We investigated the effect of TNF-alpha on interleukin-8 (IL-8) and endothelin-1 (ET-1) expression, and their different signal transduction pathways. Human dermal microvascular endothelial cells (HMECs) were treated with TNF-alpha. By Northern blot analysis, TNF-alpha at 50, 100, 200, and 400 U/ml significantly induced IL-8 mRNA expression by 206%, 252%, 211%, and 158%, respectively, as compared to controls (p < 0.05). Overexpression of human superoxide dismutase (SOD) by adenovirus-mediated gene transfer or addition of exogenous hydrogen peroxide (H(2)O(2)) significantly enhanced TNF-alpha-induced IL-8 mRNA expression. Furthermore, HMECs treated with TNF-alpha at 50, 100, and 200 U/ml significantly increased ET-1 mRNA expression by 71%, 82%, and 66%, respectively (p < 0.05). By contrast, SOD gene transfer and exogenous H(2)O(2) significantly inhibited TNF-alpha-induced ET-1 mRNA expression. Thus, TNF-alpha significantly induces both IL-8 and ET-1 gene expression in HMECs possibly through different redox signaling pathways. H(2)O(2) enhances TNF-alpha-induced IL-8 expression, but inhibits TNF-alpha-induced ET-1 expression.