Obacunone acts as a histone deacetylase 1 inhibitor to limit p38MAPK signaling and alleviate osteoarthritis progression.

Background: Osteoarthritis (OA) is an age-related progressive degenerative disorder characterized by cartilage extracellular matrix degradation and inflammation. In this study, we explored the function and mechanism of action of obacunone (OB) in inhibiting OA progression.

Methods: The degradation of articular cartilage and its severity were examined using Safranin O-fast green and hematoxylin and eosin (HE) staining. Chondrocyte survival was evaluated using a cell counting kit-8 assay. In addition, qRT-PCR, western blot analysis, immunohistochemical staining, and enzyme-linked immunosorbent assay were performed to evaluate the effects of OB on cartilage injury.

Results: OB mitigated cartilage lesions in rats with anterior cruciate ligament transaction-induced OA. The protein expression of collagen II was increased and the protein expression of ADAM metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS-5), matrix metalloproteinase (MMP)-13, and RUNX family transcription factor 2 (RUNX2) was reduced in the articular cartilage of OB-treated rats. Moreover, OB exhibited anti-inflammatory activities by reducing the serum levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-1β, and IL-18. In IL-1β-stimulated primary chondrocytes, OB dose-dependently elevated the expression of collagen II, and decreased the expression of ADAMTS-5, MMP-13, RUNX2 and inflammatory cytokines. Histone deacetylase 1 (HDAC1) was identified as a predicted OB target. OB inhibited HDAC1 expression to limit the activation of p38MAPK signaling. The transfection of chondrocytes with HDAC1 or p38MAPK overexpression plasmids reversed the chondroprotective effects of OB.

Conclusion: OB mitigated OA progression by binding to HDAC1 and inhibiting p38MAPK signaling, indicating that OB may be a promising drug for the treatment of OA.