title: Hepcidin-ferroportin axis controls toll-like receptor 4 dependent macrophage inflammatory responses in human atherosclerotic plaques.
abstract: OBJECTIVE
  Toll-like Receptor 4 (TLR4) is implicated in modulating inflammatory cytokines though its role in atherosclerosis remains uncertain. We have recently described a non-foam cell macrophage phenotype driven by ingestion of hemoglobin:haptoglobin complexes (HH), via the scavenger receptor CD163, characterized by reduced inflammatory cytokine production. In this study, we examined the role of iron metabolism in modulating TLR4 signaling in these cells.
  
  
  RESULTS
  Areas in human atherosclerotic plaque with non-foam cell, CD163 positive macrophages demonstrated reduced expression of tumor necrosis factor alpha (TNF-α) and interferon-beta (INF-β) compared to foam cells. Human macrophages differentiated in hemoglobin:haptoglobin (HH) complexes expressed the CD163 positive non-foam cell phenotype and demonstrated significantly less TNF-α and INF-β compared to control macrophages when exposed to oxidized LDL (oxLDL) or lipopolysaccharide (LPS). LPS stimulated expression of TNF-α and INF-β could be restored in HH macrophages by pretreatment with hepcidin, an endogenous suppressor of ferroportin1 (FPN), or by genetic suppression of FPN in macrophages derived from myeloid specific FPN knockout mice. LPS stimulated control macrophages demonstrated increase in TLR4 trafficking to lipid rafts; this response was suppressed in HH macrophages but was restored upon pretreatment with hepcidin. Using a pharmacologic hepcidin suppressor, we observed a decrease in cytokine expression and TLR4-lipid raft trafficking in LPS-stimulated in a murine macrophage model.
  
  
  CONCLUSIONS
  TLR4 dependent macrophage signaling is controlled via hepcidin-ferroportin1 axis by influencing TLR4-lipid raft interactions. Pharmacologic manipulation of iron metabolism may represent a promising approach to limiting TLR4-mediated inflammatory responses.
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Anwer
authors.initials: A
authors.lastname: Habib
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Rohini
authors.initials: R
authors.lastname: Polavarapu
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Vinit
authors.initials: V
authors.lastname: Karmali
authors.affiliation: CVPath Institute, Gaithersburg, MD, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Guo
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Van Dam
authors.affiliation: CVPath Institute, Gaithersburg, MD, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Cheng
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Hirokuni
authors.initials: H
authors.lastname: Akahori
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Omar
authors.initials: O
authors.lastname: Saeed
authors.affiliation: CVPath Institute, Gaithersburg, MD, USA.
authors.forename: Masataka
authors.initials: M
authors.lastname: Nakano
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Pachura
authors.affiliation: Vanderbilt University, Dept. of Internal Medicine, Division of Cardiology, and Research Medicine, Veterans Affairs TVHS, Nashville, TN, USA.
authors.forename: Charles C
authors.initials: CC
authors.lastname: Hong
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Shin
authors.affiliation: CVPath Institute, Gaithersburg, MD, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Kolodgie
authors.affiliation: CVPath Institute, Gaithersburg, MD, USA.
authors.forename: Renu
authors.initials: R
authors.lastname: Virmani
authors.affiliation: Emory University, Dept. of Internal Medicine, Division of Cardiology, Atlanta, GA, USA. Electronic address: avfinn@emory.edu.
authors.forename: Aloke V
authors.initials: AV
authors.lastname: Finn
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism*; D005487:Foam Cells / Q000166:cytology; D006242:Haptoglobins / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry; D064451:Hepcidins / Q000737:chemistry*; D006801:Humans; D007249:Inflammation; D007501:Iron / Q000737:chemistry; D008070:Lipopolysaccharides / Q000737:chemistry; D008077:Lipoproteins, LDL / Q000737:chemistry; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000378:metabolism; D008297:Male; D021962:Membrane Microdomains / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D058226:Plaque, Atherosclerotic / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000098902:CD163 Antigen; D000098742:Ferroportin
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D027682:Cation Transport Proteins; D006242:Haptoglobins; D006454:Hemoglobins; D064451:Hepcidins; D008070:Lipopolysaccharides; D008077:Lipoproteins, LDL; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D000098742:Ferroportin; C099252:oxidized low density lipoprotein; D007501:Iron
keywords: Atherosclerosis; Inflammation; Macrophage