Susana Llesuy

Antioxidant properties of natural compounds used in popular medicine for gastric ulcers

There is evidence concerning the participation of reactive oxygen species in the etiology and physiopathology of human diseases, such as neurodegenerative disorders, inflammation, viral infections, autoimmune pathologies, and digestive system disorders such as gastrointestinal inflammation and gastric ulcer. The role of these reactive oxygen species in several diseases and the potential antioxidant protective effect of natural compounds on affected tissues are topics of high current interest. To consider a natural compound or a drug as an antioxidant substance it is necessary to investigate its antioxidant properties in vitro and then to evaluate its antioxidant functions in biological systems. In this review article, we shall consider the role of natural antioxidants derived from popular plants to reduce or prevent the oxidative stress in gastric ulcer induced by ethanol.

Hydroperoxide-initiated chemiluminescence: An assay for oxidative stress in biopsies of heart, liver, and muscle

Hydroperoxide-initiated chemiluminescence was standardized as a microassay to evaluate the occurrence of oxidative stress in human biopsies. Samples of 10 to 50 mg of rat liver or heart were homogenized, diluted in reaction medium, added with tert-butyl hydroperoxide, and assayed for chemiluminescence in a liquid scintillation counter in the out-of-coincidence mode. Optimal conditions for the assay were: 0.3 to 1.2 mg/mL of homogenate protein in 120 mM KCl, 30 mM phosphate buffer (pH 7.4), and 3 mM tert-butyl hydroperoxide at 30 degrees C. In these conditions, maximal chemiluminescence values were 550 +/- 30 and 1100 +/- 40 cps/mg protein, for liver and heart homogenates, respectively. Liver and heart homogenates were subjected to in vitro oxidative stresses such as supplementation with organic hydroperoxide or with enzymatic systems generating superoxide anion or hydrogen peroxide. Chemiluminescence was higher in the poststress samples than in the control ones. The ratio: poststress chemiluminescence/control chemiluminescence (B/A) was about 1.4 or higher for both tissues. Human heart biopsies were utilized to investigate the occurrence of oxidative stress after clinical situations associated to ischemia-reperfusion. B/A ratios were 2.1 +/- 0.4, 1.4 +/- 0.1, and 2.8 +/- 0.4 for human heart, liver, and skeletal muscle, respectively.

Heme oxygenase and oxidative stress. Evidence of involvement of bilirubin as physiological protector against oxidative damage

Cobalt chloride (CoCl2), a well-known inducer of heme oxygenase, produced a strong increase of in vivo rat liver chemiluminescence (QLV) 6 h after its administration. The activity of antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) was found to be significantly decreased 9 h after CoCl2 injection. Heme oxygenase activity increased 9 h after treatment, reaching a maximum value around 18 to 24 h after CoCl2 administration. This induction was preceded by a decrease in the intrahepatic GSH pool and an increase in hydrogen peroxide steady state concentration, both effects taking place several hours before induction of the heme-oxygenase. Co-administration of Sn-protoporphyrin IX, a potent inhibitor of heme oxygenase, completely prevented the enzyme induction, increasing the QLV levels. Administration of bilirubin, the end product of heme catabolism in mammals, prevented the heme oxygenase induction as well as the decrease in hepatic GSH and the increase of chemiluminescence when it was administered 2 h before CoCl2 treatment. These results support the proposal that the induction of heme oxygenase by cobalt chloride may be a general response to oxidant stress and, by increasing bilirubin levels, could constitute an important cellular defense mechanism against oxidative damage.

Oxidative stress markers in aqueous humor of glaucoma patients.

PURPOSE Oxidative stress and antioxidant status in eye tissues may be associated with glaucomatous damage. The aim of this study was to establish the antioxidant status of aqueous humor of patients with primary open-angle glaucoma. For this purpose the authors measured the total reactive antioxidant potential (TRAP) and the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase. DESIGN Case control study. METHODS Aqueous humor was obtained at the time of surgery from 24 patients with glaucoma and 24 cataract patients; TRAP was measured by chemiluminescence. Activities of the antioxidant enzymes were measured spectrophotometrically. Superoxide dismutase activity was determined by inhibition of the rate of adrenochrome formation at 480 nm. Catalase activity was evaluated by decrease of H(2)O(2) absorbance at 240 nm. Glutathione peroxidase (GPx) activity was determined following nicotinamide adenine dinucleotide phosphate oxidation at 340 nm. RESULTS Total reactive antioxidant potential value of the cataract group was 124 +/- 5 micromol/l Trolox. This value was significantly decreased, by 64%, in glaucoma patients. An increase of 57% in SOD activity was observed in glaucoma patients when compared with cataract patients (41.7 +/- 2.7 U SOD/ml). Glutathione activity was threefold higher in glaucoma patients than in the cataract group (6.1 +/- 0.6 U/ml). No significant changes were found in catalase levels. CONCLUSIONS Oxidative stress may lead to an induction of antioxidant enzymes and contribute to TRAP decrease. Superoxide dismutase, GPx activities, and TRAP may be useful oxidative stress markers in aqueous humor of glaucoma patients.

Comparison of Lipid Peroxidation and Myocardial Damage Induced by Adriamycin and 4′-Epiadriamycin in Mice

Adriamycin (ADM) and 4′-epiadriamycin (4′-ADM) were given to mice in a single dose of 15 mg/kg body weight (i.p.). Twenty-five mice were alloted to 3 groups. One group (Group I; n = 8) was given ADM; another group (Group II; n = 9) was similarly treated with 4′-ADM, and a control group (n = 8) received an equivalent volume of 0.9 % NaCl solution. Mice were sacrificed 4 days after the described treatment. A complete autopsy was carried out in each animal. Hydroperoxide-initiated chemihuninescence and malonaldehyde formation were measured in mouse heart homogenates. Control mice showed a maximal photoemission of 52 ± 2 (×10–3) (mean values ± S.E.M.) cpm/mg protein and a formation of 20 ± 4 nmol malonaldehyde/g organ after a 2 hr-incubation. The ADM-treated mice showed a 24 % enhanced hydroperoxide-initiated photoemission and a 370 % increased malonaldehyde formation. The 4′-ADM-treated mice showed a 15 % increased hydroperoxide-stimulated chemiluminescence and an 85 % increased malonaldehyde formation. Vitamin A (5000 IU), vitamin E (85 IU) and vitamins A and E (same doses as before) given as a single dose i.p. 1 day before doxorubicin administration were able to decrease the hydroperoxide-initiated chemihuninescence by 24 %, 26 % and 44 %, respectively. Microscopically, only scarce isolated microvacuolated subendocardial fibers were found in the ADM-treated animals. Our data showing that 4′-ADM lacks a statistically significant effect in increasing heart peroxidation as compared to ADM may explain its lower myocardial toxicity.

Oxidative stress in blood of HIV infected patients

The oxidative stress in human erythrocytes was studied in asymptomatic and symptomatic patients infected by the human immunodeficiency virus (HIV), and patients with the acquired immunodeficiency syndrome (AIDS). tert-Butyl hydroperoxide initiated chemiluminescence, superoxide dismutase and catalase activities, and total glutathione were evaluated in the erythrocytes and the total antioxidant capacity in the plasma of control, patients infected with HIV that have not yet developed acquired immunodeficiency syndrome, and patients in the later stage of AIDS. tert-Butyl hydroperoxide initiated chemiluminescence was increased by 33% in asymptomatic (stage A1) and symptomatic patients (stage B2) infected with HIV and 82% for patients with AIDS (stage B3) (P < 0.05). While catalase activity did not show any difference between patients and controls, other indices showed differences that, in some cases, reached statistical significance. Superoxide dismutase activity was increased by 24% in stages A1 and B2 of HIV infection and 65% in patients in stage B3 (P < 0.05). Glutathione was decreased by 20% in stages A1 and B2, and by 32% in stage B3 patients (P < 0.05). Total plasma antioxidant capacity was increased in 30 and 57% for the asymptomatic and AIDS patients groups, respectively (P < 0.05). The data indicate that erythrocytes oxidative stress is associated with the progressive development of HIV disease. Parameters indicating oxidative stress could be an interesting form to screen the evolution of these patients and their response to anti-oxidant therapies.

Soccer players under regular training show oxidative stress but an improved plasma antioxidant status

Physical activity is known to induce oxidative stress in individuals subjected to intense exercise. In this study, we investigated the lipoprotein profile and the plasma antioxidant status in a group of soccer players engaged in a regular training programme. As was expected for aerobic exercise, high-density lipoprotein-cholesterol (HDL-C) and HDL3-C levels were significantly increased in the sportsmen (P<0.05). Total plasma antioxidant capacity was 25% higher in sportsmen than in controls (P<0.005). Accordingly, plasma hydrosoluble antioxidant levels (ascorbic acid and uric acid) were found to be significantly elevated in the soccer players (P<0.005). In addition, these subjects showed high concentrations of alpha-tocopherol in plasma compared with controls (P<0.005). Furthermore, an increase in plasma superoxide dismutase activity was also observed in relation to exercise (P<0.01). The elevation in plasma activities of antioxidant enzymes and the higher levels of free radical scavengers of low molecular mass may compensate the oxidative stress caused by physical activity. High levels of high-density lipoprotein in plasma may offer additional protection by inhibiting low-density lipoprotein oxidation and thus liposoluble antioxidant consumption. Therefore, soccer players under regular training show an improved plasma antioxidant status in comparison to sedentary controls.

OXIDATIVE STRESS BY ACUTE ACETAMINOPHEN ADMINISTRATION IN MOUSE LIVER

Acetaminophen was given to mice at a single dose of 375 mg/kg. In situ liver chemiluminescence, H2O2 steady-state concentration, and the liver concentrations of total and oxidized glutathione were measured 15, 30, and 60 min after acetaminophen administration. Increases of 145% and 72% in spontaneous chemiluminescence and H2O2 concentration were observed 15 min after the injection, respectively. Total glutathione was decreased by acetaminophen administration at all the times studied. The maximal decrease, 83%, was found 60 min postinjection. The ratio GSH/GSSG was found significantly decreased at all the times studied. Microsomal superoxide production was increased by 2.4-fold by addition of acetaminophen. The activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase were determined. Catalase was slightly inhibited (30%) 15 min after acetaminophen administration. No significant changes were found in superoxide dismutase activity. Se and non-Se glutathione peroxidase activities were decreased by 40% and 53% respectively, 15 min after acetaminophen administration. The decrease in catalase and glutathione peroxidase would result in an increased steady state level of H2O2 and hydroperoxides, contributing to cell injury. Damaged hepatocytes were observed, and severe lesions and necrosis appeared 60 min after acetaminophen administration. Our results indicate the occurrence of oxidative stress as a possible mechanism for acetaminophen-induced hepatotoxicity.

Oxidative stress in muscle and liver of rats with septic syndrome

Sepsis, as infection associated to systemic manifestations, was produced in rats by cecal ligation and double perforation. Sham-operated rats were used as controls. The spontaneous chemiluminescence of rat adductor muscle and liver were measured at 6, 12, 24, and 30 h after the surgical procedure. Muscle chemiluminescence showed a maximal increase of about twofold (control emission 10 +/- 1 cps/cm2) after 6-12 h of sepsis, while liver chemiluminescence increased by about 80% (control emission: 11 +/- 1 cps/cm2) after 24 h of sepsis. The activities of muscle antioxidant enzymes were found maximally diminished after 12 h of sepsis: 46% decrease for Mn-superoxide dismutase, 83% decrease for catalase, and 55% decrease for glutathione peroxidase. In liver, only catalase activity showed a 52% decrease after 24 h of sepsis. State 3 oxygen uptake of muscle mitochondria with either malate-glutamate or succinate as substrates was 40% decreased after 12 h of sepsis in both cases. State 4 oxygen uptake of muscle mitochondria was not affected. The rate of H2O2 production of muscle mitochondria after 12 h of sepsis with either malate-glutamate or succinate as substrates was increased about 2.5 times but was not affected when assayed in the presence of as rotenone and antimycin. The oxygen uptake of liver mitochondria isolated from septic rats did not show differences as compared with those of control rats after 6 to 24 h of sepsis. Oxidative stress appears to occur in skeletal muscle early at the onset of the septic syndrome, with inhibition of active mitochondrial respiration and inactivation of antioxidant enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of reperfusion injury with preoperative rapid intravenous infusion of taurine during myocardial revascularization

To assess a possible free-radical scavenging action of taurine during coronary artery bypass grafting, 12 patients were randomly divided into two equal groups. One to 3 hours before surgery, they received a rapid intravenous infusion of either placebo (group 1) or taurine (5 gm) (group 2). During surgery, biopsy samples were taken before ischemia (preischemic samples) and after 10 minutes of reperfusion (reperfusion samples). Lipoperoxidation was determined by hydroperoxide-initiated chemiluminescence of heart homogenates, and myocardial cell damage was assessed by electron microscopy. The values for chemiluminescence in preischemic and reperfusion samples from group 1 were 7500 +/- 1600 and 18,600 +/- 4600 cpm/mg of protein, respectively (p less than 0.03). This difference was not observed in group 2 where the values were 10,050 +/- 2700 and 11,800 +/- 4200 cpm/mg of protein, for preischemic and reperfusion samples, respectively. The number of severely damaged mitochondria (grades 3 and 4) in reperfusion samples from group 1 increased significantly compared to preischemic samples (25 +/- 8% vs 12 +/- 3%, p less than 0.01). Conversely no differences were observed between the number of severely damaged mitochondria in reperfusion and preischemic samples from group 2 (8 +/- 3% vs 8 +/- 2%). The number of damaged and necrotic myocytes increased in group 1 after reperfusion from 22 +/- 9% to 34 +/- 10% (p less than 0.03) and from 10 +/- 7% to 26 +/- 20% (p = NS), respectively. No changes were observed between reperfusion and preischemic samples in group 2. Treatment with taurine seems to reduce lipoperoxidation and decrease cell damage at the time of reperfusion.