Functional proteomics revealed IL-1β amplifies TNF downstream protein signals in human synoviocytes in a TNF-independent manner.

IL-1β is readily detectable in numerous joint inflammations. It can change the transcriptomic signature of fibroblast-like synoviocytes (FLS) of arthritis toward promoting migration and invasion that are relevant to arthritis progression. We hypothesize that IL-1β partially contributes to the onset of osteoarthritis (OA). We compared the tissue samples from OA and fracture subjects and found that IL-1β expression was significantly higher in the OA synovium, while TNF-α expression showed no significance. We demonstrated that IL-1β significantly increases the IL-6 and IL-8 secretions of human normal FLS; however, IL-1β does not induce TNF secretion. With metabolic labeling based proteomics and pathway analysis, we found that IL-1β significantly increases the TNF downstream protein expression in FLS even with complete absence of TNF and/or blocking of the NF-κB pathway. Among these proteins, we verified that p62 can differentiate the OA from fracture synovitis. In conclusion, we demonstrated that IL-1β can amplify the TNF downstream protein signals in human synoviocytes in a TNF-independent manner; in addition, p62 is a potential FLS biomarker for synovitis.