Arachidonic acid pretreatment enhances smooth muscle cell migration via increased Ca2+ influx

It is well known that vascular smooth muscle cell (SMC) migration is an initial step in atheromatous plaque formation. In the present study, we investigated the effects of arachidonic acid (AA, 20:4 n-6) on bovine carotid artery SMC migration using the modified Boyden chamber technique. SMCs pretreated with 2.5 microg/ml of AA for 2 days, showed an enhanced migration response to fetal bovine serum. AA pretreatment (0.5-5.0 microg/ml) increased fetal bovine serum-induced SMC migration dose-dependently, and maximum stimulation was observed at a concentration of 2.5 microg/ml. However, AA pretreatment did not enhance fetal bovine serum-induced endothelial cell migration. Using lipid analysis, we found that AA was substantially incorporated into cellular phospholipids. When SMC migration was induced by platelet derived growth factor (PDGF)-BB, instead of serum, the stimulative effect of AA pretreatment was retained. SMCs pretreated with AA showed greater mobilization of intracellular Ca2+ in response to PDGF-BB than SMCs without AA pretreatment (controls). Nifedipine, a Ca2+ channel blocker, and glycoletherdiamine-tetraacetic acid (EGTA) had no effect on PDGF-induced migration of controls but both drugs reduced the enhanced PDGE-induced migration of AA-pretreated SMCs to the control level. Baicalein, an inhibitor of 12-lipoxygenase, reduced PDGF-BB-induced migration of both control and AA pretreated SMCs, however the AA-pretreated cells still showed enhanced migration compared to control cells. These findings suggest that AA accelerates SMC migration in the thickening of the intima during atheroma formation, via stimulation of extracellular Ca2+ influx.