Longitudinal analysis of the behavioral phenotype in a novel transgenic rat model of early stages of Alzheimer's disease

Intraneuronal accumulation of amyloid beta (iAbeta) has been linked to mild cognitive impairment that may precede Alzheimers disease (AD) onset. This neuropathological trait was recently mimicked in a novel animal model of AD, the hemizygous transgenic McGill-R-Thy1-APP (Tg+/-) rat. The characterization of the behavioral phenotypes in this animal model could provide a baseline of efficacy for earlier therapeutic interventions. The aim of the present study was to undertake a longitudinal study of Abeta accumulation and a comprehensive behavioral evaluation of this transgenic rat model. We assessed exploratory activity, anxiety-related behaviors, recognition memory, working memory, spatial learning and reference memory at 3, 6 and 12 months of age. In parallel, we measured Abeta by ELISA, Western blots and semiquantitative immunohistochemistry in hippocampal samples. SDS-soluble Abeta peptide accumulated at low levels (9 pg/mg) without differences among ages. However, Western blots showed SDS-resistant Abeta oligomers (30 kDa) at 6 and 12 months, but not at 3 months. When compared to wild-type (WT), male Tg+/- rats exhibited a spatial reference memory deficit in the Morris Water Maze (MWM) as early as 3 months of age, which persisted at 6 and 12 months. In addition, Tg+/- rats displayed a working memory impairment in the Y-maze and higher anxiety levels in the Open Field (OF) at 6 and 12 months of age, but not at 3 months. Exploratory activity in the OF was similar to that of WT at all time points. Spatial learning in the MWM and the recognition memory, as assessed by the Novel Object Recognition Test, were unimpaired at any time point. The data from the present study demonstrate that the hemizygous transgenic McGill-R-Thy1-APP rat has a wide array of behavioral and cognitive impairments from young adulthood to middle-age. The low Abeta burden and early emotional and cognitive deficits in this transgenic rat model supports its potential use for drug discovery purposes in early AD.Fil: Galeano, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Cardiológicas (i); ArgentinaFil: Martino Adami, Pamela Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Do Carmo, Sonia. Mc Gill University; CanadáFil: Blanco, Eduardo. Universitat de Leida; EspañaFil: Rotondaro, Cecilia. Fundación Instituto Leloir; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; ArgentinaFil: Capani, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Cardiológicas (i); ArgentinaFil: Castaño, Eduardo Miguel. Fundación Instituto Leloir; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; ArgentinaFil: Cuello, A. Claudio. Mc Gill University; CanadáFil: Morelli, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; Argentin

Perturbed mitochondria-ER contacts in live neurons that model the amyloid pathology of Alzheimer\u27s disease.

The use of fixed fibroblasts from familial and sporadic Alzheimer\u27s disease patients has previously indicated an upregulation of mitochondria-ER contacts (MERCs) as a hallmark of Alzheimer\u27s disease. Despite its potential significance, the relevance of these results is limited because they were not extended to live neurons. Here we performed a dynamic in vivo analysis of MERCs in hippocampal neurons from McGill-R-Thy1-APP transgenic rats, a model of Alzheimer\u27s disease-like amyloid pathology. Live FRET imaging of neurons from transgenic rats revealed perturbed \u27lipid-MERCs\u27 (gap width \u3c10 nm), while \u27Ca2+-MERCs\u27 (10-20 nm gap width) were unchanged. In situ TEM showed no significant differences in the lipid-MERCs:total MERCs or lipid-MERCs:mitochondria ratios; however, the average length of lipid-MERCs was significantly decreased in neurons from transgenic rats as compared to controls. In accordance with FRET results, untargeted lipidomics showed significant decreases in levels of 12 lipids and bioenergetic analysis revealed respiratory dysfunction of mitochondria from transgenic rats. Thus, our results reveal changes in MERC structures coupled with impaired mitochondrial functions in Alzheimer\u27s disease-related neurons.This article has an associated First Person interview with the first author of the paper

NADPH oxidase and mitochondria are relevant sources of superoxide anion in the oxinflammatory response of macrophages exposed to airborne particulate matter

Exposure to ambient air particulate matter (PM) is associated with increased cardiorespiratory morbidity and mortality. In this context, alveolar macrophages exhibit proinflammatory and oxidative responses as a result of the clearance of particles, thus contributing to lung injury. However, the mechanisms linking these pathways are not completely clarified. Therefore, the oxinflammation phenomenon was studied in RAW 264.7 macrophages exposed to Residual Oil Fly Ash (ROFA), a PM surrogate rich in transition metals. While cell viability was not compromised under the experimental conditions, a proinflammatory phenotype was observed in cells incubated with ROFA 100 μg/mL, characterized by increased levels of TNF-α and NO production, together with PM uptake. This inflammatory response seems to precede alterations in redox metabolism, characterized by augmented levels of H2O2, diminished GSH/GSSG ratio, and increased SOD activity. This scenario resulted in increased oxidative damage to phospholipids. Moreover, alterations in mitochondrial respiration were observed following ROFA incubation, such as diminished coupling efficiency and spare respiratory capacity, together with augmented proton leak. These findings were accompanied by a decrease in mitochondrial membrane potential. Finally, NADPH oxidase (NOX) and mitochondria were identified as the main sources of superoxide anion ([Formula presented]) in our model. These results indicate that PM exposure induces direct activation of macrophages, leading to inflammation and increased reactive oxygen species production through NOX and mitochondria, which impairs antioxidant defense and may cause mitochondrial dysfunction

Nicotinamide as potential biomarker for Alzheimer’s disease: A translational study based on metabolomics

Introduction: The metabolic routes altered in Alzheimer's disease (AD) brain are poorly understood. As the metabolic pathways are evolutionarily conserved, the metabolic profiles carried out in animal models of AD could be directly translated into human studies.Methods: We performed untargeted Nuclear Magnetic Resonance metabolomics in hippocampus of McGill-R-Thy1-APP transgenic (Tg) rats, a model of AD-like cerebral amyloidosis and the translational potential of these findings was assessed by targeted Gas Chromatography-Electron Impact-Mass Spectrometry in plasma of participants in the German longitudinal cohort AgeCoDe.Results: In rat hippocampus 26 metabolites were identified. Of these 26 metabolites, nine showed differences between rat genotypes that were nominally significant. Two of them presented partial least square-discriminant analysis (PLS-DA) loadings with the larger absolute weights and the highest Variable Importance in Projection (VIP) scores and were specifically assigned to nicotinamide adenine dinucleotide (NAD) and nicotinamide (Nam). NAD levels were significantly decreased in Tg rat brains as compared to controls. In agreement with these results, plasma of AD patients showed significantly reduced levels of Nam in respect to cognitively normal participants. In addition, high plasma levels of Nam showed a 27% risk reduction of progressing to AD dementia within the following 2.5 years, this hazard ratio is lost afterwards.Discussion: To our knowledge, this is the first report showing that a decrease of Nam plasma levels is observed couple of years before conversion to AD, thereby suggesting its potential use as biomarker for AD progression

Mendelian Randomisation Confirms the Role of Y-Chromosome Loss in Alzheimer’s Disease Aetiopathogenesis in Men

Mosaic loss of chromosome Y (mLOY) is a common ageing-related somatic event and has been previously associated with Alzheimer’s disease (AD). However, mLOY estimation from genotype microarray data only reflects the mLOY degree of subjects at the moment of DNA sampling. Therefore, mLOY phenotype associations with AD can be severely age-confounded in the context of genome-wide association studies. Here, we applied Mendelian randomisation to construct an age-independent mLOY polygenic risk score (mloy-PRS) using 114 autosomal variants. The mloy-PRS instrument was associated with an 80% increase in mLOY risk per standard deviation unit (p = 4.22 × 10−20) and was orthogonal with age. We found that a higher genetic risk for mLOY was associated with faster progression to AD in men with mild cognitive impairment (hazard ratio (HR) = 1.23, p = 0.01). Importantly, mloy-PRS had no effect on AD conversion or risk in the female group, suggesting that these associations are caused by the inherent loss of the Y chromosome. Additionally, the blood mLOY phenotype in men was associated with increased cerebrospinal fluid levels of total tau and phosphorylated tau181 in subjects with mild cognitive impairment and dementia. Our results strongly suggest that mLOY is involved in AD pathogenesis.P.G.-G. (Pablo García-González) is supported by CIBERNED employment plan CNV-304-PRF-866. CIBERNED is integrated into ISCIII (Instituto de Salud Carlos III). I.d.R is supported by a national grant from the Instituto de Salud Carlos III FI20/00215. A.C. (Amanda Cano) acknowledges the support of the Spanish Ministry of Science, Innovation, and Universities under the grant Juan de la Cierva (FJC2018-036012-I). M.B. (Mercé Boada) and A.R. (Agustín Ruiz) are also supported by national grants PI13/02434, PI16/01861, PI17/01474, PI19/01240, and PI19/01301. The Genome Research @ Fundació ACE project (GR@ACE) is supported by Grifols SA, Fundación bancaria “La Caixa”, Fundació ACE, and CIBERNED. Acción Estratégica en Salud is integrated into the Spanish National R + D + I Plan and funded by ISCIII (Instituto de Salud Carlos III)—Subdirección General de Evaluación—and the Fondo Europeo de Desarrollo Regional (FEDER—“Una manera de hacer Europa”). Genotyping of the ACE MCI-EADB samples was performed in the context of EADB (European Alzheimer DNA biobank) funded by the JPco-fuND FP-829-029 (ZonMW project number 733051061). This work was supported by a grant (European Alzheimer DNA BioBank, EADB) from the EU Joint Program—Neurodegenerative Disease Research (JPND). Partial funding for open access charge: Universidad de Málag

Multiomics integrative analysis identifies APOE allele-specific blood biomarkers associated to Alzheimer's disease etiopathogenesis

Alzheimer’s disease (AD) is the most common form of dementia, currently affecting 35 million people worldwide. Apolipoprotein E (APOE) ε4 allele is the major risk factor for sporadic, late-onset AD (LOAD), which comprises over 95% of AD cases, increasing the risk of AD 4-12 fold. Despite this, the role of APOE in AD pathogenesis is still a mystery. Aiming for a better understanding of APOE-specific effects, the ADAPTED consortium analysed and integrated publicly available data of multiple OMICS technologies from both plasma and brain stratified by APOE haplotype (APOE2, APOE3 and APOE4). Combining genome-wide association studies (GWAS) with differential mRNA and protein expression analyses and single-nuclei transcriptomics, we identified genes and pathways contributing to AD in both APOE dependent and independent fashion. Interestingly, we characterised a set of biomarkers showing plasma and brain consistent protein profiles and opposite trends in APOE2 and APOE4 AD cases that could constitute screening tools for a disease that lacks specific blood biomarkers. Beside the identification of APOE-specific signatures, our findings advocate that this novel approach, based on the concordance across OMIC layers and tissues, is an effective strategy for overcoming the limitations of often underpowered single-OMICS studies

Aging, Senescence, and Dementia

The underlying processes occurring in aging are complex, involving numerous biological changes that result in chronic cellular stress and sterile inflammation. One of the main hallmarks of aging is senescence. While originally the term senescence was defined in the field of oncology further research has established that also microglia, astrocytes and neurons become senescent. Since age is the main risk factor for neurodegenerative diseases, it is reasonable to argue that cellular senescence might play a major role in Alzheimer's disease. Specific cellular changes seen during Alzheimer's disease are similar to those observed during senescence across all resident brain cell types. Furthermore, increased levels of senescence-associated secretory phenotype proteins such as IL-6, IGFBP, TGF-beta and MMP-10 have been found in both CSF and plasma samples from Alzheimer's disease patients. In addition, genome-wide association studies have identified that individuals with Alzheimer's disease carry a high burden of genetic risk variants in genes known to be involved in senescence, including ADAMIO, ADAMTS4, and BIN1. Thus, cellular senescence is emerging as a potential underlying disease process operating in Alzheimer's disease. This has also attracted more attention to exploiting cellular senescence as a therapeutic target. Several senolytic compounds with the capability to eliminate senescent cells have been examined in vivo and in vitro with notable results, suggesting they may provide a novel therapeutic avenue. Here, we reviewed the current knowledge of cellular senescence and discussed the evidence of senescence in various brain cell types and its putative role in inflammaging and neurodegenerative processes

Proteolytically inactive insulin-degrading enzyme inhibits amyloid formation yielding non-neurotoxic aβ peptide aggregates.

Insulin-degrading enzyme (IDE) is a neutral Zn(2+) peptidase that degrades short peptides based on substrate conformation, size and charge. Some of these substrates, including amyloid β (Aβ) are capable of self-assembling into cytotoxic oligomers. Based on IDE recognition mechanism and our previous report of the formation of a stable complex between IDE and intact Aβ in vitro and in vivo, we analyzed the possibility of a chaperone-like function of IDE. A proteolytically inactive recombinant IDE with Glu111 replaced by Gln (IDEQ) was used. IDEQ blocked the amyloidogenic pathway of Aβ yielding non-fibrillar structures as assessed by electron microscopy. Measurements of the kinetics of Aβ aggregation by light scattering showed that 1) IDEQ effect was promoted by ATP independent of its hydrolysis, 2) end products of Aβ-IDEQ co-incubation were incapable of "seeding" the assembly of monomeric Aβ and 3) IDEQ was ineffective in reversing Aβ aggregation. Moreover, Aβ aggregates formed in the presence of IDEQ were non-neurotoxic. IDEQ had no conformational effects upon insulin (a non-amyloidogenic protein under physiological conditions) and did not disturb insulin receptor activation in cultured cells. Our results suggest that IDE has a chaperone-like activity upon amyloid-forming peptides. It remains to be explored whether other highly conserved metallopeptidases have a dual protease-chaperone function to prevent the formation of toxic peptide oligomers from bacteria to mammals

Effect of IDEQ upon solubility and secondary structure of Aβ aggregates.

<p>(<b>A</b>) samples containing Aβ1-42 before incubation (“dead time”) and after incubation for 5 days with or without IDEQ were centrifuged at 3,000× g for 5 min and supernatants and pellets analyzed by Western blots with anti-Aβ 6E10 and 4G8. Arrowheads indicate: H, high molecular mass oligomers, T, Aβ tetramers and <i>t</i>, Aβ trimers. (<b>B</b>) Densitometric quantification of Aβ1-42 obtained from Western blots shown in panel (<b>A</b>). Bars represent the mean ± SEM of total Aβ immunoreactivity in arbitrary units (AU). * p<0.05, Student's <i>t</i> test. (<b>C</b>) Far UV-CD spectra recorded at “dead time” of Aβ1-42 (solid black line), IDEQ alone (dotted line) and Aβ1-42 co-incubated with IDEQ (solid gray line) at a 1∶300 molar ratio (IDEQ:Aβ). (<b>D</b>) Far UV-spectra recorded after 6 days of incubation of Aβ1-42 alone or Aβ1-42 with IDEQ at 1∶300 molar ratio. Samples were centrifuged as described above and supernatants analyzed. IDEQ alone, dotted line; Aβ1-42 alone, solid black line; Aβ1-42 co-incubated with IDEQ, solid gray line.</p

IDEQ does not modify insulin conformation.

<p>(<b>A</b>) <i>Circular dichroism (CD) spectra</i> of 10 μM insulin (ins.) in working buffer (solid black line), insulin with IDEQ at 1∶100 molar ratio, enzyme:insulin (solid gray line) and IDEQ alone (dotted line) with no prior incubation. (<b>B</b>) Same samples as in panel (<b>A</b>) after incubation for 24 h at 25°C. Insulin alone (solid black line), insulin with IDEQ (solid gray line) and IDEQ alone (dotted line). (<b>C</b>) Western blot with anti-phospho-Akt and anti-total Akt of U-87 cell lysates. Cells were exposed for 30 min with insulin alone, insulin previously co-incubated with IDEwt or IDEQ, as indicated. Wortmannin (wort) was incubated at 10 nM for 30 min before treatments.</p