Classification and basic pathology of Alzheimer disease

LMTK2 and CRB1 are two novel risk genes for Alzheimer's disease in Han Chinese

BACKGROUND

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease with a substantial genetic background. However, its underlying genetic architecture remains to be elucidated.

METHODS

In this study, we performed whole-exome sequencing in 282 familial and/or early-onset AD patients and 1086 cognitively normal controls in the Han Chinse populations. According to minor allele frequency, variants were divided into common variants (MAF ≥ 0.01) and rare variants (MAF < 0.01). Common variant-based association analysis and gene-based association test aggregating rare variants were performed by PLINK 1.9 and Sequence Kernel Association Test-Optimal, respectively. We replicated the significant results by using the same AD samples and controls from whole genome sequencing (n = 1879). Furthermore, we determined the functions of the novel AD risk genes in vitro.

RESULTS

Common variants association analysis revealed that APOE rs429358 reached statistical whole-exome significance. Gene-level aggregation testing identified that rare damaging variants in LMTK2 and CRB1 conferred risk to AD. All variants are located in highly conserved amino acid regions and are predicted to be damaging. Furthermore, functional studies showed that LMTK2 rare damaging variants (R234P and S974G) enhanced tau phosphorylation levels, tau aggregates formation, and Aβ generation. Meanwhile, the CRB1 Y556X variant caused incomplete translation of CRB1 protein and increased the Aβ42 level and Aβ42/Aβ40 ratio.

CONCLUSION

Our findings indicated that LMTK2 and CRB1 are two novel AD risk genes in Han Chinese, which may provide promising targets for diagnosis and intervention.

Iatrogenic Dementia: Providing Insight into Transmissible Subtype of Alzheimer's Disease, Creutzfeldt-Jakob Disease and Cerebral Amyloid Angiopathy

Within the phenotypic spectrum of Alzheimer's disease (AD), Creutzfeldt-Jakob disease (CJD) and cerebral amyloid angiopathy (CAA), dementia that is attributed to iatrogenic transmission has increasingly gained scientific attention recently. Newly recognized, this treatment-induced form of dementia may result from exposure to certain medical or surgical procedures. The present review aims to explore the distinct features of acquired dementia encompassing a history of potential exposure and relatively early age of onset, highlighting transmission potential with a rather prion-like pattern. Having reviewed all available relevant literature, dementia of iatrogenic etiology represents a new disease entity that requires an individualized investigation process and poses a great clinical challenge as far as patients with AD, CJD and CAA are concerned. Understanding the underlying pathophysiology of these rare forms of dementia may significantly enhance awareness within clinical field of neurodegenerative diseases and facilitate their prompt management.

Role of Testosterone Signaling in Microglia: A Potential Role for Sex-Related Differences in Alzheimer's Disease

Alzheimer's disease (AD) is less prevalent in men than in women, although mechanisms remain unclear. Microglia degrade aggregated amyloid β (Aβ) through the lysosomal system, including autophagy. G protein-coupled receptor family C group 6 member A (GPRC6A), predominantly expressed in mouse microglial MG6 cells, is a primary mediator of testosterone signaling. This study examines testosterone's role in modulating Aβ-induced autophagy in microglia. Testosterone promotes Aβ-induced autophagy leading to Aβ clearance in MG6 cells by suppressing extracellular signal-regulated kinase (ERK) phosphorylation and subsequently inhibiting mammalian target of rapamycin (mTOR) activation, which is abrogated by shRNA knockdown of GPRC6A. In in vivo experiments with male 5xFAD AD model mice, Aβ clearance activity is associated with autophagy in microglia and is reduced by orchiectomy, but restored by testosterone supplementation. ERK phosphorylation in the brains of male AD model mice is upregulated by orchiectomy. Therefore, testosterone is involved in autophagy-mediated Aβ clearance in microglia. Aβ accumulation in human brain samples from patients with AD is significantly lower in men than in women, with less pronounced colocalization of Aβ with p62 aggregates, suggesting enhanced autophagic activity in men. In conclusion, testosterone enhances Aβ-induced autophagy in microglia, possibly contributing to lower susceptibility to AD in men.

Pharmacological Evaluation of Aescin for Neuroprotection in Intracerebroventricular Streptozotocin Model of Alzheimer's Disease in Experimental Rats

Alzheimer's disease (AD) is a neurological disorder that results in the loss of memory and cognitive functions linked to redox disbalance, neuroinflammation, neurotransmitters changes, and the accumulation of amyloid-beta (1-42) plaques in AD. In this study, rats were administered with intracerebroventricular (ICV) streptozotocin (STZ) to produce AD-like symptoms in rats. ICV-STZ bilaterally, 3 mg/kg, was infused on days 1 and 3 with the help of Hamilton syringe by fixing cannula at the target position of rat brain using coordinates -2 mm (anteriposterior), 1.6 mm Mediolateral (ML), and 1.5 mm (dorsoventral). Learning and spatial memory were checked using Morris water maze and elevated plus maze apparatus. In ICV-STZ, rats lost their spatial and learning memory, increased level of prooxidant like Lipid peroxidation (LPO), nitrite and reduced glutathione (GSH), catalase, and superoxide dismutase (SOD) level. The increased level acetylcholinesterase (AChE) catalyzed acetylcholine (ACh) concentration indicates cholinergic neuron degeneration. Furthermore, we found raised inflammatory markers and altered neurotransmitters level after ICV-STZ. Administration of aescin (10, 20, and 30 mg/kg, p.o.) dose-dependently ameliorated the behavioral alteration and inhibited inflammatory markers like tumor necrosis factor-alpha, interleukin-6 (IL-6), and IL-1β. Furthermore, aescin restored antioxidants like GSH, SOD, and catalase and reduced the nitrite and lipid peroxidation level. AChE enzyme causes degradation of ACh, and its level was declined after treatment with aescin. Aescin also restored GABA, norepinephrine, and serotonin level in the brain with prevention of raised glutamate level. Moreover, the histopathological study confirmed neuronal pathogenesis, and aescin significantly achieved neuroprotective effect via preventing neuroinflammation, balancing redox potential, and inhibiting AChE enzyme.

Targeting JNK3 for Alzheimer's disease: Design and synthesis of novel inhibitors with aryl group diversity utilizing wide pocket

JNK3, a brain-specific stress-activated protein kinase, plays a critical role in Alzheimer's disease pathogenesis through phosphorylation of Tau and APP. This study aimed to develop selective JNK3 inhibitors based on a pyrazole scaffold, focusing on (E)-1-(2-aminopyrimidin-4-yl)-4-styryl-1H-pyrazole-3-carboxamide derivatives. Through systematic structural modifications and extensive SAR analysis, we identified compounds 24a and 26a as highly potent JNK3 inhibitors, with IC50 values of 12 and 19 nM, respectively. Especially, 24a revealed its potent and selective inhibition of JNK3, coupled with inhibition of the GSK3α/β kinases involved in Tau phosphorylation. In vitro studies revealed significant neuroprotective effects against Aβ1-42-induced toxicity in primary neuronal cells and western blot analyses confirmed the compounds' ability to mitigate Aβ1-42-induced c-Jun and APP phosphorylation, suggesting a multi-faceted approach to neuroprotection. Docking studies validated the retention of optimal interactions within the JNK3 binding pocket. Importantly, BBB PAMPA assays and ADME predictions indicated favorable blood-brain barrier permeability and pharmacokinetic profiles for the lead compounds. These findings represent a significant advancement in the development of selective JNK3 inhibitors, providing a strong foundation for further preclinical development of potential Alzheimer's disease therapeutics.

EBP1 potentiates amyloid β pathology by regulating γ-secretase

The abnormal deposition of amyloid β (Aβ), produced by proteolytic cleavage events of amyloid precursor protein involving the protease γ-secretase and subsequent polymerization into amyloid plaques, plays a key role in the neuropathology of Alzheimer's disease (AD). Here we show that ErbB3 binding protein 1 (EBP1)/proliferation-associated 2G4 (PA2G4) interacts with presenilin, a catalytic subunit of γ-secretase, inhibiting Aβ production. Mice lacking forebrain Ebp1/Pa2g4 recapitulate the representative phenotypes of late-onset sporadic AD, displaying an age-dependent increase in Aβ deposition, amyloid plaques and cognitive dysfunction. In postmortem brains of patients with AD and 5x-FAD mice, we found that EBP1 is proteolytically cleaved by asparagine endopeptidase at N84 and N204 residues, compromising its inhibitory effect on γ-secretase, increasing Aβ aggregation and neurodegeneration. Accordingly, injection of AAV2-Ebp1 wild-type or an asparagine endopeptidase-uncleavable mutant into the brains of 5x-FAD mice decreased Aβ generation and alleviated the behavioral impairments. Thus, our study suggests that EBP1 acts as an inhibitor of γ-secretase on amyloid precursor protein cleavage and preservation of functional EBP1 could be a therapeutic strategy for AD.

Stacked CNN-based multichannel attention networks for Alzheimer disease detection

Alzheimer's Disease (AD) is a progressive condition of a neurological brain disorder recognized by symptoms such as dementia, memory loss, alterations in behaviour, and impaired reasoning abilities. Recently, many researchers have been working to develop an effective AD recognition system using deep learning (DL) based convolutional neural network (CNN) model aiming to deploy the automatic medical image diagnosis system. The existing system is still facing difficulties in achieving satisfactory performance in terms of accuracy and efficiency because of the lack of feature ineffectiveness. This study proposes a lightweight Stacked Convolutional Neural Network with a Channel Attention Network (SCCAN) for MRI based on AD classification to overcome the challenges. In the procedure, we sequentially integrate 5 CNN modules, which form a stack CNN aiming to generate a hierarchical understanding of features through multi-level extraction, effectively reducing noise and enhancing the weight's efficacy. This feature is then fed into a channel attention module to select the practical features based on the channel dimension, facilitating the selection of influential features. . Consequently, the model exhibits reduced parameters, making it suitable for training on smaller datasets. Addressing the class imbalance in the Kaggle MRI dataset, a balanced distribution of samples among classes is emphasized. Extensive experiments of the proposed model with the ADNI1 Complete 1Yr 1.5T, Kaggle, and OASIS-1 datasets showed 99.58%, 99.22%, and 99.70% accuracy, respectively. The proposed model's high performance surpassed state-of-the-art (SOTA) models and proved its excellence as a significant advancement in AD classification using MRI images.

Pathogenesis and therapeutic applications of microglia receptors in Alzheimer's disease

Microglia, the resident immune cells of the central nervous system, continuously monitor the brain's microenvironment through their array of specific receptors. Once brain function is altered, microglia are recruited to specific sites to perform their immune functions, including phagocytosis of misfolded proteins, cellular debris, and apoptotic cells to maintain homeostasis. When toxic substances are overproduced, microglia are over-activated to produce large amounts of pro-inflammatory cytokines, which induce chronic inflammatory responses and lead to neurotoxicity. Additionally, microglia can also monitor and protect neuronal function through microglia-neuron crosstalk. Microglia receptors are important mediators for microglia to receive external stimuli, regulate the functional state of microglia, and transmit signals between cells. In this paper, we first review the role of microglia-expressed receptors in the pathogenesis and treatment of Alzheimer's disease; moreover, we emphasize the complexity of targeting microglia for therapeutic interventions in neurodegenerative disorders to inform the discovery of new biomarkers and the development of innovative therapeutics.

Cholinergic neurotransmission in the brain of streptozotocin-induced rat model of sporadic Alzheimer's disease: long-term follow up

Rats treated intracerebroventricularly with streptozotocin (STZ-icv) develop pathologic features, which resemble those in Alzheimer's disease and have been proposed as a non-transgenic model for sporadic type of the disease (sAD). We aimed to characterize cholinergic transmission in the rat brain as a function of STZ-icv dose and time after the treatment. Acetylcholinesterase (AChE) activity and expression of muscarinic (M1, M4) and nicotinic (α7) receptors, cholin acetyltransferase (ChAT) and glial fibrillary acidic protein (GFAP) were measured in hippocampus (HPC) and parietotemporal cortex (CTX) of STZ-icv and age-matched control rats one week, and one, three, six and nine months after the icv administration of STZ (0.3, 1 and 3 mg/kg), respectively. Cholinergic and astroglial changes were found most pronounced with a highest STZ dose in time-dependent manner. The cortex and hippocampus exhibited specific alterations in cholinergic transmission following STZ-icv administration, with either similar or distinct patterns depending on the parameter observed: increased AChE activity in HPC and invariable in CTX; increased M4 and ChAT levels in both regions; substantial cortical M1 level increment and moderate hippocampal M1 decrement; and decreased α7 levels in both regions, with subsequent increase observed only in HPC. Alterations in cerebral cholinergic neurotransmission in STZ-icv rat model were mostly following a threephasic time pattern: acute response (Phase I), complete/partial compensation (Phase II), and reappearance/progression of changes (Phase III). Staging structure of cholinergic changes in STZ-icv rat model might be speculated to partly correlate with cholinergic pathology in clinical AD stages.

Proteostasis restoration: a new metric for tau immunotherapy efficacy

This scientific commentary refers to ‘Proteostasis as a fundamental principle of Tau immunotherapy’ by Cruz et al. (https://doi.org/10.1093/brain/awae254).

Cerebral perfusion alterations in healthy young adults due to two genetic risk factors of Alzheimer's disease: APOE and MAPT

Functional brain changes such as altered cerebral blood flow occur long before the onset of clinical symptoms in Alzheimer's disease (AD) and other neurodegenerative disorders. While cerebral hypoperfusion occurs in established AD, middle-aged carriers of genetic risk factors for AD, including APOE ε4, display regional hyperperfusion due to hypothesised pleiotropic or compensatory effects, representing a possible early biomarker of AD and facilitating earlier AD diagnosis. However, it is not clear whether hyperperfusion already exists even earlier in life. Here, 160 young and cognitively healthy participants from the Chinese PREVENT cohort underwent 3 T arterial spin labelling and T1 MRI and genetic testing for APOE and MAPT rs242557 status. Using FSL, we performed a whole brain voxel-wise analysis and a global mean grey matter analysis comparing for the effects of both risk genes on cerebral perfusion. No significant alterations were seen for APOE genotype, but in MAPT rs242557 A carriers, we observed a significantly hyperperfusion in the left anterior cingulate cortex and left insular cortex. There were no effects of APOE or MAPT status on the global perfusion. These results are novel and may suggest that MAPT genotypes demonstrated a distinct hemodynamic profile in a very young age.

Cerebrospinal fluid β2-microglobulin promotes the tau pathology through microglia-astrocyte communication in Alzheimer's disease

BACKGROUND

Cerebrospinal fluid (CSF) β2-microglobulin (β2M) has been demonstrated as an important factor in β-amyloid (Aβ) neurotoxicity and a potential target for Alzheimer's disease (AD). However, more investigation is required to ascertain the relationship between β2M and glial activities in AD pathogenesis.

METHODS

In this study, 211 participants from the Alzheimer's disease Neuroimaging Initiative (ADNI) with CSF and Plasma β2M, CSF glial fibrillary acidic protein (GFAP), soluble triggering receptor expressed on myeloid cells 2 (sTREM2), Aβ42, phosphorylated-tau (P-tau) and total tau (T-tau) were divided into four groups, stage 0, 1, 2, and suspected non-AD pathology (SNAP) based on the National Institute on Aging- Alzheimer's Association (NIA-AA) criteria. Multiple linear regression, linear mixed effects models, and causal mediation analyses bootstrapped 10,000 iterations were used to investigate the underlying associations among β2M and CSF biomarkers at baseline and during a longitudinal visit.

RESULTS

CSF β2M concentration decreased with amyloid in stage 1 compared with stage 0 and increased with tau pathology and neurodegeneration in stage 2 and SNAP compared with stage 1. Moreover, CSF β2M level was positively correlated with the Aβ42 (β = 0.230), P-tau (β = 0.564), T-tau (β = 0.603), GFAP (β = 0.552), and sTREM2 (β = 0.641) (all P < 0.001). CSF β2M was only longitudinally correlated with T-tau change. The correlation of CSF β2M with P-tau (proportion = 25.4%, P < 0.001) and T-tau (proportion = 26.7%, P < 0.001) was partially mediated by GFAP in total participants, reproduced in late-life individuals. Furthermore, the astrocyte cascade also partially mediated the pathological relationship between CSF β2M and tau pathology (β2M → GFAP → YKL-40 → P-tau/T-tau, IE: 0.424-0.435, all P < 0.001). Nevertheless, the mediation effects of sTREM2 were not significant. Additionally, there was no association between plasma β2M and CSF biomarkers.

CONCLUSIONS

CSF β2M is dynamic in AD pathology and associated with neuroinflammation. CSF GFAP might mediate the association between β2M and tau pathology, complementing the existing research on the effect of β2M in AD pathology and providing a new perspective on treatment.

Troriluzole rescues glutamatergic deficits, amyloid and tau pathology, and synaptic and memory impairments in 3xTg-AD mice

Alzheimer's disease (AD) is a neurodegenerative condition in which clinical symptoms are highly correlated with the loss of glutamatergic synapses. While later stages of AD are associated with markedly decreased glutamate levels due to neuronal loss, in the early stages, pathological accumulation of glutamate and hyperactivity contribute to AD pathology and cognitive dysfunction. There is increasing awareness that presynaptic dysfunction, particularly synaptic vesicle (SV) alterations, play a key role in mediating this early-stage hyperactivity. In the current study, we sought to determine whether the 3xTg mouse model of AD that exhibits both beta-amyloid (Aβ) and tau-related pathology would exhibit similar presynaptic changes as previously observed in amyloid or tau models separately. Hippocampal cultures from 3xTg mice were used to determine whether presynaptic vesicular glutamate transporters (VGlut) and glutamate are increased at the synaptic level while controlling for postsynaptic activity. We observed that 3xTg hippocampal cultures exhibited increased VGlut1 associated with an increase in glutamate release, similar to prior observations in cultures from tau mouse models. However, the SV pool size was also increased in 3xTg cultures, an effect not previously observed in tau mouse models but observed in Aβ models, suggesting the changes in pool size may be due to Aβ and not tau. Second, we sought to determine whether treatment with troriluzole, a novel 3rd generation tripeptide prodrug of the glutamate modulator riluzole, could reduce VGlut1 and glutamate release to restore cognitive deficits in 8-month-old 3xTg mice. Treatment with troriluzole reduced VGlut1 expression, decreased basal and evoked glutamate release, and restored cognitive deficits in 3xTg mice. Together, these findings suggest presynaptic alterations are early events in AD that represent potential targets for therapeutic intervention, and these results support the promise of glutamate-modulating drugs such as troriluzole in Alzheimer's disease.

Ferroptosis and pathogenesis of neuritic plaques in Alzheimer disease

Neuritic plaques are pathognomonic and terminal lesions of Alzheimer disease (AD). They embody AD pathogenesis because they harbor in one space critical pathologic features of the disease: amyloid deposits, neurofibrillary degeneration, neuroinflammation, and iron accumulation. Neuritic plaques are thought to arise from the conversion of diffuse extracellular deposits of amyloid-β protein (Aβ), and it is believed that during conversion, amyloid toxicity creates the dystrophic neurites of neuritic plaques, as well as neurofibrillary tangles However, recent evidence from human postmortem studies suggests a much different mechanism of neuritic plaque formation, where the first step in their creation is neuronal degeneration driven by iron overload and ferroptosis. Similarly, neurofibrillary tangles represent the corpses of iron-laden neurons that develop independently of Aβ deposits. In this review, we will focus on the role of free redox-active iron in the development of typical AD pathology, as determined largely by evidence obtained in the human temporal lobe during early, preclinical stages of AD. The findings have allowed the construction of a scheme of AD pathogenesis where brain iron is center stage and is involved in every step of the sequence of events that produce characteristic AD pathology. We will discuss how the study of preclinical AD has produced a fresh and revised assessment of AD pathogenesis that may be important for reconsidering current therapeutic efforts and guiding future ones. SIGNIFICANCE STATEMENT: This review offers a novel perspective on Alzheimer disease pathogenesis where elevated brain iron plays a central role and is involved throughout the development of lesions. Herein, we review arguments against the amyloid cascade theory and explain how recent findings in humans during early preclinical disease support iron-mediated cell death and endogenous iron containment mechanisms as critical components of neuritic plaque formation and ensuing dementia.

Physiopathological mechanisms underlying Alzheimer's disease: a narrative review

The neuropathological signature of Alzheimer's disease (AD) comprises mainly amyloid plaques, and neurofibrillary tangles, resulting in synaptic and neuronal loss. These pathological structures stem from amyloid dysfunctional metabolism according to the amyloid cascade hypothesis, leading to the formation of plaques, and apparently inducing the initiation of the abnormal tau pathway, with phosphorylation and aggregation of these proteins, ultimately causing the formation of tangles. In this narrative review, the existing hypothesis related to the pathophysiology of AD were compiled, and biological pathways were highlighted in order to identify the molecules that could represent biological markers of the disease, necessary to establish early diagnosis, as well as the selection of patients for therapeutical interventional strategies.

Targeting 5-HT Is a Potential Therapeutic Strategy for Neurodegenerative Diseases

There is increasing interest in the potential therapeutic role of 5-HT (serotonin) in the treatment of neurodegenerative diseases, which are characterized by the progressive degeneration and death of nerve cells. 5-HT is a vital neurotransmitter that plays a central role in regulating mood, cognition, and various physiological processes in the body. Disruptions in the 5-HT system have been linked to several neurological and psychiatric disorders, making it an attractive target for therapeutic intervention. Although the exact causes of neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) are not fully understood, researchers believe that regulating the 5-HT system could help alleviate symptoms and potentially slow the progression of these diseases. Here, we delve into the potential of harnessing 5-HT as a therapeutic target for the treatment of neurodegenerative diseases. It is important to note that the current clinical drugs targeting 5-HT are still limited in the treatment of these complex diseases. Therefore, further research and clinical trials are needed to evaluate the feasibility and effectiveness of its clinical application.

Fluorescence Detection and Inhibition Mechanisms of DNTPH on Aβ42 Oligomers Characterized as Products in the Four Stages of Aggregation

Aβ42 aggregation was implicated in the pathogenesis of Alzheimer's disease (AD) without effective treatment available currently. Future efforts in clinical trials should instead focus on applying those antiamyloid treatment strategies to the preclinical stage and "the earlier, the better". How to identify and inhibit Aβ42 oligomers in the different stages of aggregation is therefore becoming the key to controlling primary aggregation and consequent AD development. Aggregation-induced emission probe DNTPH was demonstrated recently, enabling detection of amyloid at wavelengths up to 710 nm and exhibiting strong inhibitory effects on Aβ fibrosis at low dose. However, the detection and inhibition mechanisms of Aβ oligomers at various early stages of aggregation remain unknown. To this end, we built four different morphologies of Aβ42 pentamers characterized by products in monomeric aggregate (PM), primary nucleation (PP), secondary nucleation (PS), and fibril stages (PF) to explore the distinguishable ability and inhibition mechanisms of DNTPH with different concentrations upon binding. The results showcased that DNTPH does detect the four different Aβ42 oligomers with conspicuous fluorescence (λPM = 657 nm, λPP = 639 nm, λPS = 630 nm, and λPF = 648 nm) but fails to distinguish them, indicating that additional improvements are required further for the probe to achieve it. The inhibition mechanisms of DNTPH on the four Aβ42 aggregation are however of amazing differences. For PM and PP, aggregation was inhibited by altering the secondary structural composition, i.e., by decreasing the β-sheet and toxic turn (residues 22-23) probabilities, respectively. For PS, inhibition was achieved by segregating and keeping the two disordered monomeric species (PSM) away from the ordered secondary seed species (PSF) and consequently blocking further growth of the PSF seed. The inhibition mechanism for PS is first probed and proposed so far, as far as we know, and the corresponding aggregation stage of PS is the most important one among the four stages. The inhibition of PF was triggered by distorting the fibril chains, disrupting the ordered fibril surface for the contact of monomers. In addition, the optimal inhibitory concentrations of DNTPH for PM, PP, and PF were determined to be 1:3, while for PS, it was 1:5. This outcome offers a novel perspective for designing drugs targeting Aβ42 oligomers at different aggregation stages.

Inhibition of high-fat diet-induced miRNA ameliorates tau toxicity in Drosophila

Alzheimer's disease (AD), caused by amyloid beta (Aβ) plaques and Tau tangles, is a neurodegenerative disease characterized by progressive memory impairment and cognitive dysfunction. High-fat diet (HFD), which induces type 2 diabetes, exacerbates Aβ plaque deposition in the brain. To investigate the function of HFD in Tau-mediated AD, we fed an HFD to the Drosophila Tau model and found that HFD aggravates Tau-induced neurological phenotypes. Since microRNAs (miRNAs) are biomarkers for diabetes and AD, we evaluated the expression levels of common miRNAs of HFD and AD in HFD-fed Tau model fly brains. Among the common miRNAs, the expression levels of Let-7 and miR-34 were increased. We found that the inhibition of these miRNAs alleviates Tau-mediated AD phenotypes. Our research provides valuable insights into how HFD accelerates tau toxicity. Additionally, our work highlights the therapeutic potential of targeting Let-7 and miR-34 to develop innovative treatment approaches for AD.

Guidelines for the use and interpretation of Alzheimer's disease biomarkers in clinical practice in Brazil: recommendations from the Scientific Department of Cognitive Neurology and Aging of the Brazilian Academy of Neurology

In recent years, the diagnostic accuracy of Alzheimer's disease has been enhanced by the development of different types of biomarkers that indicate the presence of neuropathological processes. In addition to improving patient selection for clinical trials, biomarkers can assess the effects of new treatments on pathological processes. However, there is concern about the indiscriminate and poorly supported use of biomarkers, especially in asymptomatic individuals or those with subjective cognitive decline. Difficulties interpreting these tests, high costs, and unequal access make this scenario even more challenging in healthcare. This article presents the recommendations from the Scientific Department of Cognitive Neurology and Aging of the Brazilian Academy of Neurology (Departamento Científico de Neurologia Cognitiva e Envelhecimento da Academia Brasileira de Neurologia) regarding the rational use and interpretation of Alzheimer's disease biomarkers in clinical practice. The clinical diagnosis of cognitive-behavioral syndrome is recommended as the initial step to guide the request for biomarkers.

Alzheimer's Disease: Exploring the Landscape of Cognitive Decline

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and impaired daily functioning. The pathology of AD is marked by the accumulation of amyloid beta plaques and tau protein tangles in the brain, along with neuroinflammation and synaptic dysfunction. Genetic factors, such as mutations in APP, PSEN1, and PSEN2 genes, as well as the APOE ε4 allele, contribute to increased risk of acquiring AD. Currently available treatments provide symptomatic relief but do not halt disease progression. Research efforts are focused on developing disease-modifying therapies that target the underlying pathological mechanisms of AD. Advances in identification and validation of reliable biomarkers for AD hold great promise for enhancing early diagnosis, monitoring disease progression, and assessing treatment response in clinical practice in effort to alleviate the burden of this devastating disease. In this paper, we analyze data from the CAS Content Collection to summarize the research progress in Alzheimer's disease. We examine the publication landscape in effort to provide insights into current knowledge advances and developments. We also review the most discussed and emerging concepts and assess the strategies to combat the disease. We explore the genetic risk factors, pharmacological targets, and comorbid diseases. Finally, we inspect clinical applications of products against AD with their development pipelines and efforts for drug repurposing. The objective of this review is to provide a broad overview of the evolving landscape of current knowledge regarding AD, to outline challenges, and to evaluate growth opportunities to further efforts in combating the disease.

Molecular Signatures of Resilience to Alzheimer's Disease in Neocortical Layer 4 Neurons

Single-cell omics is advancing our understanding of selective neuronal vulnerability in Alzheimer's disease (AD), revealing specific subtypes that are either susceptible or resilient to neurodegeneration. Using single-nucleus and spatial transcriptomics to compare neocortical regions affected early (prefrontal cortex and precuneus) or late (primary visual cortex) in AD, we identified a resilient excitatory population in layer 4 of the primary visual cortex expressing RORB, CUX2, and EYA4. Layer 4 neurons in association neocortex also remained relatively preserved as AD progressed and shared overlapping molecular signatures of resilience. Early in the disease, resilient neurons upregulated genes associated with synapse maintenance, synaptic plasticity, calcium homeostasis, and neuroprotective factors, including GRIN2A, RORA, NRXN1, NLGN1, NCAM2, FGF14, NRG3, NEGR1, and CSMD1. We also identified KCNIP4, which encodes a voltage-gated potassium (Kv) channel-interacting protein that interacts with Kv4.2 channels and presenilins, as a key factor linked to resilience. KCNIP4 was consistently upregulated in the early stages of pathology. Furthermore, AAV-mediated overexpression of Kcnip4 in a humanized AD mouse model reduced the expression of the activity-dependent genes Arc and c-Fos, suggesting compensatory mechanisms against neuronal hyperexcitability. Our dataset provides a valuable resource for investigating mechanisms underlying resilience to neurodegeneration.

Evaluation of the protective bioactivity and molecular mechanism verification of lactoferrin in an Alzheimer's mouse model with ulcerative enteritis

The development of new drug therapies for Alzheimer's disease (AD) is an important research topic today, but the pathogenesis of AD has not been thoroughly studied, and there are still several shortcomings in existing drug therapies. Therefore, this study aimed to explore the molecular mechanism of lactoferrin (LF) in the treatments of AD and ulcerative colitis (UC) that is susceptible to AD, starting from the principle of one drug, two diseases, and the same treatment. This study used pathological staining and specific indicator staining to preliminarily evaluate the interventions of LF on UC injury and AD progression. We also used 16s RNA full-length sequencing to investigate the effect of LF on the abundance of intestinal microbiota in AD mice. Intestinal tissue and brain tissue metabolomics analysis were then used to screen specific metabolic pathways and preliminarily verify the metabolic mechanism of LF in alleviating the 2 diseases by regulating certain specific metabolites. Moreover, LF significantly changed the types and abundance of gut microbiota in AD mice complicated by UC. To conclude, this study proved the clinical phenomenon of AD susceptibility to UC, and verified the therapeutic effect of LF on 2 diseases. More importantly, we revealed the possible molecular mechanism of LF: Not only does it enrich the cognitive level of LF in alleviating AD by regulating the gut microbiota through the brain gut axis from the perspective of the theory of food nutrition promoting human health, but it also provides a practical basis for the subsequent research and development of LF and drug validation from the perspective of drug food homology.

Gut Microbiota Alterations in Alzheimer's Disease: Relation with Cognitive Impairment and Mediterranean Lifestyle

Recently, an association between dysbiosis of the gut microbiota (GMB) and the development of several diseases, such as Alzheimer's disease (AD), has been proposed. Dysbiosis involves changes in microbial diversity influenced by environmental factors, like diet or lifestyle. In this study, we investigated the role of GMB parameters in Spanish AD patients, assessing the impact of adherence to the Mediterranean lifestyle (ML), as well as to characterize these parameters in relation to neuropsychological, neuropsychiatric, emotional, and functionality parameters. A case-control study was conducted to investigate the association between the composition of the GMB and cognitive, emotional, neuropsychiatric, and functionality status in Spanish AD patients, along with a shotgun metagenomics approach. Richness and alpha-diversity were significantly lower in the AD group compared to the controls. PERMANOVA and ANOSIM tests of Bray-Curtis dissimilarity, Aitchison distance, and Jaccard similarity did not showed significant differences in beta-diversity between the two groups. Moreover, associations between various phyla of the AD group and orientation performance, food consumption, and activities of daily living were identified. Dysbiosis observed in Spanish AD patients is characterized by reductions in richness and alpha-diversity, alongside alterations in GMB composition, which may be linked to adherence to the ML and cognitive and functionality symptoms.

Erlotinib regulates short-term memory, tau/Aβ pathology, and astrogliosis in mouse models of AD

Introduction

Erlotinib is an epidermal growth factor receptor (EGFR) inhibitor that is approved by the FDA to treat non-small cell lung cancer (NSCLC). Several membrane receptors, including EGFR, interact with amyloid β (Aβ), raising the possibility that erlotinib could have therapeutic effects on Alzheimer's disease (AD). However, the effects of erlotinib on Aβ/tau-related pathology and cognitive function in mouse models of AD and its mechanisms of action have not been examined in detail.

Methods

To investigate the effects of erlotinib on cognitive function and AD pathology, 3 to 6-month-old PS19 mice and 3 to 3.5-month-old 5xFAD mice and WT mice were injected with vehicle (5% DMSO + 10% PEG + 20% Tween80 + 65% D.W.) or erlotinib (20 mg/kg, i.p.) daily for 14 or 21 days. Then, behavioral tests, Golgi staining, immunofluorescence staining, western blotting ELISA, and real-time PCR were conducted.

Results and discussion

We found that erlotinib significantly enhanced short-term spatial memory and dendritic spine formation in 6-month-old P301S tau transgenic (PS19) mice. Importantly, erlotinib administration reduced tau phosphorylation at Ser202/Thr205 (AT8) and Thr231 (AT180) and further aggregation of tau into paired helical fragments (PHFs) and neurofibrillary tangles (NFTs) in 3-month-old and/or 6-month-old PS19 mice by suppressing the expression of the tau kinase DYRK1A. Moreover, erlotinib treatment decreased astrogliosis in 6-month-old PS19 mice and reduced proinflammatory responses in primary astrocytes (PACs) from PS19 mice. In 3- to 3.5-month-old 5xFAD mice, erlotinib treatment improved short-term spatial memory and hippocampal dendritic spine number and diminished Aβ plaque deposition and tau hyperphosphorylation. Furthermore, erlotinib-treated 5xFAD mice exhibited significant downregulation of astrocyte activation, and treating PACs from 5xFAD mice with erlotinib markedly reduced cxcl10 (reactive astrocyte marker) and gbp2 (A1 astrocyte marker) mRNA levels and proinflammatory cytokine mRNA and protein levels. Taken together, our results suggest that erlotinib regulates tau/Aβ-induced AD pathology, cognitive function, and Aβ/tau-evoked astrogliosis and therefore could be a potent therapeutic drug for ameliorating AD symptoms.

Analysis of Brain Protein Stability Changes in a Mouse Model of Alzheimer's Disease

The stability of proteins from rates of oxidation (SPROX), thermal proteome profiling (TPP), and limited proteolysis (LiP) techniques were used to profile the stability of ∼2500 proteins in hippocampus tissue cell lysates from 2- and 8-months-old wild-type (C57BL/6J; n = 7) and transgenic (5XFAD; n = 7) mice with five Alzheimer's disease (AD)-linked mutations. Approximately 200-500 protein hits with AD-related stability changes were detected by each technique at each age point. The hit overlap from technique to technique was low, and all of the techniques generated protein hits that were more numerous and largely different from those identified in protein expression level analyses, which were also performed here. The hit proteins identified by each technique were enriched in a number of the same pathways and biological processes, many with known connections to AD. The protein stability hits included 25 high-value conformation biomarkers with AD-related stability changes detected using at least 2 techniques at both age points. Also discovered were subunit- and age-specific AD-related stability changes in the proteasome, which had reduced function at both age points. The different folding stability profiles of the proteasome at the two age points are consistent with a different mechanism for proteasome dysfunction at the early and late stages of AD.

Increased extracellular free water is related to white matter hyperintensity burden

BACKGROUND

Extracellular free water (FW) has important roles in the occurrence and development of white matter hyperintensity (WMH).

PURPOSE

To explore the correlations between FW and WMH burden.

MATERIAL AND METHODS

A prospective analysis was conducted using magnetic resonance imaging (MRI) data from 126 individuals. WMH burden was determined based on WMH volumes and Fazekas scores from deep and periventricular white matter hyperintensity (DWMH and PWMH, respectively) in fluid-attenuated inversion recovery (FLAIR) images. FW values were taken from diffusion tensor imaging (DTI).

RESULTS

Univariate analysis showed that FW values were correlated with WMH burden, including WMH volumes and DWMH and PWMH Fazekas scores (P < 0.05). After multivariate analysis, FW values were correlated with WMH volumes and DWMH and PWMH Fazekas scores when adjusted for age and hypertension (P < 0.05).

CONCLUSION

Using MRI, increasing extracellular FW was related to WMH burden.

Physical Exercise Counteracts Aging-Associated White Matter Demyelination Causing Cognitive Decline

In the central nervous system, oligodendrocytes wrap around neuronal axons to form myelin, an insulating layer or sheath that allows for the efficient conductance of action potentials. In addition to structural insulation, myelin provides encased axons with nutrient, metabolic and defensive support. Demyelination, or myelin loss, can therefore cause axonal dysfunction, leading to neurological impairment and disease. In Alzheimer's disease (AD), progressive white matter demyelination is acknowledged as one of the earliest pathologies preceding symptom onset. Unfortunately, current pharmacotherapy for slowing demyelination or promoting remyelination in AD is nonexistent. Exercise is recognized for its wide-ranging benefits to human health, including improved mental health and the prevention of lifestyle-related diseases. Mounting evidence suggests the contribution of physical activity in delaying the progression of dementia in elderly populations. Recent mechanistic studies have shown that exercise facilitates myelination in the brain through the vitalization of intrinsic pro-myelination cues, such as increased neurotrophic factors and electrical activity. In this review, we summarize and discuss the potential of physical exercise on counteracting aging-associated white matter demyelination, which causes cognitive decline in AD. We highlight the need of further basic and clinical research investigations on this topic to establish novel approaches for healthy and improved brain aging.

Proteomic changes in Alzheimer's disease associated with progressive Aβ plaque and tau tangle pathologies

Proteomics can shed light on the dynamic and multifaceted alterations in neurodegenerative disorders like Alzheimer's disease (AD). Combining radioligands measuring β-amyloid (Aβ) plaques and tau tangles with cerebrospinal fluid proteomics, we uncover molecular events mirroring different stages of AD pathology in living humans. We found 127 differentially abundant proteins (DAPs) across the AD spectrum. The strongest Aβ-related proteins were mainly expressed in glial cells and included SMOC1 and ITGAM. A dozen proteins linked to ATP metabolism and preferentially expressed in neurons were independently associated with tau tangle load and tau accumulation. Only 20% of the DAPs were also altered in other neurodegenerative diseases, underscoring AD's distinct proteome. Two co-expression modules related, respectively, to protein metabolism and microglial immune response encompassed most DAPs, with opposing, staggered trajectories along the AD continuum. We unveil protein signatures associated with Aβ and tau proteinopathy in vivo, offering insights into complex neural responses and potential biomarkers and therapeutics targeting different disease stages.

NMDA Receptors: Distribution, Role, and Insights into Neuropsychiatric Disorders

BACKGROUND

N-methyl-D-aspartate receptors (NMDARs) are members of the ionotropic glutamate receptor family. These ligand-gated channels are entwined with numerous fundamental neurological functions within the central nervous system (CNS), and numerous neuropsychiatric disorders may arise from their malfunction.

METHODS

The purpose of the present review is to provide a detailed description of NMDARs by addressing their molecular structures, activation mechanisms, and physiological roles in the mammalian brain. In the second part, their role in various neuropsychiatric disorders including stroke, epilepsy, anti-NMDA encephalitis, Alzheimer's and Huntington's diseases, schizophrenia, depression, neuropathic pain, opioid-induced tolerance, and hyperalgesia will be covered.

RESULTS

Finally, through a careful exploration of the main non-competitive NMDARs antagonists (channel-blockers).

CONCLUSION

We discuss the strengths and limitations of the various molecular structures developed for diagnostic or therapeutic purposes.

The intricate interplay between microglia and adult neurogenesis in Alzheimer's disease

Microglia, the resident immune cells of the central nervous system, play a crucial role in regulating adult neurogenesis and contribute significantly to the pathogenesis of Alzheimer's disease (AD). Under physiological conditions, microglia support and modulate neurogenesis through the secretion of neurotrophic factors, phagocytosis of apoptotic cells, and synaptic pruning, thereby promoting the proliferation, differentiation, and survival of neural progenitor cells (NPCs). However, in AD, microglial function becomes dysregulated, leading to chronic neuroinflammation and impaired neurogenesis. This review explores the intricate interplay between microglia and adult neurogenesis in health and AD, synthesizing recent findings to provide a comprehensive overview of the current understanding of microglia-mediated regulation of adult neurogenesis. Furthermore, it highlights the potential of microglia-targeted therapies to modulate neurogenesis and offers insights into potential avenues for developing novel therapeutic interventions.

Automated deep learning segmentation of neuritic plaques and neurofibrillary tangles in Alzheimer disease brain sections using a proprietary software

Neuropathological diagnosis of Alzheimer disease (AD) relies on semiquantitative analysis of phosphorylated tau-positive neurofibrillary tangles (NFTs) and neuritic plaques (NPs), without consideration of lesion heterogeneity in individual cases. We developed a deep learning workflow for automated annotation and segmentation of NPs and NFTs from AT8-immunostained whole slide images (WSIs) of AD brain sections. Fifteen WSIs of frontal cortex from 4 biobanks with varying tissue quality, staining intensity, and scanning formats were analyzed. We established an artificial intelligence (AI)-driven iterative procedure to improve the generation of expert-validated annotation datasets for NPs and NFTs thereby increasing annotation quality by >50%. This strategy yielded an expert-validated annotation database with 5013 NPs and 5143 NFTs. We next trained two U-Net convolutional neural networks for detection and segmentation of NPs or NFTs, achieving high accuracy and consistency (mean Dice similarity coefficient: NPs, 0.77; NFTs, 0.81). The workflow showed high generalization performance across different cases. This study serves as a proof-of-concept for the utilization of proprietary image analysis software (Visiopharm) in the automated deep learning segmentation of NPs and NFTs, demonstrating that AI can significantly improve the annotation quality of complex neuropathological features and enable the creation of highly precise models for identifying these markers in AD brain sections.

Amyloid-β peptide signature associated with cerebral amyloid angiopathy in familial Alzheimer's disease with APPdup and Down syndrome

Alzheimer's disease (AD) is characterized by extracellular amyloid plaques containing amyloid-β (Aβ) peptides, intraneuronal neurofibrillary tangles, extracellular neuropil threads, and dystrophic neurites surrounding plaques composed of hyperphosphorylated tau protein (pTau). Aβ can also deposit in blood vessel walls leading to cerebral amyloid angiopathy (CAA). While amyloid plaques in AD brains are constant, CAA varies among cases. The study focuses on differences observed between rare and poorly studied patient groups with APP duplications (APPdup) and Down syndrome (DS) reported to have higher frequencies of elevated CAA levels in comparison to sporadic AD (sAD), most of APP mutations, and controls. We compared Aβ and tau pathologies in postmortem brain tissues across cases and Aβ peptides using mass spectrometry (MS). We further characterized the spatial distribution of Aβ peptides with MS-brain imaging. While intraparenchymal Aβ deposits were numerous in sAD, DS with AD (DS-AD) and AD with APP mutations, these were less abundant in APPdup. On the contrary, Aβ deposits in the blood vessels were abundant in APPdup and DS-AD while only APPdup cases displayed high Aβ deposits in capillaries. Investigation of Aβ peptide profiles showed a specific increase in Aβx-37, Aβx-38 and Aβx-40 but not Aβx-42 in APPdup cases and to a lower extent in DS-AD cases. Interestingly, N-truncated Aβ2-x peptides were particularly increased in APPdup compared to all other groups. This result was confirmed by MS-imaging of leptomeningeal and parenchymal vessels from an APPdup case, suggesting that CAA is associated with accumulation of shorter Aβ peptides truncated both at N- and C-termini in blood vessels. Altogether, this study identified striking differences in the localization and composition of Aβ deposits between AD cases, particularly APPdup and DS-AD, both carrying three genomic copies of the APP gene. Detection of specific Aβ peptides in CSF or plasma of these patients could improve the diagnosis of CAA and their inclusion in anti-amyloid immunotherapy treatments.

CryoET of β-amyloid and tau within postmortem Alzheimer's disease brain

A defining pathological feature of most neurodegenerative diseases is the assembly of proteins into amyloid that form disease-specific structures1. In Alzheimer's disease, this is characterized by the deposition of β-amyloid and tau with disease-specific conformations. The in situ structure of amyloid in the human brain is unknown. Here, using cryo-fluorescence microscopy-targeted cryo-sectioning, cryo-focused ion beam-scanning electron microscopy lift-out and cryo-electron tomography, we determined in-tissue architectures of β-amyloid and tau pathology in a postmortem Alzheimer's disease donor brain. β-amyloid plaques contained a mixture of fibrils, some of which were branched, and protofilaments, arranged in parallel arrays and lattice-like structures. Extracellular vesicles and cuboidal particles defined the non-amyloid constituents of β-amyloid plaques. By contrast, tau inclusions formed parallel clusters of unbranched filaments. Subtomogram averaging a cluster of 136 tau filaments in a single tomogram revealed the polypeptide backbone conformation and filament polarity orientation of paired helical filaments within tissue. Filaments within most clusters were similar to each other, but were different between clusters, showing amyloid heterogeneity that is spatially organized by subcellular location. The in situ structural approaches outlined here for human donor tissues have applications to a broad range of neurodegenerative diseases.

Rodent Models of Alzheimer's Disease: Past Misconceptions and Future Prospects

Alzheimer's disease (AD) is a progressive neurodegenerative disease with no effective treatments, not least due to the lack of authentic animal models. Typically, rodent models recapitulate the effects but not causes of AD, such as cholinergic neuron loss: lesioning of cholinergic neurons mimics the cognitive decline reminiscent of AD but not its neuropathology. Alternative models rely on the overexpression of genes associated with familial AD, such as amyloid precursor protein, or have genetically amplified expression of mutant tau. Yet transgenic rodent models poorly replicate the neuropathogenesis and protein overexpression patterns of sporadic AD. Seeding rodents with amyloid or tau facilitates the formation of these pathologies but cannot account for their initial accumulation. Intracerebral infusion of proinflammatory agents offer an alternative model, but these fail to replicate the cause of AD. A novel model is therefore needed, perhaps similar to those used for Parkinson's disease, namely adult wildtype rodents with neuron-specific (dopaminergic) lesions within the same vulnerable brainstem nuclei, 'the isodendritic core', which are the first to degenerate in AD. Site-selective targeting of these nuclei in adult rodents may recapitulate the initial neurodegenerative processes in AD to faithfully mimic its pathogenesis and progression, ultimately leading to presymptomatic biomarkers and preventative therapies.

Neuromodulatory subcortical nucleus integrity is associated with white matter microstructure, tauopathy and APOE status

The neuromodulatory subcortical nuclei within the isodendritic core (IdC) are the earliest sites of tauopathy in Alzheimer's disease (AD). They project broadly throughout the brain's white matter. We investigated the relationship between IdC microstructure and whole-brain white matter microstructure to better understand early neuropathological changes in AD. Using multiparametric quantitative magnetic resonance imaging we observed two covariance patterns between IdC and white matter microstructure in 133 cognitively unimpaired older adults (age 67.9 ± 5.3 years) with familial risk for AD. IdC integrity related to 1) whole-brain neurite density, and 2) neurite orientation dispersion in white matter tracts known to be affected early in AD. Pattern 2 was associated with CSF concentration of phosphorylated-tau, indicating AD specificity. Apolipoprotein-E4 carriers expressed both patterns more strongly than non-carriers. IdC microstructure variation is reflected in white matter, particularly in AD-affected tracts, highlighting an early mechanism of pathological development.

The influence of APOEε4 on the pTau interactome in sporadic Alzheimer's disease

APOEε4 is the major genetic risk factor for sporadic Alzheimer's disease (AD). Although APOEε4 is known to promote Aβ pathology, recent data also support an effect of APOE polymorphism on phosphorylated Tau (pTau) pathology. To elucidate these potential effects, the pTau interactome was analyzed across APOE genotypes in the frontal cortex of 10 advanced AD cases (n = 5 APOEε3/ε3 and n = 5 APOEε4/ε4), using a combination of anti-pTau pS396/pS404 (PHF1) immunoprecipitation (IP) and mass spectrometry (MS). This proteomic approach was complemented by an analysis of anti-pTau PHF1 and anti-Aβ 4G8 immunohistochemistry, performed in the frontal cortex of 21 advanced AD cases (n = 11 APOEε3/ε3 and n = 10 APOEε4/ε4). Our dataset includes 1130 and 1330 proteins enriched in IPPHF1 samples from APOEε3/ε3 and APOEε4/ε4 groups (fold change ≥ 1.50, IPPHF1 vs IPIgG ctrl). We identified 80 and 68 proteins as probable pTau interactors in APOEε3/ε3 and APOEε4/ε4 groups, respectively (SAINT score ≥ 0.80; false discovery rate (FDR) ≤ 5%). A total of 47/80 proteins were identified as more likely to interact with pTau in APOEε3/ε3 vs APOEε4/ε4 cases. Functional enrichment analyses showed that they were significantly associated with the nucleoplasm compartment and involved in RNA processing. In contrast, 35/68 proteins were identified as more likely to interact with pTau in APOEε4/ε4 vs APOEε3/ε3 cases. They were significantly associated with the synaptic compartment and involved in cellular transport. A characterization of Tau pathology in the frontal cortex showed a higher density of plaque-associated neuritic crowns, made of dystrophic axons and synapses, in APOEε4 carriers. Cerebral amyloid angiopathy was more frequent and severe in APOEε4/ε4 cases. Our study supports an influence of APOE genotype on pTau-subcellular location in AD. These results suggest a facilitation of pTau progression to Aβ-affected brain regions in APOEε4 carriers, paving the way to the identification of new therapeutic targets.

Deep Learning-Based Eye-Tracking Analysis for Diagnosis of Alzheimer's Disease Using 3D Comprehensive Visual Stimuli

Alzheimer's Disease (AD) is a neurodegenerative disorder that causes a continuous decline in cognitive functions and eventually results in death. An early AD diagnosis is important for taking active measures to slow its deterioration. Traditional diagnoses are usually based on clinical experience, which is limited by several realistic factors. In this paper, we focus on exploiting deep learning techniques to diagnose AD based on eye-tracking behaviors. Visual attention, as a typical eye-tracking behavior, is of great clinical value in detecting cognitive abnormalities in AD patients. To better analyze the differences in visual attention between AD patients and normals, we first conducted a 3D comprehensive visual task on a noninvasive eye-tracking system to collect visual attention heatmaps. Then a multilayered comparison convolutional neural network (MC-CNN) is proposed to distinguish the visual attention differences between AD patients and normals. In MC-CNN, the multilayered feature representations of heatmaps were obtained by hierarchical residual blocks to better encode eye movement behaviors, which were further integrated into a distance vector to benefit the comprehensive visual task. From evaluation, MC-CNN can distinguish AD patients from normals with 0.84 accuracy, 0.86 recall, 0.82 precision, 0.83 F1-score and 0.90 area under the curve (AUC). The above results demonstrate the effectiveness of the proposed MC-CNN in AD diagnosis based on the comprehensive 3D visual task.

In silico design of misfolding resistant proteins: the role of structural similarity of a competing conformational ensemble in the optimization of frustration

Most state-of-the-art in silico design methods fail due to misfolding of designed sequences to a conformation other than the target. Thus, a method to design misfolding resistant proteins will provide a better understanding of the misfolding phenomenon and will also increase the success rate of in silico design methods. In this work, we optimize the conformational ensemble to be selected for negative design purposes based on the similarity of the conformational ensemble to the target. Five ensembles with different degrees of similarity to the target are created and destabilized and the target is stabilized while designing sequences using mean field theory and Monte Carlo simulation methods. The results suggest that the degree of similarity of the non-native conformations to the target plays a prominent role in designing misfolding resistant protein sequences. The design procedures that destabilize the conformational ensemble with moderate similarity to the target have proven to be more promising. Incorporation of either highly similar or highly dissimilar conformations to the target conformation into the non-native ensemble to be destabilized may lead to sequences with a higher misfolding propensity. This will significantly reduce the conformational space to be considered in any protein design procedure. Interestingly, the results suggest that a sequence with higher frustration in the target structure does not necessarily lead to a misfold prone sequence. A successful design method may purposefully choose a frustrated sequence in the target conformation if that sequence is even more frustrated in the competing non-native conformations.

The impact of seasonal variation on the composition of the volatile oil of Polyalthia suberosa (Roxb.) Thwaites leaves and evaluation of its acetylcholinesterase inhibitory activity

BACKGROUND

Polyalthia suberosa (Roxb.) Thwaites (Annonaceae) is a medicinal plant that has been reported for its various pharmacological potentials, such as its anti-inflammatory, analgesic, antioxidant, and neuropharmacological activities. This study aimed to analyze the leaf essential oils of P. suberosa (PSLO) collected in different seasons, to evaluate the acetylcholinesterase inhibitory activity, and to corroborate the obtained results via in-silico molecular docking studies.

METHODS

The leaf essential oils of P. suberosa collected in different seasons were analyzed separately by GC/MS. The acetylcholinesterase inhibitory activity of the leaves oil was assessed via colorimetric assay. In-silico molecular docking studies were elucidated by virtual docking of the main compounds identified in P. suberosa leaf essential oil to the active sites in human acetylcholinesterase crystal structure.

RESULTS

A total of 125 compounds were identified where D-limonene (0.07 - 24.7%), α-copaene (2.25 - 15.49%), E-β-caryophyllene (5.17 - 14.42%), 24-noroleana-3,12-diene (12.92%), β-pinene (0.14 - 8.59%), and α-humulene (2.49-6.9%) were the most abundant components. Results showed a noteworthy influence of the collection season on the chemical composition and yield of the volatile oils. The tested oil adequately inhibited acetylcholinesterase enzyme with an IC50 value of 91.94 µg/mL. Additionally, in-silico molecular docking unveiled that palmitic acid, phytol, p-cymene, and caryophyllene oxide demonstrated the highest fitting scores within the active sites of human acetylcholinesterase enzyme.

CONCLUSIONS

From these findings, it is concluded that P. suberosa leaf oil should be evaluated as a food supplement for enhancing memory.

The concept of resilience to Alzheimer's Disease: current definitions and cellular and molecular mechanisms

Some individuals are able to maintain their cognitive abilities despite the presence of significant Alzheimer's Disease (AD) neuropathological changes. This discrepancy between cognition and pathology has been labeled as resilience and has evolved into a widely debated concept. External factors such as cognitive stimulation are associated with resilience to AD, but the exact cellular and molecular underpinnings are not completely understood. In this review, we discuss the current definitions used in the field, highlight the translational approaches used to investigate resilience to AD and summarize the underlying cellular and molecular substrates of resilience that have been derived from human and animal studies, which have received more and more attention in the last few years. From these studies the picture emerges that resilient individuals are different from AD patients in terms of specific pathological species and their cellular reaction to AD pathology, which possibly helps to maintain cognition up to a certain tipping point. Studying these rare resilient individuals can be of great importance as it could pave the way to novel therapeutic avenues for AD.

Insights from the neural guidance factor Netrin-1 into neurodegeneration and other diseases

Netrin-1 was initially discovered as a neuronal growth cue for axonal guidance, and its functions have later been identified in inflammation, tumorigenesis, neurodegeneration, and other disorders. We have recently found its alterations in the brains with Alzheimer's disease, which might provide important clues to the mechanisms of some unique pathologies. To provide better understanding of this promising molecule, we here summarize research progresses in genetics, pathology, biochemistry, cell biology and other studies of Netrin-1 about its mechanistic roles and biomarker potentials with an emphasis on clinical neurodegenerative disorders in order to expand understanding of this promising molecular player in human diseases.

FABP7 drives an inflammatory response in human astrocytes and is upregulated in Alzheimer's disease

Alzheimer's disease (AD), the most common cause of dementia in the elderly, is characterized by the accumulation of intracellular neurofibrillary tangles, extracellular amyloid plaques, and neuroinflammation. In partnership with microglial cells, astrocytes are key players in the regulation of neuroinflammation. Fatty acid binding protein 7 (FABP7) belongs to a family of conserved proteins that regulate lipid metabolism, energy homeostasis, and inflammation. FABP7 expression is largely restricted to astrocytes and radial glia-like cells in the adult central nervous system. We observed that treatment of primary hippocampal astrocyte cultures with amyloid β fragment 25-35 (Aβ25-35) induces FABP7 upregulation. In addition, FABP7 expression is upregulated in the brain of APP/PS1 mice, a widely used AD mouse model. Co-immunostaining with specific astrocyte markers revealed increased FABP7 expression in astrocytes. Moreover, astrocytes surrounding amyloid plaques displayed increased FABP7 staining when compared to non-plaque-associated astrocytes. A similar result was obtained in the brain of AD patients. Whole transcriptome RNA sequencing analysis of human astrocytes differentiated from induced pluripotent stem cells (i-astrocytes) overexpressing FABP7 identified 500 transcripts with at least a 2-fold change in expression. Gene Ontology enrichment analysis identified (i) positive regulation of cytokine production and (ii) inflammatory response as the top two statistically significant overrepresented biological processes. We confirmed that wild-type FABP7 overexpression induces an NF-κB-driven inflammatory response in human i-astrocytes. On the other hand, the expression of a ligand-binding impaired mutant FABP7 did not induce NF-κB activation. Together, our results suggest that the upregulation of FABP7 in astrocytes could contribute to the neuroinflammation observed in AD.

Long-Term High-Fat Diet Consumption Aggravates β-Amyloid Deposition and Tau Pathology Accompanied by Microglial Activation in an Alzheimer's Disease Model

Alzheimer's disease (AD) is the most prevailing form of dementia, with long-term high-fat diet (HFD) consumption being a pivotal contributor to AD pathogenesis. As microglial dysfunction is a crucial factor in the AD onset, it becomes imperative to explore the effects of HFD on microglial function and AD pathogenesis. In the present study, 3xTg-AD model mice at the age of 9-month are subjected to random allocation, with one group receiving a standard diet (ND) and the other an HFD for 3 months. Subsequently, transcriptomic profiling of microglia unveils that HFD alters fatty acid metabolism and mediates T cell infiltration. Within the hippocampus, microglia exhibit aberrant morphology and lipid accretion in response to the HFD, evidenced by conspicuously enlarged microglial cell bodies and accumulation of lipid droplets. These lipid-droplet-accumulating microglia exhibit diminished migratory capacity and compromise plaque consolidation, thereby exacerbating the accumulation of β-amyloid. Noteworthy, the HFD induces T cell infiltration, thereby aggravating neuroinflammation and Tau phosphorylation. Morris water maze test reveals that HFD-consuming mice display marked impairment in memory performance. In summary, this study demonstrates that prolonged HFD consumption exacerbates amyloid deposition, tau pathology, and cognitive deficits, which is associated with the accumulation of lipid droplets within microglia.

Normal-Tension Glaucoma and Potential Clinical Links to Alzheimer's Disease

Glaucoma is a group of optic neuropathies and the world's leading cause of irreversible blindness. Normal-tension glaucoma (NTG) is a subtype of glaucoma that is characterized by a typical pattern of peripheral retinal loss, in which the patient's intraocular pressure (IOP) is considered within the normal range (<21 mmHg). Currently, the only targetable risk factor for glaucoma is lowering IOP, and patients with NTG continue to experience visual field loss after IOP-lowering treatments. This demonstrates the need for a better understanding of the pathogenesis of NTG and underlying mechanisms leading to neurodegeneration. Recent studies have found significant connections between NTG and cerebral manifestations, suggesting NTG as a neurodegenerative disease beyond the eye. Gaining a better understanding of NTG can potentially provide new Alzheimer's Disease diagnostics capabilities. This review identifies the epidemiology, current biomarkers, altered fluid dynamics, and cerebral and ocular manifestations to examine connections and discrepancies between the mechanisms of NTG and Alzheimer's Disease.

The association of GNB5 with Alzheimer disease revealed by genomic analysis restricted to variants impacting gene function

Disease-associated variants identified from genome-wide association studies (GWASs) frequently map to non-coding areas of the genome such as introns and intergenic regions. An exclusive reliance on gene-agnostic methods of genomic investigation could limit the identification of relevant genes associated with polygenic diseases such as Alzheimer disease (AD). To overcome such potential restriction, we developed a gene-constrained analytical method that considers only moderate- and high-risk variants that affect gene coding sequences. We report here the application of this approach to publicly available datasets containing 181,388 individuals without and with AD and the resulting identification of 660 genes potentially linked to the higher AD prevalence among Africans/African Americans. By integration with transcriptome analysis of 23 brain regions from 2,728 AD case-control samples, we concentrated on nine genes that potentially enhance the risk of AD: AACS, GNB5, GNS, HIPK3, MED13, SHC2, SLC22A5, VPS35, and ZNF398. GNB5, the fifth member of the heterotrimeric G protein beta family encoding Gβ5, is primarily expressed in neurons and is essential for normal neuronal development in mouse brain. Homozygous or compound heterozygous loss of function of GNB5 in humans has previously been associated with a syndrome of developmental delay, cognitive impairment, and cardiac arrhythmia. In validation experiments, we confirmed that Gnb5 heterozygosity enhanced the formation of both amyloid plaques and neurofibrillary tangles in the brains of AD model mice. These results suggest that gene-constrained analysis can complement the power of GWASs in the identification of AD-associated genes and may be more broadly applicable to other polygenic diseases.

Discovery of small molecules from natural compound databases as potent retinoid X alpha receptor agonists to treat Alzheimer's disease

Alzheimer's is characterized as a progressive neurodegenerative disease due to beta-amyloid accumulation in the brain. Some previous studies reported that RXR agonists could be effective in the treatment of Alzheimer's disease. There are currently numerous attempts being made to discover a natural RXR agonist that is more potent than 9-cis-retinoic acid (9CR). One of the most efficient resources for finding high-potential compounds is natural databases. In this study, 81215 compounds from the IB screen library as natural databases were docked against the RXR-alpha binding site. The best compounds discovered interact with the RXR-alpha binding site with a lower binding energy (-11 to -13 kcal/mol) than the binding energy of -10.94 kcal/mol for 9-cis, which means that these compounds could interact stronger with RXR-alpha than 9CR. All selected compounds could pass the blood-brain barrier. Physiochemical properties assessment indicated that all compounds passed Lipinski's rule and had the potential to be oral drug candidates. The stability of protein-ligand complexes during a timescale of 100 ns by Molecular Dynamics simulation demonstrated that all compounds could effectively interact with the RXR binding site. The molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) represented that all selected hit compounds had a better binding affinity to the alpha RXR binding site compared to 9CR, which means these hit compounds had potential drug candidates for the treatment of Alzheimer's disease. However, experimental assessment is needed to validate this result.

Cognitive, functional, and neuropsychiatric correlates of regional tau pathology in autopsy-confirmed chronic traumatic encephalopathy

BACKGROUND

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease characterized by hyperphosphorylated tau (p-tau) accumulation. The clinical features associated with CTE pathology are unclear. In brain donors with autopsy-confirmed CTE, we investigated the association of CTE p-tau pathology density and location with cognitive, functional, and neuropsychiatric symptoms.

METHODS

In 364 brain donors with autopsy confirmed CTE, semi-quantitative p-tau severity (range: 0-3) was assessed in 10 cortical and subcortical regions. We summed ratings across regions to form a p-tau severity global composite (range: 0-30). Informants completed standardized scales of cognition (Cognitive Difficulties Scale, CDS; BRIEF-A Metacognition Index, MI), activities of daily living (Functional Activities Questionnaire), neurobehavioral dysregulation (BRIEF-A Behavioral Regulation Index, BRI; Barratt Impulsiveness Scale, BIS-11), aggression (Brown-Goodwin Aggression Scale), depression (Geriatric Depression Scale-15, GDS-15), and apathy (Apathy Evaluation Scale, AES). Ordinary least squares regression models examined associations between global and regional p-tau severity (separate models for each region) with each clinical scale, adjusting for age at death, racial identity, education level, and history of hypertension, obstructive sleep apnea, and substance use treatment. Ridge regression models that incorporated p-tau severity across all regions in the same model assessed which regions showed independent effects.

RESULTS

The sample was predominantly American football players (333; 91.2%); 140 (38.5%) had low CTE and 224 (61.5%) had high CTE. Global p-tau severity was associated with higher (i.e., worse) scores on the cognitive and functional scales: MI ([Formula: see text] standardized = 0.02, 95%CI = 0.01-0.04), CDS ([Formula: see text] standardized = 0.02, 95%CI = 0.01-0.04), and FAQ ([Formula: see text] standardized = 0.03, 95%CI = 0.01-0.04). After false-discovery rate correction, p-tau severity in the frontal, inferior parietal, and superior temporal cortex, and the amygdala was associated with higher CDS ([Formula: see text] sstandardized = 0.17-0.29, ps < 0.01) and FAQ ([Formula: see text] sstandardized = 0.21-0.26, ps < 0.01); frontal and inferior parietal cortex was associated with higher MI ([Formula: see text] sstandardized = 0.21-0.29, ps < 0.05); frontal cortex was associated with higher BRI ([Formula: see text] standardized = 0.21, p < 0.01). Regions with effects independent of other regions included frontal cortex (CDS, MI, FAQ, BRI), inferior parietal cortex (CDS) and amygdala (FAQ). P-tau explained 13-49% of variance in cognitive and functional scales and 6-14% of variance in neuropsychiatric scales.

CONCLUSION

Accumulation of p-tau aggregates, especially in the frontal cortex, are associated with cognitive, functional, and certain neurobehavioral symptoms in CTE.

Transgenic amyloid precursor protein mouse models of amyloidosis. Incomplete models for Alzheimer's disease but effective predictors of anti-amyloid therapies

INTRODUCTION

Amyloid precursor protein (APP) transgenic mice are models of Alzheimer's disease (AD) amyloidosis, not all of AD. Diffuse, compacted, and vascular deposits in APP mice mimic those found in AD cases.

METHODS

Most interventional studies in APP mice start treatment early in the process of amyloid deposition, consistent with a prevention treatment regimen. Most clinical trials treat patients with established amyloid deposits in a therapeutic treatment regimen.

RESULTS

The first treatment to reduce amyloid and cognitive impairment in mice was immunotherapy. The APP mouse models not only predicted efficacy, but presaged the vascular leakage called ARIA. The recent immunotherapy clinical trials that removed amyloid and slowed cognitive decline confirms the utility of these early APP models when used in therapeutic designs.

DISCUSSION

New mouse models of AD pathologies will add to the research armamentarium, but the early models have accurately predicted responses to amyloid therapies in humans.

Intranasally Administered EVs from hiPSC-derived NSCs Alter the Transcriptomic Profile of Activated Microglia and Conserve Brain Function in an Alzheimer's Model

Antiinflammatory extracellular vesicles (EVs) derived from human induced pluripotent stem cell (hiPSC)-derived neural stem cells (NSCs) hold promise as a disease-modifying biologic for Alzheimer's disease (AD). This study directly addressed this issue by examining the effects of intranasal administrations of hiPSC-NSC-EVs to 3-month-old 5xFAD mice. The EVs were internalized by all microglia, which led to reduced expression of multiple genes associated with disease-associated microglia, inflammasome, and interferon-1 signaling. Furthermore, the effects of hiPSC-NSC-EVs persisted for two months post-treatment in the hippocampus, evident from reduced microglial clusters, inflammasome complexes, and expression of proteins and/or genes linked to the activation of inflammasomes, p38/mitogen-activated protein kinase, and interferon-1 signaling. The amyloid-beta (Aβ) plaques, Aβ-42, and phosphorylated-tau concentrations were also diminished, leading to better cognitive and mood function in 5xFAD mice. Thus, early intervention with hiPSC-NSC-EVs in AD may help maintain better brain function by restraining the progression of adverse neuroinflammatory signaling cascades.

Pharmacological Approaches Using Diabetic Drugs Repurposed for Alzheimer's Disease

Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) are chronic, progressive disorders affecting the elderly, which fosters global healthcare concern with the growing aging population. Both T2DM and AD have been linked with increasing age, advanced glycosylation end products, obesity, and insulin resistance. Insulin resistance in the periphery is significant in the development of T2DM and it has been posited that insulin resistance in the brain plays a key role in AD pathogenesis, earning AD the name "type 3 diabetes". These clinical and epidemiological links between AD and T2DM have become increasingly pronounced throughout the years, and serve as a means to investigate the effects of antidiabetic therapies in AD, such as metformin, intranasal insulin, incretins, DPP4 inhibitors, PPAR-γ agonists, SGLT2 inhibitors. The majority of these drugs have shown benefit in preclinical trials, and have shown some promising results in clinical trials, with the improvement of cognitive faculties in participants with mild cognitive impairment and AD. In this review, we have summarize the benefits, risks, and conflicting data that currently exist for diabetic drugs being repurposed for the treatment of AD.