Suppressive effect of tritoqualine on lipid peroxidation and enzyme leakage induced by carbon tetrachloride in rat hepatocytes

Since tritoqualine (TRQ) is effective in suppressing the increase of serum transaminases in acute hepatic injured rats induced by some hepatotoxins, protection of the hepatocyte membrane is suggested to be one of the pharmacological effects of TRQ. In the present study, we investigated the effects of TRQ on lipid peroxidation and enzyme leakage caused by carbon tetrachloride (CCl4) exposure in isolated hepatocytes and the liver in vivo, compared with vitamin E. The results were as follows: Hepatocytes isolated from TRQ-administered rats showed less enzyme leakage than those from control rats after CCl4 addition. TRQ displayed strong inhibition of lipid peroxidation in isolated hepatocytes. In comparison with vitamin E, TRQ showed almost the same inhibitory action on lipid peroxidation, but a stronger suppression of enzyme leakage. Vitamin E showed a weaker protection from increase of glutamic oxaloacetic transaminase than TRQ, in spite of its stronger inhibition of lipid peroxidation in vivo. From these results, it is suggested that the membrane protecting action of TRQ is partially derived from its suppression of lipid peroxidation, but "another action" may also play an important role in protecting the fragile membrane.     

Lipid Peroxidation Induced by Adriamycin in Linolenic Acid-Loaded Cultured Hepatocytes

Abstract: Addition of more than 10 μM of adriamycin to cultured rat hepatocytes loaded with α-linolenic acid (linolenic acid-loaded hepatocytes) caused marked lipid peroxidation as measured by an accumulation of malondialdehyde during a 9 hr incubation. After addition of 50 μM of adriamycin to linolenic acid-loaded hepatocytes, malondialdehyde accumulation significantly increased at 3 hr, followed by cellular reduced glutathione decrease and lactate dehydrogenase leakage after 6 hr. Inhibition of adriamycin-induced lipid peroxidation by addition of N, N′-diphenyl-p-phenylenediamine or α-tocopherol, both lipid radical scavengers, or deferoxamine, which is a Fe ion chelator, prevented both glutathione decrease and lactate dehydrogenase leakage, indicating that lipid peroxidation caused cellular damage to linolenic acid-loaded hepatocytes exposed to adriamycin. The effect of SKF 525-A, which is a cytochrome P450 inhibitor, on adriamycin-induced lipid peroxidation and on 7-ethoxycoumarin O-deethylase activity was determined by 6 hr incubation of linolenic acid-loaded cells. Addition of SKF 525–A suppressed adriamycin-induced lipid peroxidation comparably with its 7-ethoxycoumarin 0-deethylase inhibitory activity. These results suggest that cytochrome P450 contributes to the one-electron bioreduction of adriamycin into its semiquinone radical in rat hepatocytes.     

A 43-kDa protein from the leaves of the herb Cajanus indicus L. modulates chloroform induced hepatotoxicity in vitro

A 43-kDa protein isolated from the leaves of the herb Cajanus indicus L. has been shown to possess a protective role against drug- and toxin- induced hepatotoxicity both in vivo and in vitro. The current study was conducted to evaluate its protective action against chloroform (CHCl3)-induced cytotoxicity in hepatocytes. Cellular viability and biochemical parameters such as glutamate pyruvate transaminase (GPT) and lactate dehydrogenase (LDH) release from the cells were measured. In addition, the antioxidant effect of the protein was investigated from the DPPH radical scavenging assay and by determining the levels of the antioxidant enzyme catalase (CAT), cellular reserves of reduced glutathione (GSH), and lipid peroxidation end products (measured as TBARS). Treatment of the cells with CHCl3 decreased cellular viability and increased GPT and LDH. Cells treated with the protein before and immediately after CHCl3 application showed a marked improvement in their viability and reduced leakage of GPT and LDH. The levels of CAT and GSH, which were diminished in cells treated with CHCl3, were restored by protein treatment. CHCl3 induced enhancement of lipid peroxidation in hepatocytes was significantly reduced by protein treatment. Results of the DPPH assay with the protein showed its radical scavenging activity. This data suggests that the protein possesses protective activity against CHCl3-induced cytotoxicity in hepatocytes and protects against CHCl3-induced hepatic damage.     

Further examination of the selective toxicity of CCl4 in rat liver slices.

Lipid peroxidation and loss of enzymes located predominantly in either periportal or centrilobular hepatocytes were investigated in precision-cut liver slices from male Sprague-Dawley rats. Pretreatment of animals with 80 mg/kg phenobarbital for the site-specific enzyme studies enhanced and accelerated CCl4 toxicity in slices resulting from increased radical formation. Liver slices were exposed to 0.57 mM CCl4 by vaporization using a roller incubation system at 37 degrees C for a total of 9 hr. Conjugated diene formation, an index of lipid peroxidation, was detected 15 min following CCl4 administration and increased over time. Loss of cytochrome P450 occurred in a time-dependent manner relative to controls where levels in treated slices were 42% of controls at 9 hr. A 48-hr fast prior to termination increased intracellular K+ leakage relative to that present in slices from fed animals. Significant leakage of glucose-6-phosphate dehydrogenase and beta-glucuronidase from centrilobular hepatocytes occurred 9 hr following CCl4 administration. The content of the periportal enzymes (lactate dehydrogenase and sorbitol dehydrogenase) was unchanged in the same slices over the duration of the experiment. Reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide, a mitochondrial selective dye and indicator of viability, was significantly lower in treated slices from phenobarbital-treated animals at 9 hr relative to controls. These studies demonstrate that precision-cut slices are an ideal in vitro system for mechanistic studies and the investigation of site-specific toxicants since the integral architecture of the liver and cellular identity are maintained.     

Effects of green tea extract on galactosamine-induced hepatic injury in rats]

The present study examined the preventive effects of green tea extract on D-galactosamine (GalN)-induced hepatic injury in rats, an animal model of viral hepatitis. A single i.p.-injection of GalN (700 mg/kg) to male Wistar rats caused fulminant hepatitis by 48 hr as assessed by marked increases in the serum aspartate aminotransferase (GOT), alanine aminotransferase (GPT) and alkaline phosphatase (ALP) activities; decreases in the serum protein and cholesterol levels and the amount of liver microsome P-450; and marked changes in organ weights. The lecithin: cholesterol acyltransferase (LCAT) activity markedly increased at 8 hr and markedly decreased at 24 hr after the GalN injection. In the experiment, animals were orally administered green tea extract at doses of 50, 100 or 200 mg/kg five times each before and after the GalN injection. Treatment with green tea extract significantly prevented the increases in the GOT, GPT and ALP activities in a dose-related manner. It also significantly prevented the decreases in serum albumin and total cholesterol, although not in a dose-related manner. A tendency to prevent the increase in LCAT activity and the decrease in liver microsome P-450 was also noted. Little effect was found on the other abnormal changes in the serum lipids and proteins and the organ weights. These results suggest that green tea may have an ameliorating effect on hepatic dysfunction.     

Kinetic evaluation of free malondialdehyde and enzyme leakage as indices of iron damage in rat hepatocyte cultures. Involvement of free radicals

The present study relates to the effect of ferric iron supplementation on lipid peroxidation of adult rat hepatocyte pure cultures. Lipid peroxidation was evaluated by free malondialdehyde (MDA) using size exclusion chromatography (HPLC) as a specific and sensitive method. The ferric iron used under its complexed form with nitrilotriacetic acid (NTA) exhibited a prooxidant activity corresponding to an increase of free MDA recovery in the cells and in the culture medium. This enhancement of lipid peroxidation in the hepatocyte cultures supplemented with ferric iron was correlated with an intracellular enzyme leakage (lactate dehydrogenase and transaminase), suggesting that lipid peroxidation and enzyme release represented good parameters for cytotoxicity evaluation. The toxic effect of Fe-NTA on hepatocyte cultures was a function of the incubation time (from 0 to 48 hr) and of the concentration of ferric iron loading (i.e. 5, 20 and 100 microM). The mechanism by which Fe-NTA induced cellular damage involved free radical production, as increasing amounts of free radical scavengers corresponded to diminishing rates of both total free MDA and enzyme release. However, this reducing capacity varied from one scavenger to another, where they exhibited preferentially a decrease in lipid peroxidation or in enzyme leakage. This suggested a dissociation between the two parameters of cytotoxicity considered. Lipid peroxidation corresponding to alterations of both inner membranes and the plasma membrane, whereas enzyme release mainly corresponded to the damage of plasma membrane. Subsequently, some scavengers (superoxide dismutase, mannitol, alpha tocopherol, beta carotene) presented an intracellular activity, as they reduced mostly lipid peroxidation. Other ones (catalase, dimethylpyrroline N-oxide, thiourea) seemed essentially efficient in protecting the external plasma membrane, as shown an important decrease in enzyme leakage.     

Changes in glutathione and cellular energy as potential mechanisms of papaverine-induced hepatotoxicity in vitro

The purpose of this study was to elucidate the mechanism of hepatotoxicity of papaverine hydrochloride (papaver) in vitro. To evaluate the role of metabolism in the toxicity of papaver, cells were pretreated with SKF-525A or benzyl imidazole (cytochrome P450 system inhibitors) for 24 hr at 1 x 10(-5) or 1 x 10(-4) M, respectively, or with phenobarbital sodium (cytochrome P450 system inducer) for 3 days at 2 x 10(-3) M. Cells then were exposed to concentrations of papaver ranging from 1 x 10(-5) to 1 x 10(-3) M for 4 to 24 hr. Cytotoxicity was evaluated by enzyme leakage (lactate dehydrogenase) and by energy status of the cells (ATP/ADP). The role of biological reactive intermediates in the toxicity of papaver was investigated by measuring changes in cellular reduced glutathione levels (GSH), by inhibiting GSH synthesis, and by determining the production of lipid peroxidation (LPX). Papaverine produced concentration- and time-dependent increases in enzyme leakage, with significant effects occurring by the 8-hr exposure period. Pretreatment with SKF-525A or benzyl imidazole increased enzyme leakage induced by papaver especially at a later time frame (24 hr), but pretreatment with phenobarbital delayed the onset of cytotoxicity from 8 to 12 hr. Decreases in GSH levels paralleled the time course of enzyme leakage. However, the administration of buthionine sulfoximine to cell cultures dramatically decreased the time by which papaver induced cellular injury (2 hr vs 8 hr). Changes in cellular energy status (ATP/ADP) were also detected earlier than enzyme leakage (4 hr vs 8 hr). In contrast, no significant production of lipid peroxidation was noted in papaver-treated cultures. We suggest that the mechanism of papaver-induced hepatotoxicity may be related to alterations in glutathione balance of the cells and to disruption of energy homeostasis.     

Lipid peroxidation and protein thiol depletion are not involved in the cytotoxicity of N-hydroxy-2-acetylaminofluorene in isolated rat hepatocytes

Freshly isolated rat hepatocytes were used to study the mechanism of cell death induced by N-hydroxy-2-acetylaminofluorene (N-OH-AAF). Exposure to 1.0 mM N-OH-AAF resulted in more than 90% cell death (as measured by LDH leakage) of hepatocytes isolated from male rats within 6 hr. Only 36% of the hepatocytes isolated from female rats died within this period. When inorganic sulfate was omitted from the incubation medium, a 6 hr exposure to 1.0 mM N-OH-AAF resulted in only 40% cell death of male hepatocytes. These findings are in accordance with the sex difference and sulfation dependence of N-OH-AAF hepatotoxicity observed in the rat in vivo. N-OH-AAF decreased glutathione (GSH) in male hepatocytes in a concentration-dependent manner. This GSH consumption was only partly dependent on the presence of inorganic sulfate. No lipid peroxidation was observed during N-OH-AAF exposure; N-OH-AAF even prevented endogenous and diethyl maleate (DEM)-induced lipid peroxidation. No reduction of free protein thiol groups was found after exposure to N-OH-AAF, even after 75% cell death had occurred. A reduction of protein thiols after N-OH-AAF exposure was observed in GSH depleted hepatocytes (obtained by DEM plus vitamin E pretreatment). Under these conditions N-OH-AAF-induced cell death occurred earlier. Therefore, GSH protects against protein thiol depletion by N-OH-AAF in control cells. N-OH-AAF-induced cell death was preceded by a loss of intracellular ATP. It is concluded, therefore, that neither lipid peroxidation nor depletion of protein thiols, but possibly loss of intracellular ATP, is involved in the sulfation-dependent cytotoxic mechanism of N-OH-AAF in isolated rat hepatocytes.     

Preventive effects of a purified extract isolated from Salvia miltiorrhiza enriched with tanshinone I,tanshinone IIA and cryptotanshinone on hepatocyte injury in vitro and in vivo

Salvia miltiorrhiza is traditionally used to treat liver disease in Asia. In this study, we tested the ability of a purified extract of S. miltiorrhiza (PF2401-SF) and its constituents, tanshinone I, tanshinone IIA, and cryptotanshinone, to protect against acute and subacute liver damage induced by carbon tetrachloride by measuring serum transaminase levels, the reduced form of glutathione (GSH), antioxidant enzyme activities, and lipid peroxidation levels in the liver. We also evaluated their ability to protect primary cultured rat hepatocytes from tertiary-butylhydroperoxide (tBH) or d-galactosamine (GalN). PF2401-SF was protective at 50–200 mg/kg per day in acute liver injury and 25–100 mg/kg per day in subacute liver injury. Tanshinone I, tanshinone IIA, and cryptotanshinon (40 μM), inhibited lactate dehydrogenase leakage, GSH depletion, lipid peroxidation and free radical generation in vitro. PF2401-SF and its major constituents, tanshinone I, tanshinone IIA and cryptotanshinone, can protect against liver toxicity in vivo and in vitro due to its antioxidant effects.     

Effects of essential oils on erythrocytes and hepatocytes from rats and dipalmitoyl phosphatidylcholine-liposomes

The effect of essential oils, eugenol, thymol and menthol, on erythrocytes, hepatocytes, dipalmitoyl phosphatidylcholine (DPPC)-liposomes and surface tension were studied at various concentrations. Maximal inhibition of eugenol, thymol and menthol on the hypotonic hemolysis in rat erythrocytes were observed at a concentration of 2 mM, 1 mM and 1 mM, respectively. Eugenol at 4 mM and thymol at 2 mM caused an acceleration of hypotonic hemolysis. In isolated rat hepatocytes, thymol caused an increase in GOT leakage, but eugenol at 4 mM and menthol at 0.1 and 0.4 mM inhibited the GOT leakage. The leakage of GPT from hepatocytes was inhibited by eugenol at 0.1 mM and 0.4 to 4 mM and menthol at 0.1 to 0.6 mM. The inhibition of eugenol and menthol on the LDH leakage in hepatocytes were observed at a concentration of 0.001 to 4 mM and 0.1, 0.4 and 0.6 mM, respectively. Thymol caused no change in GPT and LDH leakage. Eugenol, thymol and menthol indicated a depression of surface tension at a concentration of 0.1 mM. The rank by order of surface activity was eugenol greater than thymol. Eugenol, thymol and menthol depressed the phase-transition temperature of DPPC-liposomes. The depression of phase-transition temperature by thymol was greater than that by eugenol and menthol. These results suggest the periapical tissue damage produced by essential oils may be related to membrane lysis and surface activity and that their tissue penetration may be related to membrane affinity and lipid solubility.     

Potentiation of carbon tetrachloride-induced lipid peroxidation by trichloroethylene in isolated rat hepatocytes: no role in enhanced toxicity

Hepatocytes isolated from Sprague-Dawley rats were exposed to carbon tetrachloride together with various concentrations of trichloroethylene over a 40-fold range. A potentiation of carbon tetrachloride-induced lipid peroxidation by trichloroethylene and an enhanced toxicity on combined exposure were clearly demonstrated. Additionally, rats were treated 2.5 hr before isolation of hepatocytes, which were then exposed to carbon tetrachloride. Lipid peroxidation and potassium ion leakage were increased in these cells. Some incubations included the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) while others contained dithiothreitol (DTT), a thiol reducing compound. DPPD inhibited lipid peroxidation while DTT did not. Neither, however, was able to inhibit the toxicity. Assays to estimate total and nonprotein bound sulfhydryl groups were also performed. There was no indication of a causative role for cellular sulfhydryl groups in the enhanced toxicity. Therefore, our data show that lipid peroxidation is not responsible for the trichloroethylene-induced enhancement of toxicity in hepatocytes due to carbon tetrachloride. Furthermore, there is no evidence to indicate a role for sulfhydryl groups in this response.     

Toxicity of ethacrynic acid in isolated rat hepatocytes.

Ethacrynic acid, a loop diuretic drug, caused lipid peroxidation in isolated rat hepatocytes. The thiobarbituric acid reactive substances (TBARS) formation showed a good correlation with the leakage of glutamic-oxaloacetic acid transaminase (GOT) from the hepatocytes. The addition of antioxidants such as N, N'-diphenyl-p-phenylenediamine (DPPD) and promethazine to the isolated rat hepatocyte suspension containing ethacrynic acid prevented the lipid peroxidation and decreased the GOT leakage to some extent. SKF-525A inhibited the oxidative metabolism of ethacrynic acid and decreased the TBARS formation, suggesting that the lipid peroxidation was caused by the oxidative metabolism. The intracellular reduced glutathione markedly decreased in the hepatocyte suspension containing ethacrynic acid and the hepatocellular protein sulfhydryls were decreased, which was negatively correlated with the GOT leakage. Thus the ethacrynic acid-induced hepatotoxicity was found to be related to the lipid peroxidation and the decrease of cellular protein sulfhydryls.     

肝细胞生长因子对四氯化碳损伤原代培养大鼠肝细胞的保护作用

采用大鼠离体肝细胞原代培养24 h，并利用CCl₄造成急性肝细胞损伤模型，检定肝细胞生长因子(HGF)对肝细胞损伤的影响. 结果表明：HGF可显著降低中毒肝细胞及细胞膜脂质过氧化物水平, 抑制肝细胞脂质过氧化, 并降低谷丙转氨酶和谷草转氨酶水平, 稳定质膜；显著促进中毒肝细胞RNA和DNA的合成；超微病理证实HGF能减轻CCl₄对肝细胞质膜，染色质, 线粒体, 内质网及核蛋白体的损害.     

Palmatine attenuates d-galactosamine/lipopolysaccharide-induced fulminant hepatic failure in mice

Palmatine is an isoquinoline alkaloid from Coptis chinensis, an herbal medicine used to treat various inflammatory diseases such as gastritis, edema and dermatitis. The present study examined the cytoprotective properties of palmatine on d(+)-galactosamine (GalN)/lipopolysaccharide (LPS)-induced fulminant hepatic failure. Mice were intraperitoneally given GalN (700 mg/kg)/LPS (10 μg/kg). Palmatine (25, 50, 100, and 200 mg/kg) was administered 1 h before GalN/LPS. GalN/LPS increased the mortality and serum aminotransferase activities. These increases were attenuated by palmatine. GalN/LPS increased hepatic lipid peroxidation and decreased the contents of reduced glutathione. Palmatine did not affect the lipid peroxidation and glutathione content. GalN/LPS increased the circulating levels of tumor necrosis factor (TNF)-α, interleukin-6 (IL-6) and IL-10. Palmatine prevented the increase of serum TNF-α and augmented that of serum IL-10. GalN/LPS treatment also increased the levels of TNF-α, IL-6 and IL-10 mRNA expression in liver tissue. Palmatine decreased the TNF-α mRNA expression and increased the IL-10 mRNA expression. Palmatine attenuated the apoptosis of hepatocytes, as evidenced by the TUNEL method and capase-3 analysis. Our data suggest that palmatine alleviates GalN/LPS-induced liver injury by modulating the cytokine response and inhibiting apoptosis.     

The Involvement of Cytochrome P4502E1 in 2-Bromoethanol-Induced Hepatocyte Cytotoxicity

Abstract: The cytotoxicity of 2-bromoethanol towards hepatocytes isolated from rats was concentration-dependent (EC₅₀-100 μM, 2 hr). Bromoacetaldehyde was more toxic (EC₅₀-60 μM, 2 hr) and bromoacetic acid was less toxic (EC₅₀-150 μM, 2 hr). Glutathione (GSH) depletion occurred before cytotoxicity ensued and GSH depleted hepatocytes were more susceptible to 2-bromoethanol. Lipid peroxidation increased steadily 1 hr after 2-bromoethanol addition and antioxidants, iron chelators or hypoxia prevented 2-bromoethanol induced lipid peroxidation and cell lysis. Alcohol de-hydrogenase inhibitors, methyl pyrazole or dimethyl sulfoxide only partly prevented 2-bromoethanol induced GSH depletion, lipid peroxidation and cytotoxicity. However, cytochrome P4502E1 (CYP2EI) inhibitors/substrates were more effective at preventing 2-bromoethanol-induced GSH depletion, lipid peroxidation and cytotoxicity suggesting that 2-bromoethanol is mostly metabolically activated by CYP2E1. Also, hepatocytes isolated from CYP2E1 induced rats were more susceptible to 2-bromoethanol and hepatocytes isolated from rats pretreated with carbon disulfide to inactivate CYP2E1 were more resistant to 2-bromoethanol treatment. Formation of S-(formylmethyl)glutathione during 2-bromoethanol metabolism by microsomal mixed function oxidase in the presence of GSH was also prevented by cytochrome P4502E1 inhibitors/substrates or by Anti-Rat CYP2E1. Furthermore, aldehyde dehydrogenase inhibitors-cyanamide or chloral hydrate increased 2-bromoethanol dependent hepatocyte susceptibility. This suggests that 2-bromoethanol is preferably metabolised by CYP2E1 dependent monoxygenase to form 2-bromoacetaldehyde which causes cell lysis as a result of GSH depletion and lipid peroxidation.     

Protective effects of honokiol and magnolol on tertiary butyl hydroperoxide- or D-galactosamine-induced toxicity in rat primary hepatocytes

The aim of this study was to investigate the protective effect of honokiol and magnolol on hepatocyte injury induced by either tertiary butyl hydroperoxide (tBH)- or D-galactosamine (GalN). The cellular leakage of LDH and AST, and cell death by treatment with 1.5 mM tBH for 1 h, were significantly inhibited by treatment with honokiol (40 and 20 microM) or magnolol (40 microM). Treatment with honokiol or magnolol significantly inhibited lipid peroxidation in both cells and media, the generation of intracellular reactive oxygen species (ROIs), and intracellular glutathione (GSH) depletion induced by tBH. The cellular leakage of LDH and AST, and cell death, by 24-hour treatment with 30 mM GalN were significantly inhibited by treatment with honokiol (20, 5 and 1 microM) or magnolol (20, 5 and 1 microM). Treatment with honokiol (20, 5 and 1 microM) or magnolol (20 and 5 microM) significantly inhibited the intracellular GSH depletion induced by GalN. The hepatoprotective effects of honokiol and magnolol on oxidative stress induced by tBH were probably the result of their antioxidant activity. Honokiol and magnolol also had a protective effect against GalN-induced hepatotoxicity, which was used as an alternate model to oxidative stress, acting by inhibiting intracellular GSH depletion.     

Effects of phenol and related compounds on erythrocytes and hepatocytes from rats and dipalmitoyl phosphatidylcholine-liposomes

The effects of phenol, guaiacol and m-cresol on erythrocytes, hepatocytes, dipalmitoyl phosphatidylcholine (DPPC)-liposomes and surface tension were studied at various concentrations. Phenol at 10 mM caused a slight inhibition of hypotonic hemolysis in rat erythrocytes. Guaiacol at 4 and 10 mM and m-cresol at 0.6 to 10 mM caused a significant inhibition of hypotonic hemolysis. In the enzyme leakage from isolated rat hepatocytes, phenol at 0.001 to 0.4 mM and 2 to 10 mM, guaiacol at 2 to 10 mM and m-cresol at 0.001 to 4 mM caused an inhibition in GOT leakage. The leakage of GPT from hepatocytes was inhibited by phenol at 0.4 to 10 mM, guaiacol at 2 to 10 mM, and m-cresol at 0.001 to 4 mM. m-Cresol at 10 mM caused increases in GOT and GPT leakage. The inhibition of phenol and m-cresol on the LDH leakage in hepatocytes were observed at a concentration of 0.001 mM and 0.1 to 1 mM, respectively. Guaiacol or m-cresol at 10 mM caused an increase in LDH leakage. Phase-transition temperature of DPPC-liposomes was depressed by phenol and m-cresol at 1 to 10 mM and by guaiacol at 5 and 10 mM. Guaiacol at 1 and 10 mM and m-cresol at 10 mM caused a depression of surface tension, but phenol caused no change in surface tension. The order of effects on erythrocyte, hepatocyte and DPPC-liposome membranes was m-cresol greater than phenol greater than or equal to guaiacol. In the present study, phenol and its related compound showed a positive correlation between their effects on various membranes and germicidal effects as evaluated by the phenol coefficient, but the effects were not related to a depression of surface tension.     

Cadmium toxicity and lipid peroxidation in isolated rat hepatocytes

The toxicity of cadmium may be due to alteration in membrane structure which may be caused by peroxidation of the composite lipids. Isolated hepatocytes provide a suitable system to examine the role of lipid peroxidation in a toxic response at the cellular level. Therefore, isolated rat hepatocytes were incubated with varying cadmium concentrations (50–400 μm) for up to 75 min. An increase in lipid peroxidation due to cadmium was observed. The integrity of the cell membrane, as measured by loss of intracellular potassium ion and leakage of aspartate aminotransferase, was adversely affected in the presence of cadmium. The lactate to pyruvate ratio of hepatocyte suspensions was increased upon incubation with cadmium. Several chelating compounds were found to reduce intracellular accumulation of cadmium, cellular toxicity and lipid peroxidation. However, amelioration of toxicity was not consistently associated with inhibition of the lipid peroxidation response. The antioxidant compounds, sodium diethyldithiocarbamate and N,N′-diphenyl-p-phenylene-diamine were found to inhibit the lipid peroxidation attributable to cadmium, but did not have any consistent protective effect against loss of intracellular potassium ion. The results of this study show that the toxicity induced by cadmium in isolated rat hepatocytes can be dissociated from the concurrently observed lipid peroxidation, which indicates that the toxic response is not caused by the lipid peroxidation.     

Screening of antioxidant action of various molds and protection of Monascus anka against experimentally induced liver injuries of rats

Antioxidant action of various molds, which are traditionally used for the production of foods or alcoholic beverages in Japan, was studied in vitro and in vivo. Antioxidant action was evaluated by scavenging stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and lipid peroxidation of rat liver microsomes. Among 40 molds, 16 species showed the DPPH scavenging action, and the molds that can scavenge the DPPH radical inhibited lipid peroxidation. The mold with the strongest action, Monascus anka, was chosen for the investigation of a protective action against liver injury of rats. When galactosamine (GalN, 400 mg/kg) or GalN plus lipopolysaccharide (LPS, 0.5 microg/kg) was given intraperitoneally to rats (Sprague-Dawley), aspartate aminotransferase (AST) and glutathione (GSH) S-transferase (GST) activities in serum were significantly increased. However, such hepatotoxicities seen in the increase in serum enzyme levels were depressed when the extract prepared from M. anka was given 1 and 15 h before the toxic insultant. Liver microsomal GST activity, which is known to be activated by oxidative stress, was increased by GalN or GaIN plus LPS treatment and the increase was also inhibited by pretreatment with the extract. Pathomorphological changes in the liver caused by GalN treatment also were prevented by the mold extract. These results indicate that the extract of M. anka has radical scavenging action and ameliorates chemically induced hepatotoxicity.