Molecular Brain最新文献

Brain-derived neurotrophic factor (BDNF) is known for its potent prosurvival effect. Despite successfully replicating this effect in various clinical and pre-clinical models, the complete characterization of the molecular mechanisms underlying its neuroprotective action remains incomplete. Emerging research suggests a vital role for A-kinase anchoring proteins (AKAPs) as central nodal points orchestrating BDNF-dependent signaling. Among the over 50 identified AKAPs, AKAP6 has recently gained special attention due to its involvement in the neurotrophin-mediated survival of injured retinal ganglion cells (RGCs). However, the mechanisms by which AKAP6 responds to pro-survival BDNF signaling remain unknown. In this study, we shown that AKAP6 plays a crucial role in regulating BDNF-mediated NFAT transcriptional activity in neuronal survival by anchoring protein phosphatase calcineurin (CaN) and nuclear factor of activated T cells (NFATc4). Furthermore, we demonstrate that disrupting the anchoring of CaN diminishes the pro-survival effect of BDNF. Lastly, through experiments with NFATc4-/- mice, we provide evidence that NFATc4 acts downstream to BDNF's neuroprotection in vivo. These findings could offer valuable insights for developing neuroprotective strategies aimed at preserving injured neurons from degeneration and promoting their regeneration.

Neuroinflammation is a significant contributor to the pathology of glaucoma. Targeting key-mediators in this process is a realistic option to slow disease progression. Galectin-3 is a β-galactoside binding lectin that has been associated with inflammation in both systemic and central nervous system diseases. Elevated Galectin-3 has recently been detected in multiple animal models of glaucoma and inhibiting Galectin-3 using an intravitreal injection of TD139 (a Galectin-3 small molecule inhibitor) is neuroprotective. We queried whether this neuroprotective effect was translatable to another animal model and species. TD139 was intravitreally injected, in a rat ocular hypertensive model of glaucoma, 3 days after the induction of ocular hypertension (at peak intraocular pressure). Retinal ganglion cell survival and glial morphological markers were quantified. The degeneration of retinal ganglion cells was prevented by TD139 injection, but gross glial markers remained unaffected. These data confirm that the intravitreal injection of TD139 is neuroprotective in a rat ocular hypertensive model of glaucoma, while suggesting that the inhibition of Galectin-3 is not sufficient to alter the gross inflammatory outcome.

P/Q-type (Ca_v2.1) calcium channels mediate Ca²⁺ influx essential for neuronal excitability and synaptic transmission. The CACNA1A gene, encoding the Ca_v2.1 pore forming subunit, is highly expressed throughout the mammalian central nervous system. Alternative splicing of Ca_v2.1 pre-mRNA generates diverse channel isoforms with distinct biophysical properties and drug affinities, which are differentially expressed in nerve tissues. Splicing variants can also affect channel function under pathological conditions although their phenotypic implication concerning inherited neurological disorders linked to CACNA1A mutations remains unknown. Here, we quantified the expression of Ca_v2.1 exon 24 (e24) spliced transcripts in human nervous system samples, finding different levels of expression within discrete regions. The corresponding Ca_v2.1 variants, differing by the presence (+) or absence (Δ) of Ser-Ser-Thr-Arg residues (SSTR) in the domain III S3-S4 linker, were functionally characterized using patch clamp recordings. Further, the + /ΔSSTR isoforms were used to demonstrate the differential impact of the Familial Hemiplegic Migraine Type 1 (FHM-1) S218L mutation, located in the domain I S4-S5 linker, on the molecular structure and electrophysiological properties of Ca_v2.1 isoforms. S218L has a prominent effect on the voltage-dependence of activation of +SSTR channels when compared to ΔSSTR, indicating a differential effect of the mutation depending on splice-variant context. Structural modeling based upon Cav2.1 cryo-EM data provided further insight reflecting independent contributions of amino acids in distant regions of the channel on gating properties. Our modelling indicates that by increasing hydrophobicity the Leu218 mutation contributes to stabilizing a structural conformation in which the domain I S4-S5 linker is oriented alongside the inner plasma membrane, similar to that occurring when S4 is translocated upon activation.The SSTR insertion appears to exert an influence in the local electric field of domain III due to an change in the distribution of positively charged regions surrounding the voltage sensing domain, which we hypothesize impacts its movement during the transition to the open state. In summary, we reveal molecular changes correlated with distinct functional effects provoked by S218L FHM-1 mutation in hCa_v2.1 splice isoforms whose differential expression could impact the manifestation of the neurological disorder.

CNS tumours encompass a diverse group of neoplasms with significant morbidity and mortality. The SHH signalling pathway plays a critical role in the pathogenesis of several CNS tumours, including gliomas, medulloblastomas and others. By influencing cellular proliferation, differentiation and migration in CNS tumours, the SHH pathway has emerged as a promising target for therapeutic intervention. Current strategies such as vismodegib and sonidegib have shown efficacy in targeting SHH pathway activation. However, challenges such as resistance mechanisms and paradoxical effects observed in clinical settings underscore the complexity of effectively targeting this pathway. Advances in gene editing technologies, particularly CRISPR/Cas9, have provided valuable tools for studying SHH pathway biology, validating therapeutic targets and exploring novel treatment modalities. These innovations have paved the way for a better understanding of pathway dynamics and the development of more precise therapeutic interventions. In addition, the identification and validation of biomarkers of SHH pathway activation are critical to guide clinical decision making and improve patient outcomes. Molecular profiling and biomarker discovery efforts are critical steps towards personalised medicine approaches in the treatment of SHH pathway-associated CNS tumours. While significant progress has been made in understanding the role of the SHH pathway in CNS tumorigenesis, ongoing research is essential to overcome current therapeutic challenges and refine treatment strategies. The integration of molecular insights with advanced technologies and clinical expertise holds great promise for developing more effective and personalised therapies for patients with SHH pathway-driven CNS tumours.

Alzheimer's disease (AD), an age-related neurodegenerative disorder, is characterized by irreversible brain tissue degeneration. The amyloid-β (Aβ) cascade hypothesis stands as the predominant paradigm explaining AD pathogenesis. This study aimed to elucidate the mechanisms underlying Aβ-induced pyroptosis in AD. AD models were established using amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice and Aβ-treated BV-2 cells (5 µM, 24 h). NEK7 expression was evaluated in vitro and in vivo. Cell pyroptosis was assessed before and after NEK7 expression was inhibited in BV-2 cells. Adeno-associated virus (AAV) vectors carrying short hairpin RNA (shRNA) against NEK7 (AAV-sh-NEK7) were administered to mice to knockdown NEK7 in vivo. Spatial learning and memory abilities were evaluated using the Morris water maze test. The interaction between NEK7 and histone H4 lysine 12 lactylation (H4K12la) were then investigated. The results suggested that NEK7 expression was markedly elevated in both in vitro and in vivo AD models. Treatment with Aβ significantly reduced cell viability and enhanced pyroptosis in BV-2 cells; these effects were reversed by inhibiting NEK7. Furthermore, AD mice with NEK7 knockdown exhibited shorter escape latencies and increased time spent in the target quadrant, suggesting that NEK7 inhibition improved cognitive function and memory retention. Mechanistically, Aβ treatment induced histone lactylation in BV-2 cells, and suppression of lactylation attenuated NEK7 transcriptional activity and mRNA levels. In summary, elevated NEK7 expression promoted histone lactylation in BV-2 cells, thereby facilitating pyroptosis. Inhibition of NEK7 conferred protection against Aβ-induced cellular damage and enhanced cognitive performance and memory retention in AD model mice. Collectively, targeting NEK7 represents a potential therapeutic strategy for alleviating AD symptoms.

The mechanisms through which systemic inflammation exerts its effect on the central nervous system (CNS) are still not completely understood. Exosomes are small (30 to 100 nm) membrane-bound extracellular vesicles released by most of the mammalian cells. Exosomes play a vital role in cell-to-cell communication. This includes regulation of inflammatory responses by shuttling mRNAs, miRNAs, and cytokines, both locally and systemically to the neighboring as well as distant cells to further modulate the transcriptional and/or translational states and affect the functional phenotype of those cells that have taken up these exosomes. The role of circulating blood exosomes leading to neuroinflammation during systemic inflammatory conditions was hereby characterized. Serum-derived exosomes from LPS-challenged mice (SDEL) were freshly isolated from the sera of the mice that were earlier treated with LPS and used to study the effects on neuroinflammation. Exosomes isolated from the sera of the mice injected with saline were used as a control. In-vitro studies showed that the SDEL upregulate pro-inflammatory cytokine gene expression in the murine cell lines of microglia (BV-2), astrocytes (C8-D1A), and cerebral microvascular endothelial cells (bEnd.3). To further study their effects in-vivo, SDEL were intravenously injected into normal adult mice. Elevated mRNA expression of pro-inflammatory cytokines was observed in the brains of SDEL recipient mice. Proteomic analysis of the SDEL confirmed the increased expression of inflammatory cytokines in them. Together, these results demonstrate and strengthen the novel role of peripheral circulating exosomes in causing neuroinflammation during systemic inflammatory conditions.

Understanding the mechanisms of synaptic plasticity is crucial for elucidating how the brain adapts to internal and external stimuli. A key objective of plasticity is maintaining physiological activity states during perturbations by adjusting synaptic transmission through negative feedback mechanisms. However, identifying and characterizing novel molecular targets orchestrating synaptic plasticity remains a significant challenge. This study investigated the effects of tetrodotoxin (TTX)-induced synaptic plasticity within organotypic entorhino-hippocampal tissue cultures, offering insights into the functional, transcriptomic, and proteomic changes associated with network inhibition via voltage-gated sodium channel blockade. Our experiments demonstrate that TTX treatment induces substantial functional plasticity of excitatory synapses, as evidenced by increased miniature excitatory postsynaptic current (mEPSC) amplitudes and frequencies in both dentate granule cells and CA1 pyramidal neurons. Correlating transcriptomic and proteomic data, we identified novel targets for future research into homeostatic plasticity, including cytoglobin, SLIT-ROBO Rho GTPase Activating Protein 3, Transferrin receptor, and 3-Hydroxy-3-Methylglutaryl-CoA Synthase 1. These data provide a valuable resource for future studies aiming to understand the orchestration of homeostatic plasticity by metabolic pathways in distinct cell types of the central nervous system.

Chronic exposure to glucocorticoids in response to long-term stress is thought to be a risk factor for major depression. Depression is associated with disturbances in the gut microbiota composition and peripheral and central energy metabolism. However, the relationship between chronic glucocorticoid exposure, the gut microbiota, and brain metabolism remains largely unknown. In this study, we first investigated the effects of chronic corticosterone exposure on various domains of behavior in adult male C57BL/6J mice treated with the glucocorticoid corticosterone to evaluate them as an animal model of depression. We then examined the gut microbial composition and brain and plasma metabolome in corticosterone-treated mice. Chronic corticosterone treatment resulted in reduced locomotor activity, increased anxiety-like and depression-related behaviors, decreased rotarod latency, reduced acoustic startle response, decreased social behavior, working memory deficits, impaired contextual fear memory, and enhanced cued fear memory. Chronic corticosterone treatment also altered the composition of gut microbiota, which has been reported to be associated with depression, such as increased abundance of Bifidobacterium, Turicibacter, and Corynebacterium and decreased abundance of Barnesiella. Metabolomic data revealed that long-term exposure to corticosterone led to a decrease in brain neurotransmitter metabolites, such as serotonin, 5-hydroxyindoleacetic acid, acetylcholine, and gamma-aminobutyric acid, as well as changes in betaine and methionine metabolism, as indicated by decreased levels of adenosine, dimethylglycine, choline, and methionine in the brain. These results indicate that mice treated with corticosterone have good face and construct validity as an animal model for studying anxiety and depression with altered gut microbial composition and brain metabolism, offering new insights into the neurobiological basis of depression arising from gut-brain axis dysfunction caused by prolonged exposure to excessive glucocorticoids.

Protein turnover is crucial for cell survival, and the impairment of proteostasis leads to cell death. Aging is associated with a decline in proteostasis, as the progressive accumulation of damaged proteins is a hallmark of age-related disorders such as neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). We previously discovered that the declining function of the ubiquitin-proteasome system (UPS) in motor neurons contributes to sporadic ALS pathologies, such as progressive motor neuron loss, protein accumulation, and glial activation. However, the mechanisms of UPS dysfunction-induced cell damage, such as cell death and aggregation, are not fully understood. This study used transcriptome analysis of motor neurons with UPS dysfunction and found that the expression of N-myc downstream regulated 1 (NDRG1) gets upregulated by UPS dysfunction. Additionally, the upregulation of NDRG1 induces cell death in the Neuro2a mouse neuroblastoma cell line. These results suggest that NDRG1 is a potential marker for UPS dysfunction and may play a role in neurodegeneration, such as that seen in ALS.

The present study uses electron microscopy to document ultrastructural characteristics of hippocampal GABAergic inhibitory synapses under resting and stimulated conditions in three experimental systems. Synaptic profiles were sampled from stratum pyramidale and radiatum of the CA1 region from (1) perfusion fixed mouse brains, (2) immersion fixed rat organotypic slice cultures, and from (3) rat dissociated hippocampal cultures of mixed cell types. Synapses were stimulated in the brain by a 5 min delay in perfusion fixation to trigger an ischemia-like excitatory condition, and by treating the two culture systems with 90 mM high K⁺ for 2-3 min to depolarize the neurons. Upon such stimulation conditions, the presynaptic terminals of the inhibitory synapses exhibited similar structural changes to those seen in glutamatergic excitatory synapses, with depletion of synaptic vesicles, increase of clathrin-coated vesicles and appearance of synaptic spinules. However, in contrast to excitatory synapses, no structural differences were detected in the postsynaptic compartment of the inhibitory synapses upon stimulation. There were no changes in the appearance of material associated with the postsynaptic membrane or the length and curvature of the membrane. Also no change was detected in the labeling density of gephyrin, a GABAergic synaptic marker, lining the postsynaptic membrane. Furthermore, virtually all inhibitory synaptic clefts remained rigidly apposed, unlike in the case of excitatory synapses where ~ 20-30% of cleft edges were open upon stimulation, presumably to facilitate the clearance of neurotransmitters from the cleft. The fact that no open clefts were induced in inhibitory synapses upon stimulation suggests that inhibitory input may not need to be toned down under these conditions. On the other hand, similar to excitatory synapse, EGTA (a calcium chelator) induced open clefts in ~ 18% of inhibitory synaptic cleft edges, presumably disrupting similar calcium-dependent trans-synaptic bridges in both types of synapses.