Soluble RAGE: a hot new biomarker for the hot joint?

Unveiling Novel Drug Targets and Emerging Therapies for Rheumatoid Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) is a chronic debilitating autoimmune disease, that causes joint damage, deformities, and decreased functionality. In addition, RA can also impact organs like the skin, lungs, eyes, and blood vessels. This autoimmune condition arises when the immune system erroneously targets the joint synovial membrane, resulting in synovitis, pannus formation, and cartilage damage. RA treatment is often holistic, integrating medication, physical therapy, and lifestyle modifications. Its main objective is to achieve remission or low disease activity by utilizing a "treat-to-target" approach that optimizes drug usage and dose adjustments based on clinical response and disease activity markers. The primary RA treatment uses disease-modifying antirheumatic drugs (DMARDs) that help to interrupt the inflammatory process. When there is an inadequate response, a combination of biologicals and DMARDs is recommended. Biological therapies target inflammatory pathways and have shown promising results in managing RA symptoms. Close monitoring for adverse effects and disease progression is critical to ensure optimal treatment outcomes. A deeper understanding of the pathways and mechanisms will allow new treatment strategies that minimize adverse effects and maintain quality of life. This review discusses the potential targets that can be used for designing and implementing precision medicine in RA treatment, spotlighting the latest breakthroughs in biologics, JAK inhibitors, IL-6 receptor antagonists, TNF blockers, and disease-modifying noncoding RNAs.

Biomarkers in Systemic Juvenile Idiopathic Arthritis, Macrophage Activation Syndrome and Their Importance in COVID Era

Systemic juvenile idiopathic arthritis (sJIA) and its complication, macrophage activation syndrome (sJIA-MAS), are rare but sometimes very serious or even critical diseases of childhood that can occasionally be characterized by nonspecific clinical signs and symptoms at onset-such as non-remitting high fever, headache, rash, or arthralgia-and are biologically accompanied by an increase in acute-phase reactants. For a correct positive diagnosis, it is necessary to rule out bacterial or viral infections, neoplasia, and other immune-mediated inflammatory diseases. Delays in diagnosis will result in late initiation of targeted therapy. A set of biomarkers is useful to distinguish sJIA or sJIA-MAS from similar clinical entities, especially when arthritis is absent. Biomarkers should be accessible to many patients, with convenient production and acquisition prices for pediatric medical laboratories, as well as being easy to determine, having high sensitivity and specificity, and correlating with pathophysiological disease pathways. The aim of this review was to identify the newest and most powerful biomarkers and their synergistic interaction for easy and accurate recognition of sJIA and sJIA-MAS, so as to immediately guide clinicians in correct diagnosis and in predicting disease outcomes, the response to treatment, and the risk of relapses. Biomarkers constitute an exciting field of research, especially due to the heterogeneous nature of cytokine storm syndromes (CSSs) in the COVID era. They must be selected with utmost care-a fact supported by the increasingly improved genetic and pathophysiological comprehension of sJIA, but also of CSS-so that new classification systems may soon be developed to define homogeneous groups of patients, although each with a distinct disease.

Markers for the involvement of endothelial cells and the coagulation system in chronic urticaria: A systematic review

Chronic urticaria (CU) is a chronic inflammatory mast cell-driven disorder. Endothelial cells (ECs) contribute importantly to key features of CU. Several markers of EC (dys)function in CU have been reported, but have not yet been systematically reviewed. In this study, we systematically reviewed and categorized all published markers of EC functions in CU through a comprehensive search in Pubmed, The Cochrane Library, Web of Science, and SCOPUS using the following Mesh terms: CU AND pathogenesis AND (vasculopathy OR microangiopathy OR ECs OR marker). In total, 79 articles were selected and the identified biomarkers were categorized according to EC (dys)function in CU. The most frequent and consistently reported upregulated biomarkers in CU skin were adhesion molecules, TF, and P-selectin. The most frequently reported upregulated and reliable biomarkers in sera of CU patients were F1+2 for coagulation cascade involvement, D-dimers for fibrinolysis, and MMP-9 for vascular permeability. Emerging biomarkers described in the selected articles were endostatin, heat shock proteins, cleaved high molecular weight kininogen, and adipokines. This systematic review contributes to the pool of growing evidence for vascular involvement in CU where EC dysfunction is present in different aspects of cell survival, maintenance of vascular structure, and coagulation/fibrinolysis balance.

Intake of high-fructose corn syrup sweetened soft drinks, fruit drinks and apple juice is associated with prevalent arthritis in US adults, aged 20-30 years

OBJECTIVE

There is a link between joint and gut inflammation of unknown etiology in arthritis. Existing research indicates that regular consumption of high-fructose corn syrup sweetened (HFCS) soft drinks, but not diet soft drinks, may be associated with increased risk of seropositive rheumatoid arthritis (RA) in women, independent of other dietary and lifestyle factors. One unexplored hypothesis for this association is that fructose malabsorption, due to regular consumption of excess free fructose (EFF) and HFCS, contributes to fructose reactivity in the gastrointestinal tract and intestinal in situ formation of enFruAGEs, which once absorbed, travel beyond the intestinal boundaries to other tissues and promote inflammation. In separate studies, the accumulation of advanced glycation end-products has been associated with joint inflammation in RA. Objective of this study was to assess the association between EFF beverages intake and non-age, non-wear and tear-associated arthritis in US young adults.

METHODS

In this cross sectional study of 1209 adults aged 20-30y, (Nutrition and Health Examination Surveys 2003-2006) exposure variables were high EFF beverages, including HFCS sweetened soft drinks, and any combination of HFCS sweetened soft drinks, fruit drinks (FD) and apple juice, referred to as tEFF. Analyses of diet soda and diet FD were included for comparison. The outcome was self-reported arthritis. Rao Scott Ҳ(2) was used for prevalence differences and logistic regression for associations, adjusted for confounders.

RESULTS

Young adults consuming any combination of high EFF beverages (tEFF) ⩾5 times/week (but not diet soda) were three times as likely to have arthritis as non/low consumers (odds ratios=3.01; p⩽0.021; 95% confidence intervals=1.20-7.59), independent of all covariates, including physical activity, other dietary factors, blood glucose and smoking.

CONCLUSION

EFF beverage intake is significantly associated with arthritis in US adults aged 20-30 years, possibly due to the intestinal in situ formation of enFruAGEs.

Circulating soluble receptor for advanced glycation end products is decreased and inversely associated with acute phase response in chronic spontaneous urticaria

BACKGROUND

Activation of receptor for advanced glycation end products (RAGE) leads to the proinflammatory response and the release of its soluble form (sRAGE) which appears to function as an anti-inflammatory feedback mechanism.

AIM

To determine serum sRAGE concentration in CSU patients and its association with C-reactive protein (CRP) concentration, a nonspecific inflammatory marker of the disease activity.

METHODS

Concentrations of sRAGE and CRP were measured in serum of CSU patients and compared with the healthy controls.

RESULTS

Serum sRAGE concentrations were significantly decreased in CSU patients, especially those more severely affected. In addition, significant inverse correlations were observed between sRAGE and CRP concentrations.

CONCLUSIONS

Down-regulation of sRAGE and its association with acute phase response suggest a role for RAGE activation in the pathogenesis of CSU. It seems that lower serum sRAGE concentration may enhance the urticarial processes.

The role of receptor for advanced glycation end products in airway inflammation in CF and CF related diabetes

Cystic Fibrosis (CF) is often accompanied by diabetes leading to worsening lung function, the reason for which is unclear. The receptor for advanced-glycation-end-products (RAGE) regulates immune responses and inflammation and has been linked to diabetes and possibly CF. We performed a pilot study to determine if CF and CF-related diabetes (CFRD) are associated with enhanced RAGE expression. Full length (fl)RAGE, soluble (s)RAGE, endogenous soluble (es)RAGE, S100A12 (enRAGE) and advanced-glycation-end-products (AGE) expression was assessed in serum, white blood cells and sputum of patients with CF; diabetes; CFRD and healthy subjects. Sputum enRAGE/sRAGE ratios were high in CF but particularly in CFRD which negatively correlated with % predicted FEV1. Serum AGE and AGE/sRAGE ratios were high in diabetics but not in CF. A complex, multifaceted approach was used to assess the role of RAGE and its ligands which is fundamental to determining their impact on airway inflammation. There is a clear association between RAGE activity in the airways of CF and CFRD patients that is not evident in the vascular compartment and correlates with lung function, in contrast to diabetes. This strongly suggests a role for RAGE in contributing to the inflammatory overdrive seen in CF and to a greater extent in CFRD.

The presence of high mobility group box-1 and soluble receptor for advanced glycation end-products in juvenile idiopathic arthritis and juvenile systemic lupus erythematosus

BACKGROUND

The involvement of high mobility group box-1 (HMGB1) in various inflammatory and autoimmune diseases has been documented but clinical trials on the contribution of this pro-inflammatory alarmin in children with juvenile idiopathic arthritis (JIA) and systemic lupus erythematosus (SLE) are basically absent. To address the presence of HMGB1 and a soluble receptor for advanced glycation end products (sRAGE) in different subtypes of JIA and additionally in children with SLE, we enrolled a consecutive sample of children harvested peripheral blood as well as synovial fluids (SF) at diagnosis and correlated it with ordinary acute-phase reactants and clinical markers.

METHODS

Serum and synovial fluids levels of HMGB1 and sRAGE in total of 144 children (97 with JIA, 19 with SLE and 27 healthy controls) were determined by ELISA.

RESULTS

The children with JIA and those with SLE were characterised by significantly higher serum levels of HMGB1 and significantly lower sRAGE levels compared to the healthy controls. A positive correlation between serum HMGB1 and ESR, CRP, α2 globulin was found while serum sRAGE levels were inversely correlated with the same inflammatory markers in children with JIA. Additionally, high level of serum HMGB1 was related to hepatosplenomegaly or serositis in systemic onset JIA.

CONCLUSION

The inverse relationship of the HMGB1 and its soluble receptor RAGE in the blood and SF indicates that inflammation triggered by alarmins may play a role in pathogenesis of JIA as well as SLE. HMGB1 may serve as an inflammatory marker and a potential target of biological therapy in these patients. Further studies need to show whether the determination of HMGB1 levels in patients with JIA can be a useful guideline for detecting disease activity.

RAGE expression in human T cells: a link between environmental factors and adaptive immune responses

The Receptor for Advanced Glycation Endproducts (RAGE) is a scavenger ligand that binds glycated endproducts as well as molecules released during cell death such as S100b and HMGB1. RAGE is expressed on antigen presenting cells where it may participate in activation of innate immune responses but its role in adaptive human immune responses has not been described. We have found that RAGE is expressed intracellularly in human T cells following TCR activation but constitutively on T cells from patients with diabetes. The levels of RAGE on T cells from patients with diabetes are not related to the level of glucose control. It co-localizes to the endosomes. Its expression increases in activated T cells from healthy control subjects but bystander cells also express RAGE after stimulation of the antigen specific T cells. RAGE ligands enhance RAGE expression. In patients with T1D, the level of RAGE expression decreases with T cell activation. RAGE+ T cells express higher levels of IL-17A, CD107a, and IL-5 than RAGE− cells from the same individual with T1D. Our studies have identified the expression of RAGE on adaptive immune cells and a role for this receptor and its ligands in modulating human immune responses.

The receptor for advanced glycation endproducts and its ligands in patients with myasthenia gravis

OBJECTIVE

Myasthenia gravis (MG) is a T- and B-cell mediated autoimmune disorder affecting the neuromuscular junction. The receptor for advanced glycation endproducts (RAGE) plays a role in the amplification of chronic inflammatory disorders and autoimmune diseases. We sought to investigate the role of RAGE and its ligands in the pathophysiology of MG.

METHODS

In this cross-sectional study we enrolled 42 patients with MG and 36 volunteers. We employed enzyme-linked immunosorbent assays to determine the concentration of soluble RAGE (sRAGE) and high mobility group box 1 (HMGB1) in serum of patients and volunteers. In a subpopulation of patients we measured the serum levels of endogenous secretory (es) RAGE and various RAGE ligands, such as S100B, S100A8 and advanced glycation endproducts (AGE-CML). Reported are means and standard error mean.

RESULTS

We found significantly reduced levels of the soluble receptors sRAGE and esRAGE in patients with MG compared to volunteers without MG (sRAGE [pg/ml] 927.2 ± 80.8 vs. 1400.1 ± 92.4; p<0.001; esRAGE [pg/ml] 273.5±24.6 vs. 449.0 ± 22.4; p<0.001). Further categorization of patients with MG according to the distribution of muscle involvement revealed the following sRAGE concentrations: generalized MG 999.4 ± 90.8 and ocular MG 696.1 ± 161.8 (vs. control; One-way ANOVA: p<0.001; Post hoc analysis: generalized vs. ocular MG: p=0.264, generalized MG vs. control: p=0.008, ocular MG vs. control: p=0.001). In patients with detectable antibodies specific for acetylcholine receptors (Anti-AChR positive) the sRAGE concentration was 970.0 ± 90.2 compared to those without (seronegative) 670.6 ± 133.1 (vs. control; One-way ANOVA: p<0.001; Post hoc analysis: Pos vs. Neg.: p=0.418, Pos vs. control: p=0.003, Neg. vs. control: p=0.008). We next investigated the role of RAGE ligands in MG. The concentrations of RAGE ligands in patients with MG and controls were as follows: (HMGB1 [ng/ml] 1.7 ± 0.1 vs. 2.1 ± 0.2; p=0.058; S100B [pg/ml] 22.5 ± 22.5 vs. 14.4 ± 9.2; p=0.698; S100A8 [pg/ml] 107.0 ± 59.3 vs. 242.5 ± 103.6; p=0.347; and AGE-CML [ng/ml] 1100.8 ± 175.1 vs. 1399.8 ± 132.8; p=0.179).

CONCLUSIONS

Our data suggest a role for the RAGE pathway in the pathophysiology of MG. Further studies are warranted to elucidate more about this immunological axis in patients with MG.

Soluble receptor for advanced glycation end products (sRAGE) in plasma and synovial fluid is inversely associated with disease severity of knee osteoarthritis

OBJECTIVES

The aim of this study was to measure soluble receptor for advanced glycation end products (sRAGE) in plasma and synovial fluid of knee osteoarthritis (OA) patients and to determine the correlation between sRAGE levels and disease severity.

DESIGN AND METHODS

Thirty-six OA patients and 15 healthy controls were enrolled in this study. OA grading was performed using the Kellgren-Lawrence classification. sRAGE levels in plasma and synovial fluid were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Plasma sRAGE levels were significantly lower in OA patients than in healthy controls (P=0.01). sRAGE levels in plasma were remarkably higher with regard to paired synovial fluid (P=0.001). Additionally, sRAGE concentrations in plasma and synovial fluid showed significant inverse correlation with disease severity (r=-0.65, P<0.001 and r=-0.55, P=0.001, respectively). Further analysis showed that there was a strong positive correlation between plasma and synovial sRAGE concentration (r=0.81, P<0.001).

CONCLUSIONS

sRAGE levels were significantly lower in OA patients compared with controls, and sRAGE levels in plasma and synovial fluid also decreased significantly as the disease severity increased. Accordingly, sRAGE levels could be used as a biochemical marker for assessing the severity and progression of knee OA.

Receptor for advanced glycation end products: its role in Alzheimer's disease and other neurological diseases

The receptor for advanced glycation end products (RAGE) has been demonstrated to play a central role in the pathogenic mechanisms of a growing number of important neurological diseases, including Alzheimer's disease (AD) and stroke. Two functional types of RAGE have been associated with neurological diseases: cell membrane-bound (full length) and soluble. In general, ligand binding to full-length RAGE initiates sustained cellular activation and receptor-dependent signaling resulting in inflammation and cellular stress, and is ultimately associated with increased RAGE expression. By comparison, soluble forms of RAGE, generated either by alternative splicing or by proteolysis, can reduce the severity of the consequence of ligand-membrane RAGE interactions by preventing ligands from binding to the full-length RAGE. This can inhibit the neurotoxic or proinflammatory responses involved in disease states. This article reviews the pathobiology of RAGE, with emphasis on soluble forms of RAGE, and discusses its relevance to AD and to other neurological diseases, as well as how manipulation of the different forms of RAGE is becoming a powerful therapeutic strategy.

Detection of feto-maternal infection/inflammation by the soluble receptor for advanced glycation end products (sRAGE): results of a pilot study

OBJECTIVE

The receptor for advanced glycation end products, RAGE, plays an important role in the pathogenesis of several diseases. sRAGE, soluble receptor for advanced glycation end products, is an inhibitor of the pathological effect mediated via RAGE. The aim of this study was to assess the usefulness of measuring sRAGE concentration in pregnant women with threatening preterm labor.

METHODS

Serum levels of sRAGE, interleukin-6 (IL-6) and routine markers of inflammation were determined in 46 pregnant women with threatening preterm labor, 35 healthy pregnant women and 15 non-pregnant controls.

RESULTS

Serum levels of sRAGE in healthy pregnant women were significantly lower than in non-pregnant controls (669+/-296 vs. 1929+/-727 pg/mL, P<0.05). Women with threatening preterm birth had a significantly higher concentration of serum sRAGE in comparison with healthy pregnant women (819+/-329 pg/mL vs. 669+/-296 pg/mL, P<0.05). Conversely, patients with PPROM had significantly lower levels of sRAGE compared with patients with threatening premature labor (600+/-324 pg/mL, P<0.05). sRAGE correlated negatively with leukocyte counts (r=-0.325, P<0.05).

CONCLUSIONS

sRAGE might be a new and promising marker of premature labor, especially with the symptoms of PPROM.

Pulmonary biomarkers based on alterations in protein expression after exposure to arsenic

OBJECTIVE

Environmental exposure to arsenic results in multiple adverse effects in the lung. Our objective was to identify potential pulmonary protein biomarkers in the lung-lining fluid of mice chronically exposed to low-dose As and to validate these protein changes in human populations exposed to As.

METHODS

Mice were administered 10 or 50 ppb As (sodium arsenite) in their drinking water for 4 weeks. Proteins in the lung-lining fluid were identified using two-dimensional gel electrophoresis (n = 3) or multidimensional protein identification technology (MUDPIT) (n = 2) coupled with mass spectrometry. Lung-induced sputum samples were collected from 57 individuals (tap water As ranged from ~ 5 to 20 ppb). Protein levels in sputum were determined by ELISA, and As species were analyzed in first morning void urine.

RESULTS

Proteins in mouse lung-lining fluid whose expression was consistently altered by As included glutathione-S-transferase (GST)-omega-1, contraspin, apolipoprotein A-I and A-IV, enolase-1, peroxiredoxin-6, and receptor for advanced glycation end products (RAGE). Validation of the putative biomarkers was carried out by evaluating As-induced alterations in RAGE in humans. Regression analysis demonstrated a significant negative correlation (p = 0.016) between sputum levels of RAGE and total urinary inorganic As, similar to results seen in our animal model.

CONCLUSION

Combinations of proteomic analyses of animal models followed by specific analysis of human samples provide an unbiased determination of important, previously unidentified putative biomarkers that may be related to human disease.

Receptor for advanced glycation endproducts mediates neutrophil migration across intestinal epithelium

Receptor for advanced glycation endproducts (RAGE) is an Ig superfamily cell surface receptor that interacts with a diverse array of ligands associated with inflammatory responses. In this study, we provide evidence demonstrating that RAGE is involved in inflammatory responses in the intestines. We showed that RAGE is expressed in intestinal epithelial cells, primarily concentrated at the lateral membranes close to the apical cell junction complexes. Although RAGE expression was low in epithelium under normal conditions, this protein was up-regulated after treatment with the inflammatory cytokines IFN-gamma and/or TNF-alpha. RAGE expression was also elevated in colon tissue samples from patients with inflammatory bowel diseases. Using in vitro transmigration assays, we found that RAGE mediates neutrophil (polymorphonuclear leukocytes (PMN)) adhesion to, and subsequent migration across, intestinal epithelial monolayers. This activity appears to be mediated by the binding of RAGE to the PMN-specific beta(2) integrin CD11b/CD18. Thus, these results provide a novel mechanism for the regulation of PMN transepithelial migration and may suggest a new therapeutic target for intestinal inflammation.

Upregulation of RAGE and its ligands in proliferative retinal disease

We sought to study the presence of the receptor for advanced glycation endproducts (RAGE) and its ligands, advanced glycation endproducts (AGEs), S100/calgranulins and amphoterin (high mobility group box 1 protein; HMGB1), in the vitreous cavity and epiretinal membranes (ERMs) of eyes of patients with proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR). Undiluted vitreous specimens were collected from 30 eyes of 30 patients undergoing pars plana vitrectomy for repair of retinal detachment (RD) secondary to PDR (n = 15) or PVR (n = 15). The vitreous samples obtained from 10 eyes undergoing macular hole repair were used as controls. Epiretinal membranes were obtained from eight eyes with PDR and from 10 eyes with PVR. The levels of AGEs in the vitreous were measured using ELISA. The vitreous levels of soluble RAGE (sRAGE), S100/calgranulins and amphoterin were measured using Western blot analyses. The localization of RAGE and its ligands in ERMs was determined with immunohistochemistry. The vitreous levels of sRAGE were significantly increased in both PDR and PVR (p < or = 0.05) compared to control vitreous. In both PDR and PVR, the vitreous levels of AGEs (p < or = 0.01), S100/calgranulins (p < or = 0.05), and amphoterin (p < or = 0.01) were also elevated compared to control eyes. Expression of RAGE was detected in six of eight ERMs from eyes with PDR and eight of 10 ERMs from eyes with PVR. Many cells expressing RAGE also expressed vimentin, suggesting a glial cell origin. Ligands for RAGE were also detected in ERMs, with AGEs detected in five eyes with PDR and eight eyes with PVR. Similarly, S100 and amphoterin ERM expression was observed in six eyes with PDR; these ligands were also expressed in ERMs from eyes with PVR (8 and 7 cases, respectively). We conclude that RAGE and its ligands are increased in the vitreous cavity of eyes with PDR and PVR and are present in ERMs of eyes with these proliferative retinal disorders. These findings suggest a role for the proinflammatory RAGE axis in the pathogenesis of proliferative retinal diseases.