Trauma to Developing Brain-Injury and Repair Mechanisms

描述（由申请人提供）：创伤性脑损伤（TBI）是儿童残疾的主要原因，并与严重的认知缺陷相关。最近的研究表明，与年龄较大的儿童相比，TBI 对 4 岁以下儿童认知功能的损害更大。尽管人们在了解成人大脑中 TBI 的病理学方面付出了相当大的努力，但人们对 TBI 对儿童的后果知之甚少，特别是在发育的关键时期。我们假设，未成熟大脑创伤性损伤后的认知障碍部分是早期炎症导致的细胞死亡的结果。我们进一步假设，由于抗氧化剂储备不足，这种早期炎症反应在受伤、不成熟的大脑中被夸大。为了检验这些假设，我们将确定炎症对 TBI 后早期组织损伤的影响，并确定抗氧化剂谷胱甘肽过氧化物酶 (GPx) 活性的增加是否会减少炎症和细胞损伤，从而支持结构和功能恢复。 这些研究将依靠新开发的未成熟小鼠 TBI 模型来实现 4 个目标。具体目标 1 将检验以下假设：浸润性白细胞和小胶质细胞/巨噬细胞会导致细胞损伤并损害认知恢复。炎症阻断和白细胞去除将与流式细胞术、免疫细胞化学和磁共振成像（MRI）结合使用，以评估炎症对损伤和恢复过程的影响。具体目标 2 将检验以下假设：受伤大脑中 GPx 活性增加可减少氧化应激/损伤、白细胞募集和屏障破坏。将过度表达 GPx 的脑损伤转基因小鼠 (Tg) 与野生型 (Wt) 同窝小鼠的抗氧化剂储备、氧化还原状态和炎症进行比较。具体目标 3 将检验以下假设：GPx 活性增加可增加抗氧化剂储备，通过调节血管粘附分子和趋化因子来减弱早期炎症反应。我们将确定由 Rnase 保护测定定义的血管粘附分子和趋化因子以及白细胞浸润是否优先发生在氧化应激区域，以及与 Wt 小鼠相比，这些事件在 GPx Tg 中是否发生改变。具体目标 4 将检验这一假设：丰富的抗氧化剂储备是 TBI 后结构和认知恢复的决定因素。解剖学和行为测量以及 MRI 将用于确定 GPx 活性的持续增加是否会改变细胞损失和脱髓鞘，从而改善认知结果。

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) is the leading cause of disability in children and is associated with significant cognitive deficits. Recent studies indicate that TBI impairs cognitive function to a greater extent in children less than 4 years of age than in older children. Although there has been a considerable effort directed toward understanding the pathobiology of TBI in the adult brain little is known about the consequences of TBI in the child, particularly during the critical period of development. We hypothesize that cognitive impairment after traumatic injury to the immature brain is in part a consequence of cell death resulting from early inflammation. We further hypothesize that this early inflammatory response is exaggerated in the injured, immature brain because of inadequate antioxidant reserves. To test these hypotheses, we will define the contribution of inflammation to early tissue damage after TBI and will determine if increased activity of the antioxidant glutathione peroxidase (GPx) will reduce inflammation and cell injury thereby supporting structural and functional recovery. These studies will rely on a newly developed model of TBI in the immature mouse to address 4 aims. Specific Aim 1 will test the hypothesis that infiltrating leukocytes and microglia/macrophages contribute to cell injury and impair cognitive recovery. Inflammatory blockade and leukocyte depletion will be used in conjunction with flow cytometry, immunocytochemistry and magnetic resonance imaging (MRI) to assess the contribution of inflammation to injury and recovery processes. Specific Aim 2 will test the hypothesis that increased GPx activity in the injured brain reduces oxidative stress/injury, leukocyte recruitment, and barrier disruption. Antioxidant reserve, redox state, and inflammation will be compared in brain injured transgenic mice (Tg) that overexpress GPx with wildtype (Wt) littermates. Specific Aim 3 will test the hypothesis that enriched antioxidant reserves from increased GPx activity attenuates the early inflammatory response through modulation of vascular adhesion molecules and chemokines. We will determine if vascular adhesion molecules and chemokines, defined by Rnase protection assays, and leukocyte infiltration occur preferentially in regions of oxidative stress and if these events are altered in GPx Tg as compared to Wt mice. Specific Aim 4 will test the hypothesis that enriched antioxidant reserves are a determinant of structural and cognitive recovery after TBI. Anatomical and behavioral measures and MRI, will be used to determine if a sustained increase in GPx activity alters cell loss and demyelination, thereby improving cognitive outcome.