Possible Role of NF-ĸB Signals in Heat Stress-Associated Increase in Protein Content of Cultured C2C12 Cells

Abstract

Heat stress is one of the hypertrophic stimuli on mammalian skeletal muscle. Nuclear factor-ĸB (NF-ĸB) signaling plays an important role in the regulation of skeletal muscle mass. However, the effects of heat stress on NF-ĸB signaling in skeletal muscle cells remain unclear. Effects of heat stress and/or administration of BAY11-7082, an inhibitor of NF-ĸB, on NF-ĸB signals and protein content of skeletal muscle were studied by using cell culture system. Differentiated mouse myoblasts (C2C12) were subjected to either (1) control (cultured at 37°C without BAY11-7082), (2) heat stress at 41°C for 60 min, (3) BAY11-7082 administration (1.25 µM) or (4) heat stress combined with BAY11-7082 administration. Heat shock protein 72 (HSP72) was upregulated by heat stress with or without administration of BAY11-7082. The increase in inhibitor of ĸBα (IĸBα), which regulates the phosphorylation of NF-ĸB, and the decrease in phosphorylated NF-ĸB were also induced by administration of BAY11-7082 and/or heat stress. Protein content in C2C12 cells was increased by the administration of BAY11-7082 with a semi-logarithm fashion. Significant increases in the protein content of C2C12 cells were observed 48 h following heating with or without administration of BAY11-7082. These observations suggest that heat stress might increase muscle protein through the downregulation of NF-ĸB signaling. Inhibition of NF-ĸB induced by application of heat stress might be one of the hypertrophic stimuli on skeletal muscle cells.