Abstract 11928: Cardiospecific Overexpression of Carnosine Synthase Attenuates Myocardial Ischemia Reperfusion Injury

Abstract

Even though myocardial ischemia/reperfusion (I/R) remains the leading cause of death, the underlying mechanisms remain incompletely understood. Increased formation of reactive carbonyl has been shown to be a common biochemical feature of I/R injury. These carbonyls are generated from the oxidation of proteins and membrane lipids. Reactive carbonyls such as methylglyoxal are generated from increased glycolytic activity during ischemia. Previous work in our lab has shown that the endogenous dipeptide carnosine (β-alanine-histidine) quenches both protein and lipid derived carbonyls. It can also buffer changes in intracellular pH and chelate metals that catalyze ROS production. In the heart, carnosine is synthesized by the ATP grasp enzyme (ATPGD1). Hence, we examined whether overexpression of ATPGD1 could increase carnosine synthesis in the heart and attenuate I/R injury. To overexpress ATPGD1, we generated mice in which the expression of the transgene was driven by cardiospecific α-MHC promoter. Two different ATPGD1Tg mouse lines were generated, which showed 10-15 fold higher abundance of ATPGD1 protein in the heart compared with their wild-type (WT) littermates. Cardiac levels of the histidyl dipeptides anserine and carnosine were approximately 100 fold higher in the ATPGD1Tg than WT mice hearts (WT: anserine 1.8±0.3 pmoles/mg protein, carnosine 6±1 pmoles/mg protein; ATPGD1-Tg: anserine 114±15 pmoles/mg protein, carnosine 615±44 pmoles/mg protein). No changes in the levels of these dipeptides were observed in other tissues of the ATPGD1Tg mice. Echocardiographic analysis showed that ATPGD1 overexpression did not affect cardiac function. When subjected to 30 min of coronary occlusion followed by 24 h of reperfusion, the infarct size was significantly lower in ATPGD1Tg than WT mice. Infarct size as the area of risk of left ventricle was 59±3.02% in WT mice and 38±2.73% in the ATPGD1-Tg mice (p<0.05 vs WT; n=7-8), indicating that increasing carnosine levels attenuates myocardial I/R injury. These findings reveal a novel cardioprotective role of endogenous histidyl dipeptides in decreasing I/R injury and suggest that treatment with such peptides may be a potential therapy for decreasing myocardial I/R injury and its progression of heart failure.