TAK1 inhibition restores p53 expression and suppresses inflammation and hyperplasia in JIA synovial fibroblasts.

OBJECTIVES: This study investigated the role of TGF-β-activated kinase 1 (TAK1) in synovial inflammation and hyperplasia in JIA synovial fibroblasts (JIASFs).

METHODS: Patient-derived JIASFs were treated with TNF-α, IL-1β and IFN-γ with and without various TAK1 inhibitors. ELISA, Western blotting, RNA sequencing, cell proliferation and immunofluorescence were performed to study protein expression and JIASFs' functions. In vivo efficacy of TAK1 inhibitors was tested in a collagen antibody-induced arthritis (CAIA) model in IFN-γ knock-out mice.

RESULTS: JIASFs exhibited elevated TAK1 and reduced basal p53 expression compared with human foreskin fibroblasts. IL-1β-activated TAK1 suppressed p53, promoting inflammatory marker expression. TAK1 inhibitors 5Z-7-oxozeaenol or 5Z (IC50: 22.8 nM) and NG-25 (IC50: 492 nM) effectively blocked IL-1β-induced TAK1 activation, reducing inflammation. Notably, 5Z selectively restored IL-1β-suppressed p53 and p21 levels and demonstrated anti-proliferative effects via cell proliferation assays and reduced PCNA expression. Among tested inhibitors, 5Z was most effective in suppressing the combined pro-inflammatory effects of IL-1β, TNF-α and IFN-γ, reducing COX-2, VCAM-1, cadherin-1, IL-6, IL-8, CXCL5 and MMP-3 expression by 80%. Furthermore, 5Z restored p53 expression more efficiently than MAPK or NF-κB pathway inhibitors. RNA sequencing confirmed its anti-inflammatory and anti-proliferative properties in JIASFs. In vivo, daily intraperitoneal administration of 5Z (2 mg/kg) from day 3 significantly ameliorated collagen antibody-induced arthritis (CAIA) in IFN-γ knock-out mice, highlighting its therapeutic potential.

CONCLUSION: TAK1 inhibition restores p53 functions in JIASFs and downregulates synovial inflammation, which warrants further studies that target TAK1 to treat JIA.