Key Laboratory of Neonatal Diseases, Ministry of Health, Children's Hospital, Fudan University, 399 Wanyuan Road, Shanghai 201102, China.
Neurochem Int. 2011 May;58(6):625-33. doi: 10.1016/j.neuint.2011.01.026. Epub 2011 Feb 12.
Hypothermia is a potential therapy for cerebral hypoxic ischemic injury in adults and neonates. However, the mechanism of hypothermia neuroprotection after hypoxic-ischemia (HI) on the developing rat brain remains unclear. In this research, 7-day-old rats were subjected to left carotid artery ligation followed by 8% oxygen for 2h. They were divided into hypothermia (rectal temperature, 32-33°C for 24h) and normothermia (36-37°C for 24h) groups immediately after hypoxia-ischemia. All rats were given 50mg/kg/day 5-bromodeoxyuridine (BrdU) intraperitoneally at 4-6 days and sacrificed at 1 or 2 weeks after HI. There was a significant decrease in infarct volume in the hypothermia group at 7 days after HI compared with that in the normothermia group. The numbers of nestin-labeled cells did not change greatly, but β-tubulin III (Tuj-1) immuno-positive cells increased significantly in the striatum at 1 and 2 weeks after HI in the hypothermia compared to normothermia group. Neurogenesis was assessed by double immunohistochemical/immunofluorescent labeling of BrdU with nestin, Tuj-1 or microtubule-associated protein 2 (Map-2). Newborn neural progenitors (BrdU(+)-nestin(+)) did not change dramatically, but newborn immature (BrdU(+)-Tuj-1(+)) and mature (BrdU(+)-Map-2(+)) neurons increased significantly in the hypothermia compared with normothermia group. Meanwhile, the apoptosis rate of neural precursors, immature and mature neurons, assessed by double labeling of active Casp-3 with nestin/Tuj-1/Map-2, decreased noticeably in the hypothermia compared with normothermia group. We also found that hypothermia significantly increased expression of Bcl-2, which coexisted with nestin/Tuj-1/Map-2. Inhibition of Bcl-2 expression reversed the decreased apoptosis rate of neural precursors and neurons in hypothermia animal striatum of neonatal rat brain. These results suggest that neuroprotection effects of hypothermia on injured developing rat brain may associate with enhanced generation of neuronal cells and Bcl-2-mediated reduction of apoptosis of these cells. These observations are noteworthy regarding clinical hypothermia therapy following cerebral HI injury during the perinatal period.
低温是治疗成人和新生儿缺氧缺血性脑损伤的一种潜在疗法。然而，低温对缺氧缺血（HI）后发育中大鼠脑的神经保护机制仍不清楚。在这项研究中，7 日龄大鼠行左侧颈总动脉结扎，随后 8%氧气 2 小时。HI 后立即分为低温组（直肠温度 32-33°C 24 小时）和常温组（36-37°C 24 小时）。所有大鼠于 HI 后 4-6 天腹腔内给予 50mg/kg/天 5-溴脱氧尿苷（BrdU），HI 后 1 或 2 周处死。与常温组相比，HI 后 7 天低温组梗死体积明显减少。巢蛋白标记细胞数量变化不大，但低温组纹状体β-微管蛋白 III（Tuj-1）免疫阳性细胞在 HI 后 1 周和 2 周显著增加。神经发生通过 BrdU 与巢蛋白、Tuj-1 或微管相关蛋白 2（Map-2）的双重免疫组织化学/免疫荧光标记进行评估。新生神经前体细胞（BrdU(+)-巢蛋白(+））变化不大，但新生未成熟（BrdU(+)-Tuj-1(+））和成熟（BrdU(+)-Map-2(+））神经元在低温组明显增加。同时，通过巢蛋白/Tuj-1/Map-2 与活性 Casp-3 的双重标记评估神经前体细胞、未成熟和成熟神经元的凋亡率，低温组明显降低。我们还发现，低温显著增加了 Bcl-2 的表达，Bcl-2 与巢蛋白/Tuj-1/Map-2 共存。Bcl-2 表达抑制逆转了低温动物纹状体神经前体细胞和神经元凋亡率的降低。这些结果表明，低温对损伤发育中大鼠脑的神经保护作用可能与增强神经元细胞的生成和 Bcl-2 介导的这些细胞凋亡减少有关。这些观察结果对于围产期大脑 HI 损伤后临床低温治疗具有重要意义。
