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  • Title: Methotrexate promotes the release of granulocyte-macrophage colony-stimulating factor from rheumatoid arthritis fibroblast-like synoviocytes via autocrine interleukin-1 signaling.
    Author: Bergström B, Selldén T, Bollmann M, Svensson MND, Ekwall AH.
    Journal: Arthritis Res Ther; 2024 Oct 11; 26(1):178. PubMed ID: 39394168.
    Abstract:
    BACKGROUND: Activated fibroblast-like synoviocytes (FLS) are drivers of synovitis and structural joint damage in rheumatoid arthritis (RA). Despite the use of disease-modifying drugs, only about 50% of RA patients reach remission in real-world settings. We used an unbiased approach to investigate the effects of standard-of-care methotrexate (MTX) and a Janus kinase inhibitor, tofacitinib (TOFA), on gene expression in RA-FLS, in order to identify untargeted disease mediators. METHODS: Primary RA-FLS were activated by stimulation with interleukin-1β (IL-1β) or platelet-derived growth factor + IL-1β in the presence or absence of MTX or TOFA, with or without additional inhibitors. Co-cultures of synovial cells were performed in direct and indirect systems. Cells were collected for RNA sequencing or qPCR, and supernatants were analyzed for protein concentrations. RESULTS: Six thousand three hundred fifty genes were differentially expressed, the majority being upregulated, in MTX-treated activated RA-FLS and 970 genes, the majority being downregulated, in TOFA-treated samples. Pathway analysis showed that MTX had largest effects on 'Molecular mechanisms of cancer' and TOFA on 'Interferon signaling'. Targeted analysis of disease-associated genes revealed that MTX increased the expression of cell cycle-regulating genes but also of pro-inflammatory mediators like IL-1α (IL1A) and granulocyte-macrophage colony-stimulating factor, GM-CSF (CSF2). The MTX-promoted expression of CSF2 in activated RA-FLS peaked at 48 h, could be mediated via either NF-κB or AP-1 transcription factors, and was abrogated by IL-1 inhibitors (IRAK4 inhibitor and anakinra). In a co-culture setting, MTX-treatment of activated RA-FLS induced IL1B expression in macrophages. CONCLUSIONS: MTX treatment induces secretion of IL-1 from activated RA-FLS which by autocrine signaling augments their release of GM-CSF. This unexpected effect of MTX might contribute to the persistence of synovitis.
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