耐力运动对增龄大鼠脑皮层突触可塑性的影响及相关调控机制

Effects of endurance exercise on synaptic plasticity in cerebral cortex of aged rats and related regulatory mechanism

目的:探讨规律性耐力运动对脑皮层增龄性老化适应性的作用与机制。方法:将三个不同年龄段的健康SPF级雄性Sprague-Dawley大鼠分为3月龄(青年,n=20)、13月龄(中年,n=24)和23月龄(老年,n=24)组,每组又随机分为静息组和运动组;静息组三组静息,运动组三组实施10周递增负荷规律的中等强度耐力运动:运动方式为跑台运动(坡度0),运动强度从最大摄氧量(VO2max) 60%~65%逐渐递增到70%~75%,运动时间为10周;取大鼠脑皮层,HE染色测试大鼠脑皮层增龄性形态学变化,检测BDNF和SOD的蛋白表达及突触素-1(SYN1)和Ca MK Ⅱα/AMPKα1/m TOR通路等相关基因。结果:静息各组大鼠的脑皮层结构呈现年龄增龄性衰老变化,脑皮层SOD表达呈增龄性下降趋势,BDNF表达变化呈增龄性上升趋势,SYN1和Ca MK Ⅱα表达水平随增龄性趋势变化不大,AMPKα1和Sir T2以及IP3R、AKT1、m TOR mRNA表达水平随年龄变化呈现中年略上升而老年下降趋势;与静息各组大鼠相比,运动各组大鼠脑皮层神经细胞核排列紧密有序,显微镜下观察细胞核的数量明显增加,运动促进大鼠脑皮层SOD、BDNF和突触素SYN1表达水平增加,其中老年大鼠SOD、BDNF表达水平显著上调(P<0.01),青年和老年大鼠SYN1表达水平显著上调(P<0.05),运动上调中年和老年大鼠脑皮层Ca MK Ⅱα表达水平上调(P<0.01),而对青年大鼠Ca MK Ⅱα表达水平却是下调(P<0.01),运动可上调青年大鼠脑皮层的AMPKα1表达水平(P<0.05),而对中年和老年大鼠AMPKα1的影响不显著,运动均可上调各年龄大鼠脑皮层的Sir T2表达水平(P<0.05),运动上调各年龄大鼠脑皮层的IP3R/AKT1/m TOR表达水平,其中青年IP3R显著上调(P<0.01),青年和中年m TOR显著上调(P<0.01),老年m TOR也显著上调(P<0.05)。结论:耐力运动通过上调BDNF的表达水平,调控Ca MK Ⅱα信号、激活AMPK信号通路和IP3R/AKT1/m TOR信号通路,改善脑皮层的突触可塑性。

Objective: To understand and analyze the rules of endurance exercise on the cerebral cortex adaptive mechanism in aged rats. Methods: In this study,3-month-old( n = 20),13-month-old( n = 24) and 23-month-old( n = 24) specific-pathogen free( SPF) male Sprague-Dawley Rat( SD) rats were divided into young( Y-SED),middle-aged( M-SED) and old-aged( O-SED) sedentary control group,and the corresponding Y-EX,M-EX and O-EX in the endurance exercise runner group. The 10-weeks of regular moderate-intensity aerobic exercise intervention were carried out in the endurance exercise runner group. The exercise mode is treadmill exercise( slope 0),and the exercise intensity gradually increases from 60%~ 65% of the maximum oxygen consumption( VO2max) to70%~ 75%,and the exercise time is 10 weeks. Hematoxylin and eosin( HE) staining was used to detect age-related morphological changes. The expressions of superoxide dismutase( SOD) and brain-derived neurotrophic factor( BDNF) and the expressions of synapsin 1( SYN1) and Ca2+/calmodulin-dependent protein kinases Ⅱα( Ca MK Ⅱα)/AMP-activated protein kinase α1( AMPKα1)/mammalian target of rapamycin( m TOR) pathway-related genes were detected. Results: The cerebral cortex structure of the rats in each group showed age-related aging changes,the expression of SOD in the cortex showed a gradual decline,the expression of BDNF showed an age-increasing trend,and the expression levels of SYN1 and Ca MK Ⅱα were increased with age. The changes in AMPKα1 and Sir T2 and IP3 R,AKT1 and m TOR mRNA levels were increased slightly in middle-aged rats and decreased in aged rats. Compared with the rats in each sedentary control group,the nucleus of the cerebral cortex was tightly arranged and the number of nuclei observed under the microscope was increased significantly in each exercise group. Exercise promoted the expressions of SOD,BDNF and synaptophysin SYN1 in the cortex of rats,and the expression levels of SOD and BDNF in aged rats were up-regulated significantly( P <0. 01). The expression level of SYN1 in rats was up-regulated significantly( P<0. 05) in the young and aged rats. The expression of Ca MK Ⅱα in the cortex of middle-aged and aged rats was up-regulated( P<0. 01),while the expression level of Ca MK Ⅱα in young rats was down-regulated( P < 0. 01). Exercise could up-regulate the expression level of AMPKα1 in the cortex of young rats( P <0. 05),but not in middle-aged and old-age rats. Exercise could up-regulate the expression of Sir T2 in the cortex of rats in all age groups( P<0. 05). Exercise up-regulated the expression of phosphoinositide 3-kinase( IP3 R)/protein kinase B 1( AKT1)/m TOR in the cortex of rats,among which young IP3 R was significantly up-regulated( P<0. 01) in the young group,m TOR was significantly upregulated in young and middle-aged group( P<0. 01),and m TOR was also significantly up-regulated in the aged group( P<0. 05).Conclusion: Endurance exercise up-regulates BDNF expression,regulates Ca MKⅡα signaling,activates AMPK signaling pathway and IP3 R/AKT1/m TOR signaling pathway,and improves synaptic plasticity in the cortex.