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Peroxynitrite was demonstrated to inhibit the active efflux of glutathione S-conjugates (2,4-dinitrophenyl-S-glutathione and bimane-S-glutathione) from human erythrocytes and the erythrocyte membrane ATPase activity stimulated by glutathione S-conjugates. As the multidrug resistance-associated protein (MRP) is responsible for the transport of glutathione S-conjugates in mammalian cells, these results point to the possibility of the effect of peroxynitrite on the MRP function.

Exposure to high glucose concentrations in vitro is often employed as a model for understanding erythrocyte modifications in diabetes. However, effects of such experiments may be affected by glucose consumption during prolonged incubation and changes of cellular parameters conditioned by impaired energy balance. The aim of this study was to compare alterations in various red cell parameters in this type of experiment to differentiate between those affected by glycoxidation and those affected by energy imbalance. Erythrocytes were incubated with 5, 45 or 100 mM glucose for up to 72 h. High glucose concentrations intensified lipid peroxidation and loss of activities of erythrocyte enzymes (glutathione S-transferase and glutathione reductase). On the other hand, hemolysis, eryptosis, calcium accumulation, loss of glutathione and increase in the GSSG/GSH ratio were attenuated by high glucose apparently due to maintenance of energy supply to the cells. Loss of plasma membrane Ca2+-ATPase activity and decrease in superoxide production were not affected by glucose concentration, being seemingly determined by processes independent of both glycoxidation and energy depletion. These results point to the necessity of careful interpretation of data obtained in experiments, in which erythrocytes are subject to treatment with high glucose concentrations in vitro.

Proliferation of human umbilical vein endothelial cells in vitro was inhibited by high concentrations of oxidants and nitric oxide donors but stimulated by low (micromolar or submicromolar) concentrations of hydrogen peroxide, menadione, tert-butyl hydroperoxide, AAPH, nitroglycerin, SIN-1 and sodium nitroprusside. The stimulation seems to be dependent upon generation of secondary reactive oxygen species as inferred from attenuation of cell proliferation by superoxide dismutase and catalase. These results point to another type of possible artefact of cell culture, viz. stimulation of cell proliferation by low concentrations of oxidants.

One of the nutritional benefits of mushrooms is the presence of bioactive secondary metabolites which have been reported to exert various beneficial effects in vivo. Therefore, we selected thirteen frequently consumed species of Polish mushrooms and determined the concentration of polyphenols, flavonoids, β-carotene, and lycopene in aqueous and methanolic extracts of dried fruiting bodies as well as their reducing power and ability to scavenge ABTS cation radical. We found that the concentration of antioxidants is different in different species and in various parts of the fruiting body of mushrooms. We observed a strong correlation (r > 0.9) between the concentration of total phenolics and reducing power/scavenging effects in both aqueous and methanolic extracts, while this correlation was moderate for flavonoids. Beta-carotene did not contribute discernibly to the antioxidative properties of the extracts, while lycopene had a significant contribution to the scavenging activity of methanolic mushroom extracts.

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Novel approaches to cancer chemotherapy employ metabolic differences between normal and tumor cells, including the high dependence of cancer cells on glycolysis ("Warburg effect"). 3-Bromopyruvate (3-BP), inhibitor of glycolysis, belongs to anticancer drugs basing on this principle. 3-BP was tested for its capacity to kill human non-invasive MCF-7 and invasive MDA-MB-231 breast cancer cells. We found that 3-BP was more toxic for MDA-MB-231 cells than for MCF-7 cells. In both cell lines, a statistically significant decrease of ATP and glutathione was observed in a time- and 3-BP concentration-dependent manner. Transient increases in the level of reactive oxygen species and reactive oxygen species was observed, more pronounced in MCF-7 cells, followed by a decreasing tendency. Activities of glutathione peroxidase, glutathione reductase (GR) and glutathione S-transferase (GST) decreased in 3-BP treated MDA-MB-231 cells. For MCF-7 cells decreases of GR and GST activities were noted only at the highest concentration of 3-BP.These results point to induction of oxidative stress by 3-BP via depletion of antioxidants and inactivation of antioxidant enzymes, more pronounced in MDA-MB-231 cells, more sensitive to 3-BP.