Induction of mitogen-activated protein kinase phosphatase-1 by arachidonic acid in vascular smooth muscle cells

Arachidonic acid (AA) and its metabolites play important roles in a variety of biological processes, such as signal transduction, contraction, chemotaxis, and cell proliferation and differentiation. It was demonstrated recently that AA can activate mitogen-activated protein kinases (MAPKs), which are crucial for transducing signals initiating cell growth and apoptosis. Here we studied the effect of AA on the induction of MAPK phosphatase-1 (MKP-1) in vascular smooth muscle cells (VSMCs) and found that AA stimulated induction of MKP-1 mRNA and proteins in VSMCs in a time- and dose-dependent manner. Specific inhibitors of cyclooxygenase-, lipoxygenase-, and cytochrome P450-dependent metabolism did not affect AA-induced MKP-1 expression, indicating that eicosanoid biosynthesis was not involved in this process. The glutathione precursor N-acetylcysteine, an antioxidant, abolished AA-stimulated MKP-1 gene expression, whereas inhibition of protein kinase C by calphostin C had no influence on MKP-1 induction. VSMC pretreatment with genistein, a tyrosine kinase inhibitor, completely blocked AA-stimulated MKP-1 induction. MAPK kinase inhibitor PD 98059 did abolish AA-stimulated activation of extracellular signal-regulated kinases but not MKP-1 induction. Furthermore, agonists that increase AA release stimulated MKP-1 induction and activation of MAPKs, including extracellular signal-regulated kinases and c-Jun NH2-terminal protein kinases or stress-activated protein kinases, Taken together, our findings demonstrate that AA induced MKP-1 expression in VSMCs via activation of tyrosine kinases involving AA-induced free radical generation, suggesting an important role for MKP-1 in the regulation of AA-initiated signal transduction in VSMCs.