Iron Accumulation in Lung Allografts After Transplantation*

doi:10.1378/chest.112.2.435

Chest

Volume 112, Issue 2, August 1997, Pages 435-439

https://doi.org/10.1378/chest.112.2.435 Get rights and content

Lung transplantation has become a therapeutic option for end-stage pulmonary diseases, but after transplantation, infections and obliterative bronchiolitis (OB) are major causes of long-term morbidity and mortality. OB is a fibroproliferative disease, of poorly understood etiology, characterized by an irreversible decline in allograft function. Because diseases with tissue iron overload are characterized by fibrosis and end-organ failure, we studied the iron concentrations in BAL fluid and lung tissue in 10 lung allograft patients. BAL fluid revealed significantly elevated iron concentrations in allograft patients compared with five normal volunteers (135±16.54 µmol/L vs 33.65±7.48 µmol/L, respectively). Prussian blue staining of biopsy specimens of lung allograft tissue revealed an accumulation of iron primarily in alveolar macrophages. Immunohistochemical stains for ferritin revealed accumulation of the protein in macrophages, interstitium, vascular walls, and bronchiolar epithelium. Iron studies of the blood (serum ferritin and iron concentrations) revealed no evidence for systemic iron overload. In conclusion, patients with pulmonary allografts appear to have elevated concentrations of iron in lung tissue. This iron overload may place the allografts at increased risk of metal-mediated injury and fibrosis.

Section snippets

Subject Groups and Study Protocol

Five healthy volunteers (29 to 38 years old) were recruited to obtain control data for BAL measurements. The subjects were all nonsmokers and were not taking any medications. All had normal results of spirometry and chest radiographs.

Ten patients who underwent lung transplantation at Duke University were included in the study population (Table 1). All donor lungs received prostaglandin E in their main pulmonary artery, followed by 5 to 6 L infusion of modified Eurocollins solution for lung

Results

Microscopic examination of transbronchial lung biopsy tissue stained for iron, lactoferrin, and ferritin demonstrated evidence of iron sequestration in all of the cases. The Prussian blue stain showed the presence of iron primarily within alveolar macrophages (Fig 1, left panel, top and bottom), and these corresponded to the macrophages with fine brown cytoplasmic staining observed on hematoxylin-eosinstained sections. A similar distribution was observed with immunohistochemical staining for

Discussion

The presence of chemically reactive iron in tissue can increase the formation of reactive oxygen species that have the potential to injure tissues. Consequently, living systems have designed efficient means of controlling iron transport and storage in complexes that minimize the risk of electron transport to molecular oxygen. Despite this, an excess of intracellular iron stored in ferritin may increase the potential to promote the formation of metal-catalyzed hydroxyl radical.¹⁰

Our study shows

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Diesel exhaust PM2.5 greatly deteriorates fibrosis process in pre-existing pulmonary fibrosis via ferroptosis
2023, Environment International
Citation Excerpt :
In addition, iron deposition accompanied by ferroptosis and EMT in alveolar type II cells suggested to promote the development of pulmonary fibrosis (Cheng et al., 2021). Further, the iron levels in the lung tissue and alveolar lavage fluid are elevated during lung transplantation, which may lead to occurrence of oxidative damage in the allografts and subsequent initiation of fibrosis (Baz et al., 1997). The present study also showed that PM2.5 induced the ferroptosis of TGF-β1-treated lung epithelial cells mediated by HO-1, and this process may be associated with impaired mitochondrial function.
Fine particulate matter (PM2.5) has been widely reported to contribute to the pathogenesis of pulmonary diseases. The direct hazardous effect of PM2.5 on the respiratory system at high concentrations in vitro and in vivo have been well identified. However, its effect on the pre-existing respiratory diseases of patients at environment-related concentrations remains unclear. Diesel exhaust PM2.5 as a primary representative of ambient PM2.5 fine particles were used to investigated the effect of PM2.5 on the fibrosis progression of existing pulmonary fibrosis disease models. This study reported that PM2.5 could result in the enhanced sensitivity to fibrotic response, which may be ascribed to ferroptosis induced by PM2.5 in damaged lung areas. Proteomic analysis revealed that the upregulation of HO-1 as a key mechanism in the ferroptosis and exacerbation of pulmonary fibrosis induced by PM2.5. As a result, HO-1 degraded heme-containing protein and released iron in fibrotic cells, leading to generation of mitochondrial ROS and impaired mitochondrial function. Transmission electron microscopic assay verified that PM2.5 entered the mitochondria of fibrotic cells and was accompanied by significant mitochondrial morphological changes characterized by increased mitochondrial membrane density and reduced mitochondrial size. The HO-1 inhibitor zinc protoporphyrin and mitochondrion-targeted antioxidant Mito-TEMPO significantly attenuated PM2.5-induced ferroptosis and exacerbation of fibrosis. In addition, AMPK-ULK1 axis-triggered autophagy activation and NCOA4-mediated degradation of ferritin by autophagy were found to be related to the PM2.5-induced ferroptosis of fibrotic cells. As evidenced by the inhibition of autophagy with 3-methyladenine or AMPK inhibitor, NCOA4 knockdown decreased intracellular iron accumulation and lipid peroxidation, thereby relieving PM2.5-induced epithelial–mesenchymal transition and cell death in fibrotic cells. Overall, this study provided experimental support for the idea that PM2.5 greatly deteriorates fibrosis process in pre-existing pulmonary fibrosis, and HO-1-mediated mitochondrial dysfunction and NCOA4-mediated ferritinophagy are jointly required for the PM2.5-induced ferroptosis and enhanced fibrosis effects.
Role of iron in the pathogenesis of respiratory disease
2017, International Journal of Biochemistry and Cell Biology
Citation Excerpt :
TRALI is induced by transfusion of blood products, which is known to elevate systemic iron levels in patients, resulting in oxidative stress and a number of pathological consequences (Collard, 2014; Dani et al., 2004; Gattermann and Rachmilewitz, 2011; Jenkins et al., 2007; Peters et al., 2015). Increased iron accumulation is also observed following lung transplantation, with higher levels of iron accumulation associated with increased risk of acute organ rejection (Baz et al., 1997; Reid et al., 2001; Sandmeier et al., 2005). Pulmonary alveolar proteinosis (PAP) is characterised by abnormal accumulation of protein-rich surfactant and inflammation, with unusual accumulation in the lung of alveolar macrophages containing intracellular surfactant-like material and is associated with impaired lung function (Rosen et al., 1958; Shimizu et al., 2011).
Iron is essential for many biological processes, however, too much or too little iron can result in a wide variety of pathological consequences, depending on the organ system, tissue or cell type affected. In order to reduce pathogenesis, iron levels are tightly controlled in throughout the body by regulatory systems that control iron absorption, systemic transport and cellular uptake and storage. Altered iron levels and/or dysregulated homeostasis have been associated with several lung diseases, including chronic obstructive pulmonary disease, lung cancer, cystic fibrosis, idiopathic pulmonary fibrosis and asthma. However, the mechanisms that underpin these associations and whether iron plays a key role in the pathogenesis of lung disease are yet to be fully elucidated. Furthermore, in order to survive and replicate, pathogenic micro-organisms have evolved strategies to source host iron, including freeing iron from cells and proteins that store and transport iron. To counter these microbial strategies, mammals have evolved immune-mediated defence mechanisms that reduce iron availability to pathogens. This interplay between iron, infection and immunity has important ramifications for the pathogenesis and management of human respiratory infections and diseases. An increased understanding of the role that iron plays in the pathogenesis of lung disease and respiratory infections may help inform novel therapeutic strategies. Here we review the clinical and experimental evidence that highlights the potential importance of iron in respiratory diseases and infections.
Disruption of iron homeostasis and lung disease
2009, Biochimica et Biophysica Acta - General Subjects
As a result of a direct exchange with the external environment, the lungs are exposed to both iron and agents with a capacity to disrupt the homeostasis of this metal (e.g. particles). An increased availability of catalytically reactive iron can result from these exposures and, by generating an oxidative stress, this metal can contribute to tissue injury. By importing this Fe³⁺ into cells for storage in a chemically less reactive form, the lower respiratory tract demonstrates an ability to mitigate both the oxidative stress presented by iron and its potential for tissue injury. This means that detoxification is accomplished by chemical reduction to Fe²⁺ (e.g. by duodenal cytochrome b and other ferrireductases), iron import (e.g. by divalent metal transporter 1 and other transporters), and storage in ferritin. The metal can subsequently be exported from the cell (e.g. by ferroportin 1) in a less reactive state relative to that initially imported. Iron is then transported out of the lung via the mucociliary pathway or blood and lymphatic pathways to the reticuloendothelial system for long term storage. This coordinated handling of iron in the lung appears to be disrupted in several acute diseases on the lung including infections, acute respiratory distress syndrome, transfusion-related acute lung injury, and ischemia–reperfusion. Exposures to bleomycin, dusts and fibers, and paraquat similarly alter iron homeostasis in the lung to affect an oxidative stress. Finally, iron homeostasis is disrupted in numerous chronic lung diseases including pulmonary alveolar proteinosis, transplantation, cigarette smoking, and cystic fibrosis.
Single-institution Study Evaluating the Utility of Surveillance Bronchoscopy After Lung Transplantation
2009, Journal of Heart and Lung Transplantation
Citation Excerpt :
These percentages may be accurate, as corroborated by Baz et al,28 who found that 31% of their procedures had clinical indications. Other programs with surveillance protocols reported higher percentages of clinical indications, ranging from 43% to 63%.24,25,28,29 In the present study, 38 of 89 (43%) procedures in the SB group had clinical indications, primarily by PFT criteria, with pulmonary mechanics in 3 patients not improving as expected soon after transplantation.
Many lung transplant physicians advocate surveillance bronchoscopy with transbronchial lung biopsy and bronchoalveolar lavage (TBB/BAL) to monitor lung recipients despite limited evidence this strategy improves outcomes. This report compares rates of infection (INF), acute rejection (AR), bronchiolitis obliterans syndrome (BOS) and survival in lung allograft recipients managed with surveillance TBB/BAL (SB) versus those with clinically indicated TBB/BAL (CIB).
We reviewed 47 consecutive recipients transplanted between March 2002 and August 2005. Of these recipients, 24 consented to a multi-center trial requiring SB and 23 were managed by our usual practice of CIB. Rates of freedom from INF, AR, BOS and survival were compared. BOS and AR were diagnosed according to published guidelines from the International Society for Heart and Lung Transplantation.
A total of 240 TBB/BALs were performed. CIB and SB groups underwent 84 (3.7 ± 3.4/patient) and 156 (6.5 ± 2.0/patient) TBB/BALs, respectively. In the SB group, 54 (2.2 ± 1.6/patient) TBB/BALs were true surveillance procedures, whereas 102 (4.2 ± 2.3/patient) were clinically indicated. No AR episode requiring treatment was detected by true surveillance. Freedom from respiratory INF, AR, BOS and survival in the SB and CIB groups showed no significant differences. Five patients in the CIB group remained stable without requiring TBB/BAL. In the SB group, 4 previously asymptomatic patients developed pneumonia within 2 weeks of surveillance TBB/BAL.
With no obvious advantage identified, surveillance bronchoscopy may pose a risk to stable lung transplant recipients. A multi-center, controlled trial is required to validate the utility and safety of surveillance bronchoscopy in lung transplantation.
Disruption of iron homeostasis in the lungs of transplant patients
2005, Journal of Heart and Lung Transplantation
Oxidative stress has been proposed as a mechanism of injury underlying obliterative bronchiolitis. Catalytically reactive iron is a potential source of reactive oxygen species in transplanted tissue. Using samples acquired from surveillance bronchoalveolar lavage (BAL), we tested the postulate that there is a disruption of iron equilibrium in transplanted lung, which can worsen with time.
A control group of 5 healthy, non-smoking volunteers underwent BAL. Five bilateral lung transplant patients underwent surveillance BAL with transbronchial lung biopsies. The BAL fluid concentrations of protein, albumin, total iron, lactoferrin, ferritin, transferrin receptor and total iron binding capacity were measured.
The mean ages in the control and transplant groups were 25.0 ± 2.4 and 34.6 ± 5.0 years, respectively. Patients were transplanted for cystic fibrosis (n = 3), primary ciliary dyskinesia (n = 1) and bronchiolitis obliterans (n = 1). Surveillance bronchoscopies were performed at 100.6 ± 63.3, 175.0 ± 87.7 and 259.2 ± 82 days post-transplant. No significant differences were noted in BAL protein, albumin and total iron binding capacity (TIBC) levels between the 2 groups. The BAL iron, transferrin, transferrin receptor, lactoferrin and ferritin levels were significantly elevated in transplant patients relative to controls. With time after transplantation, there were increases in lavage iron, transferrin receptor, lactoferrin and ferritin concentrations.
Abnormally high levels of iron and its homeostatic proteins were found in the lung allografts, and levels appeared to increase with time. This supports a disruption in the normal homeostasis of this metal after transplantation and a potential role for a catalyzed oxidative stress in bronchiolitis obliterans. The use of iron-depleting therapy is a possible means for preventing injury in the lung allograft.
Iron accumulation in lung allografts is associated with acute rejection but not with adverse outcome
2005, Chest
Citation Excerpt :
Both suggestions, however, seem to be impractical. In the literature,12, 13 it is argued that elevated iron content in the lung allograft may cause metal-induced injury and fibrosis mediated by iron-generated oxidative stress. However, from our results we cannot confirm this apprehension.
Iron content in lung allografts is increased after transplantation. It was hypothesized that this may lead to fibrosis and posttransplant bronchiolitis obliterans syndrome (BOS).
In a prospective study, we evaluated 399 BAL fluid (BALF) and transbronchial lung biopsy samples obtained concurrently from 72 consecutive lung transplant recipients.
The hemosiderin scores (HSs) of the BALF samples increased steadily during the postoperative period (p < 0.001). Patients with at least one acute rejection episode (AR) grade ≥ A2 event had higher mean HSs, the difference being significant after the second (p < 0.008) and the sixth postoperative months (p < 0.05). The HS correlated with the number of ARs (p < 0.004), and it significantly increased after the first AR (p < 0.04). Except for oral anticoagulation, no other risk factors for elevated iron content were found. There was no correlation between HS or number of ARs and the development of BOS or survival, respectively.
Progressive iron accumulation in lung allografts seems to be caused mainly by an AR, possibly due to perivascular leakage of erythrocytes. Neither increased HS nor the frequency of ARs were risk factors for subsequent development of BOS. Early detection and treatment of ARs might uncouple their association with BOS.

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Chest

Iron Accumulation in Lung Allografts After Transplantation*

Section snippets

Subject Groups and Study Protocol

Results

Discussion

Biochem Pharmacol

J Thorac Cardiovasc Surg

Chest

J Biol Chem

Arch Biochem Biophys

Chest

The registry of the International Society for Heart and Lung Transplantation: 11th official report

J Heart Lung Transplant

Sequelae of cytomegalovirus pulmonary infections in lung allograft recipients

Am Rev Respir Dis

Risk factors for obliterative bronchiolitis in heart-lung transplant recipients

Transplant

Glutathione depletion in epithelial lining fluid of lung allograft patients

Am J Respir Crit Care Med

Idiopathic pulmonary hemosiderosis and related disorders in infancy and childhood

Perspect Pediatr Pathol

Pathogenesis of hepatic fibrosis in experimental iron overload

Br J Haematol

A working formulation for the standardization of nomenclature in the diagnosis of heart and lung rejection: lung rejection study group

J Heart Transplant