Two-day radial-arm water maze learning and memory task; robust resolution of amyloid-related memory deficits in transgenic mice

The radial arm water maze (RAWM) contains six swim paths (arms) extending out of an open central area, with an escape platform located at the end of one arm (the goal arm). The goal arm location remains constant for a given mouse. On day 1, mice are trained for 15 trials (spaced over 3 h), with trials alternating between visible and hidden platform. On day 2, mice are trained for 15 trials with the hidden platform. Entry into an incorrect arm is scored as an error. The RAWM has the spatial complexity and performance measurement simplicity of the dry radial arm maze combined with the rapid learning and strong motivation observed in the Morris water maze without requiring foot shock or food deprivation as motivating factors. With two sessions each day, 16 mice can be tested over 2 days.     

Thalidomide attenuates learning and memory deficits induced by intracerebroventricular administration of streptozotocin in rats

Abstract

Neuroinflammatory responses caused by amyloid β (Aβ) peptide deposits are involved in the pathogenesis of Alzheimer’s disease (AD). Thalidomide has a significant anti-inflammatory effect by inhibiting TNF-α, which plays role in Aβ neurotoxicity. We investigated the effect of thalidomide on AD-like cognitive deficits caused by intracerebroventricular injection of streptozotocin (STZ). Intraperitoneal thalidomide was administered 1 h before the first dose of STZ and continued for 21 days. Learning and memory behavior was evaluated on days 17, 18 and 19, and the rats were sacrificed on day 21 to examine histopathological changes. STZ injection caused a significant decrease in the mean escape latency in passive avoidance and decreased improvement of performance in Morris water maze tests. Histopathological changes were examined using hematoxylin-eosin and Bielschowsky staining. Brain sections of STZ treated rats showed increased neurodegeneration and disturbed linear arrangement of cells in the cortical area compared to controls. Thalidomide treatment attenuated significantly STZ induced cognitive impairment and histopathological changes. Thalidomide appears to provide neuroprotection from the memory deficits and neuronal damage induced by STZ.     

Deficiency of aminopeptidase P1 causes behavioral hyperactivity,cognitive deficits,and hippocampal neurodegeneration

Metabolic diseases affect various organs including the brain. Accumulation or depletion of substrates frequently leads to brain injury and dysfunction. Deficiency of aminopeptidase P1, a cytosolic proline‐specific peptidase encoded by the Xpnpep1 gene, causes an inborn error of metabolism (IEM) characterized by peptiduria in humans. We previously reported that knockout of aminopeptidase P1 in mice causes neurodevelopmental disorders and peptiduria. However, little is known about the pathophysiological role of aminopeptidase P1 in the brain. Here, we show that loss of aminopeptidase P1 causes behavioral and neurological deficits in mice. Mice deficient in aminopeptidase P1 (Xpnpep1^?/?) display abnormally enhanced locomotor activities in both the home cage and open‐field box. The aminopeptidase P1 deficiency in mice also resulted in severe impairments in novel‐object recognition, the Morris water maze task, and contextual, but not cued, fear memory. These behavioral dysfunctions were accompanied by epileptiform electroencephalogram activity and neurodegeneration in the hippocampus. However, mice with a heterozygous mutation for aminopeptidase P1 (Xpnpep1^+/?) exhibited normal behaviors and brain structure. These results suggest that loss of aminopeptidase P1 leads to behavioral, cognitive and neurological deficits. This study may provide insight into new pathogenic mechanisms for brain dysfunction related to IEMs.     

Short-term environmental enrichment rescues adult neurogenesis and memory deficits in APP(Sw,Ind) transgenic mice

Epidemiological studies indicate that intellectual activity prevents or delays the onset of Alzheimer's disease (AD). Similarly, cognitive stimulation using environmental enrichment (EE), which increases adult neurogenesis and functional integration of newborn neurons into neural circuits of the hippocampus, protects against memory decline in transgenic mouse models of AD, but the mechanisms involved are poorly understood. To study the therapeutic benefits of cognitive stimulation in AD we examined the effects of EE in hippocampal neurogenesis and memory in a transgenic mouse model of AD expressing the human mutant β-amyloid (Aβ) precursor protein (APP(Sw,Ind)). By using molecular markers of new generated neurons (bromodeoxiuridine, NeuN and doublecortin), we found reduced neurogenesis and decreased dendritic length and projections of doublecortin-expressing cells of the dentate gyrus in young APP(Sw,Ind) transgenic mice. Moreover, we detected a lower number of mature neurons (NeuN positive) in the granular cell layer and a reduced volume of the dentate gyrus that could be due to a sustained decrease in the incorporation of new generated neurons. We found that short-term EE for 7 weeks efficiently ameliorates early hippocampal-dependent spatial learning and memory deficits in APP(Sw,Ind) transgenic mice. The cognitive benefits of enrichment in APP(Sw,Ind) transgenic mice were associated with increased number, dendritic length and projections to the CA3 region of the most mature adult newborn neurons. By contrast, Aβ levels and the total number of neurons in the dentate gyrus were unchanged by EE in APP(Sw,Ind) mice. These results suggest that promoting the survival and maturation of adult generated newborn neurons in the hippocampus may contribute to cognitive benefits in AD mouse models.     

Acute tau knockdown in the hippocampus of adult mice causes learning and memory deficits

Misfolded and hyperphosphorylated tau accumulates in several neurodegenerative disorders including Alzheimer's disease, frontotemporal dementia with Parkinsonism, corticobasal degeneration, progressive supranuclear palsy, Down syndrome, and Pick's disease. Tau is a microtubule‐binding protein, and its role in microtubule stabilization is well defined. In contrast, while growing evidence suggests that tau is also involved in synaptic physiology, a complete assessment of tau function in the adult brain has been hampered by robust developmental compensation of other microtubule‐binding proteins in tau knockout mice. To circumvent these developmental compensations and assess the role of tau in the adult brain, we generated an adeno‐associated virus (AAV) expressing a doxycycline‐inducible short‐hairpin (Sh) RNA targeted to tau, herein referred to as AAV‐ShRNATau. We performed bilateral stereotaxic injections in 7‐month‐old C57Bl6/SJL wild‐type mice with either the AAV‐ShRNATau or a control AAV. We found that acute knockdown of tau in the adult hippocampus significantly impaired motor coordination and spatial memory. Blocking the expression of the AAV‐ShRNATau, thereby allowing tau levels to return to control levels, restored motor coordination and spatial memory. Mechanistically, the reduced tau levels were associated with lower BDNF levels, reduced levels of synaptic proteins associated with learning, and decreased spine density. We provide compelling evidence that tau is necessary for motor and cognitive function in the adult brain, thereby firmly supporting that tau loss‐of‐function may contribute to the clinical manifestations of many tauopathies. These findings have profound clinical implications given that anti‐tau therapies are in clinical trials for Alzheimer's disease.     

Decreasing oxidative stress and neuroinflammation with a multifunctional peptide rescues memory deficits in mice with Alzheimer disease

Alzheimer disease (AD) is characterized by extracellular senile plaques, intracellular neurofibrillary tangles, and memory loss. Aggregated amyloid-β (Aβ), oxidative stress, and inflammation have pivotal roles in the pathogenesis of AD. Therefore, the inhibition of Aβ-induced neurotoxicity, oxidative stress, and inflammation is a potential therapeutic strategy for the treatment of AD. In this study, a heptapeptide, isolated from a Ph.D.-C7C library by phage display, attenuated Aβ42-induced cytotoxicity in SH-SY5Y neuroblastoma cells and reduced Aβ42-induced oxidative stress by decreasing the production of reactive oxygen species and glutathione disulfide. As a result, glutathione level increased and superoxide dismutase and glutathione peroxidase activities were enhanced in vitro and in vivo. This peptide also suppressed the inflammatory response by decreasing the release of proinflammatory cytokines, such as tumor necrosis factor α and interleukin 1β, in microglia and by reducing microgliosis and astrogliosis in AD transgenic mice. This peptide was intracerebroventricularly administered to APPswe/PS1dE9 transgenic mice. We found that this peptide significantly improved spatial memory and reduced the amyloid plaque burden and soluble and insoluble Aβ levels. Our findings suggest that this multifunctional peptide has therapeutic potential for an Aβ-targeted treatment of AD.     

Restoring miR-132 expression rescues adult hippocampal neurogenesis and memory deficits in Alzheimer’s disease

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ABI2-deficient mice exhibit defective cell migration, aberrant dendritic spine morphogenesis, and deficits in learning and memory

The Abl-interactor (Abi) family of adaptor proteins has been linked to signaling pathways involving the Abl tyrosine kinases and the Rac GTPase. Abi proteins localize to sites of actin polymerization in protrusive membrane structures and regulate actin dynamics in vitro. Here we demonstrate that Abi2 modulates cell morphogenesis and migration in vivo. Homozygous deletion of murine abi2 produced abnormal phenotypes in the eye and brain, the tissues with the highest Abi2 expression. In the absence of Abi2, secondary lens fiber orientation and migration were defective in the eye, without detectable defects in proliferation, differentiation, or apoptosis. These phenotypes were consistent with the localization of Abi2 at adherens junctions in the developing lens and at nascent epithelial cell adherens junctions in vitro. Downregulation of Abi expression by RNA interference impaired adherens junction formation and correlated with downregulation of the Wave actin-nucleation promoting factor. Loss of Abi2 also resulted in cell migration defects in the neocortex and hippocampus, abnormal dendritic spine morphology and density, and severe deficits in short- and long-term memory. These findings support a role for Abi2 in the regulation of cytoskeletal dynamics at adherens junctions and dendritic spines, which is critical for intercellular connectivity, cell morphogenesis, and cognitive functions.     

初步探讨鸟嘌呤核苷、姜黄素对AD双转基因小鼠学习记忆的影响

目的通过Morris水迷宫检测学习记忆和记忆保持能力,判断鸟嘌呤核苷、姜黄素对4月龄APPswe/PS1dE9双转基因小鼠认知功能的影响。方法将3月龄APPswe/PS1dE9双转基因小鼠随机分为模型组、盐酸多奈哌齐组0.92 mg/(kg·d)、鸟嘌呤核苷组20 mg/(kg·d)、姜黄素组200 mg/(kg·d)、姜黄素200 mg/(kg·d)和鸟嘌呤核苷组20 mg/(kg·d),每组12只;并以同月龄野生型C57/BL6J小鼠作对照。每天给药1次,连续给药1个月。应用Morris水迷宫进行行为学检测。结果鸟嘌呤核苷、姜黄素对空间探索、定位航行障碍有改善作用,尤其以姜黄素组明显。结论鸟嘌呤核苷、姜黄素能改善APPswe/PS1dE9双转基因小鼠的早期出现的认知障碍。     

Neurotrophic peptides incorporating adamantane improve learning and memory, promote neurogenesis and synaptic plasticity in mice

Development of neurotrophic peptidergic drugs that can mimic neurotrophins and promote neurogenesis and maturation of newborn cells into mature functional neurons represents an exciting therapeutic opportunity for treatment of Alzheimer disease and other learning and memory disorders as well as enhancing cognition of normal individuals. Here we report the design of a peptidergic compound, Ac-DGGL^AG-NH₂, called P21, when administered peripherally, enhanced learning as well as both short-term and spatial reference memories of normal adult C57Bl6 mice. P21 induced enhancement of neurogenesis and maturation of newly born neurons in the granular cell layer and subgranular zone of the dentate gyrus.     

Endogenous mitochondrial oxidative stress: neurodegeneration, proteomic analysis, specific respiratory chain defects, and efficacious antioxidant therapy in superoxide dismutase 2 null mice

Oxidative stress and mitochondrial dysfunction have been linked to neurodegenerative disorders such as Parkinson's and Alzheimer's disease. However, it is not yet understood how endogenous mitochondrial oxidative stress may result in mitochondrial dysfunction. Most prior studies have tested oxidative stress paradigms in mitochondria through either chemical inhibition of specific components of the respiratory chain, or adding an exogenous insult such as hydrogen peroxide or paraquat to directly damage mitochondria. In contrast, mice that lack mitochondrial superoxide dismutase (SOD2 null mice) represent a model of endogenous oxidative stress. SOD2 null mice develop a severe neurological phenotype that includes behavioral defects, a severe spongiform encephalopathy, and a decrease in mitochondrial aconitase activity. We tested the hypothesis that specific components of the respiratory chain in the brain were differentially sensitive to mitochondrial oxidative stress, and whether such sensitivity would lead to neuronal cell death. We carried out proteomic differential display and examined the activities of respiratory chain complexes I, II, III, IV, V, and the tricarboxylic acid cycle enzymes alpha-ketoglutarate dehydrogenase and citrate synthase in SOD2 null mice in conjunction with efficacious antioxidant treatment and observed differential sensitivities of mitochondrial proteins to oxidative stress. In addition, we observed a striking pattern of neuronal cell death as a result of mitochondrial oxidative stress, and were able to significantly reduce the loss of neurons via antioxidant treatment.     

Accelerated plaque accumulation, associative learning deficits, and up-regulation of alpha 7 nicotinic receptor protein in transgenic mice co-expressing mutant human presenilin 1 and amyloid precursor proteins

Familial Alzheimer's disease-associated mutations in presenilin 1 or 2 or amyloid precursor protein result in elevated beta-amyloid, beta-amyloid accumulation, and plaque formation in the brains of affected individuals. By crossing presenilin 1 transgenic mice carrying the A246E mutation with plaque-producing amyloid precursor protein K670N/M671L transgenic mice (Tg2576), we show that co-expression of both mutant transgenes results in acceleration of amyloid accumulation and associative learning deficits. At 5 months of age with no detectable plaque pathology, amyloid precursor protein transgenic animals are impaired in contextual fear learning following two pairings of conditioned and unconditioned stimuli but appear normal following a more robust five-pairing training. At 9 months of age when beta-amyloid deposition is evident, these mice are impaired following both two-pairing and five-pairing protocols. Mice carrying both transgenes are impaired in contextual fear conditioning at either age. All transgenic animal groups performed as well as controls in cued fear conditioning, indicating that the contextual fear learning deficits are hippocampus-specific. The associative learning impairments are coincident with elevated alpha 7 nicotinic acetylcholine receptor protein in the dentate gyrus. These findings provide two robust and rapid assays for beta-amyloid-associated effects that can be performed on young animals: impaired contextual fear learning and up-regulation of alpha 7 nicotinic receptors.     

Altered longevity‐assurance activity of p53:p44 in the mouse causes memory loss,neurodegeneration and premature death

The longevity‐assurance activity of the tumor suppressor p53 depends on the levels of Δ40p53 (p44), a short and naturally occurring isoform of the p53 gene. As such, increased dosage of p44 in the mouse leads to accelerated aging and short lifespan. Here we show that mice homozygous for a transgene encoding p44 (p44^+/+) display cognitive decline and synaptic impairment early in life. The synaptic deficits are attributed to hyperactivation of insulin‐like growth factor 1 receptor (IGF‐1R) signaling and altered metabolism of the microtubule‐binding protein tau. In fact, they were rescued by either Igf1r or Mapt haploinsufficiency. When expressing a human or a ‘humanized’ form of the amyloid precursor protein (APP), p44^+/+ animals developed a selective degeneration of memory‐forming and ‐retrieving areas of the brain, and died prematurely. Mechanistically, the neurodegeneration was caused by both paraptosis‐ and autophagy‐like cell deaths. These results indicate that altered longevity‐assurance activity of p53:p44 causes memory loss and neurodegeneration by affecting IGF‐1R signaling. Importantly, Igf1r haploinsufficiency was also able to correct the synaptic deficits of APP_695/swe mice, a model of Alzheimer’s disease.     

Ergothioneine and melatonin attenuate oxidative stress and protect against learning and memory deficits in C57BL/6J mice treated with D-galactose

Abstract

Male C57BL/6J mice treated with D-galactose (DG) were used to examine the effects of ergothioneine (EGT), melatonin (MEL), or their combination (EGT+MEL) on learning and memory abilities. The mice were divided into five groups and injected subcutaneously with DG (0.3 mL of 1% DG/mouse) except for group 1 (normal controls). Group 3 was orally supplemented with EGT [0.5 mg/kg body weight (bw)], group 4 with MEL (10 mg/kg bw, p.o.), and group 5 with EGT+MEL. EGT and MEL were provided daily for 88 days, while DG was provided between days 7 to 56. Active avoidance task and Morris water-maze task were used to evaluate learning and memory abilities. DG treatment markedly increased escape latency and decreased the number of avoidance in the active avoidance test, whereas EGT and MEL alone significantly improved the performance. DG also impaired the learning and memory abilities in the water-maze task, and EGT and MEL alone also significantly improved the performance. EGT+MEL produced the strongest effects in both tasks. EGT and MEL alone markedly decreased β-amyloid protein accumulation in the hippocampus and significantly inhibited lipid peroxidation and maintained glutathione/glutathione disulfide ratio and superoxide dismutase activity in brain tissues of DG-treated mice. MEL alone completely prevented the rise in brain acetylcholine esterase activity induced by DG, whereas EGT and EGT+MEL were only partially effective. Overall, EGT, MEL, and, in particular, the combination of EGT and MEL effectively protect against learning and memory deficits in C57BL/6J mice treated with DG, possibly through attenuation of oxidative damage.     

Overexpression of glutaminyl cyclase, the enzyme responsible for pyroglutamate A{beta} formation, induces behavioral deficits, and glutaminyl cyclase knock-out rescues the behavioral phenotype in 5XFAD mice

Pyroglutamate-modified Aβ (AβpE3-42) peptides are gaining considerable attention as potential key players in the pathology of Alzheimer disease (AD) due to their abundance in AD brain, high aggregation propensity, stability, and cellular toxicity. Overexpressing AβpE3-42 induced a severe neuron loss and neurological phenotype in TBA2 mice. In vitro and in vivo experiments have recently proven that the enzyme glutaminyl cyclase (QC) catalyzes the formation of AβpE3-42. The aim of the present work was to analyze the role of QC in an AD mouse model with abundant AβpE3-42 formation. 5XFAD mice were crossed with transgenic mice expressing human QC (hQC) under the control of the Thy1 promoter. 5XFAD/hQC bigenic mice showed significant elevation in TBS, SDS, and formic acid-soluble AβpE3-42 peptides and aggregation in plaques. In 6-month-old 5XFAD/hQC mice, a significant motor and working memory impairment developed compared with 5XFAD. The contribution of endogenous QC was studied by generating 5XFAD/QC-KO mice (mouse QC knock-out). 5XFAD/QC-KO mice showed a significant rescue of the wild-type mice behavioral phenotype, demonstrating the important contribution of endogenous mouse QC and transgenic overexpressed QC. These data clearly demonstrate that QC is crucial for modulating AβpE3-42 levels in vivo and prove on a genetic base the concept that reduction of QC activity is a promising new therapeutic approach for AD.     

Metformin protects against seizures,learning and memory impairments and oxidative damage induced by pentylenetetrazole-induced kindling in mice

Cognitive impairment, the most common and severe comorbidity of epilepsy, greatly diminishes the quality of life. However, current therapeutic interventions for epilepsy can also cause untoward cognitive effects. Thus, there is an urgent need for new kinds of agents targeting both seizures and cognition deficits. Oxidative stress is considered to play an important role in epileptogenesis and cognitive deficits, and antioxidants have a putative antiepileptic potential. Metformin, the most commonly prescribed antidiabetic oral drug, has antioxidant properties. This study was designed to evaluate the ameliorative effects of metformin on seizures, cognitive impairment and brain oxidative stress markers observed in pentylenetetrazole-induced kindling animals. Male C57BL/6 mice were administered with subconvulsive dose of pentylenetetrazole (37 mg/kg, i.p.) every other day for 14 injections. Metformin was injected intraperitoneally in dose of 200 mg/kg along with alternate-day PTZ. We found that metformin suppressed the progression of kindling, ameliorated the cognitive impairment and decreased brain oxidative stress. Thus the present study concluded that metformin may be a potential agent for the treatment of epilepsy as well as a protective medicine against cognitive impairment induced by seizures.     

Effects of exercise and poor indoor air quality on learning,memory and blood IGF-1 in adolescent mice

It is known that regular aerobic exercise enhances cognitive functions and increases blood insulin-like growth factor 1 (IGF-1) levels. People living in urban areas spend most of their time indoors and indoor air quality can affect health. We investigated the effects of aerobic exercise in poor and good air quality environments on hippocampus and prefrontal cortex (PFC) neurons, anxiety, and spatial learning and memory in adolescent mice. Poor air quality impaired spatial learning and memory; exercise did not affect learning or memory impairment. Exercise in a good air quality environment improved spatial learning and memory. Poor air quality increased apoptosis in the hippocampus and PFC. Both exercised and sedentary groups living in a poor air quality environment had lower serum IGF-1 levels than those living in a good air quality environment. Living in a poor air quality environment has negative effects on the hippocampus, PFC and blood IGF-1 levels in adolescent mice, but exercise did not alter the negative effects of poor air quality.     

Effects of sodium benzoate,a commonly used food preservative,on learning,memory, and oxidative stress in brain of mice

Sodium benzoate (SB) is a widely used preservative and antimicrobial substance in many foods and soft drinks. However, this compound is generally recognized as safe food additives, but evidence has suggested that a high intake of SB may link to attention deficit‐hyperactivity disorder in children. Present study investigate the effects of oral administration of different concentrations of SB (0.56, 1.125, and 2.25 mg/mL) for 4 weeks, on the learning and memory performance tests, and also the levels of malondialdehyde (MDA), reduced glutathione (GSH), and acetylcholinesterase activity (AChE) in the mouse brain. The results showed that SB significantly impaired memory and motor coordination. Moreover, SB decreased reduced GSH and increased the MDA level in the brain significantly (P < 0.001). However, nonsignificant alteration was observed in the AChE activity. These findings suggest that short‐term consumption of SB can impair memory performance and increased brain oxidative stress in mice.