Coordinated expression of multidrug resistance-associated proteins (Mrps) in mouse liver during toxicant-induced injury.

Following acute chemical injury, hepatocytes are generally more resistant to toxicant re-exposure. Alterations in expression of hepatobiliary transport systems may contribute to this resistance by preventing accumulation of potentially toxic chemicals. Previous data demonstrate the concomitant reduction of uptake transporter and induction of efflux transporter mRNA during chemical liver injury. The present study further characterizes the expression of multidrug resistance-associated proteins 1-4 (Mrp1-4), breast cancer resistance protein (Bcrp) and sodium-taurocholate co-transporting polypeptide (Ntcp) in mouse liver following administration of the hepatotoxicants acetaminophen (APAP) and carbon tetrachloride (CCl4). Mice received hepatotoxic doses of APAP (400 mg/kg), CCl4 (10 or 25 microl/kg), or vehicle, ip. Livers were collected at 6, 24, and 48 h for Western blot quantification and immunofluorescence analysis. Protein expression of Bcrp was unchanged with treatment. Ntcp levels were preserved in APAP-exposed livers and reduced to 30-50% of control after CCl4. Conversely, Mrp1-4 expression was differentially up-regulated. CCl4 increased Mrp1 (3.5-fold), Mrp2 (1.4-fold), and Mrp4 (26-fold) while reducing Mrp3 levels to 20% of control. Administration of APAP enhanced expression of Mrp2 (1.6-fold), Mrp3 (3.5-fold), and Mrp4 (16-fold). Immunostaining of liver sections obtained 48 h after hepatotoxicant treatment confirmed expression patterns of a subset of transporters (Bcrp, Ntcp, Mrp3, and Mrp4). Double immunofluorescence imaging demonstrated the simultaneous down-regulation of Ntcp and up-regulation of Mrp4 in hepatocytes adjacent to the central vein after CCl4. Altered expression of transporters may reduce the overall chemical burden of an injured liver during recovery and contribute to the resistance of hepatocytes to subsequent toxicant exposure.     

Discovery of common urinary biomarkers for hepatotoxicity induced by carbon tetrachloride, acetaminophen and methotrexate by mass spectrometry-based metabolomics

Liver toxicity represents an important healthcare issue because it causes significant morbidity and mortality and can be difficult to predict before symptoms appear owing to drug therapy or exposure to toxicants. Using metabolomic techniques, we discovered common biomarkers for the prediction of hepatotoxicity in rat urine using mass spectrometry. For this purpose, liver toxicity was induced by 5 days of oral administration of carbon tetrachloride (1 ml kg^?1 per day), acetaminophen (1000 mg kg^?1 per day) and methotrexate (50 mg kg^?1 per day). Serum levels of alkaline phosphatase aspartate aminotransferase, alanine aminotransferase and histopathology in liver tissue were then checked to demonstrate liver toxicity. Global metabolic profiling with UPLC‐TOF‐MS (ultraperformance liquid chromatography–mass spectrometry), multivariate analysis (partial least square‐discriminant analysis, hierarchical analysis) and database searching were performed to discover common biomarkers for liver toxicity induced by these three compounds. Urinary concentrations of the newly discovered biomarkers were then quantified to confirm them as biomarkers of hepatotoxicity with targeted metabolic profiling using GC (gas chromatography)–MS and CE (capillary electrophoresis)–MS. In the results, steroids, amino acids and bile acids were metabolically changed between the control and drug‐treated groups in global metabolic profiling; 11β‐hydroxyandrosterone, epiandrosterone, estrone, 11‐dehydrocorticosterone, glycine, alanine, valine, leucine, dl ‐ornithine, 3‐methylhistidine, cholic acid and lithocholic acid were selected as liver toxicity biomarkers after performing targeted metabolic profiling. In conclusion, we discovered metabolite biomarkers belonging to three different metabolic pathways to check for liver toxicity with mass spectrometry from a metabolomics study that could be used to evaluate hepatotoxicity induced by drugs or other toxic compounds. Copyright © 2011 John Wiley & Sons, Ltd.     

Oral administration of diphenyl diselenide potentiates hepatotoxicity induced by carbon tetrachloride in rats

Carbon tetrachloride (CCl4) is a model for studying free radical-induced liver injury and screening hepato-protective drugs. Numerous studies have reported the involvement of oxidative stress in CCl4-induced liver damage and the hepato-protective effects mediated by different antioxidants. The present study examined the effects of diphenyl diselenide, (PhSe)2, on hepatotoxicity induced by CCl4 in rats. To this end, male Wistar rats received (PhSe)2 by oral route at the dosage of 31.2 mg/kg for one or two days. After the second day of treatment, rats received CCl4 orally in a single dose. The liver and kidney were utilized for determination of histopathology, biochemical [aspartate (ALT) and alanine (AST) aminotransferases, alkaline phosphatase (ALP), total bilirrubin (TB) and gamaglutamyl transferase (GGT)] and toxicological parameters [thiobarbituric reactive species (TBARS) levels, catalase activity, ascorbic acid, nonprotein thiols (NPSH) and aminolevulinate dehydratase (-ALA-D) activity]. Repeated administration of (PhSe)2 caused a marked potentiation of hepatotoxicity induced by CCl4 exposure, as manifested by an increase in biochemical parameters (AST, ALT, ALP, GGT and BT) and severe alteration in histopathology. This study also demonstrated a potentiation of TBARS levels and a consequent depletion of important antioxidant defenses including catalase and ascorbic acid. Pre-treatment with a single dose of (PhSe)2 prevented the effect of strychnine, a substrate for CYPs, abolishing lethality in mice. This result indicates that (PhSe)2 prevented animal death, suggesting an activator action of (PhSe)2 in CYPs. This study clearly indicates that (PhSe)2 potentiated acute hepatic damage induced by CCl4.     

Inhibition of matrix metalloproteinases minimizes hepatic microvascular injury in response to acetaminophen in mice.

The acetaminophen (APAP)-induced hepatic centrilobular necrosis is preceded by hepatic microcirculatory dysfunction including the infiltration of erythrocytes into the space of Disse. The purpose of this study was to examine the involvement of matrix metalloproteinases (MMPs) in the hepatic microvascular injury elicied by APAP. Male C57Bl/6 mice were pretreated with 2-[(4-biphenylsulfonyl) amino]-3-phenyl-propionic acid, an MMP-2/MMP-9 inhibitor (5 mg/kg, ip) 30 min before oral gavage with 600 mg/kg of APAP. The hepatic microvasculature in anesthetized mice was observed using established in vivo microscopic methods 2 and 6 h after APAP. The levels of mRNAs and activities of MMP-2 and MMP-9 in the liver were increased from 1 h through 6 h after APAP gavage. APAP increased alanine transferase (ALT) levels (41.1-fold) and resulted in centrilobular hemorrhagic necrosis at 6 h. Pretreatment with 2-[(4-biphenylsulfonyl) amino]-3-phenyl-propionic acid attenuated ALT values by 71% as well as the necrosis. APAP decreased the numbers of perfused sinusoids in centrilobular regions by 30% and increased the area occupied by infiltrated erythrocytes into Disse space. 2-[(4-Biphenylsulfonyl) amino]-3-phenyl-propionic acid restored the sinusoidal perfusion to 90% of control levels and minimized extrasinusoidal area occupied by erythrocytes. The present study showed that increased MMPs during APAP intoxication are associated with hepatocellular damage and with hepatic microcirculatory dysfunction including impaired sinusoidal perfusion and infiltration of erythrocytes in Disse space. 2-[(4-Biphenylsulfonyl) amino]-3-phenyl-propionic acid attenuated APAP-induced parenchymal and microvascular injury. These results suggest that MMPs participate in APAP hepatotoxicity mediated by sinusoidal endothelial cell injury, which results in impairment of microcirculation.     

Comparative effects of dimethylsulfoxide on metabolism and toxicity of carbon tetrachloride and dichloromethane

The effects of dimethylsulfoxide (DMSO) on the metabolism and toxicity of chlorinated methanes were examined. Male mice were treated with DMSO (1, 2.5 or 5 ml kg(-1), i.p.) prior to challenge with dichloromethane (CH(2)Cl(2)) or carbon tetrachloride (CCl(4)). Blood carboxyhemoglobin elevation resulting from metabolic conversion of CH(2)Cl(2) to carbon monoxide was inhibited dose-dependently by DMSO pretreatment. The elevation of serum aspartate aminotransferase, alanine aminotransferase and sorbitol dehydrogenase activities induced by CCl(4) (0.1 mmol kg(-1)) was not changed in mice pretreated with DMSO at 1 ml kg(-1), but depressed significantly at a greater dose of DMSO. However, DMSO failed to alter the hepatotoxicity of CCl(4) injected at a dose of 0.2 mmol kg(-1). DMSO induced the microsomal p-nitrophenol hydroxylase and p-nitroanisole O-demethylase activities as early as 2 h following the treatment. Microsomal disposition of CH(2)Cl(2) and CCl(4) was measured using a vial equilibration technique. The disappearance of CH(2)Cl(2) was inhibited competitively by addition of DMSO. But DMSO did not affect the metabolic degradation of CCl(4). The results indicate that DMSO has multiple effects on metabolism and toxicity of xenobiotics. DMSO induces the hepatic metabolizing activity mediated by CYP2E1, but the presence of this solvent in the enzyme site may inhibit directly the enzymatic interaction with a substrate. The toxicological significance of DMSO-induced effects on such an interaction may be variable depending on the properties of each substrate. The invulnerability of CCl(4) metabolism to the effects of DMSO appears to be related to its high affinity for the lipophilic CYP enzyme site.     

木犀草素对四氯化碳致大鼠肝纤维化的保护作用及其机制研究

目的观察木犀草素对四氯化碳(CC l4)致大鼠肝纤维化的保护作用。方法用CC l4复制大鼠中毒性肝纤维化模型,观察木犀草素对大鼠血清中透明质酸(HA)、层黏蛋白(LN)、丙氨酸氨基转移酶(ALT/GPT)、天冬氨酸氨基转移酶(AST/GOT)、总蛋白(TP)、白蛋白(A lb)、肝组织病理学及超氧化物歧化酶(SOD)、丙二醛(MDA)、羟脯氨酸(Hyp)的变化;MTT比色法检测木犀草素对大鼠肝星状细胞(HSC)和人肝星状细胞(Lx-2)的增殖的影响。结果与模型组比较,木犀草素给药组血清学指标(HA、LN)明显降低(P<0.05),ALT、AST减少,TP、A lb升高,病理组织学检查明显改善,肝组织内SOD升高,MDA、Hyp降低,并对HSC、Lx-2细胞的增殖有抑制作用(P<0.05)。结论木犀草素对CC l4致大鼠肝纤维有较好的保护作用,其机制可能与抑制肝内胶原合成、降低自由基生成、减轻脂质过氧化及抑制HSC增殖活化有关。     

六味五灵片对四氯化碳致大鼠肝纤维化的保护作用

目的研究六味五灵片对四氯化碳(CCl4)所致大鼠肝纤维化的保护作用。方法用CCl4-植物油溶液腹腔注射造模,将造模成功的大鼠随机分为5组,每组12只,分别为模型组、复方鳖甲软肝片组、六味五灵片低剂量组(4 g.kg-1)、六味五灵片中剂量组(8 g.kg-1)、六味五灵片高剂量组(16 g.kg-1)。以血清中谷草转氨酶(AST)、谷丙转氨酶(ALT)、透明质酸(HA)、层粘连蛋白(LN)及羟脯氨酸(HyP)和肝组织中还原型谷胱甘肽(GSH)、超氧化物歧化酶(SOD)及丙二醛(MDA)为评价指标,以肝组织Masson染色追踪其肝纤维化程度。结果六味五灵片能明显降低CCl4所致的大鼠血清中ALT、AST、HA、LN和HyP的含量(P<0.05),降低肝组织中的MDA含量(P<0.05),明显升高肝组织中的GSH和SOD含量(P<0.05),肝组织纤维化变性明显减轻,肝组织结构比较完好。结论六味五灵片对四氯化碳所致大鼠肝纤维化具有保护作用。     

Effect of allyl alcohol on hepatic transporter expression: Zonal patterns of expression and role of Kupffer cell function

During APAP toxicity, activation of Kupffer cells is critical for protection from hepatotoxicity and up-regulation of multidrug resistance-associated protein 4 (Mrp4) in centrilobular hepatocytes. The present study was performed to determine the expression profile of uptake and efflux transporters in mouse liver following treatment with allyl alcohol (AlOH), a periportal hepatotoxicant. This study also investigated the role of Kupffer cells in AlOH hepatotoxicity, and whether changes in transport protein expression by AlOH are dependent on the presence of Kupffer cells. C57BL/6J mice received 0.1 ml clodronate liposomes to deplete Kupffer cells or empty liposomes 48 h prior to dosing with 60 mg/kg AlOH, i.p. Hepatotoxicity was assessed by plasma ALT and histopathology. Hepatic transporter mRNA and protein expression were determined by branched DNA signal amplification assay and Western blotting, respectively. Depletion of Kupffer cells by liposomal clodronate treatment resulted in heightened susceptibility to AlOH toxicity. Exposure to AlOH increased mRNA levels of several Mrp genes, while decreasing organic anion transporting polypeptides (Oatps) mRNA expression. Protein analysis mirrored many of these mRNA changes. The presence of Kupffer cells was not required for the observed changes in uptake and efflux transporters induced by AlOH. Immunofluorescent analysis revealed enhanced Mrp4 staining exclusively in centrilobular hepatocytes of AlOH treated mice. These findings demonstrate that Kupffer cells are protective from AlOH toxicity and that induction of Mrp4 occurs in liver regions away from areas of AlOH damage independent of Kupffer cell function. These results suggest that Kupffer cell mediators do not play a role in mediating centrilobular Mrp4 induction in response to periportal damage by AlOH.     

汉防已甲素对四氧化碳损伤大鼠肝的保护作用

本研究发现,汉防已甲素一次性预处理能使大鼠肝脏对毒性物质的损伤产生保护作用。用四氯化碳造成大鼠急性肝损伤模型,若预先2小时腹腔注射汉防已甲素(50mg/kg),则血清谷丙转氨酶、胆红素及死亡率都显著降低,肝组织学检查也显示损伤程度明显减轻。     

Phenobarbital and phenytoin increased acetaminophen hepatotoxicity due to inhibition of UDP-glucuronosyltransferases in cultured human hepatocytes.

Here we present a preclinical model to assess drug-drug interactions due to inhibition of glucuronidation. Treatment with the antiepileptics phenobarbital (PB) or phenytoin (PH) has been associated with increased incidence of acetaminophen (APAP) hepatotoxicity in patients. In human hepatocytes, we found that the toxicity of APAP (5 mM) was increased by simultaneous treatment with phenobarbital (2 mM) or phenytoin (0.2 mM). In contrast, pretreatment with PB for 48 h prior to APAP treatment did not increase APAP toxicity unless both drugs were present simultaneously. Cells treated with APAP in combination with PB or PH experienced decreases in protein synthesis as early as 1 h, ultrastructural changes by 24 h, and release of liver enzymes by 48 h. Toxicity correlated with inhibition of APAP glucuronidation. PB or PH also inhibited APAP glucuronidation in rat and human liver microsomes and expressed human UGT1A6, 1A9, and 2B15. As with intact hepatocytes, PB and PH were neither hydroxylated nor glucuronidated, suggesting the direct inhibition of UGTs. Our findings suggest that, in multiple drug therapy, an inhibitory complex between UGT and one of the drugs can lead to decreased glucuronidation and increased systemic exposure and toxicity of a coadministered drug.     

磷,砷,四氯化碳肝损伤线粒体和微粒体乳酸脱氢酶同工酶的改变

本文对P4,NaAsO_2,CCl_4亚慢性肝损伤大鼠肝细胞线粒体,微粒体LDH同工酶进行聚丙烯酰胺凝胶电泳,光密度扫描定量,对其标志酶组化染色,微机图象定量分析,结果表明,三组动物肝小叶线粒体标志酶SDH活性均有下降,其中以CCl_4组SDH下降较迟.NaAsO_2组染毒第8wk可见线粒体LDH_5升高,染毒12wk LDH_(2,3)下降,LDH_5升高与对照组比较无显著性差异,但仍高于P_4组,各组间微粒体LDH同工酶和其标志酶G-6-P酶活性变化存在差异;P_4组微粒体LDH同工酶改变明显且较其他两组早。     

Gene expression profiling of rat livers reveals indicators of potential adverse effects.

This study tested the hypothesis that gene expression profiling can reveal indicators of subtle injury to the liver induced by a low dose of a substance that does not cause overt toxicity as defined by conventional criteria of toxicology (e.g., abnormal clinical chemistry and histopathology). For the purpose of this study we defined this low dose as subtoxic, i.e., a dose that elicits effects which are below the detection of conventional toxicological parameters. Acetaminophen (APAP) was selected as a model hepatotoxicant because (1) considerable information exists concerning the mechanism of APAP hepatotoxicity that can occur following high doses, (2) intoxication with APAP is the leading cause of emergency room visits involving acute liver failure within the United States, and (3) conventional clinical markers have poor predictive value. Rats treated with a single dose of 0, 50, 150, or 1500 mg/kg APAP were examined at 6, 24, or 48 h after exposure for conventional toxicological parameters and for gene expression alterations. Patterns of gene expression were found which indicated cellular energy loss as a consequence of APAP toxicity. Elements of these patterns were apparent even after exposure to subtoxic doses. With increasing dose, the magnitude of changes increased and additional members of the same biological pathways were differentially expressed. The energy loss suggested by gene expression changes was confirmed at the 1500 mg/kg dose exposure by measuring ATP levels. Only by ultrastructural examination could any indication of toxicity be identified after exposure to a subtoxic dose of APAP and that was occasional mitochondrial damage. In conclusion, this study provides evidence that supports the hypothesis that gene expression profiling may be a sensitive means of identifying indicators of potential adverse effects in the absence of the occurrence of overt toxicity.     

Naringenin attenuates CCl4‐induced hepatic inflammation by the activation of an Nrf2‐mediated pathway in rats

The possible protective effects of naringenin, a naturally occurring citrus flavonone, on carbon tetrachloride (CCl₄)‐induced liver injury in rats and the mechanism underlying its effects were investigated. Forty rats were divided into five groups. Rats in Groups I and II served as the normal and injured liver groups, respectively; Group III rats were treated with the standard drug silymarin as a positive control; and rats in Groups IV and V (naringenin‐treated groups) were administrated 50 mg/kg, p.o., naringenin for 7 days. Liver samples were collected to evaluate mRNA and protein expression, histological changes and oxidative stress. Naringenin inhibited lipid peroxidation and reduced serum levels of hepatic enzymes induced by CCl₄. In addition, naringenin increased the liver content of reduced glutathione and the activity of anti‐oxidant enzymes in rats treated with CCl₄. Naringenin attenuated liver inflammation by downregulating CCl₄‐induced activation of tumour necrosis factor (TNF)‐α, inducible nitric oxide synthase (iNOS) and cyclo‐oxygenase (COX‐2) at both the protein and mRNA levels. Naringenin treatment significantly increased NF‐E2‐related factor 2 (Nrf2) and heme oxygenase (HO‐1) expression in injured livers. In rats treated with CCl₄ alone, decreases were seen in nuclear Nrf2 expression and in the mRNA levels of its target genes (e.g. HO‐1, NQO1 and glutathione S‐transferase alpha 3 (GST‐a3)). Together, the results suggest that naringenin can protect the liver against oxidative stress, presumably by activating the nuclear translocation of Nrf2 as well as attenuating the TNF‐α pathway to elicit an anti‐inflammatory response in liver tissue.     

四氯化碳致大鼠肝纤维化模型血液流变学性质的研究

目的：研究大鼠肝纤维化时血液流变学性质的变化特征。方法：以四氯化碳诱导大鼠肝纤维化模型,检测血液粘度、血浆粘度、红细胞压积、红细胞特性指数等血液流变学参数,分析其变化特征。结果：与正常组比较,模型组大鼠全血粘度、全血还原粘度、红细胞压积、红细胞聚集 数及红细胞刚性指数明显增高。结论：大鼠肝纤维化时血液粘增大,红细胞流变性能减弱,易引发微循环障碍,加重肝纤维化的发展。     

Acetaminophen metabolism does not contribute to gender difference in its hepatotoxicity in mouse.

Gender is an important factor in pharmacokinetics and pharmacodynamics. In the current study, gender difference in acetaminophen (APAP)-induced hepatotoxicity has been examined. Male and female mice were injected with a toxic dose of APAP (500 mg/kg, ip). Female mice were resistant to the hepatotoxic effects of APAP, depicted by serum alanine aminotransferase and sorbital dehydrogenase activities and histological analysis. Basal hepatic reduced glutathione (GSH) levels were lower in females than in males, suggesting that basal GSH level may not be a factor in determining the gender difference of APAP hepatotoxicity. APAP metabolism was slower in females than males, revealed by lower levels of glucuronidation and sulfation and higher amounts of free APAP in the livers of female mice. Lower basal Cyp1a2 mRNA levels and lower expression of Cyp1a2 and Cyp3a11 mRNAs after APAP dosing were also observed in females compared with males. However, there was no gender difference in N-acetyl-p-benzoquinone imine covalent binding 2 h after APAP administration, suggesting similar APAP bioactivation between genders. Moreover, liver Gst pi mRNA levels were significantly lower in females than males. This finding is consistent with a previous report, which showed that Gst pi knockout mice are protected from APAP-induced liver toxicity. In conclusion, gender difference of APAP-induced hepatotoxicity is not likely due to APAP metabolism. Perhaps, it is in part due to gender-dependent Gst pi expression. However, the mechanism underlying the association between reduction in Gst pi expression and hepatoprotective effect against APAP toxicity remains to be further explored.     

Potentiating effect of acetaminophen and carbon tetrachloride-induced hepatotoxicity is mediated by activation of receptor interaction protein in mice

When multiple drugs or chemicals are used in combination, it is important to understand the risk of their interactions and predict potential additive effects. The aim of the current study was to investigate the molecular mechanism(s) accounting for the additive/synergistic effect of combination treatment with acetaminophen (APAP) and carbon tetrachloride (CCl₄). Mice were intraperitoneally administered vehicle or 100?mg/kg (5?mL/kg) APAP and 30?min after vehicle or 15?mg/kg (5?mL/kg) CCl₄. Sixteen hours after treatment, mice from each group were sacrificed and the livers were removed. CCl₄ administration caused slight glycogen depletion; this effect was more pronounced following co-administration of APAP and CCl₄. ATP and NADPH levels showed the same trend as glycogen levels. The levels of receptor interacting protein 1 and 3 increased following combination treatment with APAP and CCl₄. In contrast, levels of the glutamate cysteine ligase catalytic subunit and glutamate cysteine ligase modifier subunits were not significantly affected by combination treatment. APAP and CCl₄ co-administration potentiated the phosphorylation of c-Jun N-terminal kinase and p38 kinases, although phosphorylated activation of extracellular signal-regulated kinase was not changed. Our results suggest that APAP and CCl₄ co-administration potentiates hepatotoxicity in an additive/synergistic manner via receptor interacting protein activation.     

Binding of carbon tetrachloride metabolites to rat hepatic mitochondrial DNA

Radioactivity from [14C]CCl4 was bound to highly purified mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) prepared from livers of rats after a single dose of [14C]CCl4. At a low, non-necrotizing dose as well as at an acutely toxic dose, mtDNA bound 20-50-fold more radioactivity per mg than did nDNA. Extensive enzymatic digestion and purification of mtDNA did not remove radioactivity. Binding of radioactivity to mtDNA could also be demonstrated after anaerobic incubation of isolated mitochondria with [14C]CCl4, NADPH, ADP, and succinate. Our results suggest that CCl4 can be activated by rat hepatic mitochondrial enzymes to metabolites which bind covalently to mtDNA.