Green tea polyphenols attenuate LPS-induced inflammation through upregulating microRNA-9 in murine chondrogenic ATDC5 cells.

BACKGROUND: Osteoarthritis (OA), a universal chronic musculoskeletal disorder, is closely related to inflammation. More effective drugs for improving OA outcome are definitely needed. Herein, we attempted to verify the protective role of green tea polyphenols (GTP) after treatment with murine in ATDC5 cells to reveal the regulatory mechanism. METHODS: ATDC5 cells were stimulated with lipopolysaccharide (LPS) to mimic an inflammatory response during OA. Cell activity, apoptosis, levels of relative proteins, and prophlogistic factors were tested via a Cell Counting Kit-8 experiment, a flow cytometry experiment, western blot, and RT-qPCR (ELISA and Western blot), separately. miR-9 level was detected by RT-qPCR and altered via miR-9 mimic and inhibitor transfection. We finally studied MAPK and NF-κB pathways in GTP-related modulations using western blot. RESULTS: LPS caused inflammatory cell damage in ATDC5 cells, showing decreased cell activity, enhanced apoptosis, and increased levels of pro-inflammatory cytokines. GTP pretreatments could significantly attenuate LPS-induced alterations. In addition, LPS-induced miR-9 upregulation was further positively regulated in ATDC5 cells. The effects of GTP pretreatments in LPS-caused ATDC5 cells were enhanced via miR-9 upregulation, whereas they were reduced via miR-9 suppression. Finally, we found that GTP pretreatments could suppress the MAPK and NF-κB pathways through miR-9 regulation. CONCLUSION: GTP pretreatments attenuated LPS-induced inflammatory response accompanied by the suppression of the MAPK and NF-κB pathways via positively regulating miR-9 in ATDC5 cells.