Glycolaldehyde-derived advanced glycation end products (glycol-AGEs)-induced vascular smooth muscle cell dysfunction is regulated by the AGES-receptor (RAGE) axis in endothelium

Using Redox Proteomics to Gain New Insights into Neurodegenerative Disease and Protein Modification

Antioxidant defenses in biological systems ensure redox homeostasis, regulating baseline levels of reactive oxygen and nitrogen species (ROS and RNS). Oxidative stress (OS), characterized by a lack of antioxidant defenses or an elevation in ROS and RNS, may cause a modification of biomolecules, ROS being primarily absorbed by proteins. As a result of both genome and environment interactions, proteomics provides complete information about a cell's proteome, which changes continuously. Besides measuring protein expression levels, proteomics can also be used to identify protein modifications, localizations, the effects of added agents, and the interactions between proteins. Several oxidative processes are frequently used to modify proteins post-translationally, including carbonylation, oxidation of amino acid side chains, glycation, or lipid peroxidation, which produces highly reactive alkenals. Reactive alkenals, such as 4-hydroxy-2-nonenal, are added to cysteine (Cys), lysine (Lys), or histidine (His) residues by a Michael addition, and tyrosine (Tyr) residues are nitrated and Cys residues are nitrosylated by a Michael addition. Oxidative and nitrosative stress have been implicated in many neurodegenerative diseases as a result of oxidative damage to the brain, which may be especially vulnerable due to the large consumption of dioxygen. Therefore, the current methods applied for the detection, identification, and quantification in redox proteomics are of great interest. This review describes the main protein modifications classified as chemical reactions. Finally, we discuss the importance of redox proteomics to health and describe the analytical methods used in redox proteomics.

Glycolaldehyde-derived advanced glycation end products promote macrophage proliferation via the JAK-STAT signaling pathway

BACKGROUND

Advanced glycation end products (AGEs) are heterogeneous proinflammatory molecules produced by a non-enzymatic glycation reaction between reducing sugars (and their metabolites) and biomolecules with amino groups, such as proteins. Although increases in and the accumulation of AGEs have been implicated in the onset and exacerbation of lifestyle- or age-related diseases, including diabetes, their physiological functions have not yet been elucidated in detail.

METHODS AND RESULTS

The present study investigated the cellular responses of the macrophage cell line RAW264.7 stimulated by glycolaldehyde-derived AGEs (Glycol-AGEs) known as representative toxic AGEs. The results obtained showed that Glycol-AGEs significantly promoted the proliferation of RAW264.7 cells at a low concentration range (1-10 µg/mL) in a concentration-dependent manner. On the other hand, neither TNF-α production nor cytotoxicity were induced by the same concentrations of Glycol-AGEs. The increases observed in cell proliferation by low concentrations of Glycol-AGEs were also detected in receptor triple knockout (RAGE-TLR4-TLR2 KO) cells as well as in wild-type cells. Increases in cell proliferation were not affected by various kinase inhibitors, including MAP kinase inhibitors, but were significantly suppressed by JAK2 and STAT5 inhibitors. In addition, the expression of some cell cycle-related genes was up-regulated by the stimulation with Glycol-AGEs.

CONCLUSIONS

These results suggest a novel physiological role for AGEs in the promotion of cell proliferation via the JAK-STAT pathway.

Advanced Glycation End Products: key player of the pathogenesis of atherosclerosis

Atherosclerosis is the most common type of cardiovascular disease, and it causes intima thickening, plaque development, and ultimate blockage of the artery lumen. Advanced glycation end products (AGEs) are thought to have a role in the development and progression of atherosclerosis. there is developing an enthusiasm for AGEs as a potential remedial target. AGES mainly induce arterial damage and exacerbate the development of atherosclerotic plaques by triggering cell receptor-dependent signalling. The interplay of AGEs with RAGE, a transmembrane signalling receptor present across all cells important to atherosclerosis, changes cell activity, boosts expression of genes, and increases the outflow of inflammatory compounds, resulting in arterial wall injury and plaque formation. Here in this review, function of AGEs in the genesis, progression, and instability of atherosclerosis is discussed. In endothelial and smooth muscle cells, as well as platelets, the interaction of AGEs with their transmembrane cell receptor, RAGE, triggers intracellular signalling, resulting in endothelial damage, vascular smooth muscle cell function modification, and changed platelet activity.

Glycolaldehyde, an Advanced Glycation End Products Precursor, Induces Apoptosis via ROS-Mediated Mitochondrial Dysfunction in Renal Mesangial Cells

Glycolaldehyde (GA) is a reducing sugar and a precursor of advanced glycation end products (AGEs). The role of precursor and precursor-derived AGEs in diabetes and its complications have been actively discussed in the literature. This study aimed to elucidate the mechanism of GA-induced apoptosis in renal cells. Immunoblotting results showed that GA (100 μM) caused cytotoxicity in murine renal glomerular mesangial cells (SV40 MES 13) and induced apoptosis via major modulators, decreasing Bcl-2 and increasing Bax, cytochrome c, and cleaved caspase-3/-9 expression. GA-derived AGE accumulation and receptor for AGE (RAGE) expression increased in mesangial cells; however, cells that were cotreated with aminoguanidine (AG) showed no increase in GA-derived AGE concentration. Furthermore, reactive oxygen species (ROS) production was increased by GA, while AG inhibited AGE formation, leading to a decrease in ROS levels in mesangial cells. We evaluated apoptosis through fluorescence-activated cell sorting, and used TUNEL staining to study DNA fragmentation. Additionally, we measured ATP generation and used MitoTracker staining to access changes in mitochondrial membrane potential. This study showed that GA increased AGE concentration, RAGE expression, and excessive ROS generation, leading to renal mesangial cell damage via GA-induced apoptosis pathway caused by mitochondrial dysfunction.

Differences in advanced glycation endproducts (AGEs) in plasma from birds and mammals of different body sizes and ages

Birds and mammals provide a physiological paradox: similar-sized mammals live shorter lives than birds; yet, birds have higher blood glucose concentrations than mammals, and higher basal metabolic rates. We have previously shown that oxidative stress patterns between mammals and birds differ, so that birds, generally, have lower blood antioxidant capacity, and lower lipid peroxidation concentration. There is a close association between oxidative stress and the production of carbohydrate-based damaged biomolecules, Advanced Glycation End-products (AGEs). In mammals, AGEs can bind to their receptor (RAGE), which can lead to increases in reactive oxygen species (ROS) production, and can decrease antioxidant capacity. Here, we used plasma from birds and mammals to address whether blood plasma AGE-BSA concentration is associated with body mass and age in these two groups. We found a statistically significantly higher average concentrations of AGE-BSA in birds compared with mammals, and we found a significantly positive correlation between AGE-BSA and age in mammals, though, this correlation disappeared after phylogenetic correction. We propose that the higher AGE concentration in birds is mainly attributable to greater AGE-production due to elevated basal glucose concentrations and decreased AGE-clearance given differences in glomerular filtration rates in birds compared with mammals. Additionally, due to the potential lack of an AGE receptor in birds, AGE accumulation may not be closely linked to oxidative stress and therefore pose a lesser physiological challenge in birds compared to mammals.

Glycation and Glycosylation in Cardiovascular Remodeling: Focus on Advanced Glycation End Products and O-Linked Glycosylations as Glucose-Related Pathogenetic Factors and Disease Markers

Glycation and glycosylation are non-enzymatic and enzymatic reactions, respectively, of glucose, glucose metabolites, and other reducing sugars with different substrates, such as proteins, lipids, and nucleic acids. Increased availability of glucose is a recognized risk factor for the onset and progression of diabetes-mellitus-associated disorders, among which cardiovascular diseases have a great impact on patient mortality. Both advanced glycation end products, the result of non-enzymatic glycation of substrates, and O-linked-N-Acetylglucosaminylation, a glycosylation reaction that is controlled by O-N-AcetylGlucosamine (GlcNAc) transferase (OGT) and O-GlcNAcase (OGA), have been shown to play a role in cardiovascular remodeling. In this review, we aim (1) to summarize the most recent data regarding the role of glycation and O-linked-N-Acetylglucosaminylation as glucose-related pathogenetic factors and disease markers in cardiovascular remodeling, and (2) to discuss potential common mechanisms linking these pathways to the dysregulation and/or loss of function of different biomolecules involved in this field.

Gliclazide alters macrophages polarization state in diabetic atherosclerosis in vitro via blocking AGE-RAGE/TLR4-reactive oxygen species-activated NF-kβ nexus

Hyperglycemic milieu in diabetes mellitus stimulates macrophages for exaggerated pro-inflammatory cytokine response, particularly IL-1β, IL-6, and TNF-α. Although hyperglycemia causes macrophages to produce pro-inflammatory cytokines, AGEs (advanced glycation end products) active inflammation, produced as a result of chronic hyperglycemia, inducers cause polarization of macrophages into pro-inflammatory M1 phenotype. AGEs in diabetes accelerate atherosclerotic plaque initiation and progression via promoting macrophages polarization towards pro-inflammatory state. Gliclazide (Glz) is a well known antidiabetic drug with excellent safety profile. Its repurposing in the management of diabetes-associated late complications has tremendous merit. The present study demonstrated that Glz retards diabetic atherosclerotic progression, and cytokines storm in a concentration dependent manner over a concentration range of 1-100 μM than those of AGEs (200 μg/ml)-treated cells through a mechanism that alters macrophage M1 polarization state. Glz exerted these beneficial effects, independent of its antidiabetic effect. Glz pretreatment significantly (P < 0.05) inhibited the AGEs-induced pro-inflammatory mediators (NO^•, reactive oxygen species, i-NOS), and production of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α. It also significantly (P < 0.05) promoted the production of anti-inflammatory cytokines (IL-10 and TGF-β) in RAW 264.7 mouse macrophages. Glz pretreatment also effectively abated the AGEs-induced RAGE (~2-fold decrease), and CD86 surface marker expressions (P < 0.001 at 100 μM) on macrophages by inhibiting the NF-kβ activation in a concentration dependent manner (1-100 μM) (P < 0.001). In conclusion, our data demonstrates that Glz alleviates the diabetic atherosclerosis progression by ameliorating the AGEs-mediated M1 pro-inflammatory phenotype via blocking AGE-RAGE/TLR4-reactive oxygen species -activated NF-kβ nexus in macrophages.

Glyoxalase System as a Therapeutic Target against Diabetic Retinopathy

Hyperglycemia, a defining characteristic of diabetes, combined with oxidative stress, results in the formation of advanced glycation end products (AGEs). AGEs are toxic compounds that have adverse effects on many tissues including the retina and lens. AGEs promote the formation of reactive oxygen species (ROS), which, in turn, boost the production of AGEs, resulting in positive feedback loops, a vicious cycle that compromises tissue fitness. Oxidative stress and the accumulation of AGEs are etiologically associated with the pathogenesis of multiple diseases including diabetic retinopathy (DR). DR is a devastating microvascular complication of diabetes mellitus and the leading cause of blindness in working-age adults. The onset and development of DR is multifactorial. Lowering AGEs accumulation may represent a potential therapeutic approach to slow this sight-threatening diabetic complication. To set DR in a physiological context, in this review we first describe relations between oxidative stress, formation of AGEs, and aging in several tissues of the eye, each of which is associated with a major age-related eye pathology. We summarize mechanisms of AGEs generation and anti-AGEs detoxifying systems. We specifically feature the potential of the glyoxalase system in the retina in the prevention of AGEs-associated damage linked to DR. We provide a comparative analysis of glyoxalase activity in different tissues from wild-type mice, supporting a major role for the glyoxalase system in the detoxification of AGEs in the retina, and present the manipulation of this system as a therapeutic strategy to prevent the onset of DR.

RAGE and its ligands: from pathogenesis to therapeutics

Receptor for advanced glycation end products (RAGE) is an immunoglobulin-like receptor present on cell surface. RAGE binds to an array of structurally diverse ligands, acts as a pattern recognition receptor (PRR) and is expressed on cells of different origin performing different functions. RAGE ligation leads to the initiation of a cascade of signaling events and is implicated in diseases, such as inflammation, cancer, diabetes, vascular dysfunctions, retinopathy, and neurodegenerative diseases. Because of the significant involvement of RAGE in the progression of numerous diseases, RAGE signaling has been targeted through use of inhibitors and anti-RAGE antibodies as a treatment strategy and therapy. Here in this review, we have summarized the physical and physiological aspects of RAGE biology in mammalian system and the importance of targeting this molecule in the treatment of various RAGE mediated pathologies. Highlights Receptor for advanced glycation end products (RAGE) is a member of immunoglobulin superfamily of receptors and involved in many pathophysiological conditions. RAGE ligation with its ligands leads to initiation of distinct signaling cascades and activation of numerous transcription factors. Targeting RAGE signaling through inhibitors and anti-RAGE antibodies can be promising treatment strategy.

Vitamin D attenuates HMGB1-mediated neointimal hyperplasia after percutaneous coronary intervention in swine

Intracoronary stenting is a common procedure in patients with coronary artery disease (CAD). Stent deployment stretches and denudes the endothelial layer, promoting a local inflammatory response, resulting in neointimal hyperplasia. Vitamin D deficiency associates with CAD. In this study, we examined the association of vitamin D status with high mobility group box 1 (HMGB1)-mediated pathways (HMGB1, receptor for advanced glycation end products [RAGE], and Toll-like receptor-2 and -4 [TLR2 and TLR4]) in neointimal hyperplasia in atherosclerotic swine following bare metal stenting. Yucatan microswine fed with a high-cholesterol diet were stratified to receive vitamin D-deficient (VD-DEF), vitamin D-sufficient (VD-SUF), and vitamin D-supplemented (VD-SUP) diet. After 6 months, PTCA (percutaneous transluminal balloon angioplasty) followed by bare metal stent implantation was performed in the left anterior descending (LAD) artery of each swine. Four months following coronary intervention, angiogram and optical coherence tomography (OCT) were performed and swine euthanized. Histology and immunohistochemistry were performed in excised LAD to evaluate the expression of HMGB1, RAGE, TLR2, and TLR4. OCT analysis revealed the greatest in-stent restenosis area in the LAD of VD-DEF compared to VD-SUF or VD-SUP swine. The protein expression of HMGB1, RAGE, TLR2, and TLR4 was significantly higher in the LAD of VD-DEF compared to VD-SUF or VD-SUP swine. Vitamin D deficiency was associated with both increased in-stent restenosis and increased HMGB1-mediated inflammation noted in coronary arteries following intravascular stenting. Inversely, vitamin D supplementation was associated with both a decrease in this inflammatory profile and in neointimal hyperplasia, warranting further investigation for vitamin D as a potential adjunct therapy following coronary intervention.

Redox Signaling and Advanced Glycation Endproducts (AGEs) in Diet-Related Diseases

Diets are currently characterized by elevated sugar intake, mainly due to the increased consumption of processed sweetened foods and drinks during the last 40 years. Diet is the main source of advanced glycation endproducts (AGEs). These are toxic compounds formed during the Maillard reaction, which takes place both in vivo, in tissues and fluids under physiological conditions, favored by sugar intake, and ex vivo during food preparation such as baking, cooking, frying or storage. Protein glycation occurs slowly and continuously through life, driving AGE accumulation in tissues during aging. For this reason, AGEs have been proposed as a risk factor in the pathogenesis of diet-related diseases such as diabetes, insulin resistance, cardiovascular diseases, kidney injury, and age-related and neurodegenerative diseases. AGEs are associated with an increase in oxidative stress since they mediate the production of reactive oxygen species (ROS), increasing the intracellular levels of hydrogen peroxide (H₂O₂), superoxide (O₂⁻), and nitric oxide (NO). The interaction of AGEs with the receptor for AGEs (RAGE) enhances oxidative stress through ROS production by NADPH oxidases inside the mitochondria. This affects mitochondrial function and ultimately influences cell metabolism under various pathological conditions. This short review will summarize all evidence that relates AGEs and ROS production, their relationship with diet-related diseases, as well as the latest research about the use of natural compounds with antioxidant properties to prevent the harmful effects of AGEs on health.

Anti-Inflammatory Effect of an Apigenin-Maillard Reaction Product in Macrophages and Macrophage-Endothelial Cocultures

Chronic inflammation is involved in the progression of various diseases, while dietary flavonoids are reported to possess antioxidative and anti-inflammatory properties against age-related diseases. Previously, an apigenin-Maillard reaction product, dimethylglyoxal apigenin (DMA), was identified by us and demonstrated to be antioxidative. In this study, we investigated the inhibitory effect of DMA on advanced glycation end product- (AGE-) induced inflammation in macrophages and macrophage-endothelial cocultures. Results showed that DMA remarkably inhibited the mRNA and protein expression of receptor for AGEs (RAGE), thereby inhibiting the production of ROS and proinflammatory cytokines, including tumor necrosis factor- (TNF-) α, interleukin (IL) 1, IL 6, and monocyte chemoattractant protein- (MCP-) 1 in RAW 264.7 cells. In the coculture system which was performed in the Boyden chamber, macrophage infiltration and adhesion to endothelial cells were significantly suppressed by DMA. Further study indicated that DMA decreased AGE-evoked IL 6 and MCP-1 secretion, which might be achieved through RAGE and its downstream-regulated transforming growth factor- (TGF-) β1 and intercellular adhesion molecule (ICAM) 1 expression in the coculture system. In conclusion, our study demonstrates that DMA, a thermally induced compound, has anti-inflammatory activity in both macrophages and macrophage-endothelial cocultures, offering a promising approach for slowing down the development of chronic diseases.

Galectins in the Pathogenesis of Cerebrovascular Accidents: An Overview

Due to limitations of neuroimaging, such as the isodense appearance of blood to neuronal tissue in subacute hemorrhagic stroke, a body of studies have been performed to evaluate candidate biomarkers which may aid in accurate determination of cerebrovascular accident type. Beyond aiding in the delineation of stroke cause, biomarkers could also confer useful prognostic information to help clinicians plan use of resources. One of the candidate biomarkers studied for detection of cerebrovascular accident (CVA) includes a class of proteins called galectins. Galectins bind β-galactoside through a highly conserved carbohydrate recognition domain, endowing an ability to interact with carbohydrate moieties on glycoproteins, some of which are relevant to CVA response. Furthermore, galectins-1, -2, -3, -9, and -12 are expressed in tissues relevant to CVA, and some exhibit characteristics (eg, extracellular secretion) that could render feasible their detection in serum. Galectins-1 and -3 appear to have the largest amounts of preclinical evidence, consistently demonstrating increased activity and expression levels during CVA. However, a lack of standardization of biochemical assays across cohort studies limits further translation of these basic science studies. This review aims to increase awareness of the biochemical roles of galectins in CVA, while also highlighting challenges and remaining questions preventing the translation of basic science observations into a clinically useful test.

Advanced glycation end-products disrupt human endothelial cells redox homeostasis: new insights into reactive oxygen species production

Advanced glycation end-products (AGEs) trigger multiple metabolic disorders in the vessel wall that may in turn lead to endothelial dysfunction. The molecular mechanisms by which AGEs generate these effects are not completely understood. Oxidative stress plays a key role in the development of deleterious effects that occur in endothelium during diabetes. Our main objectives were to further understand how AGEs contribute to reactive oxygen species (ROS) overproduction in endothelial cells and to evaluate the protective effect of an antioxidant plant extract. The human endothelial cell line EA.hy926 was treated with native or modified bovine serum albumin (respectively BSA and BSA-AGEs). To monitor free radicals formation, we used H₂DCF-DA, dihydroethidium (DHE), DAF-FM-DA and MitoSOX Red dyes. To investigate potential sources of ROS, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and mitochondrial inhibitors were used. The regulation of different types of ROS by the polyphenol-rich extract from the medicinal plant Doratoxylon apetalum was also studied for a therapeutic perspective. BSA-AGEs exhibited not only less antioxidant properties than BSA, but also pro-oxidant effects. The degree of albumin glycoxidation directly influenced oxidative stress through a possible communication between NADPH oxidase and mitochondria. D. apetalum significantly decreased intracellular hydrogen peroxide and superoxide anions mainly detected by H₂DCF-DA and DHE respectively. Our results suggest that BSA-AGEs promote a marked oxidative stress mediated at least by NADPH oxidase and mitochondria. D. apetalum plant extract appeared to be an effective antioxidant compound to protect endothelial cells.

Food advanced glycation end products as potential endocrine disruptors: An emerging threat to contemporary and future generation

Mankind exposure to chemicals in the past century has increased dramatically throughout environment. There is no question that chemicals interfere with the physiology of biological system. Abundance of chemicals is documented to be detrimental to human and wildlife. The mammalian endocrine system is comprised of many interacting tissues mediate themselves through hormones that are essential for metabolism, growth and development. Humans secrete over fifty different hormones to orchestrate major physiological functions however; these vital functions can be intervened by huge number of internal and external chemical stressors that are identified as endocrine disruptors. Advanced glycation end products (AGEs), familiarly known as Maillard products, formed through non-enzymatic glycation whose production is augmented on aging as well as environmental stressors. Processed foods have become very popular today due to their taste, convenience, and inexpensiveness. Manufacture of these day-to-day foods involves extreme temperatures on processing results in the formation of AGEs could independently promote oxidative stress, aging, diabetes, cancer, degenerative diseases, more fascinatingly hormonal disruption is the subject of interest of this review. Based on some substantial observations documented till time, we discuss the emergence of dietary AGEs as potential endocrine disruptors by emphasizing their occurrence, mechanisms and participation in endocrine interruption. Both economically and in terms of human life, AGEs may represent an enormous cost for the future society. Therefore, by explicating their novel role in endocrine diseases, the review strives to make an impact on AGEs and their exposure among public as well as scientific communities.

Association between RAGE variants and the susceptibility to atherosclerotic lesions in Chinese Han population

Receptor for advanced glycation end products (RAGE) is a major proinflammatory receptor and its role in atherosclerosis has only been emphasized recently. Increasing evidence has demonstrated an association between RAGE and the susceptibility to atherosclerosis development. Therefore, the role of RAGE in atherogenesis and the possible impact of genetic variations in RAGE on the atherosclerotic process in subjects with coronary artery disease (CAD) was investigated in the present study. The RAGE expression in carotid specimens was analyzed by immunohistochemistry and sequence variations of the RAGE gene selected from the Hapmap database were also screened. The plasma levels of S100 calcium binding protein B (S100B) were determined by ELISA. Immunohistochemical staining of tissue samples demonstrated an increased RAGE expression in atherosclerotic carotid plaques compared with that in normal arteries. Furthermore, compared with the corresponding wild-type genotype, the rs2269422 single-nucleotide polymorphism of RAGE was associated with the susceptibility of patients with CAD to atherosclerosis. Furthermore, reverse transcription polymerase chain reaction and western blot analyses indicated increased coronary artery RAGE mRNA levels and protein expression, respectively, in CAD patients vs. control subjects. Furthermore, the plasma levels of S100B in CAD patients that were carriers of the AA/AT genotype of the rs2269422 variant of RAGE was increased compared with that in TT genotype carriers; as this was also identified in control subjects, it may not be CAD-specific. The RAGE rs2269422 variant is therefore significantly associated with an increased occurrence of CAD in the present Han Chinese population. Thus, RAGE variants significantly impact the risk of CAD in Han Chinese subjects.

Impact of advanced glycation end products (AGEs) signaling in coronary artery disease

Coronary artery disease remains the leading cause of mortality in adult diabetic population with however, a high predominance also in non-diabetic subjects. In search of common molecular mechanisms and metabolic by-products with potential pathogenic role, increased advanced glycation end products (AGEs) present a critical biomarker for CAD development in both cases. Interaction of AGEs with their transmembrane cell receptor, RAGE in endothelial and smooth muscle cells as well as in platelets, activates intracellular signaling that leads to endothelial injury, modulation of vascular smooth muscle cell function and altered platelet activity. Furthermore, tissue accumulation of AGEs affects current treatment approaches being involved in stent restenosis. The present review provides an update of AGE-induced molecular mechanisms involved in CAD pathophysiology while it discusses emerging therapeutic interventions targeting AGE reduction and AGE-RAGE signaling with beneficial clinical outcome.

Phagocytosis of Advanced Glycation End Products (AGEs) in Macrophages Induces Cell Apoptosis

Advanced glycation end products (AGEs) are the products of a series of nonenzymatic modifications of proteins by reducing sugars. AGEs play a pivotal role in development of diabetic complications and atherosclerosis. Accumulation of AGEs in a vessel wall may contribute to the development of vascular lesions. Although AGEs have a diverse range of bioactivities, the clearance process of AGEs from the extracellular space, including the incorporation of AGEs into specific cells, subcellular localization, and the fate of AGEs, remains unclear. In the present study, we examined the kinetics of the uptake of AGEs by mouse macrophage J774.1 cells in vitro and characterized the process. We demonstrated that AGEs bound to the surface of the cells and were also incorporated into the cytoplasm. The temperature- and time-dependent uptake of AGEs was saturable with AGE concentration and was inhibited by cytochalasin D but not chlorpromazine. We also observed the granule-like appearance of AGE immunoreactivity in subcellular localizations in macrophages. Higher concentrations of AGEs induced intracellular ROS and 4-HNE, which were associated with activation of the NF-κB pathway and caspase-3. These results suggest that incorporation of AGEs occurred actively by endocytosis in macrophages, leading to apoptosis of these cells through NF-κB activation.

The role of damage- and pathogen-associated molecular patterns in inflammation-mediated vulnerability of atherosclerotic plaques

Atherosclerosis is a chronic inflammatory disease resulting in the formation of the atherosclerotic plaque. Plaque formation starts with the inflammation in fatty streaks and progresses through atheroma, atheromatous plaque, and fibroatheroma leading to development of stable plaque. Hypercholesterolemia, dyslipidemia, and hyperglycemia are the risk factors for atherosclerosis. Inflammation, infection with viruses and bacteria, and dysregulation in the endothelial and vascular smooth muscle cells leads to advanced plaque formation. Death of the cells in the intima due to inflammation results in secretion of damage-associated molecular patterns (DAMPs) such as high mobility group box 1 (HMGB1), receptor for advanced glycation end products (RAGE), alarmins (S100A8, S100A9, S100A12, and oxidized low-density lipoproteins), and infection with pathogens leads to secretion of pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharides, lipoteichoic acids, and peptidoglycans. DAMPs and PAMPs further activate the inflammatory surface receptors such as TREM-1 and toll-like receptors and downstream signaling kinases and transcription factors leading to increased secretion of pro-inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)-1β, IL-6, and interferon-γ and matrix metalloproteinases (MMPs). These mediators and cytokines along with MMPs render the plaque vulnerable for rupture leading to ischemic events. In this review, we have discussed the role of DAMPs and PAMPs in association with inflammation-mediated plaque vulnerability.

Advanced glycation end products promote the proliferation and migration of primary rat vascular smooth muscle cells via the upregulation of BAG3

The present study was aimed to investigate the role of reactive oxygen species (ROS) on advanced glycation end product (AGE)-induced proliferation and migration of vascular smooth muscle cells (VSMCs) and whether Bcl-2‑associated athanogene 3 (BAG3) is involved in the process. Primary rat VSMCs were extracted and cultured in vitro. Cell viability was detected by MTT assay and cell proliferation was detected by EdU incorporation assay. Cell migration was detected by wound healing and Transwell assays. BAG3 was detected using qPCR and western blot analysis. Transcriptional and translational inhibitors (actinomycin D and cycloheximide, respectively) were used to study the effect of AGEs on the expression of BAG3 in VSMCs. Lentiviral plasmids containing short hairpin RNA (shRNA) against rat BAG3 or control shRNA were transduced into VSMCs. Cellular ROS were detected by 2',7'-dichlorofluorescein diacetate (DCFH-DA) staining. Mitochondrial membrane potential was detected by tetramethylrhodamine methyl ester (TMRE) staining. AGEs significantly increased the expression of BAG3 in a dose-and time-dependent manner. Furthermore, AGEs mainly increased the expression of BAG3 mRNA by increasing the RNA synthesis rather than inhibiting the RNA translation. BAG3 knockdown reduced the proliferation and migration of VSMCs induced by AGEs. BAG3 knockdown reduced the generation of ROS and sustained the mitochondrial membrane potential of VSMCs. Reduction of ROS production by N-acetylcysteine (NAC), a potent antioxidant, also reduced the proliferation and migration of VSMCs. On the whole, the present study demonstrated for the first time that AGEs could increase ROS production and promote the proliferation and migration of VSMCs by upregulating BAG3 expression. This study indicated that BAG3 should be considered as a potential target for the prevention and/or treatment of vascular complications of diabetes.

Plantamajoside from Plantago asiatica modulates human umbilical vein endothelial cell dysfunction by glyceraldehyde-induced AGEs via MAPK/NF-κB

Background

Plantago asiatica has been traditionally used for traditional medicine around East Asia. Plantamajoside (PM), which is isolated from this plant, is known for biological properties including anti-inflammation and antioxidant activity. To demonstrate the biological activity of PM against endothelial dysfunction induced by advanced glycation end-products (AGEs), a cellular inflammatory mechanism system was evaluated in human umbilical vein endothelial cells (HUVECs).

Methods

We obtained PM through previous research in our laboratory. We formed the AGEs from bovine serum albumin with glyceraldehyde in the dark for seven days. To confirm the modulation of the inflammatory mechanism in endothelial dysfunction, we quantified the various pro-inflammatory cytokines and endothelial dysfunction-related proteins in the HUVECs with Western blotting and with real-time and quantitative real-time polymerase chain reactions.

Results

Co-treatment with PM and AGEs significantly suppressed inflammatory cytokines and adhesion molecule expression. Moreover, the PM treatment for down-regulated inflammatory signals and blocked monocyte adhesion on the HUVECs.

Conclusions

Theses results demonstrated that PM, as a potential natural compound, protects AGE-induced endothelial cells against inflammatory cellular dysfunction.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1570-1) contains supplementary material, which is available to authorized users.