scholarly journals Protein contributions to brain atrophy acceleration in Alzheimer’s disease and primary age-related tauopathy

Brain ◽  
2020 ◽  
Vol 143 (11) ◽  
pp. 3463-3476
Author(s):  
Keith A Josephs ◽  
Peter R Martin ◽  
Stephen D Weigand ◽  
Nirubol Tosakulwong ◽  
Marina Buciuc ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Brain Atrophy ◽  
Neurofibrillary Tangle ◽  
Amyloid Β ◽  
Brain Regions ◽  
Hippocampal Atrophy ◽  
Brain Volumes ◽  
Age Related ◽  
Over Time

Abstract Alzheimer’s disease is characterized by the presence of amyloid-β and tau deposition in the brain, hippocampal atrophy and increased rates of hippocampal atrophy over time. Another protein, TAR DNA binding protein 43 (TDP-43) has been identified in up to 75% of cases of Alzheimer’s disease. TDP-43, tau and amyloid-β have all been linked to hippocampal atrophy. TDP-43 and tau have also been linked to hippocampal atrophy in cases of primary age-related tauopathy, a pathological entity with features that strongly overlap with those of Alzheimer’s disease. At present, it is unclear whether and how TDP-43 and tau are associated with early or late hippocampal atrophy in Alzheimer’s disease and primary age-related tauopathy, whether either protein is also associated with faster rates of atrophy of other brain regions and whether there is evidence for protein-associated acceleration/deceleration of atrophy rates. We therefore aimed to model how these proteins, particularly TDP-43, influence non-linear trajectories of hippocampal and neocortical atrophy in Alzheimer’s disease and primary age-related tauopathy. In this longitudinal retrospective study, 557 autopsied cases with Alzheimer’s disease neuropathological changes with 1638 ante-mortem volumetric head MRI scans spanning 1.0–16.8 years of disease duration prior to death were analysed. TDP-43 and Braak neurofibrillary tangle pathological staging schemes were constructed, and hippocampal and neocortical (inferior temporal and middle frontal) brain volumes determined using longitudinal FreeSurfer. Bayesian bivariate-outcome hierarchical models were utilized to estimate associations between proteins and volume, early rate of atrophy and acceleration in atrophy rates across brain regions. High TDP-43 stage was associated with smaller cross-sectional brain volumes, faster rates of brain atrophy and acceleration of atrophy rates, more than a decade prior to death, with deceleration occurring closer to death. Stronger associations were observed with hippocampus compared to temporal and frontal neocortex. Conversely, low TDP-43 stage was associated with slower early rates but later acceleration. This later acceleration was associated with high Braak neurofibrillary tangle stage. Somewhat similar, but less striking, findings were observed between TDP-43 and neocortical rates. Braak stage appeared to have stronger associations with neocortex compared to TDP-43. The association between TDP-43 and brain atrophy occurred slightly later in time (∼3 years) in cases of primary age-related tauopathy compared to Alzheimer’s disease. The results suggest that TDP-43 and tau have different contributions to acceleration and deceleration of brain atrophy rates over time in both Alzheimer’s disease and primary age-related tauopathy.

Alzheimer's Disease-Like Pathologies and Cognitive Impairments Induced by Formaldehyde in Non-Human Primates

2018 ◽  
Vol 15 (14) ◽  
pp. 1304-1321 ◽  
Author(s):  
Rongwei Zhai ◽  
Joshua Rizak ◽  
Na Zheng ◽  
Xiaping He ◽  
Zhenhui Li ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Tau Protein ◽  
Spatial Working Memory ◽  
Cognitive Impairments ◽  
Neurofibrillary Tangle ◽  
Amyloid Β ◽  
Histopathological Analysis ◽  
Related Factor ◽  
Age Related

Background: Formaldehyde (FA) has been implicated in Alzheimer’s disease (AD) pathology as an age-related factor and as a protein cross-linker known to aggregate Amyloid-Beta (Aβ) and tau protein in vitro. Higher levels of FA have also been found in patients with greater cognitive impairment and in AD patient brains. Objective: To directly evaluate the effect of chronically elevated FA levels on the primate brain with respect to AD pathological markers. Method: Young rhesus macaques (5-8 yrs, without AD related mutations) were given chronic intracerebroventricular (i.c.v.) injections of FA or vehicle over a 12-month period. Monkeys were monitored for changes in cognitive ability and evaluated post-mortem for common AD pathological markers. Results: Monkeys injected with FA were found to have significant spatial working memory impairments. Histopathological analysis revealed the presence of amyloid-β+ neuritic-like plaques, neurofibrillary tangle-like formations, increased tau protein phosphorylation, neuronal loss and reactive gliosis in three memory (and AD) related brain areas (the hippocampus, entorhinal cortex and prefrontal cortex (PFC)) of monkeys receiving i.c.v. injections of FA. ELISA assays revealed that the amounts of pT181 and Aβ42 were markedly higher in the PFC and hippocampus of FA treated monkeys. Conclusion: FA was found to induce major AD-like pathological markers and cognitive impairments in young rhesus monkeys independent of genetic predispositions. This suggests FA may play a significant role in the initiation and progression of the disease.

scholarly journals Disruption of a RAC1-centred network is associated with Alzheimer’s disease pathology and causes age-dependent neurodegeneration

2020 ◽  
Vol 29 (5) ◽  
pp. 817-833 ◽  
Author(s):  
Masataka Kikuchi ◽  
Michiko Sekiya ◽  
Norikazu Hara ◽  
Akinori Miyashita ◽  
Ryozo Kuwano ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Genetic Model ◽  
Neurofibrillary Tangle ◽  
Neuronal Cell ◽  
Brain Regions ◽  
Protein Domain ◽  
Expression Data ◽  
Integrated Network ◽  
Age Dependent

Abstract The molecular biological mechanisms of Alzheimer’s disease (AD) involve disease-associated crosstalk through many genes and include a loss of normal as well as a gain of abnormal interactions among genes. A protein domain network (PDN) is a collection of physical bindings that occur between protein domains, and the states of the PDNs in patients with AD are likely to be perturbed compared to those in normal healthy individuals. To identify PDN changes that cause neurodegeneration, we analysed the PDNs that occur among genes co-expressed in each of three brain regions at each stage of AD. Our analysis revealed that the PDNs collapsed with the progression of AD stage and identified five hub genes, including Rac1, as key players in PDN collapse. Using publicly available as well as our own gene expression data, we confirmed that the mRNA expression level of the RAC1 gene was downregulated in the entorhinal cortex (EC) of AD brains. To test the causality of these changes in neurodegeneration, we utilized Drosophila as a genetic model and found that modest knockdown of Rac1 in neurons was sufficient to cause age-dependent behavioural deficits and neurodegeneration. Finally, we identified a microRNA, hsa-miR-101-3p, as a potential regulator of RAC1 in AD brains. As the Braak neurofibrillary tangle (NFT) stage progressed, the expression levels of hsa-miR-101-3p were increased specifically in the EC. Furthermore, overexpression of hsa-miR-101-3p in the human neuronal cell line SH-SY5Y caused RAC1 downregulation. These results highlight the utility of our integrated network approach for identifying causal changes leading to neurodegeneration in AD.

scholarly journals Reported Hearing Loss in Alzheimer’s Disease Is Associated With Loss of Brainstem and Cerebellar Volume

2021 ◽  
Vol 15 ◽  
Author(s):  
Daniel A. Llano ◽  
Susanna S. Kwok ◽  
Viswanath Devanarayan ◽  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Hearing Loss ◽  
Normal Subjects ◽  
Neural Substrates ◽  
Epidemiological Studies ◽  
Brain Regions ◽  
Pathological State ◽  
Brain Volumes ◽  
The Relationship

Multiple epidemiological studies have revealed an association between presbycusis and Alzheimer’s Disease (AD). Unfortunately, the neurobiological underpinnings of this relationship are not clear. It is possible that the two disorders share a common, as yet unidentified, risk factor, or that hearing loss may independently accelerate AD pathology. Here, we examined the relationship between reported hearing loss and brain volumes in normal, mild cognitive impairment (MCI) and AD subjects using a publicly available database. We found that among subjects with AD, individuals that reported hearing loss had smaller brainstem and cerebellar volumes in both hemispheres than individuals without hearing loss. In addition, we found that these brain volumes diminish in size more rapidly among normal subjects with reported hearing loss and that there was a significant interaction between cognitive diagnosis and the relationship between reported hearing loss and these brain volumes. These data suggest that hearing loss is linked to brainstem and cerebellar pathology, but only in the context of the pathological state of AD. We hypothesize that the presence of AD-related pathology in both the brainstem and cerebellum creates vulnerabilities in these brain regions to auditory deafferentation-related atrophy. These data have implications for our understanding of the potential neural substrates for interactions between hearing loss and AD.

The Trajectory of Cerebrospinal Fluid Growth-Associated Protein 43 in the Alzheimer’s Disease Continuum: A Longitudinal Study

2021 ◽  
pp. 1-12
Author(s):  
Heng Zhang ◽  
Diyang Lyu ◽  
Jianping Jia ◽  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cerebrospinal Fluid ◽  
Amyloid Β ◽  
Dementia Patients ◽  
Positron Emission ◽  
Potential Biomarker ◽  
Synaptic Degeneration ◽  
Over Time

Background: Synaptic degeneration has been suggested as an early pathological event that strongly correlates with severity of dementia in Alzheimer’s disease (AD). However, changes in longitudinal cerebrospinal fluid (CSF) growth-associated protein 43 (GAP-43) as a synaptic biomarker in the AD continuum remain unclear. Objective: To assess the trajectory of CSF GAP-43 with AD progression and its association with other AD hallmarks. Methods: CSF GAP-43 was analyzed in 788 participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), including 246 cognitively normal (CN) individuals, 415 individuals with mild cognitive impairment (MCI), and 127 with AD dementia based on cognitive assessments. The associations between a multimodal classification scheme with amyloid-β (Aβ), tau, and neurodegeneration, and changes in CSF GAP-43 over time were also analyzed. Results: CSF GAP-43 levels were increased at baseline in MCI and dementia patients, and increased significantly over time in the preclinical (Aβ-positive CN), prodromal (Aβ-positive MCI), and dementia (Aβ-positive dementia) stages of AD. Higher levels of CSF GAP-43 were also associated with higher CSF phosphorylated tau (p-tau) and total tau (t-tau), cerebral amyloid deposition and hypometabolism on positron emission tomography, the hippocampus and middle temporal atrophy, and cognitive performance deterioration at baseline and follow-up. Furthermore, CSF GAP-43 may assist in effectively predicting the probability of dementia onset at 2- or 4-year follow-up. Conclusion: CSF GAP-43 can be used as a potential biomarker associated with synaptic degeneration in subjects with AD; it may also be useful for tracking the disease progression and for monitoring the effects of clinical trials.

scholarly journals Suppression of AMD-Like Pathology by Mitochondria-Targeted Antioxidant SkQ1 Is Associated with a Decrease in the Accumulation of Amyloid β and in mTOR Activity

Antioxidants ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 177 ◽  
Author(s):  
Natalia A. Muraleva ◽  
Oyuna S. Kozhevnikova ◽  
Anzhela Z. Fursova ◽  
Nataliya G. Kolosova
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Developed Countries ◽  
Term Treatment ◽  
Age Related Macular Degeneration ◽  
Eye Health ◽  
Age Related ◽  
Long Term Treatment

Age-related macular degeneration (AMD) is a major cause of irreversible visual impairment and blindness in developed countries, and the molecular pathogenesis of AMD is poorly understood. Recent studies strongly indicate that amyloid β (Aβ) accumulation —found in the brain and a defining feature of Alzheimer’s disease—also forms in the retina in both Alzheimer’s disease and AMD. The reason why highly neurotoxic proteins of consistently aggregate in the aging retina, and to what extent they contribute to AMD, remains to be fully addressed. Nonetheless, the hypothesis that Aβ is a therapeutic target in AMD is debated. Here, we showed that long-term treatment with SkQ1 (250 nmol/[kg body weight] daily from the age of 1.5 to 22 months) suppressed the development of AMD-like pathology in senescence-accelerated OXYS rats by reducing the level of Aβ and suppressing the activity of mTOR in the retina. Inhibition of mTOR signaling activity, which plays key roles in aging and age-related diseases, can be considered a new mechanism of the prophylactic effect of SkQ1. It seems probable that dietary supplementation with mitochondria-targeted antioxidant SkQ1 can be a good prevention strategy to maintain eye health and possibly a treatment of AMD.

scholarly journals Repositioning of Immunomodulators: A Ray of Hope for Alzheimer’s Disease?

2020 ◽  
Vol 14 ◽  
Author(s):  
Antonio Munafò ◽  
Chiara Burgaletto ◽  
Giulia Di Benedetto ◽  
Marco Di Mauro ◽  
Rosaria Di Mauro ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Immune System ◽  
Neurodegenerative Disorder ◽  
Drug Repositioning ◽  
Amyloid Β ◽  
Deep Understanding ◽  
Current Status ◽  
Age Related ◽  
Tnf Α

Alzheimer’s disease (AD) is the most common age-related neurodegenerative disorder characterized by cognitive decline and by the presence of amyloid β plaques and neurofibrillary tangles in the brain. Despite recent advances in understanding its pathophysiological mechanisms, to date, there are no disease-modifying therapeutic options, to slow or halt the evolution of neurodegenerative processes in AD. Current pharmacological treatments only transiently mitigate the severity of symptoms, with modest or null overall improvement. Emerging evidence supports the concept that AD is affected by the impaired ability of the immune system to restrain the brain’s pathology. Deep understanding of the relationship between the nervous and the immune system may provide a novel arena to develop effective and safe drugs for AD treatment. Considering the crucial role of inflammatory/immune pathways in AD, here we discuss the current status of the immuno-oncological, immunomodulatory and anti-TNF-α drugs which are being used in preclinical studies or in ongoing clinical trials by means of the drug-repositioning approach.

scholarly journals Neuron loss associated with age but not Alzheimer's disease pathology in the chimpanzee brain

2020 ◽  
Vol 375 (1811) ◽  
pp. 20190619 ◽  
Author(s):  
Melissa K. Edler ◽  
Emily L. Munger ◽  
Richard S. Meindl ◽  
William D. Hopkins ◽  
John J. Ely ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurofibrillary Tangle ◽  
Cell Loss ◽  
Tau Proteins ◽  
Middle Temporal Gyrus ◽  
Neuron Death ◽  
Neuron Loss ◽  
Neuron Density ◽  
Age Related

In the absence of disease, ageing in the human brain is accompanied by mild cognitive dysfunction, gradual volumetric atrophy, a lack of significant cell loss, moderate neuroinflammation, and an increase in the amyloid beta (A β ) and tau proteins. Conversely, pathologic age-related conditions, particularly Alzheimer's disease (AD), result in extensive neocortical and hippocampal atrophy, neuron death, substantial A β plaque and tau-associated neurofibrillary tangle pathologies, glial activation and severe cognitive decline. Humans are considered uniquely susceptible to neurodegenerative disorders, although recent studies have revealed A β and tau pathology in non-human primate brains. Here, we investigate the effect of age and AD-like pathology on cell density in a large sample of postmortem chimpanzee brains ( n = 28, ages 12–62 years). Using a stereologic, unbiased design, we quantified neuron density, glia density and glia:neuron ratio in the dorsolateral prefrontal cortex, middle temporal gyrus, and CA1 and CA3 hippocampal subfields. Ageing was associated with decreased CA1 and CA3 neuron densities, while AD pathologies were not correlated with changes in neuron or glia densities. Differing from cerebral ageing and AD in humans, these data indicate that chimpanzees exhibit regional neuron loss with ageing but appear protected from the severe cell death found in AD. This article is part of the theme issue ‘Evolution of the primate ageing process’.

Commentary on: L-Methylfolate, Methylcobolamine, and N-Acetylcysteine in the Treatment of Alzheimer's Disease-Related Cognitive Decline

CNS Spectrums ◽  
2010 ◽  
Vol 15 (S1) ◽  
pp. 7-7 ◽  
Author(s):  
Jeffrey L Cummings
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Methylation Status ◽  
Neurofibrillary Tangle ◽  
Amyloid Β ◽  
Vitamin B ◽  
Amyloid Β Protein ◽  
In Vivo Models ◽  
The Impact

Drs. McCaddon and Hudson provide a thorough review of the multiple ways in which vitamin B12, vitamin B6, folate, and homocysteine (Hey) are implicated in the pathogenesis of Alzheimer's disease (AD). They noted that Hey is more often elevated in AD and in mild cognitive impairment (MCI) than in cognitively healthy elderly; phosphatases needed to limit tau hyperphosphoryalation and neurofibrillary tangle formation require methylation and are dependent on folate and methylation status; cerebrospinal fluid (CSF) tau levels correlated with markers of methylation status; reduced folate and B12 levels lead to increase β-secretase and pesenilin 1 (PS1) actions leading to greater amyloid-β production in in vitro models; elevated Hey levels in rates are associated with increased PS1 activity and spatial memory deficits that are reversed following treatment with B12 and folate; raised Hey levels in vitro increase amyloid-β protein neurotoxicity; methylation impacts transmitters and transmitter function relevant to AD; in cultured neurons, Hey induces injury in DNA and stimulates cell death pathways. B12 deficiency leads to accumulation of methyl malonic acid, which inhibits mitochondrial function and may compromise energy generation and impair maintenance of synaptic plasticity. Methylation abnormalities result in excessive generation of reactive oxygen species that contribute importantly to cell injury. Biomarkers of oxidative injury, such as isoprostanes, are elevated in AD and suggest excess oxidation. Thus, there are multiple pathways through which deficient methylation may contribute to AD. In some cases, the observations are derived from models with B12 or folate deficiency and some in vitro observations have not been tested in in vivo models. There are no biomarkers specific to some of the pathways implicated and the magnitude of the impact of the deficiency or its treatment has not been established for all the relationships. Two open-label experiments in early- and late-stage AD patients have suggested benefit.

scholarly journals Amyloid-β dimers in the absence of plaque pathology impair learning and synaptic plasticity

Brain ◽  
2015 ◽  
Vol 139 (2) ◽  
pp. 509-525 ◽  
Author(s):  
Andreas Müller-Schiffmann ◽  
Arne Herring ◽  
Laila Abdel-Hafiz ◽  
Aisa N. Chepkova ◽  
Sandra Schäble ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Synaptic Plasticity ◽  
Learning And Memory ◽  
Biological Effects ◽  
Amyloid Β ◽  
Long Term Potentiation ◽  
Amyloid Β Peptide ◽  
Age Related ◽  
Plaque Pathology

Abstract Despite amyloid plaques, consisting of insoluble, aggregated amyloid-β peptides, being a defining feature of Alzheimer’s disease, their significance has been challenged due to controversial findings regarding the correlation of cognitive impairment in Alzheimer’s disease with plaque load. The amyloid cascade hypothesis defines soluble amyloid-β oligomers, consisting of multiple amyloid-β monomers, as precursors of insoluble amyloid-β plaques. Dissecting the biological effects of single amyloid-β oligomers, for example of amyloid-β dimers, an abundant amyloid-β oligomer associated with clinical progression of Alzheimer’s disease, has been difficult due to the inability to control the kinetics of amyloid-β multimerization. For investigating the biological effects of amyloid-β dimers, we stabilized amyloid-β dimers by an intermolecular disulphide bridge via a cysteine mutation in the amyloid-β peptide (Aβ-S8C) of the amyloid precursor protein. This construct was expressed as a recombinant protein in cells and in a novel transgenic mouse, termed tgDimer mouse. This mouse formed constant levels of highly synaptotoxic soluble amyloid-β dimers, but not monomers, amyloid-β plaques or insoluble amyloid-β during its lifespan. Accordingly, neither signs of neuroinflammation, tau hyperphosphorylation or cell death were observed. Nevertheless, these tgDimer mice did exhibit deficits in hippocampal long-term potentiation and age-related impairments in learning and memory, similar to what was observed in classical Alzheimer’s disease mouse models. Although the amyloid-β dimers were unable to initiate the formation of insoluble amyloid-β aggregates in tgDimer mice, after crossbreeding tgDimer mice with the CRND8 mouse, an amyloid-β plaque generating mouse model, Aβ-S8C dimers were sequestered into amyloid-β plaques, suggesting that amyloid-β plaques incorporate neurotoxic amyloid-β dimers that by themselves are unable to self-assemble. Our results suggest that within the fine interplay between different amyloid-β species, amyloid-β dimer neurotoxic signalling, in the absence of amyloid-β plaque pathology, may be involved in causing early deficits in synaptic plasticity, learning and memory that accompany Alzheimer’s disease. 10.1093/brain/awv355_video_abstract awv355_video_abstract

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