Neuronal cholesterol synthesis is essential for repair of chronically demyelinated lesions in mice

Astrocyte lactoferrin deficiency affects the construction and function of spinal neurons by regulating cholesterol metabolism

Astrocytes play pivotal roles in central nervous system (CNS) homeostasis, with emerging evidence implicating astrocyte-derived lactoferrin (Lf) in neurodevelopmental and neurodegenerative processes. This study investigates Lf's functional significance in spinal cord integrity using astrocyte-specific Lf knockout (cKO) mice. Behavioral analyses of 1-month-old male cKO mice revealed impaired motor coordination (increased balance beam scores and prolonged pole-climbing latency) and delayed nociceptive responses (increased thermal withdrawal latency). Morphological assessments demonstrated neuron-specific pathology: motor neurons exhibited atrophy and reduced Nissl substance staining, spinal ganglion cells showed quantitative depletion with vacuolar degeneration, and protein expression analyses confirmed declines in neuronal markers (NeuN), synaptic components (SNAP25, PSD95), axonal and myelin related proteins (NF-L, MBP), and neurotransmitter transporters (AChE). Notably, glial cell populations remained unaffected. Mechanistic investigations identified reduced spinal cholesterol content accompanied by downregulation of cholesterol biosynthesis and transport regulators (Srebp2, HMGCR, ApoE, ABCA1) and activation of AMP-activated protein kinase (AMPK). These findings establish astrocytic Lf as a critical modulator of cholesterol metabolism essential for maintaining neuronal structural and functional integrity in the spinal cord. The discovered Lf-cholesterol regulatory axis provides novel insights into the pathogenesis of spinal cord disorders and highlights potential therapeutic targets for neurodegenerative conditions.

Dynamic Proteome Changes in Cuprizone-Induced Demyelination and Remyelination in the Mouse Brain

This study aimed to gain insights into the dynamic proteome changes and underlying molecular mechanisms of de/remyelination in a cuprizone model, a widely used preclinical model of multiple sclerosis (MS). Longitudinal sampling of control or cuprizone-treated mouse brains was executed at 6 time points over 6 weeks. Data analysis included 8489 quantified proteins. Differential proteomic and GO analyses revealed that 5.9% of the quantified proteome was altered, including reported and novel de/remyelination-relevant protein changes and underlying pathways. We found that oligodendrocyte proteins (Fa2h and Ugt8) were significantly changed during demyelination, suggesting that dysregulated sphingolipid metabolism in MS may stem from oligodendrocyte pathology. Importantly, we showed that the cholesterol biosynthesis pathway was the most enriched biological process in a subset of significantly changed proteins, where myelination was highly enriched. We further validated the changes in the cholesterol biosynthesis pathway through targeted GC-MS analysis of intermediate sterols, supporting the critical role of cholesterol biosynthesis in de/remyelination. Unexpectedly, changes of myelin-associated proteins, Mbp and Plp1, were minimal, while Ermn showed significant reduction tracking with demyelination, indicating that some myelin protein changes are more sensitive to demyelination. Together with a list of significantly altered proteins, the results of this study could benefit future remyelination research.

Plasticity of the Arabidopsis leaf lipidome and proteome in response to pathogen infection and heat stress

Plants must cope with a variety of stressors during their life cycle, and the adaptive responses to these environmental cues involve all cellular organelles. Among them, comparatively little is known about the contribution of cytosolic lipid droplets (LDs) and their core set of neutral lipids and associated surface proteins to the rewiring of cellular processes in response to stress. Here, we analyzed the changes that occur in the lipidome and proteome of Arabidopsis (Arabidopsis thaliana) leaves after pathogen infection with Botrytis cinerea or Pseudomonas syringae, or after heat stress. Analyses were carried out in wild-type plants and the oil-rich double mutant trigalactosyldiacylglycerol1-1 sugar dependent 1-4 (tgd1-1 sdp1-4) that allowed for an allied study of the LD proteome in stressed leaves. Using liquid chromatography-tandem mass spectrometry-based methods, we showed that a hyperaccumulation of the primary LD core lipid TAG is a general response to stress and that acyl chain and sterol composition are remodeled during cellular adaptation. Likewise, comparative analysis of the LD protein composition in stress-treated leaves highlighted the plasticity of the LD proteome as part of the general stress response. We further identified at least two additional LD-associated proteins, whose localization to LDs in leaves was confirmed by confocal microscopy of fluorescent protein fusions. Taken together, these results highlight LDs as dynamic contributors to the cellular adaptation processes that underlie how plants respond to environmental stress.

Lipids shape brain function through ion channel and receptor modulations: physiological mechanisms and clinical perspectives

Lipids represent the most abundant molecular type in the brain, with a fat content of ∼60% of the dry brain weight in humans. Despite this fact, little attention has been paid to circumscribe the dynamic role of lipids in brain function and disease. Membrane lipids such as cholesterol, phosphoinositide, sphingolipids, arachidonic acid, and endocannabinoids finely regulate both synaptic receptors and ion channels that ensure critical neural functions. After a brief introduction on brain lipids and their respective properties, we review here their role in regulating synaptic function and ion channel activity, action potential propagation, neuronal development, and functional plasticity and their contribution in the development of neurological and neuropsychiatric diseases. We also provide possible directions for future research on lipid function in brain plasticity and diseases.

TMAO is involved in sleep deprivation-induced cognitive dysfunction through regulating astrocytic cholesterol metabolism via SREBP2

Sleep deprivation (SD) contributes to cognitive impairment. Astrocytic cholesterol biosynthesis is crucial for brain cholesterol homeostasis and cognitive function. However, the underlying mechanism of astrocytic cholesterol metabolism in SD-induced cognitive impairment has not been fully explored. Trimethylamine N-oxide (TMAO), a product of liver flavin-containing monooxygenase-3 (FMO3), has been shown to be increased in the urine of sleep-deprived humans and implicated with peripheral cholesterol metabolism. Nevertheless, how TMAO affects brain cholesterol metabolism remains unclear. In our study, increased FMO3 and brain TMAO levels were observed in the SD mice, and elevated levels of TMAO were confirmed to lead to SD-induced cognitive dysfunction. In addition, we found that the expression of sterol regulatory element-binding protein 2 (SREBP2) is decreased in the brain of SD mice, resulting in the reduction in brain cholesterol content, which in turn causes synaptic damage. Moreover, we demonstrated that TMAO inhibits the expression of SREBP2. In contrast, FMO3 inhibitor 3,3'-diindolylmethane (DIM) alleviates SD-induced cognitive impairment by targeting the liver-brain axis. In conclusion, our study revealed that the TMAO pathway is involved in memory impairment in SD mice through deregulating astrocytic cholesterol metabolism.

All roads lead to cholesterol: Modulating lipid biosynthesis in multiple sclerosis patient-derived models

Studies from Ionescu et al.1 and Clayton et al.2 using multiple sclerosis (MS) patient-derived cell models underscore cholesterol metabolism's role in inflammatory and dysfunctional cell phenotypes in the disease. Inhibiting cholesterol biosynthesis ameliorated critical cellular phenotypes, emphasizing the need to further investigate this pathway as a potential target for MS treatment.

Dyslipidemias in multiple sclerosis

PURPOSE

To investigate the frequency of dyslipidemia phenotypes in multiple sclerosis and to assess the associations with lipoprotein particle size distributions.

METHODS

This cross-sectional study included 203 healthy controls (HC), 221 relapsing-remitting MS (RRMS), and 126 progressive MS (PMS). A lipid profile with total cholesterol, high-density lipoprotein cholesterol (HDL-C), triglycerides, and apolipoprotein B levels were measured. Low density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol, large buoyant LDL-C and small dense LDL-C were calculated using the Sampson-NIH equations method. Dyslipidemia phenotypes were categorized by their nonHDL-C and triglyceride values. The diameters and concentrations of triglyceride-rich lipoprotein particles (TRLP), LDL particles (LDLP), and HDL particles (HDLP) were measured with proton NMR lipoprotein profiling. Serum proprotein convertase subtilisin/kexin type 9 (PCSK9) levels were obtained using immunoassay.

RESULTS

The frequencies of normolipidemia, and various dyslipidemia phenotypes were similar in HC, RRMS, and PMS. The size of the TRLP, very large TRLP, large TRLP, and small LDLP concentrations had a decreasing pattern of HC>RR>PMS. The lowest tertile of EDSS was associated with higher concentrations of HDLP and small HDLP in PMS. PCSK9 was associated with concentration of HDL particles, primarily via its effects on the concentration of small HDL particles.

CONCLUSIONS

There were no differences in the frequency of dyslipidemias in MS compared to healthy controls. Higher HDLP concentrations are associated with lower disability in PMS.

White matter lipid alterations during aging in the rhesus monkey brain

The brain of higher organisms, such as nonhuman primates, is particularly rich in lipids, with a gray to white matter ratio of approximately 40 to 60%. White matter primarily consists of lipids, and during normal aging, it undergoes significant degeneration due to myelin pathology, which includes structural abnormalities, like sheath splitting, and local inflammation. Cognitive decline in normal aging, without neurodegenerative diseases, is strongly linked to myelin pathology. Although the exact cause of myelin damage is unclear, older myelin differs from younger myelin, as shown by electron microscopy and altered expression of myelin-related RNAs. However, changes in lipid composition during brain aging remain poorly understood. This study assessed lipid profiles from the frontal lobe corpus callosum, an area where age-related myelin pathology is linked to cognitive decline. Results showed significant changes in lipids with age, revealing distinct age-related profiles. Some lipids that are enriched in myelin sheaths become more saturated, while important structural components, like ceramides, decrease. Disease-associated biomarkers such as cholesterol ester Che (22:6) and sulfatide ST (42:2) also change in older monkeys. Additionally, gene expression of lipid biosynthetic enzymes declines with age, while lipid peroxidation remains stable in the same brain region. This suggests that changes in lipid biosynthesis, rather than oxidative damage, likely account for the differences in lipid composition. Our findings indicate that myelin in the normal aging monkey brain shows diverse lipid changes, which may relate to age-related myelin pathology and could constitute targets for designing nutrient supplements or drugs to rejuvenate the brain's lipidome.

3D chromatin-based variant-to-gene maps across 57 human cell types reveal the cellular and genetic architecture of autoimmune disease susceptibility

A portion of the genetic basis for many common autoimmune disorders has been uncovered by genome-wide association studies (GWAS), but GWAS do not reveal causal variants, effector genes, or the cell types impacted by disease-associated variation. We have generated 3D genomic datasets consisting of promoter-focused Capture-C, Hi-C, ATAC-seq, and RNA-seq and integrated these data with GWAS of 16 autoimmune traits to physically map disease-associated variants to the effector genes they likely regulate in 57 human cell types. These 3D maps of gene cis-regulatory architecture are highly powered to identify the cell types most likely impacted by disease-associated genetic variation compared to 1D genomic features, and tend to implicate different effector genes than eQTL approaches in the same cell types. Most of the variants implicated by these cis-regulatory architectures are highly trait-specific, but nearly half of the target genes connected to these variants are shared across multiple autoimmune disorders in multiple cell types, suggesting a high level of genetic diversity and complexity among autoimmune diseases that nonetheless converge at the level of target gene and cell type. Substantial effector gene sharing led to the common enrichment of similar biological networks across disease and cell types. However, trait-specific pathways representing potential areas for disease-specific intervention were identified. To test this, we pharmacologically validated squalene synthase, a cholesterol biosynthetic enzyme encoded by the FDFT1 gene implicated by our approach in MS and SLE, as a novel immunomodulatory drug target controlling inflammatory cytokine production by human T cells. These data represent a comprehensive resource for basic discovery of gene cis-regulatory mechanisms, and the analyses reported reveal mechanisms by which autoimmune-associated variants act to regulate gene expression, function, and pathology across multiple, distinct tissues and cell types.

miR-223 accelerates lipid droplets clearance in microglia following spinal cord injury by upregulating ABCA1

BACKGROUND

Spinal cord injury (SCI) is characterized by extensive demyelination and inflammatory responses. Facilitating the clearance of lipid droplets (LDs) within microglia contributes to creating a microenvironment that favors neural recovery and provides essential materials for subsequent remyelination. Therefore, investigating MicroRNAs (miRNAs) that regulate lipid homeostasis after SCI and elucidating their potential mechanisms in promoting LDs clearance in microglia have become focal points of SCI research.

METHODS

We established a subacute C5 hemicontusion SCI model in mice and performed transcriptomic sequencing on the injury epicenter to identify differentially expressed genes and associated pathways. Confocal imaging was employed to observe LDs accumulation. Multi-omics analyses were conducted to identify differentially expressed mRNA and miRNA post-SCI. Pathway enrichment analysis and protein-protein interaction network construction were performed using bioinformatics methods, revealing miR-223-Abca1 as a crucial miRNA-mRNA pair in lipid metabolism regulation. BV2 microglia cell lines overexpressing miR-223 were engineered, and immunofluorescence staining, western blot, and other techniques were employed to assess LDs accumulation, relevant targets, and inflammatory factor expression, confirming its role in regulating lipid homeostasis in microglia.

RESULTS

Histopathological results of our hemicontusion SCI model confirmed LDs aggregation at the injury epicenter, predominantly within microglia. Our transcriptomic analysis during the subacute phase of SCI in mice implicated ATP-binding cassette transporter A1 (Abca1) as a pivotal gene in lipid homeostasis, cholesterol efflux and microglial activation. Integrative mRNA-miRNA multi-omics analysis highlighted the crucial role of miR-223 in the neuroinflammation process following SCI, potentially through the regulation of lipid metabolism via Abca1. In vitro experiments using BV2 cells overexpressing miR-223 demonstrated that elevated levels of miR-223 enhance ABCA1 expression in myelin debris and LPS-induced BV2 cells. This promotes myelin debris degradation and LDs clearance, and induces a shift toward an anti-inflammatory M2 phenotype.

CONCLUSIONS

In summary, our study unveils the critical regulatory role of miR-223 in lipid homeostasis following SCI. The mechanism by which this occurs involves the upregulation of ABCA1 expression, which facilitates LDs clearance and myelin debris degradation, consequently alleviating the lipid burden, and inhibiting inflammatory polarization of microglia. These findings suggest that strategies to enhance miR-223 expression and target ABCA1, thereby augmenting LDs clearance, may emerge as appealing new clinical targets for SCI treatment.

The interplay of inflammation and remyelination: rethinking MS treatment with a focus on oligodendrocyte progenitor cells

BACKGROUND

Multiple sclerosis (MS) therapeutic goals have traditionally been dichotomized into two distinct avenues: immune-modulatory-centric interventions and pro-regenerative strategies. Oligodendrocyte progenitor cells (OPCs) were regarded for many years solely in concern to their potential to generate oligodendrocytes and myelin in the central nervous system (CNS). However, accumulating data elucidate the multifaceted roles of OPCs, including their immunomodulatory functions, positioning them as cardinal constituents of the CNS's immune landscape.

MAIN BODY

In this review, we will discuss how the two therapeutic approaches converge. We present a model by which (1) an inflammation is required for the appropriate pro-myelinating immune function of OPCs in the chronically inflamed CNS, and (2) the immune function of OPCs is crucial for their ability to differentiate and promote remyelination. This model highlights the reciprocal interactions between OPCs' pro-myelinating and immune-modulating functions. Additionally, we review the specific effects of anti- and pro-inflammatory interventions on OPCs, suggesting that immunosuppression adversely affects OPCs' differentiation and immune functions.

CONCLUSION

We suggest a multi-systemic therapeutic approach, which necessitates not a unidimensional focus but a harmonious balance between OPCs' pro-myelinating and immune-modulatory functions.

TREM2 alleviates white matter injury after traumatic brain injury in mice might be mediated by regulation of DHCR24/LXR pathway in microglia

BACKGROUND

White matter injury (WMI) is an important pathological process after traumatic brain injury (TBI). The correlation between white matter functions and the myeloid cells expressing triggering receptor-2 (TREM2) has been convincingly demonstrated. Moreover, a recent study revealed that microglial sterol metabolism is crucial for early remyelination after demyelinating diseases. However, the potential roles of TREM2 expression and microglial sterol metabolism in WMI after TBI have not yet been explored.

METHODS

Controlled cortical injury was induced in both wild-type (WT) and TREM2 depletion (TREM2 KO) mice to simulate clinical TBI. COG1410 was used to upregulate TREM2, while PLX5622 and GSK2033 were used to deplete microglia and inhibit the liver X receptor (LXR), respectively. Immunofluorescence, Luxol fast blue staining, magnetic resonance imaging, transmission electron microscopy, and oil red O staining were employed to assess WMI after TBI. Neurological behaviour tests and electrophysiological recordings were utilized to evaluate cognitive functions following TBI. Microglial cell sorting and transcriptomic sequencing were utilized to identify alterations in microglial sterol metabolism-related genes, while western blot was conducted to validate the findings.

RESULTS

TREM2 expressed highest at 3 days post-TBI and was predominantly localized to microglial cells within the white matter. Depletion of TREM2 worsened aberrant neurological behaviours, and this phenomenon was mediated by the exacerbation of WMI, reduced renewal of oligodendrocytes, and impaired phagocytosis ability of microglia after TBI. Subsequently, the upregulation of TREM2 alleviated WMI, promoted oligodendrocyte regeneration, and ultimately facilitated the recovery of neurological behaviours after TBI. Finally, the expression of DHCR24 increased in TREM2 KO mice after TBI. Interestingly, TREM2 inhibited DHCR24 and upregulated members of the LXR pathway. Moreover, LXR inhibition could partially reverse the effects of TREM2 upregulation on electrophysiological activities.

CONCLUSIONS

We demonstrate that TREM2 has the potential to alleviate WMI following TBI, possibly through the DHCR24/LXR pathway in microglia.

Maternal history of Alzheimer's disease predisposes to altered serum cholesterol levels in adult offspring

Controversial findings regarding the association between serum cholesterol levels and Alzheimer's disease (AD) have been identified through observational studies. The genetic basis shared by both factors and the causality between them remain largely unknown. The objective of this study is to examine the causal impact of maternal history of AD on changes in serum cholesterol levels in adult offspring. By retrieving genetic variants from summary statistics of large-scale genome-wide association study of maternal history of AD (European-based: Ncase = 27 696, Ncontrol = 260 980). The causal association between genetically predicted maternal history of AD and changes in serum cholesterol levels in adult offspring was examined using the two-sample Mendelian randomization (MR) method. Causal impact estimates were calculated using single-nucleotide polymorphisms in both univariable MR (UMR) and multivariable MR (MVMR) analyses. Additionally, other approaches, such as Cochran's Q test and leave-one-out variant analysis, were employed to correct for potential biases. The results of UMR presented that genetically predicted maternal history of AD was positively associated with hypercholesterolemia (OR = 1.014; 95% CI: 1.009-1.018; p < 0.001), total cholesterol (OR = 1.29; 95% CI: 1.134-1.466; p < 0.001) and low-density lipoprotein (OR = 1.525; 95% CI: 1.272-1.828; p < 0.001) among adult offspring. Genetic predisposition for maternal history of AD to be negatively associated with high-density lipoprotein (OR = 0.889; 95% CI: 0.861-0.917; p < 0.001). The MVMR analysis remained robust and significant after adjusting for diabetes and obesity in offspring. Sufficient evidence was provided in this study to support the putative causal impact of maternal history of AD on the change of serum cholesterol profile in adult offspring. In clinical practice, priority should be given to the detection and monitoring of cholesterol levels in individuals with a maternal history of AD, particularly in the early stages.

Astrocyte signaling and interactions in Multiple Sclerosis

Multiple Sclerosis (MS) is a common cause of impairment in working-aged adults. MS is characterized by neuroinflammation and infiltration of peripheral immune cells to the brain, which cause myelin loss and death of oligodendrocytes and neurons. Many studies on MS have focused on the peripheral immune sources of demyelination and repair. However, recent studies revealed that a glial cell type, the astrocytes, undergo robust morphological and transcriptomic changes that contribute significantly to demyelination and myelin repair. Here, we discuss recent findings elucidating signaling modalities that astrocytes acquire or lose in MS and how these changes alter the interactions of astrocytes with other nervous system cell types.

Extracellular vesicle-associated cholesterol supports the regenerative functions of macrophages in the brain

Macrophages play major roles in the pathophysiology of various neurological disorders, being involved in seemingly opposing processes such as lesion progression and resolution. Yet, the molecular mechanisms that drive their harmful and benign effector functions remain poorly understood. Here, we demonstrate that extracellular vesicles (EVs) secreted by repair-associated macrophages (RAMs) enhance remyelination ex vivo and in vivo by promoting the differentiation of oligodendrocyte precursor cells (OPCs). Guided by lipidomic analysis and applying cholesterol depletion and enrichment strategies, we find that EVs released by RAMs show markedly elevated cholesterol levels and that cholesterol abundance controls their reparative impact on OPC maturation and remyelination. Mechanistically, EV-associated cholesterol was found to promote OPC differentiation predominantly through direct membrane fusion. Collectively, our findings highlight that EVs are essential for cholesterol trafficking in the brain and that changes in cholesterol abundance support the reparative impact of EVs released by macrophages in the brain, potentially having broad implications for therapeutic strategies aimed at promoting repair in neurodegenerative disorders.

Cholesterol Levels, Hormone Replacement Therapy, and Incident Dementia among Older Adult Women

Previous studies revealed that hormone replacement therapy (HRT) probably has a protective effect for preventing dementia in post-menopausal women. However, the results were still controversial. The association between cholesterol levels and incident dementia in older women is not fully understood either. We conducted a retrospective analysis on a cohort of non-demented women aged older than 50 years, which was registered in the History-based Artificial Intelligence Clinical Dementia Diagnostic System database from September 2015 to August 2021. We followed this cohort longitudinally to examine the rates of conversion to dementia. Using a Cox regression model, we investigated the impact of the quartile of total cholesterol (TC) levels on incident dementia, adjusting for age, sex, education, neuropsychiatric symptoms, neuropsychological assessments, HRT, as well as various vascular risk factors and medications. We examined a cohort of 787 participants, comprising 539 (68.5%) individuals who did not develop dementia (non-converters). Among these non-converters, 68 individuals (12.6%) were treated with HRT. By contrast, there were 248 (31.5%) who did develop dementia (converters). Among the converters, 28 individuals (11.3%) were treated with HRT. The average follow-up durations were 2.9 ± 1.5 and 3.3 ± 1.6 years for non-converters and converters, respectively. Compared to the lowest quartile of TC levels (<153), the hazard ratios (HR) for converting to dementia were 0.61, 0.58, and 0.58 for the second (153-176), third (177-201), and highest (>201) quartiles, respectively (all p < 0.05). However, the low-density lipoprotein cholesterol (LDL-C) level and HRT did not alter the rate of conversion to dementia. In conclusion, the lowest quartile of TC increased incident dementia in post-menopausal women without dementia; however, HRT did not contribute to conversion to dementia. Some studies suggest that post-menopausal women who have reduced estrogen levels might have an increased risk of Alzheimer's disease if they also have high cholesterol. Nonetheless, the evidence is inconclusive, as not all studies support this finding. The "Lower LDL-C is better" strategy for preventing cardiac vascular disease should be re-examined for the possible serial adverse effects of new onset dementia due to very low cholesterol levels.

Farnesol brain transcriptomics in CNS inflammatory demyelination

BACKGROUND

Farnesol (FOL) prevents the onset of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS).

OBJECTIVE

We examined the transcriptomic profile of the brains of EAE mice treated with daily oral FOL using next-generation sequencing (RNA-seq).

METHODS

Transcriptomics from whole brains of treated and untreated EAE mice at the peak of EAE was performed.

RESULTS

EAE-induced mice, compared to naïve, healthy mice, overall showed increased expression in pathways for immune response, as well as an increased cytokine signaling pathway, with downregulation of cellular stress proteins. FOL downregulates pro-inflammatory pathways and attenuates the immune response in EAE. FOL downregulated the expression of genes involved in misfolded protein response, MAPK activation/signaling, and pro-inflammatory response.

CONCLUSION

This study provides insight into the molecular impact of FOL in the brain and identifies potential therapeutic targets of the isoprenoid pathway in MS patients.

Cholesterol-dependent amyloid β production: space for multifarious interactions between amyloid precursor protein, secretases, and cholesterol

Amyloid β is considered a key player in the development and progression of Alzheimer's disease (AD). Many studies investigating the effect of statins on lowering cholesterol suggest that there may be a link between cholesterol levels and AD pathology. Since cholesterol is one of the most abundant lipid molecules, especially in brain tissue, it affects most membrane-related processes, including the formation of the most dangerous form of amyloid β, Aβ42. The entire Aβ production system, which includes the amyloid precursor protein (APP), β-secretase, and the complex of γ-secretase, is highly dependent on membrane cholesterol content. Moreover, cholesterol can affect amyloidogenesis in many ways. Cholesterol influences the stability and activity of secretases, but also dictates their partitioning into specific cellular compartments and cholesterol-enriched lipid rafts, where the amyloidogenic machinery is predominantly localized. The most complicated relationships have been found in the interaction between cholesterol and APP, where cholesterol affects not only APP localization but also the precise character of APP dimerization and APP processing by γ-secretase, which is important for the production of Aβ of different lengths. In this review, we describe the intricate web of interdependence between cellular cholesterol levels, cholesterol membrane distribution, and cholesterol-dependent production of Aβ, the major player in AD.

Hydrogel-based treatments for spinal cord injuries

Spinal cord injury (SCI) is characterized by damage resulting in dysfunction of the spinal cord. Hydrogels are common biomaterials that play an important role in the treatment of SCI. Hydrogels are biocompatible, and some have electrical conductivity that are compatible with spinal cord tissues. Hydrogels have a high drug-carrying capacity, allowing them to be used for SCI treatment through the loading of various types of active substances, drugs, or cells. We first discuss the basic anatomy and physiology of the human spinal cord and briefly discuss SCI and its treatment. Then, we describe different treatment strategies for SCI. We further discuss the crosslinking methods and classification of hydrogels and detail hydrogel biomaterials prepared using different processing methods for the treatment of SCI. Finally, we analyze the future applications and limitations of hydrogels for SCI. The development of biomaterials opens up new possibilities and options for the treatment of SCI. Thus, our findings will inspire scholars in related fields and promote the development of hydrogel therapy for SCI.

Cholesterol Metabolism in Aging and Age-Related Disorders

All mammalian cell membranes contain cholesterol to maintain membrane integrity. The transport of this hydrophobic lipid is mediated by lipoproteins. Cholesterol is especially enriched in the brain, particularly in synaptic and myelin membranes. Aging involves changes in sterol metabolism in peripheral organs and also in the brain. Some of those alterations have the potential to promote or to counteract the development of neurodegenerative diseases during aging. Here, we summarize the current knowledge of general principles of sterol metabolism in humans and mice, the most widely used model organism in biomedical research. We discuss changes in sterol metabolism that occur in the aged brain and highlight recent developments in cell type-specific cholesterol metabolism in the fast-growing research field of aging and age-related diseases, focusing on Alzheimer's disease. We propose that cell type-specific cholesterol handling and the interplay between cell types critically influence age-related disease processes.

Cortical glia in SOD1(G93A) mice are subtly affected by ALS-like pathology

The role of glia in amyotrophic lateral sclerosis (ALS) is undeniable. Their disease-related activity has been extensively studied in the spinal cord, but only partly in the brain. We present herein a comprehensive study of glia in the cortex of SOD1(G93A) mice-a widely used model of ALS. Using single-cell RNA sequencing (scRNA-seq) and immunohistochemistry, we inspected astrocytes, microglia, and oligodendrocytes, in four stages of the disease, respecting the factor of sex. We report minimal changes of glia throughout the disease progression and regardless of sex. Pseudobulk and single-cell analyses revealed subtle disease-related transcriptional alterations at the end-stage in microglia and oligodendrocytes, which were supported by immunohistochemistry. Therefore, our data support the hypothesis that the SOD1(G93A) mouse cortex does not recapitulate the disease in patients, and we recommend the use of a different model for future studies of the cortical ALS pathology.

Brain vitamin D3-auto/paracrine system in relation to structural, neurophysiological, and behavioral disturbances associated with glucocorticoid-induced neurotoxicity

Introduction

Vitamin D3 (VD3) is a potent para/autocrine regulator and neurosteroid that can strongly influence nerve cell function and counteract the negative effects of glucocorticoid (GC) therapy. The aim of the study was to reveal the relationship between VD3 status and behavioral, structural-functional and molecular changes associated with GC-induced neurotoxicity.

Methods

Female Wistar rats received synthetic GC prednisolone (5 mg/kg b.w.) with or without VD3 (1000 IU/kg b.w.) for 30 days. Behavioral, histological, physiological, biochemical, molecular biological (RT-PCR, Western blotting) methods, and ELISA were used.

Results and discussion

There was no difference in open field test (OFT), while forced swim test (FST) showed an increase in immobility time and a decrease in active behavior in prednisolone-treated rats, indicative of depressive changes. GC increased the perikaryon area, enlarged the size of the nuclei, and caused a slight reduction of cell density in CA1-CA3 hippocampal sections. We established a GC-induced decrease in the long-term potentiation (LTP) in CA1-CA3 hippocampal synapses, the amplitude of high K+-stimulated exocytosis, and the rate of Ca2+-dependent fusion of synaptic vesicles with synaptic plasma membranes. These changes were accompanied by an increase in nitration and poly(ADP)-ribosylation of cerebral proteins, suggesting the development of oxidative-nitrosative stress. Prednisolone upregulated the expression and phosphorylation of NF-κB p65 subunit at Ser311, whereas downregulating IκB. GC loading depleted the circulating pool of 25OHD3 in serum and CSF, elevated VDR mRNA and protein levels but had an inhibitory effect on CYP24A1 and VDBP expression. Vitamin D3 supplementation had an antidepressant-like effect, decreasing the immobility time and stimulating active behavior. VD3 caused a decrease in the size of the perikaryon and nucleus in CA1 hippocampal area. We found a recovery in depolarization-induced fusion of synaptic vesicles and long-term synaptic plasticity after VD3 treatment. VD3 diminished the intensity of oxidative-nitrosative stress, and suppressed the NF-κB activation. Its ameliorative effect on GC-induced neuroanatomical and behavioral abnormalities was accompanied by the 25OHD3 repletion and partial restoration of the VD3-auto/paracrine system.

Conclusion

GC-induced neurotoxicity and behavioral disturbances are associated with increased oxidative-nitrosative stress and impairments of VD3 metabolism. Thus, VD3 can be effective in preventing structural and functional abnormalities in the brain and behavior changes caused by long-term GC administration.

Cholesterol metabolism: Towards a therapeutic approach for multiple sclerosis

Growing evidence points to the importance of cholesterol in preserving brain homeostasis. Cholesterol makes up the main component of myelin in the brain, and myelin integrity is vital in demyelinating diseases such as multiple sclerosis. Because of the connection between myelin and cholesterol, the interest in cholesterol in the central nervous system increased during the last decade. In this review, we provide a detailed overview on brain cholesterol metabolism in multiple sclerosis and its role in promoting oligodendrocyte precursor cell differentiation and remyelination.

Erythrocyte Plasma Membrane Lipid Composition Mirrors That of Neurons and Glial Cells in Murine Experimental In Vitro and In Vivo Inflammation

Lipid membrane turnover and myelin repair play a central role in diseases and lesions of the central nervous system (CNS). The aim of the present study was to analyze lipid composition changes due to inflammatory conditions. We measured the fatty acid (FA) composition in erythrocytes (RBCs) and spinal cord tissue (gas chromatography) derived from mice affected by experimental allergic encephalomyelitis (EAE) in acute and remission phases; cholesterol membrane content (Filipin) and GM1 membrane assembly (CT-B) in EAE mouse RBCs, and in cultured neurons, oligodendroglial cells and macrophages exposed to inflammatory challenges. During the EAE acute phase, the RBC membrane showed a reduction in polyunsaturated FAs (PUFAs) and an increase in saturated FAs (SFAs) and the omega-6/omega-3 ratios, followed by a restoration to control levels in the remission phase in parallel with an increase in monounsaturated fatty acid residues. A decrease in PUFAs was also shown in the spinal cord. CT-B staining decreased and Filipin staining increased in RBCs during acute EAE, as well as in cultured macrophages, neurons and oligodendrocyte precursor cells exposed to inflammatory challenges. This regulation in lipid content suggests an increased cell membrane rigidity during the inflammatory phase of EAE and supports the investigation of peripheral cell membrane lipids as possible biomarkers for CNS lipid membrane concentration and assembly.

Long noncoding RNA lincsc5d regulates hepatic cholesterol synthesis by modulating sterol C5 desaturase in large yellow croaker

Although long noncoding RNA (lncRNA) plays a vital role in cholesterol metabolism, very little information is available in fish. Thus, a 10-week feeding experiment was performed to estimate the effects of lncRNA on cholesterol metabolism in large yellow croaker fed with fish oil (FO), soybean oil (SO), olive oil (OO), and palm oil (PO) diets. Results showed that fish fed with OO and PO diets had higher liver total cholesterol (TC) and cholesterol ester (CE) contents compared with fish fed with FO diets. Analysis of the KEGG pathway showed that the steroid biosynthesis pathway was enriched in comparisons FO vs SO, FO vs OO, and FO vs PO. Meanwhile, sterol C5 desaturase (SC5D), a cholesterol synthase, was up-regulated in the steroid biosynthesis pathway. SC5D was widely expressed in all tissues examined, and the highest expression of SC5D was detected in brain. More importantly, a novel lncRNA associated with sc5d gene was identified by RNA sequencing and named as lincsc5d. The tissue distribution of lincsc5d was similar to that of sc5d. A nuclear/cytoplasmic RNA separation assay showed that lincsc5d was a nucleus-enriched lncRNA. qRT-PCR results demonstrated that lincsc5d was markedly up-regulated in the SO, OO, and PO groups. Furthermore, the results of TC content and the lincsc5d and sc5d expression in hepatocytes agreed with in vivo results. In conclusion, this study indicated that vegetable oils, especially OO and PO, increased hepatic cholesterol levels by promoting cholesterol synthesis, and lncRNA lincsc5d and sc5d might be involved in cholesterol synthesis.

Astrocytic MicroRNAs and Transcription Factors in Alzheimer's Disease and Therapeutic Interventions

Astrocytes are important for maintaining cholesterol metabolism, glutamate uptake, and neurotransmission. Indeed, inflammatory processes and neurodegeneration contribute to the altered morphology, gene expression, and function of astrocytes. Astrocytes, in collaboration with numerous microRNAs, regulate brain cholesterol levels as well as glutamatergic and inflammatory signaling, all of which contribute to general brain homeostasis. Neural electrical activity, synaptic plasticity processes, learning, and memory are dependent on the astrocyte-neuron crosstalk. Here, we review the involvement of astrocytic microRNAs that potentially regulate cholesterol metabolism, glutamate uptake, and inflammation in Alzheimer's disease (AD). The interaction between astrocytic microRNAs and long non-coding RNA and transcription factors specific to astrocytes also contributes to the pathogenesis of AD. Thus, astrocytic microRNAs arise as a promising target, as AD conditions are a worldwide public health problem. This review examines novel therapeutic strategies to target astrocyte dysfunction in AD, such as lipid nanodiscs, engineered G protein-coupled receptors, extracellular vesicles, and nanoparticles.

Microglial-oligodendrocyte interactions in myelination and neurological function recovery after traumatic brain injury

Differential microglial inflammatory responses play a role in regulation of differentiation and maturation of oligodendrocytes (OLs) in brain white matter. How microglia-OL crosstalk is altered by traumatic brain injury (TBI) and its impact on axonal myelination and neurological function impairment remain poorly understood. In this study, we investigated roles of a Na⁺/H⁺ exchanger (NHE1), an essential microglial pH regulatory protein, in microglial proinflammatory activation and OL survival and differentiation in a murine TBI model induced by controlled cortical impact. Similar TBI-induced contusion volumes were detected in the Cx3cr1-Cre^ERT2 control (Ctrl) mice and selective microglial Nhe1 knockout (Cx3cr1-Cre^ERT2;Nhe1^flox/flox, Nhe1 cKO) mice. Compared to the Ctrl mice, the Nhe1 cKO mice displayed increased resistance to initial TBI-induced white matter damage and accelerated chronic phase of OL regeneration at 30 days post-TBI. The cKO brains presented increased anti-inflammatory phenotypes of microglia and infiltrated myeloid cells, with reduced proinflammatory transcriptome profiles. Moreover, the cKO mice exhibited accelerated post-TBI sensorimotor and cognitive functional recovery than the Ctrl mice. These phenotypic outcomes in cKO mice were recapitulated in C57BL6J wild-type TBI mice receiving treatment of a potent NHE1 inhibitor HOE642 for 1-7 days post-TBI. Taken together, these findings collectively demonstrated that blocking NHE1 protein stimulates restorative microglial activation in oligodendrogenesis and neuroprotection, which contributes to accelerated brain repair and neurological function recovery after TBI.

Comparative Account of Biomolecular Changes Post Epstein Barr Virus Infection of the Neuronal and Glial Cells Using Raman Microspectroscopy

Raman microspectroscopy is a vibrational spectroscopy technique used for investigating molecular fingerprints of a wide range of liquid or solid samples. The technique can be efficiently utilized to understand the virus-mediated cellular changes and could provide valuable insights into specific biomolecular alterations. The Epstein Barr virus (EBV) has been associated with various types of cancers as well as neurodegenerative diseases. However, EBV-mediated neurological ailments are yet underexplored in terms of biomolecular changes in neuronal and glial cells (astrocytes and microglia). In continuation of our earlier exploration of EBV-influenced glial cells, we tried to decipher biomolecular changes in EBV-infected neuronal cells using Raman microspectroscopy. Additionally, we compared the consecutive biomolecular changes observed in neuronal cells with both the glial cells. We observed that EBV infection gets differentially regulated in the neuronal cells, astrocytes, and microglia. The viral entry and initiation of infection-mediated cellular modulation could start as soon as 2 h post infection but may regulate a distinct biomolecular milieu in different time intervals. Similar to the early timespan, the 24-36 h interval could also be important for EBV to manipulate neuronal as well as glial cells as depicted from elevated biomolecular activities. At these time intervals, some common biomolecules such as proline, glucose, lactic acid, nucleotides, or cholesterol were observed in the cells. However, at these time intervals, some distinct biomolecules were also observed in each cell, such as collagen, lipid, and protein stretches in the neuronal nucleus (2-4 h); tyrosine and RNA in the astrocyte nucleus (2-4 h nucleus); and fatty acids in the microglia nucleus (24-36 h). The observed biomolecular entities could ultimately play pivotal roles in the viral usurpation of cells. We also provided insights into whether these biomolecular changes can be correlated to each other and mediate virus-associated manifestations which can be linked to neurological complications. Our study aids in the understanding of EBV-mediated biomolecular changes in the various compartments of the central nervous system.

Overview of myelin, major myelin lipids, and myelin-associated proteins

Myelin is a modified cell membrane that forms a multilayer sheath around the axon. It retains the main characteristics of biological membranes, such as lipid bilayer, but differs from them in several important respects. In this review, we focus on aspects of myelin composition that are peculiar to this structure and differentiate it from the more conventional cell membranes, with special attention to its constituent lipid components and several of the most common and important myelin proteins: myelin basic protein, proteolipid protein, and myelin protein zero. We also discuss the many-fold functions of myelin, which include reliable electrical insulation of axons to ensure rapid propagation of nerve impulses, provision of trophic support along the axon and organization of the unmyelinated nodes of Ranvier, as well as the relationship between myelin biology and neurologic disease such as multiple sclerosis. We conclude with a brief history of discovery in the field and outline questions for future research.