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Query: UNIPROT:P30536 (PBS)
 9,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several lines of evidence indicate that oxidized LDL (Ox-LDL) may promote atherogenesis. Hence, the role of antioxidants in the prevention of LDL oxidation needs to be determined. beta-Carotene, in addition to being an efficient quencher of singlet oxygen, can also function as a radical-trapping antioxidant. Since previous studies have failed to show that beta-carotene inhibits LDL oxidation, we re-examined its effect on the oxidative modification of LDL. For these studies, LDL was oxidized in both a cell-free (2.5 microM Cu2+ in PBS) and a cellular system (human monocyte macrophages in Ham's F-10 medium). beta-Carotene inhibited the oxidative modification of LDL in both systems as evidenced by a decrease in the lipid peroxide content (thiobarbituric-acid-reacting substances activity), the negative charge of LDL (electrophoretic mobility) and the formation of conjugated dienes. By inhibiting LDL oxidation, beta-carotene substantially decreased its degradation by macrophages. beta-Carotene (2 microM) was more potent than alpha-tocopherol (40 microM) in inhibiting LDL oxidation. Thus, beta-carotene, like ascorbate and alpha-tocopherol, inhibits LDL oxidation and might have an important role in the prevention of atherosclerosis.
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PMID:beta-Carotene inhibits the oxidative modification of low-density lipoprotein. 195 40

Serpulina hyodysenteriae produces an oxygen-stable heat-labile hemolysin that may be an important virulence factor in the pathogenesis of swine dysentery. We examined the effect of Ca2+, Co2+, Cu2+, Fe2+, Mg2+, Mn2+, Ni2+, and Zn2+ on the hemolytic activity of cell-free supernatant (CFS) from S. hyodysenteriae, isolate B204. Cells harvested from late logarithmic phase cultures were incubated in phosphate-buffered saline containing glucose and RNA-core (PBS-GR) with or without cations and the hemolytic activity of CFS obtained after successive 30 min incubation and washing cycles was determined. The addition of either ZnSO4 or CuSO4 to the PBS-GR caused complete inhibition of hemolytic activity after 3 cycles; other cations gave results similar to control extracts. Reduction in the concentration of Zn2+ in CFS by 60 to 80% after each incubation cycle and binding of Zn2+ by EDTA indicated that Zn2+ was associated with the cell fraction, and inhibition of hemolysin activity was specifically mediated by Zn2+. When the spirochetes were washed after incubation in the presence of ZnSO4 for 2 cycles and incubated in fresh PBS-GR without Zn2+, inhibition of hemolysin activity remained unchanged, indicating that the inhibitory effect of ZnSO4 was due to a direct action of ZnSO4 on the spirochetes. Since neither the viability of the spirochetes nor the activity of pre-formed hemolysin were affected by the presence of ZnSO4, the inhibitory effect of Zn2+ cations was attributed to reduced biosynthesis by viable S. hyodysenteriae cells rather than interference of Zn2+ cations with lysis of erythrocytes by the hemolysin. Transmission electron microscopic examination of spirochetes after incubation in PBS-GR containing ZnSO4 revealed clumping of ribosomes and clearing of cell cytoplasm.
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PMID:Effect of divalent cations on hemolysin synthesis by Serpulina (Treponema) hyodysenteriae: inhibition induced by zinc and copper. 780 26

Oxidation of lipids and lipoproteins by macrophages is an important event during atherogenesis. Activation of monocytic cells by zymosan and other agonists results in the release of multiple oxidant species and consequent oxidation of LDL. We now show evidence that ceruloplasmin, a copper-containing acute phase reactant, is secreted by zymosan-activated U937 monocytic cells, and that the protein has an important role in LDL oxidation by these cells. In one approach, ceruloplasmin has been shown to exhibit oxidant activity under the appropriate conditions. Exogenous addition of purified human ceruloplasmin stimulates U937 cell oxidation of LDL to nearly the same extent as activation by zymosan. In contrast to previous cell-free experiments (Ehrenwald, E., G.M. Chisom, and P.L. Fox. 1994. Intact human ceruloplasmin oxidatively modifies low density lipoprotein. J. Clin. Invest. 93:1493-1501.) in which ceruloplasmin by itself (in PBS) oxidizes LDL, under the conditions of the current experiments (in RPMI 1640 medium) ceruloplasmin only oxidizes LDL in the presence of cells; the mechanism by which cells overcome the inhibition by medium components has not been ascertained. As further evidence for a role of ceruloplasmin, activation of U937 cells with zymosan induces ceruloplasmin mRNA and ceruloplasmin protein synthesis after a 5-6 h lag that is consistent with that preceding LDL oxidation. Finally, neutralization by a highly specific polyclonal antibody to human ceruloplasmin inhibits LDL oxidation by at least 65%. Moreover, multiple antisense oligodeoxynucleotides targeted to different regions of the ceruloplasmin mRNA block LDL oxidation by up to 95%. The specific action of the antisense oligonucleotides has been verified by showing inhibition of ceruloplasmin synthesis and by the ability of exogenous ceruloplasmin to overcome the inhibition. In summary, these results are consistent with a mechanism in which cell-derived ceruloplasmin participates in oxidation of LDL by U937 monocytic cells. The data also show that cellular factors in addition to ceruloplasmin, possibly active oxygen species and/or lipoxygenases, are essential and act synergistically with ceruloplasmin to oxidize LDL.
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PMID:Role of endogenous ceruloplasmin in low density lipoprotein oxidation by human U937 monocytic cells. 860 49

Cu/Zn-superoxide dismutase (Cu/Zn-SOD) has been shown to modulate the autoxidation of a variety of phenoic compounds, including 1,4-hydroquinone (HQ), a benzene-derived metabolite. The acceleration of autoxidation of HQ by Cu/Zn-SOD results in the production of 1,4-benzoquinone (BQ). It has been proposed that the chemical mechanism involved in the Cu/Zn-SOD-catalyzed autoxidation of HQ may be occur through either its conventional activity as a superoxide:superoxide oxidoreductase or as a semiquinone:superoxide oxidoreductase. However, Cu/Zn-SOD-accelerated oxidation of HQ has not been resolved experimentally. In this study, with ESR spectroscopy we investigated further the chemical reactions involved in the SOD-accelerated oxidation of HQ. In phosphate-buffered saline (PSB), HQ underwent a slow autoxidation to BQ, which was accelerated by Cu/Zn-SOD, Mn-SOD, or Fe-SOD with similar efficiency. In contrast, among free metals, only Cu(II) strongly mediated the oxidation of HQ to BQ. Mn(II) exhibited a slight capacity to oxidize HQ, whereas neither FE(II) nor FE(III) was capable of modulating the autoxidation of HG. The presence of either form of SOD also dramatically enhanced the formation of semiquinone anion radicals SQ-. from HQ. The SOD-accelerated oxidation of HQ was also accompanied by the generation of H202. In PBS containing bovine serum albumin (BSA) (PBS/BSA), HQ did not undergo autoxidation to SQ-., and as such the presence of SOD was unable to induce the formation of either SQ-. or BQ or the consumption of O2. The addition of 10 microM BQ to HQ (100 or 1000 microM) in PBS/BSA resulted in the formation of SQ-. and initiated a slow rate of oxidation of HQ to BQ. In this case, the presence of Cu/Zn-SOD strongly accelerated the oxidation of HQ to SQ-. and BQ and the utilization of O2. Furthermore, the enhancement by Cu/Zn-SOD of the generation of SQ-. or BQ from HQ in PBS/BSA was extensively inhibited under anaerobic conditions. The enhancement of SQ-. generation from HQ by all three forms of SOD does not support the possibility that Cu/Zn-SOD can oxidize SQ-. to BQ. Taken together, this study demonstrates that unlike free copper, Cu/Zn-SOD does not directly interact with HQ to cause its oxidation to BQ. Rather, the autoxidation of HQ to SQ-. is a prerequisite for the enhancing capacity of Cu/Zn-SOD, and the dismutation of superoxide anion radicals generated from the SQ-. in the presence of O2 appears to be the underlying mechanism responsible for the enhancement by Cu/Zn-SOD of the oxidation of HQ.
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PMID:Role of Cu/Zn-superoxide dismutase in xenobiotic activation. I. Chemical reactions involved in the Cu/Zn-superoxide dismutase-accelerated oxidation of the benzene metabolite 1,4-hydroquinone. 864 79

The membrane permeability and intracellular fate of ([N,N'-bis(2 pyridyl-phenyl-methylene)-1,4-butanediamine](N,N ',N",N"')-copper(II))-diperchlorate (CuPuPhePy), a copper-diSchiff-base complex of superoxide dismutase(SOD)-mimetic activity surviving biochelation, were examined using rat hepatocytes. Lipophilicity was quantified by determining the octanol/water partition coefficients (K(p)) employing PBS as the aqueous phase. K(p)(octanol/water) was close to 1 (0.7 +/- 0.31) for Cu-PuPhePy. The complex associates with phosphatidylcholine liposomes, as deduced from ultracentrifugation and gel filtration experiments. The ability of the complex to permeate cellular membranes was proven by correlating copper release and viability of rat hepatocytes preincubated with CuPuPhePy and treated with digitonin and diethylmaleate (DEM), respectively. The toxicity and reactivity of CuPuPhePy (LD (50) approximately 10 muM for rat hepatocytes under the given conditions) were higher than those of CuSO (4)(LD(50) approximately 16 mu M) and CuZn-SOD (no toxicity in the tested range of concentration). Unlike CuSO(4) and CuZn-SOD, the toxicity and reactivity of the diSchiff-base complex were increased (LD(50) approximately 5 muM) when the concentration of intracellular glutathione was reduced to 16% of the initial content, by preincubating the cells with DEM. The toxicity of Cu-PuPhePy paralleled lipid peroxidation. This phenomenon was strongly enhanced when Cu-PuPhePy and cumene hydroperoxide (CumOOH) were simultaneously allowed to react with rat hepatocytes. This effect was intensified following preincubation with DEM. A decline in Cu(II)-EPR signals was indicative of the reduction of CuPuPhePy by GSH and liver extract, respectively. The concomitant formation of the Cu(I)-GSH complex during this reduction was monitored by the formation of luminescent Cu(I)-thiolate chromophores.
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PMID:Reactivity of lipophilic diSchiff-Base coordinated copper in rat hepatocytes. 865 42

Nitric oxide (NO) is a free radical produced enzymatically in biological systems from the guanidino group of L-arginine. Its large spectrum of biological effects is achieved through chemical interactions with different targets including oxygen (O2), superoxide (O2o-) and other oxygen reactive species (ROS), transition metals and thiols. Superoxide anions and other ROS have been reported to react with NO to produce peroxynitrite anions that can decompose to form nitrogen dioxide (NO2) and hydroxyl radial (OHo). Thus, NO has been reported to have a dual effect on lipid peroxidation (prooxidant via the peroxynitrite or antioxydant via the chelation of ROS). In the present study we have investigated in different models the in vitro and in vivo action of NO on lipid peroxidation. Copper-induced LDL oxidation were used as an in vitro model. Human LDL (100 micrograms ApoB/ml) were incubated in oxygene-saturated PBS buffer in presence or absence of Cu2+ (2.5 microM) with increasing concentrations of NO donnors (sodium nitroprussiate or nitroso-glutathione). LDL oxidation was monitored continuously for conjugated diene formation (234 nm) and 4-hydroxynonenal (HNE) accumulation. Exogenous NO prevents in a dose dependent manner the progress of copper-induced oxidation. Ischaemia-reperfusion injury (I/R), characterized by an overproduction of ROS, is used as an in vivo model. Anaesthetized rats were submitted to 1 hour renal ischaemia following by 2 hours of reperfusion. Sham-operated rats (SOP) were used as control. Lipid peroxidation was evaluated by measuring the HNE accumulated in rats kidneys in presence or absence of L-arginine or D-arginine infusion. L-arginine, but not D-arginine, enhances HNE accumulation in I/R but not in SOP (< 0.050 pmol/g tissue in SOP versus 0.6 nmol/g tissue in I/R), showing that, in this experimental conditions, NO produced from L-arginine, enhances the toxicity of ROS. This study shows that the pro- or antioxydant effects of NO are different in vivo and in vitro and could be driven by environmental conditions such as pH, relative concentrations of NO and ROS, ferryl species.
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PMID:[Nitric oxide and lipid peroxidation]. 867 27

Insulin-dependent diabetics have a greatly increased risk of developing premature coronary artery disease which is not entirely explained by known risk factors. A possible explanation may be enhanced oxidative modification of low density lipoprotein (LDL). The aim of this study was to determine firstly, whether or not LDL from moderately well controlled type 1 diabetics is more readily oxidisable than LDL from healthy non-diabetics and, secondly, to assess whether potential predictors of LDL oxidisability differ between type 1 diabetics and controls. Twenty type 1 diabetic men were carefully matched with healthy non-diabetic men on the basis of age and body mass index and each pair attended the department on the same morning for blood sampling. LDL oxidisability was assessed using both copper in PBS, 15 and 30 mM glucose, and with AAPH. There was no difference between type 1 diabetics and controls in the susceptibility of the LDL to either copper-dependent or non-transition metal-dependent oxidation. Furthermore, there was no difference between the groups for LDL vitamin E content, LDL fatty acid composition in cholesteryl esters, triglycerides or phospholipids, or LDL copper reductive capacity, but LDL glycation was elevated in the IDDM subjects. Given the absence of increased LDL oxidisability in these subjects, the recommendation of vitamin E supplementation in type 1 diabetics should be considered a secondary priority to achieving adequate glucose control.
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PMID:Absence of increased susceptibility of LDL to oxidation in type 1 diabetics. 886 59

8-Epi PGF2alpha, a potent vasocontrictor, is a specific product of non-enzymatic peroxidation of arachidonic acid. It seems likely that similar products could arise from other polyunsaturated fatty acids (PUFAs) and might be useful biomarkers of their peroxidation in vivo. This was investigated using eicosapentaenoic acid (EPA). EPA liposomes (1 mg/ml PBS) were exposed at 37 degrees C to either 2,2'-azobis-(2-amidinopropane) dichloride (AAPH) or copper ions at final concentrations of 1 mM and 10 microM, respectively. Sample processing involved solid-phase extraction on a C18-followed by an NH2 cartridge. After conversion to pentafluorobenzyl ester/trimethylsilyl derivatives, F3-isoprostanes were analysed by negative ion-chemical ionisation mass spectrometry (GC-MS/NICI) using tetradeuterated PGF2alpha (PGF2-d4) as the internal standard. Quantitative analysis was carried out by selected ion monitoring of the carboxylated anion [M-180] at m/z 567 and 573 for the PGF3-like compounds and PGF2-d4, respectively. EPA oxidised by AAPH or by copper ions gave rise to a family of F3-isoprostanes with 8-epi PGF3alpha as a minor product. Formation of F3-isoprostanes correlated well with other indices of lipid peroxidation (hydroperoxides and thiobarbituric acid reactive substances). The possibility of analysing specific lipid peroxidation products from individual fatty acids should facilitate nutritional and biomedical studies.
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PMID:Evidence for the formation of F3-isoprostanes during peroxidation of eicosapentaenoic acid. 924 Apr 62

Oxidation of LDL (0.1 microM) in PBS with copper concentrations ranging from 0.03 to 10 microM, equal to 0.3-100 Cu2+/LDL, was investigated by monitoring the formation of conjugated dienes at 234 nm. With all 8 LDL samples examined, the kinetics changed strongly at submicromolar Cu2+ concentrations. Based on time-course of the formation of conjugated dienes, cholesteryl linoleate hydroxides and hydroperoxides as well as the antioxidant consumption, two oxidation types were distinguished. Type A oxidations, observed at relatively high Cu2+ concentrations of 10-100 Cu2+/ LDL, represented the conventional kinetics of LDL oxidation with an inhibition period (= lag-time) followed by a propagation phase. In contrast, type C oxidations proceeded after a negligibly short lag time followed by a distinct propagation phase. The rate of this propagation increased rapidly to 0.5 mol diene/mol LDL and then slowed down in the presence of alpha-,gamma-tocopherols and carotenoids, which were consumed faster than tocopherols. The increase in diene absorption was due to the formation of both hydroxides and hydroperoxides suggesting a high initial decomposition of hydroperoxides. At submicromolar concentrations of about 0.1 to 0.5 microM, type C and type A oxidation can be combined resulting in 4 consecutive oxidation phases, i.e. 1st inhibition and 1st propagation (belonging to type C), followed by 2nd inhibition and 2nd propagation (belonging to type A). Increasing copper concentrations lowered the 1st propagation and shortened the 2nd inhibition periods until they melted into one apparent kinetic phase. Decreasing [Cu2+] increased the 1st propagation and 2nd inhibition but lowered the 2nd propagation phase until it completely disappeared. A threshold copper concentration, denoted as Cu(lim), can be calculated as a kinetic constant based on the Cu2+-dependence for the rate of 2nd propagation. Below Cu(lim), LDL oxidation proceeds only via type C kinetics. The Cu2+-dependence of the oxidation kinetics suggests that LDL contains two different Cu2+ biding sites. Cu2+ at the low-affinity binding sites, with half-saturation at 5-50 Cu2+/LDL, initiates and accelerates the 2nd propagation by decomposing lipid hydroperoxides. Cu2+ bound to the high-affinity binding sites, with half-saturation at 0.3-2.0 Cu2+/LDL, is responsible for the 1st propagation. Arguments in favor and against this propagation being due to tocopherol mediated peroxidation (TMP) are discussed. If the lag-time concept is extended to the conjugated diene curves seen for combined oxidation profiles, then a true inhibition phase does not apply to this time interval, but instead represents the time elapsed before the onset of the 2nd propagation phase.
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PMID:Copper can promote oxidation of LDL by markedly different mechanisms. 955 73

Haemoglobin has been previously identified as responsible for the decreased enzymatic activity of copper bovine serum amine oxidase (BSAO) in suspensions of human or bovine hemolyzed erythrocytes [Marcocci, L., Pietrangeli, P., Befani, O., Mavelli, I., & Mondovi', B. (1991b) Life Chem. Report, 9, 171-177]. This is confirmed by present results on bovine methaemoglobin. Bovine globin and horse skeletal muscle mioglobin showed a similar inhibiting ability, but neither bovine serum albumin nor cytochrome c inhibited BSAO activity under the same experimental conditions. The inhibitory effect of bovine haemoglobin was dependent on pH only at high buffer ionic strength. It was highest in physiological conditions (PBS) where haemoglobin acted as a reversible non competitive inhibitor of BSAO activity, with apparent Ki of 0.5 mM at 37 degrees C. The inhibition was unaffected by partial BSAO deglycosylation (40% of glucidic residues removed) but decreased when haemoglobin lysine groups were derivatised using citraconic anhydride. A possible molecular mechanism underlying the inhibitory effect is discussed.
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PMID:Characterization of the haemoglobin-mediated inhibition of the enzymatic activity of bovine serum amine oxidase. 964 84


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