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Introduction: Current anti-rheumatic drugs are primarily modulating immune cell activation, yet their effectiveness remained suboptimal. Therefore, novel therapeutics targeting alternative mechanisms, such as synovial activation, is urgently needed. Objectives: To explore the role of Midline-1 (Mid1) in synovial activation. Methods: NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice were used to establish a subcutaneous xenograft model. Wild-type C57BL/6, Mid1-/-, Dpp4-/-, and Mid1-/- Dpp4-/- mice were used to establish a collagen-induced arthritis model. Cell viability, cell cycle, qPCR and western blotting analysis were used to detect MH7A proliferation, dipeptidyl peptidase-4 (DPP4) and Mid1 levels. Co-immunoprecipitation and proteomic analysis identified the candidate protein of Mid1 substrates. Ubiquitination assays were used to determine DPP4 ubiquitination status. Results: An increase in Mid1, an E3 ubiquitin ligase, was observed in human RA synovial tissue by GEO dataset analysis, and this elevation was confirmed in a collagen-induced mouse arthritis model. Notably, deletion of Mid1 in a collagen-induced arthritis model completely protected mice from developing arthritis. Subsequent overexpression and knockdown experiments on MH7A, a human synoviocyte cell line, unveiled a previously unrecognized role of Mid1 in synoviocyte proliferation and migration, the key aspects of synovial activation. Co-immunoprecipitation and proteomic analysis identified DPP4 as the most significant candidate of Mid1 substrates. Mechanistically, Mid1 promoted synoviocyte proliferation and migration by inducing ubiquitin-mediated proteasomal degradation of DPP4. DPP4 deficiency led to increased proliferation, migration, and inflammatory cytokine production in MH7A, while reconstitution of DPP4 significantly abolished Mid1-induced augmentation of cell proliferation and activation. Additionally, double knockout model showed that DPP4 deficiency abolished the protective effect of Mid1 defect on arthritis. Conclusion: Overall, our findings suggest that the ubiquitination of DPP4 by Mid1 promotes synovial cell proliferation and invasion, exacerbating synovitis in RA. These results reveal a novel mechanism that controls synovial activation, positioning Mid1 as a promising target for therapeutic intervention in RA.

Background: C-reactive protein (CRP) is a well-recognized biomarker of inflammation, which can be used as a predictor of cardiovascular disease. Evidence have suggested exposure to multiple metals/metalloids may affect immune system and give rise to cardiovascular disease. However, it is lack of study to comprehensively evaluate the association of multiple metals and CRP, the interactions between metals, and the gene-metal interaction in relation to CRP levels. Aims: To explore the associations of multiple plasma metals with serum CRP, and to test the interactions between metals, and gene-metal interactions on the levels of serum CRP. Methods: We included 2882 participants from the Dongfeng-Tongji cohort, China, and measured 23 plasma metals and serum CRP concentrations. The genetic risk score (GRS) was calculated based on 7 established CRP-associated variants. For metals which were associated with the levels of CRP, we further tested the interactions between metals on CRP, and analyzed the gene-metal interactions on CRP. Results: The median level for CRP in the total population was 1.17 mg/L. After multivariable adjustment, plasma copper was positively associated with serum CRP (FDR

Background: The prevalence of metabolic syndrome (MetS) persistently increased. Several studies have found serum creatinine (SCr) concentrations related to cardiovascular disease and type 2 diabetes. The relationship between SCr concentrations and MetS is unknown., Methods: We measured SCr concentrations and MetS in 22363 individuals (10,151 males, 12,212 females) from the Dongfeng-Tongji Cohort in Shiyan, China from 2008 to 2009., Results: The prevalence of MetS was 30.6% in the study population. In the multivariable-adjusted logistic regression analyses, higher SCr concentrations were associated with a higher risk of MetS (P trend<0.0001). Compared with the lowest extreme quintiles, subjects with the highest quintiles had 1.34 fold risk of MetS (95% confidence interval (CI): 1.22-1.47). The SCr concentrations were also associated with the individual component of MetS. In addition, higher SCr concentrations were associated with higher risk of MetS with more components., Conclusions: There is a graded positive association between the SCr concentrations and MetS risk in a middle aged and older Chinese population. Higher SCr concentrations, even within normal ranges, were associated with higher risk of MetS. The SCr might be a useful indicator of MetS and its related diseases., (Copyright © 2014 Elsevier B.V. All rights reserved.)