Hepatic CYP2E1 Expression Research Articles

ERRγ-inducible FGF23 promotes alcoholic liver injury through enhancing CYP2E1 mediated hepatic oxidative stress

Fibroblast growth factor 23 (FGF23) is a member of endocrine FGF family, along with FGF15/19 and FGF21. Recent reports showed that under pathological conditions, liver produces FGF23, although the role of hepatic FGF23 remains nebulous. Here, we investigated the role of hepatic FGF23 in alcoholic liver disease (ALD) and delineated the underlying molecular mechanism. FGF23 expression was compared in livers from alcoholic hepatitis patients and healthy controls. The role of FGF23 was examined in hepatocyte-specific knock-out (LKO) mice of cannabinoid receptor type 1 (CB1R), estrogen related receptor γ (ERRγ), or FGF23. Animals were fed with an alcohol-containing liquid diet alone or in combination with ERRγ inverse agonist. FGF23 is mainly expressed in hepatocytes in the human liver, and it is upregulated in ALD patients. In mice, chronic alcohol feeding leads to liver damage and induced FGF23 in liver, but not in other organs. FGF23 is transcriptionally regulated by ERRγ in response to alcohol-mediated activation of the CB1R. Alcohol induced upregulation of hepatic FGF23 and plasma FGF23 levels is lost in ERRγ-LKO mice, and an inverse agonist mediated inhibition of ERRγ transactivation significantly improved alcoholic liver damage. Moreover, hepatic CYP2E1 induction in response to alcohol is FGF23 dependent. In line, FGF23-LKO mice display decreased hepatic CYP2E1 expression and improved ALD through reduced hepatocyte apoptosis and oxidative stress. We recognized CBIR-ERRγ-FGF23 axis in facilitating ALD pathology through hepatic CYP2E1 induction. Thus, we propose FGF23 as a potential therapeutic target to treat ALD.

Phenylpropionic acid produced by gut microbiota alleviates acetaminophen-induced hepatotoxicity

ABSTRACT The gut microbiota affects hepatic drug metabolism. However, gut microbial factors modulating hepatic drug metabolism are largely unknown. In this study, using a mouse model of acetaminophen (APAP)-induced hepatotoxicity, we identified a gut bacterial metabolite that controls the hepatic expression of CYP2E1 that catalyzes the conversion of APAP to a reactive, toxic metabolite. By comparing C57BL/6 substrain mice from two different vendors, Jackson (6J) and Taconic (6N), which are genetically similar but harbor different gut microbiotas, we established that the differences in the gut microbiotas result in differential susceptibility to APAP-induced hepatotoxicity. 6J mice exhibited lower susceptibility to APAP-induced hepatotoxicity than 6N mice, and such phenotypic difference was recapitulated in germ-free mice by microbiota transplantation. Comparative untargeted metabolomic analysis of portal vein sera and liver tissues between conventional and conventionalized 6J and 6N mice led to the identification of phenylpropionic acid (PPA), the levels of which were higher in 6J mice. PPA supplementation alleviated APAP-induced hepatotoxicity in 6N mice by lowering hepatic CYP2E1 levels. Moreover, PPA supplementation also reduced carbon tetrachloride-induced liver injury mediated by CYP2E1. Our data showed that previously known PPA biosynthetic pathway is responsible for PPA production. Surprisingly, while PPA in 6N mouse cecum contents is almost undetectable, 6N cecal microbiota produces PPA as well as 6J cecal microbiota in vitro, suggesting that PPA production in the 6N gut microbiota is suppressed in vivo. However, previously known gut bacteria harboring the PPA biosynthetic pathway were not detected in either 6J or 6N microbiota, suggesting the presence of as-yet-unidentified PPA-producing gut microbes. Collectively, our study reveals a novel biological function of the gut bacterial metabolite PPA in the gut-liver axis and presents a critical basis for investigating PPA as a modulator of CYP2E1-mediated liver injury and metabolic diseases.

Extract of Jasminum grandiflorum L. alleviates CCl4-induced liver injury by decreasing inflammation, oxidative stress and hepatic CYP2E1 expression in mice.

Jasminum grandiflorum L. (JG) is a medicinal plant containing many bioactive ingredients. Herein, we analyzed the effects of four different extracts and two compounds of JG on acute liver injury caused by carbon tetrachloride (CCl4) and underlying molecular mechanisms. 7 weeks old C57BL/6 male mice were used to establish a liver injury model by injecting with 1% CCl4, 10mL/kg ip. Four different extracts and two compounds of JG were given to mice by gavage for 3 days. Clinical and histological chemistry assays were performed to assess liver injury. Moreover, hepatic oxidative stress and inflammation related markers were determined by immunohistochemistry and western blotting. As a result, JG extracts and two functional components showed different degree of protect effects against CCl4-induced liver injury by the decrease of elevated serum transaminases and liver index, and the attenuation of histopathological changes in mice, among which JG extracted with petroleum ether (PET) had the most significant effect. In addition, PET remarkably alleviated hepatic oxidative stress and inflammation. Further studies revealed that PET significantly inhibited the TNF-α expression, signal pathway expression, NF-κB p65 and inflammatory factors IL-1β and IL-6 expression in CCl4-induced liver injury mice. Nevertheless, hydroxytyrosol (HT) alleviated liver injury by reducing oxidative stress. Apart from PET extract, other extracts of JG can inhibit cytochrome CYP2E1 expression to protect liver tissue. These findings suggest that the extracts and its components of JG possesses the potential protective effects against CCl4-induced liver injury in mice by exerting antioxidative stress and anti-inflammation.

The nuclear receptor REV-ERBα regulates CYP2E1 expression and acetaminophen hepatotoxicity

CYP2E1 plays an important role in drug metabolism and drug-induced hepatotoxicity. Here, we aimed to investigate a potential role for the nuclear receptor REV-ERBα in regulation of CYP2E1 expression and acetaminophen (APAP)-induced hepatotoxicity, and to determine the underlying mechanisms. Regulatory effects of REV-ERBα on CYP2E1 expression were assessed in vivo (using Rev-erbα -/- mice) and in vitro (using AML12 and HepG2 cells). In vitro microsomal CYP2E1 activity was probed using its specific substrate p-nitrophenol. Pharmacokinetic and acute toxicity studies were performed with Rev-erbα −/− and wild-type mice after APAP administration. We found that Rev-erbα ablation led to decreases in hepatic CYP2E1 expression and activity in mice. In line with this, APAP-induced hepatotoxicity was attenuated in Rev-erbα-deficient mice. The attenuated toxicity was due to down-regulation of APAP metabolism mediated by CYP2E1, which was evidenced by a decrease in formation of the toxic intermediate metabolite NAPQI (i.e. reduced APAP-cysteine and APAP-N-acetylcysteine levels). Furthermore, positive regulation of CYP2E1 expression by REV-ERBα was confirmed in both AML12 and HepG2 cells. Based on luciferase reporter assays, it was found that REV-ERBα regulated Cyp2e1 transcription and expression through repression of DEC2. In conclusion, REV-ERBα positively regulates CYP2E1 expression in mice, thereby affecting APAP metabolism and hepatotoxicity.

Nanocurcumin and curcumin prevent N, N'-methylenebisacrylamide-induced liver damage and promotion of hepatic cancer cell growth

Acrylamide (AC) is an environmental contaminant with cancer-promoting and cytotoxic properties, while curcumin (Cur.) is a phytochemical with documented anticancer and cytoprotective efficacy. Nanoparticle formulations can increase the efficacy of phytochemicals, so we examined the anticancer and hepatoprotective efficacies of nanocurcumin (N.Cur). Curcumin and nanocurcumin reduced HepG2 and Huh-7 cancer cell viability and increased apoptosis in the presence and absence of AC, while AC alone promoted proliferation. Furthermore, the anticancer efficacy of nanocurcumin was greater than that of curcumin. In mice, AC greatly increased hepatic expression of CYP2E1, P53, cleaved caspase-3, and COL1A1 as well as serum alanine aminotransferase and aspartate aminotransferase activities. These effects were reversed by nanocurcumin and curcumin. Nanocurcumin also reduced the histopathology and fibrosis caused by AC, and reversed AC-induced glycogen depletion. Nanoparticle formulation can increase the anticancer and hepatoprotective efficiencies of curcumin.

Deep Sea Water-Dissolved Organic Matter Intake Improves Hyperlipidemia and Inhibits Thrombus Formation and Vascular Inflammation in High-Fat Diet Hamsters.

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease caused by oxidative stress, inflammation and lipid deposition within liver cells, and is subsequently contributing to cardiovascular diseases such as atherosclerosis. Deep sea water (DSW) is characterized by its clearance and abundant nutrients with antioxidant and anti-inflammatory activity to confer therapeutic potential. We aimed to explore the therapeutic capability of our prepared multi-filtration DSW-dissolved organic matter (DSW-DOM) on high-fat diet-induced hyperlipidemia and endothelial dysfunction in hamsters. A high-fat/high-cholesterol diet led to increased oxidative stress, including blood reactive oxygen species (ROS), plasma malondialdehyde (MDA) and hepatic CYP2E1 expression; an increased hyperlipidemic profile and SREBP 1-mediated fatty liver; promoted NFκB p65-mediated hepatic inflammation; triggered PARP-mediated hepatic apoptosis; and enhanced endothelial intercellular adhesion molecule-1 (ICAM-1) and von Willebrand factor (VWF)-mediated atherosclerosis associated with the depressed hepatic antioxidant Paraoxonase 1 (PON1) expression. The DSW-DOM-enriched 1295 fraction, with strong H2O2 scavenging activity, efficiently reduced several oxidative stress parameters, the lipid profile, inflammation, and apoptosis, possibly through the PON1-mediated antioxidant capability. Furthermore, DSW-DOM treatment significantly decreased the endothelial ICAM-1 and VWF expression, subsequently leading to the elongation of time to occlusion of FeCl3-induced arterial thrombosis and to the inhibition of FeCl3-induced fluorescent platelet adhesion to mesentery arterioles in the high-fat diet. Based on the above results, our data suggest that DSW-DOM intake via antioxidant defense mechanisms confers protective effects against high-fat diet-enhanced, oxidative stress-mediated hyperlipidemia, and endothelial dysfunction evoked atherosclerosis by downregulating oxidative injury, lipogenesis, inflammation and apoptosis.

Alteration of murine cytochrome P450 profiles in fatty liver disease by hesperidin and myricetin

Background: Hesperidin and myricetin are anti-inflammatory and anti-oxidant flavonoids that have beneficial effects in fatty liver disease (FLD), but information regarding their effects on cytochrome P450 (CYP450) enzymes in FLD is limited. Objectives: This study determined the impacts of hesperidin and myricetin on CYP450 profiles in FLD mice. Materials and Methods: Adult female mice were fed a high fat diet (HFD, 60 kcal % fat of total food) with daily intragastrically administered ethanol (0.5 g/kg/day) in combination with either fenofibrate (40 mg/kg/day), hesperidin (50 and 200 mg/kg/day), or myricetin (50 and 200 mg/kg/day) for 60 consecutive days. Liver histomorphology was examined by oil red O staining. Hepatic enzyme activity and mRNA expression of CYP1A2, CYP2E1, CYP3A11, CYP3A13, and CYP4A11 were assessed. Results: HFD-induced hepatocellular damage was prevented by low dose hesperidin and myricetin. Expression of Cyp1a2, Cyp2e1, and Cyp4a11 mRNAs as well as CYP2E1 and CYP3A activities was significantly induced by HFD plus ethanol (HE) while Cyp3a13 expression was slightly increased. Fenofibrate and low dose hesperidin prevented HE-induced Cyp1a2 and Cyp2e1 expression while HE-induced Cyp4a11 expression was prevented by all treatments. The expression of Cyp3a13 was extensively suppressed by high-dose hesperidin and myricetin, and CYP2E1 and CYP3A activities were significantly decreased by all treatments. Conclusion: Alteration of CYP450 profiles by high doses of hesperidin and myricetin could lead to drug interactions. Nevertheless, low dose hesperidin prevented dysregulation of CYP450 expression in FLD and is a promising candidate for FLD treatment.

Acetaminophen and the Developing Lung: Could There Be Lifelong Consequences?

Acetaminophen and the Developing Lung: Could There Be Lifelong Consequences?

2,3,4\u2032,5-tetrahydroxystilbene-2-O-\u03b2-D-glucoside exacerbates acetaminophen-induced hepatotoxicity by inducing hepatic expression of CYP2E1, CYP3A4 and CYP1A2

Hepatotoxicity induced by medicinal herb Polygonum multiflorum Thunb. attracts wide attention in the world recently. 2,3,4′,5-tetrahydroxystilbene-2-O-β-D-glucoside (TSG) is a main active compound in Polygonum multiflorum Thunb. This study aims to observe TSG-provided the aggravation on acetaminophen (APAP)-induced hepatotoxicity in mice by inducing hepatic expression of cytochrome P450 (CYP450) enzymes. Serum alanine/aspartate aminotransferase (ALT/AST) analysis and liver histological evaluation showed that TSG (200, 400, 800 mg/kg) exacerbated the hepatotoxicity induced by sub-toxic dose of APAP (200 mg/kg) in mice, but TSG alone had no hepatotoxicity. TSG aggravated hepatic reduced glutathione (GSH) depletion and APAP-cysteine adducts (APAP-CYS) formation induced by APAP in mice. TSG increased the expression of CYP2E1, CYP3A4 and CYP1A2 both in mice and in human normal liver L-02 hepatocytes. TSG also enhanced liver catalytic activity of CYP2E1, CYP3A4 and CYP1A2 in mice. TSG induced the nuclear translocation of aryl hydrocarbon receptor (AHR) and pregnane X receptor (PXR), and TSG-provided the aggravation on APAP-induced hepatotoxicity in mice was reversed by PXR or AHR inhibitors. In summary, our results demonstrate that TSG enhances hepatic expression of CYP3A4, CYP2E1 and CYP1A2, and thus exacerbates the hepatotoxicity induced by APAP in mice. PXR and AHR both play some important roles in this process.

Anti-steatotic and anti-inflammatory effects of Hovenia dulcis Thunb. extracts in chronic alcohol-fed rats

The anti-steatotic and anti-inflammatory effects of fruit water extract (FW) and seed ethanol extract (SE) of Hovenia dulcis Thunb. in chronic alcohol-fed rats were investigated. Rats were fed a liquid diet containing 36% calories from alcohol and orally administered FW or SE (300 and 500mg/kg/day). Both FW and SE reduced hepatic lipid contents and droplets, serum lipid concentration and inflammatory markers (hs-CRP, TNF-α and IL-6) levels compared with the alcohol control group. Alcohol led to significant decreases in the hepatic fatty acid oxidative gene (Ppargc1a, Cpt1a and Acsl1) levels, while it significantly increased the Myd88 and Tnfa gene levels. However, FW or SE supplementation significantly up-regulated gene expression of Ppargc1a, Ppara, Cpt1a and Acsl1, and down-regulated gene expression of Myd88, Tnfa and Crp compared with the alcohol control group. FW or SE supplementation also significantly decreased hepatic activities of fatty acid synthase and phosphatidate phosphohydrolase in chronic alcohol-fed rats. Plasma alcohol and acetaldehyde levels, hepatic enzyme activity and protein expression of CYP2E1 were lowered by FW or SE supplementation. These results indicate that both FW and SE play an important role in improvement of alcoholic hepatic steatosis and inflammation via regulation of lipid and inflammation metabolism.

Metallothionein protects against isoniazid-induced liver injury through the inhibition of CYP2E1-dependent oxidative and nitrosative impairment in mice

Oxidative stress mediated by hepatic CYP2E1 during isoniazid (INH) metabolism is considered responsible for INH hepatotoxicity. This study attempts to determine whether metallothionein (MT), a cysteine-rich antioxidant can protect against INH-induced liver injury by using a MT-I/II deficient mouse model (MT−/− mice). MT−/− mice and the corresponding wild-type mice received intragastric administrations of 0, 75, 150 and 300 mg/kg of INH for 15 days. The results showed that 150 and 300 mg/kg of INH induced liver injury in both types of mice, as evidenced by increased liver index and histopathological change of liver vacuolar degeneration. Increased hepatic MDA level and 3-NT expression, and decreased GSH content and SOD activity were also observed in both types of mice, indicating the involvement of oxidative and nitrosative stress. INH treatment upregulated hepatic CYP2E1 expression in both types of mice, and the severity of liver injury was in concert with the elevation of CYP2E1 expression. Comparative analyses revealed liver vacuolar degeneration and oxidative and nitrosative stress were more severe in MT−/− mice than wild-type mice, suggesting the hepatoprotection of MT against INH hepatotoxicity. Taken together, these findings clearly demonstrate that MT protects against INH-induced liver toxicity by ameliorating CYP2E1-dependent oxidative and nitrosative impairment.

Chronic administration of caderofloxacin, a new fluoroquinolone, increases hepatic CYP2E1 expression and activity in rats.

Caderofloxacin is a new fluoroquinolone that is under phase III clinical trials in China. Here we examined the effects of caderofloxacin on rat hepatic cytochrome P450 (CYP450) isoforms as well as the potential of caderofloxacin interacting with co-administered drugs. Male rats were treated with caderofloxacin (9 mg/kg, ig) once or twice daily for 14 consecutive days. The effects of caderofloxacin on CYP3A, 2D6, 2C19, 1A2, 2E1 and 2C9 were evaluated using a "cocktail" of 6 probes (midazolam, dextromethorphan, omeprazole, theophylline, chlorzoxazone and diclofenac) injected on d 0 (prior to caderofloxacin exposure) and d 15 (after caderofloxacin exposure). Hepatic microsomes from the caderofloxacin-treated rats were used to assess CYP2E1 activity and chlorzoxazone metabolism. The expression of CYP2E1 mRNA and protein in hepatic microsomes was analyzed with RT-PCR and Western blotting, respectively. Fourteen-day administration of caderofloxacin significantly increased the activity of hepatic CYP2E1, leading to enhanced metabolism of chlorzoxazone. In vitro microsomal study confirmed that CYP2E1 was a major metabolic enzyme involved in chlorzoxazone metabolism, and the 14-d administration of caderofloxacin significantly increased the activity of CYP2E1 in hepatic microsomes, resulting in increased formation of 6-hydroxychlorzoxazone. Furthermore, the 14-d administration of caderofloxacin significantly increased the expression of CYP2E1 mRNA and protein in liver microsomes, which was consistent with the pharmacokinetic results. Fourteen-day administration of caderofloxacin can induce the expression and activity of hepatic CYP2E1 in rats. When caderofloxacin is administered, a potential drug-drug interaction mediated by CYP2E1 induction should be considered.

Gene copy number variation analysis reveals dosage-insensitive expression of CYP2E1.

Gene copy number variants (CNVs) of CYP2E1 have been described but not functionally characterized. Here we investigated effects of CNVs on hepatic and lymphoblastoid CYP2E1 expression. Using available single-nuleotide polymorphism microarray data and quantitative PCR, CYP2E1 gene duplication and deletion carriers were identified. CYP2E1 mRNA, protein and enzyme activity (chlorzoxazone-6-hydroxylation) phenotypes of CYP2E1 were not associated with gene copy number. Analysis of gene expression in lymphoblastoid cell lines in relation to CNV confirmed this finding in an extrahepatic tissue and for other ethnicities. Further analyses identified a linked haplotype cluster with possible influence on gene expression. In summary, our data suggest a homeostatic, gene dosage-insensitive regulation of CYP2E1 expression by unknown gene dosage compensation mechanisms. This is in striking contrast to well-known structural variations of CYP2A6 and CYP2D6 that have a strong impact on expression and activity. These findings are important in the context of pharmacogenetic prediction.

Involvement of hepatic stellate cell cytoglobin in acute hepatocyte damage through the regulation of CYP2E1-mediated xenobiotic metabolism

Oxygen (O2) is required for cytochrome P450 (CYP)-dependent drug metabolism. Cytoglobin (CYGB) is a unique globin expressed exclusively in hepatic stellate cells (HSCs). However, its role in O2-dependent metabolism in neighboring hepatocytes remains unknown. This study provides evidence that CYGB in HSCs is involved in acetaminophen (N-acetyl-p-aminophenol; APAP)-induced hepatotoxicity. Serum alanine aminotransferase levels were higher in wild-type mice than in Cygb-null mice. Wild-type mice exhibited more severe hepatocyte necrosis around the central vein area compared with Cygb-null mice, thus indicating that CYGB deficiency protects against APAP-induced liver damage. Although no difference in the hepatic expression of CYP2E1, a key enzyme involved in APAP toxicity, was observed between wild-type and Cygb-null mice, the serum levels of the APAP metabolites cysteinyl-APAP and N-acetyl-cysteinyl-APAP were decreased in Cygb-null mice, suggesting reduced APAP metabolism in the livers of Cygb-null mice. In primary cultures, APAP-induced hepatocyte damage was increased by co-culturing with wild-type HSCs but not with Cygb-null HSCs. In addition, cell damage was markedly alleviated under low O2 condition (5% O2), suggesting the requirement of O2 for APAP toxicity. Carbon tetrachloride-induced liver injury (CYP2E1-dependent), but not lipopolysaccharide/D-galactosamine-induced injury (CYP2E1-independent), was similarly alleviated in Cygb-null mice. Considering the function of CYGB as O2 carrier, these results strongly support the hypothesis that HSCs are involved in the CYP2E1-mediated xenobiotic activation by augmenting O2 supply to hepatocytes. In conclusion, CYGB in HSCs contributes to the CYP-mediated metabolism of xenobiotics in hepatocytes by supplying O2 for enzymatic oxidation.

Dietary saturated fatty acids reduce hepatic lipid accumulation but induce fibrotic change in alcohol-fed rats.

In this study, we evaluated the influence of an ethanol-containing diet with high saturated fatty acids (SFAs) on alcoholic liver disease (ALD) in rats. Male Wistar rats weighing about 160 g were divided into four groups: an ethanol (E) group fed an ethanol-containing liquid diet with 36% total calories as fat (corn oil, olive oil and safflower oil); a control (C) group pair-fed an isoenergetic diet without ethanol; an ethanol with saturated fat (EHS) group fed an ethanol-containing diet which contained 40% total calories as fat (90% lard); and a control with saturated fat (CHS) group fed an isoenergetic diet without ethanol, which contained 40% total calories as fat. After 8 weeks of treatment, the liver weight and plasma aspartate aminotransferase (AST) activities in E and EHS groups were significantly higher than those of C group. Significantly higher scores of inflammation, necrosis, and fatty changes were found in E group, whereas significantly higher scores of necrosis, bile duct hyperplasia, and fibrosis were found in EHS group. Although significantly lower plasma adiponectin concentrations were observed in both E and EHS groups, compared to C group, plasma adiponectin in EHS group was significantly higher than that in E group. There was no change in hepatic peroxisome proliferator activated receptor (PPAR)-α expression between E and C groups, and rats in EHS group showed a significantly elevated level compared to the other groups. A lower hepatic sirtuins (SIRT)-1 level was found in E group, but it did not reach statistical significance. Moreover, the highest plasma TGF-β1 level was found in EHS group. Compared to C group, the hepatic reduced glutathione/oxidized glutathione ratio and thiobarbituric acid (TBA)-reactive substance level were significantly increased in E and EHS groups; however, there was no significant difference between E and EHS groups. Significantly increased hepatic CYP2E1 expression was observed in both E and EHS groups, while at the same time, hepatic CYP2E1 in EHS group was the highest among all groups. The hepatic tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10 concentrations in the E group were significantly higher than those in C group, whereas the hepatic IL-6 and IL-10 concentrations in ES group were significantly lower than those of E group. These results suggested that dietary saturated fats may inhibit hepatic fat accumulation and induce hepatic fibrosis in rats under chronic alcohol intake.

The role of intestinal microbiota in murine models of acetaminophen-induced hepatotoxicity.

Background & AimVariations in intestinal microbiota may influence acetaminophen metabolism. This study aimed to determine whether intestinal microbiota are a source of differential susceptibility to acetaminophen-induced hepatotoxicity.MethodsConventionally housed C3H/HeH (CH) and C3H/HeH germ free (GF) mice were administered a 200mg/kg IP dose of acetaminophen. The severity of hepatotoxicity at 8 hours was assessed by histology and biochemical indices. A urinary metabolic profile was obtained using 1H-NMR. Baseline hepatic glutathione content and CYP2E1 expression were quantified. An additional group of C3H/HeJ (LPS-r) mice were assessed to determine the contribution of LPS/TLR4 signalling.ResultsBaseline glutathione levels were significantly reduced (p=0.03) in GF mice. CYP2E1 mRNA expression and protein levels were not altered. Inter-individual variability did not differ between GF and CH groups. No significant differences in the extent of hepatocellular injury (ALT or percentage necrosis) were demonstrated. However, a milder acute liver failure (ALF) phenotype was shown in GF compared with CH mice, with reduced plasma bilirubin and creatinine and increased blood glucose. Differential acetaminophen metabolism was demonstrated. GF mice displayed a higher urinary acetaminophen-sulphate:glucuronide ratio compared with CH (p=0.01). Urinary analysis showed metabolic differentiation of GF and CH groups at baseline and 8 hours(cross-validated ANOVA p=1x10-22). Interruption of TLR4 signalling in LPS-r mice had additional protective effects.ConclusionVariations in intestinal microbiota do not fully explain differential susceptibility to acetaminophen-induced hepatotoxicity. GF mice experienced some protection from secondary complications following acetaminophen overdose and this may be mediated through reduced TLR4/LPS signalling.

Protection afforded by pre- or post-treatment with 4-phenylbutyrate against liver injury induced by acetaminophen overdose in mice

Acetaminophen (paracetamol, N-acetyl-p-aminophenol; APAP) is a widely used analgesic/antipyretic drug with few adverse effects at therapeutic doses; suicidal or unintentional overdose of APAP frequently induces severe hepatotoxicity. To explore a new and effective antidote for APAP hepatotoxicity, this study examined the effects of sodium 4-phenylbutyrate (4-PBA) on liver injury induced by APAP overdose in mice. Liver injury was induced in C57BL/6 male mice by intraperitoneal injection of APAP (400mg/kg). The effects of 4-PBA (100–200mg/kg) treatment at 1h before the APAP injection were evaluated with serum alanine aminotransferase (ALT) and blood ammonia levels, hepatic pathological changes, including histopathology, DNA damage, nitrotyrosine formation, and mRNA or protein expression involved in the development of hepatotoxicity, such as X-box binding protein-1 (XBP1), c-Jun N-terminal kinase (JNK), C/EBP homologous protein (CHOP) and B-cell lymphoma 2 interacting mediator of cell death (Bim). In addition, glutathione depletion and CYP2E1 protein expression, which are measures of the metabolic conversion of APAP to a toxic metabolite, were examined. Furthermore, we examined the effects of post-treatment with 4-PBA against APAP-induced hepatotoxicity in mice. When administered at 1h before APAP injection, 4-PBA significantly prevented the increase in serum ALT and blood ammonia levels, centrilobular necrosis of hepatocytes, DNA fragmentation, and nitrotyrosine formation induced by APAP in mice. 4-PBA also inhibited hepatic Xbp1 mRNA splicing and JNK phosphorylation induced by APAP, but did not suppress CHOP and Bim mRNA and protein expression. In addition, 4-PBA had little effect on hepatic glutathione depletion and CYP2E1 expression, parameters of toxic APAP metabolite production. Post-treatment with 4-PBA administration at 1 or 2h after APAP injection also attenuated the increase in serum ALT and blood ammonia levels and hepatic pathological changes in APAP-induced hepatotoxicity in mice. Although post-treatment with 4-PBA did not show any effects on hepatic Xbp1 mRNA splicing and JNK phosphorylation, it drastically attenuated the DNA fragmentation induced by APAP. The precise molecular mechanisms of the protection afforded by 4-PBA against APAP hepatotoxicity in mice are unclear, but they seem to involve inhibition of hepatocellular DNA fragmentation. We suggest that 4-PBA is a promising candidate as an antidote against APAP-induced liver injury.

Role of receptor interacting protein (RIP)1 on apoptosis-inducing factor-mediated necroptosis during acetaminophen-evoked acute liver failure in mice

Acetaminophen (APAP) overdose induces apoptosis-inducing factor (AIF)-dependent necroptosis, but the mechanism remains obscure. The present study investigated the role of receptor interacting protein (RIP)1, a critical mediator of necroptosis, on AIF-dependent necroptosis during APAP-induced acute liver failure. Mice were intraperitoneally injected with APAP (300mg/kg). As expected, hepatic RIP1 was activated as early as 1h after APAP, which is earlier than APAP-induced hepatic RIP3 upregulation. APAP-evoked RIP1 activation is associated with hepatic glutathione (GSH) depletion. Either pretreatment or post-treatment with Nec-1, a selective inhibitor of RIP1, significantly alleviated APAP-induced acute liver failure. Moreover, Nec-1 improved the survival and prevented APAP-induced necroptosis, as determined by TdT-mediated dUTP-biotin nick end labeling (TUNEL) assay. Further analysis showed that Nec-1 significantly inhibited APAP-induced hepatic c-Jun N-terminal kinase (JNK) phosphorylation and mitochondrial Bax translocation. In addition, Nec-1 blocked APAP-induced translocation of AIF from the mitochondria to the nucleus. Of interest, no changes were induced by Nec-1 on hepatic CYP2E1 expression. In addition, Nec-1 had little effect on APAP-induced hepatic GSH depletion at early stage. Taken together, these results suggest that RIP1 is involved in APAP-induced necroptosis. Nec-1 is an effective antidote for APAP-induced acute liver failure.

Reduction of Hepatotoxicity Induced by Acetaminophen Overdoses in a Mouse Model of Inflammation Induced by Freund´s Adjuvants

Acetaminophen (APAP) is often used as an analgesic and antipyretic during the inflammatory process. Its toxicity in overdoses depends on the integrity of the hepatic cytochrome P450 (CYP). The oxidative drug metabolism mediated by CYP can be inhibited during inflammatory diseases or after use of immuno-stimulants drugs and vaccines. The objective of this work was to evaluate if inflammation is able to modulate the toxicity of APAP. Five female Balb/c mice were injected subcutaneously with Freund Complete Adjuvant (FCA), and boosted with Freund’s Incomplete Adjuvant (FIA) at 14th day. Then, they were treated with 360 mg/kg of acetaminophen orally during the 14th, 15th and 16th days. Convenient control groups were included with APAP administration without immuno-stimulation. Serum levels of IL-1β, TNFα, IFNγ, α-1-acid glycoprotein (α-1-AGP), alanine transaminase (ALT), aspartic acid aminotransferase (AST), lactate dehydrogenase (LDH) and hepatic CYP2E1 expression were measured. Inoculation site of adjuvants and liver histopathological responses were also evaluated. FCA/FIA injection produced acute inflammatory response in the inoculation site and increased serum levels of the pro-inflammatory cytokines, α-1-AGP and LDH with reduction of hepatic CYP2E1 expression. A reduction of liver damage induced by APAP overdoses was also observed, suggesting that inflammatory processes can be protective against APAP hepatotoxicity.

Lactobacillus rhamnosus GG reduces hepatic TNFα production and inflammation in chronic alcohol-induced liver injury

The therapeutic effects of probiotic treatment in alcoholic liver disease (ALD) have been studied in both patients and experimental animal models. Although the precise mechanisms of the pathogenesis of ALD are not fully understood, gut-derived endotoxin has been postulated to play a crucial role in hepatic inflammation. Previous studies have demonstrated that probiotic therapy reduces circulating endotoxin derived from intestinal gram-negative bacteria in ALD. In this study, we investigated the effects of probiotics on hepatic tumor necrosis factor-α (TNFα) production and inflammation in response to chronic alcohol ingestion. Mice were fed Lieber DeCarli liquid diet containing 5% alcohol for 8weeks, and Lactobacillus rhamnosus GG (LGG) was supplemented in the last 2 weeks. Eight-week alcohol feeding caused a significant increase in hepatic inflammation as shown by histological assessment and hepatic tissue myeloperoxidase activity assay. Two weeks of LGG supplementation reduced hepatic inflammation and liver injury and markedly reduced TNFα expression. Alcohol feeding increased hepatic mRNA expression of Toll-like receptors (TLRs) and CYP2E1 and decreased nuclear factor erythroid 2-related factor 2 expression. LGG supplementation attenuated these changes. Using human peripheral blood monocytes-derived macrophages, we also demonstrated that incubation with ethanol primes both lipopolysaccharide- and flagellin-induced TNFα production, and LGG culture supernatant reduced this induction in a dose-dependent manner. In addition, LGG treatment also significantly decreased alcohol-induced phosphorylation of p38 MAP kinase. In conclusion, probiotic LGG treatment reduced alcohol-induced hepatic inflammation by attenuation of TNFα production via inhibition of TLR4- and TLR5-mediated endotoxin activation.