Mechanisms of Bradykinin-induced Expression of Cyclooxygenase-2 in Human Synovial Fibroblasts of Rheumatoid Arthritis

• Main Authors: Yu Wen Chen, 陳毓文
• Other Authors: C. M. Yang
• Format: Others
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/18891870483767016613

碩士 === 長庚大學 === 生物醫學研究所 === 97 === Rheumatoid arthritis (RA) is characterized by attack of cartilage and bone by a hyperplastic synovium. In synovial fluid, Prostaglandins are mediators involved in complex interactions leading to articular cartilage erosions. Previous papers have demonstrated that patients with RA contain a large COX-2 from synovial tissues. In RA tissues, increased kinin levels have been found in the synovial fluid of RA patients. Bradykinin (BK) is an important inflammatory mediator which has been shown to induce the expression of inflammatory proteins, including COX-2. Here, our study aimed to investigate the mechanisms underlying the intracellular signalings involved in COX-2 expression in BK-induced inflammatory of human RASFs. Western blotting, RT-PCR analyses, transfect siRNA and promoter assay showed that BK induced COX-2 expression as well as phosphorylation of MAPKs, RTK transactivation and PKC which were attenuated by pharmacological inhibitors. BK stimulated both IkBa degradation and NF-kB translocation was attenuated by Bay11-7082, U0126, SB202190, or SP600125. BK-stimulated NF-kB translocation into nucleus was further confirmed by immunofluorescence staining. These results suggest that in RASFs, BK-induced COX-2 expression was mediated through phosphorylation of MAPKs and NF-kB pathways. Moreover, BK-induced NF-kB promoter by Akt activity was required for COX-2 expression. Recruitment of Akt, p300 and p65 formed a complex was required for BK-induced COX-2 expression. We reported that BK regulated c-Fos mRNA expression, AP-1 promoter activities and AP-1 recruitment was mediated through p44/p42 MAPK and JNK in RASFs. Besides, BK-induced PGE2 generation through COX-2 expression was decreased by pretreatment with inhibitors of MAPKs, transactivation, PKC, Bay11-7082 and Tanshinone IIA. These results suggest that BK induces COX-2 expression via BK B2 receptors PKC, calcium, PDGFR, Src, PI3K/Akt, MAPKs, NF-kB and AP-1 pathways. These results will provide a new insight into the mechanisms of BK in RA. Increased understanding of signal transduction mechanisms underlying COX-2 gene regulation will create opportunities for the development of anti-inflammation therapeutic strategies.