PGC-1α attenuates TNF-α-induced inflammatory responses in OCCM-30 cells

Background and objectives: Peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, a master regulator of mitochondrial biogenesis and oxidative metabolism, has been associated with many inflammatory diseases. However, little is known about the function and mechanism of PGC-1α in cementoblasts under periodontitis. Our study aimed to investigate the effects of PGC-1α in immortalized cementoblast cell line OCCM-30 under TNF-α stimulation.

Materials and methods: OCCM-30 cells were cultured and exposed to TNF-α, and PGC-1α expression was assessed by Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting. Chemical inhibitors targeting various signaling pathways including NF-κB, p38 MAPK, Akt, and p53 were used to identify the regulatory mechanism involved. ZLN005 was used to upregulate PGC-1α and the subsequent alteration of inflammatory cytokines expression under TNF-α stimulation were examined by qRT-PCR and Elisa. PGC-1α siRNA was employed to further verify the role of PGC-1α in inflammatory response. Dual-reporter gene assays were performed to examine the transcriptional activity of p65, and the phosphorylation level of p65 was evaluated by western blotting. Immunofluorescence assays and nuclear and cytoplasmic extractions were performed to check the nuclear translocation of p65. Coimmunoprecipitation studies were also performed to check whether there is direct binding between p65 and PGC-1α.

Results: TNF-α suppressed PGC-1α expression in OCCM-30 cells. Blocking p38 MAPK pathways restored the expression of PGC-1α. ZLN005 can upregulate PGC-1α in OCCM-30 cells. The upregulation of PGC-1α by ZLN005 inhibited TNF-α-induced proinflammatory cytokine expression, which was impaired by the transfection of PGC-1α siRNA. Knocking down PGC-1α also partially restored the ZLN005-decreased transcriptional activity of p65. However, the phosphorylation level and nuclear translocation of p65 were not significantly affected by PGC-1α. It was found that p65 was bound to PGC-1α in OCCM-30 cells stimulated by TNF-α, and the binding was increased upon ZLN005 treatment.

Conclusions: PGC-1α can attenuate TNF-α-induced inflammatory responses in OCCM-30 cells.