Protective effects of hydrogen­rich saline against experimental diabetic peripheral neuropathy via activation of the mitochondrial ATP­sensitive potassium channel channels in rats.

It has previously been demonstrated that hyperglycemia­induced oxidative stress and inflammation are closely associated with the development of diabetic complications, including diabetic neuropathy. Additionally, mitochondrial ATP­sensitive potassium (Mito­K­ATP) channels play a homeostatic role on blood glucose regulation in organisms. Molecular hydrogen (H2) exhibits anti­inflammatory, anti­antioxidative and anti­apoptotic properties and can be used to treat more than 71 diseases safely. In addition, the diabetes animal models which are set up using streptozotocin (STZ) injection, is a type of high long­term stability, low animal mortality rate and security method. The aim of the current study was to assess the value of hydrogen­rich saline (HS) in diabetic peripheral neuropathy (DPN) treatment and to determine its associated mechanisms in STZ­induced diabetic experimental rats. Additionally, the effects of the Mito­K­ATP channels, oxidative stress, inflammatory cytokines and apoptosis on DPN were also evaluated. From week 5 of STZ injections, HS (2.5, 5 and 10 ml/kg) was injected into the rat abdominal cavity every day for a period of 4 weeks. The results of the current study demonstrated that HS significantly reduced behavioral, biochemical and molecular effects caused by DPN. However, 5­hydroxydecanoate, a selective Mito­K­ATP channels general pathway inhibitor, partially eliminated the therapeutic effect of HS on DPN. These results indicated that the use of HS may be a novel strategy to treat DPN by activating the Mito­K­ATP pathway and reducing oxidative stress, inflammatory cytokines and apoptosis.

Effect of Exercise Preconditioning on Cell Apoptosis and Expression of Mitochondrial ATP-sensitive Potassium Channels Proteins in Rats after Cerebral Ischemia-reperfusion / 中国康复理论与实践

@#Objective To explore the effect and mechanism of exercise preconditioning on neurological deficits in rats after cerebral ischemia-reperfusion. Methods Thirty-six healthy Sprague-Dawley rats were randomly divided into sham group (n=12), model group (n=12) and exercise preconditioning group (n=12). The latter two groups were occluded middle cerebral artery for 120 minutes and reperfused with modified suture method. The rats were evaluated with Longa's score two, twelve and 24 hours after reperfusion. The expression of mitochondrial ATP-sensitive potassium (mitoKATP) channel proteins inwardly rectifying potassium channel (Kir6.2) and sulphonylurea receptor 1 (SUR1) were detected with Western blotting and the cerebral cell apoptosis was detected with TUENL assay 24 hours after reperfusion. Results Compared with the model group, the Longa's score decreased in the exercise preconditioning group 24 hours after reperfusion (P<0.05), while the expression of Kir6.2 and SUR1 decreased (P<0.05), and TUNEL-positive cells decreased (P<0.05).Conclusion Exercise preconditioning may improve neurological function after cerebral ischemia-reperfusion, which may associate with inhibiting the expression of mitoKATP channel proteins and cell apoptosis.

Sevoflurane postconditioning affects post-ischaemic myocardial mitochondrial ATP-sensitive potassium channel function and apoptosis in ageing rats.

This study investigated the effect of sevoflurane postconditioning on post-ischaemic cardiac function, infarct size, myocardial mitochondrial ATP-sensitive potassium channel (mitoKATP) function and apoptosis in ageing rats to determine the possible mechanism underlying the cardioprotective property of sevoflurane. Ageing rat hearts were isolated and attached to a Langendorff apparatus. The hearts were then exposed or not to sevoflurane postconditioning in the presence or absence of 100 µmol/L 5-hydroxydecanoate (5-HD), a selective mitoKATP inhibitor. The infarct size was measured by triphenyltetrazolium chloride (TTC) staining. Mitochondrial morphology was observed by electron microscopy and scored using FlaMeng semiquantitative analysis. In addition, the expression levels of Bax, Bcl-2, and cytochrome-C (Cyt-C) were determined by Western blot analysis at the end of reperfusion. Sevoflurane postconditioning increased coronary flow, improved functional recovery, reduced Bax/Bcl-2 and Cyt-C phosphorylation levels, and decreased mitochondrial lesion severity and the extent of apoptosis. The protective effects of sevoflurane postconditioning were prevented by the mitoKATP inhibitor 5-HD. Sevoflurane postconditioning significantly protected the function of ageing hearts that were subjected to ischaemia and reperfusion, and these protective effects were mediated by mitoKATP opening.

Depolarization of mitochondria in neurons promotes activation of nitric oxide synthase and generation of nitric oxide.

The diverse signaling events following mitochondrial depolarization in neurons are not clear. We examined for the first time the effects of mitochondrial depolarization on mitochondrial function, intracellular calcium, neuronal nitric oxide synthase (nNOS) activation, and nitric oxide (NO) production in cultured neurons and perivascular nerves. Cultured rat primary cortical neurons were studied on 7-10 days in vitro, and endothelium-denuded cerebral arteries of adult Sprague-Dawley rats were studied ex vivo. Diazoxide and BMS-191095 (BMS), activators of mitochondrial KATP channels, depolarized mitochondria in cultured neurons and increased cytosolic calcium levels. However, the mitochondrial oxygen consumption rate was unaffected by mitochondrial depolarization. In addition, diazoxide and BMS not only increased the nNOS phosphorylation at positive regulatory serine 1417 but also decreased nNOS phosphorylation at negative regulatory serine 847. Furthermore, diazoxide and BMS increased NO production in cultured neurons measured with both fluorescence microscopy and electron spin resonance spectroscopy, which was sensitive to inhibition by the selective nNOS inhibitor 7-nitroindazole (7-NI). Diazoxide also protected cultured neurons against oxygen-glucose deprivation, which was blocked by NOS inhibition and rescued by NO donors. Finally, BMS induced vasodilation of endothelium denuded, freshly isolated cerebral arteries that was diminished by 7-NI and tetrodotoxin. Thus pharmacological depolarization of mitochondria promotes activation of nNOS leading to generation of NO in cultured neurons and endothelium-denuded arteries. Mitochondrial-induced NO production leads to increased cellular resistance to lethal stress by cultured neurons and to vasodilation of denuded cerebral arteries.

Atorvastatin protects myocardium against ischemia-reperfusion arrhythmia by increasing Connexin 43 expression: A rat model.

Atorvastatin has protective effects against myocardial ischemia-reperfusion injuries and ischemia-reperfusion arrhythmia. This study was designed to investigate whether atorvastatin is able to protect against myocardial ischemia-reperfusion injury by enhancing the expression of Connexin 43 (Cx43) via the activation of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway and mitochondrial ATP-sensitive potassium (K(ATP)) channels. Isolated perfused rat hearts were treated with classic ischemia postconditioning (IPOST), atorvastatin, and atorvastatin combined with inhibitor of PI3K and K(ATP) channels, respectively, after 30min of LAD ischemia and then subjected to reperfusion for 120min. The QRS duration and the ischemia-reperfusion ventricular arrhythmia were assessed. The lactate dehydrogenase (LDH) and creatine kinase isoenzyme (CK-MB) levels were measured and the Cx43 expression was assessed by immunoblotting and immunohistochemistry. After 120min of reperfusion, atorvastatin and IPOST significantly decreased the QRS duration and inhibited ventricular arrhythmia. They also decreased the levels of LDH and CK-MB. Meanwhile, atorvastatin and IPOST also significantly enhanced the Cx43 expression and the phosphorylation of Cx43. Such protective effects were abolished in the presence of the inhibitor of PI3K or the inhibitor of mitochondrial K(ATP) channels. This study suggests that atorvastatin protected against myocardial ischemia-reperfusion injury and enhanced the expression of Cx43 by activating the PI3K/Akt pathway and mitochondrial K(ATP) channels.

Dioxin-induced acute cardiac mitochondrial oxidative damage and increased activity of ATP-sensitive potassium channels in Wistar rats.

The environmental dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is classified as a Group 1 human carcinogen and teratogenic agent. We hypothesize that TCDD-induced oxidative stress may also interfere with mitochondrial ATP-sensitive potassium channels (mitoKATP), which are known to regulate and to be regulated by mitochondrial redox state. We investigated the effects of an acute treatment of male Wistar rats with TCDD (50 µg/kg i.p.) and measured the regulation of cardiac mitoKATP. While the function of cardiac mitochondria was slightly depressed, mitoKATP activity was 52% higher in animals treated with TCDD. The same effects were not observed in liver mitochondria isolated from the same animals. Our data also shows that regulation of mitochondrial ROS production by mitoKATP activity is different in both groups. To our knowledge, this is the first report to show that TCDD increases mitoKATP activity in the heart, which may counteract the increased oxidative stress caused by the dioxin during acute exposure.

Increased phosphorylation of mTOR is involved in remote ischemic preconditioning of hippocampus in mice.

Different signaling pathways are involved in tissue protection against ischemia reperfusion (IR) injury, among them mammalian target of rapamycin (mTOR) and related pathways have been examined in many recent studies. Present study evaluated the role of mTOR in remote ischemic preconditioning (RIPC) of hippocampus. Renal ischemia was induced (3 cycles of 5min occlusion and 5min reperfusion of unilateral renal artery) 24h before global brain ischemia (20min bilateral common carotid artery occlusion). Saline or rapamycin (mTOR inhibitor; 5mg/kg, i.p.) was injected 30min before RIPC. mTOR and phosphorylated mTOR (p-mTOR) expression, superoxide dismutase (SOD) activity and retention trial of passive avoidance test were determined 24h after global ischemia. Apoptosis and neuronal cell density were assessed 72h after hippocampal ischemia. RIPC decreased apoptosis (p<0.05 vs. IR), improved memory (p<0.05 vs. IR), and augmented p-mTOR expression and SOD activity after hippocampal ischemia (p<0.05 vs. IR). Rapamycin abolished all protective effects of RIPC (p<0.05 vs. RIPC+IR) suggesting a role for mTOR in RIPC induced hippocampal protection.

Protection of hearts from reperfusion injury by propofol without involvement of the mitochondrial ATP-sensitive potassium channels / 中国药理学通报

0 05) group. Treatment with propofol or the combination of propofol and 5 HD delayed the onset of contracture during ischemia compared with control or 5 HD treatments for (6 4?2 1) min or (6 8?2 5) min vs (4 4?1 4) min or (4 2?1 6) min, respectively; P 0 05). The LVEDP in propofol or propofol plus 5 HD increased more slowly than in the control or 5 HD group. Maximal LVEDP occurred 17 min or 16 min,respectively after ischemia in the control group,whereas it occurred 20 and 22 min after ischemia in propofol and propofol plus 5 HD groups, respectively( P