The Early Events That Initiate β-Amyloid Aggregation in Alzheimer's Disease

Downregulation of ATF-4 Attenuates the Endoplasmic Reticulum Stress-Mediated Neuroinflammation and Cognitive Impairment in Experimentally Induced Alzheimer's Disease Model

Protein aggregation is invariably associated with the inflammation as a factor in Alzheimer's disease (AD). We investigated the interaction between downstream factors of endoplasmic reticulum (ER) stress pathway and inflammation, with implications in cognitive impairment in AD. Amyloid-β (Aβ)(1-42) was administered by bilateral intracerebroventricular (icv) injection in the brain of adult male Wistar rats to experimentally develop AD. The cognitive impairment was assessed by measuring behavioral parameters such as Morris water maze and novel object recognition tests. Levels of pro-inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α and anti-inflammatory cytokines IL-4 and IL-10 were measured by the enzyme-linked immunosorbent assay (ELISA) in different rat brain regions. Inflammatory marker proteins such as cyclo-oxygenase (COX)-2 and phosphorylation of nuclear factor kappa B (NF-КB) (p65) were measured by the western blotting. Gene expression of ER stress downstream factors such as ATF-4, CHOP, and GADD-34 was analyzed by qRT-PCR. Histological studies were performed to check Aβ accumulation and neuronal degeneration. Integrated stress response inhibitor (ISRIB) was used to confirm the specific role of ER stress-mediated inflammation in cognitive impairment. Administration of Aβ(1-42) resulted in alteration in levels of inflammatory cytokines, inflammatory proteins, and mRNA levels of ER stress downstream factors. ISRIB treatment resulted in attenuation of Aβ(1-42)-induced ER stress, inflammation, neurodegeneration, and cognitive impairment in rats. These results indicate that ER stress-mediated inflammation potentiates the cognitive impairment in AD. An understanding of cascade of events, interaction of ER stress which was a hallmark of the present investigation together with inflammation and modulation of downstream signalling factors could serve as potent biomarkers to study AD progression.

Rhei Undulati Rhizoma attenuates memory decline and reduces amyloid-β induced neuritic dystrophy in 5xFAD mouse

BACKGROUND

Alzheimer's disease (AD) is a common type of dementia characterized by amyloid-β (Aβ) accumulation, lysosomal dysfunction, and tau hyperphosphorylation, leading to neurite dystrophy and memory loss. This study aimed to investigate whether Rhei Undulati Rhizoma (RUR), which has been reported to have anti-neuroinflammatory effect, attenuates Aβ-induced memory impairment, neuritic dystrophy, and tau hyperphosphorylation, and to reveal its mode of action.

METHODS

Five-month-old 5xFAD mice received RUR (50 mg/kg) orally for 2 months. The Y-maze test was used to assess working memory. After behavioral testing, brain tissue was analyzed using thioflavin S staining, western blotting, and immunofluorescence staining to investigate the mode of action of RUR. To confirm whether RUR directly reduces Aβ aggregation, a thioflavin T assay and dot blot were performed after incubating Aβ with RUR.

RESULTS

RUR administration attenuated the Aβ-induced memory impairment in 5xFAD mice. Furthermore, decreased accumulation of Aβ was observed in the hippocampus of the RUR-treated 5xFAD group compare to the vehicle-treated 5xFAD group. Moreover, RUR reduced the dystrophic neurites (DNs) that accumulate impaired endolysosomal organelles around Aβ. In particular, RUR treatment downregulated the expression of β-site amyloid precursor protein cleaving enzyme 1 and the hyperphosphorylation of tau within DNs. Additionally, RUR directly suppressed the aggregation of Aβ, and eliminated Aβ oligomers in vitro.

CONCLUSIONS

This study showed that RUR could attenuate Aβ-induced pathology and directly regulate the aggregation of Aβ. These results suggest that RUR could be an efficient material for AD treatment through Aβ regulation.

Exploring Curcumin-Loaded Lipid-Based Nanomedicine as Efficient Targeted Therapy for Alzheimer's Diseases

Alzheimer's disease (AD) is a neurological condition currently with 47 million people suffering from it globally. AD might have many reasons such as genetic issues, environmental factors, and Aβ accumulation, which is the biomarker of the disease. Since the primary reason is unknown, there is no targeted treatment at the moment, but ongoing research aims to slow its progression by managing amyloid-beta peptide production rather than symptomatic improvement. Since phytochemicals have been demonstrated to possess antioxidant, anti-inflammatory, and neuroprotective properties, they may target multiple pathological factors and can reduce the risk of the disease. Curcumin, as a phytochemical found in turmeric known for its antioxidant, free radical scavenging properties, and as an antiamyloid in treating AD, has come under investigation. Although its low bioavailability limits its efficacy, a prominent drug delivery system (DDS) is desired to overcome it. Hence, the potency of lipid-based nanoparticles encapsulating curcumin (LNPs-CUR) is considered in this study as a promising DDS. In vivo studies in animal models indicate LNPs-CUR effectively slow amyloid plaque formation, leading to cognitive enhancement and reduced toxicity compared to free CUR. However, a deeper understanding of CUR's pharmacokinetics and safety profile is crucial before LNPs-CUR can be considered as a medicine. Future investigations may explore the combination of NPs with other therapeutic agents to increase their efficacy in AD cases. This review provides the current position of CUR in the AD therapy paradigm, the DDS suggestions for CUR, and the previous research from the point of analytical view focused on the advantages and challenges.

Computational identification of potential acetylcholinesterase (AChE) and monoamine oxidase-B inhibitors from Vitis vinifera: a case study of Alzheimer's disease (AD)

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease that affects people aged 60 years and above. Yet, the discovery of potent therapeutic agents against this disease has no utmost progress and a number of drug candidates could not make it out of the clinical trials at varied stages. At the same time, the currently available anti-cholinesterase (AChE) and monoamine oxidase-B (MAO-B) for the treatment of AD can only improve the clinical symptoms while the recently approved immunotherapy agent "remains questionable. Thus, the need for novel therapeutic agents with the potential to treat the aetiology of the disease. Herein, this study sought to examine the potential of a number of bioactive compounds derived from Vitis vinifera as a promising agent against AChE and MAO-B. Using a computational approach via molecular docking 23 bioactive agents were screened against AChE and MAO-B, and the compounds with a binding score below that of the standard ligand were further subjected to drug-likeness and pharmacokinetic screening. Eight and thirteen of the studied agents optimally saturated the active pocket of the AChE and MAO-B respectively, forming principal interactions with a number of amino acids at the active pocket of the targets and among these compounds only rutin failed the drug-likeness test by violating four parameters while all showed moderate pharmacokinetics features. A number of Vitis vinifera-derived bioactive compounds show excellent inhibitory potential against AChE and MAO-B, and moderate pharmacokinetic features when compared to the reference ligand (tacrine). These compounds are therefore proposed as novel AChE and MAO-B inhibitors for the treatment of AD and wet-lab analysis is necessary to affirm their potency.

Cerebral Amyloidosis in Individuals with Subjective Cognitive Decline: From Genetic Predisposition to Actual Cerebrospinal Fluid Measurements

The possible relationship between Subjective Cognitive Decline (SCD) and dementia needs further investigation. In the present study, we explored the association between specific biomarkers of Alzheimer's Disease (AD), amyloid-beta 42 (Aβ42) and Tau with the odds of SCD using data from two ongoing studies. In total, 849 cognitively normal (CN) individuals were included in our analyses. Among the participants, 107 had available results regarding cerebrospinal fluid (CSF) Aβ42 and Tau, while 742 had available genetic data to construct polygenic risk scores (PRSs) reflecting their genetic predisposition for CSF Aβ42 and plasma total Tau levels. The associations between AD biomarkers and SCD were tested using logistic regression models adjusted for possible confounders such as age, sex, education, depression, and baseline cognitive test scores. Abnormal values of CSF Aβ42 were related to 2.5-fold higher odds of SCD, while higher polygenic loading for Aβ42 was associated with 1.6-fold higher odds of SCD. CSF Tau, as well as polygenic loading for total Tau, were not associated with SCD. Thus, only cerebral amyloidosis appears to be related to SCD status, either in the form of polygenic risk or actual CSF measurements. The temporal sequence of amyloidosis being followed by tauopathy may partially explain our findings.

Cacao consumption improves passive avoidance memory impairment in a rat model of Alzheimer's disease: the role of hippocampal synaptic plasticity and oxidative stress

Introduction: Alzheimer's disease (AD) causes progressive loss of cognitive function and synaptic plasticity, which is the most common form of dementia. The present study was designed to scrutinize the effects of cacao on passive avoidance memory function and to identify the roles of hippocampal synaptic plasticity and oxidative stress in an AD rat model induced by unilateral intracerebroventricular (UICV) injection of amyloid-beta (Aβ). Methods: Oral administration of cacao (500 mg/kg/ day) was given for 2 consecutive months. A memory retention test was conducted 24 h after passive avoidance training was completed. Subsequently, the amplitude of population spike (PS) and slope of field excitatory postsynaptic potentials (fEPSPs) were assessed at hippocampal long-term potentiation (LTP) in perforant pathway-dentate gyrus (PP-DG) synapses. Moreover, total thiol group (TTG) and malondialdehyde (MDA) concentrations were evaluated in the plasma. Furthermore, compact Aβ plaques were detected in the hippocampal DG by performing Congo red staining. Results: As a result of AD induction, passive avoidance memory was impaired; also, reduced fEPSP slopes, PS amplitudes, and content of TTG, and increase in MDA levels in the rats were observed. In contrast, cacao treatment ameliorated passive avoidance memory impairment, improved hippocampal LTP impairment, modulated oxidative-antioxidative status, and delayed Aβ plaques production in AD rats. Disscussion: Conclusively, cacao alleviates Aβ-induced cognitive deficit, probably by the amelioration of hippocampal LTP impairment, modulation of oxidative-antioxidative status, and inhibition of Aβ plaque accumulation.

Amyloids, amorphous aggregates and assemblies of peptides - Assessing aggregation

Amyloid and amorphous aggregates represent the two major categories of aggregates associated with diseases, and although exhibiting distinct features, researchers often treat them as equivalent, which demonstrates the need for more thorough characterization. Here, we compare amyloid and amorphous aggregates based on their biochemical properties, kinetics, and morphological features. To further decipher this issue, we propose the use of peptide self-assemblies as minimalistic models for understanding the aggregation process. Peptide building blocks are significantly smaller than proteins that participate in aggregation, however, they make a plausible means to bridge the gap in discerning the aggregation process at the more complex, protein level. Additionally, we explore the potential use of peptide-inspired models to research the liquid-liquid phase separation as a feasible mechanism preceding amyloid formation. Connecting these concepts can help clarify our understanding of aggregation-related disorders and potentially provide novel drug targets to impede and reverse these serious illnesses.

Neurotoxic Microglial Activation via IFNγ-Induced Nrf2 Reduction Exacerbating Alzheimer's Disease

Microglial neuroinflammation appears to be neuroprotective in the early pathological stage, yet neurotoxic, which often precedes neurodegeneration in Alzheimer's disease (AD). However, it remains unclear how the microglial activities transit to the neurotoxic state during AD progression, due to complex neuron-glia interactions. Here, the mechanism of detrimental microgliosis in AD by employing 3D human AD mini-brains, brain tissues of AD patients, and 5XFAD mice is explored. In the human and animal AD models, amyloid-beta (Aβ)-overexpressing neurons and reactive astrocytes produce interferon-gamma (IFNγ) and excessive oxidative stress. IFNγ results in the downregulation of mitogen-activated protein kinase (MAPK) and the upregulation of Kelch-like ECH-associated Protein 1 (Keap1) in microglia, which inactivate nuclear factor erythroid-2-related factor 2 (Nrf2) and sensitize microglia to the oxidative stress and induces a proinflammatory microglia via nuclear factor kappa B (NFκB)-axis. The proinflammatory microglia in turn produce neurotoxic nitric oxide and proinflammatory mediators exacerbating synaptic impairment, phosphorylated-tau accumulation, and discernable neuronal loss. Interestingly, recovering Nrf2 in the microglia prevents the activation of proinflammatory microglia and significantly blocks the tauopathy in AD minibrains. Taken together, it is envisioned that IFNγ-driven Nrf2 downregulation in microglia as a key target to ameliorate AD pathology.

Ubiquitin E3 ligases assisted technologies in protein degradation: Sharing pathways in neurodegenerative disorders and cancer

E3 ligases, essential components of the ubiquitin-proteasome-mediated protein degradation system, play a critical role in cellular regulation. By covalently attaching ubiquitin (Ub) molecules to target proteins, these ligases mark them for degradation, influencing various bioprocesses. With over 600 E3 ligases identified, there is a growing realization of their potential as therapeutic candidates for addressing proteinopathies in cancer and neurodegenerative disorders (NDDs). Recent research has highlighted the need to delve deeper into the intricate roles of E3 ligases as nexus points in the pathogenesis of both cancer and NDDs. Their dysregulation is emerging as a common thread linking these seemingly disparate diseases, necessitating a comprehensive understanding of their molecular intricacies. Herein, we have discussed (i) the fundamental mechanisms through which different types of E3 ligases actively participate in selective protein degradation in cancer and NDDs, followed by an examination of common E3 ligases playing pivotal roles in both situations, emphasising common players. Moving to, (ii) the functional domains and motifs of E3 ligases involved in ubiquitination, we have explored their interactions with specific substrates in NDDs and cancer. Additionally, (iii) we have explored techniques like PROTAC, molecular glues, and other state-of-the-art methods for hijacking neurotoxic and oncoproteins. Lastly, (iv) we have provided insights into ongoing clinical trials, offering a glimpse into the evolving landscape of E3-based therapeutics for cancer and NDDs. Unravelling the intricate network of E3 ligase-mediated regulation holds the key to unlocking targeted therapies that address the specific molecular signatures of individual patients, heralding a new era in personalized medicines.

Alzheimer's Disease-Related Epigenetic Changes: Novel Therapeutic Targets

Aging is a significant risk factor for Alzheimer's disease (AD), although the precise mechanism and molecular basis of AD are not yet fully understood. Epigenetic mechanisms, such as DNA methylation and hydroxymethylation, mitochondrial DNA methylation, histone modifications, and non-coding RNAs (ncRNAs), play a role in regulating gene expression related to neuron plasticity and integrity, which are closely associated with learning and memory development. This review describes the impact of dynamic and reversible epigenetic modifications and factors on memory and plasticity throughout life, emphasizing their potential as target for therapeutic intervention in AD. Additionally, we present insight from postmortem and animal studies on abnormal epigenetics regulation in AD, as well as current strategies aiming at targeting these factors in the context of AD therapy.

Identifying repurposed drugs as potential inhibitors of Apolipoprotein E: A bioinformatics approach to target complex diseases associated with lipid metabolism and neurodegeneration

Apolipoprotein E (ApoE), a pivotal contributor to lipid metabolism and neurodegenerative disorders, emerges as an attractive target for therapeutic intervention. Within this study, we deployed an integrated in-silico strategy, harnessing structure-based virtual screening, to identify potential compounds from DrugBank database. Employing molecular docking, we unveil initial hits by evaluating their binding efficiency with ApoE. This first tier of screening narrows our focus to compounds that exhibit a strong propensity to bind with ApoE. Further, a detailed interaction analysis was carried out to explore the binding patterns of the selected hits towards the ApoE binding site. The selected compounds were then evaluated for the biological properties in PASS analysis, which showed anti-neurodegenerative properties. Building upon this foundation, we delve deeper, employing all-atom molecular dynamics (MD) simulations extending over an extensive 500 ns. In particular, Ergotamine and Dihydroergocristine emerge as noteworthy candidates, binding to ApoE in a competitive mode. This intriguing binding behavior positions these compounds as potential candidates warranting further analysis in the pursuit of novel therapeutics targeting complex diseases associated with lipid metabolism and neurodegeneration. This approach holds the promise of catalyzing advancements in therapeutic intervention for complex disorders, thereby reporting a meaningful pace towards improved healthcare outcomes.

Alzheimer's-specific brain amyloid interactome: Neural-network analysis of intra-aggregate crosslinking identifies novel drug targets

Alzheimer's disease (AD) is characterized by peri-neuronal amyloid plaque and intra-neuronal neurofibrillary tangles. These aggregates are identified by the immunodetection of "seed" proteins (Aβ1-42 and hyperphosphorylated tau, respectively), but include many other proteins incorporated nonrandomly. Using click-chemistry intra-aggregate crosslinking, we previously modeled amyloid "contactomes" in SY5Y-APPSw neuroblastoma cells, revealing that aspirin impedes aggregate growth and complexity. By an analogous strategy, we now construct amyloid-specific aggregate interactomes of AD and age-matched-control hippocampi. Comparing these interactomes reveals AD-specific interactions, from which neural-network (NN) analyses predict proteins with the highest impact on pathogenic aggregate formation and/or stability. RNAi knockdowns of implicated proteins, in C. elegans and human-cell-culture models of AD, validated those predictions. Gene-Ontology meta-analysis of AD-enriched influential proteins highlighted the involvement of mitochondrial and cytoplasmic compartments in AD-specific aggregation. This approach derives dynamic consensus models of aggregate growth and architecture, implicating highly influential proteins as new targets to disrupt amyloid accrual in the AD brain.

Oxymatrine-mediated prevention of amyloid β-peptide-induced apoptosis on Alzheimer's model PC12 cells: in vitro cell culture studies and in vivo cognitive assessment in rats

Alzheimer's disease (AD) is a major neurological disease affecting elderly individuals worldwide. Existing drugs only reduce the symptoms of the disease without addressing the underlying causes. Commonly, Aβ25-35 peptide aggregation is the main reason for AD development. Recently, the discovery of multiple protein-targeting molecules has provided a new strategy for treating AD. This study demonstrates the neuroprotective potential of oxymatrine against multiple mechanisms, such as acetylcholinesterase, mitochondrial damage, and β-amyloid-induced cell toxicity. The in vitro cell culture studies showed that oxymatrine possesses significant potential to inhibit acetylcholine esterase and promotes antioxidant, antiapoptotic effects while preventing Aβ25-35 peptide aggregation in PC12 cells. Furthermore, oxymatrine protects PC12 cells against Aβ25-35-induced cytotoxicity and down-regulates the reactive oxygen species generation. The in vivo acute toxicological studies confirm the safety of oxymatrine without causing organ damage or death in animals. Overall, this study provided evidence that oxymatrine is an efficient neuroprotective agent, with a potential to be a multifunctional drug for Alzheimer's disease treatment. These findings present a reliable and synergistic approach for treating AD.

Apolipoprotein ε in Brain and Retinal Neurodegenerative Diseases

Alzheimer's disease (AD) is the most common form of dementia that remains incurable and has become a major medical, social, and economic challenge worldwide. AD is characterized by pathological hallmarks of senile plaques (SP) and neurofibrillary tangles (NFTs) that damage the brain up to twenty years before a clinical diagnosis is made. Interestingly these pathological features have also been observed in retinal neurodegenerative diseases including age related macular degeneration (ARMD), glaucoma and diabetic retinopathy (DR). An association of AD with these diseases has been suggested in epidemiological studies and several common pathological events and risk factors have been identified between these diseases. The E4 allele of Apolipoprotein E (APOE) is a well-established genetic risk factor for late onset AD. The ApoE ε4 allele is also associated with retinal neurodegenerative diseases however in contrast to AD, it is considered protective in AMD, likewise ApoE E2 allele, which is a protective factor for AD, has been implicated as a risk factor for AMD and glaucoma. This review summarizes the evidence on the effects of ApoE in retinal neurodegenerative diseases and discusses the overlapping molecular pathways in AD. The involvement of ApoE in regulating amyloid beta (Aβ) and tau pathology, inflammation, vascular integrity, glucose metabolism and vascular endothelial growth factor (VEGF) signaling is also discussed.

Design, synthesis, and biological evaluation of thienopyrimidine derivatives as multifunctional agents against Alzheimer's disease

A series of 12 S-substituted tetrahydrobenzothienopyrimidines were designed and synthesized based on the donepezil scaffold. All the newly synthesized compounds were evaluated for their acetylcholinesterase (AChE) inhibitory activity and the most active compounds were tested for their butyrylcholinesterase (BuChE) inhibitory activity. Moreover, all the synthesized compounds were evaluated for their inhibitory effects against Aβ aggregation and antioxidant activity using the oxygen radical absorbance capacity method. Compounds 4b, 6b, and 8b displayed the most prominent AChE inhibitory action comparable to donepezil. Compound 6b showed the greatest AChE inhibitory action (IC50  = 0.07 ± 0.003 µM) and the most potent BuChE inhibitory action (IC50  = 0.059 ± 0.004 µM). Furthermore, the three compounds exhibited significant antioxidant activity. Compounds 6b and 8b exerted more inhibitory action on Aβ aggregation than donepezil. The cytotoxic activity of compounds 4b, 6b, and 8b against the WI-38 cell line in comparison with donepezil was examined using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay. The results revealed that compounds 6b and 8b were less cytotixic than donepezil, while compound 4b showed nonsignificant cytotoxicity compared to donepezil. For more insights about the binding patterns of the most promising compounds (4b, 6b, and 8b) with the AChE at molecular levels; molecular docking and molecular dynamics simulations were performed. The density functional theory calculations and absorption, distribution, metabolism, excretion and toxicity properties were described as well. The results highlighted compound 6b, which incorporates a phenylpiperazine moiety coupled to a thienopyrimidone scaffold via two-atom spacer, to be a promising multifunctional therapeutic agent for the treatment of Alzheimer's disease. It is a potent dual AChE and BuChE inhibitor. Furthermore, it had stronger Aβ aggregation inhibitory action than donepezil. Additionally, compound 6b exerted significant antioxidant activity.

Towards early detection of neurodegenerative diseases: A gut feeling

The gastrointestinal tract communicates with the nervous system through a bidirectional network of signaling pathways called the gut-brain axis, which consists of multiple connections, including the enteric nervous system, the vagus nerve, the immune system, endocrine signals, the microbiota, and its metabolites. Alteration of communications in the gut-brain axis is emerging as an overlooked cause of neuroinflammation. Neuroinflammation is a common feature of the pathogenic mechanisms involved in various neurodegenerative diseases (NDs) that are incurable and debilitating conditions resulting in progressive degeneration and death of neurons, such as in Alzheimer and Parkinson diseases. NDs are a leading cause of global death and disability, and the incidences are expected to increase in the following decades if prevention strategies and successful treatment remain elusive. To date, the etiology of NDs is unclear due to the complexity of the mechanisms of diseases involving genetic and environmental factors, including diet and microbiota. Emerging evidence suggests that changes in diet, alteration of the microbiota, and deregulation of metabolism in the intestinal epithelium influence the inflammatory status of the neurons linked to disease insurgence and progression. This review will describe the leading players of the so-called diet-microbiota-gut-brain (DMGB) axis in the context of NDs. We will report recent findings from studies in model organisms such as rodents and fruit flies that support the role of diets, commensals, and intestinal epithelial functions as an overlooked primary regulator of brain health. We will finish discussing the pivotal role of metabolisms of cellular organelles such as mitochondria and peroxisomes in maintaining the DMGB axis and how alteration of the latter can be used as early disease makers and novel therapeutic targets.

Cross interactions between Apolipoprotein E and amyloid proteins in neurodegenerative diseases

Three common Apolipoprotein E isoforms, ApoE2, ApoE3, and ApoE4, are key regulators of lipid homeostasis, among other functions. Apolipoprotein E can interact with amyloid proteins. The isoforms differ by one or two residues at positions 112 and 158, and possess distinct structural conformations and functions, leading to isoform-specific roles in amyloid-based neurodegenerative diseases. Over 30 different amyloid proteins have been found to share similar characteristics of structure and toxicity, suggesting a common interactome. The molecular and genetic interactions of ApoE with amyloid proteins have been extensively studied in neurodegenerative diseases, but have not yet been well connected and clarified. Here we summarize essential features of the interactions between ApoE and different amyloid proteins, identify gaps in the understanding of the interactome and propose the general interaction mechanism between ApoE isoforms and amyloid proteins. Perhaps more importantly, this review outlines what we can learn from the interactome of ApoE and amyloid proteins; that is the need to see both ApoE and amyloid proteins as a basis to understand neurodegenerative diseases.

Type 2 Diabetes and Alzheimer's Disease: The Emerging Role of Cellular Lipotoxicity

Type 2 diabetes (T2D) and Alzheimer's diseases (AD) represent major health issues that have reached alarming levels in the last decades. Although growing evidence demonstrates that AD is a significant comorbidity of T2D, and there is a ~1.4-2-fold increase in the risk of developing AD among T2D patients, the involvement of possible common triggers in the pathogenesis of these two diseases remains largely unknown. Of note, recent mechanistic insights suggest that lipotoxicity could represent the missing ring in the pathogenetic mechanisms linking T2D to AD. Indeed, obesity, which represents the main cause of lipotoxicity, has been recognized as a major risk factor for both pathological conditions. Lipotoxicity can lead to inflammation, insulin resistance, oxidative stress, ceramide and amyloid accumulation, endoplasmic reticulum stress, ferroptosis, and autophagy, which are shared biological events in the pathogenesis of T2D and AD. In the current review, we try to provide a critical and comprehensive view of the common molecular pathways activated by lipotoxicity in T2D and AD, attempting to summarize how these mechanisms can drive future research and open the way to new therapeutic perspectives.

Neuroprotective effects of resistance physical exercise on the APP/PS1 mouse model of Alzheimer's disease

Introduction

Physical exercise has beneficial effects by providing neuroprotective and anti-inflammatory responses to AD. Most studies, however, have been conducted with aerobic exercises, and few have investigated the effects of other modalities that also show positive effects on AD, such as resistance exercise (RE). In addition to its benefits in developing muscle strength, balance and muscular endurance favoring improvements in the quality of life of the elderly, RE reduces amyloid load and local inflammation, promotes memory and cognitive improvements, and protects the cortex and hippocampus from the degeneration that occurs in AD. Similar to AD patients, double-transgenic APPswe/PS1dE9 (APP/PS1) mice exhibit Αβ plaques in the cortex and hippocampus, hyperlocomotion, memory deficits, and exacerbated inflammatory response. Therefore, the aim of this study was to investigate the effects of 4 weeks of RE intermittent training on the prevention and recovery from these AD-related neuropathological conditions in APP/PS1 mice.

Methods

For this purpose, 6-7-month-old male APP/PS1 transgenic mice and their littermates, negative for the mutations (CTRL), were distributed into three groups: CTRL, APP/PS1, APP/PS1+RE. RE training lasted four weeks and, at the end of the program, the animals were tested in the open field test for locomotor activity and in the object recognition test for recognition memory evaluation. The brains were collected for immunohistochemical analysis of Aβ plaques and microglia, and blood was collected for plasma corticosterone by ELISA assay.

Results

APP/PS1 transgenic sedentary mice showed increased hippocampal Aβ plaques and higher plasma corticosterone levels, as well as hyperlocomotion and reduced central crossings in the open field test, compared to APP/PS1 exercised and control animals. The intermittent program of RE was able to recover the behavioral, corticosterone and Aβ alterations to the CTRL levels. In addition, the RE protocol increased the number of microglial cells in the hippocampus of APP/PS1 mice. Despite these alterations, no memory impairment was observed in APP/PS1 mice in the novel object recognition test.

Discussion

Altogether, the present results suggest that RE plays a role in alleviating AD symptoms, and highlight the beneficial effects of RE training as a complementary treatment for AD.

Interactions of Polyphenolic Gallotannins with Amyloidogenic Polypeptides Associated with Alzheimer's Disease: From Molecular Insights to Physiological Significance

Polyphenols are natural compounds abundantly found in plants. They are known for their numerous benefits to human health, including antioxidant properties and anti-inflammatory activities. Interestingly, many studies have revealed that polyphenols can also modulate the formation of amyloid fibrils associated with disease states and can prevent the formation of cytotoxic oligomer species. In this review, we underline the numerous effects of four hydrolysable gallotannins (HGTs) with high conformational flexibility, low toxicity, and multi-targeticity, e.g., tannic acid, pentagalloyl glucose, corilagin, and 1,3,6-tri-O-galloyl-β-D-glucose, on the aggregation of amyloidogenic proteins associated with the Alzheimer's Disease (AD). These HGTs have demonstrated interesting abilities to reduce, at different levels, the formation of amyloid fibrils involved in AD, including those assembled from the amyloid β-peptide, the tubulin-associated unit, and the islet amyloid polypeptide. HGTs were also shown to disassemble pre-formed fibrils and to diminish cognitive decline in mice. Finally, this manuscript highlights the importance of further investigating these naturally occurring HGTs as promising scaffolds to design molecules that can interfere with the formation of proteotoxic oligomers and aggregates associated with AD pathogenesis.

Amyloid-beta aggregation implicates multiple pathways in Alzheimer's disease: Understanding the mechanisms

Alzheimer's disease (AD) is a progressive neurodegenerative condition characterized by tau pathology and accumulations of neurofibrillary tangles (NFTs) along with amyloid-beta (Aβ). It has been associated with neuronal damage, synaptic dysfunction, and cognitive deficits. The current review explained the molecular mechanisms behind the implications of Aβ aggregation in AD via multiple events. Beta (β) and gamma (γ) secretases hydrolyzed amyloid precursor protein (APP) to produce Aβ, which then clumps together to form Aβ fibrils. The fibrils increase oxidative stress, inflammatory cascade, and caspase activation to cause hyperphosphorylation of tau protein into neurofibrillary tangles (NFTs), which ultimately lead to neuronal damage. Acetylcholine (Ach) degradation is accelerated by upstream regulation of the acetylcholinesterase (AChE) enzyme, which leads to a deficiency in neurotransmitters and cognitive impairment. There are presently no efficient or disease-modifying medications for AD. It is necessary to advance AD research to suggest novel compounds for treatment and prevention. Prospectively, it might be reasonable to conduct clinical trials with unclean medicines that have a range of effects, including anti-amyloid and anti-tau, neurotransmitter modulation, anti-neuroinflammatory, neuroprotective, and cognitive enhancement.

Unveiling the Potential of Polyphenols as Anti-Amyloid Molecules in Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease that mostly affects the elderly population. Mechanisms underlying AD pathogenesis are yet to be fully revealed, but there are several hypotheses regarding AD. Even though free radicals and inflammation are likely to be linked with AD pathogenesis, still amyloid-beta (Aβ) cascade is the dominant hypothesis. According to the Aβ hypothesis, a progressive buildup of extracellular and intracellular Aβ aggregates has a significant contribution to the AD-linked neurodegeneration process. Since Aβ plays an important role in the etiology of AD, therefore Aβ-linked pathways are mainly targeted in order to develop potential AD therapies. Accumulation of Aβ plaques in the brains of AD individuals is an important hallmark of AD. These plaques are mainly composed of Aβ (a peptide of 39-42 amino acids) aggregates produced via the proteolytic cleavage of the amyloid precursor protein. Numerous studies have demonstrated that various polyphenols (PPHs), including cyanidins, anthocyanins, curcumin, catechins and their gallate esters were found to markedly suppress Aβ aggregation and prevent the formation of Aβ oligomers and toxicity, which is further suggesting that these PPHs might be regarded as effective therapeutic agents for the AD treatment. This review summarizes the roles of Aβ in AD pathogenesis, the Aβ aggregation pathway, types of PPHs, and distribution of PPHs in dietary sources. Furthermore, we have predominantly focused on the potential of food-derived PPHs as putative anti-amyloid drugs.

The effects of resistance exercise on cognitive function, amyloidogenesis, and neuroinflammation in Alzheimer's disease

With the increasing prevalence of Alzheimer's disease (AD) and difficulties in finding effective treatments, it is essential to discover alternative therapies through new approaches. In this regard, non-pharmacological therapies, such as physical exercise, have been proposed and explored for the treatment of AD. Recent studies have suggested that resistance exercise (RE) is an effective strategy for promoting benefits in memory and cognitive function, producing neuroprotective and anti-inflammatory effects, and reducing amyloid load and plaques, thereby reducing the risk, and alleviating the neurodegeneration process of AD and other types of dementia in the elderly. In addition, RE is the exercise recommended by the World Health Organization for the elderly due to its benefits in improving muscle strength and balance, and increasing autonomy and functional capacity, favoring improvements in the quality of life of the elderly population, who is more likely to develop AD and other types of dementia. In this mini-review, we discuss the impact of RE on humans affected by MCI and AD, and animal models of AD, and summarize the main findings regarding the effects of RE program on memory and cognitive functions, neurotrophic factors, Aβ deposition and plaque formation, as well as on neuroinflammation. Overall, the present review provides clinical and preclinical evidence that RE plays a role in alleviating AD symptoms and may help to understand the therapeutic potential of RE, thereby continuing the advances in AD therapies.

The Anti-Aggregative Peptide KLVFF Mimics Aβ1-40 in the Modulation of Nicotinic Receptors: Implications for Peptide-Based Therapy

In recent years, the inhibition of beta-amyloid (Aβ) aggregation has emerged as a potential strategy for Alzheimer’s disease. KLVFF, a small peptide corresponding to the aminoacidic sequence 16-20 of Aβ, reduces Aβ fibrillation dose dependently. Therefore, the toxic and functional characterization of its brain activity is fundamental for clarifying its potential therapeutic role. Accordingly, we studied the modulatory role of KLVFF on the cholinergic receptors regulating dopamine and noradrenaline release in rat synaptosomes. Nicotinic receptors on dopaminergic nerve terminals in the nucleus acccumbens are inhibited by KLVFF, which closely resembles full-length Aβ1-40. Moreover, KLVFF entrapped in synaptosomes does not modify the nicotinic receptor’s function, suggesting that external binding to the receptor is required for its activity. The cholinergic agent desformylflustrabromine counteracts the KLVFF effect. Remarkably, muscarinic receptors on dopaminergic terminals and nicotinic receptors regulating noradrenaline release in the hippocampus are completely insensitive to KLVFF. Based on our findings, KLVFF mimics Aβ1-40 as a negative modulator of specific nicotinic receptor subtypes affecting dopamine transmission in the rat brain. Therefore, new pharmacological strategies using the anti-aggregative properties of KLVFF need to be evaluated for potential interference with nicotinic receptor-mediated transmission.

A quantitative meta-analysis of vitamin C in the pathophysiology of Alzheimer’s disease

Purpose

Alzheimer’s disease (AD) is a multifaceted neurodegenerative disorder with many complex pathways feeding into its pathogenesis and progression. Vitamin C, an essential dietary antioxidant, is vital for proper neurological development and maintenance. This meta-analysis and systematic review attempted to define the relationship between vitamin C plasma levels and AD while highlighting the importance and involvement of vitamin C in the pathogenesis of AD.

Materials and methods

PRISMA guidelines were used to obtain studies quantifying the plasma levels of vitamin C in AD and control subjects. The literature was searched in the online databases PubMed, Google Scholar, and Web of Science. A total of 12 studies were included (n = 1,100) and analyzed using Comprehensive Meta-Analysis 3.0.

Results

The results show that there is a significant decrease in the plasma vitamin C levels of AD patients as compared to healthy controls (pooled SMD with random-effect model: −1.164, with 95%CI: −1.720 to −0.608, Z = −4.102, p = 0.00) with significant heterogeneity (I² = 93.218). The sensitivity analysis showed directionally similar results. Egger’s regression test (p = 0.11) and visual inspection of the funnel plot showed no publication bias.

Conclusion

Based on these studies, it can be deduced that the deficiency of vitamin C is involved in disease progression and supplementation is a plausible preventive and treatment strategy. However, clinical studies are warranted to elucidate its exact mechanistic role in AD pathophysiology and prevention.

Cornuside ameliorates cognitive impairments in scopolamine induced AD mice: Involvement of neurotransmitter and oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

Cornus officinalis Sieb. et Zucc., traditional Chinese medicine, has been widely used in the treatment of dementia. Cornel iridoid glycosides of Cornus officinalis is therapeutic to Alzheimer's disease (AD), while its pharmacodynamic material basis is not clear. Cornuside, an iridoid glycoside extracted from of Cornus officinalis Sieb. et Zucc, might be a potential anti-AD candidate.

AIM OF THE STUDY

Cornuside was evaluated for its effect on scopolamine induced AD mice, and its action mechanisms were explored.

MATERIALS AND METHODS

ICR mice were administered with 1 mg/kg scopolamine intraperitoneally to induce amnesia. The therapeutic effect of cornuside of cognitive function was evaluated via series of behavioral tests, including Morris water maze test, step-through test and step-down test. In addition, specific enzyme reaction tests were used to detect the content of acetylcholine (ACh) and malondialdehyde (MDA), as well as the activities of acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), choline acetyltransferase (ChAT), superoxide dismutase (SOD), catalase (CAT), monoamine oxidase (MAO) in the brain. The levels of monoamine neurotransmitters were detected by high performance liquid chromatography-electrochemical detection (HPLC-ECD).

RESULTS

Cornuside ameliorated the spatial memory impairment in Morris water maze test and cognitive disruption in step-through and step-down test. Furthermore, cornuside improved the level of ACh by reducing the activities of AChE and BuChE, and increasing the activity of ChAT in hippocampus. Cornuside also increased the levels of monoamine neurotransmitters by inhibiting MAO activity in hippocampus and cortex. In addition, cornuside attenuated MDA by enhancing the activities of SOD and CAT in hippocampus and cortex.

CONCLUSION

Cornuside improved cognitive dysfunction induced by scopolamine in behavioral tests. The mechanisms of cornuside were further investigated from the aspects of neurotransmitters and oxidative stress. Cornuside could inhibit oxidative stress and neurotransmitter hydrolases, increase ACh and monoamine neurotransmitters, which finally contributed to its therapeutic effect on scopolamine induced amnesia.

Prophylactic evaluation of verubecestat on disease- and symptom-modifying effects in 5XFAD mice

Introduction

Alzheimer's disease (AD) is the most common form of dementia. Beta-secretase (BACE) inhibitors have been proposed as potential therapeutic interventions; however, initiating treatment once disease has significantly progressed has failed to effectively stop or treat disease. Whether BACE inhibition may have efficacy when administered prophylactically in the early stages of AD has been under-investigated. The present studies aimed to evaluate prophylactic treatment of the BACE inhibitor verubecestat in an AD mouse model using the National Institute on Aging (NIA) resources of the Model Organism Development for Late-Onset Alzheimer's Disease (MODEL-AD) Preclinical Testing Core (PTC) Drug Screening Pipeline.

Methods

5XFAD mice were administered verubecestat ad libitum in chow from 3 to 6 months of age, prior to the onset of significant disease pathology. Following treatment (6 months of age), in vivo imaging was conducted with 18F-florbetapir (AV-45/Amyvid) (18F-AV45) and 18-FDG (fluorodeoxyglucose)-PET (positron emission tomography)/MRI (magnetic resonance imaging), brain and plasma amyloid beta (Aβ) were measured, and the clinical and behavioral characteristics of the mice were assessed and correlated with the pharmacokinetic data.

Results

Prophylactic verubecestat treatment resulted in dose- and region-dependent attenuations of 18F-AV45 uptake in male and female 5XFAD mice. Plasma Aβ40 and Aβ42 were also dose-dependently attenuated with treatment. Across the dose range evaluated, side effects including coat color changes and motor alterations were reported, in the absence of cognitive improvement or changes in 18F-FDG uptake.

Discussion

Prophylactic treatment with verubecestat resulted in attenuated amyloid plaque deposition when treatment was initiated prior to significant pathology in 5XFAD mice. At the same dose range effective at attenuating Aβ levels, verubecestat produced side effects in the absence of improvements in cognitive function. Taken together these data demonstrate the rigorous translational approaches of the MODEL-AD PTC for interrogating potential therapeutics and provide insight into the limitations of verubecestat as a prophylactic intervention for early-stage AD.

Bio-Evaluation of 99mTc-Labeled Homodimeric Chalcone Derivative as Amyloid-β-Targeting Probe

Chalcone derivatives have been successfully utilized for a range of biological applications and can cross the blood–brain barrier easily. β-amyloid-specific bis-chalcone derivative, 6,9-bis(carboxymethyl)-14-(4-[(E)-3-(4-(dimethylamino)phenyl)acryloyl]phenoxy)-3-(2-[(2-(4-[(E)-3-(4-(dimethylamino)phenyl)acryloyl]phenoxy)ethyl)amino]-2-oxoethyl)-11-oxo-3,6,9,12-tetraazatetradecanoic acid, DT(Ch)₂, was analyzed using molecular modeling to explain the binding modes of the ligand with amyloid fibril and monomer followed by ^99mTc-complexation in 95% yield and 98.7% efficiency. High-binding specificity of the radiocomplex was established following in vitro evaluation against 100-fold excess of DT(Ch)₂. ^99mTc–DT(Ch)₂ exhibited <3% trans-complexation in human serum after 24 h, indicating high stability. A fast clearance rate in pharmacokinetics studies displayed a biphasic pattern with t_1/2(F) = 30 min ± 0.09 and t_1/2(S) = 4 h 20 min ± 0.06. In vivo single-photon emission computed tomography (SPECT) imaging in rabbits reiterated the pharmacokinetics data with initially high brain uptake followed by rapid washout. Biodistribution studies confirmed the initial brain uptake as 1.16 ± 0.02% ID/g after 2 min and the brain_2min/brain_30min ratio was 3.74. Radioactivity distribution in the brain was >40% in the cingulate cortex followed by >25% in the hippocampus, a distribution pattern aligned to Alzheimer’s affected brain regions. Radiocomplex also displayed rapid plasma clearance followed by hepatobolic and renal modes of excretion.

Cerebrospinal fluid proteomic profiling of individuals with mild cognitive impairment and suspected non-Alzheimer's disease pathophysiology

BACKGROUND

Suspected non-Alzheimer's disease pathophysiology (SNAP) is a biomarker concept that encompasses individuals with neuronal injury but without amyloidosis. We aim to investigate the pathophysiology of SNAP, defined as abnormal tau without amyloidosis, in individuals with mild cognitive impairment (MCI) by cerebrospinal fluid (CSF) proteomics.

METHODS

Individuals were classified based on CSF amyloid beta (Aβ)1-42 (A) and phosphorylated tau (T), as cognitively normal A-T- (CN), MCI A-T+ (MCI-SNAP), and MCI A+T+ (MCI-AD). Proteomics analyses, Gene Ontology (GO), brain cell expression, and gene expression analyses in brain regions of interest were performed.

RESULTS

A total of 96 proteins were decreased in MCI-SNAP compared to CN and MCI-AD. These proteins were enriched for extracellular matrix (ECM), hemostasis, immune system, protein processing/degradation, lipids, and synapse. Fifty-one percent were enriched for expression in the choroid plexus.

CONCLUSION

The pathophysiology of MCI-SNAP (A-T+) is distinct from that of MCI-AD. Our findings highlight the need for a different treatment in MCI-SNAP compared to MCI-AD.

The Influence of Selected Antipsychotic Drugs on Biochemical Aspects of Alzheimer's Disease

The aim of this study was to assess the potency of selected antipsychotic drugs (haloperidol (HAL), bromperidol (BRMP), benperidol (BNP), penfluridol (PNF), pimozide (PIM), quetiapine (QUET) and promazine (PROM)) on the main pathological hallmarks of Alzheimer's disease (AD). Binary mixtures of donepezil and antipsychotics produce an anti-BuChE effect, which was greater than either compound alone. The combination of rivastigmine and antipsychotic drugs (apart from PNF) enhanced AChE inhibition. The tested antipsychotics (excluding HAL and PNF) significantly reduce the early stage of Aβ aggregation. BRMP, PIM, QUET and PROM were found to substantially inhibit Aβ aggregation after a longer incubation time. A test of human erythrocytes hemolysis showed that short-term incubation of red blood cells (RBCs) with QUET resulted in decreased hemolysis. The antioxidative properties of antipsychotics were also proved in human umbilical vein endothelial cells (HUVEC); all tested drugs were found to significantly increase cell viability. In the case of astrocytes, BNP, PNF, PIM and PROM showed antioxidant potential.

K. J, P. A, Ranganatha LV, Khanum SA, Silina E, Stupin V, Achar RR. Discovery of novel benzophenone integrated derivatives as anti-Alzheimer's agents targeting presenilin-1 and presenilin-2 inhibition: A computational approach

The most commonly accepted hypothesis of Alzheimer’s disease (AD) is the amyloid hypothesis caused due to formation of accumulation of Aβ42 isoform, which leads to neurodegeneration. In this regard, presenilin-1 (PSEN-1) and -2 (PSEN-2) proteins play a crucial role by altering the amyloid precursor protein (APP) metabolism, affecting γ-secretase protease secretion, finally leading to the increased levels of Aβ. In the absence of reported commercial pharmacotherapeutic agents targeting presenilins, we aim to propose benzophenone integrated derivatives (BIDs) as the potential inhibitors of presenilin proteins through in silico approach. The study evaluates the interaction of BIDs through molecular docking simulations, molecular dynamics simulations, and binding free energy calculations. This is the first ever computational approach to discover the potential inhibitors of presenilin proteins. It also comprises druglikeliness and pharmacotherapeutic potential analysis of the compounds. Out of all the screened BIDs, BID-16 was found to be the lead compound against both the presenilin proteins. Based on these results, one can evaluate BID-16 as an anti-Alzheimer’s potential specifically targeting presenilin proteins in near future using in vitro and in vivo methods.

Anti-aging effect of phlorizin on D-galactose-induced aging in mice through antioxidant and anti-inflammatory activity, prevention of apoptosis, and regulation of the gut microbiota

Aging is an inevitable and complicated process involving many physiological changes. Screening of natural biologically active anti-aging substances is a current research hotspot. Phlorizin (PZ), an important dihydrochalcone phytoconstituent, has been demonstrated to have antioxidant and anti-tumor effects. In this paper, different doses of PZ (20 and 40 mg/kg) were used to research the protective effect on D-galactose (D-gal)-induced aging mice. Following hematoxylin and eosin staining and by observing the hippocampus, we found that PZ alleviated the damage caused by D-gal in neuronal cells, while PZ enhanced the learning and memory abilities of aging mice in a radical eight-arm maze. In order to explain the reasons for these anti-aging effects, we tested the antioxidant enzyme activity and malonic dialdehyde concentration in mouse serum, liver, and brain tissue. The contents of proteins related to anti-inflammation and apoptosis in brain tissue were analyzed, and the gut microbiota was also analyzed. The results indicated that PZ improved antioxidant enzyme activity while significantly reducing the malonic dialdehyde content. Western blotting analysis suggested that PZ effectively alleviated neuro-apoptosis via regulating the expressions of Bax, Bcl-2, and caspase-3. PZ also exerted anti-inflammation effects by regulating the interleukin-1β/inhibitor of nuclear factor kappa B alpha/nuclear factor kappa-light-chain-enhancer of activated B-cells signaling pathways in brain tissues. Importantly, PZ improved the structure and diversity of the gut microbiota, and the microbiota-gut-brain axis may hold a key role in PZ-induced anti-aging effects. In conclusion, PZ can be used as a potential drug candidate to combat aging.

A Possible Pathogenic PSEN2 Gly56Ser Mutation in a Korean Patient with Early-Onset Alzheimer's Disease

Early-onset Alzheimer’s disease (EOAD) is characterized by the presence of neurological symptoms in patients with Alzheimer’s disease (AD) before 65 years of age. Mutations in pathological genes, including amyloid protein precursor (APP), presenilin-1 (PSEN1), and presenilin-2 (PSEN2), were associated with EOAD. Seventy-six mutations in PSEN2 have been found around the world, which could affect the activity of γ-secretase in amyloid beta processing. Here, a heterozygous PSEN2 point mutation from G to A nucleotide change at position 166 (codon 56; c.166G>A, Gly56Ser) was identified in a 64-year-old Korean female with AD with progressive cognitive memory impairment for the 4 years prior to the hospital visit. Hippocampal atrophy was observed from magnetic resonance imaging-based neuroimaging analyses. Temporal and parietal cortex hypometabolisms were identified using fluorodeoxyglucose positron emission tomography. This mutation was at the N-terminal portion of the presenilin 2 protein on the cytosolic side. Therefore, the serine substitution may have promoted AD pathogenesis by perturbing to the mutation region through altered phosphorylation of presenilin. In silico analysis revealed that the mutation altered protein bulkiness with increased hydrophilicity and reduced flexibility of the mutated region of the protein. Structural changes were likely caused by intramolecular interactions between serine and other residues, which may have affected APP processing. The functional study will clarify the pathogenicity of the mutation in the future.

Quantitative systems pharmacology model for Alzheimer’s disease to predict the effect of aducanumab on brain amyloid

Alzheimer's disease (AD) is an irreversible, progressive brain disorder that impairs memory and cognitive function. Dysregulation of the amyloid‐β (Aβ) pathway and amyloid plaque accumulation in the brain are hallmarks of AD. Aducanumab is a human, immunoglobulin gamma 1 monoclonal antibody targeting aggregated forms of Aβ. In phase Ib and phase III studies, aducanumab reduced Aβ plaques in a dose dependent manner, as measured by standard uptake value ratio of amyloid positron emission tomography imaging. The goal of this work was to develop a quantitative systems pharmacology model describing the production, aggregation, clearance, and transport of Aβ as well as the mechanism of action for the drug to understand the relationship between aducanumab dosing regimens and changes of different Aβ species, particularly plaques in the brain. The model was used to better understand the pharmacodynamic effects observed in the clinical trials of aducanumab and assist in the clinical development of future Aβ therapies.

How well does molecular simulation reproduce environment-specific conformations of the intrinsically disordered peptides PLP, TP2 and ONEG?

Understanding the conformational ensembles of intrinsically disordered proteins and peptides (IDPs) in their various biological environments is essential for understanding their mechanisms and functional roles in the proteome, leading to a greater knowledge of, and potential treatments for, a broad range of diseases. To determine whether molecular simulation is able to generate accurate conformational ensembles of IDPs, we explore the structural landscape of the PLP peptide (an intrinsically disordered region of the proteolipid membrane protein) in aqueous and membrane-mimicking solvents, using replica exchange with solute scaling (REST2), and examine the ability of four force fields (ff14SB, ff14IDPSFF, CHARMM36 and CHARMM36m) to reproduce literature circular dichroism (CD) data. Results from variable temperature (VT) 1H and Rotating frame Overhauser Effect SpectroscopY (ROESY) nuclear magnetic resonance (NMR) experiments are also presented and are consistent with the structural observations obtained from the simulations and CD. We also apply the optimum simulation protocol to TP2 and ONEG (a cell-penetrating peptide (CPP) and a negative control peptide, respectively) to gain insight into the structural differences that may account for the observed difference in their membrane-penetrating abilities. Of the tested force fields, we find that CHARMM36 and CHARMM36m are best suited to the study of IDPs, and accurately predict a disordered to helical conformational transition of the PLP peptide accompanying the change from aqueous to membrane-mimicking solvents. We also identify an α-helical structure of TP2 in the membrane-mimicking solvents and provide a discussion of the mechanistic implications of this observation with reference to the previous literature on the peptide. From these results, we recommend the use of CHARMM36m with the REST2 protocol for the study of environment-specific IDP conformations. We believe that the simulation protocol will allow the study of a broad range of IDPs that undergo conformational transitions in different biological environments.

Relationship between astrocyte reactivity, using novel 11C-BU99008 PET, and glucose metabolism, grey matter volume and amyloid load in cognitively impaired individuals

Post mortem neuropathology suggests that astrocyte reactivity may play a significant role in neurodegeneration in Alzheimer's disease. We explored this in vivo using multimodal PET and MRI imaging. Twenty subjects (11 older, cognitively impaired patients and 9 age-matched healthy controls) underwent brain scanning using the novel reactive astrocyte PET tracer ¹¹C-BU99008, ¹⁸F-FDG and ¹⁸F-florbetaben PET, and T1-weighted MRI. Differences between cognitively impaired patients and healthy controls in regional and voxel-wise levels of astrocyte reactivity, glucose metabolism, grey matter volume and amyloid load were explored, and their relationship to each other was assessed using Biological Parametric Mapping (BPM). Amyloid beta (Aβ)-positive patients showed greater ¹¹C-BU99008 uptake compared to controls, except in the temporal lobe, whilst further increased ¹¹C-BU99008 uptake was observed in Mild Cognitive Impairment subjects compared to those with Alzheimer's disease in the frontal, temporal and cingulate cortices. BPM correlations revealed that regions which showed reduced ¹¹C-BU99008 uptake in Aβ-positive patients compared to controls, such as the temporal lobe, also showed reduced ¹⁸F-FDG uptake and grey matter volume, although the correlations with ¹⁸F-FDG uptake were not replicated in the ROI analysis. BPM analysis also revealed a regionally-dynamic relationship between astrocyte reactivity and amyloid uptake: increased amyloid load in cortical association areas of the temporal lobe and cingulate cortices was associated with reduced ¹¹C-BU99008 uptake, whilst increased amyloid uptake in primary motor and sensory areas (in which amyloid deposition occurs later) was associated with increased ¹¹C-BU99008 uptake. These novel observations add to the hypothesis that while astrocyte reactivity may be triggered by early Aβ-deposition, sustained pro-inflammatory astrocyte reactivity with greater amyloid deposition may lead to astrocyte dystrophy and amyloid-associated neuropathology such as grey matter atrophy and glucose hypometabolism, although the evidence for glucose hypometabolism here is less strong.

Adiponectin alleviated Alzheimer-like pathologies via autophagy-lysosomal activation

Adiponectin (APN) deficiency has also been associated with Alzheimer‐like pathologies. Recent studies have illuminated the importance of APN signaling in reducing Aβ accumulation, and the Aβ elimination mechanism remains rudimentary. Therefore, we aimed to elucidate the APN role in reducing Aβ accumulation and its associated abnormalities by targeting autophagy and lysosomal protein changes. To assess, we performed a combined pharmacological and genetic approach while using preclinical models and human samples. Our results demonstrated that the APN level significantly diminished in the plasma of patients with dementia and 5xFAD mice (6 months old), which positively correlated with Mini‐Mental State Examination (MMSE), and negatively correlated with Clinical Dementia Rating (CDR), respectively. APN deficiency accelerated cognitive impairment, Aβ deposition, and neuroinflammation in 5xFAD mice (5xFAD*APN KO), which was significantly rescued by AdipoRon (AR) treatment. Furthermore, AR treatment also markedly reduced Aβ deposition and attenuated neuroinflammation in APP/PS1 mice without altering APP expression and processing. Interestingly, AR treatment triggered autophagy by mediating AMPK‐mTOR pathway signaling. Most importantly, APN deficiency dysregulated lysosomal enzymes level, which was recovered by AR administration. We further validated these changes by proteomic analysis. These findings reveal that APN is the negative regulator of Aβ deposition and its associated pathophysiologies. To eliminate Aβ both extra‐ and intracellular deposition, APN contributes via the autophagic/lysosomal pathway. It presents a therapeutic avenue for AD therapy by targeting autophagic and lysosomal signaling.

Is Aducanumab for LMICs? Promises and Challenges

Aducanumab, a human monoclonal antibody, was approved in June of 2021 as the first disease-modifying treatment for Alzheimer's disease by the United States Food and Drug Administration (U.S. FDA). A substantial proportion of patients with Alzheimer's disease live in low- and middle-income countries (LMICs), and the debilitating effects of this disease exerts burdens on patients and caregivers in addition to the significant economic strains many nations bear. While the advantages of a disease-modifying therapy are clear in delaying the progression of disease to improve patient outcomes, aducanumab's approval by the U.S. FDA was met with controversy for a plethora of reasons. This paper will provide precursory insights into aducanumab's role, appropriateness, and cost-effectiveness in low- and middle-income countries. We extend some of the controversies associated with aducanumab, including the contradicting evidence from the two trials (EMERGE and ENGAGE) and the resources required to deliver the treatment safely and effectively to patients, among other key considerations.

Polymorphism of Alpha-Synuclein Amyloid Fibrils Depends on Ionic Strength and Protein Concentration

Protein aggregate formation is linked with multiple amyloidoses, including Alzheimer's and Parkinson's diseases. Currently, the understanding of such fibrillar structure formation and propagation is still not sufficient, the outcome of which is a lack of potent, anti-amyloid drugs. The environmental conditions used during in vitro protein aggregation assays play an important role in determining both the aggregation kinetic parameters, as well as resulting fibril structure. In the case of alpha-synuclein, ionic strength has been shown as a crucial factor in its amyloid aggregation. In this work, we examine a large sample size of alpha-synuclein aggregation reactions under thirty different ionic strength and protein concentration combinations and determine the resulting fibril structural variations using their dye-binding properties, secondary structure and morphology. We show that both ionic strength and protein concentration determine the structural variability of alpha-synuclein amyloid fibrils and that sometimes even identical conditions can result in up to four distinct types of aggregates.

Hypothesis: Modulation of microglial phenotype in Alzheimer's disease drives neurodegeneration

The pathophysiology of Alzheimer's disease (AD) remains to be elucidated. The amyloid hypothesis holds explanatory power but has limitations. This article suggests that amyloid deposition and increased permeability of the blood-brain barrier are independent early events in the disease process, which together fashion a distinct microglial activation phenotype. Downstream events including, phagocytosis of synapses and persistent glutamate signaling through N-methyl-D-aspartate receptors drive neurodegeneration and tau pathology. This hypothesis draws on several strands of evidence and aims to illuminate several of the unexplained temporal and spatial features of AD.

Importance of extracellular vesicle secretion at the blood-cerebrospinal fluid interface in the pathogenesis of Alzheimer's disease

Increasing evidence indicates that extracellular vesicles (EVs) play an important role in the pathogenesis of Alzheimer’s disease (AD). We previously reported that the blood–cerebrospinal fluid (CSF) interface, formed by the choroid plexus epithelial (CPE) cells, releases an increased amount of EVs into the CSF in response to peripheral inflammation. Here, we studied the importance of CP-mediated EV release in AD pathogenesis. We observed increased EV levels in the CSF of young transgenic APP/PS1 mice which correlated with high amyloid beta (Aβ) CSF levels at this age. The intracerebroventricular (icv) injection of Aβ oligomers (AβO) in wild-type mice revealed a significant increase of EVs in the CSF, signifying that the presence of CSF-AβO is sufficient to induce increased EV secretion. Using in vivo, in vitro and ex vivo approaches, we identified the CP as a major source of the CSF-EVs. Interestingly, AβO-induced, CP-derived EVs induced pro-inflammatory effects in mixed cortical cultures. Proteome analysis of these EVs revealed the presence of several pro-inflammatory proteins, including the complement protein C3. Strikingly, inhibition of EV production using GW4869 resulted in protection against acute AβO-induced cognitive decline. Further research into the underlying mechanisms of this EV secretion might open up novel therapeutic strategies to impact the pathogenesis and progression of AD.

Identification of Novel Cathepsin B Inhibitors with Implications in Alzheimer's Disease: Computational Refining and Biochemical Evaluation

Amyloid precursor protein (APP), upon proteolytic degradation, forms aggregates of amyloid β (Aβ) and plaques in the brain, which are pathological hallmarks of Alzheimer’s disease (AD). Cathepsin B is a cysteine protease enzyme that catalyzes the proteolytic degradation of APP in the brain. Thus, cathepsin B inhibition is a crucial therapeutic aspect for the discovery of new anti-Alzheimer’s drugs. In this study, we have employed mixed-feature ligand-based virtual screening (LBVS) by integrating pharmacophore mapping, docking, and molecular dynamics to detect small, potent molecules that act as cathepsin B inhibitors. The LBVS model was generated by using hydrophobic (HY), hydrogen bond acceptor (HBA), and hydrogen bond donor (HBD) features, using a dataset of 24 known cathepsin B inhibitors of both natural and synthetic origins. A validated eight-feature pharmacophore hypothesis (Hypo III) was utilized to screen the Maybridge chemical database. The docking score, MM-PBSA, and MM-GBSA methodology was applied to prioritize the lead compounds as virtual screening hits. These compounds share a common amide scaffold, and showed important interactions with Gln23, Cys29, His110, His111, Glu122, His199, and Trp221. The identified inhibitors were further evaluated for cathepsin-B-inhibitory activity. Our study suggests that pyridine, acetamide, and benzohydrazide compounds could be used as a starting point for the development of novel therapeutics.

Bacterial Extracellular DNA Promotes β-Amyloid Aggregation

Alzheimer’s disease is associated with prion-like aggregation of the amyloid β (Aβ) peptide and the subsequent accumulation of misfolded neurotoxic aggregates in the brain. Therefore, it is critical to clearly identify the factors that trigger the cascade of Aβ misfolding and aggregation. Numerous studies have pointed out the association between microorganisms and their virulence factors and Alzheimer’s disease; however, their exact mechanisms of action remain unclear. Recently, we discovered a new pathogenic role of bacterial extracellular DNA, triggering the formation of misfolded Tau aggregates. In this study, we investigated the possible role of DNA extracted from different bacterial and eukaryotic cells in triggering Aβ aggregation in vitro. Interestingly, we found that the extracellular DNA of some, but not all, bacteria is an effective trigger of Aβ aggregation. Furthermore, the acceleration of Aβ nucleation and elongation can vary based on the concentration of the bacterial DNA and the bacterial strain from which this DNA had originated. Our findings suggest that bacterial extracellular DNA might play a previously overlooked role in the Aβ protein misfolding associated with Alzheimer’s disease pathogenesis. Moreover, it highlights a new mechanism of how distantly localized bacteria can remotely contribute to protein misfolding and diseases associated with this process. These findings might lead to the use of bacterial DNA as a novel therapeutic target for the prevention and treatment of Alzheimer’s disease.

Systemic Actions of SGLT2 Inhibition on Chronic mTOR Activation as a Shared Pathogenic Mechanism between Alzheimer's Disease and Diabetes

Alzheimer's disease (AD) affects tens of millions of people worldwide. Despite the advances in understanding the disease, there is an increased urgency for pharmacological approaches able of impacting its onset and progression. With a multifactorial nature, high incidence and prevalence in later years of life, there is growing evidence highlighting a relationship between metabolic dysfunction related to diabetes and subject's susceptibility to develop AD. The link seems so solid that sometimes AD and type 3 diabetes are used interchangeably. A candidate for a shared pathogenic mechanism linking these conditions is chronically-activated mechanistic target of rapamycin (mTOR). Chronic activation of unrestrained mTOR could be responsible for sustaining metabolic dysfunction that causes the breakdown of the blood-brain barrier, tau hyperphosphorylation and senile plaques formation in AD. It has been suggested that inhibition of sodium glucose cotransporter 2 (SGLT2) mediated by constant glucose loss, may restore mTOR cycle via nutrient-driven, preventing or even decreasing the AD progression. Currently, there is an unmet need for further research insight into molecular mechanisms that drive the onset and AD advancement as well as an increase in efforts to expand the testing of potential therapeutic strategies aimed to counteract disease progression in order to structure effective therapies.

The Participation of Microglia in Neurogenesis: A Review

Adult neurogenesis was one of the most important discoveries of the last century, helping us to better understand brain function. Researchers recently discovered that microglia play an important role in this process. However, various questions remain concerning where, at what stage, and what types of microglia participate. In this review, we demonstrate that certain pools of microglia are determinant cells in different phases of the generation of new neurons. This sheds light on how cells cooperate in order to fine tune brain organization. It also provides us with a better understanding of distinct neuronal pathologies.

Resistance Exercise Decreases Amyloid Load and Modulates Inflammatory Responses in the APP/PS1 Mouse Model for Alzheimer's Disease

Neuroinflammation has been shown to play a crucial role in the development of Alzheimer's disease (AD) and also has an association with amyloid-β (Aβ) plaques, a hallmark of this disease. Physical exercise has emerged as an alternative treatment for pathological impairment in AD. In light of this evidence, together with the fact that the hippocampus is one of the first structures to be affected in AD, we analyzed hippocampal changes in Aβ load, inflammatory responses, and locomotor activity in transgenic APP/PS1 mouse model for AD submitted to a resistance exercise (RE) program. One month after the start of the RE program, the locomotor hyperactivity related to AD behavior was reduced and microglia recruitment was increased, which in turn may have contributed to the decrease in the volume of Aβ plaques. In addition, the RE program restored the levels of IL-1α, IL-4, and IL-6 cytokines to control levels. Our study indicates that RE has beneficial effects on the locomotor behavior, amyloid burden, and inflammation of AD pathology and can therefore be used as a therapy to improve the clinical symptoms and neurophysiological alterations in AD. To the best of our knowledge, this is the first study to use a resistance exercise program in transgenic AD model.

Exploring the Multifunctional Neuroprotective Promise of Rasagiline Derivatives for Multi-Dysfunctional Alzheimer's Disease

Alzheimer's disease (AD) is a chronic, age-related, and irreversible brain disorder that typically develops slowly and gets worse over time. The potent auspicious drug candidate for the treatment of AD is supposed to perform the simultaneous modulation of several targets linked to AD. The new therapeutic approach involves drug candidates that are designed to act on multiple targets and have various pharmacological properties. This trend has triggered the development of various multimodal drugs including TV-3326 (i.e. ladostigil) and M-30 (i.e. a new multitarget iron chelator). TV-3326 combines the neurorestorative/neuroprotective effects of the cholinesterase (ChE) inhibitory activity of rivastigmine with rasagiline (a selective monoamine oxidase-B inhibitor and novel antiparkinsonian agent) in a single molecule. M-30, the second derivative of rasagiline, was developed by combining the propargyl moiety of rasagiline into the skeleton of VK-28 (i.e. a novel brain permeable neuroprotective iron chelator). It has been revealed that both the compounds possess anti-AD effects and therefore, the clinical development is directed to the treatment of this type of neurodegenerative diseases (NDs). In this article, we have reviewed the neuroprotective molecular mechanisms and multimodal effects of TV-3326 and M-30.

Implication of post-translationally modified SOD1 in pathological aging

Why certain people relish healthy aging throughout their life span while others suffer pathological consequences? In this review, we focus on some of the dominant paradigms of pathological aging, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Parkinson's disease (PD), and predict that the antioxidant superoxide dismutase 1 (SOD1), when post-translationally modified by aging-associated oxidative stress, acts as a mechanism to accelerated aging in these age-related neurodegenerative diseases. Oxidative modifications of natively reduced SOD1 induce pathological confirmations such as misfolding, leading to a subsequent formation of monomeric, oligomeric, and multimeric aggregates. Misfolded SOD1 propagates like prions from cell to cell. These modified conformations are detected in brain tissues in ALS, AD, and PD, and are considered a contributing factor to their initial pathogenesis. We have also elaborated on oxidative stress-induced non-native modifications of SOD1 and offered a logistic argument on their global implication in accelerated or pathological aging in the context of ALS, AD, and PD.

History in perspective: How Alzheimer's Disease came to be where it is?

Treatment of Alzheimer's Disease (AD) remains an unsolved issue despite the pronounced global attention it has received from researchers over the last four decades. Determining the primary cause of the disease is challenging due to its long prodromal phase and multifactorial etiology. Regardless, academic disagreements amongst the scientific community have helped in making significant advancements in underpinning the molecular basis of disease pathogenesis. Substantial development in fluid and imaging biomarkers for AD led to a sharp turn in defining the disease as a molecular construct, dispensing its clinical definition. With conceptual progress, revisions in the diagnostic criteria of AD were made, culminating into the research framework proposed by National Institute on Aging and Alzheimer's Association in 2018 which unified different stages of the disease continuum, giving a common language of AT(N)¹ classification to researchers. With realization that dementia is the final stage of AD spectrum, its early diagnosis by means of cerebrospinal fluid biomarkers, Positron Emission Tomography and Magnetic Resonance Imaging of the brain holds crucial importance in discovering ways of halting the disease progression. This article maps the insights into the pathogenesis as well as the diagnostic criteria and tests for AD as these have evolved over time. A contextualized timeline of how the understanding of AD has matured with advancing knowledge allows future research to be directed and unexplored avenues to be prioritized.