Convergence of redox-sensitive and mitogen-activated protein kinase signaling pathways in tumor necrosis factor-alpha-mediated monocyte chemoattractant protein-1 induction in vascular smooth muscle cells

Monocyte chemoattractant protein-1 (MCP-1) is an important component of the inflammatory response of the vessel wall and has been shown to be regulate d by cytokines, such as tumor necrosis factor-alpha (TNF-alpha). However, t he precise signaling pathways leading to MCP-1 induction have not been full y elucidated in vascular smooth muscle cells (VSMCs). Cytokine signal trans duction involves protein kinases as well as reactive oxygen species (ROS). The relation between these 2 factors is not clear. In this study, we show t hat TNF-alpha induces a parallel phosphorylation of extracellular signal-re gulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38MA PK) and increases MCP-1 mRNA expression in cultured VSMCs. Inhibition of ER K1/2 but not p38MAPK caused a partial attenuation of MCP-1 induction (43+/- 10% inhibition). Incubation of VSMCs with multiple antioxidants (diphenylen e iodonium, liposomal superoxide dismutase, catalase, N-acetylcysteine, dim ethylthiourea, and pyrrolidine dithiocarbamate) had no effect on TNF-alpha- mediated MCP-1 upregulation. However, simultaneous blockade of the ERKl/2 a nd ROS pathways by using PD098059 combined with diphenylene iodonium or N-a cetylcysteine potently enhanced the ability of MAPK kinase inhibitors to ab rogate MCP-1 mRNA expression (100+/-2% inhibition). Thus, parallel ROS-depe ndent and ERK1/2-dependent pathways converge to regulate TNF-alpha-induced MCP-1 gene expression in VSMCs. These data unmask a complex but organized i ntegration of ROS and protein kinases that mediates cytokine-induced vascul ar inflammatory gene expression.