GADD45a promoter regulation by a functional genetic variant associated with acute lung injury

Deficiency of the Deubiquitinase UCHL1 Attenuates Pulmonary Arterial Hypertension

BACKGROUND

The ubiquitin-proteasome system regulates protein degradation and the development of pulmonary arterial hypertension (PAH), but knowledge about the role of deubiquitinating enzymes in this process is limited. UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), a deubiquitinase, has been shown to reduce AKT1 (AKT serine/threonine kinase 1) degradation, resulting in higher levels. Given that AKT1 is pathological in pulmonary hypertension, we hypothesized that UCHL1 deficiency attenuates PAH development by means of reductions in AKT1.

METHODS

Tissues from animal pulmonary hypertension models as well as human pulmonary artery endothelial cells from patients with PAH exhibited increased vascular UCHL1 staining and protein expression. Exposure to LDN57444, a UCHL1-specific inhibitor, reduced human pulmonary artery endothelial cell and smooth muscle cell proliferation. Across 3 preclinical PAH models, LDN57444-exposed animals, Uchl1 knockout rats (Uchl1-/-), and conditional Uchl1 knockout mice (Tie2Cre-Uchl1fl/fl) demonstrated reduced right ventricular hypertrophy, right ventricular systolic pressures, and obliterative vascular remodeling. Lungs and pulmonary artery endothelial cells isolated from Uchl1-/- animals exhibited reduced total and activated Akt with increased ubiquitinated Akt levels. UCHL1-silenced human pulmonary artery endothelial cells displayed reduced lysine(K)63-linked and increased K48-linked AKT1 levels.

RESULTS

Supporting experimental data, we found that rs9321, a variant in a GC-enriched region of the UCHL1 gene, is associated with reduced methylation (n=5133), increased UCHL1 gene expression in lungs (n=815), and reduced cardiac index in patients (n=796). In addition, Gadd45α (an established demethylating gene) knockout mice (Gadd45α-/-) exhibited reduced lung vascular UCHL1 and AKT1 expression along with attenuated hypoxic pulmonary hypertension.

CONCLUSIONS

Our findings suggest that UCHL1 deficiency results in PAH attenuation by means of reduced AKT1, highlighting a novel therapeutic pathway in PAH.

Polymorphisms within DIO2 and GADD45A genes increase the risk of liver disease progression in chronic hepatitis b carriers

The study enrolled 284 patients with chronic hepatitis B virus infection. Participants included people with mild fibrotic lesions (32.5%), moderate to severe fibrotic lesions (27.5%), cirrhotic lesions (22%), hepatocellular carcinoma (HCC) in 5%, and people with no fibrotic lesions in 13%. Eleven SNPs within DIO2, PPARG, ATF3, AKT, GADD45A, and TBX21 were genotyped by mass spectrometry. The rs225014 TT (DIO2) and rs10865710 CC (PPARG) genotypes were independently associated with susceptibility to advanced liver fibrosis. However, cirrhosis was more prevalent in individuals with the GADD45A rs532446 TT and ATF3 rs11119982 TT genotypes. In addition, the rs225014 CC variant of DIO2 was more frequently found in patients with a diagnosis of HCC. These findings suggest that the above SNPs may play a role in HBV-induced liver damage in a Caucasian population.

A Trans-Agency Workshop on the Pathophysiology of Radiation-Induced Lung Injury

Research and development of medical countermeasures (MCMs) for radiation-induced lung injury relies on the availability of animal models with well-characterized pathophysiology, allowing effective bridging to humans. To develop useful animal models, it is important to understand the clinical condition, advantages and limitations of individual models, and how to properly apply these models to demonstrate MCM efficacy. On March 20, 2019, a meeting sponsored by the Radiation and Nuclear Countermeasures Program (RNCP) within the National Institute of Allergy and Infectious Diseases (NIAID) brought together medical, scientific and regulatory communities, including academic and industry subject matter experts, and government stakeholders from the Food and Drug Administration (FDA) and the Biomedical Advanced Research and Development Authority (BARDA), to identify critical research gaps, discuss current clinical practices for various forms of pulmonary damage, and consider available animal models for radiation-induced lung injury.

Endothelial eNAMPT amplifies pre-clinical acute lung injury: efficacy of an eNAMPT-neutralising monoclonal antibody

RATIONALE

The severe acute respiratory syndrome coronavirus 2/coronavirus disease 2019 pandemic has highlighted the serious unmet need for effective therapies that reduce acute respiratory distress syndrome (ARDS) mortality. We explored whether extracellular nicotinamide phosphoribosyltransferase (eNAMPT), a ligand for Toll-like receptor (TLR)4 and a master regulator of innate immunity and inflammation, is a potential ARDS therapeutic target.

METHODS

Wild-type C57BL/6J or endothelial cell (EC)-cNAMPT -/- knockout mice (targeted EC NAMPT deletion) were exposed to either a lipopolysaccharide (LPS)-induced ("one-hit") or a combined LPS/ventilator ("two-hit")-induced acute inflammatory lung injury model. A NAMPT-specific monoclonal antibody (mAb) imaging probe (99mTc-ProNamptor) was used to detect NAMPT expression in lung tissues. Either an eNAMPT-neutralising goat polyclonal antibody (pAb) or a humanised monoclonal antibody (ALT-100 mAb) were used in vitro and in vivo.

RESULTS

Immunohistochemical, biochemical and imaging studies validated time-dependent increases in NAMPT lung tissue expression in both pre-clinical ARDS models. Intravenous delivery of either eNAMPT-neutralising pAb or mAb significantly attenuated inflammatory lung injury (haematoxylin and eosin staining, bronchoalveolar lavage (BAL) protein, BAL polymorphonuclear cells, plasma interleukin-6) in both pre-clinical models. In vitro human lung EC studies demonstrated eNAMPT-neutralising antibodies (pAb, mAb) to strongly abrogate eNAMPT-induced TLR4 pathway activation and EC barrier disruption. In vivo studies in wild-type and EC-cNAMPT -/- mice confirmed a highly significant contribution of EC-derived NAMPT to the severity of inflammatory lung injury in both pre-clinical ARDS models.

CONCLUSIONS

These findings highlight both the role of EC-derived eNAMPT and the potential for biologic targeting of the eNAMPT/TLR4 inflammatory pathway. In combination with predictive eNAMPT biomarker and NAMPT genotyping assays, this offers the opportunity to identify high-risk ARDS subjects for delivery of personalised medicine.

Pathogenetic profiling of COVID-19 and SARS-like viruses

The novel coronavirus (2019-nCoV) has recently emerged, causing COVID-19 outbreaks and significant societal/global disruption. Importantly, COVID-19 infection resembles SARS-like complications. However, the lack of knowledge about the underlying genetic mechanisms of COVID-19 warrants the development of prospective control measures. In this study, we employed whole-genome alignment and digital DNA-DNA hybridization analyses to assess genomic linkage between 2019-nCoV and other coronaviruses. To understand the pathogenetic behavior of 2019-nCoV, we compared gene expression datasets of viral infections closest to 2019-nCoV with four COVID-19 clinical presentations followed by functional enrichment of shared dysregulated genes. Potential chemical antagonists were also identified using protein-chemical interaction analysis. Based on phylogram analysis, the 2019-nCoV was found genetically closest to SARS-CoVs. In addition, we identified 562 upregulated and 738 downregulated genes (adj. P ≤ 0.05) with SARS-CoV infection. Among the dysregulated genes, SARS-CoV shared ≤19 upregulated and ≤22 downregulated genes with each of different COVID-19 complications. Notably, upregulation of BCL6 and PFKFB3 genes was common to SARS-CoV, pneumonia and severe acute respiratory syndrome, while they shared CRIP2, NSG1 and TNFRSF21 genes in downregulation. Besides, 14 genes were common to different SARS-CoV comorbidities that might influence COVID-19 disease. We also observed similarities in pathways that can lead to COVID-19 and SARS-CoV diseases. Finally, protein-chemical interactions suggest cyclosporine, resveratrol and quercetin as promising drug candidates against COVID-19 as well as other SARS-like viral infections. The pathogenetic analyses, along with identified biomarkers, signaling pathways and chemical antagonists, could prove useful for novel drug development in the fight against the current global 2019-nCoV pandemic.

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.

Genetic variants of GADD45A, GADD45B and MAPK14 predict platinum-based chemotherapy-induced toxicities in Chinese patients with non-small cell lung cancer

The JNK and P38α pathways play a crucial role in tissue homeostasis, apoptosis and autophagy under genotoxic stresses, but it is unclear whether single nucleotide polymorphisms (SNPs) of genes in these pathways play a role in platinum-based chemotherapy-induced toxicities in patients with advanced non-small cell lung cancer (NSCLC). We genotyped 11 selected, independent, potentially functional SNPs of nine genes in the JNK and P38α pathways in 689 patients with advanced NSCLC treated with platinum-combination chemotherapy regimens. Associations between these SNPs and chemotherapy toxicities were tested in a discovery group of 345 patients and then validated in a replication group of 344 patients. In both discovery and validation groups as well as their pooled analysis, carriers of GADD45B rs2024144T variant allele had a significantly higher risk for severe hematologic toxicity and carriers of MAPK14 rs3804451A variant allele had a significantly higher risk for both overall toxicity and gastrointestinal toxicity. In addition, carriers of GADD45A rs581000C had a lower risk of anemia, while carriers of GADD45B rs2024144T had a significantly higher risk for leukocytopenia or agranulocytosis. The present study provides evidence that genetic variants in genes involved in the JNK and P38α pathways may predict platinum-based chemotherapy toxicity outcomes in patients with advanced NSCLC. Larger studies of other patient populations are needed to validate our findings.

Endothelial cell signaling and ventilator-induced lung injury: molecular mechanisms, genomic analyses, and therapeutic targets

Mechanical ventilation is a life-saving intervention in critically ill patients with respiratory failure due to acute respiratory distress syndrome (ARDS). Paradoxically, mechanical ventilation also creates excessive mechanical stress that directly augments lung injury, a syndrome known as ventilator-induced lung injury (VILI). The pathobiology of VILI and ARDS shares many inflammatory features including increases in lung vascular permeability due to loss of endothelial cell barrier integrity resulting in alveolar flooding. While there have been advances in the understanding of certain elements of VILI and ARDS pathobiology, such as defining the importance of lung inflammatory leukocyte infiltration and highly induced cytokine expression, a deep understanding of the initiating and regulatory pathways involved in these inflammatory responses remains poorly understood. Prevailing evidence indicates that loss of endothelial barrier function plays a primary role in the development of VILI and ARDS. Thus this review will focus on the latest knowledge related to 1) the key role of the endothelium in the pathogenesis of VILI; 2) the transcription factors that relay the effects of excessive mechanical stress in the endothelium; 3) the mechanical stress-induced posttranslational modifications that influence key signaling pathways involved in VILI responses in the endothelium; 4) the genetic and epigenetic regulation of key target genes in the endothelium that are involved in VILI responses; and 5) the need for novel therapeutic strategies for VILI that can preserve endothelial barrier function.

New role and molecular mechanism of Gadd45a in hepatic fibrosis

AIM: To investigate the role of Gadd45a in hepatic fibrosis and the transforming growth factor (TGF)-β/Smad signaling pathway.

METHODS: Wild-type male BALB/c mice were treated with CCl₄ to induce a model of chronic liver injury. Hepatic stellate cells (HSCs) were isolated from the liver of BALB/c mice and were treated with small interfering RNAs (siRNAs) targeting Gadd45a or the pcDNA3.1-Gadd45a recombinant plasmid. Cellular α-smooth muscle actin (α-SMA), β-actin, type I collagen, phospho-Smad2, phospho-Smad3, Smad2, Smad3, and Smad4 were detected by Western blots. The mRNA levels of α-SMA, β-actin, and type I collagen were determined by quantitative real-time (qRT)-PCR analyses. Reactive oxygen species production was monitored by flow cytometry using 2,7-dichlorodihydrofluorescein diacetate. Gadd45a, Gadd45b, anti-Gadd45g, type I collagen, and SMA local expression in liver tissue were measured by histologic and immunohistochemical analyses.

RESULTS: Significant downregulation of Gadd45a, but not Gadd45b or Gadd45g, accompanied by activation of the TGF-β/Smad signaling pathways was detected in fibrotic liver tissues of mice and isolated HSCs with chronic liver injury induced by CCl₄ treatment. Overexpression of Gadd45a reduced the expression of extracellular matrix proteins and α-SMA in HSCs, whereas transient knockdown of Gadd45a with siRNA reversed this process. Gadd45a inhibited the activity of a plasminogen activator inhibitor-1 promoter construct and (CAGA)₉ MLP-Luc, an artificial Smad3/4-specific reporter, as well as reduced the phosphorylation and nuclear translocation of Smad3. Gadd45a showed protective effects by scavenging reactive oxygen species and upregulating antioxidant enzymes.

CONCLUSION: Gadd45a may counteract hepatic fibrosis by regulating the activation of HSCs via the inhibition of TGF-β/Smad signaling.

Sp1-mediated nonmuscle myosin light chain kinase expression and enhanced activity in vascular endothelial growth factor-induced vascular permeability

Despite the important role played by the nonmuscle isoform of myosin light chain kinase (nmMLCK) in vascular barrier regulation and the implication of both nmMLCK and vascular endothelial growth factor (VEGF) in the pathogenesis of acute respiratory distress syndrome (ARDS), the role played by nmMLCK in VEGF-induced vascular permeability is poorly understood. In this study, the role played by nmMLCK in VEGF-induced vascular hyperpermeability was investigated. Human lung endothelial cell barrier integrity in response to VEGF is examined in both the absence and the presence of nmMLCK small interfering RNAs. Levels of nmMLCK messenger RNA (mRNA), protein, and promoter activity expression were monitored after VEGF stimulation in lung endothelial cells. nmMYLK promoter activity was assessed using nmMYLK promoter luciferase reporter constructs with a series of nested deletions. nmMYLK transcriptional regulation was further characterized by examination of a key transcriptional factor. nmMLCK plays an important role in VEGF-induced permeability. We found that activation of the VEGF signaling pathway in lung endothelial cells increases MYLK gene product at both mRNA and protein levels. Increased nmMLCK mRNA and protein expression is a result of increased nmMYLK promoter activity, regulated in part by binding of the Sp1 transcription factor on triggering by the VEGF signaling pathway. Taken together, these findings suggest that MYLK is an important ARDS candidate gene and a therapeutic target that is highly influenced by excessive VEGF concentrations in the inflamed lung.