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, NF-κB, 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 NF-κB activation. Antioxidants such as N-acetyl cysteine, N-mercaptopropionyl glycine, and vitamin E attenuated the NF-κB activation. Infection of cardiomyocytes with an adenovirus expressing a degradation-resistant mutant of IκBα 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 NF-κB activation and cardiac hypertrophy. Overexpression of a constitutively active mutant of ASK1 led to NF-κB activation and cardiac hypertrophy. Activated ASK1-induced hypertrophy was abolished by inhibition of NF-κB activation.

Conclusions— These data indicate that GPCR agonist–induced cardiac hypertrophy is mediated through NF-κB activation via the generation of ROS. ASK1 is involved in GPCR agonist–induced NF-κB activation and resulting hypertrophy.