Antiepileptic Drug-Activated Constitutive Androstane Receptor Inhibits Peroxisome Proliferator-Activated Receptor and Peroxisome Proliferator-Activated Receptor Coactivator 1-Dependent Gene Expression to Increase Blood Triglyceride Levels.

Long-term administration of some antiepileptic drugs often increases blood lipid levels. In this study, we investigated its molecular mechanism by focusing on the nuclear receptors constitutive active/androstane receptor (CAR) and peroxisome proliferator-activated receptor (PPAR), which are key transcription factors for enzyme induction and lipid metabolism, respectively, in the liver. Treatment of mice with the CAR activator phenobarbital, an antiepileptic drug, increased plasma triglyceride levels and decreased the hepatic expression of PPAR target genes related to lipid metabolism.

Nuclear receptor CAR-ERα signaling regulates the estrogen sulfotransferase gene in the liver.

Estrogen sulfotransferase (SULT1E1) inactivates estrogen and regulates its metabolic homeostats. Whereas SULT1E1 is expressed low in the liver of adult mice, it is induced by phenobarbital (PB) treatment or spontaneously in diabetic livers via nuclear receptors. Utilizing constitutive active/androstane receptor (CAR) KO, estrogen receptor α (ERα KO, phosphorylation-blocked ERα S216A KI mice, it is now demonstrated that, after being activated by PB, CAR binds and recruits ERα onto the Sulte1 promoter for subsequent phosphorylation at Ser216.

Enhancement of InN Luminescence by Introduction of Graphene Interlayer.

Indium nitride (InN) luminescence is substantially enhanced by the introduction of a multilayer graphene interlayer, mitigating the lattice mismatch between the InN epilayer and the Gallium nitride (GaN) template on a sapphire substrate via weak van der Waals interaction between graphene and nitride layers. The InN epilayers are deposited by radio-frequency plasma-assisted molecular beam epitaxy (MBE), and are characterized by spatially-resolved photoluminescence spectroscopy using confocal microscopy. A small blue shift of the emission band from the band gap evidences a low density of equilibrium carriers, and a high quality of InN on multilayer graphene.

Effect of the metabolic capacity in rat liver S9 on the positive results of in vitro micronucleus tests.

A high incidence of positive results is obtained with in vitro genotoxicity tests, which do not correlate with the in vivo negative results in many cases. To address this issue, the metabolic profile of rat liver 9000 × g supernatant fraction (S9) pretreated with phenobarbital (PB) and 5,6-benzoflavone (BNF) was characterized. Furthermore, the in vitro micronucleus tests of 10 compounds were performed with PB-BNF-induced rat S9.

Decreased hepatic phosphorylated p38 mitogen-activated protein kinase contributes to attenuation of thioacetamide-induced hepatic necrosis in diet-induced obese mice.

We previously reported that thioacetamide (TA)-induced hepatocellular necrosis was attenuated in mice fed a high-fat diet (HFD mice) compared with mice fed a normal rodent diet (ND mice). In this study, we investigated whether p38 mitogen-activated protein kinase (p38 MAPK) was involved in this attenuation. Western blot analysis revealed that hepatic phosphorylated p38 MAPK protein decreased at 8 and 24 hours (hr) after TA dosing in the HFD mice, while it decreased only at 24 hr in the ND mice in comparison to the time- and diet-matched, vehicle-treated mice.

Role of connexin 32 in acetaminophen toxicity in a knockout mice model.

Gap junctional intercellular communication (GJIC), by which glutathione (GSH) and inorganic ions are transmitted to neighboring cells, is recognized as being largely involved in toxic processes of chemicals. We examined acetaminophen (APAP)-induced hepatotoxicity clinicopathologically using male wild-type mice and mice lacking the gene for connexin32, a major gap junction protein in the liver [knockout (Cx32KO) mice]. When APAP was intraperitoneally administered at doses of 100, 200, or 300mg/kg, hepatic centrilobular necrosis with elevated plasma aminotransferase activities was observed in wild-type mice receiving 300mg/kg, and in Cx32KO mice given 100mg/kg or more.

Thioacetamide-induced Hepatocellular Necrosis Is Attenuated in Diet-induced Obese Mice.

To assess modification of thioacetamide-induced hepatotoxicity in mice fed a high-fat diet, male C57BL/6J mice were fed a normal rodent diet or a high-fat diet for 8 weeks and then treated once intraperitoneally with thioacetamide at 50 mg/kg body weight. At 24 and 48 hours after administration, massive centrilobular hepatocellular necrosis was observed in mice fed the normal rodent diet, while the necrosis was less severe in mice fed the high-fat diet. In contrast, severe swelling of hepatocytes was observed in mice fed the high-fat diet.

Utilization of glutathione S-transferase Mu 1- and Theta 1-null mice as animal models for absorption, distribution, metabolism, excretion and toxicity studies.

Introduction: Glutathione S-transferases (GSTs) are Phase II drug-metabolizing enzymes that catalyze the conjugation of electrophilic compounds to glutathione. This reaction generally detoxifies reactive metabolites of xenobiotics, such as drugs and environmental chemicals, and therefore, GSTs are considered toxicologically important enzymes. Human GST genes display genetic polymorphisms, and the impact of null genotypes of GST Mu 1 (GSTM1) and GST Theta 1 (GSTT1) have been extensively studied.

Resistance to acetaminophen-induced hepatotoxicity in glutathione S-transferase Mu 1-null mice.

We investigated the role of glutathione S-transferases Mu 1 (GSTM1) in acetaminophen (APAP)-induced hepatotoxicity using Gstm1-null mice. A single oral administration of APAP resulted in a marked increase in plasma alanine aminotransferase accompanied by hepatocyte necrosis 24 hr after administration in wild-type mice, but its magnitude was unexpectedly attenuated in Gstm1-null mice. Therefore, it is suggested that Gstm1-null mice are resistant to APAP-induced hepatotoxicity.

Evaluation of hepatic glutathione transferase Mu 1 and Theta 1 activities in humans and mice using genotype information.

We investigated the impact of glutathione transferases Mu 1 (GSTM1)- and glutathione transferase Theta 1 (GSTT1)-null genotypes on hepatic GST activities in humans and compared the results with those of Gstm1- and Gstt1-null mice. In liver with GSTM1/Gstm1-null genotype, GST activity toward p-nitrobenzyl chloride (NBC) was significantly decreased in both humans and mice. In addition, in liver with GSTT1/Gstt1-null genotype, GST activity toward dichloromethane (DCM) was significantly decreased in both humans and mice.

Sex and circadian modulatory effects on rat liver as assessed by transcriptome analyses.

The present study was designed to fully uncover sex and circadian modulatory effects on rat liver. Hepatic transcriptome analyses were performed at 4 hr intervals of a day-night cycle using young adult male and female rats. Sexually dimorphic genes, which were identified by a cross-sex comparison of time series data, included representative sex-predominant genes such as male- or female-predominant cytochrome P450 subfamilies (Cyp2c11, Cyp2c12, Cyp2c13, and Cyp3a2), sulfotransferases, and glutathione S-transferase Yc2.

Circadian modulation of hepatic transcriptome in transgenic rats expressing human growth hormone.

The secretory profile of growth hormone (GH) is sexually dimorphic in rats. In male transgenic (TG) rats expressing human GH (hGH) that we generated, the circulating levels of both hGH and endogenous GH are flattened with no male-type pulsatility. To elucidate the regulatory role of episodic GH profile on the liver, the hepatic transcriptome of male TG rats at the middle of the light and dark phases was characterized by genome-wide analyses as compared with that of male wild-type (WT) rats.

Methemoglobinemia induced by 1,2-dichloro-4-nitrobenzene in mice with a disrupted glutathione S-transferase Mu 1 gene.

A specific substrate to Mu class glutathione S-transferase (GST), 1,2-dichloro-4-nitrobenzene (DCNB), was administered to mice with a disrupted GST Mu 1 gene (Gstm1-null mice) to investigate the in vivo role of murine Gstm1 in toxicological responses to DCNB. A single oral administration of DCNB at doses of 500 and 1000 mg/kg demonstrated a marked increase in blood methemoglobin (MetHB) in Gstm1-null mice but not in wild-type mice. Therefore, Gstm1-null mice were considered to be more predisposed to methemoglobinemia induced by a single dosing of DCNB.

Comprehensive analysis of hepatic gene and protein expression profiles on phenobarbital- or clofibrate-induced hepatic hypertrophy in dogs.

In order to characterize the hepatic effects of phenobarbital (PB) and clofibrate (CPIB) in dogs, PB and CPIB were administered to male beagle dogs for 14 days, and biochemical and histopathological examinations and comprehensive genomic and proteomic analyses, including GeneChip analysis and proteomics analysis using the 2-dimension difference gel electrophoresis (2D-DIGE) technique, were performed. Both compounds caused centrilobular hepatocellular hypertrophy, which were related to smooth endoplasmic reticulum (SER) proliferation in PB-treated dogs and to mitochondrial proliferation in CPIB-treated dogs. In the PB-treated dogs, drug-metabolizing enzyme induction was observed by Western blot and genomic analyses.

Sensitivity of liver injury in heterozygous Sod2 knockout mice treated with troglitazone or acetaminophen.

Recently, it was reported that the intraperitoneal administration of 30 mg/kg/day troglitazone to heterozygous superoxide dismutase 2 gene knockout (Sod2+/-) mice for twenty-eight days caused liver injury, manifested by increased serum ALT activity and hepatic necrosis. Therefore, we evaluated the reproducibility of troglitazone-induced liver injury in Sod2+/- mice, as well as their validity as an animal model with higher sensitivity to mitochondrial toxicity by single-dose treatment with acetaminophen in Sod2+/- mice. Although we conducted a repeated dose toxicity study in Sod2+/- mice treated orally with 300 mg/kg/day troglitazone for twenty-eight days, no hepatocellular necrosis was observed in our study.

Toxicokintic and toxicodynamic analysis of clofibrate based on free drug concentrations in nagase analbuminemia rats (NAR).

Toxicokinetics (TK) is usually performed by measurement of the total drug concentrations in plasma. However, free drug concentrations in plasma are considered to correlate directly with toxicodynamics (TD). In the present study, to evaluate the applicability of TK/TD analysis based on free drug concentrations, we investigated the TK/TD of clofibrate, which binds to albumin with a higher ratio, using an albumin-deficient mutant strain, Nagase analbuminemia rats (NAR).

Generation and functional characterization of mice with a disrupted glutathione S-transferase, theta 1 gene.

Glutathione S-transferase (GST) theta 1 (GSTT1) has been regarded as one of the key enzymes involved in phase II reactions because of its unique substrate specificity. In this study, we generated mice with the disrupted Gstt1 gene (Gstt1-null mice) by gene targeting and analyzed the metabolic properties in cytosolic and in vivo studies. The resulting Gstt1-null mice failed to express the Gstt1 mRNA and GSTT1 protein by reverse transcriptase-polymerase chain reaction analysis and two-dimensional fluorescence difference gel electrophoresis/mass spectrometry analysis, respectively.

Characterization of phenotypes in Gstm1-null mice by cytosolic and in vivo metabolic studies using 1,2-dichloro-4-nitrobenzene.

Glutathione S-transferase Mu 1 (GSTM1) has been regarded as one of the key enzymes involved in phase II reactions in the liver, because of its high expression level. In this study, we generated mice with disrupted glutathione S-transferase Mu 1 gene (Gstm1-null mice) by gene targeting, and characterized the phenotypes by cytosolic and in vivo studies. The resulting Gstm1-null mice appeared to be normal and were fertile.

Effects of restricted feeding on daily fluctuations of hepatic functions including p450 monooxygenase activities in rats.

Hepatic P450 monooxygenase activities, assessed by measurement of 7-alkoxycoumarin O-dealkylase (ACD) activities, show obvious daily fluctuations in male rats with high values during the dark period and low values during the light period. We have already confirmed that the ACD activities are controlled by the suprachiasmatic nucleus (SCN), which is well known as the oscillator of circadian rhythm. Recently, it is reported that circadian oscillators exist not only in the SCN but also in peripheral organs.

Expression of the theta class GST isozyme, YdfYdf, in low GST dogs.

We have reported the existence of low glutathione S-transferase (GST) dogs whose GST activity to 1,2-dichloro-4-nitrobenzene (DCNB) as a substrate (GST-D activity) is quite low, and have also reported significant individual differences in dog liver GST-D activity. The dogs were classified as "low", "middle", or "high" GST dogs based on their GST-D activity. In the present study, in order to investigate the causes of quite low GST-D activity in low GST dogs and the individual differences in dog GST-D activity, glutathione (GSH) conjugation of DCNB was kinetically analyzed.

A novel model of continuous depletion of glutathione in mice treated with L-buthionine (S,R)-sulfoximine.

L-buthionine (S,R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, was administered to mice via drinking water for 14 days in order to establish an animal model with continuously depleted levels of GSH. No toxicity was observed at 20 mM BSO, even though a significant decrease in liver weight was observed at 30 mM BSO. GSH levels in the liver, kidney, brain, lung, heart, spleen, pancreas, small intestine, large intestine, skeletal muscle, plasma and blood cells from mice given 20 mM of BSO were all less than those from the control mice continuously throughout a 24-hr period.