大量证据证实肠道微生物群组成的改变与类风湿性关节炎 (RA) 之间存在关联。然而，我们对支撑这种关联的复杂机制的理解是有限的。 为了研究肠道微生物群是否通过代谢或免疫影响 RA 的发病机制，我们使用已发表的全基因组关联研究 (GWAS) 的汇总统计数据进行了严格的合成分析，其中使用了两种方法-孟德尔随机化 (MR) 和介导 MR 技术样本，包括两步 MR 和多变量 MR 分析。随后，我们对分析的微生物-细胞因子-RA 途径进行了体外细胞验证。我们通过涉及浓度和时间的共培养实验确定了最佳培养条件。采用细胞计数试剂盒-8 (CCK-8) 测定法评估细胞活力，并采用酶联免疫吸附测定法 (ELISA) 评估肿瘤坏死因子诱导基因 6 蛋白 (TSG-6) 和肿瘤坏死因子-α (TNF-α) 水平。我们的单变量 MR 结果证实了 15 种微生物特征、7 种代谢物和 2 种细胞因子可能与 RA 存在因果关系 (P FDR < 0.05)。中介分析显示，微生物特征通过代谢物或细胞因子影响RA风险（中介比例：7.75% - 58.22%）。体外实验表明，TSG-6 在 Subdolicapsulum variabile 治疗组中高表达，并且与 RA 严重程度降低（TNF-α 表达减少）相关。无论是否用变异链球菌进行处理，沉默 TSG-6 基因都会显着增加 TNF-α 的表达。此外，S. variabile 分泌的外泌体也表现出相同的效果。本研究结果表明，S. variabile 具有促进 TSG-6 分泌的潜力，从而减轻 RA 炎症。版权所有 © 2024 Li, Dai, Zhu, Hu, Zhu 、王和张。

A burgeoning body of evidence has substantiated the association between alterations in the composition of the gut microbiota and rheumatoid arthritis (RA). Nevertheless, our understanding of the intricate mechanisms underpinning this association is limited.To investigate whether the gut microbiota influences the pathogenesis of RA through metabolism or immunity, we performed rigorous synthesis analyses using aggregated statistics from published genome-wide association studies (GWAS) using two-sample Mendelian randomization (MR) and mediated MR techniques, including two-step MR and multivariate MR analyses. Subsequently, we conducted in vitro cellular validation of the analyzed Microbial-Cytokine-RA pathway. We determined the optimal culture conditions through co-culture experiments involving concentration and time. Cell Counting Kit-8 (CCK-8) assays were employed to assess cellular viability, and enzyme-linked immunosorbent assays (ELISA) were performed to assess tumor necrosis factor-inducible gene 6 protein (TSG-6) and tumor necrosis factor-α (TNF-α) levels.Our univariable MR results confirmed 15 microbial traits, 7 metabolites and 2 cytokines that may be causally associated with RA (P FDR < 0.05). Mediation analysis revealed that microbial traits influence the risk of RA through metabolite or cytokine (proportion mediated: 7.75% - 58.22%). In vitro experiments demonstrated that TSG-6 was highly expressed in the Subdoligranulum variabile treatment group and was correlated with decreased RA severity (reduced TNF-α expression). Silencing the TSG-6 gene significantly increased TNF-α expression, regardless of treatment with S. variabile. Additionally, S. variabile-secreted exosomes exhibited the same effect.The results of this study suggest that S. variabile has the potential to promote TSG-6 secretion, thereby reducing RA inflammation.Copyright © 2024 Li, Dai, Zhao, Hu, Zhao, Wang and Zhang.