Localization and characterization of cytochrome P450 in the brain. In vivo and in vitro investigations on phenytoin- and phenobarbital-inducible isoforms

Volk, Benedikt; Meyer, Ralf Peter; Lintig, Friederike von; Ibach, Bernd; Knoth, Rolf

doi:10.1016/0378-4274(95)03511-7

Cited by 39 publications

(23 citation statements)

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“…Immunohistochemical studies with antibodies against hepatic CYP2B1/2 isoforms revealed the presence of P450 isoform(s) in rat astrocytes and endothelial cells in vivo and in vitro (Kempermann et al, 1994;Volk et al, 1995). Their inducibility by the anticonvulsant drug phenytoin has been demonstrated in mouse brain (Volk et al, 1988).…”

Section: Introductionmentioning

confidence: 94%

Effect of phenytoin on cytochrome P450 2B mRNA expression in primary rat astrocyte cultures

et al. 1998

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Studies on cytochrome P450 2B (CYP2B) in the brain have essentially been focused on protein characterization and regional distribution. Due to the high sequence homology between the closely related CYP2B1 and 2B2 isoforms and the low amounts of the corresponding mRNAs few efforts have been made to analyze the expression, regulation, and inducibility of these P450 genes in a specific cell type. In the present study, we investigated CYP2B mRNA expression in primary rat astrocyte cultures under the influence of the anti-epileptic drug phenytoin, which is known to be a CYP2B inducing agent in liver. In situ hybridization with a digoxigenin (DIG)-labeled cRNA probe demonstrated that 30-40% of the astrocytes strongly expressed a CYP2B mRNA-specific signal within the first week of cultivation. With increasing age (> 14 days) a greater percentage of cells (>90%) expressed mRNA for P450 2B. However, the level of transcriptional activity was substantially lower than in younger cultures. To discriminate between the 2B1 and 2B2 isoforms the reverse transcription/polymerase chain reaction (RT/PCR) procedures were proved for rat hepatic mRNA as a control assay. Subsequently, the application of this method on cultured astrocytes confirmed that these brain cells may express CYP2B1 mRNA. CYP2B2 mRNA could not be detected in astrocyte cultures at any age examined. Phenytoin led to the down regulation of CYP2B1 mRNA, which contrasts with the drug inducing effect on hepatic CYP2B1 and 2B2 levels. After 4 hr of exposure of phenytoin to the astrocytes no amplification product could be detected at all. Phenytoin did not induce either CYP2B1 or 2B2 expression.

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Section: Introductionmentioning

confidence: 94%

Effect of phenytoin on cytochrome P450 2B mRNA expression in primary rat astrocyte cultures

et al. 1998

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“…However, it is now evident that P450s are expressed in a number of extrahepatic tissues, including brain (Ding and Kaminsky, 2003;Ferguson and Tyndale, 2011). Although total P450 content in the human and rodent brain is generally significantly lower than that in the liver (Warner et al, 1988;Bhamre et al, 1992;Volk et al, 1995), recent evidence from rat studies demonstrates that P450-mediated metabolism in the brain can contribute significantly to neurotoxicity (Khokhar and Tyndale, 2012;Zhou et al, 2013). These data coupled with reports that P450 expression in the brain may vary between anatomic regions of the brain (Warner et al, 1988;Dutheil et al, 2009) have led to growing interest in the putative role of brain P450s in determining sensitivity and response to neurotoxic compounds via modulation of local metabolite levels (Meyer et al, 2007;Ferguson and Tyndale, 2011;Ravindranath and Strobel, 2013).…”

Section: Introductionmentioning

confidence: 99%

Cytochrome P450 mRNA Expression in the Rodent Brain: Species-, Sex-, and Region-Dependent Differences

Stamou

Kania-Korwel

et al. 2013

Drug Metab Dispos

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Cytochrome P450 (P450) enzymes play a critical role in the activation and detoxication of many neurotoxic chemicals. Although research has largely focused on P450-mediated metabolism in the liver, emerging evidence suggests that brain P450s influence neurotoxicity by modulating local metabolite levels. As a first step toward better understanding the relative role of brain P450s in determining neurotoxic outcome, we characterized mRNA expression of specific P450 isoforms in the rodent brain. Adult mice (male and female) and rats (male) were treated with vehicle, phenobarbital, or dexamethasone. Transcripts for CYP2B, CYP3A, CYP1A2, and the orphan CYP4X1 and CYP2S1 were quantified in the liver, hippocampus, cortex, and cerebellum by quantitative (real-time) polymerase chain reaction. These P450s were all detected in the liver with the exception of CYP4X1, which was detected in rat but not mouse liver. P450 expression profiles in the brain varied regionally. With the exception of the hippocampus, there were no sex differences in regional brain P450 expression profiles in mice; however, there were marked species differences. In the liver, phenobarbital induced CYP2B expression in both species. Dexamethasone induced hepatic CYP2B and CYP3A in mice but not rats. In contrast, brain P450s did not respond to these classic hepatic P450 inducers. Our findings demonstrate that P450 mRNA expression in the brain varies by region, regional brain P450 profiles vary between species, and their induction varies from that of hepatic P450s. These novel data will be useful for designing mechanistic studies to examine the relative role of P450-mediated brain metabolism in neurotoxicity. IntroductionThe cytochrome P450 (P450) superfamily is a diverse group of enzymes that catalyze the oxidative metabolism of not only endogenous substrates but also xenobiotics, including environmental contaminants of significant public health concern that target the nervous system, including polychlorinated biphenyls, polybrominated diphenyl ethers, and organophosphorus pesticides (Ariyoshi et al., 1995;Foxenberg et al., 2007;Erratico et al., 2013;Feo et al., 2013). Biotransformation of these compounds by P450s can result in bioactivation or detoxication, and the balance between these activities influences the bioeffective dose, and thus the neurotoxic outcome, following environmental exposures, as shown in studies of humans and animal models (Foxenberg et al., 2007;Curran et al., 2011;Kim et al., 2011;Crane et al., 2012;Khokhar and Tyndale, 2012).Much of the research effort to characterize P450-mediated metabolism of neurotoxic compounds has focused on the liver. However, it is now evident that P450s are expressed in a number of extrahepatic tissues, including brain (Ding and Kaminsky, 2003;Ferguson and Tyndale, 2011). Although total P450 content in the human and rodent brain is generally significantly lower than that in the liver (Warner et al., 1988;Bhamre et al., 1992;Volk et al., 1995), recent evidence from rat studies demonstrates that P45...

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“…We applied the commonly used CYP3A-inducers phenytoin and phenobarbital as equivalents in both cell lines (Volk et al, 1995).…”

Section: Induction Model: Treatment Of Hepatic and Neuronal Cells Witmentioning

confidence: 99%

“…Although the main site for P450-dependent drug metabolism is the liver, P450 isoforms also occur in defined neuronal or glial cell populations of the brain (Volk et al, 1995;Strobel et al, 2001). The function of P450 in brain is poorly understood and the object of intense discussion.…”

mentioning

confidence: 99%

“…These compounds have a lipophilic structure that facilitates passing the blood-brain barrier and penetration into the central nervous system (Meyer et al, 2004). The cerebral isoforms CYP2B1, CYP2B10, CYP2C29, CYP3A11, and CYP3A13 have been found to be inducible by antiepileptic drugs (AEDs) such as phenytoin or phenobarbital in rats and mice (Volk et al, 1995;Thuerl et al, 1997;Meyer et al, 2001;Hagemeyer et al, 2003). Therefore, a major endeavor in clinic and research is to understand the underlying molecular mechanisms of drug therapy within the central nervous system to improve present therapeutic strategies.…”

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confidence: 99%

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Antiepileptic Drugs Affect Neuronal Androgen Signaling via a Cytochrome P450-Dependent Pathway

Gehlhaus

Schmitt²,

Volk³

et al. 2007

J Pharmacol Exp Ther

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Localization and characterization of cytochrome P450 in the brain. In vivo and in vitro investigations on phenytoin- and phenobarbital-inducible isoforms

Cited by 39 publications

References 9 publications

Effect of phenytoin on cytochrome P450 2B mRNA expression in primary rat astrocyte cultures

Effect of phenytoin on cytochrome P450 2B mRNA expression in primary rat astrocyte cultures

Cytochrome P450 mRNA Expression in the Rodent Brain: Species-, Sex-, and Region-Dependent Differences

Antiepileptic Drugs Affect Neuronal Androgen Signaling via a Cytochrome P450-Dependent Pathway

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