Phosphorylation/Dephosphorylation Steps Are Crucial for the Induction of CYP2B1 and CYP2B2 Gene Expression by Phenobarbital

Kawamura, Akino; Yoshida, Yukiko; Kimura, Noriko; Oda, Hiroaki; Kakinuma, Atsushi

doi:10.1006/bbrc.1999.1544

Cited by 40 publications

(31 citation statements)

References 36 publications

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“…This could indicate that in human primary hepatocytes EGF is acting as a negative regulator of PB-mediated gene expression, which is similar to reports in primary hepatocytes in the rat (Kawamura et al 1999) and mouse (Koike et al 2007). …”

Section: Discussionsupporting

confidence: 84%

“…We show that PB-mediated potentiation of Erk signalling appears to be specific to Egf as we could not demonstrate the same response with Hgf ( Figure 4). In primary rat hepatocytes, Egf has been reported to inhibit PB-induced Cyp2b1/2 mRNA, while Hgf did not (Kawamura et al 1999). However, in mouse primary hepatocytes both Egf and Hgf appear to be inhibitory to the PB response (Koike et al 2007).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2016

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

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

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

et al. 2016

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“…In rat hepatocyte cultures, Kawamura et al (1999) demonstrated a significant suppression of PBinduced CYP2B1/2B2 mRNA and protein when rat hepatocytes were concurrently exposed to TNF␣. The study described herein provides evidence that endogenous TNF␣ signaling inhibits the PB induction response of CY2B in mice.…”

Section: Discussionmentioning

confidence: 97%

Enhanced Induction of Cytochrome P450 Enzymes and CAR Binding in TNF (p55^−/−/p75^−/−) Double Receptor Knockout Mice Following Phenobarbital Treatment

Ess

Mattson

Blouin

2002

J Pharmacol Exp Ther

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Phenobarbital (PB) is a well characterized inducer of cytochrome P450 (P450) 2B and 3A subfamilies. Several proinflammatory cytokines have been shown to negatively modulate the induction of P450 by PB. In addition, PB is known to elicit an inflammatory mitogenic effect on the liver. To date, no studies have evaluated the PB induction profile of hepatic P450 in the absence of an intact tumor necrosis factor-alpha (TNF␣) response. To test the hypothesis that endogenous TNF␣ signaling modulates hepatic P450 induction by PB in vivo, PB induction was examined in TNF (p55 Ϫ/Ϫ /p75 Ϫ/Ϫ ) double receptor knockout mice (ko-TNF) and wild-type mice (wt-TNF). CYP2B-and CYP3A-associated activities and protein content were induced to a significantly greater extent (p Ͻ 0.05) in ko-TNF mice compared with wt-TNF mice. In parallel with enhanced CYP2B induction, an apparent elevation in the nuclear accumulation of the principal regulatory protein for transcription of CYP2B genes, the constitutively activated receptor (CAR), was detected in ko-TNF nuclear extracts following PB treatment. Additionally, nuclear factor -B binding was induced by PB in wt-TNF mice, but not in ko-TNF mice, indicating that the hepatic inflammatory response following PB treatment differed between wt-TNF and ko-TNF mice. These data demonstrate that endogenous TNF␣ signaling modulates PB induction of hepatic CYP2B and CYP3A isoforms in vivo. Further, the data presented herein suggest that endogenous TNF␣ signaling influences PB induction of CYP2B through inhibition of CAR nuclear accumulation.

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“…Although insulin repression of PB induction was reported for rat primary hepatocytes (17,42), it has not been demonstrated in mouse primary hepatocytes. Upon finding that FOXO1 is a key coactivator of CAR in HepG2 cells, we examined whether insulin repressed the induction of the Cyp2b10 gene by TCPOBOP in mouse primary hepatocytes (Fig.…”

Section: Figmentioning

confidence: 88%

“…In contrast, insulin is known to repress the induction of drug-metabolizing activity by certain drugs and in diabetic livers (44,49,56). Insulin treatment either eliminated or significantly reduced PB induction of CYP2B in rat primary hepatocytes (17,42,58). Hepatic CYP2B, CYP3A, and CYP4A were increased in experimentally generated diabetic rats and mice and were reduced to normal levels by insulin treatment (37, 56).…”

mentioning

confidence: 99%

Nuclear Receptors CAR and PXR Cross Talk with FOXO1 To Regulate Genes That Encode Drug-Metabolizing and Gluconeogenic Enzymes

Kodama

Koike

Negishi

et al. 2004

Molecular and Cellular Biology

301

269

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The nuclear receptors CAR and PXR activate hepatic genes in response to therapeutic drugs and xenobiotics, leading to the induction of drug-metabolizing enzymes, such as cytochrome P450. Insulin inhibits the ability of FOXO1 to express genes encoding gluconeogenic enzymes. Induction by drugs is known to be decreased by insulin, whereas gluconeogenic activity is often repressed by treatment with certain drugs, such as phenobarbital (PB). Performing cell-based transfection assays with drug-responsive and insulin-responsive enhancers, glutathione S-transferase pull down, RNA interference (RNAi), and mouse primary hepatocytes, we examined the molecular mechanism by which nuclear receptors and FOXO1 could coordinately regulate both enzyme pathways. FOXO1 was found to be a coactivator to CAR-and PXR-mediated transcription. In contrast, CAR and PXR, acting as corepressors, downregulated FOXO1-mediated transcription in the presence of their activators, such as 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) and pregnenolone 16␣-carbonitrile, respectively. A constitutively active mutant of the insulin-responsive protein kinase Akt, but not the kinase-negative mutant, effectively blocked FOXO1 activity in cell-based assays. Thus, insulin could repress the receptors by activating the Akt-FOXO1 signal, whereas drugs could interfere with FOXO1-mediated transcription by activating CAR and/or PXR. Treatment with TCPOBOP or PB decreased the levels of phosphoenolpyruvate carboxykinase 1 mRNA in mice but not in Car ؊/؊ mice. We conclude that FOXO1 and the nuclear receptors reciprocally coregulate their target genes, modulating both drug metabolism and gluconeogenesis.Liver plays a major role in the metabolism of therapeutic drugs and environmental contaminants. It is endowed with a mechanism to induce hepatic enzymes, leading to increased detoxification and elimination of those xenobiotics. Drug induction is generally regulated by transcriptional activation of hepatic genes encoding drug-metabolizing enzymes, such as cytochrome P450s (CYPs) and specific transferases. Acting as the principal transcription factors which also form complexes with RXR, the nuclear receptors CAR and PXR play a central role in induction by binding to the phenobarbital (PB)-and xenobiotic-responsive enhancer modules PBREM and XREM (5,6,11,12,18,46,53), respectively, and activating transcription of their target genes, such as CYP genes, in response to a distinct but overlapping group of xenobiotics (23, 36, 50). However, induction is heavily influenced by endocrine conditions; glucocorticoid hormone, for example, augments CYP induction by PB (31). In contrast, insulin is known to repress the induction of drug-metabolizing activity by certain drugs and in diabetic livers (44,49,56). Insulin treatment either eliminated or significantly reduced PB induction of CYP2B in rat primary hepatocytes (17,42,58). Hepatic CYP2B, CYP3A, and CYP4A were increased in experimentally generated diabetic rats and mice and were reduced to normal levels by insulin treatmen...

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Phosphorylation/Dephosphorylation Steps Are Crucial for the Induction of CYP2B1 and CYP2B2 Gene Expression by Phenobarbital

Cited by 40 publications

References 36 publications

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

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

Enhanced Induction of Cytochrome P450 Enzymes and CAR Binding in TNF (p55^−/−/p75^−/−) Double Receptor Knockout Mice Following Phenobarbital Treatment

Nuclear Receptors CAR and PXR Cross Talk with FOXO1 To Regulate Genes That Encode Drug-Metabolizing and Gluconeogenic Enzymes

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Phosphorylation/Dephosphorylation Steps Are Crucial for the Induction of CYP2B1 and CYP2B2 Gene Expression by Phenobarbital

Cited by 40 publications

References 36 publications

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

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

Enhanced Induction of Cytochrome P450 Enzymes and CAR Binding in TNF (p55−/−/p75−/−) Double Receptor Knockout Mice Following Phenobarbital Treatment

Nuclear Receptors CAR and PXR Cross Talk with FOXO1 To Regulate Genes That Encode Drug-Metabolizing and Gluconeogenic Enzymes

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Enhanced Induction of Cytochrome P450 Enzymes and CAR Binding in TNF (p55^−/−/p75^−/−) Double Receptor Knockout Mice Following Phenobarbital Treatment