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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Arthritis, Rheumatoid, Cells, Cultured, Cytokines, DNA-Binding Proteins, Feedback, Physiological, Fibroblasts, Gene Transfer Techniques, Humans, Inflammation Mediators, MicroRNAs, NF-kappa B, Real-Time Polymerase Chain Reaction, Signal Transduction, Synovial Membrane, Tumor Necrosis Factor-alpha.
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Does tumor necrosis factor α-induced microRNA-18a activate rheumatoid arthritis synovial fibroblasts through a feedback loop in NF-κB signaling? Context: To elucidate whether the microRNA (miRNA) cluster miR-17-92 contributes to the activated phenotype of rheumatoid arthritis synovial fibroblasts (RASFs). RASFs were stimulated with tumor necrosis factor α (TNFα), and the expression and regulation of the miR-17-92 cluster were studied using real-time quantitative PCR (PCR) and promoter activity assays. RASFs were transfected with single precursor molecules of miRNAs from miR-17-92 and the expression of matrix-degrading enzymes and cytokines was measured by quantitative PCR and enzyme-linked immunosorbent assay. Potential miRNA targets were identified by computational prediction and were validated using reporter gene assays and Western blotting. The activity of NF-κB signaling was determined by reporter gene assays. We found that TNFα induces the expression of miR-17-92 in RASFs in an NF-κB-dependent manner. Transfection of RASFs with precursor molecules of single members of miR-17-92 revealed significantly increased expression levels of matrix-degrading enzymes, proinflammatory cytokines, and chemokines in precursor miR-18a (pre-miR-18a)-transfected RASFs. Using reporter gene assays, we identified the NF-κB pathway inhibitor TNFα-induced protein 3 as a new target of miR-18a. In addition, pre-miR-18a-transfected RASFs showed stronger activation of NF-κB signaling, both constitutively and in response to TNFα stimulation.
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Our data suggest that the miR-17-92-derived miR-18a contributes to cartilage destruction and chronic inflammation in the joint through a positive feedback loop in NF-κB signaling, with concomitant up-regulation of matrix-degrading enzymes and mediators of inflammation in RASFs. Final Decision: yes