Hippocampal injury following neonatal hypoxia-ischemia (HI) leads to memory impairments despite therapeutic hypothermia (TH). In the hippocampus, the expression of calbindin-1 (Calb1), a Ca2+-buffering protein, increases during postnatal development and decreases with aging and neurodegenerative disorders. Since persistent Ca2+ dysregulation after HI may lead to ongoing injury, persistent changes in hippocampal expression of Calb1 may contribute to memory impairments after neonatal HI. We hypothesized that, despite TH, neonatal HI persistently decreases Calb1 expression in the hippocampus, a change associated with memory deficits in the mouse. We induced cerebral HI in C57BL6 mice at postnatal day 10 (P10) with right carotid ligation and 45 min of hypoxia (FiO2 = 0.08), followed by normothermia (36°C, NT) or TH (31°C) for 4 h with anesthesia-shams as controls. Nissl staining and glial fibrillary acidic protein (GFAP) immunohistochemistry (IHC) were used to grade brain injury and astrogliosis at P11, P18, and P40 prior to the assessment of Calb1 expression by IHC. The subset of mice followed to P40 also performed a memory behavior task (Y-maze) at P22-P26. Nonparametric statistics stratified by sex were applied. In both anterior and posterior coronal brain sections, hippocampal Calb1 expression doubled between P11 and P40 due to an increase in the cornus ammonis (CA) field (Kruskal-Wallis [KW] p < 0.001) and not the dentate gyrus (DG). Neonatal HI produced delayed (P18) and late (P40) deficits in the expression of Calb1 exclusively in the CA field (KW p = 0.02) in posterior brain sections. TH did not attenuate Calb1 deficits after HI. Thirty days after HI injury (at P40), GFAP scores in the hippocampus (p < 0.001, r = -0.47) and CA field (p < 0.001, r = -0.39) of posterior brain sections inversely correlated with their respective Calb1 expression. Both sexes demonstrated deficits in Y-maze testing, including approximately 40% lower spontaneous alterations performance and twice as much total impairment compared to sham mice (KW p < 0.001), but it was only in females that these deficits correlated with the Calb1 expression in the hippocampal CA field (p < 0.05) of the posterior sections. Hippocampal atrophy after neonatal HI also correlated with worse deficits in Y-maze testing, but it did not predict Calb1 deficits. Neonatal HI produces a long-lasting Calb1 deficit in the hippocampal CA field during development, which is not mitigated by TH. Late Calb1 deficit after HI may be the result of persistent astrogliosis and can lead to memory impairment, particularly in female mice.

中文翻译：

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新生儿缺氧缺血和治疗性体温过低后海马体内Calbindin-1的表达和空间记忆障碍。

尽管治疗性低温（TH），新生儿缺氧缺血（HI）后海马损伤仍导致记忆障碍。在海马中，钙结合蛋白1（Cabindin-1）（Calb1）的表达在产后发育过程中增加，并随着衰老和神经退行性疾病而降低。由于HI后持续的Ca2 +失调可能导致持续的损伤，因此新生儿HI后海马Calb1表达的持续变化可能导致记忆障碍。我们假设，尽管有TH，但新生儿HI持续降低海马体中Calb1的表达，这种变化与小鼠的记忆缺陷有关。我们在出生后第10天（P10）用右颈动脉结扎和缺氧45分钟（FiO2 = 0.08），然后进行正常体温（36°C，NT）或TH（31°C），持续4 h，以麻醉假手术为对照。在通过IHC评估Calb1表达之前，使用Nissl染色和神经胶质原纤维酸性蛋白（GFAP）免疫组织化学（IHC）对P11，P18和P40处的脑损伤和星形胶质变进行分级。跟随P40的小鼠亚组还在P22-P26执行记忆行为任务（Y迷宫）。应用按性别分层的非参数统计。在冠状动脉的前部和后部，海马Calb1表达在P11和P40之间增加了一倍，这是由于角膜羊膜（CA）场增加（Kruskal-Wallis [KW] p <0.001），而不是齿状回（DG）。新生儿HI仅在后脑切片的CA区域（KW p = 0.02）中产生Calb1表达的延迟（P18）和晚期（P40）缺陷。TH不能减轻HI后的Calb1缺陷。HI损伤后第30天（在P40处），大脑后部海马区的GFAP评分（p <0.001，r = -0.47）和CA场（p <0.001，r = -0.39）与各自的Calb1表达成反比。两种性别在Y迷宫测试中均表现出缺陷，包括与假小鼠相比约40％的自发改变表现和总损伤的两倍（KW p <0.001），但这些缺陷与雌性小鼠中的Calb1表达相关仅在雌性中。后部的海马CA区（p <0.05）。新生儿HI后的海马萎缩也与Y迷宫测试中更严重的缺陷相关，但并未预测Calb1缺陷。新生儿HI在发育过程中会在海马CA区产生持久的Calb1缺乏症，TH并不能缓解这种缺陷。