PRDX6 Alleviates Lipopolysaccharide-induced Inflammation in Human Gingival Fibroblasts by Regulation of NRF2

Purpose: Periodontitis is a progressive and inflammatory oral disease and results in the damage of the supporting tissues of teeth. Peroxiredoxin 6 (PRDX6) is an antioxidant enzyme identified as a redox balance regulator. This study aimed to investigate whether PRDX6 could protect human gingival fibroblasts (HGFs) from lipopolysaccharide (LPS) induced inflammation and its mechanisms.Methods: Both inflamed and non-inflamed human gingival tissues were collected to assess the expression of PRDX6 and NRF2 by Immunohistochemistry and Western blotting. Furthermore, HGFs were stimulated with LPS, MJ33 (PRDX6 phospholipase A2 inhibitor), or ML385 (NRF2 inhibitor). The expression levels of inflammatory cytokines were measured by RT-qPCR and ELISA, and reactive oxygen species (ROS) were detected using DCFH-DA.Results: PRDX6 was downregulated in inflamed gingival tissues. In HGFs, LPS induced inflammatory cytokines and ROS was upregulated in PRDX6 knockdown cells. Furthermore, co-treatment with MJ33 alleviated LPS-induced inflammatory cytokines and ROS while inhibiting NRF2 upregulated those in HGFs.Conclusion: Therefore, this study provided a new mechanistic insight that PRDX6, regulated by the NRF2 signaling, alleviates LPS-induced periodontitis in human gingival fibroblasts.