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Regulated accumulation of desmosterol integrates macrophage lipid metabolism and inflammatory responses.

ABSTRACT: Inflammation and macrophage foam cells are characteristic features of atherosclerotic lesions, but the mechanisms linking cholesterol accumulation to inflammation and LXR-dependent response pathways are poorly understood. To investigate this relationship, we utilized lipidomic and transcriptomic methods to evaluate the effect of diet and LDL receptor genotype on macrophage foam cell formation within the peritoneal cavities of mice. Foam cell formation was associated with significant changes in hundreds of lipid species and unexpected suppression, rather than activation, of inflammatory gene expression. We provide evidence that regulated accumulation of desmosterol underlies many of the homeostatic responses, including activation of LXR target genes, inhibition of SREBP target genes, selective reprogramming of fatty acid metabolism, and suppression of inflammatory-response genes, observed in macrophage foam cells. These observations suggest that macrophage activation in atherosclerotic lesions results from extrinsic, proinflammatory signals generated within the artery wall that suppress homeostatic and anti-inflammatory functions of desmosterol.

SUBMITTER: Spann NJ

PROVIDER: S-EPMC3464914 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Regulated accumulation of desmosterol integrates macrophage lipid metabolism and inflammatory responses.

Spann Nathanael J NJ Garmire Lana X LX McDonald Jeffrey G JG Myers David S DS Milne Stephen B SB Shibata Norihito N Reichart Donna D Fox Jesse N JN Shaked Iftach I Heudobler Daniel D Raetz Christian R H CR Wang Elaine W EW Kelly Samuel L SL Sullards M Cameron MC Murphy Robert C RC Merrill Alfred H AH Brown H Alex HA Dennis Edward A EA Li Andrew C AC Ley Klaus K Tsimikas Sotirios S Fahy Eoin E Subramaniam Shankar S Quehenberger Oswald O Russell David W DW Glass Christopher K CK

Cell 20120901 1

Inflammation and macrophage foam cells are characteristic features of atherosclerotic lesions, but the mechanisms linking cholesterol accumulation to inflammation and LXR-dependent response pathways are poorly understood. To investigate this relationship, we utilized lipidomic and transcriptomic methods to evaluate the effect of diet and LDL receptor genotype on macrophage foam cell formation within the peritoneal cavities of mice. Foam cell formation was associated with significant changes in h ...[more]

PMID: 23021221

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Project description: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.

Dataset Information

Regulated accumulation of desmosterol integrates macrophage lipid metabolism and inflammatory responses.

Publications

Regulated accumulation of desmosterol integrates macrophage lipid metabolism and inflammatory responses.

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