Cell-based models to predict human hepatotoxicity of drugs / Modelos celulares para predecir la hepatotoxicidad humana de fármacos

Drug-induced liver injury is a significant leading cause of liver disease and post-market attrition of approved drugs. Several hepatic cell-based models have been used for early safety risk assessment during drug development. Their capacity to predict hepatotoxicity depends on cells' functional performance. Cultured hepatocytes have contributed to increase knowledge of the metabolic patterns and mechanisms involved in drug toxicity. A major limitation of monolayer hepatocytes is that they undergo rapid loss of hepatic functionality over time, particularly drug metabolising capability. The sandwich culture model promotes polarised cell surface and stabilises hepatocyte functionality, particularly transport systems, better than monolayer cultures. As 3D spatial organisation and complex heterotypic cell interactions are essential for the functional homeostasis of the liver, hepatocyte models (3D cultures, co-cultures with NPCs and microfluidic systems) that mimic cell-cell, cell- matrix interactions and nutrient flow characteristic of the liver microenvironment have been shown to improve the metabolic competency of hepatocytes and have been proposed for better in vitro predictions of drug hepatotoxicity. In addition to hepatocytes, other cell-based models have been proposed for hepatotoxicity studies. Hepatoma cell lines are metabolically poor compared to hepatocytes, but offer key advantages, such as unlimited life span, reproducibility, high availability and easy handling, which make them useful for screening purposes. Alternatively, hepatic cell lines engineered for stable or transient expression of key drug-metabolising enzymes have also been used. Finally, stem cell-derived hepatocytes are emerging in vitro systems that would provide a stable source of hepatocytes from individuals with highly valuable particular polymorphic characteristics for preclinical drug metabolism and toxicity prediction of new drugs (AU)

La lesión del hígado por fármacos es una de las causas principales de enfermedad hepática y de retirada del mercado de fármacos autorizados. Son varios los modelos de células hepáticas utilizados durante el desarrollo de fármacos para la valoración temprana de su seguridad. Los estudios basados en hepatocitos cultivados han contribuido al conocimiento de los mecanismos implicados en la toxicidad por fármacos. Una limitación fundamental de los hepatocitos cultivados en monocapa es la pérdida temprana de funciones hepáticas, en particular la capacidad para metabolizar fármacos. El cultivo tipo sándwich mantiene la polaridad de los hepatocitos y los sistemas de transporte y estabiliza su funcionalidad mejor que el cultivo en monocapa. Puesto que la organización espacial 3D y las interacciones celulares heterotípicas son esenciales para la homeostasis funcional del hígado, los hepatocitos cultivados en sistemas que reproducen las interacciones entre células, célula-biomatriz y el flujo de nutrientes característicos del microambiente hepático (cultivos 3D, co-cultivos con células no parenquimales, sistemas microfluidicos) presentan mayor capacidad metabólica y han sido propuestos para mejorar la predicción in vitro de la hepatotoxicidad. Otras células hepáticas han sido propuestas como alternativa a los hepatocitos para evaluar la hepatotoxicidad. Si bien las líneas celulares de hepatoma tienen menor capacidad metabólica que los hepatocitos, presentan ventajas clave para el cribado de fármacos (vida ilimitada, reproducibilidad, gran disponibilidad, fácil manejo). También se utilizan células manipuladas para la expresión estable o transitoria de enzimas de biotransformación. Por último, los hepatocitos procedentes de células madre son sistemas in vitro emergentes que proporcionarían una fuente estable de hepatocitos, a partir de individuos con características polimórficas especiales, sumamente valiosa para la predicción preclínica de la toxicidad de nuevos fármacos (AU)

[Liver cell therapy in the treatment of inborn errors of metabolism in children]. / Terapia celular hepática en el tratamiento de las metabolopatías congénitas en niños.

Liver transplantation has been remarkably effective in the treatment of patients with end-stage liver disease. However, disparity between solid-organ supply and increased demand is the main limitation, resulting in longer waiting times and an increase in the mortality of transplant recipients. This situation creates the need to seek alternatives to orthotopic liver transplantation. Hepatocyte transplantation or liver cell transplantation has been proposed as the best method to support patients, a bridge to restore liver function or liver transplant. The procedure consists in transplanting individual cells in a recipient organ in enough quantity to survive and restore the function. The capacity of hepatic regeneration constitutes the biological basis of hepatocyte transplantation. Liver cell transplantation is carried out by means of the isolation of hepatocytes from donor liver rejected for orthotopic transplantation, to prepare a cell suspension for infusion, cryopreservation and, finally, hepatocytes are implanted into the recipient. This may be an optional therapeutic procedure in some patients with inborn errors of metabolism, fulminant hepatic failure, and acute and chronic liver failure, as a bridge to orthotopic liver transplantation. The first hepatocyte transplantation in Spain was performed in the Cell Therapy Unit of the Hospital La Fe of Valencia, creating a new research line in the transplant program.

Human hepatocyte transplantation in patients with hepatic failure awaiting a graft.

BACKGROUND: Hepatocyte transplantation (HT) has the potential to become a promising treatment to temporarily support liver function in patients with liver failure. METHODS: Two patients, who had already received a liver transplant (LT) in the past, with an end-stage liver disease due to recurrent hepatitis C virus cirrhosis, suffering acute-on-chronic liver failure while on the waiting list for an LT, received HT as a bridge to whole-organ retransplantation. After HT and during intensive care unit admission, blood tests and ammonia levels were determined every 12 and 24 h, respectively, before and after each hepatocyte infusion. RESULTS: The present study describes monitoring of analytical and clinical parameters and improvement of liver function following HT. In both patients, we managed to lower the blood ammonia levels and clinically improve the degree of hepatic encephalopathy, thus serving as a bridge to liver retransplantation in 1 patient. CONCLUSIONS: We believe that this therapy may be an alternative treatment in patients with chronic liver disease who suffer episodes of acute decompensation as a bridge to conventional LT.

Comparative analysis of eight cytotoxicity assays evaluated within the ACuteTox Project.

A comparative analysis of eight cytotoxicity assays [the 3T3 and normal human keratinocytes Neutral Red Uptake (NRU) assay, the primary rat hepatocytes, human HepG2 and 3T3 MTT assay, and the human A.704, SH-SY5Y and HepG2 cells propidium iodide (PI) assay] included in several work packages of the EU Integrated Project ACuteTox, has been carried out. The aim was to evaluate whether cells originating from liver, kidney and brain provided different in vitro acute toxicity results, and the influence of primary liver cells versus cell lines originated from the same tissue. Spearman rank correlation analysis and Hierarchical Cluster Analysis were performed based on the IC50 (50% inhibitory concentrations for the endpoint measured) values generated for 57 chemicals. A relatively large number of neurotoxicants and hepatotoxicants were included which allowed to examine the impact of chemicals with specific tissue toxicity on the results. Our analyses confirmed the similarity between the NRU assays and between the two hepatic cell systems related MTT assays. The type of assay appears to have the greatest influence upon the clustering result regardless of the origin of the cells used. The information provided by the NRU and MTT assays differed from that provided by the PI assay. This approach did not allow to show tissue specific toxicity but it does reveal the effectiveness of the clustering methodology for choosing assays for a testing program for predicting e.g. acute oral toxicity in humans.

Evaluation of genotoxicity and DNA protective effects of mangiferin, a glucosylxanthone isolated from Mangifera indica L. stem bark extract.

Mangiferin is a glucosylxantone isolated from Mangifera indica L. stem bark. Several studies have shown its pharmacological properties which make it a promising candidate for putative therapeutic use. This study was focused to investigate the in vitro genotoxic effects of mangiferin in the Ames test, SOS Chromotest and Comet assay. The genotoxic effects in bone marrow erythrocytes from NMRI mice orally treated with mangiferin (2000 mg/kg) were also evaluated. Additionally, its potential antimutagenic activity against several mutagens in the Ames test and its effects on CYP1A1 activity were assessed. Mangiferin (50-5000 µg/plate) did not increased the frequency of reverse mutations in the Ames test, nor induced primary DNA damage (5-1000 µg/mL) to Escherichia coli PQ37 cells under the SOS Chromotest. It was observed neither single strand breaks nor alkali-labile sites in blood peripheral lymphocytes or hepatocytes after 1h exposition to 10-500 µg/mL of mangiferin under the Comet assay. Furthermore, micronucleus studies showed mangiferin neither induced cytotoxic activity nor increased the frequency of micronucleated/binucleated cells in mice bone marrow. In short, mangiferin did not induce cytotoxic or genotoxic effects but it protect against DNA damage which would be associated with its antioxidant properties and its capacity to inhibit CYP enzymes.

In vitro evaluation of potential hepatotoxicity induced by drugs.

The liver is the most important target for toxicity caused by drugs. This vulnerability is a consequence of the functional features of the liver and their role in the metabolic elimination of most drugs. Therefore, evaluation of potential hepatotoxicity represents a critical step in the development of new drugs. The liver is very active in metabolising foreign compounds and, although biotransformation reactions generally parallel detoxification processes, the formation of reactive metabolites is relatively frequent. Thus, drug-induced hepatotoxicity can be due to the administered compound itself or to metabolites formed by hepatic metabolism. The most important systems to study hepatotoxicity and metabolic activity in vitro are liver slices, isolated liver cells in suspensions or in primary cultures including co-culture methods and special 3D techniques, various subcellular fractions and hepatic cell lines. These models can be used for cytotoxicity and genotoxicity screening, and also to identify the mechanisms involved in drug-induced hepatotoxicity. Assessment of current cytotoxicity and hepatic-specific biochemical effects are limited by the inability to measure a wide spectrum of potential mechanistic changes involved in the drug-induced toxic injury. A convenient selection of end-points allows a multiparametric evaluation of drug toxicity. In this regard, omic (cytomic, metabonomic, proteomic and toxicogemic) approaches help defining patterns of hepatotoxicity for early identification of potential adverse effects of the drug to the liver. The development of robust in vitro-based multiparametric screening assays covering a wider spectrum of key effects will heighten the predictive capacity for human hepatotoxicity, and accelerate the drug development process.

Influence of peritoneal fluid on the expression of angiogenic and proteolytic factors in cultures of endometrial cells from women with endometriosis.

BACKGROUND: Endometriosis, defined as the presence of endometrium outside the uterus, is one of the most frequent benign gynaecological diseases. It has been suggested that both endometrial and peritoneal factors, related to angiogenesis and proteolysis, can be implicated in this disease. The aim of this study was to evaluate the influence of peritoneal fluid on the expression of angiogenic and proteolytic factors in cultures of endometrial cells from women with and without endometriosis. METHODS: Endometrial cells were isolated, cultured and treated with endometriotic or normal peritoneal fluid. Vascular endothelial growth factor-A (VEGF-A), urokinase plasminogen activator (uPA), matrix metalloproteinase-3 (MMP-3) and their inhibitors including thrombospondin-1, plasminogen activator inhibitor-1 and MMP inhibitor type 1 (TIMP-1) mRNA levels were evaluated by quantitative RT-PCR, and protein levels were quantified by ELISA. RESULTS: Peritoneal fluid from women with endometriosis induced an increase in VEGF-A and uPA protein and VEGF-A mRNA and uPA mRNA levels in endometrial cell culture from women with (P < 0.01) and without endometriosis (P < 0.05). The highest levels of VEGF-A and uPA were observed in endometrial cell cultures from patients with endometriosis and treated with peritoneal fluid from women with endometriosis. CONCLUSIONS: Peritoneal fluid from women with endometriosis induced more VEGF and uPA expression in endometrial cell culture from women with endometriosis than did normal peritoneal fluid. Endometrial-peritoneal interactions increased angiogenic and proteolytic factors in endometrial cells, which could contribute to the development of endometriotic lesions.

Functional characterization of hepatocytes for cell transplantation: customized cell preparation for each receptor.

The first indication of hepatocyte transplantation is inborn liver-based metabolic disorders. Among these, urea cycle disorders leading to the impairment to detoxify ammonia and Crigler-Najjar Syndrome type I, a deficiency in the hepatic UDP-glucuronosyltransferase 1A1 present the highest incidence. Metabolically qualified human hepatocytes are required for clinical infusion. We proposed fast and sensitive procedures to determine their suitability for transplantation. For this purpose, viability, attachment efficiency, and metabolic functionality (ureogenic capability, cytochrome P450, and phase II activities) are assayed prior to clinical cell infusion to determine the quality of hepatocytes. Moreover, the evaluation of urea synthesis from ammonia and UDP-glucuronosyltransferase 1A1 activity, a newly developed assay using beta-estradiol as substrate, allows the possibility of customizing cell preparation for receptors with urea cycle disorders or Crigler-Najjar Syndrome type I. Sources of human liver and factors derived from the procurement of the liver sample (warm and cold ischemia) have also been investigated. The results show that grafts with a cold ischemia time exceeding 15 h and steatosis should not be accepted for hepatocyte transplantation. Finally, livers from non-heart-beating donors are apparently a potential suitable source of hepatocytes, which could enlarge the liver donor pool.

Sequential hepatogenic transdifferentiation of adipose tissue-derived stem cells: relevance of different extracellular signaling molecules, transcription factors involved, and expression of new key marker genes.

Adipose tissue contains a mesenchymal stem cell (MSC) population known as adipose-derived stem cells (ASCs) capable of differentiating into different cell types. Our aim was to induce hepatic transdifferentiation of ASCs by sequential exposure to several combinations of cytokines, growth factors, and hormones. The most efficient hepatogenic protocol includes fibroblastic growth factors (FGF) 2 and 4 and epidermal growth factor (EGF) (step 1), hepatocyte growth factor (HGF), FGF2, FGF4, and nicotinamide (Nic) (step 2), and oncostatin M (OSM), dexamethasone (Dex), and insulin-tranferrin-selenium (step 3). This protocol activated transcription factors [GATA6, Hex, CCAAT/enhancer binding protein alpha and beta (CEBPalpha and beta), peroxisome proliferator-activated receptor-gamma, coactivator 1 alpha (PGC1alpha), and hepatocyte nuclear factor 4 alpha (HNF4alpha)], which promoted a characteristic hepatic phenotype, as assessed by new informative markers for the step-by-step hepatic transdifferentiation of hMSC [early markers: albumin (ALB), alpha-2-macroglobuline (alpha2M), complement protein C3 (C3), and selenoprotein P1 (SEPP1); late markers: cytochrome P450 3A4 (CYP3A4), apolipoprotein E (APOE), acyl-CoA synthetase long-chain family member 1 (ACSL1), and angiotensin II receptor, type 1 (AGTR1)]. The loss of adipose adult stem cell phenotype was detected by losing expression of Thy1 and inhibitor of DNA binding 3 (Id3). The reexpression of phosphoenolpyruvate corboxykinase (PEPCK), apolipoprotein C3 (APOCIII), aldolase B (ALDOB), and cytochrome P450 1A2 (CYP1A2) was achieved by transduction with a recombinant adenovirus for HNF4alpha and finally hepatic functionality was also assessed by analyzing specific biochemical markers. We conclude that ASCs could represent an alternative tool in clinical therapy for liver dysfunction and regenerative medicine.

Potential hepatoprotective effects of new Cuban natural products in rat hepatocytes culture.

The protective effects of five Cuban natural products (Mangifera indica L. (MSBE), Erythroxylum minutifolium, Erythroxylum confusum, Thalassia testudinum and Dictyota pinnatifida extracts and mangiferin) on the oxidative damage induced by model toxicants in rat hepatocyte cultures were studied. Cells were pre-incubated with the natural products (5-200 microg/mL) for 24 h. Then hepatotoxins (tert-butyl hydroperoxide, ethanol, carbon tetrachloride and lipopolysaccharide) were individually added and post-incubated for another 24 h. After treatments, cell viability was determined using the MTT assay. Mangiferin and MSBE exhibited the highest cytoprotective potential (EC50 between 50 and 125 microg/mL), followed by T. testudinum and Erythroxylum extracts, whereas no significant protective effects was produced by Dictyota extract treatment. Antioxidant properties of the natural products against lipid peroxidation and GSH depletion induced by tert-butyl hydroperoxide were then investigated. The results show that at 36 h pre-treatment of cells with mangiferin or MSBE, concentrations of T. testudinum and Erythroxylum extracts ranging from 25 to 100 microg/mL significantly inhibited lipid peroxidation induced by tert-butyl hydroperoxide (100 and 250 microM) and increased the GSH levels reduced by the toxicant. D. pinnatifida inhibited lipid peroxidation, but did not preserve GSH levels. In conclusion, MSBE, E. minutifolium, E. confusum and T. testudinum extracts and mangiferin showed hepatoprotective activity against induced damage in all the experimental series, where mangiferin and the extracts of MSBE and T. testudinum were the best candidates to inhibit "in vitro" damage to rat hepatocytes. This hepatoprotective effect found could be associated with the antioxidant properties observed for the products.

Interactions of polyphenols with the P450 system: possible implications on human therapeutics.

Polyphenols are a family of natural compounds with many biological properties. This review focuses on their potential interaction on the cytochrome P450 system. Effects of phenolic acids, anthocyanins, stilbenes, catechins and other flavonoids on the drug metabolising function are revised. Their daily intake and presence in herbal medicines justify the study of potential drug-interaction to prevent undesirable clinical consequences.

Cell lines: a tool for in vitro drug metabolism studies.

Primary cultured hepatocytes are a valuable in vitro model for drug metabolism studies. However, their widespread use is greatly hindered by the scarcity of suitable human liver samples. Moreover, the well-known in vitro phenotypic instability of hepatocytes, the irregular availability of fresh human liver for cell harvesting purposes, and the high batch-to-batch functional variability of hepatocyte preparations obtained from different human liver donors, seriously complicate their use in routine testing. To overcome these limitations, different cell line models have been proposed for drug metabolism screening. Human liver-derived cell lines would be ideal models for this purpose given their availability, unlimited life-span, stable phenotype, and the fact that they are easy to handle. However, the human hepatoma cells currently used (i.e. HepG2, Mz-Hep-1) show negligible levels of drug-metabolizing and do not constitute a real alternative to primary hepatocytes. Different strategies have been proposed to generate metabolically competent immortalized hepatocytes (transformation of human hepatocytes with plasmids encoding immortalizing genes, hepatocyte-like cells derived from stem cells, cell lines generated from transgenic animals, hepatocyte/hepatoma hydrid cells). Moreover, recombinant models heterologously expressing P450 enzymes in different host cells have been developed and successfully used in drug metabolism testing. In addition, new strategies have recently been explored to upregulate the expression of drug-metabolizing enzymes in cell lines of a human origin (i.e. transfection with expression vectors encoding key hepatic transcription factors). Among metabolic-based drug-drug interactions, P450 inhibition seems to be the most important. A major application of recombinant models expressing a single P450 is the screening of potential enzyme inhibitors. Therefore, pharmaceutical companies increasingly make use of cell lines to speed up the selection of new drugs with favourable pharmacokinetic and metabolic properties.

Strategies to in vitro assessment of major human CYP enzyme activities by using liquid chromatography tandem mass spectrometry.

At the early stage of drug discovery, thousands of new chemical entities (NCEs) may be screened before a single candidate can be identified for development. Determining the role of CYP enzymes in the metabolism of a compound and evaluating the effect of NCEs on human CYP activities are key issues in pharmaceutical development as they may explain inter-subject variability, drug-drug interactions, non-linear pharmacokinetics and toxic effects. Reliable methods for determining enzyme activities are needed to characterize an individual CYP enzyme and to obtain a tool for the evaluation of its role in drug metabolism in humans. Different liquid chromatography tandem mass spectrometry methodologies have been developed for the fast and routine analysis of major in vivo and in vitro CYPs enzyme activities. The high sensitivity and selectivity of mass spectrometry allow traditional assays to be minimized, thus saving time, efforts and money. Therefore this technology has become the method of choice for the fast assessment of CYP enzyme activities in early drug discovery development. Our intention herein is to review the most recent approaches that have been developed to quickly assess CYPs activities using in vitro models and liquid chromatography coupled with mass spectrometry, as well as their application in early drug discovery.

Modulation of P450 enzymes by Cuban natural products rich in polyphenolic compounds in rat hepatocytes.

This paper reports cytotoxic effects and changes in the P450 system after exposing rat hepatocytes to four polyphenol-rich products widely used in Cuban traditional medicine (Mangifera indica L. (MSBE), Thalassia testudinum (Tt), Erythroxylum minutifolium and confusum extracts). Effects of mangiferin, the main polyphenol in MSBE, were also evaluated. Cytotoxicity was assayed by the MTT test after exposure of cells to the products (50-1000 microg/mL) for 24 or 72 h. The results showed that 500 microg/mL MSBE was moderately cytotoxic after 72 h, while mangiferin was not. Marked reductions in cell viability were produced by Erythroxylum extracts at concentrations > or = 200 microg/mL, whereas only moderate effects were induced by 1000 microg/mL Tt. Seven specific P450 activities were evaluated after 48 h exposure of cells to the products. MSBE reduced phenacetin O-deethylation (POD; CYP1A2) activity in a concentration-dependent manner (IC(50)=190 microg/mL). No decreases were observed in other activities. In contrast, mangiferin produced reductions in five P450 activities: IC(50) values of 132, 194, >200, 151 and 137 microg/ml for POD (CYP1A2), midazolam 1'-hydroxylation (M1OH; CYP3A1), diclofenac 4'-hydroxylation (D4OH; CYP2C6), S-mephenytoin 4'-hydroxylation (SM4OH), and chlorzoxazone 6-hydroxyaltion (C6OH; CYP2E1), respectively. E. minutifolium, E. confusum and Tt extracts produced small reductions in SM4OH and C6OH activities, but no significant changes were noted in the other P450 activities. On the other hand, all the products increased the benzyloxyresorufin O-debenzylation (BROD; CYP2B1) activity, with MSBE, mangiferin or E. minutifolium showing the highest effects (about 2-fold over control). Our results showed in vitro effects of these natural products on P450 systems, possibly leading to potential metabolic-based interactions.

Effects of Mangifera indica L. aqueous extract (Vimang) on primary culture of rat hepatocytes.

Vimang is an aqueous extract from stem bark of Mangifera indica L. (Mango) with pharmacological properties. It is a mixture of polyphenols (as main components), terpenoids, steroids, fatty acids and microelements. In the present work we studied the cytotoxic effects of Vimang on rat hepatocytes, possible interactions of the extract with drug-metabolizing enzymes and its effects on GSH levels and lipid peroxidation. No cytotoxic effects were observed after 24 h exposure to Vimang of up to 1000 microg/mL, while a moderate cytotoxicity was observed after 48 and 72 h of exposure at higher concentrations (500 and 1000 microg/mL). The effect of the extract (50-400 microg/mL) on several P450 isozymes was evaluated. Exposure of hepatocytes to Vimang at concentrations of up to 100 microg/mL produced a significant reduction (60%) in 7-methoxyresorufin-O-demethylase (MROD; CYP1A2) activity, an increase (50%) in 7-penthoxyresorufin-O-depentylase (PROD; CYP2B1) activity, while no significant effect was observed with other isozymes. To our knowledge, this is the first report regarding the modulation of the activity of the P450 system by an extract of Mangifera indica L. The antioxidant properties of Vimang were also evaluated in t-butyl-hydroperoxide-treated hepatocytes. A 36-h pre-treatment of cells with Vimang (25-200 microg/mL) strongly inhibited the decrease of GSH levels and lipid peroxidation induced by t-butyl-hydroperoxide dose- and time-dependently.

Determination of major human cytochrome P450s activities in 96-well plates using liquid chromatography tandem mass spectrometry.

At the early stage of drug discovery, thousands of new chemical entities (NCEs) may be screened before a single candidate can be identified for development. Evaluation of the effect of NCEs on human CYP450 enzyme activities is a key issue in pharmaceutical development as it may explain inter-subject variability, drug-drug interactions, non-linear pharmacokinetics and toxic effects. A liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method has been developed for the fast and routine analysis of major human CYP450s enzyme activities (CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4) in primary hepatocyte cell cultures. The high sensitivity and selectivity of mass spectrometry has allowed traditional assays to be minimized, thus enabling the use of 96-well plate format which markedly reduced the number of hepatocytes needed for each cytochrome CYP450 activity measurement, a fact that is particularly critical concerning human hepatocytes.

Ethanol affects calmodulin and the calmodulin-binding proteins neuronal nitric oxide synthase and alphaII-spectrin (alpha-fodrin) in the nucleus of growing and differentiated rat astrocytes in primary culture.

The distribution of calmodulin (CaM) and the CaM-binding proteins neuronal nitric oxide synthase (nNOS) and alphaII-spectrin (alpha-fodrin) in the nucleus of growing and differentiated astrocytes was analysed using immunogold electronmicroscopy. We also analysed the effect of moderate ethanol exposure on these proteins. For this, female Wistar rat were fed with an alcoholic liquid diet and exposed to males after several weeks. Pregnant rats were fed with this diet and, after birth, the foetuses brains were used to establish primary cultures of astrocytes. Astrocytes from control and ethanol-exposed rats foetuses were cultured in the absence or presence of ethanol (30 mM) for 7 days (growing cells) and 21 days (differentiated astrocytes). Our results indicate that all the proteins studied appeared mainly on the condensed chromatin of both control- and alcohol-exposed cells and that there are significant variations in the amount of these proteins between quiescent and dividing astrocytes. Altogether, we have not found a co-localisation between CaM and the CaM-binding proteins.

Human mesenchymal stem cells from adipose tissue: Differentiation into hepatic lineage.

Adipose tissue represents an accessible source of mesenchymal stem cells (ADSCs), with similar characteristics to bone marrow-derived stem cells. The aim of this work was to investigate the transdifferentiation of ADSCs into hepatic lineage cells in vitro. ADSCs were obtained from human adipose tissue from lipectomy. Cells were grown in medium containing 15% AB human serum. Cultures were serum deprived for two days and exposed to a two-step protocol with two different media using growth factors and cytokines. Hepatic differentiation was assessed by RT-PCR of liver-marker genes. ADSCs exhibited a fibroblastic morphology that changed to a cuboidal shape when cells differentiated. Expression of liver genes increased when using one of the two studied media consisting of DMEM supplemented with HGF, bFGF and nicotinamide for 14 days. The results indicate that, under certain specific inducing conditions, ADSCs can be induced to differentiate into hepatic lineage in vitro. Adipose tissue may be an ideal source of high amounts of autologous stem cells.

Effects of steatosis on drug-metabolizing capability of primary human hepatocytes.

The suitability of liver grafts discarded for transplantation because of macrosteatosis for preparing human hepatocyte cultures for in vitro drug metabolism studies has been examined. Lower cell viability and yield of isolation procedure were obtained from fatty livers (>40% steatosis) with respect to normal tissue. Significant reductions in 7-ethoxycoumarin O-deethylation (ECOD) and testosterone oxidations were found in hepatocytes prepared from steatotic livers. The potential impact of lipid accumulation on P450 enzymes was studied in vitro by incubation of cultured hepatocytes with long chain free fatty acids (FFA). Treatment of cells with 0.25-3mM FFA induced dose-dependent accumulation of lipids in the cytosol. Decreased ECOD and testosterone oxidation were found after 14h of exposure to 1mM or 2mM FFA (about 60-70% and 30-60% of control, respectively). The effects of fat-overloading on individual P450s were analyzed both at activity and mRNA level. CYP1A2, CYP2C9, CYP2E1 and CYP3A4 activities were reduced after hepatocyte incubation with 1mM (to 45-65% of control) or 2mM (to 20-50%) FFA for 14h. Reductions in P450 transcripts were also found in hepatocytes treated with 1mM FFA. Our findings showed a general down-regulation of P450s involved in drug metabolism in fat-overloaded hepatocytes. The results suggest that, despite their reduced P450 function, human hepatocytes obtained from donors with steatosis are metabolically competent and could be used for drug metabolism studies.

In vitro ADME medium/high-throughput screening in drug preclinical development.

The study of the ADME features of the huge number of new chemical entities (NCEs) produced mainly by combinatorial chemistry has become a bottleneck in the drug development process. In response the pharmaceutical industry is involved in the development of new medium/high-throughput screening capabilities. The aim of this paper is to review some of the available in vitro ADME systems adapted to screening requirements together with the technological approaches which can be linked to medium/high-throughput molecular screening.