| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2000: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1999: ¥1,800,000 (Direct Cost: ¥1,800,000)
|
|---|
| Research Abstract |
Upon pathological changes such as brain ischemia or inflammation, microglia are rapidly activated and secrete various cytokines, including TNF-α, which plays not only harmful, but also protective roles for neurons. Despite importance of microglia-derived TNF-α, it remains unknown how the release of TNF-α is regulated. Recently it was revealed that ATP, which is released from nerve terminals, activated immune cells or damaged cells, activates microglia via cell surface P2 receptors, at least G-protein-coupled P2Y_2 and ionotropic P2X_7. In this study, we found that ATP stimulates the release of TNF-α, resulting from mRNA expression in rat cultured brain microglia. The release of TNF-α was maximally elicited by 1 mM ATP and also induced by a P2X_7 selective agonist, 2'-and 3'-O-(4-benzoylbenzoyl)-adenosine 5'-triphosphate (BzATP), and BzATP-induced TNF-α was inhibited by Brilliant Blue G, a selective antagonist of rat P2X_7 receptor. ATP-or BzATP-induced TNF-α release was inhibited by PD98059 and U-0126, inhibitors of MEK1, which activates ERK, and also by SB203580, an inhibitor of p38 MAP kinase, while BzATP-stimulated mRNA expression of TNF-α was inhibited by U-0126, but not by SB203580. These results indicate that extracellular ATP triggers TNF-α release in rat microglia at least via P2X_7 receptor and suggest that signaling to the release of TNF-α involves ERK and p38 MAP kinase, which play distinct roles at the transcriptional and the post-transcriptional levels, respectively.
|
