[Current views on antioxidative activity of glutathione and glutathione-depending enzymes].

Reduced glutathione (GSH), gamma-glutamyl-L-cysteineglycine, is a tripeptide widespread in plants, animals, and man as a low-molecular weight SH-containing compound. This review presents results of published and original studies concerned with the synthesis and the role of glutathione and glutathione-dependent enzymes in antioxidative processes, such as maintenance and regulation of cell status, glutathionilation and deglutathionilation, redox-dependent signaling, and apoptosis.

Involvement of thio-, peroxi-, and glutaredoxins in cellular redox-dependent processes.

Among the key antioxidant enzymes, thioredoxin and glutaredoxin systems play an important role in cell defense against oxidative stress and maintenance of redox homeostasis owing to the regulation of thiol-disulfide exchange. The thioredoxin isoforms Trx1 (cytoplasmic form) and Trx2 (mitochondrial form) can reduce inter- and intramolecular disulfide bonds in proteins, in particular, in oxidized peroxiredoxins, which disrupt organic hydroperoxides, H2O2, and peroxynitrite. NADPH-dependent thioredoxin reductase, which reduces a broad range of substrates including oxidized form of thioredoxin, can also directly reduce lipid hydroperoxides, H2O2, and dehydroascorbic and lipoic acids. Glutaredoxin, whose major isoforms in mammals are Grx1, Grx2, and Grx5, as well as thioredoxin, catalyzes S-glutathionylation and deglutathionylation of proteins to protect SH-groups from oxidation and restore functionally active thiols. However, in contrast to thioredoxin, glutaredoxin reduces GSH-mixed disulfides and catalyzes the reaction not only via a dithiol mechanism but also via monothiol reduction. In addition to the role in cellular antioxidant defense, all of the reviewed redox proteins (thioredoxin, thioredoxin reductase, peroxiredoxin, and glutaredoxin) have a number of significant functions required for cell viability: they regulate transcription factor activities, play the role of growth factors, serve as enzyme cofactors, take part in regulation of cell cycle, and are involved in antiapoptotic mechanisms.

[Why does iron abrogate the cytotoxic effect of S-nitrosothiols on human and animal cultured cells?].

It was found that dinitrosyl iron complexes (DNIC) with thiol-containing ligands (cysteine or glutathione) of concentrations up to 1 mM produce no cytotoxic effect on cultured cells from human milk gland carcinoma (MCF-7). The cytotoxic action on MCF-7 cells was produced by S-nitrosocysteine: at a concentration of 1 mM, it induced the death of 50% cells. A more stable S-nitrosothiol, S-nitrosoglutathione, did not produce any cytotoxic effect at the same concentration. It is assumed that the negative action of nitrosocysteine is due to its rapid degradation, which results in the accumulation of large amounts of free NO molecules followed by their oxidation by superoxide ions to peroxynitrite, an efficient inhibitor of metabolic processes. These processes seem to be not characteristic of the more stable S-nitrosoglutathione. The cytotoxic effect of nitrosocysteine was completlly abrogated by the addition of 0.2 mM ferrous citrate complex to the medium. When S-nitrosoglutathione NO (0.5 mM) or S-nitrosoglutathione (0.5 mM) + Fe(2+)-citrate (0.2 mM) were added to the medium, protein-bound dinitrosyl iron complexes formed with the involvement of endogenous or exogenous iron were detected in cells. The amount of the complexes in the presence of exogenous iron increased four times, reaching the value of 1.6 nmole/5 x 10(6) cells. Therefore, it was proposed that the blockade of the cytotoxic action of S-nitrosoglutathione by iron complexes is due to Cys-NO transformation of S-nitrosocysteine into dinitrosyl iron complexes. The high stability of these complexes ensures only a gradual accumulation of nitric oxide in cells.

Expression of genes for thioredoxin 1 and thioredoxin 2 in multidrug resistance ovarian carcinoma cells SKVLB.

The expression of genes for thioredoxin isoforms Trx1 and Trx2 was studied in sensitive SKOV-3 and resistant SKVLB human ovarian carcinoma cells. The development of doxorubicin resistance was accompanied by a significant increase in the expression of TRX1 gene and less pronounced increase in TRX2 gene expression.

Expression of genes for redox-dependent glutathione S-transferase isoforms GSTP1-1 and GSTA4-4 in tumor cell during the development doxorubicin resistance.

Expression of genes for redox-dependent glutathione S-transferase isoforms GSTP1-1 and GSTA4-4 in tumor cells K562, MCF-7, and SKOV-3 was studied during the development of resistance to doxorubicin. It was found that the development of resistance was accompanied by predominant increase in the expression of hGSTP1 gene in MCF-7 cells, and hGSTA4 gene in resistant K562/DOX and SKVLB cells.

Changes in expression of genes encoding antioxidant enzymes, heme oxygenase-1, Bcl-2, and Bcl-xl and in level of reactive oxygen species in tumor cells resistant to doxorubicin.

The relationship between expression of genes encoding key antioxidant enzymes, heme oxygenase-1, Bcl-2, and Bcl-xl and change in production of reactive oxygen species (ROS) resulting from development of resistance of cancer cells K562, MCF-7, and SKOV-3 to the prooxidant chemotherapeutic agent doxorubicin (DOX) has been studied. Significant increase in mRNA level and activity of Mn-superoxide dismutase (Mn-SOD), catalase, and selenium-dependent glutathione peroxidase-1 (GPx-1) and reduced ROS level was found in resistant K562/DOX and SKVLB cells. In contrast, no change in ROS level was observed in MCF-7/DOX cells in parallel with decrease in Mn-SOD and catalase mRNAs and corresponding activities concurrently with high increase in GPx-1 mRNA and activity. As a result of the development of resistance, a similarity was found between the change in ROS level and the change in ho-1 and bcl-2 gene expression, whereas elevation of bcl-xl gene expression was observed in all three types of resistant cells. Particular features of development of adaptive antioxidant response as well as redox-dependent change in bcl-2 gene expression under formation of DOX resistance of cancer cells of different genesis are discussed.

[Changes in the free-radical state and level of free iron during the formation of drug resistance in tumor cells].

The development of resistance of K562 human erythroleukemia cells to doxorubicin, a widely used antitumor antibiotic with the prooxidant action, leads to changes in the free-radical state of cells. It has been found that the formation of superoxide anion in resistant cells decreases. The introduction of doxorubicin to the culture medium induced a considerably lesser increase in the formation of O2*- in resistant cells compared to sensitive cells. At the same time, a strong decrease in the ESR signal of semiquinone type with a g-factor of 2.006 was observed in a culture of resistant cells grown in the absence of doxorubicin as compared with sensitive cells grown under similar conditions. At the same time, a decrease in the level of paramagnetic nitrosyl complexes of nonheme iron in resistant cells was recorded, indicating a decrease in the content of free nonheme iron as a result of the formation of drug resistance. In addition, a decrease in the level of mRNA of the transferrin receptor in resistant cells was found by the RT-PCR. These data indicate the development of a coodinated redox-dependent adaptive response, which makes itself evident as a suppression of free radical processes during the formation of resistance of K562 cells to doxorubicin.

[Enzymatic system of metabolism and detoxication of xenobiotics as a basis for metabolic profiling in prognosis of risk of the pathological processes]. / Fermentnaia sistema metabolizma i detoksikatsii ksenobiotikov kak osnova metabolicheskogo portretirovaniia pri prognozirovanii riska razvitiia patologicheskikh protsessov.

We studied intraspecific features of the main enzymes of metabolism and detoxication of xenobiotics on mice (eight inbred lines) and rats (five lines) for estimation of possible variants of complete or incomplete metabolic equality. Significant genetically determined intraspecific differences for activities of the enzymes of metabolism and detoxication of xenobiotics were described. Generalized criteria for comparison of the metabolic status were proposed on the basis of activities of the main enzymes: cytochrome P-450 (hydroxylation and epoxidation), epoxyhydrolase, glutathione-S-transferase, UDP-glucuronosyl transferase, and sulfotransferase. The proposed criteria for estimation of the metabolic parameters of an individual can serve as a basis of metabolic portraiting.

[Role of the antioxidant system and redox-dependent regulation of transcription factors bcl-2 and p53 in forming resistance of human K562 erythroleukemia cells to doxorubicin]. / Rol' antioksidantnoi sistemy i redoks-zavisimoi reguliatsii transkriptsionnykh faktorov bcl-2 i p53 formirovanii rezistentnosti kletok K562 éritroleikemii cheloveka k doksorubitsinu.

Prooxidant effect of chemotherapeutic agents is of significant interest in connection with activation of oxidative stress in cancer cells. Role of development of adaptive antioxidant response to the rise of resistance to cytotoxical effect of doxorubicin (DOX) has been studied in human erythroleukemia K562 cells. Growth of resistance to DOX caused enhancement of antioxidant enzymes (Cu, Zn-SOD, Mn-SOD, catalase) elevation of Mn-SOD activity being predominant. Additional increasing of antioxidant level was elevation of GSH maintenance and level of GST-related enzymes (glutathione peroxidase, glutathione S-transferase, glutathione reductase) in resistance K562/DOX cells. The enhancement of antioxidant system prevented activation of lipid peroxidation. Furthermore, the antioxidant growth caused decrease of level of proteintyrosine kinases, thioredoxin, thioredoxin reductase in contrary to elevation of glutaredoxin activity. Increasing of Bcl-2 and suppression of p53 levels was found to be caused by the change of redox state of K562DOX cells. The data support the suggestion that adaptive antioxidant response to prooxidant effect of DOX promotes the development of cellular drug resistance.

[Inhibitory effect of progesterone P1-1 on glutathione-s-transferase and its antiproliferative effect on human erythroleukemia K562 cells]. / Ingibiruiushchee deistvie progesterona na glutation-s-transferazy P1-1 i ego antiproliferativnyi èffekt na kletki linii K562 èritroleikemii cheloveka.

Since glutathione S-transferase P1-1 (GST P1-1) is predominantly expressed in many types of tumor cells it is regarded as its marker protein. The report discusses data on a relationship between progesterone (PS) inhibition of GST P1-1 and proliferation of human erythroleukemia K562 cells. Unlike such steroids as estrone, dexamethasone, testosterone and hydrocortisone, PS showed significant inhibitory effect (I50 = 32.5(M) and noncompetitively (Ki = 25(M) inhibited GST P1-1 isolated from human placenta. Pronounced inhibition of K562 cell proliferation by PS was in inverse correlation with the intracellular activity of GST P1-1. Also, PS injected into culture suppressed GST P1-1 expression in leukemia cells. At concentrations of 10(-8)-10(-5) M, both effects proved dose-dependent. The correlation between PS antiproliferative effect on GST P1-1 activity and expression in K562 cells is discussed in terms of its possible role played in malignant growth regulation.

Effect of perfluorodecalin on activities of hepatic phase II xenobiotic biotransformation enzymes.

The activity of the hepatic phase II enzymes of xenobiotic biotransformation after intravenous administration of perfluorodecalin emulsion to rats was measured. Perfluorodecalin was found to increase the microsomal glutathione S-transferase and UDP-glucuronosyltransferase activities 1.4- and 2.3-fold, respectively. The activity of sulphotransferase was decreased 2-fold. These results show that perfluorodecalin is an inducer of both the enzymes of cytochrome P-450-dependent monooxygenase system [Mishin V. et al (1989) Chem.-Biol. Interactions, 72, 143-155.] and those catalyzing conjugation reactions: microsomal glutathione S-transferase and UDP-glucuronosyltransferase.

[The effect of perfluordecaline on the activity of phase III xenobiotic transformation enzymes]. / Vliianie perftordekalina na aktivnost' fermentov II fazy biotransformatsii ksenobiotikov.

Injection of perfluorodecaline to rats caused an increase of the phase II xenobiotic biotransformation enzyme activities followed by cytochrome P-450 induction. The activities of liver microsomal UDP-glucuronosyl transferase and glutathione transferase increased by 130 and 40%, respectively, against the control level. The increase of the cytosolic glutathione transferase activity was insignificant In contrast, the activity of sulfotransferase decreased about 2-fold. The role of modification of xenobiotic biotransformation enzymes in the biological effect of perfluorodecaline is discussed.

Antitoxic properties of a preparation of glutathione S-transferase.

Pretreatment of rats with a preparation of the cationic form of rat liver cytosolic glutathione S-transferase 1-3 h before injection of a dose of N-nitroso-N-diethylamine equivalent to the LD50 of the drug completely protects the animals against the toxic effects of the drug. The mechanism of the protective action of glutathione S-transferase is discussed.