Bronchoalveolar Lavage Protein Research Articles

Biologic Correlates of Radiologic Features of Systemic Sclerosis Interstitial Lung Disease

Background and objectivesThe extent and pattern of radiological features (e.g., fibrosis, ground glass) can influence treatment approaches for systemic sclerosis-related interstitial lung disease (SSc-ILD). However, the pathobiology underlying these radiologic features is poorly understood and warrants further investigation.MethodsSixty-eight proteins were measured in bronchoalveolar lavage (BAL) fluid from 103 SSc-ILD participants in Scleroderma Lung Study I. Quantitative image analysis calculated the extent of fibrosis (QLF) and ground glass opacity (QGG) from concurrent high-resolution computerized tomography (HRCT) scans. The relationship between BAL proteins and quantitative HRCT scores was assessed by univariate and multivariate analyses.ResultsQLF scores correlated weakly with the extent of QGG, suggesting two distinct processes. In a univariate analysis, 25 proteins from several biologic pathways correlated with QLF scores, including pro-fibrotic factors, tissue remodeling proteins, proteins involved in monocyte/macrophage migration and activation, and proteins linked to inflammation and immune regulation. In contrast, QGG scores correlated with only 6 proteins of which four were unique and related to granulocyte activation, mobilization of bone marrow mesenchymal stem cells, and activation of T cells, B cells, macrophages and eosinophils. In the multivariate models, IL-4, CCL7, receptor activator of NF-κB, and tumor necrosis factor alpha were independently associated with QLF, whereas, IFN-γ was independently associated with QGG.InterpretationQLF and QGG represent distinct radiologic features of SSc-ILD, a conclusion reinforced by the presence of different biologic pathways present within BAL fluid that associate with each. The identified proteins and related biologic pathways may represent important therapeutic targets.

Matrix metalloproteinases mediate influenza A-associated shedding of the alveolar epithelial glycocalyx.

The alveolar epithelium is protected by a heparan sulfate-rich, glycosaminoglycan layer called the epithelial glycocalyx. It is cleaved in patients with acute respiratory distress syndrome (ARDS) and in murine models of influenza A (IAV) infection, shedding fragments into the airspace from the cell surface. Glycocalyx shedding results in increased permeability of the alveolar-capillary barrier, amplifying acute lung injury. The mechanisms underlying alveolar epithelial glycocalyx shedding in IAV infection are unknown. We hypothesized that induction of host sheddases such as matrix metalloproteinases (MMPs) during IAV infection results in glycocalyx shedding and increased lung injury. We measured glycocalyx shedding and lung injury during IAV infection with and without treatment with the pan-MMP inhibitor Ilomastat (ILO) and in an MMP-7 knock out (MMP-7KO) mouse. C57BL/6 or MMP-7KO male and female mice were given IAV A/PR/8/34 (H1N1) at 30,000 PFU/mouse or PBS intratracheally. For some experiments, C56BL/6 mice were infected in the presence of ILO (100mg/kg) or vehicle given daily by IP injection. Bronchoalveolar lavage (BAL) and lung tissue were collected on day 1, 3, and 7 for analysis of glycocalyx shedding (BAL Syndecan-1) and lung injury (histology, BAL protein, BAL cytokines, BAL immune cell infiltrates, BAL RAGE). Expression and localization of the sheddase MMP-7 and its inhibitor TIMP-1 was examined by RNAScope. For in vitro experiments, MLE-12 mouse lung epithelial cells were cultured and treated with active or heat-inactivated heparinase (2.5 U/mL) prior to infection with IAV (MOI 1) and viral load and MMP-7 and TIMP-1 expression analyzed. IAV infection caused shedding of the epithelial glycocalyx into the BAL. Inhibition of MMPs with ILO reduced glycocalyx shedding by 36% (p = 0.0051) and reduced lung epithelial injury by 40% (p = 0.0404). ILO also reduced viral load by 68% (p = 0.027), despite having no significant effect on lung cytokine production. Both MMP-7 and its inhibitor TIMP-1 were upregulated in IAV infected mice: MMP-7 colocalized with IAV, while TIMP-1 was limited to cells adjacent to infection. However, MMP-7KO mice had similar glycocalyx shedding, epithelial injury, and viral load compared to WT littermates, suggesting redundancy in MMP sheddase function in the lung. In vitro, heparinase treatment before infection led to a 52% increase in viral load (p = 0.0038) without altering MMP-7 or TIMP-1 protein levels. Glycocalyx shedding and MMPs play key roles in IAV-induced epithelial injury, with significant impact on IAV viral load. Further studies are needed to understand which specific MMPs regulate lung epithelial glycocalyx shedding.

Nebulized Lipopolysaccharide Causes Delayed Cortical Neuroinflammation in a Murine Model of Acute Lung Injury.

Lung injury caused by respiratory infection is a major cause of hospitalization and mortality and a leading origin of sepsis. Sepsis-associated encephalopathy and delirium are frequent complications in patients with severe lung injury, yet the pathogenetic mechanisms remain unclear. Here, 70 female C57BL/6 mice were subjected to a single full-body-exposure with nebulized lipopolysaccharide (LPS). Neuromotor impairment was assessed repeatedly and brain, blood, and lung samples were analyzed at survival points of 24 h, 48 h, 72 h, and 96 h after exposure. qRT-PCR revealed increased mRNA-expression of TNFα and IL-1β 24 h and 48 h after LPS-exposure in the lung, concomitantly with increased amounts of proteins in bronchoalveolar lavage and interstitial lung edema. In the cerebral cortex, at 72 h and/or 96 h after LPS exposure, the inflammation- and activity-associated markers TLR4, GFAP, Gadd45b, c-Fos, and Arc were increased. Therefore, single exposure to nebulized LPS not only triggers an early inflammatory reaction in the lung but also induces a delayed neuroinflammatory response. The identified mechanisms provide new insights into the pathogenesis of sepsis-associated encephalopathy and might serve as targets for future therapeutic approaches.

Novel approach to exploring protease activity and targets in HIV-associated obstructive lung disease using combined proteomic-peptidomic analysis

BackgroundObstructive lung disease (OLD) is increasingly prevalent among persons living with HIV (PLWH). However, the role of proteases in HIV-associated OLD remains unclear.MethodsWe combined proteomics and peptidomics to comprehensively characterize protease activities. We combined mass spectrometry (MS) analysis on bronchoalveolar lavage fluid (BALF) peptides and proteins from PLWH with OLD (n = 25) and without OLD (n = 26) with a targeted Somascan aptamer-based proteomic approach to quantify individual proteases and assess their correlation with lung function. Endogenous peptidomics mapped peptides to native proteins to identify substrates of protease activity. Using the MEROPS database, we identified candidate proteases linked to peptide generation based on binding site affinities which were assessed via z-scores. We used t-tests to compare average forced expiratory volume in 1 s per predicted value (FEV1pp) between samples with and without detection of each cleaved protein and adjusted for multiple comparisons by controlling the false discovery rate (FDR).FindingsWe identified 101 proteases, of which 95 had functional network associations and 22 correlated with FEV1pp. These included cathepsins, metalloproteinases (MMP), caspases and neutrophil elastase. We discovered 31 proteins subject to proteolytic cleavage that associate with FEV1pp, with the top pathways involved in small ubiquitin-like modifier mediated modification (SUMOylation). Proteases linked to protein cleavage included neutrophil elastase, granzyme, and cathepsin D.InterpretationsIn HIV-associated OLD, a significant number of proteases are up-regulated, many of which are involved in protein degradation. These proteases degrade proteins involved in cell cycle and protein stability, thereby disrupting critical biological functions.

Sex-specific alterations in pulmonary metabolic, xenobiotic and lipid signalling pathways after e-cigarette aerosol exposure during adolescence in mice

BackgroundE-cigarette use is now prevalent among adolescents and young adults, raising concerns over potential adverse long-term health effects. Although it is hypothesised that e-cigarettes promote inflammation, studies have yielded conflicting...

Novel Approach to Exploring Protease Activity and Targets in HIV-associated Obstructive Lung Disease using Combined Proteomic-Peptidomic Analysis.

Obstructive lung disease (OLD) is increasingly prevalent among persons living with HIV (PLWH). However, the role of proteases in HIV-associated OLD remains unclear. We combined proteomics and peptidomics to comprehensively characterize protease activities. We combined mass spectrometry (MS) analysis on bronchoalveolar lavage fluid (BALF) peptides and proteins from PLWH with OLD (n=25) and without OLD (n=26) with a targeted Somascan aptamer-based proteomic approach to quantify individual proteases and assess their correlation with lung function. Endogenous peptidomics mapped peptides to native proteins to identify substrates of protease activity. Using the MEROPS database, we identified candidate proteases linked to peptide generation based on binding site affinities which were assessed via z-scores. We used t-tests to compare average forced expiratory volume in 1 second per predicted value (FEV1pp) between samples with and without detection of each cleaved protein and adjusted for multiple comparisons by controlling the false discovery rate (FDR). We identified 101 proteases, of which 95 had functional network associations and 22 correlated with FEV1pp. These included cathepsins, metalloproteinases (MMP), caspases and neutrophil elastase. We discovered 31 proteins subject to proteolytic cleavage that associate with FEV1pp, with the top pathways involved in small ubiquitin-like modifier mediated modification (SUMOylation). Proteases linked to protein cleavage included neutrophil elastase, granzyme, and cathepsin D. In HIV-associated OLD, a significant number of proteases are up-regulated, many of which are involved in protein degradation. These proteases degrade proteins involved in cell cycle and protein stability, thereby disrupting critical biological functions.

Tissue Factor Maintains Lung Epithelial Barrier Integrity in Acute Lung Injury Through Cell Adhesion

Background. Acute Respiratory Distress Syndrome (ARDS) is a common cause of acute respiratory failure. While loss of lung epithelial barrier integrity is a pathologic mechanism of ARDS, little is known about the factors that regulate epithelial barrier integrity in the lung. Our previously published mouse studies showed that deletion of alveolar type II epithelial cell Tissue Factor (TF) caused impaired lung barrier integrity in models of Acute Lung Injury (ALI). TF is an integral membrane protein that both initiates the extrinsic coagulation cascade and serves several non-coagulant functions. Notably, TF promotes cell adhesion through interactions with cell surface integrin heterodimers, comprised of individual α and β integrin subunits. As such, we hypothesize that epithelial TF is necessary for maintaining lung barrier integrity and that its overexpression is protective in ALI through increased cell adhesion. Methods. To determine whether supraphysiologic overexpression of TF in the lung epithelium can enhance barrier integrity we created a novel transgenic mouse in which TF was inducibly overexpressed in the lung epithelium (TFEpi+) using a CMV-TetO promoter and crossed with SPC-rtTA59 mice. High alveolar epithelial TF expression compared to wild-type littermates (WT) was confirmed through immunohistochemistry and western blot analysis after one week of doxycycline in drinking water. To induce ALI, mice were intranasally infected with 2000 colony forming units of Klebsiella pneumoniae (KP) or PBS control. At 24-hours post infection, mice were euthanized, lung tissue was collected, and a bronchoalveolar lavage (BAL) was performed. BAL protein, clot time, and leukocyte influx were measured. Lung wet-to-dry weight ratios and bacterial burden were measured. To better understand TF regulation of β1 integrin function, TF-knockout A549 cells were created using CRISPR and cultured on specific β1 integrin ligands (Collagen I, IV, Laminin-511, and Fibronectin). On-cell western blots and crystal violet were used to assess cell surface β1 integrin expression and cell adhesion. Results. TFEpi+ mice showed higher lung TF protein expression (median 38031 [IQR 25033, 57948] vs 1801 [IQR 804.3, 2083] expression normalized to total protein; p=0.0016) compared to WT. TFEpi+ mice infected with KP showed lower BAL protein (mean 248.51 [SD 98.03] vs 366.3 [SD 159.8] μg/ml; p=0.0035) and lung wet-to-dry weight ratios (mean 4.27 [SD 0.37] vs 5.29 [SD 0.75]; p=0.0152) compared to WT. Bacterial burden and BAL inflammatory cell counts were higher, while BAL clot time was lower in infected WT mice compared to control. However, these outcomes did not differ between infected TFEpi+ and WT mice. Loss of TF in alveolar epithelial cells reduced cell surface β1 integrin expression and cell adhesion to Laminin-511. Conclusion: Alveolar epithelial TF overexpression is protective for maintaining lung barrier integrity independent of coagulation and inflammation. Further, cell adhesion studies suggest that this is potentially mediated through increased a6β1 epithelial cell adhesion. AHA Postdoctoral Fellowship, National Institute of Health Grants (HL150783, I01BX002288). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Yes-associated Protein Mediates Acute Lung Injury in Adult but not Juvenile Mice

Objective: Adults with The Acute Respiratory Distress Syndrome (ARDS) have worse outcomes than children with Pediatric ARDS. This finding can be reproduced in animal models, suggesting a difference in Acute Lung Injury (ALI) mechanisms. Understanding these mechanistic differences could inform age-specific treatment. Hypothesis: Since Yes-associated protein (YAP) is important for lung development and reactive to mechanical stretch, we hypothesized that YAP is important for ALI mechanisms. Methods: To induce ALI, we intranasally instilled mice with Pseudomonas aeruginosa strain K (2.5 x 105 colony forming units (c.f.u.)) in juvenile (3-week-old) and adult (10-week-old) C57BL/6J mice. 24 h later, we collected bronchoalveolar lavage (BAL) fluid and measured protein, cell count, and c.f.u. To knockdown YAP expression, we injected siRNA 24 h before P. aeruginosa instillation. We removed the lungs and enriched for CD45+ and CD41+ fraction, and CD31+ fraction using Dynabeads sheep anti-rat IgG (Invitrogen). In separate experiments, lungs were separated into nuclear and cytosolic fractions for immunoblot analysis. For immunoprecipitation, the cytosolic fraction was added to beads coated with anti-YAP antibody (rabbit monoclonal). We washed the beads and eluted bound proteins, which were identified by label-free mass spectrometry. Data and results: While both juvenile and adult mice had significantly increased BAL cell counts and protein 24 h after P. aeruginosa instillation, adult mice had significantly greater cell counts and protein than juveniles. BAL c.f.u. were similar in both groups, suggesting equal instillation of P. aeruginosa. P. aeruginosa instillation increased whole lung YAP expression in both cytosolic and nuclear fractions in adult mice by >3-fold, but YAP expression was not increased in P. aeruginosa-treated juvenile mice. YAP protein increases occurred in CD31+ fraction (endothelial cells), but no YAP was quantified in CD45+/CD41+ fraction (leukocytes and platelets). Vascular knockdown of YAP expression by ~75% in adult mice blocked P. aeruginosa-induced BAL cell count increases. Proteomics analysis revealed 62 proteins that had significantly altered YAP binding upon P. aeruginosa treatment (47 with increased YAP binding). The complement factors H and I had a log2-fold-change for YAP binding of 4.56 and 2.26, respectively, upon P. aeruginosa treatment. Conclusions: Adult mice exhibited YAP-dependent Acute Lung Injury; juveniles did not. YAP-dependent mechanisms of injury may be secondary to YAP binding to the complement inhibitory proteins H and I. More work is needed to establish the cell-specificity of YAP-complement factor binding and to determine the location of complement signaling. HL148403, Parker B Francis, and Columbia University Department of Pediatrics Children’s Health Innovation Nucleation Fund to RFH; Ernest E Just Summer Scholarship to AMD. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Circadian disruption dysregulates lung gene expression associated with inflammatory lung injury.

Circadian systems drive the expression of multiple genes in nearly all cells and coordinate cellular-, tissue-, and system-level processes that are critical to innate immunity regulation. We examined the effects of circadian rhythm disorganization, produced by light shift exposure, on innate immunity-mediated inflammatory lung responses including vascular permeability and gene expression in a C57BL/6J murine model of inflammatory lung injury. A total of 32 C57BL/6J mice were assigned to circadian phase shifting (CPS) with intratracheal phosphate-buffered saline (PBS), CPS with intratracheal lipopolysaccharide (LPS), control (normal lighting) condition with intratracheal PBS, and control condition with intratracheal LPS. Bronchoalveolar lavage (BAL) protein, cell counts, tissue immunostaining, and differentially expressed genes (DEGs) were measured in lung tissues at 2 and 10 weeks. In mice exposed to both CPS and intratracheal LPS, both BAL protein and cell counts were increased at both 2 and 10 weeks compared to mice exposed to LPS alone. Multiple DEGs were identified in CPS-LPS-exposed lung tissues compared to LPS alone and were involved in transcriptional pathways associated with circadian rhythm disruption, regulation of lung permeability, inflammation with Rap1 signaling, and regulation of actin cytoskeleton. The most dysregulated pathways included myosin light chain kinase, MAP kinase, profilin 2, fibroblast growth factor receptor, integrin b4, and p21-activated kinase. Circadian rhythm disruption results in exacerbated immune response and dysregulated expression of cytoskeletal genes involved in the regulation of epithelial and vascular barrier integrity-the mechanistic underpinnings of acute lung injury. Further studies need to explore circadian disorganization as a druggable target.

Dimethyl sulfoxide as a novel therapy in a murine model of acute lung injury.

The endothelial glycocalyx on the luminal surface of endothelial cells contributes to the permeability barrier of the pulmonary vasculature. Dimethyl sulfoxide (DMSO) has a disordering effect on plasma membranes, which prevents the formation of ordered membrane domains important in the shedding of the endothelial glycocalyx. We hypothesized that DMSO would protect against protein leak by preserving the endothelial glycocalyx in a murine model of acute respiratory distress syndrome (ARDS). C57BL/6 mice were given ARDS via intratracheally administered lipopolysaccharide (LPS). Dimethyl sulfoxide (220 mg/kg) was administered intravenously for 4 days. Animals were sacrificed postinjury day 4 after bronchoalveolar lavage (BAL). Bronchoalveolar lavage cell counts and protein content were quantified. Lung sections were stained with fluorescein isothiocyanate-labeled wheat germ agglutinin to quantify the endothelial glycocalyx. Human umbilical vein endothelial cells (HUVECs) were exposed to LPS. Endothelial glycocalyx was measured using fluorescein isothiocyanate-labeled wheat germ agglutinin, and co-immunoprecipitation was performed to measure interaction between sheddases and syndecan-1. Dimethyl sulfoxide treatment resulted in greater endothelial glycocalyx staining intensity in the lung when compared with sham (9,641 vs. 36,659 arbitrary units, p < 0.001). Total BAL cell counts were less for animals receiving DMSO (6.93 × 10 6 vs. 2.49 × 10 6 cells, p = 0.04). The treated group had less BAL macrophages (189.2 vs. 76.9 cells, p = 0.02) and lymphocytes (527.7 vs. 200.0 cells, p = 0.02). Interleukin-6 levels were lower in DMSO treated. Animals that received DMSO had less protein leak in BAL (1.48 vs. 1.08 μg/μL, p = 0.02). Dimethyl sulfoxide prevented LPS-induced endothelial glycocalyx loss in HUVECs and reduced the interaction between matrix metalloproteinase 16 and syndecan-1. Systemically administered DMSO protects the endothelial glycocalyx in the pulmonary vasculature, mitigating pulmonary capillary leak after acute lung injury. Dimethyl sulfoxide also results in decreased inflammatory response. Dimethyl sulfoxide reduced the interaction between matrix metalloproteinase 16 and syndecan-1 and prevented LPS-induced glycocalyx damage in HUVECs. Dimethyl sulfoxide may be a novel therapeutic for ARDS.

Levocetrizine attenuates cyclophosphamide-induced lung injury through inhibition of TNF-α, IL-1β, TGF-β and MMP-9

Cyclophosphamide (CP) is an antineoplastic drug commonly used worldwide. Despite its spread, it causes fatal organ toxicity. Lung toxicity is a serious side effect of CP. Actually, in the past three years the world has been facing an un-predicted crisis following COVID-19 pandemic and the associated high-mortality rates attributed to respiratory distress. Accordingly; this study aimed to probe the potential prophylactic role of levocetrizine against CP-induced lung injury. Animals were allocated into three sets; control; CP and CP/Levo. CP was intraperitoneally injected in rats 150 mg/kg once on day 7. Levocetrizine was given orally for 14 days starting 7 days before CP injection. On the last day, all rats were sacrificed and lung tissues were kept for analysis. CP significantly elevated lung/body weight index, inflammatory cell counts, LDH, total protein, TNF-α, IL-1β, TGF-β and histamine levels in bronchoalveolar lavage (BAL). Moreover, it markedly increased expression of MMP-9 and contents of MDA, hydroxyproline, collagen and NOx besides decreasing GSH level and SOD activity in lung tissues. These biochemical results were further confirmed by histopathological examination. In contrast, treatment with levocetrizine significantly attenuated CP-induced pathological alterations. These findings propose that levocetrizine can attenuate CP-induced lung injury via exerting antioxidant, anti-inflammatory and anti-fibrotic effects.

Effective-compound combination of Bufei Yishen formula III combined with ER suppress airway mucus hypersecretion in COPD rats: via EGFR/MAPK signaling.

The aim of this study was to explore the combined efficacy ofeffective-component compatibility of Bufei Yishen formula III (ECC-BYF III) and exercise rehabilitation (ER) in inhibiting airway mucus hypersecretion in a chronic obstructive pulmonary disease (COPD) rat model. A total of 48 SD rats were divided into control, model, acetylcysteine (NAC), ECC-BYF III, ER, and ECC-BYF III + ER groups (n=8). COPD rats were exposed to cigarette smoke and bacteria for 8 weeks and administered various treatments over the next eight weeks. Rats were euthanized at week 17 after pulmonary function testing. Pathological examination of lung tissues was performed. IL-6 and IL-10 levels were measured in bronchoalveolar lavage fluid (BALF) and protein levels of MUC5AC, MUC5B, AQP-5, EGFR, ERK, JNK, and p38 were measured in lung tissues. Improved pulmonary function and pathological changes were observed in ECC-BYF III, ECC-BYF III + ER, and NAC groups. ECC-BYF III and ECC-BYF III + ER had greater mean alveolar number (MAN) compared with NAC. Lung inflammation and goblet cell generation were reduced and MUC5AC, MUC5B and AQP-5 expressions were lower in all treatment groups. ECC-BYF III has more significant effect on MUC5AC than ER and NAC. ECC-BYFIII + ER had a greater effect on suppressing IL-6 in BALF compared with other treatments. ECC-BYFIII, ER, and ECC-BYF III + ER reduced EGFR, ERK, JNK, and p38 phosphorylated protein levels. ECC-BYFIII+ER had a greater effect on p-JNK and p-p38 than ECC-BYFIII and NAC. ECC-BYF III, ER, and ECC-BYF III + ER have efficacy in inhibiting airway mucus hypersecretion with improved pulmonary function and pathological changes. ECC-BYF III had a greater effect in improving MAN and MUC5AC in lung tissue. ECC-BYF III+ER had a greater effect in alleviating pulmonary pathology and inflammation. These effects may be mediated by inhibition of the EGFR/MAPK pathway.

Sphingosine-1-Phosphate Receptor 3 Induces Endothelial Barrier Loss via ADAM10-Mediated Vascular Endothelial-Cadherin Cleavage.

Mechanical ventilation (MV) is a life-supporting strategy employed in the Intensive Care Unit (ICU). However, MV-associated mechanical stress exacerbates existing lung inflammation in ICU patients, resulting in limited improvement in mortality and a condition known as Ventilator-Induced Lung Injury (VILI). Sphingosine-1-phosphate (S1P) is a circulating bioactive lipid that maintains endothelial integrity primarily through S1P receptor 1 (S1PR1). During VILI, mechanical stress upregulates endothelial S1PR3 levels. Unlike S1PR1, S1PR3 mediates endothelial barrier disruption through Rho-dependent pathways. However, the specific impact of elevated S1PR3 on lung endothelial function, apart from Rho activation, remains poorly understood. In this study, we investigated the effects of S1PR3 in endothelial pathobiology during VILI using an S1PR3 overexpression adenovirus. S1PR3 overexpression caused cytoskeleton rearrangement, formation of paracellular gaps, and a modified endothelial response towards S1P. It resulted in a shift from S1PR1-dependent barrier enhancement to S1PR3-dependent barrier disruption. Moreover, S1PR3 overexpression induced an ADAM10-dependent cleavage of Vascular Endothelial (VE)-cadherin, which hindered endothelial barrier recovery. S1PR3-induced cleavage of VE-cadherin was at least partially regulated by S1PR3-mediated NFκB activation. Additionally, we employed an S1PR3 inhibitor TY-52156 in a murine model of VILI. TY-52156 effectively attenuated VILI-induced increases in bronchoalveolar lavage cell counts and protein concentration, suppressed the release of pro-inflammatory cytokines, and inhibited lung inflammation as assessed via a histological evaluation. These findings confirm that mechanical stress associated with VILI increases S1PR3 levels, thereby altering the pulmonary endothelial response towards S1P and impairing barrier recovery. Inhibiting S1PR3 is validated as an effective therapeutic strategy for VILI.

Downregulation of TAZ elicits a mitochondrial redox imbalance and ferroptosis in lung epithelial cells exposed to diesel exhaust particles

Mitochondrial dysfunction was reported to be involved in the development of lung diseases including chronic obstructive pulmonary disease (COPD). However, molecular regulation underlying metabolic disorders in the airway epithelia exposed to air pollution remains unclear. In the present study, lung bronchial epithelial BEAS-2B and alveolar epithelial A549 cells were treated with diesel exhaust particles (DEPs), the primary representative of ambient particle matter. This treatment elicited cell death accompanied by induction of lipid reactive oxygen species (ROS) production and ferroptosis. Lipidomics analyses revealed that DEPs increased glycerophospholipid contents. Accordingly, DEPs upregulated expression of the electron transport chain (ETC) complex and induced mitochondrial ROS production. Mechanistically, DEP exposure downregulated the Hippo transducer transcriptional co-activator with PDZ-binding motif (TAZ), which was further identified to be crucial for the ferroptosis-associated antioxidant system, including glutathione peroxidase 4 (GPX4), the glutamate-cysteine ligase catalytic subunit (GCLC), and glutathione-disulfide reductase (GSR). Moreover, immunohistochemistry confirmed downregulation of GPX4 and upregulation of lipid peroxidation in the bronchial epithelium of COPD patients and Sprague-Dawley rats exposed to air pollution. Finally, proteomics analyses confirmed alterations of ETC-related proteins in bronchoalveolar lavage from COPD patients compared to healthy subjects. Together, our study discovered that involvement of mitochondrial redox dysregulation plays a vital role in pulmonary epithelial cell destruction after exposure to air pollution.

Aging-Related Accumulation of Truncated Oxidized Phospholipids Augments Infectious Lung Injury and Endothelial Dysfunction via Cluster of Differentiation 36-Dependent Mechanism.

Truncated phospholipid oxidation products (Tr-OxPL) increase in blood circulation with aging; however, their role in the severity of vascular dysfunction and bacterial lung injury in aging groups remains poorly understood. We investigated the effects of six Tr-OxPL species: KOdiA-PC, POVPC, PONPC, PGPC, Paz-PC, and Lyso-PC on endothelial dysfunction and lung inflammation caused by heat-killed Staphylococcus aureus (HKSA) in young (aged 2-4 months) and old (aged 12-18 months) mice, organotypic culture of precisely cut lung slices, and endothelial cells (mLEC) isolated from young and old mice. HKSA and Tr-OxPL combination caused a higher degree of vascular leak, the accumulation of inflammatory cells and protein in bronchoalveolar lavage, and inflammatory gene expression in old mice lungs. HKSA caused a greater magnitude of inflammatory gene activation in cell and ex vivo cultures from old mice, which was further augmented by Tr-OxPLs. L37pA peptide targeting CD36 receptor attenuated Tr-OxPL-induced endothelial cell permeability in young and old mLEC and ameliorated KOdiA-PC-induced vascular leak and lung inflammation in vivo. Finally, CD36 knockout mice showed better resistance to KOdiA-PC-induced lung injury in both age groups. These results demonstrate the aging-dependent vulnerability of pulmonary vasculature to elevated Tr-OxPL, which exacerbates bacterial lung injury. CD36 inhibition is a promising therapeutic approach for improving pneumonia outcomes in aging population.

Differential effects of two-hit models of acute and ventilator-induced lung injury on lung structure, function, and inflammation.

Acute respiratory distress syndrome (ARDS) and acute lung injury have a diverse spectrum of causative factors including sepsis, aspiration of gastric contents, and near drowning. Clinical management of severe lung injury typically includes mechanical ventilation to maintain gas exchange which can lead to ventilator-induced lung injury (VILI). The cause of respiratory failure is acknowledged to affect the degree of lung inflammation, changes in lung structure, and the mechanical function of the injured lung. However, these differential effects of injury and the role of etiology in the structure-function relationship are not fully understood. To address this knowledge gap we caused lung injury with intratracheal hydrochloric acid (HCL) or endotoxin (LPS) 2days prior to ventilation or with an injurious lavage (LAV) immediately prior to ventilation. These injury groups were then ventilated with high inspiratory pressures and positive end expiratory pressure (PEEP) = 0cmH2O to cause VILI and model the clinical course of ARDS followed by supportive ventilation. The effects of injury were quantified using invasive lung function measurements recorded during PEEP ladders where the end-expiratory pressure was increased from 0 to 15cm H2O and decreased back to 0cmH2O in steps of 3cmH2O. Design-based stereology was used to quantify the parenchymal structure of lungs air-inflated to 2, 5, and 10cmH2O. Pro-inflammatory gene expression was measured with real-time quantitative polymerase chain reaction and alveolocapillary leak was estimated by measuring bronchoalveolar lavage protein content. The LAV group had small, stiff lungs that were recruitable at higher pressures, but did not demonstrate substantial inflammation. The LPS group showed septal swelling and high pro-inflammatory gene expression that was exacerbated by VILI. Despite widespread alveolar collapse, elastance in LPS was only modestly elevated above healthy mice (CTL) and there was no evidence of recruitability. The HCL group showed increased elastance and some recruitability, although to a lesser degree than LAV. Pro-inflammatory gene expression was elevated, but less than LPS, and the airspace dimensions were reduced. Taken together, those data highlight how different modes of injury, in combination with a 2nd hit of VILI, yield markedly different effects.

Liraglutide pretreatment attenuates sepsis-induced acute lung injury.

There are no effective targeted therapies to treat acute respiratory distress syndrome (ARDS). Recently, the commonly used diabetes and obesity medications, glucagon-like peptide-1 (GLP-1) receptor agonists, have been found to have anti-inflammatory properties. We, therefore, hypothesized that liraglutide pretreatment would attenuate murine sepsis-induced acute lung injury (ALI). We used a two-hit model of ALI (sepsis+hyperoxia). Sepsis was induced by intraperitoneal injection of cecal slurry (CS; 2.4 mg/g) or 5% dextrose (control) followed by hyperoxia [HO; fraction of inspired oxygen ([Formula: see text]) = 0.95] or room air (control; [Formula: see text] = 0.21). Mice were pretreated twice daily with subcutaneous injections of liraglutide (0.1 mg/kg) or saline for 3 days before initiation of CS+HO. At 24-h post CS+HO, physiological dysfunction was measured by weight loss, severity of illness score, and survival. Animals were euthanized, and bronchoalveolar lavage (BAL) fluid, lung, and spleen tissues were collected. Bacterial burden was assessed in the lung and spleen. Lung inflammation was assessed by BAL inflammatory cell numbers, cytokine concentrations, lung tissue myeloperoxidase activity, and cytokine expression. Disruption of the alveolar-capillary barrier was measured by lung wet-to-dry weight ratios, BAL protein, and epithelial injury markers (receptor for advanced glycation end products and sulfated glycosaminoglycans). Histological evidence of lung injury was quantified using a five-point score with four parameters: inflammation, edema, septal thickening, and red blood cells (RBCs) in the alveolar space. Compared with saline treatment, liraglutide improved sepsis-induced physiological dysfunction and reduced lung inflammation, alveolar-capillary barrier disruption, and lung injury. GLP-1 receptor activation may hold promise as a novel treatment strategy for sepsis-induced ARDS. Additional studies are needed to better elucidate its mechanism of action.NEW & NOTEWORTHY In this study, pretreatment with liraglutide, a commonly used diabetes medication and glucagon-like peptide-1 (GLP-1) receptor agonist, attenuated sepsis-induced acute lung injury in a two-hit mouse model (sepsis + hyperoxia). Septic mice who received the drug were less sick, lived longer, and displayed reduced lung inflammation, edema, and injury. These therapeutic effects were not dependent on weight loss. GLP-1 receptor activation may hold promise as a new treatment strategy for sepsis-induced acute respiratory distress syndrome.

Asynchrony Injures Lung and Diaphragm in Acute Respiratory Distress Syndrome.

Patient-ventilator asynchrony is often observed during mechanical ventilation and is associated with higher mortality. We hypothesized that patient-ventilator asynchrony causes lung and diaphragm injury and dysfunction. Prospective randomized animal study. University research laboratory. Eighteen New Zealand White rabbits. Acute respiratory distress syndrome (ARDS) model was established by depleting surfactants. Each group (assist control, breath stacking, and reverse triggering) was simulated by phrenic nerve stimulation. The effects of each group on lung function, lung injury (wet-to-dry lung weight ratio, total protein, and interleukin-6 in bronchoalveolar lavage), diaphragm function (diaphragm force generation curve), and diaphragm injury (cross-sectional area of diaphragm muscle fibers, histology) were measured. Diaphragm RNA sequencing was performed using breath stacking and assist control (n = 2 each). Inspiratory effort generated by phrenic nerve stimulation was small and similar among groups (esophageal pressure swing ≈ -2.5 cm H2O). Breath stacking resulted in the largest tidal volume (>10 mL/kg) and highest inspiratory transpulmonary pressure, leading to worse oxygenation, worse lung compliance, and lung injury. Reverse triggering did not cause lung injury. No asynchrony events were observed in assist control, whereas eccentric contractions occurred in breath stacking and reverse triggering, but more frequently in breath stacking. Breath stacking and reverse triggering significantly reduced diaphragm force generation. Diaphragmatic histology revealed that the area fraction of abnormal muscle was ×2.5 higher in breath stacking (vs assist control) and ×2.1 higher in reverse triggering (vs assist control). Diaphragm RNA sequencing analysis revealed that genes associated with muscle differentiation and contraction were suppressed, whereas cytokine- and chemokine-mediated proinflammatory responses were activated in breath stacking versus assist control. Breath stacking caused lung and diaphragm injury, whereas reverse triggering caused diaphragm injury. Thus, careful monitoring and management of patient-ventilator asynchrony may be important to minimize lung and diaphragm injury from spontaneous breathing in ARDS.

Mitochondria of lung venular capillaries mediate lung-liver cross talk in pneumonia.

Failure of the lung's endothelial barrier underlies lung injury, which causes the high mortality acute respiratory distress syndrome (ARDS). Multiple organ failure predisposes to the mortality, but mechanisms are poorly understood. Here, we show that mitochondrial uncoupling protein 2 (UCP2), a component of the mitochondrial inner membrane, plays a role in the barrier failure. Subsequent lung-liver cross talk mediated by neutrophil activation causes liver congestion. We intranasally instilled lipopolysaccharide (LPS). Then, we viewed the lung endothelium by real-time confocal imaging of the isolated, blood-perfused mouse lung. LPS caused alveolar-capillary transfer of reactive oxygen species and mitochondrial depolarization in lung venular capillaries. The mitochondrial depolarization was inhibited by transfection of alveolar Catalase and vascular knockdown of UCP2. LPS instillation caused lung injury as indicated by increases in bronchoalveolar lavage (BAL) protein content and extravascular lung water. LPS or Pseudomonas aeruginosa instillation also caused liver congestion, quantified by liver hemoglobin and plasma aspartate aminotransferase (AST) increases. Genetic inhibition of vascular UCP2 prevented both lung injury and liver congestion. Antibody-mediated neutrophil depletion blocked the liver responses, but not lung injury. Knockdown of lung vascular UCP2 mitigated P. aeruginosa-induced mortality. Together, these data suggest a mechanism in which bacterial pneumonia induces oxidative signaling to lung venular capillaries, known sites of inflammatory signaling in the lung microvasculature, depolarizing venular mitochondria. Successive activation of neutrophils induces liver congestion. We conclude that oxidant-induced UCP2 expression in lung venular capillaries causes a mechanistic sequence leading to liver congestion and mortality. Lung vascular UCP2 may present a therapeutic target in ARDS.NEW & NOTEWORTHY We report that mitochondrial injury in lung venular capillaries underlies barrier failure in pneumonia, and venular capillary uncoupling protein 2 (UCP2) causes neutrophil-mediated liver congestion. Using in situ imaging, we found that epithelial-endothelial transfer of H2O2 activates UCP2, depolarizing mitochondria in venular capillaries. The conceptual advance from our findings is that mitochondrial depolarization in lung capillaries mediates liver cross talk through circulating neutrophils. Pharmacologic blockade of UCP2 could be a therapeutic strategy for lung injury.

The impact of intravenous dodecafluoropentane on a murine model of acute lung injury

IntroductionIntravenous oxygen therapeutics present an appealing option for improving arterial oxygenation in patients with acute hypoxemic respiratory failure, while limiting iatrogenic injury from conventional respiratory management.MethodsWe used an established two-hit murine model of acute lung injury (ARDS/VILI) to evaluate the effect of intravenous dodecafluoropentane (DDFPe) on oxygen saturation and bronchoalveolar lavage cell counts and protein levels. Twenty hours after challenge with intratracheal lipopolysaccharide, mice were intubated and ventilated with high tidal volumes (4 h) to produce acute lung injury. DDFPe (0.6 mL/kg) or saline was administered by IV bolus injection at the initiation of mechanical ventilation and again at 2 h. Oxygen saturation was measured every 15 min. Bronchoalveolar lavage was performed at the conclusion of the experiment.ResultsThe two-hit ARDS/VILI model produced substantial inflammatory acute lung injury reflected by markedly increased bronchoalveolar lavage (BAL) cell counts compared to BAL cell counts in spontaneous breathing controls (5.29 ± 1.50 × 10–6 vs 0.74 ± 0.014 × 10–6 cells/mL) Similarly, BAL protein levels were markedly elevated in ARDS/VILI-challenged mice compared with spontaneous breathing controls (1109.27 ± 223.80 vs 129.6 ± 9.75 ng/mL). We fit a linear mixed effects model that showed a significant difference in oxygen saturation over time between DDFPe-treated mice and saline-treated mice, with separation starting after the 2-h injection. DDFPe-treated ARDS/VILI-challenged mice also exhibited significant reductions in BAL cell counts but not in BAL protein.ConclusionDDFPe improves oxygen saturation in a murine model of ARDS/VILI injury with the potential for serving as an intravenous oxygen therapeutic.