Lipid-droplet-accumulating microglia represent a dysfunctional and proinflammatory state in the aging brain

Metabolic reprogramming: a new option for the treatment of spinal cord injury

Spinal cord injuries impose a notably economic burden on society, mainly because of the severe after-effects they cause. Despite the ongoing development of various therapies for spinal cord injuries, their effectiveness remains unsatisfactory. However, a deeper understanding of metabolism has opened up a new therapeutic opportunity in the form of metabolic reprogramming. In this review, we explore the metabolic changes that occur during spinal cord injuries, their consequences, and the therapeutic tools available for metabolic reprogramming. Normal spinal cord metabolism is characterized by independent cellular metabolism and intercellular metabolic coupling. However, spinal cord injury results in metabolic disorders that include disturbances in glucose metabolism, lipid metabolism, and mitochondrial dysfunction. These metabolic disturbances lead to corresponding pathological changes, including the failure of axonal regeneration, the accumulation of scarring, and the activation of microglia. To rescue spinal cord injury at the metabolic level, potential metabolic reprogramming approaches have emerged, including replenishing metabolic substrates, reconstituting metabolic couplings, and targeting mitochondrial therapies to alter cell fate. The available evidence suggests that metabolic reprogramming holds great promise as a next-generation approach for the treatment of spinal cord injury. To further advance the metabolic treatment of the spinal cord injury, future efforts should focus on a deeper understanding of neurometabolism, the development of more advanced metabolomics technologies, and the design of highly effective metabolic interventions.

Senescent microglia: The hidden culprits accelerating Alzheimer's disease

Ageing is a major risk factor for neurodegenerative diseases like Alzheimer's disease (AD). Microglia, as the principal innate immune cells within the brain, exert homeostatic and active immunological defense functions throughout human lifespan. The age-related dysfunction of microglia is currently recognized as a pivotal trigger for brain diseases associated with aging. In AD, microglia exhibit alterations in gene expression, cellular morphology, and functional behavior. By focusing on the immunomodulatory functions of factors secreted by senescent microglia, such as cytokines, chemokines, complement factors, and reactive oxygen species (ROS), we explore the diverse detrimental effects of microglia in aging and AD pathogenesis, including Aβ accumulation, Tau deposition, synaptic dysfunction, and neuroinflammation. These collectively contribute to hastening the progression of. In this review, we highlight the key role of senescent microglia in the pathological processes of AD. Then we propose that targeting senescent microglia holds great promise for therapeutic interventions in neurodegenerative diseases.

Multiple synergistic anti-aging effects of vascular cell adhesion molecule 1 functionalized nanoplatform to improve age-related neurodegenerative diseases

Aging is a critical factor in the onset and progression of neurodegenerative diseases and cognitive decline, with aging-related neuroinflammation and cellular senescence being major contributors. In the aging brain, the cerebral vascular endothelium overexpresses vascular cell adhesion molecule 1 (VCAM1), activating microglia and leading to neuroinflammation and cognitive impairment. Quercetin, a natural neuroprotective agent widely used for treating neurodegenerative diseases, their therapeutic efficacy, however, is limited by its poor water solubility and inability to penetrate the blood-brain barrier (BBB). To address these challenges, we developed a multifunctional micellar platform (Anti-VCAM1-GM1@Q) to improve age-related neurodegenerative diseases. The micelles incorporate anti-VCAM1 antibodies to target cerebral vascular endothelial cells and block VCAM1. Additionally, monosialoganglioside (GM1) was utilized to deliver quercetin due to its biparental properties, high BBB permeability, and neuroprotective effects. Anti-VCAM1-GM1@Q micelles demonstrated strong anti-aging properties. They improved quercetin's bioavailability, effectively penetrated the BBB, targeted cerebral vascular endothelial cells, and reduced neuroinflammation. In animal models, these micelles provided effective neuroprotection, improved memory function and age-related cognitive impairment, and mitigated age-related neurodegeneration. Notably, this system exhibited remarkable treatment efficacy and high safety, indicating substantial potential for clinical translational applications.

The Aging Immune System: A Critical Attack on Ischemic Stroke

Ischemic stroke caused by cerebrovascular embolism is an age-related disease with high rates of disability and mortality. Although the mechanisms of immune and inflammatory development after stroke have been of great interest, most studies have neglected the critical and unavoidable factor of age. As the global aging trend intensifies, the number of stroke patients is constantly increasing, emphasizing the urgency of finding effective measures to address the needs of elderly stroke patients. The concept of "immunosenescence" appears to explain the worse stroke outcomes in older individuals. Immune remodeling due to aging involves dynamic changes at all levels of the immune system, and the overall consequences of central (brain-resident) and peripheral (non-brain-resident) immune cells in stroke vary according to the age of the individual. Lastly, the review outlines recent strategies aimed at immunosenescence to improve stroke prognosis.

Arsenic exposure induces neural cells senescence and abnormal lipid droplet accumulation leading to social memory impairment in mice

The long-term harmful effects of arsenic exposure remain one of the important public health issues. The effects of arsenic exposure on the central nervous system, particularly concerning brain structure and function, have been garnering increasing attention. Hence, the aim of this study was to investigate the impact of chronic low-dose arsenic exposure on murine social memory and to elucidate the underlying molecular mechanisms. Male C57BL/6 mice at six months of age were randomly assigned to a control group and three treatment groups with different arsenic concentrations (50, 100, and 200 μg/L), with exposure durations of 30, 90, 180, and 360 days. The five-social memory test and three-chamber social memory test results indicated that chronic low-dose arsenic exposure disrupted social memory in mice. Further analysis revealed that arsenic exposure led to degeneration of neurons within the dorsal CA2 of the hippocampus (dCA2) and the lateral entorhinal cortex (LEC), which are pivotal for the modulation of social memory, and dCA2 neurons demonstrated structural disruptions and cytoplasmic fragmentation. In addition, arsenic exposure induced neurons and glial cells senescence in both dCA2 and LEC, with a particularly pronounced effect in microglia, and worse with dosage increasing of arsenic exposure, correlating with elevated expression levels of p16INK4A, ferritin light chain and the senescence-associated secretory factors TNF-α and IL-1β, and reduced expression of Lamin B1. Moreover, arsenic exposure triggered substantial cytoplasmic lipid droplets accumulation in neurons, astrocytes and microglia, with an upregulation of PLIN2 expression, a protein associated with lipid droplet formation in astrocytes. At the same time, the aberrant accumulation of lipid droplets further aggravated the astrocytes and microglia aging, especially microglia. Additionally, correlation analysis revealed that social memory impairment was negatively correlated with nerve cell senescence and lipid accumulation. Our findings suggest that arsenic exposure induced cellular functional abnormalities by triggering cellular senescence and the accumulation of lipid droplets, thereby exacerbated neuronal degeneration and result in impaired social memory in mice.

Lipid droplets in the nervous system: involvement in cell metabolic homeostasis

Lipid droplets serve as primary storage organelles for neutral lipids in neurons, glial cells, and other cells in the nervous system. Lipid droplet formation begins with the synthesis of neutral lipids in the endoplasmic reticulum. Previously, lipid droplets were recognized for their role in maintaining lipid metabolism and energy homeostasis; however, recent research has shown that lipid droplets are highly adaptive organelles with diverse functions in the nervous system. In addition to their role in regulating cell metabolism, lipid droplets play a protective role in various cellular stress responses. Furthermore, lipid droplets exhibit specific functions in neurons and glial cells. Dysregulation of lipid droplet formation leads to cellular dysfunction, metabolic abnormalities, and nervous system diseases. This review aims to provide an overview of the role of lipid droplets in the nervous system, covering topics such as biogenesis, cellular specificity, and functions. Additionally, it will explore the association between lipid droplets and neurodegenerative disorders. Understanding the involvement of lipid droplets in cell metabolic homeostasis related to the nervous system is crucial to determine the underlying causes and in exploring potential therapeutic approaches for these diseases.

Multiple Sclerosis: Glial Cell Diversity in Time and Space

Multiple sclerosis (MS) is the most prevalent human inflammatory disease of the central nervous system with demyelination and glial scar formation as pathological hallmarks. Glial cells are key drivers of lesion progression in MS with roles in both tissue damage and repair depending on the surrounding microenvironment and the functional state of the individual glial subtype. In this review, we describe recent developments in the context of glial cell diversity in MS summarizing key findings with respect to pathological and maladaptive functions related to disease-associated glial subtypes. A particular focus is on the spatial and temporal dynamics of glial cells including subtypes of microglia, oligodendrocytes, and astrocytes. We contextualize recent high-dimensional findings suggesting that glial cells dynamically change with respect to epigenomic, transcriptomic, and metabolic features across the inflamed rim and during the progression of MS lesions. In summary, detailed knowledge of spatially restricted glial subtype functions is critical for a better understanding of MS pathology and its pathogenesis as well as the development of novel MS therapies targeting specific glial cell types.

Stress causes lipid droplet accumulation in chondrocytes by impairing microtubules

OBJECTIVE

Abnormal mechanical stress is intimately coupled with osteoarthritis. Microtubules play a vital role in the regulation of mechanotransduction and intracellular transport. The purpose of the present study was to investigate the impact of stress-induced microtubule impairment on intracellular transport and lipid droplet (LD) accumulation in chondrocytes.

METHOD

Rats were subjected to unilateral anterior crossbite (UAC), which is inducible for degeneration of temporomandibular joint (TMJ) cartilage. Chondrocytes derived from rat TMJ cartilage were subjected to fluid flow shear stress (FFSS) and analyzed via LCMS/MS-based proteomics. The microtubule destabilization agent nocodazole and/or the microtubule stabilizer docetaxel were used in the UAC and FFSS models.

RESULTS

In both FFSS- and UAC-treated chondrocytes, decreased acetylated α-Tubulin (ac-Tubulin) expression and LD accumulation were observed. Proteomic data revealed increased levels of the LD-associated protein perilipin 3 (Plin3) and decreased levels of cytoskeleton components in FFSS-treated chondrocytes. Live-cell imaging revealed that the colocalization of LDs with lysosomes was significantly decreased after FFSS treatment. Impairment of microtubules by nocodazole reduced the protein level of ac-Tubulin and disrupted the Hsc70-mediated interaction between Plin3 and Lamp2a, as shown by co-IP assays. In contrast, docetaxel reversed the suppression of ac-Tubulin expression, reduced the accumulation of LDs, and decreased the expression of Plin3 in chondrocytes exposed to FFSS and UAC, and docetaxel ameliorated UAC-induced osteoarthritic lesions in the TMJ cartilage.

CONCLUSION

Microtubule impairment under aberrant stress conditions disrupts intracellular transport and blocks lipophagy, causing LD accumulation in chondrocytes. Microtubule stabilization could be a new approach for treating stress-induced cartilage degeneration.

Structural alteration of hippocampal subfields in type 2 diabetes mellitus patients with dyslipidemia

OBJECTIVE

To explore alterations in hippocampal subfield volumes in type 2 diabetes mellitus (T2DM) patients with dyslipidemia using hippocampal subfield segmentation.

METHODS

A total of 99 T2DM patients were prospectively recruited and divided into two groups based on the presence or absence of dyslipidemia: the T2DM dyslipidemia group and the T2DM normal lipidemia group. Additionally, 57 healthy volunteers were recruited as the healthy control (HC) group. General clinical data and cognitive psychological scale scores were collected. Subgroup analyses of T2DM patients were conducted based on the presence or absence of mild cognitive impairment (MCI). Hippocampal subfield volumes were analyzed using a general linear model with post-hoc Bonferroni correction. Significant differential hippocampal subfields were further analyzed in subgroups using the general linear model with post-hoc Bonferroni tests. Partial correlation analyses were performed to assess correlations between subfield-specific volumes and lipid and glucose metabolism indicators, as well as cognitive psychological scale scores. P-values from partial correlation analyses were corrected using the false discovery rate (FDR).

RESULTS

Volumes of the bilateral hippocampal tail, left presubiculum_body, and right subiculum_body were significantly reduced in the T2DM dyslipidemia group compared to both the HC group and the T2DM normal lipidemia group. Post-hoc analyses revealed that the T2DM dyslipidemia group had the smallest hippocampal subfield volumes. Further subgroup analysis showed that T2DM dyslipidemia patients with MCI exhibited the most pronounced volume reductions in the bilateral hippocampal tail and right subiculum_body. After FDR correction, partial correlation analysis indicated that, in the T2DM dyslipidemia group, the left hippocampal tail volume was positively correlated with the Montreal Cognitive Assessment score. In the T2DM dyslipidemia without MCI group, the volume of the right subiculum_body was negatively correlated with fasting insulin levels and the insulin resistance index, but positively correlated with total cholesterol and low-density lipoprotein cholesterol levels. In T2DM patients with normal lipidemia without MCI, the volume of the right subiculum_body was positively correlated with TC levels.

CONCLUSION

T2DM patients with dyslipidemia, especially those with MCI, exhibit significant atrophy in hippocampal subfield volumes, with correlations observed between lipid levels and hippocampal subfield volume changes. These findings suggest that lipid alterations may play an essential role in hippocampal structural abnormalities and cognitive impairment in T2DM patients. This study provides new insights into the neuropathophysiological mechanisms underlying brain alterations and cognitive decline in T2DM.

Ageing-related changes in the regulation of microglia and their interaction with neurons

Ageing is one of the most important risk factors for chronic health conditions, including neurodegenerative diseases. Inflammation is a feature of ageing, as well as a key pathophysiological mechanism for degenerative diseases. Microglia play multiple roles in the central nervous system; their states entail a complex assemblage of responses reflecting the multiplicity of functions they fulfil both under homeostatic basal conditions and in response to stimuli. Whereas glial cells can promote neuronal homeostasis and limit neurodegeneration, age-related inflammation (i.e. inflammaging) leads to the functional impairment of microglia and astrocytes, exacerbating their response to stimuli. Thus, microglia are key mediators for age-dependent changes of the nervous system, participating in the generation of a less supportive or even hostile environment for neurons. Whereas multiple changes of ageing microglia have been described, here we will focus on the neuron-microglia regulatory crosstalk through fractalkine (CX3CL1) and CD200, and the regulatory cytokine Transforming Growth Factor β1 (TGFβ1), which is involved in immunomodulation and neuroprotection. Ageing results in a dysregulated activation of microglia, affecting neuronal survival, and function. The apparent unresponsiveness of aged microglia to regulatory signals could reflect a restriction in the mechanisms underlying their homeostatic and reactive states. The spectrum of functions, required to respond to life-long needs for brain maintenance and in response to disease, would progressively narrow, preventing microglia from maintaining their protective functions. This article is part of the Special Issue on "Microglia".

Pectolinarin Promotes Functional Recovery after Spinal Cord Injury by Regulating Microglia Polarization Through the PI3K/AKT Signaling Pathway

After spinal cord injury (SCI), microglia polarization plays an important role in spinal cord recovery and axon regeneration. In this study, we conducted mRNA microarrays to identify genes associated with different microglial phenotypes. The results showed a correlation between microglial polarization and the PI3K/AKT signaling pathway, a key regulator of inflammatory responses. In addition, we found that Pectolinarin (PTR) could effectively inhibit lipopolysaccharide (LPS)-induced M1 polarization of microglia and facilitate their transition to the M2 phenotype by directly suppressing the PI3K/AKT signaling pathway. In our established animal model of SCI, it was confirmed that PTR treatment induced microglial polarization towards the M2 phenotype, resulting in reduced fibrous scar formation, enhanced myelin reconstitution, and improved axonal regeneration. In conclusion, targeting the PI3K/AKT signaling pathway with PTR presents a promising new direction for SCI treatment.

25-Hydroxycholesterol modulates microglial function and exacerbates Alzheimer's disease pathology: mechanistic insights and therapeutic potential of cholesterol esterification inhibition

This study investigates the role of 25-hydroxycholesterol (25HC), a metabolite produced by cholesterol hydroxylase encoded by the Ch25h gene, in modulating microglial function and its potential implications in Alzheimer's disease (AD) pathology. We demonstrated that 25HC impairs microglial surveillance, reduces phagocytic capacity, and increases the production of pro-inflammatory cytokines. In vivo two-photon microscopy revealed that 25HC administration diminishes microglial response to brain lesions, while flow cytometry confirmed reduced phagocytosis in both in vivo and in vitro models. Additionally, amyloid-beta (Aβ) was shown to upregulate Ch25h expression and elevate 25HC levels in microglia, exacerbating these functional impairments. Mechanistically, 25HC was found to enhance cholesterol esterification, disrupt cell membrane dynamics, and further reduce microglial mobility and phagocytosis. Treatment with Avasimibe, a cholesterol esterification inhibitor, restored membrane dynamics and microglial function, leading to attenuated AD pathology in a 5XFAD mouse model. These findings suggest that 25HC-induced changes in microglial function contribute to AD progression, and targeting cholesterol metabolism could offer therapeutic potential.

A single-cell atlas to map sex-specific gene-expression changes in blood upon neurodegeneration

The clinical course and treatment of neurodegenerative disease are complicated by immune-system interference and chronic inflammatory processes, which remain incompletely understood. Mapping immune signatures in larger human cohorts through single-cell gene expression profiling supports our understanding of observed peripheral changes in neurodegeneration. Here, we employ single-cell gene expression profiling of over 909k peripheral blood mononuclear cells (PBMCs) from 121 healthy individuals, 48 patients with mild cognitive impairment (MCI), 46 with Parkinson's disease (PD), 27 with Alzheimer's disease (AD), and 15 with both PD and MCI. The dataset is interactively accessible through a freely available website ( https://www.ccb.uni-saarland.de/adrcsc ). In this work, we identify disease-associated changes in blood cell type composition and the gene expression in a sex-specific manner, offering insights into peripheral and solid tissue signatures in AD and PD.

Fokker-Planck diffusion maps of microglial transcriptomes reveal radial differentiation into substates associated with Alzheimer's pathology

The identification of microglia subtypes is important for understanding the role of innate immunity in neurodegenerative diseases. Current methods of unsupervised cell type identification assume a small noise-to-signal ratio of transcriptome measurements to produce well-separated cell clusters. However, identification of subtypes can be obscured by gene expression noise, which diminishes the distances in transcriptome space between distinct cell types, blurs boundaries, and reduces reproducibility. Here we use Fokker-Planck (FP) diffusion maps to model cellular differentiation as a stochastic process whereby cells settle into local minima that correspond to cell subtypes, in a potential landscape constructed from transcriptome data using a nearest neighbor graph approach. By applying critical transition fields, we identify individual cells on the verge of transitioning between subtypes, revealing microglial cells in an inactivated, homeostatic state before radially transitioning into various specialized subtypes. Specifically, we show that cells from Alzheimer's disease patients are enriched in a microglia subtype associated to antigen presentation and T-cell recruitment, and are depleted in an anti-inflammatory subtype.

Mechanisms of astrocyte aging in reactivity and disease

Normal aging alters brain functions and phenotypes. However, it is not well understood how astrocytes are impacted by aging, nor how they contribute to neuronal dysfunction and disease risk as organisms age. Here, we examine the transcriptional, cell biology, and functional differences in astrocytes across normal aging. Astrocytes at baseline are heterogenous, responsive to their environments, and critical regulators of brain microenvironments and neuronal function. With increasing age, astrocytes adopt different immune-related and senescence-associated states, which relate to organelle dysfunction and loss of homeostasis maintenance, both cell autonomously and non-cell autonomously. These perturbed states are increasingly associated with age-related dysfunction and the onset of neurodegeneration, suggesting that astrocyte aging is a compelling target for future manipulation in the prevention of disease.

Lipid droplets deposition in perihematoma tissue is associated with neurological dysfunction after intracerebral hemorrhage

Secondary brain injury following intracerebral hemorrhage (ICH) significantly reduces patients' quality of life due to impaired neurological function. Lipid droplets are implicated in secondary brain injury in various central nervous system diseases. Thus, the role and mechanisms of lipid droplets in secondary brain injury post-ICH require further investigation. We analyzed the changes of genes related to lipid metabolism in brain tissue of ICH mice. Lipid droplets around the hematoma were detected by BODIPY staining. Mice received intraperitoneal injections of Triacsin C (10 mg/kg, once daily) after ICH. Subsequently, neuronal damage was evaluated using TUNEL and Nissl staining, and ethological tests assessed sensorimotor function. After ICH, notable changes occurred in lipid metabolism pathways and genes (Plin2, Ucp2, Apoe), and a large number of lipid droplets accumulated around the hematoma. Triacsin C significantly reduced lipid droplets deposition, decreased neuronal damage, and improved sensory and motor functions. Peripheral administration to prevent lipid droplets formation can greatly reduce nerve damage and enhance nerve function. Our findings indicate that targeting lipid droplets could be a promising treatment for ICH.

Lipid metabolism, remodelling and intercellular transfer in the CNS

Lipid metabolism encompasses the catabolism and anabolism of lipids, and is fundamental for the maintenance of cellular homeostasis, particularly within the lipid-rich CNS. Increasing evidence further underscores the importance of lipid remodelling and transfer within and between glial cells and neurons as key orchestrators of CNS lipid homeostasis. In this Review, we summarize and discuss the complex landscape of processes involved in lipid metabolism, remodelling and intercellular transfer in the CNS. Highlighted are key pathways, including those mediating lipid (and lipid droplet) biogenesis and breakdown, lipid oxidation and phospholipid metabolism, as well as cell-cell lipid transfer mediated via lipoproteins, extracellular vesicles and tunnelling nanotubes. We further explore how the dysregulation of these pathways contributes to the onset and progression of neurodegenerative diseases, and examine the homeostatic and pathogenic impacts of environment, diet and lifestyle on CNS lipid metabolism.

A neurodegenerative cellular stress response linked to dark microglia and toxic lipid secretion

The brain's primary immune cells, microglia, are a leading causal cell type in Alzheimer's disease (AD). Yet, the mechanisms by which microglia can drive neurodegeneration remain unresolved. Here, we discover that a conserved stress signaling pathway, the integrated stress response (ISR), characterizes a microglia subset with neurodegenerative outcomes. Autonomous activation of ISR in microglia is sufficient to induce early features of the ultrastructurally distinct "dark microglia" linked to pathological synapse loss. In AD models, microglial ISR activation exacerbates neurodegenerative pathologies and synapse loss while its inhibition ameliorates them. Mechanistically, we present evidence that ISR activation promotes the secretion of toxic lipids by microglia, impairing neuron homeostasis and survival in vitro. Accordingly, pharmacological inhibition of ISR or lipid synthesis mitigates synapse loss in AD models. Our results demonstrate that microglial ISR activation represents a neurodegenerative phenotype, which may be sustained, at least in part, by the secretion of toxic lipids.

Red fluorescent AIE bioprobes with a large Stokes shift for droplet-specific imaging and fatty liver diagnosis

Lipid droplets (LDs) as spherical dynamic subcellular organelles, play an important role in various cellular functions such as protein degradation, lipid metabolism, energy storage, signal transduction, and membrane formation. Abnormal function of LDs will lead to a series of diseases and hence monitoring the status of LDs is particularly important. In this study, we synthesized a water-insoluble red fluorescent emitting small molecule fluorescent probe (TPE-TCF), which exhibited aggregation-induced emission (AIE) properties and enabled highly selective real-time imaging of LDs (Pearson's R value was 0.90). More interestingly, this probe was able to track the dynamic processes of LDs in living cells, including lipophagy, and monitor fatty liver disease in mice. Therefore, TPE-TCF with red fluorescence emission, good biocompatibility, large Stokes shift, AIE properties, LDs imaging, and fatty liver recognition capabilities can be practically used in more LDs-related diseases.

Effects of electroacupuncture on microglia phenotype and epigenetic modulation of C/EBPβ in SAMP8 mice

BACKGROUND

Alzheimer's disease (AD), an age-progressive neurodegenerative disease, is featured by a relentless deterioration of cognitive abilities. In parallel with the hypotheses of Aβ and tau, microglia-mediated neuroinflammation is a core pathological hallmark of AD. Promoting the transition of microglia from M1 to M2 phenotype and inhibition of neuroinflammatory response provide new insights into the treatment of AD. And substantial studies have confirmed that overexpression of C/EBPβ accelerates the progression of AD pathology. Acupuncture is renowned for its unique advantages including safety and effectiveness, which has gained wide application in geriatric diseases, and thoroughly exploring the mechanism for its treatment of AD will provide scientific basis for its clinical application.

METHODS

In this study, SAMP8 mice were employed and EA therapy was performed as the main intervention. The combination of behavioural experiments (including water maze and novel objective recognition), Immunofluorescence, Western blot, and Chip-qPCR assay were performed to compare between different groups.

RESULTS

EA therapy facilitates the polarization of microglia from M1 to M2 phenotype, reduces pro-inflammatory cytokines (IL-6, IL-1β and TNF-α) and promotes the expression of anti-inflammatory factors (IL-4 and IL-10), as well as attenuates neuroinflammation. Simultaneously, EA also inhibits the enrichment of H3K9ac at C/EBPβ promoter region and expression of C/EBPβ. Thus, it was evident that EA had a favorable effect on ameliorating cognitive decline in SAMP8 mice.

CONCLUSION

EA therapy may ameliorate cognitive deficits in AD via facilitating microglia shift from M1 to M2 phenotype and epigenetically regulating C/EBPβ. And further studies are required to better understand how the mechanism between microglia and epigenetic modulation of C/EBPβ are effective in reversing AD.

Age-Related Impairments in Immune Cell Efferocytosis and Autophagy Hinder Atherosclerosis Regression

BACKGROUND

Aging is a well-established risk factor for the development and progression of atherosclerosis, but the molecular mechanisms underlying this relationship remain poorly defined, and its role in atherosclerosis regression is unknown. To uncover age-related alterations that may impair atherosclerosis regression, we investigated the response of young and old macrophages to atherogenic lipoproteins in vitro and in vivo.

METHODS

Metabolic and proteomic studies were performed in vitro using macrophages differentiated from the bone marrow of young or old mice. To test the role of immune cell aging in atherosclerosis regression, bone marrow from young and old donors was transplanted into irradiated young recipient mice expressing gain-of-function AAV-PCSK9. Following 14 weeks of Western diet feeding, atherosclerosis regression was induced by switching to a standard laboratory diet for 4 weeks.

RESULTS

Compared with young macrophages, old macrophages accumulated more lipid droplets upon lipid loading with the pro-atherogenic lipoprotein aggregated LDL (low-density lipoprotein), accompanied by a failure to proportionally induce autophagy and cholesterol efflux. Proteomic analysis of bone marrow-derived macrophages revealed that pathways related to endocytosis, engulfment, and phagocytosis were downregulated in old lipid-loaded macrophages. Functional studies confirmed a reduction in efferocytic capacity in old macrophages. In recipient mice transplanted with old bone marrow, atherosclerosis regression was impaired, as evidenced by inefficient resolution of circulating inflammatory cell levels, reduced activation of plaque autophagy and apoptotic cell clearance, and persistent plaque CD45+ and CD68+ content.

CONCLUSIONS

Aging impairs macrophage function through reduced efferocytosis and autophagy activation, limiting atherosclerosis regression. These results highlight the need to better define the mechanisms linking aging to atherosclerosis to develop targeted therapies for the aging population.

Spatially restricted and ontogenically distinct hepatic macrophages are required for tissue repair

Our understanding of the functional heterogeneity of resident versus recruited macrophages in the diseased liver is limited. A population of recruited lipid-associated macrophages (LAMs) has been reported to populate the diseased liver alongside resident Kupffer cells (KCs). However, the precise roles of these distinct macrophage subsets remain elusive. Here, using proteogenomics, we have identified LAMs in multiple models of liver injury. Moreover, we found that this phenotype is not specific to recruited macrophages, as a subset of resident KCs can also adopt a LAM-like phenotype in the mouse and human liver. By combining genetic mouse models targeting the distinct populations, we determined that both recruited LAMs and resident LAM-like KCs play crucial roles in tissue repair. Specifically, triggering receptor expressed on myeloid cells 2 (TREM2) expression on either resident or recruited macrophages is required for the efficient clearance of dying cells, enhancing repair and preventing exacerbated fibrosis.

Multi-omic Characterization of HIV Effects at Single Cell Level across Human Brain Regions

HIV infection exerts profound and long-lasting neurodegenerative effects on the central nervous system (CNS) that can persist despite antiretroviral therapy (ART). Here, we used single-nucleus multiome sequencing to map the transcriptomic and epigenetic landscapes of postmortem human brains from 13 healthy individuals and 20 individuals with HIV who have a history of treatment with ART. Our study spanned three distinct regions-the prefrontal cortex, insular cortex, and ventral striatum-enabling a comprehensive exploration of region-specific and cross-regional perturbations. We found widespread and persistent HIV-associated transcriptional and epigenetic alterations across multiple cell types. Detailed analyses of microglia revealed state changes marked by immune activation and metabolic dysregulation, while integrative multiomic profiling of astrocytes identified multiple subpopulations, including a reactive subpopulation unique to HIV-infected brains. These findings suggest that cells from people with HIV exhibit molecular shifts that may underlie ongoing neuroinflammation and CNS dysfunction. Furthermore, cell-cell communication analyses uncovered dysregulated and pro-inflammatory interactions among glial populations, underscoring the multifaceted and enduring impact of HIV on the brain milieu. Collectively, our comprehensive atlas of HIV-associated brain changes reveals distinct glial cell states with signatures of pro-inflammatory signaling and metabolic dysregulation, providing a framework for developing targeted therapies for HIV-associated neurological dysfunction.

Reducing microglial lipid load enhances β amyloid phagocytosis in an Alzheimer's disease mouse model

Macrophages accumulate lipid droplets (LDs) under stress and inflammatory conditions. Despite the presence of LD-loaded macrophages in many tissues, including the brain, their contribution to neurodegenerative disorders remains elusive. This study investigated the role of lipid metabolism in Alzheimer's disease (AD) by assessing the contribution of LD-loaded brain macrophages, including microglia and border-associated macrophages (BAMs), in an AD mouse model. Particularly, BAMs and activated CD11c+ microglia localized near β amyloid (Aβ) plaques exhibited a pronounced lipid-associated gene signature and a high LD load. Having observed that elevated intracellular LD content correlated inversely with microglial phagocytic activities, we subsequently inhibited LD formation specifically in CX3CR1+ brain macrophages using an inducible APP-KI/Fit2iΔMφ transgenic mouse model. We demonstrated that reducing LD content in microglia and CX3CR1+ BAMs remarkably improved their phagocytic ability. Furthermore, lowering microglial LDs consistently enhanced their efferocytosis capacities and notably reduced Aβ deposition in the brain parenchyma. Therefore, mitigating LD accumulation in brain macrophages provides perspectives for AD treatment.

Revealing rutaecarpine's promise: A pathway to parkinson's disease relief through PPAR modulation

The pathological mechanisms of Parkinson's disease (PD) is complex, and no definitive cure currently exists. This study identified Rutaecarpine (Rut), an alkaloid extracted from natural plants, as a potential therapeutic agent for PD. To elucidate its mechanisms of action and specific effects in PD, network pharmacology, molecular docking, and experimental validation methods were employed. Our findings demonstrated the efficacy of Rut in ameliorating PD symptoms. Network pharmacology analysis indicated that Rut exerts its therapeutic effects through the PPAR signaling pathway and the lipid pathway. Molecular docking results revealed that Rut forms stable protein-ligand complexes with PPARα and PPARγ. Animal experiments showed that Rut improved motor function in PD mice, protected dopaminergic neurons, ameliorated lipid metabolism disorders, and reduced neuroinflammation. This study identified the critical molecular mechanisms and therapeutic targets of Rut in the treatment of PD, providing a theoretical foundation for future investigations into the pharmacodynamics of Rut as a potential anti-PD agent.

Identification of Lipophagy-Related Gene Signature for Diagnosis and Risk Prediction of Alzheimer's Disease

Background: Recent research indicates that lipid metabolism and autophagy play crucial roles in the development of Alzheimer's disease (AD). Investigating the relationship between AD diagnosis and gene expression related to lipid metabolism, autophagy, and lipophagy may improve early diagnosis and the identification of therapeutic targets. Methods: Transcription datasets from AD patients were obtained from the Gene Expression Omnibus (GEO). Genes associated with lipid metabolism, autophagy, and lipophagy were sourced from the Gene Set Enrichment Analysis (GSEA) database and the Human Autophagy Database (HADb). Lipophagy-related hub genes were identified using a combination of Limma analysis, weighted gene co-expression network analysis (WGCNA), and machine learning techniques. Based on these hub genes, we developed an AD risk prediction nomogram and validated its diagnostic accuracy using three external validation datasets. Additionally, the expression levels of the hub genes were assessed through quantitative reverse transcription polymerase chain reaction (qRT-PCR). Results: Our analysis identified three hub genes-ACBD5, GABARAPL1, and HSPA8-as being associated with AD progression. The nomogram constructed from these hub genes achieved an area under the curve (AUC) value of 0.894 for AD risk prediction, with all validation sets yielding AUC values greater than 0.8, indicating excellent diagnostic efficacy. qRT-PCR results further corroborated the associations between these hub genes and AD development. Conclusions: This study identified and validated three lipophagy-related hub genes and developed a reliable diagnostic model, offering insights into the pathology of AD and facilitating the diagnosis of AD patients.

VEGFD/VEGFR3 signaling contributes to the dysfunction of the astrocyte IL-3/microglia IL-3Rα cross-talk and drives neuroinflammation in mouse ischemic stroke

Astrocyte-derived IL-3 activates the corresponding receptor IL-3Rα in microglia. This cross-talk between astrocytes and microglia ameliorates the pathology of Alzheimer's disease in mice. In this study we investigated the role of IL-3/IL-3Rα cross-talk and its regulatory mechanisms in ischemic stroke. Ischemic stroke was induced in mice by intraluminal occlusion of the right middle cerebral artery (MCA) for 60 min followed by reperfusion (I/R). Human astrocytes or microglia subjected to oxygen-glucose deprivation and reoxygenation (OGD/Re) were used as in vitro models of brain ischemia. We showed that both I/R and OGD/Re significantly induced decreases in astrocytic IL-3 and microglial IL-3Rα protein levels, accompanied by pro-inflammatory activation of A1-type astrocytes and M1-type microglia. Importantly, astrocyte-derived VEGFD acting on VEGFR3 of astrocytes and microglia contributed to the cross-talk dysfunction and pro-inflammatory activation of the two glial cells, thereby mediating neuronal cell damage. By using metabolomics and multiple biochemical approaches, we demonstrated that IL-3 supplementation to microglia reversed OGD/Re-induced lipid metabolic reprogramming evidenced by upregulated expression of CPT1A, a rate-limiting enzyme for the mitochondrial β-oxidation, and increased levels of glycerophospholipids, the major components of cellular membranes, causing reduced accumulation of lipid droplets, thus reduced pro-inflammatory activation and necrosis, as well as increased phagocytosis of microglia. Notably, exogenous IL-3 and the VEGFR antagonist axitinib reestablished the cross-talk of IL-3/IL-3Rα, improving microglial lipid metabolic levels via upregulation of CPT1A, restoring microglial phagocytotic function and attenuating microglial pro-inflammatory activation, ultimately contributing to brain recovery from I/R insult. Our results demonstrate that VEGFD/VEGFR3 signaling contributes to the dysfunction of the astrocyte IL-3/microglia IL-3Rα cross-talk and drives pro-inflammatory activation, causing lipid metabolic reprogramming of microglia. These insights suggest VEGFR3 antagonism or restoring IL-3 levels as a potential therapeutic strategy for ischemic stroke.

Microglial Nrf2-mediated lipid and iron metabolism reprogramming promotes remyelination during white matter ischemia

BACKGROUND

Oxidative stress and microglial activation are critical pathomechanisms in ischemic white matter injury. Microglia, as resident immune cells in the brain, are the main cells undergoing oxidative stress response. However, the role and molecular mechanism of oxidative stress in microglia have not been clearly elucidated during white matter ischemia.

METHODS

Extensive histological analysis of the corpus callosum was performed in BCAS mice at different time points to assess white matter injury, oxidative stress and microglial activation. Flow cytometric sorting and transcriptomic sequencing were combined to explore the underlying mechanisms regulating microglial oxidative stress and functional phenotypes. The expression of critical molecule in microglia was regulated using Cx3cr1CreER mice and clinical-stage drugs to assess its effect on white matter injury and cognitive function.

RESULTS

Our study identified nuclear factor erythroid-2 related factor 2 (Nrf2) as a key transcription factor regulating oxidative stress and functional phenotype in microglia. Interestingly, we found that the sustained decrease in transiently upregulated expression of Nrf2 following chronic cerebral hypoperfusion resulted in abnormal microglial activation and white matter injury. In addition, high loads of myelin debris promoted lipid peroxidation and ferroptosis in microglia with diminished antioxidant function. Microglia with pharmacologically or genetically stimulated Nrf2 expression exhibited enhanced resistance to ferroptosis and pro-regenerative properties to myelination due to lipid and iron metabolism reprogramming.

CONCLUSION

Weakened Nrf2-mediated antioxidant responses in microglia induced metabolic disturbances and ferroptosis during chronic cerebral hypoperfusion. Targeted enhancement of Nrf2 expression in microglia may be a potential therapeutic strategy for ischemic white matter injury.

Intermittent Fasting Ameliorates β-Amyloid Deposition and Cognitive Impairment Accompanied by Decreased Lipid Droplet Aggregation Within Microglia in an Alzheimer's Disease Model

SCOPE

Alzheimer's disease (AD) is the most prevalent form of dementia, lack of effective therapeutic interventions. In this study, we investigate the impact of intermittent fasting (IF), an alternative strategy of calorie restriction, on cognitive functions and AD-like pathology in a transgenic mouse model of AD.

METHODS AND RESULTS

APP/PS1 mice at 6 months were randomly allocated to two dietary groups: one receiving ad libitum (AL) feeding and the other undergoing IF for 1 month. Y maze, Barnes maze, western blotting, and immunofluorescence were employed. Behavioral assessments revealed that the APP/PS1-IF group demonstrated notable improvements in cognitive function compared to the AL group. Further analysis showed that microglia in the APP/PS1-IF mice exhibited enhanced phagocytic activity, characterized by prominent enlargement of soma and reduced complexity of their processes. Importantly, IF significantly decreased the accumulation of lipid droplets (LDs) within microglia. These microglia with less LDs may contribute to enhanced β-amyloid (Aβ) phagocytosis, thereby ameliorating Aβ deposition in the brains of APP/PS1-IF mice.

CONCLUSION

Our findings demonstrate that IF ameliorates amyloid deposition and cognitive deficits in the AD model mice, which is associated with the reduction of LDs within microglia, providing support for the use of the dietary intervention against AD pathology.

Alzheimer's disease: insights into pathology, molecular mechanisms, and therapy

Alzheimer's disease (AD), the leading cause of dementia, is characterized by the accumulation of amyloid plaques and neurofibrillary tangles in the brain. This condition casts a significant shadow on global health due to its complex and multifactorial nature. In addition to genetic predispositions, the development of AD is influenced by a myriad of risk factors, including aging, systemic inflammation, chronic health conditions, lifestyle, and environmental exposures. Recent advancements in understanding the complex pathophysiology of AD are paving the way for enhanced diagnostic techniques, improved risk assessment, and potentially effective prevention strategies. These discoveries are crucial in the quest to unravel the complexities of AD, offering a beacon of hope for improved management and treatment options for the millions affected by this debilitating disease.

Upregulation of LXRβ/ABCA1 pathway alleviates cochlear hair cell senescence of C57BL/6 J mice via reducing lipid droplet accumulation

Senescence and loss of cochlear hair cells is an important pathologic basis of age-related hearing loss. Lipid droplet accumulation has previously been shown to play an important role in neurodegeneration; however, its role in age-related hearing loss has not yet been investigated. LXRβ/ABCA1 is a key pathway that regulates lipid metabolism, while its dysfunction can cause abnormal accumulation of lipid droplets in neurons, leading to neurodegeneration. In this study, we found that decreased expression of LXRβ/ABCA1, elevated levels of lipid droplet accumulation, and increased activation of the NLRP3 inflammasome were demonstrated in senescent cochlear hair cells in both animal and cellular models of age-related hearing loss. We then manipulated the LXRβ/ABCA1 pathway transduction of cochlear hair cells. Upregulation of LXRβ/ABCA1 in senescent hair cells was found to reduce the accumulation of lipid droplets, inhibit NLRP3 inflammasome activation, and ultimately alleviate cochlear hair cell senescence. In our study, we also found that NLRP3 inflammasome activation can abrogate the alleviated effect of LXRβ/ABCA1 pathway on the senescence of cochlear hair cells but did not affect the expression of LXRβ/ABCA1.Our study are the first to demonstrate that abnormal lipid droplet accumulation and decreased LXRβ/ABCA1 pathway are observed in cochlear hair cells following the occurrence of age-related hearing loss. Upregulation of LXRβ/ABCA1 in senescent cochlear hair cells can reduce lipid droplet accumulation in cochlear hair cells and alleviate their senescence, which may be related to the inhibition of NLRP3 inflammasome activation. These findings provide potential targets for the treatment of age-related hearing loss.

Cold induces brain region-selective cell activity-dependent lipid metabolism

It has been well documented that cold is an enhancer of lipid metabolism in peripheral tissues, yet its effect on central nervous system lipid dynamics is underexplored. It is well recognized that cold acclimations enhance adipocyte functions, including white adipose tissue lipid lipolysis and beiging, and brown adipose tissue thermogenesis in mammals. However, it remains unclear whether and how lipid metabolism in the brain is also under the control of ambient temperature. Here, we show that cold exposure predominantly increases the expressions of the lipid lipolysis genes and proteins within the paraventricular nucleus of the hypothalamus (PVH) in male mice. Mechanistically, by using innovatively combined brain-region selective pharmacology and in vivo time-lapse photometry monitoring of lipid metabolism, we find that cold activates cells within the PVH and pharmacological inactivation of cells blunts cold-induced effects on lipid peroxidation, accumulation of lipid droplets, and lipid lipolysis in the PVH. Together, these findings suggest that PVH lipid metabolism is cold sensitive and integral to cold-induced broader regulatory responses.

APOEε4 alters ApoE and Fabp7 in frontal cortex white matter in prodromal Alzheimer's disease

The ApoE ε4 allele (APOEε4) is a major genetic risk factor for sporadic Alzheimer's disease (AD) and is linked to demyelination and cognitive decline. However, its effects on the lipid transporters apolipoprotein E (ApoE) and fatty acid-binding protein 7 (Fabp7), which are crucial for the maintenance of myelin in white matter (WM) during the progression of AD remain underexplored. To evaluate the effects of APOEε4 on ApoE, Fabp7 and myelin in the WM of the frontal cortex (FC), we examined individuals carrying one ε4 allele that came to autopsy with a premortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI) and mild to moderate AD compared with non-carrier counterparts. ApoE, Fabp7 and Olig2 immunostaining was used to visualize cells, whereas myelin basic protein (MBP) immunocytochemistry and luxol fast blue (LFB) histochemistry of myelin in the WM of the FC were combined with quantitative morphometry. We observed increased numbers of ApoE-positive astrocytes in the WM of both NCI and MCI APOEε4 carriers compared with non-carriers, whereas Fabp7-positive cells were elevated only in AD. Conversely, Olig2 cell counts and MBP immunostaining decreased in MCI APOEε4 carriers compared to non-carriers, while LFB levels were higher in NCI APOEε4 carriers compared to non-carriers. Although no correlations were found between ApoE, Fabp7, and cognitive status, LFB measurements were positively correlated with perceptual speed, global cognition, and visuospatial scores in APOEε4 carriers across clinical groups. The present findings suggest that the ε4 allele compromises FC myelin homeostasis by disrupting the lipid transporters ApoE, Fabp7 and myelination early in the onset of AD. These data support targeting cellular components related to WM integrity as possible treatments for AD.

Inhibition of CD36 ameliorates mouse spinal cord injury by accelerating microglial lipophagy

Spinal cord injury (SCI) is a serious trauma of the central nervous system (CNS). SCI induces a unique lipid-dense environment that results in the deposition of large amounts of lipid droplets (LDs). The presence of LDs has been shown to contribute to the progression of other diseases. Lipophagy, a selective type of autophagy, is involved in intracellular LDs degradation. Fatty acid translocase CD36, a multifunctional transmembrane protein that facilitates the uptake of long-chain fatty acids, is implicated in the progression of certain metabolic diseases, and negatively regulates autophagy. However, the precise mechanisms of LDs generation and degradation in SCI, as well as whether CD36 regulates SCI via lipophagy, remain unknown. In this study, we investigated the role of LDs accumulation in microglia for SCI, as well as the regulatory mechanism of CD36 in microglia lipophagy during LDs elimination in vivo and in vitro. SCI was induced in mice by applying moderate compression on spina cord at T9-T10 level. Locomotion recovery was evaluated at days 0, 1, 3, 7 and 14 following the injury. PA-stimulated BV2 cells was established as the in vitro lipid-loaded model. We observed a marked buildup of LDs in microglial cells at the site of injury post-SCI. More importantly, microglial cells with excessive LDs exhibited elevated activation and stimulated inflammatory response, which drastically triggered the pyroptosis of microglial cells. Furthermore, we found significantly increased CD36 expression, and the breakdown of lipophagy in microglia following SCI. Sulfo-N-succinimidyl oleate sodium (SSO), a CD36 inhibitor, has been shown to promote the lipophagy of microglial cells in SCI mice and PA-treated BV2 cells, which enhanced LDs degradation, ameliorated inflammatory levels and pyroptosis of microglial cells, and ultimately promoted SCI recovery. As expected, inhibition of lipophagy with Baf-A1 reversed the effects of SSO. We conclude that microglial lipophagy is essential for the removal of LDs during SCI recovery. Our research implies that CD36 could be a potential therapeutic target for the treatment and management of SCI.

The glial UDP-glycosyltransferase Ugt35b regulates longevity by maintaining lipid homeostasis in Drosophila

Lipid droplets (LDs) are dynamic organelles essential for lipid storage and organismal survival. Studies have highlighted the importance of glial function in brain LD formation during aging; however, the genes and mechanisms involved remain elusive. Here, we found that Ugt35b, a member of the uridine diphosphate (UDP)-glycosyltransferases that catalyze the transfer of glycosyl groups to acceptors, is highly expressed in glia and crucial for Drosophila lifespan. By integrating multiomics data, we demonstrated that glial Ugt35b plays key roles in regulating glycerolipid and glycerophospholipid metabolism in the brain. Notably, we found that Ugt35b and Lsd-2 are co-expressed in glia and confirmed their protein interaction in vivo. Knockdown of Ugt35b significantly reduced LD formation by downregulating Lsd-2 expression, while overexpression of Lsd-2 partially rescued the shortened lifespan in glial Ugt35b RNAi flies. Our findings reveal the crucial role of glial Ugt35b in regulating LD formation to maintain brain lipid homeostasis and support Drosophila lifespan.

NAD World 3.0: the importance of the NMN transporter and eNAMPT in mammalian aging and longevity control

Over the past five years, systemic NAD+ (nicotinamide adenine dinucleotide) decline has been accepted to be a key driving force of aging in the field of aging research. The original version of the NAD World concept was proposed in 2009, providing an integrated view of the NAD+-centric, systemic regulatory network for mammalian aging and longevity control. The reformulated version of the concept, the NAD World 2.0, was then proposed in 2016, emphasizing the importance of the inter-tissue communications between the hypothalamus and peripheral tissues including adipose tissue and skeletal muscle. There has been significant progress in our understanding of the importance of nicotinamide mononucleotide (NMN), a key NAD+ intermediate, and nicotinamide phosphoribosyltransferase (NAMPT), particularly extracellular NAMPT (eNAMPT). With these exciting developments, the further reformulated version of the concept, the NAD World 3.0, is now proposed, featuring multi-layered feedback loops mediated by NMN and eNAMPT for mammalian aging and longevity control.

Lipidome disruption in Alzheimer's disease brain: detection, pathological mechanisms, and therapeutic implications

Alzheimer's disease (AD) is among the most devastating neurodegenerative disorders with limited treatment options. Emerging evidence points to the involvement of lipid dysregulation in the development of AD. Nevertheless, the precise lipidomic landscape and the mechanistic roles of lipids in disease pathology remain poorly understood. This review aims to highlight the significance of lipidomics and lipid-targeting approaches in the diagnosis and treatment of AD. We summarized the connection between lipid dysregulation in the human brain and AD at both genetic and lipid species levels. We briefly introduced lipidomics technologies and discussed potential challenges and areas of future advancements in the lipidomics field for AD research. To elucidate the central role of lipids in converging multiple pathological aspects of AD, we reviewed the current knowledge on the interplay between lipids and major AD features, including amyloid beta, tau, and neuroinflammation. Finally, we assessed the progresses and obstacles in lipid-based therapeutics and proposed potential strategies for leveraging lipidomics in the treatment of AD.

Beyond Amyloid and Tau: The Critical Role of Microglia in Alzheimer's Disease Therapeutics

Alzheimer's disease (AD) is traditionally viewed through the lens of the amyloid cascade hypothesis, implicating amyloid-beta and tau protein aggregates as the main pathological culprits. However, burgeoning research points to the brain's resident immune cells, microglia, as critical players in AD pathogenesis, progression, and potential therapeutic interventions. This review examines the dynamic roles of microglia within the intricate framework of AD. We detail the involvement of these immune cells in neuroinflammation, explaining how their activation and response fluctuations may influence the disease trajectory. We further elucidate the complex relationship between microglia and amyloid-beta pathology. This study highlights the dual nature of these cells, which contribute to both aggregation and clearance of the amyloid-beta protein. Moreover, an in-depth analysis of the interplay between microglia and tau unveils the significant, yet often overlooked, impact of this interaction on neurodegeneration in AD. Shifting from the conventional therapeutic approaches, we assess the current AD treatments primarily targeting amyloid and tau and introduce novel strategies that involve manipulating microglial functions. These innovative methods herald a potential paradigm shift in the management of AD. Finally, we explore the burgeoning field of precision diagnosis and the pursuit of robust AD biomarkers. We underline how a more profound comprehension of microglial biology could enrich these essential areas, potentially paving the way for more accurate diagnostic tools and tailored treatment strategies. In conclusion, this review expands on the conventional perspective of AD pathology and treatment, drawing attention to the multifaceted roles of microglia. As we continue to enhance our understanding of these cells, microglial-focused therapeutic interventions emerge as a promising frontier to bolster our arsenal to fight against AD.

Metabolism and metabolomics in senescence, aging, and age-related diseases: a multiscale perspective

The pursuit of healthy aging has long rendered aging and senescence captivating. Age-related ailments, such as cardiovascular diseases, diabetes, and neurodegenerative disorders, pose significant threats to individuals. Recent studies have shed light on the intricate mechanisms encompassing genetics, epigenetics, transcriptomics, and metabolomics in the processes of senescence and aging, as well as the establishment of age-related pathologies. Amidst these underlying mechanisms governing aging and related pathology metabolism assumes a pivotal role that holds promise for intervention and therapeutics. The advancements in metabolomics techniques and analysis methods have significantly propelled the study of senescence and aging, particularly with the aid of multiscale metabolomics which has facilitated the discovery of metabolic markers and therapeutic potentials. This review provides an overview of senescence and aging, emphasizing the crucial role metabolism plays in the aging process as well as age-related diseases.

The TRPV1-PKM2-SREBP1 axis maintains microglial lipid homeostasis in Alzheimer's disease

Microglia are progressively activated by inflammation and exhibit phagocytic dysfunction in the pathogenesis of neurodegenerative diseases. Lipid-droplet-accumulating microglia were identified in the aging mouse and human brain; however, little is known about the formation and role of lipid droplets in microglial neuroinflammation of Alzheimer's disease (AD). Here, we report a striking buildup of lipid droplets accumulation in microglia in the 3xTg mouse brain. Moreover, we observed significant upregulation of PKM2 and sterol regulatory element binding protein 1 (SREBP1) levels, which were predominantly localized in microglia of 3xTg mice. PKM2 dimerization was necessary for SREBP1 activation and lipogenesis of lipid droplet-accumulating microglia. RNA sequencing analysis of microglia isolated from 3xTg mice exhibited transcriptomic changes in lipid metabolism, innate inflammation, and phagocytosis dysfunction; these changes were improved with capsaicin-mediated pharmacological activation of TRPV1 via inhibition of PKM2 dimerization and reduction of SREBP1 activation. Lipid droplet-accumulating microglia exhibited increased mitochondrial injury accompanied by impaired mitophagy, which was abrogated upon of TRPV1 activation. Capsaicin also rescued neuronal loss, tau pathology, and memory impairment in 3xTg mice. Our study suggests that TRPV1-PKM2-SREBP1 axis regulation of microglia lipid metabolism could be a therapeutic approach to alleviate the consequences of AD.

The immunology of stroke and dementia

Ischemic stroke and vascular cognitive impairment, caused by a sudden arterial occlusion or more subtle but protracted vascular insufficiency, respectively, are leading causes of morbidity and mortality worldwide with limited therapeutic options. Innate and adaptive immunity have long been implicated in neurovascular injury, but recent advances in methodology and new experimental approaches have shed new light on their contributions. A previously unappreciated dynamic interplay of brain-resident, meningeal, and systemic immune cells with the ischemic brain and its vasculature has emerged, and new insights into the frequent overlap between vascular and Alzheimer pathology have been provided. Here, we critically review these recent findings, place them in the context of current concepts on neurovascular pathologies and Alzheimer's disease, and highlight their impact on recent stroke and Alzheimer therapies.

Lipid droplets in central nervous system and functional profiles of brain cells containing lipid droplets in various diseases

Lipid droplets (LDs), serving as the convergence point of energy metabolism and multiple signaling pathways, have garnered increasing attention in recent years. Different cell types within the central nervous system (CNS) can regulate energy metabolism to generate or degrade LDs in response to diverse pathological stimuli. This article provides a comprehensive review on the composition of LDs in CNS, their generation and degradation processes, their interaction mechanisms with mitochondria, the distribution among different cell types, and the roles played by these cells-particularly microglia and astrocytes-in various prevalent neurological disorders. Additionally, we also emphasize the paradoxical role of LDs in post-cerebral ischemia inflammation and explore potential underlying mechanisms, aiming to identify novel therapeutic targets for this disease.

High-density lipoprotein alleviates ocular inflammation by downregulating M1 microglia and pyroptosis through regulating lipid accumulation and Caveolin-1 expression

Uveitis encompasses a group of intraocular inflammatory diseases that are often associated with low levels of high-density lipoprotein (HDL). The role of HDL in intraocular inflammatory diseases remains unclear. In our research, we established an endotoxin-induced uveitis (EIU) model to investigate the role of HDL. Our study indicated that HDL could suppress ocular inflammation and restore retinal function in EIU mice. Specifically, HDL intervention effectively inhibited microglial activation and promoted the transformation of microglia from the M1 phenotype to the M2 phenotype. Furthermore, HDL intervention reduced microglial pyroptosis. Additionally, HDL was found to inhibit lipid accumulation in LPS-induced microglia, which is associated with inflammation, M1 polarization, and pyroptosis, by enhancing the expression of Caveolin-1 (CAV-1). Finally, we demonstrated that the function of HDL may be partially dependent on CAV-1 expression. We conclude that HDL inhibits pathological ocular inflammation by regulating M1/M2 phenotype polarization and pyroptosis through the modulation of lipid accumulation and CAV-1 expression. This suggests that HDL may represent a novel therapeutic strategy for ocular inflammation.

Chronological versus immunological aging: Immune rejuvenation to arrest cognitive decline

The contemporary understanding that the immune response significantly supports higher brain functions has emphasized the notion that the brain's condition is linked in a complex manner to the state of the immune system. It is therefore not surprising that immunity is a key factor in shaping brain aging. In this perspective article, we propose amending the Latin phrase "mens sana in corpore sano" ("a healthy mind in a healthy body") to "a healthy mind in a healthy immune system." Briefly, we discuss the emerging understanding of the pivotal role of the immune system in supporting lifelong brain maintenance, how the aging of the immune system impacts the brain, and how the potential rejuvenation of the immune system could, in turn, help revitalize brain function, with the ultimate ambitious goal of developing an anti-aging immune therapy.

Brain aging and rejuvenation at single-cell resolution

Brain aging leads to a decline in cognitive function and a concomitant increase in the susceptibility to neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. A key question is how changes within individual cells of the brain give rise to age-related dysfunction. Developments in single-cell "omics" technologies, such as single-cell transcriptomics, have facilitated high-dimensional profiling of individual cells. These technologies have led to new and comprehensive characterizations of brain aging at single-cell resolution. Here, we review insights gleaned from single-cell omics studies of brain aging, starting with a cell-type-centric overview of age-associated changes and followed by a discussion of cell-cell interactions during aging. We highlight how single-cell omics studies provide an unbiased view of different rejuvenation interventions and comment on the promise of combinatorial rejuvenation approaches for the brain. Finally, we propose new directions, including models of brain aging and neural stem cells as a focal point for rejuvenation.

White matter aging and its impact on brain function

Aging has a detrimental impact on white matter, resulting in reduced volume, compromised structural integrity of myelinated axons, and an increase in white matter hyperintensities. These changes are closely linked to cognitive decline and neurological disabilities. The deterioration of myelin and its diminished ability to regenerate as we age further contribute to the progression of neurodegenerative disorders. Understanding these changes is crucial for devising effective disease prevention strategies. Here, we will discuss the structural alterations in white matter that occur with aging and examine the cellular and molecular mechanisms driving these aging-related transformations. We highlight how the progressive disruption of white matter may initiate a self-perpetuating cycle of inflammation and neural damage.

Mitochondria-Associated Endoplasmic Reticulum Membranes in Microglia: One Contact Site to Rule Them all

Microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in maintaining tissue homeostasis by monitoring and responding to environmental changes through processes such as phagocytosis, cytokine production or synapse remodeling. Their dynamic nature and diverse functions are supported by the regulation of multiple metabolic pathways, enabling microglia to efficiently adapt to fluctuating signals. A key aspect of this regulation occurs at mitochondria-associated ER membranes (MAM), specialized contact sites between the ER and mitochondria. These structures facilitate the exchange of calcium, lipids, and metabolites and serve as metabolic and signaling hubs. This review synthesizes current research on how MAM influence microglial physiology, with an emphasis on their role in immunometabolism, offering new insights into the integration of metabolic and immune functions in the CNS and its impact in the context of neurodegeneration.

Blockage of ATGL-mediated breakdown of lipid droplets in microglia alleviates neuroinflammatory and behavioural responses to lipopolysaccharides

Lipid droplets (LD) are triglyceride storing organelles that have emerged as an important component of cellular inflammatory responses. LD lipolysis via adipose triglyceride lipase (ATGL), the enzyme that catalyses the rate-limiting step of triglyceride lipolysis, regulates inflammation in peripheral immune and non-immune cells. ATGL elicits both pro- and anti-inflammatory responses in the periphery in a cell-type dependent manner. The present study determined the impact of ATGL inhibition and microglia-specific ATGL genetic loss-of-function on acute inflammatory and behavioural responses to pro-inflammatory insult. First, we evaluated the impact of lipolysis inhibition on lipopolysaccharide (LPS)-induced expression and secretion of cytokines and phagocytosis in mouse primary microglia cultures. Lipase inhibitors (ORlistat and ATGListatin) and LPS led to LD accumulation in microglia. Pan-lipase inhibition with ORlistat alleviated LPS-induced expression of IL-1β and IL-6. Specific inhibition of ATGL had a similar action on CCL2, IL-1β and IL-6 expression in both neonatal and adult microglia cultures. CCL2 and IL-6 secretion were also reduced by ATGListatin or knockdown of ATGL. ATGListatin increased phagocytosis in neonatal cultures independently from LPS treatment. Second, targeted and untargeted lipid profiling revealed that ATGListatin reduced LPS-induced generation of pro-inflammatory prostanoids and modulated ceramide species in neonatal microglia. Finally, the role of microglial ATGL in neuroinflammation was assessed using a novel microglia-specific and inducible ATGL knockout mouse model. Loss of microglial ATGL in adult male mice dampened LPS-induced expression of IL-6 and IL-1β and microglial density. LPS-induced sickness- and anxiety-like behaviours were also reduced in male mice with loss of ATGL in microglia. Together, our results demonstrate potent anti-inflammatory effects produced by pharmacological or genetic inhibition of ATGL-mediated triglyceride lipolysis and thereby propose that supressing microglial LD lipolysis has beneficial actions in acute neuroinflammatory conditions.

Lipidomic and transcriptomic characteristics of boar seminal plasma extracellular vesicles associated with sperm motility

Seminal plasma extracellular vesicles (SPEVs) play an important role in regulating sperm motility by delivering various cargoes, such as miRNAs, mRNAs, proteins and metabolites. However, information on the lipid compositions of SPEVs and their roles in semen quality is limited. Here, we performed high-throughput transcriptomic and lipidomic analysis on SPEVs isolated from 20 boars with high or low sperm motility. Then, we evaluated the lipid composition and gene expression characteristics of SPEVs and identified the specific lipids and genes related to sperm motility. As a result, a total of 26 lipid classes were identified in SPEVs, and five subclasses, CerG2, CerG3, LPE, LPS and TG, were significantly different in boars with high and low sperm motility. In addition, 195 important lipids and 334 important genes were identified by weighted gene coexpression analysis (WGCNA) and differential expression analysis. We observed that several important genes and lipids in SPEVs potentially influence sperm motility via glycerophospholipid metabolism, glycerolipid metabolism, the sphingolipid signaling pathway and the ferroptosis pathway. Furthermore, we found a significant correlation between the content of 22 lipids and the expression levels of 67 genes (|cor| > 0.8, P < 0.05). Moreover, we observed that three important gene-lipid linkages (CerG1 (d22:0/24:0) - RCAN3, Cer (d18:1/24:0) - SCFD2 and CerG1 (d18:0/24:1) - SCFD2) were strongly correlated with sperm motility. Based on the results, some genes and lipids in SPEVs may play important roles in sperm motility by interacting with sperm through important pathways.