Amyloid-ß peptide signature associated with cerebral amyloid angiopathy in familial Alzheimer's disease with APPdup and Down syndrome.

Alzheimer's disease (AD) is characterized by extracellular amyloid plaques containing amyloid-ß (Aß) peptides, intraneuronal neurofibrillary tangles, extracellular neuropil threads, and dystrophic neurites surrounding plaques composed of hyperphosphorylated tau protein (pTau). Aß can also deposit in blood vessel walls leading to cerebral amyloid angiopathy (CAA). While amyloid plaques in AD brains are constant, CAA varies among cases. The study focuses on differences observed between rare and poorly studied patient groups with APP duplications (APPdup) and Down syndrome (DS) reported to have higher frequencies of elevated CAA levels in comparison to sporadic AD (sAD), most of APP mutations, and controls. We compared Aß and tau pathologies in postmortem brain tissues across cases and Aß peptides using mass spectrometry (MS). We further characterized the spatial distribution of Aß peptides with MS-brain imaging. While intraparenchymal Aß deposits were numerous in sAD, DS with AD (DS-AD) and AD with APP mutations, these were less abundant in APPdup. On the contrary, Aß deposits in the blood vessels were abundant in APPdup and DS-AD while only APPdup cases displayed high Aß deposits in capillaries. Investigation of Aß peptide profiles showed a specific increase in Aßx-37, Aßx-38 and Aßx-40 but not Aßx-42 in APPdup cases and to a lower extent in DS-AD cases. Interestingly, N-truncated Aß2-x peptides were particularly increased in APPdup compared to all other groups. This result was confirmed by MS-imaging of leptomeningeal and parenchymal vessels from an APPdup case, suggesting that CAA is associated with accumulation of shorter Aß peptides truncated both at N- and C-termini in blood vessels. Altogether, this study identified striking differences in the localization and composition of Aß deposits between AD cases, particularly APPdup and DS-AD, both carrying three genomic copies of the APP gene. Detection of specific Aß peptides in CSF or plasma of these patients could improve the diagnosis of CAA and their inclusion in anti-amyloid immunotherapy treatments.

Quantum dots-based "chemical tongue" for the discrimination of short-length Aß peptides.

A "chemical tongue" is proposed based on thiomalic acid-capped quantum dots (QDs) with signal enrichment provided by excitation-emission matrix (EEM) fluorescence spectroscopy for the determination of close structural analogs-short-length amyloid ß (Aß) peptides related to Alzheimer's disease. Excellent discrimination is obtained by principal component analysis (PCA) for seven derivatives: Aß1-16, Aß4-16, Aß4-9, Aß5-16, Aß5-12, Aß5-9, Aß12-16. Detection of Aß4-16, Aß4-16, and Aß5-9 in binary and ternary mixtures performed by QDs-based chemical tongue using partial least squares-discriminant analysis (PLS-DA) provided perfect 100% accuracy for the two studied peptides (Aß4-16 and Aß4-16), while for the third one (Aß5-9) it was slightly lower (97.9%). Successful detection of Aß4-16 at 1 pmol/mL (1.6 ng/mL) suggests that the detection limit of the proposed method for short-length Aß peptides can span nanomolar concentrations. This result is highly promising for the development of simple and efficient methods for sequence recognition in short-length peptides and better understanding of mechanisms at the QD-analyte interface.

Mass spectrometric studies of the variety of beta-amyloid proteoforms in Alzheimer's disease.

This review covers the results of the application of mass spectrometric (MS) techniques to study the diversity of beta-amyloid (Aß) peptides in human samples. Since Aß is an important hallmark of Alzheimer's disease (AD), which is a socially significant neurodegenerative disorder of the elderly worldwide, analysis of its endogenous variations is of particular importance for elucidating the pathogenesis of AD, predicting increased risks of the disease onset, and developing effective therapy. MS approaches have no alternative for the study of complex samples, including a wide variety of Aß proteoforms, differing in length and modifications. Approaches based on matrix-assisted laser desorption/ionization time-of-flight and liquid chromatography with electrospray ionization tandem MS are most common in Aß studies. However, Aß forms with isomerized and/or racemized Asp and Ser residues require the use of special methods for separation and extra sensitive and selective methods for detection. Overall, this review summarizes current knowledge of Aß species found in human brain, cerebrospinal fluid, and blood plasma; focuses on application of different MS approaches for Aß studies; and considers the potential of MS techniques for further studies of Aß-peptides.

Titanium dioxide and carbon black nanoparticles disrupt neuronal homeostasis via excessive activation of cellular prion protein signaling.

BACKGROUND: Epidemiological emerging evidence shows that human exposure to some nanosized materials present in the environment would contribute to the onset and/or progression of Alzheimer's disease (AD). The cellular and molecular mechanisms whereby nanoparticles would exert some adverse effects towards neurons and take part in AD pathology are nevertheless unknown. RESULTS: Here, we provide the prime evidence that titanium dioxide (TiO2) and carbon black (CB) nanoparticles (NPs) bind the cellular form of the prion protein (PrPC), a plasma membrane protein well known for its implication in prion diseases and prion-like diseases, such as AD. The interaction between TiO2- or CB-NPs and PrPC at the surface of neuronal cells grown in culture corrupts PrPC signaling function. This triggers PrPC-dependent activation of NADPH oxidase and subsequent production of reactive oxygen species (ROS) that alters redox equilibrium. Through PrPC interaction, NPs also promote the activation of 3-phosphoinositide-dependent kinase 1 (PDK1), which in turn provokes the internalization of the neuroprotective TACE α-secretase. This diverts TACE cleavage activity away from (i) TNFα receptors (TNFR), whose accumulation at the plasma membrane augments the vulnerability of NP-exposed neuronal cells to TNFα -associated inflammation, and (ii) the amyloid precursor protein APP, leading to overproduction of neurotoxic amyloid Aß40/42 peptides. The silencing of PrPC or the pharmacological inhibition of PDK1 protects neuronal cells from TiO2- and CB-NPs effects regarding ROS production, TNFα hypersensitivity, and Aß rise. Finally, we show that dysregulation of the PrPC-PDK1-TACE pathway likely occurs in the brain of mice injected with TiO2-NPs by the intra-cerebro-ventricular route as we monitor a rise of TNFR at the cell surface of several groups of neurons located in distinct brain areas. CONCLUSION: Our in vitro and in vivo study thus posits for the first time normal cellular prion protein PrPC as being a neuronal receptor of TiO2- and CB-NPs and identifies PrPC-coupled signaling pathways by which those nanoparticles alter redox equilibrium, augment the intrinsic sensitivity of neurons to neuroinflammation, and provoke a rise of Aß peptides. By identifying signaling cascades dysregulated by TiO2- and CB-NPs in neurons, our data shed light on how human exposure to some NPs might be related to AD.

Endogenous Aß peptide promote Aß oligomerization tendency of spiked synthetic Aß in Alzheimer's disease plasma.

Alzheimer's disease (AD) is the most common form of age-associated dementia. Several studies have predicted that AD is caused by the production and deposition of the ß-amyloid peptide (Aß) in the brain, which is one of pathologic hallmarks of AD. In particular, Aß oligomers are reportedly the most toxic and pathogenic of other peptide forms. We previously developed Multimer Detection System-Oligomeric Amyloid-ß (MDS-OAß), a technique for measuring Aß oligomerization in plasma to diagnose AD. Here, we clarified the molecular sizes of oligomers that can be detected by the MDS and investigated differences in plasma spiking with a synthetic Aß peptide in the plasma of AD patients and individuals with non-AD neurological conditions. To determine Aß oligomer sizes detectable by MDS, size exclusion chromatography (SEC) was first performed on incubated samples of synthetic Aß42 peptides. As a result, no MDS signals were observed for the Aß42 monomer fractions, but strong signals were found for oligomers of 7-35-mers long. Also, an amplified luminescent proximity homogeneous assay-linked immunoassay (AlphaLISA) was used to confirm that synthetic Aß peptides not only recruited endogenous Aß in plasma but also induced significantly stronger seeding in AD plasma than in healthy control plasma. In addition, the absence of the MDS signals in Aß-depleted plasma confirmed that the increased oligomerization tendency in AD plasma is dependent on the presence of endogenous Aß in plasma. Therefore, the MDS-OAß measurement of oligomerization differences in plasma after incubation with spiked synthetic Aß peptides has significant potential in AD diagnosis.

Study on the relationships between molecular weights of chondroitin sulfate oligosaccharides and Aß-induced oxidative stress and the related mechanisms.

In the present study, we studied anti-Alzheimer's disease (AD) activities of chondroitin sulfate (CS) oligosaccharides with different molecular weights. CS from shark cartilage was degraded by a recombinant CS endolyase, chondroitinase ABC I (CHSase ABC I), and CS disaccharide (DP2), tetrasaccharide (DP4), hexasaccharide (DP6), octasaccharide (DP8), decasaccharide (DP10) and dodecasaccharide (DP12) were obtained by separation with gel filtration. Anti-AD activities of CS oligosaccharides were assessed using Aß-injured SH-SY5Y cells and BV2 cells. It was shown that CS oligosaccharides could block Aß-induced oxidative stress, mitochondrial dysfunction and activation of intrinsic apoptotic pathway for SH-SY5Y cells. Furthermore, these activities increased with the increase of molecular weights. For Aß-injured BV2 cells, CS oligosaccharides inhibited oxidative stress, the production of proinflammatory cytokines and the activation of toll-like receptor pathway, and CS DP2 had the best activity among them. In conclusion, CS oligosaccharides suppressed Aß-induced oxidative stress and relevant injury in vitro, and these effects had different relationships with the molecular weights of CS oligosaccharides for different cell lines, which might be caused by different mechanisms.

Abelson Kinases Mediate the Depression of Spontaneous Synaptic Activity Induced by Amyloid Beta 1-42 Peptides.

Amyloid beta (Aß) peptides represent one of the most studied etiological factors of Alzheimer's disease. Nevertheless, the effects elicited by different molecular forms of amyloid beta peptides widely vary between the studies, mostly depending on experimental conditions. Despite the enormous amount of accumulated evidences concerning the pathological effects of amyloid beta peptides, the exact identity of the amyloid beta species is still controversial, and even less is clear as regards to the downstream effectors that mediate the devastating impact of these peptides on synapses in the central nervous system. Recent publications indicate that some of the neurotoxic effects of amyloid beta peptides may be mediated via the activation of proteins belonging to the Abelson non-receptor tyrosine kinase (Abl) family, that are known to regulate actin cytoskeleton structure as well as phosphorylate microtubule-associated tau protein, a hallmark of Alzheimer's disease. By performing series of miniature excitatory postsynaptic currents (mEPSC) recordings in cultured hippocampal cells, we demonstrate that activation of Abl kinases by acute application of 42 amino acid-length monomeric amyloid beta (Aß1-42) peptides reduces spontaneous synaptic release, while this effect can be rescued by pharmacologic inhibition of Abl kinase activity, or by reduction of Abl expression with small interfering RNAs. Our electrophysiological data are further reinforced by a subsequent biochemical analysis, showing enhanced phosphorylation of Abl kinase substrate CT10 Regulator of Kinase-homolog-Like (Crkl) upon treatment of hippocampal neurons with Aß peptides. Thus, we conclude that Abl kinase activation may be involved in Aß-induced weakening of synaptic transmission.

Role of ABCA7 in Human Health and in Alzheimer's Disease.

Several studies, including genome wide association studies (GWAS), have strongly suggested a central role for the ATP-binding cassette transporter subfamily A member 7 (ABCA7) in Alzheimer's disease (AD). This ABC transporter is now considered as an important genetic determinant for late onset Alzheimer disease (LOAD) by regulating several molecular processes such as cholesterol metabolism and amyloid processing and clearance. In this review we shed light on these new functions and their cross-talk, explaining its implication in brain functioning, and therefore in AD onset and development.

Sleep deprivation regulates availability of PrPC and Aß peptides which can impair interaction between PrPC and laminin and neuronal plasticity.

PrPC is a glycoprotein capable to interact with several molecules and mediates diverse signaling pathways. Among numerous ligands, laminin (LN) is known to promote neurite outgrowth and memory consolidation, while amyloid-beta oligomers (Aßo) trigger synaptic dysfunction. In both pathways, mGluR1 is recruited as co-receptor. The involvement of PrPC /mGluR1 in these opposite functions suggests that this complex is a key element in the regulation of synaptic activity. Considering that sleep-wake cycle is important for synaptic homeostasis, we aimed to investigate how sleep deprivation affects the expression of PrPC and its ligands, laminin, Aßo, and mGluR1, a multicomplex that can interfere with neuronal plasticity. To address this question, hippocampi of control (CT) and sleep deprived (SD) C57BL/6 mice were collected at two time points of circadian period (13 hr and 21 hr). We observed that sleep deprivation reduced PrPC and mGluR1 levels with higher effect in active state (21 hr). Sleep deprivation also caused accumulation of Aß peptides in rest period (13 hr), while laminin levels were not affected. In vitro binding assay showed that Aßo can compete with LN for PrPC binding. The influence of Aßo was also observed in neuritogenesis. LN alone promoted longer neurite outgrowth than non-treated cells in both Prnp+/+ and Prnp0/0 genotypes. Aßo alone did not show any effects, but when added together with LN, it attenuated the effects of LN only in Prnp+/+ cells. Altogether, our findings indicate that sleep deprivation regulates the availability of PrPC and Aß peptides, and based on our in vitro assays, these alterations induced by sleep deprivation can negatively affect LN-PrPC interaction, which is known to play roles in neuronal plasticity.

Ion channel formation by N-terminally truncated Aß (4-42): relevance for the pathogenesis of Alzheimer's disease.

Aß deposition is a pathological hallmark of Alzheimer's disease (AD). Besides the full-length amyloid forming peptides (Aß1-40 and Aß1-42), biochemical analyses of brain deposits have identified a variety of N- and C-terminally truncated Aß variants in sporadic and familial AD patients. However, their relevance for AD pathogenesis remains largely understudied. We demonstrate that Aß4-42 exhibits a high tendency to form ß-sheet structures leading to fast self-aggregation and formation of oligomeric assemblies. Atomic force microscopy and electrophysiological studies reveal that Aß4-42 forms highly stable ion channels in lipid membranes. These channels that are blocked by monoclonal antibodies specifically recognizing the N-terminus of Aß4-42. An Aß variant with a double truncation at phenylalanine-4 and leucine 34, (Aß4-34), exhibits unstable channel formation capability. Taken together the results presented herein highlight the potential benefit of C-terminal proteolytic cleavage and further support an important pathogenic role for N-truncated Aß species in AD pathophysiology.

Analysis of 138 pathogenic mutations in presenilin-1 on the in vitro production of Aß42 and Aß40 peptides by γ-secretase.

A hallmark of Alzheimer's disease (AD) is the aggregation of ß-amyloid peptides (Aß) into amyloid plaques in patient brain. Cleavage of amyloid precursor protein (APP) by the intramembrane protease γ-secretase produces Aß of varying lengths, of which longer peptides such as Aß42 are thought to be more harmful. Increased ratios of longer Aßs over shorter ones, exemplified by the ratio of Aß42 over Aß40, may lead to formation of amyloid plaques and consequent development of AD. In this study, we analyzed 138 reported mutations in human presenilin-1 (PS1) by individually reconstituting the mutant PS1 proteins into anterior-pharynx-defective protein 1 (APH-1)aL-containing γ-secretases and examining their abilities to produce Aß42 and Aß40 in vitro. About 90% of these mutations lead to reduced production of Aß42 and Aß40. Notably, 10% of these mutations result in decreased Aß42/Aß40 ratios. There is no statistically significant correlation between the Aß42/Aß40 ratio produced by a γ-secretase variant containing a specific PS1 mutation and the mean age at onset of patients from whom the mutation was isolated.

The metalloprotease ADAMTS4 generates N-truncated Aß4-x species and marks oligodendrocytes as a source of amyloidogenic peptides in Alzheimer's disease.

Brain accumulation and aggregation of amyloid-ß (Aß) peptides is a critical step in the pathogenesis of Alzheimer's disease (AD). Full-length Aß peptides (mainly Aß1-40 and Aß1-42) are produced through sequential proteolytic cleavage of the amyloid precursor protein (APP) by ß- and γ-secretases. However, studies of autopsy brain samples from AD patients have demonstrated that a large fraction of insoluble Aß peptides are truncated at the N-terminus, with Aß4-x peptides being particularly abundant. Aß4-x peptides are highly aggregation prone, but their origin and any proteases involved in their generation are unknown. We have identified a recognition site for the secreted metalloprotease ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs 4) in the Aß peptide sequence, which facilitates Aß4-x peptide generation. Inducible overexpression of ADAMTS4 in HEK293 cells resulted in the secretion of Aß4-40 but unchanged levels of Aß1-x peptides. In the 5xFAD mouse model of amyloidosis, Aß4-x peptides were present not only in amyloid plaque cores and vessel walls, but also in white matter structures co-localized with axonal APP. In the ADAMTS4-/- knockout background, Aß4-40 levels were reduced confirming a pivotal role of ADAMTS4 in vivo. Surprisingly, in the adult murine brain, ADAMTS4 was exclusively expressed in oligodendrocytes. Cultured oligodendrocytes secreted a variety of Aß species, but Aß4-40 peptides were absent in cultures derived from ADAMTS4-/- mice indicating that the enzyme was essential for Aß4-x production in this cell type. These findings establish an enzymatic mechanism for the generation of Aß4-x peptides. They further identify oligodendrocytes as a source of these highly amyloidogenic Aß peptides.

N-Terminally Truncated Amyloid-ß(11-40/42) Cofibrillizes with its Full-Length Counterpart: Implications for Alzheimer's Disease.

Amyloid-ß peptide (Aß) isoforms of different lengths and aggregation propensities coexist in vivo. These different isoforms are able to nucleate or frustrate the assembly of each other. N-terminally truncated Aß(11-40) and Aß(11-42) make up one fifth of plaque load yet nothing is known about their interaction with full-length Aß(1-40/42) . We show that in contrast to C-terminally truncated isoforms, which do not co-fibrillize, deletions of ten residues from the N terminus of Aß have little impact on its ability to co-fibrillize with the full-length counterpart. As a consequence, N-terminally truncated Aß will accelerate fiber formation and co-assemble into short rod-shaped fibers with its full-length Aß counterpart. This has implications for the assembly kinetics, morphology, and toxicity of all Aß isoforms.

The Na+/K+-ATPase and the amyloid-beta peptide aß1-40 control the cellular distribution, abundance and activity of TRPC6 channels.

The Na(+)/K(+)-ATPase interacts with the non-selective cation channels TRPC6 but the functional consequences of this association are unknown. Experiments performed with HEK cells over-expressing TRPC6 channels showed that inhibiting the activity of the Na(+)/K(+)-ATPase with ouabain reduced the amount of TRPC6 proteins and depressed Ca(2+) entry through TRPC6. This effect, not mimicked by membrane depolarization with KCl, was abolished by sucrose and bafilomycin-A, and was partially sensitive to the intracellular Ca(2+) chelator BAPTA/AM. Biotinylation and subcellular fractionation experiments showed that ouabain caused a multifaceted redistribution of TRPC6 to the plasma membrane and to an endo/lysosomal compartment where they were degraded. The amyloid beta peptide Aß(1-40), another inhibitor of the Na(+)/K(+)-ATPase, but not the shorter peptide Aß1-16, reduced TRPC6 protein levels and depressed TRPC6-mediated responses. In cortical neurons from embryonic mice, ouabain, veratridine (an opener of voltage-gated Na(+) channel), and Aß(1-40) reduced TRPC6-mediated Ca(2+) responses whereas Aß(1-16) was ineffective. Furthermore, when Aß(1-40) was co-added together with zinc acetate it could no longer control TRPC6 activity. Altogether, this work shows the existence of a functional coupling between the Na(+)/K(+)-ATPase and TRPC6. It also suggests that the abundance, distribution and activity of TRPC6 can be regulated by cardiotonic steroids like ouabain and the naturally occurring peptide Aß(1-40) which underlines the pathophysiological significance of these processes.

Copper-Aß Peptides and Oxidation of Catecholic Substrates: Reactivity and Endogenous Peptide Damage.

The oxidative reactivity of copper complexes with Aß peptides 1-16 and 1-28 (Aß16 and Aß28) against dopamine and related catechols under physiological conditions has been investigated in parallel with the competitive oxidative modification undergone by the peptides. It was found that both Aß16 and Aß28 markedly increase the oxidative reactivity of copper(II) towards the catechol compounds, up to a molar ratio of about 4:1 of peptide/copper(II). Copper redox cycling during the catalytic activity induces the competitive modification of the peptide at selected amino acid residues. The main modifications consist of oxidation of His13/14 to 2-oxohistidine and Phe19/20 to ortho-tyrosine, and the formation of a covalent His6-catechol adduct. Competition by the endogenous peptide is rather efficient, as approximately one peptide molecule is oxidized every 10 molecules of 4-methylcatechol.

Development of 2-aminooxazoline 3-azaxanthenes as orally efficacious ß-secretase inhibitors for the potential treatment of Alzheimer's disease.

The ß-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is one of the most hotly pursued targets for the treatment of Alzheimer's disease. We used a structure- and property-based drug design approach to identify 2-aminooxazoline 3-azaxanthenes as potent BACE1 inhibitors which significantly reduced CSF and brain Aß levels in a rat pharmacodynamic model. Compared to the initial lead 2, compound 28 exhibited reduced potential for QTc prolongation in a non-human primate cardiovascular safety model.

Plasma amyloid-ß and risk of Alzheimer's disease in the Framingham Heart Study.

BACKGROUND: Plasma amyloid-ß (Aß) peptide levels have been examined as a low-cost accessible marker for risk of incident Alzheimer's disease (AD) and dementia, but results have varied between studies. We reassessed these associations in one of the largest, prospective, community-based studies to date. METHODS: A total of 2189 dementia-free, Framingham Study participants aged >60 years (mean age, 72 ± 8 years; 56% women) had plasma Aß1-42 and Aß1-40 measured and were followed prospectively (mean, 7.6 ± 3.0 years) for dementia/AD. RESULTS: Increased plasma Aß1-42 levels were associated with lower risk of dementia (Aß1-42: hazard ratio [HR] = 0.80 [0.71‒0.90], P < .001; Aß1-42-to-Aß1-40 ratio: HR = 0.86 [0.76‒0.98], P = .027) and AD (Aß1-42: HR = 0.79 [0.69‒0.90], P < .001; Aß1-42-to-Aß1-40 ratio: HR = 0.83 [0.72‒0.96], P = .012). CONCLUSION: Our results suggest that lower plasma Aß levels are associated with risk of incident AD and dementia. They encourage further evaluation of plasma Aß levels as a biomarker for risk of developing clinical AD and dementia.

Calcium-sensing receptor antagonist (calcilytic) NPS 2143 specifically blocks the increased secretion of endogenous Aß42 prompted by exogenous fibrillary or soluble Aß25-35 in human cortical astrocytes and neurons-therapeutic relevance to Alzheimer's disease.

The "amyloid-ß (Aß) hypothesis" posits that accumulating Aß peptides (Aßs) produced by neurons cause Alzheimer's disease (AD). However, the Aßs contribution by the more numerous astrocytes remains undetermined. Previously we showed that fibrillar (f)Aß25-35, an Aß42 proxy, evokes a surplus endogenous Aß42 production/accumulation in cortical adult human astrocytes. Here, by using immunocytochemistry, immunoblotting, enzymatic assays, and highly sensitive sandwich ELISA kits, we investigated the effects of fAß25-35 and soluble (s)Aß25-35 on Aß42 and Aß40 accumulation/secretion by human cortical astrocytes and HCN-1A neurons and, since the calcium-sensing receptor (CaSR) binds Aßs, their modulation by NPS 2143, a CaSR allosteric antagonist (calcilytic). The fAß25-35-exposed astrocytes and surviving neurons produced, accumulated, and secreted increased amounts of Aß42, while Aß40 also accrued but its secretion was unchanged. Accordingly, secreted Aß42/Aß40 ratio values rose for astrocytes and neurons. While slightly enhancing Aß40 secretion by fAß25-35-treated astrocytes, NPS 2143 specifically suppressed the fAß25-35-elicited surges of endogenous Aß42 secretion by astrocytes and neurons. Therefore, NPS 2143 addition always kept Aß42/Aß40 values to baseline or lower levels. Mechanistically, NPS 2143 decreased total CaSR protein complement, transiently raised proteasomal chymotrypsin activity, and blocked excess NO production without affecting the ongoing increases in BACE1/ß-secretase and γ-secretase activity in fAß25-35-treated astrocytes. Compared to fAß25-35, sAß25-35 also stimulated Aß42 secretion by astrocytes and neurons and NPS 2143 specifically and wholly suppressed this effect. Therefore, since NPS 2143 thwarts any Aß/CaSR-induced surplus secretion of endogenous Aß42 and hence further vicious cycles of Aß self-induction/secretion/spreading, calcilytics might effectively prevent/stop the progression to full-blown AD.

Unveiling the therapeutic potential of Lobaria extract and its depsides/depsidones in combatting Aß42 peptides aggregation and neurotoxicity in Alzheimer's disease.

Background: The development of effective inhibitors that can inhibit amyloid ß (Aß) peptides aggregation and promote neurite outgrowth is crucial for the possible treatment of Alzheimer's disease (AD). Lobaria (Schreb.) Hoffm., a traditional Chinese medicine used in Himalaya region for inflammatory diseases, contains depsides/depsidones (DEPs) such as gyrophoric acid, norstictic acid, and stictic acid known for their anti-cancer and anti-inflammation properties. Methods: Lobaria extracts were analyzed using HPLC to identify DEPs and establish standards. The inhibitory effects of Lobaria on Aß42 fibrillization and depolymerization were assessed using various approaches with biophysical and cellular methods. The neuroprotective activity of Lobaria extracts and its DEPs aganist Aß-mediated cytotoxicity was also evaluated. Results: Norstictic and stictic acid were found in the water extract, while norstictic, stictic, and gyrophoric acid were detected in the ethanol extract of Lobaria. Both extracts, and their DEPs effectively inhibited Aß42 fibrillation and disaggregate mature Aß42 fibrils. Notably, the ethanol extract showed superior inhibitory effect compared to the water extract, with gyrophoric acid being the most effective DEPs. Additionally, herbal extract-treated Aß42 aggregation species significantly protected neuronal cells from Aß42-induced cell damage and promoted neurite outgrowth. Conclusion: This study is the first to investigate the effect of Lobaria on Aß42 and neuronal cell in AD. Given that Lobaria is commonly used in ethnic medicine and food with good safety records, our findings propose that Lobaria extracts and DEPs have potential as neuroprotective and therapeutic agents for AD patients.

Navigating the Maze of Alzheimer's disease by exploring BACE1: Discovery, current scenario, and future prospects.

Alzheimer's disease (AD) is a chronic neurological condition that has become a leading cause of cognitive decline in elder individuals. Hardly any effective medication has been developed to halt the progression of AD due to the disease's complexity. Several theories have been put forward to clarify the mechanisms underlying AD etiology. The identification of amyloid plaques as a hallmark of AD has sparked the development of numerous drugs targeting the players involved in the amyloidogenic pathway, such as the ß-site of amyloid precursor protein cleavage enzyme 1 (BACE1) blockers. Over the last ten years, preclinical and early experimental research has led several pharmaceutical companies to prioritize producing BACE1 inhibitors. Despite all these efforts, earlier discovered inhibitors were discontinued in consideration of another second-generation small molecules and recent BACE1 antagonists failed in the final stages of clinical trials because of the complications associated either with toxicity or effectiveness. In addition to discussing the difficulties associated with development of BACE1 inhibitors, this review aims to provide an overview of BACE1 and offer perspectives on the causes behind the failure of five recent BACE1 inhibitors, that would be beneficial for choosing effective treatment approaches in the future.