Potassium Channel Opener Research Articles

Effect of asiaticoside on systolic blood pressure and relaxation of isolated thoracic aorta of rats

To investigate the effect of asiaticoside on blood pressure and relaxation of thoracic aorta in rats and explore the underlying mechanism. SD rats treated with 50 and 100 mg/kg asiaticoside by daily gavage for 2 weeks were monitored for systolic blood pressure changes, and histological changes of the thoracic aorta were evaluated using HE staining. In isolated rat endothelium-intact and endothelium-denuded thoracic aorta rings, the effects of asiaticoside on relaxation of the aortic rings were tested at baseline and following norepinephrine (NE)- and KCl-induced constriction. The vascular relaxation effect of asiaticoside was further observed in NE-stimulated endothelium-intact rat aortic rings pretreated with L-nitroarginine methyl ester, indomethacin, zinc protoporphyrin Ⅸ, tetraethyl ammonium chloride, glibenclamide, barium chloride, Iberiotoxin, 4-aminopyridine, or TASK-1-IN-1. The aortic rings were treated with KCl and NE followed by increasing concentrations of CaCl2 to investigate the effect of asiaticoside on vasoconstriction induced by external calcium influx and internal calcium release. Asiaticoside at 50 and 100 mg/kg significantly lowered systolic blood pressure in rats without affecting the thoracic aorta histomorphology. While not obviously affecting resting aortic rings with intact endothelium, asiaticoside at 100 mg/kg induced significant relaxation of the rings constricted by KCl and NE, but its effects differed between endothelium-intact and endothelium-denuded rings. In endothelium-intact aortic rings pretreated with indomethacin, ZnPP Ⅸ, barium chloride, glyburide, TASK-1-IN-1 and 4-aminopyridine, asiaticoside did not produce significant effect on NE-induced vasoconstriction, and tetraethylammonium, Iberiotoxin and L-nitroarginine methyl ester all inhibited the relaxation effect of asiaticoside. In KCland NE-treated rings, asiaticoside obviously inhibited CaCl2-induced vascular contraction. Asiaticoside induces thoracic aorta relaxation by mediating high-conductance calcium-activated potassium channel opening, promoting nitric oxide release from endothelial cells and regulating Ca2+ influx and outflow, thereby reducing systolic blood pressure in rats.

Ivermectin Exerts Anticonvulsant Effects Against Status Epilepticus Induced by Lithium-Pilocarpine in Rats via GABAA Receptor and Neuroinflammation Modulation: Possible Interaction of Opioidergic Pathways and KATP Channel with Nitrergic System.

Status epilepticus (SE) is a critical medical emergency marked by persistent or rapidly repeating seizures, posing a threat to life. Using the lithium-pilocarpine-induced SE model, we decide to evaluate the anti-seizure effects of ivermectin as a positive allosteric modulator of GABAA receptor and the underlying mechanisms involved. Lithium chloride was injected intraperitoneally at a dose of 127 mg/kg, followed by the administration of pilocarpine at a dose of 60 mg/kg after a 20-h interval in order to induce SE. Subsequently, the rats received varying amounts of ivermectin (0.3, 1, 3, 5, and 10 mg/kg, i.p.) 30 min before the onset of SE. To study the underlying molecular mechanisms, we had pharmacological interventions of diazepam (1 mg/kg), glibenclamide and nicorandil as ATP-sensitive potassium channel blocker and opener (both 1 mg/kg, i.p.), naltrexone and morphine, as opioid receptor antagonist and agonist (1 mg/kg and 0.5 mg/kg, i.p., respectively). In addition, three nitric oxide inhibitors, namely, L-NAME (10 mg/kg, i.p.), 7-NI (30 mg/kg, i.p.), and aminoguanidine (100 mg/kg, i.p.), were administered to the rats in the experiment. Finally, we use ELISA and western blotting, respectively, to examine the amounts of pro-inflammatory cytokines (TNF-α and IL-1β), nitrite, and GABAA receptors in the rat hippocampal tissue. The study found that ivermectin, at doses of 3, 5, and 10 mg/kg, exerts anti-seizure effects and decrease Racine's scale SE score. Interestingly glibenclamide and naltrexone reduced the anti-seizure effects of ivermectin, and from other hand diazepam, nicorandil, morphine, L-NAME, 7-NI, and aminoguanidine, enhance the effects when co-administrated with subeffective dose of ivermectin. Additionally, the study found that ivermectin decreased the elevated levels of TNF-α and IL-1β following SE, while increased the reduced expression of GABAA receptors. Overall, these findings suggest that ivermectin has anti-seizure effects in a SE seizure which may be mediated by the modulation of GABAergic, opioidergic, and nitrergic pathways and KATP channels.

Divergent electrophysiologic action of dapagliflozin and empagliflozin on ventricular and atrial tachyarrhythmias in isolated rabbit hearts.

The use of SGLT-2 inhibitors has revolutionized heart failure therapy. Evidence suggests a reduced incidence of ventricular and atrial arrhythmias in patients with dapagliflozin or empagliflozin treatment. It is unclear to what extent the reduced arrhythmia burden is due to direct effects of the SGLT2 inhibitors or is solely a marker of improved cardiac function. One hundred five rabbit hearts were allocated to eight groups and retrogradely perfused, employing a Langendorff setup. Action potential duration at 90% of repolarization (APD90), QT intervals, effective refractory periods, conduction velocity, and dispersion of repolarization were obtained with monophasic action potential catheters. A model for tachyarrhythmias was established with the IKr blocker erythromycin for QT prolongation associated proarrhythmia as well as the potassium channel opener pinacidil for a short-QT model. An atrial fibrillation (AF) model was created with isoproterenol and acetylcholine. With increasing concentrations of both SGLT2 inhibitors, reductions in QT intervals and APD90 were observed, accompanied by a slight increase in ventricular arrhythmia episodes. During drug-induced proarrhythmia, empagliflozin succeeded in decreasing QT intervals, APD90, and VT burden whereas dapagliflozin demonstrated no significant effects. In the presence of pinacidil induced arrhythmogenicity, neither SGLT2 inhibitor had a significant impact on cardiac electrophysiology. In the AF setting, perfusion with dapagliflozin showed significant suppression of AF in the course of restitution of electrophysiological parameters whereas empagliflozin showed no significant effect on atrial fibrillation incidence. In this model, empagliflozin and dapagliflozin demonstrated opposite antiarrhythmic properties. Empagliflozin reduced ventricular tachyarrhythmias whereas dapagliflozin showed effective suppression of atrial arrhythmias.

Experimental pharmacological approaches to reverse impaired awareness of hypoglycemia-a review.

The colossal global burden of diabetes management is compounded by the serious complication of hypoglycemia. Protective physiologic hormonal and neurogenic counterregulatory responses to hypoglycemia are essential to preserve glucose homeostasis and avert serious morbidity. With recurrent exposure to hypoglycemic episodes over time, these counterregulatory responses to hypoglycemia can diminish, resulting in an impaired awareness of hypoglycemia (IAH). IAH is characterized by sudden neuroglycopenia rather than preceding cautionary autonomic symptoms. IAH increases the risk of subsequent sudden and severe hypoglycemic episodes in patients with diabetes. The postulated causative mechanisms behind IAH are complex and varied. It is therefore challenging to identify a single effective therapeutic strategy. In this review, we closely examine the efficacy and feasibility of a myriad of pharmaceutical interventions in preventing and treating IAH as described in clinical and preclinical studies. Pharmaceutical agents outlined include N-acetyl cysteine, GABA A receptor blockers, opioid receptor antagonists, AMP activated protein kinase agonists, potassium channel openers, dehydroepiandrosterone, metoclopramide, antiadrenergic agents, antidiabetic agents and glucagon.

Beta-adrenergic receptor stimulation, histamine receptor inhibition, and potassium channel opening contribute to the relaxant effects of crocetin on airway smooth muscle.

In the present study, the relaxant effect of crocetin on tracheal smooth muscle cells (TSM) and its possible mechanisms were evaluated. The study was conducted on 54 male Wistar rats in 8 groups. TSM was contracted by methacholine (10 μM) and KCl (60 mM), and the relaxant effects of four cumulative concentrations of crocetin, petal extract of saffron, and theophylline were examined on non-incubated and TSM incubated with propranolol, chlorpheniramine, diltiazem, atropine, glibenclamide, and indomethacin were investigated. In non-incubated TSM contracted by methacholine or KCl, crocetin and theophylline showed concentration-dependent relaxant effects (all, P<0.001). However, various concentrations of crocetin showed significantly lower relaxant effects compared to those of theophylline (all, P<0.001). In the methacholine-induced contraction of TSM, the relaxation effect of the last concentration of crocetin in the TSM incubated with propranolol was lower than in non-incubated TSM (P<0.05). In the incubated TSM with chlorpheniramine, the relaxant effects of the two last concentrations of crocetin were significantly lower than in the non-incubated tissues contracted by KCl (P<0.05 and P<0.0). The levels of EC50 crocetin in the incubated TSM with glibenclamide, chlorpheniramine, and indomethacin were markedly lower than in non-incubated (all, P<0.05). The results showed potent relaxation effects of crocetin on TSM and were suggested to be through stimulation of ß-adrenergic receptors, inhibition of histamine (H1) receptors, and potassium channel opening mechanisms.

Nicorandil attenuates cisplatin-induced acute kidney injury in rats via activation of PI3K/AKT/mTOR signaling cascade and inhibition of autophagy

Cisplatin is a highly effective antitumor agent, but its clinical use is limited due to critical adverse reactions including acute kidney injury (AKI). Nicorandil is an approved antianginal agent decreasing ischemia by potassium channel opening. The aim of this study was to investigate the nephroprotective effects of nicorandil and the possible role of activating PI3K/AKT/mTOR pathway in ameliorating cisplatin-induced AKI. Forty male Wistar rats were randomly allocated in 4 groups (n = 10). Group I: rats received the vehicle and served as control. Group II: rats received a single dose of cisplatin (7 mg/kg, i.p) on the 10th day of the experiment and served as AKI group. Group III: rats received cisplatin as in group II and nicorandil (3 mg/kg/day, p.o) for 14 days. Group IV: rats received cisplatin and nicorandil as in group III as well as wortmannin (15 μg/kg, i.v) for 14 days. Nicorandil exhibited obvious nephroprotective effects via the activation of PI3K/AKT/mTOR pathway. Moreover, nicorandil succeed to reduce the expression of the autophagy markers beclin-1 and LC-3II/I. In parallel, nicorandil showed anti-inflammatory and antiapoptotic effects via inhibition of NF-κB inflammatory pathway and depression of Bax/Bcl-2 ratio. Wortmannin, the PI3K inhibitor, was used to demonstrate the proposed pathway. Our study showed the nephroprotective effects of nicorandil in cisplatin-induced AKI in rats via activation of PI3K/AKT/mTOR signaling cascade, inhibition of autophagy, anti-inflammatory, anti-apoptotic, anti-oxidant activities. Thus, nicorandil could represent a promising renoprotective agent in cancer patients treated with cisplatin.

Novel Potassium Channel Opener Appears Promising For Refractory Focal Epilepsy

Novel Potassium Channel Opener Appears Promising For Refractory Focal Epilepsy

Efficacy and Safety of XEN1101, a Novel Potassium Channel Opener, in Adults With Focal Epilepsy

Many patients with focal epilepsy experience seizures despite treatment with currently available antiseizure medications (ASMs) and may benefit from novel therapeutics. To evaluate the efficacy and safety of XEN1101, a novel small-molecule selective Kv7.2/Kv7.3 potassium channel opener, in the treatment of focal-onset seizures (FOSs). This phase 2b, randomized, double-blind, placebo-controlled, parallel-group, dose-ranging adjunctive trial investigated XEN1101 over an 8-week treatment period from January 30, 2019, to September 2, 2021, and included a 6-week safety follow-up. Adults experiencing 4 or more monthly FOSs while receiving stable treatment (1-3 ASMs) were enrolled at 97 sites in North America and Europe. Patients were randomized 2:1:1:2 to receive XEN1101, 25, 20, or 10 mg, or placebo with food once daily for 8 weeks. Dosage titration was not used. On completion of the double-blind phase, patients were offered the option of entering an open-label extension (OLE). Patients not participating in the OLE had follow-up safety visits (1 and 6 weeks after the final dose). The primary efficacy end point was the median percent change from baseline in monthly FOS frequency. Treatment-emergent adverse events (TEAEs) were recorded and comprehensive laboratory assessments were made. Modified intention-to-treat analysis was conducted. A total of 325 patients who were randomized and treated were included in the safety analysis; 285 completed the 8-week double-blind phase. In the 325 patients included, mean (SD) age was 40.8 (13.3) years, 168 (51.7%) were female, and 298 (91.7%) identified their race as White. Treatment with XEN1101 was associated with seizure reduction in a robust dose-response manner. The median (IQR) percent reduction from baseline in monthly FOS frequency was 52.8% (P < .001 vs placebo; IQR, -80.4% to -16.9%) for 25 mg, 46.4% (P < .001 vs placebo; IQR, -76.7% to -14.0%) for 20 mg, and 33.2% (P = .04 vs placebo; IQR, -61.8% to 0.0%) for 10 mg, compared with 18.2% (IQR, -37.3% to 7.0%) for placebo. XEN1101 was generally well tolerated and TEAEs were similar to those of commonly prescribed ASMs, and no TEAEs leading to death were reported. The efficacy and safety findings of this clinical trial support the further clinical development of XEN1101 for the treatment of FOSs. ClinicalTrials.gov Identifier: NCT03796962.

Lack of activity of the mitochondrial large-conductance calcium-regulated potassium channels in senescent vascular smooth muscle cells.

A limited number of studies have shown functional changes in mitochondrial ion channels in aging and senescent cells. We have identified, for the first time, mitochondrial large-conductance calcium-regulated potassium channels in human smooth muscle mitochondria. This channel, with a conductance of 273 pS, was regulated by calcium ions and membrane potential. Additionally, it was activated by the potassium channel opener NS11021 and blocked by paxilline. Importantly, we have shown that senescence of these cells induced by hydrogen peroxide treatment leads to the disappearance of potassium channel protein levels and channel activity measured by the single channel patch-clamp technique. Our data suggest that disturbances in the expression of mitochondrial large conductance calcium-regulated potassium channels may be hallmarks of cellular senescence and contribute to the misregulation of mitochondrial function in senescent cells.

Hypoxia Promotes Atrial Tachyarrhythmias via Opening of ATP-Sensitive Potassium Channels.

Hypoxia-ischemia predisposes to atrial arrhythmia. Atrial ATP-sensitive potassium channel (KATP) modulation during hypoxia has not been explored. We investigated the effects of hypoxia on atrial electrophysiology in mice with global deletion of KATP pore-forming subunits. Whole heart KATP RNA expression was probed. Whole-cell KATP current and action potentials were recorded in isolated wild-type (WT), Kir6.1 global knockout (6.1-gKO), and Kir6.2 global knockout murine atrial myocytes. Langendorff-perfused hearts were assessed for atrial effective refractory period (ERP), conduction velocity, wavefront path length (WFPL), and arrhymogenicity under normoxia/hypoxia using a microelectrode array and programmed electrical stimulation. Heart histology was assessed. Expression patterns were essentially identical for all KATP subunit RNA across human heart, whereas in mouse, Kir6.1 and SUR2 (sulphonylurea receptor) were higher in ventricle than atrium, and Kir6.2 and SUR1 were higher in atrium. Compared with WT, Kir6.2 global knockout atrial myocytes had reduced tolbutamide-sensitive current and action potentials were more depolarized with slower upstroke and reduced peak amplitude. Action potential duration was prolonged in 6.1-gKO atrial myocytes, absent of changes in other ion channel gene expression or atrial myocyte hypertrophy. In Langendorff-perfused hearts, baseline atrial ERP was prolonged and conduction velocity reduced in both KATP knockout mice compared with WT, without histological fibrosis. Compared with baseline, hypoxia led to conduction velocity slowing, stable ERP, and WFPL shortening in WT and 6.1-gKO hearts, whereas WFPL was stable in Kir6.2 global knockout hearts due to ERP prolongation with conduction velocity slowing. Tolbutamide reversed hypoxia-induced WFPL shortening in WT and 6.1-gKO hearts through ERP prolongation. Atrial tachyarrhythmias inducible with programmed electrical stimulation during hypoxia in WT and 6.1-gKO mice correlated with WFPL shortening. Spontaneous arrhythmia was not seen. KATP block/absence leads to cellular and tissue level atrial electrophysiological modification. Kir6.2 global knockout prevents hypoxia-induced atrial WFPL shortening and atrial arrhythmogenicity to programmed electrical stimulation. This mechanism could be explored translationally to treat ischemically driven atrial arrhythmia.

A Novel KCNH2 S981fs Mutation Identified by Whole-Exome Sequencing Is Associated with Type 2 Long QT Syndrome.

KCNH2 loss-of-function mutations cause long QT syndrome type 2 (LQT2), an inherited cardiac disorder associated with life-threatening ventricular arrhythmia. Through whole-exome sequencing, we discovered a novel AGCGACAC deletion (S981fs) in the hERG gene of an LQT2 patient. Using a heterologous expression system and patch clamping, we found that the mutant K channel had reduced cell surface expression and lower current amplitude compared to the wild type. However, functional expression was restored by lowering temperature and using potassium channel inhibitors or openers (E4031, cisapride, nicorandil). Co-immunoprecipitation experiments confirmed the assembly of mutant proteins with wild-type hERG. Confocal imaging showed decreased hERG distribution on the cell membrane in cells expressing S981fs. Notably, treatment with G418 significantly increased hERG current in wild-type/S981fs heterozygotes. In conclusion, our study identifies a novel hERG mutation leading to impaired Kv11.1 function due to trafficking and nonsense-mediated RNA decay defects. These findings shed light on the mechanisms underlying LQT2 and offer potential therapeutic avenues.

Antispasmodic Effect of Valeriana pilosa Root Essential Oil and Potential Mechanisms of Action: Ex Vivo and In Silico Studies.

Infusions of Valeriana pilosa are commonly used in Peruvian folk medicine for treating gastrointestinal disorders. This study aimed to investigate the spasmolytic and antispasmodic effects of Valeriana pilosa essential oil (VPEO) on rat ileum. The basal tone of ileal sections decreased in response to accumulative concentrations of VPEO. Moreover, ileal sections precontracted with acetylcholine (ACh), potassium chloride (KCl), or barium chloride (BaCl2) were relaxed in response to VPEO by a mechanism that depended on atropine, hyoscine butylbromide, solifenacin, and verapamil, but not glibenclamide. The results showed that VPEO produced a relaxant effect by inhibiting muscarinic receptors and blocking calcium channels, with no apparent effect on the opening of potassium channels. In addition, molecular docking was employed to evaluate VPEO constituents that could inhibit intestinal contractile activity. The study showed that α-cubebene, β-patchoulene, β-bourbonene, β-caryophyllene, α-guaiene, γ-muurolene, valencene, eremophyllene, and δ-cadinene displayed the highest docking scores on muscarinic acetylcholine receptors and voltage-gated calcium channels, which may antagonize M2 and/or M3 muscarinic acetylcholine receptors and block voltage-gated calcium channels. In summary, VPEO has both spasmolytic and antispasmodic effects. It may block muscarinic receptors and calcium channels, thus providing a scientific basis for its traditional use for gastrointestinal disorders.

Rapid Characterization of the Functional and Pharmacological Consequences of Cantú Syndrome KATP Channel Mutations in Intact Cells.

Gain-of-function of KATP channels, resulting from mutations in either KCNJ8 (encoding inward rectifier sub-family 6 [Kir6.1]) or ABCC9 (encoding sulphonylurea receptor [SUR2]), cause Cantú syndrome (CS), a channelopathy characterized by excess hair growth, coarse facial appearance, cardiomegaly, and lymphedema. Here, we established a pipeline for rapid analysis of CS mutation consequences in Landing pad HEK 293 cell lines stably expressing wild type (WT) and mutant human Kir6.1 and SUR2B. Thallium-influx and cell membrane potential, reported by fluorescent Tl-sensitive Fluozin-2 and voltage-sensitive bis-(1,3-dibutylbarbituric acid)trimethine oxonol (DiBAC4(3)) dyes, respectively, were used to assess channel activity. In the Tl-influx assay, CS-associated Kir6.1 mutations increased sensitivity to the ATP-sensitive potassium (KATP) channel activator, pinacidil, but there was strikingly little effect of pinacidil for any SUR2B mutations, reflecting unexpected differences in the molecular mechanisms of Kir6.1 versus SUR2B mutations. Compared with the Tl-influx assay, the DiBAC4(3) assay presents more significant signal changes in response to subtle KATP channel activity changes, and all CS mutants (both Kir6.1 and SUR2B), but not WT channels, caused marked hyperpolarization, demonstrating that all mutants were activated under ambient conditions in intact cells. Most SUR2 CS mutations were markedly inhibited by <100 nM glibenclamide, but sensitivity to inhibition by glibenclamide, repaglinide, and PNU37883A was markedly reduced for Kir6.1 CS mutations. Understanding functional consequences of mutations can help with disease diagnosis and treatment. The analysis pipeline we have developed has the potential to rapidly identify mutational consequences, aiding future CS diagnosis, drug discovery, and individualization of treatment. SIGNIFICANCE STATEMENT: We have developed new fluorescence-based assays of channel activities and drug sensitivities of Cantú syndrome (CS) mutations in human Kir6.1/SUR2B-dependent KATP channels, showing that Kir6.1 mutations increase sensitivity to potassium channel openers, while SUR2B mutations markedly reduce K channel opener (KCO) sensitivity. However, both Kir6.1 and SUR2B CS mutations are both more hyperpolarized than WT cells under basal conditions, confirming pathophysiologically relevant gain-of-function, validating DiBAC4(3) fluorescence to characterize hyperpolarization induced by KATP channel activity under basal, non KCO-activated conditions.

Pregabalin can interact synergistically with Kv7 channel openers to exert antinociception in mice

Chronic pain is a common public health problem and remains an unmet medical need. Currently available analgesics usually have limited efficacy for the treatment of chronic pain, including neuropathic pain and persistent inflammatory pain, or they are accompanied by many adverse side effects. The voltage-gated calcium channel blocker (pregabalin) and potassium channel openers (flupirtine and retigabine) have been widely used for the management of chronic pain, but their effectiveness in combination is unclear. In this research, we evaluated the antinociceptive effects of pregabalin in combination with flupirtine or retigabine in carrageenan-induced inflammatory pain and paclitaxel-induced peripheral neuropathy in mice using the von Frey test. Isobolographic analysis indicated that pregabalin exerted synergistic antinociceptive effects when combined with flupirtine or retigabine in neuropathic and inflammatory pain models. Furthermore, the antinociceptive effects of pregabalin, flupirtine/retigabine, and their combinations were significantly attenuated by the Kv7 channel blocker XE991. The favored dose ratio between pregabalin and flupirtine/retigabine in combinations was also investigated. Finally, we evaluated the motor coordination of their combinations using the rotarod test, and the outcomes underpinned their safety. Collectively, our results support the potential use of pregabalin in combination with flupirtine or retigabine to alleviate chronic pain.

Kir1.1 and SUR1 are not implicated as subunits of an adenosine triphosphate-sensitive potassium channel involved in diazoxide cardioprotection

ObjectiveThe adenosine triphosphate-sensitive potassium channel opener diazoxide mimics ischemic preconditioning and is cardioprotective. Clarification of diazoxide's site and mechanism of action could lead to targeted pharmacologic therapies for patients undergoing cardiac surgery. Several mitochondrial candidate proteins have been investigated as potential adenosine triphosphate-sensitive potassium channel components. Renal outer medullary potassium (Kir1.1) and sulfonylurea sensitive regulatory subunit 1 have been suggested as subunits of a mitochondrial adenosine triphosphate-sensitive potassium channel. We hypothesized that pharmacologic blockade or genetic deletion (knockout) of renal outer medullary potassium and sensitive regulatory subunit 1 would result in loss of diazoxide cardioprotection in models of global ischemia with cardioplegia. MethodsMyocyte volume and contractility were compared after Tyrode's physiologic solution (20 minutes), stress (hyperkalemic cardioplegia ± diazoxide, ± VU591 (Kir1.1 inhibitor), N = 9 to 23 each, 20 min), and Tyrode's (20 minutes). Isolated mouse (wild-type, sensitive regulatory subunit 1 [−/−], and cardiac knockout renal outer medullary potassium) hearts were given cardioplegia ± diazoxide (N = 9-16 each) before global ischemia (90 minutes) and 30 minutes reperfusion. Left ventricular pressures were compared before and after ischemia. ResultsStress (cardioplegia) was associated with reduced myocyte contractility that was prevented by diazoxide. Isolated myocytes were not responsive to diazoxide in the presence of VU591. In isolated hearts, diazoxide improved left ventricular function after prolonged ischemia compared with cardioplegia alone in wild-type and knockout (sensitive regulatory subunit 1 [−/−] and cardiac knockout renal outer medullary potassium) mice. ConclusionsIsolated myocyte and heart models may measure independent and separate actions of diazoxide. By definitive genetic deletion, these data indicate that sensitive regulatory subunit 1 and renal outer medullary potassium are not implicated in cardioprotection by diazoxide.

Ancient medicinal plant rosemary contains a highly efficacious and isoform-selective KCNQ potassium channel opener

Voltage-gated potassium (Kv) channels in the KCNQ subfamily serve essential roles in the nervous system, heart, muscle and epithelia. Different heteromeric KCNQ complexes likely serve distinct functions in the brain but heteromer subtype-specific small molecules for research or therapy are lacking. Rosemary (Salvia rosmarinus) is an evergreen plant used medicinally for millennia for neurological and other disorders. Here, we report that rosemary extract is a highly efficacious opener of heteromeric KCNQ3/5 channels, with weak effects on KCNQ2/3. Using functional screening we find that carnosic acid, a phenolic diterpene from rosemary, is a potent, highly efficacious, PIP2 depletion-resistant KCNQ3 opener with lesser effects on KCNQ5 and none on KCNQ1 or KCNQ2. Carnosic acid is also highly selective for KCNQ3/5 over KCNQ2/3 heteromers. Medicinal chemistry, in silico docking, and mutagenesis reveal that carboxylate-guanidinium ionic bonding with an S4-5 linker arginine underlies the KCNQ3 opening proficiency of carnosic acid, the effects of which on KCNQ3/5 suggest unique therapeutic potential and a molecular basis for ancient neurotherapeutic use of rosemary.

The nitric oxide-cyclic GMP-KATP channels pathway contributes to the effects of montelukast against gastric damage induced by ethanol

The leukotrienes, lipid mediators, have a role in gastric damage induced by ethanol. Here, the gastroprotective effect of montelukast, an antagonist of the leukotriene receptor, and the involvement of the NO-cGMP-KATP channel pathway, were evaluated in gastric damage induced by ethanol in rats. For this, l-arginine, l-NAME, methylene blue (guanylate cyclase inhibitor), sildenafil, diazoxide, or glibenclamide (ATP-sensitive potassium channel blocker) were administered 30 min before montelukast (0.1, 1, 10, and 20 mg/kg, by mouth [p.o.]). After 1 h, to induce gastric damage, the rats received absolute ethanol (4 mL/kg, p.o.), and then microscopic, macroscopic, and pro-inflammatory parameters (TNF-α and IL-1β) were assessed. Results obtained here revealed that montelukast significantly attenuated the macroscopic and microscopic lesions induced by ethanol. Montelukast also reduced IL-1β and TNF-α levels. It was also observed that NOS inhibitor (l-NAME), methylene blue, and glibenclamide inhibited the effects of montelukast in the stomach. Moreover, the NO precursor (l-arginine), the PDE-5 inhibitor (sildenafil), and a potassium channel opener (diazoxide) before montelukast produced gastroprotective effects. In conclusion, the effect of montelukast against gastric lesions induced by ethanol is mediated, at least in part, through the pathway of the NO-cGMP-KATP channel.

Structure-Activity Relationships of Flupirtine Analogues for the Liver Esterase-mediated Cleavage of the 4-Fluorobenzylamine Moiety and its possible Relevance to Liver Toxicity.

Flupirtine and retigabine were essential drugs to combat pain and epilepsy. However, the Kv7 potassium channel openers are fraught with hepatotoxicity and tissue discoloration, respectively, limiting their therapeutic value. Both adverse events are likely due to reactive metabolites arising from oxidative metabolism. Designing safer analogues lacking the structural elements leading to described side effects is an active area of current research. One of the main metabolites of flupirtine is the biologically inactive 4-fluorohippuric acid. Hitherto unexplained, the proposed metabolic pathway leading to the formation of 4-fluorohippuric acid from flupirtine is verified here. Through the use of eighteen flupirtine analogues, mechanistic details of this pathway could be elucidated. A possible connection with the in vitro hepatotoxicity of the flupirtine analogues and the levels of 4-fluorobenzoic acid formed in enzyme incubations was examined by correlation analysis. These findings provide important information for the design of new flupirtine analogues as potential drug candidates.

Suppression of the excitability of rat nociceptive secondary sensory neurons following local administration of the Phytochemical, (-)-Epigallocatechin-3-gallate

The phytochemical, polyphenolic compound, (-)-epigallocatechin-3-gallate (EGCG), is the main catechin found in green tea. Although a modulatory effect of EGCG on voltage-gated sodium and potassium channels has been reported in excitable tissues, the in vivo effect of EGCG on the excitability of nociceptive sensory neurons remains to be determined. Our aim was to investigate whether local administration of EGCG to rats attenuates the excitability of nociceptive spinal trigeminal nucleus caudalis (SpVc) neurons in response to mechanical stimulation in vivo. Extracellular single unit recordings were made from SpVc neurons in response to orofacial mechanical stimulation of anesthetized rats. The mean firing frequency of SpVc wide-dynamic range neurons following both non-noxious and noxious mechanical stimuli was significantly inhibited by EGCG in a dose-dependent and reversible manner. The mean magnitude of inhibition by EGCG on SpVc neuronal discharge frequency was similar to that of the local anesthetic, 1% lidocaine. Local injection of half-dose of lidocaine replaced the half-dose of EGCG. These results suggest that local injection of EGCG suppresses the excitability of nociceptive SpVc neurons, possibly via the inhibition of voltage-gated sodium channels and opening of voltage-gated potassium channels in the trigeminal ganglion. Therefore, administration of EGCG as a local anesthetic may provide relief from trigeminal nociceptive pain without side effects.

Metabolomics analysis in rat hearts with ischemia/reperfusion injury after diazoxide postconditioning.

Background: Diazoxide is a selective mitochondrial-sensitive potassium channel opening agent that has a definite effect on reducing myocardial ischemia/reperfusion injury (MIRI). However, the exact effects of diazoxide postconditioning on the myocardial metabolome remain unclear, which might contribute to the cardioprotective effects of diazoxide postconditioning. Methods: Rat hearts subjected to Langendorff perfusion were randomly assigned to the normal (Nor) group, ischemia/reperfusion (I/R) group, diazoxide (DZ) group and 5-hydroxydecanoic acid + diazoxide (5-HD + DZ) group. The heart rate (HR), left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), and maximum left ventricular pressure (+dp/dtmax) were recorded. The mitochondrial Flameng scores were analysed according to the ultrastructure of the ventricular myocardial tissue in the electron microscopy images. Rat hearts of each group were used to investigate the possible metabolic changes relevant to MIRI and diazoxide postconditioning. Results: The cardiac function indices in the Nor group were better than those in the other groups at the end point of reperfusion, and the HR, LVDP and +dp/dtmax of the Nor group at T2 were significantly higher than those of the other groups. Diazoxide postconditioning significantly improved cardiac function after ischaemic injury, and the HR, LVDP and +dp/dtmax of the DZ group at T2 were significantly higher than those of the I/R group, which could be abolished by 5-HD. The HR, LVDP and +dp/dtmax of the 5-HD + DZ group at T2 were significantly lower than those of the DZ group. The myocardial tissue in the Nor group was mostly intact, while it exhibited considerable damage in the I/R group. The ultrastructural integrity of the myocardium in the DZ group was higher than that in the I/R and 5-HD + DZ groups. The mitochondrial Flameng score in the Nor group was lower than that in the I/R, DZ and 5-HD + DZ groups. The mitochondrial Flameng score in the DZ group was lower than that in the I/R and 5-HD + DZ groups. Five metabolites, namely, L-glutamic acid, L-threonine, citric acid, succinate, and nicotinic acid, were suggested to be associated with the protective effects of diazoxide postconditioning on MIRI. Conclusion: Diazoxide postconditioning may improve MIRI via certain metabolic changes. This study provides resource data for future studies on metabolism relevant to diazoxide postconditioning and MIRI.