Molecular Brain最新文献

Passage of molecules across the central nervous system is tightly regulated by the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB), which restrict entry of many substances, including opioid medications. Here, we examined the effects of opioid withdrawal on BBB and BSCB integrity by measuring extravascular levels of peripherally injected dyes - Evans Blue (high molecular weight) and sodium fluorescein (NaFl, low molecular weight) - in the brain and spinal cord. In morphine-dependent male and female mice, repeated naloxone challenge induced robust withdrawal behaviors concomitant with region specific dye extravasation. In a fixed dose morphine paradigm, Evans Blue extravasation was highest within the cortex, hippocampus, cerebellum, and brainstem (pons and medulla) in male mice, and in the hypothalamus in female mice. By contrast, NaFl extravasation remained unchanged in both sexes. In an escalating dose morphine paradigm, Evans Blue extravasation was most prominent in the brainstem (pons and medulla) of both sexes, as well as in the lumbar of male mice and cervical spinal cord of female mice. NaFl extravasation in these regions was unchanged in male but reduced in female mice. These findings suggest that repeated opioid withdrawal alters permeability of the BBB and BSCB in discrete regions of the brain and spinal cord.

Background: N6-methyladenosine (m6A) methylation is an essential epigenetic modification that regulates mRNA stability, splicing, and translation. Its role in neurological diseases, including epilepsy, ischemic stroke, and vascular dementia (VaD), remains poorly understood.

Methods: We integrated multi-omics data, including GWAS, m6A quantitative trait loci (QTL), expression QTL (eQTL), and protein QTL (pQTL), and using FUSION to assess the association of m6A with these diseases. Transcriptome-wide association studies (TWAS) and Mendelian Randomization (MR) were performed to identify causal relationships between m6A sites, gene expression, and disease. Differentially expressed genes (DEGs) were analyzed via RNA sequencing and enriched for biological pathways. Protein-protein interaction (PPI) networks and m6A-related gene-disease associations were constructed to reveal regulatory mechanisms.

Results: We identified 218 m6A sites significantly associated with the three diseases, highlighting 3,430 associations between m6A sites and gene expression. Functional enrichment analysis revealed key pathways, including base excision repair and chemokine-mediated signaling. MR analysis identified causal relationships, such as NBL1 in epilepsy, TPGS2 in ischemic stroke, and SERINC2 in VaD. PPI analysis revealed interactions involving critical proteins like PARP1, MCL1, and CD40, underscoring their role in neuroinflammation and apoptosis.

Conclusion: Our findings elucidate the genetic and epigenetic roles of m6A in epilepsy, ischemic stroke, and VaD, uncovering potential mechanisms by which m6A modulates gene and protein expression to influence disease outcomes. These insights highlight m6A as a promising biomarker and therapeutic target for neurological diseases.

The nucleus accumbens (NAcc) is a key brain region in reward circuitry, mediating responses to psychostimulants, such as amphetamine (AMPH), including locomotor activity. This effect is known to be enhanced by the orexigenic neuropeptide ghrelin acting through growth hormone-secretagogue receptors (GHSR) expressed in the region. Recently, liver-expressed antimicrobial peptide 2 (LEAP2) was identified as another ligand for GHSR that opposes ghrelin's action. Based on its antagonism, we hypothesized that LEAP2 modulates AMPH-induced locomotor activity in the NAcc. To examine this, we first confirmed the presence of LEAP2 protein in this NAcc and observed that its fluorescent signals were predominantly localized in neurons, including medium spiny neurons (MSNs). We then investigated whether LEAP2 microinjection alters AMPH-induced locomotor activity. Our findings showed that LEAP2 inhibited acute AMPH-induced locomotor activity in a dose-dependent manner. However, its inhibitory effects were absent following chronic AMPH exposure, indicating that the effect of LEAP2 on AMPH-induced locomotor activity varies depending on drug-exposed physiological status. These results provide new insights into a state-dependent regulatory role of LEAP2 in AMPH-induced locomotor activity.

The prefrontal cortex plays a crucial role in procedural rule learning; however, the specific neuronal mechanism through which it represents rules is unknown. We hypothesized that sequential neuronal activities in the prefrontal cortex encode these rules. To investigate this, we recorded neuronal activities in the medial prefrontal cortex of mice during rule learning using Ca²⁺ imaging. We utilized a method based on convolutional negative matrix factorization, iSeq, to automatically detect temporal neuronal sequences in the recorded data. As rule learning advanced, these neuronal sequences began to encode critical information for rule execution. In mice that had mastered the rule, the dynamics of neuronal sequences could predict success and failure of reward acquisition. Furthermore, the composition of cell populations within the neuronal sequences was rearranged throughout the learning process. These findings suggest that as animals learn a rule, the medial prefrontal cortex continually updates its neuronal sequences to assign significance to behavioural actions crucial for reward acquisition.

Glaucoma is a neurodegenerative disease affecting retinal ganglion cells (RGCs), with a multifactorial genesis that includes inflammation and vascular dysfunction. Emerging evidence suggests that glucagon-like peptide 1 receptor agonist (GLP-1RAs) may serve as promising neuroprotective agents in glaucoma. In this study, we investigated the neuroprotective potential of the GLP-1RA semaglutide (SEM) in a rat model of ocular hypertension (OHT) induced by paramagnetic bead injections in Brown Norwegian rats. Rats were divided into four cohorts, two normotensive (NT) cohorts, and two OHT cohorts, treated with either SEM or saline (HBSS), which served as control. Systemic SEM or HBSS administration was initiated simultaneously with OHT induction. We observed that SEM administration seemed to delay the increase in intraocular pressure (IOP) associated with OHT. Although SEM administration did not improve RGC survival, it significantly improved astrocytic fractal dimension value and lacunarity. In conclusion, our findings suggest that GLP-1RAs may exert neuroprotective effects by delaying IOP elevation and preventing OHT-induced reactive astrocyte and vascular remodeling. These findings highlight the potential of GLP-1RAs for retinal neuroprotection, but further studies are needed to elucidate their applicability in glaucoma.

Amyloid-β42 (Aβ42) regulates synaptic plasticity and memory formation at physiological levels in the brain, but in Alzheimer's disease (AD), it can disrupt brain function and glucose metabolism. This disruption contributes to cognitive decline and neuropsychiatric symptoms, highlighting the need to better understand its complex effects. This study investigated the associations among cerebrospinal fluid (CSF) Aβ42 levels, cerebral glucose metabolism (assessed via FDG-PET), neuropsychiatric symptoms (evaluated using the NPI), and cognitive performance (measured by ADAS-Cog13 and MoCA) in individuals with AD, mild cognitive impairment (MCI), and cognitively normal (CN) participants. After adjusting for age, gender, education, and ApoE ɛ4 status, a significant positive relationship between CSF Aβ42 levels and cerebral glucose metabolism was observed in the MCI and AD groups, but not in the CN group. In the MCI group, higher cerebral glucose metabolism was associated with reductions in both neuropsychiatric and depressive symptoms, suggesting that higher glucose metabolism reflect higher activation state of investigated brain regions. In contrast, in the CN group, elevated CSF Aβ42 levels were directly linked to increased depressive symptoms, indicating that higher CSF Aβ42 may contribute to depression even in the absence of cognitive decline. Further analysis revealed that CSF Aβ42 levels were indirectly associated with reduced neuropsychiatric and depressive symptoms through enhanced cerebral glucose metabolism as mediator solely in the MCI group. Regarding cognitive performance, cerebral glucose metabolism showed a strong relationship with cognition in both the MCI and AD groups. Furthermore, higher CSF Aβ42 levels were positively associated with better cognitive performance in the MCI and AD groups, with cerebral glucose metabolism potentially mediating this relationship, while no effect was seen in the CN group. In short, CSF Aβ42 positively influenced cerebral glucose metabolism, which was linked to reduced neuropsychiatric and depressive symptoms as well as improved cognitive performance in MCI and AD groups.

Alzheimer's disease (AD) is an age-related neurodegenerative disorder. Different types of Aβ plaques are likely to play distinct roles in the brains of patients with AD. In this study, through the combination of pathological techniques and analysis of the human brain database, we discovered that focal Aβ plaques (FAPs), rather than diffuse Aβ plaques (DAPs), are significantly correlated with AD-related neuropathological changes and cognitive impairment. By using laser capture microdissection in conjunction with microproteomics, the protein components of different Aβ plaques were characterized. Bioinformatic analysis indicated that FAP-enriched proteins are associated mainly with immune-related pathways, such as neutrophil extracellular trap formation. We further confirmed that myeloperoxidase (MPO) is significantly upregulated in the AD brain and colocalizes with FAPs but not with DAPs. Immunohistochemical staining demonstrated that neutrophils expressing MPO accumulated in the capillary lumen and brain parenchyma. The number of neutrophils significantly increases in the cortex and hippocampus of AD donors. Our study revealed a potential role for neutrophil-derived MPO in FAPs, providing insights into the pathogenesis mechanisms and potential therapeutic targets of AD.

Vincristine is an important chemotherapy drug to treat various types of cancer, but it induces peripheral neuropathy, leading to numbness and mechanical allodynia in the hands and feet of patients. The peripheral neuropathy is a dose-limiting toxicity of vincristine chemotherapy. How vincristine treatment causes numbness and mechanical allodynia remains incompletely understood. In the present study, we utilized Nav1.8-ChR2 transgenic mice in which Nav1.8-ChR2-positive and Nav1.8-ChR2-negative mechanoreceptors could be characterized using the opto-electrophysiological method. Nav1.8-ChR2-negative Aβ- and Aδ-fiber mechanoreceptors are primarily low-threshold mechanoreceptors (LTMRs). On the other hand, Nav1.8-ChR2-positive Aβ- and Aδ-fiber mechanoreceptors are mainly high-threshold mechanoreceptors (HTMRs). We have shown that the mechanical threshold of Nav1.8-ChR2-negative Aβ-fiber mechanoreceptors, but not Nav1.8-ChR2-negative Aδ-fiber mechanoreceptors, were increased significantly in the animals treated with vincristine. In contrast, the mechanical threshold of Nav1.8-ChR2-positive Aβ-fiber mechanoreceptors were significantly reduced following vincristine treatment. Vincristine treatment did not significantly affect the mechanical sensitivity of Nav1.8-ChR2-positive Aδ- and C-fiber mechanoreceptors. Vincristine treatment also did not affect the opto-sensitivity of Nav1.8-ChR2-positive Aβ-, Aδ-, and C-fiber mechanoreceptors. Our findings suggest that mechanical sensitivity is decreased in Aβ-fiber LTMRs and increased in Aβ-HTMRs following vincristine treatment, providing insights into vincristine-induced numbness and mechanical allodynia.

Physical exercise has lasting positive influence on mental health. However, its cellular substrate remains to be elucidated. Recently, dopamine D₁-like receptor activation induced by noradrenaline has been suggested to underlie exercise-dependent augmentation of antidepressant effects. The present study demonstrates that exercise induces a long-term enhancement of this atypical catecholaminergic signaling. Noradrenaline potentiates hippocampal mossy fiber synaptic transmission by activating D₁-like receptors in mice. Voluntary exercise by wheel running enhanced this noradrenaline-D₁-like receptor signaling within 5 days. The enhancement of the noradrenaline-D₁-like receptor signaling did not require the integrity of noradrenergic fibers and was maintained for more than 2 weeks after cessation of wheel running. Notably, the effect of exercise was more robustly seen in D₁-like receptor signaling activated by noradrenaline as compared with dopamine, indicating particular responsiveness of the noradrenaline-activated D₁-like receptor signaling to exercise. These results suggest that exercise could exert lasting influence on brain functioning via plasticity of the hippocampal noradrenaline-D₁-like receptor signaling.