Posttranslationally modified proteins as mediators of sustained intestinal inflammation

A Gently Processed Skim Milk-Derived Whey Protein Concentrate for Infant Formula: Effects on Gut Development and Immunity in Preterm Pigs

SCOPE

Processing of whey protein concentrate (WPC) for infant formulas may induce protein modifications with severe consequences for preterm newborn development. The study investigates how conventional WPC and a gently processed skim milk-derived WPC (SPC) affect gut and immune development after birth.

METHODS AND RESULTS

Newborn, preterm pigs used as a model of preterm infants were fed formula containing WPC, SPC, extra heat-treated SPC (HT-SPC), or stored HT-SPC (HTS-SPC) for 5 days. SPC contained no protein aggregates and more native lactoferrin, and despite higher Maillard reaction product (MRP) formation, the clinical response and most gut and immune parameters are similar to WPC pigs. SPC feeding negatively impacts intestinal MRP accumulation, mucosa, and bacterial diversity. In contrast, circulating T-cells are decreased and oxidative stress- and inflammation-related genes are upregulated in WPC pigs. Protein aggregation and MRP formation increase in HTS-SPC, leading to reduced antibacterial activity, lactase/maltase ratio, circulating neutrophils, and cytotoxic T-cells besides increased gut MRP accumulation and expression of TNFAIP3.

CONCLUSION

The gently processed SPC has more native protein, but higher MRP levels than WPC, resulting in similar tolerability but subclinical adverse gut effects in preterm pigs. Additional heat treatment and storage further induce MRP formation, gut inflammation, and intestinal mucosal damage.

Pathogenic role of S100 proteins in psoriasis

Psoriasis is a chronic inflammatory skin disease. The histopathological features of psoriasis include excessive proliferation of keratinocytes and infiltration of immune cells. The S100 proteins are a group of EF-hand Ca2+-binding proteins, including S100A2, -A7, -A8/A9, -A12, -A15, which expression levels are markedly upregulated in psoriatic skin. These proteins exert numerous functions such as serving as intracellular Ca2+ sensors, transduction of Ca2+ signaling, response to extracellular stimuli, energy metabolism, and regulating cell proliferation and apoptosis. Evidence shows a crucial role of S100 proteins in the development and progress of inflammatory diseases, including psoriasis. S100 proteins can possibly be used as potential therapeutic target and diagnostic biomarkers. This review focuses on the pathogenic role of S100 proteins in psoriasis.

Short-term feeding of defatted bovine colostrum mitigates inflammation in the gut via changes in metabolites and microbiota in a chicken animal model

BACKGROUND

Nondrug supplement strategies to improve gut health have largely focused on the effects of individual compounds to improve one aspect of gut homeostasis. However, there is no comprehensive assessment of the reproducible effects of oral, short-term, low-level colostrum supplementation on gut inflammation status that are specific to the ileum. Herein, a chicken animal model highly responsive to even mild gut inflammatory stimuli was employed to compare the outcomes of feeding a standard diet (CON) to those of CON supplemented with a centrifuge-defatted bovine colostrum (BC) or a nonfat dried milk (NFDM) control on the efficiency of nutrient use, ileal morphology, gut nitro-oxidative inflammation status, metabolites, and the composition of the microbiota.

RESULTS

A repeated design, iterative multiple regression model was developed to analyze how BC affected ileal digesta-associated anti-inflammatory metabolite abundance coincident with observed changes in the ileal microbiome, mitigation of epithelial inflammation, and ileal surface morphology. An improved whole body nutrient use efficiency in the BC group (v CON and NFDM) coincided with the observed increased ileum absorptive surface and reduced epithelial cell content of tyrosine-nitrated protein (NT, biomarker of nitro-oxidative inflammatory stress). Metabolome analysis revealed that anti-inflammatory metabolites were significantly greater in abundance in BC-fed animals. BC also had a beneficial BC impact on microbiota, particularly in promoting the presence of the bacterial types associated with eubiosis and the segmented filamentous bacteria, Candidatus Arthromitus.

CONCLUSION

The data suggest that an anti-inflammatory environment in the ileum was more evident in BC than in the other feeding groups and associated with an increased content of statistically definable groups of anti-inflammatory metabolites that appear to functionally link the observed interactions between the host's improved gut health with an observed increase in whole body nutrient use efficiency, beneficial changes in the microbiome and immunometabolism.

Advanced Glycation End-Products and Their Effects on Gut Health

Dietary advanced glycation end-products (AGEs) are a heterogeneous group of compounds formed when reducing sugars are heated with proteins, amino acids, or lipids at high temperatures for a prolonged period. The presence and accumulation of AGEs in numerous cell types and tissues are known to be prevalent in the pathology of many diseases. Modern diets, which contain a high proportion of processed foods and therefore a high level of AGE, cause deleterious effects leading to a multitude of unregulated intracellular and extracellular signalling and inflammatory pathways. Currently, many studies focus on investigating the chemical and structural aspects of AGEs and how they affect the metabolism and the cardiovascular and renal systems. Studies have also shown that AGEs affect the digestive system. However, there is no complete picture of the implication of AGEs in this area. The gastrointestinal tract is not only the first and principal site for the digestion and absorption of dietary AGEs but also one of the most susceptible organs to AGEs, which may exert many local and systemic effects. In this review, we summarise the current evidence of the association between a high-AGE diet and poor health outcomes, with a special focus on the relationship between dietary AGEs and alterations in the gastrointestinal structure, modifications in enteric neurons, and microbiota reshaping.

The Intake of Dicarbonyls and Advanced Glycation Endproducts as Part of the Habitual Diet Is Not Associated with Intestinal Inflammation in Inflammatory Bowel Disease and Irritable Bowel Syndrome Patients

A Western diet comprises high levels of dicarbonyls and advanced glycation endproducts (AGEs), which may contribute to flares and symptoms in inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). We therefore investigated the intake of dietary dicarbonyls and AGEs in IBD and IBS patients as part of the habitual diet, and their association with intestinal inflammation. Food frequency questionnaires from 238 IBD, 261 IBS as well as 195 healthy control (HC) subjects were used to calculate the intake of dicarbonyls methylglyoxal, glyoxal, and 3-deoxyglucosone, and of the AGEs Nε-(carboxymethyl)lysine, Nε-(1-carboxyethyl)lysine and methylglyoxal-derived hydroimidazolone-1. Intestinal inflammation was assessed using faecal calprotectin. The absolute dietary intake of all dicarbonyls and AGEs was higher in IBD and HC as compared to IBS (all p < 0.05). However, after energy-adjustment, only glyoxal was lower in IBD versus IBS and HC (p < 0.05). Faecal calprotectin was not significantly associated with dietary dicarbonyls and AGEs in either of the subgroups. The absolute intake of methylglyoxal was significantly higher in patients with low (<15 μg/g) compared to moderate calprotectin levels (15−<50 μg/g, p = 0.031). The concentrations of dietary dicarbonyls and AGEs generally present in the diet of Dutch patients with IBD or IBS are not associated with intestinal inflammation, although potential harmful effects might be counteracted by anti-inflammatory components in the food matrix.

High Molecular Weight Fucoidan Restores Intestinal Integrity by Regulating Inflammation and Tight Junction Loss Induced by Methylglyoxal-Derived Hydroimidazolone-1

Fucoidan from brown seaweeds has several biological effects, including preserving intestinal integrity. To investigate the intestinal protective properties of high molecular weight fucoidan (HMWF) from Undaria pinnatifida on intestinal integrity dysfunction caused by methylglyoxal-derived hydroimidazolone-1 (MG-H1), one of the dietary advanced-glycation end products (dAGEs) in the human-colon carcinoma-cell line (Caco-2) cells and ICR mice. According to research, dAGEs may damage the intestinal barrier by increasing gut permeability. The findings of the study showed that HMWF + MG-H1 treatment reduced by 16.8% the amount of reactive oxygen species generated by MG-H1 treatment alone. Furthermore, HMWF + MGH-1 treatment reduced MG-H1-induced monolayer integrity disruption, as measured by alterations in transepithelial electrical resistance (135% vs. 75.5%) and fluorescein isothiocyanate incorporation (1.40 × 10^-6 cm/s vs. 3.80 cm/s). HMWF treatment prevented the MG-H1-induced expression of tight junction markers, including zonula occludens-1, occludin, and claudin-1 in Caco-2 cells and mouse colon tissues at the mRNA and protein level. Also, in Caco-2 and MG-H1-treated mice, HMWF plays an important role in preventing receptor for AGEs (RAGE)-mediated intestinal damage. In addition, HMWF inhibited the nuclear factor kappa B activation and its target genes leading to intestinal inflammation. These findings suggest that HMWF with price competitiveness could play an important role in preventing AGEs-induced intestinal barrier dysfunction.

A Structural Perspective on Calprotectin as a Ligand of Receptors Mediating Inflammation and Potential Drug Target

Calprotectin, a heterodimer of S100A8 and S100A9 EF-hand calcium-binding proteins, is an integral part of the innate immune response. Calprotectin (CP) serves as a ligand for several pattern recognition cell surface receptors including the receptor for advanced glycation end products (RAGE), toll-like receptor 4 (TLR4), and cluster of differentiation 33 (CD33). The receptors initiate kinase signaling cascades that activate inflammation through the NF-kB pathway. Receptor activation by CP leads to upregulation of both receptor and ligand, a positive feedback loop associated with specific chronic inflammatory syndromes. Hence, CP and its two constituent homodimers have been viewed as potential targets to suppress certain chronic inflammation pathologies. A variety of inhibitors of CP and other S100 proteins have been investigated for more than 30 years, but no candidates have advanced significantly into clinical trials. Here, current knowledge of the interactions of CP with its receptors is reviewed along with recent progress towards the development of CP-directed chemotherapeutics.

Dual Nature of RAGE in Host Reaction and Nurturing the Mother-Infant Bond

Non-enzymatic glycation is an unavoidable reaction that occurs across biological taxa. The final products of this irreversible reaction are called advanced glycation end-products (AGEs). The endogenously formed AGEs are known to be bioactive and detrimental to human health. Additionally, exogenous food-derived AGEs are debated to contribute to the development of aging and various diseases. Receptor for AGEs (RAGE) is widely known to elicit biological reactions. The binding of RAGE to other ligands (e.g., high mobility group box 1, S100 proteins, lipopolysaccharides, and amyloid-β) can result in pathological processes via the activation of intracellular RAGE signaling pathways, including inflammation, diabetes, aging, cancer growth, and metastasis. RAGE is now recognized as a pattern-recognition receptor. All mammals have RAGE homologs; however, other vertebrates, such as birds, amphibians, fish, and reptiles, do not have RAGE at the genomic level. This evidence from an evolutionary perspective allows us to understand why mammals require RAGE. In this review, we provide an overview of the scientific knowledge about the role of RAGE in physiological and pathological processes. In particular, we focus on (1) RAGE biology, (2) the role of RAGE in physiological and pathophysiological processes, (3) RAGE isoforms, including full-length membrane-bound RAGE (mRAGE), and the soluble forms of RAGE (sRAGE), which comprise endogenous secretory RAGE (esRAGE) and an ectodomain-shed form of RAGE, and (4) oxytocin transporters in the brain and intestine, which are important for maternal bonding and social behaviors.

The Role of AGE-RAGE Signalling as a Modulator of Gut Permeability in Diabetes

There is increasing evidence for the role of intestinal permeability as a contributing factor in the pathogenesis of diabetes; however, the molecular mechanisms are poorly understood. Advanced glycation endproducts, of both exogenous and endogenous origin, have been shown to play a role in diabetes pathophysiology, in part by their ligation to the receptor for advanced glycation endproducts (RAGE), leading to a proinflammatory signalling cascade. RAGE signalling has been demonstrated to play a role in the development of intestinal inflammation and permeability in Crohn's disease and ulcerative colitis. In this review, we explore the role of AGE-RAGE signalling and intestinal permeability and explore whether activation of RAGE on the intestinal epithelium may be a downstream event contributing to the pathogenesis of diabetes complications.

Anti-inflammatory and -apoptotic effects of a long-term herbal extract treatment on DSS-induced colitis in mice fed with high AGEs-fat diet

Background

Obesity is associated with many comorbidities including inflammatory bowel disease (IBD). We investigated prophylactic effects of an herbal extract (HE) on the DSS-induced colitis mice challenged with high AGEs-fat diet 60% (HFD).

Methods

Six-week-old C57BL/6 male mice were fed with either HFD (8 groups, 6 mice in each group), or normal diet (ND) (8 groups, 6 mice in each group). After 6 weeks, animals received HE (combination of turmeric, ginger, boswellia and cat’s claw extract) for 7 weeks in three doses (high dose (0.6 mg/g); low dose (0.15 mg/g) and mid dose (0.3 mg/g)). Next, mice were subjected to 2.5% DSS in drinking water. Control mice received ND and instead of HE and DSS they received distilled water. Obesity index markers were determined, H&E staining and TUNEL assay evaluated apoptosis. Colonic expressions of IL-6, RAGE, AGER1, Sirt1, Bax, Bcl2, ZO-1 and P53 were determined.

Results

HE ameliorated colitis in HFD mice by reducing colonic myeloperoxidase activity (by 2.3-fold), macrophage accumulation (by 2.6-fold) and mRNA expression of IL-6 (by 2.3-fold) in HFD mice. Moreover, HE restored ZO-1 (by 2.7-fold), prevented apoptosis and maintained immune homeostasis. HE reduced activation of NF-κB protein (by 1.3-fold) through decreasing RAGE (by 1.93-fold) and up-regulation of Sirt1 (by 7.71-fold) and prevented down-regulation of DDOST (by 6.6-fold) in HFD mice.

Conclusions

HE ameliorated colitis in prophylactic in HFD mice and it was, at least partly, due to the restoration of the gut integrity, suppression of inflammation and apoptosis via modulation of colonic Sirt1, RAGE and DDOST signaling.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00603-x.

A fragment-based approach to discovery of Receptor for Advanced Glycation End products inhibitors

The Receptor for Advanced Glycation End products (RAGE) is a pattern recognition receptor that signals for inflammation via the NF-κB pathway. RAGE has been pursued as a potential target to suppress symptoms of diabetes and is of interest in a number of other diseases associated with chronic inflammation, such as inflammatory bowel disease and bronchopulmonary dysplasia. Screening and optimization have previously produced small molecules that inhibit the activity of RAGE in cell-based assays, but efforts to develop a therapeutically viable direct-binding RAGE inhibitor have yet to be successful. Here, we show that a fragment-based approach can be applied to discover fundamentally new types of RAGE inhibitors that specifically target the ligand-binding surface. A series of systematic assays of structural stability, solubility, and crystallization were performed to select constructs of the RAGE ligand-binding domain and optimize conditions for NMR-based screening and co-crystallization of RAGE with hit fragments. An NMR-based screen of a highly curated ~14 000-member fragment library produced 21 fragment leads. Of these, three were selected for elaboration based on structure-activity relationships generated through cycles of structural analysis by X-ray crystallography, structure-guided design principles, and synthetic chemistry. These results, combined with crystal structures of the first linked fragment compounds, demonstrate the applicability of the fragment-based approach to the discovery of RAGE inhibitors.

Alteration of oxidative-stress and related marker levels in mouse colonic tissues and fecal microbiota structures with chronic ethanol administration: Implications for the pathogenesis of ethanol-related colorectal cancer

Chronic ethanol consumption is a risk factor for colorectal cancer, and ethanol-induced reactive oxygen species have been suggested to play important roles in the pathogenesis of ethanol-related colorectal cancer (ER-CRC). In this study, the effects of 10-week chronic administration of ethanol on the colonic levels of oxidative stress and advance glycation end product (AGE) levels, as well as fecal microbiota structures, were examined in a mouse model. Chronic oral administration of ethanol in mice (1.0 mL of 1.5% or 5.0% ethanol (v/v) per day per mouse, up to 10 weeks) resulted in the elevation of colonic levels of oxidative stress markers (such as 8-hydroxy-2'-deoxyguanosine and 4-hydroxynonenal) compared to control mice, and this was consistently accompanied by elevated levels of inflammation-associated cytokines and immune cells (Th17 and macrophages) and a decreased level of regulatory T (Treg) cells to produce colonic lesions. It also resulted in an alteration of mouse fecal microbiota structures, reminiscent of the alterations observed in human inflammatory bowel disease, and this appeared to be consistent with the proposed sustained generation of oxidative stress in the colonic environment during chronic ethanol consumption. Moreover, the first experimental evidence that chronic ethanol administration results in elevated levels of advanced glycation end products (AGEs) and their receptors (RAGE) in the colonic tissues in mice is also shown, implying enhanced RAGE-mediated signaling with chronic ethanol administration. The RAGE-mediated signaling pathway has thus far been implicated as a link between the accumulation of AGEs and the development of many types of chronic colitis and cancers. Thus, enhancement of this pathway likely exacerbates the ethanol-induced inflammatory states of colonic tissues and might at least partly contribute to the pathogenesis of ER-CRC.

S100A8/A9 in Myocardial Infarction: A Promising Biomarker and Therapeutic Target

Myocardial infarction (MI), the main cause of cardiovascular-related deaths worldwide, has long been a hot topic because of its threat to public health. S100A8/A9 has recently attracted an increasing amount of interest as a crucial alarmin that regulates the pathogenesis of cardiovascular disease after its release from myeloid cells. However, the role of S100A8/A9 in the etiology of MI is not well understood. Here, we elaborate on the critical roles and potential mechanisms of S100A8/A9 driving the pathogenesis of MI. First, cellular source of S100A8/A9 in infarcted heart is discussed. Then we highlight the effect of S100A8/A9 heterodimer in the early inflammatory period and the late reparative period of MI as well as myocardial ischemia/reperfusion (I/R) injury. Moreover, the predictive value of S100A8/A9 for the risk of recurrence of cardiovascular events is elucidated. Therefore, this review focuses on the molecular mechanisms of S100A8/A9 in MI pathogenesis to provide a promising biomarker and therapeutic target for MI.

Glycation of gut proteins initiates microbial dysbiosis and can promote establishment of diabetes in experimental animals

Diabetes and obesity is associated with change in the gut microbiota, however, the reason for such transition is still unknown. The secondary complications in diabetes mainly stem from protein glycation, oxidative stress and inflammatory response. It is intended to study the correlation between gut proteins glycation and microbial dysbiosis and thereby progression to diabetes. The study was carried out through feeding high fructose to male Wistar rats and evaluating their gut microbiota. The rate of gut flora excretion via faecal matter was found to decrease on fructose feed for 7 days. Intestinal flora was drastically reduced and pathogenic succession observed. Intestinal fluorescence studies confirmed that there is heavy glycation of gut proteins. Microbes obtained from fructose fed animals could grow on glycated BSA. There was significant increase in level of TNF-α and IFN-γ providing evidence of inflammation. Though microbial dysbiosis was observed in diabetes, the cause for this remained elusive. In the present study we prove that high fructose feed and glycation of the gut proteins probably prevent adherence/survival of the gut microflora in control animals and promotes transition to a changed microflora which is capable of adhering/utilizing glycated proteins as well as high fructose. The changed microbiota, enhanced protein glycation and inflammation help in establishing insulin resistance.

Dietary Advanced Glycation Endproducts and the Gastrointestinal Tract

The prevalence of inflammatory bowel diseases (IBD) is increasing in the world. The introduction of the Western diet has been suggested as a potential explanation of increased prevalence. The Western diet includes highly processed food products, and often include thermal treatment. During thermal treatment, the Maillard reaction can occur, leading to the formation of dietary advanced glycation endproducts (dAGEs). In this review, different biological effects of dAGEs are discussed, including their digestion, absorption, formation, and degradation in the gastrointestinal tract, with an emphasis on their pro-inflammatory effects. In addition, potential mechanisms in the inflammatory effects of dAGEs are discussed. This review also specifically elaborates on the involvement of the effects of dAGEs in IBD and focuses on evidence regarding the involvement of dAGEs in the symptoms of IBD. Finally, knowledge gaps that still need to be filled are identified.

Role of Advanced Glycation End Products in Carcinogenesis and their Therapeutic Implications

Aging is one of the biggest risk factors for the major prevalent diseases such as cardiovascular diseases, neurodegeneration and cancer, but due to the complex and multifactorial nature of the aging process, the molecular mechanisms underlying age-related diseases are not yet fully understood. Research has been intensive in the last years aiming to characterize the pathophysiology of aging and develop therapies to fight age-related diseases. In this context advanced glycation end products (AGEs) have received attention. AGEs, when accumulated in tissues, significantly increase the level of inflammation in the body which has long been associated with the development of cancer. Here we discuss the classical settings promoting AGE formation, as well as reduction strategies, occurrence and relevance of AGEs in cancer tissues and the role of AGE-interaction with the receptor for advanced glycation end products (RAGE) in cancer initiation and progression.

Systemic RAGE ligands are upregulated in tuberculosis individuals with diabetes co-morbidity and modulated by anti-tuberculosis treatment and metformin therapy

Background

Ligands of the receptor for advanced glycation end products (RAGE) are key signalling molecules in the innate immune system but their role in tuberculosis-diabetes comorbidity (TB-DM) has not been investigated.

Methods

We examined the systemic levels of soluble RAGE (sRAGE), advanced glycation end products (AGE), S100A12 and high mobility group box 1 (HMGB1) in participants with either TB-DM, TB, DM or healthy controls (HC).

Results

Systemic levels of AGE, sRAGE and S100A12 were significantly elevated in TB-DM and DM in comparison to TB and HC. During follow up, AGE, sRAGE and S100A12 remained significantly elevated in TB-DM compared to TB at 2nd month and 6th month of anti-TB treatment (ATT). RAGE ligands were increased in TB-DM individuals with bilateral and cavitary disease. sRAGE and S100A12 correlated with glycated hemoglobin levels. Within the TB-DM group, those with known diabetes (KDM) revealed significantly increased levels of AGE and sRAGE compared to newly diagnosed DM (NDM). KDM participants on metformin treatment exhibited significantly diminished levels of AGE and sRAGE in comparison to those on non-metformin regimens.

Conclusions

Our data demonstrate that RAGE ligand levels reflect disease severity and extent in TB-DM, distinguish KDM from NDM and are modulated by metformin therapy.

Metabolic Variability of a Multispecies Probiotic Preparation Impacts on the Anti-inflammatory Activity

Background: In addition to strain taxonomy, the ability of probiotics to confer beneficial effects on the host rely on a number of additional factors including epigenetic modulation of bacterial genes leading to metabolic variability and might impact on probiotic functionality.

Aims: To investigate metabolism and functionality of two different batches of a probiotic blend commercialized under the same name in Europe in models of intestinal inflammation.

Methods: Boxes of VSL#3, a probiotic mixture used in the treatment of pouchitis, were obtained from pharmacies in UK subjected to metabolomic analysis and their functionality tested in mice rendered colitis by treatment with DSS or TNBS.

Results: VSL#3-A (lot DM538), but not VSL#3-B (lot 507132), attenuated “clinical” signs of colitis in the DSS and TNBS models. In both models, VSL#3-A, but not VSL#3-B, reduced macroscopic scores, intestinal permeability, and expression of TNFα, IL-1β, and IL-6 mRNAs, while increased the expression of TGFβ and IL-10, occludin, and zonula occludens-1 (ZO-1) mRNAs and shifted colonic macrophages from a M1 to M2 phenotype (P < 0.05 vs. TNBS). In contrast, VSL#3-B failed to reduce inflammation, and worsened intestinal permeability in the DSS model (P < 0.001 vs. VSL#3-A). A metabolomic analysis of the two formulations allowed the identification of two specific patterns, with at least three-folds enrichment in the concentrations of four metabolites, including 1–3 dihydroxyacetone (DHA), an intermediate in the fructose metabolism, in VSL#3-B supernatants. Feeding mice with DHA, increased intestinal permeability.

Conclusions: Two batches of a commercially available probiotic show divergent metabolic activities. DHA, a product of probiotic metabolism, increases intestinal permeability, highlighting the complex interactions between food, microbiota, probiotics, and intestinal inflammation.

22016 ATVB Plenary Lecture: Receptor for Advanced Glycation Endproducts and Implications for the Pathogenesis and Treatment of Cardiometabolic Disorders: Spotlight on the Macrophage

The receptor for advanced glycation endproducts (RAGE) interacts with a unique repertoire of ligands that form and collect in the tissues and circulation in diabetes mellitus, aging, inflammation, renal failure, and obesity. RAGE is expressed on multiple cell types linked to tissue perturbation in these settings. This brief review focuses on the role of RAGE in monocytes/macrophages and how RAGE ligand engagement on these cells mediates seminal changes in monocyte/macrophage migration, oxidative stress, cholesterol efflux, and pro- versus anti-inflammatory cues that signal to tissue damage. Studies using mice devoid of Ager (gene encoding RAGE) or pharmacological antagonists of RAGE are protective in animal models of diabetes mellitus, atherosclerosis, and high-fat diet-induced obesity, in least in part through key roles in monocytes/macrophages. RAGE signal transduction requires the interaction of RAGE cytoplasmic domain with the formin, DIAPH1 (diaphanous 1) and novel antagonists of this interaction show significant promise in attenuation of the maladaptive effects of RAGE ligands in cellular and in vivo models. Finally, this brief review discusses evidence for RAGE axis perturbation in human monocytes/macrophages and how tracing RAGE activity in these cells may identify target engagement biomarkers of RAGE antagonism for future clinical trials.

RAGE-mediated inflammation in patients with septic shock

BACKGROUND

The receptor for advanced glycation end-products (RAGE)-pathway is described to be a crucial component of the innate immune response in sepsis. The aims of the present study were, therefore, to delineate the kinetics of membrane-bound RAGE expression, to quantify its soluble isoforms, and to determine the extent of metabolic (e.g., AGE-CML) as well as immunologic (e.g., S100A8/A9) ligands in different inflammatory settings in humans.

MATERIALS AND METHODS

The presented data result from secondary analyses of an observational clinical pilot study, including patients with septic shock (n = 60), postoperative controls (n = 30), and healthy volunteers (n = 30). Surface-bound expression of RAGE by peripheral blood leukocytes was determined by flow cytometry. In addition, plasma levels of sRAGE, esRAGE, AGE-CML, S100A8/A9, S100A8/A9-CML, RBP, RBP-CML, HSA-CML, HMBG-1, and ß-Amyloid were measured using ELISA.

RESULTS

In patients with septic shock, RAGE expression was significantly increased in comparison to both control groups, which was paralleled by a significant increase in sRAGE plasma levels. Formation of AGE-CML was shown to be dependent on the availability of the unmodified protein. However, the total amount of AGE-CML did not differ significantly between septic patients and healthy volunteers at early stages or was even lower in patients with sepsis at later stages. In contrast, immunologic ligands (e.g., S100A8/A9) were shown to be significantly elevated in septic patients within the entire study period.

CONCLUSIONS

Activation of the RAGE-pathway was shown to be of relevance in patients with septic shock, mainly driven by an increase in immunologic (e.g., S100A8/A9) rather than metabolic ligands (e.g., CML-derived AGE-formation).

Critical role of RAGE and HMGB1 in inflammatory heart disease

Autoimmune response to cardiac troponin I (TnI) induces inflammation and fibrosis in the myocardium. High-mobility group box 1 (HMGB1) is a multifunctional protein that exerts proinflammatory activity by mainly binding to receptor for advanced glycation end products (RAGE). The involvement of the HMGB1-RAGE axis in the pathogenesis of inflammatory cardiomyopathy is yet not fully understood. Using the well-established model of TnI-induced experimental autoimmune myocarditis (EAM), we demonstrated that both local and systemic HMGB1 protein expression was elevated in wild-type (wt) mice after TnI immunization. Additionally, pharmacological inhibition of HMGB1 using glycyrrhizin or anti-HMGB1 antibody reduced inflammation in hearts of TnI-immunized wt mice. Furthermore, RAGE knockout (RAGE-ko) mice immunized with TnI showed no structural or physiological signs of cardiac impairment. Moreover, cardiac overexpression of HMGB1 using adeno-associated virus (AAV) vectors induced inflammation in the hearts of both wt and RAGE-ko mice. Finally, patients with myocarditis displayed increased local and systemic HMGB1 and soluble RAGE (sRAGE) expression. Together, our study highlights that HMGB1 and its main receptor, RAGE, appear to be crucial factors in the pathogenesis of TnI-induced EAM, because inhibition of HMGB1 and ablation of RAGE suppressed inflammation in the heart. Moreover, the proinflammatory effect of HMGB1 is not necessarily dependent on RAGE only. Other receptors of HMGB1 such as Toll-like receptors (TLRs) may also be involved in disease pathogenesis. These findings could be confirmed by the clinical relevance of HMGB1 and sRAGE. Therefore, blockage of one of these molecules might represent a novel therapeutic strategy in the treatment of autoimmune myocarditis and inflammatory cardiomyopathy.

Effect of diet-derived advanced glycation end products on inflammation

Advanced glycation end products (AGEs) formed via the Maillard reaction during the thermal processing of food contributes to the flavor, color, and aroma of food. A proportion of food-derived AGEs and their precursors is intestinally absorbed and accumulates within cells and tissues. AGEs have been implicated in the pathogenesis of diabetes-related complications and several chronic diseases via interaction with the receptor for AGEs, which promotes the transcription of genes that control inflammation. The dicarbonyls, highly reactive intermediates of AGE formation, are also generated during food processing and may incite inflammatory responses through 1) the suppression of protective pathways, 2) the incretin axis, 3) the modulation of immune-mediated signaling, and 4) changes in gut microbiota profile and metabolite sensors. In animal models, restriction of dietary AGEs attenuates chronic low-grade inflammation, but current evidence from human studies is less clear. Here, the emerging relationship between excess dietary AGE consumption and inflammation is explored, the utility of dietary AGE restriction as a therapeutic strategy for the attenuation of chronic diseases is discussed, and possible avenues for future investigation are suggested.

Possible role of methylglyoxal and glyoxalase in arthritis

OA (osteoarthritis) and RA (rheumatoid arthritis) lead to deterioration of the joints. Early OA is associated with loss of bone due to increased bone remodelling. A role for inflammation is thought to be integral to the pathology. RA is a chronic inflammatory disease of the synovium, a membrane lining the non-weight-bearing surfaces of the joint. The mainstay of RA diagnostic testing is for autoantibodies. Rheumatoid factor has been a primary diagnostic test; however, sensitivity is approximately 75%, but specificity is limited. Recently, detection of antibodies against cyclic citrullinated peptide, identified as a screening marker and marker of disease progression, has been proposed. Studies of glycation in arthritis have focused mostly on levels of AGEs (advanced glycation end-products), Nε-carboxymethyl-lysine and pentosidine. There was a weak correlation of skin and urinary pentosidine with joint damage in early-stage OA. RAGE (receptor for AGEs) is a cell-surface receptor in the synovial tissue of patients with OA and RA. The RAGE agonist S100A12 is increased in RA and OA. Activation of RAGE may decrease expression of Glo1 (glyoxalase I). Conflict between RAGE-activated inflammatory signalling and Nrf2 (nuclear factor-erythroid 2-related factor 2) regulation of basal and inducible expression of Glo1 may be involved. Thereby glyoxal- and methylglyoxal-derived AGEs may be increased in OA and RA. Further studies are now required to investigate the role of glyoxalase and dicarbonyl glycation in OA and RA for early-stage diagnosis and potential novel preventive therapy.

Influence of nonenzymatic posttranslational modifications on constitution, oligomerization and receptor binding of S100A12

This study examined the effect of methylglyoxal (MGO)-derived nonenzymatic posttranslational modifications (nePTMs) on the binding affinity of S100A12 to its natural receptor for advanced glycation end-products (RAGE). Binding of MGO-modified S100A12 to RAGE decreased significantly with increasing MGO concentration and incubation time. Ca²⁺-induced S100A12 hexamerization was impaired only at higher MGO concentrations indicating that the loss of affinity is not predominantly caused by disturbance of ligand oligomerization. nePTM mapping showed carboxyethylation of lysine (CEL) and the N-terminus without preferential modification sites. Besides, hydroimidazolone, hemiaminals, argpyrimidine, and tetrahydropyrimidine rapidly formed at R21. Even at the highest modification rate, hexamerization of synthesized CEL-S100A12 was unaffected and RAGE-binding only slightly impaired. Thus, nePTMs at R21 seem to be the major cause of MGO-induced impairment of S100A12 oligomerization and RAGE binding.

Role of bone-marrow- and non-bone-marrow-derived receptor for advanced glycation end-products (RAGE) in a mouse model of diabetes-associated atherosclerosis

RAGE (receptor for advanced glycation end-products) is expressed on multiple cell types implicated in the progression of atherosclerosis and plays a role in DAA (diabetes-associated atherosclerosis). The aim of the present study was to determine the relative role of either BM (bone marrow)- or non-BM-derived RAGE in the pathogenesis of STZ (streptozotocin)-induced DAA. Male ApoE (apolipoprotein E)-null (ApoE-/-:RAGE+/+) and ApoE:RAGE-null (ApoE-/-:RAGE-/-) mice at 7 weeks of age were rendered diabetic with STZ. At 8 weeks of age, ApoE-/- and ApoE-/-:RAGE-/- control and diabetic mice received BM from either RAGE-null or RAGE-bearing mice, generating various chimaeras. After 10 and 20 weeks of diabetes, mice were killed and gene expression and atherosclerotic lesion formation were evaluated respectively. Deletion of RAGE in either the BM cells or non-BM cells both resulted in a significant attenuation in DAA, which was associated with reduced VCAM-1 (vascular cell adhesion molecule-1) expression and translated into reduced adhesion in vitro. In conclusion, the results of the present study highlight the importance of both BM- and non-BM-derived RAGE in attenuating the development of DAA.

Controlling the receptor for advanced glycation end-products to conquer diabetic vascular complications

Diabetic vascular complications, such as cardiovascular disease, stroke and microangiopathy, lead to high rates of morbidity and mortality in patients with long‐term diabetes. Extensive intracellular and extracellular formation of advanced glycation end‐products (AGE) is considered a causative factor in vascular injuries in diabetes. Receptor‐dependent mechanisms are involved in AGE‐induced cellular dysfunction and tissue damage. The receptor for AGE (RAGE), originally an AGE‐binding receptor, is now recognized as a member of pattern‐recognition receptors and a pro‐inflammatory molecular device that mediates danger signals to the body. Previous animal studies have shown RAGE dependent of diabetic vascular injuries. Prophylactic and therapeutic strategies focusing on RAGE and its ligand axis will be of great importance in conquering diabetic vascular complications. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00191.x, 2012)

Pathophysiological importance of aggregated damaged proteins

Reactive oxygen species (ROS) are formed continuously in the organism even under physiological conditions. If the level of ROS in cells exceeds the cellular defense capacity, components such as RNA/DNA, lipids, and proteins are damaged and modified, thus affecting the functionality of organelles as well. Proteins are especially prominent targets of various modifications such as oxidation, glycation, or conjugation with products of lipid peroxidation, leading to the alteration of their biological function, nonspecific interactions, and the production of high-molecular-weight protein aggregates. To ensure the maintenance of cellular functions, two proteolytic systems are responsible for the removal of oxidized and modified proteins, especially the proteasome and organelles, mainly the autophagy-lysosomal systems. Furthermore, increased protein oxidation and oxidation-dependent impairment of proteolytic systems lead to an accumulation of oxidized proteins and finally to the formation of nondegradable protein aggregates. Accordingly, the cellular homeostasis cannot be maintained and the cellular metabolism is negatively affected. Here we address the current knowledge of protein aggregation during oxidative stress, aging, and disease.

Purification and characterization of the human cysteine-rich S100A3 protein and its pseudo citrullinated forms expressed in insect cells

High quantity and quality of recombinant Ca(2+)-binding proteins are required to study their molecular interactions, self-assembly, posttranslational modifications, and biological activities to elucidate Ca(2+)-dependent cellular signaling pathways. S100A3 is a unique member of the S100 protein family with the highest cysteine content (10%). This protein, derived from human hair follicles and cuticles, is characterized by an N-terminal acetyl group and irreversible posttranslational citrullination by peptidylarginine deiminase causing its homotetramer assembly. Insect cells, capable of introducing eukaryotic N-terminus and disulfide bonds, are an appropriate host in which to express this cysteine-rich protein. Four out of ten cysteines in the recombinant S100A3 form two intramolecular disulfide bridges that modulate its Ca(2+)-affinity. Three free thiol groups located at the C-terminus are predicted to form the high-affinity Zn(2+)-binding site. Citrullination of specific arginine residues in native S100A3 can be mimicked by site-directed mutagenic substitution of Arg/Ala. This chapter details our procedures used for the purification and characterization of the human S100A3 protein and its pseudo citrullinated forms expressed in insect cells.

CD166/ALCAM mediates proinflammatory effects of S100B in delayed type hypersensitivity

Promiscuity of pattern recognition receptors, such as receptor for advanced glycation end products (RAGE), allows for a complex regulatory network controlling inflammation. Scavenging of RAGE ligands by soluble RAGE treatment is effective in reducing delayed-type hypersensitivity (DTH), even in RAGE(-/-) mice by 50% (p < 0.001). This has led to the hypothesis that molecules scavenged by soluble RAGE bind to receptors other than RAGE. This study identifies CD166/ALCAM (ALCAM) as a close structural and functional homolog of RAGE, and it shows that binding of S100B to CD166/ALCAM induces dose- and time-dependent expression of members of the NF-κB family in wild type (WT) and RAGE(-/-) mouse endothelial cells. Blocking CD166/ALCAM expression using small interfering RNA completely inhibited S100B-induced NF-κB activation in RAGE(-/-), but not in WT cells. The in vivo significance of these observations was demonstrated by attenuation of DTH in WT and RAGE(-/-) animals pretreated with CD166/ALCAM small interfering RNA by 50% and 40%, respectively (p < 0.001). Experiments in ALCAM(-/-) animals displayed an only slight reduction of 16% in DTH, explained by compensatory reciprocal upregulation of RAGE in animals devoid of CD166/ALCAM, and vice versa. Consistently, ALCAM(-/-) mice, but not WT mice treated with RAGE small interfering RNA show a 35% reduction in DTH, and ALCAM(-/-) RAGE(-/-) double-knockout mice show a 27% reduction in DTH reaction. Thus, S100B is a proinflammatory cytokine bridging RAGE and CD166/ALCAM downstream effector mechanisms, both being compensatory upregulated after genetic deletion of its counterpart.

Role of scavenger receptors in glia-mediated neuroinflammatory response associated with Alzheimer's disease

It is widely accepted that cells serving immune functions in the brain, namely, microglia and astrocytes, are important mediators of pathological phenomena observed in Alzheimer's disease. However, it is unknown how these cells initiate the response that results in cognitive impairment and neuronal degeneration. Here, we review the participation of the immune response mediated by glial cells in Alzheimer's disease and the role played by scavenger receptors in the development of this pathology, focusing on the relevance of class A scavenger receptor (SR-A) for A β clearance and inflammatory activation of glial cell, and as a potential target for Alzheimer's disease therapy.

S100A12 suppresses pro-inflammatory, but not pro-thrombotic functions of serum amyloid A

S100A12 is elevated in the circulation in patients with chronic inflammatory diseases and recent studies indicate pleiotropic functions. Serum amyloid A induces monocyte cytokines and tissue factor. S100A12 did not stimulate IL-6, IL-8, IL-1β or TNF-α production by human peripheral blood mononuclear cells but low amounts consistently reduced cytokine mRNA and protein levels induced by serum amyloid A, by ∼49% and ∼46%, respectively. However, S100A12 did not affect serum amyloid A-induced monocyte tissue factor. In marked contrast, LPS-induced cytokines or tissue factor were not suppressed by S100A12. S100A12 did not alter cytokine mRNA stability or the cytokine secretory pathway. S100A12 and serum amyloid A did not appear to form complexes and although they may have common receptors, suppression was unlikely via receptor competition. Serum amyloid A induces cytokines via activation of NF-κB and the MAPK pathways. S100A12 reduced serum amyloid A-, but not LPS-induced ERK1/2 phosphorylation to baseline. It did not affect JNK or p38 phosphorylation or the NF-κB pathway. Reduction in ERK1/2 phosphorylation by S100A12 was unlikely due to changes in intracellular reactive oxygen species, Ca²⁺ flux or to recruitment of phosphatases. We suggest that S100A12 may modulate sterile inflammation by blunting pro-inflammatory properties of lipid-poor serum amyloid A deposited in chronic lesions where both proteins are elevated as a consequence of macrophage activation.

Protein oxidation in aging and the removal of oxidized proteins

Reactive oxygen species (ROS) are generated constantly within cells at low concentrations even under physiological conditions. During aging the levels of ROS can increase due to a limited capacity of antioxidant systems and repair mechanisms. Proteins are among the main targets for oxidants due to their high rate constants for several reactions with ROS and their abundance in biological systems. Protein damage has an important influence on cellular viability since most protein damage is non-repairable, and has deleterious consequences on protein structure and function. In addition, damaged and modified proteins can form cross-links and provide a basis for many senescence-associated alterations and may contribute to a range of human pathologies. Two proteolytic systems are responsible to ensure the maintenance of cellular functions: the proteasomal (UPS) and the lysosomal system. Those degrading systems provide a last line of antioxidative protection, removing irreversible damaged proteins and recycling amino acids for the continuous protein synthesis. But during aging, both systems are affected and their proteolytic activity declines significantly. Here we highlight the recent advantages in the understanding of protein oxidation and the fate of these damaged proteins during aging. This article is part of a Special Issue entitled: Posttranslational Protein modifications in biology and Medicine.

Receptor for advanced glycation end products (RAGE) and implications for the pathophysiology of heart failure

The receptor for advanced glycation end products (RAGE) is expressed in the heart in cardiomyocytes, vascular cells, fibroblasts, and in infiltrating inflammatory cells. Experiments in murine, rat, and swine models of injury suggest that RAGE and the ligands of RAGE are upregulated in key injuries to the heart, including ischemia/reperfusion injury, diabetes, and inflammation. Pharmacological antagonism of RAGE or genetic deletion of the receptor in mice is strikingly protective in models of these stresses. Data emerging from human studies suggest that measurement of levels of RAGE ligands or soluble RAGEs in plasma or serum may correlate with the degree of heart failure. Taken together, the ligand-RAGE axis is implicated in heart failure and we predict that therapeutic antagonism of RAGE might be a unique target for therapeutic intervention in this disorder.

Advanced glycation end products: possible link between metabolic syndrome and periodontal diseases

On a planetary scale, Metabolic Syndrome (MetS)is the third cause of inability after malnutrition and nicotinism, even higher than water shortage and sedentariness. In the USA, the prevalence is estimated at over 25 percent of the population; in Italy, it involves approximately 25 percent of men and even 27 percent of women. These are very high figures, corresponding to approximately 14 million affected individuals. The prevalence is alarming and must not be underestimated, particularly in the dental field, where more than one patient out of four sitting in a dentist chair is affected. The etiology of periodontal disease has not yet been clarified, and recently the idea to consider it as a multifactor pathology has been developed. Cofactors such as the formation of free radicals of oxygen (ROS), oxidative stress, lipid peroxidation, and formation of glycation end-products (AGEs) probably play an important role in the onset of periodontal disease. The AGEs are compounds physiologically produced by the cells. However, they accumulate and cause pro-inflammatory conditions, when the cellular clearance fails, or in hyperglycemic and oxidative states. All these conditions can be clinically summarized as Metabolic Syndrome. The purpose of this literature review is to establish a relationship between two pathologies with very high prevalence: Metabolic Syndrome and Periodontal Disorder. The literature seems to have clarified that MetS involves a pro-oxidation status, which induces AGE formation. AGEs play a very important role in the course and severity of periodontal diseases.

Microglial scavenger receptors and their roles in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is increasing in prevalence with the aging population. Deposition of amyloid-β (Aβ) in the brain of AD patients is a hallmark of the disease and is associated with increased microglial numbers and activation state. The interaction of microglia with Aβ appears to play a dichotomous role in AD pathogenesis. On one hand, microglia can phagocytose and clear Aβ, but binding of microglia to Aβ also increases their ability to produce inflammatory cytokines, chemokines, and neurotoxic reactive oxygen species (ROS). Scavenger receptors, a group of evolutionally conserved proteins expressed on the surface of microglia act as receptors for Aβ. Of particular interest are SCARA-1 (scavenger receptor A-1), CD36, and RAGE (receptor for advanced glycation end products). SCARA-1 appears to be involved in the clearance of Aβ, while CD36 and RAGE are involved in activation of microglia by Aβ. In this review, we discuss the roles of various scavenger receptors in the interaction of microglia with Aβ and propose that these receptors play complementary, nonredundant functions in the development of AD pathology. We also discuss potential therapeutic applications for these receptors in AD.

S100A8/A9 aggravates post-ischemic heart failure through activation of RAGE-dependent NF-κB signaling

The extracellular heterodimeric protein S100A8/A9 activates the innate immune system through activation of the receptor of advanced glycation end products (RAGE) and Toll-like receptors. As activation of RAGE has recently been associated with sustained myocardial inflammation and heart failure (HF) we studied the role of S100A8/A9 in the development of post-ischemic HF. Hypoxia led to sustained induction of S100A8/A9 accompanied by increased nuclear factor (NF-)κB binding activity and increased expression of pro-inflammatory cytokines in cardiac fibroblasts and macrophages. Knockdown of either S100A8/A9 or RAGE rescued the induction of pro-inflammatory cytokines and NF-κB activation after hypoxia. In a murine model of post-ischemic HF both cardiac RNA and protein levels of S100A8/A9 were elevated as soon as 30 min after hypoxia with sustained activation up to 28 days after ischemic injury. Treatment with recombinant S100A8/A9 resulted in reduced cardiac performance following ischemia/reperfusion. Chimera experiments after bone marrow transplantation demonstrated the importance of RAGE expression on immune cells for their recruitment to the injured myocardium aggravating post-ischemic heart failure. Signaling studies in isolated ventricles indicated that MAP kinases JNK, ERK1/2 as well as NF-κB mediate signals downstream of S100A8/A9-RAGE in post-ischemic heart failure. Interestingly, cardiac performance was not affected by administration of S100A8/A9 in RAGE(-/-)-mice, which demonstrated significantly improved cardiac recovery compared to WT-mice. Our study provides evidence that sustained activation of S100A8/A9 critically contributes to the development of post-ischemic HF driving the progressive course of HF through activation of RAGE.

Serum levels of soluble receptor for advanced glycation endproducts (sRAGE) are higher in ulcerative colitis and correlate with disease activity

Interaction of the receptor for advanced glycation endproducts (RAGE) with its ligands results in expression of inflammatory mediators, activation of NF-κB, and induction of oxidative stress, all of which have been implicated in the pathogenesis of inflammatory bowel diseases (IBD). Soluble receptor for advanced glycation endproducts (sRAGE) has recently emerged as a reliable biomarker of inflammation in numerous RAGE-mediated disorders.

OBJECTIVE

To assess sRAGE levels in adult patients with IBD.

METHOD

Serum was collected from adult patients with Crohn's disease (CD, 56 patients), ulcerative colitis (UC, 60 patients), and healthy controls (HC, 113 subjects). Levels of sRAGE were determined by enzyme-linked immunosorbent assay.

RESULTS

Serum sRAGE levels were elevated in IBD compared to HC and were higher in UC patients compared to CD and HC. Levels of sRAGE were significantly higher in the serum of UC patients with active disease compared to patients with inactive disease, but no association with the Montreal Classification was evident. Serum sRAGE was lower in CD patients with biological therapies.

CONCLUSIONS

These findings suggest that serum levels of sRAGE are altered in patients with intestinal inflammation and may reflect distinct immunoinflammatory pathogenesis of UC and CD.

A race for RAGE ligands

In experimental animals a causal involvement of the multiligand receptor for advanced glycation end products (RAGE) in the development of diabetic vascular complications has been demonstrated. However, the nature of RAGE ligands present in patients with diabetic nephropathy has not yet been defined; this leaves open the relevance of the RAGE system to the human disease.

HMGB1: the missing link between diabetes mellitus and heart failure

Diabetes mellitus (DM) is a major independent risk factor for cardiovascular disease, but also leads to cardiomyopathy. However, the etiology of the cardiac disease is unknown. Therefore, the aim of this study was to identify molecular mechanisms underlying diabetic heart disease. High glucose treatment of isolated cardiac fibroblasts, macrophages and cardiomyocytes led to a sustained induction of HMGB1 on the RNA and protein level followed by increased NF-κB binding activity with consecutively sustained TNF-α and IL-6 expression. Short interference (si) RNA knock-down for HMGB1 and RAGE in vitro confirmed the importance of this axis in diabetes-driven chronic inflammation. In a murine model of post-myocardial infarction remodeling in type 1 diabetes, cardiac HMGB1 expression was significantly elevated both on RNA and protein level paralleled by increased expression of pro-inflammatory cytokines up to 10 weeks. HMGB1-specific blockage via box A treatment significantly reduced post-myocardial infarction remodeling and markers of tissue damage in vivo. The protective effects of box A indicated an involvement of the mitogen-activated protein-kinases jun N-terminal kinase and extracellular signal-regulated kinase 1/2, as well as the transcription factor nuclear factor-kappaB. Interestingly, remodeling and tissue damage were not affected by administration of box A in RAGE(-/-) mice. In conclusion, HMGB1 plays a major role in DM and post-I/R remodeling by binding to RAGE, resulting in activation of sustained pro-inflammatory pathways and enhanced myocardial injury. Therefore, blockage of HMGB1 might represent a therapeutic strategy to reduce post-ischemic remodeling in DM.

Sumoylation and nuclear translocation of S100A4 regulate IL-1beta-mediated production of matrix metalloproteinase-13

S100A4, a member of the S100 family of proteins, plays an important role in matrix remodeling by up-regulating the expression of matrix metalloproteinases (MMPs). We have previously shown that S100A4 is overexpressed in diseased cartilage and that extracellular S100A4 stimulates MMP-13 production, a major type II collagen-degrading enzyme, via activation of receptor for advanced glycation end product signaling. In the present study, using human articular chondrocytes, we show that intracellular S100A4 translocated into the nucleus upon interleukin-1β (IL-1β) stimulation and translocation required post-translational modification of S100A4 by the sumo-1 protein. Two sumoylation sites were identified on the S100A4 molecule, Lys(22) and Lys(96). Mutation of these lysine residues abolished the ability of S100A4 to be sumoylated and to translocate into the nucleus. Blocking of sumoylation and nuclear transport of S100A4 inhibited the IL-1β-induced production of MMP-13. Nuclear S100A4 was bound to the promoter region of MMP-13 in IL-1β-treated cells. Thus, we demonstrate a novel mechanism for sumoylated S100A4 as a regulator of expression of the MMP-13 gene.

Effects of S100A9 in a rat model of asthma and in isolated tracheal spirals

S100A9 is a member of the S100 family of proteins that contain two EF-hand calcium-binding motifs. We previously reported that S100A9 was differentially expressed during the early airway response phase of asthma and can be regulated by acupuncture. To understand the possible role of S100A9 in asthma, the effects of the S100A9 were investigated in a rat model of asthma and in isolated tracheal spirals. The pulmonary function and isometric tension were measured after the administration of purified recombinant S100A9. The results of in vivo experiments showed that S100A9 (0.1microg/kg) significantly decreased the pulmonary resistance and increased the dynamic compliance. The in vitro experimental results showed that S100A9 (100, 200, 400, or 800ng/ml, final concentrations) significantly reduced the isometric tension of isolated tracheal spirals. These results suggest that S100A9 elicits dose-dependent anti-asthmatic effects and may provide further insight into the treatment of asthma.