Small molecule inhibitors of WNT/β-catenin signaling block IL-1β- and TNFα-induced cartilage degradation.

Introduction: In this study, we tested the ability of small molecule inhibitors of WNT/beta-catenin signaling to block interleukin 1 beta (IL-1 beta)-and tumor necrosis factor alpha (TNF alpha)-induced cartilage degradation. Proinflammatory cytokines such as IL-1 beta and TNF alpha are potent inducers of cartilage degradation by upregulating matrix metalloproteinase (MMP) expression and activity. Because WNT/beta-catenin signaling was found to be involved in IL-1 beta-and TNF alpha-induced upregulation of MMP activity, we hypothesized that inhibition of WNT/beta-catenin signaling might block IL-1 beta-and TNF alpha-induced cartilage degradation. We tested the effect of small molecules that block the interaction between beta-catenin and TCF/Lef transcription factors on IL-1 beta-and TNF alpha-induced cartilage degradation in mouse fetal metatarsals. Methods: We used mouse fetal metatarsals treated with IL-1 beta and TNF alpha as an ex vivo model for cytokine-induced cartilage degradation. Metatarsals were treated with IL-1 beta and TNF alpha in combination with the small molecules PKF115-584, PKF118-310 and CGP049090 at different concentrations and then harvested them for histological and gene expression analysis. Results: We found that IL-1 beta-and TNF alpha-induced cartilage degradation in mouse fetal metatarsals was blocked by inhibiting WNT/beta-catenin signaling using small molecule PKF115-584 and partially using CGP049090 dosedependently. In addition, we found that PKF115-584 blocked IL-1 beta and TNF alpha-induced MMP mRNA expression, but did not reverse the inhibitory effect of IL-1 beta on the expression of cartilage anabolic genes. Conclusion: In this study, we show that inhibition of WNT/beta-catenin signaling by small molecules can effectively prevent IL-1 beta-and TNF alpha-induced cartilage degradation by blocking MMP expression and activity. Furthermore, we elucidate the involvement of WNT/beta-catenin signaling in IL-1 beta-and TNF alpha-induced cartilage degradation.