Zinc finger protein A20 regulates the development and progression of osteoarthritis by affecting the activity of NF-κB p65

Objective: To investigate the role of Zinc finger protein A20 in osteoarthritis (OA) by regulating NF-κB p65.

Methods: A20, MMP1, MMP13 and IL-1β expressions in human OA cartilage samples were detected by qRT-PCR. IL-1β-induced chondrocyte was treated with A20 lentivirus activation particle, pyrrolidine dithiocarbamate (PDTC, a NF-κB inhibitor) with/without A20 siRNA. IL-6, TNF-α, and PGE2 levels were measured by ELISA, and NO production by Greiss reaction. Destabilization of the medial meniscus (DMM) surgery was used to construct the OA models, followed by injection of A20 adenovirus. MMP1 and MMP13 expression was measured by immunohistochemistry. The mRNA and protein expression were performed by qRT-PCR and western blotting, respectively.

Results: A20 was down-regulated in human OA cartilage samples, and negatively correlated with the expressions of MMP1, MMP13 and IL-1β. The IL-1β-induced chondrocyte manifested decreased A20 with increased NF-κB p65 activity. A20 overexpression suppressed the NF-κB p65 activity in IL-1β-induced chondrocyte. Furthermore, PDTC decreased IL-1β-induced chondrocyte apoptosis with the upregulated COL1A1, COL2A1, COL10A1 and ACAN, as well as the down-regulated MMP1, MMP13, COX2, iNOS, IL-6, TNF-α, NO and PGE2, which was reversed by A20 siRNA. In vivo, OA mice gained higher OARSI score and Mankin's score, exhibited up-regulations of MMP1 and MMP13, and decreased NF-κB p65 activity, which was improved after injection of A20 adenovirus.

Conclusion: A20 was reduced in OA cartilage samples, and its overexpression, by suppressing the activity of NF-κB p65, could improve IL-1β-induced chondrocyte degradation and apoptosis in vitro, as well as mitigate the inflammation in OA mice.