Primary Cultures Of Rat Hepatocytes Research Articles

Genipin Inhibits the Induction of Inducible Nitric Oxide Synthase Through the Inhibition of NF-κB Activation in Rat Hepatocytes.

Genipin is a component of Japanese traditional herbal medicine (Kampo), inchinkoto, and is used for the treatment of various liver injuries. However, there are few scientific evidence for its anti-inflammatory effects and mechanisms. In inflamed liver, proinflammatory cytokines including tumor necrosis factor (TNF)-α and interleukin (IL)-1β stimulate liver cells, followed by the expression of inducible nitric oxide synthase (iNOS). Excessive levels of NO produced by iNOS have been implicated as one of the factors in liver injury. Thus it is essential to inhibit iNOS induction for the prevention of liver injury. In this study, we examined IL-1β-stimulated hepatocytes as a simple "in vitro liver injury model" to investigate liver protective effects of genipin. Primary cultured rat hepatocytes were treated with IL-1β in the presence or absence of genipin. The induction of NO production and iNOS, and its signaling pathway were analyzed. In IL-1β-stimulated hepatocytes, genipin inhibited the production of NO dose- and timedependently, and reduced the levels of iNOS protein and its mRNA expression. Genipin also reduced mRNA expressions of TNF-α and IL-6. Genipin inhibited two essential signaling pathways for iNOS induction, IκB degradation/NF-κB activation and type I IL-1 receptor upregulation. Transfection experiments revealed that genipin decreased the expression of iNOS mRNA through both inhibitions of the promoter activation and mRNA stabilization. Delayed administration of genipin after IL-1β addition also inhibited iNOS induction. Genipin influenced the induction of inflammatory mediators, iNOS and TNF-α, in part through the inhibition of NF-κB activation in hepatocytes. Genipin may have therapeutic potential for organ injuries including liver.

Acetaminophen toxicity in rat and mouse hepatocytes in vitro

Context: Acetaminophen (APAP) hepatotoxicity is often studied in primary cultures of hepatocytes of various species, but there are only few works comparing interspecies differences in susceptibility of hepatocytes to APAP in vitro. Objectives: The aim of our work was to compare hepatotoxicity of APAP in rat and mouse hepatocytes in primary cultures. Materials and methods: Hepatocytes isolated from male Wistar rats and C57Bl/6J mice were exposed to APAP for up to 24 h. We determined lactate dehydrogenase (LDH) activity in culture medium, activity of cellular dehydrogenases (WST-1) and activity of caspases 3 in cell lysate as markers of cell damage/death. We assessed content of intracellular reduced glutathione, production of reactive oxygen species (ROS) and malondialdehyde (MDA). Respiration of digitonin-permeabilized hepatocytes was measured by high resolution respirometry and mitochondrial membrane potential (MMP) was visualized (JC-1). Results: APAP from concentrations of 2.5 and 0.75 mmol/L induced a decrease in viability of rat (p < 0.001) and mouse (p < 0.001) hepatocytes (WST-1), respectively. In contrast to rat hepatocytes, there was no activation of caspase-3 in mouse hepatocytes after APAP treatment. Earlier damage to plasma membrane and faster depletion of reduced glutathione were detected in mouse hepatocytes. Mouse hepatocytes showed increased glutamate + malate-driven respiration in state 4 and higher susceptibility of the outer mitochondrial membrane (OMM) to APAP-induced injury. Conclusion: APAP displayed dose-dependent toxicity in hepatocytes of both species. Mouse hepatocytes in primary culture however had approximately three-fold higher susceptibility to the toxic effect of APAP when compared to rat hepatocytes.

&lt;i&gt;In vitro&lt;/i&gt; and &lt;i&gt;in vivo&lt;/i&gt; hepatoprotective activity of extracts of aerial parts of &lt;i&gt;Bidens pilosa&lt;/i&gt; L (Asteraceae)

Purpose: To investigate the protective effects of aqueous and methanol extracts of Bidens pilosa using various in vivo and in vitro models of hepatic injury. Methods: One kilogram of the aerial parts of Bidens pilosa was used to prepare 80 % methanol and aqueous extracts of the plant (500 g for each extract). The total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity of both extracts were evaluated. The hepatoprotective activity of these extracts in carbon tetrachloride (CCl 4 , 0.1 %) and D-galactosamine (700 mg/kg)-induced liver injury, respectively, was investigated in mice. Paracetamol-induced liver injury was used as in vitro reference standard. Results: TPC and TFC of methanol extract were higher than those of the aqueous extract. The combination of methanol extract and silymarin showed the highest antioxidant activity. In vivo administration of CCl 4 and D-galactosamine significantly increased the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP), but decreased the total protein, albumin and glutathione (GSH) contents of liver. Co-administration of the extracts (50 mg/kg) and silymarin (100 mg/kg) effectively countered the effects of CCl 4 and Dgalactosamine, while also exerting their antioxidant properties. Both methanol and aqueous extracts showed hepatoprotective activity in paracetamol-induced cytotoxicity in primary cultures of rat hepatocytes. Conclusion: Bidens pilosa possesses significant in vivo and in vitro hepatoprotective activity in mice and may be therapeutically useful as a protective agent in acute liver injury. Keywords: Bidens pilosa , D-galactosamine, Carbon tetrachloride, Paracetamol, Liver injury, Hepatoprotective, Antioxidant, Silymarin, Hepatocytes

Abstracts from the In Vitro Toxicology Society Annual Meeting Radisson Blu Hotel Glasgow, United Kingdom November 14–15, 2016

Abstracts from the In Vitro Toxicology Society Annual Meeting Radisson Blu Hotel Glasgow, United Kingdom November 14–15, 2016

Differential toxicities of albendazole and its two main metabolites to Balb/c 3T3, HepG2, and FaO lines and rat hepatocytes

Abstract Introduction: The cytotoxicity of anthelmintic agent, albendazole (ABZ) and its two major metabolites, sulfoxide (ABZSO) and sulfone (ABZ-SO2), on non-hepatic Balb/c 3T3 line, two hepatoma cell lines (FaO, HepG2), and isolated rat hepatocytes was investigated. Material and Methods: Cell cultures were exposed for 24, 48, and 72 h to eight concentrations of the compounds ranging from 0.05 to 100 μg/mL (ABZ) and from 0.78 to 100 μg/mL (ABZ-SO and ABZ-SO2). Three different assays were applied in which various biochemical endpoints were assessed: lysosomal activity - neutral red uptake (NRU) assay, proliferation - total protein contents (TPC) assay and lactate dehydrogenase (LDH) leakage assay. Results: The most toxic was albendazole whose EC50 values calculated from the concentration effect curves ranged from 0.2 to 0.5 μg/mL (Balb/c 3T3 ) and from 0.4 to 73.3 μg/mL (HepG2). Rat hepatoma line and isolated rat hepatocytes were less sensitive to the impact of ABZ. Toxic action expressed as EC50 was recorded after 72 h exposure only in LDH release assay at 0.8 μg/mL and 9.7 μg/mL respectively. The toxicity of metabolites was much lower. The most sensitive to ABZ-SO were fibroblasts and EC50-72h values were similar in all three assays used, i.e. NRU (14.1 μg/mL), TPC (15.8 μg/mL), and LDH (20.9 μg/mL). In the case of ABZ-SO2 the mean effective concentrations were the highest, and could be reached only in one LDH assay. These values (μg/mL) were as follows: 65.3 (FaO), 65.4 (HepG2), 75.8 (hepatocytes), and 77.4 (Balb/c 3T3). Conclusion: The differences in in vitro toxicity of albendazole depend on metabolic ability of the cellular models. Primary cultured rat hepatocytes represent a valuable tool to study the impact of biotransformation on the cytotoxicity of drugs.

The protective effect of the natural compound hesperetin against fulminant hepatitis in vivo and in vitro.

Liver diseases are mostly accompanied by inflammation and hepatocyte death. Therapeutic approaches targeting both hepatocyte injury and inflammation are not available. Natural compounds are considered as potential treatment for inflammatory liver diseases. Hesperetin, a flavonoid component of citrus fruits, has been reported to have anti-inflammatory properties. The aim of this study was to evaluate the cytoprotective and anti-inflammatory properties of hesperetin both in vitro and in models of fulminant hepatitis. Apoptotic cell death and inflammation were induced in primary cultures of rat hepatocytes by bile acids and cytokine mixture respectively. Apoptosis was quantified by caspase-3 activity and necrosis by LDH release. The concanavalin A (ConA) and D-galactosamine/LPS (D-GalN/LPS) were used as models of fulminant hepatitis. Liver injury was assessed by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, liver histology and TUNEL assay and inflammation by inducible NOS (iNOS) expression. Hesperetin blocked bile acid-induced apoptosis and cytokine-induced inflammation in rat hepatocytes. Moreover, hesperetin improved liver histology and protected against hepatocyte injury in ConA- and D-GalN/LPS-induced fulminant hepatitis, as assessed by TUNEL assay and serum AST and ALT levels. Hesperetin also reduced expression of the inflammatory marker iNOS and the expression and serum levels of TNFα and IFN-γ, the main mediators of cell toxicity in fulminant hepatitis. Hesperetin has anti-inflammatory and cytoprotective actions in models of acute liver toxicity. Hesperetin therefore has therapeutic potential for the treatment of inflammatory liver diseases accompanied by extensive hepatocyte injury, such as fulminant hepatitis.

Antioxidant properties of tea blunt ROS-dependent lipogenesis: beneficial effect on hepatic steatosis in a high fat-high sucrose diet NAFLD obese rat model

Oxidative stress could trigger lipid accumulation in liver and thus hepatic steatosis. Tea is able to prevent liver disorders, but a direct link between antioxidant capacities and prevention of steatosis has not been reported yet. We aimed to investigate such relationship in a rat model of high fat-high sucrose diet (HFS)-induced obesity and to explore more deeply the mechanisms in isolated hepatocytes. Wistar rats were divided into a control group (standard diet), an HFS group (high fat-sucrose diet) and an HFS+tea group (HFS diet with ad-libitum access to tea drink). Body weight, fat mass, glycemic parameters in blood, lipid and oxidative stress parameters in blood and liver were measured in each group after 14 weeks. Isolated hepatocytes were treated with the reactive oxygen species (ROS) inducer t-BHP in the presence or not of antioxidants (tempol or tea), and superoxide anion production and lipid accumulation were measured using specific fluorescent probes. We reported that the HFS diet highly increased hepatic lipids content, while tea consumption attenuated steatosis and improved the oxidative status (decrease in hepatic oxidative stress, increase in plasma total antioxidant capacity). The role of antioxidant properties of tea in such phenomenon was confirmed in primary cultured rat hepatocytes. Indeed, the increase of mitochondrial ROS production with t-BHP resulted in lipid accumulation in hepatocytes (positive linear regression), and antioxidants (tempol or tea) normalized both. We reported that the antioxidant properties of tea protect rats from an obesogenic HFS diet-induced hepatic steatosis by counteracting the ROS-dependent lipogenesis.

UDCA and CDCA alleviate 17α-ethinylestradiol-induced cholestasis through PKA-AMPK pathways in rats

Estrogen-induced cholestasis, known as intrahepatic cholestasis of pregnancy (ICP), is an estrogen-related liver disease that is widely recognized as female or pregnancy-specific. Our previous findings showed that the synthetic estrogen, 17α-ethinylestradiol (EE), induced cholestatic injury through ERK1/2-LKB1-AMP-activated protein kinase (AMPK) signaling pathway and its mediated suppression of farnesoid X receptor (FXR). To investigate the role played by bile acids in EE-induced cholestasis, we evaluated the effects of chenodeoxycholic acid (CDCA), ursodeoxycholic acid (UDCA) and deoxycholic acid (DCA) on sandwich cultured rat primary hepatocytes (SCRHs) and an in vivo rat model. Our results showed that, both CDCA and UDCA significantly induced time- and concentration-dependent reduction in AMPK phosphorylation in SCRHs. Despite having different effects on FXR activation, CDCA and UDCA both inhibited EE-induced AMPK activation, accompanied with the up-regulation of FXR and its downstream bile acid transporters. However, although DCA activates FXR and induces SHP, it was unable to alleviate EE-induced FXR suppression and further aggravated EE-induced cholestasis. We further demonstrated that both CDCA and UDCA, but not DCA, activated cyclic AMP dependent protein kinase (PKA) in SCRHs and the livers of male rats (8weeks old) liver. Furthermore, PKA antagonist, H89, blocked the AMPK inhibition by CDCA and UDCA, and pharmacological and genetic activation of PKA suppressed EE-induced AMPK activation and its downstream effects. Collectively, these results suggest that CDCA and UDCA protect against estrogen-induced cholestatic injury via PKA signaling pathway and up-regulation of EE-suppressed FXR, which suggests a potential therapeutic target for ICP.

MEK and ERK Kinase Inhibitors Increase Circulating Ceruloplasmin and Cause Green Serum in Rats

Inhibition of the mitogen-activated protein kinase/extracellular signal-regulated (MAPK/ERK) pathway is an attractive therapeutic approach for human cancer therapy. In the course of evaluating structurally distinct small molecule inhibitors that target mitogen-activated protein kinase kinase (MEK) and ERK kinases in this pathway, we observed an unusual, dose-related increase in the incidence of green serum in preclinical safety studies in rats. Having ruled out changes in bilirubin metabolism, we demonstrated a 2- to 3-fold increase in serum ceruloplasmin levels, likely accounting for the observed green color. This was not associated with an increase in α-2-macroglobulin, the major acute phase protein in rats, indicating that ceruloplasmin levels increased independently of an inflammatory response. Elevated serum ceruloplasmin was also not correlated with changes in total hepatic copper, adverse clinical signs, or pathology findings indicative of copper toxicity, therefore discounting copper overload as the etiology. Both ERK and MEK inhibitors led to increased ceruloplasmin secretion in rat primary hepatocyte cultures in vitro, and this increase was associated with activation of the Forkhead box, class O1 (FOXO1) transcription factor. In conclusion, increased serum ceruloplasmin induced by MEK and ERK inhibition is due to increased synthesis by hepatocytes from FOXO1 activation and results in the nonadverse development of green serum in rats.

Cyto- and genotoxic potential of water samples from polluted areas in Kosovo.

Reports on the state of the environment in Kosovo have emphasized that river and ground water quality is affected by pollution from untreated urban water as well as the waste water from the industry. One of the main contributors to this pollution is located in Obiliq (coal power plants). Prishtina-the capital city of Kosovo-is heavily influenced too. Furthermore, the pollutants combined together with those from heavy traffic are dissolved in Prishtina runoff water, which is discharged into the creek entering the river Sitnica together with urban waste water. The available data show the complex pollution with excessive quantities of nitrites, suspended materials, organic compounds, detergents, heavy metals, polychlorinated biphenyls, etc. In this study, the cytotoxic and genotoxic potential of water samples taken at these sites was tested in primary rat hepatocytes. The results obtained indicate that water samples collected in Prishtina and Obiliq had a significant cytotoxic potential in primary rat hepatocyte cultures even when diluted to 1%. The increased cytotoxicity, however, was not accompanied by an increased genotoxicity as measured by the percentage of micronucleated cells. Further investigations addressing the chemical composition of the samples and the identification of the toxicants responsible for the cytotoxic effects found will be carried out in a next step.

Glutamic Acid - Amino Acid, Neurotransmitter, and Drug - Is Responsible for Protein Synthesis Rhythm in Hepatocyte Populations in vitro and in vivo.

Primary cultures of rat hepatocytes were studied in serum-free media. Ultradian protein synthesis rhythm was used as a marker of cell synchronization in the population. Addition of glutamic acid (0.2mg/ml) to the medium of nonsynchronous sparse cultures resulted in detection of a common protein synthesis rhythm, hence in synchronization of the cells. The antagonist of glutamic acid metabotropic receptors MCPG (0.01mg/ml) added together with glutamic acid abolished the synchronization effect; in sparse cultures, no rhythm was detected. Feeding rats with glutamic acid (30mg with food) resulted in protein synthesis rhythm in sparse cultures obtained from the rats. After feeding without glutamic acid, linear kinetics of protein synthesis was revealed. Thus, glutamic acid, a component of blood as a non-neural transmitter, can synchronize the activity of hepatocytes and can form common rhythm of protein synthesis in vitro and in vivo. This effect is realized via receptors. Mechanisms of cell-cell communication are discussed on analyzing effects of non-neural functions of neurotransmitters. Glutamic acid is used clinically in humans. Hence, a previously unknown function of this drug is revealed.

Alpha-naphthylisothiocyanate impairs bile acid homeostasis through AMPK-FXR pathways in rat primary hepatocytes.

Alpha-naphthylisothiocyanate (ANIT) is widely used to induce cholestasis in basic researches. Although direct damage induced by ANIT to bile duct epithelial cells has been documented in previous studies, few works investigated ANIT-induced effects on hepatocytes. Our previous study indicated that activated AMP-activated protein kinase (AMPK) inhibited farnesoid X receptor (FXR) expression and further participated in the pathogenesis of estrogen-induced cholestasis. However, whether ANIT has effects on bile acid homeostasis in hepatocytes, and the role of AMPK-FXR pathway played in these effects remain unclear. In this study, our results showed that ANIT induced intracellular bile acid accumulation without obvious cellular toxicity in sandwich cultured rat primary hepatocytes (SCRHs), accompanied with significant decreased expression of FXR and bile acid transporters. AMPK activation via ERK1/2-LKB1 pathway was critical for ANIT-induced effects on hepatocytes. Compound C, specific AMPK inhibitor, blocked ANIT-regulated gene expression, decreased bile acid accumulation and recovered bile canalicular structure both in vitro and in vivo. Furthermore, the expression of A1 adenosine receptor (A1AR), a potential cholestatic target, was relatively low in hepatocytes compared with expression in rat whole livers. Consistent with these findings, DPCPX, a classic antagonist of A1AR, had no effect on ANIT-induced hepatocytes injury. In summary, our results indicate that AMPK-FXR signaling is critical for ANIT-induced toxic effects on hepatocytes, provide new insights into the pathogenesis of ANIT-induced cholestasis, and suggest AMPK-FXR pathway as a potential therapeutic target for cholestasis.

Pigment Epithelium Derived Factor Peptide Protects Murine Hepatocytes from Carbon Tetrachloride-Induced Injury.

Fibrogenesis is induced by repeated injury to the liver and reactive regeneration and leads eventually to liver cirrhosis. Pigment epithelium derived factor (PEDF) has been shown to prevent liver fibrosis induced by carbon tetrachloride (CCl4). A 44 amino acid domain of PEDF (44-mer) was found to have a protective effect against various insults to several cell types. In this study, we investigated the capability of synthetic 44-mer to protect against liver injury in mice and in primary cultured hepatocytes. Acute liver injury, induced by CCl4, was evident from histological changes, such as cell necrosis, inflammation and apoptosis, and a concomitant reduction of glutathione (GSH) and GSH redox enzyme activities in the liver. Intraperitoneal injection of the 44-mer into CCl4-treated mice abolished the induction of AST and ALT and markedly reduced histological signs of liver injury. The 44-mer treatment can reduce hepatic oxidative stress as evident from lower levels of lipid hydroperoxide, and higher levels of GSH. CCl4 caused a reduction of Bcl-xL, PEDF and PPARγ, which was markedly restored by the 44-mer treatment. Consequently, the 44-mer suppressed liver fibrosis induced by repeated CCl4 injury. Furthermore, our observations in primary culture of rat hepatocytes showed that PEDF and the 44-mer protected primary rat hepatocytes against apoptosis induced by serum deprivation and TGF-β1. PEDF/44-mer induced cell protective STAT3 phosphorylation. Pharmacological STAT3 inhibition prevented the antiapoptotic action of PEDF/44-mer. Among several PEDF receptor candidates that may be responsible for hepatocyte protection, we demonstrated that PNPLA2 was essential for PEDF/44-mer-mediated STAT3 phosphorylation and antiapoptotic activity by using siRNA to selectively knockdown PNPLA2. In conclusion, the PEDF 44-mer protects hepatocytes from single and repeated CCl4 injury. This protective effect may stem from strengthening the counter oxidative stress capacity and induction of hepatoprotective factors.

Transdifferentiated rat pancreatic progenitor cells (AR42J-B13/H) respond to phenobarbital in a rat hepatocyte-specific manner.

Phenobarbital (PB) is known to produce species-specific effects in the rat and mouse, being carcinogenic in certain mouse strains, but only in rats if treated after a DNA damaging event. PB treatment in the rat and mouse also produces disparate effects on cell signalling and miRNA expression profiles. These responses are induced by short term and prolonged PB exposure, respectively, with the latter treatments being difficult to examine mechanistically in primary hepatocytes due to rapid loss of the original hepatic phenotype and limited sustainability in culture. Here we explore the rat hepatocyte-like B13/H cell line as a model for hepatic response to PB exposure in both short-term and longer duration treatments. We demonstrate that PB with Egf treatment in the B13/H cells resulted in a significant increase in Erk activation, as determined by the ratio of phospho-Erk to total Erk, compared to Egf alone. We also show that an extended treatment with PB in the B13/H cells produces a miRNA response similar to that seen in the rat in vivo, via the time-dependent induction of miR-182/96. Additionally, we confirm that B13/H cells respond to Car activators in a typical rat-specific manner. These data suggest that the B13/H cells produce temporal responses to PB that are comparable to those reported in short-term primary rat hepatocyte cultures and in the longer term are similar to those in the rat in vivo. Finally, we also show that Car-associated miR-122 expression is decreased by PB treatment in B13/H cells, a PB-induced response that is common to the rat, mouse and human. We conclude that the B13/H cell system produces a qualitative response comparable to the rat, which is different to the response in the mouse, and that this model could be a useful tool for exploring the functional consequences of PB-sensitive miRNA changes and resistance to PB-mediated tumours in the rat.

Chiral enantioresolution of cathinone derivatives present in "legal highs", and enantioselectivity evaluation on cytotoxicity of 3,4-methylenedioxypyrovalerone (MDPV).

Recently, great interest has been focused on synthetic cathinones since their consumption has increased exponentially. All synthetic cathinones exist as chiral molecules; the biological and/or toxicological properties of cathinones generally differ according to the enantiomers in human body. In this study, a chiral liquid chromatography method was developed to separate and determine the enantiomeric ratio of synthetic cathinones present in “legal highs” acquired in old smart shops or over the Internet. All the synthetic cathinones were efficiently enantio-separated with α and Rs ranging from 1.24 to 3.62 and from 1.24 to 10.52, respectively, using polysaccharide-based chiral stationary phases. All synthetic cathinones, with the exception of 4-methylethcathinone (4-MEC), were present in the commercialized “legal highs” in an enantiomeric proportion of 50:50. One of the studied chiral compounds was 3,4-methylenedioxypyrovalerone (MDPV), one of the most consumed cathinone derivative worldwide. Our research group has recently reported its hepatotoxicity in the racemic form. Thus, the analytical enantioresolution of the MDPV was scaled up to multi-milligram using a semi-preparative amylose tris-3,5-dimethylphenylcarbamate column (20 cm × 7.0 mm ID, 7 µm particle size). Both enantiomers were isolated with high enantiomeric purity (enantiomeric excess > 99 %). The toxicity of S-(−)-MDPV and R-(+)-MDPV was evaluated, for the first time, using primary cultures of rat hepatocytes. It was also possible to verify that MDPV enantiomers showed hepatotoxicity in a concentration-dependent manner, but displayed no enantioselective toxicity in this cell culture model.

Hepatoprotective effects of Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase] on alcohol-damaged primary rat hepatocyte culture in vitro

We have prepared a novel nanobiotherapeutic, Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase], which not only transports both oxygen and carbon dioxide but also a therapeutic antioxidant. Our previous study in a severe sustained 90 min hemorrhagic shock rat model shows that it has a hepatoprotective effect. We investigate its hepatoprotective effect further in this present report using an alcohol-damaged primary hepatocyte culture model. Results show that it significantly reduced ethanol-induced AST release, lipid peroxidation, and ROS production in rat primary hepatocytes culture. It also significantly enhanced the viability of ethanol-treated hepatocytes. Thus, the result shows that Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase] also has some hepatoprotective effects against alcohol-induced injury in in vitro rat primary hepatocytes cell culture. This collaborate our previous observation of its hepatoprotective effect in a severe sustained 90-min hemorrhagic shock rat model.

Inducible Nitric Oxide Synthase Expression in Liver Injury: Liver Protective Effects on Primary Rat Hepatocytes.

Following injury to the liver, liver cells, including Kupffer cells and hepatocytes express inducible nitric oxide synthase (iNOS), followed by the production of excess levels of nitric oxide (NO). NO produced by iNOS has been found to contribute to liver injury. Treatment of primary cultures of rat hepatocytes with the proinflammatory cytokine interleukin (IL)-1β stimulated iNOS expression and NO production. Experiments with this in vitro hepatocyte model of liver injury and with in vivo animal models of liver injury have demonstrated that drugs showing a liver-protective effect in vivo also inhibited the induction of iNOS expression and NO production both in vivo and in vitro. Thus, in this in vitro hepatocyte model, the prevention of iNOS expression and NO production are considered indicators of liver protection. This review describes a simple in vitro liver injury model, consisting of IL-1β-stimulated cultured hepatocytes, and methods used to analyze the mechanisms of action of drugs that inhibit iNOS expression. This in vitro hepatocyte model may be used to assess the liver-protective effects of pharmaceutical agents, herbal medicines, and certain types of foods.

Assessment of mitochondrial dysfunction-related, drug-induced hepatotoxicity in primary rat hepatocytes

Evidence that mitochondrial dysfunction plays a central role in drug-induced liver injury is rapidly accumulating. In contrast to physiological conditions, in which almost all adenosine triphosphate (ATP) in hepatocytes is generated in mitochondria via aerobic respiration, the high glucose content and limited oxygen supply of conventional culture systems force primary hepatocytes to generate most ATP via cytosolic glycolysis. Thus, such anaerobically poised cells are resistant to xenobiotics that impair mitochondrial function, and are not suitable to identify drugs with mitochondrial liabilities. In this study, primary rat hepatocytes were cultured in galactose-based medium, instead of the conventional glucose-based medium, and in hyperoxia to improve the reliance of energy generation on aerobic respiration. Activation of mitochondria was verified by diminished cellular lactate release and increased oxygen consumption. These conditions improved sensitivity to the mitochondrial complex I inhibitor rotenone. Since oxidative stress is also a general cause of mitochondrial impairment, cells were exposed to test compounds in the presence of transferrin to increase the generation of reactive oxygen species via increased uptake of iron. Finally, 14 compounds with reported mitochondrial liabilities were tested to validate this new drug-induced mitochondrial toxicity assay. Overall, the culture of primary rat hepatocytes in galactose, hyperoxia and transferrin is a useful model for the identification of mitochondrial dysfunction-related drug-induced hepatotoxicity.

Dietary Carbohydrates but Not Proteins Are the Main Nutritional Determinant of FGF21 Production in Mice

Fibroblast growth factor 21 (FGF21) is a polypeptide secreted by the liver and involved in various metabolic processes, such as ketogenesis, lipid oxidation, thermogenesis and white adipose tissue browning. Nutritional mechanisms controlling its secretion are poorly understood. The aim of the present study was to investigate the influence of changes in the protein to carbohydrate ratio in the diet on FGF21 synthesis and secretion by the liver and the subsequent impact on energy metabolic pathways.25 male C57BL/6 mice aged 7 weeks were divided into 3 groups (n = 8–9/group) and fed during three weeks with a low‐protein/high‐carb diet (LPHC), a normo‐protein/normo‐carb diet (NPNC) or a high‐protein/low‐carb diet (HPLC). Food intake and body weight were measured throughout the experiment. At the end of the first week, the thermogenic response to feeding (TEF) was followed during 6 hours after ingestion of a 1g‐calibrated meal of their test‐diet given after an overnight fast. At the end of the experiment, the same test‐meal procedure was repeated and mice were killed four hours latr, for measurement of gene expression in liver, brown and epidydymal adipose tissues. In parallel with this in vivo experiment, primary cultures of rat hepatocytes were conducted to measure the specific effects of amino acids, leucine and glucose in the presence or absence of insulin and/or glucagon on the synthesis of FGF21.Plasma FGF21 measured 4 hours after ingestion of the test‐meals was positively correlated with the carbohydrate content of the diet. Consumption of LPHC and HPLC diets increased TEF but with different kinetics compared to the NPNC diet. In LPHC‐fed mice expression of UCP2 in the epididymal adipose was increased while in HPLC‐fed mice, ketogenesis, measured before ingestion of the test‐meal (fasted state), was increased. In primary cultured of hepatocytes high glucose concentrations in the presence of insulin increased FGF21 synthesis. Amino acid or leucine alone had no effect on FGF21 synthesis, glucagon decreased FGF21 synthesis and this last effect was antagonized by insulin.These results indicate that FGF21 synthesis is stimulated by carbohydrate and glucose but not protein and amino acid. Therefore, the increased TEF observed in response to ingestion of the LPHC diet was probably mediated by FGF21 whereas the influence of HPLC diet on fasting ketogenesis and TEF did not involve FGF21.

0149 : Antioxidant molecules of tea (Camellia sinensis) decrease hepatic lipogenesis and steatosis in a high fat-sucrose diet NAFLD rat model

Recent studies suggested that oxidative stress could trigger lipid accumulation in liver and thus subsequent development of hepatic steatosis which contributes to alter blood lipid level leading to increase cardiovascular risk factors. Tea has been described to prevent liver disorders and decrease cardiovascular risk. However, whether tea decreases oxidative stress and thus prevents hepatic steatosis has never been investigated. Therefore we aimed to investigate the effects of tea on oxidative stress and lipid accumulation in a rat model of high fatsucrose diet (HFS) induced metabolic syndrome (fed during 14 weeks) and in isolated rat hepatocytes.Wistar rats were randomly divided into three groups: Ctrl, HFS and HFS+Tea rats which had free access to tea infusion drink instead of water (n=15). Lipid profile of the liver, lipogenesis gene expression and oxidative stress were measured in each group of rat. Isolated hepatocytes were treated with the ROS inducer t-BHP in the presence or not of antioxidant tempol or tea. Then, superoxide anion production and lipid accumulation were measured using specific fluorescent probes. We reported that HFS diet-induced elevated hepatic lipid content by enhancing lipogenic gene expression in HFS rats compared to Ctrl ones. HFS diet-induced hepatic steatosis was attenuated by tea which was mainly associated with decrease hepatic oxidative stress and increased plasma total antioxidant capacity. The key role of antioxidant properties of tea in such phenomenon was confirmed in primary culture of rat hepatocytes. Indeed, we reported that increased ROS production with t-BHP resulted in lipid accumulation in hepatocytes, which was normalized by both tempol and tea. To conclude, we clearly reported that the antioxidant properties of tea protect rats from HFS diet-induced hepatic steatosis via its anti-lipogenesis effects. The consequence of such nutritional strategy on cardiovascular risk factor would constitute the next step of this work. The author declares a conflict of interest : Les travaux ont été réalisés dans le cadre d’une bourse CIFRE Thés de la Pagode-Université de Toulon