Inhibitor Of ATP-sensitive Potassium Channels Research Articles

Unveiling the antinociceptive mechanisms of Methyl-2-(4-chloro-phenyl)-5-benzoxazoleacetate: insights from nociceptive assays in mice.

Methyl-2-(4-chloro- phenyl)-5-benzoxazoleacetate (MCBA), a synthetic benzoxazole derivative with established antipsoriatic efficacy, was investigated for potential antinociceptive effects. This study employs various nociceptive assays in mice to elucidate MCBA's antinociceptive mechanisms. MCBA's antinociceptive potential was tested against various nociception models induced by formalin, glutamate, capsaicin, a transient receptor potential vanilloid 1 (TRPV1) receptor agonist, and phorbol 12-myristate 13-acetate, a protein kinase C (PKC) activator. It was then assessed using the hot plate test and examined within the acetic acid-induced writhing test. During the acetic acid-induced writhing test, MCBA was pre-challenged against selective receptor antagonists such as naloxone, caffeine, atropine, yohimbine, ondansetron, and haloperidol. It was also pre-challenged with ATP-sensitive potassium channel inhibitor (glibenclamide) to further elucidate its antinociceptive mechanism. The results showed that oral administration of MCBA led to a dose-dependent and significant inhibition (p < 0.05) of nociceptive effects across all evaluated models at doses of 60, 120, and 240 mg/kg. Moreover, the efficacy of MCBA's antinociceptive potential was significantly counteracted (p < 0.0001) by specific antagonists: (i) directed at adenosinergic, alpha-2 adrenergic, and cholinergic receptors using caffeine, yohimbine, and atropine, respectively; and (ii) targeting ATP-sensitive potassium channels, employing glibenclamide. Antagonists aimed at opioidergic and serotoninergic receptors (naloxone and ondansetron, respectively) had poor utility in inhibiting antinociceptive activity. Conversely, the dopaminergic receptor antagonist haloperidol potentiated locomotor abnormalities associated with MCBA treatment. MCBA-induced antinociception involves modulation of glutamatergic-, TRVP1 receptors- and PKC-signaling pathways. It impacts adenosinergic, alpha-2 adrenergic, and cholinergic receptors and opens ATP-sensitive potassium channels.

The PACAP pathway is independent of CGRP in mouse models of migraine: possible new drug target?

Calcitonin gene-related peptide (CGRP)-antagonizing drugs represent a major advance in migraine treatment. However, up to 50% of patients do not benefit from monoclonal antibodies against CGRP or its receptor. Here, we test the hypothesis that a closely related peptide, pituitary adenylate cyclase-activating peptide (PACAP-38), works independently of CGRP and thus might represent a new, alternative drug target. To understand differences in CGRP- and PACAP-mediated migraine pain, we used mouse models of provoked migraine-like pain based on multiple stimulations and subsequent measurement of tactile sensitivity response with von Frey filaments. Genetically modified mice lacking either functional CGRP receptors (Ramp1 knockout) or TRPA1 channels (Trpa1 knockout) were used together with CGRP-targeting antibodies and chemical inhibitors in wild-type mice (ntotal = 299). Ex vivo myograph studies were used to measure dilatory responses to CGRP and PACAP-38 in mouse carotid arteries. PACAP-38 provoked significant hypersensitivity and dilated the carotid arteries independently of CGRP. In contrast, glyceryl trinitrate-induced hypersensitivity is dependent on CGRP. Contrary to previous results with the migraine-inducing substances glyceryl trinitrate, cilostazol and levcromakalim, PACAP-38-induced hypersensitivity worked only partially through inhibition of ATP-sensitive potassium channels. Using multiple migraine-relevant models, these findings establish the PACAP-38 pathway as distinct from other migraine provoking pathways such as CGRP and glyceryl trinitrate. PACAP antagonism may therefore be a novel therapeutic target of particular interest in patients unresponsive to CGRP-antagonizing drugs.

Pharmacological Evaluation of the Bronchorelaxant Effect of Waltheria indica L. (Malvaceae) Extracts on Rat Trachea.

Waltheria indica L. (Malvaceae) is a plant used in Burkina Faso for the treatment of various ailments including asthma. The aim of the study was to evaluate the pharmacological relaxant effect of the leafy stem extracts of Waltheria indica and thereby verify claim of use in treating asthma. Aqueous decoction and hydroalcoholic extracts obtained from the powdered leafy stems were screened for the presence of some phytoconstituents. The in vitro relaxant effect of the two extracts was evaluated on acetylcholine- (ACh 10−5 M) and potassium chloride- (KCl 6 × 10−2 M) induced contractions on rat-isolated tracheal preparations. To examine whether the potassium (K+) channels are involved in the relaxant effect, glibenclamide, an ATP-sensitive potassium channel inhibitor, was used. Moreover, to assess the safety of the extracts, acute oral toxicity was carried out on mice. The phytochemical screening revealed the presence of alkaloids, flavonoids, saponins, steroids, triterpenoids, tannins, and coumarins in the hydroalcoholic extract. Tannins, steroids, triterpenoids, and coumarins were not detected in the aqueous decoction. With respective EC50 values of 1.517 ± 0.002 mg/mL and 1.433 ± 0.001 mg/mL on ACh-and KCl-provoked contractions, the hydroalcoholic extract was found more potent in relaxing the isolated rat tracheal preparations compared to the aqueous decoction. In the presence of glibenclamide, the relaxant effect of the hydroalcoholic extract (EC50 = 0.191 ± 0.002 mg/mL) increased and was higher than that of the aqueous decoction. At dose of 5000 mg/kg of body weight, the extracts did not produce deaths or any significant changes in the general behavior of mice. The results suggest that different mechanisms including modulation of calcium and potassium channels, particularly the ATP-sensitive K+ channels, could be involved in the relaxation effect. These findings could justify the traditional use of W. indica in the management of asthma.

Hypoxia induces the translocation of glucose transporter 1 to the plasma membrane in vascular endothelial cells

Glucose uptake and adenosine triphosphate (ATP) generation are important for the survival and growth of endothelial cells. An increase of glucose uptake under hypoxia was previously shown to be associated with the increased expression of glucose transporters (GLUTs). However, the regulation of GLUT trafficking to the cell surface has not been examined in detail. Here, we report the characterization of GLUT1 translocation to the plasma membrane during hypoxia in endothelial cells. Human umbilical vein endothelial cells (HUVECs) were exposed to hypoxia (1% O2) for 12 h, which significantly induced GLUT1 expression and translocation to the plasma membrane. GLUT1 translocation was associated with a decrease of intracellular ATP by hypoxia. Decreasing ATP levels with antimycin-A and 2-deoxyglucose induced GLUT1 translocation under normoxia. The induction of hypoxia-inducible factor-1α under normoxia did not influence the cell surface expression of GLUT1 or cellular ATP concentration. Interestingly, the translocation of GLUT1 induced by hypoxia was inhibited by the ATP-sensitive potassium (KATP) channel inhibitor glibenclamide, while the mitochondrial KATP channel inhibitor 5-HD did not influence GLUT1 translocation during hypoxia. These observations indicate that a decrease of intracellular ATP triggers GLUT1 translocation to the plasma membrane and is mediated by KATP channels, which would contribute to glucose uptake in HUVECs during hypoxia.

The AMP-activated protein kinase modulates hypothermia-induced J wave.

The mechanism underlying the occurrence of the J wave in low temperature remains unclear. However, low temperature is associated with metabolic disorder and 5' AMP-activated protein kinase (AMPK), which modulates ionic currents and cardiac metabolism. This study investigated whether AMPK regulation can modulate the occurrence of the J wave at low temperature. Unipolar and bipolar leads were used to record monophasic action potential (the endocardium and epicardium) and pseudo-electrocardiograms (inferior leads) to study the cardiac electrical activity. Measurements were taken in isolated Langendorff rabbit hearts at both 30℃ and 37℃ before and after administration of 4-aminopyridine (an ultrarapid delayed rectifier potassium current inhibitor, IKur , 50µmol L-1 ), PF06409577 (an AMPK activator, 1µmol L-1 ), compound C (an AMPK inhibitor, 10µmol L-1 ) and glibenclamide (an ATP-sensitive inward rectifier potassium channel inhibitor, IKATP , 20µmol L-1 ). The amplitude of the J wave (2.46±0.34mV vs. 1.11±0.23mV, P<.01) at 30℃ (n=15) was larger than that at 37℃ (n=15). PF06409577 (1µmol L-1 ) increased the J waves at both 30℃ and 37℃. In contrast, compound C (10µmol L-1 ) reduced J wave at both 37℃ and 30℃. Low-temperature-induced J waves were individually suppressed by 4-AP (50µmol L-1 ) and glibenclamide (20µmol L-1 ). AMPK inhibition reduces low-temperature-induced J waves and possible ventricular arrhythmogenesis by modulating IKATP and IKur channels.

Choline attenuates inflammatory hyperalgesia activating nitric oxide/cGMP/ATP-sensitive potassium channels pathway

New findings on neural regulation of immunity are allowing the design of novel pharmacological strategies to control inflammation and nociception. Herein, we report that choline, a 7-nicotinic acetylcholine receptor (α7nAChRs) agonist, prevents carrageenan-induced hyperalgesia without affecting inflammatory parameters (neutrophil migration or cytokine/chemokines production) or inducing sedation or even motor impairment. Choline also attenuates prostaglandin-E2 (PGE2)-induced hyperalgesia via α7nAChR activation and this antinociceptive effect was abrogated by administration of LNMMA (a nitric oxide synthase inhibitor), ODQ (an inhibitor of soluble guanylate cyclase; cGMP), andglibenclamide(an inhibitor of ATP-sensitive potassium channels). Furthermore, choline attenuates long-lasting Complete Freund’s Adjuvant and incision-induced hyperalgesia suggesting its therapeutic potential to treat pain in rheumatoid arthritis or post-operative recovery, respectively. Our results suggest that choline modulates inflammatory hyperalgesia by activating the nitric oxide/cGMP/ATP-sensitive potassium channels without interfering in inflammatory events, and could be used in persistent pain conditions.

Bevacizumab Versus Anti-preeclamptic Drugs: Evaluation With Three-dimensionally Co-cultured Human Mini Tumors.

Both bevacizumab (BEV) and soluble fms-like tyrosine kinase-1 (sFlt-1) have demonstrated anti-angiogenic effects, thereby causing hypertension and proteinuria. We hypothesized that anti-preeclamptic drugs that combat the action of sFlt-1 may reduce BEV's anti-tumor efficacy. 3D co-cultured human mini-tumors consisting of endothelial cells, fibroblasts, and cancer cells were developed. The influence of anti-preeclamptic drugs and BEV on the invasion of mini-tumors embedded in collagen gel was evaluated. Mini-tumor spheroids that contained MDA-MB-231 cells showed higher invasion ability than spheroids with A549. Among the six anti-preeclamptic drugs investigated, only nicorandil enhanced the invasion of mini-tumors and inhibited the action of BEV. Glibenclamide, an ATP-sensitive potassium channel inhibitor, completely quenched the action of nicorandil on mini-tumors. In the human mini-tumor model, nicorandil aggravated the invasion of mini-tumors. These data raise the possibility that concomitant use of nicorandil counteracts the efficacy of BEV therapy.

Genetical and pharmacological inhibition of ATP-sensitive potassium channels induces anxiety-like behavior in mice

Genetical and pharmacological inhibition of ATP-sensitive potassium channels induces anxiety-like behavior in mice

The role of potassium channels and calcium in the relaxation mechanism of magnesium sulfate on the isolated rat uterus

MgSO4 is used as a tocolytic agent. It is considered to be a calcium channel antagonist, but a different mechanism of its action might be involved. The aim of this study was to examine the contribution of calcium concentrations and potassium channels in the mechanism of MgSO4-mediated uterine relaxation. Isolated uteri from female Wister rats were treated with increasing MgSO4 concentrations (0.1-30 mM). MgSO4 induced dose-dependent inhibition of spontaneous activity. Addition of Ca2+ (6 mM and 12 mM) stimulated uterine contractile activity and attenuated the inhibitory activity of MgSO4. In order to analyze the role of different subtypes of potassium channels, Ca2+-stimulated uteri were pretreated with glibenclamide (Glib), a selective ATP-sensitive potassium channel inhibitor (KATP), tetraethylammonium (TEA), a non-specific inhibitor of large conductance calcium-activated potassium channels (BKCa), and 4-aminopyridine (4-AP), a voltage-sensitive potassium channel inhibitor (Kv), at concentrations that had no effect per se. Pretreatment with 4-AP had no effect on MgSO4-mediated relaxation of Ca2+-stimulated uteri. The relaxing effect of MgSO4 was potentiated by pretreatment with glibenclamide. Pretreatment with TEA attenuated the MgSO4-mediated decrease in frequency. Our results suggest that MgSO4 acts as a general calcium antagonist that influences Ca2+-mediated potassium channels. Furthermore, it seems that MgSO4 uterine relaxation activity is partially mediated by selective ATP-sensitive potassium channels, suggesting an ATP-dependent role.

Mitochondrial depolarization stimulates vascular repair-relevant functions of CD34+ cells via reactive oxygen species-induced nitric oxide generation.

CD34+ haematopoietic stem/progenitor cells have revascularization potential and are now being tested for the treatment of ischaemic vascular diseases in clinical trials. We tested the hypothesis that mitochondrial depolarization stimulates the reparative functions of CD34+ cells. Peripheral blood was obtained from healthy individuals (n=63), and mononuclear cells (MNCs) were separated. MNCs were enriched for lineage negative cells, followed by isolation of CD34+ cells. Vascular repair-relevant functions of CD34+ cells, proliferation and migration, were evaluated in the presence and absence of diazoxide. Mitochondrial membrane potential, ROS and NO levels were evaluated by flow cytometry by using JC-1, mitoSOX and DAF-FM respectively. Diazoxide stimulated the proliferation and migration of CD34+ cells that were comparable to the responses induced by stromal-derived factor-1α (SDF) or VEGF. Effects of diazoxide were blocked by either 5-hydroxydecanoate (5HD), a selective mitochondrial ATP-sensitive potassium channel (mitoKATP ) inhibitor, or by L-NAME. Diazoxide induced mitochondrial depolarization, and NO and cGMP generation that were 5HD-sensitive. The generation of NO and cGMP by diazoxide was blocked by an endothelial NOS (eNOS)-selective inhibitor, NIO, but not by a neuronal (n)NOS-selective inhibitor, Nω -propyl-L-arginine (NPA). A Ca2+ chelator, BAPTA, Akt inhibitor, triciribine, or PI3K inhibitor, LY294002, inhibited the NO release induced by diazoxide. Phosphorylation of eNOS at Ser1177 and dephosphorylation at Thr495 were increased. Diazoxide-induced ROS generation and phosphorylation of eNOS at Ser1177 were reduced by NPA. Diazoxide stimulates vascular repair-relevant functions of CD34+ cells via the mitoKATP -dependent release of NO and ROS. This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

ATP-sensitive potassium-channel inhibitor glibenclamide attenuates HPA axis hyperactivity, depression- and anxiety-related symptoms in a rat model of Alzheimer's disease

Affective disorders including depression and anxiety are among the most prevalent behavioral abnormalities in patients with Alzheimer's disease (AD), which affect the quality of life and progression of the disease. Dysregulation of the hypothalamic-pituitary-adrenal-(HPA) axis has been reported in affective disorders and AD. Recent studies revealed that current antidepressant drugs are not completely effective for treating anxiety- and depression-related disorders in people with dementia. ATP-sensitive-potassium-(KATP) channels are well-known to be involved in AD pathophysiology, HPA axis function and the pathogenesis of depression and anxiety-related behaviors. Thus, targeting of KATP channel may be a potential therapeutic strategy in AD. Hence, we investigated the effects of intracerebroventricular injection of Aβ25-35 alone or in combination with glibenclamide, KATP channel inhibitor on depression- and anxiety-related behaviors as well as HPA axis response to stress in rats. To do this, non-Aβ25-35- and Aβ25-35-treated rats were orally treated with glibenclamide, then the behavioral consequences were assessed using sucrose preference, forced swim, light-dark box and plus maze tests. Stress-induced corticosterone levels following forced swim and plus maze tests were also evaluated as indicative of abnormal HPA-axis-function. Aβ25-35 induced HPA axis hyperreactivity and increased depression- and anxiety-related symptoms in rats. Our results showed that blockade of KATP channels with glibenclamide decreased depression- and anxiety-related behaviors by normalizing HPA axis activity in Aβ25-35-treated rats. This study provides additional evidence that Aβ administration can induce depression- and anxiety-like symptoms in rodents, and suggests that KATP channel inhibitors may be a plausible therapeutic strategy for treating affective disorders in AD patients.

Metabolic Syndrome Induced Bladder Cannabinoid Receptor Changes in the Fructose-Fed Rats.

To investigate the effect of metabolic syndrome on the bladder cannabinoid receptors 1 and 2 (CB1/CB2) expression and function in the fructose-fed rats (FR). Adult male Sprague-Dawley rats were divided into two groups: (i) Control rats fed with normal chow; and (ii) Rats fed with high-fructose diet (FR) for 9 weeks. The body weight, blood pressure, plasma sugar, insulin, triglyceride and cholesterol were measured. Bladder muscle strips were prepared in organ bath and pre-contracted with 1 µM/L acetylcholine (ACh) or 50 mM/L KCl. The relaxation responses to CB1/CB2 agonist Bay59-3047 (0.01-1 µM/L) were recorded. The effects of CB1 antagonist AM251, CB2 antagonist AM630, protein kinase A (PKA) inhibitor H-89 and ATP-sensitive potassium channel (KATP) inhibitor glibenclamide on the Bay59-3047-induced response were tested. Western blotting and real-time polymerase chain reaction (RT-PCR) analyses were performed for bladder CB1/CB2 receptors. Significant increases of body weight, blood pressure, plasma glucose, insulin, cholesterol and triglyceride levels were found in the FR. Bay59-3047 reduced ACh and KCl pre-contracted bladder strip tension in a dose-dependent fashion. The relaxation responses were significantly decreased in the FR. The Bay59-3047-induced relaxation was attenuated by AM251, glibenclamide and H-89. Western blotting and RT-PCR showed decreased expressions of FR bladder CB1 and CB2 receptor protein and mRNA. CB1/CB2 receptors mediate rat bladder relaxation through the PKA and KATP pathway. The CB1 receptor may play a more prominent role. The response is decreased in the FR bladder due to reduced expressions of the cannabinoid receptors.

Intracolonic hydrogen sulfide lowers blood pressure in rats

Research suggests that hydrogen sulfide (H2S) is an important biological mediator involved in various physiological processes including the regulation of arterial blood pressure (BP). Although H2S is abundant in the colon, the effects of gut-derived H2S on the circulatory system have not yet been investigated. We studied the effects of intracolonic administration of Na2S, a H2S donor, on systemic hemodynamics. Hemodynamics were recorded in anesthetized, normotensive Wistar Kyoto and spontaneously hypertensive rats at baseline and after intracolonic injection of either saline (controls) or Na2S·9H2O saline solution at a dose range of 10–300 mg/kg of BW. The H2S donor produced a significant, dose-dependent decrease in mean arterial blood pressure (MABP), which lasted several times longer than previously reported after parenteral infusions (>90 min). The effect was more pronounced in hypertensive than in normotensive rats. The Na2S-induced decrease in MABP was reduced by pretreatment with glibenclamide, an inhibitor of ATP-sensitive potassium-channels. Na2S did not affect mesenteric vein blood flow. Rats treated with Na2S showed increased portal blood levels of thiosulfate and sulfane sulfur, products of H2S oxidation. In contrast, rats treated with neomycin, an antibiotic, showed significantly decreased levels of thiosulfate and sulfane sulfur, and a tendency for greater hypotensive response to Na2S. The H2S donor decreased heart rate but did not affect ECG morphology and QTc interval. In conclusion the gut-derived H2S may contribute to the control of BP and may be one of the links between gut microbiota and hypertension. Furthermore, gut-derived H2S may be a therapeutic target in hypertension.

Evidence for a functional vasodilatatory role for hydrogen sulphide in the human cutaneous microvasculature.

Hydrogen sulphide (H2 S) is vasoprotective, attenuates inflammation and modulates blood pressure in animal models; however, its specific mechanistic role in the human vasculature remains unclear. In the present study, we report the novel finding that the enzymes responsible for endogenous H2 S production, cystathionine-γ-lyase and 3-mercaptopyruvate sulphurtransferase, are expressed in the human cutaneous circulation. Functionally, we show that H2 S-induced cutaneous vasodilatation is mediated, in part, by tetraethylammonium-sensitive calcium-dependent potassium channels and not by ATP-sensitive potassium channels. In addition, nitric oxide and cyclo-oxygenase-derived byproducts are required for full expression of exogenous H2 S-mediated cutaneous vasodilatation. Future investigations of the potential role for H2 S with respect to modulating vascular function in humans may have important clinical implications for understanding the mechanisms underlying vascular dysfunction characteristic of multiple cardiovascular pathologies. The present study aimed to identify the presence of cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulphurtransferase (3-MST), which endogenously produce hydrogen sulphide (H2 S), and to functionally examine the mechanisms of H2 S-induced vasodilatation in the human cutaneous microcirculation. CSE and 3-MST were quantified in forearm skin samples from 5 healthy adults (24±3years) using western blot analysis. For functional studies, microdialysis fibres were placed in the forearm skin of 12 healthy adults (25±3years) for graded infusions (0.01-100mm) of sodiumsulphide (Na2 S) and sodium hydrogen sulphide (NaHS). To define the mechanisms mediating H2 S-induced vasodilatation, microdialysis fibres were perfused with Ringer solution (control), a ATP-sensitive potassium channel (KATP ) inhibitor, an intermediate calcium-dependent potassium channel (KCa ) inhibitor, a non-specific KCa channel inhibitor or triple blockade. To determine the interaction of H2 S-mediated vasodilatation with nitric oxide (NO) and cyclo-oxygenase (COX) signalling pathways, microdialysis fibres were perfused with Ringer solution (control), a non-specific NO synthase inhibitor, a non-selective COX inhibitor or combined inhibition during perfusion of increasing doses of Na2 S. CSE and 3-MST were expressed in all skin samples. Na2 S and NaHS elicited dose-dependent vasodilatation. Non-specific KCa channel inhibition and triple blockade blunted Na2 S-induced vasodilatation (P<0.05), whereas KATP and intermediate KCa channel inhibition had no effect (P>0.05). Separate and combined inhibition of NO and COX attenuated H2 S-induced vasodilatation (all P<0.05). CSE and 3-MST are expressed in the human microvasculature. Exogenous H2 S elicits cutaneous vasodilatation mediated by KCa channels and has a functional interaction with both NO and COX vasodilatatory signalling pathways.

The ruthenium nitric oxide donor, [Ru(HEDTA)NO], inhibits acute nociception in mice by modulating oxidative stress, cytokine production and activating the cGMP/PKG/ATP-sensitive potassium channel signaling pathway.

Nitric oxide plays an important role in various biological processes including antinociception. The control of its local concentration is crucial for obtaining the desired effect and can be achieved with exogenous nitric oxide-carriers such as ruthenium complexes. Therefore, we evaluated the analgesic effect and mechanism of action of the ruthenium nitric oxide donor [Ru(HEDTA)NO] focusing on the role of cytokines, oxidative stress and activation of the cyclic guanosine monophosphate/protein kinase G/ATP-sensitive potassium channel signaling pathway. It was observed that [Ru(HEDTA)NO] inhibited in a dose-dependent (1-10 mg/kg) manner the acetic acid-induced writhing response. At the dose of 1 mg/kg, [Ru(HEDTA)NO] inhibited the phenyl-p-benzoquinone-induced writhing response, and formalin- and complete Freund's adjuvant-induced licking and flinching responses. Systemic and local treatments with [Ru(HEDTA)NO] also inhibited the carrageenin-induced mechanical hyperalgesia and increase of myeloperoxidase activity in paw skin samples. Mechanistically, [Ru(HEDTA)NO] inhibited carrageenin-induced production of the hyperalgesic cytokines tumor necrosis factor-α and interleukin-1β, and decrease of reduced glutathione levels. Furthermore, the inhibitory effect of [Ru(HEDTA)NO] in the carrageenin-induced hyperalgesia and myeloperoxidase activity was prevented by the treatment with ODQ (soluble guanylyl cyclase inhibitor), KT5823 (protein kinase G inhibitor) and glybenclamide (ATP-sensitive potassium channel inhibitor), indicating that [Ru(HEDTA)NO] inhibits inflammatory hyperalgesia by activating the cyclic guanosine monophosphate/protein kinase G/ATP-sensitive potassium channel signaling pathway, respectively. These results demonstrate that [Ru(HEDTA)NO] exerts its analgesic effect in inflammation by inhibiting pro-nociceptive cytokine production, oxidative imbalance and activation of the nitric oxide/cyclic guanosine monophosphate/protein kinase G/ATP-sensitive potassium channel signaling pathway in mice.

The antidiabetic agent glibenclamide protects airway hyperresponsiveness and inflammation in mice.

Glibenclamide has a newly discovered role in inflammation regulation besides its antidiabetic effect. As an inhibitor of ATP-sensitive potassium (KATP) channel, glibenclamide antagonizes the relaxation of the tracheal smooth muscle. This indicates that glibenclamide might attenuate airway inflammation while aggravate airway hyperresponsiveness (AHR) in asthmatics. Clinically, many diabetics with asthma are prescribed with glibenclamide to control blood glucose. However, whether glibenclamide could exert any effects on asthmatic inflammation remains unknown. Using an ovalbumin (OVA)-induced mouse model of asthma, we evaluated the effects of glibenclamide on the AHR and inflammation. Interestingly, glibenclamide reduced all the cardinal features of asthma in OVA-challenged mice, including AHR, airway inflammation, and T-helper type 2 (Th2) cytokines. Glibenclamide also downregulated OVA-induced expressions of vascular cell adhesion molecule 1 (VCAM-1) and phosphorylated signal transducer and activator of transcription 6 (p-STAT6) in the lung. In addition, increased sulfonylurea receptor 1 (SUR1) expression in the lung was observed after the OVA challenge. These findings suggest that the classic sulfonylurea glibenclamide plays an important protective role in the development of asthma, which not only provides the evidence for the safety of prescribed glibenclamide in diabetics combined with asthma but also indicates a possible new therapeutic for asthma via targeting glibenclamide-related pathways.

Protective effect of proanthocyanidins on anoxia-reoxygenation injury of myocardial cells mediated by the PI3K/Akt/GSK-3β pathway and mitochondrial ATP-sensitive potassium channel.

The aim of the present study was to examine the protective effect of proanthocyanidins anoxia-reoxygenation injury of myocardial cells and its association with phosphatidylinositol-3-kinase/Akt and glycogen synthase kinase (PI3K/Akt/GSK)-3β and ATP-sensitive potassium channels. Neonatal rat myocardial cells were cultured and an anoxia-reoxygenation model was established following pretreatment with various drugs. The experiment was divided into five groups according to an experimental scheme. An MTT assay was used to examine the cell survival, and reactive oxygen species (ROS) levels and apoptosis were detected by flow cytometry. Myocardial apoptosis was also examined by terminal deoxynucleotidyl transferase dUTP nick end labeling staining and western blot analysis was employed to detect the expression levels of caspase-3, p-Akt and p-glycogen synthase kinase (GSK)-3β. The results revealed that myocardial cells in the anoxia-reoxygenation group (A/R) exhibited reduced survival rates, increased ROS levels and enhanced caspase-3 expression, as compared with the control group (CN; P<0.05). However, the increase in p-Akt and p-GSK-3β expression was not significantly different. In the proanthocyanidin pretreatment group (PC) the myocardial cell survival rate was increased, ROS levels were reduced, caspase-3 expression was decreased and p-Akt and p-GSK-3β expression levels were significantly increased as compared with the A/R group (P<0.05). Blockade of the PIK3/Akt channel by LY294002 eliminated the protective effects of proanthocyanidins and induced a significant decrease in p-Akt protein and p-GSK-3β expression levels as compared with the PC group. The inhibitor of mitochondrial ATP-sensitive potassium (mitoKATP) channels, 5-HD, also significantly suppressed the protective effects of proanthocyanidins, but had no evident impact on p-Akt and p-GSK-3β expression as compared with the PC group. In conclusion, pretreatment with proanthocyanidins had a protective effect on rat myocardial cell anoxia/reoxygenation injury. This effect is associated with the activation of the PI3K/Akt/GSK-3β signaling pathway and the opening of mitoKATP channels, which may have important roles downstream of PI3K.

The insulin sensitizing effect of topiramate involves KATP channel activation in the central nervous system

Topiramate improves insulin sensitivity, in addition to its antiepileptic action. However, the underlying mechanism is unknown. Therefore, the present study was aimed at investigating the mechanism of the insulin-sensitizing effect of topiramate both in vivo and in vitro. Male C57Bl/6J mice were fed a run-in high-fat diet for 6 weeks, before receiving topiramate or vehicle mixed in high-fat diet for an additional 6 weeks. Insulin sensitivity was assessed by hyperinsulinaemic-euglycaemic clamp. The extent to which the insulin sensitizing effects of topiramate were mediated through the CNS were determined by concomitant i.c.v. infusion of vehicle or tolbutamide, an inhibitor of ATP-sensitive potassium channels in neurons. The direct effects of topiramate on insulin signalling and glucose uptake were assessed in vivo and in cultured muscle cells. In hyperinsulinaemic-euglycaemic clamp conditions, therapeutic plasma concentrations of topiramate (∼4 μg·mL(-1) ) improved insulin sensitivity (glucose infusion rate + 58%). Using 2-deoxy-D-[(3) H]glucose, we established that topiramate improved the insulin-mediated glucose uptake by heart (+92%), muscle (+116%) and adipose tissue (+586%). Upon i.c.v. tolbutamide, the insulin-sensitizing effect of topiramate was completely abrogated. Topiramate did not directly affect glucose uptake or insulin signalling neither in vivo nor in cultured muscle cells. In conclusion, topiramate stimulates insulin-mediated glucose uptake in vivo through the CNS. These observations illustrate the possibility of pharmacological modulation of peripheral insulin resistance through a target in the CNS.

Relationship Between Mitochondrial Matrix Volume and Cellular Volume in Response to Stress and the Role of ATP-Sensitive Potassium Channel

Cardiac myocytes demonstrate significant swelling and associated reduced contractility in response to stress that is prevented by the ATP-sensitive potassium channel opener, diazoxide (DZX) via an unknown mechanism. One proposed mechanism of cardioprotection is mitochondrial matrix swelling. To establish the relationship between mitochondrial and cellular volume during stress, this study examined the effect of DZX on mitochondrial volume. Isolated mouse mitochondria were exposed to the following solutions: Tyrode, isolation buffer, cardioplegia (CPG)±DZX±ATP-sensitive potassium channel inhibitor, 5-hydroxydecanoate, and metabolic inhibition (MI) ± DZX ± 5-hydroxydecanoate. Mitochondrial volume was measured. DZX resulted in significant mitochondrial swelling (P<0.0001 versus Tyrode). MI and CPG resulted in significant mitochondrial swelling compared with baseline volume. The addition of DZX did not alter the response of mitochondrial volume to CPG (P=0.912) but increased swelling in response to MI (P=0.036). The addition of 5-hydroxydecanoate to MI + DZX or CPG+DZX significantly reduced mitochondrial swelling (P<0.003 MI+DZX versus MI + DZX + 5HD; P<0.001 CPG+DZX versus CPG + DZX + 5HD). Both cellular and mitochondrial volume increased during exposure to MI and CPG. DZX did not alter mitochondrial volume during CPG; however, it was associated with an increase in mitochondrial volume during MI. 5-Hydroxydecanoate reduced mitochondrial volume during exposure to both stresses with DZX, supporting a role for a mitochondrial ATP-sensitive potassium channel in the mechanism of cardioprotection by DZX.

Ropivacaine-Induced Contraction Is Attenuated by Both Endothelial Nitric Oxide and Voltage-Dependent Potassium Channels in Isolated Rat Aortae

This study investigated endothelium-derived vasodilators and potassium channels involved in the modulation of ropivacaine-induced contraction. In endothelium-intact rat aortae, ropivacaine concentration-response curves were generated in the presence or absence of the following inhibitors: the nonspecific nitric oxide synthase (NOS) inhibitor N ω-nitro-L-arginine methyl ester (L-NAME), the neuronal NOS inhibitor N ω-propyl-L-arginine hydrochloride, the inducible NOS inhibitor 1400W dihydrochloride, the nitric oxide-sensitive guanylyl cyclase (GC) inhibitor ODQ, the NOS and GC inhibitor methylene blue, the phosphoinositide-3 kinase inhibitor wortmannin, the cytochrome p450 epoxygenase inhibitor fluconazole, the voltage-dependent potassium channel inhibitor 4-aminopyridine (4-AP), the calcium-activated potassium channel inhibitor tetraethylammonium (TEA), the inward-rectifying potassium channel inhibitor barium chloride, and the ATP-sensitive potassium channel inhibitor glibenclamide. The effect of ropivacaine on endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells was examined by western blotting. Ropivacaine-induced contraction was weaker in endothelium-intact aortae than in endothelium-denuded aortae. L-NAME, ODQ, and methylene blue enhanced ropivacaine-induced contraction, whereas wortmannin, N ω-propyl-L-arginine hydrochloride, 1400W dihydrochloride, and fluconazole had no effect. 4-AP and TEA enhanced ropivacaine-induced contraction; however, barium chloride and glibenclamide had no effect. eNOS phosphorylation was induced by ropivacaine. These results suggest that ropivacaine-induced contraction is attenuated primarily by both endothelial nitric oxide and voltage-dependent potassium channels.