Tau pathology in the brainstem monoaminergic neurons reflect resilience to Alzheimer’s disease pathology in the Nun study cases

The presence of amyloid and tau pathologies are the pathological hallmarks of Alzheimer’s disease (AD). However, presence of non-demented individuals with sufficient AD pathology (NDAP) indicate that AD-linked pathology does not always lead to dementia. Current view is that NDAP cases represents individuals resilient to AD pathology. To gain insight about resilience to AD pathology in NDAP, we examined neuropathology in the brainstem monoaminergic (MAergic) neurons in the Nun Study participants with equally high Braak AD stage (V-VI) with dementia (AD) and without clinical dementia (NDAP). Because MAergic pathology is thought to occur in response to cortical AD pathology, any differences in MAergic pathology between AD and NDAP cases with similarly advanced AD pathology could reflect resilience of MAergic neurons to cortical AD pathology. Examination of Locus Coeruleus (LC) and/or Raphe for the presence of tau pathology showed that despite the similar forebrain pathology, relative levels of perikaryal and neuritic tau pathology were significantly lower in NDAP than in AD. The NDAP subjects exhibit greater pathology than control subjects without AD pathology, indicating that cortical AD pathology impacts subcortical neurons in both AD and NDAP cases. Significantly, the extent of neurodegenerative pathology in LC and Raphe neurons correlated with MMSE performance in AD cases while no such correlation was seen in NDAP cases, mostly because NDAP cases cluster at higher MMSE scores. Our results show that while cortical AD pathology is associated with increased MAergic neuropathology, quantitative differences in the extent of MAergic pathology in the brainstem may reflect underlying resistance to AD pathology. (254 words)

Biochemical analysis of tau proteins in argyrophilic grain disease, Alzheimer's disease, and Pick's disease : a comparative study.

Background:Tau pathology is common in age-related neurodegenerative diseases. Tau pathology in primary age-related tauopathy (PART) and in Alzheimer’s disease (AD) has a similar biochemical structure and anatomic distribution, which is distinct from tau pathology in other diseases. However, the molecular changes associated with intraneuronal tau pathology in PART and AD, and whether these changes are similar in the two diseases, is largely unexplored.Methods:Using GeoMx spatial transcriptomics, mRNA was quantified in CA1 pyramidal neurons with tau pathology and adjacent neurons without tau pathology in 6 cases of PART and 6 cases of AD, and compared to 4 control cases without pathology. Transcriptional changes were analyzed for differential gene expression and for coordinated patterns of gene expression associated with both disease state and intraneuronal tau pathology.Results:Synaptic gene changes and two novel gene expression signatures associated with intraneuronal tau were identified in PART and AD. Overall, gene expression changes associated with intraneuronal tau pathology were similar in PART and AD. Synaptic gene expression was decreased overall in neurons in AD and PART compared to control cases. However, this decrease was largely driven by neurons lacking tau pathology. Synaptic gene expression was increased in tau-positive neurons compared to tau-negative neurons in disease. Two novel gene expression signatures associated with intraneuronal tau were identified by examining coordinated patterns of gene expression. Genes in the up-regulated expression pattern were enriched in calcium regulation and synaptic function pathways, specifically in synaptic exocytosis. These synaptic gene changes and intraneuronal tau expression signatures were confirmed in a published transcriptional dataset of cortical neurons with tau pathology in AD.Conclusions:PART and AD show similar transcriptional changes associated with intraneuronal tau pathology in CA1 pyramidal neurons, raising the possibility of a mechanistic relationship between the tau pathology in the two diseases. Intraneuronal tau pathology was also associated with increased expression of genes associated with synaptic function and calcium regulation compared to tau-negative disease neurons. The findings highlight the power of molecular analysis stratified by pathology in neurodegenerative disease and provide novel insight into common molecular pathways associated with intraneuronal tau in PART and AD.

The APOE genotype is a known susceptibility factor for Alzheimer's disease (AD). It is apparent that the presence of the APOE ε40 allele increases the risk for developing AD, lowers the age of onset in AD, and may influence the pathological burden seen in AD. In this study, we asked whether BACE1 levels differ by APOE genotype in the AD and non-demented (ND) brain. We isolated mid-frontal cortex (MFC) and mid-temporal cortex (MTC) from post-mortem ND and AD subjects that were APOE ε3/3, ε3/4, ε4/4 carriers. All AD subjects met NINDS-ADRDA and NIA-Reagan criteria for a diagnosis of AD. The MFC and MTC were homogenized and the lysates underwent ELISA and Western blotting for BACE1. The ELISA revealed that total BACE1 levels were lower in the MFC of AD compared to ND subjects. Furthermore, in APOE ε4 carriers BACE1 levels were lower than ε3/3 carriers in the ND frontal cortex. No difference in BACE1 levels was observed in AD MFC and in ND and AD MTC tissues. The ELISA results were confirmed by Western blotting. Our data suggest that brain BACEl levels may be influenced by the apolipoprotein E genotype before the onset of AD, providing an alternative explanation for the lower amyloid beta 42 levels in CSF in ND and AD subjects.

Accumulation of Abeta protein in beta-amyloid deposits is a hallmark event in Alzheimer's disease (AD). Recent findings suggest anti-Abeta autoantibodies may have a role in AD pathology. However, a consensus has yet to emerge as to whether endogenous anti-Abeta autoantibodies are elevated, depressed, or unchanged in AD patients. Whereas experiments to date have used synthetic unmodified monomeric Abeta (Abetamon) to test autoimmunity, up to 40% of the Abeta pool inB AD brain consists of low molecular weight oligomeric cross-linked beta-amyloid protein species (CAPS). Recent studies also suggest that CAPS may be the primary neurotoxic agent in AD. In the present study, AD and nondemented control plasma were analyzed for immunoreactivity to CAPS and Abetamon. Plasma of both nondemented and AD patients were found to contain autoantibodies specific for soluble CAPS. Nondemented control and AD plasmas demonstrated similar immunoreactivity to Abetamon. In contrast, anti-CAPS antibodies in AD plasma were found to be significantly reduced compared with nondemented controls (p=0.018). Furthermore, age at onset for AD correlated significantly (p=0.041) with plasma immunoreactivity to CAPS. These data suggest that autoantibodies to CAPS are depleted in AD patients and raise the prospect that immunization with anti-CAPS antibodies might provide therapeutic benefit for AD.

Recent studies indicate that tau pathology in Alzheimer's disease (AD) does not initially manifest in the cerebral cortex but in selected subcortical nuclei, in particular the locus ceruleus (LC). In this study we correlate both olfactory and brainstem tau pathology with neuritic Braak stages. We examined 239 unselected autopsy cases (57.3% female, 42.7% male; aged 55-102, mean 82.8 ± 9.7 SD years; AD, 44.8%; non-demented controls, 31.8%; Parkinson's disease, 5.0%; dementia with Lewy bodies, 2.5%; AD+Lewy body disease, 15.9%). Neuropathological examination according to standardized methods included immunohistochemistry and semiquantitative assessment of tau lesions in LC, substantia nigra (SN), dorsal motor nucleus of nervus vagus (dmX), and olfactory bulb (OB). In Braak stage 0, tau pathology (usually very sparse pretangle material) was seen in the OB in 52.9% and in the SN/LC in 44%. The prevalence of OB and subcortical tau pathology increased with increasing Braak stages and reached 100% in OB, SN and LC and 95.2% in dmX in Braak stage VI, respectively. The severity of tau pathology in OB and subcortical nuclei significantly (P < 0.001) correlated with Braak stages and these correlations remained statistically significant when controlling for concomitant α-synuclein pathology in the respective regions. Our finding of an increase in both prevalence and severity of OB, LC, SN and dmX tau pathology in AD with increasing Braak stages suggests that these regions become increasingly involved during AD progression rather than representing sites initially affected by AD-associated tau pathology.

Neuropathological studies have shown that the typical neurofibrillary pathology of hyperphosphorylated tau protein in Alzheimer's disease (AD) preferentially affects specific brain regions whereas others remain relatively spared. It has been suggested that the distinct regional distribution profile of tau pathology in AD may be a consequence of the intrinsic network structure of the human brain. The spatially distributed brain regions that are most affected by the spread of tau pathology may hence reflect an interconnected neuronal system. Here, we characterized the brain-wide regional distribution profile of tau pathology in AD using 18F-AV 1451 tau-sensitive positron emission tomography (PET) imaging, and studied this pattern in relation to the functional network organization of the human brain. Specifically, we quantified the spatial correspondence of the regional distribution pattern of PET-evidenced tau pathology in AD with functional brain networks characterized by large-scale resting state functional magnetic resonance imaging (rs-fMRI) data in healthy subjects. Regional distribution patterns of increased PET-evidenced tau pathology in AD compared to controls were characterized in two independent samples of prodromal and manifest AD cases (the Swedish BioFINDER study, n = 44; the ADNI study, n = 35). In the BioFINDER study we found that the typical AD tau pattern involved predominantly inferior, medial, and lateral temporal cortical areas, as well as the precuneus/posterior cingulate, and lateral parts of the parietal and occipital cortex. This pattern overlapped primarily with the dorsal attention, and to some extent with higher visual, limbic and parts of the default-mode network. PET-evidenced tau pathology in the ADNI replication sample, which represented a more prodromal group of AD cases, was less pronounced but showed a highly similar spatial distribution profile, suggesting an earlier-stage snapshot of a consistently progressing regional pattern. In conclusion, the present study indicates that the regional deposition of tau aggregates in AD predominantly affects higher-order cognitive over primary sensory-motor networks, but does not appear to be specific for the default-mode or related limbic networks.

SPATIAL CORRESPONDENCE OF ALZHEIMER’S DISEASE-RELATED TAU PATHOLOGY AND GREY MATTER ATROPHY DISTRIBUTION WITH INTRINSIC FUNCTIONAL BRAIN NETWORKS

SPATIAL CORRESPONDENCE OF ALZHEIMER’S DISEASE-RELATED TAU PATHOLOGY AND GREY MATTER ATROPHY DISTRIBUTION WITH INTRINSIC FUNCTIONAL BRAIN NETWORKS

Rac1b Increases with Progressive Tau Pathology within Cholinergic Nucleus Basalis Neurons in Alzheimer's Disease

Amyloid beta peptides in human plasma and tissues and their significance for Alzheimer's disease

The molecular basis of cognitive resilience (CR) among pathologically confirmed Alzheimer's disease (AD) cases is not well understood. Abundance of 13 cell types and neuronal subtypes in brain bulk RNA-seq data from the anterior caudate, dorsolateral prefrontal cortex (DLPFC), and posterior cingulate cortex (PCC) obtained from 434 AD cases, 318 cognitively resilient AD cases, and 188 controls in the Religious Orders Study and Rush Memory and Aging Project was estimated by deconvolution. PVALB+ neuron abundance was negatively associated with cognitive status and tau pathology in the DLPFC and PCC (Padj<0.001) and the most reduced neuronal subtype in AD cases compared to controls in DLPFC (Padj=8.4×10-7) and PCC (Padj=0.0015). We identified genome-wide significant association of neuron abundance with TMEM106B single nucleotide polymorphism rs13237518 in PCC (p=6.08×10-12). rs13237518 was also associated with amyloid beta (p=0.0085) and tangles (p=0.0073). High abundance of PVALB+ neurons may be a marker of CR. TMEM106B variants may influence CR independent of AD pathology. Neuron retention and a lack of astrocytosis are highly predictive of Alzheimer's disease (AD) resilience. PVALB+ GABAergic and RORB+ glutamatergic neurons are associated with cognitive status. A TMEM106B single nucleotide polymorphism is related to lower AD risk, higher neuron count, and increased AD pathology.

Distinct cytokine profiles in human brains resilient to Alzheimer's pathology

Distinct conformers of amyloid beta accumulate in the neocortex of patients with rapidly progressive Alzheimer's disease

The new "silent" epidemic.