Rhodiola rosea ability to enrich cellular antioxidant defences of cultured human keratinocytes.

Keratinocytes are cells strongly exposed to oxidative stress, but normally good equipped for antioxidant responses. However, it has long been suggested that exogenous antioxidants could play a useful role in minimizing the adverse skin responses associated with such oxidant species. In this work it was paid attention to the extract of Rhodiola rosea L. roots by using the phytocomplex as a whole because of the important activity of its composition and mutual distribution of its components. We have measured the protection afforded by the extract to reduced glutathione levels, glyceraldehyde-3-phosphate dehydrogenase activity, and thiobarbituric acid reactive substances levels in cultured human keratinocytes (NCTC 2544) exposed to different oxidative insults: Fe(II)/ascorbate, Fe(II)/H(2)O(2), and tert-butyl-hydroperoxide. We also have investigated the influence of the R. rosea extract on the production of intracellular reactive oxygen species and on the activity of antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase). Furthermore, we have demonstrated that R. rosea extract was able to increase in a time- and dose-dependent manner the activity of the trans plasma membrane oxido reductase activity as an indirect evaluation of the intracellular redox status and this effect was already evident with small concentration of the extract and in a long time. As a result, NCTC 2544 are able to better counteract to several oxidative insults if incubated with R. rosea extract demonstrating a very good antioxidant activity of this phytocomplex.

Effects of a static magnetic field on cell growth and gene expression in Escherichia coli.

Escherichia coli cultures exposed to a 300mT static magnetic field (SMF) were studied in order to analyse possible induced changes in cellular growth and gene expression. Biomass was evaluated by visible-light spectrometry and gene expression analyses were carried out by use of RNA arbitrarily primed PCR. The bacterial strain XL-1Blue, cultivated in traditional and modified Luria-Bertani medium, was exposed to SMF generated by permanent neodymium magnetic disks. The results show alterations induced by SMF in terms of increased cell proliferation and changes in gene expression compared with control groups. Three cDNAs were found to be expressed only in the exposed cells, whereas one cDNA was more expressed in the controls. One clone, expressed only in the exposed cells, corresponds to a putative transposase. This is of particular interest in that it suggests that exposure to a magnetic field may stimulate transposition activity.

In vitro protective effect of Rhodiola rosea extract against hypochlorous acid-induced oxidative damage in human erythrocytes.

Rhodiola rosea L. (Crassulaceae) is a plant living at high altitudes in Europe and Asia. Its roots have long been used in the traditional medical system of these geographical areas to increase the organism resistance to physical stress; today, it has become an important component of many dietary supplements. In this study we investigate the antioxidant capacity of the R. rosea aqueous extract evaluating its ability to counteract some of the main damages induced by hypochlorous acid (HOCl), a powerful oxidant generated by activated phagocytes, to human erythrocytes. Ascorbic acid was used as a reference substance because of its physiological HOCl-scavenging ability. Our study demonstrates that R. rosea is able to significantly protect, in a dose-dependent manner, human RBC from glutathione (GSH) depletion, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) inactivation and hemolysis induced by the oxidant. Furthermore, we demonstrate that R. rosea aqueous extract acts from the inside of the erythrocyte suggesting a probable involving of cell components. The protection on GSH afforded by the R. rosea extract with respect to ascorbic acid, occurred also if added 2 or 5 min. later than the oxidant, suggesting a more rapid or powerful effect.

Intracellular flavonoids as electron donors for extracellular ferricyanide reduction in human erythrocytes.

Reduction of extracellular ferricyanide [Fe(CN)(6)](-3) to ferrocyanide by intact cells reflects the activity of a trans-plasma membrane oxidoreductase that, in human red blood cells, utilizes ascorbic acid as an electron donor. We herein report that the flavonoids quercetin and myricetin, while inhibiting dehydroascorbic acid uptake-and thus the erythrocyte ascorbic acid content-effectively stimulate the extracellular reduction of ferricyanide. Other flavonoids such as rutin, acacetin, apigenin, and genistein do not show the same effect. The notion that quercetin or myricetin may serve as an intracellular donor for a trans-plasma membrane oxidoreductase is supported by the following lines of evidence: (i) they afford direct reduction of ferricyanide; (ii) extracellular reduction of ferricyanide was not mediated by direct effects of the flavonoids released by the cells and was abolished by the sulphydryl reagent parachloromercuribenzenesulfonic acid (pCMBS); (iii) the intracellular concentrations of quercetin or myricetin well correlate with increases in ferricyanide reduction; (iv) the intracellular concentration of the flavonoids dramatically declines after ferricyanide exposure. Taken together, the results presented in this study demonstrate that myricetin and quercetin, which accumulate in large amounts in red blood cells, act as intracellular substrates of a pCMBS-sensitive trans-plasma membrane oxidoreductase. This may represent a novel mechanism whereby these flavonoids exert beneficial effects under oxidative stress conditions.