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Cholesterol was used as an in situ probe for studying mechanisms of lipid peroxidation in isolated erythrocyte membranes subjected
to different prooxidant conditions. The membranes were labeled with [14C]cholesterol by exchange with prelabeled unilamellar liposomes and photosensitized with hematoporphyrin derivative. Irradiation
with a dose of blue light resulted in thiobarbituric acid-detectable lipid peroxidation that was increased markedly by subsequent
dark incubation with 0.5–1.0 mM ascorbate (AH−). Ascorbate-stimulated lipid peroxidation was inhibited by EDTA, desferrioxamine (DOX) and butylated hydroxytoluene (BHT),
suggesting that the process is free radical in nature and catalyzed by membrane-bound iron. Thin layer chromatography and
radiometric scanning of extracted lipids from photooxidized membranes revealed that the major oxidation product of cholesterol
was the 5α-hydroperoxide (5α-OOH), a singlet oxygen adduct. Post-irradiation treatment with AH−/Fe(III) resulted in an almost-total disappearance of 5α-OOH and the preponderance of free radical oxidation products, e.g.
7-ketocholesterol, the epimeric 7α-/7β-hydroperoxides (7α-/7β-OOH) and their respective alcohols (7α-/7β-OH). EDTA, DOX and
BHT inhibited the formation of these products, while catalase and superoxide dismutase had no effect. These results are consistent
with a mechanism involving 1-electron reduction of photogenerated hydroperoxides to oxyl radical, which trigger bursts of
free radical lipid peroxidation. Though generated in this system, partially reduced oxygen species, viz. superoxide, hydrogen
peroxide and hydroxyl radical, appear to be relatively unimportant in the autoxidation process.
Presented at the symposium “Free Radicals Antioxidants, Skin Cancer and Related Diseases” at the 78th AOCS Annual Meeting
in New Orleans, LA, May 1987. 相似文献
3.
Lipid hydroperoxide was generated in human erythrocyte membranes by irradiation with near ultraviolet (UV) light in the presence
of a photosensitizer, hematoporphyrin, but no production of 2-thiobarbituric acid-reactive materials (malonaldehyde and its
precursors) was detected. Incubation of the irradiated membranes with CuSO4 led to increased levels of hydroperoxide and formation of malonaldehyde. Hydroperoxides were essential for initiating the
Cu(II)-catalyzed peroxidation as no significant activity was observed with nonirradiated membranes and Cu(II) unless an organic
peroxide, either t-butyl hydroperoxide or cumene hydroperoxide, was added. Catalytic activity was also found with Fe(II),
but not with other metal ions tested. The peroxidation catalyzed with Cu(II) was partially inhibited by several singlet oxygen
quenchers but was not affected by superoxide dismutase, catalase or OH• radical scavengers. The possible involvement of singlet oxygen in the Cu(II)-catalyzed peroxidation reaction was further
supported by a 3-fold enhancement of malonaldehyde production in D2O. 相似文献
4.
Cu++ was uniquely capable of catalyzing the peroxidation of rat erythrocyte membrane lipid in the presence of 10 mM H2O2, whereas several other transition metal ions were without significant effect. In contrast, peroxidation of soybean phospholipid
liposomes could be catalyzed with decreasing efficiency by Co++, Cu++, Pb++, or Cr+++ also in the presence of H2O2. The effect of imidazole on Cu++-catalyzed lipid peroxidation was stimulatory in liposomes and inhibitory in membrane preparations, whereas EDTA, histidine,
citrate and alanine inhibited peroxidation in both systems. EDTA could stop the peroxidation after initiation, but catalase
could not, indicating that Cu++ alone was necessary for the propagation of the chain reaction. Competitive inhibition studies with various scavengers of
hydroxyl radicals or singlet oxygen and the absence of significant reaction enhancement by D2O indicated that neither of these reactive oxygen species was a major mediator in the Cu++-H2O2 oxidative system. A copper-oxygen complex may be directly involved in the initiation of peroxidation. Normal erythrocyte
membranes and phospholipid liposomes also differ in their sensitivities toward external oxidative stress. In the absence of
H2O2, Cu++ (0.2 mM) was capable of catalyzing lipid peroxidation in liposomes, aged erythrocyte membranes and membranes from vitamin-E-deficient
rats; however, freshly prepared membranes from control rats and liposomes containing α-tocopherol required H2O2 greater than 2 mM for the catalytic effect of Cu++ to be observed. 相似文献
5.
Lipid peroxidation has gained renewed attention with increasing evidence showing its biological role in producing toxic compounds
and cellular signaling mediators. The assessment of lipid peroxidation levels in vivo is difficult partly because lipids are
oxidized by different oxidants by different mechanisms to give versatile types of products, which may undergo metabolism and
secondary reactions. In the present study, total hydroxyoctadecadienoic acids (tHODE) and 7α- and 7β-hydroxycholesterol (t7-OHCh)
from 44 healthy human subjects were assessed as biomarkers after reduction with sodium borohydride followed by saponification
with potassium hydroxide comparing with the prevailing standard 8-isoprostaglandin F2α (t8-iso-PGF2α). The average concentrations of tHODE, total 8-isoprostaglandin F2α (t8-iso-PGF2α), t7α-OHCh, and t7β-OHCh were 203, 0.727, 87.1, and 156 nmol/l plasma and 1,917, 12.8, 1,372, and 3,854 nmol/l packed erythrocytes,
respectively. The ratios of tHODE and t7-OHCh to the parent substrates were 194 and 3,519 μmol tHODE/mol linoleates and 40.9
and 686 μmol t7-OHCh/mol cholesterol in plasma and erythrocytes, respectively. It was found that (1) t7-OHCh in blood was
unexpectedly high, as high as or even higher than tHODE, (2) the amounts of tHODE was more than 100 fold higher than t8-iso-PGF2α (3) the level of lipid oxidation products in erythrocytes was higher than that in plasma, and (4) lipid peroxidation products
level tended to increase while antioxidant level decrease with age. These products may be used as potential biomarker for
assessment of lipid peroxidation and oxidative stress in vivo. 相似文献
6.
Chronic ethanol treated rats were found to have enhanced ethanol metabolism and to metabolize ethanol in vivo in the presence
of an inhibitor of alcohol dehydrogenase. In vitro studies of the hepatic microsomal system thought to the responsible for
this activity showed it to be markedly induced. Lipid peroxidation also was enhanced in the ethanol treated animals. The lipid
peroxidation was shown to be uncoupled from the microsomal nicotinamide adenine dinucleotide phosphate, reduced form, oxidase
activity by a low concentration of azide. 相似文献
7.
A new method for modelling of liquid-phase decomposition reactions was developed. The method is based on rapid on-line mass spectrometric analysis of liberated products in gas phase. The experimental set-up and the generalized modelling principles were introduced. The approach was demonstrated with first and zero order as well as for complex decomposition kinetics (decomposition of peracetic acid). The interaction of decomposition kinetics and mass-transfer effects was illustrated with theoretical and real reaction conditions. The approach is generally applicable to any liquid-phase decomposition, provided that gaseous products can be quantitatively analyzed. 相似文献
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Antioxidant Phenolics of Millet Control Lipid Peroxidation in Human LDL Cholesterol and Food Systems
Anoma Chandrasekara Fereidoon Shahidi 《Journal of the American Oil Chemists' Society》2012,89(2):275-285
Phenolic extracts from seven millet varieties, namely kodo, finger (Ravi), finger (local), proso, foxtail, little and pearl
were evaluated for their inhibitory effects on lipid peroxidation in in-vitro copper-mediated human LDL cholesterol oxidation
and several food model systems, namely cooked comminuted pork, stripped corn oil, and linoleic acid emulsion. The total phenolic
content (TPC) and free radical scavenging activities were measured. The TPC ranged from 146 to 1156 μmol ferulic acid equiv
(FAE)/g crude extract and the corresponding values based on defatted weight of grain ranged from 8.6 to 32.4 μmol FAE/g. At
a final concentration of 0.05 mg/mL, millet extracts inhibited LDL cholesterol oxidation by 1–41%. All seven varieties exhibited
effective inhibition of lipid oxidation in food systems used in this study and kodo millet exhibited superior inhibition of
lipid peroxidation, similar to butylated hydroxyanisole at 200 ppm. Thus, millets may serve as a natural source of antioxidants
in food applications and as a nutraceutical and functional food ingredient in health promotion and disease risk reduction. 相似文献
10.
Free fatty acids accumulate in plant membranes after exposure of plants to environmental stress, such as freezing and desiccation.
Fatty acid accumulation has been linked to various biophysical changes and to the occurrence of lipid peroxidation, but the
relationships appear complex and inconsistent. The interactions between oxygen free radicals, free fatty acids and lipid peroxidation
in plant membranes were examined further by studying peroxidation reactions in a model membrane system composed of a complex
mixture of plant phospholipids, including various free fatty acids. Multilamellar liposomes were treated with oxygen free
radicals generated from iron ascorbate. Increased concentrations of free palmitic acid up to 10 mol% (fatty acid/phospholipid)
reduced the production of aldehydes detected by the thiobarbituric acid assay, but enhanced the production of fluorescent
products. By contrast, increased concentrations of free linolenic acid increased aldehyde production and reduced the formation
of fluorescent products. The two free fatty acids both enhanced the susceptibility of phospholipids to degradation as shown
by the reduced recovery of esterified polyunsaturated fatty acids (linoleic and linolenic). The free radical reactions with
or without free fatty acid additions catalyzed the selective degradation of phospholipids in the order phosphatidylethanolamine
> phosphatidylcholine > phosphatidylinositol > phosphatidylglycerol. Selective degradation of phospholipids is often observed
after periods of environmental stress or during senescence of plants, and has been cited as evidence for the involvement of
phospholipases in these degenerative processes. The results indicate that selectivity is not a criterion for eliminating the
involvement of oxygen free radicals in these degenerative processes. Furthermore, the results suggest that modifications of
lipid composition during a plant's acclimation to adverse environments may determine the types of free radical reactions that
occur due to stress. 相似文献
11.
The purpose of this study was to investigate in healthy humans the effect of eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA) intake, alone or in combination with dL-α-tocopherol acetate (vitamin E) supplements on lipid peroxidation. Eightly
men were randomly assigned in a double-blind fashion to take daily for 6 wk either menhaden oil (6.26 g, n−3 fatty acids)
or olive oil supplements with either vitamin E (900 IU) or its placebo. Antioxidant vitamins, phospholipid composition, malondialdehyde
(MDA), and lipid peroxides were measured in the plasma at baseline and week 6. At the same time, breath alkane output was
measured. Plasma α-tocopherol concentration increased in those receiving vitamin E (P<0.0001). In those supplemented with n−3 fatty acids, EPA and DHA increased in plasma phospholipids (P<0.0001) and plasma MDA and lipid peroxides increased (P<0.001 and P<0.05, respectively). Breath alkane output did not change significantly and vitamin E intake did not prevent the increase
in lipid peroxidation during menhaden oil supplementation. The results demonstrate that supplementing the diet with n−3 fatty
acids resulted in an increase in lipid peroxidation, as measured by plasma MDA release and lipid peroxide products, which
was not suppressed by vitamin E supplementation. 相似文献
12.
Lipid peroxidation in rat tissue homogenates: Interaction of iron and ascorbic acid as the normal catalytic mechanism 总被引:1,自引:0,他引:1
Iron and ascorbic acid appear to be the normal catalytic components responsible for the lipid peroxidation reaction in aerobically
incubated rat tissue homogenates. The amounts of each present in the catalytically-active fractions of rat liver, brain, testis,
and kidney are appropriate to explain the lipid peroxidation reaction measured. Utilization of ascorbic acid as part of the
normal catalytic mechanism is indicated by the following: The catalytic activity of the tissue soluble phase occurs only in
the small molecule fraction eluted from Sephadex, and ascorbic acid occurs only in this fraction; the extent of catalysis
by the small molecule fractions of the soluble phases from several tissues is proportional to their ascorbic acid content;
and pH effect on lipid peroxidation is the same for both soluble-phase and ascorbic acid catalysis. Utilization of iron as
part of the normal catalytic mechanism is indicated by EDTA inhibition studies and by measurements of pH effects. Previous
studies have demonstrated the lack of catalytic activity by cations other than iron for the lipid peroxidation reaction in
homogenates. Lipid peroxidation is inhibited at high tissue concentration and the inhibition is due to components occurring
in the large molecule fraction of the soluble phase. 相似文献
13.
Rats were fed for 5 weeks either 10% (w/w) menhaden oil (MO) or a 10% corn oil-lard (COL) mixture (1∶1) in diets with ≤5 IU
or ≤2 IU/kg vitamin E, respectively, or the same diets supplemented with d-α-tocopheryl succinate to a total of 35 and 180
IU vitamin E/kg, respectively. Slices of liver and heart from these rats were used to study lipid peroxidationin vitro. Thiobarbituric acid-reactive substances (TBARS) were measured in the medium after incubation of the slices at 37°C for 1
hr in the absence (uninduced) and presence of 0.5 mM tert-butyl hydroperoxide (induced). The release of TBARS from slices
of heart and liver from rats fed either lipid decreased with increasing levels of dietary vitamin E. At the same level of
dietary vitamin E, TBARS release was greater for slices of liver and heart from the MO-fed rats than from the COL-fed rats.
Application of the TBARS data to a model simulating the experimental conditions showed a good correlation (r=0.95, p<0.001)
between experimental and simulated values. Of the 16∶0–22∶6 fatty acids measured in liver from MO-fed rats, 15.4% was n−6
fatty acids and 29.9% was n−3 fatty acids; in liver from COL-fed rats, the respective values were 37.4% and 3.7%. Liver and
kidney vitamin E levels were unaffected by the dietary lipid. This study demonstrated that a dietary fish oil increased the
susceptibility of rat liver and heart toin vitro lipid peroxidation, and that vitamin E decreased TBARS in tissues from rats fed COL to lower levels than for tissues from
rats fed MO. The results suggest that there might also be an increased requirement for dietary antioxidants by humans using
fish oil supplements. 相似文献
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Zhaoyuan Zhu Li Zhang Ruilong Sheng Jian Chen 《International journal of molecular sciences》2022,23(7)
Safe and efficient delivery of small interfering RNA (siRNA) is essential to gene therapy towards intervention of genetic diseases. Herein, we developed a novel cationic cholesterol lipid derivative (CEL) in which cholesterol hydrophobic skeleton was connected to L-lysine cationic headgroup via a hexanediol linker as the non-viral siRNA delivery carrier. Well-organized CEL/siRNA nanocomplexes (100–200 nm) were prepared by microfluidic-assisted assembly of CEL and siRNA at various N/P ratios. The CEL and CEL/siRNA nanocomplexes have lower cytotoxicity compared with bPEI25k. Delightfully, we disclosed that, in Hela–Luc and H1299–Luc cell lines, the micro-fluidic-based CEL/siRNA nanocomplexes exhibited high siRNA transfection efficiency under both serum-free condition (74–98%) and low-serum circumstances (80–87%), higher than that of lipofectamine 2000. These nanocomplexes also showed high cellular uptake through the caveolae/lipid-raft mediated endocytosis pathway, which may greatly contribute to transfection efficiency. Moreover, the time-dependent (0–12 h) dynamic intracellular imaging demonstrated the efficient delivery to cytoplasm after lysosomal co-localization. The results indicated that the microfluidic-based CEL/siRNA nanosystems possessed good stability, low cytotoxicity, high siRNA delivery efficiency, rapid cellular uptake and caveolae/lipid raft-dependent internalization. Additionally, this study provides a simple approach for preparing and applying a “helper lipid-free” cationic lipid siRNA delivery system as potential nanotherapeutics towards gene silencing treatment of (tumor) diseases. 相似文献
16.
Haikal Z Play B Landrier JF Giraud A Ghiringhelli O Lairon D Jourdheuil-Rahmani D 《Lipids》2008,43(5):401-408
In the human intestinal content after a meal, cholesterol is dispersed in a complex mixture of emulsified droplets, vesicles, mixed micelles and precipitated material. The aim of this study was to determine the contribution of the main intestinal cholesterol transporters (NPC1L1, SR-BI) to the absorption processes, using different cholesterol-solubilizing donors. Cholesterol donors prepared with different taurocholate concentrations were added to an apical medium of differentiated TC7/Caco-2 cells. As the taurocholate concentrations increased, cholesterol donor size decreased (from 712 to 7 nm in diameter), which enhanced cholesterol absorption in a dose-dependent manner (38-fold). Two transport processes were observed: (1) absorption from large donors exhibited low-capacity transport with no noticeable transporter contribution; (2) efficient cholesterol absorption occurs from small lipid donors (相似文献
17.
Karli Lipinski Matthew J. McKay Fahmida Afrose Dr. Ashley N. Martfeld Prof. Roger E. Koeppe II Dr. Denise V. Greathouse 《Chembiochem : a European journal of chemical biology》2019,20(21):2784-2792
Membrane proteins are essential for many cell processes yet are more difficult to investigate than soluble proteins. Charged residues often contribute significantly to membrane protein function. Model peptides such as GWALP23 (acetyl-GGALW5LAL8LALALAL16ALW19LAGA-amide) can be used to characterize the influence of specific residues on transmembrane protein domains. We have substituted R8 and R16 in GWALP23 in place of L8 and L16, equidistant from the peptide center, and incorporated specific 2H-labeled alanine residues within the central sequence for detection by solid-state 2H NMR spectroscopy. The resulting pattern of [2H]Ala quadrupolar splitting (Δνq) magnitudes indicates the core helix for R8,16GWALP23 is significantly tilted to give a similar transmembrane orientation in thinner bilayers with either saturated C12:0 or C14:0 acyl chains (1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)) or unsaturated C16:1 Δ9 cis acyl chains. In bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC; C18:1 Δ9 cis) multiple orientations are indicated, whereas in longer, unsaturated 1,2-dieicosenoyl-sn-glycero-3-phosphocholine (DEiPC; C20:1 Δ11 cis) bilayers, the R8,16GWALP23 helix adopts primarily a surface orientation. The inclusion of 10–20 mol % cholesterol in DOPC bilayers drives more of the R8,16GWALP23 helix population to the membrane surface, thereby allowing both charged arginines access to the interfacial lipid head groups. The results suggest that hydrophobic thickness and cholesterol content are more important than lipid saturation for the arginine peptide dynamics and helix orientation in lipid membranes. 相似文献
18.
Janicka M Kot-Wasik A Kot J Namieśnik J 《International journal of molecular sciences》2010,11(11):4631-4659
Isoprostanes (IsoPs) are key biomarkers for investigating the role of free radical generation in the pathogenesis of human disorders. To solve IsoPs-related problems with regard to isoprostanes, analytical tools are required. This paper reviews the problems and trends in this field focusing on the methodology for assaying biomarkers in exhaled breath condensate (EBC) samples. A large amount of work has been done in the qualitative and quantitative analysis of IsoPs, but a standardized method has yet to emerge. The methodologies described differ, either in the sample preparation steps or in the detection techniques, or both. Requiring a number of chromatographic steps, the relevant extraction and purification procedures are often critical and time-consuming, and they lead to a substantial loss of target compounds. Recent data show that EBC is a promising non-invasive tool for the evaluation of different diseases. Two main analytical approaches have been adopted for IsoPs measurement: immunological methods and mass spectrometry. The methodologies for the extraction, purification and analysis of IsoPs in EBC samples are presented. 相似文献
19.
J. Irwandi Y. B. Che Man D. D. Kitts J. Bakar S. Jinap 《Journal of the American Oil Chemists' Society》2000,77(9):945-951
A study was conducted to investigate the oxidative behavior of various mixtures of rosemary, sage, and citric acid in a linoleic acid model system by oxygen consumption measurement and in a palm olein system by differential scanning calorimetry (DSC) analysis. Response surface methodology was used to optimize the use of the mixtures. Results showed that rosemary and sage were two important factors for the protective index (PI). The two antioxidants were highly significantly (P<0.001) in influencing PI values. There was a significant (P<0.01) synergistic effect between rosemary and sage on PI values. Citric acid was also found to be significant (P<0.05) for PI. With respect to onset time (T o ), all three antioxidants were significant (P<0.05). However, no significant interaction among antioxidants was found for T o . Mathematical models for both PI and T o could be developed with confidence. The R 2 values for PI and T o were 0.992 and 0.926, respectively. A combination of 0.078% rosemary, 0.067% sage and 0.037% citric acid was the optimal combination for PI, whereas a combination of 0.068% rosemary, 0.075% sage, and 0.039% citric acid was required to reach the optimal T o value. 相似文献
20.
When choosing which colors to offer in their product lines, firms often rely upon consumer preference models that do not account for the heterogeneity of their target market and do not consider the trade‐offs consumers are willing to make for different color options. For this research we used visual conjoint analysis to assess preference for backpack color and then modeled respondent utilities with a Bayesian hierarchal multinomial logit model. This provided counter intuitive results in which product line color options are not additive but each color changes depending on the number of options the firm is willing to offer and that colors which seem to dominate secondary preferences within a target market may not be the best colors to choose for product line expansion. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 445–456, 2016 相似文献