Soluble amyloid-β oligomers as synaptotoxins leading to cognitive impairment in Alzheimer's disease

Are the promnestic effects of neurokinin 3 receptor mediated by hippocampal neurogenesis in a Aβ-induced rat model of Alzheimer's disease?

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterised by cognitive dysfunction, memory loss and mood changes. Hippocampal neurogenesis has been suggested to play a role in learning and memory. Neurokinin 3 receptor (NK3R) has been shown to be prevalent in the hippocampus region. The aim of the project was to investigate the role of hippocampal neurogenesis in the promnestic effects of NK3R agonist administration in an amyloid beta-induced AD rat model. Wistar albino rats were divided into control, Alzheimer, NK3R agonist and Alzheimer + NK3R agonist groups. The open field (OF) test and Morris water maze (MWM) test were performed for locomotor activity and memory analysis. Peptide gene expression levels (Nestin, DCX, Neuritin, MASH1, Neun, BDNF) were analysed by quantitative reverse transcription polymerase chain reaction (RT-PCR). In the OF test, the group-time relationship was found to be statistically different in the parameters of distance travelled and percentage of movement (p < 0.05). In MWM, the time to reach the platform and the time spent in the target quadrant were statistically significant between the groups (p < 0.05). Statistically significant differences were observed in gene expression levels (Nestin, DCX, Neuritin, MASH1) in the hippocampal tissue of rats between the groups (p < 0.05). NK3 receptor agonism favourably affected hippocampal neurogenesis in AD model rats. It was concluded that NK3 receptor agonism in the hippocampus, which is the first affected region in the physiopathology of AD, may be effective in both the formation of neural precursor cells and the reduction of neuronal degeneration. The positive effect of NK3R on cognitive functions may be mediated by hippocampal neurogenesis.

Impaired hippocampal functions underlying memory encoding and consolidation precede robust Aβ deposition in a mouse model of Alzheimer's disease

Current therapeutic strategies for Alzheimer's disease (AD) target amyloid-beta (Aβ) fibrils and high molecular weight protofibrils associated with plaques, but molecular cascades associated with AD may drive neural systems failure before Aβ plaque deposition in AD. Employing hippocampal electrophysiological recordings and dynamic calcium imaging across the sleep-wake cycle in the APP/PS1 mouse model of AD before Aβ plaques accumulated, we detected marked impairments of hippocampal systems function: In a spatial behavioral task, but not REM sleep, phase-amplitude coupling (PAC) of the hippocampal theta and gamma oscillations was impaired and place cell calcium fluctuations were hyper-synchronized with the theta oscillation. In subsequent slow wave sleep (SWS), place cell reactivation was reduced. These degraded neural functions underlying memory encoding and consolidation support targeting pathological processes of the pre-plaque phase of AD to treat and prevent hippocampal impairments.

A new neuroprotective candidate TJ1 targeting amyloidogenesis in 5xFAD Alzheimer's disease mice

As one of the main pathmechanisms of Alzheimer's disease (AD), amyloid-β (Aβ) is widely considered to be the prime target for the development of AD therapy. Recently, imidazolylacetophenone oxime ethers or esters (IOEs) have shown neuroprotective effects against neuronal cells damage, suggesting their potential use in the prevention and treatment of AD. Thirty IOEs compounds from our lab in-house library were constructed and screened for the inhibitory effects on Aβ42-induced cytotoxicity. Among them, TJ1, as a new IOEs hit, preliminarily showed the effect on inhibiting Aβ42-induced cytotoxicity. Furthermore, the inhibitory effects of TJ1 on Aβ42 aggregation were tested by ThT assays and TEM. The neuroprotective effects of TJ1 were evaluated in Aβ42-stimulated SH-SY5Y cells, LPS-stimulated BV-2 cells, and H2O2- and RSL3-stimulated PC12 cells. The cognitive improvement of TJ1 was assessed in 5xFAD (C57BL/6J) transgenic mouse. These results showed that TJ1 had strong neuroprotective effects and high blood-brain barrier (BBB) permeability without obvious cytotoxicity. TJ1 impeded the self-accumulation process of Aβ42 by acting on Aβ oligomerization and fibrilization. Besides, TJ1 reversed Aβ-, H2O2- and RSL3-induced neuronal cell damage and decreased neuroinflammation. In 5xFAD mice, TJ1 improved cognitive impairment, increased GSH level, reduced the level of Aβ42 and Aβ plaques, and attenuated the glia reactivation and inflammatory response in the brain,. Taken together, our results demonstrate that TJ1 improves cognitive impairments as a new neuroprotective candidate via targeting amyloidogenesis, which suggests the potential of TJ1 as a treatment for AD.

Psychobiotic Properties of Lactiplantibacillus plantarum in Neurodegenerative Diseases

Neurodegenerative disorders are the main cause of cognitive and physical disabilities, affect millions of people worldwide, and their incidence is on the rise. Emerging evidence pinpoints a disturbance of the communication of the gut-brain axis, and in particular to gut microbial dysbiosis, as one of the contributors to the pathogenesis of these diseases. In fact, dysbiosis has been associated with neuro-inflammatory processes, hyperactivation of the neuronal immune system, impaired cognitive functions, aging, depression, sleeping disorders, and anxiety. With the rapid advance in metagenomics, metabolomics, and big data analysis, together with a multidisciplinary approach, a new horizon has just emerged in the fields of translational neurodegenerative disease. In fact, recent studies focusing on taxonomic profiling and leaky gut in the pathogenesis of neurodegenerative disorders are not only shedding light on an overlooked field but are also creating opportunities for biomarker discovery and development of new therapeutic and adjuvant strategies to treat these disorders. Lactiplantibacillus plantarum (LBP) strains are emerging as promising psychobiotics for the treatment of these diseases. In fact, LBP strains are able to promote eubiosis, increase the enrichment of bacteria producing beneficial metabolites such as short-chain fatty acids, boost the production of neurotransmitters, and support the homeostasis of the gut-brain axis. In this review, we summarize the current knowledge on the role of the gut microbiota in the pathogenesis of neurodegenerative disorders with a particular focus on the benefits of LBP strains in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, autism, anxiety, and depression.

Human brain organoids containing microglia that have arisen innately adapt to a β-amyloid challenge better than those in which microglia are integrated by co-culture

BACKGROUND

Alzheimer disease (AD) is a heterogenous and multifactorial disease, and its pathology is partly driven by microglia and their activated phenotype. Brain organoids (BOs) are gaining prominence as a relevant model of the human brain for the study of AD; however, BOs are commonly devoid of microglia. To overcome this limitation, current protocols incorporate microglia through either (1) co-culture (BO co-culture), or (2) molecular manipulation at critical windows of BO development to have microglia arise innately (BO innate cultures). It is currently unclear whether the microglia incorporated into BOs by either of these two protocols differ in function.

METHODS

At in vitro day 90, BO innate cultures and BO-co-cultures were challenged with the AD-related β-amyloid peptide (Aβ) for up to 72 h. After Aβ challenge, BOs were collected for immunoblotting. Immunoblots compared immunodensity and protein banding of Aβ and ionized calcium-binding adapter molecule 1 (IBA1, a marker of microglial activation) in BOs. The translational potential of these observations was supported using 56 human cortical samples from neurocognitively normal donors and patients with early-onset AD and late-onset AD. Statistical analyses were conducted using the Kruskal-Wallis test, a two-way ANOVA, or a simple linear regression, and where applicable, followed by Dunn's or Sidak's test.

RESULTS

We show that BO co-cultures promote Aβ oligomerization as early as 24 h and this coincides with a significant increase in IBA1 levels. In contrast, the Aβs do not oligomerize in BO innate cultures and the IBA1 response was modest and only emerged after 48 h. In human cortical samples, we found IBA1 levels correlated with age at onset, age at death, and the putative diagnostic Aβ(1-42)/Aβ(1-40) ratio (particularly in their oligomeric forms) in a sex-dependent manner.

CONCLUSIONS

Our unique observations suggest that BOs with innate microglia model the response of a healthy brain to Aβ, and by extension the initial stages of Aβ challenge. It would be impossible to model these early stages of pathogenesis in BOs where microglia are already compromised, such as those with microglia incorporated by co-culture.

Transient sleep apnea results in long-lasting increase in β-amyloid generation and tau hyperphosphorylation

Sleep apnea is regarded as an important risk factor in the pathogenesis of Alzheimer disease (AD). Chronic intermittent hypoxia treatment (IHT) given during the sleep period of the circadian cycle in experimental animals is a well-established sleep apnea model. Here we report that transient IHT for 4 days on AD model mice causes Aβ overproduction 2 months after IHT presumably via upregulation of synaptic BACE1, side-by-side with tau hyperphosphorylation. These results suggest that even transient IHT may be sufficient to cause long-lasting changes in the molecules measured as AD biomarkers in the brain.

mTOR signaling and Alzheimer's disease: What we know and where we are?

Despite the great body of research done on Alzheimer's disease, the underlying mechanisms have not been vividly investigated. To date, the accumulation of amyloid-beta plaques and tau tangles constitutes the hallmark of the disease; however, dysregulation of the mammalian target of rapamycin (mTOR) seems to be significantly involved in the pathogenesis of the disease as well. mTOR, as a serine-threonine protein kinase, was previously known for controlling many cellular functions such as cell size, autophagy, and metabolism. In this regard, mammalian target of rapamycin complex 1 (mTORC1) may leave anti-aging impacts by robustly inhibiting autophagy, a mechanism that inhibits the accumulation of damaged protein aggregate and dysfunctional organelles. Formation and aggregation of neurofibrillary tangles and amyloid-beta plaques seem to be significantly regulated by mTOR signaling. Understanding the underlying mechanisms and connection between mTOR signaling and AD may suggest conducting clinical trials assessing the efficacy of rapamycin, as an mTOR inhibitor drug, in managing AD or may help develop other medications. In this literature review, we aim to elaborate mTOR signaling network mainly in the brain, point to gaps of knowledge, and define how and in which ways mTOR signaling can be connected with AD pathogenesis and symptoms.

Distinguishing IDH mutation status in gliomas using FTIR-ATR spectra of peripheral blood plasma indicating clear traces of protein amyloid aggregation

BACKGROUND

Glioma is a primary brain tumor and the assessment of its molecular profile in a minimally invasive manner is important in determining treatment strategies. Among the molecular abnormalities of gliomas, mutations in the isocitrate dehydrogenase (IDH) gene are strong predictors of treatment sensitivity and prognosis. In this study, we attempted to non-invasively diagnose glioma development and the presence of IDH mutations using multivariate analysis of the plasma mid-infrared absorption spectra for a comprehensive and sensitive view of changes in blood components associated with the disease and genetic mutations. These component changes are discussed in terms of absorption wavenumbers that contribute to differentiation.

METHODS

Plasma samples were collected at our institutes from 84 patients with glioma (13 oligodendrogliomas, 17 IDH-mutant astrocytoma, 7 IDH wild-type diffuse glioma, and 47 glioblastomas) before treatment initiation and 72 healthy participants. FTIR-ATR spectra were obtained for each plasma sample, and PLS discriminant analysis was performed using the absorbance of each wavenumber in the fingerprint region of biomolecules as the explanatory variable. This data was used to distinguish patients with glioma from healthy participants and diagnose the presence of IDH mutations.

RESULTS

The derived classification algorithm distinguished the patients with glioma from healthy participants with 83% accuracy (area under the curve (AUC) in receiver operating characteristic (ROC) = 0.908) and diagnosed the presence of IDH mutation with 75% accuracy (AUC = 0.752 in ROC) in cross-validation using 30% of the total test data. The characteristic changes in the absorption spectra suggest an increase in the ratio of β-sheet structures in the conformational composition of blood proteins of patients with glioma. Furthermore, these changes were more pronounced in patients with IDH-mutant gliomas.

CONCLUSIONS

The plasma infrared absorption spectra could be used to diagnose gliomas and the presence of IDH mutations in gliomas with a high degree of accuracy. The spectral shape of the protein absorption band showed that the ratio of β-sheet structures in blood proteins was significantly higher in patients with glioma than in healthy participants, and protein aggregation was a distinct feature in patients with glioma with IDH mutations.

Orexin Receptor Antagonism: Normalizing Sleep Architecture in Old Age and Disease

Sleep is essential for human well-being, yet the quality and quantity of sleep reduce as age advances. Older persons (>65 years old) are more at risk of disorders accompanied and/or exacerbated by poor sleep. Furthermore, evidence supports a bidirectional relationship between disrupted sleep and Alzheimer's disease (AD) or related dementias. Orexin/hypocretin neuropeptides stabilize wakefulness, and several orexin receptor antagonists (ORAs) are approved for the treatment of insomnia in adults. Dysregulation of the orexin system occurs in aging and AD, positioning ORAs as advantageous for these populations. Indeed, several clinical studies indicate that ORAs are efficacious hypnotics in older persons and dementia patients and, as in adults, are generally well tolerated. ORAs are likely to be more effective when administered early in sleep/wake dysregulation to reestablish good sleep/wake-related behaviors and reduce the accumulation of dementia-associated proteinopathic substrates. Improving sleep in aging and dementia represents a tremendous opportunity to benefit patients, caregivers, and health systems.

Immunological dimensions of neuroinflammation and microglial activation: exploring innovative immunomodulatory approaches to mitigate neuroinflammatory progression

The increasing life expectancy has led to a higher incidence of age-related neurodegenerative conditions. Within this framework, neuroinflammation emerges as a significant contributing factor. It involves the activation of microglia and astrocytes, leading to the release of pro-inflammatory cytokines and chemokines and the infiltration of peripheral leukocytes into the central nervous system (CNS). These instances result in neuronal damage and neurodegeneration through activated nucleotide-binding domain and leucine-rich repeat containing (NLR) family pyrin domain containing protein 3 (NLRP3) and nuclear factor kappa B (NF-kB) pathways and decreased nuclear factor erythroid 2-related factor 2 (Nrf2) activity. Due to limited effectiveness regarding the inhibition of neuroinflammatory targets using conventional drugs, there is challenging growth in the search for innovative therapies for alleviating neuroinflammation in CNS diseases or even before their onset. Our results indicate that interventions focusing on Interleukin-Driven Immunomodulation, Chemokine (CXC) Receptor Signaling and Expression, Cold Exposure, and Fibrin-Targeted strategies significantly promise to mitigate neuroinflammatory processes. These approaches demonstrate potential anti-neuroinflammatory effects, addressing conditions such as Multiple Sclerosis, Experimental autoimmune encephalomyelitis, Parkinson's Disease, and Alzheimer's Disease. While the findings are promising, immunomodulatory therapies often face limitations due to Immune-Related Adverse Events. Therefore, the conduction of randomized clinical trials in this matter is mandatory, and will pave the way for a promising future in the development of new medicines with specific therapeutic targets.

Aducanumab in Alzheimer's Disease: A Critical Update

Alzheimer's disease (AD) is a complex neurological disorder that results in cognitive decline. The incidence rates of AD have been increasing, particularly among individuals 60 years of age or older. In June 2021, the US FDA approved aducanumab, the first humanized monoclonal antibody, as a potential therapeutic option for AD. Clinical trials have shown this drug to effectively target the accumulation of Aβ (beta-amyloid) plaques in the brain, and its effectiveness is dependent on the dosage and duration of treatment. Additionally, aducanumab has been associated with improvements in cognitive function. Biogen, the pharmaceutical company responsible for developing and marketing aducanumab, has positioned it as a potential breakthrough for treating cerebral damage in AD. However, the drug has raised concerns due to its high cost, limitations, and potential side effects. AD is a progressive neurological condition that affects memory, cognitive function, and behaviour. It significantly impacts the quality of life of patients and caregivers and strains healthcare systems. Ongoing research focuses on developing disease-modifying therapies that can halt or slow down AD progression. The pathogenesis of AD involves various molecular cascades and signaling pathways. However, the formation of extracellular amyloid plaques is considered a critical mechanism driving the development and progression of the disease. Aducanumab, as a monoclonal antibody, has shown promising results in inhibiting amyloid plaque formation, which is the primary pathological feature of AD. This review explores the signaling pathways and molecular mechanisms through which aducanumab effectively prevents disease pathogenesis in AD.

Research and progress of focused ultrasound in the treatment of Alzheimer's disease

Alzheimer's disease is one of the most common degenerative diseases of the central nervous system, with progressive cognitive and memory impairment and decreased ability of daily life as the cardinal symptoms, influencing the life quality of patients severely. There are currently approximately 46 million people living with Alzheimer's disease worldwide, and the number is expected to triple by 2050, which will pose a huge challenge for healthcare. At present, the Food and Drug Administration of the United States has approved five main drugs for the clinical treatment of Alzheimer's disease, which are cholinesterase inhibitors tacrine, galantamine, capalatine and donepezil, and N-methyl-d-aspartate receptor antagonist memantine, although these drugs have shown good efficacy in clinical trials, the actual clinical effect is less effective due to the existence of blood brain barrier. With the continuous development of ultrasound technology in recent years, focused ultrasound, as a non-invasive treatment technique, may target ultrasound energy to the deep brain for treatment without damaging the surrounding tissue. For the past few years, some studies could use focused ultrasound combined with microvesicles to induce blood brain barrier opening and targeted drug delivery to treat Alzheimer's disease, providing new opportunities for the treatment of Alzheimer's disease. This article reviews the application research and progress of focused ultrasound in the treatment of Alzheimer's disease, in order to provide new directions and ideas for the treatment of Alzheimer's disease.

A novel apoE-mimetic increases brain apoE levels, reduces Aβ pathology and improves memory when treated before onset of pathology in male mice that express APOE3

BACKGROUND

Alzheimer's disease (AD) is characterized by cognitive dysfunction and amyloid plaques composed of the amyloid-beta peptide (Aβ). APOE is the greatest genetic risk for AD with APOE4 increasing risk up to ~ 15-fold compared to APOE3. Evidence suggests that levels and lipidation of the apoE protein could regulate AD progression. In glia, apoE is lipidated via cholesterol efflux from intracellular pools, primarily by the ATP-binding cassette transporter A1 (ABCA1). Therefore, increasing ABCA1 activity is suggested to be a therapeutic approach for AD. CS-6253 (CS) is a novel apoE mimetic peptide that was developed to bind and stabilize ABCA1 and maintain its localization into the plasma membrane therefore promoting cholesterol efflux. The goal of this study was to determine whether CS could modulate apoE levels and lipidation, Aβ pathology, and behavior in a model that expresses human APOE and overproduce Aβ.

METHODS

In vitro, APOE3-glia or APOE4-glia were treated with CS. In vivo, male and female, E3FAD (5xFAD+/-/APOE3+/+) and E4FAD (5xFAD+/-/APOE4+/+) mice were treated with CS via intraperitoneal injection at early (from 4 to 8 months of age) and late ages (from 8 to 10 months of age). ApoE levels, ABCA1 levels and, apoE lipidation were measured by western blot and ELISA. Aβ and amyloid levels were assessed by histochemistry and ELISA. Learning and memory were tested by Morris Water Maze and synaptic proteins were measured by Western blot.

RESULTS

CS treatment increased apoE levels and cholesterol efflux in primary glial cultures. In young male E3FAD mice, CS treatment increased soluble apoE and lipid-associated apoE, reduced soluble oAβ and insoluble Aβ levels as well as Aβ and amyloid deposition, and improved memory and synaptic protein levels. CS treatment did not induce any therapeutic benefits in young female E3FAD and E4FAD mice or in any groups when treatment was started at later ages.

CONCLUSIONS

CS treatment reduced Aβ pathology and improved memory only in young male E3FAD, the cohort with the least AD pathology. Therefore, the degree of Aβ pathology or Aβ overproduction may impact the ability of targeting ABCA1 to be an effective AD therapeutic. This suggests that ABCA1-stabilizing treatment by CS-6253 works best in conditions of modest Aβ levels.

Synaptic proteasome is inhibited in Alzheimer's disease models and associates with memory impairment in mice

The proteasome plays key roles in synaptic plasticity and memory by regulating protein turnover, quality control, and elimination of oxidized/misfolded proteins. Here, we investigate proteasome function and localization at synapses in Alzheimer's disease (AD) post-mortem brain tissue and in experimental models. We found a marked increase in ubiquitinylated proteins in post-mortem AD hippocampi compared to controls. Using several experimental models, we show that amyloid-β oligomers (AβOs) inhibit synaptic proteasome activity and trigger a reduction in synaptic proteasome content. We further show proteasome inhibition specifically in hippocampal synaptic fractions derived from APPswePS1ΔE9 mice. Reduced synaptic proteasome activity instigated by AβOs is corrected by treatment with rolipram, a phosphodiesterase-4 inhibitor, in mice. Results further show that dynein inhibition blocks AβO-induced reduction in dendritic proteasome content in hippocampal neurons. Finally, proteasome inhibition induces AD-like pathological features, including reactive oxygen species and dendritic spine loss in hippocampal neurons, inhibition of hippocampal mRNA translation, and memory impairment in mice. Results suggest that proteasome inhibition may contribute to synaptic and memory deficits in AD.

Amyloid β-Oligomers Inhibit the Nuclear Ca2+ Signals and the Neuroprotective Gene Expression Induced by Gabazine in Hippocampal Neurons

Hippocampal neuronal activity generates dendritic and somatic Ca2+ signals, which, depending on stimulus intensity, rapidly propagate to the nucleus and induce the expression of transcription factors and genes with crucial roles in cognitive functions. Soluble amyloid-beta oligomers (AβOs), the main synaptotoxins engaged in the pathogenesis of Alzheimer's disease, generate aberrant Ca2+ signals in primary hippocampal neurons, increase their oxidative tone and disrupt structural plasticity. Here, we explored the effects of sub-lethal AβOs concentrations on activity-generated nuclear Ca2+ signals and on the Ca2+-dependent expression of neuroprotective genes. To induce neuronal activity, neuron-enriched primary hippocampal cultures were treated with the GABAA receptor blocker gabazine (GBZ), and nuclear Ca2+ signals were measured in AβOs-treated or control neurons transfected with a genetically encoded nuclear Ca2+ sensor. Incubation (6 h) with AβOs significantly reduced the nuclear Ca2+ signals and the enhanced phosphorylation of cyclic AMP response element-binding protein (CREB) induced by GBZ. Likewise, incubation (6 h) with AβOs significantly reduced the GBZ-induced increases in the mRNA levels of neuronal Per-Arnt-Sim domain protein 4 (Npas4), brain-derived neurotrophic factor (BDNF), ryanodine receptor type-2 (RyR2), and the antioxidant enzyme NADPH-quinone oxidoreductase (Nqo1). Based on these findings we propose that AβOs, by inhibiting the generation of activity-induced nuclear Ca2+ signals, disrupt key neuroprotective gene expression pathways required for hippocampal-dependent learning and memory processes.

Ginsenoside Rg1 improved learning and memory ability and reduces neuronal apoptosis in epileptic rats through ERK/CREB/BDNF signal pathway

OBJECTIVE

This research was devoted to estimating the outcomes of ginsenoside Rg1 on learning and memory ability and neuronal apoptosis in epileptic rats through ERK/CREB/BDNF pathway.

METHODS

The epileptic rats induced by lithium chloride were stochastically separated into model subgroup, ginsenoside Rg1 different dose subgroups. The ginsenoside Rg1 subgroups were given 20, 30 and 40 mg/kg ginsenoside Rg1 by gavage individually. Another 6 normal rats were selected as the control subgroup. The seizures of each subgroup were estimated. Morris water maze was utilized for estimating the changes of cognitive function changes of rats. The injury and apoptosis of hippocampal neurons in each subgroup were detected by Nissl and TUNEL assays. HE staining was applied for the structural and pathomorphological changes of hippocampal neurons detection. The oxidative stress level in hippocampus of rats was estimated by ELISA. DCFH-DA probe was applied for the changes of reactive oxygen species (ROS) in brain tissue detection. The Bcl-2, Bax, ERK, p-ERK, CREB, p-CREB and BDNF levels in cerebral cortex were estimated by western blot, and PD98059, a blocker of ERK pathway, was used to intervene.

RESULTS

In the control subgroup, Nissl bodies were abundant and evenly distributed, and cortical neurons were arranged neatly. In the model subgroup, the cytoplasmic staining of cortical neurons was insufficient and the arrangement of neurons was disordered. After treatment with ginsenoside Rg1, the morphology of neurons in the cerebral cortex was restored. The frequency of seizures, duration of seizures, Racine grade, escape latency, target quadrant residence time, MDA, TNF-α and ROS levels of cerebral cortex in the model subgroup boosted notablely versus the control subgroup. The frequency of crossing the original platform, the activity of SOD, the IL-10, p-ERK/ERK, p-CREB/CREB and BDNF levels in cerebral cortex were notablely lessened. The above-mentioned indexes in the ginsenoside Rg1 subgroup were notablely improved versus the model subgroup, and the three proteins levels in the PD98059 intervention subgroup were notablely lower.

CONCLUSION

Ginsenoside Rg1 can improve cognitive dysfunction in epileptic rats, which may be concerned with ERK/CREB/BDNF pathway activation in cerebral cortex and lessening oxidative stress and inflammation.

The intracerebral injection of Aβ1-42 oligomers does not invariably alter seizure susceptibility in mice

Objectives

Epileptiform activity and seizures are present in patients with Alzheimer's disease (AD) and genetic animal models of AD. Amyloid beta 1-42 (Aβ1-42) oligomers are thought to be crucial in AD and can cause neuronal hyperexcitability in vitro. However, it is unclear whether these Aβ1-42 oligomers cause the increased seizure susceptibility in vivo in people with AD and in AD animal models, nor via which mechanisms it would do so. We investigated this question by injecting Aβ1-42 oligomers intracerebrally in mice and assessed its impact on seizure susceptibility.

Materials and methods

We performed a single intracerebral injection of synthetic Aβ1-42 oligomers or scrambled Aβ1-42 in NMRI mice in three different cohorts and subjected them to an i.v. infusion of a chemoconvulsant. We evoked the seizures 1.5 h, 1 week, or 3 weeks after the intracerebral injection of Aβ1-42 oligomers, covering also the timepoints and injection locations that were used by others in similar experimental set-ups.

Results

With a thioflavine T assay and transmission electron microscopy we confirmed that Aβ1-42 monomers spontaneously aggregated to oligomers. We did not find an effect of Aβ1-42 oligomers on susceptibility to seizures - evoked 1.5 h, 1 week or 3 weeks - after their intracerebral injection.

Significance

The lack of effect of Aβ1-42 oligomers on seizure susceptibility in our experiments contrasts with recent findings in similar experimental set-ups. Contradicting conclusions are frequent in experiments with Aβ1-42 and they are often attributed to subtle differences in the various aggregation forms of the Aβ1-42 used in different experiments. We confirmed the presence of Aβ1-42 oligomers with state-of-the-art methods but cannot ascertain that the protein aggregates we used are identical to those used by others. Whether our findings or those previously published best represent the role of Aβ1-42 oligomers on seizures in AD remains unclear.

A novel peptide derived from vascular endothelial growth factor prevents amyloid beta aggregation and toxicity

Amyloid-β oligomers (Aβo) are the most pathologically relevant Aβ species in Alzheimer's disease (AD), because they induce early synaptic dysfunction that leads to learning and memory impairments. In contrast, increasing VEGF (Vascular Endothelial Growth Factor) brain levels have been shown to improve learning and memory processes, and to alleviate Aβ-mediated synapse dysfunction. Here, we designed a new peptide, the blocking peptide (BP), which is derived from an Aβo-targeted domain of the VEGF protein, and investigated its effect on Aβ-associated toxicity. Using a combination of biochemical, 3D and ultrastructural imaging, and electrophysiological approaches, we demonstrated that BP strongly interacts with Aβo and blocks Aβ fibrillar aggregation process, leading to the formation of Aβ amorphous aggregates. BP further impedes the formation of structured Aβo and prevents their pathogenic binding to synapses. Importantly, acute BP treatment successfully rescues long-term potentiation (LTP) in the APP/PS1 mouse model of AD, at an age when LTP is highly impaired in hippocampal slices. Moreover, BP is also able to block the interaction between Aβo and VEGF, which suggests a dual mechanism aimed at both trapping Aβo and releasing VEGF to alleviate Aβo-induced synaptic damage. Our findings provide evidence for a neutralizing effect of the BP on Aβ aggregation process and pathogenic action, highlighting a potential new therapeutic strategy.

Emerging concepts towards a translational framework in Alzheimer's disease

Over the past decades, significant efforts have been made to understand the precise mechanisms underlying the pathogenesis of Alzheimer's disease (AD), the most common cause of dementia. However, clinical trials targeting AD pathological hallmarks have consistently failed. Refinement of AD conceptualization, modeling, and assessment is key to developing successful therapies. Here, we review critical findings and discuss emerging ideas to integrate molecular mechanisms and clinical approaches in AD. We further propose a refined workflow for animal studies incorporating multimodal biomarkers used in clinical studies - delineating critical paths for drug discovery and translation. Addressing unresolved questions with the proposed conceptual and experimental framework may accelerate the development of effective disease-modifying strategies for AD.

Move Your Body toward Healthy Aging: Potential Neuroprotective Mechanisms of Irisin in Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia in older adults, having a significant global burden and increasing prevalence. Current treatments for AD only provide symptomatic relief and do not cure the disease. Physical activity has been extensively studied as a potential preventive measure against cognitive decline and AD. Recent research has identified a hormone called irisin, which is produced during exercise, that has shown promising effects on cognitive function. Irisin acts on the brain by promoting neuroprotection by enhancing the growth and survival of neurons. It also plays a role in metabolism, energy regulation, and glucose homeostasis. Furthermore, irisin has been found to modulate autophagy, which is a cellular process involved in the clearance of protein aggregates, which are a hallmark of AD. Additionally, irisin has been shown to protect against cell death, apoptosis, oxidative stress, and neuroinflammation, all of which are implicated in AD pathogenesis. However, further research is needed to fully understand the mechanisms and therapeutic potential of irisin in AD. Despite the current gaps in knowledge, irisin holds promise as a potential therapeutic target for slowing cognitive decline and improving quality of life in AD patients.

A review of the auditory-gut-brain axis

Hearing loss places a substantial burden on medical resources across the world and impacts quality of life for those affected. Further, it can occur peripherally and/or centrally. With many possible causes of hearing loss, there is scope for investigating the underlying mechanisms involved. Various signaling pathways connecting gut microbes and the brain (the gut-brain axis) have been identified and well established in a variety of diseases and disorders. However, the role of these pathways in providing links to other parts of the body has not been explored in much depth. Therefore, the aim of this review is to explore potential underlying mechanisms that connect the auditory system to the gut-brain axis. Using select keywords in PubMed, and additional hand-searching in google scholar, relevant studies were identified. In this review we summarize the key players in the auditory-gut-brain axis under four subheadings: anatomical, extracellular, immune and dietary. Firstly, we identify important anatomical structures in the auditory-gut-brain axis, particularly highlighting a direct connection provided by the vagus nerve. Leading on from this we discuss several extracellular signaling pathways which might connect the ear, gut and brain. A link is established between inflammatory responses in the ear and gut microbiome-altering interventions, highlighting a contribution of the immune system. Finally, we discuss the contribution of diet to the auditory-gut-brain axis. Based on the reviewed literature, we propose numerous possible key players connecting the auditory system to the gut-brain axis. In the future, a more thorough investigation of these key players in animal models and human research may provide insight and assist in developing effective interventions for treating hearing loss.

Amyloid-Lowering Monoclonal Antibodies for the Treatment of Early Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia worldwide. Numerous biomarker studies have clearly demonstrated that AD has a long asymptomatic phase, with the development of pathology occurring at least 2 decades prior to the development of any symptoms. These pathological changes include a stepwise development of amyloid-β (Aβ) plaques, followed by tau neurofibrillary tangles and subsequently extensive neurodegeneration in the brain. In this review, we discuss the first class of drugs intended to be disease modifying to be approved by the US Food and Drug Administration (FDA) for AD-anti-Aβ monoclonal antibodies-and the scientific rationale with which they were developed.

Inhibition of ACAT as a Therapeutic Target for Alzheimer's Disease Is Independent of ApoE4 Lipidation

APOE4, encoding apolipoprotein E4 (apoE4), is the greatest genetic risk factor for Alzheimer's disease (AD), compared to the common APOE3. While the mechanism(s) underlying APOE4-induced AD risk remains unclear, increasing the lipidation of apoE4 is an important therapeutic target as apoE4-lipoproteins are poorly lipidated compared to apoE3-lipoproteins. ACAT (acyl-CoA: cholesterol-acyltransferase) catalyzes the formation of intracellular cholesteryl-ester droplets, reducing the intracellular free cholesterol (FC) pool. Thus, inhibiting ACAT increases the FC pool and facilitates lipid secretion to extracellular apoE-containing lipoproteins. Previous studies using commercial ACAT inhibitors, including avasimibe (AVAS), as well as ACAT-knock out (KO) mice, exhibit reduced AD-like pathology and amyloid precursor protein (APP) processing in familial AD (FAD)-transgenic (Tg) mice. However, the effects of AVAS with human apoE4 remain unknown. In vitro, AVAS induced apoE efflux at concentrations of AVAS measured in the brains of treated mice. AVAS treatment of male E4FAD-Tg mice (5xFAD+/-APOE4+/+) at 6-8 months had no effect on plasma cholesterol levels or distribution, the original mechanism for AVAS treatment of CVD. In the CNS, AVAS reduced intracellular lipid droplets, indirectly demonstrating target engagement. Surrogate efficacy was demonstrated by an increase in Morris water maze measures of memory and postsynaptic protein levels. Amyloid-beta peptide (Aβ) solubility/deposition and neuroinflammation were reduced, critical components of APOE4-modulated pathology. However, there was no increase in apoE4 levels or apoE4 lipidation, while amyloidogenic and non-amyloidogenic processing of APP were significantly reduced. This suggests that the AVAS-induced reduction in Aβ via reduced APP processing was sufficient to reduce AD pathology, as apoE4-lipoproteins remained poorly lipidated.

A Systematic Review of the Effects of Capsaicin on Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder characterised by cognitive impairment, and amyloid-β plaques and neurofibrillary tau tangles at neuropathology. Capsaicin is a spicy-tasting compound found in chili peppers, with anti-inflammatory, antioxidant, and possible neuroprotective properties. Capsaicin intake has been associated with greater cognitive function in humans, and attenuating aberrant tau hyperphosphorylation in a rat model of AD. This systematic review discusses the potential of capsaicin in improving AD pathology and symptoms. A systematic analysis was conducted on the effect of capsaicin on AD-associated molecular changes, cognitive and behaviour resulting in 11 studies employing rodents and/or cell cultures, which were appraised with the Cochrane Risk of Bias tool. Ten studies showed capsaicin attenuated tau deposition, apoptosis, and synaptic dysfunction; was only weakly effective on oxidative stress; and had conflicting effects on amyloid processing. Eight studies demonstrated improved spatial and working memory, learning, and emotional behaviours in rodents following capsaicin treatment. Overall, capsaicin showed promise in improving AD-associated molecular, cognitive, and behavioural changes in cellular and animal models, and further investigations are recommended to test the readily available bioactive, capsaicin, to treat AD.

CARD9 attenuates Aβ pathology and modifies microglial responses in an Alzheimer's disease mouse model

Recent advances have highlighted the importance of several innate immune receptors expressed by microglia in Alzheimer's disease (AD). In particular, mounting evidence from AD patients and experimental models indicates pivotal roles for TREM2, CD33, and CD22 in neurodegenerative disease progression. While there is growing interest in targeting these microglial receptors to treat AD, we still lack knowledge of the downstream signaling molecules used by these receptors to orchestrate immune responses in AD. Notably, TREM2, CD33, and CD22 have been described to influence signaling associated with the intracellular adaptor molecule CARD9 to mount downstream immune responses outside of the brain. However, the role of CARD9 in AD remains poorly understood. Here, we show that genetic ablation of CARD9 in the 5xFAD mouse model of AD results in exacerbated amyloid beta (Aβ) deposition, increased neuronal loss, worsened cognitive deficits, and alterations in microglial responses. We further show that pharmacological activation of CARD9 promotes improved clearance of Aβ deposits from the brains of 5xFAD mice. These results help to establish CARD9 as a key intracellular innate immune signaling molecule that regulates Aβ-mediated disease and microglial responses. Moreover, these findings suggest that targeting CARD9 might offer a strategy to improve Aβ clearance in AD.

Aβ-oligomers: A potential therapeutic target for Alzheimer's disease

The cascade of amyloid formation relates to multiple complex events at the molecular level. Previous research has established amyloid plaque deposition as the leading cause of Alzheimer's disease (AD) pathogenesis, detected mainly in aged population. The primary components of the plaques are two alloforms of amyloid-beta (Aβ), Aβ_1-42 and Aβ_1-40 peptides. Recent studies have provided considerable evidence contrary to the previous claim indicating that amyloid-beta oligomers (AβOs) as the main culprit responsible for AD-associated neurotoxicity and pathogenesis. In this review, we have discussed the primary features of AβOs, such as assembly formation, the kinetics of oligomer formation, interactions with various membranes/membrane receptors, the origin of toxicity, and oligomer-specific detection methods. Recently, the discovery of rationally designed antibodies has opened a gateway for using synthesized peptides as a grafting component in the complementarity determining region (CDR) of antibodies. Thus, the Aβ sequence motif or the complementary peptide sequence in the opposite strand of the β-sheet (extracted from the Protein Data Bank: PDB) helps design oligomer-specific inhibitors. The microscopic event responsible for oligomer formation can be targeted, and thus prevention of the overall macroscopic behaviour of the aggregation or the associated toxicity can be achieved. We have carefully reviewed the oligomer formation kinetics and associated parameters. Besides, we have depicted a thorough understanding of how the synthesized peptide inhibitors can impede the early aggregates (oligomers), mature fibrils, monomers, or a mixture of the species. The oligomer-specific inhibitors (peptides or peptide fragments) lack in-depth chemical kinetics and optimization control-based screening. In the present review, we have proposed a hypothesis for effectively screening oligomer-specific inhibitors using the chemical kinetics (determining the kinetic parameters) and optimization control strategy (cost-dependent analysis). Further, it may be possible to implement the structure-kinetic-activity-relationship (SKAR) strategy instead of structure-activity-relationship (SAR) to improve the inhibitor's activity. The controlled optimization of the kinetic parameters and dose usage will be beneficial for narrowing the search window for the inhibitors.

Defective proteostasis in Alzheimer's disease

The homeostasis of cellular proteins, or proteostasis, is critical for neuronal function and for brain processes, including learning and memory. Increasing evidence indicates that defective proteostasis contributes to the progression of neurodegenerative disorders, including Alzheimer's disease (AD), the most prevalent form of dementia in the elderly. Proteostasis comprises a set of cellular mechanisms that control protein synthesis, folding, post-translational modification and degradation, all of which are deregulated in AD. Importantly, deregulation of proteostasis plays a key role in synapse dysfunction and in memory impairment, the major clinical manifestation of AD. Here, we discuss molecular pathways involved in protein synthesis and degradation that are altered in AD, and possible pharmacological approaches to correct these defects.

Protective Potential of β-Hydroxybutyrate against Glucose-Deprivation-Induced Neurotoxicity Involving the Modulation of Autophagic Flux and the Monomeric Aβ Level in Neuro-2a Cells

Hypoglycemia has been known as a potential contributory factor to neurodegenerative diseases, such as Alzheimer’s disease. There may be shared pathogenic mechanisms underlying both conditions, and the ketone body, β-hydroxybutyrate (BHB), as an alternative substrate for glucose may exert neuroprotection against hypoglycemia-induced injury. To investigate this, Neuro-2a cells were subjected to a 24 h period of glucose deprivation with or without the presence of BHB. Cell viability, reactive oxygen species (ROS) production, apoptosis, autophagy, and adenosine triphosphate (ATP) and beta-amyloid peptide (Aβ) levels were evaluated. The results show that Neuro-2a cells deprived of glucose displayed a significant loss of cell survival with a corresponding decrease in ATP levels, suggesting that glucose deprivation was neurotoxic. This effect was likely attributed to the diverse mechanisms including raised ROS, defective autophagic flux and reduced basal Aβ levels (particularly monomeric Aβ). The presence of BHB could partially protect against the loss of cell survival induced by glucose deprivation. The mechanisms underlying the neuroprotective actions of BHB might be mediated, at least in part, through restoring ATP, and modulating ROS production, autophagy flux efficacy and the monomeric Aβ level. Results imply that a possible link between the basal monomeric Aβ and glucose deprivation neurotoxicity, and treatments designed for the prevention of energy impairment, such as BHB, may be beneficial for rescuing surviving cells in relation to neurodegeneration.

Oxidative Stress and Natural Antioxidants: Back and Forth in the Neurological Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the progressive degeneration of neuronal cells. With the increase in aged population, there is a prevalence of irreversible neurodegenerative changes, causing a significant mental, social, and economic burden globally. The factors contributing to AD are multidimensional, highly complex, and not completely understood. However, it is widely known that aging, neuroinflammation, and excessive production of reactive oxygen species (ROS), along with other free radicals, substantially contribute to oxidative stress and cell death, which are inextricably linked. While oxidative stress is undeniably important in AD, limiting free radicals and ROS levels is an intriguing and potential strategy for deferring the process of neurodegeneration and alleviating associated symptoms. Therapeutic compounds from natural sources have recently become increasingly accepted and have been effectively studied for AD treatment. These phytocompounds are widely available and a multitude of holistic therapeutic efficiencies for treating AD owing to their antioxidant, anti-inflammatory, and biological activities. Some of these compounds also function by stimulating cholinergic neurotransmission, facilitating the suppression of beta-site amyloid precursor protein-cleaving enzyme 1, α-synuclein, and monoamine oxidase proteins, and deterring the occurrence of AD. Additionally, various phenolic, flavonoid, and terpenoid phytocompounds have been extensively described as potential palliative agents for AD progression. Preclinical studies have shown their involvement in modulating the cellular redox balance and minimizing ROS formation, displaying them as antioxidant agents with neuroprotective abilities. This review emphasizes the mechanistic role of natural products in the treatment of AD and discusses the various pathological hypotheses proposed for AD.

Early Chronic Stress Induced Changes within the Locus Coeruleus in Sporadic Alzheimer's Disease

Chronic exposure to stress throughout the lifespan has been the focus of many studies on Alzheimer's disease (AD) because of the similarities between the biological mechanisms involved in chronic stress and the pathophysiology of AD. In fact, the earliest abnormality associated with the disease is the presence of phosphorylated tau protein in locus coeruleus neurons, a brain structure highly responsive to stress and perceived threat. Here, we introduce allostatic load as a useful concept for understanding many of the complex, interacting neuropathological changes involved in the AD degenerative process. In response to chronic stress, aberrant tau proteins that begin to accumulate within the locus coeruleus decades prior to symptom onset appear to represent a primary pathological event in the AD cascade, triggering a wide range of interacting brain changes involving neuronal excitotoxicity, endocrine alterations, inflammation, oxidative stress, and amyloid plaque exacerbation. While it is acknowledged that stress will not necessarily be the major precipitating factor in all cases, early tau-induced changes within the locus coeruleus-norepinephrine pathway suggests that a therapeutic window might exist for preventative measures aimed at managing stress and restoring balance within the HPA axis.

Aberrant Expression of GABA-Related Genes in the Hippocampus of 3xTg-AD Model Mice from the Early to End Stages of Alzheimer's Disease

BACKGROUND

We explored the gene expression levels in the brain of 3xTg-AD model mice to elucidate the molecular pathological changes from the early to end stages of Alzheimer's disease (AD).

OBJECTIVE

We re-analyzed our previously published microarray data obtained from the hippocampus of 3xTg-AD model mice at 12 and 52 weeks of age.

METHODS

Functional annotation and network analyses of the up- and downregulated differentially expressed genes (DEGs) in mice aged 12 to 52 weeks were performed. Validation tests for gamma-aminobutyric acid (GABA)-related genes were also performed by quantitative polymerase chain reaction (qPCR).

RESULTS

In total, 644 DEGs were upregulated and 624 DEGs were downregulated in the hippocampus of both the 12- and 52-week-old 3xTg-AD mice. In the functional analysis of the upregulated DEGs, 330 gene ontology biological process terms, including immune response, were found, and they interacted with each other in the network analysis. In the functional analysis of the downregulated DEGs, 90 biological process terms, including several terms related to membrane potential and synapse function, were found, and they also interacted with each other in the network analysis. In the qPCR validation test, significant downregulation was seen for Gabrg3 at the ages of 12 (p = 0.02) and 36 (p = 0.005) weeks, Gabbr1 at the age of 52 weeks (p = 0.001), and Gabrr2 at the age of 36 weeks (p = 0.02).

CONCLUSION

Changes in immune response and GABAergic neurotransmission may occur in the brain of 3xTg mice from the early to end stages of AD.

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.

Influence of amyloid beta on impulse spiking of isolated hippocampal neurons

One of the signs of Alzheimer's disease (AD) is the formation of β-amyloid plaques, which ultimately lead to the dysfunction of neurons with subsequent neurodegeneration. Although extensive researches have been conducted on the effects of different amyloid conformations such as oligomers and fibrils on neuronal function in isolated cells and circuits, the exact contribution of extracellular beta-amyloid on neurons remains incompletely comprehended. In our experiments, we studied the effect of β-amyloid peptide (Aβ1-42) on the action potential (APs) generation in isolated CA1 hippocampal neurons in perforated patch clamp conditions. Our findings demonstrate that Aβ1-42 affects the generation of APs differently in various hippocampal neurons, albeit with a shared effect of enhancing the firing response of the neurons within a minute of the start of Aβ1-42 application. In the first response type, there was a shift of 20-65% toward smaller values in the firing threshold of action potentials in response to inward current. Conversely, the firing threshold of action potentials was not affected in the second type of response to the application of Aβ1-42. In these neurons, Aβ1-42 caused a moderate increase in the frequency of spiking, up to 15%, with a relatively uniform increase in the frequency of action potentials generation regardless of the level of input current. Obtained data prove the absence of direct short-term negative effect of the Aβ1-42 on APs generation in neurons. Even with increasing the APs generation frequency and lowering the neurons' activation threshold, neurons were functional. Obtained data can suggest that only the long-acting presence of the Aβ1-42 in the cell environment can cause neuronal dysfunction due to a prolonged increase of APs firing and predisposition to this process.

Aβ42 oligomer-specific antibody ALZ-201 reduces the neurotoxicity of Alzheimer's disease brain extracts

BACKGROUND

In Alzheimer's disease (AD), amyloid-β 1-42 (Aβ42) neurotoxicity stems mostly from its soluble oligomeric aggregates. Studies of such aggregates have been hampered by the lack of oligomer-specific research tools and their intrinsic instability and heterogeneity. Here, we developed a monoclonal antibody with a unique oligomer-specific binding profile (ALZ-201) using oligomer-stabilising technology. Subsequently, we assessed the etiological relevance of the Aβ targeted by ALZ-201 on physiologically derived, toxic Aβ using extracts from post-mortem brains of AD patients and controls in primary mouse neuron cultures.

METHODS

Mice were immunised with stable oligomers derived from the Aβ42 peptide with A21C/A30C mutations (AβCC), and ALZ-201 was developed using hybridoma technology. Specificity for the oligomeric form of the Aβ42CC antigen and Aβ42 was confirmed using ELISA, and non-reactivity against plaques by immunohistochemistry (IHC). The antibody's potential for cross-protective activity against pathological Aβ was evaluated in brain tissue samples from 10 individuals confirmed as AD (n=7) and non-AD (n=3) with IHC staining for Aβ and phosphorylated tau (p-Tau) aggregates. Brain extracts were prepared and immunodepleted using the positive control 4G8 antibody, ALZ-201 or an isotype control to ALZ-201. Fractions were biochemically characterised, and toxicity assays were performed in primary mouse neuronal cultures using automated high-content microscopy.

RESULTS

AD brain extracts proved to be more toxic than controls as demonstrated by neuronal loss and morphological determinants (e.g. synapse density and measures of neurite complexity). Immunodepletion using 4G8 reduced Aβ levels in both AD and control samples compared to ALZ-201 or the isotype control, which showed no significant difference. Importantly, despite the differential effect on the total Aβ content, the neuroprotective effects of 4G8 and ALZ-201 immunodepletion were similar, whereas the isotype control showed no effect.

CONCLUSIONS

ALZ-201 depletes a toxic species in post-mortem AD brain extracts causing a positive physiological and protective impact on the integrity and morphology of mouse neurons. Its unique specificity indicates that a low-abundant, soluble Aβ42 oligomer may account for much of the neurotoxicity in AD. This critical attribute identifies the potential of ALZ-201 as a novel drug candidate for achieving a true, clinical therapeutic effect in AD.

Urolithin A reduces amyloid-beta load and improves cognitive deficits uncorrelated with plaque burden in a mouse model of Alzheimer's disease

In the present study, we investigated the effects of urolithin A (UA), a metabolite generated from ellagic acid via its metabolism by gut bacteria, as an autophagy activator with potential neuroprotective activity. WT and 3xTg-AD mice were administered long-term intermittent dietary supplementation with UA. UA was found to prevent deficits in spatial memory, cued fear response, and exploratory behavior in this model. It also decreased the Aβ plaque burden in areas of the hippocampus where these protein deposits are prominent in the model. Interestingly, correlation analyses demonstrate that Aβ plaque burden positively correlates with enhanced spatial memory in 3xTg-AD mice on a control diet but not in those supplemented with UA. In contrast, Aβ42 abundance in cortical and hippocampal homogenates negatively correlate with spatial memory in UA-fed mice. Our data suggest that plaque formation may be a protective mechanism against neurodegeneration and cognitive decline and that targeting the generation of proteotoxic Aβ species might be a more successful approach in halting disease progression. UA was also found to extend lifespan in normal aging mice. Mechanistically, we demonstrate that UA is able to induce autophagy and to increase Aβ clearance in neuronal cell lines. In summary, our studies reveal UA, likely via its actions as a autophagy inducer, is capable of removing Aβ from neurons and its dietary administration prevents the onset of cognitive deficits associated with pathological Aβ deposition in the 3xTg-AD mouse model as well as extending lifespan in normal aging mice.

Aβ-Targeting Bifunctional Chelators (BFCs) for Potential Therapeutic and PET Imaging Applications

Currently, more than 55 million people live with dementia worldwide, and there are nearly 10 million new cases every year. Alzheimer's disease (AD) is the most common neurodegenerative disease resulting in personality changes, cognitive impairment, memory loss, and physical disability. Diagnosis of AD is often missed or delayed in clinical practice due to the fact that cognitive deterioration occurs already in the later stages of the disease. Thus, methods to improve early detection would provide opportunities for early treatment of disease. All FDA-approved PET imaging agents for Aβ plaques use short-lived radioisotopes such as ¹¹C (t_1/2 = 20.4 min) and ¹⁸F (t_1/2 = 109.8 min), which limit their widespread use. Thus, a novel metal-based imaging agent for visualization of Aβ plaques is of interest, due to the simplicity of its synthesis and the longer lifetimes of its constituent isotopes. We have previously summarized a metal-containing drug for positron emission tomography (PET), magnetic resonance imaging (MRI), and single-photon emission computed tomography (SPECT) imaging of Alzheimer's disease. In this review, we have summarized a recent advance in design of Aβ-targeting bifunctional chelators for potential therapeutic and PET imaging applications, reported after our previous review.

APC/C-Cdh1-targeted substrates as potential therapies for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and the main cause of dementia in the elderly. The disease has a high impact on individuals and their families and represents a growing public health and socio-economic burden. Despite this, there is no effective treatment options to cure or modify the disease progression, highlighting the need to identify new therapeutic targets. Synapse dysfunction and loss are early pathological features of Alzheimer's disease, correlate with cognitive decline and proceed with neuronal death. In the last years, the E3 ubiquitin ligase anaphase promoting complex/cyclosome (APC/C) has emerged as a key regulator of synaptic plasticity and neuronal survival. To this end, the ligase binds Cdh1, its main activator in the brain. However, inactivation of the anaphase promoting complex/cyclosome-Cdh1 complex triggers dendrite disruption, synapse loss and neurodegeneration, leading to memory and learning impairment. Interestingly, oligomerized amyloid-β (Aβ) peptide, which is involved in Alzheimer's disease onset and progression, induces Cdh1 phosphorylation leading to anaphase promoting complex/cyclosome-Cdh1 complex disassembly and inactivation. This causes the aberrant accumulation of several anaphase promoting complex/cyclosome-Cdh1 targets in the damaged areas of Alzheimer's disease brains, including Rock2 and Cyclin B1. Here we review the function of anaphase promoting complex/cyclosome-Cdh1 dysregulation in the pathogenesis of Alzheimer's disease, paying particular attention in the neurotoxicity induced by its molecular targets. Understanding the role of anaphase promoting complex/cyclosome-Cdh1-targeted substrates in Alzheimer's disease may be useful in the development of new effective disease-modifying treatments for this neurological disorder.

Microglia and Alzheimer's Disease

There is a huge need for novel therapeutic and preventative approaches to Alzheimer's disease (AD) and neuroinflammation seems to be one of the most fascinating solutions. The primary cell type that performs immunosurveillance and helps clear out unwanted chemicals from the brain is the microglia. Microglia work to reestablish efficiency and stop further degeneration in the early stages of AD but mainly fail in the illness's later phases. This may be caused by a number of reasons, e.g., a protracted exposure to cytokines that induce inflammation and an inappropriate accumulation of amyloid beta (Aβ) peptide. Extracellular amyloid and/or intraneuronal phosphorylated tau in AD can both activate microglia. The activation of TLRs and scavenger receptors, inducing the activation of numerous inflammatory pathways, including the NF-kB, JAK-STAT, and NLRP3 inflammasome, facilitates microglial phagocytosis and activation in response to these mediators. Aβ/tau are taken up by microglia, and their removal from the extracellular space can also have protective effects, but if the illness worsens, an environment that is constantly inflamed and overexposed to an oxidative environment might encourage continuous microglial activation, which can lead to neuroinflammation, oxidative stress, iron overload, and neurotoxicity. The complexity and diversity of the roles that microglia play in health and disease necessitate the urgent development of new biomarkers that identify the activity of different microglia. It is imperative to comprehend the intricate mechanisms that result in microglial impairment to develop new immunomodulating therapies that primarily attempt to recover the physiological role of microglia, allowing them to carry out their core function of brain protection.

Synaptogenic effect of APP-Swedish mutation in familial Alzheimer's disease

Mutations in β-amyloid (Aβ) precursor protein (APP) cause familial Alzheimer's disease (AD) probably by enhancing Aβ peptides production from APP. An antibody targeting Aβ (aducanumab) was approved as an AD treatment; however, some Aβ antibodies have been reported to accelerate, instead of ameliorating, cognitive decline in individuals with AD. Using conditional APP mutations in human neurons for perfect isogenic controls and translational relevance, we found that the APP-Swedish mutation in familial AD increased synapse numbers and synaptic transmission, whereas the APP deletion decreased synapse numbers and synaptic transmission. Inhibition of BACE1, the protease that initiates Aβ production from APP, lowered synapse numbers, suppressed synaptic transmission in wild-type neurons, and occluded the phenotype of APP-Swedish-mutant neurons. Modest elevations of Aβ, conversely, elevated synapse numbers and synaptic transmission. Thus, the familial AD-linked APP-Swedish mutation under physiologically relevant conditions increased synaptic connectivity in human neurons via a modestly enhanced production of Aβ. These data are consistent with the relative inefficacy of BACE1 and anti-Aβ treatments in AD and the chronic nature of AD pathogenesis, suggesting that AD pathogenesis is not simply caused by overproduction of toxic Aβ but rather by a long-term effect of elevated Aβ concentrations.

Mechanisms of Influence of Intestinal Microbiota on the Processes of Aging of the CNS and the Formation of Cognitive Disorders in Alzheimer’s Disease

Background: the increase in the life expectancy of a modern person is accompanied by an increase in the prevalence of neurocognitive disorders. Various indicators associated with biological age are consistent with neurocognitive deficits. In the process of ontogeny, a complex symbiotic relationship develops between the host and the microbe. Presumably, they are realized along the microbiota-gut-brain axis. The participation of the intestinal microbiota in the ontogeny of the brain is assumed. The purpose of review: based on a systematic review of the scientific literature, to summarize research data on the mechanisms of the influence of the intestinal microbiota on the aging processes of the central nervous system and the formation of cognitive disorders in Alzheimer’s disease.Materials and methods: 27 Russian-language and 257 English-language articles were selected from MedLine/PubMed and eLibrary from 2000 to 2022 by the keywords “gut microbiota”, “neurocognitive disorders”, “aging”, “neurodegeneration”, “Alzheimer’s disease”. The hypothesis about the participation of the microbiota in cerebral ontogeny made it possible to select 110 articles for analysis.Conclusion: this scientific review reflects the authors’ ideas about the systemic mechanisms of normal and pathological aging of the CNS and the multifactorial nature of the pathogenesis of neurocognitive disorders.

Novel Anti-Neuroinflammatory Properties of a Thiosemicarbazone–Pyridylhydrazone Copper(II) Complex

Neuroinflammation has a major role in several brain disorders including Alzheimer’s disease (AD), yet at present there are no effective anti-neuroinflammatory therapeutics available. Copper(II) complexes of bis(thiosemicarbazones) (Cu^II(gtsm) and Cu^II(atsm)) have broad therapeutic actions in preclinical models of neurodegeneration, with Cu^II(atsm) demonstrating beneficial outcomes on neuroinflammatory markers in vitro and in vivo. These findings suggest that copper(II) complexes could be harnessed as a new approach to modulate immune function in neurodegenerative diseases. In this study, we examined the anti-neuroinflammatory action of several low-molecular-weight, charge-neutral and lipophilic copper(II) complexes. Our analysis revealed that one compound, a thiosemicarbazone–pyridylhydrazone copper(II) complex (CuL⁵), delivered copper into cells in vitro and increased the concentration of copper in the brain in vivo. In a primary murine microglia culture, CuL⁵ was shown to decrease secretion of pro-inflammatory cytokine macrophage chemoattractant protein 1 (MCP-1) and expression of tumor necrosis factor alpha (Tnf), increase expression of metallothionein (Mt1), and modulate expression of Alzheimer’s disease-associated risk genes, Trem2 and Cd33. CuL⁵ also improved the phagocytic function of microglia in vitro. In 5xFAD model AD mice, treatment with CuL⁵ led to an improved performance in a spatial working memory test, while, interestingly, increased accumulation of amyloid plaques in treated mice. These findings demonstrate that CuL⁵ can induce anti-neuroinflammatory effects in vitro and provide selective benefit in vivo. The outcomes provide further support for the development of copper-based compounds to modulate neuroinflammation in brain diseases.

Targeting NMDA Receptors at the Neurovascular Unit: Past and Future Treatments for Central Nervous System Diseases

The excitatory neurotransmission of the central nervous system (CNS) mainly involves glutamate and its receptors, especially N-methyl-D-Aspartate receptors (NMDARs). These receptors have been extensively described on neurons and, more recently, also on other cell types. Nowadays, the study of their differential expression and function is taking a growing place in preclinical and clinical research. The diversity of NMDAR subtypes and their signaling pathways give rise to pleiotropic functions such as brain development, neuronal plasticity, maturation along with excitotoxicity, blood-brain barrier integrity, and inflammation. NMDARs have thus emerged as key targets for the treatment of neurological disorders. By their large extracellular regions and complex intracellular structures, NMDARs are modulated by a variety of endogenous and pharmacological compounds. Here, we will present an overview of NMDAR functions on neurons and other important cell types involved in the pathophysiology of neurodegenerative, neurovascular, mental, autoimmune, and neurodevelopmental diseases. We will then discuss past and future development of NMDAR targeting drugs, including innovative and promising new approaches.

A Brain-Targeting Bispecific-Multivalent Antibody Clears Soluble Amyloid-Beta Aggregates in Alzheimer's Disease Mice

Amyloid-β (Aβ) oligomers and protofibrils are suggested to be the most neurotoxic Aβ species in Alzheimer's disease (AD). Hence, antibodies with strong and selective binding to these soluble Aβ aggregates are of therapeutic potential. We have recently introduced HexaRmAb158, a multivalent antibody with additional Aβ-binding sites in the form of single-chain fragment variables (scFv) on the N-terminal ends of Aβ protofibril selective antibody (RmAb158). Due to the additional binding sites and the short distance between them, HexaRmAb158 displayed a slow dissociation from protofibrils and strong binding to oligomers in vitro. In the current study, we aimed at investigating the therapeutic potential of this antibody format in vivo using mouse models of AD. To enhance BBB delivery, the transferrin receptor (TfR) binding moiety (scFv8D3) was added, forming the bispecific-multivalent antibody (HexaRmAb158-scFv8D3). The new antibody displayed a weaker TfR binding compared to the previously developed RmAb158-scFv8D3 and was less efficiently transcytosed in a cell-based BBB model. HexaRmAb158 detected soluble Aβ aggregates derived from brains of tg-ArcSwe and AppNL-G-F mice more efficiently compared to RmAb158. When intravenously injected, HexaRmAb158-scFv8D3 was actively transported over the BBB into the brain in vivo. Brain uptake was marginally lower than that of RmAb158-scFv8D3, but significantly higher than observed for conventional IgG antibodies. Both antibody formats displayed similar brain retention (72 h post injection) and equal capacity in clearing soluble Aβ aggregates in tg-ArcSwe mice. In conclusion, we demonstrate a bispecific-multivalent antibody format capable of passing the BBB and targeting a wide-range of sizes of soluble Aβ aggregates.

Therapeutic roles of plants for 15 hypothesised causal bases of Alzheimer's disease

Alzheimer's disease (AD) is progressive and ultimately fatal, with current drugs failing to reverse and cure it. This study aimed to find plant species which may provide therapeutic bioactivities targeted to causal agents proposed to be driving AD. A novel toolkit methodology was employed, whereby clinical symptoms were translated into categories recognized in ethnomedicine. These categories were applied to find plant species with therapeutic effects, mined from ethnomedical surveys. Survey locations were mapped to assess how this data is at risk. Bioactivities were found of therapeutic relevance to 15 hypothesised causal bases for AD. 107 species with an ethnological report of memory improvement demonstrated therapeutic activity for all these 15 causal bases. The majority of the surveys were found to reside within biodiversity hotspots (centres of high biodiversity under threat), with loss of traditional knowledge the most common threat. Our findings suggest that the documented plants provide a large resource of AD therapeutic potential. In demonstrating bioactivities targeted to these causal bases, such plants may have the capacity to reduce or reverse AD, with promise as drug leads to target multiple AD hallmarks. However, there is a need to preserve ethnomedical knowledge, and the habitats on which this knowledge depends.

Cucurbit[7]uril Macrocyclic Sensors for Optical Fingerprinting: Predicting Protein Structural Changes to Identifying Disease-Specific Amyloid Assemblies

In a three-dimensional (3D) representation, each protein molecule displays a specific pattern of chemical and topological features, which are altered during its misfolding and aggregation pathway. Generating a recognizable fingerprint from such features could provide an enticing approach not only to identify these biomolecules but also to gain clues regarding their folding state and the occurrence of pathologically lethal misfolded aggregates. We report here a universal strategy to generate a fluorescent fingerprint from biomolecules by employing the pan-selective molecular recognition feature of a cucurbit[7]uril (CB[7]) macrocyclic receptor. We implemented a direct sensing strategy by covalently tethering CB[7] with a library of fluorescent reporters. When CB[7] recognizes the chemical and geometrical features of a biomolecule, it brings the tethered fluorophore into the vicinity, concomitantly reporting the nature of its binding microenvironment through a change in their optical signature. The photophysical properties of the fluorophores allow a multitude of probing modes, while their structural features provide additional binding diversity, generating a distinct fluorescence fingerprint from the biomolecule. We first used this strategy to rapidly discriminate a diverse range of protein analytes. The macrocyclic sensor was then applied to probe conformational changes in the protein structure and identify the formation of oligomeric and fibrillar species from misfolded proteins. Notably, the sensor system allowed us to differentiate between different self-assembled forms of the disease-specific amyloid-β (Aβ) aggregates and segregated them from other generic amyloid structures with a 100% identification accuracy. Ultimately, this sensor system predicted clinically relevant changes by fingerprinting serum samples from a cohort of pregnant women.

Model scenarios for cell cycle re-entry in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease. Aberrant production and aggregation of amyloid beta (Aβ) peptide into plaques is a frequent feature of AD, but therapeutic approaches targeting Aβ accumulation fail to inhibit disease progression. The approved cholinesterase inhibitor drugs are symptomatic treatments. During human brain development, the progenitor cells differentiate into neurons and switch to a postmitotic state. However, cell cycle re-entry often precedes loss of neurons. We developed mathematical models of multiple routes leading to cell cycle re-entry in neurons that incorporate the crosstalk between cell cycle, neuronal, and apoptotic signaling mechanisms. We show that the integration of multiple feedback loops influences disease severity making the switch to pathological state irreversible. We observe that the transcriptional changes associated with this transition are also characteristics of the AD brain. We propose that targeting multiple arms of the feedback loop may bring about disease-modifying effects in AD.

•

Developed mathematical models of cell cycle re-entry in Alzheimer's disease (AD)

•

Integration of multiple feedback loops drives irreversible transition to AD

•

Predicted transcriptional dysregulation is validated using AD gene expression data

•

Inhibition of self-amplifying feedback loops brings about disease-modifying effects

A Novel Multifunctional 5,6-Dimethoxy-Indanone-Chalcone-Carbamate Hybrids Alleviates Cognitive Decline in Alzheimer’s Disease by Dual Inhibition of Acetylcholinesterase and Inflammation

Backgrounds

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disease. The treatment of AD through multiple pathological targets may generate therapeutic efficacy better. The multifunctional molecules that simultaneously hit several pathological targets have been of great interest in the intervention of AD.

Methods

Here, we combined the chalcone scaffold with carbamate moiety and 5,6-dimethoxy-indanone moiety to generate a novel multi-target-directed ligand (MTDL) molecule (E)-3-((5,6-dimethoxy-1-oxo-1,3-dihydro-2H-inden-2-ylidene)-methyl)phenylethyl(methyl) carbamate (named AP5). In silico approaches were used to virtually predict the binding interaction of AP5 with AChE, the drug-likeness, and BBB penetrance, and later validated by evaluation of pharmacokinetics (PK) in vivo by LC-MS/MS. Moreover, studies were conducted to examine the potential of AP5 for inhibiting AChE and AChE-induced amyloid-β (Aβ) aggregation, attenuating neuroinflammation, and providing neuroprotection in the APP/PS1 model of AD.

Results

We found that AP5 can simultaneously bind to the peripheral and catalytic sites of AChE by molecular docking. AP5 exhibited desirable pharmacokinetic (PK) characteristics including oral bioavailability (67.2%), >10% brain penetrance, and favorable drug-likeness. AP5 inhibited AChE activity and AChE-induced Aβ aggregation in vivo and in vitro. Further, AP5 lowered Aβ plaque deposition and insoluble Aβ levels in APP/PS1 mice. Moreover, AP5 exerted anti-inflammatory responses by switching microglia to a disease-associated microglia (DAM) phenotype and preventing A1 astrocytes formation. The phagocytic activity of microglial cells to Aβ was recovered upon AP5 treatment. Importantly, chronic AP5 treatment significantly prevented neuronal and synaptic damage and memory deficits in AD mice.

Conclusion

Together, our work demonstrated that AP5 inhibited the AChE activity, decreased Aβ plaque deposition by interfering Aβ aggregation and promoting microglial Aβ phagocytosis, and suppressed inflammation, thereby rescuing neuronal and synaptic damage and relieving cognitive decline. Thus, AP5 can be a new promising candidate for the treatment of AD.

LILRB2-mediated TREM2 signaling inhibition suppresses microglia functions

Background

Microglia plays crucial roles in Alzheimer’s disease (AD) development. Triggering receptor expressed on myeloid cells 2 (TREM2) in association with DAP12 mediates signaling affecting microglia function. Here we study the negative regulation of TREM2 functions by leukocyte immunoglobulin-like receptor subfamily B member 2 (LILRB2), an inhibitory receptor bearing ITIM motifs.

Methods

To specifically interrogate LILRB2-ligand (oAβ and PS) interactions and microglia functions, we generated potent antagonistic LILRB2 antibodies with sub-nanomolar level activities. The biological effects of LILRB2 antagonist antibody (Ab29) were studied in human induced pluripotent stem cell (iPSC)–derived microglia (hMGLs) for migration, oAβ phagocytosis, and upregulation of inflammatory cytokines. Effects of the LILRB2 antagonist antibody on microglial responses to amyloid plaques were further studied in vivo using stereotaxic grafted microglia in 5XFAD mice.

Results

We confirmed the expression of both LILRB2 and TREM2 in human brain microglia using immunofluorescence. Upon co-ligation of the LILRB2 and TREM2 by shared ligands oAβ or PS, TREM2 signaling was significantly inhibited. We identified a monoclonal antibody (Ab29) that blocks LILRB2/ligand interactions and prevents TREM2 signaling inhibition mediated by LILRB2. Further, Ab29 enhanced microglia phagocytosis, TREM2 signaling, migration, and cytokine responses to the oAβ-lipoprotein complex in hMGL and microglia cell line HMC3. In vivo studies showed significantly enhanced clustering of microglia around plaques with a prominent increase in microglial amyloid plaque phagocytosis when 5XFAD mice were treated with Ab29.

Conclusions

This study revealed for the first time the molecular mechanisms of LILRB2-mediated inhibition of TREM2 signaling in microglia and demonstrated a novel approach of enhancing TREM2-mediated microglia functions by blocking LILRB2-ligand interactions. Translationally, a LILRB2 antagonist antibody completely rescued the inhibition of TREM2 signaling by LILRB2, suggesting a novel therapeutic strategy for improving microglial functions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13024-022-00550-y.

Aberrant Synaptic Pruning in CNS Diseases: A Critical Player in HIV-Associated Neurological Dysfunction?

Even in the era of effective antiretroviral therapies, people living with Human Immunodeficiency Virus (HIV) are burdened with debilitating neurological dysfunction, such as HIV-associated neurocognitive disorders (HAND) and HIV-associated pain, for which there are no FDA approved treatments. Disruption to the neural circuits of cognition and pain in the form of synaptic degeneration is implicated in developing these dysfunctions. Glia-mediated synaptic pruning is a mechanism of structural plasticity in the healthy central nervous system (CNS), but recently, it has been discovered that dysregulated glia-mediated synaptic pruning is the cause of synaptic degeneration, leading to maladaptive plasticity and cognitive deficits in multiple diseases of the CNS. Considering the essential contribution of activated glial cells during the development of HAND and HIV-associated pain, it is possible that glia-mediated synaptic pruning is the causative mechanism of synaptic degeneration induced by HIV. This review will analyze the known examples of synaptic pruning during disease in order to better understand how this mechanism could contribute to the progression of HAND and HIV-associated pain.