Synapse elimination is an essential process in the healthy nervous system and is dysregulated in many neuropathologies. Yet, the underlying molecular mechanisms and under what conditions they occur remain unclear. MFG-E8 is a secreted glycoprotein well known to act as an opsonin, tagging stressed and dying cells for engulfment by phagocytes. Opsonization of cells and debris by MFG-E8 for microglial phagocytosis in the CNS is well established, and its role in astrocytic phagocytosis, and trogocytosis-like engulfment of synapses is beginning to be explored. However, MFG-E8's function in other tissues is highly diverse, and evidence suggests that its role in the nervous system and on synapse elimination in particular may be more complex and varied than opsonization. In this review, we outline the documented direct and indirect effects of MFG-E8 on synapse elimination, while also proposing potential roles to be explored further, in particular, cytoskeletal reorganization of neurites and glia leading to synapse elimination by various mechanisms. Finally, we demonstrate the need for several open questions to be answered-chiefly, under what conditions might MFG-E8-mediated synapse elimination occur in favor of other mechanisms, and when might its activity be dysregulated, increasing unwanted synapse elimination and neurotoxicity?

Enhancing protein O-GlcNAcylation by pharmacological inhibition of the enzyme O-GlcNAcase (OGA) has been considered as a strategy to decrease tau and amyloid-beta phosphorylation, aggregation, and pathology in Alzheimer's disease (AD). There is still more to be learned about the impact of enhancing global protein O-GlcNAcylation, which is important for understanding the potential of using OGA inhibition to treat neurodegenerative diseases. In this study, we investigated the acute effect of pharmacologically increasing O-GlcNAc levels, using the OGA inhibitor Thiamet G (TG), in normal mouse brains. We hypothesized that the transcriptome signature in response to a 3 h TG treatment (50 mg/kg) provides a comprehensive view of the effect of OGA inhibition. We then performed mRNA sequencing of the brain using NovaSeq PE 150 (n = 5 each group). We identified 1234 significant differentially expressed genes with TG versus saline treatment. Functional enrichment analysis of the upregulated genes identified several upregulated pathways, including genes normally down in AD. Among the downregulated pathways were the cell adhesion pathway as well as genes normally up in AD and aging. When comparing acute to chronic TG treatment, protein autophosphorylation and kinase activity pathways were upregulated, whereas cell adhesion and astrocyte markers were downregulated in both datasets. AMPK subunit Prkab2 was one gene in the kinase activity pathway, and the increase after acute and chronic treatment was confirmed using qPCR. Interestingly, mitochondrial genes and genes normally down in AD were up in acute treatment and down in chronic treatment. Data from this analysis will enable the evaluation of the mechanisms underlying the impact of OGA inhibition in the treatment of AD. In particular, OGA inhibitors appear to have downstream effects related to bioenergetics which may limit their therapeutic benefits.

Proton magnetic resonance spectroscopy (MRS) offers a non-invasive, repeatable, and reproducible method for in vivo metabolite profiling of the brain and other tissues. However, metabolite fingerprinting by MRS requires high signal-to-noise ratios for accurate metabolite quantification, which has traditionally been limited to large volumes of interest, compromising spatial fidelity. In this study, we introduce a new optimized pipeline that combines LASER MRS acquisition at 11.7 T with a cryogenic coil and advanced offline pre- and post-processing. This approach achieves a signal-to-noise ratio sufficient to reliably quantify 19 distinct metabolites in a volume as small as 0.7 μL within the mouse brain. The resulting high spatial resolution and spectral quality enable the identification of distinct metabolite fingerprints in small, specific regions, as demonstrated by characteristic differences in N-acetylaspartate, glutamate, taurine, and myo-inositol between the motor and somatosensory cortices. We demonstrated a decline in taurine and glutamate in the primary motor cortex between 5 and 11 months of age, against the stability of other metabolites. Further exploitation to cortical layer-specific metabolite fingerprinting of layer I-III to layer VI-V in the primary motor cortex, with the latter showing reduced taurine and phosphoethanolamine levels, demonstrates the potential of this pipeline for detailed in vivo metabolite fingerprinting of cortical areas and subareas.

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-beta (Aβ) plaques in the brain, contributing to neurodegeneration. This study investigates lipid alterations within these plaques using a novel, label-free, multimodal approach. Combining infrared (IR) imaging, machine learning, laser microdissection (LMD), and flow injection analysis mass spectrometry (FIA-MS), we provide the first comprehensive lipidomic analysis of chemically unaltered Aβ plaques in post-mortem human AD brain tissue. IR imaging revealed decreased lipid unsaturation within plaques, evidenced by a reduction in the alkene (=C-H) stretching vibration band. The high spatial resolution of IR imaging, coupled with machine learning-based plaque detection, enabled precise and label-free extraction of plaques via LMD. Subsequent FIA-MS analysis confirmed a significant increase in short-chain saturated lipids and a concomitant decrease in long-chain unsaturated lipids within plaques compared to the surrounding tissue. These findings highlight a substantial depletion of unsaturated fatty acids (UFAs) in Aβ plaques, suggesting a pivotal role for lipid dysregulation and oxidative stress in AD pathology. This study advances our understanding of the molecular landscape of Aβ plaques and underscores the potential of lipid-based therapeutic strategies in AD.

Epitranscriptomic regulation of cell functions involves multiple post-transcriptional chemical modifications of coding and non-coding RNA that are increasingly recognized in studying human brain disorders. Although rodent models are presently widely used in neuroepitranscriptomic research, the zebrafish (Danio rerio) has emerged as a useful and promising alternative model species. Mounting evidence supports the importance of RNA modifications in zebrafish CNS function, providing additional insights into epitranscriptomic mechanisms underlying a wide range of brain disorders. Here, we discuss recent data on the role of RNA modifications in CNS regulation, with a particular focus on zebrafish models, as well as evaluate current problems, challenges, and future directions of research in this field of molecular neurochemistry.

Highly abundant in neurons, the cellular prion protein (PrP) is an obligatory precursor to the disease-associated misfolded isoform denoted PrP that accumulates in the rare neurodegenerative disorders referred to either as transmissible spongiform encephalopathies (TSEs) or as prion diseases. The ability of PrP to serve as a substrate for this template-mediated conversion process depends on several criteria but importantly includes the presence or absence of certain endoproteolytic events performed at the cell surface or in acidic endolysosomal compartments. The major endoproteolytic events affecting PrP are referred to as α- and β-cleavages, and in this review we outline the sites within PrP at which the cleavages occur, the mechanisms potentially responsible and their relevance to pathology. Although the association of α-cleavage with neuroprotection is well-supported, we identify open questions regarding the importance of β-cleavage in TSEs and suggest experimental approaches that could provide clarification. We also combine findings from in vitro cleavage assays and mass spectrometry-based studies of prion protein fragments in the brain to present an updated view in which α- and β-cleavages may represent two distinct clusters of proteolytic events that occur at multiple neighbouring sites rather than at single positions. Furthermore, we highlight the candidate proteolytic mechanisms best supported by the literature; currently, despite several proteases identified as capable of processing PrP in vitro, in cell-based models and in some cases, in vivo, none have been shown conclusively to cleave PrP in the brain. Addressing this knowledge gap will be crucial for developing therapeutic interventions to drive PrP endoproteolysis in a neuroprotective direction. Finally, we end this review by briefly addressing other cleavage events, specifically ectodomain shedding, γ-cleavage, the generation of atypical pathological fragments in the familial prion disorder Gerstmann-Sträussler-Scheinker syndrome and the possibility of an additional form of endoproteolysis close to the PrP N-terminus.

Alzheimer disease is a neurodegenerative pathology-modifying mitochondrial metabolism with energy impairments where the effects of biological sex and DNA repair deficiencies are unclear. We investigated the therapeutic potential of dietary ketosis alone or with supplemental nicotinamide riboside (NR) on hippocampal intermediary metabolism and mitochondrial bioenergetics in older male and female wild-type (Wt) and 3xTgAD-DNA polymerase-β-deficient (3xTg/POLβ) (AD) mice. DNA polymerase-β is a key enzyme in DNA base excision repair (BER) of oxidative damage that may also contribute to mitochondrial DNA repair. Metabolic alterations imparted by ketosis and/or NR were assessed in 16 male and female groups, 4 Wt and 4 AD. At 73 weeks of age, mice were divided into: (A) carbohydrate diet (Carb); (B) Carb diet with NR (Carb-NR); (C) Ket diet (Ket); and (D) Ket diet with NR (Ket-NR) groups and remained on their respective treatments for 12 weeks. Mice were euthanized and hippocampi were rapidly removed and frozen. Glycolytic and TCA cycle intermediates were determined by quantitative GC-MS and the ratios of the mitochondrial free [NAD]/[NADH] and coenzyme ubiquinone (CoQ/CoQH) couples and the Gibbs free energy of the Complex I-II system of the electron transport chain (ETC) ( ) were calculated from selected metabolites. Mice in Groups C and D had elevated blood ketones (1-2 mM). In most groupings, male mice had higher concentrations of TCA cycle intermediates than females. Moreover, higher concentrations of fumarate in Wt males were associated with elevations in the ΔG' of Complex I-II compared to females. In Wt males, NR treatments were associated with elevated concentrations of α-ketoglutarate and malate and linked to increased energy of Complex I-II. In AD males, both NR treatment and dietary ketosis restored the ΔG' of Complex I-II, where the ratio of the CoQ/CoQH couple was oxidized and the [NAD]/[NADH] couple was reduced. In AD females, only mice in the Ket diet group had a sufficiently reduced [NAD]/[NADH] couple to restore the free energy profile.

Severe trauma frequently leads to nerve damage. Peripheral nerves possess a degree of regenerative ability, and actively promoting their recovery can help restore the sensory and functional capacities of tissues. The neuropeptide calcitonin gene-related peptide (CGRP) is believed to regulate the repair of injured peripheral nerves, with neuronal transient receptor potential vanilloid type 1 (TRPV1) potentially serving as a crucial upstream factor. In this study, we established a mouse model of sciatic nerve (SN) crush injury and found that intrathecal injection of capsaicin (Cap) activated the neuronal TRPV1-CGRP axis, thereby promoting SN repair. Conversely, the application of capsazepine (Cpz), which inhibits the neuronal TRPV1-CGRP axis, delayed SN repair. Local restoration of CGRP expression at the injury site enhanced the repair process. In vitro experiments, we employed the rat Schwann cell (SC) line RSC96 to establish an indirect co-culture model of neurons and SCs. We observed that the proliferation, migration, expression of myelination-associated proteins, and neurotrophic secretion functions of RSC96 cells are positively correlated with the degree of activation of neuronal TRPV1. Inhibition of neuronal TRPV1, followed by the restoration of CGRP levels, improved these functions in RSC96 cells. Furthermore, activation of the neuronal TRPV1-CGRP axis resulted in an upregulation of extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation levels and an increase in hypoxia-inducible factor 1α (HIF-1α) accumulation in RSC96 cells, thereby promoting their proliferation and migration. In summary, this study demonstrates that neuronal TRPV1-CGRP axis can regulate biological behavior of SCs and axon regeneration by activating the ERK/HIF-1 signaling pathway following peripheral nerve injury. This finding clarifies the role of CGRP in neuroregulatory networks and provides a novel reference point for the development of drugs and biomaterials for treating nerve damage.

Oligodendrocytes, the myelinating cells in the central nervous system, are implicated in several neurological disorders marked by dysfunctional RNA-binding proteins (RBPs). The present study aimed at investigating the role of hnRNP A1 in the proteome of the corpus callosum, prefrontal cortex, and hippocampus of a murine cuprizone-induced demyelination model. Right after the cuprizone insult, we administered an hnRNP A1 splicing activity inhibitor and analyzed its impact on brain remyelination by nanoESI-LC-MS/MS label-free proteomic analysis to assess the biological processes affected in these brain regions. Significant alterations in essential myelination proteins highlighted the involvement of hnRNP A1 in maintaining myelin integrity. Pathways related to sphingolipid and endocannabinoid signaling were affected, as well as the synaptic vesicle cycle and GABAergic synapses. Although behavioral impairments were not observed, molecular changes suggest potential links to memory, synaptic function, and neurotransmission processes. These findings enhance our understanding of the multifaceted roles of hnRNP A1 in the central nervous system, providing valuable insights for future investigations and therapeutic interventions in neurodegenerative and demyelinating diseases.

Synaptic vesicle protein 2A (SV2A) is an abundant synaptic vesicle cargo with an as yet unconfirmed role in presynaptic function. It is also heavily implicated in epilepsy, firstly being the target of the leading anti-seizure medication levetiracetam and secondly with loss of function mutations culminating in human disease. A range of potential presynaptic functions have been proposed for SV2A; however its interaction with the calcium sensor for synchronous neurotransmitter release, synaptotagmin-1 (Syt1), has received particular attention over the past decade. In this review we will assess the evidence that the primary role of SV2A is to control the expression and localisation of Syt1 at the presynapse. This will integrate biochemical, cell biological and physiological studies where the interaction, trafficking and functional output of Syt1 is altered by SV2A. The potential for SV2A-dependent epilepsy to be a result of dysfunctional Syt1 expression and localisation is also discussed. Finally, a series of key open questions will be posed that require resolution before a definitive role for SV2A in Syt1 function in health and disease can be confirmed.

GABA receptor (GABAR) activation is known to alleviate pain by reducing neuronal excitability, primarily through inhibition of high voltage-activated (HVA) calcium (Ca2.2) channels and potentiating G protein-coupled inwardly rectifying potassium (GIRK) channels. Although the analgesic properties of small molecules and peptides have been primarily tested on isolated murine dorsal root ganglion (DRG) neurons, emerging strategies to develop, study, and characterise human pluripotent stem cell (hPSC)-derived sensory neurons present a promising alternative. In this study, hPSCs were efficiently differentiated into peripheral DRG-induced sensory neurons (iSNs) using a combined chemical and transcription factor-driven approach via a neural crest cell intermediate. Molecular characterisation and transcriptomic analysis confirmed the expression of key DRG markers such as BRN3A, ISLET1, and PRPH, in addition to GABAR and ion channels including Ca2.2 and GIRK1 in iSNs. Functional characterisation of GABAR was conducted using whole-cell patch clamp electrophysiology, assessing neuronal excitability under current-clamp conditions in the absence and presence of GABAR agonists baclofen and α-conotoxin Vc1.1. Both baclofen (100 μM) and Vc1.1 (1 μM) significantly reduced membrane excitability by hyperpolarising the resting membrane potential and increasing the rheobase for action potential firing. In voltage-clamp mode, baclofen and Vc1.1 inhibited HVA Ca channel currents, which were attenuated by the selective GABAR antagonist CGP 55845. However, modulation of GIRK channels by GABARs was not observed in the presence of baclofen or Vc1.1, suggesting that functional GIRK1/2 channels were not coupled to GABARs in hPSC-derived iSNs. This study is the first to report GABAR modulation of membrane excitability in iSNs by baclofen and Vc1.1, highlighting their potential as a future model for studying analgesic compounds.

Parkinson's disease (PD) is a prevalent neurodegenerative disease caused by the death of dopaminergic neurons within the substantia nigra pars compacta (SNpc) region of the midbrain. Recent genomic and single cell sequencing data identified oligodendrocytes and oligodendrocyte precursor cells (OPCs) to confer genetic risk in PD, but their biological role is unknown. Although SNpc dopaminergic neurons are scarcely or thinly myelinated, there is a gap in the knowledge concerning the physiological interactions between dopaminergic neurons and oligodendroglia. We sought to investigate the distribution of OPCs with regard to the myelination state in the mouse substantia nigra (SN) by high-resolution imaging to provide a morphological assessment of OPC-dopaminergic neuron interactions and quantification of cell numbers across different age groups. OPCs are evenly distributed in the midbrain throughout the lifespan and they physically interact with both the soma and axons of dopaminergic neurons. The presence of OPCs and their interaction with dopaminergic neurons does not correlate with the distribution of myelin. Myelination is sparse in the SNpc, including dopaminergic fibers originating from the SNpc and projecting through the substantia nigra pars reticulata (SNpr). We report that OPCs and dopaminergic neurons exist in a 1:1 ratio in the SNpc, with OPCs accounting for 15%-16% of all cells in the region across all age groups. This description of OPC-dopaminergic neuron interaction in the midbrain provides a first look at their longitudinal distribution in mice, suggesting additional functions of OPCs beyond their differentiation into myelinating oligodendrocytes.

Activation of the brain-penetrant beta3-adrenergic receptor (Adrb3) is implicated in the treatment of depressive disorders. Enhancing GABAergic inputs from interneurons onto pyramidal cells of prefrontal cortex (PFC) represents a strategy for antidepressant therapies. Here, we probed the effects of the activation of Adrb3 on GABAergic transmission onto pyramidal neurons in the PFC using in vitro electrophysiology. We found that Adrb3 agonist SR58611A increased both the frequency and the amplitude of miniature IPSCs (mIPSCs). Ca influx through T-type voltage-gated Ca channel (T-type VGCC) contributed to SR58611A-enhanced mIPSC frequency. We also found that SR58611A facilitated GABA release probability and the number of releasable vesicles through interaction with T-type VGCC. SR58611A depolarized somatostatin (Sst) interneurons with no effects on the firing rate of action potential of Sst interneurons. SR58611A-induced depolarization of Sst interneurons and enhancement of mIPSC frequency required inward rectifier K channel (Kir). Our results suggest that Kir and T-type VGCC in Sst interneurons participate in SR58611A-induced increase in GABA release in PFC.

The guidance cue netrin-1 promotes both growth cone attraction and growth cone repulsion. How netrin-1 elicits diverse axonal responses, beyond engaging the netrin receptor DCC and UNC5 family members, remains elusive. Here, we demonstrate that murine netrin-1 induces biphasic axonal responses in cortical neurons: Attraction at lower concentrations and repulsion at higher concentrations using both a microfluidic-based netrin-1 gradient and bath application of netrin-1. We find that repulsive turning in a netrin gradient is blocked by knockdown of UNC5C, whereas attractive turning is impaired by knockdown of DCC. TRIM9 is a brain-enriched E3 ubiquitin ligase previously shown to bind and cluster the attractive receptor DCC at the plasma membrane and regulate netrin-dependent attractive responses. However, whether TRIM9 also regulated repulsive responses to netrin-1 remained to be seen. In this study, we show that TRIM9 localizes and interacts with both the attractive netrin receptor DCC and the repulsive netrin receptor, UNC5C. We find that deletion of murine Trim9 alters both attractive and repulsive axon turning and changes in growth cones size in response to murine netrin-1. TRIM9 was required for netrin-1-dependent changes in the surface levels of DCC and UNC5C in the growth cone during morphogenesis. We demonstrate that DCC at the membrane regulates the growth cone area and show that TRIM9 negatively regulates FAK activity in the absence of both repulsive and attractive concentrations of netrin-1. Together, our work demonstrates that TRIM9 interacts with and regulates both DCC and UNC5C during attractive and repulsive axonal responses to netrin-1.

Autism spectrum disorder (ASD) is a complex developmental disorder characterized by several behavioral impairments, especially in socialization, communication, and the occurrence of stereotyped behaviors. In rats, prenatal exposure to valproic acid (VPA) induces autistic-like behaviors. Previous studies by our group have suggested that the autistic-like phenotype is possibly related to dopaminergic system modulation because tyrosine hydroxylase (TH) expression was affected. The objective of the present study was to understand the dopaminergic role in autism. Wistar rats on gestational day 12.5 received VPA (400 mg/kg) and behaviors related to rat models of ASD were evaluated in juvenile offspring. Neurochemical and genetic dopaminergic components were studied in different brain areas of both juvenile and adult rats. Prenatal VPA-induced autistic-like behaviors in comparison to a control group: decreased maternal solicitations by ultrasonic vocalizations, cognitive inflexibility and stereotyped behavior in the T-maze test, decreased social interaction and play behavior, as well as motor hyperactivity. Prenatal VPA also decreased dopamine synthesis and activity in the striatum and prefrontal cortex, as well as dopamine transporter, D1 and D2 receptors, and TH expressions. Moreover, prenatal VPA increased TH+ immunoreactive neurons of the ventral tegmental area-substantia nigra complex. In conclusion, the dopaminergic hypoactivity associated with the behavioral impairments exhibited by the rats that received prenatal VPA suggests the important role of this system in the establishment of the characteristic symptoms of ASD in juvenile and adult males. Dopamine was demonstrated to be an important biomarker and a potential pharmacological target for ASD.

Mutations in the Transcription Factor 20 (TCF20) have been identified in patients with autism spectrum disorders (ASDs), intellectual disabilities (IDs), and other neurological issues. Recently, a new syndrome called TCF20-associated neurodevelopmental disorders (TAND) has been described, with specific clinical features. While TCF20's role in the neurogenesis of mouse embryos has been reported, little is known about its molecular function in neurons. In this study, we demonstrate that TCF20 is expressed in all analyzed brain regions in mice, and its expression increases during brain development but decreases in muscle tissue. Our findings suggest that TCF20 plays a central role in dendritic arborization and dendritic spine formation processes. RNA sequencing analysis revealed a downregulation of pre- and postsynaptic pathways in TCF20 knockdown neurons. We also found decreased levels of GABRA1, BDNF, PSD-95, and c-Fos in total homogenates and in synaptosomal preparations of knockdown TCF20 rat cortical cultures. Furthermore, synaptosomal preparations of knockdown TCF20 rat cortical cultures showed significant downregulation of GluN2B and GABRA5, while GluA2 was significantly upregulated. Overall, our data suggest that TCF20 plays an essential role in neuronal development and function by modulating the expression of proteins involved in dendrite and synapse formation and function.

Obesity leads to a number of health problems, including learning and memory deficits that can be passed on to the offspring via a developmental programming process. However, the mechanisms involved in the deleterious effects of obesity on cognition remain largely unknown. This study aimed to assess the impact of obesity on the production of sphingolipids (ceramides and sphingomyelins) in the brain and its relationship with the learning deficits displayed by obese individuals. We also sought to determine whether the effects of obesity on brain sphingolipid synthesis could be passed on to the offspring. Learning abilities and brain concentration of sphingolipids in male and female control and obese founder rats (F0) and their offspring (F1) were evaluated, respectively, by the novel object recognition test and by ultra-performance liquid chromatography tandem mass spectrometry. In addition, a global lipidome profiling of the cerebral cortex and hippocampus was performed. Both male and female F0 rats showed impaired learning and increased concentrations of ceramides and sphingomyelins in the hippocampus and frontal cortex compared to their control counterparts. However, the overall lipidome profile of these brain regions did not change with obesity. Remarkably, the alterations in brain sphingolipid synthesis, as well as the cognitive impairment induced by obesity, were also present in adult F1 male rats born to obese mothers or sired by obese fathers and were associated with enhanced expression of mRNAs coding for enzymes involved in the de novo synthesis of ceramides. These results show that the cognitive deficits and impaired sphingolipid metabolism induced by obesity can be transmitted to the offspring through both the maternal and paternal lineages and suggest that an increase in the brain concentration of sphingolipids could play a causal role in the cognitive deficits associated with obesity.

Brain damage induced by ischemia promotes the development of cognitive dysfunction, thus increasing the risk of dementia such as Alzheimer's disease (AD). Studies indicate that cellular acidification-triggered activation of asparagine endopeptidase (AEP) plays a key role in ischemic brain injury, through multiple molecular pathways, including cleavage of its substrates such as SET (inhibitor 2 of PP2A, I ) and Tau. However, whether direct targeting AEP can effectively prevent post-stroke cognitive impairment (PSCI) remains unanswered. Here, we explored the therapeutic effect and underlying mechanism of the AEP inhibitor AENK on cognitive impairment of the rats with middle cerebral artery occlusion (MCAO) and on neuronal damage in cultured primary neurons exposed to oxygen and glucose deprivation (OGD). We found that the administration of AENK significantly reduces activated AEP levels in ischemic rat brains, attenuates cognitive deficits, and rescues synaptic dysfunction. For the mechanism, with AEP inhibition, cleavage of SET, inhibition of protein phosphatase 2A (PP2A), and Tau hyperphosphorylation resulted from PP2A inhibition, were all completely or partially reversed. In primary neurons, AENK effectively prevents AEP activation, SET cleavage and cytoplasmic retention, tau hyperphosphorylation and synaptic damage induced by OGD. We conclude that AENK ameliorates cognitive impairment and prevents tau hyperphosphorylation, through inhibiting AEP-mediated cleavage of SET in ischemic brain injury, and direct inhibition of AEP might be a potential therapeutic strategy for preventing synaptic damage and cognitive impairment after stroke.

Aging is the most common risk factor for Multiple Sclerosis (MS) disease progression. Cellular senescence, the irreversible state of cell cycle arrest, is the main driver of aging and has been found to accumulate prematurely in neurodegenerative diseases, including Alzheimer's and Parkinson's disease. Cellular senescence in the central nervous system of MS patients has recently gained attention, with several studies providing evidence that demyelination induces cellular senescence, with common hallmarks of p16INK4A and p21 expression, oxidative stress, and senescence-associated secreted factors. Here we discuss the current evidence of cellular senescence in animal models of MS and different glial populations in the central nervous system, highlighting the major gaps in the field that still remain. As premature senescence in MS may exacerbate demyelination and inflammation, resulting in inhibition of myelin repair, it is critical to increase understanding of cellular senescence in vivo, the functional effects of senescence on glial cells, and the impact of removing senescent cells on remyelination and MS. This emerging field holds promise for opening new avenues of treatment for MS patients.

Hemorrhagic stroke (HS) mainly includes intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH), both of which seriously affect the patient's prognosis. Cerebrospinal fluid (CSF) metabolites and HS showed a link in observational studies. However, the causal association between them is not clear. We aimed to establish the optimal causality of CSF metabolites with HS. Mendelian randomization (MR) was employed to identify associations between CSF metabolites and different sources of HS. Univariable MR and false discovery rates (FDR) were used to identify initial causal associations. Linkage disequilibrium score regression determined genetic correlations. Multiple sensitive analyses ensured the reliability of the results. Multivariable MR and MR Bayesian Model Averaging were used to identify the optimal causal associations. The combined effects of metabolites and HS were assessed by meta-analyses. Pathway analyses were performed to identify potential pathways of action. Reverse MR was also conducted to identify reverse causal associations. Finally, Corresponding blood metabolites were used to explore the multiple roles of metabolites. We identified 20 CSF metabolites and six metabolic pathways associated with ICH; 15 CSF metabolites and three metabolic pathways associated with SAH. Nineteen and seven metabolites were causally associated with deep and lobar ICH, respectively. CSF levels of mannose (OR 0.63; 95% CI 0.45-0.88; P = 0.0059) and N-acetyltaurine (OR 0.68; 95% CI 0.47-0.98; P = 0.0395) may serve as the optimal exposures for ICH and SAH, respectively. Additionally, CSF ascorbic acid 3-sulfate levels significantly decrease the risk of deep ICH (OR 0.79; 95% CI 0.66-0.94; p = 0.0065; P = 0.091). Supplemental analysis of blood metabolites suggested multiple roles for CSF and blood N-formylanthranilic acid and hippurate. There are significant causal associations between CSF metabolites and HS, which provides a further rationale for the prevention and monitoring of ICH and SAH.

The natural compound orotic acid and its anionic form, orotate, play a pivotal role in various biological processes, serving as essential intermediates in pyrimidine de novo synthesis, with demonstrated connections to dietary, supplement, and neurodrug applications. A novel perspective on biomolecular aggregation at the nanoscale, particularly pertinent to neurodegeneration, challenges the established paradigm positing that peptide (amyloid beta) and protein (tau) aggregation mainly govern the molecular events underlying prevalent neuropathologies. Emerging biological evidence indicates a notable role for G-quadruplex (G4) DNA aggregation in neurodegenerative processes affecting neuronal cells, particularly in the presence of extended (GC) repeats in nuclear DNA sequences. Our study concerns d[(GGGGCC)GGGG], a G4-forming DNA model featuring GC repeats that is in correlation with neurodegeneration. Through different investigations utilizing spectroscopic techniques (CD, UV, and thermal denaturations), PAGE electrophoresis, and molecular docking, the study explores the influence of orotate on the aggregation of this neurodegeneration-associated DNA. A computational approach was employed to construct an in silico model of the DNA aggregate, which involved the docking of multiple G4 units and subsequent integration of the ligand into both the DNA monomer and its in silico aggregated model. The convergence of computational analyses and empirical data collectively supports the hypothesis that orotate possesses the capability to modulate the aggregation of neurodegeneration-related DNA. Notably, the findings suggest the potential utility of orotate as a neurodrug, especially for the therapy of amyotrophic lateral sclerosis (ALS) and Frontotemporal Dementia (FTD), with its current status as a dietary supplement indicating minimal safety concerns. Additionally, orotate demonstrated a slight increase in mitochondrial dehydrogenase activity as assessed by the MTT assay, which is beneficial for a neurodrug as it suggests a potential role in enhancing mitochondrial function and supporting neuronal health.