Nutritional biochemistry of cellular glutathione

Nutrition and oral health in Africa

Poverty, low birth weight, low life expectation at birth, widespread malnutrition, numerous endemic infections, little or no access to safe water, poor oral hygiene, deplorable environmental sanitation and political instability among other problems, characterise the lives of many Africans, particularly in sub-Saharan Africa. In African countries undergoing rapid urbanisation, health problems associated with undernutrition and overnutrition coexist, and these result from lifestyle changes which promote physical inactivity, increased consumption of fats and refined carbohydrates, as well as abuse of tobacco and alcohol. Thus, in several African countries, inflammatory oral diseases (e.g. periodontal diseases, acute necrotising gingivitis, noma) resulting from inappropriate interactions between microorganisms and the malnourished, immunocompromised host, have continued to pose serious health problems. There are suggestions of increasing incidence of squamous cell carcinoma, probably related to increased use of alcohol and tobacco, which elicit nutrient deficiencies and oxidative stress. Additionally, there is an increase in caries prevalence particularly in the poor urban areas. The latter is related not only to increased availability of refined sugars, but also to limited access to the caries preventive effects of fluorides. Good dietary practices through judicious combination of available foods should therefore feature prominently in the promotion of optimal oral health in Africa.

Tocotrienol: The Natural Vitamin E to Defend the Nervous System?

Vitamin E is essential for normal neurological function. It is the major lipid-soluble, chain-breaking antioxidant in the body, protecting the integrity of membranes by inhibiting lipid peroxidation. Mostly on the basis of symptoms of primary vitamin E deficiency, it has been demonstrated that vitamin E has a central role in maintaining neurological structure and function. Orally supplemented vitamin E reaches the cerebrospinal fluid and brain. Vitamin E is a generic term for all tocopherols and their derivatives having the biological activity of RRR-alpha-tocopherol, the naturally occurring stereoisomer compounds with vitamin E activity. In nature, eight substances have been found to have vitamin E activity: alpha-, beta-, gamma- and delta-tocopherol; and alpha-, beta-, gamma- and delta-tocotrienol. Often, the term vitamin E is synonymously used with alpha-tocopherol. Tocotrienols, formerly known as zeta, , or eta-tocopherols, are similar to tocopherols except that they have an isoprenoid tail with three unsaturation points instead of a saturated phytyl tail. Although tocopherols are predominantly found in corn, soybean, and olive oils, tocotrienols are particularly rich in palm, rice bran, and barley oils. Tocotrienols possess powerful antioxidant, anticancer, and cholesterol-lowering properties. Recently, we have observed that alpha-tocotrienol is multi-fold more potent than alpha-tocopherol in protecting HT4 and primary neuronal cells against toxicity induced by glutamate as well as by a number of other toxins. At nanomolar concentration, tocotrienol, but not tocopherol, completely protected neurons by an antioxidant-independent mechanism. Our current work identifies two major targets of tocotrienol in the neuron: c-Src kinase and 12-lipoxygenase. Dietary supplementation studies have established that tocotrienol, fed orally, does reach the brain. The current findings point towards tocotrienol as a potent neuroprotective form of natural vitamin E.

Oxidative stress in viral hepatitis and AIDS

Dominant types of viral hepatitis are presently A, B, and C with prophylactic immunization available only for A and B. Hepatitis B and C and human immunodeficiency virus (HIV) infection constitute a worldwide scourge and treatment is far from satisfactory. Each produces severe oxidative stress (OS) and secondary cellular damage of varying severity and, as in toxic hepatitis, progression and regression are dependent on redox balance between oxidation and antioxidation. Experimental and clinical studies suggest that xenobiotics and co-infections exert cumulative, detrimental effects on their pathogeneses and further deplete antioxidants. It is proposed therefore that in the clinical management of these infections and especially in their early stages, considerable benefit should accrue from antioxidant repletion at dosages substantially above recommended daily allowances (RDAs) in conjunction with a nutritious high protein diet. Because plasma zinc and selenium concentrations are very low, their replenishment by high dosages is urgent and mandatory particularly in advanced HIV infections bordering on acrodermatitis enteropathica. Also recommended is their long-term continuance at high normal levels.

Variable effects of exercise intensity on reduced glutathione, thiobarbituric acid reactive substance levels, and glucose concentration

BACKGROUND

Physical exercise may be associated with a 10- to 20-fold increase in whole body oxygen uptake. Generation of free oxygen radicals (FORs) is elevated to a level that overwhelms tissue antioxidant defense systems in exercise. One of the most reliable indices of exercise-induced oxidant production is tissue glutathione oxidation.

METHODS

In this study three different volunteer groups carried out various sports disciplines and worked at least as amateurs for 6-7 years before and after aerobic (Aer)-, anaerobic (Anae)-, or aerobic + anaerobic (Aer-Anae)-dominant exercises. Thiobarbituric acid reactive substances (TBARS) reduced glutathione (GSH) levels, glucose concentration was measured, and we investigated their relationships with different types of exercise. From all groups (n=60, each group comprising 10 females and 10 males), we collected blood samples at the following five different times: before exercise; immediately after exercise, and 4, 24, and 48 h after completion of exercise. These samples were assayed for whole blood GSH, plasma TBARS levels, and glucose concentration.

RESULTS

Significant increase in Aer-Anae was noted in levels of TBARS while decrease was observed in glutathione levels in exercise group as compared with prior levels in all groups. However, no statistical difference was observed in total group levels before and after exercise and in male and female groups compared before and after exercise. When gender differences were taken into account, females generally had higher levels of GSH, whereas TBARS levels were higher in males. When compared either before or after exercise, levels of glucose concentration--especially immediately after exercise period in all groups--were higher. In addition, in Anae groups glucose concentrations were higher at 4 and 24 h in females than in males. Aer exercise caused oxidative stress to a lesser degree, whereas Aer-Anae exercise caused oxidative stress of higher degree that was statistically significant.

CONCLUSIONS

According to our findings, exercise increased TBARS level significantly in all groups, especially more so in Aer-Anae groups. In addition, GSH was increased more in females than in males, while concentration of glucose did not change remarkably. Additionally, it can be stated that women are more resistant to oxidative stress.

Brain antioxidant systems in human methamphetamine users

Animal data suggest that the widely abused psychostimulant methamphetamine can damage brain dopamine neurones by causing dopamine-dependent oxidative stress; however, the relevance to human methamphetamine users is unclear. We measured levels of key antioxidant defences [reduced (GSH) and oxidized (GSSG) glutathione, six major GSH system enzymes, copper-zinc superoxide dismutase (CuZnSOD), uric acid] that are often altered after exposure to oxidative stress, in autopsied brain of human methamphetamine users and matched controls. Changes in the total (n = 20) methamphetamine group were limited to the dopamine-rich caudate (the striatal subdivision with the most severe dopamine loss) in which only activity of CuZnSOD (+ 14%) and GSSG levels (+ 58%) were changed. In the six methamphetamine users with severe (- 72 to - 97%) caudate dopamine loss, caudate CuZnSOD activity (+ 20%) and uric acid levels (+ 63%) were increased with a trend for decreased (- 35%) GSH concentration. Our data suggest that brain levels of many antioxidant systems are preserved in methamphetamine users and that GSH depletion, commonly observed during severe oxidative stress, might occur only with severe dopamine loss. Increased CuZnSOD and uric acid might reflect compensatory responses to oxidative stress. Future studies are necessary to establish whether these changes are associated with oxidative brain damage in human methamphetamine users.

FT-Raman spectroscopic investigation of lens proteins of tilapia treated with dietary vitamin E

FT-Raman spectroscopy was employed to explore the structural changes of lens proteins in Tilapia lenses affected by dietary vitamin E supplementation. The microenvironment of major lens constituents including thiol compounds, tyrosine, and tryptophan exhibited significant change upon vitamin E treatment, while the protein secondary structure was unaltered and remained as an antiparallel beta-pleated sheet. These structures in the cortex were more susceptible to vitamin E treatment than in the nucleus. Protein sulfhydryls in the cortex were predominantly in the reduced form, while in the nucleus both the oxidized and reduced forms coexisted as evidenced by the vibrational mode of SH (2580 cm(-1)) and SS (507 cm(-1)), respectively. Both tyrosine and tryptophan were more accessible to water or more exposed in the cortex than in the nucleus. The symmetrically inverse response of vitamin E, between Raman intensity of 1090 cm(-1) and the glutathione level, was consistent with a close relationship of GSH and vitamin E in defending the lens from external insults.

Acute ingestion of dietary proteins improves post-exercise liver glutathione in rats in a dose-dependent relationship with their cysteine content

Dietary sulfur amino acids affect glutathione synthesis, but their acute effect under conditions of oxidative stress is unknown. We assessed the effect of the selective ingestion of alpha-lactalbumin, a cysteine-rich protein, on glutathione homeostasis before a single bout of exhaustive exercise. One hour before a 2-h run on a treadmill, untrained rats ingested a meal enriched with either milk protein (TMP), alpha-lactalbumin-enriched milk protein (alpha-LAC), glucose (GLUC) or milk protein plus 150 mg N-acetyl-L-cysteine, a pharmacologic cysteine donor (NAC). Glutathione status was monitored in the blood and measured postexercise in the liver and heart. A group of fed sedentary rats was used as a control (CON). Blood total glutathione levels declined over time in all test groups. Although postexercise heart glutathione did not differ among groups, postexercise liver glutathione was curvilinearly related to prior cysteine intake (R2=0.999, P<0.05). In alpha-LAC rats, liver glutathione was 60-80% higher than in GLUC or CON rats (P<0.05) and did not differ from that of NAC rats. Cysteine from dietary proteins exhibits a considerable, dose-dependent and acute stimulatory effect on liver glutathione during exercise but does not immediately benefit whole-body glutathione homeostasis, presumably because of an overlap between the postprandial and exercise-related states.

The general case for redox control of wound repair

The orthodox view has been that reactive oxygen species are primarily damaging to cells. There is general agreement that while high (3%) doses of H(2)O(2) may serve as a clinical disinfectant, its overall effect on healing is not positive. Current work shows that at very low concentrations, reactive oxygen species may regulate cellular signaling pathways by redox-dependent mechanisms. Recent discoveries show that almost all cells of the wound microenvironment contain specialized enzymes that utilize O(2) to generate reactive oxygen species. Numerous aspects of wound healing are subject to redox control. An understanding of how endogenous reactive oxygen species are generated in wound-related cells may influence the healing process and could result in new redox-based therapeutic strategies. Current results with growth factor therapy of wounds have not met clinical expectations. Many of these growth factors, such as platelet-derived growth factor, rely on reactive oxygen species for functioning. Redox-based strategies may serve as effective adjuncts to jump-start healing of chronic wounds. The understanding of wound-site redox biology is also likely to provide novel insights into the fundamental mechanisms that would help to optimize conditions for oxygen therapy. While a window of therapeutic opportunity seems to exist under conditions of low concentrations of reactive oxygen species, high levels may complicate regeneration and remodeling of nascent tissue.

Analysis of glutathione: implication in redox and detoxification

BACKGROUND

Glutathione is a ubiquitous thiol-containing tripeptide, which plays a central role in cell biology. It is implicated in the cellular defence against xenobiotics and naturally occurring deleterious compounds, such as free radicals and hydroperoxides. Glutathione status is a highly sensitive indicator of cell functionality and viability. Its levels in human tissues normally range from 0.1 to 10 mM, being most concentrated in liver (up to 10 mM) and in the spleen, kidney, lens, erythrocytes and leukocytes. In humans, GSH depletion is linked to a number of disease states including cancer, neurodegenerative and cardiovascular diseases. The present review proposes an analysis of the current knowledge about the methodologies for measuring glutathione in human biological samples and their feasibility as routine methods in clinical chemistry. Furthermore, it elucidates the fundamental role of glutathione in pathophysiological conditions and its implication in redox and detoxification process.

TESTS AVAILABLE

Several methods have been optimised in order to identify and quantify glutathione forms in human biological samples. They include spectrophotometric, fluorometric and bioluminometric assays, often applied to HPLC analysis. Recently, a liquid chromatography-mass spectrometry technique for glutathione determination has been developed that, however, suffers from the lack of total automation and the high cost of the equipment.

CONCLUSION

Glutathione is a critical factor in protecting organisms against toxicity and disease. This review may turn useful for analysing the glutathione homeostasis, whose impairment represents an indicator of tissue oxidative status in human subjects.

An optimized method for determination of intracellular glutathione in mouse macrophage cultures by fluorimetric high-performance liquid chromatography

We have optimized a method for the determination of intracellular glutathione by high-performance liquid chromatography, using fluorimetric detection. To minimize artifacts and provide an accurate determination of intracellular glutathione, cell extracts were prepared using extraction conditions specifically designed to inhibit autoxidation and enzymatic degradation of glutathione. The sensitivity of the method was enhanced by adjusting the dansyl chloride derivatization reaction with regard to parameters such as pH, reaction time and dansyl chloride concentration. Both oxidized and reduced forms of glutathione were quantified using the refined method in extracts of oxidatively stressed J774A.1 mouse macrophage cells and reflected an expected shift in cellular redox status.

Effects of alpha lipoic acid, ascorbic acid-6-palmitate, and fish oil on the glutathione, malonaldehyde, and fatty acids levels in erythrocytes of streptozotocin induced diabetic male rats

In this research, it has been aimed to evaluate the improvement effects of alpha lipoic acid (ALA), ascorbic acid-6-palmitate (AA6P), fish oil (FO), and their combination (COM) on some biochemical properties in erythrocytes of streptozotocin (STZ)-induced diabetic male rats. According to experimental results, glutathione (GSH) level in erythrocytes decreased in diabetes (P < 0.01), D + ALA, and D + AA6P groups (P < 0.001). Malonaldehyde (MA) level increased in diabetes (P < 0.05), D + FO, and D + COM groups (P < 0.001), but its level in D + AA6P and D + ALA groups was lower in diabetes group (P < 0.01). Total lipid level in diabetes and diabetes plus antioxidant administered groups were higher than control. Total cholesterol level was high in diabetes and D + ALA groups (P < 0.05), but its level reduced in D + FO compared to control and diabetes groups, P < 0.05, < 0.001, respectively. Total triglyceride (TTG) level was high in the D + ALA (P < 0.05) and D + COM (P < 0.001) groups. In contrast, TTG level in blood of diabetes group was higher than diabetes plus antioxidant and FO administered groups (P < 0.001). According to gas chromatography analysis results, while the palmitic acid raised in diabetes group (P < 0.05), stearic acid in D + FO, D + ALA, and diabetes groups was lower than control (P < 0.05), oleic acid reduced in D + COM and D + FO groups, but its level raised in D + AA6P and D + ALA groups (P < 0.01). As the linoleic acid (LA) elevated in ALA + D, D + AA6P, and diabetes groups, linolenic acid level in diabetes, D + AA6P, and D + FO groups was lower than control (P < 0.001). Arachidonic acid (AA) decreased in D + ALA, D+ AA6P, and diabetes groups (P < 0.01), but its level in D + COM and D + FO was higher than control (P < 0.05). Docosahexaenoic acid (DHA) increased in D + AA6P and D + COM (P < 0.05). While the total saturated fatty acid level raised in diabetes group, its level reduced in D + ALA and D + FO groups (P < 0.05). In contrast, total unsaturated fatty acid level in D + ALA and D + FO groups was higher than control (P < 0.05). In conclusion, present data have confirmed that the combination of the ALA, AA6P, and FO have improvement effects on the recycling of GSSG to reduced GSH in erythrocytes of diabetic rats, and in addition to this, oxidative stress was suppressed by ALA and AA6P, and unsaturated fatty acid degree was raised by the effects of ALA and FO.

Effect of whey protein isolate on intracellular glutathione and oxidant-induced cell death in human prostate epithelial cells

Cysteine is the rate-limiting amino acid for synthesis of the ubiquitous antioxidant glutathione (GSH). Bovine whey proteins are rich in cystine, the disulfide form of the amino acid cysteine. The objective of this study was to determine whether enzymatically hydrolyzed whey protein isolate (WPI) could increase intracellular GSH concentrations and protect against oxidant-induced cell death in a human prostate epithelial cell line (designated RWPE-1). Treatment of RWPE-1 cells with hydrolyzed WPI (500 microg/ml) significantly increased intracellular GSH by 64%, compared with control cells receiving no hydrolyzed WPI (P<0.05). A similar increase in GSH was observed with N-acetylcysteine (500 microM), a cysteine-donating compound known to elevate intracellular GSH. In contrast, treatment with hydrolyzed sodium caseinate (500 microg/ml), a cystine-poor protein source, did not significantly elevate intracellular GSH. Hydrolyzed WPI (500 microg/ml) significantly protected RWPE-1 cells from oxidant-induced cell death, compared with controls receiving no WPI (P<0.05). The results of this study indicate that WPI can increase GSH synthesis and protect against oxidant-induced cell death in human prostate cells.

Intracellular redox regulation by a cystine derivative suppresses UV-induced NF-kappa B activation

Nuclear factor (NF)-kappa B pathways are influenced by the intracellular reduction-oxidation (redox) balance. While NF-kappa B is activated through inhibitor (I)-kappa B degradation by oxidative stress, its DNA binding is accelerated in the reduced state. We found that N,N'-diacetyl-L-cystine dimethylester (DACDM) suppressed the UVB-induced NF-kappa B binding activity at a much lower concentration (50-100 microM) than N-acetyl-L-cysteine (NAC, 10-30 mM). While NAC suppressed the I-kappa B degradation but not the DNA binding, DACDM prevented the activated NF-kappa B from binding DNA, without influencing the I-kappa B degradation. These properties of DACDM make it possible to effectively regulate the intracellular redox balance.

Effects of endurance training on tissue glutathione homeostasis and lipid peroxidation in streptozotocin-induced diabetic rats

The aims of our study were to assess whether endurance training strengthens glutathione-dependent antioxidant defenses and decreases oxidative stress in experimental diabetes. Streptozotocin-induced diabetic rats were divided into trained and untrained groups, which were further divided into resting and acute exercise groups. Endurance training consisted of treadmill running for 8 weeks. For acute exhaustive exercise, graded treadmill running was conducted until exhaustion. Eight weeks' treadmill training increased the endurance, favorably decreased lipid peroxidation as measured by thiobarbituric acid reactive substances but not conjugated dienes levels in kidney and vastus lateralis muscle and upregulated glutathione peroxidase in red gastrocnemius muscle. However, it adversely decreased total glutathione level and glutathione peroxidase activity in kidney. Acute exhaustive exercise up-regulated glutathione peroxidase activity in liver. Endurance training did not prevent the increase in thiobarbituric acid reactive substances level in liver due to acute exhaustive exercise. Activities of glutathione disulfide reductase and glutathione S-transferase were not affected. Even though endurance training appeared to upregulate glutathione dependent antioxidant defense in skeletal muscle and to decrease lipid peroxidation in kidney and vastus lateralis muscle as measured by TBARS, our results suggests that beneficial effects of 8 weeks of endurance training are limited in this rat model of uncontrolled diabetes mellitus.

Update on thiol status and supplements in physical exercise

Strenuous physical exercise represents a condition that is often associated with increased production of reactive oxygen species in various tissues. One of the most reliable indices of exercise-induced oxidant production is tissue glutathione oxidation. In humans, exercise-induced blood glutathione oxidation is rapid and subject to control by antioxidant supplementation. The objective of this brief review is to provide an update of our current understanding of cellular thiols and thiol antioxidants. Cellular thiols are critically important in maintaining the cellular antioxidant defense network. In addition, thiols play a key role in regulating redox-sensitive signal transduction process. Lipoic acid is a highly promising thiol antioxidant supplement. Recent studies have clarified that while higher levels of oxidants may indeed inflict oxidative damage, oxidants are not necessarily deleterious. Under certain conditions oxidants may function as cellular messengers that regulate a multitude of signal transduction pathways. In light of this, the significance of oxidants in various aspects of biology needs to be revisited.

Antioxidants in exercise nutrition

Physical exercise may be associated with a 10- to 20-fold increase in whole body oxygen uptake. Oxygen flux in the active peripheral skeletal muscle fibres may increase by as much as 100- to 200-fold during exercise. Studies during the past 2 decades suggest that during strenuous exercise, generation of reactive oxygen species (ROS) is elevated to a level that overwhelms tissue antioxidant defence systems. The result is oxidative stress. The magnitude of the stress depends on the ability of the tissues to detoxify ROS, that is, antioxidant defences. Antioxidants produced by the body act in concert with their exogenous, mainly dietary, counterparts to provide protection against the ravages of reactive oxygen as well as nitrogen species. Antioxidant supplementation is likely to provide beneficial effects against exercise-induced oxidative tissue damage. While universal recommendations specifying types and dosages of antioxidants are difficult to make, it would be prudent for competitive athletes routinely engaged in strenuous exercise to seek an estimate of individual requirement. A new dimension in oxidant biology has recently unfolded. Although excessive oxidants may cause damage to tissues, lower levels of oxidants in biological cells may act as messenger molecules enabling the function of numerous physiological processes. It is plausible that some exercise-induced beneficial effects are actually oxidant-mediated. Such developments call for an even more careful analysis of the overall significance of types and amounts of antioxidants in diet. While these complexities pose significant challenges, experts agree that if used prudently, oxidants and antioxidants may serve as potent therapeutic tools. Efforts to determine individual needs of athletes and a balanced diet rich in antioxidant supplements are highly recommended.

Regulative potential of glutamine--relation to glutathione metabolism

Glutamine (GLN) is the most abundant free amino acid (AA) in the human body. Under GLN-free conditions, which can be obtained when cells are cultivated in vitro, tissue cells cannot grow. Therefore, when classifying GLN as a "non-essential" AA, one must consider that in the human body GLN is synthesized from essential AAs and is continuously delivered from skeletal muscle to other organs. It is fascinating that a relatively simple AA like GLN can stimulate a large variety of cellular reactions. GLN stimulates not only the growth of cells but also the expression of surface antigens, the formation of cytokines, and the synthesis of heat shock proteins. Further, a GLN deficiency leads to a cell cycle arrest in G(0) to G(1) and reduces apoptosis. Interestingly, many of these biological activities also are associated with the cellular reduced oxygen potential, which depends mainly on the ratio of reduced to oxidized glutathione. Experimental animal studies have shown that the administration of GLN increases tissue concentrations of reduced glutathione. This review describes the relation of GLN to reduced glutathione metabolism and discusses the alteration of reduced glutathione metabolism under a variety of clinical conditions such as reperfusion injury, myocardial infarction, respiratory insufficiency, cancer, diabetes, liver disease, and clinical protein catabolism.

Spatial and temporal ontogenies of glutathione peroxidase and glutathione disulfide reductase during development of the prenatal rat

Spatial and temporal expression and regulation of the antioxidant enzymes, glutathione peroxidase (GSH-Px), glutathione disulfide reductase (GSSG-Rd) may be important in determining cell-specific susceptibility to embryotoxicants. Creation of tissue-specific ontogenies for antioxidant enzyme activities during development is an important first step in understanding regulatory relationships. Early organogenesis-stage embryos were grouped according to the somite number (GD 9-13), and fetuses were evaluated by gestational day (GD 14-21). GSH-Px activities in the visceral yolk sac (VYS) increased on consecutive days from GD 9 to GD 13, representing a 5.7-fold increase during this period of development. GSH-Px activities in VYS decreased after GD 13, ultimately constituting a 37% decrease at GD 21. Head, heart, and trunk specific activities generally increased from GD 9 to GD 13 albeit not to the same magnitude as detected in the VYS. GSSG-Rd activities showed substantial increases in the VYS from GD 9 to GD 13, 6.3-fold and decreased thereafter to 50% by GD 21. The greatest changes in enzyme activities were noted in the period between GD 10 and GD 11, where the embryo establishes an active cardiovascular system and begins to convert to aerobic metabolism. Generally, from GD 14-21, embryonic organ GSH-Px and GSSG-Rd activities either remained constant or increased as gestation progressed. These studies suggest the importance of the VYS in dealing with ROS and protecting the embryo. Furthermore, understanding the consequences of lower antioxidant activities during organogenesis may help to pinpoint periods of teratogenic susceptibility to xenobiotics and increased oxygen.

Antioxidant and antiprotease status in peripheral blood and BAL fluid after cardiopulmonary bypass

OBJECTIVE

Cardiopulmonary bypass (CPB) triggers systemic inflammation. Recent evidence suggests that metabolic and oxygenation management can affect the outcome of patients after cardiac surgery. We investigated the influence of oxidant/antioxidant and protease/antiprotease imbalance during the course of systemic and pulmonary inflammation.

METHODS

In a study of 61 patients, we measured the intracellular thiol concentration, the intracellular activity of cathepsins and elastase, and the concentrations of secreted elastase, soluble alpha(1)-proteinase inhibitor (alpha(1)-PI), and secretory leukoprotease inhibitor (SLPI). Peripheral blood and BAL fluid (BALF) were obtained preoperatively and 2 h after CPB.

RESULTS

A post-CPB depletion of thiol was found in blood granulocytes, lymphocytes, and monocytes, as well as BALF lymphocytes and macrophages. The degree of postoperative depletion correlated with PO(2) and blood glucose levels during CPB. Concomitant reduction of FEV(1) showed positive correlation with thiol depletion of blood monocytes and granulocytes. Elastase and cathepsin activities were increased in blood cells but not in lymphocytes or macrophages from BALF. The concentrations of secreted elastase were significantly increased in blood plasma but not in BALF. Enhanced antiprotease (alpha(1)-PI, SLPI) concentrations were measured in BALF but not in peripheral blood.

CONCLUSIONS

The inflammatory response of the intra-alveolar compartment is clearly distinguishable from systemic inflammation. CPB causes a differentiated impairment of the antioxidant defense system as well as a protease/antiprotease imbalance in blood and BALF. Oxygenation under circumstances of CPB and concomitant pulmonary disease, as well as blood glucose metabolism, influence the antioxidative defense. Individual perioperative management of blood glucose and oxygenation could improve cellular defense systems in the peripheral blood and BALF and therefore result in a more favorable patient outcome.

Redox control of caspases

Caspases are critical mediators of apoptotic cell death. All members of the caspase family contain the sequence QACXG which contains the active site cysteine. The putative active site of caspase 3 contains a cysteine residue that is subject to redox control. Both thioredoxin and glutathione have been shown to be required for caspase-3 activity to induce apoptosis. The regulation of inducible caspase 3 activity by oxidation-reduction (redox) dependent mechanisms is reviewed. Up until a few years ago, reactive oxygen species (ROS) research mostly focussed on oxidative damage and ROS were thought to be a key trigger for cell death. This view has been refined, leading to the understanding that the biological function of ROS is determined by numerous variables such as concentration, chemical type and cellular localization. For example, ROS and reactive nitrogen species may intercept inducible cell death under certain circumstances via the redox regulation of inducible caspase activity and/or by depleting cellular energy stores. Likewise, death of unwanted diseased or degenerative cells may be facilitated by pharmacologically enhancing the thiol status of such cells using redox-active α-lipoic acid.

Antioxidant regulation of cell adhesion

Cell-cell and cell-matrix contacts are dependent on cell surface density, localization, and avidity state of surface-localized adhesion molecules. Cell adhesion represents a process that is centrally important in immune function and inflammation. This process is sensitive to various agonists including oxidants. Oxidants may directly as well as indirectly induce cell adhesion. In other cases, cytokines and related agents may induce cell adhesion by oxidant-dependent mechanisms. Various redox-sensitive sites in the signal transduction path leading to cell adhesion have been identified. Different chemical classes of nutritional antioxidants regulate cell adhesion by modulating specific signal transduction pathways. Numerous studies have confirmed that physical exercise influences the redox status of various cells and tissues. Recent evidences also show that physical exercise influences several cell adhesion related molecules. Whether such regulation has a redox component remains to be tested. Antioxidant supplementation studies testing the effect of exercise on cell adhesion should provide critical insight.

Restoration of the cellular thiol status of peritoneal macrophages from CAPD patients by the flavonoids silibinin and silymarin

During continuous ambulatory peritoneal dialysis (CAPD) the peritoneal immune cells, mainly macrophages, are highly compromised by multiple factors including oxidative stress, resulting in a loss of functional activity. One reason for the increase of inflammatory reactions could be an imbalance in the thiol-disulfide status. Here, the possible protective effects of the antioxidant flavonoid complex silymarin and its major component silibinin on the cellular thiol status were investigated. Peritoneal macrophages from dialysis fluid of 30 CAPD patients were treated with silymarin or silibinin up to 35 days. A time-dependent increase of intracellular thiols was observed with a nearly linear increment up to 2.5-fold after 96 hours, reaching a maximum of 3.5-fold after 20 days of culture. Surface-located thiols were also elevated. The stabilization of the cellular thiol status was followed by an improvement of phagocytosis and the degree of maturation as well as significant changes in the synthesis of IL-6 and IL-1ra. Furthermore, the treatment of peritoneal macrophages with flavonoids in combination with cysteine donors resulted in a shortened and more efficient time course of thiol normalization as well as in a further increased phagocytosis. In addition, GSH-depletion in thiol-deficient media simulating CAPD procedures led to intracellular thiol deficiency similar to the in vivo situation. It is concluded that treatment with milk thistle extracts silymarin and silibinin alone or, more effectively in combination with cysteine donors, provide a benefit for peritoneal macrophages of CAPD-patients due to a normalization and activation of the cellular thiol status followed by a restoration of specific functional capabilities.

Cellular thiols and redox-regulated signal transduction

In contrast to the conventional notion that reactive oxygen is mostly a trigger for oxidative damage of biological structures, now we know that low physiologically relevant concentrations of ROS can regulate a variety of key molecular mechanisms that may be linked with important cell functions (Fig. 4). Redox-based regulation of gene expression has emerged as a fundamental regulatory mechanism in cell biology. Several proteins, with apparent redox-sensing activity, have been described. Electron flow through side-chain functional CH2-SH groups of conserved cysteinyl residues in these proteins account for the redox-sensing properties. Protein thiol groups with high thiol-disulfide oxidation potentials are likely to be redox-sensitive. The ubiquitous endogenous thiols thioredoxin and glutathione are of central importance in redox signaling. Signals are transduced from the cell surface to the nucleus through phosphorylation and dephosphorylation chain reactions of cellular proteins at tyrosine and serine/threonine. Protein phosphorylation, one of the most fundamental mediators of cell signaling, is redox-sensitive. DNA-binding proteins are involved in the regulation of cellular processes such as replication, recombination, viral integration and transcription. Several studies show that the interaction of certain transcription regulatory proteins with their respective cognate DNA sites is also redox-regulated. Changes in the concentration of Ca2+i control a wide variety of cellular functions, including transcription and gene expression; Ca(2+)-driven protein phosphorylation and proteolytic processing of proteins are two major intracellular events that are implicated in signal transduction from the cell surface to the nucleus. Intracellular calcium homeostasis is regulated by the redox state of cellular thiols, and it is evident that cell calcium may play a critical role in the activation of the redox-sensitive transcription factor NF-kappa B. Among the several thiol agents tested for their efficacy in modulating cellular redox status, N-acetyl-L-cysteine and alpha-lipoic acid hold most promise for human use. A strong therapeutic potential of strategies that would modulate the cellular thioredoxin system has been also evident.

Effect of combined supplementation with vitamin E and alpha-lipoic acid on myocardial performance during in vivo ischaemia-reperfusion

Reactive oxygen species (ROS) contribute significantly to myocardial ischaemia-reperfusion (I-R) injury. Recently the combination of the antioxidants vitamin E (VE) and alpha-lipoic acid (alpha-LA) has been reported to improve cardiac performance and reduce myocardial lipid peroxidation during in vitro I-R. The purpose of these experiments was to investigate the effects of VE and alpha-LA supplementation on cardiac performance, incidence of dysrhythmias and biochemical alterations during an in vivo myocardial I-R insult. Female Sprague-Dawley rats (4-months old) were assigned to one of the two dietary treatments: (1) control diet (CON) or (2) VE and alpha-LA supplementation (ANTIOXID). The CON diet was prepared to meet AIN-93M standards, which contains 75 IU VE kg-1 diet. The ANTIOXID diet contained 10 000 IU VE kg(-1) diet and 1.65 g alpha-LA kg(-1) diet. After the 14-week feeding period, significant differences (P<0.05) existed in mean myocardial VE levels between dietary groups. Animals in each experimental group were subjected to an in vivo I-R protocol which included 25 min of left anterior coronary artery occlusion followed by 10 min of reperfusion. No group differences (P>0.05) existed in cardiac performance (e.g. peak arterial pressure or ventricular work) or the incidence of ventricular dysrhythmias during the I-R protocol. Following I-R, two markers of lipid peroxidation were lower (P<0.05) in the ANTIOXID animals compared with CON. These data indicate that dietary supplementation of the antioxidants, VE and alpha-LA do not influence cardiac performance or the incidence of dysrhythmias but do decrease lipid peroxidation during in vivo I-R in young adult rats.

Thiol homeostasis and supplements in physical exercise

Thiols are a class of organic sulfur derivatives (mercaptans) characterized by the presence of sulfhydryl residues. In biological systems, thiols have numerous functions, including a central role in coordinating the antioxidant defense network. Physical exercise may induce oxidative stress. In humans, a consistent marker of exercise-induced oxidative stress is blood glutathione oxidation. Physical training programs have specific effects on tissue glutathione metabolism that depend on the work program and the type of tissue. Experimental studies show that glutathione metabolism in several tissues sensitively responds to an exhaustive bout of exercise. Study of glutathione-deficient animals clearly indicates the central importance of having adequate tissue glutathione to protect against exercise-induced oxidative stress. Among the various thiol supplements studied, N-acetyl-L-cysteine and alpha-lipoic acid hold the most promise. These agents may have antioxidant effects at the biochemical level but are also known to influence redox-sensitive cell signaling.

Effect of procyanidins from Pinus maritima on glutathione levels in endothelial cells challenged by 3-morpholinosydnonimine or activated macrophages

The effects of reactive nitrogen species on glutathione homeostasis in human endothelial ECV 304 cells challenged by 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1) on RAW 264.7 activated macrophages using a co-culture model were investigated. SIN-1 or macrophages activated by lipopolysaccharide plus interferon-gamma induced a significant glutathione decrease in ECV 304 cells. Pre-incubation of ECV 304 cells with French maritime pine bark extract containing mainly oligomeric procyanidins protected endothelial cells from activated macrophage-induced glutathione depletion. Data demonstrate that reactive nitrogen species generated with different kinetics and mechanisms impair glutathione levels in endothelial cells, and that pine bark extract significantly enhances antioxidant defenses.

Alpha-lipoic acid supplementation: tissue glutathione homeostasis at rest and after exercise

Antioxidant nutrients have demonstrated potential in protecting against exercise-induced oxidative stress. alpha-Lipoic acid (LA) is a proglutathione dietary supplement that is known to strengthen the antioxidant network. We studied the effect of intragastric LA supplementation (150 mg/kg, 8 wk) on tissue LA levels, glutathione metabolism, and lipid peroxidation in rats at rest and after exhaustive treadmill exercise. LA supplementation increased the level of free LA in the red gastrocnemius muscle and increased total glutathione levels in the liver and blood. The exercise-induced decrease in heart glutathione S-transferase activity was prevented by LA supplementation. Exhaustive exercise significantly increased thiobarbituric acid-reactive substance levels in the liver and red gastrocnemius muscle. LA supplementation protected against oxidative lipid damage in the heart, liver, and red gastrocnemius muscle. This study reports that orally supplemented LA is able to favorably influence tissue antioxidant defenses and counteract lipid peroxidation at rest and in response to exercise.

Flow cytometric determination of cellular thiols

Several biochemical techniques are based on chromatography or electrophoresis for the determination of thiols from biological samples. These techniques are indispensable for the accurate and sensitive detection of specific thiols. Flow cytometric determination of cellular thiols is a powerful technique that is perhaps best suited for clinical application, particularly for cells in blood or other body fluids. Information can be obtained from a small sample amount with a relatively little and quick sample treatment. This technique offers an unique advantage to study the thiol status of a subset of cells because data are collected from individual cells. Multiparameter flow cytometry allows the study of different subsets of immunotyped cells. A major drawback of the flow cytometric method is the lack of specificity for the determination of distinct thiols. The reaction between MBB and thiols is not specific for any particular intracellular thiol, although almost all of the entire thiol-reacted bimane emission is specific for thiols in general. This limitation can be partly overcome by the treatment of cells with known thiol regulatory agents as described in the section on the differential assessment of cellular thiols.

Phospholipase D activation in endothelial cells is redox sensitive

Reactive oxygen species (ROS) are implicated in the pathophysiology of a number of vascular disorders, including atherosclerosis. Recent studies indicate that ROS modulate signal transduction in mammalian cells. Previously, we have shown that ROS (hydrogen peroxide, fatty acid hydroperoxide, diperoxovanadate, and 4-hydroxynonenal) enhance protein tyrosine phosphorylation and activate phospholipase D (PLD) in bovine pulmonary artery endothelial cells (BPAECs). In the present study, our aim was to investigate the role of exogenous thiol agents on ROS-induced PLD activation in conjunction with the role of cellular thiols--glutathione (GSH) and protein thiols--on PLD activation and protein tyrosine phosphorylation. Pretreatment of BPAECs with N-acetyl-L-cysteine (NAC) or 2-mercaptopropionylglycine (MPG) blocked ROS-induced changes in intracellular GSH and PLD activation. Also, pretreatment with NAC attenuated diperoxovanadate-induced protein tyrosine phosphorylation. Pretreatment of BPAECs with diamide or L-buthionine-(S,R)-sulfoximine (BSO), agents that lower intracellular GSH and thiols, enhanced PLD activity. Furthermore, NAC blocked diamide- or BSO-mediated changes in GSH levels, PLD activity, and protein tyrosine phosphorylation. NAC also attenuated diamide-induced tyrosine phosphorylation of proteins between 69 and 118 KDa. These results support the hypothesis that modulation of thiol-redox status (cellular nonprotein and protein thiols) may contribute to the regulation of ROS-induced protein tyrosine phosphorylation and PLD activation in vascular endothelium.

Liver immunity and glutathione

Redox processes have been implicated in various biologic processes, including signal transduction, gene expression, and cell proliferation, and several molecules have been identified as redox regulators in cell activation. Glutathione is the oldest and most investigated molecule among them. Although details of the mechanisms by which glutathione regulates various aspects of cell biology remains to be characterized, the relationship between immunodeficiency and cellular glutathione status is well established. Redox dysregulation contributes to the pathogenesis of acquired immunodeficiency syndrome (AIDS). Human immunodeficiency virus (HIV)-infected patients and simian immunodeficiency virus (SIV)-infected rhesus macaques have, on the average, significantly decreased plasma cysteine and intracellular glutathione levels. Liver contains abundant levels of reducing factors. However, glutathione levels in serum and peripheral blood mononuclear cells of cirrhosis patients are lower compared to values detected in healthy individuals. In the present article, the significance of glutathione in regulating the functions of lymphocytes, especially those of liver-associated lymphocytes, has been described. A novel strategy for immune therapy of liver neoplasms with the use of redox-modulating agents has been proposed.

Rat striatal levels of the antioxidant glutathione are decreased following binge administration of methamphetamine

Involvement of the glutathione antioxidant system is a characteristic feature of oxidative stress. We examined the influence of binge (4 x 20 mg/kg every 5 h) and chronic daily (20 mg/kg per day for 10 days) administration of methamphetamine (MA) on brain levels of total glutathione and major glutathione-related enzymes (glutathione peroxidase and reductase; gamma-glutamyltranspeptidase; glucose-6-phosphate dehydrogenase) in the rat. Binge, but not chronic MA administration was associated with a regionally specific reduction (-17%, P < 0.05) in striatal levels of glutathione 3 h after the last dose of MA, whereas striatal levels of the glutathione-related enzymes were normal. Although the magnitude of the reduction was only modest, these data are compatible with a more severe glutathione decrease localized to dopamine/serotonin nerve terminal areas. Our observations provide further evidence in support of the oxidative stress hypothesis of MA neurotoxicity and indirectly suggest that drugs designed to increase glutathione might protect against such damage.

Antioxidant regulation of phorbol ester-induced adhesion of human Jurkat T-cells to endothelial cells

Regulation of adhesion molecule expression and function by reactive oxygen species via specific redox sensitive mechanisms have been reported. The effects of clinically safe antioxidants in the regulation of adhesion molecule expression in human endothelial cells (ECV), and adherence of human Jurkat T cells to ECV cells were investigated. The thiol antioxidant, alpha-lipoate, at clinically relevant doses down-regulated phorbol 12-myristate 13-acetate (PMA)-induced adhesion molecule expression and cell-cell adhesion. Inhibition of PMA-induced ICAM-1 and VCAM-1 expression as well as PMA-induced adhesion of Jurkat T-cells to ECV cells by alpha-lipoate was dose dependent (50-250 microM). The effect was significant for ICAM-1 (p < .01) and VCAM-1 (p < .01) expression in cells pretreated with 100 microM alpha-lipoate compared to PMA-activated untreated cells. Inhibition of PMA-induced adhesion molecule expression and cell-cell adhesion was more pronounced when a combination of antioxidants, alpha-lipoate and alpha-tocopherol, were used compared to the use of either of these antioxidant alone. The regulation of adhesion molecule expression and function by low concentration of antioxidants investigated does not appear to be NF-kappaB regulated or transcription dependent because no change in the mRNA response was observed. Protein kinase C (PKC) has been suggested to regulate PMA-induced adhesion molecule expression by post-transcriptional stabilization of adhesion molecule mRNA. Alpha-lipoate pretreatment did not influence the response of PKC activity to PMA. Oxidants are known to be involved in the regulation of cell adhesion processes. Treatment of ECV cells with PMA induced generation of intracellular oxidants. Alpha-lipoate (100 or 250 microM) treatment decreased PMA-induced generation of intracellular oxidants. The inhibitory effect of low concentration of alpha-lipaote alone or in combination with alpha-tocopherol on agonist-induced adhesion processes observed in this study may be of potential therapeutic value.

Protective effects of anethole dithiolethione against oxidative stress-induced cytotoxicity in human Jurkat T cells

The protective effects of anethole dithiolethione (ADT) against H2O2- or 4-hydroxynonenal (HNE)-induced cytotoxicity in human Jurkat T cells were investigated. Jurkat T cells were pretreated with ADT (10-50 microM) for 18 hr and then challenged with H202 or HNE for up to 4 hr. Cytotoxicity was assessed by measuring: 1) leakage of lactate dehydrogenase from cells to medium; and 2) exclusion of the DNA intercalating fluorescent probe propidium iodide by viable cells. Pretreatment of cells with ADT (10 or 25 microM) for 18 hr significantly protected cells against H202- or HNE-induced cytotoxicity. Treatment of cells with ADT (10-50 microM) for 72 hr significantly increased the activities of catalase and glutathione reductase. The maximum effect of ADT treatment on the activity of these enzymes was observed when cells were treated with 25 microM of ADT for 72 hr. A significant increase in cellular GSH was observed in cells that were treated with ADT for 72 hr. Using monobromobimane as a thiol probe, we consistently observed that cells pretreated for 18 hr with ADT (25 or 50 microM) had also increased total thiol content. Exposure of Jurkat T cells to H202 or HNE resulted in a time-dependent decrease in cellular GSH. ADT (10-50 microM, 18 hr) pretreatment circumvented H202-dependent lowering of cellular GSH. In conclusion, ADT proved to be a potent cytoprotective thiol antioxidant with multifaceted mechanisms of action, suggesting that the drug has a remarkable therapeutic potential.

A positively charged alpha-lipoic acid analogue with increased cellular uptake and more potent immunomodulatory activity

alpha-Lipoic acid (LA) is taken up by cells and reduced to its potent dithiol form, dihydrolipoate(DHLA), much of which is rapidly effluxed out from cells. To improve retention in cells, the LA molecule was modified to confer a positive charge at physiological pH. N,N-dimethyl,N'-2-amidoethyl-lipoate was synthesized. The protonated form of the new molecule is referred to as LA-Plus. The uptake of LA-Plus by human Wurzburg T cells was higher compared to that of LA. Several-fold higher amounts of DHLA-Plus, the corresponding reduced form of LA-Plus, were detected in LA-Plus treated cells compared to the amount of DHLA found in cells treated with LA. At 100 microM, LA did not but LA-Plus inhibited H2O2 induced NF-kappaB activation and NF-kappaB directed IL-2 receptor expression. Both LA and LA-Plus synergised with selenium in inhibiting H2O2 induced NF-kappaB activation. At 150 microM LA-Plus, but not LA, inhibited TNFalpha induced NF-kappaB activation. At 5 microM LA-Plus, but not LA, protected against both spontaneous and etoposide induced apoptosis in rat thymocytes. LA-Plus is thus an improved form of LA with increased therapeutic potential.

Redox signaling and the emerging therapeutic potential of thiol antioxidants

Oxidation-reduction (redox) based regulation of signal transduction and gene expression is emerging as a fundamental regulatory mechanism in cell biology. Electron flow through side chain functional CH2-SH groups of conserved cysteinyl residues in proteins account for their redox-sensing properties. Because in most intracellular proteins thiol groups are strongly "buffered" against oxidation by the highly reduced environment inside the cell, only accessible protein thiol groups with high thiol-disulfide oxidation potentials are likely to be redox sensitive. The list of redox-sensitive signal transduction pathways is steadily growing, and current information suggests that manipulation of the cell redox state may prove to be an important strategy for the management of AIDS and some forms of cancer. The endogenous thioredoxin and glutathione systems are of central importance in redox signaling. Among the thiol agents tested for their efficacy to modulate cellular redox status, N-acetyl-L-cysteine (NAC) and alpha-lipoic acid hold promise for clinical use. A unique advantage of lipoate is that it is able to utilize cellular reducing equivalents, and thus it harnesses the metabolic power of the cell to continuously regenerate its reductive vicinal dithiol form. Because lipoate can be readily recycled in the cell, it has an advantage over N-acetyl-L-cysteine on a concentration:effect basis. Our current knowledge of redox regulated signal transduction has led to the unfolding of the remarkable therapeutic potential of cellular thiol modulating agents.