Genomics of Acute Lung Injury

Abstract

Acute lung injury (ALI) is a complex syndrome involving the interplay of both environmental (such as the addition of mechanical ventilation) and genetic factors. Clinical models have identified risk factors for development and poor outcome but these strategies remain imprecise. To better understand the mechanisms of pathogenesis associated with mechanisms of ALI, candidate genes identified by global expression profiling or related literature searches are being explored for relevant polymorphisms (single base pair substitutions) that can affect both ALI susceptibility and outcome. This article summarizes several specific genetic association studies that have been conducted in ALI and reviews supporting data from in vitro and in vivo models of the disease and clinical observations. Although valuable information has been reported to date, intense analyses are needed in this developing discipline to assure significant clinical utility. The detailing of specific associated polymorphisms will continue to provide new insights in the understanding of disease pathogenesis, and promise to reveal novel molecular targets and personalized treatments to prevent the disease.

MicroRNA Regulation of Nonmuscle Myosin Light Chain Kinase Expression in Human Lung Endothelium

“…Prior studies have indicated that genes with increased expression and function variability have longer 39UTRs that are enriched in miRNA-binding sites (35,36). The MYLK gene has a relatively long 39UTR (1,825 base pair), with several splice variants that contribute to the risk and severity of ALI and VILI (4)(5)(6)(7)(8). Because miRNAs regulate a variety of pathophysiological processes, nmMLCK expression may be influenced by ALImodulating miRNAs that bind to the MYLK 39UTR region, consistent with the recognition that multiple inflammatory processes and IL1b-, LPS-, and TNF-a2induced cell activation (macrophages, neutrophils, monocytes, and epithelium) are regulated by specific miRNAs (miR-21, -9, -25, -27b, -100, -140, -142-3p, -181c-, -194, -223, -224, -16, -199a, -155, -146a, -let-7a, -31, 17-3p, and -125b) (37)(38)(39)(40)(41)(42)(43).…”

“…All cyclic stretch (CS) experiments were performed using the FX-4000T Flexcell Tension Plus system (Flexcell International, Hillsborough, NC) equipped with a 25-mm BioFlex loading station designed to provide uniform radial and circumferential strain across a membrane surface along all radii, as described previously (6). Briefly, ECs were seeded at standard densities (8 3 10 5 cells/well) onto collagen type I-coated, flexible-bottomed BioFlex plates transfected with MYLK luciferase reporter and/or miRNA mimics/antagomirs and cultured in EGM-2 complete medium containing 2% FBS at 37 8 C. After 24 hours of culture, the medium was changed in each plate, and confluent EC monolayers were subjected to cyclic stretch (0.5 Hz; 18% linear elongation; 25 cycles/min for 20 min) of desired duration (0-48 h).…”

“…Disruption of this vascular barrier induced by inflammatory agonists, such as IL-1b, TNF-a, and LPS, and by excessive mechanical stress, such as produced by shear stress or mechanical ventilation, leads to potentially lethal physiological dysfunction, such as hypoxemia and severe lung edema, which are hallmarks of acute inflammatory lung injury (ALI) (1)(2)(3). We previously demonstrated that MYLK, the gene encoding the critical cytoskeletal effector myosin light chain kinase (MLCK), is a compelling candidate gene in inflammatory lung injuries with critical modulation of vascular EC barrier integrity such as ALI and asthma (4)(5)(6). We cloned the full-length human MYLK gene encoding a novel nonmuscle MLCK isoform (nmMLCK) (210 kD) (7) and several nmMLCK splice variants that are also highly expressed in endothelium (8) and convincingly demonstrated nmMLCK as a multifunctional enzyme driving cytoskeletal participation in vascular barrier disruption and in barrier-restorative processes (9,10).…”

“…In addition, nmMLCK regulates lung trafficking of inflammatory cells (11) and is robustly activated by biophysical forces (excessive mechanical stress) that are key to ventilatorinduced lung injury (VILI) (5). Levels of nmMLCK gene expression and enzymatic activities contribute to the risk and severity of ALI and VILI, as shown in preclinical models and humans (4)(5)(6). Despite the multifunctionality of nmMLCK, the regulatory mechanisms governing nmMLCK gene and protein expression and spatially directed kinase activities are poorly understood.…”

Macrophage migration inhibitory factor in acute lung injury: expression, biomarker, and associations

“…We recognize however, that due to sample size and a MAF<20% in this population, our design is underpowered to detect effects in the order of OR∼2.0. Baugh et al 50 also showed in reporter assays that the CATT (5)(6)(7)(8) microsatellite, located in the promoter of MIF gene and in linkage disequilibrium with rs755622, determined the activity of the promoter by the number of repeats. Contrary to these studies, our major findings are focused on the 3′UTR region of the gene, and do not involve individual SNPs but rather involve haplotypes, a finding that is not surprising given the greater power of haplotype analyses.…”