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Journal of Alzheimer's Disease : JAD 2024A hypothesis of Alzheimer's disease etiology is proposed describing how cellular stress induces excessive polyamine synthesis and recycling which can disrupt nucleoli....
A hypothesis of Alzheimer's disease etiology is proposed describing how cellular stress induces excessive polyamine synthesis and recycling which can disrupt nucleoli. Polyamines are essential in nucleolar functions, such as RNA folding and ribonucleoprotein assembly. Changes in the nucleolar pool of anionic RNA and cationic polyamines acting as counterions can cause significant nucleolar dynamics. Polyamine synthesis reduces S-adenosylmethionine which, at low levels, triggers tau phosphorylation. Also, polyamine recycling reduces acetyl-CoA needed for acetylcholine, which is low in Alzheimer's disease. Extraordinary nucleolar expansion and/or contraction can disrupt epigenetic control in peri-nucleolar chromatin, such as chromosome 14 with the presenilin-1 gene; chromosome 21 with the amyloid precursor protein gene; chromosome 17 with the tau gene; chromosome 19 with the APOE4 gene; and the inactive X chromosome (Xi; aka "nucleolar satellite") with normally silent spermine synthase (polyamine synthesis) and spermidine/spermine-N1-acetyltransferase (polyamine recycling) alleles. Chromosomes 17, 19 and the Xi have high concentrations of Alu elements which can be transcribed by RNA polymerase III if positioned nucleosomes are displaced from the Alu elements. A sudden flood of Alu RNA transcripts can competitively bind nucleolin which is usually bound to Alu sequences in structural RNAs that stabilize the nucleolar heterochromatic shell. This Alu competition leads to loss of nucleolar integrity with leaking of nucleolar polyamines that cause aggregation of phosphorylated tau. The hypothesis was developed with key word searches (e.g., PubMed) using relevant terms (e.g., Alzheimer's, lupus, nucleolin) based on a systems biology approach and exploring autoimmune disease tautology, gaining synergistic insights from other diseases.
Topics: Humans; Polyamines; Alzheimer Disease; Cell Nucleolus; Autoimmune Diseases; RNA
PubMed: 38489184
DOI: 10.3233/JAD-231184 -
Neural Regeneration Research Oct 2024JOURNAL/nrgr/04.03/01300535-202410000-00029/figure1/v/2024-02-06T055622Z/r/image-tiff Disturbances in the microbiota-gut-brain axis may contribute to the development of...
JOURNAL/nrgr/04.03/01300535-202410000-00029/figure1/v/2024-02-06T055622Z/r/image-tiff Disturbances in the microbiota-gut-brain axis may contribute to the development of Alzheimer's disease. Magnesium-L-threonate has recently been found to have protective effects on learning and memory in aged and Alzheimer's disease model mice. However, the effects of magnesium-L-threonate on the gut microbiota in Alzheimer's disease remain unknown. Previously, we reported that magnesium-L-threonate treatment improved cognition and reduced oxidative stress and inflammation in a double-transgenic line of Alzheimer's disease model mice expressing the amyloid-β precursor protein and mutant human presenilin 1 (APP/PS1). Here, we performed 16S rRNA amplicon sequencing and liquid chromatography-mass spectrometry to analyze changes in the microbiome and serum metabolome following magnesium-L-threonate exposure in a similar mouse model. Magnesium-L-threonate modulated the abundance of three genera in the gut microbiota, decreasing Allobaculum and increasing Bifidobacterium and Turicibacter. We also found that differential metabolites in the magnesium-L-threonate-regulated serum were enriched in various pathways associated with neurodegenerative diseases. The western blotting detection on intestinal tight junction proteins (zona occludens 1, occludin, and claudin-5) showed that magnesium-L-threonate repaired the intestinal barrier dysfunction of APP/PS1 mice. These findings suggest that magnesium-L-threonate may reduce the clinical manifestations of Alzheimer's disease through the microbiota-gut-brain axis in model mice, providing an experimental basis for the clinical treatment of Alzheimer's disease.
PubMed: 38488562
DOI: 10.4103/1673-5374.391310 -
International Journal of Molecular... Feb 2024Alzheimer's disease (AD), the leading cause of dementia, presents a significant global health challenge with no known cure to date. Central to our understanding of AD... (Review)
Review
Alzheimer's disease (AD), the leading cause of dementia, presents a significant global health challenge with no known cure to date. Central to our understanding of AD pathogenesis is the β-amyloid cascade hypothesis, which underlies drug research and discovery efforts. Despite extensive studies, no animal models of AD have completely validated this hypothesis. Effective AD models are essential for accurately replicating key pathological features of the disease, notably the formation of β-amyloid plaques and neurofibrillary tangles. These pathological markers are primarily driven by mutations in the amyloid precursor protein (APP) and presenilin 1 (PS1) genes in familial AD (FAD) and by tau protein mutations for the tangle pathology. Transgenic mice models have been instrumental in AD research, heavily relying on the overexpression of mutated APP genes to simulate disease conditions. However, these models do not entirely replicate the human condition of AD. This review aims to provide a comprehensive evaluation of the historical and ongoing research efforts in AD, particularly through the use of transgenic mice models. It is focused on the benefits gathered from these transgenic mice models in understanding β-amyloid toxicity and the broader biological underpinnings of AD. Additionally, the review critically assesses the application of these models in the preclinical testing of new therapeutic interventions, highlighting the gap between animal models and human clinical realities. This analysis underscores the need for refinement in AD research methodologies to bridge this gap and enhance the translational value of preclinical studies.
Topics: Mice; Animals; Humans; Alzheimer Disease; Mice, Transgenic; Disease Models, Animal; tau Proteins; Amyloid beta-Protein Precursor; Amyloid beta-Peptides; Presenilin-1; Plaque, Amyloid
PubMed: 38474051
DOI: 10.3390/ijms25052805 -
International Journal of Molecular... Feb 2024Several genetic variants that affect microglia function have been identified as risk factors for Alzheimer's Disease (AD), supporting the importance of this cell type in...
Several genetic variants that affect microglia function have been identified as risk factors for Alzheimer's Disease (AD), supporting the importance of this cell type in disease progression. However, the effect of autosomal dominant mutations in the amyloid precursor protein () or the presenilin () genes has not been addressed in microglia in vivo. We xenotransplanted human microglia derived from non-carriers and carriers of autosomal dominant AD (ADAD)-causing mutations in the brain of hCSF1 WT or 5XFAD mice. We observed that ADAD mutations in microglia are not sufficient to trigger amyloid pathology in WT mice. In 5XFAD mice, we observed a non-statistically significant increase in amyloid plaque volume and number of dystrophic neurites, coupled with a reduction in plaque-associated microglia in the brain of mice xenotransplanted with ADAD human microglia compared to mice xenotransplanted with non-ADAD microglia. In addition, we observed a non-statistically significant impairment in working and contextual memory in 5XFAD mice xenotransplanted with ADAD microglia compared to those xenotransplanted with non-ADAD-carrier microglia. We conclude that, although not sufficient to initiate amyloid pathology in the healthy brain, mutations in and in human microglia might cause mild changes in pathological and cognitive outcomes in 5XFAD mice in a manner consistent with increased AD risk.
Topics: Humans; Animals; Mice; Alzheimer Disease; Microglia; Amyloidogenic Proteins; Amyloid beta-Protein Precursor; Mutation; Plaque, Amyloid; Presenilin-1; Amyloid beta-Peptides; Mice, Transgenic; Disease Models, Animal
PubMed: 38473822
DOI: 10.3390/ijms25052565 -
International Journal of Molecular... Feb 2024Alzheimer's disease (AD) is the leading cause of dementia and is characterized by a presence of amyloid plaques, composed mostly of the amyloid-β (Aβ) peptides, in the...
Alzheimer's disease (AD) is the leading cause of dementia and is characterized by a presence of amyloid plaques, composed mostly of the amyloid-β (Aβ) peptides, in the brains of AD patients. The peptides are generated from the amyloid precursor protein (APP), which undergoes a sequence of cleavages, referred as trimming, performed by γ-secretase. Here, we investigated conformational changes in a series of β-amyloid substrates (from less and more amyloidogenic pathways) in the active site of presenilin-1, the catalytic subunit of γ-secretase. The substrates are trimmed every three residues, finally leading to Aβ and Aβ, which are the major components of amyloid plaques. To study conformational changes, we employed all-atom molecular dynamics simulations, while for unfolding, we used steered molecular dynamics simulations in an implicit membrane-water environment to accelerate changes. We have found substantial differences in the flexibility of extended C-terminal parts between more and less amyloidogenic pathway substrates. We also propose that the positively charged residues of presenilin-1 may facilitate the stretching and unfolding of substrates. The calculated forces and work/energy of pulling were exceptionally high for Aβ, indicating why trimming of this substrate is so infrequent.
Topics: Humans; Amyloid Precursor Protein Secretases; Presenilin-1; Catalytic Domain; Plaque, Amyloid; Amyloid beta-Peptides; Alzheimer Disease
PubMed: 38473811
DOI: 10.3390/ijms25052564 -
BioRxiv : the Preprint Server For... Feb 2024PDZ domain mediated interactions with voltage-gated calcium (Ca ) channel C-termini play important roles in localizing and compartmentalizing membrane Ca signaling....
PDZ domain mediated interactions with voltage-gated calcium (Ca ) channel C-termini play important roles in localizing and compartmentalizing membrane Ca signaling. The first such interaction discovered was between the neuronal multi-domain protein Mint-1, and the presynaptc calcium channel Ca 2.2 in mammals. Although the physiological significance of this interaction is unclear, its occurrence in vertebrates and bilaterian invertebrates suggests important and conserved functions. In this study, we explore the evolutionary origins of Mint and its interaction with Ca 2 channels. Phylogenetic and structural in silico analyses revealed that Mint is an animal-specific gene, like Ca 2 channels, which bears a highly divergent N-terminus but strongly conserved C-terminus comprised of a phosphotyrosine binding domain, two tandem PDZ domains (PDZ-1 and PDZ-2), and a C-terminal auto-inhibitory element that binds and inhibits PDZ-1. Also deeply conserved are other Mint interacting proteins, namely amyloid precursor and related proteins, presenilins, neurexin, as well as CASK and Veli which form a tripartite complex with Mint in bilaterians. Through yeast 2-hybrid and bacterial 2-hybrid experiments, we show that Mint and Ca 2 channels from cnidarians and placozoans interact , and hybridization revealed co-expression of corresponding transcripts in dissociated neurons from the cnidarian . Unexpectedly, the Mint orthologue from the ctenophore was able to strongly bind the divergent C-terminal ligands of cnidarian and placozoan Ca 2 channels, despite neither the ctenophore Mint, nor the placozoan and cnidarian orthologues, binding the ctenophore Ca 2 channel C-terminus. Altogether, our analyses provide a model for the emergence of this interaction in early animals first via adoption of a PDZ ligand by Ca 2 channels, followed by sequence changes in the ligand that caused a modality switch for binding to Mint.
PubMed: 38463976
DOI: 10.1101/2024.02.26.582151 -
Aging Cell May 2024Although studies have demonstrated that genome instability is accumulated in patients with Alzheimer's disease (AD), the specific types of genome instability linked to...
Telomere length and micronuclei trajectories in APP/PS1 mouse model of Alzheimer's disease: Correlating with cognitive impairment and brain amyloidosis in a sexually dimorphic manner.
Although studies have demonstrated that genome instability is accumulated in patients with Alzheimer's disease (AD), the specific types of genome instability linked to AD pathogenesis remain poorly understood. Here, we report the first characterization of the age- and sex-related trajectories of telomere length (TL) and micronuclei in APP/PS1 mice model and wild-type (WT) controls (C57BL/6). TL was measured in brain (prefrontal cortex, cerebellum, pituitary gland, and hippocampus), colon and skin, and MN was measured in bone marrow in 6- to 14-month-old mice. Variation in TL was attributable to tissue type, age, genotype and, to a lesser extent, sex. Compared to WT, APP/PS1 had a significantly shorter baseline TL across all examined tissues. TL was inversely associated with age in both genotypes and TL shortening was accelerated in brain of APP/PS1. Age-related increase of micronuclei was observed in both genotypes but was accelerated in APP/PS1. We integrated TL and micronuclei data with data on cognition performance and brain amyloidosis. TL and micronuclei were linearly correlated with cognition performance or Aβ and Aβ levels in both genotypes but to a greater extent in APP/PS1. These associations in APP/PS1 mice were dominantly driven by females. Together, our findings provide foundational knowledge to infer the TL and micronuclei trajectories in APP/PS1 mice during disease progression, and strongly support that TL attrition and micronucleation are tightly associated with AD pathogenesis in a female-biased manner.
Topics: Animals; Alzheimer Disease; Mice; Disease Models, Animal; Amyloidosis; Female; Cognitive Dysfunction; Male; Mice, Transgenic; Brain; Telomere; Amyloid beta-Protein Precursor; Sex Characteristics; Mice, Inbred C57BL; Presenilin-1; Micronuclei, Chromosome-Defective
PubMed: 38450924
DOI: 10.1111/acel.14121 -
Alzheimer's & Dementia : the Journal of... Apr 2024Rate of cognitive decline (RCD) in Alzheimer's disease (AD) determines the degree of impairment for patients and of burden for caretakers. We studied the association of...
INTRODUCTION
Rate of cognitive decline (RCD) in Alzheimer's disease (AD) determines the degree of impairment for patients and of burden for caretakers. We studied the association of RCD with genetic variants in AD.
METHODS
RCD was evaluated in 62 familial AD (FAD) and 53 sporadic AD (SAD) cases, and analyzed by whole-exome sequencing for association with common exonic functional variants. Findings were validated in post mortem brain tissue.
RESULTS
One hundred seventy-two gene variants in FAD, and 227 gene variants in SAD associated with RCD. In FAD, performance decline of the immediate recall of the Rey-Osterrieth figure test associated with 122 genetic variants. Olfactory receptor OR51B6 showed the highest number of associated variants. Its expression was detected in temporal cortex neurons.
DISCUSSION
Impaired olfactory function has been associated with cognitive impairment in AD. Genetic variants in these or other genes could help to identify risk of faster memory decline in FAD and SAD patients.
Topics: Humans; Alzheimer Disease; Cognitive Dysfunction; Brain; Neurons; Presenilin-1; Mutation
PubMed: 38450831
DOI: 10.1002/alz.13754 -
Advanced Science (Weinheim,... May 2024The hepatic content of amyloid beta (Aβ) decreases drastically in human and rodent cirrhosis highlighting the importance of understanding the consequences of Aβ...
The hepatic content of amyloid beta (Aβ) decreases drastically in human and rodent cirrhosis highlighting the importance of understanding the consequences of Aβ deficiency in the liver. This is especially relevant in view of recent advances in anti-Aβ therapies for Alzheimer's disease (AD). Here, it is shown that partial hepatic loss of Aβ in transgenic AD mice immunized with Aβ antibody 3D6 and its absence in amyloid precursor protein (APP) knockout mice (APP-KO), as well as in human liver spheroids with APP knockdown upregulates classical hallmarks of fibrosis, smooth muscle alpha-actin, and collagen type I. Aβ absence in APP-KO and deficiency in immunized mice lead to strong activation of transforming growth factor-β (TGFβ), alpha secretases, NOTCH pathway, inflammation, decreased permeability of liver sinusoids, and epithelial-mesenchymal transition. Inversely, increased systemic and intrahepatic levels of Aβ42 in transgenic AD mice and neprilysin inhibitor LBQ657-treated wild-type mice protect the liver against carbon tetrachloride (CCl)-induced injury. Transcriptomic analysis of CCl-treated transgenic AD mouse livers uncovers the regulatory effects of Aβ42 on mitochondrial function, lipid metabolism, and its onco-suppressive effects accompanied by reduced synthesis of extracellular matrix proteins. Combined, these data reveal Aβ as an indispensable regulator of cell-cell interactions in healthy liver and a powerful protector against liver fibrosis.
Topics: Animals; Mice; Amyloid beta-Peptides; Mice, Transgenic; Liver; Alzheimer Disease; Disease Models, Animal; Humans; Mice, Knockout; Mice, Inbred C57BL
PubMed: 38430535
DOI: 10.1002/advs.202307734 -
Signal Transduction and Targeted Therapy Mar 2024Mutations in the Contactin-associated protein-like 2 (CNTNAP2) gene are associated with autism spectrum disorder (ASD), and ectodomain shedding of the CNTNAP2 protein...
Mutations in the Contactin-associated protein-like 2 (CNTNAP2) gene are associated with autism spectrum disorder (ASD), and ectodomain shedding of the CNTNAP2 protein plays a role in its function. However, key enzymes involved in the C-terminal cleavage of CNTNAP2 remain largely unknown, and the effect of ASD-associated mutations on this process and its role in ASD pathogenesis remain elusive. In this report we showed that CNTNAP2 undergoes sequential cleavages by furin, ADAM10/17-dependent α-secretase and presenilin-dependent γ-secretase. We identified that the cleavage sites of ADAM10 and ADAM17 in CNTNAP2 locate at its C-terminal residue I79 and L96, and the main α-cleavage product C79 by ADAM10 is required for the subsequent γ-secretase cleavage to generate CNTNAP2 intracellular domain (CICD). ASD-associated CNTNAP2 mutations impair the α-cleavage to generate C79, and the inhibition leads to ASD-like repetitive and social behavior abnormalities in the Cntnap2 knock-in mice. Finally, exogenous expression of C79 improves autism-like phenotypes in the Cntnap2 knock-in and Cntnap2 knockout mice. This data demonstrates that the α-secretase is essential for CNTNAP2 processing and its function. Our study indicates that inhibition of the cleavage by pathogenic mutations underlies ASD pathogenesis, and upregulation of its C-terminal fragments could have therapeutical potentials for ASD treatment.
Topics: Animals; Mice; Autistic Disorder; Amyloid Precursor Protein Secretases; Autism Spectrum Disorder; Mutation; Mice, Knockout; Contactins; Phenotype; Membrane Proteins; Nerve Tissue Proteins
PubMed: 38424048
DOI: 10.1038/s41392-024-01768-6