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Background: 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., Materials and Methods: 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., Results: 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., Conclusions: 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., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Schaaf et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Large population-based DNA biobanks linked to electronic health records (EHRs) may provide advantages over traditional study designs for identifying genetic drivers of ARDS., Research Question: Can ARDS be identified in an EHR biobank, and can this approach validate a previously reported genetic risk factor for ARDS?, Study Design and Methods: We analyzed two genotyped cohorts from one academic medical center: a prospective biomarker study of critically ill adults (VALID cohort), and hospitalized participants in a de-identified EHR biobank (BioVU). ARDS status was assessed by clinician-investigator review in VALID and an EHR-derived algorithm in BioVU (EHR-ARDS). We tested the association between the MUC5B promoter polymorphism (rs35705950) with development of ARDS/EHR-ARDS in each cohort., Results: In VALID, 2,795 patients were included, age was 55 [43, 66] (median [IQR]) years, and 718 (25.7%) developed ARDS. In BioVU, 9,025 hospitalized participants were included, age was 60 [48, 70] , and 1,056 (11.7%) developed EHR-ARDS. We observed a significant interaction between age and rs35705950 on ARDS risk in VALID: in older patients rs35705950 was associated with increased ARDS risk (OR: 1.44; 95%CI 1.08-1.92; p=0.012) whereas among younger patients this effect was attenuated (OR: 0.84; 95%CI: 0.62-1.14; p=0.26). In BioVU, rs35705950 was associated with increased risk for EHR-ARDS among all participants (OR: 1.20; 95%CI: 1.00-1.43, p=0.043) and this relationship did not vary by age. The polymorphism was also associated with more severe oxygenation impairment among BioVU participants who required mechanical ventilation., Interpretation: The MUC5B promoter polymorphism was associated with ARDS in two cohorts of at-risk hospitalized adults. Although age-related effect modification was observed only in the prospective biomarker cohort, the EHR cohort identified a consistent association between MUC5B and ARDS risk regardless of age and a novel association with oxygenation impairment. Our study highlights the potential for EHR biobanks to enable precision-medicine ARDS studies., Competing Interests: Conflicts of Interest: Dr. Ware reports consulting fees from Novartis, Arrowhead, Akebia, and Global Blood Therapeutics, stock ownership in Virtuoso Surgical, and an institutional research contract with Genentech, Inc. The remaining authors report no conflicts of interest with the reported study.

Importance: Acetaminophen (paracetamol) has many pharmacological effects that might be beneficial in sepsis, including inhibition of cell-free hemoglobin-induced oxidation of lipids and other substrates., Objective: To determine whether acetaminophen increases days alive and free of organ dysfunction in sepsis compared with placebo., Design, Setting, and Participants: Phase 2b randomized, double-blind, clinical trial conducted from October 2021 to April 2023 with 90-day follow-up. Adults with sepsis and respiratory or circulatory organ dysfunction were enrolled in the emergency department or intensive care unit of 40 US academic hospitals within 36 hours of presentation., Intervention: Patients were randomized to 1 g of acetaminophen intravenously every 6 hours or placebo for 5 days., Main Outcome and Measures: The primary end point was days alive and free of organ support (mechanical ventilation, vasopressors, and kidney replacement therapy) to day 28. Treatment effect modification was evaluated for acetaminophen by prerandomization plasma cell-free hemoglobin level higher than 10 mg/dL., Results: Of 447 patients enrolled (mean age, 64 [SD, 15] years, 51% female, mean Sequential Organ Failure Assessment [SOFA] score, 5.4 [SD, 2.5]), 227 were randomized to acetaminophen and 220 to placebo. Acetaminophen was safe with no difference in liver enzymes, hypotension, or fluid balance between treatment arms. Days alive and free of organ support to day 28 were not meaningfully different for acetaminophen (20.2 days; 95% CI, 18.8 to 21.6) vs placebo (19.6 days; 95% CI, 18.2 to 21.0; P = .56; difference, 0.6; 95% CI, -1.4 to 2.6). Among 15 secondary outcomes, total, respiratory, and coagulation SOFA scores were significantly lower on days 2 through 4 in the acetaminophen arm as was the rate of development of acute respiratory distress syndrome within 7 days (2.2% vs 8.5% acetaminophen vs placebo; P = .01; difference, -6.3; 95% CI, -10.8 to -1.8). There was no significant interaction between cell-free hemoglobin levels and acetaminophen., Conclusions and Relevance: Intravenous acetaminophen was safe but did not significantly improve days alive and free of organ support in critically ill sepsis patients., Trial Registration: ClinicalTrials.gov Identifier: NCT04291508.

Cell-free hemoglobin (CFH) is used to detect hemolysis and was recently suggested to trigger acute lung injury. However, its role has not been elucidated in severe acute respiratory distress syndrome (ARDS) patients undergoing extracorporeal membrane oxygenation (ECMO). We investigated the association of carboxyhemoglobin (COHb) and haptoglobin-two indirect markers of hemolysis-with mortality in critically ill patients undergoing veno-venous ECMO (VV-ECMO) with adjusted and longitudinal models (primary aim). Secondary aims included assessment of association between COHb and haptoglobin with the development of ventilator-associated pneumonia (VAP) and with hemodynamics. We retrospectively collected physiological, laboratory biomarkers, and outcome data in 147 patients undergoing VV-ECMO for severe ARDS. Forty-seven patients (32%) died in the intensive care unit (ICU). Average levels of COHb and haptoglobin were higher and lower, respectively, in patients who died. Higher haptoglobin was associated with lower pulmonary (PVR) and systemic vascular resistance, whereas higher COHb was associated with higher PVR. Carboxyhemoglobin was an independent predictor of VAP. Both haptoglobin and COHb independently predicted ICU mortality. In summary, indirect signs of hemolysis including COHb and haptoglobin are associated with modulation of vascular tone, VAP, and ICU mortality in respiratory ECMO. These findings suggest that CFH may be a mechanism of injury in this patient population., Competing Interests: Disclosure: The authors have no conflicts of interest to report., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the ASAIO.)

Background: Primary graft dysfunction (PGD) contributes substantially to both short- and long-term mortality after lung transplantation, but the mechanisms that lead to PGD are not well understood. Exposure to ambient air pollutants is associated with adverse events during waitlisting for lung transplantation and chronic lung allograft dysfunction, but its association with PGD has not been studied. We hypothesized that long-term exposure of the lung donor and recipient to high levels of ambient air pollutants would increase the risk of PGD in lung transplant recipients., Methods: Using data from 1428 lung transplant recipients and their donors enrolled in the Lung Transplant Outcomes Group observational cohort study, we evaluated the association between the development of PGD and zip-code-based estimates of long-term exposure to 6 major air pollutants (ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, particulate matter 2.5, and particulate matter 10) in both the lung donor and the lung recipient. Exposure estimates used daily EPA air pollutant monitoring data and were based on the geographic centroid of each subject's residential zip code. Associations were tested in both univariable and multivariable models controlling for known PGD risk factors., Results: We did not find strong associations between air pollutant exposures in either the donor or the recipient and PGD., Conclusions: Exposure to ambient air pollutants, at the levels observed in this study, may not be sufficiently harmful to prime the donor lung or the recipient to develop PGD, particularly when considering the robust associations with other established PGD risk factors., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The pathophysiology of silicosis is poorly understood, limiting development of therapies for those who have been exposed to the respirable particle. We explored mechanisms of silica-induced pulmonary fibrosis in human lung samples collected from patients with occupational exposure to silica and in a longitudinal mouse model of silicosis using multiple modalities including whole-lung single-cell RNA sequencing and histological, biochemical, and physiologic assessments. In addition to pulmonary inflammation and fibrosis, intratracheal silica challenge induced osteoclast-like differentiation of alveolar macrophages and recruited monocytes, driven by induction of the osteoclastogenic cytokine, receptor activator of nuclear factor κΒ ligand (RANKL) in pulmonary lymphocytes, and alveolar type II cells. Anti-RANKL monoclonal antibody treatment suppressed silica-induced osteoclast-like differentiation in the lung and attenuated pulmonary fibrosis. We conclude that silica induces differentiation of pulmonary osteoclast-like cells leading to progressive lung injury, likely due to sustained elaboration of bone-resorbing proteases and hydrochloric acid. Interrupting osteoclast-like differentiation may therefore constitute a promising avenue for moderating lung damage in silicosis.

Background: Hypoinflammatory and hyperinflammatory phenotypes have been identified in both Acute Respiratory Distress Syndrome (ARDS) and sepsis. Attributable mortality of ARDS in each phenotype of sepsis is yet to be determined. We aimed to estimate the population attributable fraction of death from ARDS (PAF ARDS ) in hypoinflammatory and hyperinflammatory sepsis, and to determine the primary cause of death within each phenotype., Methods: We studied 1737 patients with sepsis from two prospective cohorts. Patients were previously assigned to the hyperinflammatory or hypoinflammatory phenotype using latent class analysis. The PAF ARDS in patients with sepsis was estimated separately in the hypo and hyperinflammatory phenotypes. Organ dysfunction, severe comorbidities, and withdrawal of life support were abstracted from the medical record in a subset of patients from the EARLI cohort who died (n = 130/179). Primary cause of death was defined as the organ system that most directly contributed to death or withdrawal of life support., Results: The PAF ARDS was 19% (95%CI 10,28%) in hypoinflammatory sepsis and, 14% (95%CI 6,20%) in hyperinflammatory sepsis. Cause of death differed between the two phenotypes (p < 0.001). Respiratory failure was the most common cause of death in hypoinflammatory sepsis, whereas circulatory shock was the most common cause in hyperinflammatory sepsis. Death with severe underlying comorbidities was more frequent in hypoinflammatory sepsis (81% vs. 67%, p = 0.004)., Conclusions: The PAF ARDS is modest in both phenotypes whereas primary cause of death among patients with sepsis differed substantially by phenotype. This study identifies challenges in powering future clinical trials to detect changes in mortality outcomes among patients with sepsis and ARDS., (© 2024. The Author(s).)

Purpose: The purpose of this study was to determine associations between markers of inflammation and endogenous anticoagulant activity with delirium and coma during critical illness., Methods: In this prospective cohort study, we enrolled adults with respiratory failure and/or shock treated in medical or surgical intensive care units (ICUs) at 5 centers. Twice per day in the ICU, and daily thereafter, we assessed mental status using the Richmond Agitation Sedation Scale (RASS) and the Confusion Assessment Method-Intensive Care Unit (CAM-ICU). We collected blood samples on study days 1, 3, and 5, measuring levels of C-reactive protein (CRP), interferon gamma (IFN-γ), interleukin (IL)-1 beta (IL-1β), IL-6, IL-8, IL-10, IL-12, matrix metalloproteinase-9 (MMP-9), tumor necrosis factor-alpha (TNF-α), tumor necrosis factor receptor 1 (TNFR1), and protein C using validated protocols. We used multinomial logistic regression to analyze associations between biomarkers and the odds of delirium or coma versus normal mental status the following day, adjusting for age, sepsis, Sequential Organ Failure Assessment (SOFA), study day, corticosteroids, and sedatives., Results: Among 991 participants with a median age (interquartile range, IQR) of 62 [53-72] years and enrollment SOFA of 9 [7-11], higher concentrations of IL-6 (odds ratio [OR] [95% CI]: 1.8 [1.4-2.3]), IL-8 (1.3 [1.1-1.5]), IL-10 (1.5 [1.2-1.8]), TNF-α (1.2 [1.0-1.4]), and TNFR1 (1.3 [1.1-1.6]) and lower concentrations of protein C (0.7 [0.6-0.8])) were associated with delirium the following day. Higher concentrations of CRP (1.4 [1.1-1.7]), IFN-γ (1.3 [1.1-1.5]), IL-6 (2.3 [1.8-3.0]), IL-8 (1.8 [1.4-2.3]), and IL-10 (1.5 [1.2-2.0]) and lower concentrations of protein C (0.6 [0.5-0.8]) were associated with coma the following day. IL-1β, IL-12, and MMP-9 were not associated with mental status., Conclusion: Markers of inflammation and possibly endogenous anticoagulant activity are associated with delirium and coma during critical illness., (© 2024. Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: Improving the efficiency of clinical trials in acute hypoxemic respiratory failure (HRF) depends on enrichment strategies that minimize enrollment of patients who quickly resolve with existing care and focus on patients at high risk for persistent HRF. We aimed to develop parsimonious models predicting risk of persistent HRF using routine data from ICU admission and select research immune biomarkers., Design: Prospective cohorts for derivation ( n = 630) and external validation ( n = 511)., Setting: Medical and surgical ICUs at two U.S. medical centers., Patients: Adults with acute HRF defined as new invasive mechanical ventilation (IMV) and hypoxemia on the first calendar day after ICU admission., Interventions: None., Measurements and Main Results: We evaluated discrimination, calibration, and practical utility of models predicting persistent HRF risk (defined as ongoing IMV and hypoxemia on the third calendar day after admission): 1) a clinical model with least absolute shrinkage and selection operator (LASSO) selecting Pa o2 /F io2 , vasopressors, mean arterial pressure, bicarbonate, and acute respiratory distress syndrome as predictors; 2) a model adding interleukin-6 (IL-6) to clinical predictors; and 3) a comparator model with Pa o2 /F io2 alone, representing an existing strategy for enrichment. Forty-nine percent and 69% of patients had persistent HRF in derivation and validation sets, respectively. In validation, both LASSO (area under the receiver operating characteristic curve, 0.68; 95% CI, 0.64-0.73) and LASSO + IL-6 (0.71; 95% CI, 0.66-0.76) models had better discrimination than Pa o2 /F io2 (0.64; 95% CI, 0.59-0.69). Both models underestimated risk in lower risk deciles, but exhibited better calibration at relevant risk thresholds. Evaluating practical utility, both LASSO and LASSO + IL-6 models exhibited greater net benefit in decision curve analysis, and greater sample size savings in enrichment analysis, compared with Pa o2 /F io2 . The added utility of LASSO + IL-6 model over LASSO was modest., Conclusions: Parsimonious, interpretable models that predict persistent HRF may improve enrichment of trials testing HRF-targeted therapies and warrant future validation., Competing Interests: Drs. Sathe, Morrell, Bhatraju, and Ware received support for article research from the National Institutes of Health (NIH). Dr. Kerchberger’s institution received funding from the National Heart, Lung, and Blood Institute and the American Thoracic Society. Dr. Hough’s institution received funding from the NIH, the American Lung Association, and the Centers for Disease Control and Prevention. Dr. Ware’s institution received funding from the NIH; she received funding from Arrowhead, Akebia, Santhera, Global Blood Therapeutics, and Boehringer Ingelheim; she received support for article research from Genentech and Boehringer Ingelheim; and she disclosed they are a stockholder of Virtuoso Surgical. The remaining authors have disclosed that they do not have any potential conflicts of interest., (Copyright © 2024 by the Society of Critical Care Medicine and Wolters Kluwer Health, Inc. All Rights Reserved.)

Common genetic variants confer substantial risk for chronic lung diseases, including pulmonary fibrosis. Defining the genetic control of gene expression in a cell-type-specific and context-dependent manner is critical for understanding the mechanisms through which genetic variation influences complex traits and disease pathobiology. To this end, we performed single-cell RNA sequencing of lung tissue from 66 individuals with pulmonary fibrosis and 48 unaffected donors. Using a pseudobulk approach, we mapped expression quantitative trait loci (eQTLs) across 38 cell types, observing both shared and cell-type-specific regulatory effects. Furthermore, we identified disease interaction eQTLs and demonstrated that this class of associations is more likely to be cell-type-specific and linked to cellular dysregulation in pulmonary fibrosis. Finally, we connected lung disease risk variants to their regulatory targets in disease-relevant cell types. These results indicate that cellular context determines the impact of genetic variation on gene expression and implicates context-specific eQTLs as key regulators of lung homeostasis and disease., (© 2024. The Author(s).)

Cell-free hemoglobin (CFH) is elevated in the airspace of patients with acute respiratory distress syndrome (ARDS) and is sufficient to cause acute lung injury in a murine model. However, the pathways through which CFH causes lung injury are not well understood. Toll-like receptor 4 (TLR4) is a mediator of inflammation after detection of damage- and pathogen-associated molecular patterns. We hypothesized that TLR4 signaling mediates the proinflammatory effects of CFH in the airspace. After intratracheal CFH, BALBc mice deficient in TLR4 had reduced inflammatory cell influx into the airspace [bronchoalveolar lavage (BAL) cell counts, median TLR4 knockout (KO): 0.8 × 10 4 /mL [IQR 0.4-1.2 × 10 4 /mL], wild-type (WT): 3.0 × 10 4 /mL [2.2-4.0 × 10 4 /mL], P < 0.001] and attenuated lung permeability (BAL protein, TLR4KO: 289 µg/mL [236-320], WT: 488 µg/mL [422-536], P < 0.001). These mice also had attenuated production of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in the airspace. C57Bl/6 mice lacking TLR4 on myeloid cells only (LysM.Cre +/- TLR4 fl/fl ) had reduced cytokine production in the airspace after CFH, without attenuation of lung permeability. In vitro studies confirm that WT primary murine alveolar macrophages exposed to CFH (0.01-1 mg/mL) had dose-dependent increases in IL-6, IL-1 β, CXC motif chemokine ligand 1 (CXCL-1), TNF-α, and IL-10 ( P < 0.001). Murine MH-S alveolar-like macrophages show TLR4-dependent expression of IL-1β, IL-6, and CXCL-1 in response to CFH. Primary alveolar macrophages from mice lacking TLR4 adaptor proteins myeloid differentiation primary response 88 (MyD88) or TIR-domain-containing adapter-inducing interferon-β (TRIF) revealed that MyD88KO macrophages had 71-96% reduction in CFH-dependent proinflammatory cytokine production ( P < 0.001), whereas macrophages from TRIFKO mice had variable changes in cytokine responses. These data demonstrate that myeloid TLR4 signaling through MyD88 is a key regulator of airspace inflammation in response to CFH. NEW & NOTEWORTHY Cell-free hemoglobin (CFH) is elevated in the airspace of most patients with acute respiratory distress syndrome and causes severe inflammation. Here, we identify that CFH contributes to macrophage-induced cytokine production via Toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) signaling. These data increase our knowledge of the mechanisms through which CFH contributes to lung injury and may inform development of targeted therapeutics to attenuate inflammation.

Background: Since publication of the 2012 Berlin definition of acute respiratory distress syndrome (ARDS), several developments have supported the need for an expansion of the definition, including the use of high-flow nasal oxygen, the expansion of the use of pulse oximetry in place of arterial blood gases, the use of ultrasound for chest imaging, and the need for applicability in resource-limited settings. Methods: A consensus conference of 32 critical care ARDS experts was convened, had six virtual meetings (June 2021 to March 2022), and subsequently obtained input from members of several critical care societies. The goal was to develop a definition that would 1 ) identify patients with the currently accepted conceptual framework for ARDS, 2 ) facilitate rapid ARDS diagnosis for clinical care and research, 3 ) be applicable in resource-limited settings, 4 ) be useful for testing specific therapies, and 5 ) be practical for communication to patients and caregivers. Results: The committee made four main recommendations: 1 ) include high-flow nasal oxygen with a minimum flow rate of ⩾30 L/min; 2 ) use Pa O 2 :Fi O 2  ⩽ 300 mm Hg or oxygen saturation as measured by pulse oximetry Sp O 2 :Fi O 2  ⩽ 315 (if oxygen saturation as measured by pulse oximetry is ⩽97%) to identify hypoxemia; 3 ) retain bilateral opacities for imaging criteria but add ultrasound as an imaging modality, especially in resource-limited areas; and 4 ) in resource-limited settings, do not require positive end-expiratory pressure, oxygen flow rate, or specific respiratory support devices. Conclusions: We propose a new global definition of ARDS that builds on the Berlin definition. The recommendations also identify areas for future research, including the need for prospective assessments of the feasibility, reliability, and prognostic validity of the proposed global definition.

Rationale: Acute lung injury (ALI) carries a high risk of mortality but has no established pharmacologic therapy. We previously found that experimental ALI occurs through natural killer (NK) cell NKG2D receptor activation and that the cognate human ligand, MICB, was associated with ALI after transplantation. Objectives: To investigate the association of a common missense variant, MICB G406A , with ALI. Methods: We assessed MICB G406A genotypes within two multicenter observational study cohorts at risk for ALI: primary graft dysfunction ( N  = 619) and acute respiratory distress syndrome ( N  = 1,376). Variant protein functional effects were determined in cultured and ex vivo human samples. Measurements and Main Results: Recipients of MICB G406A -homozygous allografts had an 11.1% absolute risk reduction (95% confidence interval [CI], 3.2-19.4%) for severe primary graft dysfunction after lung transplantation and reduced risk for allograft failure (hazard ratio, 0.36; 95% CI, 0.13-0.98). In participants with sepsis, we observed 39% reduced odds of moderately or severely impaired oxygenation among MICB G406A -homozygous individuals (95% CI, 0.43-0.86). BAL NK cells were less frequent and less mature in participants with MICB G406A . Expression of missense variant protein MICB D136N in cultured cells resulted in reduced surface MICB and reduced NKG2D ligation relative to wild-type MICB. Coculture of variant MICB D136N cells with NK cells resulted in less NKG2D activation and less susceptibility to NK cell killing relative to the wild-type cells. Conclusions: These data support a role for MICB signaling through the NKG2D receptor in mediating ALI, suggesting a novel therapeutic approach.

Sepsis-associated acute kidney injury is associated with high morbidity and mortality in critically ill patients. Cell-free hemoglobin (CFH) is released into the circulation of patients with severe sepsis and the levels of CFH are independently associated with mortality. CFH treatment increased cytotoxicity in the human tubular epithelial cell line HK-2. To better model the intact kidney, we cultured human kidney organoids derived from induced pluripotent stem cells. We treated human kidney organoids grown using both three-dimensional and transwell protocols with CFH for 48 h. We found evidence for increased tubular toxicity, oxidative stress, mitochondrial fragmentation, endothelial cell injury and injury-associated transcripts compared to those of the untreated control group. To evaluate the protective effect of clinically available small molecules, we co-treated CFH-injured organoids with ascorbate (vitamin C) or acetaminophen for 48 h. We found significantly decreased toxicity, preservation of endothelial cells and reduced mitochondrial fragmentation in the group receiving ascorbate following CFH treatment. This study provides direct evidence that ascorbate or ascorbic acid protects human kidney cells from CFH-induced damage such as that in sepsis-associated acute kidney injury., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

Background: In sepsis and acute respiratory distress syndrome (ARDS), heterogeneity has contributed to difficulty identifying effective pharmacotherapies. In ARDS, two molecular phenotypes (hypoinflammatory and hyperinflammatory) have consistently been identified, with divergent outcomes and treatment responses. In this study, we sought to derive molecular phenotypes in critically ill adults with sepsis, determine their overlap with previous ARDS phenotypes, and evaluate whether they respond differently to treatment in completed sepsis trials., Methods: We used clinical data and plasma biomarkers from two prospective sepsis cohorts, the Validating Acute Lung Injury biomarkers for Diagnosis (VALID) study (N=1140) and the Early Assessment of Renal and Lung Injury (EARLI) study (N=818), in latent class analysis (LCA) to identify the optimal number of classes in each cohort independently. We used validated models trained to classify ARDS phenotypes to evaluate concordance of sepsis and ARDS phenotypes. We applied these models retrospectively to the previously published Prospective Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis and Septic Shock (PROWESS-SHOCK) trial and Vasopressin and Septic Shock Trial (VASST) to assign phenotypes and evaluate heterogeneity of treatment effect., Findings: A two-class model best fit both VALID and EARLI (p<0·0001). In VALID, 804 (70·5%) of the 1140 patients were classified as hypoinflammatory and 336 (29·5%) as hyperinflammatory; in EARLI, 530 (64·8%) of 818 were hypoinflammatory and 288 (35·2%) hyperinflammatory. We observed higher plasma pro-inflammatory cytokines, more vasopressor use, more bacteraemia, lower protein C, and higher mortality in the hyperinflammatory than in the hypoinflammatory phenotype (p<0·0001 for all). Classifier models indicated strong concordance between sepsis phenotypes and previously identified ARDS phenotypes (area under the curve 0·87-0·96, depending on the model). Findings were similar excluding participants with both sepsis and ARDS. In PROWESS-SHOCK, 1142 (68·0%) of 1680 patients had the hypoinflammatory phenotype and 538 (32·0%) had the hyperinflammatory phenotype, and response to activated protein C differed by phenotype (p=0·0043). In VASST, phenotype proportions were similar to other cohorts; however, no treatment interaction with the type of vasopressor was observed (p=0·72)., Interpretation: Molecular phenotypes previously identified in ARDS are also identifiable in multiple sepsis cohorts and respond differently to activated protein C. Molecular phenotypes could represent a treatable trait in critical illness beyond the patient's syndromic diagnosis., Funding: US National Institutes of Health., Competing Interests: Declaration of interests PS reports funding from the US National Institutes of Health (NIH) and National Institute of General Medical Sciences; and consulting fees from AstraZeneca. LBW reports funding from NIH, Department of Defense (DoD), Genentech, Boehringer Ingelheim, and CSL Behring; consulting fees from Akebia Therapeutics, Santhera, Global Blood Therapeutics, and Boehringer Ingelheim; and stock options in Virtuoso Surgical. CSC reports funding from NIH; research grants from Roche Genentech and Quantum Leap Healthcare Collaborative; consulting fees from Vasomune Therapeutics, GEn1E Lifesciences, NGM Bio, Cellenkos, and Janssen; and a patent on metagenomic sequencing for sepsis diagnosis (co-recipient). MAM reports funding from Roche Genentech, Quantum Therapeutics, NIH/National Heart, Lung, and Blood Institute/National Institute of Allergy and Infectious Diseases, DoD, and California Institute for Regenerative Medicine; and consulting fees from Johnson & Johnson, Gilead Sciences, and Novartis. MMC reports funding from NIH and DoD; and intellectual property royalties from an issued patent (#11 410 777). JAR reports an investigator-initiated grant from Grifols provided to and administered by the University of British Columbia, Canadian Institutes of Health Research; three grants from the St Paul's Foundation; patents owned by the University of British Columbia related to the use of PCSK9 inhibitor(s) in sepsis and the use of vasopressin in septic shock, and by Ferring Pharmaceuticals for use of selepressin in septic shock; formerly being a founder, Director, and shareholder in Cyon Therapeutics (now closed); being a shareholder in Molecular You; receiving consulting fees in the last 3 years from SIB, Ferring Pharmaceuticals, and Par Pharmaceutical; and having been a funded member of the Data and Safety Monitoring Board of an NIH-sponsored trial of plasma in COVID-19 (PASS-IT-ON). KDL reports grants from NIH: National Institute of Diabetes and Digestive and Kidney Diseases; consulting fees from bioMérieux, UpToDate, SeaStar Medical, AM-Pharma, and Baxter; and stock or stock options in Amgen. All other authors declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

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.

Purpose: Exposures to ambient air pollutants may prime the lung enhancing risk of acute respiratory distress syndrome (ARDS) in sepsis. Our objective was to determine the association of short-, medium-, and long-term pollutant exposures and ARDS risk in critically ill sepsis patients., Methods: We analyzed a prospective cohort of 1858 critically ill patients with sepsis, and estimated short- (3 days), medium- (6 weeks), and long- (5 years) term exposures to ozone, nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), carbon monoxide (CO), particulate matter < 2.5 μm (PM 2.5 ), and PM < 10 μm (PM 10 ) using weighted averages of daily levels from monitors within 50 km of subjects' residences. Subjects were followed for 6 days for ARDS by the Berlin Criteria. The association between each pollutant and ARDS was determined using multivariable logistic regression adjusting for preselected confounders. In 764 subjects, we measured plasma concentrations of inflammatory proteins at presentation and tested for an association between pollutant exposure and protein concentration via linear regression., Results: ARDS developed in 754 (41%) subjects. Short- and long-term exposures to SO 2 , NO 2 , and PM 2.5 were associated with ARDS risk (SO 2 : odds ratio (OR) for the comparison of the 75-25th long-term exposure percentile 1.43 (95% confidence interval (CI) 1.16, 1.77); p < 0.01; NO 2 : 1.36 (1.06, 1.74); p = 0.04, PM 2.5 : 1.21 (1.04, 1.41); p = 0.03). Long-term exposures to these three pollutants were also associated with plasma interleukin-1 receptor antagonist and soluble tumor necrosis factor receptor-1 concentrations., Conclusion: Short and long-term exposures to ambient SO 2 , PM 2.5 , and NO 2 are associated with increased ARDS risk in sepsis, representing potentially modifiable environmental risk factors for sepsis-associated ARDS., (© 2023. Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Despite the availability of COVID-19 vaccinations, there remains a need to investigate treatments to reduce the risk or severity of potentially fatal complications of COVID-19, such as acute respiratory distress syndrome (ARDS). This study evaluated the efficacy and safety of the transient receptor potential channel C6 (TRPC6) inhibitor, BI 764198, in reducing the risk and/or severity of ARDS in patients hospitalised for COVID-19 and requiring non-invasive, supplemental oxygen support (oxygen by mask or nasal prongs, oxygen by non-invasive ventilation or high-flow nasal oxygen)., Methods: Multicentre, double-blind, randomised phase II trial comparing once-daily oral BI 764198 (n=65) with placebo (n=64) for 28 days (+2-month follow-up)., Primary Endpoint: proportion of patients alive and free of mechanical ventilation at day 29. Secondary endpoints: proportion of patients alive and discharged without oxygen (day 29); occurrence of either in-hospital mortality, intensive care unit admission or mechanical ventilation (day 29); time to first response (clinical improvement/recovery); ventilator-free days (day 29); and mortality (days 15, 29, 60 and 90)., Results: No difference was observed for the primary endpoint: BI 764198 (83.1%) versus placebo (87.5%) (estimated risk difference -5.39%; 95% CI -16.08 to 5.30; p=0.323). For secondary endpoints, a longer time to first response (rate ratio 0.67; 95% CI 0.46 to 0.99; p=0.045) and longer hospitalisation (+3.41 days; 95% CI 0.49 to 6.34; p=0.023) for BI 764198 versus placebo was observed; no other significant differences were observed. On-treatment adverse events were similar between trial arms and more fatal events were reported for BI 764198 (n=7) versus placebo (n=2). Treatment was stopped early based on an interim observation of a lack of efficacy and an imbalance of fatal events (Data Monitoring Committee recommendation)., Conclusions: TRPC6 inhibition was not effective in reducing the risk and/or severity of ARDS in patients with COVID-19 requiring non-invasive, supplemental oxygen support., Trial Registration Number: NCT04604184., Competing Interests: Competing interests: LW reports receipt of research support from Boehringer Ingelheim, Genentech and CSL Behring and consulting fees from Merck, Citius, Foresee and Quark. NS, WC and AG are employees of Boehringer Ingelheim. DFM reports personal fees from consultancy for GlaxoSmithKline, Boehringer Ingelheim, Bayer, Novartis, SOBI and Eli Lilly, and from sitting on Data Monitoring and Ethics Committees for trials undertaken by Vir Biotechnology and Faron Pharmaceuticals. DFM’s institution has received funds from grants from the NIHR Wellcome Trust, MRC, Innovate UK and NIHSC R&D, and others for studies in patients with ARDS and COVID-19; he also has a patent (US8962032) issued to his institution for a treatment for inflammatory disease. DFM is the MRC/NIHR EME Programme Director; DFM’s spouse is joint Editor-in-Chief for Thorax. VE reports clinical trial support and consulting fees from Gilead. GAD reports receipt of clinical trial research support from Boehringer Ingelheim, Edesa Biotech, Gilead Sciences, Regeneron and Roche, and scientific advisory board membership for Safeology., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

The aim of these guidelines is to update the 2017 clinical practice guideline (CPG) of the European Society of Intensive Care Medicine (ESICM). The scope of this CPG is limited to adult patients and to non-pharmacological respiratory support strategies across different aspects of acute respiratory distress syndrome (ARDS), including ARDS due to coronavirus disease 2019 (COVID-19). These guidelines were formulated by an international panel of clinical experts, one methodologist and patients' representatives on behalf of the ESICM. The review was conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations and the quality of reporting of each study based on the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network guidelines. The CPG addressed 21 questions and formulates 21 recommendations on the following domains: (1) definition; (2) phenotyping, and respiratory support strategies including (3) high-flow nasal cannula oxygen (HFNO); (4) non-invasive ventilation (NIV); (5) tidal volume setting; (6) positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM); (7) prone positioning; (8) neuromuscular blockade, and (9) extracorporeal life support (ECLS). In addition, the CPG includes expert opinion on clinical practice and identifies the areas of future research., (© 2023. The Author(s).)

Cell-free hemoglobin is a pathophysiological driver of endothelial injury during sepsis and acute respiratory distress syndrome (ARDS), but the precise mechanisms are not fully understood. We hypothesized that hemoglobin (Hb) increases leukocyte adhesion and endothelial activation in human lung microvascular endothelial cells (HLMVEC). We stimulated primary HLMVEC, or leukocytes isolated from healthy human donors, with Hb (0.5 mg/mL) and found that leukocyte adhesion to lung endothelium in response to Hb is an endothelial-dependent process. Next, we stimulated HLMVEC with Hb over time (1, 3, 6, and 24 h) and found increased transcription and release of inflammatory cytokines (IL-1β, IL-8, and IL-6). In addition, Hb exposure variably upregulated transcription, total protein expression, and cell-surface localization of adhesion molecules E-selectin, P-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1). Since VCAM-1 was most upregulated by Hb, we further tested mechanisms for Hb-mediated upregulation of VCAM-1 in HLMVEC. Although upregulation of VCAM-1 was not prevented by hemoglobin scavenger haptoglobin, heme scavenger hemopexin, or inhibition of nod-like receptor protein 3 (NLRP3) signaling, blocking Toll-like receptor 4 (TLR4) with small molecule inhibitor TAK-242 (1 µM) prevented upregulation of VCAM-1 in response to Hb. Consistently, Hb increased nuclear factor-κB (NF-κB) activation and intracellular reactive oxygen species (ROS), which were both prevented by TLR4 inhibition. Together, these data demonstrate that Hb increases leukocyte-endothelial adhesion and activates HLMVEC through TLR4 signaling, indicating a potential mechanism for Hb-mediated pulmonary vascular injury during inflammatory and hemolytic conditions.

Circulating cell-free hemoglobin (CFH) is elevated in pulmonary arterial hypertension (PAH) and associated with poor outcomes but the mechanisms are unknown. We hypothesized that CFH is generated from the pulmonary circulation and inadequately cleared in PAH. Transpulmonary CFH (difference between wedge and pulmonary artery positions) and lung hemoglobin α were analyzed in patients with PAH and healthy controls. Haptoglobin genotype and plasma hemoglobin processing proteins were analyzed in patients with PAH, unaffected bone morphogenetic protein receptor type II mutation carriers (UMCs), and control subjects. Transpulmonary CFH was increased in patients with PAH ( p  = 0.04) and correlated with pulmonary vascular resistanc (PVR) ( r s  = 0.75, p  = 0.02) and mean pulmonary arterial pressure (mPAP) ( r s  = 0.78, p  = 0.02). Pulmonary vascular hemoglobin α protein was increased in patients with PAH ( p  = 0.006), especially in occluded vessels ( p  = 0.04). Haptoglobin genotype did not differ between groups. Plasma haptoglobin was higher in UMCs compared with both control subjects ( p  = 0.03) and patients with HPAH ( p  < 0.0001); patients with IPAH had higher circulating haptoglobin levels than patients with HPAH ( p  = 0.006). Notably, circulating CFH to haptoglobin ratio was elevated in patients with HPAH compared to control subjects ( p  = 0.02) and UMCs ( p  = 0.006). Moreover, in patients with PAH, CFH: haptoglobin correlated with PVR ( r s  = 0.37, p  = 0.0004) and mPAP ( r s  = 0.25, p  = 0.02). Broad alterations in other plasma hemoglobin processing proteins (hemopexin, heme oxygenase-1, and sCD163) were observed. In conclusion, pulmonary vascular CFH is associated with increased PVR and mPAP in PAH and dysregulated CFH clearance may contribute to PAH pathology. Further study is needed to determine whether targeting CFH is a viable therapeutic for pulmonary vascular dysfunction in PAH., Competing Interests: The authors declare no conflict of interest., (© 2023 The Authors. Pulmonary Circulation published by John Wiley & Sons Ltd on behalf of Pulmonary Vascular Research Institute.)

Elevated levels of circulating cell-free hemoglobin (CFH) are an integral feature of several clinical conditions including sickle cell anemia, sepsis, hemodialysis and cardiopulmonary bypass. Oxidized (Fe 3+ , ferric) hemoglobin contributes to the pathophysiology of these disease states and is therefore widely studied in experimental models, many of which use commercially sourced CFH. In this study, we treated human endothelial cells with commercially sourced ferric hemoglobin and observed the appearance of dense cytoplasmic aggregates (CAgg) over time. These CAgg were intensely autofluorescent, altered intracellular structures (such as mitochondria), formed in multiple cell types and with different media composition, and formed regardless of the presence or absence of cells. An in-depth chemical analysis of these CAgg revealed that they contain inorganic components and are not pure hemoglobin. To oxidize freshly isolated hemoglobin without addition of an oxidizing agent, we developed a novel method to convert ferrous CFH to ferric CFH using ultraviolet light without the need for additional redox agents. Unlike commercial ferric hemoglobin, treatment of cells with the fresh ferric hemoglobin did not lead to CAgg formation. These studies suggest that commercially sourced CFH may contain stabilizers and additives which contribute to CAgg formation., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: We sought to describe trends in extracorporeal membrane oxygenation (ECMO) use, and define the impact on PGD incidence and early mortality in lung transplantation., Methods: Patients were enrolled from August 2011 to June 2018 at 10 transplant centers in the multi-center Lung Transplant Outcomes Group prospective cohort study. PGD was defined as Grade 3 at 48 or 72 hours, based on the 2016 PGD ISHLT guidelines. Logistic regression and survival models were used to contrast between group effects for event (i.e., PGD and Death) and time-to-event (i.e., death, extubation, discharge) outcomes respectively. Both modeling frameworks accommodate the inclusion of potential confounders., Results: A total of 1,528 subjects were enrolled with a 25.7% incidence of PGD. Annual PGD incidence (14.3%-38.2%, p = .0002), median LAS (38.0-47.7 p = .009) and the use of ECMO salvage for PGD (5.7%-20.9%, p = .007) increased over the course of the study. PGD was associated with increased 1 year mortality (OR 1.7 [95% C.I. 1.2, 2.3], p = .0001). Bridging strategies were not associated with increased mortality compared to non-bridged patients (p = .66); however, salvage ECMO for PGD was significantly associated with increased mortality (OR 1.9 [1.3, 2.7], p = .0007). Restricted mean survival time comparison at 1-year demonstrated 84.1 days lost in venoarterial salvaged recipients with PGD when compared to those without PGD (ratio 1.3 [1.1, 1.5]) and 27.2 days for venovenous with PGD (ratio 1.1 [1.0, 1.4])., Conclusions: PGD incidence continues to rise in modern transplant practice paralleled by significant increases in recipient severity of illness. Bridging strategies have increased but did not affect PGD incidence or mortality. PGD remains highly associated with mortality and is increasingly treated with salvage ECMO., (Copyright © 2022 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.)

It is increasingly recognized that cigarette smoke (CS) exposure increases the incidence and severity of acute respiratory distress syndrome (ARDS) in critical ill humans and animals. However, the mechanism(s) is not well understood. This study aims to investigate mechanism underlying the priming effect of CS on Pseudomonas aeruginosa-triggered acute lung injury, by using pre-clinic animal models and genetically modified mice. We demonstrated that CS impaired P. aeruginosa-induced mitophagy flux, promoted p62 accumulation, and exacerbated P. aeruginosa-triggered mitochondrial damage and NLRP3 inflammasome activation in alveolar macrophages; an effect associated with increased acute lung injury and mortality. Pharmacological inhibition of caspase-1, a component of inflammasome, attenuated CS primed P. aeruginosa-triggered acute lung injury and improved animal survival. Global or myeloid-specific knockout of IL-1β, a downstream component of inflammasome activation, also attenuated CS primed P. aeruginosa-triggered acute lung injury. Our results suggest that NLRP3 inflammasome activation is an important mechanism for CS primed P. aeruginosa-triggered acute lung injury. (total words: 155)., Competing Interests: Declaration of competing interest None., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

The diagnosis of acute respiratory distress syndrome (ARDS) traditionally requires calculation of the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (PaO 2 /FiO 2 ) using arterial blood, which can be costly and is not possible in many resource-limited settings. By contrast, pulse oximetry is continuously available, accurate, inexpensive, and non-invasive. Pulse oximetry-based indices, such as the ratio of pulse-oximetric oxygen saturation to FiO 2 (SpO 2 /FiO 2 ), have been validated in clinical studies for the diagnosis and risk stratification of patients with ARDS. Limitations of the SpO 2 /FiO 2 ratio include reduced accuracy in poor perfusion states or above oxygen saturations of 97%, and the potential for reduced accuracy in patients with darker skin pigmentation. Application of pulse oximetry to the diagnosis and management of ARDS, including formal adoption of the SpO 2 /FiO 2 ratio as an alternative to PaO 2 /FiO 2 to meet the diagnostic criterion for hypoxaemia in ARDS, could facilitate increased and earlier recognition of ARDS worldwide to advance both clinical practice and research., Competing Interests: Declaration of interests KDW has received research grant support from the US National Institutes of Health (NIH; 5T32GM008440-24). MAM has received research grant support from the NIH (HL134828, HL126456, HL140026, and 143896), the US Department of Defense, and Roche-Genentech for observational studies on acute respiratory distress syndrome; he reports consultancy fees from Citius Pharmaceuticals, Johnson & Johnson, Gilead Pharmaceuticals, Plant Therapeutics, and Novartis pharmaceuticals, outside of the submitted work. LBW has received research grant support from the NIH (HL103836, HL126176, HL158906) and the US Department of Defense, and grants or contracts from Genentech, Boehringer Ingelheim, and CSL Behring; she reports consultancy fees from Foresee, Merck, Citius Pharmaceuticals, Quark, and Boehringer Ingelheim, outside of the submitted work., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

While the coronavirus disease 2019 (COVID-19) pandemic placed a heavy burden on healthcare systems worldwide, it also induced urgent mobilisation of research teams to develop treatments preventing or curing the disease and its consequences. It has, therefore, challenged critical care research to rapidly focus on specific fields while forcing critical care physicians to make difficult ethical decisions. This narrative review aims to summarise critical care research -from organisation to research fields- in this pandemic setting and to highlight opportunities to improve research efficiency in the future, based on what is learned from COVID-19. This pressure on research revealed, i.e., (i) the need to harmonise regulatory processes between countries, allowing simplified organisation of international research networks to improve their efficiency in answering large-scale questions; (ii) the importance of developing translational research from which therapeutic innovations can emerge; (iii) the need for improved triage and predictive scores to rationalise admission to the intensive care unit. In this context, key areas for future critical care research and better pandemic preparedness are artificial intelligence applied to healthcare, characterisation of long-term symptoms, and ethical considerations. Such collaborative research efforts should involve groups from both high and low-to-middle income countries to propose worldwide solutions. As a conclusion, stress tests on healthcare organisations should be viewed as opportunities to design new research frameworks and strategies. Worldwide availability of research networks ready to operate is essential to be prepared for next pandemics. Importantly, researchers and physicians should prioritise realistic and ethical goals for both clinical care and research., (Copyright © 2022 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Acute respiratory distress syndrome (ARDS) is a common clinical syndrome of acute respiratory failure as a result of diffuse lung inflammation and oedema. ARDS can be precipitated by a variety of causes. The pathophysiology of ARDS is complex and involves the activation and dysregulation of multiple overlapping and interacting pathways of injury, inflammation, and coagulation, both in the lung and systemically. Mechanical ventilation can contribute to a cycle of lung injury and inflammation. Resolution of inflammation is a coordinated process that requires downregulation of proinflammatory pathways and upregulation of anti-inflammatory pathways. The heterogeneity of the clinical syndrome, along with its biology, physiology, and radiology, has increasingly been recognised and incorporated into identification of phenotypes. A precision-medicine approach that improves the identification of more homogeneous ARDS phenotypes should lead to an improved understanding of its pathophysiological mechanisms and how they differ from patient to patient., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Clinical and molecular heterogeneity are common features of human disease. Understanding the basis for heterogeneity has led to major advances in therapy for many cancers and pulmonary diseases such as cystic fibrosis and asthma. Although heterogeneity of risk factors, disease severity, and outcomes in survivors are common features of the acute respiratory distress syndrome (ARDS), many challenges exist in understanding the clinical and molecular basis for disease heterogeneity and using heterogeneity to tailor therapy for individual patients. This report summarizes the proceedings of the 2021 Aspen Lung Conference, which was organized to review key issues related to understanding clinical and molecular heterogeneity in ARDS. The goals were to review new information about ARDS phenotypes, to explore multicellular and multisystem mechanisms responsible for heterogeneity, and to review how best to account for clinical and molecular heterogeneity in clinical trial design and assessment of outcomes. The report concludes with recommendations for future research to understand the clinical and basic mechanisms underlying heterogeneity in ARDS to advance the development of new treatments for this life-threatening critical illness.

The acute respiratory distress syndrome (ARDS) is a common critical illness syndrome with high morbidity and mortality. There are no proven pharmacological therapies for ARDS. The current definition of ARDS is based on shared clinical characteristics but does not capture the heterogeneity in clinical risk factors, imaging characteristics, physiology, timing of onset and trajectory, and biology of the syndrome. There is increasing interest within the ARDS clinical trialist community to design clinical trials that reduce heterogeneity in the trial population. This effort must be balanced with ongoing work to craft an inclusive, global definition of ARDS, with important implications for trial design. Ultimately, the two aims-to design trials that are applicable to the diverse global ARDS population while also advancing opportunities to identify targetable traits-should coexist. In this Personal View, we recommend two primary strategies to improve future ARDS trials: the development of new methods to target treatable traits in clinical trial populations, and improvements in the representativeness of ARDS trials, with the inclusion of global populations. We emphasise that these two strategies are complementary. We also discuss how a proposed expansion of the definition of ARDS could affect the future of clinical trials., Competing Interests: Declaration of interests SJ receives consulting fees from Drager, Fisher-Paykel, Medtronic, Mindray, and Baxter. NL receives grant funding from Guerbet. GL receives consulting fees from Abbott, Abiomed, and Baxter; and speaking fees from LivaNova. AM receives grants from 4TEEN4, Abbott, Roche, and Sphyngotec; and consulting fees from Orion, Roche, Adrenomed, and Fire1. AM participates on the data and safety monitoring board for Roche. LBW declares grants from Genentech, Boehringer Ingelheim, and CSL Behring, outside the submitted work; and consulting fees from Foresee, Merck, Citius Pharmaceuticals, Quark, and Boehringer Ingelheim. MAM declares grant support from Roche-Genentech for ARDS observational studies; and consulting income from Citius Pharmaceuticals, Johnson & Johnson, Gilead Pharmaceuticals, Plant Therapeutics, and Novartis Pharmaceuticals, outside the submitted work. All other authors declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Loss of secretory IgA (SIgA) is common in chronic obstructive pulmonary disease (COPD) small airways and likely contributes to disease progression. We hypothesized that loss of SIgA results from reduced expression of pIgR (polymeric immunoglobulin receptor), a chaperone protein needed for SIgA transcytosis, in the COPD small airway epithelium. pIgR-expressing cells were defined and quantified at single-cell resolution in human airways using RNA in situ hybridization, immunostaining, and single-cell RNA sequencing. Complementary studies in mice used immunostaining, primary murine tracheal epithelial cell culture, and transgenic mice with secretory or ciliated cell-specific knockout of pIgR. SIgA degradation by human neutrophil elastase or secreted bacterial proteases from nontypeable Haemophilus influenzae was evaluated in vitro . We found that secretory cells are the predominant cell type responsible for pIgR expression in human and murine airways. Loss of SIgA in small airways was not associated with a reduction in secretory cells but rather a reduction in pIgR protein expression despite intact PIGR mRNA expression. Neutrophil elastase and nontypeable H. influenzae -secreted proteases are both capable of degrading SIgA in vitro and may also contribute to a deficient SIgA immunobarrier in COPD. Loss of the SIgA immunobarrier in small airways of patients with severe COPD is complex and likely results from both pIgR-dependent defects in IgA transcytosis and SIgA degradation.

Rationale: Constrictive bronchiolitis (ConB) is a relatively rare and understudied form of lung disease whose underlying immunopathology remains incompletely defined. Objectives: Our objectives were to quantify specific pathological features that differentiate ConB from other diseases that affect the small airways and to investigate the underlying immune and inflammatory phenotype present in ConB. Methods: We performed a comparative histomorphometric analysis of small airways in lung biopsy samples collected from 50 soldiers with postdeployment ConB, 8 patients with sporadic ConB, 55 patients with chronic obstructive pulmonary disease, and 25 nondiseased control subjects. We measured immune and inflammatory gene expression in lung tissue using the NanoString nCounter Immunology Panel from six control subjects, six soldiers with ConB, and six patients with sporadic ConB. Measurements and Main Results: Compared with control subjects, we found shared pathological changes in small airways from soldiers with postdeployment ConB and patients with sporadic ConB, including increased thickness of the smooth muscle layer, increased collagen deposition in the subepithelium, and lymphocyte infiltration. Using principal-component analysis, we showed that ConB pathology was clearly separable both from control lungs and from small airway disease associated with chronic obstructive pulmonary disease. NanoString gene expression analysis from lung tissue revealed T-cell activation in both groups of patients with ConB with upregulation of proinflammatory pathways, including cytokine-cytokine receptor interactions, NF-κB (nuclear factor-κB) signaling, TLR (Toll-like receptor) signaling, T-cell receptor signaling, and antigen processing and presentation. Conclusions: These findings indicate shared immunopathology among different forms of ConB and suggest that an ongoing T-helper cell type 1-type adaptive immune response underlies airway wall remodeling in ConB.

Adipocyte iron overload is a maladaptation associated with obesity and insulin resistance. The objective of the current study was to determine whether and how adipose tissue macrophages (ATMs) regulate adipocyte iron concentrations and whether this is impacted by obesity. Using bone marrow-derived macrophages (BMDMs) polarized to M0, M1, M2, or metabolically activated (MMe) phenotypes, we showed that MMe BMDMs and ATMs from obese mice have reduced expression of several iron-related proteins. Furthermore, the bioenergetic response to iron in obese ATMs was hampered. ATMs from iron-injected lean mice increased their glycolytic and respiratory capacities, thus maintaining metabolic flexibility, while ATMs from obese mice did not. Using an isotope-based system, we found that iron exchange between BMDMs and adipocytes was regulated by macrophage phenotype. At the end of the co-culture, MMe macrophages transferred and received more iron from adipocytes than M0, M1, and M2 macrophages. This culminated in a decrease in total iron in MMe macrophages and an increase in total iron in adipocytes compared with M2 macrophages. Taken together, in the MMe condition, the redistribution of iron is biased toward macrophage iron deficiency and simultaneous adipocyte iron overload. These data suggest that obesity changes the communication of iron between adipocytes and macrophages and that rectifying this iron communication channel may be a novel therapeutic target to alleviate insulin resistance.

Unique challenges arise when conducting trials to evaluate therapies already in common clinical use, including difficulty enrolling patients owing to widespread open-label use of trial therapies and the need for large sample sizes to detect small but clinically meaningful treatment effects. Despite numerous successes in trials evaluating novel interventions such as vaccines, traditional explanatory trials have struggled to provide definitive answers to time-sensitive questions for acutely ill patients with COVID-19. Pragmatic trials, which can increase efficiency by allowing some or all trial procedures to be embedded into clinical care, are increasingly proposed as a means to evaluate therapies that are in common clinical use. In this Personal View, we use two concurrently conducted COVID-19 trials of hydroxychloroquine (the US ORCHID trial and the UK RECOVERY trial) to contrast the effects of explanatory and pragmatic trial designs on trial conduct, trial results, and the care of patients managed outside of clinical trials. In view of the potential advantages and disadvantages of explanatory and pragmatic trial designs, we make recommendations for their optimal use in the evaluation of therapies in the acute care setting., Competing Interests: Declaration of interests SMB reports personal fees from Hamilton for chairing a data safety and monitoring board (DSMB). EG reports grants and research contracts from Philips and Radiometer, consulting fees from Baxter, and speaker's fees from Edwards. MNG reports fees from Regeneron for DSMB participation; she has received support to attend board meetings for the American Thoracic Society. MOH reports fees from Elsevier for statistical peer review, from Berkeley Research Group, Pura Vida Investments, and Guidepoint Advisers for statistical consulting, and from the American Thoracic Society for contributions as a statistical editor of the Annals of the American Thoracic Society. SJ reports fees from Drager, Fisher-Paykel, Baxter, Medtronic, and Fresenius-Xenios for lectures and training courses for physicians and nurses. JCM reports consulting fees from Gilead, and travel support from the Bill and Melinda Gates Foundation. MAM reports research funding from Roche-Genentec; he has received fees from Novartis, Johnson & Johnson, and Citius for DSMB participation. TWR reports personal fees from Sanofi for DSMB participation, and consulting fees and stock options from Cumberland Pharmaceuticals for contributions on a consultancy basis as Director of Medical Affairs. LBW has received research contracts from Boehringer Ingelheim, Genentech, and CSL Behring; she reports consulting fees from Boehringer Ingelheim, Merck, Quark, Citius, and Foresee; she has served on a data monitoring committee for the SIGNET trial and on DSMBs for the INVENT COVID and CounterCovid trials. WHS has received research funding from Endpoint Health and Merck; he reports personal consulting fees from Aerpio Pharmaceuticals, Merck, and Baxter; he has received personal fees for DSMB participation from BioAegis. SPC reports consulting fees from Vir Biotechnology. The other authors declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Immune cells have been implicated in idiopathic pulmonary fibrosis (IPF), but the phenotypes and effector mechanisms of these cells remain incompletely characterized. We performed mass cytometry to quantify immune cell subsets in lungs of 12 patients with IPF and 15 organ donors without chronic lung disease and used existing single-cell RNA-sequencing data to investigate transcriptional profiles of immune cells overrepresented in IPF. Among myeloid cells, we found increased numbers of alveolar macrophages (AMØs) and dendritic cells (DCs) in IPF, as well as a subset of monocyte-derived DCs. In contrast, monocyte-like cells and interstitial macrophages were reduced in IPF. Transcriptomic profiling identified an enrichment for IFN-γ response pathways in AMØs and DCs from IPF, as well as antigen processing in DCs and phagocytosis in AMØs. Among T cells, we identified three subsets of memory T cells that were increased in IPF, including CD4 + and CD8 + resident memory T cells (T RM ) and CD8 + effector memory cells. The response to the IFN-γ pathway was enriched in CD4 T RM and CD8 T RM cells in IPF, together with T cell activation and immune response-regulating signaling pathways. Increased AMØs, DCs, and memory T cells were present in IPF lungs compared with control subjects. In IPF, these cells possess an activation profile indicating increased IFN-γ signaling and upregulation of adaptive immunity in the lungs. Together, these studies highlight critical features of the immunopathogenesis of IPF.

Sepsis is a devastating disease with high morbidity and mortality and no specific treatments. The pathophysiology of sepsis involves a hyperinflammatory response and release of damage-associated molecular patterns (DAMPs), including adenosine triphosphate (ATP), from activated and dying cells. Purinergic receptors activated by ATP have gained attention for their roles in sepsis, which can be pro- or anti-inflammatory depending on the context. Current data regarding the role of ATP-specific purinergic receptor P2X7 (P2X7R) in vascular function and inflammation during sepsis are conflicting, and its role on the endothelium has not been well characterized. In this study, we hypothesized that the P2X7R antagonist AZ 10606120 (AZ106) would prevent endothelial dysfunction during sepsis. As proof of concept, we first demonstrated the ability of AZ106 (10 µM) to prevent endothelial dysfunction in intact rat aorta in response to IL-1β, an inflammatory mediator upregulated during sepsis. Likewise, blocking P2X7R with AZ106 (10 µg/g) reduced the impairment of endothelial-dependent relaxation in mice subjected to intraperitoneal injection of cecal slurry (CS), a model of polymicrobial sepsis. However, contrary to our hypothesis, AZ106 did not improve microvascular permeability or injury, lung apoptosis, or illness severity in mice subjected to CS. Instead, AZ106 elevated spleen bacterial burden and circulating inflammatory markers. In conclusion, antagonism of P2X7R signaling during sepsis appears to disrupt the balance between its roles in inflammatory, antimicrobial, and vascular function., (© 2022 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)

Research and practice in critical care medicine have long been defined by syndromes, which, despite being clinically recognizable entities, are, in fact, loose amalgams of heterogeneous states that may respond differently to therapy. Mounting translational evidence-supported by research on respiratory failure due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-suggests that the current syndrome-based framework of critical illness should be reconsidered. Here we discuss recent findings from basic science and clinical research in critical care and explore how these might inform a new conceptual model of critical illness. De-emphasizing syndromes, we focus on the underlying biological changes that underpin critical illness states and that may be amenable to treatment. We hypothesize that such an approach will accelerate critical care research, leading to a richer understanding of the pathobiology of critical illness and of the key determinants of patient outcomes. This, in turn, will support the design of more effective clinical trials and inform a more precise and more effective practice at the bedside., (© 2022. Springer Nature America, Inc.)

Preclinical studies have shown that volatile anesthetics may have beneficial effects on injured lungs, and pilot clinical data support improved arterial oxygenation, attenuated inflammation, and decreased lung epithelial injury in patients with acute respiratory distress syndrome (ARDS) receiving inhaled sevoflurane compared to intravenous midazolam. Whether sevoflurane is effective in improving clinical outcomes among patients with ARDS is unknown, and the benefits and risks of inhaled sedation in ARDS require further evaluation. Here, we describe the SESAR (Sevoflurane for Sedation in ARDS) trial designed to address this question. SESAR is a two-arm, investigator-initiated, multicenter, prospective, randomized, stratified, parallel-group clinical trial with blinded outcome assessment designed to test the efficacy of sedation with sevoflurane compared to intravenous propofol in patients with moderate to severe ARDS. The primary outcome is the number of days alive and off the ventilator at 28 days, considering death as a competing event, and the key secondary outcome is 90 day survival. The planned enrollment is 700 adult participants at 37 French academic and non-academic centers. Safety and long-term outcomes will be evaluated, and biomarker measurements will help better understand mechanisms of action. The trial is funded by the French Ministry of Health, the European Society of Anaesthesiology, and Sedana Medical.

Background: Two acute respiratory distress syndrome (ARDS) subphenotypes (hyperinflammatory and hypoinflammatory) with distinct clinical and biological features and differential treatment responses have been identified using latent class analysis (LCA) in seven individual cohorts. To facilitate bedside identification of subphenotypes, clinical classifier models using readily available clinical variables have been described in four randomised controlled trials. We aimed to assess the performance of these models in observational cohorts of ARDS., Methods: In this observational, multicohort, retrospective study, we validated two machine-learning clinical classifier models for assigning ARDS subphenotypes in two observational cohorts of patients with ARDS: Early Assessment of Renal and Lung Injury (EARLI; n=335) and Validating Acute Lung Injury Markers for Diagnosis (VALID; n=452), with LCA-derived subphenotypes as the gold standard. The primary model comprised only vital signs and laboratory variables, and the secondary model comprised all predictors in the primary model, with the addition of ventilatory variables and demographics. Model performance was assessed by calculating the area under the receiver operating characteristic curve (AUC) and calibration plots, and assigning subphenotypes using a probability cutoff value of 0·5 to determine sensitivity, specificity, and accuracy of the assignments. We also assessed the performance of the primary model in EARLI using data automatically extracted from an electronic health record (EHR; EHR-derived EARLI cohort). In Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE; n=2813), a multinational, observational ARDS cohort, we applied a custom classifier model (with fewer variables than the primary model) to determine the prognostic value of the subphenotypes and tested their interaction with the positive end-expiratory pressure (PEEP) strategy, with 90-day mortality as the dependent variable., Findings: The primary clinical classifier model had an area under receiver operating characteristic curve (AUC) of 0·92 (95% CI 0·90-0·95) in EARLI and 0·88 (0·84-0·91) in VALID. Performance of the primary model was similar when using exclusively EHR-derived predictors compared with manually curated predictors (AUC=0·88 [95% CI 0·81-0·94] vs 0·92 [0·88-0·97]). In LUNG SAFE, 90-day mortality was higher in patients assigned the hyperinflammatory subphenotype than in those with the hypoinflammatory phenotype (414 [57%] of 725 vs 694 [33%] of 2088; p<0·0001). There was a significant treatment interaction with PEEP strategy and ARDS subphenotype (p=0·041), with lower 90-day mortality in the high PEEP group of patients with the hyperinflammatory subphenotype (hyperinflammatory subphenotype: 169 [54%] of 313 patients in the high PEEP group vs 127 [62%] of 205 patients in the low PEEP group; hypoinflammatory subphenotype: 231 [34%] of 675 patients in the high PEEP group vs 233 [32%] of 734 patients in the low PEEP group)., Interpretation: Classifier models using clinical variables alone can accurately assign ARDS subphenotypes in observational cohorts. Application of these models can provide valuable prognostic information and could inform management strategies for personalised treatment, including application of PEEP, once prospectively validated., Funding: US National Institutes of Health and European Society of Intensive Care Medicine., Competing Interests: Declaration of interests MC has a patent (ARCD P0535US.P2) pending to the University of Chicago (IL, USA) related to clinical deterioration risk prediction algorithms for patients admitted to hospital. MAM reports grants from Roche/Genentech, and personal fees from Johnson and Johnson, Novartis Pharmaceuticals, Gilead Pharmaceuticals, and Pliant Therapeutics, outside the submitted work. LBW reports grants and personal fees from Boehringer Ingelheim, outside the submitted work; grants from Genentech and CSL Behring, outside the submitted work; and personal fees from Merck, Citius, Quark, and Foresee, outside the submitted work. JGL reports personal fees from GlaxoSmithKline and Baxter, outside of the submitted work. GB reports grants and personal fees from Draeger Medical, and personal fees from Ge Healthcare, Hamilton Medical, and Flowmeter SPA, outside the submitted work. CSC reports grants and personal fees from Roche/Genentech and Bayer, outside the submitted work; personal fees from Quark Pharmaceuticals, Gen1e Life Sciences, and Vasomune, outside the submitted work; and grants from Quantum Leap Healthcare Collaborative, outside the submitted work. All other authors declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The pathophysiology of acute respiratory distress syndrome (ARDS) includes the accumulation of protein-rich pulmonary edema in the air spaces and interstitial areas of the lung, variable degrees of epithelial injury, variable degrees of endothelial barrier disruption, transmigration of leukocytes, alongside impaired fluid and ion clearance. These pathophysiological features are different between patients contributing to substantial biological heterogeneity. In this context, it is perhaps unsurprising that a wide range of pharmacological interventions targeting these pathophysiological processes have failed to improve patient outcomes. In this manuscript, our goal is to provide a narrative summary of the potential methods to capture the underlying biological heterogeneity of ARDS and discuss how this information could inform future ARDS redefinitions. We discuss what biological tests are available to identify patients with any of the following predominant biological patterns: (1) epithelial and/or endothelial injury, (2) protein rich pulmonary edema and (3) systemic or within lung inflammatory responses., (© 2022. The Author(s).)

Cigarette smoke is the primary cause of Chronic Obstructive Pulmonary Disorder (COPD). Cigarette smoke extract (CSE)-induced oxidative damage of the lungs results in mitochondrial dysfunction and apoptosis of epithelium. Mitochondrial cardiolipin (CL) present in the inner mitochondrial membrane plays an important role in mitochondrial function, wherein its fatty acid composition is regulated by lysocardiolipin acyltransferase (LYCAT). In this study, we investigated the role of LYCAT expression and activity in mitochondrial oxidative stress, mitochondrial dynamics, and lung epithelial cell apoptosis. LYCAT expression was increased in human lung specimens from smokers, and cigarette smoke-exposed-mouse lung tissues. Cigarette smoke extract (CSE) increased LYCAT mRNA levels and protein expression, modulated cardiolipin fatty acid composition, and enhanced mitochondrial fission in the bronchial epithelial cell line, BEAS-2B in vitro. Inhibition of LYCAT activity with a peptide mimetic, attenuated CSE-mediated mitochondrial (mt) reactive oxygen species (ROS), mitochondrial fragmentation, and apoptosis, while MitoTEMPO attenuated CSE-induced MitoROS, mitochondrial fission and apoptosis of BEAS-2B cells. Collectively, these findings suggest that increased LYCAT expression promotes MitoROS, mitochondrial dynamics and apoptosis of lung epithelial cells. Given the key role of LYCAT in mitochondrial cardiolipin remodeling and function, strategies aimed at inhibiting LYCAT activity and ROS may offer an innovative approach to minimize lung inflammation caused by cigarette smoke., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Women have higher prevalence of asthma compared with men. In asthma, allergic airway inflammation is initiated by IL-33 signaling through ST2, leading to increased IL-4, IL-5, and IL-13 production and eosinophil infiltration. Foxp3+ Tregs suppress and ST2+ Tregs promote allergic airway inflammation. Clinical studies showed that the androgen dehydroepiandrosterone (DHEA) reduced asthma symptoms in patients, and mouse studies showed that androgen receptor (AR) signaling decreased allergic airway inflammation. Yet the impact of AR signaling on lung Tregs remains unclear. Using AR-deficient and Foxp3 fate-mapping mice, we determined that AR signaling increased Treg suppression during Alternaria extract (Alt Ext; allergen) challenge by stabilizing Foxp3+ Tregs and limiting the number of ST2+ ex-Tregs and IL-13+ Th2 cells and ex-Tregs. AR signaling also decreased Alt Ext-induced ST2+ Tregs in mice by limiting expression of Gata2, a transcription factor for ST2, and by decreasing Alt Ext-induced IL-33 production from murine airway epithelial cells. We confirmed our findings in human cells where 5α-dihydrotestosterone (DHT), an androgen, decreased IL-33-induced ST2 expression in lung Tregs and decreased Alt Ext-induced IL-33 secretion in human bronchial epithelial cells. Our findings showed that AR signaling stabilized Treg suppressive function, providing a mechanism for the sex difference in asthma.

Mouse models of acute lung injury (ALI) have been instrumental for studies of the biological underpinnings of lung inflammation and permeability, but murine models of sepsis generate minimal lung injury. Our goal was to create a murine sepsis model of ALI that reflects the inflammation, lung edema, histological abnormalities, and physiological dysfunction that characterize ALI. Using a cecal slurry (CS) model of polymicrobial abdominal sepsis and exposure to hyperoxia (95%), we systematically varied the timing and dose of the CS injection, fluids and antibiotics, and dose of hyperoxia. We found that CS alone had a high mortality rate that was improved with the addition of antibiotics and fluids. Despite this, we did not see evidence of ALI as measured by bronchoalveolar lavage (BAL) cell count, total protein, C-X-C motif chemokine ligand 1 (CXCL-1) or by lung wet:dry weight ratio. Addition of hyperoxia [95% fraction of inspired oxygen ([Formula: see text])] to CS immediately after CS injection increased BAL cell counts, CXCL-1, and lung wet:dry weight ratio but was associated with 40% mortality. Splitting the hyperoxia treatment into two 12-h exposures (0-12 h and 24-36 h) after CS injection increased survival to 75% and caused significant lung injury compared with CS alone as measured by increased BAL total cell count (92,500 vs. 240,000, P = 0.0004), BAL protein (71 vs. 103 µg/mL, P = 0.0030), and lung wet:dry weight ratio (4.5 vs. 5.5, P = 0.0005), and compared with sham as measured by increased BAL CXCL-1 (20 vs. 2,372 pg/mL, P < 0.0001) and histological lung injury score (1.9 vs. 4.2, P = 0.0077). In addition, our final model showed evidence of lung epithelial [increased BAL and plasma receptor for advanced glycation end products (RAGE)] and endothelial (increased Syndecan-1 and sulfated glycosaminoglycans) injury. In conclusion, we have developed a clinically relevant mouse model of sepsis-induced ALI using intraperitoneal injection of CS, antibiotics and fluids, and hyperoxia. This clinically relevant model can be used for future studies of sepsis-induced ALI.

Acute respiratory distress syndrome (ARDS) is a common cause of respiratory failure yet has few pharmacologic therapies, reflecting the mechanistic heterogeneity of lung injury. We hypothesized that damage to the alveolar epithelial glycocalyx, a layer of glycosaminoglycans interposed between the epithelium and surfactant, contributes to lung injury in patients with ARDS. Using mass spectrometry of airspace fluid noninvasively collected from mechanically ventilated patients, we found that airspace glycosaminoglycan shedding (an index of glycocalyx degradation) occurred predominantly in patients with direct lung injury and was associated with duration of mechanical ventilation. Male patients had increased shedding, which correlated with airspace concentrations of matrix metalloproteinases. Selective epithelial glycocalyx degradation in mice was sufficient to induce surfactant dysfunction, a key characteristic of ARDS, leading to microatelectasis and decreased lung compliance. Rapid colorimetric quantification of airspace glycosaminoglycans was feasible and could provide point-of-care prognostic information to clinicians and/or be used for predictive enrichment in clinical trials.