TNFalpha induces ABCA1 through NF-kappaB in macrophages and in phagocytes ingesting apoptotic cells.
Recent evidence suggests that tumor necrosis factor alpha (TNFalpha) signaling in vascular cells can have antiatherogenic consequences, but the mechanisms are poorly understood. TNFalpha is released by free cholesterol-loaded apoptotic macrophages, and the clearance of these cells by phagocytic macrophages may help to limit plaque development. Macrophage cholesterol uptake induces ATP-binding cassette (ABC) transporter ABCA1 promoting cholesterol efflux to apolipoprotein A-I and reducing atherosclerosis. We show that TNFalpha induces ABCA1 mRNA and protein in control and cholesterol-loaded macrophages and enhances cholesterol efflux to apolipoprotein A-I. The induction of ABCA1 by TNFalpha is reduced by 65% in IkappaB kinase beta-deficient macrophages and by 30% in p38alpha-deficient macrophages, but not in jun kinase 1 (JNK1)- or JNK2-deficient macrophages. To evaluate the potential pathophysiological significance of these observations, we fed TNFalpha-secreting free cholesterol-loaded apoptotic macrophages to a healthy macrophage monolayer (phagocytes). ABCA1 mRNA and protein were markedly induced in the phagocytes, a response that was mediated both by TNFalpha signaling and by liver X receptor activation. Thus, TNFalpha signals primarily through NF-kappaB to induce ABCA1 expression in macrophages. In atherosclerotic plaques, this process may help phagocytic macrophages to efflux excess lipids derived from the ingestion of cholesterol-rich apoptotic corpses.
Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY 10032, USA.
Marie-Christine
MC
Gerbod-Giannone
Yankun
Y
Li
Adriaan
A
Holleboom
Seongah
S
Han
Li-Chung
LC
Hsu
Ira
I
Tabas
Alan R
AR
Tall
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D002784:Cholesterol / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D000071518:Liver X Receptors; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism*; D057093:Orphan Nuclear Receptors; D010586:Phagocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D000906:Antibodies; D004268:DNA-Binding Proteins; D000071518:Liver X Receptors; D016328:NF-kappa B; D057093:Orphan Nuclear Receptors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014409:Tumor Necrosis Factor-alpha; D002784:Cholesterol