Evolving epidemiology and definitions of the acute respiratory distress syndrome and early acute lung injury

Monochasma savatieri Franch. protects against acute lung injury via α7nAChR-TLR4/NF-κB p65 signaling pathway based on integrated pharmacology analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Acute lung injury (ALI) is a life-threatening condition with high morbidity and mortality, underscoring the urgent need for novel treatments. Monochasma savatieri Franch. (LRC) is commonly used clinically to treat wind-heat cold, bronchitis, acute pneumonia and acute gastroenteritis. However, its role in the treatment of ALI and its mechanism of action are still unclear.

AIM OF THE STUDY

This study aimed to demonstrate the pharmacological effects and underlying mechanisms of LRC extract, and provide important therapeutic strategies and theoretical basis for ALI.

MATERIALS AND METHODS

In this study, a research paradigm of integrated pharmacology combining histopathological analysis, network pharmacology, metabolomics, and biochemical assays was used to elucidate the mechanisms underlaying the effects of LRC extract on LPS-induced ALI in BALB/c mice.

RESULTS

The research findings demonstrated that LRC extract significantly alleviated pathological damage in lung tissues and inhibited apoptosis in alveolar epithelial cells, and the main active components were luteolin, isoacteoside, and aucubin. Lung tissue metabolomic and immunohistochemical methods confirmed that LRC extract could restore metabolic disorders in ALI mice by correcting energy metabolism imbalance, activating cholinergic anti-inflammatory pathway (CAP), and inhibiting TLR4/NF-κB signaling pathway.

CONCLUSIONS

This study showed that LRC extract inhibited the occurrence and development of ALI inflammation by promoting the synthesis of antioxidant metabolites, balancing energy metabolism, activating CAP and suppressing the α7nAChR-TLR4/NF-κB p65 signaling pathway. In addition, our study provided an innovative research model for exploring the effective ingredients and mechanisms of traditional Chinese medicine. To the best of our knowledge, this is the first report describing the protective effects of LRC extract in LPS-induced ALI mice.

Endothelial dysfunction triggers acute respiratory distress syndrome in patients with sepsis: a narrative review

Acute respiratory distress syndrome (ARDS) is a severe organ failure occurring mainly in critically ill patients as a result of different types of insults such as sepsis, trauma or aspiration. Sepsis is the main cause of ARDS, and it contributes to a high mortality and resources consumption both in hospital setting and in the community. ARDS develops mainly an acute respiratory failure with severe and often refractory hypoxemia. ARDS also has long term implications and sequelae. Endothelial damage plays an important role in the pathogenesis of ARDS. Understanding the mechanisms of ARDS presents opportunities for novel diagnostic and therapeutic targets. Biochemical signals can be used in concert to identify and classify patients into ARDS phenotypes allowing earlier effective treatment with personalised therapies. This is a narrative review where we aimed to flesh out the pathogenetic mechanisms and heterogeneity of ARDS. We examine the links between endothelium damage and its contribution to organ failure. We have also investigated future strategies for treatment with a special emphasis in endothelial damage.

Inhibition of a Microbiota-derived Peptide Ameliorates Established Acute Lung Injury

Acute lung injury is a clinical syndrome characterized by a diffuse lung inflammation that commonly evolves into acute respiratory distress syndrome and respiratory failure. The lung microbiota is involved in the pathogenesis of acute lung injury. Corisin, a proapoptotic peptide derived from the lung microbiota, plays a role in acute lung injury and acute exacerbation of pulmonary fibrosis. Preventive therapeutic intervention with a monoclonal anticorisin antibody inhibits acute lung injury in mice. However, whether inhibition of corisin with the antibody ameliorates established acute lung injury is unknown. Here, the therapeutic effectiveness of the anticorisin antibody in already established acute lung injury in mice was assessed. Lipopolysaccharide was used to induce acute lung injury in mice. After causing acute lung injury, the mice were treated with a neutralizing anticorisin antibody. Mice treated with the antibody showed significant improvement in lung radiological and histopathological findings, decreased lung infiltration of inflammatory cells, reduced markers of lung tissue damage, and inflammatory cytokines in bronchoalveolar lavage fluid compared to untreated mice. In addition, the mice treated with anticorisin antibody showed significantly increased expression of antiapoptotic proteins with decreased caspase-3 activation in the lungs compared to control mice treated with an irrelevant antibody. In conclusion, these observations suggest that the inhibition of corisin is a novel and promising approach for treating established acute lung injury.

Dexamethasone for the treatment of acute respiratory distress syndrome: A systematic review and meta-analysis

BACKGROUND

This meta-analysis aimed to evaluate the efficacy and safety of dexamethasone in the treatment of acute respiratory distress syndrome (ARDS).

METHODS

A systematic search of electronic databases was carried out from inception to May 1, 2022, including PUBMED, EMBASE, Cochrane Library, Wangfang, VIP, and CNKI. Other searches were also checked for dissertations/theses and the reference lists of the included studies. Two team members examined all citations and selected eligible articles. Randomized controlled trials (RCTs) reporting the efficacy and safety of dexamethasone for the treatment of ARDS were included, and the quality of eligible RCTs was assessed using the Cochrane Risk of Bias Tool. If necessary, we conducted data synthesis and meta-analysis. The primary outcome was all-cause mortality. Secondary outcomes were mechanical ventilation duration (day), ventilator-free status at 28 days; intensive care unit (ICU) free (day), ICU mortality, hospital mortality, sequential organ failure assessment (SOFA) as mean and range, SOFA as No. of patients, peak airway pressure (cmH2O), arterial oxygen pressure (mm Hg), days with PaO2 > 10kPa, PaO2, and the occurrence rate of adverse events.

RESULTS

Four studies involving 702 patients were included in this analysis. This study showed that dexamethasone could significantly reduce all-cause mortality (odds ratio (OR) = 0.62, 95% confidence interval (CI) [0.44, 0.88], I2 = 30%, P < .001), and decrease ventilator-free status at 28 days (MD = 3.65, 95% CI [1.49, 5.80], I2 = 51%, P < .001). No significant differences in occurrence rates of adverse events were found between dexamethasone and routine or standard care.

CONCLUSIONS

Evidence from the meta-analysis suggests that dexamethasone is an effective and relatively safe treatment for all-cause mortality and ventilator-free status at 28 days in patients with ARDS. Owning to the small number of eligible RCTs, the conclusions of present study are warranted in the future study.

Integrated Pharmacology Reveals the Molecular Mechanism of Gegen Qinlian Decoction Against Lipopolysaccharide-induced Acute Lung Injury

ALI is a severe inflammatory disease of the lungs. In previous studies, we found that GQD was effective against ALI, but specific molecular mechanism is still unclear. Therefore, this study was to examine effect of GQD on LPS-induced ALI rats and underlying mechanisms using multi-omics and molecular methods. The results showed that GQD significantly improved lung tissue damage, reduced pulmonary edema, inhibited MPO activity, and improved respiratory function in ALI rat. Additionally, GQD significantly reduced the levels of TNF-α, IL-1β, and IL-6 in serum and BALF. Furthermore, metabolomic analysis showed that GQD reduced pulmonary inflammation by improving metabolic remodeling. Moreover, transcriptomic analysis showed that GQD inhibited the activation of complement pathway and regulated Th17 and Treg cells balance. Additionally, GQD inhibited the expression of C3, C5a, and IL-17, and promoted the expression of TGF-β and CYP1A1 at the mRNA and protein levels. Gut microbial assay showed that GQD treatment increased the relative abundance of Firmicutes and their genera in intestinal microbiota, and increased short-chain fatty acids concentration. Overall, GQD treated ALI by improving metabolic remodeling, affecting immune-related pathways and regulating intestinal microbiota. This study provides a solid scientific basis for promoting the clinical use of GQD in treating ALI.

Endothelial Damage in Acute Respiratory Distress Syndrome

The pulmonary endothelium is a metabolically active continuous monolayer of squamous endothelial cells that internally lines blood vessels and mediates key processes involved in lung homoeostasis. Many of these processes are disrupted in acute respiratory distress syndrome (ARDS), which is marked among others by diffuse endothelial injury, intense activation of the coagulation system and increased capillary permeability. Most commonly occurring in the setting of sepsis, ARDS is a devastating illness, associated with increased morbidity and mortality and no effective pharmacological treatment. Endothelial cell damage has an important role in the pathogenesis of ARDS and several biomarkers of endothelial damage have been tested in determining prognosis. By further understanding the endothelial pathobiology, development of endothelial-specific therapeutics might arise. In this review, we will discuss the underlying pathology of endothelial dysfunction leading to ARDS and emerging therapies. Furthermore, we will present a brief overview demonstrating that endotheliopathy is an important feature of hospitalised patients with coronavirus disease-19 (COVID-19).

Alleviation of Lipopolysaccharide-Induced Acute Respiratory Distress Syndrome in Rats by Yiqi Huayu Jiedu Decoction: A Tandem Mass Tag-Based Proteomics Study

Background

To study the effect of Yiqi Huayu Jiedu Decoction (YQHYJD) on protein expression in the lung tissue of acute respiratory distress syndrome (ARDS) rats and to explore the underlying molecular therapeutic mechanism of YQHYJD.

Methods

Sprague Dawley rats were administered with YQHYJD by oral gavage for 1 week. The rats were injected with lipopolysaccharide (LPS) to induce ARDS. The lung injury was assessed pathologically. Differentially expressed proteins (DEPs) were screened by quantitative proteomics and analyzed using bioinformatic tools, such as Metascape and Kyoto Encyclopedia of Genes and Genomes (KEGG) mapper. DEPs were verified by parallel reaction monitoring (PRM).

Results

YQHYJD alleviated the LPS-induced pathological damage of lung tissue in rats. There were 134 DEPs among the YQHYJD treatment and model groups. The Genomes pathway analyses revealed that the DEPs were closely related to immune system pathway. The mass spectrometry analysis revealed that YQHYJD exhibits a protective effect on lung tissue by significantly upregulating hematopoietic cell kinase (Hck), phospholipid phosphatase 3 (Plpp3), myristoylated-alanine rich C-kinase substrate (Marcks), and Actin-related protein 2/3 complex subunit 2 (Arpc2), which are related to Fc gamma receptor-mediated phagocytosis pathway.

Conclusion

YQHYJD can alleviate the lung injury of ARDS rats by regulating the Fc gamma receptor-mediated phagocytosis pathway, which is related to immune system.

Lung epithelial cell-derived IL-25 negatively regulates LPS-induced exosome release from macrophages

BACKGROUND

Acute lung injury (ALI) is a major component of multiple organ dysfunction syndrome (MODS) following pulmonary and systemic infection. Alveolar macrophages (AMϕ) are at the center of ALI pathogenesis. Emerging evidence has shown that cell-cell interactions in the lungs play an important regulatory role in the development of acute lung inflammation. However, the underneath mechanisms remain poorly addressed. In this study, we explore a novel function of lung epithelial cells (LEPCs) in regulating the release of exosomes from AMϕ following LPS stimulation.

METHODS

For the in vivo experiments, C57BL/6 wildtype (WT) mice were treated with lipopolysaccharide (LPS) (2 mg/kg B.W.) in 0.2 ml of saline via intratracheal aerosol administration. Bronchoalveolar lavage fluid was collected at 0-24 h after LPS treatment, and exosomes derived from AMϕ were measured. For the in vitro studies, LEPCs and bone marrow-derived Mϕ (BMDM) were isolated from WT or TLR4^-/- mice and were then cocultured in the Transwell™ system. After coculture for 0-24 h, the BMDM and supernatant were harvested for the measurement of exosomes and cytokines.

RESULTS

We demonstrate that LPS induces macrophages (Mϕ) to release exosomes, which are then internalized by neighboring Mϕ to promote TNF-α expression. The secreted interleukin (IL)-25 from LEPCs downregulates Rab27a and Rab27b expression in Mϕ, resulting in suppressed exosome release and thereby attenuating exosome-induced TNF-α expression and secretion.

CONCLUSION

These findings reveal a previously unidentified crosstalk pathway between LEPCs and Mϕ that negatively regulates the inflammatory responses of Mϕ to LPS. Modulating IL-25 signaling and targeting exosome release may present a new therapeutic strategy for the treatment of ALI.

Alternative and Natural Therapies for Acute Lung Injury and Acute Respiratory Distress Syndrome

Introduction

Acute respiratory distress syndrome (ARDS) is a complex clinical syndrome characterized by acute inflammation, microvascular damage, and increased pulmonary vascular and epithelial permeability, frequently resulting in acute respiratory failure and death. Current best practice for ARDS involves “lung-protective ventilation,” which entails low tidal volumes and limiting the plateau pressures in mechanically ventilated patients. Although considerable progress has been made in understanding the pathogenesis of ARDS, little progress has been made in the development of specific therapies to combat injury and inflammation.

Areas Covered

In recent years, several natural products have been studied in experimental models and have been shown to inhibit multiple inflammatory pathways associated with acute lung injury and ARDS at a molecular level. Because of the pleiotropic effects of these agents, many of them also activate antioxidant pathways through nuclear factor erythroid-related factor 2, thereby targeting multiple pathways. Several of these agents are prescribed for treatment of inflammatory conditions in the Asian subcontinent and have shown to be relatively safe.

Expert Commentary

Here we review natural remedies shown to attenuate lung injury and inflammation in experimental models. Translational human studies in patients with ARDS may facilitate treatment of this devastating disease.

Pulmonary vascular endothelium: the orchestra conductor in respiratory diseases

The European Respiratory Society (ERS) Research Seminar entitled “Pulmonary vascular endothelium: orchestra conductor in respiratory diseases - highlights from basic research to therapy” brought together international experts in dysfunctional pulmonary endothelium, from basic science to translational medicine, to discuss several important aspects in acute and chronic lung diseases. This review will briefly sum up the different topics of discussion from this meeting which was held in Paris, France on October 27–28, 2016. It is important to consider that this paper does not address all aspects of endothelial dysfunction but focuses on specific themes such as: 1) the complex role of the pulmonary endothelium in orchestrating the host response in both health and disease (acute lung injury, chronic obstructive pulmonary disease, high-altitude pulmonary oedema and pulmonary hypertension); and 2) the potential value of dysfunctional pulmonary endothelium as a target for innovative therapies.

β-Nitrostyrene derivatives attenuate LPS-mediated acute lung injury via the inhibition of neutrophil-platelet interactions and NET release

Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are high-mortality and life-threatening diseases that are associated with neutrophil activation and accumulation within lung tissue. Emerging evidence indicates that neutrophil-platelet aggregates (NPAs) at sites of injury increase acute inflammation and contribute to the development of ALI. Although numerous studies have increased our understanding of the pathophysiology of ALI, there is still a lack of innovative and useful treatments that reduce mortality, emphasizing that there is an urgent need for novel treatment strategies. In this study, a new series of small compounds of β-nitrostyrene derivatives (BNSDs) were synthesized, and their anti-inflammatory bioactivities on neutrophils and platelets were evaluated. The new small compound C7 modulates neutrophil function by inhibiting superoxide generation and elastase release. Compound C7 elicits protective effects on LPS-induced paw edema and acute lung injury via the inhibition of neutrophil accumulation, proinflammatory mediator release, platelet aggregation, myeloperoxidase activity, and neutrophil extracellular trap (NET) release. NET formation was identified as the bridge for the critical interactions between neutrophils and platelets by confocal microscopy and flow cytometry. This research provides new insights for elucidating the complicated regulation of neutrophils and platelets in ALI and sheds further light on future drug development strategies for ALI/ARDS and acute inflammatory diseases.

Sevoflurane Posttreatment Attenuates Lung Injury Induced by Oleic Acid in Dogs

BACKGROUND

In animal models, both sevoflurane and propofol protect against acute lung injury (ALI), especially when administered prior to ALI onset. We hypothesized that when compared to propofol, sevoflurane administration after the onset of acute respiratory distress syndrome would mitigate oleic acid (OA)-induced ALI in dogs.

METHODS

Dogs were randomly assigned to receive intravenous OA to induce ALI (n = 7 for each OA group) or saline as an OA control (n = 6 for each control). Dogs were then mechanically ventilated for 6 hours during which propofol (5 mg/kg/h) or sevoflurane (1.0 minimum alveolar concentration) was administered for sedation. Study end points included PO2/FIO2 ratio, pulmonary arterial pressure, pulmonary edema, histology, and tumor nuclear factor-α.

RESULTS

In OA-injured animals, oxygenation was worse at 1, 2, 3, and 4 hours after 6-hour mechanical ventilation in sevoflurane-sedated animals compared with propofol-sedated animals, with mean difference (95% confidence interval; propofol minus sevoflurane) of 75 (39-111), 87 (55-119), 66 (44-87), and 67 (27-107) mm Hg for the respective time points. However, sevoflurane reduced the elevated pulmonary arterial pressure and vascular resistance, attenuated pulmonary edema as evidenced by reduced extravascular lung water index, and decreased tumor nuclear factor-α and diffuse alveolar damage score compared with propofol in the OA-injured lungs.

CONCLUSIONS

When compared with propofol, sevoflurane attenuates OA-induced lung damage. However, despite this effect on lung histology and inflammation, sevoflurane worsened oxygenation in OA-induced ALI, possibly via inhibition of hypoxic pulmonary vasoconstriction.

Pulmonary Arterial Compliance in Acute Respiratory Distress Syndrome: Clinical Determinants and Association With Outcome From the Fluid and Catheter Treatment Trial Cohort

OBJECTIVES

Pulmonary vascular dysfunction is associated with adverse prognosis in patients with the acute respiratory distress syndrome; however, the prognostic impact of pulmonary arterial compliance in acute respiratory distress syndrome is not established.

DESIGN, SETTING, PATIENTS

We performed a retrospective analysis of 363 subjects with acute respiratory distress syndrome who had complete baseline right heart catheterization data from the Fluid and Catheter Treatment Trial to test whether pulmonary arterial compliance at baseline and over the course of treatment predicted mortality.

MAIN RESULTS

Baseline pulmonary arterial compliance (hazard ratio, 1.18 per interquartile range of 1/pulmonary arterial compliance; 95% CI, 1.02-1.37; p = 0.03) and pulmonary vascular resistance (hazard ratio, 1.28 per interquartile range; 95% CI, 1.07-1.53; p = 0.006) both modestly predicted 60-day mortality. Baseline pulmonary arterial compliance remained predictive of mortality when pulmonary vascular resistance was in the normal range (p = 0.02). Between day 0 and day 3, pulmonary arterial compliance increased in acute respiratory distress syndrome survivors and remained unchanged in nonsurvivors, whereas pulmonary vascular resistance did not change in either group. The resistance-compliance product (resistance-compliance time) increased in survivors compared with nonsurvivors, suggesting improvements in right ventricular load.

CONCLUSIONS

Baseline measures of pulmonary arterial compliance and pulmonary vascular resistance predict mortality in acute respiratory distress syndrome, and pulmonary arterial compliance remains predictive even when pulmonary vascular resistance is normal. Pulmonary arterial compliance and right ventricular load improve over time in acute respiratory distress syndrome survivors. Future studies should assess the impact of right ventricular protective acute respiratory distress syndrome treatment on right ventricular afterload and outcome.

Recent advances in understanding and treating ARDS

Acute respiratory distress syndrome represents a complex syndrome with considerable morbidity and mortality, for which there exist no targeted treatment strategies. However, recent advances in clinical care have improved outcomes, and we will review a number of these approaches here, as well as explore the mechanisms underlying the benefit of intervention that might point us in the direction toward future treatment and preventive strategies for this devastating syndrome.

Viral Infection in the Development and Progression of Pediatric Acute Respiratory Distress Syndrome

Viral infections are an important cause of pediatric acute respiratory distress syndrome (ARDS). Numerous viruses, including respiratory syncytial virus (RSV) and influenza A (H1N1) virus, have been implicated in the progression of pneumonia to ARDS; yet the incidence of progression is unknown. Despite acute and chronic morbidity associated with respiratory viral infections, particularly in "at risk" populations, treatment options are limited. Thus, with few exceptions, care is symptomatic. In addition, mortality rates for viral-related ARDS have yet to be determined. This review outlines what is known about ARDS secondary to viral infections including the epidemiology, the pathophysiology, and diagnosis. In addition, emerging treatment options to prevent infection, and to decrease disease burden will be outlined. We focused on RSV and influenza A (H1N1) viral-induced ARDS, as these are the most common viruses leading to pediatric ARDS, and have specific prophylactic and definitive treatment options.

Endothelial-Leukocyte Interaction in Severe Malaria: Beyond the Brain

Malaria is the most important parasitic disease worldwide, accounting for 1 million deaths each year. Severe malaria is a systemic illness characterized by dysfunction of brain tissue and of one or more peripheral organs as lungs and kidney. The most severe and most studied form of malaria is associated with cerebral complications due to capillary congestion and the adhesion of infected erythrocytes, platelets, and leukocytes to brain vasculature. Thus, leukocyte rolling and adhesion in the brain vascular bed during severe malaria is singular and distinct from other models of inflammation. The leukocyte/endothelium interaction and neutrophil accumulation are also observed in the lungs. However, lung interactions differ from brain interactions, likely due to differences in the blood-brain barrier and blood-air barrier tight junction composition of the brain and lung endothelium. Here, we review the importance of endothelial dysfunction and the mechanism of leukocyte/endothelium interaction during severe malaria. Furthermore, we hypothesize a possible use of adjunctive therapies to antimalarial drugs that target the interaction between the leukocytes and the endothelium.

Hyperbaric oxygen therapy palliates lipopolysaccharide-induced acute lung injury in rats by upregulating AQP1 and AQP5 expression

PURPOSE

Hyperbaric oxygen (HBO) therapy has been suggested to palliate acute lung injury (ALI), but the mechanisms involved are not well understood. This study is to elucidate the involvement of AQP1 and AQP5 in the HBO related ALI therapy.

MATERIALS AND METHODS

lipopolysaccharide (LPS) was administrated into SD rats to obtain ALI models. Pressure of oxygen (PaO2) and carbon dioxide (PaCO2) in arterial blood and oxygenation index in rats after LPS and HBO treatments were determined. Pathological changes of the lungs were examined by hematoxylin and eosin staining. Alteration of TNF-α level during LPS and HBO treatments was evaluated with ELISA analysis. Western blot was employed to assess the expression of AQP1 and AQP5.

RESULTS

Blood gas indexes were largely decreased by LPS administration, which responded to HBO. Pathological examination showed that the inflammation symptoms in lungs induced by LPS were also palliated after HBO preconditioning. LPS induced the expression of TNF-α at a high level which could be downregulated by HBO and TNF-α antagonist treatments. Results of AQP1 and AQP5 determination found that HBO and TNF-α antagonist would upregulate the expression of AQP1 and AQP5 which was inhibited in rats with ALI.

CONCLUSIONS

HBO therapy palliated LPS-induced ALI in rats by downregulating TNF-α expression. HBO also upregulated AQP1 and AQP5 expression. These results could serve as guidelines for the full understanding of ALI therapy by HBO, thus achieving maximized therapeutic efficiency.