Dysfunctional proteins in neuropsychiatric disorders: From neurodegeneration to autism spectrum disorders

Identification of proteotoxic and proteoprotective bacteria that non-specifically affect proteins associated with neurodegenerative diseases

Neurodegenerative protein conformational diseases (PCDs), such as Alzheimer's, Parkinson's, and Huntington's, are a leading cause of death and disability worldwide and have no known cures or effective treatments. Emerging evidence suggests a role for the gut microbiota in the pathogenesis of neurodegenerative PCDs; however, the influence of specific bacteria on the culprit proteins associated with each of these diseases remains elusive, primarily due to the complexity of the microbiota. In the present study, we employed a single-strain screening approach to identify human bacterial isolates that enhance or suppress the aggregation of culprit proteins and the associated toxicity in Caenorhabditis elegans expressing Aβ1-42, α-synuclein, and polyglutamine tracts. Here, we reveal the first comprehensive analysis of the human microbiome for its effect on proteins associated with neurodegenerative diseases. Our results suggest that bacteria affect the aggregation of metastable proteins by modulating host proteostasis rather than selectively targeting specific disease-associated proteins. These results reveal bacteria that potentially influence the pathogenesis of PCDs and open new promising prevention and treatment opportunities by altering the abundance of beneficial and detrimental microbes.

Calpain signaling: from biology to therapeutic opportunities in neurodegenerative disorders

Neurodegenerative disorders represent a major and growing healthcare challenge globally. Among the numerous molecular pathways implicated in their pathogenesis, calpain signaling has emerged as a crucial player in neuronal dysfunction and cell death. Calpain is a family of calcium-dependent cysteine proteases that is involved in many biological processes, such as signal transduction, cytoskeleton remodeling, and protein turnover. Dysregulation of calpain activation and activity has been associated with several neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's diseases. Understanding the intricate structure of calpains is crucial for unraveling their roles in cellular physiology and their implications in pathology. In addition, the identification of diverse abnormalities in both humans and other animal models with deficiencies in calpain highlights the significant progress made in understanding calpain biology. In this comprehensive review, we delve into the recent roles attributed to calpains and provide an overview of the mechanisms that govern their activity during the progression of neurodegenerative diseases. The possibility of utilizing calpain inhibition as a potential therapeutic approach for treating neuronal dysfunctions in neurodegenerative disorders would be an area of interest in future calpain research.

A Review on Integrated ZnO-Based SERS Biosensors and Their Potential in Detecting Biomarkers of Neurodegenerative Diseases

Surface-enhanced Raman spectroscopy (SERS) applications in clinical diagnosis and spectral pathology are increasing due to the potential of the technique to bio-barcode incipient and differential diseases via real-time monitoring of biomarkers in fluids and in real-time via biomolecular fingerprinting. Additionally, the rapid advancements in micro/nanotechnology have a visible influence in all aspects of science and life. The miniaturization and enhanced properties of materials at the micro/nanoscale transcended the confines of the laboratory and are revolutionizing domains such as electronics, optics, medicine, and environmental science. The societal and technological impact of SERS biosensing by using semiconductor-based nanostructured smart substrates will be huge once minor technical pitfalls are solved. Herein, challenges in clinical routine testing are addressed in order to understand the context of how SERS can perform in real, in vivo sampling and bioassays for early neurodegenerative disease (ND) diagnosis. The main interest in translating SERS into clinical practice is reinforced by the practical advantages: portability of the designed setups, versatility in using nanomaterials of various matter and costs, readiness, and reliability. As we will present in this review, in the frame of technology readiness levels (TRL), the current maturity reached by semiconductor-based SERS biosensors, in particular that of zinc oxide (ZnO)-based hybrid SERS substrates, is situated at the development level TRL 6 (out of 9 levels). Three-dimensional, multilayered SERS substrates that provide additional plasmonic hot spots in the z-axis are of key importance in designing highly performant SERS biosensors for the detection of ND biomarkers.

GM1 Reduced the Symptoms of Autism Spectrum Disorder by Suppressing α-Syn Through Activating Autophagy

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that cannot be cured. The ASD rat model was developed in this study to demonstrate the role and mechanism of ganglioside GM1 (GM1). Rats were given valproic acid (VPA) to create the ASD rat model. The rats' behaviors were assessed using the Y-maze test, open-field test, three-chamber social interaction test, and Morris water maze test. Relative levels of glutathione (GSH), malondialdehyde (MDA), catalase (CAT), reactive oxygen species (ROS), and superoxide dismutase (SOD) were quantitated using relative kits. Nissl, TUNEL, immunofluorescent, and immunohistochemistry staining techniques were used. GM1 treatment improved the ASD model rats' behavior disorders, including locomotor activity and exploratory behavior, social interaction, learning and memory capacity, and repetitive behavior. Following GM1 injection, striatal neurons grew and apoptosis decreased. GM1 reduced the excessively elevated α-Syn in ASD by encouraging autophagy. The behavior disorder of ASD model rats was exacerbated by autophagy inhibition, which also increased α-Syn levels. By increasing autophagy, GM1 reduced α-Syn levels and, ultimately, improved behavioral abnormalities in ASD model rats.

Microtubule Cytoskeletal Network Alterations in a Transgenic Model of Tuberous Sclerosis Complex: Relevance to Autism Spectrum Disorders

Tuberous sclerosis complex (TSC) is a rare genetic multisystem disorder caused by loss-of-function mutations in the tumour suppressors TSC1/TSC2, both of which are negative regulators of the mammalian target of rapamycin (mTOR) kinase. Importantly, mTOR hyperactivity seems to be linked with the pathobiology of autism spectrum disorders (ASD). Recent studies suggest the potential involvement of microtubule (MT) network dysfunction in the neuropathology of "mTORopathies", including ASD. Cytoskeletal reorganization could be responsible for neuroplasticity disturbances in ASD individuals. Thus, the aim of this work was to study the effect of Tsc2 haploinsufficiency on the cytoskeletal pathology and disturbances in the proteostasis of the key cytoskeletal proteins in the brain of a TSC mouse model of ASD. Western-blot analysis indicated significant brain-structure-dependent abnormalities in the microtubule-associated protein Tau (MAP-Tau), and reduced MAP1B and neurofilament light (NF-L) protein level in 2-month-old male B6;129S4-Tsc2^tm1Djk/J mice. Alongside, pathological irregularities in the ultrastructure of both MT and neurofilament (NFL) networks as well as swelling of the nerve endings were demonstrated. These changes in the level of key cytoskeletal proteins in the brain of the autistic-like TSC mice suggest the possible molecular mechanisms responsible for neuroplasticity alterations in the ASD brain.

A comprehensive assessment of cell type-specific differential expression methods in bulk data

Accounting for cell type compositions has been very successful at analyzing high-throughput data from heterogeneous tissues. Differential gene expression analysis at cell type level is becoming increasingly popular, yielding biomarker discovery in a finer granularity within a particular cell type. Although several computational methods have been developed to identify cell type-specific differentially expressed genes (csDEG) from RNA-seq data, a systematic evaluation is yet to be performed. Here, we thoroughly benchmark six recently published methods: CellDMC, CARseq, TOAST, LRCDE, CeDAR and TCA, together with two classical methods, csSAM and DESeq2, for a comprehensive comparison. We aim to systematically evaluate the performance of popular csDEG detection methods and provide guidance to researchers. In simulation studies, we benchmark available methods under various scenarios of baseline expression levels, sample sizes, cell type compositions, expression level alterations, technical noises and biological dispersions. Real data analyses of three large datasets on inflammatory bowel disease, lung cancer and autism provide evaluation in both the gene level and the pathway level. We find that csDEG calling is strongly affected by effect size, baseline expression level and cell type compositions. Results imply that csDEG discovery is a challenging task itself, with room to improvements on handling low signal-to-noise ratio and low expression genes.

Photobiomodulation Attenuated Cognitive Dysfunction and Neuroinflammation in a Prenatal Valproic Acid-Induced Autism Spectrum Disorder Mouse Model

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social communication and interaction disorders, as well as repetitive and restrictive behaviors. To date, no effective treatment strategies have been identified. However, photobiomodulation (PBM) is emerging as a promising treatment for neurological and neuropsychiatric disorders. We used mice exposed to valproic acid (VPA) as a model of ASD and found that pathological behavioral and histological changes that may have been induced by VPA were attenuated by PBM treatment. Pregnant mice that had been exposed to VPA were treated with PBM three times. Thereafter, we evaluated the offspring for developmental disorders, motor function, hyperactivity, repetitive behaviors, and cognitive impairment. PBM attenuated many of the pathological behaviors observed in the VPA-induced ASD mouse model. In addition, pathophysiological analyses confirmed that the increase in activated microglia and astrocytes observed in the VPA-induced ASD mouse model was attenuated by PBM treatment. This suggests that PBM can counteract the behavioral changes caused by neuroinflammation in ASD. Therefore, our data show that PBM has therapeutic potential and may reduce the prevalence of neurodevelopmental disorders such as ASD.

Identification of the common neurobiological process disturbed in genetic and non-genetic models for autism spectrum disorders

Autism spectrum disorders (ASD) are neurodevelopmental disorders. Genetic factors, along with non-genetic triggers, have been shown to play a causative role. Despite the various causes, a triad of common symptoms defines individuals with ASD; pervasive social impairments, impaired social communication, and repeated sensory-motor behaviors. Therefore, it can be hypothesized that different genetic and environmental factors converge on a single hypothetical neurobiological process that determines these behaviors. However, the cellular and subcellular signature of this process is, so far, not well understood. Here, we performed a comparative study using "omics" approaches to identify altered proteins and, thereby, biological processes affected in ASD. In this study, we mined publicly available repositories for genetic mouse model data sets, identifying six that were suitable, and compared them with in-house derived proteomics data from prenatal zinc (Zn)-deficient mice, a non-genetic mouse model with ASD-like behavior. Findings derived from these comparisons were further validated using in vitro neuronal cell culture models for ASD. We could show that a protein network, centered on VAMP2, STX1A, RAB3A, CPLX2, and AKAP5, is a key convergence point mediating synaptic vesicle release and recycling, a process affected across all analyzed models. Moreover, we demonstrated that Zn availability has predictable functional effects on synaptic vesicle release in line with the alteration of proteins in this network. In addition, drugs that target kinases, reported to regulate key proteins in this network, similarly impacted the proteins' levels and distribution. We conclude that altered synaptic stability and plasticity through abnormal synaptic vesicle dynamics and function may be the common neurobiological denominator of the shared behavioral abnormalities in ASD and, therefore, a prime drug target for developing therapeutic strategies.

Genetic Dysruption of the Histaminergic Pathways: A Novel Deletion at the 15q21.2 locus Associated with Variable Expressivity of Neuropsychiatric Disorders

The involvement of the Histaminergic System (HS) in neuropsychiatric disease is not well-documented, and few studies have described patients affected by different neuropsychiatric conditions harbouring disruptions in genes involved in the HS. In humans, histamine is synthetised from histidine by the histidine decarboxylase enzyme encoded by the HDC gene (OMIM*142704). This is the sole enzyme in our organism able to synthetise histamine from histidine. Histamine is also contained in many different food types. We hereby describe a twenty-one-year-old female diagnosed with a borderline intellectual disability with autistic traits and other peculiar neuropsychological features carrying a 175-Kb interstitial deletion on chromosome 15q21.2. The deletion was inherited from the mother, who was affected by a severe anxiety disorder. The deleted region contains entirely the HDC and the SLC27A2 genes and partially the ATP8B4 gene. The HDC gene has been previously associated with Tourette Syndrome (TS). Based on the functional role of the HDC, we propose this gene as the best candidate to explain many traits associated with the clinical phenotype of our patient and of her mother.

Taurine inhibits KDM3a production and microglia activation in lipopolysaccharide-treated mice and BV-2 cells

Microglia activation has been suggested as the key factor in neuro-inflammation and thus participates in neurological diseases. Although taurine exhibits anti-inflammatory and neuro-protective effects, its underlying epigenetic mechanism is unknown. In this study, taurine was administered to lipopolysaccharide (LPS)-treated mice and BV-2 cells. Behavioral test, morphological analyze, detection of microglia activation, and lysine demethylase 3a (KDM3a) measurements were performed to investigate the mechanism by which taurine regulates KDM3a and subsequently antagonizes microglia activation. Taurine improved the sociability of LPS-treated mice, inhibited microglia activation in the hippocampus, and reduced generation of brain inflammatory factors, such as interleukin-6, tumor necrosis factor-α, inducible nitric oxide synthase, and cyclooxygenase-2. Meanwhile, taurine suppressed the LPS-induced increase in microglial KDM3a, and increased the level of mono-, di- or tri-methylation of lysine 9 on histone H3 (H3K9me1/2/3). Furthermore, taurine inhibited the LPS-induced increase in KDM3a, elevated the H3K9me1/2/3 level, and reduced inflammatory factors and reactive oxygen species in a concentration-dependent manner in LPS-stimulated BV-2 cells. In conclusion, taurine inhibited KDM3a and microglia activation, thereby playing an anti-inflammatory role in LPS-treated mice and BV-2 cells.

Developmental pyrethroid exposure and age influence phenotypes in a Chd8 haploinsufficient autism mouse model

Hundreds of genes have been associated with autism spectrum disorder (ASD), including loss-of-function mutations in chromodomain helicase DNA binding protein 8 (Chd8). Environmental factors also are implicated in autism risk and have the potential to exacerbate phenotypes in genetically sensitized backgrounds. Here we investigate transcriptional and behavioral phenotypes in a Chd8 haploinsufficient (Chd8^V986*/+) mouse line exposed to the pesticide deltamethrin (DM) from conception to postnatal day 22. Vehicle-exposed Chd8^V986*/+ mice displayed ASD-associated phenotypes, including anxiety-like behavior and altered sociability, replicating a previous study with this mouse line. A core set of genes was altered in Chd8^V986*/+ mice at multiple ages, including Usp11, Wars2, Crlf2, and Eglf6, and proximity ligation data indicated direct binding of CHD8 to the 5’ region of these genes. Moreover, oligodendrocyte and neurodegenerative transcriptional phenotypes were apparent in 12 and 18 month old Chd8^V986*/+ mice. Following DM exposure, the mutant mice displayed an exacerbated phenotype in the elevated plus maze, and genes associated with vascular endothelial cells were downregulated in the cerebral cortex of older Chd8^V986*/+ animals. Our study reveals a gene x environment interaction with a Chd8 haploinsufficient mouse line and points to the importance of investigating phenotypes in ASD animal models across the lifespan.

Glutamate and GABA in Microglia-Neuron Cross-Talk in Alzheimer's Disease

The physiological balance between excitation and inhibition in the brain is significantly affected in Alzheimer’s disease (AD). Several neuroactive compounds and their signaling pathways through various types of receptors are crucial in brain homeostasis, among them glutamate and γ-aminobutyric acid (GABA). Activation of microglial receptors regulates the immunological response of these cells, which in AD could be neuroprotective or neurotoxic. The novel research approaches revealed the complexity of microglial function, including the interplay with other cells during neuroinflammation and in the AD brain. The purpose of this review is to describe the role of several proteins and multiple receptors on microglia and neurons, and their involvement in a communication network between cells that could lead to different metabolic loops and cell death/survival. Our review is focused on the role of glutamatergic, GABAergic signaling in microglia–neuronal cross-talk in AD and neuroinflammation. Moreover, the significance of AD-related neurotoxic proteins in glutamate/GABA-mediated dialogue between microglia and neurons was analyzed in search of novel targets in neuroprotection, and advanced pharmacological approaches.

Cerebral Expression of Metabotropic Glutamate Receptor Subtype 5 in Idiopathic Autism Spectrum Disorder and Fragile X Syndrome: A Pilot Study

Multiple lines of evidence suggest that dysfunction of the metabotropic glutamate receptor subtype 5 (mGluR5) plays a role in the pathogenesis of autism spectrum disorder (ASD). Yet animal and human investigations of mGluR5 expression provide conflicting findings about the nature of dysregulation of cerebral mGluR5 pathways in subtypes of ASD. The demonstration of reduced mGluR5 expression throughout the living brains of men with fragile X syndrome (FXS), the most common known single-gene cause of ASD, provides a clue to examine mGluR5 expression in ASD. We aimed to (A) compare and contrast mGluR5 expression in idiopathic autism spectrum disorder (IASD), FXS, and typical development (TD) and (B) show the value of positron emission tomography (PET) for the application of precision medicine for the diagnosis and treatment of individuals with IASD, FXS, and related conditions. Two teams of investigators independently administered 3-[18F]fluoro-5-(2-pyridinylethynyl)benzonitrile ([18F]FPEB), a novel, specific mGluR5 PET ligand to quantitatively measure the density and the distribution of mGluR5s in the brain regions, to participants of both sexes with IASD and TD and men with FXS. In contrast to participants with TD, mGluR5 expression was significantly increased in the cortical regions of participants with IASD and significantly reduced in all regions of men with FXS. These results suggest the feasibility of this protocol as a valuable tool to measure mGluR5 expression in clinical trials of individuals with IASD and FXS and related conditions.