Enhanced recovery of injury-caused downregulation of paxillin protein by eNOS gene expression in rat carotid artery - Mechanism of NO inhibition of intimal hyperplasia?

Injury-caused dedifferentiation accompanied by proliferation and migration of smooth muscle cells (SMCs) is an important process in the development of the neointima. Nitric oxide (NO) stimulates differentiation and inhibits proliferation and migration of SMCs. Paxillin has been found to play an important role in cell differentiation, and its phosphorylation is regulated by NO in cultured SMCs. However, the regulation of paxillin by NO in the injured artery has not been investigated. Therefore, the aim of this study was to study the effects of in vivo endothelial NO synthase (eNOS) gene transfection on paxillin expression and intimal hyperplasia. A catheter balloon-denuded rat carotid artery was transfected in vivo with the replication-deficient adenovirus Ad5/RSVeNOS or with Ad5/RSVLacZ as the control. Transfected eNOS gene expression was determined by immunostaining, Western blot analysis, and citrulline assay. The expression of paxillin and its associated proteins was determined in injured arteries by Western blot analysis. The area of the intima and the ratio of intima to media were examined on cross sections by morphometry. The data showed that the expression of paxillin was significantly downregulated after injury. eNOS gene transfer showed no effect on paxillin downregulation 2 days after injury but significantly enhanced the recovery of paxillin protein 5 days and 2 weeks after injury. Vinculin, a paxillin-binding protein, was not altered by vascular injury or by eNOS gene transfer, eNOS gene transfer significantly inhibited intimal hyperplasia for up to 4 weeks. These results suggest that NO inhibition of intimal hyperplasia may be mediated by enhancing the recovery of injury-caused downregulation of paxillin.