Progesterone attenuates temporomandibular joint inflammation through inhibition of NF-κB pathway in ovariectomized rats

Sex hormones may contribute to the symptomatology of female-predominant temporomandibular disorders (TMDs) inflammatory pain. Pregnant women show less symptoms of TMDs than that of non-pregnant women. Whether progesterone (P4), one of the dominant sex hormones that regulates multiple biological functions, is involved in symptoms of TMDs remains to be explored. Freund's complete adjuvant were used to induce joint inflammation. We evaluated the behavior-related and histologic effects of P4 and the expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, and IL-6 in the synovial membrane. Primary TMJ synoviocytes were treated with TNF-alpha or IL-1 beta with the combination of P4. Progesterone receptor antagonist RU-486 were further applied. We found that P4 replacement attenuated TMJ inflammation and the nociceptive responses in a dose-dependent manner in the ovariectomized rats. Correspondingly, P4 diminished the DNA-binding activity of NF-kappa B and the transcription of its target genes in a dose-dependent manner in the synovial membrane of TMJ. Furthermore, P4 treatment showed decreased mRNA expression of proinflammatory cytokines, and partially reversed TNF-alpha and IL-1 beta induced transcription of proinflammatory cytokines in the primary synoviocytes. Moreover, progesterone receptor antagonist RU-486 partially reversed the effects of P4 on NF-kappa B pathway. In conclusion, progesterone ameliorated TMJ inflammation through inhibition of NF-kappa B pathway.