RAGE Ligands Research Articles

Inhibition of the Receptor for Advanced Glycation End Products Enhances the Cytotoxic Effect of Gemcitabine in Murine Pancreatic Tumors.

Pancreatic ductal adenocarcinoma (PDAC) remains a very difficult cancer to treat. Recent in vitro and in vivo studies suggest that the activation of the receptor for advanced glycation end products (RAGE) by its ligands stimulates pancreatic cancer cell proliferation and tumor growth. Additional studies show that, in the RAGE ligand, the high mobility group box 1 (HMGB1) protein plays an important role in chemoresistance against the cytotoxic agent gemcitabine by promoting cell survival through increased autophagy. We hypothesized that blocking the RAGE/HMGB1 interaction would enhance the cytotoxic effect of gemcitabine by reducing cell survival and autophagy. Using a preclinical mouse model of PDAC and a monoclonal antibody (IgG 2A11) as a RAGE inhibitor, we demonstrate that RAGE inhibition concurrent with gemcitabine treatment enhanced the cytotoxic effect of gemcitabine. The combination of IgG 2A11 and gemcitabine resulted in decreased autophagy compared to treatment with gemcitabine combined with control antibodies. Notably, we also observed that RAGE inhibition protected against excessive weight loss during treatment with gemcitabine. Our data suggest that the combination of gemcitabine with a RAGE inhibitor could be a promising therapeutic approach for the treatment of pancreatic cancer and needs to be further investigated.

The use of the soluble receptor for advanced glycation-end products (sRAGE) as a potential biomarker of disease risk and adverse outcomes

The soluble receptor for advanced glycation end-products (sRAGE) has been classically considered a sink for pro-inflammatory RAGE ligands and as such has been associated with protection from inflammatory stress and disease. An alternative, though not mutually exclusive view is that high levels of sRAGE in circulation reflect the overstimulation of cell surface RAGE which if persistent, lead to the amplification of pro-inflammatory processes and the exacerbation of pathological states. With these two scenarios in mind this review focuses on the potential role of sRAGE as a prospective biomarker of disease risk and adverse outcomes.

Heme & RAGE: A new opportunistic relationship?

Heme is an iron-containing complex involved in fundamental cellular functions including oxygen transport. Free heme accumulation in blood, during intravascular hemolysis and other pathological conditions, triggers vascular dysfunction, pro-inflammatory, and prothrombotic cascade. Studies by May et al present a novel finding that heme is a ligand for RAGE and that heme binds to the V domain of RAGE and induces RAGE oligomerization. Furthermore, they show that the in vivo consequences of heme-RAGE interaction lead to a pro-inflammatory and procoagulant phenotype in the lungs. This discovery of heme as a ligand for RAGE sets the stage for probing the role of RAGE in heme homeostasis and the pathogenic role of heme-RAGE interaction in hemolytic diseases.

DYSREGULATION OF GASTROINTESTINAL RAGE (RECEPTOR FOR ADVANCED GLYCATION END PRODUCTS) EXPRESSION IN A SPONTANEOUS ANIMAL MODEL OF INFLAMMATORY BOWEL DISEASE

Abstract The receptor for advanced glycation end products (RAGE), a pattern recognition receptor, plays a role in chronic inflammation. Abrogation of proinflammatory RAGE signaling by ligand binding (e.g., S100/calgranulins) to soluble RAGE decoy (sRAGE) is a promising novel therapeutic avenue for chronic inflammatory diseases, such as inflammatory bowel disease (IBD). However, the opportunities for studying S100/calgranulin-RAGE pathways in conventional animal models are limited due to species differences in the expression and function of S100/calgranulins (e.g., lack of the S100A12 protein in rodents). The pathogenesis of IBD in dogs involves dysregulated innate immune responses, and serum sRAGE levels are decreased in canine IBD and normalize only with clinical remission. Thus, canine IBD may serve as a spontaneous model of IBD for such studies. This study evaluated gastrointestinal mucosal RAGE expression in dogs with IBD and the binding of RAGE to canine S100/calgranulin ligands. Epithelial RAGE expression was quantified in endoscopic gastrointestinal (i.e., gastric, duodenal, ileal, and colonic) biopsies from 12 dogs with IBD and 9 healthy control dogs by laser scanning microscopy. RAGE expression was compared between both groups of dogs and was tested for an association with patient characteristics, clinical variables, histologic lesion severity, and biomarkers of extra-gastrointestinal disease, systemic or gastrointestinal inflammation, function, or protein loss. Statistical significance (non-parametric tests) was set at p<0.05. RAGE:S100/calgranulin binding was investigated by immunoassay and electrophoretic techniques. RAGE expression was detected in all biopsies evaluated. Epithelial RAGE expression in the duodenum and colon was significantly higher in dogs with IBD than in healthy controls (p<0.04), with a trend for overexpression in the ileum, underexpression in the stomach, and a general shift towards more basal than apical epithelial RAGE expression. Serum sRAGE was correlated with duodenal RAGE expression. Several histologic (structural and inflammatory) lesion criteria and markers of gastrointestinal inflammation or protein loss were related to segmental RAGE expression (all p<0.04). In vitro, canine RAGE:S100A12 binding appeared more pronounced than RAGE:S100A8/A9 binding. Alterations in the epithelial expression of RAGE along the gastrointestinal tract provide evidence for a dysregulated sRAGE/RAGE axis as a characteristic of canine IBD. S100/calgranulin (S100A8/A9 and S100A12) proteins are ligands for RAGE in dogs. The role of RAGE signaling in IBD pathogenesis and its potential for developing novel targeted therapeutics warrants further exploration. Furthermore, canine IBD is a suitable spontaneous model for human IBD that may benefit further research into pathway-specific IBD treatment options that target the sRAGE/RAGE axis.

Increased Expression of S100B and RAGE in a Mouse Model of Bile Duct Ligation-induced Liver Fibrosis.

BackgroundLiver fibrosis is defined as the accumulation of the extracellular matrix and scar formation. The receptor for advanced glycation end products (RAGE) has been demonstrated to participate in fibrogenesis. S100B is a ligand of RAGE and exerts extracellular functions by inducing a series of signal transduction cascades. However, the involvement of S100B and RAGE in cholestasis-induced liver fibrosis remains unclear. In this study, we investigated S100B and RAGE expression during liver fibrosis in mice that underwent common bile duct ligation (BDL).MethodsBDL was performed in 10-week-old male C57BL/6J mice with sham control (n = 26) and BDL (n = 26) groups. Expression levels of S100B, RAGE and fibrotic markers in the livers from both groups at week 1 and 3 after BDL were examined by western blot and quantitative real-time reverse transcription polymerase chain reaction analysis. Liver fibrotic changes were examined by histological and ultrastructural analysis.ResultsHistological staining with Sirius Red and the evaluation of the messenger RNA expression of fibrotic markers showed noticeable periportal fibrosis and bile duct proliferation. S100B was mainly present in bile duct epithelial cells, and its expression was upregulated in proportion to the ductular reaction during fibrogenesis by BDL. RAGE expression was also increased, and interestingly, triple immunofluorescence staining and transmission electron microscopy showed that both S100B and RAGE were expressed in proliferating bile duct epithelial cells and activated hepatic stellate cells (HSCs) of the BDL livers. In addition, in rat HSCs (HSC-T6), treatment with recombinant S100B protein significantly increased fibrotic markers in a dose-dependent manner, and RAGE small interfering RNA (siRNA) suppressed S100B-stimulated upregulation of fibrotic markers compared with cells treated with scramble siRNA and S100B.ConclusionThese findings suggest that the increased expression of S100B and RAGE and the interaction between S100B and RAGE may play an important role in ductular reaction and liver fibrosis induced by BDL.

Upregulation of Matrix Metalloproteinase-9 Protects against Sepsis-Induced Acute Lung Injury via Promoting the Release of Soluble Receptor for Advanced Glycation End Products.

Dysregulation of matrix metalloproteinase- (MMP-) 9 is implicated in the pathogenesis of acute lung injury (ALI). However, it remains controversial whether MMP-9 improves or deteriorates acute lung injury of different etiologies. The receptor for advanced glycation end products (RAGE) plays a critical role in the pathogenesis of acute lung injury. MMPs are known to mediate RAGE shedding and release of soluble RAGE (sRAGE), which can act as a decoy receptor by competitively inhibiting the binding of RAGE ligands to RAGE. Therefore, this study is aimed at clarifying whether and how pulmonary knockdown of MMP-9 affected sepsis-induced acute lung injury as well as the release of sRAGE in a murine cecal ligation and puncture (CLP) model. The analysis of GEO mouse sepsis datasets GSE15379, GSE52474, and GSE60088 revealed that the mRNA expression of MMP-9 was significantly upregulated in septic mouse lung tissues. Elevation of pulmonary MMP-9 mRNA and protein expressions was confirmed in CLP-induced mouse sepsis model. Intratracheal injection of MMP-9 siRNA resulted in an approximately 60% decrease in pulmonary MMP-9 expression. It was found that pulmonary knockdown of MMP-9 significantly increased mortality of sepsis and exacerbated sepsis-associated acute lung injury. Pulmonary MMP-9 knockdown also decreased sRAGE release and enhanced sepsis-induced activation of the RAGE/nuclear factor-κB (NF-κB) signaling pathway, meanwhile aggravating sepsis-induced oxidative stress and inflammation in lung tissues. In addition, administration of recombinant sRAGE protein suppressed the activation of the RAGE/NF-κB signaling pathway and ameliorated pulmonary oxidative stress, inflammation, and lung injury in CLP-induced septic mice. In conclusion, our data indicate that MMP-9-mediated RAGE shedding limits the severity of sepsis-associated pulmonary edema, inflammation, oxidative stress, and lung injury by suppressing the RAGE/NF-κB signaling pathway via the decoy receptor activities of sRAGE. MMP-9-mediated sRAGE production may serve as a self-limiting mechanism to control and resolve excessive inflammation and oxidative stress in the lung during sepsis.

The receptor for advanced glycation end products is a sensor for cell-free heme.

Heme's interaction with Toll-like receptor 4 (TLR4) does not fully explain the proinflammatory properties of this hemoglobin-derived molecule during intravascular hemolysis. The receptor for advanced glycation end products (RAGE) shares many features with TLR4 such as common ligands and proinflammatory, prothrombotic, and pro-oxidative signaling pathways, prompting us to study its involvement as a heme sensor. Stable RAGE-heme complexes with micromolar affinity were detected as heme-mediated RAGE oligomerization. The heme-binding site was located in the V domain of RAGE. This interaction was Fe3+ -dependent and competitive with carboxymethyllysine, another RAGE ligand. We confirmed a strong basal gene expression of RAGE in mouse lungs. After intraperitoneal heme injection, pulmonary TNF-α, IL1β, and tissue factor gene expression levels increased in WT mice but were significantly lower in their RAGE-/- littermates. This may be related to the lower activation of ERK1/2 and Akt observed in the lungs of heme-treated, RAGE-/- mice. Overall, heme binds to RAGE with micromolar affinity and could promote proinflammatory and prothrombotic signaling invivo, suggesting that this interaction could be implicated in heme-overload conditions.

Effects of S100B neutralization on the long-term cognitive impairment and neuroinflammatory response in an animal model of sepsis

The nervous system is one of the first systems to be affected during sepsis. Sepsis not only has a high risk of mortality, but could also lead to cerebral dysfunction and cognitive impairment in long-term survival patients. The receptor for advanced glycation end products (RAGE) can interact with several ligands, and its activation triggers a series of cell signaling events, resulting in the hyperinflammatory condition related to sepsis. Recent studies show that elevated levels of S100B (RAGE ligand) are associated with the pathophysiology of neurodegenerative disorders. They also participate in inflammatory brain diseases and may lead to an increased activation of microglia and astrocytes, leading to neuronal death. This study aimed to determine the effect of S100B inhibition on the neuroinflammatory response in sepsis. Sepsis was induced in Wistar rats by cecal ligation and perforation (CLP). There were three groups: Sham, CLP, and CLP +10 μg/kg of monoclonal antibody (Anti-S100B) administered intracerebroventricularly. The animals were killed 30 days after sepsis following behavioral evaluation by open field, novel object recognition, and splash test. The hippocampus, prefrontal cortex, and amydgala were used for the determination of S100B and RAGE proteins by western blotting and for the evaluation of cytokine levels and verification of the number of microglial cells by immunohistochemistry. On day 30, both the Sham and CLP + anti-S100B groups were capable of recovering the habitual memory in the open field task. Regarding novel object recognition, Sham and CLP + anti-S100B groups increased the recognition index during the test session in comparison to the training session. There was a significant increase in the time of grooming in CLP + anti-S100B in comparison to the CLP group. There was a modulation of cytokine levels and immunohistochemistry showed that the CLP + anti-S100B group had a decrease in the number of microglial cells only in the hippocampus. These results helped to understand the role of S100B protein in the pathophysiology of sepsis-associated encephalopathy and could be helpful to further experimental studies regarding this subject.

Circulating Ligands of the Receptor for Advanced Glycation End Products and the Soluble Form of the Receptor Modulate Cardiovascular Cell Apoptosis in Diabetes.

We determined whether plasma concentrations of the receptor for advanced glycation end products (RAGE) and the soluble (s) form of RAGE (sRAGE) in healthy individuals and patients with type 2 diabetes (T2D) modulate vascular remodeling. Healthy individuals and patients with T2D were divided into two age groups: young = <35 years old or middle-aged (36–64 years old) and stratified based on normal glucose tolerance (NGT), impaired (IGT), and T2D. Plasma titers of sRAGE, the RAGE ligands, AGEs, S100B, S100A1, S100A6, and the apoptotic marker Fas ligand Fas(L) were measured by enzyme-linked immunosorbent assay (ELISA). The apoptotic potential of the above RAGE ligands and sRAGE were assessed in cultured adult rat aortic smooth muscle cells (ASMC). In NGT individuals, aging increased the circulating levels of AGEs and S100B and decreased sRAGE, S100A1 and S100A6. Middle-aged patients with T2D presented higher levels of circulating S100B, AGEs and FasL, but lower levels of sRAGE, S100A1 and S100A6 than individuals with NGT or IGT. Treatment of ASMC with either AGEs or S100B at concentrations detected in T2D patients increased markers of inflammation and apoptosis. Responses attenuated by concomitant administration of sRAGE. In middle-aged patients with T2D, lower circulating plasma levels of sRAGE may limit decoy and exogenous trapping of deleterious pro-apoptotic/pro-inflammatory RAGE ligands AGEs and S100B, increasing the risk for diabetic complications.

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.

The Gly82Ser polymorphism in the receptor for advanced glycation end products is associated with increased risk for coronary events in the general population

Abstract Background/Introduction Activation of the receptor for advanced glycation end products (RAGE) by AGEs and various immune mediators has pro-inflammatory and pro-atherogenic effects. RAGE also exists in a soluble form, sRAGE, that acts as a decoy receptor for RAGE ligands. Low plasma sRAGE has previously been found to be associated with a higher risk for major adverse coronary events (MACE) in the population. Purpose The purpose of our study was to examine the causality of the association, by exploring whether genetic variants that influence sRAGE are associated with atherosclerosis progression and incident MACE and mortality in the population. Methods We performed a genome-wide association study (GWAS) in 4192 individuals from a randomly selected subgroup of a population-based cohort. Subsequently, we explored the associations between the identified single nucleotide polymorphims (SNPs) associated with plasma sRAGE levels, baseline intima media thickness (IMT) and IMT progression in the common carotid artery during a median follow-up of 16.5 years. Further, we analyzed the prospective relationships between the sRAGE-associated SNPs, incident MACE and mortality in the entire population-based cohort of 29245 individuals. The median follow-up time from baseline was 21.2 years for MACE and 21.6 years for total mortality (time to event or end of follow-up). Results We found the minor alleles of two single nucleotide polymorphisms (SNPs), rs2070600 and rs204993, to be independently associated with lower plasma sRAGE. While rs204993 is a silent intronic mutation, rs2070600 is known to cause a Gly82Ser polymorphism in the ligand binding domain, enhancing RAGE propensity for activation. In Cox regression analyses, we found an association between the minor T (vs. C) allele of rs2070600 and increased risk for first-time MACE [HR 1.12 (1.02–1.23); P=0.023]. The association was independent of traditional cardiovascular risk factors, blood pressure-lowering medication and lipid-lowering medication at baseline. rs204993 was not associated with MACE. Neither SNP was associated with carotid IMT at baseline or with IMT progression. We did not identify any relationships with total mortality. Conclusions We demonstrate for the first time an independent link between a genetic RAGE determinant and the risk for MACE in the population. Despite both identified SNPs being associated with lower sRAGE levels, only the functional rs2070600 mutation was associated with MACE, suggesting that the link is probably due to the enhancement of RAGE function rather than to the sRAGE lowering effect. Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): This study was supported by grants from the Swedish Research Council and the Swedish Heart and Lung foundation.

The role of RAGE in host pathology and crosstalk between RAGE and TLR4 in innate immune signal transduction pathways.

Although the innate immune receptor protein, Receptor for Advanced Glycation End products (RAGE), has been extensively studied, there has been renewed interest in RAGE for its potential role in sepsis, along with a host of other inflammatory diseases of chronic, noninfectious origin. In contrast to other innate immune receptors, for example, Toll-like receptors (TLRs), that recognize ligands derived from pathogenic organisms that are collectively known as "pathogen-associated molecular patterns" (PAMPs) or host-derived "damage-associated molecular patterns" (DAMPs), RAGE has been shown to recognize a broad collection of DAMPs exclusively. Historically, these DAMPs have been shown to be pro-inflammatory in nature. Early studies indicated that the adaptor molecule, MyD88, might be important for this change. More recent studies have explored further the mechanisms underlying this inflammatory change. Overall, the newer results have shown that there is extensive crosstalk between RAGE and TLRs. The three canonical RAGE ligands, Advanced Glycation End products (AGEs), HMGB1, and S100 proteins, have all been shown to activate both TLRs and RAGE to varying degrees in order to induce inflammation in in vitro models. As with any field that delves deeply into innate signaling, obstacles of reagent purity may be a cause of some of the discrepancies in the literature, and we have found that commercial antibodies that have been widely used exhibit a high degree of nonspecificity. Nonetheless, the weight of published evidence has led us to speculate that RAGE may be physically interacting with TLRs on the cell surface to elicit inflammation via MyD88-dependent signaling.

Lysophosphatidic acid-RAGE axis promotes lung and mammary oncogenesis via protein kinase B and regulating tumor microenvironment

BackgroundReceptor for advanced glycation end products (RAGE) is a multi-ligand transmembrane receptor of the immunoglobulin superfamily. Lysophosphatidic acid (LPA) is a ligand for RAGE and is involved in physiological and pathophysiological conditions including cancer. However, RAGE-LPA axis is unexplored in lung and mammary cancer.MethodsRAGE was silenced in A549, MDA MB-231 and MCF7 using RAGE shRNA. For in vitro tumorigenesis, we performed wound healing, colony formation, cell proliferation and invasion assays. Evaluation of expression of oncogenes, EMT markers and downstream signaling molecules was done by using western blot and immunohistochemistry. For subcellular expression of RAGE, immunofluorescence was done. In vivo tumorigenesis was assessed by intraperitoneal injection of cancer cells in nude mice.ResultsHere we show RAGE mediated profound increase in proliferation, migration and invasion of lung and mammary cancer cells via LPA in Protein kinase B (PKB) dependent manner. LPA mediated EMT transition is regulated by RAGE. In vivo xenograft results show significance of RAGE in LPA mediated lung and mammary tumor progression, angiogenesis and immune cell infiltration to tumor microenvironment.ConclusionOur results establish the significance and involvement of RAGE in LPA mediated lung and mammary tumor progression and EMT transition via RAGE. RAGE-LPA axis may be a therapeutic target in lung and mammary cancer treatment strategies.EdVB1f1yrz4Do4i3nWt_5KVideo

Prothrombin is a binding partner of the human receptor of advanced glycation end products

The receptor for advanced glycation end products (RAGE) plays a key role in mammal physiology and in the etiology and progression of inflammatory and oxidative stress-based diseases. In adults, RAGE expression is normally high only in the lung where the protein concentrates in the basal membrane of alveolar Type I epithelial cells. In diseases, RAGE levels increase in the affected tissues and sustain chronic inflammation. RAGE exists as a membrane glycoprotein with an ectodomain, a transmembrane helix, and a short carboxyl-terminal tail, or as a soluble ectodomain that acts as a decoy receptor (sRAGE). VC1 domain is responsible for binding to the majority of RAGE ligands including advanced glycation end products (AGEs), S100 proteins, and HMGB1. To ascertain whether other ligands exist, we analyzed by MS the material pulled down by VC1 from human plasma. Twenty of 295 identified proteins were selected and associated to coagulation and complement processes and to extracellular matrix. Four of them contained a γ-carboxyl glutamic acid (Gla) domain, a calcium-binding module, and prothrombin (PT) was the most abundant. Using MicroScale thermophoresis, we quantified the interaction of PT with VC1 and sRAGE in the absence or presence of calcium that acted as a competitor. PT devoid of the Gla domain (PT des-Gla) did not bind to sRAGE, providing further evidence that the Gla domain is critical for the interaction. Finally, the presence of VC1 delayed plasma clotting in a dose-dependent manner. We propose that RAGE is involved in modulating blood coagulation presumably in conditions of lung injury.

Sensory Neuron Sensitization By Pkc-induced Trpv1 Phosphorylation In Type 2 Diabetic Rats

Skeletal muscle reflex-induced increases in blood pressure are exaggerated during exercise in type 2 diabetes mellitus (T2DM). We previously demonstrated that skeletal muscle afferent discharge in response to capsaicin, a transient receptor potential cation channel subfamily V member 1 (TRPV1) agonist, is heightened in T2DM likely contributing to the potentiated pressor response. However, the underlying mechanisms remain unclear. Evidence suggests that the high glucose levels in T2DM sensitize sensory neurons through the receptor for advanced glycation end products (RAGE)/protein kinase C (PKC) pathway in dorsal root ganglia (DRG). Moreover, early-stage diabetes associated with TRPV1 overactivity is mediated through PKC. Therefore, it was hypothesized that the augmentation in muscle afferent discharge in T2DM previously reported is due to the phosphorylation of TRPV1 via an overactive RAGE/PKC pathway. PURPOSE: To investigate 1) the impact of T2DM on plasma levels of advanced glycation end products (AGE) and high-mobility group box-protein 1 (HMGB-1), both RAGE ligands, and 2) the impact of T2DM on the RAGE/PKC pathway including the phosphorylation of TRPV1 in DRG subserving skeletal muscle afferents. METHODS: For 14-16 weeks, Sprague-Dawley rats were given either a normal diet (control) or a high fat diet in combination with a low dose (35 mg/kg) of streptozotocin (T2DM). Plasma insulin, HMGB1 and AGE were determined using ELISA. RAGE, phosphorylated PKC and TRPV1 protein levels were quantified in DRG by western blotting. RESULTS: After overnight fasting, T2DM rats exhibited hyperglycemia (95±6 vs. 156±18 mg/dL, P<0.05) and hyperinsulinemia (1.6±0.2 vs. 4.1±0.4 ng/mL, P<0.05). HMGB1, AGE and RAGE did not differ between groups. Phosphorylated PKC (1.0±0.1 vs. 1.2±0.2 arb unit, P=0.08) and TRPV1 (1.0±0.3 vs. 1.3±0.4 arb unit, P=0.08) levels in DRG tended to be greater in T2DM than control. CONCLUSIONS: These findings suggest that phosphorylated TRPV1 may be increased by PKC overactivity in DRG of T2DM but acts independently of RAGE. Importantly, these changes may mediate the sensitization of skeletal muscle afferents facilitating the exaggerated pressor response to exercise characteristic of T2DM. Supported by Lawson & Rogers Lacy Research Fund and SHP Interdisciplinary Research Grant Program.

Occurrence of a RAGE-Mediated Inflammatory Response in Human Fetal Membranes.

Context:Sterile inflammation has been shown to play a key role in the rupture of the fetal membranes (FMs). Moreover, an early and exacerbated runaway inflammation can evolve into a preterm premature rupture of membranes and lead to potential preterm birth. In this context, we investigated the receptor for advanced glycation end products (RAGE), an axis implied in physiological sterile inflammation, in conjunction with two major ligands: AGEs and High-Mobility Group Box 1 (HMGB1). Our first objective was to determine the spatiotemporal expression profiles of the different actors of the RAGE-signaling axis in human FMs, including its intracellular adaptors Diaphanous-1 and Myd88. Our second goal was to evaluate the functionality of RAGE signaling in terms of FMs inflammation.MethodsThe presence of the actors (RAGE, HMGB1, Myd88, and Diaphanous-1) at the mRNA level was investigated by reverse transcription quantitative polymerase chain reaction (RT-qPCR) in the human amnion and choriodecidua at the three trimesters and at term. Measurements were conducted at two distinct zones: the zone of intact morphology (ZIM) and the zone of altered morphology (ZAM). Then, proteins were quantified using Western blot analysis, and their localization was evaluated by immunofluorescence in term tissues. In addition, pro-inflammatory cytokine secretion was quantified using a Multiplex assay after the treatment of amnion and choriodecidua explants with two RAGE ligands (AGEs and HMGB1) in the absence or presence of a RAGE inhibitor (SAGEs).ResultsThe FMs expressed the RAGE-signaling actors throughout pregnancy. At term, RNA and protein overexpression of the RAGE, HMGB1, and Diaphanous-1 were found in the amnion when compared to the choriodecidua, and the RAGE was overexpressed in the ZAM when compared to the ZIM. The two RAGE ligands (AGEs and HMGB1) induced differential cytokine production (IL1β and TNFα) in the amnion and choriodecidua.ConclusionConsidered together, these results indicate that RAGE signaling is present and functional in human FMs. Our work opens the way to a better understanding of FMs weakening dependent on a RAGE-based sterile inflammation.

Sensitization of group lV skeletal muscle afferents in type 1 diabetic rats

The blood pressure (BP) response to exercise is abnormally exaggerated in type 1 diabetes mellitus (T1DM). However, the mechanisms underlying the potentiated BP response remain largely unclear. Sensory information from working muscle, generated by activation of mechanically and metabolically sensitive muscle afferents, is known to contribute importantly to this exercise‐induced exaggeration in BP. Moreover, receptors for advanced glycation end products (RAGE) and protein kinase C (PKC) interact to modulate neuronal function, including muscle afferents. It is possible that the interactive relationship between RAGE and PKC is altered in T1DM. Therefore, it was hypothesized that the potentiated exercise‐induced BP response in T1DM is mediated by sensitization of skeletal muscle afferent fibers via an overactive RAGE/PKC signaling pathway.PURPOSETo investigate 1) action potential responses to mechanical and chemical stimulation in muscle afferents of healthy and T1DM rats in vitro, 2) the impact of T1DM on plasma levels of high‐mobility group box‐protein 1 (HMGB‐1), a RAGE ligand, and 3) the impact of T1DM on PKC activation in dorsal root ganglion (DRG) subserving skeletal muscle afferent neurons.METHODST1DM was induced in Sprague‐Dawley rats by intraperitoneally injecting a single dose of 50 mg/kg streptozotocin. In healthy control animals, only saline was injected. At 1–3 weeks after the injection, the function of mechanically (application of a 0–196 mN ramped stimulus) or chemically (administration of 1 μM capsaicin) activated group IV fibers were assessed by obtaining single‐fiber recordings using the extensor digitorum longus muscle‐nerve preparation. Plasma HMGB1 was determined using ELISA. Phosphorylated PKC protein levels were quantified in DRG (L3‐L5) by western blotting.RESULTST1DM rats exhibited hyperglycemia after overnight fasting (P&lt;0.05). Plasma insulin in T1DM tended to be lower as compared to control animals (P=0.09). Spontaneous activity in group IV fibers was significantly larger in diabetic rats than in control animals (P&lt;0.05). Compared to control, response magnitudes to mechanical stimulation (P&lt;0.01) and capsaicin exposure (P=0.01) in group IV afferents were significantly greater in T1DM. Plasma HMGB1 levels were significantly higher in T1DM as compared with control (P&lt;0.01). T1DM showed markedly increased phosphorylated PKC levels in DRGs compared with control (P&lt;0.05).CONCLUSIONSIn T1DM, the sensitivity of group IV skeletal muscle afferent fibers to mechanical and chemical stimuli is abnormally increased. The data likewise suggest this enhanced afferent sensitivity may be due to augmented activation of the RAGE/PKC pathway. Importantly, these changes likely contribute significantly to the exaggerated pressor response to exercise characteristic of T1DM.Support or Funding InformationSupported by Lawson &amp; Rogers Lacy Research Fund and SHP Interdisciplinary Research Grant Program.

RAGE p.82G&gt;S Polymorphism Is Not Associated with the Risk of Multiple Sclerosis in Iranian Population

Background and Aims: Multiple sclerosis (MS) is known as a partially inheritable inflammatory autoimmune disease which involves the nervous system. Different studies suggest that immune dysregulation has an important role in the pathogenesis of MS, but its exact pathomechanism has not yet been explicated. The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface molecules. In MS patients, the expression of membrane-bound RAGE on peripheral blood mononuclear cells, as well as the serum levels of the RAGE ligands are upregulated. Materials and Methods: In this case-control study, we evaluated the association between MS incidence and RAGE p.82G&gt;S polymorphism (rs2070600) compared with healthy controls in an Iranian population. A total of 158 patients and 156 healthy blood donors were enrolled. This polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism. Results: Allele frequencies (p=0.319) and genotype distribution (p=0.315) of the RAGE p.82G&gt;S gene polymorphism in MS patients and controls were not significantly different. Conclusions: The present study indicated no relationship between RAGE p.82G&gt;S polymorphism and the risk of MS in Iranian population.

Targeting the receptor for advanced glycation end products (RAGE) in type 1 diabetes.

Type 1 diabetes (T1D) is one of the most common chronic diseases manifesting in early life, with the prevalence increasing worldwide at a rate of approximately 3% per annum. The prolonged hyperglycaemia characteristic of T1D upregulates the receptor for advanced glycation end products (RAGE) and accelerates the formation of RAGE ligands, including advanced glycation end products, high-mobility group protein B1, S100 calcium-binding proteins, and amyloid-beta. Interestingly, changes in the expression of RAGE and these ligands are evident in patients before the onset of T1D. RAGE signals via various proinflammatory cascades, resulting in the production of reactive oxygen species and cytokines. A large number of proinflammatory ligands that can signal via RAGE have been implicated in several chronic diseases, including T1D. Therefore, it is unsurprising that RAGE has become a potential therapeutic target for the treatment and prevention of disease. In this review, we will explore how RAGE might be targeted to prevent the development of T1D.

Unraveling the Role of Receptor for Advanced Glycation End Products (RAGE) and Its Ligands in Myasthenia Gravis.

Myasthenia gravis (MG) is an autoimmune T cell-dependent B cell-mediated disorder of the neuromuscular junction (NMJ) characterized by fluctuating skeletal muscle weakness, most commonly attributed to pathogenic autoantibodies against postsynaptic nicotinic acetylcholine receptors (AChRs). Although MG pathogenesis is well-documented, there are no objective biomarkers that could effectively correlate with disease severity or MG clinical subtypes, and current treatment approaches are often ineffective. The receptor for advanced glycation end products (RAGE) is a multiligand cell-bound receptor highly implicated in proinflammatory responses and autoimmunity. Preclinical evidence demonstrates that RAGE and its ligand S100B are upregulated in rat models of experimental autoimmune myasthenia gravis (EAMG). S100B-mediated RAGE activation has been shown to exacerbate EAMG, by enhancing T cell proinflammatory responses, aggravating T helper (Th) subset imbalance, increasing AChR-specific T cell proliferative capacity, and promoting the production of antibodies against AChRs from the spleen. Soluble sRAGE and esRAGE, acting as decoys of RAGE ligands, are found to be significantly reduced in MG patients. Moreover, MG has been associated with increased serum levels of S100A12, S100B and HMGB1. Several studies have shown that the presence of thymic abnormalities, the onset age of MG, and the duration of the disease may affect the levels of these proteins in MG patients. Herein, we discuss the emerging role of RAGE and its ligands in MG immunopathogenesis, their clinical significance as promising biomarkers, as well as the potential therapeutic implications of targeting RAGE signaling in MG treatment.