The role of protein kinase C and PI3-kinase in the mechanism of the cardioprotective effect of remote ischemic postconditioning

Background. Acute myocardial infarction (AMI) with ST segment elevation is associated with high incidence of complications. Mortality from AMI is about 5%, which has not decreased in recent years. Revascularization provides recovery of coronary blood flow, but also contributes to the occurrence of reperfusion injury to the heart. Remote ischemic postconditioning (RIPostC) is a promising, non-invasive method that can effectively and safely reduce the infarct size.The aim of the study was to investigate the role of protein kinase C and PI3-kinase in the development of the infarct-limiting effect of remote ischemic postconditioning.Materials and methods. The study was performed on Wistar rats. Coronary artery occlusion (45 min) and reperfusion (2 h) were performed. The infarct size (IS) and the size of area at risk (AAR) were assessed. RIPostC was modeled by applying tourniquets to the hind limbs in the hip joint immediately after the restoration of coronary blood flow. All inhibitors were administered intravenously 10 min before reperfusion.Results. In the control group, the IS / AAR ratio was 44%. RIPostC reduced the IS / AAR ratio by about 50%. Preliminary administration of the protein kinase C inhibitor chelerythrine and the PI3-kinase inhibitor wortmannin eliminated the cardioprotective effect of RIPostC.Conclusion. The mechanism of the infarct-limiting effect of RIPostC is implemented through activation of protein kinase C and PI3-kinase.

Remote Limb Ischemic Postconditioning Ameliorated Microglia-Mediated Inflammation Against Cerebral Ischemia/Reperfusion through Modulating Microglial Activation and Polarization via TLR4 Pathway

Accumulating researches have indicated that remote limb ischemic postconditioning (RIPC) mediates neuroprotection by inhibition inflammatory response against cerebral ischemia/reperfusion (I/R), which is proved to correlated with microglial activation and polarization. However, the underlying mechanism remains unclear. In this study, middle cerebral artery occlusion /reperfusion model in Sprague-Dawley rats were conducted and treated with vehicle or RIPC immediately after reperfusion. Infarct size, and neurological scores were performed to asses stroke outcomes for 7 days. Brain damage and neuronal survival were detected using HE and Nissl staining. ELISA, western blotting and immunohistochemistry staining were utilized to evaluate inflammatory response, neuronal apoptosis, and microglial activation and polarization to M1- or M2-subtypes respectively. Results showed that RIPC significantly attenuated infarct size at 3d and alleviated the neurological deficits of rats at 3d and 7d post-ischemia. Furthermore, RIPC decreased expression of inflammatory cytokines IL-β, TNF-α and neuronal loss, and increased expression of cytokines IL-10 and Bcl-2. In addition, RIPC suppressed microglial activation and promoted microglial polarization to M2 type along with downregulation of TLR4 expression. These results suggested that RIPC was neuroprotective against ischemic stroke by modulating the activation of microglia/macrophages and encouraging polarization to M2 phenotype possibly through TLR4 signaling pathway.

Molecular Network Approach Reveals Rictor as a Central Target of Cardiac ProtectomiRs

Cardioprotective medications are still unmet clinical needs. We have previously identified several cardioprotective microRNAs (termed ProtectomiRs), the mRNA targets of which may reveal new drug targets for cardioprotection. Here we aimed to identify key molecular targets of ProtectomiRs and confirm their association with cardioprotection in a translational pig model of acute myocardial infarction (AMI). By using a network theoretical approach, we identified 882 potential target genes of 18 previously identified protectomiRs. The Rictor gene was the most central and it was ranked first in the protectomiR-target mRNA molecular network with the highest node degree of 5. Therefore, Rictor and its targeting microRNAs were further validated in heart samples obtained from a translational pig model of AMI and cardioprotection induced by pre- or postconditioning. Three out of five Rictor-targeting pig homologue of rat ProtectomiRs showed significant upregulation in postconditioned but not in preconditioned pig hearts. Rictor was downregulated at the mRNA and protein level in ischemic postconditioning but not in ischemic preconditioning. This is the first demonstration that Rictor is the central molecular target of ProtectomiRs and that decreased Rictor expression may regulate ischemic postconditioning-, but not preconditioning-induced acute cardioprotection. We conclude that Rictor is a potential novel drug target for acute cardioprotection.

The Cardioprotective Effect of Combined Therapy With α-Lipoic Acid Preconditioning and Ischemic Postconditioning Is Mediated by the Improvement of Autophagy Flux and Mitochondrial Function in Myocardial Reperfusion Injury of Diabetic Rats

Investigating the interaction of diabetes with ischemic postconditioning (IPostC)-associated cardioprotection in myocardial ischemia/reperfusion (I/R) damage is of great clinical importance. The present work was performed to evaluate the combined effects of α-lipoic acid (LA) and IPostC on autophagy flux and mitochondrial function following myocardial I/R damage in type-II diabetic rats. Diabetes with duration of 12 weeks was induced by high-fat diet/low dose of streptozotocin. LA (500 mg/kg/day) was administered orally in diabetic rats for 5 weeks before I/R. The hearts were removed and mounted on Langendorff apparatus. I/R was induced through the ligation of left anterior descending coronary artery for 35 min and reperfusion for 60 min. IPostC was applied immediately at the onset of the reperfusion. Lastly, myocardial infarct size (IS), autophagy markers at both gene and protein levels, and mitochondrial ROS production and membrane potential were assessed. Combination of LA and IPostC significantly decreased the IS of diabetic hearts (P < 0.05). IPostC alone could not significantly decrease p62 gene and protein expressions, and mitochondrial membrane depolarization in diabetic hearts. However, combination of LA and IPostC more significantly decreased LC3 and p62 gene expressions (P < 0.01), LC3II/LC3I and p62 protein expressions (P < 0.01), and mitochondrial ROS generation and membrane depolarization (P < 0.01) in diabetic hearts. Pretreatment with LA in diabetic rats notably restored cardioprotection by IPostC via modulation of autophagy flux and restoring mitochondrial function. This combined conditioning might be an effective strategy to diminish I/R injury in diabetic hearts.