Increased Concentrations of Iron and Isoferritins in the Lower Respiratory Tract of Patients with Stable Cystic Fibrosis

Abstract

Reactive oxygen species may contribute to airway injury in patients with cystic fibrosis (CF) and iron catalyzes oxidant injury by promoting generation of highly reactive hydroxyl radicals. Iron in the lower respiratory tract may be free, ferritin bound (from which iron can be reductively mobilized), or transferrin bound (which generally prevents iron mobilization). Ferritin is composed of subunits that are heavy (H) or light (L), and H-rich ferritins have additional biologic effects including inhibition of lymphocyte proliferation and cell growth. To assess concentrations of iron and iron-binding proteins in the lower respiratory tract of patients with CF, we measured iron (ferrozine), L-ferritin, H-ferritin, and transferrin (enzyme-linked immunosorbent assay [ELISA]) in bronchoalveolar lavage (BAL) fluid recovered from stable patients with CF (n = 8), healthy nonsmokers (NS; n = 8), or heavy cigarette smokers (HS; n = 8). Iron was detected in BAL fluid from patients with CF and HS, but not NS, with higher iron concentrations in patients with CF (42.0 +/- 11.6 microgram/dl) than in HS (9.9 +/- 2.6 microgram/dl, p < 0.05). Ferritin was present in all BAL fluids, with higher total ferritin (L + H) in patients with CF (647 +/- 84 ng/ml) than in HS (181 +/- 25 ng/ml, p < 0.005) or NS (9 +/- 3 ng/ml, p < 0.0005). Ferritin recovered from HS and NS lungs was < 2% H type, whereas ferritin in CF lungs was > 40% H-type ferritin. Transferrin concentrations in BAL fluid were not different in any group. Tumor necrosis factor (TNF)-alpha was present only in BAL samples from patients with CF. To assess whether TNF-alpha contributed to H-ferritin accumulation in CF lungs, we treated lung epithelial cells (A549) with iron alone (FeSO(4), 10-40 microM) or with iron and TNF-alpha (5-20 ng/ml). Iron-treated A549 cells synthesized almost entirely L-ferritin whereas exposure to TNF-alpha with iron caused a dose-dependent increase in accumulation of H-type ferritin. These findings suggest that oxidant injury could be promoted in lungs of patients with cystic fibrosis by iron mobilized from extracellular ferritin and, in addition, that TNF-alpha-promoted accumulation of H-type ferritin may impair local immune function and cell growth.

Expression of the H-subunit and L-subunit of ferritin in bone marrow macrophages and cells of the erythron during cellular immune activation

“…The findings of this quantitative, in vivo study on bone marrow macrophages are in line with in vitro experiments with various cell types that showed an increase in H-subunit expression relative to L-subunit expression upon cytokine activation [15,36,[40][41][42][43].…”

Iron acquisition in the cystic fibrosis lung and potential for novel therapeutic strategies

“…In a recent study of CF pulmonary exacerbation, patients following treatment with intravenous antibiotics had lower hepcidin and IL-6 levels in serum, increased serum iron, and a trend towards lower sputum iron levels -further evidence of the impact of infection and inflammation on iron metabolism (Gifford et al, 2012). Not surprisingly, given the inflammatory environment of the CF lung, elevated levels of iron and ferritin have been detected in CF sputum by a number of studies (Stites et al, 1998(Stites et al, , 1999Reid et al, 2004Reid et al, , 2007Gray et al, 2010). More recently in a comprehensive study of iron in CF, Ghio et al (2013) demonstrated increased levels of iron and iron-related proteins in bronchoalveolar lavage fluids from CF children, in macrophages of explanted CF lungs and in lung tissue from CF patients -clear evidence of altered iron homeostasis and of iron accumulation in the CF airways (Ghio et al, 2013).…”

Acute Phase Proteins: Ferritin and Ferritin Isoforms

“…Cytokines, central mediators of the inflammatory activity of the acute phase response, have been shown to up-regulate the expression of ferritin (Konijn & Hershko, 1977;Piñero et al, 2000). Pro-inflammatory cytokines reported to have the ability to induce ferritin expression include Il-1α, Il-1β, Il-2, Il-6, tumour necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) (Miller et al, 1991;Pang et al, 1996;Rogers et al, 1990;Rogers, 1996;Stites et al, 1999;. These cytokines modulate ferritin expression by both transcriptional and translational mechanisms (Piñero et al, 2000), but largely by an increase in the rate of transcription of the ferritin genes (Miller et al, 1991;.…”