17β-estradiol down-regulates lipopolysaccharide-induced MCP-1 production and cell migration in vascular smooth muscle cells

Atherosclerosis is an inflammatory disease where lipopolysaccharide (LPS) triggers the release of inflammatory cytokines that accelerate its initiation and progression. Estrogen has been proven to be vasoprotective against atherosclerosis; however, the anti-inflammatory function of estrogen in the vascular system remains obscure. In this study, we investigated the effect of estrogen on LPS-induced monocyte chemoattractant protein-1 (MCP-1; listed as CCL2 in the MGI database) production in vascular smooth muscle cells (VSMCs). LPS significantly enhances MCP-1 production and this is dependent on nuclear factor k B (NFkB) signaling, since the use of NFkB inhibitor pyrrolidine dithiocarbamate or the silencing of NFkB subunit p65 expression with specific siRNA largely impairs LPS-enhanced MCP-1 production. On the contrary, 17b-estradiol (E2) inhibits LPS-induced MCP-1 production in a time- and dosedependent manner, which is related to the suppression of p65 translocation to nucleus. Furthermore, p38 MAPK is rapidly activated in response to LPS, while E2 markedly inhibits p38 MAPK activation. Transfection with p38 MAPK siRNA or the use of p38 MAPK inhibitor SB203580 markedly attenuates LPS-stimulated p65 translocation to nucleus and MCP-1 production, suggesting that E2 suppresses NFkB signaling by the inactivation of p38 MAPK signaling. LPS promotes VSMCs migration and this is abrogated by MCP-1 antibody, implying that MCP-1 may play a major role as an autocrine factor in atherosclerosis. In addition, E2 inhibits LPS-promoted cell migration by downregulation of MCP-1 production. Overall, our results demonstrate that E2 exerts anti-inflammatory property antagonistic to LPS in VSMCs by reducing MCP-1 production, and this effect is related to the inhibition of p38 MAPK/NFkB cascade.