Expression of proteinase-activated receptors (PAR)-2 in articular chondrocytes is modulated by IL-1β, TNF-α and TGF-β

Objective: To investigate the modulation of expression of proteinase-activated receptor-2 (PAR-2) in articular chondrocytes by inflammatory cytokines. Design: Articular synovium and cartilage tissues were collected from eight patients with osteoarthritis (OA), and three patients without arthropathy ("normal"). Chondrocytes were stimulated with interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha or transforming growth factor (TGF)-beta 1. The expression of PAR-2 was detected using reverse transcriptase-polymerase chain reaction (PCR), Western blotting and immunofluorescence. Quantitative PCR was performed to assess the expression levels of PAR-2 messenger RNA (mRNA). Results: The expression of PAR-2 mRNA was demonstrated in both OA and normal chondrocytes as well as in synovial fibroblasts. However, the level of PAR-2 in OA chondrocytes was much higher than in normal chondrocytes. Long-term culture revealed that PAR-2 mRNA expression was maintained up to three passages in OA but not in normal chondrocytes. IL-1 beta and TNF-alpha both upregulated PAR-2 expression in normal and OA chondrocytes. In contrast, TGF-beta 1 significantly decreased expression of PAR-2 in OA chondrocytes but increased PAR-2 in normal chondrocytes. Conclusions: Overexpression of PAR-2 in OA chondrocytes is upregulated by proinflammatory cytokines IL-1 beta and TNF-alpha, and down-regulated by regulatory cytokine TGF-beta 1. PAR-2 may be involved in the pathogenesis of OA. (C) 2006 OsteoArthritis Research Society International. Published by Elsevier Ltd. All rights reserved.