title: Iron primes 3T3-L1 adipocytes to a TLR4-mediated inflammatory response.
abstract: OBJECTIVE
  Iron participates in several mechanisms involving inflammation and innate immunity, yet the dysregulation of its homeostasis is a major cause of metabolic syndrome. Adipocytes should play a major role in iron metabolism, as an impairment in iron turnover is closely related to insulin resistance, obesity, and type 2 diabetes. The aim of this study was to investigate the role of iron in an in vitro-inflamed adipocyte model.
  
  
  METHODS
  Gene expression of tumor necrosis factor-α, interleukin-6, inflammatory chemokines (CCL3, CCL4, and CXCL12), and molecules involved in iron metabolism were evaluated in an in vitro mouse 3T3-L1 cell model. Cells underwent treatment with FeSO4 heptahydrate and lipopolysaccharide (LPS) stimulation. Toll-like receptor 4 (TLR4) membrane expression, lipid droplet immunohystochemistry, and lipolysis were also evaluated.
  
  
  RESULTS
  Iron sulphate heptahydrate elicited gene expression of hepcidin, hemojuvelin, and ferroportin at different time courses. Additionally, it activated lipolysis but did not trigger any adipokine gene expression. When cells treated with physiological doses of iron were also stimulated with LPS, an enhancement in the LPS-induced gene expression of cytokines and chemokines was observed. The enhancement occurred with different patterns depending on different time courses and investigated genes, showing its maximal effect for IL-6 gene expression.
  
  
  CONCLUSIONS
  FeSO4 heptahydrate at a relatively physiological dose, induced gene expression of iron modulatory proteins and also enhanced RNA transcripts of several inflammatory cytokines and chemokines through a priming/synergistic mechanism involving membrane TLR4.
authors.affiliation: Department of Medicine University of Verona, Verona, Italy. Electronic address: salvatore.chirumbolo@univr.it.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Chirumbolo
authors.affiliation: Department of Medicine University of Verona, Verona, Italy; Section of Geriatry Azienda Ospedaliera Universitaria Integrata, Verona, Italy.
authors.forename: Andrea P
authors.initials: AP
authors.lastname: Rossi
authors.affiliation: Department of Medicine University of Verona, Verona, Italy.
authors.forename: Vanni
authors.initials: V
authors.lastname: Rizzatti
authors.affiliation: Department of Medicine University of Verona, Verona, Italy; Section of Geriatry Azienda Ospedaliera Universitaria Integrata, Verona, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Zoico
authors.affiliation: Department of Medicine University of Verona, Verona, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Franceschetti
authors.affiliation: Department of Medicine, Unit of Internal Medicine, Azienda Ospedaliera Universitaria Integrata, University of Verona, Verona, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Girelli
authors.affiliation: Department of Medicine University of Verona, Verona, Italy; Section of Geriatry Azienda Ospedaliera Universitaria Integrata, Verona, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Zamboni
mesh_terms: D041721:3T3-L1 Cells / Q000378:metabolism*; D017667:Adipocytes / Q000276:immunology*; D000818:Animals; D027682:Cation Transport Proteins / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D005290:Ferric Compounds / Q000008:administration & dosage / Q000378:metabolism; D058851:GPI-Linked Proteins; D015870:Gene Expression; D000071020:Hemochromatosis Protein; D064451:Hepcidins / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism; D007333:Insulin Resistance; D007501:Iron / Q000008:administration & dosage / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D009765:Obesity / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000276:immunology*; D000098742:Ferroportin
chemical_list: D027682:Cation Transport Proteins; D018925:Chemokines; D016207:Cytokines; D005290:Ferric Compounds; D058851:GPI-Linked Proteins; C504414:HJV protein, mouse; D000071020:Hemochromatosis Protein; D064451:Hepcidins; D008070:Lipopolysaccharides; D008565:Membrane Proteins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D000098742:Ferroportin; C024823:ferric sulfate; D007501:Iron
keywords: Adipocyte: Lipopolysaccharide; Chemokine; Inflammation; Iron; Toll-like receptors