常压高氧对淀粉样蛋白前体／早老素1双重转基因小鼠脑内老年斑及β-淀粉样蛋白的影响

The effect of normobaric hyperoxia on senile plaques and beta-amyloid protein in brain of amyloid protein precursor/presenilin 1 double transgenic mouse

目的探讨常压高氧（40％O2，60％空气）处理淀粉样蛋白前体／早老素1（APP／PSl）双重转基因小鼠是否发挥神经保护作用。方法对APP／PSl双重转基因阿尔茨海默病（AD）模型种鼠交配后产下的子代小鼠进行基因分型，待子代达10周龄时，取双重转基因小鼠40只，随机分成A、B、C、D4组，每组10只，A、B2组小鼠喂养于常压高氧中8ICd，A组持续4周，B组持续8周；C、D组喂养于空气中4或8周，分别作为A、B组的对照。高氧处理后采用免疫组织化学、Thioflavin S染色检测小鼠脑组织形态学的变化，Western blot检测APP代谢过程中相关蛋白的表达变化，ELISA定量检测小鼠脑内β-淀粉样蛋白（Aβ）水平的变化。结果免疫组织化学和Thioflavin S染色均显示，与对照组相比，高氧处理组小鼠皮质和海马内老年斑数量明显减少，B组比A组减少更显著。高氧处理组小鼠脑内C99、C83，水平显著高于对照组，Aβ水平明显低于对照组，但各组小鼠脑内全长APP及β位淀粉样前体蛋白裂解酶1（BACEl）蛋白水平无明显改变。ELISA结果提示，B组小鼠海马和皮质内Aβ40[（783．6±97．2）pg／ml]和A％[（175．3±17．1）pg／ml]含量明显低于对照组A‰[（1251．6±42．3）pg／ml，t：9．36，P〈0．01]和Aβ42[（286．8±13．0）pg／ml，t=13．7，P〈0．01]的含量。结论常压高氧处理能显著减少AD模型小鼠脑内Aβ的产生、沉积及老年斑的形成；这种改变可能通过减少Aβ产生或加速Aβ清除实现。

Objective In order to investigate whether normobaric hyperoxia exert neuroprotective effect on amyloid protein prccursor/presenilin 1 （APP/PS1） double transgenic Alzheimer＇ s disease （AD） mouse model. Methods Forty APP/PS1 double transgenic mice were randomly divided into 4 groups （ A, B, C and D）. Mice were treated with 40% oxygen for 8 h per day for4 weeks in group A and for 8 weeks in group B. Group C and group D were given regular air for 4 weeks and 8 weeks, respectively, as controls. Immunohistochemical staining, Thioflavin S staining, Western blot and ELISA assay were performed on mice brain tissues in all groups after the treatment. Results Immuohistochemical and Thioflavin S staining showed that in hyperoxia-treated mice, number and size of senile plaques in the cerebral cortex and hippocampus were notably decreased, and deposition of Aβ in the brain of group B decreased more than that of group A. Western blot revealed that in the hyperoxia-treated mice, the levels of C99 and Cs3 were greatly increased while the Aβ level notably decreased, compared with controls. However, the expression of holoprotein APP and β-site amyloid cleavage enzyme 1 （ BACE1 ） showed no difference among 4 groups. ELISAassay showed that Aβ40 （（783.6 ±97.2） pg/ml） and Aβ42 （（175.3 ± 17.1） pg/ml） were significantly decreased in the brain of 8 weeks hyperoxia-treated mice compared with the control group Aβ40 （ （ 1251.6 ±42. 3 ） pg/ml, t = 9. 36, P 〈 0. 01 ）, and Aβ42 （ （286. 8 ± 13.0） pg/ml, t = 13.7, P 〈 0. 01 ）. Conclusion Treatment with hyperoxia can significantly decrease Aβ levels and lower the number and size of senile plaques in the brain of APP/PS1 transgenic mouse. This study indicates that hyperoxia may exert its neuroprotective effect through decreasing the generation of Aβ or accelerating the clearance of Aβ.