Mechanisms of Cardiac Cell Death in Duchenne Muscular Dystrophy

Abstract

Duchenne muscular dystrophy (DMD) is a genetic disorder caused by mutations in the DMD gene, resulting in the loss of dystrophin protein. Dystrophin is expressed in striated muscle and stabilizes the sarcolemma during muscle contraction; its absence leads to rapid muscle degeneration. Cardiomyopathy is the leading cause of death for DMD patients, with aberrant calcium mishandling in dystrophic cardiomyocytes representing a contributing mechanism.  However, the cell death pathway underlying cardiomyocyte death remains poorly understood. To identify dystrophic cardiomyocyte cell death mechanisms, cardiac tissue from three wild-type and four D2.mdx mice (male, aged 12 months) were analyzed for proteins that regulate common apoptotic and pyroptotic pathways (caspases –1, 3, and 9) and their downstream cleavage products (IL-1β, IL-18, and poly (ADP-ribose) polymerase-1 (PARP)).  Results show that pro-caspase-1 and IL-1β expression is not significantly different between groups (p = 0.306 and 0.125, respectively). Similarly, cleaved PARP levels did not differ significantly between groups (p = 0.128). These results suggest that apoptotic and pyroptotic pathways are not active in these tissue samples. Alternative cell death pathways, such as necroptosis, may be responsible, or these animals had not undergone significant cardiomyocyte cell death.