scholarly journals Endosomal structure and APP biology are not altered in preclinical cellular models of Down syndrome

2021 ◽  
Author(s):  
Claudia Cannavo ◽  
Karen Cleverley ◽  
Cheryl Maduro ◽  
Paige Mumford ◽  
Dale Moulding ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Down Syndrome ◽  
Cell Biology ◽  
Amyloid Β ◽  
Chromosome 21 ◽  
App Processing ◽  
Cellular Models ◽  
Increased Risk ◽  
Primary Mouse

Individuals who have Down syndrome (trisomy 21) are at greatly increased risk of developing Alzheimer’s disease – dementia. Alzheimer’s disease is characterised by the accumulation in the brain of amyloid-β plaques that are a product of amyloid precursor protein, encoded by the APP gene on chromosome 21. In Down syndrome the first site of amyloid-β accumulation is within endosomes and changes to endosome biology occur early in disease. Here we determine if primary mouse embryonic fibroblasts isolated from two mouse models of Down syndrome can be used to study endosome and APP cell biology. We report that in these cellular models of Down syndrome endosome number, size and APP processing are not altered, likely because APP is not dosage sensitive in these models, despite three copies of App .

The Search for Biomarkers of Alzheimer's Disease in Down Syndrome

2020 ◽  
Vol 125 (2) ◽  
pp. 97-99 ◽  
Author(s):  
Benjamin L. Handen
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Down Syndrome ◽  
Longitudinal Study ◽  
High Risk ◽  
Amyloid Precursor Protein ◽  
Current Knowledge ◽  
Amyloid Β ◽  
Chromosome 21 ◽  
Increased Risk

Abstract Adults with Down syndrome are at high risk for Alzheimer's disease (AD), with most individuals developing clinical dementia by their late 60s. This increased risk for AD has been attributed, at least in part, to triplication and overexpression of the gene for amyloid precursor protein (APP) on chromosome 21, leading to elevated levels of amyloid β peptides. This article offers a brief overview of our current knowledge of AD in the DS population. In addition, information on a NIA/NICHD-funded, multicenter longitudinal study of biomarkers of AD in adults with DS is provided.

scholarly journals Genetic dissection of down syndrome-associated alterations in APP/amyloid-β biology using mouse models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Justin L. Tosh ◽  
◽  
Elena R. Rhymes ◽  
Paige Mumford ◽  
Heather T. Whittaker ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Down Syndrome ◽  
Amyloid Precursor Protein ◽  
Mouse Models ◽  
Early Onset ◽  
Amyloid Β ◽  
Chromosome 21 ◽  
Extra Copy ◽  
Early Onset Alzheimer’S Disease

AbstractIndividuals who have Down syndrome (caused by trisomy of chromosome 21), have a greatly elevated risk of early-onset Alzheimer’s disease, in which amyloid-β accumulates in the brain. Amyloid-β is a product of the chromosome 21 gene APP (amyloid precursor protein) and the extra copy or ‘dose’ of APP is thought to be the cause of this early-onset Alzheimer’s disease. However, other chromosome 21 genes likely modulate disease when in three-copies in people with Down syndrome. Here we show that an extra copy of chromosome 21 genes, other than APP, influences APP/Aβ biology. We crossed Down syndrome mouse models with partial trisomies, to an APP transgenic model and found that extra copies of subgroups of chromosome 21 gene(s) modulate amyloid-β aggregation and APP transgene-associated mortality, independently of changing amyloid precursor protein abundance. Thus, genes on chromosome 21, other than APP, likely modulate Alzheimer’s disease in people who have Down syndrome.

scholarly journals Genetic dissection of Down syndrome-associated alterations in APP/amyloid-β biology using mouse models

2020 ◽  
Author(s):  
Justin L. Tosh ◽  
Ellie Rhymes ◽  
Paige Mumford ◽  
Heather T. Whittaker ◽  
Laura J. Pulford ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Down Syndrome ◽  
Amyloid Precursor Protein ◽  
Mouse Models ◽  
Early Onset ◽  
Amyloid Β ◽  
Chromosome 21 ◽  
Extra Copy ◽  
Early Onset Alzheimer’S Disease

AbstractIndividuals who have Down syndrome (caused by trisomy of chromosome 21), have a greatly elevated risk of early-onset Alzheimer’s disease, in which amyloid-β accumulates in the brain. Amyloid-β is a product of the chromosome 21 gene APP (amyloid precursor protein) and the extra copy or ‘dose’ of APP is thought to be the cause of this early-onset Alzheimer’s disease. However, other chromosome 21 genes likely modulate disease when in three-copies in people with Down syndrome. Here we show that an extra copy of chromosome 21 genes, other than APP, influences APP/Aβ biology. We crossed Down syndrome mouse models with partial trisomies, to an APP transgenic model and found that extra copies of subgroups of chromosome 21 gene(s) modulate amyloid-β aggregation and APP transgene-associated mortality, independently of changing amyloid precursor protein abundance. Thus, genes on chromosome 21, other than APP, likely modulate Alzheimer’s disease in people who have Down syndrome.

scholarly journals Shotgun lipidomics of liver and brain tissue of Alzheimer’s disease model mice treated with acitretin

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anna A. Lauer ◽  
Daniel Janitschke ◽  
Malena dos Santos Guilherme ◽  
Vu Thu Thuy Nguyen ◽  
Cornel M. Bachmann ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurodegenerative Disorder ◽  
Amyloid Β ◽  
Lipid Homeostasis ◽  
Medical Surveillance ◽  
Shotgun Lipidomics ◽  
App Processing ◽  
Cognitive Improvement ◽  
The Impact

AbstractAlzheimer’s disease (AD) is a very frequent neurodegenerative disorder characterized by an accumulation of amyloid-β (Aβ). Acitretin, a retinoid-derivative and approved treatment for Psoriasis vulgaris, increases non-amyloidogenic Amyloid-Precursor-Protein-(APP)-processing, prevents Aβ-production and elicits cognitive improvement in AD mouse models. As an unintended side effect, acitretin could result in hyperlipidemia. Here, we analyzed the impact of acitretin on the lipidome in brain and liver tissue in the 5xFAD mouse-model. In line with literature, triglycerides were increased in liver accompanied by increased PCaa, plasmalogens and acyl-carnitines, whereas SM-species were decreased. In brain, these effects were partially enhanced or similar but also inverted. While for SM and plasmalogens similar effects were found, PCaa, TAG and acyl-carnitines showed an inverse effect in both tissues. Our findings emphasize, that potential pharmaceuticals to treat AD should be carefully monitored with respect to lipid-homeostasis because APP-processing itself modulates lipid-metabolism and medication might result in further and unexpected changes. Moreover, deducing effects of brain lipid-homeostasis from results obtained for other tissues should be considered cautiously. With respect to acitretin, the increase in brain plasmalogens might display a further positive probability in AD-treatment, while other results, such as decreased SM, indicate the need of medical surveillance for treated patients.

scholarly journals Polymorphisms inHSD17B1: Early Onset and Increased Risk of Alzheimer’s Disease in Women with Down Syndrome

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Joseph H. Lee ◽  
Susan Gurney ◽  
Deborah Pang ◽  
Alexis Temkin ◽  
Naeun Park ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Down Syndrome ◽  
Age At Onset ◽  
Nucleotide Polymorphisms ◽  
Risk Alleles ◽  
Increased Risk ◽  
Estrogen Activity ◽  
Intron 4

Background/Aims. Genetic variants that affect estrogen activity may influence the risk of Alzheimer's disease (AD). In women with Down syndrome, we examined the relation of polymorphisms in hydroxysteroid-17beta-dehydrogenase (HSD17B1) to age at onset and risk of AD.HSD17B1encodes the enzyme 17β-hydroxysteroid dehydrogenase (HSD1), which catalyzes the conversion of estrone to estradiol.Methods. Two hundred and thirty-eight women with DS, nondemented at baseline, 31–78 years of age, were followed at 14–18-month intervals for 4.5 years. Women were genotyped for 5 haplotype-tagging single-nucleotide polymorphisms (SNPs) in theHSD17B1gene region, and their association with incident AD was examined.Results. Age at onset was earlier, and risk of AD was elevated from two- to threefold among women homozygous for the minor allele at 3 SNPs in intron 4 (rs676387), exon 6 (rs605059), and exon 4 inCOASY(rs598126). Carriers of the haplotype TCC, based on the risk alleles for these three SNPs, had an almost twofold increased risk of developing AD (hazard ratio = 1.8, 95% CI, 1.1–3.1).Conclusion. These findings support experimental and clinical studies of the neuroprotective role of estrogen.

scholarly journals Neuronal aging potentiates beta-amyloid generation via amyloid precursor protein endocytosis

2019 ◽  
Author(s):  
Tatiana Burrinha ◽  
Ricardo Gomes ◽  
Ana Paula Terrasso ◽  
Cláudia Guimas Almeida
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Precursor Protein ◽  
Precursor Protein ◽  
App Processing ◽  
Early Endosomes ◽  
Primary Mouse ◽  
Β Amyloid ◽  
Aβ Production

AbstractAging increases the risk of Alzheimer’s disease (AD). During normal aging synapses decline and β-Amyloid (Aβ) accumulates. An Aβ defective clearance with aging is postulated as responsible for Aβ accumulation, although a role for increased Aβ production with aging can also lead to Aβ accumulation. To test this hypothesis, we established a long-term culture of primary mouse neurons that mimics neuronal aging (lysosomal lipofuscin accumulation and synapse decline). Intracellular endogenous Aβ42 accumulated in aged neurites due to increased amyloid-precursor protein (APP) processing. We show that APP processing is up-regulated by a specific age-dependent increase in APP endocytosis. Endocytosed APP accumulated in early endosomes that, in turn were found augmented in aged neurites. APP processing and early endosomes up-regulation was recapitulated in vivo. Finally, we found that inhibition of Aβ production reduced the decline in synapses in aged neurons. We propose that potentiation of APP endocytosis by neuronal aging increases Aβ production, which contributes to aging-dependent decline in synapses.SummaryHow aging increases the risk of Alzheimer’s disease is not clear. We show that normal neuronal aging increases the intracellular production of β-amyloid, due to an upregulation of the amyloid precursor protein endocytosis. Importantly, increased Aβ production contributes to the aging-dependent synapse loss.

scholarly journals Enhancing α-secretase Processing for Alzheimer’s Disease—A View on SFRP1

2020 ◽  
Vol 10 (2) ◽  
pp. 122 ◽  
Author(s):  
Bor Luen Tang
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Experimental Therapeutics ◽  
Related Protein ◽  
Endogenous Inhibitor ◽  
Aβ Peptides ◽  
App Processing ◽  
Promising Therapeutic Target ◽  
A Disintegrin And Metalloproteinase

Amyloid β (Aβ) peptides generated via sequential β- and γ-secretase processing of the amyloid precursor protein (APP) are major etiopathological agents of Alzheimer’s disease (AD). However, an initial APP cleavage by an α-secretase, such as the a disintegrin and metalloproteinase domain-containing protein ADAM10, precludes β-secretase cleavage and leads to APP processing that does not produce Aβ. The latter appears to underlie the disease symptom-attenuating effects of a multitude of experimental therapeutics in AD animal models. Recent work has indicated that an endogenous inhibitor of ADAM10, secreted-frizzled-related protein 1 (SFRP1), is elevated in human AD brains and associated with amyloid plaques in mouse AD models. Importantly, genetic or functional attenuation of SFRP1 lowered Aβ accumulation and improved AD-related histopathological and neurological traits. Given SFRP1′s well-known activity in attenuating Wnt signaling, which is also commonly impaired in AD, SFRP1 appears to be a promising therapeutic target for AD. This idea, however, needs to be addressed with care because of cancer enhancement potentials resulting from a systemic loss of SFRP1 activity, as well as an upregulation of ADAM10 activity. In this focused review, I shall discuss α-secretase-effected APP processing in AD with a focus on SFRP1, and explore the contrasting perspectives arising from the recent findings.

Identification of chromosome 21 DNA polymorphisms for genetic studies in Alzheimer's disease and Down syndrome

1991 ◽  
Vol 87 (6) ◽  
pp. 649-653 ◽  
Author(s):  
G. Van Camp ◽  
H. Backhovens ◽  
M. Cruts ◽  
A. Wehnert ◽  
W. Van Hul ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Down Syndrome ◽  
Chromosome 21 ◽  
Dna Polymorphisms ◽  
Genetic Studies

scholarly journals Phosphorylation Signaling in APP Processing in Alzheimer’s Disease

2019 ◽  
Vol 21 (1) ◽  
pp. 209 ◽  
Author(s):  
Tao Zhang ◽  
Dongmei Chen ◽  
Tae Ho Lee
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Signaling Pathways ◽  
Physiological Function ◽  
Amyloid Β ◽  
Proteolytic Processing ◽  
App Processing ◽  
Abnormal Accumulation ◽  
The Central Nervous System ◽  
The Brain

The abnormal accumulation of amyloid-β (Aβ) in the central nervous system is a hallmark of Alzheimer’s disease (AD). The regulation of the processing of the single- transmembrane amyloid precursor protein (APP) plays an important role in the generation of Aβ in the brain. The phosphorylation of APP and key enzymes involved in the proteolytic processing of APP has been demonstrated to be critical for modulating the generation of Aβ by either altering the subcellular localization of APP or changing the enzymatic activities of the secretases responsible for APP processing. In addition, the phosphorylation may also have an impact on the physiological function of these proteins. In this review, we summarize the kinases and signaling pathways that may participate in regulating the phosphorylation of APP and secretases and how this further affects the function and processing of APP and Aβ pathology. We also discuss the potential of approaches that modulate these phosphorylation-signaling pathways or kinases as interventions for AD pathology.

Therapeutic Strategies Targeting Amyloid-β in Alzheimer’s Disease

2019 ◽  
Vol 16 (5) ◽  
pp. 418-452 ◽  
Author(s):  
Lídia Pinheiro ◽  
Célia Faustino
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Protein Misfolding ◽  
Neurodegenerative Disorder ◽  
Neuronal Degeneration ◽  
Senile Plaques ◽  
Symptomatic Relief ◽  
Amyloid Β ◽  
Therapeutic Strategies ◽  
App Processing

Alzheimer’s disease (AD) is a neurodegenerative disorder linked to protein misfolding and aggregation. AD is pathologically characterized by senile plaques formed by extracellular Amyloid-β (Aβ) peptide and Intracellular Neurofibrillary Tangles (NFT) formed by hyperphosphorylated tau protein. Extensive synaptic loss and neuronal degeneration are responsible for memory impairment, cognitive decline and behavioral dysfunctions typical of AD. Amyloidosis has been implicated in the depression of acetylcholine synthesis and release, overactivation of N-methyl-D-aspartate (NMDA) receptors and increased intracellular calcium levels that result in excitotoxic neuronal degeneration. Current drugs used in AD treatment are either cholinesterase inhibitors or NMDA receptor antagonists; however, they provide only symptomatic relief and do not alter the progression of the disease. Aβ is the product of Amyloid Precursor Protein (APP) processing after successive cleavage by β- and γ-secretases while APP proteolysis by α-secretase results in non-amyloidogenic products. According to the amyloid cascade hypothesis, Aβ dyshomeostasis results in the accumulation and aggregation of Aβ into soluble oligomers and insoluble fibrils. The former are synaptotoxic and can induce tau hyperphosphorylation while the latter deposit in senile plaques and elicit proinflammatory responses, contributing to oxidative stress, neuronal degeneration and neuroinflammation. Aβ-protein-targeted therapeutic strategies are thus a promising disease-modifying approach for the treatment and prevention of AD. This review summarizes recent findings on Aβ-protein targeted AD drugs, including β-secretase inhibitors, γ-secretase inhibitors and modulators, α-secretase activators, direct inhibitors of Aβ aggregation and immunotherapy targeting Aβ, focusing mainly on those currently under clinical trials.

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