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Background: Sepsis-associated destruction of the pulmonary microvascular endothelial glycocalyx (EGCX) creates a vulnerable endothelial surface, contributing to the development of acute respiratory distress syndrome (ARDS). Constituents of the EGCX shed into circulation, glycosaminoglycans and proteoglycans, may serve as biomarkers of endothelial dysfunction. We sought to define the patterns of plasma EGCX degradation products in children with sepsis-associated pediatric ARDS (PARDS), and test their association with clinical outcomes., Methods: We retrospectively analyzed a prospective cohort (2018-2020) of children (≥1 month to <18 years of age) receiving invasive mechanical ventilation for acute respiratory failure for ≥72 h. Children with and without sepsis-associated PARDS were selected from the parent cohort and compared. Blood was collected at time of enrollment. Plasma glycosaminoglycan disaccharide class (heparan sulfate, chondroitin sulfate, and hyaluronan) and sulfation subtypes (heparan sulfate and chondroitin sulfate) were quantified using liquid chromatography tandem mass spectrometry. Plasma proteoglycans (syndecan-1) were measured through an immunoassay., Results: Among the 39 mechanically ventilated children (29 with and 10 without sepsis-associated PARDS), sepsis-associated PARDS patients demonstrated higher levels of heparan sulfate (median 639 ng/mL [interquartile range, IQR 421-902] vs 311 [IQR 228-461]) and syndecan-1 (median 146 ng/mL [IQR 32-315] vs 8 [IQR 8-50]), both p  = 0.01. Heparan sulfate subtype analysis demonstrated greater proportions of N -sulfated disaccharide levels among children with sepsis-associated PARDS ( p =  0.01). Increasing N- sulfated disaccharide levels by quartile were associated with severe PARDS (n = 9/29) with the highest quartile including >60% of the severe PARDS patients (test for trend, p  = 0.04). Higher total heparan sulfate and N- sulfated disaccharide levels were independently associated with fewer 28-day ventilator-free days in children with sepsis-associated PARDS (all p <  0.05)., Conclusions: Children with sepsis-associated PARDS exhibited higher plasma levels of heparan sulfate disaccharides and syndecan-1, suggesting that EGCX degradation biomarkers may provide insights into endothelial dysfunction and PARDS pathobiology., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objectives: Soluble receptor for advanced glycation end products is a known plasma marker of alveolar epithelial injury. However, RAGE is also expressed on cell types beyond the lung, and its activation leads to up-regulation of pro-inflammatory mediators. We sought to examine the relationship between plasma soluble receptor for advanced glycation end products and primary pulmonary dysfunction, extrapulmonary organ dysfunction, and mortality in pediatric acute respiratory distress syndrome patients at two early time points following acute respiratory distress syndrome diagnosis and compare these results to plasma surfactant protein-D, a marker of pure alveolar epithelial injury., Design: Prospective observational study., Setting: Five academic PICUs., Patients: Two hundred fifty-eight pediatric patients 30 days to 18 years old meeting Berlin Criteria for acute respiratory distress syndrome., Interventions: None., Measurements and Main Results: Plasma was collected for soluble receptor for advanced glycation end products and surfactant protein-D measurements within 24 hours (day 1) and 48 to 72 hours (day 3) after acute respiratory distress syndrome diagnosis. Similar to surfactant protein-D, plasma soluble receptor for advanced glycation end products was associated with a higher oxygenation index (p < 0.01) and worse lung injury score (p < 0.001) at the time of acute respiratory distress syndrome diagnosis. However, unlike surfactant protein-D, plasma soluble receptor for advanced glycation end products was associated with worse extrapulmonary Pediatric Logistic Organ Dysfunction score during ICU stay (day 3; p < 0.01) and positively correlated with plasma levels of interleukin-6 (p < 0.01), tumor necrosis factor-α (p < 0.01), and angiopoietin-2 (p < 0.01). Among children with indirect lung injury, plasma soluble receptor for advanced glycation end products was associated with mortality independent of age, sex, race, cancer/bone marrow transplant, and Pediatric Risk of Mortality score (day 3; odds ratio, 3.14; 95% CI, 1.46-6.75; p < 0.01)., Conclusions: Unlike surfactant protein-D, which is primarily localized to the alveolar epithelium plasma soluble receptor for advanced glycation end products is systemically expressed and correlates with markers of inflammation, extrapulmonary multiple organ dysfunction, and death in pediatric acute respiratory distress syndrome with indirect lung injury. This suggests that unlike surfactant protein-D, soluble receptor for advanced glycation end products is a multifaceted marker of alveolar injury and increased inflammation and that receptor for advanced glycation end products activation may contribute to the pathogenesis of multiple organ failure among children with indirect acute respiratory distress syndrome., Competing Interests: Drs. Lim’s and Sapru’s institutions received funding from the National Institutes of Health (NIH). Drs. Lim, Zinter, Alkhouli, and Sapru received support for article research from the NIH. Drs. Zinter’s and Alkhouli’s institution received funding from the National Heart, Lung, and Blood Institute (K23HL146936). Dr. Zinter’s institution received funding from the National Institute of Child Health and Human Development (K12HD000850); he disclosed the off-label product use of anti-receptor for advanced glycation end products antibodies. Dr. Matthay’s institution received funding from Roche-Genetec; he received funding from Citius Pharmaceuticals and Novartis Pharmaceuticals. The remaining authors have disclosed that they do not have any potential conflicts of interest., (Copyright © 2022 by the Society of Critical Care Medicine and Wolters Kluwer Health, Inc. All Rights Reserved.)

Mechanical ventilation (MV) and oxygen therapy (hyperoxia; HO) comprise the cornerstones of life-saving interventions for patients with acute respiratory distress syndrome (ARDS). Unfortunately, the side effects of MV and HO include exacerbation of lung injury by barotrauma, volutrauma, and propagation of lung inflammation. Despite significant improvements in ventilator technologies and a heightened awareness of oxygen toxicity, besides low tidal volume ventilation few if any medical interventions have improved ARDS outcomes over the past two decades. We are lacking a comprehensive understanding of mechanotransduction processes in the healthy lung and know little about the interactions between simultaneously activated stretch-, HO-, and cytokine-induced signaling cascades in ARDS. Nevertheless, as we are unraveling these mechanisms we are gathering increasing evidence for the importance of stretch-activated ion channels (SACs) in the activation of lung-resident and inflammatory cells. In addition to the discovery of new SAC families in the lung, e.g., two-pore domain potassium channels, we are increasingly assigning mechanosensing properties to already known Na(+), Ca(2+), K(+), and Cl(-) channels. Better insights into the mechanotransduction mechanisms of SACs will improve our understanding of the pathways leading to ventilator-induced lung injury and lead to much needed novel therapeutic approaches against ARDS by specifically targeting SACs. This review 1) summarizes the reasons why the time has come to seriously consider SACs as new therapeutic targets against ARDS, 2) critically analyzes the physiological and experimental factors that currently limit our knowledge about SACs, and 3) outlines the most important questions future research studies need to address., (Copyright © 2016 the American Physiological Society.)

Objective: Low-dose methylprednisolone therapy in adults with early acute respiratory distress syndrome reduces systemic inflammation, duration of mechanical ventilation, and ICU length of stay. We report a pilot randomized trial of glucocorticoid treatment in early pediatric acute respiratory distress syndrome., Design: Double-blind, placebo-controlled randomized clinical trial., Setting: Le Bonheur Children's Hospital, Memphis, TN., Patients: Children (0-18 yr) with acute respiratory distress syndrome undergoing mechanical ventilation., Interventions: Patients were randomly assigned to steroid or placebo groups within 72 hours of intubation. IV methylprednisolone administered as loading dose (2 mg/kg) and continuous infusions (1 mg/kg/d) on days 1-7 and then tapered over days 8-14. Both groups were ventilated according to the Acute Respiratory Distress Syndrome Network protocol modified for children. Daily surveillance was performed for adverse effects., Measurements and Main Results: Thirty-five patients were randomized to the steroid (n = 17, no death) and placebo groups (n = 18, two deaths). No differences occurred in length of mechanical ventilation, ICU stay, hospital stay, or mortality between the two groups. At baseline, higher plateau pressures (p = 0.006) and lower Pediatric Logistic Organ Dysfunction scores (p = 0.04) occurred in the steroid group; other characteristics were similar. Despite higher plateau pressures on days 1 (p = 0.006) and 2 (p = 0.025) due to poorer lung compliance in the steroid group, they had lower PaCO2 values on days 2 (p = 0.009) and 3 (p = 0.014), higher pH values on day 2 (p = 0.018), and higher PaO2/FIO2 ratios on days 8 (p = 0.047) and 9 (p = 0.002) compared with the placebo group. Fewer patients in the steroid group required treatment for postextubation stridor (p = 0.04) or supplemental oxygen at ICU transfer (p = 0.012). Steroid therapy was not associated with detectable adverse effects., Conclusion: This study demonstrates the feasibility of administering low-dose glucocorticoid therapy and measuring clinically relevant outcomes in pediatric acute respiratory distress syndrome. Changes in oxygenation and/or ventilation are consistent with early acute respiratory distress syndrome pathophysiology and results of similar clinical trials in adults. We propose and design a larger randomized trial to define the role of glucocorticoid therapy in pediatric acute respiratory distress syndrome.

Acute Respiratory Distress Syndrome remains challenging partially because the underlying mechanisms are poorly understood. While inflammation and loss of barrier function are associated with disease progression, our understanding of the biophysical mechanisms associated with ventilator-associated lung injury is incomplete. In this line of thinking, we recently showed that changes in the F-actin content and deformability of AECs lead to cell detachment with mechanical stretch. Elsewhere, we discovered that cytokine secretion and proliferation were regulated in part by the stretch-activated 2-pore domain K(+) (K2P) channel TREK-1 in alveolar epithelial cells (AECs). As such, the aim of the current study was to determine whether TREK-1 regulated the mechanobiology of AECs through cytoskeletal remodeling and cell detachment. Using a TREK-1-deficient human AEC line (A549), we examined the cytoskeleton by confocal microscopy and quantified differences in the F-actin content. We used nano-indentation with an atomic force microscope to measure the deformability of cells and detachment assays to quantify the level of injury in our monolayers. We found a decrease in F-actin and an increase in deformability in TREK-1 deficient cells compared to control cells. Although total vinculin and focal adhesion kinase (FAK) levels remained unchanged, focal adhesions appeared to be less prominent and phosphorylation of FAK at the Tyr(925) residue was greater in TREK-1 deficient cells. TREK-1 deficient cells have less F-actin and are more deformable making them more resistant to stretch-induced injury.

BACKGROUND: Sepsis-associated destruction of the pulmonary microvascular endothelial glycocalyx (EGCX) creates a vulnerable endothelial surface, contributing to the development of acute respiratory distress syndrome (ARDS). Constituents of the EGCX shed into circulation, glycosaminoglycans and proteoglycans, may serve as biomarkers of endothelial dysfunction. We sought to define the patterns of plasma EGCX degradation products in children with sepsis-associated pediatric ARDS (PARDS), and test their association with clinical outcomes. METHODS: We retrospectively analyzed a prospective cohort (2018-2020) of children (≥1 month to 60% of the severe PARDS patients (test for trend, p = 0.04). Higher total heparan sulfate and N-sulfated disaccharide levels were independently associated with fewer 28-day ventilator-free days in children with sepsis-associated PARDS (all p