热习服对大鼠高原脑水肿的预防效应及其机制研究

Preventive effects and mechanism of heat acclimation on high altitude cerebral edema in rats

目的探讨热习服对大鼠高原脑水肿的预防效应及其机制。方法雄性成年SD大鼠按随机数字表法分为正常对照(C)组、热习服(HA)组(34℃,30 d)、缺氧(H)组(7 600 m,1 d)、热习服+缺氧(HHA)组(34℃30 d+7 600 m 1 d)。各组处理结束后,取脑组织比较其湿干质量比,对脑组织HE染色、FJB染色后观察病理形态学改变,透射电镜观察脑组织超微结构改变,取血液标本检测血常规、血气分析和血红蛋白氧解离曲线,同时检测脑组织中丙二醛(MDA)含量和热休克蛋白70(HSP70)及水通道蛋白4(AQP4)蛋白的表达。结果与C组(4.50±0.07)相比,H组脑组织湿干质量比(4.62±0.08)显著升高(P<0.05);HHA组脑组织湿干质量比(4.52±0.06)显著低于H组(P<0.05)。与C组相比,H组脑组织HE染色和透射电镜结果显示细胞肿胀,胞质疏松,染色质分布不均匀,核明显固缩、破裂、溶解,细胞空泡化明显,FJB染色提示神经元变性增多;与H组相比,HHA组细胞损伤、神经元变性和凋亡程度显著改善。与C组相比,H组血红蛋白、红细胞计数、红细胞压积和中性粒细胞百分比显著升高,血氧饱和度、血氧分压显著降低(P<0.05);与H组相比,HHA组血红蛋白、红细胞和红细胞压积进一步升高,但中性粒细胞百分比显著降低,血氧饱和度、血氧分压显著升高(P<0.05)。与C组相比,H组氧解离曲线发生右移;与H组相比,HHA组氧解离曲线发生右移。与C组相比,H组脑组织MDA含量和AQP4蛋白表达显著升高(P<0.05);与H组相比,HHA组MDA含量和AQP4蛋白表达显著降低,HSP70蛋白表达显著升高(P<0.05)。结论热习服可以有效预防大鼠高原脑水肿的发生,其机制与提高氧气供应、减轻氧化应激、改善细胞损伤等有关。

Objective To investigate the effects and mechanism of heat acclimation(HA) on rats with high altitude cerebral edema. Methods Adult male SD rats were randomly divided into normal control group(C group), hypoxia group(H group, 7 600 m, 1 d), HA group(34 ℃, 30 d) and hypoxia+HA group(HHA group). All rats were sacrificed after the treatment, and then brain water content, pathological changes(HE staining), neuronal degeneration(Fluoro-Jade B staining) and ultrastructure changes(transmission electron microscopy) were measured and observed. Blood samples were harvested to make blood routine test, blood gas and oxygen dissociation curves. The content of MDA and protein levels of HSP70 and AQP4 in brain tissues were detected. Results Compared with group C(4.50±0.07), the wet to dry weight ratio of brain tissue was significantly increased in group H(4.62±0.08, P<0.05), meanwhile, that in the HHA group(4.52±0.06) was significantly lower than that of the H group(P<0.05). In pathological observation, swollen cells, rarefaction cytoplasm, uneven distribution of chromatin and nuclear pyknosis, rupture, dissolved, obvious vacuolation, and aggravated neuronal degeneration were seen in the group H. While in the HHA group, the injury, apoptosis and neuronal degeneration were attenuated. When compared with the values in the group C, hemoglobin level, erythrocyte count, hematocrit, and neutrophil percentage were significantly increased(P<0.05), and SaO2 and PaO2 was significantly reduced(P<0.05) in group H. HHA group had further increased hemoglobin level, erythrocyte count and hematocrit(P<0.05), decreased percentage of neutrophils, and reduced SaO2 and PaO2 in comparison with group H(P<0.05). Oxygen dissociation curve was shifted to right in the group H compared with group C, and that of the HHA group was further shifted right than that of the group H. In addition, compared with group C, MDA content and AQP4 protein level were significantly increased in group H(P<0.05), and in group HHA, those were further decreased(P<0.05), while HSP70 protein was significantly increased(P<0.05). Conclusion HA exerts effective protection on brain edema caused by hypoxia in rats, which may due to its increasing oxygen supply, reducing oxidative stress, and improve cell damage.