[Estrogen exerts anti-inflammatory effects by inhibiting NF-κB pathway through binding with estrogen receptor β on...

Objective To investigate the mechanism of estrogen's anti-inflammatory effects on synovial cells during the pathogenic process of osteoarthritis. Methods We isolated synovicytes from synovium tissues and identified the cells with flow cytometry. Then we detected the expression level of estrogen receptor β (ERβ) in synovicytes with immunofluorescence staining. The synovicytes were divided into control group, group pretreated with 10 ng/mL IL-1β, group pretreated with 10 ng/mL IL-1β and 10^-7 mol/L estrogen, group pretreated with 10 ng/mL IL-1β, 10^-7 mol/L estrogen and specific antagonist of ERβ, 10^-5 mol/L tetrahydrocannabinol (THC). Thirty-six hours later, we observed the mRNA and protein levels of IκBα, phospho-IκBα (p-IκBα) and IL-6. Results Immunofluorescence staining showed the high expression level of ERβ in synovicytes. In IL-1β treated cells, IL-6 mRNA and protein level, IκBα mRNA and p-IκBα protein levels were elevated compared with the control group, while IκBα protein level declined. In the cells pretreated with IL-1β and estrogen, the mRNA and protein levels of IL-6, IκBα and p-IκBα were inhibited compared with IL-1β treated cells. THC blocked the effects of estrogen on the IL-1β and estrogen treated cells, and the mRNA and protein levels of IL-6, IκBα and p-IκBα had no significant difference compared with IL-1β treated cells. Conclusion The estrogen can restrain the activation of NF-κB pathway in synovicytes via ERβ, thus playing a vital role in anti-inflammation.