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Autism is a neurodevelopmental disorder, the prevalence of which has increased dramatically in the United States over the past two decades. It is characterized by stereotyped behaviors and impairments in social interaction and communication. In this paper, we present evidence that autism can be viewed as a PIN1 deficiency syndrome. Peptidyl‐prolyl cis/trans isomerase, NIMA‐Interacting 1 (PIN1) is a peptidyl‐prolyl cis/trans isomerase, and it has widespread influences in biological organisms. Broadly speaking, PIN1 deficiency is linked to many neurodegenerative diseases, whereas PIN1 over‐expression is linked to cancer. Death‐associated protein kinase 1 (DAPK1) strongly inhibits PIN1, and the hormone melatonin inhibits DAPK1. Melatonin deficiency is strongly linked to autism. It has recently been shown that glyphosate exposure to rats inhibits melatonin synthesis as a result of increased glutamate release from glial cells and increased expression of metabotropic glutamate receptors. Glyphosate's inhibition of melatonin leads to a reduction in PIN1 availability in neurons. In this paper, we show that PIN1 deficiency can explain many of the unique morphological features of autism, including increased dendritic spine density, missing or thin corpus callosum, and reduced bone density. We show how PIN1 deficiency disrupts the functioning of powerful high‐level signaling molecules, such as nuclear factor erythroid 2‐related factor 2 (NRF2) and p53. Dysregulation of both of these proteins has been linked to autism. Severe depletion of glutathione in the brain resulting from chronic exposure to oxidative stressors and extracellular glutamate leads to oxidation of the cysteine residue in PIN1, inactivating the protein and further contributing to PIN1 deficiency. Impaired autophagy leads to increased sensitivity of neurons to ferroptosis. It is imperative that further research be conducted to experimentally validate whether the mechanisms described here take place in response to chronic glyphosate exposure and whether this ultimately leads to autism. [ABSTRACT FROM AUTHOR]

Cholecystokinin (CCK) has been confirmed to be essential in NMDA‐dependent long‐term potentiation (LTP) at mouse cortical synapses. This paper has proven that CCK is necessary for LTP induced by high‐frequency stimulation of mouse hippocampal synapses projected from the entorhinal cortex. We show that the subunit of the axonal NMDA receptor dominant modulates the activity‐induced LTP by triggering pre‐synaptic CCK release. A functional pre‐synaptic NMDA receptor is required to induce LTP mediated by the axonal Ca2+ elevation and CCK exocytosis at CCK‐specific neurons. Genetic depletion of the GluN1 subunit of NMDA receptors on CCK neurons, which projected from the entorhinal cortex largely abolished the axonal Ca2+ elevation and disturbed the secretion of CCK in hippocampus. These results demonstrate that activity‐induced LTP at the hippocampal synapse is CCK‐dependent, and CCK secretion from the axonal terminal is modulated by pre‐synaptic NMDA receptors. [ABSTRACT FROM AUTHOR]

Isotopic assays of brain glucose utilization rates have been used for more than four decades to establish relationships between energetics, functional activity, and neurotransmitter cycling. Limitations of these methods include the relatively long time (1–60 min) for the determination of labeled metabolite levels and the lack of cellular resolution. Identification and quantification of fuels for neurons and astrocytes that support activation and higher brain functions are a major, unresolved issues. Glycolysis is preferentially up-regulated during activation even though oxygen level and supply are adequate, causing lactate concentrations to quickly rise during alerting, sensory processing, cognitive tasks, and memory consolidation. However, the fate of lactate (rapid release from brain or cell–cell shuttling coupled with local oxidation) is long disputed. Genetically encoded biosensors can determine intracellular metabolite concentrations and report real-time lactate level responses to sensory, behavioral, and biochemical challenges at the cellular level. Kinetics and time courses of cellular lactate concentration changes are informative, but accurate biosensor calibration is required for quantitative comparisons of lactate levels in astrocytes and neurons. An in vivo calibration procedure for the Laconic lactate biosensor involves intracellular lactate depletion by intravenous pyruvate-mediated trans-acceleration of lactate efflux followed by sensor saturation by intravenous infusion of high doses of lactate plus ammonium chloride. In the present paper, the validity of this procedure is questioned because rapid lactate–pyruvate interconversion in blood, preferential neuronal oxidation of both monocarboxylates, on-going glycolytic metabolism, and cellular volumes were not taken into account. Calibration pitfalls for the Laconic lactate biosensor also apply to other metabolite biosensors that are standardized in vivo by infusion of substrates that can be metabolized in peripheral tissues. We discuss how technical shortcomings negate the conclusion that Laconic sensor calibrations support the existence of an in vivo astrocyte–neuron lactate concentration gradient linked to lactate shuttling from astrocytes to neurons to fuel neuronal activity. [ABSTRACT FROM AUTHOR]

While brain glucose metabolism is known to contribute the carbons to support brain saturated and monounsaturated fatty biosynthesis de novo in the developing brains of young rodents, such a contribution to fatty acid biosynthesis in the adult brain is poorly understood. Recent work from the Bazinet laboratory illuminates the role of brain glucose metabolism in providing a carbon source from which palmitic acid is synthesized. In "The Majority of Brain Palmitic Acid is Maintained by Lipogenesis from Dietary Sugars and is Augmented in Offspring fed low Palmitic Acid Levels from Birth", the Bazinet lab demonstrates the importance of glucose as a key contributing source of carbon for brain palmitic synthesis and that a low palmitate diet exacerbates its utilization for brain palmitate synthesis de novo. Further, this impact is found in male mice rather than female mice, which adds an additional layer of importance. Mammals are known to conserve carbon and the brain has the ability to convert a variety of carbon sources to needed molecules, depending on the physiological needs of the brain. Overall, this paper contributes an important missing piece of the puzzle regarding carbon recycling in the brain and is a key piece of evidence that indeed the adult mammalian brain can convert glucose to carbons for use in saturated fatty acid synthesis. [ABSTRACT FROM AUTHOR]

Xanthurenic acid (XA) raises a growing multidisciplinary interest based upon its oxidizing properties, its ability to complex certain metal ions, and its detoxifier capacity of 3‐hydroxykynurenine (3‐HK), its brain precursor. However, little is still known about the role and mechanisms of action of XA in the central nervous system (CNS). Therefore, many research groups have recently investigated XA and its central functions extensively. The present paper critically reviews and discusses all major data related to XA properties and neuronal activities to contribute to the improvement of the current knowledge on XA's central roles and mechanisms of action. In particular, our data showed the existence of a specific G‐protein‐coupled receptor (GPCR) for XA localized exclusively in brain neurons exhibiting Ca2+‐dependent dendritic release and specific electrophysiological responses. XA properties and central activities suggest a role for this compound in brain intercellular signaling. Indeed, XA stimulates cerebral dopamine (DA) release contrary to its structural analog, kynurenic acid (KYNA). Thus, KYNA/XA ratio could be fundamental in the regulation of brain glutamate and DA release. Cerebral XA may also represent an homeostatic signal between the periphery and several brain regions where XA accumulates easily after peripheral administration. Therefore, XA status in certain psychoses or neurodegenerative diseases seems to be reinforced by its brain‐specific properties in balance with its formation and peripheral inputs. [ABSTRACT FROM AUTHOR]

It has been more than 10 years since the hopes for disease modeling and drug discovery using induced pluripotent stem cell (iPSC) technology boomed. Recently, clinical trials have been conducted with drugs identified using this technology, and some promising results have been reported. For amyotrophic lateral sclerosis (ALS), a devastating neurodegenerative disease, several groups have identified candidate drugs, ezogabine (retigabine), bosutinib, and ropinirole, using iPSCs‐based drug discovery, and clinical trials using these drugs have been conducted, yielding interesting results. In our previous study, an iPSCs‐based drug repurposing approach was utilized to show the potential of ropinirole hydrochloride (ROPI) in reducing ALS‐specific pathological phenotypes. Recently, a phase 1/2a trial was conducted to investigate the effects of ropinirole on ALS further. This double‐blind, randomized, placebo‐controlled study confirmed the safety and tolerability of and provided evidence of its ability to delay disease progression and prolong the time to respiratory failure in ALS patients. Furthermore, in the reverse translational research, in vitro characterization of patient‐derived iPSCs‐motor neurons (MNs) mimicked the therapeutic effects of ROPI in vivo, suggesting the potential application of this technology to the precision medicine of ALS. Interestingly, RNA‐seq data showed that ROPI treatment suppressed the sterol regulatory element‐binding protein 2‐dependent cholesterol biosynthesis pathway. Therefore, this pathway may be involved in the therapeutic effect of ROPI on ALS. The possibility that this pathway may be involved in the therapeutic effect of ALS was demonstrated. Finally, new future strategies for ALS using iPSCs technology will be discussed in this paper. [ABSTRACT FROM AUTHOR]

Subtype 3 metabotropic glutamate receptor (mGlu3R) displays a broad range of neuroprotective effects. We previously demonstrated that mGlu3R activation in astrocytes protects hippocampal neurons from Aβ neurotoxicity through stimulation of both neurotrophin release and Aβ uptake. Alternative‐spliced variants of mGlu3R were found in human brains. The most prevalent variant, mGlu3Δ4, lacks exon 4 encoding the transmembrane domain and can inhibit ligand binding to mGlu3R. To date, neither its role in neurodegenerative disorders nor its endogenous expression in CNS cells has been addressed. The present paper describes for the first time an association between altered hippocampal expression of mGlu3Δ4 and Alzheimer's disease (AD) in the preclinical murine model PDAPP‐J20, as well as a deleterious effect of mGlu3Δ4 in astrocytes. As assessed by western blot, hippocampal mGlu3R levels progressively decreased with age in PDAPP‐J20 mice. On the contrary, mGlu3Δ4 levels were drastically increased with aging in nontransgenic mice, but prematurely over‐expressed in 5‐month‐old PDAPP‐J20‐derived hippocampi, prior to massive senile plaque deposition. Also, we found that mGlu3Δ4 co‐precipitated with mGlu3R mainly in 5‐month‐old PDAPP‐J20 mice. We further showed by western blot that primary cultured astrocytes and neurons expressed mGlu3Δ4, whose levels were reduced by Aβ, thereby discouraging a causal effect of Aβ on mGlu3Δ4 induction. However, heterologous expression of mGlu3Δ4 in astrocytes induced cell death, inhibited mGlu3R expression, and prevented mGlu3R‐dependent Aβ glial uptake. Indeed, mGlu3Δ4 promoted neurodegeneration in neuron–glia co‐cultures. These results provide evidence of an inhibitory role of mGlu3Δ4 in mGlu3R‐mediated glial neuroprotective pathways, which may lie behind AD onset. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) affects a significant proportion of the population over the age of 60 years, and its prevalence is increasing. While symptomatic treatment is available for motor symptoms of PD, non‐motor complications such as dementia result in diminished life quality for patients and are far more difficult to treat. In this study, we analyzed PD‐associated alterations in the hippocampus of PD patients, since this brain region is strongly affected by PD dementia. We focused on synapses, analyzing the proteome of post‐mortal hippocampal tissue from 16 PD cases and 14 control subjects by mass spectrometry. Whole tissue lysates and synaptosomal fractions were analyzed in parallel. Differential analysis combined with bioinformatic network analyses identified neuronal pentraxin 1 (NPTX1) to be significantly dysregulated in PD and interacting with proteins of the synaptic compartment. Modulation of NPTX1 protein levels in primary hippocampal neuron cultures validated its role in synapse morphology. Our analysis suggests that NPTX1 contributes to synaptic pathology in late‐stage PD and represents a putative target for novel therapeutic strategies. [ABSTRACT FROM AUTHOR]

The neurotensin system spans across the central nervous system, to the enteric nervous system (gut), and the periphery to govern behaviors and physiological responses that tune energy balance to maintain homeostasis. Neurotensin transmission is not only modulated by metabolic signals, neurotensin transmission itself can also impact metabolic state by exerting control over consumption, physical activity, and satiety signals. Many responses to sensory experiences and sleep processes are dictated by neurotensinergic activity via mechanisms that allow the organism to balance energy seeking and utilization to thrive in its environment. Given the broad reach neurotensin signaling has across the homeostatic landscape, understanding this system as a whole and examining new ways to target this system for therapeutic efficacy across many different conditions is necessary. [ABSTRACT FROM AUTHOR]

This special issue of the Journal of Neurochemistry, entitled "Cholinergic Mechanisms," presents 15 reviews and two original papers, which have been selected to cover the broad spectrum of topics and disciplines presented at the XVIth International Symposium on Cholinergic Mechanisms (ISCM‐XVI), ranging from the molecular and the cellular to the clinical and the cognitive mechanisms of cholinergic transmission. The authors discuss recent developments in the field, for instance, the association of cholinergic transmission with a number of important neurological and neuromuscular diseases in the central and peripheral nervous systems. [ABSTRACT FROM AUTHOR]

Microglia play a vital role in maintaining brain homeostasis. Their continuous sensing of surrounding micro‐environments is crucial for their activity. Cross talk between specific neurons and microglia might occur through specific neurotransmitter receptors on microglia. Impairment with this interaction might result in pathological activity of microglia against potential insults. The reason for this activity in many neurodegenerative diseases such as Alzheimer's disease (AD) is not known. However, several papers report of the effects of different neurotransmitter agonists on microglial cells function that relate to their activity in AD. This review aims to summarize those works and to raise potential fundamental questions for future research. [ABSTRACT FROM AUTHOR]

The neurotransmitter glycine is an agonist at the strychnine-sensitive glycine receptors. In addition, it has recently been discovered to act at two new receptors, the excitatory glycine receptor and metabotropic glycine receptor. Glycine's neurotransmitter roles have been most extensively investigated in the spinal cord, where it is known to play essential roles in pain, itch, and motor function. In contrast, less is known about supraspinal glycinergic functions, and their contributions to pain circuits are largely unrecognized. As glycinergic neurons are absent from cortical regions, a clearer understanding of how supraspinal glycine modulates pain could reveal new pharmacological targets. This review aims to synthesize the published research on glycine's role in the adult brain, highlighting regions where glycine signaling may modulate pain responses. This was achieved through a scoping review methodology identifying several key regions of supraspinal pain circuitry where glycine signaling is involved. Therefore, this review unveils critical research gaps for supraspinal glycine's potential roles in pain and pain-associated responses, encouraging researchers to consider glycinergic neurotransmission more widely when investigating neural mechanisms of pain., (© 2024 The Author(s). Journal of Neurochemistry published by John Wiley & Sons Ltd on behalf of International Society for Neurochemistry.)

Viral infections of the central nervous system (CNS) often cause worse neurological outcomes in younger hosts. Throughout childhood, the brain undergoes extensive development and refinement to produce functional neural networks. Network function is maintained partly with the help of neural stem cells (NSCs) that replace neuronal and glia subtypes in the two neurogenic niches of the brain (the hippocampus and subventricular zone). Accumulating evidence suggests that viruses disrupt NSC function in adulthood and infancy, but the in vivo impact of childhood infections on acute and long‐term NSC function is unknown. Using a juvenile mouse model of measles virus (MeV) infection, where only mature neurons in the brain are infected, we defined the effects of the antiviral immune response on NSCs from juvenile to adult stages of life. We found that (a) virus persists in the brains of survivors despite an anti‐viral immune response; (b) NSC numbers decrease dramatically during early infection, but ultimately stabilize in adult survivors; (c) infection is associated with mild apoptosis throughout the juvenile brain, but NSC proliferation is unchanged; (d) the loss of NSC numbers is dependent upon the stage of NSC differentiation; and (e) immature neurons increase early during infection, concurrent with depletion of NSC pools. Collectively, we show that NSCs are exquisitely sensitive to the inflammatory microenvironment created during neuron‐restricted MeV infection in juveniles, responding with an early loss of NSCs but increased neurogenesis. These studies provide insight into potential cellular mechanisms associated with long‐term neurological deficits in survivors of childhood CNS infections. [ABSTRACT FROM AUTHOR]

Development of the mammalian neocortex requires proper inside‐out migration of developing cortical neurons from the germinal ventricular zone toward the cortical plate. The mechanics of this migration requires precise coordination of different cellular phenomena including cytoskeleton dynamics, membrane trafficking, and cell adhesion. The small GTPases play a central role in all these events. The small GTPase Rab21 regulates migration and neurite growth in developing neurons. Moreover, regulators and effectors of Rab21 have been implicated in brain pathologies with cortical malformations, suggesting a key function for the Rab21 signaling pathway in cortical development. Mechanistically, it has been posited that Rab21 influences cell migration by controlling the trafficking of endocytic vesicles containing adhesion molecules. However, direct evidence of the participation of Rab21 or its mechanism of action in the regulation of cortical migration is still incomplete. In this study, we demonstrate that Rab21 plays a critical role in the differentiation and migration of pyramidal neurons by regulating the levels of the amyloid precursor protein on the neuronal cell surface. Rab21 loss of function increased the levels of membrane‐exposed APP, resulting in impaired cortical neuronal differentiation and migration. These findings further our understanding of the processes governing the development of the cerebral cortex and shed light onto the molecular mechanisms behind cortical development disorders derived from the malfunctioning of Rab21 signaling effectors. [ABSTRACT FROM AUTHOR]

Disordered SOD1 protein deposition and mislocalization was also frequently accompanied by TDP-43 and p62 pathology in these same patients, suggesting interactions with these ALS-linked proteins may modulate the formation of SOD1 pathology. B 03-04 Effect of Moringa oleifera supplemented diets on cognition and inflammations in the brain of... Idowu Oyeleye, Ganiyu Oboh, Omamuyovwi Ijomone Federal University of Technology, Akure, Biomedical Technology, Akure, Nigeria The progression of diabetes mellitus (DM) has been associated with changes in brain function, as well as cognitive and neurochemical dysfunction, and structural changes on brain imaging. RNA-sequencing of isolated microglia demonstrated that the expression of "disease-associated microglia" genes is not responsible for these beneficial effects. B 10-03 Targeting stress inducible phosphoprotein 1 can reduce -Syn and TDP-43 mixed pathologies in... Vladislav Novikov 1, Rachel Lackie 1, Thomas Durcan 2, Edward Fon 2, Vania Prado 1, Marc... 1 University of Western Ontario, Schulich School of Medicine and Dentistry, Robarts Research... TDP-43, a nuclear protein involved in RNA processing, is an aggregation prone protein found to be elevated and mislocalized to the cytoplasm of neurons in diseases such as Amyotrophic lateral sclerosis (ALS). B 01-01 A novel RNA-targeted therapeutic approach against tau-driven neuronal pathology in Alzheimer'... CarlosCampos-Marques 1, Bruno Godinho 2,3, Jonathan Watts 2,4, Nuno Sousa 1, Ioannis Soti... 1 School of Medicine, University of Minho, Life and Health Sciences Research Institute (ICVS)... Despite disorders with different etiology, Alzheimer's disease (AD) and Down syndrome (DS) share many neuropathological features, such as brain accumulation of amyloid- (A ) and Tau protein. [Extracted from the article]

Sanfilippo syndrome (MPS III) is an autosomal recessive inherited disorder causing dementia in children, following an essentially normal early developmental period. First symptoms typically include delayed language development, hyperactivity and/or insomnia from 2 years of age, followed by unremitting and overt loss of previously acquired skills. There are no approved treatments, and the median age of death is 18 years. Treatments under clinical trial demonstrate therapeutic benefit when applied pre‐symptomatically in children diagnosed early through known familial inheritance risk. Newborn screening for Sanfilippo syndrome would enable pre‐symptomatic diagnosis and optimal therapeutic benefit, however, many fold more patients with Sanfilippo syndrome are expected to be identified in the population than present with childhood dementia. Therefore, the capacity to stratify which Sanfilippo infants will need treatment in toddlerhood is necessary. While diagnostic methods have been developed, and continue to be refined, currently there are no tools or laboratory‐based biomarkers available to provide pre‐symptomatic prognosis. There is also a lack of progression and neurocognitive response‐to‐treatment biomarkers; disease stage and rate of progression are currently determined by age at symptom onset, loss of cerebral grey matter volume by magnetic resonance imaging and developmental quotient score for age. Robust blood‐based biomarkers are an urgent unmet need. In this review, we discuss the development of biomarker assays for Sanfilippo based on the neuropathological pathways known to change leading into symptom onset and progression, and their performance as biomarkers in other neurodegenerative diseases. We propose that neural‐derived exosomes extracted from blood may provide an ideal liquid biopsy to detect reductions in synaptic protein availability, and mitochondrial function. Furthermore, given the prominent role of neuroinflammation in symptom expression, glial fibrillary acidic protein detection in plasma/serum, alongside measurement of active brain atrophy by neurofilament light chain, warrant increased investigation for prognostic, progression and neurocognitive response‐to‐treatment biomarker potential in Sanfilippo syndrome and potentially other childhood dementias. [ABSTRACT FROM AUTHOR]

The neuroinflammatory process characterizing multiple sclerosis (MS) is associated with changes in excitatory synaptic transmission and altered central concentrations of the primary excitatory amino acid, L‐glutamate (L‐Glu). Recent findings report that cerebrospinal fluid (CSF) levels of L‐Glu positively correlate with pro‐inflammatory cytokines in MS patients. However, to date, there is no evidence about the relationship between the other primary excitatory amino acid, L‐aspartate (L‐Asp), its derivative D‐enantiomer, D‐aspartate, and the levels of pro‐inflammatory and anti‐inflammatory cytokines in the CSF of MS. In the present study, we measured by HPLC the levels of these amino acids in the cortex, hippocampus, cerebellum, and spinal cord of mice affected by experimental autoimmune encephalomyelitis (EAE). Interestingly, in support of glutamatergic neurotransmission abnormalities in neuroinflammatory conditions, we showed reduced L‐Asp levels in the cortex and spinal cord of EAE mice and increased D‐aspartate/total aspartate ratio within the cerebellum and spinal cord of these animals. Additionally, we found significantly decreased CSF levels of L‐Asp in both relapsing–remitting (n = 157) MS (RR‐MS) and secondary progressive/primary progressive (n = 22) (SP/PP‐MS) patients, compared to control subjects with other neurological diseases (n = 40). Importantly, in RR‐MS patients, L‐Asp levels were correlated with the CSF concentrations of the inflammatory biomarkers G‐CSF, IL‐1ra, MIP‐1β, and Eotaxin, indicating that the central content of this excitatory amino acid, as previously reported for L‐Glu, reflects a neuroinflammatory environment in MS. In keeping with this, we revealed that CSF L‐Asp levels were positively correlated with those of L‐Glu, highlighting the convergent variation of these two excitatory amino acids under inflammatory synaptopathy occurring in MS. [ABSTRACT FROM AUTHOR]

Brain aging is a naturally occurring process resulting in the decline of cognitive functions and increased vulnerability to develop age‐associated disorders. Fluctuation in lipid species is crucial for normal brain development and function. However, impaired lipid metabolism and changes in lipid composition in the brain have been increasingly recognized to play a crucial role in physiological aging, as well as in several neurodegenerative diseases. In the last decades, the role of sexual dimorphism in the vulnerability to develop age‐related neurodegeneration has increased. However, further studies are warranted for detailed assessment of how age, sex, and additional non‐biological factors may influence the lipid changes in brains. The aim of this work is to address the presence of sex differences in the brain lipid changes that occur along aging, and in the two most common age‐related neurodegenerative disorders (Alzheimer's and Parkinson's diseases). We included the studies that assessed lipid‐related alterations in the brain of both humans and experimental models. Additionally, we explored the influence of sex on lipid‐lowering therapies. We conclude that sex exerts a notable effect on lipid modifications occurring with age and neurodegeneration, and in lipid‐reducing interventions. Therefore, the application of sex as an experimental variable is strongly encouraged for future research in the field of precision medicine approach. [ABSTRACT FROM AUTHOR]

Neuronal circuits in the brain that utilize the neurotransmitter serotonin are essential to the regulation of mood and emotional expression. Disruptions in serotonin signaling underlie neuropsychiatric conditions such as depression and anxiety. However, the cellular mechanisms that regulate serotonergic signaling in the brain in healthy and diseased states remain to be better understood. In particular, as more is learned about serotonin in the brain, we recognize an urgent need to develop techniques capable of mapping its complex spatiotemporal dynamics in awake, behaving animals. Notably, analytical methods to detect serotonin in situ, including tomography, are widely used but still recognized as limited in terms of their spatiotemporal resolution, their methodological caveats, and their technical limitations when cross‐referenced with behavioral studies. To overcome such limitations, genetically encoded serotonin indicators were developed, leading to the introduction of novel imaging modalities that enable researchers to achieve remarkable spatiotemporal resolution in the study of serotonergic circuits in preclinical models of neuropsychiatric disorders. These novel approaches, while remarkably powerful, are also not without limitations. Here, we review the current techniques for detecting and quantifying serotonin in vivo within the brain and discuss how novel approaches such as genetically encoded serotonin indicators will lead to new insights into the roles of serotonergic circuits in health and disease. [ABSTRACT FROM AUTHOR]

Astrocytes associate with amyloid plaques in Alzheimer's disease (AD). Astrocytes react to changes in the brain environment, including increasing concentrations of amyloid‐β (Aβ). However, the precise response of astrocytes to soluble small Aβ oligomers at concentrations similar to those present in the human brain has not been addressed. In this study, we exposed astrocytes to media from neurons that express the human amyloid precursor protein (APP) transgene with the double Swedish mutation (APPSwe), and which contains APP‐derived fragments, including soluble human Aβ oligomers. We then used proteomics to investigate changes in the astrocyte secretome. Our data show dysregulated secretion of astrocytic proteins involved in the extracellular matrix and cytoskeletal organization and increase secretion of proteins involved in oxidative stress responses and those with chaperone activity. Several of these proteins have been identified in previous transcriptomic and proteomic studies using brain tissue from human AD and cerebrospinal fluid (CSF). Our work highlights the relevance of studying astrocyte secretion to understand the brain response to AD pathology and the potential use of these proteins as biomarkers for the disease. [ABSTRACT FROM AUTHOR]

BACE1 is essential for the generation of amyloid‐β (Aβ) that likely initiates the toxicity in Alzheimer's disease (AD). BACE1 activity is mainly regulated by post‐translational modifications, but the relationship between these modifications is not fully characterized. Here, we studied the effects of BACE1 SUMOylation on its phosphorylation and ubiquitination. We demonstrate that SUMOylation of BACE1 inhibits its phosphorylation at S498 and its ubiquitination in vitro. Conversely, BACE1 phosphorylation at S498 suppresses its SUMOylation, which results in promoting BACE1 degradation in vitro. Furthermore, an increase in BACE1 SUMOylation is associated with the progression of AD pathology, while its phosphorylation and ubiquitination are decreased in an AD mouse model. Our findings suggest that BACE1 SUMOylation reciprocally influences its phosphorylation and competes against its ubiquitination, which might provide a new insight into the regulations of BACE1 activity and Aβ accumulation. [ABSTRACT FROM AUTHOR]

This preface introduces the Journal of Neurochemistry Special Issue on Brain Proteostasis. Adequate control of protein homeostasis, or proteostasis, has been at the center stage of brain physiology, and its deregulation may contribute to brain diseases, including several neuropsychiatric and neurodegenerative conditions. Therefore, delineating the processes underlying protein synthesis, folding, stability, function, and degradation in brain cells is key to promoting brain function and identifying effective therapeutic options for neurological disorders. This special issue comprises four review articles and four original articles covering the roles of protein homeostasis in several mechanisms that are of relevance to sleep, depression, stroke, dementia, and COVID‐19. Thus, these articles highlight different aspects of proteostasis regulation in the brain and present important evidence on this growing and exciting field. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is the most common form of dementia. Obesity in middle age increases AD risk and severity, which is alarming given that obesity prevalence peaks at middle age and obesity rates are accelerating worldwide. Midlife, but not late-life obesity increases AD risk, suggesting that this interaction is specific to preclinical AD. AD pathology begins in middle age, with accumulation of amyloid beta (Aβ), hyperphosphorylated tau, metabolic decline, and neuroinflammation occurring decades before cognitive symptoms appear. We used a transcriptomic discovery approach in young adult (6.5 months old) male and female TgF344-AD rats that overexpress mutant human amyloid precursor protein and presenilin-1 and wild-type (WT) controls to determine whether inducing obesity with a high-fat/high-sugar "Western" diet during preclinical AD increases brain metabolic dysfunction in dorsal hippocampus (dHC), a brain region vulnerable to the effects of obesity and early AD. Analyses of dHC gene expression data showed dysregulated mitochondrial and neurotransmission pathways, and up-regulated genes involved in cholesterol synthesis. Western diet amplified the number of genes that were different between AD and WT rats and added pathways involved in noradrenergic signaling, dysregulated inhibition of cholesterol synthesis, and decreased intracellular lipid transporters. Importantly, the Western diet impaired dHC-dependent spatial working memory in AD but not WT rats, confirming that the dietary intervention accelerated cognitive decline. To examine later consequences of early transcriptional dysregulation, we measured dHC monoamine levels in older (13 months old) AD and WT rats of both sexes after long-term chow or Western diet consumption. Norepinephrine (NE) abundance was significantly decreased in AD rats, NE turnover was increased, and the Western diet attenuated the AD-induced increases in turnover. Collectively, these findings indicate obesity during prodromal AD impairs memory, potentiates AD-induced metabolic decline likely leading to an overproduction of cholesterol, and interferes with compensatory increases in NE transmission., (© 2023 International Society for Neurochemistry.)

The traditional medicinal mushroom Hericium erinaceus is known for enhancing peripheral nerve regeneration through targeting nerve growth factor (NGF) neurotrophic activity. Here, we purified and identified biologically new active compounds from H. erinaceus, based on their ability to promote neurite outgrowth in hippocampal neurons. N‐de phenylethyl isohericerin (NDPIH), an isoindoline compound from this mushroom, together with its hydrophobic derivative hericene A, were highly potent in promoting extensive axon outgrowth and neurite branching in cultured hippocampal neurons even in the absence of serum, demonstrating potent neurotrophic activity. Pharmacological inhibition of tropomyosin receptor kinase B (TrkB) by ANA‐12 only partly prevented the NDPIH‐induced neurotrophic activity, suggesting a potential link with BDNF signaling. However, we found that NDPIH activated ERK1/2 signaling in the absence of TrkB in HEK‐293T cells, an effect that was not sensitive to ANA‐12 in the presence of TrkB. Our results demonstrate that NDPIH acts via a complementary neurotrophic pathway independent of TrkB with converging downstream ERK1/2 activation. Mice fed with H. erinaceus crude extract and hericene A also exhibited increased neurotrophin expression and downstream signaling, resulting in significantly enhanced hippocampal memory. Hericene A therefore acts through a novel pan‐neurotrophic signaling pathway, leading to improved cognitive performance. [ABSTRACT FROM AUTHOR]

Ceroid lipofuscinosis neuronal (CLN) genes encode 13 proteins that localize throughout the endomembrane system to regulate a variety of cellular processes. In humans, mutations in CLN genes cause a devastating form of neurodegeneration called neuronal ceroid lipofuscinosis (NCL), commonly known as Batten disease. Each CLN gene is associated with a specific subtype of the disease that differ from each other in severity and age of onset. The NCLs affect all ages and ethnicities worldwide but primarily affect children. The pathology underlying the NCLs is poorly understood, which has prevented the development of a cure or effective therapy for most subtypes of the disease. A growing body of literature supports the networking of CLN genes and proteins within cells, which aligns with the broadly similar cellular and clinical manifestations among the different subtypes of NCL. Here, all relevant literature is reviewed to provide a comprehensive overview of our current understanding of how CLN genes and proteins are networked in mammalian cells with an aim toward revealing new molecular targets for therapy development. Intriguingly, CLN gene and protein networking extends beyond the NCLs as recent work has linked several CLN genes and proteins to other forms of neurodegeneration such as Alzheimer's disease and Parkinson's disease. Thus, a deeper understanding of the pathways and cellular processes impacted by mutations in CLN genes will not only strengthen our knowledge of the pathological mechanisms underlying the NCLs but may also provide new insight into related forms of neurodegeneration. [ABSTRACT FROM AUTHOR]

Neuron‐restrictive silencer factor/repressor element 1 (RE1)‐silencing transcription factor (NRSF/REST) is a transcriptional repressor of a large cluster of neural genes containing RE1 motifs in their promoter region. NRSF/REST is ubiquitously expressed in non‐neuronal cells, including astrocytes, while it is down‐regulated during neuronal differentiation. While neuronal NRSF/REST homeostatically regulates intrinsic excitability and synaptic transmission, the role of the high NRSF/REST expression levels in the homeostatic functions of astrocytes is poorly understood. Here, we investigated the functional consequences of NRSF/REST deletion in primary cortical astrocytes derived from NRSF/REST conditional knockout mice (KO). We found that NRSF/REST KO astrocyte displayed a markedly reduced activity of inward rectifying K+ channels subtype 4.1 (Kir4.1) underlying spatial K+ buffering that was associated with a decreased expression and activity of the glutamate transporter‐1 (GLT‐1) responsible for glutamate uptake by astrocytes. The effects of the impaired astrocyte homeostatic functions on neuronal activity were investigated by co‐culturing wild‐type hippocampal neurons with NRSF/REST KO astrocytes. Interestingly, neurons experienced increased neuronal excitability at high firing rates associated with decrease after hyperpolarization and increased amplitude of excitatory postsynaptic currents. The data indicate that astrocytic NRSF/REST directly participates in neural circuit homeostasis by regulating intrinsic excitability and excitatory transmission and that dysfunctions of NRSF/REST expression in astrocytes may contribute to the pathogenesis of neurological disorders. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) is a common movement disorder caused by a characteristic loss of dopaminergic neurons in the substantia nigra and degeneration of dopamine terminals in the dorsal striatum. Previous studies have suggested that oxidative stress‐induced DNA damage may be involved in PD pathogenesis, as steady‐state levels of several types of oxidized nucleobases were shown to be elevated in PD brain tissues. These DNA lesions are normally removed from the genome by base excision repair, which is initiated by DNA glycosylase enzymes such as endonuclease VIII‐like 1 (Neil1). In this study, we show that Neil1 plays an important role in limiting oxidative stress‐induced degeneration of dopaminergic neurons. In particular, Neil1‐deficient male mice exhibited enhanced sensitivity to nigrostriatal degeneration after 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) administration, and Neil1‐deficient animals had higher levels of γH2AX‐marked DNA damage than wild‐type (WT) controls, regardless of treatment status. Moreover, MPTP‐treated Neil1−/− male mice had slightly elevated expression of genes related to the nuclear factor erythroid 2‐related factor 2 (Nrf2)‐dependent antioxidant pathway. Treatment with the Nrf2 activator, monomethyl fumarate, reduced PD‐like behaviors and pathology in Neil1−/− male mice, suggesting that Neil1 is an important defense molecule in an oxidative cellular environment. Taken together, these results suggest that Neil1 DNA glycosylase may play an important role in limiting oxidative stress‐mediated PD pathogenesis. [ABSTRACT FROM AUTHOR]

Schwann cells (SCs) are known to produce myelin for saltatory nerve conduction in the peripheral nervous system (PNS). Schwann cell differentiation and myelination processes are controlled by several transcription factors including Sox10, Oct6/Pou3f1, and Krox20/Egr2. Chicken ovalbumin upstream promoter‐transcription factor II (COUP‐TFII/NR2F2) is an orphan receptor that plays a role in the development and differentiation. However, the role of COUP‐TFII in the transcriptional regulatory network of SC differentiation has not been fully identified yet. Thus, the objective of this study was to investigate the role and molecular hierarchy of COUP‐TFII during cAMP‐induced SC differentiation. Our results showed that dibutyryl‐cAMP (db‐cAMP) increased expression levels of COUP‐TFII along with the expressions of Oct6, Krox20, and myelin‐related genes known to be related to SC differentiation. Our mechanistic studies showed that COUP‐TFII acted downstream of Hsp90/ErbB2/Gab1/ERK‐AKT pathway during db‐cAMP‐induced SC differentiation. In addition, we found that COUP‐TFII induced Krox20 expression by directly binding to Krox20‐MSE8 as revealed by chromatin immunoprecipitation assay and promoter activity assay. In line with this, the expression of COUP‐TFII was increased before up‐regulation of Oct6, Krox20, and myelin‐related genes in the sciatic nerves during early postnatal myelination period. Finally, COUP‐TFII knockdown by COUP‐TFII siRNA or via AAV‐COUP‐TFII shRNA in SCs inhibited db‐cAMP‐induced SC differentiation and in vitro myelination of sensory axons, respectively. Taken together, these findings indicate that COUP‐TFII might be involved in postnatal myelination through induction of Krox20 in SCs. Our results present a new insight into the transcriptional regulatory mechanism in SC differentiation and myelination. [ABSTRACT FROM AUTHOR]

Ischemic stroke triggers a cascade of events that facilitates neural protection and spontaneous recovery, which accounts for a major part of functional recovery. Despite the cellular and molecular facilitations on neural protection, the molecular mechanisms of spontaneous recovery have not been fully understood. Ca2+‐dependent activator protein for secretion 1 (CAPS1), a member of CAPS family, plays a major role in synaptic transmission and synaptic effectiveness by regulating vesicle exocytosis. Here, the molecular mechanism of CAPS1 in spontaneous recovery after ischemic stroke was studied. In this study, transient left middle cerebral artery occlusion (MCAO) was used as the ischemic stroke model. The whole brain magnetic resonance imaging (MRI) and neurological score analysis showed decreased infarct volume and neurological scores at 7 days as compared with 1 day after MCAO, suggesting the spontaneous recovery. Elisa and Western blot analysis showed elevated BDNF and CAPS1 expression levels in bilateral hippocampus at both 1 day and 3 days after MCAO. Then, inhibition of CAPS1 by adeno‐associated virus (AAV) microinjection in the hippocampus attenuated the spontaneous recovery of both motor and memory impairment induced by MCAO. In addition, elevated p‐TrkB levels were detected after MCAO, which were reduced by CAPS1‐AAV microinjection, indicating that CAPS1 could induce BDNF secretion after ischemic stroke. Moreover, we found elevated combination of CAPS1 with dense core vesicles (DCV) in the hippocampus at both 1 day and 3 days after MCAO, which could also be inhibited by CAPS1‐AAV microinjection, indicating the potential mechanism of CAPS1 in regulating BDNF release after MCAO. Finally, we found that CAPS1/BDNF signaling could influence the neurogenesis in the hippocampus after MCAO. In conclusion, CAPS1 regulates neurogenesis by up‐regulating BDNF release in the hippocampus, which finally facilitate spontaneous recovery after ischemic stroke. [ABSTRACT FROM AUTHOR]

Neddylation is a cellular process in which the neural precursor cell expressed, developmentally down‐regulated 8 (NEDD8) is conjugated to the lysine residue of target proteins via serial enzymatic cascades. Recently, it has been demonstrated that neddylation is required for synaptic clustering of metabotropic glutamate receptor 7 (mGlu7) and postsynaptic density protein 95 (PSD‐95), and the inhibition of neddylation impairs neurite outgrowth and excitatory synaptic maturation. Similar to the balanced role of deubiquitylating enzymes (DUBs) in the ubiquitination process, we hypothesized that deneddylating enzymes can regulate neuronal development by counteracting the process of neddylation. We find that the SUMO peptidase family member, NEDD8 specific (SENP8) acts as a key neuronal deneddylase targeting the global neuronal substrates in primary rat cultured neurons. We demonstrate that SENP8 expression levels are developmentally regulated, peaking around the first postnatal week and gradually diminishing in mature brain and neurons. We find that SENP8 negatively regulates neurite outgrowth through multiple pathways, including actin dynamics, Wnt/β‐catenin signaling, and autophagic processes. Alterations in neurite outgrowth by SENP8 subsequently result in the impairment of excitatory synapse maturation. Our data indicate that SENP8 plays an essential role in neuronal development and is a promising therapeutic target for neurodevelopmental disorders. [ABSTRACT FROM AUTHOR]

Early life stress (ELS) is defined as a period of severe and/or chronic trauma, as well as environmental/social deprivation or neglect in the prenatal/early postnatal stage. Presently, the impact of ELS on the retina in the adult stage is unknown. The long‐term consequences of ELS at retinal level were analyzed in an animal model of maternal separation with early weaning (MSEW), which mimics early life maternal neglect. For this purpose, mice were separated from the dams for 2 h at postnatal days (PNDs) 4–6, for 3 h at PNDs 7–9, for 4 h at PNDs 10–12, for 6 h at PNDs 13–16, and weaned at PND17. At the end of each separation period, mothers were subjected to movement restriction for 10 min. Control pups were left undisturbed from PND0, and weaned at PND21. Electroretinograms, visual evoked potentials, vision‐guided behavioral tests, retinal anterograde transport, and retinal histopathology were examined at PNDs 60–80. MSEW induced long‐lasting functional and histological effects at retinal level, including decreased retinal ganglion cell function and alterations in vision‐guided behaviors, likely associated to decreased synaptophysin content, retina‐superior colliculus communication deficit, increased microglial phagocytic activity, and retinal ganglion cell loss through a corticoid‐dependent mechanism. A treatment with mifepristone, injected every 3 days between PNDs 4 and16, prevented functional and structural alterations induced by MSEW. These results suggest that retinal alterations might be included among the childhood adversity‐induced threats to life quality, and that an early intervention with mifepristone avoided ELS‐induced retinal disturbances. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a progressive neurodegenerative disease originating partly from amyloid β protein‐induced synaptic failure. As damaging of noradrenergic neurons in the locus coeruleus (LC) occurs at the prodromal stage of AD, activation of adrenergic receptors could serve as the first line of defense against the onset of the disease. Activation of β2‐ARs strengthens long‐term potentiation (LTP) and synaptic activity, thus improving learning and memory. Physical stimulation of animals exposed to an enriched environment (EE) leads to the activation of β2‐ARs and prevents synaptic dysfunction. EE also suppresses neuroinflammation, suggesting that β2‐AR agonists may play a neuroprotective role. The β2‐AR agonists used for respiratory diseases have been shown to have an anti‐inflammatory effect. Epidemiological studies further support the beneficial effects of β2‐AR agonists on several neurodegenerative diseases. Thus, I propose that β2‐AR agonists may provide therapeutic value in combination with novel treatments for AD. [ABSTRACT FROM AUTHOR]

The interest for developing antibody‐driven therapeutic interventions has exponentially grown over the last few decades. Even though there have been promising leaps in the development of efficacious antibody therapies, problems revolving around production and site‐directed delivery of these large macromolecules persist. This is especially pertinent when it comes to designing and producing antibodies to penetrate the blood–brain barrier (BBB) to tackle neurodegenerative diseases. One of the most effective approaches to alleviating this problem is to employ a "Trojan Horse" approach, using receptor‐mediated transcytosis, such as those governed by the transferrin receptor (TfR)‐mediated pathways, to deliver large protein payloads into the brain. Even though this method is effective, ideal limiting factors, related to how the antibody binds to the TfR, need to be elucidated to improve BBB penetrance. With this said, we have designed and produced a single‐chain Fc antibody, conjugated to an scFv8D3 TfR binding motif, creating a single‐chain monovalent BBB transporter (scFc‐scFv8D3). This recombinant protein is easy to produce and purify, demonstrates monovalent binding to the TfR and is structurally stable at physiologically relevant temperatures. Using an in vitro BBB model system, we show a positive correlation between the concentration of administered antibody and transcytosis efficacy, with scFc‐scFv8D3 demonstrating significantly higher transcytosis levels compared with scFv8D3‐conjugated bivalent antibodies at elevated administered concentrations. Furthermore, in vivo studies recapitulate the in vitro results, with the scFc‐scFv8D3 demonstrating an elevated brain uptake at higher therapeutic doses in wild‐type mice, comparable with that of the scFv8D3‐conjugated bivalent antibody control. In addition, the half‐life of the single‐chain monovalent BBB transporter is comparable with that of standard IgG antibodies, indicating that the scFc format does not exacerbate physiological degradation. Our results lead us to the conclusion that valency and affinity are important variables to consider when discerning optimal transport across the BBB using TfR‐mediated transcytosis pathways. In addition, we believe the single‐chain Fc antibody we have described, which can easily be manipulated to accommodate a bispecific target tactic, provides a simple and efficacious approach for delivering therapeutic payloads to the brain milieu. [ABSTRACT FROM AUTHOR]

Dopamine (DA) is involved in neurological and physiological functions such as motor control. L‐3,4‐dihydroxyphenylalanine (L‐DOPA), a precursor of DA, is conventionally believed to be an inert amino acid precursor of DA, and its major therapeutic effects in Parkinson's disease (PD) are mediated through its conversion to DA. On the contrary, accumulating evidence suggests that L‐DOPA itself is a neurotransmitter. We here show that L‐DOPA potentiates DA D2 receptor (DRD2) signaling through GPR143, the gene product of X‐linked ocular albinism 1, a G‐protein‐coupled receptor for L‐DOPA. In Gpr143‐gene‐deficient (Gpr143−/y) mice, quinpirole, a DRD2/DRD3 agonist, ‐induced hypolocomotion was attenuated compared to wild‐type (WT) mice. Administration of non‐effective dose of L‐DOPA methyl ester augmented the quinpirole‐induced hypolocomotion in WT mice but not in Gpr143−/y mice. In cells co‐expressing GPR143 and DRD2, L‐DOPA enhanced the interaction between GPR143 and DRD2 and augmented quinpirole‐induced decrease in cAMP levels. This augmentation by L‐DOPA was not observed in cells co‐expressing GPR143 and DRD1 or DRD3. Chimeric analysis in which the domain of GPR143 was replaced with GPR37 revealed that GPR143 interacted with DRD2 at the fifth transmembrane domain. Intracerebroventricular administration of a peptide that disrupted the interaction mitigated quinpirole‐induced behavioral changes in WT mice but not in Gpr143−/y mice. These findings provide evidence that coupling between GPR143 and DRD2 is required for selective DRD2 modulation by L‐DOPA in the dorsal striatum. [ABSTRACT FROM AUTHOR]

Studies have shown that rapid eye movement (REM) sleep behavior disorder (RBD) is a subtype of Parkinson's disease (PD) characterized by severe cognitive impairment and rapid disease progression. However, reliable biological markers are lacking presently. Neurofilament light chain (NFL) and glial fibrillary acidic protein (GFAP) have been widely studied as biomarkers of cognition impairment. This study aimed to find biomarkers for the RBD subtype of PD by investigating the possible relationship between serum NFL, GFAP levels, and the RBD subtype. A total of 109 PD patients and 37 healthy controls (HCs) were included, and their clinical characteristics were evaluated. PD patients were divided into two groups based on whether they had probable RBD or not. Serum NFL and GFAP levels were measured using the ultrasensitive single molecule array (Simoa) platform. The obtained data were statistically analyzed using SPSS 25.0 (IBM, Chicago, IL, USA). NFL and GFAP in the PD‐RBD group were elevated compared with the PD‐nRBD and control groups. Moreover, serum NFL and GFAP levels positively correlated with RBD. The combination of NFL and GFAP showed good performance in identifying PD‐RBD patients from PD‐nRBD. After considering potential confounding factors such as age, and disease duration, serum NFL and GFAP emerged as independent risk factors for RBD. Serum NFL and GFAP were related to RBD in PD patients. Concludingly, serum NFL and GFAP might serve as promising biomarkers for the RBD subtype of PD. [ABSTRACT FROM AUTHOR]

The bank vole (BV) prion protein (PrP) can function as a universal acceptor of prions. However, the molecular details of BVPrP's promiscuity for replicating a diverse range of prion strains remain obscure. To develop a cultured cell paradigm capable of interrogating the unique properties of BVPrP, we generated monoclonal lines of CAD5 cells lacking endogenous PrP but stably expressing either hamster (Ha), mouse (Mo), or BVPrP (M109 or I109 polymorphic variants) and then challenged them with various strains of mouse or hamster prions. Cells expressing BVPrP were susceptible to both mouse and hamster prions, whereas cells expressing MoPrP or HaPrP could only be infected with species‐matched prions. Propagation of mouse and hamster prions in cells expressing BVPrP resulted in strain adaptation in several instances, as evidenced by alterations in conformational stability, glycosylation, susceptibility to anti‐prion small molecules, and the inability of BVPrP‐adapted mouse prion strains to infect cells expressing MoPrP. Interestingly, cells expressing BVPrP containing the G127V prion gene variant, identified in individuals resistant to kuru, were unable to become infected with prions. Moreover, the G127V polymorphic variant impeded the spontaneous aggregation of recombinant BVPrP. These results demonstrate that BVPrP can facilitate cross‐species prion replication in cultured cells and that a single amino acid change can override the prion‐permissive nature of BVPrP. This cellular paradigm will be useful for dissecting the molecular features of BVPrP that allow it to function as a universal prion acceptor. [ABSTRACT FROM AUTHOR]

Heat shock factor 1 (HSF1) is a master stress‐responsive transcriptional factor, protecting cells from death. However, its gene regulation in vivo in the brain in response to neuronal stimuli remains elusive. Here, we investigated its direct regulation of the brain‐derived neurotrophic factor (BDNF) gene (Bdnf) in response to acute neuronal stress stimuli in the brain. The results of immunohistochemistry and chromatin immunoprecipitation quantitative PCR (ChIP‐qPCR) showed that administration of kainic acid (a glutamate receptor agonist inducing excitotoxity) to young adult mice induced HSF1 nuclear translocation and its binding to multiple Bdnf promoters in the hippocampus. Footshock, a physical stressor used for learning, also induced HSF1 binding to selected Bdnf promoters I and IV. This is, to our knowledge, the first demonstration of HSF1 gene regulation in response to neuronal stimuli in the hippocampus in vivo. HSF1 binding sites (HSEs) in Bdnf promoters I and IV were also detected when immunoprecipitated by an antibody of phosphorylated (p)CREB (cAMP‐responsive element‐binding protein), suggesting their possible interplay in acute stress‐induced Bdnf transcription. Interestingly, their promoter binding patterns differed by KA and footshock, suggesting that HSF1 and pCREB orchestrate to render fine‐tuned promoter control depending on the types of stress. Further, HSF1 overexpression increased Bdnf promoter activity in a luciferase assay, while virus infection of constitutively active‐form HSF1 increased levels of BDNF mRNA and protein in vitro in primary cultured neurons. These results indicated that HSF1 activation of Bdnf promoter was sufficient to induce BDNF expression. Taken together, these results suggest that HSF1 promoter‐specific control of Bdnf gene regulation plays an important role in neuronal protection and plasticity in the hippocampus in response to acute stress, possibly interplaying with pCREB. [ABSTRACT FROM AUTHOR]

As the world continues to experience the effects of SARS‐CoV‐2, there is evidence to suggest that the sequelae of viral infection (the post‐COVID‐19 condition; PCC) at both an individual and population level will be significant and long‐lasting. The history of pandemics or epidemics in the last 100 years caused by members of the RNA virus family, of which coronaviruses are a member, provides ample evidence of the acute neurological effects. However, except for the H1N1 influenza pandemic of 1918/1919 (the Spanish flu) with its associated encephalitis lethargica, there is little information on long‐term neurological sequelae. COVID‐19 is the first pandemic that has occurred in a setting of an aging population, especially in several high‐income countries. Its survivors are at the greatest risk for developing neurodegenerative conditions as they age, rendering the current pandemic a unique paradigm not previously witnessed. The SARS‐CoV‐2 virus, among the largest of the RNA viruses, is a single‐stranded RNA that encodes for 29 proteins that include the spike protein that contains the key domains required for ACE2 binding, and a complex array of nonstructural proteins (NSPs) and accessory proteins that ensure the escape of the virus from the innate immune response, allowing for its efficient replication, translation, and exocytosis as a fully functional virion. Increasingly, these proteins are also recognized as potentially contributing to biochemical and molecular processes underlying neurodegeneration. In addition to directly being taken up by brain endothelium, the virus or key protein constituents can be transported to neurons, astrocytes, and microglia by extracellular vesicles and can accelerate pathological fibril formation. The SARS‐CoV‐2 nucleocapsid protein is intrinsically disordered and can participate in liquid condensate formation, including as pathological heteropolymers with neurodegenerative disease‐associated RNA‐binding proteins such as TDP‐43, FUS, and hnRNP1A. As the SARS‐CoV‐2 virus continues to mutate under the immune pressure exerted by highly efficacious vaccines, it is evolving into a virus with greater transmissibility but less severity compared with the original strain. The potential of its lingering impact on the nervous system thus has the potential to represent an ongoing legacy of an even greater global health challenge than acute infection. [ABSTRACT FROM AUTHOR]

Epilepsy is a common neurological disorder associated with alterations of excitation‐inhibition balance within brain neuronal networks. GABAA receptor neurotransmission is the most prevalent form of inhibitory neurotransmission and is strongly implicated in both the pathophysiology and treatment of epilepsy, serving as a primary target for antiseizure medications for over a century. It is now established that GABA exerts a multifaceted influence through an array of GABAA receptor subtypes that extends far beyond simply negating excitatory activity. As the role of GABAA neurotransmission within inhibitory circuits is elaborated, this will enable the development of precision therapies that correct the network dysfunction underlying epileptic pathology. [ABSTRACT FROM AUTHOR]

Cerebral clearance of amyloid β‐protein (Aβ) is decreased in early‐onset and late‐onset Alzheimer's disease (AD). Aβ is cleared from the brain by enzymatic degradation and by transport out of the brain. More than 20 Aβ‐degrading enzymes have been described. Increasing the degradation of Aβ offers an opportunity to decrease brain Aβ levels in AD patients. This review discusses the direct and indirect approaches which have been used in experimental systems to alter the expression and/or activity of Aβ‐degrading enzymes. Also discussed are the enzymes' regulatory mechanisms, the conformations of Aβ they degrade, where in the scheme of Aβ production, extracellular release, cellular uptake, and intracellular degradation they exert their activities, and changes in their expression and/or activity in AD and its animal models. Most of the experimental approaches require further confirmation. Based upon each enzyme's effects on Aβ (some of the enzymes also possess β‐secretase activity and may therefore promote Aβ production), its direction of change in AD and/or its animal models, and the Aβ conformation(s) it degrades, investigating the effects of increasing the expression of neprilysin in AD patients would be of particular interest. Increasing the expression of insulin‐degrading enzyme, endothelin‐converting enzyme‐1, endothelin‐converting enzyme‐2, tissue plasminogen activator, angiotensin‐converting enzyme, and presequence peptidase would also be of interest. Increasing matrix metalloproteinase‐2, matrix metalloproteinase‐9, cathepsin‐B, and cathepsin‐D expression would be problematic because of possible damage by the metalloproteinases to the blood brain barrier and the cathepsins' β‐secretase activity. Many interventions which increase the enzymatic degradation of Aβ have been shown to decrease AD‐type pathology in experimental models. If a safe approach can be found to increase the expression or activity of selected Aβ‐degrading enzymes in human subjects, then the possibility that this approach could slow the AD progression should be examined in clinical trials. [ABSTRACT FROM AUTHOR]

The mechanisms of amyloid accumulation in familial Alzheimer's disease (FAD) and sporadic AD (SAD) are controversial. In FAD, mutations in presenilin (PSEN) impair γ‐secretase activity and lead to abnormal amyloid β–protein (Aβ) production, thereby increasing the Aβ42/40 ratio. SAD is postulated to be caused by decreased Aβ clearance of apolipoprotein E4 (APOE4), the strongest risk factor for SAD. However, whether intracellular APOE4 affects Aβ production is unclear. Using APOE3 and APOE4 knock‐in (KI) mouse brain and primary cultured fibroblasts from these mice, in this study, we demonstrated that APOE3 and APOE4 bind to the γ‐secretase complex and isoform‐dependently regulate its activity and Aβ production. We found that Aβ40 levels and γ‐secretase activity were higher in APOE knockout mouse brain than in wild‐type mouse brain. APOE4‐KI fibroblasts had significant lower Aβ levels and γ‐secretase activity but higher Aβ42/40 ratio compared with APOE3‐KI cells, indicating that APOE4‐KI reduces Aβ production by inhibiting γ‐secretase activity. Interestingly, the levels of γ‐secretase complex bound to APOE4 are higher than those bound to APOE3, and the levels of γ‐secretase complex in the brain and fibroblasts of APOE4‐KI mice were higher than those of APOE3‐KI mice. Taken together, our findings demonstrate that intracellular APOE4 inhibits Aβ production, more preferentially inhibits Aβ40 production, and thereby induces an increase in the Aβ42/40 ratio via binding to the γ‐secretase complex. These results suggest a novel mechanism in which intracellular APOE4 contributes to the pathogenesis of SAD by inhibiting γ‐secretase activity. [ABSTRACT FROM AUTHOR]

Early life stress alters brain‐derived neurotrophic factor (BDNF) promoter IV methylation and BDNF expression, which is closely related to the pathophysiological process of depression. However, the role of abnormal methylation of BDNF induced by stress during adolescence due to depression has not yet been clarified. In this study, adolescent mice were exposed to chronic unpredictable mild stress (CUMS). Depression‐like behaviors, BDNF promoter IV methylation, expression of DNA methyltransferases (DNMTs), demethylation machinery enzymes, BDNF protein levels, and neuronal development in the prefrontal cortex (PFC) and hippocampus (HIP) were assessed in adolescent and adult mice. The DNMT inhibitor, 5‐Aza‐2‐deoxycytidine (5‐AzaD), was used as an intervention. Stress in adolescence induces behavioral dysfunction, elevated methylation levels of BDNF promoter IV, changes in the expression of DNMT, and demethylation machinery enzymes in adolescent and adult mice. Additionally, the stress in adolescence induced lower levels of BDNF and abnormal hippocampal doublecortin (DCX) expression in adolescent and adult mice. However, DNMT inhibitor treatment in adolescent‐stressed mice relieved the abnormal behaviors, normalized the methylation level of BDNF promoter IV, BDNF protein expression, expression of DNMTs, and demethylation machinery enzymes, and improved the neuronal development of adult mice. These results suggest that stress in adolescence induces short‐ and long‐term hypermethylation of BDNF promoter IV, which is regulated by DNMTs, and leads to the development of depression. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that selectively attacks motor neurons, and leads to progressive muscle weakness and death. A common pathological feature is the misfolding, aggregation, and cytoplasmic mislocalization of TAR DNA‐binding protein 43 (TDP‐43) proteins in more than 95% of ALS patients, suggesting a universal role TDP‐43 proteinopathy in ALS. Mutations in SQSTM1/p62 have been identified in familial and sporadic cases of ALS. MicroRNAs (miRNAs) are small non‐coding RNAs that post‐transcriptionally regulate their target genes. Emerging evidence indicates that miRNA dysregulation is associated with neuronal toxicity and mitochondrial dysfunction, and also plays a pivotal role in ALS pathogenesis. Here, we report the first evidence that miR‐183‐5p is aberrantly upregulated in spinal cords of patients with ALS. Using luciferase reporter assays and miR‐183‐5p agomirs, we demonstrate that miR‐183‐5p regulates the SQSTM1/p62 3′‐untranslated region to suppress expression. A miR‐183‐5p agomir attenuated SOSTM1/p62 expression and led to an increase in TDP‐43 protein levels in neuronal and non‐neuronal cells. In contrast, a miR‐183‐5p antagomir decreased TDP‐43 but increased SQSTM1/p62 protein levels. The antagomir repressed formation of stress granules and aggregated TDP43 protein in neuronal cells under stress‐induced conditions and protected against cytotoxicity. Knockdown of SQSTM1/p62 decreased total ubiquitination and increased TDP‐43 protein aggregation, indicating that SQSTM1/p62 may play a protective role in cells. In summary, our study reveals a novel mechanism of TDP‐43 proteinopathy mediated by the miR‐183‐5p and provides a molecular link between aberrant RNA processing and protein degradation, two major pillars in ALS pathogenesis. [ABSTRACT FROM AUTHOR]

Oligodendrocyte progenitor cells (OPCs) originate in the ventricular zone (VZ) of the brain and spinal cord, and their primary function is to differentiate into oligodendrocytes (OLs). Studies have shown that OPCs and OLs are pathologically and physiologically heterogeneous. Previous transcriptome analyses used Bulk RNA‐seq, which compares average gene expression in cells and does not allow for heterogeneity. In recent years, the development of single‐cell sequencing (scRNA‐seq) and single‐cell nuclear sequencing (snRNA‐seq) has allowed us to study an individual cell. In this review, sc/snRNA‐seq was used to study the different subpopulations of OL lineage cells, their developmental trajectories, and their applications in related diseases. These techniques can distinguish different subpopulations of cells, and identify differentially expressed genes in particular cell types under certain conditions, such as treatment or disease. It is of great significance to the study of the occurrence, prevention, and treatment of various diseases. [ABSTRACT FROM AUTHOR]

The two hallmarks of Alzheimer's disease (AD) are amyloid‐β (Aβ) plaques and neurofibrillary tangles marked by phosphorylated tau. Increasing evidence suggests that aggregating Aβ drives tau accumulation, a process that involves synaptic degeneration leading to cognitive impairment. Conversely, there is a realization that non‐fibrillar (oligomeric) forms of Aβ mediate toxicity in AD. Fibrillar (filamentous) aggregates of proteins across the spectrum of the primary and secondary tauopathies were the focus of recent structural studies with a filament structure‐based nosologic classification, but less emphasis was given to non‐filamentous co‐aggregates of insoluble proteins in the fractions derived from post‐mortem human brains. Here, we revisited sarkosyl‐soluble and ‐insoluble extracts to characterize tau and Aβ species by quantitative targeted mass spectrometric proteomics, biochemical assays, and electron microscopy. AD brain sarkosyl‐insoluble pellets were greatly enriched with Aβ42 at almost equimolar levels to N‐terminal truncated microtubule‐binding region (MTBR) isoforms of tau with multiple site‐specific post‐translational modifications (PTMs). MTBR R3 and R4 tau peptides were most abundant in the sarkosyl‐insoluble materials with a 10‐fold higher concentration than N‐terminal tau peptides. This indicates that the major proportion of the enriched tau was the aggregation‐prone N‐terminal and proline‐rich region (PRR) of truncated mixed 4R and 3R tau with more 4R than 3R isoforms. High concentration and occupancies of site‐specific phosphorylation pT181 (~22%) and pT217 (~16%) (key biomarkers of AD) along with other PTMs in the PRR and MTBR indicated a regional susceptibility of PTMs in aggregated tau. Immunogold labelling revealed that tau may exist in globular non‐filamentous form (N‐terminal intact tau) co‐localized with Aβ in the sarkosyl‐insoluble pellets along with tau filaments (N‐truncated MTBR tau). Our results suggest a model that Aβ and tau interact forming globular aggregates, from which filamentous tau and Aβ emerge. These characterizations contribute towards unravelling the sequence of events which lead to end‐stage AD changes. [ABSTRACT FROM AUTHOR]

With the emergence of positron emission tomography (PET) in the late 1970s, psychiatry had access to a tool capable of non‐invasive assessment of human brain function. Early applications in psychiatry focused on identifying characteristic brain blood flow and metabolic derangements using radiotracers such as [15O]H2O and [18F]FDG. Despite the success of these techniques, it became apparent that more specific probes were needed to understand the neurochemical bases of psychiatric disorders. The first neurochemical PET imaging probes targeted sites of action of neuroleptic (dopamine D2 receptors) and psychoactive (serotonin receptors) drugs. Based on the centrality of monoamine dysfunction in psychiatric disorders and the measured success of monoamine‐enhancing drugs in treating them, the next 30 years witnessed the development of an armamentarium of PET radiopharmaceuticals and imaging methodologies for studying monoamines. Continued development of monoamine‐enhancing drugs over this time however was less successful, realizing only modest gains in efficacy and tolerability. As patent protection for many widely prescribed and profitable psychiatric drugs lapsed, drug development pipelines shifted away from monoamines in search of novel targets with the promises of improved efficacy, or abandoned altogether. Over this period, PET radiopharmaceutical development activities closely paralleled drug development priorities resulting in the development of new PET imaging agents for non‐monoamine targets. Part one of this review will briefly survey novel PET imaging targets with relevance to the field of psychiatry, which include the metabotropic glutamate receptor type 5 (mGluR5), purinergic P2X7 receptor, type 1 cannabinoid receptor (CB1), phosphodiesterase 10A (PDE10A), and describe radiotracers developed for these and other targets that have matured to human subject investigations. Current limitations of the targets and techniques will also be discussed. [ABSTRACT FROM AUTHOR]

Neuropsychiatric symptoms (NPS) severely affect patients and their caregivers, and are associated with worse long‐term outcomes. This study tested the hypothesis that altered protein levels in blood plasma could serve as biomarkers of NPS; and that altered protein levels are associated with persisting NPS and cognitive decline over time. We performed a cross‐sectional and longitudinal study in older subjects with cognitive impairment and cognitively unimpaired in a memory clinic setting. NPS were recorded through the Neuropsychiatric Inventory Questionnaire (NPI‐Q) while cognitive and functional impairment was assessed using the clinical dementia rating sum of boxes (CDR‐SoB) score at baseline and follow‐up visits. Shotgun proteomic analysis based on liquid chromatography‐mass spectrometry was conducted in blood plasma samples, identifying 420 proteins. The presence of Alzheimer's Disease (AD) pathology was determined by cerebrospinal fluid biomarkers. Eighty‐five subjects with a mean age of 70 (±7.4) years, 62% female and 54% with mild cognitive impairment or mild dementia were included. We found 15 plasma proteins with altered baseline levels in participants with NPS (NPI‐Q score > 0). Adding those 15 proteins to a reference model based on clinical data (age, CDR‐SoB) significantly improved the prediction of NPS (from receiver operating characteristic area under the curve [AUC] 0.75 to AUC 0.91, p = 0.004) with a specificity of 89% and a sensitivity of 74%. The identified proteins additionally predicted both persisting NPS and cognitive decline at follow‐up visits. The observed associations were independent of the presence of AD pathology. Using proteomics, we identified a panel of specific blood proteins associated with current and future NPS, and related cognitive decline in older people. These findings show the potential of untargeted proteomics to identify blood‐based biomarkers of pathological alterations relevant for NPS and related clinical disease progression. [ABSTRACT FROM AUTHOR]

Leucine‐rich repeat kinase 2 (LRRK2) gene, which is the gene most commonly associated with Parkinson's disease (PD), is also a susceptibility gene for Crohn's disease, thereby suggesting that LRRK2 may sit at the crossroads of gastrointestinal inflammation, Parkinson's, and Crohn's disease. LRRK2 protein has been studied intensely in both CNS neurons and in immune cells, but there are only few studies on LRRK2 in the enteric nervous system (ENS). LRRK2 is present in ENS ganglia and the existing studies on LRRK2 expression in colonic biopsies from PD subjects have yielded conflicting results. Herein, we propose to extend these findings by studying in more details LRRK2 expression in the ENS. LRRK2 expression was evaluated in full thickness segments of colon of 16 Lewy body, 12 non‐Lewy body disorders cases, and 3 non‐neurodegenerative controls and in various enteric neural cell lines. We showed that, in addition to enteric neurons, LRRK2 is constitutively expressed in enteric glial cells in both fetal and adult tissues. LRRK2 immunofluorescence intensity in the myenteric ganglia was not different between Lewy body and non‐Lewy body disorders. Additionally, we identified the cAMP pathway as a key signaling pathway involved in the regulation of LRRK2 expression and phosphorylation in the enteric glial cells. Our study is the first detailed characterization of LRRK2 in the ENS and the first to show that enteric glial cells express LRRK2. Our findings provide a basis to unravel the functions of LRRK2 in the ENS and to further investigate the pathological changes in enteric synucleinopathies. [ABSTRACT FROM AUTHOR]