Glia最新文献

We previously reported that in the absence of Prostaglandin D2 synthase (L-PGDS) peripheral nerves are hypomyelinated in development while in adulthood they present aberrant myelin sheaths. We now demonstrate that L-PGDS expressed in Schwann cells is part of a coordinated program that controls myelin homeostasis, describing a new physiological pathway implicated in preserving peripheral myelin. In vivo and in vitro lipidomic, metabolomic, and transcriptomic analyses confirmed that myelin lipids composition, Schwann cells' energetic metabolism, and key enzymes controlling these processes are altered in the absence of L-PGDS. Moreover, Schwann cells undergo a metabolic rewiring, turn to acetate as the main energetic source, and produce ketone bodies to ensure glial cell and neuronal survival. All these changes correlate with morphological myelin alterations. Collectively, we posit that myelin lipids serve as a reservoir to provide ketone bodies, which together with acetate represent the adaptive substrates Schwann cells can rely on to sustain the axo-glial unit and preserve the integrity of the PNS.

Cortical demyelination is a critical contributor to progressive disease in multiple sclerosis (MS). The barriers to cortical remyelination following demyelination are not fully understood, and there are no remyelinating treatments for MS. We previously took advantage of the spatial and temporal resolution of longitudinal in vivo imaging to study cortical oligodendrocyte regeneration following cuprizone-induced demyelination and found that oligodendrocyte regeneration was impaired. In this study, we investigated whether cortical reactive microglia disrupt oligodendrocyte regeneration. To do so, we used a combination of in situ RNA and immunofluorescence labeling to characterize cortical microglia reactive states following cuprizone-mediated demyelination. We then depleted cortical microglia by administering a Csf1r inhibitor during the recovery period from cuprizone and quantified oligodendrocyte recovery. We found that following cortical demyelination, deep cortical microglia change morphology, downregulate homeostatic markers (P2RY12, TMEM119), and upregulate a marker (CD68) associated with activated macrophages. These reactive changes persisted through early recovery post-cuprizone but resolved by late recovery. Depleting cortical microglia post-cuprizone restored the baseline density of deep cortical ASPA+ oligodendrocytes at early and late recovery. There were also more deep cortical BCAS1+ differentiating oligodendrocytes at early recovery when microglia were depleted, suggesting that transient deep cortical reactive microglia impair oligodendrocyte differentiation following demyelinating injury. Together, we found that cortical microglia adopt spatially restricted reactive functions after demyelination and deep cortical reactive microglia transiently reduce differentiating oligodendrocytes. A potential therapeutic strategy for progressive MS could involve targeting transiently reactive microglia at the right time and place in cortical lesions to promote oligodendrocyte regeneration.

Alzheimer's disease (AD), particularly late-onset AD (LOAD), affects millions worldwide, with the apolipoprotein ε4 (APOE4) allele being a significant genetic risk factor. Retinal abnormalities are a hallmark of LOAD, and our recent study demonstrated significant age-related retinal impairments in APOE4-knock-in (KI) mice, highlighting that retinal impairments occur before the onset of cognitive decline in these mice. Müller cells (MCs), key retinal glia, are vital for retinal health, and their dysfunction may contribute to retinal impairments seen in AD. MCs maintain potassium balance via specialized inwardly rectifying K⁺ channels 4.1 (Kir4.1). This study posits that Kir4.1 channels will be impaired in APOE4-KI, resulting in MC dysfunction. Additionally, we demonstrate that MC dysfunction in APOE4-KI stems from alterations in mitochondrial dynamics and oxidative stress. Kir4.1 expression and function were studied using immunofluorescence and through the whole-cell voltage clamp, respectively. In parallel, rat Müller cells (rMC-1) were used to create an in vitro model for further mechanistic studies. MitoQ was used to evaluate its potential to mitigate APOE4-induced deficits. APOE4 retinas and APOE4-transfected rMC-1 significantly reduced Kir4.1 expression, K+ buffering capacity, and increased mitochondrial damage. APOE4-transfected rMC-1 showed reduced mitochondrial membrane potential (ΔΨm) and increased mitochondrial reactive oxygen species (ROS). MitoQ treatment significantly reduced mitochondrial ROS and restored Kir4.1 expression in APOE4-expressing cells. Our results demonstrate that APOE4 causes mitochondrial dysfunction and MC impairment, which may contribute to retinal pathology in AD. MitoQ restored mitochondrial health and Kir4.1 expression in APOE4-expressing rMC-1, suggesting targeting mitochondria may offer a promising therapeutic strategy for AD.

Oligodendrocytes, traditionally recognized for their role in central nervous system myelination, have emerged during the last decades as key participants maintaining brain homeostasis in response to metabolic demands and stress. In addition, injury to myelin prompts a regenerative response that leads to the formation of new myelin sheaths. However, the signals regulating effective remyelination by oligodendrocytes are still not completely understood. Here, we report that oligodendrocytes can internalize exogenous myelin both in vitro and in vivo, which leads to an increase in oligodendroglial lineage progression. RNA sequencing reveals that myelin debris alters the oligodendrocyte transcriptional profile, leading to the suppression of immune-related pathways and de novo cholesterol and fatty acid biosynthesis, while promoting lipid droplet formation for the storage and processing internalized myelin particles. In primary cultures, myelin exposure increases oligodendrocyte progenitor (OPC) proliferation and overall oligodendroglia lineage progression, accompanied by greater cellular complexity and a larger myelinated area per cell, without altering the relative OPC-to-mature oligodendrocyte ratio. Stereotaxic injection of fluorescent myelin into mouse cortex and zebrafish ventricles shows internalization by microglia and, to a lesser extent, by oligodendroglia. Notably, in the zebrafish model, ventricular injections of myelin also increase the number of ventral oligodendrocytes in the spinal cord, further supporting that myelin can promote lineage progression. These findings challenge the classical view that myelin debris intrinsically inhibits oligodendrocyte proliferation, suggesting instead that oligodendrocytes can use myelin to support self-renewal and maturation across vertebrate species, acting as a trophic factor in the absence of pathological cues.

Microglia, the brain's innate immune cells, possess complex, highly motile branched processes. These act independently, enabling individual processes to carry out entirely distinct functions in parallel. Intracellular Ca²⁺ signaling is implicated in many of these distinct microglial functions. However, it has been difficult to quantify how such Ca²⁺ activity is compartmentalized in space and time to prevent unwanted cross-talk between signaling pathways. Previous studies have typically relied on manually drawn regions-of-interest (ROIs), which averages fluorescence within predefined compartments and therefore cannot resolve the fine-scale spatio-temporal propagation patterns that may be functionally relevant. To address this, we adopt an unbiased non-ROI-based analytical approach to comprehensively characterize the temporal, spatial and spatio-temporal dimensions of microglial Ca²⁺ activity in vivo. We find that microglial Ca²⁺ activity predominantly occurs in processes, tends to remain localized at its site of origin, and, when it propagates, often follows a well-defined direction (either toward or away from the soma) rather than spreading isotropically as would be expected under purely passive diffusion. The tendency of microglial Ca²⁺ activity to spread between intracellular regions does not correlate with peak amplitude, but appears to be limited by the branching points of the microglial processes. Finally, we show that Ca²⁺ activity can differ between the microglial soma and its processes in response to various pharmacological stimuli. These results suggest that Ca²⁺ signals are actively compartmentalized within microglia in a context dependent manner, rather than being synchronized across the entire cell.

Astrocytes are central to lipid metabolism in the central nervous system. Due to their morphological and functional characteristics, astrocytes can uptake fatty acids (FAs) from the bloodstream and extracellular space and store them in lipid droplets (LD). LD are dynamic organelles, whose accumulation in astrocytes has been shown to occur upon exposure to various stress stimuli. Different hypotheses proposed to explain motor neuron degeneration in amyotrophic lateral sclerosis (ALS) implicate mitochondrial dysfunction and oxidative stress. Mitochondrial dysfunction in astrocytes is associated with elevation of cytoplasmic lipids and lipid-binding proteins. We observed increased LD in the spinal cord of symptomatic ALS mice, as well as in human transdifferentiated astrocytes obtained from ALS patients. Using a co-culture model, we examined the effect of FA overload and its impact on astrocyte–motor neuron interaction. LD accumulation was tightly coupled with an NF-κB-driven proinflammatory response in nontransgenic astrocytes, correlating with motor neuron toxicity. These results provide additional evidence to the notion that altered energy balance may contribute to neuronal death in ALS. Furthermore, pharmacological inhibition of lactate dehydrogenase (LDH) reversed LD accumulation in mouse and human astrocytes expressing ALS-linked mutations. Genetic ablation of LDHA similarly reduced LD accumulation in response to FA treatment. Collectively, our data underscore the role of lipid metabolism in astrocyte–neuron interactions in ALS models and suggest that LD accumulation, rather than serving solely as a protective mechanism, reflects a metabolic stress state linked to a detrimental phenotypic transformation in astrocytes.

Streptococcus pneumoniae (Spn) meningitis remains a lethal central nervous system (CNS) infection with limited therapies. This study identifies the lncRNA ZEB1-AS1 as a central coordinator of microglial immunity against Spn through a multi-tiered regulatory cascade. Transcriptomic analysis revealed Spn-induced ZEB1-AS1 upregulation in human microglia, driven by ZNF148, which directly binds its promoter. Functional interrogation demonstrated that ZEB1-AS1 knockdown impairs bacterial clearance and pro-inflammatory cytokine production (IL-1β, IL-6, TNF-α, p < 0.01), while its overexpression amplifies these responses. Crucially, ZEB1-AS1 recruits the m6A reader IGF2BP2 to stabilize NOD2 mRNA in cytoplasmic complexes, extending transcript stability. This molecular scaffolding enables NOD2-dependent antimicrobial functions, as evidenced by rescue experiments in which IGF2BP2 overexpression reversed ZEB1-AS1 deficiency phenotypes. In vivo, microglial manipulation of the murine homolog Zeb1-os1 regulated cerebral Spn burdens, NOD2 expression, and infection-induced cognitive outcomes in both directions. The tripartite ZEB1-AS1/IGF2BP2/NOD2 interaction was validated by RNA pulldown and co-immunoprecipitation, establishing a linear pathway from ZNF148-mediated transcriptional activation to IGF2BP2-dependent mRNA stabilization. Collectively, this ZNF148 to ZEB1-AS1 to IGF2BP2 to NOD2 axis bridges the gap between transcriptional and post-transcriptional immune regulation, proposing IGF2BP2's RNA-binding domain as a therapeutic target against drug-resistant Spn meningitis.

Multiple sclerosis (MS) affects women more frequently than men, but the disease progresses more aggressively in men. We have demonstrated that acute intermittent hypoxia (AIH), a noninvasive therapy, promotes repair and remyelination and alters disease course in the female MOG_35-55 experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Given the importance of understanding sex-specific responses to potential MS therapies, we investigated whether AIH exerts similar therapeutic effects in male EAE mice. EAE was induced by MOG_35-55 immunization in C57BL/6 male mice. Male EAE mice received either AIH (10 cycles-5 min 11% oxygen alternating with 5 min 21% oxygen) or Normoxia (21% oxygen for same duration) once daily for 7d beginning at near peak EAE disease clinical score of 2.5. Mice were followed post-last treatment for an additional 7d or 14d before assessing histopathology. Clinical scores, inflammation, myelination, and neurorepair were evaluated. Compared to Normoxia, AIH significantly improved clinical scores in male EAE mice with mice exhibiting reduced inflammation and increased myelination/remyelination within inflamed regions. Further, AIH polarized remaining immune cells toward a pro-repair phenotype, promoted OPC recruitment to demyelinated regions, and increased the presence of mature, myelinating oligodendrocytes, and myelination. An axon protective phenotype was also significantly improved with AIH, supporting enhanced neuroprotection. Our findings reveal that AIH has comparable, albeit slightly less robust beneficial therapeutic effects in male as was previously shown in female EAE mice. Altogether, this study highlights the potential of AIH as a therapy for MS, capable of addressing the disease's differential impacts in both sexes.

Recent studies suggest the involvement of insulin signaling in the timing of photoreceptor differentiation in Drosophila and mammals. The molecular and cellular mechanisms underlying temporal control of photoreceptor differentiation by insulin signaling, however, remain largely undefined. In this study, we reveal a key role for sub-retinal glia in timing the differentiation of photoreceptor neurons (R cells) in the developing Drosophila eye imaginal disc. Decreasing the signaling of epidermal growth factor receptor (EGFR) in sub-retinal glia delayed R-cell differentiation. In contrast, hyperactivating the EGFR pathway in sub-retinal glia caused the precocious R-cell differentiation. Cell-type-specific knockdown, epistasis analysis, and transgene rescue indicate that insulin-like peptides ILP3 and ILP6 are key downstream targets of the EGFR pathway in sub-retinal glia. We propose that the activation of the EGFR pathway in sub-retinal glia stimulates the release of ILP3 and ILP6, which in turn activate the insulin receptor (InR) in eye precursor cells to positively regulate the timing of photoreceptor differentiation.