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Epigallocatechin gallate (EGCG) is a green tea antioxidant with adverse effects on rat liver mitochondria and hepatocytes at high doses. Here, we assessed whether low doses of EGCG would protect these systems from damage induced by tert-butyl hydroperoxide (tBHP). Rat liver mitochondria or permeabilized rat hepatocytes were pretreated with EGCG and then exposed to tBHP. Oxygen consumption, mitochondrial membrane potential (MMP), and mitochondrial retention capacity for calcium were measured. First, 50  μ M EGCG or 0.25 mM tBHP alone increased State 4 Complex I-driven respiration, thus demonstrating uncoupling effects; tBHP also inhibited State 3 ADP-stimulated respiration. Then, the coexposure to 0.25 mM tBHP and 50  μ M EGCG induced a trend of further decline in the respiratory control ratio beyond that observed upon tBHP exposure alone. EGCG had no effect on MMP and no effect, in concentrations up to 50  μ M, on mitochondrial calcium retention capacity. tBHP led to a decline in both MMP and mitochondrial retention capacity for calcium; these effects were not changed by pretreatment with EGCG. In addition, EGCG dose-dependently enhanced hydrogen peroxide formation in a cell- and mitochondria-free medium. Conclusion . Moderate nontoxic doses of EGCG were not able to protect rat liver mitochondria and hepatocytes from tBHP-induced mitochondrial dysfunction., Competing Interests: The authors declare that there are no competing interests regarding the publication of this paper.

The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor, important for combating electrophilic and oxidative stress in the liver and other organs. This encompasses detoxification of hepatotoxic drugs, including acetaminophen (APAP). Recently, an association between apolipoprotein E (ApoE) genotype and Nrf2 expression was described. We compared the toxicity of APAP on primary culture hepatocytes isolated from transgenic mice carrying two different human ApoE alleles and wild-type controls. The cells were exposed to APAP in concentrations from 0.5 to 4 mM for up to 24 hours. APAP led to a dose-dependent hepatotoxicity from 1 mM after 16 h exposure in all mice tested. The toxicity was higher in hepatocytes isolated from both transgenic strains than in wild-type controls and most pronounced in ApoE3 mice. Concurrently, there was a decline in mitochondrial membrane potential, especially in ApoE3 hepatocytes. The formation of reactive oxygen species was increased after 24 hours with 2.5 mM APAP in hepatocytes of all strains tested, with the highest increase being in the ApoE3 genotype. The activity of caspases 3 and 7 did not differ among groups and was minimal after 24 hour incubation with 4 mM APAP. We observed higher lipid accumulation in hepatocytes isolated from both transgenic strains than in wild-type controls. The expression of Nrf2-dependent genes was higher in ApoE3 than in ApoE4 hepatocytes and some of these genes were induced by APAP treatment. In conclusion, transgenic mice with ApoE4 and ApoE3 alleles displayed higher susceptibility to acute APAP toxicity in vitro than wild-type mice. Of the two transgenic genotypes tested, ApoE3 allele carriers were more prone to injury.

Nonalcoholic fatty liver disease is associated with chronic oxidative stress. In our study, we explored the antioxidant effect of antidiabetic metformin on chronic [high-fat diet (HFD)-induced] and acute oxidative stress induced by short-term warm partial ischemia-reperfusion (I/R) or on a combination of both in the liver. Wistar rats were fed a standard diet (SD) or HFD for 10 wk, half of them being administered metformin (150 mg·kg body wt(-1)·day(-1)). Metformin treatment prevented acute stress-induced necroinflammatory reaction, reduced alanine aminotransferase and aspartate aminotransferase serum activity, and diminished lipoperoxidation. The effect was more pronounced in the HFD than in the SD group. The metformin-treated groups exhibited less severe mitochondrial damage (markers: cytochrome c release, citrate synthase activity, mtDNA copy number, mitochondrial respiration) and apoptosis (caspase 9 and caspase 3 activation). Metformin-treated HFD-fed rats subjected to I/R exhibited increased antioxidant enzyme activity as well as attenuated mitochondrial respiratory capacity and ATP resynthesis. The exposure to I/R significantly increased NADH- and succinate-related reactive oxygen species (ROS) mitochondrial production in vitro. The effect of I/R was significantly alleviated by previous metformin treatment. Metformin downregulated the I/R-induced expression of proinflammatory (TNF-α, TLR4, IL-1β, Ccr2) and infiltrating monocyte (Ly6c) and macrophage (CD11b) markers. Our data indicate that metformin reduces mitochondrial performance but concomitantly protects the liver from I/R-induced injury. We propose that the beneficial effect of metformin action is based on a combination of three contributory mechanisms: increased antioxidant enzyme activity, lower mitochondrial ROS production, and reduction of postischemic inflammation., (Copyright © 2015 the American Physiological Society.)

Epigallocatechin-3-gallate (EGCG) is the main compound of green tea with well-described antioxidant, anti-inflammatory, and tumor-suppressing properties. However, EGCG at high doses was reported to cause liver injury. In this study, we evaluated the effect of EGCG on primary culture of rat hepatocytes and on rat liver mitochondria in permeabilized hepatocytes. The 24-hour incubation with EGCG in concentrations of 10 μmol/L and higher led to signs of cellular injury and to a decrease in hepatocyte functions. The effect of EGCG on the formation of reactive oxygen species (ROS) was biphasic. While low doses of EGCG decreased ROS production, the highest tested dose induced a significant increase in ROS formation. Furthermore, we observed a decline in mitochondrial membrane potential in cells exposed to EGCG when compared to control cells. In permeabilized hepatocytes, EGCG caused damage of the outer mitochondrial membrane and an uncoupling of oxidative phosphorylation. EGCG in concentrations lower than 10 μmol/L was recognized as safe for hepatocytes in vitro.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the Western world, and it persists at a high prevalence. NAFLD is characterised by the accumulation of triglycerides in the liver and includes a spectrum of histopathological findings, ranging from simple fatty liver through non-alcoholic steatohepatitis (NASH) to fibrosis and ultimately cirrhosis, which may progress to hepatocellular carcinoma. The pathogenesis of NAFLD is closely related to the metabolic syndrome and insulin resistance. Understanding the pathophysiology and treatment of NAFLD in humans has currently been limited by the lack of satisfactory animal models. The ideal animal model for NAFLD should reflect all aspects of the intricate etiopathogenesis of human NAFLD and the typical histological findings of its different stages. Within the past several years, great emphasis has been placed on the development of an appropriate model for human NASH. This paper reviews the widely used experimental models of NAFLD in rats. We discuss nutritional, genetic and combined models of NAFLD and their pros and cons. The choice of a suitable animal model for this disease while respecting its limitations may help to improve the understanding of its complex pathogenesis and to discover appropriate therapeutic strategies. Considering the legislative, ethical, economical and health factors of NAFLD, animal models are essential tools for the research of this disease.

Epigallocatechin gallate (EGCG) is an antioxidant found in green tea. In this study, male Wistar rats were subjected either to partial hepatectomy (PHx), or a sham operation (LAP). Twenty-four hours after surgery, hepatocytes were isolated and treated with various concentrations of EGCG for up to 72 h. We then measured markers of cell viability, oxidative stress, DNA synthesis, and caspase activity. Morphological criteria, cell viability tests, and albumin synthesis revealed toxicity starting at 10 μmol/L. DNA synthesis was higher in hepatocytes isolated from rats after PHx and inhibited by EGCG. Furthermore, EGCG increased the activity of caspases 3 and 7, seen more in hepatocytes from PHx rats. In conclusion, EGCG at a concentration of 10 μmol/L was toxic for hepatocytes isolated from both PHx and LAP rats.

Literature data support that green tea and its major component epigallocatechin gallate (EGCG) have powerful antioxidant effects. Contrary, hepatotoxicity can be induced by high-dose EGCG. The timing of exposure to green tea in relation to administration of hepatotoxic agent plays an import role too. The aim of our work was a verification of antioxidative effect of EGCG on D-galactosamine-induced injury in primary culture of rat hepatocytes. Hepatocytes were incubated with EGCG at concentrations of 1.25-10 μM and toxic D-galactosamine (GalN) for 24 hrs. Alternatively, hepatocytes were pretreated with EGCG for 24 hrs, and then incubated with EGCG and GalN for further 24 hrs. Cytotoxicity was analysed by lactate dehydrogenase activity, functional capacity by albumin production. Oxidative stress was evaluated from a production of malondialdehyde and glutathione content in the cells. EGCG protected hepatocytes against GalN-induced cytotoxicity but preventive treatment of intact hepatocytes with EGCG was required to diminish the development of hepatocyte injury. Oxidative stress induced in our study seems to overcome the ability of hepatocytes to improve GSH depletion and albumin production. Prolongation of the pretreatment with EGCG could be a promising strategy leading to amelioration of its hepatoprotective effect.

Epigallocatechin gallate (EGCG) has been shown to be protective in various experimental models of liver injury, although opposite effects have also been reported. Since its effect on biliary physiology has not been thoroughly investigated, the present study evaluated effect of EGCG on bile flow and bile acid homeostasis in rats. Compared to controls, EGCG treatment decreased bile flow by 23%. Hepatic paracellular permeability and biliary bile acid excretion were not altered by EGCG administration, but biliary glutathione excretion was reduced by 70%. Accordingly, the main glutathione transporter on the hepatocyte canalicular membrane, multidrug resistance-associated protein 2 (Mrp2), was significantly decreased at the protein level. EGCG administration also doubled plasma bile acid levels compared to controls. While protein levels of the main hepatic bile acid transporters were unchanged, the rate-limiting enzyme in the bile acid synthesis, Cyp7a1, was significantly increased by EGCG. Enhanced bile acid synthesis in these animals was also confirmed by a 2-fold increase in plasma marker 7α-hydroxy-4-cholesten-3-one. In contrast, EGCG markedly downregulated major bile acid transporters (Asbt and Ostα) and regulatory molecules (Shp and Fgf15) in the ileum. When EGCG was coadministered with ethinylestradiol, a potent cholestatic agent, it did not show any additional effect on the induced cholestasis. This study shows ability of EGCG to raise plasma bile acid concentrations, mainly through Cyp7a1 upregulation, and to decrease bile production through reduction in Mrp2-mediated bile acid-independent bile flow. In conclusion, our data demonstrate that under certain conditions EGCG may induce cholestasis., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Aims: Several groups found different impact of erythropoietin (EPO) on liver regeneration. Both pro-proliferative as well as anti-proliferative and non-proliferative activities have been reported using high dosage of EPO. Systemic administration of high doses of this cytokine is a clinical concern due to risk of thrombosis. Herein, we applied EPO in low dosages and investigated whether it can stimulate liver regeneration after liver resection., Main Methods: Parameters of liver regeneration were assessed 3 days after 70% hepatectomy by means of immunochemistry and proteomics. EPO was given twice in low dosages (200 and 600 IU/kg BW)., Key Findings: We showed that EPO facilitated hepatic regeneration in rats. Enhanced hepatocyte proliferation (Ki67, BrdU-positive cells) was observed in all EPO-treated groups. By performing Differential Proteomic analysis, we identified two proteins which resulted sensitive to EPO treatment after hepatectomy: Peroxiredoxin-1 and glutathione S-transferase Mu 1., Significance: Based on our results, low doses of rhEPO increase the hepatic regenerative capacity after partial hepatectomy in rats by enhancing hepatocyte proliferation and acting on antioxidant enzymes. Both proteins identified by proteomic analysis have not previously been associated with liver regeneration and will aid in the understanding of EPO's regenerative response having clinical implications to treat liver failure., (Copyright © 2011. Published by Elsevier Inc.)

Although amiodarone (AMD) is known to produce drug-drug interactions through inhibition of transporter-mediated excretion of drugs, its impact on these mechanisms during chronic treatment has not been described yet. Therefore, the aim of this study was to investigate the influence of AMD pretreatment on the main multidrug transporting proteins, Mdr1 and Mrp2, in the liver and kidney. The expression of the transporters and pharmacokinetics of their substrates, rhodamine-123 (Rho123) and endogenous conjugated bilirubin (CB), were evaluated in rats after either AMD oral pretreatments (4-14 days) or single intravenous bolus. AMD pretreatment of all durations up-regulated renal Mdr1 and Mrp2 protein expression to 155-190% and 152-223% of the control values, respectively. In agreement, we observed a corresponding increase in renal clearance of both substrates. Hepatic expression was increased only for Mdr1 to 234-270% of controls, which was associated with increased biliary elimination of amiodarone without change in Rho123 biliary clearance. Interestingly, hepatic expression of another Mdr transporter, Mdr2, was progressively decreased by amiodarone administration. Acute administration of AMD reduced Rho123 biliary clearance by 64%. Our results indicate that repeated administration of AMD to rats is associated with significant increase in hepatic and renal expression of Mdr1 and Mrp2 transporters, which may contribute to variability in pharmacokinetics of AMD and simultaneously applied drugs., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Responses of cell populations in vitro to toxic substances are very dynamic and exceed hours or even days. Toxicologists realise that cell-based dynamic assays can acquire important additional information about toxic responses of individual cell within a treated population. In the past, this type of cellular dynamics could have been monitored only with the help of time-lapse microcinematography. In spite of several advantages, the time-lapse approach has been used relatively infrequently in the routine in vitro cytotoxicity assessment. The main reasons were demanding time and work schedules, problems with quantification of visual information, and lack of mechanistic data. Recently, the situation has changed dramatically. The progress in digital imaging technology coincides with enormous development in the field of fluorescence microscopy. With the help of specific fluorochromes or fluorescent proteins we can now analyse practically all sub-cellular and cellular events. Some producers developed large-scale high-throughput systems for live cell imaging. Nevertheless, there has been significant progress in small-scale approach as well. New versions of motorised microscopes are fulfilling principal demands for in vitro assessment of toxic effects: ease of performance, high-throughput of data, quantitative cell-based analysis, simultaneous assessment of several parameters, and control of the environment conditions for cultivation of cells. In this paper, we present our experience with two of these systems designed for long-lasting observation of living cells in phase contrast and fluorescence. Our aim is to draw attention to the suitability of small-scale cell-based assays for determination of cytotoxicity in vitro. We believe that these methods could be considered as a further step towards the replacement of animal testing.