Role of lipid peroxidation in the toxicity of T-2 toxin

A. , G. , B. and W. . Role of lipid peroxidation in the toxicity of T-2 toxin. Toxicon 25, 1321 – 1328, 1987.—Recent reports suggest that lipid peroxidation may be involved in the toxicity of T-2 toxin. In the present study the influence of T-2 toxin on two parameters of lipid peroxidation was examined: the formation of thiobarbituric acid reactive material in isolated hepatocytes and liver homogenates from rats and ethane exhalation in vivo. In isolated hepatocytes there was no significant increase in thiobarbituric acid reactive material, neither after addition of T-2 toxin in vitro nor when the toxin had been applied to the rats 15 hr before preparation of hepatocytes. In liver homogenates the amount of thiobarbituric acid reactive material was increased up to 50% over the controls, depending on the dose of T-2 toxin. The increased values are difficult to interpret, because the extent of the increase depends on the method used for determination of thiobarbituric acid reactive material. Measuring another parameter of lipid peroxidation, i.e. ethane exhalation, there was no difference between the T-2 toxin treated rats and the controls whereas carbon tetrachloride treated rats exhaled high amounts of ethane. These results suggest that lipid peroxidation does not play a major role in T-2 toxin toxicity.     

Effect of T-2 toxin on lipid peroxidation in rats: Elevation of conjugated diene formation

A single dose of T-2 toxin (3.6 mg/kg, oral) enhanced conjugated diene formation in rat liver, spleen, kidney, thymus and bone marrow, implying that lipid peroxidation was stimulated. Lipid peroxidation showed apparent specificity in each organ as time elapsed (1–6 h). In liver and kidney maximum stimulation (+74% and +72%, respectively) was noted at l h after T-2 treatment. In spleen and thymus, maximum values were observed at 3 h (+95% and +32%, respectively). In bone marrow, a continuous elevation was noted which reached a maximum at 6 h (+ 112%). Results obtained from serum transaminase assay and histological examination suggested that T-2 toxin exhibited low hepatotoxicity even when the rat received a dose close to the oral LD₅₀.     

Effect of vitamin E on carbon tetrachloride-induced lipid peroxidation as demonstrated by in vivo pentane production

Pentane production by rats fed a stock diet exhibited a dose-dependent relationship with carbon tetrachloride (CCl₄) administered intraperitoneally. Total pentane produced during a 2-h test period following administration of a single dose of 30 μl CCl₄/100 g body wt. was greater by rats fed a vitamin Edeficient diet than by rats fed a diet supplemented with vitamin E. Vitamin Esupplemented rats pretreated with 30 μl CCl₄ daily for 4 days produced less pentane following administration of 60 μl CCl₄ on day 5 than did rats not pretreated with CCl₄; conversely, rats fed a vitamin E-deficient diet and similarly treated produced more pentane than did non-pretreated rats. This study confirmed that CCl₄ toxicity involves lipid peroxidation and that protection is provided by vitamin E. The usefulness in toxicological studies of monitoring pentane as an index of lipid peroxidation in vivo was shown.     

Effect of oral administration of T-2 toxin on glutathione shuttle enzymes, microsomal reductases and lipid peroxidation in rat liver

Effects of T-2 toxin on liver lipid peroxidation, glutathione shuttle enzymes and microsomal reductases have been studied in rats at 8, 16 and 24 hr after feeding a single dose of toxin (2.0 mg/kg) and at 7, 14 and 21 days after feeding of toxin (0.75 mg/kg) daily. Feeding of a single dose of T-2 toxin caused significant increase in liver lipid peroxidation in rats at 8, 16 and 24 hr post treatment. The liver lipid peroxidation was also significantly increased at 14 and 21 days after feeding of 0.75 mg/kg of T-2 toxin daily to rats. The activities of liver GSH-shuttle enzymes, i.e. glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase, were significantly higher in rats after both feeding schedules of T-2 toxin. NADPH-cytochrome c reductase activity was significantly lower at 8, 16 and 24 hr in liver of rats fed a single dose of T-2 toxin, whereas NADH-cytochrome b5 reductase was significantly higher until 16 hr and then declined below normal at 24 hr post treatment. In rats fed multiple doses of T-2 toxin, both liver microsomal reductases were significantly reduced. These results suggest that T-2 toxin/or its metabolites in the liver may be involved in the generation of free radicals which cause the observed increase in lipid peroxidation.     

Effect of T-2 toxin administration to rats on lipid metabolism in liver

The effect of oral dosing of rats with 1.5 mg T-2 toxin/kg body weight daily for 4 days on metabolism of liver lipids was studied. T-2 toxin significantly elevated total liver lipids, triglycerides, free cholesterol, total phospholipids and phosphatidyl choline, whereas the level of sphingomyelin + lysophosphatidyl ethanolamine was reduced. No change in the esterified cholesterol and phosphatidyl ethanolamine contents was observed. Incorporation of [1-14C]acetate into liver lipids, esterified cholesterol, triglycerides, free cholesterol and phosphatidyl ethanolamine was reduced in T-2 toxin-treated animals, implying reduced lipogenesis. Increased lipids in liver in T-2 toxin-treated rats are possibly due to an impaired secretion of lipids from the liver.     

Effect of in vivo administration of T-2 toxin on peritoneal murine macrophages

We investigated the effect of in vivo administration of T-2 toxin, a 12,13-epoxytrichothecene produced by several Fusarium species, on murine macrophage metabolism. Cytoplasmic and lysosomal enzyme levels, generation and release of superoxide anion, phagocytosis and intracellular killing of Salmonella typhi and murine P815 tumour cell lysis were measured under different experimental conditions. When T-2 toxin was administered to mice at sublethal doses (0.50-1.00 mg/kg/24 hr), the levels of lysosomal and cytoplasmic enzyme activity and the generation of superoxide anion were significantly enhanced as compared to controls. This correlated with increased phagocytosis and intracellular killing of S. typhi. Cytotoxic activity against murine P815 mastocytoma cells exhibited by macrophages isolated from mice treated with T-2 toxin was inhibited in a dose-dependent manner. In vivo administration of T-2 toxin may result in the activation of specific metabolic pathways of peritoneal macrophages, while inhibiting other paths.     

Suppressive effect of vitamin E on lipid peroxidation in halothane-administered guinea pig liver.

The effect of vitamin E on halothane-induced liver damage was studied in guinea pig halothane hepatitis. Twenty animals were divided into 3 groups, consisting of a control group, a halothane group and a vitamin E + halothane (H) group. The animals in the control group (n = 6) were allowed to inhale air only. The animals in the halothane group (n = 6) and the vitamin E + H group (n = 8) were allowed to inhale 1% halothane with air. Animals in the vitamin E + H group were additionally injected with 30 mg kg-1 of vitamin E 30 minutes prior to inhalation of halothane. Blood was aspirated from the heart immediately after sacrificing to measure the serum activity of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT). A microsomal suspension was prepared from the excised liver. Then the amount of thiobarbituric acid (TBA) reactive products in the microsomes were measured. The amount of tissue TBA-reactive products was increased by inhalation of halothane. The increase in the amount of TBA-reactive product was inhibited by the administration of vitamin E. The serum GPT activity was increased by halothane inhalation. Increased serum GOT and GPT activity were inhibited by the administration of vitamin E. These results demonstrated that vitamin E suppressed halothane-induced liver damage in the guinea pig by inhibiting lipid peroxidation.     

Effect of vitamin E on lipid peroxidation and liver monooxigenase activity in experimental influenza virus infection

Influenza virus infection was associated with development of oxidative stress in liver of mice, viz. increase in amount of lipid peroxidation products, decrease in cytochrome P-450 and NADP. H-cytochrome c-reductase activity, and inhibition of liver monooxygenases (aniline hydroxylase, ethylmorphine-N-demethylase, amidopyrine-N-demethylase and analgin-N-demethylase). These effects were most pronounced on the 7th day after virus inoculation as compared to the 5th one. Supplementation of mice with vitamin E before virus inoculation leads to liver protection against oxidative stress and toxicosis. A marked decrease of lipid peroxidation products and an increase of cytochrome P-450 and activities of monooxygenases was established. The stabilizing effect of vitamin E was dose-dependent and was most pronounced on the 5th day after virus inoculation as compared to the 7th one.     

Effect of an acute dose of ethanol on lipid peroxidation in rats: action of vitamin E.

Free radical generation is an important step in the pathogenesis of ethanol-associated liver injury. Administration of ethanol induces an increase in lipid peroxidation both by enhancing the production of oxygen reactive species and by decreasing the levels of endogenous antioxidants. This work focuses on the generation of free radicals provoked by an acute ethanol dose in rats, and the role of different dietary levels of vitamin E. The objective of this investigation was to study the effect of three different dietary levels of vitamin E (deficient, control and supplemented with 20 times higher levels) on plasma and liver lipid peroxidation (assayed by TBARS), vitamin E in plasma and liver, and hepatic glutathione concentration, in rats receiving the different diets. The animals were submitted to an acute dose of ethanol (5 g/kg body weight) administered by gavage at the end of an experimental 4 week period and were sacrificed at 0, 2, 4, 8 and 24 h after ethanol administration. Dietary vitamin E caused a dose-dependent increase in liver and plasma concentration of the vitamin, but ethanol administration decreased hepatic vitamin E in all groups. TBARS concentrations were higher in liver of rats that received the deficient diet, independent of ethanol, however, liver TBARS concentrations were low in control and supplemented groups, but increased with ethanol ingestion. Glutathione levels were lowered by ethanol administration in all groups, in different times, but recovered to this original level in 24 h time. In conclusion, vitamin E deficiency alone induces liver lipid peroxidation in rats, acute administration of ethanol affect vitamin E and GSH level and maintenance of adequate or higher vitamin E levels acts as a protective factor against free radical generation.     

Hepatic lipid peroxidation, sulfhydryl status, and toxicity of the blue-green algal toxin microcystin-LR in mice

Microcystin-LR (MCLR), a cyclic heptapeptide produced by the blue-green algae Microcystis aeruginosa, produces death in female mice treated with 100 micrograms MCLR/kg. Kupffer-cell hyperplasia was observed histologically after treatment with 50 or 100 micrograms MCLR/kg. No other changes or lethality were observed with the 50 micrograms MCLR/kg, while 100% lethality occurred in less than 2 h in mice treated with 100 micrograms/kg. In these animals liver weights increased by 45% and hepatic hemoglobin content increased 106% at 60 min posttreatment. Liver histology showed loss of hepatic architecture and necrosis 30 min after treatment, and congestion with blood became evident at 45 min after treatment. Serum enzymes were significantly increased 45 min posttreatment. Hepatic nonprotein sulfhydryl content decreased 19% when calculated on the basis of cytosolic protein and 39% when based upon the total protein content, respectively. The sulfhydryl content of the liver cytoskeletal fraction decreased 26% by 30 min after treatment. Decreased enzyme-mediated and increased non-enzyme-mediated lipid peroxidation were observed in hepatic microsomes following both in vivo and in vitro exposure of hepatic microsomes to MCLR. The toxicity of MCLR may be related to alterations in the sulfhydryl content of the cytoskeletal protein. Furthermore, MCLR may either directly or indirectly affect microsomes, suggesting alterations in structure and function of smooth endoplasmic reticulum.     

维生素E对创伤小鼠T细胞功能以及脂质过氧化和膜流动性的影响

观察了创伤小鼠Ｔ细胞丙二醛（ＭＤＡ）含量、膜流动性、Ｔ细胞功能的变化以及维生素Ｅ（Ｖ－Ｅ）的治疗作用。结果显示，创伤后Ｔ细胞ＭＤＡ含量增加；Ｔ细胞质膜，线粒体膜及微粒体膜流动性降低；Ｔ淋巴细胞转化、白介素２（ＩＬ－２）的产生、ＩＬ－２受体（ＩＬ－２Ｒ）的表达以及ＩＬ－２介导的淋巴细胞增殖反应均受抑。这些变化同ＭＤＡ的改变均密切相关。Ｖ－Ｅ（５０或１００ｍｇ·ｋｇ－１·ｄ－１，ｉｍ×４ｄ）可明显逆转各指标的变化。表明创伤后脂质过氧化反应是导致Ｔ细胞膜流动性降低及Ｔ细胞功能受抑的重要原因，而Ｖ－Ｅ则具有明显的治疗效果。     

T2毒素对大鼠红细胞膜脂流动性及脂质过氧化的影响

Ｔ２毒素对大鼠红细胞膜脂流动性及脂质过氧化的影响彭双清，杨进生（北京毒物药物研究所，北京１００８５０）Ｔ２毒素是倍半萜类两歧性分子，极易与膜发生作用［１］．它能抑制ＤＮＡ，ＲＮＡ和蛋白质的合成，引起ＤＮＡ单链断裂及多核蛋白体分裂，以及与巯基酶相结合［...     

Influence of vitamin E and selenium on glutathione-dependent protection against microsomal lipid peroxidation

A GSH-dependent microsomal protein which inhibits lipid peroxidation has been described [R. F. Burk, Biochim. biophys. Acta 757, 21 (1983)]. Studies of its mechanism indicate that it scavenges free radicals. Vitamin E (alpha-tocopherol) and selenium are micronutrients which protect against lipid peroxidation. The effect of nutritional deficiencies of these substances on the GSH-dependent protection against rat liver microsomal lipid peroxidation was studied to determine whether GSH, selenium and alpha-tocopherol function through separate or shared mechanisms. In the ascorbate-iron microsomal lipid peroxidation system, there is a 1-3 min lag phase before lipid peroxidation begins. The length of the lag correlated well (r = 0.87) with the microsomal alpha-tocopherol content as measured by high pressure liquid chromatography. Thus, the selenium-deficient microsomes, which had a shorter lag than controls, had a somewhat lower alpha-tocopherol content. The vitamin E-deficient microsomes, which had no detectable alpha-tocopherol, had the shortest lag, but a distinct lag was present. Addition of 0.1 mM GSH to control microsomes prolonged the lag by 270%. In selenium-deficient and vitamin E-deficient microsomes, which had shorter initial lags, GSH addition caused 345 and 280% increases respectively. This suggests that the function of the GSH-dependent protective mechanism is unimpaired in these deficiencies. Trypsin digestion of microsomes, which abolished the lag completely and destroyed the GSH-dependent protection, had no effect on microsomal alpha-tocopherol content, however. These experiments illustrate the importance of two defenses against microsomal lipid peroxidation: the GSH-dependent protein which is responsible for the existence of the lag, and alpha-tocopherol which affects the length of the lag. They suggest that these defenses function separately to prevent peroxidation of membrane polyunsaturated fatty acids. Selenium appears to affect microsomal alpha-tocopherol content but to have no other effect on the microsomal lipid peroxidation system.     

Effect of occupation on lipid peroxidation and antioxidants' status in masons

Effect of occupation on haematological factors, lipid peroxidation and antioxidants' status was studied in masons and compared with normal subjects. Red blood corpuscles (RBC), haemoglobin (Hb), Vitamin C, Vitamin E, beta-carotene levels and glutathione peroxidase (GSHPx), superoxide dismutase (SOD) and catalase (CAT) activities decreased. Thiobarbituric acid reacting substances (TBARS) level increased. Occupational exposure to cement increased lipid peroxidation but decreased antioxidants' levels in masons. Increased lipid peroxidation seems to be responsible for the reduction in RBC and Hb.     

Nuclear lipid peroxidation induced in rat liver by T-2 mycotoxin

Oral administration to rats of T-2 mycotoxin (1.25 mg/kg) for five days causes an increase in lipid peroxidation (ascorbate-induced as well as NADPH-dependent) in hepatic nuclei, while the activity of liver glutathione-S-transferase (EC. 2.5.1.18) is decreased. The hepatotoxicity could be due to lipid peroxidation induced by depletion of hepatic reduced glutathione and/or production of free radicals.     

Acute paracetamol intoxication of starved mice leads to lipid peroxidation in vivo.

Lipid peroxidation was monitored in female mice in vivo by the measurement of exhalated hydrocarbons. In liver homogenates in vitro lipid peroxidation as determined by malondialdehyde formation, and hepatic total glutathione levels were measured. After a dose of 500 mg/kg i.p. of paracetamol, the hepatic glutathione of fed mice decreased from 61 nmoles/mg liver protein to 30 nmoles/mg, while the animals expired 5 nmoles of ethane/kga · hr. The same dose in starved mice led to a glutathione level of 6 nmoles/mg and an exhalation rate of 125–150 nmoles ethane/kg · hr. In vivo determined and post-mortem in vitro determined lipid peroxidation correlated with a coefficient of 0.66. If hepatic glutathione was depleted to the same extent by administration of diethylmaleate, no significant lipid peroxidation was found. Our findings demonstrate that the drug-induced depletion of liver glutathione leads in vivo to lipid peroxidation, provided that the glutathione level has been diminished by starvation. The data indicate that glutathione depletion alone by other mechanisms does not account for lipid peroxidation. Hence the hepatoprotective role of liver glutathione against drug-induced liver injury has to be reconsidered in detail. This investigation shows a suitable model for such studies.     

维生素E和锌对肝硬化大鼠脂质过氧化和糖代谢的影响

采用半乳糖胺(Galn)诱导大鼠肝硬化.其血清和肝中脂质过氧化物升高,谷胱甘肽氧化还原系统失衡;谷草转氨酶,羟脯氨酸水平升高;肝铜蓄积,锌,铁丢失;血清锌,铜,铁含量升高,血糖,胰岛素,胰高血糖素代谢异常,补充维生素E可使谷草转氨酶,羟脯氨酸,脂质过氧化水平降低,肝脏和血中谷胱甘肽和微量元素维持平衡,并能纠正血糖,胰岛素,胰高血糖素代谢紊乱,减轻肝损伤及纤维增生。肝硬化大鼠锌代谢异常,大剂量或长时间不适当补锌同样可以造成肝锌,铜,铁比例失调,对保护肝脏免受Galn毒性及纠正血糖,胰岛素,胰高血糖素代谢紊乱产生不利影响。     

Effect of cadmium chloride on hepatic lipid peroxidation in mice

Intraperitoneal administration of cadmium chloride to 8-12 weeks old CBA-mice enhanced hepatic lipid peroxidation. A positive correlation between cadmium chloride dose and level of peroxidation was observed in both male and female mice. A sex-related difference in mortality was not observed but at a dose of 25 mumol CdCl2/kg the level of hepatic lipid peroxidation was higher in male mice than in female mice. The hepatic lipid peroxidation was not increased above the control level in 3 weeks old mice, while 6 weeks old mice responded with increased peroxidation as did 8-12 weeks old mice. The mortality after an acute toxic dose of cadmium chloride was the same in the three age groups. Pretreatment of mice with several low intraperitoneal doses of cadmium chloride alleviated cadmium induced mortality and lipid peroxidation. The results demonstrate both age dependency and a protective effect of metallothionein induction on cadmium chloride induced hepatic lipid peroxidation.     

5种抗肿瘤药对小鼠脂质过氧化作用的影响

研究抗肿瘤药甲氨蝶呤、阿糖胞苷、环磷酰胺、5—氟尿嘧啶和丝裂霉素C对小鼠脂质过氧化作用的影响、结果显示:5种抗肿瘤药使小鼠血清和肝、脑中MDA含量显著升高.但对肝组织体外生成MDA的速度无明显影响。提示这些药物对过氧化脂质的代谢有严重干扰。