Monocyte chemotactic protein 1 amplifies serotonin-induced vascular smoothmuscle cell proliferation

Monocyte chemotactic protein 1 (MCP-1), which is synthesized by vascular ce lls, is a chemoattractant for monocytes and has been implicated in a wide r ange of acute and chronic inflammatory processes characterized by monocyte infiltration, including atherosclerosis. However, it is unclear whether MCP -1 is able to modulate vascular smooth muscle cell (VSMC) proliferation. We assessed the effect of MCP-1 on VSMC proliferation and its interaction wit h serotonin (5-HT), a mitogen for VSMCs. Growth-arrested VSMCs were stimula ted with different concentrations of MCP-1 (25-200 ng/ml) and 5-HT (5 and 5 0 muM) in serum-free medium. DNA synthesis in VSMCs was measured by [H-3]th ymidine incorporation. 5-HT at concentrations of 5 and 50 muM significantly stimulated DNA synthesis by 1.8- and 2.1-fold over the control value, resp ectively Ip < 0.0001). However, MCP-1 at the concentrations tested did not have any significant effect on DNA synthesis. Even though MCP-1 (50 ng/ml) by itself is not mitogenic, when added to 5-HT, it significantly amplified the mitogenic effect of 5-HT compared with that of 5-HT alone (p < 0.0001). The 5-HT2A receptor antagonist sarpogrelate (10 muM) and its major metabol ite M-1 (0.1 muM), pertussis toxin (10 ng/ml), Src family protein tyrosine kinase (PTK) inhibitor PP2 (1 muM), protein kinase C (PKC) inhibitor Ro31-8 220 (0.1 muM) and mitogen-activated protein kinase (MAPK) kinase inhibitor PD098059 (10 CIM) significantly inhibited the mitogenic effect of 5-HT and its interaction with MCP-1. Anti-MCP-1 antibody (2 mug/ml) and the Janus ki nase 2 (JAK2) inhibitor AG490 (10 muM) significantly inhibited the interact ion of MCP-1 with 5-MT. Further, the amplified mitogenic effect of 5-HT wit h MCP-1 was completely reversed by the combined use of sarpogrelate with an ti-MCP-1 antibody. Our results suggest that MCP-1 amplifies the mitogenic e ffect of 5-HT on VSMCs. The mitogenic effect of 5-HT may be mediated by the G protein-Src family PTK-PKC-MAPK pathway. The activation of the JAK2/sign al transducer and activator of transcription 3 pathway by MCP-1 in addition to the MAPK pathway by 5-HT may explain the potentiating effect of MCP-1 o n 5-HT-jnduced mitogenesis. Copyright (C) 2001 S.,KargerAG,Basel.