|Budget Amount *help
¥18,200,000 (Direct Cost : ¥18,200,000)
Fiscal Year 1997 : ¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1996 : ¥5,100,000 (Direct Cost : ¥5,100,000)
Fiscal Year 1995 : ¥9,800,000 (Direct Cost : ¥9,800,000)
This year, we tried the following two investigations.
I) The role of endogenous endothelin (ET) -1 in astrocytic growth and neuronal degeneration after CNS damage
We have already suggested the possibility that endogenous ET-1 participates in astrocytic growth at early stage after acute ischemic injury of rat brain (J.Neurosci.Res.47,590-602,1997). Then, we tried to further clarify this possibility by virtue of SB209670, a potent ET receptor blocker. We produced rat spinal cord injury model, becausc of easier delivery of SB compound to injury site, compared with the case of brain injury model. In the preliminary studies, we confirmed that the response to ET-1 of cultured astrocyte from spinal cord is similar to that from brain. 24h after spinal cord injury, tissue content of endogenous ET-1 was significantly elevated. In conjunction with this phenomenon, astrocytic growth was clearly observed. On the other hand, 7 days after the injury, the degeneration of axon and gliosis was observed. T
he application of SB compound to injury site significantly inhibited both the early onset of astrocytic growth leading to gliosis and the late onset of neuronal degeneration after the injury. These results suggested that endogenous ET-1 plays an important role in tissue regeneration process after CNS damage (Brain Res.728,255-259,1996 & Brain Res.1998 in press).
2) The regulation of ET_B receptor expression in cultured rat astrocytes (ACs)
We have already confirmed that ET_B receptor, one of ET receptor subtypes, is highly expressed on ACs and that the expression level of ET_B receptor is elevated in accordance with difrefentiation of ACs in vitro and in vivo (Biochem.Biophys.Res.Commun.186,355-362,1992 ; Biochem.Biophys.Res.Commun. 204,1325-1333,1994 ; Jap.J.Pharmacol. (Suppl.), 67,242P,1995). The dramatic morphological changes induced by cytodifferentiation is accompanied by rearrangement of the cytoskeletal system. We think that, if possible, the level of ET_B receptor in ACs could be regulated by the cytoskeletal system. To elucidate this possibility, we investigated the changes in ET_B receptor expression by the treatment of ACs with cytoskeleton modulators such as colchicine. Then, we clarified that microtubule dynamics possibly regulates ET_B receptor expression in ACs by affecting the stability of ET_B receptor mRNA (J.Neurochem.69,562-569,1997).
申請者らはすでに,アストロサイトにおけるET_B受容体の項頻度な発現および,この発現が細胞の分化誘導によってさらに惹起されること,また,発生過程においてもグリア細胞の分化に準じてET_B受容体の発現が上昇することを確認している(Biochem.Biophys.Res.Commun.,186,355-362,Hama et al.;Biochem.Biophys.Res.Commun.,204,1325-1333,Kasuya et al,.;Jap.J.Pharmacol.(Suppl.),67,242p,Tanaka et al.).細胞の分化と細胞骨格の変化は密度に関係しているいるので,申請者らはアストロサイトの細胞骨格の変化によるET_B受容体の発現調節について検討を行った.その結果,ET_B受容体の発現は,アクチンフィラメントの変化には影響されないものの,チュープリンのmonomer/polymerの平衡状態の変化によって変動することが判明した.また,その調節様式は,転写後のET_B受容体mRNAの安定化の変化を通じて行われることを確認した(研究発表の項4参照).
現在,rescued ET_B-knock outマウスを用いて,ETと中枢神経系障害の関連性についてさらに検討を加えている. Less