Increased Pressure Induces Sustained Protein Kinase C–Independent Herbimycin A–Sensitive Activation of Extracellular Signal–Related Kinase 1/2 in the Rabbit Aorta in Organ Culture

Abstract

Abstract The 42- and 44-kD mitogen-activated protein kinases, also referred to as extracellular signal–related kinase (ERK) 2 and 1, respectively, may be transiently activated by stretching vascular smooth muscle cells (VSMCs). Using an organ culture model of rabbit aorta, we studied short- and long-term ERK1/2 activation by intraluminal pressure (150 mm Hg). Activation of ERK1/2 was biphasic: it reached a maximum (217.5±8.4% of control) 5 minutes after pressurizing and decreased to 120.7±5.1% of control after 2 hours. Furthermore, after 24 hours of pressurizing, ERK1/2 activity was as high (241.8±14.7% of control) as in the acute phase. Long-term pressure-induced ERK1/2 activation correlated with stimulation of tyrosine phosphorylation of proteins in the 125- to 140-kD range. Neither protein kinase C inhibitors (1 μmol/L staurosporine or 50 μmol/L bisindolylmaleimide-I) nor tyrosine kinase inhibitors (50 μmol/L tyrphostin A48 or 50 μmol/L genistein) affected pressure-induced ERK1/2 activation. However, the Src-family tyrosine kinase inhibitor herbimycin A (500 nmol/L) did reduce both 5-minute (by 92±8%) and 24-hour (by 63±7%) pressure-induced ERK1/2 activation. Thus, our results demonstrate a sustained activation of ERK1/2 and tyrosine kinases by intraluminal pressure in the arterial wall. Pressure-induced ERK1/2 activation is PKC independent and Src-family tyrosine kinase dependent and possibly includes activation of extracellular matrix–associated tyrosine kinases.