Astaxanthin attenuates joint inflammation induced by monosodium urate crystals.

Gouty arthritis is the one of the most painful arthritis and is caused by an inflammatory reaction. This study investigated whether astaxanthin (AXT), which has documented anti-inflammatory and antioxidant properties, exhibits protective effects against monosodium urate (MSU) crystal-induced inflammation. Cell viability of J774A.1 murine macrophages was assessed by AXT dose-dependent incubation by MTT assays, and expression levels of iNOS and COX-2 proteins as well as secretion of IL-1β were also analyzed under MSU crystals stimulation with or without AXT treatment. The production of inflammatory mediators was found to significantly decrease with AXT treatment, and the formation of the inflammasome complex was also attenuated when cells were co-stimulated with MSU crystals and AXT. Furthermore, we found that expression of the MAPK pathway was downregulated in J774A.1 cells. AXT also inhibited the induction of COX-2 and IL-6 in human chondrocytes and synovial fibroblasts by western blots. Finally, an MSU crystal intra-articular injection rat model for gouty arthritis was utilized in which treatment groups received 5-daily intraperitoneal injections of AXT prior to MSU crystal stimulation, or once intra-articular injections of AXT following MSU crystal stimulation for 6 hours. Results of synovitis score analysis revealed that inflammation was significantly attenuated in the group which received intraperitoneal AXT injection prior to MSU crystal stimulation compared to the group which received MSU only. These results indicate that AXT attenuates the effects of MSU crystal-induced inflammation by suppressing the production of pro-inflammatory cytokines and inflammatory mediators. Our findings that the anti-inflammatory activities of AXT may be beneficial in the treatment of MSU crystal-induced arthritis.