Abstract

We have recently shown that hyperosmotic stress activates p65/RelB NF?B in cultured cardiomyocytes with dichotomic actions on caspase activation and cell death. It remains unexplored how NF?B is regulated in cultured rat cardiomyocytes exposed to hyperosmotic stress. We study here: (a) if hyperosmotic stress triggers reactive oxygen species (ROS) generation and in turn whether they regulate NF?B and (b) if insulin-like growth factor-1 (IGF-1) modulates ROS production and NF?B activation in hyperosmotically-stressed cardiomyocytes. The results showed that hyperosmotic stress generated ROS in cultured cardiac myocytes, in particular the hydroxyl and superoxide species, which were inhibited by N-acetylcysteine (NAC). Hyperosmotic stress-induced NF?B activation as determined by I?B? degradation and NF?B DNA binding. NF?B activation and procaspase-3 and -9 fragmentation were prevented by NAC and IGF-1. However, this growth factor did not decrease ROS generation induced by hyperosmotic stress, suggesting that its actions over NF?B and caspase activation may be due to modulation of events downstream of ROS generation. We conclude that hyperosmotic stress induces ROS, which in turn activates NF?B and caspases. IGF-1 prevents NF?B activation by a ROS-independent mechanism. © 2006 Federation of European Biochemical Societies.