Assessment of hepatic prostaglandin E2 level in carbamazepine induced liver injury.

Objective. Carbamazepine (CBZ), a widely used antiepileptic drug, is one major cause of the idiosyncratic liver injury along with immune reactions. Conversely, prostaglandin E2 (PGE2) demonstrates a hepatoprotective effect by regulating immune reactions and promoting liver repair in various types of liver injury. However, the amount of hepatic PGE2 during CBZ-induced liver injury remains elusive. In this study, we aimed to evaluate the hepatic PGE2 levels during CBZ-induced liver injury using a mouse model. Methods. Mice were orally administered with CBZ at a dose of 400 mg/kg for 4 days, and 800 mg/kg on the 5th day. Results. Plasma alanine transaminase (ALT) level increased in some of mice 24 h after the last CBZ administration. Although median value of hepatic PGE2 amount in the CBZ-treated mice showed same extent as vehicle-treated control mice, it exhibited significant elevated level in mice with severe liver injury presented by a plasma ALT level >1000 IU/L. According to these results, mice had a plasma ALT level >1000 IU/L were defined as responders and the others as non-responders in this study. Even though, the hepatic PGE2 levels increased in responders, the hepatic expression and enzyme activity related to PGE2 production were not upregulated when compared with vehicle-treated control mice. However, the hepatic 15-hydroxyprostaglandin dehydrogenase (15-PGDH) expression and activity decreased significantly in responders when compared with control mice. Conclusions. These results indicate that elevated hepatic PGE2 levels can be attributed to the downregulation of 15-PGDH expression under CBZ-induced liver injury.

Species differences in liver microsomal hydrolysis of acyl glucuronide in humans and rats.

Acyl glucuronides (AGs) are known as one of the causes of idiosyncratic drug toxicity (IDT). Although AGs can be enzymatically hydrolysed by ß-glucuronidase and esterase, much information on their characteristics and species differences is lacking. This study was aimed to clarify species differences in AG hydrolysis between human and rat liver microsomes (HLM and RLM).To evaluate the AG hydrolysis profile, and the contribution of ß-glucuronidase and esterase towards AG hydrolysis in HLM and RLM, nonsteroidal anti-inflammatory drugs (NSAIDs) were used. AGs were incubated with 0.1 M Tris-HCl buffer (pH 7.4) and 0.3 mg/mL HLM or RLM in the absence or presence of ß-glucuronidase inhibitor, D-saccharic acid 1,4-lactone (D-SL) and esterase inhibitor, phenylmethylsulfonyl fluoride (PMSF).AGs of mefenamic acid (MEF-AG) and etodolac (ETO-AG) showed significantly higher AG hydrolysis rates in RLM than in HLM. Esterases were found to serve as AG hydrolases dominantly in HLM, whereas both esterases and ß-glucuronidase equally contribute to AG hydrolysis in RLM. However, MEF-AG and ETO-AG were hydrolysed only by ß-glucuronidase.We demonstrated for the first time that the activity of AG hydrolases towards NSAID-AGs differs between humans and rats.

Slc25a39 and Slc25a40 Expression in Mice with Bile Duct Ligation or Lipopolysaccharide Treatment.

SLC25A39/40, involved in mitochondrial GSH (mGSH) import from the cytoplasm, is essential for protection against oxidative stress and mitochondrial dysfunction. We examined the effects of cholestasis, through bile duct ligation (BDL) and lipopolysaccharide (LPS)-induced inflammation in mice, on Slc25a39/40 expression. Additionally, we used human clear cell renal carcinoma (KMRC-1) cells to elucidate the mechanism of regulation of SLC25A39/40 expression in the kidneys after LPS treatment. BDL resulted in a decrease in Slc25a39 mRNA in the liver and a decrease in Slc25a39/40 mRNA and protein in the kidneys. Consequently, there was a significant decrease in mGSH levels in the kidneys of BDL mice compared with those in sham mice. LPS treatment resulted in increased Slc25a40 expression in the kidneys. In KMRC-1 cells, the combination treatment of LPS-RS or FPS-ZM1 with LPS suppressed the LPS-induced increase in SLC25A40, suggesting that SLC25A40 expression could be regulated by the signaling pathway via toll-like receptor 4 and the receptor for advanced glycation end products, respectively. Our findings contribute to understanding the role of mGSH in the maintenance of the mitochondrial redox state. To the best of our knowledge, this is the first study that demonstrates the changes in Slc25a39/40 expression in mice with cholestasis-associated renal injury and LPS-induced inflammation.

Diclofenac-Induced Cytotoxicity in Direct and Indirect Co-Culture of HepG2 Cells with Differentiated THP-1 Cells.

Non-steroidal anti-inflammatory drugs (NSAIDs) such as diclofenac (DIC) frequently induce drug-induced liver injury (DILI). It is unclear whether macrophages such as M1 and M2 participate in NSAID-associated DILI; elucidating this relationship could lead to a better understanding of the detailed mechanism of DILI. We co-cultured human hepatoma HepG2 cells with M1 or M2 derived from human monocytic leukemia THP-1 cells to examine the roles of M1 and M2 in DIC-induced cytotoxicity. DIC was added to the direct or indirect co-cultures of HepG2 cells with M1 or M2 (HepG2/M1 or HepG2/M2, respectively) at cell ratios of (1:0, 1:0.1, 1:0.4, and 1:1). In both direct and indirect HepG2/M2 co-cultures (1:0.4), there was lower lactate dehydrogenase release compared with HepG2/M1 co-cultures. Other NSAIDs as well as DIC showed similar protective effects of DIC-induced cytotoxicity. There were only slight differences in mRNA levels of apoptosis- and endoplasmic reticulum stress-associated factors between M1 and M2 after DIC treatment, suggesting that other factors determined the protective effects of M2 on DIC-induced cytotoxicity. Levels of high mobility group box 1 (HMGB1) in the medium and the mRNA expression levels of HMGB1 receptors were different between M1 and M2 after DIC treatment. Increased HMGB1 concentrations and expression of toll-like receptor 2 mRNA in M1 were observed compared with M2 after DIC treatment. In conclusion, these results suggested that the HMGB1/TLR2 signaling axis can be suppressed in M2 but not M1, leading to the different roles of M1 and M2 in NSAID-induced cytotoxicity.

Stereoselective Covalent Adduct Formation of Acyl Glucuronide Metabolite of Nonsteroidal Anti-Inflammatory Drugs with UDP-Glucuronosyltransferase.

A reactive metabolite of nonsteroidal anti-inflammatory drugs (NSAIDs), acyl-ß-D-glucuronide (AG), covalently binds to endogenous proteins. The covalent adduct formation of NSAIDs-AG may lead to the dysfunction of target proteins. Therefore, it is important to clarify the detailed characterization of the formation of covalent protein adducts of NSAID-AG. UDP-glucuronosyltransferase (UGT) catalyzes the conversion of NSAIDs to NSAIDs-AG. The aim of this study was to perform a quantitative analysis of the covalent adduct formation of NSAIDs-AG with UGT. Diclofenac-AG and ketoprofen-AG formed covalent adducts with organelle proteins. Next, the number of covalent adducts formed between NSAIDs-AG and UGT isoforms (UGT1A1, UGT1A9, UGT2B4, and UGT2B9) was determined. The capacity of diclofenac-AG to form covalent adducts with UGT1A9 or UGT2B7 was approximately 10 times higher than that of mefenamic acid-AG. The amounts of covalent adducts of AG of propionic acid derivative NSAIDs with UGT2B were higher than those with UGT1A. Stereoselectivity was observed upon covalent binding to UGT. A significant negative correlation between the half-lives of NSAIDs-AG in phosphate buffers and the amount of covalent adduct with UGT2B7 was observed, suggesting the more labile NSAID-AG forms higher irreversible bindings to UGT. This report provides comprehensive information on the covalent adduct formation of NSAIDs-AGs with UGT.

Protein Kinase N Family Negatively Regulates Constitutive Androstane Receptor-Mediated Transcriptional Induction of Cytochrome P450 2b10 in the Livers of Mice.

In receptor-type transcription factors-mediated cytochrome P450 (P450) induction, few studies have attempted to clarify the roles of protein kinase N (PKN) in the transcriptional regulation of P450s. This study aimed to examine the involvement of PKN in the transcriptional regulation of P450s by receptor-type transcription factors, including the aryl hydrocarbon receptor, constitutive androstane receptor (CAR), and pregnane X receptor. The mRNA and protein levels and metabolic activity of P450s in the livers of wild-type (WT) and double-mutant (D) mice harboring both PKN1 kinase-negative knock-in and PKN3 knockout mutations [PKN1 T778A/T778A; PKN3 -/-] were determined after treatment with activators for receptor-type transcription factors. mRNA and protein levels and metabolic activity of CYP2B10 were significantly higher in D mice treated with the CAR activator phenobarbital (PB) but not with 1,4-bis((3,5-dichloropyridin-2-yl)oxy)benzene compared with WT mice. We examined the CAR-dependent pathway regulated by PKN after PB treatment because the extent of CYP2B10 induction in WT and D mice was notably different in response to treatment with different CAR activators. The mRNA levels of Cyp2b10 in primary hepatocytes from WT and D mice treated with PB alone or in combination with Src kinase inhibitor 1 (SKI-1) or U0126 (a mitogen-activated protein kinase inhibitor) were evaluated. Treatment of hepatocytes from D mice with the combination of PB with U0126 but not SKI-1 significantly increased the mRNA levels of Cyp2b10 compared with those from the corresponding WT mice. These findings suggest that PKN may have inhibitory effects on the Src-receptor for activated C kinase 1 (RACK1) pathway in the CAR-mediated induction of Cyp2b10 in mice livers. SIGNIFICANCE STATEMENT: This is the first report of involvement of PKN in the transcriptional regulation of P450s. The elucidation of mechanisms responsible for induction of P450s could help optimize the pharmacotherapy and improve drug development. We examined whether the mRNA and protein levels and activities of P450s were altered in double-mutant mice harboring both PKN1 kinase-negative knock-in and PKN3 knockout mutations. PKN1/3 negatively regulates CAR-mediated induction of Cyp2b10 through phosphorylation of a signaling molecule in the Src-RACK1 pathway.

Drug interactions between tacrolimus and clotrimazole troche: a data mining approach followed by a pharmacokinetic study.

PURPOSE: This study investigated the effects of clotrimazole troche on the risk of transplant rejection and the pharmacokinetics of tacrolimus. METHODS: The data mining approach was used to investigate whether the use of clotrimazole increased the risk of transplant rejection in patients receiving tacrolimus therapy. Patient data were acquired from the US Food and Drug Administration's Adverse Event Reporting System (FAERS) from the first quarter of 2004 to the end of 2017. Next, we retrospectively investigated the effect of clotrimazole troche on tacrolimus pharmacokinetics in seven patients who underwent heart transplantation between March and December 2017. RESULTS: The FAERS subset data indicated a significant association between transplant rejection and tacrolimus with clotrimazole [reporting odds ratio 1.92, 95% two-sided confidence interval (95% CI) 1.43-2.58, information component 0.81, 95% CI 0.40-1.23]. The pharmacokinetic study demonstrated a significant correlation between trough concentration (C0) and area under the concentration-time curve of tacrolimus after discontinuation of clotrimazole (R2 = 0.60, P < 0.05) but not before its discontinuation. Furthermore, the median clearance/bioavailability of tacrolimus after discontinuation of clotrimazole was 2.2-fold greater than that before its discontinuation (0.27 vs. 0.59 L/h/kg, P < 0.05). The median C0 decreased from 10.7 ng/mL on the day after discontinuation of clotrimazole to 6.5 ng/mL at 1 day and 5.3 ng/mL at 2 days after its discontinuation. CONCLUSION: Immediate dose adjustments of tacrolimus may be beneficial to avoid transplant rejection when clotrimazole troche is added or discontinued.

Effects of clotrimazole on tacrolimus pharmacokinetics in patients with heart transplants with different CYP3A5 genotypes.

PURPOSE: This study aimed to investigate the effects of clotrimazole on the pharmacokinetics of tacrolimus in Japanese patients with heart transplants with different CYP3A5 genotypes. METHODS: Twenty-six patients who underwent heart transplantation between June 2012 and July 2017 were enrolled in this retrospective study. The CYP3A5 (rs776746; CYP3A5*3) genotype was determined after monitoring and analysing tacrolimus blood concentrations. The pharmacokinetic profile of tacrolimus was examined before and after the discontinuation of clotrimazole and in patients with different CYP3A5 genotypes. RESULTS: The CYP3A5*1/*1, *1/*3 and *3/*3 genotypes were detected in 2, 8 and 16 patients, respectively. After clotrimazole was discontinued, the CYP3A5 expresser (CYP3A5*1/*1 or *1/*3) group had a 3.3-fold median increase in apparent oral clearance of tacrolimus (0.27 vs. 0.89 L/h/kg, P = 0.002) compared with the CYP3A5 non-expresser (CYP3A5*3/*3) group with a 2.2-fold median increase (0.18 vs. 0.39 L/h/kg, P < 0.0001). Significant correlations were observed between C0 and area under the concentration-time curve (AUC0-12) of tacrolimus after the discontinuation of clotrimazole in the CYP3A5 expresser and non-expresser groups, respectively (R2 = 0.49 and 0.42, all P < 0.05), but not before the discontinuation of clotrimazole. CONCLUSION: The effects of clotrimazole on tacrolimus pharmacokinetics in the CYP3A5 expresser patients were significantly greater than those in the CYP3A5 non-expresser patients. In addition, clotrimazole disturbed the correlation between C0 and AUC0-12 of tacrolimus. Careful dose adjustment of tacrolimus based on CYP3A5 genotypes may be beneficial for the patients with heart transplants who are concomitantly treated with clotrimazole.

Prediction of Hepatic Clearance of Stereoselective Metabolism of Carvedilol in Liver Microsomes and Hepatocytes of Sprague-Dawley and Cytochrome P450 2D-Deficient Dark Agouti Rats.

Hepatic clearance (CLh) of carvedilol (CAR), which is eliminated via stereoselective metabolism by the CYP2D subfamily of cytochromes P450 (CYPs), was predicted using liver microsomes and hepatocytes from Sprague-Dawley (SD) rats and CYP2D-deficient Dark Agouti (DA) rats to determine the usefulness of prediction method. Plasma concentrations of CAR following intravenous injection to DA rats were higher than those in SD rats. The volume of distribution at steady state and total clearance (CLtot) of S-CAR were approximately two times greater than those of R-CAR in both strains. CLh predicted from in vitro studies using DA rat liver microsomes was different from that obtained from in vivo studies. In contrast, in vitro CLh prediction using DA rat hepatocytes was nearly identical to the CLh observed in DA rats in vivo, and was lower than that in SD rats. The predicted CLh in vitro using hepatocytes correlated well with the observed CLtot in vivo, which is expected to be nearly the same as CLh. These results suggest that in vitro metabolic studies using hepatocytes are more relevant with regard to stereoselectively predicting CLh of CAR than those using liver microsomes.

Changes in transporters and metabolizing enzymes in the livers of rats with bile duct ligation.

PURPOSE: Bile duct ligation (BDL) in experimental animals is widely used as an animal model of liver cholestasis and fibrosis. The transcriptional process and plasma membrane localization of transporters are regulated by nuclear receptors and scaffold proteins, respectively. However, the detailed changes of these factors in the livers of BDL rats remain unclear. To clarify the effects of BDL on the levels of transporters and metabolizing enzymes, nuclear receptors, and scaffold proteins, we investigated changes in mRNA and protein levels of livers from BDL rats. METHODS: Membrane proteins and microsomes were prepared from rats with BDL. The mRNA levels of transporters and nuclear receptors in livers of control and BDL rats were examined by real-time reverse transcription polymerase chain reaction. The protein levels of transporters, metabolizing enzymes and scaffold proteins in membrane proteins and microsomes were determined by liquid chromatography-tandem mass spectrometry-based targeted proteomics. RESULTS: Mdr1a mRNA was significantly decreased at 1 and 2 weeks of BDL. The mRNA levels of MRP2 were significantly decreased. The mRNA levels of nuclear receptors were significantly decreased in livers of 1-week BDL rats. The protein levels of P-gp were significantly increased by BDL. Regarding scaffold proteins, the protein levels of ezrin, moesin and EBP50 were significantly decreased at 2 weeks of BDL. The protein levels of radixin were significantly increased at 1 week of BDL. In 1-week BDL rats, the protein levels of metabolizing enzymes such as CYP and UGT were significantly decreased. CONCLUSIONS: This study reports the comprehensive changes of transporters, metabolizing enzymes, nuclear receptors, and ezrin/radixin/moesin proteins in the livers of BDL rats. The expression levels of nuclear receptors and radixin that regulate the transcription and localization of CYP and/or transporters were decreased by BDL.

Decrease in Multidrug Resistance-associated Protein 2 Activities by Knockdown of Phosphatidylinositol 4-phosphate 5-kinase in Hepatocytes and Cancer Cells.

PURPOSE: The plasma membrane localization and transport activity of multidrug resistance- associated protein 2 (MRP2/ABCC2) and P-glycoprotein (P-gp/ABCB1) efflux transporters are governed by transporter-associated proteins. Phosphatidylinositol 4,5-bisphosphate (PIP2) formed by phosphatidylinositol 4-phosphate 5-kinase type 1 (PIP5K1) activates the linker function of radixin for efflux transporters. Radixin is involved in the plasma membrane localization of efflux transporters. We examined whether PIP5K1 could be a target for the modulation of transporter activities in hepatocytes and cancer cells. METHODS: The effects of PIP5K1 depletion by siRNA in mouse primary hepatocytes, PANC1 human pancreatic carcinoma cells, and HepG2 human hepatocellular carcinoma cells on the intracellular accumulation of MRP2 and P-gp substrates were examined. RESULTS: PIP5K1A depletion resulted in increased intracellular accumulation of carboxydichlorofluorescein, a MRP2 fluorescent substrate, in mouse primary hepatocytes, PANC1 cells, and HepG2 cells. In PANC1 and HepG2 cells, the transport activities of MRP2 were significantly decreased by PIP5K1C depletion. However, the transport activities of P-gp were unchanged by PIP5K1 depletion. PIP2 levels were unchanged between control and PIP5K1A- or PIP5K1C-depleted HepG2 cells. MRP2 mRNA levels showed few changes in HepG2 cells following PIP5K1A or PIP5K1C depletion. The expression of phosphorylated radixin was decreased by PIP5K1A and PIP5K1C depletion, although total radixin levels were unchanged. CONCLUSIONS: These data suggest that PIP5K1A and PIP5K1C could be target proteins for modulating MRP2 function, partly because of the resulting changes of the linker function of radixin.

Involvement of diclofenac acyl-ß-d-glucuronide in diclofenac-induced cytotoxicity in glutathione-depleted isolated murine hepatocytes co-cultured with peritoneal macrophages.

Direct hepatotoxic effects of drugs can occur when a parent drug and/or its reactive metabolites induces the formation of reactive oxygen species. Reactive metabolites of diclofenac (DIC) such as DIC acyl-ß-d-glucuronide (DIC-AG) bind covalently to proteins, potentially decreasing protein function or inducing an immune response. However, it is unclear whether the macrophages and GSH depletion participate in DIC-induced cytotoxicity. Mouse hepatocytes (Hep) co-cultured with peritoneal macrophages (PMs) were used to clarify the effects of presence of PM with GSH depletion on DIC-induced cytotoxicity in Hep. DIC-AG but not hydroxy-DIC concentrations in medium were significantly increased in Hep co-cultured with PM with GSH depletion. Depletion of GSH resulted in significantly higher LDH leakage. Interestingly, LDH leakage in Hep/PM (1:0.4) with GSH depletion was significantly higher than in Hep/PM (1:0 and 1:0.1) with BSO. It is likely that macrophages with GSH depletion could facilitate DIC-induced cytotoxicity.

Profiling of hepatic metabolizing enzymes and nuclear receptors in rats with adjuvant arthritis by targeted proteomics.

Inflammatory conditions alter the expression and activity of factors influencing pharmacokinetics, such as metabolizing enzymes. The study examined alterations of hepatic protein levels of cytochrome P450 (CYP), UDP-glucuronosyltransferase (UGT) and nuclear receptors in rats with adjuvant-induced arthritis (AA rats), an inflammatory animal model, by liquid chromatography-tandem mass spectrometry-based targeted proteomics. The protein levels of CYP1A1, CYP1A2, CYP2A1, CYP2A3, CYP2C6, CYP2C12, CYP2D3, CYP2E1, CYP3A9, UGT1A1 and UGT1A2/3 in liver microsomes of AA rats were significantly lower than those in control rats. The protein levels of constitutive androstane receptor (CAR) and retinoid X receptor α (RXRα) in the cytoplasm and nucleus were also significantly decreased, to approximately 60% of the control levels. The decreased protein levels of CYP1A2, CYP2C6, CYP2D3, CYP2E1 and UGT1A1 were potentially associated with downregulation of CAR or RXRα expression in the nucleus.

Stereoselective Pharmacokinetics and Chiral Inversion of Ibuprofen in Adjuvant-induced Arthritic Rats.

2-Arylpropionic acid (2-APA) nonsteroidal anti-inflammatory drugs are commonly used in racemic mixtures (rac) for clinical use. 2-APA undergoes unidirectional chiral inversion of the in vivo inactive R-enantiomer to the active S-enantiomer. Inflammation causes the reduction of metabolic activities of drug-metabolizing enzymes such as cytochrome P450 (P450) and UDP-glucuronosyltransferase. However, it is unclear whether inflammation affects the stereoselective pharmacokinetics and chiral inversion of 2-APA such as ibuprofen (IB). We examined the effects of inflammation on the pharmacokinetics of R-IB and S-IB after intravenous administration of rac-IB, R-IB, and S-IB to adjuvant-induced arthritic (AA) rats, an animal model of inflammation. The plasma protein binding of rac-IB, glucuronidation activities for R-IB and S-IB, and P450 contents of liver microsomes in AA rats were determined. Total clearance (CLtot) of IB significantly increased in AA rats, although the glucuronidation activities for IB, and P450 contents of liver microsomes decreased in AA rats. We presumed that the increased CLtot of IB in AA rats was caused by the elevated plasma unbound fraction of IB due to decreased plasma albumin levels in AA rats. Notably, CLtot of R-IB but not S-IB significantly increased in AA rats after intravenous administration of rac-IB. These results suggested that AA could affect drug efficacies after stereoselective changes in the pharmacokinetics of R-IB and S-IB.

Stereoselective hepatic disposition of ibuprofen in the perfused liver of rat with adjuvant-induced arthritis.

1. The effects of adjuvant-induced arthritis (AA) on the stereoselective hepatic disposition and chiral inversion of "profens" have scarcely been investigated. Ibuprofen (IB) undergoes unidirectional chiral inversion from R-IB to S-IB and is metabolized to IB-glucuronide (IB-Glu). 2. We used an in situ perfused rat liver system to clarify the effects of inflammation on the metabolic activities and chiral inversion of IB without protein binding. 3. After dosing of R-IB, AA had minimal effect on the elimination of R-IB from the perfusate. Larger amounts of S-IB-Glu than R-IB-Glu were observed in the bile at the dose of 2.4 and 4.8 µmol. However, after dosing of S-IB, the elimination of S-IB from the perfusate in AA rats was delayed, indicating a significant decrease in the hepatic clearance in AA rats. The cumulative biliary excretion of S-IB-Glu in AA rats was promoted after dosing with S-IB. There was little difference between the chiral inversion ratios of the control and AA rats. 4. The present study demonstrated that AA results in the delayed elimination of S-IB, the active form, without changes to the chiral inversion ratio. Thus, further attention to the altered stereoselective pharmacokinetics of IB during inflammation is required.

Involvement of Reactive Metabolites of Diclofenac in Cytotoxicity in Sandwich-Cultured Rat Hepatocytes.

BACKGROUND AND OBJECTIVES: Diclofenac (DIC) is metabolized to reactive metabolites such as diclofenac acyl-ß-d-glucuronide (DIC-AG). It is possible that such reactive metabolites could cause tissue damage by formation of covalent protein adducts and other modification of cellular proteins or by induction of immune responses against its covalent protein adducts. However, the detailed mechanisms of idiosyncratic drug-induced liver injury (DILI) have been unclear. The objective is to clarify the involvement of DIC-AG and 4'hydroxydiclofenac (4'OH-DIC) in acute DILI. METHODS: We examined the effects of inhibiting DIC-AG and 4'OH-DIC production on covalent protein adduct formation and lactate dehydrogenase leakage using sandwich-cultured rat hepatocytes (SCRHs). RESULTS: After pretreatment of SCRH with (-)-borneol (BOR, a uridine diphosphate (UDP)-glucuronosyltransferase inhibitor) or sulfaphenazole (SUL, a cytochrome P450 2C9 inhibitor) for 30 minutes, intracellular concentrations of DIC, DIC-AG, and 4'OH-DIC were determined after further treating cells with 300 µM DIC for 3 hours. The decreased levels of reactive metabolites caused by BOR or SUL pretreatment resulted in decreased lactate dehydrogenase leakage from SCRH, although the formation of covalent protein adducts was not affected. CONCLUSION: These results suggested that both DIC-AG and 4'OH-DIC may be involved in acute cytotoxicity by DIC.

Stereoselective Inhibition of Methotrexate Excretion by Glucuronides of Nonsteroidal Anti-inflammatory Drugs via Multidrug Resistance Proteins 2 and 4.

Combined administration of methotrexate (MTX) and nonsteroidal anti-inflammatory drugs (NSAIDs) can result in a decreased systemic clearance of MTX. To date, inhibition of renal uptake via organic anion transporters and efflux via multidrug resistance-associated protein (MRPs) by NSAIDs has been recognized as possible sites of drug interaction between MTX and NSAIDs. Although most NSAIDs are glucuronidated in kidney tissue and excreted mainly as glucuronide conjugates, it is not fully known whether the glucuronides of NSAIDs (NSAIDs-Glu) inhibit MTX excretion via MRP2 and MRP4. The purpose of this study was to investigate the inhibitory effects of the glucuronides of several NSAIDs (diclofenac, R- and S-ibuprofen, R- and S-flurbiprofen, and R- and S-naproxen), as well as the parent NSAIDs on MTX uptake using human MRP2- and MRP4-expressing inside-out vesicles. Results confirm that all NSAIDs and NSAIDs-Glu examined exhibited stereoselective and concentration-dependent inhibitory effects on MTX uptake via MRP2 and MRP4. Notably, NSAIDs-Glu potently inhibited MTX uptake via MRP2 and MRP4 compared with the corresponding parent NSAIDs except for naproxen in MRP2 and S-flurbiprofen in MRP4. The present results support that the glucuronides of NSAIDs, as well as the parent NSAIDs, are involved in the inhibition of urinary excretion of MTX via MRP2 and MRP4.

Pravastatin Modulate Niemann-Pick C1-Like 1 and ATP-Binding Cassette G5 and G8 to Influence Intestinal Cholesterol Absorption.

PURPOSE: Niemann-Pick C1-like 1 (NPC1L1), ATP-binding cassette (ABC)G5, and ABCG8 mediate intestinal cholesterol absorption. It is unclear whether pravastatin (PR) or ezetimibe (EZ) affect expression of these transporters. We examined the effects of PR and EZ on NPC1L1, ABCG5, and ABCG8 expression in human hepatoma HepG2 cells and the murine small intestine. We also assessed expression of the transcription factors liver X receptor (LXR)a, LXRb and sterol regulatory element-binding protein. METHODS: Transporter mRNA levels were determined in murine small intestines 6 and 24 h after oral PR and EZ administration by real-time reverse-transcriptase polymerase chain reaction (RT-PCR). In PR- and EZ-treated HepG2 cells, transporter and transcription factor mRNA and protein levels were examined by RT-PCR and western blot, respectively. RESULTS: Significant decreases in NPC1L1, ABCG5, and ABCG8 mRNA expression were observed in the duodenum, but not jejunum and ileum, of mice 24 h after treatment with PR, but not EZ. In HepG2 cells, PR but not EZ treatment for 24 h also significantly decreased NPC1L1 protein and ABCG5, and ABCG8 mRNA expression, while increasing LXRa mRNA levels. CONCLUSION: PR but not EZ treatment reduced duodenal cholesterol transporter expression in mice. PR-induced increases in LXRa mRNA levels may be involved in attenuation of NPC1L1 expression, subsequently decreasing intestinal cholesterol absorption.

Age-related changes in mRNA levels of hepatic transporters, cytochrome P450 and UDP-glucuronosyltransferase in female rats.

Hepatic transporters and metabolic enzymes affect drug pharmacokinetics. Limited information exists on the alteration in mRNA levels of hepatic transporters and metabolic enzymes with aging. We examined the effects of aging on the mRNA levels of representative hepatic drug transporters and metabolic enzymes by analyzing their levels in 10-, 30- and 50-week-old male and female rats. Levels of mRNA of drug transporters including multidrug resistance protein (Mdr)1a, multidrug resistance-associated protein (Mrp)2, breast cancer resistance protein (Bcrp) and organic anion-transporting polypeptide (Oatp)1a1, and the metabolic enzymes cytochrome P450 (CYP)3A1, CYP3A2 and UDP-glucuronosyltransferase (UGT)1A1 were analyzed using real-time reverse transcriptase polymerase chain reaction. The mRNA levels of transporters in male rats did not decrease with age, while the mRNA levels of Bcrp and Oatp1a1 in female rats decreased with age. The mRNA levels of CYP3A1 and CYP3A2 in male rats were higher than those in female rats. The mRNA levels of metabolic enzymes decreased with age in female but not male rats. In particular, the mRNA levels of UGT1A1 in 10-week-old female rats were higher than those in male rats. mRNA expression of hepatic transporters and metabolic enzymes are more susceptible to aging in female than male rats. The age-related decreases in the mRNA levels of Bcrp, Oatp1a1, CYP3A1 and CYP3A2 in female rats may affect the metabolism and transport of substrates. This study showed that aging affected the mRNA expression of hepatic transporters and metabolic enzymes in rats.