Antioxidant effect of cupric complex on NADPH-dependent lipid peroxidation in rat liver microsomes

The antioxidant effect of His-Cu (Histidine and cupric ion) on NADPH-dependent lipid peroxidation was proportional to the inhibitory effect on cytochrome c reduction i the presence of microsomes and ADP-Fe (ADP and ferric ion). The inhibiton of cytochrome c reduction by His-Cu caused no inhibition of NADPH oxidation. ADP-Fe stimulated NADPH oxidation in the absence of cytochrome c, and inhibited cytochrome c reduction. His-Cu inhibited NADPH-oxidation stimulated by ADP-Fe, but the antioxidant effect of His-Cu was independent of the effect on cytochrome b5 reduction. These results suggest that the antioxidant effect of His-Cu depends on the inhibitory effect on the electron transport from NADPH-cytochrome c reductase to ADP-Fe, but not on the inhibitory effect on the activity of the reductase.     

Dehydroepiandrosterone-induced lipid peroxidation in rat liver mitochondria

Administration of dehydroepiandrosterone (DHEA), a steroid hormone of the adrenal cortex which acts as a peroxisome proliferator and hepatocarcinogen in the rat, caused an increase in NADPH-dependent lipid peroxidation in mitochondria isolated from the liver, kidney and heart, but not from the brain. The effect of DHEA on rat liver mitochondrial lipid peroxidation became discernible after feeding steroid-containing diet (0.6% w/w) for 3 days, and reached maximal levels between 1 and 2 weeks. DHEA in the concentration range 0.001-0.02% did not significantly increase lipid peroxidation compared to the control. Lipid peroxidation was significantly enhanced in animals given a diet containing > or = 0.05% DHEA. The addition of DHEA in the concentration range 0.1-100 microM to mitochondria isolated from control rats had no effect on lipid peroxidation. It seems, therefore, that the steroid effect is mediated by an intracellular process. Our data indicate that induction of mitochondrial membrane lipid peroxidation is an early effect of DHEA administration at pharmacological doses.     

Effect of L-carnitine on lipid peroxidation and lipid composition in blood serum in hemic hypoxia]

Sodium nitrite has been studied for its effect on lipid metabolism of Wistar line rats. It is shown that a single administration of sodium nitrite in account 5 mg per 100 g of the body weight results in the intensification of lipids peroxidation, hyperbetalipoproteinemia, hypertriglyceridemia, hypercholesterolemia and to the decrease of the coefficient phospholipids/cholesterin/. Prophylactic administration of carnitine chloride in account of 20 mg per 100 g of the body weight stabilizes the level of lipids peroxidation, decreases concentration of total lipids, triglycerides, total cholesterin, phospholipids, lipoproteids of low and very low density, in the rat blood serum, normalizes the coefficient phospholipids/cholesterin.     

Smoking-associated mitochondrial DNA mutations and lipid peroxidation in human lung tissues

BACKGROUND/AIMS: The objective of the present study was to analyze the expression and regulation of intercellular adhesion molecule-1 (ICAM-1) in organotypic cultures of rat liver slices, which preserve the normal microenvironment of liver cells. METHODS: Rat liver slices were maintained in culture for 15 min to 24 h and examined for ICAM-1 expression by immunohistochemistry and Western blotting in basal conditions and after stimulation with 1000 IU/ml interferon-gamma (IFNgamma), 1000 IU/ml tumor necrosis factor-alpha (TNF alpha) and 50 microg/ml endotoxin. Immunohistochemical results were evaluated using a semiquantitative scoring system. RESULTS: In uncultured slices, ICAM-1 was not detected on hepatocytes. In unstimulated liver slices maintained in organotypic culture, ICAM-1 was induced at the surface of scattered hepatocytes (score at 15 min, 0.33+/-0.47 and at 24 h, 1.17+/-0.69). After 4 h of stimulation, a significant increase in ICAM-1 expression by hepatocytes and adjacent sinusoidal cells, but not by intra-hepatic biliary epithelial cells, was observed for IFNgamma (score: 2.35+/-0.47) and endotoxin (score: 2.67+/-0.47), but not with TNF alpha (score: 0.66+/-0.47). After 24 h of stimulation, a further increase in the extent of ICAM-1 expression by hepatocytes was observed for IFNgamma (score: 3.67+/-0.47) and endotoxin (score: 4.0+/-0.0), and a significant overexpression of ICAM-1 by hepatocytes was detectable after treatment with TNF alpha (score: 3.67+/-0.47). CONCLUSIONS: In rat liver organotypic cultures, TNF alpha, IFNgamma and endotoxin induce the expression of ICAM-1 in hepatocytes and adjacent sinusoidal endothelial cells, but not in portal tracts.     

Ilex aquifolium: protection against enzymatic and non-enzymatic lipid peroxidation

The ethanolic extract of Ilex aquifolium L. (Aquifoliaceae) concentration-dependently inhibited leukotriene B4 biosynthesis in isolated bovine PMNL with an IC50 value of about 60 micrograms/ml, whereas the effect on epidermal 12(S)-HETE biosynthesis was much less pronounced. The extract also inhibited the non-enzymatic, peroxyl radical-stimulated lipid peroxidation in model membranes and was further a scavenger of the iron-dependent generation of hydroxyl radicals from hydrogen peroxide as determined by protection against deoxyribose degradation. While inhibition of leukotriene biosynthesis was not mediated by its known phenolic constituents such as hyperoside, rutoside, and chlorogenic acid, these compounds were responsible for the inhibitory effects of I. aquifolium against non-enzymatic lipid peroxidation and deoxyribose degradation.     

Nitric oxide protection of rat liver from lipid peroxidation, collagen accumulation, and liver damage induced by carbon tetrachloride

The evaluation of continuing medical education (CME) courses will soon become one of the tools used to assess post-graduate training, particularly in compliance with the recent legislation. In 1997, the organization committee of the French congress of pneumology decided to analyze the different methodologies used to assess the congress CME courses. The analysis was based on a satisfaction questionnaire, a before-after assessment of 4 workshops, and a comparison between participants and non-participants in 3 plenary sessions. Mann-Whitney and Wilcoxon non-parametric tests were used for statistical analysis. Satisfaction scores were high. For the plenary sessions, test results were better for participants than for the non-participant controls and for the workshops, test results were higher after completion. This type of study can only evaluate the level of knowledge acquired and is subject to a selection bias. It cannot analyze the practical impact of the courses nor their effect on patient health. Such assessment methodologies should be used more widely in order to improve future training sessions.     

beta-Carotene accumulation in mouse tissues and a protective role against lipid peroxidation

Recent population-based efficacy trials of the synthetic malaria vaccine SPf66 have shown restricted, if any, clinical protection against Plasmodium falciparum infection. Despite the well-established role of antibodies in effector responses against asexual blood-stage malaria parasites, the titres of anti-SPf66 IgG antibodies do not correlate with the ability of sera from vaccine recipients to inhibit parasite growth in vitro nor with partial clinical protection which could be detected in some trials. Qualitative or functional parameters of SP66-induced antibody responses, such as IgG subclass composition and affinity, may be more predictive of clinical protection against malaria than quantitative estimates of antibody concentration or titre. Since these parameters are readily estimated by laboratory techniques currently available, and may be modulated by changes in vaccination protocols and by the use of different adjuvants, a better understanding of qualitative antibody responses induced by SPf66 and other asexual blood-stage malaria vaccine candidates, and of their relationship with clinical protection in vivo, is urgently needed for the improvement of currently used immunization schedules.     

Possible mechanism of inhibition by polyamines of lipid peroxidation in rat liver microsomes

The rate of malondialdehyde formation in rat liver microsomes decreased as concentration of spermine added to the reaction mixture was increased. Inhibitory effect on lipid peroxidation was observed even when spermine was added at 15 min after the onset of reaction. Microsomal lipid peroxidation was markedly increased when extracted lipids were added to the reaction mixture. It was, moreover, found that in the presence of exogeneous microsomal lipids, spermine inhibition was weakened. The character of spermine inhibition with respect to the amounts of exogeneous and endogeneous lipids was shown to be competitive. From these results, it was suggested that spermine interaction with microsomal lipids may be responsible for the inhibition of lipid peroxidation.     

Glutathione-dependent factors and inhibition of rat liver microsomal lipid peroxidation

The effects of reduced glutathione (GSH) and glutathione disulfide (GSSG) on lipid peroxidation were investigated in rat liver microsomes containing deficient or adequate amounts of alpha-tocopherol (alpha-TH). Rates of formation of thiobarbituric acid reactive substances (TBARS) as well as rates of consumption of alpha-TH and O2 were decreased by GSH and were more pronounced in the NADPH-dependent assay system than in the ascorbate-dependent system. The GSH-dependent inhibition of lipid peroxidation was potentiated by GSSG in the NADPH-dependent assay system, but it had no effect in the nonenzymatic system. Diphenyliodonium chloride, an inhibitor of NADPH cytochrome P-450 reductase, completely prevented lipid peroxidation in the NADPH-dependent assay system whereas it had no effect on the ascorbate-dependent system. This is further evidenced by the fact that purified rat liver microsomal NADPH cytochrome P-450 reductase (EC 1.6.2.4) was inhibited approximately 24% and 52% by 5 mM GSH and 5 mM GSH + 2.5 mM GSSG, respectively. Glutathione disulfide alone had no effect on reductase activity. Similarly, other disulfides such as cystine, cystamine and lipoic acid were without effect on reductase activity. These results clearly delineate different mechanisms underlying the combined effects of GSH and GSSG on microsomal lipid peroxidation in rat liver. One mechanism involves recycling of microsomal alpha-TH by GSH during oxidative stress via a labile protein, ostensibly associated with "free radical reductase" activity. A second glutathione-dependent mechanism appears to be mediated through the inhibition of NADPH cytochrome P-450 reductase. The enhanced inhibition by GSH + GSSG of microsomal lipid peroxidation in the NADPH-dependent assay system suggests suppression of the initiation phase at the level of NADPH cytochrome P-450 reductase which is independent of microsomal alpha-TH.     

A possible mechanism for initiation of lipid peroxidation by ascorbate in rat liver microsomes

RRR-alpha-tocopheryl succinate (VES) was studied for effects on murine EL-4 cell proliferation and production of interleukin-2 (IL-2) and transforming growth factor-beta (TGF-beta). VES was biphasic in its actions: 0.1 microgram/ml enhanced EL-4 cell proliferation, whereas 10-20 microgram/ml inhibited cellular proliferation. Cell-conditioned media (CM) from EL-4 cells treated with 0.2 ng/ml phorbol myristate acetate (PMA) + 0.1 microgram/ml VES contained increased amounts of IL-2, as determined by the murine cytotoxic T cell IL-2-dependent CTLL-2 bioassay. VES at 0.1 microgram/ml or 0.1 microgram/ml VES + 0.2 ng/ml PMA induced the expression of IL-2 mRNA by EL-4 cells three to nine hours after treatment. CM from EL-4 cells treated with VES at 10-20 microgram/ml exhibited potent antiproliferative activity when tested in the TGF-beta-responsive mink lung cell (Mv1Lu) bioassay and showed reduced inhibitory effects when tested on TGF-beta receptor-negative mink lung (DRA-27) cells. CM from control-treated EL-4 cells exhibited no antiproliferative activity. The VES-induced antiproliferative activity was characterized as TGF-beta by neutralization analyses and immunoprecipitation of metabolically labeled proteins with TGF-beta-specific reagents. VES treatment of EL-4 cells had no effect on TGF-beta 1 mRNA expression while downregulating TGF-beta 3 mRNA expression. In summary, these studies showed that 0.1 microgram/ml VES enhanced cellular proliferation, in part, via increased IL-2 production, whereas 10-20 micrograms/ml VES inhibited cellular proliferation, in part, via the secretion of biologically active TGF-beta.     

Protective effect of dehydroepiandrosterone against copper-induced lipid peroxidation in the rat

This study investigates the effectiveness and multitargeted activity of dehydroepiandrosterone (DHEA) as antioxidant in vivo. A single dose of DHEA was given IP to male rats. Liver and brain microsomes, and plasma low density lipoprotein (LDL), were isolated from rats sacrificed 17 h later. Liver and brain microsomes were challenged with CuSO(4) and, as index of lipid peroxidation, the production of thiobarbituric acid reactive substances (TBARS) was measaured. Also, plasma low-density lipoprotein (LDL) were challenged with copper and the time course of lipid peroxidation was evaluated following the formation of conjugated dienes. The onset of TBARS generation induced by copper was marked delayed in both liver and brain microsomes from DHEA-treated animals. Also, the resistance of LDL to oxidation, expressed by the duration of the lag-phase of the kinetic curve, was significantly enhanced in DHEA-treated rats. Results indicate that in vivo DHEA supplementation makes subcellular fractions isolated from different tissues and plasma constituents (LDL) more resistant to lipid peroxidation triggered by copper. The antioxidant effect on plasma LDL might be of special relevance to the proposed antiatherogenic activity of DHEA. Moreover, multitargeted antioxidant activity of DHEA might protect tissues from oxygen radicals damage.     

The protective effect of metallothionein against lipid peroxidation caused by retinoic acid in human breast cancer cells

The treatment of breast cancer by retinoic acid (RA) may be mediated by lipid peroxidation. Expression of metallothionein (MT) in cancer cells, however, can protect against lipid peroxidation by scavenging hydroxyl radicals. In this study, a two-by-six factorial design was used to investigate the interactive effects of all-trans-RA and zinc (Zn)-induced MT on the growth of two human breast cancer cell lines differing in basal expression of MT and estrogen receptors; MCF7 cells express estrogen receptor, BT-20 cells do not. Cells were treated with Zn to induce MT and then treated with six RA concentrations. Cell proliferation, lipid peroxidation, MT protein, MT mRNA and glutathione concentrations were measured. BT-20 cells expressed higher constitutive MT concentrations than MCF7 cells. MT was significantly increased by Zn treatment in BT-20 cells but not in MCF7 cells. Low RA concentrations stimulated growth proliferation but higher concentrations inhibited cell proliferation. Elevated RA concentrations increased lipid peroxidation as measured by thiobarbituric acid reactive substances. There was a significant negative correlation between lipid peroxidation and cell proliferation. Growth inhibition and lipid peroxidation were reduced by Zn pretreatment in BT-20 cells but not in MCF7 cells. RA increased MT levels in both cell lines, which suggests that RA may generate free radicals which will induce MT mRNA expression. Glutathione did not appear to be a significant factor. Therefore, induction of MT by Zn may modulate the growth inhibitory effects of RA in human breast cancer cells. One mechanism of growth inhibition may be through increased lipid peroxidation. Induction of MT by RA may be one explanation for acquired RA resistance in cancer.     

Regional lipid peroxidation and protein oxidation in rat brain after hyperbaric oxygen exposure

Reactive oxygen species may participate in development of neurological toxicity resulting from hyperbaric oxygen exposure. To explore the possibility that increased reactive O2 metabolite generation may result in oxidative modification of lipids and proteins, rats were exposed to five atmospheres (gauge pressure) of O2 until development of an electroencephalographic seizure. Lipid peroxidation (as thiobarbituric acid-reactive substances) and protein oxidation (as 2,4-dinitrophenyl-hydrazones) were measured in five brain regions. Oxidized and reduced glutathione were also determined because of their role in regulating lipid peroxidation. Lipid peroxidation was confined to the frontal cortex and hippocampus, while protein oxidation (in both cytoplasmic and membranous fractions) and increased oxidized glutathione was evident throughout the brain. These results support a role for formation of reactive O2 metabolites from hyperbaric O2 exposure and suggest that protein oxidation, especially in soluble proteins, may be one of the most sensitive measures.     

Inhibition of lipid peroxidation mediated by indolizines

Esters, ethers, carbonates and carbamates of 1-indolizinols and azaindolizinols exhibit a profound inhibition of lipid peroxidation in vitro. The antioxidants were prepared by cyclization of pyridines and diazines with diphenylcyclopropenone followed by introduction of the O-substituent.     

Inhibitory effect of Garcinia kola on lipid peroxidation in rat liver homogenate

Garcinia kola, (a herb grown in Nigeria; calorific value 358.54 k.cal/100 g) inhibited in vitro lipid peroxidation of rat liver homogenate in a dose dependent manner. The inhibitory activity of G.kola was not affected by heating (100 degrees C/10 min). The antioxidant component of G.kola was soluble in aqueous and ethanolic media. The active component(s) in G. kola responsible for its inhibitory activity on lipid peroxidation is tentatively identified as isoflavones.     

Nitric oxide and lipid peroxidation

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.     

Synergistic renal protection by combining alkaline-diuresis with lipid peroxidation inhibitors in rhabdomyolysis: possible interaction between oxidant and non-oxidant mechanisms

BACKGROUND AND PURPOSE: Heme-proteins, besides causing renal tubular obstruction, may contribute to rhabdomyolysis-induced renal injury through a heme-iron-mediated lipid peroxidation process. In the present study, we compared the combined therapy of a lipid peroxidation inhibitor, 21-aminosteroid (21-AS) and fluid-alkaline-mannitol (FAM) diuresis with either of them alone to determine the efficacy of the combination therapy and to delineate the roles of lipid peroxidation and cast formation. METHODS AND RESULTS: Employing Raman spectroscopy, we confirmed in vitro the ability of 21-AS to inhibit iron-induced fatty acid peroxidation. 21-AS was then administered to rats developing renal failure from glycerol-induced rhabdomyolysis. Although 21-AS inhibited rhabdomyolysis-induced plasma and renal lipid peroxidation, renal protection was incomplete. Administration of FAM to inhibit cast formation afforded a better renal protection. However, when these therapies were combined to inhibit both lipid peroxidation and cast formation, there was a synergistic renal functional protection. This was accompanied by a maximum inhibition of renal and plasma lipid peroxidation, as well as, renal tubular necrosis and cast formation. Compared to combination therapy, FAM therapy alone, despite identical volume, was accompanied by a higher tubular necrosis and cast formation. CONCLUSIONS: That combining a lipid peroxidation inhibitor with fluid-alkaline diuresis in rhabdomyolysis further lowers renal lipid peroxidation, tubular necrosis and cast formation and synergistically limits renal dysfunction (i) supports a role for lipid peroxidation in the pathophysiology of rhabdomyolysis ARF, (ii) underscores the role of the intratubular heme retention, a cause for tubular obstruction as well as a source for prodigious amount of iron, likely involved in the lipid peroxidation, and (iii) raises the possibility of interactions between non-oxidant and oxidant mechanisms.     

Relations between tocopherol depletion and coenzyme Q during lipid peroxidation in rat liver mitochondria

In order to evaluate different mitochondrial antioxidant systems, the depletion of alpha-tocopherol and the levels of the reduced and oxidized forms of CoQ were measured in rat liver mitochondria during Fe++/ascorbate and NADPH/ADP/Fe++ induced lipid peroxidation. During the induction phase of malondialdehyde formation, alpha-tocopherol declined moderately to about 80% of initial contents, whereas the total CoQ pool remained nearly unchanged, but reduced CoQ9 continuously declined. At the start of massive malondialdehyde formation, CoQ9 reaches its fully oxidized state. At the same time alpha-tocopherol starts to decline steeply, but never becomes fully exhausted in both experimental systems. Evidently the oxidation of the CoQ9 pool constitutes a prerequisite for the onset of massive lipid peroxidation in mitochondria and for the subsequent depletion of alpha-tocopherol. Trapping of the GSH by addition of dinitrochlorbenzene (a substrate of the GSH transferase), results in a moderate acceleration of lipid peroxidation, but alpha-tocopherol and ubiquinol levels remained unchanged when compared with the controls. Addition of succinate to GSH depleted mitochondria effectively suppressed MDA formation as well as alpha-tocopherol and ubiquinol depletion. The data support the assumption that the protective effect of respiratory substrates against lipid peroxidation in the absence of mitochondrial GSH is mediated by the regeneration of the lipid soluble antioxidants CoQ and alpha-tocopherol.