TRIM72 promotes alveolar epithelial cell membrane repair and ameliorates lung fibrosis.

BACKGROUND: Chronic tissue injury was shown to induce progressive scarring in fibrotic diseases such as idiopathic pulmonary fibrosis (IPF), while an array of repair/regeneration and stress responses come to equilibrium to determine the outcome of injury at the organ level. In the lung, type I alveolar epithelial (ATI) cells constitute the epithelial barrier, while type II alveolar epithelial (ATII) cells play a pivotal role in regenerating the injured distal lungs. It had been demonstrated that eukaryotic cells possess repair machinery that can quickly patch the damaged plasma membrane after injury, and our previous studies discovered the membrane-mending role of Tripartite motif containing 72 (TRIM72) that expresses in a limited number of tissues including the lung. Nevertheless, the role of alveolar epithelial cell (AEC) repair in the pathogenesis of IPF has not been examined yet. METHOD: In this study, we tested the specific roles of TRIM72 in the repair of ATII cells and the development of lung fibrosis. The role of membrane repair was accessed by saponin assay on isolated primary ATII cells and rat ATII cell line. The anti-fibrotic potential of TRIM72 was tested with bleomycin-treated transgenic mice. RESULTS: We showed that TRIM72 was upregulated following various injuries and in human IPF lungs. However, TRIM72 expression in ATII cells of the IPF lungs had aberrant subcellular localization. In vitro studies showed that TRIM72 repairs membrane injury of immortalized and primary ATIIs, leading to inhibition of stress-induced p53 activation and reduction in cell apoptosis. In vivo studies demonstrated that TRIM72 protects the integrity of the alveolar epithelial layer and reduces lung fibrosis. CONCLUSION: Our results suggest that TRIM72 protects injured lungs and ameliorates fibrosis through promoting post-injury repair of AECs.

Inhaled TRIM72 Protein Protects Ventilation Injury to the Lung through Injury-guided Cell Repair.

Studies showed that TRIM72 is essential for repair of alveolar cell membrane disruptions, and exogenous recombinant human TRIM72 protein (rhT72) demonstrated tissue-mending properties in animal models of tissue injury. Here we examine the mechanisms of rhT72-mediated lung cell protection in vitro and test the efficacy of inhaled rhT72 in reducing tissue pathology in a mouse model of ventilator-induced lung injury. In vitro lung cell injury was induced by glass beads and stretching. Ventilator-induced lung injury was modeled by injurious ventilation at 30 ml/kg tidal volume. Affinity-purified rhT72 or control proteins were added into culture medium or applied through nebulization. Cellular uptake and in vivo distribution of rhT72 were detected by imaging and immunostaining. Exogenous rhT72 maintains membrane integrity of alveolar epithelial cells subjected to glass bead injury in a dose-dependent manner. Inhaled rhT72 decreases the number of fatally injured alveolar cells, and ameliorates tissue-damaging indicators and cell injury markers after injurious ventilation. Using in vitro stretching assays, we reveal that rhT72 improves both cellular resilience to membrane wounding and membrane repair after injury. Image analysis detected rhT72 uptake by rat alveolar epithelial cells, which can be inhibited by a cholesterol-disrupting agent. In addition, inhaled rhT72 distributes to the distal lungs, where it colocalizes with phosphatidylserine detection on nonpermeabilized lung slices to label wounded cells. In conclusion, our study showed that inhaled rhT72 accumulates in injured lungs and protects lung tissue from ventilator injury, the mechanisms of which include improving cell resilience to membrane wounding, localizing to injured membrane, and augmenting membrane repair.

Plasma membrane wounding and repair in pulmonary diseases.

Various pathophysiological conditions such as surfactant dysfunction, mechanical ventilation, inflammation, pathogen products, environmental exposures, and gastric acid aspiration stress lung cells, and the compromise of plasma membranes occurs as a result. The mechanisms necessary for cells to repair plasma membrane defects have been extensively investigated in the last two decades, and some of these key repair mechanisms are also shown to occur following lung cell injury. Because it was theorized that lung wounding and repair are involved in the pathogenesis of acute respiratory distress syndrome (ARDS) and idiopathic pulmonary fibrosis (IPF), in this review, we summarized the experimental evidence of lung cell injury in these two devastating syndromes and discuss relevant genetic, physical, and biological injury mechanisms, as well as mechanisms used by lung cells for cell survival and membrane repair. Finally, we discuss relevant signaling pathways that may be activated by chronic or repeated lung cell injury as an extension of our cell injury and repair focus in this review. We hope that a holistic view of injurious stimuli relevant for ARDS and IPF could lead to updated experimental models. In addition, parallel discussion of membrane repair mechanisms in lung cells and injury-activated signaling pathways would encourage research to bridge gaps in current knowledge. Indeed, deep understanding of lung cell wounding and repair, and discovery of relevant repair moieties for lung cells, should inspire the development of new therapies that are likely preventive and broadly effective for targeting injurious pulmonary diseases.

Quantitative assessment of lung stiffness in patients with interstitial lung disease using MR elastography.

PURPOSE: To investigate the use of magnetic resonance elastography (MRE) in the quantitative assessment of pulmonary fibrosis by comparing quantitative shear stiffness measurements of lung parenchyma in patients diagnosed with fibrotic interstitial lung disease (ILD) and healthy controls. MATERIALS AND METHODS: A 1.5T spin-echo, echo planar imaging MRE (SE-EPI MRE) pulse sequence was utilized to assess absolute lung shear stiffness in 15 patients with diagnosed ILD and in 11 healthy controls. Data were collected at residual volume (RV) and total lung capacity (TLC). Spirometry data were obtained immediately prior to scanning. To test for statistical significance between RV and TLC shear stiffness estimates a two-sample t-test was performed. To assess variability within individual subject shear stiffness estimates, the intraclass correlation coefficient (ICC) and Krippendorff's alpha were calculated. RESULTS: Patients with ILD exhibited an average (±1 standard deviation) shear stiffness of 2.74 (±0.896) kPa at TLC and 1.32 (±0.300) kPa at RV. The corresponding values for healthy individuals were 1.33 (±0.195) kPa and 0.849 (±0.250) kPa, respectively. The difference in shear stiffness between RV and TLC was statistically significant (P < 0.001). At TLC, the ICC and alpha values were 0.909 and 0.887, respectively. At RV, the ICC and alpha values were 0.852 and 0.862, respectively. CONCLUSION: In subjects with known fibrotic interstitial lung disease, parenchymal shear stiffness is increased when compared to normal controls at both RV and TLC, with TLC demonstrating the most significant difference. MRE-derived parenchymal shear stiffness is a promising new noninvasive imaging-based biomarker of interstitial lung disease. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:365-374.

Transpulmonary Pressure: The Importance of Precise Definitions and Limiting Assumptions.

Recent studies applying the principles of respiratory mechanics to respiratory disease have used inconsistent and mutually exclusive definitions of the term "transpulmonary pressure." By the traditional definition, transpulmonary pressure is the pressure across the whole lung, including the intrapulmonary airways, (i.e., the pressure difference between the opening to the pulmonary airway and the pleural surface). However, more recently transpulmonary pressure has also been defined as the pressure across only the lung tissue (i.e., the pressure difference between the alveolar space and the pleural surface), traditionally known as the "elastic recoil pressure of the lung." Multiple definitions of the same term, and failure to recognize their underlying assumptions, have led to different interpretations of lung physiology and conclusions about appropriate therapy for patients. It is our view that many current controversies in the physiological interpretation of disease are caused by the lack of consistency in the definitions of these common physiological terms. In this article, we discuss the historical uses of these terms and recent misconceptions that may have resulted when these terms were confused. These misconceptions include assertions that normal pleural pressure must be negative (subatmospheric) and that a pressure in the pleural space may not be substantially positive when a subject is relaxed with an open airway. We urge specificity and uniformity when using physiological terms to define the physical state of the lungs, the chest wall, and the integrated respiratory system.

TRIM72 modulates caveolar endocytosis in repair of lung cells.

Alveolar epithelial and endothelial cell injury is a major feature of the acute respiratory distress syndrome, in particular when in conjunction with ventilation therapies. Previously we showed [Kim SC, Kellett T, Wang S, Nishi M, Nagre N, Zhou B, Flodby P, Shilo K, Ghadiali SN, Takeshima H, Hubmayr RD, Zhao X. Am J Physiol Lung Cell Mol Physiol 307: L449-L459, 2014.] that tripartite motif protein 72 (TRIM72) is essential for amending alveolar epithelial cell injury. Here, we posit that TRIM72 improves cellular integrity through its interaction with caveolin 1 (Cav1). Our data show that, in primary type I alveolar epithelial cells, lack of TRIM72 led to significant reduction of Cav1 at the plasma membrane, accompanied by marked attenuation of caveolar endocytosis. Meanwhile, lentivirus-mediated overexpression of TRIM72 selectively increases caveolar endocytosis in rat lung epithelial cells, suggesting a functional association between these two. Further coimmunoprecipitation assays show that deletion of either functional domain of TRIM72, i.e., RING, B-box, coiled-coil, or PRY-SPRY, abolishes the physical interaction between TRIM72 and Cav1, suggesting that all theoretical domains of TRIM72 are required to forge a strong interaction between these two molecules. Moreover, in vivo studies showed that injurious ventilation-induced lung cell death was significantly increased in knockout (KO) TRIM72(KO) and Cav1(KO) lungs compared with wild-type controls and was particularly pronounced in double KO mutants. Apoptosis was accompanied by accentuation of gross lung injury manifestations in the TRIM72(KO) and Cav1(KO) mice. Our data show that TRIM72 directly and indirectly modulates caveolar endocytosis, an essential process involved in repair of lung epithelial cells through removal of plasma membrane wounds. Given TRIM72's role in endomembrane trafficking and cell repair, we consider this molecule an attractive therapeutic target for patients with injured lungs.

Volume Delivered During Recruitment Maneuver Predicts Lung Stress in Acute Respiratory Distress Syndrome.

OBJECTIVE: Global lung stress varies considerably with low tidal volume ventilation for acute respiratory distress syndrome. High stress despite low tidal volumes may worsen lung injury and increase risk of death. No widely available parameter exists to assess global lung stress. We aimed to determine whether the volume delivered during a recruitment maneuver (V(RM)) is inversely associated with lung stress and mortality in acute respiratory distress syndrome. DESIGN: Substudy of an acute respiratory distress syndrome clinical trial on esophageal pressure-guided positive end-expiratory pressure titration. SETTING: U.S. academic medical center. PATIENTS: Forty-two patients with acute respiratory distress syndrome in whom airflow, airway pressure, and esophageal pressure were recorded during the recruitment maneuver. INTERVENTIONS: A single recruitment maneuver was performed before initiating protocol-directed ventilator management. Recruitment maneuvers consisted of a 30-second breath hold at 40 cm H2O airway pressure under heavy sedation or paralysis. V(RM) was calculated by integrating the flow-time waveform during the maneuver. End-inspiratory stress was defined as the transpulmonary (airway minus esophageal) pressure during end-inspiratory pause of a tidal breath and tidal stress as the transpulmonary pressure difference between end-inspiratory and end-expiratory pauses. MEASUREMENTS AND MAIN RESULTS: V(RM) ranged between 7.4 and 34.7 mL/kg predicted body weight. Lower V(RM) predicted high end-inspiratory and tidal lung stress (end-inspiratory: ß = -0.449; 95% CI, -0.664 to -0.234; p < 0.001; tidal: ß = -0.267; 95% CI, -0.423 to -0.111; p = 0.001). After adjusting for PaO2/FIO2 and either driving pressure, tidal volume, or plateau pressure and positive end-expiratory pressure, V(RM) remained independently associated with both end-inspiratory and tidal stress. In unadjusted analysis, low V(RM) predicted increased risk of death (odds ratio, 0.85; 95% CI, 0.72-1.00; p = 0.026). V(RM) remained significantly associated with mortality after adjusting for study arm (odds ratio, 0.84; 95% CI, 0.71-1.00; p = 0.022). CONCLUSIONS: Low V(RM) independently predicts high lung stress and may predict risk of death in patients with acute respiratory distress syndrome.

Extravascular lung water and pulmonary vascular permeability index as markers predictive of postoperative acute respiratory distress syndrome: a prospective cohort investigation.

OBJECTIVE: Robust markers of subclinical perioperative lung injury are lacking. Extravascular lung water indexed to predicted body weight and pulmonary vascular permeability index are two promising early markers of lung edema. We aimed to evaluate whether extravascular lung water indexed to predicted body weight and pulmonary vascular permeability index would identify patients at risk for clinically significant postoperative pulmonary edema, particularly resulting from the acute respiratory distress syndrome. DESIGN: Prospective cohort study. SETTING: Tertiary care academic medical center. PATIENTS: Adults undergoing high-risk cardiac or aortic vascular surgery (or both) with risk of acute respiratory distress syndrome. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Extravascular lung water indexed to predicted body weight and pulmonary vascular permeability index measurements were obtained intraoperatively and in the early postoperative period. We assessed the accuracy of peak extravascular lung water indexed to predicted body weight and pulmonary vascular permeability index as predictive markers of clinically significant pulmonary edema (defined as acute respiratory distress syndrome or cardiogenic pulmonary edema) using area under the receiver-operating characteristic curves. Associations between extravascular lung water indexed to predicted body weight and pulmonary vascular permeability patient-important with important outcomes were assessed. Of 150 eligible patients, 132 patients (88%) had extravascular lung water indexed to predicted body weight and pulmonary vascular permeability index measurements. Of these, 13 patients (9.8%) had postoperative acute respiratory distress syndrome and 15 patients (11.4%) had cardiogenic pulmonary edema. Extravascular lung water indexed to predicted body weight effectively predicted development of clinically significant pulmonary edema (area under the receiver-operating characteristic curve, 0.79; 95% CI, 0.70-0.89). Pulmonary vascular permeability index discriminated acute respiratory distress syndrome from cardiogenic pulmonary edema alone or no edema (area under the receiver-operating characteristic curve, 0.77; 95% CI, 0.62-0.93). Extravascular lung water indexed to predicted body weight was associated with the worst postoperative PaO2/FIO2, duration of mechanical ventilation, ICU stay, and hospital stay. Peak values for extravascular lung water indexed to predicted body weight and pulmonary vascular permeability index were obtained within 2 hours of the primary intraoperative insult for the majority of patients (> 80%). CONCLUSIONS: Perioperative extravascular lung water indexed to predicted body weight is an early marker that predicts risk of clinically significant postoperative pulmonary edema in at-risk surgical patients. Pulmonary vascular permeability index effectively discriminated postoperative acute respiratory distress syndrome from cardiogenic pulmonary edema. These measures will aid in the early detection of subclinical lung injury in at-risk surgical populations.

Cytokines and clinical predictors in distinguishing pulmonary transfusion reactions.

BACKGROUND: Pulmonary transfusion reactions are important complications of blood transfusion, yet differentiating these clinical syndromes is diagnostically challenging. We hypothesized that biologic markers of inflammation could be used in conjunction with clinical predictors to distinguish transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO), and possible TRALI. STUDY DESIGN AND METHODS: In a nested case-control study performed at the University of California at San Francisco and Mayo Clinic, Rochester, we evaluated clinical data and blood samples drawn before and after transfusion in patients with TRALI (n = 70), possible TRALI (n = 48), TACO (n = 29), and controls (n = 147). Cytokines measured included granulocyte-macrophage-colony-stimulating factor, interleukin (IL)-6, IL-8, IL-10, and tumor necrosis factor-α. Logistic regression and receiver operating characteristics curve analyses were used to determine the accuracy of clinical predictors and laboratory markers in differentiating TACO, TRALI, and possible TRALI. RESULTS: Before and after transfusion, IL-6 and IL-8 were elevated in patients with TRALI and possible TRALI relative to controls, and IL-10 was elevated in patients with TACO and possible TRALI relative to that of TRALI and controls. For all pulmonary transfusion reactions, the combination of clinical variables and cytokine measurements displayed optimal diagnostic performance, and the model comparing TACO and TRALI correctly classified 92% of cases relative to expert panel diagnoses. CONCLUSIONS: Before transfusion, there is evidence of systemic inflammation in patients who develop TRALI and possible TRALI but not TACO. A predictive model incorporating readily available clinical and cytokine data effectively differentiated transfusion-related respiratory complications such as TRALI and TACO.

Recipient clinical risk factors predominate in possible transfusion-related acute lung injury.

BACKGROUND: Possible transfusion-related acute lung injury (pTRALI) cases by definition have a clear temporal relationship to an alternative recipient risk factor for acute respiratory distress syndrome (ARDS). We questioned whether transfusion factors are important for the development of pTRALI. STUDY DESIGN AND METHODS: In this nested case-control study, we prospectively identified 145 consecutive patients with pTRALI and randomly selected 163 transfused controls over a 4-year period at the University of California at San Francisco and the Mayo Clinic (Rochester, Minnesota). RESULTS: For pTRALI, we found evidence against transfusion being important: receipt of plasma from female donors (odds ratio [OR], 0.82; 95% confidence interval [CI], 0.29-2.3; p = 0.70), total number of units transfused (OR, 0.99; 95% CI, 0.89-1.10; p = 0.86), and number of red blood cell and whole blood units transfused (OR, 0.78; 95% CI, 0.59-1.03; p = 0.079). In contrast, we found that risk for pTRALI was associated with additional recipient factors: chronic alcohol abuse (OR, 12.5; 95% CI, 2.8-55; p < 0.001), current smoker (OR, 4.2; 95% CI, 1.67-10.8; p = 0.0024), shock before transfusion (OR, 4.6; 95% CI, 2.0-10.7; p < 0.001), and positive fluid balance before transfusion (OR, 1.32/L; 95% CI, 1.20-1.44; p < 0.001). CONCLUSION: Recipient risk factors for ARDS rather than transfusion risk factors predominate in pTRALI.

TRIM72 is required for effective repair of alveolar epithelial cell wounding.

The molecular mechanisms for lung cell repair are largely unknown. Previous studies identified tripartite motif protein 72 (TRIM72) from striated muscle and linked its function to tissue repair. In this study, we characterized TRIM72 expression in lung tissues and investigated the role of TRIM72 in repair of alveolar epithelial cells. In vivo injury of lung cells was introduced by high tidal volume ventilation, and repair-defective cells were labeled with postinjury administration of propidium iodide. Primary alveolar epithelial cells were isolated and membrane wounding and repair were labeled separately. Our results show that absence of TRIM72 increases susceptibility to deformation-induced lung injury whereas TRIM72 overexpression is protective. In vitro cell wounding assay revealed that TRIM72 protects alveolar epithelial cells through promoting repair rather than increasing resistance to injury. The repair function of TRIM72 in lung cells is further linked to caveolin 1. These data suggest an essential role for TRIM72 in repair of alveolar epithelial cells under plasma membrane stress failure.

Prospective study on the clinical course and outcomes in transfusion-related acute lung injury*.

OBJECTIVE: Transfusion-related acute lung injury is the leading cause of transfusion-related mortality. A prospective study using electronic surveillance was conducted at two academic medical centers in the United States with the objective to define the clinical course and outcomes in transfusion-related acute lung injury cases. DESIGN: Prospective case study with controls. SETTING: University of California, San Francisco and Mayo Clinic, Rochester. PATIENTS: We prospectively enrolled 89 patients with transfusion-related acute lung injury, 164 transfused controls, and 145 patients with possible transfusion-related acute lung injury. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients with transfusion-related acute lung injury had fever, tachycardia, tachypnea, hypotension, and prolonged hypoxemia compared with controls. Of the patients with transfusion-related acute lung injury, 29 of 37 patients (78%) required initiation of mechanical ventilation and 13 of 53 (25%) required initiation of vasopressors. Patients with transfusion-related acute lung injury and possible transfusion-related acute lung injury had an increased duration of mechanical ventilation and increased days in the ICU and hospital compared with controls. There were 15 of 89 patients with transfusion-related acute lung injury (17%) who died, whereas 61 of 145 patients with possible transfusion-related acute lung injury (42%) died and 7 of 164 of controls (4%) died. Patients with transfusion-related acute lung injury had evidence of more systemic inflammation with increases in circulating neutrophils and a decrease in platelets compared with controls. Patients with transfusion-related acute lung injury and possible transfusion-related acute lung injury also had a statistically significant increase in plasma interleukin-8, interleukin-10, and interleukin-1 receptor antagonist posttransfusion compared with controls. CONCLUSIONS: In conclusion, transfusion-related acute lung injury produced a condition resembling the systemic inflammatory response syndrome and was associated with substantial in-hospital morbidity and mortality in patients with transfusion-related acute lung injury compared with transfused controls. Patients with possible transfusion-related acute lung injury had even higher in-hospital morbidity and mortality, suggesting that clinical outcomes in this group are mainly influenced by the underlying acute lung injury risk factor(s).

Estimation of the absolute shear stiffness of human lung parenchyma using (1) H spin echo, echo planar MR elastography.

PURPOSE: To develop a rapid proton MR elastography (MRE) technique that can quantify the absolute shear stiffness of lung parenchyma, to investigate the ability to differentiate respiration-dependent stiffness variations of the lung, and to demonstrate clinical feasibility. MATERIALS AND METHODS: A spin-echo echo planar imaging MRE sequence (SE-EPI MRE) with a very short echo time was developed and tested in a series of five healthy volunteers at three different lung volumes: (i) residual volume (RV), (ii) total lung capacity (TLC), (iii) and midway between RV and TLC (MID). At each volume, lung density was quantified using a MR-based density mapping sequence. For reference, data were acquired using the previously described spin-echo lung MRE sequence (SE-MRE). MRE data were also acquired in a patient with proven Idiopathic Pulmonary Fibrosis (IPF) to test clinical feasibility. RESULTS: The SE-EPIMRE sequence reduced total acquisition time by a factor of 2 compared with the SE-MRE sequence. Lung parenchyma median shear stiffness for the 5 volunteers quantified with the SE-EPI MRE sequence was 0.9 kPa, 1.1 kPa, and 1.6 kPa at RV, MID, and TLC, respectively. The corresponding values obtained with the SE-MRE sequence were 0.9 kPa, 1.1 kPa, and 1.5 kPa. Absolute shear stiffness was also successfully measured in the IPF patient. CONCLUSION: The results indicate that stiffness variations due to respiration could be measured with the SE-EPIMRE technique and were equivalent to values generated by the previously described SE-MRE approach. Preliminary data obtained from the patient demonstrate clinical feasibility.

Biophysical determinants of alveolar epithelial plasma membrane wounding associated with mechanical ventilation.

Mechanical ventilation may cause harm by straining lungs at a time they are particularly prone to injury from deforming stress. The objective of this study was to define the relative contributions of alveolar overdistension and cyclic recruitment and "collapse" of unstable lung units to membrane wounding of alveolar epithelial cells. We measured the interactive effects of tidal volume (VT), transpulmonary pressure (PTP), and of airspace liquid on the number of alveolar epithelial cells with plasma membrane wounds in ex vivo mechanically ventilated rat lungs. Plasma membrane integrity was assessed by propidium iodide (PI) exclusion in confocal images of subpleural alveoli. Cyclic inflations of normal lungs from zero end-expiratory pressure to 40 cmH2O produced VT values of 56.9 ± 3.1 ml/kg and were associated with 0.12 ± 0.12 PI-positive cells/alveolus. A preceding tracheal instillation of normal saline (3 ml) reduced VT to 49.1 ± 6 ml/kg but was associated with a significantly greater number of wounded alveolar epithelial cells (0.52 ± 0.16 cells/alveolus; P < 0.01). Mechanical ventilation of completely saline-filled lungs with saline (VT = 52 ml/kg) to pressures between 10 and 15 cmH2O was associated with the least number of wounded epithelial cells (0.02 ± 0.02 cells/alveolus; P < 0.01). In mechanically ventilated, partially saline-filled lungs, the number of wounded cells increased substantially with VT, but, once VT was accounted for, wounding was independent of maximal PTP. We found that interfacial stress associated with the generation and destruction of liquid bridges in airspaces is the primary biophysical cell injury mechanism in mechanically ventilated lungs.

Fresh red blood cell transfusion and short-term pulmonary, immunologic, and coagulation status: a randomized clinical trial.

RATIONALE: Transfusion-related pulmonary complications are leading causes of morbidity and mortality attributed to transfusion. Observational studies suggest an important role for red blood cell (RBC) storage duration in these adverse outcomes. OBJECTIVES: To evaluate the impact of RBC storage duration on short-term pulmonary function as well as immunologic and coagulation status in mechanically ventilated patients receiving RBC transfusion. METHODS: This is a double-blind, randomized, clinical trial comparing fresh (≤5 d of storage) versus standard issue single-unit RBC transfusion in adult intubated and mechanically ventilated patients. The primary outcome is the change in pulmonary gas exchange as assessed by the partial pressure of arterial oxygen to fraction of inspired oxygen concentration ratio (ΔPa(O(2))/Fi(O(2))). Secondary outcomes include changes in immune and coagulation status. MEASUREMENTS AND MAIN RESULTS: Fifty patients were randomized to receive fresh RBCs and an additional 50 patients to standard issue RBCs. Median storage age was 4.0 days (interquartile range, 3.0-5.0) and 26.5 days (interquartile range, 21.0-36.0) in the fresh RBC group and standard issue RBC group, respectively. No differences were noted in the primary outcome of ΔPa(O(2))/Fi(O(2)) (difference between the mean ΔPa(O(2))/Fi(O(2)) in the standard issue RBC group vs. the fresh RBC group, -11.5; 95% confidence interval, -35.3 to 12.3; P = 0.22). Similarly, no significant differences were noted in markers of immunologic or coagulation status. CONCLUSIONS: In this randomized clinical trial, no differences were noted in early measures of pulmonary function or in immunologic or coagulation status when comparing fresh versus standard issue single-unit RBC transfusion. Clinical trial registered with ClinicalTrials.gov (NCT00751322).

Hypercapnia: a nonpermissive environment for the lung.

Patients with severe acute and chronic lung diseases develop derangements in gas exchange that may result in increased levels of CO(2) (hypercapnia), the effects of which on human health are incompletely understood. It has been proposed that hypercapnia may have beneficial effects in patients with acute lung injury, and the concepts of "permissive" and even "therapeutic" hypercapnia have emerged. However, recent work suggests that CO(2) can act as a signaling molecule via pH-independent mechanisms, resulting in deleterious effects in the lung. Here we review recent research on how elevated CO(2) is sensed by cells in the lung and the potential harmful effects of hypercapnia on epithelial and endothelial barrier, lung edema clearance, innate immunity, and host defense. In view of these findings, we raise concerns about the potentially deleterious effects hypercapnia may have in patients with acute and chronic lung diseases.

Dopamine inhibits pulmonary edema through the VEGF-VEGFR2 axis in a murine model of acute lung injury.

The neurotransmitter dopamine and its dopamine receptor D2 (D2DR) agonists are known to inhibit vascular permeability factor/vascular endothelial growth factor (VEGF)-mediated angiogenesis and vascular permeability. Lung injury is a clinical syndrome associated with increased microvascular permeability. However, the effects of dopamine on pulmonary edema, a phenomenon critical to the pathophysiology of both acute and chronic lung injuries, have yet to be established. Therefore, we sought to determine the potential therapeutic effects of dopamine in a murine model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Compared with sham-treated controls, pretreatment with dopamine (50 mg/kg body wt) ameliorated LPS-mediated edema formation and lowered myeloperoxidase activity, a measure of neutrophil infiltration. Moreover, dopamine significantly increased survival rates of LPS-treated mice, from 0-75%. Mechanistically, we found that dopamine acts through the VEGF-VEGFR2 axis to reduce pulmonary edema, as dopamine pretreatment in LPS-treated mice resulted in decreased serum VEGF, VEGFR2 phosphorylation, and endothelial nitric oxide synthase phosphorylation. We used D2DR knockout mice to confirm that dopamine acts through D2DR to block vascular permeability in our lung injury model. As expected, a D2DR agonist failed to reduce pulmonary edema in D2DR(-/-) mice. Taken together, our results suggest that dopamine acts through D2DR to inhibit pulmonary edema-associated vascular permeability, which is mediated through VEGF-VEGFR2 signaling and conveys protective effects in an ALI model.

Magnetic resonance elastography of the lung parenchyma in an in situ porcine model with a noninvasive mechanical driver: correlation of shear stiffness with trans-respiratory system pressures.

Quantification of the mechanical properties of lung parenchyma is an active field of research due to the association of this metric with normal function, disease initiation and progression. A phase contrast MRI-based elasticity imaging technique known as magnetic resonance elastography is being investigated as a method for measuring the shear stiffness of lung parenchyma. Previous experiments performed with small animals using invasive drivers in direct contact with the lungs have indicated that the quantification of lung shear modulus with (1) H based magnetic resonance elastography is feasible. This technique has been extended to an in situ porcine model with a noninvasive mechanical driver placed on the chest wall. This approach was tested to measure the change in parenchymal stiffness as a function of airway opening pressure (P(ao) ) in 10 adult pigs. In all animals, shear stiffness was successfully quantified at four different P(ao) values. Mean (±STD error of mean) pulmonary parenchyma density corrected stiffness values were calculated to be 1.48 (±0.09), 1.68 (±0.10), 2.05 (±0.13), and 2.23 (±0.17) kPa for P(ao) values of 5, 10, 15, and 20 cm H2O, respectively. Shear stiffness increased with increasing P(ao) , in agreement with the literature. It is concluded that in an in situ porcine lung shear stiffness can be quantitated with (1) H magnetic resonance elastography using a noninvasive mechanical driver and that it is feasible to measure the change in shear stiffness due to change in P(ao) .

Poloxamer 188 facilitates the repair of alveolus resident cells in ventilator-injured lungs.

RATIONALE: Wounded alveolus resident cells are identified in human and experimental acute respiratory distress syndrome models. Poloxamer 188 (P188) is an amphiphilic macromolecule shown to have plasma membrane-sealing properties in various cell types. OBJECTIVES: To investigate whether P188 (1) protects alveolus resident cells from necrosis and (2) is associated with reduced ventilator-induced lung injury in live rats, isolated perfused rat lungs, and scratch and stretch-wounded alveolar epithelial cells. METHODS: Seventy-four live rats and 18 isolated perfused rat lungs were ventilated with injurious or protective strategies while infused with P188 or control solution. Alveolar epithelial cell monolayers were subjected to scratch or stretch wounding in the presence or absence of P188. MEASUREMENTS AND MAIN RESULTS: P188 was associated with fewer mortally wounded alveolar cells in live rats and isolated perfused lungs. In vitro, P188 reduced the number of injured and necrotic cells, suggesting that P188 promotes cell repair and renders plasma membranes more resilient to deforming stress. The enhanced cell survival was accompanied by improvement in conventional measures of lung injury (peak airway pressure, wet-to-dry weight ratio) only in the ex vivo-perfused lung preparation and not in the live animal model. CONCLUSIONS: P188 facilitates plasma membrane repair in alveolus resident cells, but has no salutary effects on lung mechanics or vascular barrier properties in live animals. This discordance may have pathophysiological significance for the interdependence of different injury mechanisms and therapeutic implications regarding the benefits of prolonging the life of stress-activated cells.