Endothelin-1 potentiates smoke-induced acute lung inflammation

Vitamin C as prophylaxis and adjunctive medical treatment for COVID-19?

Severe acute respiratory syndrome coronavirus 2 causes the potentially fatal coronavirus disease 2019 (COVID-19). Already during the outbreak of the severe acute respiratory syndrome coronavirus 1, the use of vitamin C was suggested. Many patients with severe COVID-19 have elevated levels of the mediators interleukin-6 and endothelin-1. These mediators may explain the age dependence of COVID-19 pneumonia, the preponderance of male and obese or hypertensive patients, as well as of persons of color and smokers. There is clear evidence that vitamin C in high doses can reduce these mediators. Vitamin C is cheap and safe. Hence, using a relatively low dose of vitamin C as prophylaxis, and in cases of severe COVID-19, an (intravenous) high-dose regimen may be beneficial. Ongoing clinical trials are expected to provide more definitive evidence.

Acute exposure to diesel and sewage biodiesel exhaust causes pulmonary and systemic inflammation in mice

Biodiesel is a renewable energy source that reduces particle emission, but few studies have assessed its effects. To assess the effects of acute inhalation of two doses (600 and 1200 μg/m³) of diesel (DE) and biodiesel (BD) fuels on the inflammatory pulmonary and systemic profile of mice. Animals were exposed for 2 h in an inhalation chamber inside the Container Laboratory for Fuels. Heart rate, heart rate variability (HRV) and blood pressure were determined 30 min after exposure. After 24 h, we analyzed the lung inflammation using bronchoalveolar lavage fluid (BALF); neutrophil and macrophage quantification in the lung parenchyma was performed, and blood and bone marrow biomarkers as well as receptor of endothelin-A (ET-Ar), receptor of endothelin-B (ET-Br), vascular cell adhesion molecule 1 (VCAM-1), inducible nitric oxide synthase (iNOs) and isoprostane (ISO) levels in the pulmonary vessels and bronchial epithelium were evaluated. HRV increased for BD600, D600 and D1200 compared to filtered air (FA). Both fuels (DE and BD) produced alterations in red blood cells independent of the dose. BALF from the BD600 and BD1200 groups showed an increase in neutrophils compared to those of the FA group. Numeric density of the polymorphonuclear and mononuclear cells was elevated with BD600 compared to FA. In the peribronchiolar vessels, there was an increase in ET-Ar and ET-Br expression following BD600 compared to FA; and there was a reduction in the iNOs expression for BD1200 and the VCAM-1 for D1200 compared to FA. In the bronchial epithelium, there was an increase in ETAr at BD600, ET-Br at two doses (600 and 1200 μg/m³) of DE and BD, iNOs at D600 and VCAM-1 at BD1200 and D600; all groups were compared to the FA group. Acute exposure to DE and BD derived from sewage methyl esters triggered pulmonary and cardiovascular inflammatory alterations in mice.

Time-dependent effects of HJP272, an endothelin receptor antagonist, in bleomycin-induced pulmonary fibrosis

Using a lipopolysaccharide (LPS) model of acute lung injury, we have previously shown that endothelin-1 (ET-1), a potent mediator of vasoconstriction, may act as a "gatekeeper" for the influx of inflammatory cells into the lung. To further investigate the potential of ET-1 to limit the progression of lung injury, hamsters were treated with an endothelin receptor antagonist (ERA), HJP272, either 1 h prior to intratracheal instillation of bleomycin (BLM) or 24 h afterwards. Lung injury and repair were examined by measuring the following parameters: 1) histopathological changes; 2) neutrophil content in bronchoalveolar lavage fluid (BALF); 3) lung collagen content; 4) tumor necrosis factor receptor 1 (TNFR1) expression by BALF macrophages; 5) BALF levels of: a) transforming growth factor beta-1 (TGF-β1), b) stromal cell-derived factor 1 (commonly referred to as CXCL12), and c) platelet-derived growth factor BB (PDGF-BB); 6) alveolar septal cell apoptosis (as measured by the TUNEL assay). For each of these parameters, animals pretreated with HJP272 showed significant reductions compared to those receiving BLM alone. In contrast, post-treatment with HJP272 was either ineffective or produced only marginally significant changes. The efficacy of a single pretreatment with HJP272 prior to induction of lung injury suggests that subsequent features of the disease are determined at a very early stage. This may explain why ERAs are not an effective treatment for human pulmonary fibrosis. Nevertheless, our findings suggest that they may be useful as prophylactic agents when given in combination with drugs that have fibrogenic potential.

Nur77 attenuates endothelin-1 expression via downregulation of NF-κB and p38 MAPK in A549 cells and in an ARDS rat model

Acute respiratory distress syndrome (ARDS) is characterized by inflammatory injury to the alveolar and capillary barriers that results in impaired gas exchange and severe acute respiratory failure. Nuclear orphan receptor Nur77 has emerged as a regulator of gene expression in inflammation, and its role in the pathogenesis of ARDS is not clear. The objective of this study is to investigate the potential role of Nur77 and its underlying mechanism in the regulation of endothelin-1 (ET-1) expression in lipopolysaccharide (LPS)-induced A549 cells and an ARDS rat model. We demonstrate that LPS induced Nur77 expression and nuclear export in A549 cells. Overexpression of Nur77 markedly decreased basal and LPS-induced ET-1 expression in A549 cells, whereas knockdown of Nur77 increased the ET-1 expression. LPS-induced phosphorylation and nuclear translocation of NF-κB and p38 MAPK were blocked by Nur77 overexpression and augmented by Nur77 knockdown in A549 cells. In vivo, LPS induced Nur77 expression in lung in ARDS rats. Pharmacological activation of Nur77 by cytosporone B (CsnB) inhibited ET-1 expression in ARDS rats, decreased LPS-induced phosphorylation of NF-κB and p38 MAPK, and relieved lung, liver, and kidney injury. Pharmacological deactivation of Nur77 by 1,1-bis-(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH, C-DIM8) had no effect on ET-1 expression and lung injury. These results indicated that Nur77 decreases ET-1 expression by suppressing NF-κB and p38 MAPK in LPS-stimulated A549 cells in vitro, and, in an LPS-induced ARDS rat model, CsnB reduced ET-1 expression and lung injury in ARDS rats.

The heart as an extravascular target of endothelin-1 in particulate matter-induced cardiac dysfunction

Exposure to particulate matter air pollution has been causally linked to cardiovascular disease in humans. Several broad and overlapping hypotheses describing the biological mechanisms by which particulate matter exposure leads to cardiovascular disease have been explored, although linkage with specific factors or genes remains limited. These hypotheses may or may not also lead to particulate matter-induced cardiac dysfunction. Evidence pointing to autocrine/paracrine signaling systems as modulators of cardiac dysfunction has increased interest in the emerging role of endothelins as mediators of cardiac function following particulate matter exposure. Endothelin-1, a well-described small peptide expressed in the pulmonary and cardiovascular systems, is best known for its ability to constrict blood vessels, although it can also induce extravascular effects. Research on the role of endothelins in the context of air pollution has largely focused on vascular effects, with limited investigation of responses resulting from the direct effects of endothelins on cardiac tissue. This represents a significant knowledge gap in air pollution health effects research, given the abundance of endothelin receptors found on cardiac tissue and the ability of endothelin-1 to modulate cardiac contractility, heart rate, and rhythm. The plausibility of endothelin-1 as a mediator of particulate matter-induced cardiac dysfunction is further supported by the therapeutic utility of certain endothelin receptor antagonists. The present review examines the possibility that endothelin-1 release caused by exposure to PM directly modulates extravascular effects on the heart, deleteriously altering cardiac function.

HJP272, a novel endothelin receptor antagonist, attenuates lipopolysaccharide-induced acute lung injury in hamsters

INTRODUCTION

Previous studies from this laboratory indicate that endothelin-1 (ET-1), a potent vasoconstrictor, may play an important role in lipopolysaccharide (LPS)-induced release of neutrophils from the pulmonary microvasculature. To further test this concept, Syrian hamsters were treated with a novel endothelin receptor A (ETA) antagonist (HJP272) prior to intratracheal instillation of LPS.

METHODS

The effect of HJP272 on the LPS-induced inflammatory reaction was determined by measuring: (1) lung histopathological changes, (2) total neutrophils in bronchoalveolar lavage fluid (BALF), (3) expression of tumor necrosis factor receptor 1 (TNFR1) by BALF macrophages, and (4) alveolar septal cell apoptosis.

RESULTS

Treatment with HJP272 significantly reduced each of these parameters during a 24-hr period following LPS instillation, supporting the concept that limiting the activity of ET-1 may reduce the extent of lung injury. This hypothesis was further tested by giving ET-1 prior to LPS instillation, which resulted in a marked enhancement of LPS-induced lung inflammation, as measured by BALF neutrophils and TNFR1-positive macrophages. Furthermore, the increase in neutrophils resulting from treatment with ET-1 was significantly reduced by HJP272, again demonstrating the ability of ETA receptor antagonists to limit the influx of these cells into the lung.

CONCLUSIONS

These findings suggest a potential therapeutic role for these agents in diseases where neutrophils are a significant cause of lung injury, such as bronchopneumonia, respiratory distress syndrome, and chronic obstructive pulmonary disease.

Pro-fibrotic processes in human lung fibroblasts are driven by an autocrine/paracrine endothelinergic system

BACKGROUND AND PURPOSE

Since endothelin (ET) may act as pro-fibrotic mediator, expression and release of ET isoforms, their receptors and potential pro-fibrotic ET effects were studied in human lung fibroblasts.

EXPERIMENTAL APPROACH

MRC-5 and primary human lung fibroblasts (phLFb) were cultured. Expression of prepro-ET isoforms was determined by qPCR and release of ET-1 by elisa. ET receptor function was analysed by real-time measurement of dynamic mass redistribution (DMR). Incorporation of [(3) H]-thymidine was determined as measure of proliferation and that of [(3) H]-proline for collagen synthesis. Phospho-p42/44 MAP kinase was determined by Western blot.

KEY RESULTS

ET-1 is the predominant ET in human lung fibroblasts (hLF), and TGF-β caused a further, selective and sustained up-regulation of ET-1 resulting in increased extracellular ET-1 accumulation. hLFb express mRNA encoding ET-A and ET-B receptors. Expression of both receptors was confirmed at protein level. ET-1 induced marked DMR signals, an effect that involved ET-A and ET-B receptors. Stimulatory effects of ET-1 on hLFb proliferation and collagen synthesis were mediated exclusively via ET-A receptors. ET-1, again via ET-A receptors, induced rapid activation of ERK MAPK, shown to be a crucial cellular signal in ET-1-induced collagen synthesis. ET-1-induced activation of ERK and collagen synthesis was, in contrast to corresponding effect of a muscarinic agonist, largely insensitive to pertussis toxin.

CONCLUSIONS AND IMPLICATIONS

hLFb are endowed with all elements necessary to build a functional autocrine/paracrine endothelinergic system, which appears to drive pro-fibrotic airway and lung remodelling processes, effects for which only ET-A, but not ET-B receptors appear to be of significance.

Prevention and endothelial therapy of coronary artery disease

Functional integrity of endothelial cells is an indicator and a prerequisite for vascular health and counteracts the development of atherosclerosis. This concept of 'endothelial therapy' was developed in the late 1990s as an approach to preserve or restore endothelial cell health given that 'the knowledge of the mechanisms involved in 'endothelial dysfunction' allows us to interfere specifically with pathogenic pathways at very early time points and to slow down the progression of disease'. In the present review, the principles underlying endothelial cell health will be discussed as well as the role of endothelial therapy as a preventive measure to reduce the prevalence of coronary artery disease or to delay disease progression in patients with chronic coronary artery disease. This article also highlights the importance of active participation, the need to reduce the number of future patients in view of the rising prevalence of childhood obesity, and the potential of endothelial therapy to improve survival, reduce disability and health costs, and to improve overall quality of life in patients at risk for or already diagnosed with coronary artery disease. The preventive and therapeutic approaches and considerations described herein can be applied by physicians, patients, parents, educators, health agencies, and political decision makers to help reducing the global cardiovascular disease burden in the decades to come.

Evaluation of the pulmonary effects of short-term nose-only cigarette smoke exposure in mice

Much is known about the chronic effects of cigarette smoke (CS) on lung function and inflammation and development of chronic obstructive pulmonary disease. However, the underlying pathophysiological mechanisms related to the short-term exposure to CS are not fully understood. Here, we assessed the effect of CS generated by nine consecutive cigarettes per day for four days in a nose-only exposure system on airway resistance measured using forced oscillation technique, lung inflammation and oxidative stress in BALB/c mice. Control mice were exposed to air. Mice exposed to CS showed a significant increase of neutrophils and lymphocytes numbers in bronchoalveolar lavage (BAL). The total protein and endothelin levels in BAL fluid were significantly augmented suggesting an increase of alveolar-capillary barrier permeability. Similarly, airway resistance was significantly increased in the CS group compared with controls. Furthermore, reactive oxygen species and lipid peroxidation levels in lung tissue were significantly increased. The antioxidant activities of reduced glutathione, glutathione S transferase and superoxide dismutase were all significantly increased following CS exposure, indicating that CS could trigger adaptive responses that counterbalance the potentially damaging activity of oxygen radicals induced by CS exposure. In conclusion, our data indicate that short-term nose-only exposure to CS causes lung inflammation and increase of airway resistance mediated at least partly through the oxidative stress.

Cigarette smoke-induced emphysema in A/J mice is associated with pulmonary oxidative stress, apoptosis of lung cells, and global alterations in gene expression

Cigarette smoking is the major risk factor for developing chronic obstructive pulmonary disease, the fourth leading cause of deaths in the United States. Despite recent advances, the molecular mechanisms involved in the initiation and progression of this disease remain elusive. We used Affymetrix Gene Chip arrays to determine the temporal alterations in global gene expression during the progression of pulmonary emphysema in A/J mice. Chronic cigarette smoke (CS) exposure caused pulmonary emphysema in A/J mice, which was associated with pronounced bronchoalveolar inflammation, enhanced oxidative stress, and increased apoptosis of alveolar septal cells. Microarray analysis revealed the upregulation of 1,190, 715, 260, and 246 genes and the downregulation of 1,840, 730, 442, and 236 genes in the lungs of mice exposed to CS for 5 h, 8 days, and 1.5 and 6 mo, respectively. Most of the genes belong to the functional categories of phase I genes, Nrf2-regulated antioxidant and phase II genes, phase III detoxification genes, and others including immune/inflammatory response genes. Induction of the genes encoding multiple phase I enzymes was markedly higher in the emphysematous lungs, whereas reduced expression of various cytoprotective genes constituting ubiquitin-proteasome complex, cell survival pathways, solute carriers and transporters, transcription factors, and Nrf2-regulated antioxidant and phase II-responsive genes was noted. Our data indicate that the progression of CS-induced emphysema is associated with a steady decline in the expression of various genes involved in multiple pathways in the lungs of A/J mice. Many of the genes discovered in this study could rationally play an important role in the susceptibility to CS-induced emphysema.