Smooth muscle cell response to mechanical injury involves intracellular calcium release and ERK1/ERK2 phosphorylation

We have investigated possible signaling pathways coupled to injury-induced ERK1/2 activation and the subsequent initiation of vascular rat smooth musc le cell migration and proliferation. Aortic smooth muscle cells were cultur ed to confluency and subjected to in vitro injury under serum-free conditio ns. In fluo-4-loaded cells, injury induced a rapid wave of intracellular C2 + release that propagated about 200 mum in radius from the injured zone, re ached a peak in about 20 s, and subsided to the baseline within 2 min. The wave was abolished by prior treatment with the sarcoplasmic reticulum ATPas e inhibitor thapsigargin, but not by omission of extracellular Ca2+. ERK1/2 activation reached a peak at 10 min after injury and was inhibited by the MEK1 inhibitor PD98059, as well as by thapsigargin, fluphenazine, genistein , and the Src inhibitor PP2. These inhibitors also reduced [H-3]thymidine i ncorporation and migration of cells into the injured area determined at 48 h after injury. These results show that mechanical injury to vascular smoot h muscle cells induces a Ca2+ wave which is dependent on intracellular Ca2 release. Furthermore, the injury activates ERK1/2 phosphorylation as well as cell migration and replication. (C) 2001 Academic Press.