ADAR1 is targeted by miR-143 to regulate IL-1β-induced endothelial activation through the NFκB pathway

Excessive endothelial activation by inflammatory mediators is a critical contributing factor of sepsis pathophysiology. ADAR1 (adenosine deaminase acting on RNA), an enzyme that binds and edits double-stranded RNAs, exhibits immune regulatory properties. Whether ADAR1 is involved in the pathophysiology of sepsis is unclear. In the present study, we used human umbilical endothelial cells (HUVECs) as an in vitro model system to investigate the roles of ADAR1 in interleukin (IL)-1β-induced endothelial activation. We found that stimulation with IL-1β caused opposite changes in the expression of ADAR1 and the adherence molecules VCAM-1 and ICAM-1. ADAR1 overexpression reduced while ADAR1 knockdown enhanced IL-1β-induced HUVEC activation as assessed by ICAM-1 and VCAM-1 expression and THP-1 monocyte recruitment. Furthermore, ADAR1 was confirmed to be a direct target of miR-143 in HUVECs by a luciferase reporter assay, and miR-143 overexpression promoted while miR-143 knockdown inhibited HUVEC activation by IL-1β. In addition, ADAR1 overexpression prevented the enhancement effects of miR-143 overexpression on IL-1β-induced HUVEC activation. Our mechanistic studies revealed that ADAR1 overexpression reduced while ADAR1 knockdown enhanced PKR, IκBα, and NFκB phosphorylation induced by IL-1β. In addition, blocking NFκB signaling with the specific NFκB inhibitor PDTC (pyrrolidine dithiocarbamate) prevented IL-1β-induced HUVEC activation enhanced by ADAR1 knockdown. Collectively, these data indicated that ADAR1 is targeted by miR-143 to regulate IL-1β-induced HUVEC activation, and the NFκB pathway acts as the downstream mediator of ADAR1. In conclusion, miR-143 and ADAR1 may serve as therapeutic targets for sepsis.