Mitochondrial ATP-sensitive Potassium Channel Research Articles

Mechanistic Pathways of ATP Sensitive Potassium Channels Referring to Cardio-Protective Effects and Cellular Functions.

A study of potassium channels correlates the fundamentals of mechanistic pathways and various physiological functions. The knowledge of these pathways provides the background, how to determine unit cell functions and to affect cardio protection. ATP sensitive potassium channels adjust excitability of membrane and functions as per metabolic status of cell. A lot of energy consumption primarily occurred in skeletal muscles which also express high number of potassium channels. The increase in calcium release and high heat production is occurred due to loss of potassium channels. Such type of mediations determines metabolic changes and energy required in the dissipation. IPC reduces infarct size in anesthetized mice. In ischemic-reperfusion, pressure in left ventricle was watched while contractile power recovery did not happen. It was seen that elements of intact potassium channel are fundamental for Ischemic preconditioning (IPC). If more prominent is enactment of potassium channels and their cardiologic effects create high heart rate. All the more as of late, it has been suggested that mitochondrial ATP sensitive potassium channels are critical as closing stage effectors which trigger IPC as opposed to sarcolemmal potassium channels. Nevertheless, the importance of the potassium channels reconsidered in cardio-protection in present findings. These discoveries recommend that potassium channels in the adjusting ischemic-reperfusion damage in mice. The heart rate of the mouse occurred during ischemia; enhance watchful extrapolation applied to larger warm blooded animals.

Effects of mitochondrial ATP-sensitive potassium channel activation (nicorandil) in patients with angina pectoris undergoing elective percutaneous coronary interventions: A meta-analysis of randomized controlled trials.

Nicorandil, which is a mitochondrial ATP-sensitive potassium channel opener, is believed to improve perioperative myocardial injury (PMI) in patients undergoing percutaneous coronary intervention (PCI), but recent studies have shown that nicorandil treatment did not improve functional and clinical outcomes in patients with angina pectoris who underwent elective PCI. We performed a meta-analysis to investigate the protective effect of nicorandil on perioperative injury in patients with angina pectoris who underwent elective PCI. The Medline, EMBASE, and Cochrane databases were searched for randomized clinical trials examining the effects of nicorandil. Two investigators independently selected suitable trials, extracted data, and assessed trial quality. Seven studies of patients undergoing elective PCI, comprising a total of 979 patients, were included in this review. The results showed that nicorandil did not reduce the levels of markers of myocardial injury (standardized mean difference [SMD] 0.31 [95%CI -0.6, 1.22] for creatine kinase-MB [CK-MB] and 1.29 [95%CI -2.18, 4.76] for troponin I [TNI]), perioperative complications (relative risk [RR] 0.91 [95%CI 0.46-1.81]), target vessel revascularization (RR 0.79 [95%CI 0.50-1.25]) or major adverse cardiac events (MACE) (RR 0.83 [95%CI 0.49-1.43]). Nicorandil did reduce the corrected TIMI frame count (SMD-0.30 [95%CI -0.52, -0.09]). Although nicorandil did not reduce the overall incidence of perioperative complications and the incidence of major adverse cardiac events (MACE) in patients with angina pectoris who underwent elective PCI, it could still improve no reflow and slow coronary flow.

Hypoxic Preconditioning Attenuates Reoxygenation-Induced Skeletal Muscle Dysfunction in Aged Pulmonary TNF-α Overexpressing Mice

Aim: Skeletal muscle subjected to hypoxia followed by reoxygenation is susceptible to injury and subsequent muscle function decline. This phenomenon can be observed in the diaphragm during strenuous exercise or in pulmonary diseases such as chronic obstructive pulmonary diseases (COPD). Previous studies have shown that PO2 cycling or hypoxic preconditioning (HPC), as it can also be referred to as, protects muscle function via mechanisms involving reactive oxygen species (ROS). However, this HPC protection has not been fully elucidated in aged pulmonary TNF-α overexpressing (Tg+) mice (a COPD-like model). We hypothesize that HPC can exert protection on the diaphragms of Tg+ mice during reoxygenation through pathways involving ROS/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/extracellular signal regulated kinase (ERK), as well as the downstream activation of mitochondrial ATP-sensitive potassium channel (mitoKATP) and inhibition of mitochondrial permeability transition pore (mPTP).Methods: Isolated Tg+ diaphragm muscle strips were pre-treated with inhibitors for ROS, PI3K, Akt, ERK, or a combination of mitoKATP inhibitor and mPTP opener, respectively, prior to HPC. Another two groups of muscles were treated with either mitoKATP activator or mPTP inhibitor without HPC. Muscles were treated with 30-min hypoxia, followed by 15-min reoxygenation. Data were analyzed by multi-way ANOVA and expressed as means ± SE.Results: Muscle treated with HPC showed improved muscle function during reoxygenation (n = 5, p < 0.01). Inhibition of ROS, PI3K, Akt, or ERK abolished the protective effect of HPC. Simultaneous inhibition of mitoKATP and activation of mPTP also diminished HPC effects. By contrast, either the opening of mitoKATP channel or the closure of mPTP provided a similar protective effect to HPC by alleviating muscle function decline, suggesting that mitochondria play a role in HPC initiation (n = 5; p < 0.05).Conclusion: Hypoxic preconditioning may protect respiratory skeletal muscle function in Tg+ mice during reoxygenation through redox-sensitive signaling cascades and regulations of mitochondrial channels.

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.

Diazoxide induces endoplasmic reticulum stress-related neuroprotection mediated by p38 MAPK against Aβ25-35 insults.

The endoplasmic reticulum (ER) -resident caspase-12 was identified as a mediator of Aβ neurotoxicity. Recent evidence indicates that mitochondrial ATP-sensitive potassium (KATP) channel openers mediate their neuroprotective role by adjusting ER stress pathways, but the molecular details remain largely unknown and have been investigated. In this study, the protein expression levels of calreticulin (CRT) and caspase-12 activation and phosphorylated p38 MAPK were observed by immunoblotting in cultured PC12 cells from different groups: treatment with Aβ25-35 (group Aβ25-35), treatment with diazoxide (group diazoxide), pretreatment with diazoxide and then exposure to Aβ25-35 (group diazoxide + Aβ25-35), pretreatment with p38 MAPK inhibitor SB 203580 and then exposure to diazoxide and Aβ25-35 (group SB 203580 + diazoxide + Aβ25-35), and the control (group control). In response to the treatment with Aβ25-35 (10 µM) for 24 h, the protein expression levels of CRT and caspase-12 activation were increased and phosphorylated p38 MAPK was decreased significantly. Diazoxide reduced CRT overexpression and caspase-12 activation and increased the up-regulation of phosphorylated p38 MAPK. When SB 203580 was presented before exposure to diazoxide and Aβ25-35, CRT expression was markedly suppressed, and the inhibition effect of diazoxide on caspase-12 activation was almost eliminated. We showed that diazoxide induced ERS-related neuroprotection mediated by p38 MAPK against Aβ25-35 insults. From the clinical point of view, these results are of considerable importance for the understanding of AD pathogenesis. However, further studies are required to explore more detailed mechanisms of the observed effects.

Opening of mitoKATP improves cardiac function and inhibits apoptosis via the AKT-Foxo1 signaling pathway in diabetic cardiomyopathy.

Decreasing phosphorylation of AKT-Foxo1 is closely associated with the onset of insulin resistance and apoptosis during diabetic cardiomyopathy (DCM). Opening of mitochondrial ATP-sensitive potassium channels (mitoKATP) increases the expression of p-AKT in the process of reperfusion injury. It was therefore hypothesized that opening of mitoKATP may regulate the AKT-Foxo1 signaling pathway and improve cardiac function in DCM. In the present study, opening of mitoKATP by diazoxide (DZX) was found to improve cardiac function and attenuate cardiomyocyte apoptosis in db/db mice. DZX also significantly increased the expression of p-AKT and p-Foxo1. Similarly, DZX decreased the expression of the heart failure marker NT-proBNP, increased mitochondrial membrane potential, inhibited apoptosis, and increased the expression of p-AKT and p-Foxo1 when mimicking insulin resistance in cultured cardiomyocytes. Moreover, the protective effects of DZX were completely blocked by the specific AKT inhibitor MK-2206. These data suggest that the regulation of the AKT-Foxo1 signaling pathway by mitoKATP plays an important role in improving cardiac function and inhibiting apoptosis in DCM, and may therefore be a new potential therapeutic target for DCM.

"Malignant" right coronary artery presenting as an ST-segment elevation myocardial infarction-a case report.

BackgroundIschemia/reperfusion injury (IRI) is an inflammatory response that occurs when tissue is reperfused following a prolonged period of ischemia. Several studies have indicated that C-reactive protein (CRP) might play an important role in inducing IRI. However, the effects of CRP on myocardial IRI and the underlying mechanisms have not been fully elucidated. This study aimed to investigate the association between CRP and myocardial IRI and the underlying mechanisms.MethodsWe simulated ischemia/reperfusion using oxygen-glucose deprivation/ reoxygenation (OGD/R) in neonatal Sprague-Dawley rat cardiomyocytes; reperfusion injury was induced by three hours of hypoxia with glucose and serum deprivation followed by one hour of reperfusion. Cell viability was tested with MTS assays, and cardiomyocyte damage was evaluated by lactate dehydrogenase (LDH) leakage. Mitochondrial membrane potential was measured using tetramethylrhodamine ethyl ester (TMRE) and mitochondrial permeability transition pore (mPTP) opening was measured using calcein/AM; both TMRE and caocein/AM were visualized with laser scanning confocal microscopy. In addition, we studied the signaling pathways underlying CRP-mediated ischemia/reperfusion injury via Western blot analysis.ResultsCompared with the simple OGD/R group, after intervention with 10 µg/mL CRP, cell viability decreased markedly (82.36 % ± 6.18% vs. 64.84% ± 4.06%, P = 0.0007), and the LDH leakage significantly increased (145.3 U/L ± 16.06 U/L vs. 208.2 U/L ± 19.23 U/L, P = 0.0122). CRP also activated mPTP opening and reduced mitochondrial membrane potential during myocardial ischemia/reperfusion. Pretreatment with 1 µM atorvastatin (Ator) before CRP intervention protected cardiomyocytes from IRI. Mitochondrial KATP channel opener diazoxide and mPTP inhibitor cyclosporin A also offset the effects of CRP in this process. The level of phosphorylated extracellular-signal-regulated kinase (ERK) 1/2 was significantly higher after pre-treatment with CRP compared with the OGD/R group (170.4% ± 3.00% vs. 93.53% ± 1.94%, P < 0.0001). Western blot analysis revealed that Akt expression was markedly activated (184.2% ± 6.96% vs. 122.7% ± 5.30%, P = 0.0003) and ERK 1/2 phosphorylation significantly reduced after co-treatment with Ator and CRP compared with the level after CRP pretreatment alone.ConclusionsOur results suggested that CRP directly aggravates myocardial IRI in myocardial cells and that this effect is primarily mediated by inhibiting mitochondrial ATP-sensitive potassium (mitoKATP) channels and promoting mPTP opening. Ator counteracts these effects and can reduce CRP-induced IRI. One of the mechanisms of CRP-induced IRI may be related to the sustained activation of the ERK signaling pathway.

The effect of the KATP channel opener Nicorandil in lipid‐peroxidation in skeletal muscle atrophy

Muscle atrophy is defined as a decrease muscle tissue size due to cellular shrinkage caused by loss of organelles, cytoplasm and proteins. The main characteristic of this pathology is the increase in protein degradation and a decrease in protein re‐synthesis. It has been documented that the mitochondrial ATP sensitive potassium channel (mitoKATP), is involved in the resistance of the muscle fatigue and recovery from ischemia‐reperfusion injury and protection during atrophy process; Nicorandil has been described as a selective mitoKATP opener which confers protection to muscle during stressful conditions, the aim of this study was to determine the protective effect of Nicorandil over the damage caused by atrophy.C57BL/6 male mice 14–16 weeks‐old were used for the experimental basis; these animals were separated into 4 groups: 1) Control, 2) Nicorandil, 3) Atrophy and 4) Atrophy treated with Nicorandil. Atrophy was induced by hindlimb unloading by the tail method. Nicorandil was purveying in 40 mg/kg doses by intramuscular injection during 14 days. Once finished the treatment, the animals were sacrificed by cervical dislocation and the hindlimb were used for mitochondria isolation, once obtained the isoled mitochondria the lipid‐peroxidation was measured by the TBARS method. This reaction was measured in a Spectrophotometer Perkin Elmer Lambda 18 UV/VIS in ʎ of 523 nm. The results were for the group Nicorandil was higher against the Control group 50.5827%, the Atrophy group was 53.03% against the Control group, and the Nicrandil+Atrophy group had an increase in the activity against the Control group.Lipid‐peroxidation had been used as a marker of oxidative stress, as we know, this has been stablished that atrophy leads to an accumulation of toxic substances as reactive oxygen species, like we observe here the Nicorandil treatment has no effect in healthy mice but the opening of this channel downregulates lipid oxidation in the atrophied that can give us a thought of cytoprotection.Support or Funding InformationRMP‐CIC2017This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Mitochondrial ATP-sensitive potassium channel regulates mitochondrial dynamics to participate in neurodegeneration of Parkinson's disease

Parkinson's disease (PD) is the second most common age-related neurodegenerative disease. Mitochondrial dysfunction has been the focus of the pathogenesis of PD. The mitochondrial ATP-sensitive potassium channel (mitoKATP) plays a significant role in mitochondrial physiology and has been extensively shown to protect against ischemic and brain reperfusion injury. However, there have long been controversies regarding its role in Parkinson's disease. We investigated the role of mitoKATP channels in rotenone-induced PD model in vivo and vitro and the interactions of mitoKATP channels, mitochondrial dynamics and PD. The results indicated that the use of diazoxide to activate mitoKATP channels resulted in the aggravation of rotenone-induced dopamine neurodegeneration in PC12 cells and SD rats. In contrast, the use of 5-hydroxydecanoate (5-HD) to inhibit mitoKATP channels improved rotenone-induced dopamine neurodegeneration, which was not consistent with mitoKATP channels in ischemic and brain reperfusion injury. Further analysis determined that the mitoKATP channel was involved in PD mainly via the regulation of mitochondrial biogenesis and fission/fusion. And the pore subunits of Kir6.1, the major component of mitoKATP channels, was the key contributor in its interaction with mitochondrial dynamics in rotenone-induced dopamine neurodegeneration. Therefore, it can be concluded that mitoKATP channels regulate mitochondrial dynamics to participate in rotenone-induced PD mainly attributes to the pore subunits of Kir6.1. And additionally, though mitoKATP channels may represent a direction of one potential target for neuroprotection, it should be noted that the effects are different in the activation or inhibition of mitoKATP channels in different models.

Role of mitochondrial ATP-sensitive potassium channels in dexmedetomidine-induced attenuation of myocardial ischemia-reperfusion injury in rats

Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mito-KATP) channels in dexmedetomidine-induced attenuation of myocardial ischemia-reperfusion (I/R) injury in rats. Methods Forty pathogen-free healthy male Sprague-Dawley rats, aged 8-12 weeks, weighing 200-350 g, were divided into 5 groups (n=8 each) using a random number table: sham operation group (group S), I/R group, dexmedetomidine group (group DEX), a specific mito-KATP channel blocker 5-hydroxydecanoate (5-HD) group (group 5-HD) and dexmedetomidine plus 5-HD group (group DEX+ 5-HD). Myocardial I/R was produced by occlusion of the anterior descending branch of the left coronary artery for 30 min followed by 120 min reperfusion in pentobarbital sodium-anesthetized rats.Dexmedetomidine 5 μg/kg was intraperitoneally injected at 15 min prior to reperfusion in group DEX.5-HD 40 mg/kg was intraperitoneally injected at 30 min prior to reperfusion in group 5-HD.In group DEX+ 5-HD, 5-HD 40 mg/kg and dexmedetomidine 5 μg/kg were intraperitoneally injected at 30 and 15 min prior to reperfusion, respectively.The parameters of cardiac function such as left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and the maximum rate of increase or decrease in left ventricular pressure (±dp/dtmax) were recorded before ischemia (T0) and at 60 and 120 min of reperfusion (T1, 2). Blood samples were collected from the carotid artery at the end of reperfusion for determination of the concentrations of creatine kinase-MB (CK-MB) and cardiac troponin I (cTnI) in serum.The animals were then sacrificed, and hearts were removed for determination of the myocardial infarct size in the left ventricular myocardial tissues. Results Compared with group S, the LVSP and ±dp/dtmax were significantly decreased, and the LVEDP was increased at T1-2, and the concentrations of CK-MB and cTnI in serum and myocardial infarct size were increased in the other groups (P 0.05). Compared with group DEX, the LVSP and ±dp/dtmax were significantly decreased, and the LVEDP was increased at T1-2, and the concentrations of CK-MB and cTnI in serum and myocardial infarct size were increased in DEX+ 5-HD group (P<0.05). Conclusion The mechanism by which dexmedetomidine attenuates myocardial I/R injury is partially related to promotion of mito-KATP channel opening in rats. Key words: KATP channels; Dexmedetomidine; Myocardial reperfusion injury

MitoKATP channels promote the proliferation of hypoxic human pulmonary artery smooth muscle cells via the ROS/HIF/miR-210/ISCU signaling pathway.

Previous results have indicated that mitochondrial ATP-sensitive potassium (mitoKATP) channels are associated with the hypoxic proliferation of pulmonary artery smooth muscle cells (PASMCs). However, the mechanism underlying the promotive effects of mitoKATP channels on cell proliferation in response to hypoxia remains unknown. mitoKATP channel opening results in a collapse of mitochondrial membrane potential and generation of mitochondrial reactive oxygen species (ROS). As hypoxia-inducible factor-1α (HIF-1α) is a critical oxygen sensor and major transcriptional regulator of the hypoxic adaptive response, the current study assessed whether mitoKATP opening contributes to the chronic proliferation of human PASMCs (hPASMCs) in collaboration with HIF-1α and its downstream targets under hypoxic conditions. The present study demonstrated that there was crosstalk between mitoKATP channels and HIF-1α signaling in PASMCs under hypoxic conditions. The results suggest that mitoKATP channels are involved in the proliferation of PASMCs during hypoxia through upregulation of the ROS/HIF/microRNA-210/iron-sulfur cluster protein signaling pathway.

Diazoxide prevents H2O2-induced chondrocyte apoptosis and cartilage degeneration in a rat model of osteoarthritis by reducing endoplasmic reticulum stress

Osteoarthritis (OA) is a common disease affecting elderly individuals. Its incidence rises sharply with age, and chondrocyte apoptosis plays a vital role in its pathogenesis. Diazoxide opens mitochondrial ATP-sensitive potassium (mitoKATP) channels and exerts multiple pharmacological effects, including reductions in blood pressure and blood sugar levels. It also exerts anti-apoptotic activities, but the cellular and molecular mechanisms by which diazoxide inhibits chondrocyte apoptosis are unknown, as is whether apoptosis is related to endoplasmic reticulum stress (ERS). In the present study, we explored the mechanism underlying the chondroprotective effect of diazoxide on hydrogen peroxide (H2O2)-stimulated chondrocyte apoptosis in rats with surgically induced OA. A cell counting kit-8 (CCK-8) assay showed that the viability of H2O2-stimulated chondrocytes was enhanced in a dose-dependent manner. However, at a concentration ≥400μM, diazoxide had other, negative effects. The protective effect of diazoxide in vitro included inhibition of the ERS response and of mitochondrial dysfunction induced by H2O2 stimulation. These responses were related to activation of the PERK1/2 and ERK1/2 signaling pathways; the prevention of chondrocyte apoptosis; the down-regulation of caspase-3, Bax, ATF-6 and C/EBP-homologous protein (CHOP) expression; and the up-regulation of Bcl-2 and Col II. In vivo, histological and immunohistochemical analyses of caspase-3 and CHOP expression revealed that diazoxide ameliorated cartilage degeneration in a rat model of OA, as revealed by histological and immunohistochemical analyses of caspase-3 and CHOP expression. Diazoxide suppressed H2O2-triggered chondrocyte apoptosis, and ameliorated cartilage degeneration, by inhibiting the development of ERS.

Diazoxide Attenuates Ischemic Myocardial Injury in a Porcine Model.

We hypothesized that diazoxide, a mitochondrial ATP-sensitive potassium channel opener, has cardioprotective effects during acute myocardial ischemia. Diazoxide is suggested to act through protein kinase Cε (PKCε) activation. Twelve piglets were randomly assigned to receive intravenous infusion of diazoxide (3.5 mg/kg) with solvent or only solvent (6 animals per group) before cardiac ischemia. Myocardial ischemia was induced by occluding the left circumflex artery (LCX) for 40 minutes. The reperfusion and follow-up period lasted for three hours. Throughout the experiment hemodynamic measurements and blood samples were collected, and after the follow-up period the hearts were harvested for transmission electron microscopy (TEM) as well as histopathological and immunohistochemical analyses. TEM showed less ischemic damage on a cellular level in the diazoxide group (P = .004) than in the control group. Creatinine kinase MB levels (Pt*g = .030) were lower, and oxygen consumption (Pt*g = .037) and delivery (Pg = .038) were higher in the diazoxide group compared to the controls. Diazoxide preserves myocardial cellular structure and cellular function, and thus it may have benefits in treating ischemic myocardial injury.

Role of mito-KATP channels in sevoflurane postconditioning-induced inhibition of oxygen-glucose deprivation and restoration-induced pyroptosis in primary rat cardiomyocytes

Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mito-KATP) channels in sevoflurane postconditioning-induced inhibition of oxygen-glucose deprivation and restoration (OGD/R)-induced pyroptosis in primary rat cardiomyocytes. Methods Cardiomyocytes of newborn Sprague-Dawley rats (<48 h after birth) were cultured in vitro and seeded in 6-well dishes (2 cm in diameter) or in 96-well plates.The cells were divided into 6 groups (n=15 each) using a random number table: control group (group C), OGD/R group (group O), sevoflurane postconditioning group (group Sev), sevoflurane postconditioning plus 5-hydroxydecanoate (5-HD) group (group SH), 5-HD group (group H) and OGD/R plus 5-HD group (group HO). The cardiomyocytes were subjected to oxygen-glucose deprivation for 4 h followed by restoration of oxygen-glucose supply for 24 h. After oxygen-glucose restoration, the cardiomyocytes in the culture media were exposed to 2% sevoflurane for 1 h to perform sevoflurane postconditioning.At 1 h before oxygen-glucose deprivation, a specific mito-KATP channel blocker 5-HD 100 μmol/L was added to the culture media.Cardiomyocytes were cultured in normal culture atmosphere in group C. Cardiomyocytes were collected at 24 h of oxygen-glucose restoration.Cell pyroptosis was detected by double flow cytometry AlexaFour488 (caspase-1 FLICA staining) and TMR red (DNA staining) staining.The pyroptosis rate was calculated.The cell survival rate was measured by methyl thiazolyl tetrazolium assay.The content of reactive oxygen species (ROS) in mitochondria was determined by 2′, 7′-dichlorofluorescin diacetate assay.The mitochondrial membrane potential (MMP) was measured by using JC-1 fluorescent probe.The expression of interleukin-1beta (IL-1β) was determined by Western blot. Results Compared with group C, the pyroptosis rate and ROS content were significantly increased, the cell survival rate and MMP were decreased, and the expression of IL-1β was up-regulated in group O (P<0.05). Compared with group O, the pyroptosis rate and ROS content were significantly decreased, the cell survival rate and MMP were increased, and the expression of IL-1β was down-regulated in group Sev (P<0.05). Compared with group Sev, the pyroptosis rate and ROS content were significantly increased, the cell survival rate and MMP were decreased, and the expression of IL-1β was up-regulated in group SH (P<0.05). Compared with group SH, the pyroptosis rate and ROS content were significantly increased, the cell survival rate and MMP were decreased, and the expression of IL-1β was up-regulated in group HO (P<0.05). Conclusion The mechanism by which sevoflurane postconditioning inhibits OGD/R-induced pyroptosis in primary rat cardiomyocytes is probably associated with increasing mito-KATP channel opening. Key words: Anesthetics, inhalation; Anoxia; Myocytes, cardiac; Cell death; Postconditioning

Role of mitochondrial ATP-sensitive potassium channel in reduction of myocardial ischemia-reperfusion injury by calcitonin gene-related peptide in rats: an in vitro experiment

Objective To evaluate the role of the mitochondrial ATP-sensitive potassium (mito-KATP) channel in reduction of myocardial ischemia-reperfusion (I/R) injury by calcitonin gene-related peptide (CGRP) in rats in an in vitro experiment. Methods Healthy adult male Sprague-Dawley rats, weighing 250-300 g, were used in this study.After the animals were anesthetized, their hearts were immediately removed and retrogradely perfused with oxygenated K-H solution at 37 ℃ in a Langendorff apparatus.Twenty-four isolated rat hearts were assigned into 4 groups (n=6 each) using a random number table: control group (C group), I/R group, CGRP group and 5-hydroxydecanoate (5-HD) group.The hearts were first perfused with K-H solution for 30 min in the three groups.The hearts were continuously perfused with K-H solution for 150 min in group C. The hearts were subjected to ischemia for 30 min followed by 120 min of reperfusion to establish the model of myocardial I/R injury.In group CGRP, after the hearts were perfused with K-H solution for 10 min, 10-8 mol/L CGRP was infused for 20 min at a rate of 0.5 ml/min via the aorta, and then the model of myocardial I/R injury was established.In 5-HD group, specific mito-KATP channel blocker 5-HD 100 μmol/L was infused for 10 min at a rate of 0.5 ml/min via the aorta, and the other treatments were similar to those previously described in CGRP group.At the end of equilibration and 30, 60, 90 and 120 min of reperfusion, heart rate (HR), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and the maximum rate of increase or decrease in left ventricular pressure (±dp/dtmax) were recorded.The myocardial infarct size was measured by 2, 3, 5-triphenyltetrazolium chloride staining at 120 min of reperfusion. Results Compared with C group, HR, LVSP and ±dp/dtmax were significantly decreased and LVEDP was increased during reperfusion, and the percentage of myocardial infarct size was increased at 120 min of reperfusion in the other three groups (P<0.05). Compared with I/R group, HR, LVSP and ±dp/dtmax were significantly increased and LVEDP was decreased during reperfusion, and the percentage of myocardial infarct size was decreased at 120 min of reperfusion in CGRP group (P<0.05). Compared with CGRP group, HR, LVSP and ±dp/dtmax were significantly decreased and LVEDP was increased during reperfusion, and the percentage of myocardial infarct size was increased at 120 min of reperfusion in 5-HD group (P<0.05). Conclusion Opening of mito-KATP channels is involved in CGRP-induced reduction of myocardial I/R injury in rats in an in vitro experiment. Key words: Calcitonin gene-related peptide; Myocardial reperfusion injury; Mitochondria; KATP channels

Research progress of the protection mechanism of sevoflurane postconditioning to cerebral ischemia/reperfusion injury

Background Cerebral ischemia/reperfusion injury(CI/RI) may be occur in the patients during subarachnoid hemorrhage, severe brain injury, cerebral infarction and hemorrhagic shock. Sevoflurane postconditioning which is in accordance with the pathophysiologic process in timing sequence and as a novel method of potential value for cerebral protection, have attracted extensive attention in recent years. Objective This paper reviewed the mechanisms of sevoflurane postconditioning against CI/RI. Content Phosphatidylinositol 3-kinase, protein kinase(PI3K/Akt), oxidativestress, mitochondrial ATP-sensitive potassium channel(mitoKATP), mitochondrial permeability transition pore(mPTP), extracellular signaling-regulated kinase 1/2(ERK1/2) are involved in neuroprotection by sevoflurane postconditioning under the setting of CI/RI. Trend To understand the mechanisms of sevoflurane postconditioning against CI/RI, and provide a theoretical basis for better treatment of CI/RI. Key words: Sevoflurane; Postconditioning; Cerebral; Ischemia/reperfusion injury; Protection mechanism

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

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

Mitochondrial ATP-Sensitive Potassium Channels Play a Role in Reducing Both Myocardial Infarction and Reperfusion Arrhythmia in Remote Ischemic Preconditioned Hearts.

BackgroundMitochondrial ATP-sensitive potassium (mKATP) channels play a role in reperfusion arrhythmias (RAs) in ischemia-reperfusion (I/R) injury. Evidence suggests that remote ischemic preconditioning (RIPC) reduces RAs, however not much is known on the mechanistic role of mKATP in RIPC. We evaluated whether mKATP channels are associated with reducing arrhythmia and infarct size in RIPC.MethodsIsolated rat hearts received 30 minutes of regional ischemia followed by 2 hours of reperfusion through the Langendorff perfusion system. RIPC was induced by 3 cycles of 5 minutes occlusion and 5 minutes release of the bilateral femoral artery. The animals were randomly divided into 4 groups as follows: 1) CON, I/R injury but not RIPC, 2) RIPC, 3) HD+RIPC, pretreatment of the selective mKATP channel blocker, 5-hydroxydecanoate (5-HD), in RIPC, and 4) HD, pretreatment of 5-HD in CON. Cardiodynamics and infarct size were determined. The severity of arrhythmia was quantitated via the Curtis and Walker scoring system as well as the Lepran scoring system.ResultsRIPC significantly reduced the infarct size over AR (25.7 ± 2.6%) compared to CON (37.0 ± 2.6%, P < 0.05). The selective mKATP channel blocker 5-HD significantly inhibited the infarct-reducing effect of RIPC (39.3 ± 3.0%, P < 0.05 vs. RIPC). Additionally, RIPC significantly reduced the arrhythmia score compared to CON (14.6 ± 1.9 to 8.7 ± 0.4, P = 0.023, by Curtis and Walker’s system, 16.1 ± 2.1 to 9.1 ± 0.5, P = 0.006, by Lepran’s system). The anti-arrhythmic effect of RIPC was blocked by 5-HD (15.5 ± 1.6 and 16.0 ± 1.2, by Curtis and Walker’s and Lepran’s system, respectively).ConclusionsThe selective mKATP channel blocker, 5-HD, inhibited the infarct-limitation and anti-arrhythmic effect of RIPC. The mKATP channels play a role in the reduction of both infarct size and RAs in RIPC.

Direct and Off-Target Effects of ATP-Sensitive Potassium Channels Opener Diazoxide

Diazoxide (DZ) is a well-known cardioprotective drug capable of mimicking ischemic preconditioning. Being primarily a pharmacological opener of mitochondrial ATP-sensitive potassium channels (mKATP channels), DZ is known to produce multiple side effects because of its interactions with different cellular targets (such as plasma membrane KATP channels, F0F1 ATP synthase, succinate dehydrogenase and others), capable of confounding an understanding of direct bioenergetic effects of mKATP channels opening in mitochondria. In this review direct and offtarget effects of DZ were discussed. The emphasis was made on molecular basis of DZ interaction with KATP channels and different KATP channels isoforms sensitivity to this drug. The present knowledge on DZ interaction with mKATP channels is outlined as well as DZ interactions with other molecular targets affecting mitochondrial functions and bioenergetics. Conclusion was reached that high sensitivity of mKATP channel to DZ allows for avoiding offtarget effects of this drug in studies on isolated mitochondria, which makes it a useful tool in an appraisal of diverse functional effects of mKATP channel opening.

Effect of dexmedetomidine on cerebral ischemia-reperfusion rats by activating mitochondrial ATP-sensitive potassium channel.

The aim of the study reported here was to evaluate whether the mitochondrial ATP-sensitive potassium (mitoKATP) channel could participate in the effect of dexmedetomidine on cerebral ischemia-reperfusion (I/R) rats. Forty rats were randomly assigned into 5 groups: sham operation (S) group; cerebral I/R group; dexmedetomidine (D) group; 5-hydroxydecanoate (5-HD) group; 5-HD+D group. The cerebral I/R were produced by 2h right middle cerebral artery occlusion followed by 24h reperfusion. Dexmedetomidine (50μg/kg) was injected intraperitoneally before ischemia and after the onset of reperfusion. 5-HD (30mg/kg) was injected intraperitoneally at 1h before ischemia. The neurological deficit score (NDS) and the levels of super oxide dismutase (SOD), malondialdehyde (MDA), myeloperoxidase (MPO), Interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α) were evaluated. Compared to group S, NDS and the levels of MDA, MPO, IL-6 and TNF-α were significantly higher, and SOD levels were significantly lower in the other groups (P<0.05). Compared to group I/R,NDS and the levels of MDA, MPO, IL-6 and TNF-α were significantly lower, and SOD level was significantly higher in group D (P<0.05). Compared to group D, NDS and the levels of MDA, MPO, IL-6 and TNF-α were significantly higher, and SOD level was significantly lower in group5-HD+D (P<0.05). The activation of the mitoKATP channel could contribute to the protective effect of dexmedetomidine on rats induced by focal cerebral ischemia-reperfusion injury.