Lability of red blood cell membranes to lipid peroxidation: application to humans fed polyunsaturated lipids

Influence of endogenous reproductive hormones on F2-isoprostane levels in premenopausal women: the BioCycle Study

Endogenous reproductive hormones and oxidative stress have been independently linked to risk of chronic disease but mostly in postmenopausal women. The interplay between endogenous reproductive hormones and oxidative stress among premenopausal women, however, has yet to be clearly elucidated. The objective of this study was to investigate the association between endogenous reproductive hormones and F(2)-isoprostanes in the BioCycle Study. Women aged 18-44 years from western New York State were followed prospectively for up to 2 menstrual cycles (n = 259) during 2005-2007. Estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, sex hormone-binding globulin, F(2)-isoprostanes, and thiobarbituric acid-reactive substances were measured up to 8 times per cycle at clinic visits timed by using fertility monitors. F(2)-Isoprostane levels had an independent positive association with estradiol (beta = 0.02, 95% confidence interval: 0.01, 0.03) and inverse associations with sex hormone-binding globulin and follicle-stimulating hormone (beta = -0.04, 95% confidence interval: -0.07, -0.003; beta = -0.02, 95% confidence interval: -0.03, -0.002, respectively) after adjustment for age, race, age at menarche, gamma-tocopherol, beta-carotene, total cholesterol, and homocysteine by inverse probability weighting. Thiobarbituric acid-reactive substances, a less specific marker of oxidative stress, had similar associations. If F(2)-isoprostanes are specific markers of oxidative stress, these results call into question the commonly held hypothesis that endogenous estradiol reduces oxidative stress.

Fatty acid profile of erythrocyte membranes as possible biomarker of longevity

Offspring of long-lived individuals are a useful model to discover biomarkers of longevity. The lipid composition of erythrocyte membranes from 41 nonagenarian offspring was compared with 30 matched controls. Genetic loci were also tested in 280 centenarians and 280 controls to verify a potential genetic predisposition in determining unique lipid profile. Gas chromatography was employed to determine fatty acid composition, and genotyping was performed using Taqman assays. Outcomes were measured for erythrocyte membrane percentage content of saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids (omega-6 and omega-3), geometrical isomers of arachidonic and oleic acids, and total trans-fatty acids. Also, allele and genotyping frequencies at endothelial-nitric oxide synthase and delta-5/delta-6 and delta-9 desaturase loci were considered. Erythrocyte membranes from nonagenarian offspring had significantly higher content of C16:1 n-7, trans C18:1 n-9, and total trans-fatty acids, and reduced content of C18:2 n-6 and C20:4 n-6. No association was detected at endothelial-nitric oxide synthase and delta-5/delta-6 and delta-9 desaturase loci that could justify genetic predisposition for the increased trans C18:1 n-9, monounsaturated fatty acids and decreased omega-6 synthesis. We concluded that erythrocyte membranes derived from nonagenarian offspring have a different lipid composition (reduced lipid peroxidation and increased membrane integrity) to that of the general population.

Oxidative stress after reperfusion with primary coronary angioplasty: lack of effect of glucose-insulin-potassium infusion

OBJECTIVE

To evaluate the oxidative stress status and the modification with glucose-insulin-potassium (GIK) therapy in patients with acute myocardial infarction undergoing primary percutaneous transluminal coronary angioplasty.

DESIGN

Prospective, randomized, double-blinded, placebo-controlled study.

SETTING

Cardiac intensive care unit at the university hospital.

PATIENTS

Twenty patients were randomized to GIK solution (30% glucose in water with insulin 50 IU/L, and KCl 40 mM) vs. placebo (normal saline) at 1.5 mL/kg/hr for 24 hrs. The control group was 15 healthy volunteers with no heart disease.

INTERVENTIONS

Eligible patients were randomized by a blinded pharmacist, patients with acute myocardial infarction were treated by primary percutaneous transluminal coronary angioplasty and randomized to GIK or placebo (saline solution). Primary angioplasty was successful in nine of ten patients (90%) and ten of ten patients (100%) in the GIK and placebo groups, respectively. Nine (100%) and six (60%) patients from GIK and placebo groups, respectively, underwent stent implantation.

MEASUREMENTS AND MAIN RESULTS

We determined plasma levels of lipid peroxidation estimated by the malondialdehyde assay, superoxide dismutase, glutathione peroxidase, and catalase erythrocyte activities at admission and 0.5 and 24 hrs after angioplasty. Baseline determinations were compared with a control group (n = 15). Baseline clinical characteristics and time to treatment (4.5 +/- 3.5 hrs) were similar between groups. Angioplasty success rate (Thrombolysis in Myocardial Infarction [TIMI] 3 flow with residual stenosis < or = 30%) was 90% and 100% in GIK and placebo groups, respectively. Patients with acute myocardial infarction had an increase of malondialdehyde at baseline (2.9 +/- 1.7 vs. 1.1 +/- 0.3 microM, p <.01) and lower enzymatic activities of superoxide dismutase (0.5 +/- 0.5 vs. 1.3 +/- 0.4 U/mg hemoglobin, p <.01) and catalase (147 +/- 73 vs. 198 +/- 31 U/g hemoglobin, p <.01). These measurements did not change significantly after angioplasty and no differences were observed between GIK and placebo groups.

CONCLUSION

Patients with acute myocardial infarction had increased levels of oxidative stress associated with a reduction in enzymatic antioxidant reserve. Administration of GIK solution did not improve these abnormalities among patients undergoing primary angioplasty.

Comparison between fat intake assessed by a 3-day food record and phospholipid fatty acid composition of red blood cells: results from the Monitoring of Cardiovascular Disease-Lille Study

We investigated the relationship between assessment of fatty acid intake by a 3-day food record and by capillary gas chromatography of erythrocyte phospholipid fatty acid. The study was performed in a sample of 244 men aged 45 to 66 years from the general population who were participating in the Monitoring of Cardiovascular Disease (MONICA)-Lille survey. The relationship between each nutrient and food item and erythrocyte phospholipid fatty acid was investigated by a regression model on proportion including each food item and nutrient as a dependent variable and percentage of fatty acid and covariables (nonalcoholic energy intake, age, alcohol intake, and smoking) as independent variables. Polyunsaturated fat and linoleic acid intake were positively correlated with linoleic acid content of erythrocytes (beta = 0.641 and 0.604, respectively, P < .001). Monounsaturated and saturated fat intake were correlated with oleic acid (beta = 0.375 and 0.373, respectively, P < .01). Fish intake correlated positively with docosahexaenoic acid (DHA) (beta = 0.383, P < .001) and negatively with arachidonic acid (beta = -0.509, P < .01). These data confirm, on a group level, a good relationship between assessment of polyunsaturated fat intake by a 3-day record and linoleic acid content of erythrocyte membranes. These data suggest that erythrocyte oleic acid content is a marker of both saturated and monounsaturated fat intake.

Actions of arachidonic acid on erythrocyte membrane Rb permeability

The effects of non-esterified arachidonic acid (AA) on erythrocyte membrane ion permeability have been studied using 86Rb flux measurements. [14C]AA was used to quantify membrane incorporation of AA and to show AA removal by albumin washing. The actions of vitamin E and other antioxidants on the effects of AA were examined. Reversible membrane incorporation of 700-2000 nmol AA per ml cells was achieved without significant haemolysis or morphological change. AA incorporation caused a reversible mean increase in bumetanide-sensitive Rb influx of 34% (S.E.M. 4.5, n = 23). This action could be partially prevented by co-incubation with vitamin E, but not by Trolox or dithioerythritol. AA incorporation caused an irreversible mean increase in residual Rb permeability (bumetanide and ouabain insensitive) of 130% (S.E.M. 22, n = 20), associated with a rise in intracellular Na and a fall in intracellular K concentrations. This action was also partially prevented by co-incubation with vitamin E. The effects of AA incorporation on Na,K-ATPase function were difficult to quantify because of the concomitant rises in intracellular Na but the data are consistent with approximately 20% inhibition of activity. Modulation of membrane ion permeability by AA appears to be partially mediated by lipid peroxidation and may have pathophysiological significance.

Free radical-mediated lipid peroxidation in cells: oxidizability is a function of cell lipid bis-allylic hydrogen content

Oxidizability of lipids in homogeneous solution varies linearly with the extent of their unsaturation. In vitro cellular, as well as in vivo, studies of oxidizability have generally relied upon chemical indicators of peroxidation such as thiobarbituric acid-reactive substances. To examine the oxidizability of lipids in cells, we have measured oxygen uptake and, using electron paramagnetic resonance spin trapping with alpha-(1-oxo-4-pyridyl)-N-tert-butylnitrone (POBN), the real time generation of lipid-derived free radicals. We have used our experimental in vitro cellular lipid modification model to examine the rate and extent of lipid peroxidation versus the degree of lipid unsaturation in L1210 murine leukemia cells. Lipid peroxidation was stimulated using the prooxidants iron, ascorbate, and the ether lipid compound 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine. We did a total cellular lipid analysis to determine the number of lipid carbon-carbon double bonds contained in L1210 cells enriched with eight fatty acids of different degrees of unsaturation. We found in cellular lipids that (i) lipid chain length had no apparent effect on the rate or extent of radical formation; (ii) the maximum amount of lipid radical generated increases with the total number of bis-allylic positions in the cellular lipids; and, most importantly, (iii) the rate of cellular lipid peroxidation increases exponentially with the number of bis-allylic positions. Our quantitative results clearly demonstrate, for the first time, that the number of bis-allylic positions contained in the cellular lipids of intact cells determines their susceptibility, i.e., oxidizability, to free radical-mediated peroxidative events.

Bioefficiency of different tocopherols in chicken as assessed by haemolysis test and microsomal pentane production

Bioefficiencies of alpha-, gamma- and delta-tocopherol in comparison with all-rac-alpha-tocopherol were established in broiler chickens. For this, 1-d-old male broiler chickens received a diet deficient in vitamin E and supplemented with increasing doses of the corresponding tocopheryl acetates. After 2 and 3 weeks of feeding, the animals were killed to obtain blood and liver samples. The ex vivo tests used were detergent-induced haemolysis and pentane production by liver microsomes. Bioefficiencies were calculated by comparison of the dose-response curves. It is concluded that haemolysis and pentane production are appropriate indicators of the bioefficiency of tocopherols in broiler chickens. The values obtained by both tests hardly differed and agree well with the figures previously obtained from rats and other species.

Abnormal rheological response of erythrocytes caused by nitroimidazoles and hyperthermia

The aim of the present study was to investigate the response of erythrocytes to hyperthermia in combined treatment with nitroimidazoles. The efficiency of nitroimidazoles and physical agents on the rheological response of erythrocytes was measured by the viscosimetric-diffractometric method in a continuous osmotic gradient with constant shear stress of 100 dyn/cm2. We found that three newly synthesized dinitro- or nitroimidazole derivatives caused oxidative damage of erythrocytes in aerobic conditions. Nitroimidazole structure-dependent decrease of erythrocyte deformability was accompanied by oxidation of haemoglobin and depletion of reduced glutathione, lipid peroxidation and alteration of membrane structure indicated by a decrease of the ANS fluorescence intensity and increased production of MDA. Heat treatment per se (from 42 to 45 degrees C) only slightly decreased the erythrocyte deformability, but markedly enhanced the structure-dependent effect of nitroimidazoles. Erythrocytes heated at 45 degrees C with dinitroimidazole derivative III lost their deformability without haemolysis. Dithiothreitol used in combination with nitroimidazoles during a heating period to 43.5 degrees C protected cell deformability entirely, indicating an important role for disulphide bond formation in membrane proteins submitted to oxidative stress and hyperthermia.

Headspace gas chromatography of volatile lipid peroxidation products from human red blood cell membranes

An improved headspace capillary gas chromatographic (GC) method was developed to measure the oxidative susceptibility of human red blood cell (RBC) membranes. This method analyzed volatile peroxidation products of both n-6 (hexanal and pentane) and n-3 (propanal) polyunsaturated fatty acids. Oxidative susceptibility tests were standardized by incubating in a sealed 10-mL headspace bottle 0.25 or 1 mL of human RBC membrane in 40 mM phosphate buffer for 1 hr at 37 degrees C with a mixture of Fe++, ascorbic acid and H2O2. Sodium dodecyl sulfate increased significantly the amount of hexanal measured by headspace GC. By this standard headspace method, in one series of red blood cell membranes (RBCM) samples a four-fold variation in oxidative susceptibility was observed in RBCM from blood freshly drawn from six healthy subjects. In another series of RBCM samples a sixteen-fold variation in oxidative susceptibility was noted in frozen RBCM from blood freshly drawn from five healthy subjects. Correlation between hexanal formation and polyunsaturated fatty acids (PUFA) depletion provided good evidence that under these standard conditions hexanal is exclusively derived from the oxidation of arachidonic acid. Hydroperoxides of arachidonic acid are more readily formed and decomposed than those of linoleic acid in the presence of Fe++, ascorbic acid and H2O2 to produce hexanal as the main product that can be readily analyzed by headspace GC. This method may provide a useful tool to study susceptibility toward lipid peroxidative damage in human RBC membranes.

Effect of dietary menhaden, Canola and partially hydrogenated soy oil supplemented with vitamin E upon plasma lipids and platelet aggregation

Male Fisher rats were fed chow diets for two weeks after which they were divided into seven groups of ten rats each and fed 20% Canola, 20% menhaden, 20% partially hydrogenated soy oil (PHSO) or chow only, with or without 500 mg/Kg dietary vitamin E in chow containing 2% cholesterol for six weeks. Triglycerides were lower in the menhaden group and were essentially the same in the E supplemented groups as in their unsupplemented cohorts. Plasma cholesterol was higher in the Canola, and lower in the menhaden, groups, compared to the PHSO group. Cholesterol was the same in the E supplemented groups as in their unsupplemented cohorts. Plasma thiobarbituric acid reactant substances (TBARS) were higher in the menhaden group, compared to the chow group. Vitamin E supplementation lowered TBARS in the menhaden and PHSO groups, compared to the unsupplemented cohorts. Collagen induced platelet aggregation was lower in both Canola and menhaden groups, compared to the PHSO group. Vitamin E supplementation lowered collagen induced platelet aggregation only in the PHSO group. Thrombin induced platelet aggregation was lower in the Canola group, compared to the PHSO group. Vitamin E supplementation did not affect thrombin induced platelet aggregation compared to unsupplemented cohorts. Plasma vitamin E levels were lowest in the menhaden supplemented group compared to all other groups not receiving E, suggesting a greater requirement for E in this group. Finally, vitamin E supplementation raised the plasma E levels in all groups except the menhaden group when compared to unsupplemented cohorts.