Objective The molecular basis for spontaneous resolution of acute gouty arthritis (GA) remains unclear. The hypothesis that extracellular and intracellular mechanisms play roles in resolving acute GA was tested.

Methods Synovial fluid (SF) levels of transforming growth factor β1 (TGFβ1), interleukin 1 (IL-1) receptor antagonist (IL-1ra), IL-10 and soluble tumour necrosis factor (TNF) receptor I (sTNFRI) and II (sTNFRII) were measured by ELISA in patients with acute GA and osteoarthritis (OA). Monosodium urate (MSU) crystal-stimulated RAW264.7 mouse macrophages were analysed for cytokine inducible SH2-containing protein (CIS) and suppressors of cytokine signalling (SOCS)1-7 mRNA expression by reverse transcription (RT)-PCR. Immunohistochemical analysis, quantitative PCR and immunoblotting were performed to detect CIS and SOCS3 expression in synovial tissue, SF mononuclear cells (SFMCs) from patients with GA and MSU crystal-stimulated monocyte-derived macrophages from healthy donors. CIS overexpression and small interfering RNA-mediated knockdown in RAW264.7 cells were used to investigate the role of CIS in resolving MSU crystal-induced acute inflammation.

Results SF levels of anti-inflammatory molecules TGFβ1, IL-1ra, IL-10 and sTNFR-I/II were significantly elevated in GA compared to OA. CIS and SOCS3 were upregulated in the synovium and SFMCs from acute GA and MSU crystal-stimulated monocyte-derived macrophages and RAW264.7 cells. CIS overexpression in RAW264.7 cells attenuated MSU crystal-induced IL-1β and TNFα but enhanced TGFβ1 production via increased binding of signal transducer and activator of transcription 3 (STAT3) to the TGFβ1 promoter. Conversely, CIS knockdown reversed the effect of CIS overexpression, resulting in enhanced IL-1β and TNFα but reduced TGFβ1 production in MSU crystal-stimulated RAW264.7 cells.

Conclusions Increased production of TGFβ1, IL-1ra, IL-10 and sTNFR-I/II and upregulation of intracellular CIS and SOCS3 expression are associated with spontaneous resolution of acute GA.