Insights into Abeta and presenilin from a canine model of human brain aging

Cordyceps cicadae NTTU 868 Mycelia Fermented with Deep Ocean Water Minerals Prevents D-Galactose-Induced Memory Deficits by Inhibiting Oxidative Inflammatory Factors and Aging-Related Risk Factors

Cordyceps cicadae, a medicinal fungus that is abundant in bioactive compounds such as N6-(2-hydroxyethyl)-adenosine (HEA) and polysaccharides, possesses remarkable anti-inflammatory, antioxidant, and nerve damage recovery properties. Deep ocean water (DOW) contains minerals that can be absorbed and transformed into organic forms by fungi fermentation. Recent studies have shown that culturing C. cicadae in DOW can enhance its therapeutic benefits by increasing the levels of bioactive compounds and minerals' bioavailibility. In this study, we investigated the effects of DOW-cultured C. cicadae (DCC) on brain damage and memory impairment induced by D-galactose in rats. Our results indicate that DCC and its metabolite HEA can improve memory ability and exhibit potent antioxidant activity and free radical scavenging in D-galactose-induced aging rats (p < 0.05). Additionally, DCC can mitigate the expression of inflammatory factors, such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS), thereby preventing brain aging. Furthermore, DCC showed a significant decrease in the expression of the aging-related proteins glial fibrillary acidic protein (GFAP) and presenilin 1 (PS1). By reducing brain oxidation and aging-related factors, DOW-cultured C. cicadae demonstrate enhanced anti-inflammatory, antioxidant, and neuroprotective effects, making it a promising therapeutic agent for preventing and treating age-related brain damage and cognitive impairment.

Ageing changes in cat brains demonstrated by β-amyloid and AT8-immunoreactive phosphorylated tau deposits

The life expectancy of domestic pet cats is increasing, along with the occurrence of geriatric-onset behavioural problems, such as cognitive dysfunction syndrome (CDS). While the cause of CDS is unclear, it has been suggested that it may result from age-related neurodegeneration. In aged and in particular senile human beings, histopathological changes may include the extracellular accumulation of plaque-like deposits of β-amyloid (Aβ) protein and the intracellular accumulation of an abnormally hyperphosphorylated form of the microtubule-associated protein, tau. In severe cases, the latter may form into neurofibrillary tangles. Brain material was assessed from 19 cats, aged from 16 weeks to 14 years; 17 of which had clinical signs of neurological dysfunction. Immunohistochemical methods were used to detect Aβ and its intracellular precursor protein (amyloid precursor protein (APP)) and hyperphosphorylated-tau.

APP was constitutively expressed, with diffuse staining of neurons and blood vessels being detected in all cats. More intense staining and diffuse extracellular Aβ staining deposits were found within the deep cortical areas of the anterior- and occasionally mid-cerebrum of seven cats, all of which were over 10 years of age. Neurons staining intensely positive for AT8-immunoreactivity were seen in two cats, aged 11 and 13 years. However, no mature neurofibrillary tangles were detected. This study demonstrated that extracellular Aβ accumulation and AT8-immunoreactivity within neurons are age-related phenomena in cats, and that they can occur concurrently. There are similarities between these changes and those observed in the brains of aged people and other old mammals.

Computational Prediction of Alzheimer's and Parkinson's Disease MicroRNAs in Domestic Animals

As the most common neurodegenerative diseases, Alzheimer’s disease (AD) and Parkinson’s disease (PD) are two of the main health concerns for the elderly population. Recently, microRNAs (miRNAs) have been used as biomarkers of infectious, genetic, and metabolic diseases in humans but they have not been well studied in domestic animals. Here we describe a computational biology study in which human AD- and PD-associated miRNAs (ADM and PDM) were utilized to predict orthologous miRNAs in the following domestic animal species: dog, cow, pig, horse, and chicken. In this study, a total of 121 and 70 published human ADM and PDM were identified, respectively. Thirty-seven miRNAs were co-regulated in AD and PD. We identified a total of 105 unrepeated human ADM and PDM that had at least one 100% identical animal homolog, among which 81 and 54 showed 100% sequence identity with 241 and 161 domestic animal miRNAs, respectively. Over 20% of the total mature horse miRNAs (92) showed perfect matches to AD/PD-associated miRNAs. Pigs, dogs, and cows have similar numbers of AD/PD-associated miRNAs (63, 62, and 59). Chickens had the least number of perfect matches (34). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses suggested that humans and dogs are relatively similar in the functional pathways of the five selected highly conserved miRNAs. Taken together, our study provides the first evidence for better understanding the miRNA-AD/PD associations in domestic animals, and provides guidance to generate domestic animal models of AD/PD to replace the current rodent models.

Oxidative stress in aging: advances in proteomic approaches

Aging is a gradual, complex process in which cells, tissues, organs, and the whole organism itself deteriorate in a progressive and irreversible manner that, in the majority of cases, implies pathological conditions that affect the individual's Quality of Life (QOL). Although extensive research efforts in recent years have been made, the anticipation of aging and prophylactic or treatment strategies continue to experience major limitations. In this review, the focus is essentially on the compilation of the advances generated by cellular expression profile analysis through proteomics studies (two-dimensional [2D] electrophoresis and mass spectrometry [MS]), which are currently used as an integral approach to study the aging process. Additionally, the relevance of the oxidative stress factors is discussed. Emphasis is placed on postmitotic tissues, such as neuronal, muscular, and red blood cells, which appear to be those most frequently studied with respect to aging. Additionally, models for the study of aging are discussed in a number of organisms, such as Caenorhabditis elegans, senescence-accelerated probe-8 mice (SAMP8), naked mole-rat (Heterocephalus glaber), and the beagle canine. Proteomic studies in specific tissues and organisms have revealed the extensive involvement of reactive oxygen species (ROS) and oxidative stress in aging.

A preclinical cognitive test battery to parallel the National Institute of Health Toolbox in humans: bridging the translational gap

A major goal of animal research is to identify interventions that can promote successful aging and delay or reverse age-related cognitive decline in humans. Recent advances in standardizing cognitive assessment tools for humans have the potential to bring preclinical work closer to human research in aging and Alzheimer's disease. The National Institute of Health (NIH) has led an initiative to develop a comprehensive Toolbox for Neurologic Behavioral Function (NIH Toolbox) to evaluate cognitive, motor, sensory and emotional function for use in epidemiologic and clinical studies spanning 3 to 85 years of age. This paper aims to analyze the strengths and limitations of animal behavioral tests that can be used to parallel those in the NIH Toolbox. We conclude that there are several paradigms available to define a preclinical battery that parallels the NIH Toolbox. We also suggest areas in which new tests may benefit the development of a comprehensive preclinical test battery for assessment of cognitive function in animal models of aging and Alzheimer's disease.

Therapeutic interventions targeting Beta amyloid pathogenesis in an aging dog model

Aged dogs and humans share complex cognitive and pathological responses to aging. Specifically, dogs develop Alzheimer's Disease (AD) like beta-amyloid (Aβ) that are associated with cognitive deficits. Currently, therapeutic approaches to prevent AD are targeted towards reduced production, aggregation and increased clearance of Aβ. The current review discusses cognition and neuropathology of the aging canine model and how it has and continues to be useful in further understanding the safety and efficacy of potential AD prevention therapies targeting Aβ.

Amyloid-modifying therapies for Alzheimer's disease: therapeutic progress and its implications

Alzheimer's disease (AD) is the most prevalent form of dementia, affecting an estimated 4.8 million people in North America. For the past decade, the amyloid cascade hypothesis has dominated the field of AD research. This theory posits that the deposition of amyloid-beta protein (Abeta) in the brain is the key pathologic event in AD, which induces a series of neuropathological changes that manifest as cognitive decline and eventual dementia. Based on this theory, interventions that reduce Abeta burden in the brain would be expected to alleviate both the neuropathological changes and dementia, which characterize AD. Several diverse pharmacological strategies have been developed to accomplish this. These include inhibiting the formation of Abeta, preventing the aggregation of Abeta into insoluble aggregates, preventing the entry of Abeta into the brain from the periphery and enhancing the clearance of Abeta from the central nervous system. To date, no amyloid-modifying therapy has yet been successful in phase 3 clinical trials; however, several trials are currently underway. This article provides a review of the status of amyloid-modifying therapies and the implications for the amyloid cascade hypothesis.

Knockout of plasminogen activator inhibitor 1 gene reduces amyloid beta peptide burden in a mouse model of Alzheimer's disease

Accumulation of amyloid beta peptide (Aβ) in the brain is a pathological hallmark of Alzheimer's disease (AD); the underlying mechanism, however, is not well understood. In this study, we show that expression of plasminogen activator inhibitor 1 (PAI-1), a physiological inhibitor of tissue type and urokinase type plasminogen activators (tPA and uPA), increases with age in the brain of wild type and Aβ precursor protein-presenilin 1 (APP/PS1) transgenic mice as well as in AD patients. Most importantly, we show that knocking out the PAI-1 gene dramatically reduces Aβ burden in the brain of APP/PS1 mice but has no effect on the levels of full-length APP, alpha or beta C-terminal fragments. Furthermore, we show that knocking out the PAI-1 gene leads to increases in the activities of tPA and plasmin, and the plasmin activity inversely correlates with the amounts of SDS insoluble Aβ40 and Aβ42. Together, these data suggest that increased PAI-1 expression/activity contributes importantly to Aβ accumulation during aging and in AD probably by inhibiting plasminogen activation and thus Aβ degradation.

Oxidatively modified proteins in Alzheimer's disease (AD), mild cognitive impairment and animal models of AD: role of Abeta in pathogenesis

Oxidative stress has been implicated in the pathogenesis of a number of diseases including Alzheimer's disease (AD). The oxidative stress hypothesis of AD pathogenesis, in part, is based on beta-amyloid peptide (Abeta)-induced oxidative stress in both in vitro and in vivo studies. Oxidative modification of the protein may induce structural changes in a protein that might lead to its functional impairment. A number of oxidatively modified brain proteins were identified using redox proteomics in AD, mild cognitive impairment (MCI) and Abeta models of AD, which support a role of Abeta in the alteration of a number of biochemical and cellular processes such as energy metabolism, protein degradation, synaptic function, neuritic growth, neurotransmission, cellular defense system, long term potentiation involved in formation of memory, etc. All the redox proteomics-identified brain proteins fit well with the appearance of the three histopathological hallmarks of AD, i.e., synapse loss, amyloid plaque formation and neurofibrillary tangle formation and suggest a direct or indirect association of the identified proteins with the pathological and/or biochemical alterations in AD. Further, Abeta models of AD strongly support the notion that oxidative stress induced by Abeta may be a driving force in AD pathogenesis. Studies conducted on arguably the earliest stage of AD, MCI, may elucidate the mechanism(s) leading to AD pathogenesis by identifying early markers of the disease, and to develop therapeutic strategies to slow or prevent the progression of AD. In this review, we summarized our findings of redox proteomics identified oxidatively modified proteins in AD, MCI and AD models.

Beta-amyloid cortical deposits are accompanied by the loss of serotonergic neurons in the dog

Dogs may naturally suffer an age-related cognitive impairment that has aroused a great deal of interest, even beyond the field of the veterinary clinic. This canine senile dementia reproduces several key aspects of Alzheimer's disease (AD), including the presence of beta-amyloid (A beta) deposits in the cerebral cortex, neurodegeneration, and learning and memory impairments. In the present study, we have used unbiased stereological procedures to estimate the number of the dorsal and median raphe nuclei (DRN and MRN, respectively) serotonergic neurons immunolabeled with an anti-tryptophan hydroxylase (TrH) monoclonal antibody in young and aged dogs without A beta cortical deposits and in aged dogs with A beta cortical deposits. The estimated total number of TrH-labeled neurons (mean +/- SD) was 94,790 +/- 26,341 for the DRN and 40,404 +/- 8,692 for the MRN. The statistical analyses revealed that aged dogs with A beta cortical pathology had 33% fewer serotonergic neurons in the DRN and MRN than aged dogs without A beta cortical deposits (108,043 +/- 18,800 vs. 162,242 +/- 39,942, respectively; P = 0.01). In contrast, no significant variations were found between young and aged dogs without A beta cortical deposits. These results suggest that degeneration of the serotonergic neurons could be involved in the cognitive damage that accompanies A beta cortical pathology in the dog and reinforce the use of the canine model for exploring the potential mechanisms linking the cortical A beta pathology and serotonergic neurodegeneration that occurs during the course of AD.

Immunoreactivities and levels of mineralocorticoid and glucocorticoid receptors in the hippocampal CA1 region and dentate gyrus of adult and aged dogs

Corticosteroids are important factors in the maintenance of homeostasis in the brain. They are regulated via the interaction with two corticosteroid receptor systems-the mineralocorticoid (MR) and glucocorticoid receptor (GR). In the present study, we observed age-related changes in serum cortisol levels, and immunoreactivities and protein levels of MR and GR in the hippocampal CA1 region and dentate gyrus. The serum cortisol levels were significantly high (about twofold) in the aged group compared to that in the adult group. In the adult dog (2-3 years old), MR and GR immunoreactivity was detected in neurons in the pyramidal layer of the CA1 region, and in the granular and multiform layers of the dentate gyrus. In the aged dog (10-12 years old), MR immunoreactivity in the CA1 region was significantly decreased, especially, in the dentate multiform layer. In contrast, GR immunoreactivity in the aged dog was slightly decreased in the CA1 region and dentate gyrus. In the Western blot analysis, MR protein level in the aged dog was significantly lower compared to that of the adult dog; GR protein level in the aged dog was not significantly decreased. This result indicates that the reduction of MR immunoreactivity and protein level in the hippocampus of the aged dog may be associated with neural dysfunction in the aged hippocampus.

Differences in doublecortin immunoreactivity and protein levels in the hippocampal dentate gyrus between adult and aged dogs

Doublecortin (DCX), a microtubule-associated protein, specifically expresses in neuronal precursors. This protein has been used as a marker for neuronal precursors and neurogenesis. In the present study, we observed differences in DCX immunoreactivity and its protein levels in the hippocampal dentate gyrus between adult and aged dogs. In the adult dog, DCX immunoreactive cells with well-stained processes were detected in the subgranular zone of the dentate gyrus. Numbers of DCX immunoreactive cells in the dentate gyrus of the aged dog were significantly decreased compared to those in the adult dog. DCX immunoreactive cells in both adult and aged dog did not show NeuN (a marker for mature neurons) immunoreactivity. NeuN immunoreactivity in the aged dog was poor compared to that in the adult dog. DCX protein level in the aged dentate gyrus was decreased by 80% compared to that in the adult dog. These results suggest that the reduction of DCX in the aged hippocampal dentate gyrus may be involved in some neural deficits related to the hippocampus.

Canine cognitive dysfunction and the cerebellum: acetylcholinesterase reduction, neuronal and glial changes

The specific functional and pathological alterations observed in Alzheimer's disease are less severe in the cerebellum than in other brain areas, particularly the entorhinal cortex and hippocampus. Since dense core amyloid-beta plaque formation has been associated with an acetylcholinesterase heterogeneous nucleator action, we examined if an acetylcholinesterase imbalance was involved in cerebellum plaque deposition. By using the canine counterpart of senile dementia of the Alzheimer's type, a promising model of human brain aging and early phases of Alzheimer's disease, we investigated how cerebellar pathology and acetylcholinesterase density could be related with cognitive dysfunction. As in Alzheimer's disease, the late affectation of the cerebellum was evidenced by its lack of amyloid-beta plaque and the presence of diffuse deposition throughout all cortical grey matter layers. The highest acetylcholinesterase optic density corresponded to cerebellar islands of the granular layer and was predominantly associated with synaptic glomeruli and the somata of Golgi cells. Its reduction correlated with aging and loss of granule cells, whereas cognitive deficit only correlated with loss of Purkinje cells. The observed Bergmann glia alterations may correspond to a reactive response to the loss and damage of the Purkinje cells, their specific neuronal partner. Regarding the role of acetylcholinesterase mediation in amyloid-beta deposition, our data argue against an interaction between these two proteins because acetylcholinesterase reduction correlates with aging but not with cognitive deficit. Finally, our data support the use of companion dogs of all breeds to study aging and early phases of Alzheimer's disease.

Proteomic identification of brain proteins in the canine model of human aging following a long-term treatment with antioxidants and a program of behavioral enrichment: relevance to Alzheimer's disease

Aging and age-related disorders such as Alzheimer's disease (AD) are usually accompanied by oxidative stress as one of the main mechanisms contributing to neurodegeneration and cognitive decline. Aging canines develop cognitive dysfunction and neuropathology similar to those seen in humans, and the use of antioxidants results in reductions in oxidative damage and in improvement in cognitive function in this canine model of human aging. In the present study, the effect of a long-term treatment with an antioxidant-fortified diet and a program of behavioral enrichment on oxidative damage was studied in aged canines. To identify the neurobiological mechanisms underlying these treatment effects, the parietal cortex from 23 beagle dogs (8.1-12.4 years) were treated for 2.8 years in one of four treatment groups: i.e., control food-control behavioral enrichment (CC); control food-behavioral enrichment (CE); antioxidant food-control behavioral enrichment (CA); enriched environment-antioxidant-fortified food (EA). We analyzed the levels of the oxidative stress biomarkers, i.e., protein carbonyls, 3-nitrotyrosine (3-NT), and the lipid peroxidation product, 4-hydroxynonenal (HNE), and observed a decrease in their levels on all treatments when compared to control, with the most significant effects found in the combined treatment, EA. Since EA treatment was most effective, we also carried out a comparative proteomics study to identify specific brain proteins that were differentially expressed and used a parallel redox proteomics approach to identify specific brain proteins that were less oxidized following EA. The specific protein carbonyl levels of glutamate dehydrogenase [NAD (P)], glyceraldehyde-3-phosphate dehydrogenase (GAPDH), alpha-enolase, neurofilament triplet L protein, glutathione-S-transferase (GST) and fascin actin bundling protein were significantly reduced in brain of EA-treated dogs compared to control. We also observed significant increases in expression of Cu/Zn superoxide dismutase, fructose-bisphosphate aldolase C, creatine kinase, glutamate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase. The increased expression of these proteins and in particular Cu/Zn SOD correlated with improved cognitive function. In addition, there was a significant increase in the enzymatic activities of glutathione-S-transferase (GST) and total superoxide dismutase (SOD), and significant increase in the protein levels of heme oxygenase (HO-1) in EA treated dogs compared to control. These findings suggest that the combined treatment reduces the levels of oxidative damage and improves the antioxidant reserve systems in the aging canine brain, and may contribute to improvements in learning and memory. These observations provide insights into a possible neurobiological mechanism underlying the effects of the combined treatment. These results support the combination treatments as a possible therapeutic approach that could be translated to the aging human population who are at risk for age-related neurodegenerative disorders, including Alzheimer's disease.

A molecular study of hippocampus in dogs with convulsion during canine distemper virus encephalitis

In this study, we have investigated the expression of the nuclear transcription factor (c-Fos, NFkB), growth factors (nerve growth factor--NGF, brain-derived neurotrophic factor--BDNF), peptides (enkephalin, galanin) and glutamate transporter (AA 504-523 rat EAAC1) in 6 dogs sacrificed immediately after seizure attack during encephalomyelitis due to canine distemper virus (CDV) (as assessed by clinical examination, RT-PCR and viral RNA detection either in blood or brain tissue and CDV immunohistochemistry in brain slices). In all these CDV affected dogs, the observed neurological signs included untreatable seizures, leading to cluster seizure activity and status epilepticus. In the inter-ictal phase abnormal mentation, postural and gait deficits and sometimes involuntary movements such as myoclonus were recorded. The same investigation was carried out in 5 control dogs affected by different disorders, all characterized by the absence of seizures. Brains were dissected out immediately after euthanasia and fixed; sections collected from the dorsal hippocampus were processed for immunohistochemistry. By comparing hippocampus sections obtained from dog with and without seizure, the following regulations were observed. A strong up-regulation of glutamate transporter throughout the cell layers was found together with the onset of nuclear Fos and NFkB-IR in the pyramidal cell layer X. Among the investigated peptides, we observed a slight increase in enkephalinergic fibers and a strong up-regulation of mu-opioid receptors, whereas galanin-IR seemed to be weaker. Finally, both NGF and BDNF expression was strongly up-regulated. BDNF-IR was mainly localized in the apical dendrite in pyramidal neurons. To our knowledge, these data offer the first indication that molecular events described in experimental kindling also occur during spontaneous pathology in animal species sharing close similarities to human neuropathology.

The immunohistochemical localization of neuronal nitric oxide synthase in the basal forebrain of the dog

The present work describes for the first time the anatomical distribution of neuronal nitric oxide synthase (nNOS) immunoreactivity and NADPH-d activity in the basal forebrain of the dog. As in other species, small, intensely nNOS-immunoreactive cells were seen within the olfactory tubercle, caudate nucleus, putamen, nucleus accumbens and amygdala. In addition, a population of mixed large and small nNOS positive cells was found in the medial septum, diagonal band and nucleus basalis overlapping the distribution of the magnocellular cholinergic system of the basal forebrain. Our results show that the distribution of NOS containing neurons in these nuclei in the dog is more extensive and uniform than that reported in rodents and primates. When double labeling of nNOS and NADPH-d was performed in the same tissue section most neurons were double labeled. However, a considerable number of large perikarya in the diagonal band and nucleus basalis appeared to be single labeled for nNOS. Thought a certain degree of interference between the two procedures could not be completely excluded, these findings suggest that NADPH-d histochemistry, which is frequently used to show the presence of NOS, underestimates the potential of basal forebrains neurons to produce nitric oxide. In addition, a few neurons mainly localized among the fibers of the internal capsule, appeared to be labeled only for NADPH-d. These neurons could be expressing a different isoform of NOS, not recognized by our anti-nNOS antibody, as has been reported in healthy humans and AD patients.

Application of an automated voxel-based morphometry technique to assess regional gray and white matter brain atrophy in a canine model of aging

In recent years, voxel-based morphometry (VBM) has emerged as a technique to examine regional brain changes associated with normal and pathological aging. Despite its popularity in studies of human aging, application of VBM to animal models of brain aging is rare. In the present study, VBM techniques were developed to validate earlier region of interest (ROI) measures of brain aging in the dog and to provide a more comprehensive analysis of local changes in a canine model of brain aging. Consistent with previous findings, frontal lobe atrophy increased with age, most notably in aged male dogs. Age-related gray matter reductions were also observed in parietal and temporal lobes, thalamus, cerebellum, and brainstem. Temporal lobe atrophy was particularly prominent in old females. A number of age-related changes in white matter not previously explored in the dog were also identified with VBM. Specifically, aged males exhibited greater decreases in the internal capsula and cranial nerve bundles compared to decreased volumes in the alveus of the hippocampus in old female dogs. Together, the present results indicate that application of VBM techniques in a canine model of aging yields more comprehensive information regarding topographical patterns of brain aging in male and female dogs than previously reported using traditional manual ROI methods.

Effects of scopolamine challenge on regional cerebral blood volume. A pharmacological model to validate the use of contrast enhanced magnetic resonance imaging to assess cerebral blood volume in a canine model of aging

Cognitive impairment resulting from disruption of cholinergic function may occur through modulation of cerebrovascular volume (CBV). In the present study, dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) was used to examine cerebrovascular volume in young and old dogs during baseline and after administration of a cholinergic antagonist (scopolamine). In the first study, 24 animals (2-15 years of age) were given a baseline scan followed by a second scan after scopolamine administration (30 microg/kg). Gray matter rCBV was significantly higher than white matter rCBV during baseline and scopolamine administration. In the second study a subset of 7 dogs (4 young and 3 old) received scopolamine before anesthesia was induced for a second DSC-MRI scan. Consistent with the first study, gray matter rCBV was significantly higher than white matter rCBV. Scopolamine administered before anesthesia however, resulted in higher rCBV values compared to baseline in cerebral gray matter. Additionally, rCBVs were higher in young dogs at baseline in gray and white matter and marginally higher in gray matter when scopolamine was administered before anesthesia. These results indicate that in the dog, rCBV varies with brain compartment, decreases with age, and that DSC-MRI provides a measure of cerebrovascular function which may be related to age-dependent changes in cognition, brain structure, and neuropathology.

The canine model of human cognitive aging and dementia: pharmacological validity of the model for assessment of human cognitive-enhancing drugs

For the past 15 years we have investigated the aged beagle dog as a model for human aging and dementia. We have shown that dogs develop cognitive deficits and neuropathology seen in human aging and dementia. These similarities increase the likelihood that the model will be able to accurately predict the efficacy of Alzheimer's disease (AD) treatments as well as detect therapeutics with limited or no efficacy. Better predictive validity of cognitive-enhancing therapeutics (CETs) could lead to enormous cost savings by reducing the number of failed human clinical trials and also may reduce the likelihood of negative outcomes such as those recently observed in the AN-1792 clinical trials. The current review assesses the pharmacological validity of the canine model of human aging and dementia. We tested the efficacy of (1) CP-118,954 and phenserine, two acetylcholinesterase inhibitors, (2) an ampakine, (3) selegiline hydrochloride, two drugs that have failed human AD trials, and (4) adrafinil, a putative CET. Our research demonstrates that dogs not only develop isomorphic changes in human cognition and brain pathology, but also accurately predict the efficacy of known AD treatments and the absence or limited efficacy of treatments that failed clinical trials. These findings collectively support the utilization of the dog model as a preclinical screen for identifying novel CETs for both age-associated memory disorder and dementia.

Distribution of ACTH immunoreactivity in the diencephalon and the brainstem of the dog

The present work describes for the first time the anatomical distribution of adrenocorticotropic hormone (ACTH) in the diencephalon and the brainstem of the dog by means of the indirect immunoperoxidase technique. The distribution found in this species agrees well with the pattern found in other mammals and particularly confirms much of the findings reported in the cat. An exception to that concordance is the presence of ACTH perikarya in the nucleus of the solitary tract of the dog, a population that has been described in the rat but not in the cat, and in the ventral mesencephalon. This last population spread across the ventral tegmental area from the raphe to the cerebral peduncle and appeared to be a specific feature of the canine brain. On the other hand, we can not see ACTH fibers in the substantia nigra of the dog which could be a characteristic of the domestic carnivores, opposite to rodents, since these fibers appeared to be also lacking in the cat. Nevertheless, the widespread distribution of ACTH fibers in the brain of the dog included many other nuclei containing monoaminergic neurons which supported a possible role for ACTH in the regulation of these neurotransmitter systems.

Histochemical accumulation of oxidative damage products is associated with Alzheimer-like pathology in the canine

An important lesion in Alzheimer's disease (AD) patient brains is the neurofibrillary tangle (NFT). Hyperphosphorylated tau is its major component. In a former paper we described some NFT in the canine brain. During aging, moreover, advanced glycation end products (AGE) might accumulate. Glycated tau induces lipid peroxidation in vivo and tau and AGE antigens have been mentioned to co-localize in NFT. This indicates that AGE may play an important role in Alzheimer disease (AD) by oxidation of tau. The aim of the present study was to investigate amyloid, neurofibrillary tangles, Abeta precursor protein, Abeta, tau, ubiquitin, advanced glycation end products, 4-hyroxynonenal protein and lipofuscin in a series of dogs of varying ages. The results showed a significant positive correlation between age and amyloid quantity (Congo red staining), HNE staining and lipofuscin (LF), and between amyloid quantity and HNE staining and LF. Staining for AbetaPP seemed to have a tendency to increase with age, whereas staining for tau, ubiquitin and AGE each only gave limited positive results in a proportion of the older dogs. Preliminary studies including loss of cognitive capabilities in the older dogs and chemical measurement of lipofuscin-like pigment (LFP) accumulation in brain extracts revealed an increase with old age and dementia. The Congo red, HNE and LF results suggest that deposition of amyloid with aging might be associated with formation of end products of lipid peroxidation. The finding of the limited positive signals for tau, ubiquitin and AGE in some old cases might indicate that the spontaneous brain pathology of the aged dog reveals similarities to early stages observed in AD in humans especially those with Down syndrome.

Canine counterpart of senile dementia of the Alzheimer type: amyloid plaques near capillaries but lack of spatial relationship with activated microglia and macrophages

Senile plaques and cerebrovascular amyloidosis are major histopathological lesions in the brains of aged dogs. Different types of amyloid beta protein (A beta) positive plaques are known: diffuse ones and neuritic plaques. Diffuse plaques may contain membrane-bound A beta and/or small amounts of amyloid fibrils. Neuritic plaques are cored plaques with clusters of amyloid fibrils and degenerating neurities. In human amyloid plaques, a pathogenetic role for microglia cells has been described. The aim of this investigation was to study microglia cells in relationship to canine plaques and to investigate the localisation of amyloid plaques in relationship to vasculature. The lesions were studied by hematoxylin and eosin Congo red staining and immunohistochemistry with anti-A beta for plaques, with Mac 387, anti lysozyme and a series of lectins for mononuclear cells, with anti von Willebrand Factor and Lycopersicon esculentum (tomato) lectin for the endothelium of brain capillaries. Diffuse A beta-positive plaques were found in dogs of 10.8 years and older, and cored A beta-positive plaques with birefringent amyloid in Congo red-stained sections in subjects of 15 years and older. Accumulation of microglia cells in relationship to the plaques was not obvious. With anti A beta 8-17 the distribution of the plaques in the cortical layers varied. The younger dogs had primarily diffuse plaques in the deeper layers of the cortical grey matter. The older dogs showed more cored plaques than diffuse plaques which were found throughout all cortical grey matter layers. With anti A beta x-42 more plaques were found positive, especially diffuse ones, whereas staining results of anti A beta x-40 were more confined to amyloid plaques and vascular amyloid. A close spatial relationship was found between the cored plaques and capillaries.