Effect of chronic hypoxia on RAGE and its soluble forms in lungs and plasma of mice

AbstractThe receptor for advanced glycation end products (RAGE) is a multi-ligand receptor. Alternative splicing and enzymatic shedding produce soluble forms that protect against damage by ligands including Advanced Glycation End products (AGEs). A link between RAGE and oxygen levels is evident from studies showing RAGE-mediated injury following hyperoxia. The effect of hypoxia on pulmonary RAGE expression and circulating sRAGE levels is however unknown. Therefore mice were exposed to chronic hypoxia for 21d and expression of RAGE, sheddases in lungs and circulating sRAGE were determined. In addition, accumulation of AGEs in lungs and expression of the AGE detoxifying enzyme GLO1 and receptors were evaluated.In lung tissue gene expression of total RAGE, variants 1 and 3 were elevated in mice exposed to hypoxia, whereas mRAGE and sRAGE protein levels were decreased. In the hypoxic group plasma sRAGE levels were enhanced. Although the levels of pro-ADAM10 were elevated in lungs of hypoxia exposed mice, the relative amount of the active form was decreased and gelatinase activity unaffected. In the lungs, the RAGE ligand HMGB1 was decreased and of the AGEs, only LW-1 was increased by chronic hypoxia. Gene expression of AGE receptors 2 and 3 was significantly upregulated.Chronic hypoxia is associated with downregulation of pulmonary RAGE protein levels, but a relative increase in sRAGE. These alterations might be part of the adaptive and protective response mechanism to chronic hypoxia and are not associated with AGE formation except for the fluorophore LW-1 which emerges as a novel marker of tissue hypoxia

Copper-Heparin Inhalation Therapy To Repair Emphysema: A Scientific Rationale

Current pharmacotherapy of chronic obstructive pulmonary disease (COPD) aims at reducing respiratory symptoms and exacerbation frequency. Effective therapies to reduce disease progression, however, are still lacking. Furthermore, COPD medications showed less favorable effects in emphysema than in other COPD phenotypes. Elastin fibers are reduced and disrupted, whereas collagen levels are increased in emphysematous lungs. Protease/antiprotease imbalance has historically been regarded as the sole cause of emphysema. However, it is nowadays appreciated that emphysema may also be provoked by perturbations in the sequential repair steps following elastolysis. Essentiality of fibulin-5 and lysyl oxidase-like 1 in the elastin restoration process is discussed, and it is argued that copper deficiency is a plausible reason for failing elastin repair in emphysema patients. Since copper-dependent lysyl oxidases crosslink elastin as well as collagen fibers, copper supplementation stimulates accumulation of both proteins in the extracellular matrix. Restoration of abnormal elastin fibers in emphysematous lungs is favorable, whereas stimulating pulmonary fibrosis formation by further increasing collagen concentrations and organization is detrimental. Heparin inhibits collagen crosslinking while stimulating elastin repair and might therefore be the ideal companion of copper for emphysema patients. Efficacy and safety considerations may lead to a preference of pulmonary administration of copper-heparin over systemic administration

Early origins of lung disease: Towards an interdisciplinary approach

The prenatal and perinatal environments can have profound effects on the development of chronic inflammatory diseases. However, mechanistic insight into how the early-life microenvironment can impact upon development of the lung and immune system and consequent initiation and progression of respiratory diseases is still emerging. Recent studies investigating the developmental origins of lung diseases have started to delineate the effects of early-life changes in the lung, environmental exposures and immune maturation on the development of childhood and adult lung diseases. While the influencing factors have been described and studied in mostly animal models, it remains challenging to pinpoint exactly which factors and at which time point are detrimental in lung development leading to respiratory disease later in life. To advance our understanding of early origins of chronic lung disease and to allow for proper dissemination and application of this knowledge, we propose four major focus areas: 1) policy and education; 2) clinical assessment; 3) basic and translational research; and 4) infrastructure and tools, and discuss future directions for advancement. This review is a follow-up of the discussions at the European Respiratory Society Research Seminar “Early origins of lung disease: towards an interdisciplinary approach” (Lisbon, Portugal, November 2019)

Copper-heparin inhalation therapy to repair emphysema: A scientific rationale

Current pharmacotherapy of chronic obstructive pulmonary disease (COPD) aims at reducing respiratory symptoms and exacerbation frequency. Effective therapies to reduce disease progression, however, are still lacking. Furthermore, COPD medications showed less favorable effects in emphysema than in other COPD phenotypes. Elastin fibers are reduced and disrupted, whereas collagen levels are increased in emphysematous lungs. Protease/antiprotease imbalance has historically been regarded as the sole cause of emphysema. However, it is nowadays appreciated that emphysema may also be provoked by perturbations in the sequential repair steps following elastolysis. Essentiality of fibulin-5 an

Glutathione biochemistry in asthma

Oxidative stress in an important hallmark of asthma and much research has therefore focused on the predominant antioxidant in the lungs, namely the tripeptide glutathione. In lung samples of patients with asthma increased levels of glutathione are typically observed which appear to relate to the level of pulmonary inflammation and are therefore regarded as an adaptive response to the associated oxidative stress. Also in blood samples increased total GSH levels have been reported, representing the systemic inflammatory component of the disease. In addition, a number of the antioxidant enzymes involved in the maintenance of the GSH/GSSG ratio as well as enzymes that utilize GSH have been found to be altered in the lungs and blood of asthmatics and will be summarized in this review. Very few studies have however linked enzymatic alterations to GSH levels or found that either of these correlated with disease severity. Some animal studies have started to investigate the pathophysiological role of GSH biochemistry in asthma and have yielded surprising results. Important in this respect is the physiological role of the GSH redox equilibrium in determining the outcome of immune responses which could be deregulated in asthmatics and contribute to the disease. Clinical data as well as animal and cell culture studies regarding these aspects of GSH in the context of asthma will be summarized and discussed in this review

Immune Homeostasis in Epithelial Cells: Evidence and Role of Inflammasome Signaling Reviewed

The epithelium regulates the interaction between the noxious xenogenous, as well as the microbial environment and the immune system, not only by providing a barrier but also by expressing a number of immunoregulatory membrane receptors, and intracellular danger sensors and their downstream effectors. Amongst these are a number of inflammasome sensor subtypes, which have been initially characterized in myeloid cells and described to be activated upon assembly into multiprotein complexes by microbial and environmental triggers. This review compiles a vast amount of literature that supports a pivotal role for inflammasomes in the various epithelial barriers of the human body as essential factors maintaining immune signaling and homeostasis

Systemic and local inflammation in asthma and chronic obstructive pulmonary disease: is there a connection?

Increasing evidence indicates that chronic obstructive pulmonary disease (COPD) and probably asthma are associated with low-grade systemic inflammatory changes. In patients with COPD, systemic inflammation is considered a key factor in the pathogenesis of the multicomponent disease manifestations. Spillover of inflammatory mediators into the circulation is generally considered to be the source of this systemic inflammation. Despite this attractive hypothesis, the nature of systemic inflammation in COPD and asthma remains unclear. Available scientific data challenge the spill-over hypothesis. Interventions with biologicals such as TNF-alpha do not modify local or systemic inflammation in these inflammatory respiratory diseases. Adipose tissue-mediated inflammation is discussed as a connecting link of systemic inflammation in asthma and COPD

Silica induces NLRP3 inflammasome activation in human lung epithelial cells

ABSTRACT: BACKGROUND: In myeloid cells the inflammasome plays a crucial innate immune defenses against pathogen- and danger-associated patterns crystalline silica. Respirable mineral particles impinge upon the lung causing irreversible damage, sustained inflammation and silicosis. In we investigated lung epithelial cells as a target for silica-induced activation. METHODS: A human bronchial epithelial cell line (BEAS-2B) normal human bronchial epithelial cells (NHBE) were exposed to toxic but nonlethal doses of crystalline silica over time to perform functional characterization of NLRP3, caspase-1, IL-1beta, bFGF and HMGB1. RT-PCR, caspase-1 enzyme activity assay, Western blot techniques, cytokine-specific ELISA and fibroblast (MRC-5 cells) proliferation performed. RESULTS: We were able to show transcriptional and upregulation of the components of the NLRP3 intracellular platform, as activation of caspase-1. NLRP3 activation led to maturation of pro-IL- secreted IL-1beta, and a significant increase in the unconventional the alarmins bFGF and HMGB1. Moreover, release of bFGF and HMGB1 was dependent on particle uptake. Small interfering RNA experiments using revealed the pivotal role of the inflammasome in diminished release of pro-inflammatory cytokines, danger molecules and growth factors, and proliferation. CONCLUSION: Our novel data indicate the presence and activation of the NLRP3 inflammasome by crystalline silica in human lung epithelial cells, which prolongs an inflammatory signal and affects proliferation, mediating a cadre of lung diseases