Protein nitration, metabolites of reactive nitrogen species, and inflammation in lung allografts

Multiphase Kinetic Modeling of Air Pollutant Effects on Protein Modification and Nitrotyrosine Formation in Epithelial Lining Fluid

Exposure to ambient air pollution is a major risk factor for human health. Inhalation of air pollutants can enhance the formation of reactive species in the epithelial lining fluid (ELF) of the respiratory tract and can lead to oxidative stress and oxidative damage. Here, we investigate the chemical modification of proteins by reactive species from air pollution and endogenous biological sources using an extended version of the multiphase chemical kinetic model KM-SUB-ELF 2.0 with a detailed mechanism of protein modification. Fine particulate matter (PM2.5) and nitrogen dioxide (•NO2) act synergistically and increase the formation of nitrotyrosine (Ntyr), a common biomarker of oxidative stress. Ozone (O3) is found to be a burden on the antioxidant defense system but without substantial influence on the Ntyr concentration. In simulations with low levels of air pollution, the Ntyr concentration in the ELF is consistent with the range of literature values for bronchoalveolar lavage fluid from healthy individuals. With high levels of air pollution, however, we obtain strongly elevated Ntyr concentrations. Our model analysis shows how chemical reactions of air pollutants can modify proteins and thus their functionality in the human body, elucidating a molecular pathway that may explain air pollutant effects on human health.

Recent advances in methamphetamine neurotoxicity mechanisms and its molecular pathophysiology

Methamphetamine (METH) is a sympathomimetic amine that belongs to phenethylamine and amphetamine class of psychoactive drugs, which are widely abused for their stimulant, euphoric, empathogenic, and hallucinogenic properties. Many of these effects result from acute increases in dopamine and serotonin neurotransmission. Subsequent to these acute effects, METH produces persistent damage to dopamine and serotonin release in nerve terminals, gliosis, and apoptosis. This review summarized the numerous interdependent mechanisms including excessive dopamine, ubiquitin-proteasome system dysfunction, protein nitration, endoplasmic reticulum stress, p53 expression, inflammatory molecular, D₃ receptor, microtubule deacetylation, and HIV-1 Tat protein that have been demonstrated to contribute to this damage. In addition, the feasible therapeutic strategies according to recent studies were also summarized ranging from drug and protein to gene level.

Up-regulation of protein tyrosine nitration in methamphetamine-induced neurotoxicity through DDAH/ADMA/NOS pathway

Protein tyrosine nitration is an important post-translational modification mediated by nitric oxide (NO) associated oxidative stress, occurring in a variety of neurodegenerative diseases. In our previous study, an elevated level of dimethylarginine dimethylaminohydrolase 1 (DDAH1) protein was observed in different brain regions of acute methamphetamine (METH) treated rats, indicating the possibility of an enhanced expression of protein nitration that is mediated by excess NO through the DDAH1/ADMA (Asymmetric Dimethylated l-arginine)/NOS (Nitric Oxide Synthase) pathway. In the present study, proteomic methods, including stable isotope labeling with amino acids in cell culture (SILAC) and two dimensional electrophoresis, were used to determine the relationship between protein nitration and METH induced neurotoxicity in acute METH treated rats and PC12 cells. We found that acute METH administration evokes a positive activation of DDAH1/ADMA/NOS pathway and results in an over-production of NO in different brain regions of rat and PC12 cells, whereas the whole signaling could be repressed by DDAH1 inhibitor N(ω)-(2-methoxyethyl)-arginine (l-257). In addition, enhanced expressions of 3 nitroproteins were identified in rat striatum and increased levels of 27 nitroproteins were observed in PC12 cells. These nitrated proteins are key factors for Cdk5 activation, cytoskeletal structure, ribosomes function, etc. l-257 also displayed significant protective effects against METH-induced protein nitration, apoptosis and cell death. The overall results illustrate that protein nitration plays a significant role in the acute METH induced neurotoxicity via the activation of DDAH1/ADMA/NOS pathway.

The roles of glutathione, glutathione peroxidase, glutathione reductase and the carbonyl protein in pulmonary and extra pulmonary tuberculosis

BACKGROUND

This study determines the protein carbonyls which cause cellular damage and glutathione, glutathione peroxidase, glutathione reductase act as antioxidants.

MATERIALS AND METHODS

This study was carried out in different categories of pulmonary and extra pulmonary tuberculosis cases of newly sputum culture positive diagnosed pulmonary categorie I (n=100), extra pulmonary patients categorie (n=35) before and after the DOTS treatment of 6 months, categorie II (n=100), categorie III (n=100) and in normal control subjects (n=100).

RESULTS

The serum protein carbonyl levels were significantly increased in the pulmonary and extra pulmonary tuberculosis patients. The activities of blood glutathione, glutathione peroxidase, and glutathione reductase were found to be significantly decreased in subjects of all the categories of pulmonary and extra pulmonary tuberculosis. A negative correlation between the carbonyl protein content and glutathione, glutathione peroxidase, and glutathione reductase was seen in pulmonary tuberculosis, p<0.001.

CONCLUSION

Increased antioxidant defense mechanism due to increase oxidative stress in tuberculosis. The changes were reversed after 6 months of antitubercular treatment in patients with a good recovery, but the increase in the oxidative stress was not completely reversed.

Activation of Tissue Remodeling Precedes Obliterative Bronchiolitis in Lung Transplant Recipients

Obliterative bronchiolitis (OB) and Bronchiolitis Obliterans Syndrome (BOS) are frequent complications in the lung transplant recipient, and are the leading cause of mortality after transplantation. The mechanisms responsible for OB remain elusive, but inflammatory and tissue remodeling responses are implicated. We hypothesized that alterations in markers of tissue remodeling in BALF of lung transplant recipients could predict development of OB. To test this, we identified 13 lung transplant recipients who developed both BOS and histologic OB (OB group) at median post-operative day (POD) 485 (range 73–2070). Bronchoalveolar lavage fluid (BALF) was obtained at median POD 387 (range 45–2205), which preceded the onset of OB and BOS by a median of 140 days (range 60–365). As a control, BALF was also obtained from a group of 21 stable recipients without OB (non-OB group) at median POD 335 (range 270–395). BALF was examined for gelatinolytic activity, fibronectin gene transcription, and transforming growth factor-β1 (TGF-β1) expression. Gelatin zymography of BALF from the OB group showed increased matrix metalloproteinase-9 (MMP-9) activity over that of the non-OB group (p < 0.005). Similarly, BALF from the OB group induced greater fibronectin expression in fibroblasts compared to the non-OB group (p < 0.03). The induction of fibronectin also correlated with the amount of TGF-β1 protein in BALF (r = 0.71) from the OB group. We conclude that activation of tissue remodeling precedes the onset of OB, and analysis of gelatinolytic and/or fibronectin-inducing activity in BALF can serve as an early, pre-clinical marker for OB.

Identification and Validation of Proteinase 3 and Latent Matrix-Metalloproteinase 9 as Potential Biomarkers for Chronic Lung Transplant Rejection

Introduction

This study examined potential biomarkers for the diagnosis and early detection of chronic allograft rejection after lung transplantation.

Methods

Protein ratios in pooled samples of bronchoalveolar lavage fluid (BALF) from lung transplant recipients at different stages of pre- and postchronic rejection were determined by iTRAQ labeling and mass spectrometry. The potential biomarkers were validated using enzyme-linked immunosorbent assay (ELISA) assay.

Results

Two hundred sixty-five proteins were identified, about two thirds of which showed more than a twofold difference between a pooled control sample (individuals who did not develop chronic rejection in 100 months) and a pooled sample from those with chronic rejection. Proteinase 3 (PR-3) and matrix metalloproteinase 9 (MMP-9) were validated by ELISA assay of 124 individual samples. PR-3 and the latent form of MMP-9 (proMMP9) both demonstrated a specificity of 92% with sensitivities of 76% and 82%, respectively, for disease diagnosis; both were also predictors of developing chronic rejection up to 15 months before diagnosis. While immunoglobulin M (IgM) was upregulated in the pooled samples, individual sample analysis revealed that this arose from outlier values.

Conclusions

iTRAQ can be used to detect a large number of proteins in pooled samples for the discovery of potential biomarkers, but the findings must be validated with technology capable of distinguishing broadly based changes from outcomes as a result of a few extreme cases. The proteins identified in this study expanded the panel of potential biomarkers for the diagnosis and prediction of chronic rejection and provided additional insight into the mechanism of the disease.

Peroxynitrite mediates TNF-alpha-induced endothelial barrier dysfunction and nitration of actin

We tested the hypothesis that tumor necrosis factor (TNF)-alpha induces a peroxynitrite (ONOO(-))-dependent increase in permeability of pulmonary microvessel endothelial monolayers (PMEM) that is associated with generation of nitrated beta-actin (NO(2)-beta-actin). The permeability of PMEM was assessed by the clearance rate of Evans blue-labeled albumin. beta-Actin was extracted from PMEM lysate with a DNase-Sepharose column. The extracted beta-actin was quantified in terms of its nitrotyrosine/beta-actin ratio with anti-nitrotyrosine and anti-beta-actin antibodies, sequentially, by dot-blot assays. The cellular compartmentalization of NO(2)-beta-actin was displayed by showing confocal localization of nitrotyrosine-immunofluorescence with beta-actin-immunofluorescence but not with F-actin fluorescence. Incubation of PMEM with TNF (100 ng/ml) for 0.5 and 4.0 h resulted in increases in permeability to albumin. There was an increase in the nitrotyrosine/beta-actin ratio at 0.5 h with minimal association of the NO(2)-beta-actin with F-actin polymers. The TNF-induced increase in the nitrotyrosine/beta-actin ratio and permeability were prevented by the anti-ONOO(-) agent Urate. The data indicate that TNF induces an ONOO(-)-dependent barrier dysfunction, which is associated with the generation of NO(2)-beta-actin.

Lung transplantation: opportunities for research and clinical advancement

Lung transplantation is the only definitive therapy for many forms of end-stage lung diseases. However, the success of lung transplantation is limited by many factors: (1) Too few lungs available for transplantation due to limited donors or injury to the donor lung; (2) current methods of preservation of excised lungs do not allow extended periods of time between procurement and implantation; (3) acute graft failure is more common with lungs than other solid organs, thus contributing to poorer short-term survival after lung transplant compared with that for recipients of other organs; (4) lung transplant recipients are particularly vulnerable to pulmonary infections; and (5) chronic allograft dysfunction, manifest by bronchiolitis obliterans syndrome, is frequent and limits long-term survival. Scientific advances may provide significant improvements in the outcome of lung transplantation. The National Heart, Lung, and Blood Institute convened a working group of investigators on June 14-15, 2004, in Bethesda, Maryland, to identify opportunities for scientific advancement in lung transplantation, including basic and clinical research. This workshop provides a framework to identify critical issues related to clinical lung transplantation, and to delineate important areas for productive scientific investigation.

3-nitrotyrosine attenuates respiratory syncytial virus infection in human bronchial epithelial cell line

3-nitrotyrosine (NO2Tyr), an L-tyrosine derivative during nitrative stress, can substitute the COOH-terminal tyrosine of alpha-tubulin, posttranslationally altering microtubular functions. Because infection of the cells by respiratory syncytial virus (RSV) may require intact microtubules, we tested the hypothesis that NO2Tyr would inhibit RSV infection and intracellular signaling via nitrotyrosination of alpha-tubulin. A human bronchial epithelial cell line (BEAS-2B) was incubated with RSV with or without NO2Tyr. The release of chemokines and viral particles and activation of interferon regulatory factor-3 (IRF-3) were measured. Incubation with NO2Tyr increased nitrotyrosinated alpha-tubulin, and NO2Tyr colocalized with microtubules. RSV-infected cells released viral particles, RANTES, and IL-8 in a time- and dose-dependent manner, and intracellular RSV proteins coprecipitated with alpha-tubulin. NO2Tyr attenuated the RSV-induced release of RANTES, IL-8, and viral particles by 50-90% and decreased alpha-tubulin-associated RSV proteins. 3-chlorotyrosine, another L-tyrosine derivative, had no effects. NO2Tyr also inhibited the RSV-induced shift of the unphosphorylated form I of IRF-3 to the phosphorylated form II. Pre-exposure of the cells to NO(2) (0.15 ppm, 4 h), which produced diffuse protein tyrosine nitration, did not affect RSV-induced release of RANTES, IL-8, or viral particles. NO2Tyr did not affect the potential of viral spreading to the neighboring cells since the RSV titers were not decreased when the uninfected cells were cocultured with the preinfected cells in NO2Tyr-containing medium. These results indicate that NO2Tyr, by replacing the COOH-terminal tyrosine of alpha-tubulin, attenuated RSV infection, and the inhibition appeared to occur at the early stages of RSV infection.

Proteins as biomarkers of oxidative/nitrosative stress in diseases: the contribution of redox proteomics

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the pathogenesis and/or progression of several human diseases. Proteins are important molecular signposts of oxidative/nitrosative damage. However, it is generally unresolved whether the presence of oxidatively/nitrosatively modified proteins has a causal role or simply reflects secondary epiphenomena. Only direct identification and characterization of the modified protein(s) in a given pathophysiological condition can decipher the potential roles played by ROS/RNS-induced protein modifications. During the last few years, mass spectrometry (MS)-based technologies have contributed in a significant way to foster a better understanding of disease processes. The study of oxidative/nitrosative modifications, investigated by redox proteomics, is contributing to establish a relationship between pathological hallmarks of disease and protein structural and functional abnormalities. MS-based technologies promise a contribution in a new era of molecular medicine, especially in the discovery of diagnostic biomarkers of oxidative/nitrosative stress, enabling early detection of diseases. Indeed, identification and characterization of oxidatively/nitrosatively modified proteins in human diseases has just begun.

Pulmonary MnSOD Is Nitrated Following Hepatic Ischemia-Reperfusion

BACKGROUND

Ischemia-reperfusion (I/R) of remote organs is a common cause of lung injury. We observed that lung injury after partial hepatic I/R in mice coincides with the appearance of 3-nitrotyrosine (NT) in the lung tissue, a marker of peroxynitrite involvement and oxidant stress. Peroxynitrite can cause mitochondrial dysfunction by inactivation of manganese superoxide dismutase (MnSOD), the major antioxidant enzyme in mitochondria. Our aims were to examine whether pulmonary MnSOD is a target of nitration following hepatic I/R and whether nitrated MnSOD (N-MnSOD) correlates with acute lung injury.

METHODS

Five 20-25-g male C57BL/6 mice underwent laparotomy, and atraumatic occlusion of the portal and arterial blood supply to the upper three lobes of the liver for 90 min. This warm ischemic period was followed by 4 h of reperfusion, and the animals were then euthanized. Lung injury was assessed by LDH and protein levels in bronchoalveolar lavage (BAL) fluid. Pulmonary MnSOD activity in pulmonary homogenates was measured by the cytochrome c reduction method. The presence of N-MnSOD was determined by immunoprecipitation (IP) and Western Blot analysis. Controls (N = 5) underwent sham operation.

RESULTS

Elevated plasma transaminases confirmed hepatic injury. Lung injury was demonstrated by elevation in BAL protein and LDH levels (495.7 (48.4) versus 644.9 (37.3) [p < 0.05] and 56.5 (11.8) versus 345.2 (80) [p < 0.01], respectively). Immunoprecipitation and Western blot demonstrated N-MnSOD in the lung tissue of I/R animals but not controls. MnSOD activity decreased following I/R (8.1 (0.7) versus 10.8 (0.3) [p < 0.05]).

CONCLUSIONS

Pulmonary MnSOD is both nitrated and inactivated following hepatic I/R and is associated with acute lung injury. These findings suggest that MnSOD incapacitance may contribute to I/R-induced lung injury and provide a therapeutic target in attenuating multisystem injury following hepatic I/R.

Pulmonary edema fluid antioxidants are depressed in acute lung injury

OBJECTIVE

To test the hypothesis that low concentrations of distal airspace water-soluble antioxidants are associated with acute lung injury.

DESIGN

Prospective, cohort study.

SETTING

Medical intensive care unit of two tertiary care hospitals.

SUBJECTS

Subjects were 29 patients with acute lung injury and 23 normal, healthy, volunteers.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pulmonary edema fluid from subjects with acute lung injury was aspirated immediately after intubation. Compared with the bronchoalveolar lavage from normal subjects (corrected for dilution using urea concentrations), undiluted edema fluid from acute lung injury subjects had significantly lower concentrations of the antioxidants urate (757 +/- 232 microM vs. 328 +/- 75 microM), glutathione (138 +/- 25 microM vs. 7 +/- 4 microM), and ascorbate (85 +/- 21 microM vs. 27 +/- 10 microM).

CONCLUSIONS

Acute lung injury is associated with decreased concentrations of water-soluble antioxidants in the distal airspaces. In acute lung injury, the distal airspace antioxidants ascorbate, urate, and glutathione may play a role in attenuating lung injury.

3-Chlorotyrosine as a marker of protein damage by myeloperoxidase in tracheal aspirates from preterm infants: association with adverse respiratory outcome

Oxidative injury is implicated in the development of chronic lung disease in preterm infants with respiratory distress. However, direct evidence of a causal role is limited and the source of reactive oxidants has not been identified. We have previously shown that protein carbonyl levels in tracheal aspirates correlate positively with myeloperoxidase, suggesting that neutrophil oxidants could be the source of this protein injury. We have extended these observations by measuring 3-chlorotyrosine, a specific biomarker of the neutrophil oxidant, hypochlorous acid, in tracheal aspirate proteins (144 samples) from 69 infants with birth weight <1500 g. 3-Chlorotyrosine levels were higher in these infants than in larger infants without respiratory distress (median 83 compared with 13 micromol/mol tyrosine). They correlated strongly with myeloperoxidase activity (correlation coefficient 0.75, p < 0.0001) and to a lesser extent with protein carbonyls. 3-Chlorotyrosine levels (at 1 wk after birth) correlated negatively with birth weight or gestational age. They were significantly higher in infants who developed chronic lung disease (oxygen requirement at 36 wk postmenstrual age) than in those who did not (median 88 and 49 micromol/mol tyrosine, respectively) and correlated with days of supplemental oxygen. 3-Chlorotyrosine was also significantly higher in infants who had lung infection or were Ureaplasma urealyticum positive. Our results are the first evidence that chlorinated proteins are produced in the lungs of premature infants and that they are higher in infection. The higher 3-chlorotyrosine levels in infants who develop chronic lung disease suggest that neutrophil oxidants contribute to the pathology of this disease.

Oxidant-antioxidant balance in acute lung injury

ARDS is a disease process that is characterized by diffuse inflammation in the lung parenchyma. The involvement of inflammatory mediators in ARDS has been the subject of intense investigation, and oxidant-mediated tissue injury is likely to be important in the pathogenesis of ARDS. In response to various inflammatory stimuli, lung endothelial cells, alveolar cells, and airway epithelial cells, as well as activated alveolar macrophages, produce both nitric oxide and superoxide, which may react to form peroxynitrite, which can nitrate and oxidize key amino acids in various lung proteins, such as surfactant protein A, and inhibit their functions. The nitration and oxidation of a variety of crucial proteins present in the alveolar space have been shown to be associated with diminished function in vitro and also have been identified ex vivo in proteins sampled from patients with acute lung injury (ALI)/ARDS. Various enzymes and low-molecular-weight scavengers that are present in the lung tissue and alveolar lining fluid decreased the concentration of these toxic species. The purpose of this brief chapter is to review the results from various studies demonstrating increased levels of reactive oxygen-nitrogen intermediates in the alveolar spaces of patients with ALI/ARDS.

Recipient iNOS but not eNOS deficiency reduces luminal narrowing in tracheal allografts

Chronic airway rejection is characterized by prolonged inflammation, epithelial damage, and eventual luminal obliterative bronchiolitis (OB). In cardiac allografts, the inducible nitric oxide synthase (iNOS) promotes acute rejection but paradoxically reduces neointimal formation, the hallmark of chronic rejection. The specific roles of NOS isoforms in modulating lymphocyte traffic and airway rejection are not known. Using a double lumen mouse tracheal transplant model, tracheal grafts from B10.A (allo) or C57BL/6J (iso) mice were transplanted into cyclosporine-treated wild-type (WT) iNOS(-/-) or endothelial NOS (eNOS)(-/-) recipients. OB was observed in WT tracheal allografts at 3 weeks (53 +/- 2% luminal occlusion vs. 17 +/- 1% for isografts, P < 0.05) with sites of obstructive lesion formation coinciding with areas of CD3(+) CD8(+) T cell-rich lymphocytic bronchitis. In contrast, allografts in iNOS(-/-) recipients exhibited reductions in local expression of proinflammatory chemokines and cytokines, graft T cell recruitment and apoptosis, and luminal obliteration (29 +/- 2%, P < 0.05 vs. WT allografts). Recipient eNOS deficiency, however, suppressed neither chemokine expression, lymphocyte infiltration, nor airway occlusion (54 +/- 2%). These data demonstrate that iNOS exacerbates luminal obliteration of airway allografts in contrast with the known suppression by iNOS of cardiac allograft vasculopathy. Because iNOS(-/-) airways transplanted into WT allograft hosts are not protected from rejection, these data suggest that iNOS expressed by graft-infiltrating leukocytes exerts the dominant influence on airway rejection.

Reactive oxygen nitrogen species decrease cystic fibrosis transmembrane conductance regulator expression and cAMP-mediated Cl- secretion in airway epithelia

We investigated putative mechanisms by which nitric oxide modulates cystic fibrosis transmembrane conductance regulator (CFTR) expression and function in epithelial cells. Immunoprecipitation followed by Western blotting, as well as immunocytochemical and cell surface biotinylation measurements, showed that incubation of both stably transduced (HeLa) and endogenous CFTR expressing (16HBE14o-, Calu-3, and mouse tracheal epithelial) cells with 100 microm diethylenetriamine NONOate (DETA NONOate) for 24-96 h decreased both intracellular and apical CFTR levels. Calu-3 and mouse tracheal epithelial cells, incubated with DETA NONOate but not with 100 microm 8-bromo-cGMP for 96 h, exhibited reduced cAMP-activated short circuit currents when mounted in Ussing chambers. Exposure of Calu-3 cells to nitric oxide donors resulted in the nitration of a number of proteins including CFTR. Nitration was augmented by proteasome inhibition, suggesting a role for the proteasome in the degradation of nitrated proteins. Our studies demonstrate that levels of nitric oxide that are likely to be encountered in the vicinity of airway cells during inflammation may nitrate CFTR resulting in enhanced degradation and decreased function. Decreased levels and function of normal CFTR may account for some of the cystic fibrosis-like symptoms that occur in chronic inflammatory lung diseases associated with increased NO production.

Inhibition of hypochlorous acid-induced cellular toxicity by nitrite

Chronic inflammation results in increased nitrogen monoxide (.NO) formation and the accumulation of nitrite (NO(2-)). Neutrophils stimulated by various inflammatory mediators release myeloperoxidase to produce the cytotoxic agent hypochlorous acid (HOCl). Exposure of chondrocytic SW1353 cells to HOCl resulted in a concentration- and time-dependent loss in viability, ATP, and glutathione levels. Treatment of cells with NO(2-) but not nitrate (NO(3-)) substantially decreased HOCl-dependent cellular toxicity even when NO(2-) was added at low (microM) concentrations. In contrast, NO(2-) alone (even at 1 mM concentrations) did not affect cell viability or ATP and glutathione levels. These data suggest that NO(2-) accumulation at chronic inflammatory sites, where both HOCl and.NO are overproduced, may be cytoprotective against damage caused by HOCl. We propose that this is because HOCl is removed by reacting with NO(2-) to give nitryl chloride (NO2Cl), which is less damaging in our cell system.

Nitric oxide in the development of obliterative bronchiolitis in a heterotopic pig model

BACKGROUND

Inflammation, epithelial cell injury, and development of fibrosis and airway obliteration are the major histological features of posttransplant obliterative bronchiolitis (OB). The expression of inducible nitric oxide synthase (iNOS) in the damaged epithelium, accompanied by peroxynitrite, suggests that endogenous nitric oxide (NO) mediates the epithelial destruction preceding obliteration. To elucidate the role of NO in this cascade, heterotopic bronchial allografts were studied in pigs.

METHODS

Allografts or autografts were harvested serially 3-90 days after transplantation and processed for histology and immunocytochemistry for iNOS, nitrotyrosine, a marker of peroxynitrite formation, and superoxide dismutase (SOD).

RESULTS

During initial ischemic damage to the epithelium, iNOS, nitrotyrosine, and SOD were found to be strongly expressed in the epithelium of all implants as well as later, after partial recovery, parallel to onset of epithelial destruction and subsequent airway obliteration in allografts. The levels of expression of iNOS in fibroblasts during the early phase of obliteration paralleled the onset of fibrosis. Constant expression of iNOS and SOD, but not nitrotyrosine, occurred in autografts and allografts with blocked alloimmune response.

CONCLUSIONS

These findings suggest that an excessive amount of NO promotes posttransplant obliterative bronchiolitis by destroying airway epithelium and stimulating fibroblast activity. SOD may provide protection by binding reactive molecules and preventing peroxynitrite formation.

Deficiency in inducible nitric oxide synthase protects mice from ozone-induced lung inflammation and tissue injury

Inhalation of ozone causes Type I epithelial cell necrosis and Type II cell hyperplasia and proliferation. This is associated with an accumulation of activated macrophages in the lower lung, which we have demonstrated contribute to tissue injury. Nitric oxide (NO) is a highly reactive cytotoxic macrophage-derived mediator that has been implicated in lung damage. In the present studies we used knockout mice with a targeted disruption of the gene for inducible nitric oxide synthase (NOSII) to analyze the role of NO in ozone-induced lung inflammation and tissue injury. Treatment of wild-type control mice with ozone (0.8 ppm) for 3 h resulted in a time-dependent increase in protein and cells in bronchoalveolar lavage fluid, which reached a maximum 24-48 h after exposure. Alveolar macrophages isolated from animals treated with ozone were found to produce increased amounts of NO, as well as peroxynitrite. This was correlated with induction of NOSII protein and nitrotyrosine staining of lung macrophages in tissue sections and in culture. Production of superoxide anion and prostaglandin (PG)E2 by alveolar macrophages was also increased after ozone inhalation. In contrast, alveolar macrophages from NOSII knockout mice did not produce reactive nitrogen intermediates even after ozone inhalation. Moreover, production of PGE2 was at control levels. NOSII knockout mice were also protected from ozone-induced inflammation and tissue injury, as measured by bronchoalveolar lavage protein and cell number. There was also no evidence of peroxynitrite-mediated lung damage in these animals. Taken together, these data demonstrate that NO, produced via NOSII, and potentially, its reactive oxidative product peroxynitrite, play a critical role in ozone-induced release of inflammatory mediators and in tissue injury.

The role of neutrophils in the pathogenesis of obliterative bronchiolitis after lung transplantation

Obliterative bronchiolitis (OB) represents the most important long-term complication after lung transplantation. Elevated numbers of neutrophils within the airways are a hallmark of OB. It is unclear what causes the recruitment and activation of neutrophils in the airways of patients with OB: the process of chronic rejection itself or infection, which may (especially in latent virus infection) often be overlooked by the currently applied diagnostic procedures. It is well known that besides their physiologic functions in the clearance of invading micro-organisms, activated neutrophils have a remarkable potential to cause damage to lung tissue. This is attributable to their capability to generate reactive oxygen species and to release potentially toxic proteases. It has been shown that the increased numbers of neutrophils in bronchoalveolar lavage fluid of patients with bronchiolitis obliterans syndrome (BOS) after lung transplantation are associated with elevated levels of interleukin-8, the predominant neutrophil chemotactic factor in the lung. As evidence for the impact of neutrophils on the pathogenesis of BOS, there is significant oxidative stress within the airways of patients with BOS. In addition, the milieu within the airways is characterized by an imbalance between neutrophil elastase (NE) and molecules that inhibit NE as a result of an increased burden of NE released by neutrophils. A defective antiprotease shield due to the loss of secretory leukoprotease inhibitor could be demonstrated in BOS. These mechanisms may provide possible targets to develop new therapeutic strategies that either prevent neutrophil sequestration and activation, or inhibit neutrophil products in order to prevent or attenuate airway damage.

Association of reactive nitrogen species metabolites, myeloperoxidase, and airway inflammation in lung transplants

BACKGROUND

We have previously reported that patients who had single or double lung transplants had higher concentrations than controls of nitrite and nitrate, which are metabolites of reactive nitrogen species (RNS), in bronchoalveolar lavage fluid (BALF) and serum.

METHODS

This study investigates implications of RNS metabolites as markers of airway inflammation in a distinct group of lung transplant patients (n = 40). All patients underwent spirometry, routine surveillance transbronchial lung biopsies, and bronchoalveolar lavage as required by clinical protocol. Four normal controls also had bronchoscopy for measurement of BALF nitrite (NO2-) and nitrate (NO3-). BALF NO2- and NO3-, myeloperoxidase (MPO), protein, and urea were assayed. Total nitrite (NO2- plus enzymatically reduced NO3-) and urea were measured in serum.

RESULTS

BALF RNS metabolites were mainly NO3-. Forced expiratory volume in 1 s (FEV1) obtained near bronchoscopy was compared with best postoperative FEV1. Total nitrite in transplant patients' BALF and serum were 3.8 +/- 0.2 and 49 +/- 5 microM, respectively. Total nitrite in controls' BALF and serum were 2.2 +/- 0.7 and 19 +/- 2 microM, respectively (P < 0.05 compared with transplant values). Serum total nitrite correlated (Pearson product moment) with percentage of neutrophils in BALF (R = 0.650, P < 0.0001), MPO (R = 0.431, P = 0.0055), change in FEV1 from baseline (deltaFEV1) (R = -0348, P = 0.0298), and days after transplantation (R = 0.345, P = 0.0294). None of the associated variables, airway inflanmmation (quantified as a score, "B"), deltaFEV1, serum, or BALF total nitrite, were explained by infection. Univariate analysis of airway inflammation in patients showed that it was associated with BALF neutrophils, deltaFEV1, and serum total nitrite.

CONCLUSIONS

Serum nitrite appears to reflect the degree of airway inflammation in this lung-transplant study group.

Increased levels of nitrate and surfactant protein a nitration in the pulmonary edema fluid of patients with acute lung injury

Levels of nitrite (NO2-) and nitrate (NO3-) were measured in pulmonary edema fluid and plasma from 34 patients with early acute lung injury (ALI) and 20 patients with hydrostatic pulmonary edema. Pulmonary edema fluid from patients with ALI had significantly higher levels of NO2- + NO3- compared with pulmonary edema fluid from patients with hydrostatic pulmonary edema (108 +/- 13 microM versus 66 +/- 9 microM; means +/- SEM; p < 0.05). In addition, patients with shock had higher plasma NO2- + NO3- levels than those without shock (79 +/- 11 microM versus 53 +/- 12 microM, p < 0.05). Acidemia and increased anion gap, markers of systemic hypoperfusion, were also associated with twofold higher plasma NO2- + NO3- levels (p < 0.01). Increased levels of NO2- + NO3- in edema fluid samples were associated with slower rates of alveolar fluid clearance. Nitrated pulmonary surfactant protein A (SP-A) was also detected in the edema fluid of patients with ALI after immunoprecipitation with a specific antibody against this protein. Previously, we have shown that nitration of SP-A impairs its host- defense properties. In aggregate, the results of this study indicate that reactive oxygen-nitrogen species may play a role in the pathogenesis of human ALI.