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PubMedDate not supplied

[The effect of cadmium chloride and hydrogen peroxide on the lipid peroxidation and fractional composition of lipids in hepatocytes of rats].

The isolated hepatocytes were incubated in the medium, containing cadmium chloride or hydrogen peroxide. Influence of the latter on the intensity of lipid peroxidation and contents of some lipids fractions, as well as viability of hepatocytes in these conditions has been studied. It is shown that under such cultivation conditions the activation of lipid peroxidation in the hepatocytes takes place. Its activation in presence of cadmium chloride was one of the factors of the membranes damage. The changes in the content of some fractions of lipids were similar both under the incubations of the cells with cadmium chloride and hydrogen peroxide. This allows one to suppose that cadmium chloride causes changes in the lipid composition of membranes as a result of intensification of lipid peroxidation.

Animals↗
PubMedDate not supplied

Comparison of the clinical efficacy and safety of carbamide peroxide and hydrogen peroxide in at-home bleaching gels.

OBJECTIVE: The aim of this study was to evaluate the clinical efficacy of home-administered vital bleaching procedures and possible adverse effects derived from their use. One gel containing 3.5% hydrogen peroxide with a 5% potassium nitrate component (FKD, Kin Lab) was compared with a carbamide peroxide-based gel with a concentration of 10% (Opalescence, Ultradent). METHOD AND MATERIALS: Two sample groups were designed, each composed of 8 patients. All patients employed both bleaching products, 1 in the maxillary arch and the other in the mandibular arch on a random basis. The treatment was applied for 3 hours a day for 4 weeks. The degree of bleaching was evaluated using the Vita guide arranged by brightness. Dental sensitivity was measured with a specially designed 4-point scale. Gingival irritation was registered by the presence or absence of lesions in the marginal gingiva related to treatment. RESULTS: The degree of bleaching was similar with both products (4.8 Vita shade tabs). The hydrogen peroxide product with potassium nitrate provoked less dental sensitivity, although the difference between the 2 products was insignificant (P = .063). Gingival irritation appeared in 6 subjects, but was unrelated to the applied product. CONCLUSION: Under the conditions of this study, no statistically significant differences were detected between 3.5% hydrogen peroxide containing 5% potassium nitrate (FKD) and the 10% carbamide peroxide-based product (Opalescence).

Acrylic Resins↗
PubMed2000

Reactivity of alkyl versus silyl peroxides. The consequences of 1, 2-silicon bridging on the epoxidation of alkenes with silyl hydroperoxides and bis(trialkylsilyl)peroxides.

The bond dissociation energies for a series of silyl peroxides have been calculated at the G2 and CBS-Q levels of theory. A comparison is made with the O-O BDE of the corresponding dialkyl peroxides, and the effect of the O-O bond strength on the activation barrier for oxygen atom transfer is discussed. The O-O bond dissociation enthalpies (DeltaH(298)) for bis (trimethylsilyl) peroxide (1) and trimethylsilyl hydroperoxide (2) are 54.8 and 53.1 kcal/mol, respectively at the G2 (MP2) and CBS-Q levels of theory. The O-O bond dissociation energies computed at G2 and G2(MP2) levels for bis(tert-butyl) peroxide and tert-butyl hydroperoxide are 45.2 and 48.3 kcal/mol, respectively. The barrier height for 1,2-methyl migration from silicon to oxygen in trimethylsilyl hydroperoxide is 47.9 kcal/mol (MP4//MP2/6-31G). The activation energy for the oxidation of trimethylamine to its N-oxide by bis(trimethylsilyl) peroxide is 28.2 kcal/mol (B3LYP/6-311+G(3df,2p)// B3LYP/6-31G(d)). 1,2-Silicon bridging in the transition state for oxygen atom transfer to a nucleophilic amine results in a significant reduction in the barrier height. The barrier for the epoxidation of E-2-butene with bis(dimethyl(trifluoromethyl))silyl peroxide is 25.8 kcal/mol; a reduction of 7.5 kcal/mol relative to epoxidation with 1. The activation energy calculated for the epoxidation of E-2-butene with F(3)SiOOSiF(3) is reduced to only 2.2 kcal/mol reflecting the inductive effect of the electronegative fluorine atoms.

Journal Article↗
PubMed1994

Differential role of hydrogen peroxide and organic peroxides in augmenting asbestos-mediated DNA damage: implications for asbestos induced carcinogenesis.

The incubation of asbestos with DNA in presence of peroxides augmented DNA damage several fold as compared to the damage caused by individual treatments. Asbestos in presence of hydrogen peroxide causes DNA double strand breaks, damage to its deoxyribose sugar moiety and enhanced DNA fidelity. However, only DNA double strand breaks and enhanced DNA fidelity could be recorded in presence of organic hydroperoxide/peroxide but no DNA sugar damage could be observed. Further, the extent of DNA damage could be correlated to the carcinogenic potential of asbestos fibre. Crocidolite, the most carcinogenic variety of asbestos, produces maximum damage to DNA in presence of both hydrogen peroxide and organic hydroperoxide/peroxide while chrysolite which is only a co-carcinogen produces significantly less DNA damage. The observed differences in DNA damage by hydrogen peroxide and organic hydroperoxide/peroxide have been ascribed to the differential reactivity of DNA with hydroxyl and alkoxy/aryloxy free radicals produced respectively from these inorganic and organic peroxides.

Animals↗
PubMed1984

Effects of paraquat on peroxide metabolism enzymes and lipid peroxidation in the rat.

Investigation has been made of how the LD50 and LD100 of PQ influence the peroxide metabolism enzymes and lipid peroxidation in organ homogenates and blood samples of the rat. The peroxide metabolism enzyme activities were changed in a concentration dependent manner. In general, the effect of the lower doses of PQ on the superoxide dismutase, catalase activities and lipid peroxidation are increased. The glutathione peroxidase activity was decreased. Higher doses of PQ enhanced all of enzyme activities and lipid peroxidation studied.

Animals↗
PubMed1999

Nitrogen dioxide radical generated by the myeloperoxidase-hydrogen peroxide-nitrite system promotes lipid peroxidation of low density lipoprotein.

Myeloperoxidase, a heme protein secreted by activated phagocytes, is present and enzymatically active in human atherosclerotic lesions. In the current studies, we explored the possibility that reactive nitrogen species generated by myeloperoxidase promote lipid peroxidation of low density lipoprotein (LDL) -- a modification that may render the lipoprotein atherogenic. We found that myeloperoxidase, an H2O2-generating system and nitrite (NO2-) peroxidized LDL lipids. The process required NO2- and each component of the enzymatic system; it was inhibited by catalase, cyanide and ascorbate, a potent scavenger of aqueous phase radicals. LDL peroxidation did not require chloride ion, and it was little affected by the hypochlorous acid scavenger taurine. Collectively, these results suggest that lipid peroxidation is promoted by a nitrogen dioxide radical-like species. These observations indicate that myeloperoxidase, by virtue of its ability to form reactive nitrogen intermediates, may promote lipid peroxidation and atherogenesis.

Antioxidants↗
PubMed2000

Protective effect of beta-carbolines and other antioxidants on lipid peroxidation due to hydrogen peroxide in rat brain homogenates.

Tryptoline and pinoline are two beta-carbolines isolated from the nervous system of mammals. We investigated the ability of these compounds to prevent lipid peroxidation induced by hydrogen peroxide in rat brain homogenates. We also compared their effects with other known antioxidants including melatonin, trolox and ascorbic acid. Lipid peroxidation was assessed by measuring malonaldehyde (MDA) and 4-hydroxy-alkenals (4-HDA) concentrations in the brain homogenates. Incubation with hydrogen peroxide (5 mM) increased MDA+4-HDA levels, which were totally prevented by tryptoline, pinoline, melatonin and trolox in a concentration-dependent manner. By contrast, higher MDA-4-HDA concentrations compared with control experiments were found after incubation with ascorbic acid, thus reflecting an increase of lipid peroxidation induced by this compound. Although in vivo studies are needed, the data suggest that these beta-carbolines may be potential neuroprotective agents because of their antioxidant activities.

Aldehydes↗
PubMed1998

Strong synergistic anti-peroxidative effects of HDL3 and ascorbic acid against copper-catalyzed LDL peroxidation.

The aim of this study was to investigate the effects of high density lipoprotein 3 (HDL3) and ascorbic acid (AsA) in combination on copper-catalyzed low density lipoprotein (LDL) peroxidation. LDL and HDL3 were isolated from sera of healthy volunteers. LDL protein, 200 microg/ml, was incubated in phosphate-buffered saline (PBS) containing 2.5 microM CuSO4 in the absence or presence of AsA, with HDL3 protein alone, or with coincubation of HDL3, 200 microg/ml, and AsA, 20 microg/ml, at 37 degrees C for up to 24 h. As a control, the same amount of control LDL protein was added to PBS. The protective effects of the HDL3 and AsA were examined by both electrophoresis and determination of the lipid hydroperoxide (LPO) level in each sample. The concentration of AsA was also measured in samples containing AsA. The coincubation of HDL3 and AsA exerts more powerful anti-peroxidative effects against copper-catalyzed LDL peroxidation, than either of these agents alone. In addition, AsA was retained in the media by the addition of HDL3. The findings suggest that there are strong synergistic anti-peroxidative effects of HDL3 and AsA and these two may act in concert in vivo to inhibit LDL peroxidation and thus exert an anti-atherosclerotic effect.

Antioxidants↗
PubMed1987

Mouse keratinocytes derived from initiated skin or papillomas are resistant to DNA strand breakage by benzoyl peroxide: a possible mechanism for tumor promotion mediated by benzoyl peroxide.

Alkaline elution was used to examine DNA single-strand breaks in cultured normal and carcinogen-altered mouse keratinocytes exposed to 12-O-tetradecanoyl phorbol-13-acetate and benzoyl peroxide. Seven cell lines derived from carcinogen-induced mouse skin papillomas and three cell lines derived from N-methyl-N'-nitro-N-nitrosoguanidine-treated non-tumor bearing mouse skin were resistant to phorbol ester-mediated DNA strand breaks after 6 or 24 h. Normal keratinocytes sustained strand breaks after 24 h but not after 6 h. Benzoyl peroxide induced extensive strand breaks in normal keratinocytes at both 6 and 24 h, and this was associated with marked cytotoxicity. In contrast, 9 of 10 cell lines showed complete or partial resistance to strand breaks following benzoyl peroxide exposure. It is proposed that differential resistance to DNA strand breaks and cytotoxicity among normal and carcinogen-altered keratinocytes provides the biological basis for the promoting action of benzoyl peroxide. Furthermore, sublethal DNA damage in preneoplastic or neoplastic keratinocytes may account for the potency of benzoyl peroxide in causing malignant conversion.

Animals↗
PubMed1987

The requirement for iron (III) in the initiation of lipid peroxidation by iron (II) and hydrogen peroxide.

The initiation of lipid peroxidation by Fe2+ and H2O2 (Fenton's reagent) is often proposed to be mediated by the highly reactive hydroxyl radical. Using Fe2+, H2O2, and phospholipid liposomes as a model system, we have found that lipid peroxidation, as assessed by malondialdehyde formation, is not initiated by the hydroxyl radical, but rather requires Fe3+ and Fe2+. EPR spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide and the bleaching of para-nitrosodimethylaniline confirmed the generation of the hydroxyl radical in this system. Accordingly, catalase and the hydroxyl radical scavengers mannitol and benzoate efficiently inhibited the generation and the detection of hydroxyl radical. However, catalase, mannitol, and benzoate could either stimulate or inhibit lipid peroxidation. These unusual effects were found to be consistent with their ability to modulate the extent of Fe2+ oxidation by H2O2 and demonstrated that lipid peroxidation depends on the Fe3+:Fe2+ ratio, maximal initial rates occurring at 1:1. These studies suggest that the initiation of liposomal peroxidation by Fe2+ and H2O2 is mediated by an oxidant which requires both Fe3+ and Fe2+ and that the rate of the reaction is determined by the absolute Fe3+:Fe2+ ratio.

Animals↗
PubMed1979

Elevation of serum lipid peroxide level associated with doxorubicin toxicity and its amelioration by [dl]-alpha-tocopheryl acetate or coenzyme Q10 in mouse (doxorubicin, toxicity, lipid peroxide, tocopherol, coenzyme Q10).

Elevations of serum lipid peroxide levels were demonstrated in mice after an equitoxic dose of doxorubicin. When BDF1 mice were injected with doxorubicin (20 mg/kg body weight, IP), lipid peroxide levels in sera were elevated 1 day after the injection and the levels declined on subsequent days. 5-Fluorouracil (400 mg/kg body weight, IP) never changed the peroxide levels in serum. Furthermore, it was found that the co-administration of [dl]-alpha-tocopheryl acetate or coenzyme Q10 IM strongly inhibited the doxorubicin-induced elevation of lipid peroxides in serum. The effectiveness of [dl]-alpha-tocopheryl acetate or coenzyme Q10 in reducing the lethality of doxorubicin in mice was also confirmed. These results indicate that the measurement of serum 2-thiobarbituric acid-reacting substances provided a useful measurement of lipid peroxide levels, which may be involved in some way with doxorubicin toxicity, and that the administration of antioxidants provide protection against some of the side effects of doxorubicin.

Animals↗
PubMed1987

Effect of succinate on mitochondrial lipid peroxidation. 2. The protective effect of succinate against functional and structural changes induced by lipid peroxidation.

The damaging effects of ADP/Fe/NADPH-induced lipid peroxidation were studied on the enzymes and membranes of rat liver mitochondria. Succinate, an inhibitor of mitochondrial lipid peroxidation, prevented or delayed most of the damage caused by the peroxidation on different mitochondrial structures and functions. There were marked abnormalities on the electrophoretic pattern of mitochondrial proteins during the course of lipid peroxidation. The disappearance of particular polypeptide bands and the accumulation of high-molecular-weight aggregates could be observed. Succinate was found to delay these effects. As a consequence of lipid peroxidation the succinate oxidase activity of mitochondria was decreased. The succinate dehydrogenase enzyme and the component(s) of the respiratory chain were inactivated. Succinate prevented the inactivation of succinate dehydrogenase but did not protect the other components of terminal oxidation chain. From the matrix enzymes the glutamate dehydrogenase retained its full activity but the NADP-linked isocitrate dehydrogenase was inactivated. The mitochondrial membranes became permeable to large protein molecules. Succinate prevented the inactivation of isocitrate dehydrogenase and delayed the release of protein molecules from mitochondria.

Animals↗
PubMed1992

Peroxide dependent and independent lipid peroxidation: site-specific mechanisms of initiation by chelated iron and inhibition by alpha-tocopherol.

Peroxidation of linoleic acid (LA) was catalyzed by Fenton reagent (H2O2 and Fe2+) in positively charged tetradecyltrimethylammonium bromide (TTAB) micelles, but not in negatively charged sodium dodecylsulfate (SDS) micelles. However, more hydroxyl radicals formed via the Fenton reaction were trapped by N-t-butyl-alpha-phenyl-nitrone (PBN) in SDS micelles than in TTAB micelles. Generation of linoleic acid alkoxy (LO) radicals by Fe2+ via reductive cleavage of linoleic acid hydroperoxide (LOOH) resulted in peroxidation of LA and formation of PBN-LO. adducts in SDS micelles, but not in TTAB micelles. This LOOH dependent lipid peroxidation could be catalyzed in TTAB micelles in the presence of a negatively charged iron chelator, nitrilotriacetic acid (NTA). LO radicals formed by the LOOH dependent Fenton reaction were also trapped by PBN at the surface of TTAB micelles in the presence of NTA, but not in its absence. The consumption of a spin probe, 16-(N-oxyl-4,4'-dimethyloxazolidin-2-yl)stearic acid (16-NS) during the LOOH dependent Fenton reaction in the presence of NTA was higher in TTAB micelles of LA than in those of lauric acid (LauA), although the rates and amounts of LO radicals formed in the two types of fatty acid micelles were similar. The rates of 5-NS consumption in LA and LauA micelles were almost the same, and were lower than the rate of 16-NS in LA micelles. NTA-Fe2+ initiated peroxidation of LA in TTAB micelles without a lag time in the presence of LOOH, but after a lag period, peroxidation occurred without LOOH.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron Spin Resonance Spectroscopy↗
PubMed1988

Peroxidation-dependent and peroxidation-independent mechanisms by which acetaminophen kills cultured rat hepatocytes.

Acetaminophen killed cultured hepatocytes prepared from male rats induced with 3-methylcholanthrene by two distinct mechanisms. With 0.5 to 5 mM acetaminophen, cell killing within 4 h depended on the inhibition of glutathione reductase by 1,3-bis(chloroethyl)-1-nitrosourea (BCNU) and was accompanied by the peroxidation of cellular lipids as assessed by the accumulation of malondialdehyde. The antioxidant diphenylphenylenediamine (DPPD) prevented both the peroxidation of lipids and the death of the cells. By contrast, DPPD had no effect on the metabolism of acetaminophen as assessed by the extent of the covalent binding of [3H]acetaminophen; by the rate and extent of the depletion of glutathione; and by the accumulation of acetaminophen metabolites in the culture medium. It is concluded that the peroxidation of the phospholipids of cellular membranes is the mechanism whereby 0.5 to 5 mM acetaminophen lethally injures cultured hepatocytes. With 10-20 mM acetaminophen, cell killing at 4 h still depended on BCNU. However, the amount of malondialdehyde in the cultures progressively decreased in parallel with the decreasing ability of DPPD to protect the cells. With 20 mM acetaminophen, there was no evidence of lipid peroxidation, and DPPD had no protective effect. Thus, a second mechanism of lethal cell injury with 10-20 mM acetaminophen is independent of lipid peroxidation and insensitive to antioxidants.

Acetaminophen↗
PubMed1989

Extracellular calcium alleviates cell toxicity due to hepatotoxins that induce lipid peroxidation, but has no effect on toxins that do not cause lipid peroxidation. A study in isolated rat hepatocytes.

The effect of extracellular calcium on cell death, induced by hepatotoxins that induce lipid peroxidation [diethyl maleate (DEM), allyl alcohol (AA) and bromoisovalerylurea (BIU)] and hepatotoxins that do not induce lipid peroxidation [disulfiram (DSF), N-hydroxy-2-acetyl-aminofluorene (N-OH-AAF) and tetrahydroaminoacridine (THA)] was studied in freshly isolated rat hepatocytes. Extracellular calcium strongly delayed the onset of toxicity of DEM, AA and BIU as detected by lipid peroxidation, depletion of free protein thiol groups and cell death. This protective effect of calcium was decreased at higher concentrations of the toxic compounds. In contrast, no effect of calcium was observed on toxicity induced in the absence of lipid peroxidation by DSF, N-OH-AAF and THA. Addition of calcium was also without effect on the protein thiol depletion. These results indicate that calcium only alleviates cytotoxicity which is induced by thiol depletion resulting from lipid peroxidation. Cytotoxicity as a result of protein thiol depletion through disulfide formation is not affected by extracellular calcium.

1-Propanol↗
PubMed1993

Differential effects of extracellular calcium on lipid peroxidation dependent (ethacrynic acid and allyl alcohol) and lipid peroxidation independent (disulfiram)-induced cytotoxicity in normal and vitamin E-deficient rat hepatocytes.

Hepatocytes have been isolated from normal and vitamin E-deficient rats in which the hepatic vitamin E level was less than 6% that of controls. The hypothesis was tested that extracellular calcium ameliorates chemical-induced cell killing because it decreases the extent of vitamin E loss induced by oxidative stress: such a retarding effect of calcium on cytotoxicity should be lost in hepatocytes from vitamin E-deficient rats. In normal hepatocytes, allyl alcohol and ethacrynic acid induced oxidative stress as indicated by GSH depletion, lipid peroxidation and cell death. Extracellular calcium retarded the induction of lipid peroxidation and cell death without affecting the GSH depletion. In vitamin E-deficient cells, extracellular calcium had lost its protective effect on ethacrynic acid- and allyl-alcohol induced cytotoxicity; it did not affect the GSH depletion and subsequent induction of lipid peroxidation and cell death by ethacrynic acid. However, in vitamin E-deficient hepatocytes, extracellular calcium even potentiated the cytotoxicity of allyl alcohol; under those conditions it also increased GSH loss. Neither in normal, nor in vitamin E-deficient hepatocytes, extracellular calcium had an effect on disulfiram-induced cytotoxicity, i.e. cell death in the absence of lipid peroxidation. These results support the hypothesis that the protecting effect of extracellular calcium on cytotoxicity, associated with lipid peroxidation in normal hepatocytes, is mediated by its protection against intracellular vitamin E loss.

1-Propanol↗
PubMed1996

Mature human atherosclerotic plaque contains peroxidized phosphatidylcholine as a major lipid peroxide.

The initial stage of atherosclerotic plaque formation involves oxidation of the phosphatidyl-choline moiety of low density lipoprotein (LDL) and subsequent uptake by macrophages. Ongoing uptake in developing plaque also may involve oxidized LDL and would require an oxidizing environment in plaque lipids. Atherosclerotic plaque lipids from 12 patients undergoing peripheral vascular procedures were extracted in chloroform: methanol (2:1). This extract was applied to a 25 cm 5 micron silica HPLC column and eluted with a ternary gradient mobile phase utilizing a laser light scattering (ELSD) mass detector. Individual lipid fractions were then analyzed. Cholesterol, both free and esterified, was the most prominent lipid in plaque (104 +/- 74 mg/gm tissue. However, lipid peroxides were present in much higher concentrations (3.52 +/- 2.84 FU X 10(4)/mg phospholipid) and overall level (21.27 +/- 10.10 FU X 10(4)/gm plaque) in the phospholipid component (*p< 0.05). Phosphatidyl-choline (PC) accounted for 63% of the total phospholipid peroxides recovered (6.31 +/- 5.09 mg/gm plaque; *p<0.05). PC and phosphatidylinositol (PI) content were linearly related to lipid peroxide fluorescence (PC; r=0.696; p=0.01) (PI; r=0.809; p=0.001). Lipid peroxides in human atherosclerotic plaque are present primarily in the phospholipid component and phosphatidyl-choline forms the bulk of these peroxides. PC may play an important role in ongoing plaque lipid accumulation.

Analysis of Variance↗
PubMed1988

Reconstituted microsomal lipid peroxidation: ADP-Fe3+-dependent peroxidation of phospholipid vesicles containing NADPH-cytochrome P450 reductase and cytochrome P450.

A reconstituted lipid peroxidation system consisting of rat liver microsomal NADPH-cytochrome P450 reductase and cytochrome P450 incorporated into phospholipid vesicles was developed and characterized. Peroxidation of the vesicles required NADPH and ADP-Fe3+, just as in the NADPH-dependent peroxidation of microsomes. The peroxidation of the vesicles was inhibited 30-50% by superoxide dismutase, depending upon their cytochrome P450 content: those with higher cytochrome P450 contents exhibited greater rates of malondialdehyde formation which were less sensitive to inhibition by superoxide dismutase. When cytochrome P450 was incorporated into vesicles, EDTA-Fe3+ was not required for lipid peroxidation, distinguishing this system from the one previously described by Pederson and Aust [Biochem. Biophys. Res. Comm. 48, 789; 1972]. Since at least 50% of the malondialdehyde formation in the vesicular system was not inhibited by superoxide dismutase, alternative means of iron reduction (O2-.-independent) were examined. It was found that rat liver microsomes or a reconstituted mixed function oxidase system consisting of NADPH-cytochrome P450 reductase and cytochrome P450 in dilauroylphosphatidylcholine micelles reduced ADP-Fe3+ under anaerobic conditions.

Adenosine Diphosphate↗