Radioprotective effect of silymarin against radiation induced hepatotoxicity

The radioprotective effect of silymarin using different modes of treatment against radiation (3 or 6 Gy) induced hepatotoxicity 1, 3 and 7 days post-irradiation was studied. Whole-body gamma-irradiation revealed an increase in serum alkaline phosphatase (AP) activity as well as liver glutathione reductase (GR) and glutathione peroxidase (GSH-PX) activities on the first post-exposure day with respect to the control value. However, 3 days after radiation exposure, these parameters showed a significant decrease below the control level which persisted till the end of the experimental time except for serum AP activity that showed another increase on the seventh post-exposure day at 3 Gy dose of radiation. A gradual increase in serum alanine and aspartate aminotransferase (ALT&AST) as well as gamma glutamyl transpeptidase activities were observed due to irradiation throughout the experimental time. Administration of silymarin as single (70 mg kg (-1)), fractionated (490 mg kg (-1)) oral doses or as intravenous (i.v.) injection (50 mg kg (-1)), caused significant protection. Intravenous treatment showed the most pronounced protection. The protective effect of silymarin was attributed to its antioxidant and free radicals scavenging properties.     

Protection against carbon tetrachloride-induced hepatotoxicity by protein A

Protection from carbon tetrachloride (CCL4)-induced hepatotoxicity by protein A was assessed histologically in rats. Carbon tetrachloride exposure produced swollen, vacuolated and necrotic cells in the centrilobular region of the hepatocyte in rats. Animals given protein A prior to and during CCL1 treatment showed a complete absence of hepatic lesions. Our study showed that protein A, a potent immunomodulator, has the potential to reduce liver injury caused by carbon tetrachloride, a known hepatotoxin in the rat.     

Protection against paracetamol-induced hepatotoxicity by acetylsalicylic acid in rats

Acetylsalicylic acid (ASA) given simultaneously with paracetamol decreased paracetamol-induced hepatotoxicity (measured by plasma transaminase activities as well as histology) without any effect on glutathione depletion, indicating that ASA prevents a process (or processes) subsequent to the metabolic activation of paracetamol. Delayed treatment with ASA also reduced paracetamol-induced liver toxicity, suggesting that reduction of the absorption rate of paracetamol does not contribute essentially to the protection by ASA. Combinations of paracetamol and ASA may have potential use in the development of safer analgesic combinations containing paracetamol (or ASA).     

Protection against acetaminophen-induced hepatotoxicity by prior treatment with fenitrothion

This study was undertaken to determine if interactions of toxicologic importance might occur during simultaneous exposure of mice to acetaminophen and fenitrothion. Acetaminophen administration induced dose-dependent hepatic morphologic changes which were accompanied by leakage of sorbitol dehydrogenase (SDH) into plasma 18 hr after dosing. Glutathione (GSH) depletion was maximal 2 hr after acetaminophen even at doses below those required for hepatic necrosis. Pretreatments with fenitrothion (50 or 500 mg/kg, ip) decreased hepatic GSH concentration and inhibited microsomal aniline hydroxylase and paranitroanisole O-demethylase activities. Similar treatments in mice subsequently challenged with acetaminophen (400 or 600 mg/kg, po) prevented the elevations in plasma SDH activity and lethality. Massive necrosis and 70% lethality were observed after 800 mg acetaminophen/kg and these effects were prevented by earlier pretreatment with 50 mg fenitrothion/kg. This pretreatment also decreased the degree of hepatic GSH depletion detected at 2 hr after 800 mg of acetaminophen. This finding would suggest that production of acetaminophen electrophile had been deceased by the pretreatment. Thus, with respect to interaction with acetaminophen, these results suggest that fenitrothion inhibition of mixed function oxidases predominated over fenitrothion depletion of GSH. Thus, even though GSH stores were lowered, less acetaminophen electrophile was generated and critical macromolecules were spared.     

Protection against acetaminophen hepatotoxicity by ribose-cysteine (RibCys).

2(RS)-D-ribo-(1',2',3',4'-Tetrahydroxybutyl)thiazolidine-4(R)-carb oxylic acid (Ribose-Cysteine, RibCys), a latent form of L-cysteine, releases the sulfhydryl amino acid in vivo by non-enzymatic ring opening and solvolysis. The liberated L-cysteine then stimulates hepatic glutathione biosynthesis. In the present studies, the efficacy of hepatoprotection by RibCys was evaluated to explore its potential utility as an acetaminophen (APAP) antidote. Protection was evaluated in the Swiss-Webster mouse model both by survival data as well as by quantitative histological criteria of hepatic damage. A dose-response study showed increased protection with increased intraperitoneal doses of RibCys ranging from 0.5 to 8.0 mmol/kg. RibCys administration 30 min. prior to and up to four hours after the APAP dose showed varying degrees of protection; however, the best protection was seen when RibCys was given shortly after APAP administration. A single RibCys dose given by the intraperitoneal or intravenous route gave better protection than when administered orally; however, RibCys given in three doses, one hour apart, regardless of the mode of administration, offered the best protection after an LD90 dose of APAP. Overall, RibCys continues to exhibit promising protective capabilities against APAP hepatotoxicity, which may be capitalized upon in clinical overdose situations.     

Protection against carbon tetrachloride-induced hepatotoxicity by pretreatment with methylmercury hydroxide

Pretreatment of rats with methylmercury hydroxide (MMH) (15 mg/kg s.c. for 2 days) protected against hepatotoxicity due to the inhalation of CCl4 vapor (4800–6100 ppm for 2 h). This was evidenced by lessening of the changes due to CCl₄ in liver glucose-6-phosphatase, serum glutamic oxal-acetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), serum isocitrate dehydrogenase and serum sorbitol dehydrogenase. Decreases in p-nitroanisole demethylation and cytochrome P-450 were also altered. Lipid peroxidation due to CCl₄ was decreased by MMH. These biochemical indices of protection were supported by histopathological observations.These results lend further support to the concept that metabolism of CCl₄ is necessary for its hepatoxicity.     

Hepatocurative effect of picroliv and silymarin against aflatoxin B1 induced hepatotoxicity in rats

Single doses of aflatoxin B1 (2 mg/kg, i.p.) caused significant increases in the activities of tau-glutamyl transpeptidase, 5'-nucleotidase, acid phosphatase and acid ribonuclease, and decreases in the activities of succinate dehydrogenase and glucose-6-phosphatase in liver, after 8 weeks. The level of lipid peroxides, DNA, RNA, and cholesterol increased while glycogen decreased. It also increased the serum level of transaminases, sorbitol dehydrogenase, glutamate dehydrogenase, lactate dehydrogenase, acid phosphatase, alkaline phosphatase, and bilirubin. Oral administration of picroliv (25 mg/kg/day for 15 days), a standardised iridoid glycoside fraction of Picrorhiza kurroa, 6 weeks after aflatoxin B1 toxication, significantly prevented the biochemical changes induced in liver and serum of aflatoxin B1 treated rats. The hepatocurative effect of picroliv and silymarin, a plant based standard hepatoprotective are comparable.     

乙酰紫堇灵对小鼠对乙酰氨基酚肝中毒的保护作用

乙酰紫堇灵（Ａｃｅ）是从中药紫堇中提取的生物碱，本文研究了Ａｃｅ对小鼠对乙酰氨基酚（ＡＰＡＰ）肝损伤的影响。Ａｃｅ显著降低ＡＰＡＰ引起的小鼠血清谷丙转氨酶升高，病理观察肝细胞损伤明显减轻。Ａｃｅ显著防止小鼠ｉｐＡＰＡＰ引起的肝脏谷胱甘肽耗竭，降低小鼠血中ＡＰＡＰ浓度。Ａｃｅ对肝脏细胞色素Ｐ４５０总量及谷胱甘肽巯基转移酶（ＧＳＨ－Ｓ－Ｔ）有显著诱导作用，而对代谢ＡＰＡＰ的Ｐ４５０同工酶ⅡＥ１有抑制作用。以上结果表明Ａｃｅ对小鼠ＡＰＡＰ中毒的保护作用与其选择性地调节Ｐ４５０同工酶，诱导ＧＳＨ－Ｓ－Ｔ，从而加快ＡＰＡＰ在体内的解毒代谢密切相关。     

Protection of rats against 3-butene-1,2-diol-induced hepatotoxicity and hypoglycemia by N-acetyl-l-cysteine

3-Butene-1,2-diol (BDD), an allylic alcohol and major metabolite of 1,3-butadiene, has previously been shown to cause hepatotoxicity and hypoglycemia in male Sprague-Dawley rats, but the mechanisms of toxicity were unclear. In this study, rats were administered BDD (250 mg/kg) or saline, ip, and serum insulin levels, hepatic lactate levels, and hepatic cellular and mitochondrial GSH, GSSG, ATP, and ADP levels were measured 1 or 4 h after treatment. The results show that serum insulin levels were not causing the hypoglycemia and that the hypoglycemia was not caused by an enhancement of the metabolism of pyruvate to lactate because hepatic lactate levels were either similar (1 h) or lower (4 h) than controls. However, both hepatic cellular and mitochondrial GSH and GSSG levels were severely depleted 1 and 4 h after treatment and the mitochondrial ATP/ADP ratio was also lowered 4 h after treatment relative to controls. Because these results suggested a role for hepatic cellular and mitochondrial GSH in BDD toxicity, additional rats were administered N-acetyl-l-cysteine (NAC; 200 mg/kg) 15 min after BDD administration. NAC treatment partially prevented depletion of hepatic cellular and mitochondrial GSH and preserved the mitochondrial ATP/ADP ratio. NAC also prevented the severe depletion of serum glucose concentration and the elevation of serum alanine aminotransferase activity after BDD treatment without affecting the plasma concentration of BDD. Thus, depletion of hepatic cellular and mitochondrial GSH followed by the decrease in the mitochondrial ATP/ADP ratio was likely contributing to the mechanisms of hepatotoxicity and hypoglycemia in the rat.     

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.     

Effect of silymarin on pyrogallol- and rifampicin-induced hepatotoxicity in mouse

Rifampicin and pyrogallol, besides beneficial effects, elicit hepatotoxicity in experimental animals and humans. The present investigation was undertaken to elucidate the role of drug/toxicant-metabolizing enzymes in rifampicin- and pyrogallol-induced hepatotoxicity and the effect of silymarin, a herbal antioxidant, on rifampicin- and pyrogallol-induced alterations in mouse liver. Male Swiss albino mice were treated intraperitoneally with and without rifampicin (20 mg/kg) and/or pyrogallol (40 mg/kg) for 1, 2, 3 and 4 weeks. In some experiments, animals were treated with silymarin (40 mg/kg), 2 h prior to rifampicin and/or pyrogallol. The differential expression and catalytic activity of cytochrome P-450 (CYP) 1A1, CYP1A2 and CYP2E1, the activity of glutathione-S-transferase, glutathione peroxidase and glutathione reductase, and lipid peroxidation were measured in the liver of control and treated groups. CYP1A1 expression and catalytic activity were not altered following individual or combinational treatment. A significant augmentation in the expression and activity of CYP1A2 and CYP2E1 was observed following pyrogallol and rifampicin+pyrogallol treatment; however, rifampicin exhibited a significant induction of CYP2E1 only. Attenuation of glutathione-S-transferase, glutathione reductase and glutathione peroxidase activities and augmentation of lipid peroxidation were observed following rifampicin and/or pyrogallol treatment and a cumulative effect was seen when the two drugs were administered in combination. Silymarin restored the rifampicin- and/or pyrogallol-induced alterations in the expression and activity of CYP1A2 and CYP2E1, the activity of glutathione-S-transferase, glutathione reductase, and glutathione peroxidase, and lipid peroxidation. The results demonstrate the role of CYP1A2, CYP2E1, glutathione-S-transferase, glutathione reductase and glutathione peroxidase in rifampicin- and pyrogallol-induced hepatotoxicity and provide evidence for the involvement of silymarin in attenuation of drug-induced hepatotoxicity.     

Protection against lipopolysaccharide-induced sepsis and inhibition of interleukin-1beta and prostaglandin E2 synthesis by silymarin

Silymarin is known to have hepatoprotective and anticarcinogenic effects. Recently, anti-inflammatory effect of silymarin is attracting an increasing attention, but the mechanism of this effect is not fully understood. Here, we report that silymarin protected mice against lipopolysaccharide (LPS)-induced sepsis. In this model of sepsis, silymarin improved the rate of survival of LPS-treated mice from 6 to 38%. To further investigate the mechanism responsible for anti-septic effect of silymarin, we examined the inhibitory effect of silymarin on interleukin-1beta (IL-1beta) and prostaglandin E2 (PGE2) production in macrophages. Silymarin dose-dependently suppressed the LPS-induced production of IL-1beta and PGE2 in isolated mouse peritoneal macrophages and RAW 264.7 cells. Consistent with these results, the mRNA expression of IL-1beta and cyclooxygenase-2 was also completely blocked by silymarin in LPS-stimulated RAW 264.7 cells. Moreover, the LPS-induced DNA binding activity of nuclear factor-kappaB/Rel was also inhibited by silymarin in RAW 264.7 cells. Taken together, these results demonstrate that silymarin has a protective effect against endotoxin-induced sepsis, and suggest that this is mediated, at least in part, by the inhibitory effect of silymarin on the production of IL-1beta and PGE2.     

Mechanism of protection by metallothionein against acetaminophen hepatotoxicity

Acetaminophen (APAP) overdose is the most frequent cause of drug-induced liver failure in the US. Metallothionein (MT) expression attenuates APAP-induced liver injury. However, the mechanism of this protection remains incompletely understood. To address this issue, C57BL/6 mice were treated with 100 μmol/kg ZnCl₂ for 3 days to induce MT. Twenty-four hours after the last dose of zinc, the animals received 300 mg/kg APAP. Liver injury (plasma ALT activities, area of necrosis), DNA fragmentation, peroxynitrite formation (nitrotyrosine staining), MT expression, hepatic glutathione (GSH), and glutathione disulfide (GSSG) levels were determined after 6 h. APAP alone caused severe liver injury with oxidant stress (increased GSSG levels), peroxynitrite formation, and DNA fragmentation, all of which were attenuated by zinc-induced MT expression. In contrast, MT knockout mice were not protected by zinc. Hydrogen peroxide-induced cell injury in primary hepatocytes was dependent only on the intracellular GSH levels but not on MT expression. Thus, the protective effect of MT in vivo was not due to the direct scavenging of reactive oxygen species. Zinc treatment had no effect on the early GSH depletion kinetics after APAP administration, which is an indicator of the metabolic activation of APAP to its reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI). However, MT was able to effectively trap NAPQI by covalent binding. We conclude that MT scavenges some of the excess NAPQI after GSH depletion and prevents covalent binding to cellular proteins, which is the trigger for the propagation of the cell injury mechanisms through mitochondrial dysfunction and nuclear DNA damage.     

吲哚-3-原醇对乙醇损伤性大鼠肝切片的保护作用

目的　采用精密肝切片技术 ,研究十字花科类蔬菜提取物吲哚 3 原醇 (I3C)对乙醇肝损伤的作用及机制。方法　制作大鼠乙醇损伤肝切片模型 ,观察不同剂量I3C对培养液中肝损伤标志酶及肝细胞浆苯胺羟化酶 (ANH)、乙醇脱氢酶 (ADH)活性的影响 ,并进行组织学检查。结果　乙醇5 0mmol·L-1作用肝切片 4h时 ,培养液谷丙转氨酶、谷草转氨酶、乳酸脱氢酶和谷胱甘肽S 转移酶活性明显升高 ,同时肝细胞浆ANH活性升高、ADH活性降低 ;加入 10 0～ 4 0 0μmol·L-1的I3C后 ,培养液中各酶活性降低的同时 ,肝细胞ANH和ADH活性恢复正常。肝切片病理学检查也证实I3C的保护作用。结论　I3C能有效拮抗乙醇所致的肝损伤 ,其机制与改变乙醇代谢途径有关。     

Sulforaphane protects against acetaminophen-induced hepatotoxicity

Oxidative stress is closely associated with acetaminophen (APAP)-induced toxicity. Heme oxygenase-1 (HO-1), an antioxidant defense enzyme, has been shown to protect against oxidant-induced tissue injury. This study investigated whether sulforaphane (SFN), as a HO-1 inducer, plays a protective role against APAP hepatotoxicity in vitro and in vivo. Pretreatment of primary hepatocyte with SFN induced nuclear factor E2-factor related factor (Nrf2) target gene expression, especially HO-1 mRNA and protein expression, and suppressed APAP-induced glutathione (GSH) depletion and lipid peroxidation, which eventually leads to hepatocyte cell death. A comparable effect was observed in mice treated with APAP. Mice were treated with 300 mg/kg APAP 30 min after SFN (5 mg/kg) administration and were then sacrificed after 6 h. APAP alone caused severe liver injuries as characterized by increased plasma AST and ALT levels, GSH depletion, apoptosis, and 4-hydroxynonenal (4-HNE) formations. This APAP-induced liver damage was significantly attenuated by pretreatment with SFN. Furthermore, while hepatic reactive oxygen species (ROS) levels were increased by APAP exposure, pretreatment with SFN completely blocked ROS formation. These results suggest that SFN plays a protective role against APAP-mediated hepatotoxicity through antioxidant effects mediated by HO-1 induction. SFN has preventive action in oxidative stress-mediated liver injury.     

Mechanism for the protective effects of silymarin against carbon tetrachloride-induced lipid peroxidation and hepatotoxicity in mice. Evidence that silymarin acts both as an inhibitor of metabolic activation and as a chain-breaking antioxidant

Administration of silymarin (800 mg/kg i.p.) 30 min before carbon tetrachloride (18 microL/kg i.p.) did not modify total hepatic levels of CCl4 and metabolites in mice, but decreased by 40% the in vivo covalent binding of CCl4 metabolites to hepatic lipids at 2 hr. This pretreatment decreased by 60% the exhalation of ethane during the first hour after CCl4, and decreased by 50% the incidence of liver cell necrosis. In vitro, silymarin (800 micrograms/mL) decreased by 50 to 70% various monooxygenase activities, and decreased by 20% the covalent binding of CCl4 metabolites to microsomal proteins. Silymarin (800 micrograms/mL) decreased by 70% in vitro lipid peroxidation mediated by CCl4 metabolites, and decreased by 90% peroxidation mediated by NADPH alone. Silibinin, one of the three isomers composing silymarin, also decreased carbon tetrachloride-induced lipid peroxidation; this effect, however, was less than that of silymarin in vitro, and was more transient in vivo. Pretreatment with silibinin (800 mg/kg i.p.) 30 min before CCl4 (18 microL/kg i.p.) did not improve SGPT activity or liver histology at 24 hr. We conclude that silymarin prevents carbon tetrachloride-induced lipid peroxidation and hepatotoxicity in mice, firstly, by decreasing the metabolic activation of CCl4, and, secondly, by acting as a chain-breaking antioxidant.     

Protection of carbon tetrachloride-induced hepatotoxicity by zinc: role of metallothionein

The dose-dependent release of alanine aminotransferase and aspartate aminotransferase into plasma 24 hr following various doses of CCl₄ (ip) was markedly lower in rats pretreated for 3 days with zinc chloride (150 μmol/kg/day) than in control rats. Although this dose of zinc produced a 34% decrease in hepatic concentration of cytochrome P-450 and a 50% decrease in binding of ¹⁴C derived from ¹⁴CCl₄ to hepatic microsomal protein and lipid in vitro, prior treatment with a single injection of zinc (250 μmol/kg) resulted in protection against CCl₄ toxicity without changing P-450 concentrations or ¹⁴C binding. Administration of a single dose (250 μmol/kg) of zinc or pretreatment on 3 consecutive days with 150 μmol/kg zinc produced a 700 or 1900% increase in hepatic concentration of metallothionein (MT), respectively. Following administration of ¹⁴CCl₄ to zinc-treated rats, radioactivity was present in the same elution volume as MT following gel filtration (G-75) of liver cytosol. This suggests that MT may protect against CCl₄-induced liver damage by sequestering reactive metabolites of CCl₄.     

Protection of chlordecone-potentiated carbon tetrachloride hepatotoxicity and lethality by partial hepatectomy

Chlordecone (CD) pretreatment is known to markedly potentiate CCl₄ hepatotoxicity. Previous studies have shown that prior exposure to CD obtunds the increased hepatocellular regeneration and repair observed in non-treated rats challenged with a single, low dose of CCl₄. These observations allowed us to hypothesize that suppression of hepatic regeneration and tissue repair by CD + CCl₄ combination treatment might be involved in this interaction. To test this hypothesis, CCl₄ hepatotoxicity was evaluated in actively regenerating livers using CD-treated (10 ppm in the diet for 15 days), surgically partially hepatectomized (PH) male Sprague-Dawley rats. Rats undergoing no surgical manipulation (CTRL) and sham operation (SH) were included as appropriate controls. Surgical manipulations were conducted on day 15 of the dietary protocol. Based on liver-to-body weight ratios (LW/BW), mitotic indices, hepatic cytochrome P-450 content, and hepatic glutathione (GSH and GSSG) levels, PH-induced hepatocellular regeneration was not affected by pretreatment with CD. Thus, the PH model was considered valid for assessing the effects of CD + CCl₄ combination treatment. CCl₄ (100 l/kg; i.p.) was administered 1, 2, 4 or 7 days after the surgical manipulations. Hepatotoxicity was assessed 24 h later by measuring LW/BW and serum enzymes (SGPT, SGOT and ICD) in all four groups. Hepatic histopathological, histomorphometric and lethal effects were assessed in animals receiving CCl₄ 1 or 7 days after the surgical manipulations. CCl₄-induced increases in LW/BW were observed in CD + PH rats receiving CCl₄ 4 or 7 days post-PH, but not in the 1 or 2 day post-PH groups in which the hepatocellular regeneration was maximal. CCl₄-induced serum enzyme elevations were significantly less in the CD + PH rats as compared to CD + SH. This decrease in the serum enzyme elevations was most prominent in the 1 day post-PH group, where the hepatocellular mitotic activity was most pronounced. CCl₄ lethality, assessed in the 1 day post-surgical manipulation group, was also decreased in the CD + PH rats in comparison to CD + SH rats. Such a protection was not observed in rats receiving CCl₄ 7 days post-PH. These data are consistent with and are supportive of the hypothesis that a suppression of otherwise normally stimulated hepatocellular regeneration following low-dose CCl₄ administration is involved in the marked amplification of CCl₄ toxicity by CD.Abbreviations CD chlordecone - GSH reduced glutathione - GSSG oxidized glutathione - PH partial hepatectomy - SH shamhepatectomy - CTRL control, not surgically manipulated - N normal diet - LW/BW liver weight-to-body weight ratio - SGPT serum glutamic; pyruvic transaminase - SGOT serum glutamic oxaloacetic transaminase - ICD isocitrate dehydrogenase These studies were made possible by a grant from the US Environmental Protection Agency R-811072A preliminary report of these findings was presented at the 70th Annual Meetings of the Federation of American Societies for Experimental Biology at St. Louis, MO (Fed Proc 45: 1051, 1986)A. N. Bell is a Predoctoral Toxicology Trainee and Robert A. Young is a Postdoctoral Trainee supported by Toxicology Training grant from National Institute of Environmental Health Science ES-07045     

Effects of silymarin nanoemulsion against carbon tetrachloride-induced hepatic damage

Silymarin is a complex mixture of four flavonolignan isomers (silybin, isosilybin, silydianin and silychristin) obtained from ‘milk thistle’ (Silybum marianum). This plant compound is used almost exclusively for hepatoprotection. Because of its low and poor oral bioavailability, silymarin was formulated as a nanoemulsion to increase its solubility (and so its oral bioavailability) as well as therapeutic activity. The present study assessed the hepatoprotective activity on Wistar rats by determining biochemical parameters and histopathological properties of the nanoemulsion formulation of silymarin against carbon tetrachloride (CCl₄)-induced hepatotoxicity. Hepatoprotective activity was evaluated by the activity of serum alkaline phosphatase, alanine transaminase and aspartate transaminase; antioxidative defence markers (concentration of reduced glutathione); oxidative stress parameter (thiobarbituric acid reactive substances) and liver histopathology. The nanoemulsion-treated group showed significant decreases in glutamate oxaloacetate transaminase, pyruvate transaminase, alkaline phosphotase, total bilirubin and tissue lipid peroxides and increased total protein, albumin, globulin and tissue glutathione as compared to toxicant. The results indicate an excellent potential of the nanoemulsion formulation for the reversal of CCl₄-induced liver toxicity in rats as compared to standard silymarin.