Abstract 1430: Redox Impairment Of Mitochondrial Function Drives The Pathogenesis Of Human R120g αB-crystallin Cardiomyopathy
We have demonstrated recently that transgenic mice overexpressing cardiac-specific human R120G αB-crystallin (hR120GCryAB Tg) recapitulate protein aggregation cardiomyopathy linked to reductive stress caused by alterations in glutathione homeostasis. In this study, we tested the hypothesis that cardiotoxicity from reductive stress might trigger opening of the mitochondria permeability transition pore (MPTP), which plays a pivotal role in apoptotic and necrotic cell death. To determine the effects of reductive stress on MPTP, we assessed isolated mitochondria in response to either 50 or 100μM Ca++ from the nontransgenic (NTg) and hR120GCryAB mice at 6 months, a transition stage associated with significant cardiac decompensation, hypertrophy and failure. MPTP opening was significantly greater for hR120GCryAB than Ntg (p<0.05). We next examined MPTP complex proteins, such as ANT, VDAC and cyclophilin-D, all of which were significantly down-regulated in hR120GCryAB hearts compared with NTg mice. From reducing and non-reducing PAGE and immunoblotting with anti-GSH antibody, protein disulfides (P-SSG) and glutathione (GSH) adducts of mitochondrial proteins exhibited differential expression between experimental groups. LS/MS spectroscopy is used to analyze the target MPTP and other candidate proteins that are sensitive to thiol modifications. Our findings suggest for the first time that hR120GCryAB-induced reductive stress mediates hitherto profound consequences on MPTP complex in the pathogenesis of hR120GCryAB cardiomyopathy. Therefore, abrogating mitochondrial insult before the transition from compensatory to de-compensatory heart failure might yield therapeutic benefits in R120GCryAB cardiomyopathy.