间歇低氧大鼠细胞外信号调节激酶与认知功能变化

The effect of intermittent hypoxia on hippocampal ERK signaling and cognitive function in rats

目的探讨间歇低氧对大鼠海马细胞外信号调节激酶(extracellular signal-regulated kinase,ERK)通路及认知功能变化的影响。方法采用大鼠间歇低氧模型,将成年雄性Wistar大鼠(n=48)随机均分为5%间歇低氧组(5%intermittent hypoxia group,5%IH组)和空白对照组(unhandled control group,UC组),每组分别为24只大鼠,分别于间歇低氧第2、4、6、8周后采用Morris水迷宫实验检测大鼠学习记忆功能;免疫组化及免疫印迹法检测大鼠海马区磷酸化P-ERK1/2表达水平、免疫组化检测c-fos蛋白表达水平;TUNEL法检测神经元凋亡情况。结果与UC组比较,5%IH组在2、4、6、8周大鼠逃避潜伏期时间分别为(50.22±8.42)s、(57.13±9.06)s、(67.56±5.42)s、(71.71±5.49)s,从第2周起随低氧时间延长大鼠逃避潜伏期时间延长(P<0.05),5%IH组在2、4、6、8周大鼠跨越目标象限时间分别为(46.23±3.68)s、(39.36±3.42)s、(33.35±4.01)s、(26.82±4.30)s,从第2周起随低氧时间延长大鼠跨越目标象限时间缩短(P<0.05),5%IH组p-ERKl/2、c-fos蛋白表达及凋亡指数在2、4、6、8周均多于UC组(P<0.05),5%IH组p-ERKl/2、c-fos蛋白表达及凋亡指数均有明显的时间差异性(P<0.05),均随间歇低氧时间的延长其表达先升高后降低,6周达到高峰(P<0.05),8周逐渐下降(P<0.05);UC组p-ERKl/2、c-fos蛋白表达及凋亡指数无时间差异性(P>0.05),5%IH组p-ERKl/2与c-fos蛋白的阳性表达相对值呈正相关(r值为0.977,P<0.05),c-fos蛋白的阳性表达相对值与神经元凋亡指数呈正相关(r值为0.963,P<0.05)。结论ERK通路的激活可能是OSAHS大鼠早中期认知功能损害发生的重要机制。

Objective To investigate ERK pathway and cognitive function after intermittent hypoxia in rats. Methods Chronic intermittent hypoxia was adopted to mimic obstructive sleep apnea-hypopnea syndrome （OSAHS） in rats. Male Wistar rats （n=48） were randomly divided into two groups （24 animal each）： 5% IH group and UC group. Morris water maze was used to assess learning and memory function at 2, 4, 6 and 8 weeks following chronic intermittent hypoxia. Immunohistochemical and Western blot were used to detect the expression of P-ERK1/2 and c-fos in CA1. TUNEL was used to examine apoptosis in CA1. Results The escape latency time was 50.22 ± 8.42, 57.13 ± 9.06, 67.56 ± 5.42, and 71.71±5.49 at 2,4, 6 and 8 weeks in 5% IH group, respectively. Compared with UC group, the escape latency time was significantly prolonged at all time points （P〈O.05）. The escape latency time was 46.23±3.68, 39.36±3.42, 33.35±4.01 and 26.82±4.30 at 2 ,4, 6 and 8 weeks in 5% IH group, respectively. Compared with UC group, the time across the target quadrant was significantly prolonged at all time points （P〈0.05） , Chronic hypoxia-induced expression of p-ERK1 / 2, c-los and apoptotic index started from 2 weeks, peaked at 6 weeks （P〈0.05） and then decreased at 8 weeks （P〈0.0.5） following chronic hypoxia induced activation. There were positive correlations between p-ERK1 / 2 and c-los expression values （r=0.977, P〈0.05 ）and between c-los relative expression values and apoptotic index （r=0.963, P〈0.05 ）. Conclusion Activation of ERK pathway may be an important mechanism underlying early and middle cognitive impairment in a rat model of OSAHS.