NADPH oxidase inhibitors attenuate IL-4-induced MCP-1 expression in human aortic endothelial cells. HAEC were pre-treated with indicated concentrations of apocynin (APO) or diphenylene iodonium (DPI) for 30 min, and then incubated with 10 ng/ml of IL-4 for 4 h (a, c) or 16 h(b, d). The mRNA and protein expression levels of MCP-1 were determined by real-time RT-PCR (a, c) and ELISA (b, d). Values represent mean ± SEM (n = 4). *p < 0.05 versus control; #p < 0.05 versus IL-4