MAPK Activation and Cell Viability after H<SUB>2</SUB>O<SUB>2</SUB> Stimulation in Cultured Feline Ileal Smooth Muscle Cells

MAPK Activation and Cell Viability after H<SUB>2</SUB>O<SUB>2</SUB> Stimulation in Cultured Feline Ileal Smooth Muscle Cells

Recent data have shown the importance of oxidative stresses in the pathogenesis of inflammatory bowel disease, crohn s disease and ulcerative colitis. H<SUB>2</SUB>O<SUB>2</SUB>, reactive oxygen species (ROS) donor, has been reported to act as a signaling molecule involved in a variety of cellular functions such as apoptosis and proliferation. In the present study, we investigated viability of cultured ileal smooth muscle cells (ISMC) after stimulation with H<SUB>2</SUB>O<SUB>2</SUB>. Trypan blue method revealed that the cell viability of ISMC treated with 1 mM H<SUB>2</SUB>O<SUB>2</SUB> was not different from that of controls at up to 2 h time point, while treatment of ISMC with 1 mM H<SUB>2</SUB>O<SUB>2</SUB> for 48 h finally induced significant decrease in the cell viability. Therefore, we evaluated whether H<SUB>2</SUB>O<SUB>2</SUB> was capable of ERKs activation in ISMC for the short-term exposure and examined whether tyrosine kinase was involved in the process of ERK activation by H<SUB>2</SUB>O<SUB>2</SUB> in ISMC. We also investigated the effects of H<SUB>2</SUB>O<SUB>2</SUB> on activation of SAPK/JNK and p38 MAP kinase in ISMC. Thus, ISMC were cultured and exposed to H<SUB>2</SUB>O<SUB>2</SUB>, and western blot analysis was performed with phospho- specific MAP kinase antibodies. Robust activation of ERK occurred within 30 min of 1 mM H<SUB>2</SUB>O<SUB>2</SUB> treatment. H<SUB>2</SUB>O<SUB>2</SUB>-induced ERK activation was attenuated by a tyrosine kinase inhibitor, genistein, indicating that tyrosine kinase was probably involved in the ERK activation by H<SUB>2</SUB>O<SUB>2</SUB>. H<SUB>2</SUB>O<SUB>2</SUB> was a moderate activator of SAPK/JNK, while p38 MAP kinase was not activated by H<SUB>2</SUB>O<SUB>2</SUB>. We suggest that ERK activation induced by short-term H<SUB>2</SUB>O<SUB>2</SUB> treatment plays a critical role in cellular protection in the early stage of response to oxidative stress. The present study suggests the necessity of identification of MAPK signaling pathways affected by ROS, since it could ultimately elucidate cellular consequences involved in initiation and perpetuation of intestinal tissue damage in the diseases such as crohn s disease and ulcerative colitis, resulted from excessive ROS.