Studies on the Molecular Basis of Spontaneous Resolution in Acute Gouty Arthritis
Date Issued
2011
Date
2011
Author(s)
Chen, Yu-Hsuan
Abstract
ABSTRACT
Acute gouty arthritis (GA) is an autoinflammatory disease that is caused by the deposition of monosodium urate (MSU) crystals in articular joints and periarticular tissues. The inflammatory response in acute GA is typically self-limiting. Recent studies have indicated that the rising prevalence of GA is primarily due to factors such as changes in dietary habits and lifestyle, improved medical care and increased longevity. To date, the molecular basis that underlies spontaneous resolution of acute gouty inflammation remains poorly understood. In this study, we tested the hypothesis that extracellular anti-inflammatory factors and intracellular negative regulators of cytokine signaling play a role in the spontaneous resolution of acute GA.
The gold standard for the diagnosis of GA is to confirm the presence of MSU crystals in the synovial fluid, and the measurement of cytokines in the synovial fluid serves as a tool for studying the inflammatory process in vivo. Using ELISA, we assessed the levels of the primary anti-inflammatory cytokines in the synovial fluid of patients with acute GA in relation to patients with osteoarthritis (OA). The synovial fluid levels of transforming growth factor β1 (TGF-β1), interleukin 1 (IL-1) receptor antagonist (IL-1ra), IL-10 and soluble tumor necrosis factor (TNF) receptors I (sTNFR-I) and II (sTNFR-II) were all significantly elevated in patients with acute GA relative to the levels in patients with OA.
Next, we determined the mRNA levels of intracellular cytokine-inducible SH2 protein (CIS) and suppressors of cytokine signaling (SOCS) 1-7 in MSU crystal-stimulated RAW264.7 mouse macrophages by reverse transcription (RT)-PCR. In this context, the levels of CIS and SOCS3 mRNA were increased in response to stimulation with MSU crystals. Using immunohistochemical analyses, quantitative PCR and immunoblotting, we further confirmed the expression levels of CIS and SOCS3 in both the synovial tissue and synovial fluid mononuclear cells (SFMCs) from patients with GA, and MSU crystal-stimulated peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages from healthy donors.
Finally, we used CIS overexpression and small interfering RNA-mediated knockdown in RAW264.7 cells to investigate the role of CIS in resolving MSU crystal-induced acute inflammation. CIS overexpression in RAW264.7 cells attenuated the MSU crystal-induced IL-1β and TNF-α production but enhanced TGF-β1 production via increased binding of signal transducers and activators of transcription 3 (STAT3) to the TGF-β1 promoter. Conversely, CIS knockdown reversed the effect of CIS overexpression, resulting in enhanced IL-1β and TNF-α production but reduced TGFβ1 production in MSU crystal-stimulated RAW264.7 cells.
In conclusion, we demonstrate for the first time that increased production of TGF-β1, IL-1ra, IL-10 and sTNFR-I/II and upregulation of intracellular CIS and SOCS3 expression are associated with the spontaneous resolution of acute GA. These results both advance our understanding of the molecular basis of gouty inflammation resolution and have the potential to provide insights into new therapeutic strategies that can be aimed at triggering the resolution of gouty inflammation, thus preventing the clinical progression of the disease.
Subjects
acute gouty arthritis
MSU crystals
Spontaneous resolution
Type
thesis
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