Adenosine Diphosphate Receptor P2Y12-Mediated Migration of Host Smooth Muscle-Like Cells and Leukocytes in the Development of Transplant Arteriosclerosis

Abstract

We have recently reported that platelet P2Y12 receptors may play a role in the development of transplant arteriosclerosis (TA). In the present study, we investigated the role of P2Y12 receptors on host-derived smooth muscle-like cells (SMLCs, including bone-marrow-derived SMLCs) and CD45+ leukocytes, both of which are believed to be associated with the development of TA, using P2Y12-deficient (KO) mice. Orthotopic carotid artery transplantation was performed from C3H/He (H-2k) donors into KO or wild-type (WT) recipient mice (129S:C57BL/6, H-2b). Grafts were harvested at 8 weeks after transplantation for histology. Plasma monocyte chemoattractant protein-1 (MCP-1) levels were analyzed with a kit. Cell migration was examined using a Boyden chamber system. The expression of MCP-1 messenger RNA was assessed by real-time polymerase chain reaction. Eight weeks after allotransplantation, KO recipient mice showed a significant reduction of luminal occlusion, host-derived SMLCs, CD45+ leukocytes, MCP-1+ cells in the grafts, and of plasma MCP-1 levels. In addition, the migration of host-derived SMLCs (including bone-marrow-derived SMLCs) and CD45+ leukocytes stimulated with adenosine diphosphate (ADP) or 2-methylthio-ADP (2MeSADP, a stable ADP analog) was significantly decreased in KO mice. There were no significant changes in MCP-1-induced cell migration between WT and KO mice. The low concentration of 2MeSADP plus MCP-1 significantly increased cell migration in WT but not KO mice. Furthermore, 2MeSADP-induced MCP-1 messenger RNA expression was significantly reduced in the cells of KO mice. Thus, the P2Y12-mediated migration of host-derived SMLCs and CD45+ leukocytes may play an important role in the development of TA, partly by MCP-1 pathways.