Involvement of Nuclear Factor- B and Apoptosis Signal-Regulating Kinase 1 in G-Protein–Coupled Receptor Agonist–Induced Cardiomyocyte Hypertrophy

Background—Recently, reactive oxygen species (ROS) have emerged as important molecules in cardiac hypertrophy. However, the ROS-dependent signal transduction mechanism remains to be elucidated. In this study, we examined the role of an ROS-sensitive transcriptional factor, NFB, and a mitogen-activated protein kinase kinase kinase, apoptosis signal-regulating kinase 1 (ASK1), in G-protein–coupled receptor (GPCR) agonist (angiotensin II, endothelin-1, phenylephrine)-induced cardiac hypertrophy in isolated rat neonatal cardiomyocytes. Methods and Results—Using an ROS-sensitive fluorescent dye, we observed an increase in fluorescence signal on addition of the GPCR agonists. The GPCR agonists induced NFB activation. Antioxidants such as N-acetyl cysteine, N-mercaptopropionyl glycine, and vitamin E attenuated the NFB activation. Infection of cardiomyocytes with an adenovirus expressing a degradation-resistant mutant of I B led to suppression of the hypertrophic responses. The GPCR agonists rapidly and transiently activated ASK1 in a dose-dependent manner. Infection of an adenovirus expressing a dominant-negative ASK1 attenuated the GPCR agonist–induced NFB activation and cardiac hypertrophy. Overexpression of a constitutively active mutant of ASK1 led to NFB activation and cardiac hypertrophy. Activated ASK1-induced hypertrophy was abolished by inhibition of NFB activation. Conclusions—These data indicate that GPCR agonist–induced cardiac hypertrophy is mediated through NFB activation via the generation of ROS. ASK1 is involved in GPCR agonist–induced NFB activation and resulting hypertrophy. (Circulation. 2002;105:509-515.)