Cytokine stimulation of pregnancy-associated plasma protein A expression in human coronary artery smooth muscle cells: inhibition by resveratrol
Through specific cleavage of proteins that bind and inhibit insulin-like growth factor-I (IGF-I), pregnancy-associated plasma protein-A (PAPP-A) enhances local IGF-I availability, and, consequently, receptor activation. PAPP-A expression is increased in experimental models of vascular injury and in human atherosclerotic plaque; however, little is known about the regulation of PAPP-A gene expression in vascular cells. In this study, we tested the hypothesis that proinflammatory cytokines involved in the vascular injury response stimulate PAPP-A gene expression in human coronary artery smooth muscle cells (hCASMC) in culture. Tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta stimulated PAPP-A gene expression in a time- and dose-dependent manner. The effect of these cytokines appears to be at the level of transcription because actinomycin D completely prevented the induction of PAPP-A gene expression. Accumulation of PAPP-A in cell-conditioned medium paralleled mRNA synthesis, as did proteolytic activity against IGF binding protein-4 (IGFBP-4). Interestingly, pretreatment of hCASMC with resveratrol, a polyphenol found in the skin of grapes and in red wine purported to underlie the "French paradox," inhibited TNF-alpha- and IL-1beta-induced PAPP-A expression and, hence, its IGFBP-4 proteolytic activity. Resveratrol had no effect on basal PAPP-A expression and protease activity. Our finding that PAPP-A gene expression in hCASMC is stimulated by TNF-alpha and IL-1beta suggests a mechanism for the regulation of PAPP-A in response to vascular injury that may contribute to the enhanced IGF-I bioactivity in intimal hyperplasia and atherosclerotic plaque development. Our results also suggest that PAPP-A may be a target of the cardiovascular system-protective effects of resveratrol.