Iron-binding and storage proteins in sputum.
Induced sputum (IS) and bronchoalveolar lavage (BAL) sample different lung compartments, with IS obtaining secretions from the surfaces of the bronchial airways and BAL sampling secretions from the alveolar airspaces. Deposition of iron-containing particulate matter occurs preferentially in the bronchial airways compared to the distal airspaces. Iron-binding and storage proteins have been measured in BAL in healthy humans, where they act to sequester and detoxify available iron; however, their comparative levels in the airways are not well defined. Seventeen (n = 17) healthy, nonsmoking volunteers underwent sputum induction and fiber-optic bronchoscopy with lavage in order to measure and compare the levels of iron and iron-binding and storage proteins in BAL, bronchial lavage (BL), and IS. Relative to BAL and BL specimens, concentrations of total iron, ferritin, lactoferrin, and total iron binding capacity (TIBC) were significantly increased and transferrin decreased in IS. Immunohistochemical staining showed increased ferritin, lactoferrin, and TIBC in IS. Constitutive levels of iron and iron-binding and storage proteins (except for transferrin) are in greatest concentration in the bronchial airways relative to the alveolar airspaces in healthy humans. We speculate that these proteins reflect activated antioxidant defense mechanisms resulting from the preferential deposition of iron-containing particulate matter in the airways. The finding of decreased transferrin with increased ferritin suggests a local cellular response via iron-response elements (IRE) associated with the mRNAs for these two iron-binding proteins.
Alexis
Neil E
NE
Center for Environmental Medicine and Lung Biology, and Division of Pulmonary Medicine and Allergy, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina 27599, USA. Neil_Alexis@med.unc.edu
Richards
Judy H
JH
Carter
Jacqueline D
JD
Ghio
Andrew J
AJ
D000293:Adolescent; D000328:Adult; D000393:Air Pollutants / Q000009:adverse effects*; D000975:Antioxidants; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D001999:Bronchoscopy; D002352:Carrier Proteins / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D033862:Iron-Binding Proteins; D010316:Particle Size; D013183:Sputum / Q000737:chemistry; D033863:Transferrin-Binding Proteins
D000393:Air Pollutants; D000975:Antioxidants; D002352:Carrier Proteins; D033862:Iron-Binding Proteins; D033863:Transferrin-Binding Proteins