Mitochondrial aldehyde dehydrogenase 2 accentuates aging-induced cardiac remodeling and contractile dysfunction: role of AMPK, Sirt1, and mitochondrial function

摘要

Cardiac aging is associated with compromised myocardial function and morphology although the underlying mechanism remains elusive. Aldehyde dehydrogenase 2 (ALDH2), an essential mitochondrial enzyme governing cardiac function, displays polymorphism in humans. This study was designed to examine the role of ALDH2 in aging-induced myocardial anomalies. Myocardial mechanical and intracellular Ca~(2+) properties were examined in young (4-5 months) and old (26-28 months) wild-type and ALDH2 transgenic mice. Cardiac histology, mitochondrial integrity, O_2~- generation, apoptosis, and signaling cascades, including AMPK activation and Sirtl level were evaluated. Myocardial function and intracellular Ca~(2+) handling were compromised with advanced aging; the effects were accentuated by ALDH2. Hematoxylin and eosin and Masson trichrome staining revealed cardiac hypertrophy and interstitial fibrosis associated with greater left-ventricular mass and wall thickness in aged mice. ALDH2 accentuated aging-induced cardiac hypertrophy but not fibrosis. Aging promoted O_2~- release, apoptosis, and mitochondrial injury (mitochondrial membrane potential, levels of UCP-2 and PGC-1alpha), and the effects were also exacerbated by ALDH2. Aging dampened AMPK phosphorylation and Sirtl, the effects of which were exaggerated by ALDH2. Treatment with the ALDH2 activator Alda-1 accentuated aging-induced O_2~- generation and mechanical dysfunction in cardiomyocytes, the effects of which were mitigated by cotreatment with activators of AMPK and Sirtl, AICAR, resveratrol, and SRT1720. Examination of human longevity revealed a positive correlation between life span and ALDH2 gene mutation. Taken together, our data revealed that ALDH2 enzyme may accentuate myocardial remodeling and contractile dysfunction in aging, possibly through AMPK/Sirt1-mediated mitochondrial injury.