Abstract 429: Intensive Necroptosis Due to Enhanced RIP3-CaMKII Signaling Contributes to Diabetic Myocardial Ischemic Susceptibility

Abstract

Diabetes increases the vulnerability of the heart to ischemic injury. Recent advances have shown that necroptosis is crucially involved in myocardial ischemia/reperfusion (I/R) injury. Our objectives were thus to extend our knowledge to whether and how necroptosis renders diabetic hearts more vulnerable to I/R injury, which involves activation of Ca 2+ -calmodulin-dependent protein kinase (CaMKII) by receptor-interacting protein 3 (RIP3). In this study, diabetes was induced by streptozotocin (40mg/kg, i.v.) and after 6 weeks, anesthetized open-chest diabetic and age-matched control C57 mice were subjected to 30-min regional ischemia (occlusion of LAD coronary artery) followed by 4-h reperfusion. Diabetic animals manifested significantly greater cardiac injury than their littermate controls. Notably, diabetic hearts were sensitized to I/R-induced myocardial necrosis, as evidenced by rise in lactate dehydrogenase (LDH) release and Evans blue dye (EBD) penetration. Notably, compared with control mice, the activation pattern of CaMKII in diabetic hearts subjected to I/R is altered by earlier advanced (60 min after reperfusion) phosphorylation and enhanced oxidation (21.5% increase). Then we proved that inhibition of CaMKII in early stage of I/R could effectively reduce myocardial necroptosis. Further, RIP3 expression and RIP3-CaMKII interaction are markedly enhanced in diabetic hearts during I/R. Inhibition of RIP3 markedly suppresses CaMKII activation and reduces necroptosis. Collectively, these findings identify enhanced RIP3-CaMKII pathway as a key regulator that increases myocardial necroptosis in diabetic I/R hearts.