BACE1 Research Articles

Deregulated lncRNA MAGI2-AS3 in Alzheimer's disease attenuates amyloid-β induced neurotoxicity and neuroinflammation by sponging miR-374b-5p.

Alzheimer's disease (AD) is a common neurodegenerative disease, which is characterized by aberrant accumulation of amyloid-β (Aβ) and neuroinflammation. The purpose of this study was to explore the regulatory effects of long non-coding RNA (lncRNA) MAGI2-AS3 and microRNA-374b-5p (miR-374b-5p) on Aβ-induced neurotoxicity and neuroinflammation, as well as the relationship between MAGI2-AS3 and miR-374b-5p in AD patients. A luciferase reporter assay was used to analyze the interaction between MAGI2-AS3 and miR-374b-5p and between miR-374b-5p and beta-site amyloid precursor protein cleaving enzyme 1 (BACE1). SH-SY5Y and BV2 cells treated with Aβ25-35 were used to mimic neuronal injury and neuroinflammation in AD pathogenesis. Cell viability was evaluated using a MTT assay, and pro-inflammatory cytokine levels were measured using ELISA kits. MAGI2-AS3 and miR-374b-5p expression was examined using quantitative real-time PCR. BACE1 served as a target gene of miR-374b-5p, and MAGI2-AS3 could sponge miR-374b-5p. The expression of MAGI2-AS3 was increased, and miR-374b-5p was decreased in both SH-SY5Y and BV2 cells exposed to Aβ25-35. MAGI2-AS3 reduction enhanced neuronal viability and attenuated neuroinflammation in AD cell models, and miR-374b-5p overexpression led to same effects, but miR-374b-5p inhibition reversed these effects. Serum MAGI2-AS3 and miR-374b-5p levels in AD patients were negatively correlated and correlated with disease severity. The findings indicated that the MAGI2-AS3/miR-374b-5p axis regulates Aβ-induced neurotoxicity in SH-SY5Y cells and neuroinflammation in BV2 cells. The MAGI2-AS3/miR-374b-5p axis may provide novel biomarkers and therapeutic targets for AD.

Is there still a rationale for BACE‐inhibition in Alzheimer’s disease? A quantitative systems pharmacology analysis

AbstractBackgroundSo far all clinical trials with BACE inhibitors have failed to generate a cognitive benefit and many have demonstrated a reversible cognitive worsening. Lack of understanding of the biological reason for this clinical effect hampers the study of which patient subpopulations might still benefit from lower levels of target exposure.MethodWe present computer‐based Quantitative Systems Pharmacology (QSP) simulations of cognitive ADAS‐Cog readouts to identify relevant PD‐PD interactions between comedications, common genotype variants, disease state and amyloid modulating agents, in particular BACE inhibition. This platform is based on a computer model of biophysically realistic neuronal cortical microcircuit with 35 CNS targets and calibrated for ADAS‐Cog. Long and short amyloid peptides affect glutamate and nAChR neurotransmission differentially that reproduces three clinical datasets. APOE, COMTVal158Met and 5‐HTTLPR rs23351 genotype are introduced using human imaging studies.ResultThe 5‐HTTLPR rs23351 L/L genotype defines a set of responders that are more resilient to amyloid increase with a 3‐4 point smaller worsening on ADAS‐Cog. Differential interaction with tau pathology can further reduce the effect with up to a 0.5 point. When simulating 2 year BACE‐I treatment in MCI, the platform predicts a worsening of up to 3 points compared to baseline on ADAS‐Cog for subjects with 5‐HTTLPR s/s genotype and slow amyloid progression while placebo deteriorates only 2 points. Conversely, BACE‐I is anticipated to improve cognition by about 0.4 point compared to baseline in subjects with 5‐HTTLPR L/L genotype and fast amyloid progression with placebo deteriorating 0.1 point. Lower levels of target engagement slightly improve the effect of BACE‐I but only in subjects with already elevated amyloid baseline levels. This is likely because of the beneficial effect of low doses of short amyloid forms that are also reduced by BACE‐I.ConclusionQSP is a hypothesis‐generating engine based on mechanistic, integrative and quantitative modeling of pharmacological and biological data and is particular informative at the individual patient level. The platform explains the reversible worsening of cognition with high exposure levels of BACE‐I in prodromal AD. Further simulations suggest that BACE inhibition can have modest benefits at lower levels of target engagement and in well‐defined patient populations.

Depletion of the AD risk gene SORL1 selectively impairs neuronal endosomal traffic independent of amyloidogenic APP processing

AbstractBackgroundThe SORL1 gene encodes for the protein SorLA, a sorting receptor involved in retromer‐related endosomal traffic. Many SORL1 genetic variants increase Alzheimer’s disease (AD) risk, and rare loss‐of‐function truncation mutations have been found to be causal of AD. SORL1 is expressed in neurons and glia of the central nervous system and loss of SORL1 has been reported AD tissue.MethodTo model the causal loss‐of‐function mutations, we used CRISPR/Cas9 technology to deplete SORL1 in human induced pluripotent stem cells (hiPSCs) to test the hypothesis that loss of SORL1 contributes to AD pathogenesis by leading to endosome dysfunction.ResultWe report that loss of SORL1 in hiPSC‐derived neurons leads to early endosome enlargement, a cellular phenotype that is indicative of ‘traffic jams’ and is now considered a hallmark cytopathology AD. We validate defects in neuronal endosomal traffic by showing decreased localization of amyloid‐precursor protein (APP) in the trans‐Golgi network (TGN), and increased localization of APP in early endosomes, a site of APP cleavage by the b secretase BACE1. Microglia, immune cells of the CNS, which also play a role in the AD pathology also express SORL1. We therefore tested and found no effect of SORL1 depletion on endosome size or morphology in hiPSC‐derived microglia, suggesting a selective effect on neuronal endocytic trafficking. Finally, because BACE1 dependent APP fragments can cause endosome enlargement, we treated SORL1 deficient hiPSC‐derived neurons with BACE1 inhibitors and demonstrate that endosome enlargement occurs independent of amyloidogenic APP fragments.ConclusionCollectively, these findings clarify where and how SORL1 links to AD. Moreover, our data, together with recent findings, underscores how sporadic AD pathways that regulate endosomal trafficking, and autosomal‐dominant AD pathways that regulate APP cleavage, independently converge on AD’s defining cytopathology.

The API Generation program: Umibecestat treatment and discontinuation effects on hippocampal and whole brain volumes in the overall population and amyloid‐negative APOE4 homozygotes

AbstractBackgroundIn addition to early mild non‐progressive cognitive worsening, BACE inhibitors have been associated with early non‐progressive reductions in hippocampal and whole brain volume in trial participants with elevated amyloid (A+, Egan et al, 2019). We have begun to evaluate the effects of umibecestat treatment and discontinuation on cognitively unimpaired amyloid‐positive (A+) and A‐ APOE4 homozygotes and A+ heterozygotes, testing the hypotheses that BACE inhibitor‐related hippocampal and whole brain shrinkage is apparent soon after treatment initiation, non‐progressive, limited to A+ participants, and reversible following discontinuation.MethodThe API Generation Program had begun to evaluate umibecestat in 1,623 cognitively unimpaired 60‐75 year‐old participants including 921 A+ APOE4 heterozygotes and 702 homozygotes (A+ or A‐).Following randomization, volumetric brain MRIs were scheduled at month 6, month 12 and then annually. After discontinuation of study medication, participants continued to be assessed under double‐blind conditions, and MRIs were acquired within 3 months after the last dose. We investigated 6‐month hippocampal and whole brain volume changes and their relationship to RBANS immediate, delayed and total memory score changes; and we plan to investigate the persistence or reversibility of these changes within 3 months of discontinuation after study completion in Q2 2020.ResultUmibecestat was associated with significant 6‐month hippocampal and whole brain shrinkage in the aggregate APOE4 homozygote and A+ heterozygote group, but not in the A‐ homozygotes. While an early non‐progressive worsening in RBANS immediate, delayed, and total memory scores (Graf et al, AAIC 2020 submitted) was seen in the overall population as well as in A‐ HMs, we failed to demonstrate any significant association between brain shrinkage and cognitive worsening in the overall group (R2 coefficient <0.1) in the active treatment group for any of the visits (on‐ and off‐ treatment).ConclusionBACE inhibitor‐related brain shrinkage appears to be early, non‐progressive, related to pre‐existing amyloid plaque burden, and unrelated to its cognitive worsening. Pending findings will help to clarify the extent to which it is also reversible. Together, our cognitive and MRI findings could help to assess potential benefits versus risks of BACE inhibitors in future prevention trials.

Quantitative systems pharmacology model of Alzheimer’s disease to study efficacy of combinatorial therapy on multiple pathology components

AbstractBackgroundImmunotherapies targeting tau or Aβ remain the key focus for neurologists. But low brain penetration and limited scope of targeting may restrict efficacy. This restriction may be overcome by combinations with other treatments targeting protein degradation systems. Quantitative systems pharmacology model allows for integration of available information from multiple preclinical studies to simulate clinical studies. The goal was to develop the translational model of key AD markers, verified and validated on the literature data and to simulate effects of combinations.MethodPredeveloped Ab and tau pathology submodels have been merged through the model of intracellular protein degradation systems (proteasome, autophagy), which is known to fail progressively in AD. Literature data (concentration baselines and dynamics, SUVR) from mice and human have been used for calibration. Multiple in vitro data for intracellular dynamics perturbations (rapamycin, proteasome inhibitors, vinblastine) available from the literature were used to estimate the intracellular regulation parameters. Immunotherapy mechanism is described through 1) binding of antibodies and prevention of seeding and growth of aggregates, 2) activation of microglia for Ab degradation. Data from clinical studies for immunotherapy (BAN2401) and BACE inhibitor (verubecestat) have been used for retrospective model validation, together with data for treatment by rapamycin, calpain inhibitors, proteasome activation in mouse AD models.ResultModel correctly describes the Aβ and tau accumulation and mutual exacerbation in mice and humans. It correctly predicts effect of rapamycin, calpain inhibitors, proteasome activation on tau tangles in tau‐transgenic mouse and absence of effect of Aβ targeting on tau pathology markers in humans. Simulation of Aβ immunotherapy starting from 65 years (Braak stage 3‐4), predicts 80% Aβ plaque difference vs placebo within 2 years, without effect on tau markers. Rapamycin is predicted to clear tau pathology, with modest efficacy (up to 30‐40%) of Aβ clearing. An example of combination, anti‐Aβ immunotherapy with rapamycin is most effective in retarding both pathologies (up to 80‐90%) in hippocampus.ConclusionQSP modeling allows for choice of combinations of newly emerging biologics combined with targeting cell metabolism, to lead optimization and increase of treatment efficacy.

The API Generation program: Biomarker phenotyping of cognitively unimpaired participants screened in Generation study 1 and Generation study 2

AbstractBackgroundAPI Generation Program evaluated the effectiveness of the BACE1 inhibitor umibecestat and the active immunotherapy CAD106 in delaying the onset of AD symptoms in APOE4 carriers. Data from imaging (vMRI and PET scans), and fluid biomarkers (blood and CSF) were collected during the 12‐week Screening phase. In this presentation, we will summarize results across the two studies and investigate the relationships between the various biomarkers and key baseline characteristics.MethodAmyloid levels were assessed via CSF and/or Amyloid PET scan in both studies for the APOE4 carriers. Generation Study 2 enrolled heterozygotes based on the following elevated amyloid inclusion criteria: Roche Elecsys® CSF p‐Tau/Abeta42 ratio > 0.024 and/or PET scans with any of the 3 amyloid F18 tracers (florbetapir, flutemetamol or florbetaben). If the centralized visual read of PET scan was negative, the SUVr was calculated (cortical composite in reference to whole cerebellum) for the three tracers in order to assess borderline cases. Thresholds for amyloid positivity equivalent to SUVR of 1.1 with florbetapir were used for the final decision on inclusion.ResultAcross both studies, over 500 lumbar punctures, 2700 amyloid PET scans and about 150 tau PET scans (conducted using flortaucipir) were performed. In Generation Study 1, over 200 FDG PET scans were also performed. Participants underwent amyloid testing during screening, blood sampling (plasma and serum) and underwent MRI scans for safety and to measure brain volumes. All baseline biomarker data will be presented, including available concentrations from CSF Tau/p‐Tau/Aβ42/Aβ40 along with the eligibility ratio for pTau/ab42. In about 150 participants, concordance between elevated/non elevated amyloid status by CSF and PET (using centiloids) will be shown. Baseline brain volume (whole brain and hippocampus) will be summarized for the different co‐variates (age, sex, cognition, genotype and amyloid status). Correlations among the various fluid biomarkers and imaging will be discussed.ConclusionThese data describe the biomarker signature of the world’s largest cohort of cognitively unimpaired APOE4 carriers with and without elevated amyloid. The anonymized study data, biomarker samples as well as images collected will be shared with the scientific community after study completion and reporting. ELECSYS is a registered trademark of Roche.

BACE inhibition causes rapid, regional, and non-progressive volume reduction in Alzheimer's disease brain.

In the phase 3 EPOCH trial (Clinicaltrials.gov; NCT01739348), treatment with the BACE inhibitor verubecestat failed to improve cognition in patients with mild-to-moderate Alzheimer's disease, but was associated with reduced hippocampal volume after 78 weeks as assessed by MRI. The aims of the present exploratory analyses were to: (i) characterize the effect of verubecestat on brain volume by evaluating the time course of volumetric MRI changes for a variety of brain regions; and (ii) understand the mechanism through which verubecestat might cause hippocampal (and other brain region) volume loss by assessing its relationship to measures of amyloid, neurodegeneration, and cognition. Participants were aged 55-85 years with probable Alzheimer's disease dementia and a Mini Mental State Examination score ≥15 and ≤26. MRIs were obtained at baseline and at Weeks 13, 26, 52 and 78 of treatment. MRIs were segmented using Freesurfer and analysed using a tensor-based morphometry method. PET amyloid data were obtained with 18F-flutemetamol (Vizamyl®) at baseline and Week 78. Standardized uptake value ratios were generated with subcortical white matter as a reference region. Neurofilament light chain in the CSF was assessed as a biomarker of neurodegeneration. Compared with placebo, verubecestat showed increased MRI brain volume loss at Week 13 with no evidence of additional loss through Week 78. The verubecestat-related volumetric MRI loss occurred predominantly in amyloid-rich brain regions. Correlations between amyloid burden at baseline and verubecestat-related volumetric MRI reductions were not significant (r = 0.05 to 0.26, P-values > 0.27). There were no significant differences between verubecestat and placebo in changes from baseline in CSF levels of neurofilament light chain at Week 78 (increases of 7.2 and 14.6 pg/ml for verubecestat versus 19.7 pg/ml for placebo, P-values ≥ 0.1). There was a moderate correlation between volumetric MRI changes and cognitive decline in all groups including placebo at Week 78 (e.g. r = -0.45 to -0.55, P < 0.001 for whole brain), but the correlations were smaller at Week 13 and significant only for the verubecestat groups (e.g. r = -0.15 and -0.11, P < 0.04 for whole brain). Our results suggest that the verubecestat-associated MRI brain volume loss is not due to generalized, progressive neurodegeneration, but may be mediated by specific effects on BACE-related amyloid processes.

Inhibition of BACE1, MAO-B, cholinesterase enzymes, and anti-amyloidogenic potential of selected natural phytoconstituents: Multi-target-directed ligand approach.

Alzheimer's disease (AD) is a neurodegenerative disorder, and multiple factors are involved in disease progression. This is why there is an urgent need to develop novel molecules with multi-target-directed ligands (MTDLs) potential. The current study explores the active phytoconstituents from traditionally used medicinal spices, namely piperine, cinnamaldehyde, eugenol, cuminaldehyde, and alpha-terpinyl acetate for the inhibition of β-secretase, monoamine oxidase, cholinesterase enzymes, anti-aggregation of amyloid β (Aβ) fibrils, and their protective effect against hydrogen peroxide (H2 O2 ) and Aβ-induced toxicity. Eugenol showed inhibitory activity against MAO-B enzyme, free radical scavenging activity, and anti-aggregation activity against Aβ peptides than other phytoconstituents. It also demonstrated a significant cytoprotective effect against H2 O2 -induced oxidative stress and Aβ-induced cytotoxicity in pheochromocytoma (PC) 12 cells. A molecular docking study of eugenol showed interactions with active site residue of the target enzymes. The study successfully demonstrated that eugenol could have an MTDLs potential better than synthesized drugs used in the treatment of AD. PRACTICAL APPLICATIONS: The present study demonstrated multi-target-directed ligand potential of eugenol and can be developed to treat complex diseases like Alzheimer's. Eugenol can bind to different Alzheimer's targets such as β-secretase (BACE1), Monoamine oxidase B (MAO-B), Cholinesterase's, and amyloid β1-42 fibrils and might have a disease-modifying potential. The other natural phytoconstituents such as piperine, cinnamaldehyde, cuminaldehyde, and alpha-terpinyl acetate also demonstrated MTDL potential could also be used for developing novel molecules for disease-modifying effect. It also protects against oxidative stress.

Chronic BACE-1 Inhibitor Administration in TASTPM Mice (APP KM670/671NL and PSEN1 M146V Mutation): An EEG Study.

Objective. In this exploratory study, we tested whether electroencephalographic (EEG) rhythms may reflect the effects of a chronic administration (4 weeks) of an anti-amyloid β-site amyloid precursor protein (APP) cleaving enzyme 1 inhibitor (BACE-1; ER-901356; Eisai Co., Ltd., Tokyo, Japan) in TASTPM (double mutation in APP KM670/671NL and PSEN1 M146V) producing Alzheimer’s disease (AD) amyloid neuropathology as compared to wild type (WT) mice. Methods. Ongoing EEG rhythms were recorded from a bipolar frontoparietal and two monopolar frontomedial (prelimbic) and hippocampal channels in 11 WT Vehicle, 10 WT BACE-1, 10 TASTPM Vehicle, and 11 TASTPM BACE-1 mice (males; aged 8/9 months old at the beginning of treatment). Normalized EEG power (density) was compared between the first day (Day 0) and after 4 weeks (Week 4) of the BACE-1 inhibitor (10 mg/Kg) or vehicle administration in the 4 mouse groups. Frequency and magnitude of individual EEG delta and theta frequency peaks (IDF and ITF) were considered during animal conditions of behaviorally passive and active wakefulness. Cognitive status was not tested. Results. Compared with the WT group, the TASTPM group generally showed a significantly lower reactivity in frontoparietal ITF power during the active over the passive condition (p < 0.05). Notably, there was no other statistically significant effect (e.g., additional electrodes, recording time, and BACE-1 inhibitor). Conclusions. The above EEG biomarkers reflected differences between the WT and TASTPM groups, but no BACE-1 inhibitor effect. The results suggest an enhanced experimental design with the use of younger mice, longer drug administrations, an effective control drug, and neuropathological amyloid markers.

Drug-specific T-cell responses in patients with liver injury following treatment with the BACE inhibitor atabecestat.

Atabecestat is an orally administered BACE inhibitor developed to treat Alzheimer's disease. Elevations in hepatic enzymes were detected in a number of in trial patients, which resulted in termination of the drug development programme. Immunohistochemical characterization of liver tissue from an index case of atabecestat-mediated liver injury revealed an infiltration of T-lymphocytes in areas of hepatocellular damage. This coupled with the fact that liver injury had a delayed onset suggests that the adaptive immune system may be involved in the pathogenesis. The aim of this study was to generate and characterize atabecestat(metabolite)-responsive T-cell clones from patients with liver injury. Peripheral blood mononuclear cells were cultured with atabecestat and its metabolites (diaminothiazine [DIAT], N-acetyl DIAT & epoxide) and cloning was attempted in a number of patients. Atabecestat(metabolite)-responsive clones were analysed in terms of T-cell phenotype, function, pathways of T-cell activation and cross-reactivity with structurally related compounds. CD4+ T-cell clones activated with the DIAT metabolite were detected in 5 out of 8 patients (up to 4.5% cloning efficiency). Lower numbers of CD4+ and CD8+ clones displayed reactivity against atabecestat. Clones proliferated and secreted IFN-γ, IL-13 and cytolytic molecules following atabecestat or DIAT stimulation. Certain atabecestat and DIAT-responsive clones cross-reacted with N-acetyl DIAT; however, no cross-reactivity was observed between atabecestat and DIAT. CD4+ clones were activated through a direct, reversible compound-HLA class II interaction with no requirement for protein processing. The detection of atabecestat metabolite-responsive T-cell clones activated via a pharmacological interactions pathway in patients with liver injury is indicative of an immune-based mechanism for the observed hepatic enzyme elevations.

Efficient Method for the Synthesis of Amino-1,3-Oxazines from Thioureas

The synthesis of a subtype-selective inhibitor BACE-1 inhibitor is presented. One of the key transformations in this sequence is the conversion of a thiourea to the bicyclic 1,3-aminooxazine. This ...

Novel N-benzylpiperidine derivatives of 5-arylisoxazole-3-carboxamides as anti-Alzheimer's agents.

The complex pathophysiology of Alzheimer's disease (AD) has prompted researchers to develop multitarget-directed molecules to find an effective therapy against the disease. In this context, a novel series of N-(1-benzylpiperidin-4-yl)-5-arylisoxazole-3-carboxamide derivatives were designed, synthesized, and evaluated against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). In vitro biological evaluation demonstrated that compound 4e was the best AChE (IC50 = 16.07 μM) and BuChE inhibitor (IC50 = 15.16 μM). A kinetic study of 4e was also conducted, which presented a mixed-type inhibition for both enzymes. Molecular docking studies revealed that compound 4e fitted well into the active sites of AChE and BuChE, forming stable and strong interactions with key residues Glu199, Trp84, Asp72, Tyr121, and Phe288 in AChE and His438, Trp82, Ala328, Tyr332, Phe329, Thr120, and Pro285 in BuChE. Besides, the inhibition of BACE1 by 4e and the biometal chelation activity of 4e were measured. The neuroprotective assessment revealed that 4e exhibited 23.2% protection at 50 µM toward amyloid-beta-induced PC12 neuronal cells. Overall, this study exhibited that compound 4e was a promising compound targeting multiple factors associated with AD.

Sulfuretin exerts diversified functions in the processing of amyloid precursor protein

Sulfuretin is a flavonoid that protects cell from damage induced by reactive oxygen species and inflammation. In this study, we investigated the role of sulfuretin in the processing of amyloid precursor protein (APP), in association with the two catalytic enzymes the α-secretase a disintegrin and metalloproteinase (ADAM10), and the beta-site APP cleaving enzyme 1 (BACE1) that play important roles in the generation of β amyloid protein (Aβ) in Alzheimer's disease (AD). We found that sulfuretin increased the levels of the immature but not the mature form of ADAM10 protein. The enhanced ADAM10 transcription by sulfuretin was mediated by the nucleotides −444 to −300 in the promoter region, and was attenuated by silencing or mutation of transcription factor retinoid X receptor (RXR) and by GW6471, a specific inhibitor of peroxisome proliferator-activated receptor α (PPAR-α). We further found that sulfuretin preferentially increased protein levels of the immature form of APP (im-APP) but significantly reduced those of BACE1, sAPPβ and β-CTF, whereas Aβ1-42 levels were slightly increased. Finally, the effect of sulfuretin on BACE1 and im-APP was selectively attenuated by the translation inhibitor cycloheximide and by lysosomal inhibitor chloroquine, respectively. Taken together, (1) RXR/PPAR-α signaling was involved in sulfuretin-mediated ADAM10 transcription. (2) Alteration of Aβ protein level by sulfuretin was not consistent with that of ADAM10 and BACE1 protein levels, but was consistent with the elevated level of im-APP protein, suggesting that im-APP, an isoform mainly localized to trans-Golgi network, plays an important role in Aβ generation.

Retinal Optical Coherence Tomography Metrics Are Unchanged in Verubecestat Alzheimer's Disease Clinical Trial but Correlate with Baseline Regional Brain Atrophy.

We performed exploratory analyses of retinal thickness data from a clinical trial of the AβPP cleaving enzyme (BACE) inhibitor verubecestat in patients with Alzheimer's disease (AD). To evaluate: 1) possible retinal thickness changes following BACE inhibition; and 2) possible association between retinal thickness and brain atrophy. Retinal thickness was measured using spectral-domain optical coherence tomography in a 78-week randomized placebo-controlled trial of verubecestat in 1,785 patients with mild-to-moderate AD. Changes from baseline in retinal pigment epithelium, macular grid retinal nerve fiber layer, central subfield retinal thickness, and macular grid volume were evaluated for verubecestat versus placebo. Correlation analyses were performed to investigate the potential association between macular grid retinal nerve fiber layer and central subfield retinal thickness with brain volumetric magnetic resonance imaging (vMRI) data at baseline, as well as correlations for changes from baseline at Week 78 in patients receiving placebo. Verubecestat did not significantly alter retinal thickness during the trial compared with placebo. At baseline, mean macular grid retinal nerve fiber layer and central subfield retinal thickness were weakly but significantly correlated (Pearson's r values≤0.23, p-values < 0.01) with vMRI of several brain regions including whole brain, hippocampus, and thalamus. At Week 78, correlations between retinal thickness and brain vMRI changes from baseline in the placebo group were small and mostly not statistically significant. BACE inhibition by verubecestat was not associated with adverse effects on retinal thickness in patients with mild-to-moderate AD. Correlations between retinal thickness and brain volume were observed at baseline. Clinicaltrials.gov NCT01739348 (registered December 3, 2012; https://clinicaltrials.gov/ct2/show/NCT01739348).

Epigenetic profiling of Italian patients identified methylation sites associated with hereditary transthyretin amyloidosis

Hereditary transthyretin (TTR) amyloidosis (hATTR) is a rare life-threatening disorder caused by amyloidogenic coding mutations located in TTR gene. To understand the high phenotypic variability observed among carriers of TTR disease-causing mutations, we conducted an epigenome-wide association study (EWAS) assessing more than 700,000 methylation sites and testing epigenetic difference of TTR coding mutation carriers vs. non-carriers. We observed a significant methylation change at cg09097335 site located in Beta-secretase 2 (BACE2) gene (standardized regression coefficient = −0.60, p = 6.26 × 10–8). This gene is involved in a protein interaction network enriched for biological processes and molecular pathways related to amyloid-beta metabolism (Gene Ontology: 0050435, q = 0.007), amyloid fiber formation (Reactome HSA-977225, q = 0.008), and Alzheimer’s disease (KEGG hsa05010, q = 2.2 × 10–4). Additionally, TTR and BACE2 share APP (amyloid-beta precursor protein) as a validated protein interactor. Within TTR gene region, we observed that Val30Met disrupts a methylation site, cg13139646, causing a drastic hypomethylation in carriers of this amyloidogenic mutation (standardized regression coefficient = −2.18, p = 3.34 × 10–11). Cg13139646 showed co-methylation with cg19203115 (Pearson’s r2 = 0.32), which showed significant epigenetic differences between symptomatic and asymptomatic carriers of amyloidogenic mutations (standardized regression coefficient = −0.56, p = 8.6 × 10–4). In conclusion, we provide novel insights related to the molecular mechanisms involved in the complex heterogeneity of hATTR, highlighting the role of epigenetic regulation in this rare disorder.

Manganese Exposure Aggravates β-Amyloid Pathology by Microglial Activation

Human epidemiological evidence and animal experimental data suggest that chronic manganese (Mn) exposure increases the risk of Alzheimer’s disease (AD) and amyloid plaques, a hallmark of AD brain pathology, but the underlying mechanisms were not fully understood. Using the transgenic APP/PS1/Tau triple transgenic AD (3×Tg-AD) mouse model and mouse-derived microglia and neuroblastoma cell lines, we found that chronic 5-month Mn treatment increased beta amyloid peptide (Aβ) expression and Aβ plaques in the cerebral cortex and hippocampus in these 3×Tg-AD mice. Furthermore, we found that the β- and γ-secretase cleavage activities were markedly increased, while α-secretase cleavage activity was reduced in the brain of Mn-treated AD mice; these effects increase Aβ production and thus are amyloidogenic. Equally important, Mn treatment alone did not alter β-secretase 1 (BACE1) gene expression or Aβ production in amyloidogenic mutant amyloid precursor protein (APP) gene hAPPsw-transfected N2a cells (APPsw-N2a), but in APPsw-N2a cells either co-cultured with microglia or cultured with microglia-conditioned media, Mn exposure increased BACE1 expression and amyloidogenesis. We further determined that Mn exposure promoted the activation of microglia both in 3×Tg-AD mouse brains and in cultured microglia cells, and increased the secretion of the inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Taken together, these results suggest that Mn may increase the release of IL-1β and TNF-α from microglia that in turn stimulates the expression of BACE1 gene and protein and consequently Aβ production; this novel molecular mechanism not only advances our understanding about the amyloidogenic effect of chronic Mn exposure reported for special human populations but also indicates Mn dyshomeostasis as a potential contributor to AD pathogenesis.

Neuroprotective compounds from the resinous heartwood of Aquilaria sinensis

Six undescribed compounds, including three sesquiterpenoids [(4S,5S,7S,8S,11R)-7-hydroxyguai-1(10)-en-8,12-olide, aquilarisinone, and 2Z,7(13),9E-humulatrien-12-ol-5-one], one diphenylpentanone [1-(2-hydroxyphenyl)-5-phenylpentan-3-one], and two 2-(2-phenylethyl)chromones (6-epiagarotetrol and triepoxyhexahydrochromone A), along with 15 known compounds, were isolated from the resinous heartwood of Aquilaria sinensis (Thymelaeaceae). Their structures were determined by mass (MS) and nuclear magnetic resonance (NMR) spectroscopic data. The absolute configuration of (4S,5S,7S,8S,11R)-7-hydroxyguai-1(10)-en-8,12-olide was confirmed by X-ray diffraction analysis, and the configurations of (4S,7S,8S,10R,11R)-7,10-epoxyguai-1(5)-en-8,12-olide, aquilarisinone, 6-epiagarotetrol, and triepoxyhexahydrochromone A were confirmed by electronic circular dichroism (ECD) calculations. The neuroprotective activities of the compounds were evaluated using models of BACE1 inhibition and PC12 cells with corticosterone- and 1-methyl-4-phenylpyridine ion (MPP+)-induced damage. At concentrations of 1, 2, and 5 μM, triepoxyhexahydrochromone A, (+)-(7R,10R)-selina-4,11(13)-diene-12,15-dial, (−)-(5R,7R,10R)-12,15-dioxo-α-selinene, and (+)-(1R,4S,5R)-1β-hydroxyeremophila-7(11),9-dien-8-one exerted significant protective effects (p < 0.01) on PC12 cell injury induced by corticosterone, while triepoxyhexahydrochromone A and (−)-(5R,7R,10R)-12,15-dioxo-α-selinene exerted significant protective effects (p < 0.01) on MPP+-induced PC12 cell injury at concentrations of 1, 2, and 5 μM. No compounds produced significant inhibitory effects on BACE1, with inhibition rates of less than 20% observed at a concentration of 20 μM.

Scope of β-Secretase (BACE1)-Targeted Therapy in Alzheimer's Disease: Emphasizing the Flavonoid Based Natural Scaffold for BACE1 Inhibition.

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the most common form of dementia in the world. Studies report the presence of extracellular amyloid plaques consisting of β-amyloid peptide and intracellular tangles consisting of hyperphosphorylated tau proteins as the histopathological indicators of AD. The process of β-amyloid peptide generation by sequential cleavage of amyloid precursor protein by β-secretase (BACE1) and γ-secretase, followed by its aggregation to form amyloid plaques, is the mechanistic basis of the amyloid hypothesis. Other popular hypotheses related to the pathogenesis of AD include the tau hypothesis and the oxidative stress hypothesis. Various targets of the amyloid cascade are now in prime focus to develop drugs for AD. Many BACE1 inhibitors, β-amyloid aggregation inhibitors, and Aβ clearance strategies using monoclonal antibodies are in various stages of clinical trials. This review provides an in-depth evaluation of the role of BACE1 in disease pathogenesis and also highlights the therapeutic approaches developed to find more potent but less toxic inhibitors for BACE1, particularly emphasizing the natural scaffold as a nontoxic lead for BACE1 inhibition. Cellular targets and signaling cascades involving BACE1 have been highlighted to understand the physiological role of BACE1. This knowledge is extremely crucial to understand the toxicity evaluations for BACE1-targeted therapy. We have particularly highlighted the scope of flavonoids as a new generation of nontoxic BACE1 inhibitory scaffolds. The structure-activity relationship of BACE1 inhibition for this group of compounds has been highlighted to provide a guideline to design more selective highly potent inhibitors. The review aims to provide a holistic overview of BACE1-targeted therapy for AD that paves the way for future drug development.

Exercise-mediated alteration of hippocampal Dicer mRNA and miRNAs is associated with lower BACE1 gene expression and Aβ1-42 in female 3xTg-AD mice

Changes to cerebral miRNA expression have been implicated in the progression of Alzheimer's disease (AD), as miRNAs that regulate the expression of gene products involved in amyloid beta (Aβ) processing, such as BACE1, are dysregulated in those that suffer from AD. Exercise training improves cognition and reduces BACE1 and Aβ-plaque burden; however, the mechanisms are not fully understood. Using our progressive weighted wheel running (PoWeR) exercise program, we assessed the effect of 20 wk of exercise training on changes in hippocampal miRNA expression in female 3xTg-AD (3xTg) mice. PoWeR was sufficient to promote muscle hypertrophy and increase myonuclear abundance. Furthermore, PoWeR elevated hippocampal Dicer gene expression in 3xTg mice, while altering miRNA expression toward a more wild-type profile. Specifically, miR-29, which is validated to target BACE1, was significantly lower in sedentary 3xTg mice when compared with wild-type but was elevated following PoWeR. Accordingly, BACE1 gene expression, along with detergent-soluble Aβ1-42, was lower in PoWeR-trained 3xTg mice. Our data suggest that PoWeR training upregulates Dicer gene expression to alter cerebral miRNA expression, which may contribute to reduced Aβ accumulation and delay AD progression.NEW & NOTEWORTHY Previous studies have outlined the beneficial effects of exercise on lowering BACE1 expression and reducing Aβ plaques. This study extends upon the work of others by outlining a new potential mechanism by which exercise elicits beneficial effects on Alzheimer's disease pathology, specifically through modulation of Dicer and miRNA expression. This is the first study to examine Dicer and miRNA expression in the hippocampus of the 3xTg model within the context of exercise.

Cognitive outcomes in trials of two BACE inhibitors in Alzheimer's disease.

The APECS and AMARANTH trials showed that beta-secretase (BACE) inhibitors verubecestat and lanabecestat failed to slow cognitive and functional decline in individuals with prodromal or early Alzheimer's disease. Here, the performance on secondary and exploratory cognitive measures in both studies is reported. APECS (verubecestat) and AMARANTH (lanabecestat) were randomized, double-blind, placebo-controlled, parallel-group, 104-week clinical trials conducted by different sponsors. Measures included the 3-Domain Composite Cognition Score (CCS-3D), Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Letter/Category Fluency, and Digit Symbol Coding. Verubecestat showed worsening on the CCS-3D Total Score, Episodic Memory, and Attention/Processing Speed domains. Lanabecestat showed worsening on the RBANS Total Score, Immediate Memory, and Visuospatial/Constructional Indexes. Both BACE inhibitors showed worsening on Digit Symbol Coding and improvements on Letter/Category Fluency. In both studies, many measures showed treatment-associated cognitive worsening, whereas verbal fluency tasks showed improvement.