Role of 20-HETE in Pediatric Traumatic Brain Injury

 描述(申请人提供)：数以百万计的婴儿、儿童和青壮年因童年时期的创伤性脑损伤(TBI)而生活在残疾中。在最初的侮辱之后，一连串的次要事件会导致进行性神经退化。由于发育成熟的特征，发育中的大脑可能特别容易受到这些二次侮辱中的一些。在非常年轻的时候，这种损伤可能会干扰生命后期发育计划的执行，导致学习、注意力和社会行为异常。目前，治疗仅限于支持性护理。在这里，我们将研究新出现的途径，涉及细胞信号通过20-HETE，一种细胞色素P450的花生四烯酸的代谢物。我们发现，已知的合成20-HETE的特异性细胞色素P450在神经元和小胶质细胞中表达，20-HETE可以诱导NMDA受体和Na，K-ATPase的磷酸化。在我们以前工作的基础上，我们开始研究20-HETE抑制剂在新生大鼠缺氧缺血和成人缺血性出血性卒中模型中的神经保护作用，并在出生后第10天开始研究其在控制皮质撞击模型中的作用。初步数据显示，病变体积大幅缩小，长期感觉运动功能改善，小胶质细胞形态改变减弱，促炎细胞因子减少。20-HETE抑制剂还减弱了小胶质细胞培养中对脂多糖的反应。该项目的目标是研究20-HETE在儿童脑外伤模型中对男性和女性的作用。在目标1中，我们将确定20-HETE抑制剂给药的最佳持续时间和提供疗效的最大延迟，以告知20-HETE信号在脑创伤后何时产生不良影响。在目标2中，我们将确定脑损伤后抑制20-HETE对NADPH氧化酶的影响以及随后对caspase依赖和独立的关键细胞死亡途径的下游影响。在目标3中，我们将确定脑创伤后20-HETE抑制对小胶质细胞形态和细胞因子谱的影响。通过在非常不成熟的大脑中使用一种药物同时针对细胞死亡和炎症途径，这项工作具有巨大的潜力来改善婴儿和蹒跚学步的婴儿和幼儿的预后，这些婴儿和幼儿往往是儿科脑损伤中预后最差的。此外，新出现的脑缺血证据表明，在未成熟和成熟的脑中，细胞死亡机制和炎症机制存在性别差异，但在儿童脑损伤模型中，性别差异一直未得到充分研究。因此，这项拟议的工作也是创新的，因为它将开始揭示在未成熟的大脑中脑外伤后，神经保护疗法的反应是否存在性别差异。最后，阐明神经元和小胶质细胞中20-HETE的新途径可能对脑损伤以外的其他神经退行性疾病具有重要影响，包括兴奋性毒性和神经炎症，因此可能会激发新的研究领域。

 DESCRIPTION (provided by applicant): Millions of infants, children and young adults are living with disabilities resulting from traumatic brain injury (TBI) in childhood. Following the intial insult, a cascade of secondary events produces progressive neurodegeneration. The developing brain may be uniquely vulnerable to some of these secondary insults, due to maturational features. In the very young, the injury may interfere with the execution of the developmental program later in life, leading to learning, attention, and social behavior abnormalities. Currently, treatment is limited to supportive care. Here, we will investigate novel emerging pathways involving cell signaling by 20- HETE, a cytochrome P450 metabolite of arachidonic acid. We find that specific cytochrome P450s known to synthesize 20-HETE are expressed in neurons and microglia and that 20-HETE can induce phosphorylation of NMDA receptors and Na,K-ATPase. Based on our previous work showing that a 20-HETE inhibitor is neuroprotective in models of neonatal hypoxia-ischemia and adult ischemic and hemorrhagic stroke, we began to study its effect in the controlled cortical impact model in postnatal day 10 rats. Preliminary data show large reductions in lesion volume, improved long-term sensorimotor function, attenuated morphological changes in microglia, and a reduction of pro-inflammatory cytokines. The 20-HETE inhibitor also attenuated the response to lipopolysaccharide in microglia cultures. The goal of this project is to investigate the role of 20-HETE in males and females in a model of pediatric TBI. In Aim 1, we will determine the optimal duration of 20-HETE inhibitor administration and the maximum delay that provides efficacy so as to inform when 20-HETE signaling is exerting adverse effects after TBI. In Aim 2, we will determine the effects of 20-HETE inhibition after TBI on NADPH oxidase and the consequent downstream effects on key caspase-dependent and independent cell death pathways. In Aim 3, we will determine the effects of 20-HETE inhibition after TBI on microglia morphology and the cytokine profile. By targeting both cell death and inflammatory pathways with a single drug in the very immature brain, this work has great potential for improving outcome from TBI in infants and toddlers who often have the poorest prognosis in pediatric TBI. Moreover, emerging evidence with cerebral ischemia indicates sex differences in cell death mechanisms and inflammation in both immature and mature brain, yet sex differences have been understudied in pediatric TBI models. Thus, the proposed work also is innovative in that it will begin to reveal whether sex differences in response to neuroprotective therapies are operative after TBI in the immature brain. Finally, elucidation of new pathways of 20-HETE in neurons and microglia could have an important bearing beyond TBI for other neurodegenerative disorders involving excitotoxicity and neuroinflammation and, hence, may stimulate new areas of investigation.