Characterization of a phenobarbital-inducible cytochrome P-450, NADPH-cytochrome P-450 reductase and reconstituted cytochrome P-450 mono-oxygenase system from rat brain. Evidence for constitutive presence in rat and human brain

Anandatheerthavarada, Hindupur K.; Boyd, Michael R.; Ravindranath, Vijayalakshmi

doi:10.1042/bj2880483

Cited by 26 publications

(7 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One variant of CYP2B6, CYP2B6*6, results in a reduction of CYP2B protein levels (Lang, 2001); this protein reduction is also found in the brains of individuals with a CYP2B6*6 allele (Miksys, 2003). CYP2B expression can also be altered by environmental factors: for example, phenobarbital can induce CYP2B expression in both the liver and brain of rats (Anandatheerthavarada et al, 1992;Schilter and Omiecinski, 1993) and monkeys (Lee et al, 2006). Thus, variation in brain CYP2B activity may alter levels of a substrate locally, possibly altering the resulting drug response.…”

Section: Cyp2b Expression Is Influenced By Both Genetic and Environmementioning

confidence: 96%

Effect of Brain CYP2B Inhibition on Brain Nicotine Levels and Nicotine Self-Administration

Garcia

Coen

Miksys

et al. 2015

Neuropsychopharmacol

View full text Add to dashboard Cite

The CYP2B enzyme is expressed in human and rat brain, and metabolizes many CNS-acting drugs. The gene that encodes human CYP2B6 is highly polymorphic, where the variation in brain enzyme levels could result in altered brain drug levels. CYP2B can metabolize nicotine, the main psychoactive ingredient in cigarettes; if altered brain CYP2B activity can influence nicotine brain levels, it could influence nicotine-mediated behaviors. To investigate this, a mechanism-based inhibitor selective for CYP2B, C8-xanthate (20 μg), was administered intracerebroventricularly (ICV) into the brain of rats, and 22 h later, nicotine levels were measured by in vivo microdialysis following nicotine (150 μg/kg intravenous). Brain nicotine levels from 15 to 30 min and the AUC0-45 min were both twofold higher (p<0.05) with C8-xanthate vs vehicle pretreatment; there was no difference in peripheral nicotine levels. Rats were then given ICV pretreatment with C8-xanthate/ASCF and underwent intravenous nicotine self-administration with 3.75-30 μg/kg per infusion dose. C8-xanthate pretreatment increased responding in progressive ratio (15 μg/kg per infusion dose, p<0.05). In a separate cohort, C8-xanthate increased the percentage of rats that acquired self-administration (7.5 μg/kg per infusion dose, p<0.05) from 40% after vehicle pretreatment to 100%, with no difference in peripheral nicotine levels measured at the end of behavior. In a third cohort, C8-xanthate increased the number of sessions required to meet extinction criteria (p<0.05). Together these data demonstrate that the brain CYP2B activity can influence nicotine brain levels and subsequent behaviors independent of hepatic metabolism. This suggests that human smokers with variable CYP2B brain levels could have different nicotine levels and reinforcement, which might have a role in smoking behaviors and dependence.

show abstract

Section: Cyp2b Expression Is Influenced By Both Genetic and Environmementioning

confidence: 96%

Effect of Brain CYP2B Inhibition on Brain Nicotine Levels and Nicotine Self-Administration

Garcia

Coen

Miksys

et al. 2015

Neuropsychopharmacol

View full text Add to dashboard Cite

show abstract

“…Phenobarbital induction of human hepatic CYP2B6 is well documented (Wang & Negishi, 2003); however, nothing is known about phenobarbital induction of human CYP2B6 in brain. Studies show that rat brain CYP2B1 protein (Anandatheerthavarada et al ., 1992) and mRNA (Schilter & Omiecinski, 1993; Schilter et al ., 2000) are induced after phenobarbital treatment.…”

Section: Introductionmentioning

confidence: 99%

Phenobarbital increases monkey in vivo nicotine disposition and induces liver and brain CYP2B6 protein

Lee

Miksys

Tyndale

2006

British J Pharmacology

View full text Add to dashboard Cite

1 CYP2B6 is a drug-metabolizing enzyme expressed in the liver and brain that can metabolize bupropion (Zyban s , a smoking cessation drug), activate tobacco-smoke nitrosamines, and inactivate nicotine. Hepatic CYP2B6 is induced by phenobarbital and induction may affect in vivo nicotine disposition, while brain CYP2B6 induction may affect local levels of centrally acting substrates. We investigated the effect of chronic phenobarbital treatment on induction of in vivo nicotine disposition and CYP2B6 expression in the liver and brain of African Green (Vervet) monkeys. 2 Monkeys were split into two groups (n ¼ 6 each) and given oral saccharin daily for 22 days; one group was supplemented with 20 mg kg À1 phenobarbital. Monkeys were given a 0.1 mg kg À1 nicotine dose subcutaneously before and after treatment. 3 Phenobarbital treatment resulted in a significant, 56%, decrease (P ¼ 0.04) in the maximum nicotine plasma concentration and a 46% decrease (P ¼ 0.003) in the area under the concentration-time curve. Phenobarbital also increased hepatic CYP2B6 protein expression. In monkey brain, significant induction (Po0.05) of CYP2B6 protein levels was observed in all regions tested (caudate, putamen, hippocampus, cerebellum, brain stem and frontal cortex) ranging from 2-fold to 150-fold. CYP2B6 expression was induced in specific cells, such as frontal cortical pyramidal cells and thalamic neurons. 4 In conclusion, chronic phenobarbital treatment in monkeys resulted in increased in vivo nicotine disposition, and induced hepatic and brain CYP2B6 protein levels and cellular expression. This induction may alter the metabolism of CYP2B6 substrates including peripherally acting drugs such as cyclophosphamide and centrally acting drugs such as bupropion, ecstasy and phencyclidine.

show abstract

“…Total cytochrome P450 content in membrane preparation was measured from a carbon monoxide reduced minus oxidized difference spectrum (9). Membrane preparation (150 g of protein) was incubated at 37°C in Tris-HCl (50 mM, pH 7.4) containing 20 mM MgCl 2 , 1 unit of purified liver NADPH-cytochrome P450 reductase (20), and 0.01-1 mM codeine. The reaction was initiated by the addition of 1 mM NADPH and stopped after 30 min by addition of acetonitrile (10% of total volume).…”

mentioning

confidence: 99%

A Frameshift Mutation and Alternate Splicing in Human Brain Generate a Functional Form of the Pseudogene Cytochrome P4502D7 That Demethylates Codeine to Morphine

Pai

Kommaddi

Chinta

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

A frameshift mutation 138delT generates an open reading frame in the pseudogene, cytochrome P4502D7 (CYP2D7), and an alternate spliced functional transcript of CYP2D7 containing partial inclusion of intron 6 was identified in human brain but not in liver or kidney from the same individual. mRNA and protein of the brain variant CYP2D7 were detected in 6 of 12 human autopsy brains. Genotyping revealed the presence of the frameshift mutation 138delT only in those human subjects who expressed the brain variant CYP2D7. Genomic DNA analysis in normal volunteers revealed the presence of functional CYP2D7 in 4 of 8 individuals. In liver, the major organ involved in drug metabolism, a minor metabolic pathway mediated by CYP2D6 metabolizes codeine (pro-drug) to morphine (active drug), whereas norcodeine is the major metabolite. In contrast, when expressed in Neuro2a cells, brain variant CYP2D7 metabolized codeine to morphine with greater efficiency compared with the corresponding activity in cells expressing CYP2D6. Morphine binds to -opioid receptors in certain regions of the central nervous system, such as periaqueductal gray, and produces pain relief. The brain variant CYP2D7 and -opioid receptor colocalize in neurons of the periaqueductal gray area in human brain, indicating that metabolism of codeine to morphine could occur at the site of opioid action. Histiospecific isoforms of P450 generated by alternate splicing, which mediate selective metabolism of pro-drugs within tissues, particularly the brain, to generate active drugs may play an important role in drug action and provide newer insights into the genetics of metabolism.Cytochrome P450 (EC 1.14.14.1; P450) 1 and associated monooxygenases, a family of heme proteins, are the principal class of drug-metabolizing enzymes. A supergene family encodes them, and the member proteins exist as multiple forms having distinct yet overlapping substrate specificities. Multiple forms of P450, which are selectively induced or inhibited by a variety of drugs, are known to exist in liver, the major organ involved in P450-mediated metabolism (1). However, the potential to generate active metabolite(s) at the site of action has generated interest in extrahepatic P450. This has prompted extensive investigations into the xenobiotic metabolizing capability of extrahepatic organs, such as lung, kidney, skin, and nasal epithelium, and the far reaching consequences of such metabolism, in situ, within specific cells in target organs have been recognized in laboratory animals (2) and humans (3). The preferential localization of drug-metabolizing enzymes within specific cell types in these organs renders such cells significantly capable of metabolizing drugs (4). Thus, even minor metabolic pathways of xenobiotic metabolism can produce major effects if they take place at the site of action. These observations have prompted investigation into P450-associated monooxygenases in brain with an effort to determine the capability of the brain to metabolize psychoactive drugs (5, 6). P450-mediated ...

show abstract

Characterization of a phenobarbital-inducible cytochrome P-450, NADPH-cytochrome P-450 reductase and reconstituted cytochrome P-450 mono-oxygenase system from rat brain. Evidence for constitutive presence in rat and human brain

Cited by 26 publications

References 30 publications

Effect of Brain CYP2B Inhibition on Brain Nicotine Levels and Nicotine Self-Administration

Effect of Brain CYP2B Inhibition on Brain Nicotine Levels and Nicotine Self-Administration

Phenobarbital increases monkey in vivo nicotine disposition and induces liver and brain CYP2B6 protein

A Frameshift Mutation and Alternate Splicing in Human Brain Generate a Functional Form of the Pseudogene Cytochrome P4502D7 That Demethylates Codeine to Morphine

Contact Info

Product

Resources

About