Journal of Neurochemistry最新文献

Nicotinic acetylcholine receptors (nAChRs) are well-recognized as ionotropic ligand-gated ion channels in the central and peripheral nervous systems. However, their role in non-neuronal cells such as microglia is less well understood due to challenges in detecting ion channel activity in the plasma membrane of immune cells, which hampers functional characterization. This study investigated nAChR-mediated intracellular signaling pathways in human microglia, exploring possible mechanisms underlying cholinergic modulation of neuroinflammation. We verified transcript expression of nAChR subunits α7, α9, and α10 in human C06 microglia and demonstrated that acetylcholine (ACh) triggers intracellular signaling consistent with nAChR-mediated metabotropic responses, concurrent with pharmacological ablation of muscarinic activity. In the absence of extracellular Ca²⁺, ACh evoked transient elevations in intracellular Ca²⁺ concentration ([Ca²⁺]_i) in functionally enriched microglia. These responses were sensitive to U73122 and 2-APB, indicating the mobilization of internal Ca²⁺ stores via the phospholipase C (PLC) and inositol 1,4,5-trisphosphate (IP₃) pathways, respectively. In C06 microglia, extracellular Ca²⁺ is crucial for replenishing Ca²⁺ stores. Once replenished, repeated ACh exposure enhanced both the incidence and amplitude of microglial [Ca²⁺]_i responses, indicating agonist-induced sensitization. These findings uncover previously unrecognized pathways for nAChR signaling in human microglia, potentially opening new therapeutic avenues for suppressing inflammation.

Iron deficiency (ID) is the most common micronutrient deficiency globally. ID in pre- and post-natal periods has been associated with impaired neurological development and altered behavior, which may persist despite iron supplementation. However, the neurobiological changes responsible for these findings have not been fully identified yet. Here, we develop an invertebrate experimental model using Drosophila melanogaster to study the impact of ID on glial cells. ID induced by dietary deferoxamine altered locomotor activity in adult flies. Glial-specific downregulation of the iron transporter Malvolio (Mvl) resulted in reduced locomotion, an effect prevented by iron supplementation in the fly medium. We confirmed that Mvl downregulation led to ID in the brain, where Mvl is partially expressed. Interestingly, Mvl reduction in ensheathing glia replicated locomotor activity deficits, which suggests that this glial subpopulation is particularly sensitive to iron levels. Mvl downregulation also altered mitochondrial morphology and size, in correlation with altered expression of mitochondrial fission and fusion genes, and mitochondrial electron transport chain complex genes. These results suggest that glial ID impairs normal mitochondrial dynamics and impacts energy production. Additionally, glial overexpression of mitochondrial ferritin, Fer3HCH, known to induce ID in the cytosol and mitochondria, also impaired locomotor activity, which highlights the importance of iron availability in both compartments. These findings demonstrate, for the first time, the importance of iron availability in Drosophila glial cells and its impact on behavior and mitochondrial dynamics. Most importantly, the Drosophila model proves useful in unveiling previously unknown cellular and molecular mechanisms associated with ID in glial cells.

The establishment of new behaviors requires epigenetic modifications that regulate the expression of genes underlying neuroplasticity in relevant circuits. Dopamine plays a central role in many physiological and pathological behavioral changes, including learning, memory, and addictive behaviors. In this study, we explored the relationship between dopaminergic neurotransmission and the epigenetic enzyme lysine-specific demethylase 1 (LSD1, KDM1a). LSD1 has a neurospecific isoform (neuroLSD1) generated by alternative splicing, which acts as a dominant-negative regulator, counteracting the ubiquitous LSD1 (uLSD1) functions. Notably, neuroLSD1 regulates immediate early gene expression, neuroplasticity, learning, and memory, making it a candidate regulator of dopamine-dependent behaviors. Our findings show that mice lacking neuroLSD1 have greater interindividual differences in their locomotor response to acute and repeated amphetamine (AMPH) exposure compared with their wild-type littermates. The analysis of the neurochemical effect of this psychostimulant using fast-scan cyclic voltammetry and microdialysis showed a reduced dopamine efflux in the nucleus accumbens (NAc). On the other hand, while a single dose of the AMPH did not alter uLSD1 and neuroLSD1 isoforms' expression, repeated AMPH administration led to a transient increase followed by a reduction of neuroLSD1 transcripts' abundance in the striatum and hippocampus. In conclusion, our data reveal a critical interplay between dopaminergic neurotransmission and the expression of LSD1 isoforms in the brain, highlighting their potential role in modulating dopamine-dependent behaviors.

The dorsal root ganglion (DRG) plays a critical role in mediating neuropathic pain (NP) following peripheral nerve injury (PNI), although the underlying mechanism remains unclear. This study investigated how Schwann cell (SCs)-derived extracellular vesicles (SC-EVs) regulate neuronal ferroptosis in NP after PNI. After validating isolated SCs (S-100) and DRG neurons (NeuN), SC-EVs were characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blotting for exosomal markers (Alix/CD9/CD63) and the absence of Calnexin. Co-localization of PKH67 with β-Tubulin-III confirmed SC-EVs uptake by DRG neurons. Biochemical assays and flow cytometry demonstrated SC-EVs suppressed ferroptosis in both LPS-stimulated DRG neurons and chronic constriction injury (CCI) rat models, while simultaneously inhibiting apoptosis, inflammation, and NP progression. Mechanistically, RT-qPCR and western blotting revealed aberrant expression of PPARγ, p53, SAT1, and ALOX15 in LPS/CCI models. Co-immunoprecipitation demonstrated that binding between PPARγ and p53 inhibits SAT1/ALOX15-mediated ferroptosis in DRG neurons. Notably, SC-EVs delivered MFG-E8 to upregulate PPARγ and suppress the activation of the p53/SAT1/ALOX15, thereby attenuating neuronal ferroptosis and ameliorating CCI-induced NP. In conclusion, MFG-E8 delivered via SC-EVs alleviates NP after PNI by modulating the PPARγ/p53/SAT1/ALOX15 signaling axis to inhibit CCI-induced ferroptosis, offering novel therapeutic insights.

Patients with chronic pain often present with depression, and the specific neuronal populations and circuits underlying this phenomenon are yet to be fully characterized. Here, using a neuropathic pain model, we found that the development of chronic pain is accompanied by anxiety- and depressive-like behavior. Concurrently, we observed increased activity of Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus (ARC), and acute inhibition of this elevated ARC^POMC neuron activity could reverse the behavioral manifestations of depression. While activating POMC neurons in naïve mice did not induce significant behavioral changes, stimulating these neurons during the early phase of peripheral nerve injury promoted susceptibility to depression, thereby inducing depressive phenotypes. Further studies established a projection pathway from the ARC to the central amygdala (CeA), which controls the development of depressive-like behaviors in states of chronic neuropathic pain, rather than those due to chronic stress. These findings collectively indicate that chronic pain leads to persistent hyperactivity of POMC neurons. Our discoveries suggest that POMC neuronal dysfunction contributes to behavioral deficits associated with chronic pain.

The endocannabinoid system regulates neuronal activity and plasticity, but its role in non-mammalian vertebrates remains poorly understood. In zebrafish (Danio rerio), the pallium processes cognitive functions such as memory, learning, and emotional behavior. This region expresses cannabinoid receptors and undergoes continuous neuronal remodeling through adult neurogenesis. Here, we investigate whether cannabinoid receptor type 1 (CB1R) modulates synaptic activity and adult neurogenesis in zebrafish pallial circuits. Using immunofluorescence and single-cell mRNA analysis, we mapped CB1R expression in the pallium and found it to be distributed in a scattered pattern within the dorsomedial (Dm) and dorsolateral (Dl) regions, predominantly in glutamatergic neurons. Electrophysiological recordings showed that acute application of rimonabant, a CB1R antagonist, reduced the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) without altering intrinsic or other synaptic properties, suggesting a tonic role for CB1R in modulating synaptic transmission. Additionally, prolonged rimonabant treatment (13 days) significantly reduced ERK phosphorylation, a marker of neuronal activity, further supporting the involvement of CB1R in maintaining basal synaptic activity in the pallium. To assess whether cannabinoid signaling shapes adult neurogenesis, we analyzed the proliferation of neural stem cells (NSCs) and maturation of adult-born neurons. Acute phytocannabinoid exposure resulted in a reduction in NSC proliferation, specifically in the anterior Dm. To assess the neurogenic outcome, the cannabinoid treatment was administered during neuronal maturation (12–24 days after BrdU labeling). We observed an increase in the number of 25-day-old neurons (BrdU⁺, HuC/D⁺) in both Dm and Dl regions. This effect was reverted by the CB1R antagonist rimonabant. These results indicate that cannabinoid signaling modulates synaptic activity and neuronal integration, highlighting a conserved control of neurogenesis by the endocannabinoid system across vertebrates.