Beta Amyloid Hallmarks: From Intrinsically Disordered Proteins to Alzheimer’s Disease

Faster Amylin Aggregation on Fibrillar Collagen I Hastens Diabetic Progression through β-Cell Death and Loss of Function

Amyloid deposition of the neuroendocrine peptide amylin in islet tissues is a hallmark of type 2 diabetes (T2DM), leading to β-cell toxicity through nutrient deprivation, membrane rupture, and apoptosis. Though accumulation of toxic amylin aggregates in islet matrices is well documented, the role of the islet extracellular matrix in mediating amylin aggregation and its pathological consequences remains elusive. Here, we address this question by probing amylin interaction with collagen I (Col)─whose expression in the islet tissue increases during diabetes progression. By combining multiple biophysical techniques, we show that hydrophobic, hydrophilic, and cation-π interactions regulate amylin binding to Col, with fibrillar Col driving faster amylin aggregation. Amylin-entangled Col matrices containing high amounts of amylin induce death and loss of function in INS1E β-cells. Together, our results illustrate how amylin incorporation in islet matrices through amylin-Col interactions drives T2DM progression by impacting β-cell viability and insulin secretion.

From Plant to Pathway: Molecular Mechanisms of Ruscogenin in Preventing Amyloid-Beta Aggregation through Computational and Experimental Approaches

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, extracellular amyloid-β (Aβ) plaque accumulation, and intracellular neurofibrillary tangles. Recent efforts to find effective therapies have increased interest in natural compounds with multifaceted effects on AD pathology. This study explores natural compounds for their potential to mitigate AD pathology using molecular docking, ADME screening, and in vitro assays, with ruscogenin─a steroidal sapogenin from Ruscus aculeatus─emerging as a promising candidate. Ruscogenin, known for its antioxidant and anti-inflammatory properties, was investigated for its effects on Aβ aggregation, a critical process in AD progression. In vitro assays demonstrated that ruscogenin inhibits Aβ oligomerization at equimolar and higher molar ratios. Molecular dynamics (MD) simulations further revealed that ruscogenin targets aggregation-prone regions, reducing noncovalent interactions and the solvent-accessible surface area of Aβ aggregates. These effects were concentration-dependent, with higher concentrations yielding optimal inhibition, pointing to a multiphasic behavior in ruscogenin's modulation of Aβ aggregation. This study highlights ruscogenin's potential as a natural therapeutic agent for AD, capable of addressing both oxidative stress and inflammation. The findings lay the groundwork for further exploration of ruscogenin-based interventions and underscore the broader potential of natural compounds in AD treatment strategies.

Survey of the Aβ-peptide structural diversity: molecular dynamics approaches

The review deals with the application of Molecular Dynamics (MD) to the structure modeling of beta-amyloids (Aβ), currently classified as intrinsically disordered proteins (IDPs). In this review, we strive to relate the main advances in this area but specifically focus on the approaches and methodology. All relevant papers on the Aβ modeling are cited in the Tables in Supplementary Data, including a concise description of the applied approaches, sorted according to the types of the studied systems: modeling of the monomeric Aβ and Aβ aggregates. Similar sections focused according to the type of modeled object are present in the review. In the final part of the review, novel methods of general IDP modeling not confined to Aβ are described.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-024-01253-y.

Streamlining NMR Chemical Shift Predictions for Intrinsically Disordered Proteins: Design of Ensembles with Dimensionality Reduction and Clustering

By merging advanced dimensionality reduction (DR) and clustering algorithm (CA) techniques, our study advances the sampling procedure for predicting NMR chemical shifts (CS) in intrinsically disordered proteins (IDPs), making a significant leap forward in the field of protein analysis/modeling. We enhance NMR CS sampling by generating clustered ensembles that accurately reflect the different properties and phenomena encapsulated by the IDP trajectories. This investigation critically assessed different rapid CS predictors, both neural network (e.g., Sparta+ and ShiftX2) and database-driven (ProCS-15), and highlighted the need for more advanced quantum calculations and the subsequent need for more tractable-sized conformational ensembles. Although neural network CS predictors outperformed ProCS-15 for all atoms, all tools showed poor agreement with HN CSs, and the neural network CS predictors were unable to capture the influence of phosphorylated residues, highly relevant for IDPs. This study also addressed the limitations of using direct clustering with collective variables, such as the widespread implementation of the GROMOS algorithm. Clustered ensembles (CEs) produced by this algorithm showed poor performance with chemical shifts compared to sequential ensembles (SEs) of similar size. Instead, we implement a multiscale DR and CA approach and explore the challenges and limitations of applying these algorithms to obtain more robust and tractable CEs. The novel feature of this investigation is the use of solvent-accessible surface area (SASA) as one of the fingerprints for DR alongside previously investigated α carbon distance/angles or ϕ/ψ dihedral angles. The ensembles produced with SASA tSNE DR produced CEs better aligned with the experimental CS of between 0.17 and 0.36 r2 (0.18-0.26 ppm) depending on the system and replicate. Furthermore, this technique produced CEs with better agreement than traditional SEs in 85.7% of all ensemble sizes. This study investigates the quality of ensembles produced based on different input features, comparing latent spaces produced by linear vs nonlinear DR techniques and a novel integrated silhouette score scanning protocol for tSNE DR.

Structure Comparison of Beta Amyloid Peptide Aβ 1-42 Isoforms. Molecular Dynamics Modeling

Beta amyloid peptide Aβ 1-42 (Aβ42) has a unique dual role in the human organism, as both the peptide with an important physiological function and one of the most toxic biological compounds provoking Alzheimer's disease (AD). There are several known Aβ42 isoforms that we discuss here that are highly neurotoxic and lead to the early onset of AD. Aβ42 is an intrinsically disordered protein with no experimentally solved structure under physiological conditions. The objective of this research was to establish the appropriate molecular dynamics (MD) methodology and model a uniform set of structures for the Aβ42 isoforms that form the core of this study. For that purpose, force field selection and verification including convergence testing for MD simulations was made. Replica exchange MD and conventional MD modeling of several Aβ42 and Aβ16 isoforms that have neurotoxic and amyloidogenic effects impacting the severity of Alzheimer's disease were carried out with the optimal force field and solvent parameters. A standardized ensemble of structures for the Aβ42 and Aβ16 isoforms covering 30-50% of the conformational ensembles extracted from the free energy minima was calculated from MD trajectories. The resulting data set of modeled structures includes Aβ42 wild type, isoD7, pS8, D7H, and H6R-Aβ42 and Aβ16 wild type, isoD7, pS8, D7H, and H6R-Aβ16. The representative structures are given in the Supporting Information; they are open for public access. In the study, we also evaluated the differences between the structures of Aβ42 isoforms and speculate on their possible relevance to the known functions. Utilizing several representative structures for a single disordered protein for docking, with their subsequent averaging by conformations, would markedly increase the reliability of docking results.

Computational screening for new neuroprotective ingredients against Alzheimer's disease from bilberry by cheminformatics approaches

Bioactive ingredients from natural products have always been an important resource for the discovery of drugs for Alzheimer's disease (AD). Senile plaques, which are formed with amyloid-beta (Aβ) peptides and excess metal ions, are found in AD brains and have been suggested to play an important role in AD pathogenesis. Here, we attempted to design an effective and smart screening method based on cheminformatics approaches to find new ingredients against AD from Vaccinium myrtillus (bilberry) and verified the bioactivity of expected ingredients through experiments. This method integrated advanced artificial intelligence models and target prediction methods to realize the stepwise analysis and filtering of all ingredients. Finally, we obtained the expected new compound malvidin-3-O-galactoside (Ma-3-gal-Cl). The in vitro experiments showed that Ma-3-gal-Cl could reduce the OH· generation and intracellular ROS from the Aβ/Cu²⁺/AA mixture and maintain the mitochondrial membrane potential of SH-SY5Y cells. Molecular docking and Western blot results indicated that Ma-3-gal-Cl could reduce the amount of activated caspase-3 via binding with unactivated caspase-3 and reduce the expression of phosphorylated p38 via binding with mitogen-activated protein kinase kinases-6 (MKK6). Moreover, Ma-3-gal-Cl could inhibit the Aβ aggregation via binding with Aβ monomer and fibers. Thus, Ma-3-gal-Cl showed significant effects on protecting SH-SY5Y cells from Aβ/Cu²⁺/AA induced damage via antioxidation effect and inhibition effect to the Aβ aggregation.

On the Dependence of Prion and Amyloid Structure on the Folding Environment

Currently available analyses of amyloid proteins reveal the necessity of the existence of radical structural changes in amyloid transformation processes. The analysis carried out in this paper based on the model called fuzzy oil drop (FOD) and its modified form (FOD-M) allows quantifying the role of the environment, particularly including the aquatic environment. The starting point and basis for the present presentation is the statement about the presence of two fundamentally different methods of organizing polypeptides into ordered conformations—globular proteins and amyloids. The present study shows the source of the differences between these two paths resulting from the specificity of the external force field coming from the environment, including the aquatic and hydrophobic one. The water environment expressed in the fuzzy oil drop model using the 3D Gauss function directs the folding process towards the construction of a micelle-like system with a hydrophobic core in the central part and the exposure of polarity on the surface. The hydrophobicity distribution of membrane proteins has the opposite characteristic: Exposure of hydrophobicity at the surface of the membrane protein with an often polar center (as in the case of ion channels) is expected. The structure of most proteins is influenced by a more or less modified force field generated by water through the appropriate presence of a non-polar (membrane-like) environment. The determination of the proportion of a factor different from polar water enables the assessment of the protein status by indicating factors favoring the structure it represents.

Fluspirilene Analogs Activate the 20S Proteasome and Overcome Proteasome Impairment by Intrinsically Disordered Protein Oligomers

Oligomerization of aggregation-prone intrinsically disordered proteins (IDPs), such as α-synuclein, amyloid β, and tau, has been shown to be associated with the pathogenesis of several neurodegenerative diseases, including Parkinson's and Alzheimer's disease. The proteasome is charged with regulating cellular levels of IDPs, but this degradation pathway can become dysregulated leading to their accumulation and subsequent aggregation. Although the pathogenesis of these neurodegenerative diseases is still under intense investigation, it has been shown that the oligomeric forms of IDPs, including α-synuclein and amyloid β, can impair proteasome function. This leads to additional accumulation of the IDPs, further promoting disease progression. Herein, we report the use of small molecule activators of the 20S subcomplex of the proteasome to restore impaired 20S proteasome activity and prevent IDP accumulation and oligomerization. We found that fluspirilene and its new synthetic analog (16) show strong 20S proteasome enhancement (doubling 20S proteolytic activity at ∼2 μM, with maximum fold enhancement of ∼1000%), overcome impaired proteasome function, and prevent the accumulation of pathogenic IDPs. These findings provide support for the use of 20S enhancers as a possible therapeutic strategy to combat neurodegenerative diseases.

Dihydroquinazolines enhance 20S proteasome activity and induce degradation of α-synuclein, an intrinsically disordered protein associated with neurodegeneration

Aggregates or oligomeric forms of many intrinsically disordered proteins (IDPs), including α-synuclein, are hallmarks of neurodegenerative diseases, like Parkinson's and Alzheimer's disease, and key contributors to their pathogenesis. Due to their disordered nature and therefore lack of defined drug-binding pockets, IDPs are difficult targets for traditional small molecule drug design and are often referred to as "undruggable". The 20S proteasome is the main protease that targets IDPs for degradation and therefore small molecule 20S proteasome enhancement presents a novel therapeutic strategy by which these undruggable IDPs could be targeted. The concept of 20S activation is still relatively new, with few potent activators having been identified thus far. Herein, we synthesized and evaluated a library of dihydroquinazoline analogues and discovered several promising new 20S proteasome activators. Further testing of top hits revealed that they can enhance 20S mediated degradation of α-synuclein, the IDP associated with Parkinson's disease.

Collagen I Weakly Interacts with the β-Sheets of β2-Microglobulin and Enhances Conformational Exchange To Induce Amyloid Formation

Amyloidogenesis is significant in both protein function and pathology. Amyloid formation of folded, globular proteins is commonly initiated by partial or complete unfolding. However, how this unfolding event is triggered for proteins that are otherwise stable in their native environments is not well understood. The accumulation of the immunoglobulin protein β₂-microglobulin (β₂m) into amyloid plaques in the joints of long-term hemodialysis patients is the hallmark of dialysis-related amyloidosis (DRA). While β₂m does not form amyloid unassisted near neutral pH in vitro, the localization of β₂m deposits to joint spaces suggests a role for the local extracellular matrix (ECM) proteins, specifically collagens, in promoting amyloid formation. Indeed, collagen and other ECM components have been observed to facilitate β₂m amyloid formation, but the large size and anisotropy of the complex, combined with the low affinity of these interactions, have limited atomic-level elucidation of the amyloid-promoting mechanism(s) by these molecules. Using solution NMR approaches that uniquely probe weak interactions in large molecular weight complexes, we are able to map the binding interfaces on β₂m for collagen I and detect collagen I-induced μs–ms time-scale dynamics in the β₂m backbone. By combining solution NMR relaxation methods and ¹⁵N-dark-state exchange saturation transfer experiments, we propose a model in which weak, multimodal collagen I−β₂m interactions promote exchange with a minor population of amyloid-competent species to induce fibrillogenesis. The results portray the intimate role of the environment in switching an innocuous protein into an amyloid-competent state, rationalizing the localization of amyloid deposits in DRA.

Proteasome Activation to Combat Proteotoxicity

Loss of proteome fidelity leads to the accumulation of non-native protein aggregates and oxidatively damaged species: hallmarks of an aged cell. These misfolded and aggregated species are often found, and suggested to be the culpable party, in numerous neurodegenerative diseases including Huntington's, Parkinson's, Amyotrophic Lateral Sclerosis (ALS), and Alzheimer's Diseases (AD). Many strategies for therapeutic intervention in proteotoxic pathologies have been put forth; one of the most promising is bolstering the efficacy of the proteasome to restore normal proteostasis. This strategy is ideal as monomeric precursors and oxidatively damaged proteins, so called "intrinsically disordered proteins" (IDPs), are targeted by the proteasome. This review will provide an overview of disorders in proteins, both intrinsic and acquired, with a focus on susceptibility to proteasomal degradation. We will then examine the proteasome with emphasis on newly published structural data and summarize current known small molecule proteasome activators.

Interference with Amyloid-β Nucleation by Transient Ligand Interaction

Amyloid-β peptide (Aβ) is an intrinsically disordered protein (IDP) associated with Alzheimer's disease. The structural flexibility and aggregation propensity of Aβ pose major challenges for elucidating the interaction between Aβ monomers and ligands. All-D-peptides consisting solely of D-enantiomeric amino acid residues are interesting drug candidates that combine high binding specificity with high metabolic stability. Here we characterized the interaction between the 12-residue all-D-peptide D3 and Aβ42 monomers, and how the interaction influences Aβ42 aggregation. We demonstrate for the first time that D3 binds to Aβ42 monomers with submicromolar affinities. These two highly unstructured molecules are able to form complexes with 1:1 and other stoichiometries. Further, D3 at substoichiometric concentrations effectively slows down the β-sheet formation and Aβ42 fibrillation by modulating the nucleation process. The study provides new insights into the molecular mechanism of how D3 affects Aβ assemblies and contributes to our knowledge on the interaction between two IDPs.

Lipid bilayer position and orientation of novel carprofens, modulators of γ-secretase in Alzheimer's disease

γ-Secretase is an integral membrane protein complex and is involved in the cleavage of the amyloid precursor protein APP to produce amyloid-β peptides. Amyloid-β peptides are considered causative agents for Alzheimer's disease and drugs targeted at γ-secretase are investigated as therapeutic treatments. We synthesized new carprofen derivatives, which showed γ-secretase modulating activity and determined their precise position, orientation, and dynamics in lipid membranes by combining neutron diffraction, solid-state NMR spectroscopy, and molecular dynamics simulations. Our data indicate that the carprofen derivatives are inserted into the membrane interface, where the exact position and orientation depends on the lipid phase. This knowledge will help to understand the docking of carprofen derivatives to γ-secretase and in the design of new potent drugs. The approach presented here promises to serve as a general guideline how drug/target interactions in membranes can be analyzed in a comprehensive manner.

Small Molecule Modulation of Proteasome Assembly

The 20S proteasome is the main protease that directly targets intrinsically disordered proteins (IDPs) for proteolytic degradation. Mutations, oxidative stress, or aging can induce the buildup of IDPs resulting in incorrect signaling or aggregation, associated with the pathogenesis of many cancers and neurodegenerative diseases. Drugs that facilitate 20S-mediated proteolysis therefore have many potential therapeutic applications. We report herein the modulation of proteasome assembly by the small molecule TCH-165, resulting in an increase in 20S levels. The increase in the level of free 20S corresponds to enhanced proteolysis of IDPs, including α-synuclein, tau, ornithine decarboxylase, and c-Fos, but not structured proteins. Clearance of ubiquitinated protein was largely maintained by single capped proteasome complexes (19S-20S), but accumulation occurs when all 19S capped proteasome complexes are depleted. This study illustrates the first example of a small molecule capable of targeting disordered proteins for degradation by regulating the dynamic equilibrium between different proteasome complexes.

β-Ecdysterone protects SH-SY5Y cells against β-amyloid-induced apoptosis via c-Jun N-terminal kinase- and Akt-associated complementary pathways

Recently, the significantly higher incidence of Alzheimer's disease (AD) in women than in men has been attributed to the loss of neuroprotective estrogen after menopause. Does phytoestrogen have the ability to protect against amyloid-β (Aβ) toxicity? The aim of this study was to evaluate hypothesis that β-ecdysterone (β-Ecd) protects SH-SY5Y cells from Aβ-induced apoptosis by separate signaling pathways involving protein kinase B (Akt) and c-Jun N-terminal kinase (JNK). Here, we demonstrate that phytoestrogen β-Ecd inhibits Aβ-triggered mitochondrial apoptotic pathway, as indicated by Bcl-2/Bax ratio elevation, cytochrome c (cyt c) release reduction, and caspase-9 inactivation. Interestingly, β-Ecd upregulates Bcl-2 expression in SH-SY5Y cells under both basal and Aβ-challenged conditions, but downregulates Bax expression only in Aβ-challenged conditions. Subsequently, Akt-dependent NF-κB activation is required for Bcl-2 upregulation, but not Bax downregulation, in response to β-Ecd, which was validated by the use of LY294002 and Bay11-7082. Notably, β-Ecd attenuates the Aβ-evoked reactive oxygen species (ROS) production, apoptosis signal-regulating kinase 1 (ASK1) phosphorylation and JNK activation without altering the basal ASK1 phosphorylation and JNK activation. ROS-scavenging by diphenyleneiodonium (DPI) abrogated the ability of β-Ecd to alter the activation of ASK1. Simultaneously, inhibition of JNK by SP600125 abolished β-Ecd-induced Bax downregulation in Aβ-challenged SH-SY5Y cells, whereas LY294002 failed to do so. Consequently, β-Ecd possesses neuroprotection by different and complementary pathways, which together promote a Bcl-2/Bax ratio. These data support our hypothesis and suggest that β-Ecd is a promising candidate for the treatment of AD.

Aptamers Selected for Recognizing Amyloid β-Protein-A Case for Cautious Optimism

Aptamers are versatile oligonucleotide ligands used for molecular recognition of diverse targets. However, application of aptamers to the field of amyloid β-protein (Aβ) has been limited so far. Aβ is an intrinsically disordered protein that exists in a dynamic conformational equilibrium, presenting time-dependent ensembles of short-lived, metastable structures and assemblies that have been generally difficult to isolate and characterize. Moreover, despite understanding of potential physiological roles of Aβ, this peptide has been linked to the pathogenesis of Alzheimer disease, and its pathogenic roles remain controversial. Accumulated scientific evidence thus far highlights undesirable or nonspecific interactions between selected aptamers and different Aβ assemblies likely due to the metastable nature of Aβ or inherent affinity of RNA oligonucleotides to β-sheet-rich fibrillar structures of amyloidogenic proteins. Accordingly, lessons drawn from Aβ–aptamer studies emphasize that purity and uniformity of the protein target and rigorous characterization of aptamers’ specificity are important for realizing and garnering the full potential of aptamers selected for recognizing Aβ or other intrinsically disordered proteins. This review summarizes studies of aptamers selected for recognizing different Aβ assemblies and highlights controversies, difficulties, and limitations of such studies.

Structural Characterization of the Amyloid Precursor Protein Transmembrane Domain and Its γ-Cleavage Site

Alzheimer's disease is the most common form of dementia that affects about 50 million of sufferers worldwide. A major role for the initiation and progression of Alzheimer's disease has been associated with the amyloid β-peptide (Aβ), which is a protease cleavage product of the amyloid precursor protein. The amyloid precursor protein is an integral membrane protein with a single transmembrane domain. Here, we assessed the structural integrity of the transmembrane domain within oriented phosphatidylcholine lipid bilayers and determined the tilt angle distribution and dynamics of various subdomains using solid-state NMR and attenuated total reflectance Fourier transform infrared spectroscopies. Although the overall secondary structure of the transmembrane domain is α-helical, pronounced conformational and topological heterogeneities were observed for the γ- and, to a lesser extent, the ζ-cleavage site, with pronounced implications for the production of Aβ and related peptides, the development of the disease, and pharmaceutical innovation.

Trehalose induced conformational changes in the amyloid-β peptide

Alzheimer's disease is an irreversible and progressive brain disorder featured by the accumulation of Amyloid-β (Aβ) peptide, which forms insoluble assemblies that builds up into plaques resulting in cognitive decline and memory loss. The formation of fibrillar amyloid deposits is accompanied by conformational changes of the soluble Aβ peptide into β-sheet structures. Strategies to prevent or reduce Aβ aggregation using small molecules such as trehalose have shown beneficial effects under in vitro cell- and in vivo mouse- models. However, the role of trehalose in reducing Aβ peptide aggregation is still not clear. In the present study, using circular dichroism- and fluorescence emission- spectroscopies, we demonstrated that in the presence of trehalose, Aβ peptide adopts more helical content and undergoes a disorder/order conformational transition. Based on our findings, we conclude that trehalose affects the conformation of Aβ peptide to form α-helical structure, which may inhibit the formation of β-sheets and thereby aggregation.

Advantages of synchrotron radiation circular dichroism spectroscopy to study intrinsically disordered proteins

The unordered secondary structural content of an intrinsically disordered protein (IDP) is susceptible to conformational changes induced by many different external factors, such as the presence of organic solvents, removal of water, changes in temperature, binding to partner molecules, and interaction with lipids and/or other ligands. In order to characterize the high-flexibility nature of an IDP, circular dichroism (CD) spectroscopy is a particularly useful method due to its capability of monitoring both subtle and remarkable changes in different environments, relative ease in obtaining measurements, the small amount of sample required, and the capability for sample recovery (sample not damaged) and others. Using synchrotron radiation as the light source for CD spectroscopy represents the state-of-the-art version of this technique with feasibility of accessing the lower wavelength UV region, and therefore presenting a series of advantages over conventional circular dichroism (cCD) to monitor a protein conformational behavior, check protein stability, detect ligand binding, and many others. In this paper, we have performed a comparative study using cCD and SRCD methods for investigating the secondary structure and the conformational behavior of natively unfolded proteins: MEG-14 and soybean trypsin inhibitor. We show that the SRCD technique greatly improves the analysis and accuracy of the studies on the conformations of IDPs.

Aluminum, the genetic apparatus of the human CNS and Alzheimer's disease (AD)

The genomes of eukaryotes orchestrate their expression to ensure an effective, homeostatic and functional gene signaling program, and this includes fundamentally altered patterns of transcription during aging, development, differentiation and disease. These actions constitute an extremely complex and intricate process as genetic operations such as transcription involve the very rapid translocation and polymerization of ribonucleotides using RNA polymerases, accessory transcription protein complexes and other interrelated chromatin proteins and genetic factors. As both free ribonucleotides and polymerized single-stranded RNA chains, ribonucleotides are highly charged with phosphate, and this genetic system is extremely vulnerable to disruption by a large number of electrostatic forces, and primarily by cationic metals such as aluminum. Aluminum has been shown by independent researchers to be particularly genotoxic to the genetic apparatus, and it has become reasonably clear that aluminum disturbs genetic signaling programs in the CNS that bear a surprising resemblance to those observed in Alzheimer's disease (AD) brain. This paper will focus on a discussion of two molecular-genetic aspects of aluminum genotoxicity: (1) the observation that micro-RNA (miRNA)-mediated global gene expression patterns in aluminum-treated transgenic animal models of AD (Tg-AD) strongly resemble those found in AD; and (2) the concept of "human biochemical individuality" and the hypothesis that individuals with certain gene expression patterns may be especially sensitive and perhaps predisposed to aluminum genotoxicity.

Liver X receptor-β improves autism symptoms via downregulation of β-amyloid expression in cortical neurons

Background

We study the effect of liver X receptor β (LXRβ) on β-amyloid (Aβ) peptide generation and autism behaviors by conducting an animal experiment.

Methods

In autistic mice treated with LXRβ agonist T0901317, enzyme linked immunosorbent assay was used to measure Aβ in brain tissue homogenates. Western blot was used to detect Aβ precursors, Aβ degradation and secretase enzymes, and expression of autophagy-related proteins and Ras/Raf/Erkl/2 signaling pathway proteins in brain tissue. Changes in autism spectrum disorder syndromes of the BTBR mice were compared before and after T0901317 treatment.

Results

Compared with the control group, autistic mice treated with LXRβ agonist T0901317 showed significantly lower Aβ level in brain tissue (P < 0.05), significantly higher Aβ degradation enzyme (NEP, IDE proteins) levels (all P < 0.05), significantly lower Aβ secretase enzyme BACE1 protein level (P < 0.05), and significantly lower Ras, P-C-Raf, C-Raf, P-Mekl/2, P-Erkl/2 protein levels (all P < 0.05). BTBR mice treated with T0901317 showed improvements in repetitive stereotyped behavior, inactivity, wall-facing standing time, self-combing time and center stay time, stayed longer in platform quadrant, and crossed the platform more frequently (all P < 0.05).

Conclusions

LXRβ could potentially reduce brain Aβ generation by inhibiting Aβ production and promoting Aβ degradation, thereby increasing the expression of autophagy-related proteins, reducing Ras/Raf/Erkl/2 signaling pathway proteins, and improving autism behaviors.