GSSG Concentrations Research Articles

Interaction of exercise and adenosine receptor agonist and antagonist on rat heart antioxidant defense system

This study investigated the interactive effects of acute exercise and adenosine receptor agonist and antagonist on antioxidant enzyme activities, glutathione and lipid peroxidation in the heart of the rat. Male Fisher-344 rats were divided into six groups and treated as follows: (1) saline control; (2) acute exercise (100% VO2max); (3) R-Phenyl isopropyl adenosine (R-PIA) (3.46 micromol/kg, i.p.); (4) theophylline (1.70 micromol/kg, i.p.) plus acute exercise; (5) theophylline plus R-PIA; and (6) theophylline. Animals were sacrificed 1 h after treatments; hearts were isolated and analyzed. The results show that acute exercise as well as adenosine receptor agonist R-PIA significantly enhanced cardiac superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione reductase (GR) activity by 36-135% and 16-51%, respectively. Adenosine receptor agonist R-PIA significantly decreased cardiac GSSG concentration and enhanced GSH/GSSG ratio by 22 and 30%, respectively. Whereas theophylline treatment blocked the activation of antioxidant enzyme activities enhanced by acute exercise and R-PIA. Theophylline treatment significantly increased lipid peroxidation by 43% in the heart of exercised rats. The study concluded that the adenosine receptors are involved in the upregulation of cardiac antioxidant defense system and attenuation of lipid peroxidation due to acute exercise in rats.

Determination of glutathione and glutathione disulfide in hepatocytes by liquid chromatography with an electrode modified with functionalized carbon nanotubes

Glutathione (GSH) and glutathione disulfide (GSSG) are important thiols, which provide defence against oxidative stress by scavenging free radicals or causing the reduction of hydrogen peroxide. The ratio GSH/GSSG is often used as a sensitive index of oxidative stress in vivo. In this paper, a direct electrochemical method using an electrode modified with functionalized carbon nanotubes as electrochemical detector (ED) for liquid chromatography (LC) was described. The electrochemical behaviors of GSH and GSSG on this modified electrode were investigated by cyclic voltammetry and it was found that the functionalized carbon nanotubes exhibited efficiently electrocatalysis on the current responses of GSH and GSSG. In LC-ED, both of the analytes showed good and stable current responses. The detection limit of GSH was 0.2 pmol on column and that of GSSG was 1.2 pmol on column, which were low enough for the analysis of real small samples. The method was sensitive enough to detect difference in concentration of GSH and GSSG in hepatocytes from animals with and without introduction of oxidation stress by glucose or hydrogenperoxide.

Redox modulation of human prostate carcinoma cells by selenite increases radiation-induced cell killing

Although selenium compounds have been extensively studied as chemopreventative agents for prostate cancer, little is known about the potential use of selenium compounds for chemotherapy. We have shown that selenite inhibits cell growth and induces apoptosis in androgen-dependent LAPC-4 prostate cancer cells. LAPC-4 cells were more sensitive to selenite-induced apoptosis than primary cultures of normal prostate cells. Selenite-induced apoptosis in LAPC-4 cells correlated with a decrease in the Bcl-2:Bax expression ratio. Selenite-induced oxidative stress and apoptosis are dependent upon its reaction with reduced GSH. LAPC-4 cells treated with selenite showed decreased levels of total GSH and increased concentrations of GSSG. Thus, selenite altered the intracellular redox status toward an oxidative state by decreasing the ratio of GSH:GSSG. Because increased levels of Bcl-2 and GSH are associated with radioresistance, we examined the ability of selenite to sensitize prostate cancer cells to γ-irradiation. Both LAPC-4 and androgen-independent DU 145 cells pretreated with selenite showed increased sensitivity to γ-irradiation as measured by clonogenic survival assays. Importantly, selenite-induced radiosensitization was observed in combination with a clinically relevant dose of 2 Gy. These data suggest that altering the redox environment of prostate cancer cells with selenite increases the apoptotic potential and sensitizes them to radiation-induced cell killing.

Increased Glutathione Disulfide and Nitrosothiols in Sputum Supernatant of Patients With Stable COPD

Increased oxidant burden is involved in the pathogenesis of COPD. Glutathione (GSH) is a major antioxidant scavenging reactive oxygen and nitrogen species. We studied the concentrations of total and reduced GSH, glutathione disulfide (GSSG), and nitrosothiols in sputum supernatant of patients with COPD. Twenty-five patients with moderate-to-severe COPD (FEV(1) 61 +/- 12% of predicted) and 25 healthy nonsmoking control subjects underwent sputum induction. Sputum total GSH and GSSG were measured spectrophotometrically, and nitrosothiols were quantified by enzyme assay. Exhaled nitric oxide (eNO) was also measured to correlate eNO with nitrosothiols in induced sputum. Compared with healthy subjects, patients with COPD had increased sputum neutrophils (geometric mean, 65%; 95% confidence interval [CI], 57.5 to 71; vs 21%; 95% CI, 13.2 to 31.6; p < 0.001); total GSH (geometric mean, 7.1 micromol/L; 95% CI, 2.95 to 17; vs 5.1 micromol/L; 95% CI, 3.2 to 8.1; p = 0.024); GSSG (geometric mean, 4.1 micromol/L; 95% CI, 1.7 to 10; vs 0.84 micromol/L; 95% CI, 0.35 to 1.99; p = 0.002); and nitrosothiols (geometric mean, 60.4 micromol/L; 95% CI, 40 to 95.5; vs 38 micromol/L; 95% CI, 31.6 to 43.6; p = 0.04). Sputum GSSG was positively correlated with neutrophils (rho = 0.47, p = 0.016) and nitrosothiols (rho = 0.49, p = 0.024) in patients with COPD, whereas there was no correlation of eNO with nitrosothiols (rho = 0.38, p = 0.1). Sputum concentrations of GSSG and nitrosothiols are increased in patients with COPD and associated with neutrophilic inflammation. These data underline the role of oxidative stress in the pathogenesis of COPD, and suggest that GSH is important to scavenge both reactive oxygen and nitrogen species.

Comparison of thiol redox state of mitochondria and homogenates of various tissues between two strains of mice with different longevities

The main purpose of this study was to determine if differences in life spans of two different strains of mice are associated with the thiol redox state of their tissues and mitochondria. A comparison, based on amounts of reduced and oxidized glutathione (GSH, GSSG) and reactive protein thiols, was made between short-lived SAM (P8) mice and the longer-lived C57BL/6 mice at 13 months of age. The average life span of the latter mouse strain is approximately 48% longer than the former strain. Analyses of plasma, tissue homogenates and mitochondria of liver, kidney, heart, brain and skeletal muscle indicated that, in general, amounts of GSH and reactive protein sulfhydryls and GSH:GSSG ratios were lower and concentrations of GSSG were higher in the SAM than the C57BL/6 mice. Differences in the redox state between the two strains were more consistent and pronounced in skeletal muscle than in other tissues, and in mitochondria than in their respective tissue homogenates. Overall, the results support the view that the shorter-lived SAM mice exhibit a relatively higher level of oxidative stress than the longer-lived C57BL/6 mice, which is consistent with the predictions of the oxidative stress hypothesis of aging. Intra-species comparisons may be useful for the identification of biochemical characteristics associated with the variations in life spans.

Sputum Levels of Reduced Glutathione Increase 24 Hours after Allergen Challenge in Isolated Early, but Not Dual Asthmatic Responders

Background: The pathogenesis of late asthmatic reactions after allergen challenge in contrast to isolated early responses is incompletely understood. Recently, the antioxidant glutathione and endogenous nitrosothiols were shown to protect against bronchoconstriction. We compared reduced (GSH) and oxidized glutathione (GSSG) and nitrosothiols in induced sputum following allergen challenge in mild asthmatics with isolated early (EAR) and dual early and late (LAR) asthmatic responses. Methods: Exhaled nitric oxide, sputum cells and sputum supernatant concentrations of GSH, GSSG and nitrosothiols were quantified 2–5 days prior to and 24 h after allergen challenge in 24 mild asthmatics (12 EAR, 12 LAR, only beta-agonists prn). Results: There were no differences at baseline between EAR and LAR asthmatics for any of the parameters (p > 0.1, all comparisons). Mean ± SD fall in forced expiratory volume in 1 s, expressed as the percentage decrease compared to the baseline value, between 3 and 8 h after allergen challenge was 1 ± 5% in the group of patients without LAR vs. 24.9 ± 8.7% in the group of patients with LAR (p < 0.001). Sputum eosinophils increased in both groups (p < 0.05, both comparisons), whereas neutrophils only increased in LAR subjects (p = 0.06 vs. EAR). In contrast, GSH was significantly increased 24 h after challenge only in EAR asthmatics [geometric mean with 95% confidence intervals: before: 3.3 µM (1.25–7.9 µM), after: 5.9 µM (2.7–12.9 µM), p = 0.05; mean difference vs. LAR subjects: 6 µM (0.1–12 µM), p = 0.048], and the proportion of GSSG was positively correlated with postallergen eosinophils in all patients (rho = 0.4, p = 0.05). There was no change in nitrosothiols after 24 h in either EAR or LAR subjects (p > 0.23, all comparisons). Conclusions: GSH increases 24 h after allergen challenge in isolated early responders. These data suggest that different adoptive responses to allergen may result in different physiologic phenotypes. Further studies on the role of glutathione in allergen-induced bronchoconstriction are clearly warranted.

Heterotopic rat heart transplantation: Severe loss of glutathione in 8-hour ischemic hearts

Background Tissue damage caused by reactive oxygen species (ROS) formed during ischemia/reperfusion seems to be an important risk factor in the failure of transplanted hearts. Although endogenous anti-oxidants protect the myocardium against free radical attack under physiologic conditions, their capacity may become limited during severe oxidative stress. Thus, we investigated the effect of 8-hour cold ischemia on the myocardial anti-oxidative defense system in a heterotopic rat heart transplantation model. Methods Lewis rat hearts were subjected to 30 or 480 minutes of 4°C cold ischemia in Bretschneider cardioplegic solution with or without transplantation and reperfusion (30 or 240 minutes) into F344 recipients. Activity levels of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione S-transferase (GST), and concentrations of glutathione (GSH), glutathione disulfide (GSSG) and lipid hydroperoxides (LOOH) were analyzed in heart homogenates. For histology, cross-sections of the ventricles were stained with hematoxylin-eosin. Results Except for GST, enzyme activities and GSSG concentration increased and the glutathione redox ratio (GSH/GSH + 2GSSG) significantly decreased in 480-minute ischemic hearts compared with those with 30-minute ischemia. Reperfusion dramatically decreased both GSH and GSSG and increased LOOH formation but without severe histopathologic findings in the transplants. Applying a tree-structured classifier technique, GSH and LOOH were identified as significant features indicative of transplantation-induced oxidative stress. Conclusions In the present study severe loss of glutathione and formation of LOOH indicated transplantation-induced oxidative stress in the rat heart; therefore, alterations of these parameters may hint at relevant deficits in the myocardial anti-oxidative defense and may also predict subsequent tissue damage.

Malanga (Xanthosoma sagittifolium) and Purslane (Portulaca oleracea) Leaves Reduce Oxidative Stress in Vitamin A-Deficient Rats

Aim: This study examined the ability of tropical vegetables to reduce oxidative stress induced by vitamin A deficiency. Methods: Vitamin A-deficient male Wistar rats were divided into four groups which were treated for 30 days with different diets: AIN-93G vitamin A-deficient diet (DD), DD supplemented with pure β-carotene (β-D) and DD supplemented with malanga (Xanthosoma sagittifolium) (MD) or purslane (Portulaca oleracea) (PD) leaves as the only source of vitamin A. The thiobarbituric acid-reactive substances (TBARS), reduced (GSH) and oxidized (GSSG) glutathione, and antioxidant enzyme activities were determined in the heart and liver. Results: The rats fed β-D, MDand PD showed liver and heart TBARS concentrations lower than did DD rats. The liver GSH concentration of β-D, MD and PD rats was lower compared to DD rats. The heart GSSG concentration of the vegetable groups was significantly lower than in DD rats. Liver and heart catalase activities were not significantly different among the groups, nor was heart glutathione peroxidase (GPX) activity, however the β-D rats showed the highest liver GPX activity. There was no difference in liver glutathione-S-transferase level among the groups, while heart activity was higher in rats fed the vegetable leaves. Conclusion: This study evidences that the ingestion of purslane or malanga leaves may have a protective effect against oxidative stress caused by vitamin A deficiency.

Purification, characterization and kinetic properties of the multifunctional thioredoxin-glutathione reductase from Taenia crassiceps metacestode (cysticerci).

The multifunctional enzyme thioredoxin-glutathione reductase (TGR) was purified to homogeneity from the soluble fraction of Taenia crassiceps metacestode (cysticerci). Specific activities of 17.5 and 4.7 U mg(-1) were obtained with Plasmodium falciparum thioredoxin and GSSG, respectively, at pH 7.75. Under the same conditions, Km values of 17, 15, and 3 microM were respectively calculated for thioredoxin, GSSG and NADPH. The kcat/Km ratio of T. crassiceps TGR for both thioredoxin and GSSG falls in the range observed for typical thioredoxin reductases and glutathione reductases. Purified enzyme also showed glutaredoxin activity, with a specific activity of 19.2 U mg(-1) with hydroxyethyl disulfide as substrate. Both thioredoxin and GSSG disulfide reductase activities were fully inhibited by nanomolar concentrations of the gold compound auranofin, supporting the existence of an essential selenocysteine residue. Relative molecular mass of native enzyme was 136,000 +/- 3000, while the corresponding value per subunit, obtained under denaturing conditions, was 66,000 +/- 1000. These results suggest TGR exists as a dimeric protein. Isoelectric point of the enzyme was at pH 5.2. Moderate or high concentrations of GSSG, but neither thioredoxin nor NADPH, resulted in a markedly hysteretic kinetic, characterized by a lag time before the steady state velocity was reached. The magnitude of the lag time was dependent on GSSG and enzyme concentration. Preincubation of the enzyme with micromolar concentrations of GSH or DTT abolished the hysteresis, suggesting that a thiol-disulfide exchange mechanism is involved.

Actin S-glutathionylation: evidence against a thiol-disulphide exchange mechanism.

Many proteins, including actin, are targets for S-glutathionylation, the reversible formation of mixed disulphides between protein cysteinyl thiol groups and glutathione (GSH) that can be induced in cells by oxidative stress. Proposed mechanisms of protein S-glutathionylation follow mainly two distinct pathways. One route involves the initial oxidative modification of a reduced protein thiol to an activated protein, which may then react with GSH to the mixed disulphide. The second route involves the oxidative modification of GSH to an activated form such as glutathione disulphide (GSSG), which may then react with a reduced protein thiol, yielding the corresponding protein mixed disulphide. We show here that physiological levels of GSSG induce a little extent of actin S-glutathionylation. Instead, actin with the exposed cysteine thiol activated by diamide or 5,5'-dithiobis(2-nitrobenzoic acid) reacts with physiological levels of GSH, incorporating about 0.7 mol GSH/mol protein. Differently, an extremely high concentration of GSSG induces an increased level of S-glutathionylation that causes a 50% inhibition in actin polymerization not reversed by dithiotreitol. In mammalian cells, GSH is present in millimolar concentrations and is in about 100-fold excess over GSSG. The high concentration of GSSG required for obtaining a significant actin S-glutathionylation as well as attendant irreversible changes in protein functions make unlikely that actin may be S-glutathionylated by a thiol-disulphide exchange mechanism within the cell.

New equations for redox and nano-signal transduction

Cells maintain redox potentials ( E h ) in intracellular compartments, sometimes referred to as redox environments. These potentials are often very reducing, for example in the cytoplasm, but throughout the cell different potentials are maintained, commensurate with the functionality of that particular part of the cell. Furthermore, within a simple cellular compartment, “hot-spots” of redox poise may be maintained. However, despite this complexity, the quantification of such redox potentials has been attempted, and there is indeed a need to accurately assess such potentials, and to monitor how they might change with time. Changes in intracellular potentials may control the oxidation or reduction of protein residues, such as cysteine, which would alter the conformation of those proteins and so modulate their function. Although there are several methods for estimating the intracellular redox potential, the most accessible technique is the measurement of intracellular concentrations of GSH and GSSG, and the calculation of E h using the Nernst equation. However, using this equation shows that the E h imposed by the glutathione couple is dependent on the total concentration of glutathione present, and therefore values of E h obtained may be erroneous. Here, we suggest new equations that can be used to calculate the redox environments of cells.

Effects of age and caloric restriction on glutathione redox state in mice.

The main purpose of this study was to determine whether the aging process in the mouse is associated with a pro-oxidizing shift in the redox state of glutathione and whether restriction of caloric intake, which results in the extension of life span, retards such a shift. Amounts of reduced and oxidized forms of glutathione (GSH and GSSG, respectively) and protein-glutathione mixed disulfides (protein-SSG) were measured in homogenates and mitochondria of liver, kidney, heart, brain, eye, and testis of 4, 10, 22, and 26 month old ad libitum-fed (AL) mice and 22 month old mice fed a diet containing 40% fewer calories than the AL group from the age of 4 months. The concentrations of GSH, GSSG, and protein-SSG vary greatly (approximately 10-, 30-, and 9-fold, respectively) from one tissue to another. During aging, the ratios of GSH:GSSG in mitochondria and tissue homogenates decreased, primarily due to elevations in GSSG content, while the protein-SSG content increased significantly. Glutathione redox potential in mitochondria became less negative, i.e., more pro-oxidizing, as the animal aged. Caloric restriction (CR) lowered the GSSG and protein-SSG content. Results suggest that the aging process in the mouse is associated with a gradual pro-oxidizing shift in the glutathione redox state and that CR attenuates this shift.

Hibernation induces glutathione redox imbalance in ground squirrel intestine.

Glutathione (GSH) is the major thiol-disulfide redox buffer in cells and is a critical component of antioxidant defense. Here we examined GSH redox balance in the intestinal mucosa during the annual cycle of 13-lined ground squirrels (Spermophilus tridecemlineatus). The ratio of reduced GSH to its oxidized form (glutathione disulfide, GSSG), which is an index of oxidative stress, was five-fold lower in hibernating compared with summer-active squirrels, an effect due primarily to elevated GSSG concentration in hibernators. During hibernation the total pool of GSH equivalents was lowest in squirrels undergoing arousal and highest in squirrels during interbout arousals. Hibernation decreased intestinal GSSG reductase activity by approximately 50%, but had no effect on activities of glutathione peroxidase or glucose-6-phosphate dehydrogenase. Within the hibernation season, expression of the stress protein HSP70 in intestinal mucosa was highest in squirrels entering torpor and early in a torpor bout, and lowest in squirrels arousing from torpor and during interbout euthermia. The results suggest that hibernation in ground squirrels is associated with a shift in intestinal GSH redox balance to a more oxidized state. Higher levels of HSP70 during the early phases of torpor may reflect induction of the stress response due to aberrations in protein folding or may be a mechanism to increase enterocyte tolerance to subsequent stress imposed by extended torpor or the arousal process.

Non-reciprocal regulation of the redox state of the glutathione-glutaredoxin and thioredoxin systems.

Our studies in yeast show that there is an essential requirement for either an active thioredoxin or an active glutathione (GSH)-glutaredoxin system for cell viability. Glutathione reductase (Glr1) and thioredoxin reductase (Trr1) are key regulatory enzymes that determine the redox state of the GSH-glutaredoxin and thioredoxin systems, respectively. Here we show that Trr1 is required during normal cell growth, whereas there is no apparent requirement for Glr1. Analysis of the redox state of thioredoxins and glutaredoxins in glr1 and trr1 mutants reveals that thioredoxins are maintained independently of the glutathione system. In contrast, there is a strong correlation between the redox state of glutaredoxins and the oxidation state of the GSSG/2GSH redox couple. We suggest that independent redox regulation of thioredoxins enables cells to survive in conditions under which the GSH-glutaredoxin system is oxidized.

Effects of different mitogens on intrasplenic liver tissue transplants in comparison to orthotopic liver

Ectopic liver cell transplants, when compared to orthotopic liver, can serve as a tool to study topic influences on liver cell differentiation, multiplication, function and responsiveness to xenobiotics. The aim of the present study was to evaluate, if characteristic effects of mitogens are exerted in both liver and intrasplenic liver cell transplants in a similar manner. Fetal liver tissue suspensions were transplanted into the spleens of adult male syngenic rats. Four months later, transplant recipients and controls were treated with fluorene (FEN), fluorenone (FON), 2-acetylaminofluorene (AAF), N-nitrosodibenzylamine (NDBA) or the solvent 48 hours before sacrifice. The following parameters were assessed within livers and spleens: mitotic activity of hepatocytes, glycogen content, cytochrome P450 (P450) isoforms expression, P450 mediated monooxygenase functions, tissue content of lipid peroxides (LPO) and of reduced and oxidized glutathione (GSH; GSSG). In both orthotopic livers and intrasplenic transplants FEN, FON or NDBA administration increased the mitotic activity of the hepatocytes. Treatment with the mitogens caused a distinct and characteristic induction of the P450 isoforms expression and of the respective monooxygenase functions in the livers and (with certain differences) also in the transplants. FEN and FON slightly increased, AAF and NDBA reduced liver glycogen content. The latter effect was also seen in the transplants. NDBA administration caused a slight increase in tissue LPO content in livers, but not in spleens. Additionally, AAF or NDBA treatment led to an elevation of liver (but not of spleen) GSH and GSSG concentrations. The results of the present investigation show that characteristic effects of mitogens on orthotopic liver occur with certain differences also in ectopic liver cell transplants.

Redox control of platelet aggregation.

Sulfhydryl and disulfide metabolism in platelet function has recently reemerged as a focus of platelet research. In this study we tested the effect of redox buffer on platelet aggregation and the effect of reduced glutathione (GSH) and platelet activation on sulfhydryl exposure in the platelet fibrinogen receptor, alpha IIb beta 3. In the presence of subthreshold concentrations of agonist, physiologic concentrations of GSH (10 microM) stimulated platelet aggregation and secretion. These effects were found with more than one platelet agonist and with different low molecular weight thiols, including homocysteine. The effect of low molecular weight thiols was reproduced with the peptide LSARLAF which directly activates platelets through alpha IIb beta 3, suggesting that the mechanism is at the level of this integrin. After determining optimal sulfhydryl labeling conditions for alpha IIb beta 3 (5 mM EDTA, 37 degrees C, 60 min), we found that GSH (10 microM) generated sulfhydryls in the beta 3 subunit. To determine if the requirement was for reducing equivalents or for a redox potential (ratio of GSH to GSSG), aggregation was further studied with the addition of low concentrations of GSSG to the GSH. With a ratio of GSH/GSSG of 5/1, similar to that of blood, the addition of GSSG potentiated the stimulatory effect as compared to GSH alone. This indicates that, for potentiation of aggregation, GSH is not simply reducing disulfide bonds; there is rather a requirement for a certain redox potential. Additional studies performed in the absence of added glutathione showed an increase in sulfhydryl labeling in the beta 3 subunit during platelet activation. Finally, we show that vicinal dithiols of platelet surface proteins are involved in the sulfhydryl-dependent pathways of platelet activation. In summary, these data imply that the redox potential of blood regulates activation of the alpha IIb beta 3 integrin and together with other reports in the literature suggest that disulfide bond cleavage with sulfhydryl generation in beta 3 is involved in activation of this receptor.

Hyperoxemia caused by resuscitation with pure oxygen may alter intracellular redox status by increasing oxidized glutathione in asphyxiated newly born infants

In a prospective, randomized, blinded trial we have studied the effects of resuscitation upon oxygenation in a group of asphyxiated newly born infants receiving room air or 100% oxygen as the gas source. During the acute phase of asphyxia and until the resuscitation procedure concluded, we determined serial blood gases as well as reduced and oxidized glutathione, enzymes involved in the glutathione redox cycle, and antioxidant enzyme activities. The use of 100% oxygen caused a remarkable increase of partial pressures of oxygen in arterial blood, with values that were frequently above physiological levels (> 100 mm Hg). In addition, we have found a significant correlation between hyperoxemia and the intra-erythrocyte GSSG (oxidized glutathione) concentration. We hypothesize that hyperoxemia may be 1 of the triggering factors responsible for an increased oxidation of GSH (reduced glutathione). Moreover, an increased antioxidant enzyme activity, which reflects an oxidative stress, indicates that the antioxidant capacity of the newly born infant may have been surpassed.

Glutathione redox system, GSH-Px activity and lipid peroxidation (LPO) levels in tadpoles of R.r.ridibunda and B.viridis.

Total glutathione (t-GSH), reduced glutathione (GSH), glutathione disulphide (GSSG) levels, t-GSH/GSSG ratio, glutathione peroxidase (GSH-Px) activity and lipid peroxidation (LPO) levels were investigated during the development period of a predominantly aquatic amphibian R.r.ridibunda and a predominantly terrestrial amphibian B. viridis. While t-GSH and GSH showed a similar trend, GSSG concentration increased significantly (p<0.05) during the larval stages in R.r.ridibunda larvae. In contrast to R.r.ridibunda larvae, there was no significant (p>0.05) change between 1 and 5 weeks in the t-GSH and GSH concentrations of B. viridis. t-GSH and GSH concentrations of B. viridis larvae became sharply elevated after the fifth week, GSSG levels increased 3.25-fold during the metamorphosis. The t-GSH/GSSG ratio fluctuated and the lowest t-GSH/GSSG ratios were observed at the third week for both species. GSH-Px activities for both species increased significantly (p<0.05) during the growing period. The highest GSH-Px activities in R.r.ridibunda and B.viridis were observed at the eighth week and they were 3.45 +/- 0.17 and 4.1 +/- 0.21 IU mg(-1), respectively. The membrane LPO levels in the R.r.ridibunda and B. viridis tadpoles significantly (p<0.001) decreased from 206 +/- 10.3 to 146 +/- 7.3 and from 198 +/- 9.9 to 23 +/- 1.15 nmol MDA g(-1) w.w., respectively.

Accumulation of glutathione disulfide mediates NF-kappaB activation during immune stimulation with CpG DNA.

Innate immune cells recognize pathogens by detecting molecular patterns that are distinct from those of the host. One such pattern is unmethylated CpG dinucleotides, which are common in bacterial DNA but not in vertebrate genomes. Macrophages respond to such CpG motifs in bacterial DNA or synthetic oligodeoxynucleotides (ODN) by inducing NF-kappaB and secreting proinflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), but the mechanisms regulating this have been unclear. CpG ODN-stimulated cells produce reactive oxygen species (ROS) and have a decreased ratio of intracellular glutathione/glutathione disulfide (GSH/GSSG), indicating a shift to a more oxidized intracellular redox state. To determine whether this may play a role in mediating the CpG-induced macrophage activation, the GSH/GSSG redox state was manipulated in the murine macrophagelike cell line RAW264.7. Treatment of cells with BCNU to inhibit glutathione reductase (GR) enhanced the CpG-induced intracellular oxidation and decreased the GSH/GSSG, with increased activation of NF-kappaB and a doubling in the CpG-induced production of IL-6 and TNF-alpha. Experimental manipulation of the intracellular GSSG concentration during inhibition of cellular prooxidant production demonstrated that increased intracellular GSSG is a primary signal that is directly or indirectly required for CpG-induced NF-kappaB activation but is not in itself sufficient to trigger this in the absence of CpG ODN. These data suggest the existence of a second CpG-induced intracellular signal, independent of GSSG, mediating the activation of innate immunity by bacterial DNA.

Oxidation of the Glutathione/Glutathione Disulfide Redox State Is Induced by Cysteine Deficiency in Human Colon Carcinoma HT29 Cells

Glutathione (GSH) has a central role in the maintenance of the thiol-disulfide redox state in mammalian cells. GSH synthesis can be physiologically limited by the availability of cysteine (Cys), and Cys and its precursors are variable in the human diet. The purpose of this study was to determine the effect of severe Cys deficiency and readdition of Cys on the redox state of the GSH/glutathione disulfide (GSSG) pool in human colon carcinoma HT29 cells. Cells were cultured in Cys- (and cystine-)limiting medium for 48 h followed by culture in medium containing either Cys or cystine for 24 h. GSH and GSSG were measured by HPLC. Cys limitation decreased cellular GSH and GSSG concentrations with an associated >80 mV oxidation of the GSH/GSSG redox state. Upon addition of either Cys or its disulfide cystine (CySS), redox of GSH/GSSG recovered in 4 h, whereas GSH concentration continued to increase over 12 h. Maximal GSH concentrations attained were 200% of control cell values. These results show that severe Cys deficiency can have marked effects on cellular redox state but that redox recovers rapidly upon resupply. The magnitude of oxidation during Cys limitation in this cell model is sufficient to result in a >100-fold change in the reduced/oxidized ratio of redox-sensitive dithiol/disulfide motifs in proteins. If redox changes occur in vivo in association with variations in dietary Cys and its precursors, these changes could have important physiologic effects through altered redox signaling and control of cell proliferation and apoptosis.