Studies on the Signaling Pathway of Peptidoglycan-Mediated Cyclooxygenase-2 Expression in RAW 264.7 Macrophages

• Main Authors: Ya-Hsuan Chan, 詹雅琁
• Other Authors: Chien-Huang Lin
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/69596452317662270733

碩士 === 台北醫學院 === 生物醫學技術研究所 === 90 === Peptidoglycan (PGN), a main cell wall component of Gram-positive bacteria, activates the innate immune system of host and induces release of inflammatory molecules. The signaling pathway in PGN-mediated cyclooxgenase-2 (COX-2) expression is poorly understood. In this study, we investigated the signaling pathway of PGN-induced COX-2 expression in murine RAW 264.7 macrophages. PGN caused a concentration- and time-dependent increase in COX-2 expression. The PGN-induced increase in COX-2 expression was significantly inhibited by transcription inhibitor (actinomycin D) or translation inhibitor (cyclohexamide). Polymyxin B, which binds and inactivates endotoxin, attenuated lipopolysaccharie (LPS)-induced COX-2 expression, while it has no effect on PGN-induced effect. The Ras inhibitor (manumycin A), Raf inhibitor (GW 5074) or MEK inhibitor (PD 98059) reduced the PGN-induced increases in COX-2 expression. Treatment of RAW 264.7 macrophages with PGN caused an activation of p44/42 mitogen-activated protein kinase (p44/42 MAPK); this effect was inhibited by manumycin A, GW 5074 or PD 98059, but not by the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor, SB 203580. The tyrosine kinase inhibitor (genistein) and p38 MAPK inhibitor (SB 203580) decreased the PGN-induced increase in COX-2 expression. Treatment of RAW 264.7 macrophages with PGN caused an activation of p38 MAPK; this effect was inhibited by genistein, manumycin A or p38 MAPK inhibitor. The protein kinase C (PKC) inhibitor (Go 6976) also attenuated PGN-induced COX-2 expression. On the other hand, the NF-kB inhibitor (pyrrolidine dithiocarbamate, PDTC) or IkB protease inhibitor (L-1-tosylamido-2-phenylethyl chloromethyl ketone, TPCK and Calpain inhibitor Ι) also decreaseed PGN-induced increases in COX-2 expression. Exposure of RAW 264.7 macrophages to PGN caused a translocation of p65 NF-kB from the cytosol to the nucleus and a degradation of IkBa in the cytosol. Treatment of RAW 264.7 macrophages with PGN caused NF-kB activation by detecting the formation of NF-kB-specific DNA-protein complex in the nucleus; this effect was inhibited by Go 6976, but not by manumycin A, GW 5074, PD 98059, genistein, or SB 203580. These results indicated that the activation of p44/42 MAPK, p38 MAPK, and PKC involved in the PGN-mediated COX-2 expression. The PGN-mediated PKC involves NF-kB activation, rather than by p44/42 MAPK or p38.