Anti-receptor for advanced glycation end products therapies as novel treatment for abdominal aortic aneurysm

RAGE deficiency ameliorates abdominal aortic aneurysm progression

BACKGROUND

Abdominal aortic aneurysm (AAA) is a vascular disease characterized by inflammation and arterial wall degradation. The receptor for advanced glycation end products (RAGE) plays a pivotal role in regulating inflammatory pathways, but its specific contribution to AAA pathogenesis remains unclear.

PURPOSE

This study aimed to investigate the role of RAGE in AAA development by examining its expression in human and mice AAA tissues and exploring the effects of RAGE deficiency on aneurysm progression, macrophage polarization, and inflammatory responses.

METHODS

RAGE expression was analyzed in human AAA samples and porcine pancreatic elastase (PPE) induced AAA mouse models using Western blotting, immunohistochemistry, and immunofluorescence. In vivo RAGE-deficient (RAGE-/-) mice were generated to assess the impact of RAGE knockout on AAA progression. In vitro experiments utilized RAW264.7 transfected with RAGE-targeting siRNA to study macrophage polarization and NF-κB signaling.

RESULTS

RAGE expression was elevated in AAA tissues, particularly in macrophages. RAGE-/- mice exhibited reduced AAA incidence, mortality, and aortic dilation compared to wild-type mice. Histological analysis showed preserved elastic fibers and smooth muscle layers, along with decreased inflammatory cell infiltration and MMP2/MMP9 expression. RAGE deficiency inhibited M1-like macrophage polarization and pro-inflammatory cytokine secretion, mediated through suppression of the NF-κB pathway.

CONCLUSIONS

RAGE deficiency mitigates AAA progression by modulating macrophage polarization and reducing inflammation via the NF-κB pathway. These findings highlight RAGE as a potential therapeutic target for AAA treatment.

A population-based study on hyperinsulinaemia and arterial stiffness in men with and without abdominal aortic aneurysm

Objectives

Patients with type 2 diabetes mellitus (DM) run lower risk for abdominal aortic aneurysm (AAA, aortic diameter ≥ 30 mm) and its complications. We aimed to evaluate associations between disturbances in glucose metabolism and arterial stiffness, AAA, and abdominal aortic diameter in 65-year-old men.

Methods

Forty-eight 65-year-old men with screening-detected AAA and 115 men with normal abdominal aortic diameter underwent examination of glucose metabolism and arterial stiffness.

Results

Men with AAA had higher BMI, waist-hip ratio (WHR), frequency of DM, haemoglobin A1c, smoking exposure, and plasma insulin levels at 0, 60 and 120 min during OGTT compared to those without. The increase in p-insulin (P < 0.001) after OGTT was also higher in men with AAA, adjusted for smoking, WHR, and nadir value of p-insulin. In analyses adjusted for smoking, use of lipid-lowering agents, and WHR, the increase in p-insulin at 2-hours (P = 0.006) after OGTT and p-homocysteine were associated with abdominal aortic diameter. There were no differences between groups in aortic stiffness or skin autofluorescence Advanced Glycation End products.

Conclusion

In this population-based study hyperinsulinaemia as a marker of insulin resistance, but not hyperglycaemia or aortic stiffness, was associated with AAA and abdominal aortic diameter in 65-year-old men.

Oxidative Stress in Health and Disease

Oxidative stress, resulting from the excessive intracellular accumulation of reactive oxygen species (ROS), reactive nitrogen species (RNS), and other free radical species, contributes to the onset and progression of various diseases, including diabetes, obesity, diabetic nephropathy, diabetic neuropathy, and neurological diseases, such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Oxidative stress is also implicated in cardiovascular disease and cancer. Exacerbated oxidative stress leads to the accelerated formation of advanced glycation end products (AGEs), a complex mixture of crosslinked proteins and protein modifications. Relatively high levels of AGEs are generated in diabetes, obesity, AD, and other I neurological diseases. AGEs such as Ne-carboxymethyllysine (CML) serve as markers for disease progression. AGEs, through interaction with receptors for advanced glycation end products (RAGE), initiate a cascade of deleterious signaling events to form inflammatory cytokines, and thereby further exacerbate oxidative stress in a vicious cycle. AGE inhibitors, AGE breakers, and RAGE inhibitors are therefore potential therapeutic agents for multiple diseases, including diabetes and AD. The complexity of the AGEs and the lack of well-established mechanisms for AGE formation are largely responsible for the lack of effective therapeutics targeting oxidative stress and AGE-related diseases. This review addresses the role of oxidative stress in the pathogenesis of AGE-related chronic diseases, including diabetes and neurological disorders, and recent progress in the development of therapeutics based on antioxidants, AGE breakers and RAGE inhibitors. Furthermore, this review outlines therapeutic strategies based on single-atom nanozymes that attenuate oxidative stress through the sequestering of reactive oxygen species (ROS) and reactive nitrogen species (RNS).

Soluble CD93 lectin-like domain sequesters HMGB1 to ameliorate inflammatory diseases

Rationale: CD93, a C-type lectin-like transmembrane glycoprotein, can be shed in a soluble form (sCD93) upon inflammatory stimuli. sCD93 effectively enhances apoptotic cell clearance and has been proposed as an inflammatory disease biomarker. The function of sCD93 involved directly in inflammation remains to be determined. Herein, we attempted to examine the hypothesis that sCD93 might sequester proinflammatory high-mobility group box 1 protein (HMGB1), exerting anti-inflammatory properties. Methods: Different forms of soluble recombinant human CD93 (rCD93) were prepared by a mammalian protein expression system. rCD93-HMGB1 interaction was assessed using co-immunoprecipitation and solid-phase binding assays. Effects of soluble rCD93 were evaluated in HMGB1-induced macrophage and vascular smooth muscle cells (VSMC) activation and receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis, CaCl2-induced and angiotensin II-infused abdominal aortic aneurysm (AAA) formation and ovariectomized-induced osteoporosis in mice. Results: Protein binding studies revealed that soluble rCD93, via the lectin-like domain (D1), can bind to HMGB1 and intercept HMGB1-receptor interaction. Soluble rCD93 containing D1 inhibited HMGB1-induced proinflammatory cytokine production and intracellular mitogen-activated protein kinase (MAPK)/nuclear factor (NF)-κB activation in macrophages and VSMCs, thereby attenuating CaCl2-induced and angiotensin II-infused AAA models. During osteoclastogenesis, RANKL stimulated HMGB1 secretion that promoted RANKL-induced osteoclastogenesis in return. Soluble rCD93 containing D1 impeded RANKL-induced osteoclastogenic marker gene expression and intracellular MAPK/NF-κB signaling, thereby mitigating ovariectomized-induced osteoporosis. Conclusion: These findings demonstrate the therapeutic potential of soluble recombinant CD93 containing D1 in inflammatory diseases. Our study highlights a novel anti-inflammatory mechanism, i.e., sequestration of HMGB1, through which sCD93 prevents HMGB1-receptor interaction on effector cells and alleviates inflammation.

Treatment With Small Molecule Inhibitors of Advanced Glycation End-Products Formation and Advanced Glycation End-Products-Mediated Collagen Cross-Linking Promotes Experimental Aortic Aneurysm Progression in Diabetic Mice

Background Although diabetes attenuates abdominal aortic aneurysms (AAAs), the mechanisms by which diabetes suppresses AAAs remain incompletely understood. Accumulation of advanced glycation end- (AGEs) reduces extracellular matrix (ECM) degradation in diabetes. Because ECM degradation is critical for AAA pathogenesis, we investigated whether AGEs mediate experimental AAA suppression in diabetes by blocking AGE formation or disrupting AGE-ECM cross-linking using small molecule inhibitors. Methods and Results Male C57BL/6J mice were treated with streptozotocin and intra-aortic elastase infusion to induce diabetes and experimental AAAs, respectively. Aminoguanidine (AGE formation inhibitor, 200 mg/kg), alagebrium (AGE-ECM cross-linking disrupter, 20 mg/kg), or vehicle was administered daily to mice from the last day following streptozotocin injection. AAAs were assessed via serial aortic diameter measurements, histopathology, and in vitro medial elastolysis assays. Treatment with aminoguanidine, not alagebrium, diminished AGEs in diabetic AAAs. Treatment with both inhibitors enhanced aortic enlargement in diabetic mice as compared with vehicle treatment. Neither enhanced AAA enlargement in nondiabetic mice. AAA enhancement in diabetic mice by aminoguanidine or alagebrium treatment promoted elastin degradation, smooth muscle cell depletion, mural macrophage accumulation, and neoangiogenesis without affecting matrix metalloproteinases, C-C motif chemokine ligand 2, or serum glucose concentration. Additionally, treatment with both inhibitors reversed suppression of diabetic aortic medial elastolysis by porcine pancreatic elastase in vitro. Conclusions Inhibiting AGE formation or AGE-ECM cross-linking enhances experimental AAAs in diabetes. These findings support the hypothesis that AGEs attenuate experimental AAAs in diabetes. These findings underscore the potential translational value of enhanced ECM cross-linking as an inhibitory strategy for early AAA disease.

Relationship between the Levels of Calprotectin and Soluble Receptor for Advanced Glycation End Products with Abdominal Aortic Aneurysm Diameter: A Preliminary Clinical Trial

An abdominal aortic aneurysm (AAA) is a dilatation of the abdominal aorta greater than 50% of the diameter of a healthy aorta. Previous experimental studies confirm the effect of calprotectin (CAL) on the onset of arterial pathology. It has been suggested that low levels of soluble receptors for advanced glycation end products (RAGEs) increase levels of cytokines that lead to the inhibition of matrix metalloproteinases (MMPs), affecting AAA formation. This study aimed to analyze the correlation of levels of RAGE and CAL with AAA diameter. A group of 32 patients aged 50−75 with diagnosed AAA was enrolled in the study. This group of patients was further divided into three subgroups based on AAA diameter: (1) <4.5 cm, (2) 4.5−5.5 cm, (3) >5.5 cm. Peripheral blood was drawn from all participants on admission to measure the serum CAL and RAGE levels. An enumeration survey was performed three months after AAA surgical treatment. CAL and RAGE plasma levels were measured with the enzyme-linked immunosorbent assay (ELISA). The median CAL levels were 2273.0 ng/mL before and 1217.0 ng/mL after treatment. There was a statistically significant decrease in CAL levels following the surgical treatment (p = 0.003). The correlation analysis between CAL levels and RAGE levels before and after surgical treatment showed no statistically significant correlations. In addition, there were no statistically significant correlations between CAL and RAGE levels with AAA size. In conclusion, CAL levels appear to be a significant marker in patients with AAA. There is an almost twofold decrease in CAL levels after AAA excision.

Identification of MEDAG and SERPINE1 Related to Hypoxia in Abdominal Aortic Aneurysm Based on Weighted Gene Coexpression Network Analysis

Purpose: Abdominal aortic aneurysm (AAA) is a severe cardiovascular disease that often results in high mortality due to sudden rupture. This paper aims to explore potential molecular mechanisms and effective targeted therapies to prevent and delay AAA rupture. Methods: We downloaded two microarray datasets (GSE98278 and GSE17901) from the Gene Expression Omnibus (GEO) database. Differential analysis and single-sample gene set enrichment analysis (ssGSEA) of hypoxia scores were performed on 48 AAA patients in GSE98278. We identified hypoxia- and ruptured AAA-related gene modules using weighted gene coexpression network analysis (WGCNA). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed using the R package clusterProfiler. For candidate genes, validation was conducted on the mouse dataset GSE17901. Finally, we predicted drug candidates associated with the hub genes using the HERB Chinese medicine database. Results: Eighty-two differentially expressed genes were screened in the ruptured and stable groups; 103 differentially expressed genes were identified between the high- and low-hypoxia groups; and WGCNA identified 58 differentially expressed genes. Finally, nine candidate genes were screened, including two hub genes (MEDAG and SERPINE1). We identified pathways such as cytokine-cytokine receptor interaction and T-helper 1-type immune response involved in AAA hypoxia and rupture. We predicted 93 traditional Chinese medicines (TCMs) associated with MEDAG and SERPINE1. Conclusion: We identified the hypoxic molecules MEDAG and SERPINE1 associated with AAA rupture. Our study provides an additional direction for the association between hypoxia and AAA rupture.

Moxibustion attenuates inflammation in intestinal mucosal by regulating RAGE-mediated TLR4-NF-κBp65 signaling pathway in vivo and in vitro

This study was performed to investigate the effect of moxibustion on the RAGE/TLR4-NF-κBp65 pathways and mucosal damage in rat model of 5-fluorouracil (5-Fu)-induced intestinal mucositis (IM) and the underlying mechanisms. 5-Fu treatment significantly increased the expression of the receptor for advanced glycation end products (RAGE) and its ligand, thehigh-mobility group box 1 protein (HMGB1), in the rat intestinal tissue. The inhibition of RAGE could induce the repair of intestinal mucosal damage and downregulate the expression of Toll-like receptor (TLR)-4 and nuclear factor kappa-B (NF-κB) p65 in intestinal tissues of 5-Fu-treated rats. Moxibustion treatment significantly improved the physical symptoms and repaired the intestinal mucosal damage of IM rats and increased the expression of tight junction proteins in these rats. The expression of RAGE, HMGB1, TLR4, NF-κBp65, and related downstream inflammatory factors, namely, tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β, were significantly decreased after moxibustion treatment. A moxibustion dose of 15 min/day exerted a better therapeutic effect than a dose of 30 min/day. The phosphorylation of NF-κBp65 and IκBa is involved in reducing inflammation by regulating the RAGE signaling pathway. Moxibustion can reduce intestinal mucosal damage and inflammation in 5-Fu-induced IM rats via modulation of the RAGE/TLR4-NF-κBp65 signaling pathways.

Targeting Scavenger Receptors in Inflammatory Disorders and Oxidative Stress

Oxidative stress and inflammation cannot be considered as diseases themselves; however, they are major risk factors for the development and progression of the pathogenesis underlying many illnesses, such as cancer, neurological disorders (including Alzheimer's disease and Parkinson's disease), autoimmune and metabolic disorders, etc. According to the results obtained from extensive studies, oxidative stress-induced biomolecules, such as advanced oxidation protein products, advanced glycation end products, and advanced lipoxidation end products, are critical for an accelerated level of inflammation and oxidative stress-induced cellular damage, as reflected in their strong affinity to a wide range of scavenger receptors. Based on the limitations of antioxidative and anti-inflammatory molecules in practical applications, targeting such interactions between harmful molecules and their cellular receptors/signaling with advances in gene engineering technology, such as CRISPR or TALEN, may prove to be a safe and effective alternative. In this review, we summarize the findings of recent studies focused on the deletion of scavenger receptors under oxidative stress as a development in the therapeutic approaches against the diseases linked to inflammation and the contribution of advanced glycation end products (AGEs), advanced lipid peroxidation products (ALEs), and advanced oxidation protein products (AOPPs).

ADAM10 attenuates the development of abdominal aortic aneurysms in a mouse model

An abdominal aortic aneurysm (AAA) is a life-threatening disease associated with a high mortality rate. At present, surgery or minimally invasive interventions are used in clinical treatment, especially for small aneurysms. However, the benefits of surgical repair are not obvious, and AAA ruptures can be prevented by aneurysm therapy to inhibit the growth of small aneurysms. Therefore, evaluating effective drugs to treat small AAAs is urgently required. Chronic inflammation is the main pathological feature of aneurysmal tissues. The aim of the present study was to investigate the protective role and underlying mechanism of ADAM metallopeptidase domain 10 (ADAM10). In the present study, a mouse model of AAA was established via porcine pancreatic elastase perfusion for 5 min per day for 14 days. ADAM10 (6 mg/kg) was injected intraperitoneally following 3 days of porcine pancreatic elastase perfusion in the ADAM10 group and the treatment continued for 10 days. The maximum inner luminal diameters of the infrarenal abdominal aortas were measured using an animal ultrasound system. The levels of high mobility group box 1 (HMGB1) and soluble receptor for advanced glycosylation end products in serum samples were measured by ELISA. Hematoxylin and eosin and elastin van Gieson staining were performed to observe morphology, integrity of the elastin layers and elastin degradation. CD68 expression was detected by immunohistochemical staining. Reverse transcription-quantitative PCR and western blotting were used for detection of mRNA and protein levels. The gelatinolytic activities of MMP-2 and MMP-9 were quantified via gelatin zymography analysis. These results showed that ADAM10 inhibited HMGB1/RAGE/NF-κB signaling and MMP activity in the pathogenesis of pancreatic elastase-induced AAA, which provide insight into the molecular mechanism of AAA and suggested that ADAM10 may be a potential therapeutic target for AAA.

Circular RNA Expression: Its Potential Regulation and Function in Abdominal Aortic Aneurysms

Abdominal aortic aneurysms (AAAs) have posed a great threat to human life, and the necessity of its monitoring and treatment is decided by symptomatology and/or the aneurysm size. Accumulating evidence suggests that circular RNAs (circRNAs) contribute a part to the pathogenesis of AAAs. circRNAs are novel single-stranded RNAs with a closed loop structure and high stability, having become the candidate biomarkers for numerous kinds of human disorders. Besides, circRNAs act as molecular "sponge" in organisms, capable of regulating the transcription level. Here, we characterize that the molecular mechanisms underlying the role of circRNAs in AAA development were further elucidated. In the present work, studies on the biosynthesis, bibliometrics, and mechanisms of action of circRNAs were aims comprehensively reviewed, the role of circRNAs in the AAA pathogenic mechanism was illustrated, and their potential in diagnosing AAAs was examined. Moreover, the current evidence about the effects of circRNAs on AAA development through modulating endothelial cells (ECs), macrophages, and vascular smooth muscle cells (VSMCs) was summarized. Through thorough investigation, the molecular mechanisms underlying the role of circRNAs in AAA development were further elucidated. The results demonstrated that circRNAs had the application potential in the diagnosis and prevention of AAAs in clinical practice. The study of circRNA regulatory pathways would be of great assistance to the etiologic research of AAAs.

AGE-RAGE Stress and Coronary Artery Disease

Coronary artery atherosclerosis and atherosclerotic plaque rupture cause coronary artery disease (CAD). Advanced glycation end products (AGE) and its cell receptor RAGE, and soluble receptor (sRAGE) and endogenous secretory RAGE (esRAGE) may be involved in the development of atherosclerosis. AGE and its interaction with RAGE are atherogenic, while sRAGE and esRAGE have antiatherogenic effects. AGE-RAGE stress is a ratio of AGE/sRAGE. A high AGE-RAGE stress results in development and progression of CAD and vice-versa. AGE levels in serum and skin, AGE/sRAGE in patients with CAD, and expression of RAGE in animal model of atherosclerosis were higher, while serum levels of esRAGE were lower in patients with CAD compared with controls. Serum levels of sRAGE in CAD patients were contradictory, increased or decreased. This contradictory data may be due to type of patients used, because the sRAGE levels are elevated in diabetics and end-stage renal disease. AGE/sRAGE ratio is elevated in patients with reduced or elevated levels of serum sRAGE. It is to stress that AGE, RAGE, sRAGE, or esRAGE individually cannot serve as universal biomarker. AGE and sRAGE should be measured simultaneously to assess the AGE-RAGE stress. The treatment of CAD should be targeted at reduction in AGE levels, prevention of AGE formation, degradation of AGE in vivo, suppression of RAGE expression, blockade of RAGE, elevation of sRAGE, and use of antioxidants. In conclusion, AGE-RAGE stress would initiate the development and progression of atherosclerosis. Treatment modalities would prevent, regress, and slow the progression of CAD.

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.

Diabetes and aortic aneurysm: current state of the art

Aortic aneurysm is a life-threatening disease due to the risk of aortic rupture. The only curative treatment available relies on surgical approaches; drug-based therapies are lacking, highlighting an unmet need for clinical practice. Abdominal aortic aneurysm (AAA) is frequently associated with atherosclerosis and cardiovascular risk factors including male sex, age, smoking, hypertension, and dyslipidaemia. Thoracic aortic aneurysm (TAA) is more often linked to genetic disorders of the extracellular matrix and the contractile apparatus but also share similar cardiovascular risk factors. Intriguingly, a large body of evidence points to an inverse association between diabetes and both AAA and TAA. A better understanding of the mechanisms underlying the negative association between diabetes and aortic aneurysm could help the development of innovative diagnostic and therapeutic approaches to tackle the disease. Here, we summarize current knowledge on the relationship between glycaemic parameters, diabetes, and the development of aortic aneurysm. Cellular and molecular pathways that underlie the protective effect of diabetes itself and its treatment are reviewed and discussed, along with their potential implications for clinical translation.

Translational applications of glucose metabolism in abdominal aortic aneurysm

Even though diabetes mellitus is a major risk for cardiovascular events and atherosclerosis-related diseases, it is negatively associated with abdominal aortic aneurysm. The understanding of the mechanisms underlying this negative association could bring new insights to identify prognostic and therapeutic targets. Here we summarize current knowledge of the relationship between glycemic parameters and clinical outcomes of patients with abdominal aortic aneurysm. Translational applications of glucose-targeted approaches as well as their potential interest for clinical practice are discussed in this context.

Association of abdominal aortic aneurysm diameter with insulin resistance index

Introduction

Epidemiological studies have highlighted a negative association between diabetes and abdominal aortic aneurysm (AAA). The aim of this study was to investigate the association between insulin resistance and AAA size.

Materials and methods

This prospective cross sectional monocentric study analysed fasting blood samples from 55 patients with AAA eligible for surgical repair. They were divided into 2 groups according to the median AAA diameter: diameter < 50 mm (N = 28) and diameter > 50 mm (N = 27). The median ages were respectively 73 years (62 - 79) and 72 years (67 - 81). Glucose and fructosamine concentrations were determined by spectrophotometry; insulin and C-peptide using chemiluminescent technology. Homeostasis model assessment 2 calculator was used to estimate insulin resistance index (HOMA2 IR).

Results

There was no significant difference for fasting glucose concentration between the groups (6.1 vs. 5.9 mmol/L, P = 0.825). C-peptide and insulin concentrations, as well as HOMA2 IR index were significantly higher in patients with AAA > 50 mm (0.82 vs. 0.54 nmol/L, P = 0.012; 9 vs. 5 mU/L, P = 0.019 and 1.72 vs. 1.26, P = 0.028, respectively). No linear correlation was identified between AAA diameter and HOMA2 IR. Fructosamine concentration was lower in patients with AAA > 50 mm (225.5 vs. 251 μmol/L, P = 0.005) and negatively correlated with AAA diameter (r = - 0.54, P < 0.001).

Conclusion

This study evidenced an association between AAA diameter and insulin resistance. Further studies are required to determine a causal link between insulin resistance and AAA development.

Diabetes mellitus and abdominal aortic aneurysms: A review of the mechanisms underlying the negative relationship

INTRODUCTION

Diabetes mellitus appears to be negatively associated with abdominal aortic aneurysm; however, the mechanisms underlying this relationship remain poorly understood. The aim of this article is to provide a comprehensive review of the currently understood biological pathways underlying this relationship.

METHODS

A review of the literature ('diabetes' OR 'hyperglycaemia' AND 'aneurysm') was performed and relevant studies grouped into biological pathways.

RESULTS

This review identified a number of biological pathways through which diabetes mellitus may limit the presence, growth and rupture of abdominal aortic aneurysms. These include those influencing extracellular matrix volume, extracellular matrix glycation, the formation of advanced glycation end-products, inflammation, oxidative stress and intraluminal thrombus biology. In addition, there is an increasing evidence to suggest that the medications used to treat diabetes can also limit the development and progression of abdominal aortic aneurysms.

CONCLUSION

The negative association between diabetes and abdominal aortic aneurysm is robust. Future studies should attempt to target the pathways identified in this review to develop novel therapeutic agents aimed at slowing or even halting aneurysm progression.

Microarray Analysis Reveals a Potential Role of lncRNA Expression in 3,4-Benzopyrene/Angiotensin II-Activated Macrophage in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a fatal disease, and exposure to 3,4-benzopyrene (Bap) is closely related to the development of AAA. We have found that Bap could impair the biological function of endothelial progenitor cells (EPCs), which are associated with the occurrence of AAA. We have also demonstrated that macrophage activation plays a key role in Bap-induced AAA, but the mechanism is unknown. Here, we used a mouse lncRNA array to investigate the expression signatures of lncRNAs and mRNAs in Bap-activated macrophage. A total of 457 lncRNAs and 219 mRNAs were found to be differentially expressed. The function of differential mRNAs was determined by pathway and Gene Ontology analysis. Eight pathways associated with inflammation were upregulated, and seven pathways including cell apoptosis were downregulated. It was worth noting that AGE-RAGE pathway, which was involved in Bap-induced EPC dysfunction, was significantly upregulated in Bap-activated macrophage and may contribute to AAA formation. Thus, lncRNAs may exert a key role in activated macrophages and intervene the core lncRNAs and may inhibit the occurrence of a series of cascade reactions in the macrophages, which may provide potential targets for AAA caused by smoking.

Panax notoginseng Saponins for Treating Coronary Artery Disease: A Functional and Mechanistic Overview

Coronary artery disease (CAD) is a major public health problem and the chief cause of morbidity and mortality worldwide. Panax notoginseng, a valuable herb in traditional Chinese medicine (TCM) with obvious efficacy and favorable safety, shows a great promise as a novel option for CAD and is increasingly recognized clinically. Firstly, this review introduced recent clinical trials on treatment with PNS either alone or in combination with conventional drugs as novel treatment strategies. Then we discussed the mechanisms of P. notoginseng and Panax notoginseng saponins (PNS), which can regulate signaling pathways associated with inflammation, lipid metabolism, the coagulation system, apoptosis, angiogenesis, atherosclerosis, and myocardial ischaemia.

Blockade of HMGB1 preserves vascular homeostasis and improves blood perfusion in rats of acute limb ischemia/reperfusion

Acute limb ischemia is one of the most common peripheral arterial disease, while surgical restoration of blood flow often results in ischemia/reperfusion (I/R) injury. Our previous study revealed the inflammation intensity in arterial tissue, characterized by expression of high mobility group box protein 1 (HMGB1), was contrary to the fluctuation of hemodynamics in reperfusion limbs in a rat model. This study meant to clarify the role of HMGB1 during this process. Laser Doppler perfusion imaging evaluated limb hemodynamics in mean and max perfusion unit (PU). Femoral arterial tissue was collected for molecular biology examination. The results revealed that HMGB1 promoted vascular structure remodeling and vasomotor dysfunction during acute I/R, characterized by degradation of collagenous fibers, disruption of elastic lamellae, intensive inflammation and phenotype transfer of smooth muscle cells. Blockade of HMGB1 preserved vascular homeostasis and improved PUs (PmeanPU<0.001, PmaxPU<0.001). The elevated expression of TNF-α, IL-6, ICAM, VCAM, MMP-2, MMP-9, α-SM actin correlated with HMGB1 positively. In conclusion, HMGB1 promoted vascular remodeling and dysfunction via initiating an inflammation cascade during I/R. Blockade of HMGB1 would preserve vascular homeostasis and facilitate the blood perfusion of ischemic limb.

Skin accumulation of advanced glycation end products is increased in patients with an abdominal aortic aneurysm

OBJECTIVE

Advanced glycation end products (AGEs) are implicated in the pathogenesis of cardiovascular disease. Accumulation of AGEs is driven by oxidative or glycemic stress and can be assessed by skin autofluorescence (SAF). SAF is increased in patients with peripheral artery disease (PAD) and independently associated with mortality and major adverse cardiovascular events in these patients. PAD and abdominal aortic aneurysm (AAA) share several risk factors. Inflammation is an important process in AAA formation and increases levels of oxidative stress. We therefore hypothesized that SAF would be increased in AAA patients compared with controls.

METHODS

A case-control study was performed in 248 AAA patients and 124 controls without AAA or PAD matched for age and presence of diabetes mellitus. SAF was noninvasively assessed with the AGE Reader (Diagnoptics Technologies BV, Groningen, The Netherlands).

RESULTS

SAF was higher in AAA patients than in controls: 2.89 ± 0.63 vs 2.68 ± 0.63 arbitrary units (P = .003). PAD comorbidity was associated with increased SAF within the AAA patient group (P = .01). After correction for known factors influencing SAF (age, current smoking, hypertension, and estimated glomerular filtration rate), PAD comorbidity remained an independent determinant of SAF. Logistic regression analysis of the total cohort showed an unadjusted odds ratio (OR) of 1.74 (95% confidence interval [CI], 1.20-2.51) for the presence of AAA with each unit increase of SAF and an adjusted OR of 1.78 (95% CI, 1.22-2.60) after correction for cardiovascular comorbidity (cerebrovascular disease and coronary artery disease). After additional correction for sex, current smoking, hypertension, and use of lipid-lowering drugs, this significance was lost (adjusted OR, 1.53; 95% CI, 0.94-2.48).

CONCLUSIONS

Skin accumulation of AGEs, measured by SAF, is increased in patients with AAA compared with controls without AAA or PAD, independent of the presence of coronary artery disease and cerebrovascular disease. In AAA patients, SAF is closely associated with the presence of PAD and cardiovascular risk factors.

Effects of age-related shifts in cellular function and local microenvironment upon the innate immune response to implants

The host macrophage response is now well recognized as a predictor of the success or failure of biomaterial implants following placement. More specifically, shifts from an "M1" pro-inflammatory towards a more "M2-like" anti-inflammatory macrophage polarization profile have been shown to result in enhanced material integration and/or tissue regeneration downstream. As a result, a number of biomaterials-based approaches to controlling macrophage polarization have been developed. However, the ability to promote such activity is predicated upon an in-depth, context-dependent understanding of the host response to biomaterials. Recent work has shown the impacts of both tissue location and tissue status (i.e. underlying pathology) upon the host innate immune response to implants, representing a departure from a focus upon implant material composition and form. Thus, the ideas of "biocompatibility," the host macrophage reaction, and ideal material requirements and modification strategies may need to be revisited on a patient, tissue, and disease basis. Immunosenescence, dysregulation of macrophage function, and delayed resolution of immune responses in aged individuals have all been demonstrated, suggesting that the host response to biomaterials in aged individuals should differ from that in younger individuals. However, despite the increasing usage of implantable medical devices in aged patients, few studies examining the effects of aging upon the host response to biomaterials and the implications of this response for long-term integration and function have been performed. The objective of the present manuscript is to review the putative effects of aging upon the host response to implanted materials and to advance the hypothesis that age-related changes in the local microenvrionement, with emphasis on the extracellular matrix, play a previously unrecognized role in determining the host response to implants.

Metformin treatment status and abdominal aortic aneurysm disease progression

OBJECTIVE

In population-based studies performed on multiple continents during the past two decades, diabetes mellitus has been negatively associated with the prevalence and progression of abdominal aortic aneurysm (AAA) disease. We investigated the possibility that metformin, the primary oral hypoglycemic agent in use worldwide, may influence the progression of AAA disease.

METHODS

Preoperative AAA patients with diabetes were identified from an institutional database. After tabulation of individual cardiovascular and demographic risk factors and prescription drug regimens, odds ratios for categorical influences on annual AAA enlargement were calculated through nominal logistical regression. Experimental AAA modeling experiments were subsequently performed in normoglycemic mice to validate the database-derived observations as well as to suggest potential mechanisms of metformin-mediated aneurysm suppression.

RESULTS

Fifty-eight patients met criteria for study inclusion. Of 11 distinct classes of medication considered, only metformin use was negatively associated with AAA enlargement. This association remained significant after controlling for gender, age, cigarette smoking status, and obesity. The median enlargement rate in AAA patients not taking oral diabetic medication was 1.5 mm/y; by nominal logistic regression, metformin, hyperlipidemia, and age ≥70 years were associated with below-median enlargement, whereas sulfonylurea therapy, initial aortic diameter ≥40 mm, and statin use were associated with above-median enlargement. In experimental modeling, metformin dramatically suppressed the formation and progression, with medial elastin and smooth muscle preservation and reduced aortic mural macrophage, CD8 T cell, and neovessel density.

CONCLUSIONS

Epidemiologic evidence of AAA suppression in diabetes may be attributable to concurrent therapy with the oral hypoglycemic agent metformin.

Cold-inducible RNA-binding protein plays a central role in the pathogenesis of abdominal aortic aneurysm in a murine experimental model

BACKGROUND

Cold-inducible RNA-binding protein (CIRP) is a recently identified proinflammatory cytokine. We hypothesize that CIRP is involved in the progression of abdominal aortic aneurysms (AAA) and that anti-CIRP treatment could inhibit this progression.

METHODS

We investigated CIRP expression in the sera and aneurysmal tissues of human AAA patients and elastase-induced AAA rats. To further examine the role of CIRP in the development of AAA, anti-CIRP antibody (1 mg/kg) or nonimmunized control immunoglobulin (Ig)G (1 mg/kg) was injected via the caudal vein in the experimental AAA model. To further investigate the underlying mechanisms, RAW 267.4 cells were stimulated with recombinant murine CIRP (rmCIRP).

RESULTS

In human AAA tissue, CIRP exhibited a 5.6-fold and 93% increase in mRNA and protein expression, respectively. In a rat AAA model, CIRP was upregulated significantly in a time-dependent manner in the serum and AAA tissue. The anti-CIRP antibody treatment significantly suppressed the dilation of experimental AAA. Simultaneously, inhibition of CIRP significantly attenuated the expression of matrix metalloproteinase (MMP)-2, MMP-9, tumor necrosis factor-α, and monocyte chemoattractant protein-1, and the number of CD68-positive macrophages in the experimental AAA tissue. In vitro, rmCIRP significantly increased MMP-9 messenger RNA expression in a dose-dependent manner by 1.2-fold, 2.9-fold, and 5.5-fold, respectively. Simultaneously, rmCIRP promoted RAW 264.7 cell migration, with an approximately 2.7-fold increase in the number of migrated cells.

CONCLUSION

Our findings demonstrate that CIRP mediates experimental AAA development by promoting the inflammatory response and inducing MMP-9 expression, demonstrating its potential as a novel target for inhibiting the progression of AAA.

Toll-Like Receptor 4 Is Essential in the Development of Abdominal Aortic Aneurysm

Toll-like receptor (TLR) family plays a key role in innate immunity and various inflammatory responses. TLR4, one of the well-characterized pattern-recognition receptors, can be activated by endogenous damage-associated molecular pattern molecules such as high mobility group box 1 (HMGB1) to sustain sterile inflammation. Evidence suggested that blockade of TLR4 signaling may confer protection against abdominal aortic aneurysm (AAA). Herein we aimed to obtain further insight into the mechanism by which TLR4 might promote aneurysm formation. Characterization of the CaCl₂-induced AAA model in mice revealed that upregulation of TLR4 expression, localized predominantly to vascular smooth muscle cells (VSMCs), was followed by a late decline during a 28-day period of AAA development. In vitro, TLR4 expression was increased in VSMCs treated with HMGB1. Knockdown of TLR4 by siRNA attenuated HMGB1-enhanced production of proinflammatory cytokines, specifically interleukin-6 and monocyte chemoattractant protein-1 (MCP-1), and matrix-degrading matrix metalloproteinase (MMP)-2 from VSMCs. In vivo, two different strains of TLR4-deficient (C57BL/10ScNJ and C3H/HeJ) mice were resistant to CaCl₂-induced AAA formation compared to their respective controls (C57BL/10ScSnJ and C3H/HeN). Knockout of TLR4 reduced interleukin-6 and MCP-1 levels and HMGB1 expression, attenuated macrophage accumulation, and eventually suppressed MMP production, elastin destruction and VSMC loss. Finally, human AAA exhibited higher TLR4 expression that was localized to VSMCs. These data suggest that TLR4 signaling contributes to AAA formation by promoting a proinflammatory status of VSMCs and by inducing proteinase release from VSMCs during aneurysm initiation and development.

Association of polymorphisms of the receptor for advanced glycation end products gene and susceptibility to sporadic abdominal aortic aneurysm

Accumulating evidence has suggested that receptor for advanced glycation end products (RAGE) is involved in the development and progression of human abdominal aortic aneurysms (AAAs). However, the association between RAGE gene polymorphisms and AAA has not yet been determined. The present study was aimed at analyzing the potential association between the RAGE gene polymorphisms and AAAs. A cohort of 381 patients and 436 age-matched healthy controls were genotyped to detect the three RAGE polymorphisms (-374 T/A, -429 T/C, and G82S) using SNaPshot. Our study demonstrated a significant difference in the genotype and allele frequencies of the RAGE G82S polymorphism between the AAA patients and the controls. Further stratification by gender and smoking status revealed that the presence of the RAGE 82S allele confers a higher risk for developing AAA in men and smokers. Moreover, AAA patients with the variant 82S allele of RAGE presented with reduced serum soluble RAGE (sRAGE) production, and this decrease was more significant in men and smokers with AAA. Our study provides preliminary evidence that the 82S allele of RAGE is a risk factor for AAA. This new piece of knowledge regarding RAGE may be clinically important for the prevention and therapy of AAAs.

Shexiang Tongxin dropping pill attenuates atherosclerotic lesions in ApoE deficient mouse model

ETHNOPHARMACOLOGICAL RELEVANCE

Shexiang Tongxin dropping pill (STDP) is a formulation of Traditional Chinese Medicine mainly used for clinical treatment of stable angina pectoris in China.

AIM OF THE STUDY

To investigate the effects and mechanisms of STDP treatment on atherosclerosis.

MATERIALS AND METHODS

ApoE deficient (ApoE(-/-)) mice were utilized to evaluate the effect of STDP treatment (30 mg/kg/day) on atherosclerotic lesions. Histopathological features of atherosclerotic lesions, serum levels of lipid proteins, parameters of oxidative stress and pro-inflammatory cytokines were measured by H&E staining, Masson's trichrome staining and ELISA, respectively. Real-time PCR analyses were performed to examine the aortic expression of atherosclerosis-associated microRNAs.

RESULTS

The STDP treatment resulted in attenuated atherosclerotic lesion manifested by reduced lipid deposition, fibrosis and oxidative stress. It also led to increase in serum levels of GSH and SOD, decrease in MDA, decrease in CHO, TG, LDL, ox-LDL and increase in HDL, respectively. Additionally, the levels of pro-inflammatory cytokines including IL-2, IL-6, TNF-α and γ-IFN were markedly reduced by STDP treatment. Furthermore, STDP treatment was associated with a significant reduction in the aortic expression of miR-21a, miR-132, miR-126a, miR-155 and increased expression of miR-20a.

CONCLUSION

Our results demonstrated for the first time that STDP attenuated atherosclerotic lesions in ApoE(-/-) mouse model. Moreover, STDP treatment exhibited multi-targeting effects on pathological, biochemical and molecular aspects of atherosclerosis implicating lipid regulation, fibrosis, inflammation and oxidative stress. Findings from the current study warrant further evaluation of the clinical application of STDP in atherosclerosis treatment.

Phosphatidylserine receptors: enhancers of enveloped virus entry and infection

A variety of both RNA and DNA viruses envelop their capsids in a lipid bilayer. One of the more recently appreciated benefits this envelope is incorporation of phosphatidylserine (PtdSer). Surface exposure of PtdSer disguises viruses as apoptotic bodies; tricking cells into engulfing virions. This mechanism is termed apoptotic mimicry. Several PtdSer receptors have been identified to enhance virus entry and we have termed this group of proteins PtdSer-mediated virus entry enhancing receptors or PVEERs. These receptors enhance entry of a range of enveloped viruses. Internalization of virions by PVEERs provides a broad mechanism of entry with little investment by the virus itself. PVEERs may allow some viruses to attach to cells, thereby making viral glycoprotein/cellular receptor interactions more probable. Alternatively, other viruses may rely entirely on PVEERs for internalization into endosomes. This review provides an overview of PtdSer receptors that serve as PVEERs and the biology behind virion/PVEER interaction.

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Phosphatidylserine (PtdSer) receptors can mediate entry of enveloped viruses.

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PtdSer is present on the outer leaflet of the virion envelope.

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PtdSer receptors are expressed on a variety of primary cells and cell lines.

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Characteristics of PtdSer receptors that mediate virus entry are defined.

Low levels of serum soluble receptors for advanced glycation end products, biomarkers for disease state: myth or reality

Advanced glycation end products (AGEs) interact with the receptor for AGEs (RAGE) on the membrane and induce deleterious effects via activation of nuclear factor kappa-B, and increased oxidative stress and inflammatory mediators. AGEs also combine with circulating soluble receptors (endogenous secretory RAGE [esRAGE] and soluble receptor for RAGE [sRAGE]) and sequester RAGE ligands and act as a cytoprotective agent. esRAGE is secreted from the cells and is a spliced variant of RAGE. The sRAGE on the other hand is proteolytically cleaved from cell surface receptor via matrix metalloproteinase (MMPs). sRAGE is elevated in type 1 and type 2 diabetes and in patients with decreased renal function. Serum levels of sRAGE are reduced in diseases including coronary artery disease, atherosclerosis, essential hypertension, chronic obstructive lung disease, heart failure, and hypercholesterolemia. Serum levels of AGEs are elevated in patients with coronary artery disease and atherosclerosis. However, the increases in serum AGEs are very high in patients with diabetes and renal disease. There is a positive correlation between serum levels of AGEs and RAGE and sRAGE. The elevated levels of sRAGE in patients with diabetes and impaired renal function may be due to increased levels of MMPs. AGEs increase in the expression and production of MMPs, which would increase the cleavage of sRAGE from cell surface. In conclusion, low level of serum sRAGE is a good biomarker for disease other than diabetes and renal disease. A unified formula that takes into consideration of AGEs, sRAGE, and esRAGE such as AGE/sRAGE or AGEs/esRAGE would be better biomarker than sRAGE or esRAGE for all AGE-RAGE-associated diseases including diabetes and renal disease.

Recombinant human thrombomodulin suppresses experimental abdominal aortic aneurysms induced by calcium chloride in mice

OBJECTIVE

To investigate whether recombinant thrombomodulin containing all the extracellular domains (rTMD123) has therapeutic potential against aneurysm development.

SUMMARY BACKGROUND DATA

The pathogenesis of abdominal aortic aneurysm (AAA) is characterized by chronic inflammation and proteolytic degradation of extracellular matrix. Thrombomodulin, a transmembrane glycoprotein, exerts anti-inflammatory activities such as inhibition of cytokine production and sequestration of proinflammatory high-mobility group box 1 (HMGB1) to prevent it from engaging the receptor for advanced glycation end product (RAGE) that may sustain inflammation and tissue damage.

METHODS

The in vivo effects of treatment and posttreatment with rTMD123 on aortic dilatation were measured using the CaCl2-induced AAA model in mice.

RESULTS

Characterization of the CaCl2-induced model revealed that HMGB1 and RAGE, both localized mainly to macrophages, were persistently upregulated during a 28-day period of AAA development. In vitro, rTMD123-HMGB1 interaction prevented HMGB1 binding to macrophages, thereby prohibiting activation of HMGB1-RAGE signaling in macrophages. In vivo, short-term treatment with rTMD123 upon AAA induction suppressed the levels of proinflammatory cytokines, HMGB1, and RAGE in the aortic tissue; reduced the infiltrating macrophage number; and finally attenuated matrix metalloproteinase production, extracellular matrix destruction, and AAA formation without disturbing vascular calcification. Consistently, posttreatment with rTMD123 seven days after AAA induction alleviated vascular inflammation and retarded AAA progression.

CONCLUSIONS

These data suggest that rTMD123 confers protection against AAA development. The mechanism of action may be associated with reduction of proinflammatory mediators, blockade of macrophage recruitment, and suppression of HMGB1-RAGE signaling involved in aneurysm formation and downstream macrophage activation.

Role of advanced glycation end products in cellular signaling

Improvements in health care and lifestyle have led to an elevated lifespan and increased focus on age-associated diseases, such as neurodegeneration, cardiovascular disease, frailty and arteriosclerosis. In all these chronic diseases protein, lipid or nucleic acid modifications are involved, including cross-linked and non-degradable aggregates, such as advanced glycation end products (AGEs). Formation of endogenous or uptake of dietary AGEs can lead to further protein modifications and activation of several inflammatory signaling pathways. This review will give an overview of the most prominent AGE-mediated signaling cascades, AGE receptor interactions, prevention of AGE formation and the impact of AGEs during pathophysiological processes.

Conditional over-expression of RAGE by embryonic alveolar epithelium compromises the respiratory membrane and impairs endothelial cell differentiation

Background

Receptors for advanced glycation end-products (RAGE) are cell surface receptors prominently expressed by lung epithelium. Previous research demonstrated that over-expression of RAGE by murine alveolar epithelial cells during embryogenesis caused severe lung hypoplasia and neonatal lethality. However, the effects of RAGE over-expression on adjacent matrix and endothelial cells remained unknown.

Methods

RAGE transgenic (TG) mice were generated that conditionally over-expressed RAGE in alveolar type II cells when fed doxycycline (dox) from conception to E18.5. To evaluate effects on the basement membrane, immunostaining and immunoblotting were performed for collagen IV and MMP-9, a matrix metalloprotease capable of degrading basement membranes. To assess changes in vasculature, immunostaining, immunoblotting and qRT-PCR were performed for Pecam-1, a platelet endothelial cell adhesion marker also known as CD31. Lastly, to characterize potential regulatory mechanisms of endothelial cell differentiation, immunoblotting and qRT-PCR for FoxM1, a key endothelium-specific transcription factor of the Forkhead Box (Fox) family, were completed.

Results

Qualitative immunostaining for collagen IV was less in RAGE TG mice compared to controls and immunoblotting revealed decreased collagen IV in the RAGE TG mouse lung. Additionally, elevated MMP-9 detected via immunostaining and immunoblotting implicated MMP-9 as a possible down stream effector in matrix destabilization mediated by RAGE signaling. Lastly, Pecam-1 assessment revealed a decrease in the prevalence of microvascular endothelial cells coincident with FoxM1 abrogation in RAGE TG mice compared to controls.

Conclusions

RAGE over-expression by alveolar epithelium weakened the basement membrane and associated matrix via increased MMP-9 activity. Furthermore, over-expression of RAGE inhibited FoxM1, suggesting that anomalous transcriptional control contributes to decreased endothelial cell prevalence in the TG mouse lung.

Reasons to Investigate the Soluble Receptor for Advanced Glycation End-Product (sRAGE) Pathway in Aortic Disease

Aortic disease has a high rate of morbidity and mortality, and there are no documented screening methods to date. Yet biochemical research does show a significant link between soluble receptor for advanced glycation end-products (sRAGE) protein and cardiovascular disease. Therefore, it can be hypothesized that sRAGE plasma levels may help differentiate patients with aortic disease from the general population, which this paper will review and present.

Intracranial aneurysm formation in type-one diabetes rats

BACKGROUND & OBJECTIVE

Diabetes mellitus (DM) plays an important role in the pathogenesis of vascular complications including arteriosclerosis and ischemic stroke. Whether DM impacts intracranial aneurysm (IA) formation has not been extensively investigated. In this study, we tested the underlying mechanism of type one DM (T1DM) induced IA formation in rats.

EXPERIMENTAL APPROACHES

T1DM was induced by streptozotocin injection. Rats were euthanized at 0, 4 and 10 weeks after T1DM induction. To evaluate cerebral vascular perfusion, Fluorescein isothiocyanate - dye was injected at 5 min prior to euthanasia. Vascular perfusion was measured by laser scanning confocal microscopy. Trichrome, Elastica van Gieson, alpha-smooth muscle actin (a-SMA) and receptor of advanced glycation end-products (RAGE), toll-like receptor 4 (TLR4) and matrix metalloproteinase 9 (MMP9) immunostaining were performed. The IA formation was classified by 0-3 stages: 0: Normal; 1: Endothelial damage; 2: Moderate protrusion; and 3: Saccular aneurysm formation.

RESULTS

T1DM significantly increased IA formation identified by the classification of aneurysmal changes compared with non-DM rats (p<0.05). However, T1DM induced IA formations were classified as stage 1 and stage 2, but not stage 3. Cerebral vascular perfusion was significantly decreased in T1DM rats compared to non-DM rats (p<0.01). DM10W rats exhibited a significant decrease of cerebral vascular perfusion compared to DM4W rats (p<0.05). T1DM rats also significantly increased the internal carotid artery (ICA) intimae and media thickness, and decreased the internal carotid artery diameter compared to non-DM rats. RAGE, MMP9 and TLR4 expression were significantly increased in T1DM rats compared to non-DM rats. The increased RAGE, TLR4 and MMP9 significantly correlated with IA formation (p<0.05).

CONCLUSION

T1DM increases IA formation. The increased RAGE, MMP9 and TLR4 expressions might contribute to IA formation in T1DM rats.

SMAD3 deficiency promotes inflammatory aortic aneurysms in angiotensin II-infused mice via activation of iNOS

Background

Ninety percent of the patients carrying distinct SMAD3 mutations develop aortic aneurysms and dissections, called aneurysms‐osteoarthritis syndrome (AOS). However, the etiology and molecular events downstream of SMAD3 leading to the pathogenesis of aortic aneurysms in these patients still remain elusive. Therefore, we aimed to investigate the vascular phenotypes of SMAD3‐knockout mice.

Methods and Results

We have shown that angiotensin II–induced vascular inflammation, but not hypertension, leads to aortic aneurysms and dissections, ultimately causing aortic rupture and death in mice. Lipopolysaccharide‐triggered inflammation confirmed that enhanced aortic macrophage recruitment was essential for aneurysm formation in angiotensin II–infused SMAD3‐knockout mice. In contrast, phenylephrine‐triggered hypertension alone was insufficient to induce aortic aneurysms in mice. Using uniaxial tensile and contractility tests, we showed that SMAD3 deficiency resulted in defective aortic biomechanics and physiological functions, which caused weakening of the aortic wall and predisposed the mice to aortic aneurysms. Chromatin immunoprecipitation (ChIP) and re‐ChIP assays revealed that the underlying mechanism involved aberrant upregulation of inducible nitric oxide synthase (iNOS)–derived nitric oxide production and activation of elastolytic matrix metalloproteinases 2 and 9. Administration of clodronate‐liposomes and iNOS inhibitor completely abrogated these aortic conditions, thereby identifying iNOS‐mediated nitric oxide secretion from macrophages as the downstream event of SMAD3 that drives this severe pathology.

Conclusions

Macrophage depletion and iNOS antagonism represent 2 promising approaches for preventing aortic aneurysms related to SMAD3 mutations and merit further investigation as adjunctive strategies for the life‐threatening manifestations of AOS.

S100A12 expression in thoracic aortic aneurysm is associated with increased risk of dissection and perioperative complications

OBJECTIVES

The purpose of this study was to determine the relevance of S100A12 expression to human thoracic aortic aneurysms and type A thoracic aortic aneurysm dissection and to study mechanisms of S100A12-mediated dysfunction of aortic smooth muscle cells.

BACKGROUND

Transgenic expression of proinflammatory S100A12 protein in murine aortic smooth muscle causes thoracic aneurysm in genetically modified mice.

METHODS

Immunohistochemistry of aortic tissue (n = 50) for S100A12, myeloperoxidase, and caspase 3 was examined and S100A12-mediated pathways were studied in cultured primary aortic smooth muscle cells.

RESULTS

We found S100A12 protein expressed in all cases of acute thoracic aortic aneurysm dissection and in approximately 25% of clinically stable thoracic aortic aneurysm cases. S100A12 tissue expression was associated with increased length of stay in patients undergoing elective surgical repair for thoracic aortic aneurysm, despite similar preoperative risk as determined by European System for Cardiac Operative Risk Evaluation. Reduction of S100A12 expression in human aortic smooth muscle cells using small hairpin RNA attenuates gene and protein expression of many inflammatory- and apoptosis-regulating factors. Moreover, genetic ablation of the receptor for S100A12, receptor for advanced glycation end products (RAGE), in murine aortic smooth muscle cells abolished cytokine-augmented activation of caspase 3 and smooth muscle cell apoptosis in S100A12-expressing cells.

CONCLUSIONS

S100A12 is enriched in human thoracic aortic aneurysms and dissections. Reduction of S100A12 or genetic ablation of its cell surface receptor, the receptor for advanced glycation end products (RAGE), in aortic smooth muscle resulted in decreased activation of caspase 3 and in reduced apoptosis. By establishing a link between S100A12 expression and apoptosis of aortic smooth muscle cells, this study identifies novel S100A12 signaling pathways and indicates that S100A12 may be a useful molecular marker and possible target for treatment for human aortic diseases.

Involvement of RAGE, MAPK and NF-κB pathways in AGEs-induced MMP-9 activation in HaCaT keratinocytes

Advanced glycation end products (AGEs) exert divergent effects on the pathogenesis of diabetes complications. Excessive expression of matrix metalloproteinases-9 (MMP-9) is deleterious to the cutaneous wound-healing process in the context of diabetes. However, the effect of AGEs on MMP-9 induction in skin cells and the exact molecular mechanisms involved are still poorly understood. In this study, we investigated the effect of AGEs on the production of MMP-9 in HaCaT keratinocytes and characterized the signal transduction pathways activated by AGEs that are involved in MMP-9 regulation. We showed that AGE-BSA increased MMP-9 expression in HaCaT cells at both the protein and mRNA levels. The stimulatory effect of AGE-BSA on MMP-9 was attenuated by inhibitors of extracellular-signal-regulated kinase (ERK1/2, U0126), p38 mitogen-activated protein kinase (MAPK, SB203580) and NF-κB, but not c-Jun N-terminal kinase. Furthermore, receptor for advanced glycation end products (RAGE) was expressed in keratinocytes, and incubation with AGE-BSA resulted in a significant upregulation of RAGE expression in a dose-dependent manner. Silencing of the RAGE gene prevented AGE-BSA-induced MMP-9 activation and the phosphorylation of ERK1/2 and p38 MAPK. We also observed the involvement of NF-κB in AGE-BSA-induced MMP-9 activation, which was not blocked by U0126 and SB203580. These results suggest that AGEs may play an important role in the impairment of diabetic wound healing by upregulating MMP-9 expression in keratinocytes via the RAGE, ERK1/2 and p38 MAPK pathways; activation of NF-κB is also involved in this process. These pathways may represent potential targets for drug interventions to improve diabetic wound healing, a process in which MMP-9 plays a critical role.

Biology of metabolic syndrome in a vascular patient

Metabolic syndrome is highly prevalent in vascular patients and has a significant impact on the outcomes of vascular interventions. It comprises of a set of metabolically driven risk factors, including truncal obesity, dyslipidemia, elevated blood pressure and elevated fasting blood glucose. Increased insulin resistance within the context of obesity and hypertension contributes to atherogenic dyslipidemia, hyperglycemia, and prothrombotic and proinflammatory states which lead to the adverse impact of metabolic syndrome on the response to injury and on atherosclerotic disease progression. This review focuses on the complex biology of metabolic syndrome and its relevance to management of vascular patients, including outcomes and implications for the coronary, cerebrovascular and lower-extremity vascular beds.

The novel function of advanced glycation end products in regulation of MMP-9 production

BACKGROUND

Advanced glycation end products (AGEs), formed from proteins and peptides by nonenzymatic glycoxidation after contact with aldose sugars, have been implicated in the pathogenesis of age-related cardiac and vascular dysfunction. Our previous study demonstrated significantly elevated levels of AGE and the receptor for AGE (RAGE) in human abdominal aortic aneurysm (AAA) tissues. Inhibition of AGE signaling by targeted gene deletion of RAGE markedly reduced the development of aneurysm in a mouse model of AAA. We also showed that AGE may stimulate aneurysm formation by promoting metalloproteinase (MMP)-9 expression. In this study, we investigated the molecular mechanism underlying this novel function of AGE.

METHODS

The murine macrophage cell line RAW 264.7 was pretreated with AGE, TGF-β, and MAPK inhibitors. The protein was collected for Western blot analysis. Culture supernatants were collected to determine MMP-9 activity by gelatin zymography.

RESULTS

We found that AGE induced the production of MMP-9 in macrophages in a dose-dependent manner. This induction of MMP-9 was markedly diminished by pretreatment with TGF-β. To delineate the underlying molecular mechanism, we showed that AGE increased phosphorylation of p44/42 ERK, p38, JNK, and PI3K in macrophages. Moreover, AGE induced active p65 subunit of NF- κB. Inhibition of ERK (UO126) or p38 (SB203580), but not PI3K (LY294002 or wortmannin), blocked AGE-induced MMP-9 expression. In contrast, inhibition of JNK (SP-600125) significantly enhanced the stimulatory effect of AGE on MMP-9. Furthermore, TGF-β suppressed AGE-induced expression of the active p65 subunit of NF-κB.

CONCLUSIONS

Our data indicate that AGE induces MMP-9 through activation of ERK, p38 mitogen-activated protein and NF-κB, a pathway that is antagonized by TGF-β. This finding in conjunction with previously reported AGE functions in inflammation suggests that anti-AGE therapies could be effective in the prevention of human AAA development and progression.

Circulating levels of matrix metalloproteinase-9 and abdominal aortic pathology: from the Dallas Heart Study

Prior reports have associated increased circulating levels of matrix metalloproteinase-9 (MMP-9), an endopeptidase active in the extracellular matrix, with the formation and rupture of aortic aneurysms, raising the possibility that MMP-9 may be a useful diagnostic or therapeutic target for aortic pathology. However, associations between MMP-9 and pathological abdominal aortic phenotypes in the general population have not been reported. In the Dallas Heart Study, a population-based sample of Dallas County residents (n = 2304), we measured MMP-9 and performed magnetic resonance imaging (MRI) of the abdominal aorta, measuring aortic compliance, plaque, wall thickness and luminal diameter. After adjustment for traditional cardiac risk factors and body size, higher MMP-9 quartiles were independently associated with higher aortic wall thickness and larger luminal diameter (p < 0.0001 for each), but not abdominal aortic plaque (p = 0.08), coronary artery calcium (p = 0.20) or the aortic luminal diameter/aortic wall thickness ratio (p = 0.37), supporting the hypothesis that therapies targeting MMP-9 may affect the abdominal aortic wall and modify aortic pathology.

The antioxidant N-acetylcysteine promotes atherosclerotic plaque stabilization through suppression of RAGE, MMPs and NF-κB in ApoE-deficient mice

AIMS

N-acetylcysteine (NAC) has antioxidant and anti-inflammatory properties. To explore the mechanisms underlying atherosclerotic plaque stabilization induced by NAC, we examined the effects of NAC administration in apoE-deficient mice on the expression of the receptor of advanced glycation end products (RAGE), matrix metalloproteinases (MMPs) and the activation of nuclear factor kappa B (NF-κB) in atherosclerotic plaques.

METHODS

10-week-old ApoE(-/-) mice fed with atherogenic diet were treated with NAC (200 mg/kg/ day) for 8 weeks. Serum lipid, glucose and malondialdehyde (MDA) were detected. The size and composition of atherosclerotic plaques were measured by en face analysis, Movat staining, immunofluorescence and immunohistochemistry, respectively. Reactive oxygen species (ROS) generation in aortic root was tested by DHE staining. The levels of vascular cell adhesion molecule-1(VCAM-1), NF-κB, phosphor-NF-κB, I-κB, phosphor-I-κB, RAGE, MMP2 and MMP9 in descending arteries were analyzed by Western blot.

RESULTS

ApoE(-/-) mice administrated with NAC displayed reduced serum MDA level and impaired ROS generation in aortic root. However, NAC did not affect the levels of plasma glucose, lipids and the size of atherosclerotic lesions. Analysis of plaque composition showed decreased amounts of macrophages, lipid deposition, but not smooth muscle cells, and increased collagen content in atherosclerotic lesions in apoE(-/-) mice administered with NAC. Moreover, we found that NAC down-regulated the expression of VCAM-1, MMP2 and MMP9, accompanied by inhibition of NF-κB activation and reduced expression of RAGE.

CONCLUSION

In the present study, we show novel data to suggest that NAC promotes atherosclerotic plaque stabilization through suppression of RAGE, MMPs and NF-κB in apoE(-/-) mice.

Impairment of human keratinocyte mobility and proliferation by advanced glycation end products-modified BSA

The migration and proliferation of keratinocytes is critical to wound re-epithelialization and defects in this function are associated with the clinical phenomenon of chronic non-healing wounds. Advanced glycation end products (AGEs) occur through non-enzymatic glycation of long-lived proteins in diabetes and play important roles in diabetic complications. However, specific roles for AGEs in keratinocyte migration and proliferation, and the underlying molecular mechanisms, have not been fully established. The aim of the current study was to elucidate the interaction between AGE-modified bovine serum albumin (AGE-BSA) and keratinocytes. As a result, we found that AGE-BSA had no effect on the viability of keratinocytes for up to 48 h of incubation with 50 μg/ml of AGE-BSA. AGE-BSA (but not non-glycated BSA) exerted a concentration-dependent suppression of keratinocyte migration at a range of concentrations. The expression of matrix metalloproteinase-9 (MMP-9) was significantly up-regulated in keratinocytes incubated with increasing AGE-BSA, but tissue inhibitor of metalloproteinases-1 (TIMP-1) expression was down-regulated. AGE-BSA also profoundly depressed phospho-focal adhesion kinase-Tyr397 (p-FAK) and α2β1 integrin expression, while total-FAK expression levels remained constant, in keratinocytes. The proliferative capacity of keratinocytes was diminished after 72 h AGE-BSA incubation. Taken together, these findings suggested that in the presence of AGE-BSA, keratinocytes lose their migratory and proliferation abilities. These data also indicated that, in the context of the chronic hyperglycemia in diabetes, the effects of AGE-BSA on keratinocyte migration might be mediated through MMP-9/TIMP-1, p-FAK and α2β1 integrin.

Hyperglycemia limits experimental aortic aneurysm progression

OBJECTIVE

Diabetes mellitus (DM) is associated with reduced progression of abdominal aortic aneurysm (AAA) disease. Mechanisms responsible for this negative association remain unknown. We created AAAs in hyperglycemic mice to examine the influence of serum glucose concentration on experimental aneurysm progression.

METHODS

Aortic aneurysms were induced in hyperglycemic (DM) and normoglycemic models by using intra-aortic porcine pancreatic elastase (PPE) infusion in C57BL/6 mice or by systemic infusion of angiotensin II (ANG) in apolipoprotein E-deficient (ApoE(-/-)) mice, respectively. In an additional DM cohort, insulin therapy was initiated after aneurysm induction. Aneurysmal aortic enlargement progression was monitored with serial transabdominal ultrasound measurements. At sacrifice, AAA cellularity and proteolytic activity were evaluated by immunohistochemistry and substrate zymography, respectively. Influences of serum glucose levels on macrophage migration were examined in separate models of thioglycollate-induced murine peritonitis.

RESULTS

At 14 days after PPE infusion, AAA enlargement in hyperglycemic mice (serum glucose ≥ 300 mg/dL) was less than that in euglycemic mice (PPE-DM: 54% ± 19% vs PPE: 84% ± 24%, P < .0001). PPE-DM mice also demonstrated reduced aortic mural macrophage infiltration (145 ± 87 vs 253 ± 119 cells/cross-sectional area, P = .0325), elastolysis (% residual elastin: 20% ± 7% vs 12% ± 6%, P = .0209), and neovascularization (12 ± 8 vs 20 ± 6 vessels/high powered field, P = .0229) compared with PPE mice. Hyperglycemia limited AAA enlargement after ANG infusion in ApoE(-/-) mice (ANG-DM: 38% ± 12% vs ANG: 61% ± 37% at day 28). Peritoneal macrophage production was reduced in response to thioglycollate stimulation in hyperglycemic mice, with limited augmentation noted in response to vascular endothelial growth factor administration. Insulin therapy reduced serum glucose levels and was associated with AAA enlargement rates intermediate between euglycemic and hyperglycemic mice (PPE: 1.21 ± 0.14 mm vs PPE-DM: 1.00 ± 0.04 mm vs PPE-DM + insulin: 1.14 ± 0.05 mm).

CONCLUSIONS

Hyperglycemia reduces progression of experimental AAA disease; lowering of serum glucose levels with insulin treatment diminishes this protective effect. Identifying mechanisms of hyperglycemic aneurysm inhibition may accelerate development of novel clinical therapies for AAA disease.