Effect of etanercept on iNOS, IL-6, and COX-2 expression in human chondrocytes in vitro.

Purpose: Erosive osteoarthritis (EOA) is considered as an aggressive variant of hand OA characterized by a prominent local inflammation and radiographic aspects of central bone erosion on interphalangeal joints. Cytokines, such as Interleukin (IL)-1b and Tumor Necrosis Factor (TNF)-a, are involved in the pathophysiology of OA, directly and by stimulation of synoviocytes and chondrocytes to produce inflammatory molecules like nitric oxide (NO), Il-6 and cyclooxygenase (COX)-2. In inflamed joints, NO is involved in joint destruction by enhancing cytokine production and suppressing collagen and proteoglycan synthesis while Il-6 is implicated in bone erosion. Moreover, COX-2 could indirectly affect chondrocytes metabolism by the production of prostaglandins that mediate pain, support the inflammatory process and inhibit aggrecan synthesis. The aim of the present study was to investigate the effects of the TNFa- antagonist etanercept on Il-6, COX-2 and iNOS gene expression in human chondrocytes Methods: Primary human chondrocytes were obtained from non-weight bearing articular cartilage of femoral heads after sequential digestions with trypsin and collagenase. Chondrocytes were treated with different concentrations of human recombinant Il-1b (5 ng/ml) and TNFa (20 or 40 ng/ml) and simultaneously with etanercept at 100 mg/ml for 24 hours; gene expression of iNOS Il-6, and COX-2 and was assessed by the RT/PCR method using 18S rRNA as the housekeeping gene. Results: Etanercept determined a complete suppression of TNFa- induced iNOS, Il-6, and COX-2 gene expression. This anti-TNFa drug also downregulated, with a dose-dependent effect, iNOS and COX-2 gene expression (−20% and −30% respectively, p < 0.05) after stimulation with Il-1b. Etanercept seemed to have no effects on Il-1b-induced Il-6 gene expression. Conclusions: To our knowledge, this is the first report of the effects of etanercept on iNOS, Il-6 and COX-2 gene expression, after inflammatory stimulation, on a human chondrocyte population. In summary, these data suggest that the beneficial effects of the treatment with etanecerpt in EOA could be further explained by the action of this biological drug at cartilage level.