DELAYED NEURODEGENERATION IN THE IMMATURE BRAIN.

新生儿脑损伤导致存活婴儿终身残疾，运动感觉障碍通常最为突出。利用Rice- Vannucci模型研究新生儿缺氧缺血性（H/I）脑损伤，我们发现与前脑损伤相比，腹侧基底丘脑损伤的发病延迟（24小时），并表现出明显的细胞凋亡结构特征。由于在大多数新生儿脑损伤模型中都会发生腹侧基底丘脑损伤，并可能导致感觉-运动整合异常，因此腹侧基底丘脑损伤可能导致运动和感觉障碍。患有脑瘫的儿童。在初步研究中，我们发现生物化学证据表明，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表明，线粒体在H/I损伤后的最初24小时内积聚并表现出细胞色素氧化酶活性增加。新生儿缺氧缺血后3 ~ 6小时，基底丘脑腹侧细胞色素氧化酶亚单位1蛋白表达增加。这些线粒体细胞色素氧化酶组织化学和蛋白表达异常在基底丘脑腹侧明显早于24小时神经变性和凋亡谱的出现。发现caspase-3在24小时内裂解为活性形式，进一步支持了线粒体的这些生化变化与H/I损伤后基底丘脑腹侧凋亡相关的观点。最后，在初步研究中，线粒体相关的促凋亡蛋白BAS在缺氧缺血后3至24小时内在基底丘脑腹侧上调。基于这些初步数据，我们假设基底丘脑腹侧的延迟性神经退行性变是细胞凋亡，是线粒体相关细胞凋亡蛋白改变的结果。由于基底丘脑腹侧的延迟性神经退行性变可能为神经元救援提供了合理的机会，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，本研究的目的是：1)证明新生儿缺氧缺血后基底丘脑腹侧延迟性神经退行性变是程序性细胞死亡；2)证明新生儿缺氧缺血后基底丘脑腹侧促凋亡蛋白BAX和BAK的表达增加，以及促和抗凋亡bcl-2家族蛋白相互作用的变化；3)证明BAX缺陷小鼠在新生儿H/I后的神经保护作用。

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.