Phospholipase Cc1 Mediates Intima Formation Through Akt-Notch1 Signaling Independent of the Phospholipase Activity

Methods and Results-—There was a timeand dose-dependent activation of Notch1 by angiotensin II and platelet-derived growth factor in vascular smooth muscle cells. When phospholipase Cc1 (PLCc1) expression was reduced by small interfering RNA, Notch1 activation and Hey2 expression (Notch target gene) induced by angiotensin II or platelet-derived growth factor were remarkably inhibited, while Notch2 degradation was not affected. Mechanistically, we observed an association of PLCc1 and Akt, which increased after angiotensin II or platelet-derived growth factor stimulation. PLCc1 knockdown significantly inhibited Akt activation. Importantly, PLCc1 phospholipase site mutation (no phospholipase activity) did not affect Akt activation. Furthermore, PLCc1 depletion inhibited platelet-derived growth factor–induced vascular smooth muscle cell proliferation, migration, and dedifferentiation, while it increased apoptosis. In vivo, PLCc1 and control small interfering RNA were delivered periadventitially in pluronic gel and complete carotid artery ligation was performed. Morphometric analysis 21 days after ligation demonstrated that PLCc1 small interfering RNA robustly attenuated intima area and intima/media ratio compared with the control group.