Cardiomyocyte Dimethylarginine Dimethylaminohydrolase1 Attenuates Left-ventricular Remodeling After Acute Myocardial Infarction: Involvement in Oxidative Stress and Apoptosis

Asymmetric dimethylarginine (ADMA) is a risk factor for heart diseases. Dimethylarginine dimethylaminohydrolase (DDAH) enzymes are key proteins for ADMA degradation. Endothelial DDAH1 is a vital regulator of angiogenesis. DDAH1 is also expressed in cardiomyocytes. However, the role of DDAH1 in cardiomyocytes needs further clarification. Herein, we used an inducible cardiac-specific DDAH1 knockdown mouse (cardiac DDAH1) to investigate the role of cardiomyocyte DDAH1 in left-ventricular (LV) remodeling after acute myocardial infarction (AMI). DDAH1flox/flox and α-MHC mice were used to generate cardiac DDAH1 mice. Deletion of DDAH1 in cardiomyocytes was confirmed by Western blotting. No significant differences were observed in plasma ADMA levels and LV function between cardiac DDAH1 mice and control mice. Cardiac DDAH1 mice showed aggravated LV remodeling 4 weeks after AMI, as demonstrated by a large infarct area and impaired LV function. The rate of cardiomyocyte apoptosis and level of oxidative stress were higher in the LV tissue of cardiac DDAH1 mice than in that of control mice. However, treatment of cardiomyocytes with exogenous ADMA had no effect on reactive oxygen species (ROS) levels or apoptosis sensitivity. Cardiac DDAH1 LV tissue showed downregulated superoxide dismutase2 (SOD2) expression, and treatment of DDAH1 cardiomyocytes with the SOD mimic tempol significantly attenuated apoptosis and ROS levels under hypoxic conditions. Tempol administration also attenuated oxidative stress and apoptosis in cardiac DDAH1 LV tissue and partially alleviated LV remodeling after AMI. DDAH1 in cardiomyocytes plays a vital role in attenuating LV remodeling after AMI by regulating intracellular ROS levels and apoptosis sensitivity via a SOD2-dependent pathway.