APP Expression in Primary Neuronal Cell Cultures fromP6 Mice during in vitro Differentiation

Primary neuronal cell cultures from P6 mice were investigated in order to study amyloid protein precursor (APP) gene expression in differentiating neurons. Cerebellar granule cells which strongly express APP 695 allowed the identification of three distinct isoforms of neuronal APP 695. The high-molecular-weight form of APP 695 is sialylated. The expression pattern of neuronal APP 695 changes during in vitro differentiation. Sialylated forms become more abundant upon longer cultivation time. The secreted forms of sialylated, neuronal APP 695 are shown to comigrate with APP isolated from cerebrospinal fluid. We suggest that the different sialylation states of APP 695 may reflect the modulation of cell-cell and cell-substrate interactions during in vitro differentiation and regeneration

Correlating familial Alzheimer’s disease gene mutations with clinical phenotype

Alzheimer’s disease (AD) causes devastating cognitive impairment and an intense research effort is currently devoted to developing improved treatments for it. A minority of cases occur at a particularly young age and are caused by autosomal dominantly inherited genetic mutations. Although rare, familial AD provides unique opportunities to gain insights into the cascade of pathological events and how they relate to clinical manifestations. The phenotype of familial AD is highly variable and, although it shares many clinical features with sporadic AD, it also possesses important differences. Exploring the genetic and pathological basis of this phenotypic heterogeneity can illuminate aspects of the underlying disease mechanism, and is likely to inform our understanding and treatment of AD in the future

A genetic cause of Alzheimer disease: mechanistic insights from Down syndrome

Down syndrome, caused by an extra copy of chromosome 21, is associated with a greatly increased risk of early onset Alzheimer disease. It is thought that this risk is conferred by the presence of three copies of the gene encoding amyloid precursor protein (APP), an Alzheimer risk factor, although the possession of extra copies of other chromosome 21 genes may also play a role. Further study of the mechanisms underlying the development of Alzheimer disease in Down syndrome could provide insights into the mechanisms that cause dementia in the general population

Intranasal rapamycin ameliorates Alzheimer-like cognitive decline in a mouse model of Down syndrome

Background: Down syndrome (DS) individuals, by the age of 40s, are at increased risk to develop Alzheimer-like dementia, with deposition in brain of senile plaques and neurofibrillary tangles. Our laboratory recently demonstrated the disturbance of PI3K/AKT/mTOR axis in DS brain, prior and after the development of Alzheimer Disease (AD). The aberrant modulation of the mTOR signalling in DS and AD age-related cognitive decline affects crucial neuronal pathways, including insulin signaling and autophagy, involved in pathology onset and progression. Within this context, the therapeutic use of mTOR-inhibitors may prevent/attenuate the neurodegenerative phenomena. By our work we aimed to rescue mTOR signalling in DS mice by a novel rapamycin intranasal administration protocol (InRapa) that maximizes brain delivery and reduce systemic side effects. Methods: Ts65Dn mice were administered with InRapa for 12 weeks, starting at 6 months of age demonstrating, at the end of the treatment by radial arms maze and novel object recognition testing, rescued cognition. Results: The analysis of mTOR signalling, after InRapa, demonstrated in Ts65Dn mice hippocampus the inhibition of mTOR (reduced to physiological levels), which led, through the rescue of autophagy and insulin signalling, to reduced APP levels, APP processing and APP metabolites production, as well as, to reduced tau hyperphosphorylation. In addition, a reduction of oxidative stress markers was also observed. Discussion: These findings demonstrate that chronic InRapa administration is able to exert a neuroprotective effect on Ts65Dn hippocampus by reducing AD pathological hallmarks and by restoring protein homeostasis, thus ultimately resulting in improved cognition. Results are discussed in term of a potential novel targeted therapeutic approach to reduce cognitive decline and AD-like neuropathology in DS individuals

Environment, epigenetics and neurodegeneration: Focus on nutrition in Alzheimer's disease

Many different environmental factors (nutrients, pollutants, chemicals, physical activity, lifestyle, physical and mental stress) can modulate epigenetic markers in the developing and adult organism. Epigenetics, in turn, can cause and is associated with several neurodegenerative and aging-dependent human diseases. Alzheimer's disease certainly represents one of the most relevant neurodegenerative disorders due to its incidence and its huge socio-economic impact. Therefore, it is easy to understand why recent literature focuses on the epigenetic modifications associated with Alzheimer's disease and other neurodegenerative disorders. One of the most intriguing and, at the same time, worrying evidence is that even "mild" environmental factors (such as behavioral or physical stress) as well as the under-threshold exposure to pollutants and chemicals, can be effective. Finally, even mild nutrients disequilibria can result in long-lasting and functional alterations of many epigenetic markers, although they don't have an immediate acute effect. Therefore, we will probably have to re-define the current risk threshold for many factors, molecules and stresses. Among the many different environmental factors affecting the epigenome, nutrition represents one of the most investigated fields; the reasons are probably that each person interacts with nutrients and that, in turn, nutrients can modulate at molecular level the epigenetic biochemical pathways. The role that nutrition can exert in modulating epigenetic modifications in Alzheimer's disease will be discussed with particular emphasis on the role of B vitamins and DNA methylation

Serum cholesterol and variant in cholesterol-related gene CETP predict white matter microstructure

Several common genetic variants influence cholesterol levels, which play a key role in overall health. Myelin synthesis and maintenance are highly sensitive to cholesterol concentrations, and abnormal cholesterol levels increase the risk for various brain diseases, including Alzheimer's disease. We report significant associations between higher serum cholesterol (CHOL) and high-density lipoprotein levels and higher fractional anisotropy in 403 young adults (23.8 ± 2.4years) scanned with diffusion imaging and anatomic magnetic resonance imaging at 4Tesla. By fitting a multi-locus genetic model within white matter areas associated with CHOL, we found that a set of 18 cholesterol-related, single-nucleotide polymorphisms implicated in Alzheimer's disease risk predicted fractional anisotropy. We focused on the single-nucleotide polymorphism with the largest individual effects, CETP (rs5882), and found that increased G-allele dosage was associated with higher fractional anisotropy and lower radial and mean diffusivities in voxel-wise analyses of the whole brain. A follow-up analysis detected white matter associations with rs5882 in the opposite direction in 78 older individuals (74.3 ± 7.3years). Cholesterol levels may influence white matter integrity, and cholesterol-related genes may exert age-dependent effects on the brain

Effects of Ultrasound on Amyloid Beta 42 (Aβ42) Mediated Neurodegeneration

Alzheimer’s disease (AD) is an age related progressive neurodegenerative disease. The exact mechanisms that lead to cell death are not entirely understood. It has been shown that accumulation of amyloid-beta-42 (Aβ42) plaques generated by mis-cleavage of amyloid-precursor-protein is the cause of neurodegeneration seen in AD. This is due to the hydrophobic nature of Aβ42 due to extra two amino acids added to the typical and naturally occurring Aβ40 in the body. These Aβ42 plaques trigger neuronal death because of the toxic nature and stress they exert on the neurons. In this study, Drosophila melanogaster transgenic model where human Aβ42 coding cDNA is ectopically expressed in the developing fly retina comprising of retinal neurons to study the effect of ultrasound waves. Our hypothesis is to employ ultrasound wave exposure as a possible treatment to Alzheimer’s Disease. Ultrasound is a high frequency and lower energy sound wave, which may have less deleterious effect on cells in the tissue. In theory, using energy emitted from these waves would break down the plaques limiting damage due to degeneration. The wild type will be used as a control to see any side effects of the ultrasound treatment, while an AD affected fly will be used to determine effectiveness of the treatments. The goal of this project is to standardize the optimum ultrasound treatment, to observe the effects on survival rates, prevent neurodegeneration by removing or decreasing plaque damage. By varying the height, medium, time, and number of treatments, the survival rate and rescue can be tracked. Further studies using larval imaging approach can be used to see early stage effects of the ultrasound. These studies will allow testing the efficacy of commonly used treatment in sports related tissue injuries to cure inflammation and also to dislodge protein aggregations in Alzheimer’s disease where accumulation of Aβ42 plaques is the hallmark

Normalizing the gene dosage of Dyrk1A in a mouse model of Down syndrome rescues several Alzheimer's disease phenotypes

The intellectual disability that characterizes Down syndrome (DS) is primarily caused by prenatal changes in central nervous system growth and differentiation. However, in later life stages, the cognitive abilities of DS individuals progressively decline due to accelerated aging and the development of Alzheimer's disease (AD) neuropathology. The AD neuropathology in DS has been related to the overexpression of several genes encoded by Hsa21 including DYRK1A (dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A), which encodes a protein kinase that performs crucial functions in the regulation of multiple signaling pathways that contribute to normal brain development and adult brain physiology. Studies performed in vitro and in vivo in animal models overexpressing this gene have demonstrated that the DYRK1A gene also plays a crucial role in several neurodegenerative processes found in DS. The Ts65Dn (TS) mouse bears a partial triplication of several Hsa21 orthologous genes, including Dyrk1A, and replicates many DS-like abnormalities, including age-dependent cognitive decline, cholinergic neuron degeneration, increased levels of APP and A?, and tau hyperphosphorylation. To use a more direct approach to evaluate the role of the gene dosage of Dyrk1A on the neurodegenerative profile of this model, TS mice were crossed with Dyrk1A KO mice to obtain mice with a triplication of a segment of Mmu16 that includes this gene, mice that are trisomic for the same genes but only carry two copies of Dyrk1A, euploid mice with a normal Dyrk1A dosage, and CO animals with a single copy of Dyrk1A. Normalizing the gene dosage of Dyrk1A in the TS mouse rescued the density of senescent cells in the cingulate cortex, hippocampus and septum, prevented cholinergic neuron degeneration, and reduced App expression in the hippocampus, A? load in the cortex and hippocampus, the expression of phosphorylated tau at the Ser202 residue in the hippocampus and cerebellum and the levels of total tau in the cortex, hippocampus and cerebellum. Thus, the present study provides further support for the role of the Dyrk1A gene in several AD-like phenotypes found in TS mice and indicates that this gene could be a therapeutic target to treat AD in DS.This work was supported by the Jerome Lejeune Foundation, Fundación Tatiana Pérez de Guzmán el Bueno and the Spanish Ministry of Economy and Competitiveness (PSI-2016-76194-R, AEI/FEDER, EU). The authors wish to express their gratitude to Mariona Arbonés for providing Dyrk1A +/− KO mice and to Eva García Iglesias for technical assistance

Pathological Alterations Induced by intraneuronal in Alzheimer’s Disease

Die Alzheimer Demenz (AD) ist neuropathologisch durch das Auftreten von β-Amyloid (Aβ) und Neurofibrillenbündeln, die aus hyperphosphoryliertem Tau Protein bestehen, charakterisiert. Die Ablagerung von Aβ Peptiden wird als ursächlicher pathologischer Mechanismus betrachtet, da familiär auftretende Mutationen in Proteinen die in der Aβ?Kaskade eine Rolle spielen unweigerlich zur AD führen. Im Gegensatz dazu führen Mutationen im Tau Protein zu Fronto-Temporaler Demenz. Die Amyloid-Hypothese geht davon aus, dass die Akkumulation von Aβ42 ursächlich für die Beeinträchtigung von Nervenzellen und Synapsen ist und letztendlich zu Verhaltensdefiziten führt. Für viele Jahre galt das Hauptaugenmerk der Amyloid-Hypothese dem Auftreten extrazellulärer Aβ-Plaques. In einer Vielzahl von Mausmodellen, die auf familiären Mutationen basieren, konnte die Ablagerung dieser Plaques erfolgreich nachgebildet werden, allerdings traten nur schwache Verhaltensdefizite und kein deutlicher Nervenzellverlust auf. Extrazelluläre Plaque-Pathologie korreliert darüber hinaus nicht mit bei AD Patienten beobachteten kognitiven Defiziten und kommt auch bei Kontrollpatienten vor, die keine Anzeichen einer Demenz aufweisen. Kürzlich wurde eine modifizierte Amyloid-Hypothese vorgestellt, in der frühen intrazellulären Aβ-Akkumulationen, im Gegensatz zu extrazellulären Aβ Plaques eine zentrale Rolle in der pathologischen Kaskade zukommt. Allerdings ist das Vorkommen intrazellulärer Aβ Peptide bei der AD noch Gegenstand wissenschaftlicher Diskussion. Die vorliegende Arbeit untersucht das Vorkommen intrazellulärer Aβ Peptide im Hirngewebe von Alzheimer Patienten, sowie deren Rolle im Gegensatz zu extrazellulärer Plaquepathologie in transgenen Mausmodellen der AD. Nervenzellverlust, axonale Pathologie und funktionelle Defizite im Hinblick auf die Regulation der Expression früher Gene (immediate early genes, IEG) werden dabei besonders berücksichtigt. Im Hinblick auf pathologische Veränderungen bestätigt die vorliegende Arbeit die modifizierte Amyloid-Hypothese. Die Ergebnisse unterstützen die Rolle von intraneuronalem Aβ als früher Auslöser der pathologischen Kaskade und zeigen einen deutlichen Zusammenhang zu axonaler Degeneration und Nervenzellverlust auf. Im Gegensatz dazu scheinen extrazelluläre Plaques eher an funktionellen Defiziten wie etwa der Induktion von IEGs bei neuronaler Aktivität, nicht aber am Nervenzellverlust beteiligt zu sein. Durch eine Optimierung des immunhistochemischen Färbeprotokolls konnte eine deutliche Färbung intraneuronaler Aβ Peptide in Nervenzellen des Hippokampus im Hirngewebe von AD Patienten nachgewiesen werden. Darüber hinaus wurde ein Zusammenhang zwischen der Präsenz des ApoE4 Allels, einem bekannten Risikofaktor für die AD, und intraneuronalem Aβ gefunden, was die wichtige Rolle von Aβ Peptiden innerhalb von Nervenzellen bei der Pathologie der AD unterstreicht