Arthropod steroid hormone (20-Hydroxyecdysone) suppresses IL-1β-induced catabolic gene expression in cartilage

Background: In osteoarthritis (OA), the imbalance of chondrocytes' anabolic and catabolic factors can induce cartilage destruction. Interleukin-1 beta (IL-1 beta) is a potent pro-inflammatory cytokine that is capable of inducing chondrocytes and synovial cells to synthesize MMPs. The hypoxia-inducible factor-2alpha (HIF-2alpha, encoded by Epas1) is the catabolic transcription factor in the osteoarthritic process. The purpose of this study is to validate the effects of ecdysteroids (Ecd) on IL-1 beta-induced cartilage catabolism and the possible role of Ecd in treatment or prevention of early OA. Methods: Chondrocytes and articular cartilage was harvested from newborn ICR mice. Ecd effect on chondrocytes viability was tested and the optimal concentration was determined by MTT assay. The effect of HIF-2 alpha (EPAS1) in cartilage catabolism simulated by IL-1 beta (5 ng/ml) was evaluated by articular cartilage explants culture. The effects of Ecd on IL-1 beta-induced inflammatory conditions and their related catabolic genes expression were analyzed. Results: Interleukin-1 beta (IL-1 beta) treatment on primary mouse articular cartilage explants enhanced their Epas1, matrix metalloproteinases (MMP-3, MMP-13) and ADAMTS-5 genes expression and down-regulated collagen type II (Col2a1) gene expression. With the pre-treatment of 10(-8)M Ecd, the catabolic effects of IL-1 beta on articular cartilage were scavenged. Conclusion: In conclusions, Ecd can reduce the IL-1 beta-induced inflammatory effect of the cartilage. Ecd may suppress IL-1 beta-induced cartilage catabolism via HIF-2a pathway.