Lung Atelectasis Promotes Immune and Barrier Dysfunction as Revealed by Transcriptome Sequencing in Female Sheep.

BACKGROUND: Pulmonary atelectasis is frequent in clinical settings. Yet there is limited mechanistic understanding and substantial clinical and biologic controversy on its consequences. The authors hypothesize that atelectasis produces local transcriptomic changes related to immunity and alveolar-capillary barrier function conducive to lung injury and further exacerbated by systemic inflammation. METHODS: Female sheep underwent unilateral lung atelectasis using a left bronchial blocker and thoracotomy while the right lung was ventilated, with (n = 6) or without (n = 6) systemic lipopolysaccharide infusion. Computed tomography guided samples were harvested for NextGen RNA sequencing from atelectatic and aerated lung regions. The Wald test was used to detect differential gene expression as an absolute fold change greater than 1.5 and adjusted P value (Benjamini-Hochberg) less than 0.05. Functional analysis was performed by gene set enrichment analysis. RESULTS: Lipopolysaccharide-unexposed atelectatic versus aerated regions presented 2,363 differentially expressed genes. Lipopolysaccharide exposure induced 3,767 differentially expressed genes in atelectatic lungs but only 1,197 genes in aerated lungs relative to the corresponding lipopolysaccharide-unexposed tissues. Gene set enrichment for immune response in atelectasis versus aerated tissues yielded negative normalized enrichment scores without lipopolysaccharide (less than -1.23, adjusted P value less than 0.05) but positive scores with lipopolysaccharide (greater than 1.33, adjusted P value less than 0.05). Leukocyte-related processes (e.g., leukocyte migration, activation, and mediated immunity) were enhanced in lipopolysaccharide-exposed atelectasis partly through interferon-stimulated genes. Furthermore, atelectasis was associated with negatively enriched gene sets involving alveolar-capillary barrier function irrespective of lipopolysaccharide (normalized enrichment scores less than -1.35, adjusted P value less than 0.05). Yes-associated protein signaling was dysregulated with lower nuclear distribution in atelectatic versus aerated lung (lipopolysaccharide-unexposed: 10.0 ± 4.2 versus 13.4 ± 4.2 arbitrary units, lipopolysaccharide-exposed: 8.1 ± 2.0 versus 11.3 ± 2.4 arbitrary units, effect of lung aeration, P = 0.003). CONCLUSIONS: Atelectasis dysregulates the local pulmonary transcriptome with negatively enriched immune response and alveolar-capillary barrier function. Systemic lipopolysaccharide converts the transcriptomic immune response into positive enrichment but does not affect local barrier function transcriptomics. Interferon-stimulated genes and Yes-associated protein might be novel candidate targets for atelectasis-associated injury.

Pulmonary atelectasis during low stretch ventilation: "open lung" versus "lung rest" strategy.

OBJECTIVE: Limiting tidal volume (VT) may minimize ventilator-induced lung injury (VILI). However, atelectasis induced by low VT ventilation may cause ultrastructural evidence of cell disruption. Apoptosis seems to be involved as protective mechanisms from VILI through the involvement of mitogen-activated protein kinases (MAPKs). We examined the hypothesis that atelectasis may influence the response to protective ventilation through MAPKs. DESIGN: Prospective randomized study. SETTING: University animal laboratory. SUBJECTS: Adult male 129/Sv mice. INTERVENTIONS: Isolated, nonperfused lungs were randomized to VILI: VT of 20 mL/kg and positive end-expiratory pressure (PEEP) zero; low stretch/lung rest: VT of 6 mL/kg and 8-10 cm H2O of PEEP; low stretch/open lung: VT of 6 mL/kg, two recruitment maneuvers and 14-16 cm H2O of PEEP. Ventilator settings were adjusted using the stress index. MEASUREMENT AND MAIN RESULT: Both low stretch strategies equally blunted the VILI-induced derangement of respiratory mechanics (static volume-pressure curve), lung histology (hematoxylin and eosin), and inflammatory mediators (interleukin-6, macrophage inflammatory protein-2 [enzyme-linked immunosorbent assay], and inhibitor of nuclear factor-kB[Western blot]). VILI caused nuclear swelling and membrane disruption of pulmonary cells (electron microscopy). Few pulmonary cells with chromatin condensation and fragmentation were seen during both low stretch strategies. However, although cell thickness during low stretch/open lung was uniform, low stretch/lung rest demonstrated thickening of epithelial cells and plasma membrane bleb formation. Compared with the low stretch/open lung, low stretch/lung rest caused a significant decrease in apoptotic cells (terminal deoxynucleotidyl transferase mediated deoxyuridine-triphosphatase nick end-labeling) and tissue expression of caspase-3 (Western blot). Both low stretch strategies attenuated the activation of MAPKs. Such reduction was larger during low stretch/open lung than during low stretch/lung rest (p < 0.001). CONCLUSION: Low stretch strategies provide similar attenuation of VILI. However, low stretch/lung rest strategy is associated to less apoptosis and more ultrastructural evidence of cell damage possibly through MAPKs-mediated pathway.

The effects of pulmonary atelectasis and reexpansion on lung cellular immune defenses.

Pulmonary atelectasis predisposes the lung to infection. This condition may be partly due to impaired cellular immune response of the collapsed lung segment. We postulated that atelectasis may affect alveolar macrophage (AM) antibacterial function. To test this hypothesis, atelectasis was induced in the right upper lobes of piglet lungs. Alveolar macrophages harvested by bronchoalveolar lavage of collapsed segments for up to 24 hours showed progressive depression of their phagocytic activity against Pseudomonas aeruginosa in vitro. However, their intracellular bactericidal activity did not change. Reexpansion of the atelectatic lobes with mechanical ventilation and 100% oxygen supplementation for four hours after six hours of atelectasis resulted in reversal of the impaired AM phagocytic activity. These observations presented insight into the mechanisms of susceptibility to lung infection in pulmonary atelectasis and the potential for its reversal.

Altered cellular immune function in the atelectatic lung.

Pulmonary atelectasis is common and may predispose the lung to infection. We have previously shown that atelectasis impairs alveolar macrophage antibacterial function. This study examines the effect of atelectasis on the cytotoxic function of lymphocytes harvested from the bronchoalveolar space of atelectatic lung segments by bronchoalveolar lavage. Specifically, we studied natural killer and lectin-dependent cell-mediated cytotoxicity in peripheral blood and bronchoalveolar lavage lymphocytes from the atelectatic lower lobes and contralateral normal lobes in a group of 8 dogs. We observed a decline of natural killer and lectin-dependent cell-mediated cytotoxicity to 62.7% and 61.5%, respectively, of preatelectasis control values in the affected lung lobes (p less than 0.01). Simultaneous measurements of cytotoxic activity of bronchoalveolar lavage lymphocytes harvested from the unaffected contralateral normal lungs were comparable with control values. On the other hand, natural killer and lectin-dependent cell-mediated cytotoxicity activities in peripheral blood lymphocytes were significantly increased in animals having right lower lobe atelectasis (166.7% and 154.7% of pretreated normal control, respectively, p less than 0.01). Atelectasis was also associated with an influx of polymorphonuclear leukocytes into the bronchoalveolar compartment. These findings confirm the presence of natural killer cells and cytotoxic lymphocytes in the bronchoalveolar compartment and demonstrate an atelectasis-induced impairment of local bronchoalveolar lymphocyte function. Such a dysfunction of local lung cellular host defenses may render the atelectatic lung susceptible to infection.

Association of IL-8 and MCP-1 with the development of reexpansion pulmonary edema in rabbits.

BACKGROUND: The aim of this study is to determine the relationships between the cytokines and the inflammatory response in reexpansion pulmonary edema (RPE). METHODS: We examined the cell population, epithelial permeability measured by Evans blue dye (EB), betaglucuronidase and cytokine concentrations in bronchoalveolar lavage fluid (BALF) and/or blood using a rabbit RPE model. RESULTS: We confirmed that RPE is characterized by recruitment of polymorphonuclear leukocytes (PMNs), the release of PMN granular contents into the air spaces, and increased vascular permeability. These findings were highly correlated with increased interleukin-8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) concentrations in the BALF. Growth related oncogene (GRO) was detected in the BALF from only 2 of the 7 reexpanded lungs while TNFalpha was not detected in any rabbits. A similar but less severe inflammatory response to the reexpanded lung was found in the contralateral lung. CONCLUSIONS: IL-8 and MCP-1 may play important roles in the development of RPE; the inflammatory response is independent of TNFalpha and unilateral reexpansion of the lung induces an inflammatory response not only in the reexpanded lung but also in the contralateral lung.

Severe infusion reaction induced by trastuzumab: a case report.

We report a case of a severe infusion reaction caused by trastuzumab. A 59-year-old woman with metastatic breast cancer was treated with trastuzumab. During the first infusion, initial symptoms such as severe headache and general fatigue developed. Blood pressure fell 90 minutes after these initial symptoms. A collapsed lung was demonstrated by chest X-ray and computed tomography. Steroid therapy was successfully used for these reactions. Careful monitoring of vital signs, examination of the respiratory system, and the use of steroids are recommended for severe infusion reaction.

Increased interleukin-8 in epithelial lining fluid of collapsed lungs during one-lung ventilation for thoracotomy.

The present study was designed to evaluate inflammatory changes in collapsed lungs during one-lung ventilation using the assistance of a bronchoscopic microsampling probe. Serial albumin and interleukin (IL)-8 concentrations in epithelial lining fluid (ELF) were measured in seven patients undergoing resection of lung tumors. The samples were taken after induction of anesthesia (baseline), 30 min after one-lung ventilation was started (point 2), just before resuming two-lung ventilation (point 3), and 30 min after two-lung ventilation was restarted (point 4). The albumin and IL-8 concentrations in ELF were significantly increased at point 2 and point 3, respectively, and remained to be high, compared to the baseline. The increase in IL-8 at point 3 was correlated with the interval of one-lung ventilation; however, none developed specific acute lung injury. These findings suggest that inflammatory changes can occur on the epithelium of a collapsed lung even in patients who underwent successful and standard thoracic surgery.

Inflammatory response in ventilated left and collapsed right lungs, serum and pleural fluid, in transthoracic esophagectomy for cancer.

INTRODUCTION: Open, right-sided, transthoracic esophagectomy with one-lung ventilation (OLV) triggers a massive inflammatory reaction. The influence of the OLV on the inflammatory cascade is unclear. Data on the inflammatory response in the ventilated left and collapsed right lung, respectively, are scarce. The aim of this study was to analyze this reaction in bronchoalveolar lavage (BAL) fluid from both lungs, the right pleural space and the peripheral blood, and to study its time course. METHODS: Concentrations of interleukin (IL)-6, IL-8, IL-10 and IL-1RA in the BAL fluids from the right and left lungs, respectively, in the peripheral blood and in the right pleural space in patients undergoing transthoracic esophagectomy for cancer, were determined using enzyme-linked immunosorbent assays in 29 patients. RESULTS: Assay of the pro-inflammatory cytokines in the bilateral BAL fluids showed significantly higher concentrations in the ventilated left lung at the time of extubation. The anti-inflammatory response was only seen with respect to IL-1RA, but not IL-10, and was mostly restricted to the ventilated left lung. In the blood, only IL-6, IL-10 and IL-1RA increased, whereas IL-8 showed little change. The response was already observed at the end of surgery, indicating a rapid reaction to the surgical and anesthetic trauma. In the pleural fluid, all cytokine concentrations increased, and the highest values were detected on day one post-surgery, and decreased thereafter. Pulmonary complications or anastomotic leakage were not related to the cytokine concentrations. CONCLUSION: Both the ventilated left and the collapsed right lung showed an inflammatory response. The response was more pronounced on the ventilated left side and the time courses were significantly different. In the blood, the pro-inflammatory IL-6 and both anti-inflammatory cytokines increased early on. All cytokines increased in the pleural cavity. The findings underline the complexity of the inflammatory reaction associated with OLV in transthoracic esophagectomy.

Recombinant human deoxyribonuclease improves atelectasis in mechanically ventilated children with cardiac disease.

OBJECTIVE: To investigate whether a mucolytic agent, recombinant human deoxyribonuclease (rhDNase), improves atelectasis in children with cardiac illness requiring mechanical ventilation. DESIGN: A retrospective cohort study on consecutive patients receiving short-term (< or =14 days) rhDNase therapy for atelectasis in the cardiac intensive care unit from January 2005 through February 2007 was carried out. Data relating to patient characteristics, gas exchange, ventilatory parameters, and chest radiographs were collected and analyzed. The effectiveness of rhDNase therapy in the presence of neutrophils and/or bacteria in the pre-rhDNase therapy tracheal aspirates was also investigated. RESULTS: rhDNase was effective in significantly improving established atelectasis without any major changes in gas exchange and ventilatory parameters. Therapeutic effect of rhDNase is most effective in ameliorating atelectasis in the lungs within 10 doses. rhDNase was more effective in improving chest radiographic atelectasis score in patients who had > moderate amounts of polymophonuclear neutrophils (P value = 0.0008), or bacteria (P value = 0.007) or both (P value = 0.004) present in their pre-rhDNase therapy trachea aspirate. No adverse effects were seen with rhDNase administration in the study cohort. CONCLUSIONS: rhDNase can be safely and effectively used to improve atelectasis in mechanically ventilated children with cardiac disease especially in the presence of bacteria and/or moderate amounts of polymophonuclear neutrophils in the pre-rhDNase therapy tracheal aspirate.

Histochemical alterations in one lung ventilation.

BACKGROUND: One lung ventilation is a commonly performed surgical procedure. Although there have been several reports showing that one-lung ventilation can cause pathophysiological alterations such as pulmonary hypoxic vasoconstriction and intrapulmonary shunting, there have been virtually no reports on the effects of one-lung ventilation on lung histology. MATERIALS AND METHODS: Yorkshire pigs (11-17 kg) were anesthetized, a tracheotomy performed and a tracheal tube inserted. The chest was opened and one lung ventilation (OLV), was induced by clamping of the right main bronchus. OLV was continued for 60 min before the clamp was removed and two lung ventilation (TLV) started. TLV was continued for 30 to 60 min. Blood and lung biopsies were taken immediately before OLV, 30 min and 60 min of OLV and after restoration of TLV. RESULTS: Histological analyses revealed that the non-ventilated lung was totally collapsed during OLV. On reventilation, there was clear evidence of vascular congestion and alveolar wall thickening at 30 min after TLV. At 60 min of TLV, there was still vascular congestion. Serum nitrite levels (as an index of nitric oxide production) showed steady decline over the course of the experimental period, reaching a significantly low level on reventilation (compared with baseline levels before OLV). Lung MPO activity (marker of neutrophil sequestration) and serum TNFalpha levels were not raised during the entire experimental period. CONCLUSIONS: These results suggest that there was lung vascular injury after OLV, which was associated with reduced levels of nitric oxide production and not associated with an inflammatory response.

Intrapulmonary growth of Staphylococcus aureus in rats during induced atelectasis.

Intrinsic pulmonary antibacterial defenses are mediated by alveolar macrophages and by noncellular factors. Mechanical ventilation in the resting tidal volume range leads to alterations in the physical characteristics of alveolar surfactant, alveolar instability, regional hypoxia, and systemic hypoxemia. While a number of experimental manipulations diminish the activity of the intrinsic antibacterial defense system, the effects of mechanical ventilation per se have not been systematically evaluated previously. We found that normal rats ventilated without sighing (periodic large breaths) manifested severe defects in pulmonary clearance of Staphylococcus aureus during 6-h experiments, such that growth of the inoculum occurred. Addition of a timer-controlled mechanism to cause the animals to sigh every 2 min, without other modifications in the experimental conditions, caused significant improvement in clearance. Analysis of cellular response, compartmentalization of viable bacteria, surfactant quantities and sedimentation characteristics, and protein influx indicated that the defect in clearance paralleled alterations in the physical state of surfactant and alveolar stability but was not strongly correlated with alterations in the other parameters we measured. The data show that defective pulmonary bacterial clearance is rapidly induced by measures which alter alveolar stability and suggest that intrinsic pulmonary defenses require maintenance of normal air-liquid interfaces for optimal function.

Importance of interleukin-8 in the development of reexpansion lung injury in rabbits.

Reexpansion of a collapsed lung induces increased microvascular permeability leading to reexpansion pulmonary edema (REPE). This study was designed to prove the hypothesis that local overproduction of interleukin-8 (IL-8) induces inflammatory cell accumulation which leads to the induction of REPE. Initially, we examined the detailed characteristics of a rabbit model of REPE in association with IL-8 production and its mRNA expression. The lung tissue to plasma ratio of radiolabeled albumin (T/P ratio), the lung wet to dry ratio, and bronchoalveolar lavage (BAL) neutrophil counts were significantly increased in the reexpanded lung. IL-8 concentrations and mRNA expression were significantly increased in the reexpanded lung homogenate. Immunohistochemically, alveolar macrophages (AMs) and epithelial cells in the reexpanded lung and AMs in the collapsed lung were positive for IL-8. Second, we examined the effect of pretreatment with a specific monoclonal anti-IL-8 antibody (Ab) or control IgG on the development of REPE. The T/P ratio and BAL neutrophil counts were conspicuously decreased by pretreatment with anti-IL-8 Ab, but not with control IgG. On a histopathological study, lung injury and leukocyte infiltration were attenuated by the pretreatment with anti-IL-8 Ab. In conclusion, IL-8 production is enhanced in the reexpanded lung, and contributes to the development of REPE. The pretreatment with anti-IL-8 antibody may be useful as a novel protective therapy for this disease.

Immunological abnormalities in shrinking pleuritis with atelectasis.

The immunological status of 14 patients with shrinking pleuritis with atelectasis (SPA) was assessed by skin testing for delayed hypersensitivity reactions and in vitro tests of peripheral blood lymphocyte reactivity. The results were compared with those of 3 control groups, one consisting of healthy men, one of workers exposed to asbestos and one of workers exposed to quartz dust. Only 2 of 14 SPA patients showed a positive skin reaction to 2.4-dinitrochlorobenzene (DNCB). The cutaneous reactions to candida and varidase were significantly increased in the SPA group compared with the other groups (p less than 0.05). The response of the blood lymphocytes to stimulation with phytohaemagglutinin was significantly decreased in the SPA group (p less than 0.01), as was unstimulated lymphocyte proliferation (p less than 0.05). The results suggest a primary or secondary immune abnormality in the SPA group. The exact nature of the defect requires further elucidation.