Quenching of singlet oxygen by D-alpha-tocopherol in human granulocytes

Radioprotective agents for the prevention of side effects induced by radioiodine-131 therapy

Radioiodine 131 (131I) has been used worldwide for the ablation of remnant thyroidal tissue after surgery or as the first-line treatment for Graves’ disease. Although the use of 131I is becoming increasingly prevalent, there is evidence suggesting that this treatment is associated with side effects such as salivary gland dysfunction and an increased risk of leukemia. This article aims to review the potential use of radioprotective agents and the side effects induced by 131I therapy. Several synthetic and natural compounds have been investigated in preclinical and clinical studies. The protective agents reduced the toxicity of 131I, mainly in the salivary glands, and mitigated the genetic damage through different mechanisms. There are limited clinical studies evaluating the use of radioprotective agents in patients undergoing radioiodine therapy. However, lemon candies, lemon juice and sugarless chewing gum have been proposed to be beneficial for minimizing the side effects of radioiodine within the salivary glands.

Effects of intraperitoneally administered lipoic acid, vitamin E, and linalool on the level of total lipid and fatty acids in guinea pig brain with oxidative stress induced by H2O2

The aim of our study was to investigate the protective effects of intraperitoneally-administrated vitamin E, dlalpha lipoic acid, and linalool on the level of total lipid and fatty acid in guinea pig brains with oxidative stress that was induced by H2O2. The total brain lipid content in the H2O2 group decreased when compared to the H2O2 + vitamin E (p<0.05), H2O2+ linalool (p<0.05), ALA (p<0.05), control (p<0.01), linalool (p<0.01), and vitamin E (p<0.01) groups. While the proportion of total saturated fatty acid ( infinity SFA) in the H2O2 group significantly increased (p<0.005) when compared to the vitamin E group, it only slightly increased (p<0.01) when compared to the control and H2O2 + vitamin E groups. The ratio of the total unsaturated fatty acid (infinity USFA) in the H2O2 groups was lower (p<0.05) than the control, vitamin E, and H2O2+ vitamin E groups. The level of the total polyunsaturated fatty acid (infinity USFA) in the H2O2 group decreased in when compared to the control, vitamin E, and H2O2+vitamin E groups. While the proportion of the total w3 (omega 3), w6 (omega 6), and PUFA were found to be lowest in the H2O2 group, they were slightly increased (p<0.05) in the lipoic acid group when compared to the control and H2O2 + lipoic acid groups. However, the level of infinity SFA in the H2O2 group was highest; the level of infinity USFA in same group was lowest. As the proportion of infinity USFA and infinity PUFA were found to be highest in the linalool group, they were decreased in the H2O2 group when compared to the control group. Our results show that linalool has antioxidant properties, much the same as vitamin E and lipoic acid, to prevent lipid peroxidation. Additionally, vitamin E, lipoic acid, and linalool could lead to therapeutic approaches for limiting damage from oxidation reaction in unsaturated fatty acids, as well as for complementing existing therapy for the treatment of complications of oxidative damage.

Antioxidants suitable for use with chemiluminescence to identify oxyradical species

From a panel of 24 alleged antioxidants the most suitable antioxidants (AO) for use with chemiluminescence (CL) experiments were determined. Superoxide dismutase (SOD), using luminol as the chemiluminescence probe (Lum-CL), was inhibitory only towards O2*- and not HO* or (1)O2. SOD was thus a suitable antioxidant for O2*-, as was tiron. Tiron had advantages, however, since SOD acted as a pro-oxidant in the presence of H2O2 or H2O2/HO* generators. The two most suitable antioxidants for (1)O2 were diphenylisobenzofuran (DBF) and tryptophan, for both Lum and Lucigenin-CL (Luc-CL). Desferrioxamine, with both Lum and Luc-CL, was a very effective scavenger for HO*, but appeared to be an even more effective scavenger for (1)O2. Cysteamine showed the best discrimination between IC50s when the two (1)O2 generators NaOCl/H2O2 and NDPO2 were compared. Cysteamine was, therefore, the only scavenger that was appropriate for studies with hypochlorite. Melatonin, with Lum-CL, was found to be the most suitable scavenger for HO*. Mannitol, the classical AO for HO*, was not suitable when used with CL since it acted as a pro-oxidant. Some of the AOs revealed either calyx- or bell-shaped CL inhibition profiles and presumably, therefore, may act as both pro- or antioxidants at different concentrations. Antioxidants showing these kinds of dual activities should be used with caution in CL studies.

Reactive oxygen species in puromycin aminonucleoside nephrosis: in vitro studies

We examined the role of reactive oxygen species (ROS) in puromycin aminonucleoside (PAN)-induced changes to glomerular epithelial cells (GECs) in vitro. Levels of superoxide anion (O2.-), hydrogen peroxide (H2O2) and hydroxyl radical (HO.) were measured in rat kidney-slice cultures containing PAN with or without antioxidants (allopurinol, probucol and alpha-tocopherol/ascorbic acid). GEC morphology was assessed after three days of culture using transmission (TEM) and scanning (SEM) electron microscopy. The effects of hypoxanthine on GEC ultrastructure was also assessed. O2.-, H2O2 and HO. were generated when PAN was added to kidney-slice cultures in Medium 199. TEM morphometry revealed that incubation with PAN (100 micrograms/ml) significantly (P < 0.05 at least) retarded the loss of GEC foot processes normally seen in vitro. When the hydrophobic antioxidants probucol or alpha-tocopherol/ascorbic acid, which scavenged/inhibited generation of O2.-, H2O2 and HO., were added to cultures containing PAN, the effect of PAN on foot processes was abolished. The TEM appearance of GECs now resembled that seen in control cultures. On the other hand, SEM revealed that probucol and alpha-tocopherol/ascorbic acid provided no protection against the changes induced by PAN in GEC cell bodies or major processes. Allopurinol provided no protection against the changes induced by PAN in GEC cell bodies, major processes or foot processes. The addition of hypoxanthine to kidney-slice cultures did not result in the generation of O2.-, H2O2 or HO., or alter GEC ultrastructure. These findings indicate that ROS play a role in PAN-induced alterations to GEC foot process architecture in vitro. However, the xanthine oxidase pathway does not appear to play a major role in generating ROS from PAN in vitro.

Structure-activity relationship in the ability of flavonols to inhibit chemiluminescence

Fourteen flavonoids were evaluated for their ability to inhibit chemiluminescence, either of neutrophils that had been briefly exposed to both luminol and phorbol-myristate acetate or to an enzymatic system with H2O2, luminol and horseradish peroxidase. Using chemiluminescence as the quantitative parameter, it can be concluded that the hydroxyl group in position 3 of the flavonols is vital for their inhibitory effect, and that two hydroxyl groups on the phenyl ring are optimal for such an effect. It was also noted that the C2-C3 double bond is essential for the flavonols' anti-oxidative effect. It is suggested that the ability of flavonols to suppress chemiluminescence is reciprocally correlated with their lipophilicity.

The modulating effects of antioxidants in rat embryos and Sertoli cells in culture

The male and female reproductive systems are targets for the toxicity of a wide range of compounds. There is a paucity of information regarding the modulating effects of antioxidants in such systems. Enzymically generated oxygen radicals have been shown to be toxic and/or mutagenic in a variety of in vitro test systems. It is known that vitamins C and E can modify responses in such systems. Malformations and growth reductions have been observed in whole rat embryo cultures in this laboratory after treatment with the oxygen radical generating system of xanthine/xanthine oxidase. Groups of 9.5-day-old rat embryos were treated with this system with or without vitamin C or E. Vitamin C at the doses given totally abolished neural suture defects while vitamin E only partially did so. Vitamins C and E administered alone had no effect on the embryos. Germ cell detachment has been shown to occur in mixed cultures of Sertoli and germ cells in response to some known in vivo testicular toxins. Such cultures were also treated with the oxygen radical generating system of xanthine/xanthine oxidase. There was an increase in germ cell detachment with this treatment which was reduced by vitamin C but not by vitamin E at the doses administered. These findings would suggest that vitamin supplementation could protect somatic cells of reproductive systems against toxins that act through oxygen radical mechanisms.

Relationship between selenium, immunity and resistance against infection

1. Food selenium content, selenium supply and selenium needs are presented, along with methods of evaluation of selenium status. Glutathione peroxidase, a selenium-containing enzyme, is ubiquitous in the organism. 2. Some experimental studies on animal models reported a positive relationship between selenium status and resistance against infections. 3. Only one study in humans concerned the mechanisms of immune functions in selenium deficiency. Several experimental works suggest that severe selenium deficiency compromises T-cell dependent immune functions such as the blastogenic response to mitogens, but selenium deficiency was concomitant with vitamin E deficiency in most of them. Delayed hypersensitivity response is controversial in selenium-supplemented rats and guinea-pigs. 4. Selenium deficiency in animals decreases the antibody response, especially if associated with vitamin E deficiency. Low dietary selenium supplementation of healthy animals has a positive effect upon humoral responses. 5. Despite some controversies, most experimental studies on selenium-deficient animals report normal phagocytosis and an altered bactericidal capacity of neutrophils. The decrease in glutathione peroxidase activity of polymorphonuclear cells following selenium deficiency could explain some of these alterations. 6. Splenic Natural Killer cells activity is enhanced in selenium-supplemented, healthy animals.

Metabolism of vitamin D2 in pig liver homogenates: evidence for a free radical reaction

In vitro hydroxylation of vitamin D2 at carbon-24 (C-24) was demonstrated with pig liver homogenate. The putative 24-hydroxyvitamin D2 (24-OHD2) comigrated with standard 24-OHD2 on a Zorbax Sil column developed in hexane/isopropanol (98/2). Rechromatography in methylene chloride/methanol (99.8/0.2) resolved the putative 24-OHD2 into two components. The identity of these compounds was determined to be 24(R)-OHD2 and 24(S)-OHD2 (epimers) by low resolution mass spectroscopy and proton NMR spectroscopy. The fact that epimers of 24-OHD2 were produced from vitamin D2 in the absence of pig liver homogenate in vitro was strong evidence for the participation of free radicals in the reaction. Further support for free radical involvement was provided by the following observations: (a) hydroxyl free radical scavengers such as alpha-tocopherol, catalase, and ethanol reduced the amount of 24-OHD2 produced by 18-64%; (b) use of autoclaved homogenate in the incubation mixture had little or no effect on the amount of 24-OHD2 produced; and (c) the failure of the enzyme-substrate saturation curve to level off as expected with high levels of vitamin D2 (100-2000 micrograms = 50-1009 microM). Maximum production of 24-OHD2 was obtained at pH 4.75 and represented a sevenfold increase relative to the amount produced at pH 7.4. The omission of citrate or the addition of electron transport inhibitors, cyanide or antimycin, had little or no effect on the reaction. These data suggested that C-24 hydroxylation of vitamin D2 in vitro was a free radical-mediated process not involving the electron transport system. In vitro hydroxylation at C-24 appeared to be driven by free radicals, and the dominance of this reaction made it difficult to determine whether there was an enzyme involved in the reaction.

Peroxidative events in stored platelet concentrates

Changes in metabolic and functional activity of platelets stored as platelet concentrates in plastic bags highly permeable to gases were investigated. The following parameters were measured daily: pH, pO2, pCO2, HCO3, glucose, lactic acid, lactic dehydrogenase, cellular ATP and platelet aggregation induced by different agents (collagen and ADP). As indexes of lipid peroxidative damage, the cellular levels of conjugated dienes, malonyldialdehyde and some antioxidant molecules such as coenzyme Q10 and vitamin E were determined. A marked increase in pO2, conjugated dienes, malonyldialdehyde, lactic acid and lactic dehydrogenase activity was observed during the preservation. Platelet ATP content was unmodified and a remarkable decrease in platelet aggregability was found. pCO2, cyclooxygenase activity, vitamin E, coenzyme Q10, bicarbonate and glucose showed a rapid fall. Our data seem to indicate a preservation of platelet metabolic activity and a correlation between increased lipid peroxidation and functional impairement.

The physiology of stress and its relationship to mechanisms of disease and therapeutics

Although stress reactions are organized to protect the homeostatic state of animals, they contain elements that may either enhance or diminish susceptibility to disease processes; in many instances, however, stress reactions themselves may induce pathologic change. It is important, therefore, that the veterinary clinician recognize the elements of a stress reaction and understand the mechanisms of disease with which they interact. This article provides a classification of stress stimuli that can be applied when considering interactions between stress reactions and disease processes.

Neonatal adaptation to stress of parturition and dystocia

The fetal animal undergoes a tremendous transition from intrauterine to extrauterine life at parturition. In this article, the maternal-fetal interactions of parturition are discussed with the aim of examining the normal stress reactions of parturition. Dystocia is discussed from the standpoint of additional distress of the newborn, with an aim toward the development of rational therapeutic support.