Decreased hippocampal cell proliferation correlates with increased expression of BMP4 in the APPswe/PS1DeltaE9 mouse model of Alzheimer's disease

Alterations in hippocampal cell proliferation have been identified in transgenic (tg) mouse models of Alzheimer's disease (AD); however, relatively little is known about the underlying mechanisms. Previously, we have demonstrated that endogenous level of BMP4 in the dentate gyrus (DG) affects hippocampal cell proliferation in a pentylentetrazol kindling-induced epilepsy model. In the present study, we evaluated hippocampal cell proliferation and BMP4 mRNA level in the APPswe/PS1DeltaE9 tg mouse, a well-established mouse model in which coexpression of familial AD-linked APP "Swedish" (APPswe) and PS1DeltaE9 polypeptide variants leads to Abeta deposition throughout the hippocampus and cortex. The number of bromodeoxyuridine (BrdU)-labeled cells in the DG subgranular zone (DG-SGZ) of 9- and 12-month-old APPswe/PS1DeltaE9 tg mice was markedly reduced compared with age-matched nontransgenic littermates, whereas, the BMP4 mRNA level was significantly increased in the tg mice. There was a significant correlation between the increased BMP4 mRNA expression and the decreased number of BrdU labeled cells. After effectively blocking the expression of endogenous BMP4 with antisense oligodeoxynucleotides (ASODN), the decrease in hippocampal cell proliferation in the DG-SGZ and hilus of 9- and 12-month-old tg mice was reversed. These findings suggest that the increased expression of BMP4 mRNA within the DG of the hippocampus may contribute to the decrease in cell proliferation in APPswe/PS1DeltaE9 tg mice.     

Decreased proliferation of hippocampal progenitor cells in APPswe/PS1dE9 transgenic mice

A recent hypothesis suggests that there is impaired hippocampal neurogenesis in Alzheimer's disease. Here we examined the proliferation, the first stage in neurogenesis, of hippocampal progenitor cells in amyloid precursor protein with Swedish mutation and presenilin-1 with deletion of exon 9 (APPswe/PS1dE9) transgenic mice. Compared with age-matched wild-type mice, transgenic mice at 5 months of age with low amyloid beta-peptide (Abeta) levels and subtle Abeta deposits showed normal proliferation of hippocampal progenitor cells; however, transgenic mice at 9 months of age with high Abeta levels and numerous Abeta deposits showed decreased proliferation of these cells. The number of proliferating cells in male transgenic mice was indistinguishable from that in female transgenic mice. These results indicate that neurogenesis is decreased with degrees of Abeta pathology, and that there is no gender difference in their proliferation in APPswe/PS1dE9 transgenic mice.     

Differential regulation of neurogenesis in two neurogenic regions of APPswe/PS1dE9 transgenic mice

Neurogenesis occurs in two neurogenic regions of the adult mammalian brain: the subgranular zone and the subventricular zone. We have recently demonstrated that the number of bromodeoxyuridine-positive and doublecortin-positive cells is decreased in the subgranular zone of amyloid precursor protein with a Swedish mutation and presenilin-1 with a deletion of exon 9 transgenic mice, an animal model of Alzheimer's disease. In this study, we characterized neurogenesis in the subventricular zone of amyloid precursor protein with a Swedish mutation and presenilin-1 with a deletion of exon 9 transgenic mice at 9 months of age and compared it with neurogenesis in the subgranular zone. In the subventricular zone, the number of proliferating cell nuclear antigen-positive and bromodeoxyuridine-positive cells were normal. In the subgranular zone, the number of proliferating cell nuclear antigen-positive cells was normal; however, the number of bromodeoxyuridine-positive cells was significantly decreased. These results suggest that neurogenesis, probably reflecting the survival of neural progenitor cells, differs between the subgranular zone and the subventricular zone.     

Characterization of amyloid deposition in the APPswe/PS1dE9 mouse model of Alzheimer disease

Transgenic mice carrying disease-linked forms of genes associated with Alzheimer disease often demonstrate deposition of the beta-amyloid as senile plaques and cerebral amyloid angiopathy. We have characterized the natural history of beta-amyloid deposition in APPswe/PS1dE9 mice, a particularly aggressive transgenic mouse model generated with mutant transgenes for APP (APPswe: KM594/5NL) and PS1 (dE9: deletion of exon 9). Ex vivo histochemistry showed Abeta deposition by 4 months with a progressive increase in plaque number up to 12 months and a similar increase of Abeta levels. In vivo multiphoton microscopy at weekly intervals showed increasing beta-amyloid deposition as CAA and plaques. Although first appearing at an early age, CAA progressed at a significantly slower rate than in the Tg2576 mice. The consistent and early onset of beta-amyloid accumulation in the APPswe/PS1dE9 model confirms its utility for studies of biochemical and pathological mechanisms underlying beta-amyloid deposition, as well as exploring new therapeutic treatments.     

Huperzine A alleviates synaptic deficits and modulates amyloidogenic and nonamyloidogenic pathways in APPswe/PS1dE9 transgenic mice

Huperzine A (HupA) is a potent acetylcholinesterase inhibitor (AChEI) used in the treatment of Alzheimer's disease (AD). Recently, HupA was shown to be active in modulating the nonamyloidogenic metabolism of β-amyloid precursor protein (APP) in APP-transfected human embryonic kidney cell line (HEK293swe). However, in vivo research concerning the mechanism of HupA in APP transgenic mice has not yet been fully elucidated. The present study indicates that the loss of dendritic spine density and synaptotagmin levels in the brain of APPswe/presenilin-1 (PS1) transgenic mice was significantly ameliorated by chronic HupA treatment and provides evidence that this neuroprotection was associated with reduced amyloid plaque burden and oligomeric β-amyloid (Aβ) levels in the cortex and hippocampus of APPswe/PS1dE9 transgenic mice. Our findings further demonstrate that the amelioration effect of HupA on Aβ deposits may be mediated, at least in part, by regulation of the compromised expression of a disintegrin and metalloprotease 10 (ADAM10) and excessive membrane trafficking of β-site APP cleavage enzyme 1 (BACE1) in these transgenic mice. In addition, extracellular signal-regulated kinases 1/2 (Erk1/2) phosphorylation may also be partially involved in the effect of HupA on APP processing. In conclusion, our work for the first time demonstrates the neuroprotective effect of HupA on synaptic deficits in APPswe/PS1dE9 transgenic mice and further clarifies the potential pharmacological targets for this protective effect, in which modulation of nonamyloidogenic and amyloidogenic APP processing pathways may be both involved. These findings may provide adequate evidence for the clinical and experimental benefits gained from HupA treatment.     

Age-related changes in visual acuity, learning and memory in the APPswe/PS1dE9 mouse model of Alzheimer's disease

Mouse models of Alzheimer's disease (AD) are often tested for learning and memory deficits using visuo-spatial tasks such as the Morris water maze. Performance on these tasks is dependent on vision and the APPswe/PS1dE9 mouse model has amyloid beta plaques in their retinas which might influence their performance in these tasks. In a visual learning task, old (20-26 months) transgenic mice and their wildtype littermates of both sexes had poorer visual ability than young (5-8 months) mice and old transgenic mice had poorer visual acuity than old wildtype mice. Old transgenic mice also had deficits in visuo-spatial learning and memory on the Morris water maze. The transgenic mice had no deficits in the conditioned odour preference or conditioned taste aversion memory tests at any age. These results indicate that the old APPswe/PS1dE9 mice and their wildtype littermates both have a deficit in their visual ability and that visually dependent measures alone should not be used to assess learning and memory in this strain.     

DHA diet reduces AD pathology in young APPswe/PS1ΔE9 transgenic mice: Possible gender effects

Epidemiological and clinical trial findings suggest that consumption of docosahexaenoic acid (DHA) lowers the risk of Alzhemier's disease (AD). We examined the effects of short‐term (3 months) DHA enriched diet on plaque deposition and synaptic deficts in forebrain of young APPswe/PS1ΔE9 transgenic (tg) and non‐transgenic (ntg) mice. Gas chromatography revealed a significant increase in DHA concomitant with a decrease of arachidonic acid in both brain and liver in mice fed with DHA. Female tg mice consumed relatively more food daily than ntg female mice, independent of diet. Plaque load was significantly reduced in the cortex, ventral hippocampus and striatum of female APPswe/PS1ΔE9 tg mice on DHA diet compared to female tg mice on control diet. Immunoblot quantitation of the APOE receptor, LR11, which is involved in APP trafficking and Aβ production, were unchanged in mice on DHA or control diets. Moreover drebrin levels were significantly increased in the hippocampus of tg mice on the DHA diet. Finally, in vitro DHA treatment prevented amyloid toxicity in cell cultures. Our findings support the concept that increased DHA consumption may play and important role in reducing brain insults in female AD patients. © 2009 Wiley‐Liss, Inc.     

Episodic-like memory deficits in the APPswe/PS1dE9 mouse model of Alzheimer's disease: relationships to beta-amyloid deposition and neurotransmitter abnormalities

Transgenic mice made by crossing animals expressing mutant amyloid precursor protein (APPswe) to mutant presenilin 1 (PS1dE9) allow for incremental increases in Abeta42 production and provide a model of Alzheimer-type amyloidosis. Here, we examine cognition in 6- and 18-month old transgenic mice expressing APPswe and PS1dE9, alone and in combination. Spatial reference memory was assessed in a standard Morris Water Maze task followed by assessment of episodic-like memory in Repeated Reversal and Radial Water maze tasks. We then used factor analysis to relate changes in performance in these tasks with cholinergic markers, somatostatin levels, and amyloid burden. At 6 months of age, APPswe/PS1dE9 double-transgenic mice showed visible plaque deposition; however, all genotypes, including double-transgenic mice, were indistinguishable from nontransgenic animals in all cognitive measures. In the 18-month-old cohorts, amyloid burdens were much higher in APPswe/PS1dE9 mice with statistically significant but mild decreases in cholinergic markers (cortex and hippocampus) and somatostatin levels (cortex). APPswe/PS1dE9 mice performed all cognitive tasks less well than mice from all other genotypes. Factor and correlation analyses defined the strongest correlation as between deficits in episodic-like memory tasks and total Abeta loads in the brain. Collectively, we find that, in the APPswe/PS1dE9 mouse model, some form of Abeta associated with amyloid deposition can disrupt cognitive circuits when the cholinergic and somatostatinergic systems remain relatively intact; and that episodic-like memory seems to be more sensitive to the toxic effects of Abeta.     

Gender differences in the amount and deposition of amyloidbeta in APPswe and PS1 double transgenic mice

Transgenic mice carrying both the human amyloid precursor protein (APP) with the Swedish mutation and the presenilin-1 A246E mutation (APP/PS1 mice) develop Alzheimer's disease-like amyloidbeta protein (Abeta) deposits around 9 months of age. These mice show an age-dependent increase in the level of Abeta40 and Abeta42 and in the number of amyloid plaques in the brain. Abeta40 and Abeta42 levels were measured, and amyloid burden and plaque number were quantified, in the hippocampus at the age of 4, 12, and 17 months in both male and female APP/PS1 mice. In all mice, amyloid burden and plaque number increased markedly with age, with female mice bearing a heavier amyloid burden and higher plaque number compared to male mice of the same age, both at 12 and at 17 months of age. The level of both Abeta40 and Abeta42 significantly increased in female mice with age and was always significantly higher in female than in male mice of the same age. Further, there were significant correlations between amyloid burden and Abeta42 level in female mice and between amyloid burden and plaques in both female and male mice. Together these data show that female APP/PS1 mice accumulate amyloid at an earlier age and that they build up more amyloid deposits in the hippocampus than age-matched male mice. Together, these results provide new insights in the potential mechanisms of the observed gender differences in the pathogenesis of AD.     

Mechanisms and effects of curcumin on spatial learning and memory improvement in APPswe/PS1dE9 mice

Evidence suggests that curcumin, the phytochemical agent in the spice turmeric, might be a potential therapy for Alzheimer's disease (AD). Its antioxidant, anti‐inflammatory properties have been investigated extensively. Studies have also shown that curcumin can reduce amyloid pathology in AD. The underlying mechanism, however, is complex and is still being explored. In this study, we used the APPswe/PS1dE9 double transgenic mice, an AD model, to investigate the effects and mechanisms of curcumin in the prevention and treatment of AD. The water maze test indicated that curcumin can improve spatial learning and memory ability in mice. Immunohistochemical staining and Western blot analysis were used to test major proteins in β‐amyloid aggregation, β‐amyloid production, and β‐amyloid clearance. Data showed that, 3 months after administration, curcumin treatment reduced Aβ₄₀, Aβ₄₂, and aggregation of Aβ‐derived diffusible ligands in the mouse hippocampal CA1 area; reduced the expression of the γ‐secretase component presenilin‐2; and increased the expression of β‐amyloid‐degrading enzymes, including insulin‐degrading enzymes and neprilysin. This evidence suggests that curcumin, as a potential AD therapeutic method, can reduce β‐amyloid pathological aggregation, possibly through mechanisms that prevent its production by inhibiting presenilin‐2 and/or by accelerating its clearance by increasing degrading enzymes such as insulin‐degrading enzyme and neprilysin. © 2013 Wiley Periodicals, Inc.     

Limited expression of heparan sulphate proteoglycans associated with Aβ deposits in the APPswe/PS1dE9 mouse model for Alzheimer's disease

N. M. Timmer, M. K. Herbert, J. W. Kleinovink, A. J. Kiliaan, R. M. W. de Waal and M. M. Verbeek (2010) Neuropathology and Applied Neurobiology 36, 478–486
Limited expression of heparan sulphate proteoglycans associated with Aβ deposits in the APPswe/PS1dE9 mouse model for Alzheimer's disease Aims: Alzheimer's disease (AD) is characterized by deposition of the amyloid beta (Aβ) peptide in brain parenchyma and vasculature. Several proteins co‐deposit with Aβ, including heparan sulphate proteoglycans (HSPG). HSPG have been suggested to contribute to Aβ aggregation and deposition, and may influence plaque formation and persistence by stimulating Aβ fibrillization and by protecting Aβ against degradation. Mouse models for AD, expressing the human amyloid precursor protein (APP), produce Aβ deposits similar to humans. These models may be used to study disease pathology and to develop new therapeutic interventions. We aimed to investigate whether co‐deposition of HSPG in AD brains can be replicated in the APPswe/PS1dE9 mouse model for AD and if a temporal association of HSPG with Aβ exists. Methods: We studied the co‐deposition of several HSPG and of the glycosaminoglycan side chains of HSPG in the APPswe/PS1dE9 model at different ages by immunohistochemistry. Results: We found that, although APPswe/PS1dE9 mice did develop severe Aβ pathology with age, co‐deposition of HS glycosaminoglycan chains and the various HSPG (agrin, perlecan and glypican‐1) was scarce (<10–30% of the Aβ deposits were stained). Conclusions: Our data suggest that the molecular composition of Aβ deposits in the APPswe/PS1dE9 mouse, with respect to the several HSPG investigated in this study, does not accurately reflect the human situation. The near absence of HSPG in Aβ deposits in this transgenic mouse model may, in turn, hinder the translation of preclinical intervention studies from mice to men.     

Synaptic fatigue is more pronounced in the APP/PS1 transgenic mouse model of Alzheimer's disease

To search for potential mechanism that might alter synaptic transmission following Abeta increase we have examined the presynaptic component of transmitter release. As parameters of synaptic transmission that might underlie presynaptic mechanisms, we have used paired-pulse facilitation (PPF), post-tetanic potentiation (PTP), and synaptic fatigue (SF) at the connection between the hippocampal Schaffer-collateral pathway and CA1 pyramidal neurons in approximately 5 month old double transgenic mice overexpressing the mutated form of amyloid precursor protein (APPK670N, M671L) and presenilin 1 (PS1M146V). While the presynaptic mechanisms of PPF and PTP were not compromised in the APP/PS1 mice, SF was more pronounced in the double transgenic animals. The percentage of the 40th fEPSP slope over the first during the tetanus was 18 -/+ 3% in APP/PS1 vs. 26 -/+ 2% in WT. Thus, it is likely that presynaptic mechanisms underlying SF but not PPF and PTP, may account for synaptic dysfunction in APP/PS1 mice.     

Neurosteroid PREGS protects neurite growth and survival of newborn neurons in the hippocampal dentate gyrus of APPswe/PS1dE9 mice

Neurosteroids pregnenolone-sulfate (PREGS) and dehydroepiandrosterone (DHEA) have been shown to enhance neurogenesis in the hippocampal dentate gyrus (DG) of adult rodents. In Alzheimer's disease (AD) brain, the levels of these neurosteroids are known to be altered compared to age-matched non-demented controls. The aim of this study was to examine the effects of PREGS and DHEA on the hippocampal neurogenesis in 8-month-old male APPswe/PS1dE9 transgenic (APP/PS1) mice that show amyloid plaques and impaired spatial cognitive performance. In the DG of APP/PS1 mice the proliferation of progenitor cells was increased, while the neurite growth and survival of newborn neuronal cells were markedly impaired. Treatment with PREGS or DHEA rescued perfectly the hypoplastic neurite of newborn neurons in APP/PS1 mice, while neither of them affected the over-proliferation of progenitor cells. Notably, the administration of PREGS, but not DHEA, to APP/PS1 mice could protect the survival and maturation of newborn neuronal cells, which was accompanied by the improvement of spatial cognitive performance. The results indicate that treatment of AD like brains of APP/PS1 mice with PREGS might protect the hippocampal neurogenesis, leading to the improved spatial cognitive performance.     

APP/PS1双转基因AD传代小鼠的基因型鉴定及其行为学分析

目的 对APP/PS1双转基因AD传代小鼠进行基因型鉴定, 观察其学习记忆功能.方法 PCR鉴定APP/PS1双转基因AD传代小鼠的基因表型, 采用水迷宫实验检测记忆功能.结果 9只APP/PS1双转基因AD传代小鼠基因组DNA中5只小鼠基因组DNA扩增出约350 bp大小条带,认为成功转入APP和PS1基因.APP/PS1双转基因AD小鼠的水迷宫潜伏期比对照组小鼠明显延长.结论 利用PCR扩增APP基因可对APP/PS1双转基因AD传代小鼠进行基因型鉴定, APP/PS1双转基因AD小鼠能够较好地模拟AD患者的临床表现, 为AD的研究提供有效的实验动物模型.     

阿尔茨海默病APPswe/PS1dE9双转基因型与野生型小鼠学习记忆能力的比较

目的：比较不同年龄段阿尔茨海默病（AD）APPswe/PS1dE9双转基因型与野生型小鼠的学习记忆能力。方法：C57BL/6J雌鼠与C3H/HeJ雄鼠交配产下F1代,再将F1代与3月龄的APPswe/PS1dE9双转基因型小鼠交配产下F2代。提取F2代小鼠鼠尾DNA,PCR扩增目的基因并鉴定。依据是否含APP和PS1基因分为转基因型组和野生型对照组,小鼠分别于6、8月龄行Morris水迷宫实验,11月龄行Y迷宫实验检测学习记忆能力。结果：繁育F2代小鼠33只,其中转基因型组18只,野生型对照组15只。6月龄转基因型与野生型小鼠定位航行实验潜伏期的差异无统计学意义,空间探索实验目标象限时间和路程百分比的差异无统计学意义（P〉0.05）。与8月龄野生型小鼠比较,转基因型小鼠定位航行实验第1天潜伏期延长（P〈0.05）。与11月龄野生型小鼠比较,转基因型小鼠达到学会标准的训练次数增加（P〈0.05）。结论：ADAPPswe/PS1dE9双转基因型与野生型小鼠比较,于11月龄时出现学习记忆能力障碍。     

Sensorimotor gating and memory deficits in an APP/PS1 double transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder associated with cognitive deterioration and neuropsychiatric symptoms. Sensorimotor gating deficit has been identified in neuropsychiatric diseases. The aim of the present study was to evaluate the possible sensorimotor gating deficit and its correlation to memory impairment and cerebral β-amyloid (Aβ) plaque deposits in an amyloid precursor protein (APP)/presenilin-1 (PS1) double transgenic mouse model of AD. The sensorimotor gating in 3-, 7- and-22-month-old non-transgenic and transgenic mice was evaluated in a prepulse inhibition (PPI) task. Results revealed that the PPI was lower in the 7- and 22-month-old transgenic mice compared with the age-matched control, while the response to startle pulse-alone in the transgenic and non-transgenic mice was comparable. Congo red staining showed that Aβ neuropathology of transgenic mice aggravated with age, and the 3-month-old transgenic mice started to have minimum brain Aβ plaques, corresponding to the early stage of AD phenotype. Furthermore, memory impairment in the 7-month-old transgenic mice was detected in a water maze test. These results suggest that the sensorimotor gating is impaired with the progressing of AD phenotype, and its deficit may be correlated to cerebral Aβ neuropathology and memory impairment in the APP/PS1 transgenic mouse model of AD.