Therapeutic potential Tanshinone ⅡA in periodontitis: an in vitro study revealing its anti-inflammatory effect through activation of autophagy in lipopolysaccharide-induced human periodontal ligament fibroblasts

Background This study was designed to investigate the underlying mechanisms of Tanshinone ⅡA using an in vitro model of lipopolysaccharide (LPS)-induced human periodontal ligament fibroblasts (HPDLFs). Methods An LPS-induced periodontitis model was constructed with HPDLFs. Cell counting kit-8 (CCK-8) and flow cytometry assays were used to assess cell viability and apoptosis of model HPDLFs. The content of inflammation-relevant cytokines was quantified by ELISA, and the autophagosome formation was observed under a transmission electron microscopy. Further, correlations with mediators related to autophagy and protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway were tested via quantitative PCR and immunoblotting assays. For validation, rescue assays were performed using autophagy inhibitor 3-MA or AKT activator SC79. Results Tanshinone ⅡA effectively restored cell viability, inhibited apoptosis, and significantly downregulated the expression of inflammatory cytokines TNF-α, IL-6, IL-8, and IL-1β. Tanshinone IIA promoted autophagosome formation, upregulated the expression of Beclin 1, downregulated p62 levels, and simultaneously inhibited the phosphorylation of the AKT/mTOR signaling pathway. Intervention experiments using the autophagy inhibitor 3-MA and the AKT activator SC79 confirmed that the protective effects of Tanshinone IIA was dependent on the activation of autophagy and inhibition of the AKT/mTOR pathway. This study is limited to in vitro assays in LPS-induced HPDLFs, and lacks in vivo validation. Conclusion This study further evaluated the anti-inflammatory property of Tanshinone ⅡA on LPS-induced HPDLFs, and proposed that the activation of autophagy and suppression of AKT/mTOR pathway may account for such effects.