Inhibition of myocardial cathepsin-L release during reperfusion following myocardial infarction improves cardiac function and reduces infarct size.

Aims: Identifying novel mediators of lethal myocardial reperfusion injury that can be targeted during primary percutaneous coronary intervention (PPCI) is key to limiting the progression of patients with ST-elevated myocardial infarction (STEMI) to heart failure. Here we show through parallel clinical and integrative preclinical studies the significance of the protease cathepsin-L on cardiac function during reperfusion injury. Methods and Results: We found that direct cardiac release of cathepsin-L in STEMI patients (n = 76) immediately post-PPCI leads to elevated serum cathepsin-L levels and that serum levels of cathepsin-L in the first 24 hour post-reperfusion are associated with reduced cardiac contractile function and increased infarct size. Preclinical studies, demonstrate that inhibition of cathepsin-L release following reperfusion injury with CAA0225 reduces infarct size and improves cardiac contractile function by limiting abnormal cardiomyocyte calcium handling and apoptosis. Conclusion: Our findings suggest that cathepsin-L is a novel therapeutic target that could be exploited clinically to counteract the deleterious effects of acute reperfusion injury after an acute STEMI. Translational perspective: New therapeutic targets are urgently required to limit myocardial damage after reperfusion injury. We identified cardiac release of the protease cathepsin-L among patients following primary percutaneous coronary intervention (PPCI). Elevated serum levels of cathepsin-L were associated with reduced contractile function and increased infarct size at 24 hour and 6 months post-PPCI. Work conducted using animal models indicated that cardiac release of cathepsin-L mediated cardiac dysfunction following reperfusion injury. Specific inhibition of cathepsin-L prevented abnormal calcium handling, reduced infarct size and improved contractile function. These novel findings offer the prospect of targeting cathepsin-L-mediated cardiac dysfunction after PPCI.