Use of a quantitative real-time reverse transcription-polymerase chain reaction method to study the induction of CYP1A, CYP2B and CYP4A forms in precision-cut rat liver slices

Metabonomics and pharmacodynamics studies of Gentiana radix and wine-processed Gentiana radix in damp-heat jaundice syndrome rats

ETHNOPHARMACOLOGICAL RELEVANCE

Gentiana radix (GR) and wine-processed Gentiana radix (WGR) have been commonly used in folk medicine for the treatment of bile or liver disorders, including jaundice, hepatitis, swelling and inflammation for thousands of years. However, the therapeutic effects of gentian root (GR) and wine-made gentian root (WGR) treatment on damp-heat jaundice syndrome (DHJS) have not been studied in animal experiments.

AIM OF THE STUDY

This study aimed to investigate the protective effects and mechanisms of GR and WGR on DHJS in rats.

MATERIALS AND METHODS

In a high-fat and high-sugar diet in a humidified hot environment, hepatic injury induced by giving alpha-naphthalene isothiocyanate (ANIT) in rats were used as a DHJS model. Histological analysis, enzyme-linked immunosorbent assay (ELISA), PCR analysis, and metabolomics were used to elucidate the mechanism of GR and WGR for DHJS.

RESULTS

The results indicated that GR and WGR affected DHJS by inhibiting the release of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), direct bilirubin (D-BIL), total bilirubin (TBIL), total bile acid (TBA), malondialdehyde (MDA), glutathione S-transferase (GST) (P < 0.05). In addition, they significantly reduced the gene expression levels of Na+/taurocholate cotransporting polypeptide (NTCP), bile salt export pump (BESP), multidrug resistance-associated protein 2 (MRP2) and multidrug resistance-associated protein 3 (MRP3) (P < 0.05). The WGR group improved the above function indicators better than the GR group. GR and WGR could restore 11 potential biomarkers in rats with DHJS tended to return to normal levels, these biomarkers were involved in arachidonic acid metabolism, steroid hormone biosynthesis, biosynthesis of unsaturated fatty acids, porphyrin and chlorophyll metabolism, retinol metabolism, arginine biosynthesis. The results of the metabolic pathway showed that WGR was significantly better than GR in the improvement of porphyrin and chlorophyll metabolism.

CONCLUSIONS

These findings suggest that treatment with GR and WGR has a beneficial effect on DHJS in rats, the major mechanisms may be involved in improving functional indicators of the body and endogenous metabolism, and WGR is more effective than GR. It provides important evidence for the clinical application of GR and WGR in the treatment of DHJS.

Comparison of Bran-Processed and Crude Atractylodes Lancea Effects on Spleen Deficiency Syndrome in Rats

Background:

The rhizome of Atractylodes lancea (AL) is usually used for the treatment of various diseases such as spleen deficiency syndrome (SDS). Both bran-processed and crude AL is included in Chinese Pharmacopoeia. The different efficacies of bran-processed and crude AL on SDS are largely unknown, and the mechanisms of AL effects have not been fully elucidated.

Objective:

The objective of the study was to compare the effects of bran-processed and crude AL and then assess the mechanisms of treating SDS.

Materials and Methods:

The model of SDS in rats was established using excessive exertion, combined with an irregular diet and intragastric administration of the extract of Sennae Folium, and different doses of bran-processed and crude AL were gavaged. The serum was analyzed by an enzyme-linked immunosorbent assay (ELISA), and small intestinal tissues were analyzed by reverse transcription-polymerase chain reaction (RT-PCR).

Results:

The injury of SDS was alleviated by the treatment of bran-processed and crude AL. Compared to model group, the indexes of trypsin (TRY), amylase (AMS), vasoactive intestinal peptide (VIP), somatostatin (SS), gastrin (GAS), substance P (SP), Na⁺-K⁺-ATPase, and succinic dehydrogenase in serum of each administration group were increased by ELISA, and the mRNA expressions of VIP, SS, GAS, and SP in small intestinal tissues were increased by RT-PCR. Furthermore, in a dose-dependent manner, the bran-processed and crude AL increased the levels of TRY, AMS, VIP, and GAS and the mRNA expression levels of VIP. Compared with the crude AL, the bran-processed AL was more effective in treating SDS.

Conclusion:

Through the mechanisms of treating SDS by AL, both bran-processed and crude AL has alleviated the symptoms of SDS.

SUMMARY

Both bran-processed and crude Atractylodes lancea (AL) alleviated symptoms of spleen deficiency syndrome (SDS)

Comparing with crude AL, bran. processed AL was more effective in treating SDS

The efficacy of AL could be partly attributed to digestive enzyme activity, gastrointestinal hormone levels, membrane protein activity, and changes in mitochondrial activity.

Abbreviations used: AL: Atractylodes lancea; TRY: Trypsin; AMS: Amylase; VIP: Vasoactive intestinal peptide; SS: Somatostatin; GAS: Gastrin; SP: Substance P; ELISA: The enzyme-linked immunosorbent assay; mRNA: Messenger ribonucleic acid; SDH: Succinic dehydrogenase; RT-PCR: Reverse transcription-polymerase chain reaction; TCM: Traditional Chinese medicine; SDS: Spleen deficiency syndrome.

Comparison of the anti-ulcer activity between the crude and bran-processed Atractylodes lancea in the rat model of gastric ulcer induced by acetic acid

ETHNOPHARMACOLOGICAL RELEVANCE

The rhizome of Atractylodes lancea (AL, Compositae, Chinese name: Cangzhu; Japanese name: Sou-ju-tsu) has been used traditionally for the treatment of various diseases such as digestive disorders, rheumatic diseases, and influenza in China, Korea and Japan. The crude AL and AL bran-processed are both listed in the Chinese Pharmacopoeia. However, the differences between the effects of the crude and AL bran-processed on gastric ulcer were poorly understood, and the mechanisms for the treatment of gastric ulcer were not clear. This study aimed at comparing the anti-ulcer effects between the crude AL and AL processed in acetic acid induced model in rats and evaluating the mechanisms of action involved in the anti-ulcer properties of AL.

MATERIALS AND METHODS

The model of gastric ulcer was imitated by acetic acid in rats, and AL was gavaged. The serum and gastric tissues were collected. The levels of epidermal growth factor (EGF), trefoil factor2 (TFF2), tumor necrosis factor-α (TNF-α), interleukin 6, 8 (IL-6, 8) and prostaglandin E2 (PGE2) in serum and gastric tissues were determined by the double-antibody sandwich enzyme-linked immunosorbent assay (ELISA), and the mRNA expressions of EGF, TFF2, TNF-α, and IL-8 in stomach were analyzed by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). Meanwhile, histopathological changes were evaluated by hematoxylin and eosin (HE) stain. The protein expressions of EGF, TFF2, TNF-α, and IL-8 were examined by immunohistochemistry in stomach.

RESULTS

The results demonstrated that the damage of gastric tissue was obviously alleviated and the productions of TNF-α, IL-8, IL-6, and PGE2 and the mRNA expressions of TNF-α, and IL-8 were notably inhibited. Furthermore, the productions of EGF and TFF2 and the mRNA expressions of EGF and TFF2 were significantly stimulated by both crude AL and AL processed in a dose-dependent manner. Compared with the crude AL, the processed AL was more effective.

CONCLUSION

The AL processed had more satisfactory effects in treatment of gastric-ulcer than the crude AL. The anti-ulcer effects of AL could be attributed to the anti-inflammatory properties via down-regulating TNF-α, IL-8, IL-6 and PGE2 and to the gastroprotective effects via up-regulating EGF and TFF2.

Effects of seaweed-restructured pork diets enriched or not with cholesterol on rat cholesterolaemia and liver damage

Seaweed enriched-restructured pork (RP) is a potential functional food. However, indications of adverse effects associated with herbal medications, which include among others liver failure, toxic hepatitis, and death have been reported. Cholesterol feeding produces hepatomegalia and fat liver infiltration. The effect of seaweed-RP diet, cholesterol-enriched or not, on plasma cholesterol, liver damage markers, structure, and cytochrome CYP4A-1 were evaluated after 5 wk. Eight rat groups were fed a mix of 85% AIN-93M rodent-diet plus 15% RP. The Cholesterol-control (CC), Cholesterol-Wakame (CW), Cholesterol-Nori (CN) and Cholesterol-Sea Spaghetti (CS) groups respectively consumed similar diets to control (C), Wakame (W), Nori (N), and Sea Spaghetti (S) but as part of hypercholesterolaemic diets. CN and CS significantly blocked the hypercholesterolaemic effect observed in CC group. After 5-wk, N and S diets increased the CYP4A-1 expression. However, seaweed-RPs were unable to reduce the histological liver alterations observed in CC group. Larger and more abundant hepatocellular alterations were found in CS and CN rats suggesting that the hypocholesterolaemic effects of these seaweed-RPs seem to be a two-edged sword as they increased liver damage. Future studies are needed to understand the involved mechanisms.

Effects of unprocessed versus vinegar-processed Schisandra chinensis on the activity and mRNA expression of CYP1A2, CYP2E1 and CYP3A4 enzymes in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra chinensis (SC) is a well-known traditional Chinese herbal medicine that has been used in clinical practices for thousands of years. However, the differences between the effects of unprocessed and vinegar-processed Schisandra chinensis (VSC) on cytochrome P450 (CYP450) activities are poorly understood.

AIM OF THE STUDY

To evaluate the differences between processed and unprocessed SC on the metabolism of CYP1A2, CYP2E1 and CYP3A4 substrates in rats using a cocktail method based on a developed and validated HPLC method. We also investigate the influence of processing on the levels of CYP mRNA.

MATERIALS AND METHODS

Three probe substrates (theophylline, dapsone and chlorzoxazone) were delivered simultaneously into rats treated with single or multiple doses of processed or unprocessed SC extract. The plasma concentrations of the three probes were profiled by HPLC, and their corresponding pharmacokinetic parameters were calculated. Real-time RT-PCR was performed to determine the effects of processed and unprocessed SC on the mRNA expression of CYP1A2, CYP2E1 and CYP3A4 in the liver.

RESULTS

Treatment with single or multiple doses of either extract of SC induced CYP3A4 enzyme activity and inhibited CYP1A2 enzyme activity in rats. Furthermore, the inhibitory effect of SC was more potent after vinegar processing than without vinegar processing. CYP2E1 enzyme activity was induced after treatment with a single dose but was inhibited after multiple doses. The mRNA expression results were in accordance with the pharmacokinetic results.

CONCLUSIONS

These results provide useful scientific data for the safe clinical application of either extract of SC in combination with other drugs, which should lack the side effects induced by other herb-drug interactions.

Effects of ertiprotafib on hepatic cytochrome P450 and peroxisomal enzymes in rats and dogs, and in rat and human primary hepatocytes

Ertiprotafib (ERTI) significantly increased liver weights in male and female rats, and moderately increased liver weights in male dogs after treatment for 28 days. The present study tested the hypotheses that the organ weight increases were associated with peroxisome proliferation in rats and induction of hepatic enzymes in rats and dogs, and would have limited impacts on humans. At a dosage of 200 mg kg-1 day-1, CYP4A was induced by tenfold in male rats and 2.4-fold in female rats. In male rats, CYP2B was induced by 1.2-fold and CYP3A was induced by 1.7-fold. Palmitoyl CoA oxidase was induced by 5.1-fold in male rats and 2.9-fold in female rats; carnitine acetyltransferase was induced by 10.4-fold in male rats and 5.2-fold in female rats. CYP3A, CYP4A and peroxisomal enzymes were not induced in dogs at 150/200 mg kg-1 day-1. ERTI at 50 microM markedly induced the mRNA level of CYP4A by up to fivefold in rat hepatocytes, but not in human primary hepatocytes. In conclusion, the liver weight increases observed in rats treated with ERTI appears to be due to rodent-specific peroxisome proliferation and the substantial induction of CYP4A1. ERTI is not a potent P450 inducer in dogs or in human hepatocytes. Therefore, ERTI is not expected to exert any significant effects on hepatic drug-metabolizing enzymes in humans.

Peroxisome proliferator-activated receptor alpha-independent effects of peroxisome proliferators on cysteinyl leukotriene production in mast cells

The effects of peroxisome proliferators, the ligands of a nuclear receptor peroxisome proliferator-activated receptor (PPAR) alpha, on cysteinyl leukotriene production were investigated in rodent mast cells. Peroxisome proliferators Wy-14,643 (30 microM) and fenofibrate (100 microM) significantly inhibited the cysteinyl leukotriene production that was induced by antigen (Ag) treatment after overnight sensitization to Ag specific immunoglobulin E (IgE) in a rat basophilic leukemia (RBL)-2H3 mast cell line. Similar inhibition by these drugs was observed in IgE and Ag-treated mouse bone marrow-derived mast cells, A23187-treated RBL-2H3 and A23187-treated mouse peritoneal macrophages. Wy-14,643 (30 microM) and fenofibrate (100 microM) did not affect the release of radioactivity from RBL-2H3 pre-incubated with [(3)H]-arachidonic acid, which is considered an index of phospholipase A(2) activity. Wy-14,643 (30 microM) and fenofibrate (100 microM) did not directly inhibit 5-lipoxygenase activity. Troglitazone was found to directly inhibit the activity of 5-lipoxygenase. The PPARalpha mRNA level was at less than the limit of detection for the realtime polymerase chain reaction both in RBL-2H3 and bone marrow-derived mast cells. Wy-14,643 (30 microM) and fenofibrate (100 microM) did not induce acyl-CoA oxidase mRNA in RBL-2H3, which was reported to be induced by peroxisome proliferators via PPARalpha in hepatocytes. Wy-14,643 (30 microM) and fenofibrate (100 microM) inhibited the cysteinyl leukotriene production in bone marrow-derived mast cells from PPARalpha-null mice. It was concluded that the inhibitory effects of these peroxisome proliferators on cysteinyl leukotriene production are independent of PPARalpha in mast cells.

Induction of CYP2B and CYP2E1 in precision-cut rat liver slices cultured in defined medium

Many drugs and endogenous substances undergo biotransformation by cytochrome P450s (CYPs), and some drugs are also capable of modulating the expression of various CYPs. Knowledge of the potential of a drug to modulate CYPs is useful to help predict potential drug interactions. This study utilized precision-cut rat liver slices in dynamic organ culture to assess the effects of various media on the viability of rat liver slices and the expression of CYP2B and CYP2E1 when the slices are exposed to phenobarbital and isoniazid, which are drugs capable of inducing these respective CYPs. Liver slices were maintained in serum supplemented Waymouths medium and two different serum-free media, Hepatozyme (Life Technologies) and a new defined medium, which is named BPM. While Hepatozyme is considered a suitable medium to support primary hepatocyte cultures, this product did not maintain viable liver slices, even for 24 h. The serum containing and new defined media maintained viable liver slices for up to 96 h in culture. Phenobarbital (0.5 mM) and isoniazid (0.1 or 0.6 mM) did not affect viability in this model. In the absence of phenobarbital or isoniazid, liver slices maintained for 96 h in the new BPM medium maintained the respective levels of CYP2B and 2E1 protein at 1.8 and 1.9-fold higher than in slices maintained in the serum-containing medium. Phenobarbital exposure (0.5 mM) for 96 h induced CYP2B protein 5.2-fold in the BPM medium and 2.5-fold in the serum-containing medium. Isoniazid exposure (0.1 and 0.5 mM) for 96 h induced CYP2E1 protein 1.9 and 2.1-fold (respectively) in the BPM medium and 2.1 and 2.0-fold in the serum-containing medium. The respective CYP enzymatic activities were also increased by these drugs in a similar manner. Thus, the new defined BPM medium provides suitable conditions for maintaining CYP2B and 2E1 in liver slices and supports the investigation of drug-induced modulation of these enzymes.

Cytochrome P450 gene induction in rats ex vivo assessed by quantitative real-time reverse transcriptase-polymerase chain reaction (TaqMan)

Drug-induced changes in expression of cytochrome P450 (P450) genes are a significant issue in the preclinical development of pharmaceuticals. For example, preclinically, P450 induction can affect safety studies by reducing the systemic exposure of a compound undergoing toxicological evaluation, thus limiting the exposure that can be safely investigated in patients. Therefore, the induction potential of candidate drugs has been studied as part of the drug development process, typically using protein and/or catalytic end points. However, measuring changes in the levels of mRNA using TaqMan technology offers the opportunity to investigate this issue with the advantages of better dynamic range and specific enzyme identification. Here, we describe the TaqMan application to study ex vivo the P450 gene induction in the rat. Initially, livers from rats dosed with the prototypic P450 inducers beta-napthoflavone (BNF), phenobarbital (PB), dexamethasone (DEX), and clofibric acid (CLO) were analyzed for mRNA levels of CYP1A1, 1A2, 2B1, 2B2, 2E1, 3A2, 3A23, and 4A1 and compared with control animals. The maximum fold induction of mRNA varied: 2500-fold for CYP1A1 with BNF, 680-fold for CYP2B1 with PB, 59-fold for CYP3A23 with DEX, and 16-fold for CYP4A1 with CLO. This method was then applied to estimate the inductive potential of putative drug candidates undergoing rodent toxicological evaluation. We present a summary of these data that demonstrates the sensitivity and specificity of the TaqMan assay to distinguish between inducers and noninducers and that offers a highly specific alternative to the quantification of drug effects on P450 expression using immunodetection and substrate metabolism.

An in vivo and in vitro comparison of CYP gene induction in mice using liver slices and quantitative RT-PCR

The scope of this study was to compare in vitro and in vivo cytochrome P450 (CYP) gene induction in mice, using liver slices as an in vitro model. We have chosen to study mice to be able to better interpret CYP induction during long-term safety studies in this species. Mouse liver slices were incubated with beta-naphthoflavone (betaNF), phenobarbital (PB) or dexamethasone (DEX) for 24 h. In addition, in an in vivo study, mice were treated with the same compounds for three days. The mRNA expression of cyp1a1, cyp1a2, cyp2b10 and cyp3a11, which are important for drug metabolism and inducible by xenobiotics, were investigated in vivo and in vitro by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). Both in mouse liver slices and in vivo, betaNF was found to be a potent inducer of cyp1a1 and to a lesser extent of cyp1a2. All three compounds induced cyp2b10 mRNA levels, while the cyp3a11 mRNA level was induced only by DEX. Overall, these data demonstrated a good predictive in vitro-in vivo correlation of CYP induction.

An in vivo and in vitro comparison of CYP induction in rat liver and intestine using slices and quantitative RT-PCR

Xenobiotics, including drugs, can influence cytochrome P450 (CYP) activity by upregulating the transcription of CYP genes. To minimize potential drug interactions, it is important to ascertain whether a compound will be an inducer of CYP enzymes early in the development of new therapeutic agents. In vivo and in vitro studies are reported that demonstrate the use of liver and intestinal slices as an in vitro model to predict potential CYP induction in vivo. Rat liver slices and intestinal slices were incubated, for 24 h and 6 h, respectively, with beta-naphthoflavone (betaNF), phenobarbital (PB) or dexamethasone (DEX). In an in vivo study, rats were treated with the same compounds for 3 days. In vivo and in vitro CYP mRNA levels were measured by using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). In addition, CYP enzyme activities were determined in rat liver slices after 48 h incubation. In both rat liver and intestinal slices, betaNF significantly induced CYP1A1, CYP1A2 and CYP2B1 mRNA levels. PB significantly induced CYP2B1. In liver slices a minor induction of CYP1A1 and CYP3A1 by PB was observed, whereas DEX significantly induced CYP3A1, CYP2B1 and CYP1A2 mRNA levels. The induction profiles (qualitative and quantitative) observed in vivo and in vitro are quite similar. All together, these data demonstrate that liver and intestinal slices are a useful and predictive tool to study CYP induction.

Engineering hepatocellular morphogenesis and function via ligand-presenting hydrogels with graded mechanical compliance

In order to evaluate the sensitivity of hepatocellular cultures to variations in both substrate stiffness and bioactive ligand presentation, hepatocytes were cultured on differentially compliant polyacrylamide gel discs functionalized with varying amounts of the ECM ligand, fibronectin (FN). Subconfluent cell cultures were established in a multiwell plate format enabling the systematic evaluation of cellular response to both underlying substrate rigidity and substrate ligand concentration. Hepatocellular morphogenesis, regulated by a combination of both ligand density and substrate compliance, resulted in a broad spectrum of patterns of cellular reorganization and assembly ranging from highly two-dimensionally spread cells to highly compact, three-dimensional spheroids. Cell compaction was promoted by increasing levels of substrate mechanical compliance and generally inhibited by increasing concentrations of substrate-bound FN. We identified regimes of substrate compliance in which cells are highly responsive or relatively insensitive to the level of substrate-based ligands. For example, while FN presentation did not have a large impact on cell morphogenesis for cultures on highly compliant gels (G' = 1.9 kPa), hepatocytes on "firm" substrates of intermediate compliance (G' = 5.6 kPa) exhibited approximately a 2-fold increase in cell area between the highest and lowest FN concentrations used in this study. Further, we show that increasing substrate compliance at constant ligand concentration results in increased levels of liver-specific albumin secretion while increasing levels of FN at constant substrate rigidity yield reduced liver-specific functional activity. These substrate-elicited differences in cell function also coincided with analogous changes in the transcript levels of metabolic, growth-related, and liver-specific gene markers. Notably, these results also demonstrated that "firm" gel substrates elicit the most hepatocyte functional sensitivity to substrate-based FN presentation. Overall, our findings indicate that hepatocellular responsiveness to ligand concentration can be acutely regulated by gradation of substrate compliance, suggesting that concerted biochemical and biophysical design strategies may be critical toward the fabrication of hepatospecific biomaterials that effectively support desired levels of liver-specific function.

Quantitative PCR assay for cytochromes P450 2B and 3A induction in rat precision-cut liver slices: correlation study with induction in vivo

INTRODUCTION

In drug development, new chemical entities that cause cytochrome P450 induction are considered to be undesirable since P450 induction is linked to tumor formation and may compromise the evaluation of drug safety when autoinduction results in poor drug exposure.

METHODS

We evaluated the use of the precision-cut liver slice as a model for measuring induction of cytochrome P450 in rats. Quantitative real-time reverse-transcription polymerase chain reaction was used to analyze the induction of selected forms of cytochrome P450 at the mRNA level. Firstly, the system was validated against known inducers of CYP2B and 3A. Subsequently, 26 proprietary compounds were tested in rat liver slices and rats in vivo for CYP2B and 3A induction.

RESULTS

Exposure of liver slices to the known CYP2B inducers phenobarbital, benzoyl-pyridine, cabarmazepine, metyrapone, RU486 and dexamethasone caused elevation of CYP2B1/2 expression 10- to 40-fold compared to the control values. The CYP3A inducers PCN, dexamethasone, nicardipine, nifedipine, clotrimazole and RU486 induced a 4- to 50-fold expression of CYP3A14. For 26 proprietary compounds, a correlation with an R(2) value of 0.74 was established between the induction of CYP2B expression in liver slices and that in rats in vivo. When liver slice results were used to predict the induction of CYP2B in rats in vivo, the success rate was 91%. The induction of CYP3A in rats in vivo was analyzed by Western blot, then quantified by densitometry. There was a good correlation between CYP3A induction in liver slices and induction in vivo as assessed by Western blot, with an 86% positive prediction rate.

DISCUSSION

The use of liver slices in combination with TaqMan technology provides a good model for predicting CYP induction in the rat. This method is useful for identifying compounds with CYP2B and 3A induction liability in the early phase of drug discovery.

Exogenous cadherin microdisplay can interfere with endogenous signaling and reprogram gene expression in cultured hepatocytes

We recently found that the basal micro substrate presentation of E-cadherin, a key cell-cell adhesion molecule in the liver, can modulate hepatocellular proliferative potential and differentiated function (Brieva and Moghe, in press). In the current study, we established a similar experimental model involving rat hepatocytes cultured on collagen and incorporated 5 microm polystyrene microbeads functionalized with Protein A-anchored E-cadherin/human lgG Fc chimeric fusion constructs. We investigated the cadherin governed dose-response of cell proliferative potential and quantified the underlying changes in intracellular gene signaling processes. Hepatocellular proliferative potential was found to be intensified with an increase in the microdisplay of acellular cadherins and this effect was offset by increased cell seeding density. Notably, we report that following overnight exposure to acellular cadherins, the expression of genes known to mediate the control of cell proliferation, cyclin D1 and c-myc, was upregulated, while the expression of differentiation-related genes, namely albumin and cytochrome p450 II B1, was reduced. The exposure of cell cultures to exogenous cadherins was found to markedly disrupt the localization of endogenous E-cadherin and beta-catenin to junctions at cell-cell contacts and cause a quantitative decrease in the endogenous cadherin protein levels. Based on all of our observations, we propose that the acellular presentation of E-cadherin chimeras competitively disrupts endogenous cadherin containing complexes at cell-cell junctions and increases intracellular cadherin turnover, thereby promoting beta-catenin mediated signaling, which ultimately engenders an increase in cell proliferative potential and a decrease in differentiated function.

Studies on the induction of rat hepatic CYP1A, CYP2B, CYP3A and CYP4A subfamily form mRNAs in vivo and in vitro using precision-cut rat liver slices

1. Real-time quantitative reverse transcription-polymerase chain reaction methodology (TaqMan(R)) was used to examine the induction of some selected rat hepatic cyto-chrome P450 (CYP) forms in vivo and in vitro using cultured precision-cut liver slices. 2. TaqMan primers and probe sets were developed for rat CYP1A1, CYP1A2, CYP2B1, CYP2B1/2, CYP3A1, CYP3A2 and CYP4A1 mRNAs. 3. To characterize the responsiveness of the rat CYP mRNA TaqMan primers and probe sets, rats were treated in vivo with a single intraperitoneal dose of 500 mg kg(-1) Aroclor 1254 (ARO) and with four daily oral doses of either 50 mg kg(-1) day(-1) dexamethasone (DEX) or 75 mg kg(-1) day(-1) methylclofenapate (MCP). Treatment with ARO produced 22 600-, 5480-, 648-, 52-, 47- and 9-fold increases in levels of CYP1A1, CYP2B1, CYP2B1/2, CYP1A2, CYP3A1 and CYP3A2 mRNA, respectively. DEX treatment produced 97-, 24-, 8- and 4-fold increases, respectively, in CYP3A1, CYP2B1, CYP2B1/2 and CYP3A2 mRNA levels, and MCP produced 339-, 126- and 25-fold increases, respectively, in CYP4A1, CYP2B1 and CYP2B1/2 mRNA levels. All three CYP inducers also increased microsomal CYP content and produced corresponding increases in CYP1A, CYP2B, CYP3A and CYP4A form marker enzyme activities. 4. Rat liver slices were cultured for 6 and 24 h in medium containing 0.1 micro M insulin and 0.1 micro M DEX, and also for 24 h in medium containing only 0.1 micro M insulin (DEX-free medium). Liver slices were cultured in control medium or in medium containing either 10 micro M beta-naphthoflavone (BNF), 10 micro g ml(-1) ARO, 500 micro M sodium phenobarbitone (NaPB), 20 micro M pregnenolone-16alpha -carbonitrile (PCN), 50 micro M Wy-14,643 (WY) or 50 micro M MCP. 5. With the exception of the effect of BNF on CYP1A1 mRNA levels, the induction of all the CYP mRNAs studied was greater after 24- than after 6-h treatment. Generally, the magnitude of induction of CYP mRNA levels was greater after 24 h in liver slices cultured in DEX-free than in DEX-supplemented medium. 6. Treatment of liver slices with BNF and ARO for 24 h in DEX-free medium produced 21- and 35-fold increases, respectively, and 38- and 37-fold increases, respectively, in CYP1A1 and CYP1A2 mRNA levels. NaPB, PCN, WY and MCP did not increase either CYP1A1 or CYP1A2 mRNA levels. 7. After 24 h, levels of CYP2B1/2 mRNA were increased 18-, 20-, 9-, 16- and 13-fold by treatment with ARO, NaPB, PCN, WY and MCP, respectively. PCN also produced 56- and 4-fold increases, respectively, in CYP3A1 and CYP3A2 mRNA levels. 8. Treatment with WY and MCP for 24 h produced 437- and 186-fold increases, respectively, in levels of CYP4A1 mRNA. None of the other CYP inducers studied had any effect on CYP4A1 mRNA levels. 9. The results demonstrate the utility of cultured precision-cut liver slices as an in vitro model system to evaluate the effects of xenobiotics on rat CYP1A, CYP2B, CYP3A and CYP4A form mRNA levels.

New hepatocyte in vitro systems for drug metabolism: metabolic capacity and recommendations for application in basic research and drug development, standard operation procedures

Primary hepatocytes represent a well-accepted in vitro cell culture system for studies of drug metabolism, enzyme induction, transplantation, viral hepatitis, and hepatocyte regeneration. Recently, a multicentric research program has been initiated to optimize and standardize new in vitro systems with hepatocytes. In this article, we discuss five of these in vitro systems: hepatocytes in suspension, perifusion culture systems, liver slices, co-culture systems of hepatocytes with intestinal bacteria, and 96-well plate bioreactors. From a technical point of view, freshly isolated or cryopreserved hepatocytes in suspension represent a readily available and easy-to-handle in vitro system that can be used to characterize the metabolism of test substances. Hepatocytes in suspension correctly predict interspecies differences in drug metabolism, which is demonstrated with pantoprazole and propafenone. A limitation of the hepatocyte suspensions is the length of the incubation period, which should not exceed 4hr. This incubation period is sufficiently long to determine the metabolic stability and to allow identification of the main metabolites of a test substance, but may be too short to allow generation of some minor, particularly phase II metabolites, that contribute less than 3% to total metabolism. To achieve longer incubation periods, hepatocyte culture systems or bioreactors are used. In this research program, two bioreactor systems have been optimized: the perifusion culture system and 96-well plate bioreactors. The perifusion culture system consists of collagen-coated slides allowing the continuous superfusion of a hepatocyte monolayer with culture medium as well as establishment of a constant atmosphere of 13% oxygen, 82% nitrogen, and 5% CO2. This system is stable for at least 2 weeks and guarantees a remarkable sensitivity to enzyme induction, even if weak inducers are tested. A particular advantage of this systemis that the same bioreactor can be perfused with different concentrations of a test substance in a sequential manner. The 96-well plate bioreactor runs 96 modules in parallel for pharmacokinetic testing under aerobic culture conditions. This system combines the advantages of a three-dimensional culture system in collagen gel, controlled oxygen supply, and constant culture medium conditions, with the possibility of high throughput and automatization. A newly developed co-culture system of hepatocytes with intestinal bacteria offers the possibility to study the metabolic interaction between liver and intestinal microflora. It consists of two chambers separated by a permeable polycarbonate membrane, where hepatocytes are cultured under aerobic and intestinal bacteria in anaerobic conditions. Test substances are added to the aerobic side to allow their initial metabolism by the hepatocytes, followed by the metabolism by intestinal bacteria at the anaerobic side. Precision-cut slices represent an alternative to isolated hepatocytes and have been used fo the investigation of hepatic metabolism, hepatotoxicity, and enzyme induction. A specific advantage of liver slices is the possibility to study toxic effects on hepatocytes that are mediated or modified by nonparenchymal cells (e.g., by cytokine release from Kupffer cells) because the physiological liver microarchitecture is maintained in cultured slices. For all these in vitro systems, a prevalidation has been performed using standard assays for phase I and II enzymes. Representative results with test substances and recommendations for application of these in vitro systems, as well as standard operation procedures are given.