Role of tissue glutathione in prevention of surgical trauma

Whole-food phytochemicals antioxidative potential in alloxan-diabetic rats

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Soybean and whole-wheat have beneficial effects on the oxidative status of AD rats more than broadbean.

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Feeding dried wheat is effective in improving MDA, GSH and α-T levels.

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Germination is favorable than drying and moistened heat. Germination enhances the effect of soybeans on TAGs and in the case of soy and wheat enhanced the effect on total cholesterol.

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Diabetic patients, beside controlling their hyperglycaemia with medication, are recommended to include whole foods containing naturally occurring phytochemicals to ameliorate their oxidative status.

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Possible protective factors in the diet such as flavonoids, lutein, lycopene, lignans, and saponins, may provide new strategies to enhance diet and health of diabetic patients.

Background

The importance of whole-food antioxidants in terms of promoting antioxidant recycling in the body in complex human diseases is not fully understood. We aim to discuss the benefits of whole-food antioxidants in ameliorating the diabetic complications in vivo and to address the effect of germination versus heat processing or drying on the potential therapeutic effect of whole grains and legumes. We studied the antioxidant status of alloxan-diabetic (AD) male Spargue Dawley rats, injected intraperitoneally with alloxan dose of 150 mg/kg body weight, and fed on experimental diets based on the flour of soybean, broadbean and whole-wheat for five weeks.

Results

Diabetes-induced oxidative stress in liver was manifested by significant increase in hepatic malondialdehyde (MDA), erythrocytes superoxide dismutase (eSOD) and plasma alpha-tocopherol (α-T) levels, reduction in hepatic glutathione (GSH) levels and catalase (CAT) activity. Consumption of soybean and whole-wheat both had beneficial effects on the oxidative status of AD rats more than broadbean. Feeding dried wheat was effective in improving MDA, GSH and α-T levels. Soybeans and wheat lowered triacylglycerols (TAGs) and tended to lower total cholesterol. Germination enhanced the effect of soybeans on TAGs and in the case of soy and wheat enhanced the effect on total cholesterol.

Conclusion

Whole foods containing naturally occurring phytochemicals and antioxidant vitamins such as legumes and whole grains are recommended, alongside medication, for controlling hyperglycaemia, blood lipids and oxidative status in diabetes.

Xanthohumol suppresses inflammatory response to warm ischemia-reperfusion induced liver injury

Liver ischemia/reperfusion (I/R) leads to formation of reactive oxygen species (ROS), which cause hepatic injury and initiate an inflammatory response, which is a critical problem after liver surgery and transplantation. Xanthohumol, the major prenylated chalcone found in hops, has been discussed for its anti-inflammatory and ROS-scavenging properties, and thus, we aimed to investigate the effect of xanthohumol in a model of warm I/R liver injury. Xanthohumol was applied to BALB/c mice orally at a dose of 1 mg/g body weight for 5 days before I/R-injury was induced by clamping the vascular blood supply to the median and left lateral liver lobe for 1 h followed by a 6 h period of reperfusion. At this time, HPLC analysis revealed hepatic xanthohumol levels of approximately 2 μM, a concentration which has been shown to inhibit inflammatory effects in vitro. Assessment of hepatic HMOX1 expression, hepatic glutathione content and immunohistochemical analysis for proteins conjugated with the reactive aldehyde 4-hydroxynonenal indicated that I/R-induced oxidative stress was significantly inhibited in xanthohumol-fed compared to control mice. Histological analysis, TUNEL staining and determination of transaminase serum levels revealed no significant effects of xanthohumol on acute hepatocellular injury. However, at the same time point, pretreatment with xanthohumol almost completely blunted the I/R-induced AKT and NFκB activation and the expression of the proinflammatory genes IL-1alpha, IL-6, MCP-1 and ICAM-1, which are known to play a crucial role in the subacute phase of I/R-induced liver damage. In conclusion, these data indicate the potential of xanthohumol application to prevent adverse inflammatory responses to I/R-induced liver damage such as after surgical liver resection or transplantation.

Screening for the formation of reactive oxygen species and of NO in muscle tissue and remote organs upon mechanical trauma to the mouse hind limb

BACKGROUND

Until now, no systematic surveys exist in the literature on the early local and systemic generation of reactive oxygen species and of nitric oxide in response to muscle crush injury. Therefore, this study aims to evaluate the formation of reactive oxygen species and nitric oxide in different tissues (injured and contralateral muscle, liver, kidney, spleen and blood) that is induced by closed muscle trauma.

METHODS

5, 45 and 180 min after induction of blunt trauma to the mouse gastrocnemius muscle, animals were sacrificed, tissues harvested and homogenized, and analyzed for their content of glutathione, nitrate and thiobarbituric acid-reactive substances.

RESULTS

The local formation of reactive oxygen species in the injured muscle started immediately upon induction of the mechanical trauma as indicated by changes in the glutathione redox balance. Liver and kidney did not show any response to trauma; however, a marked and immediate increase in the splenic nitrate content was detected, thus suggesting a specific nitric oxide-dependent response of splenic cells to injury.

CONCLUSION

We conclude that immediately after the induction of trauma a formation of reactive oxygen species takes place at the site of crush injury. This might constitute the basis of further damage to the injured tissue by free radical-dependent mechanisms. The immediate formation of nitric oxide within the spleen upon muscle crush appears to represent a specific signalling mechanism of the body in response to distant organ injury.

The influence of fasting on liver sulfhydryl groups, glutathione peroxidase and glutathione-S-transferase activities in the rat

Sulfhydryl groups, glutathione peroxidase (GPx) and glutathione-S-transferase (GST) are important elements of the antioxidant defence in the organism. The efficacy of their antioxidant action is influenced by many factors. In this work, the effect of fasting on total, protein-bound and nonprotein sulfhydryl groups and on the activity of liver and serum GPx and GST in rats were determined. Male Wistar rats were divided into two groups: non-fasted and 18-hour fasted. In fasted animals liver content of nonprotein sulfhydryl groups (represented predominantly by reduced glutathione; GSH) was diminished by 22% in comparison to non-fasted group, whereas total and protein-bound -SH groups were unaffected. The activity of liver and serum GPx was unchanged in food deprived rats. In these animals the activity of GST in serum was reduced by 26%. Fasting had no significant effect on the activity of GST in the liver. Our results demonstrate that in rats deprived of food for 18 hours liver and serum GPx and GST are not involved in protection against action of reactive oxygen species formed during fasting. The observed drop in the content of liver nonprotein sulfhydryl groups without concomitant rise in the activity of GPx and GST indicates that this effect may be due to augmented degradation of GSH, its potentiated efflux from hepatocytes and formation of conjugates with intermediates arising as a result of reactive oxygen species action.

Multiple organ dysfunction syndrome

Multiple organ dysfunction syndrome, including acute respiratory distress syndrome (ARDS) and renal failure, is described, its clinical features outlined, its origins in tissue oxidative stress following severe infections, surgical trauma, ionizing radiation, high-dosage drugs and chemicals, severe hemorrhage, etc., are defined, and its prevention and treatment prescribed.

Attenuation of antioxidative capacity enhances reperfusion injury in aged rat myocardium after MI/R

Mortality due to ischemic cardiovascular diseases is significantly higher in elderly than in young adults. Myocardial ischemia-reperfusion (MI/R) can induce oxidative stress and an inflammatory response. We hypothesized that increased vulnerability of aged myocardium to reperfusion injury could be caused by decreased antioxidative capacity, rather than increased oxidant production, after MI/R. Aged (20-mo-old) and young (4-mo-old) male F344BN rats were subjected to 30 min of myocardial ischemia by ligation of the left main coronary artery followed by release of the ligature and 4 h of reperfusion. Four experimental groups were studied: young sham-operated rats, aged sham-operated rats, young rats subjected to MI/R, and aged rats subjected to MI/R. MI/R significantly increased infiltrated leukocyte number and myeloperoxidase (MPO) activity in perinecrotic areas of hearts of young rats compared with aged MI/R rats. These changes in infiltrated leukocyte number and MPO activity were associated with an increase in superoxide generation in perinecrotic areas from hearts of young rats compared with aged rats. Plasma levels of TNF-alpha and IL-1beta were significantly higher in young than in aged MI/R rats. However, plasma 8-hydroxy-2'-deoxyguanosine levels and creatine kinase activity were increased in aged compared with young MI/R rats. Increased reperfusion damage in aged rats was associated with a significant decrease in plasma ratio of GSH to GSSG. Our results suggest that enhanced ischemia-reperfusion injury in aged rat hearts may be related to reduced antioxidative capacity, rather than increased reactive oxygen species production. These findings contribute to a better understanding of effects of aging on oxidative stress and inflammatory responses of the heart after MI/R.

Hepatic cytoprotection by nitric oxide and the cGMP pathway after ischaemia-reperfusion in the rat

Many studies in diverse models suggest that nitric oxide (NO) may be protective against liver injury due to ischaemia-reperfusion (IR). We evaluated, in an experimental in vivo model of rat liver partial ischaemia, the effects of pretreatment by an NO donor (spermineNONOate, 5mg/kg), and exogenous cGMP (8Br-cGMP, 16 mg/kg) or an endogenous cGMP producer (ANP, 10 microg/kg), to assess their beneficial effects. After 6h of reperfusion, 8Br-cGMP completely prevented the adverse effect of Nomega-nitro-L-arginine (10mg/kg) and 8Br-cGMP alone showed a protective action on both hepatocytes (AST, -25%, LDH, -55%) and endothelial cells (plasma hyaluronic acid (HA), -30%). ANP caused a marked decrease in AST and LDH activities only after 1h of reperfusion (AST, -30%, LDH, -40%). Pretreatment with spermineNONOate prevented hepatocyte injury after 1 and 6h of reperfusion (AST, -22%, LDH, -27%). However, neither spermineNONOate nor ANP had any protective effect on endothelial cell damage. These results confirm the beneficial effect of an NO donor and strongly suggest the implication of a cGMP pathway that does not involve a blockade of inflammatory cytokines production (IL-6 generation was unaffected by 8Br-cGMP pre-treatment). In our model, 8Br-cGMP showed a greater protective effect than ANP or spermineNONOate and so might be used to prevent hepatic injury after IR. Finally, we propose a schematic representation of the different routes for the actions of NO in protecting the liver against IR damage.

Effects of fasting on tissue contents of coenzyme A and related intermediates in rats

Exposure of rats and mice to hyperoxia decreases lung coenzyme A (CoASH) contents, with a decrease of 50% observed in adult male Fischer-344 rats exposed to >95% O(2) for 48 h. Decreases in lung CoASH levels are not accompanied by increases in contents of the mixed glutathione disulfide of CoA, as might be expected of a primary oxidative stress on CoASH status. Animals exposed to hyperoxia exhibit decreased food intake, and the present studies were to test the hypothesis that fasting would decrease lung CoASH contents, thereby suggesting a mechanism for the effects of hyperoxia. Adult male Fischer-344 rats were examined after 0, 24, or 48 h of fasting (n = 5, 6, and 6, respectively). Fasting for 24 or 48 h did not affect lung CoASH levels or lung weights, despite 6 and 12% losses in body weight. Lung glutathione concentrations (nanomoles per gram of tissue) and contents (nanomoles per whole organ) and glutathione disulfide contents were 10 to 20% lower in rats fasted for 48 h than in fed rats. Liver weights and glutathione and glutathione disulfide contents and concentrations were 30 to 70% lower in rats fasted for 24 or 48 h than in fed rats. Hepatic CoASH concentrations increased during fasting, but hepatic contents of CoASH remained remarkably constant. Liver protein contents (milligrams of protein per whole organ) decreased after 24 and 48 h of fasting, but protein concentrations (milligrams of protein per gram of tissue) were higher in rats fasted 48 h than in fed rats. Overall, glutathione, glutathione disulfide, and protein contents in liver and skeletal muscle decreased with fasting, but significant changes in CoASH contents were not observed. Diminished food intake in animals does not explain the effects of hyperoxia on lung CoASH contents. CoASH and derived thioesters participate in many cellular functions, and if depletion of lung CoASH during hyperoxia proves to be relevant to mechanisms of lung injury, support of mechanisms needed to sustain CoA levels could be helpful in prematurely born infants and in adults.

Antioxidant Therapy in the Prevention of Organ Dysfunction Syndrome and Infectious Complications after Trauma: Early Results of a Prospective Randomized Study

Reactive oxygen species have been implicated in the etiology of multiorgan dysfunction syndrome and infectious complications in trauma patients by either direct cellular toxicity and/or the activation of intracellular signaling pathways. Studies have shown that the antioxidant defenses of the body are decreased in trauma patients; these include glutathione, for which N-acetylcysteine is a precursor, and selenium, which is a cofactor for glutathione. Eighteen trauma patients were prospectively randomized to a control or antioxidant group where they received N-acetylcysteine, selenium, and vitamins C and E for 7 days. As compared with the controls, the antioxidant group showed fewer infectious complications (8 versus 18) and fewer organs dysfunctioning (0 versus 9). There were no deaths in either group. We conclude that these preliminary data may support a role for the use of this antioxidant mixture to decrease the incidence of multiorgan dysfunction syndrome and infectious complications in the severely injured patient. This remains to be confirmed in larger trials.

Effects of glutathione depletion on oxidant-induced endothelial cell injury

Ischemia-reperfusion produces edema in vivo by disrupting endothelial cell junctional integrity. A cultured rat pulmonary artery endothelial cell (RPAEC) model was used to analyze the effects of oxidants and ischemic plasma in vitro. RPAEC cultures were treated with ischemic human plasma from transverse rectus abdominis musculocutaneous (TRAM) flaps following mastectomy or with an equal quantity of nonischemic plasma taken peripherally. Endothelial cells treated with ischemic plasma rounded and formed gaps within 5 min, then ruffled and blebbed after 10 min. Cultures treated with human nonischemic plasma had no gross morphological changes. Additionally, cultures treated with human ischemic plasma demonstrated an increase in diffusion rate of 125I-albumin across monolayers while monolayers treated with human nonischemic plasma had no increase in diffusion rate. RPAEC monolayers were treated with malic acid diethyl ester (DEM) or L-buthionine-[S, R]-sulfoximine (BSO) to decrease cellular stores of glutathione before exposure to oxidant stress. Cultures depleted of cellular glutathione stores were significantly (P < 0.05) more susceptible to 50 microM H2O2 than controls, as determined by an increase in diffusion rate of 125I-albumin across monolayers. To determine if ischemic plasma effects were mediated by oxidants, cultures were depleted of glutathione by DEM or BSO pretreatment before exposure to plasma from the ischemic hind limbs of Sprague-Dawley rats. Glutathione-depleted RPAEC monolayers were significantly (P < 0.05) and substantially (2-3 X) more susceptible to the effects of ischemic plasma than were cultures with normal glutathione levels. Glutathione depletion had no effect on cultures treated with an equal amount of nonischemic plasma from sham-operated rats. These data strongly suggest that ischemic plasma in the absence of any cellular component are able to induce an oxidant injury in endothelial cells and thereby compromise junctional integrity.

Effect of L-buthionine-(S,R)-sulphoximine, an inhibitor of gamma-glutamylcysteine synthetase on peroxynitrite- and endotoxic shock-induced vascular failure

1. Peroxynitrite, a cytotoxic oxidant formed from the reaction of nitric oxide (NO) and superoxide is a mediator of cellular injury in ischaemia/reperfusion injury, shock and inflammation. Here we investigated whether L-buthionine-(S,R)-sulphoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase, alters endothelial and vascular smooth muscle injury in response to peroxynitrite in vitro and during endotoxic shock in vivo. 2. In human umbilical vein endothelial cells and in rat aortic smooth muscle cells, BSO (1 mM, for 24 h) enhanced, whereas glutathione (3 mM) or glutathione ethyl ester (3 mM) attenuated the peroxynitrite (100-1000 microM)-induced suppression of mitochondrial respiration (measured by the conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to formazan), formation of nitrotyrosine (detected by Western blotting), protein oxidation (measured by detection of 2,4 dinitrophenylhydrazine-reactive carbonyls), and DNA single strand breakage and activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS) (measured by the incorporation of radiolabelled NAD+ into nuclear proteins and by the alkaline unwinding assay, respectively). Glutathione ethyl ester treatment reduced the BSO-induced enhancement of peroxynitrite-induced cytotoxicity. 3. In rat isolated thoracic aortic rings, BSO treatment (in vivo, at 1 g kg(-1) intraperitoneally (i.p.) for 24 h) enhanced, whereas pretreatment with glutathione (in vitro, 3 mM) attenuated the peroxynitrite-induced reduction of the contractions to noradrenaline, and the peroxynitrite-induced impairment of the endothelium-dependent relaxations to acetylcholine. 4. In BSO-pretreated rats, treatment with bacterial lipopolysaccharide (LPS, 15 mg kg(-1), i.p., for 6 h) caused a more pronounced vascular hyporeactivity and endothelial dysfunction ex vivo. BSO pretreatment also increased the degree of nitrotyrosine staining (detected by imunohistochemistry) in the aorta after LPS treatment. 5. In conclusion, our results demonstrate that L-buthionine-(S,R)-sulphoximine, an inhibitor of gamma-glutamylcysteine synthetase enhances peroxynitrite- and endotoxic shock-induced vascular failure. Based on these findings, we suggest that endogenous glutathione plays an important protective role against peroxynitrite- and LPS-induced vascular injury.

Personal reflections on 50 years of study of benzene toxicology

The metabolism of benzene is reviewed, and the objectives of a quantitative balance study begun in 1945 are outlined; problems of toxicology and metabolism research of some 50 years ago are considered. The quantitative metabolism of 14C-benzene in the rabbit is annotated and compared with that of unlabeled benzene quantified by nonisotopic methods. The anomalies of phenylmercapturic acid and trans-trans-muconic acid as metabolites of benzene are examined in detail by isotopic and nonisotopic methods; these compounds are true but minor metabolites of benzene. Oxygen radicals are involved in both the metabolism of benzene and its toxicity; the roles of CYP2E1, the redox cycling of quinone metabolites, glutathione oxidation, and oxidative stress in the unique radiomimetic, hematopoietic toxicity of benzene are discussed. Differences between the toxicity of benzene and the halobenzenes are related to fundamental differences in their electronic structures and to the consequent pathways of metabolic activation and detoxication.

Spontaneous development of fatty liver in ferrets in a toxicology study

Ferrets were maintained for 12 months on different diets (A, meat and biscuit; B, all meat; C, meat and fish; D, high fibre) to ascertain the cause of spontaneous development of fatty liver. High hepatic triglyceride contents resulted on diets B = C > D; whereas ferrets on diet A (control) showed no accumulation of lipid in liver. Serum triglyceride and total cholesterol were unchanged by diet. These ferrets (F0 generation) were mated with ferrets on the same diet and the offspring (F1 generation), maintained on the same diets as the parents, were killed at 12 months and the livers studied similarly. Histology showed that hepatic lipid accumulation in the F1 generation was identical with that in the same dietary groups of the F0 generation; liver glutathione (GSH) reductase and thiobarbituric acid-reacting substances (an index of lipid peroxidation) were increased in ferrets maintained on diets B, C and D, liver GSH concentration and GSH peroxidase activities were unchanged. Other ferrets fed a high-fat diet (diet A plus 20% w/w beef suet) for 18 days exhibited hepatic lipid accumulation and decreased hepatic cyanide-insensitive palmitoyl CoA oxidation (-30%), but hepatic lauric acid hydroxylation and carnitine acyl transferase activities were unchanged. These data indicate that ferrets on high-fat diets show no increased rates of liver fatty acid oxidation, as seen in rats, but instead accumulate triglyceride in the liver with some degree of lipid peroxidation.