Mechanisms of Death and Survival in Oligodendroglia

描述(申请人提供)：谷氨酸兴奋性毒性与缺血和创伤后少突胶质细胞及其前体细胞的丧失以及脱髓鞘疾病有关。特别是，血统的祖代阶段最容易受到包括谷氨酸过量在内的多种类型的损害。体外和体内研究表明，过量的谷氨酸通过AMPA/Kainate受体的钙内流杀死少突胶质前体细胞(OPs)，阻断AMPA/Kainate受体可以保护少突胶质前体细胞免受过量谷氨酸和缺氧缺血的影响。然而，直到最近，人们对谷氨酸介导的毒性机制知之甚少。我们以前的研究表明，过量的谷氨酸会导致促凋亡的Bcl族成员Bax移位到线粒体，释放细胞色素c，激活caspase9和caspase3，并导致少突胶质祖细胞死亡。我们还发现，IGF-I具有维持Akt激活的独特能力，并为少突胶质细胞前体细胞提供长期保护，使其免受谷氨酸或营养因子的影响，在谷氨酸存在的情况下，IGF介导的生存发生在钙内流的下游和Bax易位的上游，以及线粒体功能障碍。因此，本研究的目的是验证以下假设：1)晚期OPs的谷氨酸毒性需要Bax介导的/线粒体通路，该通路通过钙诱导的细胞级联激活；2)IGF-I通过持续的IGF-IR/Akt信号阻断Box介导的OP细胞线粒体功能障碍；3)围产期H/I通过Box介导的细胞凋亡导致OPs的死亡，这可以通过激活Akt来阻断。

DESCRIPTION (provided by applicant): Glutamate excitotoxicity has been implicated in loss of oligodendrocytes and their progenitors following ischemia and trauma and in demyelinating diseases. In particular, the progenitor stages of the lineage are most susceptible to many types of damage including excess glutamate. Studies both in vitro and in vivo have demonstrated that excess glutamate kills oligodendrocyte progenitors (OPs) via calcium influx through the AMPA/kainate receptors and that blockade of the AMPA/kainate receptors can protect oligodendrocyte progenitors from excess glutamate as well as from hypoxia-ischemia. Until recently, however, little was known about the mechanisms for glutamate-mediated toxicity. Our previous data demonstrated that excess glutamate leads to translocation of the pro-apoptotic Bcl family member Bax to the mitochondria, release of cytochrome c, activation of caspases 9 and 3 and death of oligodendrocyte progenitors. We also found that IGF-I has a unique ability to sustain activation of Akt and provide long-term protection of the oligodendrocyte progenitors from glutamate or trophic factor withdrawal, and that IGF-mediated survival in the presence of glutamate occurs downstream of calcium influx and upstream of Bax translocation and mitochondrial dysfunction. Thus, the goals of this proposal are to test the hypotheses that 1) glutamate toxicity of late OPs requires a Bax-mediated/mitochondrial pathway, which is activated through a calcium-induced cellular cascade, 2) IGF-I blocks Box-mediated mitochondrial dysfunction in OP cells through sustained IGF-IR/Akt signaling, and 3) perinatal H/I results in death of OPs through Box-mediated apoptosis, which can be blocked through activating Akt.