This study investigated the effect of single Gαo1 and Gαo2, as well as double Gαo1/2 knockout on the cerebellar anatomy and synapse formation. The alpha subunit of the G protein Go exists in two splice variants. Knockout of certain Gαo subtypes result in strong-mainly motor-deficits in mice, and mutations in the responsible gene locus in humans can result in severe encephalopathies. We aimed to decipher the hitherto incompletely understood contribution of the individual Gαo subunits to the anatomy and synapse formation of the cerebellum. Knockout of Gαo1 reduced the size of the cerebellum by 11%, accompanied by maximal reductions of the molecular layer thickness in the central lobule III (-30%) and molecular layer area in the uvula (-33%). Knockout of Gαo2 increased cerebellar size, molecular layer thickness in central lobule II (+18.6%), and area of the culmen (+37%). Combined deletion of Gαo1 and Gαo2 reduced cerebellar size by 12%, molecular layer thickness and area of the declive (by -27.3% and -23.4%, respectively). Moreover, VGLUT2-positive climbing fiber contacts to Purkinje cells were reduced in Gαo1 knockout mice (on average by 40%). Similarly, VGLUT1 expression was reduced (on average by 17.3%). The knockout of Gαo2 promoted climbing fiber contacts (+14.3% on average, at a maximum of +52.6% in the central lobule II), VGLUT1 was less affected. Double knockout mice exhibited negative effects on VGLUT2 (-35% overall number) and VGLUT1 (-23% on average in expression levels). VGAT-positive synaptic contacts were also diminished for Gαo1 and double knockout (-25% and -31% overall number, respectively) and increased for Gαo2 knockout (+13% on average). In line with this, negative effects on the dendritic outgrowth of Purkinje cells were observed in both Gαo1 -/- and Gαo -/-mice, while knockout of Gαo2 promoted dendrite outgrowth. Taken together, the two Gαo splice variants contrarily contribute to the development of the cerebellum, with Gαo1 representing the dominant subunit.
Rett syndrome (RTT), caused by mutations in MECP2, is a complex neurological disorder characterized by myriad physiological disruptions, including early closure of the critical period of developmental plasticity and precocious formation of perineuronal nets (PNNs). PNNs are lattice-like substructures of extracellular matrix (ECM) that enwrap specific subpopulations of neurons. PNNs are essential in the modulation of neuronal plasticity and brain maturation, and their enzymatic disruption can partially restore plasticity in adults and improve memory. Although precocious PNN formation is well-established in RTT, little is known of the cellular, molecular, or biochemical underpinnings of their precocious formation, or whether precocious PNN formation is due to cell-autonomous or non-cell-autonomous mechanisms. While PNNs form on subsets of neurons throughout the brain, astrocytes secrete many ECM components that form PNNs, and they play a central role in controlling closure of the critical period. We find that Mecp2-null mouse astrocyte conditioned media induces the expression of the key PNN component Hapln1 and causes enhanced PNN formation on wildtype mouse neurons in vitro, suggesting that Mecp2-null astrocytes play a key role in the precocious formation of PNNs in RTT. Further, we identify increased expression of HAPLN1 and other PNN/ECM components in the developing mouse Mecp2-null cortex, and demonstrate that PNNs are structurally and biochemically mature at an earlier developmental stage. These results provide essential insight into the mechanisms and structure of aberrant PNNs in Mecp2-null cortex and identify potential new avenues for targeted rescue or reversal of the precocious closing of the critical period in RTT.
Depression is a leading cause of global disability, yet remains insufficiently treated by conventional monoaminergic antidepressants, which are limited by their delayed onset, variable efficacy, and significant side effects. Accumulating evidence positions neuroinflammation, driven by glial dysfunction, peripheral-central immune crosstalk, and associated cellular stress pathways as a pivotal upstream mechanism in the pathogenesis of depression, contributing to both neurotransmitter dysregulation and impaired synaptic plasticity. This review examines the integrative role of the Sigma-1 receptor (Sig-1R), a ligand-operated chaperone predominantly localized at the mitochondria-associated endoplasmic reticulum membrane (MAM), as a promising therapeutic target for mitigating this neuroinflammatory cascade. We systematically synthesize preclinical evidence demonstrating that pharmacological activation of Sig-1R produces broad anti-neuroinflammatory effects, including the promotion of microglial homeostasis and a shift toward an anti-inflammatory phenotype, attenuation of reactive astrogliosis, suppression of key pro-inflammatory signaling hubs such as NF-κB and the NLRP3 inflammasome, and mitigation of oligodendrocyte dysfunction. Beyond immunomodulation, Sig-1R activation alleviates endoplasmic reticulum stress, enhances autophagic and mitophagic clearance, supports mitochondrial bioenergetics, and strengthens endogenous antioxidant defenses. Together, these actions disrupt the vicious cycle linking cellular stress, inflammation, and synaptic impairment. We also evaluate advances in representative Sig-1R agonists and review available clinical trial data, including results on the novel multi-target agent AXS-05. Genetic and pharmacological loss-of-function studies further emphasize the essential role of Sig-1R in mood regulation and stress resilience. In summary, the Sigma-1 receptor serves as a key regulator of cellular homeostasis and adaptation. Its agonists represent a promising therapeutic strategy that moves beyond symptomatic monoaminergic modulation to mechanistically target the core inflammatory and proteostatic disturbances in depression, offering the potential for improved treatment efficacy.
Reliable biomarkers for autoimmune encephalitis (AE) are limited, and emerging CSF markers are not incorporated into current diagnostic criteria. Prognostic tools remain insufficient, highlighting the need for biomarkers that support both early diagnosis and assessment of disease severity and prognosis. In this multicenter prospective cohort study, we analyzed clinical data and paired CSF-serum samples from adults with definite AE enrolled in the German Network for Research on Autoimmune Encephalitis registry and the CSF biobank of Hannover Medical School. Of 2,330 screened individuals, 92 patients with anti-N-methyl-d-aspartate receptor (NMDAR, n = 53), anti-leucine-rich glioma-inactivated 1 (LGI1, n = 20), or anti-contactin-associated protein-like 2 (CASPR2, n = 19) encephalitis were included and followed longitudinally for a median of 38 months. Control groups comprised patients with relapsing multiple sclerosis, varicella-zoster virus encephalitis, and noninflammatory neurologic conditions (each n = 30), as well as antibody-positive patients without AE (n = 15), with the groups frequency-matched for age and sex. Kappa free light chain (KFLC), neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and cytokines were measured in paired CSF-serum samples obtained at baseline and during follow-up. Disease severity and disability were assessed using the Clinical Assessment Scale in Autoimmune Encephalitis (CASE) score and the modified Rankin Scale (mRS). Intrathecal synthesis of KFLC was detected in 94% of anti-NMDAR, 50% of anti-LGI1, and 53% of anti-CASPR2 encephalitis cases, demonstrating higher diagnostic sensitivity than CSF-restricted oligoclonal bands or pleocytosis. Diagnostic specificity across pooled control groups was moderate at 44% but reached 90% when compared with noninflammatory neurologic controls. CSF NfL z-score levels were strongly associated with baseline disease severity, with each 1-standard deviation increase corresponding to an approximately 10-point higher CASE score, independent of clinical covariates (β = 0.61). Longitudinal changes in NfL concentrations in CSF and serum were associated with disease severity and neurologic disability at follow-up (CASE score: adjusted R2 = 0.401; mRS score: adjusted R2 = 0.203). GFAP and cytokines showed limited diagnostic or prognostic utility. Intrathecal KFLC synthesis represents a highly sensitive CSF marker that supports early suspicion of autoimmune encephalitis and prompts antibody testing. NfL provides robust biochemical information on baseline disease severity and longitudinal changes that may aid prognostic assessment across AE subtypes.
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterised by progressive muscle weakness in both bulbar and extremity muscles, leading to a diverse clinical phenotype with motor and non-motor symptoms. Approximately 85% of ALS cases are sporadic (sALS), while the remaining 10%-15% are familial (fALS). Biological biomarkers of sporadic ALS remain poorly understood, hindering precise patient screening, delaying diagnosis and negatively affecting prognosis. This study aims to identify potential proteomic biomarkers by comparing the cerebrospinal fluid (CSF) of sALS patients with that of patients suffering from other neurological diseases. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for proteomic profiling of CSF samples from 24 sALS patients and 26 patients with other neurological diseases. The complete protein expression profiles were compared using a two-tailed Student's t-test, with a p < 0.05 considered statistically significant with additional FDR correction at the 0.1 level. Proteomic analysis of CSF samples identified significant quantitative changes in 96 proteins with threshold p < 0.05 and 74 proteins with FDR < 0.1 between sALS and non-ALS patients, including alterations in proteins associated with neurodegenerative processes, such as amyloid precursor proteins and inflammatory markers. CSF proteomic analysis reveals altered inflammatory and neurodegenerative metabolic pathways, providing valuable insights into the proteomic landscape of sALS. Several dysregulated proteins were consistent with the disease mechanisms highlighted in previous studies. These findings represent a step forward in developing personalised approaches for diagnosing and managing the disease.
Depression can be treated with traditional pharmaceuticals targeting monoaminergic function, nontraditional drug classes and neuromodulatory interventions. To identify mechanisms of action shared across clinically-effective antidepressant treatment categories, we performed two systematic meta-analyses of public transcriptional profiling data from adult laboratory rodents (rats, mice). The outcome variable was gene expression, measured by microarray or RNA-Seq from bulk-dissected tissue from two depression-related brain regions (hippocampus, cortex). Relevant datasets were identified in the Gemma database of curated, reprocessed transcriptional profiling data using predefined search terms and inclusion/exclusion criteria (hippocampus: June 24, 2024, cortex: July 10, 2024). Differential expression results were extracted for all genes, minimizing bias. For each gene, a random effects meta-analysis model was fit to antidepressant vs. control effect sizes (Log2 Fold Changes) from each study for each brain region, with follow-up analyses exploring sources of effect heterogeneity. For the hippocampus, 15 relevant studies were identified, containing 22 antidepressant vs. control group comparisons (collective n = 313 samples), with approximately half representing traditional versus nontraditional antidepressants. Of 16 439 analyzed genes, 58 were consistently differentially expressed (False Discovery Rate (FDR) < 0.05) following treatment. Antidepressant effects were enriched in the dentate gyrus and in gene sets related to stress regulation, brain growth and plasticity, vasculature and glia, and immune function. Comparisons with single nucleus RNA-Seq confirmed effects on specific hippocampal cell types, including potential rejuvenation of dentate granule neurons. For the cortex, 13 studies were identified, containing 16 antidepressant vs. control group comparisons (collective n = 233 samples). Of 15 583 analyzed genes, only one was consistently differentially expressed (FDR < 0.05: Atp6v1b2), but overall expression patterns moderately resembled the hippocampus. These genes and pathways showing consistent differential expression across treatment categories may be promising targets for novel therapies. Future work should explore relevance to human clinical populations and potential heterogeneity introduced by sex and subregion.
Plasma phosphorylated tau (p-tau) biomarkers have improved the diagnosis of Alzheimer's disease (AD), but evidence in early-onset populations remains limited. We evaluated the diagnostic performance of plasma p-tau217 and p-tau181 levels in patients with early-onset AD (EOAD) and early-onset frontotemporal dementia (EOFTD). We analyzed 185 patients (EOAD = 150, EOFTD = 35) aged ≤ 65 years from the LEAF study (2021-2023). Plasma p-tau217, p-tau181, neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) levels were measured by immunoassays. Both plasma p-tau217 (AUC = 0.831) and p-tau181 (AUC = 0.862) levels demonstrated high discriminative performance, with no significant difference between the two p-tau isoforms. P-tau levels were higher in patients with EOAD, whereas NfL levels were higher in EOFTD and were elevated in those with EOAD participants with severe hippocampal atrophy. Adding NfL, GFAP, and APOE ε4 status further improved the discriminative accuracy for differentiating EOAD from EOFTD. Plasma p-tau217 and p-tau181 are effective biomarkers for distinguishing biologically defined EOAD from EOFTD. Incorporating NfL, GFAP, and APOE ε4 status further enhances diagnostic accuracy.
Malformations of cortical development (MCD) are major causes of refractory epilepsies, particularly in children. Cannabidiol (CBD) has demonstrated efficacy in treatment of refractory pediatric epilepsy syndromes. However, preclinical studies addressing its developmental stage-dependent effects, particularly in experimental models of MCD, remain limited. We evaluated the effects of CBD on induced hyperexcitability in cortical brain slices from Wistar rats with and without MCD at distinct developmental stages and examined whether alterations in endocannabinoid system (ECS) components are associated with CBD responsiveness. MCD was induced by bilateral cortical freeze lesion at postnatal day (P0-1) to generate microgyria in the somatosensory cortex. Local field potentials were recorded from cortical slices of juvenile (P21-30) and adolescent (P35-60) Sham and MCD rats. CBD was applied under three different timing paradigms to assess its effects on epileptiform activity induced by modified artificial cerebrospinal fluid containing 4-aminopiridine (4-AP) and 0 Mg2+ (mACSF). Gene expression of ECS components was quantified in cortical tissue by RT-qPCR at both developmental stages. CBD co-applied with mACSF reduced short (>2-10 s) ictal events in slices from Sham and decreased prolonged (>100 s) ictal events in slices mainly from MCD animals at both ages. CBD did not attenuate pre-established hyperexcitability. However, pre-exposure to CBD delayed ictal onset, reduced overall ictal events frequency, particularly in juvenile Sham animals, and abolished long-lasting ictal events in slices from adolescent animals. Cortical samples from juvenile MCD animals exhibited increased gene expression of NAPE-PLD, MGLL, CB1R and CB2R, whereas DAGL was reduced in adolescence. CBD exerted age- and context-dependent modulatory effects on cortical hyperexcitability, with stronger preventive than therapeutic actions. Developmental stage, cortical organization and alterations in ECS components may influence CBD responsiveness. These findings highlight the importance of maturational, cortical network and molecular context when evaluating cannabinoid-based strategies for MCD-related refractory epilepsies.
The SH-SY5Y human neuroblastoma cell line is widely used as an in vitro model of β-amyloid (Aβ) neurotoxicity in Alzheimer's disease (AD). However, the lack of standardized protocols for assessing Aβ toxicity-including differentiation strategies for SH-SY5Y cells-limits the comparability of results across studies. To address these issues, we conducted a systematic review and meta-analysis to evaluate how methodological factors influence Aβ-induced toxicity in SH-SY5Y cells. We included 359 eligible studies encompassing 1192 MTT-based comparisons of cell viability between Aβ-treated and control SH-SY5Y cells. A three-level meta-analysis estimated mean cell viability after Aβ exposure at 63% of control levels (95% CI [61.6; 64.3]), with very high heterogeneity (I2 = 99.6%). Meta-regression identified significant associations between increased toxicity and higher Aβ concentrations, longer exposure durations, and the use of peptide preparations described as fibrils. Conversely, differentiation protocols, duration, and cell density did not significantly influence toxicity outcomes. Reporting quality was often poor, with frequent omissions regarding cell line origin, authentication, contamination testing, Aβ preparation details, and nature of the experimental unit. Overall, our findings show robust Aβ toxicity in SH-SY5Y cells, primarily driven by dose, exposure time, and Aβ aggregation state, but not cell differentiation status. Our conclusions highlight the critical need for better reporting of Aβ exposure parameters to enhance reproducibility and translational potential in AD research.
The evolution of the human brain underlies our higher-order cognitive functions. In particular, the cerebral cortex, the outermost layer of the brain, has rapidly evolved to contain a disproportionately large number of neurons relative to the rest of the brain. Much of this expansion is attributed to the enlargement and diversification of the pool of neural precursors, which proliferate and differentiate into the neurons and glia of the brain. How the human cerebral cortex has evolved remains an active area of investigation. With the advent of pluripotent stem cell and brain organoid technologies, comparative genomic studies between humans, mice, and nonhuman primates have identified human-specific genes or pathways during neurodevelopment. The utility of these models relies on the ability of brain organoids to preserve the cytoarchitecture and species-specific developmental trajectories of diverse neural and glial cell types that are observed in vivo. This review will discuss how brain organoids recapitulate aspects of interspecies differences during cortical development, specifically neural precursor expansion, neurogenesis, and gliogenesis, and how these models can be improved to enable a deeper understanding of human brain evolution. Unraveling the cellular and molecular mechanisms underlying cross-species differences in brain expansion could also provide key insights into neurodevelopmental diseases, particularly those where brain size is affected.
Parkinson's disease (PD) is a neurodegenerative disorder marked by substantial heterogeneity in pathological distribution, disease trajectories, and coexisting neuropathologies. Despite this biological complexity, current diagnosis and staging of PD remain largely anchored in clinical manifestations. Neuronal aggregation of misfolded α-synuclein and degeneration of the nigrostriatal dopaminergic system precede the onset of motor symptoms; this phase is termed the prodromal stage of PD. Therefore, clinically based frameworks inherently limit early detection and stratification. In contrast, Alzheimer's disease has undergone a paradigm shift toward a biomarker-driven biological definition, prompting a similar reappraisal of PD as a biologically defined disease continuum. Accumulating evidence indicates that pathological α-synuclein aggregates in PD extend beyond the central nervous system and exhibit heterogeneous patterns of initiation and propagation. Methodological advances have expanded the capacity to detect these pathological species in vivo. In particular, α-synuclein seed amplification assays (SAA) enable the detection of seeding-competent α-synuclein species in biofluids and peripheral tissues, providing evidence consistent with α-synuclein pathology; however, SAA should not be interpreted as a direct reflection of disease stage, progression, or pathological burden. Furthermore, the development of α-synuclein positron emission tomography ligands offers the prospect of non-invasive visualization of pathological burden, spatial distribution, and longitudinal target engagement, thereby complementing biofluid-based approaches. Together, these biomarker advances underpin emerging biologically anchored classification and staging frameworks, such as the SynNeurGe system and the Neuronal α-Synuclein Disease Integrated Staging System (NSD-ISS). These frameworks integrate α-synuclein pathology, neurodegeneration, genetic background, and clinical features to define disease identity and progression across asymptomatic, prodromal, and manifest stages. We synthesize recent advances in α-synuclein-centered biomarkers and biological staging frameworks and discuss how their convergence is beginning to reshape PD from a primarily symptom-based diagnosis toward a molecularly grounded disease continuum. This transition has the potential to complement clinically defined PD with biologically informed perspectives.
Multiple sclerosis is a chronic demyelinating disease of the central nervous system caused by an immune-mediated inflammatory process. Its aetiology remains unclear, and numerous pathogenetic theories have been proposed. The diversity of clinical manifestations and the lack of reliable biomarkers make diagnosis challenging. Serum neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) have been investigated as potential biomarkers for disease progression and response to disease-modifying therapies; however, their specificity and sensitivity remain variable, particularly in the presence of other conditions associated with neuronal damage and neurodegeneration. This retrospective study analysed serum NfL and GFAP levels in 149 patients with multiple sclerosis and 40 healthy controls. Additionally, the association between the two biomarkers was evaluated in patients with and without polyneuropathy to assess their reliability and prognostic value for disease severity and progression. Serum NfL was found to be a reliable marker of disease activity and progression. In contrast, GFAP demonstrated limited specificity and was not suitable as a single, independent biomarker. The presence of co-existing polyneuropathy influenced biomarker levels and complicated their interpretation. Serum NfL shows promise as a reliable biomarker for monitoring disease activity and progression in multiple sclerosis. However, GFAP should not be used independently due to its limited specificity. Co-existing polyneuropathy may further reduce the reliability of these biomarkers, highlighting potential diagnostic challenges in clinical practice.
Neuromelanin-(NM) containing organelles are sub-cellular auto-lysosomal structures composed of three main compartments: NM pigment, protein matrix, and lipid bodies. These organelles accumulate during aging and are found predominantly in the catecholaminergic neurons of Substantia Nigra (SN) and Locus Coeruleus (LC), the main regions affected in Parkinson's disease (PD). NM serves a protective function by sequestering potentially toxic metals like Cu, Fe, and Al. However, NM released from degenerating neurons may lead to a cascade of events resulting in neuroinflammation and neurodegeneration. Therefore, elemental analysis of NM-containing organelles presents a crucial step to understand aging and PD. In LC, such studies are limited because NM isolation requires large postmortem cohorts and analyses may be impaired by tissue processing. By integrating high resolution electron microscopy (EM), nano-secondary ion mass spectrometry (nano-SIMS), and energy dispersive X-ray (EDX) microscpectroscopy, the elemental composition of intact NM-containing organelles was analyzed in seven postmortem LC tissues. Chemical mapping with down to 5-10 nm lateral resolution (EDX) fostered discrimination of structural composition (N, P, S, Cl) and metal storage (Al, Ca, Fe) across neurons and within individual NM-containing organelle sub-compartments (with diameters down to 0.2 μm for lipid bodies) from the same sample. NM-containing organelles were identified by an elemental fingerprint pattern. Metals accumulations were localized predominantly to the NM pigment compartment identified by its pheomelanin-rich portion (S). This confirms NM's role in accumulating physiological as well as potentially toxic metal species. Moreover, semi-quantitative analyses provided insights into inter- and intra-subject NM metal accumulation, showing that S and Fe exhibited a positive aging trend. Hemispheric asymmetry was observed for Al, Ca, and Fe, with higher levels observed in NMs of the right brain hemisphere suggesting region-specific accumulation that warrants further investigation to better understand aging-related changes and the neuronal vulnerability of the LC in PD.
Adult neurogenesis in the dentate gyrus (DG) of the hippocampus is a dynamic and tightly regulated process that is finely regulated by a diverse array of transcription factors. While the transcription factor Etv5, a member of the Erythroblast Transformation Specific (ETS) family, has been implicated in embryonic development by regulating cell proliferation and differentiation across various tissues, its specific role in adult hippocampal neurogenesis remains unexplored. Here, we show that conditional ablation of Etv5 specifically in adult-born granule cells (GCs) increases the proportion of Doublecortin (DCX)-positive immature GCs at the expense of mature neurons, without affecting the proportion of neither radial glia-like cells (RGCs) nor SOX2+ progenitor cells within the neurogenic niche. Furthermore, Etv5 conditional mutant mice exhibit reduced dendritic complexity and defects in spine development, indicating impaired neuronal maturation and suggesting deficits in synaptic integration of adult-born GC neurons.
KIBRA (WWC1) has been a subject of scientific interest and investigation for almost two decades following its initial association with nonpathological variation in human memory performance. Work in a variety of animal models confirms that KIBRA supports memory function and demonstrates that regulation of AMPA-type glutamate receptors is a key mechanism by which KIBRA modulates neuronal function. KIBRA is a scaffolding protein at excitatory synapses, and its interactome is enriched for proteins that regulate AMPA receptor (AMPAR) trafficking and synaptic plasticity as well as neurodevelopmental disorders. Here, I provide a comprehensive discussion of known and potential mechanisms by which KIBRA and its interactome regulate adaptive brain function, encompassing AMPAR trafficking, synaptic plasticity, and experience-induced modification of circuit dynamics. Disrupted KIBRA function is implicated in a variety of cognitive disorders, and I review mechanisms by which KIBRA may contribute to neuropathology as well as recent work suggesting that KIBRA manipulation may be a target for cognitive enhancement. I expand the discussion to include recent data identifying the KIBRA homolog WWC2 as a regulator of GABAA receptor expression at inhibitory synapses. In contrast to their distinct roles at excitatory and inhibitory synapses, KIBRA and WWC2 promote dendritic arborization in a non-redundant manner, and I discuss potential shared mechanisms by which WWC proteins regulate neuronal morphology as well as evidence that this function of WWC proteins may be disrupted in neurodevelopmental pathology.
During development, entry of any substances from the circulation into the brain is tightly regulated by a series of blood-brain interfaces. Notably, the choroid plexuses, which form the blood-cerebrospinal fluid barrier, serve as a key interface for molecular exchange in early life. Control mechanisms within the choroid plexuses include efflux transporters and conjugating enzymes, such as glutathione S-transferases and UDP-glucuronosyltransferases, which have been shown to play key roles in safeguarding the developing brain. Sulphotransferases are another family of conjugating enzymes reported to be highly expressed in the choroid plexus in humans and rats during development. However, their activity and functional significance in the central nervous system remain poorly understood. In the present study, sulphotransferase activity was measured in the lateral and fourth ventricle choroid plexus from rats at embryonic Day 19 and postnatal Day (P)1, 3, 8 and 30. Activity was correlated with expression of isoenzymes by RT-qPCR. Inhibition studies were performed by co-incubating a prototypical sulphotransferase substrate with a potential substrate or inhibitor. Finally, assays in freshly isolated live tissue were conducted to assess sulphoconjugation under more physiologically relevant conditions. Results showed that both sulphotransferase activity and expression of Sult1a1 in the choroid plexus were markedly increased at P1 to P3. This distinct temporal pattern suggests age- and tissue-specific roles of choroidal sulphotransferase activity during the early postnatal period. Interactions with xenobiotics and neuroendocrine factors further suggest that these enzymes may contribute to multiple processes during this critical window, including protection against potentially harmful substances and regulation of neurotransmitters. Furthermore, the observed modulation of choroidal sulphotransferase activity by various exogenous substances suggests that developmental exposure could disrupt sulphotransferase-mediated biological processes, with potential consequences for normal neurodevelopment.
Glutamate transporters are essential for maintaining CNS homeostasis by clearing extracellular glutamate following synaptic transmission. Dysregulation of these transporters contributes to glutamate-mediated excitotoxicity across numerous neurological disorders, including ischemic stroke, underscoring their potential as therapeutic targets. However, the regulatory response of these transporters following ischemic insult remains poorly defined. In this study, using a model of oxygen-glucose deprivation in primary rat glial cultures, we report aberrant trafficking of the astrocytic glutamate transporter GLT-1 following ischemic insult. This response is characterized by increased transporter internalization and degradation, accompanied by reduced glutamate uptake capacity. Focusing on post-translational modifications (PTMs), we found that GLT-1 ubiquitination is markedly increased after ischemic insult and coincides with transporter internalization. Importantly, disrupting this ubiquitination interaction through mutation of C-terminal GLT-1 lysine residues restores GLT-1 surface expression and rescues glutamate uptake capacity through preventing early endosome 1 (EEA1)-mediated internalization. Additionally, we report that inhibition of C-terminal GLT-1 PTMs confers neuroprotection following ischemic insult in organotypic hippocampal brain slices. Together, these findings demonstrate that ischemia-induced dysregulation of GLT-1 trafficking plays a critical role in impaired glutamate clearance and cellular recovery, highlighting GLT-1 ubiquitination as a potential therapeutic target for ischemic injury.
Previous studies have shown that dorsal vagal complex (DVC) astrocytes play important roles in homeostatic regulation of food intake and caloric balance, specifically upregulation of NMDA receptor-mediated glutamatergic signaling to brainstem dorsal motor nucleus of the vagus (DMV) motoneurons restores caloric balance following exposure to caloric dense diets. DMV neurons are critical to the regulation of gastric functions, including motility, tone, and emptying; hence food intake and energy homeostasis. Prior studies have also shown that caloric intake in female rats fluctuates across the estrus cycle, with food intake being lowest during periods of high estrogen levels. The aim of the current study was to investigate whether these estrus-cycle dependent oscillations in food intake also involve DVC astrocyte adaptation. Immunohistochemical measurement of astrocytes across the estrus cycle uncovered an increase in glial-fibrillary acidic protein immunoreactivity (GFAP-IR) as well as an increase in astrocyte morphological complexity associated with high estrogen levels. Chemogenetic inhibition of DVC astrocytes eliminated food intake oscillations, whereas chemogenetic activation resulted in a consistent decrease in food intake, regardless of estrus status. Electrophysiological recordings from DMV neurons revealed that the estrus-dependent decrease in food intake was associated with activation of DMV NMDA receptors, and pharmacological inhibition of either estrogen receptors or brainstem astrocytes prevented this mechanism. In contrast, application of estradiol uncovered astrocyte- and NMDA-receptor dependent signaling to DMV neurons in low estrogen states. The findings of the present study demonstrate that DVC astrocytes and/or NMDA signaling play a fundamental role in estrogen-dependent fluctuations in food intake and energy homeostasis.
Extracellular secretion of neurotransmitters, proteins, and peptides by cells of the central nervous system underpins neurological function and homeostasis. Decades of elegant research have illuminated the molecular mechanisms and machinery that support the release of neurotransmitters via synaptic vesicle exocytosis, as well as the secretion of signal-peptide bearing proteins through the endoplasmic reticulum (ER)-Golgi based secretory pathways. However, it is now increasingly appreciated that signal-peptide lacking "leaderless" proteins can also be secreted via ER-Golgi-independent mechanisms collectively termed unconventional protein secretion (UcPS). In this review, we highlight the physiological and pathological consequences of UcPS in the central nervous system. UcPS supports the secretion of aggregation-prone proteins such as α-synuclein and mutant huntingtin, pro-inflammatory mediators including interleukin-1β and high mobility group box protein 1, and neuroprotective or angiogenic factors such as fibroblast growth factor 2. Furthermore, several retroelement-derived proteins, encoded by ancient genomic elements with structural homology to retroviruses, are also secreted via unconventional pathways, and are thought to regulate essential CNS processes such as synaptic plasticity. These diverse cargoes underscore the functional range of UcPS in neuronal and glial biology. We summarize current understanding of the major UcPS pathways used by CNS cells. These mechanisms include plasma-membrane pore-mediated release facilitated by proteins such as gasdermin-D, as well as vesicular routes in which UcPS cargoes enter organelles of the autophagic and endolysosomal systems that subsequently fuse with the plasma membrane to enable extracellular release. Finally, we discuss key unresolved questionRecent evidence from HeLa cells suggests regarding the regulation of UcPS, including the molecular features that target select leaderless cargoes toward UcPS, how the balance between conventional secretion and UcPS shifts under cellular stress, and the current understanding of the diverse molecular machinery that mediates the vesicular form of UcPS.
Cytoplasmic inclusions containing TAR DNA-binding protein 43 kDa (TDP-43) are recognized as a major pathological feature of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Peptidyl-prolyl cis-trans isomerase A (PPIA) interacts with TDP-43 and influences its aggregation and function. This interaction is facilitated by PPIA Lys-acetylation. Here, we investigated whether restoring lysine acetylation homeostasis exerts protective effects on TDP-43 proteinopathy in vitro and in vivo and how this relates with PPIA. We found that vorinostat/SAHA, a broad-spectrum histone deacetylase (HDAC) inhibitor that increases PPIA acetylation, is able to reverse TDP-43 mislocalization in a cellular model of TDP-43 proteinopathy. We confirmed its effects in peripheral blood mononuclear cells from ALS patients and explored its impact on TDP-43 proteinopathy and PPIA acetylation in the Thy1-hTDP-43 mouse model. Thy1-hTDP-43 mice treated with SAHA showed a delayed onset of TDP-43 pathology, associated with PPIA nucleus-cytoplasm redistribution, lower neurodegeneration and neuroinflammation, and improved neuromuscular function markers. However, these effects were transient. When combined with arimoclomol, a heat shock protein co-inducer, a mitigation of the neurodegeneration was sustained. A synergistic effect was observed in periphery, greatly enhancing tubulin acetylation and reducing phosphorylated TDP-43 accumulation in the sciatic nerve and acetylcholine receptor γ-subunit expression in gastrocnemius muscle. This study suggests that HDAC inhibition could be beneficial in restoring TDP-43 localization and function through multiple mechanisms, including modulation of PPIA acetylation. The combination of lysine deacetylation inhibition and arimoclomol shows a synergistic effect in vivo and has potential as a therapeutic approach for patients.