IL-4-induced oxidative stress upregulates VCAM-1 gene expression in human endothelial cells

Vascular cell adhesion molecule-1 (VCAM-1) is expressed in early stages of atherosclerosis: however, the mechanisms of its upregulation are not fully understood. In the present study, we examined the effects of interleukin-4 (IL-4) on VCAM-1 gene expression and its transcriptional regulatory mechanism in human umbilical vein endothelial cells (HUVEC). Reverse transcription-polymerase chain reaction showed that VCAM-1 mRNA was induced in IL-4-treated HUVEC in a time- and close-dependent manner. Among known transcription factors that have binding sites in the promoter region of the VCAM-1 gene, IL-4 activated only SP-1. In contrast, nuclear factor-κB (NF-κB), activator protein-1 (AP-1) and interferon regulatory factor-1 (IRF-1), which also have consensus binding sequences in the 5′-flanking region of the human VCAM-1 gene, were not activated. The role of SP-1 in IL-4-induced VCAM-1 expression was confirmed in HUVEC transfected with a reporter construct of the VCAM-1 promoter with mutated SP-1 binding site. As IL-4 treatment of HUVEC enhanced the intracellular oxidizing potential, as indicated by an increase in 2′,7′-dichlorofluorescein (DCF) fluorescence, we studied the effect of antioxidants on IL-4-induced VCAM-1 expression. Pretreatment of HUVEC with pyrrolidine dithiocarbamate (PDTC) or N-acetylcysteine (NAC) completely prevented IL-4-induced VCAM-1 expression. In addition, PDTC inhibited IL-4-related activation of SP-1. These results suggest that IL-4-induced oxidative stress upregulates the expression of VCAM-1 gene in HUVEC at transcriptional levels via activation of SP-1 transcription factor. In contrast, NF-κB, AP-1 or IRF-1 do not appear to be involved in the signal transduction cascade.