Modulation of cell death pathways to apoptosis and necrosis of H2O2-treated rat thymocytes by lipocortin I.

Lipocortin I, also called annexin I, a calcium and phospholipid binding protein, protected rat thymocytes from H2O2-elicited necrosis and facilitated H2O2-induced apoptosis, while anti-lipocortin I antibody enhanced H202-elicited necrosis by blocking H202-induced apoptosis. Essentially similar results were obtained with phospholipase A2 inhibitors and activators such as 3,4-octyadecyl-benzylacrylic acid and melittin, respectively. Available evidence suggests that lipocortin I modulates signals for cell death pathways of H2O2-treated rat thymocytes to apoptosis and necrosis by regulating cellular phospholipase A2 activities but not by inhibiting membrane lipid peroxidation.