Eleutheroside B ameliorates AD-like pathological features in Caenorhabditis elegans by inducing autophagy and combating oxidative stress.

Investigation of frailty as a moderator of the relationship between neuropathology and dementia in Alzheimer's disease: a cross-sectional analysis of data from the Rush Memory and Aging Project

This study aimed to determine the pattern of 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET) related to postmortem Lewy body disease (LBD) pathology in clinical Alzheimer disease (AD). FDG-PET scans were analyzed in 62 autopsy-confirmed patients and 110 controls in the Alzheimer's Disease Neuroimaging Initiative. Based on neuropathologic evaluations on Braak stage for neurofibrillary tangle, Consortium to Establish a Registry for AD score for neuritic plaque, and Lewy-related pathology, subjects were classified into AD(-)/LBD(-), AD(-)/LBD(+), AD(+)/LBD(-), and AD(+)/LBD(+) groups. The association between postmortem LBD and AD pathologies and antemortem brain metabolism was evaluated. AD and LBD pathologies had significant interaction effects to decrease metabolism in the cerebellar vermis, bilateral caudate, putamen, basal frontal cortex, and anterior cingulate cortex in addition to the left side of the entorhinal cortex and amygdala, and significant interaction effects to increase metabolism in the bilateral parietal and occipital cortices. LBD pathology was associated with hypermetabolism in the cerebellar vermis, bilateral putamen, anterior cingulate cortex, and basal frontal cortex, corresponding to the Lewy body-related hypermetabolic patterns. AD pathology was associated with hypometabolism in the bilateral hippocampus, entorhinal cortex, and posterior cingulate cortex regardless of LBD pathology, whereas LBD pathology was associated with hypermetabolism in the bilateral putamen and anterior cingulate cortex regardless of AD pathology. Postmortem LBD and AD pathologies had significant interaction effects on the antemortem brain metabolism in clinical AD patients. Specific metabolic patterns related to AD and LBD pathologies could be elucidated when simultaneously considering the two pathologies. ANN NEUROL 2022;91:853-863.

In Vivo Spreading of Tau Pathology

New unexpected role for Wolfram Syndrome protein WFS1: a novel therapeutic target for Alzheimer's disease?

Introduction: Alzheimer's disease (AD) represents a critical global health challenge with limited therapeutic options, prompting the exploration of alternative strategies. A key pathology in AD involves amyloid beta (Aβ) aggregation, and targeting both Aβ aggregation and oxidative stress is crucial for effective intervention. Natural compounds from medicinal and food sources have emerged as potential preventive and therapeutic agents, with Nelumbo nucifera leaf extract (NLE) showing promising properties. Methods: In this study, we utilized transgenic Caenorhabditis elegans (C. elegans) models to investigate the potential of NLE in countering AD and to elucidate the underlying mechanisms. Various assays were employed to assess paralysis rates, food-searching capabilities, Aβ aggregate accumulation, oxidative stress, lifespan under stress conditions, and the expression of stress-resistance-related proteins. Additionally, autophagy induction was evaluated by measuring P62 levels and the formation of LGG-1+ structures, with RNAi-mediated inhibition of autophagy-related genes to confirm the mechanisms involved. Results: The results demonstrated that NLE significantly reduced paralysis rates in CL4176 and CL2006 worms while enhancing food-searching capabilities in CL2355 worms. NLE also attenuated Aβ aggregate accumulation and mitigated Aβ-induced oxidative stress in C. elegans. Furthermore, NLE extended the lifespan of worms under oxidative and thermal stress conditions, while concurrently increasing the expression of stress-resistance-related proteins, including SOD-3, GST-4, HSP-4, and HSP-6. Moreover, NLE induced autophagy in C. elegans, as evidenced by reduced P62 levels in BC12921 worms and the formation of LGG-1+ structures in DA2123 worms. The RNAi-mediated inhibition of autophagy-related genes, such as bec-1 and vps-34, negated the protective effects of NLE against Aβ-induced paralysis and aggregate accumulation. Discussion: These findings suggest that NLE ameliorates Aβ-induced toxicity by activating autophagy in C. elegans. The study underscores the potential of NLE as a promising candidate for further investigation in AD management, offering multifaceted approaches to mitigate AD-related pathology and stress-related challenges.

The microtubule-associated protein tau is hyperphosphorylated and forms neurofibrillary tangles in Alzheimer disease. Additionally caspase-cleaved tau is present in Alzheimer disease brains co-localized with fibrillar tau pathologies. To further understand the role of site-specific phosphorylation and caspase cleavage of tau in regulating its function, constructs of full-length tau (T4) or tau truncated at Asp421 (T4C3) to mimic caspase-3 cleavage with and without site-directed mutations that mimic phosphorylation at Thr231/Ser235, Ser396/Ser404, or at all four sites (Thr231/Ser235/Ser396/Ser404) were made and expressed in cells. Pseudophosphorylation of T4, but not T4C3, at either Thr231/Ser235 or Ser396/Ser404 increased its phosphorylation at Ser262 and Ser199. Pseudophosphorylation at Thr231/Ser235 impaired the microtubule binding of both T4 and T4C3. In contrast, pseudophosphorylation at Ser396/Ser404 only affected microtubule binding of T4C3 but did make T4 less soluble and more aggregated, which is consistent with the previous finding (Abraha, A., Ghoshal, N., Gamblin, T. C., Cryns, V., Berry, R. W., Kuret, J., and Binder, L. I. (2000) J. Cell Sci. 113, 3737-3745) that pseudophosphorylation at Ser396/Ser404 enhances tau polymerization in vitro. In situ T4C3 was more prevalent in the cytoskeletal and microtubule-associated fractions compared with T4, whereas purified recombinant T4 bound microtubules with higher affinity than did T4C3 in an in vitro assay. These data indicate the importance of cellular factors in regulating tau-microtubule interactions and that, in the cells, phosphorylation of T4 might impair its microtubule binding ability more than caspase cleavage. Treatment of cells with nocodazole revealed that pseudophosphorylation of T4 at both Thr231/Ser235 and Ser396/Ser404 diminished the ability of tau to protect against microtubule depolymerization, whereas with T4C3 only pseudophosphorylation at Ser396/Ser404 attenuated the ability of tau to stabilize the microtubules. These results show that site-specific phosphorylation and caspase cleavage of tau differentially affect the ability of tau to bind and stabilize microtubules and facilitate tau self-association.

We would like to thank Dr Exley for his thoughts [1]. To address his comment regarding data presented in Fig. 1 of our recently published paper [4], which demonstrates that 0.2–20 mM AlCl3 inhibited heparin (10μM)-induced tau (10μM) aggregation, we repeated the heparin-induced tau aggregation experiment using a lower range of AlCl3 (50 nM–2 mM). This concentration range of Al did not show clear inhibition of heparininduced tau aggregation (see Supplementary Figure). Therefore, Dr Exley’s explanation that the excess of Al absorbed heparin and inhibited tau aggregation, may be a possibility. Another possibility as described in our discussion section [4] is that, Al may directly bind to tau, and inhibit heparin-induced tau aggregation. This suggestion of the direct binding of Al to tau is further supported by the presence of Al in neurofibrillary tangles found in Alzheimer’s disease (AD) brains as well as by previous in vitro studies that showed Al-induced tau aggregation in the absence of heparin [2]. In contrast to a previous study [2], our data showed that the addition of Al (50 nM–2 mM) to 10 μM tau produced a 0.05–200 Al/tau molar ratio that failed to evoke tau aggregation with increasing thioflavin T fluorescence. This discrepancy could reflect a difference in the concentration of tau used between the two studies, as Haase and colleagues used 80 μM tau triggered by 3 mM Al. So, while the molar ratio 34.5 of Al (3 mM)/tau (80 μM) may be appropriate for inducing tau aggregation, the same ratio using 10 μM tau may not, indicating a tau-concentration dependency of the aggregation-inducing properties of Al. It seems that a higher concentration of tau, such as 80 μM, is required for Al-induced β-sheet tau aggregation in an in vitro study. Thus, the physiological concentration of tau, which has been reported as being between 1–10 μM in neurons [3], cannot induce fibrilar tau aggregation. In our cellular study [4], Dr. Exley pointed out that N2a cells may not have been exposed to the indicated concentrations (50,100, and 200μM) of Al, in our fresh Al maltorate solution, prepared by mixing an equal volume of AlCl3 solution with Maltol solution (a two fold dilution). Even though exposed to a lower concentration of Al than anticipated (according to Dr Exley’s proposition), these cells clearly exhibited Al-induced SDS-insoluble tau aggregates. However, as suggested from our in vitro tau studies, the aggregates may be amorphous and not fibrilar as shown by AFM. Regarding our animal study [4], independent of the real concentration of the exogenously administrated Al, these animals showed an overall increase (up to ∼ 20 μM) in the total concentration of brain Al in comparison to controls. Acceleration of tau aggregation, however, was not detected by either biochemical or histopathological methods. Rather than tau-based brain pathology, the increased mortality of these animals could have been induced by the peripheral effect of Al on the animal’s physiology and homeostasis. A non-direct role for Al on AD pathogenesis is further supported by Pratico and colleagues (2002). Using an alternative method of Al administration in a different AD model (APP transgenic mouse), they report-

Alzheimer's disease (AD) is characterized neuropathologically by the presence of amyloid plaques, neuritic plaques, and neurofibrillary tangles (NFTs). These lesions occur not only in demented individuals with AD but also in non-demented persons. In non-demented individuals, amyloid and neuritic plaques are usually accompanied with NFTs and are considered to represent asymptomatic or preclinical AD (pre-AD) pathology. Here, we defined and characterized neuropathological differences between clinical AD, non-demented pre-AD, and non-AD control cases. Our results show that clinical AD may be defined as cases exhibiting late stages of NFT, amyloid, and neuritic plaque pathology. This is in contrast to the neuropathological changes characteristic of pre-AD, which display early stages of these lesions. Both AD and pre-AD cases often exhibit cerebral amyloid angiopathy (CAA) and granulovacuolar degeneration (GVD), and when they do, these AD-related pathologies were at early stages in pre-AD cases and at late stages in symptomatic AD. Importantly, NFTs, GVD, and CAA were also observed in non-AD cases, i.e., in cases without amyloid plaque pathology. Moreover, soluble and dispersible, high-molecular-weight amyloid β-protein (Aβ) aggregates detected by blue-native polyacrylamide gel electrophoresis were elevated in clinical AD compared to that in pre-AD and non-AD cases. Detection of NFTs, GVD, and CAA in cases without amyloid plaques, presently classified as non-AD, is consistent with the idea that NFTs, GVD, and CAA may precede amyloid plaque pathology and may represent a pre-amyloid plaque stage of pre-AD not yet considered in the current recommendations for the neuropathological diagnosis of AD. Our finding of early stages of AD-related NFT, amyloid, and GVD pathology provides a more clear definition of pre-AD cases that is in contrast to the changes in clinical AD, which is characterized by late stages of these AD-related pathologies. The observed elevation of soluble/dispersible Aβ aggregates from pre-AD compared to that in AD cases suggests that, in addition to more widespread AD-related pathologies, soluble/dispersible Aβ aggregates in the neuropil play a role in the conversion of pre-AD to clinical AD.

BackgroundLewy body disease (LBD) is a neurodegenerative disease characterized by Lewy bodies, and it clinically presents dementia with Lewy bodies (DLB) and Parkinson's disease (PD). Alzheimer's disease (AD) pathologies frequently coexist with LBD, complicating the clinical manifestation.ObjectiveWe evaluated the impact of AD pathologies, including amyloid-β and tau depositions, on cognitive dysfunction and glucose metabolism in LBD using multiple positron emission tomography scans.MethodsOur study cohort consisted of 14 patients diagnosed with LBD, including five from the PD spectrum and nine from the DLB spectrum. In addition, 12 amyloid-negative cognitively healthy controls (HCs) and 13 amyloid-positive AD-spectrum patients were included. We subsequently explored the influence of amyloid and tau deposition on cognitive dysfunction and glucose metabolism among the LBD patients.ResultsIn the LBD group, 44.4% of the DLB patients were amyloid-positive, and all PD patients were amyloid-negative. While tau accumulation was lower than in AD and similar to HCs at the group level, tau accumulation in the AD signature region was correlated with cognitive dysfunction. Among the changes in glucose metabolism, the cingulate island sign (CIS) index was elevated compared to AD. However, as cognitive impairment progressed, the CIS index decreased, reflecting reduced metabolism in the posterior cingulate gyrus, which was closely associated with tau accumulation in the same region.ConclusionsOur findings indicate that AD pathologies, and particularly tau accumulation, significantly impact both cognitive dysfunction and glucose metabolism in LBD. This underscores the importance of addressing AD-related changes in the clinical management of LBD patients.

BackgroundRecent advancements in molecular positron emission tomography (PET) enable precise tracking of tau pathology in Alzheimer's disease (AD). Tau pathology typically begins focally in the medial temporal lobe, rapidly expanding due to amyloid‐β (Aβ) influence. This expansion may lead to neurodegeneration along connected pathways to the tau epicenters, resulting in cognitive decline. Our study utilized PET scans, diffusion Orientation Dispersion and Density Imaging (NODDI), and longitudinal memory data to investigate the intricate connections between tau accumulation and neurite microstructures in white matter bundles connected to the tau epicenter and resulting cognitive decline.MethodThe study had 155 participants, including 90 cognitively normal (CN) and 65 mild cognitive impairment (MCI) from the Alzheimer's Disease Neuroimaging Initiative dataset (Table 1). The study included cortical tau accumulations in the entorhinal cortex (EC) to the hippocampus (H) and neurite microstructures of the cingulum hippocampal bundle (CHB). The study also included longitudinal episodic memory scores measured using the Rey Auditory Verbal Learning Test Immediate (RAVLT‐I).ResultThe association between tau accumulation in EC and H in the right and left hemispheres was found to be significantly related to the increased isotropic water (FISO) of HCB (p<0.01). In contrast, the fiber complexity (ODI) along the CHBshowed a correlation with tau accumulation in the right EC (p=0.03, t=2.31) and H (p=0.02, t=‐2.33) for the entire sample. It's worth noting that significant correlations between FISO and ODI and tau accumulations in the epicenters remained significant for the amyloid‐positive group (Aβ+ CN and MCI). Also, the tau aggregation in the retrosplenial cortex (RSC) was significantly correlated with the neurite layout of CHB (p<0.05). Finally, we explored the correlation between the microstructural changes in neurites along the CHB and cognitive decline. The linear mixed effect model showed a significant interaction effect of tau_EC (left)xCHB_ODI (left)xtime (p=0.03, f=4.58) and tau_RSC (left)xCHB_ODI (left)xtime (p=0.04, f=4.4) for predicting cognitive decline over three years.ConclusionOur research has revealed significant connections between the tau accumulation in tau epicenters and posterior regions and the microstructures of neurites along CHB, suggesting that CHB plays a crucial role in tau spreading and cognitive decline.

Misfolded amyloid-β strains and their potential roles in the clinical and pathological variability of Alzheimer's disease.

Hyperphosphorylated transactive response DNA-binding protein 43 (TDP-43, encoded by TARDBP ) proteinopathy has recently been described in ageing and in association with cognitive impairment, especially in the context of Alzheimer's disease pathology. To explore the role of mixed Alzheimer's disease and TDP-43 pathologies in clinical Alzheimer's-type dementia, we performed a comprehensive investigation of TDP-43, mixed pathologies, and clinical Alzheimer's-type dementia in a large cohort of community-dwelling older subjects. We tested the hypotheses that TDP-43 with Alzheimer's disease pathology is a common mixed pathology; is related to increased likelihood of expressing clinical Alzheimer's-type dementia; and that TDP-43 pathologic stage is an important determinant of clinical Alzheimer's-type dementia. Data came from 946 older adults with ( n = 398) and without dementia ( n = 548) from the Rush Memory and Aging Project and Religious Orders Study. TDP-43 proteinopathy (cytoplasmic inclusions) was present in 496 (52%) subjects, and the pattern of deposition was classified as stage 0 (none; 48%), stage 1 (amygdala; 18%), stage 2 (extension to hippocampus/entorhinal; 21%), or stage 3 (extension to neocortex; 14%). TDP-43 pathology combined with a pathologic diagnosis of Alzheimer's disease was a common mixed pathology (37% of all participants), and the proportion of subjects with clinical Alzheimer's-type dementia formerly labelled 'pure pathologic diagnosis of Alzheimer's disease' was halved when TDP-43 was considered. In logistic regression models adjusted for age, sex, and education, TDP-43 pathology was associated with clinical Alzheimer's-type dementia (odds ratio = 1.51, 95% confidence interval = 1.11, 2.05) independent of pathological Alzheimer's disease (odds ratio = 4.30, 95% confidence interval = 3.08, 6.01) or other pathologies (infarcts, arteriolosclerosis, Lewy bodies, and hippocampal sclerosis). Mixed Alzheimer's disease and TDP-43 pathologies were associated with higher odds of clinical Alzheimer's-type dementia (odds ratio = 6.73, 95% confidence interval = 4.18, 10.85) than pathologic Alzheimer's disease alone (odds ratio = 4.62, 95% confidence interval = 2.84, 7.52). In models examining TDP-43 stage, a dose-response relationship with clinical Alzheimer's-type dementia was observed, and a significant association was observed starting at stage 2, extension beyond the amygdala. In this large sample from almost 1000 community participants, we observed that TDP-43 proteinopathy was very common, frequently mixed with pathological Alzheimer's disease, and associated with a higher likelihood of the clinical expression of clinical Alzheimer's-type dementia but only when extended beyond the amygdala.

The power of fruit fly genetics is being deployed against some of the most intractable and economically significant problems in modern medicine, the neurodegenerative diseases. Fly models of Alzheimer's disease can be exposed to the rich diversity of biological techniques that are available to the community and are providing new insights into disease mechanisms, and assisting in the identification of novel targets for therapy. Similar approaches might also help us to interpret the results of genome-wide association studies of human neurodegenerative diseases by allowing us to triage gene “hits” according to whether a candidate risk factor gene has a modifying effect on the disease phenotypes in fly model systems.

Alzheimer’s disease (AD) is neuropathologically characterized by tau-immunopositive neurofibrillary tangles (NFTs) and amyloid-β (Aβ)-immunopositive senile plaques. According to the widely accepted amyloid cascade hypothesis, Aβ pathology represents the upstream event in AD pathophysiology and induces tau aggregation. However, numerous studies have suggested that tau aggregates correlate more closely with neuronal loss and regional brain atrophy than with Aβ depositions. Tau aggregation in AD demonstrates a hierarchical spreading pattern beginning in the transentorhinal cortex, but the mechanisms underlying this spreading manner of lesions remain to be elucidated. This review aims to address current controversies regarding tau pathology in AD from the perspectives of both the ‘amyloid cascade’ and ‘tauopathy’ hypotheses. From the ‘amyloid cascade’ viewpoint, Aβ deposition prominently involves distal axon and axon terminals, and in some regions, there are anatomical correspondences between axonal Aβ pathology and cytoplasmic tau aggregations (e.g., a close relationship between senile plaques in the molecular layer of the hippocampal dentate gyrus and NFTs in the transentorhinal cortex). Nevertheless, this model cannot explain the whole body of hierarchical spreading of tau aggregation because notable spaciotemporal discrepancies also exist in many regions. From the ‘tauopathy’ perspective, the distribution of tau aggregates in AD involves key nodes within the memory circuits. Also, experimental studies have suggested that patient-derived tau exhibits seeding and neuron-to-neuron propagation properties. Interestingly, tau aggregation in AD appears to spread laterally in a proximity-dependent, cortico-cortical fashion rather than along long-range memory circuits. This contrasts with the system-selective, poly-nodal degenerations seen in four-repeat tauopathies, amyotrophic lateral sclerosis, or spinocerebellar degenerations. Moreover, the proportions of three-repeat and four-repeat isoforms shift during the maturation of NFTs in AD. Overall, spreading patterns of tau-pathology in AD cannot be fully explained by Aβ pathology and also differ from the system degeneration seen in other tauopathies.

In a host of neurodegenerative diseases Tau, a microtubule-associated protein, aggregates into insoluble lesions within neurons. Previous studies have utilized cyanine dyes as Tau aggregation inhibitors in vitro. Herein we utilize cyanine dye 3,3'-diethyl-9-methyl-thiacarbocyanine iodide (C11) to modulate Tau polymerization in two model systems, an organotypic slice culture model derived from Tau transgenic mice and a split green fluorescent protein complementation assay in Tau-expressing cells. In slice cultures, submicromolar concentrations (0.001 microm) of C11 produced a significant reduction of aggregated Tau and a corresponding increase in unpolymerized Tau. In contrast, treatment with a 1 microm dose promoted aggregation of Tau. These results were recapitulated in the complementation assay where administration of 1 microm C11 produced a significant increase in polymerized Tau relative to control, whereas treatment of cells with 0.01 microm C11 resulted in a marked reduction of aggregated Tau. In the organotypic slice cultures, modulation of Tau aggregation was independent of changes in phosphorylation at disease and microtubule binding relevant epitopes for both dosing regimes. Furthermore, treatment with 0.001 microm C11 resulted in a decrease in both total filament mass and number. There was no evidence of apoptosis or loss of synaptic integrity at either dose, however, whereas submicromolar concentrations of C11 did not interfere with microtubule binding, higher doses resulted in a decrease in the levels of microtubule-bound Tau. Overall, a cyanine dye can dissociate aggregated Tau in an ex vivo model of tauopathy with little toxicity and exploration of the use of these type of dyes as therapeutic agents is warranted.