Preventive effects of inotodiol on polyinosinic–polycytidylic acid-induced inflammation in human dermal fibroblasts

Double-strand RNA(dsRNA), which can induce inflammation, can be generated by necrotic keratinocytes in the skin environment. As an analog of dsRNA, polyinosinic–polycytidylic acid (poly(I:C)) is used to induce inflammation via the Toll-like Receptor 3 (TLR3) signaling pathway. Inotodiol, isolated from Inonotus obliquus, known as Chaga mushroom, is a natural lanostane-type triterpenoid with significant pharmacological activity and notable anti-inflammatory effects. However, the functions of inotodiol on dsRNA-induced inflammation in human dermal fibroblast (HDFs) remains unclear. In this study, we evaluated the anti-inflammatory effects of inotodiol inflammation induced on by poly(I:C) in HDFs. After pre-treatment with inotodiol, poly (I:C) was used to induce inflammation. Subsequently, mRNA expression and protein secretion of inflammatory cytokines, as well as TLR3 signaling protein levels were assessed. Inflammatory cytokines IL-1β, IL-6, and TNF-α′s increased mRNA expression by poly(I:C) in HDFs was significantly suppressed in the inotodiol pre-treatment group in a dose-dependent manner. A similar pattern was evaluated in the protein levels of these three cytokines. The inflammatory signals of TLR3 via p-IKK, p-p38, and NF-κB was reduced by inotodiol pre-treatment. Taken together, inotodiol possesses strong anti-inflammatory activity against poly(I:C)-induced inflammation in HDFs. Therefore, our findings support potential application of inotodiol as an effective anti-inflammatory agent in cosmetics.