Effects of phenolcarboxylic acids on superoxide anion and lipid peroxidation induced by superoxide anion.

The effects of phenolcarboxylic acids, caffeic acid, p-coumaric acid, and ferulic acid on the generation of superoxide anion and the production of lipid peroxide induced by superoxide anion were studied. Only ferulic acid anion among the phenolcarboxylic acids scavenged superoxide. Caffeic acid and ferulic acid inhibited lipid peroxidation induced by superoxide anion. These effects were comparable to those of superoxide dismutase or DL-alpha-tocopherol.     

Histamine-3 receptor antagonists reduce superoxide anion generation and lipid peroxidation in rat brain homogenates

Using a cyanide model to induce neurotoxic effects in rat brain homogenates, we examined the neuroprotective properties of three H3 antagonists, namely clobenpropit, thioperamide and impentamine, and compared them to aspirin, a known neuroprotective agent. Superoxide anion levels and malondialdehyde concentration were assessed using the nitroblue tetrazolium and lipid peroxidation assays. Clobenpropit and thioperamide significantly reduced superoxide anion generation and lipid peroxidation. Impentamine reduced lipid peroxidation at all concentrations used, but only reduced superoxide anion generation at a concentration of 1 mM. In the lipid peroxidation assay, all the drugs compared favourably to aspirin. This study demonstrates the potential of these agents to be neuroprotective by exerting antioxidant effects.     

云芝多糖对小鼠肝脏超氧化物歧化酶活力和脂质过氧化的影响

云芝多糖对小鼠肝脏超氧化物歧化酶活力和脂质过氧化的影响魏文树１谭建权陈海生２（第二军医大学药理学教研室，上海２００４３３）云芝多糖（Ｃｏｒｉｏｌｕｓｖｅｒｓｉｃｏｌｏｒｐｏｌｙｓａｃｃｈａｒｉｄｅｓ，ＣＶＰ）系从长白山野生云芝中提取，含６７．５３％β...     

A labile sulfur in trisulfide affects cytochrome P-450 dependent lipid peroxidation in rat liver microsomes

The effects of trisulfide derivatives were studied on cytochrome P-450-dependent lipid peroxidation using rat liver microsomal systems. Cytochrome P-450-dependent lipid peroxidation was induced by carbon tetrachloride or tert-butylhydroperoxide and was evident by an increase in thiobarbituric acid-reactive substances (TBA-RS) and oxygen consumption. In these cytochrome P-450-dependent lipid peroxidation systems, pretreatment of microsome with trisulfide derivatives (cystine trisulfide and thiocyclam) significantly inhibited TBA-RS formation and oxygen consumption compared with disulfide or thiol analogs (cystine, nereistoxin, or cysteine). The labile sulfur contained in trisulfide disappeared during incubation with liver microsomes. In the CCl₄-induced lipid peroxidation system, the cytochrome P-450 level and NAD(P)H-cytochrome P-450 reductase activity were significantly decreased by the addition of trisulfide derivatives. Therefore, in cytochrome P-450-dependent lipid peroxidation system, the potential effects of trisulfide appear to be mediated via enzyme inhibition. These results suggest that pretreatment of the trisulfide derivatives may affect the toxic function of exogenous xenobiotics or drugs, which are reduced by the liver enzyme cytochrome P-450 to radical species.     

内南五味子木脂素戈米辛J对肝线粒体膜脂质过氧化和超氧阴离子自由基的作用

目的　研究来自内南五味子的戈米辛J对脂质过氧化的影响和清除超氧阴离子自由基 (O·2 )的能力。方法　采用离体大鼠肝线粒体膜的脂质过氧化模型和黄嘌呤氧化酶 鲁米诺化学发光法。结果　戈米辛J象VitE一样能剂量依赖性抑制Fe2 + VitC和ADP/NADPH所致的脂质过氧化 ;戈米辛J的IC50 分别为 5 75 ( 95 %可信限 :5 42～ 6 11)和0 95 ( 0 14～ 6 5 4) μmol·L-1。VitE的IC50 分别为 74 8( 30 2～ 185 3)和 6 5 1( 0 13～ 319) μmol·L-1。戈米辛J抑制Fe2 + VitC和ADP/NADPH所致的脂质过氧化的作用比VitE的作用分别强 13倍和 6 8倍。戈米辛J也剂量依赖地抑制黄嘌呤 黄嘌呤氧化酶 鲁米诺化学发光 ,其抑制发光强度 5 0 %的浓度 (IC50 )为 2 18 2 2 μmol·L-1。结论　戈米辛J具有抑制OH·诱导的脂质过氧化和清除O·2 的作用     

内南五味子木脂素戈米辛J对肝线粒体膜脂质过氧化和超氧阴？…

目的　研究来自内南五味子的戈米辛J对脂质过氧化的影响和清除超氧阴离子自由基 (O·2 )的能力。方法　采用离体大鼠肝线粒体膜的脂质过氧化模型和黄嘌呤氧化酶 鲁米诺化学发光法。结果　戈米辛J象VitE一样能剂量依赖性抑制Fe2 VitC和ADP/NADPH所致的脂质过氧化 ;戈米辛J的IC50 分别为 5 75 ( 95 %可信限 :5 42～ 6 11)和0 95 ( 0 14～ 6 5 4) μmol·L-1。VitE的IC50 分别为 74 8( 30 2～ 185 3)和 6 5 1( 0 13～ 319) μmol·L-1。戈米辛J抑制Fe2 VitC和ADP/NADPH所致的脂质过氧化的作用比VitE的作用分别强 13倍和 6 8倍。戈米辛J也剂量依赖地抑制黄嘌呤 黄嘌呤氧化酶 鲁米诺化学发光 ,其抑制发光强度 5 0 %的浓度 (IC50 )为 2 18 2 2 μmol·L-1。结论　戈米辛J具有抑制OH·诱导的脂质过氧化和清除O·2 的作用     

The role of iron in 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced lipid peroxidation by rat liver microsomes

Treatment of female Sprague-Dawley rats with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) enhances hepatic lipid peroxidation, and the role of iron in TCDD-induced lipid peroxidation was examined. Ferrous and ferric ions, and the chelators adenosine diphosphate (ADP), ethylenediaminetetraacetic acid (EDTA) and desferrioxamine (DFX) were added to an in vitro microsomal lipid peroxidation system using microsomes from control and TCDD-treated animals. Both ferrous and ferric ions enhanced microsomal lipid peroxidation, with the greatest effect being produced by the combination of ferrous and ferric ions. The addition of ADP and EDTA produced modest increases in microsomal lipid peroxidation, suggesting that these chelators facilitated formation of reactive oxygen species by iron. The addition of DFX markedly inhibited microsomal lipid peroxidation, with greatest inhibition occurring with microsomes from TCD-treated animals. The results indicate that iron is involved in TCDD-induced lipid peroxidation.     

Environmentally persistent free radicals inhibit cytochrome P450 activity in rat liver microsomes

Combustion processes generate particulate matter that affects human health. When incineration fuels include components that are highly enriched in aromatic hydrocarbons (especially halogenated varieties) and redox-active metals, ultrafine particulate matter containing air-stable, environmentally persistent free radicals (EPFRs) is generated. The exposure to fine EPFRs (less than 2.5 μm in diameter) has been shown to negatively influence pulmonary and cardiovascular functions in living organisms. The goal of this study was to determine if these EPFRs have a direct effect on cytochrome P450 function. This was accomplished by direct addition of the EPFRs to rat liver microsomal preparations and measurement of several P450 activities using form-selective substrates. The EPFRs used in this study were formed by heating vapors from an organic compound (either monochlorophenol (MCP230) or 1,2-dichlorobenzene (DCB230)) and 5% copper oxide supported on silica (approximately 0.2 μm in diameter) to 230 °C under vacuum. Both types of EPFRs (but not silica, physisorbed silica, or silica impregnated with copper oxide) dramatically inhibited the activities of CYP1A, CYP2B, CYP2E1, CYP2D2 and CYP3A when incubated at concentrations less than 0.1 mg/ml with microsomes and NADPH. Interestingly, at the same concentrations, the EPFRs did not inhibit HO-1 activity or the reduction of cytochrome c by NADPH-cytochrome P450 reductase. CYP2D2-selective metabolism by rat liver microsomes was examined in more detail. The inhibition of CYP2D2-selective metabolism by both DCB230- and MCP230-EPFRs appeared to be largely noncompetitive and was attenuated in the presence of catalase suggesting that reactive oxygen species may be involved in the mechanism of inhibition.     

Carbon tetrachloride-induced lipid peroxidation of rat liver microsomes in vitro.

Characteristics of carbon tetrachloride-induced lipid peroxidation of rat liver microsomes and effect on microsomal enzymes were studies in vitro. Microsomes isolated from well-perfused livers and washed with EDTA-containing medium exhibited low endogenous lipid peroxidation when incubated in a phosphate buffer (> 0.1 M) in the presence of NADPH, whereas carbon tetrachloride stimulated to a great extent the peroxidation under these conditions. The stimulation was dependent on the concentration of NADPH, neither NADH nor ascorbic acid being replaced. The stimulatory action by bromotrichloromethane was more marked than that by carbon tetrachloride, however chloroform had no stimulatory action. N,N-Diphenyl-p-phenylene diamine, diethyldithiocarbamate and disulfiram inhibited carbon tetrachloride-induced lipid peroxidation in low concentrations. Inhibitions by thiol compounds and EDTA were weaker. Ferricyanide, cytochrome c and vitamine K₃ inhibited the stimulation by carbon tetrachloride while no inhibition was seen with carbon monoxide. An increase in the degree of carbon tetrachloride-induced lipid peroxidation resulted in a coincidental decrease in microsomal cytochrome P-450 content accompanying a parallel loss in aminopyrine demethylase activity, while NADH-ferricyanide dehydrogenase and NAD(P)H-eytochrome c reductase activities, and cytochrome b₅ content remained unaffected. Similar results were obtained when microsomes were peroxidized with NADPH in combination with ferric chloride and pyrophosphate. Regarding the mechanism of hepatotoxic action of carbon tetrachloride, these results support the hypothesis of lipid peroxidation.     

A possible mechanism of naproxen-induced lipid peroxidation in rat liver microsomes

Previous papers from our laboratory report that naproxen and salicylic acid induced lipid peroxidation in rat liver microsomes, however, the mechanism is still unclear. In the present paper, ferrous iron release, nicotinamide-adenine dinucleotide phosphate reduced form (NADPH) oxidation and hydrogen peroxide (H2O2) formation have been measured to find out which mechanisms are involved in naproxen- and salicylic acid-induced lipid peroxidation. While the increase of ferrous iron release was observed with high concentrations of naproxen, salicylic acid did not stimulate ferrous iron release. Neither of these drugs stimulated NADPH oxidation and H2O2 formation. However hexobarbital and perfluorohexane, known as uncouplers of cytochrome P450, stimulated microsomal NADPH oxidation, O2 consumption, H2O2 formation and water (H2O) formation involving four-electron oxidase reaction. These results suggest that ferrous iron release contributes to naproxen-induced microsomal lipid peroxidation and that naproxen and salicylic acid are not uncouplers of cytochrome P450. Apparently H2O2 does not play an important role in naproxen- and salicylic acid-induced microsomal lipid peroxidation.     

Dose-dependent study of the effects of acute lindane administration on rat liver superoxide anion production, antioxidant enzyme activities and lipid peroxidation

The administration of single i.p. doses of lindane (20, 40, 60 and 80 mg/kg) to rats produced a progressive increase in the liver microsomal content of cytochrome P-450 and in the rate of superoxide anion generation, as measured by adrenochrome formation. A dose-dependent increase in lipid peroxidation of liver homogenates, assessed by measuring thiobarbituric acid reactants, was also found. Lindane treatment did not alter the activity of liver glucose-6-phosphate dehydrogenase, glutathione reductase or glutathione peroxidase, while that of superoxide dismutase and catalase was significantly reduced. These changes were accompanied by a progressive liver steatosis. The collected metabolic data were interpreted in terms of a causal relationship between an increase in superoxide radical generation, secondary to cytochrome P-450 induction and a resulting increase in lipid peroxidation. The decrease in superoxide dismutase and catalase activities is likely to contribute to the increased levels of lipid peroxidation in view of their antioxidant properties.     

Propranolol as an inhibitor of some cytochrome P450-dependent monooxygenase activities in native and induced rat liver microsomes

The in vitro effect of propranolol (10(-3) M and 10(-4) M), a nonselective and extensively metabolized beta-adrenergic blocking agent, on rat liver drug metabolism in native and induced (with phenobarbital and beta-naphthoflavone [beta-NF]) microsomes was studied. The type of inhibition and the inhibitory constants of some cytochrome P450-dependent microsomal enzyme reactions (hexobarbital oxidation [HBO], ethylmorphine-N-demethylation [EMND], aniline hydroxylation [AH], ethoxycoumarin-O-deethylation [ECOD], ethoxyresorufin-O-dealkylation [EROD] and penthoxyresorufin-O-dealkylation [PROD]) were estimated. The results showed that propranolol competitively inhibited AH activity in native microsomes. The type of inhibition was changed from competitive to noncompetitive in all other enzyme activities studied. This inhibition was more pronounced after phenobarbital induction in PROD (Ki = 0.11 +/- 0.01 mM), ECOD (Ki = 0.40 +/- 0.09 mM) and EMND (Ki = 0.59 +/- 0.1 mM), and after beta-NF induction in AH (Ki = 0.28 +/- 0.05 mM) and in HBO (Ki = 0.35 +/- 0.1 mM) in native microsomes. It was assumed that the noncompetitive type of inhibition is due to the covalent binding of reactive metabolites derived from propranolol to hepatic microsomal proteins. The competitive type of inhibition of AH suggested a common P450 isoenzyme in the metabolism of propranolol and aniline. Thus, in this study, propranolol has been found to be not only a selective inhibitor of CYP2D6 isoenzyme-dependent reactions, but also a nonspecific inhibitor of other cytochrome P450 isoenzymes.     

Protection by gsh against lipid peroxidation induced by ascorbate and iron in rat liver microsomes

GSH is considered to be a potent inhibitor of 1ipid peroxidation, but the mechanisms by which it carries out this function are not clear. GSH-dependent factors which inhibit 1ipid peroxidation in the NADPH and in the ascorbate-iron microsomal 1ipid peroxidation systems have been demonstrated in rat liver 105,000 $\text{g}$ supernatant (1,2). This communication describes a GSH-dependent factor in the microsomal fraction of rat liver which inhibits ascorbate and iron-induced microsomal 1ipid peroxidation.     

Inhibitory action of Oren-gedoku-to extract on enzymatic lipid peroxidation in rat liver microsomes

We examined the inhibitory action of the extract of Oren-gedoku-to, a traditional herbal medicine known to act as an antioxidant, on enzymatic lipid peroxidation in rat liver microsomes. Simultaneous addition of a spray-dried preparation of Oren-gedoku-to extract (Tsumura TJ-15) inhibited enzymatic lipid peroxidation induced by reduced beta-nicotinamide adenine dinucleotide phosphate (NADPH) and ADP/Fe3+ complex in liver microsomes in a dose-dependent manner. When the inhibition by TJ-15 of enzymatic lipid peroxidation in liver microsomes was kinetically analyzed, this medicine showed a competitive inhibition against NADPH or ADP/Fe3+ complex. TJ-15 inhibited the NADPH-driven enzymatic reduction of ADP/Fe3+ complex or cytochrome c in liver microsomes competitively. TJ-15 enhanced NADPH consumption by liver microsomes with ADP/Fe3+ complex. Treatment with TJ-15 after the onset of enzymatic lipid peroxidation in liver microsomes inhibited the progression of lipid peroxidation in a dose-dependent manner. The present results indicate that Oren-gedoku-to extract inhibits enzymatic lipid peroxidation in rat liver microsomes in the initiation and propagation steps in a dose-dependent manner. These results also suggest that Oren-gedoku-to extract inhibits enzymatic lipid peroxidation in rat liver microsomes not only through its antioxidant action but also through reduction of the supply of electrons derived from NADPH to ADP/Fe3+ complex in liver microsomes both in a competitive manner and through stimulation of NADPH oxidation.     

Characterization of triptolide hydroxylation by cytochrome P450 in human and rat liver microsomes

Triptolide, the primary active component of a traditional Chinese medicine Tripterygium wilfordii Hook F, has a wide range of pharmacological activities. In the present study, the metabolism of triptolide by cytochrome P450s was investigated in human and rat liver microsomes. Triptolide was converted to four metabolites (M-1, M-2, M-3, and M-4) in rat liver microsomes and three (M-2, M-3, and M-4) in human liver microsomes. All the products were identified as mono-hydroxylated triptolides by liquid chromatography-mass spectrometry (LC-MS). The studies with chemical selective inhibitors, complementary DNA-expressed human cytochrome P450s, correlation analysis, and enzyme kinetics were also conducted. The results demonstrate that CYP3A4 and CYP2C19 could be involved in the metabolism of triptolide in human liver, and that CYP3A4 was the primary isoform responsible for its hydroxylation.     

Characterization of triptolide hydroxylation by cytochrome P450 in human and rat liver microsomes

Triptolide, the primary active component of a traditional Chinese medicine Tripterygium wilfordii Hook F, has a wide range of pharmacological activities. In the present study, the metabolism of triptolide by cytochrome P450s was investigated in human and rat liver microsomes. Triptolide was converted to four metabolites (M-1, M-2, M-3, and M-4) in rat liver microsomes and three (M-2, M-3, and M-4) in human liver microsomes. All the products were identified as mono-hydroxylated triptolides by liquid chromatography-mass spectrometry (LC-MS). The studies with chemical selective inhibitors, complementary DNA-expressed human cytochrome P450s, correlation analysis, and enzyme kinetics were also conducted. The results demonstrate that CYP3A4 and CYP2C19 could be involved in the metabolism of triptolide in human liver, and that CYP3A4 was the primary isoform responsible for its hydroxylation.     

Effect of multiple administration of calcium antagonists on lipid peroxidation in rat liver microsomes

The effects of three calcium antagonists, nifedipine (NF), verapamil (VP), and diltiazem (DT), on the lipid peroxidation (LPO) in rat liver microsomes were studied. The drugs were administered in oral doses of 50, 40, and 30 mg/kg daily for 21 days in male Wistar rats. Nonstimulated LPO was significantly decreased by NF and was not changed by VP and DT. There was a correlation between the extent of the previously found enzyme-inducing action and the potency of the antioxidant effects of calcium antagonists. Fe²⁺/NADPH- and Fe²⁺/ascorbate-stimulated microsomal LPO was increased by the calcium antagonists studied in the following order: VP>DT>NF (the increase caused by NF was insignificant in Fe²⁺/NADPH stimulation).