Metallothionein induction in rat liver by dietary restriction or exercise and reduction of exercise-induced hepatic lipid peroxidation

Metallothioneins (MTs) occur throughout the animal kingdom and they are induced in vivo by metals, hormones, cytotoxic agents, and some kind of stress. It is well known that various stresses such as starvation and immobilization can induce MT synthesis in animal tissues, but the influence of dietary restriction is unknown. The MT levels in the liver increased by food-deprivation and then decreased by refeeding, and a long period of starvation down-alters hepatic MT levels. When the stress is intensified, the induced quantity of hepatic MT is reduced. It became clear that hepatic MT concentrations are controlled within a two fold limit when stressed by dietary restriction. MT was also induced in rat liver at recovery stage following an exhaustive running exercise, and thionein was synthesized first and then zinc bound to the protein. The half-life of hepatic MT induced by exercise (which is a nonmetallic inducer) was estimated at 5.2 h. Preinduced MT markedly suppressed exercise-induced lipid peroxidation in rat liver.     

Evidence for carbon tetrachloride-induced lipid peroxidation in mouse liver

The involvement of lipid peroxidation in the mechanism of carbon tetrachloride-induced hepatotoxicity has been a point of controversy. Previous investigators have reported an absence of lipid peroxidative degradation products in mice after exposure to carbon tetrachloride and have used this evidence against the hypothesis that lipid peroxidation is an integral part of the events that cause tissue damage. We have compared the extent of lipid peroxidation caused by carbon tetrachloride between Sprague-Dawley rats and three strains of mice (A/J, BALB/cJ, and C57B1/6J) in in vitro and in vivo systems. Hepatic microsomes isolated from fasted mice of each strain produced more malondialdehyde (a degradation product of lipid peroxidation) per mg microsomal protein than those isolated from fasted rats at all times of incubation with CCl₄. In vivo lipid peroxidation was estimated by the lipid conjugated diene content in hepatic microsomes from the rat and three strains of mice. Increased conjugated diene formation was observed in microsomal lipids of these animals after intraperitoneal injection of CCl₄ (1 ifml/kg as a 20% solution in corn oil) when compared to animals given only corn oil, but no differences were found in the amount of conjugated dienes between mice and rats. Our observations show that the CCl₄-treated mouse undergoes hepatic lipid peroxidation at least as well as the rat, and indicate that lipid peroxidation cannot be excluded as a mechanism of carbon tetrachloride hepatotoxicity as has been claimed on the basis of its ineffectiveness in the mouse.     

An association between lipid peroxidation and alpha-naphthylisothiocyanate-induced liver injury in rats

An association between lipid peroxidation and alpha-naphthylisothiocyanate (ANIT)-induced liver injury was examined in rats injected once with the toxicant (75 mg/kg body weight). The severity of liver injury was estimated 12, 24, 48, and 72 h after ANIT injection. Liver injury appeared 24 h after ANIT injection, progressed at 48 h, and recovered at 72 h, judging from the serum levels of marker enzymes and components. Serum lipid peroxide (LPO) concentration increased 24 h after ANIT injection and further increased at 48 h, but this increase was attenuated at 72 h. In contrast, liver LPO content increased 12 h after ANIT injection and further increased 24 and 48 h, but this increase was attenuated at 72 h. Similarly, myeloperoxidase (MPO) activity, an index of neutrophil infiltration, in the liver tissue increased 12 h after ANIT injection and further increased at 24 and 48 h, but this increase was attenuated at 72 h. Either serum LPO concentration or liver LPO content was significantly correlated with liver MPO activity (r = 0.661 for serum LPO concentration; r = 0.585 for liver LPO content). These results suggest that lipid peroxidation might be associated with ANIT-induced liver injury in rats and that this lipid peroxidation might occur via oxygen radicals derived from neutrophils infiltrated into the liver tissue of ANIT-intoxicated rats.     

N-乙酰半胱氨酸对实验性肝硬化大鼠肝纤维化与脂质过氧化的影响

目的:探讨N-乙酰半胱氨酸(NAC)对肝硬化大鼠的作用及其影响肝纤维化与脂质过氧化损伤的机制。方法:雄性Wistar大鼠36只,随机分成正常组(7只)、模型组(14只)、NAC组(15只)。以10μL·kg~(-1)剂量二甲基亚硝胺(DMN)腹腔注射,每周连续3d,每日1次,共4 wk,诱导大鼠肝硬化模型。成模后,NAC组以NAC 0．1 g·kg~(-1)灌胃,每日1次,共4 wk;模型组给予等量生理盐水灌胃。HE染色与天狼猩红染色观察肝组织炎症与胶原沉积;水解法测定肝组织羟脯氨酸含量;生化法检查血清肝功能指标[丙氨酸转氧酶(ALT)、天冬氨酸转氨酶(AST)、总胆红素(TBil)、清蛋白(Alh)等],肝组织超氧化物歧化酶(SOD)活性与丙二醛(MDA)含量;Western印迹法检测肝组织α-平滑肌肌动蛋白(α- SMA)与热休克蛋白47(HSP47)表达。结果:治疗4 wk后,模型组大鼠死亡7只,NAC组死亡3只, NAC明显提高肝纤维化大鼠的生存率(P＜0．01)。与正常组相比,模型大鼠肝脏肝细胞变性、坏死明显,炎性细胞浸润,胶原沉积并形成假小叶;血清ALT、AST和TBil升高,AIb下降;肝组织羟脯氨酸与MDA含量升高,SOD活性下降(P＜0．01)。而NAC可显著减轻肝脏炎症、肝细胞坏死与肝组织胶原沉积,改善模型大鼠异常的肝功能指标,降低肝组织羟脯氧酸与MDA含量,提高SOD活性(P＜0．05,P＜0．01),抑制模型大鼠肝组织HSP47与α-SMA蛋白的表达(P＜0．01)。结论:N-乙酰半胱氨酸有良好的治疗肝硬化作用,其作用机制与促进肝纤维化逆转及抗肝脏脂质过氧化有关。     

绞股蓝在大鼠肝的抗脂质过氧化作用

目的：观察绞股蓝（GP）对四氯化碳（CCl4)所致肝脏脂质过氧化的干预作用。方法：将Wistar大鼠随机分为4组：A（对照组）;B（CCL4）;C（GP);D(CCL4＋CP）。结果：CCL4组的脂质过氧化物（LPO）含量明显高于对照组,谷胱甘肽过氧化物酶（GSH－Px）活性低于对照组;而同时给予GP的D组可减弱CCL4诱发的上述作用。结论：GP能减弱CCL4对肝脏的损害。     

胸腺和性激素对大鼠肝脏脂质过氧化的调节作用(英文)

本文应用成年去胸腺或去性腺Wistar大鼠研究了胸腺对肝脏脂质过氧化(LPO)的影响及其与性激素有关的中间途径,结果表明,雌性成年去胸腺(ATx)大鼠肝匀浆丙二醛(MDA)含量增高,但雄性ATx大鼠肝脏MDA无明显变化;同时雌性ATx大鼠血浆雌二醇水平下降,雄性ATx大鼠血浆睾酮浓度降低,雌性大鼠卵巢切除术后肝脏MDA的变化与胸腺切除术后的变化相似,给予雌二醇可逆转去卵巢大鼠肝脏MDA的增高,在雄性大鼠中,无论是切除睾丸还是睾丸切除后补充睾酮对肝脏MDA均无明显影响,此外,给雌性ATx大鼠注射雌二醇可逆转其肝脏MDA的增高,这些结果提示胸腺在调节雌性大鼠肝脏抗氧化功能中起着重要作用,这种作用可能通过雌激素介导,因此我们设想在体内可能存在:胸腺-雌激素-肝脏通路”,它参与对肝脏抗氧化功能的调节。     

Rosmarinic acid ameliorates acute liver damage and fibrogenesis in carbon tetrachloride-intoxicated mice

The aim of this study was to investigate the therapeutic potential of rosmarinic acid (RA), a natural phenolic, in the treatment of acute liver toxicity. RA at 10, 25 and 50 mg/kg was administered by gavage once daily for 2 consecutive days, 6 h after CCl₄ intoxication. CCl₄ intoxication caused hepatic necrosis and increased serum ALT activity. In the livers, oxidative/nitrosative stress was evidenced by increased 3-nitrotyrosine (3-NT) and thiobarbituric acid reactive substances (TBARS) formation and a significant decrease in Cu/Zn superoxide dismutase (SOD) activity. CCl₄ administration triggered inflammatory response in mice livers by activating nuclear factor-kappaB (NF-κB), which coincided with the induction of tumor necrosis factor-alpha (TNF-α) and cyclooxygenase-2 (COX-2). RA improved histological and serum markers of liver damage and significantly ameliorated oxidative/nitrosative stress and inflammatory response in liver tissue. Additionally, RA prevented transforming growth factor-beta1 (TGF-β1) and alpha-smooth muscle actin (α-SMA) expression, suggesting suppression of profibrotic response. Furthermore, RA significantly inhibited the CCl₄-induced apoptosis, which was evident from decreased cleavage of caspase-3. The hepatoprotective activity of RA coincided with enhanced NF-E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression. The results of this study indicates that RA possesses antioxidant, anti-inflammatory, antiapoptotic and antifibrotic activity against acute liver toxicity.     

Effect of black tea on lipid peroxidation in carbon tetrachloride treated male rats

This study examined the effects of black tea (Camellia sinensis L.) on lipid peroxidation and glutathione levels in carbon tetrachloride (CCl4)-treated male Wistar rats. Three groups of rats formed two control groups and one treatment group. The control groups were fed with a standard diet, while the black tea group were fed the standard diet plus 6% by weight dried black tea leaves. After two months, the rats in the black tea group and in one control group were administered a single dose of CCl4 (1 ml/kg, i.p.) and sacrificed two hours later. Rats in the other control group were administered olive oil in a similar fashion. Lipid peroxide levels in liver and plasma, glutathione (GSH) levels in liver and alanine transaminase (ALT) and aspartate transaminase (AST) activities in plasma were measured. Rats in the black tea group were found to have significantly decreased liver lipid peroxide levels, and ALT and AST activities compared with the rats in the CCl4-treated control group. In addition, liver glutathione levels were decreased in the black tea group. These data suggest that black tea attenuates CCl4-induced hepatic injury.     

Effect of Picroliv on impaired hepatic mixed-function oxidase system in carbon tetrachloride-intoxicated rats

A drastic impairment in hepatic mixed-function oxidase (MFO) system was observed in rats 24 h following ip injection of CCl₄ (1.0 ml/kg body weight), as indicated by a decrease in the activities of various microsomal enzymes related to drug metabolism (e.g., aniline hydroxylase, aminopyrine-N-demethylase, benzo(a)pyrene hydroxylase, NADH/NADPH cytochrome c reductase, glutathione-s-transferase, cytochrome P-450, and cytochrome b₅). In addition, total protein and reduced glutathione content in liver were decreased, while a significant elevation in the level of lipid peroxides was observed. Hepatoprotection afforded by oral pretreatment of CCl₄ intoxicated rats with multiple doses (6.0 mg/kg × 7 days) of Picroliv (standardized iridoid glycoside fraction, obtained from roots and rhizomes of Picrorhiza kurroa), was evidenced by a significant improvement in the activities of various enzymes related to drug metabolism. Alterations in levels of total proteins, reduced glutathione, and lipid peroxides in liver were also significantly prevented by Picroliv pretreatment. Drug Dev. Res. 41:44–47, 1997. © 1997 Wiley-Liss, Inc.     

Protection by diethyldithiocarbamate against carbon tetrachloride lethality in rats and against carbon tetrachloride-induced lipid peroxidation in vitro

Diethyldithiocarbamate provides excellent protection against carbon tetrachloride-induced lethality when administered 1 hr prior to the poison. Lipoperoxidation of liver microsome preparations and the pro-oxidant effect of carbon tetrachloride in vitro are inhibited by low concentrations of diethyldithiocarbamate. On the other hand, NADPH-cytochrome c reductase activity is not affected by addition of diethyldithiocarbamate. These results suggest that the action of the protective agent is not at the level of the flavoprotein of the microsomal electron transport system but elsewhere in the process of lipid peroxidation.     

Stimulation of lipid peroxidation and impairment of glutathione-dependent defence system in the liver of rats repeatedly treated with carbon tetrachloride

To study the effect of carbon tetrachloride treatment on hepatic lipid peroxidation and glutathione-dependent defence system, rats were injected with carbon tetrachloride (0.2 ml/kg body weight, i.p.) twice weekly for a period of 4 weeks. Carbon tetrachloride treatment caused a significant increase in hepatic lipid peroxide levels and significant decreases in hepatic glutathione levels and glutathione peroxidase and glutathione transferase activities. These results show that chronic carbon tetrachloride administration to rats leads to the stimulation of hepatic lipid peroxidation, which seems to be the consequence of impaired cellular defence by glutathione and glutathione-related enzymes.     

Effect of Silybum marianum oil and legalon on lipid peroxidation and liver antioxidant systems in rats intoxicated with carbon tetrachloride

An oil obtained from the seeds of Saint-Mary thistle (Silybum marianum) and the drug legalon (silybinin) prepared from this plant produce an antioxidant effect on liver tissues of rats poisoned with carbon tetrachloride. Legalon (25 mg/kg) and the oil (2000 mg) reduced the level of lipid peroxidation, increased the catalase activity, but did not reduce the concentration of selenium in liver (which decreased as a result of CCl4 intoxication). Legalon significantly increased the activity of superoxide dismutase in liver tissues, while the Saint-Mary thistle oil did not produce such effect.     

Neurobehavioral effects of dietary restriction in rats

The effects of reduced body weight gain on nervous system function of young male Fischer 344 rats were examined. The rats were fed 15% ('mild') or 50% ('severe') less than the controls. Mild and severe dietary restriction resulted in 9% and 38% lower body weight compared to the controls. Mild dietary restriction caused slight changes in flash evoked potentials, auditory brainstem responses, caudal nerve action potentials, and body temperature. Severe dietary restriction increased the magnitude of the effects noted in the mild group, as well as causing a significant decrease in grip strength. Somatosensory evoked responses were not affected by either mild or severe restriction. Diet restricted rats were more excitable while restrained for testing. Thus, dietary restriction has significant effects on numerous behavioral and neurophysiological parameters that should be considered in the interpretation of neurotoxicological data when body weight differences are present.     

Effects of lipid peroxidation on activities of drug-metabolizing enzymes in liver microsomes of rats

A relationship was found between the formation of lipid peroxides and the activities of drug-metabolizing enzymes in liver microsomes of rats. Induction of lipid peroxidation by incubation with ferrous ion led to a sharp decline in the ability of the microsomal enzyme system to demethylate ethylmorphine. Inhibition of lipid peroxidation by EDTA increased the enzyme activity about two-fold. Addition of EDTA (0.1 mM) to the incubation mixture produced marked changes in the Michaelis constants of drug-metabolizing enzymes and in inhibition constants of SKF 525-A for drug-metabolizing enzymes.     

Alkane formation during liver microsomal lipid peroxidation

During treatment of animals with the hepatotoxin carbon tetrachloride (CCl₄) short-chain alkanes, e.g. ethane and n-pentane, are formed (1–6). It is now generally accepted that these alkanes originate from the decomposition of lipid hydroperoxides (7). However, studies with model compounds demonstrated that metal ions, e.g. iron, are involved in the breakdown of lipid hydroperoxides to alkanes (8, 9). Because we were interested whether metal ions are also involved in CCl₄-induced lipid peroxidation we studied the effect of ferrous ions on CCl₄-induced alkane formation in rat liver microsomes. This could be important, because lipid peroxides are fairly stable in absence of metal ions (10). First of all we had to develop an in vitro system which gives reproducible measurements of alkanes during microsomal incubation. Furthermore, we had to examine whether these alkanes are indeed formed in hepatic microsomes due to CCl₄. On the other hand, we had to find out what the optimal iron concentration in this system would be.     

急性黄磷中毒大鼠肝脏的脂质过氧化与肝损害的关系

本研究以黄磷3,6和9mg/kg ig,观察大鼠3,6,12和24h急性中毒时肝脏发生脂质过氧化程度、部位,以及与肝损害之间的关系。结果发现中毒大鼠肝匀浆、肝线粒体与微粒体MDA含量显著升高。肝匀浆Schiff碱荧光强度显著增强。肝线柱体与微柱体各自的标志酶SDH酶与G-6-P酶活性均显著降低,而且两亚细胞器的MDA含量升高与各自标志酶活性降低存在显著的负相关。肝TG含量显著升高与肝GSH含量显著降低的肝损害指标变化与脂质过氧化指标变化存在一定的平行关系。     

Gentamicin-induced kidney damage and lipid peroxidation in rats

Although it has been reported that injections of gentamicin induces lipid peroxidation in rat renal cortex (Ramsammy et al. (1985) Biochem. Phannacol. 34, 3895–3900), our results showed no modification of thiobarbituric-reagent substances (TBARS) or in analysis of the polyunsaturated fatty acid profile. Moreover, endogenous vitamin E and glutathione were not consumed. In in vitro systems, gentamicin incubated with microsomes, homogenates and kidney slices from the normal rat failed to induce lipid peroxidation. We show that the increase in TBARS in vivo detected by Ramsammy et al. was wrongly attributed to the oxidant power of gentamicin. As this antibiotic does react positively to thiobarbituric acid in the presence of a system generating free radicals, it is possible that these authors accidentally introduced such a system into their experiments.     

Mechanism of enhanced lipid peroxidation in the liver of Long-Evans cinnamon (LEC) rats

The Long-Evans Cinnamon (LEC) rat is a mutant strain of rats that accumulate copper (Cu) in the liver in much the same way as individuals who suffer from Wilson's disease (WD) and has been suggested as a model for this disease. Lipid peroxidation (LPO) is considered to be involved in the toxic action of Cu in the livers of LEC rats. We investigated the mechanism of LPO in the livers of LEC rats showing apparent signs of hepatitis. Several-fold higher LPO levels were observed in post-mitochondrial supernatant (S-9) fraction of livers from hepatitic LEC rats than in those from Wistar rats. To mimic living cells, we introduced NADPH-generating system (NADPH-gs) into the S-9 incubation system. Thus was ensured a constant supply of NADPH to vital enzymes that may be directly or indirectly involved in the generation and/or elimination of reactive oxygen species (ROSs), such as glutathione reductase (GSSG-R), which require NADPH for their reactions. The levels of LPO in liver S-9 from hepatitic LEC rats were further increased by incubating liver S-9 at 37 °C in the presence of NADPH-gs. This increase was inhibited by EDTA, butylated hydroxytoluene (BHT), and catalase (CAT), suggesting that some metal, most likely the accumulated Cu, and ROSs derived from hydrogen peroxide (H₂O₂) are involved in the increased levels of LPO in the livers of hepatitic LEC rats. The requirement of NADPH-gs for enhanced LPO in the livers of hepatitic LEC rats indicates the consumption of NADPH during reactions leading to LPO. It is known that H₂O₂, and consequently hydroxyl radical are generated during Cu–catalyzed glutathione (GSH) oxidation. The cyclic regeneration of GSH from GSSG by NADPH-dependent GSSG-R in the presence of NADPH-gs may cause sustained generation of hydroxyl radical in the presence of excess free Cu. The generation of H₂O₂ in S-9 fraction of livers from hepatitic LEC rats was observed to be significantly higher than that in S-9 fraction of livers from non-hepatitic LEC rats and Wistar rats. Moreover, in addition to the reported decrease in glutathione peroxidase (GPX) activity, we found that CAT activity was markedly decreased in LEC rats with hepatitis. The increased generation of H₂O₂ with reduced activities of GPX and CAT may result in cellular accumulation of H₂O₂ in the liver of hepatitic LEC rats. Taken altogether, it is suggested that the accumulated H₂O₂ undergoes the Fenton-type reaction with also accumulated free Cu, thus generating hydroxyl radical in the livers of hepatitic LEC rats and increasing LPO levels in these animals. Received: 20 April 1999 / Accepted: 2 September 1999