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Effect of solution ionic strength on lipid peroxidation initiation by the perhydroxyl (xanthine oxidase-derived) and peroxyl radicals.

The role of solution ionic strength in perhydroxyl (HOO.) and peroxyl (ROO.) radical initiated lipid peroxidation has been defined and investigated. Xanthine oxidase activity was used as the source of superoxide (O2-) and its conjugate acid (HOO.) in these experiments. While the enzyme's activity varied with changes in ionic strength, the effect could be factored out of the lipid peroxidation studies. Both HOO.- and ROO.-initiated peroxidations of linoleic acid were promoted by increases in solution ionic strength: the inclusion of 0.1 M of various alkali metal salts in the reaction resulted in up to a 4-fold increase in the overall peroxidation rate. Significant differences between alkali metal cations (Li+, Na+, K+, Cs+) and halogen anions (F-, Cl-, Br-) were not observed. Thus, the increased rates of lipid peroxidation were attributable to changes in solution ionic strength rather than specific ion-reaction interactions. Ionic stimulation of lipid peroxidation occurred only in the presence of preexisting fatty acid hydroperoxides (LOOHs), which provided additional support for the hydrogen atom transfer mechanism previously proposed [Aikens, J., and Dix, T. A. (1991) J. Biol. Chem. 266, 15091] for the HOO./LOOH initiation process. Physiologically appropriate salt concentrations were used in these studies, hence the results may have biological significance.

Amidines↗
PubMed1995

Reaction between peroxynitrite and hydrogen peroxide: formation of oxygen and slowing of peroxynitrite decomposition.

Peroxynitrite, the reaction product of nitric oxide and superoxide, is a potent and versatile oxidant that can attack a wide range of targets. In this work, we studied the oxidation of hydrogen peroxide by peroxynitrite, which led to oxygen evolution. Oxygen yields increased at alkaline pH with an apparent pKa of 7.05 +/- 0.04. The maximum yields were 16% and 32% of added peroxynitrite at pH 5.9 and 7.4, respectively, assuming that two molecules of peroxynitrite are needed to produce one of oxygen. Hydroxyl radical scavengers (dimethyl sulfoxide, mannitol, ethanol, formate, and acetate) inhibited oxygen evolution to a similar extent to that predicted from their rate constants with hydroxyl radical. The apparent rate constant of peroxynitrite decomposition was zero-order in hydrogen peroxide at acidic pH. At neutral and alkaline pH, the rate of peroxynitrite disappearance decreased in the presence of millimolar concentrations of hydrogen peroxide by up to 50%. The apparent activation enthalpy and entropy for peroxynitrite decomposition increased by 1.7 kcal mol-1 and 4.7 cal mol-1 K-1, respectively, in the presence of hydrogen peroxide. We propose that an activated intermediate of peroxynitrous acid is responsible for hydrogen peroxide oxidation at acidic pH, while at more alkaline pH the formation of a stabilizing complex between hydrogen peroxide and transperoxynitrite anion is involved.

Hydrogen Peroxide↗
PubMed2000

Ursodeoxycholic acid suppresses extent of lipid peroxidation in diseased liver in experimental cholestatic liver disease.

The therapeutic benefit of ursodeoxycholic acid (UDCA) in treating cholestatic liver disease is globally recognized. It is generally accepted that the mechanism of action of UDCA can be attributed to several diverse processes that appear to be uniformly targeted towards minimizing the deleterious actions of accumulated hydrophobic bile acids in the cholestatic liver. Since hydrophobic bile acids are prooxidants, emerging in vitro evidence suggests that UDCA may have an antioxidant mechanism of action. We hypothesize that UDCA suppresses the extent of lipid peroxidation in the cholestatic liver. This hypothesis was tested by assessing the extent of lipid peroxidation in livers harvested from chronic bile duct ligated (CBDL) rats dosed daily for 24 days with 5, 10, or 15 mg/kg UDCA. The extent of lipid peroxidation was evaluated by determining the hepatic content of conjugated dienes, lipid peroxides, and malondialdehyde. The data were compared with identical data collected from unoperated control and 24-day bile duct manipulated (SO) rats. In the two groups of control rats, UDCA has no effect on the serum indices of liver function. In CBDL rats, UDCA suppressed the increased extent of lipid peroxidation in the liver in a dose-dependent manner in the absence of improvement of laboratory parameters of liver function and hepatic architecture. In conclusion, UDCA suppresses the augmented extent of lipid peroxidation in the diseased liver of CBDL rats.

Animals↗
PubMed1999

Peroxide sensitivity of endothelin responses in coronary artery smooth muscle: ET(A) vs. ET(B) pathways.

Endothelins (ETs) contract de-endothelialized rings from left descending coronary artery via ET(A) or ET(B) receptors. Here we test the hypothesis that the actions of EA(A) and ET(B) receptors are similar in their sensitivities to damage by hydrogen peroxide. In Ca2+-containing Krebs' solution, 100 nM of the ET(B) agonist IRL1620 produced contractions with significantly smaller force (17.6+/-1.7 mN) than 50 nM of the ET(A) + ET(B) agonist ET-1 (73.2+/-4.6 mN) (p < 0.05). In Ca2+-free solutions, the contractions due to both agents were significantly smaller (p < 0.05). Pretreating the tissues with peroxide inhibited the contractions produced by either agent. The IC50 values for peroxide were significantly higher (p < 0.05) using ET-1 (1.0+/-0.3 mM in Ca2+, 1.4+/-0.1 mM in Ca2+-free) than using IRL 1620 (0.32+/-0.08 in Ca2+, 0.25+/-0.01 mM in Ca2+-free). Pretreating microsomes isolated from the artery smooth muscle with up to 10 mM peroxide did not significantly affect 125I-ET-1 binding to ET(A) or ET(B) receptors (p > 0.05). In comparing the peroxide induced inactivation of the various processes in this artery and based on literature, we conclude that the actions of ET(A) may also involve a peroxide resistant Ca2+-independent pathway(s).

Animals↗
PubMed2000

Role of high-energy phosphate metabolism in hydrogen peroxide-induced cardiac dysfunction.

This study was undertaken to clarify the role of high-energy phosphate metabolism in hydrogen peroxide-induced cardiac dysfunction using phosphorus and fluorine nuclear magnetic resonance spectroscopy. The exposure of a Langendorff-perfused heart to hydrogen peroxide (200-400 micromol/L, 8 min) provoked biphasic contractile dysfunction characterized by a transient depression of left ventricular developed pressure during the administration of hydrogen peroxide and a delayed elevation of left ventricular end-diastolic pressure after the washout of hydrogen peroxide. The initial phase of cardiac dysfunction correlated well with the accumulation of sugar phosphates (r = 0.89, p < 0.01). Furthermore, we demonstrated that glibenclamide, a potent inhibitor of the ATP-sensitive K+ channel, attenuated the initial depression of developed pressure. On the other hand, the delayed elevation of end-diastolic pressure correlated well with the total ATP depletion (r = 0.96, p < 0.01). However, ATP loss was supposed to be a mere result from the increased ATP consumption corresponding to a rise in intracellular free Ca2+ (from the control value of 315+/-23 nmol/L to 708+/-104 after the administration of hydrogen peroxide, p < 0.01), which also paralleled the elevation of end-diastolic pressure. Thus glycolytic inhibition and intracellular Ca2+ overload are independently responsible for the biphasic contractile dysfunction induced by hydrogen peroxide.

Adenosine Triphosphate↗
PubMed2000

Myelin membranes isolated from rats intracranially injected with apotransferrin are more susceptible to in vitro peroxidation.

Purified myelin obtained from 17 day old rats intracranially injected with aTf at 3 days of age was submitted to in vitro peroxidation using Fe + ascorbic acid (FeA) or Cu + H2O2 (CuH), to investigate the susceptibility of this membrane to in vitro metal catalyzed peroxidation. There was an increase in thiobarbituric acid-reactive-substances (TBARS) (60%) and in protein-associated carbonyls (PAC) (20%) in the myelin from aTf injected rats in comparison to myelin from controls, indicating a higher susceptibility to peroxidation. Desferoxamine (DFX) injected simultaneously with aTf did not change the response of myelin to aTf. CNS myelin is highly vulnerable to oxidative stress, and its susceptibility to peroxidation increases in myelin isolated from aTf injected rats. This increased liability to peroxidation as well as the previously reported aTf-dependent increment in certain myelin proteins and lipids and in the expression of specific myelin mRNAS, does not appear to be due to an increased amount of iron bound to the injected aTf. The changes in composition that we have previously reported could result in an abnormal myelin, allowing the peroxidative system to act upon the membrane more easily than in normal circumstances.

Animals↗
PubMed1999

Cadmium induced lipid peroxidation in rat testes and protection by selenium.

The main goal of this study was to investigate the role of cadmium in the promotion of lipid peroxidation in the homogenates of rat testes and the effect of selenium on lipid peroxidation in testes of rats after cadmium injection. Treatment of rats with cadmium resulted in a time- and dose-related accumulation of the metal ions in testes. The concentrations of cadmium, copper, zinc, selenium and iron in the tissues were determined by an atomic absorption spectrophotometer and lipid peroxidation in testes was measured by a spectrophotometer. Cadmium produced enhanced lipid peroxidation in testes. These cadmium-induced changes were accompanied by a significant increase of iron and copper, and a decrease of zinc in testes. Concurrent treatment with selenium and cadmium reduced the cadmium-induced alterations in lipid peroxidation and essential metal levels. Data suggest that lipid peroxidation was associated with cadmium toxicity in testes and that the addition of selenium was found to be effective in attenuation of this effect.

Animals↗
PubMed2000

A comparative study of the effects of cholesterol, beta-sitosterol, beta-sitosterol glucoside, dehydroepiandrosterone sulphate and melatonin on in vitro lipid peroxidation.

The free radical scavenging abilities of the structurally related steroids beta-sitosterol, beta-sitosterol glucoside (plant sterols and sterolins), cholesterol, and dehydroepiandrosterone sulphate (DHEAS) were compared with melatonin (an efficient free radical scavenger) in an in vitro system which measures lipid peroxidation of platelet membranes in the presence of iron (Fe2+). Lipid peroxidation is a process whereby cellular membranes are damaged due to the oxidative deterioration of polyunsaturated lipids, which may lead to cell death and disease in living organisms. Substances such as vitamin E protect cellular membranes against oxidative damage due to their chemical structures. The steroids cholesterol, beta-sitosterol, beta-sitosterol glucoside and dehydroepiandrosterone (DHEA) are structurally related to each other. During aging, serum concentrations of DHEA, DHEAS and melatonin decrease, while the concentration of cholesterol tends to increase. The aim of the present study was to compare the role these substances play in lipid peroxidation over a wide concentration range. At concentrations lower than the free iron in the reaction mixture, all the steroids investigated decreased lipid peroxidation. At higher concentrations, cholesterol and beta-sitosterol increased lipid peroxidation, while DHEAS and melatonin continued to decrease lipid peroxidation.

Aging↗
PubMed2002

Hydrogen peroxide enhances iron-induced injury in isolated heart and ventricular cardiomyocyte in rats.

To explore the cardiac effects of iron with or without hydrogen peroxide, the isolated perfused rat heart and enzymatically isolated ventricular cardiomyocyte were used. It was shown that treatment with cell-permeable iron (Fe-HQ) for 10 min reduced the contractile amplitude and velocity and end diastolic cell length in the cardiomyocyte and increased the contents of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary effluent and malondialdehyde (MDA) in the myocardium. The left ventricular developed pressure (LVDP), +/-dP/dtmax, and heart rate and coronary flow are showed a biphasic phase, an increase at first followed by a decline. Treatment with hydrogen peroxide for 10 min following Fe-HQ augmented the effect of iron with an increase in coronary LDH and CK release and myocardial MDA content, and decrease in LVDP, +/-dP/dtmax and heart rate. Perfusion of reduced glutathione with hydrogen peroxide counteracted these effects of Fe-HQ and hydrogen peroxide while dimethyl sulfoxide had no effect on the injury induced by Fe-HQ and hydrogen peroxide in the isolated rat heart. This suggests that augmentation of myocardial injury as a result of an increase in intracellular iron by hydrogen peroxide might involve the dysfunction of sulfydryl group containing proteins but not the hydroxyl radicals.

Animals↗
PubMed2003

Chronic exposure to subtoxic levels of peroxidized lipids suppresses mucosal cell turnover in rat small intestine and reversal by glutathione.

Oxidative challenge can compromise intestinal growth and death responses. This studyexamines the effect of chronic consumption of subtoxic levels of peroxidized lipids on intestinal redox balance and turnover and the effect of glutathione (GSH) supplementation. Male Sprague-Dawley rats were fed standard rat chow or 4% peroxidized menhaden oil chow (2-8 weeks). Intestinal GSH and glutathione disulfide (GSSG), GSH synthetic and redox enzymes as well as proliferative (ornithine decarboxylase, ODC) and apoptotic activities were evaluated. Chronic peroxide intake did not affect overall animal growth, but decreased intestinal GSH/GSSG ratio that directly correlated with decreased GSH and increased GSSG, and suppressed peak circadian ODC activities and post-prandial mucosal apoptosis. Supplementation with GSH restored the mucosal GSH/GSSG ratio and abrogated the peroxide-induced suppression of intestinal cell turnover. Collectively, the results show that chronic lipid peroxide consumption induces intestinal GSH redox imbalance that interferes with regulation of enterocyte death and proliferation in vivo. These disruptive effects of lipid peroxides were reversed by GSH supplementation in accordance with the normalization of tissue GSH/GSSG redox balance.

Animals↗
PubMed2003

Lipid peroxidation in the striatum of rats during stress after administration of cortisol.

Lipid peroxidation processes were studied in the striatum during stress in conditions of prior administration of cortisol. Three doses of cortisol (25 mg/kg, daily) had no significant effect on the levels of lipid peroxidation products six days after injections ended. However, lipid peroxidation responses to stress during this period in animals given cortisol were significantly stronger than in controls (there were decreases in the intermediate products of lipid peroxidation and increases in the quantities of Schiff bases). Thus, administration of hormone leads to long-term changes in one of the most important regulatory systems of the body--lipid peroxidation--and has sensitizing effects on changes in the levels of stress-induced lipid peroxidation products.

Animals↗
PubMed1998

Endogenous antioxidant enzymes and glutathione S-transferase in protection of mesothelioma cells against hydrogen peroxide and epirubicin toxicity.

We have previously shown that cultured malignant mesothelioma cells contain elevated manganese superoxide dismutase (MnSOD) mRNA levels and activities compared with non-malignant mesothelial cells. As many cytotoxic drugs generate both superoxide and hydrogen peroxide, we assessed the relative significance of catalase and the glutathione redox cycle, as well as glutathione S-transferase (GST), in protecting these cells against hydrogen peroxide and epirubicin toxicity. Mesothelioma cell lines containing high (M38K cells) and low (M14K cells) MnSOD, and non-malignant MeT-5A mesothelial cells were selected for the study. M38K cells were the most resistant of these three cell types to hydrogen peroxide (0.1-0.5 mM, 4 h) and epirubicin (0.1-0.5 microg ml(-1), 48 h) as judged by lactate dehydrogenase (LDH) release and by high-energy nucleotide (ATP, ADP, AMP) depletion. Total glutathione was higher in M38K cells (63.8 +/- 20.3 nnmol mg(-1) protein) than in M14K (25.2 +/- 8.2 nmol mg[-1]) or MeT-5A cells (23.5 +/- 4.5 nmol mg[-1]). Furthermore, GST specific activity was higher in M38K cells (111.3 +/- 15.8 U mg[-1]) than in M14K cells (77.4 +/- 6.6 U mg[-1]) or in MeT-5A cells (68.8 +/- 7.6 U mg[-1]). Western blotting indicated the presence of GST-pi in all these cells, the reactivity again being highest in M38K cells. Depletion of glutathione by buthionine sulphoximine and inhibition of catalase by aminotriazole enhanced hydrogen peroxide toxicity in all cell types, while only the depletion of glutathione increased epirubicin toxicity. We conclude that simultaneous induction of multiple antioxidant enzymes can occur in human mesothelioma cells. In addition to the high MnSOD activity, hydrogen peroxide scavenging antioxidant enzymes, glutathione and GST can partly explain the high hydrogen peroxide and epirubicin resistance of these cells in vitro.

Antibiotics, Antineoplastic↗
PubMed1998

High-performance liquid chromatography of selected organic peroxides with oxidative amperometric detection.

Reversed-phase high-performance liquid chromatography with oxidative amperometric detection was optimized for the determination of several organic peroxides in drinking water under ideal conditions. The determinations were performed under isocratic conditions using acetonitrile and methanol as the organic modifiers with 0.05 M potassium phosphate buffer solution. The oxidative amperometric response of the organic peroxides was dependent on the concentration of organic modifier and the electrode potential. The optimum electrode potential (EOxAPP), for the simultaneous determination of the organic peroxides was approximately +1.150 +/- 0.05 V versus the Ag/AgCl reference electrode. The maximum analytical signal for butan-2-one peroxide and tert-butyl hydroperoxide, when using acetonitrile, was obtained with 20% v/v organic modifier. For cumene hydroperoxide, the maximum analytical signal was achieved with approximately 35% v/v acetonitrile. The retention time of cumene hydroperoxide, on an octyldecylsilane column (250 x 4 mm id), decreased sharply from > 100 to < 10 min when the organic modifier concentration was varied from 5 to 50% v/v. The retention time of butan-2-one and tert-butyl hydroperoxide, under the same conditions, varied by < 10 min. The calibration curves for the aliphatic peroxides and aromatic peroxide were linear from 2 to 200 ng and from 0.2 to 200 ng injected, respectively.

Chromatography, High Pressure Liquid↗
PubMed1969

Lipid peroxide formation in microsomes. The role of non-haem iron.

1. Metal ion-chelating agents such as EDTA, o-phenanthroline or desferrioxamine inhibit lipid peroxide formation when rat liver microsomes prepared from homogenates made in pure sucrose are incubated with ascorbate or NADPH. 2. Microsomes treated with metal ion-chelating agents do not form peroxide on incubation unless inorganic iron (Fe(2+) or Fe(3+)) in a low concentration is added subsequently. No other metal ion can replace inorganic iron adequately. 3. Microsomes prepared from sucrose homogenates containing EDTA (1mm) do not form lipid peroxide on incubation with ascorbate or NADPH unless Fe(2+) is added. Washing the microsomes with sucrose after preparation restores most of the capacity to form lipid peroxide. 4. Lipid peroxide formation in microsomes prepared from sucrose is stimulated to a small extent by inorganic iron but to a greater extent if adenine nucleotides, containing iron compounds as a contaminant, are added. 5. The iron contained in normal microsome preparations exists in haem and in non-haem forms. One non-haem component in which the iron may be linked to phosphate is considered to be essential for both the ascorbate system and NADPH system that catalyse lipid peroxidation in microsomes.

Animals↗
PubMed1982

Alteration of inner-membrane components and damage to electron-transfer activities of bovine heart submitochondrial particles induced by NADPH-dependent lipid peroxidation.

We investigated the changes of the inner-membrane components and the electron-transfer activities of bovine heart submitochondrial particles induced by the lipid peroxidation supported by NADPH in the presence of ADP-Fe3+. Most of the polyunsaturated fatty acids were lost as a result of the peroxidation, and phospholipids were changed to polar species. Ubiquinone was also modified to polar substances as the peroxidation proceeded. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis showed the disappearance of 27000-Mr and 30000-Mr proteins and the appearance of highly polymerized substances. Flavins and cytochromes were not diminished, but the respiratory activity was lost. The reactions of NADH oxidase and NADH-cytochrome c reductase were most sensitive to the peroxidation, followed by those of succinate oxidase and succinate-cytochrome c reductase. Succinate dehydrogenase and duroquinol-cytochrome c reductase were inactivated by more extensive peroxidation, but cytochrome c oxidase was only partially inactivated. NADH-ferricyanide reductase was not inactivated. The pattern of the inactivation indicated that the lipid peroxidation affected the electron transport intensively between NADH dehydrogenase and ubiquinone, and moderately at the succinate dehydrogenase step and between ubiquinone and cytochrome c.

Animals↗
PubMed1984

Inhibition of microsomal lipid peroxidation by glutathione and glutathione transferases B and AA. Role of endogenous phospholipase A2.

Lipid peroxidation in vitro in rat liver microsomes (microsomal fractions) initiated by ADP-Fe3+ and NADPH was inhibited by the rat liver soluble supernatant fraction. When this fraction was subjected to frontal-elution chromatography, most, if not all, of its inhibitory activity could be accounted for by the combined effects of two fractions, one containing Se-dependent glutathione (GSH) peroxidase activity and the other the GSH transferases. In the latter fraction, GSH transferases B and AA, but not GSH transferases A and C, possessed inhibitory activity. GSH transferase B replaced the soluble supernatant fraction as an effective inhibitor of lipid peroxidation in vitro. If the microsomes were pretreated with the phospholipase A2 inhibitor p-bromophenacyl bromide, neither the soluble supernatant fraction nor GSH transferase B inhibited lipid peroxidation in vitro. Similarly, if all microsomal enzymes were heat-inactivated and lipid peroxidation was initiated with FeCl3/sodium ascorbate neither the soluble supernatant fraction nor GSH transferase B caused inhibition, but in both cases inhibition could be restored by the addition of porcine pancreatic phospholipase A2 to the incubation. It is concluded that the inhibition of microsomal lipid peroxidation in vitro requires the consecutive action of phospholipase A2, which releases fatty acyl hydroperoxides from peroxidized phospholipids, and GSH peroxidases, which reduce them. The GSH peroxidases involved are the Se-dependent GSH peroxidase and the Se-independent GSH peroxidases GSH transferases B and AA.

Acetophenones↗
PubMed1989

The mechanism of initiation of lipid peroxidation. Evidence against a requirement for an iron(II)-iron(III) complex.

When Fe2+ ions are added to rat-liver microsomes, lipid peroxidation begins after a short lag period. Fe2+-dependent peroxidation in the first few minutes of the incubation can be increased by adding Fe3+, ascorbic acid or Pb2+ ions; these stimulations are not additive. By contrast, Pb2+ ions inhibit peroxidation of microsomes in the presence of Fe3+/ascorbate or Fe3+-ADP/NADPH. In liposomes made from ox-brain phospholipids, Fe2+-dependent peroxidation is stimulated slightly by Fe3+, but much more so by ascorbic acid, Al3+ or Pb2+; these stimulations are not additive. Liposomal peroxidation in the presence of Fe3+/ascorbate is inhibited by Pb2+ or Al3+. These results argue against the participation of an Fe2+-Fe3+-O2 complex, or a critical 1:1 ratio of Fe2+ to Fe3+, in the initiation of lipid peroxidation in liposomes and rat-liver microsomes.

Aluminum↗
PubMed1996

Resistance of lipoprotein(a) to lipid peroxidation induced by oxygenated free radicals produced by gamma radiolysis: a comparison with low-density lipoprotein.

Lipid peroxidation of lipoprotein(a) [Lp(a)] by defined oxygen-centred free radicals (O2-/OH, O2-, O2-/HO2) produced by gamma radiolysis was compared with that of paired samples of low-density lipoprotein (LDL). Lp(a) appeared to be more resistant to oxidation than LDL, as indicated by the kinetic study of four markers of lipid peroxidation; decrease in vitamin E, formation of conjugated dienes and aldehydic products, and modification of electrophoretic mobility. In contrast, similar kinetics of lipid peroxidation were obtained for LDL and Lp(a-), which is the lipoparticle issued following the reductive cleavage of apolipoprotein(a) from Lp(a), thus suggesting that the greater resistance of Lp(a) to lipid peroxidation was due to the presence of apolipoprotein(a). Lipid peroxidation of Lp(a) and LDL induced by peroxyl radicals, which were produced by an azo compound [2,2'-azobis-(2-amidinopropane)dihydrochloride], confirmed both the resistance of Lp(a) to lipid peroxidation and the propensity of Lp(a-) to exhibit a greater susceptibility to oxidation than intact Lp(a). Our findings also indicated that the high content of apolipoprotein(a) in N-acetylneuraminic acid residues was only partly responsible for the resistance of Lp(a) to oxidation.

Amidines↗