Decreased RIPK1 expression in chondrocytes alleviates osteoarthritis via the TRIF/MyD88-RIPK1-TRAF2 negative feedback...

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by cartilage degradation, osteophyte formation, and inflammation.
• Receptor interacting serine/threonine kinase 1 (RIPK1) has known anti-inflammatory and anti-apoptotic roles, but its specific involvement in OA pathogenesis is not well understood.

Purpose of the Study:

• To investigate the role of RIPK1 in osteoarthritis.
• To elucidate the molecular mechanisms by which RIPK1 influences chondrocyte behavior and OA progression.

Main Methods:

• Utilized in vitro and in vivo models to assess the effects of RIPK1 knockdown on chondrocytes.
• Investigated the involvement of RIPK1 in Myeloid differentiation primary response 88 (MyD88), TIR-domain-containing adapter-inducing interferon b (TRIF), matrix metalloproteinases (MMPs), tumor necrosis factor receptor-associated factor 2 (TRAF2), nuclear factor-κB (NF-κB), and c-Jun N-terminal kinase (JNK) signaling pathways.

Main Results:

• RIPK1 knockdown demonstrated protective effects against interleukin-1β (IL-1β)-induced inflammation and apoptosis in chondrocytes.
• RIPK1 was essential for MyD88- and TRIF-mediated MMP production in OA.
• Overexpression of RIPK1 led to TRAF2 upregulation, which in turn inhibited RIPK1 activity and decreased TRIF, MyD88, and MMP expression.
• RIPK1 knockdown suppressed NF-κB and JNK signaling pathway activation.

Conclusions:

• RIPK1 plays a critical role in osteoarthritis pathogenesis.
• Targeting RIPK1 may offer a therapeutic strategy for OA by modulating the TRIF/MyD88-RIPK1-TRAF2 negative feedback loop and inhibiting NF-κB and JNK pathways.