Abstract 118: Protein Kinase C-delta Prompts Adventitial Cell Migration Through Regulation of Monocyte Chemoattractant Protein-1 Signaling Pathway in Intimal Hyperplasia

Abstract

Introduction: Increasing evidence indicates that adventitial cells directly contribute to intimal hyperplasia via migration. Protein kinase C delta (PKC δ), a master mediator of apoptosis of smooth muscle cells (SMCs), is known to mediate expression of monocyte chemoattractant protein-1(MCP-1). In the current study, we hypothesize that PKCδ promotes adventitial cells migration by regulation of MCP-1 signaling pathway in injured arteries.

Methods and results: Using isolated carotid SMCs and adventitial fibroblasts, we showed that conditioned media from PKCδ-overexpressing SMCs stimulated migration of adventitial cells, which was blocked by neutralizing MCP-1 or by CCR2 mRNA knocking down. In vivo, PKCδ gene transfer increased SMC apoptosis and levels of MCP-1 and CCR2 expression (MCP-1 protein measured by immunostaining in pixel: 397±20*103 vs 99±18*103, p<0.05; CCR2 mRNA fold induction: 3.45±0.09 vs 1, p<0.01). Next, we evaluated adventitia cells migration by labeling adventitial cells with AdLacZ administered to the adventitial surface immediately following the carotid angioplasty procedure. Overexpresison of PKCδ in SMCs increased the accumulation of adventitial cells in the neointima by close to 10 times (LacZ positive area in pixel of AdPKCd- and AdNull-infected arteries: 769±67*103 vs 84±11*103, p<0.01). Blocking the MCP-1 signaling with an anti-MCP-1 antibody dramatically diminished the number of adventitia-originated cells detected in the medial/intimal region (LacZ positive area in pixel: 357±37*103 vs 894±42*103, p<0.01). The joint treatment of PKCδ and anti-MCP-1 markedly inhibited the I/M ratio by 62% as compared to a 36.3% and 30.8% reduction induced by a single treatment of PKCδ and anti-MCP-1, respectively. None of the treatments altered macrophage infiltration.

Conclusions: PKCδ appears to play multiple functions in arterial injury response. Apart from inducing apoptosis, PKCδ regulates migration of adventitial cells via upregulation of the MCP-1/CCR2 signaling axis. A combined strategy targeting both SMC apoptosis and adventitial cell migration may be an efficient approach to inhibit intimal hyperplasia.