Anti-inflammatory effects of the advanced glycation end product inhibitor LR-90 in human monocytes

1,2,4-Triazine derivatives as agents for the prevention of AGE-RAGE-mediated inflammatory cascade in THP-1 monocytes: An approach to prevent inflammation-induced late diabetic complications

INTRODUCTION

Monocytes mainly contribute to the development and progression of vascular inflammatory conditions via the M1 polarization. The elevated levels of advanced glycation end products (AGEs) in diabetic environment lead to severe inflammation, and the release of pro-inflammatory mediators. This shifts the balance towards the pro-inflammatory state of monocytes.

OBJECTIVE

The current study was aimed to determine the antiglycation activity of 1,2,4-triazine derivatives, and study of their molecular basis in regulating the AGEs-mediated inflammatory responses in THP-1 monocytes.

METHODS

Primarily, the antiglycation activity of a series of 1,2,4-triazine derivatives was evaluated against MGO-AGEs in vitro. The toxicity of antiglycation compounds was determined by a metabolic assay, using human hepatocyte (HepG2) and monocyte (THP-1) cell lines. DCFH-DA probe was used to evaluate the antioxidant potential of the compounds. Immunocytochemistry, Western blotting, and ELISA techniques were employed to determine the levels of pro-inflammatory markers (NF-κB, RAGE, COX-1, COX-2, and PGE2) in THP-1 monocytes under in-vitro hyperglycemic conditions.

RESULTS

Results indicate that the triazine derivatives 22, and 23 were the most potent antiglycation agents among the entire series, while non-toxic to HepG2, and THP-1 cells. Both compounds inhibited the AGEs-induced upstream and downstream signaling of NADPH oxidase and inflammatory mediators p38 and NF-κβ, respectively, in THP-1 monocytes. They also inhibited the induction of COX-2 and its product PGE2 by suppressing AGE-RAGE interactions. Moreover, compounds 22, and 23 reversed the AGEs-mediated suppression of COX-1 in THP-1 monocytes.

CONCLUSION

In conclusion, 1,2,4-triazine derivatives 22, and 23 have the potential to suppress inflammatory responses under the diabetic environment through AGE-RAGE-NF-κβ/p38 nexus in THP-1 monocytes. These findings identify triazines 22, and 23 as compelling candidates for drug development, potentially beneficial for the diabetic patients with an elevated risk of vascular complications, such as atherosclerosis.

Diabetes and Impaired Fracture Healing: A Narrative Review of Recent Literature

PURPOSE OF THE REVIEW

Diabetes mellitus is a chronic metabolic disorder commonly encountered in orthopedic patients. Both type 1 and type 2 diabetes mellitus increase fracture risk and impair fracture healing. This review examines complex etiology of impaired fracture healing in diabetes.

RECENT FINDINGS

Recent findings point to several mechanisms leading to orthopedic complications in diabetes. Hyperglycemia and chronic inflammation lead to increased formation of advanced glycation end products and generation of reactive oxygen species, which in turn contribute to the disruption in osteoblast and osteoclast balance leading to decreased bone formation and heightening the risk of nonunion or delayed union as well as impaired fracture healing. The mechanisms attributing to this imbalance is secondary to an increase in pro-inflammatory mediators leading to premature resorption of callus cartilage and impaired bone formation due to compromised osteoblast differentiation and their apoptosis. Other mechanisms include disruption in the bone's microenvironment supporting different stages of healing process including hematoma and callus formation, and their resolution during bone remodeling phase. Complications of diabetes including peripheral neuropathy and peripheral vascular disease also contribute to the impairment of fracture healing. Certain diabetic drugs may have adverse effects on fracture healing. The pathophysiology of impaired fracture healing in diabetic patients is complex. This review provides an update of the most recent findings on how key mediators of bone healing are affected in diabetes.

Indole-linked 1,2,3-triazole derivatives efficiently modulate COX-2 protein and PGE2 levels in human THP-1 monocytes by suppressing AGE-ROS-NF-kβ nexus

AIMS

AGEs augment inflammatory responses by activating inflammatory cascade in monocytes, and hence lead to vascular dysfunction. The current study aims to study a plausible role and mechanism of a new library of indole-tethered 1,2,3-triazoles 2-13 in AGEs-induced inflammation.

MATERIAL AND METHODS

Initially, the analogs 2-13 were synthesized by cycloaddition reaction between prop-2-yn-1-yl-2-(1H-indol-3-yl) acetate (1) and azidoacetophenone (1a). In vitro glycation, and metabolic assays were employed to investigate antiglycation and cytotoxicity activities of new indole-triazoles. DCFH-DA, immunostaining, Western blotting, and ELISA techniques were used to study the reactive oxygen species (ROS), and pro-inflammatory mediators levels.

KEY FINDINGS

Among all the synthesized indole-triazoles, compounds 1-3, and 9-13, and their precursor molecule 1 were found to be active against AGEs production in in vitro glucose- and methylglyoxal (MGO)-BSA models. Compounds 1-2, and 11-13 were also found to be nontoxic against HEPG2, and THP-1 cells. Our results show that pretreatment of THP-1 monocytes with selected lead compounds 1-2, and 11-13, particularly compounds 12, and 13, reduced glucose- and MGO-derived AGEs-mediated ROS production (P < 0.001), as compared to standards, PDTC, rutin, and quercetin. They also significantly (P < 0.001) suppressed NF-ĸB translocation in THP-1 monocytes. Moreover, compounds 12, and 13 attenuated the AGEs-induced COX-2 protein levels (P < 0.001), and PGE₂ production (P < 0.001) in THP-1 monocytes.

SIGNIFICANCE

Our data revealed that the indole-triazoles 12, and 13 can significantly attenuate the AGEs-induced proinflammatory COX-2 levels, and associated PGE₂ production by suppressing AGE-ROS-NF-Kβ nexus in THP-1 monocytes. These compounds can thus serve as leads for further evaluation as treatment to delay early onset of diabetic complications.

In Vitro Methodologies to Study the Role of Advanced Glycation End Products (AGEs) in Neurodegeneration

Advanced glycation end products (AGEs) can be present in food or be endogenously produced in biological systems. Their formation has been associated with chronic neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and amyotrophic lateral sclerosis. The implication of AGEs in neurodegeneration is related to their ability to bind to AGE-specific receptors and the ability of their precursors to induce the so-called “dicarbonyl stress”, resulting in cross-linking and protein damage. However, the mode of action underlying their role in neurodegeneration remains unclear. While some research has been carried out in observational clinical studies, further in vitro studies may help elucidate these underlying modes of action. This review presents and discusses in vitro methodologies used in research on the potential role of AGEs in neuroinflammation and neurodegeneration. The overview reveals the main concepts linking AGEs to neurodegeneration, the current findings, and the available and advisable in vitro models to study their role. Moreover, the major questions regarding the role of AGEs in neurodegenerative diseases and the challenges and discrepancies in the research field are discussed.

Inhibitory effect of Salvia coccinea on inflammatory responses through NF-κB signaling pathways in THP-1 cells and acute rat diabetes mellitus

Hyperglycemia-induced oxidative stress has been implicated in diabetes and its complications. Medicinal plants possessing antioxidant activity may decrease oxidative stress by scavenging radicals and reducing power activity and would be a promising strategy for the treatment of inflammatory disorders like diabetes. This study was designed to evaluate the antioxidant effect of Aqueous Extract of  S.coccinea leaf (AESL) in HG treated THP-1 cells and streptozotocin (STZ)-induced diabetic Wistar rats. AESL and the standard antidiabetic drug glibenclamide were administered orally by intragastric tube for 14 days and pre-treated HG grown THP-1 cells. AESL treatment reduced HG induced increase in ROS production, NF-κB dependent proinflammatory gene expression by influencing NF-κB nuclear translocation in THP-1 cells. Oral administration of AESL inhibited STZ-induced increase in serum lipid peroxidation, aspartate transaminase, alanine transaminase, and Lactate dehydrogenase of diabetic rats. Significant increase in activity of superoxide dismutase, catalase and glutathione peroxidase, and a reduced level of glutathione, were observed in AESL treatment. The results demonstrate that AESL is useful in controlling blood glucose and also has antioxidant potential to influence the translocation of NF-κB, protect damage caused by hyperglycemia-induced inflammation.

Pharmaceutical Values of Calycosin: One Type of Flavonoid Isolated from Astragalus

Astragalus is a popular Materia Medica in China, and it could be applied in the treatment of various diseases. It contains a variety of chemically active ingredients, such as saponins, flavonoids, and polysaccharides. Plant-derived bioactive chemicals are considered natural, safe, and beneficial. Among the infinite plant-identified and isolated molecules, flavonoids have been reported to have positive effects on human health. Calycosin is the most important active flavonoid substance identified predominantly within this medicinal plant. In recent years, calycosin has been reported to have anticancer, antioxidative, immune-modulatory, and estrogenic-like properties. This review collected recent relevant literatures on calycosin and summarized its potential pharmaceutical properties and working mechanism involved, which provided solid basis for future clinical research.

Glycolaldehyde-modified advanced glycation end-products inhibit differentiation of human monocytes into osteoclasts via upregulation of IL-10

Diabetes patients are at high risk of bone fracture due to accumulation of advanced glycation end products (AGEs) and low bone turnover. Although AGEs inhibit osteoblast functions, little is known about their roles in regulation of human osteoclast differentiation. The aim of this study was to determine the roles of AGEs in regulation of human osteoclast differentiation. Human CD14⁺ monocytes collected from healthy individuals were stimulated in vitro with conventional cytokines to induce osteoclast differentiation. Simultaneously, glucose-modified AGEs-BSA (Glu-AGEs-BSA) and glycolaldehyde-modified AGEs-BSA (Glyco-AGEs-BSA) were added to analyze their role in regulation of osteoclast differentiation. Human CD14⁺ cells expressed endogenous receptor for AGE (RAGE). Stimulation with Glyco-AGEs-BSA, but not Glu-AGEs-BSA, reduced the number of tartrate-resistant acid phosphatase-positive cells in a dose-dependent manner and suppressed mRNA expression of nuclear factor of activated T-cells 1 and cathepsin K. Glyco-AGEs-BSA up-regulated pro-inflammatory cytokines and anti-inflammatory cytokine IL-10. The addition of IL-10-neutralizing antibodies abrogated the suppressive effect of Glyco-AGEs-BSA on osteoclast differentiation. Stimulation of Glyco-AGE-BSA resulted in nuclear factor (NF)-κB phosphorylation, and addition of an inhibitor of κB kinase suppressed IL-10 production. We conclude that Glyco-AGEs-BSA inhibited human osteoclast differentiation through induction of IL-10 expression via NF-κB. It can be assumed that AGE bioaccumulation in diabetic patients increases the risk of bone fracture, through inhibition of osteoclast differentiation, reduction of bone turnover, and disruption of bone remodeling.

Protective effects of Paeoniflorin against AOPP-induced oxidative injury in HUVECs by blocking the ROS-HIF-1α/VEGF pathway

BACKGROUND

Paeoniflorin, a monoterpene glycoside, exerts protective vascular effects, showing good antioxidant properties. However, whether Paeoniflorin has protective effect against the oxidative damage induced by advanced oxidation protein products (AOPPs) in Human umbilical vein endothelial cells (HUVECs) is unknown, as is the underlying mechanism.

PURPOSE

The present study was designed to investigate the effect of Paeoniflorin on oxidative damage of HUVECs and elucidate its underlying molecular mechanisms.

METHODS

The fluorescence intensity of 2', 7'-dichlorofluorescein-diacetate (DCFH-DA) staining was detected for intracellular reactive oxygen species (ROS) production. The increases mitochondrial membrane potential (MMP) was measured via flow cytometry and confocal microscopy using MitoTracker® Deep Red/ MitoTracker® Green staining. The intracellular adenosine triphosphate (ATP) was measured by ATP Determination Kit according to the manufacturer's protocol. Nox2, Nox4, hypoxia inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and nuclear factor-κB (NF-κB) p65 expressions were detected by western blot.

RESULTS

Our results showed that Paeoniflorin increases MMP and ATP levels of HUVECs induced by AOPPs, and attenuates NF-κB p65 expression on HUVECs might mainly result from its antioxidant capability by suppressing ROS production. Moreover, we also found that Paeoniflorin can suppress HIF-1α and VEGF protein expression through a decrease of ROS production via down-regulation of Nox2/Nox4 expression in HUVECs. AOPP-induced RAGE mRNA up-regulation was blocked by Paeoniflorin treatment in HUVECs.

CONCLUSION

Our results provided the first experimental that Paeoniflorin protects against AOPP-induced oxidative damage in HUVECs, mainly through a mechanism involving a decrease in ROS production by the inhibition of Nox2/Nox4 and RAGE expression; restored ATP depletion and mitochondria dysfunction via ROS suppression; and down-regulated HIF-1α/VEGF, possibly via the ROS-NF-κB axis.

Advanced glycation end-products produced systemically and by macrophages: A common contributor to inflammation and degenerative diseases

Advanced glycation end products (AGEs) and their receptor have been implicated in the progressions of many intractable diseases, such as diabetes and atherosclerosis, and are also critical for pathologic changes in chronic degenerative diseases, such as Alzheimer's disease, Parkinson's disease, and alcoholic brain damage. Recently activated macrophages were found to be a source of AGEs, and the most abundant form of AGEs, AGE-albumin excreted by macrophages has been implicated in these diseases and to act through common pathways. AGEs inhibition has been shown to prevent the pathogenesis of AGEs-related diseases in human, and therapeutic advances have resulted in several agents that prevent their adverse effects. Recently, anti-inflammatory molecules that inhibit AGEs have been shown to be good candidates for ameliorating diabetic complications as well as degenerative diseases. This review was undertaken to present, discuss, and clarify current understanding regarding AGEs formation in association with macrophages, different diseases, therapeutic and diagnostic strategy and links with RAGE inhibition.

The next generation of therapeutics for chronic kidney disease

Chronic kidney disease (CKD) represents a leading cause of death in the United States. There is no cure for this disease, with current treatment strategies relying on blood pressure control through blockade of the renin-angiotensin system. Such approaches only delay the development of end-stage kidney disease and can be associated with serious side effects. Recent identification of several novel mechanisms contributing to CKD development - including vascular changes, loss of podocytes and renal epithelial cells, matrix deposition, inflammation and metabolic dysregulation - has revealed new potential therapeutic approaches for CKD. This Review assesses emerging strategies and agents for CKD treatment, highlighting the associated challenges in their clinical development.

Bioactive compounds isolated from apple, tea, and ginger protect against dicarbonyl induced stress in cultured human retinal epithelial cells

BACKGROUND

Methylglyoxal (MGO) is known to be a major precursor of advanced glycation end products (AGEs) which are linked to diabetes and its related complications. Naturally occurring bioactive compounds could play an important role in countering AGEs thereby minimizing the risk associated with their formation.

METHODS

In this study, eight specific bioactive compounds isolated from apple, tea and ginger were evaluated for their AGEs scavenging activity using Human Retinal Pigment Epithelial (H-RPE) cells treated with MGO.

RESULTS

Among the eight specific compounds evaluated, (-)-epigallocatechin 3-gallate (EGCG) from tea, phloretin in apple, and [6]-shogaol and [6]-gingerol from ginger were found to be most effective in preventing MGO-induced cytotoxicity in the epithelial cells. Investigation of possible underlying mechanisms suggests that that these compounds could act by modulating key regulative detoxifying enzymes via modifying nuclear factor-erythroid 2-related factor 2 (Nrf2) function. MGO-induced cytotoxicity led to increased levels of AGEs causing increase in Nε-(Carboxymethyl) lysine (CML) and glutathione (GSH) levels and over expression of receptor for advanced glycation end products (RAGE). Data also showed that translocation of Nrf2 from cytosol to nucleus was inhibited, which decreased the expression of detoxifying enzyme like heme oxygenase-1 (HO-1). The most potent bioactive compounds scavenged dicarbonyl compounds, inhibited AGEs formation and significantly reduced carbonyl stress by Nrf2 related pathway and restoration of HO-1 expression.

CONCLUSIONS

These findings demonstrated the protective effect of bioactive compounds derived from food sources against MGO-induced carbonyl stress through activation of the Nrf2 related defense pathway, which is of significant importance for therapeutic interventions in complementary treatment/management of diabetes-related complications.

Soluble RAGE and atherosclerosis in youth with type 1 diabetes: a 5-year follow-up study

BACKGROUND

Advanced glycation end products (AGEs) play a role in the development of late complications and atherosclerosis in diabetes by engaging the receptor for advanced glycation end products, RAGE. Receptor binding leads to activation of the vascular endothelium and increased inflammation in the vessel wall. The soluble variants of the receptor, endogenous secretory RAGE (esRAGE) and the cleaved cell-surface part of RAGE, which together comprise soluble RAGE (sRAGE), are suggested to have a protective effect acting as decoys for RAGE. We aimed to test whether high levels of soluble variants of RAGE could be protective against atherosclerosis development.

METHODS

Participants in the prospective atherosclerosis and childhood diabetes study were examined at baseline (aged 8-18) and at follow-up after 5 years. Both sRAGE and esRAGE were measured by immunoassay in 299 patients with type 1 diabetes and 112 healthy controls at baseline and 241 patients and 128 controls at follow-up. The AGEs methylglyoxal-derived hydroimidazolone-1 (MG-H1) and carboxymethyllysine (CML) were measured by immunoassay. The surrogate markers of atherosclerosis assessed were carotid intima-media thickness (cIMT), C-reactive protein (CRP) and Young's modulus, measures of arterial wall thickness, inflammation and arterial stiffness, respectively.

RESULTS

Levels of sRAGE and esRAGE correlated strongly both at baseline and at follow-up in both diabetes patients and controls. With increasing age, mean values of both variants declined, independent of gender, diabetes or pubertal stage. In the diabetes group, multiple regression analysis showed a positive association between both variants of soluble RAGE and cIMT. There was no significant relationship with Young's modulus, but a negative association between sRAGE at baseline and CRP at follow-up. The ratios between the AGEs and the variants of soluble RAGE were increased in diabetes patients compared to controls.

CONCLUSIONS

The results show a possible protective effect of high levels of sRAGE at baseline against inflammation 5 years later, but not on arterial stiffness or wall thickness, in this cohort of adolescents and young adults with T1D.

LR-90 prevents methylglyoxal-induced oxidative stress and apoptosis in human endothelial cells

Methylglyoxal (MGO) is a highly reactive dicarbonyl compound known to induce cellular injury and cytoxicity, including apoptosis in vascular cells. Vascular endothelial cell apoptosis has been implicated in the pathophysiology and progression of atherosclerosis. We investigated whether the advanced glycation end-product inhibitor LR-90 could prevent MGO-induced apoptosis in human umbilical vascular endothelial cells (HUVECs). HUVECs were pre-treated with LR-90 and then stimulated with MGO. Cell morphology, cytotoxicity and apoptosis were evaluated by light microscopy, MTT assay, and Annexin V-FITC and propidium iodide double staining, respectively. Levels of Bax, Bcl-2, cytochrome c, mitogen-activated protein kinases (MAPKs) and caspase activities were assessed by Western blotting. Reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP) were measured with fluorescent probes. LR-90 dose-dependently prevented MGO-associated HUVEC cytotoxicity and apoptotic biochemical changes such as loss of MMP, increased Bax/Bcl-2 protein ratio, mitochondrial cytochrome c release and activation of caspase-3 and 9. Additionally, LR-90 blocked intracellular ROS formation and MAPK (p44/p42, p38, JNK) activation, though the latter seem to be not directly involved in MGO-induced HUVEC apoptosis. LR-90 prevents MGO-induced HUVEC apoptosis by inhibiting ROS and associated mitochondrial-dependent apoptotic signaling cascades, suggesting that LR-90 possess cytoprotective ability which could be beneficial in prevention of diabetic related-atherosclerosis.

Pharmaceutical properties of calycosin, the major bioactive isoflavonoid in the dry root extract of Radix astragali

CONTEXT

Radix astragali (Fabaceae astragalus propinquus Schischkin) is a Chinese medicinal herb traditionally used for the treatment of several diseases. Calycosin is the major bioactive chemical in the dry root extract of this medical plant.

OBJECTIVE

This work presents a brief overview of recent reports on the potential effects of calycosin on several diseases and the possible mechanisms of action of this chemical.

MATERIALS AND METHODS

This review gathers information from the scientific literature (before 1 June 2013) that was compiled from various databases, such as Science Direct, PubMed, Google Scholar, and Scopus.

RESULTS

The potential pharmaceutical properties of calycosin in the treatment of tumors, inflammation, stroke, and cardiovascular diseases have gained increasing attention in the recent years. The literature survey showed that calycosin exhibits promising effects for the treatment of several diseases and that these effects may be due to its isoflavonoid and phytoestrogenic properties. The effects of calycosin most likely result from its interaction with the ER receptors on the cell membrane and the modulation of the MAPK signaling pathway.

CONCLUSION

Calycosin exhibits great potential as a therapeutic drug and may be a successful example of the standardization and modernization of traditional Chinese herbal medicine.

Oxidative damage in diabetics: insights from a graduate study in La Reunion University

Due to the growing incidence of diabetes in developed nations, there is a compelling case to be made for teaching graduate students more deeply about mechanisms underlying this disease. Diabetes is associated with enhanced oxidative stress and protein glycation via the covalent binding of glucose molecules. Albumin represents the major plasmatic protein and undergoes enhanced glycoxidative modifications in diabetic condition. La Réunion Island, a French department located in the Indian Ocean exhibit a growing incidence of diabetes. At the University of La Réunion, our research group named GEICO (Groupe d'Etude sur l'Inflammation Chronique et l'Obésité) participated to foster research and training in diabetes context and focuses on the impact of glycated albumin mediated oxidative stress on cell physiopathology. A laboratory course was designed by our group to introduce graduate students to cutting edge techniques in redox biology while providing insights into scientific processes and methods. This two weeks research laboratory training took place at CYROI, a local biotechnology center that provides advanced facilities for research, business, and education. Using histochemistry, molecular biology, biochemical techniques, student investigated oxidative damages in liver from leptin receptor deficient diabetic mice compared to control littermates. In addition, they used an in vitro model by assaying oxidative impact of glycated albumin on hepatoma carcinoma HepG2 cells. This article gives an overview of the organization and protocol used by the students during their two weeks training in the laboratory. Therefore, it may be helpful for teaching graduate students techniques used in research laboratory working on redox biology.

The anti-inflammation effect of Moutan Cortex on advanced glycation end products-induced rat mesangial cells dysfunction and High-glucose-fat diet and streptozotocin-induced diabetic nephropathy rats

ETHNOPHARMACOLOGICAL RELEVANCE

Moutan Cortex (MC, family: Paeonia suffruticosa Andr.) is a well-known traditional herbal medicine that has been shown to hold a protective effect on inflammation in several diseases. However, its anti-inflammatory activity on diabetic nephropathy (DN) has been less reported. The present study was conducted to evaluate the potential attenuation activities of MC on inflammation in AGEs-induced rat mesangial cells dysfunction and high-glucose-fat diet and streptozotocin (STZ)-induced DN rats and explore the possible mechanism underlying its DN effect.

MATERIALS AND METHODS

The inflammation in mesangial cells (HBZY-1) was induced by 200 μg/ml advanced glycation end products (AGEs). DN rats model was established by an administration high-glucose-fat diet and an intraperitoneal injection of STZ (30 mg/kg). Interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) level in cell supernatant and rats serum were detected by appropriate kits. A co-culture system of mesangial cells and macrophages was performed to evaluate the migration of macrophages. Immunohistochemical assay was applied to examine transforming growth factor beta1 (TGF-β1), IL-6, MCP-1 and intercellular adhesion molecule-1 (ICAM-1) expression in kidney tissues of rats. Furthermore, western blot analysis was carried out to examine TGF-β1, IL-6, MCP-1, ICAM-1 and RAGE protein expressions in mesangial cells.

RESULTS

Pretreatment with MC could significantly inhibit AGEs-induced migration of macrophages in the co-culture system of mesangial cell and macrophage. MC could decrease IL-6 and MCP-1 levels in serum of DN rats in a dose-dependent manner. Furthermore, MC also improved the blood glucose, serum creatinine and urine protein levels. Both immunocytochemistry analysis and western blot analysis showed that MC decreased significantly the over-expression of IL-6, MCP-1, TGF-β1, ICAM-1 and RAGE in mesangial cells or kidney tissues. Additionally, the protein expression of proinflammatory cytokine could also be down-regulated by the pretreatment of RAGE-Ab (5 μg/ml).

CONCLUSION

These findings indicated that the extract of MC had an amelioration activity on the inflammation in AGEs-induced mesangial cells dysfunction and high-glucose-fat diet and STZ-induced DN rats. The protective effect might be associated with the intervention of MC via target of RAGE. These findings suggested that MC might be a benefit agent for the prevention and treatment of DN.

Effects of monascin on anti-inflammation mediated by Nrf2 activation in advanced glycation end product-treated THP-1 monocytes and methylglyoxal-treated wistar rats

Hyperglycemia is associated with advanced glycation end products (AGEs). This study was designed to evaluate the inhibitory effects of monascin on receptor for advanced glycation end product (RAGE) signal and THP-1 monocyte inflammation after treatment with S100b, a specific ligand of RAGE. Monascin inhibited cytokine production by S100b-treated THP-1 monocytes via up-regulation of nuclear factor-erythroid 2-related factor-2 (Nrf2) and alleviated p47phox translocation to the membrane. Methylglyoxal (MG, 600 mg/kg bw) was used to induce diabetes in Wistar rats. Inhibitions of RAGE and p47phox by monascin were confirmed by peripheral blood mononuclear cells (PBMCs) of MG-induced rats. Silymarin (SM) was used as a positive control group. It was found that monascin promoted heme oxygenase-1 (HO-1) expression mediated by Nrf2. Suppressions of AGEs, tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-β) in serum of MG-induced rats were attenuated in the monascin administration group treated with retinoic acid (RA). RA treatment resulted in Nrf2 inactivation by increasing RA receptor-α (RARα) activity, suggesting that RA acts as an inhibitor of Nrf2. The results showed that monascin exerted anti-inflammatory and antioxidative effects mediated by Nrf2 to prevent the development of diseases such as type 2 diabetes caused by inflammation.

Proinflammatory effects of malondialdehyde in lymphocytes

Diabetes is an inflammatory disease promoted by alterations in immune cell function. Animal study indicates that T cells are important mediators of inflammation in diabetes. Lipid peroxidation by reactive oxygen species leads to the formation of highly reactive malondialdehyde (MDA), and extensive MDA is found in diabetes. However, the biological functions of MDA have not been studied yet. We hypothesized that increased MDA, as in diabetes, can regulate inflammatory cytokines via specific signaling pathways. This could then result in increased lymphocyte activation and skewing a particular inflammatory subset thereby exacerbates diabetes complications. Commercial cytokine antibody and RT(2)-PCR array profiling were performed with Jurkat T cells grown with or without MDA. Ingenuity pathways analysis (IPA) and pharmacological inhibitors were used for networks and signaling pathway identification, respectively. For validation, real-time PCR, RT-PCR, and Western blots were performed. MDA induced significant increases in 47 key proinflammatory molecules such as IL-25, IL-6, IL-8, ICAM-1, and light mRNA in Jurkat T cells and primary peripheral blood lymphocytes (PBLCs). A significant 2-fold increase in serum MDA also correlated the increased IL-25 and IL-8 mRNA in PBLCs of diabetic patients. Pharmacological inhibitor studies showed that MDA induced its effect via p38MAPK and protein kinase C pathways. Furthermore, IPA uncovered 5 groups of inflammatory networks and placed our candidate genes in canonical IL-6 and NF-κB signaling pathways and also suggested 5 toxic lists and 3 major toxic functions, namely cardiotoxicity, hepatotoxicity, and nephrotoxicity. These new results suggest that MDA can promote lymphocyte activation via induction of inflammatory pathways and networks.

Attenuation of aortic injury by ursolic acid through RAGE-Nox-NFκB pathway in streptozocin-induced diabetic rats

Vascular complications are the leading causes of morbidity and mortality in diabetes mellitus (DM). The RAGE (receptor for advanced glycation end products)-NADPH oxidase-NF-κB signal transduction pathway plays an important role in the development of oxidative stress-related vascular complications in DM. Ursolic acid (UA), a pentacyclic triterpenoid derived from plants, has been reported to have multiple pharmacological effects, including a potent antioxidant activity. This study aimed to investigate both the effect of UA on aortic injury in streptozotocin (STZ)-induced diabetic rats and the drug's mechanism of action. STZ-induced diabetic animals were randomized in one of the following 4 groups: no treatment (diabetic model group), aminoguanidine (AG, 100 mg/kg), high-dose UA (50 mg/kg), and low-dose UA (25 mg/kg). A non-diabetic control group was followed concurrently. After 8 weeks, the diabetic model rats exhibited: severe aortic arch injury, histologically elevated serum glucose, fructosamine, and glycosylated hemoglobin; and accumulation of advanced glycation end products (AGEs) in the arota. In addition, the levels of RAGE protein, transcription factor NF-κB p65, and the p22phox subunit of NADPH oxidase were increased, as were the serum levels of malondialdehyde and tumor necrosis factor-alpha (TNF-α; p < 0.01 vs control), suggesting that the mechanisms of oxidative stress contributed to vascular injury in the diabetic model group. In contrast, rats treated with UA (50 mg/kg) had a markedly less vascular injury and significantly improved biochemical parameters. Oxidative balance was also normalized in the UA-treated rats, and a marked reduction in the levels of RAGE and p22phox paralleled the reduced activation of NF-κB p65 and TNF-α (p < 0.01 and p < 0.05, respectively, vs diabetic model). These findings suggest that UA may suppress oxidative stress, thus blunting activation of the RAGE-NADPH oxidase-NF-κB signal transduction pathway, to ameliorate vascular injury in the STZ-induced DM rats.

Phytoestrogen calycosin-7-O-β-D-glucopyranoside ameliorates advanced glycation end products-induced HUVEC damage

Vasculopathy including endothelial cell (EC) apoptosis and inflammation contributes to the high incidence of stroke and myocardial infarction in diabetic patients. The aim of the present study was to investigate the effect of calycosin-7-O-β-D-glucopyranoside (CG), a phytoestrogen, on advanced glycation end products (AGEs)-induced HUVEC damage. We observed that CG can significantly ameliorate AGEs-induced HUVEC oxidative stress and apoptosis. The ratio of SOD/MDA was significantly increased to the normal level by CG pretreatment. CG preincubation dramatically increased anti-apoptotic Bcl-2 while decreased pro-apoptotic Bax and Bad expressions as detected by immunocytochemistry. Moreover, CG ameliorated macrophage migration and adhesion to HUVEC; the monocyte chemotactic protein-1 and interleukin-6 levels in the culture supernatant were dramatically reduced by CG as determined by ELISA; the expressions of inflammatory proteins including ICAM-1, TGF-β1, and RAGE in both protein and mRNA levels were significantly reduced to the normal level by CG pretreatment as determined by immunocytochemistry and real-time RT-PCR. The intracellular investigation suggests that CG can reverse AGEs-activated ERK1/2 and NF-κB phosphorylation, in which estrogen receptors were involved in. Our results strongly indicate that CG can modulate EC dysfunction by ameliorating AGEs-induced cell apoptosis and inflammation.

Chelation: a fundamental mechanism of action of AGE inhibitors, AGE breakers, and other inhibitors of diabetes complications

This article outlines evidence that advanced glycation end product (AGE) inhibitors and breakers act primarily as chelators, inhibiting metal-catalyzed oxidation reactions that catalyze AGE formation. We then present evidence that chelation is the most likely mechanism by which ACE inhibitors, angiotensin receptor blockers, and aldose reductase inhibitors inhibit AGE formation in diabetes. Finally, we note several recent studies demonstrating therapeutic benefits of chelators for diabetic cardiovascular and renal disease. We conclude that chronic, low-dose chelation therapy deserves serious consideration as a clinical tool for prevention and treatment of diabetes complications.

Deletion of bone marrow-derived receptor for advanced glycation end products inhibits atherosclerotic plaque progression

BACKGROUND

The multiligand receptor for advanced glycation end products (RAGE) of the immunoglobulin superfamily is expressed on multiple cell types implicated in the inflammatory response in atherosclerosis. We sought to determine the role of bone marrow-derived RAGE in different stages of atherosclerotic development in apolipoprotein E-deficient mice (apoE(-/-)).

METHODS

Seven- and 23-week-old apoE(-/-) mice (n = 40) were lethally irradiated and given bone marrow from RAGE null (RAGE(-/-)/apoE(-/-)) or RAGE-bearing (RAGE(+/+)/apoE(-/-)) mice to apoE(-/-) mice to generate double knockout bone marrow chimera (RAGE(-/-)/apoE(-/-bmc) and RAGE(+/+)/apoE(-/-bmc)-, respectively). After 16 weeks on a standard chow diet, mice were sacrificed and atherosclerotic lesion formation was evaluated.

RESULTS

Plaques in the aortic root of the young mice showed no significant difference in maximum plaque size (217,470 ± 17,480 μm(2) for the RAGE(-/-) /apoE(-/-bmc) mice compared to 244,764 ± 45,840 μm(2)), whereas lesions in the brachiocephalic arteries of the older RAGE(-/-)/apoE(-/-bmc) mice had significantly smaller lesions (94,049 ± 13,0844 μm(2) vs. 145,570 ± 11,488 μm(2), P < 0.05) as well as reduced average necrotic core area (48,600 ± 9220 μm(2) compared to 89,502 ± 10,032 μm(2), P < 0.05) when compared to RAGE(+/+)/apoE(-/-bmc) mice. Reduced plaque size and more stable plaque morphology was associated with significant reduced expression of VCAM-1, ICAM-1 and MCP-1. Accumulation of the RAGE ligand HMGB-1 was also significantly reduced within the lesions of RAGE(-/-)/apoE(-/-bmc) mice.

CONCLUSIONS

This study demonstrates that bone marrow-derived RAGE is an important factor in the progression of atherosclerotic plaques.

Calycosin protects HUVECs from advanced glycation end products-induced macrophage infiltration

ETHNOPHARMACOLOGICAL RELEVANCE

Astragali radix is a traditional Chinese medicine that has long been used for treatment of diabetes and diabetes-associated disease, but its active component and mechanism on the disease is not well defined.

AIM OF THE STUDY

Infiltration of leukocytes within the glomeruli and vasculature is one of the early and characteristic features of diabetic nephropathy. Advanced glycation end products (AGEs) play pivotal role in the progression of diabetic-associated diseases. The present study was designed to explore the therapeutic effect of calycosin, an active component from A. radix, on AGEs-induced macrophages infiltration in HUVECs.

MATERIALS AND METHODS

Transwell HUVEC-macrophage co-culture system was established to evaluate macrophage migration and adhesion. Immunocytochemistry was applied to examine TGF-beta1, ICAM-1 and RAGE protein expressions; real-time PCR was carried out to determine mRNA expression of TGF-beta1, ICAM-1 and RAGE. Immunofluorescence was carried out to observe estrogen receptor-alpha, ICAM-1, RAGE expression and the phosphorylation status of ERK1/2 and NF-κB.

RESULTS

Calycosin significantly reduced AGEs-induced macrophage migration and adhesion to HUVEC. Pre-treatment with calycosin strikingly down-regulated HUVEC TGF-beta1, ICAM-1 and RAGE expressions in both protein and mRNA levels. Furthermore, calycosin incubation significantly increased estrogen receptor expression and reversed AGEs-induced ERK1/2 and NF-κB phosphorylation and nuclear translocation in HUVEC, and this effect of calycosin could be inhibited by estrogen receptor inhibitor, ICI182780.

CONCLUSIONS

These findings suggest that calycosin can reduce AGEs-induced macrophage migration and adhesion to endothelial cells and relieve the local inflammation; furthermore, this effect was via estrogen receptor-ERK1/2-NF-κB pathway.

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.

Combination of Medicinal Herbs KIOM-79 Reduces Advanced Glycation End Product Accumulation and the Expression of Inflammatory Factors in the Aorta of Zucker Diabetic Fatty Rats

Previous studies have reported that KIOM-79 shows a strong inhibitory effect on AGE formation and inhibited a proinflammatory state in a murine macrophage cell line. In the present study, we investigated the effect of KIOM-79 on AGE accumulation and vascular inflammation in the aorta of Zucker diabetic fatty (ZDF) rats, a commonly used model of type 2 diabetes. Seven-week-old male ZDF rats were treated with KIOM-79 (50 mg/kg) once a day orally for 13 weeks. We examined the dissected aortas for AGE accumulation, expression of the receptor for AGEs (RAGE), and the expression of proinflammatory factors, including monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF), and vascular adhesion molecule-1 (VCAM-1). Nuclear factor-kappaB (NF-κB) and inducible nitric oxide synthase (iNOS) were also measured by Southwestern histochemistry, electrophoretic mobility shift assay (EMSA), and immunohistochemistry, respectively. KIOM-79 markedly reduced the accumulation of AGEs and the expression of RAGE in the aorta. We also found that KIOM-79 attenuated the expression of inflammatory factors including NF-κB, MCP-1, VEGF, VCAM-1, and iNOS in the aortas of ZDF rats. These data suggest that KIOM-79 may prevent or retard the development of inflammation in diabetic vascular disease.

Silymarin: a novel antioxidant with antiglycation and antiinflammatory properties in vitro and in vivo

The current study was designed to evaluate the effects of silymarin (SM) on advanced glycation endproduct (AGE) formation and monocyte activation induced by S100b, a specific ligand of receptor for AGEs. The in vivo verification of antiglycation, antioxidant, and antiinflammatory capacities was examined by 12 weeks of SM administration in streptozotocin-diabetic rats. In vitro glycation assays demonstrated that SM exerted marked inhibition during the late stages of glycation and subsequent crosslinking. Dual action mechanisms, namely, antioxidant and reactive carbonyl trapping activities, may contribute to its antiglycation effect. SM produced a significant decrease in monocytic interleukin-1β and COX-2 levels and prevented oxidant formation caused by S100b, which appeared to be mediated by inhibition of p47phox membrane translocation. Chromatin immunoprecipitation demonstrated that S100b increased the recruitment of nuclear factor-kappaB transcription factor as well as cAMP response element-binding-binding protein and coactivator-associated arginine methyltransferase-1 cofactors to the interleukin-1β promoter, whereas these changes were inhibited with SM treatment. In vivo, SM reduced tissue AGE accumulation, tail collagen crosslinking, and concentrations of plasma glycated albumin. Levels of oxidative and inflammatory biomarkers were also significantly decreased in SM-treated groups compared with the diabetic group. These data suggest that SM supplementation may reduce the burden of AGEs in diabetics and may prevent resulting complications.

Anti-inflammatory effect of the 5,7,4'-trihydroxy-6-geranylflavanone isolated from the fruit of Artocarpus communis in S100B-induced human monocytes

The fruit of Artocarpus communis Moraceae, a traditional starch crop, is a rich source of phytochemicals, such as flavonoids and their derivatives. The aim of this study was to investigate whether 5,7,4'-trihydroxy-6-geranylflavanone (AC-GF), a geranyl flavonoid derivative isolated from the fruits of A. communis, could decrease the activation of inflammatory mediators induced by S100B (ligand of receptor for advanced glycation end products, RAGE) in THP-1 monocytes. According to the results, low levels of AC-GF (≤2.5 μM) showed a great inhibitory effect on gene expression of RAGE and down-regulated both TNF-α and IL-1β secretion and gene expression (p < 0.05). AC-GF also decreased reactive oxygen species (ROS) production in response to S100B (p < 0.05). Additionally, Western blotting revealed that AC-GF could effectively attenuate RAGE-dependent signaling, including expression of protein kinase C (PKC) and p47phox, phosphorylation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK), and particularly NF-κB activation (p < 0.05). In conclusion, this is the first report that AC-GF possesses great antioxidant and anti-inflammatory properties in vitro. This finding may contribute to increased implication and utilization of the fruit of A. communis Moraceae in functional foods.

Plasma pentosidine: a potential biomarker in the management of multiple sclerosis

Background: The chronic inflammation associated with multiple sclerosis (MS) may lead to the upregulation of pentosidine.

Objectives: This cross-sectional study compares plasma pentosidine levels among healthy controls (HCs) and patients with MS at different disease stages. The study also determines pentosidine's usefulness as a biomarker of MS disease activity and/or severity via its correlation with a number of indicators of MS disease.

Methods: Pentosidine levels were analyzed in 98 MS patients and 43 HCs using reverse-phase high-pressure liquid chromatography with fluorescence detection.

Results: Plasma pentosidine levels were significantly higher in MS patients when compared with HCs ( p = 0.02). Patients on disease-modifying therapies (DMTs) had lower plasma pentosidine levels when compared with DMT-naïve patients ( p =  0.01). Pentosidine plasma levels correlated with indicators of MS disease severity, including Extended Disability Status Scale ( p = 0.03), MS Severity Scale ( p = 0.01), and MS Functional Composite ( p = 0.03). No correlation between pentosidine levels and age, rate of clinical relapse, and disease duration was observed.

Conclusions: Our results suggest that pentosidine could be a novel, inflammatory biomarker in MS clinical practice. Longitudinal studies are warranted to determine any causal relationship between changes in plasma pentosidine levels and MS disease pathology. These studies may pave the way for use of advanced glycation end product (AGE) inhibitors and AGE-breaking agents as new therapeutic modalities in MS.

[Oxidative stress: a review on metabolic signaling in type 1 diabetes]

Diabetic complications appear to be multifactorial process. The biochemical and pathological mechanisms are associated with chronic hyperglycemia of diabetes and the increased oxidative stress which has been postulated to play a central role in these disorders. Accumulating evidence suggests that oxidative cell injury caused by free radicals contributes to the development of type 1 diabetes (DM1) complications and decreased efficiency of antioxidant defenses (both enzymatic and nonenzymatic) seems to correlate with the severity of pathological tissue changes in DM1. In this review, we report as oxidative stress may exert deleterious effects in diabetes, as well as address current strategies in study to down-regulating vascular injury.

Advanced glycation end products enhance monocyte activation during human mixed lymphocyte reaction

Posttransplant diabetes mellitus (PTDM) is a frequent complication among transplant recipients. Ligation of advanced glycation end products (AGEs) with their receptor (RAGE) on monocytes/macrophages plays roles in the diabetes complications. The enhancement of adhesion molecule expression on monocytes/macrophages activates T-cells, leading to reduced allograft survival. We investigated the effect of four distinct AGE subtypes (AGE-2/AGE-3/AGE-4/AGE-5) on the expressions of intracellular adhesion molecule (ICAM)-1, B7.1, B7.2 and CD40 on monocytes, the production of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha and the proliferation of T-cells during human mixed lymphocyte reaction (MLR). AGE-2 and AGE-3 selectively induced the adhesion molecule expression, cytokine production and T-cell proliferation. The AGE-induced up-regulation of adhesion molecule expression was involved in the cytokine production and T-cell proliferation. AGE-2 and AGE-3 up-regulated the expression of RAGE on monocytes; therefore, the AGEs may activate monocytes, leading to the up-regulation of adhesion molecule expression, cytokine production and T-cell proliferation.

Naturally occurring flavonoids attenuate high glucose-induced expression of proinflammatory cytokines in human monocytic THP-1 cells

Activation of circulating monocytes by hyperglycemia is bound to play a role in inflammatory and atherosclerosis. In this study, we examined whether flavonoids (catechin, EGCG, luteolin, quercetin, rutin) - phytochemicals that may possible belong to a new class of advanced glycation end products (AGEs) inhibitors - can attenuate high glucose (15 mmol/L, HG)-induced inflammation in human monocytes. Our results show that all flavonoids significantly inhibited HG-induced expression of proinflammatory genes and proteins, including TNF-alpha, interleukin-1beta (IL-1beta), and cyclooxygenase (COX)-2, at a concentration of 20 microM. Flavonoids also prevented oxidative stress in activated monocytes, as demonstrated by their inhibitory effects on intracellular reactive oxygen species (ROS) and N(epsilon)-(carboxymethyl)lysine formation caused by HG. These inhibitory effects may involve inhibition of nuclear factor-kappaB activation and may be supported by downregulation of the following: i) PKC-dependent NADPH oxidase pathway; ii) phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated protein kinase, and iii) mRNA expression of receptor of AGEs. In addition, we found for the first time that lower levels of Bcl-2 protein under HG conditions could be countered by the action of flavonoids. Our data suggest that, along with their antioxidant activities, flavonoids possess anti-inflammatory properties and might therefore have additional protective effects against glycotoxin-related inflammation.

Advanced glycation end products subspecies-selectively induce adhesion molecule expression and cytokine production in human peripheral blood mononuclear cells

Advanced glycation end products (AGEs) are proteins or lipids that become glycated after exposure to diverse reducing sugars. Accumulation of AGEs induces diabetes complications. Microinflammation is a common major mechanism in the pathogenesis of diabetic vascular complications. Activation of monocytes/macrophages and T cells plays roles in the pathogenesis of atherosclerosis. The activation of T cells requires the enhanced expression of adhesion molecules on monocytes. AGEs activate monocytes by engaging the receptor for AGE (RAGE); however, little is known about the profile of agonist activity of diverse AGE moieties on monocytes. We investigated the effect of four distinct AGE subtypes (AGE-modified bovine serum albumin; AGE-2, AGE-3, AGE-4, and AGE-5) at concentrations ranging from 0.1 to 100 microg/ml on the expression of intercellular adhesion molecule-1, B7.1, B7.2, and CD40 on monocytes and its impact on the production of interferon-gamma and tumor necrosis factor-alpha in human peripheral blood mononuclear cells. Among the AGEs examined, AGE-2 and AGE-3 selectively induced adhesion molecule expression and cytokine production. Antagonism experiments using antibodies against adhesion molecules demonstrated that cell-to-cell interaction between monocytes and T/natural killer cells was involved in AGE-2- and AGE-3-induced cytokine production. AGE-2 and AGE-3 up-regulated the expression of RAGE on monocytes. The effects of AGE-2 and AGE-3 were inhibited by nuclear factor-kappaB and p38 mitogen-activated protein kinase inhibitors. These results indicated that AGE-2 and AGE-3 activated monocytes via RAGE, leading to the up-regulation of adhesion molecule expression and cytokine production.

Curcumin ameliorates high glucose-induced acute vascular endothelial dysfunction in rat thoracic aorta

1. The aims of the present study were to explore the protective effect of curcumin against the acute vascular endothelial dysfunction induced by high glucose and to investigate the possible role of heme oxygenase (HO)-1 in this protective action. 2. Thoracic aortic rings, with or without endothelium, obtained from male Sprague-Dawley rats were mounted in an organ bath. Isometric contraction of the rings was recorded. After completion of the organ bath studies, rings were homogenized and centrifuged (30,000 g, 4 degrees C, 15 min) and HO activity was determined in the supernatant. 3. After 2 h incubation of aortic rings in the presence of high glucose (44 mmol/L), the relaxation evoked by acetylcholine (3 x 10(-8) to 3 x 10(-5) mol/L) was significantly decreased only in rings with an intact endothelium. When rings were coincubated in the presence of curcumin (10(-13) to 10(-11) mol/L) and high glucose, curcumin reversed the vasodilator dysfunction induced by high glucose dose dependently. 4. Curcumin (10(-11) mol/L) increased HO activity in the aortic rings compared with activity in control rings (63.1 +/- 3.6 vs control 43.2 +/- 2.9 pmol/mg per h, respectively; P < 0.01). Protoporphyrin IX zinc (10(-6) mol/L), an inhibitor of HO-1, offset the protective effects of curcumin. In addition, the non-selective guanylate cyclase (GC) inhibitor methylene blue (10(-6) mol/L) completely abolished the protective effects of curcumin. 5. In conclusion, the results of the present study show that curcumin alleviates the acute endothelium-dependent vasodilator dysfunction induced by high glucose in rat aortic rings. Increased HO-1 activity and stimulation of GC may be involved in the protective effects of curcumin.

The role of inflammation on atherosclerosis, intermediate and clinical cardiovascular endpoints in type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with increased cardiovascular morbidity and mortality. Sub-clinical systemic inflammation is often present in T2DM patients. Systemic inflammation has also been implicated in the pathophysiology of atherosclerosis. This review investigates the direct evidence present in literature for the effect of inflammation on atherosclerosis, specifically in the setting of T2DM. Special emphasis is given to the pathogenesis of atherosclerosis as well as intermediate and clinical cardiovascular endpoints. The important role of deteriorated endothelial function in T2DM was excluded from the analysis.

METHODS

Extensive literature searches were performed using the PubMed and Web of Science databases. Articles were identified, retrieved and accepted or excluded based on predefined criteria.

RESULTS

Substantial evidence was found for an important inflammatory component in the pathogenesis of atherosclerosis in T2DM, demonstrated by inflammatory changes in plaque characteristics and macrophage infiltration. Most epidemiologic studies found a correlation between inflammation markers and intermediate cardiovascular endpoints, especially intima-media thickness. Several, but not all clinical trials in T2DM found that reducing sub-clinical inflammation had a beneficial effect on intermediate endpoints. When regarding cardiovascular events however, current literature consistently indicates a strong relationship between inflammation and clinical endpoints in subjects with T2DM.

CONCLUSION

Current literature provides direct evidence for a contribution of inflammatory responses to the pathogenesis of atherosclerosis in T2DM. The most consistent relation was observed between inflammation and clinical endpoints.

Ablation of NF-kappaB expression by small interference RNA prevents the dysfunction of human umbilical vein endothelial cells induced by high glucose

Diabetes is a major independent risk factor for cardiovascular disease and stroke. High glucose (HG) reduces endothelial cell (EC) proliferation with a concomitant increase in apoptosis. HG also induces the translocation of nuclear factor (NF)-kappaB in human umbilical vein endothelial cells (HUVECs). However, data regarding the relationship between NF-kappaB signaling and HG-induced endothelial dysfunction are limited. In the present study, we constructed an NF-kappaB-targeting RNA interference (RNAi) adenovirus vector and cultured HUVECs in 5.5, 20.5, or 30.5 mM D: -glucose or in daily alternating 5.5 or 30.5 mM D: -glucose. We assessed the effects of the NF-kappaB pathway on proliferation under HG conditions by measuring bromodeoxyuridine incorporation and conducting methyl thiazolyltetrazolium assays. We also tested apoptosis by performing flow cytometry and terminal deoxynucleotidyl transferase nick-end labeling assay. The RNAi adenovirus effectively downregulated expression of the p65 protein in HUVECs for more than 6 days. Blockage of the NF-kappaB pathway with the RNAi adenovirus substantially protected HUVECs from decreased proliferation and reduced cellular apoptosis in HG conditions. These findings may explain how hyperglycemia promotes dysfunction of ECs and could elucidate a potential new target for therapeutic interventions.

Agents in development for the treatment of diabetic nephropathy

BACKGROUND

Nephropathy is a major cause of morbidity and mortality in diabetic patients. Current treatments include optimization of glycemic and blood pressure control, but more innovative strategies are needed for the prevention and treatment of diabetic nephropathy.

OBJECTIVES

To review emerging therapies for diabetic nephropathy.

METHODS

This paper discusses the molecular mechanisms of diabetic nephropathy and the potential therapeutic interventions.

RESULTS/CONCLUSION

New therapies, including those targeting the accumulation of advanced glycation end products (AGEs) and reactive oxygen species (ROS) generation, are likely to feature in future treatment regimens. Other approaches that at this stage do not appear to be progressing include the glycosaminoglycan sulodexide and the protein kinase C-beta (PKC-beta) inhibitor, ruboxistaurin.

Oxidative stresses induced by glycoxidized human or bovine serum albumin on human monocytes

Oxidative stress and protein modifications are frequently observed in numerous disease states. Albumin, the major circulating protein in blood, can undergo increased glycoxidation in diabetes. Protein glycoxidation can lead to the formation of advanced glycoxidation end products, which induce various deleterious effects on cells. Herein, we report the effect of glucose or methylglyoxal-induced oxidative modifications on BSA or HSA protein structures and on THP1 monocyte physiology. The occurrence of oxidative modifications was found to be enhanced in glycoxidized BSA and HSA, after determination of their free thiol group content, relative electrophoretic migration, carbonyl content, and antioxidant activities. Cells treated with glycoxidized albumin exhibited an overgeneration of intracellular reactive oxygen species, impairments in proteasomal activities, enhancements in RAGE expression, and an accumulation of carbonylated proteins. These novel observations made in the presence of a range of modified BSA and HSA facilitate the comparison of the glycoxidation extent of albumin with the oxidative stress induced in cultured monocytes. Finally, this study reconfirms the influence of experimental conditions in which AGEs are generated and the concentration levels in experiments designed to mimic pathological conditions.

LR-90 prevents dyslipidaemia and diabetic nephropathy in the Zucker diabetic fatty rat

AIMS/HYPOTHESIS

Previous studies have shown that LR-90, a new inhibitor of AGE formation, prevented the development of experimental type 1 diabetic nephropathy. In this study, we examined the effects of LR-90 in the Zucker diabetic fatty (ZDF) rat, a model of type 2 diabetes and metabolic syndrome, and investigated the mechanisms by which it may protect against renal injury.

METHODS

Male ZDF rats were treated without or with LR-90 from age 13 to 40 weeks. Metabolic and kidney functions and renal histology were evaluated. AGE accumulation and the production of the receptor for AGE (AGER) were measured. Profibrotic growth factors, extracellular matrix proteins and intracellular signalling pathways associated with glomerular and tubular damage were also analysed.

RESULTS

LR-90 dramatically reduced plasma lipids in ZDF rats, with only modest effects on hyperglycaemia. Renal AGE, AGER and lipid peroxidation were all attenuated by LR-90. LR-90 significantly retarded the increase in albuminuria and proteinuria. This was associated with reduction in glomerulosclerosis and tubulointerstitial fibrosis, concomitant with marked inhibition of renal overproduction of TGF-beta1, connective tissue growth factor, fibronectin and collagen IV. Additionally, LR-90 downregulated the activation of key mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NF-kappaB) in the renal cortex.

CONCLUSIONS/INTERPRETATION

These results support our earlier studies on the renoprotective effects of LR-90 on type 1 diabetic nephropathy and provide further evidence that LR-90, an AGE inhibitor with pleiotrophic effects, may also be beneficial for the prevention of type 2 diabetic nephropathy, where multiple risk factors, such as hyperglycaemia, dyslipidaemia, obesity, insulin resistance and hypertension, contribute to renal injury.