Enhancement of tissue glutathione for antioxidant and immune functions in malnutrition

D-Ribose-L-Cysteine Improves Glutathione Levels, Neuronal and Mitochondrial Ultrastructural Damage, Caspase-3 and GFAP Expressions Following Manganese-Induced Neurotoxicity

Repeated manganese (Mn) exposure may cause increased production of reactive oxygen species (ROS), with a consequent imbalance in the glutathione (GSH) antioxidant defence system, resulting in cellular dysfunctions, and eventually cell death, particularly in the brain. D-ribose-L-cysteine (RibCys) has been demonstrated to effectively promote the synthesis of glutathione, a potent neutralizer of ROS. In the present study, we examined the effects of RibCys on glutathione levels, apoptotic and astrocytic responses, neuronal ultrastructural integrity, following Mn exposure. Wild-type rats were exposed to either saline, Mn, or/and RibCys for 2 weeks. The Mn-exposed rats received RibCys either as pre-, co-, or post-treatments. Mn caused a marked decrease in GSH levels, overexpression of GFAP and caspase-3, reflecting astrocytosis and apoptosis, and altered ultrastructural integrities of the neuronal nuclei, mitochondria, and myelin sheath of the striatum and motor cortex respectively, while all interventions with RibCys minimized and prevented the neurotoxic events. Our study demonstrates that RibCys effectively attenuates the neurotoxic effects of Mn and may be useful as a therapeutic strategy against neurological consequences of Mn overexposure.

In Vitro Antioxidant Potential and Effect of a Glutathione-Enhancer Dietary Supplement on Selected Rat Liver Cytochrome P450 Enzyme Activity

BACKGROUND

There is considerable evidence that many people take dietary supplements including those of herbal origin as an alternative therapy to improve their health. One such supplement, with an amalgam of constituents, is CellGevity®. However, the effect of this dietary supplement on drug-metabolizing enzymes is poorly understood, as it has not been studied extensively. Therefore, we investigated the effect of CellGevity dietary supplement on selected rat liver microsomal cytochrome P450 (CYP) enzymes, the most common drug-metabolizing enzymes. We also determined the total antioxidant potential of this dietary supplement in vitro.

METHODS

To determine the antioxidant potential of CellGevity dietary supplement, 2,2-diphenyl-2-picryl-hydrazyl (DPPH), total phenolic, and flavonoid assays were used after initial preparation of a solution form of the supplement (low dose, LD; 4 mg/kg and high dose, HD; 8 mg/kg). Rats received oral administration of these doses of the supplement for 7 days, after which the effect of the supplement on selected liver CYP enzymes was assessed using probe substrates and spectroscopic and high-performance liquid chromatographic methods. Rats which received daily administration of 80 mg/kg of phenobarbitone and distilled water served as positive and negative controls, respectively.

RESULTS

The IC₅₀ value of the supplement 0.34 ± 0.07 mg/ml compared to 0.076 ± 0.03 mg/ml of the BHT (positive control). The total phenolic content of the supplement at a concentration of 2.5 mg/ml was 34.97 g gallic acid equivalent (GAE)/100 g while its total flavonoid content at a concentration of 2.5 mg/ml was 6 g quercetin equivalent (QE)/100 g. The supplement significantly inhibited rat CYP2B1/2B2 (LDT 92.4%; HDT 100%), CYP3A4 (LDT 81.2%; HDT 71.7%), and CYP2C9 (LDT 21.7%; HDT 28.5%) while it had no significant inhibitory effect on CYPs 1A1/1A2, CYP1A2, and CYP2D6.

CONCLUSION

CellGevity dietary supplement possesses moderate antioxidant activity in vitro and has an inhibitory effect on selected rat liver CYP enzymes, suggesting its potential interaction with drugs metabolized by CYP enzymes.

Biopolymeric agents for skin wrinkle treatment

Skin aging is caused by several factors capable of deteriorating dermal matrix and is visibly noticed in skin color and skin contour deformities. In addition to the prevention of skin aging by application of antioxidants and sunscreens, treatment of skin wrinkles with those of dermal fillers is also recommended. Dermal filler products with enhanced injectability and longer duration are being developed continuously. Biodegradable polymers such as skin elastic fibers and dermal matrix mimetic used for treatment of skin wrinkle are summarized in this article. Additionally, the importance of amino acids, enzymes, and proteins in aesthetic of skin is addressed. Thus, elective agents are proposed for the dermatologists, cosmetic formulators, and the individuals facing skin aging problems. The candidate natural peptides from marine sources are additionally presented for widening the choice of actives application for treating aging.

Contribution of polyunsaturated fatty acids to intestinal repair in protein-energy malnutrition

The aim of this study was to assess the effect of polyunsaturated fatty acids supplied in the diet on intestinal mucosa repair in a rat model of protein-energy malnutrition. Rats were fed either a standard semipurified diet or the same diet containing lactose as the only source of carbohydrate to cause protein-energy malnutrition. Diarrhea was induced within 24 h and was maintained for 2 weeks, after which both groups of rats were fed for 1 week either the standard diet or the standard diet supplemented with different sources of fatty acids, such as olive oil (OO), fish oil (FO), and purified phospholipids from pig brain (BPL). The lactose-enriched diet caused loss of enterocyte microvilli, lymphocyte infiltration, supranuclear cytoplasmic vesiculation, decreased number of goblet cells, low-density enlarged mitochondria, and less cristae. The FO diet improved the pathology score according to the histological and ultrastructural analysis, with an increased number of goblet cells, ratio of microvilli length to crypt depth, and percentage of intraepithelial lymphocytes compared to those found in rats with protein-energy malnutrition. We previously reported that chronic diarrhea depletes the antioxidant defense in rat intestine; we now show that both, the FO and the BPL diets, increase GSH levels in colon and that some antioxidant enzyme activities vary according to the source of fatty acids, with higher catalase and superoxide dismutase by the FO diet in jejunum, increased catalase by the BPL diet in jejunum, and elevated glutathione peroxidase by the OO diet in colon. The fatty acid profile of intestinal mucosa reflects the source of fat in the diet, with the lowest ratio of n-6/n-3 for rats fed the FO diet. These results suggest that dietary polyunsaturated fatty acids, particularly those in the n-3 series, may play an important role in intestinal repair in chronic diarrhea due to protein-energy malnutrition.

Protective effect of selenium on protein-undernutrition-induced brain damage in rats

The effect of ad libitum ingestion of selenium (Se) in drinking water (0.15 mg SeO2/L) for 3 wk on the brain weight, total brain protein, glutathione (GSH) level, catalase activity, and lipid peroxidation in the brain of protein-undernourished (PU) rats was investigated, in an attempt to determine whether antioxidants alone can reverse some of the neuropathological changes associated with protein undernutrition in rats. Feeding on a normal diet (16% casein) by well-fed rats or a low-protein diet (5% casein) by PU rats and Se-treated PU rats lasted 14 wk. Se-treated PU rats were given Se in drinking water during the last 3 wk of the experiment. Results show that protein undernutrition induced significant reductions (p < 0.001) in brain weight, total brain protein, and catalase activity (p < 0.05) while it induced a significant increase (p < 0.05) in lipid peroxidation when compared with well-nourished rats; but no significant effect was observed for the GSH level. However, the ingestion of Se in drinking water by PU rats for 3 wk resulted in significant increases (p < 0.05) in brain weight, catalase activity, and total brain protein but induced a significant reduction (p < 0.05) in lipid peroxidation when compared with PU rats given water. The values obtained for Se-treated PU rats are comparable with those obtained for well-nourished rats. The GSH level was, however, not affected by Se ingestion. We suggest that Se, by inducing increases in the concentration of certain proteins, including catalase, in the brain, abolished some of the pathological changes associated with protein undernutrition in the brain, and appears as a promising antioxidant in the prevention and management of pro-oxidant-induced brain damage.

Immunomodulation by a Malleable Matrix Composed of Fermented Whey Proteins and Lactic Acid Bacteria

Functional foods and nutraceuticals have gained in popularity over the last 10 years. Among natural health products, whey proteins and fermented milk products are paramount. A malleable protein matrix (MPM), composed of whey fermented by a lactic acid bacterium, capsular exopolysaccharides, vitamins, minerals, and peptides generated during the fermentation process, has the potential to be unique by combining multiple health-promoting components. Forced feeding experiments on healthy animals were performed to evaluate the immunomodulatory effect of MPM. Glutathione production, antibody response, and the modulation of leukocyte populations were monitored. The stimulation of the immune system by MPM consumption was evident as seen by the increased polymorphonuclear cell counts and intracellular glutathione levels. The absence of MPM-specific antibody production indicated a lack of undesirable immune recognition of MPM. The MPM, with its immunomodulatory properties, has the potential to be a food substitute or a functional food for maintenance of general immune health.

Effect of Saffron (Crocus sativus) on Neurobehavioral and Neurochemical Changes in Cerebral Ischemia in Rats

The modifying effects of Crocus sativus (CS) stigma extract on neurobehavioral activities, malondialdehyde (MDA), reduced glutathione (GSH), glutathione peroxidase, glutathione reductase, glutathione S-transferase, superoxide dismutase (SOD), catalase (CAT), and Na(+),K(+)-ATPase activities, and glutamate (Glu) and aspartate (Asp) content were examined in the middle cerebral artery (MCA) occlusion (MCAO) model of acute cerebral ischemia in rats. The right MCA of male Wistar rats was occluded for 2 hours using intraluminal 4-0 monofilament, and reperfusion was allowed for 22 hours. MCAO caused significant depletion in the contents of GSH and its dependent enzymes while significant elevation of MDA, Glu, and Asp. The activities of Na(+),K(+)-ATPase, SOD, and CAT were decreased significantly by MCAO. The neurobehavioral activities (grip strength, spontaneous motor activity, and motor coordination) were also decreased significantly in the MCAO group. All the alterations induced by ischemia were significantly attenuated by pretreatment of CS (100 mg/kg of body weight, p.o.) 7 days before the induction of MCAO and correlated well with histopathology by decreasing the neuronal cell death following MCAO and reperfusion. The present results may suggest the effectiveness of CS in focal ischemia most probably by virtue of its antioxidant property.

Effects of Choto-san and its related constituents on endogenous antioxidant systems

We previously reported that Choto-san acts as an antioxidant and cytoprotective agents against H2O2-induced oxidative damage in NG108-15 cells, and the effect is due at least partly to the phenolic compounds. To further investigate the detail mechanisms of this cytoprotection effects of Choto-san and related compounds on enzyme activities of antioxidant systems were examined. Choto-san (5-100 microg/ml) and Chotoko (5-100 mg/ml) stimulated the activity of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPX). These also increased the level of glutathione. Although Choto-san without Chotoko (w/o CKO) did not show the effects on SOD and catalase, GPX activity and glutathion content also, but weakly, stimulated by w/o CKO. The effects of phenolic compounds, epicatechin, caffeic acid and quercetin were also investigated. Epicatechin stimulated catalase, GPX and glutathion content, but not SOD. On the other hand, caffeic acid stimulated SOD activity but had no effects on others. Quercetin stimulated all, although intensities were different among. These results suggest that simultaneous induction of cellular antioxidant defense systems by Choto-sam and its related constituents may be an important mechanisms underlying the protective effects of Choto-san on ischemia-induced neuronal cells injury, and the characteristics of the stimulative effects of phenolic compounds were depend on enzymes.

Effect of protein malnutrition on redox state of the hippocampus of rat

The protein malnutrition is a worldwide problem, affecting mainly newborns and children of developing countries. This deficiency reaches the brain in the most critical period of the development. Various consequences are related to this insult, such as memory disturbance, learning, and behavioral impairment. Protein content of the diet plays an important role on antioxidant mechanisms. This study observed the effects of protein malnutrition on rat hippocampus redox state. Wistar rats were separate in four groups, receiving different diets: first group with 25% casein, protein deficient group with 8% casein, and the same two groups supplemented with methionine (0.15%). Diets were isocaloric and were administered since the prenatal period up to the sacrifice. Rats were decapitated at 21 or 75 days old and hippocampus were isolated for measuring the lipoperoxidation by TBARS method, protein oxidative damage by carbonyl (DNPH) levels, and the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). There was significant alterations in the activities of the enzyme SOD, lipoperoxidation, and protein oxidation in hippocampus of 21 and 75 day-old rats fed with 25% of protein with methionine and the groups fed with low levels of protein (8%) both supplemented or not with methionine. Our data suggest that both the content of protein in the diet and the essential amino acid methionine may alter the antioxidant system and the redox state of the brain.

Effects of cysteine on amino acid concentrations and transsulfuration enzyme activities in rat liver with protein-calorie malnutrition

The changes in amino acid concentrations and transsulfuration enzyme activities in liver were investigated after 4-week fed on 23% casein diet (control group) and 5% casein diet without (protein-calorie malnutrition, PCM group) or with (PCMC group) oral administration of cysteine, 250 mg/kg (twice daily, starting from the fourth week) using rats as an animal model. By supplementation with cysteine in PCM rats (PCMC group), cysteine level was elevated almost close to the control level, and glutathione (GSH), aspartic acid and serine levels were restored greater than the control levels. The measurement of transsulfuration enzyme activities exhibited that gamma-glutamylcysteine ligase (gamma-GCL) activity was up-regulated in rats with protein restriction (PCM group), and cysteine supplementation (PCMC group) down-regulated to the control level. One-week supplementation of cysteine (PCMC group) significantly down-regulated the cysteine sulfinate decarboxylase activity. These results indicate that the availability of sulfur amino acid(s) especially cysteine appears to play a role in determining the flux of cysteine between cysteine catabolism and GSH synthesis.

The effects of dietary sulfur amino acid deficiency on rat brain glutathione concentration and neural damage in global hemispheric hypoxia-ischemia

Primary brain injury in stroke is followed by an excitotoxic cascade, oxidative stress and further neural damage. Glutathione is critical and depleted in oxidative stress. Since cysteine is limiting in glutathione synthesis, this study investigated the effect of dietary sulfur amino acid (SAA) deficiency on neural damage in a rat model of global hemispheric hypoxia-ischemia (GHHI). Animals were fed with SAA deficient ("deficient") or control diet for 3 days, subjected to right common carotid artery ligation and hypoxia, and diet continued for 3 more days. Histologically evaluated neural damage at 7 days post hypoxia-ischemia was greater in "deficient" rats, shown by mean (+/- SEM) global and hippocampal grid scores of 2.5 +/- 0.7 and 34.9 +/- 9.3%, respectively, vs. controls' scores of 0.1 +/- 0.1 and 0.1 +/- 0.1%, respectively. Mean brain (+/- SEM) reduced glutathione was not different between groups at 6h post hypoxia-ischemia, but was decreased in "deficient" animals 3 days later in neocortex (1.46 micromoles/g wet weight +/- 0.05 vs. 1.67 +/- 0.04 in controls) and thalamus (1.60 micromoles/g wet weight +/- 0.05 vs. 1.78 +/- 0.03 in controls). Administration of a cysteine precursor to "deficient" animals did not ameliorate neural damage. These findings suggest that well-nourished but not "deficient" animals tolerate a mild brain insult. The decline in brain glutathione in the "deficient" animals may be one of several contributing mechanisms.

Glutathione supplementation and training increases myocardial resistance to ischemia-reperfusion in vivo

The present study examined the effects of oral reduced glutathione (GSH) supplementation in conjunction with endurance training on contractile function, antioxidant defense, and oxidative damage in response to ischemia-reperfusion (I/R) in rat hearts. Female Sprague-Dawley rats (age 4 mo, n = 72) were randomly assigned to a treadmill-trained (T; 25 m/min, 15% grade, for 75 min/day, 5 days/wk, for 10 wk) or untrained (U) group. Each group was further divided into rats receiving 5 g GSH/kg diet during the final 17 days of training (GSH-S) and control (C) groups. One-half of each group of rats was subjected to I/R by surgical occlusion of the main coronary artery for 45 min, followed by 30-min reperfusion or sham operation. Left ventriclar (LV) peak systolic pressure (LVSP) and contractility (+dP/dt), measured with a catheter inserted into the LV via the carotid artery, decreased with I/R in all groups (P < 0.05). However, LVSP with I/R in the T/GSH-S group was 9.5%, 17%, and 18% higher (P < 0.05) than that in the U/GSH-S, T/C, and U/C groups, respectively. +dP/dt with I/R was 19%, 27%, and 29% (P < 0.05) greater in the T/GSH-S group versus the T/C, U/GSH-S, and U/C groups, respectively. I/R decreased heart GSH content by 12-17% (P < 0.05) and increased oxidized glutathione (GSSG) by 20-27% (P < 0.05). T/GSH-S hearts showed 15% higher GSH (P < 0.05) and a 32% higher GSH-to-GSSG ratio (P < 0.05) than the U/C group at the end of I/R. Myocardial superoxide dismutase, GSH peroxidase, glutathione reductase, and gamma-glutamyl transpeptidase activities were increased with treadmill training in both GSH-S and C rats. I/R induced myocardial lipid peroxidation and lactate dehydrogenase release were attenuated with T/GSH-S treatment. The present data indicate that training in conjunction with dietary GSH supplementation can increase myocardial GSH content and antioxidant defense capacity, thereby protecting the intact heart against oxidative damage and functional retardation caused by I/R.

Altered anti-oxidant status and increased lipid peroxidation in marasmic children

BACKGROUND

Protein energy malnutrition (PEM) is a common pediatric health problem in developing countries. Although the clinical features of PEM are well known, its pathophysiology is still unclear. Free radicals have been implicated in pathogenesis of PEM. In the present study, oxidant/anti-oxidant status in marasmus was investigated.

METHODS

Red cell glutathione, glutathione peroxidase and superoxide dismutase and their related cofactors, serum selenium and copper, were studied in marasmic and control children. Serum lipid peroxidation was also evaluated to assess oxidative stress.

RESULTS

The red cell glutathione levels and glutathione peroxidase activities were found to be significantly lower in the marasmic children than in the controls. Red cell superoxide dismutase (SOD) activity was not different between two groups. Serum selenium and copper concentrations were significantly lower in the marasmic children than in the control subjects. The malondialdehyde concentration, which is an index of lipid peroxidation, was significantly higher in the marasmic group compared with the controls.

CONCLUSION

The anti-oxidant defense system was affected in marasmic children. Reduced anti-oxidant status and increased oxidative stress occurs in marasmic children.

Management of oxidative stress in the CNS: the many roles of glutathione

An outline is given of mechanisms that generate oxidative stress and inflammation. Considered are the metabolic mechanisms that give rise to peroxides, the source of strong oxidants; the production of dicarbonyls that interact with macromolecules to form advanced glycation endproducts; and the role that activation of the transcription factor NF(Kappa)B has in the expression of pro-inflammatory genes. Management of oxidative stress is considered by outlining the central role of reduced glutathione (GSH) in peroxide scavenging, dicarbonyl scavenging and activation of NF(Kappa)B. Cellular GSH levels are dictated by the balance between consumption, oxidation of GSH, reduction of oxidized-glutathione, and synthesis. The rate-limiting enzyme in GSH synthesis is L-gamma-glutamyl-L-cysteine synthase, a phase II enzyme. Phase II enzyme inducers are found in many fruits and vegetables. It is suggested that dietary phase II enzyme inducers be investigated for their potential for preventing or retarding the development of degenerative diseases that have an underlying oxidative stress and inflammatory component.

Survival of guinea pig pups in hyperoxia is improved by enhanced nutritional substrate availability for glutathione production

The imbalance between high oxidant loads and immature antioxidant defenses is associated with long-term complications of prematurity. Glutathione is a central element among the antioxidants. Depletion of pulmonary glutathione accelerates the development of oxygen-induced lung injury in neonatal animal models. After the observation that newborn infants exposed to oxygen have low glutathione levels, a study was designed to test the hypothesis that in neonates from a species susceptible to oxygen toxicity, the lethal effect of hyperoxia is related to a low availability of substrates for glutathione production rather than an impairment in synthetic activity. One-day-old guinea pigs, randomly assigned to room air or oxygen (>95%), were fed by their mothers (n = 16) or i.v. by dextrose (n = 14) or by total parenteral nutrition (TPN, n = 20). After 3 d, glutathione and activities of enzymes involved in maintaining intracellular glutathione levels were determined in lungs and liver. The lethal effect of oxygen (p < 0.05) observed in animals without TPN was not related to glutathione depletion, as oxygen induced a 33% increase in lung glutathione, positively correlated (r2 = 0.35) with enhanced synthesis. With TPN, the animals were protected against the lethal effects of hyperoxia and lung glutathione increased by 67% in oxygen. The results suggest that the glutathione demand by the lungs in the presence of an oxidant stimulus was met by the increased (p < 0.001) hepatic production supported by TPN. Under hyperoxic conditions, early nutritional support is of vital importance.

Humic acid-mediated oxidative damages to human erythrocytes: a possible mechanism leading to anemia in Blackfoot disease

Humic acid (HA) has been proposed as a factor that causes Blackfoot disease, an endemic peripheral vascular disease prevailing in the southwest coast of Taiwan. However, the relationship between HA and anemia associated with Blackfoot disease remains unclear. In this study, we showed that HA imposed damages on human red blood cells (RBCs), which were manifested as reduction in deformability of RBCs and hemolysis. At concentrations ranging from 10 to 100 microg/ml, HA caused lipid peroxidation in a dose-dependent manner. Such changes were accompanied by a depletion of glutathione and a reduction in activities of the antioxidant enzymes including catalase, superoxide dismutase, and glucose-6-phosphate dehydrogenase. These results indicate that HA initiates oxidative stress on RBCs and results in their dysfunction. Consistent with our previous findings, the present study supports the notion that HA plays an important role in the pathogenesis of Blackfoot disease.

Keratinocyte growth factor enhances glutathione redox state in rat intestinal mucosa during nutritional repletion

Malnutrition decreases tissue levels of glutathione (GSH), a major endogenous antioxidant that detoxifies reactive oxygen species and promotes cell growth. This study determined the effects of the gut trophic peptide keratinocyte growth factor (KGF) on intestinal mucosal GSH concentrations and redox state in malnourished rats. Adult rats were food-deprived for 3 d, then consumed food ad libitum or 25% of ad libitum intake for 3 d with daily intraperitoneal administration of saline or KGF (5 mg.kg-1.d-1). Mucosal GSH and glutathione disulfide (GSSG) concentrations, crypt depth and total mucosal height were measured in the jejunum, ileum and colon. In the 25% of ad libitum-refed, saline-treated group, mucosal GSH was lower in all gut tissues (42% in jejunum, 38% in ileum, and 57% in colon), and the GSH/GSSG ratio was lower in the jejunum and ileum compared to that in the ad libitum-refed controls. KGF treatment with ad libitum refeeding increased GSH/GSSG in the jejunum, ileum and colon. Furthermore, in 25% of ad libitum refeeding, KGF normalized jejunal, ileal and colonic mucosal GSH content and significantly increased the mucosal GSH/GSSG ratio relative to rats treated with saline. Increased crypt depth and total mucosal height induced by KGF and feeding could be explained in part by increased mucosal GSH content. KGF treatment improved gut mucosal glutathione redox state in malnourished, refed rats. These data provide evidence that gut trophic hormones and food intake may independently support gut mucosal glutathione antioxidant capacity during nutritional repletion.

Nutritional regulation of glutathione in stroke

In contrast to cardiovascular disease, the impact of nutritional status on the prevention and outcome of stroke has received limited investigation. We present a mechanism based on animal studies, clinical data, and epidemiological data by which protein-energy status in the acute stroke and immediate postinjury periods may affect outcome by regulating reduced glutathione (GSH), a key component of antioxidant defense. As cysteine is the limiting amino acid for GSH synthesis, the GSH concentration of a number of nonneural tissues has been shown to be decreased by fasting, low-protein diets, or diets limiting in sulfur amino acids. The mechanism may also be relevant in brain since GSH in some brain regions is responsive to dietary sulfur amino acid supply and to the pro-cysteine drug, L-2-oxothiazolidine-4-carboxylate. The latter is an intracellular cysteine delivery system used to overcome the toxicity associated with cysteine supplementation. These findings may provide the mechanism to explain both the inverse correlation between dietary protein and stroke mortality and the documented association between suboptimal protein-energy status and diminished functional status following a stroke. Future investigations should examine the role of nutritional intervention in neuroprotective strategies aimed at improving stroke outcome. Pharmacological interventions such as L-2-oxothiazolidine-4-carboxylate should be investigated in animal models of stroke, as well as the impact of nutritional status on the response to these agents. Finally, micronutrient deficiencies that may accompany protein-energy malnutrition, such as selenium, should also be investigated for their role in antioxidant defense in cerebral ischemia.

Glutathone and glutathione ethyl ester supplementation of mice alter glutathione homeostasis during exercise

The present study examined the effect of glutathione (GSH) and glutathione ethyl ester (GSH-E) supplementation on GSH homeostasis and exercise-induced oxidative stress. Male Swiss-Webster mice were randomly divided into 4 groups: starved for 24 h and injected with GSH or GSH-E (6 mmol/kg body wt, i.p.) 1 h before exercise, starved for 24 h and injected with saline (S); and having free access to food and injected with saline (C). Half of each group of mice was killed either after an acute bout of exhaustive swimming (E) or after rest (R). Plasma GSH concentration was 100-160% (P < 0.05) higher in GSH mice vs. C or S mice at rest, whereas GSH-E injection had no effect. Plasma GSH was not affected by exercise in C or S mice, but was 44 and 34% lower (P < 0.05) in E vs. R mice with GSH or GSH-E injection, respectively. S, GSH- and GSH-E-treated mice had significantly lower liver GSH concentration and the GSH:glutathione disulfide (GSSG) ratio than C mice. Hepatic and renal GSH and the GSH:GSSG ratio were significantly lower in E vs. R mice in all groups. GSH-E-treated mice had a significantly smaller exercise-induced decrease in GSH vs. C, S, and GSH-treated mice and no difference in the GSH:GSSG ratio in the kidney. Activities of gamma-glutamylcysteine synthetase and gamma-glutamyltranspeptidase in the liver and kidney were not affected by either GSH treatment or exercise. GSH concentration and the GSH:GSSG ratio in quadriceps muscle were not different among C, S and GSH-treated mice, but significantly lower in GSH-E-treated mice (P < 0.05). Hepatic malondialdehyde (MDA) content was greater in exercised mice in all but GSH-E-treated groups. GSH and GSH-E increased MDA levels in the kidney of E vs. R mice, but attenuated exercise-induced lipid peroxidation in muscle. Swim endurance time was approximately 2 h longer in GSH (351 +/- 22 min) and GSH-E (348 +/- 27) than S mice (237 +/- 17). We conclude that 1) acute GSH and GSH-E supplementation at the given doses does not increase tissue GSH content or redox status; 2) both GSH and GSH-E improve endurance performance and prevent muscle lipid peroxidation during prolonged exercise; and 3) while both compounds may impose a metabolic and oxidative stress to the kidney, this side effect is smaller with GSH-E supplementation.

Glutamine enhances gut glutathione production

BACKGROUND

The gastrointestinal tract is recognized as having important metabolic functions. This study examined gut glutathione (GSH) extraction and the effect of supplemental oral glutamine (GLN) on gut GSH fractional release.

METHODS

Healthy female Fisher-344 rats weighing approximately 150 to 200 g were pair-fed chow and supplemented by gavage with 1 g/kg/d GLN or an isonitrogenous amount of Freamine (McGaw, St. Louis, MO). Rats were sacrificed at 6 weeks. Arterial and portal blood was assayed for GLN and GSH content. The gut GLN and GSH extractions were calculated.

RESULTS

The gut GLN fractional uptake was increased by approximately 50%, and there was a near threefold increase in gut GSH fractional release in the GLN-supplemented group.

CONCLUSIONS

The discovery of gut's role as a major producer of GSH may give insight into why feeding via the gut rather than by the venous route is so important. Supplemental oral GLN further enhances GLN extraction as well as GSH fractional release in the gut.

Selective elevation of glutathione levels in target tissues with L-2-oxothiazolidine-4-carboxylate (OTC) protects against hyperoxia-induced lung damage in protein-energy malnourished rats: implications for a new treatment strategy

It has become recognized that enhancing the antioxidant defense system during the early phase of rehabilitation is important to the survival of wasting protein-energy malnourished (PEM) patients. In this study, we compared the efficacy of dietary protein replenishment and supplementation with L-2-oxothiazolidine-4-carboxylate (OTC, 3.5 mg/d), a cysteine precursor, to protect against hyperoxia-induced lung damage in PEM rats. The PEM rats were produced by feeding weanling rats a protein-deficient diet (0.5% protein) for 14 d. PEM rats were then divided in three dietary treatment groups, 0.5% protein (-Pr), 0.5% protein plus the OTC supplement (+OTC), or 15% protein (+Pr) during 4 d of either hyperoxia (85% O2) or air exposure. Increased lung-to-body weight ratios, indicative of oxidative tissue damage, were observed following exposure to hyperoxia in -Pr and +Pr rats, but not in +OTC rats, even though the OTC supplement and the 15% protein diet contained a comparable amount of cysteine. Tissue reduced glutathione (GSH) status, GSH-dependent enzyme activity and antioxidant defense enzyme activities were monitored in the lung, liver and blood during 4 d of hyperoxia exposure. OTC supplementation enhanced GSH levels significantly in the lung of PEM rats, whereas protein repletion significantly elevated blood GSH concentrations. The protective effect of OTC was not a function of changes in activity of GSH-dependent enzymes or oxygen defense enzymes in the lung. These results indicate that a short-term strategy that selectively elevates GSH levels in the lung is more effective than protein repletion in protecting against hyperoxia-induced oxidative lung damage in PEM rats.

Exercise and oxidative stress: Sources of free radicals and their impact on antioxidant systems

Strenuous exercise is characterized by increased oxygen consumption and the disturbance between intracellular pro-oxidant and antioxidant homeostasis. At lease three biochemical pathways (i.e., mitochondrial electron transport chain, xanthine oxidase, and polymorphoneutrophil) have been identified as potential sources of intracellular free radical generation during exercise. These deleterious reactive oxygen species pose a serious threat to the cellular antioxidant defense system, such as diminished reserves of antioxidant vitamins and glutathione. However, enzymatic and non-enzymatic antioxidants have demonstrated great versitility and adaptability in response to acute and chronic exercise. The delicate balance between pro-oxidants and antioxidants suggests that supplementation with antioxidants may be desirable for physically active individuals under certain physiological conditions by providing a larger protective margin.

Gender and maturation affect glutathione status in human neonatal tissues

Gender and maturation affect glutathione status in human neonatal tissues. The objective was to verify if human tissues derived from baby girls had a greater ability then tissues derived from males to stimulate the glutathione-reductase, when faced with an oxidative challenge. In vitro, the effect of a calibrated oxidative challenge was studied in endothelial cells. In vivo, the effect of a clinically relevant oxidative challenge was studied in cells from tracheal aspirates derived from oxygen-dependent newborn infants. In endothelial cells, the oxidant tert-butylhydroperoxide had a stimulating effect on GSSG-R activity in cells derived from females. The peroxide produced a time, concentration and gender-dependent cytotoxicity, with female-derived cells exhibiting a better viability. In vivo, the intracellular total glutathione content was higher in female-derived cells and in cells from more mature babies; postnatal age and gestational age had a positive effect on the activity of GSSG-R. Oxygen (FiO2 > or = 0.3) was associated with a lower activity of GSSG-R in boys, early in life. Considering that glutathione is a central element in the antioxidant defense, these results suggest that specific tissues derived from the baby girl are potentially better protected against an oxidative stress than those derived from the boy.

Splenocyte glutathione and CD3-mediated cell proliferation are reduced in mice fed a protein-deficient diet

Protein-energy malnutrition (PEM) is associated with decreased host immune defense. Glutathione (GSH) status is reported to be decreased in PEM, and GSH is important for lymphocyte function. The objective of the present study was to investigate the effects of PEM and dietary repletion (RP) on GSH status in various tissues and splenocytes and on CD3-mediated calcium mobilization and cell proliferation of splenic T-lymphocytes. For the PEM model, mice were fed a 0.5% protein diet (LP group) for 4 or 6 wk, and control mice were fed a 15% protein diet (CP group). In the RP study, LP mice were fed the 15% protein diet for 3 d, 1 wk, 2 wk or 3 wk (RP groups). Glutathione concentrations were significantly lower in liver, lung, heart and spleen of LP mice compared with CP mice at 4 and 6 wk. Splenocytes from LP mice were significantly lower in number and had a lower intracellular GSH concentration, depressed CD3-stimulated T-lymphocyte proliferation in culture media without thiol supplementation (2-mercaptoethanol), and enhanced CD3-stimulated proliferation in thiol-supplemented culture media compared with splenocytes from CP mice. CD3-stimulated calcium mobilization was significantly lower in CD8+, but not CD4+, splenocytes from LP mice. Within 1 wk of dietary repletion, splenocyte GSH concentration was normal and splenocyte numbers were greater, and in vitro sensitivity of CD3-stimulated T-lymphocyte proliferation to thiol was lower, compared with LP mice. Glutathione status in vivo and thiol supplementation in vitro seem to modulate the signal transduction pathway for T-lymphocyte proliferation in mice with PEM.

Cytotoxicity of unsaturated metabolites of valproic acid and protection by vitamins C and E in glutathione-depleted rat hepatocytes

Valproic acid (VPA) and the unsaturated metabolites, 2-ene VPA and (E)-2,(Z)-3'-diene VPA, demonstrated dose-dependent cytotoxicity in primary cultures of rat hepatocytes, as evaluated by lactate dehydrogenase (LDH) leakage. Cellular glutathione (GSH) was depleted by adding buthionine sulfoximine (BSO) to the culture medium. Induction of cytochrome P450 by pretreatment of rats with phenobarbital or pregnenolone-16 alpha-carbonitrile enhanced the cytotoxicity of parent VPA in BSO-treated hepatocytes. The cytotoxicity of 4-ene VPA was apparent in BSO-treated hepatocytes with detectable loss of cell viability at 1 microM of added 4-ene VPA. Depletion of cellular GSH also increased the cytotoxicities of 2-ene VPA and (E)-2,(Z)-3'-diene VPA. The cytotoxicity of 2-ene VPA was comparable to or higher than that of VPA, producing loss of viability at concentrations > or = 5 mM. Time-course evaluation of hepatocyte response to 4-ene VPA in the GSH-depleted state revealed a delayed cytotoxicity with no effect during the first 12 h of exposure followed by a pronounced toxicity between 12 and 14 h. Two major GSH conjugates of 4-ene VPA metabolites, namely 5-GS-4-hydroxy VPA lactone and 5-GS-3-ene VPA, were detected in 4-ene VPA treated hepatocytes. Consistent with this finding, a 50% decrease in cellular GSH levels was observed following 4-ene VPA treatment. Under similar conditions, neither toxicity nor the GSH conjugated metabolite were detected in cells treated with the alpha-fluorinated 4-ene VPA analogue (alpha-F-4-ene VPA). The antioxidants, vitamin C and vitamin E, demonstrated a cytoprotective effect against 4-ene VPA-induced injury in GSH-depleted hepatocytes. These results are in support of hepatocellular bioactivation of VPA via 4-ene VPA to highly reactive species, which are detoxified by GSH. The susceptibility of hepatocytes to VPA metabolite-mediated cytotoxicity depends on cellular GSH homeostasis.

Methionine derivatives diminish sulphide damage to colonocytes--implications for ulcerative colitis

BACKGROUND

Bacterial production of anionic sulphide is increased in the colon of ulcerative colitis and sulphides can cause metabolic damage to colonocytes.

AIMS

To assess the reversal of the damaging effect of sulphide to isolated colonocytes by methionine and methionine derivatives.

METHODS AND SUBJECTS

Isolated colonocytes were prepared from rat colons and 12 human colectomy specimens. In cell suspensions 14CO2/acetoacetate generation was measured from [1-14C]-butyrate (5.0 mmol/l) in the presence of 0-2.0 mmol/l sodium hydrogen sulphide. The effect of 5.0 mmol/l L-methionine, S-adenosylmethionine 1,4 butane disulphonate and DL-methionine-S-methylsulphonium chloride on sulphide inhibited oxidation was observed.

RESULTS

In rat colonocytes sodium hydrogen sulphide dose dependently reduced oxidative metabolite formation from n-butyrate, an action reversed in order of efficacy by S-adenosylmethionine 1,4 butane disulphonate > DLmethionine-S-methyl-sulphonium chloride > L-methionine. In human colonocytes S-adenosylmethionine 1,4 butane disulphonate most significantly improved 14CO2 production (p = < 0.005) suppressed by sodium hydrogen sulphide.

CONCLUSION

Sulphide toxicity in colonocytes is reversible by methyl donors. The efficiency of sulphide detoxification may be an important factor in the pathogenesis and treatment of ulcerative colitis for which S-adenosylmethionine 1,4 butane disulphonate may be of therapeutic value.

Effect of food deprivation on glutathione and amino acid levels in brain and liver of young and aged rats

The effect of short-term food deprivation on glutathione (GSH) and amino acid levels in brain regions of young and aged rats was compared with changes observed in liver. Animals aged 3 months and 24 months were deprived of food for 48 h. GSH and amino acid levels from cerebral cortex, cerebellum, pons medulla, and liver were assayed and compared with levels in animals of the same age fed normal diets. In liver in both young and old rats, GSH levels fell 30%, from 13 mumol/g tissue to 8.7 mumol/g tissue. Significant changes were observed in other amino acids, including an increase of 30-50% in methionine, glycine, and glutamine, and a decrease of 30-50% in alanine in liver of both young and aged rats, and a 4-fold increase in taurine in young. In brain, little change was observed upon food deprivation. No decrease was observed in GSH, and only small changes were observed in other amino acids. In the aged animal aspartate, glutamate, and alanine levels were slightly lower; tyrosine in cerebellum was reduced by 30%, and both glycine and tyrosine in the pons medulla were reduced by 20-30%. In the brain areas examined, levels of GSH ranged from 1-2 mumol/g in young and 0.8-1.4 mumol/g in old; with levels in pons medulla being lower than those in cerebral cortex. In brain, in contrast to liver, levels were scarcely affected by short-term food deprivation.(ABSTRACT TRUNCATED AT 250 WORDS)