The relationship between total sialic acid levels and antioxidant status in the tadpoles of Bufo viridis and Rana ridibunda ridibunda

Total sialic acid levels (TSA), antioxidant enzymes activities such as superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO) levels were investigated during the developmental period in tadpoles of the predominantly terrestrial amphibian B. viridis and the predominantly aquatic amphibian R. r. ridibunda. Maximum TSA levels were observed in B. viridis and R. r. ridibunda at the fifth and third week of their development, respectively. SOD and CAT activity variations during development in B. viridis were higher than in R. r. ridibunda. Although SOD activity in B. viridis was higher than R. r. ridibunda at the eighth week, SOD activity increased 19.2-fold in R. r. ridibunda and 10.4-fold in B. viridis between the first and eighth week. CAT activity in R. r. ridibunda did not significantly change (p>0.001) until the fifth week then increased, whereas in B. viridis CAT increased after the third week. In contrast to the rise in the antioxidant enzyme activities, LPO levels tended to decrease during the developmental period. Levels of LPO showed a similar trend until the third week for both species. The minimum LPO levels in B. viridis and R. r. ridibunda were 23+/-1.2 and 146+/-7.3 nmol MDA g(-1) tissue, at the eighth week, respectively. While decreasing LPO levels correlated with increasing antioxidant enzyme activities, TSA tended to decrease after reaching a maximum point.     

Redox regulation of neutral sphingomyelinase-1 activity in HEK293 cells through a GSH-dependent mechanism

Phospholipases are essential enzymes in cellular signalling processes such as cellular differentiation, proliferation and apoptosis. Based on its high degree of homology with sequences of prokaryote SMases, a type of Mg(2+)-dependent PLC (nSMase-1) was recently discovered which displayed strong redox dependence for activity in vitro [F. Rodrigues-Lima, A.C. Fensome, M. Josephs, J. Evans, R.J. Veldman, M. Katan (2000), J. Biol. Chem. 275 (36) 28316-28325]. The aim of this work was to test the hypothesis that glutathione could be a natural regulator of nSMase-1 activity ex vivo. We studied how altering glutathione levels and redox ratio modulate nSMase-1 activity in a HEK293 cell line that ectopically overexpressed the nSMase-1 gene. Diminishing total glutathione with BSO without altering significantly the GSH/GSSG ratio did not affect nSMase-1 activity. Treatment of cells with diamide produced a transient decrease of total glutathione and a sharp, but also transient, decrease of the GSH/GSSG ratio. Under these conditions, nSMase-1 activity was temporarily activated and then returned to normal levels. Simultaneous treatment with BSO and diamide that resulted in permanent decreases of total glutathione and GSH/GSSG redox ratio produced a sustained activation of nSMase-1 activity. Taken together, these data indicate that altering the GSH/GSSG ratio by increasing GSSG or decreasing GSH levels, but not the total concentration of glutathione, modulates nSMase-1 activity. Our findings are the first evidence supporting the ex vivo regulation of nSMase-1 through a redox glutathione-dependent mechanism.     

Antioxidant status of Lobiger serradifalci and Oxynoe olivacea (Opisthobranchia, Mollusca)

Invasion of the Mediterranean Sea by the two world-wide famous exotic algae species, Caulerpa taxifolia and Caulerpa racemosa, is still a problem and has adverse effects on the Mediterranean sublittoral ecosystem. Biological control studies revealed that the two native Sacoglossans, Oxynoe olivacea and Lobiger serradifalci, may have an effect on the expansion of invasive Caulerpa spp. in the Mediterranean. In the framework of this study, antioxidant enzyme activities, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), lipid peroxidation (LPO) and oxidized glutathione (GSSG) levels, as oxidative stress markers in L. serradifalci and O. olivacea were determined at two different temperature conditions (20 and 27 °C). In both species, SOD, CAT and GSH-Px activities were found to be positively correlated with temperature. The SOD activities in L. serradifalci were higher than those in O. olivacea at both temperatures, whereas the CAT and GSH-Px activities were significantly (p<0.05) higher in O. olivacea, compared to L. serradifalci. As expected, both species showed decreased LPO levels at 27 °C compared to 20 °C. GSSG level at 27 °C in O.olivacea was significantly (p<0.05) higher than that of 20 °C. On the other hand, no statistical (p>0.05) difference in L.serradifalci existed between GSSG levels at two temperatures. But, despite the variations in the antioxidant enzyme activities, there was no significant difference in LPO levels between the species, suggesting that the oxidative consequences of a given environmental condition may vary among different species. Inasmuch as the GSSG levels were in accordance with antioxidant enzyme activities, GSH might have acted as a cofactor of GSH-Px and an individual antioxidant in these sea slugs.     

Chloramine T induced oxidative stress and the response of antioxidant system in <Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis>

In this study, the effect of chloramine T (Chl-T) on the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione S-transferase (GST); the levels of reduced (GSH) and oxidised glutathione (GSSG) and their ratios; and also membrane lipid peroxidation (LPO) levels in Phanerochaete chrysosporium were investigated in a dose- (0.25–1 mmol/L) and time-dependent (1.5–9 h) manner. The highest SOD activity was observed in 0.5 mmol/L Chl-T at 6th hour as 1.48-fold of its control. The observed highest level in CAT activities was 4.6-fold of control in 0.5 and 0.75 mmol/L at the 6th hour. The GSH levels that were over the control showed decreasing tendency from the beginning of incubation, except 0.25 mmol/L. In contrast with GSH level variations, GSSG levels reached 10.0-fold of its control by showing increasing tendency with the increases in concentration and time. While the GSH/GSSG ratios were over the control at 0.25 mmol/L during all incubation, they fell under the control values at the earlier hours of incubation with the increasing concentrations of Chl-T. Glutathione-related enzymes GSH-Px, GR and GST were also induced with Chl-T treatment, and the highest activities were 3.29-, 7.5- and 6.56-fold of their controls, respectively. On the other hand, the increases in LPO levels with increasing concentration and time up to 5.27-fold of its control showed that the inductions observed in antioxidant system could not prevent the Chl-T-based oxidative stress.     

The glutathione-related detoxication responses to juvenile and ecdysone hormones in Galleria mellonella

The effect of 20-hydroxyecdysone (20E) and juvenile hormone (JH) on the glutathione pathway of the greater wax moth Galleria mellonella (Lepidoptera: Pyralidae) was determined by investigating glutathione peroxidase (GSH-Px), glutathione S-transferases (GST), and glutathione reductase (GR) activities as well as reduced and oxidized glutathione (GSH and GSSG) content with respect to developmental stage. The continuous decreases of GSH-Px and GST activities dependent on the growth period of G. mellonella occurred in JH and 20E groups over and under their controls, respectively. While the GR activities of G. mellonella showed increases in young pupa (YP) for both control and in old larvae (OL) for the 20E groups after the minimum at these periods, they also increased after old pupa (OP) for the JH group with a maximum in OL period. Although GR activity levels in the JH group were significantly higher compared with controls and 20E groups up to OP period, the activity levels for the control and 20E groups were higher than those of the JH group at adult (AD) and old pupa (OP) periods, respectively. In spite of increases in the GR activity of 20E and control groups of G. mellonella, decreased GSH and increased GSSG levels were observed at aging period. GSH levels in the JH group reached a maximum at prepupa (PP) and then decreased with non-significant changes from OL to AD period. According to the results, GSH and GSSG levels, as well as GSH/GSSG ratios, were below and over control levels in 20E and JH groups, respectively, during all of the investigated developmental stages. On the contrary, the LPO levels were higher than the control for 20E and lower for the JH groups during the developmental period. These results show that while ecdysone hormone has a negative effect on the glutathione-related detoxication capacity of G. mellonella, the juvenile hormone has a positive effect on this process.     

Age-related changes in the glutathione redox system

The effect of aging on the glutathione redox system was evaluated in this study. For this purpose, we determined reduced glutathione (GSH) and oxidized glutathione (GSSG) in whole blood, glutathione peroxidase (GPx) and glutathione reductase (GSSGR) in erythrocytes and selenium (Se) in plasma in 176 healthy individuals. We also calculated GSH/GSSG molar ratios. These subjects were divided into five groups: group 1 (n=25; 0.2-1 years old); group 2 (n=28; 2-11 years old); group 3 (n=23; 12-24 years old); group 4 (n=40; 25-40 years old); group 5 (n=60; 41-69 years old). GSH levels in groups 1 and 5 were significantly lower than the other groups (p<0.001). Conversely, GSSG levels were significantly high in these periods (p<0.001). The GSH/GSSG molar ratio was found to be low both in the first year of life and in the oldest group (p<0.001, respectively). GPx activity in group 5 was increased as compared to the other groups (p<0.001). GSSGR activity was significantly lower in the oldest groups than in the other groups (p<0.001). Se levels were found to be low in the oldest group (p<0.001). Selenium levels of women in group 5 were significantly high as compared to the men (p<0.01). We found negative correlations between age and GSH levels (r=0.402; p<0.001), selenium levels (r=0.454; p<0.001), GSH/GSSG molar ratio (r=0.557; p<0.001) and GSSGR activity (r=0.556; p<0.001). There were positive correlations between age and GPx (r=0.538; p<0.001) and GSSG level (r=0.551; p<0.001). In conclusion, our findings show that the glutathione redox system is affected by age. Oxidative stress increases during the aging process. There is no effect of aging on the glutathione redox system according to sex except for the Se level.     

Glutathione and antioxidant enzymes in skeletal muscle: effects of fiber type and exercise intensity.

Glutathione status and antioxidant enzymes in various types of rat skeletal muscle were studied after an acute bout of exercise (Ex) at different intensities. Glutathione (GSH) and glutathione disulfide (GSSG) concentrations were the highest in soleus (SO) muscle, followed by those in deep (DVL) and then superficial (SVL) portions of vastus lateralis. In DVL, but not in SO or SVL, muscle GSH increased proportionally with Ex intensity and reached 1.8 +/- 0.08 mumol/g wet wt compared with 1.5 +/- 0.03 (P < 0.05) in resting controls (R). GSSG in DVL was increased from 0.10 +/- 0.01 mumol/g wet wt in R to 0.14 +/- 0.01 (P < 0.05) after Ex. Total glutathione (GSH + GSSG) contents in DVL were also significantly elevated with Ex, whereas GSH/GSSG ratio was unchanged. Activities of GSH peroxidase (GPX), GSSG reductase (GR), and catalase (CAT) were significantly higher in SO than in DVL and SVL, but there was no difference in superoxide dismutase activity between the three muscle types. Furthermore, Ex at moderate intensities elicited significant increases in GPX, GR, and CAT activities in DVL muscle. None of the antioxidant enzymes was affected by exercise in SO. It is concluded that rat DVL muscle is particularly vulnerable to exercise-induced free radical damage and that a disturbance of muscle GSH status is indicative of an oxidative stress.     

Zinc toxicity in various lung cell lines is mediated by glutathione and GSSG reductase activity

In a previous work, it was shown that in cells after a decrease of cellular glutathione content, toxic zinc effects, such as protein synthesis inhibition or GSSG (glutathione, oxidized form) increases, were enhanced. In this study, zinc toxicity was determined by detection of methionine incorporation as a parameter of protein synthesis and GSSG increase in various lung cell lines (A549, L2, 11Lu, 16Lu), dependent on enhanced GSSG reductase activities and changed glutathione contents. After pretreatment of cells with dl-buthionine-[R,S]-sulfoximine (BSO) for 72 h, cellular glutathione contents were decreased to 15–40% and GSSG reductase activity was increased to 120–135% in a concentration-dependent manner. In BSO pretreated cells, the IC₅₀ values of zinc for methionine incorporation inhibition were unchanged as compared to cells not pretreated. The GSSG increase in BSO pretreated cells by zinc was enhanced in L2, 11Lu, and 16Lu cells, whereas in A549 cells, the GSSG increase by zinc was enhanced only after pretreatment with the highest BSO concentration. Inhibition of GSSG reductase in alveolar epithelial cells was observed at lower zinc concentrations than needed for methionine incorporation inhibition, whereas in fibroblastlike cells, inhibition of GSSG reductase occurred at markedly higher zinc concentrations as compared to methionine incorporation inhibition. These results demonstrate that GSSG reductase is an important factor in cellular zinc susceptibility. We conclude that reduction of GSSG is reduced in zinc-exposed cells. Therefore, protection of GSH oxidation by various antioxidants as well as enhancement of GSH content are expected to be mechanisms of diminishing toxic cellular effects after exposure to zinc.     

Effects of glutathione reductase inhibition on cellular thiol redox state and related systems

Although inhibition of glutathione reductase (GR) has been demonstrated to cause a decrease in reduced glutathione (GSH) and increase in glutathione disulfide (GSSG), a systematic study of the effects of GR inhibition on thiol redox state and related systems has not been noted. By employing a monkey kidney cell line as the cell model and 2-acetylamino-3-[4-(2-acetylamino-2-carboxy-ethylsulfanylthio carbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA) as a GR inhibitor, an investigation of the effects of GR inhibition on cellular thiol redox state and related systems was conducted. Our study demonstrated that, in addition to a decrease in GSH and increase in GSSG, 2-AAPA increased the ratios of NADH/NAD⁺ and NADPH/NADP⁺. Significant protein glutathionylation was observed. However, the inhibition did not affect the formation of reactive oxygen species or expression of antioxidant defense enzyme systems [GR, glutathione peroxidase, catalase, and superoxide dismutase] and enzymes involved in GSH biosynthesis [γ-glutamylcysteine synthetase and glutathione synthetase].     

Plasma Glutathione and Carotenoid Coloration as Potential Biomarkers of Environmental Stress in Great Tits

Measures of oxidative stress in animals may be useful biomarkers of environmental stressors, such as anthropogenic pollution. In birds, studies of oxidative stress have focused on dietary antioxidants, primarily carotenoids, which are interesting due to their multiple physiological and pigmentary functions but therefore also unspecifically related to oxidative stress. A useful complementary biomarker may be the glutathione system, commonly used in human medicine, but rarely applied to wild, terrestrial vertebrates. In this study of urban versus rural adult and nestling great tits Parus major, we investigated both the carotenoid-based yellow plumage (by reflectance spectrometry) and the plasma levels of glutathione, the latter measured as total glutathione (tGSH) and as the ratio between oxidized and reduced glutathione (GSSG:GSH), respectively. We found that urban adults had higher current oxidative stress (GSSG:GSH) and paler yellow plumage compared to rural adults, suggesting elevated stress in the urban environment. Total glutathione levels (tGSH), however, which may indicate long-term up-regulation of the GSH reservoir, did not differ between the environments. Nestlings did not show any consistent pattern between environments in either tGSH or GSSG:GSH and, among individuals, glutathione levels were uncorrelated with carotenoid coloration. The results thus suggest some population-level correspondence between the two stress biomarkers in adult birds, but more work is obviously needed to understand how the two antioxidant systems interact in different individuals and in response to different environmental disturbances.     

Alterations of oxidative-antioxidative status in human cutaneous leishmaniasis

Enhanced lipid peroxidation and decreased antioxidant defences have been defined in several diseases. In the present study, we aimed to evaluate the oxidative-antioxidative status of patients with cutaneous leishmaniasis (CL). Concentrations of erythrocyte lipid peroxidation (LPO), as an indicator for the oxidative status, reduced glutathione (GSH), glutathione peroxidase (GSH-Px) and serum vitamin C levels, as indicators for the antioxidative status, were measured. Seventy patients aged between 15 and 50 years (38 patients had active CL and 32 patients had healed CL) and 40 healthy controls aged between 19 and 50 years were included in the study. LPO and GSH of the patients with active CL were significantly higher (p < 0.001), whereas erythrocyte GSH-Px and serum vitamin C levels were lower (p < 0.001, p < 0.01 respectively) than those of healthy controls. There was a significant inverse correlation between LPO and serum vitamin C level (r=-0.32, p < 0.05) in active CL. No significant correlation of LPO, GSH, GSH-Px and serum vitamin C levels in control groups or in the group with healed CL was detected. In the light of our findings it is possible to conclude that patients having CL are affected by oxidative stress, which most likely induces the endogenous antioxidant system. An imbalance between the oxidant and antioxidant systems occurs and the suppressed antioxidants and increased lipid peroxidation may contribute to the progression of the disease.     

The effects of some antioxidant vitamin- and trace element-supplemented diets on activities of SOD, CAT, GSH-Px and LPO levels in chicken tissues

The effect of diets containing antioxidant vitamins and trace elements on chicken tissue activities of SOD, CAT, GSH-Px and of LPO levels was investigated. Chickens, 45 weeks of age were divided into six groups: control group, Cu group (13.2 mg Cu kg(-1) diet); Se group (0.07 mg Se kg(-l) diet); vitamin E group (70 mg DL-alpha-tocopherol acetate kg(-1) diet) and a constant level vitamin C, 200 mg kg(-1) diet); vitamin A group (240 mg retinol acetate kg(-1) diet) and vitamin C group (500 mg ascorbic acid kg(-1) diet). Significant variation of these antioxidant enzyme activities and LPO levels according to gender was demonstrated statistically. In the Cu group, CuZnSOD activity in the liver, erythrocyte, kidney and heart significantly increased by 75, 40, 12, 12% respectively (P<0.05). MnSOD activity in the heart, liver, kidney and brain of the vitamin C and in the heart of Cu group were found to be increased by approximately 15%, while in liver tissue of the Cu group it was reduced by 19% (P<0.05). GSH-Px activities in the Se, vitamin E and C groups were significantly increased, conversely LPO levels decreased (P<0.001). CAT activities in the liver and heart of the vitamin C group were significantly decreased (by 32%), but in kidney tissue only that of the Cu group was increased from 30.2 +/- 4.767 to 144.49 +/- 6.93 U mg(-1) P<0.001. The resistance to stress of the vitamin E and C groups, which had significantly increased activities of antioxidant enzymes and decreased lipid peroxide levels, were determined in 60% moisture medium at 45 degrees C.     

Parameters related to oxygen free radicals in erythrocytes,plasma and epidermis of the hairless rat

The following parameters related to oxygen free radicals (OFR) were determined in erythrocytes and the epidermis of hairless rats: catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), reduced (GSH) and oxidized (GSSG) glutathione, glutathione S-transferase (GST), superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS). GSH, GSSG and TBARS were also analyzed in plasma. In erythrocytes, the Pearson correlation coefficients (r) were significant (p < 0.001) between glutathione and other parameters as follows: GSH correlated negatively with GSSG (r = -0.665) and TBARS (r = -0.669); GSSG correlated positively with SOD (r = 0.709) and TBARS (r = 0.752). Plasma GSSG correlated negatively with erythrocytic thermostable GST activity (r = -0.608; p=0.001) and with erythrocytic total GST activity (r = -0.677; p < 0.001). In epidermis (p < 0.001 in all cases), GSH content correlated with GSSG (r = 0.682) and with GPx (r = 0.663); GSSG correlated with GPx (r = 0.731) and with GR (r = 0.794). By multiple linear regression analysis some predictor variables (R(2)) were found: in erythrocytes, thermostable GST was predicted by total GST activity and GSSG, GSSG content was predicted by GSH and by the GSH/GSSG ratio and GPx activity was predicted by GST, CAT and SOD activities; in epidermis, GSSG was predicted by GR and SOD activities and GR was predicted by GSSG, TBARS and GPx. It is concluded that the hairless rat is a good model for studying OFR-related parameters simultaneously in blood and skin, and that it may provide valuable information about other animals under oxidative stress.     

Glutathione metabolism in Urtica dioica in response to cadmium based oxidative stress

To investigate the antioxidative response of glutathione metabolism in Urtica dioica L. to a cadmium induced oxidative stress, activities of glutathione reductase (GR), glutathione-S-transferase (GST), and glutathione peroxidase (GSH-Px), content of reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation (LPO), and also accumulation of Fe, Zn, Mn, Cu besides Cd were determined in the roots, stems, and leaves of plants exposed to 0 (control), 0.045, and 0.09 mM CdCl₂ for 58 h. Whereas the Cd content continuously increased in all organs, the Fe, Zn, Mn, and Cu content decreased in dependence on the applied Cd concentration and incubation time. The Cd treatment resulted in increased GR and GST activities in all organs, however, GSH-Px activity was dependent on Cd concentration and plant organ. The GSH/GSSG ratio maintained above the control level in the stems at both Cd concentrations. The LPO was generally close to the control values in the roots and stems but it increased in the leaves especially at 0.09 mM Cd.     

Metabolic aspects of aspirin-induced apoptosis in yeast

We have previously shown that aspirin induces apoptosis in manganese superoxide dismutase (MnSOD)-deficient Saccharomyces cerevisiae cells cultivated in ethanol medium, and that it exhibits a significant antioxidant effect until the onset of overt apoptosis. We here report that glucose-6-phosphate dehydrogenase activity in these cells is not inhibited by aspirin. However, the reducing power, as measured by the NADPH/NADP(+) concentration ratio, is significantly lower than in wild-type cells. With aspirin, the levels of NADPH, NADP(+) and catalase in MnSOD-deficient cells decrease significantly after 72 h of cultivation, without significant decrease of the NADPH/NADP(+) ratio. This ratio is higher when the cells are grown in glycerol or acetate medium. This seems to prevent loss in viability and induction of apoptosis on treatment with aspirin. Additionally, the glutathione (GSH) level is maintained, but the level of oxidized glutathione (GSSG) increases, leading to a significant decrease in the GSH/GSSG ratio in aspirin-treated cells. This decrease in the GSH/GSSG ratio is much less in cells grown in glycerol medium, while there is an increase in the GSH/GSSG ratio of cells grown in acetate medium. Consequently, the decreased reducing power may be linked to apoptotic induction by aspirin. This occurs independently of the level of reactive oxygen species which, as shown in our previous studies, do not play a primary role in the apoptosis of cells exposed to aspirin. The protective effect of MnSOD appears to be related to the cellular reducing power.     

Oxygen consumption of a terrestrial toad (Bufo viridis) and semi-aquatic frog (Rana ridibunda)

1. Oxygen consumption was measured before and after dehydration at different ambient temperatures (Ta) in the terrestrial toad Bufo viridis and the semi-aquatic frog Rana ridibunda. 2. The metabolic rates at Tas between 14 and 27 degrees C were almost the same for R. ridibunda and B. viridis. 3. The metabolic rate at higher Tas (between 27 and 36 degrees C) was higher in R. ridibunda than in B. viridis. This situation was found before and after dehydration. 4. A similar situation was found with CO2 production, which was higher at high Tas in R. ridibunda compared with B. viridis.     

A sensitive fluorimetric microassay for the determination of glutathione peroxidase activity. Application to human blood platelets

The method proposed for measuring glutathione peroxydase (GSH-Px) activity is based on the determination of oxidized glutathione (GSSG) using o-phtalaldehyde (OPT) as a fluorescent reagent. This method makes it possible to study the kinetics of both substrates (peroxide and reduced glutathione, GSH), and allosteric kinetics were found for GSH, with human platelets as the source of GSH-Px. Different methods for platelet disruption were compared. The reference values obtained for GSH-Px activity in human blood platelets by this fluorimetric procedure and the conventional enzymatic method were very similar and significantly higher than those previously reported; the reasons for this difference are discussed.     

Depression of biliary glutathione excretion by chronic ethanol feeding in the rat

The effects of chronic alcohol feeding on biliary glutathione excretion were studied in rats pair fed diets containing either ethanol (36% of total energy) or isocaloric carbohydrate for 4-6 weeks. An exteriorized biliary-duodenal fistula was established and total glutathione (GSH) and oxidized glutathione (GSSG) were measured. A significant decrease was observed in rats fed alcohol chronically compared to their pair fed controls in the biliary excretion of GSH (55.7 +/- 37.0 vs 243.1 +/- 29.0 micrograms/ml bile, p less than 0.025) as well as biliary GSSG (12.5 +/- 5.0 vs 49.9 +/- 8.0 micrograms/ml bile, p less than 0.05) and in bile flow (23.1 +/- 1.6 vs 29.2 +/- 1.3 micrograms/min, p less than 0.05). An acute dose of ethanol tended to exaggerate the decrease on biliary GSH and GSSG in the two groups of animals. The depression in biliary GSH could not be attributed to decreased GSH synthesis since S35-L-methionine incorporation into hepatic and biliary GSH was unchanged or even increased after chronic ethanol feeding.     

In vivo and in vitro influence of selenium on DNA/RNA synthesis in spleen and lymphocytes in culture--possible mediation of changes in GSH/GSSG ratio

Effect of superanutritional levels of selenium (Se) as sodium selenite (0.5 and 1.5 ppm) given orally to Balb/c mice for one and two weeks was observed on the rate of DNA/RNA synthesis, levels of reduced as well as oxidized glutathione (GSH and GSSG) and glutathione peroxidase (GSH-Px)/glutathione-S-transferase (GSH-S-transferase) activities in spleen. Similar effect of three different concentrations of Se (10(-7), 10(-5) and 10(-3) M) in culture media was also observed on the rate of DNA/RNA synthesis in proliferating lymphocytes taken from mice spleen. The results of the present study indicated that with increasing concentration and duration of Se treatment in vivo and in vitro, a marked inhibition of the rate of DNA/RNA synthesis was observed. Levels of total glutathione and GSSG in spleen were elevated significantly only after two weeks in 1.5 ppm treatments. Glutathione peroxidase activities in spleen decreased (p < 0.05) in 1.5 ppm group at one week and in 0.5 ppm group at two week treatment. At higher Se treatment, the activity recovered towards control. However, GSH-S-transferase in spleen remained unchanged at all treatment intervals. The results indicated that changes in glutathione system by increasing Se concentration might account for inhibition of rate of DNA/RNA synthesis.     

Hepatocyte susceptibility to glyoxal is dependent on cell thiamin content

Glyoxal, a reactive dicarbonyl, is detoxified primarily by the glyoxalase system utilizing glutathione (GSH) and by the aldo-keto reductase enzymes which utilizes NAD[P]H as the co-factor. Thiamin (Vitamin B(1)) is an essential coenzyme for transketolase (TK) that is part of the pentose phosphate pathway which helps maintain cellular NADPH levels. NADPH plays an intracellular role in regenerating glutathione (GSH) from oxidized GSH (GSSG), thereby increasing the antioxidant defenses of the cell. In this study we have focused on the prevention of glyoxal toxicity by supplementation with thiamin (3mM). Thiamin was cytoprotective and restored NADPH levels, glyoxal detoxification and mitochondrial membrane potential. Hepatocyte reactive oxygen species (ROS) formation, lipid peroxidation and GSH oxidation were decreased. Furthermore, hepatocytes were made thiamin deficient with oxythiamin (3mM) as measured by the decreased hepatocyte TK activity. Under thiamin deficient conditions a non-toxic dose of glyoxal (2mM) became cytotoxic and glyoxal metabolism decreased; while ROS formation, lipid peroxidation and GSH oxidation was increased.