Autophagic Flux Impairment Exacerbates Myocardial Ischemia-Reperfusion Injury in Experimental Diabetes Through Atg5/LAMP2 Cleavage by Calpains

Abstract Background: is a chronic metabolic disease characterized by hyperglycemia, which has negative effects on cardiac revascularization in patients with coronary artery disease (CAD). Methods: This study focused on the role of autophagic flux in regulating susceptibility of STZ-induced diabetic heart to ischemia-reperfusion (I/R) injury. We established STZ-induced diabetes mice and perform I/R process by coronary artery ligation, and neonatal mice cardiomyocytes culture subjected to high glucose and hypoxia/reoxygenation(H/R). Results: Diabetic heart was more sensitive to I/R injury. Autophagic flux, represented by TEM, relative LC3Ⅱ changes under CQ intervention and P62 expression, was impaired in diabetic hearts and deteriorated during subsequent I/R. Calpains were activated in diabetic I/R heart, and the inhibition of calpains partially rescued autophagic flux, cardiac function, and cell death. The expression of autophagic flux related proteins Atg5 and LAMP2 decreased significantly in diabetic I/R heart. Further studies suggested that calpain could cleave Atg5 and LAMP2, and generate cleaved fragments, which might be reversed by calpain inhibition. Inhibition of calpain，or in company with overexpression of Atg5 and LAMP2 , could reduce myocardial injury in diabetic heart subject to I/R. But overexpression of Atg5 alone could worsen the I/R injury. Conclusion: In conclusion, calpain-mediated cleavage of Atg5 and LAMP2 accounts for the impaired autophagic flux which increases the susceptibility to myocardial I/R injury in experimental diabetic mice.