Adenosine Triphosphate-sensitive Potassium Channels Research Articles

Expression and influence of KATP in umbilical artery smooth muscle cells of patients with hypertensive disorders of pregnancy

The objective of this study is to investigate the expression and influence of adenosine triphosphate-sensitive potassium channel (KATP) in human umbilical arterial smooth muscle cells (HUASMCs) of patients with hypertensive disorders of pregnancy (HDP). Western blotting was used to detect the protein expression levels of KATP inwardly rectifying potassium channel (Kir)6.1 and sulphonylurea receptor (SUR)2B subunits in HUASMCs from patients with normal parturients (NP), gestational hypertension (GH), chronic hypertension (CH), preeclampsia (PE) and chronic hypertension with superimposed preeclampsia (CHSP), respectively. There was no significant difference in the protein expression of Kir6.1 subunit in NP group, GH group, CH group, PE group and CHSP group (P > 0.05). The protein expression of SUR2B subunit was gradually decreased in NP group, GH group, CH group, PE group and CHSP group, with statistically significant difference among the groups (P < 0.05). The altered expression level of KATP SUR2B subunit may be involved in the pathogenesis of HDP. The severity of HDP may be related to the degree of decrease of SUR2B subunit.

Vascular contraction of umbilical arteries of pregnant women with preeclampsia.

Potassium channels have an important role in the vascular adaptation during pregnancy and a reduction in the expression of adenosine triphosphate-sensitive potassium channels (Katp) has been linked to preeclampsia. Activation of Katp induces vasodilation; however, no previous study has been conducted to evaluate the effects of the inhibition of these channels in the contractility of preeclamptic arteries. Glibenclamide is an oral antihyperglycemic agent that inhibits Katp and has been widely used in vascular studies. To investigate the effects of the inhibition of Katp, umbilical arteries of preeclamptic women and women with healthy pregnancies were assessed by vascular contractility experiments, in the presence or absence of glibenclamide. The umbilical arteries were challenged with cumulative concentrations of potassium chloride (KCl) and serotonin. There were no differences between the groups concerning the maternal age and gestational age of the patients. The percentage of smokers, caucasians and primiparae per group was also similar. On the other hand, blood pressure parameters were elevated in the preeclamptic group. In addition, the preeclamptic group presented a significantly higher body mass index. The newborns of both groups presented similar APGAR scores and weights. In the presence of glibenclamide, there was an increase in the KCl-induced contractions only in vessels from the PE group, showing a possible involvement of these channels in the disorder.

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.

Direct and indirect activation of the adenosine triphosphate-sensitive potassium channel to induce spinal cord ischemic metabolic tolerance.

The mitochondrial adenosine triphosphate-sensitive potassium channel is central to pharmacologically induced tolerance to spinal cord injury. We hypothesized that both direct and nitric oxide-dependent indirect activation of the adenosine triphosphate-sensitive potassium channel contribute to the induction of ischemic metabolic tolerance. Spinal cord injury was induced in adult male C57BL/6 mice through 7minutes of thoracic aortic crossclamping. Pretreatment consisted of intraperitoneal injection 3 consecutive days before injury. Experimental groups were sham (no pretreatment or ischemia, n=10), spinal cord injury control (pretreatment with normal saline, n=27), Nicorandil 1.0mg/kg (direct and indirect adenosine triphosphate-sensitive potassium channel opener, n=20), Nicorandil 1mg/kg+carboxy-PTIO 1mg/kg (nitric oxide scavenger, n=21), carboxy-PTIO (n=12), diazoxide 5mg/kg (selective direct adenosine triphosphate-sensitive potassium channel opener, n=25), and DZ 5mg/kg+carboxy-PTIO 1mg/kg, carboxy-PTIO (n=23). Limb motor function was assessed using the Basso Mouse Score (0-9) at 12-hour intervals for 48hours after ischemia. Motor function was significantly preserved at all time points after ischemia in the Nicorandil pretreatment group compared with ischemic control. The addition of carboxy-PTIO partially attenuated Nicorandil's motor-preserving effect. Motor function in the Nicorandil+carboxy-PTIO group was significantly preserved compared with the spinal cord injury control group (P<.001), but worse than in the Nicorandil group (P=.078). Motor preservation in the diazoxide group was similar to the Nicorandil+carboxy-PTIO group. There was no significant difference between the diazoxide and diazoxide+carboxy-PTIO groups. Both direct and nitric oxide-dependent indirect activation of the mitochondrial adenosine triphosphate-sensitive potassium channel play an important role in pharmacologically induced motor function preservation.

Targeted gene panel analysis of Japanese patients with maturity-onset diabetes of the young-like diabetes mellitus: Roles of inactivating variants in the ABCC8 and insulin resistance genes.

To investigate the genetic background of Japanese patients with suspected maturity-onset diabetes of the young (MODY). On 340 proband patients referred from across Japan, genomic variants were analyzed using a targeted multigene panel analysis combined with the multiplex ligation probe amplification (MLPA) analysis, mitochondrial m.3243A > G analysis and methylation-specific polymerase chain reaction of the imprinted 6q24 locus. Pathogenic/likely pathogenic variants were listed according to the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology criteria. Additionally, variants with a population frequency <0.001 and Combined Annotation Dependent Depletion score >20 (CS >20) were listed as rare variants of uncertain significance-CS >20. A total of 157 pathogenic/likely pathogenic variants and 44 rare variants of uncertain significance-CS >20 were identified. In the pathogenic/likely pathogenic variants, alterations in the GCK gene were the most common (82, 52.2%) followed by HNF1A (29,18.5%), HNF4A (13, 8.3%) and HNF1B (13, 8.3%). One patient was a 29.5% mosaic with a truncating INSR variant. In the rare variants of uncertain significance-CS >20, 20 (45.5%) were in the genes coding for the adenosine triphosphate-sensitive potassium channel, KCNJ11 or ABCC8, and four were in the genes of the insulin-signaling pathway, INSR and PIK3R1. Four variants in ABCC8 were previously reported in patients with congenital hyperinsulinism, suggesting the inactivating nature of these variants, and at least two of our patients had a history of congenital hyperinsulinism evolving into diabetes. In two patients with INSR or PIK3R1 variants, insulin resistance was evident at diagnosis. Causative genomic variants could be identified in at least 46.2% of clinically suspected MODY patients. ABCC8-MODY with inactivating variants could represent a distinct category of MODY. Genes of insulin resistance should be included in the sequencing panel for MODY.

Comparison of Mitochondrial Adenosine Triphosphate–Sensitive Potassium Channel High- vs Low-Affinity Sulfonylureas and Cardiovascular Outcomes in Patients With Type 2 Diabetes Treated With Metformin

Sulfonylureas are frequently used as add-on to metformin in type 2 diabetes (T2D), and individual sulfonylurea agents carry different risks of cardiovascular disease. Sulfonylureas' different affinities to cardiac mitochondrial adenosine triphosphate-sensitive potassium (mitoKATP) channels have been speculated to account for the intraclass difference in cardiovascular risk from in vitro and ex vivo studies; however, this hypothesis has not been assessed in a general population with diabetes receiving sulfonylureas added to metformin. To compare the risk of myocardial infarction (MI), ischemic stroke, or cardiovascular death in patients with T2D treated with mitoKATP channel high-affinity sulfonylureas and low-affinity sulfonylureas as add-on to metformin. This is a new-user, active-comparator, and propensity score-matched cohort study with analysis of the Taiwanese Diabetes Mellitus Health Database from 2006, to 2017. Data analysis was performed from August 2020 to July 2021. Cardiac mitoKATP channel high-affinity (glyburide and glipizide) and low-affinity (gliclazide and glimepiride) sulfonylureas combined with metformin. Primary outcome was major adverse cardiovascular events (MACEs), a composite of cardiovascular death or hospitalization for either MI or ischemic stroke. Secondary outcomes included individual MACE components, heart failure, arrhythmia, all-cause mortality, and severe hypoglycemia. Cox proportional hazards models were used to estimate adjusted hazard ratios (aHRs). Each sulfonylurea group comprised 53 714 patients (mean [SD] age, 54.7 [12.1] years; 31 962 men [59.5%]). MitoKATP channel high-affinity sulfonylureas vs low-affinity sulfonylureas when combined with metformin were associated with an increased risk of MACE (aHR, 1.18; 95% CI, 1.03-1.34), MI (aHR, 1.34; 95% CI, 1.04-1.73), all-cause mortality (aHR, 1.27; 95% CI, 1.03-1.57), and severe hypoglycemia (aHR, 1.82; 95% CI, 1.58-2.10), but not with increased risks of ischemic stroke, cardiovascular death, arrhythmia, and heart failure. The duration analyses revealed the highest MACE risk during 1 to 90 days after initiation of mitoKATP channel high-affinity sulfonylureas (aHR, 6.06; 95% CI, 4.86-7.55). Use of mitoKATP channel high-affinity sulfonylureas vs low-affinity sulfonylureas was associated with an increased MACE risk in patients with T2D concomitantly receiving metformin, suggesting that high-affinity blockage of the mitoKATP channels could account for sulfonylurea-associated MACEs.

Abstract 15530: Renal Outer Medullary Potassium (Kir 1.1) is not the Kir Subunit of a Cardioprotective, Diazoxide - Mediated Mitochondrial Adenosine Triphosphate - Sensitive Potassium Channel

Objective: The adenosine triphosphate-sensitive potassium (K ATP ) channel opener diazoxide (DZX) mimics ischemic preconditioning and is cardioprotective. The molecular mechanism of action is unknown, although several mitochondrial candidate protein targets have been proposed. We suggested that cardioprotection occurs at a non-sarcolemmal channel, requires the inhibition of succinate dehydrogenase, and involves K ATP channel subunit SUR1. The renal outer medullary potassium channel (ROMK, or Kir1.1) subunit was proposed as the Kir subunit of a mitochondrial (m)K ATP channel. We tested the hypothesis that genetic deletion of ROMK will result in loss of DZX cardioprotection in a model of prolonged ischemia with cardioplegia. Methods: Mice lacking ROMK in cardiac myocytes (cKO) and wild-type (WT) litter mates were randomly assigned to 90 min. global ischemia in a Langendorff model following hypothermic hyperkalemic cardioplegia (CPG) or CPG + DZX (100 μM/L) (N=6-9 per group). Left ventricular developed pressure (LVDP), end diastolic pressure (EDP), and coronary flow were compared before and after global ischemia. Data acquisition and interpretation were blinded to group. Results: Similar to previous results, prolonged global ischemia was associated with a reduction in LVDP and an increase in EDP with CPG that was prevented by DZX in WT. Unexpectedly, ROMK (cKO) mice were equally responsive to DZX (Figure), indicating that DZX protection is not mediated by ROMK channels. Conclusions: Genetic deletion of ROMK in cardiac myocytes does not negate cardioprotection provided by DZX, indicating ROMK is not a subunit of a cardioprotective mK ATP channel. Alternate proposed DZX-sensitive target channels or mechanisms of action remain to be tested. Identification of the specific subunits of a mK ATP channel would allow for targeted pharmacologic therapy to reduce myocardial stunning following prolonged ischemia, similar to that seen following cardiac surgery.

Hyper-glycemia and insulinemia induce morphological changes and modulate secretion of S100B, S100A8, amyloid β 1–40 and amyloid β 1–42, in a model of human dopaminergic neurons

Glucose metabolism in neuronal tissue declines during neurodegenerative disorders in a progressive, region-specific, and disease-specific manner. Studies have shown that extracellular hyper-glycemia affects the functioning of adenosine triphosphate (ATP) sensitive potassium channels located in neurons and astrocytes. Also, hyper-insulinemia contributes to the formation and progression of Alzheimer’s disease (AD) via competition with amyloid β (Aβ) for insulin-degrading enzyme. Aβ disruption is phosphatidylinositol 3-kinase pathway dependent, and increased circulatory insulin concentrations lead to Aβ accumulation. In 2008, based on assessment of brain glucose utilization disorders and insulin signaling disruptions, it was proposed that AD could be called "type III diabetes". Proteins from the S100 family are actively secreted during metabolic and oxidative stress, but their role in neuronal cells has yet to be clarified. However, it has been demonstrated that they act in a dose-dependent manner, which may be crucial in the modulation of glucose and insulin metabolism in the brain. The goal of this paper was to elucidate the association between high glucose and insulin concentrations with extra- and intracellular S100B and S100A8 proteins levels as well as the correlation with toxic (Aβ42) and physiologic (Aβ40) forms of Aβ. Medium and high glucose concentrations mimicking pre-diabetic and diabetic state, caused statistically significant discharge of S100b and S100A8 protein to the extracellular compartment. Similar effect was observed after 50 nM insulin incubation. Furthermore, the correlation coefficient patterns between those proteins shows similar associations which highlights possible effective and modulating role of S100 family in the metabolic disturbances occurring in neuropathological disorders.

Nicorandil attenuates ventricular dysfunction and organ injury after cardiopulmonary bypass

BackgroundNicorandil, an adenosine triphosphate-sensitive potassium channel agonist and nitric oxide donor, is a coronary vasodilator used to treat ischemia-induced chest pain, but it's potential cardioprotective benefits during open heart surgery have not been thoroughly investigated. The study objective was to assess the impact of nicorandil on postoperative ventricular dysfunction and end-organ injury in an established experimental model of open-heart surgery with cardiopulmonary bypass (CPB) and cardioplegic arrest. We hypothesized that nicorandil would attenuate myocardial ischemia-reperfusion (IR) injury, preserve ventricular function, and reduce end-organ injury. MethodsRabbits were cannulated for CPB, followed by 60 min of aortic cross-clamp (ACC) with cold cardioplegic arrest, and 120 min of recovery after ACC removal. Nicorandil (or normal saline vehicle) was given intravenously 5 min before ACC and continued throughout the recovery period. Left ventricular developed pressure (LVDP), systolic contractility (LV + dP/dt), and diastolic relaxation (LV -dP/dt) were continuously recorded, and blood and tissue samples were collected for measurement of oxidant stress (OS), inflammation, apoptosis, and organ injury. ResultsNicorandil significantly attenuated IR-induced LV dysfunction compared to saline control (R-120: LV + dP/dt: 1596 ± 397 vs. 514 ± 269 mmHg/s, p = 0.010; LV -dP/dt: −1524 ± 432 vs. -432 ± 243 mmHg/s, p < 0.001; LVDP: 55 ± 11 vs. 22 ± 5 mmHg, p = 0.046). Furthermore, nicorandil inhibited IR-induced increases in OS, inflammation, apoptosis, and organ injury. ConclusionsNicorandil exhibits myocardial protection by attenuation of IR-induced LV dysfunction associated with OS, inflammation, apoptosis, and organ injury. Nicorandil should be explored further as a potential therapeutic strategy for limiting global IR injury during open-heart surgery in humans.

Cardioprotective mechanisms of mitochondria-targeted S-nitrosating agent and adenosine triphosphate-sensitive potassium channel opener are mutually exclusive

BackgroundMyocytes exposed to stress exhibit significant swelling and reduced contractility. These consequences are ameliorated by adenosine triphosphate–sensitive potassium (KATP) channel opener diazoxide (DZX) via an unknown mechanism. KATP channel openers also provide cardioprotection in multiple animal models. Nitric oxide donors are similarly cardioprotective, and their combination with KATP activation may provide synergistic benefit. We hypothesized that mitochondria-targeted S-nitrosating agent (MitoSNO) would provide synergistic cardioprotection with DZX. MethodsMyocyte volume and contractility were compared following Tyrode's physiologic solution (20 minutes) and stress (hyperkalemic cardioplegia [CPG] ± DZX; n = 5-20 each; 20 minutes) with or without MitoSNO (n = 5-11 each) at the end of stress, followed by Tyrode's solution (20 minutes). Isolated mouse hearts received CPG ± DZX (n = 8-10 each) before global ischemia (90 minutes) with or without MitoSNO (n = 8 each) at the end of ischemia, followed by reperfusion (30 minutes). Left ventricular (LV) pressures were compared using a linear mixed model to assess the impact of treatment on the outcome, adjusting for baseline and balloon volume. ResultsStress (CPG) was associated with reduced myocyte contractility that was prevented by DZX and MitoSNO individually; however, their combination was associated with loss of cardioprotection. Similarly, DZX and MitoSNO improved LV function after prolonged ischemia compared with CPG alone, and cardioprotection was lost with their combination. ConclusionsMitoSNO and DZX provide cardioprotection that is lost with their combination, suggesting mutually exclusive mechanisms of action. The lack of a synergistic beneficial effect informs the current knowledge of the cardioprotective mechanisms of DZX and will aid planning of future clinical trials.

Clinical and Genetic Analysis of KATP Variants With Heart Failure Risk in Patients With Decreased Serum ApoA-I Levels.

Lower serum concentration of apolipoprotein A-I (ApoA-I) is causally associated with heart failure (HF) risk. Adenosine triphosphate-sensitive potassium channels (KATP), as gating channels coupling vascular reactivity and metabolism with ischemic protection, become a new potential target of management for HF. The KATP gene sequence is highly polymorphic and has a high degree of genetic heterogeneity. This work aimed to determine whether KATP variants predict the risks of decreased ApoA-I concentration and its related HF. A total of 634 individuals, including 317 patients with decreased ApoA-I concentration (< 120 mg/dL) and 317 counterpart participants (≥ 120 mg/dL), were retrospectively selected. Five KATP variants were genotyped through the MassARRAY platform. Exosome-derived microRNAs (exo-miRs) expression profiles were identified by next-generation sequencing, and the top 10 differentially expressed (DE) exo-miRs were verified using quantitative polymerase chain reaction in a validation cohort of 240 individuals with decreased ApoA-I concentration. KATP rs141294036 was related to an increased risk of lower ApoA-I levels (adjusted odds ratio [OR] = 1.95, P = .002) and HF incidence (adjusted OR = 2.38, P = .009), especially heart failure with preserved ejection fraction (HFpEF; adjusted OR = 2.13, P = .015). After a median 48.6-month follow-up, participants carrying the CC genotype of rs141294036 were associated with an elevated HF rehospitalization risk (adjusted hazard ratio = 1.91, P = .005). Thirty-six exo-miRs were significantly DE between different genotypes of rs141294036 in participants with lower ApoA-I levels, but only 5 exo-miRs (miR-31-5p, miR-126-5p, miR-106a-5p, miR-378i, and miR-181c-5p) were further confirmed. KATP rs141294036 was associated with increased risks of lower ApoA-I levels, HF incidence (especially HFpEF), and HF rehospitalization in those with the 5 confirmed exo-miRs and its related metabolic pathways.

Alterations in pore-forming subunits of adenosine triphosphate-sensitive potassium channels in pressure overload rat cardiomyocytes.

Adenosine triphosphate (ATP)-sensitive potassium channels (KATP) link cellular metabolic state and electrical activity of cardiomyocytes. Pharmacological studies indicated the involvement of KATP in pressure overload-induced left ventricular hypertrophy, but the alteration of pore-forming subunits, Kir6.1 and Kir6.2, at membranes and subcellular fractions is unclear. The objective of this study was to investigate the changes in the distribution and levels of Kir6.1 and Kir6.2 in rat cardiomyocytes responding to chronic pressure overload. Male Wistar rats were separated into a sham-operated group (sham) and a pressure overload or transverse aortic constriction (TAC) group. Echocardiography was performed to assess cardiac structure and functions at the 4th month after operation. Ventricular cardiomyocytes in both groups were isolated and then subjected to extract protein into cytoplasm, organelle membrane, and plasma membrane fractions. Immunoblotting and immunohistochemistry techniques were performed to detect and measure Kir6.1 and Kir6.2 protein levels. Echocardiographic parameters showed left ventricular hypertrophy with hypercontractility in TAC rats. The immunoblotting showed the presence of Kir6.1 and Kir6.2 at plasma membranes and only Kir6.1 at organelle membranes. Significantly, Kir6.1 and Kir6.2 levels were decreased in the plasma membrane fraction of the TAC group (n = 8 and 6 for Kir6.1 and Kir6.2, respectively), whereas Kir6.1 in the organelle membrane fraction tended to be higher in TAC but did not reach statistical significance (n = 7). These results seemed to relate to a left ventricular immunohistochemistry study, which showed the trend of decreased staining of Kir6.1 and Kir6.2 in pressure overload left ventricular tissue. In conclusion, both Kir6.1 and Kir6.2 plasma membrane subunits were decreased significantly in pressure overload-induced left ventricular hypertrophy.

Abstract 15316: Paradoxical Reduction in Myocardial Performance When Combining Two Independently Cardioprotective Agents: Mitochondrial-targeted Antioxidant MitoSNO and Adenosine Triphosphate-sensitive Potassium Channel Opener Diazoxide

Introduction: Adenosine triphosphate-sensitive potassium (K ATP ) channel opener diazoxide (DZX) and Antioxidant MitoSNO are both independently cardioprotective in animal models. The cardioprotective mechanism of diazoxide is unknown, and involves a non-sarcolemmal location, requires the inhibition of succinate dehydrogenase, and the K ATP channel subunit SUR1. Mitochondrial - targeted Antioxidant MitoSNO is a S-nitrosylating agent that stalls complex 1, reduces ROS production and succinate accumulation. In an isolated myocyte model of stress due to hyperkalemic cardioplegia (CPG), that the combination of DZX and MitoSNO negated the beneficial effects of each alone. Hypothesis: We hypothesized that the combination of DZX and MitoSNO would negate the beneficial effects of each alone in an isolated heart model of global ischemia. Methods: Isolated mouse hearts underwent assessment of end diastolic pressure (EDP) and left ventricular developed pressure (LVDP) utilizing an LV balloon in a Langendorff model before and after 90 min of global ischemia. Hearts received test solution (CPG (9°C) or CPG±DZX (100μM) at onset of ischemia +/- MitoSNO (1μM/L) at end of ischemia), followed by 30 min reperfusion. LVDP and EDP were compared between groups utilizing a linear mixed model to assess the impact of treatment on the outcome, adjusting for baseline and balloon volume. Results: Similar to previous results, DZX improved LVDP and reduced EDP after ischemia compared to CPG (Figure). Similarly, MitoSNO improved LVDP and reduced EDP compared to CPG (Figure). The addition of MitoSNO with DZX was associated with the loss of cardioprotection observed with MitoSNO or DZX alone. Conclusions: Similar to data in a myocyte model, both MitoSNO and DZX provide cardioprotection that is lost with the combination of both, suggesting mutually exclusive mechanisms of action and that DZX’s mechanism requires a functional complex 1, ROS production, or succinate accumulation.

Reactive Oxygen Species Mediate Nicorandil-induced Metabolic Tolerance to Spinal Cord Injury

Spinal cord injury remains a devastating complication of thoracoabdominal aortic surgery. We previously demonstrated that pretreatment with nicorandil preserved motor function in a murine spinal cord injury model through mitochondrial adenosine triphosphate-sensitive potassium channel activation. We hypothesized that the neuroprotective effect of nicorandil is mediated by downstream generation of reactive oxygen species. Spinal cord injury was induced by 7 minutes of thoracic aortic cross-clamping in adult male C57BL/6 mice. Five groups were evaluated: ischemic control (n= 19); nicorandil 1.0 mg/kg (n= 17); nicorandil 1.0 mg/kg plus N acetyl L-cysteine (NAC [reactive oxygen species scavenger, n= 18)]) 150 mg/kg; NAC 150 mg/kg (n= 13); and sham (n= 10). Limb motor function and the number of viable neurons within the anterior horn of the spinal cord were evaluated. Mice in the sham group showed no functional deficits after surgery. Compared with ischemic control, motor function was significantly preserved in the nicorandil pretreatment group at every timepoint after ischemia. In the nicorandil plus NAC group, the motor-preserving effect of nicorandil was completely abolished (P < .001). Viable neuron quantification showed significant neuron preservation in the nicorandil group (29.± 2.6) compared with the ischemic control group (18.5 ± 2.1, P= .024) and nicorandil plus NAC group (14 ± 8.3, P= .001); no significant difference was observed between the ischemic control group and nicorandil plus NAC group (P= 0.768). Reactive oxygen species generation plays a key role in the nicorandil-induced metabolic tolerance to spinal cord injury. Manipulation of mitochondrial adenosine triphosphate-sensitive potassium channels may lead to improvement in preventing spinal cord injury after thoracoabdominal aortic interventions.

Effects of nicorandil on p120 expression in the spinal cord and dorsal root ganglion of rats with chronic postsurgical pain.

Chronic postsurgical pain (CPSP) has a high incidence, but the underlying mechanism is not well understood. Accumulating evidence has suggested that central sensitization is the main mechanism of pain. To study the role of p120 in CPSP, a skin/muscle incision and retraction (SMIR) model was established, and immunofluorescence staining and western blotting were performed to analyze the expression of p120 in the spinal cord and dorsal root ganglion (DRG). The results demonstrated that SMIR increased the expression of p120 in the DRG and the spinal cord compared with the naive group. Furthermore, it was demonstrated that p120 was mainly distributed in the glial fibrillary acidic protein-positive astrocytes in the spinal cord, and in the neurofilament 200-positive medium and large neurons in the DRG. Our previous studies have shown that adenosine triphosphate-sensitive potassium channel (KATP) agonists can reduce postoperative pain in rats. Therefore, the changes in p120 were observed in the DRG and spinal cord of rats following the intraperitoneal injection of nicorandil, a KATP agonist. It was demonstrated that nicorandil administration could relieve mechanical pain experienced following SMIR in rats, and decrease the expression of p120 in the DRG and spinal cord. The results revealed that p120 may contribute to the prophylactic analgesic effect of nicorandil, thus providing a novel insight into the mechanism of CPSP prevention.

Regulation of the KATP-JNK gap junction signaling pathway by immunomodulator astragaloside IV attenuates neuropathic pain

Background and objectivesGap junctions play a pivotal role in contributing to the formation of astroglial networks and in chronic pain. However, the mechanisms underlying the dysfunction of astroglial gap junctions...

Diazoxide Protects against Myocardial Ischemia/Reperfusion Injury by Moderating ERS via Regulation of the miR-10a/IRE1 Pathway.

Nowadays, reperfusion is still the most effective treatment for ischemic heart disease. However, cardiac reperfusion therapy would lead to reperfusion injury, which may have resulted from endoplasmic reticulum stress (ERS) during reperfusion. Diazoxide (DZ) is a highly selective mitochondrial adenosine triphosphate-sensitive potassium channel opener. Its protective effect on I/R injury has been confirmed in many organs such as the heart and brain. However, the mechanism of its protective effect has not been fully elucidated. MicroRNAs (miRNAs) are widely involved in pathologies of heart disease. In this study, we found that miR-10a expression was highly upregulated in the myocardial I/R groups, and DZ treatment significantly reduced the expression of miR-10a. More importantly, we found that DZ treatment can moderate ERS via regulation of the miR-10a/IRE1 pathway in the I/R and H/R models, thereby protecting myocardial H/R injury.

Role of Adenosine Triphosphate Sensitive Potassium Channels in Glucocorticoid Induced Myopathy of a Rat Model

Objective: To clarify adenosine triphosphate sensitive potassium (KATP ) channels' role in glucocorticoid induced myopathy induction. Materials and methods: 48 adult male rats divided into two experiments. Experiment Ⅰ: 32 rats divided equally into four group; Group Ⅰ: control group, Group Ⅱ: (Dexa group) (Dexamethasone 500 μg/kg once daily i.p), Group ΙΙΙ (Dexa+ Nicorandil) (Nicorandil (3 mg/kg) per oral once daily), Group ΙV (Dexa+Glibenclamide) (Glibenclamide (10 mg/kg) per oral once daily) all for 10 days. By the end of the experiment, blood samples were collected for blood glucose, serum insulin, potassium and creatine kinase-MM. Tibialis anterior muscles were isolated for contractility recording, oxidative stress measurement, histopathological examination and immunohistochemistry for insulin like growth factor-1(IGF-1). Experiment Ⅱ:16 rats (8 normal and 8 glucocorticoid induced myopathy rats). From each rat, the tibialis anterior was isolated and incubated with nicorandil (100 μmol /L for 10 minutes) and glibenclamide (1μmol /L for 5 minutes) for contractility recording. Results: Contractile properties, histopathological changes and IGF-1 muscle expression are improved with glibenclamide (KATP channel blocker) and worsened with nicorandil (KATP channel opener). CK-MM level significantly increased with nicorandil, while normal with glibenclamide. Serum potassium and blood glucose significantly increased with nicorandil and decreased with glibenclamide. Serum insulin significantly decreased with nicorandil and increased with glibenclamide. The oxidative stress state insignificantly changed with both drugs (p value ≤0.05 was considered to be statistically significant). Conclusion: Opening of KATP channels seems to have a role in the induction of glucocorticoid-induced myopathy probably by decreasing IGF-1 expression.

ATP sensitive potassium (KATP) channel inhibition: A promising new drug target for migraine.

Recently, the adenosine triphosphate (ATP) sensitive potassium channel opener levcromakalim was shown to induce migraine attacks with a far higher incidence than any previous provoking agent such as calcitonin gene-related peptide. Here, we show efficacy of ATP sensitive potassium channel inhibitors in two validated rodent models of migraine. In female spontaneous trigeminal allodynic rats, the sensitivity of the frontal region of the head was tested by an electronic von Frey filament device. In mice, cutaneous hypersensitivity was induced by repeated glyceryl trinitrate or levcromakalim injections over nine days, as measured with von Frey filaments in the hindpaw. Release of calcitonin gene-related peptide from dura mater and trigeminal ganglion was studied ex vivo. The ATP sensitive potassium channel inhibitor glibenclamide attenuated the spontaneous cephalic hypersensitivity in spontaneous trigeminal allodynic rats and glyceryl trinitrate-induced hypersensitivity of the hindpaw in mice. It also inhibited CGRP release from dura mater and the trigeminal ganglion isolated from spontaneous trigeminal allodynic rats. The hypersensitivity was also diminished by the structurally different ATP sensitive potassium channel inhibitor gliquidone. Mice injected with the ATP sensitive potassium channel opener levcromakalim developed a progressive hypersensitivity that was completely blocked by glibenclamide, confirming target engagement. The results suggest that ATP sensitive potassium channel inhibitors could be novel and highly effective drugs in the treatment of migraine.

The Possible Role of the Nitroso-Sulfide Signaling Pathway in the Vasomotoric Effect of Garlic Juice.

The beneficial cardiovascular effects of garlic have been reported in numerous studies. The major bioactive properties of garlic are related to organic sulfides. This study aimed to investigate whether garlic juice works exclusively due to its sulfur compounds or rather via the formation of new products of the nitroso-sulfide signaling pathway. Changes in isometric tension were measured on the precontracted aortic rings of adult normotensive Wistar rats. We evaluated NO-donor (S-nitrosoglutathione, GSNO)-induced vasorelaxation and compare it with effects of hydrogen sulfide (H2S)/GSNO and garlic/GSNO. Incubation with garlic juice increased the maximal GSNO-induced relaxation and markedly changed the character of the relaxant response. Although incubation with an H2S donor enhanced the maximal vasorelaxant response of GSNO, neither the absolute nor the relative relaxation changed over time. The mixture of GSNO with an H2S donor evoked a response similar to GSNO-induced relaxation after incubation with garlic juice. This relaxation of the H2S and GSNO mixture was soluble guanylyl cyclase (sGC) dependent, partially reduced by HNO scavenger and it was adenosine triphosphate-sensitive potassium channels (KATP) independent. In this study, we demonstrate for the first time the suggestion that H2S itself is probably not the crucial bioactive compound of garlic juice but rather potentiates the production of new signaling molecules during the GSNO-H2S interaction.