Revised: August 16, 2026
Accepted: October 8, 2026
Published online: November 18, 2026
Processing time: 126 Days and 19.2 Hours
Rheumatoid arthritis (RA) is a chronic autoimmune disease whose pathological process involves multiple consecutive stages, such as immune activation, local inflammation, and tissue destruction. Although inflammatory cytokines play a central role in the pathogenesis of RA, existing studies still lack an in-depth understanding of how key pathogenic factors exert their effects in a causal and stage-specific manner across the disease continuum.
To investigate causal links between inflammatory cytokines and RA via Men
A 2-sample MR analysis was conducted using genome-wide association study summary data to assess causal associations between 91 inflammatory cytokines and RA risk, with sensitivity analyses testing for heterogeneity and pleiotropy. For experimental validation, serum levels of CD40, C-C motif chemokine ligand 28 (CCL28), matrix metalloproteinase-1 (MMP-1), and interleukin-18 receptor 1 (IL-18R1) were quantified by enzyme-linked immunosorbent assay (ELISA) in 41 patients with active RA and 41 age- and sex-matched healthy controls. Intergroup differences and correlations were statistically evaluated.
MR analysis showed that CD40 [false discovery rate (FDR)-adjusted P =0.0020] and IL-18R1 (FDR-adjusted P = 0.0256) had significant causal associations with RA risk, while CCL28 and MMP-1 showed nominal associations (FDR-adjusted P > 0.05) and were considered exploratory. Sensitivity analyses supported the robustness of these findings, with no statistical evidence of heterogeneity or horizontal pleiotropy detected. ELISA results showed that serum levels of CD40, CCL28, MMP-1, and IL-18R1 in patients with RA were significantly higher than those in healthy controls (all P < 0.05), and there were significant positive correlations between all 6 pairs of the 4 molecules (r = 0.436-0.609, all P < 0.05).
Under its core assumptions, MR supports causal associations of CD40 and IL-18R1 with RA risk, while the associations for CCL28 and MMP-1 remain exploratory. The discordance between the MR and ELISA findings for IL-18R1 remains unresolved. A spatiotemporal model is proposed.
Core Tip: This study integrates Mendelian randomization with enzyme-linked immunosorbent assay validation to identify CD40, C-C motif chemokine ligand 28, and matrix metalloproteinase-1 as candidate mediators in rheumatoid arthritis, while interleukin-18 receptor 1 shows discordant Mendelian randomization (protective) and enzyme-linked immunosorbent assay (elevated) findings requiring mechanistic reconciliation. A hypothesized spatiotemporal cascade links CD40 to lymphoid immunity, C-C motif chemokine ligand 28 to synovitis, and matrix metalloproteinase-1 to cartilage degradation. Their positive intercorrelations suggest a potential synergistic loop, supporting further exploration of composite biomarker panels and combination strategies. Experimental validation demonstrates protein-level consistency rather than proof of causality, and all findings should be considered hypothesis-generating.