BK-induced cytosolic phospholipase A2 expression via sequential PKC-δ, p42/p44 MAPK, and NF-κB activation in rat brain astrocytes

✍ Scribed by Hsi-Lung Hsieh; Cheng-Ying Wu; Tsong-Long Hwang; Mao-Hsiung Yen; Peter Parker; Chuen-Mao Yang

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 446 KB
• Volume: 206
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.20457

✦ Synopsis

Abstract

Bradykinin (BK), an inflammatory mediator, has been shown to induce cytosolic phospholipase A~2~ (cPLA~2~) expression implicating in inflammatory responses in various cell types. However, the detailed mechanisms underlying BK‐induced cPLA~2~ expression in astrocytes remain unclear. RT‐PCR and Western blotting analysis showed that BK induced the expression of cPLA~2~ mRNA and protein, which was inhibited by Hoe140, suggesting the involvement of B~2~ BK receptors, confirmed by immunofluorescence staining using anti‐B~2~ BK receptor antibody. BK‐induced cPLA~2~ expression and phosphorylation of p42/p44 MAPK was attenuated by PD98059, indicating the involvement of MEK1/2‐p42/p44 MAPK in these responses. BK‐induced cPLA~2~ expression might be due to the translocation of NF‐κB into nucleus which was inhibited by Hoe140, helenalin, and PD98059, implying the involvement of NF‐κB. Moreover, BK‐induced cPLA~2~ expression was attenuated by rottlerin, suggesting that PKC‐δ might be involved in these responses. This hypothesis was supported by the transfection with a dominant negative plasmid of PKC‐δ significantly attenuated BK‐induced response. In addition, BK‐stimulated translocation of PKC‐δ from cytosol to membrane fraction was inhibited by rottlerin but not by PD98059, indicating that PKC‐δ might be an upstream component of p42/p44 MAPK. Accordingly, BK‐induced phosphorylation of p42/p44 MAPK was attenuated by rottlerin but not by helenalin. These results suggest that in RBA‐1 cells, BK‐induced cPLA~2~ expression was sequentially mediated through activation of PKC‐δ, p42/p44 MAPK, and NF‐κB. Understanding the regulation of cPLA~2~ expression induced by BK in astrocytes might provide a new therapeutic strategy of brain injury and inflammatory diseases. © 2005 Wiley‐Liss, Inc.