Thrombin Induced Apoptosis through Calcium-Mediated Activation of Cytosolic Phospholipase A2 in Intestinal Myofibroblasts

Thrombin is a serine protease that participates in a variety of biological signaling through protease-activated receptors. Intestinal myofibroblasts play central roles in maintaining intestinal homeostasis. In this study, we found that thrombin-induced apoptosis is mediated by the calcium-mediated activation of cytosolic phospholipase A(2) in the CCD-18Co cell. Thrombin reduced cell viability by inducing apoptosis and proteinase-activated receptor-1 antagonist attenuated thrombin-induced cell death. Endogenous ceramide did not affect the cell viability itself, but a ceramide-mediated pathway was involved in thrombin-induced cell death. Thrombin increased intracellular calcium levels and cytosolic phospholipase A(2) activity. The ceramide synthase inhibitor Fumonisin B-1, intracellular calcium chelator BAPTA-AM, and cytosolic phospholipase A(2 )inhibitor AACOCF(3) inhibited thrombin-induced cell death. Thrombin stimulated arachidonic acid release and reactive oxygen species generation, which was blocked by AACOCF(3), BAPTA-AM, and the antioxidant reagent Trolox. Taken together, thrombin triggered apoptosis through calcium-mediated activation of cytosolic phospholipase A(2) in intestinal myofibroblasts.