Pulmonary reexpansion causes xanthine oxidase-induced apoptosis in rat lung

Synthesis of Purine Analogues: Photocatalyst-Free Visible-Light-Enhanced Annulation Approach to Pyrazolo[1,5-a][1,3,5]triazine-2,4-diamines

A new photocatalyst-free visible-light-enhanced strategy for the synthesis of pyrazolo[1,5-a][1,3,5]triazine-2,4-diamines via the formation of electron donor-acceptor (EDA) complexes is reported. The in situ generated pyrazolthiourea intermediates from 1H-pyrazol-3-amines and isothiocyanates undergo formal [4 + 2] annulation with 1,1,3,3-tetramethylguanidines (TMG) to deliver the corresponding products involved in three C-N bond formations in a one-pot protocol. The formation of EDA complex from pyrazolthiourea and TMG is confirmed by UV-vis spectroscopy and ¹H NMR experiments. Moreover, this mild reaction proceeds in the absence of any external transition metals, oxidants, bases, and ligands. This efficient methodology for the synthesis of purine analogues pyrazolo[1,5-a][1,3,5]triazine-2,4-diamines provides potential synthetic applications in the field of drug research and development.

Hydrogen Peroxide Causes Cell Death via Increased Transcription of HOXB13 in Human Lung Epithelial A549 Cells

Although homeobox protein B13 (HOXB13) is an oncogenic transcription factor, its role in stress response has rarely been examined. We previously reported that knockdown of HOXB13 reduces the cytotoxicity caused by various oxidative stress inducers. Here, we studied the role of HOXB13 in cytotoxicity caused by hydrogen peroxide in human lung epithelial A549 cells. The knockdown of HOXB13 reduced hydrogen peroxide-induced cytotoxicity; however, this phenomenon was largely absent in the presence of antioxidants (Trolox or N-acetyl cysteine (NAC)). This suggests that HOXB13 may be involved in the cytotoxicity caused by hydrogen peroxide via the production of reactive oxygen species (ROS). Hydrogen peroxide also increased both the mRNA and protein levels of HOXB13. However, these increases were rarely observed in the presence of a transcriptional inhibitor, which suggests that hydrogen peroxide increases protein levels via increased transcription of HOXB13. Furthermore, cell death occurred in A549 cells that highly expressed HOXB13. However, this cell death was mostly inhibited by treatment with antioxidants. Taken together, our findings indicate that HOXB13 may be a novel factor involved in the induction of oxidative stress, which causes cell death via intracellular ROS production.

Hepatocyte growth factor inhibits hypoxia/reoxygenation-induced activation of xanthine oxidase in endothelial cells through the JAK2 signaling pathway

Vascular endothelial cells (ECs) appear to be one of the primary targets of hypoxia/reoxygenation (H/R) injury. In our previous study, we demonstrated that hepatocyte growth factor (HGF) exhibited a protective effect in cardiac microvascular endothelial cells (CMECs) subjected to H/R by inhibiting xanthine oxidase (XO) by reducing the cytosolic Ca2+ concentration increased in response to H/R. The precise mechanisms through which HGF inhibits XO activation remain to be determined. In the present study, we examined the signaling pathway through which HGF regulates Ca2+ concentrations and the activation of XO during H/R in primary cultured rat CMECs. CMECs were exposed to 4 h of hypoxia and 1 h of reoxygenation. The protein expression of XO and the activation of the phosphoinositide 3-kinase (PI3K), janus kinase 2 (JAK2) and p38 mitogen-activated protein kinase (p38 MAPK) signaling pathways were detected by western blot analysis. Cytosolic calcium (Ca2+) concentrations and reactive oxygen species (ROS) levels were measured by flow cytometry. The small interfering RNA (siRNA)‑mediated knockdown of XO inhibited the increase in ROS production induced by H/R. LY294002 and AG490 inhibited the H/R-induced increase in the production and activation of XO. The PI3K and JAK2 signaling pathways were activated by H/R. The siRNA‑mediated knockdown of PI3K and JAK2 also inhibited the increase in the production of XO protein. HGF inhibited JAK2 activation whereas it had no effect on PI3K activation. The siRNA-mediated knockdown of JAK2 prevented the increase in cytosolic Ca2+ induced by H/R. Taken together, these findings suggest that H/R induces the production and activation of XO through the JAK2 and PI3K signaling pathways. Furthermore, HGF prevents XO activation following H/R primarily by inhibiting the JAK2 signaling pathway and in turn, inhibiting the increase in cytosolic Ca2+.

High-frequency oscillatory ventilation combined with partial liquid ventilation in experimental lung injury: effects on lung cell apoptosis

Objective

To investigate the effects of high-frequency oscillatory ventilation (HFOV) and partial liquid ventilation (PLV) on apoptosis of lung tissue induced by steam inhalation injury in rabbit.

Design

A prospective, randomized, controlled, multiple-group study.

Setting

An animal research laboratory centre in a university burns centre.

Subjects

New Zealand rabbits (n = 32; 2.25 ± 0.25 kg) of either sex.

Interventions

The animals were ventilated by HFOV with a mean airway pressure of 10 cm H₂O, a frequency of 10 Hz, an amplitude of 20 cm H₂O, an inspiratory:expiratory ratio of 1:1, and an FiO₂ of 1.0. After the induction of acute lung injury (ALI) by steam inhalation, the animals were randomly divided into four groups: CMV, HFOV, CMV + PLV, HFOV + PLV group. Then they were ventilated for 4 h by CMV, HFOV, CMV + PLV and HFOV + PLV, respectively. After the experimental period, cell apoptosis and apoptosis indexes in the lung tissue were assessed with TUNEL FragELTM (Fragment End Labeling).

Results

Lung tissue apoptosis indexes in HFOV group and HFOV + PLV group were lower than that of in CMV group and CMV + PLV group; between-group comparison had significant difference (P < 0.01). HFOV + PLV group showed lowest apoptosis indexes.

Conclusion

HFOV combined with PLV can suppress lung tissue apoptosis induced by steam inhalation.

Radiographically Severe but Clinically Mild Reexpansion Pulmonary Edema following Decompression of a Spontaneous Pneumothorax

The case is a 48-year-old female who presented with mild dyspnea on exertion and cough with unremarkable vital signs and was found to have a large right sided pneumothorax. She underwent small bore chest tube decompression with immediate reexpansion of the collapsed lung. However, she rapidly developed moderate hypoxemia and radiographic evidence of reexpansion pulmonary edema (REPE) on both the treated and contralateral sides. Within a week, she had a normal chest X-ray and was asymptomatic. This case describes a rare complication of spontaneous pneumothorax and highlights the lack of correlation between symptoms, sequelae, and radiographic severity of pneumothorax and reexpansion pulmonary edema. Proposed pathophysiologic mechanisms include increased production of reactive oxygen species with subsequent loss of surfactant and increased vascular permeability, and loss of vasoregulatory tone.

Acute lung injury and pulmonary vascular permeability: use of transgenic models

Acute lung injury is a general term that describes injurious conditions that can range from mild interstitial edema to massive inflammatory tissue destruction. This review will cover theoretical considerations and quantitative and semi-quantitative methods for assessing edema formation and increased vascular permeability during lung injury. Pulmonary edema can be quantitated directly using gravimetric methods, or indirectly by descriptive microscopy, quantitative morphometric microscopy, altered lung mechanics, high-resolution computed tomography, magnetic resonance imaging, positron emission tomography, or x-ray films. Lung vascular permeability to fluid can be evaluated by measuring the filtration coefficient (Kf) and permeability to solutes evaluated from their blood to lung clearances. Albumin clearances can then be used to calculate specific permeability-surface area products (PS) and reflection coefficients (σ). These methods as applied to a wide variety of transgenic mice subjected to acute lung injury by hyperoxic exposure, sepsis, ischemia-reperfusion, acid aspiration, oleic acid infusion, repeated lung lavage, and bleomycin are reviewed. These commonly used animal models simulate features of the acute respiratory distress syndrome, and the preparation of genetically modified mice and their use for defining specific pathways in these disease models are outlined. Although the initiating events differ widely, many of the subsequent inflammatory processes causing lung injury and increased vascular permeability are surprisingly similar for many etiologies.

The frequency of reexpansion pulmonary edema after trocar and hemostat assisted thoracostomy in patients with spontaneous pneumothorax

PURPOSE

Several risk factors for development of reexpansion pulmonary edema (REPE) after drainage of pneumothoraces have been reported, but the association between the method of thoracostomy and the development of REPE is unknown. The aim of this study was to compare the frequency of REPE after treatment of spontaneous pneumothorax with trocar or hemostat assisted closed thoracostomy.

MATERIALS AND METHODS

We performed a prospective, observational study including 173 patients with spontaneous pneumothorax who visited the emergency department from January 2007 to December 2008. In 2007, patients were treated with hemostat-assisted drainage, whereas patients in 2008 were treated with trocar-assisted drainage. The main outcome was the development of REPE, determined by computed tomography of the chest 8 hours after closed thoracostomy. Outcomes in both groups were compared using univariate and multivariate analyses.

RESULTS

Ninety-two patients were included, 48 (42 males) of which underwent hemostat-assisted drainage and 44 (41 males) underwent trocar-assisted drainage. The groups were similar in mean age (24 ± 10 vs. 26 ± 14 respectively). The frequencies of REPE after hemostat- and trocar-assisted drainage were 63% (30 patients) and 86% (38 patients) respectively (p=0.009). In multivariate analysis, trocar-assisted drainage was the major contributing factor for developing REPE (odds ratio=5.7, 95% confidence interval, 1.5-21). Age, gender, size of pneumothorax, symptom duration and laboratory results were similar between the groups.

CONCLUSION

Closed thoracostomy using a trocar is associated with an increased risk of REPE compared with hemostat- assisted drainage in patients with spontaneous pneumothorax.

Tube thoracostomy: complications and its management

Background. Tube thoracostomy is widely used throughout the medical, surgical, and critical care specialities. It is generally used to drain pleural collections either as elective or emergency. Complications resulting from tube thoracostomy can occasionally be life threatening. Aim. To present an update on the complications and management of complications of tube thoracostomy. Methods. A review of the publications obtained from Medline search, medical libraries, and Google on tube thoracostomy and its complications was done. Results. Tube thoracostomy is a common surgical procedure which can be performed by either the blunt dissection technique or the trocar technique. Complication rates are increased by the trocar technique. These complications have been broadly classified as either technical or infective. Technical causes include tube malposition, blocked drain, chest drain dislodgement, reexpansion pulmonary edema, subcutaneous emphysema, nerve injuries, cardiac and vascular injuries, oesophageal injuries, residual/postextubation pneumothorax, fistulae, tumor recurrence at insertion site, herniation through the site of thoracostomy, chylothorax, and cardiac dysrhythmias. Infective complications include empyema and surgical site infection. Conclusion. Tube thoracostomy, though commonly performed is not without risk. Blunt dissection technique has lower risk of complications and is hence recommended.

Role of nitric oxide synthases in elastase-induced emphysema

Nitric oxide (NO) in combination with superoxide produces peroxynitrites and induces protein nitration, which participates in a number of chronic degenerative diseases. NO is produced at high levels in the human emphysematous lung, but its role in this disease is unknown. The aim of this study was to determine whether the NO synthases contribute to the development of elastase-induced emphysema in mice. nNOS, iNOS, and eNOS were quantified and immunolocalized in the lung after a tracheal instillation of elastase in mice. To determine whether eNOS or iNOS had a role in the development of emphysema, mice bearing a germline deletion of the eNOS and iNOS genes and mice treated with a pharmacological iNOS inhibitor were exposed to elastase. Protein nitration was determined by immunofluorescence, protein oxidation was determined by ELISA. Inflammation and MMP activity were quantified by cell counts, RT-PCR and zymography in bronchoalveolar lavage fluid. Cell proliferation was determined by Ki67 immunostaining. Emphysema was quantified morphometrically. iNOS and eNOS were diffusely upregulated in the lung of elastase-treated mice and a 12-fold increase in the number of 3-nitrotyrosine-expressing cells was observed. Over 80% of these cells were alveolar type 2 cells. In elastase-instilled mice, iNOS inactivation reduced protein nitration and increased protein oxidation but had no effect on inflammation, MMP activity, cell proliferation or the subsequent development of emphysema. eNOS inactivation had no effect. In conclusion, in the elastase-injured lung, iNOS mediates protein nitration in alveolar type 2 cells and alleviates oxidative injury. Neither eNOS nor iNOS are required for the development of elastase-induced emphysema.

Prevention of lung ischemia-reperfusion injury by short hairpin RNA-mediated caspase-3 gene silencing

BACKGROUND

Lung ischemia-reperfusion injury remains a significant problem after lung transplantation. Caspase-mediated apoptotic pathways play an important role in lung ischemia-reperfusion injury, and caspase-3 is presumed to be the "effector" protease in the apoptotic cascade. Silencing gene expression of caspase-3 by short hairpin RNA (shRNA) can downregulate the caspase cascade. Therefore, we evaluated the therapeutic efficacy of caspase-3 shRNA in a rat model of lung ischemia-reperfusion injury.

METHODS

Lung ischemia-reperfusion injury was induced in rats by clamping the hilum of the left lung for 1 hour. In vivo delivery of caspase-3 shRNA was performed by intratracheal administration 48 hours before ischemia. As controls, animals received either scrambled shRNA or RNase-free 5% dextrose in water solution. Real-time polymerase chain reaction, Western blotting, and immunohistochemistry were used to assess the gene silencing efficacy. The therapeutic effects of shRNA were evaluated by lung function analysis and the ratio of wet/dry weight.

RESULTS

In this study, we have shown that ischemia-reperfusion injury is associated with an increased level of lung caspase-3 messenger RNA. Animals treated with caspase-3 shRNA showed a significant downregulation in lung expression of caspase-3 at transcripts and protein levels. Lung function was protected by caspase-3 shRNA therapy, inasmuch as levels of partial pressure of oxygen and carbon dioxide were significantly increased and reduced, respectively.

CONCLUSIONS

In summary, we have demonstrated the therapeutic potential of shRNA to knock down the expression of caspase-3 and prevent lung apoptotic injury. Our findings may have some potential therapeutic relevance for treating lung ischemia-reperfusion injury after transplantation.

Proanthocyanidin to prevent formation of the reexpansion pulmonary edema

Background

We aimed to investigate the preventive effect of Proanthocyanidine (PC) in the prevention of RPE formation.

Methods

Subjects were divided into four groups each containing 10 rats. In the Control Group (CG): RPE wasn't performed. Then subjects were followed up for three days and they were sacrificed after the follow up period. Samplings were made from tissues for measurement of biochemical and histopathologic parameters. In the Second Group (PCG): The same protocol as CG was applied, except the administration of PC to the subjects. In the third RPE Group (RPEG): Again the same protocol as CG was applied, but as a difference, RPE was performed. In the Treatment Group (TG): The same protocol as RPEG was applied except the administration of PC to the subjects.

Results

In RPEG group, the most important histopathological finding was severe pulmonary edema with alveolar damage and acute inflammatory cells. These findings were less in the TG group. RPE caused increased MDA levels, and decreased GPx, SOD and CAT activity significantly in lung tissue.

Conclusion

PC decreased MDA levels. Oxidative stress plays an important role in pathophysiology of RPE and PC treatment was shown to be useful to prevent formation of RPE.

Protection from pulmonary ischemia-reperfusion injury by adenosine A2A receptor activation

Background

Lung ischemia-reperfusion (IR) injury leads to significant morbidity and mortality which remains a major obstacle after lung transplantation. However, the role of various subset(s) of lung cell populations in the pathogenesis of lung IR injury and the mechanisms of cellular protection remain to be elucidated. In the present study, we investigated the effects of adenosine A_2A receptor (A_2AAR) activation on resident lung cells after IR injury using an isolated, buffer-perfused murine lung model.

Methods

To assess the protective effects of A_2AAR activation, three groups of C57BL/6J mice were studied: a sham group (perfused for 2 hr with no ischemia), an IR group (1 hr ischemia + 1 hr reperfusion) and an IR+ATL313 group where ATL313, a specific A_2AAR agonist, was included in the reperfusion buffer after ischemia. Lung injury parameters and pulmonary function studies were also performed after IR injury in A_2AAR knockout mice, with or without ATL313 pretreatment. Lung function was assessed using a buffer-perfused isolated lung system. Lung injury was measured by assessing lung edema, vascular permeability, cytokine/chemokine activation and myeloperoxidase levels in the bronchoalveolar fluid.

Results

After IR, lungs from C57BL/6J wild-type mice displayed significant dysfunction (increased airway resistance, pulmonary artery pressure and decreased pulmonary compliance) and significant injury (increased vascular permeability and edema). Lung injury and dysfunction after IR were significantly attenuated by ATL313 treatment. Significant induction of TNF-α, KC (CXCL1), MIP-2 (CXCL2) and RANTES (CCL5) occurred after IR which was also attenuated by ATL313 treatment. Lungs from A_2AAR knockout mice also displayed significant dysfunction, injury and cytokine/chemokine production after IR, but ATL313 had no effect in these mice.

Conclusion

Specific activation of A_2AARs provides potent protection against lung IR injury via attenuation of inflammation. This protection occurs in the absence of circulating blood thereby indicating a protective role of A_2AAR activation on resident lung cells such as alveolar macrophages. Specific A_2AAR activation may be a promising therapeutic target for the prevention or treatment of pulmonary graft dysfunction in transplant patients.

Delayed onset of contralateral pulmonary edema following reexpansion pulmonary edema of a collapsed lung after video-assisted thoracoscopic surgery

This case report describes a 61-year-old man who developed reexpansion pulmonary edema (RPE) of the collapsed left lung after video-assisted thoracoscopic surgery because of left thoracic empyema, complicated with secondary contralateral pulmonary edema later. The left lung was gently reexpanded after surgery under one-lung ventilation anesthesia for 2.5 hours. The patient developed RPE of the left lung immediately after surgery, and required mechanical ventilation with positive end-expiratory pressure support. RPE was resolved within 24 hours. Nevertheless, delayed onset of contralateral pulmonary edema manifested on chest radiography 4 days later without clinical symptoms such as tachypnea or dyspnea. There was no evidence of pulmonary infection, fluid overload, postoperative renal insufficiency or cardiogenic onslaught. Late manifestation of contralateral pulmonary edema in the wake of previous left-sided RPE was suspected from exclusion of possible culprits. Response to steroid therapy made inflammation-related pulmonary edema a likely diagnosis. This case demonstrates that delayed contralateral pulmonary edema with only radiographic evidence can emerge 4 days after resolution of RPE of a collapsed lung. Methods to prevent RPE and management of one-lung ventilation are described.

Fulminant unilateral pulmonary edema after insertion of a chest tube: a complication after a primary spontaneous pneumothorax

INTRODUCTION

The insertion of a chest tube in cases of large pleural effusion or spontaneous pneumothorax is a common surgical procedure often performed by a physician in training under the supervision of a senior physician.

CASE PRESENTATION

The authors report the case of a 35-year-old man with a persistent, complete spontaneous pneumothorax of approximately 30 hours' duration. Within 90 minutes after insertion of a chest tube, he developed severe unilateral pulmonary edema and required mechanical ventilation. FINDINGS AND CLINICAL COURSE: Computerized tomography revealed severe, unilateral pulmonary edema referred to as re-expansion pulmonary edema. After emergency endotracheal intubation and mechanical ventilation with continuous positive airway pressure, the pulmonary edema resolved completely and the patient recovered.

CONCLUSION

Re-expansion edema is a rare, potentially life-threatening complication of the drainage of a spontaneous pneumothorax. With early recognition and timely treatment, complete resolution can be achieved. Risk factors include rapid re-expansion of the lung, young patient age, and a large pneumothorax persisting longer than 24 hours. If these risk factors are present, the chest tube should be inserted without primary suction. Doing so allows the lung to re-expand more slowly and may prevent this severe complication.

Protective efficiacy of taurine against pulmonary edema progression: experimental study

Re-expansion pulmonary edema (RPE) is an acute, rare and potentially lethal complication [1,2]. Its beginning is sudden and dramatic. The mechanism is not yet fully understood [1]. Some authors suggest that it may occur after rapid re-inflation of a collapsed lung [1]. It was reported by other authors that it may relate to surfactant depletion or may result from hypoxic capillary damage, leading to increased capillary permeability [1,3]. In RPE, unilateral lung injury is initiated by cytotoxic oxygen metabolites and temporally associated with an influx of polymorphonuclear neutrophils [1]. These toxic oxygen products are the results of re-oxygenation of a collapsed lung. Treatment of re-expansion pulmonary edema is basically preventive [4].

Ipsilateral reexpansion pulmonary edema after drainage of a spontaneous pneumothorax: a case report

We report a case of ipsilateral reexpansion pulmonary edema occurring after the insertion of a chest tube in a patient with spontaneous pneumothorax. The patient received supplemental oxygen via a non-rebreather face mask to compensate for hypoxemia. 24 hours after the acute event, the patient recovered completely without residual hypoxemia. Reexpansion pulmonary edema after the insertion of a thoracic drainage for pneumothorax or pleural effusion is a rare complication with a high mortality rate up to 20%. It should be considered in case of hypoxemia following the insertion of a chest tube. The exact pathophysiology leading to this complication is not known. Risk factors for reexpansion pulmonary edema should be evaluated and considered prior to the insertion of chest tubes. Treatment is supportive.

One-lung ventilation: For how long?

OBJECTIVE

Lung injury induced by one-lung ventilation is rare, but it is a condition that may result in high mortality. This study evaluates the effects of one-lung ventilation and occlusion time on collapsed and contralateral lungs.

METHODS

Sprague-Dawley rats were allocated randomly into 7 groups consisting of 6 animals each: sham; O1, 1 hour of occlusion/2 hours of re-expansion; C1, 3 hours of mechanical ventilation control; O2, 2 hours of occlusion/2 hours of re-expansion; C2, 4 hours of mechanical ventilation control; O3, 3 hours of occlusion/2 hours of re-expansion; and C3, 5 hours of mechanical ventilation control groups. In the occlusion groups, the left lung was collapsed by bronchial occlusion. Malondialdehyde activity was determined in the blood, and myeloperoxidase and malondialdehyde activity was determined in the collapsed and contralateral lungs. Lung tissues were also examined histopathologically.

RESULTS

Malondialdehyde and myeloperoxidase levels rose as occlusion duration increased. This increase was greater in the occlusion groups than that in their own control groups. Increases were significant in the O2 compared with the O1 groups (P < .005). Histologically, tissue damage increased as occlusion time rose injury in collapsed and contralateral lungs. Injury was greater in the occlusion groups than injury in their own control groups (P < .005).

CONCLUSIONS

Our findings show that biochemical and histopathologic injury occur in collapsed and contralateral lungs in one-lung ventilation, and this injury increases as occlusion time rises. We believe that occlusion and occlusion time-related injury should be borne in mind in the clinic under conditions requiring the application of one-lung ventilation.

Real-time lung microscopy

Although proinflammatory cell signaling in the alveolo-capillary region predisposes to acute lung injury, key cell-signaling mechanisms remain inadequately understood. Alveolo-capillary inflammation is likely to involve coordinated signaling among cells of different phenotypes. For example, migration of inflammatory cells into the alveolus might entail coordinated signaling between adjoining alveolar epithelial and microvascular endothelial cells. The popular cultured cell experimental strategy fails to replicate this multicellular environment. Cultured lung cells, both alveolar and endothelial, undergo phenotypic transformations; hence they might inadequately reflect innate responses of native cells. Consequently, new approaches are required for the investigation of cell signaling in the native setting. Here we summarize new developments in classical intravital microscopy and discuss real-time fluorescence imaging as a novel technique for studying second-messenger mechanisms in the alveolo-capillary region.

The effects of oxidative stress on the liver and ileum in rats caused by one-lung ventilation

BACKGROUND AND AIM

Reactive oxygen radicals that cause remote organ injury are increased after the one-lung ventilation frequently used in thoracic surgery. The aim of this study was to examine the effects of one-lung ventilation on the liver and ileum.

MATERIALS AND METHODS

Thirty rats were divided into five groups: a sham group; 3- and 4-h mechanical ventilation groups; and 1- and 2-h left lung collapse/2-h re-expansion groups (n = 6 for each group). In the collapse groups, the left lung was collapsed by bronchial occlusion for 1 and 2 h and then re-expanded and ventilated for an additional 2 h. At the end of the study, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were determined to assess liver functions. Myeloperoxidase (MPO) and malondialdehyde (MDA) activity were determined in the liver and ileum tissues. The tissues were also examined by light and electron microscope. Apoptosis was assessed using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) assay.

RESULTS

Plasma ALT and AST, tissue MDA, and MPO activities in both tissues were significantly higher in the 2-h collapse/2-h re-expansion group than in the 4-h mechanical ventilation group (P < 0.05). Moreover, the levels were significantly higher in the 2-h collapse group compared to the 1-h collapse group (P < 0.016). Tissue damage and apoptotic index were most prominent in the 2-h collapse/2-h re-expansion group.

CONCLUSION

Our findings showed that one-lung ventilation causes tissue damage in the liver and ileum and that this damage increases as occlusion duration rises.

Alveolar macrophage activation is a key initiation signal for acute lung ischemia-reperfusion injury

Lung ischemia-reperfusion (I/R) injury is a biphasic inflammatory process. Previous studies indicate that the later phase is neutrophil-dependent and that alveolar macrophages (AMs) likely contribute to the acute phase of lung I/R injury. However, the mechanism is unclear. AMs become activated and produce various cytokines and chemokines in many inflammatory responses, including transplantation. We hypothesize that AMs respond to I/R by producing key cytokines and chemokines and that depletion of AMs would reduce cytokine/chemokine expression and lung injury after I/R. To test this, using a buffer-perfused, isolated mouse lung model, we studied the impact of AM depletion by liposome-clodronate on I/R-induced lung dysfunction/injury and expression of cytokines/chemokines. I/R caused a significant increase in pulmonary artery pressure, wet-to-dry weight ratio, vascular permeability, tumor necrosis factor (TNF)-alpha, monocyte chemoattractant protein (MCP)-1, and macrophage inflammatory protein (MIP)-2 expression, as well as decreased pulmonary compliance, when compared with sham lungs. After AM depletion, the changes in each of these parameters between I/R and sham groups were significantly attenuated. Thus AM depletion protects the lungs from I/R-induced dysfunction and injury and significantly reduces cytokine/chemokine production. Protein expression of TNF-alpha and MCP-1 are positively correlated to I/R-induced lung injury, and AMs are a major producer/initiator of TNF-alpha, MCP-1, and MIP-2. We conclude that AMs are an essential player in the initiation of acute lung I/R injury.