Advanced glycation end products and its receptor (RAGE) are increased in patients with COPD

Associations of dietary inflammation index and composite dietary antioxidant index with preserved ratio impaired spirometry in US adults and the mediating roles of triglyceride-glucose index: NHANES 2007-2012

BACKGROUND

Previous studies have shown that inflammatory and antioxidant dietary patterns can modify the risk of COPD, yet few studies have examined the association of these diets with its early signs (PRISm), and the potential role of metabolic disorders remains to be elucidated.

METHODS

Data from 9529 individuals who participated in the 2007-2012 National Health and Nutrition Examination Survey (NHANES) were analyzed. The Dietary Inflammation Index (DII) and the Dietary Antioxidant Composite Index (CDAI) were assessed using 24-h dietary recall, multiple metabolic indicators were calculated according to biochemical markers, and lung function parameters defined PRISm cases. Individual and joint effects of DII and CDAI were evaluated by generalized linear models and binary logistic regression models, and mediation effects of metabolic indicators were further explored by causal mediation analysis.

RESULTS

Increased DII was associated with decreased lung function (FEV1: β = -18.82, FVC: β = -29.2; OR = 1.04) and increased metabolic indicators (β = 0.316, 0.036, 0.916, 0.033, and 0.145 on MAP, UA, TC, TyG, and MS, respectively). Contrary to this, CDAI were positively and negatively associated with lung function (FEV1: β = 3.42; FVC: β = 4.91; PRISm: OR = 0.99) and metabolic indicators (β < 0), respectively. Joint effects of DII and CDAI indicated the minimal hazard effects of DII on TyG (β = -0.11), FEV1 (β = 72.62), FVC (β = 122.27), and PRISm (OR = 0.79) in subjects with high CDAI when compared with those with low CDAI (low DII + high CDAI vs. high DII + low CDAI). Furthermore, TyG mediated 13.74 %, 8.29 %, and 21.70 % of DII- and 37.30 %, 20.90 %, and 12.32 % of CDAI-FEV1, -FVC, and -PRISm associations, respectively.

CONCLUSIONS

These findings indicated that CDAI can attenuate the adverse effects of DII on metabolic disorders and lung function decline, which provides new insight for diet modification in preventing early lung dysfunction.

Breathing new life into the study of COPD with genes identified from genome-wide association studies

COPD is a major cause of morbidity and mortality globally. While the significance of environmental exposures in disease pathogenesis is well established, the functional contribution of genetic factors has only in recent years drawn attention. Notably, many genes associated with COPD risk are also linked with lung function. Because reduced lung function precedes COPD onset, this association is consistent with the possibility that derangements leading to COPD could arise during lung development. In this review, we summarise the role of leading genes (HHIP, FAM13A, DSP, AGER and TGFB2) identified by genome-wide association studies in lung development and COPD. Because many COPD genome-wide association study genes are enriched in lung epithelial cells, we focus on the role of these genes in the lung epithelium in development, homeostasis and injury.

Breath of fresh air: Investigating the link between AGEs, sRAGE, and lung diseases

Advanced glycation end products (AGEs) are compounds formed via non-enzymatic reactions between reducing sugars and amino acids or proteins. AGEs can accumulate in various tissues and organs and have been implicated in the development and progression of various diseases, including lung diseases. The receptor of advanced glycation end products (RAGE) is a receptor that can bind to advanced AGEs and induce several cellular processes such as inflammation and oxidative stress. Several studies have shown that both AGEs and RAGE play a role in the pathogenesis of lung diseases, such as chronic obstructive pulmonary disease, asthma, idiopathic pulmonary fibrosis, cystic fibrosis, and acute lung injury. Moreover, the soluble form of the receptor for advanced glycation end products (sRAGE) has demonstrated its ability to function as a decoy receptor, possessing beneficial characteristics such as anti-inflammatory, antioxidant, and anti-fibrotic properties. These qualities make it an encouraging focus for therapeutic intervention in managing pulmonary disorders. This review highlights the current understanding of the roles of AGEs and (s)RAGE in pulmonary diseases and their potential as biomarkers and therapeutic targets for preventing and treating these pathologies.

The RAGE Axis: A Relevant Inflammatory Hub in Human Diseases

In 1992, a transcendental report suggested that the receptor of advanced glycation end-products (RAGE) functions as a cell surface receptor for a wide and diverse group of compounds, commonly referred to as advanced glycation end-products (AGEs), resulting from the non-enzymatic glycation of lipids and proteins in response to hyperglycemia. The interaction of these compounds with RAGE represents an essential element in triggering the cellular response to proteins or lipids that become glycated. Although initially demonstrated for diabetes complications, a growing body of evidence clearly supports RAGE's role in human diseases. Moreover, the recognizing capacities of this receptor have been extended to a plethora of structurally diverse ligands. As a result, it has been acknowledged as a pattern recognition receptor (PRR) and functionally categorized as the RAGE axis. The ligation to RAGE leads the initiation of a complex signaling cascade and thus triggering crucial cellular events in the pathophysiology of many human diseases. In the present review, we intend to summarize basic features of the RAGE axis biology as well as its contribution to some relevant human diseases such as metabolic diseases, neurodegenerative, cardiovascular, autoimmune, and chronic airways diseases, and cancer as a result of exposure to AGEs, as well as many other ligands.

The AGE-RAGE axis associates with chronic pulmonary diseases and smoking in the Rotterdam study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and asthma associate with high morbidity and mortality. High levels of advanced glycation end products (AGEs) were found in tissue and plasma of COPD patients but their role in COPD and asthma is unclear.

METHODS

In the Rotterdam Study (n = 2577), AGEs (by skin autofluorescence (SAF)), FEV1 and lung diffusing capacity (DLCOc and DLCOc /alveolar volume [VA]) were measured. Associations of SAF with asthma, COPD, GOLD stage, and lung function were analyzed using logistic and linear regression adjusted for covariates, followed by interaction and stratification analyses. sRAGE and EN-RAGE associations with COPD prevalence were analyzed by logistic regression.

RESULTS

SAF associated with COPD prevalence (OR = 1.299 [1.060, 1.591]) but not when adjusted for smoking (OR = 1.106 [0.89, 1.363]). SAF associated with FEV1% predicted (β=-3.384 [-4.877, -1.892]), DLCOc (β=-0.212 [-0.327, -0.097]) and GOLD stage (OR = 4.073, p = 0.001, stage 3&4 versus 1). Stratified, the association between SAF and FEV1%predicted was stronger in COPD (β=-6.362 [-9.055, -3.670]) than non-COPD (β=-1.712 [-3.306, -0.118]). Association of SAF with DLCOc and DLCOc/VA were confined to COPD (β=-0.550 [-0.909, -0.191]; β=-0.065 [-0.117, -0.014] respectively). SAF interacted with former smoking and COPD prevalence for associations with lung function. Lower sRAGE and higher EN-RAGE associated with COPD prevalence (OR = 0.575[0.354, 0.931]; OR = 1.778[1.142, 2.768], respectively).

CONCLUSIONS

Associations between SAF, lung function and COPD prevalence were strongly influenced by smoking. SAF associated with COPD severity and its association with lung function was more prominent within COPD. These results fuel further research into interrelations and causality between SAF, smoking and COPD.

TAKE-HOME MESSAGE

Skin AGEs associated with prevalence and severity of COPD and lung function in the general population with a stronger effect in COPD, calling for further research into interrelations and causality between SAF, smoking and COPD.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

Nutritional State and COPD: Effects on Dyspnoea and Exercise Tolerance

Chronic Obstructive Pulmonary Disease (COPD) is a disease that is spreading worldwide and is responsible for a huge number of deaths annually. It is characterized by progressive and often irreversible airflow obstruction, with a heterogeneous clinical manifestation based on disease severity. Along with pulmonary impairment, COPD patients display different grades of malnutrition that can be linked to a worsening of respiratory function and to a negative prognosis. Nutritional impairment seems to be related to a reduced exercise tolerance and to dyspnoea becoming a major determinant in patient-perceived quality of life. Many strategies have been proposed to limit the effects of malnutrition on disease progression, but there are still limited data available to determine which of them is the best option to manage COPD patients. The purpose of this review is to highlight the main aspects of COPD-related malnutrition and to underline the importance of poor nutritional state on muscle energetics, exercise tolerance and dyspnoea.

RAGE pathway activation and function in chronic kidney disease and COVID-19

The multi-ligand receptor for advanced glycation end-products (RAGE) and its ligands are contributing factors in autoimmunity, cancers, and infectious disease. RAGE activation is increased in chronic kidney disease (CKD) and coronavirus disease 2019 (COVID-19). CKD may increase the risk of COVID-19 severity and may also develop in the form of long COVID. RAGE is expressed in essentially all kidney cell types. Increased production of RAGE isoforms and RAGE ligands during CKD and COVID-19 promotes RAGE activity. The downstream effects include cellular dysfunction, tissue injury, fibrosis, and inflammation, which in turn contribute to a decline in kidney function, hypertension, thrombotic disorders, and cognitive impairment. In this review, we discuss the forms and mechanisms of RAGE and RAGE ligands in the kidney and COVID-19. Because various small molecules antagonize RAGE activity in animal models, targeting RAGE, its co-receptors, or its ligands may offer novel therapeutic approaches to slowing or halting progressive kidney disease, for which current therapies are often inadequate.

Diesel exhaust particles distort lung epithelial progenitors and their fibroblast niche

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease characterized by inflammation and impaired tissue regeneration, and is reported as the fourth leading cause of death worldwide by the Centers for Disease Control and Prevention (CDC). Environmental pollution and specifically motor vehicle emissions are known to play a role in the pathogenesis of COPD, but little is still known about the molecular mechanisms that are altered following diesel exhaust particles (DEP) exposure. Here we used lung organoids derived from co-culture of alveolar epithelial progenitors and fibroblasts to investigate the effect of DEP on the epithelial-mesenchymal signaling niche in the distal lung, which is essential for tissue repair. We found that DEP treatment impaired the number as well as the average diameter of both airway and alveolar type of lung organoids. Bulk RNA-sequencing of re-sorted epithelial cells and fibroblasts following organoid co-culture shows that the Nrf2 pathway, which regulates antioxidants' activity, was upregulated in both cell populations in response to DEP; and WNT/β-catenin signaling, which is essential to promote epithelial repair, was downregulated in DEP-exposed epithelial cells. We show that pharmacological treatment with anti-oxidant agents such as N-acetyl cysteine (NAC) or Mitoquinone mesylate (MitoQ) reversed the effect of DEP on organoids growth. Additionally, a WNT/β-catenin activator (CHIR99021) successfully restored WNT signaling and promoted organoid growth upon DEP exposure. We propose that targeting oxidative stress and specific signaling pathways affected by DEP in the distal lung may represent a strategy to restore tissue repair in COPD.

Triglyceride-Glucose Index is a Risk Marker of Incident COPD Events in Women

Purpose

The triglyceride-glucose index (TyG index) is a marker of insulin resistance and metabolic dysfunction and has the advantage of being universally available. Although recent evidence suggests the TyG index has relevance to respiratory health, there have been no prospective studies assessing its value as a biomarker for chronic lung diseases. We aim to assess the TyG index as a potential risk marker for future incident COPD events in the general population.

Patients and Methods

Baseline TyG index was assessed in 28,282 middle-aged men and women without previous history of chronic obstructive pulmonary disease (COPD) from the Malmö Preventive Project (men between 1974 and 1982 and women between 1982 and 1992). All subjects were followed up prospectively, and Cox proportional hazards regression was used to assess incident COPD events according to quartiles of TyG index.

Results

After an average of 31 years of follow-up, TyG index was a strong predictor of future COPD events even after adjusting for potential confounders (Q4 (highest TyG index) HR (95% CI): 1.21 (1.09–1.35) vs Q1 (reference), p-trend <0.001). After stratifying by sex, the results remained statistically significant in women only (Q4 vs Q1 HR 1.72 (1.41–2.09)). Additionally, the risk remained significant in a cohort of life-long never smokers (Q4 vs Q1 HR 1.47 (1.08–2.01)).

Conclusion

A raised TyG index is a novel risk marker of future incident COPD events in women. Insulin resistance as reflected by the TyG index can precede the development of obstructive lung disease and as such may be an easily measurable and useful predictor of COPD in women.

Advanced glycation end-products and advanced oxidation protein products in schizophrenia

Schizophrenia pathophysiology is still not well understood. Genetic factors involving biochemical systems are key players and oxidative stress takes part to the development and worsening of SZ. Oxidative stress led to the permanent production of oxidation products such as advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs). These proteins interact with their receptor amplifying ROS production and pro-inflammatory cytokines sustaining a permanent loop. We tested plasma levels of AGEs and AOPPs in 30 SZ patients. Their levels were statistically higher than controls confirming their involvement in mental disorders. Antioxidant nutraceuticals and a healthy lifestyle could diminish oxidative stress and ameliorate SZ symptoms.

Protein interaction networks provide insight into fetal origins of chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a leading cause of death in adults that may have origins in early lung development. It is a complex disease, influenced by multiple factors including genetic variants and environmental factors. Maternal smoking during pregnancy may influence the risk for diseases during adulthood, potentially through epigenetic modifications including methylation.

METHODS

In this work, we explore the fetal origins of COPD by utilizing lung DNA methylation marks associated with in utero smoke (IUS) exposure, and evaluate the network relationships between methylomic and transcriptomic signatures associated with adult lung tissue from former smokers with and without COPD. To identify potential pathobiological mechanisms that may link fetal lung, smoke exposure and adult lung disease, we study the interactions (physical and functional) of identified genes using protein-protein interaction networks.

RESULTS

We build IUS-exposure and COPD modules, which identify connected subnetworks linking fetal lung smoke exposure to adult COPD. Studying the relationships and connectivity among the different modules for fetal smoke exposure and adult COPD, we identify enriched pathways, including the AGE-RAGE and focal adhesion pathways.

CONCLUSIONS

The modules identified in our analysis add new and potentially important insights to understanding the early life molecular perturbations related to the pathogenesis of COPD. We identify AGE-RAGE and focal adhesion as two biologically plausible pathways that may reveal lung developmental contributions to COPD. We were not only able to identify meaningful modules but were also able to study interconnections between smoke exposure and lung disease, augmenting our knowledge about the fetal origins of COPD.

Implication of RAGE Polymorphic Variants in COPD Complication and Anti-COPD Therapeutic Potential of sRAGE

Chronic obstructive pulmonary disease (COPD) is a slowly progressive and poorly reversible airway obstruction disease. It is caused either alone or in combination of emphysema, chronic bronchitis (CB), and small airways disease. COPD is thought to be a multi-factorial disorder in which genetic susceptibility, environmental factors and tobacco exposure could be doubly or simultaneously implicated. Available medicines against COPD include anti-inflammatory drugs, such as β2-agonists and anticholinergics, which efficiently reduce airflow limitation but are unable to avert disease progression and mortality. Advanced glycation end products (AGE) and their receptors i.e. receptor for advanced glycation end products (RAGE) are some molecules that have been implicated in the complication of COPD. Several RAGE single nucleotide polymorphic (SNP) variants are produced by the mammalian cells. Based on the ethnicity some SNPs aggravate the COPD severity. Mammalian cells produce several alternative RAGE splice variants including a soluble RAGE (sRAGE) and an endogenous soluble RAGE (esRAGE). Both of these act as decoy receptor and thus may help to arrest the COPD complications. Several lines of evidences indicate a decreased level of sRAGE in the COPD subjects. One of the new strategies to reduce COPD complication may be sRAGE therapeutic administration to the COPD subjects. This comprehensive discussion sheds light on the role of RAGE and its polymorphic variants in the COPD complication along with sRAGE therapeutic significance in the COPD prevention.

Reactive Oxygen Species and Antioxidative Defense in Chronic Obstructive Pulmonary Disease

The respiratory system is continuously exposed to endogenous and exogenous oxidants. Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation of the airways, leading to the destruction of lung parenchyma (emphysema) and declining pulmonary function. It is increasingly obvious that reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the progression and amplification of the inflammatory responses related to this disease. First, we described the association between cigarette smoking, the most representative exogenous oxidant, and COPD and then presented the multiple pathophysiological aspects of ROS and antioxidative defense systems in the development and progression of COPD. Second, the relationship between nitric oxide system (endothelial) dysfunction and oxidative stress has been discussed. Third, we have provided data on the use of these biomarkers in the pathogenetic mechanisms involved in COPD and its progression and presented an overview of oxidative stress biomarkers having clinical applications in respiratory medicine, including those in exhaled breath, as per recent observations. Finally, we explained the findings of recent clinical and experimental studies evaluating the efficacy of antioxidative interventions for COPD. Future breakthroughs in antioxidative therapy may provide a promising therapeutic strategy for the prevention and treatment of COPD.

Role of Atypical Chemokines and Chemokine Receptors Pathways in the Pathogenesis of COPD

Chronic obstructive pulmonary disease (COPD) represents a heightened inflammatory response in the lung generally resulting from tobacco smoking-induced recruitment and activation of inflammatory cells and/or activation of lower airway structural cells. Several mediators can modulate activation and recruitment of these cells, particularly those belonging to the chemokines (conventional and atypical) family. There is emerging evidence for complex roles of atypical chemokines and their receptors (such as high mobility group box 1 (HMGB1), antimicrobial peptides, receptor for advanced glycosylation end products (RAGE) or toll-like receptors (TLRs)) in the pathogenesis of COPD, both in the stable disease and during exacerbations. Modulators of these pathways represent potential novel therapies for COPD and many are now in preclinical development. Inhibition of only a single atypical chemokine or receptor may not block inflammatory processes because there is redundancy in this network. However, there are many animal studies that encourage studies for modulating the atypical chemokine network in COPD. Thus, few pharmaceutical companies maintain a significant interest in developing agents that target these molecules as potential antiinflammatory drugs. Antibody-based (biological) and small molecule drug (SMD)-based therapies targeting atypical chemokines and/or their receptors are mostly at the preclinical stage and their progression to clinical trials is eagerly awaited. These agents will most likely enhance our knowledge about the role of atypical chemokines in COPD pathophysiology and thereby improve COPD management.

Incidence of primary graft dysfunction is higher according to the new ISHLT 2016 guidelines and correlates with clinical and molecular risk factors

Background

Primary graft dysfunction (PGD) is the most important determinant of morbidity and mortality after lung transplantation, but its definition has evolved over the past decade. The implications of this refinement in clinical definition have not been evaluated. In this single-center study, we compared PGD incidence, risk factors, and outcomes using the 2005 and the updated-2016 International Society of Heart and Lung Transplantation guidelines for PGD grading in lung transplant patients.

Methods

In this retrospective study, we extracted data from the medical records of 127 patients who underwent lung transplantation between 1/1/2016–12/31/2018. PGD was defined as PGD3 present at 48 and/or 72 hours post-reperfusion. We used the 2005 and the updated 2016 guidelines to assess clinical risk factors, outcomes, and baseline biomarkers for PGD.

Results

On the basis of the 2016 and 2005 guidelines, we identified PGD in 37% and 26% of patients, respectively. PGD was significantly associated with extracorporeal life support, large body mass index, and restrictive lung disease using the 2016 but not the 2005 guidelines. Based on the 2016 guidelines, pretransplant levels of several biomarkers were associated with PGD; using the 2005 guidelines, only increased interleukin-2 levels were significantly associated with PGD. No preoperative biomarkers were associated with PGD using either guidelines after adjusting for clinical variables. Postoperative morbidity and 1-year mortality were similar regardless of guidelines used.

Conclusions

Our findings suggest that refinements in the PGD scoring system have improved the detection of graft injury and associated risk factors without changing its ability to predict postoperative morbidity and mortality.

Small Airways Disease, Biomarkers and COPD: Where are We?

The response to treatment and progression of Chronic Obstructive Pulmonary Disease (COPD) varies significantly. Small airways disease (SAD) is being increasingly recognized as a key pathological feature of COPD. Studies have brought forward pathological evidence of small airway damage preceding the development of emphysema and the detection of obstruction using traditional spirometry. In recent years, there has been a renewed interest in the early detection of SAD and this has brought along an increased demand for physiological tests able to identify and quantify SAD. Early detection of SAD allows early targeted therapy and this suggests the potential for altering the course of disease. The aim of this article is to review the evidence available on the physiological testing of small airways. The first half will focus on the role of lung function tests such as maximum mid-expiratory flow, impulse oscillometry and lung clearance index in detecting and quantifying SAD. The role of Computed Tomography (CT) as a radiological biomarker will be discussed as well as the potential of recent CT analysis software to differentiate normal aging of the lungs to pathology. The evidence behind SAD biomarkers sourced from blood as well as biomarkers sourced from sputum and broncho-alveolar lavage (BAL) will be reviewed. This paper focuses on CC-16, sRAGE, PAI-1, MMP-9 and MMP-12.

The AGE-RAGE Axis and RAGE Genetics in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a heterogeneous group of lung diseases limiting the airflow due to narrowing of airways, chronic bronchitis and emphysema that leads to difficulties in breathing. Chronic inflammation is another important characteristic of COPD which leads to immune cell infiltration and helps in the alveolar destruction. Pathology of COPD is driven by various environmental and genetic factors. COPD is mainly associated with the inhalation of toxic agents mainly the cigarette smoke. Receptor for advanced glycation end products (RAGE) has emerged as a pattern recognition receptor and is a multiligand receptor expressed moderately in various cells, tissues and highly in the lungs throughout life. RAGE recognizes various ligands produced by cigarette smoke and its role has been implicated in the pathogenesis of COPD. RAGE ligands have been reported to accumulate in the lungs of patients with COPD. RAGE is a membrane receptor but its truncated form i.e. soluble RAGE (sRAGE) mainly functions as a contender of RAGE and inhibits various RAGE dependent cell signalling. Among the various ligands of RAGE, advanced glycation end products (AGEs) are majorly linked with COPD. Accumulated AGE triggers downstream RAGE-AGE axis in COPD. Moreover, RAGE genetics has long been known to play a vital role in the pathology of various airway diseases including COPD and this gene contains an associated locus. A reliable biomarker is needed for the management of this disease. sRAGE has an inverse correlation with the RAGE showed its importance as a valuable marker in COPD. This review is focused on the role of RAGE, sRAGE, RAGE axis and RAGE genetics in COPD.

Circulating antibodies against age-modified proteins in patients with coronary atherosclerosis

Advanced glycation endproducts (AGEs) are formed in a series of non-enzymatic reactions between reducing sugars and the amino groups of proteins and accumulate during aging, diabetes mellitus, chronic kidney disease and other chronic diseases. Accumulation of AGE-modifications alters protein structure and function, transforming these molecules into potential targets of the immune system, presumably triggering the production of autoantibodies against AGEs. In this study, we detected autoantibodies against AGE-modified proteins with ELISA in plasma samples of 91 patients with documented coronary artery disease (CAD), who underwent coronary artery bypass grafting (CABG) surgery. Patients with high levels of autoantibodies had a higher body mass index (BMI 28.6 vs 27.1 kg/m²; p = 0.046), were more likely to suffer from chronic obstructive pulmonary disease (COPD 30% vs 9.8%; p = 0.018), and more likely to need dialysis after the surgery (10% vs 0%; p = 0.037). Our findings show a weak link between the levels of autoantibodies against AGEs and diabetes mellitus (DM 44% vs 24.4%; p = 0.05). In a small subpopulation of patients, antibodies against native bovine serum albumin (BSA) were detected. A growing body of research explores the potential role of antibodies against AGE-modified proteins in pathogenesis of different chronic diseases; our data confirms the presence of AGE-autoantibodies in patients with CAD and that in parallel to the AGEs themselves, they may have a potential role in concomitant clinical conditions in patients undergoing CABG surgery. Further research is necessary to verify the molecular role of these antibodies in different pathological conditions.

RAGE and its ligands: from pathogenesis to therapeutics

Receptor for advanced glycation end products (RAGE) is an immunoglobulin-like receptor present on cell surface. RAGE binds to an array of structurally diverse ligands, acts as a pattern recognition receptor (PRR) and is expressed on cells of different origin performing different functions. RAGE ligation leads to the initiation of a cascade of signaling events and is implicated in diseases, such as inflammation, cancer, diabetes, vascular dysfunctions, retinopathy, and neurodegenerative diseases. Because of the significant involvement of RAGE in the progression of numerous diseases, RAGE signaling has been targeted through use of inhibitors and anti-RAGE antibodies as a treatment strategy and therapy. Here in this review, we have summarized the physical and physiological aspects of RAGE biology in mammalian system and the importance of targeting this molecule in the treatment of various RAGE mediated pathologies. Highlights Receptor for advanced glycation end products (RAGE) is a member of immunoglobulin superfamily of receptors and involved in many pathophysiological conditions. RAGE ligation with its ligands leads to initiation of distinct signaling cascades and activation of numerous transcription factors. Targeting RAGE signaling through inhibitors and anti-RAGE antibodies can be promising treatment strategy.

Host Innate Immune Responses to Acinetobacter baumannii Infection

Acinetobacter baumannii has emerged as a major threat to global public health and is one of the key human pathogens in healthcare (nosocomial and community-acquired)-associated infections. Moreover, A. baumannii rapidly develops resistance to multiple antibiotics and is now globally regarded as a serious multidrug resistant pathogen. There is an urgent need to develop novel vaccines and immunotherapeutics as alternatives to antibiotics for clinical management of A. baumannii infection. However, our knowledge of host immune responses to A. baumannii infection and the identification of novel therapeutic targets are significantly lacking. This review highlights the recent advances and critical gaps in our understanding how A. baumannii interacts with the host innate pattern-recognition receptors, induces a cascade of inflammatory cytokine and chemokine responses, and recruits innate immune effectors (such as neutrophils and macrophages) to the site of infection for effective control of the infection. Such knowledge will facilitate the identification of new targets for the design and development of effective therapeutics and vaccines to fight this emerging threat.

Effect of 6p21 region on lung function is modified by smoking: a genome-wide interaction study

Smoking is a major risk factor for chronic obstructive pulmonary disease (COPD); however, more than 25% of COPD patients are non-smokers, and gene-by-smoking interactions are expected to affect COPD onset. We aimed to identify the common genetic variants interacting with pack-years of smoking on FEV₁/FVC ratios in individuals with normal lung function. A genome-wide interaction study (GWIS) on FEV₁/FVC was performed for individuals with FEV₁/FVC ratio ≥ 70 in the Korea Associated Resource cohort data, and significant SNPs were validated using data from two other Korean cohorts. The GWIS revealed that rs10947231 and rs8192575 met genome-wide significant levels; For \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{H}}_{0} :\beta_{SNP} = \beta_{SNP*pack - years} = 0{\text{ vs H}}_{1} : not {\text{H}}_{0} ,$$\end{document}H0:βSNP=βSNP∗pack-years=0vs H1:notH0, the likelihood ratio (LR) test was conducted, and its P values, P_LR, for rs10947231 and rs8192575 were 2.23 × 10^–12 and 1.18 × 10^–8, respectively. Interaction between rs8192575 and smoking is significantly replicated with two additional data (P_INT = 0.0454, 0.0131). Expression quantitative trait loci, topologically associated domains, and PrediXcan analyses revealed that rs8192575 is significantly associated with AGER expression. SNPs on the 6p21 region are associated with FEV₁/FVC, and the effect of smoking on FEV₁/FVC differs among the associated genotypes.

The Gly82Ser mutation in AGER contributes to pathogenesis of pulmonary fibrosis in combined pulmonary fibrosis and emphysema (CPFE) in Japanese patients

The dominant pathogenesis underlying the combined pulmonary fibrosis and emphysema (CPFE) remains unresolved. The receptor for advanced glycation end-products (RAGE) is highly expressed in lung tissues and interacts with distinct multiple ligands, implicating it in certain lung diseases. To elucidate the pathogenesis of CPFE, we genotyped three single nucleotide polymorphisms (SNPs: rs2070600, rs1800625, and rs2853807) of the gene encoding RAGE (AGER) in 111 CPFE patients and 337 chronic obstructive pulmonary disease (COPD) patients of Japanese by using StepOne Real-Time PCR System for SNP genotyping assay. Serum levels of soluble RAGE (sRAGE) were measured by ELISA. We found that the allele frequency of rs2070600 was significantly different between the two groups [corrected P (Pc) = 0.015]. In addition, the minor allele was associated with CPFE patients relative to COPD patients in a dominant effect model (Odds Ratio = 1.93; Pc = 0.018). Moreover, the serum sRAGE level was significantly lower in the CPFE group than the COPD group (P = 0.014). The rs2070600 minor allele was significantly associated with reduced sRAGE level in CPFE patients and independently affected sRAGE level reduction in this group (P = 0.020). We concluded that the AGER rs2070600 minor allele (Gly82Ser mutation) is associated with the pathogenesis of pulmonary fibrosis in CPFE in Japanese patients.

Skin autofluorescence: early sign of lung function deterioration?

Advanced glycation end products (AGEs) comprise a heterogeneous group of stable end-products of the non-enzymatic glycation reactions described by Maillard in 1912, in which reduced sugars irreparably modify proteins, lipids and DNA. This is a slow physiological process and accumulation of AGEs is part of normal ageing. Under conditions of hyperglycaemia and oxidative stress, a much faster and more substantial generation of AGEs is induced. The myriad of pathogenic signals AGEs can induce and the fact that enhanced AGE accumulation accompanies a broad spectrum of age-associated chronic inflammatory diseases [1] form the basis of the Maillard theory of ageing [2].

The relationship between SAF and FEV₁, D_LCO and X₅, independent of COPD or diabetes. Will individuals with raised SAF and subclinical lung function alterations develop disease? What mechanisms underlie parenchymal alterations indicated by SAF?https://bit.ly/2YTtdkL

Increased airway iron parameters and risk for exacerbation in COPD: an analysis from SPIROMICS

Levels of iron and iron-related proteins including ferritin are higher in the lung tissue and lavage fluid of individuals with chronic obstructive pulmonary disease (COPD), when compared to healthy controls. Whether more iron in the extracellular milieu of the lung associates with distinct clinical phenotypes of COPD, including increased exacerbation susceptibility, is unknown. We measured iron and ferritin levels in the bronchoalveolar lavage fluid (BALF) of participants enrolled in the SubPopulations and InteRmediate Outcome Measures In COPD (SPIROMICS) bronchoscopy sub-study (n = 195). BALF Iron parameters were compared to systemic markers of iron availability and tested for association with FEV1 % predicted and exacerbation frequency. Exacerbations were modelled using a zero-inflated negative binomial model using age, sex, smoking, and FEV1 % predicted as clinical covariates. BALF iron and ferritin were higher in participants with COPD and in smokers without COPD when compared to non-smoker control participants but did not correlate with systemic iron markers. BALF ferritin and iron were elevated in participants who had COPD exacerbations, with a 2-fold increase in BALF ferritin and iron conveying a 24% and 2-fold increase in exacerbation risk, respectively. Similar associations were not observed with plasma ferritin. Increased airway iron levels may be representative of a distinct pathobiological phenomenon that results in more frequent COPD exacerbation events, contributing to disease progression in these individuals.

Synergistic Effect of WTC-Particulate Matter and Lysophosphatidic Acid Exposure and the Role of RAGE: In-Vitro and Translational Assessment

World Trade Center particulate matter (WTC-PM)-exposed firefighters with metabolic syndrome (MetSyn) have a higher risk of WTC lung injury (WTC-LI). Since macrophages are crucial innate pulmonary mediators, we investigated WTC-PM/lysophosphatidic acid (LPA) co-exposure in macrophages. LPA, a low-density lipoprotein metabolite, is a ligand of the advanced glycation end-products receptor (AGER or RAGE). LPA and RAGE are biomarkers of WTC-LI. Human and murine macrophages were exposed to WTC-PM, and/or LPA, and compared to controls. Supernatants were assessed for cytokines/chemokines; cell lysate immunoblots were assessed for signaling intermediates after 24 h. To explore the translatability of our in-vitro findings, we assessed serum cytokines/chemokines and metabolites of symptomatic, never-smoking WTC-exposed firefighters. Agglomerative hierarchical clustering identified phenotypes of WTC-PM-induced inflammation. WTC-PM induced GM-CSF, IL-8, IL-10, and MCP-1 in THP-1-derived macrophages and induced IL-1α, IL-10, TNF-α, and NF-κB in RAW264.7 murine macrophage-like cells. Co-exposure induced synergistic elaboration of IL-10 and MCP-1 in THP-1-derived macrophages. Similarly, co-exposure synergistically induced IL-10 in murine macrophages. Synergistic effects were seen in the context of a downregulation of NF-κB, p-Akt, -STAT3, and -STAT5b. RAGE expression after co-exposure increased in murine macrophages compared to controls. In our integrated analysis, the human cytokine/chemokine biomarker profile of WTC-LI was associated with discriminatory metabolites (fatty acids, sphingolipids, and amino acids). LPA synergistically elaborated WTC-PM’s inflammatory effects in vitro and was partly RAGE-mediated. Further research will focus on the intersection of MetSyn/PM exposure.

Measures of lung function and their relationship with advanced glycation end-products

BACKGROUND

Advanced glycation end-products (AGEs) have been implicated in the pathophysiology of chronic obstructive pulmonary disease (COPD). However, the association between AGE accumulation in the skin measured by skin autofluorescence (SAF) and lung function in healthy subjects has not been explored in detail. We use a population-based study of 50-64-year-olds to assess spirometry, diffusing capacity of the lung for carbon monoxide (D LCO) and impulse oscillometry (IOS) in relation to SAF.

METHODS

Participants with information on SAF, lung function and potential confounding variables were included from the Swedish Cardiopulmonary Bioimage Study (SCAPIS) cohort (spirometry, n=4111; D LCO, n=3889; IOS, n=3970). Linear regression was used to assess changes in lung function (as measured by spirometry (forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC), D LCO and IOS (resistance measured at 5 (R 5) and 20 Hz (R 20), R 5-R 20, area of reactance, reactance measured at 5 Hz (X- 5), and resonant frequency)) by a 1-sd increase in SAF.

RESULTS

FEV1, FVC and D LCO were significantly and inversely associated with SAF after adjustment for potential confounding factors (per 1-sd increase in SAF: FEV1 -0.03 L (95% CI -0.04- -0.02 L), p<0.001; FVC -0.03 L (95% CI -0.05- -0.02 L), p<0.001; D LCO -0.07 mmol·min-1·kPa-1 (95% CI -0.11- -0.03 mmol·min-1·kPa-1), p<0.001). This association was also found in nonsmokers and in non-COPD subjects. Pulmonary reactance (X 5) but not pulmonary resistance (R 5, R 20 and R 5-R 20) was significantly associated with SAF (per 1-sd increase in SAF: X 5 -0.001 kPa·L-1·s (95% CI -0.003-0.00 kPa·L-1·s), p=0.042), which was mirrored in non-COPD patients but not in current nonsmokers.

CONCLUSIONS

AGE accumulation, as measured by SAF, is significantly associated with lung function decrements indicative of changes in the lung parenchyma.

Molecular and Cellular Mechanisms Responsible for Beneficial Effects of Mesenchymal Stem Cell-Derived Product "Exo-d-MAPPS" in Attenuation of Chronic Airway Inflammation

Mesenchymal stem cells (MSCs), due to their potential for differentiation into alveolar epithelial cells and their immunosuppressive characteristics, are considered a new therapeutic agent in cell-based therapy of inflammatory lung disorders, including chronic obstructive pulmonary disease (COPD). Since most of the MSC-mediated beneficent effects were the consequence of their paracrine action, herewith, we investigated the effects of a newly designed MSC-derived product "Exosome-derived Multiple Allogeneic Protein Paracrine Signaling (Exo-d-MAPPS)" in the attenuation of chronic airway inflammation by using an animal model of COPD (induced by chronic exposure to cigarette smoke (CS)) and clinical data obtained from Exo-d-MAPPS-treated COPD patients. Exo-d-MAPPS contains a high concentration of immunomodulatory factors which are capable of attenuating chronic airway inflammation, including soluble TNF receptors I and II, IL-1 receptor antagonist, and soluble receptor for advanced glycation end products. Accordingly, Exo-d-MAPPS significantly improved respiratory function, downregulated serum levels of inflammatory cytokines (TNF-α, IL-1β, IL-12, and IFN-γ), increased serum concentration of immunosuppressive IL-10, and attenuated chronic airway inflammation in CS-exposed mice. The cellular makeup of the lungs revealed that Exo-d-MAPPS treatment attenuated the production of inflammatory cytokines in lung-infiltrated macrophages, neutrophils, and natural killer and natural killer T cells and alleviated the antigen-presenting properties of lung-infiltrated macrophages and dendritic cells (DCs). Additionally, Exo-d-MAPPS promoted the expansion of immunosuppressive IL-10-producing alternatively activated macrophages, regulatory DCs, and CD4+FoxP3+T regulatory cells in inflamed lungs which resulted in the attenuation of chronic airway inflammation. In a similar manner, as it was observed in an animal model, Exo-d-MAPPS treatment significantly improved the pulmonary status and quality of life of COPD patients. Importantly, Exo-d-MAPPS was well tolerated since none of the 30 COPD patients reported any adverse effects after Exo-d-MAPPS administration. In summing up, we believe that Exo-d-MAPPS could be considered a potentially new therapeutic agent in the treatment of chronic inflammatory lung diseases whose efficacy should be further explored in large clinical trials.

Exploring the cross-phenotype network region of disease modules reveals concordant and discordant pathways between chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis

Chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) are two pathologically distinct chronic lung diseases that are associated with cigarette smoking. Genetic studies have identified shared loci for COPD and IPF, including several loci with opposite directions of effect. The existence of additional shared genetic loci, as well as potential shared pathobiological mechanisms between the two diseases at the molecular level, remains to be explored. Taking a network-based approach, we built disease modules for COPD and IPF using genome-wide association studies-implicated genes. The two disease modules displayed strong disease signals in an independent gene expression data set of COPD and IPF lung tissue and showed statistically significant overlap and network proximity, sharing 19 genes, including ARHGAP12 and BCHE. To uncover pathways at the intersection of COPD and IPF, we developed a metric, NetPathScore, which prioritizes the pathways of a disease by their network overlap with another disease. Applying NetPathScore to the COPD and IPF disease modules enabled the determination of concordant and discordant pathways between these diseases. Concordant pathways between COPD and IPF included extracellular matrix remodeling, Mitogen-activated protein kinase (MAPK) signaling and ALK pathways, whereas discordant pathways included advanced glycosylation end product receptor signaling and telomere maintenance and extension pathways. Overall, our findings reveal shared molecular interaction regions between COPD and IPF and shed light on the congruent and incongruent biological processes lying at the intersection of these two complex diseases.

Exome Sequencing Reveals Immune Genes as Susceptibility Modifiers in Individuals with α1-Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder associated to early onset emphysema, mainly imputable to Pi*ZZ genotype. In spite of the serious potential effects, many AATD individuals do not develop emphysema. To identify genes/variants potentially involved in emphysema development we studied 4 AATD families. Each family had at least one affected sibling with emphysema and one non-affected. Whole Exome Sequencing (WES) was performed on genomic DNA isolated from 9 individuals with AATD (4 affected/5 non-affected). Genetic variants confirmed at least in three families were prioritized using QueryOR and network analysis was used to verify enriched pathways. In affected subjects: 14 genes (57% immune-related) segregated in a recessive model and 21 (29% immune-related) in a dominant model. In non-affected subjects: 21 genes (43% immune-related) segregated in a recessive model and 50 (24% immune-related) in a dominant model. In affected siblings immune genes had an activating function, while where immune-suppressing in non-affected siblings involving antigen processing, MHC-I presentation, TCR and PD-1 signalling. This study describes possible genetic susceptibility factors for emphysema development in AATD, and suggests that gene variants involved in regulation of immune homeostasis and maintenance of self-tolerance contribute to the development or suppression of the disease.

Role of Diet in Chronic Obstructive Pulmonary Disease Prevention and Treatment

Chronic obstructive pulmonary disease is one of the leading causes of morbidity and mortality worldwide and a growing healthcare problem. Identification of modifiable risk factors for prevention and treatment of COPD is urgent, and the scientific community has begun to pay close attention to diet as an integral part of COPD management, from prevention to treatment. This review summarizes the evidence from observational and clinical studies regarding the impact of nutrients and dietary patterns on lung function and COPD development, progression, and outcomes, with highlights on potential mechanisms of action. Several dietary options can be considered in terms of COPD prevention and/or progression. Although definitive data are lacking, the available scientific evidence indicates that some foods and nutrients, especially those nutraceuticals endowed with antioxidant and anti-inflammatory properties and when consumed in combinations in the form of balanced dietary patterns, are associated with better pulmonary function, less lung function decline, and reduced risk of COPD. Knowledge of dietary influences on COPD may provide health professionals with an evidence-based lifestyle approach to better counsel patients toward improved pulmonary health.

Single-photon emission computed tomography/computed tomography imaging of RAGE in smoking-induced lung injury

Background

Expression of the Receptor for Advanced Glycation Endproducts (RAGE) initiates pro-inflammatory pathways resulting in lung destruction. We hypothesized that RAGE directed imaging demonstrates increased lung uptake in smoke-exposure.

Methods

After exposure to room air or to cigarette smoke for 4-weeks or 16-weeks, rabbits were injected with ^99mTc-anti-RAGE F(ab’)₂ and underwent Single-Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) imaging. Lung radiotracer uptake was calculated as percent injected dose (%ID). Lungs were dissected for gamma well counting and histological analysis.

Results

^99mTc-anti-RAGE F(ab’)₂ SPECT/CT imaging demonstrated increased lung expression of RAGE with smoke exposure compared to room air control at 4-weeks: Room air right (R) 0.75 ± 0.38%ID, left (L) 0.62 ± 0.32%ID vs. Smoke exposed R 0.17 ± 0.03, L 0.17 ± 0.02%ID (p = 0.02 and 0.028, respectively). By 16-weeks of smoke exposure, the uptake decreased to 0.19 ± 0.05%ID R and 0.17 ± 0.05%ID L, significantly lower than 4-week imaging (p = 0.0076 and 0.0129 respectively). Staining for RAGE confirmed SPECT results, with the RAGE ligand HMGB1 upregulated in the macrophages of 4-week smoke-exposed rabbits.

Conclusions

RAGE-directed imaging identified pulmonary RAGE expression acutely in vivo in an animal model of emphysema early after smoke exposure, with diminution over time. These studies document the extent and time course of RAGE expression under smoke exposure conditions and could be utilized for disease monitoring and examining response to future RAGE-targeted therapies.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1064-4) contains supplementary material, which is available to authorized users.

AGE-RAGE Stress in the Pathophysiology of Pulmonary Hypertension and its Treatment

Pulmonary hypertension (PH) is a rare and fatal disease characterized by elevation of pulmonary artery pressure ≥ 25 mm Hg. There are five groups of PH: (1) pulmonary artery (PA) hypertension (PAH), (2) PH due to heart diseases, (3) PH associated with lung diseases/hypoxia, (4) PH associated with chronic obstruction of PA, and (5) PH due to unclear and/or multifactorial mechanisms. The pathophysiologic mechanisms of group 1 have been studied in detail; however, those for groups 2 to 5 are not that well known. PH pathology is characterized by smooth muscle cells (SMC) proliferation, muscularization of peripheral PA, accumulation of extracellular matrix (ECM), plexiform lesions, thromboembolism, and recanalization of thrombi. Advanced glycation end products (AGE) and its receptor (RAGE) and soluble RAGE (sRAGE) appear to be involved in the pathogenesis of PH. AGE and its interaction with RAGE induce vascular hypertrophy through proliferation of vascular SMC, accumulation of ECM, and suppression of apoptosis. Reactive oxygen species (ROS) generated by interaction of AGE and RAGE modulates SMC proliferation, attenuate apoptosis, and constricts PA. Increased stiffness in the artery due to vascular hypertrophy, and vasoconstriction due to ROS resulted in PH. The data also suggest that reduction in consumption and formation of AGE, suppression of RAGE expression, blockage of RAGE ligand binding, elevation of sRAGE levels, and antioxidants may be novel therapeutic targets for prevention, regression, and slowing of progression of PH. In conclusion, AGE-RAGE stress may be involved in the pathogenesis of PH and the therapeutic targets should be the AGE-RAGE axis.

Receptor for advanced glycation end-products and environmental exposure related obstructive airways disease: a systematic review

Background

Our group has identified the receptor for advanced glycation end-products (RAGE) as a predictor of World Trade Center particulate matter associated lung injury. The aim of this systematic review is to assess the relationship between RAGE and obstructive airways disease secondary to environmental exposure.

Methods

A comprehensive search using PubMed and Embase was performed on January 5, 2018 utilising keywords focusing on environmental exposure, obstructive airways disease and RAGE and was registered with PROSPERO (CRD42018093834). We included original human research studies in English, focusing on pulmonary end-points associated with RAGE and environmental exposure.

Results

A total of 213 studies were identified by the initial search. After removing the duplicates and applying inclusion and exclusion criteria, we screened the titles and abstracts of 61 studies. Finally, 19 full-text articles were included. The exposures discussed in these articles include particulate matter (n=2) and cigarette smoke (n=17).

Conclusion

RAGE is a mediator of inflammation associated end-organ dysfunction such as obstructive airways disease. Soluble RAGE, a decoy receptor, may have a protective effect in some pulmonary processes. Overall, RAGE is biologically relevant in environmental exposure associated lung disease. Future investigations should focus on further understanding the role and therapeutic potential of RAGE in particulate matter exposure associated lung disease.

RAGE is biologically relevant in environmental exposure associated lung disease. Future investigations should focus on further understanding the role and therapeutic potential of RAGE in particulate matter exposure associated lung diseasehttp://ow.ly/gfZz30o7otU

Smoking-induced iron dysregulation in the lung

Iron is one of the most abundant transition elements and is indispensable for almost all organisms. While the ability of iron to participate in redox chemistry is an essential requirement for participation in a range of vital enzymatic reactions, this same feature of iron also makes it dangerous in the generation of hydroxyl radicals and superoxide anions. Given the high local oxygen tensions in the lung, the regulation of iron acquisition, utilization, and storage therefore becomes vitally important, perhaps more so than in any other biological system. Iron plays a critical role in the biology of essentially every cell type in the lung, and in particular, changes in iron levels have important ramifications on immune function and the local lung microenvironment. There is substantial evidence that cigarette smoke causes iron dysregulation, with the implication that iron may be the link between smoking and smoking-related lung diseases. A better understanding of the connection between cigarette smoke, iron, and respiratory diseases will help to elucidate pathogenic mechanisms and aid in the identification of novel therapeutic targets.

RAGE is a Critical Mediator of Pulmonary Oxidative Stress, Alveolar Macrophage Activation and Emphysema in Response to Cigarette Smoke

The receptor for advanced glycation end products (RAGE), a cell membrane receptor, recognizes ligands produced by cigarette smoke (CS) and has been implicated in the pathogenesis of COPD. We demonstrate that deletion or pharmacologic inhibition of RAGE prevents development of CS-induced emphysema. To identify molecular pathways by which RAGE mediates smoking related lung injury we performed unbiased gene expression profiling of alveolar macrophages (AM) obtained from RAGE null and C57BL/6 WT mice exposed to CS for one week or four months. Pathway analysis of RNA expression identified a number of genes integral to the pathogenesis of COPD impacted by the absence of RAGE. Altered expression of antioxidant response genes and lung protein 4-HNE immunostaining suggest attenuated oxidative stress in the RAGE null mice despite comparable CS exposure and lung leukocyte burden as the WT mice. Reduced endoplasmic reticulum stress in response to CS exposure also was observed in the AM from RAGE null mice. These findings provide novel insight into the sources of oxidative stress, macrophage activation, and the pathogenesis of lung disease due to CS exposure.

Bringing Light to Chronic Obstructive Pulmonary Disease Pathogenesis and Resilience

The pathogenesis of chronic obstructive pulmonary disease remains elusive; investigators in the field have struggled to decipher the cellular and molecular processes underlying chronic bronchitis and emphysema. Studies in the past 20 years have underscored that the tissue destruction, notably in emphysema, involves a multitude of injurious stresses, with progressive engagement of endogenous destructive processes triggered by decades of exposure to cigarette smoke and/or pollutants. These lead to an aged lung, with evidence of macromolecular damage that is unlikely to repair. Here we discuss these key pathogenetic elements in the context of organismal evolution as this concept may best capture the challenges facing chronic obstructive pulmonary disease.

Serum AGE/RAGEs as potential biomarker in idiopathic pulmonary fibrosis

Background

The soluble receptor for advanced glycation end-products (sRAGE) has been suggested that it acts as a decoy for capturing advanced glycation end-products (AGEs) and inhibits the activation of the oxidative stress and apoptotic pathways. Lung AGEs/sRAGE is increased in idiopathic pulmonary fibrosis (IPF). The objective of the study was to evaluate the AGEs and sRAGE levels in serum as a potential biomarker in IPF.

Methods

Serum samples were collected from adult patients: 62 IPF, 22 chronic hypersensitivity pneumonitis (cHP), 20 fibrotic non-specific interstitial pneumonia (fNSIP); and 12 healthy controls. In addition, 23 IPF patients were re-evaluated after 3-year follow-up period. Epidemiological and clinical features were recorded: age, sex, smoking habits, and lung function. AGEs and sRAGE were evaluated by ELISA, and the results were correlated with pulmonary functional test values.

Results

IPF and cHP groups presented a significant increase of AGE/sRAGE serum concentration compared with fNSIP patients. Moreover, an inverse correlation between AGEs and sRAGE levels were found in IPF, and serum sRAGE at diagnosis correlated with FVC and DLCO values. Additionally, changes in serum AGEs and sRAGE correlated with % change of FVC, DLCO and TLC during the follow-up. sRAGE levels below 428.25 pg/ml evolved poor survival rates.

Conclusions

These findings demonstrate that the increase of AGE/sRAGE ratio is higher in IPF, although the levels were close to cHP. AGE/sRAGE increase correlates with respiratory functional progression. Furthermore, the concentration of sRAGE in blood stream at diagnosis and follow-up could be considered as a potential prognostic biomarker.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0924-7) contains supplementary material, which is available to authorized users.

Inhibition of RAGE Attenuates Cigarette Smoke-Induced Lung Epithelial Cell Damage via RAGE-Mediated Nrf2/DAMP Signaling

The oxidative stress and cellular apoptosis by environmental factor including cigarette smoke induces alveolar airway remodeling leading to chronic obstructive pulmonary disease (COPD). Recently, the receptor for advanced glycan end products (RAGE) which is highly expressed in alveolar epithelium is emerging as a biomarker for COPD susceptibility or progression. However, it still remains unknown how RAGE plays a role in cigarette smoke extract (CSE)-exposed human alveolar type II epithelial cell line. Therefore, we determined the efficacy of RAGE-specific antagonist FPS-ZM1 in response to CSE-induced lung epithelial cells. CSE induced the elevated generation of RONS and release of pro-inflammatory cytokines, and impaired the cellular antioxidant defense system. Further, CSE induced the alteration of RAGE distribution via the activation of redox-sensitive DAMP (Damage-associated molecular patterns) signaling through Nrf2 in cells. Although pre-treatment with SB202190 (p38 inhibitor) or SP600125 (JNK inhibitor) failed to recover the alteration of RAGE distribution, treatment of FPS-ZM1 significantly exhibited anti-inflammatory and anti-oxidative/nitrosative effects, also inhibited the activation of redox-sensitive DAMP signaling through Nrf2 (nuclear factor erythroid 2-related factor 2) migration in the presence of CSE. Taken together, our data demonstrate that RAGE and Nrf2 play a pivotal role in maintenance of alveolar epithelial integrity.

Is decreased lung function associated with chronic kidney disease? A retrospective cohort study in Korea

OBJECTIVE

There is some evidence that lung function and chronic kidney disease (CKD) may be related. We evaluated the impact of lung function on the development of CKD in a large-scale longitudinal study.

METHOD

Retrospective longitudinal analyses were conducted among subjects who participated in comprehensive health check-ups at least four times during 7 years (between 2006 and 2012). We investigated the development of CKD during the follow-up period according to lung function status.

RESULTS

Ten thousand one hundred and twenty-eight individuals (mean age =51.2 years) without CKD at baseline were enrolled. During the mean follow-up of 5 years (58.5±14.4 months), 167 of the 10 128 subjects (1.6%) developed CKD. Multivariable Cox proportional hazards analyses adjusting for age, sex, body mass index, systolic blood pressure, fasting glucose, estimated glomerular filtration rate, uric acid, triglycerides, serum albumin, and the presence of diabetes and hypertension revealed that a decrease of 10% in the forced expiratory volume in 1s (FEV₁)/forced vital capacity (FVC) ratio was associated with a 35% increase in the development of CKD during the follow-up. The incidence of CKD was higher in those with an FEV₁/FVC ratio <0.8 compared with those with FEV₁/FVC ratio ≥0.8 (HR=1.454; 95% CI 1.042 to 2.028, p=0.028).

CONCLUSIONS

Limited airflow as measured by the FEV₁/FVC ratio was associated with an increased risk of CKD.

Relationship between advanced glycation end-product accumulation in the skin and pulmonary function

. [Purpose] This study aimed to evaluate the relationship between advanced glycation end-product accumulation and pulmonary function in a general population with normal spirometry results. [Subjects and Methods] A total of 201 subjects (mean age, 56 ± 11 years; males, 58%) enrolled in this study. Subjects were classified into two groups (younger group [<65 years old] and elderly group [≥65 years old]). Skin autofluorescence was assessed as an estimate of advanced glycation end-product. Forced vital capacity and forced expiratory volume in one second were measured using a spirometer, and the forced expiratory volume in one second/forced vital capacity ratio (FEV1/FVC) was calculated. [Results] Skin autofluorescence was not an independent factor associated with FEV1/FVC in the younger group, but both skin autofluorescence and pack-years of smoking were significant independent factors associated with FEV1/FVC in the elderly group. [Conclusion] Advanced glycation end-product accumulation, assessed by skin autofluorescence, is an independent factor negatively associated with FEV1/FVC in elderly people with normal spirometry results.

What do polymorphisms tell us about the mechanisms of COPD?

COPD (chronic obstructive pulmonary disease) is characterized by irreversible lung airflow obstruction. Cigarette smoke is the major risk factor for COPD development. However, only a minority number of smokers develop COPD, and there are substantial variations in lung function among smokers, suggesting that genetic determinants in COPD susceptibility. During the past decade, genome-wide association studies and exome sequencing have been instrumental to identify the genetic determinants of complex traits, including COPD. Focused studies have revealed mechanisms by which genetic variants contribute to COPD and have led to novel insights in COPD pathogenesis. Through functional investigations of causal variants in COPD, from the proteinase-antiproteinase theory to emerging roles of developmental pathways (such as Hedgehog and Wnt pathways) in COPD, we have greatly expanded our understanding on this complex pulmonary disease. In this review, we critically review functional investigations on roles of genetic polymorphisms in COPD, and discuss future challenges and opportunities in discovering novel mechanisms of functional variants.

AGEs-RAGE overexpression in a patient with smoking-related idiopathic nodular glomerulosclerosis

We report a case of smoking-related idiopathic nodular glomerulosclerosis (ING) with overexpression of glomerular advanced glycation end products (AGEs) and their receptor (RAGE). A 59-year-old Japanese man with nephrotic syndrome, who had a smoking history of one pack of cigarettes per day for approximately 40 years, presented with a 3-year history of urinalysis abnormalities without clinical evidence of diabetic mellitus. The patient's leg edema progressively worsened over the previous 2 years, and he was admitted to our hospital. Renal biopsy showed mesangial expansion with diabetic Kimmelstiel-Wilson-like nodular lesions, glomerular basement thickening, and arteriosclerosis. No electron-dense deposits, fibrils, or microtubule deposits were seen in the glomeruli on electron microscopy. Skin AGE level measured using AGE reader was higher in this case than the average level in age-matched Caucasians. In addition, immunohistochemical analysis revealed that N-carboxymethyl lysine, one of the major AGEs, and RAGE were overexpressed and podocin expression was decreased in the peripheral area of the glomerular nodular lesions. These observations suggest that AGEs-RAGE system may be activated in smoking-related ING, possibly leading to the progression of renal dysfunction.

Involvement of new oxidative stress markers in chronic spontaneous urticaria

Introduction

Oxidative stress is a result of an imbalance between endogenous production of free reactive oxygen species and reduced effectiveness of antioxidant defence mechanisms. Advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs) are compounds formed by transformation of macromolecules, including proteins which can serve as markers of oxidative stress and inflammation in several diseases.

Aim

To investigate the role of AGEs and AOPPs as new markers of oxidative stress and inflammation in patients with chronic spontaneous urticaria (CSU).

Material and methods

Advanced glycation end products and AOPP levels were determined in the sera of 85 patients with CSU and 64 healthy controls, using spectrofluorimetry and spectrophotometry, respectively.

Results

Advanced oxidation protein products levels in patients were statistically higher than those in controls. These levels were not affected by the presence of positive autologous serum test results or autologous plasma test results. No statistically significant differences were found between AGE levels in patients and controls.

Conclusions

Formation of AGEs and AOPPs may be accelerated in immunological and allergic disorders. Depending on the sites evaluated, the presence or absence of oxidative stress in chronic urticaria is controversial. To our knowledge, this is the first study showing the possible involvement of AOPPs in CSU. The different behaviour observed for these two biomarkers is very likely due to the activation of specific related biochemical pathways associated with the condition under study.

Receptor for advanced glycation end-products and World Trade Center particulate induced lung function loss: A case-cohort study and murine model of acute particulate exposure

World Trade Center-particulate matter(WTC-PM) exposure and metabolic-risk are associated with WTC-Lung Injury(WTC-LI). The receptor for advanced glycation end-products (RAGE) is most highly expressed in the lung, mediates metabolic risk, and single-nucleotide polymorphisms at the AGER-locus predict forced expiratory volume(FEV). Our objectives were to test the hypotheses that RAGE is a biomarker of WTC-LI in the FDNY-cohort and that loss of RAGE in a murine model would protect against acute PM-induced lung disease. We know from previous work that early intense exposure at the time of the WTC collapse was most predictive of WTC-LI therefore we utilized a murine model of intense acute PM-exposure to determine if loss of RAGE is protective and to identify signaling/cytokine intermediates. This study builds on a continuing effort to identify serum biomarkers that predict the development of WTC-LI. A case-cohort design was used to analyze a focused cohort of male never-smokers with normal pre-9/11 lung function. Odds of developing WTC-LI increased by 1.2, 1.8 and 1.0 in firefighters with soluble RAGE (sRAGE)≥97pg/mL, CRP≥2.4mg/L, and MMP-9≤397ng/mL, respectively, assessed in a multivariate logistic regression model (ROCAUC of 0.72). Wild type(WT) and RAGE-deficient(Ager-/-) mice were exposed to PM or PBS-control by oropharyngeal aspiration. Lung function, airway hyperreactivity, bronchoalveolar lavage, histology, transcription factors and plasma/BAL cytokines were quantified. WT-PM mice had decreased FEV and compliance, and increased airway resistance and methacholine reactivity after 24-hours. Decreased IFN-γ and increased LPA were observed in WT-PM mice; similar findings have been reported for firefighters who eventually develop WTC-LI. In the murine model, lack of RAGE was protective from loss of lung function and airway hyperreactivity and was associated with modulation of MAP kinases. We conclude that in a multivariate adjusted model increased sRAGE is associated with WTC-LI. In our murine model, absence of RAGE mitigated acute deleterious effects of PM and may be a biologically plausible mediator of PM-related lung disease.

A Pilot Study Linking Endothelial Injury in Lungs and Kidneys in Chronic Obstructive Pulmonary Disease

RATIONALE

Patients with chronic obstructive pulmonary disease (COPD) frequently have albuminuria (indicative of renal endothelial cell injury) associated with hypoxemia.

OBJECTIVES

To determine whether (1) cigarette smoke (CS)-induced pulmonary and renal endothelial cell injury explains the association between albuminuria and COPD, (2) CS-induced albuminuria is linked to increases in the oxidative stress-advanced glycation end products (AGEs) receptor for AGEs (RAGE) pathway, and (3) enalapril (which has antioxidant properties) limits the progression of pulmonary and renal injury by reducing activation of the AGEs-RAGE pathway in endothelial cells in both organs.

METHODS

In 26 patients with COPD, 24 ever-smokers without COPD, 32 nonsmokers who underwent a renal biopsy or nephrectomy, and in CS-exposed mice, we assessed pathologic and ultrastructural renal lesions, and measured urinary albumin/creatinine ratios, tissue oxidative stress levels, and AGEs and RAGE levels in pulmonary and renal endothelial cells. The efficacy of enalapril on pulmonary and renal lesions was assessed in CS-exposed mice.

MEASUREMENTS AND MAIN RESULTS

Patients with COPD and/or CS-exposed mice had chronic renal injury, increased urinary albumin/creatinine ratios, and increased tissue oxidative stress and AGEs-RAGE levels in pulmonary and renal endothelial cells. Treating mice with enalapril attenuated CS-induced increases in urinary albumin/creatinine ratios, tissue oxidative stress levels, endothelial cell AGEs and RAGE levels, pulmonary and renal cell apoptosis, and the progression of chronic renal and pulmonary lesions.

CONCLUSIONS

Patients with COPD and/or CS-exposed mice have pulmonary and renal endothelial cell injury linked to increased endothelial cell AGEs and RAGE levels. Albuminuria could identify patients with COPD in whom angiotensin-converting enzyme inhibitor therapy improves renal and lung function by reducing endothelial injury.