Alpha lipoic acid protects the heart against myocardial post ischemia-reperfusion arrhythmias via KATP channel activation in isolated rat hearts.

PubMed

Dudek, Magdalena; Knutelska, Joanna; Bednarski, Marek; Nowiński, Leszek; Zygmunt, Małgorzata; Bilska-Wilkosz, Anna; Iciek, Małgorzata; Otto, Monika; Żytka, Iwona; Sapa, Jacek; Włodek, Lidia; Filipek, Barbara

2014-06-01

The cardiovascular effects of alpha lipoic acid were evaluated in isolated rat hearts exposed to ischemia-reperfusion injury in vitro. Alpha-lipoic acid raised the level of sulfane sulfur playing an important role in the release of hydrogen sulfide. H2S was shown to prevent the post-reperfusion arrhythmias and to protect the cardiomyocytes from death caused by hypoxia. The activation of potassium ATP-sensitive channels (K(ATP) channels) is one of the most important mechanisms of action of hydrogen sulfide in the cardiovascular system. The aim of this study was to investigate whether alpha lipoic acid can prevent the occurrence of post-reperfusion arrhythmias in vitro using a Langendorff model of ischemia-reperfusion in rats affecting the K(ATP) channels. Alpha lipoic acid significantly improved post-reperfusion cardiac function (reducing incidence of arrhythmias), especially in a dose of 10(-7)M. These cardiovascular effects of this compound on the measured parameters were reversed by glibenclamide, a selective K(ATP) blocker. Alpha lipoic acid increased the level of sulfane sulfur in the hearts. This may suggest that the positive effects caused by alpha lipoic acid in the cardiovascular system are not only related to its strong antioxidant activity, and the influence on the activity of such enzymes as aldehyde dehydrogenase 2, as previously suggested, but this compound can affect K(ATP) channels. It is possible that this indirect effect of alpha lipoic acid is connected with changes in the release of sulfane sulfur and hydrogen sulfide. Copyright © 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Physiology and pathophysiology of K(ATP) channels in the pancreas and cardiovascular system: a review.

PubMed

Seino, Susumu

2003-01-01

K(ATP) channels are present in pancreatic and extrapancreatic tissues such as heart and smooth muscle, and display diverse molecular composition. They contain two different structural subunits: an inwardly rectifying potassium channel subunit (Kir6.x) and a sulfonylurea receptor (SURX). Recent studies on genetically engineered Kir6.2 knockout mice have provided a better understanding of the physiological and pathophysiological roles of Kir6.2-containing K(ATP) channels. Kir6.2/SUR1 has a pivotal role in pancreatic insulin secretion. Kir6.2/SUR2A mediates the effects of K(ATP) channels openers on cardiac excitability and contractility and contributes to ischemic preconditioning. However, controversy remains on the physiological properties of the K(ATP) channels in vascular smooth muscle cells. Kir6.1 knockout mice exhibit sudden cardiac death due to cardiac ischemia, indicating that Kir6.1 rather than Kir6.2 is critical in the regulation of vascular tone. This article summarizes current understanding of the physiology and pathophysiology of Kir6.1- and Kir6.2-containing K(ATP) channels.

Interaction with caveolin-1 modulates vascular ATP-sensitive potassium (KATP) channel activity

PubMed Central

Davies, Lowri M; Purves, Gregor I; Barrett-Jolley, Richard; Dart, Caroline

2010-01-01

ATP-sensitive potassium channels (KATP channels) of arterial smooth muscle are important regulators of arterial tone, and hence blood flow, in response to vasoactive transmitters. Recent biochemical and electron microscopic evidence suggests that these channels localise to small vesicular invaginations of the plasma membrane, known as caveolae, and interact with the caveolae-associated protein, caveolin. Here we report that interaction with caveolin functionally regulates the activity of the vascular subtype of KATP channel, Kir6.1/SUR2B. Pinacidil-evoked recombinant whole-cell Kir6.1/SUR2B currents recorded in HEK293 cells stably expressing caveolin-1 (69.6 ± 8.3 pA pF−1, n= 8) were found to be significantly smaller than currents recorded in caveolin-null cells (179.7 ± 35.9 pA pF−1, n= 6; P < 0.05) indicating that interaction with caveolin may inhibit channel activity. Inclusion in the pipette-filling solution of a peptide corresponding to the scaffolding domain of caveolin-1 had a similar inhibitory effect on whole-cell Kir6.1/SUR2B currents as co-expression with full-length caveolin-1, while a scrambled version of the same peptide had no effect. Interestingly, intracellular dialysis of vascular smooth muscle cells with the caveolin-1 scaffolding domain peptide (SDP) also caused inhibition of pinacidil-evoked native whole-cell KATP currents, indicating that a significant proportion of vascular KATP channels are susceptible to block by exogenously applied SDP. In cell-attached recordings of Kir6.1/SUR2B single channel activity, the presence of caveolin-1 significantly reduced channel open probability (from 0.05 ± 0.01 to 0.005 ± 0.001; P < 0.05) and the amount of time spent in a relatively long-lived open state. These changes in kinetic behaviour can be explained by a caveolin-induced shift in the channel's sensitivity to its physiological regulator MgADP. Our findings thus suggest that interaction with caveolin-1 suppresses vascular-type KATP channel

Inhibitory effect of protopine on K(ATP) channel subunits expressed in HEK-293 cells.

PubMed

Jiang, Bo; Cao, Kun; Wang, Rui

2004-12-15

Protopine is an isoquinoline alkaloid purified from Corydalis tubers and other families of medicinal plants. The purpose of the present study was to investigate the effects of protopine on K(ATP) channels and big conductance (BKCa) channels. Protopine concentration-dependently inhibited K(ATP) channel currents in human embryonic kidney cells (HEK-293) which were cotransfected with Kir6.1 and sulfonylurea receptor 1 (SUR1) subunits, but not that with Kir6.1 cDNA transfection alone. At 25 muM, protopine reversibly decreased Kir6.1/SUR1 currents densities from -17.4+/-3 to -13.2+/-2.4 pA/pF at -60 mV (n=5, P<0.05). The heterologously expressed mSlo-encoded BK(Ca) channel currents in HEK-293 cells were not affected by protopine (25 muM), although iberiotoxin (100 nM) significantly inhibited the expressed BK(Ca) currents (n=5, P<0.05). In summary, protopine selectively inhibited K(ATP) channels by targeting on SUR1 subunit. This discovery may help design specific agents to selectively modulate the function of Kir6.1/SUR1 channel complex and facilitate the understanding of the structure-function relationship of specific subtype of K(ATP) channels.

Effect of K+ATP channel and adenosine receptor blockade during rest and exercise in congestive heart failure.

PubMed

Traverse, Jay H; Chen, YingJie; Hou, MingXiao; Li, Yunfang; Bache, Robert J

2007-06-08

K(+)(ATP) channels are important metabolic regulators of coronary blood flow (CBF) that are activated in the setting of reduced levels of ATP or perfusion pressure. In the normal heart, blockade of K(+)(ATP) channels results in a approximately 20% reduction in resting CBF but does not impair the increase in CBF that occurs during exercise. In contrast, adenosine receptor blockade fails to alter CBF or myocardial oxygen consumption (MVO(2)) in the normal heart but contributes to the increase in CBF during exercise when vascular K(+)(ATP) channels are blocked. Congestive heart failure (CHF) is associated with a decrease in CBF that is matched to a decrease in MVO(2) suggesting downregulation of myocardial energy utilization. Because myocardial ATP levels and coronary perfusion pressure are reduced in CHF, this study was undertaken to examine the role of K(+)(ATP) channels and adenosine in dogs with pacing-induced CHF. Myocardial blood flow (MBF) and MVO(2) were measured during rest and treadmill exercise before and after K(+)(ATP) channel blockade with glibenclamide (50 microg/kg/min ic) or adenosine receptor blockade with 8-phenyltheophylline (8-PT; 5 mg/kg iv). Inhibition of K(+)(ATP) channels resulted in a decrease in CBF and MVO(2) at rest and during exercise without a change in the relationship between CBF and MVO(2). In contrast, adenosine receptor blockade caused a significant increase in CBF that occurred secondary to an increase of MVO(2). These findings demonstrate that coronary K(+)(ATP) channel activity contribute to the regulation of resting MBF in CHF, and that endogenous adenosine may act to inhibit MVO(2) in the failing heart.

KATP channels in the nodose ganglia mediate the orexigenic actions of ghrelin

PubMed Central

Grabauskas, Gintautas; Wu, Xiaoyin; Lu, Yuanxu; Heldsinger, Andrea; Song, Il; Zhou, Shi-Yi; Owyang, Chung

2015-01-01

Abstract Ghrelin is the only known hunger signal derived from the peripheral tissues. Ghrelin overcomes the satiety signals evoked by anorexigenic molecules, such as cholecystokinin (CCK) and leptin, to stimulate feeding. The mechanisms by which ghrelin reduces the sensory signals evoked by anorexigenic hormones, which act via the vagus nerve to stimulate feeding, are unknown. Patch clamp recordings of isolated rat vagal neurons show that ghrelin hyperpolarizes neurons by activating K+ conductance. Administering a KATP channel antagonist or silencing Kir6.2, a major subunit of the KATP channel, abolished ghrelin inhibition in vitro and in vivo. Patch clamp studies show that ghrelin inhibits currents evoked by leptin and CCK-8, which operate through independent ionic channels. The inhibitory actions of ghrelin were abolished by treating the vagal ganglia neurons with pertussis toxin, as well as phosphatidylinositol 3-kinase (PI3K) or extracellular signal-regulated kinase 1 and 2 (Erk1/2) small interfering RNA. In vivo gene silencing of PI3K and Erk1/2 in the nodose ganglia prevented ghrelin inhibition of leptin- or CCK-8-evoked vagal firing. Feeding experiments showed that silencing Kir6.2 in the vagal ganglia abolished the orexigenic actions of ghrelin. These data indicate that ghrelin modulates vagal ganglia neuron excitability by activating KATP conductance via the growth hormone secretagogue receptor subtype 1a–Gαi–PI3K–Erk1/2–KATP pathway. The resulting hyperpolarization renders the neurons less responsive to signals evoked by anorexigenic hormones. This provides a mechanism to explain the actions of ghrelin with respect to overcoming anorexigenic signals that act via the vagal afferent pathways. Key points Ghrelin, a hunger signalling peptide derived from the peripheral tissues, overcomes the satiety signals evoked by anorexigenic molecules, such as cholecystokinin (CCK) and leptin, to stimulate feeding. Using in vivo and in vitro electrophysiological

Diadenosine tetraphosphate (AP4A) mimics cardioprotective effect of ischemic preconditioning in the rat heart: contribution of KATP channel and PKC.

PubMed

Ahmet, I; Sawa, Y; Nishimura, M; Ichikawa, H; Matsuda, H

2000-06-01

Diadenosine tetraphosphate (AP4A) administration is reported to mimic the effect of ischemic preconditioning (PC) via purine 2y receptors (P2yR) and adenosine receptors. This study was designed to test the contributions of the ATP-sensitive potassium channel (KATP channel) and protein kinase C (PKC), two of the main regulator in PC, to the effect of AP4A. Isolated buffer-perfused rat hearts were subjected to 20 min of global ischemia (37 degrees C) and 20 min of reperfusion. Three cycles of 1-min ischemia and 3-min reperfusion induced PC. Chemicals were administrated for 2 min before 20 min of ischemia. AP4A (10 microM) administration was as effective as PC in improving the recovery of post-ischemic contractile function and reducing creatine kinase leakage after reperfusion, whereas adenosine (10 and 100 microM) have not effect. AP4A had not effect on reperfusion-induced arrhythmia, whereas PC significantly prevented it. These effects of AP4A and PC were reversed by co-administration of glibenclimade (KATP channel blocker, 100 microM) and GF109203X (PKC inhibitor, 10 microM); the effects of AP4A but not PC were reversed by co-administration of reactive blue (P2yR antagonist, 13 nM). AP4A appears to activate the KATP channel and PKC via P2yR mimic the effects of PC in part. The role of P2yR indicated that trigger mechanism of the effect of PC and AP4A administration might differ in rat hearts.

Role of nitric oxide and KATP channel in the protective effect mediated by nicorandil in bile duct ligation-induced liver fibrosis in rats.

PubMed

Mohamed, Yasmin S; Ahmed, Lamiaa A; Salem, Hesham A; Agha, Azza M

2018-05-01

Liver fibrosis is one of the most serious conditions affecting patients worldwide. In the present study, the role of nitric oxide and KATP channel was investigated for the first time in the possible protection mediated by nicorandil in bile duct ligation-induced liver fibrosis in rats. Nicorandil (3 mg/kg/day) was given orally 24 h after bile duct ligation for 14 days till the end of the experiment. Nicorandil group showed marked improvement in liver function tests, hepatic oxidative stress and inflammatory markers as well as inducible and endothelial nitric oxide synthase protein expressions. Furthermore, nicorandil administration led to significant decrement of phosphorylated protein kinase C, fibrosis and hepatic stellate cells activation as indicated by decreased alpha smooth muscle actin expression. Oral co-administration of glibenclamide (5 mg/kg/day) (a KATP channel blocker) with nicorandil mostly showed similar improvement though not reaching to that of nicorandil group. However, co-adminstration of L-NAME (15 mg/kg/day) (an inhibitor of nitric oxide synthase) completely abolished the protective effects of nicorandil and produced more or less similar results to that of untreated bile duct ligated group. In conclusion, nicorandil is an effective therapy against the development of bile duct ligation-induced liver fibrosis in rats where nitric oxide plays a more prominent role in the protective effect of nicorandil than KATP channel opening. Copyright © 2018 Elsevier Inc. All rights reserved.

Preconditioning by isoflurane elicits mitochondrial protective mechanisms independent of sarcolemmal KATP channel in mouse cardiomyocytes

PubMed Central

Muravyeva, Maria; Sedlic, Filip; Dolan, Nicholas; Bosnjak, Zeljko J; Stadnicka, Anna

2013-01-01

Cardiac mitochondria and the sarcolemmal (sarc)KATP channels contribute to cardioprotective signaling of anesthetic-induced preconditioning (APC). Changes in mitochondrial bioenergetics influence the sarcKATP channel function, but whether this channel has impacts on mitochondria is uncertain. We used the mouse model with deleted pore-forming Kir6.2 subunit of sarcKATP channel (Kir6.2 KO) to investigate whether the functional sarcKATP channels are necessary for isoflurane activation of mitochondrial protective mechanisms. Ventricular cardiomyocytes were isolated from C57Bl6 wild type (WT) and Kir6.2 KO mouse hearts. Flavoprotein autofluorescence, mitochondrial ROS production and mitochondrial membrane potential were monitored by laser-scanning confocal microscopy in intact cardiomyocytes. Cell survival was assessed using H2O2-induced stress. Isoflurane (0.5 mM) increased flavoprotein fluorescence to 180±14% and 190±15% and ROS production to 118±2% and 124±6% of baseline in WT and Kir6.2 KO myocytes, respectively. TMRE fluorescence decreased to 84±6% in WT and to 86±4% in Kir6.2 KO myocytes. This effect was abolished by 5HD. Pretreatment with isoflurane decreased the stress-induced cell death from 31±1% to 21±1% in WT and from 44±2% to 35±2% in Kir6.2 KO myocytes. In conclusion, Kir6.2 deletion increases sensitivity of intact cardiomyocytes t o oxidative stress, but does not alter the isoflurane-elicited protective mitochondrial mechanisms, suggesting independent roles for cardiac mitochondria and sarcKATP channels in APC by isoflurane. PMID:23318991

Dystrophin Is Required for the Normal Function of the Cardio-Protective KATP Channel in Cardiomyocytes

PubMed Central

Graciotti, Laura; Becker, Jodi; Granata, Anna Luisa; Procopio, Antonio Domenico; Tessarollo, Lino; Fulgenzi, Gianluca

2011-01-01

Duchenne and Becker muscular dystrophy patients often develop a cardiomyopathy for which the pathogenesis is still unknown. We have employed the murine animal model of Duchenne muscular dystrophy (mdx), which develops a cardiomyopathy that includes some characteristics of the human disease, to study the molecular basis of this pathology. Here we show that the mdx mouse heart has defects consistent with alteration in compounds that regulate energy homeostasis including a marked decrease in creatine-phosphate (PC). In addition, the mdx heart is more susceptible to anoxia than controls. Since the cardio-protective ATP sensitive potassium channel (KATP) complex and PC have been shown to interact we investigated whether deficits in PC levels correlate with other molecular events including KATP ion channel complex presence, its functionality and interaction with dystrophin. We found that this channel complex is present in the dystrophic cardiac cell membrane but its ability to sense a drop in the intracellular ATP concentration and consequently open is compromised by the absence of dystrophin. We further demonstrate that the creatine kinase muscle isoform (CKm) is displaced from the plasma membrane of the mdx cardiac cells. Considering that CKm is a determinant of KATP channel complex function we hypothesize that dystrophin acts as a scaffolding protein organizing the KATP channel complex and the enzymes necessary for its correct functioning. Therefore, the lack of proper functioning of the cardio-protective KATP system in the mdx cardiomyocytes may be part of the mechanism contributing to development of cardiac disease in dystrophic patients. PMID:22066028

Functional K(ATP) channels in the rat retinal microvasculature: topographical distribution, redox regulation, spermine modulation and diabetic alteration.

PubMed

Ishizaki, Eisuke; Fukumoto, Masanori; Puro, Donald G

2009-05-15

The essential task of the circulatory system is to match blood flow to local metabolic demand. However, much remains to be learned about this process. To better understand how local perfusion is regulated, we focused on the functional organization of the retinal microvasculature, which is particularly well adapted for the local control of perfusion. Here, we assessed the distribution and regulation of functional K(ATP) channels whose activation mediates the hyperpolarization induced by adenosine. Using microvascular complexes freshly isolated from the rat retina, we found a topographical heterogeneity in the distribution of functional K(ATP) channels; capillaries generate most of the K(ATP) current. The initiation of K(ATP)-induced responses in the capillaries supports the concept that the regulation of retinal perfusion is highly decentralized. Additional study revealed that microvascular K(ATP) channels are redox sensitive, with oxidants increasing their activity. Furthermore, the oxidant-mediated activation of these channels is driven by the polyamine spermine, whose catabolism produces oxidants. In addition, our observation that spermine-dependent oxidation occurs predominately in the capillaries accounts for why they generate most of the K(ATP) current detected in retinal microvascular complexes. Here, we also analysed retinal microvessels of streptozotocin-injected rats. We found that soon after the onset of diabetes, an increase in spermine-dependent oxidation at proximal microvascular sites boosts their K(ATP) current and thereby virtually eliminates the topographical heterogeneity of functional K(ATP) channels. We conclude that spermine-dependent oxidation is a previously unrecognized mechanism by which this polyamine modulates ion channels; in addition to a physiological role, spermine-dependent oxidation may also contribute to microvascular dysfunction in the diabetic retina.

Isosteviol Sensitizes sarcKATP Channels towards Pinacidil and Potentiates Mitochondrial Uncoupling of Diazoxide in Guinea Pig Ventricular Myocytes.

PubMed

Fan, Zhuo; Wen, Ting; Chen, Yaoxu; Huang, Lijie; Lin, Wei; Yin, Chunxia; Tan, Wen

2016-01-01

KATP channel is an important mediator or factor in physiological and pathological metabolic pathway. Activation of KATP channel has been identified to be a critical step in the cardioprotective mechanism against IR injury. On the other hand, desensitization of the channel to its opener or the metabolic ligand ATP in pathological conditions, like cardiac hypertrophy, would decrease the adaption of myocardium to metabolic stress and is a disadvantage for drug therapy. Isosteviol, obtained by acid hydrolysis of stevioside, has been demonstrated to play a cardioprotective role against diseases of cardiovascular system, like anti-IR injury, antihypertension, antihyperglycemia, and so forth. The present study investigated the effect of isosteviol (STV) on sarcKATP channel current induced by pinacidil and mitochondrial flavoprotein oxidation induced by diazoxide. Our results showed that preincubating cells with STV not only increased the current amplitude and activating rate of sarcKATP channels induced by pinacidil but also potentiated diazoxide-elicited oxidation of flavoprotein in mitochondria.

BAD-Dependent Regulation of Fuel Metabolism and KATP Channel Activity Confers Resistance to Epileptic Seizures

PubMed Central

Giménez-Cassina, Alfredo; Martínez-François, Juan Ramón; Fisher, Jill K.; Szlyk, Benjamin; Polak, Klaudia; Wiwczar, Jessica; Tanner, Geoffrey R.; Lutas, Andrew; Yellen, Gary; Danial, Nika N.

2012-01-01

Summary Neuronal excitation can be substantially modulated by alterations in metabolism, as evident from the anticonvulsant effect of diets that reduce glucose utilization and promote ketone body metabolism. We provide genetic evidence that BAD, a protein with dual functions in apoptosis and glucose metabolism, imparts reciprocal effects on metabolism of glucose and ketone bodies in brain cells. These effects involve phospho-regulation of BAD and are independent of its apoptotic function. BAD modifications that reduce glucose metabolism produce a marked increase in the activity of metabolically sensitive KATP channels in neurons, as well as resistance to behavioral and electrographic seizures in vivo. Seizure resistance is reversed by genetic ablation of the KATP channel, implicating the BAD-KATP axis in metabolic control of neuronal excitation and seizure responses. PMID:22632729

CARDIAC SULFONYLUREA RECEPTOR SHORT FORM-BASED CHANNELS CONFER A GLIBENCLAMIDE-INSENSITIVE KATP ACTIVITY

PubMed Central

Pu, Jie-Lin,; Ye, Bin; Kroboth, Stacie L.; McNally, Elizabeth M.; Makielski, Jonathan C.; Shi, Nian-Qing

2008-01-01

The cardiac sarcolemmal ATP-sensitive potassium channel (KATP) consists of a Kir6.2 pore and a SUR2 regulatory subunit, which is an ATP-binding cassette (ABC) transporter. KATP channels have been proposed to play protective roles during ischemic preconditioning. A SUR2 mutant mouse was previously generated by disrupting the first nucleotide-binding domain (NBD1), where a glibenclamide action site was located. In the mutant ventricular myocytes, a non-conventional glibenclamide-insensitive (10 μM), ATP-sensitive current (IKATPn) was detected in 33% of single-channel recordings with an average amplitude of 12.3±5.4 pA per patch, an IC50 to ATP inhibition at 10 μM, and a mean burst duration at 20.6±1.8 ms. Newly designed SUR2-isoform or variant-specific antibodies identified novel SUR2 short forms in the sizes of 28 and 68 kDa in addition to a 150-kDa long form in the sarcolemmal membrane of wild-type (WT) heart. We hypothesized that channels constituted by these short forms that lack NBD1, confer IKATPn. The absence of the long form in the mutant corresponded to loss of the conventional glibenclamide-sensitive KATP currents (IKATP) in isolated cardiomyocytes and vascular smooth muscle cells but the SUR2 short forms remained intact. Nested exonic RT-PCR in the mutant indicated that the short forms lacked NBD1 but contained NBD2. The SUR2 short forms co-immunoprecipitated with Kir6.1 or Kir6.2 suggesting that the short forms may function as hemi-transporters reported in other eukaryotic ABC transporter subgroups. Our results indicate that different KATP compositions may co-exist in cardiac sarcolemmal membrane. PMID:18001767

Sarcolemmal cardiac K(ATP) channels as a target for the cardioprotective effects of the fluorine-containing pinacidil analogue, flocalin.

PubMed

Voitychuk, Oleg I; Strutynskyi, Ruslan B; Yagupolskii, Lev M; Tinker, Andrew; Moibenko, Olexiy O; Shuba, Yaroslav M

2011-02-01

A class of drugs known as K(ATP) -channel openers induce cardioprotection. This study examined the effects of the novel K(ATP) -channel opener, the fluorine-containing pinacidil derivative, flocalin, on cardiac-specific K(ATP) -channels, excitability of native cardiac myocytes and on the ischaemic heart. The action of flocalin was investigated on: (i) membrane currents through cardiac-specific K(ATP) -channels (I(KATP) ) formed by K(IR) 6.2/SUR2A heterologously expressed in HEK-293 cells (HEK-293(₆.₂/₂A) ); (ii) excitability and intracellular Ca²(+) ([Ca²(+) ](i) ) transients of cultured rat neonatal cardiac myocytes; and (iii) functional and ultrastructural characteristics of isolated guinea-pig hearts subjected to ischaemia-reperfusion. Flocalin concentration-dependently activated a glibenclamide-sensitive I(KATP) in HEK-293(₆.₂/₂A) cells with an EC₅₀= 8.1 ± 0.4 µM. In cardiac myocytes, flocalin (5 µM) hyperpolarized resting potential by 3-5 mV, markedly shortened action potential duration, reduced the amplitude of [Ca²(+) ](i) transients by 2-3-fold and suppressed contraction. The magnitude and extent of reversibility of these effects depended on the type of cardiac myocytes. In isolated hearts, perfusion with 5 µmol·L⁻¹ flocalin, before inducing ischaemia, facilitated restoration of contraction during reperfusion, decreased the number of extrasystoles, prevented the appearance of coronary vasoconstriction and reduced damage to the cardiac tissue at the ultrastructural level (state of myofibrils, membrane integrity, mitochondrial cristae structure). Flocalin induced potent cardioprotection by activating cardiac-type K(ATP) -channels with all the benefits of the presence of fluorine group in the drug structure: higher lipophilicity, decreased toxicity, resistance to oxidation and thermal degradation, decreased metabolism in the organism and prolonged therapeutic action. © 2011 The Authors. British Journal of Pharmacology © 2011 The

Structural determinants of PIP(2) regulation of inward rectifier K(ATP) channels.

PubMed

Shyng, S L; Cukras, C A; Harwood, J; Nichols, C G

2000-11-01

Phosphatidylinositol 4,5-bisphosphate (PIP(2)) activates K(ATP) and other inward rectifier (Kir) channels. To determine residues important for PIP(2) regulation, we have systematically mutated each positive charge in the COOH terminus of Kir6.2 to alanine. The effects of these mutations on channel function were examined using (86)Rb efflux assays on intact cells and inside-out patch-clamp methods. Both methods identify essentially the same basic residues in two narrow regions (176-222 and 301-314) in the COOH terminus that are important for the maintenance of channel function and interaction with PIP(2). Only one residue (R201A) simultaneously affected ATP and PIP(2) sensitivity, which is consistent with the notion that these ligands, while functionally competitive, are unlikely to bind to identical sites. Strikingly, none of 13 basic residues in the terminal portion (residues 315-390) of the COOH terminus affected channel function when neutralized. The data help to define the structural requirements for PIP(2) sensitivity of K(ATP) channels. Moreover, the regions and residues defined in this study parallel those uncovered in recent studies of PIP(2) sensitivity in other inward rectifier channels, indicating a common structural basis for PIP(2) regulation.

α-Synuclein binds the KATP channel at insulin-secretory granules and inhibits insulin secretion

PubMed Central

Geng, Xuehui; Lou, Haiyan; Wang, Jian; Li, Lehong; Swanson, Alexandra L.; Sun, Ming; Beers-Stolz, Donna; Watkins, Simon; Perez, Ruth G.

2011-01-01

α-Synuclein has been studied in numerous cell types often associated with secretory processes. In pancreatic β-cells, α-synuclein might therefore play a similar role by interacting with organelles involved in insulin secretion. We tested for α-synuclein localizing to insulin-secretory granules and characterized its role in glucose-stimulated insulin secretion. Immunohistochemistry and fluorescent sulfonylureas were used to test for α-synuclein localization to insulin granules in β-cells, immunoprecipitation with Western blot analysis for interaction between α-synuclein and KATP channels, and ELISA assays for the effect of altering α-synuclein expression up or down on insulin secretion in INS1 cells or mouse islets, respectively. Differences in cellular phenotype between α-synuclein knockout and wild-type β-cells were found by using confocal microscopy to image the fluorescent insulin biosensor Ins-C-emGFP and by using transmission electron microscopy. The results show that anti-α-synuclein antibodies labeled secretory organelles within β-cells. Anti-α-synuclein antibodies colocalized with KATP channel, anti-insulin, and anti-C-peptide antibodies. α-Synuclein coimmunoprecipitated in complexes with KATP channels. Expression of α-synuclein downregulated insulin secretion at 2.8 mM glucose with little effect following 16.7 mM glucose stimulation. α-Synuclein knockout islets upregulated insulin secretion at 2.8 and 8.4 mM but not 16.7 mM glucose, consistent with the depleted insulin granule density at the β-cell surface membranes observed in these islets. These findings demonstrate that α-synuclein interacts with KATP channels and insulin-secretory granules and functionally acts as a brake on secretion that glucose stimulation can override. α-Synuclein might play similar roles in diabetes as it does in other degenerative diseases, including Alzheimer's and Parkinson's diseases. PMID:20858756

Glucose elicits cephalic-phase insulin release in mice by activating KATP channels in taste cells

PubMed Central

Frim, Yonina G.; Hochman, Ayelet; Lubitz, Gabrielle S.; Basile, Anthony J.; Sclafani, Anthony

2017-01-01

The taste of sugar elicits cephalic-phase insulin release (CPIR), which limits the rise in blood glucose associated with meals. Little is known, however, about the gustatory mechanisms that trigger CPIR. We asked whether oral stimulation with any of the following taste stimuli elicited CPIR in mice: glucose, sucrose, maltose, fructose, Polycose, saccharin, sucralose, AceK, SC45647, or a nonmetabolizable sugar analog. The only taste stimuli that elicited CPIR were glucose and the glucose-containing saccharides (sucrose, maltose, Polycose). When we mixed an α-glucosidase inhibitor (acarbose) with the latter three saccharides, the mice no longer exhibited CPIR. This revealed that the carbohydrates were hydrolyzed in the mouth, and that the liberated glucose triggered CPIR. We also found that increasing the intensity or duration of oral glucose stimulation caused a corresponding increase in CPIR magnitude. To identify the components of the glucose-specific taste-signaling pathway, we examined the necessity of Calhm1, P2X2+P2X3, SGLT1, and Sur1. Among these proteins, only Sur1 was necessary for CPIR. Sur1 was not necessary, however, for taste-mediated attraction to sugars. Given that Sur1 is a subunit of the ATP-sensitive K+ channel (KATP) channel and that this channel functions as a part of a glucose-sensing pathway in pancreatic β-cells, we asked whether the KATP channel serves an analogous role in taste cells. We discovered that oral stimulation with drugs known to increase (glyburide) or decrease (diazoxide) KATP signaling produced corresponding changes in glucose-stimulated CPIR. We propose that the KATP channel is part of a novel signaling pathway in taste cells that mediates glucose-induced CPIR. PMID:28148491

Pretreatment with xenon protected immature rabbit heart from ischaemia/reperfusion injury by opening of the mitoKATP channel.

PubMed

Li, Qian; Lian, Chunwei; Zhou, Ronghua; Li, Tao; Xiang, Xujin; Liu, Bin

2013-04-01

The noble gas anaesthetic, xenon has previously been shown to protect the adult myocardium from ischaemia/reperfusion (I/R) injury, however its effect on immature myocardium is unclear. The aim of this study was to investigate the effect of xenon on the isolated immature heart. Isolated, immature (2-3weeks old) New Zealand rabbit hearts were perfused with Krebs-Henseleit buffer via Langendorff-mode. After 20min of baseline equilibration, hearts were pretreated with 75% xenon, 75% xenon+100μM diazoxide, or 75% xenon+100μM 5-hydroxydecanoate, and then subjected to 1h of global ischaemia and 3h of reperfusion. Pretreatment with 75% xenon significantly improved cardiac function (P<0.01 vs. the I/R group, respectively), limited myocardial infarct size (20.83±2.16%, P<0.01 vs. 35.82±2.14% of the I/R group), reduced cardiac enzyme release (CK-MB, 1.00±0.19IU/L, P<0.01 vs. 0.44±0.14IU/L of the I/R group; LDH, 6.15±1.06IU/L P<0.01 vs. 3.49±0.37IU/L of the I/R group) and decreased apoptosis (6.17±0.56%, P<0.01 vs. 11.31±0.93% of the I/R group). In addition, the mitochondrial structure changes caused by I/R injury were largely prevented by 75% xenon pretreatment (1.37±0.16, P<0.01 vs. 2.32±0.13 of the I/R group). The mitochondrial adenosine triphosphate-sensitive potassium (mitoKATP) channel opener diazoxide did not influence the effect of xenon, but the specific mitoKATP channel blocker 5-hydroxydecanoate completely abolished this effect. Our study demonstrated that pretreatment with 75% xenon protected immature heart from I/R injury, and this protection was probably mediated by preservation of myocardial mitochondria and opening of mitoKATP channel. Copyright © 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.

Calcium Channel Blockers

MedlinePlus

... Certain calcium channel blockers interact with grapefruit products. Kaplan NM, et al. Treatment of hypertension: Drug therapy. In: Kaplan's Clinical Hypertension. 11th ed. Philadelphia, Pa.: Wolters Kluwer ...

Metabolism Regulates the Spontaneous Firing of Substantia Nigra Pars Reticulata Neurons via KATP and Nonselective Cation Channels

PubMed Central

Lutas, Andrew; Birnbaumer, Lutz

2014-01-01

Neurons use glucose to fuel glycolysis and provide substrates for mitochondrial respiration, but neurons can also use alternative fuels that bypass glycolysis and feed directly into mitochondria. To determine whether neuronal pacemaking depends on active glucose metabolism, we switched the metabolic fuel from glucose to alternative fuels, lactate or β-hydroxybutyrate, while monitoring the spontaneous firing of GABAergic neurons in mouse substantia nigra pars reticulata (SNr) brain slices. We found that alternative fuels, in the absence of glucose, sustained SNr spontaneous firing at basal rates, but glycolysis may still be supported by glycogen in the absence of glucose. To prevent any glycogen-fueled glycolysis, we directly inhibited glycolysis using either 2-deoxyglucose or iodoacetic acid. Inhibiting glycolysis in the presence of alternative fuels lowered SNr firing to a slower sustained firing rate. Surprisingly, we found that the decrease in SNr firing was not mediated by ATP-sensitive potassium (KATP) channel activity, but if we lowered the perfusion flow rate or omitted the alternative fuel, KATP channels were activated and could silence SNr firing. The KATP-independent slowing of SNr firing that occurred with glycolytic inhibition in the presence of alternative fuels was consistent with a decrease in a nonselective cationic conductance. Although mitochondrial metabolism alone can prevent severe energy deprivation and KATP channel activation in SNr neurons, active glucose metabolism appears important for keeping open a class of ion channels that is crucial for the high spontaneous firing rate of SNr neurons. PMID:25471572

Activation of ATP-sensitive potassium channels antagonize nociceptive behavior and hyperexcitability of DRG neurons from rats.

PubMed

Du, Xiaona; Wang, Chao; Zhang, Hailin

2011-05-14

Nociceptive responses to noxious stimuli are initiated at peripheral nociceptor terminals. Ion channels play a vital role in pain signal initiation and conduction. Activation of KATP channels has been implicated in mediating the analgesic effects of agents such as morphine. However, systematic studies regarding the effects of KATP activators on nociception and neuronal excitability are scarce. In this study, we describe the antagonistic effects of KATP activators pinacidil and diazoxide on nocifensive behavior induced by bradykinin (BK), thermo and mechanical stimuli, and the bradykinin-induced hyperexcitability of DRG neurons. We also found that KATP activators can moderately activate KATP in DRG neurons. Because the effects of KATP activators can be reversed by the KATP blocker glyburide, direct activation of KATP is most likely the underlying mechanism. This systematic study clearly demonstrates that activation of KATP could have significant modulatory effects on the excitability of sensory neurons and thus on sensory behaviors, such as nociception. KATP activators can be evaluated clinically for the treatment of pain symptoms.

Three C-terminal residues from the sulphonylurea receptor contribute to the functional coupling between the KATP channel subunits SUR2A and Kir6.2

PubMed Central

Dupuis, Julien P; Revilloud, Jean; Moreau, Christophe J; Vivaudou, Michel

2008-01-01

Cardiac ATP-sensitive potassium (KATP) channels are metabolic sensors formed by the association of the inward rectifier potassium channel Kir6.2 and the sulphonylurea receptor SUR2A. SUR2A adjusts channel gating as a function of intracellular ATP and ADP and is the target of pharmaceutical openers and blockers which, respectively, up- and down-regulate Kir6.2. In an effort to understand how effector binding to SUR2A translates into Kir6.2 gating modulation, we examined the role of a 65-residue SUR2A fragment linking transmembrane domain TMD2 and nucleotide-binding domain NBD2 that has been shown to interact with Kir6.2. This fragment of SUR2A was replaced by the equivalent residues of its close homologue, the multidrug resistance protein MRP1. The chimeric construct was expressed in Xenopus oocytes and characterized using the patch-clamp technique. We found that activation by MgADP and synthetic openers was greatly attenuated although apparent affinities were unchanged. Further chimeragenetic and mutagenetic studies showed that mutation of three residues, E1305, I1310 and L1313 (rat numbering), was sufficient to confer this defective phenotype. The same mutations had no effects on channel block by the sulphonylurea glibenclamide or by ATP, suggesting a role for these residues in activatory – but not inhibitory – transduction processes. These results indicate that, within the KATP channel complex, the proximal C-terminal of SUR2A is a critical link between ligand binding to SUR2A and Kir6.2 up-regulation. PMID:18450778

Ketogenic diet metabolites reduce firing in central neurons by opening K(ATP) channels.

PubMed

Ma, Weiyuan; Berg, Jim; Yellen, Gary

2007-04-04

A low-carbohydrate ketogenic diet remains one of the most effective (but mysterious) treatments for severe pharmacoresistant epilepsy. We have tested for an acute effect of physiological ketone bodies on neuronal firing rates and excitability, to discover possible therapeutic mechanisms of the ketogenic diet. Physiological concentrations of ketone bodies (beta-hydroxybutyrate or acetoacetate) reduced the spontaneous firing rate of neurons in slices from rat or mouse substantia nigra pars reticulata. This region is thought to act as a "seizure gate," controlling seizure generalization. Consistent with an anticonvulsant role, the ketone body effect is larger for cells that fire more rapidly. The effect of ketone bodies was abolished by eliminating the metabolically sensitive K(ATP) channels pharmacologically or by gene knock-out. We propose that ketone bodies or glycolytic restriction treat epilepsy by augmenting a natural activity-limiting function served by K(ATP) channels in neurons.

Bio-inspired voltage-dependent calcium channel blockers.

PubMed

Yang, Tingting; He, Lin-Ling; Chen, Ming; Fang, Kun; Colecraft, Henry M

2013-01-01

Ca(2+) influx via voltage-dependent CaV1/CaV2 channels couples electrical signals to biological responses in excitable cells. CaV1/CaV2 channel blockers have broad biotechnological and therapeutic applications. Here we report a general method for developing novel genetically encoded calcium channel blockers inspired by Rem, a small G-protein that constitutively inhibits CaV1/CaV2 channels. We show that diverse cytosolic proteins (CaVβ, 14-3-3, calmodulin and CaMKII) that bind pore-forming α1-subunits can be converted into calcium channel blockers with tunable selectivity, kinetics and potency, simply by anchoring them to the plasma membrane. We term this method 'channel inactivation induced by membrane-tethering of an associated protein' (ChIMP). ChIMP is potentially extendable to small-molecule drug discovery, as engineering FK506-binding protein into intracellular sites within CaV1.2-α1C permits heterodimerization-initiated channel inhibition with rapamycin. The results reveal a universal method for developing novel calcium channel blockers that may be extended to develop probes for a broad cohort of unrelated ion channels.

Metabolism regulates the spontaneous firing of substantia nigra pars reticulata neurons via KATP and nonselective cation channels.

PubMed

Lutas, Andrew; Birnbaumer, Lutz; Yellen, Gary

2014-12-03

Neurons use glucose to fuel glycolysis and provide substrates for mitochondrial respiration, but neurons can also use alternative fuels that bypass glycolysis and feed directly into mitochondria. To determine whether neuronal pacemaking depends on active glucose metabolism, we switched the metabolic fuel from glucose to alternative fuels, lactate or β-hydroxybutyrate, while monitoring the spontaneous firing of GABAergic neurons in mouse substantia nigra pars reticulata (SNr) brain slices. We found that alternative fuels, in the absence of glucose, sustained SNr spontaneous firing at basal rates, but glycolysis may still be supported by glycogen in the absence of glucose. To prevent any glycogen-fueled glycolysis, we directly inhibited glycolysis using either 2-deoxyglucose or iodoacetic acid. Inhibiting glycolysis in the presence of alternative fuels lowered SNr firing to a slower sustained firing rate. Surprisingly, we found that the decrease in SNr firing was not mediated by ATP-sensitive potassium (KATP) channel activity, but if we lowered the perfusion flow rate or omitted the alternative fuel, KATP channels were activated and could silence SNr firing. The KATP-independent slowing of SNr firing that occurred with glycolytic inhibition in the presence of alternative fuels was consistent with a decrease in a nonselective cationic conductance. Although mitochondrial metabolism alone can prevent severe energy deprivation and KATP channel activation in SNr neurons, active glucose metabolism appears important for keeping open a class of ion channels that is crucial for the high spontaneous firing rate of SNr neurons. Copyright © 2014 the authors 0270-6474/14/3416336-12$15.00/0.

Nandrolone decanoate negatively reverses the beneficial effects of exercise on cardiac muscle via sarcolemmal, but not mitochondrial K(ATP) channel.

PubMed

Bayat, Gholamreza; Javan, Mohammad; Safari, Fatemeh; Khalili, Azadeh; Shokri, Saeed; Goudarzvand, Mahdi; Salimi, Mehdi; Hajizadeh, Sohrab

2016-03-01

ATP-sensitive potassium channels are supposed to have a substantial role in improvement of cardiac performance. This study was performed to evaluate whether nandrolone decanoate (ND) and (or) exercise training could affect the expression of cardiac K(ATP) channel subunits. Thirty-five male albino Wistar rats were randomly divided into 5 groups, including sedentary control (SC), sedentary vehicle (SV), sedentary ND (SND), exercise control (EC), and exercise and ND (E+ND). Exercise training was performed on a treadmill 5 times per week. ND was injected (10 mg/kg/week, i.m.) to the rats in the SND and E+ND groups. Following cardiac isolation, the expression of both sarcolemmal and mitochondrial subunits of K(ATP) channel was measured using Western blot method. The expression of sarcolemmal, but not mitochondrial, subunits of K(ATP) channel (Kir6.2 and SUR2) of EC group was significantly higher compared with SC group while ND administration (SND group) did not show any change in their expression. In the E+ND group, ND administration led to decrease of the over-expression of sarcolemmal Kir6.2 and SUR2 which was previously induced by exercise. There was no significant association between the mitochondrial expression of either Kir6.2 or SUR2 proteins and administration of ND or exercise. Supra-physiological dosage of ND negatively reverses the effects of exercise on the cardiac muscle expression of sarcolemmal, but not mitochondrial, K(ATP) channel subunits.

Adiponectin may be a biomarker of early atherosclerosis of smokers and decreased by nicotine through KATP channel in adipocytes.

PubMed

Fan, Li Hong; He, Ying; Xu, Wei; Tian, Hong Yan; Zhou, Yan; Liang, Qi; Huang, Xin; Huo, Jian Hua; Li, Hong Bin; Bai, Ling; Ma, Ai Qun

2015-01-01

Plasm adiponectin is decreased in smokers. Adiponectin is emerging as a potential key molecular marker in atherosclerosis and other cardiovascular diseases. The aim of this study was to investigate the association between serum adiponectin levels and early atherosclerosis in smokers. Furthermore, the role of the KATP channel in the down-regulation of adiponectin by smoking was preliminarily explored. We consecutively enrolled 96 men, including 50 smokers with atherosclerosis and 46 nonsmokers. Serum adiponectin was detected with enzyme-linked immunosorbent assay - in all participants. Large (C1) and small (C2) artery elasticity indices and carotid intima-media thickness (IMT) were measured as evaluation indexes of early atherosclerosis in smokers. Finally, the effect of nicotine via ATP-dependent potassium (KATP) channels on adiponectin secretion by 3T3-L1 preadipocytes was examined in vitro. Adiponectin levels of smokers were statistically negatively correlated to IMT (r = -.440; P < 0.001) and positively correlated to C1 (r = 0.448; P < 0.001) as well as C2 (r = 0.426; P = 0.002). In 3-T3-L1 preadipocytes, nicotine treatment significantly decreased adiponectin levels (P = 0.003), whereas the adiponectin level was rescued by the inhibition of KATP channel (P < 0.001). Serum adiponectin level was an independent predictor of early atherosclerosis in smokers. Nicotine might decrease adiponectin in part through altering KATP channels in adipocytes. Copyright © 2015 Elsevier Inc. All rights reserved.

Single K ATP channel opening in response to action potential firing in mouse dentate granule neurons.

PubMed

Tanner, Geoffrey R; Lutas, Andrew; Martínez-François, Juan Ramón; Yellen, Gary

2011-06-08

ATP-sensitive potassium channels (K(ATP) channels) are important sensors of cellular metabolic state that link metabolism and excitability in neuroendocrine cells, but their role in nonglucosensing central neurons is less well understood. To examine a possible role for K(ATP) channels in modulating excitability in hippocampal circuits, we recorded the activity of single K(ATP) channels in cell-attached patches of granule cells in the mouse dentate gyrus during bursts of action potentials generated by antidromic stimulation of the mossy fibers. Ensemble averages of the open probability (p(open)) of single K(ATP) channels over repeated trials of stimulated spike activity showed a transient increase in p(open) in response to action potential firing. Channel currents were identified as K(ATP) channels through blockade with glibenclamide and by comparison with recordings from Kir6.2 knock-out mice. The transient elevation in K(ATP) p(open) may arise from submembrane ATP depletion by the Na(+)-K(+) ATPase, as the pump blocker strophanthidin reduced the magnitude of the elevation. Both the steady-state and stimulus-elevated p(open) of the recorded channels were higher in the presence of the ketone body R-β-hydroxybutyrate, consistent with earlier findings that ketone bodies can affect K(ATP) activity. Using perforated-patch recording, we also found that K(ATP) channels contribute to the slow afterhyperpolarization following an evoked burst of action potentials. We propose that activity-dependent opening of K(ATP) channels may help granule cells act as a seizure gate in the hippocampus and that ketone-body-mediated augmentation of the activity-dependent opening could in part explain the effect of the ketogenic diet in reducing epileptic seizures.

Effect of activators and inhibitors of K+ channels on insulin secretion in the amphibian pancreas.

PubMed

Francini, F; Pirotte, B; Gagliardino, J J

1997-02-01

The aim of this study was to obtain pharmacological evidence for the presence and participation of K+ channels in amphibian pancreatic islets. Pancreases from the toad Bufo arenarum were thus incubated with activators or blockers of K+ channels and the immunoreactive insulin released into the medium was measured by radioimmunoassay. Two K(+)-ATP channel openers (diazoxide and BPDZ44) inhibited; while a K(+)-ATP channel blocker (tolbutamide) and metabolizable sugars (glucose, glyceraldehyde) significantly stimulated the output of insulin. Although a nonmetabolizable sugar (galactose) failed to increase insulin release, dinitrophenol decreased the secretagogue effect of glucose. By contrast, although somatostatin and clonidine blocked the release of insulin, tetraethylammonium significantly stimulated secretion. For each compound tested, the effects on both insulin secretion and B-cell K+ channel activity were similar to those observed in the mammalian pancreas. These findings point to the existence of mammalian-like K+ channels in the B-cells of some amphibians.

Sodium channel blockers for cystic fibrosis.

PubMed

Burrows, E; Southern, K W; Noone, P

2006-07-19

People with cystic fibrosis (CF) have increased transport of the salt, sodium across their airway lining. Over-absorption of sodium results in the dehydration of the liquid that lines the airway surface and is a primary defect in people with CF. To determine whether the topical administration of drugs that block sodium transport improves the respiratory condition of people with CF. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings. We contacted principal investigators known to work in the field, previous authors and pharmaceutical companies who manufacture ion transport agents for unpublished or follow-up data. Most recent search of the Group's register: March 2006 Published or unpublished randomised controlled trials (RCTs) or quasi-randomised controlled trials of sodium channel blockers compared to placebo or another sodium channel blocker or the same sodium channel blocker at a different dosing regimen. Two authors independently extracted data. Meta-analysis was limited due to differing study designs. Four RCTs, with a total of 205 participants, examining the topical administration of the short-acting sodium channel blocker, amiloride, compared to placebo were identified as eligible for inclusion in the review. For three studies, interventions for six months were completed and it was possible to calculate relative change in respiratory function (FVC). There was a significant difference found in relative change in FVC in favour of placebo (GIV analysis of weighted mean difference for FVC; 1.51% (95% confidence interval -2.77 to -0.25). There were no significant differences identified in other clinically relevant outcomes. We found no evidence that the topical administration of a short-acting sodium channel blocker improves respiratory condition in people with cystic

Glyburide, a K(+)(ATP)channel blocker, improves hypotension and survival in anaphylactic shock induced in Wistar rats sensitized to ovalbumin.

PubMed

Dhanasekaran, Subramanian; Nemmar, Abderrahim; Aburawi, Elhadi H; Kazzam, Elsadig E; Abdulle, Abdishakur; Bellou, Moufida; Bellou, Abdelouahab

2013-11-15

Allergens can induce anaphylactic shock and death due to serve hypotension. Potassium channel blockers (K(+)(ATP)) such as glyburide (GLY) induce vasoconstriction. The effect of (K(+)(ATP)) channel blockers on anaphylactic shock is poorly understood. Objective of the study was to test the hypothesis that GLY reduces hypotension induced in anaphylactic shock and increases survival. Rats were grouped into: G1-N=Naïve; G2-SC=Sensitized-Control; G3-SG=Sensitized-GLY (glyburide 40 mg/kg); G4-SE=Sensitized-EPI (epinephrine 10 mg/kg). G2 to G4 groups were sensitized with ovalbumin (OVA) and shock was induced by i.v. injection of OVA. Treatments were administered intravenously 5 min later. Mean arterial pressure (MAP), heart rate (HR), and mean survival time (MST) were measured for 60 min following OVA injection and treatments administration. At the end of the experiment, blood withdrawal was performed to measure plasma levels of histamine, leukotriene B(4) (LTB(4)), prostaglandin E(2) (PGE(2)) and prostaglandin F(2) (PGF(2)). Additionally blood gas (paO2, paCO2, SaO2) and electrolytes (Na(+), K(+) and Ca (++)) were measured. MAP was normal in G1-N; severe hypotension, negative inotropic and short MST were observed in G2-SC; normalization of MAP, with lesser negative inotropism and increased MST were observed in G3-SG; full recovery was observed in G4-SE. Histamine level was significantly higher in G2-SC; reduced in G3-SG and G4-SE. PGE(2) increased in G3-SG; PGF(2) increased in G2-SC and G3-SG. Na(+) and Ca (++) concentration decreased in sensitized rats but reversed in treated groups, without change in K(+) concentration. In conclusion, our data suggest that administration of GLY reduced hypotension and increases survival time in rat anaphylactic shock.

Sevoflurane postconditioning against cerebral ischemic neuronal injury is abolished in diet-induced obesity: role of brain mitochondrial KATP channels.

PubMed

Yang, Zecheng; Chen, Yunbo; Zhang, Yan; Jiang, Yi; Fang, Xuedong; Xu, Jingwei

2014-03-01

Obesity is associated with increased infarct volumes and adverse outcomes following ischemic stroke. However, its effect on anesthetic postconditioning‑induced neuroprotection has not been investigated. The present study examined the effect of sevoflurane postconditioning on focal ischemic brain injury in diet‑induced obesity. Sprague‑Dawley rats were fed a high‑fat diet (HF; 45% kcal as fat) for 12 weeks to develop obesity syndrome. Rats fed a low‑fat diet (LF; 10% kcal as fat) served as controls. The HF or LF‑fed rats were subjected to focal cerebral ischemia for 60 min, followed by 24 h of reperfusion. Postconditioning was performed by exposure to sevoflurane for 15 min immediately at the onset of reperfusion. The involvement of the mitochondrial KATP (mitoKATP) channel was analyzed by the administration of a selective inhibitor of 5‑hydroxydecanoate (5‑HD) prior to sevoflurane postconditioning or by administration of diazoxide (DZX), a mitoKATP channel opener, instead of sevoflurane. The cerebral infarct volume, neurological score and motor coordination were evaluated 24 h after reperfusion. The HF‑fed rats had larger infarct volumes, and lower neurological scores than the LF‑fed rats and also failed to respond to neuroprotection by sevoflurane or DZX. By contrast, sevoflurane and DZX reduced the infarct volumes and improved the neurological scores and motor coordination in the LF‑fed rats. Pretreatment with 5‑HD inhibited sevoflurane‑induced neuroprotection in the LF‑fed rats, whereas it had no effect in the HF‑fed rats. Molecular studies demonstrated that the expression of Kir6.2, a significant mitoKATP channel component, was reduced in the brains of the HF‑fed rats compared with the LF‑fed rats. The results of this study indicate that diet‑induced obesity eliminates the ability of anesthetic sevoflurane postconditioning to protect the brain against cerebral ischemic neuronal injury, most likely due to an impaired brain

Human hair follicles contain two forms of ATP-sensitive potassium channels, only one of which is sensitive to minoxidil.

PubMed

Shorter, Katie; Farjo, Nilofer P; Picksley, Steven M; Randall, Valerie A

2008-06-01

Hair disorders cause psychological distress but are generally poorly controlled; more effective treatments are required. Despite the long-standing use of minoxidil for balding, its mechanism is unclear; suggestions include action on vasculature or follicle cells. Similar drugs also stimulate hair, implicating ATP-sensitive potassium (K(ATP)) channels. To investigate whether K(ATP) channels are present in human follicles, we used organ culture, molecular biological, and immunohistological approaches. Minoxidil and tolbutamide, a K(ATP) channel blocker, opposed each other's effects on the growing phase (anagen) of scalp follicles cultured in media with and without insulin. Reverse transcriptase-polymerase chain reaction identified K(ATP) channel component gene expression including regulatory sulfonylurea receptors (SUR) SUR1 and SUR2B but not SUR2A and pore-forming subunits (Kir) Kir6.1 and Kir6.2. When hair bulb tissues were examined separately, epithelial matrix expressed SUR1 and Kir6.2, whereas both dermal papilla and sheath exhibited SUR2B and Kir6.1. Immunohistochemistry demonstrated similar protein distributions. Thus, human follicles respond biologically to K(ATP) channel regulators in culture and express genes and proteins for two K(ATP) channels, Kir6.2/SUR1 and Kir6.1/SUR2B; minoxidil only stimulates SUR2 channels. These findings indicate that human follicular dermal papillae contain K(ATP) channels that can respond to minoxidil and that tolbutamide may suppress hair growth clinically; novel drugs designed specifically for these channels could treat hair disorders.

BAD-dependent regulation of fuel metabolism and K(ATP) channel activity confers resistance to epileptic seizures.

PubMed

Giménez-Cassina, Alfredo; Martínez-François, Juan Ramón; Fisher, Jill K; Szlyk, Benjamin; Polak, Klaudia; Wiwczar, Jessica; Tanner, Geoffrey R; Lutas, Andrew; Yellen, Gary; Danial, Nika N

2012-05-24

Neuronal excitation can be substantially modulated by alterations in metabolism, as evident from the anticonvulsant effect of diets that reduce glucose utilization and promote ketone body metabolism. We provide genetic evidence that BAD, a protein with dual functions in apoptosis and glucose metabolism, imparts reciprocal effects on metabolism of glucose and ketone bodies in brain cells. These effects involve phosphoregulation of BAD and are independent of its apoptotic function. BAD modifications that reduce glucose metabolism produce a marked increase in the activity of metabolically sensitive K(ATP) channels in neurons, as well as resistance to behavioral and electrographic seizures in vivo. Seizure resistance is reversed by genetic ablation of the K(ATP) channel, implicating the BAD-K(ATP) axis in metabolic control of neuronal excitation and seizure responses. Copyright © 2012 Elsevier Inc. All rights reserved.

Sodium channel blockers for cystic fibrosis.

PubMed

Burrows, Elinor F; Southern, Kevin W; Noone, Peadar G

2014-04-09

People with cystic fibrosis (CF) have increased transport of the salt, sodium across their airway lining. Over-absorption of sodium results in the dehydration of the liquid that lines the airway surface and (along with defective chloride secretion) is a primary defect in people with CF. To determine whether the topical administration of drugs that block sodium transport improves the respiratory condition of people with CF. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings. We contacted principal investigators known to work in the field, previous authors and pharmaceutical companies who manufacture ion transport agents for unpublished or follow-up data.Most recent search of the Group's register: 19 December 2013. Published or unpublished randomised controlled trials (RCTs) or quasi-randomised controlled trials of sodium channel blockers compared to placebo or another sodium channel blocker or the same sodium channel blocker at a different dosing regimen. Two authors independently extracted data. Meta-analysis was limited due to differing study designs. Five RCTs, with a total of 226 participants, examining the topical administration of the short-acting sodium channel blocker, amiloride, compared to placebo were identified as eligible for inclusion in the review. In three studies over six months, there was a significant difference found in the difference in relative change in FVC in favour of placebo (weighted mean difference 1.51% (95% confidence interval -2.77 to -0.25), although heterogeneity was evident. A two-week study demonstrated that hypertonic saline with amiloride pre-treatment did not result in a significant improvement in respiratory function or mucus clearance, in contrast to pre-treatment with placebo. There were no significant differences identified in other

Sodium channel blockers for cystic fibrosis.

PubMed

Burrows, Elinor F; Southern, Kevin W; Noone, Peadar G

2012-03-14

People with cystic fibrosis (CF) have increased transport of the salt, sodium across their airway lining. Over-absorption of sodium results in the dehydration of the liquid that lines the airway surface and is a primary defect in people with CF. To determine whether the topical administration of drugs that block sodium transport improves the respiratory condition of people with CF. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings. We contacted principal investigators known to work in the field, previous authors and pharmaceutical companies who manufacture ion transport agents for unpublished or follow-up data.Most recent search of the Group's register: 22nd August 2011. Published or unpublished randomised controlled trials (RCTs) or quasi-randomised controlled trials of sodium channel blockers compared to placebo or another sodium channel blocker or the same sodium channel blocker at a different dosing regimen. Two authors independently extracted data. Meta-analysis was limited due to differing study designs. Five RCTs, with a total of 226 participants, examining the topical administration of the short-acting sodium channel blocker, amiloride, compared to placebo were identified as eligible for inclusion in the review. In three studies over six months, there was a significant difference found in the difference in relative change in FVC in favour of placebo (weighted mean difference 1.51% (95% confidence interval -2.77 to -0.25), although heterogeneity was evident. A two-week study demonstrated that hypertonic saline with amiloride pre-treatment did not result in a significant improvement in respiratory function or mucus clearance, in contrast to pre-treatment with placebo. There were no significant differences identified in other clinically relevant outcomes. We found no

Interaction of grapefruit juice and calcium channel blockers.

PubMed

Sica, Domenic A

2006-07-01

Drug-drug interactions are commonly recognized occurrences in the hypertensive population. Drug-nutrient interactions, however, are less well appreciated. The grapefruit juice-calcium channel blocker interaction is one that has been known since 1989. The basis for this interaction has been diligently explored and appears to relate to both flavanoid and nonflavanoid components of grapefruit juice interfering with enterocyte CYP3A4 activity. In the process, presystemic clearance of susceptible drugs decreases and bioavailability increases. A number of calcium channel blockers are prone to this interaction, with the most prominent interaction occurring with felodipine. The calcium channel blocker and grapefruit juice interaction should be incorporated into the knowledge base of rational therapeutics for the prescribing physician.

Pore-forming subunits of K-ATP channels, Kir6.1 and Kir6.2, display prominent differences in regional and cellular distribution in the rat brain.

PubMed

Thomzig, Achim; Laube, Gregor; Prüss, Harald; Veh, Rüdiger W

2005-04-11

K-ATP channels consist of two structurally different subunits: a pore-forming subunit of the Kir6.0-family (Kir6.1 or Kir6.2) and a sulfonylurea receptor (SUR1, SUR2, SUR2A, SUR2B) with regulatory activity. The functional diversity of K-ATP channels in brain is broad and of fundamental importance for neuronal activity. Here, using immunocytochemistry with monospecific antibodies against the Kir6.1 and Kir6.2 subunits, we analyze the regional and cellular distribution of both proteins in the adult rat brain. We find Kir6.2 to be widely expressed in all brain regions, suggesting that the Kir6.2 subunit forms the pore of the K-ATP channels in most neurons, presumably protecting the cells during cellular stress conditions such as hypoglycemia or ischemia. Especially in hypothalamic nuclei, in particular the ventromedial and arcuate nucleus, neurons display Kir6.2 immunoreactivity only, suggesting that Kir6.2 is the pore-forming subunit of the K-ATP channels in the glucose-responsive neurons of the hypothalamus. In contrast, Kir6.1-like immunolabeling is restricted to astrocytes (Thomzig et al. [2001] Mol Cell Neurosci 18:671-690) in most areas of the rat brain and very weak or absent in neurons. Only in distinct nuclei or neuronal subpopulations is a moderate or even strong Kir6.1 staining detected. The biological functions of these K-ATP channels still need to be elucidated. Copyright 2005 Wiley-Liss, Inc.

Diadenosine tetraphosphate stimulates atrial ANP release via A(1) receptor: involvement of K(ATP) channel and PKC.

PubMed

Yuan, Kuichang; Cao, Chunhua; Bai, Guang Yi; Kim, Sung Zoo; Kim, Suhn Hee

2007-07-01

Diadenosine polyphosphates (APnAs) are endogenous compounds and exert diverse cardiovascular functions. However, the effects of APnAs on atrial ANP release and contractility have not been studied. In this study, the effects of diadenosine tetraphosphate (AP4A) on atrial ANP release and contractility, and their mechanisms were studied using isolated perfused rat atria. Treatment of atria with AP4A resulted in decreases in atrial contractility and extracellular fluid (ECF) translocation whereas ANP secretion and cAMP levels in perfusate were increased in a dose-dependent manner. These effects of AP4A were attenuated by A(1) receptor antagonist but not by A(2A) or A(3) receptor antagonist. Other purinoceptor antagonists also did not show any effects on AP4A-induced ANF release and contractility. The increment of ANP release and negative inotropy induced by AP4A was similar to those induced by AP3A, AP5A, and AP6A. Protein kinase A inhibitors accentuated AP4A-induced ANP secretion. In contrast, an inhibitor of phospholipase C, protein kinase C or sarcolemma K(ATP) channel completely blocked AP4A-induced ANP secretion. However, an inhibitor of adenylyl cyclase or mitochondria K(ATP) channel had no significant modification of AP4A effects. These results suggest that AP4A regulates atrial inotropy and ANP release mainly through A(1) receptor signaling involving phospholipase C-protein kinase C and sarcolemmal K(ATP) channel and that protein kinase A negatively modulates the effects of AP4A.

[Results of an intervention to reduce potentially inappropriate prescriptions of beta blockers and calcium channel blockers].

PubMed

Machado-Alba, J E; Giraldo-Giraldo, C; Aguirre Novoa, A

2016-01-01

To determine the frequency of simultaneous prescription of β-blockers and calcium channel blockers, notify the cardiovascular risk of these patients to the health care professionals in charge of them, and achieve a reduction in the number of those who use them. Quasi-experimental, prospective study by developing an intervention on medical prescriptions of patients older than 65 years treated between January 1 and July 30, 2014, affiliated to the Health System in 101 cities in Colombia. A total of 43,180 patients received a β-blocker each month, and 14,560 receiving a calcium channel blocker were identified. Educational interventions were performed and an evaluation was made, using sociodemographic and pharmacological variables, on the number of patients that stopped taking any of the two drugs in the following three months. A total of 535 patients, with a mean age 75.8±6.7 years received concomitant β-blockers plus calcium channel blockers. Modification of therapy was achieved in 235 patients (43.9% of users) after 66 educational interventions. In 209 cases (88.9%) one of the two drugs was suspended, and 11.1% changed to other antihypertensive drugs. The variable of being more than 85 years old (OR: 1.93; 95% CI: 1.07-3.50), and receiving concomitant medication with inhibitors of the renin-angiotensin system (OR: 2.16; 95% CI: 1.28-3.65) were associated with increased risk of their doctor changing or stopping the prescription. An improved adherence to recommendations for appropriate use of β-blockers and calcium channel blockers by health service providers was achieved. Intervention programs that reduce potentially inappropriate prescriptions for patients treated for cardiovascular disease should be used more frequently. Copyright © 2015 SECA. Published by Elsevier Espana. All rights reserved.

Modification by protons of frog skeletal muscle KATP channels: effects on ion conduction and nucleotide inhibition.

PubMed Central

Vivaudou, M; Forestier, C

1995-01-01

1. The molecular mechanisms underlying pH regulation of skeletal muscle ATP-sensitive K+ (KATP) channels were studied using the patch clamp technique in the inside-out configuration. Two effects of intracellular protons were studied in detail: the decrease in magnitude of single-channel currents and the increase in open probability (Po) of nucleotide-inhibited channels. 2. The pH dependence of inward unit currents under different ionic conditions was in poor agreement with either a direct block of the pore by protons or an indirect proton-induced conformational change, but was compatible with the protonation of surface charges located near the cytoplasmic entrance of the pore. This latter electrostatic mechanism was modelled using Gouy-Chapman-Stern theory, which predicted the data accurately with a surface charge density of about 0.1 negative elementary charges per square nanometre and a pK (pH value for 50% effect) value for protonation of these charges of 6.25. The same mechanism, i.e. neutralization of negative surface charges by cation binding, could also account for the previously reported reduction of inward unit currents by Mg2+. 3. Intracellular alkalization did not affect Po of the KATP channels. Acidification increased Po. In the presence of 0.1 mM ATP (no Mg2+), the channel activation vs. pH relationship could be fitted with a sigmoid curve with a Hill coefficient slightly above 2 and a pK value of 6. This latter value was dependent on the ATP concentration, decreasing from 6.3 in 30 microM ATP to 5.3 in 1 microM ATP. 4. Conversely, the channel inhibition vs. ATP concentration curve was shifted to the right when the pH was lowered. At pH 7.1, the ATP concentration causing half-maximal inhibition was about 10 microM. At pH 5.4, it was about 400 microM. The Hill coefficient values remained slightly below 2. Similar effects were observed when ADP was used as the inhibitory nucleotide. 5. These results confirm that a reciprocal competitive link exists

Inhibition of KATP channel activity augments baroreflex-mediated vasoconstriction in exercising human skeletal muscle

PubMed Central

Keller, David Melvin; Ogoh, Shigehiko; Greene, Shane; Olivencia-Yurvati, A; Raven, Peter B

2004-01-01

In the present investigation we examined the role of ATP-sensitive potassium (KATP) channel activity in modulating carotid baroreflex (CBR)-induced vasoconstriction in the vasculature of the leg. The CBR control of mean arterial pressure (MAP) and leg vascular conductance (LVC) was determined in seven subjects (25 ± 1 years, mean ± s.e.m.) using the variable-pressure neck collar technique at rest and during one-legged knee extension exercise. The oral ingestion of glyburide (5 mg) did not change mean arterial pressure (MAP) at rest (86 versus 89 mmHg, P > 0.05), but did appear to increase MAP during exercise (87 versus 92 mmHg, P = 0.053). However, the CBR–MAP function curves were similar at rest before and after glyburide ingestion. The CBR-mediated decrease in LVC observed at rest (∼39%) was attenuated during exercise in the exercising leg (∼15%, P < 0.05). Oral glyburide ingestion partially restored CBR-mediated vasoconstriction in the exercising leg (∼40% restoration, P < 0.05) compared to control exercise. These findings indicate that KATP channel activity modulates sympathetic vasoconstriction in humans and may prove to be an important mechanism by which functional sympatholysis operates in humans during exercise. PMID:15345750

Calcium channel blockers and transmitter release at the normal human neuromuscular junction.

PubMed

Protti, D A; Reisin, R; Mackinley, T A; Uchitel, O D

1996-05-01

Transmitter release evoked by nerve stimulation is highly dependent on Ca2+ entry through voltage-activated plasma membrane channels. Calcium influx may be modified in some neuromuscular diseases like Lambert-Eaton syndrome and amyotrophic lateral sclerosis. We studied the pharmacologic sensitivity of the transmitter release process to different calcium channel blockers in normal human muscles and found that funnel web toxin and omega-Agatoxin-IVA, both P-type calcium channel blockers, blocked nerve-elicited muscle action potentials and inhibited evoked synaptic transmission. The transmitter release was not affected either by nitrendipine, an L-type channel blocker, or omega-Conotoxin-GVIA, an N-type channel blocker. The pharmacologic profile of neuromuscular transmission observed in normal human muscles indicates that P-like channels mediate transmitter release at the motor nerve terminals.

Modulation of K(ATP) currents in rat ventricular myocytes by hypoxia and a redox reaction.

PubMed

Yan, Xi-Sheng; Ma, Ji-Hua; Zhang, Pei-Hua

2009-10-01

The present study investigated the possible regulatory mechanisms of redox agents and hypoxia on the K(ATP) current (I(KATP)) in acutely isolated rat ventricular myocytes. Single-channel and whole-cell patch-clamp techniques were used to record the K(ATP) current (I(KATP)) in acutely isolated rat ventricular myocytes. Oxidized glutathione (GSSG, 1 mmol/L) increased the I(KATP), while reduced glutathione (GSH, 1 mmol/L) could reverse the increased I(KATP) during normoxia. To further corroborate the effect of the redox agent on the K(ATP) channel, we employed the redox couple DTT (1 mmol/L)/H2O2 (0.3, 0.6, and 1 mmol/L) and repeated the previous processes, which produced results similar to the previous redox couple GSH/GSSG during normoxia. H2O2 increased the I(KATP) in a concentration dependent manner, which was reversed by DTT (1 mmol/L). In addition, our results have shown that 15 min of hypoxia increased the I(KATP), while GSH (1 mmol/L) could reverse the increased I(KATP). Furthermore, in order to study the signaling pathways of the I(KATP) augmented by hypoxia and the redox agent, we applied a protein kinase C(PKC) inhibitor bisindolylmaleimide VI (BIM), a protein kinase G(PKG) inhibitor KT5823, a protein kinase A (PKA) inhibitor H-89, and Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitors KN-62 and KN-93. The results indicated that BIM, KT5823, KN-62, and KN-93, but not H-89, inhibited the I(KATP) augmented by hypoxia and GSSG; in addition, these results suggest that the effects of both GSSG and hypoxia on K(ATP) channels involve the activation of the PKC, PKG, and CaMK II pathways, but not the PKA pathway. The present study provides electrophysiological evidence that hypoxia and the oxidizing reaction are closely related to the modulation of I(KATP).

1,4,2-Benzo/pyridodithiazine 1,1-dioxides structurally related to the ATP-sensitive potassium channel openers 1,2,4-Benzo/pyridothiadiazine 1,1-dioxides exert a myorelaxant activity linked to a distinct mechanism of action.

PubMed

Pirotte, Bernard; de Tullio, Pascal; Florence, Xavier; Goffin, Eric; Somers, Fabian; Boverie, Stéphane; Lebrun, Philippe

2013-04-25

The synthesis of diversely substituted 3-alkyl/aralkyl/arylamino-1,4,2-benzodithiazine 1,1-dioxides and 3-alkylaminopyrido[4,3-e]-1,4,2-dithiazine 1,1-dioxides is described. Their biological activities on pancreatic β-cells and on smooth muscle cells were compared to those of the reference ATP-sensitive potassium channel (KATP channel) openers diazoxide and 7-chloro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide. The aim was to assess the impact on biological activities of the replacement of the 1,2,4-thiadiazine ring by an isosteric 1,4,2-dithiazine ring. Most of the dithiazine analogues were found to be inactive on the pancreatic tissue, although some compounds bearing a 1-phenylethylamino side chain at the 3-position exerted a marked myorelaxant activity. Such an effect did not appear to be related to the opening of KATP channels but rather reflected a mechanism of action similar to that of calcium channel blockers. Tightly related 3-(1-phenylethyl)sulfanyl-4H-1,2,4-benzothiadiazine 1,1-dioxides were also found to exert a pronounced myorelaxant activity, resulting from both a KATP channel activation and a calcium channel blocker mechanism. The present work highlights the critical importance of an intracyclic NH group at the 4-position, as well as an exocyclic NH group linked to the 3-position of the benzo- and pyridothiadiazine dioxides, for activity on KATP channels.

Metaflumizone is a novel sodium channel blocker insecticide.

PubMed

Salgado, V L; Hayashi, J H

2007-12-15

Metaflumizone is a novel semicarbazone insecticide, derived chemically from the pyrazoline sodium channel blocker insecticides (SCBIs) discovered at Philips-Duphar in the early 1970s, but with greatly improved mammalian safety. This paper describes studies confirming that the insecticidal action of metaflumizone is due to the state-dependent blockage of sodium channels. Larvae of the moth Spodoptera eridania injected with metaflumizone became paralyzed, concomitant with blockage of all nerve activity. Furthermore, tonic firing of abdominal stretch receptor organs from Spodoptera frugiperda was blocked by metaflumizone applied in the bath, consistent with the block of voltage-dependent sodium channels. Studies on native sodium channels, in primary-cultured neurons isolated from the CNS of the larvae of the moth Manduca sexta and on Para/TipE sodium channels heterologously expressed in Xenopus (African clawed frog) oocytes, confirmed that metaflumizone blocks sodium channels by binding selectively to the slow-inactivated state, which is characteristic of the SCBIs. The results confirm that metaflumizone is a novel sodium channel blocker insecticide.

Calcium channel blocker toxicity in dogs and cats.

PubMed

Hayes, Cristine L; Knight, Michael

2012-03-01

The widespread use and availability of calcium channel blockers in human and veterinary medicine pose a risk for inadvertent pet exposure to these medications. Clinical signs can be delayed by many hours after exposure in some cases, with hypotension and cardiac rhythm changes (bradycardia, atrioventricular block, or tachycardia) as the predominant signs. Prompt decontamination and aggressive treatment using a variety of modalities may be necessary to treat patients exposed to calcium channel blockers. The prognosis of an exposed patient depends on the severity of signs and response to treatment.

Sulfonylureas suppress the stimulatory action of Mg-nucleotides on Kir6.2/SUR1 but not Kir6.2/SUR2A KATP channels: a mechanistic study.

PubMed

Proks, Peter; de Wet, Heidi; Ashcroft, Frances M

2014-11-01

Sulfonylureas, which stimulate insulin secretion from pancreatic β-cells, are widely used to treat both type 2 diabetes and neonatal diabetes. These drugs mediate their effects by binding to the sulfonylurea receptor subunit (SUR) of the ATP-sensitive K(+) (KATP) channel and inducing channel closure. The mechanism of channel inhibition is unusually complex. First, sulfonylureas act as partial antagonists of channel activity, and second, their effect is modulated by MgADP. We analyzed the molecular basis of the interactions between the sulfonylurea gliclazide and Mg-nucleotides on β-cell and cardiac types of KATP channel (Kir6.2/SUR1 and Kir6.2/SUR2A, respectively) heterologously expressed in Xenopus laevis oocytes. The SUR2A-Y1206S mutation was used to confer gliclazide sensitivity on SUR2A. We found that both MgATP and MgADP increased gliclazide inhibition of Kir6.2/SUR1 channels and reduced inhibition of Kir6.2/SUR2A-Y1206S. The latter effect can be attributed to stabilization of the cardiac channel open state by Mg-nucleotides. Using a Kir6.2 mutation that renders the KATP channel insensitive to nucleotide inhibition (Kir6.2-G334D), we showed that gliclazide abolishes the stimulatory effects of MgADP and MgATP on β-cell KATP channels. Detailed analysis suggests that the drug both reduces nucleotide binding to SUR1 and impairs the efficacy with which nucleotide binding is translated into pore opening. Mutation of one (or both) of the Walker A lysines in the catalytic site of the nucleotide-binding domains of SUR1 may have a similar effect to gliclazide on MgADP binding and transduction, but it does not appear to impair MgATP binding. Our results have implications for the therapeutic use of sulfonylureas. © 2014 Proks et al.

Selective activation of the K(+)(ATP) channel is a mechanism by which sudden death is produced by low-energy chest-wall impact (Commotio cordis).

PubMed

Link, M S; Wang, P J; VanderBrink, B A; Avelar, E; Pandian, N G; Maron, B J; Estes, N A

1999-07-27

Sudden death due to relatively innocent chest-wall impact has been described in young individuals (commotio cordis). In our previously reported swine model of commotio cordis, ventricular fibrillation (with T-wave strikes) and ST-segment elevation (with QRS strikes) were produced by 30-mph baseball impacts to the precordium. Because activation of the K(+)(ATP) channel has been implicated in the pathogenesis of ST elevation and ventricular fibrillation in myocardial ischemia, we hypothesized that this channel could be responsible for the electrophysiologic findings in our experimental model and in victims of commotio cordis. In the initial experiment, 6 juvenile swine were given 0.5 mg/kg IV glibenclamide, a selective inhibitor of the K(+)(ATP) channel, and chest impact was given on the QRS. The results of these strikes were compared with animals in which no glibenclamide was given. In the second phase, 20 swine were randomized to receive glibenclamide or a control vehicle (in a double-blind fashion), with chest impact delivered just before the T-wave peak. With QRS impacts, the maximal ST elevation was significantly less in those animals given glibenclamide (0.16+/-0.10 mV) than in controls (0.35+/-0.20 mV; P=0.004). With T-wave impacts, the animals that received glibenclamide had significantly fewer occurrences of ventricular fibrillation (1 episode in 27 impacts; 4%) than controls (6 episodes in 18 impacts; 33%; P=0.01). In this experimental model of commotio cordis, blockade of the K(+)(ATP) channel reduced the incidence of ventricular fibrillation and the magnitude of ST-segment elevation. Therefore, selective K(+)(ATP) channel activation may be a pivotal mechanism in sudden death resulting from low-energy chest-wall trauma in young people during sporting activities.

Tolbutamide stimulates exocytosis of glucagon by inhibition of a mitochondrial-like ATP-sensitive K+ (KATP) conductance in rat pancreatic A-cells

PubMed Central

Høy, Marianne; Olsen, Hervør L; Bokvist, Krister; Buschard, Karsten; Barg, Sebastian; Rorsman, Patrik; Gromada, Jesper

2000-01-01

Capacitance measurements were used to examine the effects of the sulphonylurea tolbutamide on Ca2+-dependent exocytosis in isolated glucagon-secreting rat pancreatic A-cells. When applied extracellularly, tolbutamide stimulated depolarization-evoked exocytosis 4.2-fold without affecting the whole-cell Ca2+ current. The concentration dependence of the stimulatory action was determined by intracellular application through the recording pipette. Tolbutamide produced a concentration-dependent increase in cell capacitance. Half-maximal stimulation was observed at 33 μm and the maximum stimulation corresponded to a 3.4-fold enhancement of exocytosis. The stimulatory action of tolbutamide was dependent on protein kinase C activity. The action of tolbutamide was mimicked by the general K+ channel blockers TEA (10 mm) and quinine (10 μm). A similar stimulation was elicited by 5-hydroxydecanoate (5-HD; 10 μm), an inhibitor of mitochondrial ATP-sensitive K+ (KATP) channels. Tolbutamide-stimulated, but not TEA-induced, exocytosis was antagonized by the K+ channel openers diazoxide, pinacidil and cromakalim. Dissipating the transgranular K+ gradient with nigericin and valinomycin inhibited tolbutamide- and Ca2+-evoked exocytosis. Furthermore, tolbutamide- and Ca2+-induced exocytosis were abolished by the H+ ionophore FCCP or by arresting the vacuolar (V-type) H+-ATPase with bafilomycin A1 or DCCD. Finally, ammonium chloride stimulated exocytosis to a similar extent to that obtained with tolbutamide. We propose that during granular maturation, a granular V-type H+-ATPase pumps H+ into the secretory granule leading to the generation of a pH gradient across the granular membrane and the development of a positive voltage inside the granules. The pumping of H+ is facilitated by the concomitant exit of K+ through granular K+ channels with pharmacological properties similar to those of mitochondrial KATP channels. Release of granules that have been primed is then facilitated by the

Phorbol ester impairs electrical excitation of rat pancreatic beta-cells through PKC-independent activation of KATP channels.

PubMed

Suga, S; Wu, J; Ogawa, Y; Takeo, T; Kanno, T; Wakui, M

2001-01-01

Phorbol 12-myristate 13-acetate (PMA) is often used as an activating phorbol ester of protein kinase C (PKC) to investigate the roles of the kinase in cellular functions. Accumulating lines of evidence indicate that in addition to activating PKC, PMA also produces some regulatory effects in a PKC-independent manner. In this study, we investigated the non-PKC effects of PMA on electrical excitability of rat pancreatic beta-cells by using patch-clamp techniques. In current-clamp recording, PMA (80 nM) reversibly inhibited 15 mM glucose-induced action potential spikes superimposed on a slow membrane depolarization and this inhibition can not be prevented by pre-treatment of the cell with a specific PKC inhibitor, bisindolylmaleimide (BIM, 1 microM). In the presence of a subthreshold concentration (5.5 mM) of glucose, PMA hyperpolarized beta-cells in a concentration-dependent manner (0.8-240 nM), even in the presence of BIM. Based on cell-attached single channel recordings, PMA increased ATP-sensitive K+ channel (KATP) activity. Based on inside-out patch-clamp recordings, PMA had little effect on KATP activity if no ATP was in the bath, while PMA restored KATP activity that was suppressed by 10 microM ATP in the bath. In voltage-clamp recording, PMA enhanced tolbutamide-sensitive membrane currents elicited by repetitive ramp pulses from -90 to -50 mV in a concentration-dependent manner, and this potentiation could not be prevented by pre-treatment of cell with BIM. 4alpha-phorbol 12,13-didecanoate (4alpha-PDD), a non-PKC-activating phorbol ester, mimicked the effect of PMA on both current-clamp and voltage-clamp recording configurations. With either 5.5 or 16.6 mM glucose in the extracellular solution, PMA (80 nM) increased insulin secretion from rat islets. However, in islets pretreated with BIM (1 microM), PMA did not increase, but rather reduced insulin secretion. In rat pancreatic beta-cells, PMA modulates insulin secretion through a mixed mechanism: increases

Contractile dysfunctions in ATP-dependent K+ channel-deficient mouse muscle during fatigue involve excessive depolarization and Ca2+ influx through L-type Ca2+ channels.

PubMed

Cifelli, Carlo; Boudreault, Louise; Gong, Bing; Bercier, Jean-Philippe; Renaud, Jean-Marc

2008-10-01

Muscles deficient in ATP-dependent potassium (KATP) channels develop contractile dysfunctions during fatigue that may explain their apparently faster rate of fatigue compared with wild-type muscles. The objectives of this study were to determine: (1) whether the contractile dysfunctions, namely unstimulated force and depressed force recovery, result from excessive membrane depolarization and Ca2+ influx through L-type Ca2+ channels; and (2) whether reducing the magnitude of these two contractile dysfunctions reduces the rate of fatigue in KATP channel-deficient muscles. To reduce Ca2+ influx, we lowered the extracellular Ca2+ concentration ([Ca2+]o) from 2.4 to 0.6 mM or added 1 microM verapamil, an L-type Ca2+ channel blocker. Flexor digitorum brevis (FDB) muscles deficient in KATP channels were obtained by exposing wild-type muscles to 10 microM glibenclamide or by using FDB from Kir6.2-/- mice. Fatigue was elicited with one contraction per second for 3 min at 37 degrees C. In wild-type FDB, lowered [Ca2+]o or verapamil did not affect the decrease in peak tetanic force and unstimulated force during fatigue and force recovery following fatigue. In KATP channel-deficient FDB, lowered [Ca2+]o or verapamil slowed down the decrease in peak tetanic force recovery, reduced unstimulated force and improved force recovery. In Kir6.2-/- FDB, the rate of fatigue became slower than in wild-type FDB in the presence of verapamil. The cell membrane depolarized from -83 to -57 mV in normal wild-type FDB. The depolarizations in some glibenclamide-exposed fibres were similar to those of normal FDB, while in other fibres the cell membrane depolarized to -31 mV in 80 s, which was also the time when these fibres supercontracted. It is concluded that: (1) KATP channels are crucial in preventing excessive membrane depolarization and Ca2+ influx through L-type Ca2+ channels; and (2) they contribute to the decrease in force during fatigue.

Noradrenaline activates the NO/cGMP/ATP-sensitive K(+) channels pathway to induce peripheral antinociception in rats.

PubMed

Romero, Thiago R L; Guzzo, Luciana S; Perez, Andrea C; Klein, André; Duarte, Igor D G

2012-03-31

Despite the classical peripheral pronociceptive effect of noradrenaline (NA), recently studies showed the involvement of NA in antinociceptive effect under immune system interaction. In addition, the participation of the NO/cGMP/KATP pathway in the peripheral antinociception has been established by our group as the molecular mechanism of another adrenoceptor agonist xylazine. Thus the aim of this study was to obtain pharmacological evidences for the involvement of the NO/cGMP/KATP pathway in the peripheral antinociceptive effect induced by exogenous noradrenaline. The rat paw pressure test was used, with hyperalgesia induced by intraplantar injection of prostaglandin E(2) (2μg/paw). All drugs were locally administered into the right hind paw of male Wistar rats. NA (5, 20 and 80ng/paw) elicited a local inhibition of hyperalgesia. The non-selective NO synthase inhibitor l-NOarg (12, 18 and 24μg/paw) antagonized the antinociception effect induced by the highest dose of NA. The soluble guanylyl cyclase inhibitor ODQ (25, 50 and 100μg/paw) antagonized the NA-induced effect; and cGMP-phosphodiesterase inhibitor zaprinast (50μg/paw) potentiated the antinociceptive effect of NA low dose (5ng/paw). In addition, the local effect of NA was antagonized by a selective blocker of an ATP-sensitive K(+) channel, glibenclamide (20, 40 and 80μg/paw). On the other hand, the specifically voltage-dependent K(+) channel blocker, tetraethylammonium (30μg/paw), Ca(2+)-activated K(+) channel blockers of small and large conductance types dequalinium (50μg/paw) and paxilline (20μg/paw), respectively, were not able to block local antinociceptive effect of NA. The results provide evidences that NA probably induces peripheral antinociceptive effects by activation of the NO/cGMP/KATP pathway. Copyright © 2012 Elsevier Inc. All rights reserved.

The molecular basis of the specificity of action of KATP channel openers

PubMed Central

Moreau, Christophe; Jacquet, Hélène; Prost, Anne-Lise; D’hahan, Nathalie; Vivaudou, Michel

2000-01-01

KATP channels incorporate a regulatory subunit of the ATP-binding cassette (ABC) transporter family, the sulfonylurea receptor (SUR), which defines their pharmacology. The therapeutically important K+ channel openers (e.g. pinacidil, cromakalim, nicorandil) act specifically on the SUR2 muscle isoforms but, except for diazoxide, remain ineffective on the SUR1 neuronal/pancreatic isoform. This SUR1/2 dichotomy underpinned a chimeric strategy designed to identify the structural determinants of opener action, which led to a minimal set of two residues within the last transmembrane helix of SUR. Transfer of either residue from SUR2A to SUR1 conferred opener sensitivity to SUR1, while the reverse operation abolished SUR2A sensitivity. It is therefore likely that these residues form part of the site of interaction of openers with the channel. Thus, openers would target a region that, in other ABC transporters, is known to be tightly involved with the binding of substrates and other ligands. This first glimpse of the site of action of pharmacological openers should permit rapid progress towards understanding the structural determinants of their affinity and specificity. PMID:11118199

Sodium channel blockers as therapeutic target for treating epilepsy: recent updates.

PubMed

Zuliani, Valentina; Fantini, Marco; Rivara, Mirko

2012-01-01

The voltage-gated sodium channels (VGSCs) are a family of membrane proteins forming a pore, through which they selectively conduct sodium ions inward and outward cell's plasma membranes in response to variations of membrane potentials, playing a fundamental role in controlling cellular excitability. Growing evidences suggest that abnormal VGSCs are involved in the pathophysiology of both acquired and inherited epilepsy. Approximately two dozen drugs are currently marketed for the treatment of epilepsy and most of them act as sodium channel blockers, preventing the return of the channels to the active state by stabilizing the inactive form. Despite the many drugs on the market, 30% of patients continue to experience seizures even in the presence of optimal doses of AEDs, while others continue to suffer from medication induced side effects. Thus, there is a great need to continue the search for new AEDs that are not only more effective, but also have a better side effects profile. For this reason, many efforts have been made in the recent years to identify new sodium channel blockers for the treatment of epilepsy. These studies have led to different classes of compounds, characterized by a great structural diversity. The aim of this review is to provide an introduction on the structure and function of the sodium channels, followed by a brief historical perspective on the sodium channel blockers in use as anticonvulsant drugs. Moreover, it will focus on the medicinal chemistry of the sodium channel blockers recently published (2008-2011) and the drug design/molecular modeling studies related to the receptor.

Tempol prevents altered K(+) channel regulation of afferent arteriolar tone in diabetic rat kidney.

PubMed

Troncoso Brindeiro, Carmen M; Lane, Pascale H; Carmines, Pamela K

2012-03-01

Experiments were performed to test the hypothesis that oxidative stress underlies the enhanced tonic dilator impact of inward-rectifier K(+) channels on renal afferent arterioles of rats with streptozotocin-induced diabetes mellitus. Sham and diabetic rats were left untreated or provided Tempol in their drinking water for 26±1 days, after which afferent arteriolar lumen diameter and its responsiveness to K(+) channel blockade were measured using the in vitro blood-perfused juxtamedullary nephron technique. Afferent diameter averaged 19.4±0.8 μm in sham rats and 24.4±0.8 μm in diabetic rats (P<0.05). The decrease in diameter evoked by Ba(2+) (inward-rectifier K(+) channel blocker) was 3 times greater in diabetic rats than in sham rats. Glibenclamide (K(ATP) channel blocker) and tertiapin-Q (Kir1.1/Kir3.x channel blocker) decreased afferent diameter in diabetic rats but had no effect on arterioles from sham rats. Chronic Tempol treatment prevented diabetes mellitus-induced increases in both renal vascular dihydroethidium staining and baseline afferent arteriolar diameter. Moreover, Tempol prevented the exaggeration of afferent arteriolar responses to Ba(2+), tertiapin-Q, and glibenclamide otherwise evident in diabetic rats. Preglomerular microvascular smooth muscle cells expressed mRNA encoding Kir1.1, Kir2.1, and Kir6.1. Neither diabetes mellitus nor Tempol altered Kir1.1, Kir2.1, Kir6.1, or SUR2B protein levels in renal cortical microvessels. To the extent that the effects of Tempol reflect its antioxidant actions, our observations indicate that oxidative stress contributes to the exaggerated impact of Kir1.1, Kir2.1, and K(ATP) channels on afferent arteriolar tone during diabetes mellitus and that this phenomenon involves posttranslational modulation of channel function.

Involvement of ATP-sensitive potassium channels and the opioid system in the anticonvulsive effect of zolpidem in mice.

PubMed

Sheikhi, Mehdi; Shirzadian, Armin; Dehdashtian, Amir; Amiri, Shayan; Ostadhadi, Sattar; Ghasemi, Mehdi; Dehpour, Ahmad Reza

2016-09-01

Zolpidem is a hypnotic medication that mainly exerts its function through activating γ-aminobutyric acid (GABA)A receptors. There is some evidence that zolpidem may have anticonvulsive effects. However, the mechanisms underlying this effect have not been elucidated yet. In the present study, we used the pentylentetrazole (PTZ)-induced generalized seizure model in mice to investigate whether zolpidem can affect seizure threshold. We also further evaluated the roles of ATP-sensitive potassium (KATP) channels as well as μ-opioid receptors in the effects of zolpidem on seizure threshold. Our data showed that zolpidem in a dose-dependent manner increased the PTZ-induced seizure threshold. The noneffective (i.e., did not significantly alter the PTZ-induced seizure threshold by itself) doses of KATP channel blocker (glibenclamide) and nonselective opioid receptor antagonist (naloxone) were able to inhibit the anticonvulsive effect of zolpidem. Additionally, noneffective doses of either KATP channel opener (cromakalim) or nonselective μ-opioid receptor agonist (morphine) in combination with a noneffective dose of zolpidem exerted a significant anticonvulsive effect on PTZ-induced seizures in mice. A combination of noneffective doses of naloxone and glibenclamide, which separately did not affect zolpidem effect on seizure threshold, inhibited the anticonvulsive effects of zolpidem. These results suggest a role for KATP channels and the opioid system, alone or in combination, in the anticonvulsive effects of zolpidem. Copyright © 2016 Elsevier Inc. All rights reserved.

Putative subunits of the rat mesangial KATP: a type 2B sulfonylurea receptor and an inwardly rectifying K+ channel.

PubMed

Szamosfalvi, Balázs; Cortes, Pedro; Alviani, Rebecca; Asano, Kenichiro; Riser, Bruce L; Zasuwa, Gary; Yee, Jerry

2002-05-01

Sulfonylurea agents exert their physiological effects in many cell types via binding to specific sulfonylurea receptors (SUR). SUR couple to inwardly-rectifying K+ channel (Kir6.x) to form tetradimeric ATP-sensitive K+ channels (KATP). The SUR subunits confer ATP-sensitivity on KATP and also provide the binding sites for sulfonylureas and other pharmacological agents. Our previous work demonstrated that the exposure of mesangial cells (MC) to sulfonylureas generated profound effects on MC glucose uptake and matrix metabolism and induced heightened cell contractility in association with Ca2+ transients. Because these responses likely resulted from the binding of sulfonylurea to a mesangial SUR2, we subsequently documented [3H]-glibenclamide binding to MC and the gene expression of several mesangial SUR2 transcripts. From these data, we inferred that MC expressed the components of a mesangial KATP and sought to establish their presence in primary MC. To obtain mesangial SUR2 cDNA sequences, rapid amplification of cDNA ends (RACE) was utilized. DNA sequences were established by the fluorescent dye termination method. Gene expression of mesangial SUR2 and Kir6.1/2 was examined by reverse transcription polymerase chain reaction (RT-PCR) and Northern analysis. SUR2 proteins were identified by immunoblotting of mesangial proteins from membrane-enriched fractions with polyclonal antiserum directed against SUR2. RACE cloning yielded two mesangial SUR2 cDNAs of 4.8 and 6.7 kbp whose open reading frames translated proteins of 964 and 1535 aa, respectively. Using probes specific to each cDNA, the presence of a unique, 5.5 kbp serum-regulated mesangial SUR2 splice variant was established. The sequence of this mesangial SUR2 (mcSUR2B) shares identity with the recently cloned rat SUR2B (rSUR2B), but, in comparison to rSUR2B, is truncated by 12 exons at the N-terminus where it contains a unique insert of 16 aa. Immunoblotting studies with anti-SUR2 antiserum demonstrated SUR2

Minoxidil opens mitochondrial K(ATP) channels and confers cardioprotection.

PubMed

Sato, Toshiaki; Li, Yulong; Saito, Tomoaki; Nakaya, Haruaki

2004-01-01

1. ATP-sensitive potassium channel in the mitochondrial inner membrane (mitoK(ATP) channel) rather than in the sarcolemma (sarcK(ATP) channel) appears to play an important role in cardioprotection. We examined the effect of minoxidil, a potent antihypertensive agent and hair growth stimulator, on sarcK(ATP) and mitoK(ATP) channels in guinea-pig ventricular myocytes. 2. Minoxidil activated a glybenclamide-sensitive sarcK(ATP) channel current in the whole-cell recording mode with an EC(50) of 182.6 microm. Minoxidil reversibly increased the flavoprotein oxidation, an index of mitoK(ATP) channel activity, in a concentration-dependent manner. The EC(50) for mitoK(ATP) channel activation was estimated to be 7.3 microm; this value was notably approximately 25-fold lower than that for sarcK(ATP) channel activation. 3. Minoxidil (10 microm) significantly attenuated the ouabain-induced increase of mitochondrial Ca(2+) concentration, which was measured by loading cells with rhod-2 fluorescence. Furthermore, pretreatment with minoxidil (10 microm) before 20-min no-flow ischaemia significantly improved the recovery of developed tension measured after 60 min of reperfusion in coronary perfused guinea-pig ventricular muscles. These cardioprotective effects of minoxidil were completely abolished by the mitoK(ATP) channel blocker 5-hydroxydecanoate (500 microm). 4. Our results indicate that minoxidil exerts a direct cardioprotective effect on heart muscle cells, an effect mediated by the selective activation of mitoK(ATP) channels.

Calcium channel blockers inhibit endogenous pyrogen fever in rats and rabbits.

PubMed

Stitt, J T; Shimada, S G

1991-09-01

We have previously shown that febrile responses in both rats and rabbits are elicited by the intravenous injection of a semipurified endogenous pyrogen (EP) prepared from human monocytes. We are now presenting evidence that these febrile responses are mediated via activation of Ca2+ channels by EP. The febrile responses of male New Zealand White rabbits and Sprague-Dawley rats to a standard dose of EP were determined at their respective thermoneutral ambient temperatures. The animals were then treated with Ca2+ channel blocker verapamil (7.5 mg/kg iv) 30-60 min before the EP challenge. In every case the febrile response to EP was markedly attenuated after verapamil pretreatment, while administration of verapamil by itself had no detectable effect on body temperature. Another Ca2+ channel blocker, nifedipine (5 mg/kg iv), was shown to possess antipyretic activity in rats also. To localize where in the fever pathway these Ca2+ channel blockers were acting, we investigated the effect of verapamil at the same dose on fevers that were produced by microinjection of prostaglandin E (PGE) directly into the brain. These PGE fevers were unaffected by verapamil pretreatment, indicating that the antipyretic action of Ca2+ channel blockers occurs before the formation of PGE in response to EP stimulation. The most likely locus of action is the activation of the enzyme phospholipase A2, which regulates the production of arachidonic acid from cellular phospholipids in the prostanoid cascade.

Subclinical Doses of ATP-Sensitive Potassium Channel Modulators Prevent Alterations in Memory and Synaptic Plasticity Induced by Amyloid-β.

PubMed

Salgado-Puga, Karla; Rodríguez-Colorado, Javier; Prado-Alcalá, Roberto A; Peña-Ortega, Fernando

2017-01-01

In addition to coupling cell metabolism and excitability, ATP-sensitive potassium channels (KATP) are involved in neural function and plasticity. Moreover, alterations in KATP activity and expression have been observed in Alzheimer's disease (AD) and during amyloid-β (Aβ)-induced pathology. Thus, we tested whether KATP modulators can influence Aβ-induced deleterious effects on memory, hippocampal network function, and plasticity. We found that treating animals with subclinical doses (those that did not change glycemia) of a KATP blocker (Tolbutamide) or a KATP opener (Diazoxide) differentially restrained Aβ-induced memory deficit, hippocampal network activity inhibition, and long-term synaptic plasticity unbalance (i.e., inhibition of LTP and promotion of LTD). We found that the protective effect of Tolbutamide against Aβ-induced memory deficit was strong and correlated with the reestablishment of synaptic plasticity balance, whereas Diazoxide treatment produced a mild protection against Aβ-induced memory deficit, which was not related to a complete reestablishment of synaptic plasticity balance. Interestingly, treatment with both KATP modulators renders the hippocampus resistant to Aβ-induced inhibition of hippocampal network activity. These findings indicate that KATP are involved in Aβ-induced pathology and they heighten the potential role of KATP modulation as a plausible therapeutic strategy against AD.

Treatment for calcium channel blocker poisoning: A systematic review

PubMed Central

Dubé, P.-A.; Gosselin, S.; Guimont, C.; Godwin, J.; Archambault, P. M.; Chauny, J.-M.; Frenette, A. J.; Darveau, M.; Le sage, N.; Poitras, J.; Provencher, J.; Juurlink, D. N.; Blais, R.

2014-01-01

Context Calcium channel blocker poisoning is a common and sometimes life-threatening ingestion. Objective To evaluate the reported effects of treatments for calcium channel blocker poisoning. The primary outcomes of interest were mortality and hemodynamic parameters. The secondary outcomes included length of stay in hospital, length of stay in intensive care unit, duration of vasopressor use, functional outcomes, and serum calcium channel blocker concentrations. Methods Medline/Ovid, PubMed, EMBASE, Cochrane Library, TOXLINE, International pharmaceutical abstracts, Google Scholar, and the gray literature up to December 31, 2013 were searched without time restriction to identify all types of studies that examined effects of various treatments for calcium channel blocker poisoning for the outcomes of interest. The search strategy included the following Keywords: [calcium channel blockers OR calcium channel antagonist OR calcium channel blocking agent OR (amlodipine or bencyclane or bepridil or cinnarizine or felodipine or fendiline or flunarizine or gallopamil or isradipine or lidoflazine or mibefradil or nicardipine or nifedipine or nimodipine or nisoldipine or nitrendipine or prenylamine or verapamil or diltiazem)] AND [overdose OR medication errors OR poisoning OR intoxication OR toxicity OR adverse effect]. Two reviewers independently selected studies and a group of reviewers abstracted all relevant data using a pilot-tested form. A second group analyzed the risk of bias and overall quality using the STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) checklist and the Thomas tool for observational studies, the Institute of Health Economics tool for Quality of Case Series, the ARRIVE (Animal Research: Reporting In Vivo Experiments) guidelines, and the modified NRCNA (National Research Council for the National Academies) list for animal studies. Qualitative synthesis was used to summarize the evidence. Of 15,577 citations identified in

MitoKATP regulating HIF/miR210/ISCU signaling axis and formation of a positive feedback loop in chronic hypoxia-induced PAH rat model.

PubMed

Lu, Yang; Huang, Jing; Geng, Shuang; Chen, Hao; Song, Cheng; Zhu, Shan; Zhao, Su; Yuan, Mingli; Li, Xueying; Hu, Hongling

2017-05-01

In the present study, we studied the mechanism of mitochondrial ATP-sensitive potassium (mitoKATP) channels regulating hypoxia-inducible factor (HIF)-1α/microRNA (miR)-210/mitochondrial iron-sulfur protein integrin (ISCU) signaling axis and forming a positive feedback loop in chronic hypoxia-induced pulmonary arterial hypertension (PAH) by using in vivo animal model. Two hundred healthy adult SPF Sprague-Dawley rats were randomly divided into five groups: Control, a mimic miR-210 agent (mimic-210) intervention, a miR-210 inhibitor (anti-210) intervention, a chronic PAH and an anti-210 intervention PAH groups, with 40 rats in each group. After the chronic PAH rat model was successfully established, the rats were intervened with mimic-210 and anti-210. The pulmonary artery smooth muscle cells (PASMCs) of rats in each group were acutely isolated and the activity of mitoKATP and mitochondria-derived oxygen free radicals reactive oxygen species (ROS) was detected. RT-qPCR was used to detect the gene of HIF-1α/miR-210/ISCU and western blot analysis was used to detect the protein of HIF-1α and ISCU. The gene and protein expression were detected again after mitoKATP-specific opener diazoxide and blocker 5-HD was given via tail vein and took effect on each group of rats, respectively. Additionally, the indicators were detected again after ISCU recombinant protein was given via tail vein and ISCU small interfering RNA (siRNA) via nasal feeding and took effect on each group of rats, respectively. It was found that the activity of mitoKATP and ROS and the gene and protein levels of HIF-1α/miR-210/ISCU of the mimic-210 group were significantly higher than those of the control group while that of the anti-210 group was significantly reduced (P<0.05). The indicators in the chronic PAH group were significantly higher than those of the control group while those of the anti-210 intervention PAH group were significantly reduced (P<0.05). The indicators of all the groups were

Modeling regulation of cardiac KATP and L-type Ca2+ currents by ATP, ADP, and Mg2+.

PubMed

Michailova, Anushka; Saucerman, Jeffrey; Belik, Mary Ellen; McCulloch, Andrew D

2005-03-01

Changes in cytosolic free Mg(2+) and adenosine nucleotide phosphates affect cardiac excitability and contractility. To investigate how modulation by Mg(2+), ATP, and ADP of K(ATP) and L-type Ca(2+) channels influences excitation-contraction coupling, we incorporated equations for intracellular ATP and MgADP regulation of the K(ATP) current and MgATP regulation of the L-type Ca(2+) current in an ionic-metabolic model of the canine ventricular myocyte. The new model: 1), quantitatively reproduces a dose-response relationship for the effects of changes in ATP on K(ATP) current, 2), simulates effects of ADP in modulating ATP sensitivity of K(ATP) channel, 3), predicts activation of Ca(2+) current during rapid increase in MgATP, and 4), demonstrates that decreased ATP/ADP ratio with normal total Mg(2+) or increased free Mg(2+) with normal ATP and ADP activate K(ATP) current, shorten action potential, and alter ionic currents and intracellular Ca(2+) signals. The model predictions are in agreement with experimental data measured under normal and a variety of pathological conditions.

Modeling regulation of cardiac KATP and L-type Ca2+ currents by ATP, ADP, and Mg2+

NASA Technical Reports Server (NTRS)

Michailova, Anushka; Saucerman, Jeffrey; Belik, Mary Ellen; McCulloch, Andrew D.

2005-01-01

Changes in cytosolic free Mg(2+) and adenosine nucleotide phosphates affect cardiac excitability and contractility. To investigate how modulation by Mg(2+), ATP, and ADP of K(ATP) and L-type Ca(2+) channels influences excitation-contraction coupling, we incorporated equations for intracellular ATP and MgADP regulation of the K(ATP) current and MgATP regulation of the L-type Ca(2+) current in an ionic-metabolic model of the canine ventricular myocyte. The new model: 1), quantitatively reproduces a dose-response relationship for the effects of changes in ATP on K(ATP) current, 2), simulates effects of ADP in modulating ATP sensitivity of K(ATP) channel, 3), predicts activation of Ca(2+) current during rapid increase in MgATP, and 4), demonstrates that decreased ATP/ADP ratio with normal total Mg(2+) or increased free Mg(2+) with normal ATP and ADP activate K(ATP) current, shorten action potential, and alter ionic currents and intracellular Ca(2+) signals. The model predictions are in agreement with experimental data measured under normal and a variety of pathological conditions.

Some cannabinoid receptor ligands and their distomers are direct-acting openers of SUR1 KATP channels

PubMed Central

Zhou, Qing; Shyng, Show-Ling; Heal, David J.; Cheetham, Sharon C.; Dickinson, Keith; Gregory, Peter; Firnges, Michael; Nordheim, Ulrich; Goshorn, Stephanie; Reiche, Dania; Turski, Lechoslaw; Antel, Jochen

2012-01-01

Here, we examined the chronic effects of two cannabinoid receptor-1 (CB1) inverse agonists, rimonabant and ibipinabant, in hyperinsulinemic Zucker rats to determine their chronic effects on insulinemia. Rimonabant and ibipinabant (10 mg·kg−1·day−1) elicited body weight-independent improvements in insulinemia and glycemia during 10 wk of chronic treatment. To elucidate the mechanism of insulin lowering, acute in vivo and in vitro studies were then performed. Surprisingly, chronic treatment was not required for insulin lowering. In acute in vivo and in vitro studies, the CB1 inverse agonists exhibited acute K channel opener (KCO; e.g., diazoxide and NN414)-like effects on glucose tolerance and glucose-stimulated insulin secretion (GSIS) with approximately fivefold better potency than diazoxide. Followup studies implied that these effects were inconsistent with a CB1-mediated mechanism. Thus effects of several CB1 agonists, inverse agonists, and distomers during GTTs or GSIS studies using perifused rat islets were unpredictable from their known CB1 activities. In vivo rimonabant and ibipinabant caused glucose intolerance in CB1 but not SUR1-KO mice. Electrophysiological studies indicated that, compared with diazoxide, 3 μM rimonabant and ibipinabant are partial agonists for K channel opening. Partial agonism was consistent with data from radioligand binding assays designed to detect SUR1 KATP KCOs where rimonabant and ibipinabant allosterically regulated 3H-glibenclamide-specific binding in the presence of MgATP, as did diazoxide and NN414. Our findings indicate that some CB1 ligands may directly bind and allosterically regulate Kir6.2/SUR1 KATP channels like other KCOs. This mechanism appears to be compatible with and may contribute to their acute and chronic effects on GSIS and insulinemia. PMID:22167524

A K ATP channel-dependent pathway within alpha cells regulates glucagon release from both rodent and human islets of Langerhans.

PubMed

MacDonald, Patrick E; De Marinis, Yang Zhang; Ramracheya, Reshma; Salehi, Albert; Ma, Xiaosong; Johnson, Paul R V; Cox, Roger; Eliasson, Lena; Rorsman, Patrik

2007-06-01

Glucagon, secreted from pancreatic islet alpha cells, stimulates gluconeogenesis and liver glycogen breakdown. The mechanism regulating glucagon release is debated, and variously attributed to neuronal control, paracrine control by neighbouring beta cells, or to an intrinsic glucose sensing by the alpha cells themselves. We examined hormone secretion and Ca(2+) responses of alpha and beta cells within intact rodent and human islets. Glucose-dependent suppression of glucagon release persisted when paracrine GABA or Zn(2+) signalling was blocked, but was reversed by low concentrations (1-20 muM) of the ATP-sensitive K(+) (KATP) channel opener diazoxide, which had no effect on insulin release or beta cell responses. This effect was prevented by the KATP channel blocker tolbutamide (100 muM). Higher diazoxide concentrations (>/=30 muM) decreased glucagon and insulin secretion, and alpha- and beta-cell Ca(2+) responses, in parallel. In the absence of glucose, tolbutamide at low concentrations (<1 muM) stimulated glucagon secretion, whereas high concentrations (>10 muM) were inhibitory. In the presence of a maximally inhibitory concentration of tolbutamide (0.5 mM), glucose had no additional suppressive effect. Downstream of the KATP channel, inhibition of voltage-gated Na(+) (TTX) and N-type Ca(2+) channels (omega-conotoxin), but not L-type Ca(2+) channels (nifedipine), prevented glucagon secretion. Both the N-type Ca(2+) channels and alpha-cell exocytosis were inactivated at depolarised membrane potentials. Rodent and human glucagon secretion is regulated by an alpha-cell KATP channel-dependent mechanism. We propose that elevated glucose reduces electrical activity and exocytosis via depolarisation-induced inactivation of ion channels involved in action potential firing and secretion.

Calcium channel blockers as the treatment of choice for hypertension in renal transplant recipients: fact or fiction.

PubMed

Baroletti, Steven A; Gabardi, Steven; Magee, Colm C; Milford, Edgar L

2003-06-01

Posttransplantation hypertension has been identified as an independent risk factor for chronic allograft dysfunction and loss. Based on available morbidity and mortality data, posttransplantation hypertension must be identified and managed appropriately. During the past decade, calcium channel blockers have been recommended by some as the antihypertensive agents of choice in this population, because it was theorized that their vasodilatory effects would counteract the vasoconstrictive effects of the calcineurin inhibitors. With increasing data becoming available, reexamining the use of traditional antihypertensive agents, including diuretics and beta-blockers, or the newer agents, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers, may be beneficial. Transplant clinicians must choose antihypertensive agents that will provide their patients with maximum benefit, from both a renal and a cardiovascular perspective. Beta-blockers, diuretics, and ACE inhibitors have all demonstrated significant benefit on morbidity and mortality in patients with cardiovascular disease. Calcium channel blockers have been shown to possess the ability to counteract cyclosporine-induced nephrotoxicity. When compared with beta-blockers, diuretics, and ACE inhibitors, however, the relative risk of cardiovascular events is increased with calcium channel blockers. With the long-term benefits of calcium channel blockers on the kidney unknown and a negative cardiovascular profile, these agents are best reserved as adjunctive therapy to beta-blockers, diuretics, and ACE inhibitors.

Leptin and insulin stimulation of signalling pathways in arcuate nucleus neurones: PI3K dependent actin reorganization and KATP channel activation

PubMed Central

Mirshamsi, Shirin; Laidlaw, Hilary A; Ning, Ke; Anderson, Erin; Burgess, Laura A; Gray, Alexander; Sutherland, Calum; Ashford, Michael LJ

2004-01-01

Background Leptin and insulin are long-term regulators of body weight. They act in hypothalamic centres to modulate the function of specific neuronal subtypes, by altering transcriptional control of releasable peptides and by modifying neuronal electrical activity. A key cellular signalling intermediate, implicated in control of food intake by these hormones, is the enzyme phosphoinositide 3-kinase. In this study we have explored further the linkage between this enzyme and other cellular mediators of leptin and insulin action on rat arcuate nucleus neurones and the mouse hypothalamic cell line, GT1-7. Results Leptin and insulin increased the levels of various phosphorylated signalling intermediates, associated with the JAK2-STAT3, MAPK and PI3K cascades in the arcuate nucleus. Inhibitors of PI3K were shown to reduce the hormone driven phosphorylation through the PI3K and MAPK pathways. Using isolated arcuate neurones, leptin and insulin were demonstrated to increase the activity of KATP channels in a PI3K dependent manner, and to increase levels of PtdIns(3,4,5)P3. KATP activation by these hormones in arcuate neurones was also sensitive to the presence of the actin filament stabilising toxin, jasplakinolide. Using confocal imaging of fluorescently labelled actin and direct analysis of G- and F-actin concentration in GT1-7 cells, leptin was demonstrated directly to induce a re-organization of cellular actin, by increasing levels of globular actin at the expense of filamentous actin in a PI3-kinase dependent manner. Leptin stimulated PI3-kinase activity in GT1-7 cells and an increase in PtdIns(3,4,5)P3 could be detected, which was prevented by PI3K inhibitors. Conclusions Leptin and insulin mediated phosphorylation of cellular signalling intermediates and of KATP channel activation in arcuate neurones is sensitive to PI3K inhibition, thus strengthening further the likely importance of this enzyme in leptin and insulin mediated energy homeostasis control. The

Creation of a genetic calcium channel blocker by targeted gem gene transfer in the heart.

PubMed

Murata, Mitsushige; Cingolani, Eugenio; McDonald, Amy D; Donahue, J Kevin; Marbán, Eduardo

2004-08-20

Calcium channel blockers are among the most commonly used therapeutic drugs. Nevertheless, the utility of calcium channel blockers for heart disease is limited because of the potent vasodilatory effect that causes hypotension, and other side effects attributable to blockade of noncardiac channels. Therefore, focal calcium channel blockade by gene transfer is highly desirable. With a view to creating a focally applicable genetic calcium channel blocker, we overexpressed the ras-related small G-protein Gem in the heart by somatic gene transfer. Adenovirus-mediated delivery of Gem markedly decreased L-type calcium current density in ventricular myocytes, resulting in the abbreviation of action potential duration. Furthermore, transduction of Gem resulted in a significant shortening of the electrocardiographic QTc interval and reduction of left ventricular systolic function. Focal delivery of Gem to the atrioventricular (AV) node significantly slowed AV nodal conduction (prolongation of PR and AH intervals), which was effective in the reduction of heart rate during atrial fibrillation. Thus, these results indicate that gene transfer of Gem functions as a genetic calcium channel blocker, the local application of which can effectively modulate cardiac electrical and contractile function.

Functional role for mouse cerebellar NO/cGMP/KATP pathway in ethanol-induced ataxia.

PubMed

Saeed Dar, M

2014-01-01

We have previously shown that brain adenosine A1 receptors and nitric oxide (NO) play an important role in ethanol (EtOH)-induced cerebellar ataxia (EICA) through glutamate/NO/cGMP pathway. I now report possible modulation of EICA by the cerebellar NO/cGMP/K(ATP) pathway. EICA was evaluated by Rotorod in CD-1 male mice. All drugs (K(ATP) activators pinacidil, 0.05, 0.1, 0.5 nmol; minoxidil, 0.01, 0.1, 1.0 pmol; antagonists glipizide/glibenclamide, 0.01, 0.05, 0.1 nmol; NO donor l-arginine, 20 nmol; NOS inhibitors [iNOS] inhibitor L-NAME, 50 nmol; glutamate, 1.5 nmol; adenosine A1 receptor agonist N(6) -cyclohexyladenosine [CHA], 6, 12 pmol; antagonist DPCPX, 0.1 or 0.4 nmol) were given by direct intracerebellar microinfusion via stereotaxically implanted guide cannulas, except EtOH (2 g/kg, i.p.). Pinacidil and minoxidil dose-dependently accentuated, whereas glipizide and glibenclamide markedly attenuated EICA, indicating tonic participation of K(ATP) channels. Glipizide abolished the pinacidil potentiation of EICA, which confirmed both drugs acted via K(ATP) channels. A possible link between K(ATP) channels and glutamate/NO pathway was suggested when (i) CHA (12 pmol) totally abolished l-arginine-induced attenuation of EICA; (ii) L-NAME abolished l-arginine-induced attenuation of EICA associated with further increase in EICA; and (iii) the combined l-arginine and glutamate infusion virtually abolished EICA. Also, whereas CHA abolished glibenclamide-induced attenuation and potentiated pinacidil/minoxidil-induced accentuation of EICA, the effects of DPCPX were just the opposite to those of CHA. The results with CHA therefore suggest a functional link between K(ATP) and A1 receptors and between K(ATP) and glutamate/NO and as an extension may involve participation of NO/cGMP/K(ATP) pathway in EICA. Copyright © 2013 by the Research Society on Alcoholism.

Phenformin has a direct inhibitory effect on the ATP-sensitive potassium channel.

PubMed

Aziz, Qadeer; Thomas, Alison; Khambra, Tapsi; Tinker, Andrew

2010-05-25

The biguanides, phenformin and metformin, are used in the treatment of type II diabetes mellitus, as well as being routinely used in studies investigating AMPK activity. We used the patch-clamp technique and rubidium flux assays to determine the role of these drugs in ATP-sensitive K+ channel (K(ATP)) regulation in cell lines expressing the cloned components of K(ATP) and the current natively expressed in vascular smooth muscle cells (VSMCs). Phenformin but not metformin inhibits a number of variants of K(ATP) including the cloned equivalents of currents present in vascular and non-vascular smooth muscle (Kir6.1/SUR2B and Kir6.2/SUR2B) and pancreatic beta-cells (Kir6.2/SUR1). However it does not inhibit the current potentially present in cardiac myocytes (Kir6.2/SUR2A). The highest affinity interaction is seen with Kir6.1/SUR2B (IC50=0.55 mM) and it also inhibits the current in native vascular smooth muscle cells. The extent and rate of inhibition are similar to that seen with the known K(ATP) blocker PNU 37883A. Additionally, phenformin inhibited the current elicited through the Kir6.2DeltaC26 (functional without SUR) channel with an IC50 of 1.78 mM. Phenformin reduced the open probability of Kir6.1/SUR2B channels by approximately 90% in inside-out patches. These findings suggest that phenformin interacts directly with the pore-forming Kir6.0 subunit however the sulphonylurea receptor is able to significantly modulate the affinity. It is likely to block from the intracellular side of the channel in a manner analogous to that of PNU 37883A. Copyright 2010 Elsevier B.V. All rights reserved.

Combination treatment with a calcium channel blocker and an angiotensin blocker in a rat systolic heart failure model with hypertension.

PubMed

Namba, Masashi; Kim, Shokei; Zhan, Yumei; Nakao, Takafumi; Iwao, Hiroshi

2002-05-01

The mechanism and treatment of hypertensive systolic heart failure are not well defined. We compared the effect of an angiotensin-converting enzyme inhibitor (cilazapril, 10 mg/kg), an angiotensin receptor blocker (candesartan, 3 mg/kg), a calcium channel blocker (benidipine, 1, 3 or 6 mg/kg), and the same calcium channel blocker combined with renin-angiotensin blockers on systolic heart failure in Dahl salt-sensitive (DS) rats. DS rats were fed an 8% Na diet from 6 weeks of age and then subjected to the above drug treatments. Benidipine (1 mg/kg), cilazapril, and candesartan had compatible hypotensive effects and similar beneficial effects on cardiac hypertrophy, gene expression, and survival rate. The combination of benidipine with cilazapril or candesartan was found to have no additional beneficial effects on the above parameters, with the exception of a reduction in atrial natriuretic polypeptide gene expression. On the other hand, candesartan normalized serum creatinine, but serum creatinine was unaffected by either benidipine at 1 or 3 mg/kg or cilazapril. Further, the combined use of benidipine and either candesartan or cilazapril resulted in an additional reduction of urinary albumin excretion in DS rats. Thus systolic heart failure in DS rats is mainly mediated by hypertension, while renal dysfunction of DS rats is due to both hypertension and the AT1 receptor itself. These findings suggest that the combination of a calcium channel blocker with an AT1 receptor blocker or ACE inhibitor may be more effective in treating the renal dysfunction associated with systolic heart failure than monotherapy with either agent alone. However, further studies will be needed before reaching any definitive conclusion on the efficacy of this combination therapy in patients with heart failure.

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

Nateglinide, a D-phenylalanine derivative lacking either a sulfonylurea or benzamido moiety, specifically inhibits pancreatic beta-cell-type K(ATP) channels.

PubMed

Chachin, Motohiko; Yamada, Mitsuhiko; Fujita, Akikazu; Matsuoka, Tetsuro; Matsushita, Kenji; Kurachi, Yoshihisa

2003-03-01

A novel antidiabetic agent, nateglinide, is a D-phenylalanine derivative lacking either a sulfonylurea or benzamido moiety. We examined with the patch-clamp method the effect of nateglinide on recombinant ATP-sensitive K(+) (K(ATP)) channels expressed in human embryonic kidney 293T cells transfected with a Kir6.2 subunit and either of a sulfonylurea receptor (SUR) 1, SUR2A, and SUR2B. In inside-out patches, nateglinide reversibly inhibited the spontaneous openings of all three types of SUR/Kir6.2 channels. Nateglinide inhibited SUR1/Kir6.2 channels with high and low affinities (K(i) = 75 nM and 114 microM) but SUR2A/Kir6.2 and SUR2B/Kir6.2 channels only with low affinity (K(i) = 105 and 111 microM, respectively). Nateglinide inhibited the K(ATP) current mediated by Kir6.2 lacking C-terminal 26 amino acids only with low affinity (K(i) = 290 microM) in the absence of SUR. Replacement of serine at position 1237 of SUR1 to tyrosine [SUR1(S1237Y)] specifically abolished the high-affinity inhibition of SUR1/Kir6.2 channels by nateglinide. MgADP or MgUDP (100 microM) augmented the inhibitory effect of nateglinide on SUR1/Kir6.2 but not SUR1(S1237Y)/Kir6.2 or SUR2A/Kir6.2 channels. This augmenting effect of MgADP was also observed with the SUR1/Kir6.2(K185Q) channel, which was not inhibited by MgADP, but not with the SUR1(K1384A)/Kir6.2 channel, which was not activated by MgADP. These results indicate that therapeutic concentrations of nateglinide (approximately 10 microM) may selectively inhibit pancreatic type SUR1/Kir6.2 channels through SUR1, especially when the channel is activated by intracellular MgADP, even though the agent does not contain either a sulfonylurea or benzamido moiety.

Ca2+ channel blockers interact with alpha 2-adrenergic receptors in rabbit ileum.

PubMed

Homaidan, F R; Donowitz, M; Wicks, J; Cusolito, S; el Sabban, M E; Weiland, G A; Sharp, W G

1988-04-01

An interaction between Ca2+ channel blockers and alpha 2-adrenergic receptors has been demonstrated in rabbit ileum by studying the effect of clonidine on active electrolyte transport, under short-circuited conditions, in the presence and absence of several Ca2+ channel blocking agents. Clonidine, verapamil, diltiazem, cadmium, and nitrendipine all decrease short-circuit current and stimulate NaCl absorption to different extents with clonidine having the largest effect. Exposure to verapamil, diltiazem, and cadmium inhibited the effects of clonidine on transport, whereas nitrendipine had no such effect. Verapamil, diltiazem, and cadmium, but not nitrendipine, also decreased the specific binding of [3H]alpha 2-adrenergic agents to a preparation of ileal basolateral membranes explaining the observed decrease in the transport effects of clonidine. The effective concentrations of the Ca2+ channel blockers that inhibited the effects of clonidine on transport were fairly similar to the concentrations needed to inhibit its specific binding. The displacement of clonidine by calcium channel blockers is ascribed to a nonspecific effect of these agents, although the possibility that their effects are exerted via their binding to the calcium channels is not excluded.

Chloride channel blockers activate an endogenous cationic current in oocytes of Bufo arenarum.

PubMed

Cavarra, M S; del Mónaco, S M; Kotsias, B A

2004-07-01

A two-electrode, voltage-clamp technique was used to measure the effect of the Cl(-) channel blockers, 9-anthracene carboxylic acid and niflumic acid, upon the ionic currents of oocytes of the South American toad Bufo arenarum. The main results were: (1) both blockers produced a reversible increase of the outward currents on a dose-dependent manner; (2) the activated outward current was voltage dependent; (3) the 9-anthracene carboxylic acid-sensitive current was blocked with barium; and (4) the effect of 9-anthracene carboxylic acid was more pronounced in a zero-K(+) solution than in standard (2 mmol l(-1)) or high (20 mmol l(-1)) K(+) solutions, indicating that a K(+) conductance is activated. The effect of the Cl(-) channel blockers could be due to a direct interaction with endogenous cationic channels. Another possible explanation is that Cl(-) that enter the cell during depolarizing steps in control solution inhibit this cationic conductance; thus, the blockade of Cl(-) channels by 9-anthracene carboxylic acid and niflumic acid would remove this inhibition, allowing the cationic current to flow freely.

Are prostaglandins or calcium channel blockers efficient for free flap salvage? A review of the literature.

PubMed

Huby, M; Rem, K; Moris, V; Guillier, D; Revol, M; Cristofari, S

2018-03-01

The free flap failure rate is less than 5%. The responsible mechanisms of postoperative secondary ischemia are mostly vascular. The main postoperative complication leading to flap failure is thrombosis. Different strategies have been reported to improve the reliability of flaps and decrease the risk of partial or total necrosis: thus, pharmacologic agents have been studied to reduce the risk of microvascular thrombosis. The aim of this review was to evaluate the effect of calcium channel blockers and prostaglandins on free skin flap survival. A systematic review of the literature was performed to identify articles studying the efficacy of calcium channel blockers and prostaglandins on free flap survival. After full text reading, eleven articles were finally included. Eight articles investigated the role of prostaglandins in free tissue transfers, two in rats subjects, one in rabbits, five in humans. Two articles studied the effect of calcium channel blockers on free flaps, one in rats subjects, one in rabbits. One article studied in different groups the effect of calcium channel blockers and prostaglandins on free flaps in rabbits. Literature regarding the efficacy of calcium channel blockers and prostaglandins to salvage free flap is poor and mainly based on animal models. Nevertheless, studies on prostaglandins showed a slight efficiency of these molecules for free flap salvage. Results are less reliable for calcium channel blockers and dependent on the molecule used. In conclusion, there is a lack of evidence to use them in clinical practice. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

The roles of KCa, KATP, and KV channels in regulating cutaneous vasodilation and sweating during exercise in the heat.

PubMed

Louie, Jeffrey C; Fujii, Naoto; Meade, Robert D; McNeely, Brendan D; Kenny, Glen P

2017-05-01

We recently showed the varying roles of Ca 2+ -activated (K Ca ), ATP-sensitive (K ATP ), and voltage-gated (K V ) K + channels in regulating cholinergic cutaneous vasodilation and sweating in normothermic conditions. However, it is unclear whether the respective contributions of these K + channels remain intact during dynamic exercise in the heat. Eleven young (23 ± 4 yr) men completed a 30-min exercise bout at a fixed rate of metabolic heat production (400 W) followed by a 40-min recovery period in the heat (35°C, 20% relative humidity). Cutaneous vascular conductance (CVC) and local sweat rate were assessed at four forearm skin sites perfused via intradermal microdialysis with: 1 ) lactated Ringer solution (control); 2 ) 50 mM tetraethylammonium (nonspecific K Ca channel blocker); 3 ) 5 mM glybenclamide (selective K ATP channel blocker); or 4 ) 10 mM 4-aminopyridine (nonspecific K V channel blocker). Responses were compared at baseline and at 10-min intervals during and following exercise. K Ca channel inhibition resulted in greater CVC versus control at end exercise ( P = 0.04) and 10 and 20 min into recovery (both P < 0.01). K ATP channel blockade attenuated CVC compared with control during baseline ( P = 0.04), exercise (all P ≤ 0.04), and 10 min into recovery ( P = 0.02). No differences in CVC were observed with K V channel inhibition during baseline ( P = 0.15), exercise (all P ≥ 0.06), or recovery (all P ≥ 0.14). With the exception of K V channel inhibition augmenting sweating during baseline ( P = 0.04), responses were similar to control with all K + channel blockers during each time period (all P ≥ 0.07). We demonstrated that K Ca and K ATP channels contribute to the regulation of cutaneous vasodilation during rest and/or exercise and recovery in the heat. Copyright © 2017 the American Physiological Society.

Neuroprotective role of ATP-sensitive potassium channels in cerebral ischemia

PubMed Central

Sun, Hong-shuo; Feng, Zhong-ping

2013-01-01

ATP-sensitive potassium (KATP) channels are weak, inward rectifiers that couple metabolic status to cell membrane electrical activity, thus modulating many cellular functions. An increase in the ADP/ATP ratio opens KATP channels, leading to membrane hyperpolarization. KATP channels are ubiquitously expressed in neurons located in different regions of the brain, including the hippocampus and cortex. Brief hypoxia triggers membrane hyperpolarization in these central neurons. In vivo animal studies confirmed that knocking out the Kir6.2 subunit of the KATP channels increases ischemic infarction, and overexpression of the Kir6.2 subunit reduces neuronal injury from ischemic insults. These findings provide the basis for a practical strategy whereby activation of endogenous KATP channels reduces cellular damage resulting from cerebral ischemic stroke. KATP channel modulators may prove to be clinically useful as part of a combination therapy for stroke management in the future. PMID:23123646

Lanicemine: a low-trapping NMDA channel blocker produces sustained antidepressant efficacy with minimal psychotomimetic adverse effects.

PubMed

Sanacora, G; Smith, M A; Pathak, S; Su, H-L; Boeijinga, P H; McCarthy, D J; Quirk, M C

2014-09-01

Ketamine, an N-methyl-D-aspartate receptor (NMDAR) channel blocker, has been found to induce rapid and robust antidepressant-like effects in rodent models and in treatment-refractory depressed patients. However, the marked acute psychological side effects of ketamine complicate the interpretation of both preclinical and clinical data. Moreover, the lack of controlled data demonstrating the ability of ketamine to sustain the antidepressant response with repeated administration leaves the potential clinical utility of this class of drugs in question. Using quantitative electroencephalography (qEEG) to objectively align doses of a low-trapping NMDA channel blocker, AZD6765 (lanicemine), to that of ketamine, we demonstrate the potential for NMDA channel blockers to produce antidepressant efficacy without psychotomimetic and dissociative side effects. Furthermore, using placebo-controlled data, we show that the antidepressant response to NMDA channel blockers can be maintained with repeated and intermittent drug administration. Together, these data provide a path for the development of novel glutamatergic-based therapeutics for treatment-refractory mood disorders.

Analysis by metadynamics simulation of binding pathway of influenza virus M2 channel blockers.

PubMed

Sakai, Yuri; Kawaguchi, Atsushi; Nagata, Kyosuke; Hirokawa, Takatsugu

2018-01-01

M2 protein of influenza A virus is a proton channel spanning the viral envelope. Activity of this proton channel is required for uncoating of viral particles and equilibrating the pH across the trans Golgi apparatus, which prevents conformational change in hemagglutinin. Amantadine, an anti-influenza A virus drug, inhibits M2 proton channel activity by binding to the channel pore; however, most currently circulating influenza A viruses are amantadine-resistant. The most prevalent resistant mutation is a substitution from Ser31 to Asn31 in M2. Further atomistic analysis of ligand-M2 complexes is needed to provide new approaches for the design of novel M2 channel blockers. Here, the free energy profiles of the binding kinetics of M2 channel blockers were examined by well-tempered metadynamics simulations and it was found that amantadine first binds to Asp24 of S31 M2 and forms a metastable conformation. In contrast, the free energy profiles of adamantyl bromothiophene dual inhibitor with either S31 M2 or N31 M2 are broad funnel-shaped curves, suggesting that adamantyl bromothiophene does not form metastable complexes with M2. The trajectory of well-tempered metadynamics simulations revealed that steric hindrance between adamantyl bromothiophene and S31 M2 interrupts formation of a metastable conformation at Asp24 and that a halogen bond between the bromine atom and N31 is responsible for pulling down the ligand to the channel pore of N31 M2 in the absence of a metastable state. Binding pathways of M2 channel blockers to M2 are here proposed on the basis of these findings; they may provide new approaches to designing further M2 channel blockers. © 2017 The Societies and John Wiley & Sons Australia, Ltd.

Interaction among hERG channel blockers is a potential mechanism of death in caffeine overdose.

PubMed

Zheng, Jifeng; Zhao, Wei; Xu, Kai; Chen, Qingmao; Chen, Yingying; Shen, Yueliang; Xiao, Liping; Jiang, Liqin; Chen, Yuan

2017-04-05

Caffeine overdose death is due to cardiac arrest, but its mechanism has not been explored in detail. In this study, our data showed that caffeine significantly prolonged the heart rate-corrected QT interval (QTc) of rabbits in vivo (P<0.05; n=7). Caffeine was also found to be a hERG channel blocker with an IC 50 of 5.04mM (n=5). Although these two findings likely link caffeine overdose death with hERG channel blockade, the amount of caffeine consumption needed to reach the IC 50 is very high. Further study demonstrated that addition another hERG blocker could lower the consumption of caffeine significantly, no matter whether two hERG blockers share the same binding sites. Our data does not rule out other possibility, however, it suggests that there is a potential causal relationship between caffeine overdose death with hERG channel and the interaction among these hERG blockers. Published by Elsevier B.V.

Diadenosine tetraphosphate-gating of recombinant pancreatic ATP-sensitive K(+) channels.

PubMed

Jovanovic, S; Jovanovic, A

2001-02-01

Diadenosine tetraphosphate (Ap4A) has been recently discovered in the pancreatic beta cells where targets ATP-sensitive K(+) (K(ATP)) channels, depolarizes the cell membrane and induces insulin secretion. However, whether Ap4A inhibit pancreatic K(ATP) channels by targeting protein channel complex itself was unknown. Therefore, we coexpressed pancreatic K(ATP) channel subunits, Kir6.2 and SUR1, in COS-7 cells and examined the effect of Ap4A on the single channel behavior using the inside-out configuration of the patch-clamp technique. Ap4A inhibited channel opening in a concentration-dependent manner. Analysis of single channels demonstrated that Ap4A did not change intraburst kinetic behavior of K(ATP) channels, but rather decreased burst duration and increased between-burst duration. It is concluded that Ap4A antagonizes K(ATP) channel opening by targeting channel subunits themselves and by keeping channels longer in closed interburst states.

Protective effects of phosphodiesterase-1 (PDE1) and ATP sensitive potassium (KATP) channel modulators against 3-nitropropionic acid induced behavioral and biochemical toxicities in experimental Huntington׳s disease.

PubMed

Gupta, Surbhi; Sharma, Bhupesh

2014-06-05

Huntington׳s disease (HD), a devastating neurodegenerative disorder, is characterized by weight loss, impairment of motor function, cognitive dysfunction, neuropsychiatric disturbances and striatal damage. Phosphodiesterase-1 (PDE1) has been implicated in various neurological diseases. Mitochondrial potassium channels in the brain take part in neuroprotection. This study has been structured to investigate the role of vinpocetine, a selective PDE1 inhibitor as well as nicorandil, selective ATP sensitive potassium (KATP) channel opener in 3-nitropropionic acid (3-NP) induced HD symptoms in rats. Systemic administration of 3-NP significantly, reduced body weight, impaired locomotion, grip strength and impaired cognition. 3-NP elicited marked oxidative stress in the brain (enhanced malondialdehyde-MDA, reduced glutathione-GSH content, superoxide dismutase-SOD and catalase-CAT), elevated brain acetylcholinesterase activity and inflammation (myeloperoxidase-MPO), with marked nitrosative stress (nitrite/nitrate) in the brain. 3-NP has also induced mitochondrial dysfunction (impaired mitochondrial NADH dehydrogenase-complex I, succinate dehydrogenase-complex II and cytochrome oxidase-complex IV) activities in the striatum of the rat. Tetrabenazine was used as a positive control. Treatment with vinpocetine, nicorandil and tetrabenazine ameliorated 3-NP induced reduction in body weight, impaired locomotion, grip strength and impaired cognition. Treatment with these drugs reduced brain striatum oxidative (MDA, GSH, SOD and CAT) and nitrosative (nitrite/nitrate) stress, acetylcholinesterase activity, inflammation and mitochondrial dysfunctions. These results indicate that vinpocetine, a selective PDE1 inhibitor and nicorandil, a KATP channel opener have attenuated 3-NP induced experimental HD. Hence, pharmacological modulation of PDE1 as well as KATP channels may be considered as potential research targets for mitigation of HD. Copyright © 2014 Elsevier B.V. All rights

Molecular structure of human KATP in complex with ATP and ADP

PubMed Central

Lee, Kenneth Pak Kin

2017-01-01

In many excitable cells, KATP channels respond to intracellular adenosine nucleotides: ATP inhibits while ADP activates. We present two structures of the human pancreatic KATP channel, containing the ABC transporter SUR1 and the inward-rectifier K+ channel Kir6.2, in the presence of Mg2+ and nucleotides. These structures, referred to as quatrefoil and propeller forms, were determined by single-particle cryo-EM at 3.9 Å and 5.6 Å, respectively. In both forms, ATP occupies the inhibitory site in Kir6.2. The nucleotide-binding domains of SUR1 are dimerized with Mg2+-ATP in the degenerate site and Mg2+-ADP in the consensus site. A lasso extension forms an interface between SUR1 and Kir6.2 adjacent to the ATP site in the propeller form and is disrupted in the quatrefoil form. These structures support the role of SUR1 as an ADP sensor and highlight the lasso extension as a key regulatory element in ADP’s ability to override ATP inhibition. PMID:29286281

Role of dihydropyridinic calcium channel blockers in the management of hypertension.

PubMed

Coca, Antonio; Mazón, Pilar; Aranda, Pedro; Redón, Josep; Divisón, Juan Antonio; Martínez, Javier; Calvo, Carlos; Galcerán, Josep María; Barrios, Vivencio; Roca-Cusachs I Coll, Alexandre

2013-01-01

Dihydropyridinic calcium channel blockers are a subclass of antihypertensive drugs with growing significance in the therapeutic armamentarium. Early studies in the 1990s had aroused certain fears with regard to the safety of the first drugs from this class, since they had a fast onset of action and a short half-life, and thus they were associated with reflex adrenergic activation. New molecules with long half-lives and high lipophilia have shown safety and efficacy in the control of blood pressure, as well as in the reduction of several end points related to hypertension. Moreover, these new molecules, which block special subtypes of calcium channel receptors, provide drugs not only with an action profile that goes beyond the antihypertensive effect, but also with a lower rate of side effects. Therefore, in the light of new studies that include calcium channel blockers alone or in combination, these agents will probably be used even more extensively for the management of hypertension in the following years.

The anti-proliferative effect of cation channel blockers in T lymphocytes depends on the strength of mitogenic stimulation.

PubMed

Petho, Zoltan; Balajthy, Andras; Bartok, Adam; Bene, Krisztian; Somodi, Sandor; Szilagyi, Orsolya; Rajnavolgyi, Eva; Panyi, Gyorgy; Varga, Zoltan

2016-03-01

Ion channels are crucially important for the activation and proliferation of T lymphocytes, and thus, for the function of the immune system. Previous studies on the effects of channel blockers on T cell proliferation reported variable effectiveness due to differing experimental systems. Therefore our aim was to investigate how the strength of the mitogenic stimulation influences the efficiency of cation channel blockers in inhibiting activation, cytokine secretion and proliferation of T cells under standardized conditions. Human peripheral blood lymphocytes were activated via monoclonal antibodies targeting the TCR-CD3 complex and the co-stimulator CD28. We applied the blockers of Kv1.3 (Anuroctoxin), KCa3.1 (TRAM-34) and CRAC (2-Apb) channels of T cells either alone or in combination with rapamycin, the inhibitor of the mammalian target of rapamycin (mTOR). Five days after the stimulation ELISA and flow cytometric measurements were performed to determine IL-10 and IFN-γ secretion, cellular viability and proliferation. Our results showed that ion channel blockers and rapamycin inhibit IL-10 and IFN-γ secretion and cell division in a dose-dependent manner. Simultaneous application of the blockers for each channel along with rapamycin was the most effective, indicating synergy among the various activation pathways. Upon increasing the extent of mitogenic stimulation the anti-proliferative effect of the ion channel blockers diminished. This phenomenon may be important in understanding the fine-tuning of T cell activation. Copyright © 2016 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.

Diuretic or Beta-Blocker for Hypertensive Patients Already Receiving ACEI/ARB and Calcium Channel Blocker.

PubMed

Tsai, Min-Shan; Tang, Chao-Hsiun; Lin, Chia-Ying; Chuang, Po-Ya; Chen, Nai-Chuan; Huang, Chien-Hua; Chang, Wei-Tien; Wang, Tzung-Dau; Yu, Ping-Hsun; Chen, Wen-Jone

2017-12-01

In patients already receiving combination of angiotensin-converting enzyme inhibitor (ACEI)/angiotensin receptor blocker (ARB) and calcium channel blocker (CCB), whether the choice of additional diuretic or beta-blocker affects the cardiovascular and cerebrovascular outcomes remains unclear. A total of 13,551 patients who were concurrently receiving three anti-hypertensive agents of different classes through outpatient clinics during 2004-2006 were identified from the National Health Insurance Research Database of Taiwan. Patients were further classified into two treatment groups according to the medication possession ratio of drug combinations; the A + B + C group as those who received concurrent therapy of ACEI/ARB, beta-blocker and CCB. The A + C + D group as patients who received ACEI/ARB, CCB, and diuretics. The event-free survival of stroke, acute myocardial infarction (AMI), mortality, and major adverse cardiovascular events (MACE) between the two treatment groups was investigated. After propensity score matching, there were 5120 patients in each group. There were no differences in the incidence of cardiovascular events between the two groups. In patients with prior history of cerebrovascular accident (CVA), the A + C + D group had a significantly higher AMI-free survival (adjusted HR = 1.56; 95% CI 1.051-2.307; p < 0.05) as compared with the A + B + C group. Adding a diuretic may be better than adding a beta-blocker for treating hypertensive patients with prior CVA history who have already received ACEIs/ARBs and CCBs.

Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate

PubMed Central

Ivanov, Vadim; Ivanova, Svetlana; Kalinovsky, Tatiana; Niedzwiecki, Aleksandra; Rath, Matthias

2016-01-01

Calcium, sodium and potassium channel blockers are widely prescribed medications for a variety of health problems, most frequently for cardiac arrhythmias, hypertension, angina pectoris and other disorders. However, chronic application of channel blockers is associated with numerous side effects, including worsening cardiac pathology. For example, nifedipine, a calcium-channel blocker was found to be associated with increased mortality and increased risk for myocardial infarction. In addition to the side effects mentioned above by different channel blockers, these drugs can cause arterial wall damage, thereby contributing to vascular wall structure destabilization and promoting events facilitating rupture of plaques. Collagen synthesis is regulated by ascorbic acid, which is also essential for its optimum structure as a cofactor in lysine and proline hydroxylation, a precondition for optimum crosslinking of collagen and elastin. Therefore, the main objective in this study was to evaluate effects of various types of channel blockers on intracellular accumulation and cellular functions of ascorbate, specifically in relation to formation and extracellular deposition of major collagen types relevant for vascular function. Effects of select Na- and Ca- channel blockers on collagen synthesis and deposition were evaluated in cultured human dermal fibroblasts and aortic smooth muscle cells by immunoassay. All channel blockers tested demonstrated inhibitory effects on collagen type I deposition to the ECM by fibroblasts, each to a different degree. Ascorbic acid significantly increased collagen I ECM deposition. Nifedipine (50 µM), a representative of channel blockers tested, significantly reduced ascorbic acid and ascorbyl palmitate-dependent ECM deposition of collagen type l and collagen type lV by cultured aortic smooth muscle cells. In addition, nifedipine (50 µM) significantly reduced ascorbate-dependent collagen type l and type lV synthesis by cultured aortic smooth

Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate.

PubMed

Ivanov, Vadim; Ivanova, Svetlana; Kalinovsky, Tatiana; Niedzwiecki, Aleksandra; Rath, Matthias

2016-01-01

Calcium, sodium and potassium channel blockers are widely prescribed medications for a variety of health problems, most frequently for cardiac arrhythmias, hypertension, angina pectoris and other disorders. However, chronic application of channel blockers is associated with numerous side effects, including worsening cardiac pathology. For example, nifedipine, a calcium-channel blocker was found to be associated with increased mortality and increased risk for myocardial infarction. In addition to the side effects mentioned above by different channel blockers, these drugs can cause arterial wall damage, thereby contributing to vascular wall structure destabilization and promoting events facilitating rupture of plaques. Collagen synthesis is regulated by ascorbic acid, which is also essential for its optimum structure as a cofactor in lysine and proline hydroxylation, a precondition for optimum crosslinking of collagen and elastin. Therefore, the main objective in this study was to evaluate effects of various types of channel blockers on intracellular accumulation and cellular functions of ascorbate, specifically in relation to formation and extracellular deposition of major collagen types relevant for vascular function. Effects of select Na- and Ca- channel blockers on collagen synthesis and deposition were evaluated in cultured human dermal fibroblasts and aortic smooth muscle cells by immunoassay. All channel blockers tested demonstrated inhibitory effects on collagen type I deposition to the ECM by fibroblasts, each to a different degree. Ascorbic acid significantly increased collagen I ECM deposition. Nifedipine (50 µM), a representative of channel blockers tested, significantly reduced ascorbic acid and ascorbyl palmitate-dependent ECM deposition of collagen type l and collagen type lV by cultured aortic smooth muscle cells. In addition, nifedipine (50 µM) significantly reduced ascorbate-dependent collagen type l and type lV synthesis by cultured aortic smooth

[Molecular and functional diversity of ATP-sensitive K+ channels: the pathophysiological roles and potential drug targets].

PubMed

Nakaya, Haruaki; Miki, Takashi; Seino, Susumu; Yamada, Katsuya; Inagaki, Nobuya; Suzuki, Masashi; Sato, Toshiaki; Yamada, Mitsuhiko; Matsushita, Kenji; Kurachi, Yoshihisa; Arita, Makoto

2003-09-01

ATP-sensitive K(+) (K(ATP)) channels comprise the pore-forming subunit (Kir6.1 or Kir6.2) and the regulatory subunit sulfonylurea receptors (SUR1 or SUR2). K(ATP) channels with different combinations of these subunits are present in various tissues and regulate cellular functions. From the analysis of mouse models with targeted deletion of the gene encoding the pore-forming subunit Kir6.1 or Kir6.2, functional roles of K(ATP) channels in various organs have been clarified. Kir6.1(-/-) mice showed sudden death associated with ST elevation and atrioventricular block in ECG, a phenotype resembling Prinzmetal angina in humans. Kir6.2(-/-) mice were more susceptible to generalized seizure during hypoxia than wild-type (WT) mice, suggesting that neuronal K(ATP) channels, probably composed of Kir6.2 and SUR1, play a crucial role for the protection of the brain against lethal damage due to seizure. In Kir6.2(-/-) mice lacking the sarcolemmal K(ATP) channel activity in cardiac cells, ischemic preconditioning failed to reduce the infarct size, suggesting that sarcolemmal K(ATP) channels play an important role in cardioprotection against ischemia/reperfusion injuries in the heart. Mitochondrial K(ATP) channels have been also proposed to play a crucial role in cardioprotection, although the molecular identity of the channel has not been established. Nicorandil and minoxidil, K(+) channel openers activating mitochondrial K(ATP) channels, decreased the mitochondrial membrane potential, thereby preventing the Ca(2+) overload in the mitochondria of guinea-pig ventricular cells. SURs are the receptors for K(+) channel openers and the activating effects on sarcolemmal K(ATP) channels in cardiovascular tissues could be modulated by the interaction of nucleotides. Due to the molecular diversity of the accessory and pore subunits of K(ATP) channels, there would be considerable differences in the tissue selectivity of K(ATP) channel-acting drugs. Studies of Kir6.1 and Kir6.2 knockout

Comparative effects of sodium channel blockers in short term rat whole embryo culture

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

Nilsson, Mats F, E-mail: Mats.Nilsson@farmbio.uu.se; Sköld, Anna-Carin; Ericson, Ann-Christin

2013-10-15

This study was undertaken to examine the effect on the rat embryonic heart of two experimental drugs (AZA and AZB) which are known to block the sodium channel Nav1.5, the hERG potassium channel and the L-type calcium channel. The sodium channel blockers bupivacaine, lidocaine, and the L-type calcium channel blocker nifedipine were used as reference substances. The experimental model was the gestational day (GD) 13 rat embryo cultured in vitro. In this model the embryonic heart activity can be directly observed, recorded and analyzed using computer assisted image analysis as it responds to the addition of test drugs. The effectmore » on the heart was studied for a range of concentrations and for a duration up to 3 h. The results showed that AZA and AZB caused a concentration-dependent bradycardia of the embryonic heart and at high concentrations heart block. These effects were reversible on washout. In terms of potency to cause bradycardia the compounds were ranked AZB > bupivacaine > AZA > lidocaine > nifedipine. Comparison with results from previous studies with more specific ion channel blockers suggests that the primary effect of AZA and AZB was sodium channel blockage. The study shows that the short-term rat whole embryo culture (WEC) is a suitable system to detect substances hazardous to the embryonic heart. - Highlights: • Study of the effect of sodium channel blocking drugs on embryonic heart function • We used a modified method rat whole embryo culture with image analysis. • The drugs tested caused a concentration dependent bradycardia and heart block. • The effect of drugs acting on multiple ion channels is difficult to predict. • This method may be used to detect cardiotoxicity in prenatal development.« less

Use of calcium channel blockers in hypertension.

PubMed

Conlin, P R; Williams, G H

1998-01-01

During the past 20 years the number of subclasses of calcium channel blockers has increased from one to four. Three classes have only a single clinically approved compound: verapamil, diltiazem, and mibefradil. The fourth class, dihydropyridines, contains numerous compounds. All agents are effective in lowering blood pressure in short-term studies, and side effects that trouble the patient are infrequent. Long-term studies in hypertensive patients are limited. Short-acting agents such as nifedipine have been associated with an increased cardiovascular risk in some, but not all studies. These agents also probably create a compliance problem for hypertensive patients because of the need for multiple daily doses and their unpleasant side effects, e.g., ankle edema, palpitations, and flushing. Therefore, they are not useful or indicated for the treatment of hypertensive patients. No data have suggested that long-acting dihydropyridines or nondihydropyridine calcium channel blockers share the same fate. Indeed, several lines of evidence suggest the opposite: they have a cardioprotective effect. However, definitive information will require the completion of several long-term trials, including ALLHAT, CONVINCE, HOT, INSIGHT and NORDIL. Finally, it is important to reflect on the lessons learned from the controversy associated with the potential risks of calcium channel blockers. First, disagreements are common when one uses case-controlled studies and are reflective of the poor precision of the methods used. What is statistically relevant in one study may not hold true for another and may have no clinical relevance, particularly if the relative risk is less than 2. Investigators need to temper their enthusiasm to reflect this reality. Second, at the cutting edge of science there is probably relatively little agreement about what is correct among equally competent scientists. All have bias in their positions and should both recognize and admit so to themselves and their

[Effect of K-ATP channel opener-pinacidil on the liver mitochondria function in rats with different resistance to hypoxia during stress].

PubMed

Tkachenko, H M; Kurhaliuk, N M; Vovkanych, L S

2004-01-01

We have examined the influence of ATP-sensitive potassium (KATP) channel opener pinacidil (0.06 mg/kg) and inhibitor glibenclamide (1 mg/kg) on the changes of energy metabolism in the liver of rats under the stress conditions. The rats were divided in two groups with high and low resistance to hypoxia. The stress was modeled by placing the rats in a cage filled with water and closed with a net. The distance from water to the net was only 5 cm. The effects of KATP opener pinacidil (0.06 mg/kg) and inhibitor glibenclamide (1 mg/kg) on ADP-stimulating mitochondrial respiration by Chance, calcium capacity of organellas and processes of lipid peroxidation in the liver of rats with different resistance to hypoxia under the stress condition have been investigated. We have used the next substrates of oxidation: 0.35 mM succinate and 1 mM alpha-ketoglutarate. The additional analyses were conducted with the use of inhibitors: mitochondrial enzyme complex I 10 mM rotenone and succinate dehydrohenase 2 mM malonic acid. It was shown that the stress condition evoked the succinate oxidation and the decrease of alpha-ketoglutarate efficacy, the increase of calcium mitochondrial capacity and the intensification of lipid peroxidation processes. Under the presence of succinate, the increase of O2 uptake with simultaneous decrease of ADP/O ratio in rats with high resistance under stress was observed. Simultaneously, oxidation of alpha-ketoglutarate, a NAD-dependent substrate, was inhibited. Pinacidil caused the reorganization of mitochondrial energy metabolism in favour of NAD-dependent oxidation and the improvment of the protection against stress. The decrease of the efficacy of mitochondrial energy processes functioning was shown in animals with low resistance to hypoxia. KATP channel opener pinacidil has a protective effect on the processes of mitochondrial liver energy support under stress. These changes deal with the increase of alpha-ketoglutarate oxidation (respiratory rate and

Kir6.2-dependent high-affinity repaglinide binding to β-cell KATP channels

PubMed Central

Hansen, Ann Maria K; Hansen, John Bondo; Carr, Richard D; Ashcroft, Frances M; Wahl, Philip

2005-01-01

The β-cell KATP channel is composed of two types of subunit – the inward rectifier K+ channel (Kir6.2) which forms the channel pore, and the sulphonylurea receptor (SUR1), which serves as a regulatory subunit. The N-terminus of Kir6.2 is involved in transduction of sulphonylurea binding into channel closure, and deletion of the N-terminus (Kir6.2ΔN14) results in functional uncoupling of the two subunits. In this study, we investigate the interaction of the hypoglycaemic agents repaglinide and glibenclamide with SUR1 and the effect of Kir6.2 on this interaction. We further explore how the binding properties of repaglinide and glibenclamide are affected by functional uncoupling of SUR1 and Kir6.2 in Kir6.2ΔN14/SUR1 channels. All binding experiments are performed on membranes in ATP-free buffer at 37°C. Repaglinide was found to bind with low affinity (KD=59±16 nM) to SUR1 alone, but with high affinity (increased ∼150-fold) when SUR1 was co-expressed with Kir6.2 (KD=0.42±0.03 nM). Glibenclamide, tolbutamide and nateglinide all bound with marginally lower affinity to SUR1 than to Kir6.2/SUR1. Repaglinide bound with low affinity (KD=51±23 nM) to SUR1 co-expressed with Kir6.2ΔN14. In contrast, the affinity for glibenclamide, tolbutamide and nateglinide was only mildly changed as compared to wild-type channels. In whole-cell patch-clamp experiments inhibition of Kir6.2ΔN14/SUR1 currents by both repaglinide and nateglinde is abolished. The results suggest that Kir6.2 causes a conformational change in SUR1 required for high-affinity repaglinide binding, or that the high-affinity repaglinide-binding site includes contributions from both SUR1 and Kir6.2. Glibenclamide, tolbutamide and nateglinide binding appear to involve only SUR1. PMID:15678092

Pharmacological rescue of trafficking-impaired ATP-sensitive potassium channels

PubMed Central

Martin, Gregory M.; Chen, Pei-Chun; Devaraneni, Prasanna; Shyng, Show-Ling

2013-01-01

ATP-sensitive potassium (KATP) channels link cell metabolism to membrane excitability and are involved in a wide range of physiological processes including hormone secretion, control of vascular tone, and protection of cardiac and neuronal cells against ischemic injuries. In pancreatic β-cells, KATP channels play a key role in glucose-stimulated insulin secretion, and gain or loss of channel function results in neonatal diabetes or congenital hyperinsulinism, respectively. The β-cell KATP channel is formed by co-assembly of four Kir6.2 inwardly rectifying potassium channel subunits encoded by KCNJ11 and four sulfonylurea receptor 1 subunits encoded by ABCC8. Many mutations in ABCC8 or KCNJ11 cause loss of channel function, thus, congenital hyperinsulinism by hampering channel biogenesis and hence trafficking to the cell surface. The trafficking defects caused by a subset of these mutations can be corrected by sulfonylureas, KATP channel antagonists that have long been used to treat type 2 diabetes. More recently, carbamazepine, an anticonvulsant that is thought to target primarily voltage-gated sodium channels has been shown to correct KATP channel trafficking defects. This article reviews studies to date aimed at understanding the mechanisms by which mutations impair channel biogenesis and trafficking and the mechanisms by which pharmacological ligands overcome channel trafficking defects. Insight into channel structure-function relationships and therapeutic implications from these studies are discussed. PMID:24399968

A potent potassium channel blocker from Mesobuthus eupeus scorpion venom.

PubMed

Gao, Bin; Peigneur, Steve; Tytgat, Jan; Zhu, Shunyi

2010-12-01

Scorpion venom-derived peptidyl toxins are valuable pharmacological tools for investigating the structure-function relationship of ion channels. Here, we report the purification, sequencing and functional characterization of a new K(+) channel blocker (MeuKTX) from the venom of the scorpion Mesobuthus eupeus. Effects of MeuKTX on ten cloned potassium channels in Xenopus oocytes were evaluated using two-electrode voltage-clamp recordings. MeuKTX is the orthologue of BmKTX (α-KTx3.6), a known Kv1.3 blocker from the scorpion Mesobuthus martensii, and classified as α-KTx3.13. MeuKTX potently blocks rKv1.1, rKv1.2 and hKv1.3 channels with 50% inhibitory concentration (IC(50)) of 203.15 ± 4.06 pM, 8.92 ± 2.3 nM and 171 ± 8.56 pM, respectively, but does not affect rKv1.4, rKv1.5, hKv3.1, rKv4.3, and hERG channels even at 2 μM concentration. At this high concentration, MeuKTX is also active on rKv1.6 and Shaker IR. Our results also demonstrate that MeuKTX and BmKTX have the same channel spectrum and similar pharmacological potency. Analysis of the structure-function relationships of α-KTx3 subfamily toxins allows us to recognize several key sites which may be useful for designing toxins with improved activity on hKv1.3, an attractive target for T-cell mediated autoimmune diseases. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Discovery and Development of Calcium Channel Blockers

PubMed Central

Godfraind, Théophile

2017-01-01

In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan) and Heibrunn (USA) experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB) of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are important factors of

Pharmacological preconditioning by diazoxide downregulates cardiac L-type Ca2+ channels

PubMed Central

González, G; Zaldívar, D; Carrillo, ED; Hernández, A; García, MC; Sánchez, JA

2010-01-01

BACKGROUND AND PURPOSE Pharmacological preconditioning (PPC) with mitochondrial ATP-sensitive K+ (mitoKATP) channel openers such as diazoxide, leads to cardioprotection against ischaemia. However, effects on Ca2+ homeostasis during PPC, particularly changes in Ca2+ channel activity, are poorly understood. We investigated the effects of PPC on cardiac L-type Ca2+ channels. EXPERIMENTAL APPROACH PPC was induced in isolated hearts and enzymatically dissociated cardiomyocytes from adult rats by preincubation with diazoxide. We measured reactive oxygen species (ROS) production and Ca2+ signals associated with action potentials using fluorescent probes, and L-type currents using a whole-cell patch-clamp technique. Levels of the α1c subunit of L-type channels in the cellular membrane were measured by Western blot. KEY RESULTS PPC was accompanied by a 50% reduction in α1c subunit levels, and by a reversible fall in L-type current amplitude and Ca2+ transients. These effects were prevented by the ROS scavenger N-acetyl-L-cysteine (NAC), or by the mitoKATP channel blocker 5-hydroxydecanoate (5-HD). PPC signficantly reduced infarct size, an effect blocked by NAC and 5-HD. Nifedipine also conferred protection against infarction when applied during the reperfusion period. Downregulation of the α1c subunit and Ca2+ channel function were prevented in part by the protease inhibitor leupeptin. CONCLUSIONS AND IMPLICATIONS PPC downregulated the α1c subunit, possibly through ROS. Downregulation involved increased degradation of the Ca2+ channel, which in turn reduced Ca2+ influx, which may attenuate Ca2+ overload during reperfusion. PMID:20636393

Design, synthesis and structure-activity relationship of indoxacarb analogs as voltage-gated sodium channel blocker.

PubMed

Hao, Wenbo; Fu, Chunling; Yu, Huijuan; Chen, Jian; Xu, Hanhong; Shao, Guang; Jiang, Dingxin

2015-10-15

Indoxacarb, the first commercialized pyrazoline-type sodium-channel blocker, is a commonly used insecticide because of high selectivity. To discover sodium-channel blocker with high insecticidal activity, a series of novel indoxacarb analogs were designed and synthesized by judicious structural modifications of the substituent group of C5, C6 in indenone and C'4 in benzene ring. Some analogs exhibited significant insecticidal activities against Spodoptera litura F. and excellent BgNav1-1a channel inhibitory activity. The structure-activity analysis indicated that the presence of strong electron-withdrawing group and decreased steric hindrance of indenone ring (R(1), R(2)) in 5- and 6-position could enhance larvicidal activity and BgNav1-1a channel inhibitory activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Dependence of the concentration of the demi-maximal action of a channel blocker on the agonist concentration].

PubMed

Skorinkin, A I; Valeev, N V; Shaĭkhutdinova, A R

2005-01-01

Based on the analysis of kinetic scheme of blocking of open channels at any number of blocker binding sites, the dependence of current on blocker concentration was found. A variant of this dependence for a trapping blocker was also found. The restrictions of the applicability of the Hill equation and the necessity of taking into account the dependence of the concentration of demi-maximal blocker action (IC50) on the concentration of agonist were shown.

Noble Gas Xenon Is a Novel Adenosine Triphosphate-sensitive Potassium Channel Opener

PubMed Central

Bantel, Carsten; Maze, Mervyn; Trapp, Stefan

2010-01-01

Background Adenosine triphosphate-sensitive potassium (KATP) channels in brain are involved in neuroprotective mechanisms. Pharmacologic activation of these channels is seen as beneficial, but clinical exploitation by using classic K+ channel openers is hampered by their inability to cross the blood–brain barrier. This is different with the inhalational anesthetic xenon, which recently has been suggested to activate KATP channels; it partitions freely into the brain. Methods To evaluate the type and mechanism of interaction of xenon with neuronal-type KATP channels, these channels, consisting of Kir6.2 pore-forming subunits and sulfonylurea receptor-1 regulatory subunits, were expressed in HEK293 cells and whole cell, and excised patch-clamp recordings were performed. Results Xenon, in contrast to classic KATP channel openers, acted directly on the Kir6.2 subunit of the channel. It had no effect on the closely related, adenosine triphosphate (ATP)-regulated Kir1.1 channel and failed to activate an ATP-insensitive mutant version of Kir6.2. Furthermore, concentration–inhibition curves for ATP obtained from inside-out patches in the absence or presence of 80% xenon revealed that xenon reduced the sensitivity of the KATP channel to ATP. This was reflected in an approximately fourfold shift of the concentration causing half-maximal inhibition (IC50) from 26 ± 4 to 96 ± 6 μm. Conclusions Xenon represents a novel KATP channel opener that increases KATP currents independently of the sulfonylurea receptor-1 subunit by reducing ATP inhibition of the channel. Through this action and by its ability to readily partition across the blood–brain barrier, xenon has considerable potential in clinical settings of neuronal injury, including stroke. PMID:20179498

Discovery of talatisamine as a novel specific blocker for the delayed rectifier K+ channels in rat hippocampal neurons.

PubMed

Song, M-K; Liu, H; Jiang, H-L; Yue, J-M; Hu, G-Y; Chen, H-Z

2008-08-13

Blocking specific K+ channels has been proposed as a promising strategy for the treatment of neurodegenerative diseases. Using a computational virtual screening approach and electrophysiological testing, we found four Aconitum alkaloids are potent blockers of the delayed rectifier K+ channel in rat hippocampal neurons. In the present study, we first tested the action of the four alkaloids on the voltage-gated K+, Na+ and Ca2+ currents in rat hippocampal neurons, and then identified that talatisamine is a specific blocker for the delayed rectifier K+ channel. External application of talatisamine reversibly inhibited the delayed rectifier K+ current (IK) with an IC50 value of 146.0+/-5.8 microM in a voltage-dependent manner, but exhibited very slight blocking effect on the voltage-gated Na+ and Ca2+ currents even at the high concentration of 1-3 mM. Moreover, talatisamine exerted a significant hyperpolarizing shift of the steady-state activation, but did not influence the steady state inactivation of IK and its recovery from inactivation, suggesting that talatisamine had no allosteric action on IK channel and was a pure blocker binding to the external pore entry of the channel. Our present study made the first discovery of potent and specific IK channel blocker from Aconitum alkaloids. It has been argued that suppressing K+ efflux by blocking IK channel may be favorable for Alzheimer's disease therapy. Talatisamine can therefore be considered as a leading compound worthy of further investigations.

Regulation of Cardiac ATP-sensitive Potassium Channel Surface Expression by Calcium/Calmodulin-dependent Protein Kinase II*

PubMed Central

Sierra, Ana; Zhu, Zhiyong; Sapay, Nicolas; Sharotri, Vikas; Kline, Crystal F.; Luczak, Elizabeth D.; Subbotina, Ekaterina; Sivaprasadarao, Asipu; Snyder, Peter M.; Mohler, Peter J.; Anderson, Mark E.; Vivaudou, Michel; Zingman, Leonid V.; Hodgson-Zingman, Denice M.

2013-01-01

Cardiac ATP-sensitive potassium (KATP) channels are key sensors and effectors of the metabolic status of cardiomyocytes. Alteration in their expression impacts their effectiveness in maintaining cellular energy homeostasis and resistance to injury. We sought to determine how activation of calcium/calmodulin-dependent protein kinase II (CaMKII), a central regulator of calcium signaling, translates into reduced membrane expression and current capacity of cardiac KATP channels. We used real-time monitoring of KATP channel current density, immunohistochemistry, and biotinylation studies in isolated hearts and cardiomyocytes from wild-type and transgenic mice as well as HEK cells expressing wild-type and mutant KATP channel subunits to track the dynamics of KATP channel surface expression. Results showed that activation of CaMKII triggered dynamin-dependent internalization of KATP channels. This process required phosphorylation of threonine at 180 and 224 and an intact 330YSKF333 endocytosis motif of the KATP channel Kir6.2 pore-forming subunit. A molecular model of the μ2 subunit of the endocytosis adaptor protein, AP2, complexed with Kir6.2 predicted that μ2 docks by interaction with 330YSKF333 and Thr-180 on one and Thr-224 on the adjacent Kir6.2 subunit. Phosphorylation of Thr-180 and Thr-224 would favor interactions with the corresponding arginine- and lysine-rich loops on μ2. We concluded that calcium-dependent activation of CaMKII results in phosphorylation of Kir6.2, which promotes endocytosis of cardiac KATP channel subunits. This mechanism couples the surface expression of cardiac KATP channels with calcium signaling and reveals new targets to improve cardiac energy efficiency and stress resistance. PMID:23223335

Kv1.3 channel blocker (ImKTx88) maintains blood-brain barrier in experimental autoimmune encephalomyelitis.

PubMed

Huang, Jie; Han, Song; Sun, Qi; Zhao, Yipeng; Liu, Junchen; Yuan, Xiaolu; Mao, Wenqian; Peng, Biwen; Liu, Wanhong; Yin, Jun; He, Xiaohua

2017-01-01

Disruption of blood-brain barrier (BBB) and subsequent infiltration of auto-reactive T lymphocytes are major characteristics of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). Kv1.3 channel blockers are demonstrated potential therapeutic effects on MS patients and EAE models, maybe via reducing activation of T cells. However, it remains to be explored whether Kv1.3 channel blockers maintain integrity of BBB in MS model. In this study, ImKTx88, a highly selective Kv1.3 channel blocker, was used to determine the role of Kv1.3 channel in the pathogenesis of EAE, particularly in the maintenance of BBB. ImKTx88 ameliorated pathological severity in the EAE rats, and reduced extravasation into CNS. ImKTx88 also ameliorated the severity of loss or redistribution of tight junction proteins, and inhibited over-expression of ICAM-1 and VCAM-1 in the brain from EAE rats. Furthermore ImKTx88 protection was associated with activation of Ang-1/Tie-2 axis, and might be due to decreased IL-17 production. ImKTx88 may be a novel therapeutic agent for MS treatment by stabilizing the BBB.

The newly identified K+ channel blocker talatisamine attenuates beta-amyloid oligomers induced neurotoxicity in cultured cortical neurons.

PubMed

Wang, Yanxia; Song, Mingke; Hou, Lina; Yu, Zhihua; Chen, Hongzhuan

2012-06-19

Loss of cytosolic K(+) through up-regulated delayed rectifier K(+) channels play an important role in beta-amyloid (Aβ) induced neurotoxicity. Potent K(+) channel blocker, particular specific for I(K) channels has been suggested as an attractive candidate for the treatment of Alzheimer's disease (AD). Talatisamine is a novel I(K) channel blocker discovered by virtual screening and electrophysiological characterization. In the present study, we examined the neuroprotective effect of talatisamine against Aβ oligomers induced cytotoxicity in primarily cultured cortical neurons. The neurotoxicity related to K(+) loss caused by Aβ40 oligomers included enhanced I(K) density, increased cell membrane permeability, reduced cell viability, and impaired mitochondrial transmembrane potential. Decreased Bcl-2 and increased Bax level, activation of Caspase-3 and Caspase-9 were also observed after Aβ40 oligomers incubation. Talatisamine (120 μM) and TEA (5mM) inhibited the enhanced I(K) caused by Aβ40 oligomers, attenuated cytotoxicity of Aβ oligomers by restoring cell viability and suppressing K(+) loss related apoptotic response. Our results suggested that talatisamine may become a leading compound as I(K) channel blocker for neuroprotection. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Carbamazepine as a novel small molecule corrector of trafficking-impaired ATP-sensitive potassium channels identified in congenital hyperinsulinism.

PubMed

Chen, Pei-Chun; Olson, Erik M; Zhou, Qing; Kryukova, Yelena; Sampson, Heidi M; Thomas, David Y; Shyng, Show-Ling

2013-07-19

ATP-sensitive potassium (KATP) channels consisting of sulfonylurea receptor 1 (SUR1) and the potassium channel Kir6.2 play a key role in insulin secretion by coupling metabolic signals to β-cell membrane potential. Mutations in SUR1 and Kir6.2 that impair channel trafficking to the cell surface lead to loss of channel function and congenital hyperinsulinism. We report that carbamazepine, an anticonvulsant, corrects the trafficking defects of mutant KATP channels previously identified in congenital hyperinsulinism. Strikingly, of the 19 SUR1 mutations examined, only those located in the first transmembrane domain of SUR1 responded to the drug. We show that unlike that reported for several other protein misfolding diseases, carbamazepine did not correct KATP channel trafficking defects by activating autophagy; rather, it directly improved the biogenesis efficiency of mutant channels along the secretory pathway. In addition to its effect on channel trafficking, carbamazepine also inhibited KATP channel activity. Upon subsequent removal of carbamazepine, however, the function of rescued channels was recovered. Importantly, combination of the KATP channel opener diazoxide and carbamazepine led to enhanced mutant channel function without carbamazepine washout. The corrector effect of carbamazepine on mutant KATP channels was also demonstrated in rat and human β-cells with an accompanying increase in channel activity. Our findings identify carbamazepine as a novel small molecule corrector that may be used to restore KATP channel expression and function in a subset of congenital hyperinsulinism patients.

Hormonal crosstalk with calcium channel blocker during implantation.

PubMed

Banerjee, Aryamitra; Padh, Harish; Nivsarkar, Manish

2011-08-01

The site specific action of the calcium channel blocker diltiazem in blocking prostaglandin synthesis and hence causing blastocyst implantation failure has been previously described. Based on this understanding it was important to learn if this pathway was under the control of the fine balance in estradiol-progesterone (E2-P4) milieu, considered to be of the utmost significance for effective implantation. In the current study the circulating E2-P4 levels were monitored on the first 6 d of pregnancy at various time points using sensitive chemiluminescence based assays. Next, diltiazem was administered intra-luminally into the uterus at 10-20 h prior to implantation as this time has been previously implicated to be when the best anti-implantation activity of diltiazem can be observed. Following this, the E2-P4 in peripheral circulation was again monitored. On d 6 (post implantation) the implantation sites were observed in the uterus of both diltiazem treated and untreated groups using Chicago blue dye and correlated to the hormonal activity. The levels of both estradiol and progesterone were very similar in both untreated and diltiazem treated groups during and post implantation. However complete implantation failure was noted in the diltiazem treated group whereas prominent implantation sites were observed in the untreated animals. Thus, the previously reported inhibition of blastocyst implantation cascade by calcium channel blockers during the 'implantation window' seems to be an independent mechanism interfering with uterine receptivity without any direct estrogen-progesterone control and further studies to understand its regulation need to be performed.

Efficacy of Calcium Channel Blockers on Major Cardiovascular Outcomes for the Treatment of Hypertension in Asian Populations: A Meta-analysis.

PubMed

Tran, Karen C; Leung, Alexander A; Tang, Karen L; Quan, Hude; Khan, Nadia A

2017-05-01

Whether calcium channel blockers exert a greater effect on cardiovascular risk reduction in Asian populations than other antihypertensive agents is unclear. We conducted a meta-analysis of hypertension trials of dihydropyridine calcium channel blockers in Asian populations to clarify this association. EMBASE, MEDLINE, and Cochrane databases were searched (from inception to August 2016) for randomized controlled trials on cardiovascular death, major adverse cardiovascular events, stroke, congestive heart failure, and coronary revascularization in Asian persons with hypertension. We identified 9 trials that reported data specific to Asian populations (N = 29,643). These trials included 1 placebo-controlled trial and 8 active comparator trials; of these, 5 had angiotensin receptor blockers as the active comparator. One placebo-controlled trial (n = 9711) showed significantly reduced cardiovascular mortality, major adverse cardiovascular events, and stroke with calcium channel blockers. Among 8 active comparator trials (n = 19,932), there were no significant differences in mortality (relative risk [RR], 1.10; 95% confidence interval [CI], 0.72-1.67; I 2  = 0.0%), major adverse cardiovascular events (RR, 1.02; 95% CI, 0.90-1.15; I 2  = 0.0%), stroke (RR, 0.97; 95% CI, 0.80-1.17; I 2  = 0.0%), congestive heart failure (RR, 1.01; 95% CI, 0.51-2.00; I 2  = 53.7), or coronary revascularization rates (RR, 0.98; 95% CI, 0.76-1.25; I 2  = 0.0%) in the calcium channel blocker group compared with other antihypertensive agents. When restricting the meta-analysis to angiotensin receptor blocker comparators (n = 10,384), there were no significant differences in cardiovascular outcomes. There is no evidence that dihydropyridine calcium channel blockers are superior to other antihypertensive agents in Asian populations for the treatment of hypertension. Copyright © 2017 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Hyperkalemia induced by the calcium channel blocker, benidipine.

PubMed

Imamura, Takuroh; Matsuura, Yunosuke; Nagoshi, Toshiro; Ishikawa, Tetsunori; Date, Haruhiko; Kita, Toshihiro; Matsuyama, Akihiko; Matsuo, Takeshi; Eto, Tanenao

2003-06-01

A 73-year-old hypertensive, non-diabetic woman without obvious renal dysfunction had frequently been hyperkalemic over four years after receiving antihypertensive drugs including the calcium channel blocker (CCB) benidipine. One week after all medications were accidentally discontinued, the serum potassium level returned to normal. After we obtained the informed consent of the patient, benidipine alone was administered again for over two weeks and hyperkalemia developed once more. This previously uncommon side effect of hyperkalemia induced by benidipine is not very serious but it is apt to be overlooked. Since CCBs are now widely prescribed, the development of hyperkalemia should be considered.

Survival of Swiss-Webster mouse cerebellar granule neurons is promoted by a combination of potassium channel blockers.

PubMed

Collins, Anthony; Larson, Maureen K; Pfaff, Jilleen E; Ishmael, Jane E

2007-06-15

Cultured cerebellar granule neurons (CGN) are commonly used to assess neurotoxicity, but are routinely maintained in supraphysiological (25 mM) extracellular K(+) concentrations [K(+)](o). We investigated the effect of potassium channel blockade on survival of CGN derived from Swiss-Webster mice in supraphysiological (25 mM) and physiological (5.6 mM) [K(+)](o). CGN were cultured for 5 days in 25 mM K(+), then in 5.6 mM K(+) or 25 mM K(+) (control). Viability, assayed 24 h later by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) reduction and by lactate dehydrogenase (LDH) release, was approximately 50% in 5.6 mM K(+) versus 25 mM K(+) (p<.001). Potassium channel blockers, 2 mM 4-aminopyridine (4-AP), 2 mM tetraethylammonium (TEA) or 1 mM Ba(2+), individually afforded limited protection in 5.6 mM K(+). However, survival in 5.6 mM K(+) with a combination of 4-AP, TEA and Ba(2+) was similar to survival in 25 mM K(+) without blockers (p<.001 versus 5.6 mM K(+) alone). CGN survival in 25 mM K(+) was attenuated 25% by 2 microM nifedipine (p>.001), but nifedipine did not attenuate neuroprotection by K(+) channel blockers. Together, these results suggest that the survival of CGN depends on the K(+) permeability of the membrane rather than the activity of a particular type of K(+) channel, and that the mechanism of neuroprotection by K(+) channel blockers is different from that of elevated [K(+)](o).

[Effect of calcium channel blockers on developing nervous syndrome of high pressure and nitrogen narcosis in mice].

PubMed

Sledkov, A I

1997-01-01

In the experiments conducted on mice which prior to compression in a heliox environment have been injected the blockers of various types of calcium channels (flunarezine, verapramil and nifedipine) as well as bemethyl (actoprotector) and oxymethacye (antioxidant) there escaped detection of noticeable effect of these drugs on developing the high pressure nervous syndrome (HPNS). On exposure to the hyperbaric nitrogen-oxygen environment verapromil (phenylalkulamine blocker of L-type calcium channels) had a protection effect with respect to a convulsive component of the nitrogen narcosis.

Modulation of nucleotide sensitivity of ATP-sensitive potassium channels by phosphatidylinositol-4-phosphate 5-kinase.

PubMed

Shyng, S L; Barbieri, A; Gumusboga, A; Cukras, C; Pike, L; Davis, J N; Stahl, P D; Nichols, C G

2000-01-18

ATP-sensitive potassium channels (K(ATP) channels) regulate cell excitability in response to metabolic changes. K(ATP) channels are formed as a complex of a sulfonylurea receptor (SURx), a member of the ATP-binding cassette protein family, and an inward rectifier K(+) channel subunit (Kir6.x). Membrane phospholipids, in particular phosphatidylinositol (PI) 4,5-bisphosphate (PIP(2)), activate K(ATP) channels and antagonize ATP inhibition of K(ATP) channels when applied to inside-out membrane patches. To examine the physiological relevance of this regulatory mechanism, we manipulated membrane PIP(2) levels by expressing either the wild-type or an inactive form of PI-4-phosphate 5-kinase (PIP5K) in COSm6 cells and examined the ATP sensitivity of coexpressed K(ATP) channels. Channels from cells expressing the wild-type PIP5K have a 6-fold lower ATP sensitivity (K(1/2), the half maximal inhibitory concentration, approximately 60 microM) than the sensitivities from control cells (K(1/2) approximately 10 microM). An inactive form of the PIP5K had little effect on the K(1/2) of wild-type channels but increased the ATP-sensitivity of a mutant K(ATP) channel that has an intrinsically lower ATP sensitivity (from K(1/2) approximately 450 microM to K(1/2) approximately 100 microM), suggesting a decrease in membrane PIP(2) levels as a consequence of a dominant-negative effect of the inactive PIP5K. These results show that PIP5K activity, which regulates PIP(2) and PI-3,4,5-P(3) levels, is a significant determinant of the physiological nucleotide sensitivity of K(ATP) channels.

Modulation of nucleotide sensitivity of ATP-sensitive potassium channels by phosphatidylinositol-4-phosphate 5-kinase

PubMed Central

Shyng, S.-L.; Barbieri, A.; Gumusboga, A.; Cukras, C.; Pike, L.; Davis, J. N.; Stahl, P. D.; Nichols, C. G.

2000-01-01

ATP-sensitive potassium channels (KATP channels) regulate cell excitability in response to metabolic changes. KATP channels are formed as a complex of a sulfonylurea receptor (SURx), a member of the ATP-binding cassette protein family, and an inward rectifier K+ channel subunit (Kir6.x). Membrane phospholipids, in particular phosphatidylinositol (PI) 4,5-bisphosphate (PIP2), activate KATP channels and antagonize ATP inhibition of KATP channels when applied to inside-out membrane patches. To examine the physiological relevance of this regulatory mechanism, we manipulated membrane PIP2 levels by expressing either the wild-type or an inactive form of PI-4-phosphate 5-kinase (PIP5K) in COSm6 cells and examined the ATP sensitivity of coexpressed KATP channels. Channels from cells expressing the wild-type PIP5K have a 6-fold lower ATP sensitivity (K1/2, the half maximal inhibitory concentration, ≈ 60 μM) than the sensitivities from control cells (K1/2 ≈ 10 μM). An inactive form of the PIP5K had little effect on the K1/2 of wild-type channels but increased the ATP-sensitivity of a mutant KATP channel that has an intrinsically lower ATP sensitivity (from K1/2 ≈ 450 μM to K1/2 ≈ 100 μM), suggesting a decrease in membrane PIP2 levels as a consequence of a dominant-negative effect of the inactive PIP5K. These results show that PIP5K activity, which regulates PIP2 and PI-3,4,5-P3 levels, is a significant determinant of the physiological nucleotide sensitivity of KATP channels. PMID:10639183

Modulation of inward rectifier potassium channel by toosendanin, a presynaptic blocker.

PubMed

Wang, Z F; Shi, Y L

2001-07-01

The effect of toosendanin, a presynaptic blocker, on the inward rectifier potassium channel (K(Kir)) of hippocampal CA1 pyramidal neurons of rats was studied by the single-channel patch-clamp technique. The results showed that toosendanin had an inhibitory effect on K(Kir) in an excised inside-out patch of the neuron under a symmetrical 150 mM K(+) condition. By decreasing the slower open time constant and increasing the slower close time constant, toosendanin (1x10(-6)-1x10(-4) g/ml) significantly reduced the open probability of the channel in a concentration-dependent manner. Meanwhile, a dose-dependent reduction in unitary conductance of the channel was also detected after toosendanin application. These data offer an explanation for toosendanin-induced facilitation of neurotransmitter release and antibotulismic effect of the drug.

Pharmacological Correction of Trafficking Defects in ATP-sensitive Potassium Channels Caused by Sulfonylurea Receptor 1 Mutations*

PubMed Central

Martin, Gregory M.; Rex, Emily A.; Devaraneni, Prasanna; Denton, Jerod S.; Boodhansingh, Kara E.; DeLeon, Diva D.; Stanley, Charles A.; Shyng, Show-Ling

2016-01-01

ATP-sensitive potassium (KATP) channels play a key role in mediating glucose-stimulated insulin secretion by coupling metabolic signals to β-cell membrane potential. Loss of KATP channel function due to mutations in ABCC8 or KCNJ11, genes encoding the sulfonylurea receptor 1 (SUR1) or the inwardly rectifying potassium channel Kir6.2, respectively, results in congenital hyperinsulinism. Many SUR1 mutations prevent trafficking of channel proteins from the endoplasmic reticulum to the cell surface. Channel inhibitors, including sulfonylureas and carbamazepine, have been shown to correct channel trafficking defects. In the present study, we identified 13 novel SUR1 mutations that cause channel trafficking defects, the majority of which are amenable to pharmacological rescue by glibenclamide and carbamazepine. By contrast, none of the mutant channels were rescued by KATP channel openers. Cross-linking experiments showed that KATP channel inhibitors promoted interactions between the N terminus of Kir6.2 and SUR1, whereas channel openers did not, suggesting the inhibitors enhance intersubunit interactions to overcome channel biogenesis and trafficking defects. Functional studies of rescued mutant channels indicate that most mutants rescued to the cell surface exhibited WT-like sensitivity to ATP, MgADP, and diazoxide. In intact cells, recovery of channel function upon trafficking rescue by reversible sulfonylureas or carbamazepine was facilitated by the KATP channel opener diazoxide. Our study expands the list of KATP channel trafficking mutations whose function can be recovered by pharmacological ligands and provides further insight into the structural mechanism by which channel inhibitors correct channel biogenesis and trafficking defects. PMID:27573238

Diadenosine tetraphosphate-induced inhibition of ATP-sensitive K+ channels in patches excised from ventricular myocytes.

PubMed Central

Jovanovic, A.; Terzic, A.

1996-01-01

Diadenosine 5',5''-P1,P4-tetraphosphate (Ap4A) has been termed 'alarmone' due to its role in intracellular signaling during metabolic stress. It is not known whether Ap4A could modulate ATP-sensitive K+ (KATP) channels, a family of channels regulated by the metabolic status of a cell. We applied the single-channel patch-clamp technique to measure the effect of Ap4A on KATP channels. When applied to the intracellular side of patches, excised from guinea-pig ventricular myocytes, Ap4A inhibited KATP channel activity, in a reversible and concentration-dependent (half-maximal concentration approximately 17 microM) manner. We conclude that Ap4A, a naturally occurring diadenosine polyphosphate, is actually an inhibitor of the myocardial KATP channel. PMID:8789372

A Specific Two-pore Domain Potassium Channel Blocker Defines the Structure of the TASK-1 Open Pore*

PubMed Central

Streit, Anne K.; Netter, Michael F.; Kempf, Franca; Walecki, Magdalena; Rinné, Susanne; Bollepalli, Murali K.; Preisig-Müller, Regina; Renigunta, Vijay; Daut, Jürgen; Baukrowitz, Thomas; Sansom, Mark S. P.; Stansfeld, Phillip J.; Decher, Niels

2011-01-01

Two-pore domain potassium (K2P) channels play a key role in setting the membrane potential of excitable cells. Despite their role as putative targets for drugs and general anesthetics, little is known about the structure and the drug binding site of K2P channels. We describe A1899 as a potent and highly selective blocker of the K2P channel TASK-1. As A1899 acts as an open-channel blocker and binds to residues forming the wall of the central cavity, the drug was used to further our understanding of the channel pore. Using alanine mutagenesis screens, we have identified residues in both pore loops, the M2 and M4 segments, and the halothane response element to form the drug binding site of TASK-1. Our experimental data were used to validate a K2P open-pore homology model of TASK-1, providing structural insights for future rational design of drugs targeting K2P channels. PMID:21362619

St36 electroacupuncture activates nNOS, iNOS and ATP-sensitive potassium channels to promote orofacial antinociception in rats.

PubMed

Almeida, R T; Galdino, G; Perez, A C; Silva, G; Romero, T R; Duarte, I D

2017-02-01

Orofacial pain is pain perceived in the face and/or oral cavity, generally caused by diseases or disorders of regional structures, by dysfunction of the nervous system, or through referral from distant sources. Treatment of orofacial pain is mainly pharmacological, but it has increased the number of reports demonstrating great clinical results with the use of non-pharmacological therapies, among them electroacupuncture. However, the mechanisms involved in the electroacupuncture are not well elucidated. Thus, the present study investigate the involvement of the nitric oxide synthase (NOS) and ATP sensitive K + channels (KATP) in the antinociception induced by electroacupuncture (EA) at acupoint St36. Thermal nociception was applied in the vibrissae region of rats, and latency time for face withdrawal was measured. Electrical stimulation of acupoint St36 for 20 minutes reversed the thermal withdrawal latency and this effect was maintained for 150 min. Intraperitoneal administration of specific inhibitors of neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS) and a KATP channels blocker reversed the antinociception induced by EA. Furthermore, nitrite concentration in cerebrospinal fluid (CSF) and plasma, increased 4 and 3-fold higher, respectively, after EA. This study suggests that NO participates of antinociception induced by EA by nNOS, iNOS and ATP-sensitive K + channels activation.

Ventricular action potential adaptation to regular exercise: role of β-adrenergic and KATP channel function.

PubMed

Wang, Xinrui; Fitts, Robert H

2017-08-01

Regular exercise training is known to affect the action potential duration (APD) and improve heart function, but involvement of β-adrenergic receptor (β-AR) subtypes and/or the ATP-sensitive K + (K ATP ) channel is unknown. To address this, female and male Sprague-Dawley rats were randomly assigned to voluntary wheel-running or control groups; they were anesthetized after 6-8 wk of training, and myocytes were isolated. Exercise training significantly increased APD of apex and base myocytes at 1 Hz and decreased APD at 10 Hz. Ca 2+ transient durations reflected the changes in APD, while Ca 2+ transient amplitudes were unaffected by wheel running. The nonselective β-AR agonist isoproterenol shortened the myocyte APD, an effect reduced by wheel running. The isoproterenol-induced shortening of APD was largely reversed by the selective β 1 -AR blocker atenolol, but not the β 2 -AR blocker ICI 118,551, providing evidence that wheel running reduced the sensitivity of the β 1 -AR. At 10 Hz, the K ATP channel inhibitor glibenclamide prolonged the myocyte APD more in exercise-trained than control rats, implicating a role for this channel in the exercise-induced APD shortening at 10 Hz. A novel finding of this work was the dual importance of altered β 1 -AR responsiveness and K ATP channel function in the training-induced regulation of APD. Of physiological importance to the beating heart, the reduced response to adrenergic agonists would enhance cardiac contractility at resting rates, where sympathetic drive is low, by prolonging APD and Ca 2+ influx; during exercise, an increase in K ATP channel activity would shorten APD and, thus, protect the heart against Ca 2+ overload or inadequate filling. NEW & NOTEWORTHY Our data demonstrated that regular exercise prolonged the action potential and Ca 2+ transient durations in myocytes isolated from apex and base regions at 1-Hz and shortened both at 10-Hz stimulation. Novel findings were that wheel running shifted the �

Synthesis and biological evaluation of pyrrolidine derivatives as novel and potent sodium channel blockers for the treatment of ischemic stroke.

PubMed

Seki, Maki; Tsuruta, Osamu; Tatsumi, Ryo; Soejima, Aki

2013-07-15

A novel series of pyrrolidine derivatives as Na(+) channel blockers was synthesized and evaluated for their inhibitory effects on neuronal Na(+) channels. Structure-activity relationship (SAR) studies of a pyrrolidine analogue 2 led to the discovery of 5e as a potent Na(+) channel blocker with a low inhibitory action against human ether-a-go-go-related gene (hERG) channels. Compound 5e showed remarkably neuroprotective activity in a rat transient middle cerebral artery occlusion (MCAO) model, suggesting that 5e would act as a neuroprotectant for ischemic stroke. Copyright © 2013 Elsevier Ltd. All rights reserved.

Localization and function of ATP-sensitive potassium channels in human skeletal muscle.

PubMed

Nielsen, Jens Jung; Kristensen, Michael; Hellsten, Ylva; Bangsbo, Jens; Juel, Carsten

2003-02-01

The present study investigated the localization of ATP-sensitive K+ (KATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique or the sucrose-gradient technique in combination with Western blotting demonstrated that the KATP channels are mainly located in the sarcolemma. This localization was confirmed by immunohistochemical measurements. With the microdialysis technique, it was demonstrated that local application of the KATP channel inhibitor glibenclamide reduced (P < 0.05) interstitial K+ at rest from approximately 4.5 to 4.0 mM, whereas the concentration in the control leg remained constant. Glibenclamide had no effect on the interstitial K+ accumulation during knee-extensor exercise at a power output of 60 W. In contrast to in vitro conditions, the present study demonstrated that under in vivo conditions the KATP channels are active at rest and contribute to the accumulation of interstitial K+.

Use of calcium channel blockers in hypertrophic cardiomyopathy.

PubMed

Lorell, B H

1985-02-22

Recent studies in patients with either obstructive or nonobstructive hypertrophic cardiomyopathy have suggested that increased resistance to diastolic filling of the stiff left ventricle may be an important mechanism contributing to symptoms. These observations have led to exploration of the effects of calcium channel blockers on systolic and diastolic function in patients with hypertrophic cardiomyopathy. Acute hemodynamic studies using verapamil and nifedipine have shown that these agents tend to cause: (1) a slight fall in systemic arterial pressure and reflex increase in heart rate; (2) a reduction in left ventricular outflow gradient in most but not all patients; and (3) variable effect on left-side heart filling pressures. In contrast to beta-adrenergic blockers, these hemodynamic effects are not associated with depression of systolic function, but appear to be related to improved left ventricular distensibility. Clinical trials have suggested that long-term administration of verapamil in patients with hypertrophic cardiomyopathy promotes improvement in symptomatic status and exercise tolerance in many but not all patients; similar results have been reported in preliminary studies using nifedipine. Potential major adverse effects include depression of sinoatrial activity and atrioventricular conduction with verapamil, and marked hypotension and, rarely, pulmonary edema with both verapamil and nifedipine.

Molecular Mechanism of Action and Selectivity of Sodium Channel Blocker Insecticides

PubMed Central

Silver, Kristopher; Dong, Ke; Zhorov, Boris S.

2017-01-01

Sodium channel blocker insecticides (SCBIs) are a relatively new class of insecticides that are represented by two commercially registered compounds, indoxacarb and metaflumizone. SCBIs, like pyrethroids and DDT, target voltage-gated sodium channels (VGSCs) to intoxicate insects. In contrast to pyrethroids, however, SCBIs inhibit VGSCs at a distinct receptor site that overlaps those of therapeutic inhibitors of sodium channels, such as local anesthetics, anticonvulsants and antiarrhythmics. This review will recount the development of the SCBI insecticide class from its roots as chitin synthesis inhibitors, discuss the symptoms of poisoning and evidence supporting inhibition of VGSCs as their mechanism of action, describe the current model for SCBI-induced inhibition of VGSCs, present a model for the receptor for SCBIs on VGSCs, and highlight differences between data collected from mammalian and insect experimental models. PMID:27993108

Susceptibility of ATP-sensitive K+ channels to cell stress through mediation of phosphoinositides as examined by photoirradiation

PubMed Central

Fan, Zheng; Neff, Robert A

2000-01-01

Cell stress is implicated in a number of pathological states of metabolism, such as ischaemia, reperfusion and apoptosis in heart, neurons and other tissues. While it is known that the ATP-sensitive K+ (KATP) channel plays a role during metabolic abnormality, little information is available about the direct response of this channel to cell stress. Using photoirradiation stimulation, we studied the effects of cell stress on both native and cloned KATP channels. Single KATP channel currents were recorded from cell-attached and inside-out patches of rat ventricular myocytes and COS-1 cells coexpressing SUR2 and Kir6.2. KATP channel activity increased within < 1 min upon irradiation. The activity resulted from increased maximal open probability and decreased ATP inhibition. The effects remained after the irradiation was stopped. Irradiation also affected the channels formed only by Kir6.2ΔC35. The irradiation-induced activation was comparable to that induced by phosphoinositides. Analysis of phosphatidylinositol composition revealed an elevated phosphatidylinositol bisphosphate level with irradiation. Wortmannin, an inhibitor of phosphatidylinositol kinases, decreased both the irradiation-induced channel activity and the production of phosphatidylinositol bisphosphates. Radical scavengers also reduced the irradiation-induced activation, suggesting a role for free radicals, an immediate product of photoirradiation. We conclude that photoirradiation can modify the single-channel properties of KATP, which appears to be mediated by phosphoinositides. Our study suggests that cellular stress may be linked with KATP channels, and we offer a putative mechanism for such a linkage. PMID:11118500

ATP-Sensitive K+ Channel Knockout Induces Cardiac Proteome Remodeling Predictive of Heart Disease Susceptibility

PubMed Central

Arrell, D. Kent; Zlatkovic, Jelena; Kane, Garvan C.; Yamada, Satsuki; Terzic, Andre

2010-01-01

Forecasting disease susceptibility requires detection of maladaptive signatures prior to onset of overt symptoms. A case-in-point are cardiac ATP-sensitive K+ (KATP) channelopathies, for which the substrate underlying disease vulnerability remains to be identified. Resolving molecular pathobiology, even for single genetic defects, mandates a systems platform to reliably diagnose disease predisposition. High-throughput proteomic analysis was here integrated with network biology to decode consequences of Kir6.2 KATP channel pore deletion. Differential two-dimensional gel electrophoresis reproducibly resolved > 800 protein species from hearts of asymptomatic wild-type and Kir6.2-knockout counterparts. KATP channel ablation remodeled the cardiac proteome, significantly altering 71 protein spots, from which 102 unique identities were assigned following hybrid linear ion trap quadrupole-Orbitrap tandem mass spectrometry. Ontological annotation stratified the KATP channel-dependent protein cohort into a predominant bioenergetic module (63 resolved identities), with additional focused sets representing signaling molecules (6), oxidoreductases (8), chaperones (6), and proteins involved in catabolism (6), cytostructure (8), and transcription and translation (5). Protein interaction mapping, in conjunction with expression level changes, localized a KATP channel-associated subproteome within a nonstochastic scale-free network. Global assessment of the KATP channel deficient environment verified the primary impact on metabolic pathways and revealed overrepresentation of markers associated with cardiovascular disease. Experimental imposition of graded stress precipitated exaggerated structural and functional myocardial defects in the Kir6.2-knockout, decreasing survivorship and validating the forecast of disease susceptibility. Proteomic cartography thus provides an integral view of molecular remodeling in the heart induced by KATP channel deletion, establishing a systems

K+ channel openers restore verapamil-inhibited lung fluid resolution and transepithelial ion transport

PubMed Central

2010-01-01

Background Lung epithelial Na+ channels (ENaC) are regulated by cell Ca2+ signal, which may contribute to calcium antagonist-induced noncardiogenic lung edema. Although K+ channel modulators regulate ENaC activity in normal lungs, the therapeutical relevance and the underlying mechanisms have not been completely explored. We hypothesized that K+ channel openers may restore calcium channel blocker-inhibited alveolar fluid clearance (AFC) by up-regulating both apical and basolateral ion transport. Methods Verapamil-induced depression of heterologously expressed human αβγ ENaC in Xenopus oocytes, apical and basolateral ion transport in monolayers of human lung epithelial cells (H441), and in vivo alveolar fluid clearance were measured, respectively, using the two-electrode voltage clamp, Ussing chamber, and BSA protein assays. Ca2+ signal in H441 cells was analyzed using Fluo 4AM. Results The rate of in vivo AFC was reduced significantly (40.6 ± 6.3% of control, P < 0.05, n = 12) in mice intratracheally administrated verapamil. KCa3.1 (1-EBIO) and KATP (minoxidil) channel openers significantly recovered AFC. In addition to short-circuit current (Isc) in intact H441 monolayers, both apical and basolateral Isc levels were reduced by verapamil in permeabilized monolayers. Moreover, verapamil significantly altered Ca2+ signal evoked by ionomycin in H441 cells. Depletion of cytosolic Ca2+ in αβγ ENaC-expressing oocytes completely abolished verapamil-induced inhibition. Intriguingly, KV (pyrithione-Na), K Ca3.1 (1-EBIO), and KATP (minoxidil) channel openers almost completely restored the verapamil-induced decrease in Isc levels by diversely up-regulating apical and basolateral Na+ and K+ transport pathways. Conclusions Our observations demonstrate that K+ channel openers are capable of rescuing reduced vectorial Na+ transport across lung epithelial cells with impaired Ca2+ signal. PMID:20507598

The antiparasitic isoxazoline A1443 is a potent blocker of insect ligand-gated chloride channels.

PubMed

Ozoe, Yoshihisa; Asahi, Miho; Ozoe, Fumiyo; Nakahira, Kunimitsu; Mita, Takeshi

2010-01-01

A structurally unique isoxazoline class compound, A1443, exhibits antiparasitic activity against cat fleas and dog ticks comparable to that of the commercial ectoparasiticide fipronil. This isoxazoline compound inhibits specific binding of the gamma-aminobutyric acid (GABA) receptor channel blocker [(3)H]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB) to housefly-head membranes, with an IC(50) value of 455pM. In contrast, the IC(50) value in rat-brain membranes is>10muM. To study the mode of action of this isoxazoline, we utilized MdGBCl and MdGluCl cDNAs, which encode the subunits of housefly GABA- and glutamate-gated chloride channels, respectively. Two-electrode voltage clamp electrophysiology was used to confirm that A1443 blocks GABA- and glutamate-induced chloride currents in Xenopus oocytes expressing MdGBCl or MdGluCl channels, with IC(50) values of 5.32 and 79.9 nM, respectively. Blockade by A1443 was observed in A2'S-MdGBCl and S2'A-MdGluCl mutant channels at levels similar to those of the respective wild-types, and houseflies expressing A2'S-MdGBCl channels were as susceptible to A1443 as standard houseflies. These findings indicate that A1443 is a novel and specific blocker of insect ligand-gated chloride channels. Copyright 2009 Elsevier Inc. All rights reserved.

AMTB, a TRPM8 channel blocker: evidence in rats for activity in overactive bladder and painful bladder syndrome.

PubMed

Lashinger, Erin S R; Steiginga, Matthew S; Hieble, J Paul; Leon, Lisa A; Gardner, Scott D; Nagilla, Rakesh; Davenport, Elizabeth A; Hoffman, Bryan E; Laping, Nicholas J; Su, Xin

2008-09-01

The activation of the TRPM8 channel, a member of the large class of TRP ion channels, has been reported to be involved in overactive bladder and painful bladder syndrome, although an endogenous activator has not been identified. In this study, N-(3-aminopropyl)-2-{[(3-methylphenyl) methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride salt (AMTB) was evaluated as a TRPM8 channel blocker and used as a tool to evaluate the effects of this class of ion channel blocker on volume-induced bladder contraction and nociceptive reflex responses to noxious bladder distension in the rat. AMTB inhibits icilin-induced TRPM8 channel activation as measured in a Ca(2+) influx assay, with a pIC(50) of 6.23. In the anesthetized rat, intravenous administration of AMTB (3 mg/kg) decreased the frequency of volume-induced bladder contractions, without reducing the amplitude of contraction. The nociceptive response was measured by analyzing both visceromotor reflex (VMR) and cardiovascular (pressor) responses to urinary bladder distension (UBD) under 1% isoflurane. AMTB (10 mg/kg) significantly attenuated reflex responses to noxious UBD to 5.42 and 56.51% of the maximal VMR response and pressor response, respectively. The ID50 value on VMR response was 2.42 +/- 0.46 mg/kg. These results demonstrate that TRPM8 channel blocker can act on the bladder afferent pathway to attenuate the bladder micturition reflex and nociceptive reflex responses in the rat. Targeting TRPM8 channel may provide a new therapeutic opportunity for overactive bladder and painful bladder syndrome.

Pre-electroconvulsive shock administration of calcium channel blockers reduces retrograde amnesia induced by ECS.

PubMed

Sushma, M; Sudha, S; Guido, S

2004-11-01

Effect of pre-electroconvulsive shock (ECS) administration of calcium channel blockers (CCBs) like verapamil, diltiazem, nifedipine, nimodipine, flunarizine and cinnarizine on retrograde amnesia induced by ECS was examined using passive avoidance paradigm in rats. The groups (Gr 1-7) of adult, male Wistar rats received true ECS with CCBs (5mg/kg; i.p) or vehicle (10 ml/kg; ip) and other groups (Gr 8-14) received sham ECS with CCBs (5mg/kg; i.p) or vehicle (10 ml/kg; i.p). The anti-amnestic activity of CCBs were evaluated using the passive avoidance paradigm in rats. Results showed that, the baseline latencies for all the groups did not differ significantly. Rats receiving true ECS produced significantly lower latencies. There was increase in the post ECS step through latencies of the rats administered CCBs before ECS. Therefore, pre-ECS administration of calcium channel blockers might reduce retrograde amnesia produced by ECS without altering seizure duration.

Recent Developments Regarding Voltage-Gated Sodium Channel Blockers for the Treatment of Inherited and Acquired Neuropathic Pain Syndromes

PubMed Central

Theile, Jonathan W.; Cummins, Theodore R.

2011-01-01

Chronic and neuropathic pain constitute significant health problems affecting millions of individuals each year. Pain sensations typically originate in sensory neurons of the peripheral nervous system which relay information to the central nervous system (CNS). Pathological pain sensations can arise as result of changes in excitability of these peripheral sensory neurons. Voltage-gated sodium channels are key determinants regulating action potential generation and propagation; thus, changes in sodium channel function can have profound effects on neuronal excitability and pain signaling. At present, most of the clinically available sodium channel blockers used to treat pain are non-selective across sodium channel isoforms and can contribute to cardio-toxicity, motor impairments, and CNS side effects. Numerous strides have been made over the last decade in an effort to develop more selective and efficacious sodium channel blockers to treat pain. The purpose of this review is to highlight some of the more recent developments put forth by research universities and pharmaceutical companies alike in the pursuit of developing more targeted sodium channel therapies for the treatment of a variety of neuropathic pain conditions. PMID:22007172

Long-term effects of L- and N-type calcium channel blocker on uric acid levels and left atrial volume in hypertensive patients.

PubMed

Masaki, Mitsuru; Mano, Toshiaki; Eguchi, Akiyo; Fujiwara, Shohei; Sugahara, Masataka; Hirotani, Shinichi; Tsujino, Takeshi; Komamura, Kazuo; Koshiba, Masahiro; Masuyama, Tohru

2016-11-01

Left ventricular (LV) diastolic dysfunction is associated with hypertension and hyperuricemia. However, it is not clear whether the L- and N-type calcium channel blocker will improve LV diastolic dysfunction through the reduction of uric acid. The aim of this study was to investigate the effects of anti-hypertensive therapy, the L- and N-type calcium channel blocker, cilnidipine or the L-type calcium channel blocker, amlodipine, on left atrial reverse remodeling and uric acid in hypertensive patients. We studied 62 patients with untreated hypertension, randomly assigned to cilnidipine or amlodipine for 48 weeks. LV diastolic function was assessed with the left atrial volume index (LAVI), mitral early diastolic wave (E), tissue Doppler early diastolic velocity (E') and the ratio (E/E'). Serum uric acid levels were measured before and after treatment. After treatment, systolic and diastolic blood pressures equally dropped in both groups. LAVI, E/E', heart rate and uric acid levels decreased at 48 weeks in the cilnidipine group but not in the amlodipine group. The % change from baseline to 48 weeks in LAVI, E wave, E/E' and uric acid levels were significantly lower in the cilnidipine group than in the amlodipine group. Larger %-drop in uric acid levels were associated with larger %-reduction of LAVI (p < 0.01). L- and N-type calcium channel blocker but not L-type calcium channel blocker may improve LV diastolic function in hypertensive patients, at least partially through the decrease in uric acid levels.

Po2 cycling protects diaphragm function during reoxygenation via ROS, Akt, ERK, and mitochondrial channels.

PubMed

Zuo, Li; Pannell, Benjamin K; Re, Anthony T; Best, Thomas M; Wagner, Peter D

2015-12-01

Po2 cycling, often referred to as intermittent hypoxia, involves exposing tissues to brief cycles of low oxygen environments immediately followed by hyperoxic conditions. After experiencing long-term hypoxia, muscle can be damaged during the subsequent reintroduction of oxygen, which leads to muscle dysfunction via reperfusion injury. The protective effect and mechanism behind Po2 cycling in skeletal muscle during reoxygenation have yet to be fully elucidated. We hypothesize that Po2 cycling effectively increases muscle fatigue resistance through reactive oxygen species (ROS), protein kinase B (Akt), extracellular signal-regulated kinase (ERK), and certain mitochondrial channels during reoxygenation. Using a dihydrofluorescein fluorescent probe, we detected the production of ROS in mouse diaphragmatic skeletal muscle in real time under confocal microscopy. Muscles treated with Po2 cycling displayed significantly attenuated ROS levels (n = 5; P < 0.001) as well as enhanced force generation compared with controls during reperfusion (n = 7; P < 0.05). We also used inhibitors for signaling molecules or membrane channels such as ROS, Akt, ERK, as well as chemical stimulators to close mitochondrial ATP-sensitive potassium channel (KATP) or open mitochondrial permeability transition pore (mPTP). All these blockers or stimulators abolished improved muscle function with Po2 cycling treatment. This current investigation has discovered a correlation between KATP and mPTP and the Po2 cycling pathway in diaphragmatic skeletal muscle. Thus we have identified a unique signaling pathway that may involve ROS, Akt, ERK, and mitochondrial channels responsible for Po2 cycling protection during reoxygenation conditions in the diaphragm. Copyright © 2015 the American Physiological Society.

Hybrid assemblies of ATP-sensitive K+ channels determine their muscle-type-dependent biophysical and pharmacological properties.

PubMed

Tricarico, Domenico; Mele, Antonietta; Lundquist, Andrew L; Desai, Reshma R; George, Alfred L; Conte Camerino, Diana

2006-01-24

ATP-sensitive K(+) channels (K(ATP)) are an octameric complex of inwardly rectifying K(+) channels (Kir6.1 and Kir6.2) and sulfonylurea receptors (SUR1 and SUR2A/B), which are involved in several diseases. The tissue-selective expression of the subunits leads to different channels; however, the composition and role of the functional channel in native muscle fibers is not known. In this article, the properties of K(ATP) channels of fast-twitch and slow-twitch muscles were compared by combining patch-clamp experiments with measurements of gene expression. We found that the density of K(ATP) currents/area was muscle-type specific, being higher in fast-twitch muscles compared with the slow-twitch muscle. The density of K(ATP) currents/area was correlated with the level of Kir6.2 expression. SUR2A was the most abundant subunit expressed in all muscles, whereas the vascular SUR2B subunit was expressed but at lower levels. A significant expression of the pancreatic SUR1 was also found in fast-twitch muscles. Pharmacological experiments showed that the channel response to the SUR1 agonist diazoxide, SUR2A/B agonist cromakalim, SUR1 antagonist tolbutamide, and the SUR1/SUR2A/B-antagonist glibenclamide matched the SURs expression pattern. Muscle-specific K(ATP) subunit compositions contribute to the physiological performance of different muscle fiber types and determine the pharmacological actions of drugs modulating K(ATP) activity in muscle diseases.

Dual role of K ATP channel C-terminal motif in membrane targeting and metabolic regulation.

PubMed

Kline, Crystal F; Kurata, Harley T; Hund, Thomas J; Cunha, Shane R; Koval, Olha M; Wright, Patrick J; Christensen, Matthew; Anderson, Mark E; Nichols, Colin G; Mohler, Peter J

2009-09-29

The coordinated sorting of ion channels to specific plasma membrane domains is necessary for excitable cell physiology. K(ATP) channels, assembled from pore-forming (Kir6.x) and regulatory sulfonylurea receptor subunits, are critical electrical transducers of the metabolic state of excitable tissues, including skeletal and smooth muscle, heart, brain, kidney, and pancreas. Here we show that the C-terminal domain of Kir6.2 contains a motif conferring membrane targeting in primary excitable cells. Kir6.2 lacking this motif displays aberrant channel targeting due to loss of association with the membrane adapter ankyrin-B (AnkB). Moreover, we demonstrate that this Kir6.2 C-terminal AnkB-binding motif (ABM) serves a dual role in K(ATP) channel trafficking and membrane metabolic regulation and dysfunction in these pathways results in human excitable cell disease. Thus, the K(ATP) channel ABM serves as a previously unrecognized bifunctional touch-point for grading K(ATP) channel gating and membrane targeting and may play a fundamental role in controlling excitable cell metabolic regulation.

ATP-sensitive potassium currents from channels formed by Kir6 and a modified cardiac mitochondrial SUR2 variant

PubMed Central

Aggarwal, Nitin T; Shi, Nian-Qing; Makielski, Jonathan C

2013-01-01

Cardiac ATP-sensitive potassium channels (KATP) are found in both the sarcoplasmic reticulum (sarcKATP) and the inner membrane of mitochondria (mitoKATP). SarcKATP are composed of a pore containing subunit Kir6.2 and a regulatory sulfonylurea receptor subunit (SUR2), but the composition of mitoKATP remains unclear. An unusual intra-exonic splice variant of SUR2 (SUR2A-55) was previously identified in mitochondria of mammalian heart and brain, and by analogy with sarcKATP we proposed SUR2A-55 as a candidate regulatory subunit of mitoKATP. Although SUR2A-55 lacks the first nucleotide binding domain (NBD) and 2 transmembrane domains (TMD), it has a hybrid TMD and retains the second NBD. It resembles a hemi-ABC transporter suggesting it could multimerize to function as a regulatory subunit. A putative mitochondrial targeting signal in the N-terminal domain of SUR2A-55 was removed by truncation and when co-expressed with Kir6.1 and Kir6.2 it targeted to the plasma membrane and yielded KATP currents. Single channel conductance, mean open time, and burst open time of SUR2A-55 based KATP was similar to the full-length SUR2A based KATP. However, the SUR2A-55 KATP were 70-fold less sensitive to block by ATP, and twice as resistant to intracellular Ca2+ inhibition compared with the SUR2A KATP, and were markedly insensitive to KATP drugs, pinacidil, diazoxide, and glybenclamide. These results suggest that the SUR2A-55 based channels would tend to be open under physiological conditions and in ischemia, and could account for cardiac and mitochondrial phenotypes protective for ischemia. PMID:24037327

Inhibitors of ATP-sensitive potassium channels in guinea pig isolated ischemic hearts.

PubMed

Weyermann, A; Vollert, H; Busch, A E; Bleich, M; Gögelein, H

2004-04-01

During heart ischemia, ATP-sensitive potassium channels in the sarcolemmal membrane (sarcK(ATP)) open and cause shortening of the action potential duration. This creates heterogeneity of repolarization, being responsible for the development of re-entry arrhythmias and sudden cardiac death. Therefore, the aim is to develop selective blockers of the cardiac sarcK(ATP) channel. In the present study we established an in vitro model and classified 5 K(ATP) channel inhibitors with respect to their potency and selectivity between cardiomyocytes and the coronary vasculature and compared the results with inhibition of Kir6.2/SUR2A channels expressed in HEK293 cells, recorded with the Rb(+)-efflux methods. We used Langendorff-perfused guinea pig hearts, where low-flow ischemia plus hypoxia was performed by reducing the coronary flow (CF) to 1.2 ml/min and by gassing the perfusion solution with N(2) instead of O(2). Throughout the experiment, the monophasic action potential duration at 90% repolarization (MAPD(90)) was recorded. In separate experiments, high-flow hypoxia was produced by oxygen reduction in the perfusate from 95% to 20%, which caused an increase in the coronary flow. Under normoxic conditions, the substances glibenclamide, repaglinide, meglitinide, HMR 1402 and HMR 1098 (1 microM each) reduced the CF by 34%, 38%, 19%, 12% and 5%, respectively. The hypoxia-induced increase in CF was inhibited by the compounds half-maximally at 25 nM, approximately 200 nM, 600 nM, approximately 9 microM and >100 microM, respectively. In control experiments after 5 min low-flow ischemia plus hypoxia, the MAPD(90) shortened from 121+/-2 to 99+/-2 ms ( n=29). This shortening was half-maximally inhibited by the substances at concentrations of 95 nM, 74 nM, 400 nM, 110 nM and 550 nM, respectively. In HEK293 cells the Rb(+)-efflux through KIR6.2/SUR2A channels was inhibited by the compounds with IC(50) values of 21 nM, 67 nM, 205 nM, 60 nM and 181 nM, respectively. In summary, the

Glucose transporters and ATP-gated K+ (KATP) metabolic sensors are present in type 1 taste receptor 3 (T1r3)-expressing taste cells.

PubMed

Yee, Karen K; Sukumaran, Sunil K; Kotha, Ramana; Gilbertson, Timothy A; Margolskee, Robert F

2011-03-29

Although the heteromeric combination of type 1 taste receptors 2 and 3 (T1r2 + T1r3) is well established as the major receptor for sugars and noncaloric sweeteners, there is also evidence of T1r-independent sweet taste in mice, particularly so for sugars. Before the molecular cloning of the T1rs, it had been proposed that sweet taste detection depended on (a) activation of sugar-gated cation channels and/or (b) sugar binding to G protein-coupled receptors to initiate second-messenger cascades. By either mechanism, sugars would elicit depolarization of sweet-responsive taste cells, which would transmit their signal to gustatory afferents. We examined the nature of T1r-independent sweet taste; our starting point was to determine if taste cells express glucose transporters (GLUTs) and metabolic sensors that serve as sugar sensors in other tissues. Using RT-PCR, quantitative PCR, in situ hybridization, and immunohistochemistry, we determined that several GLUTs (GLUT2, GLUT4, GLUT8, and GLUT9), a sodium-glucose cotransporter (SGLT1), and two components of the ATP-gated K(+) (K(ATP)) metabolic sensor [sulfonylurea receptor (SUR) 1 and potassium inwardly rectifying channel (Kir) 6.1] were expressed selectively in taste cells. Consistent with a role in sweet taste, GLUT4, SGLT1, and SUR1 were expressed preferentially in T1r3-positive taste cells. Electrophysiological recording determined that nearly 20% of the total outward current of mouse fungiform taste cells was composed of K(ATP) channels. Because the overwhelming majority of T1r3-expressing taste cells also express SUR1, and vice versa, it is likely that K(ATP) channels constitute a major portion of K(+) channels in the T1r3 subset of taste cells. Taste cell-expressed glucose sensors and K(ATP) may serve as mediators of the T1r-independent sweet taste of sugars.

KATP Channel Mutations and Neonatal Diabetes.

PubMed

Shimomura, Kenju; Maejima, Yuko

2017-09-15

Since the discovery of the K ATP channel in 1983, numerous studies have revealed its physiological functions. The K ATP channel is expressed in various organs, including the pancreas, brain and skeletal muscles. It functions as a "metabolic sensor" that converts the metabolic status to electrical activity. In pancreatic beta-cells, the K ATP channel regulates the secretion of insulin by sensing a change in the blood glucose level and thus maintains glucose homeostasis. In 2004, heterozygous gain-of-function mutations in the KCNJ11 gene, which encodes the Kir6.2 subunit of the K ATP channel, were found to cause neonatal diabetes. In some mutations, diabetes is accompanied by severe neurological symptoms [developmental delay, epilepsy, neonatal diabetes (DEND) syndrome]. This review focuses on mutations of Kir6.2, the pore-forming subunit and sulfonylurea receptor (SUR) 1, the regulatory subunit of the K ATP channel, which cause neonatal diabetes/DEND syndrome and also discusses the findings of the pathological mechanisms that are associated with neonatal diabetes, and its neurological features.

Quantitative Confocal Microscopy Analysis as a Basis for Search and Study of Potassium Kv1.x Channel Blockers

NASA Astrophysics Data System (ADS)

Feofanov, Alexey V.; Kudryashova, Kseniya S.; Nekrasova, Oksana V.; Vassilevski, Alexander A.; Kuzmenkov, Alexey I.; Korolkova, Yuliya V.; Grishin, Eugene V.; Kirpichnikov, Mikhail P.

Artificial KcsA-Kv1.x (x = 1, 3) receptors were recently designed by transferring the ligand-binding site from human Kv1.x voltage-gated potassium channels into corresponding domain of the bacterial KscA channel. We found that KcsA-Kv1.x receptors expressed in E. coli cells are embedded into cell membrane and bind ligands when the cells are transformed to spheroplasts. We supposed that E. coli spheroplasts with membrane-embedded KcsA-Kv1.x and fluorescently labeled ligand agitoxin-2 (R-AgTx2) can be used as elements of an advanced analytical system for search and study of Kv1-channel blockers. To realize this idea, special procedures were developed for measurement and quantitative treatment of fluorescence signals obtained from spheroplast membrane using confocal laser scanning microscopy (CLSM). The worked out analytical "mix and read" systems supported by quantitative CLSM analysis were demonstrated to be reliable alternative to radioligand and electrophysiology techniques in the search and study of selective Kv1.x channel blockers of high scientific and medical importance.

Design, synthesis, and evaluation of polyamine-memantine hybrids as NMDA channel blockers.

PubMed

Kumamoto, Takuya; Nakajima, Marie; Uga, Reina; Ihayazaka, Naoko; Kashihara, Haruna; Katakawa, Kazuaki; Ishikawa, Tsutomu; Saiki, Ryotaro; Nishimura, Kazuhiro; Igarashi, Kazuei

2018-02-01

N-Methyl-d-aspartate (NMDA) receptors have been implicated in learning and memory, and may also play a central role in various conditions leading to neuronal degradation. NMDA receptor antagonists could therefore be of therapeutic benefit for a number of neurological disorders. We have designed hybrid compounds of polyamines and memantine, both of which function as NMDA channel blockers. The triamine derivative with a guanidine moiety showed more potent antagonistic activity than memantine. Copyright © 2017 Elsevier Ltd. All rights reserved.

Remodeling of atrial ATP-sensitive K+ channels in a model of salt-induced elevated blood pressure

PubMed Central

Lader, Joshua M.; Vasquez, Carolina; Bao, Li; Maass, Karen; Qu, Jiaxiang; Kefalogianni, Eirini; Fishman, Glenn I.; Coetzee, William A.

2011-01-01

Hypertension is associated with the development of atrial fibrillation; however, the electrophysiological consequences of this condition remain poorly understood. ATP-sensitive K+ (KATP) channels, which contribute to ventricular arrhythmias, are also expressed in the atria. We hypothesized that salt-induced elevated blood pressure (BP) leads to atrial KATP channel activation and increased arrhythmia inducibility. Elevated BP was induced in mice with a high-salt diet (HS) for 4 wk. High-resolution optical mapping was used to measure atrial arrhythmia inducibility, effective refractory period (ERP), and action potential duration at 90% repolarization (APD90). Excised patch clamping was performed to quantify KATP channel properties and density. KATP channel protein expression was also evaluated. Atrial arrhythmia inducibility was 22% higher in HS hearts compared with control hearts. ERP and APD90 were significantly shorter in the right atrial appendage and left atrial appendage of HS hearts compared with control hearts. Perfusion with 1 μM glibenclamide or 300 μM tolbutamide significantly decreased arrhythmia inducibility and prolonged APD90 in HS hearts compared with untreated HS hearts. KATP channel density was 156% higher in myocytes isolated from HS animals compared with control animals. Sulfonylurea receptor 1 protein expression was increased in the left atrial appendage and right atrial appendage of HS animals (415% and 372% of NS animals, respectively). In conclusion, KATP channel activation provides a mechanistic link between salt-induced elevated BP and increased atrial arrhythmia inducibility. The findings of this study have important implications for the treatment and prevention of atrial arrhythmias in the setting of hypertensive heart disease and may lead to new therapeutic approaches. PMID:21724863

Acute action of rotenone on excitability of catecholaminergic neurons in rostral ventrolateral medulla.

PubMed

Zhang, Zhaoqiang; Shi, Limin; Du, Xixun; Jiao, Qian; Jiang, Hong

2017-09-01

The degeneration of the rostral ventrolateral medulla (RVLM) catecholaminergic neurons was responsible for some cardiovascular symptoms in Parkinson's disease (PD). Our previous study had observed the impairment of these neurons in the early stage of PD in the rotenone-induced PD rat model, but the related mechanisms remain unclear. Rotenone is a mitochondrial inhibitor, influencing the neuronal electrophysiological activity through activation of K-ATP channels that potentially participate in cell death processes. In the present study, effects of rotenone on electrophysiological properties of RVLM catecholaminergic neurons and its underlying mechanisms were investigated. In coronal slices of brain containing the RVLM through patch clamp technique, rotenone (0.5μM) induced gradual postsynaptic inhibition on the spontaneous firing and cell membrane hyperpolarization with outward currents of catecholaminergic neurons. The electrophysiological changes were blocked by glibenclamide (30μM), a blocker of K-ATP channels, and were nearly unchanged by diazoxide (100μM), an opener of K-ATP channels. Our results also showed that effects of rotenone on catecholaminergic neurons including reactive oxygen species (ROS) generation were prevented by pretreatment of coenzyme Q10 (CoQ10, 100μM), a scavenger of ROS. These suggest that rotenone-induced electrophysiological changes of RVLM catecholaminergic neurons are caused by the opening of K-ATP channels, which are partly related to ROS generation. The changes of K-ATP channels might account for the vulnerability of RVLM catecholaminergic neurons. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of Topical Calcium Channel Blockers on Intraocular Pressure in Steroid-induced Glaucoma.

PubMed

Ganekal, Sunil; Dorairaj, Syril; Jhanji, Vishal; Kudlu, Krishnaprasad

2014-01-01

To evaluate the effect of 0.125% verapamil and 0.5% diltiazem eye drops on intraocular pressure (IOP) in steroid-induced glaucoma in rabbit eyes. A total of 18 rabbits with steroid-induced glaucoma were divided into three groups (A, B and C; n = 6 each). Right eyes in groups A, B and C received 0.5% diltiazem, 0.125% verapamil and 0.5% timolol eye drops twice daily for 12 days, respectively; whereas, left eyes received distilled water. IOP was measured with Tono-pen XL at baseline, day 4, day 8, and day 12 of treatment. Both 0.5% diltiazem and 0.125% verapamil eye drops significantly reduced IOP compared to control eyes (p < 0.05). Reduction of IOP by 0.5% diltiazem, 0.125% verapamil eye drops were comparable to 0.5% timolol. No surface toxicity or systemic side effects were noted during the study period. Calcium channel blockers, verapamil, and diltia-zem significantly reduced IOP in rabbiteyes. This group of drugs may have a potential role in treatment of glaucoma How to cite this article: Ganekal S, Dorairaj S, Jhanji V, Kudlu K. Effect of Topical Calcium Channel Blockers on Intraocular Pressure in Steroid-induced Glaucoma. J Current Glau Prac 2014;8(1):15-19.

ATP-sensitive potassium channels participate in glucose uptake in skeletal muscle and adipose tissue.

PubMed

Miki, Takashi; Minami, Kohtaro; Zhang, Li; Morita, Mizuo; Gonoi, Tohru; Shiuchi, Tetsuya; Minokoshi, Yasuhiko; Renaud, Jean-Marc; Seino, Susumu

2002-12-01

ATP-sensitive potassium (K(ATP)) channels are known to be critical in the control of both insulin and glucagon secretion, the major hormones in the maintenance of glucose homeostasis. The involvement of K(ATP) channels in glucose uptake in the target tissues of insulin, however, is not known. We show here that Kir6.2(-/-) mice lacking Kir6.2, the pore-forming subunit of these channels, have no K(ATP) channel activity in their skeletal muscles. A 2-deoxy-[(3)H]glucose uptake experiment in vivo showed that the basal and insulin-stimulated glucose uptake in skeletal muscles and adipose tissues of Kir6.2(-/-) mice is enhanced compared with that in wild-type (WT) mice. In addition, in vitro measurement of glucose uptake indicates that disruption of the channel increases the basal glucose uptake in Kir6.2(-/-) extensor digitorum longus and the insulin-stimulated glucose uptake in Kir6.2(-/-) soleus muscle. In contrast, glucose uptake in adipose tissue, measured in vitro, was similar in Kir6.2(-/-) and WT mice, suggesting that the increase in glucose uptake in Kir6.2(-/-) adipocytes is mediated by altered extracellular hormonal or neuronal signals altered by disruption of the K(ATP) channels.

Cross-talk between ATP-regulated K+ channels and Na+ transport via cellular metabolism in frog skin principal cells.

PubMed Central

Urbach, V; Van Kerkhove, E; Maguire, D; Harvey, B J

1996-01-01

Isolated frog skin epithelium, mounted in an Ussing chamber and bathed in standard NaCl Ringer solution, recycles K+ across the basolateral membrane of principal cells through an inward-rectifier K+ channel (Kir) operating in parallel with a Na+-K+-ATPase pump. Here we report on the metabolic control of the Kir channel using patch clamping, short-circuit current measurement and enzymatic determination of cellular (ATP (ATPi). 2. The constitutively active Kir channel in the basolateral membrane has the characteristics of an ATP-regulated K+ channel and is now classed as a KATP channel. In excised inside-out patches the open probability (Po) of KATP channels was reduced by ATPi with half-maximum inhibition at an ATPi concentration of 50 microM. 3. ATPi measured (under normal Na+ transport conditions) with luciferin-luciferase was 1.50 +/- 0.23 mM (mean +/- S.E.M.; range, 0.4-3.3 mM n = 11). Thus the KATP channel would be expected to be inactive in intact cells if ATPi was the sole regulator of channel activity. KATP channels which were inactivated by 1 mM ATPi in excised patches could be reactivated by addition of 100 microM ADP on the cytosolic side. When added alone, ADP blocks this channel with half-maximal inhibition at [ADPi] > 5 mM. 4. Sulphonylureas inhibit single KATP channels in cell-attached patches as well as the total basolateral K+ current measured in frog skin epithelia perforated with nystatin on the apical side. 5. Na+-K+-ATPase activity is a major determinant of cytosolic ATP. Blocking the pump activity with ouabain produced a time-dependent increase in ATPi and reduced the open probability of KATP channels in cell-attached membranes. 6. We conclude that the ratio of ATP/ADP is an important metabolic coupling factor between the rate of Na+-K+ pumping and K+ recycling. Images Figure 9 PMID:9011625

Effects of caffeine on cytoplasmic free Ca2+ concentration in pancreatic beta-cells are mediated by interaction with ATP-sensitive K+ channels and L-type voltage-gated Ca2+ channels but not the ryanodine receptor.

PubMed Central

Islam, M S; Larsson, O; Nilsson, T; Berggren, P O

1995-01-01

In the pancreatic beta-cell, an increase in the cytoplasmic free Ca2+ concentration ([Ca2+]i) by caffeine is believed to indicate mobilization of Ca2+ from intracellular stores, through activation of a ryanodine receptor-like channel. It is not known whether other mechanisms, as well, underlie caffeine-induced changes in [Ca2+]i. We studied the effects of caffeine on [Ca2+]i by using dual-wavelength excitation microfluorimetry in fura-2-loaded beta-cells. In the presence of a non-stimulatory concentration of glucose, caffeine (10-50 mM) consistently increased [Ca2+]i. The effect was completely blocked by omission of extracellular Ca2+ and by blockers of the L-type voltage-gated Ca2+ channel, such as D-600 or nifedipine. Depletion of agonist-sensitive intracellular Ca2+ pools by thapsigargin did not inhibit the stimulatory effect of caffeine on [Ca2+]i. Moreover, this effect of caffeine was not due to an increase in cyclic AMP, since forskolin and 3-isobutyl-1-methylxanthine (IBMX) failed to raise [Ca2+]i in unstimulated beta-cells. In beta-cells, glucose and sulphonylureas increase [Ca2+]i by causing closure of ATP-sensitive K+ channels (KATP channels). Caffeine also caused inhibition of KATP channel activity, as measured in excised inside-out patches. Accordingly, caffeine (> 10 mM) induced insulin release from beta-cells in the presence of a non-stimulatory concentration of glucose (3 mM). Hence, membrane depolarization and opening of voltage-gated L-type Ca2+ channels were the underlying mechanisms whereby the xanthine drug increased [Ca2+]i and induced insulin release. Paradoxically, in glucose-stimulated beta-cells, caffeine (> 10 mM) lowered [Ca2+]i. This effect was due to the fact that caffeine reduced depolarization-induced whole-cell Ca2+ current through the L-type voltage-gated Ca2+ channel in a dose-dependent manner. Lower concentrations of caffeine (2.5-5.0 mM), when added after glucose-stimulated increase in [Ca2+]i, induced fast oscillations in [Ca2

Isolation of proflavine as a blocker of G protein-gated inward rectifier potassium channels by a cell growth-based screening system.

PubMed

Kawada, Hitoshi; Inanobe, Atsushi; Kurachi, Yoshihisa

2016-10-01

The overexpression of Kir3.2, a subunit of the G protein-gated inwardly rectifying K(+) channel, is implicated in some of the neurological phenotypes of Down syndrome (DS). Chemical compounds that block Kir3.2 are expected to improve the symptoms of DS. The purpose of this study is to develop a cell-based screening system to identify Kir3.2 blockers and then investigate the mode of action of the blocker. Chemical screening was carried out using a K(+) transporter-deficient yeast strain that expressed a constitutively active Kir3.2 mutant. The mode of action of an effective blocker was electrophysiologically analyzed using Kir channels expressed in Xenopus oocytes. Proflavine was identified to inhibit the growth of Kir3.2-transformant cells and Kir3.2 activity in a concentration-dependent manner. The current inhibition was strong when membrane potentials (Vm) was above equilibrium potential of K(+) (EK). When Vm was below EK, the blockage apparently depended on the difference between Vm and [K(+)]. Furthermore, the inhibition became stronger by lowering extracellular [K(+)]. These results indicated that the yeast strain serves as a screening system to isolate Kir3.2 blockers and proflavine is a prototype of a pore blocker of Kir3.2. Copyright © 2016 Elsevier Ltd. All rights reserved.

A G-protein-activated inwardly rectifying K+ channel (GIRK4) from human hippocampus associates with other GIRK channels.

PubMed

Spauschus, A; Lentes, K U; Wischmeyer, E; Dissmann, E; Karschin, C; Karschin, A

1996-02-01

Transcripts of a gene, GIRK4, that encodes for a 419-amino-acid protein and shows high structural similarity to other subfamily members of G-protein-activated inwardly rectifying K+ channels (GIRK) have been identified in the human hippocampus. When expressed in Xenopus oocytes, GIRK4 yielded functional GIRK channels with activity that was enhanced by the stimulation of coexpressed serotonin 1A receptors. GIRK4 potentiated basal and agonist-induced currents mediated by other GIRK channels, possibly because of channel heteromerization. Despite the structural similarity to a putative rat KATP channel, no ATP sensitivity or KATP-typical pharmacology was observed for GIRK4 alone or GIRK4 transfected in conjunction with other GIRK channels in COS-7 cells. In rat brain, GIRK4 is expressed together with three other subfamily members, GIRK1-3, most likely in identical hippocampal neurons. Thus, heteromerization or an unknown molecular interaction may cause the physiological diversity observed within this class of K+ channels.

Angiotensin II receptor blocker-based therapy in Japanese elderly, high-risk, hypertensive patients.

PubMed

Ogawa, Hisao; Kim-Mitsuyama, Shokei; Matsui, Kunihiko; Jinnouchi, Tomio; Jinnouchi, Hideaki; Arakawa, Kikuo

2012-10-01

It is unknown whether high-dose angiotensin II receptor blocker therapy or angiotensin II receptor blocker + calcium channel blocker combination therapy is better in elderly hypertensive patients with high cardiovascular risk. The objective of the study was to compare the efficacy of these treatments in elderly, high-risk Japanese hypertensive patients. The OlmeSartan and Calcium Antagonists Randomized (OSCAR) study was a multicenter, prospective, randomized, open-label, blinded-end point study of 1164 hypertensive patients aged 65 to 84 years with type 2 diabetes or cardiovascular disease. Patients with uncontrolled hypertension during treatment with olmesartan 20 mg/d were randomly assigned to receive 40 mg/d olmesartan (high-dose angiotensin II receptor blocker) or a calcium channel blocker + 20 mg/d olmesartan (angiotensin II receptor blocker + calcium channel blocker). The primary end point was a composite of cardiovascular events and noncardiovascular death. During a 3-year follow-up, blood pressure was significantly lower in the angiotensin II receptor blocker + calcium channel blocker group than in the high-dose angiotensin II receptor blocker group. Mean blood pressure at 36 months was 135.0/74.3 mm Hg in the high-dose angiotensin II receptor blocker group and 132.6/72.6 mm Hg in the angiotensin II receptor blocker + calcium channel blocker group. More primary end points occurred in the high-dose angiotensin II receptor blocker group than in the angiotensin II receptor blocker + calcium channel blocker group (58 vs 48 events, hazard ratio [HR], 1.31, 95% confidence interval, 0.89-1.92; P=.17). In patients with cardiovascular disease at baseline, more primary events occurred in the high-dose angiotensin II receptor blocker group (HR, 1.63, P=.03); in contrast, fewer events were observed in the subgroup without cardiovascular disease (HR, 0.52, P=.14). This treatment-by-subgroup interaction was significant (P=.02). The angiotensin II receptor blocker and

Chronic Glucose Exposure Systematically Shifts the Oscillatory Threshold of Mouse Islets: Experimental Evidence for an Early Intrinsic Mechanism of Compensation for Hyperglycemia

PubMed Central

Glynn, Eric; Thompson, Benjamin; Vadrevu, Suryakiran; Lu, Shusheng; Kennedy, Robert T.; Ha, Joon; Sherman, Arthur

2016-01-01

Mouse islets exhibit glucose-dependent oscillations in electrical activity, intracellular Ca2+ and insulin secretion. We developed a mathematical model in which a left shift in glucose threshold helps compensate for insulin resistance. To test this experimentally, we exposed isolated mouse islets to varying glucose concentrations overnight and monitored their glucose sensitivity the next day by measuring intracellular Ca2+, electrical activity, and insulin secretion. Glucose sensitivity of all oscillation modes was increased when overnight glucose was greater than 2.8mM. To determine whether threshold shifts were a direct effect of glucose or involved secreted insulin, the KATP opener diazoxide (Dz) was coapplied with glucose to inhibit insulin secretion. The addition of Dz or the insulin receptor antagonist s961 increased islet glucose sensitivity, whereas the KATP blocker tolbutamide tended to reduce it. This suggests insulin and glucose have opposing actions on the islet glucose threshold. To test the hypothesis that the threshold shifts were due to changes in plasma membrane KATP channels, we measured cell KATP conductance, which was confirmed to be reduced by high glucose pretreatment and further reduced by Dz. Finally, treatment of INS-1 cells with glucose and Dz overnight reduced high affinity sulfonylurea receptor (SUR1) trafficking to the plasma membrane vs glucose alone, consistent with insulin increasing KATP conductance by altering channel number. The results support a role for metabolically regulated KATP channels in the maintenance of glucose homeostasis. PMID:26697721

Vascular ATP-sensitive potassium channels are over-expressed and partially regulated by nitric oxide in experimental septic shock.

PubMed

Collin, Solène; Sennoun, Nacira; Dron, Anne-Gaëlle; de la Bourdonnaye, Mathilde; Montemont, Chantal; Asfar, Pierre; Lacolley, Patrick; Meziani, Ferhat; Levy, Bruno

2011-05-01

To study the activation and expression of vascular (aorta and small mesenteric arteries) potassium channels during septic shock with or without modulation of the NO pathway. Septic shock was induced in rats by peritonitis. Selective inhibitors of vascular K(ATP) (PNU-37883A) or BK(Ca) [iberiotoxin (IbTX)] channels were used to demonstrate their involvement in vascular hyporeactivity. Vascular response to phenylephrine was measured on aorta and small mesenteric arteries mounted on a wire myograph. Vascular expression of potassium channels was studied by PCR and Western blot, in the presence or absence of 1400W, an inducible NO synthase (iNOS) inhibitor. Aortic activation of the transcriptional factor nuclear factor-kappaB (NF-κB) was assessed by electrophoretic mobility shift assay. Arterial pressure as well as in vivo and ex vivo vascular reactivity were reduced by sepsis and improved by PNU-37883A but not by IbTX. Sepsis was associated with an up-regulation of mRNA and protein expression of vascular K(ATP) channels, while expression of vascular BK(Ca) channels remained unchanged. Selective iNOS inhibition blunted the sepsis-induced increase in aortic NO, decreased NF-κB activation, and down-regulated vascular K(ATP) channel expression. Vascular K(ATP) but not BK(Ca) channels are activated, over-expressed, and partially regulated by NO via NF-κB activation during septic shock. Their selective inhibition restores arterial pressure and vascular reactivity and decreases lactate concentration. The present data suggest that selective vascular K(ATP) channel inhibitors offer potential therapeutic perspectives for septic shock.

Beta-blockers for hypertension

PubMed Central

Wiysonge, Charles S; Bradley, Hazel A; Volmink, Jimmy; Mayosi, Bongani M; Opie, Lionel H

2017-01-01

close to that of the estimate of effect), moderate (if the true effect is likely to be close to the estimate of effect), low (if the true effect may be substantially different from the estimate of effect), and very low (if we are very uncertain about the estimate of effect). Main results Thirteen RCTs met inclusion criteria. They compared beta-blockers to placebo (4 RCTs, 23,613 participants), diuretics (5 RCTs, 18,241 participants), calcium-channel blockers (CCBs: 4 RCTs, 44,825 participants), and renin-angiotensin system (RAS) inhibitors (3 RCTs, 10,828 participants). These RCTs were conducted between the 1970s and 2000s and most of them had a high risk of bias resulting from limitations in study design, conduct, and data analysis. There were 40,245 participants taking beta-blockers, three-quarters of them taking atenolol. We found no outcome trials involving the newer vasodilating beta-blockers (e.g. nebivolol). There was no difference in all-cause mortality between beta-blockers and placebo (RR 0.99, 95% CI 0.88 to 1.11), diuretics or RAS inhibitors, but it was higher for beta-blockers compared to CCBs (RR 1.07, 95% CI 1.00 to 1.14). The evidence on mortality was of moderate-certainty for all comparisons. Total CVD was lower for beta-blockers compared to placebo (RR 0.88, 95% CI 0.79 to 0.97; low-certainty evidence), a reflection of the decrease in stroke (RR 0.80, 95% CI 0.66 to 0.96; low-certainty evidence) since there was no difference in coronary heart disease (CHD: RR 0.93, 95% CI 0.81 to 1.07; moderate-certainty evidence). The effect of beta-blockers on CVD was worse than that of CCBs (RR 1.18, 95% CI 1.08 to 1.29; moderate-certainty evidence), but was not different from that of diuretics (moderate-certainty) or RAS inhibitors (low-certainty). In addition, there was an increase in stroke in beta-blockers compared to CCBs (RR 1.24, 95% CI 1.11 to 1.40; moderate-certainty evidence) and RAS inhibitors (RR 1.30, 95% CI 1.11 to 1.53; moderate-certainty evidence

Levcromakalim- and isoprenaline-induced relaxation of human isolated airways--role of the epithelium and of K+ channel activation.

PubMed

Black, J L; Johnson, P R; McKay, K O; Carey, D; Armour, C L

1994-06-01

In this study we have investigated the mechanism of action of levcromakalim and isoprenaline in human isolated airways with respect to the K+ channels they activate and the possibility that these smooth muscle relaxants activate K+ channels on the airway epithelium. Mechanical removal of the epithelial layer (mean percentage of epithelium present 20 +/- 3%, n = 20 tissues) did not affect the relaxation responses to levcromakalim or isoprenaline, either in terms of maximal relaxation or sensitivity. Whilst having no effect on isoprenaline-induced relaxation, studied from basal tone, the ATP-sensitive K+ channel blocker BRL 31660 (10, 30 and 50 microM) reduced relaxation responses induced (from basal tone) by levcromakalim from 74 +/- 6% (of the maximal response to isoprenaline) to 48 +/- 12% (n = 7), 9 +/- 9% (n = 4) and 0 (n = 4), respectively. Charybdotoxin, a blocker of high conductance Ca(2+)-activated K+ channels, at concentrations of 30 and 100 nM, had no effect on either levcromakalim- or or isoprenaline-induced relaxation responses and yet charybdotoxin was active at KCa channels in outside-out patches of hippocampal granule cells. Moreover, tetraethylammonium (10 mM) inhibited neither isoprenaline- nor levcromakalim-induced relaxation. This study has demonstrated that the relaxation responses elicited in human bronchus to isoprenaline and levcromakalim are likely to be the result of direct effects on the smooth muscle with no contribution from epithelial receptors or K+ channels. The actions of levcromakalim appear to be mediated only via activation of KATP channels. Further, we have made the important observation that, under the experimental conditions of our study, isoprenaline does not activate the KCa channel to produce relaxation in human bronchus.

Cilnidipine, an L/N-type calcium channel blocker prevents acquisition and expression of ethanol-induced locomotor sensitization in mice.

PubMed

Bhutada, Pravinkumar; Mundhada, Yogita; Patil, Jayshree; Rahigude, Anand; Zambare, Krushna; Deshmukh, Prashant; Tanwar, Dhanshree; Jain, Kishor

2012-04-11

Several evidences indicated the involvement of L- and N-type calcium channels in behavioral effects of drugs of abuse, including ethanol. Calcium channels are implicated in ethanol-induced behaviors and neurochemical responses. Calcium channel antagonists block the psychostimulants induced behavioral sensitization. Recently, it is demonstrated that L-, N- and T-type calcium channel blockers attenuate the acute locomotor stimulant effects of ethanol. However, no evidence indicated the role of calcium channels in ethanol-induced psychomotor sensitization. Therefore, present study evaluated the influence of cilnidipine, an L/N-type calcium channel blocker on acquisition and expression of ethanol-induced locomotor sensitization. The results revealed that cilnidipine (0.1 and 1.0μg/mouse, i.c.v.) attenuates the expression of sensitization to locomotor stimulant effect of ethanol (2.0g/kg, i.p.), whereas pre- treatment of cilnidipine (0.1 and 1.0μg/mouse, i.c.v.) during development of sensitization blocks acquisition and attenuates expression of sensitization to locomotor stimulant effect of ethanol. Cilnidipine per se did not influence locomotor activity in tested doses. Further, cilnidipine had no influence on effect of ethanol on rotarod performance. These results support the hypothesis that neuroadaptive changes in calcium channels participate in the acquisition and the expression of ethanol-induced locomotor sensitization. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

The effect of long-term administered CRAC channels blocker on the functions of respiratory epithelium in guinea pig allergic asthma model.

PubMed

Sutovska, Martina; Kocmalova, Michaela; Joskova, Marta; Adamkov, Marian; Franova, Sona

2015-04-01

Previously, therapeutic potency of CRAC channels blocker was evidenced as a significant decrease in airway smooth muscle hyperreactivity, antitussive and anti-inflammatory effects. The major role of the respiratory epithelium in asthma pathogenesis was highlighted only recently and CRAC channels were proposed as the most significant route of Ca2+ entry into epithelial cells. The aim of the study was to analyse the impact of long-term administered CRAC channels blocker on airway epithelium, e.g. cytokine production and ciliary beat frequency (CBF) using an animal model of allergic asthma. Ovalbumin-induced allergic airway inflammation of guinea pigs was followed by long-term (14 days lasted) therapy by CRAC blocker (3-fluoropyridine-4-carboxylic acid, FPCA). The influence of long-term therapy on cytokines (IL-4, IL-5 and IL-13) in BALF and in plasma, immunohistochemical staining of pulmonary tissue (c-Fos positivity) and CBF in vitro were used for analysis. Decrease in cytokine levels and in c-Fos positivity confirmed an anti-inflammatory effect of long-term administered FPCA. Cytokine levels in BALF and distribution of c-Fos positivity suggested that FPCA was a more potent inhibitor of respiratory epithelium secretory functions than budesonide. FPCA and budesonide reduced CBF only insignificantly. All findings supported CRAC channels as promising target in the new strategy of antiasthmatic treatment.

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.

The K(ATP)+ channel is involved in a low-amplitude permeability transition in plant mitochondria.

PubMed

Petrussa, Elisa; Casolo, Valentino; Peresson, Carlo; Braidot, Enrico; Vianello, Angelo; Macrì, Francesco

2004-04-01

Pea (Pisum sativum) stem mitochondria, energized by NADH, succinate or malate plus glutamate, underwent a spontaneous low-amplitude permeability transition (PT), which could be monitored by dissipation of the electrical potential (deltapsi) or swelling. The occurrence of the latter effects was dependent on O2 availability, because O2 shortage anticipated the manifestation of both deltapsi dissipation and swelling. Spontaneous deltapsi collapse was also monitored in sucrose-resuspended mitochondria and again O2 deprivation caused an anticipation of the phenomenon. However, in this case deltapsi dissipation was not accompanied by a parallel mitochondrial swelling. The latter effect was, indeed, evident only if mitochondria were resuspended in KCl (as osmoticum), or other cations with a molecular mass up to 100 Da (choline+). PT was also induced by protonophores (carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) or free fatty acids) or valinomycin (only in KCl). The FCCP-induced dissipation of deltapsi and swelling were inhibited by ATP and stimulated (anticipated) by cyclosporin A or O2 shortage. The FCCP-induced PT was accompanied by the release of pyridine nucleotides from the matrix and of cytochrome c from the intermembrane space of KCl-resuspended mitochondria. The spontaneous and FCCP-induced low-amplitude PT of plant mitochondria are interpreted as due to the activity of a recently identified K(ATP)+ channel whose open/closed state is dependent on polarization of the inner membrane and on the oxidoreductive state of some sulfhydryl groups.

Regulation of ENaC and CFTR expression with K+ channel modulators and effect on fluid absorption across alveolar epithelial cells.

PubMed

Leroy, Claudie; Privé, Anik; Bourret, Jean-Charles; Berthiaume, Yves; Ferraro, Pasquale; Brochiero, Emmanuelle

2006-12-01

In a recent study (Leroy C, Dagenais A, Berthiaume Y, and Brochiero E. Am J Physiol Lung Cell Mol Physiol 286: L1027-L1037, 2004), we identified an ATP-sensitive K(+) (K(ATP)) channel in alveolar epithelial cells, formed by inwardly rectifying K(+) channel Kir6.1/sulfonylurea receptor (SUR)2B subunits. We found that short applications of K(ATP), voltage-dependent K(+) channel KvLQT1, and calcium-activated K(+) (K(Ca)) channel modulators modified Na(+) and Cl(-) currents in alveolar monolayers. In addition, it was shown previously that a K(ATP) opener increased alveolar liquid clearance in human lungs by a mechanism possibly related to epithelial sodium channels (ENaC). We therefore hypothesized that prolonged treatment with K(+) channel modulators could induce a sustained regulation of ENaC activity and/or expression. Alveolar monolayers were treated for 24 h with inhibitors of K(ATP), KvLQT1, and K(Ca) channels identified by PCR. Glibenclamide and clofilium (K(ATP) and KvLQT1 inhibitors) strongly reduced basal transepithelial current, amiloride-sensitive Na(+) current, and forskolin-activated Cl(-) currents, whereas pinacidil, a K(ATP) activator, increased them. Interestingly, K(+) inhibitors or membrane depolarization (induced by valinomycin in high-K(+) medium) decreased alpha-, beta-, and gamma-ENaC and CFTR mRNA. alpha-ENaC and CFTR proteins also declined after glibenclamide or clofilium treatment. Conversely, pinacidil augmented ENaC and CFTR mRNAs and proteins. Since alveolar fluid transport was found to be driven, at least in part, by Na(+) transport through ENaC, we tested the impact of K(+) channel modulators on fluid absorption across alveolar monolayers. We found that glibenclamide and clofilium reduced fluid absorption to a level similar to that seen in the presence of amiloride, whereas pinacidil slightly enhanced it. Long-term regulation of ENaC and CFTR expression by K(+) channel activity could benefit patients with pulmonary diseases affecting ion

Misperceptions About β-Blockers and Diuretics

PubMed Central

Ubel, Peter A; Jepson, Christopher; Asch, David A

2003-01-01

BACKGROUND Based on a series of clinical trials showing no difference in the effectiveness or tolerability of most major classes of antihypertensive medications, the Joint National Commission on High Blood Pressure Treatment recommends that physicians prescribe β-blockers or diuretics as initial hypertensive therapy unless there are compelling indications for another type of medication. Nevertheless, many physicians continue to favor more expensive medications like angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers as first line agents. The persistent use of these agents raises questions as to whether physicians perceive ACE inhibitors and calcium channel blockers to be better than β-blockers and diuretics. METHODS We surveyed 1,200 primary care physicians in 1997, and another 500 primary care physicians in 2000, and asked them to estimate the relative effectiveness and side effects of 4 classes of medication in treating a hypothetical patient with uncomplicated hypertension: ACE inhibitors, β-blockers, calcium channel blockers, and diuretics. In addition, we asked them to indicate whether they ever provided free samples of hypertension medications to their patients. RESULTS Perceptions of the relative effectiveness and side effects of the 4 classes of hypertension medications did not significantly change over the 3 years, nor did prescription recommendations. Physicians perceive that diuretics are less effective at lowering blood pressure than the other 3 classes (P < .001). They also perceive that β-blockers are less tolerated than the other 3 classes (P < .001). In a multivariate model, perceptions of effectiveness and tolerability displayed significant associations with prescription preference independent of background variables. The only other variable to contribute significantly to the model was provision of free medication samples to patients. CONCLUSIONS Despite numerous clinical trials showing no difference in the effectiveness

Treatment of essential hypertension with calcium channel blockers: what is the place of lercanidipine?

PubMed

Burnier, Michel; Pruijm, Menno; Wuerzner, Gregoire

2009-08-01

In all actual clinical guidelines, dihydropyridine calcium channel blockers (CCBs) belong to the recommended first line antihypertensive drugs to treat essential hypertension. Several recent large clinical trials have confirmed their efficacy not only in lowering blood pressure but also in reducing cardiovascular morbidity and mortality in hypertensive patients with a normal or high cardiovascular risk profile. In clinical trials such as ALLHAT, VALUE or ASCOT, an amlodipine-based therapy was at least as effective, when not slightly superior, in lowering blood pressure and sometimes more effective in preventing target organ damages than blood pressure lowering strategies based on the use of diuretics, beta-blockers and blockers of the renin-angiotensin system. One of the main clinical side effects of the first and second generation CCBs including amlodipine is the development of peripheral edema. The incidence of leg edema can be markedly reduced by combining the CCB with a blocker of the renin-angiotensin system. This strategy has now led to the development of several fixed-dose combinations of amlodipine and angiotensin II receptor antagonists. Another alternative to lower the incidence of edema is to use CCBs of the third generation such as lercanidipine. Indeed, although no major clinical trials have been conducted with this compound, clinical studies have shown that lercanidipine and amlodipine have a comparable antihypertensive efficacy but with significantly less peripheral edema in patients receiving lercanidipine. In some countries, lercanidipine is now available in a single-pill association with an ACE inhibitor thereby further improving its efficacy and tolerability profile.

Development of selective blockers for Ca2+-activated Cl- channel using Xenopus laevis oocytes with an improved drug screening strategy

PubMed Central

Oh, Soo-Jin; Park, Jung Hwan; Han, Sungyu; Lee, Jae Kyun; Roh, Eun Joo; Lee, C Justin

2008-01-01

Background Ca2+-activated Cl- channels (CaCCs) participate in many important physiological processes. However, the lack of effective and selective blockers has hindered the study of these channels, mostly due to the lack of good assay system. Here, we have developed a reliable drug screening method for better blockers of CaCCs, using the endogeneous CaCCs in Xenopus laevis oocytes and two-electrode voltage-clamp (TEVC) technique. Results Oocytes were prepared with a treatment of Ca2+ ionophore, which was followed by a treatment of thapsigargin which depletes Ca2+ stores to eliminate any contribution of Ca2+ release. TEVC was performed with micropipette containing chelerythrine to prevent PKC dependent run-up or run-down. Under these conditions, Ca2+-activated Cl- currents induced by bath application of Ca2+ to oocytes showed stable peak amplitude when repetitively activated, allowing us to test several concentrations of a test compound from one oocyte. Inhibitory activities of commercially available blockers and synthesized anthranilic acid derivatives were tested using this method. As a result, newly synthesized N-(4-trifluoromethylphenyl)anthranilic acid with trifluoromethyl group (-CF3) at para position on the benzene ring showed the lowest IC50. Conclusion Our results provide an optimal drug screening strategy suitable for high throughput screening, and propose N-(4-trifluoromethylphenyl)anthranilic acid as an improved CaCC blocker. PMID:18959787

An orally active TRPV4 channel blocker prevents and resolves pulmonary edema induced by heart failure.

PubMed

Thorneloe, Kevin S; Cheung, Mui; Bao, Weike; Alsaid, Hasan; Lenhard, Stephen; Jian, Ming-Yuan; Costell, Melissa; Maniscalco-Hauk, Kristeen; Krawiec, John A; Olzinski, Alan; Gordon, Earl; Lozinskaya, Irina; Elefante, Lou; Qin, Pu; Matasic, Daniel S; James, Chris; Tunstead, James; Donovan, Brian; Kallal, Lorena; Waszkiewicz, Anna; Vaidya, Kalindi; Davenport, Elizabeth A; Larkin, Jonathan; Burgert, Mark; Casillas, Linda N; Marquis, Robert W; Ye, Guosen; Eidam, Hilary S; Goodman, Krista B; Toomey, John R; Roethke, Theresa J; Jucker, Beat M; Schnackenberg, Christine G; Townsley, Mary I; Lepore, John J; Willette, Robert N

2012-11-07

Pulmonary edema resulting from high pulmonary venous pressure (PVP) is a major cause of morbidity and mortality in heart failure (HF) patients, but current treatment options demonstrate substantial limitations. Recent evidence from rodent lungs suggests that PVP-induced edema is driven by activation of pulmonary capillary endothelial transient receptor potential vanilloid 4 (TRPV4) channels. To examine the therapeutic potential of this mechanism, we evaluated TRPV4 expression in human congestive HF lungs and developed small-molecule TRPV4 channel blockers for testing in animal models of HF. TRPV4 immunolabeling of human lung sections demonstrated expression of TRPV4 in the pulmonary vasculature that was enhanced in sections from HF patients compared to controls. GSK2193874 was identified as a selective, orally active TRPV4 blocker that inhibits Ca(2+) influx through recombinant TRPV4 channels and native endothelial TRPV4 currents. In isolated rodent and canine lungs, TRPV4 blockade prevented the increased vascular permeability and resultant pulmonary edema associated with elevated PVP. Furthermore, in both acute and chronic HF models, GSK2193874 pretreatment inhibited the formation of pulmonary edema and enhanced arterial oxygenation. Finally, GSK2193874 treatment resolved pulmonary edema already established by myocardial infarction in mice. These findings identify a crucial role for TRPV4 in the formation of HF-induced pulmonary edema and suggest that TRPV4 blockade is a potential therapeutic strategy for HF patients.

Efficient syntheses of polyamine and polyamine amide voltage-sensitive calcium channel blockers: FTX-3.3 and sFTX-3.3.

PubMed

Moya, E; Blagbrough, I S

1996-02-01

Efficient syntheses of FTX-3.3 and sFTX-3.3, voltage-sensitive calcium channel blockers are described. These modified polyamines were prepared from selectively protected polyamines and purified on a practical scale.

Calcium channel blockers in hypertension: reappraisal after new trials and major meta-analyses.

PubMed

Opie, L H

2001-10-01

This review evaluates the current position of calcium channel blockers (CCB) in antihypertensive treatment in the light of three major comparative studies and two extensive meta-analyses. The latter both show that CCB are equivalent to conventional (initial beta-blocker or diuretic therapy) when total and cardiovascular mortality are the end points. Divergent points between the meta-analyses include stroke and myocardial infarction (MI). One meta-analysis compared CCB with conventional therapy, to find a small 13% reduction in stroke and a small, nonsignificant 12% increase in MI. The other meta-analysis found a 26% increase in MI when CCB were compared with all other therapies including the angiotensin converting enzyme (ACE) inhibitors. This increase was most robust (P < .001) when comparing CCB with ACE inhibitors, consonant with proposed protective effects of ACE inhibitors on cardiovascular risk. At present, only the comparison of CCB with conventional therapy, and not that with ACE inhibitors, rests on secure comparative data. When cost is compelling, conventional therapy is less expensive. For the individual patient, issues of quality of life (for example, impotence with diuretics and beta-blockers) might be decisive. Nonetheless, beta-blockers are preferred in postinfarct patients or in those with heart failure or unstable angina (a contraindication to dihydropyridines in the absence of beta-blockade). In others, the benefits of only a borderline stroke reduction with CCB versus an equally borderline increase in MI should be evaluated for each individual patient, taking into account the age group and the patient's preferences. In conclusion, overall CCB are neither better nor worse than conventional therapy, allowing for possible small differences in stroke and MI. The ACE inhibitors may protect better, although data are incomplete.

Remote ischaemic preconditioning and prevention of cerebral injury.

PubMed

Rehni, Ashish K; Shri, Richa; Singh, Manjeet

2007-03-01

Bilateral carotid artery occlusion of 10 min followed by reperfusion for 24 hr was employed in present study to produce ischaemia and reperfusion induced cerebral injury in mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Short-term memory was evaluated using elevated plus maze. Inclined beam walking test was employed to assess motor incoordination. Bilateral carotid artery occlusion followed by reperfusion produced cerebral infarction and impaired short-term memory, motor co-ordination and lateral push response. A preceding episode of mesenteric artery occlusion for 15 min and reperfusion of 15 min (remote mesenteric ischaemic preconditioning) prevented markedly ischaemia-reperfusion-induced cerebral injury measured in terms of infarct size, loss of short-term memory, motor coordination and lateral push response. Glibenclamide (5 mg/kg, iv) a KATP channel blocker and caffeine (7 mg/kg, iv) an adenosine receptor blocker attenuated the neuroprotective effect of remote mesenteric ischaemic preconditioning. It may be concluded that neuroprotective effect of remote mesenteric ischaemic preconditioning may be due to activation of adenosine receptors and consequent activation of KATP channels in mice.

A Critical Assessment of Combined Ligand-based and Structure-based Approaches to hERG Channel Blocker Modeling

PubMed Central

Du-Cuny, Lei; Chen, Lu; Zhang, Shuxing

2014-01-01

Blockade of hERG channel prolongs the duration of the cardiac action potential and is a common reason for drug failure in preclinical safety trials. Therefore, it is of great importance to develop robust in silico tools to predict potential hERG blockers in the early stages of drug discovery and development. Herein we described comprehensive approaches to assess the discrimination of hERG-active and -inactive compounds by combining QSAR modeling, pharmacophore analysis, and molecular docking. Our consensus models demonstrated high predictive capacity and improved enrichment, and they could correctly classify 91.8% of 147 hERG blockers from 351 inactives. To further enhance our modeling effort, hERG homology models were constructed and molecular docking studies were conducted, resulting in high correlations (R2=0.81) between predicted and experimental binding affinities. We expect our unique models can be applied to efficient screening for hERG blockades, and our extensive understanding of the hERG-inhibitor interactions will facilitate the rational design of drugs devoid of hERG channel activity and hence with reduced cardiac toxicities. PMID:21902220

Antileishmanial activity and ultrastructural alterations of Leishmania (L.) chagasi treated with the calcium channel blocker nimodipine.

PubMed

Tempone, André Gustavo; Taniwaki, Noemi Nosomi; Reimão, Juliana Quero

2009-08-01

In a search for novel antileishmanial drugs, we investigated the activity of the calcium channel blocker nimodipine against Leishmania spp. and explored the ultrastructural damages of parasites induced by nimodipine after a short period of incubation. Nimodipine was highly effective against promastigotes and intracellular amastigotes of Leishmania (L.) chagasi, with 50% inhibitory concentration values of 81.2 and 21.5 muM, respectively. Nimodipine was about fourfold more effective than the standard pentavalent antimony against amastigotes and showed a Selectivity Index of 4.4 considering its mammalian cells toxicity. Leishmania (L.) amazonensis and Leishmania (L.) major promastigotes were also susceptible to nimodipine in a range concentration between 31 and 128 muM. Ultrastructural studies of L. (L.) chagasi revealed intense mitochondria damage and plasma membrane blebbing, resulting in a leishmanicidal effect as demonstrated by the lack of mitochondrial oxidative metabolism. The amastigote-killing effect suggests other mechanism than macrophage activation, as no upregulation of nitric oxide was seen. This calcium channel blocker is an effective in vitro antileishmanial compound and if adequately studied could be used as a novel drug candidate or as a novel drug lead compound for drug design studies against leishmaniasis.

Creatine kinase is physically associated with the cardiac ATP-sensitive k+ channel in vivo

PubMed Central

Crawford, Russell M.; Ranki, Harri J.; Botting, Catherine H.; Budas, Grant R.; Jovanovic, Aleksandar

2007-01-01

Cardiac sarcolemmal ATP-sensitive K+ (KATP) channels, composed of Kir6.2 and SUR2A subunits, couple the metabolic status of cells with the membrane excitability. Based on previous functional studies, we have hypothesized that creatine kinase (CK) may be a part of the sarcolemmal KATP channel protein complex. The inside-out and whole cell patch clamp electrophysiology applied on guinea pig cardiomyocytes showed that substrates of CK regulate KATP channels activity. Following immunoprecipitation of guinea-pig cardiac membrane fraction with the anti-SUR2 antibody, Coomassie blue staining revealed, besides Kir6.2 and SUR2A, a polypeptide at ∼48 kDa. Western blotting analysis confirmed the nature of putative Kir6.2 and SUR2A, whereas matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis identified p48 kDa as a muscle form of CK. In addition, the CK activity was found in the anti-SUR2A immunoprecipitate and the cross reactivity between an anti-CK antibody and the anti-SUR2A immunoprecipitate was observed as well as vice verse. Further results obtained at the level of recombinant channel subunits demonstrated that CK is directly physically associated with the SUR2A, but not the Kir6.2, subunit. All together, these results suggest that the CK is associated with SUR2A subunit in vivo, which is an integral part of the sarcolemmal KATP channel protein complex. PMID:11729098

Beta-blockers and cardiovascular outcomes in dialysis patients: a cohort study in Ontario, Canada.

PubMed

Kitchlu, Abhijat; Clemens, Kristin; Gomes, Tara; Hackam, Daniel G; Juurlink, David N; Mamdani, Muhammad; Manno, Michael; Oliver, Matthew J; Quinn, Robert R; Suri, Rita S; Wald, Ron; Yan, Andrew T; Garg, Amit X

2012-04-01

Beta-blockers may be cardioprotective in patients receiving chronic dialysis. We examined cardiovascular outcomes among incident dialysis patients receiving beta-blocker therapy. We conducted a retrospective cohort study employing linked healthcare databases in Ontario, Canada. We studied all consecutive chronic dialysis patients aged≥66 years who initiated dialysis between 1 July 1991 and 31 July 2007. Patients were divided into three groups according to new medication use after the initiation of chronic dialysis. The three groups were patients initiated on beta-blockers, calcium channel blockers and statins only. Patients in the beta-blocker and calcium channel blocker groups could also be concurrently receiving a statin. The primary outcome was time to a composite endpoint of death, myocardial infarction, stroke or coronary revascularization. There were a total of 1836 patients (504 beta-blocker, 570 calcium channel blocker and 762 statin-only users). Compared to statin-only use, beta-blocker use was not associated with improved cardiovascular outcomes [adjusted hazard ratio (aHR) 1.07, 95% confidence interval (CI) 0.92-1.23]. As expected, calcium channel blocker use was also not associated with improved cardiovascular outcomes (aHR 0.91, 95% CI 0.79-1.06). Among all subgroup analyses by beta-blocker attributes, only high-dose beta-blocker therapy was associated with better cardiovascular outcomes as compared to low-dose beta-blockers (aHR 0.50, 95% CI 0.29-0.88). We observed no beneficial effect of beta-blocker use among patients receiving chronic dialysis relative to our comparator groups. Given current uncertainty around the cardioprotective benefits of beta-blockers in patients receiving dialysis, a large randomized clinical trial is warranted.

Antagonism of Lidocaine Inhibition by Open-Channel Blockers That Generate Resurgent Na Current

PubMed Central

Bant, Jason S.; Aman, Teresa K.; Raman, Indira M.

2013-01-01

Na channels that generate resurgent current express an intracellular endogenous open-channel blocking protein, whose rapid binding upon depolarization and unbinding upon repolarization minimizes fast and slow inactivation. Na channels also bind exogenous compounds, such as lidocaine, which functionally stabilize inactivation. Like the endogenous blocking protein, these use-dependent inhibitors bind most effectively at depolarized potentials, raising the question of how lidocaine-like compounds affect neurons with resurgent Na current. We therefore recorded lidocaine inhibition of voltage-clamped, tetrodotoxin-sensitive Na currents in mouse Purkinje neurons, which express a native blocking protein, and in mouse hippocampal CA3 pyramidal neurons with and without a peptide from the cytoplasmic tail of NaVβ4 (the β4 peptide), which mimics endogenous open-channel block. To control channel states during drug exposure, lidocaine was applied with rapid-solution exchange techniques during steps to specific voltages. Inhibition of Na currents by lidocaine was diminished by either the β4 peptide or the native blocking protein. In peptide-free CA3 cells, prolonging channel opening with a site-3 toxin, anemone toxin II, reduced lidocaine inhibition; this effect was largely occluded by open-channel blockers, suggesting that lidocaine binding is favored by inactivation but prevented by open-channel block. In constant 100 μM lidocaine, current-clamped Purkinje cells continued to fire spontaneously. Similarly, the β4 peptide reduced lidocaine-dependent suppression of spiking in CA3 neurons in slices. Thus, the open-channel blocking protein responsible for resurgent current acts as a natural antagonist of lidocaine. Neurons with resurgent current may therefore be less susceptible to use-dependent Na channel inhibitors used as local anesthetic, antiarrhythmic, and anticonvulsant drugs. PMID:23486968

Cadmium and calcium uptake in the mollusc donax rugosus and effect of a calcium channel blocker

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

Sidoumou, Z.; Gnassia-Barelli, M.; Romeo, M.

Donax rugosus, a common bivalve mollusc in the coastal waters of Mauritania, has been studied for trace metal concentrations as a function of sampling site (from South of Mauritania to the North of this country) and of season. In this paper, the uptake of cadmium was experimentally studied in the different organs of D. rugosus. Since metals such as cadmium, copper and mercury may alter calcium homeostasis, calcium uptake was also studied in the animals treated with cadmium. Since calcium is taken up through specific channels, it appears that metals inhibit Ca uptake by interacting with these channels in themore » plasma membrane. Cadmium and calcium have very similar atomic radii, thus cadmium may be taken up through the calcium channels, particularly through voltage-dependent channels. The uptake of cadmium and calcium by D. Rugosus was therefore also studied in the presence of the calcium channel blocker verapamil. 13 refs., 3 figs., 1 tab.« less

Purification, cloning, expression, and biochemical characterization of a monofunctional catalase, KatP, from Pigmentiphaga sp. DL-8.

PubMed

Dong, Weiliang; Hou, Ying; Li, Shuhuan; Wang, Fei; Zhou, Jie; Li, Zhoukun; Wang, Yicheng; Huang, Fei; Fu, Lei; Huang, Yan; Cui, Zhongli

2015-04-01

Catalases are essential components of the cellular equipment used to cope with oxidative stress. The monofunctional catalase KatP was purified from Pigmentiphaga sp. using ammonium sulfate precipitation (ASP), diethylaminoethyl ion exchange chromatography (IEC), and hydrophobic interaction chromatography (HIC). The purified catalase formed polymer with an estimated monomer molecular mass of 54kDa, which were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and zymogram analysis. KatP exhibited a specific catalytic activity of 73,000U/mg, which was higher than that of catalase-1 of Comamonas terrigena N3H (55,900U/mg). Seven short tryptic fragments of this catalase were obtained by electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF MS/MS), and the gene, katP, was cloned by PCR amplification and overexpressed in Escherichia coli BL21 (DE3). Based on the complete amino acid sequence, KatP was identified as a clade 3 monofunctional catalase. The specific activities of recombinant KatP for hydrogen peroxide (690,000U/mg) increased 9-fold over that of the parent strain. The Km and Vmax of recombinant KatP were 9.48mM and 81.2mol/minmg, respectively. The optimal pH and temperature for KatP were 7.0 and 37°C, respectively, and the enzyme displayed abroad pH-stable range of 4.0-11.0. The enzyme was inhibited by Zn(2+), Cu(2+), Cr(2+), and Mn(2+), whereas Fe(3+) and Mg(2+) stimulated KatP enzymatic activity. Interestingly, the catalase activity of recombinant KatP displayed high stability under different temperature and pH conditions, suggesting that KatP is a potential candidate for the production of catalase. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of calcium channel blockers on the kinetics of voltage-dependent changes in synaptosomal calcium concentrations.

PubMed

Thomas, M M; Puligandla, P S; Dunn, S M

1994-01-28

Synaptosomal preparations from rat cerebral cortex have been used in stopped-flow fluorescence studies to measure rapid changes in intrasynaptosomal calcium concentrations upon depolarization. Synaptosomes were loaded with the fluorescent calcium chelating dye, Fura-2, by incubation with the membrane permeant acetoxymethyl ester derivative. Depolarization by elevated external K+ concentration resulted in a rapid increase in cytoplasmic Ca2+ as measured by a quench in Fura-2 fluorescence when excited at 390 nm. The fluorescence change could be reasonably fit by a single exponential process with an apparent rate of 10-15 s-1 and the magnitude of the response was voltage-dependent, increasing with increasing external K+ over the range of 5-30 mM. The observed quench was blocked by micromolar concentrations of the inorganic calcium channel blockers, Cd2+, Co2+ and La3+. Nimodipine, a dihydropyridine which blocks L-type calcium channels, inhibited only 10-15% of the flux response while nitrendipine had no consistent effect. omega-Conotoxin GVIA, a blocker of N-type channels in many species, had only a small inhibitory effect at high (1-10 microM) concentrations. The response was, however, inhibited by pre-incubation of the synaptosomes with venom of the funnel web spider. Agelenopsis aperta (0.1-300 micrograms/ml). Inhibition was observed with both a purified polyamine fraction (FTX) from the venom (IC50 = 4 nl/ml) and a purified peptide toxin, omega-AgaIVA (IC50 = 30 nM). These results indicate that voltage-dependent Ca2+ uptake by mammalian nerve terminals is mediated primarily by channels that are insensitive to dihydropyridines and omega-conotoxin GVIA but are sensitive to components of funnel web spider venom.

Mechanism of allosteric activation of TMEM16A/ANO1 channels by a commonly used chloride channel blocker

PubMed Central

Ta, Chau M; Adomaviciene, Aiste; Rorsman, Nils J G; Garnett, Hannah

2016-01-01

Background and Purpose Calcium‐activated chloride channels (CaCCs) play varied physiological roles and constitute potential therapeutic targets for conditions such as asthma and hypertension. TMEM16A encodes a CaCC. CaCC pharmacology is restricted to compounds with relatively low potency and poorly defined selectivity. Anthracene‐9‐carboxylic acid (A9C), an inhibitor of various chloride channel types, exhibits complex effects on native CaCCs and cloned TMEM16A channels providing both activation and inhibition. The mechanisms underlying these effects are not fully defined. Experimental Approach Patch‐clamp electrophysiology in conjunction with concentration jump experiments was employed to define the mode of interaction of A9C with TMEM16A channels. Key Results In the presence of high intracellular Ca2+, A9C inhibited TMEM16A currents in a voltage‐dependent manner by entering the channel from the outside. A9C activation, revealed in the presence of submaximal intracellular Ca2+ concentrations, was also voltage‐dependent. The electric distance of A9C inhibiting and activating binding site was ~0.6 in each case. Inhibition occurred according to an open‐channel block mechanism. Activation was due to a dramatic leftward shift in the steady‐state activation curve and slowed deactivation kinetics. Extracellular A9C competed with extracellular Cl−, suggesting that A9C binds deep in the channel's pore to exert both inhibiting and activating effects. Conclusions and Implications A9C is an open TMEM16A channel blocker and gating modifier. These effects require A9C to bind to a region within the pore that is accessible from the extracellular side of the membrane. These data will aid the future drug design of compounds that selectively activate or inhibit TMEM16A channels. PMID:26562072

A spontaneous increase in intracellular Ca2+ in metaphase II human oocytes in vitro can be prevented by drugs targeting ATP-sensitive K+ channels

PubMed Central

Fernandes, Gonçalo; Dasai, Navin; Kozlova, Natalia; Mojadadi, Albaraa; Gall, Mandy; Drew, Ellen; Barratt, Evelyn; Madamidola, Oladipo A.; Brown, Sean G.; Milne, Alison M.; Martins da Silva, Sarah J.; Whalley, Katherine M.; Barratt, Christopher L.R.; Jovanović, Aleksandar

2016-01-01

STUDY QUESTION Could drugs targeting ATP-sensitive K+ (KATP) channels prevent any spontaneous increase in intracellular Ca2+ that may occur in human metaphase II (MII) oocytes under in vitro conditions? SUMMARY ANSWER Pinacidil, a KATP channel opener, and glibenclamide, a KATP channel blocker, prevent a spontaneous increase in intracellular Ca2+ in human MII oocytes. WHAT IS KNOWN ALREADY The quality of the oocyte and maintenance of this quality during in vitro processing in the assisted reproductive technology (ART) laboratory is of critical importance to successful embryo development and a healthy live birth. Maintenance of Ca2+ homeostasis is crucial for cell wellbeing and increased intracellular Ca2+ levels is a well-established indicator of cell stress. STUDY DESIGN, SIZE, DURATION Supernumerary human oocytes (n = 102) collected during IVF/ICSI treatment that failed to fertilize were used from October 2013 to July 2015. All experiments were performed on mature (MII) oocytes. Dynamics of intracellular Ca2+ levels were monitored in oocytes in the following experimental groups: (i) Control, (ii) Dimethyl sulfoxide (DMSO; used to dissolve pinacidil, glibenclamide and 2,4-Dinitrophenol (DNP)), (iii) Pinacidil, (iv) Glibenclamide, (v) DNP: an inhibitor of oxidative phosphorylation, (vi) Pinacidil and DNP and (vii) Glibenclamide and DNP. PARTICIPANTS/MATERIALS/SETTINGS/METHODS Oocytes were collected under sedation as part of routine treatment at an assisted conception unit from healthy women (mean ± SD) age 34.1 ± 0.6 years, n = 41. Those surplus to clinical use were donated for research. Oocytes were loaded with Fluo-3 Ca2+-sensitive dye, and monitored by laser confocal microscopy for 2 h at 10 min intervals. Time between oocyte collection and start of Ca2+ monitoring was 80.4 ± 2.1 h. MAIN RESULTS AND THE ROLE OF CHANCE Intracellular levels of Ca2+ increased under in vitro conditions with no deliberate challenge, as shown by Fluo-3 fluorescence increasing from

Calcium channel blockers for inhibiting preterm labour and birth.

PubMed

Flenady, Vicki; Wojcieszek, Aleena M; Papatsonis, Dimitri N M; Stock, Owen M; Murray, Linda; Jardine, Luke A; Carbonne, Bruno

2014-06-05

Preterm birth is a major contributor to perinatal mortality and morbidity, affecting around 9% of births in high-income countries and an estimated 13% of births in low- and middle-income countries. Tocolytics are drugs used to suppress uterine contractions for women in preterm labour. The most widely used tocolytic are the betamimetics, however, these are associated with a high frequency of unpleasant and sometimes severe maternal side effects. Calcium channel blockers (CCBs) (such as nifedipine) may have similar tocolytic efficacy with less side effects than betamimetics. Oxytocin receptor antagonists (ORAs) (e.g. atosiban) also have a low side-effect profile. To assess the effects on maternal, fetal and neonatal outcomes of CCBs, administered as a tocolytic agent, to women in preterm labour. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (12 November 2013). All published and unpublished randomised trials in which CCBs were used for tocolysis for women in labour between 20 and 36 completed weeks' gestation. Two review authors independently assessed trial eligibility, undertook quality assessment and data extraction. Results are presented using risk ratio (RR) for categorical data and mean difference (MD) for data measured on a continuous scale with the 95% confidence interval (CI). The number needed to treat to benefit (NNTB) and the number needed to treat to harm (NNTH) were calculated for categorical outcomes that were statistically significantly different. This update includes 26 additional trials involving 2511 women, giving a total of 38 included trials (3550 women). Thirty-five trials used nifedipine as the CCB and three trials used nicardipine. Blinding of intervention and outcome assessment was undertaken in only one of the trials (a placebo controlled trial). However, objective outcomes defined according to timing of birth and perinatal mortality were considered to have low risk of detection bias.Two small trials comparing CCBs

Non-Selective Calcium Channel Blocker Bepridil Decreases Secondary Pathology in Mice after Photothrombotic Cortical Lesion

PubMed Central

Lipsanen, Anu; Flunkert, Stefanie; Kuptsova, Kristina; Hiltunen, Mikko; Windisch, Manfred; Hutter-Paier, Birgit; Jolkkonen, Jukka

2013-01-01

Experimental studies have identified a complex link between neurodegeneration, β-amyloid (Aβ) and calcium homeostasis. Here we asked whether early phase β-amyloid pathology in transgenic hAPPSL mice exaggerates the ischemic lesion and remote secondary pathology in the thalamus, and whether a non-selective calcium channel blocker reduces these pathologies. Transgenic hAPPSL (n = 33) and non-transgenic (n = 30) male mice (4–5 months) were subjected to unilateral cortical photothrombosis and treated with the non-selective calcium channel blocker bepridil (50 mg/kg, p.o., once a day) or vehicle for 28 days, starting administration 2 days after the operation. Animals were then perfused for histological analysis of infarct size, Aβ and calcium accumulation in the thalamus. Cortical photothrombosis resulted in a small infarct, which was associated with atypical Aβ and calcium accumulation in the ipsilateral thalamus. Transgenic mice had significantly smaller infarct volumes than non-transgenic littermates (P<0.05) and ischemia-induced rodent Aβ accumulation in the thalamus was lower in transgenic mice compared to non-transgenic mice (P<0.01). Bepridil decreased calcium load in the thalamus (P<0.01). The present data suggest less pronounced primary and secondary pathology in hAPPSL transgenic mice after ischemic cortical injury. Bepridil particularly decreased calcium pathology in the thalamus following ischemia. PMID:23555933

Combined use of calcium-channel and beta-adrenergic blockers for the treatment of chronic stable angina. Rationale, efficacy, and adverse effects.

PubMed

Strauss, W E; Parisi, A F

1988-10-01

During the past decade, the therapy for stable angina pectoris has greatly expanded with the introduction of the calcium-channel blockers. Initially studied as monotherapy, these agents have been regularly used in combination with other antianginal medications, most notably the beta-adrenergic blockers. Although there are pharmacologic rationales for combining these agents, in daily practice, the major impetus for combination therapy is continuing angina during monotherapy. At least one well-conducted double-blind study was done to confirm that diltiazem, verapamil, and nifedipine each can markedly improve both subjective and objective measures of efficacy when used in combination with a beta-blocker. However, individual patient responses are of chief importance. Many persons do better with monotherapy than with combination treatment. The offsetting hemodynamic effects of nifedipine and a beta-blocker generally work well together; however, minor side effects are not infrequent. In the patient with underlying conduction system disease, this combination is clearly preferable. Diltiazem with a beta-blocker is usually well-tolerated, with a low incidence of adverse effects, similar to the experience with diltiazem monotherapy. Verapamil in conjunction with a beta-blocker warrants the greatest concern; approximately 10% to 15% of patients will have significant bradycardia, heart block, hypotension, or congestive failure. When these agents are used concurrently, reduced dosages, especially of the beta-blocker, will likely result in a lower incidence of adverse effects with maintained efficacy.

The effects of pure potassium channel blocker nifekalant and sodium channel blocker mexiletine on malignant ventricular tachyarrhythmias.

PubMed

Otuki, Sou; Hasegawa, Kanae; Watanabe, Hiroshi; Katsuumi, Goro; Yagihara, Nobue; Iijima, Kenichi; Sato, Akinori; Izumi, Daisuke; Furushima, Hiroshi; Chinushi, Masaomi; Aizawa, Yoshifusa; Minamino, Tohru

Patients with repetitive ventricular tachyarrhythmias - so-called electrical storm - frequently require antiarrhythmic drugs. Amiodarone is widely used for the treatment of electrical storm but is ineffective in some patients. Therefore, we investigated the efficacy of stepwise administration of nifekalant, a pure potassium channel blocker, and mexiletine for electrical storm. This study included 44 patients with repetitive ventricular tachyarrhythmias who received stepwise therapy with nifekalant and mexiletine for electrical storm. Nifekalant was initially administered, and mexiletine was subsequently added if nifekalant failed to control ventricular tachyarrhythmias. Nifekalant completely suppressed recurrences of ventricular arrhythmias in 28 patients (64%), including 6 patients in whom oral amiodarone failed to control arrhythmias. In 9 of 16 patients in whom nifekalant was partially effective but failed to suppress ventricular arrhythmias, mexiletine was added. The addition of mexiletine prevented recurrences of ventricular tachyarrhythmias in 5 of these 9 patients (56%). There was no death associated with electrical storm. In total, the stepwise treatment with nifekalant and mexiletine was effective in preventing ventricular tachyarrhythmias in 33 of 44 patients (75%). There was no difference in cycle length of the ventricular tachycardia, QRS interval, QT interval, or left ventricular ejection fraction between patients who responded to antiarrhythmic drugs and those who did not. During follow-up, 8 patients had repetitive ventricular tachyarrhythmia recurrences, and the stepwise treatment was effective in 6 of these 8 patients (75%). The stepwise treatment with nifekalant and mexiletine was highly effective in the suppression of electrical storm. Copyright © 2016. Published by Elsevier Inc.

Indistinguishable Synaptic Pharmacodynamics of the N-Methyl-d-Aspartate Receptor Channel Blockers Memantine and Ketamine

PubMed Central

Emnett, Christine M.; Eisenman, Lawrence N.; Taylor, Amanda M.; Izumi, Yukitoshi; Zorumski, Charles F.

2013-01-01

Memantine and ketamine, voltage- and activation-dependent channel blockers of N-methyl-d-aspartate (NMDA) receptors (NMDARs), have enjoyed a recent resurgence in clinical interest. Steady-state pharmacodynamic differences between these blockers have been reported, but it is unclear whether the compounds differentially affect dynamic physiologic signaling. In this study, we explored nonequilibrium conditions relevant to synaptic transmission in hippocampal networks in dissociated culture and hippocampal slices. Equimolar memantine and ketamine had indistinguishable effects on the following measures: steady-state NMDA currents, NMDAR excitatory postsynaptic current (EPSC) decay kinetics, progressive EPSC inhibition during repetitive stimulation, and extrasynaptic NMDAR inhibition. Therapeutic drug efficacy and tolerability of memantine have been attributed to fast kinetics and strong voltage dependence. However, pulse depolarization in drug presence revealed a surprisingly slow and similar time course of equilibration for the two compounds, although memantine produced a more prominent fast component (62% versus 48%) of re-equilibration. Simulations predicted that low gating efficacy underlies the slow voltage–dependent relief from block. This prediction was empirically supported by faster voltage-dependent blocker re-equilibration with several experimental manipulations of gating efficacy. Excitatory postsynaptic potential–like voltage commands produced drug differences only with large, prolonged depolarizations unlikely to be attained physiologically. In fact, we found no difference between drugs on measures of spontaneous network activity or acute effects on plasticity in hippocampal slices. Despite indistinguishable synaptic pharmacodynamics, ketamine provided significantly greater neuroprotection from damage induced by oxygen glucose deprivation, consistent with the idea that under extreme depolarizing conditions, the biophysical difference between drugs

Molecular assembly and subcellular distribution of ATP-sensitive potassium channel proteins in rat hearts.

PubMed

Kuniyasu, Akihiko; Kaneko, Kazuyoshi; Kawahara, Kohichi; Nakayama, Hitoshi

2003-09-25

Cardiac ATP-sensitive K(+) (K(ATP)) channels are proposed to contribute to cardio-protection and ischemic preconditioning. Although mRNAs for all subunits of K(ATP) channels (Kir6.0 and sulfonylurea receptors SURs) were detected in hearts, subcellular localization of their proteins and the subunit combination are not well elucidated. We address these questions in rat hearts, using anti-peptide antibodies raised against each subunit. By immunoblot analysis, all of the subunits were detected in microsomal fractions including sarcolemmal membranes, while they were not detected in mitochondrial fractions at all. Immunoprecipitation and sucrose gradient sedimentation of the digitonin-solubilized microsomes indicated that Kir6.2 exclusively assembled with SUR2A. The molecular mass of the Kir6.2-SUR2A complex estimated by sucrose sedimentation was 1150 kDa, significantly larger than the calculated value for (Kir6.2)(4)-(SUR2A)(4), suggesting a potential formation of micellar complex with digitonin but no indication of hybrid channel formation under the conditions. These findings provide additional information on the structural and functional relationships of cardiac K(ATP) channel proteins involving subcellular localization and roles for cardioprotection and ischemic preconditioning.

Cl- channel blockers NPPB and niflumic acid blunt Ca(2+)-induced erythrocyte 'apoptosis'.

PubMed

Myssina, Svetlana; Lang, Philipp A; Kempe, Daniela S; Kaiser, Stefanie; Huber, Stephan M; Wieder, Thomas; Lang, Florian

2004-01-01

Exposure to Ca2+ ionophore ionomycin, osmotic shock, oxidative stress and glucose depletion trigger cell shrinkage and scramblase-mediated phosphatidylserine exposure at the outer leaflet of the erythrocyte cell membrane. The effects are partially due to activation of GARDOS channels and subsequent cellular K+ loss leading not only to cell shrinkage but also participating in the triggering of erythrocyte scramblase. As conductive loss of K+ would depend on the parallel loss of anions we hypothesised that activation of scramblase is similarly dependent on the activity of Cl- channels. To test this hypothesis, we used Cl- channel blockers NPPB and niflumic acid. It is shown here that treatment of erythrocytes with 1 microM ionomycin leads to cellular K+ loss, decrease of hematocrit and decrease of forward scatter in FACS analysis reflecting cell shrinkage as well as increase of annexin positive cells reflecting phosphatidylserine exposure. Those events were significantly blunted in the presence of 100 microM NPPB by 34% (K+ loss), 45% (hematocrit), 32% (forward scatter) and 69% (annexin binding), or in the presence of 100 microM niflumic acid by 15% (forward scatter) and 45% (annexin binding), respectively. Moreover, oxidative stress triggered annexin binding which was again significantly inhibited (by 51%) in the presence of 100 microM NPPB. In conclusion, Cl- channels presumably participate in the regulation of erythrocyte 'apoptosis'. Copyright 2004 S. Karger AG, Basel

LPS from Escherichia coli protects against indomethacin-induced gastropathy in rats--role of ATP-sensitive potassium channels.

PubMed

Gomes, Antoniella S; Lima, Lívia M F; Santos, Camila L; Cunha, Fernando Q; Ribeiro, Ronaldo A; Souza, Marcellus H L P

2006-10-10

The effect of lipopolysaccharide (LPS) in gastric protection has not been elucidated, but ATP-sensitive potassium (K(ATP)) channels are known to be involved in gastric defense. We evaluated the effect of LPS administration on indomethacin-induced gastropathy, and the role of K(ATP) channels in this event. Rats received intravenous (i.v.) LPS administration. After 1/2, 6, 24 or 48 h, indomethacin was injected. 3H later, gastric damage and myeloperoxidase activity were determined. Another group received LPS and 5 h later, glibenclamide, diazoxide or glibenclamide plus diazoxide. After 1 h, the rats received indomethacin and 3 h later, gastric damage and myeloperoxidase activity were evaluated. LPS reduced dose dependently gastric damage and myeloperoxidase activity induced by indomethacin. Glibenclamide reversed this LPS effect on indomethacin-induced gastropathy. Glibenclamide plus diazoxide administration did not change this LPS effect. Thus LPS has a protective effect against indomethacin-induced gastropathy, probably through activation of K(ATP) channels.

Protective effects of efonidipine, a T- and L-type calcium channel blocker, on renal function and arterial stiffness in type 2 diabetic patients with hypertension and nephropathy.

PubMed

Sasaki, Hidehisa; Saiki, Atsuhito; Endo, Kei; Ban, Noriko; Yamaguchi, Takashi; Kawana, Hidetoshi; Nagayama, Daizi; Ohhira, Masahiro; Oyama, Tomokazu; Miyashita, Yoh; Shirai, Kohji

2009-10-01

The three types of calcium channel blocker (CCB), L-, T- and N-type, possess heterogeneous actions on endothelial function and renal microvascular function. In the present study, we evaluated the effects of two CCBs, efonidipine and amlodipine, on renal function and arterial stiffness. Forty type 2 diabetic patients with hypertension and nephropathy receiving angiotensin receptor II blockers were enrolled and randomly divided into two groups: the efonidipine group was administered efonidipine hydrochloride ethanolate 40 mg/day and the amlodipine group was admin-istered amlodipine besilate 5 mg/day for 12 months. Arterial stiffness was evaluated by the cardio-ankle vascular index (CAVI). Changes in blood pressure during the study were almost the same in the two groups. Sig-nificant increases in serum creatinine and urinary albumin and a significant decrease in the esti-mated glomerular filtration rate were observed in the amlodipine group, but not in the efonidipine group. On the other hand, significant decreases in plasma aldosterone, urinary 8-hydroxy-2'-deoxy-guanosine and CAVI were observed after 12 months in the efonidipine group, but not in the amlo-dipine group. These results suggest that efonidipine, which is both a T-type and L-type calcium chan-nel blocker, has more favorable effects on renal function, oxidative stress and arterial stiffness than amlodipine, an L-type calcium channel blocker.

Effect of Channel Blockers on the Smooth Muscle of the Adult Crop of the Queen Blowfly, Phormia regina

PubMed Central

Stoffolano, John G.; Danai, Laura; Chambers, James

2013-01-01

Few studies have examined the various factors affecting the rate of contraction of the supercontractile muscles of the crop lobes of adult Phormia regina Meigen (Diptera: Calliphoridae). Using an in situ bioassay of the crop organ, various ion channel blockers were tested and it was demonstrated that in all cases the blockers (i.e., against the following conductances: Cl- , Ca2+ , Na+, and a FMRF-amide action) significantly reduced the contraction rates of the crop lobes, which were filled with 4.5 µL of 1.0 M sucrose containing 10 mM of the dye amaranth. Benzyltrimethylammonium chloride, never before reported for its effect on insect muscle, was as effective in suppressing crop muscle contraction as benzethonium chloride, which is a reported agonist of dromyosuppressin. PMID:24205919

Characterization of the first K⁺ channel blockers from the venom of the Moroccan scorpion Buthus occitanus Paris.

PubMed

Martin-Eauclaire, Marie-France; Céard, Brigitte; Belghazi, Maya; Lebrun, Régine; Bougis, Pierre E

2013-12-01

The availability of a large variety of specific blockers, which inhibit different K(+) currents, would help to elucidate their differences in physiological function. Short peptide toxins isolated from scorpion venoms are able to block voltage-dependent or Ca(2+)-activated K(+) channels. Here, we have studied the venom of the Moroccan scorpion Buthus occitanus Paris (BoP) in order to find new peptides, which could enlarge our structure-function relationship knowledge on the Kv1.3 blocker Kaliotoxin (KTX) that belongs to the α-KTx3.1 family. Indeed and since more a decade, KTX is widely used by international investigators because it exhibits a quite sharp specificity and a high-affinity for the Kv1.3 channel, which is not only a neuronal channel but also a therapeutic target for diverse autoimmune diseases such as multiple sclerosis, type 1 diabetes, and rheumatoid arthritis. The BoP venom was first investigated using HPLC and MALDI-TOF/MS. Further, the HPLC fractions were screened by ELISA with antibodies raised against KTX. These antibodies recognized at least three components toxic in mice by intracerebroventricular injection. They were further pharmacologically characterized by competition using (125)I-KTX bound to its specific binding sites on rat brain synaptosomes. A single component (4161 Da) inhibited totally the (125)I-KTX binding and with high-affinity (IC50 = 0.1 nM), while the two other components poorly competed with (IC50 > 100 nM). These toxins were sequenced in full by Edman's degradation. The high-affinity ligand (BoPKTX) shares 86% sequence identity with KTX and was classified as toxin α-KTx3.17. The two others peptides (BoP1 and BoP2, 4093 Da and 4121 Da, respectively) only differ by a Lys/Arg mutation. Their amino acid sequences were related to Martentoxin, which has been characterized from the Chinese scorpion Buthus martenzi Karch and described as both a BKCa and Kv1.3 blocker. Accordingly, they belong to the α-KTx16 family. Copyright �

d-Tubocurarine and Berbamine: Alkaloids That Are Permeant Blockers of the Hair Cell's Mechano-Electrical Transducer Channel and Protect from Aminoglycoside Toxicity

PubMed Central

Kirkwood, Nerissa K.; O'Reilly, Molly; Derudas, Marco; Kenyon, Emma J.; Huckvale, Rosemary; van Netten, Sietse M.; Ward, Simon E.; Richardson, Guy P.; Kros, Corné J.

2017-01-01

Aminoglycoside antibiotics are widely used for the treatment of life-threatening bacterial infections, but cause permanent hearing loss in a substantial proportion of treated patients. The sensory hair cells of the inner ear are damaged following entry of these antibiotics via the mechano-electrical transducer (MET) channels located at the tips of the hair cell's stereocilia. d-Tubocurarine (dTC) is a MET channel blocker that reduces the loading of gentamicin-Texas Red (GTTR) into rat cochlear hair cells and protects them from gentamicin treatment. Berbamine is a structurally related alkaloid that reduces GTTR labeling of zebrafish lateral-line hair cells and protects them from aminoglycoside-induced cell death. Both compounds are thought to reduce aminoglycoside entry into hair cells through the MET channels. Here we show that dTC (≥6.25 μM) or berbamine (≥1.55 μM) protect zebrafish hair cells in vivo from neomycin (6.25 μM, 1 h). Protection of zebrafish hair cells against gentamicin (10 μM, 6 h) was provided by ≥25 μM dTC or ≥12.5 μM berbamine. Hair cells in mouse cochlear cultures are protected from longer-term exposure to gentamicin (5 μM, 48 h) by 20 μM berbamine or 25 μM dTC. Berbamine is, however, highly toxic to mouse cochlear hair cells at higher concentrations (≥30 μM) whilst dTC is not. The absence of toxicity in the zebrafish assays prompts caution in extrapolating results from zebrafish neuromasts to mammalian cochlear hair cells. MET current recordings from mouse outer hair cells (OHCs) show that both compounds are permeant open-channel blockers, rapidly and reversibly blocking the MET channel with half-blocking concentrations of 2.2 μM (dTC) and 2.8 μM (berbamine) in the presence of 1.3 mM Ca2+ at −104 mV. Berbamine, but not dTC, also blocks the hair cell's basolateral K+ current, IK,neo, and modeling studies indicate that berbamine permeates the MET channel more readily than dTC. These studies reveal key properties of MET-channel

Reduction in renal blood flow following administration of norepinephrine and phenylephrine in septic rats treated with Kir6.1 ATP-sensitive and KCa1.1 calcium-activated K+ channel blockers.

PubMed

da Rosa Maggi Sant'Helena, Bruna; Guarido, Karla L; de Souza, Priscila; Crestani, Sandra; da Silva-Santos, J Eduardo

2015-10-15

We evaluated the effects of K+ channel blockers in the vascular reactivity of in vitro perfused kidneys, as well as on the influence of vasoactive agents in the renal blood flow of rats subjected to the cecal ligation and puncture (CLP) model of sepsis. Both norepinephrine and phenylephrine had the ability to increase the vascular perfusion pressure reduced in kidneys of rats subjected to CLP at 18 h and 36 h before the experiments. The non-selective K+ channel blocker tetraethylammonium, but not the Kir6.1 blocker glibenclamide, normalized the effects of phenylephrine in kidneys from the CLP 18 h group. Systemic administration of tetraethylammonium, glibenclamide, or the KCa1.1 blocker iberiotoxin, did not change the renal blood flow in control or septic rats. Norepinephrine or phenylephrine also had no influence on the renal blood flow of septic animals, but its injection in rats from the CLP 18 h group previously treated with either glibenclamide or iberiotoxin resulted in an exacerbated reduction in the renal blood flow. These results suggest an abnormal functionality of K+ channels in the renal vascular bed in sepsis, and that the blockage of different subtypes of K+ channels may be deleterious for blood perfusion in kidneys, mainly when associated with vasoactive drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of beta-blockers and nicardipine on oxotremorine-induced tremor in common marmosets.

PubMed

Mitsuda, M; Nomoto, M; Iwata, S

1999-10-01

Effects of beta-blockers (propranolol, arotinolol and nipradilol) and a Ca2+ channel blocker (nicardipine) on oxotremorine-induced tremor were studied in common marmosets. Generalized tremor was elicited by an intraperitoneal administration of 0.25 mg/kg oxotremorine. Intensity of the tremor was classified into 7 degrees, and it was evaluated every 10 min. The total intensity of oxotremorine-induced tremor for each drug was expressed as "points", which were the sum of tremor intensity scores evaluated every 10 min up to 190 min following the administration of oxotremorine. Beta-blockers significantly suppressed the tremor. On the other hand, the Ca2+ channel blocker exacerbated the tremor.

NVP-QBE170: an inhaled blocker of the epithelial sodium channel with a reduced potential to induce hyperkalaemia

PubMed Central

Coote, K J; Paisley, D; Czarnecki, S; Tweed, M; Watson, H; Young, A; Sugar, R; Vyas, M; Smith, N J; Baettig, U; Groot-Kormelink, P J; Gosling, M; Lock, R; Ethell, B; Williams, G; Schumacher, A; Harris, J; Abraham, W M; Sabater, J; Poll, C T; Faller, T; Collingwood, S P; Danahay, H

2015-01-01

Background and Purpose Inhaled amiloride, a blocker of the epithelial sodium channel (ENaC), enhances mucociliary clearance (MCC) in cystic fibrosis (CF) patients. However, the dose of amiloride is limited by the mechanism-based side effect of hyperkalaemia resulting from renal ENaC blockade. Inhaled ENaC blockers with a reduced potential to induce hyperkalaemia provide a therapeutic strategy to improve mucosal hydration and MCC in the lungs of CF patients. The present study describes the preclinical profile of a novel ENaC blocker, NVP-QBE170, designed for inhaled delivery, with a reduced potential to induce hyperkalaemia. Experimental Approach The in vitro potency and duration of action of NVP-QBE170 were compared with amiloride and a newer ENaC blocker, P552-02, in primary human bronchial epithelial cells (HBECs) by short-circuit current. In vivo efficacy and safety were assessed in guinea pig (tracheal potential difference/hyperkalaemia), rat (hyperkalaemia) and sheep (MCC). Key Results In vitro, NVP-QBE170 potently inhibited ENaC function in HBEC and showed a longer duration of action to comparator molecules. In vivo, intratracheal (i.t.) instillation of NVP-QBE170 attenuated ENaC activity in the guinea pig airways with greater potency and duration of action than that of amiloride without inducing hyperkalaemia in either guinea pig or rat. Dry powder inhalation of NVP-QBE170 by conscious sheep increased MCC and was better than inhaled hypertonic saline in terms of efficacy and duration of action. Conclusions and Implications NVP-QBE170 highlights the potential for inhaled ENaC blockers to exhibit efficacy in the airways with a reduced risk of hyperkalaemia, relative to existing compounds. PMID:25573195

NVP-QBE170: an inhaled blocker of the epithelial sodium channel with a reduced potential to induce hyperkalaemia.

PubMed

Coote, K J; Paisley, D; Czarnecki, S; Tweed, M; Watson, H; Young, A; Sugar, R; Vyas, M; Smith, N J; Baettig, U; Groot-Kormelink, P J; Gosling, M; Lock, R; Ethell, B; Williams, G; Schumacher, A; Harris, J; Abraham, W M; Sabater, J; Poll, C T; Faller, T; Collingwood, S P; Danahay, H

2015-06-01

Inhaled amiloride, a blocker of the epithelial sodium channel (ENaC), enhances mucociliary clearance (MCC) in cystic fibrosis (CF) patients. However, the dose of amiloride is limited by the mechanism-based side effect of hyperkalaemia resulting from renal ENaC blockade. Inhaled ENaC blockers with a reduced potential to induce hyperkalaemia provide a therapeutic strategy to improve mucosal hydration and MCC in the lungs of CF patients. The present study describes the preclinical profile of a novel ENaC blocker, NVP-QBE170, designed for inhaled delivery, with a reduced potential to induce hyperkalaemia. The in vitro potency and duration of action of NVP-QBE170 were compared with amiloride and a newer ENaC blocker, P552-02, in primary human bronchial epithelial cells (HBECs) by short-circuit current. In vivo efficacy and safety were assessed in guinea pig (tracheal potential difference/hyperkalaemia), rat (hyperkalaemia) and sheep (MCC). In vitro, NVP-QBE170 potently inhibited ENaC function in HBEC and showed a longer duration of action to comparator molecules. In vivo, intratracheal (i.t.) instillation of NVP-QBE170 attenuated ENaC activity in the guinea pig airways with greater potency and duration of action than that of amiloride without inducing hyperkalaemia in either guinea pig or rat. Dry powder inhalation of NVP-QBE170 by conscious sheep increased MCC and was better than inhaled hypertonic saline in terms of efficacy and duration of action. NVP-QBE170 highlights the potential for inhaled ENaC blockers to exhibit efficacy in the airways with a reduced risk of hyperkalaemia, relative to existing compounds. © 2015 The British Pharmacological Society.

Management of life-threatening calcium channel blocker overdose with continuous veno-venous hemodiafiltration with charcoal hemoperfusion

PubMed Central

Garg, Suneel K.; Goyal, Pankaj K.; Kumar, Rahul; Juneja, Deven; Bhasin, Alka; Singh, Omender

2014-01-01

Cases of calcium channel blocker overdose reported from India are few, and although rare, they are associated with high mortality. Management includes fluids, vasopressors, calcium gluconate or chloride, glucagon infusion, and hyperinsulinemia-euglycemia therapy along with some rescue therapies tried in anecdotal reports. We report here a case of life-threatening overdose of amlodipine with shock, refractory to conventional therapies. Salvage therapy with continuous veno-venous hemodiafiltration using charcoal hemoperfusion with prior infusion of intravenous lipid emulsion resulted in a successful outcome. PMID:24987241

The relaxation induced by S-nitroso-glutathione and S-nitroso-N-acetylcysteine in rat aorta is not related to nitric oxide production.

PubMed

Ceron, P I; Cremonez, D C; Bendhack, L M; Tedesco, A C

2001-08-01

S-nitroso-glutathione (GSNO) and S-nitroso-N-acetylcysteine (NACysNO) are nitrosothiols that release nitric oxide (NO) and mimic the effects of endogenous NO. This study investigated the relaxation induced by GSNO and NACysNO in rat aorta and the relation between relaxation and NO formation. Both compounds at concentrations from 10(-9) M to 10(-4) M relaxed the rat aorta in a concentration-dependent manner. However, NO production depended on the concentration of nitrosothiols present and was detected only above 100 microM GSNO or NACysNO. To determine whether K+ channels are involved in the relaxation induced by nitrosothiols, the contractions were induced with KCl at concentrations of 30, 60, or 90 mM. The concentration-effect curves for the relaxation induced by nitrosothiols were shifted to the right for all the K+ concentrations compared with aortas precontracted with phenylephrine. These results indicate the participation of K+ channels in the relaxation induced by GSNO and NACysNO. A selective inhibitor of soluble guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, significantly inhibited the relaxation induced by the nitrosothiols. The relaxation induced by GSNO and NACysNO was inhibited by the K+ channel blockers glibenclamide, selective K(ATP) channels, and apamin, selective for low-conductance Ca2+-activated K+ channels in rat aorta, but was not inhibited by charybdotoxin, a potent and selective Ca2+-activated K+ channel blocker, or by 4-aminopyridine, a voltage-gated K+ channel blocker. These results indicate that relaxation induced by GSNO and NACysNO is partially due to activation of K(ATP) channels and partially due to activation of low-conductance Ca2+-activated K+ channels. However, the ability of the nitrosothiol compounds to overcome the inhibitory effect of high extracellular K+ concentrations suggests another mechanism of relaxation contributing to the nitrosothiol response. The most intriguing finding is that relaxation is not

The use of nitrates, calcium channel blockers and ACE inhibitors in primary care in the Northern Region: a pharmacoepidemiological study.

PubMed Central

Roberts, S J; Bateman, D N

1994-01-01

1. Prescribing rates for cardiovascular drugs have substantial local variation. The objectives of this study were to determine the prescribing prevalence of nitrates, calcium channel blockers and angiotensin-converting enzyme inhibitors in general practice, to examine the indications recorded for these prescriptions, and to identify which therapeutic areas contribute to the variation in prescribing. 2. Anonymised patient-specific prescription data were taken from computerised records in 41 VAMP research practices in the Northern Region (total population 330,749). All patients who received any prescription for calcium channel blockers, nitrates or angiotensin-converting enzyme (ACE) inhibitors during a 12 month period were included. Prescribing rates were determined in terms of patients per 1,000 population within age, sex and diagnostic groups. 3. Overall, 4.3% of the study population were prescribed one or more of the drugs. There was virtually no prescribing for patients under the age of 35 years, but thereafter the prevalences rose steeply to peak at ages 65-74 years for calcium channel blockers (91 per 1,000 population) and ACE inhibitors (34 per 1,000), and at ages 75-84 years for nitrates (100 per 1,000). Prescribing prevalence amongst the over 85's was less than half the peak rate for each drug group. Rates for men and women were comparable, except for nitrates where men had higher rates. 4. Recorded indication rates for patients with ischaemic heart disease and treated with any of these drugs reached 112 per 1,000 population in the 75-84 age group, and were higher in men than women, at all ages. Hypertension indication rates were substantially higher in women over 65; across the genders the peak rate was 88 per 1,000 for those aged 65-74 years.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7888286

Beta-blockers for hypertension.

PubMed

Wiysonge, C S; Bradley, H; Mayosi, B M; Maroney, R; Mbewu, A; Opie, L H; Volmink, J

2007-01-24

by stratified analysis. In addition, we used the Higgins statistic (I(2)) to quantify the amount of between-study variability in effect attributable to true heterogeneity rather than chance. Thirteen randomised controlled trials (N=91,561 participants), which met our inclusion criteria, compared beta-blockers to placebo or no treatment (4 trials with 23,613 participants), diuretics (5 trials with 18,241 participants), calcium-channel blockers (CCBs: 4 trials with 44,825 participants), and renin-angiotensin system (RAS) inhibitors (3 trials with 10,828 participants). The risk of all-cause mortality was not different between first-line beta-blockers and placebo (RR 0.99, 95%CI 0.88 to 1.11, I(2)=0%), diuretics or RAS inhibitors, but was higher for beta-blockers compared to CCBs (RR 1.07, 95%CI 1.00 to 1.14, I(2)=2.2%; ARI=0.5%, NNH=200). The risk of total cardiovascular disease (CVD) was lower for first-line beta-blockers compared to placebo (RR 0.88, 95%CI 0.79 to 0.97, I(2)=21.4%, ARR=0.7%, NNT=140). This is primarily a reflection of the significant decrease in stroke (RR 0.80, 95%CI 0.66 to 0.96; I(2)=0%; ARR=0.5%, NNT=200); coronary heart disease (CHD) risk was not significantly different between beta-blockers and placebo. The effect of beta-blockers on CVD was significantly worse than that of CCBs (RR 1.18, 95%CI 1.08 to 1.29, I(2)=0%; ARI=1.3%, NNH=80), but was not significantly different from that of diuretics or RAS inhibitors. Increased total CVD was due to an increase in stroke compared to CCBs (RR 1.24, 95%CI 1.11 to 1.40, I(2)=0%; ARI=0.6%, NNH=180). There was also an increase in stroke with beta-blockers as compared to RAS inhibitors (RR 1.30, 95%CI 1.11 to 1.53, I(2)=29.1%; ARI=1.5%, NNH=65). CHD was not significantly different between beta-blockers and diuretics or CCBs or RAS inhibitors. In addition, patients on beta-blockers were more likely to discontinue treatment due to side effects than those on diuretics (RR 1.86, 95%CI 1.39 to 2.50, I(2

Long-pore Electrostatics in Inward-rectifier Potassium Channels

PubMed Central

Robertson, Janice L.; Palmer, Lawrence G.; Roux, Benoît

2008-01-01

Inward-rectifier potassium (Kir) channels differ from the canonical K+ channel structure in that they possess a long extended pore (∼85 Å) for ion conduction that reaches deeply into the cytoplasm. This unique structural feature is presumably involved in regulating functional properties specific to Kir channels, such as conductance, rectification block, and ligand-dependent gating. To elucidate the underpinnings of these functional roles, we examine the electrostatics of an ion along this extended pore. Homology models are constructed based on the open-state model of KirBac1.1 for four mammalian Kir channels: Kir1.1/ROMK, Kir2.1/IRK, Kir3.1/GIRK, and Kir6.2/KATP. By solving the Poisson-Boltzmann equation, the electrostatic free energy of a K+ ion is determined along each pore, revealing that mammalian Kir channels provide a favorable environment for cations and suggesting the existence of high-density regions in the cytoplasmic domain and cavity. The contribution from the reaction field (the self-energy arising from the dielectric polarization induced by the ion's charge in the complex geometry of the pore) is unfavorable inside the long pore. However, this is well compensated by the electrostatic interaction with the static field arising from the protein charges and shielded by the dielectric surrounding. Decomposition of the static field provides a list of residues that display remarkable correspondence with existing mutagenesis data identifying amino acids that affect conduction and rectification. Many of these residues demonstrate interactions with the ion over long distances, up to 40 Å, suggesting that mutations potentially affect ion or blocker energetics over the entire pore. These results provide a foundation for understanding ion interactions in Kir channels and extend to the study of ion permeation, block, and gating in long, cation-specific pores. PMID:19001143

Effects of Na+ channel blockers on the restitution of refractory period, conduction time, and excitation wavelength in perfused guinea-pig heart.

PubMed

Osadchii, Oleg E

2017-01-01

Na+ channel blockers flecainide and quinidine can increase propensity to ventricular tachyarrhythmia, whereas lidocaine and mexiletine are recognized as safe antiarrhythmics. Clinically, ventricular fibrillation is often precipitated by transient tachycardia that reduces action potential duration, suggesting that a critical shortening of the excitation wavelength (EW) may contribute to the arrhythmic substrate. This study examined whether different INa blockers can produce contrasting effects on the rate adaptation of the EW, which would explain the difference in their safety profile. In perfused guinea-pig hearts, effective refractory periods (ERP), conduction times, and EW values were determined over a wide range of cardiac pacing intervals. All INa blockers tested were found to flatten the slope of ERP restitution, indicating antiarrhythmic tendency. However, with flecainide and quinidine, the beneficial changes in ERP were reversed owing to the use-dependent conduction slowing, thereby leading to significantly steepened restitution of the EW. In contrast, lidocaine and mexiletine had no effect on ventricular conduction, and therefore reduced the slope of the EW restitution, as expected from their effect on ERP. These findings suggest that the slope of the EW restitution is an important electrophysiological determinant which can discriminate INa blockers with proarrhythmic and antiarrhythmic profile.

The role of ATP-sensitive potassium channels in cellular function and protection in the cardiovascular system.

PubMed

Tinker, Andrew; Aziz, Qadeer; Thomas, Alison

2014-01-01

ATP-sensitive potassium channels (K(ATP)) are widely distributed and present in a number of tissues including muscle, pancreatic beta cells and the brain. Their activity is regulated by adenine nucleotides, characteristically being activated by falling ATP and rising ADP levels. Thus, they link cellular metabolism with membrane excitability. Recent studies using genetically modified mice and genomic studies in patients have implicated K(ATP) channels in a number of physiological and pathological processes. In this review, we focus on their role in cellular function and protection particularly in the cardiovascular system. © 2013 The British Pharmacological Society.

Ziconotide: neuronal calcium channel blocker for treating severe chronic pain.

PubMed

Miljanich, G P

2004-12-01

Ziconotide (PRIALT) is a neuroactive peptide in the final stages of clinical development as a novel non-opioid treatment for severe chronic pain. It is the synthetic equivalent of omega-MVIIA, a component of the venom of the marine snail, Conus magus. The mechanism of action underlying ziconotide's therapeutic profile derives from its potent and selective blockade of neuronal N-type voltage-sensitive calcium channels (N-VSCCs). Direct blockade of N-VSCCs inhibits the activity of a subset of neurons, including pain-sensing primary nociceptors. This mechanism of action distinguishes ziconotide from all other analgesics, including opioid analgesics. In fact, ziconotide is potently anti-nociceptive in animal models of pain in which morphine exhibits poor anti-nociceptive activity. Moreover, in contrast to opiates, tolerance to ziconotide is not observed. Clinical studies of ziconotide in more than 2,000 patients reveal important correlations to ziconotide's non-clinical pharmacology. For example, ziconotide provides significant pain relief to severe chronic pain sufferers who have failed to obtain relief from opiate therapy and no evidence of tolerance to ziconotide is seen in these patients. Contingent on regulatory approval, ziconotide will be the first in a new class of neurological drugs: the N-type calcium channel blockers, or NCCBs. Its novel mechanism of action as a non-opioid analgesic suggests ziconotide has the potential to play a valuable role in treatment regimens for severe chronic pain. If approved for clinical use, ziconotide will further validate the neuroactive venom peptides as a source of new and useful medicines.

Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans.

PubMed

Liu, Shuyuan; Yue, Longtao; Gu, Wenrui; Li, Xiuyun; Zhang, Liuping; Sun, Shujuan

2016-01-01

Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers), amlodipine (AML), nifedipine (NIF), benidipine (BEN) and flunarizine (FNZ) with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1) expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI) <0.5, but no interaction against sensitive strains (FICI = 0.56 ~ 2). The mechanism studies revealed that fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin) and YVC1 (encoding calcium channel protein in vacuole membrane).

Expression and isotopic labelling of the potassium channel blocker ShK toxin as a thioredoxin fusion protein in bacteria.

PubMed

Chang, Shih Chieh; Galea, Charles A; Leung, Eleanor W W; Tajhya, Rajeev B; Beeton, Christine; Pennington, Michael W; Norton, Raymond S

2012-10-01

The polypeptide toxin ShK is a potent blocker of Kv1.3 potassium channels, which play a crucial role in the activation of human effector memory T-cells (T(EM)). Selective blockers constitute valuable therapeutic leads for the treatment of autoimmune diseases mediated by T(EM) cells, such as multiple sclerosis, rheumatoid arthritis, and type-1 diabetes. We have established a recombinant peptide expression system in order to generate isotopically-labelled ShK and various ShK analogues for in-depth biophysical and pharmacological studies. ShK was expressed as a thioredoxin fusion protein in Escherichia coli BL21 (DE3) cells and purified initially by Ni²⁺ iminodiacetic acid affinity chromatography. The fusion protein was cleaved with enterokinase and purified to homogeneity by reverse-phase HPLC. NMR spectra of ¹⁵N-labelled ShK were similar to those reported previously for the unlabelled synthetic peptide, confirming that recombinant ShK was correctly folded. Recombinant ShK blocked Kv1.3 channels with a K(d) of 25 pM and inhibited the proliferation of human and rat T lymphocytes with a preference for T(EM) cells, with similar potency to synthetic ShK in all assays. This expression system also enables the efficient production of ¹⁵N-labelled ShK for NMR studies of peptide dynamics and of the interaction of ShK with Kv1.3 channels. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effects of Potassium Channel Blockers on the Negative Inotropic Responses Induced by Cromakalim and Pinacidil in Guinea Pig Atrium

DTIC Science & Technology

1992-01-01

RD-A2•4 875 EFFECTS OF POTASSIUM CHANNEL BLOCKERS ON THE NEGATIVE 1/1 INOTROPIC RESPONSES INDUCED BY CRONAKALIM RND PINACIDIL IN GUINEA PIG ATRIUM(U...INOTROPICTRSPONSES INDUCED BY CROMAKAUM AND PINACIDILIN GUINEA PIG ATRIUM a AUTHOR WAI-MAN LAU 7 FORMING ORG NAMES/ADDRESSES DEFENCE SCIENCE AND a...and Technology Organisaio Aot Val. Negative Inotropic Responses Victoria. Australia Induced by Cromakalim and Pinacidil in Guinea Pig Atrium Key

[The role of opiate receptors and ATP-dependent potassium channels of mitochondria in the formation of myocardial adaptive resistance to the arrhythmogenic effect of ischemia and reperfusion].

PubMed

Lishmanov, Iu B; Naryzhnaia, N V; Krylatov, A V; Maslov, L N; Bogomaz, S A; Ugdyzhekova, D S; Gross, G J; Stefano, J B

2003-01-01

Preliminary stimulation of opiate receptors (ORs) by intravenous administration of mu agonist DALDA (0.5 mg/kg), delta 1 agonist DPDPE (0.5 mg/kg), and kappa agonist (-)-U-50.488 (1 mg/kg) increases rat myocardial resistance to arrhythmogenic effect of coronary occlusion (10 min) and reperfusion (10 min). Activation of delta 2 ORs (DSLET, 0.5 mg/kg) has no effect on the incidence rate of ischemic and reperfusion arrhythmias. Preliminary administration of glibenclamide (0.3 mg/kg), an inhibitor of KATP channels, blocks the antiarrhythmic effect of DALDA and DPDPE. Repeated short-term exposures of rats to immobilization within two weeks increases the heart tolerance to the arrhythmogenic effect of coronary occlusion and reperfusion. This effect disappears after administration of CTAP (0.5 mg/kg), a mu antagonist, or injection of 5-hydroxydecanoate (5 mg/kg), an inhibitor of mitochondrial KATP channels. The selective antagonists of delta and kappa ORs have no effect on cardiac adaptation-induced resistance to the arrhythmogenic effect of ischemia and reperfusion. We believe that stimulation of mu, delta, and kappa ORs increases myocardial tolerance to the arrhythmogenic effect of ischemia and reperfusion through activation of KATP channels. The antiarrhythmic effect of the adaptation is mediated by stimulation of mu ORs and mitochondrial KATP channels.

Calcium channel blockers ameliorate iron overload-associated hepatic fibrosis by altering iron transport and stellate cell apoptosis

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

Zhang, Ying

Liver fibrosis is the principal cause of morbidity and mortality in patients with iron overload. Calcium channel blockers (CCBs) can antagonize divalent cation entry into renal and myocardial cells and inhibit fibrogenic gene expression. We investigated the potential of CCBs to resolve iron overload-associated hepatic fibrosis. Kunming mice were assigned to nine groups (n = 8 per group): control, iron overload, deferoxamine, high and low dose verapamil, high and low dose nimodipine, and high and low dose diltiazem. Iron deposition and hepatic fibrosis were measured in mouse livers. Expression levels of molecules associated with transmembrane iron transport were determined bymore » molecular biology approaches. In vitro HSC-T6 cells were randomized into nine groups (the same groups as the mice). Changes in proliferation, apoptosis, and metalloproteinase expression in cells were detected to assess the anti-fibrotic effects of CCBs during iron overload conditions. We found that CCBs reduced hepatic iron content, intracellular iron deposition, the number of hepatic fibrotic areas, collagen expression levels, and hydroxyproline content. CCBs rescued abnormal expression of α1C protein in L-type voltage-dependent calcium channel (LVDCC) and down-regulated divalent metal transporter-1 (DMT-1) expression in mouse livers. In iron-overloaded HSC-T6 cells, CCBs reduced iron deposition, inhibited proliferation, induced apoptosis, and elevated expression of matrix metalloproteinase-13 (MMP-13) and tissue inhibitor of metalloproteinase-1 (TIMP-1). CCBs are potential therapeutic agents that can be used to address hepatic fibrosis during iron overload. They resolve hepatic fibrosis probably correlated with regulating transmembrane iron transport and inhibiting HSC growth. - Highlights: • Calcium channel blockers (CCBs) reduced hepatic iron content. • CCBs decreased hepatic fibrotic areas and collagen expression levels. • CCBs resolve fibrosis by regulating iron transport

Characterization of selective Calcium-Release Activated Calcium channel blockers in mast cells and T-cells from human, rat, mouse and guinea-pig preparations.

PubMed

Rice, Louise V; Bax, Heather J; Russell, Linda J; Barrett, Victoria J; Walton, Sarah E; Deakin, Angela M; Thomson, Sally A; Lucas, Fiona; Solari, Roberto; House, David; Begg, Malcolm

2013-03-15

Loss of function mutations in the two key proteins which constitute Calcium-Release Activated Calcium (CRAC) channels demonstrate the critical role of this ion channel in immune cell function. The aim of this study was to demonstrate that inhibition of immune cell activation could be achieved with highly selective inhibitors of CRAC channels in vitro using cell preparations from human, rat, mouse and guinea-pig. Two selective small molecule blockers of CRAC channels; GSK-5498A and GSK-7975A were tested to demonstrate their ability to inhibit mediator release from mast cells, and pro-inflammatory cytokine release from T-cells in a variety of species. Both GSK-5498A and GSK-7975A completely inhibited calcium influx through CRAC channels. This led to inhibition of the release of mast cell mediators and T-cell cytokines from multiple human and rat preparations. Mast cells from guinea-pig and mouse preparations were not inhibited by GSK-5498A or GSK-7975A; however cytokine release was fully blocked from T-cells in a mouse preparation. GSK-5498A and GSK-7975A confirm the critical role of CRAC channels in human mast cell and T-cell function, and that inhibition can be achieved in vitro. The rat displays a similar pharmacology to human, promoting this species for future in vivo research with this series of molecules. Together these observations provide a critical forward step in the identification of CRAC blockers suitable for clinical development in the treatment of inflammatory disorders. Copyright © 2013 Elsevier B.V. All rights reserved.

Add-On Antihypertensive Medications to Angiotensin-Aldosterone System Blockers in Diabetes: A Comparative Effectiveness Study.

PubMed

Schroeder, Emily B; Chonchol, Michel; Shetterly, Susan M; Powers, J David; Adams, John L; Schmittdiel, Julie A; Nichols, Gregory A; O'Connor, Patrick J; Steiner, John F

2018-05-07

In individuals with diabetes, the comparative effectiveness of add-on antihypertensive medications added to an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker on the risk of significant kidney events is unknown. We used an observational, multicenter cohort of 21,897 individuals with diabetes to compare individuals who added β -blockers, dihydropyridine calcium channel blockers, loop diuretics, or thiazide diuretics to angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. We examined the hazard of significant kidney events, cardiovascular events, and death using Cox proportional hazard models with propensity score weighting. The composite significant kidney event end point was defined as the first occurrence of a ≥30% decline in eGFR to an eGFR<60 ml/min per 1.73 m 2 , initiation of dialysis, or kidney transplant. The composite cardiovascular event end point was defined as the first occurrence of hospitalization for acute myocardial infarction, acute coronary syndrome, stroke, or congestive heart failure; coronary artery bypass grafting; or percutaneous coronary intervention, and it was only examined in those free of cardiovascular disease at baseline. Over a maximum of 5 years, there were 4707 significant kidney events, 1498 deaths, and 818 cardiovascular events. Compared with thiazide diuretics, hazard ratios for significant kidney events for β -blockers, calcium channel blockers, and loop diuretics were 0.81 (95% confidence interval, 0.74 to 0.89), 0.67 (95% confidence interval, 0.58 to 0.78), and 1.19 (95% confidence interval, 1.00 to 1.41), respectively. Compared with thiazide diuretics, hazard ratios of mortality for β -blockers, calcium channel blockers, and loop diuretics were 1.19 (95% confidence interval, 0.97 to 1.44), 0.73 (95% confidence interval, 0.52 to 1.03), and 1.67 (95% confidence interval, 1.31 to 2.13), respectively. Compared with thiazide diuretics, hazard ratios of cardiovascular events

Investigation of the role of non-selective calcium channel blocker (flunarizine) on cerebral ischemic-reperfusion associated cognitive dysfunction in aged mice.

PubMed

Gulati, Puja; Muthuraman, Arunachalam; Kaur, Parneet

2015-04-01

The present study was designed to investigate the role of flunarizine (a non-selective calcium channel blocker) on cerebral ischemic-reperfusion associated cognitive dysfunction in aged mice. Bilateral carotid artery occlusion of 12min followed by reperfusion for 24h was given to induce cerebral injury in male Swiss mice. The assessment of learning & memory was performed by Morris water maze test; motor in-coordination was evaluated by rota rod, lateral push and inclined beam walking tests; cerebral infarct size was quantified by triphenyltetrazolium chloride staining. In addition, reduced glutathione (GSH), total calcium and acetylcholinesterase (AChE) activity were also estimated in aged brain tissue. Donepezil treated group served as a positive control in this study. Ischemia reperfusion (I/R) injury produced significant increase in cerebral infarct size. A significant loss of memory along with impairment of motor performance was also noted. Further, I/R injury also produced significant increase in levels of total calcium, AChE activity and decrease in GSH levels. Pretreatment of flunarizine significantly attenuated I/R induced infarct size, behavioral and biochemical changes. Hence, it may be concluded that, a non-selective calcium channel blocker can be useful in I/R associated cognitive dysfunction due to its anti-oxidant, anti-infarct and modulatory actions of neurotransmitters & calcium channels. Copyright © 2015 Elsevier Inc. All rights reserved.

Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans

PubMed Central

Liu, Shuyuan; Yue, Longtao; Gu, Wenrui; Li, Xiuyun; Zhang, Liuping; Sun, Shujuan

2016-01-01

Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers), amlodipine (AML), nifedipine (NIF), benidipine (BEN) and flunarizine (FNZ) with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1) expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI) <0.5, but no interaction against sensitive strains (FICI = 0.56 ~ 2). The mechanism studies revealed that fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin) and YVC1 (encoding calcium channel protein in vacuole membrane). PMID:26986478

The Kv7/KCNQ channel blocker XE991 protects nigral dopaminergic neurons in the 6-hydroxydopamine rat model of Parkinson's disease.

PubMed

Liu, Haixia; Jia, Lu; Chen, Xiaoyan; Shi, Limin; Xie, Junxia

2018-03-01

The excitability of dopaminergic neurons in the substantia nigra pars compacta (SNc) that supply the striatum with dopamine (DA) determines the function of the nigrostriatal system for motor coordination. We previously showed that 4-pyridinylmethyl-9(10H)-anthracenone (XE991), a specific blocker of Kv7/KCNQ channels, enhanced the excitability of nigral DA neurons and resulted in attenuation of haloperidol-induced catalepsy in a Parkinson's disease (PD) rat model. However, whether XE991 exhibits neuroprotective effects towards DA neuron degeneration remains unknown. The aim of this study was to investigate the effects of Kv7/KCNQ channel blocker, XE991, on 6-hydroxydopamine (6-OHDA)-induced nigral DA neuron degeneration and motor dysfunction. Using immunofluorescence staining and western blotting, we showed that intracerebroventricular administration of XE991 prevented the 6-OHDA-induced decrease in tyrosine hydroxylase (TH)-positive neurons and TH protein expression in the SNc. High-performance liquid chromatography with electrochemical detection (HPLC-ECD) also revealed that XE991 partly restored the levels of DA and its metabolites in the striatum. Moreover, XE991 decreased apomorphine (APO)-induced contralateral rotations, enhanced balance and coordination, and attenuated muscle rigidity in 6-OHDA-treated rats. Importantly, all neuroprotective effects by XE991 were abolished by co-application of Kv7/KCNQ channel opener retigabine and XE991. Thus, Kv7/KCNQ channel inhibition by XE991 can exert neuroprotective effects against 6-OHDA-induced degeneration of the nigrostriatal DA system and motor dysfunction. Copyright © 2017. Published by Elsevier Inc.

Divalent ions are potential permeating blockers of the non-selective NaK ion channel: combined QM and MD based investigations.

PubMed

Sadhu, Biswajit; Sundararajan, Mahesh; Bandyopadhyay, Tusar

2017-10-18

The bacterial NaK ion channel is distinctly different from other known ion channels due to its inherent non-selective feature. One of the unexplored and rather interesting features is its ability to permeate divalent metal ions (such as Ca 2+ and Ba 2+ ) and not monovalent alkali metal ions. Several intriguing questions about the energetics and structural aspects still remain unanswered. For instance, what causes Ca 2+ to permeate as well as block the selectivity filter (SF) of the NaK ion channel and act as a "permeating blocker"? How and at what energetic cost does another chemical congener, Sr 2+ , as well as Ba 2+ , a potent blocker of the K + ion channel, permeate through the SF of the NaK ion channel? Finally, how do their translocation energetics differ from those of monovalent ions such as K + ? Here, in an attempt to address these outstanding issues, we elucidate the structure, binding and selectivity of divalent ions (Ca 2+ , Sr 2+ and Ba 2+ ) as they permeate through the SF of the NaK ion channel using all-atom molecular dynamics simulations and density functional theory based calculations. We unveil mechanistic insight into this translocation event using well-tempered metadynamics simulations in a polarizable environment using the mean-field model of water and incorporating electronic continuum corrections for ions via charge rescaling. The results show that, akin to K + coordination, Sr 2+ and Ba 2+ bind at the SF in a very similar fashion and remain octa-coordinated at all sites. Interestingly, differing from its local hydration structure, Ca 2+ interacts with eight carbonyls to remain at the middle of the S3 site. Furthermore, the binding of divalent metals at SF binding sites is more favorable than the binding of K + . However, their permeation through the extracellular entrance faces a considerably higher energetic barrier compared to that for K + , which eventually manifests their inherent blocking feature.

BAD and KATP channels regulate neuron excitability and epileptiform activity.

PubMed

Martínez-François, Juan Ramón; Fernández-Agüera, María Carmen; Nathwani, Nidhi; Lahmann, Carolina; Burnham, Veronica L; Danial, Nika N; Yellen, Gary

2018-01-25

Brain metabolism can profoundly influence neuronal excitability. Mice with genetic deletion or alteration of Bad ( B CL-2 a gonist of cell d eath) exhibit altered brain-cell fuel metabolism, accompanied by resistance to acutely induced epileptic seizures; this seizure protection is mediated by ATP-sensitive potassium (K ATP ) channels. Here we investigated the effect of BAD manipulation on K ATP channel activity and excitability in acute brain slices. We found that BAD's influence on neuronal K ATP channels was cell-autonomous and directly affected dentate granule neuron (DGN) excitability. To investigate the role of neuronal K ATP channels in the anticonvulsant effects of BAD, we imaged calcium during picrotoxin-induced epileptiform activity in entorhinal-hippocampal slices. BAD knockout reduced epileptiform activity, and this effect was lost upon knockout or pharmacological inhibition of K ATP channels. Targeted BAD knockout in DGNs alone was sufficient for the antiseizure effect in slices, consistent with a 'dentate gate' function that is reinforced by increased K ATP channel activity. © 2018, Martínez-François et al.

The ATP-sensitive potassium (KATP) channel-encoded dSUR gene is required for Drosophila heart function and is regulated by tinman

PubMed Central

Akasaka, Takeshi; Klinedinst, Susan; Ocorr, Karen; Bustamante, Erika L.; Kim, Seung K.; Bodmer, Rolf

2006-01-01

The homeobox transcription factor Tinman plays an important role in the initiation of heart development. Later functions of Tinman, including the target genes involved in cardiac physiology, are less well studied. We focused on the dSUR gene, which encodes an ATP-binding cassette transmembrane protein that is expressed in the heart. Mammalian SUR genes are associated with KATP (ATP-sensitive potassium) channels, which are involved in metabolic homeostasis. We provide experimental evidence that Tinman directly regulates dSUR expression in the developing heart. We identified a cis-regulatory element in the first intron of dSUR, which contains Tinman consensus binding sites and is sufficient for faithful dSUR expression in the fly’s myocardium. Site-directed mutagenesis of this element shows that these Tinman sites are critical to dSUR expression, and further genetic manipulations suggest that the GATA transcription factor Pannier is synergistically involved in cardiac-restricted dSUR expression in vivo. Physiological analysis of dSUR knock-down flies supports the idea that dSUR plays a protective role against hypoxic stress and pacing-induced heart failure. Because dSUR expression dramatically decreases with age, it is likely to be a factor involved in the cardiac aging phenotype of Drosophila. dSUR provides a model for addressing how embryonic regulators of myocardial cell commitment can contribute to the establishment and maintenance of cardiac performance. PMID:16882722

Role of ATP-sensitive potassium channels in the piracetam induced blockade of opioid effects.

PubMed

Rehni, Ashish K; Singh, Nirmal; Jindal, Seema

2007-12-01

The present study has been designed to investigate the effect of piracetam on morphine/ buprenorphine-induced antinociception in rats and effect of piracetam on morphine or minoxidil induced relaxation in KCl-precontracted isolated rat aortic ring preparation. Nociceptive threshold was measured by the tail flick test in rats. The cumulative dose responses of morphine or minoxidil were recorded in KCl-precontracted isolated rat aortic ring preparation. Piracetam attenuated buprenorphine-induced antinociception in rats. Piracetam significantly reduced the morphine and minoxidil induced relaxation in KCl precontracted isolated rat aortic ring preparation suggesting that piracetam interferes with opioid receptor and ATP-sensitive potassium channel (KATP) opener mediated responses in vitro. Thus, it may be suggested that piracetam attenuates opioid effects by an opioid receptor-KATP channel linked mechanism.

Perfusion of isolated carotid sinus with hydrogen sulfide attenuated the renal sympathetic nerve activity in anesthetized male rats.

PubMed

Guo, Q; Wu, Y; Xue, H; Xiao, L; Jin, S; Wang, R

2016-07-18

The purpose of the present study was to define the indirect central effect of hydrogen sulfide (H(2)S) on baroreflex control of sympathetic outflow. Perfusing the isolated carotid sinus with sodium hydrosulfide (NaHS), a H(2)S donor, the effect of H(2)S was measured by recording changes of renal sympathetic nerve activity (RSNA) in anesthetized male rats. Perfusion of isolated carotid sinus with NaHS (25, 50, 100 micromol/l) dose and time-dependently inhibited sympathetic outflow. Preconditioning of glibenclamide (20 micromol/l), a ATP-sensitive K(+) channels (K(ATP)) blocker, the above effect of NaHS was removed. With 1, 4-dihydro-2, 6-dimethyl-5-nitro-4-(2-[trifluoromethyl] phenyl) pyridine-3-carboxylic acid methyl ester (Bay K8644, 500 nmol/l) pretreatment, which is an agonist of L-calcium channels, the effect of NaHS was eliminated. Perfusion of cystathionine gamma-lyase (CSE) inhibitor, DL-propargylglycine (PPG, 200 micromol/l), increased sympathetic outflow. The results show that exogenous H(2)S in the carotid sinus inhibits sympathetic outflow. The effect of H(2)S is attributed to opening K(ATP) channels and closing the L-calcium channels.

Discovery of a Potent, Selective T-type Calcium Channel Blocker as a Drug Candidate for the Treatment of Generalized Epilepsies.

PubMed

Bezençon, Olivier; Heidmann, Bibia; Siegrist, Romain; Stamm, Simon; Richard, Sylvia; Pozzi, Davide; Corminboeuf, Olivier; Roch, Catherine; Kessler, Melanie; Ertel, Eric A; Reymond, Isabelle; Pfeifer, Thomas; de Kanter, Ruben; Toeroek-Schafroth, Michael; Moccia, Luca G; Mawet, Jacques; Moon, Richard; Rey, Markus; Capeleto, Bruno; Fournier, Elvire

2017-12-14

We report here the discovery and pharmacological characterization of N-(1-benzyl-1H-pyrazol-3-yl)-2-phenylacetamide derivatives as potent, selective, brain-penetrating T-type calcium channel blockers. Optimization focused mainly on solubility, brain penetration, and the search for an aminopyrazole metabolite that would be negative in an Ames test. This resulted in the preparation and complete characterization of compound 66b (ACT-709478), which has been selected as a clinical candidate.

Additive effects of cilnidipine, an L-/N-type calcium channel blocker, and an angiotensin II receptor blocker on reducing cardiorenal damage in Otsuka Long-Evans Tokushima Fatty rats with type 2 diabetes mellitus.

PubMed

Mori, Yutaka; Aritomi, Shizuka; Niinuma, Kazumi; Nakamura, Tarou; Matsuura, Kenichi; Yokoyama, Junichi; Utsunomiya, Kazunori

2014-01-01

Cilnidipine (Cil), which is an L-/N-type calcium channel blocker (CCB), has been known to provide renal protection by decreasing the activity of the sympathetic nervous system (SNS) and the renin-angiotensin system. In this study, we compared the effects of the combination of Cil and amlodipine (Aml), which is an L-type CCB, with an angiotensin (Ang) II receptor blocker on diabetic cardiorenal damage in spontaneously type 2 diabetic rats. Seventeen-week-old Otsuka Long-Evans Tokushima Fatty rats were randomly assigned to receive Cil, Aml, valsartan (Val), Cil + Val, Aml + Val, or a vehicle (eight rats per group) for 22 weeks. Antihypertensive potencies were nearly equal among the CCB monotherapy groups and the combination therapy groups. The lowering of blood pressure by either treatment did not significantly affect the glycemic variables. However, exacerbations of renal and heart failure were significantly suppressed in rats administered Cil or Val, and additional suppression was observed in those administered Cil + Val. Although Val increased the renin-Ang system, Aml + Val treatment resulted in additional increases in these parameters, while Cil + Val did not show such effects. Furthermore, Cil increased the ratio of Ang-(1-7) to Ang-I, despite the fact that Val and Aml + Val decreased the Ang-(1-7) levels. These actions of Cil + Val might be due to their synergistic inhibitory effect on the activity of the SNS, and on aldosterone secretion through N-type calcium channel antagonism and Ang II receptor type 1 antagonism. Thus, Cil may inhibit the progression of cardiorenal disease in type 2 diabetes patients by acting as an N-type CCB and inhibiting the aldosterone secretion and SNS activation when these drugs were administered in combination with an Ang II receptor blocker.

State-dependent block of CNG channels by dequalinium.

PubMed

Rosenbaum, Tamara; Gordon-Shaag, Ariela; Islas, León D; Cooper, Jeremy; Munari, Mika; Gordon, Sharona E

2004-03-01

Cyclic nucleotide-gated (CNG) ion channels are nonselective cation channels with a high permeability for Ca(2+). Not surprisingly, they are blocked by a number of Ca(2+) channel blockers including tetracaine, pimozide, and diltiazem. We studied the effects of dequalinium, an extracellular blocker of the small conductance Ca(2+)-activated K(+) channel. We previously noted that dequalinium is a high-affinity blocker of CNGA1 channels from the intracellular side, with little or no state dependence at 0 mV. Here we examined block by dequalinium at a broad range of voltages in both CNGA1 and CNGA2 channels. We found that dequalinium block was mildly state dependent for both channels, with the affinity for closed channels 3-5 times higher than that for open channels. Mutations in the S4-S5 linker did not alter the affinity of open channels for dequalinium, but increased the affinity of closed channels by 10-20-fold. The state-specific effect of these mutations raises the question of whether/how the S4-S5 linker alters the binding of a blocker within the ion permeation pathway.

Optimization of ADME Properties for Sulfonamides Leading to the Discovery of a T-Type Calcium Channel Blocker, ABT-639

PubMed Central

2015-01-01

The discovery of a novel peripherally acting and selective Cav3.2 T-type calcium channel blocker, ABT-639, is described. HTS hits 1 and 2, which have poor metabolic stability, were optimized to obtain 4, which has improved stability and oral bioavailability. Modification of 4 to further improve ADME properties led to the discovery of ABT-639. Following oral administration, ABT-639 produces robust antinociceptive activity in experimental pain models at doses that do not significantly alter psychomotor or hemodynamic function in the rat. PMID:26101566

Optimization of ADME Properties for Sulfonamides Leading to the Discovery of a T-Type Calcium Channel Blocker, ABT-639.

PubMed

Zhang, Qingwei; Xia, Zhiren; Joshi, Shailen; Scott, Victoria E; Jarvis, Michael F

2015-06-11

The discovery of a novel peripherally acting and selective Cav3.2 T-type calcium channel blocker, ABT-639, is described. HTS hits 1 and 2, which have poor metabolic stability, were optimized to obtain 4, which has improved stability and oral bioavailability. Modification of 4 to further improve ADME properties led to the discovery of ABT-639. Following oral administration, ABT-639 produces robust antinociceptive activity in experimental pain models at doses that do not significantly alter psychomotor or hemodynamic function in the rat.

Polyaniline-graphene oxide nanocomposite sensor for quantification of calcium channel blocker levamlodipine.

PubMed

Jain, Rajeev; Sinha, Ankita; Khan, Ab Lateef

2016-08-01

A novel polyaniline-graphene oxide nanocomposite (PANI/GO/GCE) sensor has been fabricated for quantification of a calcium channel blocker drug levamlodipine (LAMP). Fabricated sensor has been characterized by electrochemical impedance spectroscopy, square wave and cyclic voltammetry, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The developed PANI/GO/GCE sensor has excellent analytical performance towards electrocatalytic oxidation as compared to PANI/GCE, GO/GCE and bare GCE. Under optimized experimental conditions, the fabricated sensor exhibits a linear response for LAMP for its oxidation over a concentration range from 1.25μgmL(-1) to 13.25μgmL(-1) with correlation coefficient of 0.9950 (r(2)), detection limit of 1.07ngmL(-1) and quantification limit of 3.57ngmL(-1). The sensor shows an excellent performance for detecting LAMP with reproducibility of 2.78% relative standard deviation (RSD). The proposed method has been successfully applied for LAMP determination in pharmaceutical formulation with a recovery from 99.88% to 101.75%. Copyright © 2015 Elsevier B.V. All rights reserved.

Functional expression and purification of recombinant Tx1, a sodium channel blocker neurotoxin from the venom of the Brazilian "armed" spider, Phoneutria nigriventer.

PubMed

Diniz, Marcelo R V; Theakston, R David G; Crampton, Julian M; Nascimento Cordeiro, Marta do; Pimenta, Adriano M C; De Lima, Maria Elena; Diniz, Carlos R

2006-11-01

Tx1 from the venom of the Brazilian spider, Phoneutria nigriventer, is a lethal neurotoxic polypeptide of M(r) 8600 Da with 14 cysteine residues. It is a novel sodium channel blocker which reversibly inhibits sodium currents in CHO cells expressing recombinant sodium (Nav1.2) channels. We cloned and expressed the Tx1 toxin as a thioredoxin fusion product in the cytoplasm of Escherichia coli. After semipurification by immobilized Ni-ion affinity chromatography, the recombinant Tx1 was purified by reverse phase chromatography and characterized. It displayed similar biochemical and pharmacological properties to the native toxin, and it should be useful for further investigation of structure-function relationship of Na channels.

Interaction of calcium channel blockers (CCBs) with histamine and 5-hydroxytryptamine in aorta from normal and diseased rats.

PubMed

Bhugra, P; Gulati, O D

1996-04-01

The present study attempts to investigate the interaction of calcium channel blockers (CCBs) with histamine (H) and 5-hydroxytryptamine (5-HT) in rat isolated aortic strip preparations. In preparations obtained from rats chronically treated with various CCBs the contractile responses to H were completely blocked suggesting that this may be due to inhibition of the voltage-dependent channels and inositol 1,4,5-triphosphate induced release of calcium from intracellular stores. The decreased contractions of the aortic strip preparations with 5-HT obtained from rats chronically treated with various CCBs implies a decrease in 5-HT receptor density. DOCA-saline hypertensive rats chronically treated with various CCBs showed variable responses to H and 5-HT suggesting that these changes may be due to different isoforms of L-type calcium channels. In L-thyroxine-treated preparations or those simultaneously treated with L-thyroxine and CCBs the responses to H were abolished and those to 5-HT were partially blocked with decrease in maxima which could be secondary to the primary effect on the heart and to generalised reduced senstivity of the rat aorta.

Calcium channel blockers in hypertension. Is there still a controversy?

PubMed

Izzo, Joseph L

2005-08-01

There are several reasons why no single antihypertensive drug class is ideal in all clinical situations. First, pathophysiologic heterogeneity in hypertension and diversity of mechanisms of antihypertensive drugs dictate that no single drug class can be optimally effective in all subpopulations. Second, sustained blood pressure control generally requires combination therapy to block the reflex stimulation of physiologic mechanisms that attempt to restore blood pressure to pretreatment levels. Third, while effective blood pressure control is more important than choice of initial drug in the prevention of hypertension-related morbidity and mortality, specific drug classes are indicated for optimal treatment of complications of hypertension (e.g. heart failure, kidney disease). Fourth, although antihypertensive drug side effects are uncommon, alternative strategies are required in some patients. Given these principles, past controversies regarding whether calcium channel blockers (CCBs) should be used in the treatment of hypertension become moot. CCBs are extremely effective in lowering blood pressure and in preventing stroke and cardiovascular disease. When additional blood pressure lowering is necessary to meet strict targets, CCBs may be added, even in heart failure or chronic kidney disease, where CCBs alone may not achieve optimal outcomes. Combinations of CCBs with "anti-neurohumoral" drugs such as ACE inhibitors are particularly useful to achieve sustained blood pressure control, reduce adverse effects such as edema, and improve outcomes.

Modulation of Ionic Channels and Insulin Secretion by Drugs and Hormones in Pancreatic Beta Cells.

PubMed

Velasco, Myrian; Díaz-García, Carlos Manlio; Larqué, Carlos; Hiriart, Marcia

2016-09-01

Pancreatic beta cells, unique cells that secrete insulin in response to an increase in glucose levels, play a significant role in glucose homeostasis. Glucose-stimulated insulin secretion (GSIS) in pancreatic beta cells has been extensively explored. In this mechanism, glucose enters the cells and subsequently the metabolic cycle. During this process, the ATP/ADP ratio increases, leading to ATP-sensitive potassium (KATP) channel closure, which initiates depolarization that is also dependent on the activity of TRP nonselective ion channels. Depolarization leads to the opening of voltage-gated Na(+) channels (Nav) and subsequently voltage-dependent Ca(2+) channels (Cav). The increase in intracellular Ca(2+) triggers the exocytosis of insulin-containing vesicles. Thus, electrical activity of pancreatic beta cells plays a central role in GSIS. Moreover, many growth factors, incretins, neurotransmitters, and hormones can modulate GSIS, and the channels that participate in GSIS are highly regulated. In this review, we focus on the principal ionic channels (KATP, Nav, and Cav channels) involved in GSIS and how classic and new proteins, hormones, and drugs regulate it. Moreover, we also discuss advances on how metabolic disorders such as metabolic syndrome and diabetes mellitus change channel activity leading to changes in insulin secretion. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

C-Terminal residues in small potassium channel blockers OdK1 and OSK3 from scorpion venom fine-tune the selectivity.

PubMed

Kuzmenkov, Alexey I; Peigneur, Steve; Chugunov, Anton O; Tabakmakher, Valentin M; Efremov, Roman G; Tytgat, Jan; Grishin, Eugene V; Vassilevski, Alexander A

2017-05-01

We report isolation, sequencing, and electrophysiological characterization of OSK3 (α-KTx 8.8 in Kalium and Uniprot databases), a potassium channel blocker from the scorpion Orthochirus scrobiculosus venom. Using the voltage clamp technique, OSK3 was tested on a wide panel of 11 voltage-gated potassium channels expressed in Xenopus oocytes, and was found to potently inhibit Kv1.2 and Kv1.3 with IC 50 values of ~331nM and ~503nM, respectively. OdK1 produced by the scorpion Odontobuthus doriae differs by just two C-terminal residues from OSK3, but shows marked preference to Kv1.2. Based on the charybdotoxin-potassium channel complex crystal structure, a model was built to explain the role of the variable residues in OdK1 and OSK3 selectivity. Copyright © 2017 Elsevier B.V. All rights reserved.

On the mechanism of TBA block of the TRPV1 channel.

PubMed

Oseguera, Andrés Jara; Islas, León D; García-Villegas, Refugio; Rosenbaum, Tamara

2007-06-01

The transient receptor potential vanilloid 1 (TRPV1) channel is a nonselective cation channel activated by capsaicin and responsible for thermosensation. To date, little is known about the gating characteristics of these channels. Here we used tetrabutylammonium (TBA) to determine whether this molecule behaves as an ion conduction blocker in TRPV1 channels and to gain insight into the nature of the activation gate of this protein. TBA belongs to a family of classic potassium channel blockers that have been widely used as tools for determining the localization of the activation gate and the properties of the pore of several ion channels. We found TBA to be a voltage-dependent pore blocker and that the properties of block are consistent with an open-state blocker, with the TBA molecule binding to multiple open states, each with different blocker affinities. Kinetics of channel closure and burst-length analysis in the presence of blocker are consistent with a state-dependent blocking mechanism, with TBA interfering with closing of an activation gate. This activation gate may be located cytoplasmically with respect to the binding site of TBA ions, similar to what has been observed in potassium channels. We propose an allosteric model for TRPV1 activation and block by TBA, which explains our experimental data.

Misperceptions about beta-blockers and diuretics: a national survey of primary care physicians.

PubMed

Ubel, Peter A; Jepson, Christopher; Asch, David A

2003-12-01

Based on a series of clinical trials showing no difference in the effectiveness or tolerability of most major classes of antihypertensive medications, the Joint National Commission on High Blood Pressure Treatment recommends that physicians prescribe beta-blockers or diuretics as initial hypertensive therapy unless there are compelling indications for another type of medication. Nevertheless, many physicians continue to favor more expensive medications like angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers as first line agents. The persistent use of these agents raises questions as to whether physicians perceive ACE inhibitors and calcium channel blockers to be better than beta-blockers and diuretics. We surveyed 1,200 primary care physicians in 1997, and another 500 primary care physicians in 2000, and asked them to estimate the relative effectiveness and side effects of 4 classes of medication in treating a hypothetical patient with uncomplicated hypertension: ACE inhibitors, beta-blockers, calcium channel blockers, and diuretics. In addition, we asked them to indicate whether they ever provided free samples of hypertension medications to their patients. Perceptions of the relative effectiveness and side effects of the 4 classes of hypertension medications did not significantly change over the 3 years, nor did prescription recommendations. Physicians perceive that diuretics are less effective at lowering blood pressure than the other 3 classes (P <.001). They also perceive that beta-blockers are less tolerated than the other 3 classes (P <.001). In a multivariate model, perceptions of effectiveness and tolerability displayed significant associations with prescription preference independent of background variables. The only other variable to contribute significantly to the model was provision of free medication samples to patients. Despite numerous clinical trials showing no difference in the effectiveness or side-effect profiles of these

Structure and function of μ-conotoxins, peptide-based sodium channel blockers with analgesic activity

PubMed Central

Green, Brad R; Bulaj, Grzegorz; Norton, Raymond S

2015-01-01

μ-Conotoxins block voltage-gated sodium channels (VGSCs) and compete with tetrodotoxin for binding to the sodium conductance pore. Early efforts identified μ-conotoxins that preferentially blocked the skeletal muscle subtype (NaV1.4). However, the last decade witnessed a significant increase in the number of μ-conotoxins and the range of VGSC subtypes inhibited (NaV1.2, NaV1.3 or NaV1.7). Twenty μ-conotoxin sequences have been identified to date and structure–activity relationship studies of several of these identified key residues responsible for interactions with VGSC subtypes. Efforts to engineer-in subtype specificity are driven by in vivo analgesic and neuromuscular blocking activities. This review summarizes structural and pharmacological studies of μ-conotoxins, which show promise for development of selective blockers of NaV1.2, and perhaps also NaV1.1,1.3 or 1.7. PMID:25406007

A deleterious gene-by-environment interaction imposed by calcium channel blockers in Marfan syndrome.

PubMed

Doyle, Jefferson J; Doyle, Alexander J; Wilson, Nicole K; Habashi, Jennifer P; Bedja, Djahida; Whitworth, Ryan E; Lindsay, Mark E; Schoenhoff, Florian; Myers, Loretha; Huso, Nick; Bachir, Suha; Squires, Oliver; Rusholme, Benjamin; Ehsan, Hamid; Huso, David; Thomas, Craig J; Caulfield, Mark J; Van Eyk, Jennifer E; Judge, Daniel P; Dietz, Harry C

2015-10-27

Calcium channel blockers (CCBs) are prescribed to patients with Marfan syndrome for prophylaxis against aortic aneurysm progression, despite limited evidence for their efficacy and safety in the disorder. Unexpectedly, Marfan mice treated with CCBs show accelerated aneurysm expansion, rupture, and premature lethality. This effect is both extracellular signal-regulated kinase (ERK1/2) dependent and angiotensin-II type 1 receptor (AT1R) dependent. We have identified protein kinase C beta (PKCβ) as a critical mediator of this pathway and demonstrate that the PKCβ inhibitor enzastaurin, and the clinically available anti-hypertensive agent hydralazine, both normalize aortic growth in Marfan mice, in association with reduced PKCβ and ERK1/2 activation. Furthermore, patients with Marfan syndrome and other forms of inherited thoracic aortic aneurysm taking CCBs display increased risk of aortic dissection and need for aortic surgery, compared to patients on other antihypertensive agents.

The KATP channel in migraine pathophysiology: a novel therapeutic target for migraine.

PubMed

Al-Karagholi, Mohammad Al-Mahdi; Hansen, Jakob Møller; Severinsen, Johanne; Jansen-Olesen, Inger; Ashina, Messoud

2017-08-23

To review the distribution and function of K ATP channels, describe the use of K ATP channels openers in clinical trials and make the case that these channels may play a role in headache and migraine. K ATP channels are widely present in the trigeminovascular system and play an important role in the regulation of tone in cerebral and meningeal arteries. Clinical trials using synthetic K ATP channel openers report headache as a prevalent-side effect in non-migraine sufferers, indicating that K ATP channel opening may cause headache, possibly due to vascular mechanisms. Whether K ATP channel openers can provoke migraine in migraine sufferers is not known. We suggest that K ATP channels may play an important role in migraine pathogenesis and could be a potential novel therapeutic anti-migraine target.

Time-dependent alteration in cromakalim-induced relaxation of corpus cavernosum from streptozocin-induced diabetic rats.

PubMed

Ghasemi, Mehdi; Sadeghipour, Hamed; Asadi, Shahrzad; Dehpour, Ahmad Reza

2007-09-01

The purpose of the present study was to investigate the relaxant responses to the ATP-sensitive potassium (K(ATP)) channel opener cromakalim in corpus cavernosum strips from 1-, 2-, 4-, 6-, and 8-week streptozocin-induced diabetic rats. Cromakalim (1 nM-0.1 mM) produced concentration-dependent relaxation in phenylephrine (7.5 microM)-precontracted isolated rat corporal strips. Compared with age-matched control animals, a significant enhancement in cromakalim-induced relaxation of corpus cavernosum was observed in 2-week diabetic animals, whereas the relaxant responses to cromakalim were decreased in 6-and 8-week diabetic animals. However, the cromakalim-induced relaxation was not altered in either 1-week or 4-week rat corporal strips in comparison with corresponding age-matched non-diabetic groups. Preincubation with the K(ATP) channel blocker glibenclamide (10 microM) significantly inhibited the cromakalim-induced relaxation in both non-diabetic and diabetic rat corpus cavernosum, but neither the voltage-dependent K(+) channel (K(V)) antagonist 4-aminopyridine (1 mM) nor the calcium-activated K(+) channel (K(Ca)) antagonist charybdotoxin (0.1 microM) had significant effect on cromakalim-induced relaxation in both control and diabetic rat corporal strips. Relaxation responses to the nitric oxide donor sodium nitroprusside (1 nM-0.1 mM) in diabetic rat corpus cavernosum were similar to that of age-matched controls. These data demonstrated that the relaxant responses to cromakalim were altered in diabetic cavernosal strips in a time dependent manner, suggesting that the period of diabetes mellitus may play a key role in the K(ATP) channels function in rat corpus cavernosum.

Clofilium inhibits Slick and Slack potassium channels.

PubMed

de Los Angeles Tejada, Maria; Stolpe, Kathleen; Meinild, Anne-Kristine; Klaerke, Dan A

2012-01-01

Slick and Slack high-conductance potassium channels have been recently discovered, and are found in the central nervous system and in the heart. Both channels are activated by Na(+) and Cl(-), and Slick channels are also inhibited by adenosine triphospate (ATP). An important role of setting the resting membrane potential and controlling the basal excitability of neurons has been suggested for these channels. In addition, no specific blockers for these channels are known up to the present. With the purpose of studying the pharmacological characteristics of Slick and Slack channels, the effects of exposure to the antiarrhythmic compound clofilium were evaluated. Clofilium was able to modulate the activity of Slick and Slack channels effectively, with a stronger effect on Slack than Slick channels. In order to evaluate the pharmacological behavior of Slick and Slack channels further, 38 commonly used potassium channel blockers were tested. Screening of these compounds did not reveal any modulators of Slick and Slack channels, except for clofilium. The present study provides a first approach towards elucidating the pharmacological characteristics of Slick and Slack channels and could be the basis for future studies aimed at developing potent and specific blockers and activators for these channels.

Structural and functional determinants of conserved lipid interaction domains of inward rectifying Kir6.2 channels.

PubMed

Cukras, Catherine A; Jeliazkova, Iana; Nichols, Colin G

2002-06-01

All members of the inward rectifiier K(+) (Kir) channel family are activated by phosphoinositides and other amphiphilic lipids. To further elucidate the mechanistic basis, we examined the membrane association of Kir6.2 fragments of K(ATP) channels, and the effects of site-directed mutations of these fragments and full-length Kir6.2 on membrane association and K(ATP) channel activity, respectively. GFP-tagged Kir6.2 COOH terminus and GFP-tagged pleckstrin homology domain from phospholipase C delta1 both associate with isolated membranes, and association of each is specifically reduced by muscarinic m1 receptor-mediated phospholipid depletion. Kir COOH termini are predicted to contain multiple beta-strands and a conserved alpha-helix (residues approximately 306-311 in Kir6.2). Systematic mutagenesis of D307-F315 reveals a critical role of E308, I309, W311 and F315, consistent with residues lying on one side of a alpha-helix. Together with systematic mutation of conserved charges, the results define critical determinants of a conserved domain that underlies phospholipid interaction in Kir channels.

H2 blockers

MedlinePlus

Peptic ulcer disease - H2 blockers; PUD - H2 blockers; Gastroesophageal reflux - H2 blockers; GERD - H2 blockers ... provider about your symptoms. If you have a peptic ulcer, your provider may prescribe H2 blockers along with ...

[K+ channels and lung epithelial physiology].

PubMed

Bardou, Olivier; Trinh, Nguyen Thu Ngan; Brochiero, Emmanuelle

2009-04-01

Transcripts of more than 30 different K(+) channels have been detected in the respiratory epithelium lining airways and alveoli. These channels belong to the 3 main classes of K(+) channels, i.e. i) voltage-dependent or calcium-activated, 6 transmembrane segments (TM), ii) 2-pores 4-TM and iii) inward-rectified 2-TM channels. The physiological and functional significance of this high molecular diversity of lung epithelial K(+) channels is not well understood. Surprisingly, relatively few studies are focused on K(+) channel function in lung epithelial physiology. Nevertheless, several studies have shown that KvLQT1, KCa and K(ATP) K(+) channels play a crucial role in ion and fluid transport, contributing to the control of airway and alveolar surface liquid composition and volume. K(+) channels are involved in other key functions, such as O(2) sensing or the capacity of the respiratory epithelia to repair after injury. This mini-review aims to discuss potential functions of lung K(+) channels.

The facilitating effect of systemic administration of Kv7/M channel blocker XE991 on LTP induction in the hippocampal CA1 area independent of muscarinic activation.

PubMed

Song, Ming-Ke; Cui, Yong-Yao; Zhang, Wei-Wei; Zhu, Liang; Lu, Yang; Chen, Hong-Zhuan

2009-09-11

A large amount of in vitro studies demonstrate suppression of M-current in hippocampal neurons by Kv7/M channel blocker results in depolarization of membrane potential and release of neurotransmitters, such as acetylcholine and glutamate, suggesting that Kv7/M channel may play important roles in regulating synaptic plasticity. In the present study, we examined the in vivo effect of Kv7/M channel inhibition on the long-term potentiation (LTP) induction at basal dendrites in hippocampal CA1 area of urethane-anaesthetized rats. The Kv7/M channel was inhibited by intraperitoneal injection of XE991 (10mg/kg) and the LTP of field excitatory postsynaptic potential (fEPSP) was induced by supra-threshold high frequency stimulation (S1 HFS). A weak protocol which was just below the threshold for evoking LTP was used as sub-threshold high frequency stimulation (S2 HFS). XE991 did not significantly alter the slope of fEPSP and the magnitude of LTP induced by S1 HFS, suggesting that Kv7/M channel inhibition had little or no effect on glutamatergic transmission under basal conditions. However, XE991 could make S2 HFS evoke LTP even after the application of the muscarinic cholinergic (mACh) receptor antagonist scopolamine, suggesting that Kv7/M channel inhibition lowered the threshold for LTP induction and the effect was independent of muscarinic activation. Based on the above findings, we concluded that the facilitating effect of XE991 on LTP induction is not mediated by its ability to enhance the release of acetylcholine; therefore, Kv7/M channel blockers may provide a therapeutic benefit to cholinergic deficiency-related cognitive impairment, e.g., Alzheimer's disease.

A deleterious gene-by-environment interaction imposed by calcium channel blockers in Marfan syndrome

PubMed Central

Doyle, Jefferson J; Doyle, Alexander J; Wilson, Nicole K; Habashi, Jennifer P; Bedja, Djahida; Whitworth, Ryan E; Lindsay, Mark E; Schoenhoff, Florian; Myers, Loretha; Huso, Nick; Bachir, Suha; Squires, Oliver; Rusholme, Benjamin; Ehsan, Hamid; Huso, David; Thomas, Craig J; Caulfield, Mark J; Van Eyk, Jennifer E; Judge, Daniel P; Dietz, Harry C

2015-01-01

Calcium channel blockers (CCBs) are prescribed to patients with Marfan syndrome for prophylaxis against aortic aneurysm progression, despite limited evidence for their efficacy and safety in the disorder. Unexpectedly, Marfan mice treated with CCBs show accelerated aneurysm expansion, rupture, and premature lethality. This effect is both extracellular signal-regulated kinase (ERK1/2) dependent and angiotensin-II type 1 receptor (AT1R) dependent. We have identified protein kinase C beta (PKCβ) as a critical mediator of this pathway and demonstrate that the PKCβ inhibitor enzastaurin, and the clinically available anti-hypertensive agent hydralazine, both normalize aortic growth in Marfan mice, in association with reduced PKCβ and ERK1/2 activation. Furthermore, patients with Marfan syndrome and other forms of inherited thoracic aortic aneurysm taking CCBs display increased risk of aortic dissection and need for aortic surgery, compared to patients on other antihypertensive agents. DOI: http://dx.doi.org/10.7554/eLife.08648.001 PMID:26506064

Diabetes mellitus reduces the function and expression of ATP-dependent K⁺ channels in cardiac mitochondria.

PubMed

Fancher, Ibra S; Dick, Gregory M; Hollander, John M

2013-03-28

Our goal was to determine the effects of type I diabetes mellitus on the function and expression of ATP-dependent K(+) channels in cardiac mitochondria (mitoKATP), composed of a pore-forming subunit (Kir6.1) and a diazoxide-sensitive sulphonylurea receptor (SUR1). We tested the hypothesis that diabetes reduces Kir6.1 and SUR1 expression as well as diazoxide-induced depolarization of mitochondrial membrane potential (ΔΨm). Male FVB mice were made diabetic for 5weeks with multiple low dose injections of streptozotocin. Cardiac mitochondria were separated into two populations: subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM). mitoKATP expression was determined via Western blot analysis of Kir6.1 and SUR1 proteins. mitoKATP function was determined by measuring ΔΨm with the potentiometric dye rhodamine 123. Diabetes reduced Kir6.1 and SUR1 expression in IFM by over 40% (p<0.05 for both). Similarly, diabetes reduced Kir6.1 expression in SSM by approximately 40% (p<0.05); however, SUR1 expression was unaffected. Opening mitoKATP with diazoxide (100μM) depolarized control IFM ΔΨm by 80% of the valinomycin maximum; diabetic IFM depolarized only 30% (p<0.05). Diazoxide-induced depolarization was much less in SSM (20-30%) and unaffected by diabetes. Our data indicate that diabetes reduces mitoKATP expression and function in IFM. These changes in mitoKATP may provide an opportunity to understand mechanisms leading to diabetic cardiomyopathy and loss of cardioprotective mechanisms in the diabetic heart. Copyright © 2013 Elsevier Inc. All rights reserved.

Neuronal and Cardiovascular Potassium Channels as Therapeutic Drug Targets

PubMed Central

Humphries, Edward S. A.

2015-01-01

Potassium (K+) channels, with their diversity, often tissue-defined distribution, and critical role in controlling cellular excitability, have long held promise of being important drug targets for the treatment of dysrhythmias in the heart and abnormal neuronal activity within the brain. With the exception of drugs that target one particular class, ATP-sensitive K+ (KATP) channels, very few selective K+ channel activators or inhibitors are currently licensed for clinical use in cardiovascular and neurological disease. Here we review what a range of human genetic disorders have told us about the role of specific K+ channel subunits, explore the potential of activators and inhibitors of specific channel populations as a therapeutic strategy, and discuss possible reasons for the difficulty in designing clinically relevant K+ channel modulators. PMID:26303307

Current role of beta-blockers in the treatment of hypertension.

PubMed

Aronow, Wilbert S

2010-11-01

It is important to know which patients with hypertension will benefit from beta-blocker therapy and which beta-blockers should be used in the treatment of hypertension to reduce cardiovascular events and mortality. Studies between 1981 and 2009 using a Medline search are reported. Beta-blockers should be used to treat hypertension in patients with previous myocardial infarction, acute coronary syndromes, angina pectoris, congestive heart failure, ventricular arrhythmias, supraventricular tachyarrhythmias, diabetes mellitus, after coronary artery bypass graft surgery, and in patients who are pregnant, have thyrotoxicosis, glaucoma, migraine, essential tremor, perioperative hypertension, or an excessive blood pressure response after exercise. The use of beta-blockers as first-line therapy in patients with primary hypertension has been controversial. However, the 2009 guidelines of the European Society of Hypertension state that large-scale meta-analyses of available data confirm that diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and calcium channel blockers do not significantly differ in their ability to lower blood pressure and to exert cardiovascular protection both in elderly and in younger patients. The key message of this paper is that atenolol should not be used as an antihypertensive drug and that the degree of reduction of mortality, myocardial infarction, stroke and congestive heart failure by antihypertensive therapy is dependent on the degree of lowering of aortic blood pressure. Newer vasodilator beta-blockers such as carvedilol and nebivolol may be more effective in reducing cardiovascular events than traditional beta-blockers, but this needs to be investigated by controlled clinical trials.

Targeting of sodium channel blockers into nociceptors to produce long-duration analgesia: a systematic study and review

PubMed Central

Roberson, DP; Binshtok, AM; Blasl, F; Bean, BP; Woolf, CJ

2011-01-01

BACKGROUND AND PURPOSE We have developed a strategy to target the permanently charged lidocaine derivative lidocaine N-ethyl bromide (QX-314) selectively into nociceptive sensory neurons through the large-pore transient receptor potential cation channel subfamily V (TRPV1) noxious heat detector channel. This involves co-administration of QX-314 and a TRPV1 agonist to produce a long-lasting local analgesia. For potential clinical use we propose using lidocaine as the TRPV1 agonist, because it activates TRPV1 at clinical doses. EXPERIMENTAL APPROACH We conducted experiments in rats to determine optimal concentrations and ratios of lidocaine and QX-314 that produce the greatest degree and duration of pain-selective block when administered nearby the sciatic nerve: reduction in the response to noxious mechanical (pinch) and to radiant heat stimuli, with minimal disruption in motor function (grip strength). KEY RESULTS A combination of 0.5% QX-314 and 2% lidocaine produced 1 h of non-selective sensory and motor block followed by >9 h of pain-selective block, where grip strength was unimpaired. QX-314 at this concentration had no effect by itself, while 2% lidocaine by itself produced 1 h of non-selective block. The combination of 0.5% QX-314 and 2% lidocaine was the best of the many tested, in terms of the duration and selectivity of local analgesia. CONCLUSIONS AND IMPLICATIONS Targeting charged sodium channel blockers into specific sets of axons via activation of differentially expressed large-pore channels provides an opportunity to produce prolonged local analgesia, and represents an example of how exploiting ion channels as a drug delivery port can be used to increase the specificity and efficacy of therapeutics. PMID:21457220

Variability of Potassium Channel Blockers in Mesobuthus eupeus Scorpion Venom with Focus on Kv1.1

PubMed Central

Kuzmenkov, Alexey I.; Vassilevski, Alexander A.; Kudryashova, Kseniya S.; Nekrasova, Oksana V.; Peigneur, Steve; Tytgat, Jan; Feofanov, Alexey V.; Kirpichnikov, Mikhail P.; Grishin, Eugene V.

2015-01-01

The lesser Asian scorpion Mesobuthus eupeus (Buthidae) is one of the most widely spread and dispersed species of the Mesobuthus genus, and its venom is actively studied. Nevertheless, a considerable amount of active compounds is still under-investigated due to the high complexity of this venom. Here, we report a comprehensive analysis of putative potassium channel toxins (KTxs) from the cDNA library of M. eupeus venom glands, and we compare the deduced KTx structures with peptides purified from the venom. For the transcriptome analysis, we used conventional tools as well as a search for structural motifs characteristic of scorpion venom components in the form of regular expressions. We found 59 candidate KTxs distributed in 30 subfamilies and presenting the cysteine-stabilized α/β and inhibitor cystine knot types of fold. M. eupeus venom was then separated to individual components by multistage chromatography. A facile fluorescent system based on the expression of the KcsA-Kv1.1 hybrid channels in Escherichia coli and utilization of a labeled scorpion toxin was elaborated and applied to follow Kv1.1 pore binding activity during venom separation. As a result, eight high affinity Kv1.1 channel blockers were identified, including five novel peptides, which extend the panel of potential pharmacologically important Kv1 ligands. Activity of the new peptides against rat Kv1.1 channel was confirmed (IC50 in the range of 1–780 nm) by the two-electrode voltage clamp technique using a standard Xenopus oocyte system. Our integrated approach is of general utility and efficiency to mine natural venoms for KTxs. PMID:25792741

Exchange protein activated by cAMP (Epac) mediates cAMP-dependent but protein kinase A-insensitive modulation of vascular ATP-sensitive potassium channels

PubMed Central

Purves, Gregor I; Kamishima, Tomoko; Davies, Lowri M; Quayle, John M; Dart, Caroline

2009-01-01

Exchange proteins directly activated by cyclic AMP (Epacs or cAMP-GEF) represent a family of novel cAMP-binding effector proteins. The identification of Epacs and the recent development of pharmacological tools that discriminate between cAMP-mediated pathways have revealed previously unrecognized roles for cAMP that are independent of its traditional target cAMP-dependent protein kinase (PKA). Here we show that Epac exists in a complex with vascular ATP-sensitive potassium (KATP) channel subunits and that cAMP-mediated activation of Epac modulates KATP channel activity via a Ca2+-dependent mechanism involving the activation of Ca2+-sensitive protein phosphatase 2B (PP-2B, calcineurin). Application of the Epac-specific cAMP analogue 8-pCPT-2′-O-Me-cAMP, at concentrations that activate Epac but not PKA, caused a 41.6 ± 4.7% inhibition (mean ±s.e.m.; n= 7) of pinacidil-evoked whole-cell KATP currents recorded in isolated rat aortic smooth muscle cells. Importantly, similar results were obtained when cAMP was elevated by addition of the adenylyl cyclase activator forskolin in the presence of the structurally distinct PKA inhibitors, Rp-cAMPS or KT5720. Activation of Epac by 8-pCPT-2′-O-Me-cAMP caused a transient 171.0 ± 18.0 nm (n= 5) increase in intracellular Ca2+ in Fura-2-loaded aortic myocytes, which persisted in the absence of extracellular Ca2+. Inclusion of the Ca2+-specific chelator BAPTA in the pipette-filling solution or preincubation with the calcineurin inhibitors, cyclosporin A or ascomycin, significantly reduced the ability of 8-pCPT-2′-O-Me-cAMP to inhibit whole-cell KATP currents. These results highlight a previously undescribed cAMP-dependent regulatory mechanism that may be essential for understanding the physiological and pathophysiological roles ascribed to arterial KATP channels in the control of vascular tone and blood flow. PMID:19491242

The cardioprotective effect of uridine and uridine-5'-monophosphate: the role of the mitochondrial ATP-dependent potassium channel.

PubMed

Krylova, Irina B; Kachaeva, Evgeniya V; Rodionova, Olga M; Negoda, Alexander E; Evdokimova, Nataliya R; Balina, Maria I; Sapronov, Nikolay S; Mironova, Galina D

2006-07-01

The activity of mitochondrial ATP-dependent potassium channel (mitoKATP) of rat heart and liver mitochondria was shown to decrease during aging. This partially explains the increase of risk of ischemia at a mature age since mitoKATP activation provides cardioprotection. We demonstrated that uridine-5'-diphosphate (UDP) possesses the property to activate mitoKATP. At a concentration of 30 microM, it reactivated mitoKATP in mitochondria, and 5-hydroxydecanoate (5-HD) eliminated this effect. In experimental animals, UDP precursors uridine and uridine-5'-monophosphate (UMP) (both 30 mg/kg, administered intravenously 5 min before coronary occlusion) decreased the myocardium ischemic alteration index (1.9 and 3.5 times, respectively) and the T-wave amplitude within 60 min after occlusion. Both effects were inhibited by Glibenclamide (Glib) and 5-HD. UMP and uridine decreased the number of premature ventricular beats 5.6 and 1.9 times and the duration of ventricular tachycardia 9.4 and 4.1 times, respectively. Glib and 5-HD inhibited the anti-arrhythmic parameters, 5-HD being less effective. Uridine and UMP decreased the duration of fibrillation 10.8 and 3.6 times, respectively, and this effect was not abolished by Glib and 5-HD. Thus, uridine and UMP, which are the precursors of UDP in the cell, possess cardioprotective properties. MitoKATP prevents mainly ischemic injuries and partially rhythm disorders.

Evaluation of Four Calcium Channel Blockers as Fluconazole Resistance Inhibitors in Candida glabrata.

PubMed

Alnajjar, Lina M; Bulatova, Nailya R; Darwish, Rula M

2018-04-14

In this study we aimed to evaluate the ability of four calcium channel blockers, verapamil, diltiazem, nicardipine and nifedipine to enhance sensitivity of Candida glabrata strains to fluconazole. The synergistic antifungal effect was examined by checkerboard method; fractional inhibitory concentration index (FIC) was determined. Time-kill curve method was used for the most promising combination to further evaluate the synergetic effects. nicardipine showed additive effect with fluconazole against fluconazole-resistant and fluconazole-susceptible-dose-dependent strains (DSY565 and CBS138) known to express efflux pumps but not against fluconazole-sensitive strains. Nifedipine exhibited additive effect with fluconazole in both checkerboard (0.5< FIC <1) and time-kill curve methods (<2 log10 colony-forming units (CFU)/ml decrease in viable count). Additionally, nifedipine had own antifungal effect consistently against most of the strains used in this study with minimum inhibitory concentration of 8μg/ml. nicardipine showed additive effect with fluconazole in fluconazole-resistant strains of Candida glabrata-most probably via efflux pump inhibition as demonstrated selectively in fluconazole-resistant strains with known efflux pumps. Nifedipine displayed promising antifungal effect alone and additive effects with fluconazole. Copyright © 2018. Published by Elsevier Ltd.

Electrophysiological characterization of 14-benzoyltalatisamine, a selective blocker of the delayed rectifier K+ channel found in virtual screening.

PubMed

Song, Ming-Ke; Liu, Hong; Jiang, Hua-Liang; Yue, Jian-Min; Hu, Guo-Yuan

2006-02-15

14-Benzoyltalatisamine is a potent and selective blocker of the delayed rectifier K+ channel found in a computational virtual screening study. The compound was found to block the K+ channel from the extracellular side. However, it is unclear whether 14-benzoyltalatisamine shares the same block mechanism with tetraethylammonium (TEA). In order to elucidate how the hit compound found by the virtual screening interacts with the outer vestibule of the K+ channel, the effects of 14-benzoyltalatisamine and TEA on the delayed rectifier K+ current of rat dissociated hippocampal neurons were compared using whole-cell voltage-clamp recording. External application of 14-benzoyltalatisamine and TEA reversibly inhibited the current with IC50 values of 10.1+/-2.2 microM and 1.05+/-0.21 mM, respectively. 14-Benzoyltalatisamine exerted voltage-dependent inhibition, markedly accelerated the decay of the current, and caused a significant hyperpolarizing shift of the steady-state activation curve, whereas TEA caused voltage-independent inhibition, without affecting the kinetic parameters of the current. The blockade by 14-benzoyltalatisamine, but not by TEA, was significantly diminished in a high K+ (60 mM) external solution. The potency of 14-benzoyltalatisamine was markedly reduced in the presence of 15 mM TEA. The results suggest that 14-benzoyltalatisamine bind to the external pore entry of the delayed rectifier K+ channel with partial insertion into the selectivity filter, which is in conformity with that predicted by the molecular docking model in the virtual screening.

A meta-analysis of the effect of angiotensin receptor blockers and calcium channel blockers on blood pressure, glycemia and the HOMA-IR index in non-diabetic patients.

PubMed

Yang, Yue; Wei, Ri-bao; Xing, Yue; Tang, Lu; Zheng, Xiao-yong; Wang, Zi-cheng; Gao, Yu-wei; Li, Min-xia; Chen, Xiang-mei

2013-12-01

This study compared the efficacy of angiotensin receptor blockers (ARBs) and calcium channel blockers (CCBs) in the effect of insulin resistance (IR) as assessed using the homeostasis model assessment of insulin resistance (HOMA-IR) in non-diabetic patients. The MEDLINE, EMBASE, and Cochrane Library databases were searched to identify studies published before December 2012 that investigated the use of ARBs and CCBs to determine the effect on the HOMA-IR index in non-diabetics. Parameters on IR and blood pressure were collected. Review Manager 5.2 and Stata 12.0 were used to perform the meta-analysis. Fixed and random effects models were applied to various aspects of the meta-analysis, which assessed the therapeutic effects of the two types of drug using the HOMA-IR index in non-diabetic patients. The meta-analysis included five clinical trials. Patient comparisons before and after treatment with ARBs and CCBs revealed that ARBs reduced the HOMA-IR index (weighted mean difference (WMD) -0.65, 95% confidence interval (CI) -0.93 to -0.38) and fasting plasma insulin (FPI) (WMD -2.01, 95% CI -3.27 to -0.74) significantly more than CCBs. No significant differences in the therapeutic effects of these two types of drug on blood pressure were observed. Given that there are no significant differences in the therapeutic effects of ARBs and CCBs on blood pressure, as ARBs are superior to CCBs in their effect on the HOMA-IR index in non-diabetics, they might be a better choice in hypertension patients without diabetes. © 2013.

The calcium channel blocker amlodipine promotes the unclamping of eNOS from caveolin in endothelial cells.

PubMed

Batova, Suzan; DeWever, Julie; Godfraind, Théophile; Balligand, Jean-Luc; Dessy, Chantal; Feron, Olivier

2006-08-01

Amlodipine is a calcium channel blocker (CCB) known to stimulate nitric oxide production from endothelial cells. Whether this ancillary property can be related to the capacity of amlodipine to concentrate and alter the structure of cholesterol-containing membrane bilayers is a matter of investigation. Here, we reasoned that since the endothelial nitric oxide synthase is, in part, expressed in cholesterol-rich plasmalemmal microdomains (e.g., caveolae and rafts), amlodipine could interfere with this specific locale of the enzyme and thereby modulate NO production in endothelial cells. Using a method combining lubrol-based extraction and subcellular fractionation on sucrose gradient, we found that amlodipine, but not verapamil or nifedipine, induced the segregation of endothelial NO synthase (eNOS) from caveolin-enriched low-density membranes (8+/-2% vs. 42+/-3% in untreated condition; P<0.01). We then performed co-immunoprecipitation experiments and found that amlodipine dose-dependently disrupted the caveolin/eNOS interaction contrary to other calcium channel blockers, and potentiated the stimulation of NO production by agonists such as bradykinin and vascular endothelial growth factor (VEGF) (+138+/-28% and +183+/-27% over values obtained with the agonist alone, respectively; P<0.01). Interestingly, we also documented that the dissociation of the caveolin/eNOS heterocomplex induced by amlodipine was not mediated by the traditional calcium-dependent calmodulin binding to eNOS and that recombinant caveolin expression could compete with the stimulatory effects of amlodipine on eNOS activity. Finally, we showed that the amlodipine-triggered, caveolin-dependent mechanism of eNOS activation was independent of other pleiotropic effects of the CCB such as superoxide anion scavenging and angiotensin-converting enzyme (ACE) inhibition. This study unravels the modulatory effects of amlodipine on caveolar integrity and the capacity of caveolin to maintain eNOS in its vicinity

Chronic fluoxetine treatment increases NO bioavailability and calcium-sensitive potassium channels activation in rat mesenteric resistance arteries.

PubMed

Pereira, Camila A; Ferreira, Nathanne S; Mestriner, Fabiola L; Antunes-Rodrigues, José; Evora, Paulo R B; Resstel, Leonardo B M; Carneiro, Fernando S; Tostes, Rita C

2015-10-15

Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), has effects beyond its antidepressant properties, altering, e.g., mechanisms involved in blood pressure and vasomotor tone control. Although many studies have addressed the acute impact of fluoxetine on the cardiovascular system, there is a paucity of information on the chronic vascular effects of this SSRI. We tested the hypothesis that chronic fluoxetine treatment enhances the vascular reactivity to vasodilator stimuli by increasing nitric oxide (NO) signaling and activation of potassium (K+) channels. Wistar rats were divided into two groups: (I) vehicle (water for 21 days) or (II) chronic fluoxetine (10 mg/kg/day in the drinking water for 21 days). Fluoxetine treatment increased endothelium-dependent and independent vasorelaxation (analyzed by mesenteric resistance arteries reactivity) as well as constitutive NO synthase (NOS) activity, phosphorylation of eNOS at Serine1177 and NO production, determined by western blot and fluorescence. On the other hand, fluoxetine treatment did not alter vascular expression of neuronal and inducible NOS or guanylyl cyclase (GC). Arteries from fluoxetine-treated rats exhibited increased relaxation to pinacidil. Increased acetylcholine vasorelaxation was abolished by a calcium-activated K+ channel (KCa) blocker, but not by an inhibitor of KATP channels. On the other hand, vascular responses to Bay 41-2272 and 8-bromo-cGMP were similar between the groups. In conclusion, chronic fluoxetine treatment increases endothelium-dependent and independent relaxation of mesenteric resistance arteries by mechanisms that involve increased eNOS activity, NO generation, and KCa channels activation. These effects may contribute to the cardiovascular effects associated with chronic fluoxetine treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

Relationship between calcium channel blocker class and mortality in dialysis.

PubMed

Wetmore, James B; Mahnken, Jonathan D; Phadnis, Milind A; Ellerbeck, Edward F; Shireman, Theresa I

2015-12-01

The comparative effectiveness of dihydropyridine (DHP) and non-DHP calcium channel blockers (CCBs) in maintenance dialysis patients has not been well-studied. A retrospective cohort of hypertensive patients initiating dialysis was created. New CCB initiators, defined as individual who had no evidence of CCB use in the first 90 days of dialysis but who were initiated by day 180, were followed from their first day of medication exposure until event or censoring; events consisted of all-cause mortality (ACM) and a combined endpoint of cardiovascular morbidity or mortality (CVMM). Cox proportional hazards models were used to determine adjusted hazard ratios (AHRs) comparing the effect of DHPs vs. non-DHPs. There were 2900 and 2704 new initiators of CCBs in the ACM and CVMM models, respectively. Adjusted for other factors, use of DHPs, compared to non-DHPs, was associated with an AHR of 0.77 (99% confidence intervals, 0.64 - 0.93, P = 0.0004) for ACM and 0.86 (0.72 - 1.02, P = 0.024) for CVMM. Results were similar when individuals who initiated therapy at any point after the cohort inception were included, with AHRs of 0.60 (0.53 - 0.69, P < 0.0001) and 0.77 (0.67 - 0.89, P < 0.0001) for ACM and CVMM, respectively. Further, elimination of individuals with chronic atrial fibrillation resulted in AHRs of 0.71 and 0.70 for ACM and CVVM, respectively. DHPs, as compared to non-DHPs, were associated with reduced hazard of death or cardiovascular morbidity and mortality; potential mechanisms of action require further study. Copyright © 2015 John Wiley & Sons, Ltd.

Relationship between calcium channel blocker class and mortality in dialysis

PubMed Central

Wetmore, James B.; Mahnken, Jonathan D.; Phadnis, Milind A.; Ellerbeck, Edward F.; Shireman, Theresa I.

2015-01-01

Background and objective The comparative effectiveness of dihydropyridine (DHP) and non-DHP alcium channel blockers (CCBs) in maintenance dialysis patients has not been well-studied Methods A retrospective cohort of hypertensive patients initiating dialysis was created. New CCB initiators, defined as individual who had no evidence of CCB use in the first 90 days of dialysis but who were initiated by day 180, were followed from their first day of medication exposure until event or censoring; events consisted of all-cause mortality (ACM) and a combined endpoint of cardiovascular morbidity or mortality (CVMM). Cox proportional hazards models were used to determine adjusted hazard ratios (AHRs) comparing the effect of DHPs vs. non-DHPs. Results There were 2900 and 2704 new initiators of CCBs in the ACM and CVMM models, respectively. Adjusted for other factors, use of DHPs, compared to non-DHPs, was associated with an AHR of 0.77 (99% confidence intervals, 0.64 – 0.93, P = 0.0004) for ACM and 0.86 (0.72 – 1.02, P = 0.024) for CVMM. Results were similar when individuals who initiated therapy at any point after the cohort inception were included, with AHRs of 0.60 (0.53 – 0.69, P < 0.0001) and 0.77 (0.67 – 0.89, P < 0.0001) for ACM and CVMM, respectively. Further, elimination of individuals with chronic atrial fibrillation resulted in AHRs of 0.71 and 0.70 for ACM and CVVM, respectively. Conclusion DHPs, as compared to non-DHPs, were associated with reduced hazard of death or cardiovascular morbidity and mortality; potential mechanisms of action require further study. PMID:26371369

Interaction of SR 33557 with skeletal muscle calcium channel blocker receptors in the baboon: characterization of its binding sites

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

Sol-Rolland, J.; Joseph, M.; Rinaldi-Carmona, M.

1991-05-01

A procedure for the isolation of primate skeletal microsomal membranes was initiated. Membranes exhibited specific enzymatic markers such as 5'-nucleotidase, Ca{sup 2}{sup +},Mg({sup 2}{sup +})-adenosine triphosphatase and an ATP-dependent calcium uptake. Baboon skeletal microsomes bound specifically with high-affinity potent Ca{sup 2}{sup +} channel blockers such as dihydropyridine, phenylalkylamine and benzothiazepine derivatives. Scatchard analysis of equilibrium binding assays with ({sup 3}H)(+)-PN 200-110, ({sup 3}H)(-)-desmethoxyverapamil (( {sup 3}H)(-)-D888) and ({sup 3}H)-d-cis-dilitiazem were consistent with a single class of binding sites for the three radioligands. The pharmacological profile of SR 33557, an original compound with calcium antagonist properties, was investigated using radioligand bindingmore » studies. SR 33557 totally inhibited the specific binding of the three main classes of Ca{sup 2}{sup +} channel effectors and interacted allosterically with them. In addition, SR 33557 bound with high affinity to a homogeneous population of binding sites in baboon skeletal muscle.« less

Beta-blockers in the management of hypertension: focus on nebivolol.

PubMed

Wojciechowski, David; Papademetriou, Vasilios

2008-04-01

Hypertension is a major cardiovascular risk factor but most patients remain asymptomatic for many years. Successful therapy not only needs to be effective, it also needs to be well tolerated. beta-blockers are well established as effective antihypertensive agents. However, one major drawback to the currently available beta-blockers, particularly the noncardioselective beta-blockers, is their side-effect profile, including sexual dysfunction, fatigue, depression and metabolic abnormalities such as impaired glucose tolerance and lipid abnormalities. Nebivolol (Bystolic), a novel, highly cardioselective, third-generation beta-blocker that recently received approval by the US FDA for the treatment of hypertension in the USA, is effective in treating blood pressure and has a favorable side-effect profile. Studies conducted in Europe, where nebivolol has been available for some time for the treatment of hypertension, have shown that nebivolol achieves blood pressure reductions comparable to other beta-blockers but with fewer side effects. Additionally, nebivolol has demonstrated similar efficacy in blood pressure reduction when compared with calcium channel blockers and inhibitors of the renin-angiotensin system. When combined with hydrochlorothiazide there was an additive antihypertensive effect. Lastly, nebivolol exhibits a vasodilatory property that is related to its effect on nitric oxide, an intrinsic vasodilator produced in the vascular endothelium. Nebivolol enhances nitric oxide bioavailability. Studies have also demonstrated nebivolol's ability to function as an antioxidant and decrease markers of oxidative stress. These effects are believed to ultimately produce a modulation of the endothelial dysfunction typically seen in hypertension.

Meroterpenoid Chrodrimanins Are Selective and Potent Blockers of Insect GABA-Gated Chloride Channels

PubMed Central

Ihara, Makoto; Ling, Yun; Yang, Xinling; Kai, Kenji; Hayashi, Hideo; Matsuda, Kazuhiko

2015-01-01

Meroterpenoid chrodrimanins, produced from Talaromyces sp. YO-2, are known to paralyze silkworm (Bombyx mori) larvae, but their target is unknown. We have investigated the actions of chrodrimanin B on ligand-gated ion channels of silkworm larval neurons using patch-clamp electrophysiology. Chrodrimanin B had no effect on membrane currents when tested alone at 1 μM. However, it completely blocked the γ-aminobutyric acid (GABA)-induced current and showed less pronounced actions on acetylcholine- and L-glutamate-induced currents, when delivered at 1 μM for 1 min prior to co-application with transmitter GABA. Thus, chrodrimanins were also tested on a wild-type isoform of the B. mori GABA receptor (GABAR) RDL using two-electrode voltage-clamp electrophysiology. Chrodrimanin B attenuated the peak current amplitude of the GABA response of RDL with an IC50 of 1.66 nM. The order of the GABAR-blocking potency of chrodrimanins B > D > A was in accordance with their reported insecticidal potency. Chrodrimanin B had no open channel blocking action when tested at 3 nM on the GABA response of RDL. Co-application with 3 nM chrodrimanin B shifted the GABA concentration response curve to a higher concentration and further increase of chrodrimanin B concentration to10 nM; it reduced maximum current amplitude of the GABA response, pointing to a high-affinity competitive action and a lower affinity non-competitive action. The A282S;T286V double mutation of RDL, which impairs the actions of fipronil, hardly affected the blocking action of chrodrimanin B, indicating a binding site of chrodrimanin B distinct from that of fipronil. Chrodrimanin B showed approximately 1,000-fold lower blocking action on human α1β2γ2 GABAR compared to RDL and thus is a selective blocker of insect GABARs. PMID:25902139

Atrial natriuretic peptide administered just prior to reperfusion limits infarction in rabbit hearts.

PubMed

Yang, Xi-Ming; Philipp, Sebastian; Downey, James M; Cohen, Michael V

2006-07-01

We investigated whether atrial natriuretic peptide (ANP) given just prior to reperfusion reduces infarction in rabbit hearts and whether protection is related to activation of protein kinase G (PKG). Isolated rabbit hearts were subjected to a 30-min period of regional ischemia; treated hearts received a 20-min infusion of ANP (0.1 microM) starting 5 min before 2 h of reperfusion. ANP infusion decreased infarction from 31.5+/-2.4% of the risk zone in untreated hearts to 12.5+/-2.0% (P<0.001). To explore mechanisms of protection ischemic hearts were treated simultaneously with ANP and isatin, a blocker of the natriuretic peptide receptor, shortly before reperfusion. ANP's protective effect was aborted (36.8+/-2.9% infarction). There is no acceptable blocker of protein kinase G that can be used in intact organs. However, 8-(4-chlorophenylthio)-guanosine 3', 5'-cyclic monophosphate (10 microM), a cell-permeable cGMP analog that directly activates PKG, was infused from 5 min before to 15 min after reperfusion. The PKG activator mimicked ANP's protection with only 18.2+/-3.6% infarction (P<0.001). 5-Hydroxyde-canoate (5-HD), a putative mitochondrial KATP channel (mKATP) inhibitor, abrogated ANP's protection (34.4+/-2.6% infarction). Unexpectedly, 1H-[1,2,4]oxadiazole- [4,3-a]quinoxalin-1-one (ODQ), a blocker of soluble guanylyl cyclase also prevented ANP's infarct-sparing effect. It is unclear whether this observation implicated participation of soluble guanylyl cyclase in the mechanism or simply a lack of selectivity of ODQ. Finally the reperfusion injury salvage kinases (RISK), phosphatidylinositol 3-kinase and extracellular signal-regulated kinase, were implicated in ANP's mechanism since either wortmannin or PD98059 infused at reperfusion prevented ANP's infarct-sparing effect. ANP administered just prior to reperfusion protects hearts against infarction, likely by activation of PKG, opening of mKATP, and stimulation of downstream kinases.

Dissection of the Mechanical Impedance Components of the Outer Hair Cell Using a Chloride-Channel Blocker

NASA Astrophysics Data System (ADS)

Harasztosi, Csaba; Gummer, Anthony W.

2011-11-01

The voltage-dependent chloride-channel blocker anthracene-9-carboxylic acid (9AC) has been found to reduce the imaginary but not the real part of the mechanical impedance of the organ of Corti, suggesting that the effective stiffness of outer hair cells (OHCs) is reduced by 9AC. To examine whether 9AC interacts directly with the motor protein prestin to reduce the membrane component of the impedance, the patch-clamp technique in whole-cell configuration was used to measure the nonlinear capacitance (NLC) of isolated OHCs and, as control, prestin-transfected human embryonic kidney 293 (HEK293) cells. Extracellular application of 9AC significantly reduced the NLC of both OHCs and HEK293 cells. Intracellular 9AC did not influence the blocking effect of the extracellular applied drug. These results suggest that 9AC interacts directly with prestin, reducing the effective stiffness of the motor, and that the interaction is extracellular.

Analgesic activity of ZC88, a novel N-type voltage-dependent calcium channel blocker, and its modulation of morphine analgesia, tolerance and dependence.

PubMed

Meng, Ge; Wu, Ning; Zhang, Cheng; Su, Rui-Bin; Lu, Xin-Qiang; Liu, Yin; Yun, Liu-Hong; Zheng, Jian-Quan; Li, Jin

2008-05-31

ZC88 is a novel non-peptide N-type voltage-sensitive calcium channel blocker synthesized by our institute. In the present study, the oral analgesic activity of ZC88 in animal models of acute and neuropathic pain, and functional interactions between ZC88 and morphine in terms of analgesia, tolerance and dependence were investigated. In mice acetic acid writhing tests, ZC88 (10-80 mg/kg) administered by oral route showed significant antinociceptive effects in a dose-dependent manner. The ED50 values of ZC88 were 14.5 and 14.3 mg/kg in male and female mice, respectively. In sciatic nerve chronic constriction injury rats, mechanical allodynia was ameliorated by oral administration of ZC88 at doses of 14, 28 and 56 mg/kg, suggesting ZC88 relieved allodynic response of neuropathic pain. When concurrently administered with morphine, ZC88 (20-80 mg/kg) dose-dependently potentiated morphine analgesia and attenuated morphine analgesic tolerance in hot-plate tests. ZC88 also prevented chronic exposure to morphine-induced physical dependence and withdrawal, but not morphine-induced psychological dependence in conditioned place preference model. These results suggested that ZC88, a new non-peptide N-type calcium channel blocker, had notable oral analgesia and anti-allodynia for acute and neuropathic pain. ZC88 might be used in pain relief by either application alone or in combination with opioids because it enhanced morphine analgesia while prevented morphine-induced tolerance and physical dependence.

Neuroprotective effect of gadolinium: a stretch-activated calcium channel blocker in mouse model of ischemia-reperfusion injury.

PubMed

Gulati, Puja; Muthuraman, Arunachalam; Jaggi, Amteshwar S; Singh, Nirmal

2013-03-01

The present study was designed to investigate the potential of gadolinium, a stretch-activated calcium channel blocker in ischemic reperfusion (I/R)-induced brain injury in mice. Bilateral carotid artery occlusion of 12 min followed by reperfusion for 24 h was given to induce cerebral injury in male Swiss mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using Morris water maze test and motor incoordination was evaluated using rota-rod, lateral push, and inclined beam walking tests. In addition, total calcium, thiobarbituric acid reactive substance (TBARS), reduced glutathione (GSH), and acetylcholinesterase (AChE) activity were also estimated in brain tissue. I/R injury produced a significant increase in cerebral infarct size. A significant loss of memory along with impairment of motor performance was also noted. Furthermore, I/R injury also produced a significant increase in levels of TBARS, total calcium, AChE activity, and a decrease in GSH levels. Pretreatment of gadolinium significantly attenuated I/R-induced infarct size, behavioral and biochemical changes. On the basis of the present findings, we can suggest that opening of stretch-activated calcium channel may play a critical role in ischemic reperfusion-induced brain injury and that gadolinium has neuroprotective potential in I/R-induced injury.

The Association Between Calcium Channel Blocker Use and Prostate Cancer Outcome

PubMed Central

Poch, Michael A.; Mehedint, Diana; Green, Dawn J.; Payne-Ondracek, Rochelle; Fontham, Elizabeth T.H.; Bensen, Jeannette T.; Attwood, Kristopher; Wilding, Gregory E.; Guru, Khurshid A.; Underwood, Willie; Mohler, James L.; Heemers, Hannelore V.

2018-01-01

BACKGROUND Epidemiological studies indicate that calcium channel blocker (CCB) use is inversely related to prostate cancer (PCa) incidence. The association between CCB use and PCa aggressiveness at the time of radical prostatectomy (RP) and outcome after RP was examined. METHODS Medication use, PCa aggressiveness and post-RP outcome were retrieved from a prospectively populated database that contains clinical and outcome for RP patients at Roswell Park Cancer Institute (RPCI) from 1993 to 2010. The database was queried for anti-hypertensive medication use at diagnosis for patients with ≥1 year follow-up. Recurrence was defined using NCCN guidelines. Chi-Square tests assessed the relationship between CCB use and PCa aggressiveness. Cox regression models compared the distribution of progression-free survival (PFS) and overall survival (OS) with adjustment for covariates. Results for association between CCB usage and PCa aggressiveness were validated using data from the population-based North Carolina-Louisiana Prostate Cancer Project (PCaP). RESULTS 48%, 37%, and 15% of RPCI’s RP patients (n = 875) had low, intermediate, and high aggressive PCa, respectively. 104 (11%) had a history of CCB use. Patients taking CCBs were more likely to be older, have a higher BMI and use additional anti-hypertensive medications. Diagnostic PSA levels, PCa aggressiveness, and margin status were similar for CCB users and non-users. PFS and OS did not differ between the two groups. Tumor aggressiveness was associated with PFS. CCB use in the PCaP study population was not associated with PCa aggressiveness. CONCLUSIONS CCB use is not associated with PCa aggressiveness at diagnosis, PFS or OS. PMID:23280547

Transformation of postingestive glucose responses after deletion of sweet taste receptor subunits or gastric bypass surgery

PubMed Central

Geraedts, Maartje C. P.; Takahashi, Tatsuyuki; Vigues, Stephan; Markwardt, Michele L.; Nkobena, Andongfac; Cockerham, Renee E.; Hajnal, Andras; Dotson, Cedrick D.; Rizzo, Mark A.

2012-01-01

The glucose-dependent secretion of the insulinotropic hormone glucagon-like peptide-1 (GLP-1) is a critical step in the regulation of glucose homeostasis. Two molecular mechanisms have separately been suggested as the primary mediator of intestinal glucose-stimulated GLP-1 secretion (GSGS): one is a metabotropic mechanism requiring the sweet taste receptor type 2 (T1R2) + type 3 (T1R3) while the second is a metabolic mechanism requiring ATP-sensitive K+ (KATP) channels. By quantifying sugar-stimulated hormone secretion in receptor knockout mice and in rats receiving Roux-en-Y gastric bypass (RYGB), we found that both of these mechanisms contribute to GSGS; however, the mechanisms exhibit different selectivity, regulation, and localization. T1R3−/− mice showed impaired glucose and insulin homeostasis during an oral glucose challenge as well as slowed insulin granule exocytosis from isolated pancreatic islets. Glucose, fructose, and sucralose evoked GLP-1 secretion from T1R3+/+, but not T1R3−/−, ileum explants; this secretion was not mimicked by the KATP channel blocker glibenclamide. T1R2−/− mice showed normal glycemic control and partial small intestine GSGS, suggesting that T1R3 can mediate GSGS without T1R2. Robust GSGS that was KATP channel-dependent and glucose-specific emerged in the large intestine of T1R3−/− mice and RYGB rats in association with elevated fecal carbohydrate throughout the distal gut. Our results demonstrate that the small and large intestines utilize distinct mechanisms for GSGS and suggest novel large intestine targets that could mimic the improved glycemic control seen after RYGB. PMID:22669246

Role of diuretics, β blockers, and statins in increasing the risk of diabetes in patients with impaired glucose tolerance: reanalysis of data from the NAVIGATOR study.

PubMed

Shen, Lan; Shah, Bimal R; Reyes, Eric M; Thomas, Laine; Wojdyla, Daniel; Diem, Peter; Leiter, Lawrence A; Charbonnel, Bernard; Mareev, Viacheslav; Horton, Edward S; Haffner, Steven M; Soska, Vladimir; Holman, Rury; Bethel, M Angelyn; Schaper, Frank; Sun, Jie-Lena; McMurray, John J V; Califf, Robert M; Krum, Henry

2013-12-09

To examine the degree to which use of β blockers, statins, and diuretics in patients with impaired glucose tolerance and other cardiovascular risk factors is associated with new onset diabetes. Reanalysis of data from the Nateglinide and Valsartan in Impaired Glucose Tolerance Outcomes Research (NAVIGATOR) trial. NAVIGATOR trial. Patients who at baseline (enrolment) were treatment naïve to β blockers (n=5640), diuretics (n=6346), statins (n=6146), and calcium channel blockers (n=6294). Use of calcium channel blocker was used as a metabolically neutral control. Development of new onset diabetes diagnosed by standard plasma glucose level in all participants and confirmed with glucose tolerance testing within 12 weeks after the increased glucose value was recorded. The relation between each treatment and new onset diabetes was evaluated using marginal structural models for causal inference, to account for time dependent confounding in treatment assignment. During the median five years of follow-up, β blockers were started in 915 (16.2%) patients, diuretics in 1316 (20.7%), statins in 1353 (22.0%), and calcium channel blockers in 1171 (18.6%). After adjusting for baseline characteristics and time varying confounders, diuretics and statins were both associated with an increased risk of new onset diabetes (hazard ratio 1.23, 95% confidence interval 1.06 to 1.44, and 1.32, 1.14 to 1.48, respectively), whereas β blockers and calcium channel blockers were not associated with new onset diabetes (1.10, 0.92 to 1.31, and 0.95, 0.79 to 1.13, respectively). Among people with impaired glucose tolerance and other cardiovascular risk factors and with serial glucose measurements, diuretics and statins were associated with an increased risk of new onset diabetes, whereas the effect of β blockers was non-significant. ClinicalTrials.gov NCT00097786.

Role of diuretics, β blockers, and statins in increasing the risk of diabetes in patients with impaired glucose tolerance: reanalysis of data from the NAVIGATOR study

PubMed Central

Shen, Lan; Shah, Bimal R; Reyes, Eric M; Thomas, Laine; Wojdyla, Daniel; Diem, Peter; Leiter, Lawrence A; Charbonnel, Bernard; Mareev, Viacheslav; Horton, Edward S; Haffner, Steven M; Soska, Vladimir; Holman, Rury; Bethel, M Angelyn; Schaper, Frank; Sun, Jie-Lena; McMurray, John JV; Califf, Robert M

2013-01-01

Objective To examine the degree to which use of β blockers, statins, and diuretics in patients with impaired glucose tolerance and other cardiovascular risk factors is associated with new onset diabetes. Design Reanalysis of data from the Nateglinide and Valsartan in Impaired Glucose Tolerance Outcomes Research (NAVIGATOR) trial. Setting NAVIGATOR trial. Participants Patients who at baseline (enrolment) were treatment naïve to β blockers (n=5640), diuretics (n=6346), statins (n=6146), and calcium channel blockers (n=6294). Use of calcium channel blocker was used as a metabolically neutral control. Main outcome measures Development of new onset diabetes diagnosed by standard plasma glucose level in all participants and confirmed with glucose tolerance testing within 12 weeks after the increased glucose value was recorded. The relation between each treatment and new onset diabetes was evaluated using marginal structural models for causal inference, to account for time dependent confounding in treatment assignment. Results During the median five years of follow-up, β blockers were started in 915 (16.2%) patients, diuretics in 1316 (20.7%), statins in 1353 (22.0%), and calcium channel blockers in 1171 (18.6%). After adjusting for baseline characteristics and time varying confounders, diuretics and statins were both associated with an increased risk of new onset diabetes (hazard ratio 1.23, 95% confidence interval 1.06 to 1.44, and 1.32, 1.14 to 1.48, respectively), whereas β blockers and calcium channel blockers were not associated with new onset diabetes (1.10, 0.92 to 1.31, and 0.95, 0.79 to 1.13, respectively). Conclusions Among people with impaired glucose tolerance and other cardiovascular risk factors and with serial glucose measurements, diuretics and statins were associated with an increased risk of new onset diabetes, whereas the effect of β blockers was non-significant. Trial registration ClinicalTrials.gov NCT00097786. PMID:24322398

β-Adrenergic blockers.

PubMed

Frishman, William H; Saunders, Elijah

2011-09-01

KEY POINTS AND PRACTICAL RECOMMENDATIONS: •  β-Blockers are appropriate treatment for patients with hypertension and those who have concomitant ischemic heart disease, heart failure, obstructive cardiomyopathy, or certain arrhythmias. •  β-Blockers can be used in combination with other antihypertensive drugs to achieve maximal blood pressure control. Labetalol can be used in hypertensive emergencies and urgencies. •  β-Blockers may be useful in patients having hyperkinetic circulation (palpitations, tachycardia, hypertension, and anxiety), migraine headache, and essential tremor. •  β-Blockers are highly heterogeneous with respect to various pharmacologic effects: degree of intrinsic sympathomimetic activity, membrane-stabilizing activity, β(1) selectivity, α(1) -adrenergic-blocking effect, tissue solubility, routes of systemic elimination, potencies and duration of action, and specific effects may be important in the selection of a drug for clinical use. •  β-Blocker usage to reduce perioperative ischemia and cardiovascular complications may not benefit as many patients as was once hoped and may actually cause harm in some individuals. Currently the best evidence supports β-blocker use in two patient groups: patients undergoing vascular surgery with known ischemic heart disease or multiple risk factors for it and for patients already receiving β-blockers for known cardiovascular conditions. © 2011 Wiley Periodicals, Inc.

Relative similarity within purine nucleotide and ligand structures operating on nitric oxide synthetase, guanylyl cyclase and potassium (K ATP, BK Ca) channels.

PubMed

Williams, W Robert

2011-01-01

Purine nucleotides play a central role in signal transduction events initiated at the cell membrane. The NO-cGMP-cGK pathway, in particular, mediates events involving NOS and some classes of K(+) ion channel. The aim of this study is to investigate relative molecular similarity within the ligands binding to NOS, K(ATP), BK(Ca) channels and regulatory nucleotides. Minimum energy conformers of the ligand structures were superimposed and fitted to L-arginine and the nucleotides of adenine and guanine using a computational program. Distinctive patterns were evident in the fitting of NOS isoform antagonists to L-arginine. K(ATP) channel openers and antagonists superimposed on the glycosidic linkage and imidazole ring of the purine nucleotides, and guanidinium and ribose groups of GTP in the case of glibenclamide. The fits of BK(Ca) channel openers and antagonists to cGMP were characterized by the linear dimensions of their structures; distances between terminal oxy groups in respect of dexamethasone and aldosterone. The findings provide structural evidence for the functional interaction between K(+) channel openers/antagonists and the regulatory nucleotides. Use of the purine nucleotide template systematizes the considerable heterogeneity evident within the structures of ligands operating on K(+) ion channels. © 2010 The Author. JPP © 2010 Royal Pharmaceutical Society.

Bioelectric modulation of macrophage polarization

NASA Astrophysics Data System (ADS)

Li, Chunmei; Levin, Michael; Kaplan, David L.

2016-02-01

Macrophages play a critical role in regulating wound healing and tissue regeneration by changing their polarization state in response to local microenvironmental stimuli. The native roles of polarized macrophages encompass biomaterials and tissue remodeling needs, yet harnessing or directing the polarization response has been largely absent as a potential strategy to exploit in regenerative medicine to date. Recent data have revealed that specific alteration of cells’ resting potential (Vmem) is a powerful tool to direct proliferation and differentiation in a number of complex tissues, such as limb regeneration, craniofacial patterning and tumorigenesis. In this study, we explored the bioelectric modulation of macrophage polarization by targeting ATP sensitive potassium channels (KATP). Glibenclamide (KATP blocker) and pinacidil (KATP opener) treatment not only affect macrophage polarization, but also influence the phenotype of prepolarized macrophages. Furthermore, modulation of cell membrane electrical properties can fine-tune macrophage plasticity. Glibenclamide decreased the secretion and gene expression of selected M1 markers, while pinacidil augmented M1 markers. More interestingly, glibencalmide promoted macrophage alternative activation by enhancing certain M2 markers during M2 polarization. These findings suggest that control of bioelectric properties of macrophages could offer a promising approach to regulate macrophage phenotype as a useful tool in regenerative medicine.

Multiattribute evaluation in formulary decision making as applied to calcium-channel blockers.

PubMed

Schumacher, G E

1991-02-01

The use of multiattribute utility theory (MAUT) to make a formulary decision involving calcium-channel blockers (CCBs) is described. The MAUT method is a procedure for identifying, characterizing, and comparing the many variables that may affect a decision. Although applications in pharmacy have been infrequent, MAUT should be particularly appealing to formulary committees. The steps of the MAUT method are (1) determine the viewpoint of the decision makers, (2) identify the decision alternatives, (3) identify the attributes to be evaluated, (4) identify the factors to be used in evaluating the attributes, (5) establish a utility scale for scoring each factor, (6) transform the values for each factor to its utility scale, (7) determine weights for each attribute and factor, (8) calculate the total utility score for each decision alternative, (9) determine which decision alternative has the greatest total score, and (10) perform a sensitivity analysis. The viewpoint of a formulary committee in a health maintenance organization was simulated to develop a model for using the MAUT method to compare CCBs for single-agent therapy of chronic stable angina in ambulatory patients for one year. The attributes chosen were effectiveness, safety, patient acceptance, and cost and weighted 36%, 29%, 21%, and 14%, respectively, as contributions to the evaluation. The rank order of the decision alternatives was (1) generic verapamil, (2) brand-name verapamil, (3) diltiazem, (4) nicardipine, and (5) nifedipine. The MAUT method provides a standardized yet flexible format for comparing and selecting among formulary alternatives.

Voltage-sensing domain of voltage-gated proton channel Hv1 shares mechanism of block with pore domains.

PubMed

Hong, Liang; Pathak, Medha M; Kim, Iris H; Ta, Dennis; Tombola, Francesco

2013-01-23

Voltage-gated sodium, potassium, and calcium channels are made of a pore domain (PD) controlled by four voltage-sensing domains (VSDs). The PD contains the ion permeation pathway and the activation gate located on the intracellular side of the membrane. A large number of small molecules are known to inhibit the PD by acting as open channel blockers. The voltage-gated proton channel Hv1 is made of two VSDs and lacks the PD. The location of the activation gate in the VSD is unknown and open channel blockers for VSDs have not yet been identified. Here, we describe a class of small molecules which act as open channel blockers on the Hv1 VSD and find that a highly conserved phenylalanine in the charge transfer center of the VSD plays a key role in blocker binding. We then use one of the blockers to show that Hv1 contains two intracellular and allosterically coupled gates. Copyright © 2013 Elsevier Inc. All rights reserved.

Pharmacogenetics of β-Blockers

PubMed Central

Shin, Jaekyu; Johnson, Julie A.

2009-01-01

β-Blockers are an important cardiovascular drug class, recommended as first-line treatment of numerous diseases such as heart failure, hypertension, and angina, as well as treatment after myocardial infarction. However, responses to a β-blocker are variable among patients. Results of numerous studies now suggest that genetic polymorphisms may contribute to variability in responses to β-blockers. This review summarizes the pharmacogenetic data for β-blockers in patients with various diseases and discusses the potential implications of β-blocker pharmacogenetics in clinical practice. PMID:17542770

A new candidate of calcium channel blocker in silico from Tectona grandis for treatment of gestational hypertension

NASA Astrophysics Data System (ADS)

Azizah, A.; Suselo, Y. H.; Muthmainah, M.; Indarto, D.

2018-05-01

grandis. Obtusifolin 2-glucoside computationally becomes a potensial candidate of calcium channel blocker. In vitro assays should be performed to evaluate the antagonist effect of obtusifolin 2-glucoside on calcium channel Cav1.2.

Closure of mitochondrial potassium channels favors opening of the Tl(+)-induced permeability transition pore in Ca(2+)-loaded rat liver mitochondria.

PubMed

Korotkov, Sergey M; Brailovskaya, Irina V; Shumakov, Anton R; Emelyanova, Larisa V

2015-06-01

It is known that a closure of ATP sensitive (mitoKATP) or BK-type Ca(2+) activated (mitoKCa) potassium channels triggers opening of the mitochondrial permeability transition pore (MPTP) in cells and isolated mitochondria. We found earlier that the Tl(+)-induced MPTP opening in Ca(2+)-loaded rat liver mitochondria was accompanied by a decrease of 2,4-dinitrophenol-uncoupled respiration and increase of mitochondrial swelling and ΔΨmito dissipation in the medium containing TlNO3 and KNO3. On the other hand, our study showed that the mitoKATP inhibitor, 5-hydroxydecanoate favored the Tl(+)-induced MPTP opening in the inner membrane of Ca(2+)-loaded rat heart mitochondria (Korotkov et al. 2013). Here we showed that 5-hydroxydecanoate increased the Tl(+)-induced MPTP opening in the membrane of rat liver mitochondria regardless of the presence of mitoKATP modulators (diazoxide and pinacidil). This manifested in more pronounced decrease in the uncoupled respiration and acceleration of both the swelling and the ΔΨmito dissipation in isolated rat liver mitochondria, incubated in the medium containing TlNO3, KNO3, and Ca(2+). A slight delay in Ca(2+)-induced swelling of the mitochondria exposed to diazoxide could be result of an inhibition of succinate oxidation by the mitoKATP modulator. Mitochondrial calcium retention capacity (CRC) was markedly decreased in the presence of the mitoKATP inhibitor (5-hydroxydecanoate) or the mitoKCa inhibitor (paxilline). We suggest that the closure of mitoKATP or mitoKCa in calcium loaded mitochondria favors opening of the Tl(+)-induced MPTP in the inner mitochondrial membrane.

Ion channel blockers for the treatment of neuropathic pain.

PubMed

Colombo, Elena; Francisconi, Simona; Faravelli, Laura; Izzo, Emanuela; Pevarello, Paolo

2010-05-01

Neuropathic pain, a severe chronic pain condition characterized by a complex pathophysiology, is a largely unmet medical need. Ion channels, which underlie cell excitability, are heavily implicated in the biological mechanisms that generate and sustain neuropathic pain. This review highlights the biological evidence supporting the involvement of voltage-, proton- and ligand-gated ion channels in the neuropathic pain setting. Ion channel modulators at different research or development stages are reviewed and referenced. Ion channel modulation is one of the main avenues to achieve novel, improved neuropathic pain treatments. Voltage-gated sodium and calcium channel and glutamate receptor modulators are likely to produce new, improved agents in the future. Rationally targeting subtypes of known ion channels, tackling recently discovered ion channel targets or combining drugs with different mechanism of action will be primary sources of new drugs in the longer term.

Effects of Anti-Hypertensive Monotherapy with Either Calcium Channel Blocker or Angiotensin Receptor Blocker on Arterial Stiffness, Central Hemodynamics, and Ventriculo-Arterial Coupling in Uncomplicated Hypertension Patients

PubMed Central

Lin, Heng-Hsu; Wang, Chia-Sung; Lin, Jiunn-Lee; Hwang, Juey-Jen; Lin, Lian-Yu

2013-01-01

Objectives This study is designed to investigate the effects of anti-hypertensive monotherapy [either calcium channel blocker (CCB) or angiotensin receptor blocker (ARB)] on pulsatile hemodynamic parameters in patients with uncomplicated hypertension. Methods This is a longitudinal observational study. For simplicity, we included patients with uncomplicated hypertension who receivedmono anti-hypertensive therapy with ARB or CCB. Hemodynamic parameters including central arterial pressure (CAP), aortic characteristic impedance (Zc), augmentation index (AI), brachial-ankle pulse wave velocity (baPWV), heart-ankle pulse wave velocity (haPWV), cardiac ultrasonographic parameters and ventriculo-arterial (VA) coupling were measured before, 1 month and 3 months after treatment. Results A total of 74 subjects were included in our study for analysis from 2007-2008. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and central systolic arterial pressure (CSAP) were significantly reduced 1 and 3 months after initiation of therapy. Among the pulsatile hemodynamic parameters, only the baPWV was significantly reduced (from1537.78 ± 200.63 cm/s to 1460.06 ± 186.09 cm/s to 1456.53 ± 196.03 cm/s, p for trend = 0.016). The haPWV only decreased with borderline significance (from 1015.38 ± 124.26 cm/s to 978.88 ± 126.55 cm/s to 967.99 ± 103.37 cm/s, p for trend = 0.041). The other pulsatile hemodynamic parameters remained unchanged before and after therapy. Subgroup analysis (age above or below52 years) showed that the baPWVwas significantly reduced only in the younger group. Conclusions Among the pulsatile hemodynamic parameters, only the baPWV was effectively reduced by either CCB or ARB. The improvement of PWV was more evident in younger subjects. PMID:27122681

The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

PubMed Central

Zamponi, Gerald W.; Striessnig, Joerg; Koschak, Alexandra

2015-01-01

Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type CaV1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (CaV3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (CaV2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., CaV1.2 and CaV1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective CaV1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson’s disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and

Bovine chromaffin cells possess FTX-sensitive calcium channels.

PubMed

Gandía, L; Albillos, A; García, A G

1993-07-30

The effects of the synthetic analogue of the toxin from the venom of the funnel-web spider Agenelopsis aperta (sFTX) on whole-cell Ba2+ currents through Ca2+ channels were studied in cultured bovine chromaffin cells. sFTX selectively and reversibly blocked a significant component (55 +/- 3%) of the whole-cell IBa. Effects of sFTX were additive to those of omega-conotoxin GVIA, a selective blocker of N-type Ca2+ channels, and those of furnidipine, a novel dihydropyridine L-type Ca2+ channel blocker. We conclude that the cultured bovine chromaffin cells, in addition to N- and L-type Ca2+ channels, possess a P-type component in their whole-cell currents through their Ca2+ channels.

Glibenclamide, a Blocker of K+ATP Channels, Shows Antileishmanial Activity in Experimental Murine Cutaneous Leishmaniasis▿

PubMed Central

Serrano-Martín, Xenón; Payares, Gilberto; Mendoza-León, Alexis

2006-01-01

Glibenclamide reduced the rate of lesion growth in BALB/c mice infected with Leishmania (Leishmania) mexicana, the effect was dose dependent, and the highest dose proved more effective than glucantime. Cross-resistance to glucantime was found in animals infected with a glibenclamide-resistant line, but combined therapy reduced lesion progression even in the glibenclamide-resistant strain. PMID:17015627

Fixed-Dose Combinations of Renin–Angiotensin System Inhibitors and Calcium Channel Blockers in the Treatment of Hypertension

PubMed Central

Hsiao, Fu-Chih; Tung, Ying-Chang; Chou, Shing-Hsien; Wu, Lung-Sheng; Lin, Chia-Pin; Wang, Chun-Li; Lin, Yu-Sheng; Chang, Chee-Jen; Chu, Pao-Hsien

2015-01-01

Abstract Fixed-dose combinations (FDCs) of different regimens are recommended in guidelines for the treatment of hypertension. However, clinical studies comparing FDCs of angiotensin receptor blocker (ARB)/calcium channel blocker (CCB) and angiotensin-converting enzyme inhibitor (ACE inhibitor)/CCB in hypertensive patients are lacking. Using a propensity score matching of 4:1 ratio, this retrospective claims database study compared 2 FDC regimens, ARB/CCB and ACE inhibitor/CCB, in treating hypertensive patients with no known atherosclerotic cardiovascular disease. All patients were followed for at least 3 years or until the development of major adverse cardiovascular events (MACEs) during the study period. In addition, the effect of medication adherence on clinical outcomes was evaluated in subgroup analysis based on different portions of days covered. There was no significant difference in MACE-free survival (hazard ratio [HR]: 1.21; 95% confidence interval [CI]: 0.98–1.50; P = 0.08) and survival free from hospitalization for heart failure (HR: 1.15; 95% CI: 082–1.61; P = 0.431), new diagnosis of chronic kidney disease (HR: 0.98; 95% CI: 071–1.36; P = 0.906), and initiation of dialysis (HR: 0.99; 95% CI: 050–1.92; P = 0.965) between the 2 study groups. The results remained the same within each subgroup of patients with different adherence statuses. ARBs in FDC regimens with CCBs in the present study were shown to be as effective as ACE inhibitors at reducing the risks of MACEs, hospitalization for heart failure, new diagnosis of chronic kidney disease, and new initiation of dialysis in hypertensive patients, regardless of the medication adherence status. PMID:26705234

Inhibitory effect of DIDS, NPPB, and phloretin on intracellular chloride channels.

PubMed

Malekova, Lubica; Tomaskova, Jana; Novakova, Marie; Stefanik, Peter; Kopacek, Juraj; Lakatos, Boris; Pastorekova, Silvia; Krizanova, Olga; Breier, Albert; Ondrias, Karol

2007-11-01

We studied the effects of the chloride channel blockers, 5-nitro-2-(phenylpropylamino)-benzoate (NPPB), dihydro-4,4' diisothiocyanostilbene-2,2'-disulphonic acid (DIDS), and phloretin on H2O2-induced primary culture cardiomyocyte apoptosis and activity of intracellular chloride channels obtained from rat heart mitochondrial and lysosomal vesicles. The chloride channel blockers (100 micromol/l) inhibited the H2O2-induced cardiomyocytes apoptosis. We characterized the effect of the blockers on single channel properties of the chloride channels derived from the mitochondrial and lysosomal vesicles incorporated into a bilayer lipid membrane. The single chloride channel currents were measured in 250:50 mmol/l KCl cis/trans solutions. NPPB, DIDS, and phloretin inhibited the chloride channels by decreasing the channel open probability in a concentration-dependent manner with EC50 values of 42, 7, and 20 micromol/l, respectively. NPPB and phloretin inhibited the channel's conductance and open dwell time, indicating that they could affect the chloride selective filter, pore permeability, and gating mechanism of the chloride channels. DIDS and NPPB inhibited the channels from the other side than bongkrekic acid and carboxyatractyloside. The results may contribute to understand a possible involvement of intracellular chloride channels in apoptosis and cardioprotection.

N- and P-type Ca2+ channels are involved in acetylcholine release at a neuroneuronal synapse: only the N-type channel is the target of neuromodulators.

PubMed Central

Fossier, P; Baux, G; Tauc, L

1994-01-01

Cholinergic transmission in an identified neuro-neuronal synapse of the Aplysia buccal ganglion was depressed by application of a partially purified extract of the funnel-web-spider venom (FTx) or of its synthetic analog (sFTx). This specific blocker of voltage-dependent P-type Ca2+ channels did not interfere with the effect of the N-type Ca2+ channel blocker omega-conotoxin, which could further decrease synaptic transmission after a previous application of FTx. Similar results were obtained when the reversal order of application of these two Ca2+ channel blockers was used. Both P- and N-type Ca2+ currents trigger acetylcholine release in the presynaptic neuron. The neuromodulatory effects of FMRF-amide, histamine, and buccalin on transmitter release disappeared after the blockade of the N-type Ca2+ channels but remained still effective in the presence of FTx. These results indicate that only N-type Ca2+ channels appear to be sensitive to the neuromodulators we have identified. PMID:7910963

N- and P-type Ca2+ channels are involved in acetylcholine release at a neuroneuronal synapse: only the N-type channel is the target of neuromodulators.

PubMed

Fossier, P; Baux, G; Tauc, L

1994-05-24

Cholinergic transmission in an identified neuro-neuronal synapse of the Aplysia buccal ganglion was depressed by application of a partially purified extract of the funnel-web-spider venom (FTx) or of its synthetic analog (sFTx). This specific blocker of voltage-dependent P-type Ca2+ channels did not interfere with the effect of the N-type Ca2+ channel blocker omega-conotoxin, which could further decrease synaptic transmission after a previous application of FTx. Similar results were obtained when the reversal order of application of these two Ca2+ channel blockers was used. Both P- and N-type Ca2+ currents trigger acetylcholine release in the presynaptic neuron. The neuromodulatory effects of FMRF-amide, histamine, and buccalin on transmitter release disappeared after the blockade of the N-type Ca2+ channels but remained still effective in the presence of FTx. These results indicate that only N-type Ca2+ channels appear to be sensitive to the neuromodulators we have identified.

Atrial fibrillation: Therapeutic potential of atrial K+ channel blockers.

PubMed

Ravens, Ursula; Odening, Katja E

2017-08-01

Despite the epidemiological scale of atrial fibrillation, current treatment strategies are of limited efficacy and safety. Ideally, novel drugs should specifically correct the pathophysiological mechanisms responsible for atrial fibrillation with no other cardiac or extracardiac actions. Atrial-selective drugs are directed toward cellular targets with sufficiently different characteristics in atria and ventricles to modify only atrial function. Several potassium (K + ) channels with either predominant expression in atria or distinct electrophysiological properties in atria and ventricles can serve as atrial-selective drug targets. These channels include the ultra-rapidly activating, delayed outward-rectifying Kv1.5 channel conducting I Kur , the acetylcholine-activated inward-rectifying Kir3.1/Kir3.4 channel conducting I K,ACh , the Ca 2+ -activated K + channels of small conductance (SK) conducting I SK , and the two pore domain K + (K2P) channels TWIK-1, TASK-1 and TASK-3 that are responsible for voltage-independent background currents I TWIK-1 , I TASK-1 , and I TASK-3 . Here, we briefly review the characteristics of these K + channels and their roles in atrial fibrillation. The antiarrhythmic potential of drugs targeting the described channels is discussed as well as their putative value in treatment of atrial fibrillation. Copyright © 2016 Elsevier Inc. All rights reserved.

Interactions of high-affinity cationic blockers with the translocation pores of B. anthracis, C. botulinum, and C. perfringens binary toxins.

PubMed

Bezrukov, Sergey M; Liu, Xian; Karginov, Vladimir A; Wein, Alexander N; Leppla, Stephen H; Popoff, Michel R; Barth, Holger; Nestorovich, Ekaterina M

2012-09-19

Cationic β-cyclodextrin derivatives were recently introduced as highly effective, potentially universal blockers of three binary bacterial toxins: anthrax toxin of Bacillus anthracis, C2 toxin of Clostridium botulinum, and iota toxin of Clostridium perfringens. The binary toxins are made of two separate components: the enzymatic A component, which acts on certain intracellular targets, and the binding/translocation B component, which forms oligomeric channels in the target cell membrane. Here we studied the voltage and salt dependence of the rate constants of binding and dissociation reactions of two structurally different β-cyclodextrins (AmPrβCD and AMBnTβCD) in the PA(63), C2IIa, and Ib channels (B components of anthrax, C2, and iota toxins, respectively). With all three channels, the blocker carrying extra hydrophobic aromatic groups on the thio-alkyl linkers of positively charged amino groups, AMBnTβCD, demonstrated significantly stronger binding compared with AmPrβCD. This effect is seen as an increased residence time of the blocker in the channels, whereas the time between blockages characterizing the binding reaction on-rate stays practically unchanged. Surprisingly, the voltage sensitivity, expressed as a slope of the logarithm of the blocker residence time as a function of voltage, turned out to be practically the same for all six cases studied, suggesting structural similarities among the three channels. Also, the more-effective AMBnTβCD blocker shows weaker salt dependence of the binding and dissociation rate constants compared with AmPrβCD. By estimating the relative contributions of the applied transmembrane field, long-range Coulomb, and salt-concentration-independent, short-range forces, we found that the latter represent the leading interaction, which accounts for the high efficiency of blockage. In a search for the putative groups in the channel lumen that are responsible for the short-range forces, we performed measurements with the F427A

Selection of Inhibitor-Resistant Viral Potassium Channels Identifies a Selectivity Filter Site that Affects Barium and Amantadine Block

PubMed Central

Fujiwara, Yuichiro; Arrigoni, Cristina; Domigan, Courtney; Ferrara, Giuseppina; Pantoja, Carlos; Thiel, Gerhard; Moroni, Anna; Minor, Daniel L.

2009-01-01

Background Understanding the interactions between ion channels and blockers remains an important goal that has implications for delineating the basic mechanisms of ion channel function and for the discovery and development of ion channel directed drugs. Methodology/Principal Findings We used genetic selection methods to probe the interaction of two ion channel blockers, barium and amantadine, with the miniature viral potassium channel Kcv. Selection for Kcv mutants that were resistant to either blocker identified a mutant bearing multiple changes that was resistant to both. Implementation of a PCR shuffling and backcrossing procedure uncovered that the blocker resistance could be attributed to a single change, T63S, at a position that is likely to form the binding site for the inner ion in the selectivity filter (site 4). A combination of electrophysiological and biochemical assays revealed a distinct difference in the ability of the mutant channel to interact with the blockers. Studies of the analogous mutation in the mammalian inward rectifier Kir2.1 show that the T→S mutation affects barium block as well as the stability of the conductive state. Comparison of the effects of similar barium resistant mutations in Kcv and Kir2.1 shows that neighboring amino acids in the Kcv selectivity filter affect blocker binding. Conclusions/Significance The data support the idea that permeant ions have an integral role in stabilizing potassium channel structure, suggest that both barium and amantadine act at a similar site, and demonstrate how genetic selections can be used to map blocker binding sites and reveal mechanistic features. PMID:19834614

Meta-analysis of the efficacy and safety of adding an angiotensin receptor blocker (ARB) to a calcium channel blocker (CCB) following ineffective CCB monotherapy.

PubMed

Ma, Jin; Wang, Xiao-Yan; Hu, Zhi-De; Zhou, Zhi-Rui; Schoenhagen, Paul; Wang, Hao

2015-12-01

We conducted this meta-analysis to systematically review and analyze the clinical benefits of angiotensin receptor blocker (ARB) combined with calcium channel blocker (CCB) following ineffective CCB monotherapy. PubMed was searched for articles published until August 2015. Randomized controlled trials (RCTs) evaluating the clinical benefits of ARB combined with CCB following ineffective CCB monotherapy were included. The primary efficacy endpoint of the studies was normal rate of blood pressure, the secondary efficacy endpoints were the response rate and change in blood pressure from baseline. The safety endpoint of the studies was incidence of adverse events. Differences are expressed as relative risks (RRs) with 95% confidence intervals (CIs) for dichotomous outcomes and weighted mean differences (WMDs) with 95% CIs for continuous outcomes. Heterogeneity across studies was tested by using the I(2) statistic. Seven RCTs were included and had sample sizes ranging from 185 to 1,183 subjects (total: 3,909 subjects). The pooled analysis showed that the on-target rate of hypertension treatment was significantly higher in the amlodipine + ARB group than in the amlodipine monotherapy group (RR =1.59; 95% CI, 1.31-1.91; P<0.01). The response rate of systolic blood pressure (SBP) (RR =1.28; 95% CI, 1.04-1.58; P<0.01) and diastolic blood pressure (DBP) (RR =1.27; 95% CI, 1.12-1.44; P=0.04) were significantly higher in the amlodipine + ARB group than in the amlodipine monotherapy group. The change in SBP (RR =-3.56; 95% CI, -7.76-0.63; P=0.10) and DBP (RR =-3.03; 95% CI, -6.51-0.45; P=0.09) were higher in hypertensive patients receiving amlodipine + ARB but the difference did not reach statistical significance. ARB + amlodipine treatment carried a lower risk of adverse events relative to amlodipine monotherapy (RR =0.88; 95% CI, 0.80-0.96; P<0.01). The results of our meta-analysis demonstrate that adding an ARB to CCB after initial ineffective CCB monotherapy, significantly

Meta-analysis of the efficacy and safety of adding an angiotensin receptor blocker (ARB) to a calcium channel blocker (CCB) following ineffective CCB monotherapy

PubMed Central

Ma, Jin; Wang, Xiao-Yan; Hu, Zhi-De; Zhou, Zhi-Rui; Schoenhagen, Paul

2015-01-01

Background We conducted this meta-analysis to systematically review and analyze the clinical benefits of angiotensin receptor blocker (ARB) combined with calcium channel blocker (CCB) following ineffective CCB monotherapy. Methods PubMed was searched for articles published until August 2015. Randomized controlled trials (RCTs) evaluating the clinical benefits of ARB combined with CCB following ineffective CCB monotherapy were included. The primary efficacy endpoint of the studies was normal rate of blood pressure, the secondary efficacy endpoints were the response rate and change in blood pressure from baseline. The safety endpoint of the studies was incidence of adverse events. Differences are expressed as relative risks (RRs) with 95% confidence intervals (CIs) for dichotomous outcomes and weighted mean differences (WMDs) with 95% CIs for continuous outcomes. Heterogeneity across studies was tested by using the I2 statistic. Results Seven RCTs were included and had sample sizes ranging from 185 to 1,183 subjects (total: 3,909 subjects). The pooled analysis showed that the on-target rate of hypertension treatment was significantly higher in the amlodipine + ARB group than in the amlodipine monotherapy group (RR =1.59; 95% CI, 1.31–1.91; P<0.01). The response rate of systolic blood pressure (SBP) (RR =1.28; 95% CI, 1.04–1.58; P<0.01) and diastolic blood pressure (DBP) (RR =1.27; 95% CI, 1.12–1.44; P=0.04) were significantly higher in the amlodipine + ARB group than in the amlodipine monotherapy group. The change in SBP (RR =−3.56; 95% CI, −7.76–0.63; P=0.10) and DBP (RR =−3.03; 95% CI, −6.51–0.45; P=0.09) were higher in hypertensive patients receiving amlodipine + ARB but the difference did not reach statistical significance. ARB + amlodipine treatment carried a lower risk of adverse events relative to amlodipine monotherapy (RR =0.88; 95% CI, 0.80-0.96; P<0.01). Conclusions The results of our meta-analysis demonstrate that adding an ARB to CCB

Molecular action of sulphonylureas on KATP channels: a real partnership between drugs and nucleotides.

PubMed

de Wet, Heidi; Proks, Peter

2015-10-01

Sulphonylureas stimulate insulin secretion from pancreatic β-cells primarily by closing ATP-sensitive K(+) channels in the β-cell plasma membrane. The mechanism of channel inhibition by these drugs is unusually complex. As direct inhibitors of channel activity, sulphonylureas act only as partial antagonists at therapeutic concentrations. However, they also exert an additional indirect inhibitory effect via modulation of nucleotide-dependent channel gating. In this review, we summarize current knowledge and recent advances in our understanding of the molecular mechanism of action of these drugs. © 2015 Authors; published by Portland Press Limited.

Contribution of RhoA kinase and protein kinase C to weak relaxant effect of pinacidil on carbachol-induced contractions in sensitized guinea-pig trachealis.

PubMed

Gok, Sule; Izanli-Paksoy, Ahenk; Vural, Kamil

2009-02-01

The exact mechanisms underlying the weak bronchodilator effect of K(ATP) channel openers on cholinergic stimulations is unknown. The present study was designed to examine the relaxant efect of pinacidil in guinea-pig trachea stimulated with carbachol by the presence of calcium sensitizer inhibitors; HA 1077, a rhoA kinase inhibitor, and chelerythrine, a protein kinase C inhibitor. Adenosine (10 microM) was used as other contractile agent for comparison. Tracheal tissues were isolated from ovalbumin sensitized guineapigs and changes in tension were recorded isometrically. Pinacidil (1-100 muM, cumulatively) and HA 1077 (0.01-30 microM, cumulatively) produced concentration-dependent relaxations in unstimulated tisues. The relaxant response to pinacidil decreased in carbachol contracted tissues, but increased in adenosine-stimulated tissues. Pretreatment of the tissues with HA 1077 (0.1 microM) and chelerythrine (10 microM) increased the pinacidil-induced relaxations by approximately %100 and %40, respectively. Glibenclamide, a KATP channel blocker, partially antagonized the pinacidil response in contracted tissues. Glibenclamide also inhibited the carbachol and adenosine induced contractions. These results suggest that diminish effect of pinacidil may have related to the enhanced calcium sensitization by cholinergic stimulation. Rho kinase inhibitors appear more effective than PKC inhibitors to achieve of this failure.

Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels.

PubMed

Hansen, P B L

2013-04-01

Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore, by different mechanisms, T-type channels may contribute to both constriction and dilation of the arterioles. Finally, P-/Q-type channels are involved in the regulation of human intrarenal arterial contractility. The calcium blockers used in the clinic affect not only L-type but also P-/Q- and T-type channels. Therefore, the distinct effect obtained by inhibiting a given subtype or set of channels under experimental settings should be considered when choosing a calcium blocker for treatment. T-type channels seem to be crucial for regulating the GFR and the filtration fraction. Use of blockers is expected to lead to preferential efferent vasodilation, reduction of glomerular pressure and proteinuria. Therefore, renovascular T-type channels might provide novel therapeutic targets, and may have superior renoprotective effects compared to conventional calcium blockers. Acta Physiologica © 2013 Scandinavian Physiological Society.

Brain death provokes very acute alteration in myocardial morphology detected by echocardiography: preventive effect of beta-blockers.

PubMed

Ferrera, René; Hadour, Guylaine; Tamion, Fabienne; Henry, Jean-Paul; Mulder, Paul; Richard, Vincent; Thuillez, Christian; Ovize, Michel; Derumeaux, Geneviève

2011-03-01

Our objective was to evaluate immediate acute changes in myocardial function during the autonomic storm of brain death (BD). Wistar rats were divided into four groups (n = 8/group): controls without any treatment, β-blocker (Esmolol®, 10 mg/kg), calcium channel blocker (Diltiazem®, 10 mg/kg), or alpha-blocker (Prazosin®, 0.3 mg/kg). Treatments were administered intravenously 5 min before BD induction. Echocardiography (ATL-5000, 8 MHz) was performed to measure left ventricular (LV) dimensions and fractional shortening at baseline, during BD induction and 5 min and 15 min after BD. In controls, BD was immediately associated with an increase in wall thickness and a decrease in LV cavity dimension. This myocardial wall hypertrophy was completely prevented by β-blockers, but not with calcium- and alpha-blockers. Extensive myocardial interstitial edema was found in all groups, except in the β-blocker group. Myocardial wall hypertrophy was also prevented during a longer follow-up of 180 min after BD in β-blocker group as opposed to controls. In conclusion, BD is associated with an immediate and severe myocardial damage related to an important interstitial edema which is prevented by β-blockers. © 2010 The Authors. Transplant International © 2010 European Society for Organ Transplantation.

Interaction of triblock co-polymer micelles with phospholipid-bilayer: a spectroscopic investigation using a potential chloride channel blocker.

PubMed

Ganguly, Aniruddha; Ghosh, Soumen; Guchhait, Nikhil

2015-03-07

Interaction of a potential chloride channel blocker, 9-methyl anthroate (9-MA), has been studied with zwitterionic l-α-phosphatidylcholine (egg-PC) lipid vesicles, which ascertains the utility of the drug as an efficient molecular reporter for probing the microheterogeneous environment of lipid-bilayers. The effect of a non-ionic triblock co-polymer P123 on the stability of these drug-bound lipid-bilayers has also been investigated by means of steady state and time-resolved spectroscopic techniques exploiting the fluorescence properties of the drug. Experimental results reveal that the addition of P123 to the drug-bound lipid results in a preferential complexation of the drug with the Pluronic leaving the lipid vesicles aside, which has been attributed to a substantially stronger binding interaction of the drug with P123 than that with egg-PC. The result is of potential interest from a medical perspective owing to the context of excess drug desorption from bio-membranes.

Drug interactions with neuromuscular blockers.

PubMed

Feldman, S; Karalliedde, L

1996-10-01

Drugs administered to patients undergoing anaesthesia may complicate the use of the neuromuscular blockers that are given to provide good surgical conditions. The various sites of interaction include actions on motor nerve conduction and spinal reflexes, acetylcholine (ACh) synthesis, mobilisation and release, sensitivity of the motor end plate to ACh and the ease of propagation of the motor action potential. In addition, many drugs affect the pharmacokinetics of neuromuscular blockers, especially as most drugs depend to a greater or lesser extent upon renal excretion. The clinically significant interaction between nondepolarisers and depolarisers may be due to blockade of the pre-synaptic nicotinic receptors by the depolarisers, leading to decreased ACh mobilisation and release. Synergism between nondepolarisers probably results from post-synaptic receptor mechanisms. Volatile anaesthetic agents affect the sensitivity of the motor end-plate (post-synaptic receptor blockade) in addition to having effects on pre-synaptic nicotinic function. The effects of nondepolarisers are likely to be potentiated and their action prolonged by large doses of local anaesthetics due to depression of nerve conduction, depression of ACh formation, mobilisation and release, decreases in post-synaptic receptor channel opening times and reductions in muscular contraction. Most antibacterials have effects on pre-synaptic mechanisms. Procainamide and quinidine principally block nicotinic receptor channels. Magnesium has a marked inhibitory effect on ACh release. Calcium antagonists could theoretically interfere with neurotransmitter release and muscle contractility. Phenytoin and lithium decrease ACh release, whilst corticosteroids and furosemide (frusemide) tend to increase the release of the transmitter. Ecothiopate, tacrine, organophosphates, propanidid, metoclopramide and bambuterol depress cholinesterase activity and prolong the duration of the neuromuscular block. The probability of

Treatment of cardiac arrhythmias in a mouse model of Rett syndrome with Na+-channel-blocking antiepileptic drugs

PubMed Central

Herrera, José A.; Ward, Christopher S.; Pitcher, Meagan R.; Percy, Alan K.; Skinner, Steven; Kaufmann, Walter E.; Glaze, Daniel G.; Wehrens, Xander H. T.; Neul, Jeffrey L.

2015-01-01

One quarter of deaths associated with Rett syndrome (RTT), an X-linked neurodevelopmental disorder, are sudden and unexpected. RTT is associated with prolonged QTc interval (LQT), and LQT-associated cardiac arrhythmias are a potential cause of unexpected death. The standard of care for LQT in RTT is treatment with β-adrenergic antagonists; however, recent work indicates that acute treatment of mice with RTT with a β-antagonist, propranolol, does not prevent lethal arrhythmias. In contrast, acute treatment with the Na+ channel blocker phenytoin prevented arrhythmias. Chronic dosing of propranolol may be required for efficacy; therefore, we tested the efficacy of chronic treatment with either propranolol or phenytoin on RTT mice. Phenytoin completely abolished arrhythmias, whereas propranolol showed no benefit. Surprisingly, phenytoin also normalized weight and activity, but worsened breathing patterns. To explore the role of Na+ channel blockers on QT in people with RTT, we performed a retrospective analysis of QT status before and after Na+ channel blocker antiepileptic therapies. Individuals with RTT and LQT significantly improved their QT interval status after being started on Na+ channel blocker antiepileptic therapies. Thus, Na+ channel blockers should be considered for the clinical management of LQT in individuals with RTT. PMID:25713300

Relaxant Effects of the Selective Estrogen Receptor Modulator, Bazedoxifene, and Estrogen Receptor Agonists in Isolated Rabbit Basilar Artery.

PubMed

Castelló-Ruiz, María; Salom, Juan B; Fernández-Musoles, Ricardo; Burguete, María C; López-Morales, Mikahela A; Arduini, Alessandro; Jover-Mengual, Teresa; Hervás, David; Torregrosa, Germán; Alborch, Enrique

2016-10-01

We have previously shown that the selective estrogen receptor modulator, bazedoxifene, improves the consequences of ischemic stroke. Now we aimed to characterize the effects and mechanisms of action of bazedoxifene in cerebral arteries. Male rabbit isolated basilar arteries were used for isometric tension recording and quantitative polymerase chain reaction. Bazedoxifene relaxed cerebral arteries, as 17-β-estradiol, 4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol [estrogen receptor (ER) α agonist], and G1 [G protein-coupled ER (GPER) agonist] did it (4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol > bazedoxifene = G1 > 17-β-estradiol). 2,3-Bis(4-hydroxyphenyl)-propionitrile (ERβ agonist) had no effect. Expression profile of genes encoding for ERα (ESR1), ERβ (ESR2), and GPER was GPER > ESR1 > ESR2. As to the endothelial mechanisms, endothelium removal, N-nitro-L-arginine methyl ester, and indomethacin, did not modify the relaxant responses to bazedoxifene. As to the K channels, both a high-K medium and the Kv blocker, 4-aminopyridine, inhibited the bazedoxifene-induced relaxations, whereas tetraethylammonium (nonselective K channel blocker), glibenclamide (selective KATP blocker) or iberiotoxin (selective KCa blocker) were without effect. Bazedoxifene also inhibited both Ca- and Bay K8644-elicited contractions. Therefore, bazedoxifene induces endothelium-independent relaxations of cerebral arteries through (1) activation of GPER and ERα receptors; (2) increase of K conductance through Kv channels; and (3) inhibition of Ca entry through L-type Ca channels. Such a profile is compatible with the beneficial effects of estrogenic compounds (eg, SERMs) on vascular function and, specifically, that concerning the brain. Therefore, bazedoxifene could be useful in the treatment of cerebral disorders in which the cerebrovascular function is compromised (eg, stroke).

Influence of betel quid on effect of calcium channel blockers on isoprenaline induced myocardial necrosis in mice.

PubMed

Kumar, Vinod; Asdaq, Syed Mohammed Basheeruddin; Asad, Mohammed

2009-09-01

It is known that chewing Betel quid with tobacco (BQT) or without tobacco (BQ) is a major etiological factor for cardiovascular complications and calcium channel blockers (CCBs) are the major class of drugs prescribed widely for myocardial disturbances. The possible pharmacodynamic interaction between CCBs (verapamil, amlodipine and diltiazem) and BQ/BQT was studied on isoproterenol (ISO)-induced myocardial necrosis in mice. Influence of (CCBs) therapy on pretreated animals at times of myocardial stress were determined by estimating diagnostic marker enzymes such as lactate dehydrogenase (LDH) and creatine phosphokinase isoenzyme (CK-MB) in serum and heart tissue homogenate (HTH). Administration of CCBs to mice pretreated with BQ produced a significant decrease and increase in biomarker enzyme levels in serum and HTH respectively. Further, incorporation of diltiazem and amlodipine in BQT pretreated mice significantly elevated enzyme levels in HTH, whereas, amlodipine administration during BQT treatment showed significant fall in enzyme levels in serum. The results indicated that BQT is cardiotoxic and its effect cannot be reversed using CCBs while BQ is cardioprotective, whose activity was further augmented by amlodipine. Histopathological studies confirmed the biochemical findings.

Molecular identity of cardiac mitochondrial chloride intracellular channel proteins.

PubMed

Ponnalagu, Devasena; Gururaja Rao, Shubha; Farber, Jason; Xin, Wenyu; Hussain, Ahmed Tafsirul; Shah, Kajol; Tanda, Soichi; Berryman, Mark; Edwards, John C; Singh, Harpreet

2016-03-01

Emerging evidences demonstrate significance of chloride channels in cardiac function and cardioprotection from ischemia-reperfusion (IR) injury. Unlike mitochondrial potassium channels sensitive to calcium (BKCa) and ATP (KATP), molecular identity of majority of cardiac mitochondrial chloride channels located at the inner membrane is not known. In this study, we report the presence of unique dimorphic chloride intracellular channel (CLIC) proteins namely CLIC1, CLIC4 and CLIC5 as abundant CLICs in the rodent heart. Further, CLIC4, CLIC5, and an ortholog present in Drosophila (DmCLIC) localize to adult cardiac mitochondria. We found that CLIC4 is enriched in the outer mitochondrial membrane, whereas CLIC5 is present in the inner mitochondrial membrane. Also, CLIC5 plays a direct role in regulating mitochondrial reactive oxygen species (ROS) generation. Our study highlights that CLIC5 is localized to the cardiac mitochondria and directly modulates mitochondrial function. Copyright © 2016 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

G-protein-coupled inward rectifier potassium channels involved in corticostriatal presynaptic modulation.

PubMed

Meneses, David; Mateos, Verónica; Islas, Gustavo; Barral, Jaime

2015-09-01

Presynaptic modulation has been associated mainly with calcium channels but recent data suggests that inward rectifier potassium channels (K(IR)) also play a role. In this work we set to characterize the role of presynaptic K(IR) channels in corticostriatal synaptic transmission. We elicited synaptic potentials in striatum by stimulating cortical areas and then determined the synaptic responses of corticostriatal synapsis by using paired pulse ratio (PPR) in the presence and absence of several potassium channel blockers. Unspecific potassium channels blockers Ba(2+) and Cs(+) reduced the PPR, suggesting that these channels are presynaptically located. Further pharmacological characterization showed that application of tertiapin-Q, a specific K(IR)3 channel family blocker, also induced a reduction of PPR, suggesting that K(IR)3 channels are present at corticostriatal terminals. In contrast, exposure to Lq2, a specific K(IR)1.1 inward rectifier potassium channel, did not induce any change in PPR suggesting the absence of these channels in the presynaptic corticostriatal terminals. Our results indicate that K(IR)3 channels are functionally expressed at the corticostriatal synapses, since blockage of these channels result in PPR decrease. Our results also help to explain how synaptic activity may become sensitive to extracellular signals mediated by G-protein coupled receptors. A vast repertoire of receptors may influence neurotransmitter release in an indirect manner through regulation of K(IR)3 channels. © 2015 Wiley Periodicals, Inc.

The Mammalian Neuronal Sodium Channel Blocker μ-Conotoxin BuIIIB has a Structured N-terminus that Influences Potency

PubMed Central

Kuang, Zhihe; Zhang, Min-Min; Gupta, Kallol; Gajewiak, Joanna; Gulyas, Jozsef; Balaram, Padmanabhan; Rivier, Jean E.; Olivera, Baldomero M.; Yoshikami, Doju; Bulaj, Grzegorz; Norton, Raymond S.

2014-01-01

Among the μ-conotoxins that block vertebrate voltage-gated sodium channels (VGSCs), some have been shown to be potent analgesics following systemic administration in mice. We have determined the solution structure of a new representative of this family, μ-BuIIIB, and established its disulfide connectivities by direct mass spectrometric collision induced dissociation fragmentation of the peptide with disulfides intact. The major oxidative folding product adopts a 1-4/2-5/3-6 pattern with the following disulfide bridges: Cys5-Cys17, Cys6-Cys23 and Cys13-Cys24. The solution structure reveals that the unique N-terminal extension in μ-BuIIIB, which is also present in μ-BuIIIA and μ-BuIIIC but absent in other μ-conotoxins, forms part of a short α-helix encompassing Glu3 to Asn8. This helix is packed against the rest of the toxin and stabilized by the Cys5-Cys17 and Cys6-Cys23 disulfide bonds. As such, the side chain of Val1 is located close to the aromatic rings of Trp16 and His20, which are located on the canonical helix that displays several residues found to be essential for VGSC blockade in related μ-conotoxins. Mutations of residues 2 and 3 in the N-terminal extension enhanced the potency of μ-BuIIIB for NaV1.3. One analog, [d-Ala2]BuIIIB, showed a 40-fold increase, making it the most potent peptide blocker of this channel characterized to date and thus a useful new tool with which to characterize this channel. Based on previous results for related μ-conotoxins, the dramatic effects of mutations at the N-terminus were unanticipated, and suggest that further gains in potency might be achieved by additional modifications of this region. PMID:23557677

Regulation of ATP sensitive potassium channel of isolated guinea pig ventricular myocytes by sarcolemmal monocarboxylate transport.

PubMed

Coetzee, W A

1992-11-01

The aim was to describe the effects of extracellular application of monocarboxylates (pyruvate, lactate, or acetate) on current through KATP channels (iK,ATP) in isolated guinea pig ventricular myocytes. The iK,ATP was elicited during whole cell voltage clamping by application of metabolic poisons, 2,4-dinitrophenol (150 microM) or glucose free cyanide (1 mM) and could be blocked by glibenclamide (3 microM). Extracellular application of monocarboxylates, pyruvate (0.1-10 mM), L-lactate (0.1-10 mM), and acetate (10 mM) led to a rapid inhibition of iK,ATP--an effect which was fully reversible upon washout. Substances without any effect on iK,ATP were (10 mM each) gluconate, citrate, glutamate, creatine, succinate, and glycine. The mechanism underlying the effects of monocarboxylates on iK,ATP was unlikely to be related to an increased ATP production, since D-lactate (10 mM) essentially had the same effect on iK,ATP as the L-isomer of lactate. Furthermore, with intracellular dialysis of alpha-cyano-4-hydroxycinnamate (0.1-0.5 mM), which inhibits pyruvate uptake into mitochondria, extracellular pyruvate exerted the same inhibitory effect on iK,ATP. High concentrations of extracellular alpha-cyano-4-hydroxycinnamate (4 mM), which blocks the sarcolemmal monocarboxylate carrier, prevented the effects on iK,ATP by pyruvate, L-lactate, D-lactate, and acetate. Furthermore, intracellular dialysis with D-lactate (10 mM) led to a more rapid onset of iK,ATP when activated by ATP free dialysis. Activity of isolated KATP channels, measured in isolated membrane patches in the inside out or outside out configuration, typically had a single channel conductance of around 80 pS and was blocked by glibenclamide (3-9 microM). No significant effect of pyruvate was observed in either patch configuration. In cardiac tissue there may be some modulatory role involving monocarboxylate transport on KATP channel activity, the nature of which is unclear at present but which may involve cytosolic

Site of action of calcium channel blockers in inhibiting endogenous pyrogen fever in rats.

PubMed

Stitt, J T; Shimada, S G

1991-09-01

We have demonstrated that the Ca2+ channel blocker verapamil, administered intravenously, exerts an antipyretic effect on the febrile responses of rats to intravenously injected endogenous pyrogen (EP). We have also shown that the same intravenous dose of verapamil is ineffective in blocking fevers induced by the microinjection of exogenous prostaglandin E (PGE) into the organum vasculosum laminae terminalis (OVLT) of rats. Experiments were conducted to determine whether the site of this verapamil antipyresis was in the OVLT itself. The febrile responses of six male Sprague-Dawley rats to EP were determined at thermoneutrality. Verapamil (10 micrograms/rat) was microinjected directly into the OVLT, and the febrile responses to the EP dose were redetermined 15-30 min later. In every case the EP fevers were attenuated after verapamil pretreatment. Intra-OVLT injections of verapamil alone were without effect on body temperature. When the same dose of verapamil was injected into the OVLT 15 min before the injection of PGE into the same site, it had no effect on the ensuing PGE-induced fever. In view of the fact that less than 1/250th of the effective systemic dose of verapamil, when injected into the OVLT, was equally effective in blocking the EP fevers, we conclude that verapamil acts within the OVLT to block fever rather than peripherally. Furthermore, because verapamil administered into the OVLT does not block PGE fevers, it is unlikely that PGE produces fever by acting as a Ca2+ ionophore on hypothalamic neurons.

The effects of ion channel blockers validate the conductance-based model of saccadic oscillations

PubMed Central

Shaikh, Aasef G.; Zee, David S.; Optican, Lance M.; Miura, Kenichiro; Ramat, Stefano; Leigh, R. John

2012-01-01

Conductance-based models of reciprocally inhibiting burst neurons suggest that intrinsic membrane properties and postinhibitory rebound (PIR) determine the amplitude and frequency of saccadic oscillations. Reduction of the low-threshold calcium currents (IT) in the model decreased the amplitude but increased the frequency of the simulated oscillations. Combined reduction of hyperpolarization-activated cation current (Ih) and IT in the model abolished the simulated oscillations. We measured the effects of a selective blocker of IT (ethosuximide) in healthy subjects on the amplitude and frequency of saccadic oscillations evoked by eye closure and of a nonselective blocker of Ih and IT (propronolol) in a patient with microsaccadic oscillation and limb tremor syndrome (mSOLT). Ethosuximide significantly reduced the amplitude but increased the frequency of the saccadic oscillations during eye closure in healthy subjects. Propranolol abolished saccadic oscillations in the mSOLT patient. These results support the hypothetical role of postinhibitory rebound, Ih, and IT, in generation of saccadic oscillations and determining their kinematic properties. PMID:21950976

GAL-021, a new intravenous BKCa-channel blocker, is well tolerated and stimulates ventilation in healthy volunteers.

PubMed

McLeod, J F; Leempoels, J M; Peng, S X; Dax, S L; Myers, L J; Golder, F J

2014-11-01

Potassium-channels in the carotid body and the brainstem are important regulators of ventilation. The BKCa-channel contains response elements for CO, O2, and CO2. Its block increases carotid body signalling, phrenic nerve activity, and respiratory drive. GAL-021, a new BKCa-channel blocker, increases minute ventilation in rats and non-human primates. This study assessed the single-dose safety, tolerability, pharmacokinetics (PKs), and pharmacodynamics (PDs) of GAL-021 in healthy volunteers. Thirty subjects participated in a nine-period, randomized, double-blinded, placebo-controlled, crossover, ascending dose, first-in-human study with i.v. infusions of 0.1-0.96 mg kg(-1) h(-1) for 1 h and intermediate doses up to 4 h. Adverse event rates were generally similar among dose levels and between placebo- and GAL-021-treated subjects. At higher GAL-021 doses, a mild/moderate burning sensation at the infusion site occurred during the infusion. No clinically significant changes in vital signs or clinical chemistries were noted. Minute ventilation increased (AUE0-1 h ≈ 16%, P<0.05) and end-tidal carbon dioxide ([Formula: see text]) decreased (AUE0-1 h ≈ 6%, P<0.05) during the first hour at 0.96 mg kg(-1) h(-1) with 1/2-maximal [Formula: see text] and [Formula: see text]-change occurring by 7.5 min. Drug concentration rose rapidly during the infusion and decreased rapidly initially (distribution t1/2 of 30 min) and then more slowly (terminal t1/2 of 5.6 h). GAL-021 was safe and generally well tolerated with adverse events comparable with placebo except for an infusion site burning sensation. GAL-021 stimulated ventilation at the highest doses suggesting that greater infusion rates may be required for maximum PD effects. GAL-021 had PK characteristics consistent with an acute care medication. © The Author 2014. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

β-Blocker pharmacogenetics in heart failure

PubMed Central

Shin, Jaekyu

2009-01-01

β-Blockers (metoprolol, bisoprolol, and carvedilol) are a cornerstone of heart failure (HF) treatment. However, it is well recognized that responses to a β-blocker are variable among patients with HF. Numerous studies now suggest that genetic polymorphisms may contribute to variability in responses to a β-blocker, including left ventricular ejection fraction improvement, survival, and hospitalization due to HF exacerbation. This review summarizes the pharmacogenetic data for β-blockers in patients with HF and discusses the potential implications of β-blocker pharmacogenetics for HF patients. PMID:18437562

Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth

PubMed Central

Jackson, William F.

2017-01-01

Potassium channels importantly contribute to the regulation of vascular smooth muscle (VSM) contraction and growth. They are the dominant ion conductance of the VSM cell membrane and importantly determine and regulate membrane potential. Membrane potential, in turn, regulates the open-state probability of voltage-gated Ca2+ channels (VGCC), Ca2+ influx through VGCC, intracellular Ca2+ and VSM contraction. Membrane potential also affects release of Ca2+ from internal stores and the Ca2+ sensitivity of the contractile machinery such that K+ channels participate in all aspects of regulation of VSM contraction. Potassium channels also regulate proliferation of VSM cells through membrane potential-dependent and membrane potential-independent mechanisms. Vascular smooth muscle cells express multiple isoforms of at least five classes of K+ channels contribute to the regulation of contraction and cell proliferation (growth). This review will examine the structure, expression and function of large-conductance, Ca2+-activated K+ (BKCa) channels, intermediate-conductance Ca2+-activated K+ (KCa3.1) channels, multiple isoforms of voltage-gated K+ (KV) channels, ATP-sensitive K+ (KATP) channels, and inward-rectifier K+ (KIR) channels in both contractile and proliferating VSM cells. PMID:28212804

Binding of KATP channel modulators in rat cardiac membranes

PubMed Central

Löffler-Walz, Cornelia; Quast, Ulrich

1998-01-01

The binding of [3H]-P1075, a potent opener of adenosine-5′-triphosphate-(ATP)-sensitive K+ channels, was studied in a crude heart membrane preparation of the rat, at 37°C.Binding required MgATP. In the presence of an ATP-regenerating system, MgATP supported [3H]-P1075 binding with an EC50 value of 100 μM and a Hill coefficient of 1.4.In saturation experiments [3H]-P1075 binding was homogeneous with a KD value of 6±1 nM and a binding capacity (Bmax) of 33±3 fmol mg−1 protein.Upon addition of an excess of unlabelled P1075, the [3H]-P1075-receptor complex dissociated in a mono-exponential manner with a dissociation rate constant of 0.13±0.01 min−1. If a bi-molecular association mechanism was assumed, the dependence of the association kinetics on label concentration gave an association rate constant of 0.030±0.003 nM−1 min−1. From the kinetic experiments the KD value was calculated as 4.7±0.6 nM.Openers of the ATP-sensitive K+ channel belonging to different structural classes inhibited specific [3H]-P1075 binding in a monophasic manner to completion; an exception was minoxidil sulphate where maximum inhibition was 68%. The potencies of the openers in this assay agree with published values obtained in rat cardiocytes and are on average 3.5 times lower than those determined in rat aorta.Sulphonylureas, such as glibenclamide and glibornuride and the sulphonylurea-related carboxylate, AZ-DF 265, inhibited [3H]-P1075 binding with biphasic inhibition curves. The high affinity component comprised about 60% of the curves with the IC50 value of glibenclamide being ≈amp;90 nM; affinities for the low affinity component were in the μM concentration range. The fluorescein derivative, phloxine B, showed a monophasic inhibition curve with an IC50 value of 6 μM, a maximum inhibition of 94% and a Hill coefficient of 1.5.It is concluded that binding studies with [3H]-P1075 are feasible in rat heart membranes in the presence of MgATP and of an ATP

Potassium Channels Mediate Killing by Human Natural Killer Cells

NASA Astrophysics Data System (ADS)

Schlichter, Lyanne; Sidell, Neil; Hagiwara, Susumu

1986-01-01

Human natural killer (NK) cells in peripheral blood spontaneously recognize and kill a wide variety of target cells. It has been suggested that ion channels are involved in the killing process because there is a Ca-dependent stage and because killing by presensitized cytotoxic T lymphocytes, which in many respects resembles NK killing, is associated with changes in K and Na transport in the target cell. However, no direct evidence exists for ion channels in NK cells or in their target cells. Using the whole-cell variation of the patch-clamp technique, we found a voltage-dependent potassium (K+) current in NK cells. The K+ current was reduced in a dose-dependent manner by the K-channel blockers 4-aminopyridine and quinidine and by the traditional Ca-channel blockers verapamil and Cd2+. We tested the effects of ion-channel blockers on killing of two commonly used target cell lines: K562, which is derived from a human myeloid leukemia, and U937, which is derived from a human histiocytic leukemia. Killing of K562 target cells, determined in a standard 51Cr-release assay, was inhibited in a dose-dependent manner by verapamil, quinidine, Cd2+, and 4-aminopyridine at concentrations comparable to those that blocked the K+ current in NK cells. In K562 target cells only a voltage-dependent Na+ current was found and it was blocked by concentrations of tetrodotoxin that had no effect on killing. Killing of U937 target cells was also inhibited by the two ion-channel blockers tested, quinidine and verapamil. In this cell line only a small K+ current was found that was similar to the one in NK cells. We could not find any evidence of a Ca2+ current in target cells or in NK cells; therefore, our results cannot explain the Ca dependence of killing. Our findings show that there are K channels in NK cells and that these channels play a necessary role in the killing process. In contrast, the endogenous channel type in the target cell is probably not a factor in determining target cell

Protective effect of T-type calcium channel blocker flunarizine on cisplatin-induced death of auditory cells.

PubMed

So, Hong-Seob; Park, Channy; Kim, Hyung-Jin; Lee, Jung-Han; Park, Sung-Yeol; Lee, Jai-Hyung; Lee, Zee-Won; Kim, Hyung-Min; Kalinec, Federico; Lim, David J; Park, Raekil

2005-06-01

Changes in intracellular Ca2+ level are involved in a number of intracellular events, including triggering of apoptosis. The role of intracellular calcium mobilization in cisplatin-induced hair cell death, however, is still unknown. In this study, the effect of calcium channel blocker flunarizine (Sibelium), which is used to prescribe for vertigo and tinnitus, on cisplatin-induced hair cell death was investigated in a cochlear organ of Corti-derived cell line, HEI-OC1, and the neonatal (P2) rat organ of Corti explant. Cisplatin induced apoptotic cell death showing nuclear fragmentation, DNA ladder, and TUNEL positive in both HEI-OC1 and primary organ of Corti explant. Flunarizine significantly inhibited the cisplatin-induced apoptosis. Unexpectedly, flunarizine increased the intracellular calcium ([Ca2+]i) levels of HEI-OC1. However, the protective effect of flunarizine against cisplatin was not mediated by modulation of intracellular calcium level. Treatment of cisplatin resulted in ROS generation and lipid peroxidation in HEI-OC1. Flunarizine did not attenuate ROS production but inhibited lipid peroxidation and mitochondrial permeability transition in cisplatin-treated cells. This result suggests that the protective mechanism of flunarizine on cisplatin-induced cytotoxicity is associated with direct inhibition of lipid peroxidation and mitochondrial permeability transition.

Opiate-induced constipation related to activation of small intestine opioid μ2-receptors.

PubMed

Chen, Wency; Chung, Hsien-Hui; Cheng, Juei-Tang

2012-03-28

To investigate the role of opioid μ-receptor subtype in opiate-induced constipation (OIC). The effect of loperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension. The ileum strips were precontracted with 1 μmol/L acetylcholine (ACh). Then, decrease in muscle tone (relaxation) was characterized after cumulative administration of 0.1-10 μmol/L loperamide into the organ bath, for a concentration-dependent study. Specific blockers or antagonists were used for pretreatment to compare the changes in loperamide-induced relaxation. In addition to the delay in intestinal transit, loperamide produced a marked relaxation in isolated ileum precontracted with ACh, in a dose-dependent manner. This relaxation was abolished by cyprodime, a selective opioid μ-receptor antagonist, but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors. Also, treatment with opioid μ-1 receptor agonist failed to modify the muscle tone. Moreover, the relaxation by loperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K+ (K(ATP)) channels, and by protein kinase A (PKA) inhibitor, but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate (cAMP). Loperamide induces intestinal relaxation by activation of opioid μ-2 receptors via the cAMP-PKA pathway to open K(ATP) channels, relates to OIC.

[Single channel analysis of aconitine blockade of calcium channels in rat myocardiocytes].

PubMed

Chen, L; Ma, C; Cai, B C; Lu, Y M; Wu, H

1995-01-01

Ventricular myocardiocytes from neonatal Wistar rats were isolated and cultured. Aconitine, Ca2+ channel blocker verapamil or Ca2+ channel activator BAY K8644 were added to the bath solution separately. Using the cell-attached configuration of the patch clamp technique, the single channel activities of L type Ca2+ channel were recorded before and after addition of all three drugs. The results showed the blocking effect of aconitine (50 micrograms.ml-1) on L type Ca2+ channels. Its mechanism may be relevant to the decrease in both open state probability and the mean open time of Ca2+ channel. The difference was statistically significant compared with control group (P < 0.01). The amplitude of Ba2+ currents, which flow through open L type Ca2+ channel was unchanged.

Reversible inhibition of the platelet procoagulant response through manipulation of the Gardos channel.

PubMed

Wolfs, Jef L; Wielders, Simone J; Comfurius, Paul; Lindhout, Theo; Giddings, John C; Zwaal, Robert F; Bevers, Edouard M

2006-10-01

The platelet procoagulant response requires a sustained elevation of the intracellular Ca2+ concentration, [Ca2+]i, causing exposure of phosphatidylserine (PS) at the outer surface of the plasma membrane. An increased [Ca2+]i also activates Ca2+-dependent K+ channels. Here, we investigated the contribution of the efflux of K+ ions on the platelet procoagulant response in collagen-thrombin-activated platelets using selective K+ channel blockers. The Gardos channel blockers clotrimazol, charybdotoxin, and quinine caused a similar decrease in prothrombinase activity as well as in the number of PS-exposing platelets detected by fluorescence-conjugated annexin A5. Apamin and iberiotoxin, inhibitors of other K+ channels, were without effect. Only clotrimazol showed a significant inhibition of the collagen-plus-thrombin-induced intracellular calcium response. Clotrimazol and charybdotoxin did not inhibit aggregation and release under the conditions used. Inhibition by Gardos channel blockers was reversed by valinomycin, a selective K+ ionophore. The impaired procoagulant response of platelets from a patient with Scott syndrome was partially restored by pretreatment with valinomycin, suggesting a possible defect of the Gardos channel in this syndrome. Collectively, these results provide evidence for the involvement of efflux of K+ ions through Ca2+-activated K+ channels in the procoagulant response of platelets, opening potential strategies for therapeutic interventions.

Validation of a patch clamp screening protocol that simultaneously measures compound activity in multiple states of the voltage-gated sodium channel Nav1.2.

PubMed

Liu, Yi; Beck, Edward J; Flores, Christopher M

2011-12-01

Hyperactivity of voltage-gated sodium channels underlies, at least in part, a range of pathological states, including pain and epilepsy. Selective blockers of these channels may offer effective treatment of such disorders. Currently employed methods to screen for sodium channel blockers, however, are inadequate to rationally identify mechanistically diverse blockers, limiting the potential range of indications that may be treated by such agents. Here, we describe an improved patch clamp screening assay that increases the mechanistic diversity of sodium channel blockers being identified. Using QPatch HT, a medium-throughput, automated patch clamp system, we tested three common sodium channel blockers (phenytoin, lidocaine, and tetrodotoxin) with distinct mechanistic profiles at Nav1.2. The single-voltage protocol employed in this assay simultaneously measured the compound activity in multiple states, including the slow inactivated state, of the channel. A long compound incubation period (10 s) was introduced during channel inactivation to increase the probability of identifying "slow binders." As such, phenytoin, which preferentially binds with slow kinetics to the fast inactivated state, exhibited significantly higher potency than that obtained from a brief exposure (100 ms) used in typical assays. This assay also successfully detected the use-dependent block of tetrodotoxin, a well-documented property of this molecule yet unobserved in typical patch clamp protocols. These results indicate that the assay described here can increase the likelihood of identification and mechanistic diversity of sodium channel blockers from a primary screen. It can also be used to efficiently guide the in vitro optimization of leads that retain the desired mechanistic properties. © MARY ANN LIEBERT, INC.

Effects of calcium channel blockers comparing to angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in patients with hypertension and chronic kidney disease stage 3 to 5 and dialysis: A systematic review and meta-analysis

PubMed Central

Lin, Yen-Chung; Lin, Jheng-Wei; Wu, Mai-Szu; Chen, Kuan-Chou; Peng, Chiung-Chi

2017-01-01

Background Calcium channel blocker (CCB) or two renin angiotensin aldosterone system blockades (RAAS), angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), are major potent and prevalently used as initial antihypertensive agents for mild to moderate hypertension, but no uniform agreement as to which antihypertensive drugs should be given for initial therapy, especially among chronic kidney disease (CKD) patients. Design A systematic review and meta-analysis comparing CCBs and the two RAAS blockades for hypertensive patients with CKD stage 3 to 5D. The inclusion criteria for this systematic review was RCT that compared the effects of CCBs and the two RAAS blockades in patients with hypertension and CKD. The exclusion criteria were (1) renal transplantation, (2) CKD stage 1 or 2, (3) combined therapy (data cannot be extracted separately). Outcomes were blood pressure change, mortality, heart failure, stroke or cerebrovascular events, and renal outcomes. Results 21 randomized controlled trials randomized 9,492 patients with hypertensive and CKD into CCBs and the two RAAS blockades treatments. The evidence showed no significant differences in blood presser change, mortality, heart failure, stroke or cerebrovascular events, and renal outcomes between CCBs group and the two RAAS blockades group. The publication bias of pooled mean blood presser change that was detected by Egger’s test was non-significant. Conclusions CCBs has similar effects on long term blood pressure, mortality, heart failure, stroke or cerebrovascular events, and renal function to RAAS blockades in patients CKD stage 3 to 5D and hypertension. PMID:29240784

The effects of ion channel blockers validate the conductance-based model of saccadic oscillations.

PubMed

Shaikh, Aasef G; Zee, David S; Optican, Lance M; Miura, Kenichiro; Ramat, Stefano; Leigh, R John

2011-09-01

Conductance-based models of reciprocally inhibiting burst neurons suggest that intrinsic membrane properties and postinhibitory rebound (PIR) determine the amplitude and frequency of saccadic oscillations. Reduction of the low-threshold calcium currents (I(T)) in the model decreased the amplitude but increased the frequency of the simulated oscillations. Combined reduction of hyperpolarization-activated cation current (I(h)) and I(T) in the model abolished the simulated oscillations. We measured the effects of a selective blocker of I(T) (ethosuximide) in healthy subjects on the amplitude and frequency of saccadic oscillations evoked by eye closure and of a nonselective blocker of I(h) and I(T) (propronolol) in a patient with microsaccadic oscillation and limb tremor syndrome (mSOLT). Ethosuximide significantly reduced the amplitude but increased the frequency of the saccadic oscillations during eye closure in healthy subjects. Propranolol abolished saccadic oscillations in the mSOLT patient. These results support the hypothetical role of postinhibitory rebound, I(h), and I(T) , in generation of saccadic oscillations and determining their kinematic properties. © 2011 New York Academy of Sciences.

Variability of Potassium Channel Blockers in Mesobuthus eupeus Scorpion Venom with Focus on Kv1.1: AN INTEGRATED TRANSCRIPTOMIC AND PROTEOMIC STUDY.

PubMed

Kuzmenkov, Alexey I; Vassilevski, Alexander A; Kudryashova, Kseniya S; Nekrasova, Oksana V; Peigneur, Steve; Tytgat, Jan; Feofanov, Alexey V; Kirpichnikov, Mikhail P; Grishin, Eugene V

2015-05-08

The lesser Asian scorpion Mesobuthus eupeus (Buthidae) is one of the most widely spread and dispersed species of the Mesobuthus genus, and its venom is actively studied. Nevertheless, a considerable amount of active compounds is still under-investigated due to the high complexity of this venom. Here, we report a comprehensive analysis of putative potassium channel toxins (KTxs) from the cDNA library of M. eupeus venom glands, and we compare the deduced KTx structures with peptides purified from the venom. For the transcriptome analysis, we used conventional tools as well as a search for structural motifs characteristic of scorpion venom components in the form of regular expressions. We found 59 candidate KTxs distributed in 30 subfamilies and presenting the cysteine-stabilized α/β and inhibitor cystine knot types of fold. M. eupeus venom was then separated to individual components by multistage chromatography. A facile fluorescent system based on the expression of the KcsA-Kv1.1 hybrid channels in Escherichia coli and utilization of a labeled scorpion toxin was elaborated and applied to follow Kv1.1 pore binding activity during venom separation. As a result, eight high affinity Kv1.1 channel blockers were identified, including five novel peptides, which extend the panel of potential pharmacologically important Kv1 ligands. Activity of the new peptides against rat Kv1.1 channel was confirmed (IC50 in the range of 1-780 nm) by the two-electrode voltage clamp technique using a standard Xenopus oocyte system. Our integrated approach is of general utility and efficiency to mine natural venoms for KTxs. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Neonatal Diabetes Caused by Mutations in Sulfonylurea Receptor 1: Interplay between Expression and Mg-Nucleotide Gating Defects of ATP-Sensitive Potassium Channels

PubMed Central

Zhou, Qing; Garin, Intza; Castaño, Luis; Argente, Jesús; Muñoz-Calvo, Ma. Teresa; Perez de Nanclares, Guiomar; Shyng, Show-Ling

2010-01-01

Context: ATP-sensitive potassium (KATP) channels regulate insulin secretion by coupling glucose metabolism to β-cell membrane potential. Gain-of-function mutations in the sulfonylurea receptor 1 (SUR1) or Kir6.2 channel subunit underlie neonatal diabetes. Objective: The objective of the study was to determine the mechanisms by which two SUR1 mutations, E208K and V324M, associated with transient neonatal diabetes affect KATP channel function. Design: E208K or V324M mutant SUR1 was coexpressed with Kir6.2 in COS cells, and expression and gating properties of the resulting channels were assessed biochemically and electrophysiologically. Results: Both E208K and V324M augment channel response to MgADP stimulation without altering sensitivity to ATP4− or sulfonylureas. Surprisingly, whereas E208K causes only a small increase in MgADP response consistent with the mild transient diabetes phenotype, V324M causes a severe activating gating defect. Unlike E208K, V324M also impairs channel expression at the cell surface, which is expected to dampen its functional impact on β-cells. When either mutation was combined with a mutation in the second nucleotide binding domain of SUR1 previously shown to abolish Mg-nucleotide response, the activating effect of E208K and V324M was also abolished. Moreover, combination of E208K and V324M results in channels with Mg-nucleotide sensitivity greater than that seen in individual mutations alone. Conclusion: The results demonstrate that E208K and V324M, located in distinct domains of SUR1, enhance transduction of Mg-nucleotide stimulation from the SUR1 nucleotide binding folds to Kir6.2. Furthermore, they suggest that diabetes severity is determined by interplay between effects of a mutation on channel expression and channel gating. PMID:20810569

L-type calcium channel blockade attenuates morphine withdrawal: in vivo interaction between L-type calcium channels and corticosterone.

PubMed

Esmaeili-Mahani, Saeed; Fathi, Yadollah; Motamedi, Fereshteh; Hosseinpanah, Farhad; Ahmadiani, Abolhassan

2008-02-01

Both opioids and calcium channel blockers could affect hypothalamic-pituitary-adrenal (HPA) axis function. Nifedipine, as a calcium channel blocker, can attenuate the development of morphine dependence; however, the role of the HPA axis in this effect has not been elucidated. We examined the effect of nifedipine on the induction of morphine dependency in intact and adrenalectomized (ADX) male rats, as assessed by the naloxone precipitation test. We also evaluated the effect of this drug on HPA activity induced by naloxone. Our results showed that despite the demonstration of dependence in both groups of rats, nifedipine is more effective in preventing of withdrawal signs in ADX rats than in sham-operated rats. In groups that received morphine and nifedipine concomitantly, naloxone-induced corticosterone secretion was attenuated. Thus, we have shown the involvement of the HPA axis in the effect of nifedipine on the development of morphine dependency and additionally demonstrated an in vivo interaction between the L-type Ca2+ channels and corticosterone.

Role of potassium ion channels in detrusor smooth muscle function and dysfunction

PubMed Central

Petkov, Georgi V.

2013-01-01

Contraction and relaxation of the detrusor smooth muscle (DSM), which makes up the wall of the urinary bladder, facilitates the storage and voiding of urine. Several families of K+ channels, including voltage-gated K+ (KV) channels, Ca2+-activated K+ (KCa) channels, inward-rectifying ATP-sensitive K+ (Kir, KATP) channels, and two-pore-domain K+ (K2P) channels, are expressed and functional in DSM. They control DSM excitability and contractility by maintaining the resting membrane potential and shaping the action potentials that determine the phasic nature of contractility in this tissue. Defects in DSM K+ channel proteins or in the molecules involved in their regulatory pathways may underlie certain forms of bladder dysfunction, such as overactive bladder. K+ channels represent an opportunity for novel pharmacological manipulation and therapeutic intervention in human DSM. Modulation of DSM K+ channels directly or indirectly by targeting their regulatory mechanisms has the potential to control urinary bladder function. This Review summarizes our current state of knowledge of the functional role of K+ channels in DSM in health and disease, with special emphasis on current advancements in the field. PMID:22158596

Atrial-selective K+ channel blockers: potential antiarrhythmic drugs in atrial fibrillation?

PubMed

Ravens, Ursula

2017-11-01

In the wake of demographic change in Western countries, atrial fibrillation has reached an epidemiological scale, yet current strategies for drug treatment of the arrhythmia lack sufficient efficacy and safety. In search of novel medications, atrial-selective drugs that specifically target atrial over other cardiac functions have been developed. Here, I will address drugs acting on potassium (K + ) channels that are either predominantly expressed in atria or possess electrophysiological properties distinct in atria from ventricles. These channels include the ultra-rapidly activating, delayed outward-rectifying Kv1.5 channel conducting I Kur , the acetylcholine-activated inward-rectifying Kir3.1/Kir3.4 channel conducting I K,ACh , the Ca 2+ -activated K + channels of small conductance (SK) conducting I SK , and the two-pore domain K + (K2P) channels (tandem of P domains, weak inward-rectifying K + channels (TWIK-1), TWIK-related acid-sensitive K + channels (TASK-1 and TASK-3)) that are responsible for voltage-independent background currents I TWIK-1 , I TASK-1 , and I TASK-3 . Direct drug effects on these channels are described and their putative value in treatment of atrial fibrillation is discussed. Although many potential drug targets have emerged in the process of unravelling details of the pathophysiological mechanisms responsible for atrial fibrillation, we do not know whether novel antiarrhythmic drugs will be more successful when modulating many targets or a single specific one. The answer to this riddle can only be solved in a clinical context.

Calcium channel modulation as a target in chronic pain control

PubMed Central

Montagut‐Bordas, Carlota; Dickenson, Anthony H

2017-01-01

Neuropathic pain remains poorly treated for large numbers of patients, and little progress has been made in developing novel classes of analgesics. To redress this issue, ziconotide (Prialt™) was developed and approved as a first‐in‐class synthetic version of ω‐conotoxin MVIIA, a peptide blocker of Cav2.2 channels. Unfortunately, the impracticalities of intrathecal delivery, low therapeutic index and severe neurological side effects associated with ziconotide have restricted its use to exceptional circumstances. Ziconotide exhibits no state or use‐dependent block of Cav2.2 channels; activation state‐dependent blockers were hypothesized to circumvent the side effects of state‐independent blockers by selectively targeting high‐frequency firing of nociceptive neurones in chronic pain states, thus alleviating aberrant pain but not affecting normal sensory transduction. Unfortunately, numerous drugs, including state‐dependent calcium channel blockers, have displayed efficacy in preclinical models but have subsequently been disappointing in clinical trials. In recent years, it has become more widely acknowledged that trans‐aetiological sensory profiles exist amongst chronic pain patients and may indicate similar underlying mechanisms and drug sensitivities. Heterogeneity amongst patients, a reliance on stimulus‐evoked endpoints in preclinical studies and a failure to utilize translatable endpoints, all are likely to have contributed to negative clinical trial results. We provide an overview of how electrophysiological and operant‐based assays provide insight into sensory and affective aspects of pain in animal models and how these may relate to chronic pain patients in order to improve the bench‐to‐bedside translation of calcium channel modulators. Linked Articles This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http

KATP Channel Expression and Genetic Polymorphisms Associated with Progression and Survival in Amyotrophic Lateral Sclerosis.

PubMed

Vidal-Taboada, José M; Pugliese, Marco; Salvadó, Maria; Gámez, Josep; Mahy, Nicole; Rodríguez, Manuel J

2018-02-28

The ATP-sensitive potassium (K ATP ) channel directly regulates the microglia-mediated inflammatory response following CNS injury. To determine the putative role of the K ATP channel in amyotrophic lateral sclerosis (ALS) pathology, we investigated whether ALS induces changes in K ATP channel expression in the spinal cord and motor cortex. We also characterized new functional variants of human ABCC8, ABCC9, KCNJ8, and KCNJ11 genes encoding for the K ATP channel and analyzed their association with ALS risk, rate of progression, and survival in a Spanish ALS cohort. The expression of ABCC8 and KCNJ8 genes was enhanced in the spinal cord of ALS samples, and KCNJ11 increased in motor cortex of ALS samples, as determined by real-time polymerase chain reaction. We then sequenced the exons and regulatory regions of K ATP channel genes from a subset of 28 ALS patients and identified 50 new genetic variants. For the case-control association analysis, we genotyped five selected polymorphisms with predicted functional relevance in 185 Spanish ALS (134 spinal ALS and 51 bulbar ALS) patients and 493 controls. We found that bulbar ALS patients presenting the G/G genotype of the rs4148646 variant of ABCC8 and the T/T genotype of the rs5219 variant of KCNJ11 survived longer than other ALS patients presenting other genotypes. Also, the C/C genotype of the rs4148642 variant of ABCC8 and the T/C genotype of the rs148416760 variant of ABCC9 modified the progression rate in spinal ALS patients. Our results suggest that the K ATP channel plays a role in the pathophysiological mechanisms of ALS.

P/Q-type calcium channel modulators

PubMed Central

Nimmrich, V; Gross, G

2012-01-01

P/Q-type calcium channels are high-voltage-gated calcium channels contributing to vesicle release at synaptic terminals. A number of neurological diseases have been attributed to malfunctioning of P/Q channels, including ataxia, migraine and Alzheimer's disease. To date, only two specific P/Q-type blockers are known: both are peptides deriving from the spider venom of Agelenopsis aperta, ω-agatoxins. Other peptidic calcium channel blockers with activity at P/Q channels are available, albeit with less selectivity. A number of low molecular weight compounds modulate P/Q-type currents with different characteristics, and some exhibit a peculiar bidirectional pattern of modulation. Interestingly, there are a number of therapeutics in clinical use, which also show P/Q channel activity. Because selectivity as well as the exact mode of action is different between all P/Q-type channel modulators, the interpretation of clinical and experimental data is complicated and needs a comprehensive understanding of their target profile. The situation is further complicated by the fact that information on potency varies vastly in the literature, which may be the result of different experimental systems, conditions or the splice variants of the P/Q channel. This review attempts to provide a comprehensive overview of the compounds available that affect the P/Q-type channel and should help with the interpretation of results of in vitro experiments and animal models. It also aims to explain some clinical observations by implementing current knowledge about P/Q channel modulation of therapeutically used non-selective drugs. Chances and challenges of the development of P/Q channel-selective molecules are discussed. PMID:22670568

Peripheral antinociceptive action of mangiferin in mouse models of experimental pain: role of endogenous opioids, K(ATP)-channels and adenosine.

PubMed

Lopes, Synara C; da Silva, Ana Virginia L; Arruda, Bruno Rodrigues; Morais, Talita C; Rios, Jeison Barros; Trevisan, Maria Teresa S; Rao, Vietla S; Santos, Flávia A

2013-09-01

This study aimed to assess the possible systemic antinociceptive activity of mangiferin and to clarify the underlying mechanism, using the acute models of chemical (acetic acid, formalin, and capsaicin) and thermal (hot-plate and tail-flick) nociception in mice. Mangiferin at oral doses of 10 to 100 mg/kg evidenced significant antinociception against chemogenic pain in the test models of acetic acid-induced visceral pain and in formalin- and capsaicin-induced neuro-inflammatory pain, in a naloxone-sensitive manner, suggesting the participation of endogenous opiates in its mechanism. In capsaicin test, the antinociceptive effect of mangiferin (30 mg/kg) was not modified by respective competitive and non-competitive transient receptor potential vanilloid 1 (TRPV1) antagonists, capsazepine and ruthenium red, or by pretreatment with L-NAME, a non-selective nitric oxide synthase inhibitor, or by ODQ, an inhibitor of soluble guanylyl cyclase. However, mangiferin effect was significantly reversed by glibenclamide, a blocker of K(ATP) channels and in animals pretreated with 8-phenyltheophylline, an adenosine receptor antagonist. Mangiferin failed to modify the thermal nociception in hot-plate and tail-flick test models, suggesting that its analgesic effect is only peripheral but not central. The orally administered mangiferin (10-100 mg/kg) was well tolerated and did not impair the ambulation or the motor coordination of mice in respective open-field and rota-rod tests, indicating that the observed antinociception was unrelated to sedation or motor abnormality. The findings of this study suggest that mangiferin has a peripheral antinociceptive action through mechanisms that involve endogenous opioids, K(ATP)-channels and adenosine receptors. Copyright © 2013 Elsevier Inc. All rights reserved.

Calcium channel subtypes differ at two types of cholinergic synapse in lumbar sympathetic neurones of guinea-pigs.

PubMed

Ireland, D R; Davies, P J; McLachlan, E M

1999-01-01

1. The involvement of different presynaptic Ca2+ channels in transmission at 'weak' (subthreshold) and 'strong' (suprathreshold) synapses was investigated in guinea-pig paravertebral ganglia isolated in vitro. Selective Ca2+ channel antagonists were used to block excitatory synaptic currents evoked by stimulating single preganglionic axons. 2. The N-type Ca2+ channel blocker, omega-conotoxin GVIA (100 nM), reduced peak synaptic conductance by similar amounts at weak synapses (by 39 +/- 6 %) and strong synapses (34 +/- 6 %). 3. The P-type Ca2+ channel blocker, omega-agatoxin IVA (40 nM), significantly reduced transmitter release at weak synapses (by 42 +/- 6 %) but had only a small effect at strong synapses (reduced by 6 +/- 2 %). 4. Blockers of Q-, L- or T-type Ca2+ channels had no significant effects on peak synaptic conductance at either type of synapse. 5. We conclude that the two functionally distinct types of preganglionic terminal in sympathetic ganglia which synapse on the same neurone differ in their expression of particular types of voltage-dependent Ca2+ channels. Both types utilize N-type channels and channels resistant to blockade by specific antagonists, but Ca2+ entry through P-type channels makes a substantial contribution to acetylcholine release only at weak synapses.

Calcium channel subtypes differ at two types of cholinergic synapse in lumbar sympathetic neurones of guinea-pigs

PubMed Central

Ireland, David R; Davies, Philip J; McLachlan, Elspeth M

1999-01-01

The involvement of different presynaptic Ca2+ channels in transmission at ‘weak’ (subthreshold) and ‘strong’ (suprathreshold) synapses was investigated in guinea-pig paravertebral ganglia isolated in vitro. Selective Ca2+ channel antagonists were used to block excitatory synaptic currents evoked by stimulating single preganglionic axons.The N-type Ca2+ channel blocker, ω-conotoxin GVIA (100 nm), reduced peak synaptic conductance by similar amounts at weak synapses (by 39 ± 6%) and strong synapses (34 ± 6%).The P-type Ca2+ channel blocker, ω-agatoxin IVA (40 nm), significantly reduced transmitter release at weak synapses (by 42 ± 6%) but had only a small effect at strong synapses (reduced by 6 ± 2%).Blockers of Q-, L- or T-type Ca2+ channels had no significant effects on peak synaptic conductance at either type of synapse.We conclude that the two functionally distinct types of preganglionic terminal in sympathetic ganglia which synapse on the same neurone differ in their expression of particular types of voltage-dependent Ca2+ channels. Both types utilize N-type channels and channels resistant to blockade by specific antagonists, but Ca2+ entry through P-type channels makes a substantial contribution to acetylcholine release only at weak synapses. PMID:9831716

A-1048400 is a novel, orally active, state-dependent neuronal calcium channel blocker that produces dose-dependent antinociception without altering hemodynamic function in rats.

PubMed

Scott, Victoria E; Vortherms, Timothy A; Niforatos, Wende; Swensen, Andrew M; Neelands, Torben; Milicic, Ivan; Banfor, Patricia N; King, Andrew; Zhong, Chengmin; Simler, Gricelda; Zhan, Cenchen; Bratcher, Natalie; Boyce-Rustay, Janel M; Zhu, Chang Z; Bhatia, Pramila; Doherty, George; Mack, Helmut; Stewart, Andrew O; Jarvis, Michael F

2012-02-01

Blockade of voltage-gated Ca²⁺ channels on sensory nerves attenuates neurotransmitter release and membrane hyperexcitability associated with chronic pain states. Identification of small molecule Ca²⁺ channel blockers that produce significant antinociception in the absence of deleterious hemodynamic effects has been challenging. In this report, two novel structurally related compounds, A-686085 and A-1048400, were identified that potently block N-type (IC₅₀=0.8 μM and 1.4 μM, respectively) and T-type (IC₅₀=4.6 μM and 1.2 μM, respectively) Ca²⁺ channels in FLIPR based Ca²⁺ flux assays. A-686085 also potently blocked L-type Ca²⁺ channels (EC₅₀=0.6 μM), however, A-1048400 was much less active in blocking this channel (EC₅₀=28 μM). Both compounds dose-dependently reversed tactile allodynia in a model of capsaicin-induced secondary hypersensitivity with similar potencies (EC₅₀=300-365 ng/ml). However, A-686085 produced dose-related decreases in mean arterial pressure at antinociceptive plasma concentrations in the rat, while A-1048400 did not significantly alter hemodynamic function at supra-efficacious plasma concentrations. Electrophysiological studies demonstrated that A-1048400 blocks native N- and T-type Ca²⁺ currents in rat dorsal root ganglion neurons (IC₅₀=3.0 μM and 1.6 μM, respectively) in a voltage-dependent fashion. In other experimental pain models, A-1048400 dose-dependently attenuated nociceptive, neuropathic and inflammatory pain at doses that did not alter psychomotor or hemodynamic function. The identification of A-1048400 provides further evidence that voltage-dependent inhibition of neuronal Ca²⁺ channels coupled with pharmacological selectivity vs. L-type Ca²⁺ channels can provide robust antinociception in the absence of deleterious effects on hemodynamic or psychomotor function. Copyright © 2011 Elsevier Inc. All rights reserved.

Potassium Channels and Uterine Vascular Adaptation to Pregnancy and Chronic Hypoxia

PubMed Central

Zhu, Ronghui; Xiao, DaLiao; Zhang, Lubo

2014-01-01

During a normal course of pregnancy, uterine vascular tone is significantly decreased resulting in a striking increase in uterine blood flow, which is essential for fetal development and fetal growth. Chronic hypoxia during gestation may adversely affect the normal adaptation of uterine vascular tone and increase the risk of preeclampsia and fetal intrauterine growth restriction. In this review, we present evidence that the regulation of K+ channels is an important mechanism in the adaptation of uterine vascular tone to pregnancy and hypoxia. There are four types of K+ channels identified in arterial smooth muscle cells: 1) voltage-dependent K+ (Kv) channels, 2) Ca2+-activated K+ (KCa) channels, 3) inward rectifier K+ (KIR) channels, and 4) ATP-sensitive K+ (KATP) channels. Pregnancy differentially augments the expression and activity of K+ channels via downregulation of protein kinase C signaling in uterine and other vascular beds, leading to decreased uterine vascular tone and increased uterine blood flow. Sex steroid hormones play an important role in the pregnancy-mediated alteration of K+ channels in the uterine vasculature. In addition, chronic hypoxia alters uterine vascular K+ channels expression and activities via modulation of steroid hormones/receptors-mediated signaling, resulting in increased uterine vascular tone during pregnancy. PMID:24063385

Achieving ventricular rate control using metoprolol in β-blocker-naive patients vs patients on chronic β-blocker therapy.

PubMed

Kuang, Patricia; Mah, Nathan D; Barton, Cassie A; Miura, Andrea J; Tanas, Laura R; Ran, Ran

2016-03-01

The objective of the study is to evaluate the difference in ventricular rate control using an intravenous (IV) metoprolol regimen commonly used in clinical practice in patients receiving chronic β-blocker therapy compared to patients considered β-blocker naive admitted to the emergency department (ED) for atrial fibrillation (AF) with rapid ventricular rate. A single-center retrospective cohort study of adult ED patients who were admitted with a rapid ventricular rate of 120 beats per minute (bpm) or greater and treated with IV metoprolol was performed. Rate control was defined as either a decrease in ventricular rate to less than 100 bpm or a 20% decrease in heart rate to less than 120 bpm after metoprolol administration. Patient demographics, differences in length of stay, and adverse events were recorded. A total of 398 patients were included in the study, with 79.4% (n=316) receiving chronic β-blocker therapy. Patients considered to be β-blocker naive were more likely to achieve successful rate control with IV metoprolol compared to patients on chronic β-blocker therapy (56.1% vs 42.4%; P=.03). β-Blocker-naive status was associated with a shorter length of stay in comparison to patients receiving chronic β-blocker therapy (1.79 vs 2.64 days; P<.01). Intravenous metoprolol for the treatment of atrial fibrillation with rapid ventricular rate was associated with a higher treatment response in patients considered β-blocker naive compared to patients receiving chronic β-blocker therapy. Copyright © 2015 Elsevier Inc. All rights reserved.

Digging into Lipid Membrane Permeation for Cardiac Ion Channel Blocker d-Sotalol with All-Atom Simulations

PubMed Central

DeMarco, Kevin R.; Bekker, Slava; Clancy, Colleen E.; Noskov, Sergei Y.; Vorobyov, Igor

2018-01-01

Interactions of drug molecules with lipid membranes play crucial role in their accessibility of cellular targets and can be an important predictor of their therapeutic and safety profiles. Very little is known about spatial localization of various drugs in the lipid bilayers, their active form (ionization state) or translocation rates and therefore potency to bind to different sites in membrane proteins. All-atom molecular simulations may help to map drug partitioning kinetics and thermodynamics, thus providing in-depth assessment of drug lipophilicity. As a proof of principle, we evaluated extensively lipid membrane partitioning of d-sotalol, well-known blocker of a cardiac potassium channel Kv11.1 encoded by the hERG gene, with reported substantial proclivity for arrhythmogenesis. We developed the positively charged (cationic) and neutral d-sotalol models, compatible with the biomolecular CHARMM force field, and subjected them to all-atom molecular dynamics (MD) simulations of drug partitioning through hydrated lipid membranes, aiming to elucidate thermodynamics and kinetics of their translocation and thus putative propensities for hydrophobic and aqueous hERG access. We found that only a neutral form of d-sotalol accumulates in the membrane interior and can move across the bilayer within millisecond time scale, and can be relevant to a lipophilic channel access. The computed water-membrane partitioning coefficient for this form is in good agreement with experiment. There is a large energetic barrier for a cationic form of the drug, dominant in water, to cross the membrane, resulting in slow membrane translocation kinetics. However, this form of the drug can be important for an aqueous access pathway through the intracellular gate of hERG. This route will likely occur after a neutral form of a drug crosses the membrane and subsequently re-protonates. Our study serves to demonstrate a first step toward a framework for multi-scale in silico safety pharmacology, and

Diazoxide triggers cardioprotection against apoptosis induced by oxidative stress.

PubMed

Ichinose, Masashi; Yonemochi, Hidetoshi; Sato, Toshiaki; Saikawa, Tetsunori

2003-06-01

Although mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels have been reported to reduce the extent of apoptosis, the critical timing of mitoK(ATP) channel opening required to protect myocytes against apoptosis remains unclear. In the present study, we examined whether the mitoK(ATP) channel serves as a trigger of cardioprotection against apoptosis induced by oxidative stress. Apoptosis of cultured neonatal rat cardiomyocytes was determined by flow cytometry (light scatter and propidium iodide/annexin V-FITC fluorescence) and by nuclear staining with Hoechst 33342. Mitochondrial membrane potential (DeltaPsi) was measured by flow cytometry of cells stained with rhodamine-123 (Rh-123). Exposure to H(2)O(2) (500 microM) induced apoptosis, and the percentage of apoptotic cells increased progressively and peaked at 2 h. This H(2)O(2)-induced apoptosis was associated with the loss of DeltaPsi, and the time course of decrease in Rh-123 fluorescence paralleled that of apoptosis. Pretreatment of cardiomyocytes with diazoxide (100 microM), a putative mitoK(ATP) channel opener, for 30 min before exposure to H(2)O(2) elicited transient and mild depolarization of DeltaPsi and consequently suppressed both apoptosis and DeltaPsi loss after 2-h exposure to H(2)O(2). These protective effects of diazoxide were abrogated by the mitoK(ATP) channel blocker 5-hydroxydecanoate (500 microM) but not by the sarcolemmal K(ATP) channel blocker HMR-1098 (30 microM). Our results suggest for the first time that diazoxide-induced opening of mitoK(ATP) channels triggers cardioprotection against apoptosis induced by oxidative stress in rat cardiomyocytes.

Modulation of Myocardial Mitochondrial Mechanisms during Severe Polymicrobial Sepsis in the Rat

PubMed Central

Chopra, Mani; Golden, Honey B.; Mullapudi, Srinivas; Dowhan, William; Dostal, David E.; Sharma, Avadhesh C.

2011-01-01

Background We tested the hypothesis that 5-Hydroxydecanoic acid (5HD), a putative mitoKATP channel blocker, will reverse sepsis-induced cardiodynamic and adult rat ventricular myocyte (ARVM) contractile dysfunction, restore mitochondrial membrane permeability alterations and improve survival. Methodology/Principal Findings Male Sprague-Dawley rats (350–400 g) were made septic using 400 mg/kg cecal inoculum, ip. Sham animals received 5% dextrose water, ip. The Voltage Dependent Anion Channels (VDAC1), Bax and cytochrome C levels were determined in isolated single ARVMs obtained from sham and septic rat heart. Mitochondria and cytosolic fractions were isolated from ARVMs treated with norepinephrine (NE, 10 µmoles) in the presence/absence of 5HD (100 µmoles). A continuous infusion of 5HD using an Alzet pump reversed sepsis-induced mortality when administered at the time of induction of sepsis (−40%) and at 6 hr post-sepsis (−20%). Electrocardiography revealed that 5HD reversed sepsis-induced decrease in the average ejection fraction, Simpsons+m Mode (53.5±2.5 in sepsis and 69.2±1.2 at 24 hr in sepsis+5HD vs. 79.9±1.5 basal group) and cardiac output (63.3±1.2 mL/min sepsis and 79.3±3.9 mL/min at 24 hr in sepsis+5HD vs. 85.8±1.5 mL/min basal group). The treatment of ARVMs with 5HD also reversed sepsis-induced depressed contractility in both the vehicle and NE-treated groups. Sepsis produced a significant downregulation of VDAC1, and upregulation of Bax levels, along with mitochondrial membrane potential collapse in ARVMs. Pretreatment of septic ARVMs with 5HD blocked a NE-induced decrease in the VDAC1 and release of cytochrome C. Conclusion The data suggest that Bax activation is an upstream event that may precede the opening of the mitoKATP channels in sepsis. We concluded that mitoKATP channel inhibition via decreased mitochondrial membrane potential and reduced release of cytochrome C provided protection against sepsis-induced ARVM and myocardial

Synergistic Anti-arrhythmic Effects in Human Atria with Combined Use of Sodium Blockers and Acacetin

PubMed Central

Ni, Haibo; Whittaker, Dominic G.; Wang, Wei; Giles, Wayne R.; Narayan, Sanjiv M.; Zhang, Henggui

2017-01-01

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Developing effective and safe anti-AF drugs remains an unmet challenge. Simultaneous block of both atrial-specific ultra-rapid delayed rectifier potassium (K+) current (IKur) and the Na+ current (INa) has been hypothesized to be anti-AF, without inducing significant QT prolongation and ventricular side effects. However, the antiarrhythmic advantage of simultaneously blocking these two channels vs. individual block in the setting of AF-induced electrical remodeling remains to be documented. Furthermore, many IKur blockers such as acacetin and AVE0118, partially inhibit other K+ currents in the atria. Whether this multi-K+-block produces greater anti-AF effects compared with selective IKur-block has not been fully understood. The aim of this study was to use computer models to (i) assess the impact of multi-K+-block as exhibited by many IKur blokers, and (ii) evaluate the antiarrhythmic effect of blocking IKur and INa, either alone or in combination, on atrial and ventricular electrical excitation and recovery in the setting of AF-induced electrical-remodeling. Contemporary mathematical models of human atrial and ventricular cells were modified to incorporate dose-dependent actions of acacetin (a multichannel blocker primarily inhibiting IKur while less potently blocking Ito, IKr, and IKs). Rate- and atrial-selective inhibition of INa was also incorporated into the models. These single myocyte models were then incorporated into multicellular two-dimensional (2D) and three-dimensional (3D) anatomical models of the human atria. As expected, application of IKur blocker produced pronounced action potential duration (APD) prolongation in atrial myocytes. Furthermore, combined multiple K+-channel block that mimicked the effects of acacetin exhibited synergistic APD prolongations. Synergistically anti-AF effects following inhibition of INa and combined IKur/K+-channels were also observed. The attainable maximal

[THE ROLE PLEIOTROPIC EFFECTS OF CALCIUM CHANNEL BLOCKER LERCANIDIPINE IN PERIOPERATIVE THERAPY OF ARTERIAL HYPERTENSION.

PubMed

Melnik, M V; Afonicheva, I I; Beloborodova, A V

2016-09-01

This review presents the data of assessing antihypertensive efficacy and tolerability vasoselective high-lipophilic the 3d generations calcium channel blocker lercanidpine. The inhibition of the calcium ions flow through the membranes of smooth muscle cells of blood vessels causes peripheral, cerebral, renal and coronary vasodilation decreasing total peripheral vascular resistance and, consequently, blood pressure (BP) lowering and improve regional circulation. During reception of lercanidipine the level of norepinephrine remains the same even when using high doses of the drug. Negative inotropic effect does not occur therefore, lercanidipine can be used in the treatment of myocardial ischemia. Renal protection properties slow down the development and progression ofchronic renalfailure (CRF). The drug can be successfully used in patients with arterial hypertension, chronic renalfailure, diabetic and non-diabetic nephropathy. Lercanidpine also may be effectively used in the treatment of hypertension with associated clinical conditions: bronchial asthma, chronic obstructive pulmonary disease, bradiarrythmias, atrioventricular blockade 2-3 degree, sinus node dysfunction, peripheral arteries deseases with symptoms of the extremities ischemia, sleep disturbance, depression, dystonia, asthenic and cephalgic syndme in the frame of the cerebrovascular insufficiency manifestations. Therapy with lercanidpine, in addition to lowering blood pressure, can help to nephroprotection, neuroprotection, antianginal effect, the regression of left ventricular hypertrophy, improvement of lipid metabolism and glucose tolerance. With over 30 years experience in the application and modification of the molecular structure, slow the onset of action and superior long-lasting effect reception of letranidipine well-tolerated and provides a high adherence ofpatients to the treatment of hypertension.

Opiate-induced constipation related to activation of small intestine opioid μ2-receptors

PubMed Central

Chen, Wency; Chung, Hsien-Hui; Cheng, Juei-Tang

2012-01-01

AIM: To investigate the role of opioid μ-receptor subtype in opiate-induced constipation (OIC). METHODS: The effect of loperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension. The ileum strips were precontracted with 1 μmol/L acetylcholine (ACh). Then, decrease in muscle tone (relaxation) was characterized after cumulative administration of 0.1-10 μmol/L loperamide into the organ bath, for a concentration-dependent study. Specific blockers or antagonists were used for pretreatment to compare the changes in loperamide-induced relaxation. RESULTS: In addition to the delay in intestinal transit, loperamide produced a marked relaxation in isolated ileum precontracted with ACh, in a dose-dependent manner. This relaxation was abolished by cyprodime, a selective opioid μ-receptor antagonist, but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors. Also, treatment with opioid μ-1 receptor agonist failed to modify the muscle tone. Moreover, the relaxation by loperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K+ (KATP) channels, and by protein kinase A (PKA) inhibitor, but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate (cAMP). CONCLUSION: Loperamide induces intestinal relaxation by activation of opioid μ-2 receptors via the cAMP-PKA pathway to open KATP channels, relates to OIC. PMID:22493554

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

Nimodipine, an L-type calcium channel blocker attenuates mitochondrial dysfunctions to protect against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonism in mice.

PubMed

Singh, Alpana; Verma, Poonam; Balaji, Gillela; Samantaray, Supriti; Mohanakumar, Kochupurackal P

2016-10-01

Parkinson's disease (PD), the most common progressive neurodegenerative movement disorder, results from loss of dopaminergic neurons of substantia nigra pars compacta. These neurons exhibit Cav1.3 channel-dependent pacemaking activity. Epidemiological studies suggest reduced risk for PD in population under long-term antihypertensive therapy with L-type calcium channel antagonists. These prompted us to investigate nimodipine, an L-type calcium channel blocker for neuroprotective effect in cellular and animal models of PD. Nimodipine (0.1-10 μM) significantly attenuated 1-methyl-4-phenyl pyridinium ion-induced loss in mitochondrial morphology, mitochondrial membrane potential and increases in intracellular calcium levels in SH-SY5Y neuroblastoma cell line as measured respectively employing Mitotracker green staining, TMRM, and Fura-2 fluorescence, but only a feeble neuroprotective effect was observed in MTT assay. Nimodipine dose-dependently reduced 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonian syndromes (akinesia and catalepsy) and loss in swimming ability in Balb/c mice. It attenuated MPTP-induced loss of dopaminergic tyrosine hydroxylase positive neurons in substantia nigra, improved mitochondrial oxygen consumption and inhibited reactive oxygen species production in the striatal mitochondria measured using dichlorodihydrofluorescein fluorescence, but failed to block striatal dopamine depletion. These results point to an involvement of L-type calcium channels in MPTP-induced dopaminergic neuronal death in experimental parkinsonism and more importantly provide evidences for nimodipine to improve mitochondrial integrity and function. Copyright © 2016 Elsevier Ltd. All rights reserved.

Superior diastolic function with KATP channel opener diazoxide in a novel mouse Langendorff model.

PubMed

Makepeace, Carol M; Suarez-Pierre, Alejandro; Kanter, Evelyn M; Schuessler, Richard B; Nichols, Colin G; Lawton, Jennifer S

2018-07-01

Adenosine triphosphate-sensitive potassium (K ATP ) channel openers have been found to be cardioprotective in multiple animal models via an unknown mechanism. Mouse models allow genetic manipulation of K ATP channel components for the investigation of this mechanism. Mouse Langendorff models using 30 min of global ischemia are known to induce measurable myocardial infarction and injury. Prolongation of global ischemia in a mouse Langendorff model could allow the determination of the mechanisms involved in K ATP channel opener cardioprotection. Mouse hearts (C57BL/6) underwent baseline perfusion with Krebs-Henseleit buffer (30 min), assessment of function using a left ventricular balloon, delivery of test solution, and prolonged global ischemia (90 min). Hearts underwent reperfusion (30 min) and functional assessment. Coronary flow was measured using an inline probe. Test solutions included were as follows: hyperkalemic cardioplegia alone (CPG, n = 11) or with diazoxide (CPG + DZX, n = 12). Although the CPG + DZX group had greater percent recovery of developed pressure and coronary flow, this was not statistically significant. Following a mean of 74 min (CPG) and 77 min (CPG + DZX), an additional increase in end-diastolic pressure was noted (plateau), which was significantly higher in the CPG group. Similarly, the end-diastolic pressure (at reperfusion and at the end of experiment) was significantly higher in the CPG group. Prolongation of global ischemia demonstrated added benefit when DZX was added to traditional hyperkalemic CPG. This model will allow the investigation of DZX mechanism of cardioprotection following manipulation of targeted K ATP channel components. This model will also allow translation to prolonged ischemic episodes associated with cardiac surgery. Copyright © 2018 Elsevier Inc. All rights reserved.

Coupling of activation and inactivation gate in a K+-channel: potassium and ligand sensitivity

PubMed Central

Ader, Christian; Schneider, Robert; Hornig, Sönke; Velisetty, Phanindra; Vardanyan, Vitya; Giller, Karin; Ohmert, Iris; Becker, Stefan; Pongs, Olaf; Baldus, Marc

2009-01-01

Potassium (K+)-channel gating is choreographed by a complex interplay between external stimuli, K+ concentration and lipidic environment. We combined solid-state NMR and electrophysiological experiments on a chimeric KcsA–Kv1.3 channel to delineate K+, pH and blocker effects on channel structure and function in a membrane setting. Our data show that pH-induced activation is correlated with protonation of glutamate residues at or near the activation gate. Moreover, K+ and channel blockers distinctly affect the open probability of both the inactivation gate comprising the selectivity filter of the channel and the activation gate. The results indicate that the two gates are coupled and that effects of the permeant K+ ion on the inactivation gate modulate activation-gate opening. Our data suggest a mechanism for controlling coordinated and sequential opening and closing of activation and inactivation gates in the K+-channel pore. PMID:19661921

Adverse CNS-effects of beta-adrenoceptor blockers.

PubMed

Gleiter, C H; Deckert, J

1996-11-01

In 1962 propranolol, the first beta adrenoceptor antagonist (beta blocker), was brought on to the market. There is now a host of different beta blockers available, and these compounds are among the most commonly prescribed groups of drugs. The efficacy of beta blockers has been proven predominantly for the treatment of cardiovascular diseases. Beta blockers are also used for certain types of CNS disorders, such as anxiety disorders, essential tremor and migraine. While low toxicity means that they have a favorable risk-benefit ratio, given the high intensity of use, it is essential to have a comprehensive knowledge of adverse events. Adverse events of beta blockers that can be related to the CNS are quite often neglected, even in textbooks of clinical pharmacology or review articles, and thus often misdiagnosed. The following article, therefore, after summarizing the use of beta blockers for CNS indications, critically reviews the literature on centrally mediated adverse events. General pharmacological features of beta blockers and their molecular basis of action will briefly be addressed to the extent that they are or may become relevant for central nervous pharmacotherapy and side-effects.

R-Type Ca2+ channels couple to inhibitory neurotransmission to the longitudinal muscle in the guinea-pig ileum.

PubMed

Rodriguez-Tapia, Eileen S; Naidoo, Vinogran; DeVries, Matthew; Perez-Medina, Alberto; Galligan, James J

2017-03-01

What is the central question of this study? Subtypes of enteric neurons are coded by the neurotransmitters they synthesize, but it is not known whether enteric neuron subtypes might also be coded by other proteins, including calcium channel subtypes controlling neurotransmitter release. What is the main finding and its importance? Our data indicate that guinea-pig ileum myenteric neuron subtypes may be coded by calcium channel subtypes. We found that R-type calcium channels are expressed by inhibitory but not excitatory longitudinal muscle motoneurons. R-Type calcium channels are also not expressed by circular muscle inhibitory motoneurons. Calcium channel subtype-selective antagonists could be used to target subtypes of neurons to treat gastrointestinal motility disorders. There is evidence that R-type Ca 2+ channels contribute to synaptic transmission in the myenteric plexus. It is unknown whether R-type Ca 2+ channels contribute to neuromuscular transmission. We measured the effects of the nitric oxide synthase inhibitor nitro-l-arginine (NLA), Ca 2+ channel blockers and apamin (SK channel blocker) on neurogenic relaxations and contractions of the guinea-pig ileum longitudinal muscle-myenteric plexus (LMMP) in vitro. We used intracellular recordings to measure inhibitory junction potentials. Immunohistochemical techniques localized R-type Ca 2+ channel protein in the LMMP and circular muscle. Cadmium chloride (pan-Ca 2+ channel blocker) blocked and NLA and NiCl 2 (R-type Ca 2+ channel blocker) reduced neurogenic relaxations in a non-additive manner. Nickel chloride did not alter neurogenic cholinergic contractions, but it potentiated neurogenic non-cholinergic contractions. Relaxations were inhibited by apamin, NiCl 2 and NLA and were blocked by combined application of these drugs. Relaxations were reduced by NiCl 2 or ω-conotoxin (N-type Ca 2+ channel blocker) and were blocked by combined application of these drugs. Longitudinal muscle inhibitory junction

Mrz 2/579, a fast kinetic NMDA channel blocker, reduces the development of morphine tolerance in awake rats.

PubMed

Houghton, A K; Parsons, C G; Headley, P M

2001-04-01

The purpose of the present study was to investigate whether uncompetitive NMDA antagonists with fast channel blocking kinetics, which show fewer side effects in man than compounds such as ketamine, affect the development of tolerance to continuous exposure to morphine. Rats were trained on the Randall--Selitto apparatus before being implanted, under halothane anaesthesia, with primed mini-osmotic pumps (240 microl/day). Six rats were implanted with a vehicle filled pump, seven with a morphine filled pump (28.8 mg/kg/day), and eight with a pair of pumps, one containing morphine and the other Mrz 2/579, a new NMDA antagonist (40 mg/kg/day). A fourth group was implanted with a morphine filled pump followed 25 h later by a Mrz 2/579 filled pump. Paw withdrawal tests were undertaken immediately before, and at 2, 4, 6, 8, 10, 12, 24, 48 and 72 h after the first pump was implanted. Before pump implantation, withdrawal thresholds were 120+/-7 g (mean+/-SEM, n=30). Vehicle infusion had no effect on withdrawal thresholds, whereas morphine infusion increased them significantly at 2 and 4 h after pump implantation (+2 h: 208+/-14 g; P<0.001 vs. control). From 6 h the antinociception elicited by morphine declined progressively; at 10 h withdrawal thresholds were significantly lower than the 2 h post-treatment value (P<0.001). In rats treated with morphine plus Mrz 2/579, thresholds remained significantly higher between 10--72 h post-implantation than with morphine alone (P<0.05). In contrast, infusion of the same level of Mrz 2/579 once tolerance had developed did not reverse tolerance. These results indicate that fast NMDA channel blockers such as Mrz 2/579 may prove to be useful in enhancing analgesia to continuous morphine administration.

Interaction of a potential chloride channel blocker with a model transport protein: a spectroscopic and molecular docking investigation.

PubMed

Ganguly, Aniruddha; Paul, Bijan Kumar; Ghosh, Soumen; Dalapati, Sasanka; Guchhait, Nikhil

2014-05-14

The present work demonstrates a detailed characterization of the interaction of a potential chloride channel blocker, 9-methyl anthroate (9-MA), with a model transport protein, Bovine Serum Albumin (BSA). The modulated photophysical properties of the emissive drug molecule within the microheterogeneous bio-environment of the protein have been exploited spectroscopically to monitor the probe-protein binding interaction. Apart from evaluating the binding constant, the probable location of the neutral molecule within the protein cavity (subdomain IB) is explored by an AutoDock-based blind docking simulation. The absence of the Red-Edge Effect has been corroborated by the enhanced lifetime of the probe, being substantially greater than the solvent reorientation time. A dip-and-rise characteristic of the rotational relaxation profile of the drug within the protein has been argued to originate from a significant difference in the lifetime as well as amplitude of the free and protein-bound drug molecule. Unfolding of the protein in the presence of the drug molecule has been probed by the decrease of the α-helical content, obtained via circular dichroism (CD) spectroscopy, which is also supported by the gradual loss of the esterase activity of the protein in the presence of the drug molecule.

Emodin suppresses the nasopharyngeal carcinoma cells by targeting the chloride channels.

PubMed

Ma, Lianshun; Yang, Yaping; Yin, Zizhang; Liu, Mei; Wang, Liwei; Chen, Lixin; Zhu, Linyan; Yang, Haifeng

2017-06-01

Emodin is a natural anthraquinone derivative isolated from the Rheum palmatum. Recent studies demonstrated that emodin has anti-cancer activity in different kinds of human cancer cell lines. However, the underlying mechanism has not been very well studied. Our previous studies showed chloride channels is an important target of anti-cancer drugs. Therefore, the purpose of this research was aimed to explore the role of chloride channels involving in the anti-cancer activity of emodin. The proliferation, cell cycle arrest and apoptosis of poorly differentiated human nasopharyngeal carcinoma cells (CNE-2Z) and normal nasopharyngeal epithelial cells (NP69-SV40T) were detected by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide(MTT)and flow cytometry. The results indicated that emodin inhibited the CNE-2Z cell growth more significantly than NP69-SV40T cells and induced cell cycle arrest and apoptosis in CNE-2Z cells but not in NP69-SV40T cells. Chloride channel blocker 5-nitro-2-(3-phenylprop ylamino)-benzoate (NPPB) or tamoxifen both can prevent the apoptosis of CNE-2Z cells induced by emodin. Optical microscope and atomic force microscope (AFM) demonstrated that emodin can induce apoptotic volume decrease (AVD) and ultrastructure changes in CNE-2Z cell and inhibited by chloride channel blocker. These data could be a further evidence of chloride channel for preventing CNE-2Z cells from apoptosis induced by emodin. Whole cell patch clamp study also demonstrated that emodin can activate chloride channel in CNE-2Z cells but not in NP69-SV40T cells. Furthermore, the activated chloride currents can also be inhibited by chloride channel blockers indicating that chloride channel may be the potential target molecular of emodin exerting its anti-tumor efficiency in CNE-2Z cells. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Ultra-long acting calcium channel blockers may decrease accuracy of the acetylcholine provocation test.

PubMed

Kurabayashi, Manabu; Asano, Mitsutoshi; Shimura, Tsukasa; Suzuki, Hidetoshi; Aoyagi, Hideshi; Yamauchi, Yasuteru; Okishige, Kaoru; Ashikaga, Takashi; Isobe, Mitsuaki

2017-06-01

When drug-induced coronary spasm provocation tests are performed, a washout period of >48h for calcium channel blockers (CCBs) is uniformly recommended. However, each CCB has a distinct half-life, and little is known about the influence of prior oral administration of CCBs on acetylcholine provocation test to evaluate coronary vasomotor reaction. We examined 245 consecutive patients with suspected vasospastic angina who had undergone acetylcholine provocation test. Of those patients, 29 patients had been on amlodipine, an ultra-long term acting CCB (group A), 34 on other CCBs (group O), and 182 patients on no CCB (group N). After CCBs had been withheld > 48h, we performed acetylcholine provocation, which resulted in 152 positive, 36 intermediate, and 57 negative reactions. We evaluated coronary artery tone calculated as follows: (luminal diameter after nitrate-baseline luminal diameter)÷(luminal diameter after nitrate)×100 (%). In group A patients, coronary artery tone was lower (A:9.1±6.9% vs. O:11.7±8.3% vs. N:12.1±8.5%, p=0.0011) and the positive rate of acetylcholine provocation test was lower than group O and group N (A:41% vs. O:68% vs. N:64%, p=0.047). Multivariate logistic analysis showed that taking amlodipine until 2days before acetylcholine provocation test was a significant inverse predictor for acetylcholine-provoked coronary spasm (odds ratio 0.327; 95% confidence interval 0.125-0.858, p=0.023). Residual vasodilatory effects of ultra-long acting CCB may decrease coronary artery tone and the vasoconstrictive reaction to acetylcholine suggesting that a 2-day pre-test drug holiday may not be long enough. Copyright © 2017 Elsevier B.V. All rights reserved.

Calcium channel modulation as a target in chronic pain control.

PubMed

Patel, Ryan; Montagut-Bordas, Carlota; Dickenson, Anthony H

2018-06-01

Neuropathic pain remains poorly treated for large numbers of patients, and little progress has been made in developing novel classes of analgesics. To redress this issue, ziconotide (Prialt™) was developed and approved as a first-in-class synthetic version of ω-conotoxin MVIIA, a peptide blocker of Ca v 2.2 channels. Unfortunately, the impracticalities of intrathecal delivery, low therapeutic index and severe neurological side effects associated with ziconotide have restricted its use to exceptional circumstances. Ziconotide exhibits no state or use-dependent block of Ca v 2.2 channels; activation state-dependent blockers were hypothesized to circumvent the side effects of state-independent blockers by selectively targeting high-frequency firing of nociceptive neurones in chronic pain states, thus alleviating aberrant pain but not affecting normal sensory transduction. Unfortunately, numerous drugs, including state-dependent calcium channel blockers, have displayed efficacy in preclinical models but have subsequently been disappointing in clinical trials. In recent years, it has become more widely acknowledged that trans-aetiological sensory profiles exist amongst chronic pain patients and may indicate similar underlying mechanisms and drug sensitivities. Heterogeneity amongst patients, a reliance on stimulus-evoked endpoints in preclinical studies and a failure to utilize translatable endpoints, all are likely to have contributed to negative clinical trial results. We provide an overview of how electrophysiological and operant-based assays provide insight into sensory and affective aspects of pain in animal models and how these may relate to chronic pain patients in order to improve the bench-to-bedside translation of calcium channel modulators. This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175

Variable effects of the mitoK(ATP) channel modulators diazoxide and 5-HD in ATP-depleted renal epithelial cells.

PubMed

Nilakantan, Vani; Liang, Huanling; Mortensen, Jordan; Taylor, Erin; Johnson, Christopher P

2010-02-01

The role of mitochondrial K(ATP) (mitoK(ATP)) channels in renal ischemia-reperfusion injury is controversial with studies showing both protective and deleterious effects. In this study, we compared the effects of the putative mitoK(ATP) opener, diazoxide, and the mitoK(ATP) blocker, 5-hydroxydecanoate (5-HD) on cytotoxicity and apoptosis in tubular epithelial cells derived from rat (NRK-52E) and pig (LLC-PK1) following in vitro ischemic injury. Following ATP depletion-recovery, there was a significant increase in cytotoxicity in both NRK cells and LLC-PK1 cells although NRK cells were more sensitive to the injury. Diazoxide treatment attenuated cytotoxicity in both cell types and 5-HD treatment-increased cytotoxicity in the sensitive NRK cells in a superoxide-dependant manner. The protective effect of diazoxide was also reversed in the presence of 5-HD in ATP-depleted NRK cells. The ATP depletion-mediated increase in superoxide was enhanced by both diazoxide and 5-HD with the effect being more pronounced in the cells undergoing 5-HD treatment. Further, ATP depletion-induced activation of caspase-3 was decreased by diazoxide in NRK cells. In order to determine the signaling pathways involved in apoptosis, we examined the activation of Erk and JNK in ATP-depleted NRK cells. Diazoxide-activated Erk in ATP-depleted cells, but did not have any effect on JNK activation. In contrast, 5-HD did not impact Erk levels but increased JNK activation even under controlled conditions. Further, the use of a JNK inhibitor with 5-HD reversed the deleterious effects of 5-HD. This study demonstrates that in cells that are sensitive to ATP depletion-recovery, mitoK(ATP) channels protect against ATP depletion-mediated cytotoxicity and apoptosis through Erk- and JNK-dependant mechanisms.

Regulation of Ion Channels by Pyridine Nucleotides

PubMed Central

Kilfoil, Peter J.; Tipparaju, Srinivas M.; Barski, Oleg A.; Bhatnagar, Aruni

2014-01-01

Recent research suggests that in addition to their role as soluble electron carriers, pyridine nucleotides [NAD(P)(H)] also regulate ion transport mechanisms. This mode of regulation seems to have been conserved through evolution. Several bacterial ion–transporting proteins or their auxiliary subunits possess nucleotide-binding domains. In eukaryotes, the Kv1 and Kv4 channels interact with pyridine nucleotide–binding β-subunits that belong to the aldo-keto reductase superfamily. Binding of NADP+ to Kvβ removes N-type inactivation of Kv currents, whereas NADPH stabilizes channel inactivation. Pyridine nucleotides also regulate Slo channels by interacting with their cytosolic regulator of potassium conductance domains that show high sequence homology to the bacterial TrkA family of K+ transporters. These nucleotides also have been shown to modify the activity of the plasma membrane KATP channels, the cystic fibrosis transmembrane conductance regulator, the transient receptor potential M2 channel, and the intracellular ryanodine receptor calcium release channels. In addition, pyridine nucleotides also modulate the voltage-gated sodium channel by supporting the activity of its ancillary subunit—the glycerol-3-phosphate dehydrogenase-like protein. Moreover, the NADP+ metabolite, NAADP+, regulates intracellular calcium homeostasis via the 2-pore channel, ryanodine receptor, or transient receptor potential M2 channels. Regulation of ion channels by pyridine nucleotides may be required for integrating cell ion transport to energetics and for sensing oxygen levels or metabolite availability. This mechanism also may be an important component of hypoxic pulmonary vasoconstriction, memory, and circadian rhythms, and disruption of this regulatory axis may be linked to dysregulation of calcium homeostasis and cardiac arrhythmias. PMID:23410881

[Effects of beta blockers on lipoprotein metabolism].

PubMed

Ritter, M M; Richter, W O; Schwandt, P

1992-10-10

With respect to prevention of its most common complication--mortality from coronary heart disease--treatment of hypertension had disappointed. It is possible that this is due to negative effects of antihypertensives on lipid metabolism. The effects of beta blockers on lipid metabolism can be differentiated principally, in accordance with the classification of beta blockers into those with and those without intrinsic sympathomimetic activity (ISA), as also selectivity and non-selectivity. Thus, non-selective beta blockers with no ISA usually lead to an increase in triglycerides of 25% to 30%, and a decrease in HDL cholesterol of about 15%. On average, beta-1 selective blockers result in a smaller increase in triglycerides. Beta blockers with ISA, in contrast, are largely neutral vis-à-vis lipid metabolism. In the individual case, in particular in the presence of hyperlipoproteinemia, the effects cannot be reliably predicted. Lipoprotein concentrations should be monitored during treatment with beta blockers. If necessary, a change in the agent employed is recommended. In the case of prevention of a second myocardial infarction, for which various studies have unequivocally shown a reduction in mortality associated with treatment with beta blockers with no ISA, these side effects will, however, be accepted--with the exception of extreme changes--for a limited period of time.

Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

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

Kozuka, M.; Ito, T.; Hirose, S.

1989-02-28

Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using /sup 125/I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction thatmore » was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent.« less

The Role of NH2-terminal Positive Charges in the Activity of Inward Rectifier KATP Channels

PubMed Central

Cukras, C.A.; Jeliazkova, I.; Nichols, C.G.

2002-01-01

Approximately half of the NH2 terminus of inward rectifier (Kir) channels can be deleted without significant change in channel function, but activity is lost when more than ∼30 conserved residues before the first membrane spanning domain (M1) are removed. Systematic replacement of the positive charges in the NH2 terminus of Kir6.2 with alanine reveals several residues that affect channel function when neutralized. Certain mutations (R4A, R5A, R16A, R27A, R39A, K47A, R50A, R54A, K67A) change open probability, whereas an overlapping set of mutants (R16A, R27A, K39A, K47A, R50A, R54A, K67A) change ATP sensitivity. Further analysis of the latter set differentiates mutations that alter ATP sensitivity as a consequence of altered open state stability (R16A, K39A, K67A) from those that may affect ATP binding directly (K47A, R50A, R54A). The data help to define the structural determinants of Kir channel function, and suggest possible structural motifs within the NH2 terminus, as well as the relationship of the NH2 terminus with the extended cytoplasmic COOH terminus of the channel. PMID:12198096

The role of NH2-terminal positive charges in the activity of inward rectifier KATP channels.

PubMed

Cukras, C A; Jeliazkova, I; Nichols, C G

2002-09-01

Approximately half of the NH(2) terminus of inward rectifier (Kir) channels can be deleted without significant change in channel function, but activity is lost when more than approximately 30 conserved residues before the first membrane spanning domain (M1) are removed. Systematic replacement of the positive charges in the NH(2) terminus of Kir6.2 with alanine reveals several residues that affect channel function when neutralized. Certain mutations (R4A, R5A, R16A, R27A, R39A, K47A, R50A, R54A, K67A) change open probability, whereas an overlapping set of mutants (R16A, R27A, K39A, K47A, R50A, R54A, K67A) change ATP sensitivity. Further analysis of the latter set differentiates mutations that alter ATP sensitivity as a consequence of altered open state stability (R16A, K39A, K67A) from those that may affect ATP binding directly (K47A, R50A, R54A). The data help to define the structural determinants of Kir channel function, and suggest possible structural motifs within the NH(2) terminus, as well as the relationship of the NH(2) terminus with the extended cytoplasmic COOH terminus of the channel.

Delayed rectifier potassium channels are involved in SO2 derivative-induced hippocampal neuronal injury.

PubMed

Li, Guangke; Sang, Nan

2009-01-01

Recent studies implicate the possible neurotoxicity of SO(2), however, its mechanisms remain unclear. In the present study, we investigated SO(2) derivative-induced effect on delayed rectifier potassium channels (I(K)) and cellular death/apoptosis in primary cultured hippocampal neurons. The results demonstrate that SO(2) derivatives (NaHSO(3) and Na(2)SO(3), 3:1M/M) effectively augmented I(K) and promoted the activation of delayed rectifier potassium channels. Also, SO(2) derivatives increased neuronal death percentage and contributed to the formation of DNA ladder in concentration-dependent manners. Interestingly, the neuronal death and DNA ladder formation, caused by SO(2) derivatives, could be attenuated by the delayed rectifier potassium channel blocker (tetraethylammonium, TEA), but not by the transient outward potassium channel blocker (4-aminopyridine, 4-AP). It implies that stimulating delayed rectifier potassium channels were involved in SO(2) derivative-caused hippocampal neuronal insults, and blocking these channels might be one of the possibly clinical treatment for SO(2)-caused neuronal dysfunction.

β-Blocker Continuation After Noncardiac Surgery

PubMed Central

Kwon, Steve; Thompson, Rachel; Florence, Michael; Maier, Ronald; McIntyre, Lisa; Rogers, Terry; Farrohki, Ellen; Whiteford, Mark; Flum, David R.

2014-01-01

Background Despite limited evidence of effect, β-blocker continuation has become a national quality improvement metric. Objective To determine the effect of β-blocker continuation on outcomes in patients undergoing elective noncardiac surgery. Design, Setting, and Patients The Surgical Care and Outcomes Assessment Program is a Washington quality improvement benchmarking initiative based on clinical data from more than 55 hospitals. Linking Surgical Care and Outcomes Assessment Program data to Washington’s hospital admission and vital status registries, we studied patients undergoing elective colorectal and bariatric surgical procedures at 38 hospitals between January 1, 2008, and December 31, 2009. Main Outcome Measures Mortality, cardiac events, and the combined adverse event of cardiac events and/or mortality. Results Of 8431 patients, 23.5% were taking β-blockers prior to surgery (mean [SD] age, 61.9 [13.7] years; 63.1% were women). Treatment with β-blockers was continued on the day of surgery and during the postoperative period in 66.0% of patients. Continuation of β-blockers both on the day of surgery and postoperatively improved from 57.2% in the first quarter of 2008 to 71.3% in the fourth quarter of 2009 (P value <.001). After adjusting for risk characteristics, failure to continue β-blocker treatment was associated with a nearly 2-fold risk of 90-day combined adverse event (odds ratio, 1.97; 95% CI, 1.19-3.26). The odds were even greater among patients with higher cardiac risk (odds ratio, 5.91; 95% CI, 1.40-25.00). The odds of combined adverse events continued to be elevated 1 year postoperatively (odds ratio, 1.66; 95% CI, 1.08-2.55). Conclusions β-Blocker continuation on the day of and after surgery was associated with fewer cardiac events and lower 90-day mortality. A focus on β-blocker continuation is a worthwhile quality improvement target and should improve patient outcomes. PMID:22249847

Molecular Basis of Ion Channels and Receptors Involved in Nerve Excitation, Synaptic Transmission and Muscle Contraction

DTIC Science & Technology

1993-12-20

shows the effect of minoxidil sulphate on CFTR Cl currents; similar results were obtained with BRL 38227 and diazoxide. As was observed for the...dependent; halt-maximal inhibition occurred at about 40 l±M minoxidil sulphate, 50 pM BRI. 38227, and 250 p.M diazoxide. This effect was weaker than...their stimulation of K-ATP channels in vascular smooth muscle."’ 280 ANNALS NEW YORK ACADEMY OF SCIENCES +50 mV -90 mV A ~Bi cAMP cAMP + minoxidil

Chloride channels are necessary for full platelet phosphatidylserine exposure and procoagulant activity.

PubMed

Harper, M T; Poole, A W

2013-12-19

Platelets enhance thrombin generation at sites of vascular injury by exposing phosphatidylserine during necrosis-like cell death. Anoctamin 6 (Ano6) is required for Ca(2+)-dependent phosphatidylserine exposure and is defective in patients with Scott syndrome, a rare bleeding disorder. Ano6 may also form Cl(-) channels, though the role of Cl(-) fluxes in platelet procoagulant activity has not been explored. We found that Cl(-) channel blockers or removal of extracellular Cl(-) inhibited agonist-induced phosphatidylserine exposure. However, this was not due to direct inhibition of Ca(2+)-dependent scrambling since Ca(2+) ionophore-induced phosphatidylserine exposure was normal. This implies that the role of Ano6 in Ca(2+-)dependent PS exposure is likely to differ from any putative function of Ano6 as a Cl(-) channel. Instead, Cl(-) channel blockade inhibited agonist-induced Ca(2+) entry. Importantly, Cl(-) channel blockers also prevented agonist-induced membrane hyperpolarization, resulting in depolarization. We propose that Cl(-) entry through Cl(-) channels is required for this hyperpolarization, maintaining the driving force for Ca(2+) entry and triggering full phosphatidylserine exposure. This demonstrates a novel role for Cl(-) channels in controlling platelet death and procoagulant activity.

Antenatal calcium channel blocker exposure and subsequent patent ductus arteriosus in extremely low-birth-weight infants.

PubMed

McGuirl, Jennifer; Arzuaga, Bonnie; Lee, Ben H

2012-01-01

This study aimed to assess whether tocolytic fetal exposure to antenatal calcium channel blockers (aCCB) increases the risk for hemodynamically significant patent ductus arteriosus (hsPDA) in extremely low-birth-weight (ELBW) infants. This case-control study investigated ELBW infants (<1,000 g) without cardiac defects in a level 3 neonatal intensive care unit who had survived at least 7 days. Nifedipine was the only aCCB used for this study population. The measurements included the history of aCCB exposure, selected maternal data, hsPDA diagnosis, gestational age at birth, birth weight, mode of delivery, sex, maternal race, location of birth, Apgar scores, and selected neonatal morbidities. The end point of the study was hsPDA, defined as an echocardiographically confirmed PDA with clinical symptoms. A total of 180 infants met the study criteria. The diagnosis was hsPDA for 56% of these patients, 20% of whom had aCCB exposure. Of the infants without hsPDA, 11% had aCCB exposure (p = 0.09). No statistically significant associations were found between aCCB exposure and hsPDA after adjustment for gestational age (odds ratio [OR], 1.5; 95% confidence interval [CI], 0.6-3.7) or for gestational age and cumulative aCCB exposure of 100 mg or more (OR, 2.0; 95% CI, 0.6-6.5). A history of aCCB exposure does not appear to increase hsPDA risk in ELBW infants. Studies using neonatal serum nifedipine concentrations after antenatal exposure should be performed to confirm this conclusion.

Beta-blocker use in decompensated heart failure.

PubMed

Alharethi, Rami; Hershberger, Ray E

2006-06-01

Despite the current advances in treatment, acute decompensated heart failure accounts for more than 1 million hospital admissions annually. Many of the patients hospitalized are already receiving long-term treatment with beta-blockers. For patients who receive full dose beta-blocker therapy and suffer acute decompensated heart failure, clinicians face two key questions: what to do, if anything, with the dosage of beta-blocker and what is the best way to integrate inotropic and beta-blocker therapies for patients who require inotropes. This article discusses these issues and reviews the available literature. Because these topics have received little systematic evaluation, we also present our clinical approaches to these problems.

Beta-blockers use for hypertension in the elderly.

PubMed

Herrera, Julio

2015-01-01

Beta-blockers are considered as suitable drugs to treat essential hypertension also in elderly patients and they are currently recommended for treatment of hypertension, even in older patients, by the ESH/ESC Guidelines. Different meta-analyses and results of some large clinical trials have shown that here is no clinically difference between β-blockers and other drug classes in decreasing high blood pressure in elderly hypertensive patients. The new vasodilating β-blockers, as nebivolol, carvedilol and celiprolol, offer additional important advantages, compared with traditional β-blockers. The cardio-protective effect of β-blockers (except atenolol) is not inferior to that obtained with other drug classes which is independent of age and gender of the patients.

Evaluation of a 125I-labelled benzazepinone derived voltage-gated sodium channel blocker for imaging with SPECT.

PubMed

Pérez-Medina, Carlos; Patel, Niral; Robson, Mathew; Badar, Adam; Lythgoe, Mark F; Årstad, Erik

2012-12-21

Voltage-gated sodium channels (VGSCs) are a family of transmembrane proteins that mediate fast neurotransmission, and are integral to sustain physiological conditions and higher cognitive functions. Imaging of VGSCs in vivo holds promise as a tool to elucidate operational functions in the brain and to aid the treatment of a wide range of neurological diseases. To assess the suitability of 1-benzazepin-2-one derived VGSC blockers for imaging, we have prepared a (125)I-labelled analogue of BNZA and evaluated the tracer in vivo. In an automated patch-clamp assay, a diastereomeric mixture of the non-radioactive compound blocked the Na(v)1.2 and Na(v)1.7 VGSC isoforms with IC(50) values of 4.1 ± 1.5 μM and 0.25 ± 0.07 μM, respectively. [(3)H]BTX displacement studies revealed a three-fold difference in affinity between the two diastereomers. Iodo-destannylation of a tin precursor with iodine-125 afforded the two diastereomerically pure tracers, which were used to assess binding to VGSCs in vivo by comparing their tissue distributions in mice. Whilst the results point to a lack of VGSC binding in vivo, SPECT imaging revealed highly localized uptake in the interscapular region, an area typically associated with brown adipose tissue, which in addition to high metabolic stability of the iodinated tracer, demonstrate the potential of 1-benzazepin-2-ones for in vivo imaging.

Preliminary Studies of Acute Cadmium Administration Effects on the Calcium-Activated Potassium (SKCa and BKCa) Channels and Na+/K+-ATPase Activity in Isolated Aortic Rings of Rats.

PubMed

Vassallo, Dalton V; Almenara, Camila C P; Broseghini-Filho, Gilson Brás; Teixeira, Ariane Calazans; da Silva, David Chaves F; Angeli, Jhuli K; Padilha, Alessandra S

2018-06-01

Cadmium is an environmental pollutant closely linked with cardiovascular diseases that seems to involve endothelium dysfunction and reduced nitric oxide (NO) bioavailability. Knowing that NO causes dilatation through the activation of potassium channels and Na + /K + -ATPase, we aimed to determine whether acute cadmium administration (10 μM) alters the participation of K + channels, voltage-activated calcium channel, and Na + /K + -ATPase activity in vascular function of isolated aortic rings of rats. Cadmium did not modify the acetylcholine-induced relaxation. After L-NAME addition, the relaxation induced by acetylcholine was abolished in presence or absence of cadmium, suggesting that acutely, this metal did not change NO release. However, tetraethylammonium (a nonselective K + channels blocker) reduced acetylcholine-induced relaxation but this effect was lower in the preparations with cadmium, suggesting a decrease of K + channels function in acetylcholine response after cadmium incubation. Apamin (a selective blocker of small Ca 2+ -activated K + channels-SK Ca ), iberiotoxin (a selective blocker of large-conductance Ca 2+ -activated K + channels-BK Ca ), and verapamil (a blocker of calcium channel) reduced the endothelium-dependent relaxation only in the absence of cadmium. Finally, cadmium decreases Na + /K + -ATPase activity. Our results provide evidence that the cadmium acute incubation unaffected the calcium-activated potassium channels (SK Ca and BK Ca ) and voltage-calcium channels on the acetylcholine vasodilatation. In addition, acute cadmium incubation seems to reduce the Na + /K + -ATPase activity.

Does tight heart rate control improve beta-blocker efficacy? An updated analysis of the noncardiac surgical randomized trials.

PubMed

Beattie, W Scott; Wijeysundera, Duminda N; Karkouti, Keyvan; McCluskey, Stuart; Tait, Gordon

2008-04-01

heterogeneity in HR response to beta-blockade was found to be related, in part, to the type of beta-blocker, specifically, metoprolol, and the concomitant use of calcium channel blockers. Calcium channel blocker use and beta-blockers other than metoprolol resulted in more effective control of HR. There was wide variability in the HR response to beta-blockade. Twenty-five percent of patients receiving beta-blockers had episodes when the HRs were more than 100 bpm, although 15% of placebo patients also had bradycardia, which would have required a dose reduction had they been administered beta-blockers. Finally, this analysis found that perioperative beta-blockade was associated with an increased incidence of bradycardia (OR = 3.49; 95% CI = 2.4-5.9) and congestive heart failure (OR = 1.68; 95% CI = 1.00-2.8). The trials that achieve the most effective control of HR are associated with a reduced incidence of postoperative MI, suggesting that effective control of HR is important for achieving cardioprotection. Second, this analysis demonstrates that administration of beta-blockers does not reliably decrease HRs in all patients, and may be associated with increased side effects. Judicious use of combination therapy with other drugs may be necessary to achieve effective postoperative control of HR.

[Therapy of heart failure with beta-blockers?].

PubMed

Osterziel, K J; Dietz, R

1997-01-01

In heart failure the chronic sympathetic stimulation alters the cardiac beta-adrenergic pathway. This alteration leads to a diminished contractile response to stimulation of the cardiac beta 1 receptor. A blockade of the beta 1 receptor partly restores the physiologic response to sympathetic stimulation at rest and during exercise. Several mechanisms resulting from the competitive blockade of the beta 1 receptor may be important. The major effect of beta-blockers seems to be triggered by a reduction of the heart rate at rest resulting in an increase of the left ventricular ejection fraction on the average by 7-8%. Patients with heart failure who are treated with a beta-blocker experience initially a slight decrease of the left ventricular function. beta-blocker therapy should therefore be initiated only in patients with stable heart failure. The starting dose of the beta-blocker has to be very small, e.g, 5 mg Metoprolol, 1.25 mg Bisoprolol or 3.125 mg Carvedilol. In a stepwise fashion the dose has to be increased to a full beta blocking effect over a period of 4-8 weeks. Despite a careful dose titration only 90% of the patients tolerate this regimen. Patients with high resting heart rates and/or dilated cardiomyopathy will have the greatest benefit. The two main reasons for withdrawal of the beta-blocker are deterioration of heart failure or symptomatic hypotension. Symptomatic improvement and a significant increase of exercise capacity appear gradually and can be measured only after more than 1 month duration of therapy. Three multicenter studies (MDC. CIBIS I, Carvedilol) evaluated the influence of beta-blockers on prognosis of heart failure. The MDC trial demonstrated a slower progression of heart failure with Metoprolol. The MDC and the CIBIS I trial could not show a significant improvement of prognosis. The larger trial with carvedilol was the first study to demonstrate a decreased mortality in patients who initially tolerate the beta-blocker therapy. One

BK Channels Localize to the Paranodal Junction and Regulate Action Potentials in Myelinated Axons of Cerebellar Purkinje Cells.

PubMed

Hirono, Moritoshi; Ogawa, Yasuhiro; Misono, Kaori; Zollinger, Daniel R; Trimmer, James S; Rasband, Matthew N; Misonou, Hiroaki

2015-05-06

In myelinated axons, K(+) channels are clustered in distinct membrane domains to regulate action potentials (APs). At nodes of Ranvier, Kv7 channels are expressed with Na(+) channels, whereas Kv1 channels flank nodes at juxtaparanodes. Regulation of axonal APs by K(+) channels would be particularly important in fast-spiking projection neurons such as cerebellar Purkinje cells. Here, we show that BK/Slo1 channels are clustered at the paranodal junctions of myelinated Purkinje cell axons of rat and mouse. The paranodal junction is formed by a set of cell-adhesion molecules, including Caspr, between the node and juxtaparanodes in which it separates nodal from internodal membrane domains. Remarkably, only Purkinje cell axons have detectable paranodal BK channels, whose clustering requires the formation of the paranodal junction via Caspr. Thus, BK channels occupy this unique domain in Purkinje cell axons along with the other K(+) channel complexes at nodes and juxtaparanodes. To investigate the physiological role of novel paranodal BK channels, we examined the effect of BK channel blockers on antidromic AP conduction. We found that local application of blockers to the axon resulted in a significant increase in antidromic AP failure at frequencies above 100 Hz. We also found that Ni(2+) elicited a similar effect on APs, indicating the involvement of Ni(2+)-sensitive Ca(2+) channels. Furthermore, axonal application of BK channel blockers decreased the inhibitory synaptic response in the deep cerebellar nuclei. Thus, paranodal BK channels uniquely support high-fidelity firing of APs in myelinated Purkinje cell axons, thereby underpinning the output of the cerebellar cortex. Copyright © 2015 the authors 0270-6474/15/357082-13$15.00/0.

Effects of RAAS Blockers on Atrial Fibrillation Prophylaxis: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials.

PubMed

Chaugai, Sandip; Meng, Wen Yeng; Ali Sepehry, Amir

2016-07-01

Impact of atrial fibrillation on clinical outcomes is well recognized, and application of renin-angiotensin-aldosterone system (RAAS) blockers for the prevention of atrial fibrillation (AF) is a theoretically appealing concept. However, clinical trials have yielded inconsistent results. A pooled study of 26 randomized controlled trials (RCTs) assessing the efficacy of RAAS blockers on AF prophylaxis was performed. A total of 28 reports from 26 randomized controlled trials enrolled 165 387 patients, with an overall 24% reduction in the incidence of AF (odds ratio [OR]: 0.76, 95% confidence interval [CI]: 0.68-0.85], P = .000). Forty-nine percent reduction in the incidence of AF (OR: 0.51, 95% CI: 0.30-0.85, P = .010) in systolic heart failure was observed, whereas no significant effect was observed in patients with diastolic heart failure, postmyocardial infarction, and high cardiovascular disease risk. There was a 19% (OR: 0.81, 95% CI: 0.67-1.00, P = .037) reduction in new-onset and 54% (OR: 0.46, 95% CI: 0.33-0.62, P = .000) reduction in recurrent AF in hypertensive patients with 39% (OR: 0.61, 95% CI: 0.44-0.84, P = .003) risk reduction against calcium blockers and 41% (OR: 0.59, 95% CI: 0.44-0.80, P = .001) risk reduction against β blockers. Angiotensin-receptor blocker appeared marginally superior to angiotensin-converting enzyme inhibitor in primary and secondary prevention. This study suggests that RAAS blockade effectively suppresses AF in systolic heart failure, and hypertensives derive greater benefit against new-onset and recurrent AF compared to β blockers, calcium channel blockers, and diuretics. © The Author(s) 2016.

Leptin Suppresses Mouse Taste Cell Responses to Sweet Compounds

PubMed Central

Noguchi, Kenshi; Shigemura, Noriatsu; Jyotaki, Masafumi; Takahashi, Ichiro; Margolskee, Robert F.

2015-01-01

Leptin is known to selectively suppress neural and behavioral responses to sweet-tasting compounds. However, the molecular basis for the effect of leptin on sweet taste is not known. Here, we report that leptin suppresses sweet taste via leptin receptors (Ob-Rb) and KATP channels expressed selectively in sweet-sensitive taste cells. Ob-Rb was more often expressed in taste cells that expressed T1R3 (a sweet receptor component) than in those that expressed glutamate-aspartate transporter (a marker for Type I taste cells) or GAD67 (a marker for Type III taste cells). Systemically administered leptin suppressed taste cell responses to sweet but not to bitter or sour compounds. This effect was blocked by a leptin antagonist and was absent in leptin receptor–deficient db/db mice and mice with diet-induced obesity. Blocking the KATP channel subunit sulfonylurea receptor 1, which was frequently coexpressed with Ob-Rb in T1R3-expressing taste cells, eliminated the effect of leptin on sweet taste. In contrast, activating the KATP channel with diazoxide mimicked the sweet-suppressing effect of leptin. These results indicate that leptin acts via Ob-Rb and KATP channels that are present in T1R3-expressing taste cells to selectively suppress their responses to sweet compounds. PMID:26116698

Central Regulation of Glucose Production May Be Impaired in Type 2 Diabetes

PubMed Central

Esterson, Yonah B.; Carey, Michelle; Boucai, Laura; Goyal, Akankasha; Raghavan, Pooja; Zhang, Kehao; Mehta, Deeksha; Feng, Daorong; Wu, Licheng; Kehlenbrink, Sylvia; Koppaka, Sudha; Kishore, Preeti

2016-01-01

The challenges of achieving optimal glycemic control in type 2 diabetes highlight the need for new therapies. Inappropriately elevated endogenous glucose production (EGP) is the main source of hyperglycemia in type 2 diabetes. Because activation of central ATP-sensitive potassium (KATP) channels suppresses EGP in nondiabetic rodents and humans, this study examined whether type 2 diabetic humans and rodents retain central regulation of EGP. The KATP channel activator diazoxide was administered in a randomized, placebo-controlled crossover design to eight type 2 diabetic subjects and seven age- and BMI-matched healthy control subjects. Comprehensive measures of glucose turnover and insulin sensitivity were performed during euglycemic pancreatic clamp studies following diazoxide and placebo administration. Complementary rodent clamp studies were performed in Zucker Diabetic Fatty rats. In type 2 diabetic subjects, extrapancreatic KATP channel activation with diazoxide under fixed hormonal conditions failed to suppress EGP, whereas matched control subjects demonstrated a 27% reduction in EGP (P = 0.002) with diazoxide. Diazoxide also failed to suppress EGP in diabetic rats. These results suggest that suppression of EGP by central KATP channel activation may be lost in type 2 diabetes. Restoration of central regulation of glucose metabolism could be a promising therapeutic target to reduce hyperglycemia in type 2 diabetes. PMID:27207526

Minoxidil attenuates ischemia-induced apoptosis in cultured neonatal rat cardiomyocytes.

PubMed