Lung Endothelial Injury Research Articles

Can preoperative serum lactate dehydrogenase levels predict postoperative pulmonary complication following an emergency abdominal surgery? An observational study

Background: Postoperative pulmonary complications (PPC) are one of the commonest complications following gastrointestinal surgery. They lead to increase in morbidity and mortality. Lactate dehydrogenase (LDH) is an enzyme present in essentially all major organ systems. Studies have shown measurement of its activity levels and its isoenzyme pattern may provide additional information about lung and pulmonary endothelial cell injury. The objectives of the present study were to study the levels of serum LDH in patients with and without post-operative pulmonary complications following emergency abdominal surgery.Methods: The study was designed as an observational study. All patients ≥18 years of age undergoing gastrointestinal surgery, excluding those with prior lung pathology were included in the study. The demographic parameters, clinical parameters and laboratory parameters along with details of pulmonary complications were recorded. Serum LDH level were assessed on admission. Levels of serum LDH were compared between patients with and without post-operative pulmonary infections and were assessed for significance.Results: Incidence of PPC was 28% in our study. There was significant difference in the mean age in the group with and without PPC (p=<0.001). Smoking habit, serum albumin total protein and upper abdomen incision surgery were associated with increased incidence of PPC. Pleural effusion was the commonest PPC seen in patients. Serum LDH was not significantly associated with the incidence of PPC.Conclusions: Pre-operative serum LDH level is not a predictive factor for occurrence of postoperative pulmonary complication. Age, smoking, total protein, serum albumin, upper abdomen incision were found to associated with increased risk of PPCs.

Upregulation of sphingosine kinase1 contributes toventilator-associated lung injury in a two-hit model.

Ventilator-associated lung injury (VALI) remains a significant medical problem in intensive care units. The present study aimed to investigate the role of sphingosine kinase 1 (SPHK1) in VALI using a two-hit model and explore the potential underlying molecular mechanism. Mice were divided into five groups: i) Non-ventilated group; ii) non-ventilated + lipopolysaccharide (LPS) group; iii) ventilated group; iv) ventilated + LPS group; and v) ventilated + LPS + SPHK1 inhibitor group. Mice were administered LPS (1 mg/kg) via an intraperitoneal injection. After 12 h, the mice were anesthetized and connected to a ventilator (10 ml/kg at 150 breaths/min) for 4 h. SPHK1 inhibitor (50 mg/kg) was injected intraperitoneally 1 h prior to ventilation. Mouse lung vascular endothelial cells were treated with LPS and SPHK1 inhibitor, and then subjected to cyclic stretch for 4 h. The present results suggested that the expression of SPHK1 and sphingosine 1 phosphate was upregulated in the two-hit model of VALI; SPHK1 inhibitor could attenuate VALI in the two-hit model as observed by hematoxylin and eosin staining, and affected the cell count and the protein content levels in the bronchoalveolar lavage fluid. In addition, treatment with SPHK1 inhibitor reduced the wet-to-dry ratio of the lungs and suppressed Evans blue dye leakage into the lung tissue. Furthermore, SPHK1 inhibitor exhibited protective effects on the two-hit model of VALI by inhibiting the Ras homolog family member a-mediated phosphorylation of myosin phosphatase target subunit 1 (MYPT-1) and endothelial hyperpermeability. Additionally, mice were divided into five additional groups: i) Non-ventilated group; ii) non-ventilated + LPS group; iii) ventilated group; iv) ventilated + LPS group; and v) ventilated + LPS + Rho-associated coiled-coil forming protein kinase (ROCK)1 inhibitor group. ROCK1 inhibitor (10 mg/kg) was injected intraperitoneally 1 h prior to ventilation. The present results suggested that ROCK1 inhibitor could attenuate mechanical stretch-induced lung endothelial injury and the phosphorylation of MYPT-1 in vivo and in vitro. Collectively, the present findings indicated that upregulation of SPHK1 may contribute to VALI in a two-hit model.

Acute respiratory distress syndrome.

The acute respiratory distress syndrome (ARDS) is a common cause of respiratory failure in critically ill patients and is defined by the acute onset of noncardiogenic pulmonary oedema, hypoxaemia and the need for mechanical ventilation. ARDS occurs most often in the setting of pneumonia, sepsis, aspiration of gastric contents or severe trauma and is present in ~10% of all patients in intensive care units worldwide. Despite some improvements, mortality remains high at 30–40% in most studies. Pathological specimens from patients with ARDS frequently reveal diffuse alveolar damage, and laboratory studies have demonstrated both alveolar epithelial and lung endothelial injury, resulting in accumulation of protein-rich inflammatory oedematous fluid in the alveolar space. Diagnosis is based on consensus syndromic criteria, with modifications for under-resourced settings and in paediatric patients. Treatment focuses on lung-protective ventilation; no specific pharmacotherapies have been identified. Long-term outcomes of patients with ARDS are increasingly recognized as important research targets, as many patients survive ARDS only to have ongoing functional and/or psychological sequelae. Future directions include efforts to facilitate earlier recognition of ARDS, identifying responsive subsets of patients and ongoing efforts to understand fundamental mechanisms of lung injury to design specific treatments.

Microparticulate Caspase 1 Regulates Gasdermin D and Pulmonary Vascular Endothelial Cell Injury.

Lung endothelial cell apoptosis and injury occur throughout all stages of acute lung injury/acute respiratory distress syndrome and impact disease progression. Caspases 1, 4, and 5 are essential for completion of the apoptotic program known as pyroptosis that also involves proinflammatory cytokines. Because gasdermin D (GSDMD) mediates pyroptotic death and is essential for pore formation, we hypothesized that it might direct caspase 1-encapsulated microparticle (MP) release and mediate endothelial cell death. Our present work provides evidence that GSDMD is released by LPS-stimulated THP-1 monocytic cells, where it is packaged into microparticles together with active caspase 1. Furthermore, only MP released from stimulated monocytic cells that contain both cleaved GSDMD and active caspase 1 induce endothelial cell apoptosis. MPs pretreated with caspase 1 inhibitor Y-VAD or pan-caspase inhibitor Z-VAD do not contain cleaved GSDMD. MPs from caspase 1-knockout cells are also deficient in p30 active GSDMD, further confirming that caspase 1 regulates GSDMD function. Although control MPs contained cleaved GSDMD without caspase 1, these fractions were unable to induce cell death, suggesting that encapsulation of both caspase 1 and GSDMD is essential for cell death induction. Release of microparticulate active caspase 1 was abrogated in GSDMD knockout cells, although cytosolic caspase 1 activation was not impaired. Last, higher concentrations of microparticulate GSDMD were detected in the plasma of septic patients with acute respiratory distress syndrome than in that of healthy donors. Taken together, these findings suggest that GSDMD regulates the release of microparticulate active caspase 1 from monocytes essential for induction of cell death and thereby may play a critical role in sepsis-induced endothelial cell injury.

Higher FiO 2 and Elevated Cell-Free Hemoglobin Augment the Risk of Primary Graft Dysfunction Through Direct Effects on Lung Vascular Permeability

Elevated recipient circulating cell-free hemoglobin (CFH) prior to lung transplant is an independent risk factor for primary graft dysfunction (PGD) (JHLT 2013;32:S42-3). This association is augmented by higher reperfusion FiO2, but the mechanisms of this are unknown. We hypothesized that hyperoxia increases PGD risk through oxidation of CFH, resulting in lung endothelial injury and vascular permeability.

Cigarette smoke exposure worsens acute lung injury in antibiotic-treated bacterial pneumonia in mice.

Evidence is accumulating that exposure to cigarette smoke (CS) increases the risk of developing acute respiratory distress syndrome (ARDS). Streptococcus pneumoniae is the most common cause of bacterial pneumonia, which in turn is the leading cause of ARDS. Chronic smokers have increased rates of pneumococcal colonization and develop more severe pneumococcal pneumonia than nonsmokers; yet mechanistic connections between CS exposure, bacterial pneumonia, and ARDS pathogenesis remain relatively unexplored. We exposed mice to 3 wk of moderate whole body CS or air, followed by intranasal inoculation with an invasive serotype of S. pneumoniae. CS exposure alone caused no detectable lung injury or bronchoalveolar lavage (BAL) inflammation. During pneumococcal infection, CS-exposed mice had greater survival than air-exposed mice, in association with reduced systemic spread of bacteria from the lungs. However, when mice were treated with antibiotics after infection to improve clinical relevance, the survival benefit was lost, and CS-exposed mice had more pulmonary edema, increased numbers of BAL monocytes, and elevated monocyte and lymphocyte chemokines. CS-exposed antibiotic-treated mice also had higher serum surfactant protein D and angiopoietin-2, consistent with more severe lung epithelial and endothelial injury. The results indicate that acute CS exposure enhances the recruitment of immune cells to the lung during bacterial pneumonia, an effect that may provide microbiological benefit but simultaneously exposes the mice to more severe inflammatory lung injury. The inclusion of antibiotic treatment in preclinical studies of acute lung injury in bacterial pneumonia may enhance clinical relevance, particularly for future studies of current or emerging tobacco products.

Neuromuscular blockade is associated with the attenuation of biomarkers of epithelial and endothelial injury in patients with moderate-to-severe acute respiratory distress syndrome

BackgroundNeuromuscular blockade (NMB) is a therapy for acute respiratory distress syndrome (ARDS). However, the mechanism by which NMB may improve outcome for ARDS patients remains unclear. We sought to determine whether NMB attenuates biomarkers of epithelial and endothelial lung injury and systemic inflammation in ARDS patients, and whether the association is dependent on tidal volume size and the initial degree of hypoxemia.MethodsWe performed a secondary analysis of patients enrolled in the ARDS network low tidal volume ventilation (ARMA) study. Our primary predictor variable was the number of days receiving NMB between study enrollment and day 3. Our primary outcome variables were the change in concentration of biomarkers of epithelial injury (serum surfactant protein-D (SP-D)), endothelial injury (von Willebrand factor (VWF)), and systemic inflammation (interleukin (IL)-8). Multivariable regression analysis was used to compare the change in biomarker concentration controlling for multiple covariates. Patients were stratified by treatment arm (12 versus 6 cm3/kg) and by an initial arterial oxygen tension (PaO2) to fractional inspired oxygen (FiO2) (P/F) ratio of 120.ResultsA total of 446 (49%) patients had complete SP-D, VWF, and IL-8 measurements on study enrollment and day 3. After adjusting for baseline differences, each day of NMB was associated with a decrease in SP-D (−23.7 ng/ml/day, p = 0.029), VWF (−33.5% of control/day, p = 0.015), and IL-8 (−362.6 pg/ml/day, p = 0.030) in patients with an initial P/F less than or equal to 120 and receiving low tidal volume ventilation. However, patients with a P/F ratio of greater than 120 or receiving high tidal volume ventilation had either no change or an increase in SP-D, WVF, or IL-8 concentrations.ConclusionNBM is associated with decreased biomarkers of epithelial and endothelial lung injury and systemic inflammation in ARDS patients receiving low tidal volume ventilation and those with a P/F ratio less than or equal to 120.

Cell-free hemoglobin promotes primary graft dysfunction through oxidative lung endothelial injury.

Primary graft dysfunction (PGD) is acute lung injury within 72 hours of lung transplantation. We hypothesized that cell-free hemoglobin (CFH) contributes to PGD by increasing lung microvascular permeability and tested this in patients, ex vivo human lungs, and cultured human lung microvascular endothelial cells. In a nested case control study of 40 patients with severe PGD at 72 hours and 80 matched controls without PGD, elevated preoperative CFH was independently associated with increased PGD risk (odds ratio [OR] 2.75, 95%CI, 1.23-6.16, P = 0.014). The effect of CFH on PGD was magnified by reperfusion fraction of inspired oxygen (FiO2) ≥ 0.40 (OR 3.41, P = 0.031). Isolated perfused human lungs exposed to intravascular CFH (100 mg/dl) developed increased vascular permeability as measured by lung weight (CFH 14.4% vs. control 0.65%, P = 0.047) and extravasation of Evans blue-labeled albumin dye (EBD) into the airspace (P = 0.027). CFH (1 mg/dl) also increased paracellular permeability of human pulmonary microvascular endothelial cell monolayers (hPMVECs). Hyperoxia (FiO2 = 0.95) increased human lung and hPMVEC permeability compared with normoxia (FiO2 = 0.21). Treatment with acetaminophen (15 μg/ml), a specific hemoprotein reductant, prevented CFH-dependent permeability in human lungs (P = 0.046) and hPMVECs (P = 0.037). In summary, CFH may mediate PGD through oxidative effects on microvascular permeability, which are augmented by hyperoxia and abrogated by acetaminophen.

Hypoxemic Patients With Bilateral Infiltrates Treated With High-Flow Nasal Cannula Present a Similar Pattern of Biomarkers of Inflammation and Injury to Acute Respiratory Distress Syndrome Patients*

To examine whether patients with acute hypoxemia and bilateral opacities treated with high-flow nasal cannula and acute respiratory distress syndrome patients who were directly mechanically ventilated are similar in terms of lung epithelial, endothelial, and inflammatory biomarkers. Prospective, multicenter study. ICUs at three university tertiary hospitals. Intubated and nonintubated patients admitted to the ICU with acute hypoxemia (PaO2/FIO2 ≤ 300) and bilateral opacities. None. Either high-flow nasal cannula or mechanical ventilation was initiated, at the discretion of the attending physician. We measured plasma biomarkers of lung epithelial injury (receptor for advanced glycation end products and surfactant protein D) and endothelial injury (angiopoietin-2) and inflammation (interleukin-6, interleukin-8, and interleukin-33 and soluble suppression of tumorigenicity-2) within 24 hours of acute respiratory distress syndrome onset. Propensity score matching was performed using six different variables (Acute Physiology and Chronic Health Evaluation II, Sequential Organ Failure Assessment, PaO2/FIO2, origin of acute respiratory distress syndrome, steroids, renal failure and need for vasopressors). Nonhypoxemic mechanically ventilated critically ill patients and healthy volunteers served as controls. Of the 170 patients enrolled, 127 (74.7%) were intubated and 43 (25.3%) were treated with high-flow nasal cannula at acute respiratory distress syndrome onset. After propensity score matching (39 high-flow nasal cannula patients vs 39 mechanical ventilation patients), no significant differences were observed in receptor for advanced glycation end products, surfactant protein D, angiopoietin-2, interleukin-6, interleukin-8, interleukin-33, and soluble suppression of tumorigenicity-2 between matched patients who were treated with high-flow nasal cannula and those who were intubated at acute respiratory distress syndrome onset. After matching, no differences in mortality or length of stay were observed. All biomarkers (with the exception of interleukin-33) were higher in both groups of matched acute respiratory distress syndrome patients than in both control groups. Acute hypoxemic patients with bilateral infiltrates treated with high-flow nasal cannula presented a similar pattern of biomarkers of inflammation and injury to acute respiratory distress syndrome patients undergoing direct mechanical ventilation. The results suggest that these high-flow nasal cannula patients should be considered as acute respiratory distress syndrome patients.

Protein biomarkers associated with primary graft dysfunction following lung transplantation.

Severe primary graft dysfunction affects 15-20% of lung transplant recipients and carries a high mortality risk. In addition to known donor, recipient, and perioperative clinical risk factors, numerous biologic factors are thought to contribute to primary graft dysfunction. Our current understanding of the pathogenesis of lung injury and primary graft dysfunction emphasizes multiple pathways leading to lung endothelial and epithelial injury. Protein biomarkers specific to these pathways can be measured in the plasma, bronchoalveolar lavage fluid, and lung tissue. Clarification of the pathophysiology and timing of primary graft dysfunction could illuminate predictors of dysfunction, allowing for better risk stratification, earlier identification of susceptible recipients, and development of targeted therapies. Here, we review much of what has been learned about the association of protein biomarkers with primary graft dysfunction and evaluate this association at different measurement time points.

Mononuclear Phagocyte-Derived Microparticulate Caspase-1 Induces Pulmonary Vascular Endothelial Cell Injury.

Lung endothelial cell apoptosis and injury occurs throughout all stages of acute lung injury (ALI/ARDS) and impacts disease progression. Lung endothelial injury has traditionally been focused on the role of neutrophil trafficking to lung vascular integrin receptors induced by proinflammatory cytokine expression. Although much is known about the pathogenesis of cell injury and death in ALI/ARDS, gaps remain in our knowledge; as a result of which there is currently no effective pharmacologic therapy. Enzymes known as caspases are essential for completion of the apoptotic program and secretion of pro-inflammatory cytokines. We hypothesized that caspase-1 may serve as a key regulator of human pulmonary microvascular endothelial cell (HPMVEC) apoptosis in ALI/ARDS. Our recent experiments confirm that microparticles released from stimulated monocytic cells (THP1) induce lung endothelial cell apoptosis. Microparticles pretreated with the caspase-1 inhibitor, YVAD, or pan-caspase inhibitor, ZVAD, were unable to induce cell death of HPMVEC, suggesting the role of caspase-1 or its substrate in the induction of HPMVEC cell death. Neither un-induced microparticles (control) nor direct treatment with LPS induced apoptosis of HPMVEC. Further experiments showed that caspase-1 uptake into HPMVEC and the induction of HPMVEC apoptosis was facilitated by caspase-1 interactions with microparticulate vesicles. Altering vesicle integrity completely abrogated apoptosis of HPMVEC suggesting an encapsulation requirement for target cell uptake of active caspase-1. Taken together, we confirm that microparticle centered caspase-1 can play a regulator role in endothelial cell injury.

Distinct Molecular Phenotypes of Direct vs Indirect ARDS in Single-Center and Multicenter Studies

ARDS is a heterogeneous syndrome that encompasses lung injury from both direct and indirect sources. Direct ARDS (pneumonia, aspiration) has been hypothesized to cause more severe lung epithelial injury than indirect ARDS (eg, nonpulmonary sepsis); however, this hypothesis has not been well studied in humans. We measured plasma biomarkers of lung epithelial and endothelial injury and inflammation in a single-center study of 100 patients with ARDS and severe sepsis and in a secondary analysis of 853 patients with ARDS drawn from a multicenter randomized controlled trial. Biomarker levels in patients with direct vs indirect ARDS were compared in both cohorts. In both studies, patients with direct ARDS had significantly higher levels of a biomarker of lung epithelial injury (surfactant protein D) and significantly lower levels of a biomarker of endothelial injury (angiopoietin-2) than those with indirect ARDS. These associations were robust to adjustment for severity of illness and ARDS severity. In the multicenter study, patients with direct ARDS also had lower levels of von Willebrand factor antigen and IL-6 and IL-8, markers of endothelial injury and inflammation, respectively. The prognostic value of the biomarkers was similar in direct and indirect ARDS. Direct lung injury in humans is characterized by a molecular phenotype consistent with more severe lung epithelial injury and less severe endothelial injury. The opposite pattern was identified in indirect lung injury. Clinical trials of novel therapies targeted specifically at the lung epithelium or endothelium may benefit from preferentially enrolling patients with direct and indirect ARDS, respectively.

Functional coupling of TRPV4, IK, and SK channels contributes to Ca(2+)-dependent endothelial injury in rodent lung.

Our previous work has shown that the increased lung endothelial permeability response to 14,15-epoxyeicosatrienoic acid (14,15-EET) in rat lung requires Ca(2+) entry via vanilloid type-4 transient receptor potential (TRPV4) channels. Recent studies suggest that activation of TRPV4 channels in systemic vascular endothelium prolongs agonist-induced hyperpolarization and amplifies Ca(2+) entry by activating Ca(2+)-activated K(+) (KCa) channels, resulting in vessel relaxation. Activation of endothelial KCa channels thus has potential to increase the electrochemical driving force for Ca(2+) influx via TRPV4 channels and to amplify permeability responses to TRPV4 activation in lung. To examine this hypothesis, we used Western blot analysis, electrophysiological recordings, and isolated-lung permeability measurements to document expression of TRPV4 and KCa channels and the potential for functional coupling. The results show that rat pulmonary microvascular endothelial cells express TRPV4 and 3 KCa channels of different conductances: large (BK), intermediate (IK), and small (SK3). However, TRPV4 channel activity modulates the IK and SK3, but not the BK, channel current density. Furthermore, the TRPV4-mediated permeability response to 14,15-EET in mouse lung is significantly attenuated by pharmacologic blockade of IK and SK3, but not BK, channels. Collectively, this functional coupling suggests that endothelial TRPV4 channels in rodent lung likely form signaling microdomains with IK and SK3 channels and that the integrated response dictates the extent of lung endothelial injury caused by 14,15-EET.

Endothelial disruptive proinflammatory effects of nicotine and e-cigarette vapor exposures.

The increased use of inhaled nicotine via e-cigarettes has unknown risks to lung health. Having previously shown that cigarette smoke (CS) extract disrupts the lung microvasculature barrier function by endothelial cell activation and cytoskeletal rearrangement, we investigated the contribution of nicotine in CS or e-cigarettes (e-Cig) to lung endothelial injury. Primary lung microvascular endothelial cells were exposed to nicotine, e-Cig solution, or condensed e-Cig vapor (1-20 mM nicotine) or to nicotine-free CS extract or e-Cig solutions. Compared with nicotine-containing extract, nicotine free-CS extract (10-20%) caused significantly less endothelial permeability as measured with electric cell-substrate impedance sensing. Nicotine exposures triggered dose-dependent loss of endothelial barrier in cultured cell monolayers and rapidly increased lung inflammation and oxidative stress in mice. The endothelial barrier disruptive effects were associated with increased intracellular ceramides, p38 MAPK activation, and myosin light chain (MLC) phosphorylation, and was critically mediated by Rho-activated kinase via inhibition of MLC-phosphatase unit MYPT1. Although nicotine at sufficient concentrations to cause endothelial barrier loss did not trigger cell necrosis, it markedly inhibited cell proliferation. Augmentation of sphingosine-1-phosphate (S1P) signaling via S1P1 improved both endothelial cell proliferation and barrier function during nicotine exposures. Nicotine-independent effects of e-Cig solutions were noted, which may be attributable to acrolein, detected along with propylene glycol, glycerol, and nicotine by NMR, mass spectrometry, and gas chromatography, in both e-Cig solutions and vapor. These results suggest that soluble components of e-Cig, including nicotine, cause dose-dependent loss of lung endothelial barrier function, which is associated with oxidative stress and brisk inflammation.

Sustained Adenosine Caused Endothelial Mitochondrial Dysfunction: Implications for Cigarette Smoke‐Induced Increased Susceptibility to Acute Lung Injury

Cigarette smoke (CS) has been independently associated with the development of acute lung injury (ALI). We have previously demonstrated that CS exposure increases lung adenosine levels in mice and that sustained exposure to adenosine causes lung endothelial injury by equilibrative nucleoside transporter (ENT) 1/2-dependent mechanism. In this study we hypothesize that CS-induced increased adenosine causes lung endothelial injury, leading to increased susceptibility to ALI, via ENT1/2- mediated mitochondrial dysfunction. Using inhaled Pseudomonas aeruginosa, a clinically relevant model of ALI, we found that CS pre-exposure exacerbated P. aeruginosa-induced lung injury. Pharmacological inhibition of ENT1 attenuated P. aeruginosa-induced lung edema and inflammation. Using cultured lung endothelial cells, we found that sustained exposure to adenosine decreased mitochondrial basal respiration, increased mitochondrial reactive oxygen species (ROS), enhanced expression of fission/fusion markers (Drp1 and Mfn1) and mitophagy marker (Parkin), and promoted SOD2 expression. Inhibition of ENT1/2 attenuated sustained adenosine-induced mitochondrial ROS. Our data suggest that sustained elevated adenosine causes lung endothelial injury via ENT1/2-dependent, oxidative stress-induced mitochondrial dysfunction, which may contribute to CS-induced increased susceptibility to ALI. PH-05-015 (Lu), P20GM103652 (Lu, Rounds), PULM-811-10S (Rounds), NIH NIEHS T32 ES007272 (supporting E. C.) and Brown University Institutional UTRA (supporting J. K.)

Mitochondrial bioenergetics and permeability response in rat pulmonary microvascular endothelial cells in culture (1176.1)

Hyperoxia causes lung endothelial injury and depresses mitochondrial complex I (CI) activity. In isolated rat lung perfused with a physiological saline solution (5.5 mM glucose), CI inhibitors decrease lung tissue ATP and increase endothelial permeability (measured as Kf), effects that are overcome using a quinone (CoQ1) (Free Radic Biol Med. doi: 10.1016/j.freeradbiomed.2013.07.040). To unmask the mitochondrial contribution to pulmonary endothelial cell culture permeability responses, PMVEC were treated with the CI inhibitor rotenone (0.5 µM) in 0.2 mM glucose without or with CoQ1 (10 µM). In PMVEC monolayers, rotenone decreased ATP from 18.4 ± 1.6 (mean ± SE) to 4.6 ± 0.8 nmol/mg protein, decreased O2 consumption from 2.6 ± 0.1 to 0.3 ± 0.1 nmol/min/mg protein and increased permeability to FITC‐dextran from 8.3 ± 0.7 to 14.3 ± 0.4 nl/min/cm2. When CoQ1 was present with rotenone, ATP (17.4 ± 1.4 nmol/mg protein), O2 consumption (1.6 ± 0.2 nmol/min/mg protein) and permeability (10.1 ± 1.2 nl /min/cm2) were maintained. CoQ1 also prevented rotenone‐induced mitochondrial depolarization. Protective effects of CoQ1 on ATP, O2 consumption and mitochondrial membrane potential were blocked by inhibitors of the quinone mediated cytosol‐mitochondria electron shuttle. We conclude that, as in the lung, mitochondrial bioenergetics can be a determinant of the PMVEC permeability response.Grant Funding Source: Supported by Dept of Veterans Affairs

Protein kinase G increases antioxidant function in lung microvascular endothelial cells by inhibiting the c-Abl tyrosine kinase

Oxidant injury contributes to acute lung injury (ALI). We previously reported that activation of protein kinase GI (PKGI) posttranscriptionally increased the key antioxidant enzymes catalase and glutathione peroxidase 1 (Gpx-1) and attenuated oxidant-induced cytotoxicity in mouse lung microvascular endothelial cells (MLMVEC). The present studies tested the hypothesis that the antioxidant effect of PKGI is mediated via inhibition of the c-Abl tyrosine kinase. We found that activation of PKGI with the cGMP analog 8pCPT-cGMP inhibited c-Abl activity and decreased c-Abl expression in wild-type but not PKGI(-/-) MLMVEC. Treatment of wild-type MLMVEC with atrial natriuretic peptide also inhibited c-Abl activation. Moreover, treatment of MLMVEC with the c-Abl inhibitor imatinib increased catalase and GPx-1 protein in a posttranscriptional fashion. In imatinib-treated MLMVEC, there was no additional effect of 8pCPT-cGMP on catalase or GPx-1. The imatinib-induced increase in antioxidant proteins was associated with an increase in extracellular H2O2 scavenging by MLMVEC, attenuation of oxidant-induced endothelial barrier dysfunction, and prevention of oxidant-induced endothelial cell death. Finally, in the isolated perfused lung, imatinib prevented oxidant-induced endothelial toxicity. We conclude that cGMP, through activation of PKGI, inhibits c-Abl, leading to increased key antioxidant enzymes and resistance to lung endothelial oxidant injury. Inhibition of c-Abl by active PKGI may be the downstream mechanism underlying PKGI-mediated antioxidant signaling. Tyrosine kinase inhibitors may represent a novel therapeutic approach in oxidant-induced ALI.

In the Absence of Effector Proteins, the Pseudomonas aeruginosa Type Three Secretion System Needle Tip Complex Contributes to Lung Injury and Systemic Inflammatory Responses

Herein we describe a pathogenic role for the Pseudomonas aeruginosa type three secretion system (T3SS) needle tip complex protein, PcrV, in causing lung endothelial injury. We first established a model in which P. aeruginosa wild type strain PA103 caused pneumonia-induced sepsis and distal organ dysfunction. Interestingly, a PA103 derivative strain lacking its two known secreted effectors, ExoU and ExoT [denoted PA103 (ΔU/ΔT)], also caused sepsis and modest distal organ injury whereas an isogenic PA103 strain lacking the T3SS needle tip complex assembly protein [denoted PA103 (ΔPcrV)] did not. PA103 (ΔU/ΔT) infection caused neutrophil influx into the lung parenchyma, lung endothelial injury, and distal organ injury (reminiscent of sepsis). In contrast, PA103 (ΔPcrV) infection caused nominal neutrophil infiltration and lung endothelial injury, but no distal organ injury. We further examined pathogenic mechanisms of the T3SS needle tip complex using cultured rat pulmonary microvascular endothelial cells (PMVECs) and revealed a two-phase, temporal nature of infection. At 5-hours post-inoculation (early phase infection), PA103 (ΔU/ΔT) elicited PMVEC barrier disruption via perturbation of the actin cytoskeleton and did so in a cell death-independent manner. Conversely, PA103 (ΔPcrV) infection did not elicit early phase PMVEC barrier disruption. At 24-hours post-inoculation (late phase infection), PA103 (ΔU/ΔT) induced PMVEC damage and death that displayed an apoptotic component. Although PA103 (ΔPcrV) infection induced late phase PMVEC damage and death, it did so to an attenuated extent. The PA103 (ΔU/ΔT) and PA103 (ΔPcrV) mutants grew at similar rates and were able to adhere equally to PMVECs post-inoculation indicating that the observed differences in damage and barrier disruption are likely attributable to T3SS needle tip complex-mediated pathogenic differences post host cell attachment. Together, these infection data suggest that the T3SS needle tip complex and/or another undefined secreted effector(s) are important determinants of P. aeruginosa pneumonia-induced lung endothelial barrier disruption.

Inhibition of AMP-Activated Protein Kinase Accentuates Lipopolysaccharide-Induced Lung Endothelial Barrier Dysfunction and Lung Injury in Vivo

The aim of this study was to determine the role of AMP-activated protein kinase (AMPK) in lipopolysaccharide (LPS)-induced lung endothelial barrier dysfunction and lung injury in vivo. Both cultured human pulmonary artery endothelial cells (HPAECs) and experimental animals [AMPK subunit α-deficient mice and wild-type (WT) control mice (C57BL/6J)] were used. In cultured HPAECs, LPS increased endothelial permeability in parallel with a decrease in AMPK activity. Consistent with this observation, AMPK activation with the potent AMPK activator 5-aminoimidazole-4-carboxamide-1-d-ribofuranoside (AICAR) attenuated LPS-induced endothelial hyperpermeability in vitro. Intratracheal administration of LPS (1 mg/kg) in WT mice reduced AMPK phosphorylation at Thr172 in lung tissue extracts, increased protein content and cell count in bronchial alveolar lavage fluid, and increased Evans Blue dye infiltration into the lung. These same attributes were similarly enhanced in AMPKα-knockout mice, compared with WT mice. Pretreatment with AICAR reduced these lung injury indicators in LPS-treated WT mice. AMPK activation with AICAR attenuated LPS-induced endothelial hyperpermeability by activating the Rac/Cdc42/PAK pathway, with concomitant inhibition of the Rho pathway, and decreased VE-cadherin phosphorylation at Tyr658. We conclude that AMPK activity supports normal endothelial barrier function and that LPS exposure inhibits AMPK, thereby contributing to endothelial barrier dysfunction and lung injury.

Platelets induce neutrophil extracellular traps in transfusion-related acute lung injury

There is emerging evidence that platelets are major contributors to inflammatory processes through intimate associations with innate immune cells. Here, we report that activated platelets induce the formation of neutrophil extracellular traps (NETs) in transfusion-related acute lung injury (TRALI), which is the leading cause of death after transfusion therapy. NETs are composed of decondensed chromatin decorated with granular proteins that function to trap extracellular pathogens; their formation requires the activation of neutrophils and release of their DNA in a process that may or may not result in neutrophil death. In a mouse model of TRALI that is neutrophil and platelet dependent, NETs appeared in the lung microvasculature and NET components increased in the plasma. We detected NETs in the lungs and plasma of human TRALI and in the plasma of patients with acute lung injury. In the experimental TRALI model, targeting platelet activation with either aspirin or a glycoprotein IIb/IIIa inhibitor decreased NET formation and lung injury. We then directly targeted NET components with a histone blocking antibody and DNase1, both of which protected mice from TRALI. These data suggest that NETs contribute to lung endothelial injury and that targeting NET formation may be a promising new direction for the treatment of acute lung injury.