| Abstract: | Retinoic acid‐inducible gene‐I (RIG‐I) is a member of the DExH family of proteins, and little is known of its biological function in the oral region. We previously reported that interleukin 1β (IL‐1β) induced RIG‐I expression in gingival fibroblasts. In this study, we studied the mechanism of RIG‐I expression induced by lipopolysaccharide (LPS) or double‐stranded RNA (dsRNA) in gingival fibroblasts. We also addressed the role of RIG‐I in the expression of IL‐1β, IL‐6 and IL‐8 in gingival fibroblasts stimulated with LPS or dsRNA. We stimulated cultured human gingival fibroblasts with LPS or dsRNA, and examined the expression of RIG‐I mRNA and protein. The effect of cycloheximide, a protein synthesis inhibitor, on RIG‐I induction by these stimuli was examined. The expression of IL‐1β, IL‐6 and IL‐8 in gingival fibroblasts transfected with RIG‐I cDNA stimulated with LPS or dsRNA was examined. LPS or dsRNA induced the expression of mRNA and protein for RIG‐I in concentration‐ and time‐dependent manners. We also examined the localization of RIG‐I, and found that it was expressed in cytoplasm. Cycloheximide did not suppress the LPS or dsRNA‐induced RIG‐I expression. Introduction of RIG‐I cDNA into gingival fibroblasts resulted in enhanced expression of IL‐1β, IL‐6 and IL‐8; moreover, overexpression of RIG‐I stimulated with LPS or dsRNA synergistically increased expression of IL‐1β, IL‐6 and IL‐8. RIG‐I may have important roles in the innate immune response in the regulation of IL‐1β, IL‐6 and IL‐8 expression in gingival fibroblasts in response to LPS and dsRNA. |
