scholarly journals APOE2, E3 and E4 differentially modulate cellular homeostasis, cholesterol metabolism and inflammatory response in isogenic iPSC-derived astrocytes

2021 ◽  
Author(s):  
Sherida de Leeuw ◽  
Aron WT Kirschner ◽  
Karina Lindner ◽  
Ruslan Rust ◽  
Witold E Wolski ◽  
...  
Keyword(s):  
Proteomic Analysis ◽  
Cholesterol Efflux ◽  
Cholesterol Metabolism ◽  
Glutamate Uptake ◽  
Cholesterol Biosynthesis ◽  
Average Risk ◽  
Proteomic Data ◽  
Human Astrocytes ◽  
Β Amyloid

Apolipoprotein E (APOE) is the principal lipid carrier in the CNS and mainly expressed by astrocytes. The three different APOE alleles (E2, E3, and E4) impose differential risk to Alzheimers disease (AD); E2 is protective, E3 is defined as average risk, while E4 is the major genetic risk factor for sporadic AD. Despite recent advances, the fundamental role of different APOE alleles in brain homeostasis is still poorly understood. To uncover the functional role of APOE in human astrocytes, we differentiated human APOE-isogenic iPSCs (E4, E3, E2 and APOE-knockout (KO)) to functional astrocytes (hereafter: iAstrocytes), with a resting, non-proliferating phenotype. Functional assays indicated that polymorphisms in APOE (APOE4>E3>E2=KO) reduced iAstrocyte metabolic and clearance functions including glutamate uptake and receptor-mediated uptake of β-amyloid aggregates. We performed unlabelled mass spectrometry-based proteomic analysis of iAstrocytes at baseline and after activation with interleukin-1β showing a reduction of cholesterol and lipid metabolic and biosynthetic pathways, and an increase of immunoregulatory pathways at baseline (E4>E3>E2). Cholesterol efflux and biosynthesis were reduced in E4 iAstrocytes, and subcellular localization of cholesterol in lysosomes was increased. In APOE-KO iAstrocytes, APOE-independent mechanisms showed to be proficient in mediating cholesterol biosynthesis and efflux. Proteomic analysis of IL-1β-treated iAstrocytes showed an increase of cholesterol/lipid metabolism and biosynthesis as well as inflammatory pathways. Furthermore, cholesterol efflux, which was reduced in APOE4 iAstrocytes at baseline, was alleviated in activated E4 iAstrocytes. Inflammatory cytokine release was exacerbated upon IL-1β treatment in E4 iAstrocytes (E4>E3>E2>KO), in line with the proteomic data. Taken together, we show that APOE plays a major role in several physiological and metabolic processes in human astrocytes with APOE4 pushing iAstrocytes to a disease-relevant phenotype, causing dysregulated cholesterol/lipid homeostasis, increased inflammatory signalling and reduced β-amyloid uptake while APOE2 iAstrocytes show opposing effects. Our study provides a new reference for AD-relevant proteomic and metabolic changes, mediated by the three main APOE isoforms in human astrocytes.

scholarly journals Abnormal brain cholesterol homeostasis in Alzheimer’s disease—a targeted metabolomic and transcriptomic study

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Vijay R. Varma ◽  
H. Büşra Lüleci ◽  
Anup M. Oommen ◽  
Sudhir Varma ◽  
Chad T. Blackshear ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Brain Tissue ◽  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Cholesterol Homeostasis ◽  
Transcriptomic Data ◽  
Brain Cholesterol ◽  
Cholesterol Levels

AbstractThe role of brain cholesterol metabolism in Alzheimer’s disease (AD) remains unclear. Peripheral and brain cholesterol levels are largely independent due to the impermeability of the blood brain barrier (BBB), highlighting the importance of studying the role of brain cholesterol homeostasis in AD. We first tested whether metabolite markers of brain cholesterol biosynthesis and catabolism were altered in AD and associated with AD pathology using linear mixed-effects models in two brain autopsy samples from the Baltimore Longitudinal Study of Aging (BLSA) and the Religious Orders Study (ROS). We next tested whether genetic regulators of brain cholesterol biosynthesis and catabolism were altered in AD using the ANOVA test in publicly available brain tissue transcriptomic datasets. Finally, using regional brain transcriptomic data, we performed genome-scale metabolic network modeling to assess alterations in cholesterol biosynthesis and catabolism reactions in AD. We show that AD is associated with pervasive abnormalities in cholesterol biosynthesis and catabolism. Using transcriptomic data from Parkinson’s disease (PD) brain tissue samples, we found that gene expression alterations identified in AD were not observed in PD, suggesting that these changes may be specific to AD. Our results suggest that reduced de novo cholesterol biosynthesis may occur in response to impaired enzymatic cholesterol catabolism and efflux to maintain brain cholesterol levels in AD. This is accompanied by the accumulation of nonenzymatically generated cytotoxic oxysterols. Our results set the stage for experimental studies to address whether abnormalities in cholesterol metabolism are plausible therapeutic targets in AD.

scholarly journals Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood

2020 ◽  
Vol 61 (12) ◽  
pp. 1577-1588
Author(s):  
Ryunosuke Ohkawa ◽  
Hann Low ◽  
Nigora Mukhamedova ◽  
Ying Fu ◽  
Shao-Jui Lai ◽  
...  
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Cholesterol Efflux ◽  
Cholesterol Metabolism ◽  
Plasma Cholesterol ◽  
Translocator Protein ◽  
Plasma Lipoproteins ◽  
Cholesterol Transport ◽  
Autologous Plasma

Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1+/+ and Abca1−/− mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.

LXRβ is the dominant LXR subtype in skeletal muscle regulating lipogenesis and cholesterol efflux

2010 ◽  
Vol 298 (3) ◽  
pp. E602-E613 ◽  
Author(s):  
N. P. Hessvik ◽  
M. V. Boekschoten ◽  
M. A. Baltzersen ◽  
S. Kersten ◽  
X. Xu ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Metabolism ◽  
Cholesterol Efflux ◽  
Target Genes ◽  
Cholesterol Metabolism ◽  
Receptor Subtypes ◽  
Mrna Levels ◽  
Functional Studies ◽  
X Receptors

Liver X receptors (LXRs) are important regulators of cholesterol, lipid, and glucose metabolism and have been extensively studied in liver, macrophages, and adipose tissue. However, their role in skeletal muscle is poorly studied and the functional role of each of the LXRα and LXRβ subtypes in skeletal muscle is at present unknown. To study the importance of each of the receptor subtypes, myotube cultures derived from wild-type (WT) and LXRα and LXRβ knockout (KO) mice were established. The present study showed that treatment with the LXR agonist T0901317 increased lipogenesis and apoA1-dependent cholesterol efflux in LXRα KO and WT myotubes but not in LXRβ KO cells. The functional studies were confirmed by T0901317-induced increase in mRNA levels of LXR target genes involved in lipid and cholesterol metabolism in myotubes established from WT and LXRα KO mice, whereas only minor changes were observed for these genes in myotubes from LXRβ KO mice. Gene expression analysis using microarrays showed that very few genes other than the classical, well-known LXR target genes were regulated by LXR in skeletal muscle. The present study also showed that basal glucose uptake was increased in LXRβ KO myotubes compared with WT myotubes, suggesting a role for LXRβ in glucose metabolism in skeletal muscle. In conclusion, LXRβ seems to be the main LXR subtype regulating lipogenesis and cholesterol efflux in skeletal muscle.

scholarly journals Aberrant Cholesterol Metabolism in Ovarian Cancer: Identification of Novel Therapeutic Targets

2021 ◽  
Vol 11 ◽  
Author(s):  
Jiangnan He ◽  
Michelle K.Y. Siu ◽  
Hextan Y. S. Ngan ◽  
Karen K. L. Chan
Keyword(s):  
Ovarian Cancer ◽  
Mammalian Cells ◽  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Therapeutic Targets ◽  
Multiple Cancer ◽  
Cancer Types ◽  
Characteristic Features ◽  
Rate Limiting

Cholesterol is an essential substance in mammalian cells, and cholesterol metabolism plays crucial roles in multiple biological functions. Dysregulated cholesterol metabolism is a metabolic hallmark in several cancers, beyond the Warburg effect. Reprogrammed cholesterol metabolism has been reported to enhance tumorigenesis, metastasis and chemoresistance in multiple cancer types, including ovarian cancer. Ovarian cancer is one of the most aggressive malignancies worldwide. Alterations in metabolic pathways are characteristic features of ovarian cancer; however, the specific role of cholesterol metabolism remains to be established. In this report, we provide an overview of the key proteins involved in cholesterol metabolism in ovarian cancer, including the rate-limiting enzymes in cholesterol biosynthesis, and the proteins involved in cholesterol uptake, storage and trafficking. Also, we review the roles of cholesterol and its derivatives in ovarian cancer and the tumor microenvironment, and discuss promising related therapeutic targets for ovarian cancer.

scholarly journals Genetic deletion of Abcc6 disturbs cholesterol homeostasis in mice

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bettina Ibold ◽  
Janina Tiemann ◽  
Isabel Faust ◽  
Uta Ceglarek ◽  
Julia Dittrich ◽  
...  
Keyword(s):  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Pseudoxanthoma Elasticum ◽  
Serum Levels ◽  
Cholesterol Homeostasis ◽  
Cholesterol Depletion ◽  
Transferase Activity

AbstractGenetic studies link adenosine triphosphate-binding cassette transporter C6 (ABCC6) mutations to pseudoxanthoma elasticum (PXE). ABCC6 sequence variations are correlated with altered HDL cholesterol levels and an elevated risk of coronary artery diseases. However, the role of ABCC6 in cholesterol homeostasis is not widely known. Here, we report reduced serum cholesterol and phytosterol levels in Abcc6-deficient mice, indicating an impaired sterol absorption. Ratios of cholesterol precursors to cholesterol were increased, confirmed by upregulation of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase (Hmgcr) expression, suggesting activation of cholesterol biosynthesis in Abcc6−/− mice. We found that cholesterol depletion was accompanied by a substantial decrease in HDL cholesterol mediated by lowered ApoA-I and ApoA-II protein levels and not by inhibited lecithin-cholesterol transferase activity. Additionally, higher proprotein convertase subtilisin/kexin type 9 (Pcsk9) serum levels in Abcc6−/− mice and PXE patients and elevated ApoB level in knockout mice were observed, suggesting a potentially altered very low-density lipoprotein synthesis. Our results underline the role of Abcc6 in cholesterol homeostasis and indicate impaired cholesterol metabolism as an important pathomechanism involved in PXE manifestation.

scholarly journals AIBP-CAV1-VEGFR3 axis dictates lymphatic cell fate and controls lymphangiogenesis

2020 ◽  
Author(s):  
Xiaojie Yang ◽  
Jun-dae Kim ◽  
Qilin Gu ◽  
Qing Yan ◽  
Jonathan Astin ◽  
...  
Keyword(s):  
Cell Fate ◽  
Cholesterol Efflux ◽  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Embryonic Stem ◽  
Lymphatic Endothelial Cell ◽  
Tissue Fluid ◽  
Cell Functions ◽  
Signaling Axis ◽  
And Migration

AbstractThe lymphatics are essential for the maintenance of tissue fluid homeostasis. Accordingly, lymphatic dysfunction contributes to lymphedema. In development, lymphangiogenesis often requires lymphatic endothelial cell (LEC) lineage specification from the venous ECs and subsequent LEC proliferation and migration, all of which are regulated by the VEGFC/VEGFR3 signaling. Cholesterol is essential for proper cell functions and organ development, yet the molecular mechanism by which cholesterol metabolism controls lymphangiogenesis is unknown. We show that the secreted protein, ApoA1 binding protein (AIBP), dictates lymphatic vessel formation by accelerating cholesterol efflux. Loss of Aibp2, the human paralog in zebrafish, impairs LEC progenitor specification and impedes lymphangiogenesis. Mechanistically, we found that caveolin-1 (CAV-1) suppresses VEGFR3 activation in LECs, and that AIBP-regulated cholesterol efflux disrupts lipid rafts/caveolae and reduces CAV-1 bioavailability, which abolishes the CAV-1 inhibition of VEGFR3 signaling, thereby augmenting VEGFR3 activation and increasing lymphangiogenesis. Enhancement of cholesterol efflux with ApoA1 overexpression or inhibition of cholesterol biosynthesis using atorvastatin restores proper lymphangiogenesis in Aibp2 mutant zebrafish. Loss of Cav-1 increases LEC progenitor specification in zebrafish, and rescues lymphangiogenesis in Aibp2-deficient animals. Recombinant AIBP supplement confers profound LEC fate commitment in the mouse embryonic stem cells (mESC) to LEC differentiation model. Furthermore, enhancement of AIBP-CAV-1-VEGFR3 signaling axis promotes VEGFC-engaged adult lymphangiogenesis in mice. Consistent with these data, AIBP expression is reduced in the epidermis of human lymphedematous skin. These studies identify that AIBP-mediated cholesterol efflux is a critical contributor for lymphangiogenesis. Our studies will provide a new therapeutic avenue for the treatment of lymphatic dysfunctions.One Sentence SummaryOur studies identify that AIBP-CAV-1-VEGFR3 axis enhances VEGFC-elicited lymphangiogenesis, which will guide a new therapeutic strategy for the treatment of lymphatic dysfunctions.

scholarly journals Cultured macrophages transfer surplus cholesterol into adjacent cells in the absence of serum or high-density lipoproteins

2020 ◽  
Vol 117 (19) ◽  
pp. 10476-10483 ◽  
Author(s):  
Cuiwen He ◽  
Haibo Jiang ◽  
Wenxin Song ◽  
Howard Riezman ◽  
Peter Tontonoz ◽  
...  
Keyword(s):  
Cholesterol Efflux ◽  
Secondary Ion Mass Spectrometry ◽  
Cholesterol Metabolism ◽  
Peritoneal Macrophages ◽  
High Density ◽  
High Density Lipoproteins ◽  
Macrophage Foam Cells ◽  
Mouse Peritoneal Macrophages

Cholesterol-laden macrophage foam cells are a hallmark of atherosclerosis. For that reason, cholesterol metabolism in macrophages has attracted considerable scrutiny, particularly the mechanisms by which macrophages unload surplus cholesterol (a process referred to as “cholesterol efflux”). Many studies of cholesterol efflux in macrophages have focused on the role of ABC transporters in moving cholesterol onto high-density lipoproteins (HDLs), but other mechanisms for cholesterol efflux likely exist. We hypothesized that macrophages have the capacity to unload cholesterol directly onto adjacent cells. To test this hypothesis, we used methyl-β-cyclodextrin (MβCD) to load mouse peritoneal macrophages with [13C]cholesterol. We then plated the macrophages (in the absence of serum or HDL) onto smooth muscle cells (SMCs) that had been metabolically labeled with [15N]choline. After incubating the cells overnight in the absence of HDL or serum, we visualized 13C and 15N distribution by nanoscale secondary ion mass spectrometry (NanoSIMS). We observed substantial 13C enrichment in SMCs that were adjacent to [13C]cholesterol-loaded macrophages—including in cytosolic lipid droplets of SMCs. In follow-up studies, we depleted “accessible cholesterol” from the plasma membrane of [13C]cholesterol-loaded macrophages with MβCD before plating the macrophages onto the SMCs. After an overnight incubation, we again observed substantial 13C enrichment in the SMCs adjacent to macrophages. Thus, macrophages transfer cholesterol to adjacent cells in the absence of serum or HDL. We suspect that macrophages within tissues transfer cholesterol to adjacent cells, thereby contributing to the ability to unload surplus cholesterol.

2,3,4′,5-tetrahydroxystilbene-2-O-β-d-glycoside attenuates atherosclerosis in apolipoprotein E-deficient mice: role of reverse cholesterol transport

2018 ◽  
Vol 96 (1) ◽  
pp. 8-17 ◽  
Author(s):  
Xuemeng Chen ◽  
Kun Tang ◽  
Yi Peng ◽  
XiaoLe Xu
Keyword(s):  
Reverse Cholesterol Transport ◽  
Cholesterol Efflux ◽  
Cholesterol Metabolism ◽  
Density Lipoprotein ◽  
Serum Levels ◽  
Lipoprotein Cholesterol ◽  
Cholesterol Transport ◽  
Positive Role ◽  
Protein Expressions

The aim of this study was to evaluate the potential effects of 2,3,4′,5-tetrahydroxystilbene-2-O-β-d-glucoside (TSG) on the development of atherosclerotic plaque in ApoE−/− mice, and explore the mechanisms involved. Our data showed that after 8 weeks of treatment, TSG ameliorated serum levels of total cholesterol, triglyceride, and low density lipoprotein cholesterol, and increased serum levels of high density lipoprotein cholesterol in ApoE−/− mice. TSG suppressed hepatic steatosis, the formation of atherosclerotic lesions, and the formation of macrophage foam cells in ApoE−/− mice. Moreover, TSG improved the expressions of hepatic SR-BI, ABCG5, and CYP7A1, and up-regulated the protein expressions of aortic ABCA1 and ABCG1. An in-vitro study showed that TSG promoted macrophage cholesterol efflux and increased the protein expressions of ABCA1 and ABCG1. Our findings provide evidence for a positive role of TSG in preventing atherosclerosis by promoting reverse cholesterol transport. These effects may be achieved by stimulating cholesterol efflux through ABCA1 and ABCG1, promoting SR-BI-mediated cholesterol uptake in the liver, increasing secretion of cholesterol into bile by ABCG5, and improving cholesterol metabolism by the CYP7A1 pathway. In addition, antioxidative and anti-inflammatory effects of TSG may also contribute to its inhibitory effects on atherosclerosis. Further study is needed to investigate whether other potential mechanisms are involved in TSG-mediated atheroprotection.

scholarly journals Evaluation of a Genome-ScaleIn SilicoMetabolic Model for Geobacter metallireducens by Using Proteomic Data from a Field Biostimulation Experiment

2012 ◽  
Vol 78 (24) ◽  
pp. 8735-8742 ◽  
Author(s):  
Yilin Fang ◽  
Michael J. Wilkins ◽  
Steven B. Yabusaki ◽  
Mary S. Lipton ◽  
Philip E. Long
Keyword(s):  
Proteomic Analysis ◽  
In Silico ◽  
Field Experiments ◽  
Metabolic Model ◽  
Geobacter Metallireducens ◽  
Content Type ◽  
Proteomic Data ◽  
Subsurface Environment ◽  
A Genome ◽  
Genome Scale

ABSTRACTAccurately predicting the interactions between microbial metabolism and the physical subsurface environment is necessary to enhance subsurface energy development, soil and groundwater cleanup, and carbon management. This study was an initial attempt to confirm the metabolic functional roles within anin silicomodel using environmental proteomic data collected during field experiments. Shotgun global proteomics data collected during a subsurface biostimulation experiment were used to validate a genome-scale metabolic model ofGeobacter metallireducens—specifically, the ability of the metabolic model to predict metal reduction, biomass yield, and growth rate under dynamic field conditions. The constraint-basedin silicomodelof G. metallireducensrelates an annotated genome sequence to the physiological functions with 697 reactions controlled by 747 enzyme-coding genes. Proteomic analysis showed that 180 of the 637G. metallireducensproteins detected during the 2008 experiment were associated with specific metabolic reactions in thein silicomodel. When the field-calibrated Fe(III) terminal electron acceptor process reaction in a reactive transport model for the field experiments was replaced with the genome-scale model, the model predicted that the largest metabolic fluxes through thein silicomodel reactions generally correspond to the highest abundances of proteins that catalyze those reactions. Central metabolism predicted by the model agrees well with protein abundance profiles inferred from proteomic analysis. Model discrepancies with the proteomic data, such as the relatively low abundances of proteins associated with amino acid transport and metabolism, revealed pathways or flux constraints in thein silicomodel that could be updated to more accurately predict metabolic processes that occur in the subsurface environment.

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