Inverse Relationship between Soluble RAGE and Risk for Bronchopulmonary Dysplasia

Prospective epigenome and transcriptome analyses of cord and peripheral blood from preterm infants at risk of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a prevalent chronic lung disease of prematurity with limited treatment options. To uncover biomarkers of BPD risk, this study investigated epigenetic and transcriptomic signatures of prematurity at birth and during the neonatal period at day 14 and 28. Peripheral blood DNAs from preterm infants were applied to methylation arrays and cell-type composition was estimated by deconvolution. Covariate-adjusted robust linear regression elucidated BPD- and prolonged oxygen (≥ 14 days) exposure-associated CpGs. RNAs from cord and peripheral blood were sequenced, and differentially expressed genes (DEGs) for BPD or oxygen exposure were determined. Estimated neutrophil-lymphocyte ratios in peripheral blood at day 14 in BPD infants were significantly higher than nonBPD infants, suggesting an heightened inflammatory response in developing BPD. BPD-DEGs in cord blood indicated lymphopoiesis inhibition, altered Th1/Th2 responses, DNA damage, and organ degeneration. On day 14, BPD-associated CpGs were highly enriched in neutrophil activation, infection, and CD4 + T cell quantity, and BPD-DEGs were involved in DNA damage, cellular senescence, T cell homeostasis, and hyper-cytokinesis. On day 28, BPD-associated CpGs along with BPD-DEGs were enriched for phagocytosis, neurological disorder, and nucleotide metabolism. Oxygen supplementation markedly downregulated mitochondrial biogenesis genes and altered CpGs annotated to developmental genes. Prematurity-altered DNA methylation could cause abnormal lymphopoiesis, cellular assembly and cell cycle progression to increase BPD risk. Similar pathways between epigenome and transcriptome networks suggest coordination of the two in dysregulating leukopoiesis, adaptive immunity, and innate immunity. The results provide molecular insights into biomarkers for early detection and prevention of BPD.

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.

Biomarker Potential of the Soluble Receptor for Advanced Glycation End Products to Predict Bronchopulmonary Dysplasia in Premature Newborns

Bronchopulmonary dysplasia (BPD) is a common cause of pulmonary disease in preterm infants. The soluble receptor for advanced glycation end products (sRAGE) is implicated in the development of various pulmonary diseases. The objectives of the current study were to investigate perinatal factors associated with serum sRAGE levels at birth and to establish whether serum sRAGE could be a biomarker for BPD. This retrospective single-center study was conducted at Fukushima Medical University Hospital's Department of Pediatrics Neonatal Intensive Care Unit from April 2014 to September 2020. Mechanically ventilated or oxygenated neonates born at <32 weeks gestational age and healthy control neonates were included in this study. Serum sRAGE levels in cord blood were measured using an enzyme-linked immunosorbent assay. Eighty-four preterm infants born at <32 weeks and 40 healthy infants were identified. The 84 born at <32 weeks were categorized as BPD (n = 34) or non-BPD (n = 50) neonates. The median gestational age (GA) and birthweight (BW) were significantly lower in BPD vs. non-BPD neonates (24.4 vs. 27.6 weeks, P < 0.001, 634 vs. 952 g, P < 0.001, respectively). Serum sRAGE at birth in all 124 preterm and term infants significantly correlated with BW (r = 0.417, P < 0.0001) and GA (r = 0.415, P < 0.0001). Among those born at <32 weeks, median serum sRAGE levels at birth were significantly lower in infants with BPD than without (1,726 vs. 2,797 pg/mL, P = 0.0005). Receiver operating characteristic analysis for sRAGE levels at birth in infants with and without BPD revealed that the area under the curve was 0.724 (95% confidence interval 0.714-0.834, P = 0.001). However, serum RAGE levels were not associated with severity of BPD. Serum sRAGE levels at birth were significantly correlated with BW and GA. Furthermore, serum sRAGE levels at birth could serve as a biomarker for predicting BPD, but not its severity.

sRAGE as severe acute bronchiolitis biomarker, prospective observational study

INTRODUCTION AND OBJECTIVES

Acute bronchiolitis (AB) is the leading cause of hospitalization in infants and around 5% require intensive care treatment. Early identification of children diagnosed with AB at a high risk of severe progression is of great interest. The receptor for advanced glycation end products (RAGE), highly expressed in lung tissue, regulates immune responses and inflammation, and its soluble form, sRAGE, is believed to have an anti-inflammatory role. We hypothesized serum sRAGE might be a major determinant of AB severity and prognosis. This study was conducted to measure serum sRAGE in infants with severe AB and to assess its correlation with clinical severity, immediate complications, and outcome.

METHODS

Single-center, prospective, observational study of hospitalized children with severe bronchiolitis admitted to the Pediatric Intensive Care Unit (PICU), from September 2015 to September 2016.

RESULTS

A total of 52 children and 27 controls were included. The cases age ranged from 11 days to 21 months, resulting in a significant age difference with controls (11.85 vs 4.84 months, P < .01). Serum levels of sRAGE were lower but not significant in severe AB patients than in controls (1350.93 vs 1450.42 pg/mL; P = .399). No correlation was found between serum sRAGE and causative viruses, clinical symptoms, Wood-Downes score (a clinical severity score) on admission, respiratory support, or length of hospital stay. Serum sRAGE was also lower in the cases having had a previous respiratory disease (1463.84 vs 1072.43 pg/mL; P = .049). However, it was higher in patients with any lung consolidation on the chest X-ray (1584.79 vs 1131.62 pg/mL; P = .044) and weakly positively correlated with classical biomarkers (maximum C-reactive protein, +0.295, P = .034; maximum procalcitonin, +0.309; P = .029).

CONCLUSION

This single-center study reveals that sRAGE couldn't predict AB severity or outcome in children hospitalized at PICU. Nevertheless, it significantly increased in the presence of any lung consolidation and had a positive correlation with classical biomarkers. The utility of sRAGE in this population could be probably elucidated with a better understanding of AGE-RAGE axis.

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.