Glial Interactions in Premyelinating Oligodendrocyte Destruction

描述（由申请人提供）：脑室周围白质软化症（PVL）是脑瘫的主要白色病变，也是早产幸存者慢性神经功能缺损的主要原因。与缺血/缺氧和母体/胎儿感染相关的炎症是PVL发病机制的主要决定因素，在大脑白色物质中具有特征性星形胶质细胞增生和小胶质细胞活化。然而，在这些炎症条件下选择性损伤髓鞘前少突胶质细胞（前OL）的机制知之甚少。我们的长期目标是确定OL前损伤的分子基础，以制定预防PVL的策略。最近，我们发现，小胶质细胞，激活脂多糖（LPS），选择性地杀死前OL通过生产过氧亚硝酸盐。有趣的是，虽然星形胶质细胞不是LPS诱导的毒性所必需的，但它们的存在将活化的小胶质细胞毒性从过氧亚硝酸盐依赖性机制转换为依赖于促炎细胞因子肿瘤坏死因子1（TNF 1）的机制。在混合神经胶质细胞培养物中，暴露于TNF 1导致前OL死亡，但对纯化的前OL只有最小的影响。非损伤水平的干扰素3大大增强了TNF 1的毒性。这些观察结果强调了细胞间通讯在调节前OL死亡途径中的重要性。我们的初步研究结果还表明，神经酰胺，鞘磷脂脂质和脂质第二信使，作为一个共同的调解人前OL损伤，其表达显着增加，在反应性星形胶质细胞在人PVL。我们的总体假设是活化的小胶质细胞和星形胶质细胞共同介导PVL中前OL的损伤。我们将测试神经酰胺是炎性前OL死亡的关键因素，部分通过与TNF 1信号的相互作用。我们的具体目标是：（1）确定星形胶质细胞对过氧亚硝酸盐诱导的前OL毒性的抑制作用;（2）确定TNF 1介导的前OL死亡的潜在机制;（3）研究神经酰胺途径和TNF 1介导的毒性之间协同作用的基础;（4）检查人PVL病变中神经酰胺、促炎细胞因子和前OL细胞死亡的异常上调之间的空间相关性。我们将使用来自野生型和基因敲除小鼠的原代培养物的各种组合来特异性地剖析TNF 1信号转导在介导OL前死亡中的作用。该项目与以往的研究有很大不同，我们直接关注前OL炎症损伤的分子和细胞间机制，并将细胞培养研究与人类PVL研究相结合。对神经胶质细胞之间这种相互作用的基本认识可能会导致PVL治疗的新策略的发展。 早产儿的白色物质损伤是新生儿重症监护幸存者终身神经功能缺损的主要原因;炎症似乎在损伤中起有害作用。通过这项拟议中的研究，我们希望揭示各种细胞如何相互作用和相互加强，并对白色物质造成损害。新生儿白色物质损伤的细胞和分子机制的基本见解，将提供新的途径，开发新的战略，预防和治疗这种毁灭性的疾病。

DESCRIPTION (provided by applicant): Periventricular leukomalacia (PVL) is the principal white matter lesion underlying cerebral palsy and a leading cause of chronic neurological deficits in survivors of premature birth. Inflammation associated with ischemia/hypoxia and maternal/fetal infection is a major determinant of the pathogenesis of PVL, with characteristic astrogliosis and microglial activation in the cerebral white matter. However, the mechanism of selective injury to premyelinating oligodendrocytes (pre-OLs) under these inflammatory conditions is poorly understood. Our long-term goal is to determine the molecular basis of pre-OL injury in order to develop strategies to prevent PVL. Recently, we showed that microglia, activated by lipopolysaccaride (LPS), selectively kill pre-OLs by producing peroxynitrite. Interestingly, although astrocytes are not required for LPS-induced toxicity, their presence switches the activated microglial toxicity from a peroxynitrite- dependent mechanism to a mechanism dependent upon the proinflammatory cytokine, tumor necrosis factor 1 (TNF1). Exposure to TNF1 results in pre-OL death in mixed glial cultures but had only minimal effect to purified pre-OLs. Non-injurious levels of interferon 3 greatly potentiate the TNF1 toxicity. These observations underscore the importance of cell-to-cell communications in regulating pre-OL death pathways. Our preliminary results also suggest that ceramide, a sphingomyelin lipid and a lipid second messenger, acts as a common mediator for pre-OL injury, and that its expression is markedly increased in reactive astrocytes in human PVL. Our overall hypothesis is that activated microglia and astrocytes act corporately in mediating injury to pre-OLs in PVL. We will test the idea that ceramide is a key factor in inflammatory pre-OL death, in part via interactions with TNF1 signaling. Our Specific Aims are to: (1) determine the inhibitory effect of astrocytes on peroxynitrite-induced toxicity to pre-OLs; (2) identify the mechanisms underlying TNF1- mediated pre-OL death; (3) investigate the basis of synergy between the ceramide pathway and TNF1- mediated toxicity; and (4) examine spatial correlations among aberrant upregulation of ceramide, proinflammatory cytokines, and pre-OL cell death in human PVL lesions. We will use various combinations of primary cultures from wildtype and knockout mice to specifically dissect TNF1 signaling in mediating pre-OL death. This project is a significant departure from previous studies in that we focus directly on the molecular and intercellular mechanisms of inflammatory injury to pre-OLs and integrate cell culture studies with human PVL studies. Fundamental insights into such interactions among glial cells could lead to development of novel strategies for the treatment of PVL.PROJECT NARRATIVE White matter injury in preterm infants is a major cause of life-long neurological deficits in survivors of neonatal intensive care; and inflammation appears to play a deleterious role in the injury. Through this proposed study, we hope to reveal how various cells interact and intensify with each other and cause damage to the white matter. Such fundamental insights into the cellular and molecular mechanisms of neonatal white matter injury will provide new avenues for developing novel strategies for the prevention and treatment of this devastating disorder.