Endogenous VEGF-A is responsible for mitogenic effects of MCP-1 on vascular smooth muscle cells.
Vessel wall remodeling is a complex phenomenon in which the loss of differentiation of vascular smooth muscle cells (VSMCs) occurs. We investigated the role of rat macrophage chemoattractant protein (MCP)-1 on rat VSMC proliferation and migration to identify the mechanism(s) involved in this kind of activity. Exposure to very low concentrations (1-100 pg/ml) of rat MCP-1 induced a significant proliferation of cultured rat VSMCs assessed as cell duplication by the counting of total cells after exposure to test substances. MCP-1 stimulated VSMC proliferation and migration in a two-dimensional lateral sheet migration of adherent cells in culture. Endogenous vascular endothelial growth factor-A (VEGF-A) was responsible for the mitogenic activity of MCP-1, because neutralizing anti-VEGF-A antibody inhibited cell proliferation in response to MCP-1. On the contrary, neutralizing anti-fibroblast growth factor-2 and anti-platelet-derived growth factor-bb antibodies did not affect VSMC proliferation induced by MCP-1. RT-PCR and Western blot analyses showed an increased expression of either mRNA or VEGF-A protein after MCP-1 activation (10-100 pg/ml), whereas no fms-like tyrosine kinase (Flt)-1 receptor upregulation was observed. Because we have previously demonstrated that hypoxia (3% O2) can enhance VSMC proliferation induced by VEGF-A through Flt-1 receptor upregulation, the effects of hypoxia on the response of VSMCs to MCP-1 were investigated. Severe hypoxia (3% O2) potentiated the growth-promoting effect of MCP-1, which was able to significantly induce cell proliferation even at a concentration as low as 0.1 pg/ml. These findings demonstrate that low concentrations of rat MCP-1 can directly promote rat VSMC proliferation and migration through the autocrine production of VEGF-A.
Parenti
Astrid
A
Laboratory of Vascular Pharmacology, Department of Preclinical and Clinical Pharmacology, University of Florence, 50139 Florence, Italy.
Bellik
Lydia
L
Brogelli
Laura
L
Filippi
Sandra
S
Ledda
Fabrizio
F
D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D008938:Mitosis / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000378:metabolism
D018932:Chemokine CCL2; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1