title: Nicotine potentiates proatherogenic effects of oxLDL by stimulating and upregulating macrophage CD36 signaling.
abstract: Cigarette smoking is a major risk factor for atherosclerosis and cardiovascular disease. CD36 mediates oxidized LDL (oxLDL) uptake and contributes to macrophage foam cell formation. We investigated a role for the CD36 pathway in nicotine-induced activation of macrophages and foam cell formation in vitro and in vivo. Nicotine in the same plasma concentration range found in smokers increased the CD36(+)/CD14(+) cell population in human peripheral blood mononuclear cells, increased CD36 expression of human THP1 macrophages, and increased macrophage production of reactive oxygen species, PKCδ phosphorylation, and peroxisome proliferator-activated receptor-γ (PPARγ) expression. Nicotine-induced CD36 expression was suppressed by antioxidants and by specific PKCδ and PPARγ inhibitors, implicating mechanistic roles for these intermediates. Nicotine synergized with oxLDL to increase macrophage expression of CD36 and cytokines TNF-α, monocyte chemoattractant protein-1, IL-6, and CXCL9, all of which were prevented by CD36 small interfering (si)RNA. Incubation with oxLDL (50 μg/ml) for 72 h resulted in lipid deposition in macrophages and foam cell formation. Preincubation with nicotine further increased oxLDL-induced lipid accumulation and foam cell formation, which was also prevented by CD36 siRNA. Treatment of apoE-/- mice with nicotine markedly exacerbated inflammatory monocyte levels and atherosclerotic plaque accumulation, effects that were not seen in CD36-/- apoE-/- mice. Our results show that physiological levels of nicotine increase CD36 expression in macrophages, a pathway that may account at least in part for the known proinflammatory and proatherogenic properties of nicotine. These results identify such enhanced CD36 expression as a novel nicotine-mediated pathway that may constitute an independent risk factor for atherosclerosis in smokers. The results also suggest that exacerbated atherogenesis by this pathway may be an adverse side effect of extended use of high concentrations of nicotine independent of their mode of administration.
authors.affiliation: Department of Physiology, Liaoning Medical University, Jinzhou, Peoples Republic of China;
authors.forename: Ming-Sheng
authors.initials: MS
authors.lastname: Zhou
authors.forename: Kiranmai
authors.initials: K
authors.lastname: Chadipiralla
authors.forename: Armando J
authors.initials: AJ
authors.lastname: Mendez
authors.forename: Edgar A
authors.initials: EA
authors.lastname: Jaimes
authors.forename: Roy L
authors.initials: RL
authors.lastname: Silverstein
authors.forename: Keith
authors.initials: K
authors.lastname: Webster
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Raij
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism; D050197:Atherosclerosis / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D018955:CD36 Antigens / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D018932:Chemokine CCL2 / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005487:Foam Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009538:Nicotine / Q000633:toxicity*; D047495:PPAR gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D058226:Plaque, Atherosclerotic; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000975:Antioxidants; D001057:Apolipoproteins E; C111835:CCL2 protein, human; D018955:CD36 Antigens; D018932:Chemokine CCL2; C508600:IL6 protein, human; D018836:Inflammation Mediators; D015850:Interleukin-6; D018950:Lipopolysaccharide Receptors; D008077:Lipoproteins, LDL; D047495:PPAR gamma; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C099252:oxidized low density lipoprotein; D009538:Nicotine; C497258:PRKCD protein, human; D051745:Protein Kinase C-delta
keywords: CD36; foam cell; inflammatory cytokine; macrophage; nicotine