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Increased iron sequestration in alveolar macrophages in chronic obstructive pulmonary disease.

ABSTRACT: 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.

SUBMITTER: Philippot Q

PROVIDER: S-EPMC4006868 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Increased iron sequestration in alveolar macrophages in chronic obstructive pulmonary disease.

Philippot Quentin Q Deslée Gaëtan G Adair-Kirk Tracy L TL Woods Jason C JC Byers Derek D Conradi Susan S Dury Sandra S Perotin Jeanne Marie JM Lebargy François F Cassan Christelle C Le Naour Richard R Holtzman Michael J MJ Pierce Richard A RA

PloS one 20140501 5

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 ...[more]

PMID: 24789352

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Project description:BACKGROUND:Increased iron availability modifies cardiorespiratory function in healthy volunteers and improves exercise capacity and quality of life in patients with heart failure or pulmonary hypertension. We hypothesised that intravenous iron would produce improvements in oxygenation, exercise capacity and quality of life in patients with chronic obstructive pulmonary disease (COPD). METHODS:We performed a randomised, placebo-controlled, double-blind trial in 48 participants with COPD (mean±SD: age 69±8 years, haemoglobin 144.8±13.2?g/L, ferritin 97.1±70.0?µg/L, transferrin saturation 31.3%±15.2%; GOLD grades II-IV), each of whom received a single dose of intravenous ferric carboxymaltose (FCM; 15?mg/kg bodyweight) or saline placebo. The primary endpoint was peripheral oxygen saturation (SpO2) at rest after 1?week. The secondary endpoints included daily SpO2, overnight SpO2, exercise SpO2, 6?min walk distance, symptom and quality of life scores, serum iron indices, spirometry, echocardiographic measures, and exacerbation frequency. RESULTS:SpO2 was unchanged 1?week after FCM administration (difference between groups 0.8%, 95%?CI -0.2% to 1.7%). However, in secondary analyses, exercise capacity increased significantly after FCM administration, compared with placebo, with a mean difference in 6?min walk distance of 12.6?m (95%?CI 1.6 to 23.5?m). Improvements of ?40?m were observed in 29.2% of iron-treated and 0% of placebo-treated participants after 1?week (p=0.009). Modified MRC Dyspnoea Scale score was also significantly lower after FCM, and fewer participants reported scores ?2 in the FCM group, compared with placebo (33.3% vs 66.7%, p=0.02). No significant differences were observed in other secondary endpoints. Adverse event rates were similar between groups, except for hypophosphataemia, which occurred more frequently after FCM (91.7% vs 8.3%, p<0.001). CONCLUSIONS:FCM did not improve oxygenation over 8 weeks in patients with COPD. However, this treatment was well tolerated and produced improvements in exercise capacity and functional limitation caused by breathlessness. These effects on secondary endpoints require confirmation in future studies. TRIAL REGISTRATION NUMBER:ISRCTN09143837.

Dataset Information

Increased iron sequestration in alveolar macrophages in chronic obstructive pulmonary disease.

Publications

Increased iron sequestration in alveolar macrophages in chronic obstructive pulmonary disease.

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