Role Of Glutathione Reductase Research Articles

Immunohistochemical study of glutathione reductase in rat ocular tissues at different developmental stages.

Glutathione, which is found in high levels in eye tissues, is involved in multiple functions, including serving as an antioxidant and as an electron donor for peroxidases. Although the activities of enzymes related to glutathione metabolism have been reported in the eye, the issue of which cells produce these proteins, where they are produced and at what levels is an important one. Glutathione reductase, an enzyme which recycles oxidized glutathione by transferring electrons from NADPH, was localized immunohistochemically in adult rat eye in this study. The reductase was distributed in the corneal and conjunctival epithelia, corneal keratocytes and endothelium, iridial and ciliary epithelia, neural retina, and retinal pigment epithelium. In addition, it was highly expressed in ganglion cells, which are responsible for transmitting photophysiological signals from the retina to the higher visual centres. To clarify the correlation of glutathione reductase expression and oxidative stress, the enzymatic activity and the level of protein expression at the pre- and postnatal stages was examined. Expression of the enzyme was detected first in the ganglion cell layer of a late prenatal stage, and appeared in the inner plexyform layer after birth. Along with an increasing differentiation between the inner nuclear and outer nuclear layers, glutathione reductase expression became detectable in the outer plexyform layer. Pigment epithelial cells were positively stained only after birth. Expression was also detected in the lens epithelium from the prenatal to early postnatal stages although its level was low in the adult lens. Collectively, these data, except for lens epithelia, suggest the pivotal role of glutathione reductase in recycling oxidized glutathione for the protection of the tissues against oxidative stress, which is caused by eye opening accompanied by the initiation of various ocular processes, such as accession of light and transduction of the photochemical signal.

Leaf age- and paraquat concentration-dependent effects on the levels of enzymes protecting against photooxidative stress

Antioxidant protective enzymes are usually induced in leaves under conditions of increased active oxygen generation, such as high light intensity, low CO 2 fixation rate or in the presence of paraquat, which transports electrons from photosynthetic machinery to oxygen to form O 2 −. However, at high photooxidative stress, even protective enzymes can be destroyed and leaf cells become dead. The protective role of several chloroplastic activities was evaluated at increasing photooxidative stress in barley leaves of different ages. We investigated the effects of different paraquat concentrations (combined with low and high light intensities) in expanding and aged-senescent leaves on the activity of plastid peroxidase and on the activity and protein levels of plastid superoxide dismutase (SOD), glutathione reductase (GR) and NADH dehydrogenase of the complex including polypeptides encoded by plastid ndh genes. The chloroplastic GR was the most sensitive to inactivation when photooxidative stress increased. SOD was preferentially induced in young-expanding leaves while NADH dehydrogenase and peroxidase were preferentially induced in adult-senescent leaves. The results suggest a limited role of GR in the protection against photooxidative stress and a close relation between the actions of Ndh complex and peroxidase.

Modulation of erythrocyte photohemolysis rate by glutathione reductase inactivating alkylating agents

In order to determine the role of glutathione reductase (GR) in protection against Alphtalocyanine tetrasulfonate-sensitized human erythrocyte photolysis, we have studied the effects of antitumour alkylating agents that inactivate GR, on photohemolysis rate. The rates of inactivation of reduced GR decreased in order BCNU > pharanox (N-p-[bis-(2-chloroethyl)-amino]-phenylacetic acid N-oxide) > phenalol (N-p-[bis-(2-chloroethyl)-amino]-phenylacetyl-L- phenylalanine) > o-F- and p-F-lophenal (o- and p-isomers of N-p-[bis-(2-chloroethyl)-amino]-phenylacetyl-D,L-fluorophenylalanine) > D,L-melphalan. As supposed, erythrocyte photolysis was accelerated by BCNU and pharanox, however, it was slowed down by phenylalanine mustards. The latter effect was explained by singlet oxygen quenching and/or photooxidation reactions of these compounds. This points out to a possibility of certain phenylalanine derivatives to neutralize the side-effects of photodynamic therapy.

Low activity of superoxide dismutase and high activity of glutathione reductase in erythrocytes from centenarians.

to compare the activities of antioxidative enzymes in erythrocytes between centenarians and a younger group of elderly subjects. cross-sectional study. county of Funen, Denmark. 41 centenarians aged between 100 and 105 years and 52 community control subjects aged between 60 and 79 years. enzyme activities of superoxide dismutase (CuZn-SOD), glutathione peroxidase, catalase and glutathione reductase (GR) in erythrocytes. Functional capacity among the centenarians was evaluated by Katz' index of activities of daily living, the Physical Performance Test and Mini-Mental State Examination. the mean CuZn-SOD activity was significantly lower and the mean GR activity was significantly higher in centenarians than in the group of elderly people. The centenarians with the lowest cognitive and physical functional capacity and who did not survive at least 1 year after blood sampling tended to have the lowest CuZn-SOD activities. The range of GR activity was shifted toward higher values in the centenarian group than in the younger group and those centenarians having the best functional capacity tended to have the highest GR activity. CuZn-SOD activity is decreased in centenarians, probably because of reduced demand for the enzyme at lower metabolic rate and oxygen consumption. Subjects with high GR activity occur more frequently among centenarians than expected, possibly due to their better survival. The role of GR in disease prevention and as a predictor for longevity deserves to be further explored.

Phenobarbital-induced cytoprotective mechanisms in menadione metabolism: The role of glutathione reductase and DT-diaphorase

1. 1. Treatment with N, N-bis (2-chloroethyl)- N-nitrosourea (BCNU) (80 μM) led to decreases in cell viability in both naive and sodium phenobarbital (PB) induced hepatocytes. 2. 2. Dicumarol (30 μM) selectively increased the cytotoxicity of menadione in hepatocytes isolated from naive vs PB-pretreated rats. 3. 3. Inclusion of both BCNU and dicumarol to the incubation medium abolished the characteristic concentration-response curves of the hepatocytes for menadione. 4. 4. A greater proportion of menadione was metabolized by DT-diaphorase in the hepatocytes isolated from PB-pretreated rats. 5. 5. The role of glutathione reductase vs DT-diaphorase in mitigating menadione-cytotoxicity in the naive vs PB-induced hepatocyte is discussed.

Role of glutathione reductase during menadione-induced nadph oxidation in isolated rat hepatocytes

Metabolism of menadione (2-methyl-1,4-naphthoquinone) results in the rapid oxidation of NADPH within isolated rat hepatocytes. The glutathione redox cycle is thought to play a major role in the consumption of NADPH during menadione metabolism, chiefly through glutathione reductase (GSSG-reductase). This enzyme reduces oxidized glutathione (GSSG), formed via the glutathione-peroxidase reaction, with the concomitant oxidation of NADPH. To explore the relationship between GSSG-reductase and the consumption of NADPH during menadione metabolism, isolated rat hepatocyte suspensions were exposed to non-lethal and lethal menadione concentrations (100 and 300 μM respectively) following the inhibition of GSSG-reductase with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). Menadione produced a concentration-related depletion of GSH (measured as non-protein sulfhydryl content) which was potentiated markedly by BCNU. Menadione toxicity was potentiated at either concentration by BCNU based on lactate dehydrogenase leakage at 2hr. In addition, the NADPH content of isolated hepatocytes rapidly declined following exposure to either concentration of menadione. However, at the lower menadione concentration (100 μM), the NADPH content returned to control values or above by 60 min, whereas the NADPH content of cells exposed to 300 μM menadione with or without BCNU remained depressed for the duration of the incubation. These data suggest that, although NADPH is required by GSSG-reductase for the reduction of GSSG to GSH during quinone-induced oxidative stress, this pathway does not appear to be the major route by which NADPH is consumed during the metabolism of menadione in isolated hepatocytes.

The role of glutathione reductase in maintaining human granulocyte function and sensitivity to exogenous H2O2

Human granulocytes (polymorphonuclear leukocytes, PMN) produce H2O2 and other reactive oxygen species while undergoing phagocytosis. To examine the role of the glutathione cycle in metabolizing H2O2, we incubated PMN with 1,3-bis (2-chloroethyl) nitrosourea (BCNU). Incubation of PMN with BCNU results in a dose-dependent inhibition of PMN glutathione reductase (GRED), with 50% inhibition occurring at approximately 2 micrograms/mL BCNU. PMN hexose monophosphate shunt activity stimulated with an exogenous H2O2-generating system was inhibited only when the GRED activity was reduced to less than 30% of control. BCNU-treated cells contained lower levels of reduced sulfhydryls and reduced glutathione, which decreased even more in the presence of an exogenous H2O2-generating system. The effect of BCNU and exogenous H2O2 on various aspects of phagocytosis were examined. Exposure of BCNU-treated PMN to an H2O2-generating system resulted in an inhibition of chemotactic peptide-induced shape changes and degranulation. The ability of BCNU-treated cells to produce O2- was diminished only when the PMN were incubated with an H2O2-generating system in the presence of cyanide. Ingestion of opsonized bacteria by BCNU-treated PMN was unaffected by incubation in an H2O2-generating system even in the presence of cyanide. We conclude that PMN GRED is inhibited by BCNU, the ability of PMN to metabolize H2O2 is affected only when GRED is reduced more than 70%, this inhibition affects the glutathione content of these cells, and some, but not all of the phagocytic functions of GRED-inhibited PMN are inhibited after exposure to an H2O2-generating system.

The Role of Glutathione Reductase in Maintaining Human Granulocyte Function and Sensitivity to Exogenous H2o2

Human granulocytes (polymorphonuclear leukocytes, PMN) produce H2O2 and other reactive oxygen species while undergoing phagocytosis. To examine the role of the glutathione cycle in metabolizing H2O2, we incubated PMN with 1,3-bis (2-chloroethyl) nitrosourea (BCNU). Incubation of PMN with BCNU results in a dose-dependent inhibition of PMN glutathione reductase (GRED), with 50% inhibition occurring at approximately 2 micrograms/mL BCNU. PMN hexose monophosphate shunt activity stimulated with an exogenous H2O2-generating system was inhibited only when the GRED activity was reduced to less than 30% of control. BCNU-treated cells contained lower levels of reduced sulfhydryls and reduced glutathione, which decreased even more in the presence of an exogenous H2O2-generating system. The effect of BCNU and exogenous H2O2 on various aspects of phagocytosis were examined. Exposure of BCNU-treated PMN to an H2O2-generating system resulted in an inhibition of chemotactic peptide-induced shape changes and degranulation. The ability of BCNU-treated cells to produce O2- was diminished only when the PMN were incubated with an H2O2-generating system in the presence of cyanide. Ingestion of opsonized bacteria by BCNU-treated PMN was unaffected by incubation in an H2O2-generating system even in the presence of cyanide. We conclude that PMN GRED is inhibited by BCNU, the ability of PMN to metabolize H2O2 is affected only when GRED is reduced more than 70%, this inhibition affects the glutathione content of these cells, and some, but not all of the phagocytic functions of GRED-inhibited PMN are inhibited after exposure to an H2O2-generating system.

The coupling of metabolic to secretory events in pancreatic islets. The possible role of glutathione reductase

The participation of glutathione reductase in the process of nutrient-stimulated insulin release was investigated in rat pancreatic islets exposed to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU caused a time-and dose-related, irreversible inhibition of glutathione reductase activity. This coincided with a fall in both GSH/GSSG ratio and the thiol content of the islets. Pretreatment of the islets with BCNU inhibited the oxidation of glucose and its stimulant action upon both 45Ca net uptake and insulin release. Although BCNU (up to 0.5 mM) failed to affect the oxidation of l-leucine and l-glutamine, it also caused a dose-related inhibition of insulin release evoked by the combination of these two amino acids. The latter inhibition was apparently not fully accounted for by the modest to negligible effects of BCNU upon 45Ca uptake, 45Ca efflux, 86Rb efflux and cyclic AMP production. Since BCNU failed to inhibit insulin release evoked by the association of Ba 2+ and theophylline, these results support the view that glutathione reductase participates in the coupling of metabolic to secretory events in the process of nutrient-stimulated insulin release. However, the precise modality of such a participation, for example the control of intracellular Ca 2+ distribution, remains to be elucidated.

Regulation of thiols in the brain. I. Concentrations of thiols and glutathione reductase activity in different parts of the rat brain during hypoxia.

Abstract The effects of mild hypoxia on the concentrations of non-protein and protein thiol (SH) groups and on glutathione reductase activity in' the cerebral grey matter, cerebellum and brain stem of rats were studied. In normoxic rats the protein and non-protein SH levels were similar in the three parts studied except that the nonprotein SH level was much lower in the brain stem. In the cerebellum the glutathione reductase activity was higher than the activities in the cerebral grey matter and brain stem, which were equal. Hypoxia for I h markedly decreased the glutathione reductase activity and the SH levels in the parts studied, which implied an increase in the level of oxidized glutathione. After 2·5 h the amounts of protein and non-protein SH groups increased to the control value despite the fact that the glutathione reductase activity was still low. This suggested that hypoxia changes the role of glutathione reductase in the regulation of SH levels and in consequence the mechanism of that regulation. The dynamics of the changes observed under hypoxia were different in the three parts of the rat brain. Hypoxia made these parts change in a different way from that observed in normoxic rats. Changes of protein paralleled the non-protein SH changes during hypoxia.