Higher Braak Stage Research Articles

Resistance and resilience to tau pathology in Alzheimer's disease: Effects of age, sex, and APOE alleles.

Neurofibrillary tangles (NFTs), a hallmark of tau pathology in Alzheimer's disease (AD), accumulate in the aging brain. However, some individuals remain cognitively intact despite high Braak (III-VI) stages, which characterize NFTs' accumulation. We studied resistance and resilience to tau pathology by assessing Braak stages based on apolipoprotein E (APOE) alleles, sex, and age in a sample of 1932 cognitively intact individuals of European ancestry from the Alzheimer's Disease Sequencing Project (ADSP). Resistance, characterized by low (0-II) Braak stages, was observed in men and women younger than 85 years of age. Resilience, indicated by high (III-VI) Braak stages, increased significantly with age in both men and women for each APOE allele. It became more pronounced, with the proportion of high Braak stages exceeding 50% at 85 years and older in women, irrespective of the APOE allele. The identification of factors underlying resistance and resilience against AD-related pathologies is essential for promoting cognitively healthy aging. We investigated cognitive resistance and resilience to tau pathology in Alzheimer's disease (AD).This study included individuals who were not diagnosed with AD.Braak stages 0-II and III-VI were considered as a measure of resistance and resilience, respectively.Resistance was stronger at ages younger than 85 years in non-carriers of the apolipoprotein E (APOE) ε4 allele.Resilience increased with age for each APOE allele independently of sex.At age 85 years and older, high resilience(>50%) was observed in women regardless of the APOE allele.

Retinal ganglion cell vulnerability to pathogenic tau in Alzheimer's disease.

Accumulation of pathological tau isoforms, especially hyperphosphorylated tau at serine 396 (pS396-tau) and tau oligomers, has been demonstrated in the retinas of patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Previous studies have noted a decrease in retinal ganglion cells (RGCs) in AD patients, but the presence and impact of pathological tau isoforms in RGCs and RGC integrity, particularly in early AD stages, have not been explored. To investigate this, we examined retinal superior temporal cross-sections from 25 patients with MCI (due to AD) or AD dementia and 16 cognitively normal (CN) controls, matched for age and gender. We utilized the RGC marker ribonucleic acid binding protein with multiple splicing (RBPMS) and Nissl staining to assess neuronal density in the ganglion cell layer (GCL). Our study found that hypertrophic RGCs containing pS396-tau and T22-positive tau oligomers were more frequently observed in MCI and AD patients compared to CN subjects. Quantitative analyses indicated a decline in RGC integrity, with 46-55% and 55-56% reductions of RBPMS+ RGCs (P<0.01) and Nissl+ GCL neurons (P<0.01-0.001), respectively, in MCI and AD patients. This decrease in RGC count was accompanied by increases in necroptotic-like morphology and the cleaved caspase-3 apoptotic marker in RGCs of AD patients. Furthermore, there was a 2.1 to 3.1-fold increase (P<0.05-0.0001) in pS396-tau-laden RGCs in MCI and AD patients, with a greater abundance observed in individuals with higher Braak stages (V-VI), more severe clinical dementia ratings (CDR=3), and lower mini-mental state examination (MMSE) scores. Strong correlations were noted between the decline in RGCs and the total amount of retinal pS396-tau and pS396-tau+ RGCs, with pS396-tau+ RGC counts correlating significantly with brain neurofibrillary tangle scores (r= 0.71, P= 0.0001), Braak stage (r= 0.65, P= 0.0009), and MMSE scores (r= -0.76, P= 0.0004). These findings suggest that retinal tauopathy, characterized by pS396-tau and oligomeric tau in hypertrophic RGCs, is associated with and may contribute to RGC degeneration in AD. Future research should validate these findings in larger cohorts and explore noninvasive retinal imaging techniques that target tau pathology in RGCs to improve AD detection and monitor disease progression.

Characterization of neurofibrillary tangle immunophenotype signatures to classify tangle maturity in Alzheimer's disease.

Tau aggregation into neurofibrillary tangles in Alzheimer's disease (AD) is a dynamic process involving changes in tau phosphorylation, isoform composition, and morphology. To facilitate studies of tangle maturity, we developed an image analysis pipeline to study antibody labeling signatures that can distinguish tangle maturity levels in AD brain tissue. Using fluorescent immunohistochemistry, we co-labeled AD brain tissue with four antibodies that bind different tau epitopes. Mean fluorescence intensity of each antibody was measured, and spectral clustering was used to identify tangle immunophenotypes. Five distinct tangle populations were identified, and different tangle maturity immunophenotypes were identified with increasing Braak stage. Early tangle immunophenotypes were more prevalent in later affected regions and advanced immunophenotypes were associated with ghost morphology. Our findings indicate that tangle populations characterized by advanced tau immunophenotypes are associated with higher Braak stage and more mature morphology, providing a new framework for defining tangle maturity levels using tau antibody signatures. Populations of neurofibrillary tangles exist in Alzheimer's disease. The immunophenotype of neurofibrillary tangle populations relates to their maturity. The most advanced immunophenotypes are associated with higher Braak stage. The most advanced immunophenotypes are associated with ghost morphology. The most immature immunophenotypes are associated with later affected regions.

Micro-RNA profiles of pathology and resilience in posterior cingulate cortex of cognitively intact elders.

The posterior cingulate cortex (PCC) is a key hub of the default mode network underlying autobiographical memory retrieval, which falters early in the progression of Alzheimer's disease (AD). We recently performed RNA sequencing of post-mortem PCC tissue samples from 26 elderly Rush Religious Orders Study participants who came to autopsy with an ante-mortem diagnosis of no cognitive impairment but who collectively displayed a range of Braak I-IV neurofibrillary tangle stages. Notably, cognitively unimpaired subjects displaying high Braak stages may represent cognitive resilience to AD pathology. Transcriptomic data revealed elevated synaptic and ATP-related gene expression in Braak Stages III/IV compared with Stages I/II, suggesting these pathways may be related to PCC resilience. We also mined expression profiles for small non-coding micro-RNAs (miRNAs), which regulate mRNA stability and may represent an underexplored potential mechanism of resilience through the fine-tuning of gene expression within complex cellular networks. Twelve miRNAs were identified as differentially expressed between Braak Stages I/II and III/IV. However, the extent to which the levels of all identified miRNAs were associated with subject demographics, neuropsychological test performance and/or neuropathological diagnostic criteria within this cohort was not explored. Here, we report that a total of 667 miRNAs are significantly associated (rho > 0.38, P < 0.05) with subject variables. There were significant positive correlations between miRNA expression levels and age, perceptual orientation and perceptual speed. By contrast, higher miRNA levels correlated negatively with semantic and episodic memory. Higher expression of 15 miRNAs associated with lower Braak Stages I-II and 47 miRNAs were associated with higher Braak Stages III-IV, suggesting additional mechanistic influences of PCC miRNA expression with resilience. Pathway analysis showed enrichment for miRNAs operating in pathways related to lysine degradation and fatty acid synthesis and metabolism. Finally, we demonstrated that the 12 resilience-related miRNAs differentially expressed in Braak Stages I/II versus Braak Stages III/IV were predicted to regulate mRNAs related to amyloid processing, tau and inflammation. In summary, we demonstrate a dynamic state wherein differential PCC miRNA levels are associated with cognitive performance and post-mortem neuropathological AD diagnostic criteria in cognitively intact elders. We posit these relationships may inform miRNA transcriptional alterations within the PCC relevant to potential early protective (resilience) or pathogenic (pre-clinical or prodromal) responses to disease pathogenesis and thus may be therapeutic targets.

Association of PM2.5 Exposure and Alzheimer Disease Pathology in Brain Bank Donors-Effect Modification by APOE Genotype.

Fine particulate matter (PM2.5) exposure has been found to be associated with Alzheimer disease (AD) and is hypothesized to cause inflammation and oxidative stress in the brain, contributing to neuropathology. The APOE gene, a major genetic risk factor of AD, has been hypothesized to modify the association between PM2.5 and AD. However, little prior research exists to support these hypotheses. This study investigates the association between traffic-related PM2.5 and AD hallmark pathology, including effect modification by APOE genotype, in an autopsy cohort. A cross-sectional study was conducted using brain tissue donors enrolled in the Emory Goizueta AD Research Center who died before 2020 (n = 224). Donors were assessed for AD pathology including the Braak stage, Consortium to Establish a Registry for AD (CERAD) score, and combined AD neuropathologic change (ABC) score. Traffic-related PM2.5 concentrations were modeled for the metro-Atlanta area during 2002-2019 with a spatial resolution of 200-250 m. One-year, 3-year, and 5-year average PM2.5 concentrations before death were matched to participants' home address. We assessed the association between traffic-related PM2.5 and AD hallmark pathology and effect modification by APOE genotype, using adjusted ordinal logistic regression models. Among the 224 participants, the mean age of death was 76 years, and 57% had at least 1 APOE ε4 copy. Traffic-related PM2.5 was significantly associated with the CERAD score for the 1-year exposure window (odds ratio [OR] 1.92; 95% CI 1.12-3.30) and the 3-year exposure window (OR 1.87; 95% CI 1.01-3.17). PM2.5 was also associated with higher Braak stage and ABC score albeit nonsignificantly. The strongest associations between PM2.5 and neuropathology markers were among those without APOE ε4 alleles (e.g., for the CERAD score and 1-year exposure window, OR 2.31; 95% CI 1.36-3.94), though interaction between PM2.5 and APOE genotype was not statistically significant. Our study found traffic-related PM2.5 exposure was associated with the CERAD score in an autopsy cohort, contributing to epidemiologic evidence that PM2.5 affects β-amyloid deposition in the brain. This association was particularly strong among donors without APOE ε4 alleles. Future studies should further investigate the biological mechanisms behind this association.

High percentage of blood-based T-cell receptor gamma V9-JP recombinations associated with amyotrophic lateral sclerosis: extensive retention of the JP KKIK amino acid motif

Exome and RNAseq files prepared from blood samples can be mined for adaptive immune receptor recombinations and thus for the complementarity determining region-3 (CDR3) amino acid (AA) sequences, important for antigen binding. In this report, the T-cell receptor gamma (TRG) recombinations were mined from amyotrophic lateral sclerosis (ALS) blood sample exome and RNAseq files, mainly inspired by: (i) a high level of gamma-delta T-cells in Parkinson’s disease and (ii) TRG CDR3 AA features associated with a higher Braak stage in Alzheimer’s disease. Results indicated a high percentage of V9-JP recombinations from ALS blood sample genomics files, in comparison to TRG recombinations obtained from a large number of blood and other tissue samples not representing ALS. This result is discussed in the context of potential phospholipid sponging by adaptive immune receptors and potential impacts on membrane rigidity and amyloid development.

Evaluation of quantitative measurements of tau pathology with semi‐quantitative ratings and age

AbstractBackgroundIt is assumed quantitative digital neuropathology methods will provide more information than semi‐quantitative ratings, but this presumption lacks formal assessment. Here, we compare quantitative, whole‐slide measurements of phosphorylated tau tangles and threads with semi‐quantitative tau pathology ratings. We evaluate whether quantitative measurements provide additional prediction beyond Braak stage for variables associated with tau pathology, examining the association of quantitative tau measurements in high Braak stages with age at death and measures of severity of TDP‐43 and alpha‐synuclein co‐pathologies. We hypothesized that even within the same high Braak stage, quantitative tau measurements would decrease with age at death, as younger patients often require more tau pathology for disease severity comparable to older patients, and increase with higher co‐pathology ratings, since prior work suggests co‐pathologies increase with disease severity.MethodWe scanned 6µm tissue sections stained with phosphorylated tau PHF1 in 14 brain regions from 215 patients with Alzheimer’s Disease continuum neuropathological diagnoses (53% male, age = 74.37 ± 11.51). A machine learning method (Figure 1) generated summary measures of tangle and thread pathology for each slide (Yushkevich et al., 2021, Sadaghiani et al., 2022). Semi‐quantitative tau ratings (0‐3) were also available in nine regions and compared to quantitative measurements in matching regions. In 150 patients with high Braak stages (V/VI), correlation analyses were performed using summary scores averaging semi‐quantitative ratings of TDP‐43 in medial temporal lobe regions (“TDP‐43 severity”), and alpha‐synuclein in commonly affected regions (“alpha‐synuclein severity”).ResultFigure 2 shows high overall agreement between quantitative tau measures and corresponding semi‐quantitative ratings. When evaluating quantitative tau measurements in high Braak stage patients, after Bonferroni correction we found significant negative associations between age and tangles in middle frontal cortex, orbital frontal cortex (OFC), and thalamus, and between age and threads in OFC. We found significant positive association between TDP‐43 severity and tangles in substantia nigra, but no associations with alpha‐synuclein severity (Figure 3).ConclusionQuantitative tau measurements largely agree with established semi‐quantitative ratings. Significant associations of quantitative tau measurements with TDP43 pathology and age were found within high Braak stage patients, suggesting quantitative pathology measurements can offer additional information beyond stage alone in these patients.

Evaluation of quantitative measurements of tau pathology with semi‐quantitative ratings and age

AbstractBackgroundIt is assumed quantitative digital neuropathology methods will provide more information than semi‐quantitative ratings, but this presumption lacks formal assessment. Here, we compare quantitative, whole‐slide measurements of phosphorylated tau tangles and threads with semi‐quantitative tau pathology ratings. We evaluate whether quantitative measurements provide additional prediction beyond Braak stage for variables associated with tau pathology, examining the association of quantitative tau measurements in high Braak stages with age at death and measures of severity of TDP‐43 and alpha‐synuclein co‐pathologies. We hypothesized that even within the same high Braak stage, quantitative tau measurements would decrease with age at death, as younger patients often require more tau pathology for disease severity comparable to older patients, and increase with higher co‐pathology ratings, since prior work suggests co‐pathologies increase with disease severity.MethodWe scanned 6µm tissue sections stained with phosphorylated tau PHF1 in 14 brain regions from 215 patients with Alzheimer’s Disease continuum neuropathological diagnoses (53% male, age = 74.37 ± 11.51). A machine learning method (Figure 1) generated summary measures of tangle and thread pathology for each slide (Yushkevich et al., 2021, Sadaghiani et al., 2022). Semi‐quantitative tau ratings (0‐3) were also available in nine regions and compared to quantitative measurements in matching regions. In 150 patients with high Braak stages (V/VI), correlation analyses were performed using summary scores averaging semi‐quantitative ratings of TDP‐43 in medial temporal lobe regions (“TDP‐43 severity”), and alpha‐synuclein in commonly affected regions (“alpha‐synuclein severity”).ResultFigure 2 shows high overall agreement between quantitative tau measures and corresponding semi‐quantitative ratings. When evaluating quantitative tau measurements in high Braak stage patients, after Bonferroni correction we found significant negative associations between age and tangles in middle frontal cortex, orbital frontal cortex (OFC), and thalamus, and between age and threads in OFC. We found significant positive association between TDP‐43 severity and tangles in substantia nigra, but no associations with alpha‐synuclein severity (Figure 3).ConclusionQuantitative tau measurements largely agree with established semi‐quantitative ratings. Significant associations of quantitative tau measurements with TDP43 pathology and age were found within high Braak stage patients, suggesting quantitative pathology measurements can offer additional information beyond stage alone in these patients.

Using an ex vivo MRI atlas of the human medial temporal lobe to characterize the 3D distribution of neurofibrillary tangle burden across histologically defined subregions

AbstractBackgroundAccumulation of tau neurofibrillary tangles (NFT) in the medial temporal lobe (MTL) is an early pathological change associated with neurodegeneration in Alzheimer’s Disease (AD). Current understanding of the spread of NFTs within the MTL is based on 2‐D histological sections sampled at sparse locations. Here, using human MTL specimens from donors with diagnoses spanning the AD continuum, we examine 3‐D quantitative maps of NFT burden derived from serial histology leveraging a high‐resolution, ex vivo MRI atlas, thus enabling more granular analyses.MethodWe combined ex vivo MRI scans (0.2×0.2×0.2mm3, 9.4T) of 55 MTL specimens using a customized registration approach to construct a 3‐D atlas (Ravikumar et al., Acta Neuropathol Comm, 2021). MTL subregions in the atlas were labelled based on cytoarchitecture using serial Nissl histology (n = 17) (Fig.1). For 25 specimens with a primary diagnosis of AD or primary age‐related tauopathy (78.6±10.9 years; 16M/9F), quantitative NFT burden maps were derived from serial anti‐tau immunohistochemistry histology and registered to the atlas for group‐level analysis (Yushkevich et al., Brain, 2021). For quantitative comparisons, we computed the mean NFT burden and cortical thickness within each subregion.ResultFig.2A shows average and summary frequency maps of NFT burden, computed separately for specimens with a low Braak stage (Braak0‐II; n = 11) and high Braak stage (BraakIV‐VI), that reveal a clear anterior‐to‐posterior gradient in NFT burden. At low Braak stages, we observe high levels of NFT burden in cornu ammonis (CA)1, entorhinal cortex (EC), and Brodmann area 35 (BA35;≈transentorhinal region), particularly in the outer cortical layers. CA1 and EC also show higher NFT burden relative to BA35 (Fig.2C). At high Braak stages, overall NFT burden is visibly higher and more widespread, with significant increases found across almost all subregions (Fig.2B). Moreover, significant correlations between NFT burden and cortical thinning were found in the perforant pathway (PP; molecular layer of the subiculum), dentate gyrus, EC and Areas TE, TF and TH (Fig.3).ConclusionBuilding on earlier work, we provide a detailed characterization of the distribution of NFT burden in the MTL. Our findings of specific subregional involvement of early NFT pathology can help inform the development of improved in vivo neuroimaging biomarkers

Microtubule‐binding region tau fragment tau368 as a biomarker of Alzheimer’s disease

AbstractBackgroundRecent studies suggest that microtubule‐binding region (MTBR) tau fragments may be markers of tau tangles in Alzheimer’s disease (AD) when used in ratio with total tau (MTBR‐tau/T‐tau) to normalize for T‐tau secretion. One such candidate marker is MTBR‐tau containing residue 368 (MTBR‐tau368). In this study, it was cross‐sectionally evaluated in participants from a memory clinic cohort and an autopsy series.MethodsWe included Aβ‐negative cognitively unimpaired (CU) individuals, individuals in the AD continuum (Aβ‐positive CU, mild cognitive impairment (MCI) and AD dementia), and with non‐AD dementia from the BioFINDER‐1 study, who all underwent [18F]‐flortaucipir‐PET. Further, we included CU and CI participants from UCSD Alzheimer’s disease research center (UCSD‐ADRC) who underwent lumbar puncture (LP) antemortem and then donated their brain for autopsy, examining AD neuropathologic change (ADNC) and non‐AD pathologies. All participants had immunoassay‐based CSF measures of T‐tau and MTBR‐tau368 by commercial immunoassays (Euroimmun [BioFINDER‐1] and Lumipulse [UCSD‐ADRC] T‐tau) and an in‐house Single molecule array (Simoa) assay, respectively. Statistical analyses were performed using linear models (covarying for age and sex) and Pearson correlations.ResultsSixty‐seven individuals from UCSD‐ADRC (mean [SD] age at LP 74.3 [8.4] years, 4.3 [2.1] years before death) and 181 from BioFINDER‐1 (72.5 [7.4] years) were included for this study. There were no group‐level differences in MTBR‐tau368 levels alone in any of the cohorts. In the UCSD‐ADRC cohort, MTBR‐tau368/T‐tau was decreased in participants with high (estimated marginal mean [EM = 0.06) vs. low (EM = 0.09, P = 0.01) or no (EM = 0.1, P = 0.001) ADNC and with higher Braak stage (V‐VI; EM = 0.06 vs. III‐IV; EM = 0.08, P&lt;0.05, and I‐II; EM = 0.09, P&lt;0.001). In BioFINDER‐1, Aβ‐positive MCI and AD dementia had lower MTBR‐tau368/T‐tau (EM∼0.04) compared with all other groups (EM = 0.06‐0.07, P&lt;0.05‐&lt;0.001). Further, MTBR‐tau368/T‐tau inversely correlated with tau‐PET in Braak‐like regions III‐IV and V‐VI (r = ‐0.35 and ‐0.42, P&lt;0.001). MTBR‐tau368/T‐tau was unchanged in individuals in the frontotemporal dementia (FTD) spectrum (behavioral variant FTD/semantic dementia, and corticobasal syndrome/progressive supranuclear palsy).ConclusionConcordant with recent data, MTBR‐tau fragments alone do not change in AD or other neurodegenerative disorders. However, when normalizing MTBR fragments to T‐tau secretion, their capability of reflecting the extent of tau pathology provides opportunities of staging AD using CSF biomarkers.

ATN cerebrospinal fluid biomarkers in dementia with Lewy bodies: Initial results from the United States Dementia with Lewy Bodies Consortium.

The National Institute on Aging - Alzheimer's Association (NIA-AA) ATN research framework proposes to use biomarkers for amyloid (A), tau (T), and neurodegeneration (N) to stage individuals with AD pathological features and track changes longitudinally. The overall aim was to utilize this framework to characterize pre-mortem ATN status longitudinally in a clinically diagnosed cohort of dementia with Lewy bodies (DLB) and to correlate it with the post mortem diagnosis. The cohort was subtyped by cerebrospinal fluid (CSF) ATN category. A subcohort had longitudinal data, and a subgroup was neuropathologically evaluated. We observed a significant difference in Aβ42/40 after 12 months in the A+T- group. Post mortem neuropathologic analyses indicated that most of the p-Tau 181 positive (T+) cases also had a high Braak stage. This suggests that DLB patients who are A+ but T- may need to be monitored to determine whether they remain A+ or ever progress to T positivity. Some A+T- DLB subjects transition from A+ to negative after 12-months. Clinically diagnosed DLB with LBP-AD (A+T+) maintain their positivity. Clinically diagnosed DLB with LBP-AD (A+T+) maintain their positivity. Monitoring of the A+T- sub-type of DLB may be necessary.

Inflammation and the pathological progression of Alzheimer's disease are associated with low circulating choline levels.

Deficiency of dietary choline, an essential nutrient, is observed worldwide, with ~ 90% of Americans beingdeficient. Previous work highlights a relationship between decreased choline intake and an increased risk for cognitive decline and Alzheimer's disease (AD). The associations between blood circulating choline and the pathological progression in both mild cognitive impairment (MCI) and AD remain unknown. Here, we examined these associations ina cohort of patients with MCI with presence of either sparse or high neuritic plaque density and Braak stage and a second cohortwith either moderate AD (moderate to frequent neuritic plaques, Braak stage = IV) or severe AD (frequent neuritic plaques, Braak stage = VI), compared to age-matched controls. Metabolomic analysis was performed on serum from the AD cohort. We then assessed the effects of dietary choline deficiency (Ch-) in 3xTg-AD mice and choline supplementation (Ch+) in APP/PS1 mice, tworodent models of AD. The levels of circulating choline were reduced while pro-inflammatory cytokine TNFαwas elevated in serum of both MCI sparse and high pathology cases. Reduced choline and elevated TNFα correlated with higher neuritic plaque density and Braak stage. In AD patients, we found reductions in choline, its derivative acetylcholine (ACh), and elevated TNFα. Choline and ACh levelswere negatively correlated with neuritic plaqueload, Braak stage, and TNFα, but positively correlated with MMSE, and brain weight. Metabolites L-Valine, 4-Hydroxyphenylpyruvic, Methylmalonic, and Ferulic acids were significantly associated with circuiting choline levels. In 3xTg-AD mice, the Ch- diet increased amyloid-β levels and tau phosphorylation in cortical tissue, and TNFαin both blood and cortical tissue, paralleling the severe human-AD profile. Conversely, the Ch+ diet increased choline and ACh while reducing amyloid-βand TNFαlevels in brains of APP/PS1 mice. Collectively, low circulating choline is associated with AD-neuropathological progression, illustrating the importance of adequate dietary choline intake to offset disease.

Tau seeds occur before earliest Alzheimer’s changes and are prevalent across neurodegenerative diseases

Tau neurofibrillary tangles are a hallmark of Alzheimer’s disease neuropathological change. However, it remains largely unclear how distinctive Alzheimer’s disease tau seeds (i.e. 3R/4R) correlate with histological indicators of tau accumulation. Furthermore, AD tau co-pathology is thought to influence features and progression of other neurodegenerative diseases including Lewy body disease; yet measurements of different types of tau seeds in the setting of such diseases is an unmet need. Here, we use tau real-time quaking-induced conversion (RT-QuIC) assays to selectively quantitate 3R/4R tau seeds in the frontal lobe which accumulates histologically identifiable tau pathology at late disease stages of AD neuropathologic change. Seed quantitation across a spectrum of neurodegenerative disease cases and controls indicated tau seeding activity can be detected well before accompanying histopathological indication of tau deposits, and even prior to the earliest evidence of Alzheimer’s-related tau accumulation anywhere in the brain. In later stages of AD, 3R/4R tau RT-QuIC measures correlated with immunohistochemical tau burden. In addition, Alzheimer’s tau seeds occur in the vast majority of cases evaluated here inclusive of primary synucleinopathies, frontotemporal lobar degeneration and even controls albeit at multi-log lower levels than Alzheimer’s cases. α-synuclein seeding activity confirmed synucleinopathy cases and further indicated the co-occurrence of α-synuclein seeds in some Alzheimer’s disease and primary tauopathy cases. Our analysis indicates that 3R/4R tau seeds in the mid-frontal lobe correlate with the overall Braak stage and Alzheimer’s disease neuropathologic change, supporting the quantitative predictive value of tau RT-QuIC assays. Our data also indicate 3R/4R tau seeds are elevated in females compared to males at high (≥ IV) Braak stages. This study suggests 3R/4R tau seeds are widespread even prior to the earliest stages of Alzheimer’s disease changes, including in normal, and even young individuals, with prevalence across multiple neurodegenerative diseases to further define disease subtypes.

Polyubiquitination of Tau Increases Across Braak Stages in Alzheimer’s Disease

AbstractBackgroundThe proteolytic ubiquitin‐proteasome system (UPS) is a main control mechanism of tau degradation in eukaryotic cells. Although the UPS is an integral regulator for tau turnover in healthy neurons, preliminary data suggests that the pathological tau in Alzheimer’s Disease (AD) is polyubiquitinated. This is an intriguing conundrum where the polyubiquitinylation of tau does not result in the degradation of the protein by the UPS. This suggests that the capacity of the UPS is limited or that the UPS is unable to degrade this form of tau. In this study, we aim to validate this potential correlation between the polyubiquitination of tau and AD, which could perhaps provide more clarity on the specific mechanisms of toxicity for AD.MethodWe examined postmortem brain tissue (inferior temporal gyrus) of 11 cases across AD neuropathological spectrum (Table 1). All slides underwent multiplex immunofluorescence for four antibodies: NeuN (neurons), FK2 (to detect polyubiquitin), T231 (ptau), and GFAP (astroglia), followed by scanning and quantification on digital slides. We quantified the percentage of neurons positive for tau (T231) and polyubiquitination (FK2) and analyzed the spearman correlation and linear regression model (LRM) corrected by age on death and sex.ResultCases represent a spectrum of AD stage. As expected, the proportion of neurons with tau inclusions increase along AD progression. We failed to identify neurons positive for FK2 (polyubiquitination) in the absence of tau and neurons. Moreover, we observed a direct correlation between higher Braak Stages and proportion of neurons with polyubiquitin immunoprecipitations (Figure 1, ρ = 0.89, p = 2.33e‐4).ConclusionNeurons with polyubiquitin immunoprecipitations increase in number along the AD continuum. These neurons tend to accumulate phospho‐tau inclusions suggesting a polyubiquitination of tau in AD. Further studies are needed to identify the mechanisms underlying the lack of tau degradation by the UPS in this situation, which could lead to treatment opportunities for AD.

Neuronal loss of the nucleus basalis of Meynert in primary progressive aphasia is associated with Alzheimer's disease neuropathological changes.

Imaging studies indicated basal forebrain reduction in primary progressive aphasia (PPA), which might be a candidate marker for cholinergic treatment. Nucleus basalis of Meynert (nbM) neuronal loss has been reported, but a systematic quantitative neuropathological assessment including the three clinical PPA variants is lacking. Quantitative assessment of neuronal density and pathology was performed on nbM tissue of 47 cases: 15 PPA, constituting the different clinicopathological phenotypes, 14 Alzheimer's disease (AD), and 18 cognitively normals. Group-wise, reduced nbM neuronal density was restricted to AD. At the individual level, semantic variant PPA with underlying AD neuropathological change (ADNC) had lower neuronal densities, while those with frontotemporal lobar degeneration (FTLD) transactive response DNA binding protein 43 kDa (TDP-43) type C pathology were unaffected. Higher Braak stages and increased numbers of nbM-related pretangles were associated with nbM neuronal loss. nbM neuronal loss in PPA is related to ADNC. This study cautions against overinterpreting MRI-based basal forebrain volumes in non-AD PPA as neuronal loss.

Immunogenomics Parameters for Patient Stratification in Alzheimer's Disease.

Despite the fact that only modest adaptive immune system related approaches to treating Alzheimer's disease (AD) are available, an immunogenomics approach to the study of AD has not yet substantially advanced. Thus, we sought to better understand adaptive immune receptor chemical features in the AD setting. We characterized T-cell receptor alpha (TRA) complementarity determining region-3 (CDR3) physicochemical features and identified TRA CDR3 homology groups, represented by TRA recombination reads extracted from 2,665 AD-related, blood- and brain-derived exome files. We found that a higher isoelectric value for the brain TRA CDR3s was associated with a higher (clinically worse) Braak stage and that a number of TRA CDR3 chemical homology groups, in particular representing bloodborne TRA CDR3s, were associated with higher or lower Braak stages. Lastly, greater chemical complementarity of both blood- and brain-derived TRA CDR3s and tau, based on a recently described CDR3-candidate antigen chemical complementarity scoring process (https://adaptivematch.com), was associated with higher Braak stages. Overall, the data reported here raise the questions of (a) whether progression of AD is facilitated by the adaptive immune response to tau; and (b) whether assessment of such an anti-tau immune response could potentially serve as a basis for adaptive immune receptor related, AD risk stratification?

Ante-mortem plasma phosphorylated tau (181) predicts Alzheimer's disease neuropathology and regional tau at autopsy.

Blood-based biomarkers such as tau phosphorylated at threonine 181 (phosphorylated-tau181) represent an accessible, cost-effective and scalable approach for the in vivo detection of Alzheimer's disease pathophysiology. Plasma-pathological correlation studies are needed to validate plasma phosphorylated-tau181 as an accurate and reliable biomarker of Alzheimer's disease neuropathological changes. This plasma-to-autopsy correlation study included participants from the Boston University Alzheimer's Disease Research Center who had a plasma sample analysed for phosphorylated-tau181 between 2008 and 2018 and donated their brain for neuropathological examination. Plasma phosphorelated-tau181 was measured with single molecule array technology. Of 103 participants, 62 (60.2%) had autopsy-confirmed Alzheimer's disease. Average time between blood draw and death was 5.6 years (standard deviation = 3.1 years). Multivariable analyses showed higher plasma phosphorylated-tau181 concentrations were associated with increased odds for having autopsy-confirmed Alzheimer's disease [AUC = 0.82, OR = 1.07, 95% CI = 1.03-1.11, P < 0.01; phosphorylated-tau standardized (z-transformed): OR = 2.98, 95% CI = 1.50-5.93, P < 0.01]. Higher plasma phosphorylated-tau181 levels were associated with increased odds for having a higher Braak stage (OR = 1.06, 95% CI = 1.02-1.09, P < 0.01) and more severe phosphorylated-tau across six cortical and subcortical brain regions (ORs = 1.03-1.06, P < 0.05). The association between plasma phosphorylated-tau181 and Alzheimer's disease was strongest in those who were demented at time of blood draw (OR = 1.25, 95%CI = 1.02-1.53), but an effect existed among the non-demented (OR = 1.05, 95% CI = 1.01-1.10). There was higher discrimination accuracy for Alzheimer's disease when blood draw occurred in years closer to death; however, higher plasma phosphorylated-tau181 levels were associated with Alzheimer's disease even when blood draw occurred >5 years from death. Ante-mortem plasma phosphorylated-tau181 concentrations were associated with Alzheimer's disease neuropathology and accurately differentiated brain donors with and without autopsy-confirmed Alzheimer's disease. These findings support plasma phosphorylated-tau181 as a scalable biomarker for the detection of Alzheimer's disease.

Associations between cognition, Aβ, and tau in adults with Down syndrome

AbstractBackgroundAdults with Down syndrome (DS) are widely affected by AD pathology by their 30’s and have a 70‐80% chance of clinical dementia by their 60’s. The aim of the present study was to explore the relationship between cognitive decline and tau pathology using a regression model to explore the associations between longitudinal rates of cognition and the cross‐sectional tau burden in adults with DS.MethodNinety‐two participants (age=39.19±8.44 at time of tau scan) with DS with multiple cognitive assessments over a period of 9 years, PiB scans over a period of 8 years, and one [18F]AV‐1451 scan were analyzed. Cognitive assessments included tests of overall function (DSMSE), memory (cued recall), executive function (Stroop), and motor function (Purdue pegboard). FreeSurfer (v5.3.0) was used for the definition of ROIs. A two‐stage analysis was performed for cognition and AV‐1451 correlations or PiB and AV‐1451 correlations: 1) a linear mixed model was applied to estimate the rates of change for cognitive outcomes or PiB over time and 2) the cognitive or PiB estimated rates from the trajectories were used as predictors of interest in a correlation analysis with AV‐1451 for each Braak‐associated (1‐6) region as the outcome.ResultStatistically significant associations were found between AV‐1451 retention in all Braak regions and cognitive assessments at alpha=0.05 , including cued recall, DSMSE, and the Purdue pegboard task, but not for the Stroop test (Table 1). Statistically significant associations were also found in Braak regions 3‐6 at alpha=0.05 between longitudinal PiB estimated amyloid trajectories and cross‐sectional AV‐1451 retention.ConclusionFor this DS population, we found inverse associations between rates of neuropsychological decline and higher tau pathology. In particular, decline in global cognition, verbal memory and motor function were all associated with higher tau pathology, while executive function was not. Further, longitudinal analyses demonstrated an association between cross‐sectional and accumulating amyloid pathology with increased tau pathology in regions associated with higher Braak stages.

Tau seeds are widespread in the brain at the earliest stages of Alzheimer's disease-related changes.

Alzheimer's disease (AD) is pathologically characterized by the systematic spread of 3R/4R tau species with progressing disease. Current imaging and CSF in-vivo assessments of tau are thought to reflect more mature tangle neuropathology. However, earlier oligomeric tau species are indicated to have greater neurotoxicity than mature forms and it is largely unknown how tau seeds correlate with histological indicators of AD. Furthermore, tau co-pathology is thought to influence features and progression of other neurodegenerative diseases including Lewy body disease (LBD); yet reliable measurements of tau seeds in such diseases remains an unmet need. Here, we use tau real-time quaking-induced conversion (RT-QuIC) assays to directly measure bioactive tau seeds in brain samples across a spectrum of neurodegenerative diseases to determine tau seeding activities at different stages of AD related changes. Tau RT-QuIC exploits the seeded polymerization growth mechanism of tau filaments, with sensitivities in the low fM range, allowing quantitation of disease-associated aggregates with unprecedented sensitivity and selectivity. Tau RT-QuIC assays were used to quantitate tau seeds in mid-frontal lobe brain tissue from 64 cases including subjects with neuropathologically confirmed AD (n=15), Parkinson's disease (n=7), multiple system atrophy (n=6), LBD (n=14), frontotemporal lobar degeneration (n=4), progressive supranuclear palsy (n=6), corticobasal degeneration (n=2), early Alzheimer's changes (Braak I-III) (n=7), and controls (n=3). All cases had Braak tau staging and frontal lobes were immunohistochemically stained for tau with NFT1. 3R/4R tau seeding activity is typically 100-1000-fold higher in cases with a primary AD diagnosis compared to controls, 4R tauopathies, and synucleinopathies, consistent with our prior observations. Seeding activity positively correlated with Braak tau stage, a histological measure of tau accumulation, with increased tau seeding activities at higher Braak stages. Tau seeds are detectable in the frontal lobe even at Braak I, a stage at which frontal lobe lacks histologically visible tau deposits. Ultrasensitive RT-QuIC assays detect tau seeds at the earliest stages of disease processes, prior to histopathological evidence of more mature tau accumulations and can indicate co-occurrence of tau pathology in non-AD cases. Tau seeding activity correlates with overall Braak tau stage, raising the possibility of quantitative value of tau RT-QuIC assays.

Long-term exposure to ambient air pollution is associated with neuropathologic change of Alzheimer's Disease at Autopsy

BACKGROUND AND AIM: There is a growing body of evidence linking exposure to air pollution with dementia and Alzheimer’s disease (AD). However, the detailed molecular mechanisms explaining how air pollution exposures may affect the human brain are still largely unknown. Investigating the impact of air pollution on markers of AD neuropathology might provide mechanistic insights. We evaluated associations of long-term exposure to air pollution prior to death with three different measures of AD neuropathology: Braak stage; Consortium to Establish a Registry for AD (CERAD) neuritic plaque score; and combined AD neuropathologic change (ABC score). METHODS: We obtained data on the neuropathology markers from autopsy samples collected after 2008 from the Emory University Goizueta Alzheimer’s Disease Research Center Neuropathology Core Brain Bank (N=145 donors from Metro Atlanta, Georgia, USA). Long-term exposures to PM2.5, CO, and NOx were estimated at the deceased’s last address for a fixed 7-year period (2002-2008) via the Research LINE source model (resolution: 250m). We performed ordinal logistic regression for each marker adjusting for age at death, race, gender, educational attainment, and APOE genotype. RESULTS:The average age at death was 76 years (SD=9.5). The medians of exposure to PM2.5, CO, and NOx were 0.32µg/m3, 157.9ppb, 12.9ppb, respectively. After adjustment, one unit increase in 7-year average PM2.5 was associated with higher Braak stage [OR = 5.40 (1.30, 28.25)]. Associations with CERAD [0.83 (0.12, 5.61)] and ABC [2.41 (0.42, 13.95)] scores were not significant and no significant associations were found for CO and NOx (Braak stage: 1.00 (0.99, 1.01) and 1.04 (0.99, 1.10), respectively). CONCLUSIONS:PM2.5 was associated with neuropathologic changes assessed by Braak stage, which characterizes the abundance of neurofibrillary tangles. As Braak staging is the neuropathology marker showing the strongest association with cognitive performance and decline, these findings could have implication for both AD and AD-related dementias. KEYWORDS: Air pollution, Neurodegenerative outcomes.