Redox capacity of cells affects inactivation of glutathione reductase by nitrosative stress

Human Erythrocyte Acetylcholinesterase in Health and Disease

The biochemical properties of erythrocyte or human red blood cell (RBC) membrane acetylcholinesterase (AChE) and its applications on laboratory class and on research are reviewed. Evidence of the biochemical and the pathophysiological properties like the association between the RBC AChE enzyme activity and the clinical and biophysical parameters implicated in several diseases are overviewed, and the achievement of RBC AChE as a biomarker and as a prognostic factor are presented. Beyond its function as an enzyme, a special focus is highlighted in this review for a new function of the RBC AChE, namely a component of the signal transduction pathway of nitric oxide.

Effects of Gold Nanoparticles and Gold Anti-Arthritic Compounds on Inflammation Marker Expression in Macrophages

The ability of aurothiomalate and auranofin to alter the production of several cellular mediators of inflammation by RAW264.7 macrophages, was compared with each other and that of gold nanoparticles (Au NPs). Addition of auranofin was found to have a pronounced ability to lower the production of reactive nitrogen and oxygen species (RNS and ROS respectively), as well as interleukin-10 (IL-10) and tumour necrosis factor (TNF), by macrophages that were subsequently treated with lipopolysaccharide (LPS) to stimulate production of the mediators. In contrast, prior treatment of the cells with either aurothiomalate or Au NPs had either little or no significant effect on production of RNS and ROS. Treatment of the macrophages with Au NPs had a small effect on production of TNF by cells that were subsequently stimulated with LPS; however, the effect was much smaller than that elicited by auranofin. Similarly, aurothiomalate had a small but significant effect on production of IL-10. Varying the size of the Au NPs or the identity of the protective sheath surrounding the nanoparticles did not have a significant effect on the production of RNS or ROS by LPS-stimulated macrophages. The results of some of these investigations are discussed in the light of other studies reported in the literature. In addition, results obtained by scanning electron microscopy and energy-dispersive X-ray spectroscopy are presented that provide evidence for the accumulation of gold within macrophages exposed to Au NPs.

Glyco-redox, a link between oxidative stress and changes of glycans: Lessons from research on glutathione, reactive oxygen and nitrogen species to glycobiology

Reduction-oxidation (redox) response is one of the most important biological phenomena. The concept introduced by Helmut Sies encouraged many researchers to examine oxidative stress under pathophysiological conditions. Our group has been interested in redox regulation under oxidative stress as well as glycobiology in relation to disease. Current studies by our group and other groups indicate that functional and structural changes of glycans are regulated by redox responses resulting from the generation of reactive oxygen species (ROS) or reactive nitrogen species (RNS) in various diseases including cancer, diabetes, neurodegenerative disease such as Parkinson disease, Alzheimer's disease and amyotrophic lateral sclerosis (ALS), and chronic obstructive pulmonary disease (COPD), even though very few investigators appear to be aware of these facts. Here we propose that the field "glyco-redox" will open the door to a more comprehensive understanding of the mechanism associated with diseases in relation to glycan changes under oxidative stress. A tight link between structural and functional changes of glycans and redox system under oxidative stress will lead to the recognition and interest of these aspects by many scientists. Helmut's contribution in this field facilitated our future perspectives in glycobiology.

Application of a nitric oxide sensor in biomedicine

In the present study, we describe the biochemical properties and effects of nitric oxide (NO) in intact and dysfunctional arterial and venous endothelium. Application of the NO electrochemical sensor in vivo and in vitro in erythrocytes of healthy subjects and patients with vascular disease are reviewed. The electrochemical NO sensor device applied to human umbilical venous endothelial cells (HUVECs) and the description of others NO types of sensors are also mentioned.

ROS production and their influence on the cellular antioxidative system in human erythrocytes incubated with daunorubicin and glutaraldehyde

This study examined the effects of daunorubicin and glutaraldehyde on some parameters of erythrocytes. The aim of the article was to present the results of research aiming to identify the level of glutaraldehyde at which the hemoglobin oxidation, externalization of phosphatidylserine and the changes in the viability (hemolysis) of erythrocytes are not statistically significant and therefore this level of glutaraldehyde can be used for the drug carriers' preparation. Glutaraldehyde was used as a crosslinking agent to enhance the uptake of the drug within red blood cells and to prevent its leakage from the cells. Fluorescence microscopy, flow cytometry and fluorimetric measurements confirmed higher levels of the drug in glutaraldehyde-treated human erythrocytes. Unfortunately, substantial damage to the red blood cells was also noted. DNR increased oxidative processes in the cell, which in turn led to an increase in the reactive oxygen species (ROS) level. When the red blood cells were also treated with glutaraldehyde, ROS production was significantly higher. We also observed loss of both the reduced and the total glutathione. Moreover the decreased activity of glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD) was also observed. As hemoglobin, the erythrocytes' main component plays an essential role in the erythrocytes, the level of its oxidized form (metHb) in the erythrocytes and the phosphatidylserine exposure on the erythrocyte surface were also investigated. When higher concentrations of glutaraldehyde (0.0025-0.005%) were used for the uptake of DNR the elevated level of metHb was observed. Only at 0.0005% the level of oxidized form of Hb was within the physiological level and at that level the increase in the exposure of phosphatidylserine at the cell surface was not observed to be statistically significant. Moreover the percent of released hemoglobin was less than 1%. Based on these results it was concluded that glutaraldehyde can be used as a cross-linker between the drug (DNR) and the erythrocytes only at low concentration of about 0.0005%.

Oxidative/nitrosative stress and protein damages in aqueous humor of hyperglycemic rabbits: effects of two oral antidiabetics, pioglitazone and repaglinide

The present study was undertaken to determine oxidative/nitrosative stress in aqueous humor of alloxan-induced hyperglycemic rabbits and to investigate the effects of two oral antidiabetic drugs, pioglitazone from peroxisome proliferator-activated receptor gamma (PPARγ) agonists and repaglinide from nonsulfonylurea K_ATP channel blockers. Ascorbic acid (AA), glutathione (GSH), total antioxidant status (TAS), lipid peroxidation products (LPO), total nitrites (NO₂), advanced oxidized protein products (AOPP), and protein carbonyl groups (PCG) were determined using respective colorimetric and ELISA methods. In our hyperglycemic animals, AA decreased by 77%, GSH by 45%, and TAS by 66% as compared to control animals. Simultaneously, LPO increased by 78%, PCG by 60%, AOPP by 84%, and NO₂ by 70%. In pioglitazone-treated animals, AA and TAS increased above control values while GSH and PCG were normalized. In turn, LPO was reduced by 54%, AOPP by 84%, and NO₂ by 24%, in relation to hyperglycemic rabbits. With repaglinide, AA and TAS were normalized, GSH increased by 20%, while LPO decreased by 45%. Our results show that pioglitazone and repaglinide differ significantly in their ability to ameliorate the parameters like NO₂, PCG, and AOPP. In this area, the multimodal action of pioglitazone as PPARγ agonist is probably essential.

Bisphenol A effect on glutathione synthesis and recycling in testicular Sertoli cells

BACKGROUND AND OBJECTIVE

Controversial effects of bisphenol A (BPA) have been reported on testicular function. These differences might reflect dissimilar exposure conditions. Dose responses to toxicants may be non-linear, e.g. U-shaped, with effects at low and at high levels of exposure and lower or inexistent effects at intermediate levels. Sertoli cells produce high levels of glutathione (GSH) as a cell defense mechanism. In this study, we addressed the question whether the exposure to different doses of BPA could influence Sertoli cell GSH synthesis and recycling.

MATERIALS AND METHODS

Primary Sertoli cell cultures were exposed to various doses of BPA (0.5 nM-100 μM). Cell viability was measured as an outcome of toxic effect. GSH cell content was determined to evaluate cell response to toxicant exposure. Glutamate-cysteine ligase catalytic (GCLC) and modulatory (GCLM) subunit expression were assessed to estimate GSH synthesis, and GSH reductase (GR) expression to estimate GSH recycling.

RESULTS

BPA 100 μM, but not lower doses, decreased cell viability. BPA 10 and 50 μM, but not lower doses, induced an increment in Sertoli cell GSH levels, due to a rapid upregulation of GCLC and GR and a slower upregulation of GCLM.

CONCLUSIONS

High doses of BPA are deleterious for Sertoli cells. Intermediate doses do not affect Sertoli cell viability and increase cell content of GSH owing to increased GSH synthesis and recycling enzyme expression. Lower doses of BPA are not capable of eliciting a cell defense response. These observations may explain a non-linear dose response of Sertoli cells to BPA.

Deterioration of ischemia/reperfusion-induced acute renal failure in SOD1-deficient mice

Reactive oxygen species (ROS) are likely candidates for involvement in ischemia/reperfusion-induced acute renal failure (ARF). In this study, the issue of whether superoxide dismutase (SOD1)-deficiency exacerbates the ischemia/reperfusion-induced ARF was examined. At two weeks after a right nephrectomy of mice, the left renal vessels were clipped to induce renal ischemia and were then released after 45 min. The severe renal damage observed at one day was partially recovered at seven days after the induction of ischemia. SOD1-/- mice suffer from severe ARF compared with SOD1+ - and SOD1+/+ mice. The damage was more evident in aged animals (24-28 week old) than younger ones (10-12 week old). The expression of major antioxidative and redox enzymes, except for CuZnSOD, were substantially unchanged. Thus, the increased ARF in SOD1-/- mice appears to be mainly attributable to a deficiency in CuZnSOD. These data support the view that ROS are exacerbating factors in ischemia/reperfusion-induced ARF.

Decreasing peroxiredoxin II expression decreases glutathione, alters cell cycle distribution, and sensitizes glioma cells to ionizing radiation and H(2)O(2)

Glioblastomas are notorious for their resistance to ionizing radiation and chemotherapy. We hypothesize that this resistance to ionizing radiation is due, in part, to alterations in antioxidant enzymes. Here, we show that rat and human glioma cells overexpress the antioxidant enzyme peroxiredoxin II (Prx II). Glioma cells in which Prx II is decreased using shRNA exhibit increased hyperoxidation of the remaining cellular Prxs, suggesting that the redox environment is more oxidizing. Of interest, decreasing Prx II does not alter other antioxidant enzymes (i.e., catalase, GPx, Prx I, Prx III, CuZnSOD, and MnSOD). Analysis of the redox environment revealed that decreasing Prx II increased intracellular reactive oxygen species in 36B10 cells; extracellular levels of H(2)O(2) were also increased in both C6 and 36B10 cells. Treatment with H(2)O(2) led to a further elevation in intracellular reactive oxygen species in cells where Prx II was decreased. Decreasing Prx II expression in glioma cells also reduced clonogenic cell survival following exposure to ionizing radiation and H(2)O(2). Furthermore, lowering Prx II expression decreased intracellular glutathione and resulted in a significant decline in glutathione reductase activity, suggesting a possible mechanism for the observed increased sensitivity to oxidative insults. Additionally, decreasing Prx II expression increased cell cycle doubling times, with fewer cells distributed to S phase in C6 glioma cells and more cells redistributed to the most radiosensitive phase of the cell cycle, G2/M, in 36B10 glioma cells. These findings support the hypothesis that inhibiting Prx II sensitizes glioma cells to oxidative stress, presenting Prxs as potential therapeutic targets.

FSH and bFGF stimulate the production of glutathione in cultured rat Sertoli cells

Migration of developing germ cells from the basal to the adluminal compartment of the seminiferous epithelium requires extensive tissue restructuring, resulting in the production of reactive oxygen species. Sertoli cells are involved in this process. Glutathione (GSH), produced by Sertoli cells, has an essential role in cell protection against oxidative stress. Intracellular GSH content is maintained by de novo synthesis, involving glutamate-cysteine ligase catalytic (GCLC) and modulatory (GCLM) subunits, and by recycling from oxidized GSH, catalysed by glutathione reductase (GR). To assess whether follicle-stimulating hormone (FSH) and basic fibroblast growth factor (bFGF) modulate GSH production in Sertoli cells by regulating the expression of GCLC, GCLM and/or GR, we performed in vitro studies using rat Sertoli cells in primary culture. FSH and bFGF stimulation increased Sertoli cell GSH levels after 24 h incubation. The simultaneous addition of FSH and bFGF did not produce any further effect. GCLM expression was upregulated by FSH and bFGF 6 h. At 24 h, only the FSH-mediated effect was still observed. FSH and bFGF also upregulated GR expression. In conclusion, our results show that FSH and bFGF increase GSH levels in Sertoli cells through stimulation of the de novo synthesis and recycling by upregulating GCLM and GR expression respectively. Therefore, protection of germ cells against oxidative stress seems to be regulated by hormones and germ cell-released growth factors capable of influencing the production of Sertoli cell GSH.

Regulation of Antioxidants and Phase 2 Enzymes by Shear-Induced Reactive Oxygen Species in Endothelial Cells

Exposure of vascular endothelial cells (ECs) to steady laminar shear stress activates the NF-E2-related factor 2 (Nrf2) which binds to the antioxidant response element (ARE) and upregulates the expression of several genes. The onset of shear is known to increase the EC reactive oxygen species (ROS) production, and oxidative stress can activate the ARE. ARE-regulated genes include phase 2 enzymes, such as glutathione-S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1), and antioxidants, such as glutathione reductase (GR), glutathione peroxidase (GPx) and catalase. We examined how shear stress affects the antioxidant/phase 2 enzyme activities and whether ROS mediate these effects. ROS production, measured by dichlorofluorescin fluorescence, depended on level and time of shear exposure and EC origin, and was inhibited by either an endothelial nitric oxide synthase (eNOS) inhibitor or a superoxide dismutase (SOD) mimetic and peroxynitrite (ONOO-) scavenger. Shear stress (10 dynes/cm2, 16 h) significantly increased the NQO1 activity, did not change significantly the glutathione (GSH) content, and significantly decreased the GR, GPx, GST and catalase activities in human umbilical vein ECs. Either eNOS inhibition or superoxide radical (O2*-)/ONOO- scavenging differentially modulated the shear effects on enzyme activities suggesting that the intracellular redox status coordinates the shear-induced expression of cytoprotective genes.

Damage of cell membrane and antioxidative system in human erythrocytes incubated with microcystin-LR in vitro

The effect of the exposure of human erythrocytes to different concentrations of microcystin-LR were studied. Lipid peroxidation, membrane fluidity, cell morphology, haemoglobin oxidation and changes in the activity of antioxidant enzymes were investigated. Human erythrocytes were incubated with microcystin-LR at concentrations of 1-1000 nM for 1, 6, 12 and 24 h. We observed that microcystin-LR induces a significant increase of the level of thiobarbituric acid reactive substances (TBARS), formation of echinocytes, haemolysis, conversion of oxyhaemoglobin to methaemoglobin, decrease of membrane fluidity on the level of 16 carbon atom fat acids. The compound also changed antioxidative enzymes activities: catalase, superoxide dismutase and glutathione reductase and formation of reactive oxygen species (ROS). All of the observed changes point out that 100 nM of Microcistin LR is the liminal (threshold) toxic dose for human erythrocytes. This dose caused most of the described changes. Observed damages of erythrocytes membrane and antioxidative enzymes may be the result of direct covalent binding of microcystin-LR with -SH residues of proteins and indirectly be related with reactive oxygen species formation.

Intracellular Ca(2+) and Zn(2+) signals during monochloramine-induced oxidative stress in isolated rat colon crypts

During acute exacerbations of inflammatory bowel diseases, oxidants are generated through the interactions of bacteria in the lumen, activated granulocytes, and cells of the colon mucosa. In this study we explored the ability of one such class of oxidants, represented by monochloramine (NH(2)Cl), to serve as agonists of Ca(2+) and Zn(2+) accumulation within the colonocyte. Individual colon crypts prepared from Sprague-Dawley rats were mounted in perfusion chambers after loading with fluorescent reporters fura 2-AM and fluozin 3-AM. These reporters were characterized, in situ, for responsiveness to Ca(2+) and Zn(2+) in the cytoplasm. Responses to different concentrations of NH(2)Cl (50, 100, and 200 microM) were monitored. Subsequent studies were designed to identify the sources and mechanisms of NH(2)Cl-induced increases in Ca(2+) and Zn(2+) in the cytoplasm. Exposure to NH(2)Cl led to dose-dependent increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) in the range of 200-400 nM above baseline levels. Further studies indicated that NH(2)Cl-induced accumulation of Ca(2+) in the cytoplasm is the result of release from intracellular stores and basolateral entry of extracellular Ca(2+) through store-operated channels. In addition, exposure to NH(2)Cl resulted in dose-dependent and sustained increases in intracellular Zn(2+) concentration ([Zn(2+)](i)) in the nanomolar range. These alterations were neutralized by dithiothreitol, which shields intracellular thiol groups from oxidation. We conclude that Ca(2+)- and Zn(2+)-handling proteins are susceptible to oxidation by chloramines, leading to sustained, but not necessarily toxic, increases in [Ca(2+)](i) and [Zn(2+)](i). Under certain conditions, NH(2)Cl may act not as a toxin but as an agent that activates intracellular signaling pathways.

Glutathione reductase is expressed at high levels in pancreatic islet cells

Reactive oxygen species are, at least partly, involved in the diabetogenic agent-induced dysfunction of pancreatic beta-cells because the expression of antioxidative and redox proteins is low. We examined the levels of antioxidant/redox proteins, peroxiredoxins-1, -4, and -6 and glutathione reductase (GR), by immunohistochemistry and found that the expression of GR was very high in pancreatic islet cells compared to exocrine cells. When diabetes was induced by an intravenous injection of streptozotocin, the pre-administration of 1,3-bis[2-chloroethyl]-1-nitrosourea, an irreversible inhibitor of GR, made islet cells more vulnerable to streptozotocin. These data point to a pivotal role of the glutathione redox system in pancreatic islet cells against diabetogenic stress.

Detection of S-glutathionylated proteins by glutathione S-transferase overlay

Oxidative and nitrosative stress lead to the S-glutathionylation of proteins and subsequent functional impairment. Glutathione S-transferase (GST) from Schistosoma japonicum was found to bind to the glutathione moiety of S-glutathionylated proteins, thus establishing a convenient method for detecting S-glutathionylated proteins by biotinylated GST. Applications of this method to proteins that were prepared from cultured cells and blotted onto a membrane exhibited numerous positive bands, which were abolished by treatment with dithiothreitol. Treatment of a cellular extract with nitrosoglutathione led to enhanced staining of the bands in a dose-dependent manner. The method was also applicable for the histochemical detection of S-glutathionylated proteins in situ. The positive staining by biotin-GST became faint in the presence of S-glutathionylated ovalbumin, suggesting that the reaction is specific to S-glutathionylated proteins. Collectively, these data indicate that the method established here is simple and useful for detecting S-glutathionylated proteins on blotted membrane and in situ.

Acetylcholine and choline effects on erythrocyte nitrite and nitrate levels

Acetylcholine has been detected in human blood. Acetylcholine receptors and acetylcholinesterase are present in erythrocyte membranes. We tested the acetylcholine and choline effects on nitric oxide metabolites (NOx), namely nitrites and nitrates, and observed if they are dependent on interactions with muscarinic receptors and acetylcholinesterase. Human erythrocyte suspensions were incubated with acetylcholine and choline in the absence or presence of 10 microM atropine or 10 microM velnacrine maleate. The nitrite and nitrate concentrations were determined by the Griess method. Acetylcholine or choline increased NOx control concentrations (P <0.001). The nitrite concentrations decreased in the presence of atropine or velnacrine maleate (P <0.03). The nitrate concentrations only decreased when velnacrine maleate was incubated with acetylcholine or choline (10 microM, P <0.03). These results demonstrated that acetylcholine and choline modulate nitric oxide metabolites on erythrocytes and this effect is mediated by interactions with erythrocyte membrane muscarinic receptors and membrane enzyme acetylcholinesterase. A hypothesis for the signal transduction mechanism has been discussed for acetylcholinesterase and muscarinic receptor (M1) participation.

Increased oxidative stress with aging reduces chondrocyte survival: Correlation with intracellular glutathione levels

OBJECTIVE

To examine the role of oxidative stress in mediating cell death in chondrocytes isolated from the articular cartilage of young and old adult human tissue donors.

METHODS

Cell death induced by the oxidant SIN-1 was evaluated in the alginate bead culture system using fluorescent probes to assess membrane integrity. Generation of peroxynitrite by the decomposition of SIN-1 was confirmed by positive immunostaining of treated cells for 3-nitrotyrosine. Determinations of oxidized glutathione (GSSG) and reduced glutathione (GSH) were performed in monolayer cultures using an enzyme- recycling assay. Cells were depleted of intracellular glutathione either by the addition of DL-buthionine-(S,R)-sulfoximine or by removal of L-cystine from the culture media. The activity of cellular antioxidant enzymes was determined spectrophotometrically by the decay of substrate from the reaction mixture.

RESULTS

More chondrocytes (>2-fold) from old donors (>/=50 years) died after exposure to 1 mM SIN-1 relative to those derived from young donors (18-49 years). Although autocrine production of insulin-like growth factor 1 (IGF-1) promotes chondrocyte survival, pretreatment with IGF-1 could not prevent the cell death induced by SIN-1 exposure. Cells isolated from old donors had a higher ratio of GSSG to GSH. Glutathione reductase is the principal enzyme involved in the regeneration of GSH from GSSG. Treatment of chondrocytes with SIN-1 to induce oxidative stress in vitro resulted in the decreased activity of glutathione reductase and thioredoxin reductase, but not catalase. Cells depleted of intracellular glutathione were more susceptible to cell death induced by SIN-1.

CONCLUSION

These results provide evidence that increased oxidative stress with aging makes chondrocytes more susceptible to oxidant-mediated cell death through the dysregulation of the glutathione antioxidant system. This may represent an important contributing factor to the development of osteoarthritis in older adults.

Identification of glutathione modifications by cigarette smoke

Although it has been recognized for decades that cigarette smoke (CS) is toxic to respiratory tract tissues, and that glutathione (GSH) and other thiols are able to ameliorate some of the adverse effects of CS, the precise interactions between thiols and critical CS components are only partially characterized. In the present study, we used HPLC and MALDI-MS approaches to more rigorously characterize the products of CS reactions with GSH, the major cellular thiol and an important antioxidant constituent in respiratory tract lining fluids, in an attempt to increase our understanding of mechanisms of CS respiratory tract toxicity. Exposure of solutions of GSH to gas phase CS resulted in its rapid depletion, and about 50% of this depletion could be accounted for by reaction with acrolein and crotonaldehyde, the two major alpha, beta-unsaturated aldehydes in CS. Similar aldehyde adducts with GSH could also be detected in cells exposed to CS, although the relative yields were limited, presumably because of further reactions of these adducts and/or their excretion. Further characterization of in vivo thiol-aldehyde formation in respiratory tract cells can be expected to provide significant insights into the mechanisms of CS toxicity.

Dynamic and biphasic modulation of nitrosation reaction by superoxide dismutases

It has been shown that superoxide dismutase (SOD) can both potentiate and attenuate NO-mediated toxicity. This present study investigated the role of SOD and GSH in a sustained nitrosative and oxidative environment simulated by the nitric oxide (NO) and superoxide (O(2)(.-)) donor, 3-morpholinosydnonimine (SIN-1). We describe, for the first time, that SOD modulates nitrosative chemistry in a dynamic fashion that is both concentration and time-dependent. Specifically, our results show that SOD's effects on nitrosation are biphasic in nature i.e., while lower concentrations of SOD are pronitrosative, higher SOD concentrations inhibit nitrosation. However, even those initially inhibitory higher SOD concentrations became pronitrosative over time. In the presence of physiologically relevant levels of GSH, SOD predominantly exhibits a pronitrosative effect, with a complete loss of antinitrosative effects noted at higher levels of GSH. Our findings likely reflect the complex and dynamic nature of SOD interactions with oxidative and nitrosative species.

The expression of glutathione reductase in the male reproductive system of rats supports the enzymatic basis of glutathione function in spermatogenesis

Glutathione reductase (GR) recycles oxidized glutathione (GSSG) by converting it to the reduced form (GSH) using an NADPH as the electron source. The function of GR in the male genital tract of the rat was examined by measuring its enzymatic activity and examining the gene expression and localization of the protein. Levels of GR activity, the protein, and the corresponding mRNA were the highest in epididymis among testes, vas deferens, seminal vesicle, and prostate gland. The localization of GR, as evidenced by immunohistochemical techniques, reveals that it exists at high levels in the epithelia of the genital tract. In testis, GR is mainly localized in Sertoli cells. The enzymatic activity and protein expression of GR in primary cultured testicular cells confirmed its predominant expression in Sertoli cells. Intracellular GSH levels, expressed as mol per mg protein, was higher in spermatogenic cells than in Sertoli cells. As a result of these findings, the effects of buthionine sulfoximine (BSO), an inhibitor for GSH synthesis, and 1,3-bis(2-chlorethyl)-1-nitrosourea (BCNU), an inhibitor for GR, on cultured testicular cells were examined. Sertoli cells were prone to die as the result of BCNU, but not BSO treatment, although intracellular levels of GSH declined more severely with BSO treatment. Spermatogenic cells were less sensitive to these agents than Sertoli cells, which indicates that the contribution of these enzymes is less significant in spermatogenic cells. The results herein suggest that the GR system in Sertoli cells is involved in the supplementation of GSH to spermatogenic cells in which high levels of cysteine are required for protamine synthesis. In turn, the genital tract, the epithelia of which are rich in GR, functions in an antioxidative manner to protect sulfhydryl groups and unsaturated fatty acids in spermatozoa from oxidation during the maturation process and storage.

Alteration of glutathione reductase expression in the female reproductive organs during the estrous cycle

The enzyme glutathione reductase (GR) recycles oxidized glutathione (GSSG) by converting it to the reduced form (GSH) in an NADPH-dependent manner. A specific antibody raised against recombinant rat GR was used to localize the protein in the female reproductive organs during the estrous cycle in the rat. In the ovary, the strongest reactivity to the antibody was observed in oocytes, followed by granulosa cells, corpus luteum, and interstitial cells. A strongly positive reaction was also observed mainly in the oviduct epithelia, uterine epithelia, and endometrial gland in the reproductive tract. Oviducts contained the highest GR activity. The GR activity of uterus during metestrus was about twice as high as that for other stages of the cycle. The levels of GR proteins in the tissues roughly matched the activities. The expression of the GR mRNA was highest during metestrus. Because GSH is known to increase gamete viability and the efficiency of fertility, GR, which is expressed in these tissues, is predicted to play a pivotal role in the reproduction process as a source of GSH.

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.

Augmented expression of peroxiredoxin VI in rat lung and kidney after birth implies an antioxidative role

A family of proteins with thioredoxin (TRx)-dependent peroxidase activity, referred to as peroxiredoxins (PRx), has been identified in many species. The sixth member of this family, PRxVI, contains only one conserved cysteine residue, while other members contain additional cysteines. We have isolated a cDNA for rat PRxVI and constructed a large scale baculovirus system to produce the recombinant protein. The protein was purified by a simple two-step procedure utilizing ion-exchange and gel-filtration chromatography. The purified PRxVI exhibited a low level of glutathione-dependent peroxidase but not TRx-dependent activity. PRxVI expression was the highest in lung, followed by brain, kidney, heart, testis, etc. as judged by Northern and Western blot analyses using a rabbit antibody to the purified PRxVI. Immunohistochemical analyses showed strong staining in the epithelium of the bronchus and bronchioles in lung and in the epithelial cells of kidney tubules. In addition, Sertoli cells in testis and islet of Langerhans cells in pancreas were strongly stained. The developmental changes of PRxVI expression in lung and kidney were low in the prenatal stage but induced postnatally. Moreover, intraperitoneal administration of chloroform induced PRxVI mRNA in kidney. When the distribution and the induced expression of PRxVI under conditions of oxidative stress are considered, a physiological role of it as an antioxidative enzyme is indicated.