BK-induced COX-2 expression via PKC-delta-dependent activation of p42/p44 MAPK and NF-kappaB in astrocytes.
Bradykinin (BK) is an inflammatory mediator, elevated levels in the region of several brain injury and inflammatory diseases. It has been shown to induce cyclooxygenase-2 (COX-2) expression implicating in inflammatory responses in various cell types. However, the signaling mechanisms underlying BK-induced COX-2 expression in astrocytes remain unclear. First, RT-PCR and Western blotting analysis showed that BK induced the expression of COX-2 mRNA and protein, which was inhibited by B(2) BK receptor antagonist Hoe140, suggesting the involvement of B(2) BK receptors. BK-induced COX-2 expression and translocation of PKC-delta from cytosol to membrane fraction were inhibited by rottlerin, suggesting that PKC-delta might be involved in these responses. This hypothesis was further supported by the transfection with a dominant negative plasmid of PKC-delta significantly blocked BK-induced COX-2 expression. BK-stimulated p42/p44 MAPK phosphorylation, COX-2 mRNA expression, and prostaglandin E(2) (PGE(2)) release were attenuated by PD98059, indicating the involvement of MEK/p42/p44 MAPK in this pathway. Accordingly, BK-stimulated phosphorylation of p42/p44 MAPK was attenuated by rottlerin, indicating that PKC-delta might be an upstream component of p42/p44 MAPK. Moreover, BK-induced COX-2 expression might be mediated through the translocation of NF-kappaB into nucleus which was blocked by helenalin, rottlerin and PD98059, implying the involvement of NF-kappaB. These results suggest that in RBA-1 cells, BK-induced COX-2 expression and PGE(2) release was sequentially mediated through PKC-delta-dependent activation of p42/p44 MAPK and NF-kappaB. Understanding the regulation of COX-2 expression and PGE(2) release induced by BK in astrocytes might provide a new therapeutic strategy of brain injury and inflammatory diseases.
Hsieh
Hsi-Lung
HL
Department of Physiology and Pharmacology, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, Taiwan.
Wang
Hui-Hsin
HH
Wu
Cheng-Ying
CY
Jou
Mei-Jie
MJ
Yen
Mao-Hsiung
MH
Parker
Peter
P
Yang
Chuen-Mao
CM
D000818:Animals; D001253:Astrocytes / Q000201:enzymology* / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology*; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000378:metabolism* / Q000502:physiology; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D015533:Transcriptional Activation
D016328:NF-kappa B; D012333:RNA, Messenger; D051546:Cyclooxygenase 2; D051745:Protein Kinase C-delta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D001920:Bradykinin