Impact of DNA Damage on the Contractile Function of Cardiomyocytes

The accumulation of reactive oxygen species (ROS) has detrimental effects on heart muscle cells, including cellular apoptosis and dysfunction that contribute to the progression of cardiovascular diseases. Additionally, ROS can modify bases to form DNA lesions, leading to genetic instability and mutations. Other types of DNA damage occur when cells are exposed to mutagenic agents leading to single-stranded (SSB) and double-stranded (DSB) breaks. Although oxidative stress and ROS can negatively affect heart muscle function and cause DNA damage, the impact of oxidative DNA damage on contractile function remains poorly understood. The purpose of this project is to determine the sensitivity of cardiomyocyte contractile mechanics in response to SSBs, DSBs, and ROS. The relationship between DNA damage and cardiomyocyte activity is examined by measuring the relative abundance of SSBs and DSBs through a Comet assay in coordination with video-based analysis to evaluate contractile function of mouse HL-1 cells. In the presence of hydrogen peroxide, contraction rate increased in response to a mild amount of damage but decreased under high levels. This suggests that cardiomyocyte function is stimulated by oxidative stress until severe damage debilitates cellular processes. Subsequent conditions of camptothecin (SSB) and bleomycin (DSB) were employed to illuminate the role of specific types of DNA damage. These results indicate that DSBs contribute toward contractile function more significantly than do SSBs. Future directions include expanding these results to a human cardiac model system, such as human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) and the application of an enzyme-modified alkaline comet assay to further investigate the contribution of oxidative DNA damage on heart cell activity.