Abstract 42: Lysosomal Membrane Permeabilization Contributes to Hyperglycemia-Induced Cardiomyocytes Dysfunction

Abstract

Hyperglycemia is an independent risk factor for diabetic heart failure. However, the mechanisms that mediate hyperglycemia-induced cardiac damage remain poorly understood. Previous studies have shown an association between lysosomal dysfunction and diabetic heart failure. Lysosomal membrane permeabilization (LMP) is a prominent feature of lysosomal dysfunction. We examined if high glucose (HG) induces LMP in cardiomyocyte. Immunofluorescent microscopy showed the release of cathepsin D (CTSD) from lysosome under HG, suggesting that HG induces LMP. To determine whether LMP and the ensuing CTSD expression play a role in HG-induced cardiomyocyte injury, we treated cells with siRNA targeting CTSD or low dose of CTSD inhibitor pepstatinA (0.5ng/mL). Remarkably, both CTSD down-regulation approaches reduced HG-induced myocyte injury, as shown by elevated cleavage of Caspase3 and by propidium iodide staining. These results suggest that LMP and the ensuing CTSD expression mediate HG-induced cardiotoxicity. In addition, by using LMP/lysophagy reporter tfGalectin3, we found that HG-induced LMP was accompanied by impaired lysophagy, suggesting a failed elimination of damaged lysosomes by lysophagy, which may exacerbate HG-induced LMP. Indeed, the lysophagy inducer L-leucyl-L-leucine methyl ester (LLOMe) stimulated lysophagy flux, attenuated HG-induced LMP, and restored the beating frequency of HG-treated cardiomuyocytes. Together, these findings demonstrate a novel mechanism by which high glucose impairs lysophagy, induces LMP and triggers the release of CTSD, which collectively contribute to hyperglycemic cardiotoxicity.