Comparison of protective effects of aspirin, d-penicillamine and vitamin E against high glucose-mediated toxicity in cultured endothelial cells

Effect of Amaranthus on Advanced Glycation End-Products Induced Cytotoxicity and Proinflammatory Cytokine Gene Expression in SH-SY5Y Cells

Amaranthus plants, or spinach, are used extensively as a vegetable and are known to possess medicinal properties. Neuroinflammation and oxidative stress play a major role in the pathogenesis of many neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease. Advanced glycation end-products (AGEs) cause cell toxicity in the human neuronal cell line, SH-SY5Y, through an increase in oxidative stress, as shown by reducing cell viability and increasing cell toxicity in a dose-dependent manner. We found that preincubation of SH-SY5Y cells with either petroleum ether, dichloromethane or methanol extracts of A. lividus and A. tricolor dose-dependently attenuated the neuron toxicity caused by AGEs treatment. Moreover, the results showed that A. lividus and A. tricolor extracts significantly downregulated the gene expression of the pro-inflammatory cytokines, TNF-α, IL-1 and IL-6 genes in AGEs-induced cells. We concluded that A. lividus and A. tricolor extracts not only have a neuroprotective effect against AGEs toxicity, but also have anti-inflammatory activity by reducing pro-inflammatory cytokine gene expression. This suggests that Amaranthus may be useful for treating chronic inflammation associated with neurodegenerative disorders.

Molecular strategies to prevent, inhibit, and degrade advanced glycoxidation and advanced lipoxidation end products

The advanced glycoxidation end products (AGEs) and lipoxidation end products (ALEs) contribute to the development of diabetic complications and of other pathologies. The review discusses the possibilities of counteracting the formation and stimulating the degradation of these species by pharmaceuticals and natural compounds. The review discusses inhibitors of ALE and AGE formation, cross-link breakers, ALE/AGE elimination by enzymes and proteolytic systems, receptors for advanced glycation end products (RAGEs) and blockade of the ligand-RAGE axis.

The antioxidant 3H-1,2-dithiole-3-thione potentiates advanced glycation end-product-induced oxidative stress in SH-SY5Y cells

Oxidative stress is implicated as a major factor in the development of diabetes complications and is caused in part by advanced glycation end products (AGEs). AGEs ligate to the receptor for AGEs (RAGE), promoting protein kinase C (PKC)-dependent activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and superoxide radical generation. While scavenging antioxidants are protective against AGEs, it is unknown if induction of endogenous antioxidant defenses has the same effect. In this study, we confirmed that the compound 3H-1,2-dithiole-3-thione (D3T) increases reduced-state glutathione (GSH) concentrations and NADPH:quinone oxidoreductase 1 (NQO1) activity in SH-SY5Y cells and provides protection against H₂O₂. Surprisingly, D3T potentiated oxidative damage caused by AGEs. In comparison to vehicle controls, D3T caused greater AGE-induced cytotoxicity and depletion of intracellular GSH levels while offering no protection against neurite degeneration or protein carbonylation. D3T potentiated AGE-induced reactive oxygen species (ROS) formation, an effect abrogated by inhibitors of PKC and NADPH oxidase. This study suggests that chemical induction of endogenous antioxidant defenses requires further examination in models of diabetes.

Differential effects of α-tocopherol and N-acetyl-cysteine on advanced glycation end product-induced oxidative damage and neurite degeneration in SH-SY5Y cells

Advanced glycation end products (AGEs) result from non-enzymatic glycation of proteins and cause cellular oxidative stress in a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent manner. Due to these effects, AGEs are implicated as a causal factor in diabetic complications. Several antioxidants, including vitamin E, improve cell viability and diminish markers of oxidative damage in cells exposed to AGEs. However, vitamin E has been studied in cell culture systems with primary focus on apoptosis and lipid peroxidation, while its influences on AGE-induced protein and DNA oxidation, intracellular antioxidant status and cell morphology remain largely unknown. Here, we verify the suppression of AGE-induced cell death and lipid peroxidation by 200μM α-tocopherol in SH-SY5Y cells. We report the partial inhibition of DNA oxidation and a decrease in protein carbonyl formation by α-tocopherol with no effects on intracellular GSH concentrations. We observed that 2mM N-acetyl cysteine (NAC) also had a suppressive effect on DNA and protein oxidation, but unlike α-tocopherol, it caused a marked increase in intracellular GSH. Finally, we compared the ability of both antioxidants to maintain neurites in SH-SY5Y cells and found that α-tocopherol had no effect on neurite loss due to AGEs, while NAC fully maintained cell morphology. Thus, while α-tocopherol suppressed AGE-induced macromolecule damage, it was ineffective against neurite degeneration. These results may implicate thiol oxidation and maintenance as a major regulator of neurite degeneration in this model.

NO/peroxynitrite dynamics of high glucose-exposed HUVECs: chemiluminescent measurement and computational model

Pathogenesis of many of diabetes-related vascular complications is associated with endothelial cell (EC) dysfunction, which is reduced bioavailability of EC-released nitric oxide (NO). Interaction dynamics of NO, superoxide (O(2)(-)) and peroxynitrite (ONOO(-)) are dependent on both their productions and consumptions through various pathways. Quantitative knowledge of these interaction dynamics in high glucose-induced EC dysfunction remains poorly understood. We developed an integrated experimental and computational approach to gain a quantitative understanding of the interactions of NO, O(2)(-) and ONOO(-) in high glucose-exposed ECs. End-products, nitrite and nitrate, were measured using a chemiluminescence analyzer. A computational biochemical reaction network model was developed to predict the effect of high glucose on ECs NO, O(2)(-) and ONOO(-). ECs NO and O(2)(-) productions increased in high glucose as evidenced by increased total NOx concentration, primarily increasing nitrate concentration. The model predicted an increase in O(2)(-) and ONOO(-) concentrations and a decrease in NO concentration in high glucose conditions. Administration of superoxide dismutase (SOD) decreased O(2)(-) concentration and increased NO concentration, thus SOD improved high glucose-induced changes in these interactions. An important finding of this study was that the NO bioavailability decreased in high glucose conditions even though NO production of EC increased. The integrated approach provides a framework to predict NO, O(2)(-) and ONOO(-) concentrations and productions that are difficult to measure in one experiment and will be useful in further EC dysfunction studies.

Cellular, molecular and clinical aspects of vitamin E on atherosclerosis prevention

Randomised clinical trials and epidemiologic studies addressing the preventive effects of vitamin E supplementation against cardiovascular disease reported both positive and negative effects, and recent meta-analyses of the clinical studies were rather disappointing. In contrast to that, many animal studies clearly show a preventive action of vitamin E in several experimental settings, which can be explained by the molecular and cellular effects of vitamin E observed in cell cultures. This review is focusing on the molecular effects of vitamin E on the cells playing a role during atherosclerosis, in particular on the endothelial cells, vascular smooth muscle cells, monocytes/macrophages, T cells, and mast cells. Vitamin E may act by normalizing aberrant signal transduction and gene expression in antioxidant and non-antioxidant manners; in particular, over-expression of scavenger receptors and consequent foam cell formation can be prevented by vitamin E. In addition to that, the cellular effects of alpha-tocopheryl phosphate and of EPC-K1, a composite molecule between alpha-tocopheryl phosphate and l-ascorbic acid, are summarized.

Bilirubin increases the expression of glucose transporter-1 and the rate of glucose uptake in vascular endothelial cells

BACKGROUND AND OBJECTIVES

The close contact between the endothelial cell monolayer in blood vessels and blood plasma allows free diffusion of the hydrophobic unconjugated bilirubin (BR) into these cells. BR can exert both anti- and pro-oxidative effects in various types of cells in a dose-dependent manner. High glucose levels downregulate the expression of the glucose transporter-1 (GLUT-1) and the rate of glucose uptake in vascular endothelial cell (VEC). Pro-oxidants, on the other hand, up-regulate this system in VEC. We aimed to investigate potential effects of BR on the glucose transport system in VEC.

METHODS

Primary cultures of bovine aortic endothelial cells were exposed to BR, and the rate of hexose transport, GLUT-1 expression and plasma membrane localization were determined.

RESULTS

BR induced oxidative stress in VEC, and significantly augmented the rate of glucose transport and GLUT-1 expression and plasma membrane localization in these cells. BR also reversed the high glucose-induced downregulation of the glucose transport system in VEC.

CONCLUSION

The pro-oxidative properties of BR are responsible for its effects on the regulation of glucose transport in vascular endothelium. Pathological concentrations of BR in the vascular compartment (jaundice) may influence the cellular handling of glucose in diabetes.

Protection against glycation and similar post-translational modifications of proteins

Glycation and other non-enzymic post-translational modifications of proteins have been implicated in the complications of diabetes and other conditions. In recent years there has been extensive progress in the search for ways to prevent the modifications and prevent the consequences of the modifications. These areas are covered in this review together with newer ideas on possibilities of reversing the chemical modifications.

Systemic and brain metabolic dysfunction as a new paradigm for approaching Alzheimer's dementia

Since its definition Alzheimer's disease has been at the centre of consideration for neurologists, psychiatrists, and pathologists. With John P. Blass it has been disclosed a different approach Alzheimer's disease neurodegeneration understanding not only by the means of neurochemistry but also biochemistry opening new scenarios in the direction of a metabolic system degeneration. Nowadays, the understanding of the role of cholesterol, insulin, and adipokines among the others in Alzheimer's disease etiopathogenesis is clarifying approaches valuable not only in preventing the disease but also for its therapy.