新生小鼠缺氧缺血后p53的表达及其抑制剂对脑损伤的影响

Expression of p53 in neonatal mice following hypoxia-ischemia and effects of its-inhibitor on neonatal brain injury

摘要:

目的：p53诱导的神经细胞凋亡在缺氧缺血性脑损伤及神经系统退行病变的发生中起重要作用,p53抑制剂p ifithrin-α(PFT-α)在多种动物实验模型中显示神经保护作用。该研究旨在探讨未成熟脑在缺氧缺血(H I)后p53表达的时相变化及p53抑制剂PFT-α干预对脑损伤的影响。方法：新生9日龄C57/BL6小鼠在H I后3,8,24,72 h处死取脑组织进行p53和细胞微管相关蛋白-2(MAP-2)免疫组化染色,探讨p53表达的时相变化及其与神经细胞损伤的关系;为了探讨PFT-α是否对缺氧缺血性脑损伤有保护作用,新生9日龄C57/BL6小鼠分别于H I后即刻给予不同剂量(1,2,8 mg/kg)的PFT-α腹腔注射以及2 mg/kg的PFT-α分别在H I前1 h、H I后即刻及H I后1 h腹腔注射,在H I后72 h灌注取脑,进行脑损伤的大体形态学评分。结果：正常脑组织p53免疫组化染色偶见阳性细胞,H I后p53的免疫反应性增加,缺氧缺血侧大脑皮层、海马及纹状体的p53阳性细胞数明显高于正常对照组及对侧大脑半球(P<0.01或P<0.05)。p53阳性细胞数于H I后3~8 h达到峰值,随后逐渐下降,并且p53阳性细胞主要分布在MAP-2阴性区域(脑损伤区)。采用H I后不同剂量及H I前后不同时间给予PFT-α,干预组脑损伤大体形态学评分与对照组相比差异无显著性(均P>0.05)。结论：新生小鼠缺氧缺血后早期脑组织p53即开始表达;p53的表达与神经细胞损伤分布区域一致;单纯应用p53抑制剂PFT-α对未成熟脑缺氧缺血性损伤无明显保护作用。

Abstract:

OBJECTIVE: p53-induced apoptosis is crucial in the development of hypoxic-ischemia (HI) brain damage and neurodegenerative disorders. Some experimental research has shown that a synthetic inhibitor of p53 can protect neurons against apoptosis. This study aimed to explore the expression of p53 in neonatal mice following HI brain damage and the effect of p53 inhibitor (pifithrin-α, PFT-α) on brain damage. METHODS: HI was induced in 9-day-old mice pups by ligation of left carotid artery and 10% oxygen exposure for 55 minutes.The pups were sacrificed and the brains were taken out at 3, 8, 24, and 72 hrs post-HI. The brains were sectioned and stained with antibody against p53 and microtubule-associated protein 2 (MAP-2). PFT-α was injected intraperitoneally: in experiment 1 immediately after HI with different dosages (1, 2 and 8 mg/kg); in experiment 2 2 mg/kg at different HI times (1 hr before HI, and immediately and 1 hr after HI). Control animals without HI received injections of 0.5% dimethyl sulfoxide. Brain damage was evaluated by gross morphology scoring at 72 hrs after HI. RESULTS: The number of p53 positive cells in the cortex, hippocampus and striatum of the ipsilateral hemisphere increased significantly and peaked at 3-8 hrs post-HI when compared with those of contralateral hemisphere as well as normal controls. The positive cells distributed mainly in the MAP-2 negative area.Both different dosages and different injection time PFT-α treatment did not reduce the extent of brain damage. CONCLUSIONS: The immunoactivity of p53 increased significantly as early as 3 hrs post-HI. The distribution area of p53 expression was consistent with that of brain damage. The p53 inhibitor PFT-α has no protective effects against HI brain damage in neonatal mice.