Protein kinase C-delta regulates migration and proliferation of vascular smooth muscle cells through the extracellular signal-regulated kinase 1/2

Back,around. Smooth muscle cell (SMC) migration and proliferation are early and crucial events in the pathogenesis of intimal hyperplasia, the primary cause of restenosis after vascular intervention. We tested the hypothesis that protein kinase C-delta (PKC delta), a ubiquitously expressed intracellular protein kinase, regulates vascular SMC proliferation and migration. Methods: Exogenous PKC delta was expressed in cultured SMCs via stable transfection or adenovirus-mediated gene transfer. Conversely, endogenous PKC delta was inhibited by means of targeted gene deletion (gene knock-out). Cell proliferation and migration were determined by H-3-thymidine incorporation and 24-well transwell assay, respectively. Results: We isolated and examined three A10 SMC lines in which PKC delta was stably transfected. Compared with cells that were transfected with an empty vector, cells transfected with PKC delta exhibited reduced ability to proliferate. Moreover, PKC delta transfection inhibited SMC migration toward platelet-derived growth factor-BB. Similar inhibitory effects on proliferation and migration were also observed when PKC delta was introduced into primary aortic SMCs via an adenoviral vector. Interestingly, SMCs isolated from PKC delta knockout mice also displayed decreased chemotaxis and proliferation compared with PK delta(+/+) littermates, suggesting a complex yet critical role for PKC delta. We studied the mitogen-activated protein kinase extracellular signal-regulated kinases (ERK) 1/2 as a possible signaling pathway for PKC delta's inhibitory effect. PKC delta overexpression diminished ERK1/2 activity. Molecular restoration of ERK activation reversed the inhibitory effect of PKC delta on SMC proliferation and migration. Conclusions. We demonstrate that although normal migration and proliferation is lessened in SMCs deficient in PKC delta, its prolonged activation also diminishes those behaviors. This suggests a dual, critical role for PKC delta in SMC proliferation and migration, and thus intimal hyperplasia and restenosis.