Combination of IL-17 and TNFα induces a pro-inflammatory, pro-coagulant and pro-thrombotic phenotype in human endothelial cells

Objective Cardiovascular events remain the leading cause of death in rheumatoid arthritis (RA). To study the role of cytokines in these observations, the effects of tumour necrosis factor alpha (TNF alpha) and interleukin (IL)-17, a classical and a new key player in RA, were assessed in endothelial cell (EC) dysfunction. Methods Primary human EC were treated with IL-17 alone or combined with TNF alpha. mRNA expression was quantified by qRT PCR and Affymetrix microarrays. The role of IL-17 was studied using functional assays of platelet aggregation, EC migration and invasion. Results IL-17 alone induced 248 pro-inflammatory genes and 9803, when combined with TNF alpha. IL-17 plus TNF alpha induced synergistically chemokine genes such as CCL5, IL-8 and cytokine genes such as IL-6. In contrast, IL-17 decreased genes involved in the regulation of inflammation such as IL-33. IL-17 induced EC migration and invasion in synergy with TNF alpha. Such invasion was inhibited with an antiCXCR4 antibody, indicating the contribution of the stromal cell-derived factor-1/C-X-C chemokine receptor type 4 axis. Supernatants of IL-17-treated EC induced strong platelet aggregation. IL-17 inhibited endothelial CD39/ATPDase expression, an inhibitor of platelet activation. Finally, IL-17 enhanced genes critical for coagulation such as tissue factor and decreased thrombomodulin, leading to a pro-thrombotic state. Conclusion These results indicate that IL-17 specifically when combined with TNF alpha has major pro-coagulant and pro-thrombotic effects on vessels.