Increased iron sequestration in alveolar macrophages in chronic obstructive pulmonary disease.
Free iron in lung can cause the generation of reactive oxygen species, an important factor in chronic obstructive pulmonary disease (COPD) pathogenesis. Iron accumulation has been implicated in oxidative stress in other diseases, such as Alzheimer's and Parkinson's diseases, but little is known about iron accumulation in COPD. We sought to determine if iron content and the expression of iron transport and/or storage genes in lung differ between controls and COPD subjects, and whether changes in these correlate with airway obstruction. Explanted lung tissue was obtained from transplant donors, GOLD 2-3 COPD subjects, and GOLD 4 lung transplant recipients, and bronchoalveolar lavage (BAL) cells were obtained from non-smokers, healthy smokers, and GOLD 1-3 COPD subjects. Iron-positive cells were quantified histologically, and the expression of iron uptake (transferrin and transferrin receptor), storage (ferritin) and export (ferroportin) genes was examined by real-time RT-PCR assay. Percentage of iron-positive cells and expression levels of iron metabolism genes were examined for correlations with airflow limitation indices (forced expiratory volume in the first second (FEV1) and the ratio between FEV1 and forced vital capacity (FEV1/FVC)). The alveolar macrophage was identified as the predominant iron-positive cell type in lung tissues. Furthermore, the quantity of iron deposit and the percentage of iron positive macrophages were increased with COPD and emphysema severity. The mRNA expression of iron uptake and storage genes transferrin and ferritin were significantly increased in GOLD 4 COPD lungs compared to donors (6.9 and 3.22 fold increase, respectively). In BAL cells, the mRNA expression of transferrin, transferrin receptor and ferritin correlated with airway obstruction. These results support activation of an iron sequestration mechanism by alveolar macrophages in COPD, which we postulate is a protective mechanism against iron induced oxidative stress.
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine Washington University, St. Louis, Missouri, United States of America; Institut National de la Santé Et de la Recherche Medicale Unit 903, University Hospital, Reims, France.
Quentin
Q
Philippot
Institut National de la Santé Et de la Recherche Medicale Unit 903, University Hospital, Reims, France; Department of Pulmonary Medicine, University Hospital of Reims, France.
Gaëtan
G
Deslée
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine Washington University, St. Louis, Missouri, United States of America.
Tracy L
TL
Adair-Kirk
Department of Radiology, Washington University, St. Louis, Missouri, United States of America.
Jason C
JC
Woods
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine Washington University, St. Louis, Missouri, United States of America.
Derek
D
Byers
Department of Radiology, Washington University, St. Louis, Missouri, United States of America.
Susan
S
Conradi
Department of Pulmonary Medicine, University Hospital of Reims, France; EA4683, University of Reims, Reims, France.
Sandra
S
Dury
Institut National de la Santé Et de la Recherche Medicale Unit 903, University Hospital, Reims, France; Department of Pulmonary Medicine, University Hospital of Reims, France.
Jeanne Marie
JM
Perotin
Department of Pulmonary Medicine, University Hospital of Reims, France; EA4683, University of Reims, Reims, France.
François
F
Lebargy
EA4683, University of Reims, Reims, France.
Christelle
C
Cassan
EA4683, University of Reims, Reims, France.
Richard
R
Le Naour
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine Washington University, St. Louis, Missouri, United States of America.
Michael J
MJ
Holtzman
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine Washington University, St. Louis, Missouri, United States of America.
Richard A
RA
Pierce
D000328:Adult; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007501:Iron / Q000378:metabolism*; D016676:Macrophages, Alveolar / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism / Q000473:pathology*; D011990:Receptors, Transferrin / Q000235:genetics*; D014168:Transferrin / Q000235:genetics*; D055815:Young Adult
D011990:Receptors, Transferrin; D014168:Transferrin; D007501:Iron