adenosine signaling

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

Blundon, Jay A.; Roy, Noah C.; Teubner, Brett J. W.

Circuits in the auditory cortex are highly susceptible to acoustic influences during an early postnatal critical period. The auditory cortex selectively expands neural representations of enriched acoustic stimuli, a process important for human language acquisition. Adults lack this plasticity. We show in the murine auditory cortex that juvenile plasticity can be reestablished in adulthood if acoustic stimuli are paired with disruption of ecto-5'-nucleotidase–dependent adenosine production or A1–adenosine receptor signaling in the auditory thalamus. This plasticity occurs at the level of cortical maps and individual neurons in the auditory cortex of awake adult mice and is associated with long-term improvement ofmore » tone-discrimination abilities. We determined that, in adult mice, disrupting adenosine signaling in the thalamus rejuvenates plasticity in the auditory cortex and improves auditory perception.« less

The adenosine-triphosphatase system responsible for cation transport in electric organ: exclusion of phospholipids as intermediates

PubMed Central

Glynn, I. M.; Slayman, Carolyn W.; Eichberg, J.; Dawson, R. M. C.

1965-01-01

1. Subcellular fractions were prepared from the electric organs of Electrophorus and Torpedo and assayed for adenosine-triphosphatase activity. 2. Treatment of the `low-speed' fraction from Torpedo with m-urea gave an adenosine-triphosphatase preparation that was almost completely (98%) inhibited by ouabain (0·1mg./ml.) and dependent on the simultaneous presence of Na+ and K+. 3. The adenosine-triphosphatase preparations were exposed to [γ-32P]ATP for 30sec. in the presence of (i) Na+, (ii) K+, (iii) Na++K+ and (iv) Na++K++ouabain. No significant labelling of phosphatidic acid, triphosphoinositide or any other phospholipid was observed. 4. The results suggest that phospholipids do not act as phosphorylated intermediates in the `transport adenosine-triphosphatase' system of electric organ. PMID:14340060

Cyclic Oxidation Modeling Program Rewritten for MS Windows

NASA Technical Reports Server (NTRS)

Smialek, James L.; Auping, Judith V.

2002-01-01

Turbine superalloy components are subject to high-temperature oxidation during operation. Protection is often conferred by coatings designed to form slow-growing, adherent oxide scales. Degradation by oxidation is exacerbated by the thermal cycling encountered during normal aircraft operations. Cooling has been identified as the major contributor to stresses in the oxidation scales, and it may often cause some oxide scale spallation with a proportional loss of protective behavior. Overall oxidation resistance is, thus, studied by the weight change behavior of alloy coupons during high-temperature cyclic oxidation in furnace or burner rig tests. The various characteristics of this behavior are crucial in understanding the performance of alloys at high temperatures. This new modeling effort helps in the understanding of the major factors involved in the cyclic oxidation process. Weight change behavior in cyclic oxidation is typified by an initial parabolic weight gain response curve that eventually exhibits a maximum, then transitions into a linear rate of weight loss due to spalling. The overall shape and magnitude of the curve are determined by the parabolic growth rate, kp, the cycle duration, the type of oxide scale, and the regular, repetitive spalling process. This entire process was modeled by a computer program called the Cyclic Oxidation Spalling Program (COSP) previously developed at the NASA Glenn Research Center. Thus, by supplying appropriate oxidation input parameters, one can determine the best fit to the actual data. These parameters describe real behavior and can be used to compare alloys and project cyclic oxidation behavior for longer times or under different cycle frequencies.

Adenosine inhibits activity of hypocretin/orexin neurons via A1 receptor in the lateral hypothalamus: a possible sleep-promoting effect

PubMed Central

Liu, Zhong-Wu; Gao, Xiao-Bing

2006-01-01

Neurons in the lateral hypothalamus (LH) that contain hypocretin/orexin have been established as important promoters of arousal. Deficiencies in the hypocretin/orexin system lead to narcolepsy. The inhibition of hypocretin/orexin neurons by sleep-promoting neurotransmitters has been suggested as one part of the sleep regulation machinery. Adenosine has been identified as a sleep promoter and its role in sleep regulation in the basal forebrain has been well documented. However, the effect of adenosine on arousal-promoting hypocretin/orexin neurons has not been addressed, despite recent evidence that immunocytochemical visualization of adenosine receptors was detected in these neurons. In this study, we examined the hypothesis that adenosine inhibits the activity of hypocretin/orexin neurons by using electrophysiological methods in brain slices from mice expressing green fluorescent protein in hypocretin/orexin neurons. We found that adenosine significantly attenuated the frequency of action potentials without a change in membrane potential in hypocretin/orexin neurons. The adenosine-mediated inhibition is due to depression of excitatory synaptic transmission to hypocretin/orexin neurons, since adenosine depresses the amplitude of evoked excitatory postsynaptic potential and the frequency of spontaneous and miniature excitatory postsynaptic currents in these neurons. At the cell body of the hypocretin/orexin neurons, adenosine inhibits voltage-dependent calcium currents without the induction of GIRK current. The inhibitory effect of adenosine is dose-dependent, pertussis toxin-sensitive and mediated via A1 receptors. In summary, our data suggest that in addition to its effect in the basal forebrain, adenosine exerts its sleep-promoting effect in the LH via inhibition of hypocretin/orexin neurons. PMID:17093123

Evidence that the adenosine A3 receptor may mediate the protection afforded by preconditioning in the isolated rabbit heart.

PubMed

Liu, G S; Richards, S C; Olsson, R A; Mullane, K; Walsh, R S; Downey, J M

1994-07-01

Agonists selective for the A1 adenosine receptor mimic the protective effect of ischaemic preconditioning against infarction in the rabbit heart. Unselective adenosine antagonists block this protection but, paradoxically, the A1 adenosine receptor selective antagonist 8-cyclopentyl- 1,3-dipropylxanthine (DPCPX) does not. The aim of this study was to test the hypothesis that the newly described A3 adenosine receptor, which has an agonist profile similar to the A1 receptor but is insensitive to DPCPX, might mediate preconditioning. Isolated rabbit hearts perfused with Krebs buffer experienced 30 min of regional ischaemia followed by 120 min of reperfusion. Infarct size was measured by tetrazolium staining. In control hearts infarction was 32.2(SEM 1.5)% of the risk zone. Preconditioning by 5 min ischaemia and 10 min reperfusion reduced infarct size to 8.8(2.3)%. Replacing the regional ischaemia with 5 min perfusion with 10 microM adenosine or 65 nM N6-[2-(4-aminophenyl)ethyl]adenosine (APNEA), an adenosine A3 receptor agonist, was equally protective. The unselective antagonist 8-p-sulphophenyl theophylline at 100 microM abolished protection by preconditioning, adenosine, and APNEA, but 200 nM DPCPX did not block protection by any of the interventions. Likewise the potent but unselective A3 receptor antagonist 8-(4-carboxyethenylphenyl)-1,3-dipropylxanthine (BW A1433) completely blocked protection from ischaemic preconditioning. Because protection against infarction afforded by ischaemic preconditioning, adenosine, or the A3 receptor agonist APNEA could not be blocked by DPCPX and because the potent A3 receptor antagonist BW A1433 blocked protection from ischaemic preconditioning, these data indicate that the protection of preconditioning is not exclusively mediated by the adenosine A1 receptor in rabbit heart and could involve the A3 receptor.

Effects of nucleotides adenosine monophosphate and adenosine triphosphate in combination with L-arginine on male rabbit corpus cavernosum tissue.

PubMed

Hupertan, V; Neuzillet, Y; Stücker, O; Pons, C; Leammel, E; Lebret, T

2012-12-01

Purines and more specifically adenosine monophosphate (AMP) and adenosine triphosphate (ATP) have a strong relaxant effect on smooth muscle cells of the dog, rabbit and human corpus cavernosum, to approximately the same degree as nitric oxide (NO). However, purines are considered as modulators of erectile function rather than key mediators. This suggests that the use of purines combined with NO donors could be effective to treat some specific erectile disorders. The relaxation induced by the combination of l-arginine (Arg), a natural substrate for NO synthase, was assessed with a purine-nucleotide (AMP, ATP) on a rabbit corpus cavernosum model, to determine if these substances could potentiate each other's effect. When a pre-contraction was induced by phenylephrine, AMP alone induced a 43% CC relaxation rate and ATP alone a 26% rate. The relaxation rate induced by Arg was lower in comparison (8% at 5.10(-4) m vs. 25% at AMP 5.10(-4) m and 15% at ATP 5.10(-4) m). NO synthase inhibitor n-nitro-l-arginine did not modify the relaxing effect provoked by AMP suggesting that the mechanism of action of this nucleotide does not involve the NO pathway. The combination of Arg at 5.10(-4) m with either AMP or ATP at different doses ranging from 5.10(-4) to 10(-3) m significantly enhanced the relaxing response reaching rates of 62 and 80% respectively, leading to a synergistic effect. The present data indicate that a 'NO donor' combined with an 'adenosine donor' could be an effective therapeutic approach. © 2012 The Authors. International Journal of Andrology © 2012 European Academy of Andrology.

Cyclic Deformation of Ultra-Fine Grained Commercial Purity Aluminum Processed by Accumulative Roll-Bonding.

PubMed

Kwan, Charles C F; Wang, Zhirui

2013-08-13

Accumulative Roll-Bonding (ARB) is one of the more recently developed techniques capable of producing bulk ultra-fine grained (ufg) metals. There are still many aspects of the behavior of ufg metals that lacks an in-depth understanding, such as a generalized view of the factors that govern the cyclic deformation mechanism(s). This study aims to advance the understanding of the cyclic deformation behavior of ufg metals through the systematic investigation of ARB processed aluminum upon cyclic loading. It was found that the cyclic softening response often reported for ufg metals is largely influenced by the microstructure stability as the cyclic softening response is facilitated by grain coarsening which becomes inhibited with highly stable microstructure. On one hand, shear bands resembling braids of dislocations trespassing multiple grains have been observed to operate for the accommodation of the imposed cyclic strain in cases where grain coarsening is largely restricted. On the other hand, it was found that the microstructure stability can be overcome at higher applied cyclic plastic strain levels, leading to grain coarsening and thus a cyclic softening response. The findings in this study have further confirmed that the cyclic softening behavior found in many ufg metals, which may be detrimental in practical applications, can be inhibited by improvements in the microstructure stability.

CD73-derived adenosine and tenascin-C control cytokine production by epicardium-derived cells formed after myocardial infarction.

PubMed

Hesse, Julia; Leberling, Stella; Boden, Elisabeth; Friebe, Daniela; Schmidt, Timo; Ding, Zhaoping; Dieterich, Peter; Deussen, Andreas; Roderigo, Claudia; Rose, Christine R; Floss, Doreen M; Scheller, Jürgen; Schrader, Jürgen

2017-07-01

Epicardium-derived cells (EPDCs) play a fundamental role in embryonic cardiac development and are reactivated in the adult heart in response to myocardial infarction (MI). In this study, EPDCs from post-MI rat hearts highly expressed the ectoenzyme CD73 and secreted the profibrotic matricellular protein tenascin-C (TNC). CD73 on EPDCs extensively generated adenosine from both extracellular ATP and NAD. This in turn stimulated the release of additional nucleotides from a Brefeldin A-sensitive intracellular pool via adenosine-A 2B R signaling, forming a positive-feedback loop. A 2B R activation, in addition, strongly promoted the release of major regulatory cytokines, such as IL-6, IL-11, and VEGF. TNC was found to stimulate EPDC migration and, together with ATP-P2X 7 R signaling, to activate inflammasomes in EPDCs via TLR4. Our results demonstrate that EPDCs are an important source of various proinflammatory factors in the post-MI heart controlled by purinergic and TNC signaling.-Hesse, J., Leberling, S., Boden, E., Friebe, D., Schmidt, T., Ding, Z., Dieterich, P., Deussen, A., Roderigo, C., Rose, C. R., Floss, D. M., Scheller, J., Schrader, J. CD73-derived adenosine and tenascin-C control cytokine production by epicardium-derived cells formed after myocardial infarction. © FASEB.

Advances in targeting cyclic nucleotide phosphodiesterases

PubMed Central

Maurice, Donald H.; Ke, Hengming; Ahmad, Faiyaz; Wang, Yousheng; Chung, Jay; Manganiello, Vincent C.

2014-01-01

Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants. PMID:24687066

Impaired cerebral microcirculation induced by ammonium chloride in rats is due to cortical adenosine release.

PubMed

Bjerring, Peter Nissen; Bjerrum, Esben Jannik; Larsen, Fin Stolze

2018-06-01

Liver failure results in hyperammonaemia, impaired regulation of cerebral microcirculation, encephalopathy, and death. However, the key mediator that alters cerebral microcirculation remains unidentified. In this study we show that topically applied ammonium significantly increases periarteriolar adenosine tone on the brain surface of healthy rats and is associated with a disturbed microcirculation. Cranial windows were prepared in anaesthetized Wistar rats. The flow velocities were measured by speckle contrast imaging and compared before and after 30 min of exposure to 10 mM ammonium chloride applied on the brain surface. These flow velocities were compared with those for control groups exposed to artificial cerebrospinal fluid or ammonium plus an adenosine receptor antagonist. A flow preservation curve was obtained by analysis of flow responses to a haemorrhagic hypotensive challenge and during stepwise exsanguination. The periarteriolar adenosine concentration was measured with enzymatic biosensors inserted in the cortex. After ammonium exposure the arteriolar flow velocity increased by a median (interquartile range) of 21.7% (23.4%) vs. 7.2% (10.2%) in controls (n = 10 and n = 6, respectively, p <0.05), and the arteriolar surface area increased. There was a profound rise in the periarteriolar adenosine concentration. During the hypotensive challenge the flow decreased by 27.8% (14.9%) vs. 9.2% (14.9%) in controls (p <0.05). The lower limit of flow preservation remained unaffected, 27.7 (3.9) mmHg vs. 27.6 (6.4) mmHg, whereas the autoregulatory index increased, 0.29 (0.33) flow units per millimetre of mercury vs. 0.03 (0.21) flow units per millimetre of mercury (p <0.05). When ammonium exposure was combined with topical application of an adenosine receptor antagonist, the autoregulatory index was normalized. Vasodilation of the cerebral microcirculation during exposure to ammonium chloride is associated with an increase in the adenosine tone

The Effect of Endogenous Adenosine on Neuronal Activity in Rats: An FDG PET Study

PubMed Central

Paul, Soumen; Zhang, Dali; Mzengeza, Shadreck; Ko, Ji Hyun

2016-01-01

ABSTRACT 2–18F‐fluorodeoxy‐D‐glucose (FDG) is a glucose analog that is taken up by cells and phosphorylated. The amount of FDG accumulated by cells is a measure of the rate of glycolysis, which reflects cellular activity. As the levels and actions of the neuromodulator adenosine are dynamically regulated by neuronal activity, this study was designed to test whether endogenous adenosine affects tissue accumulation of FDG as assessed by positron emission tomography (PET) or by postmortem analysis of tissue radioactivity. Rats were given an intraperitoneal injection of the adenosine A1 receptor antagonist 8‐cyclopentyl‐1,3‐dipropyl‐xanthine (DPCPX, 3 mg/kg), the adenosine kinase inhibitor ABT‐702 (3 mg/kg), or vehicle 10 minutes prior to an intravenous injection of FDG (15.4 ± 0.7 MBq per rat). Rats were then subjected to a 15 minute static PET scan. Reconstructed images were normalized to FDG PET template for rats and standard uptake values (SUVs) were calculated. To examine the regional effect of active treatment compared to vehicle, statistical parametric mapping analysis was performed. Whole‐brain FDG uptake was not affected by drug treatment. Significant regional hypometabolism was detected, particularly in cerebellum, of DPCPX‐ and ABT‐702 treated rats, relative to vehicle‐treated rats. Thus, endogenous adenosine can affect FDG accumulation although this effect is modest in quiescent rats. PMID:27082948

Valerian extract Ze 911 inhibits postsynaptic potentials by activation of adenosine A1 receptors in rat cortical neurons.

PubMed

Vissiennon, Z; Sichardt, K; Koetter, U; Brattström, A; Nieber, K

2006-06-01

In this study we evaluated the adenosine A1 receptor-mediated effect of valerian extract (Ze 911) on postsynaptic potentials (PSPs) in pyramidal cells of the rat cingulate cortex in a slice preparation. We first observed that N6-cyclopentyladenosine (CPA, 0.01 - 10 microM), an adenosine A1 receptor agonist, inhibited PSPs in a concentration-dependent manner. The CPA (10 microM)-induced inhibition was antagonized by 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 0.1 microM), an adenosine A1 receptor antagonist. Ze 911 concentration dependently (0.1 - 15 mg/mL) inhibited PSPs in the presence of the adenosine A2A receptor antagonist 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine (CSC, 0.2 microM) and adenosine deaminase (1 U/mL). The maximal inhibition induced by 10 mg/mL was completely antagonised by DPCPX (0.1 microM), an A1 receptor blocker. The data suggest that activation of adenosine A1 receptors is involved in the pharmacological effects of the valerian extract Ze 911.