Journal of Neuroinflammation最新文献

Infection during the perinatal period can adversely affect brain development, predispose infants to ischemic stroke and have lifelong consequences. We previously demonstrated that diet enriched in n-3 polyunsaturated fatty acids (n-3 PUFA) transforms brain lipid composition in the offspring and protects the neonatal brain from stroke, in part by blunting injurious immune responses. Critical to the interface between the brain and systemic circulation is the vasculature, endothelial cells in particular, that support brain homeostasis and provide a barrier to systemic infection. Here, we examined whether maternal PUFA-enriched diets exert reprograming of endothelial cell signalling in postnatal day 9 mice after modeling aspects of infection using LPS. Transcriptome analysis was performed on microvessels isolated from brains of pups from dams maintained on 3 different maternal diets from gestation day 1: standard, n-3 enriched or n-6 enriched diets. Depending on the diet, in endothelial cells LPS produced distinct regulation of pathways related to immune response, cell cycle, extracellular matrix, and angiogenesis. N-3 PUFA diet enabled higher immune reactivity in brain vasculature, while preventing imbalance of cell cycle regulation and extracellular matrix cascades that accompanied inflammatory response in standard diet. Cytokine analysis revealed a blunted LPS response in blood and brain of offspring from dams on n-3 enriched diet. Analysis of cerebral vasculature in offspring in vivo revealed no differences in vessel density. However, vessel complexity was decreased in response to LPS at 72 h in standard and n-6 diets. Thus, LPS modulates specific transcriptomic changes in brain vessels of offspring rather than major structural vessel characteristics during early life. N-3 PUFA-enriched maternal diet in part prevents an imbalance in homeostatic processes, alters inflammation and ultimately mitigates changes to the complexity of surface vessel networks that result from infection. Importantly, maternal diet may presage offspring neurovascular outcomes later in life.

Background: We recently reported that the dopamine (DA) analogue CA140 modulates neuroinflammatory responses in lipopolysaccharide-injected wild-type (WT) mice and in 3-month-old 5xFAD mice, a model of Alzheimer's disease (AD). However, the effects of CA140 on Aβ/tau pathology and synaptic/cognitive function and its molecular mechanisms of action are unknown.

Methods: To investigate the effects of CA140 on cognitive and synaptic function and AD pathology, 3-month-old WT mice or 8-month-old (aged) 5xFAD mice were injected with vehicle (10% DMSO) or CA140 (30 mg/kg, i.p.) daily for 10, 14, or 17 days. Behavioral tests, ELISA, electrophysiology, RNA sequencing, real-time PCR, Golgi staining, immunofluorescence staining, and western blotting were conducted.

Results: In aged 5xFAD mice, a model of AD pathology, CA140 treatment significantly reduced Aβ/tau fibrillation, Aβ plaque number, tau hyperphosphorylation, and neuroinflammation by inhibiting NLRP3 activation. In addition, CA140 treatment downregulated the expression of cxcl10, a marker of AD-associated reactive astrocytes (RAs), and c1qa, a marker of the interaction of RAs with disease-associated microglia (DAMs) in 5xFAD mice. CA140 treatment also suppressed the mRNA levels of s100β and cxcl10, markers of AD-associated RAs, in primary astrocytes from 5xFAD mice. In primary microglial cells from 5xFAD mice, CA140 treatment increased the mRNA levels of markers of homeostatic microglia (cx3cr1 and p2ry12) and decreased the mRNA levels of a marker of proliferative region-associated microglia (gpnmb) and a marker of lipid-droplet-accumulating microglia (cln3). Importantly, CA140 treatment rescued scopolamine (SCO)-mediated deficits in long-term memory, dendritic spine number, and LTP impairment. In aged 5xFAD mice, these effects of CA140 treatment on cognitive/synaptic function and AD pathology were regulated by dopamine D1 receptor (DRD1)/Elk1 signaling. In primary hippocampal neurons and WT mice, CA140 treatment promoted long-term memory and dendritic spine formation via effects on DRD1/CaMKIIα and/or ERK signaling.

Conclusions: Our results indicate that CA140 improves neuronal/synaptic/cognitive function and ameliorates Aβ/tau pathology and neuroinflammation by modulating DRD1 signaling in primary hippocampal neurons, primary astrocytes/microglia, WT mice, and aged 5xFAD mice.

Astrocytes respond and contribute to neuroinflammation by adopting inflammatory reactive states. Although recent efforts have characterized the gene expression signatures associated with these reactive states, the cell biology underlying inflammatory reactive astrocyte phenotypes remains under-explored. Here, we used CRISPR-based screening in human iPSC-derived astrocytes to identify mTOR activation a driver of cytokine-induced endolysosomal system remodeling, manifesting as alkalinization of endolysosomal compartments, decreased autophagic flux, and increased exocytosis of certain endolysosomal cargos. Through endolysosomal proteomics, we identified and focused on one such cargo-IL-32, a disease-associated pro-inflammatory cytokine not present in rodents, whose secretion mechanism is not well understood. We found that IL-32 was partially secreted in extracellular vesicles likely to be exosomes. Furthermore, we found that IL-32 was involved in the polarization of inflammatory reactive astrocyte states and was upregulated in astrocytes in multiple sclerosis lesions. We believe that our results advance our understanding of cell biological pathways underlying inflammatory reactive astrocyte phenotypes and identify potential therapeutic targets.

Background: Myasthenia gravis (MG) is an autoimmune disease characterized by pathogenic antibodies that target structures of the neuromuscular junction. The evidence suggests that the regulation of long noncoding RNAs (lncRNAs) that is mediated by transcription factors (TFs) plays a key role in the pathophysiology of MG. Nevertheless, the detailed molecular mechanisms of lncRNAs in MG remain largely undetermined.

Methods: Using microarray analysis, we analyzed the lncRNA levels in MG. By bioinformatics analysis, LINC01566 was found to potentially play an important role in MG. First, qRT‒PCR was performed to verify the LINC1566 expressions in MG patients. Then, fluorescence in situ hybridization was conducted to determine the localization of LINC01566 in CD4 + T cells. Finally, the impact of LINC01566 knockdown or overexpression on CD4 + T-cell function was also analyzed using flow cytometry and CCK-8 assay. A dual-luciferase reporter assay was used to validate the binding of the TF FOSL1 to the LINC01566 promoter.

Results: Based on the lncRNA microarray and differential expression analyses, we identified 563 differentially expressed (DE) lncRNAs, 450 DE mRNAs and 19 DE TFs in MG. We then constructed a lncRNA-TF-mRNA network. Through network analysis, we found that LINC01566 may play a crucial role in MG by regulating T-cell-related pathways. Further experiments indicated that LINC01566 is expressed at low levels in MG patients. Functionally, LINC01566 is primarily distributed in the nucleus and can facilitate CD4 + T-cell apoptosis and inhibit cell proliferation. Mechanistically, we hypothesized that LINC01566 may negatively regulate the expressions of DUSP3, CCR2, FADD, SIRPB1, LGALS3 and SIRPB1, which are involved in the T-cell activation pathway, to further influence the cellular proliferation and apoptosis in MG. Moreover, we found that the effect of LINC01566 on CD4 + T cells in MG was mediated by the TF FOSL1, and in vitro experiments indicated that FOSL1 can bind to the promoter region of LINC01566.

Conclusions: In summary, our research revealed the protective roles of LINC01566 in clinical samples and cellular experiments, illustrating the potential roles and mechanism by which FOSL1/LINC01566 negatively regulates CD4 + T-cell activation in MG.

Multinucleated microglia have been observed in contexts associated with infection, inflammation, and aging. Though commonly linked to pathological conditions, the larger cell size of multinucleated microglia might enhance their phagocytic functions, potentially aiding in the clearance of brain debris and suggesting a reassessment of their pathological significance. To assess the phagocytic capacity of multinucleated microglia and its implications for brain debris clearance, we induced their formation by inhibiting Pyk2 activity using the pharmacological inhibitor PF-431396, which triggers cytokinesis regression. Multinucleated microglia demonstrate enhanced phagocytic function, as evidenced by their increased capacity to engulf β-amyloid (Aβ) oligomers. Concurrently, the phosphorylation of Pyk2, induced by Aβ peptide, was diminished upon treatment with a Pyk2 inhibitor (Pyk2-Inh, PF-431396). Furthermore, the increased expression of Lamp1, a lysosomal marker, with Pyk2-inh treatment, suggests an enhancement in proteolytic activity. In vivo, we generated an acute Alzheimer's disease (AD) model by infusing Aβ into the brains of Iba-1 EGFP transgenic (Tg) mice. The administration of the Pyk2-Inh led to an increased migration of microglia toward amyloid deposits in the brains of Iba-1 EGFP Tg mice, accompanied by morphological activation, suggesting a heightened affinity for Aβ. In human microglia, lipopolysaccharide (LPS)-induced inflammatory responses showed that inhibition of Pyk2 signaling significantly reduced the transcription and protein expression of pro-inflammatory markers. These results suggest that Pyk2 inhibition can modulate microglial functions, potentially reducing neuroinflammation and aiding in the clearance of neurodegenerative disease markers. This highlights Pyk2 as a promising target for therapeutic intervention in neurodegenerative diseases.

Lactate-derived histone lactylation is involved in multiple pathological processes through transcriptional regulation. The role of lactate-derived histone lactylation in the repair of spinal cord injury (SCI) remains unclear. Here we report that overall lactate levels and lactylation are upregulated in the spinal cord after SCI. Notably, H4K12la was significantly elevated in the microglia of the injured spinal cord, whereas exogenous lactate treatment further elevated H4K12la in microglia after SCI. Functionally, lactate treatment promoted microglial proliferation, scar formation, axon regeneration, and locomotor function recovery after SCI. Mechanically, lactate-mediated H4K12la elevation promoted PD-1 transcription in microglia, thereby facilitating SCI repair. Furthermore, a series of rescue experiments confirmed that a PD-1 inhibitor or microglia-specific AAV-sh-PD-1 significantly reversed the therapeutic effects of lactate following SCI. This study illustrates the function and mechanism of lactate/H4K12la/PD-1 signaling in microglia-mediated tissue repair and provides a novel target for SCI therapy.

Retinitis pigmentosa (RP), an inherited retinal disease, affects 1,5 million people worldwide. The initial mutation-driven photoreceptor degeneration leads to chronic inflammation, characterized by Müller cell activation and upregulation of CD44. CD44 is a cell surface transmembrane glycoprotein and the primary receptor for hyaluronic acid. It is involved in many pathological processes, but little is known about CD44's retinal functions. CD44 expression is also increased in Müller cells from our Pde6b^STOP/STOP RP mouse model. To gain a more detailed understanding of CD44's role in healthy and diseased retinas, we analyzed Cd44^-/- and Cd44^-/-Pde6b^STOP/STOP mice, respectively. The loss of CD44 led to enhanced photoreceptor degeneration, reduced retinal function, and increased inflammatory response. To understand the underlying mechanism, we performed proteomic analysis on isolated Müller cells from Cd44^-/- and Cd44^-/-Pde6b^STOP/STOP retinas and identified a significant downregulation of glutamate transporter 1 (SLC1A2). This downregulation was accompanied by higher glutamate levels, suggesting impaired glutamate homeostasis. These novel findings indicate that CD44 stimulates glutamate uptake via SLC1A2 in Müller cells, which in turn, supports photoreceptor survival and function.

Background: Infection with the protozoan parasite Toxoplasma gondii leads to the formation of lifelong cysts in neurons that can have devastating consequences in the immunocompromised. In the immunocompetent individual, anti-parasitic effector mechanisms and a balanced immune response characterized by pro- and anti-inflammatory cytokine production establishes an asymptomatic infection that rarely leads to neurological symptoms. Several mechanisms are known to play a role in this successful immune response in the brain including T cell production of IFNγ and IL-10 and the involvement of CNS resident cells. This limitation of clinical neuropathology during chronic infection suggests a balance between immune response and neuroprotective mechanisms that collectively prevent clinical manifestations of disease. However, how these two vital mechanisms of protection interact during chronic Toxoplasma infection remains poorly understood.

Main text: This study demonstrates a previously undescribed connection between innate neutrophils found chronically in the brain, termed "chronic brain neutrophils" (CBNeuts), and neuroprotective mechanisms during Toxoplasma infection. Lack of CBNeuts during chronic infection, accomplished via systemic neutrophil depletion, led to enhanced infection and deleterious effects on neuronal regeneration and repair mechanisms in the brain. Phenotypic and transcriptomic analysis of CBNeuts identified them as distinct from peripheral neutrophils and revealed two main subsets of CBNeuts that display heterogeneity towards both classical effector and neuroprotective functions in an age-dependent manner. Further phenotypic profiling defined expression of the neuroprotective molecules NRG-1 andErbB4 by these cells, and the importance of this signaling pathway during chronic infection was demonstrated via NRG-1 treatment studies.

Conclusions: In conclusion, this work identifies CBNeuts as a heterogenous population geared towards both classical immune responses and neuroprotection during chronic Toxoplasma infection and provides the foundation for future mechanistic studies of these cells.