Angiotensin II promotes nuclear oxidative damage in cardiomyocytes

Abstract

An elevated local concentration of angiotensin II (ATII) promotes cardiac dysfunction; consequent excessive reactive oxygen/nitrogen species (ROS/RNS) generation has been shown to trigger apoptosis in cardiomyocytes. Relevant species include nitric oxide (NO), superoxide, and peroxynitrite. Peroxynitrite, a metabolic product of NO and superoxide, has been shown to induce nuclear oxidative damage in other cell types, thereby stimulating poly(ADP-ribose) polymerase (PARP), a DNA repair enzyme. Peroxynitrite also forms 3-nitrotyrosated (3-NT) proteins, a marker of cellular damage. We hypothesize that ATII triggers nuclear oxidative damage and consequent cell death in cardiomyocytes via ROS/RNS-induced PARP and 3-NT upregulation. HL-1 cells were stimulated with 1μM ATII over a 4-hour time course and analyzed confocally for ROS/RNS generation, as well as changes in nitric oxide synthase (NOS), PARP, and 3-NT expression via western blot analyses. The results show that eNOS and nNOS are constitutively expressed in HL-1 cardiomyocytes. Treatment with ATII caused a robust increase in ROS/RNS, as well as formation of nuclear PAR polymers and peri-nuclear 3-NT. Thus, the results suggest that ATII-stimulated cardiomyocytes undergo nuclear oxidative damage via a nitric oxide pathway. Support: NIH PO12GM066312, R01GM060688, Shriners Hospitals for Children 8450, 8954, 8820