The heat-induced production of reactive oxygen species regulates protein content in cultured chick skeletal muscle cells

Heat stress is a major factor affecting meat production in the poultry industry, especially in hotter regions of the world. A previous in vivo study by our group highlighted that acute heat stress stimulates mitochondrial reactive oxygen species (ROS) production in the skeletal muscle of broiler chickens. Recently, we further clarified that the overproduction of mitochondrial ROS resulted from an increase in the mitochondrial membrane potential, probably due to an increase in substrate oxidation (Kikusato et al., 2010) and a decrease in avian uncoupling protein (avUCP) content (Mujahid et al., 2006). Furthermore, it was reported that heat stress increases protein oxidation and myofibrillar proteolysis in chick cultured skeletal muscle cells (Nakashima et al., 2004). Considering the fact that ROS play a pivotal role in muscle proteolysis in sepsis (Supinski and Callahan, 2007), it could be postulated that heat treatment stimulates mitochondrial ROS production, thereby leading to an increase in skeletal muscle proteolysis. To verify this possibility, we have investigated the effect of heat stress on ROS production, protein content, and the ROS-related expression of genes for avUCP, heme oxygenase-1 (HO-1) and NADPH oxidase 4 (NOX4) in chick skeletal muscle cells in primary culture. We also examine the reducing effects of 4-hydroxy-TEMPO (Tempol), which is a strong antioxidant, on these parameters.