Interferon-gamma impedes reverse cholesterol transport and promotes foam cell transformation in THP-1 human monocytes/macrophages.
BACKGROUND
Cholesterol 27-hydroxylase, an enzyme expressed at high levels by human monocytes/macrophages, provides a first line of defense against the development of atherosclerosis. Prior studies have suggested that the cytokine interferon-gamma (IFN-gamma) promotes atherosclerosis. We therefore examined the effect of IFN-g on macrophage foam cell formation and on expression of the anti-atherogenic 27-hydroxylase in THP-1 human monocytes/macrophages.


METHODS
THP-1 monocytes and acetylated LDL-treated THP-1 macrophages were incubated in the presence or absence of IFN-gamma (500 U/ml) with or without the addition of IFN- gamma receptor blocking or neutralizing antibody. Foam cell formation was quantified based on percentage of macrophages harboring oil red O-stained globules. Cellular mRNA and protein were isolated. 27-Hydroxylase message was measured by RT-PCR and 27-hydroxylase protein by immunoblot.


RESULTS
IFN-gamma -treated THP-1 macrophages exhibit increased foam cell transformation compared to untreated cells under cholesterol loading conditions. IFN-gamma-promoted foam cell formation is abolished by pre-treatment with either IFN-gamma neutralizing or IFN-gamma receptor blocking antibody. IFN-gamma diminishes cholesterol 27-hydroxylase expression in THP-1, and this IFN-gamma -induced downregulation is prevented by pre-treating the cultured cells with either IFN-gamma neutralizing or IFN-gamma receptor blocking antibody.


CONCLUSIONS
Imbalances in cellular cholesterol flux within macrophages lead to formation of lipid-laden foam cells, a critical step in the pathogenesis of atherosclerosis. We have demonstrated that IFN-gamma, acting through the IFN-gamma receptor, decreases expression of 27-hydroxylase and increases propensity to foam cell formation in the cell line THP-1. These observations suggest that one mechanism by which IFN-g promotes atherosclerosis may involve affecting expression of cholesterol 27-hydroxylase, a cholesterol homeostatic protein.
Reiss
Allison B
AB
Department of Vascular Biology, Winthrop-University Hospital, Mineola, NY 11501, USA. areiss@winthrop.org
Patel
Chirag A
CA
Rahman
Mohammad M
MM
Chan
Edwin S L
ES
Hasneen
Kowser
K
Montesinos
Maria C
MC
Trachman
Julie D
JD
Cronstein
Bruce N
BN
D000906:Antibodies / Q000276:immunology; D001161:Arteriosclerosis / Q000209:etiology; D001692:Biological Transport / Q000187:drug effects; D002454:Cell Differentiation; D002460:Cell Line; D053493:Cholestanetriol 26-Monooxygenase; D002784:Cholesterol / Q000378:metabolism*; D008078:Cholesterol, LDL / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D005487:Foam Cells / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology*; D009000:Monocytes / Q000166:cytology*; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism*
D000906:Antibodies; D008078:Cholesterol, LDL; D007371:Interferon-gamma; D002784:Cholesterol; D013250:Steroid Hydroxylases; C506831:CYP27A1 protein, human; D053493:Cholestanetriol 26-Monooxygenase