Increase In Peroxidation Levels Research Articles

Peroxide: The Second Signal

Reactive oxygen species serve an important role in the plant defense system. Plants have a biphasic response to pathogens and wounding. The first response involves expression of the early genes involved in the signaling pathway (such as, polygalacturonase, prosystemin, lipoxygenase, and allene oxide synthase); the second "late" response involves the up-regulation of the defense genes [such as, proteinase inhibitors I and II (InhI and InhII), cathepsin D inhibitor, carboxypeptidase inhibitor, and polyphenol oxidase]. Orozco-Cárdenas et al. show that inhibition of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which produces the reactive oxygen species burst, blocks the expression of the late genes and the accumulation of InhI and InhII. InhI and InhII accumulated in leaves, and the expression of defense genes was increased in leaves treated with glucose and glucose oxidase to artificially increase peroxide levels. Cytochemical localization of peroxide indicated that peroxide is initially produced by cells in the vascular system and then may diffuse to the mesophyll cells to regulate the expression of the late genes. M. L. Orozco-Cárdenas, J. Narváez-Vásquez, C. A. Ryan, Hydrogen peroxide acts as a second messenger for the induction of defense genes in tomato plants in response to wounding, systemin, and methyl jasmonate. Plant Cell 13 : 179-191 (2001). [Abstract] [Full Text]

Combinations of chlorocatechols and heavy metals cause DNA degradation in vitro but must not result in increased mutation rates in vivo.

Chlorocatechols introduced into the environment directly or as a result of degradation processes are highly toxic, particularly when combined with heavy metals. With in vitro DNA degradation assays, the high reactivity of chlorocatechols combined with heavy metals could be shown, whereby copper was shown to be more active than iron. Structure-activity analysis showed that the degradation potential of the chlorocatechols decreased with an increasing number of chloratoms. The addition of reactive oxygen species scavengers allowed the identification of hydrogen peroxide as an important agent leading to DNA damage in this reaction. The potential of other reactive compounds, however, can neither be determined nor excluded with this approach. Exposure of Escherichia coli and Salmonella typhimurium cultures to the same mixtures of chlorocatechols and copper surprisingly did not lead to an enhanced mutation rate. This phenomenon was explained by doing marker gene expression measurements and toxicity tests with E. coli mutants deficient in oxidative stress defense or DNA repair. In catechol-copper-exposed cultures an increased peroxide level could indeed be demonstrated, but the highly efficient defense and repair systems of E. coli avoid the phenotypical establishment of mutations. Increased mutation rates under chronic exposure, however, cannot be excluded.

Nonredox 5-lipoxygenase inhibitors require glutathione peroxidase for efficient inhibition of 5-lipoxygenase activity.

Nonredox type 5-lipoxygenase (5-LO) inhibitors, such as ZM 230487, its methyl analogue ZD 2138, or the Merck compound L-739,010, suppress cellular leukotriene synthesis of ionophore stimulated granulocytes with IC50 values of about 50 nM. However, in cell homogenates or in preparations of purified enzyme, up to 150-fold higher concentrations are required for similar inhibition of 5-LO activity. This loss of 5-LO inhibition in cell homogenates was reversed by addition of glutathione or dithiothreitol, which increased the inhibitory potency of ZM 230487 or L-739,010 by about 100 to 150-fold so that 5-LO inhibition was comparable with that of intact cells. In the presence of thiols, addition of hydroperoxide [13(S)-HpODE], glutathione-peroxidase inhibition by iodacetate or selenium-deficiency lead to impaired 5-LO inhibition by ZM 230487 in cell homogenates. Moreover, addition of glutathione peroxidase was required for efficient inhibition of purified human 5-LO by ZM 230487. The data suggest that low hydroperoxide concentrations are important for efficient 5-LO inhibition by ZM 230487. The kinetic analysis revealed a noncompetitive inhibition of 5-LO by ZM 230487 at low hydroperoxide levels, whereas it acted as a competitive inhibitor with low affinity under nonreducing conditions in granulocyte homogenates. No such redox-dependent effects were observed with the 5-LO inhibitor BWA4C, the 5-LO activating protein-inhibitor MK-886 or the pentacyclic triterpene acetyl-11-keto-beta-boswellic acid. These data suggest that physiological conditions associated with oxidative stress and increased peroxide levels lead to impaired efficacy of nonredox type 5-LO inhibitors like ZM 230487 or L-739,010. This could explain the reported lack of activity of this class of 5-LO inhibitors in chronic inflammatory processes.

Depletion of glutathione causes dna damage and increase of hydrogen peroxide levels in bovine embryos

Depletion of glutathione causes dna damage and increase of hydrogen peroxide levels in bovine embryos

5628931 Process for the preparation of hydrogen and carbon monoxide containing mixtures: Lednor Peter; Senden Mathijs M G; Van Der Zwet Gerardus P Amsterdam, Netherlands assigned to Shell Oil Company

The occurrence of multidrug resistance (MDR) is the major obstacle to successful anthracycline-based cancer chemotherapy. In the present study, we assessed the effects of Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, TPL), a piperidine nitroxide with growth-inhibitory properties in tumor cell lines, on a number of molecular mechanisms involved in the resistance of human breast adenocarcinoma cell lines to doxorubicin (DOX). Cytotoxicity studies in MCF-7 wildtype and their MDR variant MCF-7 AdrR cells showed a synergistic effect between TPL and DOX when exposure to TPL preceded or was simultaneous with DOX treatment in MCF-7 AdrR cells. This effect of TPL seems to be due in part to its ability to increase peroxide levels and to deplete cellular glutathione pools. In addition, TPL increased DOX accumulation in MCF-7 AdrR cells by interfering with P-glycoprotein-mediated DOX efflux, as evidenced using a specific antibody that recognizes the active form of the protein. TPL was also found to affect the expression levels of proteins involved in response to drug treatment (e.g., p53, bcl2, bax, p21). Taken together, our results indicate that TPL is a potential new agent that may improve the clinical effect of DOX in tumors exhibiting a MDR phenotype.

A Possible Mechanism for Vascular Endothelial Cell Injury Elicited by Activated Leukocytes: A Significant Involvement of Adhesion Molecules, CD11/CD18, and ICAM-1

To clarify the mechanism of vascular endothelial cell injury induced by activated leukocytes, we investigated the intracellular peroxide level in endothelial cells and the effect of antibodies against adhesion molecules on it. The change in the intracellular peroxide level was measured using the fluorescence of 2,7-dichlorofluorescein diacetate. The fluorescence intensity of the endothelial cells exposed to PMA-stimulated leukocytes increased with time up to 15 min, although neither PMA alone nor unstimulated leukocytes alone showed such increase at all. When catalase, which degrades hydrogen peroxide produced by leukocytes, was added to this system, the peroxide level in endothelial cells decreased significantly. On the other hand, pretreatment of endothelial cells with allopurinol, a specific inhibitor of xanthine oxidase, also caused significant inhibition of the increase in peroxide level in the endothelial cells. The monoclonal antibodies against CD11a, CD11b, CD18, and ICAM-1 showed almost complete inhibition of the increase in intracellular peroxide levels of the endothelial cells exposed to PMA-stimulated leukocytes. In contrast, the anti-CD11c antibody could not block the increase in fluorescence intensity due to peroxides. The endothelial injury elicited by activated leukocytes was partially inhibited by catalase alone (approximately 40%) and allopurinol alone (approximately 60%), but it was completely inhibited by the concomitant treatment of endothelial cells with catalase and allopurinol. The specific antibodies against such adhesion molecules as ICAM-1 and CD11/CD18 except CD11c/CD18 also blocked the endothelial cell injury significantly. These data suggest that there is a good correlation between the early increase in intracellular peroxides and endothelial cell injury elicited by PMA-stimulated leukocytes and that the adhesion of activated leukocytes to endothelial cells via CD11a/CD18-ICAM-1 must be deeply involved in these phenomena.

Deficient glutathione peroxidase activity in preeclampsia is associated with increased placental production of thromboxane and lipid peroxides

Thromboxane and lipid peroxide levels are abnormally increased in preeclamptic placentas. The cause of this increase is not known. Peroxides stimulate prostaglandin H2 synthase to increase thromboxane and oxygen radicals, which increase lipid peroxides. Glutathione peroxidase inactivates peroxides, thereby decreasing peroxide stimulation of prostaglandin H synthase. If glutathione peroxidase activity were deficient, then peroxides could increase, leading to increased stimulation of prostaglandin H synthase, resulting in increased production of thromboxane and lipid peroxides. The following study tested this hypothesis. Placental tissues from 11 normal and 11 preeclamptic women were immediately frozen in liquid nitrogen after delivery. One gram of tissue from each placenta was homogenized for analysis. Placental tissues were also obtained from six normal pregnancies for incubation with a glutathione peroxidase inhibitor, N-ethylmaleimide. Samples were analyzed for glutathione peroxidase activity, lipid peroxides by hydrogen peroxide equivalents, thromboxane by thromboxane B2, and prostacyclin by 6-keto-prostaglandin F1 alpha. Glutathione peroxidase activity was significantly lower in preeclamptic than in normal placentas (9.41 +/- 0.05 vs 13.41 +/- 0.63 units/gm, p < 0.001, mean +/- SE). Lipid peroxides and thromboxane were significantly higher in preeclamptic than in normal placentas (hydrogen peroxide equivalents 4.23 +/- 0.32 vs 2.84 +/- 0.27 mumol/gm, p < 0.01; thromboxane B2 215 +/- 31 vs 138 +/- 15 ng/gm, p < 0.05), whereas prostacyclin was significantly lower (6-keto-prostaglandin F1 alpha 23.3 +/- 2.2 vs 41.6 +/- 6.0 ng/gm, p < 0.01). Inhibition of glutathione peroxidase activity in normal placentas resulted in a dose-response increase in placental production of both lipid peroxides and thromboxane without affecting prostacyclin, so the ratio of thromboxane to prostacyclin increased progressively with inhibition of glutathione peroxidase. Glutathione peroxidase activity is significantly lower, and lipid peroxides and thromboxane are significantly higher, in preeclamptic placentas compared with normal placentas. Inhibition of glutathione peroxidase activity in normal placentas results in significantly increased production of lipid peroxides and thromboxane and an increase in the thromboxane to prostacyclin ratio. We speculate that in normal placentas, glutathione peroxidase limits prostaglandin H synthase activity by reducing the amount of peroxide present, thus reducing peroxide stimulation of prostaglandin H synthase. In preeclampsia deficient glutathione peroxidase activity results in in increased peroxide levels leading to increased stimulation of prostaglandin H synthase, which results in increased production of lipid peroxides and thromboxane.

Activity of Enzymes Involved in the Turnover of Hydrogen Peroxide during Fruit Senescence

Changes in activity of four enzymes associated with the turnover of hydrogen peroxide were monitored during ripening of several fruits. Glycolate oxidase activity increased during ripening in the pulp of pear (Pyrus communis L. var. Bosc), avocado (Persea americana Mill. var. Fuerte), and tomato (Lycopersicon esculentum Mill. var. Rutgers), declined in pear peel, and was not detectable in avocado peel. The changes in glycolate oxidase activity did not correspond to the changes in chlorophyll levels which occurred during ripening. Xanthine oxidase and peroxidase activity also increased during ripening in pear pulp. These changes in enzyme activity followed similar patterns whether expressed in terms of protein content or fresh weight. Catalase in pear pulp showed a continuous decline in activity per gram fresh weight but a slight increase followed by a decline in activity per milligram protein. Previously observed increases in hydrogen peroxide levels in senescent fruit tissue may be related to these chang...

Involvement of Hydrogen Peroxide in the Regulation of Senescence in Pear

Endogenous peroxide levels in pear fruit (Pyrus communis) were measured using a titanium assay method, and were found to increase during senescence in both Bartlett and Bosc varieties. Application of glycolic acid or xanthine, serving as substrates for the formation of H(2)O(2), increased the peroxide content of the tissue and accelerated the onset of ripening, as measured by increased softening and ethylene evolution. Application of ethylene also induced increased peroxide levels. Ripening processes were similarly promoted when peroxides were conserved by inhibiting the activity of catalase with hydroxylamine or potassium cyanide. By comparison, the inhibition of glycolate oxidase with alphahydroxy-2-pyridinemethanesulfonic acid decreased the peroxide content of the tissue and delayed the onset of ripening. These results indicate that the onset of ripening correlates with the peroxide content of fruit tissues as occurring under normal conditions or as influenced by the treatments. Hydrogen peroxide may be involved in oxidative processes required in the initiation and the promotion of ripening.

Increased hydrogen peroxide levels in glucose 6-phosphate dehydrogenase deficient erythrocytes exposed to acetylphenylhydrazine

Acetylphenylhydrazine (APH), a classic hemolytic drug that produces hydrogen peroxide via a coupled oxidation with oxyhemoglobin, was incubated with normal and glucose 6-phosphate dehydrogenase (G6-PD)-deficient erythrocytes. Higher concentrations of H 2O 2 were attained in the G6-PD-deficient cells. The intracellular H 2O 2 levels were monitored by studying the formation od the enzyme-substrate complexes of catalase: Two separate anticatalase effects of APH distinguished the two complexes; in both instances, the change in catalase activity was the dependent experimental variable that served as a convenient and specific amplifier of intracellular H 2O 2. The formation of Complex II was indicated by an inhibition of catalase, reversible by ethanol. The steady state concentration of Complex I was evaluated by measuring its rate of reaction with 3-amino-1,2,4-triazole, a reaction leading to irreversible inhibition. Greater anticalase action by APH alone or by APH plus aminotriazole indicated higher concentrations of H 2O 2 in the G6-PD-deficient cells. These results support the theory that drug-induced hemolysis in G6-PD-deficient individuals involves oxidant damage by H 2O 2.