Contrasting effects of phosphatidylinositol- and phosphatidylcholine-specific phospholipase C on apoptosis in cultured endothelial cells.

In the authors' previous studies, they found that phosphatidylcholine-specific phospholipase C (PC-PLC) and phosphatidylinositol-specific phospholipase C (PI-PLC) played contrary roles in the apoptosis of vascular endothelial cells (VECs), but the mechanism underlying the phenomenon remains unclear. To address this question, in this study, the authors investigated the changes of cell cycle distribution, the expression of P53, and the phosphorylation of Akt when PI-PLC was inhibited by its specific inhibitor compound 48/80, and they also examined the phosphorylation of Akt when VEC apoptosis was inhibited by D609, a specific inhibitor of PC-PLC. The results showed that suppression of PI-PLC promoted VEC apoptosis by inhibiting Akt phosphorylation, elevating P53 expression, and affecting the cell cycle distribution. Contrarily, suppression of PC-PLC promoted the phosphorylation of Akt. The data suggested that PI-PLC and PC-PLC might control the apoptosis by jointly regulating Akt phosphorylation, P53 expression, and affecting cell cycle in VECs.