Role of pro-inflammatory cytokines in the etiology of osteoarthritis

Osteoarthritis (OA) is a form of arthritis characterized by the destruction (softening, fibrillation,, ulceration and degradation) of articular cartilage, sclerosis of subchondral bone, osteophytes, and subchondral cysts and joint inflammation. The disintegration of articular cartilage induces production of pro-inflammatory cytokines (interleukin 1alpha - IL-1alpha, interleukin 1beta-IL-1beta, tumor necrosis factor alpha - TNF-alpha, interleukin 6 - IL-6, leukemic inhibitor factor - LIF, interleukin 8 - IL-8, interleukin 17 - IL-17, interleukin 18 - IL-18 and others) through the synovial membrane. Cytokines diffuse into the articular cartilage which produces matrix metalloproteinases (MMPs). MMPs play an important role in the destruction of proteoglycans, collagen and cartilage matrix. The 1 above mentioned cytokines take part in the inflammatory and catabolic process of OA because they inhibit cartilage collagen and aggrecan production, stimulate chondrocytes to produce MMPs and inducible NO-synthase (iNO), induce nitric oxide (NO) production, increase the amount of inflammatory cells in the joint, induce. and decrease a proliferation of chondrocytes, inhibit proteoglycan synthesis and stimulate their disintegration, induce apoptosis of chondrocytes and decrease their viability. Pro-inflammatory cytokines are very important and promising as objects of future studies for enabling effective therapy of OA patients.