Journal of Alzheimer's Disease - Volume 15, issue 4

Authors: Woodruff-Pak, Diana S.

Article Type: Research Article

Abstract: This Special Issue of the Journal of Alzheimer's Disease (JAD) provides an overview of animal models of Alzheimer's disease (AD). Very few species spontaneously develop the cognitive, behavioral, and neuropathological symptoms of AD, yet AD research must progress at a more rapid pace than the rate of human aging. In recent years, a variety of models have been created – from tiny invertebrates with life spans measurable in months to huge mammals that live several decades. The fruit fly, Drosophila melanogaster, is a powerful genetic tool that has recently emerged as a model of AD with neural features and assessable …learning and memory. Transgenic mice are the most widely used animal models of AD and have yielded significant research breakthroughs. Accelerated aging seen in the SAMP8 mouse is a non-transgenic model with great utility. Rat models provided early evidence about the deleterious impact of amyloid-β (Aβ) on neurons and continue to provide insights. Rabbits, as langomorphs, are more closely related to primates than are rodents and have conserved the sequence of Aβ in humans (as have canines and non-human primates). The hypercholesterolemic rabbit is an excellent AD model. The aging canine develops AD neuropathology spontaneously and is especially suitable for tests of therapeutics. Non-human primates are invaluable for the development of therapeutics translating to humans. Each animal model has limitations and strengths, but used together in complementary fashion, animal models for research on AD are essential for rapid progress toward a cure. Show more

Keywords: Dog, fruit fly, hypercholesterolemic rabbit, non-human primate, rat, transgenic mouse

DOI: 10.3233/JAD-2008-15401

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 507-521, 2008

Authors: Iijima, Koichi | Iijima-Ando, Kanae

Article Type: Research Article

Abstract: Alzheimer's disease (AD) is the most common form of senile dementia, and a cure is desperately needed. The amyloid-β42 (Aβ42) has been suggested to play a central role in the pathogenesis of AD. However, the mechanism by which Aβ42 causes AD remains unclear. To understand the pathogenesis and to develop therapeutic avenues, it is crucial to generate animal models of AD in genetically tractable organisms. Drosophila is a well-established model system for which abundant genetic tools are available. Moreover, its well organized brain permits the study of complex behaviors such as learning and memory. We have established transgenic flies that …express human Aβ42 in the nervous system. These flies developed age-dependent short-term memory impairment and neurodegeneration. In this review, we will first describe transgenic Aβ42 fly models and discuss the unique features of this system compared to mouse AD models. Secondly, we will discuss the usage of the fly models to evaluate currently proposed therapeutic strategies. Thirdly, we will briefly review the results of a genetic screen for modifiers of Aβ42 toxicity in the fly model. Finally, we will discuss how to dissect the complex mechanisms of Aβ42 toxicity focusing on its aggregation propensity using the fly model system. Show more

Keywords: Alzheimer disease, amyloid-β42, animal model, Drosophila, genome-wide screen, learning and memory, neprilysin, neurodegenerative disease, protein misfolding

DOI: 10.3233/JAD-2008-15402

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 523-540, 2008

Authors: Khurana, Vikram

Article Type: Research Article

Abstract: The fruit fly Drosophila melanogaster has emerged as a powerful system in which to model human disease. This review focuses on the utility of the fly to model tau-dependent neurodegeneration, a hallmark of Alzheimer's disease and related neurodegenerative disorders. I provide a detailed description of fly tauopathy models and summarize a number of studies that demonstrate their ability to recapitulate both primary features of tauopathy, including tau-induced neurodegeneration and phosphorylation, and secondary features, including oxidative stress, cell-cycle activation and changes in the actin cytoskeleton. Important genetic and biochemical insights are discussed, and future directions proposed.

Keywords: Actin, Alzheimer's disease, cell cycle, Drosophila, dementia, fruit fly, neurodegeneration, oxidative Stress, tau, tauopathy

DOI: 10.3233/JAD-2008-15403

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 541-553, 2008

Authors: Wilcock, Donna M. | Colton, Carol A.

Article Type: Research Article

Abstract: Therapeutic approaches to the treatment of Alzheimer's disease are focused primarily on the amyloid-β peptide which aggregates to form amyloid deposits in the brain. The amyloid hypothesis states that amyloid is the precipitating factor that results in the other pathologies of Alzheimer's disease. One such therapy that has attracted significant attention is anti-amyloid-β immunotherapy. First described in 1999, immunotherapy uses anti-amyloid-β antibodies to lower brain amyloid levels. Active and passive immunization were shown to lower brain amyloid levels and improve cognition in multiple transgenic mouse models. Mechanisms of action were studied in these mice and revealed a complex set of …mechanisms that depended on the type of antibody used. When active immunization advanced to clinical trials a subset of patients developed meningoencephalitis, an event not predicted in mouse studies. It was suspected that a T-cell response due to the type of adjuvant used was the cause. Passive immunization has also advanced to Phase III clinical trials on the basis of successful transgenic mouse studies. Reports from the active immunization clinical trial indicated that, similarly to effects observed in mouse studies, amyloid levels in brain were reduced. Show more

Keywords: Amyloid, antibody, cerebral amyloid angiopathy, clinical trial, immunization, inflammation

DOI: 10.3233/JAD-2008-15404

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 555-569, 2008

Authors: Colton, Carol A. | Wilcock, Donna M. | Wink, David A. | Davis, Judianne | Van Nostrand, William E. | Vitek, Michael P.

Article Type: Research Article

Abstract: Nitric oxide synthase 2 (NOS2) and its gene product, inducible NOS (iNOS) play an important role in neuroinflammation by generating nitric oxide (NO), a critical signaling and redox factor in the brain. Although NO is associated with tissue damage, it can also promote cell survival. We hypothesize that during long-term exposure to amyloid-β (Aβ) in Alzheimer's disease (AD), NO levels fall in the brain to a threshold at which the protective effects of NO cannot be sustained, promoting Aβ mediated damage. Two new mouse models of AD have been developed that utilize this concept of NO's action. These mice express …human amyloid-β protein precursor (AβPP) mutations that generate Aβ peptides on a mouse NOS2 knockout background. The APP/NOS2–/– bigenic mice progress from Aβ production and amyloid deposition to hyperphosphorylated normal mouse tau at AD-associated epitopes, aggregation and redistribution of tau to somatodendritic regions of neurons and significant neuronal loss including loss of interneurons. This AD-like pathology is accompanied by robust behavioral changes. As APP/NOS2–/– bigenic mice more fully model the human AD disease pathology, they may serve as a tool to better understand disease progression in AD and the role of NO in altering chronic neurological disease processes. Show more

Keywords: Alternative activation, Alzheimer's disease, amyloid, microglia, mouse models, neuroinflammation, nitric oxide

DOI: 10.3233/JAD-2008-15405

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 571-587, 2008

Authors: Foy, Michael R. | Baudry, Michel | Diaz Brinton, Roberta | Thompson, Richard F.

Article Type: Research Article

Abstract: Accumulating evidence indicates that ovarian hormones regulate a wide variety of non-reproductive functions in the central nervous system by interacting with several molecular and cellular processes. A growing animal literature using both adult and aged rodent models indicates that 17β-estradiol, the most potent of the biologically relevant estrogens, facilitates some forms of learning and memory, in particular those that involve hippocampal-dependent tasks. A recently developed triple-transgenic mouse (3xTg-AD) has been widely used as an animal model of Alzheimer's disease, as this mouse exhibits an age-related and progressive neuropathological phenotype that includes both plaque and tangle pathology mainly restricted to hippocampus, …amygdala and cerebral cortex. In this report, we examine recent studies that compare the effects of ovarian hormones on synaptic transmission and synaptic plasticity in adult and aged rodents. A better understanding of the non-reproductive functions of ovarian hormones has far-reaching implications for hormone therapy to maintain health and function within the nervous system throughout aging. Show more

Keywords: 3xTg AD, aging, estrogen, hippocampus, LTP, mouse, synaptic plasticity

DOI: 10.3233/JAD-2008-15406

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 589-603, 2008

Authors: Morgan, Dave | Munireddy, Sanjay | Alamed, Jennifer | DeLeon, Jason | Diamond, David M. | Bickford, Paula | Hutton, Michael | Lewis, Jada | McGowan, Eileen | Gordon, Marcia N.

Article Type: Research Article

Abstract: Transgenic mice expressing human tau containing the P301L tau mutation (JNPL3; tau mice) develop motor neuron loss, paralysis and death between 7 and 12 months. Surprisingly, at 5 and 7 months of age, tau transgenic mice were superior to other genotypes in the rotarod task, and had near perfect scores on the balance beam and coat hanger tests. One tau transgenic mouse was performing at a superior level in the rotarod one day prior to developing paralysis. Cognitive function was also normal in the tau mice evaluated in the radial arm water maze and the Y-maze tasks. We also crossed …the tau transgenic mice with Tg2576 amyloid-β protein precursor (AβPP) transgenic mice. Although AβPP mice were deficient in the radial arm maze task, AβPP + tau mice were not impaired, implying a benefit of the tau transgene. Some mice were homozygous for the retinal degeneration mutation (rd/rd) and excluded from the genotype analysis. Only the water maze task discriminated the rd/rd mice from nontransgenic mice. In conclusion, it seems that the modest tau overexpression or the presence of mutant tau in the JNPL3 tau mice may provide some benefit with respect to motor and cognitive performance before the onset of paralysis. Show more

Keywords: Amyloid, rotarod, tau, transgenic mice, water maze, Y-maze

DOI: 10.3233/JAD-2008-15407

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 605-614, 2008

Authors: Pallas, Merce | Camins, Antoni | Smith, Mark A. | Perry, George | Lee, Hyoung-gon | Casadesus, Gemma

Article Type: Research Article

Abstract: Current mouse models of Alzheimer's disease (AD) are restricted to the expression of AD-related pathology associated with specific mutations present in early-onset familial AD and thus represent <5% of AD cases. To date there are no mouse lines that model late-onset/age-related AD, the feature which accounts for the vast majority of cases. As such, based on current mutation-associated models, the chronology of events that lead to the disease in the aged population is difficult to establish. However, published data show that senescence-accelerated mouse (SAMP8), as a model of aging, display many features that are known to occur early in the …pathogenesis of AD such as increased oxidative stress, amyloid-β alterations, and tau phosphorylation. Therefore, SAMP8 mice may be an excellent model for studying the earliest neurodegenerative changes associated with AD and provide a more encompassing picture of human disease, a syndrome triggered by a combination of age-related events. Here, the neurochemical, neuropathological, and behavioral alterations, characterized in SAMP8 mice are critically reviewed and discussed in relation to the potential use of this mouse model in the study of AD pathogenesis. Show more

Keywords: Aging, Alzheimer's disease, amyloid-β, animal models, cognition, gliosis, neurodegeneration, oxidative stress, SAMP8, tau phosphorylation

DOI: 10.3233/JAD-2008-15408

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 615-624, 2008

Authors: Begum, Aynun N. | Yang, Fusheng | Teng, Edmond | Hu, Shuxin | Jones, Mychica R. | Rosario, Emily R. | Beech, Walter | Hudspeth, Beverly | Ubeda, Oliver J. | Cole, Greg M. | Frautschy, Sally A.

Article Type: Research Article

Abstract: The rat amyloid-β (Aβ) intracerebroventricular infusion can model aspects of Alzheimer's disease (AD) and has predicted efficacy of therapies such as ibuprofen and curcumin in transgenic mouse models. High density lipoprotein (HDL), a normal plasma carrier of Aβ, is used to attenuate Aβ aggregation within the pump, causing Aβ-dependent toxicity and cognitive deficits within 3 months. Our goal was to identify factors that might accelerate onset of Aβ-dependent deficits to improve efficiency and cost-effectiveness of model. We focused on: 1) optimizing HDL-Aβ preparation for maximal toxicity; 2) evaluating the role of copper, a factor typically in water that can impact …oligomer stability; and 3) determining impact of insulin resistance (type II diabetes), a risk factor for AD. In vitro studies were performed to determine doses of copper and methods of Aβ-HDL preparation that maximized toxicity. These preparations when infused resulted in earlier onset of cognitive deficits within 6 weeks post-infusion. Induction of insulin resistance did not exacerbate Aβ-dependent cognitive deficits, but did exacerbate synaptic protein loss. In summary, the newly described in vivo infusion model may be useful cost-effective method for screening for new therapeutic drugs for AD. Show more

Keywords: Alzheimer's disease, amyloid-β, copper, cognitive deficit, high density lipoprotein, insulin resistance

DOI: 10.3233/JAD-2008-15409

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 625-640, 2008

Authors: Sparks, D. Larry

Article Type: Research Article

Abstract: Pioneering autopsy studies revealed a possible link between coronary artery disease, cholesterol and Alzheimer's disease (AD). In the cholesterol-fed rabbit model of human coronary artery disease, we identified numerous neuropathologic features of AD including central accumulation of amyloid-β (Aβ) and cognitive deficits compared to rabbits fed unaltered diet. Removing cholesterol from the diet or treatment with cholesterol-lowering medications reversed the severity of AD-like alterations. This fostered the rationale for testing a cholesterol-lowering statin medication for benefit in the treatment of AD. Further studies suggested that the cholesterol-fed rabbit was a viable model for AD, but the severity of the neuropathology …produced exhibited gender-related differences. Furthermore the induction of AD-like neuropathology by dietary cholesterol was found to depend on the quality of water the animal was drinking. Cholesterol-fed rabbits drinking distilled water showed minimal central changes, whereas animals drinking distilled water supplemented with low levels of copper were severely affected. It was clear that cholesterol caused the over-production of Aβ in the brain and copper influenced its clearance to the blood. Emerging data suggest that low-density lipoprotein receptor-related protein-1 (LRP) on brain capillaries clears Aβ from brain and that excess circulating copper negatively influences this process. Show more

Keywords: Alzheimer's disease, cholesterol, coronary artery disease, rabbit

DOI: 10.3233/JAD-2008-15410

Citation: Journal of Alzheimer's Disease, vol. 15, no. 4, pp. 641-656, 2008