Combination of Vildagliptin and Ischemic Postconditioning in Diabetic Hearts as a Working Strategy to Reduce Myocardial Reperfusion Injury by Restoring Mitochondrial Function and Autophagic Activity

Purpose: Diabetic hearts are resistant to cardioprotection by ischemic-postconditioning (IPostC). Protection of diabetic hearts and finding related interfering mechanisms would have clinical benefits. This study investigated the combination effects of vildagliptin (Vilda) and IPostC on cardioprotection and the levels of autophagy and mitochondrial function following myocardial ischemia/reperfusion (I/R) injury in type-II diabetic rats. Methods: Diabetes was established by high fat diet/low dose of streptozotocin and lasted for 12 weeks. The diabetic rats received Vilda (6 mg/kg/day, orally) for one month before I/R. Myocardial regional ischemia was induced through the ligation of left coronary artery, and IPostC was applied immediately at the onset of reperfusion. The infarct size was assessed by a computerised planimetry and left ventricles samples were harvested for cardiac mitochondrial function studies (ROS production, membrane potential and staining) and western blotting was used for determination of autophagy markers. Results: None of Vilda or IPostC but combination of them could significantly reduce the infarct size of diabetic hearts, comparing to control (P<0.001). IPostC could not significantly affect p62 expression level in diabetic hearts, but pre-treatment with Vilda alone (p<0.05) and in combination with IPostC (p<0.01) more significantly decreased p62 expression in comparison with corresponding control group. The expression of LC3B-II and LC3BII/LC3BI as well as mitochondrial ROS production were decreased significantly in treatment groups (p<0.001). Mitochondrial membrane depolarization was significantly higher and mitochondrial density was lower in untreated diabetic I/R hearts than treated groups (p<0.001). IPostC in combination with vildagliptin prevented the mitochondrial membrane depolarization and increased the mitochondrial content more potent than IPostC alone in diabetic hearts. Conclusion: Combination of vildagliptin and IPostC in diabetic hearts was a well-working strategy to reduce myocardial I/R damages by restoring mitochondrial membrane potential and ROS production and modulating the autophagic activity in I/R hearts

The Role of Mitochondrial ATP-Sensitive Potassium Channels in Cardioprotective and Anti-Inflammatory Effects of Troxerutin in Myocardial Reperfusion Injury: Mitochondrial ATP-sensitive Potassium Channel as Target of Troxerutin in Cardioprotection

A major clinical challenge in ischemic heart disease is the prevention of myocardial injury following ischemia/reperfusion (I/R). Application of natural pharmaceuticals seems to be clinically interesting due to their multiplex activities. Protective effects of troxerutin (TXR) in myocardial I/R injury have been ever demonstrated, nevertheless, the purpose of this study is to explore the role of mitochondrial adenosine triphosphate -sensitive potassium (mitoKATP) channels and toll-like receptor 4 (TLR4)-nuclear factor kappa B (NF-κB) pathway in cardioprotective effects of TXR against I/R injury in rats. Male Wistar rats (n=72, 250–300 g, 12 weeks old) were randomized into groups with/without I/R and/or TXR and 5-hydroxydecanoate (5-HD), alone or in combination. To induce I/R model, the langendorff-perfused hearts were subjected to left anterior descending coronary artery (LAD) ligation and re-opening. TXR (150mg/kg/day) was administered for 4 weeks before I/R. Moreover, 5-HD (100 µM) was added to the perfusion solution before the ischemia. Finally, myocardial infarct size, LDH release, protein expression levels of TLR4 and NF-κB, and the levels of pro-inflammatory cytokines (TNF-α and IL-1β) were assessed. TXR preconditioning significantly reduced IS and LDH release (P&lt;0.05). Furthermore, it decreased the expression of TLR4 and NF-κB and the level of pro-inflammatory cytokines (P&lt;0.05 to P&lt;0.01). Inhibition of mitoKATP channels by 5-HD significantly reversed the cardioprotective effects of TXR. This work shed some light on the knowledge about the mechanisms involved in the anti-inflammatory effect of TXR preconditioning in myocardial I/R injury. This effect may be partly mediated through mitoKATP channels opening and subsequent suppression of the TLR4/NF-κB pathway