title: Cytokine-mediated regulation of iron transport in human monocytic cells.
abstract: Under chronic inflammatory conditions cytokines induce a diversion of iron traffic, leading to hypoferremia and retention of the metal within the reticuloendothelial system. However, the regulatory pathways underlying these disturbances of iron homeostasis are poorly understood. We investigated transferrin receptor (TfR)-dependent and -independent iron transport mechanisms in cytokine-stimulated human monocytic cell lines THP-1 and U937. Combined treatment of cells with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) reduced TfR mRNA levels, surface expression, and iron uptake, and these effects were reversed by interleukin-10 (IL-10), thus stimulating TfR-mediated iron acquisition. IFN-gamma and LPS dose-dependently increased the cellular expression of divalent metal transporter-1, a transmembrane transporter of ferrous iron, and stimulated the uptake of nontransferrin bound iron (NTBI) into cells. At the same time, IFN-gamma and LPS down-regulated the expression of ferroportin mRNA, a putative iron exporter, and decreased iron release from monocytes. Preincubation with IL-10 partly counteracted these effects. Our results demonstrate that the proinflammatory stimuli IFN-gamma and LPS increase the uptake of NTBI via stimulation of divalent metal transporter-1 expression and cause retention of the metal within monocytes by down-regulating ferroportin synthesis. Opposite, the anti-inflammatory cytokine IL-10 stimulates TfR-mediated iron uptake into activated monocytes. The regulation of iron transport by cytokines is a key mechanism in the pathogenesis of anemia of chronic disease and a promising target for therapeutic intervention.
authors.affiliation: Department of Internal Medicine, University Hospital, Innsbruck, Austria.
authors.forename: Susanne
authors.initials: S
authors.lastname: Ludwiczek
authors.forename: Elmar
authors.initials: E
authors.lastname: Aigner
authors.forename: Igor
authors.initials: I
authors.lastname: Theurl
authors.forename: Günter
authors.initials: G
authors.lastname: Weiss
mesh_terms: D001483:Base Sequence; D001692:Biological Transport / Q000187:drug effects; D027682:Cation Transport Proteins / Q000097:blood / Q000235:genetics; D016207:Cytokines / Q000494:pharmacology*; D017931:DNA Primers; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D016753:Interleukin-10 / Q000494:pharmacology; D007501:Iron / Q000097:blood*; D033862:Iron-Binding Proteins / Q000097:blood / Q000235:genetics; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011990:Receptors, Transferrin / Q000097:blood* / Q000187:drug effects; D014407:Tumor Cells, Cultured; D020298:U937 Cells; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D027682:Cation Transport Proteins; D016207:Cytokines; D017931:DNA Primers; D007371:Interferon-gamma; D016753:Interleukin-10; D007501:Iron; D033862:Iron-Binding Proteins; D008070:Lipopolysaccharides; D011990:Receptors, Transferrin; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2