Zhu Chang-lian, Wang Xiao-yang, Cheng Xiu-yong, Qiu Lin, Hu Sheng-hai, Yang Jing-li, Xu Fa-lin
Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China.
Zhonghua Er Ke Za Zhi. 2003 Dec;41(12):911-5.
Recent studies suggest that hypothermia may be a potential treatment for perinatal hypoxic-ischemic (HI) brain damage. But the mechanisms of this effect are not well known. In the present study, the protective effect of systemic hypothermia as well as effect on apoptosis and associated biochemical events were investigated on neonatal rats with HI brain damage.
Seven-day-old Wistar rats were subjected to left carotid artery ligation and hypoxia was persisted for 60 min. Immediately at the end of hypoxia, the animals were maintained either at 36 degrees C or 30 degrees C for 10 h at random. Caspase-2, 3 activity in brain homogenate was detected with Western blotting at 24 h post-HI (n = 8 for each group). Immunoactivity of microtubule-associated protein-2 (MAP-2), active caspase-3, apoptosis inducing factor (AIF) and oligonucleotide hairpin probe staining were detected at 72 h post-HI. The infarct volume, neuronal loss in CA(1) sector of hippocampus as well as brain injury scoring were calculated according to MAP-2 staining and hematoxylin and eosin staining.
Caspase-2, 3 activities were much higher in the normothermia group [(27.7 +/- 14.7), (94.9 +/- 53.1) pmol/(min.mg protein)] at 24 h post-HI than those of hypothermia [(7.9 +/- 3.4), (21.1 +/- 18.7) pmol/(min.mg protein)] and normal control groups [(7.6 +/- 0.7), (12.9 +/- 0.5) pmol/(min x mg protein)] (P < 0.01). The activities were not significantly different between hypothermia group and normal control group. Western blotting showed that caspase-3 activation process was blocked by hypothermia. The number of active caspase-3 and AIF positive cells in the cortex of ipsilateral hemisphere was much higher in the normothermia group (median: 148.5; 22/field) than that of hypothermia group (median: 48.5; 9/field) (P < 0.05). The number of apoptotic cells as judged by oligonucleotide hairpin probe labeling was much higher in normothermia group (median: 144/field) than that of hypothermia group (median: 133/field) (P < 0.05). The brain injury scoring, infarct volume and neuronal loss in CA(1) area of hippocampus were much less in the hypothermia group [10.4 +/- 2.9; 40.5 +/- 34.8)mm(3); 25.7 +/- 11.5] than that of normothermia group [14.2 +/- 3.5; (73.9 +/- 22.4) mm(3); 37.4 +/- 10.6, P < 0.05].
Systemic hypothermia for 10 h after hypoxia-ischemia seemed to be effective in reducing brain damage and the mechanism is associated with alteration of apoptotic pathway.
近期研究表明，低温可能是围产期缺氧缺血性（HI）脑损伤的一种潜在治疗方法。但其作用机制尚不清楚。在本研究中，我们探讨了全身低温对新生HI脑损伤大鼠的保护作用及其对凋亡和相关生化事件的影响。
将7日龄Wistar大鼠进行左侧颈动脉结扎，并持续缺氧60分钟。缺氧结束后，立即将动物随机置于36℃或30℃环境中维持10小时。HI后24小时，用蛋白质印迹法检测脑匀浆中半胱天冬酶-2、3的活性（每组n = 8）。HI后72小时，检测微管相关蛋白-2（MAP-2）、活化半胱天冬酶-3、凋亡诱导因子（AIF）的免疫活性及寡核苷酸发夹探针染色。根据MAP-2染色及苏木精-伊红染色计算梗死体积、海马CA1区神经元丢失及脑损伤评分。
HI后24小时，常温组半胱天冬酶-2、3的活性[（27.7±14.7），（94.9±53.1）pmol/（min·mg蛋白）]明显高于低温组[（7.9±3.4），（21.1±18.7）pmol/（min·mg蛋白）]和正常对照组[（7.6±0.7），（12.9±0.5）pmol/（min·mg蛋白）]（P < 0.01）。低温组与正常对照组活性无明显差异。蛋白质印迹法显示低温可阻断半胱天冬酶-3的激活过程。常温组同侧半球皮质中活化半胱天冬酶-3和AIF阳性细胞数（中位数：148.5；22/视野）明显高于低温组（中位数：48.5；9/视野）（P < 0.05）。寡核苷酸发夹探针标记法判断的凋亡细胞数常温组（中位数：144/视野）明显高于低温组（中位数：133/视野）（P < 0.05）。低温组脑损伤评分、梗死体积及海马CA1区神经元丢失[10.4±2.9；（40.5±34.8）mm³；25.7±11.5]明显低于常温组[14.2±3.5；（73.9±22.4）mm³；37.4±10.6，P < 0.05]。
缺氧缺血后全身低温10小时似乎能有效减轻脑损伤，其机制与凋亡途径的改变有关。
