Pathophysiological roles for IL-18 in inflammatory arthritis

Abstract

IL-18 is a unique cytokine with prominently wide spectrum biological actions. Among these, its IFN-γ/TNF-α-inducing activity primarily contributes to the development of various inflammatory diseases including inflammatory arthritis. IL-18 levels correlate with the disease activity of rheumatoid arthritis (RA) and osteoarthritis (OA). IL-18 is spontaneously released from RA synovial cells and OA chondrocytes and seems to participate in the development of the inflammatory and destructive alterations of joints via induction of TNF-α, a potent effector molecule. TNF-α, in turn, increases IL18 expression in RA synovial cells. Recent clinical trials have revealed the efficacy of TNF-α in RA with a reduction in circulatory IL-18 levels. These may implicate the positive circuit between IL-18 and TNF-α for development of RA. As IL-18-deficient mice evade collagen-induced arthritis in a mouse RA model, therapeutics targeting IL-18 may be beneficial against RA/OA. Here, the authors review the possible roles of IL-18 in inflammatory arthritis.

• caspases
• chemokines
• chondrocytes
• collagen-induced arthritis (CIA)
• IL-18
• inflammation
• innate immunity
• osteoarthritis (OA)
• pro-inflammatory cytokines
• rheumatoid arthritis (RA)
• synoviocytes
• TH1/TH2 responses
• Toll-like receptors (TLRs)