A vascular endothelial growth factor receptor gene variant is associated with susceptibility to acute respiratory distress syndrome

A Razor's Edge: Vascular Responses to Acute Inflammatory Lung Injury/Acute Respiratory Distress Syndrome

Historically considered a metabolically inert cellular layer separating the blood from the underlying tissue, the endothelium is now recognized as a highly dynamic, metabolically active tissue that is critical to organ homeostasis. Under homeostatic conditions, lung endothelial cells (ECs) in healthy subjects are quiescent, promoting vasodilation, platelet disaggregation, and anti-inflammatory mechanisms. In contrast, lung ECs are essential contributors to the pathobiology of acute respiratory distress syndrome (ARDS), as the quiescent endothelium is rapidly and radically altered upon exposure to environmental stressors, infectious pathogens, or endogenous danger signals into an effective and formidable regulator of innate and adaptive immunity. These dramatic perturbations, produced in a tsunami of inflammatory cascade activation, result in paracellular gap formation between lung ECs, sustained lung edema, and multi-organ dysfunction that drives ARDS mortality. The astonishing plasticity of the lung endothelium in negotiating this inflammatory environment and efforts to therapeutically target the aberrant ARDS endothelium are examined in further detail in this review.

Evolution of multiple omics approaches to define pathophysiology of pediatric acute respiratory distress syndrome

Pediatric acute respiratory distress syndrome (PARDS), though both common and deadly in critically ill children, lacks targeted therapies. The development of effective pharmacotherapies has been limited, in part, by lack of clarity about the pathobiology of pediatric ARDS. Epithelial lung injury, vascular endothelial activation, and systemic immune activation are putative drivers of this complex disease process. Prior studies have used either hypothesis-driven (e.g., candidate genes and proteins, in vitro investigations) or unbiased (e.g., genome-wide association, transcriptomic, metabolomic) approaches to predict clinical outcomes and to define subphenotypes. Advances in multiple omics technologies, including genomics, transcriptomics, proteomics, and metabolomics, have permitted more comprehensive investigation of PARDS pathobiology. However, omics studies have been limited in children compared to adults, and analyses across multiple tissue types are lacking. Here, we synthesized existing literature on the molecular mechanism of PARDS, summarized our interrogation of publicly available genomic databases to determine the association of candidate genes with PARDS phenotypes across multiple tissues and cell types, and integrated recent studies that used single-cell RNA sequencing (scRNA-seq). We conclude that novel profiling methods such as scRNA-seq, which permits more comprehensive, unbiased evaluation of pathophysiological mechanisms across tissue and cell types, should be employed to investigate the molecular mechanisms of PRDS toward the goal of identifying targeted therapies.

Genetics of Acute Respiratory Distress Syndrome: Pathways to Precision

Clinical risk factors alone fail to fully explain acute respiratory distress syndrome (ARDS) risk or ARDS death, suggesting that individual risk factors contribute. The goals of genomic ARDS studies include better mechanistic understanding, identifying dysregulated pathways that may be amenable to pharmacologic targeting, using genomic causal inference techniques to find measurable traits with meaning, and deconvoluting ARDS heterogeneity by proving reproducible subpopulations that may share a unique biology. This article discusses the latest advances in ARDS genomics, provides historical perspective, and highlights some of the ways that the coronavirus disease 2019 (COVID-19) pandemic is accelerating genomic ARDS research.

Association of VEGFA polymorphisms with chronic obstructive pulmonary disease in Chinese Han and Mongolian populations

NEW FINDINGS

What is the central question of this study? Vascular endothelial growth factor A (VEGFA) is an important growth factor involved in changes in the bronchial microvascular and airway inflammation in chronic obstructive pulmonary disease (COPD) progression. What is the association of single nucleotide polymorphisms (SNPs) in VEGFA with the risk of COPD in the Chinese Han and Mongolian populations? What is the main finding and its importance? The effect of five SNPs in the VEGFA gene was analysed and compared between the Chinese Han and Mongolian populations. A contribution of risk alleles rs833068, rs833070 and rs3024997 to COPD was detected in the Chinese Mongolian population only. The study provided data from different populations to validate the role of VEGFA polymorphisms in COPD and provided reliable SNPs to predict the risk of COPD.

ABSTRACT

We attempted to define the associations between single nucleotide polymorphisms (SNPs) in the vascular endothelial growth factor A (VEGFA) gene and chronic obstructive pulmonary disease (COPD) in Chinese Han and Mongolian cohorts. Five SNPs were genotyped in cohorts of 684 COPD patients (350 Mongolian and 334 Han) and 784 healthy controls (350 Mongolian and 434 Han) using SNPscan multiplex PCR. SNP frequencies, genetic models and haplotypes were analysed using the chi-square test. The associations of SNPs with COPD and linkage disequilibrium were analysed using logistic regression and HaploView, respectively. We found that only rs833068G>A, rs833070T>C and rs3024997G>A were significantly associated with the risk of COPD in the Mongolian population (rs833068: P < 0.001, rs833070: P < 0.001, rs3024997: P = 0.002). In the analysis of genotype distributions, the A/A and G/A genotypes in rs833068 (A/A: odds ratio (OR) = 0.313, P < 0.001; G/A: OR = 0.724, P < 0.001) and rs3024997 (A/A: OR = 0.513, P = 0.008; G/A: OR = 0.671, P = 0.008) and the C/C and T/C genotypes in rs833070 (C/C: OR = 0.435, P = 0.007; T/C: OR = 0.593, P = 0.007) were associated with protection against COPD in the Mongolian population. The haplotype frequencies of GCCAT and GTCGC were significantly different between the patients and controls (GCCAT: P = 0.001; GTCGC: P < 0.001) in the Mongolian population. Our findings indicate that five SNPs in the VEGFA gene play divergent roles in the Han and Mongolian populations. rs833068A, rs833070C and rs3024997A were observed to be associated with the risk of COPD in the Mongolian population.

Molecular Mechanisms of Vascular Damage During Lung Injury

A variety of pulmonary and systemic insults promote an inflammatory response causing increased vascular permeability, leading to the development of acute lung injury (ALI), a condition necessitating hospitalization and intensive care, or the more severe acute respiratory distress syndrome (ARDS), a disease with a high mortality rate. Further, COVID-19 pandemic-associated ARDS is now a major cause of mortality worldwide. The pathogenesis of ALI is explained by injury to both the vascular endothelium and the alveolar epithelium. The disruption of the lung endothelial and epithelial barriers occurs in response to both systemic and local production of pro-inflammatory cytokines. Studies that evaluate the association of genetic polymorphisms with disease risk did not yield many potential therapeutic targets to treat and revert lung injury. This failure is probably due in part to the phenotypic complexity of ALI/ARDS, and genetic predisposition may be obscured by the multiple environmental and behavioral risk factors. In the last decade, new research has uncovered novel epigenetic mechanisms that control ALI/ARDS pathogenesis, including histone modifications and DNA methylation. Enzyme inhibitors such as DNMTi and HDACi may offer new alternative strategies to prevent or reverse the vascular damage that occurs during lung injury. This review will focus on the latest findings on the molecular mechanisms of vascular damage in ALI/ARDS, the genetic factors that might contribute to the susceptibility for developing this disease, and the epigenetic changes observed in humans, as well as in experimental models of ALI/ADRS.

Development of a biomarker mortality risk model in acute respiratory distress syndrome

Background

There is a compelling unmet medical need for biomarker-based models to risk-stratify patients with acute respiratory distress syndrome. Effective stratification would optimize participant selection for clinical trial enrollment by focusing on those most likely to benefit from new interventions. Our objective was to develop a prognostic, biomarker-based model for predicting mortality in adult patients with acute respiratory distress syndrome.

Methods

This is a secondary analysis using a cohort of 252 mechanically ventilated subjects with the diagnosis of acute respiratory distress syndrome. Survival to day 7 with both day 0 (first day of presentation) and day 7 sample availability was required. Blood was collected for biomarker measurements at first presentation to the intensive care unit and on the seventh day. Biomarkers included cytokine-chemokines, dual-functioning cytozymes, and vascular injury markers. Logistic regression, latent class analysis, and classification and regression tree analysis were used to identify the plasma biomarkers most predictive of 28-day ARDS mortality.

Results

From eight biologically relevant biomarker candidates, six demonstrated an enhanced capacity to predict mortality at day 0. Latent-class analysis identified two biomarker-based phenotypes. Phenotype A exhibited significantly higher plasma levels of angiopoietin-2, macrophage migration inhibitory factor, interleukin-8, interleukin-1 receptor antagonist, interleukin-6, and extracellular nicotinamide phosphoribosyltransferase (eNAMPT) compared to phenotype B. Mortality at 28 days was significantly higher for phenotype A compared to phenotype B (32% vs 19%, p = 0.04).

Conclusions

An adult biomarker-based risk model reliably identifies ARDS subjects at risk of death within 28 days of hospitalization.

Genomic and Genetic Approaches to Deciphering Acute Respiratory Distress Syndrome Risk and Mortality

Significance: Acute respiratory distress syndrome (ARDS) is a severe, highly heterogeneous critical illness with staggering mortality that is influenced by environmental factors, such as mechanical ventilation, and genetic factors. Significant unmet needs in ARDS are addressing the paucity of validated predictive biomarkers for ARDS risk and susceptibility that hamper the conduct of successful clinical trials in ARDS and the complete absence of novel disease-modifying therapeutic strategies. Recent Advances: The current ARDS definition relies on clinical characteristics that fail to capture the diversity of disease pathology, severity, and mortality risk. We undertook a comprehensive survey of the available ARDS literature to identify genes and genetic variants (candidate gene and limited genome-wide association study approaches) implicated in susceptibility to developing ARDS in hopes of uncovering novel biomarkers for ARDS risk and mortality and potentially novel therapeutic targets in ARDS. We further attempted to address the well-known health disparities that exist in susceptibility to and mortality from ARDS. Critical Issues: Bioinformatic analyses identified 201 ARDS candidate genes with pathway analysis indicating a strong predominance in key evolutionarily conserved inflammatory pathways, including reactive oxygen species, innate immunity-related inflammation, and endothelial vascular signaling pathways. Future Directions: Future studies employing a system biology approach that combines clinical characteristics, genomics, transcriptomics, and proteomics may allow for a better definition of biologically relevant pathways and genotype-phenotype connections and result in improved strategies for the sub-phenotyping of diverse ARDS patients via molecular signatures. These efforts should facilitate the potential for successful clinical trials in ARDS and yield a better fundamental understanding of ARDS pathobiology.

Risk factors, management and prevention of transfusion-related acute lung injury: a comprehensive update

Introduction: Despite mitigation strategies that include the exclusion of females from plasma donation or the exclusion of females with a history of pregnancy or known anti-leukocyte antibody, transfusion-related acute lung injury (TRALI) remains a leading cause of transfusion-related morbidity and mortality. Areas covered: The definition of TRALI is discussed and re-aligned with the new Berlin Diagnostic Criteria for the acute respiratory distress syndrome (ARDS). The risk factors associated with TRALI are summarized as are the mitigation strategies to further reduce TRALI. The emerging basic research studies that may translate to clinical therapeutics for the prevention or treatment of TRALI are discussed. Expert opinion: At risk patients, including the genetic factors that may predispose patients to TRALI are summarized and discussed. The re-definition of TRALI employing the Berlin Criteria for ARDS will allow for increased recognition and improved research into pathophysiology and mitigation to reduce this fatal complication of hemotherapy.

Genomics and the Acute Respiratory Distress Syndrome: Current and Future Directions

The excessive hospital mortality associated with acute respiratory distress syndrome (ARDS) in adults mandates an urgent need for developing new therapies and tools for the early risk assessment of these patients. ARDS is a heterogeneous syndrome with multiple different pathogenetic processes contributing differently in different patients depending on clinical as well as genetic factors. Identifying genetic-based biomarkers holds the promise for establishing effective predictive and prognostic stratification methods and for targeting new therapies to improve ARDS outcomes. Here we provide an updated review of the available evidence supporting the presence of genetic factors that are predictive of ARDS development and of fatal outcomes in adult critically ill patients and that have been identified by applying different genomic and genetic approaches. We also introduce other incipient genomics approximations, such as admixture mapping, metagenomics and genome sequencing, among others, that will allow to boost this knowledge and likely reveal new genetic predictors of ARDS susceptibility and prognosis among critically ill patients.