Soluble Amyloid Beta Research Articles

Intrathecal Immunoselective Nanopheresis for Alzheimer’s Disease: What and How? Why and When?

Nanotechnology is transforming therapeutics for brain disorders, especially in developing drug delivery systems. Intrathecal immunoselective nanopheresis with soluble monoclonal antibodies represents an innovative approach in the realm of drug delivery systems for Central Nervous System conditions, especially for targeting soluble beta-amyloid in Alzheimer’s disease. This review delves into the concept of intrathecal immunoselective nanopheresis. It provides an overall description of devices to perform this technique while discussing the nanotechnology behind its mechanism of action, its potential advantages, and clinical implications. By exploring current research and advancements, we aim to provide a comprehensive understanding of this novel method, addressing the critical questions of what it is, how it works, why it is needed, and when it should be applied. Special attention is given to patient selection and the optimal timing for therapy initiation in Alzheimer’s, coinciding with the peak accumulation of amyloid oligomers in the early stages. Potential limitations and alternative targets beyond beta-amyloid and future perspectives for immunoselective nanopheresis are also described.

Microbiome-derived indole-3-lactic acid reduces amyloidopathy through aryl-hydrocarbon receptor activation

Alzheimer’s disease (AD) pathogenesis has been associated with the gut microbiome and its metabolites, though the specific mechanisms have remained unclear. In our study, we used a multi-omics approach to identify specific microbial strains and metabolites that could potentially mitigate amyloidopathy in 5xFAD mice, a widely used model for AD research. Among the microbial strains tested, three showed promising results in reducing soluble amyloid-beta (Aβ) levels. Plasma metabolomics analysis revealed an enrichment of tryptophan (Trp) and indole-3-lactic acid (ILA) in mice with reduced soluble Aβ levels, suggesting a potential preventative role. The administration of a combined treatment of Trp and ILA prevented both Aβ accumulation and cognitive impairment in the 5xFAD mice. Our investigation into the mechanism revealed that ILA’s effect on reducing Aβ levels was mediated through the activation of microglia and astrocytes, facilitated by the aryl hydrocarbon receptor (AhR) signaling pathway. These mechanisms were verified through experiments in 5xFAD mice that included an additional group with the administration of ILA alone, as well as in vitro experiments using an AhR inhibitor. Clinical data analysis revealed a greater abundance of Lactobacillus reuteri in the gut of healthy individuals compared to those at early stages of Aβ accumulation or with mild cognitive impairment. Additionally, human post-mortem brain analyses showed an increased expression of genes associated with the AhR signaling pathway in individuals without AD, suggesting a protective effect against AD progression. Our results indicate that ILA from gut microbes could inhibit the progression of amyloidopathy in 5xFAD mice through activation of AhR signaling in the brain.

Japanese Subgroup Analyses from EMERGE and ENGAGE, Phase 3 Clinical Trials of Aducanumab in Patients with Early Alzheimer’s Disease

BackgroundGlobal prevalence and incidence of dementia continue to rise at a rapid rate. There is a need for new Alzheimer’s disease (AD) treatments globally. Aducanumab is a human monoclonal antibody that selectively targets aggregated soluble amyloid beta oligomers and insoluble amyloid beta fibrils. In June 2021, aducanumab was approved by the US Food and Drug Administration for the treatment of AD under the accelerated approval pathway.ObjectivesWe evaluated the efficacy, safety, biomarker and pharmacokinetics (PK) of aducanumab in Japanese subgroups in EMERGE and ENGAGE studies.DesignEMERGE and ENGAGE were two randomized, double-blind, placebo-controlled, global, phase 3 studies of aducanumab in patients with early AD (mild cognitive impairment due to AD or mild AD dementia).SettingThese studies involved 348 sites in 20 countries. PARTICIPANTS: Participants enrolled in Japan included 121 (7.4% of total 1638 in EMERGE) and 100 (6.1% of total 1647 in ENGAGE) patients (aged 50–85 years with confirmed amyloid pathology) who met clinical criteria for mild cognitive impairment due to AD or mild AD dementia.InterventionParticipants were randomly assigned 1:1:1 to receive aducanumab low dose (3 or 6 mg/kg target dose), high dose (6 or 10 mg/kg target dose) or placebo via IV infusion once every 4 weeks over 76 weeks.MeasurementsThe primary outcome measure was change from baseline to Week 78 on the Clinical Dementia Rating Sum of Boxes (CDR-SB), an integrated scale that assesses both function and cognition. Other measures included safety assessments; secondary and tertiary clinical outcomes that assessed cognition, function, and behavior; biomarker endpoints (amyloid PET and plasma p-tau181); serum PK profiles and immunogenicity.ResultsResults from the Japanese subgroup analyses were generally consistent with those of the overall study population across endpoints, while a lower mean body weight (kg) and a smaller proportion of ApoE ε4 carriers were observed in the Japanese subgroup population. A treatment effect was observed in favor of aducanumab on the primary and secondary efficacy endpoints at Week 78 in EMERGE, but not ENGAGE. The incidence and type of adverse events in the Japanese subgroups were generally comparable to those observed in the overall study population; amyloid related imaging abnormalities (ARIA) were common treatment-related adverse events that appeared to be related to the aducanumab dose. ARIA incidence was generally lower in the Japanese subgroup compared with the overall population. Consistent with the overall data set, a robust dose-dependent decrease in amyloid beta levels as assessed with amyloid-PET and plasma p-tau181 was observed. Serum PK profiles and immunogenicity of aducanumab in Japanese population were consistent with the non-Japanese population.ConclusionEfficacy, safety, biomarker, and PK profiles of aducanumab were consistent between the Japanese subgroup and the overall population. A positive treatment effect of aducanumab on efficacy endpoints was observed in EMERGE, but not in ENGAGE.

ERβ mediates sex-specific protection in the App-NL-G-F mouse model of Alzheimer's disease.

Menopausal loss of neuroprotective estrogen is thought to contribute to the sex differences in Alzheimer's disease (AD). Activation of estrogen receptor beta (ERβ) can be clinically relevant since it avoids the negative systemic effects of ERα activation. However, very few studies have explored ERβ-mediated neuroprotection in AD, and no information on its contribution to the sex differences in AD exists. In the present study we specifically explored the role of ERβ in mediating sex-specific protection against AD pathology in the clinically relevant App NL-G-F knock-in mouse model of amyloidosis, and if surgical menopause (ovariectomy) modulates pathology in this model. We treated male and female App NL-G-F mice with the selective ERβ agonist LY500307 and subset of the females was ovariectomized prior to treatment. Memory performance was assessed and a battery of biochemical assays were used to evaluate amyloid pathology and neuroinflammation. Primary microglial cultures from male and female wild-type and ERβ-knockout mice were used to assess ERβ's effect on microglial activation and phagocytosis. We find that ERβ activation protects against amyloid pathology and cognitive decline in male and female App NL-G-F mice. Ovariectomy increased soluble amyloid beta (Aβ) in cortex and insoluble Aβ in hippocampus, but had otherwise limited effects on pathology. We further identify that ERβ does not alter APP processing, but rather exerts its protection through amyloid scavenging that at least in part is mediated via microglia in a sex-specific manner. Combined, we provide new understanding to the sex differences in AD by demonstrating that ERβ protects against AD pathology differently in males and females, warranting reassessment of ERβ in combating AD.

Targeting soluble amyloid-beta oligomers with a novel nanobody

The classical amyloid cascade hypothesis postulates that the aggregation of amyloid plaques and the accumulation of intracellular hyperphosphorylated Tau tangles, together, lead to profound neuronal death. However, emerging research has demonstrated that soluble amyloid-β oligomers (SAβOs) accumulate early, prior to amyloid plaque formation. SAβOs induce memory impairment and disrupt cognitive function independent of amyloid-β plaques, and even in the absence of plaque formation. This work describes the development and characterization of a novel anti-SAβO (E3) nanobody generated from an alpaca immunized with SAβO. In-vitro assays and in-vivo studies using 5XFAD mice indicate that the fluorescein (FAM)-labeled E3 nanobody recognizes both SAβOs and amyloid-β plaques. The E3 nanobody traverses across the blood–brain barrier and binds to amyloid species in the brain of 5XFAD mice. Imaging of mouse brains reveals that SAβO and amyloid-β plaques are not only different in size, shape, and morphology, but also have a distinct spatial distribution in the brain. SAβOs are associated with neurons, while amyloid plaques reside in the extracellular matrix. The results of this study demonstrate that the SAβO nanobody can serve as a diagnostic agent with potential theragnostic applications in Alzheimer’s disease.

Photobiomodulation under Electroencephalographic Controls of Sleep for Stimulation of Lymphatic Removal of Toxins from Mouse Brain.

The meningeal lymphatic vessels (MLVs) play an important role in the removal of toxins from the brain. The development of innovative technologies for the stimulation of MLV functions is a promising direction in the progress of the treatment of various brain diseases associated with MLV abnormalities, including Alzheimer's and Parkinson's diseases, brain tumors, traumatic brain injuries, and intracranial hemorrhages. Sleep is a natural state when the brain's drainage processes are most active. Therefore, stimulation of the brain's drainage and MLVs during sleep may have the most pronounced therapeutic effects. However, such commercial technologies do not currently exist. This study presents a new portable technology of transcranial photobiomodulation (tPBM) under electroencephalographic (EEG) control of sleep designed to photo-stimulate removal of toxins (e.g., soluble amyloid beta (Aβ)) from the brain of aged BALB/c mice with the ability to compare the therapeutic effectiveness of different optical resources. The technology can be used in the natural condition of a home cage without anesthesia, maintaining the motor activity of mice. These data open up new prospects for developing non-invasive and clinically promising photo-technologies for the correction of age-related changes in the MLV functions and brain's drainage processes and for effectively cleansing brain tissues from metabolites and toxins. This technology is intended both for preclinical studies of the functions of the sleeping brain and for developing clinically relevant treatments for sleep-related brain diseases.

Aβ oligomers peak in early stages of Alzheimer's disease preceding tau pathology.

Soluble amyloid beta (Aβ) oligomers have been suggested as initiating Aβ related neuropathologic change in Alzheimer's disease (AD) but their quantitative distribution and chronological sequence within the AD continuum remain unclear. A total of 526 participants in early clinical stages of AD and controls from a longitudinal cohort were neurobiologically classified for amyloid and tau pathology applying the AT(N) system. Aβ and tau oligomers in the quantified cerebrospinal fluid (CSF) were measured using surface-based fluorescence intensity distribution analysis (sFIDA) technology. Across groups, highest Aβ oligomer levels were found in A+ with subjective cognitive decline and mild cognitive impairment. Aβ oligomers were significantly higher in A+T- compared to A-T- and A+T+. APOEε4 allele carriers showed significantly higher Aβ oligomer levels. No differences in tau oligomers were detected. The accumulation of Aβ oligomers in the CSF peaks early within the AD continuum, preceding tau pathology. Disease-modifying treatments targeting Aβ oligomers might have the highest therapeutic effect in these disease stages. Using surface-based fluorescence intensity distribution analysis (sFIDA) technology, we quantified Aβ oligomers in cerebrospinal fluid (CSF) samples of the DZNE-Longitudinal Cognitive Impairment and Dementia (DELCODE) cohortAβ oligomers were significantly elevated in mild cognitive impairment (MCI)Amyloid-positive subjects in the subjective cognitive decline (SCD) group increased compared to the amyloid-negative control groupInterestingly, levels of Aβ oligomers decrease at advanced stages of the disease (A+T+), which might be explained by altered clearing mechanisms.

Transmembrane protein 97 is a potential synaptic amyloid beta receptor in human Alzheimer’s disease

Synapse loss correlates with cognitive decline in Alzheimer’s disease, and soluble oligomeric amyloid beta (Aβ) is implicated in synaptic dysfunction and loss. An important knowledge gap is the lack of understanding of how Aβ leads to synapse degeneration. In particular, there has been difficulty in determining whether there is a synaptic receptor that binds Aβ and mediates toxicity. While many candidates have been observed in model systems, their relevance to human AD brain remains unknown. This is in part due to methodological limitations preventing visualization of Aβ binding at individual synapses. To overcome this limitation, we combined two high resolution microscopy techniques: array tomography and Förster resonance energy transfer (FRET) to image over 1 million individual synaptic terminals in temporal cortex from AD (n = 11) and control cases (n = 9). Within presynapses and post-synaptic densities, oligomeric Aβ generates a FRET signal with transmembrane protein 97. Further, Aβ generates a FRET signal with cellular prion protein, and post-synaptic density 95 within post synapses. Transmembrane protein 97 is also present in a higher proportion of post synapses in Alzheimer’s brain compared to controls. We inhibited Aβ/transmembrane protein 97 interaction in a mouse model of amyloidopathy by treating with the allosteric modulator CT1812. CT1812 drug concentration correlated negatively with synaptic FRET signal between transmembrane protein 97 and Aβ. In human-induced pluripotent stem cell derived neurons, transmembrane protein 97 is present in synapses and colocalizes with Aβ when neurons are challenged with human Alzheimer’s brain homogenate. Transcriptional changes are induced by Aβ including changes in genes involved in neurodegeneration and neuroinflammation. CT1812 treatment of these neurons caused changes in gene sets involved in synaptic function. These data support a role for transmembrane protein 97 in the synaptic binding of Aβ in human Alzheimer’s disease brain where it may mediate synaptotoxicity.

Cerebral organoids with chromosome 21 trisomy secrete Alzheimer’s disease-related soluble aggregates detectable by single-molecule-fluorescence and super-resolution microscopy

Understanding the role of small, soluble aggregates of beta-amyloid (Aβ) and tau in Alzheimer’s disease (AD) is of great importance for the rational design of preventative therapies. Here we report a set of methods for the detection, quantification, and characterisation of soluble aggregates in conditioned media of cerebral organoids derived from human iPSCs with trisomy 21, thus containing an extra copy of the amyloid precursor protein (APP) gene. We detected soluble beta-amyloid (Aβ) and tau aggregates secreted by cerebral organoids from both control and the isogenic trisomy 21 (T21) genotype. We developed a novel method to normalise measurements to the number of live neurons within organoid-conditioned media based on glucose consumption. Thus normalised, T21 organoids produced 2.5-fold more Aβ aggregates with a higher proportion of larger (300–2000 nm2) and more fibrillary-shaped aggregates than controls, along with 1.3-fold more soluble phosphorylated tau (pTau) aggregates, increased inflammasome ASC-specks, and a higher level of oxidative stress inducing thioredoxin-interacting protein (TXNIP). Importantly, all this was detectable prior to the appearance of histological amyloid plaques or intraneuronal tau-pathology in organoid slices, demonstrating the feasibility to model the initial pathogenic mechanisms for AD in-vitro using cells from live genetically pre-disposed donors before the onset of clinical disease. Then, using different iPSC clones generated from the same donor at different times in two independent experiments, we tested the reproducibility of findings in organoids. While there were differences in rates of disease progression between the experiments, the disease mechanisms were conserved. Overall, our results show that it is possible to non-invasively follow the development of pathology in organoid models of AD over time, by monitoring changes in the aggregates and proteins in the conditioned media, and open possibilities to study the time-course of the key pathogenic processes taking place.

Lecanemab: A Humanized Monoclonal Antibody for the Treatment of Early Alzheimer Disease.

To review current pharmacology, pharmacokinetics/pharmacodynamics, safety, and efficacy of lecanemab in patients with Alzheimer disease. A literature search of PubMed (April 1, 2016-November 15, 2023) and ClinicalTrials.gov search were conducted using the following search terms: lecanemab and BAN2401. Additional articles were identified by hand from references. We included English-language clinical trials, randomized controlled trials, reviews, and systematic reviews evaluating lecanemab pharmacology, efficacy, or safety in humans for the management of Alzheimer disease. In the Clarity AD phase III trial, lecanemab led to a decrease in brain amyloid levels and showed moderate improvement in clinical measures of cognition and function. At 18 months, lecanemab 10 mg/kg biweekly exhibited a lower least squares mean change from baseline (1.21) compared to placebo (1.66) of Clinical Dementia Rating-Sum of Boxes score, signifying a significant difference of -0.45 (95% CI, -0.67 to -0.23; P < 0.001). In a subset of 698 participants, lecanemab reduced brain amyloid burden by -59.1 Centiloids (95% CI, -62.6 to -55.6). Lecanemab demonstrated favorable differences in Alzheimer Disease Assessment Scale-cognitive subscale 14, Alzheimer Disease Composite Score, and Alzheimer Disease Cooperative Study-Mild Cognitive Impairment-Activities of Daily Living scores. Adverse events included infusion-related reactions (26.4%) and amyloid-related imaging abnormalities (12.6%). Lecanemab reduces cognitive decline but raises concerns about intravenous administration, cost, and magnetic resonance imaging needs. Ongoing trials exploring subcutaneous dosing and positron emission tomography scans may offer solutions. Lecanemab is a humanized monoclonal antibody that is selective for soluble amyloid-beta (Aβ) aggregates. Lecanemab has exhibited a decrease in brain Aβ plaques and moderately less decline on clinical measures of cognitive function.

Baseline characteristics of INTERCEPT‐AD: A phase 1 trial with ACU193 targeting soluble amyloid beta oligomers for the treatment of early Alzheimer’s disease

AbstractBackgroundAlzheimer’s disease (AD) is a neurodegenerative disorder affecting approximately 40 million people worldwide. There are few treatments available that affect the underlying degenerative process, making AD one of the largest unmet medical needs. ACU193 is a humanized, IgG2 subclass monoclonal antibody that targets soluble amyloid beta oligomers (sAβOs). Evidence supports the view that sAβOs are one of the primary instigators of AD neurodegeneration. Thus, blocking the toxicity of sAβOs with ACU193 may be a promising approach for the treatment of AD.MethodINTERCEPT‐AD is a phase 1 randomized, placebo‐controlled, single‐ and multiple‐dose study investigating the safety, tolerability, and pharmacokinetics of intravenous ACU193 in mild cognitive impairment or mild dementia due to AD. The SAD portion includes four cohorts with 2 mg/kg, 10 mg/kg, 25 mg/kg, and 60 mg/kg ACU193 or placebo. The MAD portion includes three cohorts receiving three doses of ACU193 or placebo: 10 mg/kg once every four weeks (Q4W), 60 mg/kg Q4W and 25 mg/kg once every 2 weeks (Q2W). Key inclusion criteria are 55‐90 years of age, PET scan positive for brain amyloid, MMSE 18‐30 and CDR‐Global score 0.5 or 1.0. The INTERCEPT‐AD trial is fully enrolled.ResultAt 17 sites in the U.S., 260 participants were screened, 65 were randomized, and 62 received at least one dose of ACU193 or placebo, including 33 females (53%) and 29 males (47%). Negative PET (61%) was the most common reason for screen failure. Baseline age was 72.1 ± 7.8 years (mean ± SD), CDR Sum of Boxes score was 3.5 ± 1.8, ADAS‐Cog‐13 was 24.2 ± 9.0 and screening MMSE was 24.2 ± 3.6. ApoE e4 homozygotes accounted for 13% of the study population and ApoE e4 heterozygotes for 46.7%. Traditionally underrepresented ethnoracial populations comprised 23% of the study (5% Black/African American, 16% Hispanic/Latino, 2% Other). Additional baseline measures including demographics, clinical characteristics, AD medication, and imaging data will be presented.ConclusionWe describe key baseline demographic, clinical, and cognitive characteristics of participants in the INTERCEPT‐AD trial. Data generated from this trial will guide further development of ACU193 for the treatment of early AD.

Early loss of microglial p38α MAPK in the APPswe/PS1dE9 mouse model of Alzheimer’s disease alters soluble amyloid beta and reduces microglia co‐localization with amyloid plaques without affecting amyloid‐associated pathology

AbstractBackgroundThe p38 alpha mitogen‐activated protein kinase (p38α) pathway is linked to both innate and adaptive immune responses, and is currently under investigation as a target for drug development in the context of Alzheimer’s disease (AD) and other conditions with neuroinflammatory dysfunction (Asih et al., 2020). Preclinical data indicates that p38α inhibition can protect against AD‐associated neuropathology, although the cellular mechanisms and signaling pathways that underlie these effects have not been fully elucidated. Evidence suggests that inhibition of p38α may provide benefit by modulating microglial‐associated neuroinflammatory processes that contribute to the development of AD pathology. The present study tests this hypothesis by assessing early‐stage pathological changes in AD model mice following microglial‐specific knock out (KO) of p38α.MethodsKO of p38α in microglia was accomplished in 5‐month‐old C57BL/6J wild‐type and amyloidogenic AD model (APPswe/PS1dE9) mice using a tamoxifen‐inducible Cre/loxP system under control of the Cx3Cr1 promoter. Animals underwent behavioral assessment on the open field test at 7.5 months of age and on the radial arm water maze test at 11 months of age, followed by collection of cortical and hippocampal tissues. Other endpoint measures included quantification of proinflammatory cytokines, assessment of amyloid burden and plaque deposition, and characterization of microglia‐plaque dynamics using a combination of ELISA, immunohistochemical, and immunofluorescent techniques.ResultsSuppression of microglial p38α did not alter behavioral outcomes, proinflammatory cytokine levels, or overall amyloid plaque burden, but did significantly increase hippocampal levels of soluble Aβ42 and reduced hippocampal colocalization of Iba1 and 6E10 in a subset of microglia in close proximity to plaques.ConclusionThis work suggests that rather than reducing inflammation per se, microglial p38α inhibition in the context of early AD‐type amyloid pathology may alter hippocampal microglia‐plaque interactions. Additionally, these results support future investigations of microglial p38α signaling at different stages of disease, as well as the potential relationship between p38α and phagocytic processes in this particular cell‐type. Funding: This work is supported by the National Institutes of Health (RF1 AG064859; F32 AG058456; T32 AG057461).

Towards the Integrative Theory of Alzheimer's Disease: Linking Molecular Mechanisms of Neurotoxicity, Beta-amyloid Biomarkers, and the Diagnosis.

A major gap in amyloid-centric theories of Alzheimer's disease (AD) is that even though amyloid fibrils per se are not toxic in vitro, the diagnosis of AD clearly correlates with the density of beta-amyloid (Aβ) deposits. Based on our proposed amyloid degradation toxicity hypothesis, we developed a mathematical model explaining this discrepancy. It suggests that cytotoxicity depends on the cellular uptake of soluble Aβ rather than on the presence of amyloid aggregates. The dynamics of soluble beta-amyloid in the cerebrospinal fluid (CSF) and the density of Aβ deposits is described using a system of differential equations. In the model, cytotoxic damage is proportional to the cellular uptake of Aβ, while the probability of an AD diagnosis is defined by the Aβ cytotoxicity accumulated over the duration of the disease. After uptake, Aβ is concentrated intralysosomally, promoting the formation of fibrillation seeds inside cells. These seeds cannot be digested and are either accumulated intracellularly or exocytosed. Aβ starts aggregating on the extracellular seeds and, therefore, decreases in concentration in the interstitial fluid. The dependence of both Aβ toxicity and aggregation on the same process-cellular uptake of Aβ-explains the correlation between AD diagnosis and the density of amyloid aggregates in the brain. We tested the model using clinical data obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI), which included records of beta-amyloid concentration in the cerebrospinal fluid (CSF-Aβ42) and the density of beta-amyloid deposits measured using positron emission tomography (PET). The model predicts the probability of AD diagnosis as a function of CSF-Aβ42 and PET and fits the experimental data at the 95% confidence level. Our study shows that existing clinical data allows for the inference of kinetic parameters describing beta-amyloid turnover and disease progression. Each combination of CSF-Aβ42 and PET values can be used to calculate the individual's cellular uptake rate, the effective disease duration, and the accumulated toxicity. We show that natural limitations on these parameters explain the characteristic distribution of the clinical dataset for these two biomarkers in the population. The resulting mathematical model interprets the positive correlation between the density of Aβ deposits and the probability of an AD diagnosis without assuming any cytotoxicity of the aggregated beta-amyloid. To the best of our knowledge, this model is the first to mechanistically explain the negative correlation between the concentration of Aβ42 in the CSF and the probability of an AD diagnosis. Finally, based on the amyloid degradation toxicity hypothesis and the insights provided by mathematical modeling, we propose new pathophysiology-relevant biomarkers to diagnose and predict 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.

Hippocampal injections of soluble amyloid-beta oligomers alter electroencephalographic activity during wake and slow-wave sleep in rats

BackgroundSoluble amyloid-beta oligomers (Aβo) begin to accumulate in the human brain one to two decades before a clinical diagnosis of Alzheimer’s disease (AD). The literature supports that soluble Aβo are implicated in synapse and neuronal losses in the brain regions such as the hippocampus. This region importantly contributes to explicit memory, the first type of memory affected in AD. During AD preclinical and prodromal stages, people are also experiencing wake/sleep alterations such as insomnia (e.g., difficulty initiating sleep, decreased sleep duration), excessive daytime sleepiness, and sleep schedule modifications. In addition, changes in electroencephalographic (EEG) activity during wake and sleep have been reported in AD patients and animal models. However, the specific contribution of Aβo to wake/sleep alterations is poorly understood and was investigated in the present study.MethodsChronic hippocampal injections of soluble Aβo were conducted in male rats and combined with EEG recording to determine the progressive impact of Aβ pathology specifically on wake/sleep architecture and EEG activity. Bilateral injections were conducted for 6 consecutive days, and EEG acquisition was done before, during, and after Aβo injections. Immunohistochemistry was used to assess neuron numbers in the hippocampal dentate gyrus (DG).ResultsAβo injections did not affect the time spent in wakefulness, slow wave sleep (SWS), and paradoxical sleep but altered EEG activity during wake and SWS. More precisely, Aβo increased slow-wave activity (SWA; 0.5–5 Hz) and low-beta activity (16–20 Hz) during wake and decreased theta (5–9 Hz) and alpha (9–12 Hz) activities during SWS. Moreover, the theta activity/SWA ratio during wake and SWS was decreased by Aβo. These effects were significant only after 6 days of Aβo injections and were found with alterations in neuron counts in the DG.ConclusionsWe found multiple modifications of the wake and SWS EEG following Aβo delivery to the hippocampus. These findings expose a specific EEG signature of Aβ pathology and can serve the development of non-invasive and cost-effective markers for the early diagnosis of AD or other amyloid-related diseases.

Decreased DHA-containing phospholipids in the neocortex of dementia with Lewy bodies are associated with soluble Aβ42 , phosphorylated α-synuclein, and synaptopathology.

Docosahexaenoic acid (DHA) is an essential omega-3 polyunsaturated fatty acid implicated in cognitive functions by promoting synaptic protein expression. While alterations of specific DHA-containing phospholipids have been described in the neocortex of patients with Alzheimer's disease (AD), the status of these lipids in dementia with Lewy bodies (DLB), known to manifest aggregated α-synuclein-containing Lewy bodies together with variable amyloid pathology, is unclear. In this study, post-mortem samples from the parietal cortex of 25 DLB patients and 17 age-matched controls were processed for phospholipidomics analyses using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) platform. After controlling for false discovery rate, six out of the 46 identified putative DHA-phospholipid species were significantly decreased in DLB, with only one showing increase. Altered putative DHA-phospholipid species were subsequently validated with further LC-MS/MS measurements. Of the DHA-containing phospholipid (DCP) species showing decreases, five negatively correlated with soluble beta-amyloid (Aβ42) levels, whilst three also correlated with phosphorylated α-synuclein (all p < 0.05). Furthermore, five of these phospholipid species correlated with deficits of presynaptic Rab3A, postsynaptic neurogranin, or both (all p < 0.05). Finally, we found altered immunoreactivities of brain lysolipid DHA transporter, MFSD2A, and the fatty acid binding protein FABP5 in DLB parietal cortex. In summary, we report alterations of specific DCP species in DLB, as well as their associations with markers of neuropathological burden and synaptopathology. These results support the potential role of DHA perturbations in DLB as well as therapeutic targets.

Glyphosate - A Silent, Slow Killer?

Madam, Glyphosate, commercially known as Round Up, is one of the most widely used herbicides and pesticides worldwide. As a synthetic organophosphate compound, it comes in a crystalline, odourless and colourless form. Most of the human exposure to this compound occurs during the process of its manufacturing, formulation and transport. Further exposure may come from the inhaling toxic fumes of nitrogen gas and phosphorus oxides produced when this pesticide undergoes decomposition, when farmers and gardeners use it on their crops, and when individuals come in contact with products containing it as the active ingredient (1). As of right now, there is a multitude of studies that link glyphosate to several morbidities. When a combined 9229 cases of farmers from North America, the European Union and Australia were assessed, glyphosate was directly linked to an increase in the onset of follicular lymphoma (2). It was also associated with allergic and non-allergic wheezing among farm women in the Agricultural Health Study (2005-2010), which focused on farmers in Iowa and North Carolina (3). Additionally, when tested on mice, exposure to glyphosate was found to increase TNFa in the brain and plasma, and the levels of soluble Amyloid Beta in the brain, suggesting a detrimental role to general health. Furthermore, glyphosate was one of the 11 pesticides studied and then found to have a direct correlation with the increase in overall cancer cases in Brazil. (5) Taking into consideration the aforementioned facts, it is vital to regulate the exposure of individuals to glyphosate to reduce the rising rate of morbidities. More guidelines and policies should be formulated to protect the health of individuals involved in glyphosate manufacturing, due to their exposure risk high. Pesticide leching into water sources should also be prevented to ensure that the general population does not end up consume them indirectly.

Blood and cerebrospinal fluid biomarker changes in patients with HIV-associated neurocognitive impairment treated with lithium: analysis from a randomised placebo-controlled trial

HIV-associated neurocognitive disorders (HAND) persist in the era of antiretroviral therapy (ART). Thus, ART does not completely halt or reverse the pathological processes behind HAND. Adjuvant mitigating treatments are, therefore, prudent. Lithium treatment is known to promote neuronal brain–derived neurotrophic factors (BDNF). Lithium is also an inhibitor of glycogen synthase kinase-3 beta (GSK-3-β). We analyzed biomarkers obtained from participants in a randomized placebo-controlled trial of lithium in ART-treated individuals with moderate or severe HAND. We assayed markers at baseline and 24 weeks across several pathways hypothesized to be affected by HIV, inflammation, or degeneration. Investigated biomarkers included dopamine, BDNF, neurofilament light chain, and CD8 + lymphocyte activation (CD38 + HLADR +). Alzheimer’s Disease (AD) biomarkers included soluble amyloid precursor protein alpha and beta (sAPPα/β), Aβ38, 40, 42, and ten other biomarkers validated as predictors of mild cognitive impairment and progression in previous studies. These include apolipoprotein C3, pre-albumin, α1-acid glycoprotein, α1-antitrypsin, PEDF, CC4, ICAM-1, RANTES, clusterin, and cystatin c. We recruited 61 participants (placebo = 31; lithium = 30). The age baseline mean was 40 (± 8.35) years and the median CD4 + T-cell count was 498 (IQR: 389–651) cells/μL. Biomarker concentrations between groups did not differ at baseline. However, both groups’ blood dopamine levels decreased significantly after 24 weeks (adj. p < 002). No other marker was significantly different between groups, and we concluded that lithium did not confer neuroprotection following 24 weeks of treatment. However, the study was limited in duration and sample size.

Controlling Amyloid Beta Peptide Aggregation and Toxicity by Protease-Stable Ligands.

Polymerization of soluble amyloid beta (Aβ) peptide into protease-stable insoluble fibrillary aggregates is a critical step in the pathogenesis of Alzheimer's disease (AD). The N-terminal (NT) hydrophobic central domain fragment 16KLVFF20 plays an important role in the formation and stabilization of β-sheets by self-recognition of the parent Aβ peptide, followed by aggregation of Aβ in the AD brain. Here, we analyze the effect of the NT region inducing β-sheet formation in the Aβ peptide by a single amino acid mutation in the native Aβ peptide fragment. We designed 14 hydrophobic peptides (NT-01 to NT-14) by a single mutation at 18Val by using hydrophobic residues leucine and proline in the natural Aβ peptide fragment (KLVFFAE) and analyzed its effect on the formation of Aβ aggregates. Among all these peptides, NT-02, NT-03, and NT-13 significantly affected the Aβ aggregate formation. When the NT peptides were coincubated with the Aβ peptide, a significant reduction in β-sheet formation and increment in random coil content of Aβ was seen, confirmed by circular dichroism spectroscopy and Fourier transform infrared spectroscopy, followed by the reduction of fibril formation measured by the thioflavin-T (ThT) binding assay. The aggregation inhibition was monitored by Congo red and ThT staining and electron microscopic examination. Moreover, the NT peptides protect the PC-12 differentiated neurons from Aβ-induced toxicity and apoptosis in vitro. Thus, manipulation of the Aβ secondary structure with protease-stable ligands that promote the random coil conformation may provide a tool to control the Aβ aggregates observed in AD patients.

Differential modulation of alpha 7 nicotinic achrs by picomolar vs. high nanomolar or micromolar concentrations of amyloid beta 42 peptide.

High concentrations (0.1-1.0 μM) of soluble oligomeric amyloid beta peptide(s) [Aβ] inhibit activation of α7 nAChRs. This may contribute to Alzheimer's Disease (AD) neuropathology, since α7 Rs play important roles in learning and memory. Thus, α7 Rs may be important targets for attenuating Aβ-induced AD cognitive declines. In contrast to the synapto-/neuro-toxic effects of high Aβ concentration observed in AD brains, several studies suggest that the low (pM) Aβ concentrations present in healthy non-AD brains are critical for normal learning and memory. These beneficial effects are dependent on expression of α7, suggesting that pM Aβ's salutary effects are mediated by α7 Rs, possibly as an agonist or PAM at α7 Rs. The nature of the Aβ-α7 R interaction, however, has not been fully characterized. In this study we found that 10-100 pM Aβ produced a ∼1.7- to 2.6-fold facilitation of ACh-elicited α7 currents, but did not elicit α7 currents directly. When applied with the type II PAM PNU 120596, 100 pM Aβ occluded the facilitation of peak current produced by PNU 120596, suggesting that Aβ and PNU 120596 potentiated α7 Rs through the same or overlapping allosteric site(s). This conclusion was further supported by analysis of a mutant α7 R containing a missense mutation in a critical amino acid for potentiation by PAMs (M276L in TM 2). Peak current facilitation by 100 pM Aβ was abolished for this mutant. Surprisingly, this mutation also abolished the inhibitory effects of high (0.1-1.0 μM) Aβ concentrations. This suggests that inhibitory (nM to µM) and facilitatory (pM) Aβ concentrations exert their opposing effects on α7 R activity via the same or overlapping sites, rather than at distinct allosteric sites.