Pathophysiology of the pleura

Immunotoxicological impact of engineered nanomaterial exposure: mechanisms of immune cell modulation

Abstract Engineered nanomaterials (ENMs) are increasingly being utilized in many consumer products and various medical applications, thereby leading to the potentiality of increased human exposures. Assessment of the adverse effects on the immune system is an important component for evaluating the overall health and safety of ENM. Tasked with eliminating pathogens and removing cancerous cells, the immune system is constantly functioning to maintain homeostasis. Small modifications to the immune system, which may occur following ENM exposure, could lead to impaired protection or an inappropriate immune response resulting in autoimmunity and damage to the host. This review seeks to survey and evaluate the current literature to better understand the impact of ENM exposure on cells critical to the innate and adaptive immune systems.

Pleural mesothelial cells promote expansion of IL-17-producing CD8+ T cells in tuberculous pleural effusion

IL-17-producing CD8(+) T lymphocytes (Tc17 cells) have recently been detected in many cancers and autoimmune diseases. However, the possible implication of Tc17 cells in tuberculous pleural effusion remains unclarified. In this study, distribution and phenotypic features of Tc17 cells in both tuberculous pleural effusion (TPE) and peripheral blood from patients with tuberculosis were determined. The effects of proinflammatory cytokines and local accessory cells (pleural mesothelial cells) on Tc17 cell expansion were also explored. We found that TPE contained more Tc17 cells than the blood. Compared with IFN-γ-producing CD8(+) T cells, Tc17 cells displayed higher expression of chemokine receptors (CCRs) and lower expression of cytotoxic molecules. In particularly, Tc17 cells in TPE exhibited high expression levels of CCR6, which could migrate in response to CCL20. Furthermore, IL-1β, IL-6, IL-23, or their various combinations could promote Tc17 cell expansion from CD8(+) T cells, whereas the proliferative response of Tc17 cells to above cytokines was lower than that of Th17 cells. Pleural mesothelial cells (PMCs) were able to stimulate Tc17 cell expansion via cell contact in an IL-1β/IL-6/IL-23 independent fashion. Thus this study demonstrates that Tc17 cells marks a subset of non-cytotoxic, CCR6(+) CD8(+) T lymphocytes with low proliferative capacity. The overrepresentation of Tc17 cells in TPE may be due to Tc17 cell expansion stimulated by pleural proinflammatory cytokines and to recruitment of Tc17 cells from peripheral blood. Additionally, PMCs may promote the production of IL-17 by CD8(+) T cells at sites of TPE via cell-cell interactions.

The diagnosis and management of pleural effusions in the ICU

Pleural effusions are common in critically ill patients. Most effusions in intensive care unit (ICU) patients are of limited clinical significance; however, some are important and require aggressive management. Transudative effusions in the ICU are commonly caused by volume overload, decreased plasma oncotic pressure, and regions of altered pleural pressure attributable to atelectasis and mechanical ventilation. Exudates are sequelae of pulmonary or pleural infection, pulmonary embolism, postsurgical complications, and malignancy. Increases in pleural fluid volume are accommodated principally by chest wall expansion and, to a lesser degree, by lung collapse. Studies in mechanically ventilated patients suggest that pleural fluid drainage can result in improved oxygenation for up to 48 hours, but data on clinical outcomes are limited. Mechanically ventilated patients with pleural effusions should be semirecumbant and treated with higher levels of positive-end expiratory pressure. Rarely, large effusions can cause cardiac tamponade or tension physiology, requiring urgent drainage. Bedside ultrasound is both sensitive and specific for diagnosing pleural effusions in mechanically ventilated patients. Sonographic findings of septation and homogenous echogenicity may suggest an exudative effusion, but definitive diagnosis requires pleural fluid sampling. Thoracentesis should be carried out under ultrasound guidance. Antibiotic regimens for parapneumonic effusions should be based on current pneumonia guidelines, and anaerobic coverage should be included in the case of empyema. Decompression of the pleural space may be necessary to improve respiratory mechanics, as well as to treat complicated effusions. While small-bore catheters inserted under ultrasound guidance may be used for nonseptated effusions, surgical consultation should be sought in cases where this approach fails, or where the effusion appears complex and septated at the outset. Further research is needed to determine the effects of pleural fluid drainage on clinical outcomes in mechanically ventilated patients, to evaluate weaning strategies that include pleural fluid drainage, and to better identify patients in whom pleural effusions are more likely to be infected.

Recombinant human endostatin endostar suppresses angiogenesis and lymphangiogenesis of malignant pleural effusion in mice

Background

Malignant pleural effusion (MPE) is a common complication of lung cancer. One widely used treatment for MPE is Endostar, a recombined humanized endostatin based treatment. However, the mechanism of this treatment is still unclear. The aim of this study was to investigate the effects of Endostar in mice with MPE.

Methods and Materials

Lewis lung carcinoma (LLC) cell line expressing enhanced green fluorescent protein (EGFP) was injected into pleural cavity to establish MPE mice model. Mice were randomly divided into four groups. High dose of Endostar (30 mg/kg), low dose of Endostar (8 mg/kg), normal saline, or Bevacizumab (5 mg/kg) was respectively injected into pleural cavity three times with 3-day interval in each group. Transverse computed tomography (CT) was performed to observe pleural fluid formation 14 days after LLC cells injection. Mice were anesthetized and sacrificed 3 days after final administration. The volume of pleural effusion n was measured using 1 ml syringe. Micro blood vessel density (MVD), Lymphatic micro vessel density (LMVD), the expression level of vascular endothelial growth factor A (VEGF-A) and VEGF-C were observed by immunohistochemistry (IHC) staining.

Results

The volume of pleural effusion as well as the number of pleural tumor foci, MVD and the expression of VEGF-A were significantly reduced in high dose of Endostar treat group. More importantly, LMVD and the expression of VEGF-C were markedly lower in treat group than those in the other three control groups.

Conclusion

Our work demonstrated that Endostar played an efficient anti-cancer role in MPE through its suppressive effect on angiogenesis and lymphangiogenesis, which provided a certain theoretical basis for the effectiveness of Endostar on the MPE treatment.

TLR2 in pleural fluid is modulated by talc particles during pleurodesis

The aim of this study was to examine the role of TLR2 molecule in pleural space during thoracoscopic talc pleurodesis period in patients with malignant pleural effusion. We analyzed TLR2 molecule in soluble form as well as on membrane of granulocytes in pleural fluid. Pleural fluid examination was done at three intervals during pleurodesis procedure: 1st—before the thoracoscopic procedure, 2nd—2 hours after the terminating thoracoscopic procedure with talc insufflation, 3rd—24 hours after the thoracoscopic procedure. We reported significant increase of soluble TLR2 molecule in pleural fluid effusion during talc pleurodesis from preoperative value. This increase was approximately 8-fold in the interval of 24 hours. The changes on granulocyte population were quite different. The mean fluorescent intensity of membrane TLR2 molecule examined by flow cytometry on granulocyte population significantly decreased after talc exposure with comparison to prethoracoscopic density. To estimate the prognostic value of TLR2 expression in pleural fluid patients were retrospectively classified into either prognostically favourable or unfavourable groups. Our results proved that patients with favourable prognosis had more than 3-fold higher soluble TLR2 level in pleural fluid early, 2 hours after talc pleurodesis intervention.

The dynamics of selected local inflammatory markers to talc in the treatment of malignant pleural effusions

BACKGROUND

Malignant pleural effusions accumulate in the space between the visceral (inner) layer covering the lungs and the parietal (outer) layer covering the chest wall. Larger effusions compress the pulmonary parenchyma resulting in increasing dyspnoea. Treatment is always local and palliative. Among others, chemical pleurodesis using talc can be performed in selected patients. Talc is hydrated magnesium silicate (chemically H₂Mg₃(SiO₃)₄) and has been used for pleurodesis since 1935. Videothoracoscopic talc powder insufflation (talc poudrage) is the most effective.However, markers of inflammatory reactions to extraneous substances like talc are not fully understood. The aim of this study was to assess the course of local inflammatory changes in the pleural cavity after talc insufflation.

METHODS

The Department of Cardiac Surgery of the Faculty of Medicine and University Hospital in Hradec Kralove, treated 47 patients aged 65 on average; 29 males and 18 females with proven recurrent malignant pleural effusion of various aetiologies from January 2009 to December 2010. They were retrospectively divided into group A (40 patients) without recurring effusion, and group B (7 patients) with recurring effusion and the need for thoracentesis or chest drainage during the 9-month monitoring.

RESULTS

Major findings were made in soluble forms of cell receptors. Group B showed statistically higher levels of the anti-inflammatory form of sCD-163 receptor in pleural fluid before the talc poudrage. This showed limited ability to create an adequate inflammatory response to external stimuli. This group also showed lower levels of the inflammatory form of sTLR-2 receptor immediately after the talc insufflation. This revealed low local reactivity to external stimuli. The effect of the treatment was not influenced by morphologic tumour type. No statistically significant differences in postoperative complications were found. This confirmed the safety of both videothoracoscopy and treatment.

CONCLUSIONS

There was no correlation between the type of malignant affection and the outcome of the chemical pleurodesis. Patients with relapsing effusion have higher values of concentration of anti-inflammatory sCD-163 in pleural fluid even before the application of talc, and lower levels of concentration of inflammatory sTLR-2 immediately after application of talc.

Pleural tuberculosis: is radiological evidence of pulmonary-associated disease related to the exacerbation of the inflammatory response?

OBJECTIVE

Pleural tuberculosis is the most frequently occurring form of extra pulmonary disease in adults. In up to 40% of cases, the lung parenchyma is concomitantly involved, which can have an epidemiological impact. This study aims to evaluate the pleural and systemic inflammatory response of patients with pleural or pleuropulmonary tuberculosis.

METHODS

A prospective study of 39 patients with confirmed pleural tuberculosis. After thoracentesis, a high resolution chest tomography was performed to evaluate the pulmonary involvement. Of the 39 patients, 20 exhibited only pleural effusion, and high resolution chest tomography revealed active associated-pulmonary disease in 19 patients. The total protein, lactic dehydrogenase, adenosine deaminase, vascular endothelial growth factor, interleukin-8, tumor necrosis factor-α, and transforming growth factor-β(1) levels were quantified in the patient serum and pleural fluid.

RESULTS

All of the effusions were exudates with high levels of adenosine deaminase. The levels of vascular endothelial growth factor and transforming growth factor-β(1) were increased in the blood and pleural fluid of all of the patients with pleural tuberculosis, with no differences between the two forms of tuberculosis. The tumor necrosis factor-α levels were significantly higher in the pleural fluid of the patients with the pleuropulmonary form of tuberculosis. The interleukin-8 levels were high in the pleural fluid of all of the patients, without any differences between the forms of tuberculosis.

CONCLUSION

Tumor necrosis factor-α was the single cytokine that significantly increased in the pleural fluid of the patients with pulmonary involvement. However, an overlap in the results does not permit us to suggest that cytokine is a biological marker of concomitant parenchymal involvement. Although high resolution chest tomography can be useful in identifying these patients, the investigation of fast acid bacilli and cultures for M. tuberculosis in the sputum is recommended for all patients who are diagnosed with pleural tuberculosis.

ACE/ACE2 ratio and MMP-9 activity as potential biomarkers in tuberculous pleural effusions

OBJECTIVE

Pleural effusion is common problem, but the rapid and reliable diagnosis for specific pathogenic effusions are lacking. This study aimed to identify the diagnosis based on clinical variables to differentiate pleural tuberculous exudates from other pleural effusions. We also investigated the role of renin-angiotensin system (RAS) and matrix metalloproteinase (MMPs) in the pathogenesis of pleural exudates.

EXPERIMENTAL DESIGN

The major components in RAS and extracellular matrix metabolism, including angiotensin converting enzyme (ACE), ACE2, MMP-2 and MMP-9 activities, were measured and compared in the patients with transudative (n = 45) and exudative (n = 80) effusions. The exudative effusions were come from the patients with tuberculosis (n = 20), pneumonia (n = 32), and adenocarcinoma (n = 28).

RESULTS

Increased ACE and equivalent ACE2 activities, resulting in a significantly increased ACE/ACE2 ratio in exudates, were detected compared to these values in transudates. MMP-9 activity in exudates was significantly higher than that in transudates. The significant correlation between ACE and ACE2 activity that was found in transudates was not found in exudates. Advanced analyses showed significantly increased ACE and MMP-9 activities, and decreased ACE2 activity in tuberculous pleural effusions compared with those in pneumonia and adenocarcinoma effusions. The results indicate that increased ACE and MMP-9 activities found in the exudates were mainly contributed from a higher level of both enzyme activities in the tuberculous pleural effusions.

CONCLUSION

Interplay between ACE and ACE2, essential functions in the RAS, and abnormal regulation of MMP-9 probably play a pivotal role in the development of exudative effusions. Moreover, the ACE/ACE2 ratio combined with MMP-9 activity in pleural fluid may be potential biomarkers for diagnosing tuberculous pleurisy.

The mechanism of pleural inflammation by long carbon nanotubes: interaction of long fibres with macrophages stimulates them to amplify pro-inflammatory responses in mesothelial cells

Carbon nanotubes (CNT) are high aspect ratio nanoparticles with diameters in the nanometre range but lengths extending up to hundreds of microns. The structural similarities between CNT and asbestos have raised concern that they may pose a similar inhalation hazard. Recently CNT have been shown to elicit a length-dependent, asbestos-like inflammatory response in the pleural cavity of mice, where long fibres caused inflammation but short fibres did not. However the cellular mechanisms governing this response have yet to be elucidated. This study examined the in vitro effects of a range of CNT for their ability to stimulate the release of the acute phase cytokines; IL-1β, TNFα, IL-6 and the chemokine, IL-8 from both Met5a mesothelial cells and THP-1 macrophages. Results showed that direct exposure to CNT resulted in significant cytokine release from the macrophages but not mesothelial cells. This pro-inflammatory response was length dependent but modest and was shown to be a result of frustrated phagocytosis. Furthermore the indirect actions of the CNT were examined by treating the mesothelial cells with conditioned media from CNT-treated macrophages. This resulted in a dramatic amplification of the cytokine release from the mesothelial cells, a response which could be attenuated by inhibition of phagocytosis during the initial macrophage CNT treatments. We therefore hypothesise that long fibres elicit an inflammatory response in the pleural cavity via frustrated phagocytosis in pleural macrophages. The activated macrophages then stimulate an amplified pro-inflammatory cytokine response from the adjacent pleural mesothelial cells. This mechanism for producing a pro-inflammatory environment in the pleural space exposed to long CNT has implications for the general understanding of fibre-related pleural disease and design of safe nanofibres.

Differentiation and recruitment of IL-22-producing helper T cells stimulated by pleural mesothelial cells in tuberculous pleurisy

RATIONALE

IL-22-producing helper T cells (Th22 cells) have been reported to be involved in tuberculosis infection. However, differentiation and immune regulation of Th22 cells in tuberculous pleural effusion (TPE) remain unknown.

OBJECTIVES

To elucidate the mechanism by which Th22 cells differentiate and recruit into the pleural space.

METHODS

The distribution and phenotypic features of Th22 cells in both TPE and blood were determined. The impacts of proinflammatory cytokines and antigen presentation by pleural mesothelial cells (PMCs) on Th22-cell differentiation were explored. The chemoattractant activity of chemokines produced by PMCs for Th22 cells was observed.

MEASUREMENTS AND MAIN RESULTS

Th22 cells were significantly higher in TPE than in blood. IL-1β, IL-6, and/or tumor necrosis factor-α promoted Th22-cell differentiation from CD4(+) T cells. It was found that PMCs expressed CCL20, CCL22, and CCL27, and that TPE and PMC supernatants were chemotactic for Th22 cells. This activity was partly blocked by anti-CCL20, anti-CCL22, and anti-CCL27 antibodies. IL-22 and IL-17 significantly improved PMC wound healing. Moreover, PMCs were able to stimulate CD4(+) T-cell proliferation and Th22-cell differentiation by presenting tuberculosis-specific antigen.

CONCLUSIONS

The overrepresentation of Th22 cells in TPE may be due to pleural cytokines and to PMC-produced chemokines. Our data suggest a collaborative loop between PMCs and Th22 cells in TPE. In particular, PMCs were able to function as antigen-presenting cells to stimulate CD4(+) T-cell proliferation and Th22-cell differentiation.

Differentiation and recruitment of Th9 cells stimulated by pleural mesothelial cells in human Mycobacterium tuberculosis infection

Newly discovered IL-9–producing CD4⁺ helper T cells (Th9 cells) have been reported to contribute to tissue inflammation and immune responses, however, differentiation and immune regulation of Th9 cells in tuberculosis remain unknown. In the present study, our data showed that increased Th9 cells with the phenotype of effector memory cells were found to be in tuberculous pleural effusion as compared with blood. TGF-β was essential for Th9 cell differentiation from naïve CD4⁺ T cells stimulated with PMA and ionomycin in vitro for 5 h, and addition of IL-1β, IL-4 or IL-6 further augmented Th9 cell differentiation. Tuberculous pleural effusion and supernatants of cultured pleural mesothelial cells were chemotactic for Th9 cells, and this activity was partly blocked by anti-CCL20 antibody. IL-9 promoted the pleural mesothelial cell repairing and inhibited IFN-γ-induced pleural mesothelial cell apoptosis. Moreover, pleural mesothelial cells promoted Th9 cell differentiation by presenting antigen. Collectively, these data provide new information concerning Th9 cells, in particular the collaborative immune regulation between Th9 cells and pleural mesothelial cells in human M. tuberculosis infection. In particular, pleural mesothelial cells were able to function as antigen-presenting cells to stimulate Th9 cell differentiation.

Mechanisms of pleurodesis

Pleurodesis aims to obliterate the pleural space by producing extensive adhesion of the visceral and parietal pleura, in order to control relapse of either pleural effusions (mostly malignant) or pneumothorax. A tight and complete apposition between the two pleural layers is a necessary condition to obtain a successful pleurodesis, but--besides this mechanical aspect--there are many biological mechanisms that appear to be common to most of the sclerosing agents currently used. Following intrapleural application of the sclerosing agent, diffuse inflammation, pleural coagulation-fibrinolysis imbalance (favoring the formation of fibrin adhesions), recruitment and subsequent proliferation of fibroblasts, and collagen production are findings in the pleural space. The pleural mesothelial lining is the primary target for the sclerosant and plays a pivotal role in the whole pleurodesis process, including the release of several mediators like interleukin-8, transforming growth factor-β and basic fibroblast growth factor. When the tumor burden is high, normal mesothelial cells are scarce, and consequently the response to the sclerosing agent is decreased, leading to failure of pleurodesis. Also, the type of tumor in the pleural cavity may also affect the outcome of pleurodesis (diffuse malignant mesothelioma and metastatic lung carcinomas have a poorer response). There is general agreement that talc obtains the best results, and there are also preliminary experimental studies suggesting that it can induce apoptosis in tumor cells and inhibit angiogenesis, thus contributing to a better control of the malignant pleural effusion. There is concern about complications (possibly associated with talc but other agents as well) related to systemic inflammation and possible activation of the coagulation cascade. In order to prevent extrapleural talc dissemination, large-particle talc is recommended. Although it could--to some degree--interfere with the mechanisms leading to pleurodesis and a carefully balanced clinical decision has therefore to be made, prophylactic treatment with subcutaneous heparin is recommended during hospitalization (immediately before and after the pleurodesis procedure).

Quantification of the pathological response and fate in the lung and pleura of chrysotile in combination with fine particles compared to amosite-asbestos following short-term inhalation exposure

The marked difference in biopersistence and pathological response between chrysotile and amphibole asbestos has been well documented. This study is unique in that it has examined a commercial chrysotile product that was used as a joint compound. The pathological response was quantified in the lung and translocation of fibers to and pathological response in the pleural cavity determined. This paper presents the final results from the study. Rats were exposed by inhalation 6 h/day for 5 days to a well-defined fiber aerosol. Subgroups were examined through 1 year. The translocation to and pathological response in the pleura was examined by scanning electron microscopy and confocal microscopy (CM) using noninvasive methods.The number and size of fibers was quantified using transmission electron microscopy and CM. This is the first study to use such techniques to characterize fiber translocation to and the response of the pleural cavity. Amosite fibers were found to remain partly or fully imbedded in the interstitial space through 1 year and quickly produced granulomas (0 days) and interstitial fibrosis (28 days). Amosite fibers were observed penetrating the visceral pleural wall and were found on the parietal pleural within 7 days postexposure with a concomitant inflammatory response seen by 14 days. Pleural fibrin deposition, fibrosis, and adhesions were observed, similar to that reported in humans in response to amphibole asbestos. No cellular or inflammatory response was observed in the lung or the pleural cavity in response to the chrysotile and sanded particles (CSP) exposure. These results provide confirmation of the important differences between CSP and amphibole asbestos.

Mesothelial cells activate the plasma kallikrein-kinin system during pleural inflammation

Pleural inflammation underlies the formation of most exudative pleural effusions and the plasma kallikrein-kinin system (KKS) is known to contribute. Mesothelial cells are the predominant cell type in the pleural cavity, but their potential role in plasma KKS activation and BK production has not been studied. Bradykinin concentrations were higher in pleural fluids than the corresponding serum samples in patients with a variety of diseases. Bradykinin concentrations did not correlate with disease diagnosis, but were elevated in exudative effusions. It was demonstrated, using a range of primary and transformed mesothelial and mesothelioma cell lines, that cells assembled high molecular weight kininogen and plasma prekallikrein to liberate bradykinin, a process inhibited by novobiocin, a heat shock protein 90 (HSP90) inhibitor, cysteine, bradykinin and protamine sulphate. Of the common plasma prekallikrein activators, mesothelial cells expressed HSP90, but not prolylcarboxypeptidase or Factor XII. Calcium mobilisation was induced in some mesothelium-derived cell lines by bradykinin. Des-Arg9-bradykinin was inactive, indicating that mesothelial cells are responsive to bradykinin, mediated via the bradykinin receptor subtype 2. In summary, pleural mesothelial cells support the assembly and activation of the plasma KKS by a mechanism dependent on HSP90, and may contribute to KKS-mediated inflammation in pleural disease.

Effect of nilotinib on bleomycin-induced acute lung injury and pulmonary fibrosis in mice

BACKGROUND

The tyrosine kinase inhibitor imatinib mesylate was developed as an inhibitor of the kinase activity of BCR-ABL. However, imatinib also has potent inhibitory activity against the platelet-derived growth factor receptor (PDGFR). Nilotinib is approved for treating patients with chronic myeloid leukemia showing resistance or intolerance to imatinib. Like imatinib, nilotinib selectively inhibits the tyrosine kinase activity of PDGFR.

OBJECTIVES

We examined the effect of imatinib and nilotinib on acute lung injury and pulmonary fibrosis in a mouse model.

METHODS

Mice were treated by intratracheal instillation of bleomycin. Imatinib or nilotinib were administered by oral gavage. To study the early inflammatory and late fibrotic phases of lung injury, mice were sacrificed on days 3, 7, 14 and 21 after bleomycin instillation.

RESULTS

Histopathology showed that imatinib and nilotinib attenuated the extent of lung injury and fibrosis. The numbers of inflammatory cells and levels of IL-6, IL-1β and tumor necrosis factor-α were decreased in the imatinib and nilotinib groups on days 3 and 7. Imatinib and nilotinib therapy significantly reduced the levels of hydroxyproline on days 14 and 21, which was accompanied by decreased expression levels of transforming growth factor (TGF)-β1 and PDGFR-β. Imatinib and nilotinib also significantly reduced the expression levels of the genes for TGF-β1 and platelet-derived growth factor (PDGF). Imatinib and nilotinib treatment also significantly inhibited the PDGF-induced proliferation of lung fibroblasts in vitro. When imatinib or nilotinib was given 7 days after the instillation of bleomycin, only nilotinib attenuated pulmonary fibrosis.

CONCLUSIONS

Imatinib and nilotinib attenuated bleomycin-induced acute lung injury and pulmonary fibrosis in mice. In a therapeutic model, nilotinib showed more potent antifibrotic effects than imatinib.

Effects of downregulation of aquaporin1 by peptidoglycan and lipopolysaccharide via MAPK pathways in MeT-5A cells

This study was designed to investigate the signaling pathway involved in aquaporin1 (AQP1) expression caused by peptidoglycan (PGN) from Staphylococcus aureus and lipopolysaccharide (LPS) in human pleural mesothelial cell lines (MeT-5A) in vitro. RT-PCR, immunoblot analysis, and immunofluorescence assay were used to determine the relative mRNA and protein levels of AQP1 caused by PGN and LPS in MeT-5A cells. Activation of MAPKs by PGN and LPS was reflected by detecting the phosphorylation constituents of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 using immunoblot. MAPKs inhibitors were used to determine the effects of PGN- and LPS-induced AQP1 expression by immunoblot. AQP1 transcription and protein expression were decreased by PGN and LPS in dose- and time-dependent manners in MeT-5A cells. Both PGN and LPS activated p38/ERK/JNK pathways in MeT-5A cells. Furthermore, downregulation of AQP1 expression by LPS was blocked by SB203580, SP600125, and PD98059, which are inhibitors of p38, JNK, and ERK1/2, respectively. In contrast, downregulation of AQP1 expression by PGN was blocked only by SB203580, not by SP600125 or PD98059, underlying the importance of p38 MAPK in the downregulation of AQP1 expression by PGN in MeT-5A cells. AQP1 expression was decreased by both PGN and LPS in dose- and time-dependent manners in MeT-5A cells. AQP1 expression was down-regulated by PGN via p38 MAPK pathway, while AQP1 expression was down-regulated by LPS via p38/JNK/ERK pathways.

Molecular and cellular mechanism of lung injuries due to exposure to sulfur mustard: a review

Sulfur mustard (SM), a potent chemical weapon agent, was used by Iraqi forces against Iranian in the Iraq-Iran war (1981-1989). Chronic obstructive pulmonary disease (COPD) is a late toxic pulmonary consequence after SM exposure. The COPD observed in these patients is unique (described as Mustard Lung) and to some extent different from COPD resulted from other well-known causes. Several mechanisms have been hypothesized to contribute to the pathogenesis of COPD including oxidative stress, disruption of the balance between apoptosis and replenishment, proteinase-antiproteinase imbalance and inflammation. However, it is not obvious which of these pathways are relevant to the pathogenesis of mustard lung. In this paper, we reviewed studies addressing the pathogenicity of mustard lung, and reduced some recent ambiguities in this field. There is ample evidence in favor of crucial role of both oxidative stress and apoptosis as two known mechanisms that are more involved in pathogenesis of mustard lung comparing to COPD. However, according to available evidences there are no such considerable data supporting neither proteolytic activity nor inflammation mechanism as the main underlying pathogenesis in Mustard Lung.

Non-neoplastic and neoplastic pleural endpoints following fiber exposure

Exposure to asbestos fibers is associated with non-neoplastic pleural diseases including plaques, fibrosis, and benign effusions, as well as with diffuse malignant pleural mesothelioma. Translocation and retention of fibers are fundamental processes in understanding the interactions between the dose and dimensions of fibers retained at this anatomic site and the subsequent pathological reactions. The initial interaction of fibers with target cells in the pleura has been studied in cellular models in vitro and in experimental studies in vivo. The proposed biological mechanisms responsible for non-neoplastic and neoplastic pleural diseases and the physical and chemical properties of asbestos fibers relevant to these mechanisms are critically reviewed. Understanding mechanisms of asbestos fiber toxicity may help us anticipate the problems from future exposures both to asbestos and to novel fibrous materials such as nanotubes. Gaps in our understanding have been outlined as guides for future research.

Efficacy of tigecycline pleurodesis: a comparative experimental study

BACKGROUND

We investigated whether tigecycline (TIGE) is more effective than talc in inducing pleurodesis in rabbits.

METHODS

Fifty-six New Zealand rabbits were utilized in a two-phase study: Effects at 14 d (phase I) and at 28 d (phase II) were assessed. Saline solution (SAL n = 3), talc slurry (TALC 200 mg/kg, n = 5), and TIGE at different concentrations (mg/kg): TIGE0.5 (n = 5); TIGE1 (n = 5); TIGE3 (n = 5); TIGE25 (n = 5); TIGE50 (n = 5) were randomly injected, for each phase, through a right chest drainage. TIGE0.5 and TIGE1 were ineffective during phase I and were thus excluded from further investigation. At post mortem examination, pleurodesis was graded grossly and microscopically by three observers blinded to treatment groups.

RESULTS

Phase I: pleurodesis was more effective in TIGE25 and TIGE50 (P < 0.001); TALC was better than TIGE0.5 (P < 0.001), and TIGE1 (P = 0.49), macroscopically. Pleural thickness was significantly higher in TIGE25 compared with SAL, TALC, TIGE0.5, TIGE1, and TIGE3 (P < 0.01). No significant differences were evident between TALC and TIGE3, both macroscopically (P = 0.90) and microscopically (inflammation P = 0.99, fibrosis P = 0.96, pleural thickness P = 0.99). Phase II: better effectiveness of TIGE50 compared with all other groups (P < 0.001) except TIGE 25 (P = 0.29); results similar to phase I for TALC and TIGE3 (P = 0.99), macroscopically. Microscopically greater inflammation in TALC compared with TIGE3 (P < 0.05) and in TIGE50 to TIGE3 (P = 0.05). Significant complications occurred in all TIGE50 group. One of TIGE25 and one of TIGE50 died of respiratory distress and of right hemothorax+ascites, respectively.

CONCLUSIONS

Intrapleural TIGE3 mg/kg is as effective as talc in inducing pleurodesis in rabbits. The intrapleural TIGE toxicity threshold was reached at TIGE25 mg/kg concentration.

Pleural effects of indium phosphide in B6C3F1 mice: nonfibrous particulate induced pleural fibrosis

The mechanism(s) by which chronic inhalation of indium phosphide (InP) particles causes pleural fibrosis is not known. Few studies of InP pleural toxicity have been conducted because of the challenges in conducting particulate inhalation exposures, and because the pleural lesions developed slowly over the 2-year inhalation study. The authors investigated whether InP (1 mg/kg) administered by a single oropharyngeal aspiration would cause pleural fibrosis in male B6C3F1 mice. By 28 days after treatment, protein and lactate dehydrogenase (LDH) were significantly increased in bronchoalveolar lavage fluid (BALF), but were unchanged in pleural lavage fluid (PLF). A pronounced pleural effusion characterized by significant increases in cytokines and a 3.7-fold increase in cell number was detected 28 days after InP treatment. Aspiration of soluble InCl(3) caused a similar delayed pleural effusion; however, other soluble metals, insoluble particles, and fibers did not. The effusion caused by InP was accompanied by areas of pleural thickening and inflammation at day 28, and by pleural fibrosis at day 98. Aspiration of InP produced pleural fibrosis that was histologically similar to lesions caused by chronic inhalation exposure, and in a shorter time period. This oropharyngeal aspiration model was used to provide an initial characterization of the progression of pleural lesions caused by InP.