Tissue specific interactions of exercise, dietary fatty acids, and vitamin E in lipid peroxidation

Both physical exercise and ingestion of polyunsaturated fatty acids that play an essential role in free radical-mediated damages cause lipid peroxidation. The intake of specific fatty acids can modulate the membrane susceptibility to lipid peroxidation. Data confirmed that liver, skeletal muscle, and heart have different capabilities to adapt their membrane composition to dietary fatty acids, the heart being the most resistant to changes. Such specificity affects membrane hydroperoxide levels that depend on the type of dietary fats and the rate of fatty acid incorporation into the membrane. Sedentary rats fed a monounsaturated fatty acid-rich diet (virgin olive oil) showed a higher protection of their mitochondrial membranes against peroxidation than sedentary rats fed a polyunsaturated fatty acid-rich diet (sunflower oil). Rats subjected to training showed higher hydroperoxide contents than sedentary animals, and exhaustive effort enhanced the aforementioned results as well as in vitro peroxidation with a free radical inducer. This study suggests that peroxide levels first depend on tissue, then on diet and lastly on exercise, both in liver and muscle but not in heart. Finally, it appears that alpha-tocopherol is a less relevant protective agent against lipid peroxidation than monounsaturated fatty acids.     

Gut patterning: the case of the missing cecum

Free radicals attack lipid molecules and initiate a chain of reactions that may trigger several diseases such as atherosclerosis and cancer. Several markers of oxidative stress have been proposed, including measurements of lipid peroxides and short-chain aldehydes levels and evaluation of conjugated diene formation. Although it is generally assumed that fatty acid oxidizability is directly proportional to their degree of unsaturation, little is known about the contribution of individual fatty acids to each of these markers. We investigated such contributions in a model of AAPH-mediated peroxidation of individual fatty acid micelles by assessing several indices of oxidative stress. The results suggest that the generation of oxidation products by individual fatty acids is not directly related to their degree of unsaturation and indicate that the differential contribution of individual fatty acids should be taken into account and more than one marker of lipid peroxidation should be included in in vivo studies of oxidative stress.     

Dramatic increase of alpha-hydroxyaldehydes derived from plasmalogens in the aged human brain

Plasmalogens-substantial compounds of brain tissue--suffer degradation either by hydrolysis under production of aldehydes or by oxidation with lipid peroxylradicals by generation of plasmalogen epoxides. The latter react by addition of pentafluorobenzylhydroxylamine HCl (PFBHA HCL) under hydrolysis to alpha-hydroxyaldehydes which are immediately transformed to pentafluorobenzyloximes (PFBO). Likewise, free aldehydes are transformed to PFBO-derivatives. PFBO-derivatives of free aldehydes and PFBO-derivatives of alpha-hydroxyaldehydes were extracted and after trimethylsilylation quantified by GC/FID and by GC/MSD. The remaining aqueous phase, containing plasmalogens besides other lipids, was hydrolyzed by treatment with acid. The hydrolysis products of plasmalogens, long chain aldehydes, react with PFBHA HCl to produce PFBO-derivatives. These were also quantified by GC/FID. This method allows the quantification of plasmalogens, free aldehydes and plasmalogenepoxides in human brain samples to study changes in the relation of these compounds with increasing age. While the ratio of plasmalogens in respect to derived aldehydes seems to remain constant during life time, the quotient of plasmalogenepoxides to plasmalogens increases with age, indicating that lipid peroxidation processes are involved in the damage of plasmalogens in the brain of aged individuals, starting at an age of about 70 years.     

Low doses of eicosapentaenoic acid, docosahexaenoic acid, and hypolipidemic eicosapentaenoic acid derivatives have no effect on lipid peroxidation in plasma

It was of interest to investigate the influence of both high doses of eicosapentaenoic acid (EPA) and low doses of 2- or 3-methylated EPA on the antioxidant status, as they all cause hypolipidemia, but the dose required is quite different. We fed low doses (250 mg/d/kg body wt) of different EPA derivatives or high doses (1500 mg/d/kg body wt) of EPA and DHA to rats for 5 and 7 d, respectively. The most potent hypolipidemic EPA derivative, 2,2-dimethyl-EPA, did not change the malondialdehyde content in liver or plasma. Plasma vitamin E decreased only after supplementation of those EPA derivatives that caused the greatest increase in the fatty acyl-CoA oxidase activity. Fatty acyl-CoA oxidase activity increased after administration of both EPA and DHA at high doses. High doses of EPA and DHA decreased plasma vitamin E content, whereas only DHA elevated lipid peroxidation. In liver, however, both EPA and DHA increased lipid peroxidation, but the hepatic level of vitamin E was unchanged. The glutathione-requiring enzymes and the glutathione level were unaffected, and no significant changes in the activities of xanthine oxidase and superoxide dismutase were observed in either low- or high-dose experiments. In conclusion, increased peroxisomal beta-oxidation in combination with high amounts of polyunsaturated fatty acids caused elevated lipid peroxidation. At low doses of polyunsaturated fatty acids, lipid peroxidation was unchanged, in spite of increased peroxisomal beta-oxidation, indicating that polyunsaturation is the most important factor for lipid peroxidation.     

Induction of lipid peroxidation during heavy metal stress in Saccharomyces cerevisiae and influence of plasma membrane fatty acid unsaturation

The degree of plasma membrane fatty acid unsaturation and the copper sensitivity of Saccharomyces cerevisiae are closely correlated. Our objective was to determine whether these effects could be accounted for by differential metal induction of lipid peroxidation. S. cerevisiae S150-2B was enriched with the polyunsaturated fatty acids (PUFAs) linoleate (18:2) and linolenate (18:3) by growth in 18:2- or 18:3-supplemented medium. Potassium efflux and colony count data indicated that sensitivity to both copper (redox active) and cadmium (redox inactive) was increased in 18:2-supplemented cells and particularly in 18:3-supplemented cells. Copper- and cadmium-induced lipid peroxidation was rapid and associated with a decline in plasma membrane lipid order, detected by fluorescence depolarization measurements with the membrane probe trimethylammonium diphenylhexatriene. Levels of thiobarbituric acid-reactive substances (lipid peroxidation products) were up to twofold higher in 18:2-supplemented cells than in unsupplemented cells following metal addition, although this difference was reduced with prolonged incubation up to 3 h. Conjugated-diene levels in metal-exposed cells also increased with both the concentration of copper or cadmium and the degree of cellular fatty acid unsaturation; maximal levels were evident in 18:3-supplemented cells. The results demonstrate heavy metal-induced lipid peroxidation in a microorganism for the first time and indicate that the metal sensitivity of PUFA-enriched S. cerevisiae may be attributable to elevated levels of lipid peroxidation in these cells.     

Determination of DNA adducts of malonaldehyde in humans: effects of dietary fatty acid composition

The effects of dietary fatty acid composition on the endogenous formation of DNA adducts of malonaldehyde (MA), the major product of lipid peroxidation, were investigated in humans. A group of 59 healthy individuals of both sexes and different ages was initially fed a milk fat-based diet rich in saturated fatty acids for 14 days. Following this initial period, after which the group was considered homogeneous with respect to diet, 30 randomly chosen subjects were given a sunflower oil-based (rich in polyunsaturated fatty acids) (SO) diet and the remaining 29 individuals a low erucic acid rapeseed oil-based (rich in monounsaturated fatty acids) (RO) diet for 25 days. The fatty acid composition of plasma lipid fractions and the level of DNA adducts of MA in total white blood cells were then determined at the end of the SO and RO dietary periods. DNA adduct levels were measured by 32p-postlabelling using reversed-phase HPLC with on-line detection of radioactivity. Higher concentrations of polyunsaturated fatty acids in plasma triglycerides and higher levels of DNA adducts of MA were found in the subjects on the SO diet when compared with those in the RO dietary group. A large inter-individual variation in adduct levels was observed. The average adduct level in the SO diet group was 7.4 +/- 8.7 adducts/10(7) nucleotides (n = 23). This level was 3.6-fold higher than that found in individuals in the RO diet group (P < 0.001). Our results, in conjunction with the mutagenic and carcinogenic properties of MA, thus suggest the interaction of lipid peroxidation products such as MA with DNA as one plausible mechanism explaining the involvement of dietary fat in carcinogenesis.     

Lipid peroxidation in patients with multiple sclerosis

Questions of lipid metabolism in patients with multiple sclerosis are considered in the light of biomembrane (myelin) pathology. The results of of the study of the lipids fatty acids spectrum in the blood plasma and the secondary product of their spontaneous and NADPhH-dependent peroxidation, malonic dialdehyde, are stated. The dependence of changes in saturation of fatty acids spectrum and dialdehyde concentrations on the stage and heaviness of the multiple sclerosis is shown. Certain dynamics of lipid metabolism indices as a result of treatment was found. The authors also give some recommendations as to the use of drugs at various stages of the disease.     

Activation of human polymorphonuclear leukocytes by products derived from the peroxidation of human red blood cell membranes

Oxidation of red blood cell (RBC) ghost preparations initiated by tert-butyl hydroperoxide (tBuOOH) was employed to explore the formation of lipid products derived from endogenous phospholipids that specifically expressed biological activity toward the human polymorphonuclear leukocyte (PMN). Common measure of lipid peroxidation, thiobarbituric acid-reactive substances (TBARS) and the increased absorbance at 235 nm consistent with the formation of conjugated dienes, was observed following a 90-min incubation of RBC ghosts with tBuOOH. Saponification of phospholipids and separation of the resultant fatty acids by RP-HPLC permitted direct mass spectrometric analysis of oxidized fatty acids. Individual HPLC fractions were assayed for their ability to increase intracellular free calcium ion concentrations in human PMN to guide structural investigations. Two fractions were found to contain biologically active components, and tandem mass spectrometric analysis of the abundant ions observed in these fractions resulted in the characterization of several oxidized polyunsaturated fatty acids derived from arachidonic and linoleic acids. The major components in these fractions included 5-hydroxyeicosatetraenoic acid (5-HETE) and 5-hydroperoxyeicosatetraenoic acid (5-HpETE). The dose-dependent increases in intracellular calcium in the neutrophil using synthetic 5(rac)-HETE, 5(rac)-HpETE, and 5-oxo-ETE were found to have EC50's of 250, 6, and 3 nM, respectively. The quantity of 5-oxygenated arachidonate components present in oxidized RBC was consistent with the observed biological response elicited by fractions A and B. This study suggests that 5-HETE and 5-HpETE are abundant products of lipid peroxidation of cellular membranes and that these racemic products possess significant biological activity. Such compounds could play important roles as mediators of the cellular response to toxicologic stimuli that generate free radical species.     

Lipoproteins accumulate in immune deposits and are modified by lipid peroxidation in passive Heymann nephritis

Proteinuria in passive Heymann nephritis is primarily caused by reactive oxygen species that are produced by glomerular cells. Reactive oxygen species apparently exert their damaging effects on the glomerular filter by lipid peroxidation and subsequent adduct formation on matrix proteins of glomerular basement membranes. This raised the question as to the source of polyunsaturated fatty acids required as substrates for lipid peroxidation. Here we have localized by immunocytochemistry rat apolipoprotein E and apolipoprotein B within subepithelial immune deposits. Moreover, apolipoprotein B extracted from isolated glomeruli of proteinuric passive Heymann nephritis rats shows degradation and lipid peroxidation adduct formation, similar to apoproteins of oxidized lipoproteins in atherosclerotic lesions. These data provide evidence that lipoproteins accumulate within immune deposits and suggest that their lipids generate lipid-peroxidation-derived reactive compounds.     

Alterations in hepatocyte lysosomes in experimental hepatic copper overload in rats

BACKGROUND: Although Wilson's disease is characterized by an accumulation of copper within hepatocyte lysosomes, the effects of excess copper on hepatic lysosomes are unknown. We studied the effects of excess copper on the structure, physicochemical properties, and pH of hepatocyte lysosomes using a rodent model. METHODS: Rats were copper loaded with 0.125% copper acetate in water for 6 weeks. Copper was measured by atomic absorption spectrophotometry. Morphology was studied by electron microscopy. Lysosomal membrane fluidity was studied by fluorescence polarization, and lipid composition was determined by gas chromatography. Hepatocyte lysosomal pH was determined by flow cytometry. RESULTS: Copper overload resulted in a 10-fold increase in hepatic copper. Hepatocyte lysosomes were enlarged and abnormally shaped with a 27-fold increase in copper, increased in vitro fragility, and decreased lysosomal membrane fluidity. Thiobarbituric acid reactive substances, a measure of lipid peroxidation, doubled in isolated lysosomal membranes. Polyunsaturated fatty acids increased, saturated fatty acids decreased, and membrane content of selected fatty acids was modified after copper overload. Lysosomal pH increased from 4.67 +/- 0.02 to 4.87 +/- 0.02. CONCLUSIONS: Copper overload causes alterations in lysosomal morphology, increases lysosomal fragility, decreases membrane fluidity, alters membrane fatty acid composition, and increases lysosomal pH. Copper catalyzed lipid peroxidation represents the likely mechanism for these alterations.     

Lipid peroxidation: a review of causes, consequences, measurement and dietary influences

In this review the process of lipid peroxidation and the atherogenicity of peroxidied lipids are discussed. Recent findings with regard to the effect of selected dietary factors on susceptibility of lipids to oxidative stress and on antioxidant defences are analysed with particular reference to their potential use in the prevention and treatment of atherogenesis and, by extension, coronary heart disease. Laboratory methods of assessing antioxidant defences, lipid peroxidation and the effects of lipid peroxidation are also reviewed and discussed with particular reference to their ability to assess in vivo oxidative stress and lipid peroxidation status. A range of oxidative stress indices are presented and their limitations discussed, but the main focus is on the most commonly used laboratory test for lipid peroxidation, the thiobarbituric acid reacting substances (TBARS) test. Finally, the influence of selected dietary factors on measured peroxidation status is discussed, with particular reference to the antioxidant vitamins C (ascorbic acid) and E (alpha tocopherol) and the type of fatty acids (mono- and poly-unsaturated) in the diet.     

Phospholipid fatty acid composition affects enzymatic antioxidant defenses in cultured Swiss 3T3 fibroblasts

The aim of this work was to study the adaptation of enzymatic antioxidant cell defense to the nature of the membrane polyunsaturated fatty acids (PUFA). 3T3 Swiss fibroblasts were grown for 5 days in a medium supplemented with 50 microM linoleic acid (LA) or eicosapentaenoic acid (EPA) and compared to control cells (C). The phospholipid fatty acid content was evaluated: LA were enriched in n-6 PUFA (27.8%) in comparison to C (6.7%) or EPA (5.6%); EPA were enriched in n-3 PUFA (26.2%) in comparison to LA (4.4%) or C (4.6%). The fatty acid double bond index (DBI) increased from C to LA and EPA. The activities of the three key enzymatic antioxidant defenses, SOD, GPx and GST, increased with the degree of unsaturation of the phospholipid fatty acids. In the cells with fatty acids that are very sensitive to oxidative stress, the higher activities of SOD and GPx might act to limit the initiation of lipid peroxidation and the higher activities of GST and GPx to decrease the toxic effects of the various species produced from lipid degradation.     

Inhibition of class-3 aldehyde dehydrogenase and cell growth by restored lipid peroxidation in hepatoma cell lines

Hepatoma cells have a below-normal content of polyunsaturated fatty acids; this reduces lipid peroxidation and the production of cytotoxic and cytostatic aldehydes within the cells. In proportion to the degree of deviation, hepatoma cells also show an increase in the activity of Class-3 aldehyde dehydrogenase, an enzyme important in the metabolism of lipid peroxidation products and also in that of several drugs. When hepatoma cells with different degrees of deviation were enriched with arachidonic acid and stimulated to peroxidize by ascorbate/iron sulphate, their growth rate was reduced in proportion to the quantity of aldehydes produced and to the activity of aldehyde dehydrogenase. Therefore, 7777 cells, less deviated and with low Class-3 aldehyde dehydrogenase activity, were more susceptible to lipid peroxidation products than JM2 cells. It is noteworthy that repeated treatments with prooxidant also caused a decrease in mRNA and activity of Class-3 aldehyde dehydrogenase, contributing to the decreased growth and viability. Thus, Class-3 aldehyde dehydrogenase could be considered relevant for the growth of hepatoma cells, since it defends them against cell growth inhibiting aldehydes derived from lipid peroxidation.     

Secretion of CTLA4Ig by an SV40 T antigen-transformed islet cell line inhibits graft rejection against the neoantigen

We found that cytochrome c (Cyt c) could oxidize cardiolipin (CL), and detected monoepoxides of linoleic acid (LA) in the fatty acids constituting the oxidized CL. We also found that in the presence of CL and Cyt c, free LA was oxidized and LA monoepoxides were produced. The aim of this study was to elucidate the mechanism of this lipid peroxidation. We concluded that ferric Cyt c produced some radical species from water-soluble oxygen in the presence of CL (CL-Cyt c system) and that radicals oxidized free LA or CL. The CL-Cyt c system may be another LA monoepoxide producing system in the neutrophil and may account for the lipid peroxidation observed in the ischemia-reperfusion-induced cardiac injury.     

The effects of macrolides on the expression of bacterial virulence mechanisms

Human erythrocytes in the circulation undergo dynamic oxidative damage involving membrane lipid peroxidation and protein aggregation during aging. The present study was undertaken to determine the effect of n-3 fatty acid supplementation on lipid peroxidation and protein aggregation in the circulation and also the in vitro susceptibility of rat erythrocyte membranes to oxidative damage. Wistar male rats were fed a diet containing n-6 fatty acid-rich safflower oil or n-3 fatty acid-rich fish oil with an equal amount of vitamin E for 6 wk. n-3 Fatty acid content in erythrocyte membranes of rats fed fish oil was significantly higher than that of rats fed safflower oil. The degree of membrane lipid peroxidation and protein aggregation of rats fed fish oil was not significantly higher than that of rats fed safflower oil when the amounts of phospholipid hydroperoxides, thiobarbituric acid-reactive substances, and detergent-insoluble protein aggregates were measured. When isolated erythrocytes were oxidized under aerobic conditions in the presence of Fe(III), the degree of membrane lipid peroxidation of erythrocytes from rats fed fish oil was increased to a greater extent than that of rats fed safflower oil, whereas the degree of membrane protein aggregation of both groups was increased in a similar extent. Hence, n-3 fatty acid supplementation did not affect lipid peroxidation and protein aggregation in membranes of circulating rat erythrocytes, and the supplementation increased the susceptibility of isolated erythrocytes to lipid peroxidation, but not to protein aggregation, under the aerobic conditions. If a sufficient amount of vitamin E is supplied, n-3 fatty acid supplementation may give no undesirable oxidative effects on rat erythrocytes in the circulation.     

Effects of two hypertrophic cardiomyopathy mutations in alpha-tropomyosin, Asp175Asn and Glu180Gly, on Ca2+ regulation of thin filament motility

The biological activity of the Alzheimer's disease amyloid beta protein may be related to modulation of membrane lipid peroxidation. The effect of amyloid beta protein fragment 25-35 [A beta(25-35)] on lipid peroxidation was examined in liposomes enriched with polyunsaturated fatty acids. The activity of A beta(25-35) was compared to that of A beta(25-35) with either a scrambled sequence [A beta(25-35)scram] or a peptide sequence in which methionine was replaced with leucine [A beta(25-35) met]. A beta(25-35) inhibited lipid peroxidation in a dose- and time-dependent manner. The antioxidant activity of A beta(25-35) was observed at concentrations as low as 10 nM. The relative antioxidant activities of the amyloid beta protein fragments were as follows: A beta(25-35) > A beta(25-35) met > A beta(25-35)scram. The two more potent peptides intercalated into the membrane hydrocarbon core, as determined by small-angle x-ray diffraction approaches. These findings indicate that the amphiphilic A beta(25-35) peptide inhibits lipid peroxidation at low concentrations as a result of physicochemical interactions with the membrane lipid bilayer.     

Fasting serum triglycerides, free fatty acids, and malondialdehyde are increased in preeclampsia, are positively correlated, and decrease within 48 hours post partum

OBJECTIVE: We tested the hypothesis that serum free (nonesterified) fatty acid and triglyceride concentrations are increased in nulliparous women with preeclampsia relative to women with uncomplicated pregnancies and that these lipids decrease post partum, consistent with the known resolution of clinical symptoms. The relationships between serum concentrations of these lipids and the lipid peroxidation metabolite malondialdehyde were also examined. STUDY DESIGN: Predelivery and 24 to 48 hour postpartum venous blood samples were collected from eight women with preeclampsia and nine women with uncomplicated pregnancies after an 8- to 10-hour fast. Sera were analyzed for concentrations of triglycerides, free fatty acids, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and malondialdehyde. RESULTS: Antepartum serum triglyceride and free fatty acid concentrations were increased approximately twofold in women with preeclampsia relative to uncomplicated pregnancies (p <0.02 and 0.004, respectively). Total, high-density lipoprotein, and low-density lipoprotein cholesterol concentrations did not differ between groups. Concentrations of all lipids decreased significantly in both groups within 48 hours post partum. However, triglyceride and free fatty acid concentrations remained higher in women with preeclampsia (p<0.006, both variables). Triglyceride and free fatty acid concentrations correlated positively, both ante partum (R2 0.42, p<0.01) and post partum (R2 0.39, p<0.02). Antepartum concentrations of malondialdehyde were 50% higher in women with preeclampsia (p<0.01) and decreased post partum (p <0.02) but did not decrease in controls (p = 0.07). Antepartum serum triglycerides and free fatty acids correlated positively with malondialdehyde concentrations (R2 0.38, p <0.02, both cases). CONCLUSION: Triglycerides and free fatty acids, but not cholesterol, are increased in preeclampsia and correlate with the lipid peroxidation metabolite malondialdehyde. We speculate that these interactions may contribute to endothelial cell dysfunction in preeclampsia.     

Chronic electrical stimulation of the auditory nerve at high stimulus rates: a physiological and histopathological study

The ubiquitous distribution of peroxisomes and the identification of a number of inherited diseases associated with peroxisomal dysfunction indicate that peroxisomes play an essential part in cellular metabolism. Some of the most important metabolic functions of peroxisomes include the synthesis of plasmalogens, bile acids, cholesterol and dolichol, and the oxidation of fatty acids (very long chain fatty acids > C22, branched chain fatty acids (e.g. phytanic acid), dicarboxylic acids, unsaturated fatty acids, prostaglandins, pipecolic acid and glutaric acid). Peroxisomes are also responsible for the metabolism of purines, polyamines, amino acids, glyoxylate and reactive oxygen species (e.g. O-2 and H2O2). Peroxisomal diseases result from the dysfunction of one or more peroxisomal metabolic functions, the majority of which manifest as neurological abnormalities. The quantitation of peroxisomal metabolic functions (e.g. levels of specific metabolites and/or enzyme activity) has become the basis of clinical diagnosis of diseases associated with the organelle. The study of peroxisomal diseases has also contributed towards the further elucidation of a number of metabolic functions of peroxisomes.     

Effects of oxidative stress on glycerolipid acyl turnover in rat hepatocytes

Lipid peroxidation was induced in freshly isolated rat hepatocytes by incubation in the presence of Fe3+, resulting in accumulation of thiobarbituric acid reactive substances. Analysis of lipid classes revealed that the levels and fatty acid compositions of the two major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), remained unchanged but the levels of triacylglycerols (TAG) were significantly reduced, and some of their polyunsaturated fatty acids were selectively lost as the result of oxidant treatment. Acyl turnover in PC and PE as determined by 18O incorporation from H2 (18)O-containing media remained largely unchanged during oxidant treatment, while some increased turnover of the saturated fatty acids in TAG was observed. We hypothesize that constitutive recycling of membrane phospholipids rather than selective in situ repair eliminates peroxidized species of PC and PE. TAG could serve as an expendable fatty acid reserve, providing a limited but very dynamic pool of polyunsaturated fatty acids for the resynthesis of phospholipids.