Mechanisms of behavioral disorders following neonatal Hypoxic Ischemic-Encephalopathy and effect of treatment with Caspase inhibitor

PURPOSESCaspase在大鼠缺氧缺血(HI)后迟发性神经细胞死亡中起关键作用。HI损伤后的海马区损害与学习记忆密切相关。在本研究中，我们用Morris水迷宫检测了新生儿缺氧对学习能力的影响，用ROTA杆试验检测了新生儿缺氧对体能的影响。此外，我们还观察了半胱氨酸天冬氨酸氨基转移酶抑制剂的保护作用。方法出生后第7天的大鼠在大米低氧模型下进行2.5h的缺氧。HIE组(n：15)。对照组大鼠(n：15)不进行HI负荷，为假手术。对于治疗组，准备了两种不同的给药时间表。缺氧缺血前，BAF1组(n：15)注射泛型半胱氨酸氨基转移酶抑制剂BOC-天冬氨酸-(OME)-氟甲基酮(BAF)，BAF2组(n：5)在HI后12h加入相同剂量的BAF。结果1.尽管4组动物的体能无显著差异，但HIE组的学习能力明显低于对照组。2.对照组大鼠Caspase3活性维持在较低水平，左右侧海马区无明显差异。HIE组(未治疗组)Caspase3水平左侧明显升高(右侧：0.85±0.06u/mg蛋白/mm，左侧：6.4±1.7u/mg蛋白/mm)。BAF可抑制损伤侧海马区Caspase 3活性的升高。结论BAF治疗可抑制损伤侧海马区Caspase 3活性的升高，但不能改善新生儿HIE后的认知功能障碍。

PURPOSESCaspases play a key role in the delayed neuronal cell death observed in the rat brain following hypoxic-ischemic (HI) insult. Hippocampal damage after HI insult is strongly related to learning memory. In this study, we examined the influences of neonatal HI on learning ability by using the Morris's water maze, and on physical ability by the Rota rod test. Furthermore, we examined the protective effect of the treatment with caspase inhibitor.METHODSPostnatal day 7 rat pups were subjected to the Rice model of hypoxia for 2.5h. (HIE group, n:15). Sham-operation was completed in the control rats without HI loading (n:15). For the treatment groups, two different administration schedules were prepared. Just before HI insult, a pan-caspase inhibitor, boc-aspartyl-(OMe)-fluoromethyl-ketone (BAF), was injected into the BAF 1 group (n:15), and the same dose of BAF was added 12hrs after HI loading in the BAF 2 group (n:5) Caspase 3 activitiy of the hippocampus was measured in each group at 24 hrs after HI loading. Learning and physical abilities were assessed at the age of 35 days.RESULTS1.Although there was no significant difference in the physical ability among the four groups, learning ability was significantly decreased in the HIE groups in comparison with the control group. The effect of the treatment with BAF could not be observed in either treatment group.2.The Caspase 3 activities were remained in low value in the control rats, and there was not any difference between the right and left Hippocampus. In the HIE group(without the treatment), the level of Caspase 3 was distinctly elevated in the left side (right side:0.85± 0.06 unit/mg protein/mm, left side: 6.4±1.7 unit/mg protein/mm. The elevation of Caspase 3 activities in the injured side was inhibited by the treatment with BAF.CONCLUSIONThe treatment with BAF inhibited the elevation of Caspase 3 activity in the injured Hippocampus, but it failed to improve the cognitional dysfunction following neonatal HIE.