The role and impact of the IL-6 mediated JAK2-STAT1/3 signaling pathway in the pathogenesis of gout
Authors: Zhang Zeng , Wang Peng , Lei Tianyi , Guo Jianwei , Jiang Yi , Li Yanhui , Zheng Jianxiong , Wang Shunbing , Xu Haimuzi , Jian Guilin , Zhang Quanbo , Qing Yufeng 
Published: July 2024

BackgroundInterleukin−6 (IL−6) is a pleiotropic cytokine, the specific effects of which depend on the immune microenvironment. Extensive research has confirmed the pathological roles of the IL-6/JAK2/STAT1/3 signaling pathway in inflammation, autoimmunity, and cancer, and its involvement in the pathogenesis of various rheumatic diseases. However, the role and impact of IL-6 as an upstream regulator of the JAK2-STAT1/3 pathway in gout have been seldom reported. This study explores the influence and role of upstream IL-6 in regulating the JAK2-STAT1/3 signaling pathway on gout inflammation, offering new insights for targeted therapeutic interventions and drug development in gout management.MethodsClinical data and peripheral blood specimens were collected from gout patients and healthy individuals. PBMCs, THP-1 cells, and mice were stimulated with MSU crystals to establish acute gout inflammation models in vitro and in vivo. The expression of IL-6 was intervened using IL-6 agonists and IL-6 knockout (KO) mouse technology to observe the role and impact of the IL-6-mediated JAK2-STAT1/3 signaling pathway in gout models. RT-qPCR, WB, and ELISA were employed to measure the expression of relevant genes and proteins. Paw swelling in mice was measured using a caliper gauge. HE and IHC staining were performed to observe the inflammatory status of mouse paw pad synovial tissues and positive expression of related proteins.ResultsSerum IL-6 protein expression levels were significantly higher in GA patients compared to healthy individuals, and multifactor logistic regression showed an OR of 2.175 for IL-6. In GA patients, mRNA expression of IL-6, JAK2, STAT1/3, and IL-1β was significantly lower in the gout group than in the HC group. IL-6, JAK2, STAT1/3, p-JAK2, p-STAT1/3, and IL-1β proteins were significantly higher in the AG group than in the IG group and the HC group; and in the IG group, IL-6, JAK2, and STAT3, IL-1β proteins were significantly higher than those in the HC group, while STAT1, p-JAK2, and p-STAT1/3 proteins were significantly lower.IL-6 protein and JAK2 mRNA expression were positively correlated with some of the inflammatory indexes. In the 0-12h human blood in vitro gout inflammation model, IL-1β and IL-6 proteins were found to be significantly higher compared to 0h, as well as IL-1β, IL-6, JAK2 mRNA and IL-1β, IL-6, JAK2, STAT1/3, p-JAK2, p-STAT1/3 protein expression in the 2h model group was significantly higher than that in the blank control group and PBS-negative control group. In the acute gout cell model, IL-1β and IL-6 protein expression showed a gradual increase. 6h model group had significantly higher IL-1β, IL-6, JAK2, STAT1/3 mRNA and protein and their phosphorylated protein expression than that of the blank control group; whereas, in the model group with the addition of IL-6 agonist, IL-1β, IL-6, JAK2, STAT1/3 mRNA and protein and their phosphorylated protein expression was significantly higher than that in the model group. In the acute gout mouse model, the degree of footpad swelling and swelling index were significantly downregulated in IL-6 KO mice compared with WT mice.HE staining showed less inflammatory cell infiltration in IL-6 KO mice compared with WT mice. In IL-6 KO mice, IL-6 mRNA and protein expression was significantly reduced; IL-1β, IL-6, JAK2, STAT1/3 mRNA and protein and phosphorylated protein expression was significantly down-regulated in IL-6 KO mice when compared to 12h gout model WT mice; meanwhile, IHC staining showed reduced p-JAK2 and p-STAT1/3 positive expression. Compared with 24h gout model WT mice, IL-6 mRNA and protein expression were not statistically different, IL-1β mRNA and protein expression as well as JAK2 and STAT3 mRNA expression were down-regulated, while STAT1 mRNA expression was similar.ConclusionIL-6 may be a risk factor for acute gout attacks, and the IL-6-mediated JAK2-STAT1/3 signaling pathway participates in acute gout inflammation and its pathogenesis process through positive feedback mechanisms.