Pulsatile stretch-induced extracellular signal-regulated kinase 1/2 activation in organ culture of rabbit aorta involves reactive oxygen species

Increased steady intraluminal pressure in blood vessels activates the extra cellular signal-regulated kinase (ERK)1/2 pathway. However, signal transduc tion of pulsatile stretch has not been elucidated. Using an organ culture m odel of rabbit aorta, we studied ERK1/2 activation by pulsatility in vessel s maintained at 80 mm Hg for 24 hours. ERK1/2 activity was evaluated by in- gel kinase assays and by Western blot. Compared with control aortas without pulsatility, aortas submitted to a pulsatile 10% variation in vessel diame ter displayed a significant increase in ERK1/2 activity (207 +/- 12%, P < 0 .001), which remained high after removal of the endothelium. Unlike steady overstretch, pulsatile stretch-induced activation of ERK1/2 was not modifie d by herbimycin A, a Src family tyrosine kinase inhibitor, but was reduced by other tyrosine kinase inhibitors, tyrphostin A48 and genistein (162 +/- 27% and 144 +/- 14%, respectively). Conversely, ERK1/2 activity was markedl y decreased in pulsatile vessels treated with staurosporine (114 +/- 18%) a lthough neither of the more specific protein kinase C inhibitors, Ro-31-822 0 or Go-6976, blocked ERK1/2 activation (209 +/- 24% and 238 +/- 34%, respe ctively), whereas staurosporine had no effect on steady overstretch-induced ERK1/2 activation. Pulsatility induced superoxide anion generation, which was prevented by the NADPH oxidase inhibitor diphenyleneiodonium. Furthermo re, polyethylene glycol-superoxide dismutase completely abolished ERK1/2 ac tivation by pulsatility (114 +/- 12%); Finally, ERK1/2 and O-2(-) levels in freshly isolated vessels were equivalent to the levels found in pulsatile vessels; In conclusion, pulsatile stretch activates ERK1/2 in the arterial wall via pathways different from those induced by steady overstretch. Pulsa tility might be considered a physiological stimulus that maintains a certai n degree of ERK1/2 activation via oxygen-derived free radical production.