Inhibition of monosodium urate crystal-induced inflammation by scopoletin and underlying mechanisms

The present study determined the anti-inflammatory activity of scopoletin in gout air pouch model and revealed the underlying mechanisms by in vitro assays. Monosodium urate (MSU) crystal-induced inflammation in mouse air pouch model, an experimental model for acute gout, was used to assess the efficacy of scopoletin. The neutrophil and mononuclear phagocyte numbers and MPO levels were increased significantly six hours after MSU crystal injection into the air pouch, whereas these changes were inhibited substantially upon scopoletin (100 and 200 mg/kg, i.p.) treatment. To get insight into the underlying mechanisms, the in vitro studies were performed to investigate the effects of scopoletin on activation of macrophages and resultant production of inflammatory mediators. The secretions of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), prostaglandin E2 (PGE2) and nitric oxide (NO) were elevated in MSU crystal-stimulated RAW 264.7 cells, and scopoletin (30-300 μM) suppressed the production of all mediators. Moreover, RT-PCR assay and western blot analysis indicated that scopoletin regulated the transcriptional level of these mediators via suppression of NF-κB activation and blockade of MAPK signal pathway. Thus, the results clearly indicated that scopoletin inhibited the monosodium urate crystal-induced inflammation both in vivo and in vitro. In combination with our previous findings that scopoletin shows hypouricemic, anti-angiogenesis and pro-apoptotic activities, this compound may be a potential agent for gout therapy and could serve as a structural base for developing new drugs.

► In MSU air pouch model, scopoletin suppressed leukocyte influx and MPO activity. ► In MSU-activated macrophages, scopoletin inhibited inflammatory mediator release. ► Scopoletin down-regulated NF-κB activation and MAPK signal pathway.