DELAYED NEURODEGENERATION IN THE IMMATURE BRAIN.

新生儿脑损伤导致存活的婴儿终身残疾，其中运动感觉障碍往往最为突出。利用莱斯-万努奇新生儿缺氧缺血性脑损伤模型，我们发现与前脑损伤相比，丘脑腹侧基底核的损伤起病时间延迟(24小时)，并表现出明显的细胞凋亡结构特征。由于丘脑腹侧基底核的损伤在大多数新生儿脑损伤模型中都会发生，并可能导致感觉-运动整合的异常，因此腹侧基底核的损伤可能导致运动和感觉障碍。患有脑瘫的儿童所遭受的痛苦。在初步研究中，我们发现生化证据表明，腹侧基底丘脑的细胞死亡是通过程序性细胞死亡机制发生的。细胞色素氧化酶组织化学显示线粒体在H/I损伤后24小时内积聚并表现出细胞色素氧化酶活性的升高。细胞色素氧化酶亚单位1蛋白在新生儿缺氧缺血后3-6小时在丘脑腹侧基底核的表达也增加。腹侧基底丘脑线粒体细胞色素氧化酶组织化学和蛋白表达的这些异常明显先于24小时出现神经变性和细胞凋亡。24小时后caspase-3裂解为其活性形式的发现进一步支持了线粒体的这些生化变化与Hi损伤后腹侧基底丘脑的细胞凋亡有关的观点。最后，在初步研究中，线粒体相关的促凋亡蛋白BAS在丘脑腹侧缺氧缺血后3至24小时内上调。基于这些初步数据，我们假设丘脑腹侧基底核迟发性神经退行性变是细胞凋亡，并且是线粒体相关的凋亡蛋白改变的结果。由于丘脑腹侧基底核迟发性神经元变性可能为神经元的挽救提供了一个合理的机会，因此我们必须了解新生儿H/I脑损伤后延迟性细胞死亡的确切机制。为了实现这一目标，本方案的目的将1)证明新生儿缺氧缺血后腹侧基底核迟发性神经变性是细胞程序性死亡，2)证明促凋亡蛋白Bax和BAK的表达增加，以及新生儿缺氧缺血后腹侧基底核促凋亡和抗凋亡bcl2家族蛋白相互作用的变化，3)证明Bax缺陷小鼠在新生H/I后具有神经保护作用。

Neonatal brain injury results in lifelong disabilities for surviving infants with motor sensory disabilities often most prominent. Using the Rice- Vannucci model for neonatal hypoxic-ischemic (H/I) brain injury, we have shown the injury to the ventral basal thalamus is delayed in onset (24 hours) compared to forebrain injury and exhibits prominent structural features of apoptosis. Because injury to the ventral basal thalamus occurs in most models of neonatal brain injury and likely results in abnormalities in sensory-motor integration, injury to the ventral basal thalamus may contribute to the motor and sensory handicaps. Suffered by children with cerebral palsy. In preliminary studies, we find biochemical evidence that cell death in the ventral basal thalamus occurs by a programmed cell death mechanism. Cytochrome oxidase histochemistry indicates that mitochondria indicates that mitochondria accumulate and exhibit increased cytochrome oxidase activity in the first 24 hours after H/I injury. Cytochrome oxidase sub-unit 1 protein expression in the ventral basal thalamus is also increased at 3-6 hours after neonatal hypoxia- ischemia. These abnormalities in mitochondrial cytochrome oxidase histochemistry and protein expression in the ventral basal thalamus significantly precede the appearance the appearance of neurodegeneration and apoptotic profiles at 24 hours. The finding of cleavage of caspase-3 into its active forms by 24 hours further supports the idea that these biochemical changes in mitochondria are associated with apoptosis in the ventral basal thalamus following H/I injury. Lastly, in preliminary studies the mitochondrial associated pro-apoptosis protein, BAS is up-regulated between 3 and 24 hours following hypoxia-ischemia in the ventral basal thalamus. Based on these preliminary data, we hypothesize that delayed neurodegeneration in the ventral basal thalamus is apoptosis and occurs as the result of alterations in mitochondrial associated apoptosis proteins. Because delayed neurodegeneration in the ventral basal thalamus may offer a reasonable opportunity for neuronal rescue, we must understand the precise mechanism of delayed cell death following neonatal H/I brain injury. To accomplish this goal, the aims of this proposal will 1) demonstrate that delayed neurodegeneration in ventral basal thalamus after neonatal hypoxia-ischemia is programmed cell death, 2) demonstrate increased expression of the pro-apoptosis proteins, BAX and BAK, and changes in pro and anti-apoptosis bcl-2 family protein interactions in the ventral basal thalamus following neonatal hypoxia- ischemia, and 3) demonstrate neuroprotection in BAX deficient mice following neonatal H/I.