Oxidative stress influences cholesterol efflux in THP-1 macrophages: role of ATP-binding cassette A1 and nuclear factors.
Understanding the mechanisms involved in oxidative stress-induced foam cell formation is of fundamental importance for atherosclerosis. Our aim was to characterize the effects of oxidative stress on key receptors of macrophage cholesterol homeostasis, on the nuclear transcription factors PPAR and LXR regulating their expression, and on macrophage cholesterol handling.



The incubation of macrophages derived from the human monocyte cell line THP-1 with iron (100 microm)/ascorbate (1000 microm) for a period of 4 h induced a strong peroxidation, as demonstrated by the elevation of malondialdehyde (220%, P < 0.001). The production of lipid peroxidation affected cholesterol efflux, which was probably due to decreased ABCAI gene and protein expression. On the other hand, cholesterol influx remained unchanged as did the mRNA and protein levels of SR-BI and CD36, important protein receptors that participate in cholesterol import. Experiments using RT-PCR showed that the ABCAI modulation was orchestrated by the nuclear receptors LXRalpha, LXRbeta, PPARalpha, and PPARgamma. Treatment with powerful antioxidants (Trolox and BHT) prevented the adverse effects of iron-ascorbate on cholesterol movement, conceivably supporting the role of oxidative stress.



Our results show that oxidative stress can directly be induced in macrophages and concomitantly impairs the expression of receptors involved in cholesterol flux, which could influence foam cell formation and atherosclerosis development.
Marcil
Valérie
V
Centre de Recherche, CHU-Sainte-Justine, Université de Montréal, 3175, Côte Ste-Catherine, Montréal (Québec), Canada H3T 1C5.
Delvin
Edgard
E
Sané
Alain Théophile
AT
Tremblay
André
A
Levy
Emile
E
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000502:physiology*; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D050197:Atherosclerosis / Q000378:metabolism; D015153:Blotting, Western / Q000379:methods; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D018955:CD36 Antigens / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D002839:Chromans / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D005487:Foam Cells / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression; D006706:Homeostasis; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D018384:Oxidative Stress; D047493:PPAR alpha / Q000235:genetics / Q000378:metabolism; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D048068:PPAR-beta / Q000235:genetics / Q000378:metabolism; D047492:Peroxisome Proliferator-Activated Receptors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051122:Scavenger Receptors, Class B / Q000032:analysis / Q000235:genetics / Q000378:metabolism
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D000975:Antioxidants; D018955:CD36 Antigens; D002839:Chromans; D004268:DNA-Binding Proteins; D000071518:Liver X Receptors; C000605213:NR1H3 protein, human; D057093:Orphan Nuclear Receptors; D047493:PPAR alpha; D047495:PPAR gamma; D048068:PPAR-beta; D047492:Peroxisome Proliferator-Activated Receptors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B; D002084:Butylated Hydroxytoluene; D002784:Cholesterol; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid