Apoptosis and formation of peroxynitrite in the lungs of patients with obliterative bronchiolitis

Identification of Hub Genes in the Pathogenesis of Bronchiolitis Obliterans via Bioinformatic Analysis and Experimental Verification

Background

Bronchiolitis obliterans (BO) is a chronic disease that can arise as a complication of severe childhood pneumonia and can also impact the long-term survival of patients after lung transplantation. However, the precise molecular mechanism underlying BO remains unclear. We aimed to identify BO-associated hub genes and their molecular mechanisms.

Methods

BO-associated transcriptome datasets (GSE52761, GSE137169, and GSE94557) were downloaded from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs). Additional bioinformatics analyses, such as Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Protein-Protein Interaction (PPI) analyses, were performed to determine functional roles and DEG-associated regulatory networks. Prediction of hub genes using the 12 algorithms available in the Cytohubba plugin of Cytoscape software was also performed. Verification was performed using the BO mouse model.

Results

Our results revealed 57 DEGs associated with BO, of which 18 were down-regulated and 39 were up-regulated. The Cytohubba plugin data further narrowed down the 57 DEGs into 9 prominent hub genes (CCR2, CD1D, GM2A, TFEC, MPEG1, CTSS, GPNMB, BIRC2, and CTSZ). Genes such as CCR2, TFEC, MPEG1, CTSS, and CTSZ were dysregulated in 2,3-butanedione-induced BO mice, whereas TFEC, CTSS, and CTSZ were dysregulated in nitric acid-induced BO mouse models.

Conclusion

Our study identified and validated four novel BO biomarkers, which may allow further investigation into the development of distinct BO diagnostic markers and novel therapeutic avenues.

miR-27a-3p alleviates lung transplantation-induced bronchiolitis obliterans syndrome (BOS) via suppressing Smad-mediated myofibroblast differentiation and TLR4-induced dendritic cells maturation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS), induced by a chronic rejection, remains a significant obstacle for end-stage lung diseases after lung transplantation. We have previously determined that the small non-coding mRNA (miRNA) miR-27a-3p maintained the immature state of dendritic cells (DCs) via the interleukin 10 (IL-10)-dependent regulatory pathway. Such status helped in preventing rejection and alleviating BOS. The present study explored mechanisms how miR-27a-3p may suppress the fibrosis as well as the maturation of DCs, ultimately attenuating BOS in vitro and in vivo.

METHODS/RESULTS

In our tracheal transplantation mouse model, the expression of Smad2, Smad4, and αSMA were significantly decreased in the miR-27a-3p-transfected DCs (p < 0.0001, p = 0.0006, and p = 0.0002 respectively). Moreover, the expression of fibrosis markers (α-SMA, collagen I, and Fn) were potently inhibited in the miR-27a-3p-transfected NIH-3 T3 cells (p < 0.0001, p = 0.00148, and p < 0.0001 respectively). At the same time, reversed results were observed in the inhibitor group (p = 0.0002, p < 0.0001, and p < 0.0001 respectively), indicating that miR-27a-3p could directly inhibit myofibroblast differentiation. Furthermore, in the tracheal transplanted mice, the population of Treg cells was significantly decreased (p < 0.0001). In contrast, Th17 cells were down-regulated in the miR-27a-3p-transfected DCs group (p < 0.0001), accompanied by the decreased IL-17 levels (p = 0.0007) and the induction of TGF-β1 and IL-10 (p < 0.0001 and p = 0.0016 respectively). Further mechanistic studies indicated that miR-27a-3p altered the maturation of DCs by targeting TLR4 and IRAK (p < 0.0001 and p = 0.0002 respectively).

CONCLUSIONS

Our study suggests that miR-27a-3p selectively blocked the TGF-β1/Smad pathways to suppress the myofibroblast differentiation and targeted the TRL4/IRAK4 pathway to restrain DCs maturation, thus attenuating BOS. Our findings suggest that miR-27a-3p is a potential active molecule on BOS management after lung transplantation.

Nlrp3 Inflammasome Inhibitor MCC950 Ameliorates Obliterative Bronchiolitis by Inhibiting Th1/Th17 Response and Promoting Treg Response After Orthotopic Tracheal Transplantation in Mice

BACKGROUND

Obliterative bronchiolitis (OB) remains the major complication limiting long-term survival of patients after lung transplantation. We aimed to explore the effects of the selective NACHT, LRR, and PYD domains-containing protein 3 (Nlrp3) inflammasome inhibitor MCC950 on the pathogenesis of OB.

METHODS

Mouse orthotopic tracheal transplants were performed to mimic OB. MCC950 (50 mg/kg) or saline was intraperitoneally injected daily. The luminal occlusion rate and collagen deposition were evaluated by hematoxylin and eosin and Masson's trichrome staining, respectively. Infiltration of CD4+, CD8+ T cells, and neutrophils was detected with immunohistochemical staining. The frequencies of T helper 1 cell (Th1), T helper 17 cell (Th17), and regulatory T cells (Treg) were measured by flow cytometry. Cytokine levels were measured by ELISA kits.

RESULTS

MCC950 treatment significantly inhibited Nlrp3 inflammasome activation after allogeneic tracheal transplant and markedly decreased the luminal occlusion rate and collagen deposition in the allograft. The numbers of infiltrating CD4+, CD8+ T cells, and neutrophils in the allograft were also significantly reduced by MCC950 treatment. MCC950 dramatically decreased the frequencies of Th1/Th17 cells and the levels of interferon gamma/interleukin (IL)-17A and increased the Treg cell frequencies and IL-10 level; however, these effects were abolished by the addition of IL-1β and IL-18 both in vitro and in vivo. OB was also rescued by the addition of IL-1β and/or IL-18.

CONCLUSIONS

Blocking Nlrp3 inflammasome activation with MCC950 ameliorates OB lesions. The mechanistic analysis showed that MCC950 regulated the balance of Th1/Th17 and Treg cells and that this process is partially mediated by inhibition of IL-1β and IL-18. Therefore, targeting the Nlrp3 inflammasome is a promising strategy for controlling OB after lung transplantation.

Upregulation of miR-146a increases cisplatin sensitivity of the non-small cell lung cancer A549 cell line by targeting JNK-2

The aim of the present study was to investigate the effects of microRNA (miR-)146a on the cisplatin sensitivity of the non-small cell lung cancer (NSCLC) A549 cell line and study the underlying molecular mechanism. The differences in expression of miRNAs between A549 and A549/cisplatin (A549/DDP) cells were determined, and miR-146a was selected to study its effect on cisplatin sensitivity of A549/DDP cells. miR-146a mimic and inhibitor transient transfection systems were constructed using vectors, and A549/DDP cells were infected with miR-146a mimic and inhibitor to investigate growth, apoptosis and migration. The directed target of miR-146a was determined and the underlying molecular mechanism was validated in the present study. The results of the present study demonstrated that miR-146a was downregulated in NSCLC A549/DDP cells, compared with A549 cells. The overexpression of miR-146a induced apoptosis and inhibited the growth and invasion of A549/DDP cells, which resulted in increased cisplatin sensitivity in NSCLC cells. The JNK2 gene was determined as the direct target of miR-146a, and may be activated by the overexpression of miR-146a. Additionally, JNK2 activated the expression of p53 and inhibited B cell lymphoma 2. The upregulation of miR-146a increased cisplatin sensitivity of the A549 cell line by targeting JNK2, which may provide a novel method for treating NSCLC cisplatin resistance.

The Role of Lysophosphatidic Acid on Airway Epithelial Cell Denudation in a Murine Heterotopic Tracheal Transplant Model

Supplemental digital content is available in the text.

Background

Chronic rejection is the major leading cause of morbidity and mortality after lung transplantation. Obliterative bronchiolitis (OB), a fibroproliferative disorder of the small airways, is the main manifestation of chronic lung allograft rejection. However, there is currently no treatment for the disease. We hypothesized that lysophosphatidic acid (LPA) participates in the progression of OB. The aim of this study was to reveal the involvement of LPA on the lesion of OB.

Methods

Ki16198, an antagonist specifically for LPA₁ and LPA₃, was daily administered into the heterotopic tracheal transplant model mice at the day of transplantation. At days 10 and 28, the allografts were isolated and evaluated histologically. The messenger RNA levels of LPAR in microdissected mouse airway regions were assessed to reveal localization of lysophosphatidic acid receptors. The human airway epithelial cell was used to evaluate the mechanism of LPA-induced suppression of cell adhesion to the extracellular matrix (ECM).

Results

The administration of Ki16198 attenuated airway epithelial cell loss in the allograft at day 10. Messenger RNAs of LPA₁ and LPA₃ were detected in the airway epithelial cells of the mice. Lysophosphatidic acid inhibited the attachment of human airway epithelial cells to the ECM and induced cell detachment from the ECM, which was mediated by LPA₁ and Rho-kinase pathway. However, Ki16198 did not prevent obliteration of allograft at day 28.

Conclusions

The LPA signaling is involved in the status of epithelial cells by distinct contribution in 2 different phases of the OB lesion. This finding suggests a role of LPA in the pathogenesis of OB.

TGF-β1 as a therapeutic target for pulmonary fibrosis and COPD

TGF-β1 is a multifunctional molecule that is expressed in an exaggerated fashion during injury, inflammation and repair. Its expression is dysregulated in lung tissues from patients with pulmonary fibrosis and chronic obstructive pulmonary disease. In animal models, introduction of TGF-β1 expression in the lung causes prominent tissue fibrosis and alveolar destruction. On the other hand, the exaggerated production of TGF-β1, an inability to activate TGF-β1 or a block in TGF-β1 signaling have all been associated with the development of emphysematous pulmonary lesions. A number of studies have demonstrated that TGF-β1 is a major player in the pathogenesis of pulmonary fibrosis and emphysema. In this review, we discuss how TGF-β1 expression is regulated and mechanistically related to the development of tissue fibrosis and emphysema in experimental animal models and humans. We further highlight potential therapeutic options that control TGF-β1-associated genes or signals to restore extracellular matrix homeostasis in which TGF-β1 plays a central role.

Altered sputum granzyme B and granzyme B/proteinase inhibitor-9 in patients with non-eosinophilic asthma

BACKGROUND AND OBJECTIVE

The non-eosinophilic phenotype of asthma (NEA) is associated with chronic airway inflammation and airway neutrophilia. An accumulation of apoptotic airway epithelial cells, if not efficiently cleared by efferocytosis, can undergo secondary necrosis, with the potential for inflammation of surrounding tissues. Apoptosis may occur via the T cell granzyme B pathway. The role of granzyme B in NEA is not known. The aim of this study was to investigate production of granzyme B and its inhibitor proteinase inhibitor (PI)-9 by T cells from induced sputum and compare expression between eosinophilic, NEA and healthy controls.

METHODS

We investigated T cell intracellular granzyme B and its inhibitor, PI-9, in sputum from healthy control subjects (n = 10), and patients with NEA (n = 22) or eosinophilic asthma (EA) (n = 15) using flow cytometry.

RESULTS

Granzyme B expression and the ratio of granzyme B to PI-9 positive cells were highest in those with NEA for both CD3+ and CD4+ T cells. The expression of granzyme B was not statistically different between patients with NEA and EA; however, the ratio of granzyme B to PI-9 positive cells for CD3+ T cells was significantly higher in those with NEA compared with EA.

CONCLUSIONS

Induced sputum provides a non-invasive tool for investigating T cell cytotoxic mediators in the various asthma subtypes. Granzyme B expression is increased in NEA and the contribution of granzyme B to chronic inflammation requires further study.

Apoptosis and the airway epithelium

The airway epithelium functions as a barrier and front line of host defense in the lung. Apoptosis or programmed cell death can be elicited in the epithelium as a response to viral infection, exposure to allergen or to environmental toxins, or to drugs. While apoptosis can be induced via activation of death receptors on the cell surface or by disruption of mitochondrial polarity, epithelial cells compared to inflammatory cells are more resistant to apoptotic stimuli. This paper focuses on the response of airway epithelium to apoptosis in the normal state, apoptosis as a potential regulator of the number and types of epithelial cells in the airway, and the contribution of epithelial cell apoptosis in important airways diseases.

Chronic rejection of a lung transplant is characterized by a profile of specific autoantibodies

SUMMARY

Obliterative bronchiolitis (OB) continues to be the major limitation to long-term survival after lung transplantation. The specific aetiology and pathogenesis of OB are not well understood. To explore the role of autoreactivity in OB, we spotted 751 different self molecules onto glass slides, and used these antigen microarrays to profile 48 human serum samples for immunoglobulin G (IgG) and IgM autoantibodies; 27 patients showed no or mild bronchiolitis obliterans syndrome (BOS; a clinical correlate of OB) and 15 patients showed medium to severe BOS. We now report that these BOS grades could be differentiated by a profile of autoantibodies binding to 28 proteins or their peptides. The informative autoantibody profile included down-regulation as well as up-regulation of both IgM and IgG specific reactivities. This profile was evaluated for robustness using a panel of six independent test patients. Analysis of the functions of the 28 informative self antigens showed that eight of them are connected in an interaction network involved in apoptosis and protein metabolism. Thus, a profile of autoantibodies may reflect pathological processes in the lung allograft, suggesting a role for autoimmunity in chronic rejection leading to OB.

Differential role of the Fas/Fas ligand apoptotic pathway in inflammation and lung fibrosis associated with reovirus 1/L-induced bronchiolitis obliterans organizing pneumonia and acute respiratory distress syndrome

Bronchiolitis obliterans organizing pneumonia (BOOP) and acute respiratory distress syndrome (ARDS) are two clinically and histologically distinct syndromes sharing the presence of an inflammatory and fibrotic component. Apoptosis via the Fas/Fas ligand (FasL) pathway plays an important role in the development of acute lung injury and fibrosis characteristic of these and other pulmonary inflammatory and fibrotic syndromes. We evaluated the role of apoptosis via the Fas/FasL pathway in the development of pulmonary inflammation and fibrosis in reovirus 1/L-induced BOOP and ARDS. CBA/J mice were intranasally inoculated with saline, 1 x 10(6) (BOOP), or 1 x 10(7) (ARDS) PFU reovirus 1/L, and evaluated at various days postinoculation for in situ apoptosis by TUNEL analysis and Fas/FasL expression. Our results demonstrate the presence of apoptotic cells and up-regulation of Fas/FasL expression in alveolar epithelium and in infiltrating cells during the inflammatory and fibrotic stages of both reovirus 1/L-induced ARDS and BOOP. Treatment of mice with the caspase 8 inhibitor, zIETD-fmk, inhibited apoptosis, inflammation, and fibrotic lesion development in reovirus 1/L-induced BOOP and ARDS. However, CBA/KlJms-Fas(lpr-cg)/J mice, which carry a point mutation in the Fas cytoplasmic region that abolishes the ability of Fas to transduce an apoptotic signal, do not develop pulmonary inflammation and fibrotic lesions associated with reovirus 1/L-induced BOOP, but still develop inflammation and fibrotic lesions associated with reovirus 1/L-induced ARDS. These results suggest a differential role for the Fas/FasL apoptotic pathway in the development of inflammation and fibrotic lesions associated with BOOP and ARDS.

Transgenic modeling of transforming growth factor-beta(1): role of apoptosis in fibrosis and alveolar remodeling

Inflammation and tissue remodeling with pathologic fibrosis are common consequences of Th2 responses in the lung and other organs. Interleukin (IL)-13 and transforming growth factor-beta1 (TGF-beta(1)) are frequently coexpressed in these responses and are believed to play important roles in the pathogenesis of Th2-induced pathologies. To shed light on the mechanisms of these responses, overexpression transgenic approaches were used to selectively target each of these cytokines to the murine lung. IL-13 proved to be a potent stimulator of eosinophilic inflammation, mucus metaplasia, tissue fibrosis, and alveolar remodeling. CC chemokines, specific chemokine receptors (CCR2, CCR1), adenosine metabolism, vascular endothelial growth factor, and IL-11 contributed to the genesis of these responses. IL-13 also induced tissue fibrosis, at least in part, via its ability to induce and activate TGF-beta(1). In the TGF-beta(1) transgenic mouse, epithelial apoptosis preceded the onset of tissue fibrosis and alveolar remodeling. In addition, chemical (Z-VAD-fmk) and genetic (null mutations of early growth response gene 1) interventions blocked apoptosis and ameliorated TGF-beta(1)-induced fibrosis and alveolar restructuring. These studies define an IL-13-TGF-beta(1) pathway of tissue remodeling that regulates inflammation, mucus metaplasia, apoptosis, vascular responses, and fibrosis in the lung. They also highlight the intimate relationship between apoptosis and fibrosis induced by TGF-beta(1). By defining the complexities of this pathway, these studies highlight sites at which therapies can be directed to control these important responses.

Sequential gene expression profiling in lung transplant recipients with chronic rejection

STUDY OBJECTIVES

Chronic allograft rejection is the leading cause of morbidity and mortality for long-term survivors of lung transplantation. Previous studies have implicated only isolated genes in the development of chronic rejection and have not examined multiple pathways in an individual concurrently. Using microarray technology, we identified and compared gene expression profiling in lung transplant recipients with and without chronic rejection, and follow sequential expression of genes differentially expressed between the two groups.

DESIGN

Prospective, cohort study.

SETTING

Single lung transplant center.

PATIENTS OR PARTICIPANTS

Eleven transplant recipients with chronic rejection were matched with 9 control transplant recipients.

INTERVENTIONS

All recipients underwent surveillance bronchoscopies at predetermined times to rule out infection and/or acute rejection. Gene expression profiling was obtained from hybridizing BAL fluid cell RNA to a 96-gene microarray.

MEASUREMENTS AND RESULTS

Fifteen genes were found to be significantly differentially expressed between the two patient groups, and they are involved in inflammatory, fibrotic, and apoptotic pathways. Temporal expression of the significant genes demonstrated a change in their levels at the onset of chronic rejection, with normalization to prerejection levels as rejection continued.

CONCLUSIONS

We conclude that microarray technology is valuable in studying the mechanism of chronic lung rejection, and the expression of genes in multiple pathways is elevated in patients with chronic lung rejection.

Burying the dead: the impact of failed apoptotic cell removal (efferocytosis) on chronic inflammatory lung disease

Apoptosis and the removal of apoptotic cells (termed efferocytosis) are tightly coupled with the regulation of normal lung structure, both in the developing and adult organism. Processes that disrupt or uncouple this balance have the potential to alter normal cell turnover, ultimately resulting in the induction of lung pathology and disease. Apoptotic cells are increased in several chronic inflammatory lung diseases, including cystic fibrosis (CF), non-CF bronchiectasis, COPD, and asthma. While this may well be due to the enhanced induction of apoptosis, increasing data suggest that the clearance of dying cells is also impaired. Because efferocytosis appears to be a key regulatory checkpoint for the innate immune system, the adaptive immune system, and cell proliferation, the failure of this highly conserved process may contribute to disease pathogenesis by impeding both the resolution of inflammation and the maintenance of alveolar integrity. The recognition of impaired efferocytosis as a contributor to chronic inflammation may ultimately direct us toward the identification of new disease biomarkers, as well as novel therapeutic approaches.

Induction of obliterative airway disease by anti-HLA class I antibodies

Anti-HLA class I Abs are associated with the development of bronchiolitis obliterans syndrome (BOS) after lung transplantation. BOS is characterized histologically by fibrosis and airway epithelial cell apoptosis. We have previously shown that anti-HLA class I Abs induce proliferation, growth factor production and apoptosis in airway epithelial cells in vitro. Thus, this study was designed to determine whether anti-HLA class I Abs alone could induce obliterative airway disease (OAD) in heterotopic murine tracheal allografts. Toward this, HLA-A*0201-transgenic tracheal allografts were transplanted into Rag1-deficient mice treated with the W6/32 anti-HLA class I mAb. Allografts were harvested at days +30, +45, +60 and +90. Allografts displayed epithelial metaplasia by day +45, epithelial destruction and mild cellular infiltration by day +60 and complete lumen obliteration and moderate cellular infiltration by day +90. Anti-HLA class I Abs induced the production of several growth factors and growth factor receptors and apoptosis of parenchymal cells in the allograft. In addition, anti-HLA class I Abs induced macrophages and granulocytes infiltration. The results from this study demonstrate that anti-HLA class I Abs play an important role in the pathogenesis of OAD by inducing growth factor production, apoptosis and chemotaxis of inflammatory cells.

Immune mechanisms in the pathogenesis of bronchiolitis obliterans syndrome after lung transplantation

Lung transplantation is recognized as the only viable treatment option in a variety of end-stage pulmonary diseases. However, the long-term survival after lung transplantation is limited by the development of obliterative bronchiolitis, and its clinical correlate bronchiolitis obliterans syndrome (BOS), which is considered to represent chronic lung allograft rejection. Histopathologically, BOS is an inflammatory process that leads to fibrous scarring of the terminal and respiratory bronchioles and subsequent total occlusion of the airways. The specific etiology and pathogenesis of BOS are not well understood. The current premise is that BOS represents a common lesion in which different inflammatory insults such as ischemia-reperfusion, rejection, and infection can lead to a similar histological and clinical outcome. However, the low incidence of BOS in non-transplanted individuals and the observation that early development of BOS is predicted by the frequency and severity of acute rejection episodes indicate that alloimmune-dependent mechanisms play a crucial role in the pathogenesis of BOS. The evidence presented in this review indicates that BOS is the result of humoral and cellular immune responses developed against major histocompatibility complex molecules expressed by airway epithelial cells of the lung allograft. This process is aggravated by alloimmune-independent mechanisms such as ischemia-reperfusion and infection. Currently, treatment of BOS is frequently unsuccessful. Therefore, a better understanding of the immunopathogenesis of BOS is of paramount importance toward improving long-term patient and graft survival after lung transplantation.

Epithelial apoptosis in experimental obliterative airway disease after lung transplantation

BACKGROUND

Epithelial damage is an important feature in the pathogenesis of obliterative airway disease. We investigated the extent of epithelial apoptosis in this process in pig bronchial allografts.

METHODS

The bronchial grafts (total, n = 200) were placed subcutaneously into recipients. Three allograft groups were formed: the first group had no immunosuppression therapy; the second received triple therapy with 10 mg/kg/day cyclosporine, 2 mg/kg/day azathioprine, and 20 mg/day methylprednisolone; and the third was given triple therapy in which azathioprine was replaced with 1.5 mg/kg/day everolimus (40-O-[2-hydroxyethyl]-rapamycin). The fourth group, which had allograft and autograft implants, received only 1.5 mg/kg/day everolimus. The implants were serially removed during 3 months of follow-up. We evaluated graft histology and analyzed the apoptotic index percentage (apoptotic cells / total number of cells) of the bronchial epithelium using in situ 3'-end labeling of apoptotic DNA.

RESULTS

Epithelial destruction and subsequent obliteration of the bronchial lumen were complete by Day 28 in non-treated allografts and in most allografts with inadequate immunosuppression to prevent these changes (those treated with cyclosporine, azathioprine, and methylprednisolone and those treated with everolimus only). The apoptotic indexes of the epithelium were high (>1% of the cells were apoptotic) and increased with concomitant epithelial destruction. In allografts with adequate immunosuppression to prevent epithelial destruction (those treated with cyclosporine, everolimus, and methylprednisolone) and in autografts, after initial damage, well-pre-served epithelium was maintained with low apoptotic indexes (<1% of the cells apoptotic).

CONCLUSIONS

Apoptotic activity increased with progressing epithelial damage preceding bronchial obliteration. Our results give further evidence that apoptotic death of epithelial cells is an important mechanism in events that lead to graft deterioration in obliterative bronchiolitis after lung transplantation.

Enhanced peroxynitrite decomposition protects against experimental obliterative bronchiolitis

Obliterative bronchiolitis (OB) affects over half of all survivors following lung or heart-lung transplantation. Respiratory epithelial cell injury, peribronchial inflammation, and proliferation of fibrovascular tissue causing airway occlusion characterize the lesion. While peroxynitrite is known to participate in other models of acute lung injury, its role in the evolution of OB is unclear. Using a rat model of experimental OB, tracheas from Brown-Norway or Lewis rats were transplanted into Lewis recipients. Treated animals received FP-15, a peroxynitrite decomposition catalyst, at 1 mg/kg/day intraperitoneal for 14 days. Luminal obstruction, epithelial loss, and inflammatory infiltrate were examined, as was nitrotyrosine staining by immunohistochemistry in explanted tracheas. By postoperative day 14, control allografts demonstrated marked peribronchial inflammation, near complete loss of respiratory epithelium and extensive intraluminal proliferation of fibrovascular connective tissue, with a mean 83% reduction in airway cross-sectional area. Allograft recipients treated with FP-15 showed reduced nitrotyrosine formation, preservation of respiratory epithelium, limited peribronchial inflammation, and only 14% (P <.001) reduction in airway cross-sectional area. Peroxynitrite therefore appears to play a role in the development of obliterative bronchiolitis in rats. The peroxynitrite decomposition catalyst, FP-15, is protective when administered daily and warrants investigation into its potential clinical utility.

Alveolar macrophages from subjects with chronic obstructive pulmonary disease are deficient in their ability to phagocytose apoptotic airway epithelial cells

Chronic obstructive pulmonary disease is a highly prevalent, complex disease, usually caused by cigarette smoke. It causes serious morbidity and mortality and costs the global community billions of dollars per year. While chronic inflammation, extracellular matrix destruction and increased airway epithelial cell apoptosis are reported in chronic obstructive pulmonary disease, the understanding of the basic pathogenesis of the disease is limited and there are no effective treatments. We hypothesized that the accumulation of apoptotic airway epithelial cells chronic obstructive pulmonary disease in could be due to defective phagocytic clearance by alveolar macrophages. There have been no previous studies of the phagocytic capacity of alveolar macrophages in chronic obstructive pulmonary disease using physiologically relevant apoptotic airway epithelial cells as phagocytic targets. We developed a phagocytosis assay whereby cultured 16HBE airway epithelial cells were induced to apoptosis with ultraviolet radiation and stained with mitotracker green. Alveolar macrophages from bronchoalveolar lavage from eight control and six chronic obstructive pulmonary disease subjects were analysed following 1.5 h incubation with apoptotic airway epithelial cells, then staining with macrophage marker anti CD33. CD33+/mitotracker green + events (i.e., alveolar macrophages which had phagocytosed apoptotic airway epithelial cells) were analysed using flow cytometry. Phagocytosis of polystyrene microbeads was investigated in parallel. A significantly reduced proportion of alveolar macrophages from chronic obstructive pulmonary disease subjects ingested apoptotic airway epithelial cells compared with controls (11.6 +/- 4.1% for chronic obstructive pulmonary disease versus 25.6 +/- 9.2% for control group). Importantly, the deficiency was not observed using polystyrene beads, suggesting that the failure to resolve epithelial damage in chronic obstructive pulmonary disease may result, at least partially, from specific defects in phagocytic ability of alveolar macrophages to ingest apoptotic airway epithelial cells.

Anti-HLA class I antibody binding to airway epithelial cells induces production of fibrogenic growth factors and apoptotic cell death: a possible mechanism for bronchiolitis obliterans syndrome

Development of anti-HLA class I antibodies is associated with bronchiolitis obliterans syndrome (BOS) after lung transplantation. BOS is characterized histologically by significant fibrosis and airway epithelial cell (AEC) apoptosis. Thus, this study was designed to determine whether anti-HLA class I antibodies can activate AECs to produce growth factors and to undergo apoptosis. KCC-266 AECs were activated with the W6/32 anti-HLA class I monoclonal antibody. Proliferation and apoptosis levels were determined after 24, 48, and 72 hours. The induction of fibroblast and bronchial smooth muscle cell proliferation by anti-HLA class I activated AECs was assessed in the presence of neutralizing antibodies against various growth factors. The anti-HLA class I induced AEC proliferation after 24 hours followed by significant induction of apoptosis after 48 hours. Anti-HLA class I activated AECs produced soluble growth factors that stimulated fibroblasts but not bronchial smooth muscle cells. The stimulation of fibroblast proliferation was inhibited by antibodies against platelet-derived growth factor, heparin-binding epidermal growth factor, insulin-like growth factor 1, and basic fibroblast growth factor. The results from this study suggest that anti-HLA class I alloantibodies may play an important role in the pathogenesis of BOS by inducing proliferation, growth factor production, and apoptotic cell death in AECs.

Spatial mapping of pulmonary and vascular nitrotyrosine reveals the pivotal role of myeloperoxidase as a catalyst for tyrosine nitration in inflammatory diseases

Nitrotyrosine (NO(2)Tyr) formation is a hallmark of acute and chronic inflammation and has been detected in a wide variety of human pathologies. However, the mechanisms responsible for this posttranslational protein modification remain elusive. While NO(2)Tyr has been considered a marker of peroxynitrite (ONOO(-)) formation previously, there is growing evidence that heme-protein peroxidase activity, in particular neutrophil-derived myeloperoxidase (MPO), significantly contributes to NO(2)Tyr formation in vivo via the oxidation of nitrite (NO(2)(-)) to nitrogen dioxide (.NO(2)). Coronary arteries from a patient with coronary artery disease, liver and lung tissues from a sickle cell disease patient, and an open lung biopsy from a lung transplant patient undergoing rejection were analyzed immunohistochemically to map relative tissue distributions of MPO and NO(2)Tyr. MPO immunodistribution was concentrated along the subendothelium in coronary tissue and hepatic veins as well as in the alveolar epithelial compartment of lung tissue from patients with sickle cell disease or acute rejection. MPO immunoreactivity strongly colocalized with NO(2)Tyr formation, which was similarly distributed in the subendothelial and epithelial regions of these tissues. The extracellular matrix protein fibronectin (FN), previously identified as a primary site of MPO association in vascular inflammatory reactions, proved to be a major target protein for tyrosine nitration, with a strong colocalization of MPO, NO(2)Tyr, and tissue FN occurring. Finally, lung tissue from MPO(-/-) mice, having tissue inflammatory responses stimulated by intraperitoneal zymosan administration, revealed less subendothelial NO(2)Tyr immunoreactivity than tissue from wild-type mice, confirming the significant role that MPO plays in catalyzing tissue nitration reactions. These observations reveal that (i) sequestration of neutrophil-derived MPO in vascular endothelial and alveolar epithelial compartments is an important aspect of MPO distribution and action in vivo, (ii) MPO-catalyzed NO(2)Tyr formation occurs in diverse vascular and pulmonary inflammatory pathologies, and (iii) extracellular matrix FN is an important target of tyrosine nitration in these inflammatory processes.

Epithelial kinetics in mouse heterotopic tracheal allografts

Obliterative bronchiolitis (OB) is the most important cause of graft dysfunction post-lung transplantation. It is likely that the small airway epithelium is a target of the alloimmune response, and that epithelial integrity is a crucial determinant of airway patency. Our goals are to elucidate epithelial cell kinetics in the heterotopic mouse trachea model and to determine potential mechanisms of cell death in allografts. Allografts and isografts were obtained by transplanting BALB/c tracheas into C57BL/6 and BALB/c immunosuppressed and non-immunosuppressed hosts, respectively and harvested from day 3-20. Morphometry, BrdU and TUNEL labeling, and EM studies were performed. Columnar epithelium in isografts and allografts sloughs during day 0-3, but regenerates in both sets of grafts by day 10. Subsequently, allografts become inflamed and denuded, while isografts retain an intact epithelium. Prior to airway denudation, allografts exhibited significantly increased epithelial cell density, BrdU labeling index (LI), and TUNEL positive cells. Epithelial apoptosis was confirmed by electron microscopy. Allograft percent ciliated columnar epithelium and lumenal circumference were significantly decreased. Cyclosporin delayed airway fibrosis but did not alter the progression of the allograft through the phases of early ischemic injury, airway epithelial cell regeneration, and eventual cell death. These studies quantitatively demonstrate that the allograft epithelium actively regenerates in the alloimmune environment, but succumbs to increased apoptotic cell death, underscoring the importance of the airway epithelium as a self-renewing source of alloantigen.

Thiol antioxidants inhibit the adjuvant effects of aerosolized diesel exhaust particles in a murine model for ovalbumin sensitization

Although several epidemiological studies indicate a correlation between exposure to ambient particulate matter and adverse health effects in humans, there is still a fundamental lack of understanding of the mechanisms involved. We set out to test the hypothesis that reactive oxygen species are involved in the adjuvant effects of diesel exhaust particles (DEP) in a murine OVA sensitization model. First, we tested six different antioxidants, N-acetylcysteine (NAC), bucillamine (BUC), silibinin, luteolin, trolox (vitamin E), and ascorbic acid, for their ability to interfere in DEP-mediated oxidative stress in vitro. Of the six agents tested, only the thiol antioxidants, BUC and NAC, were effective at preventing a decrease in intracellular reduced glutathione:glutathione disulfide ratios, protecting cells from protein and lipid oxidation, and preventing heme oxygenase 1 expression. Therefore, we selected the thiol antioxidants for testing in the murine OVA inhalation sensitization model. Our data demonstrate that NAC and BUC effectively inhibited the adjuvant effects of DEP in the induction of OVA-specific IgE and IgG1 production. Furthermore, NAC and BUC prevented the generation of lipid peroxidation and protein oxidation in the lungs of OVA- plus DEP-exposed animals. These findings indicate that NAC and BUC are capable of preventing the adjuvant effects of inhaled DEP and suggest that oxidative stress is a key mechanistic component in the adjuvant effect of DEP. Antioxidant treatment strategies may therefore serve to alleviate allergic inflammation and may provide a rational basis for treating the contribution of particulate matter to asthmatic disease.

Selective nitration of histone tyrosine residues in vivo in mutatect tumors

Nitric oxide-derived reactive species have been implicated in many disorders. Protein nitrotyrosine is often used as a stable marker of these reactive species. Using immunohistochemistry, we have previously detected nitrotyrosine in murine Mutatect tumors, where neutrophils are the principal source of nitric oxide. We now report on the identification of several prominent nitrotyrosine-containing proteins. Using Western blot analysis, nitrotyrosine in higher molecular mass proteins (>20 kDa) was detected in tumors containing a high number of neutrophils but not in tumors with fewer neutrophils. Staining for nitrotyrosine was consistently seen in low molecular mass proteins (< or =15 kDa), regardless of the level of neutrophils. Protein nitrotyrosine was not seen in Mutatect cells growing in vitro. Treatment with nitric oxide donors produced nitration of < or =15-kDa proteins, but only after extended periods. These small proteins, both from tumors and cultured cells, were identified by mass spectrometry to be histones. Only a subset of tyrosine residues was nitrated. Selective nitration may reflect differential accessibility of different tyrosine residues and the influence of neighboring residues within the nucleosome. The prominence of histone nitration may reflect its relative stability, making this post-translational modification a potentially useful marker of extended exposure of cells or tissues to nitric oxide-derived reactive species.

Tyrosine nitration: localisation, quantification, consequences for protein function and signal transduction

The nitration of free tyrosine or protein tyrosine residues generates 3-nitrotyrosine the detection of which has been utilised as a footprint for the in vivo formation of peroxynitrite and other reactive nitrogen species. The detection of 3-nitrotyrosine by analytical and immunological techniques has established that tyrosine nitration occurs under physiological conditions and levels increase in most disease states. This review provides an updated, comprehensive and detailed summary of the tissue, cellular and specific protein localisation of 3-nitrotyrosine and its quantification. The potential consequences of nitration to protein function and the pathogenesis of disease are also examined together with the possible effects of protein nitration on signal transduction pathways and on the metabolism of proteins.

Nitric oxide: a pro-inflammatory mediator in lung disease?

Inflammatory diseases of the respiratory tract are commonly associated with elevated production of nitric oxide (NO*) and increased indices of NO* -dependent oxidative stress. Although NO* is known to have anti-microbial, anti-inflammatory and anti-oxidant properties, various lines of evidence support the contribution of NO* to lung injury in several disease models. On the basis of biochemical evidence, it is often presumed that such NO* -dependent oxidations are due to the formation of the oxidant peroxynitrite, although alternative mechanisms involving the phagocyte-derived heme proteins myeloperoxidase and eosinophil peroxidase might be operative during conditions of inflammation. Because of the overwhelming literature on NO* generation and activities in the respiratory tract, it would be beyond the scope of this commentary to review this area comprehensively. Instead, it focuses on recent evidence and concepts of the presumed contribution of NO* to inflammatory diseases of the lung.