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Biomedical subjects

H Esterbauer

Publications and source records attributed to H Esterbauer.

At least 73 records · Page 4Linked to original sources
PubMed1995

Assessment of growth inhibition by aldehydic lipid peroxidation products and related aldehydes by Saccharomyces cerevisiae.

The effect of pretreatment with aldehydes on the subsequent colony forming efficiency (CFE) of Saccharomyces cerevisiae was investigated. All 21 aldehydes tested inhibited CFE in a dose-dependent manner. The effective doses, however, differed markedly from 300 mM to 0.07 mM depending on the functional groups and chain length of the aldehydes. Amongst the nine representatives of n-alkanals, formaldehyde was the most potent inhibitor, reducing CFE to 50 per cent at a dose of 0.3 mM (IC50). In the series of 2-trans-alkenals, acrolein was most effective with an IC50 of 0.08 mM and amongst the 4-hydroxy 2-trans-alkenals, 4-hydroxynonenal was most effective with IC50 of 0.07 mM. In general, effectiveness decreased in the order: 4-hydroxyalkenals > 2-alkenals >> n-alkenals. It is proposed that S. cerevisiae is a promising target cell to elucidate further the molecular mechanisms by which aldehydes, particularly the lipid peroxidation product 4-hydroxynonenal, inhibits cell proliferation.

Aldehydes↗
PubMed1995

4-Hydroxynonenal formation during ischemia and reperfusion of rat small intestine.

The metabolism and the washout of 4-hydroxynonenal (HNE), a major lipid peroxidation product, was determined in jejunal intestine of rats under normoxic, ischemic and postischemic conditions. The HNE utilization was by several orders higher than the HNE washout. Under ischemic conditions a drastic decrease of HNE utilization was found, compared with normoxic and postischemic utilization rates. The real flux rate of intracellular HNE formation during ischemia and reperfusion of small intestine was for the first time estimated on the basis of tissue HNE concentration, HNE utilization rate at defined HNE tissue concentration and HNE washout by perfusate circulation. Such estimation led to intestinal HNE formation rates of about 20 nmoles/g/min at normoxia, 20 to 40 nmoles/g/min at ischemia, 100 nmoles/g/min at 10 min of reperfusion and 20 nmoles/g/min at 60 min of reperfusion. Therefore, one can conclude that the tissue concentration of HNE only partly represents the real HNE formation rate and that the formation rate is of particular pathophysiological importance.

Aldehydes↗
PubMed1995

Enhanced resistance to oxidation of low density lipoproteins and decreased lipid peroxide formation during beta-carotene supplementation in cystic fibrosis.

We investigated the effect of correcting beta-carotene deficiency in cystic fibrosis (CF) patients on two parameters of lipid peroxidation. The resistance to oxidation of low density lipoprotein (LDL) was measured by the lag time preceding the onset of conjugated diene formation during exposure to copper(II) ions, and lipid peroxide formation was quantitated by malondialdehyde concentrations in plasma (TBA/HPLC method). Simultaneously, alpha-tocopherol and beta-carotene concentrations were determined in LDL and in plasma. Thirty-four CF patients were investigated before and after 3 months of oral beta-carotene supplementation. Beta-carotene concentrations increased (p < 0.0001) in plasma (mean +/- SD) (0.09 +/- 0.06 vs. 1.07 +/- 0.86 mumol/l) and in LDL (0.02 +/- 0.02 vs. 0.31 +/- 0.28 mol/mol), without significant changes in alpha-tocopherol, either in plasma (24.7 +/- 5.9 vs. 25.4 +/- 7.6) or in LDL (8.47 +/- 2.95 vs. 9.05 +/- 4.13). Lag times, being shorter (p < 0.05) in patients than in controls, increased from 48.5 +/- 21.3 to 69.1 +/- 27.9 min (p < 0.001) and plasma MDA concentrations, being greater (p < 0.0001) in patients than in controls, decreased from 0.95 +/- 0.32 to 0.61 +/- 0.15 mumol/l (p < 0.0001). At 3 months, lag times and MDA concentrations did not any longer differ between patients and controls. These data suggest that excess lipid peroxidation occurring in beta-carotene deficiency can be limited and normalized during efficient beta-carotene supplementation in CF patients.

Carotenoids↗
PubMed1995

Transient reduction of autoantibodies against oxidized LDL in patients with acute myocardial infarction.

Fifteen consecutive patients (mean age 66 +/- 14, range 31-82) with an acute myocardial infarction (MI) suitable for thrombolytic therapy were included in this study. Autoantibodies against oxidized low-density lipoprotein (LDL) were determined by enzyme-linked immunosorbent assay (ELISA). Patients (n = 10) with marked elevation of the MB isoenzyme of creatinine kinase (CK-MB)-mass had significant decreases of oLDL-Ab during the acute phase, with a minimum after 8 h following the onset of thrombolytic therapy (within-group significance: p < .001; between groups: p = .01). Patients (n = 5) with CK-MB-mass values less than 70 ng/ml did not show this phenomenon. Furthermore, significant correlations existed between CK-MB-mass and oLDL-Ab after 6 and 8 h (n = 15; r = .72; p = .003) and the time of the highest CK-MB-mass values (after 12 h) and the time of the maximal decrease of oLDL-Ab (after 8 h) (r = .74; p = .003). Our observations provide further evidence for the release of free radicals and for increased lipid peroxidation during reperfusion after prolonged ischemia. The decrease of oLDL-Ab appears to be a marker for the severity of MI.

Adult↗
PubMed1995

Impaired resistance to oxidation of low density lipoprotein in cystic fibrosis: improvement during vitamin E supplementation.

Antioxidants such as vitamin E protect unsaturated fatty acids of LDL against oxidation. In the ex vivo model used, LDL was exposed to Cu2+ ions, a potent prooxidant capable of initiating the oxidation of LDL. The lag time, indicating the delay of conjugated diene formation in LDL due to antioxidant protection, was measured in 54 cystic fibrosis (CF) patients with plasma alpha-tocopherol levels below (Group A, n = 30) or above (Group B, n = 24) 15.9 mumol/L (mean - 2 SD of Swiss population). Patients were reevaluated after 2 months on 400 IU/d of oral RRR-alpha-tocopherol. In group A, alpha-tocopherol concentrations in LDL increased significantly from 3.2 +/- 1.6 mol/mol LDL to 8.2 +/- 2.8 mol/mol (P < 0.001) and lag times increased from 79 +/- 33 min to 126 +/- 48 min (P < 0.001), whereas in the vitamin E sufficient group B no further increase neither in LDL alpha-tocopherol concentrations or in lag times was observed. LDL oleic acid concentrations were higher, and linoleic acid concentrations were lower in patients than in controls. After efficient vitamin E supplementation, lag times were positively related to LDL alpha-tocopherol (P < 0.01) and negatively to LDL linoleic and arachidonic acid content (P < 0.001). The maximum rate of oxidation correlated positively with linoleic and arachidonic acid concentrations, as did the maximum conjugated diene absorbance. These results indicate that LDL resistance to oxidation is impaired in vitamin E deficient CF patients but can be normalized within 2 months when alpha-tocopherol is given in sufficient amounts. Linoleic and arachidonic acid content exhibit a major influence on the LDL resistance to oxidation.

Adult↗
PubMed1995

Inhibition of melanoma B16-F10 growth by lipid peroxidation product 4-hydroxynonenal.

Since a gradual benign-to-malignant progression of murine melanoma B16 after exposure in vitro to hypoxia was described recently, the aim of this study was to test if exposing melanoma B16-F10 cells to aldehyde 4-hydroxynonenal (HNE), which is considered not only as one of the major "second toxic messengers" of oxygen free radicals (or oxidative stress), but as a normal constituent of many cells and tissues, might have opposite effects. Treatment of the tumor cells with 50 microM HNE in vitro or in vivo did not prevent development of the tumors, but inhibited their growth. Tumor growth inhibition was equal for in vitro and in vivo treatment, but appeared after a delay of almost one week, since there was no difference of the tumor volume to the control observed during the initial period of the tumor growth. Similarly, both HNE treatment of the tumor cells before transplantation and HNE treatment of the melanoma bearing mice resulted in equally prolonged survival time. Thus, the results obtained suggest that while hypoxia could increase the malignancy of the murine melanoma cells, exposing these cells to one of the major "second toxic messengers" of oxygen free radicals, HNE, has almost opposite effects and further indicate the possible use of the aldehyde in vivo.

Aldehydes↗
PubMed1995

Immunologic detection and measurement of hypochlorite-modified LDL with specific monoclonal antibodies.

Oxidation of LDL is thought to contribute to the early stages of atherogenesis. Because myeloperoxidase is present in atherosclerotic lesions and can produce the strong oxidant hypochlorous acid (HOCl), which converts LDL into its high-uptake atherogenic form in vitro, we raised polyclonal and monoclonal antibodies (MoAbs) against HOCl-modified LDL (HOCl-LDL). Characterization of the polyclonal anti-human HOCl-LDL Abs showed that they cross-reacted strongly with 4-hydroxynonenal-, malondialdehyde-, and Cu(2+)-oxidized LDL. Similarly, polyclonal and some monoclonal Abs against aldehyde- and Cu(2+)-modified LDL cross-reacted with HOCl-LDL. In contrast to the polyclonal Abs, two selected hybridoma cell line supernatants containing MoAbs raised against HOCl-LDL (MoAb-A and MoAb-B) did not cross-react with either native LDL or aldehyde- or Cu(2+)-modified LDL. MoAb-A (clone 1B10A11, subtype IgG1 kappa) recognized an epitope that appeared to be specific for HOCl-LDL and depended on the tertiary structure of the (lipo)protein, as judged by a lack of cross-reactivity with HOCl-modified human and bovine serum albumin and a loss of reactivity associated with lipoprotein denaturation. MoAb-B (clone 2D10G9, subtype IgG2b kappa), on the other hand, gave identical titration curves with HOCl-LDL and HOCl-modified albumins, suggesting that this antibody recognized epitopes that are commonly generated on proteins that have been oxidized with HOCl. Thus, MoAb-A and MoAb-B may be useful tools for the investigation of a possible role for HOCl-mediated damage to (lipo)proteins in atherosclerosis and other inflammatory diseases.

Aldehydes↗
PubMed1995

7,8 Dihydroneopterin inhibits low density lipoprotein oxidation in vitro. Evidence that this macrophage secreted pteridine is an anti-oxidant.

Neopterin and its reduced form, 7,8 dihydroneopterin are pteridines released from macrophages and monocytes when stimulated with interferon gamma in vivo. The function of this response is unknown though there is an enormous amount of information available on the use of these compounds as clinical markers of monocyte/macrophage activation. We have found that in vitro 7,8-dihydroneopterin dramatically increases, in a dose dependent manner, the lag time of low density lipoprotein oxidation mediated by Cu++ ions or the peroxyl radical generator 2,2'-azobis (2-amidino propane) dihydrochloride (AAPH). 7,8-Dihydroneopterin also inhibits AAPH mediated oxidation of linoleate. The kinetic of the inhibition suggests that 7,8-dihydroneopterin is a potent chain breaking antioxidant which functions by scavenging lipid peroxyl radicals. No anti-oxidant activity was observed in any of the oxidation systems studied with the related compounds neopterin and pterin.

Adult↗
PubMed1995

Effect of temperature and phase transition on oxidation resistance of low density lipoprotein.

The study of the effect of temperature on the kinetics of low density lipoprotein (LDL) oxidation was carried out by measuring the conjugated diene (CD) versus time curves at a fixed LDL concentration (0.1 microM) and at different Cu2+ concentrations (0.5-10 microM) in a wide temperature range, from 10 degrees C to 45 degrees C. The core melting point of the LDL determined with differential scanning calorimetry was 31.1 degrees C. We have demonstrated that temperature exerts a clear effect in the Cu(2+)-mediated LDL oxidation, with a strong decrease in lag time and a notable increase in the rate of propagation. This temperature dependence of lag time and rate of propagation fully obeys the Arrhenius law, suggesting that the core melting point of the LDL has no or only a minor effect on these oxidation indices. The Arrhenius plots of the binding of Cu2+ to LDL, measured by K, gave two breaks suggesting that this value is affected by the core transition of the LDL as well as by structural changes at around 15 degrees C. The mean activation energy during rate of initiation was 13.5 kcal/mol and tended to decrease with increasing Cu2+ concentration. The activation energy in the propagation phase was 10.6 kcal/mol and was independent of Cu2+ concentration. In this work we have also shown that the CD method can be conducted with high reproducibility and that a sucrose-supplemented plasma frozen at -80 degrees C can be used as a source of LDL with an unvarying vitamin E content and reproducible oxidation properties.

Blood Preservation↗
PubMed1994

Metabolism of 4-hydroxynonenal, a cytotoxic lipid peroxidation product, in Ehrlich mouse ascites cells at different proliferation stages.

The aldehydic lipid peroxidation product 4-hydroxynonenal (HNE) is cytotoxic at high concentrations (in the range of 100 microM); at low concentrations, it disturbs cell proliferation and exhibits genotoxic effects, and in the submicromolar range, HNE is chemotactic and stimulates phospholipase C. HNE is rapidly metabolized in eukaryotic cells. Here the metabolism of HNE was studied in suspensions of Ehrlich mouse ascites cells at different periods of the tumor age. The main products of HNE which were identified in the Ehrlich ascites cells, were glutathione-HNE-conjugate, hydroxynonenoic acid, and 1,4-dihydroxynonene. The formation of glutathione conjugates following the addition of HNE was higher in early phase cells when compared with cells in the late phase of tumor growth. That was in accordance with the increased consumption of the reduced form of glutathione. Ehrlich ascites tumor cells at the proliferation phase were able to reduce a higher amount of exogenous-added HNE, compared with cells at the stationary phase.

Aldehydes↗
PubMed1994

Identification of metabolic pathways of the lipid peroxidation product 4-hydroxynonenal by mitochondria isolated from rat kidney cortex.

The cytosolic lipid peroxidation product 4-hydroxynonenal (HNE) is rapidly metabolized in mitochondria isolated from rat kidney cortex. About 80% of HNE was degraded within 3 min of incubation. Main products of HNE which were identified in mitochondria were the hydroxynonenoic acid, the 1,4-dihydroxynonene and the glutathione-HNE-conjugate. Furthermore, formation of metabolites of the tricarboxylic acid cycle from HNE is suggested. The quantitative share of HNE binding to proteins was high with about 8% of total HNE consumption after 3 min of incubation. Therefore, rapid degradation of HNE by mitochondria might be involved in an intracellular antioxidative defense system.

Aldehydes↗
PubMed1994

Low density lipoprotein is saturable by pro-oxidant copper.

The oxidative resistance of low density lipoprotein (LDL) can be experimentally described by the length of time during which no significant lipid peroxidation is observed in a pro-oxidant environment. This period of inhibited oxidation, termed the 'lag phase', is partially due to the radical scavenging reactions of the anti-oxidants contained in the LDL particle. We have shown that the LDL lag time decreases with increasing copper concentration, leveling out at a relatively high copper-to-LDL ratio. This behaviour demonstrates the existence of a finite number of saturable pro-oxidant copper binding sites within the LDL particle. The relationship is described by the equation, lag time = [Cu]-1.K.tmin+tmin where the constant, K, is the negative reciprocal of the x-axis intercept of the graphed function, and tmin is given by the y-axis intercept. By this definition of the constant, K is the amount of copper that will produce a lag time of twice tmin, while tmin is the minimum time a particular LDL will resist oxidation at a maximum copper concentration.

Adult↗
PubMed1994

Enhancement of hydrogen peroxide-induced luminol-dependent chemiluminescence by neopterin depends on the presence of iron chelator complexes.

We have previously shown that neopterin, 6-D-erythro-trihydroxypropyl-pteridine, synthesized by human monocytes/macrophages upon stimulation by interferon-gamma, enhances toxicity of reactive oxygen at neutral or slightly alkaline pH (7.5), but not at acidic pH (below 6.5). In the present study, we explored in more detail the necessary requirements for neopterin to modulate the effects of hydrogen peroxide in a luminol-dependent chemiluminescence assay. We demonstrate that neopterin enhances hydrogen peroxide effects only in the presence of iron chelator complexes like iron-(III)- or iron-(II)-EDTA or iron-(III)-DTPA. Thus, iron chelator complexes together with neopterin may play an important role in macrophage-mediated effector mechanisms.

Biopterins↗
PubMed1994

Binding of the lipid peroxidation product 4-hydroxynonenal to human polymorphonuclear leukocytes.

4-Hydroxynonenal (HNE) is produced during peroxidation of polyunsaturated fatty acids. It exerts a chemokinetic effect on human polymorphonuclear leukocytes (PMN). Investigations of this mechanism were performed. The results indicate that [3H]-HNE binding to PMN results both in non-specific bonds to the numerous SH groups of the cells and in binding to a saturable, reversible and specific HNE site. Scatchard analysis revealed that this is a single site with an apparent affinity constant of 319 nM and a density of 1.57 pmol (10(6))-1 cells. This specific binding site may be involved in the chemokinetic effect of HNE.

Aldehydes↗
PubMed1994

Activation of phosphoinositide-specific phospholipase C of rat neutrophils by the chemotactic aldehydes 4-hydroxy-2,3-trans-nonenal and 4-hydroxy-2,3-trans-octenal.

A comparison has been made between the effects of 4-hydroxy-2,3-trans-nonenal (HNE) and 4-hydroxy-2,3-trans-octenal (HOE), two lipid peroxidation products, on the basal and GTPgammaS-stimulated activities of phosphoinositide-specific phospholipase C (PL-C) of rat polymorphonuclear leukocytes. PL-C activity was determined in vitro by measuring the hydrolysis of [3H] phosphatidylinositol-4,5-bis- phosphate (PtdIns-P2) added as exogenous substrate to neutrophil plasma membranes. PL-C was activated by concentrations of HNE ranging from 10(-8) to 10(-6) M both in the presence and in the absence of 2 x 10(-5) M GTPgammaS; HOE stimulated the enzymatic activity between 10(-11) and 10(-8) M; maximal stimulation was given by 10(-11) M HOE plus GTPgammaS. The aldehyde concentrations able to accelerate PtdIns-P2 breakdown displayed a good correspondence with those which have been reported to stimulate the oriented migration of rat neutrophils. Pretreatment of neutrophils with pertussis toxin prevented the stimulation of PL-C by 10(-11) M HOE and by HOE plus GTPgammaS. Our results suggest that the chemotactic action of HNE and HOE might depend on the activation of PL-C; furthermore a regulatory G protein appears to be involved in the acceleration of PtdIns-P2 turnover by HOE.

Aldehydes↗
PubMed1994

Postischemic accumulation of the lipid peroxidation product 4-hydroxynonenal in rat small intestine.

4-Hydroxynonenal (HNE) as an indicator of lipid peroxidation was determined in rat jejunal mucosa. HNE was extracted as the dinitrophenylhydrazone derivative from the tissue, partially separated from other carbonyl compounds by thin-layer chromatography and measured by HPLC. During reperfusion of the small intestine following an ischemic period of 60 minutes a marked increase of the tissue concentration of HNE was observed. The mucosal HNE level passed a maximum value of 3.0 +/- 0.5 microM 10 min after the onset of reperfusion in comparison with 0.7 +/- 0.2 microM as initial value. The increased tissue level of the highly cytotoxic 4-hydroxyalkenal is suggested to be involved in the reperfusion induced morphological and biochemical changes of the small intestine.

Aldehydes↗
PubMed1994

Mutual dependence of growth modifying effects of 4-hydroxynonenal and fetal calf serum in vitro.

Recently, the hypothesis has been put forward that 4-hydroxynonenal (HNE), an aldehydic product of lipid peroxidation, contributes to the mechanisms of oxygen toxicity and to the selective pressure exerted by exposure to hyperoxia. Here it has been studied whether HNE itself is involved in mechanisms that convey increased resistance of the cells to the toxicity of HNE. The following four cell lines, different in their basic biological features, were used: nonmalignant Chinese hamster lung fibroblasts V79 (established cell line), human carcinoma HeLa (established cell line), pigmented murine melanoma B16f10 (primary culture), and amelanotic murine melanoma B16BL6 (primary culture). The cells were pretreated in vitro with a toxic dose of HNE (50 microM), and afterwards the effect of a second exposure to the same dose of HNE on 3H-thymidine incorporation was examined. Cells were cultured in the absence and in the presence of fetal calf serum (FCS), because it had been shown that a growth modifying effect of HNE depends on an unknown serum factor. The results showed that, regardless of the type of cells, preculturing them with 50 microM HNE in the presence of serum changed the reactivity of the cells to added serum as well as to additional HNE treatment. Thus, HNE precultured cells incorporated less 3H-thymidine in the presence of serum than if cultured under serum-free conditions. On the other hand, HNE precultured cells became less sensitive to further HNE treatment, but only if cultured in the presence of serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehydes↗