The regulated in development and DNA damage response 2 (REDD2) gene mediates human monocyte cell death through a reduction in thioredoxin-1 expression.
In a previous study, we identified the regulated in development and DNA damage response 2 (REDD2) gene as a highly expressed gene in human atherosclerotic lesions in comparison to normal artery, as well as in cultured human macrophages, and showed its implication in oxidized low-density lipoprotein (LDL)-induced macrophage death sensitivity. In this article, we attempt to identify the mechanism by which REDD2 induces such a phenomenon. Transient transfection of U-937 monocytic cells with a pCI.CMV.REDD2 expression vector increased by approximately twofold the mRNA levels of REDD2 in comparison to control cells transfected with pCI.CMV.GFP. Reactive oxygen species (ROS) production was significantly induced in REDD2-transfected cells compared with control cells (157+/-48 and 100+/-8 arbitrary units/mg cell protein, respectively; p<0.05). Moreover, a significant increase in parameters known to reflect the oxidative modifications of LDL was observed. Among enzymes involved in ROS production or degradation, we found a specific reduction in thioredoxin-1 (Trx-1) mRNA ( approximately 52+/-7% decrease, p<0.01 vs control cells) and protein ( approximately 60+/-4% decrease, p<0.001 vs control cells) levels in cells overexpressing REDD2 in comparison to control cells. In contrast, transfection of U-937 cells with siRNA against REDD2 decreased the mRNA levels of REDD2 by approximately 60% and increased Trx-1 mRNA and protein levels. Moreover, we observed no or a moderate increase in Bax (proapoptotic) and a significant decrease in Bcl2 (antiapoptotic) gene expression in cells that overexpress REDD2 compared to control cells. In addition, we showed that Trx-1 mRNA and protein levels were increased at low H(2)O(2) doses and decreased at higher doses. Interestingly, macrophages isolated from human atherosclerotic lesions differentially express REDD2 and Trx-1. Indeed, in certain patients, levels of REDD2 mRNA were low and those of Trx-1 mRNA were high. In contrast, in other patients, levels of REDD2 were high and levels of Trx-1 mRNA were low.
Imen
Jguirim-Souissi
JS
Université Pierre et Marie Curie, Paris, France.
Billiet
Ludivine
L
Cuaz-Pérolin
Clarisse
C
Michaud
Nadège
N
Rouis
Mustapha
M
D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D050197:Atherosclerosis / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000032:analysis; D009000:Monocytes / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D020298:U937 Cells; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C498040:DDIT4L protein, human; D008077:Lipoproteins, LDL; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; C099252:oxidized low density lipoprotein; D013879:Thioredoxins; D006861:Hydrogen Peroxide