HSP60 regulates monosodium urate crystal-induced inflammation by activating the TLR4-NF- κ B-MyD88 signaling pathway and disrupting mitochondrial function

Background: Acute gout is an inflammatory response induced by monosodium urate (MSU) crystals. HSP60 is a highly conserved stress protein that acts as a cellular “danger” signal for immune reactions. In this study, we aimed to investigate the role and molecular mechanism of HSP60 in the gout. Methods: HSP60 expression was detected in peripheral blood mononuclear cells (PBMCs) and plasma of gout patients. The effect and mechanism of HSP60 in gout were studied in MSU crystals treatment macrophages and C57BL/6 mice. JC-1 probe and MitoSOX Red were used to measure the mitochondrial membrane potential (MMP) and mitochondrial reactive oxygen species (mtROS). Results: HSP60 expression was significantly upregulated in the PBMCs and sera of patients with acute gout (AG) compared to those with inter-critical gout (IG) or healthy controls (HCs). MSU crystals induced expression and secretion of HSP60 in the macrophages. HSP60 knockdown or over-expression affects TLR4 and MyD88 expression, IκBα degradation and the nuclear localization of NF-κB in MSU crystal-stimulated inflammation. Further, HSP60 facilitates MMP collapse and mtROS production, and activates the NLRP3 inflammasome in MSU crystal-stimulated macrophages. In MSU crystal-induced arthritis and peritonitis mouse models pre-treated with HSP60 vivo-morpholino, paw swelling, ankle joint swelling, myeloperoxidase (MPO) activity and inflammatory cell infiltration significantly decreased. Conclusion: Our study revealed that MSU crystal stimulates the expression of HSP60 which accelerates TLR4-MyD88-NF-κB signaling pathway and exacerbates mitochondrial dysfunction.