TNF-α stimulates IL-8 and endothelin-1 expression in human endothelial cells

Abstract

Background: Pro-inflammation cytokine TNF-α may contribute inflammation response and cause endothelial dysfunction, which may play an important role in atherogenesis. However, the mechanisms are largely unknown. The objective of this study was to investigate the effect of TNF-α on IL-8 and endothelin-1 (ET-1) expression and their signal transduction pathways. Methods: Human dermal microvascular endothelial cells (HMECs) were treated with TNF-α in a dose dependent and a time course fashion. Northern blot analysis was used to determine IL-8 and ET-1 mRNA expression. GAPDH mRNA level was used for loading control. Role of redox status in TNF-α induced IL-8 and ET-1 was investigated with transfection of recombinant adenovirus expressing human superoxide dismutase (ad.SOD) or addition of exogenous hydrogen peroxide (H2O2). Results: TNF-α at 50, 100, 200, and 400 U/ml significantly induced IL-8 mRNA expression by 3.06 ± 0.48, 3.52 ± 0.20, 3.11 ± 0.51, and 2.58 ± 0.36 fold, respectively, as compared to controls in HMECs (p < 0.05). IL-8 mRNA expression was significantly increased as early as 1 hour following TNF-α treatment. Ad.SOD infected cells or H2O2 treatment along with TNF-α showed a significant increase of IL-8 mRNA expression as compared to the group with TNF-α treatment alone. The ratios of ET-1 and GAPDH mRNA densities were significantly increased by 1.71 ± 0.22, 1.82 ± 0.14, and 1.66 ± 0.18 fold in 50, 100, and 200 U/ml TNF-α treatment, respectively, as compared to controls (p < 0.05). By contract, SOD gene transfer and exogenous H2O2 significantly inhibited TNF-α induced ET-1 mRNA expression. Conclusions: TNF-α significantly induces both IL-8 and ET-1 gene expression in human endothelial cells. However, TNF-α induced IL-8 and ET-1 expression may have different redox signaling mechanisms. TNF-α induced IL-8 expression is H2O2 dependent; however, ET-1 expression is H2O2 independent.