The protective effect of tinoridine against carbon tetrachloride hepatotoxicity

The effect of tinoridine, an anti-inflammatory drug with a potent anti-peroxidative ability, on CCl₄ hepatotoxicity was investigated in rats. CCl₄ administration to rats produced not only marked increases in serum glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase but also decreases in liver microsomal cytochrome P-450 and glucose-6-phosphatase. These CCl₄-induced alterations in the enzyme activities were markedly decreased by pretreatment with tinoridine. The protective effect of tinoridine was also ascertained by histologic evaluation. α-Tocopherol also showed a similar protection, but anti-inflammatory drugs such as phenylbutazone, indomethacin, ibuprofen, and prednisolone failed to protect against the CCl₄-induced hepatotoxicity. These findings suggest that the anti-peroxidative action of tinoridine contributes to the protective effect against CCl₄ hepatotoxicity.     

Metformin protects against carbon tetrachloride hepatotoxicity in mice

In the present study, the hepatoprotective effect of metformin (Met), a dimethylbiguanide anti-hyperglycemic, was examined in a mouse model of liver damage induced by chronic repeated administration of carbon tetrachloride (CCl(4)) (5 microl/kg, twice a week for 12 weeks). Met, when given orally in drinking water at an estimated daily dose of 25 or 50 mg/kg for 10 weeks starting 2 weeks after CCl(4) challenge, protected against CCl(4) hepatotoxicity. The results indicate that the hepatoprotection afforded by Met treatment at a dose of 25 mg/kg against CCl(4) toxicity may at least in part be mediated by the enhancement of mitochondrial glutathione redox status.     

In vivo protective effect of Porphyra yezoensis polysaccharide against carbon tetrachloride induced hepatotoxicity in mice

To study the protective effect and possible mechanism of Porphyra yezoensis polysaccharide (PYP) in hepatotoxicity mice, acute liver injury was successfully induced by injecting 0.2% carbon tetrachloride (CCl(4)) intraperitoneally. Levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum and liver homogenate, content of malondialdehyde (MDA), activities of total superoxide dismutase (T-SOD) in liver were measured by biochemical methods. Liver index was calculated and pathological changes of the liver tissue were observed microscopically. PYP was found to significantly decrease the activities of ALT and AST (P<0.05), to remarkably lower the liver indexes and MDA level in hepatical tissues in mice (P<0.05), and to upregulated the lower T-SOD level in liver homogenate (P<0.01). Furthermore, histologic examination showed that PYP could attenuate and the extent of necrosis, reduce the immigration of inflammatory cells. PYP plays a protective action against hepatotoxicity induced by CCl(4) in mice, and its mechanisms may be related to free radical scavenging, increasing SOD activities and anti-lipid peroxide.     

The protective effects of PMC against chronic carbon tetrachloride-induced hepatotoxicity in vivo.

In this study, PMC (2,2,5,7,8-pentamethyl-6-hydroxychromane), a derivative of alpha-tocopherol, dose-dependently (1-10 mg/kg) ameliorated the increase in plasma aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) levels caused by chronic repeated carbon tetrachloride (CCl4) intoxication in mice. Moreover, PMC significantly improved the CCl4-induced increase of hepatic glutathione peroxidase, reductase, and superoxide dismutase activities. PMC also restored the decrement in the glutathione content of hepatic tissues in CCl4-intoxicated mice. Furthermore, it also dose-dependently inhibited the formation of lipid peroxidative products during carbon tetrachloride treatment. Histopathological changes of hepatic lesions induced by carbon tetrachloride were significantly improved by treatment with PMC in a dose-dependent manner. These results suggest that PMC exerts effective protection in chronic chemical-induced hepatic injury in vivo.     

Effect of Aerva lanata against hepatotoxicity of carbon tetrachloride in rats

The partially purified petroleum ether extractable fraction of the whole plant Aerva lanata (PF) was evaluated for the protective effect against liver damage induced by carbon tetra chloride (CCl₄) in Sprague Dawley rats. Rats were orally administered with PF (50 and 100 mg/kg body weight) for 14 days before CCl₄ challenge and 100 mg of PF alone for toxicity analysis without CCl₄ administration. The results showed that CCl₄ administration significantly damaged the liver as evident from histopathology and very high activity of serum and liver marker enzymes. It also reduced the antioxidant enzyme status of the animals. PF administration significantly reversed the histopathological changes and restored the elevated activities of liver marker enzymes and also enhanced the antioxidant enzyme activities. The extract also reduced hepatic lipid peroxidation and increased the serum total protein and albumin/globulin (A/G) ratio. Preliminary phytochemical analysis of PF showed the presence of alkaloids. These observations clearly indicate that PF contains antioxidant alkaloids capable of ameliorating the CCl₄-induced hepatic injury by virtue of its antioxidant activity.     

Effect of Aerva lanata against hepatotoxicity of carbon tetrachloride in rats

The partially purified petroleum ether extractable fraction of the whole plant Aerva lanata (PF) was evaluated for the protective effect against liver damage induced by carbon tetra chloride (CCl₄) in Sprague Dawley rats. Rats were orally administered with PF (50 and 100 mg/kg body weight) for 14 days before CCl₄ challenge and 100 mg of PF alone for toxicity analysis without CCl₄ administration. The results showed that CCl₄ administration significantly damaged the liver as evident from histopathology and very high activity of serum and liver marker enzymes. It also reduced the antioxidant enzyme status of the animals. PF administration significantly reversed the histopathological changes and restored the elevated activities of liver marker enzymes and also enhanced the antioxidant enzyme activities. The extract also reduced hepatic lipid peroxidation and increased the serum total protein and albumin/globulin (A/G) ratio. Preliminary phytochemical analysis of PF showed the presence of alkaloids. These observations clearly indicate that PF contains antioxidant alkaloids capable of ameliorating the CCl₄-induced hepatic injury by virtue of its antioxidant activity.     

Modification of carbon tetrachloride hepatotoxicity by chemicals.

Cobaltous chloride (60 mg/kg, sc, daily for 2 days), which was found to effectively decrease the microsomal cytochrome P-450 content of mouse liver to approximately half of its normal value and which impaired the oxidative metabolism or hydroxylation of aminopyrine, ethylmorphine, and hexobarbital, offered no protection against CCl₄-induced liver damage. However, this hemoprotein inhibitor had no effect on the rate of reduction of cytochrome P-450 by NADPH and exerted a slight effect on aniline hydroxylation. SKF-525A (50 mg/kg, ip) also failed to protect against CCl₄ hepatotoxicity though it has been shown to inhibit the hydroxylation of a number of substrates. This inhibitor, a type I compound, was found to enhance cytochrome P-450 reduction by NADPH. Further studies revealed that CCl₄-induced hepatic injury could be prevented by phenazine methosulfate (2 mg/kg, ip, 5 doses at 0.5-hr intervals), which in vitro was found to inhibit NADPH-cytochrome c reductase noncompetitively. All of these findings are not satisfactorily explainable by electron transfer from NADPH-cytochrome c reductase to CCl₄ as the activation reaction for CCl₄ but are compatible with the hypothesis previously proposed by others that cytochrome P-450 is the critical site for CCl₄ activation.     

Protective effect of saponins derived from the roots of Platycodon grandiflorum against carbon tetrachloride induced hepatotoxicity in mice

The purpose of this study was to investigate the protective effects of the saponins isolated from the root of Platycodi Radix (Changkil saponins: CKS) on carbon tetrachloride (CCl(4))-induced hepatotoxicities in mice. Pretreatment with CKS prior to the administration of CCl(4) significantly prevented the increase in serum alanine aminotransferase and aspartate aminotransferase activities and hepatic lipid peroxidation formation. In addition, CKS prevented CCl(4)-induced apoptosis and necrosis, as indicated by a liver histopathologic study and DNA laddering. To determine whether Fas/Fas ligand (FasL) pathway involved in CCl(4)-induced acute liver injury, Fas and FasL proteins and caspase-3, -8 activities were tested by western blotting and ELISA. CKS markedly decreased CCl(4)-induced Fas/FasL protein expression levels and in turn attenuated CCl(4)-induced caspase-3, -8 activities in mouse livers. Additionally, CKS protected the CCl(4)-induced depletion of hepatic glutathione levels. The effect of CKS on CYP2E1, the major isozyme involved in CCl(4) bioactivation, was investigated. Treatment with CKS resulted in a significant decrease in the CYP2E1-dependent hydroxylation of aniline. In addition, CKS exhibited antioxidant effects on FeCl(2)-ascorbate induced lipid peroxidation in liver homogenates, and on superoxide radical scavenging activity. These findings suggest that the protective effects of CKS against CCl(4)-induced acute liver injury possibly involve mechanisms related to its ability to block CYP2El-mediated CCl(4) bioactivation and its free radical scavenging effects, and that is also protects against Fas/FasL pathway mediated apoptosis.     

Diverse effects of antioxidants on carbon tetrachloride hepatotoxicity.

Several potent in vitro antioxidants like α-tocopherol acetate (α-T), N,N′ diphenyl p-phenylenediamine (DPPD), promethazine given at dosage regimes which prevented several manifestations of CCl₄ hepatotoxicity were not able to prevent the occurrence of CCl₄-induced lipid peroxidation or significantly modify the content in liver of administered CCl₄in vivo. DPPD but not α-T or promethazine was able to significantly decrease the extent of CCl₄ activation to ·CCl₃ free radicals as measured by the irreversible binding to microsomal lipids. These results weaken the value of previous findings with antioxidants which were used to support the lipid peroxidation theory of CCl₄ hepatotoxicity.     

The protective potential of metformin against acetaminophen-induced hepatotoxicity in BALB/C mice

Context: Acetaminophen overdose is regarded to a common cause of acute liver failure. The hepatotoxicity leads to mitochondrial oxidative stress and subsequent necrotic hepatocellular death.

Objective: This study examines the protective effect of metformin on acetaminophen-induced oxidative stress, inflammation and subsequent hepatotoxicity in mice.

Materials and methods: Male BALB/c mice were orally administered to acetaminophen (250?mg/kg/d) for a 7-day period. The mice received metformin (100 and 200?mg/kg/d, p.o.) for 21 days. To evaluate acetaminophen-induced oxidative stress, liver tissue level of malodialdehyde (MDA), end product of membrane lipid peroxidation, and activities of superoxide dismutase (SOD) and glutathione (GSH) were measured. Histological analysis and measurement of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were performed. Moreover, tissue concentrations of proinflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), along with, C-reactive protein (CRP) were assessed.

Results: Acetaminophen caused focal hepatocyte necrosis, inflammation and fatty degeneration, as well as increased tissue levels of AST, ALT, ALP and MDA, and also decreased GSH and SOD activities. Moreover, IL-6, TNF-α and CRP levels were increased following acetaminophen hepatotoxicity. Metformin (200?mg/kg/d) significantly normalized MDA, SOD and GSH levels (p?<?0.001), and exerted a hepatoprotective effect by significant decreasing ALT, AST and ALP concentrations (p?<?0.001). The tissue levels of IL-6, TNF-α and CRP were markedly decreased by 21-day treatment with metformin (200?mg/kg/d) (p?<?0.001).

Discussion: The results suggest metformin protects hepatocytes against acute acetaminophen toxicity. Metformin is indicated to diminish oxidative stress, proinflammatory cytokines, and hepatocyte necrosis.     

Effect of hypoxia on carbon tetrachloride hepatotoxicity

The effect of hypoxia on carbon tetrachloride-induced hepatotoxicity was studied. Male rats were exposed to carbon tetrachloride for 2 hr in the presence of differing oxygen concentrations. Serum glutamate-pyruvate transaminase (SGPT) activities were measured 24 hr after the end of the exposure. Exposure of rats to 5000 ppm carbon tetrachloride in the presence of 100, 21,12, or 6% oxygen resulted in SGPT activities of 489, 420, 3768, and 1788 I.U./l respectively. Exposure of rats to air and 0, 1250, 2500, 5000, or 7500 ppm carbon tetrachloride gave SGPT activities of 35, 32, 69, 420, and 2188 I.U./l respectively; when 12% oxygen was used, the corresponding SGPT activities were 32, 665, 691, 3768, and 4200 I.U./l respectively. Exposure of rats to hypoxia produced histopathologically detectable condensation of hepatic cytoplasmic material, and exposure to 5000 ppm carbon tetrachloride in the presence of air produced mild centrilobular necrosis, which was much more severe when rats were exposed to 5000 pm carbon tetrachloride in the presence of 12% oxygen. Hepatic microsomal conjugated diene concentrations were increased by hypoxia and by exposure to carbon tetrachloride, but no synergistic interaction was observed. Hepatic microsomal cytochrome P-450 concentrations were decreased after exposure to carbon tetrachloride, but were the same after exposure to carbon tetrachloride and 12 or 21% oxygen. Hepatic carbon tetrachloride concentrations were the same in rats exposed to carbon tetrachloride in the presence of 12 or 21% oxygen; hepatic chloroform concentrations were higher in rats exposed to carbon tetrachloride in the presence of air than in the presence of 12% oxygen. The covalent binding of [¹⁴C]carbon tetrachloride metabolites to hepatic microsomal lipids and proteins was increased markedly by hypoxia as compared with normoxia. The covalent binding of metabolites of carbon tetrachloride to cellular macromolecules may play a role in the potentiation of carbon tetrachloride toxicity by hypoxia.     

Potentiation of carbon tetrachloride hepatotoxicity by phenylpropanolamine

Hepatic necrosis produced by carbon tetrachloride (0.02, 0.06, or 0.20 ml/kg, ip) in mice was found to be potentiated by simultaneous cotreatment with phenylpropanolamine (200 mg/kg, ip), a drug with catecholamine-like pharmacologic effects. The ability to potentiate carbon tetrachloride-induced hepatic necrosis was shared by a compound with agonist effects relatively selective for alpha 2-adrenoreceptors (clonidine, 5 mg/kg, ip), but not by specific alpha 1-adrenoreceptor agonists (phenylephrine, up to 100 mg/kg, ip and methoxamine, up to 50 mg/kg, ip) or by the beta-adrenoreceptor agonist isoproterenol (up to 100 mg/kg, ip). Yohimbine (5 mg/kg, ip), a selective alpha 2-adrenoreceptor antagonist, completely blocked the potentiating effect of phenylpropanolamine on carbon tetrachloride hepatotoxicity, providing further evidence that the increased hepatotoxic response with phenylpropanolamine cotreatment was mediated through alpha 2-adrenoreceptor stimulation. Four potential mechanisms for phenylpropanolamine potentiation of liver injury from carbon tetrachloride were examined: (1) increased concentrations of carbon tetrachloride in the liver from greater absorption or altered distribution; (2) diminished food consumption leading to a starvation-like increase in responsiveness to carbon tetrachloride; (3) impaired detoxification through a depletion of hepatic glutathione content; and (4) enhanced toxicity produced by elevated core body temperature. None of these potential mechanisms was supported by the experimental results. It is concluded that phenylpropanolamine and related compounds potentiate carbon tetrachloride hepatotoxicity through a mechanism involving alpha 2-adrenoreceptor stimulation that has yet to be identified.     

Effect of flavonoids from Prosthechea michuacana on carbon tetrachloride induced acute hepatotoxicity in mice

Context: Prosthechea michuacana W.E. Higgins (LaLlave & Lex) (Orchidaceae) is an orchid that has been used in traditional medicine for the treatment of inflammation, diabetes, wound, and liver disorders. Therefore, we thought it would be worthwhile to study the effect of this orchid on liver damage using mice as model.

Objective: The present study investigates the effect of flavonoids isolated from methanol extract of P. michuacana on carbon tetrachloride (CCl₄)-induced liver damage in mice.

Materials and methods: The methanol extract was purified by repeated column chromatography, resulting in the identification of five metabolites whose hepatoprotective effects were evaluated by measuring aspartate transaminase, alanine transaminase, alkaline phosphatase, glutamate, total bilirubin level, lactate dehydrogenase, total serum protein, and lipid peroxidation (thiobarbituric acid reactive substances assay) in CCl₄-induced hepatic injury in mice.

Results: From the bulbs of P. michuacana, four known flavonoids were isolated (scutellarein 6-methyl ether, dihydroquercetin, apigenin 7-O-glucoside, and apigenin-7-neohesperidoside), together with the new flavonol glycoside apigenin-6-O-β-d-glucopyranosil-3-O-α-l-rhamnopyranoside. Their structures were characterized by 1D and 2D nuclear magnetic resonance experiments. Treatment with flavonoids significantly prevented the biochemical measurable changes induced by CCl₄ in the liver. Compounds 1, 4, and 5 were found to exhibit good hepatoprotective effect. These effects were comparable to that of the standard drug silymarin, a well-known hepatoprotective agent.

Discussion: These results demonstrate that flavonoids contained in the bulbs of P. michuacana contribute to the hepatoprotective activity attributed to the plant.     

Protection against carbon tetrachloride hepatotoxicity by oleanolic acid is not mediated through metallothionein

Oleanolic acid is a triterpenoid compound that has been shown to protect against liver injury produced by some hepatotoxicants. This study was designed to characterize the protective effects of oleanolic acid on carbon tetrachloride-induced hepatotoxicity, and the role of metallothionein in the protection. Oleanolic acid pretreatment (100–400 μmol/kg, sc) protected Sprague–Dawley rats and mice from carbon tetrachloride-induced liver injury in a dose- and time-dependent manner, as evidenced by serum alanine aminotransferase and sorbitol dehydrogenase activities, as well as by histopathology. The protection against carbon tetrachloride hepatotoxicity was not evident until animals were pretreated with oleanolic acid 12 h, and lasted for 72 h after a single injection. This suggests that the protection might be due to induction of some adaptive mechanisms. Metallothionein (MT), an acute-phase protein proposed to decrease carbon tetrachloride-induced liver injury, was dramatically induced following oleanolic acid treatment. To examine whether oleanolic acid protection is mediated through MT, MT-I and II knock-out (MT-null) mice were utilized. Oleanolic acid pretreatment increased MT levels in control mice (20-fold), but not in MT-null mice, however, it protected equally against carbon tetrachloride-induced hepatotoxicity in both control and MT-null mice. These data indicate that oleanolic acid is effective in protecting rats and mice from the hepatotoxicity produced by carbon tetrachloride, and the protection is not mediated through induction of MT.