Biology subjects

Haughey, N. J.

Publications and source records attributed to Haughey, N. J..

6 recordsLinked to original sources

bioRxiv2026

Remodeling oligodendrocyte lipid metabolism via liver X receptors overcomes inflammatory blockade of remyelination

Multiple sclerosis is characterized by immune-mediated demyelination and inefficient remyelination, owing to impaired differentiation of oligodendrocyte precursor cells (OPCs) into myelinating oligodendrocytes (OLs). Inflammatory cytokines within multiple sclerosis lesions inhibit OPC maturation and induce an immune-like phenotype with antigen-presenting properties, but the underlying mechanisms remain poorly defined. Here, we show that inflammation reprograms OPC lipid metabolism, linking altered metabolism to remyelination failure. In cultured rodent OPCs, interferon-{gamma} (IFN-{gamma}) induced a switch from lipid synthesis to utilization, leading to reduced intracellular fatty acid levels and increased dependence on fatty acid oxidation. Transcriptional analyses confirmed similar lipid metabolic changes in OL-lineage cells cultured from human surgical specimens or isolated from mouse models of inflammatory demyelination and human multiple sclerosis lesions. Enhancing lipid availability in OPCs through oleic acid supplementation or inhibition of fatty acid oxidation attenuated immune-like functions and increased differentiation. Pharmacologic activation of liver X receptor (LXR) transcription factors rebalanced lipid metabolism, suppressed immune-like functions, and overcame IFN-{gamma}-induced differentiation blockade in both mouse and human-derived OPCs. In an adoptive transfer-cuprizone mouse model in which inflammation directly impairs remyelination, LXR activation increased mature OL generation and augmented myelin repair. Together, these findings identify lipid metabolic remodeling as a key mechanism by which inflammation impairs OPC differentiation and highlight LXR activation as a therapeutic approach to enhance remyelination in multiple sclerosis.

neuroscience↗

bioRxiv2024

Integrated stress response associated with dark microglia promotes microglial lipogenesis and contributes to neurodegeneration

Microglia, the brains primary resident immune cells, are a heterogeneous population and can assume phenotypes with diverse functional outcomes on brain homeostasis. In Alzheimers disease (AD), where microglia are a leading causal cell type, microglia subsets with protective functions have been well characterized. Yet, the identity of microglia subsets that drive neurodegeneration remains unresolved. Here, we identify a neurodegenerative microglia phenotype that is characterized by a conserved stress signaling pathway, the integrated stress response (ISR). Using mouse models to activate or inhibit ISR in microglia, we show that ISR underlies the ultrastructurally distinct "dark" microglia subset linked to pathological synapse loss. Inducing microglial ISR in murine AD models exacerbates neurodegenerative pathologies, such as Tau pathology and synaptic terminal loss. Conversely, inhibiting microglial ISR in AD models ameliorates these pathologies. Mechanistically, we present evidence that ISR promotes the secretion of toxic long-chain lipids that impair neuron and oligodendrocyte homeostasis in vitro. Accordingly, small molecule-based inhibition of lipid synthesis in AD models ameliorates synaptic terminal loss. Our results demonstrate that activation of ISR within microglia represents a novel pathway contributing to neurodegeneration and suggest that this may be sustained, at least in part, by the secretion of long-chain lipids from ISR-activated microglia.

neuroscience↗

bioRxiv2020

Characterization of extracellular vesicles and artificial nanoparticles with four orthogonal single-particle analysis platforms

We compared four orthogonal technologies for sizing, counting, and phenotyping of extracellular vesicles (EVs) and synthetic particles. The platforms were: single-particle interferometric reflectance imaging sensing (SP-IRIS) with fluorescence, nanoparticle tracking analysis (NTA) with fluorescence, microfluidic resistive pulse sensing (MRPS), and nanoflow cytometry measurement (NFCM). EVs from the human T lymphocyte line H9 (high CD81, low CD63) and the promonocytic line U937 (low CD81, high CD63) were separated from culture conditioned medium (CCM) by differential ultracentrifugation (dUC) or a combination of ultrafiltration (UF) and size exclusion chromatography (SEC) and characterized by transmission electron microscopy (TEM) and Western blot (WB). Mixtures of synthetic particles (silica and polystyrene spheres) with known sizes and/or concentrations were also tested. MRPS and NFCM returned similar particle counts, while NTA detected counts approximately one order of magnitude lower for EVs, but not for synthetic particles. SP-IRIS events could not be used to estimate particle concentrations. For sizing, SP-IRIS, MRPS, and NFCM returned similar size profiles, with smaller sizes predominating (per power law distribution), but with sensitivity typically dropping off below diameters of 60 nm. NTA detected a population of particles with a mode diameter greater than 100 nm. Additionally, SP-IRIS, MRPS, and NFCM were able to identify at least three of four distinct size populations in a mixture of silica or polystyrene nanoparticles. Finally, for tetraspanin phenotyping, the SP-IRIS platform in fluorescence mode was able to detect at least two markers on the same particle, while NFCM detected either CD81 or CD63. Based on the results of this study, we can draw conclusions about existing single-particle analysis capabilities that may be useful for EV biomarker development and mechanistic studies.

cell biology↗

bioRxiv2020

Influence of species and processing parameters on recovery and content of brain tissue-derived extracellular vesicles

Extracellular vesicles (EVs) are involved in a wide range of physiological and pathological processes by shuttling material out of and between cells. Tissue EVs may thus lend insights into disease mechanisms and also betray disease when released into easily accessed biological fluids. Since brain-derived EVs (bdEVs) and their cargo may serve as biomarkers of neurodegenerative diseases, we evaluated modifications to a published, rigorous protocol for separation of EVs from brain tissue and studied effects of processing variables on quantitative and qualitative outcomes. To this end, size exclusion chromatography (SEC) and sucrose density gradient ultracentrifugation were compared as final separation steps in protocols involving stepped ultracentrifugation. bdEVs were separated from brain tissues of human, macaque, and mouse. Effects of tissue perfusion and a model of post-mortem interval (PMI) before final bdEV separation were probed. MISEV2018-compliant EV characterization was performed, and both small RNA and protein profiling were done. We conclude that the modified, SEC-employing protocol achieves EV separation efficiency roughly similar to a protocol using gradient density ultracentrifugation, while decreasing operator time and, potentially, variability. The protocol appears to yield bdEVs of higher purity for human tissues compared with those of macaque and, especially, mouse, suggesting opportunities for optimization. Where possible, perfusion should be performed in animal models. The interval between death/tissue storage/processing and final bdEV separation can also affect bdEV populations and composition and should thus be recorded for rigorous reporting. Finally, different populations of EVs obtained through the modified method reported herein display characteristic RNA and protein content that hint at biomarker potential. To conclude, this study finds that the automatable and increasingly employed technique of SEC can be applied to tissue EV separation, and also reveals more about the importance of species-specific and technical considerations when working with tissue EVs. These results are expected to enhance the use of bdEVs in revealing and understanding brain disease.

neuroscience↗

bioRxiv2019

Inhibition of neutral sphingomyelinase-2 facilitates remyelination

For reasons that are not completely understood, remyelination is often incomplete, producing thin myelin sheaths with disorganized structure. We investigated the cellular basis for this altered myelin structure, and found that the response of oligodendrocyte progenitor cells (OPCs), and mature oligodendrocytes to TNF and IL-1{beta} is modified by the expression of the sphingomyelin hydrolase nSMase2. OPCs do not express nSMase2, and exhibit a protective response to these cytokines manifest by decreased ceramide, increased sphingosine 1-phosphate, and increased cell motility. Mature oligodendrocytes express nSMase2, and respond to TNF and IL-1{beta} with a stress phenotype, evidenced by increased ceramide, decreased sphingosine, and active caspase 3. Pharmacological inhibition or a targeted genetic deletion of nSMase2 in vivo increased myelin thickness, and enhanced myelin compaction. These results suggest that inhibition of nSMase2 improves the quality of new myelin by protecting maturing/myelinating oligodendrocytes. Pharmacological inhibition of nSMase2 following a demyelinating event could stabilize the structure of these newly formed myelin sheaths and protect them from secondary demyelination.

molecular biology↗

bioRxiv2019

Monocarboxylate transporter 1 in Schwann cells is critical for maintenance of sensory nerve myelination during aging

Schwann cell (SC)-specific monocarboxylate transporter 1 (MCT1) knockout mice were generated by mating MCT1f/f mice with myelin protein zero (P0)-Cre mice. P0-Cre+/-, MCT1f/f mice have no detectable early developmental defects, but develop hypomyelination and reduced conduction velocity in sensory, but not motor, peripheral nerves during maturation and aging. Furthermore, enlarged node length and reduced mechanical sensitivity were evident in aged P0-Cre+/-, MCT1f/f mice. MCT1 deletion in SCs impairs both their glycolytic and mitochondrial functions, leading to altered lipid metabolism of triacylglycerides, diacylglycerides, and sphingomyelin, decreased expression of myelin-associated glycoprotein (MAG), and increased expression of c-Jun and p75-neurotrophin receptor, suggesting a regression of SCs to a less mature developmental state. Taken together, our results define the essential role of SC MCT1 in both SC metabolism and peripheral nerve maturation and aging.\n\nMain PointsO_LISC MCT1 deficiency causes hypomyelination of sensory, but not motor, axons during aging\nC_LIO_LIEnlarged node length of sensory axons is evident in mutant mouse with SC-specific MCT1 deletion\nC_LIO_LISelective ablation of MCT1 within SCs impairs glycolytic and mitochondrial functions\nC_LIO_LISC-specific MCT1 deficiency impairs proteins that regulate myelin and lipid metabolism in peripheral nerves\nC_LI

neuroscience↗