8-oxo-G在快速老化小鼠SAMP8海马中表达的增龄性变化研究

目的观察8-氧鸟嘌呤核苷(8-oxo-G)在SAMP8品系快速老化小鼠海马不同区域的表达,以探讨其与SAMP8小鼠增龄性变化的关系。方法选用1、4、8、12月龄的快速老化小鼠SAMP8以及同龄抗快速老化小鼠SAMR1(对照组),每组各6只,采用免疫组化方法检测小鼠海马不同区域8-oxo-G的表达。结果8-oxo-G主要在SAM小鼠海马神经元胞浆内表达。对照组SAMR1 1月龄小鼠海马CA1和CA3区8-oxo-G表达显著高于其他月龄组(P<0.05),4、8、12月龄小鼠间其表达差异无统计学意义(P>0.05);SAMP8 12月龄小鼠海马8-oxo-G的表达显著高于1、4、8月龄组(P<0.05);SAMP8和SAMR1小鼠之间比较,1、4月龄间差异无统计学意义(P>0.05),8、12月龄间差异有统计学意义(P<0.05)。结论SAMP8小鼠海马8-oxo-G的表达除1月龄外随月龄增加而增加,提示8-oxo-G的表达增加与SAMP8小鼠的快速老化相关,有可能为增龄,甚至AD的生物学标志。     

8-氧鸟嘌呤脱氧核苷在快速老化小鼠SAMP8海马中表达的增龄性变化研究

目的观察8-氧鸟嘌呤脱氧核苷（8-oxo-7,8-dihydroguanine,8-oxo-dG）在快速老化小鼠SAMP8海马不同区域的表达,探讨其变化与SAMP8增龄的关系。方法选用1、4、8、12月龄快速老化小鼠SAMP8（每组各6只）,对照组为同龄抗快速老化小鼠SAMR1（每组各6只）,用免疫组化法检测海马不同区域内8-oxo—dG的表达水平。结果8-oxo-dG在海马不同区域均有表达,且主要在海马神经细胞胞核内表达。对照组SAMR1小鼠海马各区域8-oxo-dG的吸光度定量结果显示各月龄组间无统计学差异（P〉0．05）;1、4月龄组SAMP8小鼠海马各区域8-oxo-dG的吸光度定量结果与同龄匹配的SAMR1小鼠间无统计学差异（P〉0．05）;8、12月龄组SAMP8小鼠海马各区域8-oxo-dG的吸光度定量结果分别显著高于1月龄和4月龄组（P〈0．05）,也分别显著高于同龄SAMP1对照组（P〈0．05）。结论8-oxo-dG在SAMP8快速老化小鼠海马中的水平随增龄而显著增高。     

快速老化模型小鼠学习记忆行为及有关脑区单胺递质水平的增龄性变化

目的 研究快速老化模型小鼠(senescence accelerated mice，SAM)学习记忆能力及其大脑皮层、海马和下丘脑单胺递质含量的增龄性变化及它们之间的关系。方法 分别采用跳台实验和穿梭箱实验测定SAM的被动和主动回避反应能力，采用高效液相色谱电化学检测法测定脑内单胺递质的含量。结果 2月龄快速老化亚系SAM-prone/8(SAMP8)的被动和主动回避反应能力已较同龄抗快速老化亚系SAM-resistance／1(SAMR1)明显降低，且其主动回避反应能力随增龄进一步降低。同时，SAMP8大脑皮层、海马及下丘脑内单胺递质水平多明显高于同龄SAMR1，且随增龄明显增高。结论 SAMP8学习记忆能力的衰退可能与其相关脑区单胺递质的变化密切相关。     

新型FKBPs配体HD5-6对SAMP8小鼠的抗老化研究

目的观察FKBPs(FK506 blinding proteins)配体噻嗪酰胺衍生物(HD5-6)对SAMP8快速老化小鼠学习记忆能力和海马神经元的影响,以及对SAMP8小鼠海马神经元基因表达谱的影响。方法选用10月龄快速老化的SAMP8小鼠20只,随机分为痴呆组、HD5-6组;另选10月龄正常老化的SAMR1小鼠10只作为正常对照组。各组分别腹腔注射药物35 d,并于29 d采用Morris水迷宫实验评价各组小鼠学习记忆能力的变化。HE染色观察海马区神经元形态;TUNEL观察海马神经元凋亡情况,用基因芯片技术检测HD5-6组和痴呆组小鼠海马神经元基因表达谱的变化差异。结果与正常对照组相比,痴呆组在定位航行实验中表现出明显的学习记忆障碍,逃避潜伏期显著延长(P0.05),HD5-6组自3 d开始逃避潜伏期比痴呆组明显缩短(P0.05);空间探索实验中HD5-6组跨平台次数、原平台象限停留时间明显多于痴呆组(P0.05)。与正常对照组相比,痴呆组海马区神经元数量明显减少,细胞排列紊乱,大量的神经元细胞核固缩,深染、坏死,其神经元凋亡指数(51.73±4.48)%明显高于正常对照组(28.02±11.25)%(P0.05),HD5-6干预的SAMP8小鼠海马区神经元病理改变明显改善,海马神经元凋亡指数(20.47±2.25)%明显降低(P0.01)。HD5-6组与痴呆组海马神经元基因表达谱相比,表达差异在2倍以上的基因有118条,表达上调的为9条,表达下调的为109条。其中有功能的mRNA中,表达上调的有4条,表达下调的有21条。结论 HD5-6能够改善快速老化小鼠SAMP8的学习记忆能力和海马神经元病理改变,并可能通过对基因表达谱产生影响而发挥明显的抗衰老作用。     

孔圣枕中丹对SAMP8鼠海马CA1区PAS染色阳性颗粒状结构及星形胶质细胞纤维酸性蛋白的影响

目的研究孔圣枕中丹对SAMP8海马CA1区形态结构、PAS染色阳性颗粒状结构(PGS)及星形胶质细胞纤维酸性蛋白(GFAP)的影响,探讨其改善SAMP8小鼠学习记忆的作用机制。方法选用7个月龄雄性的SAMP8小鼠分为模型组、治疗组;同时选用同源同月龄雄性的SAMR1小鼠作为正常老化对照组。检测指标:苏木精-伊红染色观察小鼠海马CA1区形态结构;免疫组化分析小鼠海马CA1区GFAP的表达;PAS病理特殊染色观察小鼠海马CA1区糖原的表达。结果孔圣枕中丹组海马CA1区神经元病理改变较模型组有明显改善;孔圣枕中丹PGS颗粒数有不同程度的减少,PGS颗粒体积减少,低密度颗粒数增加,与模型组比较差异有统计学意义(P<0.05);孔圣枕中丹组GFAP面密度与模型组、比较差异有统计学意义(P<0.01)。结论孔圣枕中丹能通过对海马神经元组织结构的保护作用来提高SAMP8小鼠的认知功能。     

增龄性脑血管相关改变对阿尔茨海默病模型小鼠SAMP8认知能力的影响

目的 探讨脑血流量、血脑屏障(BBB)通透性、脑葡萄糖跨膜转运蛋白表达情况随年龄增大对阿尔茨海默病(AD)模型小鼠SAMP8认知能力的影响. 方法 选择SAMP8小鼠及正常同源抗快速老化小鼠R1(SAMR1)各10只进行观察.采用Morris水迷宫测定小鼠的学习记忆能力,激光多普勒仪测定脑血流量,荧光分光光度计法测定BBB通透性,Western blotting测定葡萄糖转运蛋白(GLUT)1和3的表达. 结果 与SAMR1相比,SAMP8的认知能力早在4月龄时即已出现明显损伤,表现为思维僵化、学习过程减慢.随着年龄增大,SAMP8脑血流明显下降,BBB渗漏更为严重,皮层和海马的GLUT1和GLUT3表达也有不同程度地改变.脑血流、BBB完整性、GLUT1和GLUT3表达受年龄和品系影响明显,并与认知能力高度相关. 结论 衰老及缺血引起的血管损伤、能量供给不足是造成AD神经元功能异常及导致认知障碍的主要原因.     

快速老化动物模型SAMP8小鼠及其相关研究进展

SAMP8鼠由日本京都大学竹田俊男教授开发成功，主要以学习记忆功能呈增龄性加速衰退，中枢神经系统如皮质、海马等部位发生病理改变为主，是一种比较理想的研究脑老化和痴呆的模型，亦是目前研究快速衰老的唯一哺乳类模式动物。行为学、形态学、神经生化和分子生物学为此提供了较充足的证据。SAMP8鼠可被广泛应用于阐明年龄相关的学习记忆功能改变及认知缺陷的基本机制，研究老化相关性疾病，评价治疗老化关联疾病和改善学习记忆机能的益智药物。但SAMP8所涉及的相关疾病主要是阿尔茨海默病，能否用于其他衰老相关性疾病如帕金森病仍需进一步研究。     

快速老化小鼠海马神经元电压门控离子通道特点

目的:观察快速老化小鼠(Senescence-accelerated mouse,SAM)海马神经元的基本离子通道特点,并对抗快速老化亚系(SAM-resistance/1,SAMR1)与快速老化亚系(SAM-prone/8,SAMP8)的基本离子通道特点进行了比较,探讨离子通道变化在衰老中的可能角色.方法:应用全细胞记录方式,观察并比较原代培养SAMR1和SAMP8海马神经元的电压门控离子通道及膜参数.结果:原代培养SAMR1和SAMP8海马神经元电压门控Na+通道电流(INa)和电压门控延迟整流K+通道电流(Ik)的电学特点和幅度基本一致.SAMP8的电压门控Ca2+通道电流(ICa)和瞬时外向K+通道电流(IA)的幅值则大于相同培养天数的SAMR1.经膜电容校正所得的ICa电流密度也表现出增大的变化规律.结论:SAMP8与SAMR1神经元间IA和ICa的差异可能与其神经系统变异而产生的学习记忆功能下降有关.     

自主跑笼运动对SAMP8小鼠精神行为及血清促肾上腺皮质激素、皮质醇的影响

目的观察自主跑笼运动对快速老化P8小鼠精神行为学及血清促肾上腺皮质激素(ACTH和皮质醇(Cor)水平的影响。方法雄性3月龄快速老化P8小鼠20只,随机数字表法分为运动组和非运动组,每组10只;抗快速老化R1小鼠5只为对照组。所有小鼠均给予同样标准环境饲养,运动组施加自主跑笼运动训练(每周5天)。2月后采用自主活动仪和高架十字迷宫行为学测试评估小鼠精神行为学变化,同时放射免疫方法检测小鼠血清ACTH及Cor水平。结果快速老化P8小鼠非运动组与同月龄抗快速老化R1小鼠对照组比较,自主活动次数(104.4±33.3,150.0±39.9)和高架十字迷宫开放臂停留时间(157.1±44.9,202.8±39.2)均显著减少(P0.05)。快速老化P8小鼠自主活动次数运动组(159.6±66.6)与非运动组(104.4±33.3)比较显著增加(P0.05);高架十字迷宫测试开放臂停留时间运动组(173.6±51.4)与非运动组(157.1±44.9)比较,差异无统计学意义(P0.05)。快速老化P8小鼠非运动组与抗快速老化R1小鼠对照组比较,血清ACTH(28.49±8.24,47.86±9.52)及Cor水平(3.19±0.88,5.01±0.79)均显著减少(P0.05)。快速老化P8小鼠运动组(50.35±6.64,5.23±1.42)较非运动组(28.49±8.24,3.19±0.88)均显著增高(P0.05)。结论 5月龄快速老化P8小鼠有明显精神行为异常,自主跑笼运动对快速老化P8小鼠精神行为异常有一定改善,可能是通过上调下丘脑-垂体-肾上腺轴活性而实现的。     

快速老化小鼠海马神经元电压门控离子通道特点

目的：观察快速老化小鼠（Senescence-accelerated mouse,SAM)海马神经元的基本离子通道特点，并对抗快速老化亚系（SAM－resistance/1,SAMR1)与快速老化亚系（SAM－prone/8,SMAP8)的基本离子通道特点进行了比较，探讨了离子通道变化在衰老中的可能角度，方法：应用全细胞记录方式，观察并比较原代培养SAMR1和SAMP8海马神经元的电压门控离子通道及膜参数。结果：原代培养SAMR1和SAMP8海马神经元电压门控Na^2 通道电流（INa)和电压门控延迟整流K^ 通道电流（IK）的电学特点和幅度基本一致。SAMP8的电压门控Ca^2 通道电流（ICa)和瞬时外向K^ 通道电流（IA）的幅值则大于相同培养天数的SAMR1。经膜电容校正所得的ICa电流密度也表现出增大的变化规律。结论：SAMP8与SAMR1神经元间IA和ICa的差异可能与其神经系统变异而产生的学习记忆功能下降有关。     

Linoleic acid derivative DCP-LA improves learning impairment in SAMP8

In the water-maze test, the linoleic acid derivative, 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) (1 mg/kg, intraperitoneally), significantly shortened the prolonged latency for accelerated-senescence-prone mice 8 (SAMP8), reaching a level similar to the latency for accelerated-senescence-resistant mice 1 (SAMR1) as control. In the open-field test to assess motor activity, it was confirmed that the DCP-LA effect is not due to increased motor activity. In the passive avoidance test to assess fear memory, DCP-LA had no effect on the latency of acquisition and retention for SAMP8. The results of the present study, thus, suggest that DCP-LA could improve age-related learning impairment by enhancing cognitive functions.     

Hippocampal neuron loss is correlated with cognitive deficits in SAMP8 mice

The objective of this study is to examine whether neuron loss occurs in SAMP8 and whether neuron loss is correlated with cognitive deficits of these mice. Neuronal loss is considered as one of the most important pathological hallmarks of Alzheimer disease (AD). In addition to the early-onset, irreversible, severe deficits of learning and memory, SAMP8 mice show spontaneous age-related neurodegenerative changes and other characteristics seen in AD patients, such as amyloid plaques and neurofibrillary tangles. However, it is still unknown whether neuron loss occurs in SAMP8 and whether neuron loss is correlated with cognitive deficits of these mice. We employed 8-month-old SAMP8 and SAMR1 mice to investigate the cognitive function and neuron numbers. The behaviors were examined by the grading score of senescence and Morris water maze (MWM) test, the neuron number in hippocampus was estimated by the optical fractionator technique. The grading score of senescence and MWM test demonstrated that SAMP8 exhibited notable age-related changes in appearance and cognitive function. Moreover, severe hippocampal neuron loss was found in SAMP8 as determined by the optical fractionator stereological method. Compared to SAMR1, the neuron number of CA1, CA3 and DG in SAMP8 was reduced by 15.6, 19.8 and 20.2 %, respectively, and the neuron loss in hippocampus was associated with cognitive deficits. Collectively, these results suggest that hippocampal neuronal loss is well correlated with learning and memory deficits in SAMP8 and SAMP8 represents an important mouse model for AD.     

Deterioration in learning and memory of inferential tasks for evaluation of transitivity and symmetry in aged SAMP8 mice

This study examined age-dependent deficits in the learning and memory of inferential tasks, using an established senescence-accelerated mouse model in age-related brain dysfunction (SAMP8) and its genetically related inbred strain (SAMR1). The mice learned two sets of nonspatial odor-odor pairs by association learning successively (i.e., A-->B, X-->Y, then B-->C, Y-->Z). They were tested in transitive inference (i.e., A-->C, X-->Z) and symmetrical inference (i.e., C-->B, Z-->Y). In the probe test of A-->C, X-->Z transitive inference, 1-month-old SAMP8 and control SAMR1 at the same age significantly chose the alternative based on transitive inference, but 4- and 7-month-old SAMP8 performed at a random chance level, in comparison with unambiguous inference by control SAMR1 at the same ages. During the test of C-->B, Z-->Y symmetrical inference, SAMP8 at 1 month of age made errors as frequently as control SAMR1 at the same age, but SAMP8 at 4 and 7 months of age made more errors than SAMR1 at the same ages. At 4 and 7 months of age, SAMP8 made more errors than 1-month-old SAMP8. Control SAMR1 did not show such an age-related deficient. These results indicate that SAMP8 mice have age-related learning and memory deficits in the ability to perform inferential tasks. Age-related hippocampal dysfunction is suggested to be the cause of these age-related deficits in old SAMP8 mice during the performance of inferential tasks mediated by declarative memory.     

Expression of neurotrophin genes in the brain of senescence-accelerated mouse (SAM) during postnatal development

We compared the expression patterns of neurotrophin genes in the brain of senescence-accelerated mouse (SAMP8) which shows age-related impairment of learning behavior, with SAMR1 control which shows normal aging. By Northern blot analysis, NT-3 mRNA levels in the cortex were higher in SAMP8 than in SAMR1 mice during development, whereas in the midbrain, hippocampus and forebrain, NT-3 expression levels in SAMP8 were lower than those in SAMR1. At early stages, although NGF mRNA levels in SAMP8 were lower than those in SAMR1, BDNF mRNA levels were almost equivalent in both strains. By in situ hybridization analysis, NT-3 mRNA signals in the CA1 and CA2 regions in SAMP8 were shown to be reduced at early stages. However, BDNF mRNA signals were almost equivalent in both SAMR1 and SAMP8.     

Changes in expressions of proinflammatory cytokines IL-1beta, TNF-alpha and IL-6 in the brain of senescence accelerated mouse (SAM) P8

The senescence-accelerated mouse (SAM) is known to be a murine model for accelerated aging. The SAMP8 strain shows age-related deterioration of learning and memory at an earlier age than control mice (SAMR1). In the present study, we investigated the changes in expressions of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in the brain of SAMP8. In the hippocampus of 10 months old SAMP8, the expression of IL-1 mRNA was significantly elevated in comparison with that of SAMR1. In both strains of SAMs, increases in IL-1beta protein in the brain were observed at 10 months of age compared with 2 and 5 months. The only differences found between the strain in protein levels were at 10 months and were elevations in IL-1beta in the hippocampus and hypothalamus, and in TNF-alpha and IL-6 in the cerebral cortex and the hippocampus in SAMP8 as compared with SAMR1. However, lipopolysaccharide-induced increases in the expression of these cytokines in brain did not differ between SAMP8 and SAMR1. Increases in expression of proinflammatory cytokines in the brain may be involved in the age-related neural dysfunction and/or learning deficiency in SAMP8.     

Changes in expressions of proinflammatory cytokines IL-1β, TNF-α and IL-6 in the brain of senescence accelerated mouse (SAM) P8

The senescence-accelerated mouse (SAM) is known to be a murine model for accelerated aging. The SAMP8 strain shows age-related deterioration of learning and memory at an earlier age than control mice (SAMR1). In the present study, we investigated the changes in expressions of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the brain of SAMP8. In the hippocampus of 10 months old SAMP8, the expression of IL-1 mRNA was significantly elevated in comparison with that of SAMR1. In both strains of SAMs, increases in IL-1β protein in the brain were observed at 10 months of age compared with 2 and 5 months. The only differences found between the strain in protein levels were at 10 months and were elevations in IL-1β in the hippocampus and hypothalamus, and in TNF-α and IL-6 in the cerebral cortex and the hippocampus in SAMP8 as compared with SAMR1. However, lipopolysaccharide-induced increases in the expression of these cytokines in brain did not differ between SAMP8 and SAMR1. Increases in expression of proinflammatory cytokines in the brain may be involved in the age-related neural dysfunction and/or learning deficiency in SAMP8.     

Spatial memory performance and hippocampal neuron number in osteoporotic SAMP6 mice

The senescence-accelerated mouse strain P6 (SAMP6) is an inbred mouse that represents a clinically relevant model of senile osteoporosis. However, whether osteoporotic SAMP6 mice have cognitive deficits remains largely unexplored. Here, we used Morris water maze to assess reference memory and working memory performance in SAMP6 mice and SAMR1 controls, at 4 and 8 months of age. In addition, unbiased stereological techniques were used to estimate total neuron number in hippocampal CA1 subfield of the mice used in the behavioral study. Morris water maze test revealed impairments in working memory but not in reference memory of the 4- and 8-month-old SAMP6 mice compared with the SAMR1 mice at the same age. However, there were no significant differences in the total numbers of neurons in hippocampal CA1 subfield when comparing 4-month-old SAMR1 and 4-month-old SAMP6 and 8-month-old SAMR1 and 8-month-old SAMP6, which indicate that, in SAMP6 mice, the structural correlates of working memory deficits are to be found in parameters other than the number of neurons in hippocampal CA1 subfield. These findings suggest that SAMP6 mice exhibit selective cognitive deficits and highlight the importance of this mouse model for studying the brain alterations associated with osteoporosis.     

Age-related alteration in cerebral blood flow and energy failure is correlated with cognitive impairment in the senescence-accelerated prone mouse strain 8 (SAMP8)

Cerebrovascular dysfunction is an early pathogenic event in Alzheimer’s disease (AD) and plays a key role in the disease process. Cerebral hypoperfusion, brain glucose hypometabolism and disrupted blood–brain barrier (BBB) integrity contributed to the onset and progression of AD. However, the relationships between the age-related cognitive impairment and cerebral blood flow (CBF), energy metabolism and BBB have not been clearly explained. In this study, we investigated the cognitive function, CBF, BBB damage and expression level of glucose transporter (GLUT) 1 and 3 of senescence-accelerated mouse prone 8 (SAMP8), and the correlations between each of them were analyzed. When compared with SAMR1 (senescence-accelerated mouse resistant 1), the cognitive abilities of SAMP8 were damaged apparently even at 4 months of age, showing up a slower and more capricious acquisition in Morris water maze tasks. In both SAMP8 and SAMR1, reduced CBF and increased BBB leakage were observed with increasing age, but an earlier and more severe impairment was detected in SAMP8. In addition, alterations of GLUT1 and GLUT3 protein expression in cortex and hippocampus were more prominent in SAMP8. Correlation analysis demonstrated that the increased escape latency was correlated negatively with CBF and expression of glucose transporters; and positively with BBB permeability in the hippocampus. These results suggested that CBF, BBB integrity, the expression of GLUT1 and GLUT3 were significantly affected by age and strain, which were also closely associated with cognitive ability. The alteration in CBF and energy failure induced by aging and vascular insults resulted in cognitive decline in SAMP8.