title: Differential action of glucocorticoids on apolipoprotein E gene expression in macrophages and hepatocytes.
abstract: Apolipoprotein E (apoE) has anti-atherosclerotic properties, being involved in the transport and clearance of cholesterol-rich lipoproteins as well as in cholesterol efflux from cells. We hypothesized that glucocorticoids may exert anti-inflammatory properties by increasing the level of macrophage-derived apoE. Our data showed that glucocorticoids increased apoE expression in macrophages in vitro as well as in vivo. Dexamethasone increased ~6 fold apoE mRNA levels in cultured peritoneal macrophages and RAW 264.7 cells. Administered to C57BL/6J mice, dexamethasone induced a two-fold increase in apoE expression in peritoneal macrophages. By contrast, glucocorticoids did not influence apoE expression in hepatocytes, in vitro and in vivo. Moreover, dexamethasone enhanced apoE promoter transcriptional activity in RAW 264.7 macrophages, but not in HepG2 cells, as tested by transient transfections. Analysis of apoE proximal promoter deletion mutants, complemented by protein-DNA interaction assays demonstrated the functionality of a putative glucocorticoid receptors (GR) binding site predicted by in silico analysis in the -111/-104 region of the human apoE promoter. In hepatocytes, GR can bind to their specific site within apoE promoter but are not able to modulate the gene expression. The modulatory blockade in hepatocytes is a consequence of partial involvement of transcription factors and other signaling molecules activated through MEK1/2 and PLA2/PLC pathways. In conclusion, our study indicates that glucocorticoids (1) differentially target apoE gene expression; (2) induce a significant increase in apoE level specifically in macrophages. The local increase of apoE gene expression in macrophages at the level of the atheromatous plaque may have therapeutic implications in atherosclerosis.
authors.affiliation: Department of Genomics, Transcriptomics and Molecular Therapies, Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, Bucharest, Romania.
authors.forename: Violeta Georgeta
authors.initials: VG
authors.lastname: Trusca
authors.affiliation: Department of Genomics, Transcriptomics and Molecular Therapies, Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, Bucharest, Romania.
authors.forename: Elena Valeria
authors.initials: EV
authors.lastname: Fuior
authors.affiliation: Department of Genomics, Transcriptomics and Molecular Therapies, Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, Bucharest, Romania.
authors.forename: Ioana Madalina
authors.initials: IM
authors.lastname: Fenyo
authors.affiliation: Department of Basic Sciences, University of Crete Medical School, Heraklion, Crete, Greece.|Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology of Hellas, Heraklion, Crete, Greece.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kardassis
authors.affiliation: Department of Genomics, Transcriptomics and Molecular Therapies, Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, Bucharest, Romania.
authors.forename: Maya
authors.initials: M
authors.lastname: Simionescu
authors.affiliation: Department of Genomics, Transcriptomics and Molecular Therapies, Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, Bucharest, Romania.
authors.forename: Anca Violeta
authors.identifier: http://orcid.org/0000-0002-1290-1346
authors.initials: AV
authors.lastname: Gafencu
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000235:genetics / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009928:Organ Specificity; D054467:Phospholipases A2 / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011965:Receptors, Glucocorticoid / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D013045:Species Specificity; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism
chemical_list: D001057:Apolipoproteins E; D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone; C482128:MAP2K2 protein, human; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D054467:Phospholipases A2; D010738:Type C Phospholipases