Interleukin 6 Induces Expression of NADPH Oxidase 2 in Human Aortic Endothelial Cells Via Long Noncoding RNA MALAT1.

Human abdominal aortic aneurysm (AAA) is characterized by the induction of intracellular and extracellular inflammatory cytokines and the production of reactive oxygen species (ROS) associated with localized inflammatory responses in the vascular wall. Recent studies have shown that greater circulating levels of the proinflammatory cytokine interleukin-6 (IL-6) are closely associated with AAA presence, suggesting that IL-6 plays an important role in the development of AAA. Previous in vivo studies have indicated that excess activities of NADPH oxidase (NOX), a major oxidase system for ROS production, promote AAA development. Furthermore, long noncoding RNAs (lncRNAs) are involved in the development of AAA. LncRNA MALAT1 has been found closely involved in endothelial cell functions and dysfunctions. In the present study, we explored the effects and the underlying mechanisms of IL-6 and MALAT1 on the expression/activity of NOXs in human aortic endothelial cells (HAOECs). Primary HAOECs with or without overexpression or knockdown of MALTA1 were cultured in the presence of IL-6. We found that IL-6 concentration- and time-dependently elevated the NOX activity as well as the MALAT1 level in HAOECs. Among different NOXs, only NOX2 was induced by IL-6. Overexpression and knockdown of MALAT1 respectively augmented and abolished IL6-induced expression of NOX2, NOX activity/cellular ROS production, and activation of the human NOX2 gene promoter, whereas MALAT1 alone in the absence of IL-6 treatment showed no significant effect. Knockdown of extracellular signal-regulated kinase (ERK) abolished IL6-induced expression of MALAT1. In conclusion, this study provides the first evidence that IL-6 induces expression/activity of NOX2 in HAOECs via inducing MALAT1 by an ERK-dependent mechanism. It adds new insights into the molecular mechanisms underlying AAA development.