组蛋白乙酰化调控对新生大鼠大脑皮层损伤的保护作用

目的研究组蛋白乙酰化调控对新生大鼠缺氧缺血大脑皮层损伤的保护作用。方法将90只3日龄新生大鼠分为假手术组、缺氧缺血模型组以及组蛋白去乙酰化酶抑制剂丁酸钠组。模型组及丁酸钠组大鼠腹腔注射LPS(0.05 mg/kg)2 h后行右侧颈总动脉结扎并置于低氧舱中(6.5%氧浓度)90 min;假手术组腹腔注射生理盐水后仅分离暴露右侧颈总动脉,但不予结扎和低氧处理;丁酸钠组在建模后立即腹腔注射丁酸钠(300 mg/kg),每天1次,共治疗7 d,假手术组及模型组注射等体积生理盐水。模型建立后第7天,采用Western blot方法检测各组大脑皮层组蛋白H3(HH3),乙酰化组蛋白H3(AH3),B细胞淋巴瘤-2(Bcl-2)、Bcl-2相关X蛋白(Bax)、活化型半胱天冬酶-3(CC3),以及脑源性神经营养因子(BDNF)蛋白表达;采用免疫荧光法检测皮层细胞增殖指标Brd U表达。结果丁酸钠组HH3/AH3比值显著低于模型组(P0.05),提示丁酸钠组HH3乙酰化程度增加;丁酸钠组凋亡相关蛋白Bcl-2/Bax比值较模型组显著增高(P0.05),CC3表达显著减少(P0.05),BDNF表达显著增加(P0.05);丁酸钠组较模型组皮层Brd U阳性细胞数显著增加(P0.05),主要表达在神经元。结论组蛋白乙酰化水平增加可通过减少细胞凋亡及促进神经元再生保护新生大鼠大脑皮层损伤,其机制可能与BDNF表达增加相关。

Protective effect of histone acetylation against cortical injury in neonatal rats

Objective To investigate the protective effect of histone acetylation against hypoxic-ischemic cortical injury in neonatal rats. Methods A total of 90 neonatal rats aged 3 days were divided into three groups:sham-operation, cortical injury model, and sodium butyrate (a histone deacetylase inhibitor) treatment. The rats in the model and the sodium butyrate treatment groups were intraperitoneally injected with lipopolysaccharide (0.05 mg/kg), and then right common carotid artery ligation was performed 2 hours later and the rats were put in a hypoxic chamber (oxygen concentration 6.5%) for 90 minutes. The rats in the sham-operation group were intraperitoneally injected with normal saline and the right common carotid artery was only separated and exposed without ligation or hypoxic treatment. The rats in the sodium butyrate treatment group were intraperitoneally injected with sodium butyrate (300 mg/kg) immediately after establishment of the cortical injury model once a day for 7 days. Those in the sham-operation and the model groups were injected with the same volume of normal saline. At 7 days after establishment of the model, Western blot was used to measure the protein expression of histone H3 (HH3), acetylated histone H3 (AH3), B-cell lymphoma/leukemia-2 (Bcl-2), Bcl-2-associated X protein (BAX), cleaved caspase-3 (CC3), and brain-derived neurotrophic factor (BDNF). Immunofluorescence assay was used to measure the expression of 5-bromo-2’-deoxyuridine (BrdU) as the cortex cell proliferation index. Results The sodium butyrate treatment group had a signiifcantly lower HH3/AH3 ratio than the model group (P<0.05), which suggested that the sodium butyrate treatment group had increased acetylation of HH3. Compared with the model group, the sodium butyrate treatment group had a signiifcant increase in Bcl-2/Bax ratio, a signiifcant reduction in CC3 expression, and a signiifcant increase in BDNF expression (P<0.05). The sodium butyrate treatment group had a signiifcant increase in the number of BrdU-positive cells in the cortex compared with the model group (P<0.05), and BrdU was mainly expressed in the neurons. Conclusions Increased histone acetylation may protect neonatal rats against cortical injury by reducing apoptosis and promoting regeneration of neurons. The mechanism may be associated with increased expression of BDNF.