Beta-secretase Inhibitors Research Articles

In silico Study of Acetylcholinesterase and Beta-secretase Inhibitors: Potential Multitarget Anti-Alzheimer's Agents.

Alzheimer's disease is a progressive neurodegenerative process with multifactorial characteristics. This disease follows the natural aging process, affecting mainly people over 65 years. Pharmacotherapeutic treatment currently combats symptoms related to cognitive function. Several targets have begun to attract the interest of the scientific community to develop new drug candidates which have better pharmacokinetic and lower toxicity parameters. The present study aims to design new candidates for acetylcholinesterase/β-secretase (AChE/BACE1) multitarget inhibitor drugs. 17 natural products were selected from the literature with anticholinesterase activity and 1 synthetic molecule with inhibitory activity for BACE1. Subsequently, the molecular docking study was performed, followed by the derivation of the pharmacophoric pattern and prediction of pharmacokinetic and toxicological properties. Finally, the hybrid prototype was designed. All selected molecules showed interactions with their respective target enzymes. Derivation of the pharmacophoric pattern from molecules that interacted with the AChE enzyme resulted in 3 pharmacophoric regions: an aromatic ring, an electron-acceptor region and a hydrophobic region. The molecules showed good pharmacokinetic and toxicological results, showing no warnings of mutagenicity and/or carcinogenicity. After the hybridization process, three hybrid molecules were obtained, which showed inhibitory activity for both targets. It is concluded that research in the field of medicinal chemistry is advancing towards the discovery of new drug candidates that bring a better quality of life to patients with AD.

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

IntroductionAlzheimer's disease (AD) is the most common form of dementia. Beta‐secretase (BACE) inhibitors have been proposed as potential therapeutic interventions; however, initiating treatment once disease has significantly progressed has failed to effectively stop or treat disease. Whether BACE inhibition may have efficacy when administered prophylactically in the early stages of AD has been under‐investigated. The present studies aimed to evaluate prophylactic treatment of the BACE inhibitor verubecestat in an AD mouse model using the National Institute on Aging (NIA) resources of the Model Organism Development for Late‐Onset Alzheimer's Disease (MODEL‐AD) Preclinical Testing Core (PTC) Drug Screening Pipeline.Methods5XFAD mice were administered verubecestat ad libitum in chow from 3 to 6 months of age, prior to the onset of significant disease pathology. Following treatment (6 months of age), in vivo imaging was conducted with 18F‐florbetapir (AV‐45/Amyvid) (18F‐AV45) and 18‐FDG (fluorodeoxyglucose)–PET (positron emission tomography)/MRI (magnetic resonance imaging), brain and plasma amyloid beta (Aβ) were measured, and the clinical and behavioral characteristics of the mice were assessed and correlated with the pharmacokinetic data.ResultsProphylactic verubecestat treatment resulted in dose‐ and region‐dependent attenuations of 18F‐AV45 uptake in male and female 5XFAD mice. Plasma Aβ40 and Aβ42 were also dose‐dependently attenuated with treatment. Across the dose range evaluated, side effects including coat color changes and motor alterations were reported, in the absence of cognitive improvement or changes in 18F‐FDG uptake.DiscussionProphylactic treatment with verubecestat resulted in attenuated amyloid plaque deposition when treatment was initiated prior to significant pathology in 5XFAD mice. At the same dose range effective at attenuating Aβ levels, verubecestat produced side effects in the absence of improvements in cognitive function. Taken together these data demonstrate the rigorous translational approaches of the MODEL‐AD PTC for interrogating potential therapeutics and provide insight into the limitations of verubecestat as a prophylactic intervention for early‐stage AD.

Design and discovery of C2-fluoroalkyl iminothiazine dioxides as BACE inhibitors

This paper describes the structure–activity-relationships of novel fluoroalkyl substituents at the C2 position of iminothiazine dioxide beta secretase inhibitors. Key discoveries include reduced amidine basicity and its effect on Pgp, cell potency, and efficacy in various preclinical in vivo efficacy animal models. Findings from these structure–activity-relationships are discussed.

Systematic in silico analysis of clinically tested drugs for reducing amyloid-beta plaque accumulation in Alzheimer's disease.

IntroductionDespite strong evidence linking amyloid beta (Aβ) to Alzheimer's disease, most clinical trials have shown no clinical efficacy for reasons that remain unclear. To understand why, we developed a quantitative systems pharmacology (QSP) model for seven therapeutics: aducanumab, crenezumab, solanezumab, bapineuzumab, elenbecestat, verubecestat, and semagacestat.MethodsOrdinary differential equations were used to model the production, transport, and aggregation of Aβ; pharmacology of the drugs; and their impact on plaque.ResultsThe calibrated model predicts that endogenous plaque turnover is slow, with an estimated half‐life of 2.75 years. This is likely why beta‐secretase inhibitors have a smaller effect on plaque reduction. Of the mechanisms tested, the model predicts binding to plaque and inducing antibody‐dependent cellular phagocytosis is the best approach for plaque reduction.DiscussionA QSP model can provide novel insights to clinical results. Our model explains the results of clinical trials and provides guidance for future therapeutic development.

Recent insight into BACE1 as a potential target for treatment of Alzheimer's disease

Alzheimer’s disease (AD) is one of the most common progressive neurodegenerative diseases that represents about 60-80 % of total cases of dementia all over the world. Beta secretase (BACE1) is a membrane-anchored aspartic protease which cleaves the peptide bond between Met671-Asp672 of APP (amyloid precursor protein) where its activity is the rate limiting step of producing amyloid β, the primary neuropathological hallmark of Alzheimer's disease (AD). Therefore, inhibitors of this enzyme have the potential to be a promising and attractive target for intervention of potent therapeutics for treatment AD. Actually, there are many challenges facing the development of effective drug-like BACE1 inhibitors including penetration of BBB and selectivity against other proteases. However, many efforts have been devoted by pharmaceutical industries and academia for development of small size, potent, selective and biologically active BACE1 inhibitors. Till now, none of which is FDA approved but some of which have exhibited clinical potential. In this article, we outlined overview of beta secretase inhibitors that have been designed and developed for treatment of AD.

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.

Amyloid aggregates accumulate in melanoma metastasis modulating YAP activity.

Melanoma progression is generally associated with increased transcriptional activity mediated by the Yes‐associated protein (YAP). Mechanical signals from the extracellular matrix are sensed by YAP, which then activates the expression of proliferative genes, promoting melanoma progression and drug resistance. Which extracellular signals induce mechanotransduction, and how this is mediated, is not completely understood. Here, using secretome analyses, we reveal the extracellular accumulation of amyloidogenic proteins, i.e. premelanosome protein (PMEL), in metastatic melanoma, together with proteins that assist amyloid maturation into fibrils. We also confirm the accumulation of amyloid‐like aggregates, similar to those detected in Alzheimer disease, in metastatic cell lines, as well as in human melanoma biopsies. Mechanistically, beta‐secretase 2 (BACE2) regulates the maturation of these aggregates, which in turn induce YAP activity. We also demonstrate that recombinant PMEL fibrils are sufficient to induce mechanotransduction, triggering YAP signaling. Finally, we demonstrate that BACE inhibition affects cell proliferation and increases drug sensitivity, highlighting the importance of amyloids for melanoma survival, and the use of beta‐secretase inhibitors as potential therapeutic approach for metastatic melanoma.

An agnostic reevaluation of the amyloid cascade hypothesis of Alzheimer's disease pathogenesis: The role of APP homeostasis.

To reassess the role of amyloid beta (Aβ) and the amyloid precursor protein (APP) system in the pathogenesis of Alzheimer's disease (AD). APP is a cell adhesion molecule that has been highly conserved over the course of phylogeny that has critical roles in brain development, synaptic plasticity, and the brain's intrinsic immune system. The amyloid cascade hypothesis describes a relatively linear, deterministic sequence of events triggered by a gain of Aβ peptide fragment toxicity that results in neurodegeneration and cognitive loss, yet well designed immunotherapy and beta secretase inhibitor trials that have successfully targeted Aβ have failed to have any consistent effects on the steady decline of cognition. Mutations of the APP and presenilin genes not only alter the ratio of longer to shorter Aβ fragments (resulting in a gain of Aβ toxicity), but also disrupt the normal homeostatic roles of their respective proteins. The evolutionary history, physiological importance, and complexity of the APP and presenilin systems, as well as other critical components including tau and apolipoprotein E (APOE) imply that altered function of such systems could have severe consequences that include but need not be limited to a gain of Aβ toxicity and would more generally result in altered homeostasis of APP-related functions. Challenges that a loss of APP homeostasis addresses better than the more limited gain of Aβ toxicity model include the topographic mismatches between Aβ and tau pathology, the profile and chronology of cognitive and biomarker changes that precede the clinical expression of mild cognitive impairment and dementia, and the disappointments of Aβ targeted therapeutics among others. The importance of APP, α- and β-secretases, the presenilins and γ-secretase, as well as tau was recognized by the authors of the amyloid cascade hypothesis, and has since led multiple investigators to propose alternative, more balanced hypotheses including reduced homeostasis and frank loss-of-function of key components that include but go beyond the currently envisioned linear model of Aβ toxicity.

Inhibition of enzymes important for Alzheimer’s disease by antioxidant extracts prepared from 15 New Zealand medicinal trees and bushes

ABSTRACT Alzheimer’s disease is characterised by progressive mental deterioration, related to ageing and senility. Thirty methanol and ethyl acetate extracts from 15 native New Zealand trees and bushes were produced and tested for the inhibition of three enzymes related to neurotransmission: acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and beta-secretase (BACE). In addition the IC50 for the antioxidant potential of the extracts was determined. Weinmannia racemosa and Kunzea ericoides were effective inhibitors of AChE-BChE and beta-secretase, respectively. The IC50 for W. racemosa extracts against AChE and BChE ranged between 8.09 μg/mL and 37.07 μg/mL. The ethyl acetate extract of Schefflera digitata was also an effective inhibitor of BChE (IC50 = 25.38 μg/mL). K. ericoides IC50 for beta-secretase were 29.05 μg/mL and 36.40 μg/ml. The highest radical scavenging activity (RSA) was detected in the methanol extract of Aristotelia serrata (IC50 = 2.34 μg/mL), followed by both extracts of Hebe stricta and W. racemosa, and last the methanol extracts of K. ericoides and Pomaderris kumeraho, which presented higher RSA than the reference antioxidant (IC50 <12.0 μg/mL). W. racemosa showed inhibitory activity against AChE and BChE enzymes and antioxidant activity, which suggests these extracts may have potential for application in patients suffering from Alzheimer's disease and other dementias.

Screening of Beta-Secretase Inhibitors by Capillary Electrophoresis-Mass Spectrometry.

Alzheimer's disease is the most common cause of dementia, currently afflicting almost 40million patients worldwide. According to the amyloid cascade hypothesis, the pathogenesis of the disease could be slowed down or even stopped by the inhibition of beta-secretase, making this aspartic acid protease a potentially important drug target site. Capillary electrophoresis is a promising technique for screening putative enzyme inhibitors due to highly effective separations, minuscule sample and other chemicals consumption, compatibility with a variety of detection techniques, and high throughput via automation. This chapter presents a method based on capillary electrophoresis coupled to mass spectrometry detection for kinetic and inhibition assays of the beta-secretase reaction with a decapeptide derived from an amyloid precursor protein.

The Role of Secretase Pathway in Long-term Brain Inflammation and Cognitive Impairment in an Animal Model of Severe Sepsis.

Inflammatory cytokines are related to impaired learning and memory processes in the central nervous system, contributing to the cognitive dysfunction present in sepsis survivors. In sepsis, brain of survivors presented increased deposition of amyloid-beta (Aβ) peptide and this was associated with cognitive impairment. However, it is not known if the upregulation of secretase pathway is involved the deposition of Aβ peptide and consequent development of cognitive impairment in survivors. The aim of the study is to evaluate the effects of secretase inhibitors on behavioral, Aβ accumulation, and neuroinflammatory parameters in rats submitted to sepsis. Sepsis was induced by cecal ligation and perforation in Wistar rats, and the activity of alpha-, beta-, and gamma-secretases was determined in the hippocampus and prefrontal at different times. Additionally, in a different cohort of animal's epigallocatechin gallate, a beta-secretase inhibitor or a gamma-secretase inhibitor was administrated once a day for three consecutive days. Fifteen or 30 days after sepsis induction, Aβ content, TNF-α, IL-1β, and IL-6 and cognitive performance were determined. There was no increase in alpha-secretase activity. Both beta- and gamma-secretase activities increased, mainly late after sepsis. The inhibition of beta- or gamma-secretases improved cognitive performance 10 days after sepsis induction, and beta-secretase inhibition improved cognitive performance up to 30 days after sepsis induction. Furthermore, beta-secretase inhibition decreased IL-1β and Aβ brain levels. It was demonstrated that during sepsis development there was an increase in the amyloidogenic route, and the inhibition of this pathway promoted attenuation of neuroinflammation, Aβ peptide content, and improvement of cognitive impairment.

The Beta Amyloid Dysfunction (BAD) Hypothesis for Alzheimer's Disease.

Beta amyloid, Aβ 1–42, originally named as Amyloid A4 protein, is one of the most investigated peptides in neuroscience and has attracted substantial interest since its discovery as the main insoluble fibril-type protein in cerebrovascular amyloid angiopathy (Glenner and Wong, 1984; Masters et al., 1985) of Alzheimer’s disease (AD). From the very beginning, Aβ was regarded per se as a “bad molecule,” triggering the so-called “beta amyloid cascade hypothesis” (Hardy and Higgins, 1992). This hypothesis ignored any physiological function for in situ generated Aβ monomer with normal production and turnover rate (Bateman et al., 2006). Accordingly, pan-Aβ-related therapeutic approaches were designed to eliminate or lower the three structural isoforms in parallel: (1) the pre-amyloid monomer, (2) the misfolded oligomer, and (3) the final fibril. While we already knew about poor correlations between plaques and cognitive decline quite early (Terry et al., 1991), data for an essential benign physiological role for Aβ monomer at low concentrations were also not considered to be relevant. Here, a different Beta Amyloid hypothesis is described, the so-called “Beta Amyloid Dysfunction hypothesis,” which, in contrast to the “Beta Amyloid Cascade hypothesis,” builds on the homeostasis of essential Aβ monomer in the synaptic vesicle cycle (SVC). Disease-relevant early pathology emerges through disturbance of the Aβ homeostasis by so far unknown factors leading to the formation of misfolded Aβ oligomers. These early species interfere with the synaptic physiological Aβ monomer regulation and exert their neurotoxicity via various receptors for sticky oligomer-type Aβ aggregates. The Beta Amyloid Dysfunction (BAD) hypothesis is introduced and shown to explain negative clinical results of Gamma-secretase and Beta-secretase (BACE) inhibitors as well as pan-Aβ isotype unselective immunotherapies. This hypothesis gives guidance to what needs to be done therapeutically to revive successful clinical testing in AD for this highly validated target. The BAD hypothesis will need further refinement in particular through more detailed exploration for the role of physiological Aβ monomer.

Discovery of a series of selective and cell permeable beta-secretase (BACE1) inhibitors by fragment linking with the assistance of STD-NMR

Two β-secreatase (BACE1) inhibitors from natural products (cinnamic acid and flavone) were linked to furnish potent, cell permeable BACE1 inhibitors with noncompetitive mode of inhibition, with the assistance of saturated transfer difference (STD)-NMR technique. Some of these conjugates also exhibited selective BACE1 inhibition over other aspartyl proteases such as BACE-2 and renin, as well as poor cytotoxicity. Taken together, conjugates 4 represent a new series of BACE inhibitors warrants further investigation for their potential in Alzheimier’s disease therapy.

QSAR Classification Models for Predicting the Activity of Inhibitors of Beta-Secretase (BACE1) Associated with Alzheimer\u2019s Disease

Alzheimer’s disease is one of the most common neurodegenerative disorders in elder population. The β-site amyloid cleavage enzyme 1 (BACE1) is the major constituent of amyloid plaques and plays a central role in this brain pathogenesis, thus it constitutes an auspicious pharmacological target for its treatment. In this paper, a QSAR model for identification of potential inhibitors of BACE1 protein is designed by using classification methods. For building this model, a database with 215 molecules collected from different sources has been assembled. This dataset contains diverse compounds with different scaffolds and physical-chemical properties, covering a wide chemical space in the drug-like range. The most distinctive aspect of the applied QSAR strategy is the combination of hybridization with backward elimination of models, which contributes to improve the quality of the final QSAR model. Another relevant step is the visual analysis of the molecular descriptors that allows guaranteeing the absence of information redundancy in the model. The QSAR model performances have been assessed by traditional metrics, and the final proposed model has low cardinality, and reaches a high percentage of chemical compounds correctly classified.

Marine Microbial Metabolites as Drug Candidates for Alzheimer's Disease

With an increase in the number of mortality rates among the elderly due to Alzheimer’s disease, the need for developing a lifesaving drug is imperative. Beta secretase has become an attractive target for the development of new anti-Alzheimer’s drug which could curb the disease. Due to the advancement in screening technologies, marine microbial bioprospecting has yielded a considerable amount of bioactive molecules as drug candidates for various incurable diseases. Among all, marine fungi is known for its rich source of novel chemical entities as therapeutic molecules. Current study was envisaged to evaluate the beta secretase inhibitory property of marine microbes isolated from Arabian and Coromandel Coast. In this study, marine sediment and water samples were collected from various offshore locations. Sediment samples were diluted and plated on a selective medium to isolate fungal strains. All the isolates were screened for trypsin and beta secretase inhibitory activity using in vitro assays. A 16SrRNA sequencing and morphological characterization was done to identify the promising isolate. A total of 50 microbial strains were isolated from the sediment samples and water samples. Out of 50 isolates tested, CSS4F4 exhibited highest beta secretase (52.77± 1.99 %) and appreciable trypsin inhibition (63.10± 0.64 %). The isolate was identified as Aspergillus sp. 1 SH-2016 strain through 16SrNA sequencing. Phytochemical screening of ethyl acetate extract of the active isolate indicated the presence of flavonoids, polyphenols and terpenoids. This research extends our knowledge of the bioactive potential of marine fungal metabolites as a promising beta secretase inhibitor for the mitigation of AD

Dual BACE-1/GSK-3β Inhibitors to Combat Alzheimer's Disease: A Focused Review.

In industrialized countries, Alzheimer's disease represents the most devastating neurodegenerative disorder in elderly people and the search for a disease modifying agent is still justified by this unmet need. Several possible targets have been explored to find an appropriate drug therapy, and in this review, dual inhibitors of beta secretase and glycogen synthase kinase 3, recently reported in literature, will be appraised. Applying a ligand-based approach, the triazinone core emerged as a suitable scaffold to simultaneously bind the aspartic dyad of BACE-1 and the ATP site of GSK-3β, leading to a series of small molecules endowed with a balanced micromolar affinity and a promising pharmacokinetic profile. Differently, by means of a structure-based approach, a series of well-balanced dual binding molecules were designed, taking advantage of the versatility of the curcumin scaffold. For some of these new compounds a potential neuroprotective effect was also observed, due to their ability to counteract the oxidative stress through the inhibition of NQO1 enzyme. Finally, different virtual screening analyses were performed, leading to the identification of new potential scaffolds deserving further development.

Impact of amyloid-beta changes on cognitive outcomes in Alzheimer\u2019s disease: analysis of clinical trials using a quantitative systems pharmacology model

BackgroundDespite a tremendous amount of information on the role of amyloid in Alzheimer’s disease (AD), almost all clinical trials testing this hypothesis have failed to generate clinically relevant cognitive effects.MethodsWe present an advanced mechanism-based and biophysically realistic quantitative systems pharmacology computer model of an Alzheimer-type neuronal cortical network that has been calibrated with Alzheimer Disease Assessment Scale, cognitive subscale (ADAS-Cog) readouts from historical clinical trials and simulated the differential impact of amyloid-beta (Aβ40 and Aβ42) oligomers on glutamate and nicotinic neurotransmission.ResultsPreclinical data suggest a beneficial effect of shorter Aβ forms within a limited dose range. Such a beneficial effect of Aβ40 on glutamate neurotransmission in human patients is absolutely necessary to reproduce clinical data on the ADAS-Cog in minimal cognitive impairment (MCI) patients with and without amyloid load, the effect of APOE genotype effect on the slope of the cognitive trajectory over time in placebo AD patients and higher sensitivity to cholinergic manipulation with scopolamine associated with higher Aβ in MCI subjects. We further derive a relationship between units of Aβ load in our model and the standard uptake value ratio from amyloid imaging.When introducing the documented clinical pharmacodynamic effects on Aβ levels for various amyloid-related clinical interventions in patients with low Aβ baseline, the platform predicts an overall significant worsening for passive vaccination with solanezumab, beta-secretase inhibitor verubecestat and gamma-secretase inhibitor semagacestat. In contrast, all three interventions improved cognition in subjects with moderate to high baseline Aβ levels, with verubecestat anticipated to have the greatest effect (around ADAS-Cog value 1.5 points), solanezumab the lowest (0.8 ADAS-Cog value points) and semagacestat in between. This could explain the success of many amyloid interventions in transgene animals with an artificial high level of Aβ, but not in AD patients with a large variability of amyloid loads.ConclusionsIf these predictions are confirmed in post-hoc analyses of failed clinical amyloid-modulating trials, one should question the rationale behind testing these interventions in early and prodromal subjects with low or zero amyloid load.

Efficacy of chronic BACE1 inhibition in PS2APP mice depends on the regional Aβ deposition rate and plaque burden at treatment initiation.

Beta secretase (BACE) inhibitors are promising therapeutic compounds currently in clinical phase II/III trials. Preclinical [18F]-florbetaben (FBB) amyloid PET imaging facilitates longitudinal monitoring of amyloidosis in Alzheimer's disease (AD) mouse models. Therefore, we applied this theranostic concept to investigate, by serial FBB PET, the efficacy of a novel BACE1 inhibitor in the PS2APP mouse, which is characterized by early and massive amyloid deposition.Methods: PS2APP and C57BL/6 (WT) mice were assigned to treatment (PS2APP: N=13; WT: N=11) and vehicle control (PS2APP: N=13; WT: N=11) groups at the age of 9.5 months. All animals had a baseline PET scan and follow-up scans at two months and after completion of the four-month treatment period. In addition to this longitudinal analysis of cerebral amyloidosis by PET, we undertook biochemical amyloid peptide quantification and histological amyloid plaque analyses after the final PET session.Results: BACE1 inhibitor-treated transgenic mice revealed a progression of the frontal cortical amyloid signal by 8.4 ± 2.2% during the whole treatment period, which was distinctly lower when compared to vehicle-treated mice (15.3 ± 4.4%, p<0.001). A full inhibition of progression was evident in regions with <3.7% of the increase in controls, whereas regions with >10% of the increase in controls showed only 40% attenuation with BACE1 inhibition. BACE1 inhibition in mice with lower amyloidosis at treatment initiation showed a higher efficacy in attenuating progression to PET. A predominant reduction of small plaques in treated mice indicated a main effect of BACE1 on inhibition of de novo amyloidogenesis.Conclusions: This theranostic study with BACE1 treatment in a transgenic AD model together with amyloid PET monitoring indicated that progression of amyloidosis is more effectively reduced in regions with low initial plaque development and revealed the need of an early treatment initiation during amyloidogenesis.

GENETIC DISORDER ALZHEIMER

Alzheimer’s disease (AD), slowly continuous neurological disorder, mostly appears in older &gt;65 age that deals with the memory loss due to death or damage of brain cells and cognitive functions (thinking, reasoning, and behavior abnormalities) due to the accumulation of the specific protein (beta-amyloid protein) which form plaque and fibers (tau tangles) in the brain. Not only the genetic factors are responsible but also most of the non-genetic factors are responsible for AD. Several mutations in the gene (APP, APOE, PENS1, PENS2 on chromosome no. 21, 19, 14, 1) are responsible for causing four types of AD. Memory loss is most common sign of AD. Predisposing factors of AD are hereditary, severe brain injury or traumatic, and metabolic diseases such as diabetes mellitus, hypercholesteremia, and obesity. Although treatment can manage some symptoms in few people, but there is no current mechanism to cure AD or stop its progression. Beta-secretase inhibitor molecule prevents the first step in a chain accumulation which leads to the formation of amyloid plaque in the brain. However, the scientist or researchers have established a compound NIC5-15 they have been found NIC5-15 has safe and effectual treatment which has been used to stabilize cognitive performance in patients with mild to moderate AD.

INVESTIGATING PRESYNAPTIC DISRUPTION IN ORGANOTYPIC HIPPOCAMPAL SLICE CULTURES FROM HU-APP TRANSGENIC MICE

Loss of presynaptic proteins has been reported as an early and clinically-relevant alteration in the brains of patients with Alzheimer's disease. Understanding the mechanisms by which synapses are disrupted requires a model system that represents all major CNS cell types, is amenable to repeated analysis, and can be readily manipulated. Long-term organotypic hippocampal slice cultures (OHSCs) from neonatal amyloid mice offer an excellent compromise between in vivo and primary culture studies, largely retaining the cellular composition and neuronal architecture of the in vivo hippocampus, but with the in vitro advantages of accessibility to live imaging, sampling and intervention. OHSCs are made using tissue from P6-P9 TgCRND8 mice and maintained on membrane inserts for up to 2 months. Pathology development was closely monitored using Aβ ELISA, western blotting for synaptic proteins, and immunofluorescence for Aβ, neurons and glia. The mechanisms behind presynaptic disruption were probed via pharmacological manipulation of Aβ production and genetic knockout of endogenous mouse tau. Aβ1–40 and Aβ1–42 rise progressively in transgenic slice culture medium and stabilise when regular feeding balances continued production. In contrast, intra-axonal Aβ continues to accumulate in close correlation with a specific decline in presynaptic proteins. There are no fibrillar plaques under these conditions indicating that plaques are not needed for synaptic disruption. Beta secretase inhibitor treatment completely abolished the accumulation of Aβ1–42 in the medium but surprisingly this did not rescue synaptophysin levels, even when continually present from before synaptophysin declines. This raises the question of whether BACE1-independent APP products underlie some synaptic defects and provides an effective experimental system to test this. Interestingly, genetic deletion of tau does rescue the loss of synaptophysin, opening lines of investigation for potential therapeutics. Organotypic brain slices from TgCRND8 mice represent an important new system for understanding mechanisms of presynaptic disruption induced by the presence of mutant huAPP. The pathology observed in these cultures will allow for rapid assessment of disease modifying compounds in a system amenable to manipulation and observation. Future work will involve examination of the mechanisms resulting in synaptophysin depletion, particularly in relation to the involvement of tau and alternative APP processing products.