Soluble receptor for advanced glycation end products (sRAGE) in tracheobronchial aspirate fluid and cord blood of very low birth weight infants with chorioamnionitis and funisitis

Association of Funisitis with Short-Term Outcomes of Prematurity: A Frequentist and Bayesian Meta-Analysis

The fetal systemic inflammatory response associated with intra-amniotic inflammation may play a key role in the pathogenesis of complications of preterm birth. Funisitis is the histologic equivalent of the fetal inflammatory response, whereas chorioamnionitis represents a maternal inflammatory response. We conducted a frequentist and Bayesian model average (BMA) meta-analysis of studies investigating the effects of funisitis on short-term outcomes of prematurity. Thirty-three studies (12,237 infants with gestational age ≤ 34 weeks) were included. Frequentist meta-analysis showed that funisitis was associated with an increased risk of any bronchopulmonary dysplasia (BPD), moderate/severe BPD, retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), any sepsis, early-onset sepsis (EOS), and mortality. However, Bayesian meta-analysis showed that the evidence in favor of the alternative hypothesis (i.e., funisitis is associated with an increased risk of developing the outcome) was strong for any IVH, moderate for severe IVH and EOS, and weak for the other outcomes. When the control group was restricted to infants having chorioamnionitis without funisitis, the only outcome associated with funisitis was any IVH. In conclusion, our data suggest that the presence of funisitis does not add an additional risk to preterm birth when compared to chorioamnionitis in the absence of fetal inflammatory response.

RAGE against the Machine: Can Increasing Our Understanding of RAGE Help Us to Battle SARS-CoV-2 Infection in Pregnancy?

The receptor of advanced glycation end products (RAGE) is a receptor that is thought to be a key driver of inflammation in pregnancy, SARS-CoV-2, and also in the comorbidities that are known to aggravate these afflictions. In addition to this, vulnerable populations are particularly susceptible to the negative health outcomes when these afflictions are experienced in concert. RAGE binds a number of ligands produced by tissue damage and cellular stress, and its activation triggers the proinflammatory transcription factor Nuclear Factor Kappa B (NF-κB), with the subsequent generation of key proinflammatory cytokines. While this is important for fetal membrane weakening, RAGE is also activated at the end of pregnancy in the uterus, placenta, and cervix. The comorbidities of hypertension, cardiovascular disease, diabetes, and obesity are known to lead to poor pregnancy outcomes, and particularly in populations such as Native Hawaiians and Pacific Islanders. They have also been linked to RAGE activation when individuals are infected with SARS-CoV-2. Therefore, we propose that increasing our understanding of this receptor system will help us to understand how these various afflictions converge, how forms of RAGE could be used as a biomarker, and if its manipulation could be used to develop future therapeutic targets to help those at risk.

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.

[Method for predicting perinatal hypoxic lesions of the central nervous system in newborns.]

Perinatal lesions of the Central nervous system (CNS) in newborns occupy a leading place in the structure of perinatal morbidity and subsequent disability of children. To identify the features of the content of sRAGE in pregnant women with threatening preterm labor (UPR) in the period of 22-27 weeks, who subsequently gave birth to children with perinatal CNS lesion. Serum of venous blood of pregnant women with UPR at the term of 22-27 weeks was determined by ELISA once the content of sRAGE. If the value of sRAGE in pregnant women is 659.5 PG/ml or less, perinatal hypoxic lesions of the Central nervous system in newborns are predicted with an accuracy of 75.8% (sensitivity of 82.6%, specificity of 66.7%).

RAGE controls leukocyte adhesion in preterm and term infants

BACKGROUND

Insufficient leukocyte recruitment may be one reason for the high incidence of life-threatening infections in preterm infants. Since the receptor of advanced glycation end products (RAGE) is a known leukocyte adhesion molecule and highly expressed during early development, we asked whether RAGE plays a role for leukocyte recruitment in preterm and term infants.

METHODS

Leukocyte adhesion was analyzed in dynamic flow chamber experiments using isolated leukocytes of cord blood from extremely premature (<30 weeks of gestation), moderately premature (30-35 weeks of gestation) and mature neonates (>35 weeks of gestation) and compared to the results of adults. For fluorescent microscopy leukocytes were labeled with rhodamine 6G. In the respective age groups we also measured the plasma concentration of soluble RAGE (sRAGE) by ELISA and Mac-1 and LFA-1 expression on neutrophils by flow cytometry.

RESULTS

The adhesive functions of fetal leukocytes significantly increase with gestational age. In all age groups, leukocyte adhesion was crucially dependent on RAGE. In particular, RAGE was equally effective to mediate leukocyte adhesion when compared to ICAM-1. The plasma levels of sRAGE were high in extremely premature infants and decreased with increasing gestational age. In contrast, expression of β2-Integrins Mac-1 and LFA-1 which are known ligands for RAGE and ICAM-1 did not change during fetal development.

CONCLUSION

We conclude that RAGE is a crucial leukocyte adhesion molecule in both preterm and term infants.

Interaction of S100A13 with C2 domain of receptor for advanced glycation end products (RAGE)

S100A13 is involved in several key biological functions like angiogenesis, tumor formation and cell apoptosis. It is a homodimeric protein that belongs to the S100 protein family. S100A13 is co-expressed with acidic fibroblast growth factor (FGF1) and interleukin-1α which are key angiogenesis inducers. The S100 proteins have been shown to be involved in several cellular functions such as calcium homeostasis, cell growth and differentiation dynamic of cytoskeleton. Its biological functions are mainly mediated through the receptor for advanced glycation end products (RAGE) signaling. RAGE is involved in inflammatory processes and is associated with diabetic complications, tumor outgrowth, and neurodegenerative disorders. RAGE induces cellular signaling upon binding of different ligands, such as S100 proteins, glycated proteins, and HMGB1. RAGE signaling is complex, and it depends on the cell type and concentration of the ligand. Molecular level interactions of RAGE and S100 proteins are useful to understand the RAGE signaling diversity. In this report we focus on the molecular level interactions of S100A13 and RAGE C2 domain. The binding between RAGE C2 and S100A13 is moderately strong (Kd~1.3μM). We have solved the solution structure of the S100A13-RAGE C2 complex and pronounce the interface regions in S100A13-RAGE C2 complex which are helpful for drug development of RAGE induced diseases.

Potential contribution of type I alveolar epithelial cells to chronic neonatal lung disease

The alveolar surface is covered by large flat Type I cells (alveolar epithelial cells 1, AEC1). The normal physiological function of AEC1s involves gas exchange, based on their location in approximation to the capillary endothelium and their thinness, and in ion and water flux, as shown by the presence of solute active transport proteins, water channels, and impermeable tight junctions between cells. With the recent ability to produce relatively pure cultures of AEC1 cells, new functions have been described. These may be relevant to lung injury, repair, and the abnormal development that characterizes bronchopulmonary dysplasia (BPD). To hypothesize a potential role for AEC1 in the development of lung injury and abnormal repair/development in premature lungs, evidence is presented for their presence in the developing lung, how their source may not be the Type II cell (AEC2) as has been assumed for 40 years, and how the cell can be damaged by same type of stressors as those which lead to BPD. Recent work shows that the cells are part of the innate immune response, capable of producing pro-inflammatory mediators, which could contribute to the increase in inflammation seen in early BPD. One of the receptors found exclusively on AEC1 cells in the lung, called RAGE, may also have a role in increased inflammation and alveolar simplification. While the current evidence for AEC1 involvement in BPD is circumstantial and limited at present, the accumulating data supports several hypotheses and questions regarding potential differences in the behavior of AEC1 cells from newborn and premature lung compared with the adult lung.

Associations between maternal and infant morbidities and sRAGE within the first week of life in extremely preterm infants

Background

Soluble RAGE (sRAGE) has been associated with multiple inflammatory responses including maternal chorioamnionitis and preeclampsia. Analysis of umbilical cord blood levels have also indicated that sRAGE levels in the infant are affected by maternal inflammation. S100b is a ligand for RAGE and increases in circulating S100b levels are associated with poor neurological outcome in preterm infants. The objective of this study was to determine whether sRAGE or s100b levels in plasma samples from extremely preterm infants at the end of the first week of life were correlated with infant morbidities and whether sRAGE and s100b levels at this time point were still associated with maternal inflammation.

Methods

Plasma samples were collected from 130 preterm infants (≤28 weeks) at days of life 5, 6, or 7. sRAGE and s100b levels were measured by ELISA and data were analyzed by Pearson’s correlation or Generalized Estimating Equations.

Results

sRAGE was negatively correlated with development of sepsis (p=0.024), the FiO₂ requirement of the infant at the time of sampling (p=0.030), as well as maternal preeclampsia (p=0.046), and positively correlated with maternal chorioamnionitis (p=0.006). s100b levels were positively associated with maternal chorioamnionitis (p=0.039). No correlations were observed with other infant morbidities.

Conclusion

These data indicate that sRAGE could potentially be a biomarker of early severe inflammatory responses in the preterm infant. However, more studies are needed to confirm the present findings.

Serum levels of receptors for advanced glycation end products in normal-weight and obese children born small and large for gestational age

OBJECTIVE

To assess potential alterations in soluble and endogenous secretory receptors for advanced glycation end products (sRAGE and esRAGE) in normal-weight (NW) and obese (Ob) children born small (SGA) and large (LGA) compared with appropriate for gestational age (AGA) subjects and to explore if birth weight (BW), insulin resistance (IR), and obesity represent independent risk factors.

RESEARCH DESIGN AND METHODS

We categorized 130 prepubertal children into six groups according to BW and obesity and evaluated sRAGE, esRAGE, and homeostasis model assessment of IR.

RESULTS

sRAGE and esRAGE were lower in Ob SGA and LGA children than Ob AGA subjects (all P < 0.05), and in NW SGA and LGA children than NW AGA subjects (all P < 0.05). Interestingly, BW and IR were significantly and independently related to RAGE.

CONCLUSIONS

sRAGE and esRAGE are decreased in SGA and LGA children, and BW and IR seem to play an important role in the reduction of RAGE.