Pathogenesis of Acute Respiratory Distress Syndrome

NLRP3/GSDMD mediated pyroptosis induces lung inflammation susceptibility in diesel exhaust exposed mouse strains

BACKGROUND

Genetic diversity among species influences the disease severity outcomes linked to air pollution. However, the mechanism responsible for this variability remain elusive and needs further investigation.

OBJECTIVE

To investigate the genetic factors and pathways linked with differential susceptibility in mouse strains associated with diesel exhaust exposure.

METHODS

C57BL/6 and Balb/c mice were exposed to diesel exhaust (DE) for 5 days/week for 30 min/day for 8 weeks. Body weight of mice was recorded every week and airway hyperresponsiveness towards DE exposure was recorded after 24 h of last exposure. Mice were euthanised to collect BALF, blood, lung tissues for immunobiochemical assays, structural integrity and genetic studies.

RESULTS

C57BL/6 mice showed significantly decreased body weight in comparison to Balb/c mice (p < 0.05). Both mouse strains showed lung resistance and damage to elastance upon DE exposure compared to respective controls (p < 0.05) with more pronounced effects in C57BL/6 mice. Lung histology showed increase in bronchiolar infiltration and damage to the wall in C57BL/6 mice (p < 0.05). DE exposure upregulated pro-inflammatory and Th2 cytokine levels in C57BL/6 in comparison to Balb/c mice. C57BL/6 mice showed increase in Caspase-1 and ASC expression confirming activation of downstream pathway. This showed significant activation of inflammasome pathway in C57BL/6 mice with ∼2-fold increase in NLRP3 and elevated IL-1β expression. Gasdermin-D levels were increased in C57BL/6 mice demonstrating induction of pyroptosis that corroborated with IL-1β secretion (p < 0.05). Genetic variability among both species was confirmed with sanger's sequencing suggesting presence of SNPs in 3'UTRs of IL-1β gene influencing expression between mouse strains.

CONCLUSIONS

C57BL/6 mice exhibited increased susceptibility to diesel exhaust in contrast to Balb/c mice via activation of NLRP3-related pyroptosis. Differential susceptibility between strains may be attributed via SNPs in the 3'UTRs of the IL-1β gene.

Inhibiting caspase-3/GSDME-mediated pyroptosis ameliorates septic lung injury in mice model

Acute lung injury is one of the most serious complications of sepsis, which is a common critical illness in clinic. This study aims to investigate the role of caspase-3/ gasdermin-E (GSDME)-mediated pyroptosis in sepsis-induced lung injury in mice model. Cecal ligation (CLP) operation was used to establish mice sepsis-induced lung injury model. Lung coefficient, hematoxylin and eosin staining and transmission electron microscopy were used to observe the lung injury degree. In addition, caspase-3-specific inhibitor Z-DEVD-FMK and GSDME-derived inhibitor AC-DMLD-CMK were used in CLP model, caspase-3 activity, GSDME immunofluorescence, serum lactate dehydrogenase (LDH) and interleukin-6 (IL-6) levels, TUNEL staining, and the expression levels of GSDME related proteins were detected. The mice in CLP group showed the increased expressions of cleaved-caspase-3 and GSDME-N terminal, destruction of lung structure, and the increases of LDH, IL-6, IL-18 and IL-1β levels, which were improved in mice treated with Z-DEVD-FMK or AC-DMLD-CMK. In conclusion, caspase-3/GSDME mediated pyroptosis is involved in the occurrence of sepsis-induced lung injury in mice model, inhibiting caspase-3 or GSDME can both alleviate lung injury.

GDF11 OVEREXPRESSION ALLEVIATES SEPSIS-INDUCED LUNG MICROVASCULAR ENDOTHELIAL BARRIER DAMAGE BY ACTIVATING SIRT1/NOX4 SIGNALING TO INHIBIT FERROPTOSIS

ABSTRACT

Sepsis is a lethal clinical syndrome, and acute lung injury (ALI) is the earliest and most serious complication. We aimed to explore the role of growth differentiation factor 11 (GDF11) in sepsis-induced dysfunction of lung microvascular endothelial barrier in vivo and in vitro to elucidate its potential mechanism related to sirtuin 1 (SIRT1)/NADPH oxidase 4 (NOX4) signaling. Cecal ligation and puncture (CLP)-induced sepsis mice and lipopolysaccharide (LPS)-induced pulmonary microvascular endothelial cells (PMECs) were used in this study. Histopathological changes in lung tissues were tested by hematoxylin-eosin staining. Lung wet-to-dry weight ratio and inflammatory factors contents in bronchoalveolar lavage fluid were assessed. Evens blue index, trans-epithelial electrical resistance, and expression of zona occludens 1 (ZO-1), occludin-1, and claudin-1 were used to evaluate alveolar barrier integrity. Reactive oxygen species, lipid peroxidation, and ferroptosis markers were analyzed. Iron deposition in the lung tissues was assessed using Prussian blue staining. Intracellular Fe 2+ level was detected using FerroOrange staining. Additionally, expression of GDF11, SIRT1, and NOX4 was estimated with western blot. Then, EX527, a SIRT1 inhibitor, was employed to treat GDF11-overexpressed PMECs with LPS stimulation to clarify the regulatory mechanism. Results showed that GDF11 overexpression attenuated sepsis-induced pathological changes and inflammation and maintained alveolar barrier integrity. Moreover, GDF11 overexpression inhibited ferroptosis, upregulated SIRT1 expression and downregulated NOX4 expression. Additionally, EX527 treatment relieved the impacts of GDF11 overexpression on ferroptosis and destruction of integrity of human pulmonary microvascular endothelial cells exposed to LPS. Taken together, GDF11 overexpression could alleviate sepsis-induced lung microvascular endothelial barrier damage by activating SIRT1/NOX4 signaling to inhibit ferroptosis. Our findings potentially provide new molecular target for clinical therapy of ALI.

PAI-1 Deficiency Promotes NET-mediated Pyroptosis and Ferroptosis during Pseudomonas Aeruginosa-induced Acute Lung Injury by Regulating the PI3K/MAPK/AKT Axis

Circulating neutrophil extracellular trap (NET) formation is an adaptive process during acute lung injury (ALI). The important role of plasminogen activator inhibitor (PAI)-1 in NET formation during ALI remains unclear. This research intends to examine the impacts of the decrease in PAI-1 levels on NET formation and the underlying mechanism. We found a relative association between the increase in plasma NET levels and thromboinflammation-induced lung damage in patients with ARDS. PAI-1 knockout (KO) mice exhibited significant increases in Pseudomonas aeruginosa (PAO1 strain)-induced ALI, inflammation, inflammatory cell accumulation, and proinflammatory cytokine secretion, and wild-type mice exhibited the opposite changes. During PAO1-induced ALI, PAI-1 KO increased NET release and the levels of prothrombotic markers in mice. PAI-1 deficiency also promoted NET formation and NET-mediated pyroptosis and ferroptosis by activating the PI3K/MAPK/AKT pathway in a PAO1-induced ALI mouse model. In conclusion, PAI-1 KO exacerbated PAO1-induced pneumonia-associated injury and contributed to NET-mediated pyroptosis and ferroptosis through PI3K/MAPK/AKT pathway activation. Thus, targeting PAI-1 and NETs may be a promising therapeutic approach for ameliorating pneumonia and thromboinflammation-associated ALI.

Foxq1 Promotes Alveolar Epithelial Cell Death through Tle1-mediated Inhibition of the NF-κB Signaling Pathway

Acute lung injury (ALI) is a common respiratory disease characterized by diffuse alveolar injury and interstitial edema, as well as a hyperinflammatory response, lung cell damage, and oxidative stress. Foxq1, a member of the FOX family of transcription factors, is expressed in various tissues, such as the lungs, liver, and kidneys, and contributes to various biological processes, such as stress, metabolism, cell cycle arrest, and aging-related apoptosis. However, the role of Foxq1 in ALI is unknown. We constructed ex vivo and in vivo ALI models by LPS tracheal perfusion of ICR mice and conditioned medium stimulation of injured MLE-12 cells. Foxq1 expression was increased, and its localization was altered, in our ALI model. In normal or injured MLE-12 cells, knockdown of Foxq1 promoted cell survival, and overexpression had the opposite effect. This regulatory effect was likely mediated by Tle1 and the NF-κB/Bcl2/Bax signaling pathway. These data suggest a potential link between Foxq1 and ALI, indicating that Foxq1 can be used as a biomarker for the diagnosis of ALI. Targeted inhibition of Foxq1 expression could promote alveolar epithelial cell survival and may provide a strategy for mitigating ALI.

Sivelestat improves acute lung injury by inhibiting PI3K/AKT/mTOR signaling pathway

OBJECTIVE

To investigate the therapeutic effect and mechanism of sivelestat sodium on acute lung injury (AIL).

METHODS

A rat model for ALI/acute respiratory distress syndrome (ALI/ARDS) was established. Pathological examination of lung tissue was conducted to assess lung injury. Blood gas in the arteries was measured using a blood analyzer. Changes in PaO2, PaO2/FiO2, and lung wet/dry (W/D) weight ratio were carefully compared. ELISA assay was conducted to estimate cell adhesion and inflammation response. Finally, real-time reverse transcription polymerase chain reaction and western blotting assay was used to determine the activation of PI3K/AKT/mTOR pathway.

RESULTS

ARDS in vivo model was successfully constructed by LPS injection. Compared with the sham group, PaO2 and PaO2/FiO2 were significantly lower in the vehicle group, while the lung W/D ratio, the lung injury score, NE, VCAM-1, IL-8 andTNF-αwere significantly increased. After treatment with different doses of sivelestat sodium, we found PaO2, PaO2/FiO2 were prominently increased, while the lung W/D ratio, the lung injury score, NE, VCAM-1, IL-8, TNF-α levels were decreased in the dose-dependent manner. Meanwhile, compared with the vehicle group, the expression levels of Bax, PI3K, Akt and mTOR were significantly lower, and the expression of Bcl-2 was significantly higher after injection with sivelestat sodium.

CONCLUSION

Sivelestat sodium has an interventional effect on ALI in sepsis by inhibiting the PI3K/AKT/mTOR signalling pathway.

Pathophysiology, diagnosis and management of right ventricular failure: A state of the art review of mechanical support devices

The function of the right ventricle (RV) is to drive the forward flow of blood to the pulmonary system for oxygenation before returning to the left ventricle. Due to the thin myocardium of the RV, its function is easily affected by decreased preload, contractile motion abnormalities, or increased afterload. While various etiologies can lead to changes in RV structure and function, sudden changes in RV afterload can cause acute RV failure which is associated with high mortality. Early detection and diagnosis of RV failure is imperative for guiding initial medical management. Echocardiographic findings of reduced tricuspid annular plane systolic excursion (<1.7) and RV wall motion (RV S' <10 cm/s) are quantitatively supportive of RV systolic dysfunction. Medical management commonly involves utilizing diuretics or fluids to optimize RV preload, while correcting the underlying insult to RV function. When medical management alone is insufficient, mechanical circulatory support (MCS) may be necessary. However, the utility of MCS for isolated RV failure remains poorly understood. This review outlines the differences in flow rates, effects on hemodynamics, and advantages/disadvantages of MCS devices such as intra-aortic balloon pump, Impella, centrifugal-flow right ventricular assist devices, extracorporeal membrane oxygenation, and includes a detailed review of the latest clinical trials and studies analyzing the effects of MCS devices in acute RV failure.

Protein interactome analysis of ATP1B1 in alveolar epithelial cells using Co-Immunoprecipitation mass spectrometry and parallel reaction monitoring assay

Aims

Alveolar epithelial barrier integrity is essential for lung homeostasis. Na, K-ATPase β1 subunit (ATP1B1) involves alveolar edema fluid clearance and alveolar epithelial barrier stability. However, the underlying molecular mechanism of ATP1B1 in alveolar epithelial cells still needs to be understood.

Main methods

We utilized Co-Immunoprecipitation mass spectrometry proteomic analysis, protein-protein interaction (PPI) analysis, enrichment analysis, and parallel reaction monitoring (PRM) analysis to investigate proteins interacting with ATP1B1 in A549 cells.

Key findings

A total of 159 proteins were identified as significant proteins interacting with ATP1B1 in A549 cells. Ribosomal and heat shock proteins were major constituents of the two main functional modules based on the PPI network. Enrichment analysis showed that significant proteins were involved in protein translation, posttranslational processing, and function regulation. Moreover, 10 proteins of interest were verified by PRM, and fold changes in 6 proteins were consistent with proteomics results. Finally, HSP90AB1, EIF4A1, TUBB4B, HSPA8, STAT1, and PLEC were considered candidates for binding to ATP1B1 to function in alveolar epithelial cells.

Significance

Our study provides new insights into the role of ATP1B1 in alveolar epithelial cells and indicates that six proteins, in particular HSP90AB1, may be key proteins interacting with and regulating ATP1B1, which might be potential targets for the treatment of acute respiratory distress syndrome.

Lethal Gram-negative sepsis in healthy pigs during anaesthesia with contaminated propofol

Two healthy Landrace pigs anaesthetized with propofol suffered rapid onset of fatal sepsis. Clinical signs included severe arterial hypotension, loss of peripheral oxygenation, low end-tidal CO2, clinical onset of pulmonary oedema and cardiac dysfunction. Gross and histopathological examination revealed loss of vascular integrity with severe lung oedema and congestion, haemorrhages in several organs and fluid leakage into body cavities. Large numbers of Gram-negative bacteria, primarily Klebsiella sp., were present in the anaesthetic infusion containing propofol and were also cultured from internal organs of both pigs. The propofol was likely contaminated by bacteria after inappropriate handling and storage in the operating room. This report illustrates the potential for severe nosocomial infection when applying propofol in animals and humans and may serve as a reminder of the importance of strict aseptic practice in general, and specifically in the handling of this anaesthetic agent.

The Synthetic Surfactant CHF5633 Restores Lung Function and Lung Architecture in Severe Acute Respiratory Distress Syndrome in Adult Rabbits

PURPOSE

Acute respiratory distress syndrome (ARDS) is a major cause of hypoxemic respiratory failure in adults. In ARDS extensive inflammation and leakage of fluid into the alveoli lead to dysregulation of pulmonary surfactant metabolism and function. Altered surfactant synthesis, secretion, and breakdown contribute to the clinical features of decreased lung compliance and alveolar collapse. Lung function in ARDS could potentially be restored with surfactant replacement therapy, and synthetic surfactants with modified peptide analogues may better withstand inactivation in ARDS alveoli than natural surfactants.

METHODS

This study aimed to investigate the activity in vitro and the bolus effect (200 mg phospholipids/kg) of synthetic surfactant CHF5633 with analogues of SP-B and SP-C, or natural surfactant Poractant alfa (Curosurf®, both preparations Chiesi Farmaceutici S.p.A.) in a severe ARDS model (the ratio of partial pressure arterial oxygen and fraction of inspired oxygen, P/F ratio ≤ 13.3 kPa) induced by hydrochloric acid instillation followed by injurious ventilation in adult New Zealand rabbits. The animals were ventilated for 4 h after surfactant treatment and the respiratory parameters, histological appearance of lung parenchyma and levels of inflammation, oxidative stress, surfactant dysfunction, and endothelial damage were evaluated.

RESULTS

Both surfactant preparations yielded comparable improvements in lung function parameters, reductions in lung injury score, pro-inflammatory cytokines levels, and lung edema formation compared to untreated controls.

CONCLUSIONS

This study indicates that surfactant replacement therapy with CHF5633 improves lung function and lung architecture, and attenuates inflammation in severe ARDS in adult rabbits similarly to Poractant alfa. Clinical trials have so far not yielded conclusive results, but exogenous surfactant may be a valid supportive treatment for patients with ARDS given its anti-inflammatory and lung-protective effects.

Recent progress in mesenchymal stem cell-based therapy for acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening diseases in critically ill patients. Although pathophysiology of ALI/ARDS has been investigated in many studies, effective therapeutic strategies are still limited. Mesenchymal stem cell (MSC)-based therapy is emerging as a promising therapeutic intervention for patients with ALI. During the last two decades, researchers have focused on the efficacy and mechanism of MSC application in ALI animal models. MSC derived from variant resources exhibited therapeutic effects in preclinical studies of ALI with different mechanisms. Based on this, clinical studies on MSC treatment in ALI/ARDS has been tried recently, especially in COVID-19 caused lung injury. Emerging clinical trials of MSCs in treating COVID-19-related conditions have been registered in past two years. The advantages and potential of MSCs in the defense against COVID-19-related ALI or ARDS have been confirmed. This review provides a brief overview of recent research progress in MSC-based therapies in preclinical study and clinical trials in ALI treatment, as well as the underlying mechanisms.

Integrated mRNA-miRNA transcriptome profiling of blood immune responses potentially related to pulmonary fibrosis in forest musk deer

Background

Forest musk deer (FMD, Moschus Berezovskii) is a critically endangered species world-widely, the death of which can be caused by pulmonary disease in the farm. Pulmonary fibrosis (PF) was a huge threat to the health and survival of captive FMD. MicroRNAs (miRNAs) and messenger RNAs (mRNAs) have been involved in the regulation of immune genes and disease development. However, the regulatory profiles of mRNAs and miRNAs involved in immune regulation of FMD are unclear.

Methods

In this study, mRNA-seq and miRNA-seq in blood were performed to constructed coexpression regulatory networks between PF and healthy groups of FMD. The hub immune- and apoptosis-related genes in the PF blood of FMD were explored through Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Further, protein-protein interaction (PPI) network of immune-associated and apoptosis-associated key signaling pathways were constructed based on mRNA-miRNA in the PF blood of the FMD. Immune hub DEGs and immune hub DEmiRNAs were selected for experimental verification using RT-qPCR.

Results

A total of 2744 differentially expressed genes (DEGs) and 356 differentially expressed miRNAs (DEmiRNAs) were identified in the PF blood group compared to the healthy blood group. Among them, 42 DEmiRNAs were negatively correlated with 20 immune DEGs from a total of 57 correlations. The DEGs were significantly associated with pathways related to CD molecules, immune disease, immune system, cytokine receptors, T cell receptor signaling pathway, Th1 and Th2 cell differentiation, cytokine-cytokine receptor interaction, intestinal immune network for IgA production, and NOD-like receptor signaling pathway. There were 240 immune-related DEGs, in which 186 immune-related DEGs were up-regulated and 54 immune-related DEGs were down-regulated. In the protein-protein interaction (PPI) analysis of immune-related signaling pathway, TYK2, TLR2, TLR4, IL18, CSF1, CXCL13, LCK, ITGB2, PIK3CB, HCK, CD40, CD86, CCL3, CCR7, IL2RA, TLR3, and IL4R were identified as the hub immune genes. The mRNA-miRNA coregulation analysis showed that let-7d, miR-324-3p, miR-760, miR-185, miR-149, miR-149-5p, and miR-1842-5p are key miRNAs that target DEGs involved in immune disease, immune system and immunoregulation.

Conclusion

The development and occurrence of PF were significantly influenced by the immune-related and apoptosis-related genes present in PF blood. mRNAs and miRNAs associated with the development and occurrence of PF in the FMD.

RIP1 kinase inactivation protects against LPS-induced acute respiratory distress syndrome in mice

Acute respiratory distress syndrome (ARDS) is characterized by lung tissue oedema and inflammatory cell infiltration, with limited therapeutic interventions available. Receptor-interacting protein kinase 1 (RIPK1), a critical regulator of cell death and inflammation implicated in many diseases, is not fully understood in the context of ARDS. In this study, we employed RIP1 kinase-inactivated (Rip1K45A/K45A) mice and two distinct RIPK1 inhibitors to investigate the contributions of RIP1 kinase activity in lipopolysaccharide (LPS)-induced ARDS pathology. Our results indicated that RIPK1 kinase inactivation, achieved through both genetic and chemical approaches, significantly attenuated LPS-induced ARDS pathology, as demonstrated by reduced polymorphonuclear neutrophil percentage (PMN%) in alveolar lavage fluid, expression of inflammatory and fibrosis-related factors in lung tissues, as well as histological examination. Results by tunnel staining and qRT-PCR analysis indicated that RIPK1 kinase activity played a role in regulating cell apoptosis and inflammation induced by LPS administration in lung tissue. In summary, employing both pharmacological and genetic approaches, this study demonstrated that targeted RIPK1 kinase inactivation attenuates the pathological phenotype induced by LPS inhalation in an ARDS mouse model. This study enhances our understanding of the therapeutic potential of RIPK1 kinase modulation in ARDS, providing insights for the pathogenesis of ARDS.

Homeobox B4 optimizes the therapeutic effect of bone marrow mesenchymal stem cells on endotoxin-associated acute lung injury in rats

BACKGROUND

Alveolar capillary endothelial cell (EC) injury has a pivotal role in driving acute respiratory distress syndrome (ARDS) progression and maintaining endothelial homeostasis. A previous ex vivo study revealed that overexpression of homeobox B4 (HOXB4) in bone marrow mesenchymal stem cells (BMSCs) enhanced protection against lipopolysaccharide (LPS)-induced EC injury by activating the Wnt/β-catenin pathway. This in vivo study was performed to verify whether BMSCs overexpressing HOXB4 exert similar protective effects on LPS-induced acute lung injury (ALI) in an animal model.

METHODS

The ALI rat model was established by intraperitoneal injection of LPS. Wildtype BMSCs or BMSCs overexpressing HOXB4 were then injected via the tail vein. The lung characteristics of rats were visualized by computed tomography. Lung histopathological characteristics and collagen deposition were assessed by hematoxylin-eosin and Masson's staining, respectively, which were combined with the lung wet/dry ratio and proinflammatory factor levels in bronchoalveolar lavage fluid to further evaluate therapeutic effects. Expression of β-catenin and VE-cadherin was assessed by western blotting and immunofluorescence.

RESULTS

Compared with wildtype BMSCs, overexpression of HOXB4 optimized the therapeutic effects of BMSCs, which manifested as improvements in lung exudation and histopathological features, reduced lung collagen deposition, amelioration of lung permeability, attenuation of lung inflammation, and enhanced expression of β-catenin and VE-cadherin proteins.

CONCLUSIONS

HOXB4-overexpressing BMSCs optimized the protective effect against LPS-induced ALI by partially activating Wnt/β-catenin signaling.

Bronchoalveolar Lavage and Oleic Acid Two-hit Model for Inducing Acute Respiratory Distress Syndrome in Swine Models

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is a widespread and often fatal clinical syndrome marked by the acute onset of pulmonary edema and inflammatory-mediated disruptions in alveolar-capillary permeability resulting in impaired gas exchange and tissue oxygenation with subsequent acute respiratory failure that accounts for 10.4% of all intensive care unit admissions worldwide and boasts a mortality rate of 38.5%. The current treatment for ARDS remains largely supportive. This is largely because of the many challenges of achieving a stable and sustainable animal model that recreates the pathophysiology of ARDS experimentally in a controlled setting to allow research to elucidate potential treatments of ARDS moving forward.

MATERIALS AND METHODS

The bronchoalveolar lavage and oleic acid models are currently the 2 most frequently used experimental models in inducing ARDS in animal models. This study demonstrated that combining them into a "two-hit model" can produce sustained ARDS in swine models per the Horowitz index (PaO2/FiO2 ratio of ≤300 mmHg). Additionally, expected changes in pH, pCO2, lung compliance, cytokines, and tissue histopathology were observed and add to our confidence and reliability that the "two-hit model" produces symptomatic ARDS in a manner very similar to that observed in humans.

RESULTS AND CONCLUSIONS

In conclusion, we demonstrated a viable animal model of human ARDS that is maintained for a prolonged period, suitable for continuous monitoring of the progression, and evaluation of potential future treatments and procedures to reduce patient morbidity and mortality. To carry out this two-hit model, lung injury was induced through a combination of bronchoalveolar lavage and oleic acid administration and the disease process of ARDS is subsequently tracked through clinically relevant parameters such as respiratory mechanics, cytokine response, aretrial blood gas (ABG) changes, and observation of postmortem histopathologic changes. This promising new model has the capacity to successfully replicate human ARDS which is a well-known and notoriously multifactorial pathogenic process to reproduce experimentally for an extended period of time. The "two-hit model" is a viable and appropriate model for the research of novel treatments for ARDS.

The calcineurin-NFATc pathway modulates the lipid mediators in BAL fluid extracellular vesicles, thereby regulating microvascular endothelial cell barrier function

Extracellular vesicles mediate intercellular communication by transporting biologically active macromolecules. Our prior studies have demonstrated that the nuclear factor of activated T cell cytoplasmic member 3 (NFATc3) is activated in mouse pulmonary macrophages in response to lipopolysaccharide (LPS). Inhibition of NFATc3 activation by a novel cell-permeable calcineurin peptide inhibitor CNI103 mitigated the development of acute lung injury (ALI) in LPS-treated mice. Although pro-inflammatory lipid mediators are known contributors to lung inflammation and injury, it remains unclear whether the calcineurin-NFATc pathway regulates extracellular vesicle (EV) lipid content and if this content contributes to ALI pathogenesis. In this study, EVs from mouse bronchoalveolar lavage fluid (BALF) were analyzed for their lipid mediators by liquid chromatography in conjunction with mass spectrometry (LC-MS/MS). Our data demonstrate that EVs from LPS-treated mice contained significantly higher levels of arachidonic acid (AA) metabolites, which were found in low levels by prior treatment with CNI103. The catalytic activity of lung tissue cytoplasmic phospholipase A2 (cPLA2) increased during ALI, correlating with an increased amount of arachidonic acid (AA) in the EVs. Furthermore, ALI is associated with increased expression of cPLA2, cyclooxygenase 2 (COX2), and lipoxygenases (5-LOX, 12-LOX, and 15-LOX) in lung tissue, and pretreatment with CNI103 inhibited the catalytic activity of cPLA2 and the expression of cPLA2, COX, and LOX transcripts. Furthermore, co-culture of mouse pulmonary microvascular endothelial cell (PMVEC) monolayer and NFAT-luciferase reporter macrophages with BALF EVs from LPS-treated mice increased the pulmonary microvascular endothelial cell (PMVEC) monolayer barrier permeability and luciferase activity in macrophages. However, EVs from CNI103-treated mice had no negative impact on PMVEC monolayer barrier integrity. In summary, BALF EVs from LPS-treated mice carry biologically active NFATc-dependent, AA-derived lipids that play a role in regulating PMVEC monolayer barrier function.

HYDROGEN PREVENTS LIPOPOLYSACCHARIDE-INDUCED PULMONARY MICROVASCULAR ENDOTHELIAL CELL INJURY BY INHIBITING STORE-OPERATED Ca 2+ ENTRY REGULATED BY STIM1/ORAI1

ABSTRACT

Background: Sepsis is a type of life-threatening organ dysfunction that is caused by a dysregulated host response to infection. The lung is the most vulnerable target organ under septic conditions. Pulmonary microvascular endothelial cells (PMVECs) play a critical role in acute lung injury (ALI) caused by severe sepsis. The impairment of PMVECs during sepsis is a complex regulatory process involving multiple mechanisms, in which the imbalance of calcium (Ca 2+ ) homeostasis of endothelial cells is a key factor in its functional impairment. Our preliminary results indicated that hydrogen gas (H 2 ) treatment significantly alleviates lung injury in sepsis, protects PMVECs from hyperpermeability, and decreases the expression of plasma membrane stromal interaction molecule 1 (STIM1), but the underlying mechanism by which H 2 maintains Ca 2+ homeostasis in endothelial cells in septic models remains unclear. Thus, the purpose of the present study was to investigate the molecular mechanism of STIM1 and Ca 2+ release-activated Ca 2+ channel protein1 (Orai1) regulation by H 2 treatment and explore the effect of H 2 treatment on Ca 2+ homeostasis in lipopolysaccharide (LPS)-induced PMVECs and LPS-challenged mice. Methods: We observed the role of H 2 on LPS-induced ALI of mice in vivo . The lung wet/dry weight ratio, total protein in the bronchoalveolar lavage fluid, and Evans blue dye assay were used to evaluate the pulmonary endothelial barrier damage of LPS-challenged mice. The expression of STIM1 and Orai1 was also detected using epifluorescence microscopy. Moreover, we also investigated the role of H 2 -rich medium in regulating PMVECs under LPS treatment, which induced injury similar to sepsis in vitro . The expression of STIM1 and Orai1 as well as the Ca 2+ concentration in PMVECs was examined. Results:In vivo , we found that H 2 alleviated ALI of mice through decreasing lung wet/dry weight ratio, total protein in the bronchoalveolar lavage fluid and permeability of lung. In addition, H 2 also decreased the expression of STIM1 and Orai1 in pulmonary microvascular endothelium. In vitro , LPS treatment increased the expression levels of STIM1 and Orai1 in PMVECs, while H 2 reversed these changes. Furthermore, H 2 ameliorated Ca 2+ influx under sepsis-mimicking conditions. Treatment with the sarco/endoplasmic reticulum Ca 2+ adenosine triphosphatase inhibitor, thapsigargin, resulted in a significant reduction in cell viability as well as a reduction in the expression of junctional proteins, including vascular endothelial-cadherin and occludin. Treatment with the store-operated Ca 2+ entry inhibitor, YM-58483 (BTP2), increased the cell viability and expression of junctional proteins. Conclusions: The present study suggested that H 2 treatment alleviates LPS-induced PMVEC dysfunction by inhibiting store-operated Ca 2+ entry mediated by STIM1 and Orai1 in vitro and in vivo .

Differential changes in expression of inflammatory mRNA and protein after oleic acid-induced acute lung injury

Background: Acute Respiratory Distress syndrome (ARDS) is a clinical syndrome of noncardiac pulmonary edema and inflammation leading to acute respiratory failure. We used the oleic acid infusion pig model of ARDS resembling human disease to explore cytokine changes in white blood cells (WBC) and plasma proteins, comparing baseline to ARDS values. Methods: Nineteen juvenile female swine were included in the study. ARDS defined by a PaO2/FiO2 ratio < 300 was induced by continuous oleic acid infusion. Arterial blood was drawn before and during oleic acid infusion, and when ARDS was established. Cytokine expression in WBC was analyzed by RT-qPCR and plasma protein expression by ELISA. Results: The median concentration of IFN-γ mRNA was estimated to be 59% (p = 0.006) and of IL-6 to be 44.4% (p = 0.003) of the baseline amount. No significant changes were detected for TNF-α, IL-17, and IL-10 mRNA expression. In contrast, the concentrations of plasma IFN-γ and IL-6 were significantly higher (p = 0.004 and p = 0.048 resp.), and TNF-α was significantly lower (p = 0.006) at ARDS compared to baseline. Conclusions: The change of proinflammatory cytokines IFN-γ and IL-6 expression is different comparing mRNA and plasma proteins at oleic acid-induced ARDS compared to baseline. The migration of cells to the lung may be the cause for this discrepancy.

Preventive Effect of the Total Polyphenols from Nymphaea candida on Sepsis-Induced Acute Lung Injury in Mice via Gut Microbiota and NLRP3, TLR-4/NF-κB Pathway

This study aimed to investigate the preventive effects of the total polyphenols from Nymphaea candida (NCTP) on LPS-induced septic acute lung injury (ALI) in mice and its mechanisms. NCTP could significantly ameliorate LPS-induced lung tissue pathological injury in mice as well as lung wet/dry ratio and MPO activities (p < 0.05). NCTP could significantly decrease the blood leukocyte, neutrophil, monocyte, basophil, and eosinophil amounts and LPS contents in ALI mice compared with the model group (p < 0.05), improving lymphocyte amounts (p < 0.05). Moreover, compared with the model group, NCTP could decrease lung tissue TNF-α, IL-6, and IL-1β levels (p < 0.05) and downregulate the protein expression of TLR4, MyD88, TRAF6, IKKβ, IκB-α, p-IκB-α, NF-κB p65, p-NF-κB p65, NLRP3, ASC, and Caspase1 in lung tissues (p < 0.05). Furthermore, NCTP could inhibit ileum histopathological injuries, restoring the ileum tight junctions by increasing the expression of ZO-1 and occludin. Simultaneously, NCTP could reverse the gut microbiota disorder, restore the diversity of gut microbiota, increase the relative abundance of Clostridiales and Lachnospiraceae, and enhance the content of SCFAs (acetic acid, propionic acid, and butyric acid) in feces. These results suggested that NCTP has preventive effects on septic ALI, and its mechanism is related to the regulation of gut microbiota, SCFA metabolism, and the TLR-4/NF-κB and NLRP3 pathways.

Pharmacologic Treatments in Acute Respiratory Failure

Acute respiratory failure relies on supportive care using non-invasive and invasive oxygen and ventilatory support. Pharmacologic therapies for the most severe form of respiratory failure, acute respiratory distress syndrome (ARDS), are limited. This review focuses on the most promising therapies for ARDS, targeting different mechanisms that contribute to dysregulated inflammation and resultant hypoxemia. Significant heterogeneity exists within the ARDS population. Treatment requires prompt recognition of ARDS and an understanding of which patients may benefit most from specific pharmacologic interventions. The key to finding effective pharmacotherapies for ARDS may rely on deeper understanding of pathophysiology and bedside identification of ARDS subphenotypes.

Fluid Management in Acute Respiratory Failure

Fluid management in acute respiratory failure is an area of uncertainty requiring a delicate balance of resuscitation and fluid removal to manage hypoperfusion and avoidance of hypoxemia. Overall, a restrictive fluid strategy (minimizing fluid administration) and careful attention to overall fluid balance may be beneficial after initial resuscitation and does not have major side effects. Further studies are needed to improve our understanding of patients who will benefit from a restrictive or liberal fluid management strategy.

Lung endothelium, tau, and amyloids in health and disease

Lung endothelia in the arteries, capillaries, and veins are heterogeneous in structure and function. Lung capillaries in particular represent a unique vascular niche, with a thin yet highly restrictive alveolar-capillary barrier that optimizes gas exchange. Capillary endothelium surveys the blood while simultaneously interpreting cues initiated within the alveolus and communicated via immediately adjacent type I and type II epithelial cells, fibroblasts, and pericytes. This cell-cell communication is necessary to coordinate the immune response to lower respiratory tract infection. Recent discoveries identify an important role for the microtubule-associated protein tau that is expressed in lung capillary endothelia in the host-pathogen interaction. This endothelial tau stabilizes microtubules necessary for barrier integrity, yet infection drives production of cytotoxic tau variants that are released into the airways and circulation, where they contribute to end-organ dysfunction. Similarly, beta-amyloid is produced during infection. Beta-amyloid has antimicrobial activity, but during infection it can acquire cytotoxic activity that is deleterious to the host. The production and function of these cytotoxic tau and amyloid variants are the subject of this review. Lung-derived cytotoxic tau and amyloid variants are a recently discovered mechanism of end-organ dysfunction, including neurocognitive dysfunction, during and in the aftermath of infection.

Exploring the ferroptosis-related gene lipocalin 2 as a potential biomarker for sepsis-induced acute respiratory distress syndrome based on machine learning

BACKGROUND

Sepsis is a major cause of mortality in patients, and ARDS is one of the most common outcomes. The pathophysiology of acute respiratory distress syndrome (ARDS) caused by sepsis is significantly impacted by genes related to ferroptosis.

METHODS

In this study, Weighted gene co-expression network analysis (WGCNA), protein-protein interaction (PPI) networks, functional enrichment analysis, and machine learning were employed to identify characterized genes and to construct receiver operating characteristic (ROC) curves. Additionally, DNA methylation levels were quantified and single-cell analysis was conducted. To validate the alterations in the expression of Lipocalin-2 (LCN2) and ferroptosis-related proteins in the in vitro model, Western blotting was carried out, and the changes in intracellular ROS and Fe2+ levels were detected.

RESULTS

A combination of eight machine learning algorithms, including RFE, LASSO, RandomForest, SVM-RFE, GBDT, Bagging, XGBoost, and Boruta, were used with a machine learning model to highlight the significance of LCN2 as a key gene in sepsis-induced ARDS. Analysis of immune cell infiltration showed a positive correlation between neutrophils and LCN2. In a cell model induced by LPS, it was found that Ferrostatin-1 (Fer-1), a ferroptosis inhibitor, was able to reverse the expression of LCN2. Knocking down LCN2 in BEAS-2B cells reversed the LPS-induced lipid peroxidation, Fe2+ levels, ACSL4, and GPX4 levels, indicating that LCN2, a ferroptosis-related gene (FRG), plays a crucial role in mediating ferroptosis.

CONCLUSION

Upon establishing an FRG model for individuals with sepsis-induced ARDS, we determined that LCN2 could be a dependable marker for predicting survival in these patients. This finding provides a basis for more accurate ARDS diagnosis and the exploration of innovative treatment options.

Immunomodulatory Effects of Fluoroquinolones in Community-Acquired Pneumonia-Associated Acute Respiratory Distress Syndrome

Community-acquired pneumonia is reported as one of the infectious diseases that leads to the development of acute respiratory distress syndrome. The innate immune system is the first line of defence against microbial invasion; however, its dysregulation during infection, resulting in an increased pathogen load, stimulates the over-secretion of chemokines and pro-inflammatory cytokines. This phenomenon causes damage to the epithelial-endothelial barrier of the pulmonary alveoli and the leakage of the intravascular protein into the alveolar lumen. Fluoroquinolones are synthetic antimicrobial agents with immunomodulatory properties that can inhibit bacterial proliferation as well as exhibit anti-inflammatory activities. It has been demonstrated that the structure of fluoroquinolones, particularly those with a cyclopropyl group, exerts immunomodulatory effects. Its capability to inhibit phosphodiesterase activity leads to the accumulation of intracellular cAMP, which subsequently enhances PKA activity, resulting in the inhibition of transcriptional factor NF-κB and the activation of CREB. Another mechanism reported is the inhibition of TLR and ERK signalling pathways. Although the sequence of events has not been completely understood, significant progress has been made in comprehending the specific mechanisms underlying the immunomodulatory effects of fluoroquinolones. Here, we review the indirect immunomodulatory effects of FQs as an alternative to empirical therapy in patients diagnosed with community-acquired pneumonia.

Advances of presepsin in sepsis-associated ARDS

This article reviews the correlation between presepsin and sepsis and the resulting acute respiratory distress syndrome (ARDS). ARDS is a severe complication of sepsis. Despite the successful application of protective mechanical ventilation, restrictive fluid therapy, and neuromuscular blockade, which have effectively reduced the morbidity and mortality associated with ARDS, the mortality rate among patients with sepsis-associated ARDS remains notably high. The challenge lies in the prediction of ARDS onset and the timely implementation of intervention strategies. Recent studies have demonstrated significant variations in presepsin (PSEP) levels between patients with sepsis and those without, particularly in the context of ARDS. Moreover, these studies have revealed substantially elevated PSEP levels in patients with sepsis-associated ARDS compared to those with nonsepsis-associated ARDS. Consequently, PSEP emerges as a valuable biomarker for identifying patients with an increased risk of sepsis-associated ARDS and to predict in-hospital mortality.

GTS-21 attenuates ACE/ACE2 ratio and glycocalyx shedding in lipopolysaccharide-induced acute lung injury by targeting macrophage polarization derived ADAM-17

Acute lung injury (ALI) has received considerable attention in intensive care owing to its high mortality rate. It has been demonstrated that the selective alpha7 nicotinic acetylcholine receptor agonist Gainesville Tokushima scientists (GTS)-21 is promising for treating ALI caused by lipopolysaccharides (LPS). However, the precise underlying mechanism remains unknown. This study aimed to investigate the potential efficacy of GTS-21 in the treatment of ALI. We developed mouse models of ALI and alveolar epithelial type II cells (AT2s) injury following treatment with LPS and different polarized macrophage supernatants, respectively. Pathological changes, pulmonary edema, and lung compliance were assessed. Inflammatory cells count, protein content, and pro-inflammatory cytokine levels were analysed in the bronchoalveolar lavage fluid. The expression of angiotensin-converting enzyme (ACE), ACE2, syndecan-1 (SDC-1), heparan sulphate (HS), heparanase (HPA), exostosin (EXT)-1, and NF-κB were tested in lung tissues and cells. GTS-21-induced changes in macrophage polarization were verified in vivo and in vitro. Polarized macrophage supernatants with or without recombination a disintegrin and metalloproteinase-17 (ADAM-17) and small interfering (si)RNA ADAM-17 were used to verify the role of ADAM-17 in AT2 injury. By reducing pathological alterations, lung permeability, inflammatory response, ACE/ACE2 ratio, and glycocalyx shedding, as well as by downregulating the HPA and NF-κB pathways and upregulating EXT1 expression in vivo, GTS-21 significantly diminished LPS-induced ALI compared to that of the LPS group. GTS-21 significantly attenuated macrophage M1 polarization and augmented M2 polarization in vitro and in vivo. The destructive effects of M1 polarization supernatant can be inhibited by GTS-21 and siRNA ADAM-17. GTS-21 exerted a protective effect against LPS-induced ALI, which was reversed by recombinant ADAM-17. Collectively, GTS-21 alleviates LPS-induced ALI by attenuating AT2s ACE/ACE2 ratio and glycocalyx shedding through the inhibition of macrophage M1 polarization derived ADAM-17.

Development of an Intelligent Reactive Oxygen Species-Responsive Dual-Drug Delivery Nanoplatform for Enhanced Precise Therapy of Acute Lung Injury

Introduction

Acute lung injury (ALI) and its most severe form acute respiratory distress syndrome (ARDS) are commonly occurring devastating conditions that seriously threaten the respiratory system in critically ill patients. The current treatments improve oxygenation in patients with ALI/ARDS in the short term, but do not relieve the clinical mortality of patients with ARDS.

Purpose

To develop the novel drug delivery systems that can enhance the therapeutic efficacy of ALI/ARDS and impede adverse effects of drugs.

Methods

Based on the key pathophysiological process of ARDS that is the disruption of the pulmonary endothelial barrier, bilirubin (Br) and atorvastatin (As) were encapsulated into an intelligent reactive oxygen species (ROS)-responsive nanocarrier DSPE-TK-PEG (DPTP) to form nanoparticles (BA@DPTP) in which the thioketal bonds could be triggered by high ROS levels in the ALI tissues.

Results

BA@DPTP could accumulate in inflammatory pulmonary sites through passive targeting strategy and intelligently release Br and As only in the inflammatory tissue via ROS-responsive bond, thereby enhancing the drugs effectiveness and markedly reducing side effects. BA@DPTP effectively inhibited NF-κB signaling and NLRP3/caspase-1/GSDMD-dependent pyroptosis in mouse pulmonary microvascular endothelial cells. BA@DPTP not only protected mice with lipopolysaccharide-induced ALI and retained the integrity of the pulmonary structure, but also reduced ALI-related mortality.

Conclusion

This study combined existing drugs with nano-targeting strategies to develop a novel drug-targeting platform for the efficient treatment of ALI/ARDS.

Micromorphological features and interleukin 6, 8, and 18 expressions in post-mortem lung tissue in cases with acute respiratory distress syndrome

The purpose of this study was to analyze the presence of interleukins 6, 8, and 18 in post-mortem lung tissue of subjects deceased due to polytrauma. In addition to this, we have described different micromorphological features of lung tissue in ARDS cases associated with fatal traffic trauma. A total of 18 autopsy cases with ARDS after polytrauma and 15 control autopsy cases were analyzed in this study. From every subject, we collected one sample for each lung lobe. All of the histological sections were analyzed by using light microscopy, and for the purpose of ultrastructural analysis, we used transmission electron microscopy. Representative sections were further processed by way of immunohistochemistry analysis. Quantification of IL-6, IL-8, and IL-18-positive cells was conducted by applying the IHC score. We noticed that all samples of ARDS cases exhibited elements of the proliferative phase. Immunohistochemical analysis of lung tissue in patients with ARDS showed strong positive staining for IL-6 (2.8 ± 0.7), IL-8 (2.2 ± 1.3), and IL-18 (2.7 ± 1.2), while staining of the control samples resulted in no positivity to low/moderate positivity (for IL-6 1.4 ± 0.5; for IL-8 0.1 ± 0.4; for IL-18 0.6 ± 0.9). Only IL-6 correlated negatively with the patients' age (r =  -0.6805, p < 0.01). In this study, we described microstructural changes in lung sections of ARDS cases and control cases, as well as interleukins' expression, demonstrating that autopsy material is as informing as tissue samples collected by performing open lung biopsy.

Comprehensive landscape-style investigation of the molecular mechanism of acupuncture at ST36 single acupoint on different systemic diseases

The principle of acupoint stimulation efficacy is based on traditional meridian theory. However, the molecular mechanisms underlying the therapeutic effects of acupoints in treating diseases remain unclear in modern scientific understanding. In this study, we selected the ST36 acupoint for investigation and summarized all relevant literature from the PubMed database over the past 10 years. The results indicate that stimulation of ST36 single acupoints has therapeutic effects mainly in models of respiratory, neurological, digestive, endocrine and immune system diseases. And it can affect the inflammatory state, oxidative stress, respiratory mucus secretion, intestinal flora, immune cell function, neurotransmitter transmission, hormone secretion, the network of Interstitial Cells of Cajal (ICC) and glucose metabolism of the organism in these pathological states. Among them, acupuncture at the ST36 single point has the most prominent function in regulating the inflammatory state, which can mainly affect the activation of MAPK signaling pathway and drive the "molecular-cellular" mode involving macrophages, T-lymphocytes, mast cells (MCs) and neuroglial cells as the core to trigger the molecular level changes of the acupuncture point locally or in the target organ tissues, thereby establishing a multi-system, multi-target, multi-level molecular regulating mechanism. This article provides a comprehensive summary and discussion of the molecular mechanisms and effects of acupuncture at the ST36 acupoint, laying the groundwork for future in-depth research on acupuncture point theory.

Tau and Aβ42 in lavage fluid of pneumonia patients are associated with end-organ dysfunction: A prospective exploratory study

BACKGROUND

Bacterial pneumonia and sepsis are both common causes of end-organ dysfunction, especially in immunocompromised and critically ill patients. Pre-clinical data demonstrate that bacterial pneumonia and sepsis elicit the production of cytotoxic tau and amyloids from pulmonary endothelial cells, which cause lung and brain injury in naïve animal subjects, independent of the primary infection. The contribution of infection-elicited cytotoxic tau and amyloids to end-organ dysfunction has not been examined in the clinical setting. We hypothesized that cytotoxic tau and amyloids are present in the bronchoalveolar lavage fluid of critically ill patients with bacterial pneumonia and that these tau/amyloids are associated with end-organ dysfunction.

METHODS

Bacterial culture-positive and culture-negative mechanically ventilated patients were recruited into a prospective, exploratory observational study. Levels of tau and Aβ42 in, and cytotoxicity of, the bronchoalveolar lavage fluid were measured. Cytotoxic tau and amyloid concentrations were examined in comparison with patient clinical characteristics, including measures of end-organ dysfunction.

RESULTS

Tau and Aβ42 were increased in culture-positive patients (n = 49) compared to culture-negative patients (n = 50), independent of the causative bacterial organism. The mean age of patients was 52.1 ± 16.72 years old in the culture-positive group and 52.78 ± 18.18 years old in the culture-negative group. Males comprised 65.3% of the culture-positive group and 56% of the culture-negative group. Caucasian culture-positive patients had increased tau, boiled tau, and Aβ42 compared to both Caucasian and minority culture-negative patients. The increase in cytotoxins was most evident in males of all ages, and their presence was associated with end-organ dysfunction.

CONCLUSIONS

Bacterial infection promotes the generation of cytotoxic tau and Aβ42 within the lung, and these cytotoxins contribute to end-organ dysfunction among critically ill patients. This work illuminates an unappreciated mechanism of injury in critical illness.

Gut microbiota and its metabolic products in acute respiratory distress syndrome

The prevalence rate of acute respiratory distress syndrome (ARDS) is estimated at approximately 10% in critically ill patients worldwide, with the mortality rate ranging from 17% to 39%. Currently, ARDS mortality is usually higher in patients with COVID-19, giving another challenge for ARDS treatment. However, the treatment efficacy for ARDS is far from satisfactory. The relationship between the gut microbiota and ARDS has been substantiated by relevant scientific studies. ARDS not only changes the distribution of gut microbiota, but also influences intestinal mucosal barrier through the alteration of gut microbiota. The modulation of gut microbiota can impact the onset and progression of ARDS by triggering dysfunctions in inflammatory response and immune cells, oxidative stress, cell apoptosis, autophagy, pyroptosis, and ferroptosis mechanisms. Meanwhile, ARDS may also influence the distribution of metabolic products of gut microbiota. In this review, we focus on the impact of ARDS on gut microbiota and how the alteration of gut microbiota further influences the immune function, cellular functions and related signaling pathways during ARDS. The roles of gut microbiota-derived metabolites in the development and occurrence of ARDS are also discussed.

Extracellular vesicles in acute respiratory distress syndrome: Understanding protective and harmful signaling for the development of new therapeutics

Acute respiratory distress syndrome (ARDS) is a severe respiratory condition characterized by increased lung permeability, hyper-inflammatory state, and fluid leak into the alveolar spaces. ARDS is a heterogeneous disease, with multiple direct and indirect causes that result in a mortality of up to 40%. Due to the ongoing Covid-19 pandemic, its incidence has increased up to ten-fold. Extracellular vesicles (EVs) are small liposome-like particles that mediate intercellular communication and play a major role in ARDS pathophysiology. Indeed, they participate in endothelial barrier dysfunction and permeability, neutrophil, and macrophage activation, and also in the development of a hypercoagulable state. A more thorough understanding of the variegated and cell-specific functions of EVs may lead to the development of safe and effective therapeutics. In this review, we have collected evidence of EVs role in ARDS, revise the main mechanisms of production and internalization and summarize the current therapeutical approaches that have shown the ability to modulate EV signaling.

Prognostic value of lactic dehydrogenase-to-albumin ratio in critically ill patients with acute respiratory distress syndrome: a retrospective cohort study

Background

Lactic dehydrogenase (LDH)-to-albumin ratio (LAR) was an independent risk factor for mortality in the patients with acute respiratory distress syndrome (ARDS) due to coronavirus disease 2019 (COVID-19), while the relationship among LAR and short-term, long-term, in-hospital mortalities of ARDS remains unclear. The current study aims to investigate the association between LAR and significant prognosis in patients with ARDS.

Methods

We conducted a retrospective cohort study and analyzed patients with ARDS on the Medical Information Mart for Intensive Care IV (MIMIC-IV) version 2.0 database. In the current study, 30-day mortality was defined as the primary outcome; 90-day mortality and in-hospital mortality were defined as secondary outcomes. Multivariate regression analysis, Kaplan-Meier curve analysis and subgroup analysis were performed to research the association between LAR and prognosis in patients with ARDS.

Results

A total of 358 critically ill patients with ARDS were enrolled in the current study. The mean age of the participants was 62.6±16.0 and the median of LAR was 14.3. According to the Kaplan-Meier curve analysis, the higher LAR group had a higher 30-day, 90-day and in-hospital mortalities. We also analyzed the 30-day mortality to receiver operating characteristic (ROC) curves by comparing the value between LAR and LAR + simplified acute physiology score II (SAPS II). The area under the curve (AUC) of the LAR group was 0.694 [95% confidence interval (CI): 0.634-0.754, P<0.001], and 0.661 for the LAR + SAPS II (95% CI: 0.599-0.722, P<0.001). For 30-day mortality, after adjusting for covariates, hazard ratios (HRs) (95% CIs) for tertile 2 (LAR 8.7-30.9) and tertile 3 (LAR >30.9) were 2.00 (1.37, 2.92) and 2.50 (1.50, 4.15), respectively. Similar results were also observed for 90-day mortality and in-hospital mortality.

Conclusions

Elevated LAR levels are associated with increased 30- and 90-day mortalities, as well as in-hospital mortality in patients with ARDS, which means LAR levels may predict the mortalities of ARDS patients.

Targeting Keap1 with Inulae Herba activated the Nrf2 receptor to alleviate LPS-mediated acute lung injury

ETHNOPHARMACOLOGICAL RELEVANCE

Inulae Herba (IH) is known as Jinfeicao recorded in Chinese Pharmacopoeia with effects of lowering qi and eliminating phlegm, and used for the treatment of pulmonary diseases. However, its protective mechanism on pulmonary diseases, especially acute lung injury (ALI), is still undefined.

AIM OF THE STUDY

This study aimed to explore anti-inflammatory and anti-oxidation effects of IH and its underlying mechanism for treating ALI.

MATERIALS AND METHODS

We constructed a lipopolysaccharide (LPS)-ALI mouse model to reveal the therapeutical effect of IH. Western blot, real-time quantitative PCR, flow cytometry, small RNA interference, immunohistochemical staining, and the dual-luciferase experiment were performed to study the mechanism of IH for treating ALI.

RESULTS

IH attenuated LPS-mediated pathological changes (e.g. pneumonedema and pulmonary congestion) through inactivation of macrophages in an ALI mouse model. The result of flow cytometry demonstrated that IH regulated the homeostasis of M1 (CD80+CD206-) and M2 (CD80+CD206+) phenotype macrophages. Furthermore, IH suppressed mRNA expressions of M1 phenotype markers, such as iNOS and IL-6, whereas promoted mRNA expressions of M2 phenotype markers, such as ARG1 and RETNLA in LPS-mediated mice. Notably, IH targeted Keap1 to activate the Nrf2 receptor, exerting its anti-inflammatory and anti-oxidation effects proved by using immunohistochemical staining, dual-luciferase, and Keap1 knockdown technologies.

CONCLUSION

These findings suggested that targeting Keap1 with IH alleviated LPS-mediated ALI, and it could serve as a herbal agent for developing anti-ALI drugs.

Signaling pathways and potential therapeutic targets in acute respiratory distress syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a common condition associated with critically ill patients, characterized by bilateral chest radiographical opacities with refractory hypoxemia due to noncardiogenic pulmonary edema. Despite significant advances, the mortality of ARDS remains unacceptably high, and there are still no effective targeted pharmacotherapeutic agents. With the outbreak of coronavirus disease 19 worldwide, the mortality of ARDS has increased correspondingly. Comprehending the pathophysiology and the underlying molecular mechanisms of ARDS may thus be essential to developing effective therapeutic strategies and reducing mortality. To facilitate further understanding of its pathogenesis and exploring novel therapeutics, this review provides comprehensive information of ARDS from pathophysiology to molecular mechanisms and presents targeted therapeutics. We first describe the pathogenesis and pathophysiology of ARDS that involve dysregulated inflammation, alveolar-capillary barrier dysfunction, impaired alveolar fluid clearance and oxidative stress. Next, we summarize the molecular mechanisms and signaling pathways related to the above four aspects of ARDS pathophysiology, along with the latest research progress. Finally, we discuss the emerging therapeutic strategies that show exciting promise in ARDS, including several pharmacologic therapies, microRNA-based therapies and mesenchymal stromal cell therapies, highlighting the pathophysiological basis and the influences on signal transduction pathways for their use.

Anti-Inflammatory Effects of Clematis terniflora Leaf on Lipopolysaccharide-Induced Acute Lung Injury

For centuries, natural products are regarded as vital medicines for human survival. Clematis terniflora var. mandshurica (Rupr.) Ohwi is an ingredient of the herbal medicine, Wei Ling Xian, which has been used in Chinese medicine to alleviate pain, fever, and inflammation. In particular, C. terniflora leaves have been used to cure various inflammatory diseases, including tonsillitis, cholelithiasis, and conjunctivitis. Based on these properties, this study aimed to scientifically investigate the anti-inflammatory effect of an ethanol extract of leaves of C. terniflora (EELCT) using activated macrophages that play central roles in inflammatory response. In this study, EELCT inhibited the essential inflammatory mediators, such as nitric oxide, cyclooxygenase-2, tumor necrosis factor-α, interleukin- (IL-) 6, IL-1β, and inducible nitric oxide synthase, by suppressing the nuclear factor-κB and mitogen-activated protein kinase activation in macrophages. Acute lung injury (ALI) is a fatal respiratory disease accompanied by serious inflammation. With high mortality rate, the disease has no effective treatments. Therefore, new therapeutic agents must be developed for ALI. We expected that EELCT can be a promising therapeutic agent for ALI by reducing inflammatory responses and evaluated its action in a lipopolysaccharide- (LPS-) induced ALI model. EELCT alleviated histological changes, immune cell infiltration, inflammatory mediator production, and protein-rich pulmonary edema during ALI. Collectively, our results may explain the traditional usage of C. terniflora in inflammatory diseases and suggest the promising potential of EELCT as therapeutic candidate for ALI.

[ARDS Diagnostics and Treatment after the Coronavirus Pandemic - Everything as it was?]

ARDS is a syndrome that can develop as a result of various underlying diseases. For a long time, the prevailing belief was that the course of the disease was comparable regardless of the underlying disease. However, even before the COVID-19 pandemic, it was suspected that there were different manifestations that could be treated more individually and thus reduce the high mortality rate of ARDS, which has remained unchanged for years. The various findings on the heterogeneity of the course of the disease in COVID-related ARDS appear to confirm these assumptions. It is therefore to be expected that the diagnosis and treatment of non-COVID-related ARDS will also have to be individualised according to such phenotypes in the future. However, as long as the effectiveness of such strategies has not been proven in clinical trials, the current recommendations for ARDS therapy will remain valid for the time being. However, the adjustments already formulated in this context to individual pathophysiological conditions with regard to respiratory mechanics, ventilation-perfusion distribution and possible cardiac dysfunction should be made more meticulously than has usually been the case to date.

Novel application of nanomedicine for the treatment of acute lung injury: a literature review

Nanoparticles have attracted extensive attention due to their high degree of cell targeting, biocompatibility, controllable biological activity, and outstanding pharmacokinetics. Changing the size, morphology, and surface chemical groups of nanoparticles can increase the biological distribution of agents to achieve precise tissue targeting and optimize therapeutic effects. Examples of their use include nanoparticles designed for increasing antigen-specific immune responses, developing vaccines, and treating inflammatory diseases. Nanoparticles show the potential to become a new generation of therapeutic agents for regulating inflammation. Recently, many nanomaterials with targeted properties have been developed to treat acute lung injury/acute respiratory distress syndrome (ALI/ARDS). In this review, we provide a brief explanation of the pathological mechanism underlying ALI/ARDS and a systematic overview of the latest technology and research progress in nanomedicine treatments of ALI, including improved nanocarriers, nanozymes, and nanovaccines for the targeted treatment of lung injury. Ultimately, these nanomedicines will be used for the clinical treatment of ALI/ARDS.

Protective Effects and Mechanisms of Luteolin against Acute Respiratory Distress Syndrome: Network Pharmacology and In vivo and In vitro Studies

BACKGROUND

Acute Respiratory Distress Syndrome (ARDS) is an acute life-threatening disease, and luteolin has the potential to become a therapeutic agent for ARDS. However, its mechanism of action has not yet been clarified.

OBJECTIVE

The present study explored the potential effects and mechanisms of luteolin in the treatment of ARDS through network pharmacology analysis and verified them through biological experiments.

METHODS

The potential targets of luteolin and ARDS were obtained from online databases. Functional enrichment and protein-protein interaction (PPI) analyses were performed to explore the underlying molecular mechanisms and to identify hub targets. Molecular docking was used to verify the relationship between luteolin and target proteins. Finally, the effects of luteolin on key signaling pathways and biological processes were verified by in vitro and in vivo experiments.

RESULTS

A total of 146 luteolin- and 496 ARDS-related targets were extracted from public databases. The network pharmacological analysis suggested that luteolin could inhibit ARDS through the following potential therapeutic targets: AKT1, RELA, and NFKBIA. Inflammatory and oxidative stress responses were the main biological processes involved, with the AKT/NF-κB signaling pathway being the key signaling pathway targeted by luteolin for the treatment of ARDS. Molecular docking analysis indicated that luteolin had a good binding affinity to AKT1, RELA, and NFKBIA. The in vitro and in vivo experiments revealed that luteolin could regulate the inflammatory response and oxidative stress in the treatment of ARDS by inhibiting the AKT/NF- κB signaling pathway.

CONCLUSION

Luteolin could reduce the production of reactive oxygen species and inflammatory factors by inhibiting the AKT/NF-κB signaling pathway, thus reducing apoptosis and attenuating ARDS.

Role of gut microbiota and inflammatory factors in acute respiratory distress syndrome: a Mendelian randomization analysis

Background

Acute respiratory distress syndrome (ARDS) is a serious lung ailment marked by significant inflammation and damage in the alveoli and capillaries of the lungs. Recent research suggests a strong correlation between the onset and advancement of ARDS and an imbalance in the gut microbiota (GM).

Methods

In this investigation, Mendelian randomization (MR) analysis was utilized, drawing on data from publicly accessible genome-wide association studies. The primary focus was on examining the interplay between GM, inflammatory factors (IFs) and ARDS. Instrumental variables were established through genetic modifications of GM and IFs. Various statistical analysis methods including the inverse-variance weighted model, MR-Egger method and Wald ratio test were applied for comprehensive data analysis.

Results

Eight bacterial taxa within the GM demonstrated a potential causal link with development of ARDS. Notably, the phylum Actinobacteria and the genus Intestinibacter exhibited a negative association with the risk of ARDS. However, Erysipelotrichales (id. 2,148), Victivallis (id. 2,256), Ruminococcaceae UCG014 (id. 11,371), Eubacterium ruminantium group (id. 11,340), Erysipelotrichaceae (id. 2,149) and Erysipelotrichia (id. 2,147) demonstrated a positive association with ARDS risk. Additionally, the study identified a potential causal relationship between the inflammatory factors interleukin-16 and C-C motif chemokine 3 with the occurrence of ARDS.

Conclusion

This study strongly suggests that the interaction between gut microbiota (GM) and inflammatory factors (IFs) significantly contributes to the pathogenesis of acute respiratory distress syndrome (ARDS). This underscores their crucial involvement in both the initiation and advancement of this severe lung disorder.

S14G-humanin alleviates acute lung injury by inhibiting the activation of NF-κB

Acute lung injury (ALI) is characterized by severely damaged alveoli and blood vessels, seriously affecting the health of patients and causing a high mortality rate. The pathogenesis of ALI is complex, with inflammatory reactions and oxidative stress (OS) mainly involved. S14G humanin (HNG) is derived from humanin (HN), which is claimed with promising anti-inflammatory functions. Herein, the protective influence of HNG on ALI will be explored in a mouse model. The ALI model was established in mice via intratracheal instillation of 3 mg/kg LPS, followed by an intraperitoneal injection of 3 and 6 mg/kg HNG, respectively. Thicker alveolar walls, aggravated neutrophil infiltration, and increased wet weight/dry weight (W/D) ratio were observed in ALI mice, accompanied by an aggravated apoptotic state, all of which were notably alleviated by HNG. Furthermore, increased number of total cells and neutrophils in bronchoalveolar lavage fluid (BALF), elevated secretion of inflammatory cytokines, enhanced reactive oxygen species (ROS) and Malondialdehyde (MDA) levels, and declined superoxide dismutase-2 (SOD2) levels were observed in ALI mice, which were markedly ameliorated by HNG. Moreover, the upregulated levels of NOD-like receptor family pyrin domain containing 3 (NLRP3), caspase-1, and caspases cleave gasdermin D N/caspases cleave gasdermin D FL (GSDMD N/GSDMD FL) in ALI mice were signally repressed by HNG. Lastly, the upregulation of Toll-like receptor 4 (TLR4) and p-p65/p65, and downregulation of IκB-α observed in ALI mice were sharply reversed by HNG. Collectively, HNG alleviated the ALI in mice by inhibiting the activation of nuclear factor kappa B (NF-κB) signaling.

Sema3A inactivates the ERK/JNK signalling pathways to alleviate inflammation and oxidative stress in lipopolysaccharide-stimulated rat endothelial cells and lung tissues

Semaphorin 3A (Sema3A) is a secretory member of the semaphorin family of immune response regulators. This research focuses on its effects on inflammation and oxidative stress in acute respiratory distress syndrome (ARDS). By analysing the GEO dataset GSE57011, we obtained Sema3A as the most downregulated gene in ARDS samples. Lipopolysaccharide (LPS) was used to stimulate rat pulmonary microvascular endothelial cells (PMVECs) and rats to induce ARDS-like symptoms in vitro and in vivo, respectively. LPS induced severe damage in rat lung tissues, in which reduced immunohistochemical staining of Sema3A was detected. Sema3A overexpression reduced apoptosis and angiogenesis of LPS-induced PMVECs and alleviated lung injury and pulmonary edoema of rats. Moreover, ELISA results showed that Sema3A overexpression downregulated the levels of inflammatory cytokines and oxidative stress markers both in PMVECs and the rat lung. Activation of ERK/JNK signalling aggravated LPS-induced damage on PMVECs; however, the aggravation was partly blocked by Sema3A, which suppressed phosphorylation of ERK/JNK. Overall, this study demonstrates that Sema3A inactivates the ERK/JNK signalling to ameliorate inflammation and oxidative stress in LPS-induced ARDS models. Sema3A might therefore represent a candidate option for ARDS treatment.

A Case of Bilateral Pneumothorax With COVID-19 Infection

Bilateral spontaneous pneumothorax is a serious complication of coronavirus disease 2019 (COVID-19). The incidence of any spontaneous pneumothorax in patients with the aforementioned viral infection when hospitalized is about 1%. Treatment can involve management such as oxygen support, tube thoracostomy, pleurodesis, or even invasive surgery. The associated mortality with this complication is about 33% to 52%. We present a case of bilateral pneumothorax in a patient diagnosed with COVID-19 without any history of smoking or underlying lung disease. Careful vigilance and close monitoring of this serious complication are mandatory in inpatients.

Synthetic surfactant with a combined SP-B and SP-C analogue is efficient in rabbit models of adult and neonatal respiratory distress syndrome

Respiratory distress syndrome (RDS) in premature infants is caused by insufficient amounts of endogenous lung surfactant and is efficiently treated with replacement therapy using animal-derived surfactant preparations. On the other hand, adult/acute RDS (ARDS) occurs secondary to for example, sepsis, aspiration of gastric contents, and multitrauma and is caused by alveolar endothelial damage, leakage of plasma components into the airspaces and inhibition of surfactant activity. Instillation of surfactant preparations in ARDS has so far resulted in very limited treatment effects, partly due to inactivation of the delivered surfactants in the airspace. Here, we develop a combined surfactant protein B (SP-B) and SP-C peptide analogue (Combo) that can be efficiently expressed and purified from Escherichia coli without any solubility or purification tag. NMR spectroscopy shows that Combo peptide forms α-helices both in organic solvents and in lipid micelles, which coincide with the helical regions described for the isolated SP-B and SP-C parts. Artificial Combo surfactant composed of synthetic dipalmitoylphosphatidylcholine:palmitoyloleoylphosphatidylglycerol, 1:1, mixed with 3 weights % relative to total phospholipids of Combo peptide efficiently improves tidal volumes and lung gas volumes at end-expiration in a premature rabbit fetus model of RDS. Combo surfactant also improves oxygenation and respiratory parameters and lowers cytokine release in an acid instillation-induced ARDS adult rabbit model. Combo surfactant is markedly more resistant to inhibition by albumin and fibrinogen than a natural-derived surfactant in clinical use for the treatment of RDS. These features of Combo surfactant make it attractive for the development of novel therapies against human ARDS.

Human Placental Mesenchymal Stem Cells and Derived Extracellular Vesicles Ameliorate Lung Injury in Acute Respiratory Distress Syndrome Murine Model

This study investigates the therapeutic potential of human placental mesenchymal stem cells (P-MSCs) and their extracellular vesicles (EVs) in a murine model of acute respiratory distress syndrome (ARDS), a condition with growing relevance due to its association with severe COVID-19. We induced ARDS-like lung injury in mice using intranasal LPS instillation and evaluated histological changes, neutrophil accumulation via immunohistochemistry, bronchoalveolar lavage fluid cell count, total protein, and cytokine concentration, as well as lung gene expression changes at three time points: 24, 72, and 168 h. We found that both P-MSCs and EV treatments reduced the histological evidence of lung injury, decreased neutrophil infiltration, and improved alveolar barrier integrity. Analyses of cytokines and gene expression revealed that both treatments accelerated inflammation resolution in lung tissue. Biodistribution studies indicated negligible cell engraftment, suggesting that intraperitoneal P-MSC therapy functions mostly through soluble factors. Overall, both P-MSC and EV therapy ameliorated LPS-induced lung injury. Notably, at the tested dose, EV therapy was more effective than P-MSCs in reducing most aspects of lung injury.

Acute respiratory distress syndrome heterogeneity and the septic ARDS subgroup

Acute respiratory distress syndrome (ARDS) is an acute diffuse inflammatory lung injury characterized by the damage of alveolar epithelial cells and pulmonary capillary endothelial cells. It is mainly manifested by non-cardiogenic pulmonary edema, resulting from intrapulmonary and extrapulmonary risk factors. ARDS is often accompanied by immune system disturbance, both locally in the lungs and systemically. As a common heterogeneous disease in critical care medicine, researchers are often faced with the failure of clinical trials. Latent class analysis had been used to compensate for poor outcomes and found that targeted treatment after subgrouping contribute to ARDS therapy. The subphenotype of ARDS caused by sepsis has garnered attention due to its refractory nature and detrimental consequences. Sepsis stands as the most predominant extrapulmonary cause of ARDS, accounting for approximately 32% of ARDS cases. Studies indicate that sepsis-induced ARDS tends to be more severe than ARDS caused by other factors, leading to poorer prognosis and higher mortality rate. This comprehensive review delves into the immunological mechanisms of sepsis-ARDS, the heterogeneity of ARDS and existing research on targeted treatments, aiming to providing mechanism understanding and exploring ideas for accurate treatment of ARDS or sepsis-ARDS.

The role of neutrophil extracellular traps in sepsis and sepsis-related acute lung injury

Neutrophils release neutrophil extracellular traps (NETs) to trap pathogenic microorganisms. NETs are involved in the inflammatory response and bacterial killing and clearance. However, their excessive activation can lead to an inflammatory storm in the body, which may damage tissues and cause organ dysfunction. Organ dysfunction is the main pathophysiological cause of sepsis and also a cause of the high mortality rate in sepsis. Acute lung injury caused by sepsis accounts for the highest proportion of organ damage in sepsis. NET formation can lead to the development of sepsis because by promoting the release of interleukin-1 beta, interleukin-8, and tumor necrosis factor-alpha, thereby accelerating acute lung injury. In this review, we describe the critical role of NETs in sepsis-associated acute lung injury and review the current knowledge and novel therapeutic approaches.

Ubiquitin ligase CHFR mediated degradation of VE-cadherin through ubiquitylation disrupts endothelial adherens junctions

Vascular endothelial cadherin (VE-cadherin) expressed at endothelial adherens junctions (AJs) is vital for vascular integrity and endothelial homeostasis. Here we identify the requirement of the ubiquitin E3-ligase CHFR as a key mechanism of ubiquitylation-dependent degradation of VE-cadherin. CHFR was essential for disrupting the endothelium through control of the VE-cadherin protein expression at AJs. We observe augmented expression of VE-cadherin in endothelial cell (EC)-restricted Chfr knockout (ChfrΔEC) mice. We also observe abrogation of LPS-induced degradation of VE-cadherin in ChfrΔEC mice, suggesting the pathophysiological relevance of CHFR in regulating the endothelial junctional barrier in inflammation. Lung endothelial barrier breakdown, inflammatory neutrophil extravasation, and mortality induced by LPS were all suppressed in ChfrΔEC mice. We find that the transcription factor FoxO1 is a key upstream regulator of CHFR expression. These findings demonstrate the requisite role of the endothelial cell-expressed E3-ligase CHFR in regulating the expression of VE-cadherin, and thereby endothelial junctional barrier integrity.

Molecular markers of type II alveolar epithelial cells in acute lung injury by bioinformatics analysis

In this study, we aimed to identify molecular markers associated with type II alveolar epithelial cell injury in acute lung injury (ALI) models using bioinformatics methods. The objective was to provide new insights for the diagnosis and treatment of ALI/ARDS. We downloaded RNA SEQ datasets (GSE109913, GSE179418, and GSE119123) from the Gene Expression Omnibus (GEO) and used R language package to screen differentially expressed genes (DEGs). DEGs were annotated using Gene Ontology (GO), and their pathways were analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG). DEGs were imported into the STRING database and analyzed using Cytoscape software to determine the protein network of DEGs and calculate the top 10 nodes for the hub genes. Finally, potential therapeutic drugs for the hub genes were predicted using the DGIdb database. We identified 78 DEGs, including 70 up-regulated genes and 8 down-regulated genes. GO analysis revealed that the DEGs were mainly involved in biological processes such as granulocyte migration, response to bacterial-derived molecules, and cytokine-mediated signaling pathways. Additionally, they had cytokine activity, chemokine activity, and receptor ligand activity, and functioned in related receptor binding, CXCR chemokine receptor binding, G protein-coupled receptor binding, and other molecular functions. KEGG analysis indicated that the DEGs were mainly involved in TNF signaling pathway, IL-17 signaling pathway, NF-κB signal pathway, chemokine signal pathway, cytokine-cytokine receptor interaction signal pathway, and others. We identified eight hub genes, including IRF7, IFIT1, IFIT3, PSMB8, PSMB9, BST2, OASL2, and ZBP1, which were all up-regulated genes. We identified several hub genes of type II alveolar epithelial cells in ALI mouse models using bioinformatics analysis. These results provide new targets for understanding and treating of ALI.

Evaluating service needs for veno-venous extracorporeal membrane oxygenation in patients with severe acute respiratory distress syndrome in Saskatchewan

To determine the number of patients with acute respiratory distress syndrome (ARDS) who would be eligible to receive veno-venous extracorporeal membrane oxygenation (VV-ECMO). We conducted a retrospective observational study of ARDS patients admitted to Regina General Hospital Intensive Care Unit (ICU). VV-ECMO eligibility was assessed using selection criteria from the Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Syndrome trial (EOLIA), the Extracorporeal Life Support Organization (ELSO), New South Wales (NSW), Critical Care Services Ontario (CCSO) and a Regina-restrictive criteria. Of 415 patients admitted between October 16, 2018, and January 21, 2021, 103 (25%) had mild, 175 (42%) had moderate, and 64 (15%) had severe ARDS. Of the cohort, 144 (35%) had bacterial pneumonia, 86 (21%) had viral pneumonia (including COVID-19), and 72 (17%) had aspiration pneumonia. Using the EOLIA, ELSO, NSW, CCSO and Regina-restrictive criteria, 7/415 (1.7%), 6/415 (1.5%), 19/415 (4.6%), 26/415 (6.3%) and 12/415 (2.9%) were eligible for VV-ECMO, respectively. Of all ECMO-eligible patients, only one (2.4%) actually received VV-ECMO, 20/42 (48%) received prone positioning and 21/42 (50%) received neuromuscular blockade. There is potential for service expansion of VV-ECMO in Regina; however, there is still a need to improve the delivery of evidence-based ARDS therapies.