ObjectiveAcute respiratory distress syndrome (ARDS) is an acute and lethal clinical syndrome that is characterized by the injury of alveolar epithelium, which impairs active fluid transport in the lung, and impedes the reabsorption of edema fluid from the alveolar space. This review aimed to discuss the role of pro-resolving mediators on the regulation of alveolar fluid clearance (AFC) in ARDS.

Data SourcesArticles published up to September 2017 were selected from the PubMed, with the keywords of "alveolar fluid clearance" or "lung edema" or "acute lung injury" or "acute respiratory distress syndrome", and "specialized pro-resolving mediators" or "lipoxin" or "resolvin" or "protectin" or "maresin" or "alveolar epithelial cells" or "aspirin-triggered lipid mediators" or "carbon monoxide and heme oxygenase" or "annexin A1".

Study SelectionWe included all relevant articles published up to September 2017, with no limitation of study design.

ResultsSpecialized pro-resolving mediators (SPMs), as the proinflammatory mediators, not only upregulated epithelial sodium channel, Na,K-ATPase, cystic fibrosis transmembrane conductance regulator (CFTR), and aquaporins levels, but also improved Na,K-ATPase activity to promote AFC in ARDS. In addition to the direct effects on ion channels and pumps of the alveolar epithelium, the SPMs also inhibited the inflammatory cytokine expression and improved the alveolar epithelial cell repair to enhance the AFC in ARDS.

ConclusionsThe present review discusses a novel mechanism for pulmonary edema fluid reabsorption. SPMs might provide new opportunities to design "reabsorption-targeted" therapies with high degrees of precision in controlling ALI/ARDS.

Acute Lung Injury ; metabolism ; Animals ; Cystic Fibrosis Transmembrane Conductance Regulator ; metabolism ; Humans ; Respiratory Distress Syndrome, Adult ; metabolism

Extracellular vesicles (EVs) are anuclear particles composed of lipid bilayers that contain nucleic acids, proteins, lipids, and organelles. EVs act as an important mediator of cell-to-cell communication by transmitting biological signals or components, including lipids, proteins, messenger RNAs, DNA, microRNAs, organelles, etc, to nearby or distant target cells to activate and regulate the function and phenotype of target cells. Under physiological conditions, EVs play an essential role in maintaining the homeostasis of the pulmonary milieu but they can also be involved in promoting the pathogenesis and progression of various respiratory diseases including chronic obstructive pulmonary disease, asthma, acute lung injury/acute respiratory distress syndrome, idiopathic pulmonary fibrosis (IPF), and pulmonary artery hypertension. In addition, in multiple preclinical studies, EVs derived from mesenchymal stem cells (EVs) have shown promising therapeutic effects on reducing and repairing lung injuries. Furthermore, in recent years, researchers have explored different methods for modifying EVs or enhancing EVs-mediated drug delivery to produce more targeted and beneficial effects. This article will review the characteristics and biogenesis of EVs and their role in lung homeostasis and various acute and chronic lung diseases and the potential therapeutic application of EVs in the field of clinical medicine.
DNA/metabolism* ; Extracellular Vesicles/metabolism* ; Humans ; Lipid Bilayers/metabolism* ; Lung Diseases/therapy* ; Lung Injury/metabolism* ; MicroRNAs/metabolism* ; Proteins/metabolism* ; Respiratory Distress Syndrome

The aim of this study was to determine the role of neutrophil collagenase in the pathogenesis of acute lung injury induced by endotoxin. 28 Sprague-Dawley were randomized into control group and LPS-enduced groups. Samples of left lung were obtained in 2 h (group L1), 6 h (group L2), 12 h (group L3) after intravenous LPS. Immunohistochemsitry was employed for detection of expression of neutrophil collagenase. Pathological scores, lung wet/dry weight ratio and the number of neutrophils were measured. The results showed that the concentration of neutrophil collagenase in LPS-enduced groups (group L1, L2, L3) were significantly higher than that of control group (P<0.01). Pathological scores, lung wet/dry weight ratio and the number of neutrophils in LPS-enduced groups (group L1, L2, L3) were also significantly higher than that of control group (P<0.01). Moreover, among group L1, L2 and L3, there were significant correlations in concentration of neutrophil collagenase and pathological scores, lung wet/dry weight ratio, the number of neutrophils (P<0.05). The present study showed that neutrophil collagenase play an important role in the pathogenesis and progress of endotoxic acute lung injury.
Endotoxins ; Lung/pathology ; Matrix Metalloproteinase 8/*metabolism ; Random Allocation ; Rats, Sprague-Dawley ; Respiratory Distress Syndrome, Adult/chemically

Glucocorticoids ; adverse effects ; therapeutic use ; Humans ; Respiratory Distress Syndrome, Adult ; drug therapy ; immunology ; metabolism ; Systemic Inflammatory Response Syndrome ; drug therapy ; immunology ; metabolism

OBJECTIVETo investigate possible role of carbon monoxide (CO) and heme oxygenase (HO) in the pathogenesis of acute respiratory distress syndrome (ARDS) induced by oleic acid (OA) and to compared with that induced by nitric oxide (NO).

METHODSARDS model was established in rats by oleic acid injection and concentrations of CO and NO in pulmonary arterial, carotid jugular blood and bronchoalveolar lavage fluid (BALF) were measured sequentially. Immunohistochemical method was used to determine the expression of HO in the lung.

RESULTSPulmonary arterial pressure in ARDS rats elevated 10 min after OA injection [(13.80 +/- 1.87) mm Hg to (19.51 +/- 5.02) mm Hg]. At 0.5 h after OA injection, concentration of CO in pulmonary artery began to increase and was markedly higher at 2 h than that in control rats [(0.135 +/- 0.010) g/L versus (0.116 +/- 0.005) g/L] (P < 0.01), also higher than that in carotid artery [(0.117 +/- 0.013) g/L] and in jugular vein [(0.107 +/- 0.018) g/L] in the same group, and maintained at a relatively high level thereafter. Concentration of CO in BALF also increased at 0.5 - 24 h and diminished at 72 h, as compared with that in controls. Concentration of NO in blood of pulmonary and systemic circulation all elevated markedly at 0.5 h and 2 h after OA injection, and then declined to normal at 12 h. Concentration of NO in BALF was significantly higher than that in controls. Arterial blood gas analysis showed that PaO2 markedly decreased in ARDS rats, especially at 2 h after OA injection. HO-2 could be expressed in the lung tissues of normal rats with immunohistochemical method, the strongest in epithelial cells of the bronchi, and HO-1 could only be expressed in pulmonary blood vessel walls, bronchial epithelial cells, alveolar epithelial cells and inflammatory cells of ARDS rats, lasting for 72 h after OA injection, consistent with that of CO level.

CONCLUSIONARDS rats showed a lastecl increase of CO level in pulmonary blood circulation, suggesting CO/HO system might play a more important role in modulation of blood vessel tension than NO might do in pathogenesis of ARDS.

Animals ; Carbon Monoxide ; metabolism ; Heme Oxygenase (Decyclizing) ; metabolism ; Male ; Nitric Oxide ; metabolism ; Oleic Acid ; Rats ; Rats, Sprague-Dawley ; Respiratory Distress Syndrome, Adult ; metabolism

OBJECTIVEAcute respiratory distress syndrome (ARDS) is an acute and lethal clinical syndrome that is characterized by hypoxemic respiratory failure and diffuse alveolar inflammatory damage. This review aimed to search and discuss the mass spectrometry (MS)-based proteomic studies on different subsets of ARDS patients.

DATA SOURCESOriginal research articles were collected from the PubMed database published in English up to December 2015.

STUDY SELECTIONThe literature search was done using the term "(acute lung injury OR acute respiratory distress syndrome) AND (proteomics OR proteome OR mass spectrum OR differential in-gel electrophoresis OR two-dimensional polyacrylamide gel electrophoresis)". Related original research articles were included and were carefully analyzed.

RESULTSEight original proteomic researches on ARDS patients were found. The common proteomic modalities were two-dimensional (2D) high-performance liquid chromatography-based electronic spray ion-MS/MS and 2D-polyacrylamide gel electrophoresis/differential in-gel electrophoresis-based matrix-assisted laser desorption ionization-time of flight/MS. They compared the proteome between ARDS patients and normal controls and analyzed the dynamic changes of proteome at different ARDS stages or severity. The disturbed proteome in ARDS patients includes plasma acute-phase proteins, inflammatory/immune-associated proteins, and coagulation proteins.

CONCLUSIONSAlthough several previous studies have provided some useful information about the lung proteome in ARDS patients and gained several interesting disease-associated biomarkers, clinical proteomic studies in ARDS patients are still in the initial stage. An increased cooperation is still needed to establish a global and faithful database containing disease-specific proteome from the largest ARDS subsets.

Acute-Phase Proteins ; metabolism ; Humans ; Lung ; metabolism ; pathology ; Mass Spectrometry ; methods ; Precision Medicine ; methods ; Proteomics ; methods ; Respiratory Distress Syndrome, Adult ; metabolism

OBJECTIVEImpaired active fluid transport of alveolar epithelium may involve in the pathogenesis and resolution of alveolar edema. The objective of this study was to explore the changes in alveolar epithelial liquid clearance during lung edema following acute lung injury induced by oleic acid.

METHODSForty-eight Wistar rats were randomly divided into six groups, i.e., injured, amiloride, ouabain, amiloride plus ouabain and terbutaline groups. Twenty-four hours after the induction of acute lung injury by intravenous oleic acid (0.25 ml/kg), 5% albumin solution with 1.5 microCi (125)I-labeled albumin (5 ml/kg) was delivered into both lungs via trachea. Alveolar liquid clearance (ALC), extravascular lung water (EVLW) content and arterial blood gases were measured one hour thereafter.

RESULTSAt 24 h after the infusion of oleic acid, the rats developed pulmonary edema and severe hypoxemia, with EVLW increased by 47.9% and ALC decreased by 49.2%. Addition of either 2x10(-3) M amiloride or 5x10(-4) M ouabain to the instillation further reduced ALC and increased EVLW. ALC increased by approximately 63.7% and EVLW decreased by 46.9% with improved hypoxemia in the Terbutaline (10(-4) M) group, compared those in injured rats. A significant negative correlation was found between the increment of EVLW and the reduction of ALC.

CONCLUSIONSActive fluid transport of alveolar epithelium might play a role in the pathogenesis of lung edema in acute lung injury.

Adrenergic beta-Agonists ; pharmacology ; Animals ; Epithelium ; metabolism ; Oleic Acid ; adverse effects ; Pulmonary Alveoli ; metabolism ; Random Allocation ; Rats ; Rats, Wistar ; Respiratory Distress Syndrome, Adult ; chemically induced ; metabolism ; Terbutaline ; pharmacology

OBJECTIVE: To investigate the effects of Hippo signaling pathway on lung injury repair of mesenchymal stem cells (MSC) in acute respiratory distress syndrome (ARDS) and its mechanism. METHODS: Mouse bone marrow-derived MSC (mMSCs) cell lines with low expression of large tumor suppressor 2 (LATS2) were constructed by lentiviral vector transfection. Male C57BL/6 mice aging 6-8 weeks old were divided into four groups according to random number table (n = 36). The ARDS animal model (ARDS group) was reproduced by intratracheally injection of 2 g/L lipopolysaccharide (LPS) 50 μL, the normal saline (NS) control group was injected with an equal volume of NS. After 4 hours of model reproduction, 5×10⁴ mMSCs transfected with blank lentivirus vector (MSC-shcontrol group) or shLATS2 lentivirus vector (MSC-shLATS2 group) were transplanted intratracheally, while NS control group and ARDS group were injected with equal volume of phosphate buffered saline (PBS). Mice were sacrificed at 3, 7, and 14 days after modeling, and lung tissue and bronchoalveolar lavage fluid (BALF) were harvested. Near-infrared fluorescence imaging, immunofluorescence staining and Western Blot were used to track mMSCs in lung tissue. Retension and proportion of mMSC differentiation into type II alveolar epithelial cells (AEC II) were evaluated. Lung tissue wet weight/body weight ratio (LWW/BW) and total protein (TP) and albumin (ALB) in BALF were determined to reflect pulmonary edema. The expression of Occludin protein in lung epithelium was tested by Western Blot to reflect permeability of epithelium. The levels of interleukins (IL-1β, IL-6, IL-10) in BALF were assessed by enzyme-linked immunosorbent assay (ELISA) to reflect lung inflammation. Hematoxylin-eosin (HE) staining and modified Masson staining were carried out, and the scores were assessed to reflect lung injury and evaluate pulmonary fibrosis. RESULTS: The signal intensity of isolated lung fluorescence images at 3 days in the MSC-shLATS2 group was significantly higher than that in the MSC-shcontrol group (fluorescence intensity: 0.039±0.005 vs. 0.017±0.002, P < 0.05), the number of green fluorescent protein (GFP)-positive cells in lung tissue was also significantly higher than that in the MSC-shcontrol group (cells/HP: 29.65±6.98 vs. 17.50±4.58, P < 0.05), but they all decreased with time; and the proportion of mMSCs differentiated into AEC II was significantly increased [(64.12±15.29)% vs. (19.64±3.71)%, P < 0.05]. Compared with the NS control group, the levels of surface active protein C (SPC) and Occludin protein in the ARDS group were significantly decreased, LWW/BW ratio and TP, ALB and inflammatory factors levels in BALF were significantly increased; extensive alveolar and interstitial edema, hemorrhage and diffuse inflammatory cell infiltration were found in lung tissue, and the lung injury score was significantly increased; collagen fibers were deposited in alveolar septum and alveolar cavity, and pulmonary fibrosis score was also increased significantly. Compared with the ARDS group, the expression levels of SPC and Occludin at 14 days in the MSC-shcontrol group and the MSC-shLATS2 group were significantly increased (SPC/β-actin: 0.51±0.12, 0.68±0.10 vs. 0.27±0.08, Occludin/β-actin: 0.49±0.19, 0.79±0.11 vs. 0.25±0.08, all P < 0.05), TP, ALB, IL-1β, IL-6 levels in BALF at 3 days were significantly decreased [TP (g/L): 8.08±1.72, 5.12±0.87 vs. 12.55±2.09; ALB (g/L): 0.71±0.21, 0.44±0.18 vs. 1.18±0.29, IL-1β (ng/L): 99.26±14.32, 60.11±8.58 vs. 161.86±25.17, IL-6 (ng/L): 145.54±13.29, 101.74±11.55 vs. 258.79±27.88, all P < 0.05], and IL-10 was significantly increased (ng/L: 190.83±22.61, 316.65±37.88, both P < 0.05). Furthermore, all the above parameters in the MSC-shLATS2 group were significantly improved as compared with those in the MSC-shcontrol group (all P < 0.05). LWW/BW ratio in the MSC-shLATS2 group was significantly lower than that in the ARDS group and the MSC-shcontrol group (mg/g: 9.85±1.51 vs. 16.78±1.92, 14.88±1.74, both P < 0.05). CONCLUSIONS Inhibiting Hippo signaling pathway by low expression of LATS2 could promote the retention of mMSCs in lung tissue and differentiation into AEC II cells of ARDS mice, improve pulmonary edema and alveolar epithelial permeability, regulate pulmonary inflammatory response, and alleviate pathological damage and fibrosis of lung tissue.
Animals ; Hippo Signaling Pathway ; Lung Injury/prevention & control* ; Male ; Mesenchymal Stem Cells/metabolism* ; Mice ; Mice, Inbred C57BL ; Protein Serine-Threonine Kinases/metabolism* ; Respiratory Distress Syndrome/metabolism* ; Signal Transduction

We conducted a randomized animal study to determine whether there is a cumulative effect on hemodynamics, pulmonary function, and gas exchange when low dose nitric oxide (NO) is added to partial liquid ventilation (PLV) in acute lung injury. ighteen newborn piglets were saline-lavaged repeatedly, and randomly divided into two groups: PLV with perfluorocarbon group (n=8) and lavage only (control) group (n=10). Perfluorodecalin (30 mL/kg) was instilled into the endotracheal tube for 30 min, followed by 5-10 mL/kg/hr. Fifteen minutes after the completion of perfluorodecalin dosing, NO (10 ppm) was added to the inspiratory gas in an "on/off" manner. Perfluorodecalin instillation produced a significant improvement in gas exchange, pulmonary mechanics, shunt, and pulmonary arterial pressure (PAP). The addition of NO produced a further significant improvement in PaO2 and PAP. The "on/off" response to NO was seen apparently in PAP, PaO2, dynamic compliance, and shunt. All the variables in control group were remained at near the after-lavage levels without significant improvements until the end of the experiment. We concluded that NO might have a cumulative effect on gas exchange when combined with PLV, and this might be attributable to deceased PAP and V/Q mismatching.
Administration, Inhalation ; Animals ; Animals, Newborn ; Fluorocarbons/metabolism ; Hemodynamic Processes ; *Liquid Ventilation ; Nitric Oxide/administration & dosage/*metabolism ; Plasma Substitutes/metabolism ; Pulmonary Gas Exchange/*physiology ; Random Allocation ; *Respiratory Distress Syndrome, Adult ; Respiratory Mechanics ; *Respiratory Physiology ; Support, Non-U.S. Gov't ; Swine

BACKGROUNDHigh-frequency oscillatory ventilation (HFOV) allows for small tidal volumes at mean airway pressures (mPaw) above that of conventional mechanical ventilation (CMV), but the effect of HFOV on hemodynamics, oxygen metabolism, and tissue perfusion in acute respiratory distress syndrome (ARDS) remains unclear. We investigated the effects of HFOV and CMV in sheep models with ARDS.

METHODSAfter inducing ARDS by repeated lavage, twelve adult sheep were randomly divided into a HFOV or CMV group. After stabilization, standard lung recruitments (40 cmH2O × 40 seconds) were performed. The optimal mPaw or positive end-expiratory pressure was obtained by lung recruitment and decremental positive end-expiratory pressure titration. The animals were then ventilated for 4 hours. The hemodynamics, tissue perfusion (superior mesenteric artery blood flow, pHi, and Pg-aCO2), oxygen metabolism and respiratory mechanics were examined at baseline before saline lavage, in the ARDS model, after model stabilization, and during hourly mechanical ventilation for up to 4 hours. A two-way repeated measures analysis of variance was applied to evaluate differences between the groups.

RESULTSThe titrated mPaw was higher and the tidal volumes lower in the HFOV group than the positive end-expiratory pressure in the CMV group. There was no significant difference in hemodynamic parameters between the HFOV and CMV groups. There was no difference in the mean alveolar pressure between the two groups. After lung recruitment, both groups showed an improvement in the oxygenation, oxygen delivery, and DO2. Lactate levels increased in both groups after inducing the ARDS model. Compared with the CMV group, the superior mesenteric artery blood flow and pHi were significantly higher in the HFOV group, but the Pg-aCO2 decreased in the HFOV group.

CONCLUSIONCompared with CMV, HFOV with optimal mPaw has no significant side effect on hemodynamics or oxygen metabolism, and increases gastric tissue blood perfusion.

Animals ; Disease Models, Animal ; Hemodynamics ; physiology ; High-Frequency Ventilation ; methods ; Male ; Oxygen ; metabolism ; Positive-Pressure Respiration ; methods ; Respiration, Artificial ; methods ; Respiratory Distress Syndrome, Adult ; metabolism ; therapy ; Sheep