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At least 1,135 records · Page 63Linked to original sources
PubMed1981

Effect of fatty acid saturation on NADPH-dependent lipid peroxidation in rat liver microsomes.

NADPH-dependent lipid peroxidation in liver microsomes, as measured by malondialdehyde formation, decreased by 90% when rats were fed a diet containing 16% coconut oil. This reduction occurred within 1 to 3 days after the rats were placed on this highly saturated diet. The decrease in peroxidation activity was associated with a reduction in the polyunsaturated fatty acid content of the microsomal phospholipids, particularly arachidonic acid. When the rats were transferred to a highly polyunsaturated diet containing 16% sunflower seed oil, microsomal lipid peroxidation and arachidonic acid content were restored to normal values within 10 days. Arachidonic acid contained in the microsomal choline and ethanolamine phosphoglycerides was the main substrate for peroxidation. Addition of diarachidonyl phosphatidylcholine, but not free arachidonic acid, to the assay system restored peroxidation activity in tahe micraosomes prepared from ahe livers of the rats fed saturated fat. Likewise, prior incubation of these microsomes with a mixture of phospholipid exchange protein and liposomes containing diarachidonyl phosphatidylcholine restored peroxidation activity. These results indicate that diets rich in saturated fat reduce microsomal lipid peroxidation by decreasing the availability of polyunsaturated fatty acids in substrate phospholipids.

Adenosine Diphosphate↗
PubMed1982

[Transmembrane migration of phosphatidylcholine and peroxidation of lipids in rat liver microsomes].

The exchangeability of phosphatidylcholine in microsomes differing in the degree of lipid peroxidation was determined by incubation of microsomes labelled in vivo with [methyl-14C]choline chloride with an excess of phosphatidylcholine liposomes and phosphatidyl-exchange protein from beef liver. The phosphatidylcholine peroxidation products were shown to act as substrates for the phosphatidylcholine-exchange protein. The level of exchangeable microsomal phosphatidylcholine did not depend on the degree of lipid peroxidation in the microsomes. Stimulation of lipid peroxidation by Fe2+-ascorbate or inhibition of lipid peroxidation by alpha-tocopherol did not influence the exchange of microsomal phosphatidylcholine. However, with highly peroxidized phosphatidylcholine liposomes as acceptor particles the exchange of microsomal phosphatidylcholine in the presence of phosphatidylcholine-exchange protein was strongly inhibited. In all cases the percentage of microsomal phosphatidylcholine exchangeable within 1-2 hrs was 85-90%. It is concluded that lipid peroxidation is not responsible for the rapid translocation (flip-flop) of phosphatidylcholine in rat liver microsomes. A possible involvement of membrane proteins in this process is proposed.

Androgen-Binding Protein↗
PubMed1981

Paraquat and NADPH-dependent lipid peroxidation in lung microsomes.

Since there exists some controversy in the literature as to whether paraquat augments microsomal lipid peroxidation via superoxide anion (O2-), the role of paraquat and active oxygen species in NADPH-dependent lung microsomal lipid peroxidation was investigated. Incubation of buffered aerobic mixture of bovine lung microsome and NADPH, in the presence or absence of exogenously added iron, resulted in a progressive formation of lipid peroxides whose accumulation could be followed at 535 nm as malondialdehyde. Paraquat strongly inhibited this lipid peroxidation. Thus, malondialdehyde formation was 50% inhibited by 4 X 10(-5) M paraquat in the reaction mixture. The malondialdehyde color development by lipid peroxides was not affected by this concentration of paraquat. Lipid peroxidation was also strongly inhibited by singlet oxygen scavengers, e.g. dimethylfuran and diphenylfuran, and by catalase. Hydroxyl radical scavengers, e.g. mannitol, benzoate, and ethanol, had little effect in malondialdehyde production. Superoxide dismutase, which removes O2- efficiently, did not inhibit malondialdehyde production by lung microsomes and rather enhanced its formation. A scheme in which paraquat and active O2 species may be involved with microsomal lipid peroxidation is presented.

Animals↗
PubMed1981

Glutathione-dependent inhibition of lipid peroxidation by a soluble, heat-labile factor not glutathione peroxidase.

Both enzymic and nonenzymic lipid peroxidation in membranes are inhibited by a)certain chelating compounds, b)some metal ion (Mn2+, Co2+, and Ce3+), and c)lipid soluble antioxidants. The commonalities suggest that the processes of oxidative lipid degradation in the two types of systems may be similar, differing only in the mechanism of initiation. This is further borne out by studies with a glutathione-dependent, heat-labile cytosolic factor that inhibits malondialdehyde formation (a product of lipid peroxidation) in both systems. Studies in the authors' laboratory, however, have demonstrated that the cytosolic factor protects membranous organelles from oxidative damage to the lipids by preventing peroxidation from occurring at all. Analyses of the fatty acid composition of the membranes demonstrate that the polyunsaturated fatty acid content remains stable when the membranes are subjected to peroxidizing conditions in the presence of the cytosolic factor and GSH. Both the cytosolic factor and GSH are required for the protective action since neither can provide this marked stabilizing effects by itself. High concentrations of GSH reduce lipid peroxidation to some extent, but low concentrations are not effective without the addition of the cytosolic factor. The mechanism of this inhibition of peroxidative attack is unknown. Partial purification of rat liver cytosolic glutathione peroxidase demonstrated that the heat-labile cytosolic factor was not glutathione peroxidase. The cytosolic factor may be a glutathione transferase, but that is not known with certainty. Possibly more than one cytosolic protein possesses this GSH-dependent property for inhibiting lipid peroxidation under conditions of oxidative stress. The conditions for the functioning of this protective system in intact cells appear to be optimum and it may constitute a ubiquitous membrane-stabilizing system in that it is also present in other tissues (heart and lung, for example).

Animals↗
PubMed1994

[Protection by blockers against human low density lipoprotein peroxidation induced by oxygen free radicals].

Previous studies in other systems have shown that beta-receptor blockers may effectively inhibit oxygen radical-induced lipid peroxidation. On the other hand, it has been recently proposed that oxygen free radicals can induce peroxidation of human low density lipoproteins (LDL), and that peroxidized LDL may be an atherogenic stimulus. Chemically modified LDL are internalized by macrophages via a specific cell surface receptor that was termed the scavenger receptor. This phenomenon may induce foam cells transformation in vivo. In the present study we investigated whether beta-blockers may reduce oxygen radical-mediated LDL peroxidation. Purified human LDL were oxidized by exposure to oxygen free radicals generated by xanthine (0.2 mM) and xanthine oxidase (100 mU) at 37 degrees C after a pre-incubation (30 min) in presence of different concentrations (from 1 to 30 microM) of acebutolol, metoprolol or propranolol, three agents with a different degree of lipophilicity. Peroxidation was measured from malonyldihaldehyde (MDA) production. Data have shown a significant percent inhibition of MDA formation in presence of beta-blockers (from 33 to 85%). Thus, beta-blockers reduced peroxidation of human LDL in vitro at clinically relevant concentrations. The order of potency appears to follow the degree of lipophilicity. These data suggest that, although beta-blockers are known to adversely effect lipid metabolism, these agents might on the other hand prevent atherogenesis via a mechanism of inhibition of LDL peroxidation in vivo and reduced foam cells formation.

Acebutolol↗
PubMed1994

Stimulation by hydrogen peroxide of L-arginine metabolism to L-citrulline coupled with nitric oxide synthesis in cultured endothelial cells.

The effect of hydrogen peroxide on metabolism of L-arginine to L-citrulline in the biosynthesis of nitric oxide was investigated in bovine aortic endothelial cells. Addition of hydrogen peroxide (1-10 mM) to endothelial cells increased L-citrulline formation from L-arginine in a dose-dependent manner. Stimulation of L-citrulline formation was prevented by catalase (20 micrograms/ml), a hydrogen peroxide scavenger, but not by superoxide dismutase (SOD, 100 micrograms/ml), a superoxide anion scavenger. Pretreatment with NG-nitro-L-arginine (10(-5) M) and NG-methyl-L-arginine (10(-4) M), potent inhibitors of nitric oxide synthase, also inhibited L-citrulline formation induced by hydrogen peroxide. Moreover, hydrogen peroxide increased intracellular Ca2+ concentrations, and the removal of extracellular Ca2+ reduced the hydrogen peroxide-induced formation of L-citrulline. These findings show that hydrogen peroxide increases the intracellular Ca2+ concentration and stimulates the formation of L-citrulline from L-arginine coupled with nitric oxide synthesis in cultured endothelial cells.

Animals↗
PubMed1993

Acid phosphatase and lipid peroxidation in human cataractous lens epithelium.

The anterior lens epithelial cells undergo a variety of degenerative and proliferative changes during cataract formation. Acid phosphatase is primarily responsible for tissue regeneration and tissue repair. The lipid hydroperoxides that are obtained by lipid peroxidation of polysaturated or unsaturated fatty acids bring about deterioration of biological membranes at cellular and tissue levels. Acid phosphatase and lipid peroxidation activities were studied on the lens epithelial cells of nuclear cataract, posterior subcapsular cataract, mature cataract, and mixed cataract. Of these, mature cataractous lens epithelium showed maximum activity for acid phosphatase (516.83 moles of p-nitrophenol released/g lens epithelium) and maximum levels of lipid peroxidation (86.29 O.D./min/g lens epithelium). In contrast, mixed cataractous lens epithelium showed minimum activity of acid phosphatase (222.61 moles of p-nitrophenol released/g lens epithelium) and minimum levels of lipid peroxidation (54.23 O.D./min/g lens epithelium). From our study, we correlated the maximum activity of acid phosphatase in mature cataractous lens epithelium with the increased areas of superimposed cells associated with the formation of mature cataract. Likewise, the maximum levels of lipid peroxidation in mature cataractous lens epithelium was correlated with increased permeability of the plasma membrane. Conversely, the minimum levels of lipid peroxidation in mixed cataractous lens epithelium makes us presume that factors other than lipid peroxidation may also account for the formation of mixed type of cataract.

Acid Phosphatase↗
PubMedDate not supplied

The effects of hydrogen peroxide rinses on the normal oral mucosa.

Oral mucosal effects of hydrogen peroxide mouth rinses were investigated in normal volunteers. Following a 2-week control period, 35 subjects were randomly assigned to rinse with either normal saline, 1/4-strength hydrogen peroxide (0.75%), or 1/2-strength hydrogen peroxide (1.5%), 4 times daily for 2 weeks. Mucosal status, buccal microbial adherence, salivary flow rate (SFR), and subjective reactions were assessed weekly. In the normal saline group, no significant changes were noted in any of the observed parameters and subjective reports were unremarkable. In both hydrogen peroxide groups, significant mucosal abnormalities were observed (p < 0.001) and subjective complaints were numerous. Bacterial adherence was significantly reduced in the 1/4 hydrogen peroxide group but not in the 1/2 hydrogen peroxide group. Despite reports of dry mouth, SFRs were not altered significantly. Since hydrogen peroxide rinses are associated with mucosal abnormalities and elicit overwhelmingly negative subjective reactions in normal individuals, they are not recommended for oral care.

Adult↗
PubMed1993

Lipid peroxide levels in type II hyperlipoproteinemic subjects.

The purpose of this study was to evaluate, under the most rigorous precautionary measures against in vitro oxidation, whether the baseline lipid peroxide levels in hypercholesterolemic subjects were higher than those in normolipidemic subjects. Two methods were employed: thiobarbituric acid (TBA), and hemoglobin-methylene blue (HbMB). Blood was collected into EDTA tube and centrifuged at 4 degrees C for 30 min to collect plasma, then protected from in vitro oxidation with preservatives and N2. Serum was from blood samples allowed to clot at 20 degrees C for 1 h, then protected from oxidation. Determination of lipid peroxide was carried out within 2 h of blood collection. Results from 35 hypercholesterolemic and 34 control subjects showed that lipid peroxide levels obtained from both methods were significantly higher in serum than in plasma for both groups, suggesting a greater rate of lipid peroxidation occurred in serum during clot formation. However, no significant difference in lipid peroxide levels was found between patients and controls in either serum or plasma by either assay method. No correlation existed between lipid peroxide values and plasma cholesterol or LDL-cholesterol levels. These results suggest that the mechanism for a higher tendency towards atherosclerosis in hypercholesterolemic subjects is not related to baseline levels of plasma lipid peroxide.

Blood Specimen Collection↗
PubMed1993

Stimulation of Fe(2+)-induced lipid peroxidation in phosphatidylcholine liposomes by aluminium ions at physiological pH.

The effects of aluminium ions on Fe(2+)-induced lipid peroxidation in egg yolk phosphatidylcholine liposomes were examined under various conditions. The degree of Fe(2+)-induced lipid peroxidation of the liposomes was dependent on pH of the reaction mixture: pH 5.0 > pH 7.4. However, Fe2+ did not induce lipid peroxidation in the liposomes at pH 9.0. The addition of AlCl3 to the liposomal suspension resulted in a marked stimulation of Fe(2+)-induced liposomal peroxidation at pH 7.4, depending on the concentration of AlCl3. On the other hand, Fe3+, Cu2+, Pb2+, Cd2+ and Cr6+ did not induce lipid peroxidation in the liposomes at pH 7.4 regardless of the presence and absence of AlCl3. Fe3+ enhanced Fe(2+)-induced liposomal peroxidation at pH 7.4 but is unrelated to the stimulatory effect of AlCl3. In the absence of AlCl3, Fe(2+)-induced liposomal peroxidation was observed after a lag phase of about 15 min. The lag phase of the reaction was shortened by the addition of AlCl3 in a dose-dependent fashion. The shortening of the lag phase was also observed by the decrease of Fe2+ concentration or by the co-presence of Fe3+ in the reaction mixture. In addition, it was found that AlCl3 stimulates Fe2+ disappearance and Fe3+ formation. The addition of AlCl3 to the liposomal suspension at pH 7.4 resulted in a marked increase of the turbidity of the suspension. On the other hand, the turbidity of the liposomal suspension at pH 5.0 did not change by the addition of AlCl3.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum Chloride↗
PubMed1996

Predominant role of catalase in the disposal of hydrogen peroxide within human erythrocytes.

Purified enzymes were mixed to form a cell-free system that simulated the conditions for removal of hydrogen peroxide within human erythrocytes. Human glutathione peroxidase disposed of hydrogen peroxide (H2O2) at a rate that was only 17% of the rate at which human catalase simultaneously removed hydrogen peroxide. The relative rates observed were in agreement with the relative rates predicted from the kinetic constants of the two enzymes. These results confirm two earlier studies on intact erythrocytes, which refuted the notion that glutathione peroxidase is the primary enzyme for removal of hydrogen peroxide within erythrocytes. The present findings differ from the results with intact cells, however, in showing that glutathione peroxidase accounts for even less than 50% of the removal of hydrogen peroxide. A means is proposed for calculating the relative contribution of glutathione peroxidase and catalase in other cells and species. The present results raise the possibility that the major function of glutathione peroxidase may be the disposal of organic peroxides rather than the removal of hydrogen peroxide.

Catalase↗
PubMed1996

Macrophage activation with phorbol myristate acetate is associated with cellular lipid peroxidation.

The present study analyzed the association between two major processes that occur during atherogenesis: macrophage activation and peroxidation of the cellular lipids. Macrophage activation was achieved by cell incubation with phorbol myristate acetate (PMA) for 24 h at 37 degrees C, and was determined as: a) PMA concentration-dependent increment in the release of beta-glucuronidase, b) decrement in the procoagulant activity, and c) increment in the release of superoxides from the cells. PMA-induced macrophage activation was accompanied by cellular lipid peroxidation, as measured by increased formation of lipid peroxides (by 435%), thiobarbituric acid-reactive substances (TBARS) (by 26%), and conjugated dienes (by 77%) in comparison with control nonactivated cells. The maximal effect of PMA on lipid peroxidation in macrophages was achieved within 1 h of cell incubation with PMA. This effect was demonstrated in J-774 A.1 macrophages, as well as in mouse peritoneal, macrophages, U-937 and P-338 macrophage cell lines. Upon incubation of macrophages with 4 alpha phorbol 12, 13 didecanoate, an analogue of PMA (which, unlike PMA, does not activate protein kinase C), macrophage lipid peroxidation was lower compared with PMA, suggesting a role for protein kinase C in cellular lipid peroxidation. Analysis of cellular antioxidants under PMA-induced macrophage activation revealed a decrease of 50% in total glutathione, and in catalase levels following treatment with 100 nM PMA compared with control cells. In summary, our study demonstrates that PMA-activated macrophages undergo significant lipid peroxidation, which is associated with reduced activity of the cellular antioxidative system.

Animals↗
PubMedDate not supplied

[Comparative study of the kinetics of phospholipid liposome peroxidation, induced by hypochlorite and in the Fe2+ + ascorbate system].

The present study examined the kinetics of accumulation of lipid peroxidation products in phosphatidylcholine liposomes incubated with hypochlorite (HOCl/OCl-) or with FeSO4 in the presence of ascorbate. The incubation of liposomes with HOCl/OCl- led to the accumulation of primary (lipid hydroperoxides and conjugated dienes) and secondary (TBA-reactive substances) lipid peroxidation products identical to those generated in the presence of Fe2+/ascorbate. However the rate of the formation of lipid peroxidation products as well as the gain in their amount were sufficiently higher (4-150-fold and 3-6-fold, respectively) in the case of HOCl/OCl(-)-induced lipid peroxidation as compared to lipid peroxidation in the Fe2+/ascorbate system. The accumulation of lipid peroxidation products lasted until HOCl/OCl- was present in the reaction mixture. The data obtained support our hypothesis that hypochlorite produced by activated neutrophils and monocyte/macrophages may be reasonable for the initiation of lipid peroxidation in blood.

Animals↗
PubMed1996

Hydrogen peroxide induces complex formation of SHC-Grb2-SOS with receptor tyrosine kinase and activates Ras and extracellular signal-regulated protein kinases group of mitogen-activated protein kinases.

Protein tyrosine phosphorylation events play determinant roles in cellular processes such as proliferation and differentiation. We have recently reported that hydrogen peroxide, an active oxygen species and a cellular oxidant, stimulates growth response events in vascular smooth muscle cells (VSMC). To understand the mechanisms by which oxidant stress modulates these growth response events, we have studied the effect of hydrogen peroxide on protein tyrosine phosphorylation events in VSMC. Our findings show that hydrogen peroxide stimulates tyrosine phosphorylation of several proteins including epidermal growth factor receptor (EGFR) in VSMC. Hydrogen peroxide-induced tyrosine phosphorylation of EGFR was found to be time dependent; with a threefold increase at 5 min and a 20-fold increase at 30 min of treatment as compared to control levels. Hydrogen peroxide treatment of VSMC also resulted in a time-dependent increase in tyrosine phosphorylation of SHC proteins. In addition, hydrogen peroxide-induced tyrosine-phosphorylated EGFR formed a complex with SHC-Grb2-SOS. These events were followed by activation of Ras and extracellular signal-regulated protein kinases (ERKs) group of mitogen-activated protein kinases (MAPKs). Together these findings demonstrate for the first time that hydrogen peroxide, a cellular oxidant, possess the ability to activate EGFR-mediated signaling events in VSMC. These EGFR-mediated signaling events may be important in oxidant stress-induced cellular responses.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Lipid peroxidation inhibited by monoamines.

We investigated the inhibition of lipid peroxidation by monoamines. We found that monoamines, including dopa, dopamine, adrenaline and serotonin, strongly inhibited lipid peroxidation induced by 2,2'-azobis-(2-amidinopropane)-dihydrochroride (AAPH). In contrast, lipid peroxidation induced by 2,2'-azobis-(2,4-dimethylvaleronitrile) was not effectively inhibited by the monoamines. Degradation of R-phycoerythrin induced by AAPH was strongly prevented by these monoamines, suggesting that monoamines scavenge peroxyl radicals in the buffer and on the surface of membrane lipid layers. Methoxy derivatives of dihydroxyphenylacetic acid and 5-methoxytryptophan produced little inhibition of lipid peroxidation induced by AAPH, suggesting that hydroxy groups of monoamines donate protons to peroxyl radicals to prevent lipid peroxidation. However, the monoamines did not sharply inhibit lipid peroxidation induced by ascorbate-ADP-Fe3+ and t-butylhydroperoxide-Fe2+. Lipid peroxidation predominantly proceeding by peroxyl radicals in these reaction systems seems unlikely.

Amidines↗
PubMed1996

Effects of beta-carotene, flavonoid quercitin and quinacrine on cell proliferation and lipid peroxidation breakdown products in BHK-21 cells.

Exposure of BHK-21 (baby hamster kidney cells) to varying concentration of beta-carotene (0- 156 nM) induced a reduction in a cell proliferation rate, increased lipid peroxidation breakdown products, elevated levels of cellular reduced glutathione (GSH), and increased cellular DNA content. Similarly concentration of hydrogen peroxide (0-1.0 microM) added to growth medium truncated rates of cell proliferation as hydrogen peroxide (H2O2) concentration increased and augmented cellular DNA content dramatically. Electrophoresis analysis of DNA from cells treated with H2O2 on agarose gel indicated no excessive DNA fragmentation. Escalating concentration of flavonoid quercitin (0-10 microM) in culture cell medium enhanced the rate of cell growth and diminished levels of lipid peroxidation breakdown products. Quinacrine an inhibitor of phospholipase A2 activity not only abated the decline in cellular lipid peroxidation breakdown products but also abridged the rate of cell proliferation. A combination of beta-carotene (50 nM) and H2O2 (100 microM) added to growth medium depressed cell growth further and increased cellular lipid peroxidation breakdown products. High levels of lipid peroxidation breakdown products were also evident in newly established cultures but these levels decreased with increased growth rate.

Animals↗
PubMed1997

The protective effect of metallothionein against lipid peroxidation caused by retinoic acid in human breast cancer cells.

The treatment of breast cancer by retinoic acid (RA) may be mediated by lipid peroxidation. Expression of metallothionein (MT) in cancer cells, however, can protect against lipid peroxidation by scavenging hydroxyl radicals. In this study, a two-by-six factorial design was used to investigate the interactive effects of all-trans-RA and zinc (Zn)-induced MT on the growth of two human breast cancer cell lines differing in basal expression of MT and estrogen receptors; MCF7 cells express estrogen receptor, BT-20 cells do not. Cells were treated with Zn to induce MT and then treated with six RA concentrations. Cell proliferation, lipid peroxidation, MT protein, MT mRNA and glutathione concentrations were measured. BT-20 cells expressed higher constitutive MT concentrations than MCF7 cells. MT was significantly increased by Zn treatment in BT-20 cells but not in MCF7 cells. Low RA concentrations stimulated growth proliferation but higher concentrations inhibited cell proliferation. Elevated RA concentrations increased lipid peroxidation as measured by thiobarbituric acid reactive substances. There was a significant negative correlation between lipid peroxidation and cell proliferation. Growth inhibition and lipid peroxidation were reduced by Zn pretreatment in BT-20 cells but not in MCF7 cells. RA increased MT levels in both cell lines, which suggests that RA may generate free radicals which will induce MT mRNA expression. Glutathione did not appear to be a significant factor. Therefore, induction of MT by Zn may modulate the growth inhibitory effects of RA in human breast cancer cells. One mechanism of growth inhibition may be through increased lipid peroxidation. Induction of MT by RA may be one explanation for acquired RA resistance in cancer.

Breast Neoplasms↗
PubMedDate not supplied

[Lipid peroxidation in critical patients].

Lipid peroxidation is a part of normal metabolism. The degree of peroxidation of membrane depends on the quantity and the quality of his fatty acids, both as components of the membrane, as constituents of the cellular environment. The magnitude of the changes which result in response to an exogenous load of hydrogen peroxides, shall depend, in part, on the pre-existing tissue levels of endogenous hydrogen peroxide. The exposure of the membrane to oxygen free radicals produced in excess, stimulates the process of lipid peroxidation. An update is made on lipid peroxidation in different nosological entities, with special emphasis on the special context of critical patients, and within this group, on the concept of ischemia-reperfusion. On the other hand, a brief review is made of the possible antioxidant defenses which may be used in the clinical situation, and a more extensive review is made of the correct analytical methodology to be used for determining the peroxidation.

Antioxidants↗