CYCLIC STRAIN-INDUCED MONOCYTE CHEMOTACTIC PROTEIN-1 GENE-EXPRESSION IN ENDOTHELIAL-CELLS INVOLVES REACTIVE OXYGEN SPECIES ACTIVATION OF ACTIVATOR PROTEIN-1

Endothelial cells (ECs) are constantly exposed to blood pressure-induc ed mechanical strain. We have previously demonstrated that cyclic stra in can induce gene expression of monocyte chemotactic protein-1 (MCP-1 ). The molecular mechanisms of gene induction by strain, however, rema in unclear. Recent evidence indicates that intracellular reactive oxyg en species (ROS) can act as a second messenger for signal transduction and thus affect gene expression. The potential role of ROS in strain- induced MCP-1 expression was investigated. ECs under cyclic strain ind uced a sustained elevated production of intracellular superoxide. ECs under strain or pretreated with either H2O2 or xanthine oxidase/hypoxa nthine induced MCP-1 expression. Strain- or oxidant-induced MCP-1 mRNA levels could be inhibited by treating ECs with catalase or antioxidan t N-acetyl-cysteine (NAG). Functional analysis of MCP-1 promoter and s ite-specific mutations indicates that the proximal tissue plasminogen activator-responsive element (TRE) in the -60-bp promoter region is su fficient for strain or H2O2 inducibility. Electrophoretic mobility shi ft assays demonstrated an increase of nuclear proteins binding to TRE sequences from ECs subsequent to strain or H2O2 treatment. NAC or cata lase pretreatment of ECs inhibited the strain- or H2O2-induced AP-1 bi nding. These results clearly indicate that cyclic strain inducibility of MCP-1 in ECs uses the interaction of AP-1 proteins with TRE sites v ia the elevation of intracellular ROS levels in strained ECs. These fi ndings emphasize the importance of intracellular ROS in the modulation of hemodynamic force-induced gene expression in vascular ECs.