Oxidants/antioxidants in idiopathic pulmonary fibrosis

HIP/PAP protects against bleomycin-induced lung injury and inflammation and subsequent fibrosis in mice

Hepatocarcinoma‐intestine‐pancreas/pancreatitis‐associated protein (HIP/PAP), a C‐type lectin, exerts anti‐oxidative, anti‐inflammatory, bactericidal, anti‐apoptotic, and mitogenic functions in several cell types and tissues. In this study, we explored the role of HIP/PAP in pulmonary fibrosis (PF). Expression of HIP/PAP and its murine counterpart, Reg3B, was markedly increased in fibrotic human and mouse lung tissues. Adenovirus‐mediated HIP/PAP expression markedly alleviated bleomycin (BLM)‐induced lung injury, inflammation, and fibrosis in mice. Adenovirus‐mediated HIP/PAP expression alleviated oxidative injury and lessened the decrease in pulmonary superoxide dismutase (SOD) activity in BLM‐treated mice, increased pulmonary SOD expression in normal mice, and HIP/PAP upregulated SOD expression in cultured human alveolar epithelial cells (A549) and human lung fibroblasts (HLF‐1). Moreover, in vitro experiments showed that HIP/PAP suppressed the growth of HLF‐1 and ameliorated the H₂O₂‐induced apoptosis of human alveolar epithelial cells (A549 and HPAEpiC) and human pulmonary microvascular endothelial cells (HPMVEC). In HLF‐1, A549, HPAEpiC, and HPMVEC cells, HIP/PAP did not affect the basal levels, but alleviated the TGF‐β1‐induced down‐regulation of the epithelial/endothelial markers E‐cadherin and vE‐cadherin and the over‐expression of mesenchymal markers, such as α‐SMA and vimentin. In conclusion, HIP/PAP was found to serve as a potent protective factor in lung injury, inflammation, and fibrosis by attenuating oxidative injury, promoting the regeneration of alveolar epithelial cells, and antagonizing the pro‐fibrotic actions of the TGF‐β1/Smad signaling pathway.

Involvement of the Prion Protein in the Protection of the Human Bronchial Epithelial Barrier Against Oxidative Stress

Aim: Bronchial epithelium acts as a defensive barrier against inhaled pollutants and microorganisms. This barrier is often compromised in inflammatory airway diseases that are characterized by excessive oxidative stress responses, leading to bronchial epithelial shedding, barrier failure, and increased bronchial epithelium permeability. Among proteins expressed in the junctional barrier and participating to the regulation of the response to oxidative and to environmental stresses is the cellular prion protein (PrP^C). However, the role of PrP^C is still unknown in the bronchial epithelium. Herein, we investigated the cellular mechanisms by which PrP^C protein participates into the junctional complexes formation, regulation, and oxidative protection in human bronchial epithelium. Results: Both PrP^C messenger RNA and mature protein were expressed in human epithelial bronchial cells. PrP^C was localized in the apical domain and became lateral, at high degree of cell polarization, where it colocalized and interacted with adherens (E-cadherin/γ-catenin) and desmosomal (desmoglein/desmoplakin) junctional proteins. No interaction was detected with tight junction proteins. Disruption of such interactions induced the loss of the epithelial barrier. Moreover, we demonstrated that PrP^C protection against copper-associated oxidative stress was involved in multiple processes, including the stability of adherens and desmosomal junctional proteins. Innovation: PrP^C is a pivotal protein in the protection against oxidative stress that is associated with the degradation of adherens and desmosomal junctional proteins. Conclusion: Altogether, these results demonstrate that the loss of the integrity of the epithelial barrier by oxidative stress is attenuated by the activation of PrP^C expression, where deregulation might be associated with respiratory diseases.

Lipid Peroxidation and GPX4 Inhibition Are Common Causes for Myofibroblast Differentiation and Ferroptosis

Ferroptosis is a new form of regulated cell death. Fibroblast-to-myofibroblast differentiation is known to be involved in the pathogenesis of idiopathic pulmonary fibrosis. Utilizing HFL1 cell line treated with transforming growth factor-β1 (TGF-β1), we investigated the relationship between ferroptosis and pulmonary fibrosis, and the function of glutathione peroxidase 4 (GPX4) in them. The results indicated that α-smooth muscle actin and collagen I (COL I) mRNA expression levels increased significantly from 24 h after TGF-β1-treatment, and further rose after TGF-β1+erastin treatment. The levels of reactive oxygen species (ROS), malondialdehyde were increased, and the levels of GPX4 mRNA and protein were reduced after treatment with TGF-β1, and all these were magnified after TGF-β1+erastin treatment. All these changes induced by TGF-β1 and erastin can be recovered by Fer-1 treatment. The cell viability rate was decreased significantly when treated with TGF-β1+erastin, but no obvious variation of cell viability was found in TGF-β1-treated group and in other groups, suggesting that ROS, lipid peroxidation, and GPX4 inhibition are not sufficient conditions for ferroptosis. Collectively, our study reveals that ROS, lipid peroxidation, and GPX4 play important roles in pulmonary fibrosis and ferroptosis induced by erastin. Erastin promoted fibroblast-to-myofibroblast differentiation by increasing lipid peroxidation and inhibiting the expression of GPX4. Fer-1 may inhibit pulmonary fibrosis and ferroptosis through suppressing lipid peroxidation and enhancing GPX4 expression.

Trace metals in fluids lining the respiratory system of patients with idiopathic pulmonary fibrosis and diffuse lung diseases

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease with a poor prognosis and an undefined etiopathogenesis. Oxidative stress contributes to alveolar injury and fibrosis development and, because transition metals are essential to the functioning of most proteins involved in redox reactions, a better knowledge of metal concentrations and metabolism in the respiratory system of IPF patients may provide a valuable complementary approach to prevent and manage a disease which is often misdiagnosed or diagnosed in later stages. The present review summarizes and discusses literature data on the elemental composition of bronchoalveolar lavage (BAL), induced sputum and exhaled breath condensate (EBC) from patients affected by IPF and healthy subjects. Available data are scanty and the lack of consistent methods for the collection and analysis of lung and airways lining fluids makes it difficult to compare the results of different studies. However, the elemental composition of BAL samples from IPF patients seems to have a specific profile that can be distinguished from that of patients with other interstitial lung diseases (ILD) or control subjects. Suggestions are given towards standard sampling and analytical procedures of BAL samples, in the aim to assess typical element concentration patterns and their potential role as biomarkers of IPF.

Autophagy induction by celastrol augments protection against bleomycin-induced experimental pulmonary fibrosis in rats: Role of adaptor protein p62/ SQSTM1

Pulmonary fibrosis (PF) is a chronic pulmonary disease of unknown cause with high mortality. Autophagy is an important homeostatic process that decides the fate of cells under stress conditions. This study is aimed to investigate whether impaired autophagic activity leads to fibrosis and pharmacological induction of autophagy provides protection against bleomycin (BLM)-induced PF. A single dose of BLM (3 U/kg body weight) was administered intratracheally to induce fibrosis in rats. Celastrol, a triterpenoid (5 mg/kg body weight, intraperitoneally) was given in every 81 h for a period of 28 days. Western blot and Confocal microscopic analysis of rat lung tissue samples revealed that celastrol induces autophagy in BLM-induced rats. Transmission electron microscopic analysis supports the above findings. Celastrol increased the expressions of Beclin 1 and Vps 34, promoted the up-regulation of Atg5-Atg12-16 formation and enhanced the lipidation of LC3I to LC3II suggesting induction of autophagy by celastrol provide protection against lung fibrosis. Further, we revealed that celastrol activates autophagy by inhibiting PI3K/Akt mediated mTOR expression. In addition, we show evidences that lack of autophagy leads to accumulation of p62, an autophagy adaptor protein that is degraded by celastrol. This study helps to describe the importance of autophagic cell death as a possible therapeutic target against lung fibrosis, and celastrol as a potential candidate for the treatment options for PF.

Oxidative Modifications of Protein Tyrosyl Residues Are Increased in Plasma of Human Subjects with Interstitial Lung Disease

RATIONALE

Interstitial lung diseases (ILDs) are associated with oxidative stress. Plasma biomarkers that are directly linked to oxidative stress responses in this disease have not been identified. Stable oxidation products of tyrosine residues in proteins may reflect the oxidative microenvironment in the lung or a systemic inflammatory state.

OBJECTIVES

To determine if levels of protein tyrosine oxidation are elevated in plasma of patients with ILD compared with an age- and sex-matched healthy control cohort.

METHODS

Three tyrosine oxidation products (3-chlorotyrosine, 3-nitrotyrosine, and o,o'-dityrosine) were quantified by tandem mass spectrometry in cellular models, a mouse model of injury-induced fibrosis, and in plasma of healthy control subjects and patients with ILD (n = 42 in each group).

MEASUREMENTS AND MAIN RESULTS

Plasma levels of 3-chlorotyrosine, 3-nitrotyrosine, and o,o'-dityrosine were markedly elevated in patients with ILD compared with control subjects with receiver operating characteristic curves separating these groups of 0.872, 0.893, and 0.997, respectively. In a murine model of lung fibrosis, levels of all three oxidative tyrosine modifications were increased in plasma and lung tissue. Cellular models support a critical role for a heme peroxidase and enzymatic sources of reactive oxygen species in the generation of these oxidized products.

CONCLUSIONS

We demonstrate an increase in oxidized tyrosine moieties within proteins in the circulating plasma of patients with ILD. These data support the potential for development of oxidative stress-related biomarkers in early diagnosis, prognostication, and/or in evaluating responsiveness to emerging therapies for ILD.

Lung extracellular matrix and redox regulation

Pulmonary fibrosis affects millions worldwide and, even though there has been a significant investment in understanding the processes involved in wound healing and maladaptive repair, a complete understanding of the mechanisms responsible for lung fibrogenesis eludes us, and interventions capable of reversing or halting disease progression are not available. Pulmonary fibrosis is characterized by the excessive expression and uncontrolled deposition of extracellular matrix (ECM) proteins resulting in erosion of the tissue structure. Initially considered an 'end-stage' process elicited after injury, these events are now considered pathogenic and are believed to contribute to the course of the disease. By interacting with integrins capable of signal transduction and by influencing tissue mechanics, ECM proteins modulate processes ranging from cell adhesion and migration to differentiation and growth factor expression. In doing so, ECM proteins help orchestrate complex developmental processes and maintain tissue homeostasis. However, poorly controlled deposition of ECM proteins promotes inflammation, fibroproliferation, and aberrant differentiation of cells, and has been implicated in the pathogenesis of pulmonary fibrosis, atherosclerosis and cancer. Considering their vital functions, ECM proteins are the target of investigation, and oxidation-reduction (redox) reactions have emerged as important regulators of the ECM. Oxidative stress invariably accompanies lung disease and promotes ECM expression directly or through the overproduction of pro-fibrotic growth factors, while affecting integrin binding and activation. In vitro and in vivo investigations point to redox reactions as targets for intervention in pulmonary fibrosis and related disorders, but studies in humans have been disappointing probably due to the narrow impact of the interventions tested, and our poor understanding of the factors that regulate these complex reactions. This review is not meant to provide a comprehensive review of this field, but rather to highlight what has been learned and to raise interest in this area in need of much attention.

Lipidomics revealed idiopathic pulmonary fibrosis-induced hepatic lipid disorders corrected with treatment of baicalin in a murine model

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease. The current standard treatment with glucocorticoids (GCs) leads to many adverse effects, and its effectiveness is questionable. Thus, it is critical and urgent to find new drug(s) for treatment of IPF. Baicalin (BAI) is an attractive candidate for this purpose. Herein, utilizing shotgun lipidomics, we revealed that IPF could lead to a lipid disorder of the liver in an animal model induced by bleomycin and confirmed through histopathological studies of the lung. Lipidomics further demonstrated that this disorder could virtually be corrected after treatment with BAI, but not with dexamethasone (DEX) (a commonly used GC for treatment of IPF). In contrast, the treatment with DEX did not improve IPF but led to tremendous alterations in hepatic lipidomes and accumulation of fat in the liver, which was very different from the lipid disorder induced by IPF. The underpinning mechanisms of the IPF-resultant lipid disorder and DEX-induced lipotoxicity as revealed by shotgun lipidomics were extensively discussed. Taken together, the current study showed that IPF could lead to hepatic lipid disorder, which can be treated with BAI, and demonstrated that lipidomics could be a powerful tool for drug screening.

Increase in the protein-bound form of glutathione in human blood after the oral administration of glutathione

The present study examined the impact of the supplementation of glutathione (GSH), γ-L-glutamyl-L-cysteinyl-glycine, on human blood GSH levels. Healthy human volunteers were orally supplemented with GSH (50 mg/kg body weight). Venous blood was collected from the cubital vein before and after ingestion. Plasma was mixed with 3 volumes of ethanol. The supernatant and precipitate were used for the deproteinized and protein fractions of plasma, respectively. Blood cell and plasma fractions were pretreated with 5% trichloroacetic acid-2% 2-mercaptoethanol to reduce the oxidized form of GSH and liberate protein-bound GSH. The 2-mercaptoethanol-pretreated GSH was determined by precolumn derivatization with 6-aminoquinolyl-N-hydroxy succinimidyl carbamate and liquid chromatography-tandem mass spectrometry. There was no significant difference in GSH contents in the deproteinized fraction of plasma and blood cell fraction after GSH ingestion. However, the GSH contents in the protein-bound fraction of plasma significantly (P<0.01) increased from 60 to 120 min after GSH supplementation.

Antifibrotic effect of atorvastatin on paraquat-induced pulmonary fibrosis: role of PPARγ receptors

This study was carried out to highlight the role of PPARγ in the paraquat (PQ)-induced pulmonary fibrosis. Forty-two male Wistar rats were exposed either against saline as a control group or PQ (3.5mg/kg, i.p.) as test groups. The test groups were nominated as PQ (PQ-exposed non-treated animals), pioglitazone (PGT, 10mg/kg, orally), atorvastatin (STN, 10mg/kg, orally), PGT+STN, PGT+GW9662 (1mg/kg, i.p.) and STN+GW9662 (1mg/kg). Atorvastatin but not PGT was able to reverse significantly (P<0.05) the PQ-increased ratio of lung to body weight. STN was successfully able to recover the PQ-reduced antioxidant potency and the GW9662 administration resulted in antagonizing the protective effect of both PGT and STN. Although both PGT and STN were able to reduce the hydrxoproline content of the lungs, GW9662, however, could reverse only STN-related effect. Histochemical studies revealed that PQ exposure resulted in a remarkable increase of fibroblasts and collagen fibers in the interstitial tissue and around vessels and bronchioles, which was improved by the STN administration. Only STN-received animals showed the down-regulation of the TGF-β1 expression and GW9662 was able to antagonize this down-regulation. Co-administration of PGT and STN could not exert any synergistic protective effect. These data suggest that the PQ-induced pulmonary fibrosis could be more effectively reversed by STN rather than PGT. Moreover, STN-induced protective effects might attribute to the regulation of TGF-β1 expression, which is antagonized by PPARγ antagonist, suggesting that STN may improve the PQ-induced damages via PPARγ.

Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic condition of unknown etiology with an unfavorable outcome from progressively deteriorating respiratory function, leading ultimately to death from respiratory failure. It is characterized by sequential acute lung injury resulting in progressive fixed tissue fibrosis, architectural distortion and loss of function. An excess of profibrotic cytokines and/or a deficiency in antifibrotic cytokines have been implicated in the pathological process as has excessive oxidation. IPF is distinguished from other forms of diffuse pulmonary fibrosis by the presence of the specific histological pattern of usual interstitial pneumonitis. Oral corticosteroids are the usual treatment, but objective response rates are poor and good quality studies do not exist. Other therapies either alone or in combination with corticosteroids are widely used, including azathioprine, colchicine, cyclophosphamide and penicillamine. There is a paucity of good quality information regarding the effectiveness of most noncorticosteroid immunosuppressive agents. Older studies of lesser methodological quality have shown benefits from these drugs, generally when added to corticosteroids. Many were retrospective reviews or uncontrolled, nonrandomized, open-label, prospective studies and often included other histological patterns of disease which are now thought to respond better to immunosuppressive agents. The results of intervention with colchicine and azathioprine have been disappointing when assessed by good quality trials using modern diagnostic criteria. Modern high quality studies are lacking for several agents, notably cyclophosphamide and penicillamine. The older agents may yet prove to be effective but further good quality trials will be necessary to assess these agents adequately. Other new anti-inflammatory, antioxidant, antifibrotic or anticytokine compounds are largely untried or unreported. One trial using interferon-gamma-1b showed a significant improvement in pulmonary function but there are concerns regarding the generalizability of this study. Pirfenidone, cyclosporine and acetylcysteine may also prove to be of benefit but current studies are of insufficient quality to allow for any conclusions to be drawn. Currently there is no good evidence to support the routine use of oral corticosteroids, azathioprine, cyclophosphamide, penicillamine, colchicine, cyclosporine or any other immunosuppressive, antifibrotic or immunomodulatory agent in the management of IPF. Interferon, pirfenidone and other new agents may be of benefit but further studies are required. Any recommendations for treatment must therefore be made on an individual and empiric basis. As some other forms of pulmonary fibrosis may respond better to immunosuppressive agents, it remains important to make an accurate diagnosis, by open lung biopsy if necessary.

Novel therapeutic approaches for pulmonary fibrosis

Pulmonary fibrosis represents the end stage of a number of heterogeneous conditions and is, to a greater or lesser degree, the hallmark of the interstitial lung diseases. It is characterized by the excessive deposition of extracellular matrix proteins within the pulmonary interstitium leading to the obliteration of functional alveolar units and in many cases, respiratory failure. While a small number of interstitial lung diseases have known aetiologies, most are idiopathic in nature, and of these, idiopathic pulmonary fibrosis is the most common and carries with it an appalling prognosis - median survival from the time of diagnosis is less than 3 years. This reflects the lack of any effective therapy to modify the course of the disease, which in turn is indicative of our incomplete understanding of the pathogenesis of this condition. Current prevailing hypotheses focus on dysregulated epithelial-mesenchymal interactions promoting a cycle of continued epithelial cell injury and fibroblast activation leading to progressive fibrosis. However, it is likely that multiple abnormalities in a myriad of biological pathways affecting inflammation and wound repair - including matrix regulation, epithelial reconstitution, the coagulation cascade, neovascularization and antioxidant pathways - modulate this defective crosstalk and promote fibrogenesis. This review aims to offer a pathogenetic rationale behind current therapies, briefly outlining previous and ongoing clinical trials, but will focus on recent and exciting advancements in our understanding of the pathogenesis of idiopathic pulmonary fibrosis, which may ultimately lead to the development of novel and effective therapeutic interventions for this devastating condition.

Current perspectives of oxidative stress and its measurement in chronic obstructive pulmonary disease

Cigarette smoking, the principal aetiology of chronic obstructive pulmonary disease (COPD) in the developed countries, delivers and generates oxidative stress within the lungs. This imbalance of oxidant burden and antioxidant capacity has been implicated as an important contributing factor in the pathogenesis of COPD. Oxidative processes and free radical generation orchestrate the inflammation, mucous gland hyperplasia, and apoptosis of the airway lining epithelium which characterises COPD. Pivotal oxidative stress/pro-inflammatory molecules include reactive oxygen species such as the superoxides and hydroxyl radicals, pro-inflammatory cytokines including leukotrienes, interleukins, tumour necrosis factor alpha, and activated transcriptional factors such as nuclear factor kappa-B and activator protein 1. The lung has a large reserve of antioxidant agents such as glutathione and superoxide dismutase to counter oxidants. However, smoking also causes the depletion of antioxidants, which further contributes to oxidative tissue damage. The downregulation of antioxidant pathways has also been associated with acute exacerbations of COPD. The delivery of redox-protective antioxidants may have preventative and therapeutic potential of COPD. Although these observations have yet to translate into common clinical practice, preliminary clinical trials and studies of animal models have shown that interventions to counter this oxidative imbalance may have potential to better manage COPD. There is, thus, a need for the ability to monitor such interventions and exhaled breath condensate is rapidly emerging as a novel and noninvasive approach in the sampling of airway epithelial lining fluid which could be used for repeated analysis of oxidative stress and inflammation in the lungs.

Angiostatic versus angiogenic chemokines in IPF and EAA

BACKGROUND

Extrinsic allergic alveolitis (EAA) and idiopathic pulmonary fibrosis (IPF) share the presence of varying degree interstitial involvement and fibrosis. Vascular changes were often reported to accompany the development of fibrosis.

OBJECTIVES

The aim of our study was to examine the differences in angiostatic and angiogenic chemokine milieu in both diseases. Correlations between chemokine levels in bronchoalveolar lavage fluid (BALF), expression of chemokine receptors on CD4+ T cells (CXCR2, CXCR3) in BALF and HRCT pattern of the diseases were investigated.

METHODS

Sixteen patients with chronic EAA and 8 with IPF were enrolled to the study. Concentrations of interleukin (IL)-8, epithelial neutrophil activating protein (ENA)-78, interferon-gamma-inducible protein (IP)-10 and interferon-inducible T cell alpha chemoattractant (I-TAC) in BALF supernatants were quantified using Fluorokine MultiAnalyte profiling.

RESULTS

There was no significant difference in the BALF chemokine levels between the EAA and IPF group. IL-8 BALF concentrations correlate with the extent of fibrosis in both EAA and IPF (p<0.01). The IP-10 BALF concentrations do not correlate either with the HRCT alveolar or interstitial score and should be evaluated in the relationship with the disease course.

CONCLUSIONS

Both IL-8 and ENA-78 probably play a different role in IPF and chronic EAA pathogenesis. While we suggest ENA-78 as the marker of at least partial reversibility of the lung impairment in the EAA patients, IL-8 could be rather an indicator of continuous exposition to provoking agent in EAA patients. IL-8 might serve as a potential marker of early phase of IPF.

Oxidative stress in the pathogenesis of diffuse lung diseases: a review

Oxidative stress is an imbalance between oxidants (reactive oxygen and nitrogen species) and antioxidants that may affect lipids, DNA, carbohydrates and proteins. The lung is continuously exposed to endogenous and exogenous oxidants (cigarette smoke, mineral dust, ozone, radiation). Reactive oxygen and nitrogen species are mainly produced by phagocytes as well as by polymorphonuclear, alveolar, bronchial and endothelial cells. A potential role of oxidative stress in the pathogenesis of diffuse lung diseases (particularly idiopathic pulmonary fibrosis) has been demonstrated. Increased oxidant levels and decreased antioxidant defences can contribute to the progression of idiopathic pulmonary fibrosis and other diffuse lung diseases. The growing number of papers on the different aspects of oxidant/antioxidant imbalance in diffuse lung diseases in the last decade reflects increasing interest in this topic and suggests that specific DLDs may be characterized by specific patterns of oxidation and antioxidant responses. The study of oxidative stress can provide insights into etiopathogenesis and favour the discovery of new treatments. In this review of the literature on oxidants and antioxidants in diffuse lung diseases, the focus is on idiopathic pulmonary fibrosis, sarcoidosis, pneumoconiosis and pulmonary fibrosis associated with systemic sclerosis.

Analysis of trace elements in bronchoalveolar lavage of patients with diffuse lung diseases

Airborne trace elements are implicated in the etio-pathogenesis of a large number of pulmonary diseases. The aim of this study was to evaluate the reliability and effectiveness of direct determination of Cd, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn concentrations in bronchoalveolar lavage (BAL) samples from patients with sarcoidosis, idiopathic pulmonary fibrosis, and Langerhans cell histiocytosis and healthy (smoking and non-smoking) controls. A total of 44 individuals were recruited among sarcoidosis, idiopathic pulmonary fibrosis, and Langerhans cell histiocytosis patients and healthy (smoking and non-smoking) controls. Average Mn concentrations in BAL from patients were 45% lower than in controls (p < 0.01) and remarkable decreases in average concentrations of Cr, Ni and Zn were also found in BAL from patients with idiopathic pulmonary fibrosis and Langerhans cell histiocytosis. As these diseases are characterized by the enhanced activation of certain immunomodulatory cells and by generation of free radicals, the depressed Mn, Zn, Cr and Ni concentrations in BAL from patients may be due to oxidative stress. These preliminary results indicate that assessment of the elemental composition of BAL is a promising approach to study the pathogenesis of diffuse lung diseases and Langerhans cell histiocytosis.

Extracellular superoxide dismutase in pulmonary fibrosis

Disruption of the oxidant/antioxidant balance in the lung is thought to be a key step in the development of many airway pathologies. Hence, antioxidant enzymes play key roles in controlling or preventing pulmonary diseases related to oxidative stress. The superoxide dismutases (SOD) are a family of enzymes that play a pivotal role protecting tissues from damage by oxidant stress by scavenging superoxide anion, which prevents the formation of other more potent oxidants such as peroxynitrite and hydroxyl radical. Extracellular SOD (EC-SOD) is found predominantly in the extracellular matrix of tissues and is ideally situated to prevent cell and tissue damage initiated by extracellularly produced ROS. EC-SOD has been shown to be protective in several models of interstitial lung disease, including pulmonary fibrosis. In addition, alterations in EC-SOD expression are also present in human idiopathic pulmonary fibrosis (IPF). This review discusses EC-SOD regulation in response to pulmonary fibrosis in animals and humans and reviews possible mechanisms by which EC-SOD may protect against fibrosis.

Oxidative stress, plasminogen activator inhibitor 1, and lung fibrosis

Fibrosis is characterized by excessive accumulation of extracellular matrix (ECM) in basement membranes and interstitial tissues, resulting from increased synthesis or decreased degradation of ECM or both. The plasminogen activator/plasmin system plays an important role in ECM degradation, whereas the plasminogen activator inhibitor 1 (PAI-1) is a physiologic inhibitor of plasminogen activators. PAI-1 expression is increased in the lung fibrotic diseases and in experimental fibrosis models. The deletion of the PAI-1 gene reduces, whereas the overexpression of PAI-1 enhances, the susceptibility of animals to lung fibrosis induced by different stimuli, indicating an important role of PAI-1 in the development of lung fibrosis. Many growth factors, including transforming growth factor beta (TGF-beta) and tumor necrosis factor alpha (TNF-alpha), as well as other chemicals/agents, induce PAI-1 expression in cultured cells and in vivo. Reactive oxygen and nitrogen species (ROS/RNS) have been shown to mediate the induction of PAI-1 by many of these stimuli. This review summarizes some recent findings that help us to understand the role of PAI-1 in the development of lung fibrosis and ROS/RNS in the regulation of PAI-1 expression during fibrogenesis.

Improvement by N-acetylcysteine of acute respiratory distress syndrome through increasing intracellular glutathione, and extracellular thiol molecules and anti-oxidant power: evidence for underlying toxicological mechanisms

In acute respiratory distress syndrome (ARDS), there is extensive overproduction of free radicals to the extent that endogenous anti-oxidants are overwhelmed, permitting oxidative cell damage. The present study examined the benefit of the anti-oxidant compound N-acetylcysteine (NAC) in the management of ARDS by measuring patient's intracellular glutathione (inside red blood cells) and extracellular (plasma) anti-oxidant defense biomarkers and outcome. Twenty-seven ARDS patients were recruited from the intensive care unit of a teaching Hospital and randomly divided into two groups. Both groups were managed similarly by regular treatments but 17 patients received NAC 150 mg/kg at the first day that followed by 50 mg/kg/day for three days and 10 patients did not receive NAC. Treatment by NAC increased extracellular total anti-oxidant power and total thiol molecules and also improved intracellular glutathione and the outcome of the patients. In conclusion, patients with ARDS are in a deficient oxidant-anti-oxidant balance that can get a significant benefit if supplemented with NAC.

Epithelial expression of TIMP-1 does not alter sensitivity to bleomycin-induced lung injury in C57BL/6 mice

Matrix metalloproteinases (MMPs) are mediators of lung injury, and their activity has been associated with the development of pulmonary fibrosis. To understand how MMPs regulate the development of pulmonary fibrosis, we examined MMP expression in two strains of mice with differing sensitivities to the fibrosis-inducing drug bleomycin. After a single intratracheal injection of the drug, bleomycin-sensitive C57BL/6 mice showed increased expression for MMPs (-2, -7, -9, -13) at both 7 and 14 days posttreatment compared with the bleomycin-resistant BALB/c strain. In addition, TIMP-1, an endogenous inhibitor of MMPs, was upregulated in the lungs of C57BL/6 mice but not BALB/c mice. We designed two strategies to decrease MMP expression to potentially decrease sensitivity of C57BL/6 mice: 1) we engineered C57BL/6 mice that overexpressed TIMP-1 in their lungs via surfactant protein C (SP-C) promoter; and 2) we inhibited expression of MMPs independent of TIMP-1 by knocking out metallothionein (MT), a critical zinc binding protein. SP-C-TIMP-1 mice reduced MMP expression in response to bleomycin. However, they were equally sensitive to bleomycin as their wild-type counterparts, displaying similar levels of hydroxyproline in the lung tissue. MT null mice displayed decreased lung activity of MMPs with no change in TIMP-1. Nonetheless, there was no difference between the MT null and wild-type control littermates with regards to any of the lung injury parameters measured. We conclude that although TIMP-1 expression is differentially regulated in fibrosis-sensitive and fibrosis-resistant strains, epithelial overexpression of TIMP-1 does not appear to substantially alter fibrotic lung disease in mice.

Extracellular cysteine/cystine redox potential controls lung fibroblast proliferation and matrix expression through upregulation of transforming growth factor-beta

Oxidant stress has been implicated in the pathogenesis of chronic lung disorders like idiopathic pulmonary fibrosis. However, mechanisms that link oxidant stress to fibrogenesis remain partially elucidated. Emerging data suggest an important role for the extracellular thiol/disulfide redox environment. The cysteine (Cys)/cystine (CySS) redox couple represents the predominant low-molecular-weight thiol/disulfide pool found in plasma and is sensitive to aging, smoking, and other host factors. We hypothesized that an oxidized extracellular Cys/CySS redox potential (E(h) Cys/CySS) affects lung fibroblasts by inducing intracellular signals that stimulate proliferation and matrix expression. We tested this hypothesis in primary murine lung fibroblasts and found that an oxidized E(h) Cys/CySS (-46 mV) stimulated lung fibroblast proliferation. Furthermore, it stimulated their expression of fibronectin, a matrix glycoprotein highly expressed in fibrotic lung diseases and implicated in lung injury. This stimulatory effect was dependent on protein kinase C activation. Oxidant stress also increased the phosphorylation of cAMP response element binding protein, a transcription factor known for its ability to stimulate fibronectin expression, and increased the expression of mRNAs and proteins coding for the transcription factors nuclear factor (NF)-kappaB and mothers against decapentaplegic homolog 3. Fibroblasts cultured in normal (-80 mV) or reduced (-131 mV) E(h) Cys/CySS showed less induction. Furthermore, fibronectin expression in response to an oxidized E(h) Cys/CySS was associated with expression of transforming growth factor-beta1 (TGF-beta1) and was inhibited by an anti-TGF-beta1 antibody and SB-431542, a TGF-beta1 receptor inhibitor. These studies suggest that extracellular oxidant stress activates redox-sensitive pathways that stimulate lung fibroblast proliferation and matrix expression through upregulation of TGF-beta1.

Analysis of carbonylated proteins in bronchoalveolar lavage of patients with diffuse lung diseases

Diffuse lung diseases (DLD) are a heterogeneous group of diseases with different etiopathogenesis, clinical course, and prognosis. It has been demonstrated that oxidative stress can contribute to the pathogenesis of these diseases. In the present study we measured carbonylated protein concentrations in the BAL of patients with sarcoidosis, pulmonary fibrosis associated with systemic sclerosis, idiopathic pulmonary fibrosis, and for the first time in patients with chronic eosinophilic pneumonia and extrinsic allergic alveolitis. Our aim was to further investigate oxidation products in diffuse lung diseases. Oxidatively modified protein concentrations were increased in the BAL of patients than in that of controls (0.22 nmol/mg protein vs 0.05 nmol/mg protein; p < 0.001) and in each group of disease versus controls, suggesting that proteins that have become dysfunctional by oxidation could play a role in the pathogenesis of diffuse lung diseases. Further studies in a greater number of patients are needed to understand the contribution of oxidatively modified proteins to the pathogenesis of DLD and, in particular, to the development of extrinsic allergic alveolitis where the highest levels of carbonylated proteins were found.

Long-term administration of a small molecular weight catalytic metalloporphyrin antioxidant, AEOL 10150, protects lungs from radiation-induced injury

PURPOSE

To determine whether administration of a catalytic antioxidant, Mn(III) tetrakis(N,N'-diethylimidazolium-2-yl) porphyrin, AEOL 10150, with superoxide dismutase (SOD) mimetic properties, reduces the severity of radiation-induced injury to the lung from single-dose irradiation (RT) of 28 Gy.

METHODS AND MATERIALS

Rats were randomly divided into four different dose groups (0, 1, 10, and 30 mg/kg/day of AEOL 10150), receiving either short-term (1 week) or long-term (10 weeks) drug administration via osmotic pumps. Rats received single-dose irradiation (RT) of 28 Gy to the right hemithorax. Breathing rates, body weights, blood samples, histopathology, and immunohistochemistry were used to assess lung damage.

RESULTS

There was no significant difference in any of the study endpoints between the irradiated controls and the three groups receiving RT and short-term administration of AEOL 10150. For the long-term administration, functional determinants of lung damage 20 weeks postradiation were significantly worse for RT + phosphate-buffered saline (PBS) and RT + 1 mg/kg/day of AEOL 10150 as compared with the irradiated groups treated with higher doses of AEOL 10150 (10 or 30 mg/kg/day). Lung histology at 20 weeks revealed a significant decrease in structural damage and collagen deposition in rats receiving 10 or 30 mg/kg/day after radiation in comparison to the RT + PBS and 1 mg/kg/day groups. Immunohistochemistry demonstrated a significant reduction in macrophage accumulation, oxidative stress, and hypoxia in rats receiving AEOL 10150 (10 or 30 mg/kg/day) after lung irradiation compared with the RT + PBS and 1 mg/kg/day groups.

CONCLUSIONS

The chronic administration of a novel catalytic antioxidant, AEOL 10150, demonstrates a significant protective effect from radiation-induced lung injury. AEOL 10150 has its primary impact on the cascade of events after irradiation, and adding the drug before irradiation and its short-term administration have no significant additional benefits.

Chronic beryllium disease and glutathione biosynthesis genes

OBJECTIVE

Because glutathione (GSH) has been reported to be increased in chronic beryllium disease (CBD) and is associated with immune modulation, associations between CBD and gene polymorphisms of the rate-limiting enzyme in GSH synthesis, glutamate cysteine ligase (GCL), were investigated. Glutamate cysteine ligase consists of a catalytic subunit (GCLC) and modifier subunit (GCLM).

METHODS

Patients with CBD, beryllium-sensitized subjects (BeS), and beryllium-exposed subjects without CBD were genotyped for the GCLC GAG trinucleotide repeat polymorphism (GCLC TNR), the GCLC-129 single nucleotide polymorphism (SNP), and the GCLM-588 SNP.

RESULTS

Results indicate that GCLC TNR genotype 7/7 is negatively associated with CBD (odds ratio [OR] = 0.28, 95% confidence interval [CI] = 0.08-0.95) and the GCLM-588 C/C SNP genotype is associated with CBD susceptibility (OR = 3.07, 95% CI = 1.00-9.37). No differences were noted in the BeS group.

CONCLUSIONS

This study suggests that GSH modulation may play a role in CBD pathogenesis, but not in sensitization to beryllium.

Oxidant and antioxidant balance in the airways and airway diseases

Although oxygen is a prerequisite to life, at concentrations beyond the physiological limits it may be hazardous to the cells. Since the lungs are directly exposed to very high amounts of oxygen, it is imperative for the organ to possess defences against possible oxidative challenge. The lungs are therefore endowed with an armamentarium of a battery of endogenous agents called antioxidants. The antioxidant species help the lungs ward off the deleterious consequences of a wide variety of oxidants/reactive oxygen species such as superoxide anion, hydroxyl radical, hypohalite radical, hydrogen peroxide and reactive nitrogen species such as nitric oxide, peroxynitrite, nitrite produced endogenously and sometimes accessed through exposure to the environment. The major non-enzymatic antioxidants of the lungs are glutathione, vitamins C and E, beta-carotene, uric acid and the enzymatic antioxidants are superoxide dismutases, catalase and peroxidases. These antioxidants are the first lines of defence against the oxidants and usually act at a gross level. Recent insights into cellular redox chemistry have revealed the presence of certain specialized proteins such as peroxiredoxins, thioredoxins, glutaredoxins, heme oxygenases and reductases, which are involved in cellular adaptation and protection against an oxidative assault. These molecules usually exert their action at a more subtle level of cellular signaling processes. Aberrations in oxidant: antioxidant balance can lead to a variety of airway diseases, such as asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis which is the topic of discussion in this review.

Overexpression of extracellular superoxide dismutase reduces acute radiation induced lung toxicity

Background

Acute RT-induced damage to the lung is characterized by inflammatory changes, which proceed to the development of fibrotic lesions in the late phase of injury. Ultimately, complete structural ablation will ensue, if the source of inflammatory / fibrogenic mediators and oxidative stress is not removed or attenuated. Therefore, the purpose of this study is to determine whether overexpression of extracellular superoxide dismutase (EC-SOD) in mice ameliorates acute radiation induced injury by inhibiting activation of TGFβ1 and downregulating the Smad 3 arm of its signal transduction pathway.

Methods

Whole thorax radiation (single dose, 15 Gy) was delivered to EC-SOD overexpressing transgenic (XRT-TG) and wild-type (XRT-WT) animals. Mice were sacrificed at 1 day, 1 week, 3, 6, 10 and 14 weeks. Breathing rates, right lung weights, total/differential leukocyte count, activated TGFβ1 and components of its signal transduction pathway (Smad 3 and p-Smad 2/3) were assessed to determine lung injury.

Results

Irradiated wild-type (XRT-WT) animals exhibited time dependent increase in breathing rates and right lung weights, whereas these parameters were significantly less increased (p < 0.05) at 3, 6, 10 and 14 weeks in irradiated transgenic (XRT-TG) mice. An inflammatory response characterized predominantly by macrophage infiltration was pronounced in XRT-WT mice. This acute inflammation was significantly attenuated (p < 0.05) in XRT-TG animals at 1, 3, 6 and 14 weeks. Expression of activated TGFβ1 and components of its signal transduction pathway were significantly reduced (p < 0.05) at later time-points in XRT-TG vs. XRT-WT.

Conclusion

This study shows that overexpression of EC-SOD confers protection against RT-induced acute lung injury. EC-SOD appears to work, in part, via an attenuation of the macrophage response and also decreases TGFβ1 activation with a subsequent downregulation of the profibrotic TGFβ pathway.

Attenuation of bleomycin-induced lung fibrosis in rats by mesna

Lung fibrosis is a common side effect of the chemotherapeutic agent, bleomycin. Current evidence suggests that reactive oxygen species may play a key role in the development of lung fibrosis. The present study examined the effect of mesna on bleomycin-induced lung fibrosis in rats. Animals were divided into three groups: (1) saline control group; (2) Bleomycin group in which rats were injected with bleomycin (15 mg/kg, i.p.) three times a week for four weeks; (3) Bleomycin and mesna group, in which mesna was given to rats (180 mg/kg/day, i.p.) a week prior to bleomycin and daily during bleomycin injections for 4 weeks until the end of the treatment. Bleomycin treatment resulted in a pronounced fall in the average body weight of animals. Bleomycin-induced pulmonary injury and lung fibrosis was indicated by increased lung hydroxyproline content, and elevated nitric oxide synthase, myeoloperoxidase, platelet activating factor, and tumor necrosis factor-alpha in lung tissues. On the other hand, bleomycin induced a reduction in reduced glutathione concentration and angiotensin converting enzyme activity in lung tissues. Moreover, bleomycin-induced severe histological changes in lung tissues revealed as lymphocytes and neutrophils infiltration, increased collagen deposition and fibrosis. Co-administration of bleomycin and mesna reduced bleomycin-induced weight loss and attenuated lung injury as evaluated by the significant reduction in hydroxyproline content, nitric oxide synthase activity, and concentrations of myeoloperoxidase, platelet activating factor, and tumor necrosis factor-alpha in lung tissues. Furthermore, mesna ameliorated bleomycin-induced reduction in reduced glutathione concentration and angiotensin activity in lung tissues. Finally, histological evidence supported the ability of mesna to attenuate bleomycin-induced lung fibrosis and consolidation. Thus, the findings of the present study provide evidence that mesna may serve as a novel target for potential therapeutic treatment of lung fibrosis.

Effect of Feitai on bleomycin-induced pulmonary fibrosis in rats

The current therapeutic approaches for pulmonary fibrosis, which is characterized by fibroblast proliferation and extracellular matrix remodeling, are unsatisfactory. Feitai, consisting of several herbs, is a folk formula for pulmonary tuberculosis therapy in China. To investigate the effects of Feitai on pulmonary fibrosis, Feitai was administered orally to bleomycin (BLM)-treated rats, and the lung toxicity effects were evaluated according to inflammatory cell count, protein concentration, and lactate dehydrogenase (LDH) activity in the bronchoalveolar lavage fluid (BALF), malondialdehyde level and hydroxyproline content in lung tissue 28 days post-BLM. Serial sections of the lung were stained with hematoxylin and eosin (HE) and Masson trichrome, respectively. The degree of fibrosis was assessed quantitatively using LEICA QWin image analyzer. Results showed that Feitai inhibited BLM-induced lung fibrotic lesions in a dose-dependent manner as reflected by decreased the lung hydroxyproline content and lung fibrosis fraction 28 days after BLM instillation. Treatment with Feitai also significantly ameliorated the BLM-induced lung toxicity effects detected in BALF and lung tissue. The effects in vitro on WI-38 human lung fibroblast cell line showed that Feitai significantly reduced the cell proliferation and transforming growth factor (TGF)-beta stimulated type I collagen synthesis. These results strongly demonstrate that Feitai may be useful in the treatment of pulmonary fibrosis.

Redox regulation of lung inflammation by thioredoxin

The lungs are the richest in oxygen among the various organs of the body and are always subject to harmful reactive oxygen species. Regulation of the reduction/oxidation (redox) state is critical for cell viability, activation, proliferation, and organ functions. Although the protective importance of various antioxidants has been reported, few antioxidants have established their clinical usefulness. Thioredoxin (TRX), a key redox molecule, plays crucial roles as an antioxidant and a catalyst in protein disulfide/dithiol exchange. TRX also modulates intracellular signal transduction and exerts antiinflammatory effects in tissues. In addition to its beneficial effects in other organs, the protective effect of TRX in the lungs has been shown against ischemia/ reperfusion injury, influenza infection, bleomycin-induced injury, or lethal inflammation caused by interleukin- 2 and interleukin-18. Monitoring of TRX in the plasma, airway, or lung tissue may be useful for the diagnosis and follow-up of pulmonary inflammation. Promotion/modulation of the TRX system by the administration of recombinant TRX protein, induction of endogenous TRX, or gene therapies can be a therapeutic modality for oxidative stress-associated lung disorders.

Mechanisms of pulmonary fibrosis

Tissue injury evokes highly conserved, tightly regulated inflammatory responses and less well-understood host repair responses. Both inflammation and repair involve the recruitment, activation, apoptosis, and eventual clearance of key effector cells. In this review, we propose the concept of pulmonary fibrosis as a dysregulated repair process that is perpetually "turned on" even though classical inflammatory pathways may be dampened or "switched off." Significant regional heterogeneity, with varied histopathological patterns of inflammation and fibrosis, has been observed in individual patients with idiopathic pulmonary fibrosis. We discuss environmental factors and host response factors, such as genetic susceptibility and age, that may influence these varied manifestations. Better understanding of the mechanisms of lung repair, which include alveolar reepithelialization, myofibroblast differentiation/activation, and apoptosis, should offer more effective therapeutic options for progressive pulmonary fibrosis.

Attenuation of bleomycin induced pulmonary fibrosis in mice using the heme oxygenase inhibitor Zn-deuteroporphyrin IX-2,4-bisethylene glycol

BACKGROUND

Pulmonary fibrosis is associated with a poor prognosis. The pathogenesis of fibrotic lung disorders remains unclear, but the extent of tissue damage due to the persistent presence of oxidants or proteases is believed to be important. The heme degrading enzyme heme oxygenase (HO) has been found to be expressed in experimental fibrosis, and generation of free iron and carbon monoxide (CO) by HO has been implicated in oxidant induced lung damage. A study was undertaken to examine the effects of the HO inhibitor Zn-deuteroporphyrin-IX-2,4-bisethylene glycol (Zndtp) on the development of pulmonary fibrosis in the bleomycin model of lung injury and repair.

METHODS

Zndtp (10 micro mol/kg) was administered subcutaneously twice daily to mice 1 week following the intratracheal instillation of 0.025 U bleomycin. Animals were killed 10 or 21 days after bleomycin instillation and indices of lung damage and fibrosis were evaluated.

RESULTS

Bleomycin treatment induced pulmonary cytotoxicity, increased levels of active transforming growth factor beta (TGF-beta), enhanced lung collagen accumulation, and decreased glutathione content. Zndtp administration significantly attenuated these indices.

CONCLUSIONS

Administration of Zndtp in the bleomycin model resulted in appreciable alveolar cytoprotection and amelioration of pulmonary fibrosis. This molecule and its analogues may warrant further consideration in the treatment of acute lung injury and fibrotic lung disorders.

Feitai Attenuates Bleomycin-Induced Pulmonary Fibrosis in Rats

Pulmonary fibrosis is a common consequence of numerous pulmonary diseases. The current therapeutic approaches for this condition are unsatisfactory. Feitai, a composite formula consisting of several herbs, is used in China as a folk remedy for treating patients with pulmonary tuberculosis. In this study, we extensively investigate the effects and mechanisms of Feitai on bleomycin (BLM)-induced pulmonary fibrosis in rats. One hundred and twenty male Sprague-Dawley rats were randomly divided into four groups, referred to as the saline-water, saline-Feitai, BLM-water, and BLM-Feitai groups. Following a single instillation of BLM (5 mg/kg) or saline, rats were orally administered Feitai at a dose of 3 g/kg body weight or sterilized distilled water once daily. Rats were killed at 7, 14, or 28 d post-BLM. Inflammatory cell count, protein concentration, and lactate dehydrogenase activity in bronchoalveolar lavage fluid were measured, and myeloperoxidase activity and lipid peroxide content in lung homogenates were analyzed. Treatment with Feitai inhibited lung fibrotic progression induced by BLM, as indicated by the decrease in lung hydroproline content and lung fibrosis score at 28 d post-BLM. This was accompanied by significant amelioration of BLM-induced body weight loss, lung edema, and inflammatory response during the development of lung injury in the acute phase. The results strongly indicate the beneficial effects of Feitai in protecting against BLM-induced pulmonary fibrosis. Furthermore, the inflammatory response and lipid peroxidation were inhibited by Feitai, suggesting that the effect of this formula on BLM-induced lung injury and fibrosis is associated with antiinflammatory and antioxidant properties.

In vivo antioxidant treatment protects against bleomycin-induced lung damage in rats

1. This study examines the activity of the antioxidant N-acetylcysteine on bleomycin-induced pulmonary fibrosis in rats with emphasis on the early inflammatory phase. 2. Rats receiving N-acetylcysteine (300 mg kg(-1) day(-1), intraperitoneal) had less augmented lung wet weight, and lower levels of proteins, lactate dehydrogenase, neutrophil and macrophage counts in bronchoalveolar lavage fluid and lung myeloperoxidase activity with a betterment of histological score at 3 days postbleomycin. 3. A diminished lung GSH/GSSG ratio and augmented lipid hydroperoxides were observed 3 days postbleomycin. These changes were attenuated by N-acetylcysteine. Alveolar macrophages from bleomycin-exposed rats released augmented amounts of superoxide anion and nitric oxide. N-Acetylcysteine did not modify superoxide anion generation but reduced the increased production of nitric oxide. 4. N-Acetylcysteine suppressed the bleomycin-induced increased activation of lung NF-kappaB (shift assay and immunohistochemistry), and decreased the augmented levels of the early inflammatory cytokines, tumour necrosis factor-alpha, interleukin-beta, interleukin-6 and macrophage inflammatory protein-2 observed in bronchoalveolar lavage fluid at 1 and 3 days postbleomycin exposure. 5. At 15 days postbleomycin, N-acetylcysteine decreased collagen deposition in bleomycin-exposed rats (hydroxyproline content: 6351+/-669 and 4626+/-288 micro g per lung in drug vehicle- and N-acetylcysteine-treated rats, respectively; P<0.05). Semiquantitative histological assessment at this stage showed less collagen deposition in N-acetylcysteine-treated rats compared to those receiving bleomycin alone. 6. These results indicate that N-acetylcysteine reduces the primary inflammatory events, thus preventing cellular damage and the subsequent development of pulmonary fibrosis in the bleomycin rat model.

Immunomodulatory agents for idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic Pulmonary Fibrosis (IPF) or Usual Interstitial Pneumonia (UIP) is a form of chronic fibrosing interstitial pneumonia of unknown aetiology, with progressively deteriorating respiratory function and ultimately death from respiratory failure. Most treatments are intended to suppress inflammation but none has been proven to alter this process. The most widespread approach uses oral corticosteroids; others use immunosuppressive, immunomodulatory or anti-fibrotic agents, alone or with corticosteroids. A Cochrane review of corticosteroids in IPF has found no evidence that they are of benefit.

OBJECTIVES

To determine the effect of non-corticosteroid immunosuppressive, anti-fibrotic and immunomodulatory agents in the treatment of IPF(UIP).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL - The Cochrane Library, Issue 2 2003), MEDLINE (January 1966 to April 2003), EMBASE (January 1985 to April 2003) and with additional handsearching.

SELECTION CRITERIA

RCTs/CCTs utilising non-corticosteroid immunosuppressive, anti-fibrotic or immunomodulatory agents versus either placebo or corticosteroids alone in adult patients with histological evidence of IPF(UIP) or with a diagnosis consistent with published American Thoracic Society guidelines were included.

DATA COLLECTION AND ANALYSIS

We retrieved abstracts of identified articles and reviewed those possibly fulfilling inclusion criteria and included or excluded. Two reviewers assessed the studies for inclusion in the review. Where doubt existed a third reviewer re-assessed the article and consensus was obtained. Methodological quality was assessed using the Jadad scale and the Cochrane assessment of allocation of concealment.

MAIN RESULTS

59 studies were identified. Quality was generally poor. Only three RCT/CCTs were suitable for meta-analysis, two lesser quality RCTs were included in discussion only, 52 studies were excluded and two ongoing trials were identified. Each high quality trial used a different agent (azathioprine, colchicine, interferon-gamma 1b) and meaningful comparisons are not possible. Azathioprine and Interferon were studied as additional therapy, whilst colchicine was compared with oral corticosteroids. Only interferon was shown to produce any significant improvement in pulmonary function and arterial oxygenation. There may be a small (but undefined) long term survival advantage for azathioprine. One of the lower quality studies showed a marginal benefit for cyclophosphamide and prednisone over prednisone alone; the other showed no benefit for azathioprine and prednisone over prednisone alone. There are no high quality studies utilising cyclophosphamide.

REVIEWER'S CONCLUSIONS

There is little good quality information regarding the efficacy of non-corticosteroid agents in IPF(UIP). The older agents have generally not been well evaluated. A number of new agents require further evaluation. Currently there is little to justify the routine use of any non-corticosteroid agent in the management of IPF(UIP).

Antioxidant responses to oxidant-mediated lung diseases

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated throughout the human body. Enzymatic and nonenzymatic antioxidants detoxify ROS and RNS and minimize damage to biomolecules. An imbalance between the production of ROS and RNS and antioxidant capacity leads to a state of "oxidative stress" that contributes to the pathogenesis of a number of human diseases by damaging lipids, protein, and DNA. In general, lung diseases are related to inflammatory processes that generate increased ROS and RNS. The susceptibility of the lung to oxidative injury depends largely on its ability to upregulate protective ROS and RNS scavenging systems. Unfortunately, the primary intracellular antioxidants are expressed at low levels in the human lung and are not acutely induced when exposed to oxidative stresses such as cigarette smoke and hyperoxia. However, the response of extracellular antioxidant enzymes, the critical primary defense against exogenous oxidative stress, increases rapidly and in proportion to oxidative stress. In this paper, we review how antioxidants in the lung respond to oxidative stress in several lung diseases and focus on the mechanisms that upregulate extracellular glutathione peroxidase.

C-propeptide region of human pro alpha 1 type 1 collagen interacts with thioredoxin

Thioredoxin (TRX) is one of major components of thiol reducing systems. To investigate the molecular mechanism of TRX function in the lung tissue, we screened a human lung epithelial cell cDNA library for TRX-binding protein by yeast two-hybrid systems. We isolated a plasmid containing C-propeptide region of human pro alpha 1 type 1 collagen (CP-pro alpha 1(1)). CP-pro alpha 1(1) stably binds to wild type TRX but not to mutant TRX, in which redox-active cysteine residues are substituted. Failure of the interaction of mutant TRX with CP-pro alpha 1(1) was confirmed in yeast two-hybrid systems. The CP-pro alpha 1(1)/TRX interaction was increased by dithiothreitol treatment, but was markedly inhibited by hydrogen peroxide or diamide treatment. These data showed that the reducing status of TRX active site cysteine residues is important for the TRX-CP-pro alpha 1(1) interaction, indicating that collagen biosynthesis is under the regulation of TRX-dependent redox control.

iNOS gene upregulation is associated with the early proliferative response of human lung fibroblasts to cytokine stimulation

Increased release of oxidants has been implicated in the pathogenesis of pulmonary fibrosis. Previous work in the rat showed that formation of the early fibrotic lesion is associated with increased expression of inducible nitric oxide synthase (iNOS) in pulmonary fibroblasts. The aim of this study was to test the hypothesis that NO is involved in the activation of pulmonary fibroblasts. The effects of endogenous and exogenous NO on proliferation of human pulmonary fibroblasts were investigated by administration of cytomix or SNAP, respectively. At low concentrations, both treatments increased cell numbers, an effect attenuated by iNOS inhibitor or NO scavenger. Induction of iNOS was confirmed by measurement of nitrate/nitrite production and by immunodetection. Quantitative RT-PCR showed an increase in iNOS mRNA as early as 3 h after stimulation. These results support the hypothesis and show that upregulation of the iNOS gene is an early event in the proliferative response of human lung fibroblasts to inflammatory stimuli.

Molecular mechanism of transforming growth factor (TGF)-beta1-induced glutathione depletion in alveolar epithelial cells. Involvement of AP-1/ARE and Fra-1

Glutathione (GSH) is a ubiquitous antioxidant in lung epithelial cells and lung lining fluid. Transforming growth factor beta1 (TGF-beta1) is a pleiotropic cytokine involved in cellular proliferation and differentiation. The level of TGF-beta1 is elevated in many chronic inflammatory lung disorders associated with oxidant/antioxidant imbalance. In this study, we show that TGF-beta1 depletes GSH by down-regulating expression of the enzyme responsible for its formation, gamma-glutamylcysteine synthetase (gamma-GCS) and induces reactive oxygen species production in type II alveolar epithelial cells (A549). To investigate the molecular mechanisms of inhibition of glutathione synthesis, we employed reporters containing fragments from the promoter region of the gamma-GCS heavy subunit (h), the gene that encodes the catalytic subunit of gamma-GCS. We found that TGF-beta1 reduced the expression of the long gamma-GCSh construct (-3802/GCSh-5'-Luc), suggesting that an antioxidant response element (ARE) may be responsible for mediating the TGF-beta1 effect. Interestingly, the electrophoretic mobility shift assay revealed that the DNA binding activity of both activator protein-1 (AP-1) and ARE was increased in TGF-beta1-treated epithelial cells. The gamma-GCSh ARE contains a perfect AP-1 site embedded within it, and mutation of this internal AP-1 sequence, but not the surrounding ARE, prevented DNA binding. Further studies revealed that c-Jun and Fra-1 dimers, members of the AP-1 family previously shown to exert a negative effect on phase II gene expression, bound to the ARE sequence. We propose a novel mechanism of gamma-GCSh down-regulation by TGF-beta1 that involves the binding of c-Jun and Fra-1 dimers to the distal promoter. The findings of this study provide important information, which may be used for the modulation of glutathione biosynthesis in inflammation.

Role of extracellular superoxide dismutase in bleomycin-induced pulmonary fibrosis

Bleomycin administration results in well-described intracellular oxidative stress that can lead to pulmonary fibrosis. The role of alveolar interstitial antioxidants in this model is unknown. Extracellular superoxide dismutase (EC-SOD) is the primary endogenous extracellular antioxidant enzyme and is abundant in the lung. We hypothesized that EC-SOD plays an important role in attenuating bleomycin-induced lung injury. Two weeks after intratracheal bleomycin administration, we found that wild-type mice induced a 106 +/- 25% increase in lung EC-SOD. Immunohistochemical staining revealed that a large increase in EC-SOD occurred in injured lung. Using mice that overexpress EC-SOD specifically in the lung, we found a 53 +/- 14% reduction in bleomycin-induced lung injury assessed histologically and a 17 +/- 6% reduction in lung collagen content 2 wk after bleomycin administration. We conclude that EC-SOD plays an important role in reducing the magnitude of lung injury from extracellular free radicals after bleomycin administration.

Nacystelyn inhibits oxidant-mediated interleukin-8 expression and NF-kappaB nuclear binding in alveolar epithelial cells

Nacystelyn (NAL), a recently developed lysine salt of N-acetyl-L-cytokine (NAC) has mucolytic and antioxidant properties. In this study, we investigated the effect of NAL upon oxidant-mediated interleukin (IL)-8 release and the activation of the redox-sensitive transcription factors AP-1, NF-kappaB, and C/EBP in a human alveolar epithelial cell line (A549). NAL (5 mM) enhanced intracellular glutathione (GSH) after 4 h and abolished H(2)O(2)-induced IL-8 release from A549 cells. This was associated with inhibition of NF-kappaB and C/EBP DNA-binding, measured by the Electrophoretic Mobility Shift Assay (EMSA). NAL also abolished the transcriptional activation of IL-8 in an IL-8-chloramphenicol acetyl transferase (CAT) reporter system, transfected into A549 cells. Supernatants obtained from H(2)O(2)-treated A549 cells induced chemotaxis of polymorphonuclear neutrophils, which could be inhibited by co-incubation with NAL. These data indicate that NAL may be used to modulate pro-inflammatory process by inhibiting cytokine release in the lungs and thus has therapeutic potential in inflammatory lung diseases.

Altered expression of extracellular superoxide dismutase in mouse lung after bleomycin treatment

The antioxidant enzyme extracellular superoxide dismutase (EC-SOD) is highly expressed in the extracellular matrix of lung tissue and is believed to protect the lung from oxidative damage that results in diseases such as pulmonary fibrosis. This study tests the hypothesis that proteolytic removal of the heparin-binding domain of EC-SOD results in clearance of the enzyme from the extracellular matrix of pulmonary tissues and leads to a loss of antioxidant protection. Using a polyclonal antibody to mouse EC-SOD, the immunodistribution of EC-SOD in normal and bleomycin-injured lungs was examined. EC-SOD labeling was strong in the matrix of vessels, airways, and alveolar surfaces and septa in control lungs. At 2 d post-treatment, a slight increase in EC-SOD staining was evident. In contrast, lungs examined 4 or 7 d post-treatment, showed an apparent loss of EC-SOD from the matrix and surface of alveolar septa. Notably, at 7 d post-treatment, the truncated form of EC-SOD was found in the bronchoalveolar lavage fluid of bleomycin-treated mice, suggesting that EC-SOD is being removed from the extracellular matrix through proteolysis. However, loss of EC-SOD through proteolysis did not correlate with a decrease in overall pulmonary EC-SOD activity. The negligible effect on EC-SOD activity may reflect the large influx of intensely staining inflammatory cells at day 7. These results indicate that injuries leading to pulmonary fibrosis have a significant effect on EC-SOD distribution due to proteolytic removal of the heparin-binding domain and may be important in enhancing pulmonary injuries by altering the oxidant/antioxidant balance in alveolar interstitial spaces.

Exhaled Nitric Oxide Is Elevated in Patients With Progressive Systemic Sclerosis Without Interstitial Lung Disease

BACKGROUND

Progressive systemic sclerosis (PSS) is a multisystem disorder of unknown etiology. Interstitial lung disease (ILD) is a major cause of mortality in this condition, and a major challenge in this regard is to identify parameters that would predict the onset or progression of ILD in patients with PSS. Abnormal cellularity of BAL fluid (BALF) has been demonstrated in patients with PSS without ILD.

STUDY OBJECTIVES

We investigated exhaled nitric oxide (NO) as a noninvasive marker of pulmonary inflammation in patients with PSS with and without clinical and radiologic evidence of ILD. This was compared with the cellularity of BALF. Our hypothesis was that exhaled NO was elevated in patients with PSS without ILD who had abnormal BALF cellularity.

SETTING

Pulmonology and rheumatology units of a university-based, tertiary referral hospital in Durban, South AFRICA:

STUDY METHODS

Exhaled NO was measured using a chemiluminescence analyzer in 12 patients with PSS and ILD and in 12 patients without clinical or radiologic evidence of ILD and in 30 healthy control subjects. BAL was performed in patients with PSS with and without the presence of ILD and in six healthy control subjects.

RESULTS

Subclinical inflammation was confirmed by increased inflammatory cell counts in BALF from patients with PSS without ILD. Exhaled NO (mean [SEM]) was elevated in patients with PSS without ILD at 9.6 (0.7) parts per billion (ppb) compared to patients with PSS and ILD at 6.2 (0.6) ppb (p < 0.001) and healthy control subjects at 6.3 (0.2) ppb (p < 0.001).

CONCLUSION

Exhaled NO may therefore be an important noninvasive surrogate marker of inflammation in patients with PSS without ILD.

Regulation of redox glutathione levels and gene transcription in lung inflammation: therapeutic approaches

Glutathione (L-gamma-glutamyl-L-cysteinylglycine, GSH), is a vital intra- and extracellular protective antioxidant. Glutathione is synthesized from its constituent amino acids by the sequential action of gamma-glutamylcysteine synthetase (gamma-GCS) and GSH synthetase. The rate-limiting enzyme in GSH synthesis is gamma-GCS. Gamma-GCS expression is modulated by oxidants, phenolic antioxidants, and inflammatory and anti-inflammatory agents in various mammalian cells. The intracellular GSH redox homeostasis is strictly regulated to govern cell metabolism and protect cells against oxidative stress. Growing evidence has suggested that cellular oxidative processes have a fundamental role in inflammation through the activation of stress kinases (JNK, MAPK, p38) and redox-sensitive transcription factors such as NF-kappaB and AP-1, which differentially regulate the genes for proinflammatory mediators and protective antioxidant genes such as gamma-GCS, Mn-SOD, and heme oxygenase-1. The critical balance between the induction of proinflammatory mediators and antioxidant genes and the regulation of the levels of GSH in response to oxidative stress at the site of inflammation is not known. Knowledge of the mechanisms of redox GSH regulation and gene transcription in inflammation could lead to the development of novel therapies based on the pharmacological manipulation of the production of this important antioxidant in inflammation and injury. This FORUM article features the role of GSH levels in the regulation of transcription factors, whose activation and DNA binding leads to proinflammatory and antioxidant gene transcription. The potential role of thiol antioxidants as a therapeutic approach in inflammatory lung diseases is also discussed.