IGF I THERAPY IN NEONATAL HYPOXIC ISCHEMIC BRAIN INJURY

脑缺氧缺血仍然是严重脑损伤的主要原因 在新生儿身上。神经元损伤的分子机制及相关研究进展 后续的维修流程不是很好理解，但可能涉及 持续破坏细胞能量稳态，如以下所示 氧化磷酸化、养分吸收和利用的变化。 胰岛素样生长因子I(IGF-I)是一种合成代谢多营养因子 发育中的大脑中所有类型的细胞所需的最佳 增殖、分化和存活。缺氧缺血后不久 新生大鼠脑损伤后IGF-I基因表达下调 易损神经元，在反应性星形胶质细胞中仅在2-3小时后被激活 几天。低氧后两小时脑室注射IGF-I- 缺血损伤减少成年大鼠和大鼠脑内神经元的丢失 妊娠晚期的胎羊。IGF-I介导的这种作用机制 然而，神经保护还不是很清楚。我们假设IGF-I 在缺血后早期预防即将发生的神经元损伤 调节细胞能量代谢。这项建议的具体目的 方法：1)检测一种新基因的表达和细胞特异性。 病毒载体携带的外源IGF-I基因；2)检测 胰岛素样生长因子-I对正常大鼠大脑某些方面的调节作用 细胞代谢，如底物摄取、蛋白质合成和 神经元活性；以及3)确定缺氧缺血是否诱导 IGF-I基因增强可改善神经元损伤 表情。因此，我们将首先研究IGF-I在 分子和细胞水平通过直接将IGF-I基因转入 新生大鼠脑内使用病毒载体。在体内过度表达IGF-I将 使其更容易被驻留在所有大脑上的I型IGF受体所利用 胰岛素样生长因子结合蛋白和蛋白酶对细胞和极限受体的抑制作用 退化。我们将验证外源IGF-I基因的转导 采用原位杂交和免疫细胞化学方法。从功能上讲， 胰岛素样生长因子-I对细胞代谢水平的影响 将研究正常大鼠大脑中的过度表达 在大鼠缺氧缺血损伤过程中和损伤后。这些应该是 研究产生了令人鼓舞的结果，我们将提供强有力的证据 将IGF-I确立为对缺氧缺血的一种重要干预- 对新生儿造成脑损伤。

Cerebral hypoxia-ischemia remains a leading cause of severe brain damage in newborns. The molecular mechanisms of the neuronal injury and subsequent repair processes are not well understood but may involve persistent disruption of cellular energy homeostasis, as evidenced by alterations in oxidative phosphorylation, nutrient uptake and utilization. Insulin-like growth factor I (IGF-I) is an anabolic pleiotrophic factor required by all cell types in the developing brain for optimal proliferation, differentiation, and survival. Soon after hypoxic-ischemic insult to newborn rat brain, IGF-I gene expression is decreased in vulnerable neurons and is activated in reactive astrocytes only after 2-3 days. Intraventricular infusion of IGF-I two hours following the hypoxic- ischemic insult reduces the neuronal loss in both the adult rat and the late gestation fetal lamb. The mechanism of this IGF-I mediated neuroprotection, however, is not understood. We hypothesize that IGF-I prevents impending neuronal injury during the early post-ischemic phase by regulating cellular energy metabolism. The specific aims of this proposal are: 1) to examine both the expression and the cellular specificity of an exogenous IGF-I gene delivered by virus vectors; 2) to determine the extent to which IGF-I can regulate certain aspects of normal rat brain cellular metabolism, such as substrate uptake, protein synthesis and neuronal activity; and 3) to determine whether hypoxia-ischemia-induced neuronal damage can be ~meliorated as a result of enhanced IGF-I gene expression. Hence, we will first study the functional role of IGF-I at the molecular and cellular levels by directly transferring the IGF-I gene into neonatal rat brain using virus vectors. Overexpressing IGF-I in vivo would make it more available to the type I IGF receptor residing on all brain cells and limits receptor inhibition by IGF binding proteins and protease degradation. We will verify the transduction of the exogenous IGF-I gene with in situ hybridization and immunocytochemistry. Functionally, the alterations in cellular metabolic levels resulting from IGF-I overexpression will be investigated in the brains of both the normal rat and in rat during and after hypoxia-ischemia-induced injury. Should these studies produce encouraging results, we will have provided strong evidence in establishing IGF-I as one important intervention in hypoxia-ischemia- induced brain damage in neonates.