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Regulated accumulation of desmosterol integrates macrophage lipid metabolism and inflammatory responses

ABSTRACT: To investigate the relationship between hypercholesterolemia, foam cell formation and inflammation, we performed lipidomic and transcriptomic analyses of elicited peritoneal macrophages in wild type (WT) or LDL receptor knockout (LDLR KO) mice fed either a normal cholesterol, normal fat (NCNF) diet or a high cholesterol, high fat (HCHF) 'Western' style diet. The combination of the LDLR KO genotype and the HCHF diet results in the formation of macrophage foam cells in the elicited peritoneal macrophage population. Analysis of macrophages from the above four experimental groups revealed massive reprogramming of the lipidome in response to both diet and genotype. These studies confirmed and extended prior knowledge regarding the roles of SREBP and LXR signaling in cholesterol and fatty acid homeostasis. Unexpectedly, peritoneal macrophage foam cells exhibited a strongly 'deactivated' phenotype, with marked suppression of pro-inflammatory mediators that are normally characteristic of the inflammatory responses associated with atherosclerotic lesions. Many of these changes in gene expression and lipid metabolism appear to be related to the paradoxical accumulation of high levels of desmosterol, the last intermediate in the Bloch pathway of cholesterol biosynthesis. WT or LDLR KO mice were fed either a NCNF diet or a HCHF diet for twelve weeks to establish four experimental groups (WT-NCNF diet, WT-HCHF diet, KO-NCNF diet, and KO-HCHF diet). As expected, the combination of the HCHF diet and LDLR KO genotype resulted in a synergistic effect on serum lipid levels. Elicited peritoneal macrophages (92-96% F4/80-positive) were immediately prepared for analysis, thereby preserving in vivo gene expression and lipid profiles. Macrophages derived from LDLR KO mice fed the HCHF diet contained nearly four-fold more total cholesterol than cells from WT mice fed the same diet. Quantitative analysis of 245 lipid species revealed significant changes in nearly all major lipid classes. Using a two-way ANOVA model, we found that 176 (72%) of the lipids analyzed were significantly affected by the HCHF diet, 133 (54%) by the LDLR KO genotype, and 114 (46%) by interactions between the HCHF diet and LDLR KO genotype. Many of the observed interactions (60%) were synergistic.

ORGANISM(S): Mouse Mus Musculus

TISSUE(S): Macrophages

SUBMITTER: Eoin Fahy

PROVIDER: ST001289 | MetabolomicsWorkbench | Tue Dec 17 00:00:00 GMT 2019

REPOSITORIES: MetabolomicsWorkbench

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Project description:Data from clinical studies, cell culture, and animal models implicate the urokinase (uPA)/Plasminogen (Plg) system in the development of atherosclerosis and aneurysms. However, the mechanisms through which uPA/Plg stimulate these diseases are not yet defined. We used genetically modified, atherosclerosis-prone mice, including mice with macrophage-specific uPA overexpression to clarify mechanisms of uPA/Plg-accelerated atherosclerosis and aneurysm formation. Microarray studies were performed to identify potential mediators of uPA-accelerated atherosclerosis. These studies identified S100A8 and S100A9 mRNA as the most highly upregulated transcripts in uPA-overexpressing macrophages; upregulation of S100A9 protein in uPA-overexpressing macrophages was confirmed by Western blotting. S100A8/A9, which are atherogenic in mice and are expressed in human atherosclerotic plaques, are also upregulated in aortae of mice with uPA-overexpressing macrophages, and macrophage S100A9 mRNA is upregulated by exposure of wild-type macrophages to medium from uPA-overexpressing macrophages. Bioinformatics analysis of the microarray data suggest significant effects of uPA overexpression on cell migration and cell-matrix interactions. Our results confirm—in a second animal model—that macrophage-expressed uPA stimulates atherosclerosis and aortic dilation. They also implicate specific pathways in uPA/Plg-accelerated atherosclerosis and aneurysmal disease. Six independent biological replicate RNA samples were prepared from thioglycollate-elicited peritoneal macrophages from mice of two different genotypes: SR-uPA+/0 transgenic (overexpress uPA in macrophages) and nontransgenic, respectively), for a total of 12 independent RNA samples. Both transgenic and nontransgenic mice were Apoe-/- and were fed Western diet from 5-15 weeks before peritoneal macrophages were elicited. In addition, from the six samples of each genotype, a pooled sample was prepared by combining the six genotype-specific samples. Each of the two pooled samples was assayed on the BeadChip in two technical replicates, for a total of 16 hybridizations performed using two Illumina Mouse Ref-8 v1.1 chips.

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Regulated accumulation of desmosterol integrates macrophage lipid metabolism and inflammatory responses

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