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Sample records for p450 isoforms 2d6

  1. Selective inhibition of the cytochrome P450 isoform by hyperoside and its potent inhibition of CYP2D6.

    PubMed

    Song, Min; Hong, Miri; Lee, Min Young; Jee, Jun-Goo; Lee, You Mie; Bae, Jong-Sup; Jeong, Tae Cheon; Lee, Sangkyu

    2013-09-01

    Hyperoside, quercetin-3-O-galactoside, is a flavonoid isolated from Oenanthe javanica. In the present study, we investigated potential herb-drug inhibitory effects of hyperoside on nine cytochrome P450 (CYP) isoforms in pooled human liver microsomes (HLMs) and human recombinant cDNA expressed CYP using a cocktail probe assay. Hyperoside strongly inhibited CYP2D6-catalyzed dextromethorphan O-demethylation, with IC₅₀ values of 1.2 and 0.81 μM after 0 and 15 min of preincubation, and a Ki value of 2.01 μM in HLMs, respectively. Hyperoside strongly decreased CYP2D6 activity dose-, but not time-, dependently in HLMs. In addition, the Lineweaver-Burk and Secondary plots for the inhibition of CYP2D6 in HLMs fitted a competitive inhibition mode. Furthermore, hyperoside decreased CYP2D6-catalyzed dextromethorphan O-demethylation activity of human recombinant cDNA-expressed CYP2D6, with an IC₅₀ value of 3.87 μM. However, other CYPs were not inhibited significantly by hyperoside. In conclusion, our data demonstrate that hyperoside is a potent selective CYP2D6 inhibitor in HLMs, and suggest that hyperoside might cause herb-drug interactions when co-administrated with CYP2D substrates.

  2. Effect of antipsychotic drugs on human liver cytochrome P-450 (CYP) isoforms in vitro: preferential inhibition of CYP2D6.

    PubMed

    Shin, J G; Soukhova, N; Flockhart, D A

    1999-09-01

    The ability of antipsychotic drugs to inhibit the catalytic activity of five cytochrome P-450 (CYP) isoforms was compared using in vitro human liver microsomal preparations to evaluate the relative potential of these drugs to inhibit drug metabolism. The apparent kinetic parameters for enzyme inhibition were determined by nonlinear regression analysis of the data. All antipsychotic drugs tested competitively inhibited dextromethorphan O-demethylation, a selective marker for CYP2D6, in a concentration-dependent manner. Thioridazine and perphenazine were the most potent, with IC(50) values (2.7 and 1.5 microM) that were comparable to that of quinidine (0.52 microM). The estimated K(i) values for CYP2D6-catalyzing dextrorphan formation were ranked in the following order: perphenazine (0.8 microM), thioridazine (1.4 microM), chlorpromazine (6.4 microM), haloperidol (7.2 microM), fluphenazine (9.4 microM), risperidone (21.9 microM), clozapine (39.0 microM), and cis-thiothixene (65.0 microM). No remarkable inhibition of other CYP isoforms was observed except for moderate inhibition of CYP1A2-catalyzed phenacetin O-deethylation by fluphenazine (K(i) = 40.2 microM) and perphenazine (K(i) = 65.1). The estimated K(i) values for the inhibition of CYP2C9, 2C19, and 3A were >300 microM in almost all antipsychotics tested. These results suggest that antipsychotic drugs exhibit a striking selectivity for CYP2D6 compared with other CYP isoforms. This may reflect a remarkable commonality of structure between the therapeutic targets for these drugs, the transporters, and metabolic enzymes that distribute and eliminate them. Clinically, coadministration of these medicines with drugs that are primarily metabolized by CYP2D6 may result in significant drug interactions.

  3. Cytochrome P450-2D6 Screening Among Elderly Using Antidepressants (CYSCE)

    ClinicalTrials.gov

    2016-10-24

    Depression; Depressive Disorder; Poor Metabolizer Due to Cytochrome P450 CYP2D6 Variant; Intermediate Metabolizer Due to Cytochrome P450 CYP2D6 Variant; Ultrarapid Metabolizer Due to Cytochrome P450 CYP2D6 Variant

  4. Crystal Structure of Human Cytochrome P450 2D6 with Prinomastat Bound*

    PubMed Central

    Wang, An; Savas, Uzen; Hsu, Mei-Hui; Stout, C. David; Johnson, Eric F.

    2012-01-01

    Human cytochrome P450 2D6 contributes to the metabolism of >15% of drugs used in clinical practice. This study determined the structure of P450 2D6 complexed with a substrate and potent inhibitor, prinomastat, to 2.85 Å resolution by x-ray crystallography. Prinomastat binding is well defined by electron density maps with its pyridyl nitrogen bound to the heme iron. The structure of ligand-bound P450 2D6 differs significantly from the ligand-free structure reported for the P450 2D6 Met-374 variant (Protein Data Bank code 2F9Q). Superposition of the structures reveals significant differences for β sheet 1, helices A, F, F′, G″, G, and H as well as the helix B-C loop. The structure of the ligand complex exhibits a closed active site cavity that conforms closely to the shape of prinomastat. The closure of the open cavity seen for the 2F9Q structure reflects a change in the direction and pitch of helix F and introduction of a turn at Gly-218, which is followed by a well defined helix F′ that was not observed in the 2F9Q structure. These differences reflect considerable structural flexibility that is likely to contribute to the catalytic versatility of P450 2D6, and this new structure provides an alternative model for in silico studies of substrate interactions with P450 2D6. PMID:22308038

  5. Role of cytochrome P450 2D6 genetic polymorphism in carvedilol hydroxylation in vitro

    PubMed Central

    Wang, Zhe; Wang, Li; Xu, Ren-ai; Zhan, Yun-yun; Huang, Cheng-ke; Dai, Da-peng; Cai, Jian-ping; Hu, Guo-xin

    2016-01-01

    Cytochrome P450 2D6 (CYP2D6) is a highly polymorphic enzyme that catalyzes the metabolism of a great number of therapeutic drugs. Up to now, >100 allelic variants of CYP2D6 have been reported. Recently, we identified 22 novel variants in the Chinese population in these variants. The purpose of this study was to examine the enzymatic activity of the variants toward the CYP2D6 substrate carvedilol in vitro. The CYP2D6 proteins, including CYP2D6.1 (wild type), CYP2D6.2, CYP2D6.10, and 22 other novel CYP2D6 variants, were expressed from insect microsomes and incubated with carvedilol ranging from 1.0 μM to 50 μM at 37°C for 30 minutes. After termination, the carvedilol metabolites were extracted and detected using ultra-performance liquid chromatography tandem mass-spectrometry. Among the 24 CYP2D6 variants, CYP2D6.92 and CYP2D6.96 were catalytically inactive and the remaining 22 variants exhibited significantly decreased intrinsic clearance values (ranging from ~25% to 95%) compared with CYP2D6.1. The present data in vitro suggest that the newly found variants significantly reduced catalytic activities compared with CYP2D6.1. Given that CYP2D6 protein activities could affect carvedilol plasma levels, these findings are greatly relevant to personalized medicine. PMID:27354764

  6. A preliminary 3D model for cytochrome P450 2D6 constructed by homology model building.

    PubMed

    Koymans, L M; Vermeulen, N P; Baarslag, A; Donné-Op den Kelder, G M

    1993-06-01

    A homology model building study of cytochrome P450 2D6 has been carried out based on the crystal structure of cytochrome P450 101. The primary sequences of P450 101 and P450 2D6 were aligned by making use of an automated alignment procedure. This alignment was adjusted manually by matching alpha-helices (C, D, G, I, J, K and L) and beta-sheets (beta 3/beta 4) of P450 101 that are proposed to be conserved in membrane-bound P450s (Ouzounis and Melvin [Eur. J. Biochem., 198 (1991) 307]) to the corresponding regions in the primary amino acid sequence of P450 2D6. Furthermore, alpha-helices B, B' and F were found to be conserved in P450 2D6. No significant homology between the remaining regions of P450 101 and P450 2D6 could be found and these regions were therefore deleted. A 3D model of P450 2D6 was constructed by copying the coordinates of the residues from the crystal structure of P450 101 to the corresponding residues in P450 2D6. The regions without a significant homology with P450 101 were not incorporated into the model. After energy-minimization of the resulting 3D model of P450 2D6, possible active site residues were identified by fitting the substrates debrisoquine and dextrometorphan into the proposed active site. Both substrates could be positioned into a planar pocket near the heme region formed by residues Val370, Pro371, Leu372, Trp316, and part of the oxygen binding site of P450 2D6. Furthermore, the carboxylate group of either Asp100 or Asp301 was identified as a possible candidate for the proposed interaction with basic nitrogen atom(s) of the substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

  7. Marmoset cytochrome P450 2D8 in livers and small intestines metabolizes typical human P450 2D6 substrates, metoprolol, bufuralol and dextromethorphan.

    PubMed

    Uehara, Shotaro; Uno, Yasuhiro; Hagihira, Yuya; Murayama, Norie; Shimizu, Makiko; Inoue, Takashi; Sasaki, Erika; Yamazaki, Hiroshi

    2015-01-01

    1. Although the New World non-human primate, the common marmoset (Callithrix jacchus), is a potentially useful animal model, comprehensive understanding of drug metabolizing enzymes is insufficient. 2. A cDNA encoding a novel cytochrome P450 (P450) 2D8 was identified in marmosets. The amino acid sequence deduced from P450 2D8 cDNA showed a high sequence identity (83-86%) with other primate P450 2Ds. Phylogenetic analysis showed that marmoset P450 2D8 was closely clustered with human P450 2D6, unlike P450 2Ds of miniature pig, dog, rabbit, guinea pig, mouse or rat. 3. Marmoset P450 2D8 mRNA was predominantly expressed in the liver and small intestine among the tissues types analyzed, whereas marmoset P450 2D6 mRNA was expressed predominantly in the liver where P450 2D protein was detected by immunoblotting. 4. By metabolic assays using marmoset P450 2D8 protein heterologously expressed in Escherichia coli, although P450 2D8 exhibits lower catalytic efficiency compared to marmoset and human P450 2D6 enzymes, P450 2D8 mediated O-demethylations of metoprolol and dextromethorphan and bufuralol 1'-hydroxylation. 5. These results suggest that marmoset P450 2D8 (also expressed in the extrahepatic tissues) has potential roles in drug metabolism in a similar manner to those of human and marmoset P450 2D6.

  8. Human Liver Mitochondrial Cytochrome P450 2D6: Individual Variations and Implications in Drug Metabolism

    PubMed Central

    Cook Sangar, Michelle L.; Anandatheerthavarada, Hindupur K.; Tang, Weigang; Prabu, Subbuswamy K.; Martin, Martha V.; Dostalek, Miroslav; Guengerich, F. Peter; Avadhani, Narayan G.

    2009-01-01

    Summary Constitutively expressed human cytochrome P450 2D6 (CYP2D6) is responsible for the metabolism of approximately 25% of drugs in common clinical use. It is widely accepted that CYP2D6 is localized in the endoplasmic reticulum of cells; however, we have identified this enzyme in the mitochondria of human liver samples and found that extensive inter-individual variability exists in the level of the mitochondrial enzyme. Metabolic assays using 7-methoxy-4-aminomethylcoumarin as a substrate show that the human liver mitochondrial enzyme is capable of oxidizing this substrate and that the catalytic activity is supported by mitochondrial electron transfer proteins. Here we show that CYP2D6 contains an N-terminal chimeric signal that mediates its bimodal targeting to the endoplasmic reticulum (ER) and mitochondria. In vitro mitochondrial import studies using both N-terminal deletions and point mutations suggest that the mitochondrial targeting signal is localized between residues 23-33 and that the positively charged residues at positions 24, 25, 26, 28, and 32 are required for mitochondrial targeting. The importance of the positively charged residues was confirmed by transient transfection of a CYP2D6 mitochondrial targeting signal mutant in COS-7 cells. Both the mitochondria and the microsomes from a CYP2D6 stable expression cell line contain the enzyme and both fractions exhibit bufuralol 1′-hydroxylation activity, which is completely inhibited by CYP2D6 inhibitory antibody. Overall these results suggest that the targeting of CYP2D6 to mitochondria could be an important physiological process that has significance in xenobiotic metabolism. PMID:19438707

  9. Building Structure Feature-based Models for Predicting Isoform-specific Human Cytochrome P-450 (hCYP 3A4, 2D6 and 2C9) Inhibition Assay Results in ToxCast

    EPA Science Inventory

    EPA’s ToxCast project is using high-throughput screening (HTS) to profile and prioritize chemicals for further testing. ToxCast Phase I evaluated 309 unique chemicals, the majority pesticide actives, in over 500 HTS assays. These included 3 human cytochrome P450 (hCYP3A4, hCYP2...

  10. Activities of cytochrome P450 1A2, N-acetyltransferase 2, xanthine oxidase, and cytochrome P450 2D6 are unaltered in children with cystic fibrosis.

    PubMed

    Kennedy, Mary Jayne; Scripture, Charity D; Kashuba, Angela D M; Scott, Christy S; Gaedigk, Andrea; Kearns, Gregory L

    2004-03-01

    The activities of hepatic cytochrome P450 (CYP) 1A2, N-acetyltransferase 2 (NAT-2), xanthine oxidase (XO), and CYP2D6 were evaluated in 12 young children (aged 3-8 years) with mild cystic fibrosis (CF) and 12 age-matched healthy control subjects by use of standard caffeine and dextromethorphan phenotyping methods. Subjects were given 4 oz of Coca-Cola (approximately 35 mg caffeine) (The Coca-Cola Company, Atlanta, Ga) and a single 0.5-mg/kg dose of dextromethorphan. Urine was collected for 8 hours after biomarker administration, and enzyme activity was assessed by use of previously validated caffeine and dextromethorphan molar ratios. CYP2D6 genotyping was also performed in 10 of 12 subjects with CF and 11 of 12 control subjects. There were no significant differences in the urinary molar ratios for any of the enzyme systems evaluated. These data suggest that CF does not alter the activities of CYP1A2, NAT-2, XO, and CYP2D6. Altered biotransformation of drugs in this patient population is likely enzyme- and isoform-specific and thus is apparent for only selected compounds that are substrates for enzymes other than CYP1A2, NAT-2, XO, and CYP2D6.

  11. Cytochrome P450 2D6 variants in a Caucasian population: Allele frequencies and phenotypic consequences

    SciTech Connect

    Sachse, C.; Brockmoeller, J.; Bauer, S.; Roots, I.

    1997-02-01

    Cytochrome P450 2D6 (CYP2D6) metabolizes many important drugs. CYP2D6 activity ranges from complete deficiency to ultrafast metabolism, depending on at least 16 different known alleles. Their frequencies were determined in 589 unrelated German volunteers and correlated with enzyme activity measured by phenotyping with dextromethorphan or debrisoquine. For genotyping, nested PCR-RFLP tests from a PCR amplificate of the entire CYP2D6 gene were developed. The frequency of the CYP2D6*1 allele coding for extensive metabolizer (EM) phenotype was .364. The alleles coding for slightly (CYP2D6*2) or moderately (*9 and *10) reduced activity (intermediate metabolizer phenotype [IM]) showed frequencies of .324, .018, and .015, respectively. By use of novel PCR tests for discrimination, CYP2D6 gene duplication alleles were found with frequencies of.005 (*1 x 2), .013 (* 2 x 2), and .001 (*4 x 2). Frequencies of alleles with complete deficiency (poor metabolizer phenotype [PM]) were .207 (*4), .020 (*3 and *5), .009 (*6), and .001 (*7, *15, and *16). The defective CYP2D6 alleles *8, *11, *12, *13, and *14 were not found. All 41 PMs (7.0%) in this sample were explained by five mutations detected by four PCR-RFLP tests, which may suffice, together with the gene duplication test, for clinical prediction of CYP2D6 capacity. Three novel variants of known CYP2D6 alleles were discovered: *1C (T{sub 1957}C), *2B (additional C{sub 2558}T), and *4E (additional C{sub 2938}T). Analysis of variance showed significant differences in enzymatic activity measured by the dextromethorphan metabolic ratio (MR) between carriers of EN/PM (mean MR = .006) and IM/PM (mean MR = .014) alleles and between carriers of one (mean MR = .009) and two (mean MR = .003) functional alleles. The results of this study provide a solid basis for prediction of CYP2D6 capacity, as required in drug research and routine drug treatment. 35 refs., 4 figs., 5 tabs.

  12. Influence of amino acid residue 374 of cytochrome P-450 2D6 (CYP2D6) on the regio- and enantio-selective metabolism of metoprolol.

    PubMed Central

    Ellis, S W; Rowland, K; Ackland, M J; Rekka, E; Simula, A P; Lennard, M S; Wolf, C R; Tucker, G T

    1996-01-01

    Cytochrome P-450 2D6 (CYP2D6) is an important human drug-metabolizing enzyme responsible for the oxidation of more than 30 widely used therapeutic agents. The enzymes encoded by the published genomic [Kimura, Umeno, Skoda, Meyer and Gonzalez (1989) Am. J. Hum. Genet. 45, 889-904] and cDNA [Gonzalez, Skoda, Kimura, Umeno, Zanger, Nebert, Gelboin, Hardwick and Meyer (1988) Nature 331, 442-446] sequences of CYP2D6, and presumed to represent wild-type sequences, differ at residue 374 and encode valine (CYP2D6-Val) and methionine (CYP2D6-Met) respectively. The influence of this amino acid difference on cytochrome P-450 expression, ligand binding, catalysis and stereoselective oxidation of metoprolol was investigated by the heterologous expression of the corresponding cDNAs in the yeast Saccharomyces cerevisiae. The level of expression of apo- and holo-protein was similar with each form of CYP2D6 cDNA, and the binding affinities of a series of ligands to CYP2D6-Val and CYP2D6-Met were identical. The enantioselective O-demethylation and alpha-hydroxylation of metoprolol were also similar with each form of CYP2D6, O-demethylation being R-(+)- enantioselective (CYP2D6-Val: R/S, 1.6; CYP2D6-Met: R/S, 1.4), whereas alpha-hydroxylation showed a preference for S-(-)-metoprolol (CYP2D6-Val: R/S, 0.7; CYP2D6-Met: R/S, 0.8). However, although the favoured regiomer overall was O-demethylmetoprolol (ODM), the regioselectivity for O-demethylation of each metoprolol enantiomer was significantly greater for CYP2D6-Val [R-(+)-: ODM/alpha-hydroxymetoprolol (alpha OH), 5.9; S-(-)-: ODM/alpha OH, 2.5) than that observed for CYP2D6-Met [R-(+)-: ODM/alpha OH, 2.2; S-(-)-: ODM/alpha OH, 1.4]. The stereoselective properties of CYP2D6-Val were consistent with those observed for CYP2D6 in human liver microsomes. The difference in the stereoselective properties of CYP2D6-Val and CYP2D6-Met were rationalized with respect to a homology model of the active site of CYP2D6 based on an alignment with

  13. Increased risk of hospitalization for ultrarapid metabolizers of cytochrome P450 2D6

    PubMed Central

    Takahashi, Paul Y; Ryu, Euijung; Pathak, Jyotishman; Jenkins, Gregory D; Batzler, Anthony; Hathcock, Matthew A; Black, John Logan; Olson, Janet E; Cerhan, James R; Bielinski, Suzette J

    2017-01-01

    Background Cytochrome P450 2D6 (CYP2D6) is responsible for the metabolism of clinically used drugs and other environmental exposures, but it is unclear whether the CYP2D6 phenotype is associated with adverse health outcomes. The aim was to determine the association of CYP2D6 phenotype with the risk of hospitalization or an emergency department (ED) visit among a group of primary care patients. Methods In this study, 929 adult patients underwent CYP2D6 testing. The primary outcome was risk of hospitalization or an ED visit from January 2005 through September 2014. CYP2D6 genotypes were interpreted as 1 of 7 clinical phenotypes, from ultrarapid to poor metabolizer, and patients with the extensive metabolizer phenotype were used as the reference group. The hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for finding the association of CYP2D6 phenotypes with the risk of hospitalization or an ED visit by using Cox proportional hazard models and adjusting for age and sex. Results The median age was 49 years (interquartile range, 46–52 years); 74% of patients had 3 or fewer chronic conditions, 285 had at least 1 hospitalization, and 496 had at least 1 ED visit. The risk of hospitalization was higher among patients who were ultrarapid metabolizers compared to extensive metabolizers (47% vs 30%; HR, 1.69; 95% CI, 1.11–2.57), as was the risk of an ED visit (62% vs 49%; HR, 1.50; 95% CI, 1.05–2.14). For poor metabolizers compared to extensive metabolizers, there was no difference in the risk of hospitalization (HR, 0.95; 95% CI, 0.58–1.56), but there was an increase in the risk of an ED visit (HR, 1.38; 95% CI, 0.96–1.98) (the difference was not statistically significant). Conclusion We found an increased risk of hospitalization or an ED visit among ultrarapid compared to extensive CYP2D6 metabolizers. Further research identifying the mechanisms of the association and ultimate clinical utility is warranted. PMID:28243137

  14. Cytochrome P-450 2D6 (CYP2D6) Genotype and Breast Cancer Recurrence in Tamoxifen-Treated Patients: Evaluating the Importance of Loss of Heterozygosity.

    PubMed

    Ahern, Thomas P; Hertz, Daniel L; Damkier, Per; Ejlertsen, Bent; Hamilton-Dutoit, Stephen J; Rae, James M; Regan, Meredith M; Thompson, Alastair M; Lash, Timothy L; Cronin-Fenton, Deirdre P

    2017-01-15

    Tamoxifen therapy for estrogen receptor-positive breast cancer reduces the risk of recurrence by approximately one-half. Cytochrome P-450 2D6, encoded by the polymorphic cytochrome P-450 2D6 gene (CYP2D6), oxidizes tamoxifen to its most active metabolites. Steady-state concentrations of endoxifen (4-hydroxy-N-desmethyltamoxifen), the most potent antiestrogenic metabolite, are reduced in women whose CYP2D6 genotypes confer poor enzyme function. Thirty-one studies of the association of CYP2D6 genotype with breast cancer survival have yielded heterogeneous results. Some influential studies genotyped DNA from tumor-infiltrated tissues, and their results may have been susceptible to germline genotype misclassification from loss of heterozygosity at the CYP2D6 locus. We systematically reviewed 6 studies of concordance between genotypes obtained from paired nonneoplastic and breast tumor-infiltrated tissues, all of which showed excellent CYP2D6 genotype agreement. We applied these concordance data to a quantitative bias analysis of the subset of the 31 studies that were based on genotypes from tumor-infiltrated tissue to examine whether genotyping errors substantially biased estimates of association. The bias analysis showed negligible bias by discordant genotypes. Summary estimates of association, with or without bias adjustment, indicated no clinically important association between CYP2D6 genotype and breast cancer survival in tamoxifen-treated women.

  15. Krüppel-like factor 9 promotes hepatic cytochrome P450 2D6 expression during pregnancy in CYP2D6-humanized mice.

    PubMed

    Koh, Kwi Hye; Pan, Xian; Zhang, Wei; McLachlan, Alan; Urrutia, Raul; Jeong, Hyunyoung

    2014-12-01

    Cytochrome P450 2D6 (CYP2D6), a major drug-metabolizing enzyme, is responsible for metabolism of approximately 25% of marketed drugs. Clinical evidence indicates that metabolism of CYP2D6 substrates is increased during pregnancy, but the underlying mechanisms remain unclear. To identify transcription factors potentially responsible for CYP2D6 induction during pregnancy, a panel of genes differentially expressed in the livers of pregnant versus nonpregnant CYP2D6-humanized (tg-CYP2D6) mice was compiled via microarray experiments followed by real-time quantitative reverse-transcription polymerase chain reaction(qRT-PCR) verification. As a result, seven transcription factors-activating transcription factor 5 (ATF5), early growth response 1 (EGR1), forkhead box protein A3 (FOXA3), JUNB, Krüppel-like factor 9 (KLF9), KLF10, and REV-ERBα-were found to be up-regulated in liver during pregnancy. Results from transient transfection and promoter reporter gene assays indicate that KLF9 itself is a weak transactivator of CYP2D6 promoter but significantly enhances CYP2D6 promoter transactivation by hepatocyte nuclear factor 4 (HNF4α), a known transcriptional activator of CYP2D6 expression. The results from deletion and mutation analysis of CYP2D6 promoter activity identified a KLF9 putative binding motif at -22/-14 region to be critical in the potentiation of HNF4α-induced transactivation of CYP2D6. Electrophoretic mobility shift assays revealed a direct binding of KLF9 to the putative KLF binding motif. Results from chromatin immunoprecipitation assay showed increased recruitment of KLF9 to CYP2D6 promoter in the livers of tg-CYP2D6 mice during pregnancy. Taken together, our data suggest that increased KLF9 expression is in part responsible for CYP2D6 induction during pregnancy via the potentiation of HNF4α transactivation of CYP2D6.

  16. Diversity in mechanisms of substrate oxidation by cytochrome P450 2D6. Lack of an allosteric role of NADPH-cytochrome P450 reductase in catalytic regioselectivity.

    PubMed

    Hanna, I H; Krauser, J A; Cai, H; Kim, M S; Guengerich, F P

    2001-10-26

    Cytochrome P450 (P450) 2D6 was first identified as the polymorphic human debrisoquine hydroxylase and subsequently shown to catalyze the oxidation of a variety of drugs containing a basic nitrogen. Differences in the regioselectivity of oxidation products formed in systems containing NADPH-P450 reductase/NADPH and the model oxidant cumene hydroperoxide have been proposed by others to be due to an allosteric influence of the reductase on P450 2D6 (Modi, S., Gilham, D. E., Sutcliffe, M. J., Lian, L.-Y., Primrose, W. U., Wolf, C. R., and Roberts, G. C. K. (1997) Biochemistry 36, 4461-4470). We examined the differences in the formation of oxidation products of N-methyl-4-phenyl-1,2,5,6-tetrahydropyridine, metoprolol, and bufuralol between reductase-, cumene hydroperoxide-, and iodosylbenzene-supported systems. Catalytic regioselectivity was not influenced by the presence of the reductase in any of the systems supported by model oxidants, ruling out allosteric influences. The presence of the reductase had little effect on the affinity of P450 2D6 for any of these three substrates. The addition of the reaction remnants of the model oxidants (cumyl alcohol and iodobenzene) to the reductase-supported system did not affect reaction patterns, arguing against steric influences of these products on catalytic regioselectivity. Label from H(2)18O was quantitatively incorporated into 1'-hydroxybufuralol in the iodosylbenzene- but not in the reductase- or cumene hydroperoxide-supported reactions. We conclude that the P450 systems utilizing NADPH-P450 reductase, cumene hydroperoxide, and iodosylbenzene use similar but distinct chemical mechanisms. These differences are the basis for the variable product distributions, not an allosteric influence of the reductase.

  17. Contributions of ionic interactions and protein dynamics to cytochrome P450 2D6 (CYP2D6) substrate and inhibitor binding.

    PubMed

    Wang, An; Stout, C David; Zhang, Qinghai; Johnson, Eric F

    2015-02-20

    P450 2D6 contributes significantly to the metabolism of >15% of the 200 most marketed drugs. Open and closed crystal structures of P450 2D6 thioridazine complexes were obtained using different crystallization conditions. The protonated piperidine moiety of thioridazine forms a charge-stabilized hydrogen bond with Asp-301 in the active sites of both complexes. The more open conformation exhibits a second molecule of thioridazine bound in an expanded substrate access channel antechamber with its piperidine moiety forming a charge-stabilized hydrogen bond with Glu-222. Incubation of the crystalline open thioridazine complex with alternative ligands, prinomastat, quinidine, quinine, or ajmalicine, displaced both thioridazines. Quinine and ajmalicine formed charge-stabilized hydrogen bonds with Glu-216, whereas the protonated nitrogen of quinidine is equidistant from Asp-301 and Glu-216 with protonated nitrogen H-bonded to a water molecule in the access channel. Prinomastat is not ionized. Adaptations of active site side-chain rotamers and polypeptide conformations were evident between the complexes, with the binding of ajmalicine eliciting a closure of the open structure reflecting in part the inward movement of Glu-216 to form a hydrogen bond with ajmalicine as well as sparse lattice restraints that would hinder adaptations. These results indicate that P450 2D6 exhibits sufficient elasticity within the crystal lattice to allow the passage of compounds between the active site and bulk solvent and to adopt a more closed form that adapts for binding alternative ligands with different degrees of closure. These crystals provide a means to characterize substrate and inhibitor binding to the enzyme after replacement of thioridazine with alternative compounds.

  18. Long-Read Single Molecule Real-Time Full Gene Sequencing of Cytochrome P450-2D6.

    PubMed

    Qiao, Wanqiong; Yang, Yao; Sebra, Robert; Mendiratta, Geetu; Gaedigk, Andrea; Desnick, Robert J; Scott, Stuart A

    2016-03-01

    The cytochrome P450-2D6 (CYP2D6) enzyme metabolizes ∼25% of common medications, yet homologous pseudogenes and copy number variants (CNVs) make interrogating the polymorphic CYP2D6 gene with short-read sequencing challenging. Therefore, we developed a novel long-read, full gene CYP2D6 single molecule real-time (SMRT) sequencing method using the Pacific Biosciences platform. Long-range PCR and CYP2D6 SMRT sequencing of 10 previously genotyped controls identified expected star (*) alleles, but also enabled suballele resolution, diplotype refinement, and discovery of novel alleles. Coupled with an optimized variant-calling pipeline, CYP2D6 SMRT sequencing was highly reproducible as triplicate intra- and inter-run nonreference genotype results were completely concordant. Importantly, targeted SMRT sequencing of upstream and downstream CYP2D6 gene copies characterized the duplicated allele in 15 control samples with CYP2D6 CNVs. The utility of CYP2D6 SMRT sequencing was further underscored by identifying the diplotypes of 14 samples with discordant or unclear CYP2D6 configurations from previous targeted genotyping, which again included suballele resolution, duplicated allele characterization, and discovery of a novel allele and tandem arrangement. Taken together, long-read CYP2D6 SMRT sequencing is an innovative, reproducible, and validated method for full-gene characterization, duplication allele-specific analysis, and novel allele discovery, which will likely improve CYP2D6 metabolizer phenotype prediction for both research and clinical testing applications.

  19. Cytochrome P450 2D6 Activity Predicts Discontinuation of Tamoxifen Therapy in Breast Cancer Patients

    PubMed Central

    Rae, James M.; Sikora, Matthew J.; Henry, N. Lynn; Li, Lang; Kim, Seongho; Oesterreich, Steffi; Skaar, Todd; Nguyen, Anne T.; Desta, Zeruesenay; Storniolo, Anna Maria; Flockhart, David A.; Hayes, Daniel F.; Stearns, Vered

    2009-01-01

    The selective estrogen receptor modulator tamoxifen is routinely used for treatment and prevention of estrogen receptor positive breast cancer. Studies of tamoxifen adherence suggest that over half of patients discontinue treatment before the recommended 5 years. We hypothesized that polymorphisms in CYP2D6, the enzyme responsible for tamoxifen activation, predict for tamoxifen discontinuation. Tamoxifen-treated women (n = 297) were genotyped for CYP2D6 variants and assigned a “score” based on predicted allele activities from 0 (no activity) to 2 (high activity). Correlation between CYP2D6 score and discontinuation rates at 4 months were tested. We observed a strong non-linear correlation between higher CYP2D6 score and increased rates of discontinuation (r2 = 0.935, p = 0.018). These data suggest that presence of active CYP2D6 alleles may predict for higher likelihood of tamoxifen discontinuation. Therefore, patients who may be most likely to benefit from tamoxifen may paradoxically be most likely to discontinue treatment prematurely. PMID:19421167

  20. Differential Consequences of Tramadol in Overdosing: Dilemma of a Polymorphic Cytochrome P450 2D6-Mediated Substrate.

    PubMed

    Srinivas, Nuggehally R

    2015-09-01

    Tramadol is a centrally acting opioid analgesic that is prone to polymorphic metabolism via cytochrome P450 (CYP) 2D6. The generation of the active metabolite, O-desmethyltramadol, which occurs through the CYP 2D6 pathway, significantly contributes to the drug's activity. However, dosage adjustments of tramadol are typically not practiced in the clinic when treating patients who are homozygous extensive metabolizers, heterozygous extensive metabolizers, or poor metabolizers. In the event of a tramadol overdose, the consequences may be influenced importantly by the genotype or phenotype status of the subject. Depending on the individual subject's CYP 2D6 status, one may see excessive miotic-related toxicity driven by the excessive availability of O-desmethyltramadol or one may manifest mydriatic-related toxicity driven by the excessive availability of tramadol. This report provides pharmacokinetic perspectives in situations of tramadol overdosing.

  1. Optimizing QSAR models for predicting ligand binding to the drug-metabolizing cytochrome P450 isoenzyme CYP2D6.

    PubMed

    Saraceno, Marilena; Massarelli, Ilaria; Imbriani, Marcello; James, Thomas L; Bianucci, Anna M

    2011-08-01

    The cytochrome P450 isozyme CYP2D6 binds a large variety of drugs, oxidizing many of them, and plays a crucial role in establishing in vivo drug levels, especially in multidrug regimens. The current study aimed to develop reliable predictive models for estimating the CYP2D6 inhibition properties of drug candidates. Quantitative structure-activity relationship (QSAR) studies utilizing 51 known CYP2D6 inhibitors were carried out. Performance achieved using models based on two-dimensional (2D) molecular descriptors was compared with performance using models entailing additional molecular descriptors that depend upon the three-dimensional (3D) structure of ligands. To properly compute the descriptors, all the 3D inhibitor structures were optimized such that induced-fit binding of the ligand to the active site was accommodated. CODESSA software was used to obtain equations for correlating the structural features of the ligands to their pharmacological effects on CYP2D6 (inhibition). The predictive power of all the QSAR models obtained was estimated by applying rigorous statistical criteria. To assess the robustness and predictability of the models, predictions were carried out on an additional set of known molecules (prediction set). The results showed that only models incorporating 3D descriptors in addition to 2D molecular descriptors possessed the requisite high predictive power for CYP2D6 inhibition.

  2. Cytochrome P450-2D6 extensive metabolizers are more vulnerable to methamphetamine-associated neurocognitive impairment: preliminary findings.

    PubMed

    Cherner, Mariana; Bousman, Chad; Everall, Ian; Barron, Daniel; Letendre, Scott; Vaida, Florin; Atkinson, J Hampton; Heaton, Robert; Grant, Igor

    2010-09-01

    While neuropsychological deficits are evident among methamphetamine (meth) addicts, they are often unrelated to meth exposure parameters such as lifetime consumption and length of abstinence. The notion that some meth users develop neuropsychological impairments while others with similar drug exposure do not, suggests that there may be individual differences in vulnerability to the neurotoxic effects of meth. One source of differential vulnerability could come from genotypic variability in metabolic clearance of meth, dependent on the activity of cytochrome P450-2D6 (CYP2D6). We compared neuropsychological performance in 52 individuals with a history of meth dependence according with their CYP2D6 phenotype. All were free of HIV or hepatitis C infection and did not meet dependence criteria for other substances. Extensive metabolizers showed worse overall neuropsychological performance and were three times as likely to be cognitively impaired as intermediate/poor metabolizers. Groups did not differ in their demographic or meth use characteristics, nor did they evidence differences in mood disorder or other substance use. This preliminary study is the first to suggest that efficient meth metabolism is associated with worse neurocognitive outcomes in humans, and implicates the products of oxidative metabolism of meth as a possible source of brain injury.

  3. Differential time course of cytochrome P450 2D6 enzyme inhibition by fluoxetine, sertraline, and paroxetine in healthy volunteers.

    PubMed

    Liston, Heidi L; DeVane, C Lindsay; Boulton, David W; Risch, Samuel C; Markowitz, John S; Goldman, Juliet

    2002-04-01

    The selective serotonin reuptake inhibitors (SSRIs) paroxetine, sertraline, and fluoxetine have varying degrees of potency in inhibiting the hepatic cytochrome P450 (CYP) 2D6 enzyme. However, the time course for maximum inhibition to occur or for inhibition to dissipate when dosing is discontinued, requires clarification. In an open label, parallel group study of 45 healthy volunteers, the time course of CYP2D6 inhibition of the above SSRIs was evaluated. Subjects were randomized to receive paroxetine at 20 mg/day for 10 days; sertraline at 50 mg/day for 3 days, followed by sertraline at 100 mg/day for 10 days; or fluoxetine at 20 mg/day for 28 days. CYP2D6 activity was assessed using the dextromethorphan metabolic ratio (DMR) on antidepressant days 5 and 10 for sertraline and paroxetine and at weekly intervals for fluoxetine. Following SSRI discontinuation, calculation of a CYP2D6 inhibition half-life (t(1/2)inh) revealed the time course of fluoxetine inhibition (t(1/2)inh = 7.0 +/- 1.5 days) to be significantly longer than either paroxetine (t(1/2)inh = 2.9 +/- 1.9) or sertraline (t(1/2)inh = 3.0 +/- 3.0) (p < 0.01), but the latter were not significantly different from each other (p > 0.05). Time for the extrapolated DMR versus time log-linear plots to return to baseline was significantly different between fluoxetine (63.2 +/- 5.6 days) and both paroxetine (20.3 +/- 6.4 days) and sertraline (25.0 +/- 11.0 days) (p < 0.01), making the rank order (from longest to shortest) of time for CYP2D6 inhibition to dissipate: fluoxetine > sertraline >or= paroxetine. Differences between mean baseline DMR values and measured values obtained after drug discontinuation for each drug group became nonsignificant on discontinuation day 5 for both paroxetine and sertraline and on discontinuation day 42 for fluoxetine. These data define the time course of a persistent effect that fluoxetine, sertraline, and paroxetine have on CYP2D6 following drug discontinuation and should be

  4. Altered expression of small heterodimer partner governs cytochrome P450 (CYP) 2D6 induction during pregnancy in CYP2D6-humanized mice.

    PubMed

    Koh, Kwi Hye; Pan, Xian; Shen, Hong-Wu; Arnold, Samuel L M; Yu, Ai-Ming; Gonzalez, Frank J; Isoherranen, Nina; Jeong, Hyunyoung

    2014-02-07

    Substrates of a major drug-metabolizing enzyme CYP2D6 display increased elimination during pregnancy, but the underlying mechanisms are unknown in part due to a lack of experimental models. Here, we introduce CYP2D6-humanized (Tg-CYP2D6) mice as an animal model where hepatic CYP2D6 expression is increased during pregnancy. In the mouse livers, expression of a known positive regulator of CYP2D6, hepatocyte nuclear factor 4α (HNF4α), did not change during pregnancy. However, HNF4α recruitment to CYP2D6 promoter increased at term pregnancy, accompanied by repressed expression of small heterodimer partner (SHP). In HepG2 cells, SHP repressed HNF4α transactivation of CYP2D6 promoter. In transgenic (Tg)-CYP2D6 mice, SHP knockdown led to a significant increase in CYP2D6 expression. Retinoic acid, an endogenous compound that induces SHP, exhibited decreased hepatic levels during pregnancy in Tg-CYP2D6 mice. Administration of all-trans-retinoic acid led to a significant decrease in the expression and activity of hepatic CYP2D6 in Tg-CYP2D6 mice. This study provides key insights into mechanisms underlying altered CYP2D6-mediated drug metabolism during pregnancy, laying a foundation for improved drug therapy in pregnant women.

  5. Variable cytochrome P450 2D6 expression and metabolism of codeine and other opioid prodrugs: implications for the Australian anaesthetist.

    PubMed

    Wilcox, R A; Owen, H

    2000-12-01

    Codeine is a popular opioid prodrug dependent on the activity of the specific cytochrome P450 enzyme 2D6 (CYP2D6). This enzyme catalyses the production of the potent analgesic metabolite morphine, but genetic studies have demonstrated that individuals from different ethnic groups exhibit considerable variability in the functional capacities of their expressed CYP2D6 enzymes, and pharmacological studies have shown many commonly prescribed drugs can reduce the action of CYP2D6 enzymes. These findings have significant clinical implications for the rational prescription of effective analgesia, especially in a multicultural country like Australia.

  6. Appetite suppressant drugs as inhibitors of human cytochromes P450: in vitro inhibition of P450-2D6 by D- and L-fenfluramine, but not phentermine.

    PubMed

    von Moltke, L L; Greenblatt, D J; Ciraulo, D A; Grassi, J M; Granda, B W; Duan, S X; Harmatz, J S; Shader, R I

    1998-08-01

    The activity of D-fenfluramine, L-fenfluramine, and phentermine as inhibitors of five human cytochromes P450 was evaluated using human liver microsomes in vitro. All three compounds produced negligible inhibition of P450-1A2, -2C9, -2E1, and -3A. Phentermine also did not inhibit P450-2D6. However, D- and L-fenfluramine significantly inhibited P450-2D6 activity as measured by dextromethorphan O-demethylation, with mean 50% inhibitory concentrations (15.1 microM) within one order of magnitude of that for fluoxetine (2.7 microM). Findings from the in vitro assay are consistent with clinical studies showing significant inhibition of desipramine clearance by coadministration of fenfluramine.

  7. Altered spin state equilibrium in the T309V mutant of cytochrome P450 2D6: a spectroscopic and computational study

    PubMed Central

    Bonifacio, Alois; Groenhof, André R.; Keizers, Peter H. J.; de Graaf, Chris; Commandeur, Jan N. M.; Vermeulen, Nico P. E.; Ehlers, Andreas W.; Lammertsma, Koop; Gooijer, Cees

    2007-01-01

    Cytochrome P450 2D6 (CYP2D6) is one of the most important cytochromes P450 in humans. Resonance Raman data from the T309V mutant of CYP2D6 show that the substitution of the conserved I-helix threonine situated in the enzyme’s active site perturbs the heme spin equilibrium in favor of the six-coordinated low-spin species. A mechanistic hypothesis is introduced to explain the experimental observations, and its compatibility with the available structural and spectroscopic data is tested using quantum-mechanical density functional theory calculations on active-site models for both the CYP2D6 wild type and the T309V mutant. Electronic supplementary material The online version of this article (doi:10.1007/s00775-007-0210-5) contains supplementary material, which is available to authorized users. PMID:17318599

  8. Effects of monoamine oxidase inhibitor and cytochrome P450 2D6 status on 5-methoxy-N,N-dimethyltryptamine metabolism and pharmacokinetics.

    PubMed

    Shen, Hong-Wu; Wu, Chao; Jiang, Xi-Ling; Yu, Ai-Ming

    2010-07-01

    5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is a natural psychoactive indolealkylamine drug that has been used for recreational purpose. Our previous study revealed that polymorphic cytochrome P450 2D6 (CYP2D6) catalyzed 5-MeO-DMT O-demethylation to produce active metabolite bufotenine, while 5-MeO-DMT is mainly inactivated through deamination pathway mediated by monoamine oxidase (MAO). This study, therefore, aimed to investigate the impact of CYP2D6 genotype/phenotype status and MAO inhibitor (MAOI) on 5-MeO-DMT metabolism and pharmacokinetics. Enzyme kinetic studies using recombinant CYP2D6 allelic isozymes showed that CYP2D6.2 and CYP2D6.10 exhibited 2.6- and 40-fold lower catalytic efficiency (V(max)/K(m)), respectively, in producing bufotenine from 5-MeO-DMT, compared with wild-type CYP2D6.1. When co-incubated with MAOI pargyline, 5-MeO-DMT O-demethylation in 10 human liver microsomes showed significantly strong correlation with bufuralol 1'-hydroxylase activities (R(2)=0.98; P<0.0001) and CYP2D6 contents (R(2)=0.77; P=0.0007), whereas no appreciable correlations with enzymatic activities of other P450 enzymes. Furthermore, concurrent MAOI harmaline sharply reduced 5-MeO-DMT depletion and increased bufotenine formation in human CYP2D6 extensive metabolizer hepatocytes. In vivo studies in wild-type and CYP2D6-humanized (Tg-CYP2D6) mouse models showed that Tg-CYP2D6 mice receiving the same dose of 5-MeO-DMT (20mg/kg, i.p.) had 60% higher systemic exposure to metabolite bufotenine. In addition, pretreatment of harmaline (5mg/kg, i.p.) led to 3.6- and 4.4-fold higher systemic exposure to 5-MeO-DMT (2mg/kg, i.p.), and 9.9- and 6.1-fold higher systemic exposure to bufotenine in Tg-CYP2D6 and wild-type mice, respectively. These findings indicate that MAOI largely affects 5-MeO-DMT metabolism and pharmacokinetics, as well as bufotenine formation that is mediated by CYP2D6.

  9. Pharmacophore, QSAR, and binding mode studies of substrates of human cytochrome P450 2D6 (CYP2D6) using molecular docking and virtual mutations and an application to chinese herbal medicine screening.

    PubMed

    Mo, Sui-Lin; Liu, Wei-Feng; Li, Chun-Guang; Zhou, Zhi-Wei; Luo, Hai-Bin; Chew, Helen; Liang, Jun; Zhou, Shu-Feng

    2012-07-01

    The highly polymorphic human cytochrome P450 2D6 (CYP2D6) metabolizes about 25% of currently used drugs. In this study, we have explored the interaction of a large number of substrates (n = 120) with wild-type and mutated CYP2D6 by molecular docking using the CDOCKER module. Before we conducted the molecular docking and virtual mutations, the pharmacophore and QSAR models of CYP2D6 substrates were developed and validated. Finally, we explored the interaction of a traditional Chinese herbal formula, Fangjifuling decoction, with CYP2D6 by virtual screening. The optimized pharmacophore model derived from 20 substrates of CYP2D6 contained two hydrophobic features and one hydrogen bond acceptor feature, giving a relevance ratio of 76% when a validation set of substrates were tested. However, our QSAR models gave poor prediction of the binding affinity of substrates. Our docking study demonstrated that 117 out of 120 substrates could be docked into the active site of CYP2D6. Forty one out of 117 substrates (35.04%) formed hydrogen bonds with various active site residues of CYP2D6 and 53 (45.30%) substrates formed a strong π-π interaction with Phe120 (53/54), with only carvedilol showing π-π interaction with Phe483. The active site residues involving hydrogen bond formation with substrates included Leu213, Lys214, Glu216, Ser217, Gln244, Asp301, Ser304, Ala305, Phe483, and Phe484. Furthermore, the CDOCKER algorithm was further applied to study the impact of mutations of 28 active site residues (mostly non-conserved) of CYP2D6 on substrate binding modes using five probe substrates including bufuralol, debrisoquine, dextromethorphan, sparteine, and tramadol. All mutations of the residues examined altered the hydrogen bond formation and/or aromatic interactions, depending on the probe used in molecular docking. Apparent changes of the binding modes have been observed with the Glu216Asp and Asp301Glu mutants. Overall, 60 compounds out of 130 from Fangjifuling decoction

  10. Cytochrome b5 is a major determinant of human cytochrome P450 CYP2D6 and CYP3A4 activity in vivo.

    PubMed

    Henderson, Colin J; McLaughlin, Lesley A; Scheer, Nico; Stanley, Lesley A; Wolf, C Roland

    2015-04-01

    The cytochrome P450-dependent mono-oxygenase system is responsible for the metabolism and disposition of chemopreventive agents, chemical toxins and carcinogens, and >80% of therapeutic drugs. Cytochrome P450 (P450) activity is regulated transcriptionally and by the rate of electron transfer from P450 reductase. In vitro studies have demonstrated that cytochrome b5 (Cyb5) also modulates P450 function. We recently showed that hepatic deletion of Cyb5 in the mouse (HBN) markedly alters in vivo drug pharmacokinetics; a key outstanding question is whether Cyb5 modulates the activity of the major human P450s in drug disposition in vivo. To address this, we crossed mice humanized for CYP2D6 or CYP3A4 with mice carrying a hepatic Cyb5 deletion. In vitro triazolam 4-hydroxylation (probe reaction for CYP3A4) was reduced by >50% in hepatic microsomes from CYP3A4-HBN mice compared with controls. Similar reductions in debrisoquine 4-hydroxylation and metoprolol α-hydroxylation were observed using CYP2D6-HBN microsomes, indicating a significant role for Cyb5 in the activity of both enzymes. This effect was confirmed by the concentration-dependent restoration of CYP3A4-mediated triazolam turnover and CYP2D6-mediated bufuralol and debrisoquine turnover on addition of Escherichia coli membranes containing recombinant Cyb5. In vivo, the peak plasma concentration and area under the concentration time curve from 0 to 8 hours (AUC0-8 h) of triazolam were increased 4- and 5.7-fold, respectively, in CYP3A4-HBN mice. Similarly, the pharmacokinetics of bufuralol and debrisoquine were significantly altered in CYP2D6-HBN mice, the AUC0-8 h being increased ∼1.5-fold and clearance decreased by 40-60%. These data demonstrate that Cyb5 can be a major determinant of CYP3A4 and CYP2D6 activity in vivo, with a potential impact on the metabolism, efficacy, and side effects of numerous therapeutic drugs.

  11. Using a homology model of cytochrome P450 2D6 to predict substrate site of metabolism

    NASA Astrophysics Data System (ADS)

    Unwalla, Rayomand J.; Cross, Jason B.; Salaniwal, Sumeet; Shilling, Adam D.; Leung, Louis; Kao, John; Humblet, Christine

    2010-03-01

    CYP2D6 is an important enzyme that is involved in first pass metabolism and is responsible for metabolizing 25% of currently marketed drugs. A homology model of CYP2D6 was built using X-ray structures of ligand-bound CYP2C5 complexes as templates. This homology model was used in docking studies to rationalize and predict the site of metabolism of known CYP2D6 substrates. While the homology model was generally found to be in good agreement with the recently solved apo (ligand-free) X-ray structure of CYP2D6, significant differences between the structures were observed in the B' and F-G helical region. These structural differences are similar to those observed between ligand-free and ligand-bound structures of other CYPs and suggest that these conformational changes result from induced-fit adaptations upon ligand binding. By docking to the homology model using Glide, it was possible to identify the correct site of metabolism for a set of 16 CYP2D6 substrates 85% of the time when the 5 top scoring poses were examined. On the other hand, docking to the apo CYP2D6 X-ray structure led to a loss in accuracy in predicting the sites of metabolism for many of the CYP2D6 substrates considered in this study. These results demonstrate the importance of describing substrate-induced conformational changes that occur upon binding. The best results were obtained using Glide SP with van der Waals scaling set to 0.8 for both the receptor and ligand atoms. A discussion of putative binding modes that explain the distribution of metabolic sites for substrates, as well as a relationship between the number of metabolic sites and substrate size, are also presented. In addition, analysis of these binding modes enabled us to rationalize the typical hydroxylation and O-demethylation reactions catalyzed by CYP2D6 as well as the less common N-dealkylation.

  12. Paroxetine-induced conversion of cytochrome P450 2D6 phenotype and occurence of adverse effects.

    PubMed

    Zourková, A; Hadasová, E

    2003-03-01

    The paper is focused on a comparison of the distribution of side effects of treatment with paroxetine within a group of 30 patients genotyped and phenotyped for their CYP 2D6 metabolic status. Genotyping procedure showed that the patient group did not include any individual with poor metabolizer (PM) genotype; on the other hand, most patients (24) were classified as PMs by virtue of their phenotype, which suggests that a conversion to the poor metabolic phenotype ("phenocopy") occurred, probably as a consequence of a long-term administration of the strong CYP 2D6 inhibitor paroxetine. As to the occurence of common adverse effects, no marked difference between subjects converted into the PM group and those who had no history of such conversion was found. A significantly higher incidence of sexual dysfunction (p < 0.05) was, nevertheless, recorded in patients with the PM phenotype. The results of the study may provide evidence that it is the metabolic phenotype status, rather than the genetically given enzyme capacity (CYP 2D6 genotype), that is relevant for the actual toleration of treatment with CYP 2D6 inhibitors.

  13. Prediction of cytochrome P450 isoform responsible for metabolizing a drug molecule

    PubMed Central

    2010-01-01

    Background Different isoforms of Cytochrome P450 (CYP) metabolized different types of substrates (or drugs molecule) and make them soluble during biotransformation. Therefore, fate of any drug molecule depends on how they are treated or metabolized by CYP isoform. There is a need to develop models for predicting substrate specificity of major isoforms of P450, in order to understand whether a given drug will be metabolized or not. This paper describes an in-silico method for predicting the metabolizing capability of major isoforms (e.g. CYP 3A4, 2D6, 1A2, 2C9 and 2C19). Results All models were trained and tested on 226 approved drug molecules. Firstly, 2392 molecular descriptors for each drug molecule were calculated using various softwares. Secondly, best 41 descriptors were selected using general and genetic algorithm. Thirdly, Support Vector Machine (SVM) based QSAR models were developed using 41 best descriptors and achieved an average accuracy of 86.02%, evaluated using fivefold cross-validation. We have also evaluated the performance of our model on an independent dataset of 146 drug molecules and achieved average accuracy 70.55%. In addition, SVM based models were developed using 26 Chemistry Development Kit (CDK) molecular descriptors and achieved an average accuracy of 86.60%. Conclusions This study demonstrates that SVM based QSAR model can predict substrate specificity of major CYP isoforms with high accuracy. These models can be used to predict isoform responsible for metabolizing a drug molecule. Thus these models can used to understand whether a molecule will be metabolized or not. This is possible to develop highly accurate models for predicting substrate specificity of major isoforms using CDK descriptors. A web server MetaPred has been developed for predicting metabolizing isoform of a drug molecule http://crdd.osdd.net/raghava/metapred/. PMID:20637097

  14. Cytochrome P450 CYP2D6 genotypes: association with hair colour, Breslow thickness and melanocyte stimulating hormone receptor alleles in patients with malignant melanoma.

    PubMed

    Strange, R C; Ellison, T; Ichii-Jones, F; Bath, J; Hoban, P; Lear, J T; Smith, A G; Hutchinson, P E; Osborne, J; Bowers, B; Jones, P W; Fryer, A A

    1999-06-01

    We previously identified associations between polymorphism in the cytochrome P450 CYP2D6 gene and outcome in several cancers. We have now examined the hypothesis that homozygosity for the mutant alleles, CYP2D6*4 and CYP2D6*3, is associated with susceptibility and outcome in malignant melanoma. Outcome was assessed by Breslow thickness. We first confirmed previous reports that these mutant alleles are associated with increased susceptibility to malignant melanoma. For example, the frequency of homozygosity for CYP2D6*4 was significantly greater (P = 0.006, chi-squared 1 d.f. = 7.4, odds ratio 2.2, 95% confidence interval 1.2, 3.9) in cases (9.1%) than in control individuals (4.3%). The frequency of homozygosity for the mutant alleles was next examined in the malignant melanoma cases grouped on the basis of characteristics associated with malignant melanoma risk. Homozygosity was significantly more common (P = 0.038) in cases with red/blonde hair than in those with brown/black hair. We found no associations between the CYP2D6 genotype and sex, skin type or eye colour. The possible association of CYP2D6 with outcome was assessed by comparing genotype frequencies in patients with tumours of Breslow thickness < 1.5 mm with those whose tumours were > or = 1.5 mm. In patients with red/blonde, but not brown or black hair, homozygosity for CYP2D6*4 was significantly associated with thicker lesions in a multivariate model (P = 0.036). We further examined the association of CYP2D6*4 homozygosity with red/blonde hair by classifying patients on the basis of homo- or heterozygosity for wild-type or val92met, asp294his or asp84glu melanocyte stimulating hormone receptor (MC1R) alleles. None of the nine patients with brown/black hair with the asp294his allele were homozygotes for CYP2D6*4. By contrast, in the patients with red/blonde hair, three of five cases with asp294his were homozygotes for the mutant CYP2D6 allele. The difference in the frequency of CYP2D6*4 homozygotes in

  15. Metabolic regio- and stereoselectivity of cytochrome P450 2D6 towards 3,4-methylenedioxy-N-alkylamphetamines: in silico predictions and experimental validation.

    PubMed

    Keizers, Peter H J; de Graaf, Chris; de Kanter, Frans J J; Oostenbrink, Chris; Feenstra, K Anton; Commandeur, Jan N M; Vermeulen, Nico P E

    2005-09-22

    A series of 3,4-methylenedioxy-N-alkylamphetamines (MDAAs) were automatically docked and subjected to molecular dynamics (MD) simulations in a cytochrome P450 2D6 (CYP2D6) protein model. The predicted substrate binding orientations, sites of oxidation, and relative reactivities were compared to the experimental data of wild-type and Phe120Ala mutant CYP2D6. Automated docking results were not sufficient to accurately rationalize experimental binding orientations of 3,4-methylenedioxy-N-methylamphetamine (MDMA) in the two enzymes as measured with spin lattice relaxation NMR. Nevertheless, the docking results could be used as starting structures for MD simulations. Predicted binding orientations of MDMA and sites of oxidation of the MDAAs derived from MD simulations matched well with the experimental data. It appeared the experimental results were best described in MD simulations considering the nitrogen atoms of the MDAAs in neutral form. Differences in regioselectivity and stereoselectivity in the oxidative metabolism of the MDAAs by the Phe120Ala mutant CYP2D6 were correctly predicted, and the effects of the Phe120Ala mutation could be rationalized as well.

  16. Multiple doses of saw palmetto (Serenoa repens) did not alter cytochrome P450 2D6 and 3A4 activity in normal volunteers.

    PubMed

    Markowitz, John S; Donovan, Jennifer L; Devane, C Lindsay; Taylor, Robin M; Ruan, Ying; Wang, Jun-Sheng; Chavin, Kenneth D

    2003-12-01

    Saw palmetto (Serenoa repens) is the most commonly used herbal preparation in the treatment of benign prostatic hyperplasia. The objective of this study was to determine whether a characterized saw palmetto product affects the activity of cytochrome P450 (CYP) 2D6 or 3A4 in healthy volunteers (6 men and 6 women). The probe substrates dextromethorphan (CYP2D6 activity) and alprazolam (CYP3A4 activity) were administered orally at baseline and again after exposure to saw palmetto (320-mg capsule once daily) for 14 days. Dextromethorphan metabolic ratios and alprazolam pharmacokinetics were determined at baseline and after saw palmetto treatment. The mean ratio of dextromethorphan to its metabolite was 0.038 +/- 0.044 at baseline and 0.048 +/- 0.080 after 14 days of saw palmetto administration (P =.704, not significant [NS]), indicating a lack of effect on CYP2D6 activity. The area under the plasma alprazolam concentration versus time curve was 476 +/- 178 h. ng. mL(-1) at baseline and 479 +/- 125 h. ng. mL(-1) after saw palmetto treatment (P =.923, NS), indicating a lack of effect on CYP3A4 activity. The elimination half-life of alprazolam was 11.4 +/- 3.1 hours at baseline and 11.6 +/- 2.7 hours after saw palmetto treatment (P =.770, NS), also indicating a lack of effect on CYP3A4 activity. Our results indicate that extracts of saw palmetto at generally recommended doses are unlikely to alter the disposition of coadministered medications primarily dependent on the CYP2D6 or CYP3A4 pathways for elimination. These conclusions must be weighed in the context of the study's limited assessments and regarded as only the initial investigation into the drug interaction potential of saw palmetto.

  17. Rough Set Theory as an Interpretable Method for Predicting the Inhibition of Cytochrome P450 1A2 and 2D6.

    PubMed

    Burton, Julien; Petit, Joachim; Danloy, Emeric; Maggiora, Gerald M; Vercauteren, Daniel P

    2013-07-01

    Early prediction of ADME properties such as the cytochrome P450 (CYP) mediated drug-drug interactions is an important challenge in the drug discovery area. In this study, we propose to couple an original data mining approach based on Rough Set Theory (RST) to a structural description of molecules. The latter was achieved by using two types of structural keys: (1) the MACCS keys and (2) a set of five in-house fingerprints based on properties of the electron density distributions of chemical groups. The compounds considered are involved in the inhibition of CYP1A2 and CYP2D6. RST allowed the extraction of rules further used as classifiers to predict the inhibitory profile of an independent set of molecules. The results reached prediction accuracies of 90.6 and 88.2 % for CYP1A2 and CYP2D6, respectively. In addition, these classifiers were analyzed to determine which structural fragments were most used for building the rules, revealing relationships between the occurrence of particular molecular fragments and CYP inhibition. The results assessed RST as a suitable tool to build strongly predictive models and infer structure-activity rules associated with potency.

  18. The effects of acute hydrogen sulfide poisoning on cytochrome P450 isoforms activity in rats.

    PubMed

    Wang, Xianqin; Chen, Mengchun; Chen, Xinxin; Ma, Jianshe; Wen, Congcong; Pan, Jianchun; Hu, Lufeng; Lin, Guanyang

    2014-01-01

    Hydrogen sulfide (H2S) is the second leading cause of toxin related death (after carbon monoxide) in the workplace. H2S is absorbed by the upper respiratory tract mucosa, and it causes histotoxic hypoxemia and respiratory depression. Cocktail method was used to evaluate the influences of acute H2S poisoning on the activities of cytochrome P450 isoforms CYP2B6, CYP2D6, CYP3A4, CYP1A2, CYP2C19, and CYP2C9, which were reflected by the changes of pharmacokinetic parameters of six specific probe drugs, bupropion, metoprolol, midazolam, phenacetin, omeprazole, and tolbutamide, respectively. The experimental rats were randomly divided into two groups, control group and acute H2S poisoning group (inhaling 300 ppm for 2 h). The mixture of six probes was given to rats by oral administration and the blood samples were obtained at a series of time points through the caudal vein. The concentrations of probe drugs in rat plasma were measured by LC-MS. The results for acute H2S poisoning and control groups were as follows: there was a statistically significant difference in the AUC and C max for bupropion, metoprolol, phenacetin, and tolbutamide, while there was no statistical pharmacokinetic difference for midazolam and omeprazole. Acute H2S poisoning could inhibit the activity of CYP2B6, CYP2D6, CYP1A2, and CYP2C9 in rats.

  19. Identification of human cytochrome P450 isoforms involved in the 7-hydroxylation of chlorpromazine by human liver microsomes.

    PubMed

    Yoshii, K; Kobayashi, K; Tsumuji, M; Tani, M; Shimada, N; Chiba, K

    2000-01-01

    Studies to identify the cytochrome P450 (CYP) isoform(s) involved in chlorpromazine 7-hydroxylation were performed using human liver microsomes and cDNA-expressed human CYPs. The kinetics of chlorpromazine 7-hydroxylation in human liver microsomes showed a simple Michaelis-Menten behavior. The apparent Km and Vmax values were 3.4+/-1.0 microM and 200.5+/-83.7 pmol/min/mg, respectively. The chlorpromazine 7-hydroxylase activity in human liver microsomes showed good correlations with desipramine 2-hydroxylase activity (r = 0.763, p < 0.05), a marker activity for CYP2D6, and phenacetin O-deethylase activity (r = 0.638, p < 0.05), a marker activity for CYP1A2. Quinidine (an inhibitor of CYP2D6) completely inhibited while alpha-naphthoflavone (an inhibitor of CYP1A2) marginally inhibited the chlorpromazine 7-hydroxylase activity in a human liver microsomal sample showing high CYP2D6 activity. On the other hand, alpha-naphthoflavone inhibited the chlorpromazine 7-hydroxylase activity to 55-65% of control in a human liver microsomal sample showing low CYP2D6 activity. Among eleven cDNA-expressed CYPs studied, CYP2D6 and CYP1A2 exhibited significant activity for the chlorpromazine 7-hydroxylation. The Km values for the chlorpromazine 7-hydroxylation of both cDNA-expressed CYP2D6 and CYP1A2 were in agreement with the Km values of human liver microsomes. These results suggest that chlorpromazine 7-hydroxylation is catalyzed mainly by CYP2D6 and partially by CYP1A2.

  20. Effects of green tea catechins on cytochrome P450 2B6, 2C8, 2C19, 2D6 and 3A activities in human liver and intestinal microsomes.

    PubMed

    Misaka, Shingen; Kawabe, Keisuke; Onoue, Satomi; Werba, José Pablo; Giroli, Monica; Tamaki, Sekihiro; Kan, Toshiyuki; Kimura, Junko; Watanabe, Hiroshi; Yamada, Shizuo

    2013-01-01

    The effects of green tea catechins on the main drug-metabolizing enzymatic system, cytochrome P450 (CYP), have not been fully elucidated. The objective of the present study was to evaluate the effects of green tea extract (GTE, total catechins 86.5%, w/w) and (-)-epigallocatechin-3-gallate (EGCG) on the activities of CYP2B6, CYP2C8, CYP2C19, CYP2D6 and CYP3A in vitro, using pooled human liver and intestinal microsomes. Bupropion hydroxylation, amodiaquine N-deethylation, (S)-mephenytoin 4'-hydroxylation, dextromethorphan O-demethylation and midazolam 1'-hydroxylation were assessed in the presence or absence of various concentrations of GTE and EGCG to test their effects on CYP2B6, CYP2C8, CYP2C19, CYP2D6 and CYP3A activities, respectively. Each metabolite was quantified using UPLC/ESI-MS, and the inhibition kinetics of GTE and EGCG on CYP enzymes was analyzed. In human liver microsomes, IC50 values of GTE were 5.9, 4.5, 48.7, 25.1 and 13.8 µg/mL, for CYP2B6, CYP2C8, CYP2C19, CYP2D6 and CYP3A, respectively. ECGC also inhibited these CYP isoforms with properties similar to those of GTE, and produced competitive inhibitions against CYP2B6 and CYP2C8, and noncompetitive inhibition against CYP3A. In human intestinal microsomes, IC50 values of GTE and EGCG for CYP3A were 18.4 µg/mL and 31.1 µM, respectively. EGCG moderately inhibited CYP3A activity in a noncompetitive manner. These results suggest that green tea catechins cause clinically relevant interactions with substrates for CYP2B6 and CYP2C8 in addition to CYP3A.

  1. Modeling chemical interaction profiles: I. Spectral data-activity relationship and structure-activity relationship models for inhibitors and non-inhibitors of cytochrome P450 CYP3A4 and CYP2D6 isozymes.

    PubMed

    McPhail, Brooks; Tie, Yunfeng; Hong, Huixiao; Pearce, Bruce A; Schnackenberg, Laura K; Ge, Weigong; Valerio, Luis G; Fuscoe, James C; Tong, Weida; Buzatu, Dan A; Wilkes, Jon G; Fowler, Bruce A; Demchuk, Eugene; Beger, Richard D

    2012-03-15

    An interagency collaboration was established to model chemical interactions that may cause adverse health effects when an exposure to a mixture of chemicals occurs. Many of these chemicals--drugs, pesticides, and environmental pollutants--interact at the level of metabolic biotransformations mediated by cytochrome P450 (CYP) enzymes. In the present work, spectral data-activity relationship (SDAR) and structure-activity relationship (SAR) approaches were used to develop machine-learning classifiers of inhibitors and non-inhibitors of the CYP3A4 and CYP2D6 isozymes. The models were built upon 602 reference pharmaceutical compounds whose interactions have been deduced from clinical data, and 100 additional chemicals that were used to evaluate model performance in an external validation (EV) test. SDAR is an innovative modeling approach that relies on discriminant analysis applied to binned nuclear magnetic resonance (NMR) spectral descriptors. In the present work, both 1D ¹³C and 1D ¹⁵N-NMR spectra were used together in a novel implementation of the SDAR technique. It was found that increasing the binning size of 1D ¹³C-NMR and ¹⁵N-NMR spectra caused an increase in the tenfold cross-validation (CV) performance in terms of both the rate of correct classification and sensitivity. The results of SDAR modeling were verified using SAR. For SAR modeling, a decision forest approach involving from 6 to 17 Mold2 descriptors in a tree was used. Average rates of correct classification of SDAR and SAR models in a hundred CV tests were 60% and 61% for CYP3A4, and 62% and 70% for CYP2D6, respectively. The rates of correct classification of SDAR and SAR models in the EV test were 73% and 86% for CYP3A4, and 76% and 90% for CYP2D6, respectively. Thus, both SDAR and SAR methods demonstrated a comparable performance in modeling a large set of structurally diverse data. Based on unique NMR structural descriptors, the new SDAR modeling method complements the existing SAR

  2. In vitro inhibitory activities of the extract of Hibiscus sabdariffa L. (family Malvaceae) on selected cytochrome P450 isoforms.

    PubMed

    Johnson, Showande Segun; Oyelola, Fakeye Titilayo; Ari, Tolonen; Juho, Hokkanen

    2013-01-01

    Literature is scanty on the interaction potential of Hibiscus sabdariffa L., plant extract with other drugs and the affected targets. This study was conducted to investigate the cytochrome P450 (CYP) isoforms that are inhibited by the extract of Hibiscus sabdariffa L. in vitro. The inhibition towards the major drug metabolizing CYP isoforms by the plant extract were estimated in human liver microsomal incubations, by monitoring the CYP-specific model reactions through previously validated N-in-one assay method. The ethanolic extract of Hibiscus sabdariffa showed inhibitory activities against nine selected CYP isoforms: CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4. The concentrations of the extract which produced 50% inhibition of the CYP isoforms ranged from 306 µg/ml to 1660 µg/ml, and the degree of inhibition based on the IC50 values for each CYP isoform was in the following order: CYP1A2 > CYP2C8 > CYP2D6 > CYP2B6 > CYP2E1 > CYP2C19 > CYP3A4 > CYP2C9 > CYP2A6. Ethanolic extract of Hibiscus sabdariffa caused inhibition of CYP isoforms in vitro. These observed inhibitions may not cause clinically significant herb-drug interactions; however, caution may need to be taken in co-administering the water extract of Hibiscus sabdariffa with other drugs until clinical studies are available to further clarify these findings.

  3. Influence of Cytochrome P450, Family 2, Subfamily D, Polypeptide 6 (CYP2D6) polymorphisms on pain sensitivity and clinical response to weak opioid analgesics.

    PubMed

    Zahari, Zalina; Ismail, Rusli

    2014-01-01

      CYP2D6 polymorphisms show large geographical and interethnic differences. Variations in CYP2D6 activity may impact upon a patient's pain level and may contribute to interindividual variations in the response to opioids. This paper reviews the evidence on how CYP2D6 polymorphisms might influence pain sensitivity and clinical response to codeine and tramadol. For example, it is shown that (1) CYP2D6 poor metabolizers (PMs) may be less efficient at synthesizing endogenous morphine compared with other metabolizers. In contrast, ultra-rapid metabolizers (UMs) may be more efficient than other metabolizers at synthesizing endogenous morphine, thus strengthening endogenous pain modulation. Additionally, for codeine and tramadol that are bioactivated by CYP2D6, PMs may undergo no metabolite formation, leading to inadequate analgesia. Conversely, UMs may experience quicker analgesic effects but be prone to higher mu-opioid-related toxicity. The literature suggested the potential usefulness of the determination of CYP2D6 polymorphisms in elucidating serious adverse events and in preventing subsequent inappropriate selection or doses of codeine and tramadol. Notably, even though many studies investigated a possible role of the CYP2D6 polymorphisms on pain sensitivity, pharmacokinetics and pharmacodynamics of these drugs, the results of analgesia and adverse effects are conflicting. More studies are required to demonstrate genetically determined unresponsiveness and risk of developing serious adverse events for patients with pain and these should involve larger numbers of patients in different population types.

  4. Inhibitory properties of trapping agents: glutathione, potassium cyanide, and methoxylamine, against major human cytochrome p450 isoforms.

    PubMed

    Zhang, Chenghong; Wong, Susan; Delarosa, Erlie M; Kenny, Jane R; Halladay, Jason S; Hop, Cornelis E; Khojasteh-Bakht, Siamak Cyrus

    2009-04-01

    In the early stages of drug discovery, the formation of reactive metabolites is often assessed by co-incubating the drug in liver microsomes with a trapping agent in the presence of NADPH. Our group assessed the capability of commonly used trapping agents to reversibly inhibit major cytochrome P450 (CYP) isoforms. Glutathione and cyanide did not inhibit the enzymes at concentrations up to 10 mM; however methoxylamine did show inhibition, with IC(50) values of 0.53 mM for CYP1A2, 4.12 mM for CYP2C9, 2.04 mM for CYP2C19, 9.72 mM for CYP2D6, and 1.26 and >10 mM for CYP3A4/5 (for testosterone and midazolam, respectively, as substrates).

  5. Comparative aromatic hydroxylation and N-demethylation of MPTP neurotoxin and its analogs, N-methylated {beta}-carboline and isoquinoline alkaloids, by human cytochrome P450 2D6

    SciTech Connect

    Herraiz, Tomas . E-mail: therraiz@ifi.csic.es; Guillen, Hugo; Aran, Vicente J.; Idle, Jeffrey R.; Gonzalez, Frank J.

    2006-11-01

    1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxin is a chemical inducer of Parkinson's disease (PD) whereas N-methylated {beta}-carbolines and isoquinolines are naturally occurring analogues of MPTP involved in PD. This research has studied the oxidation of MPTP by human CYP2D6 (CYP2D6*1 and CYP2D6*10 allelic variants) as well as by a mixture of cytochrome P450s-resembling HLM, and the products generated compared with those afforded by human monoamine oxidase (MAO-B). MPTP was efficiently oxidized by CYP2D6 to two main products: MPTP-OH (p-hydroxylation) and PTP (N-demethylation), with turnover numbers of 10.09 min{sup -1} and K {sub m} of 79.36 {+-} 3 {mu}M (formation of MPTP-OH) and 18.95 min{sup -1} and K {sub m} 69.6 {+-} 2.2 {mu}M (PTP). Small amounts of dehydrogenated toxins MPDP{sup +} and MPP{sup +} were also detected. CYP2D6 competed with MAO-B for the oxidation of MPTP. MPTP oxidation by MAO-B to MPDP{sup +} and MPP{sup +} toxins (bioactivation) was up to 3-fold higher than CYP2D6 detoxification to PTP and MPTP-OH. Several N-methylated {beta}-carbolines and isoquinolines were screened for N-demethylation (detoxification) that was not significantly catalyzed by CYP2D6 or the P450s mixture. In contrast, various {beta}-carbolines were efficiently hydroxylated to hydroxy-{beta}-carbolines by CYP2D6. Thus, N(2)-methyl-1,2,3,4-tetrahydro-{beta}-carboline (a close MPTP analog) was highly hydroxylated to 6-hydroxy-N(2)-methyl-1,2,3,4-tetrahydro-{beta}-carboline and a corresponding 7-hydroxy-derivative. Thus, CYP2D6 could participate in the bioactivation and/or detoxification of these neuroactive compounds by an active hydroxylation pathway. The CYP2D6*1 enzymatic variant exhibited much higher metabolism of both MPTP and N(2)-methyl-1,2,3,4-tetrahydro-{beta}-carboline than the CYP2D6*10 variant, highlighting the importance of CYP2D6 polymorphism in the oxidation of these toxins. Altogether, these results suggest that CYP2D6 can play an important role

  6. Does Compound I Vary Significantly between Isoforms of Cytochrome P450?

    PubMed Central

    2011-01-01

    The cytochrome P450 (CYP) enzymes are important in many areas, including pharmaceutical development. Subtle changes in the electronic structure of the active species, Compound I, have been postulated previously to account partly for the experimentally observed differences in reactivity between isoforms. Current predictive models of CYP metabolism typically assume an identical Compound I in all isoforms. Here we present a method to calculate the electronic structure and to estimate the Fe–O bond enthalpy of Compound I, and apply it to several human and bacterial CYP isoforms. Conformational flexibility is accounted for by sampling large numbers of structures from molecular dynamics simulations, which are subsequently optimized with density functional theory (B3LYP) based quantum mechanics/molecular mechanics. The observed differences in Compound I between human isoforms are small: They are generally smaller than the spread of values obtained for the same isoform starting from different initial structures. Hence, it is unlikely that the variation in activity between human isoforms is due to differences in the electronic structure of Compound I. A larger difference in electronic structure is observed between the human isoforms and P450cam and may be explained by the slightly different hydrogen-bonding environment surrounding the cysteinyl sulfur. The presence of substrate in the active site of all isoforms studied appears to cause a slight decrease in the Fe–O bond enthalpy, apparently due to displacement of water out of the active site, suggesting that Compound I is less stable in the presence of substrate. PMID:21863858

  7. Binding of bufuralol, dextromethorphan, and 3,4-methylenedioxymethylamphetamine to wild-type and F120A mutant cytochrome P450 2D6 studied by resonance Raman spectroscopy

    SciTech Connect

    Bonifacio, Alois . E-mail: zwan@few.vu.nl

    2006-05-12

    Cytochrome P450 2D6 (CYP2D6) is one of the most important drug-metabolizing enzymes in humans. Resonance Raman data, reported for First time for CYP2D6, show that the CYP2D6 heme is found to be in a six-coordinated low-spin state in the absence of substrates, and it is perturbed to different extents by bufuralol, dextromethorphan, and 3,4-methylenedioxymethylamphetamine (MDMA). Dextromethorphan and MDMA induce in CYP2D6 a significant amount of five-coordinated high-spin heme species and reduce the polarity of its heme-pocket, whereas bufuralol does not. Spectra of the F120A mutant CYP2D6 suggest that Phe{sup 12} is involved in substrate-binding of dextromethorphan and MDMA, being responsible for the spectral differences observed between these two compounds and bufuralol. These differences could be explained postulating a different substrate mobility for each compound in the CYP2D6 active site, consistently with the role previously suggested for Phe{sup 12} in binding dextromethorphan and MDMA.

  8. Opioid Analgesia in P450 Gene Cluster Knockout Mice: A Search for Analgesia-Relevant Isoforms

    PubMed Central

    Nalwalk, Julia W.; Ding, Xinxin; Scheer, Nico

    2015-01-01

    Cytochrome P450 monooxygenases (P450s), which are well-known drug-metabolizing enzymes, are thought to play a signal transduction role in µ opioid analgesia and may serve as high-affinity 3H-cimetidine (3HCIM) binding sites in the brain. 3HCIM binding sites may also be related to opioid or nonopioid analgesia. However, of the more than 100 murine P450 enzymes, the specific isoform(s) responsible for either function have not been identified. Presently, three lines of constitutive P450 gene cluster knockout (KO) mice with full-length deletions of 14 Cyp2c, 9 Cyp2d, and 7 Cyp3a genes were studied for deficiencies in 3HCIM binding and for opioid analgesia. Liver and brain homogenates from all three genotypes showed normal 3HCIM binding values, indicating that gene products of Cyp2d, Cyp3a, and Cyp2c are not 3HCIM-binding proteins. Cyp2d KO and Cyp3a KO mice showed normal antinociceptive responses to a moderate systemic dose of morphine (20 mg/kg, s.c.), thereby excluding 16 P450 isoforms as mediators of opioid analgesia. In contrast, Cyp2c KO mice showed a 41% reduction in analgesic responses following systemically (s.c.) administered morphine. However, the significance of brain Cyp2c gene products in opioid analgesia is uncertain because little or no analgesic deficits were noted in Cyp2c KO mice following intracerebroventricular or intrathecalmorphine administration, respectively. These results show that the gene products of Cyp2d and Cyp3a do not contribute to µ opioid analgesia in the central nervous system. A possible role for Cyp2c gene products in opioid analgesia requires further consideration. PMID:26109562

  9. Anti-LKM-1 antibodies determined by use of recombinant P450 2D6 in ELISA and western blot and their association with anti-HCV and HCV-RNA.

    PubMed Central

    Seelig, R; Renz, M; Bünger, G; Schröter, H; Seelig, H P

    1993-01-01

    Several subtypes of anti-liver-kidney microsome antibodies (LKM) are known. LKM-1 antibodies associated with autoimmune chronic active hepatitis recognize P450 2D6, a cytochrome P450 mono-oxygenase. The frequent association of anti-LKM-1 antibodies and hepatitis C virus (HCV) infections and the probable existence of an infectious and autoimmune form of anti-LKM-1-associated hepatitis, requiring different therapeutical strategies, necessitates the exact determination of anti-LKM-1 specificities. Therefore, we compared various antibody tests (immunofluorescence, ELISA with recombinant P450 2D6, and Western blot with recombinant and natural antigens and agargel double diffusion) with sera of 27 anti-LKM-1-positive chronic active hepatitis (CAH) patients, with 61 sera harbouring anti-mitochondrial antibodies, 100 sera each from HCV-RNA-positive and HCV-RNA-negative patients, and 50 sera of healthy persons. Western blot techniques using recombinant MS2-polymerase P450 2D6 fusion protein were found to be the most sensitive and specific method for anti-LKM-1 antibody determination in routine laboratory. The recently recognized association of anti-LKM-1 antibody and HCV infection was confirmed by the results of this study. In anti-HCV and HCV-RNA-positive patients with anti-LKM-1 antibodies there was a preponderance of males with higher mean age and lower antibody titres. The results support the hypothesis of the existence of an autoimmune as well as an infectious (HCV triggered) subgroup of anti-LKM-1-positive hepatitis. Images Fig. 1 PMID:8390333

  10. Substituted Imidazole of 5-Fluoro-2-[4-[(2-phenyl-1H-imidazol-5-yl)methyl]-1-piperazinyl]pyrimidine Inactivates Cytochrome P450 2D6 by Protein Adduction

    PubMed Central

    Nagy, Leslie D.; Mocny, Catherine S.; Diffenderfer, Laura E.; Hsi, David J.; Butler, Brendan F.; Arthur, Evan J.; Fletke, Kyle J.; Palamanda, Jairam R.; Nomeir, Amin A.

    2011-01-01

    5-Fluoro-2-[4-[(2-phenyl-1H-imidazol-5-yl)methyl]-1-piperazinyl]pyrimidine (SCH 66712) is a potent mechanism-based inactivator of human cytochrome P450 2D6 that displays type I binding spectra with a Ks of 0.39 ± 0.10 μM. The partition ratio is ∼3, indicating potent inactivation that addition of exogenous nucleophiles does not prevent. Within 15 min of incubation with SCH 66712 and NADPH, ∼90% of CYP2D6 activity is lost with only ∼20% loss in ability to bind CO and ∼25% loss of native heme over the same time. The stoichiometry of binding to the protein was 1.2:1. SDS-polyacrylamide gel electrophoresis with Western blotting and autoradiography analyses of CYP2D6 after incubations with radiolabeled SCH 66712 further support the presence of a protein adduct. Metabolites of SCH 66712 detected by mass spectrometry indicate that the phenyl group on the imidazole ring of SCH 66712 is one site of oxidation by CYP2D6 and could lead to methylene quinone formation. Three other metabolites were also observed. For understanding the metabolic pathway that leads to CYP2D6 inactivation, metabolism studies with CYP2C9 and CYP2C19 were performed because neither of these enzymes is significantly inhibited by SCH 66712. The metabolites formed by CYP2C9 and CYP2C19 are the same as those seen with CYP2D6, although in different abundance. Modeling studies with CYP2D6 revealed potential roles of various active site residues in the oxidation of SCH 66712 and inactivation of CYP2D6 and showed that the phenyl group of SCH 66712 is positioned at 2.2 Å from the heme iron. PMID:21422192

  11. Malathion bioactivation in the human liver: the contribution of different cytochrome p450 isoforms.

    PubMed

    Buratti, Franca M; D'Aniello, Alessandra; Volpe, Maria Teresa; Meneguz, Annarita; Testai, Emanuela

    2005-03-01

    Among organophosphorothioate (OPT) pesticides, malathion is considered relatively safe for use in mammals. Its rapid degradation by carboxylesterases competes with the cytochrome P450 (P450)-catalyzed formation of malaoxon, the toxic metabolite. However, impurities in commercial formulations are potent inhibitors of carboxylesterase, allowing a dramatic increase in malaoxon formation. Malathion desulfuration has been characterized in human liver microsomes (HLMs) with a method based on acetylcholinesterase inhibition that is able to detect nanomolar levels of oxon. The active P450 isoforms have been identified by means of a multifaceted strategy, including the use of cDNA-expressed human P450s and correlation, immunoinhibition, and chemical inhibition studies in a panel of phenotyped HLMs. HLMs catalyzed malaoxon formation with a high level of variability (>200-fold). One or two components (K(mapp1) = 53-67 microM; K(mapp2) = 427-1721 microM) were evidenced, depending on the relative specific P450 content. Results from different approaches indicated that, at low malathion concentration, malaoxon formation is catalyzed by CYP1A2 and, to a lesser extent, 2B6, whereas the role of 3A4 is relevant only at high malathion levels. These results are in line with those found with chlorpyrifos, diazinon, azynphos-methyl, and parathion, characterized by the presence of an aromatic ring in the molecule. Since malathion has linear chains as substituents at the thioether sulfur, it can be hypothesized that, independently from the chemical structure, OPTs are bioactivated by the same P450s. These results also suggest that CYP1A2 and 2B6 can be considered as possible metabolic biomarkers of susceptibility to OPT-induced toxic effects at actual human exposure levels.

  12. Role of specific cytochrome P450 isoforms in the conversion of phenoxypropoxybiguanide analogs in human liver microsomes to potent antimalarial dihydrotriazines.

    PubMed

    Diaz, Damaris S; Kozar, Michael P; Smith, Kirsten S; Asher, Constance O; Sousa, Jason C; Schiehser, Guy A; Jacobus, David P; Milhous, Wilbur K; Skillman, Donald R; Shearer, Todd W

    2008-02-01

    Phenoxypropoxybiguanides, such as PS-15, are antimalarial prodrugs analogous to the relationship of proguanil and its active metabolite cycloguanil. Unlike cycloguanil, however, WR99210, the active metabolite of PS-15, has retained in vitro potency against newly emerging antifolate-resistant malaria parasites. Recently, in vitro metabolism of a new series of phenoxypropoxybiguanide analogs has examined the production of the active triazine metabolites by human liver microsomes. The purpose of this investigation was to elucidate the primary cytochrome P450 isoforms involved in the production of active metabolites in the current lead candidate. By using expressed human recombinant isoform preparations, specific chemical inhibitors, and isoform-specific inhibitory antibodies, the primary cytochrome P450 isoforms involved in the in vitro metabolic activation of JPC-2056 were elucidated. Unlike proguanil, which is metabolized primarily by CYP2C19, the results indicate that CYP3A4 plays a more important role in the metabolism of both PS-15 and JPC-2056. Whereas CYP2D6 appears to play a major role in the metabolism of PS-15 to WR99210, it appears less important in the conversion of JPC-2056 to JPC-2067. These results are encouraging, considering the prominence of CYP2C19 and CYP2D6 polymorphisms in certain populations at risk for contracting malaria, because the current clinical prodrug candidate from this series may be less dependent on these enzymes for metabolic activation.

  13. Polymorphism in CYP2D6 and CYP2C19, members of the cytochrome P450 mixed-function oxidase system, in the metabolism of psychotropic drugs.

    PubMed

    Stingl, J; Viviani, R

    2015-02-01

    Numerous studies in the field of psychopharmacological treatment have investigated the possible contribution of genetic variability between individuals to differences in drug efficacy and safety, motivated by the wide individual variation in treatment response. Genomewide analyses have been conducted in several large-scale studies on antidepressant drug response. However, no consistent findings have emerged from these studies. In a recent meta-analysis of genomewide data from the three studies capturing common variation for association with symptomatic improvement and remission revealed the absence of any strong genetic association and failed to replicate results of individual studies in the pooled data. However, there are good reasons to consider the possible importance of pharmacogenetic variants separately. These variants explain a large portion of the manifold variability in individual drug metabolism. More than 20 psychotropic drugs have now been relabelled by the FDA adding information on polymorphic drug metabolism and therapeutic recommendations. Furthermore, dose recommendations for polymorphisms in drug metabolizing enzymes, first and foremost CYP2D6 and CYP2C19, have been issued with the advice to reduce the dosage in poor metabolizers to 50% or less (in eight cases), or to choose an alternative treatment. Beside the well-described role in hepatic drug metabolism, these enzymes are also expressed in the brain and play a role in biotransformation of endogenous substrates. These polymorphisms may therefore modulate brain metabolism and affect the function of the neural substrates of cognition and emotion.

  14. In vivo effects of goldenseal, kava kava, black cohosh, and valerian on human cytochrome P450 1A2, 2D6, 2E1, and 3A4 phenotypes

    PubMed Central

    Gardner, Stephanie F.; Hubbard, Martha A.; Williams, D. Keith; Gentry, W. Brooks; Khan, Ikhlas A.; Shah., Amit

    2007-01-01

    Objectives Phytochemical-mediated modulation of cytochrome P-450 activity may underlie many herb-drug interactions. Single time-point, phenotypic metabolic ratios were used to determine whether long-term supplementation of goldenseal (Hydrastis canadensis), black cohosh (Cimicifuga racemosa), kava kava (Piper methysticum), or valerian (Valeriana officinalis) extracts affected CYP1A2, CYP2D6, CYP2E1, or CYP3A4/5 activity. Methods Twelve healthy volunteers (6 females) were randomly assigned to receive goldenseal, black cohosh, kava kava, or valerian for 28 days. For each subject, a 30-day washout period was interposed between each supplementation phase. Probe drug cocktails of midazolam and caffeine, followed 24 hours later by chlorzoxazone and debrisoquine were administered before (baseline) and at the end of supplementation. Pre- and post-supplementation phenotypic trait measurements were determined for CYP3A4/5, CYP1A2, CYP2E1, and CYP2D6 using 1-hydroxymidazolam/midazolam serum ratios (1-hour sample), paraxanthine/caffeine serum ratios (6-hour sample), 6-hydroxychlorzoxazone/chlorzoxazone serum ratios (2-hour sample), and debrisoquine urinary recovery ratios (8-hour collection), respectively. The content of purported “active” phytochemicals was determined for each supplement. Results Comparisons of pre- and post-supplementation phenotypic ratio means revealed significant inhibition (~40%) of CYP2D6 (difference = −0.228; 95% CI = −0.268 to −0.188) and CYP3A4/5 (difference = −1.501; 95% CI = −1.840 to −1.163) activity for goldenseal. Kava produced significant reductions (~40%) in CYP2E1 only (difference = −0.192; 95% CI = −0.325 to −0.060). Black cohosh also exhibited statistically significant inhibition of CYP2D6 (difference = −0.046; 95% CI = −0.085 to −0.007), but the magnitude of the effect (~7%) did not appear clinically relevant. No significant changes in phenotypic ratios were observed for valerian. Conclusions Botanical

  15. Binding of 7-methoxy-4-(aminomethyl)-coumarin to wild-type and W128F mutant cytochrome P450 2D6 studied by time-resolved fluorescence spectroscopy

    PubMed Central

    Stortelder, Aike; Keizers, Peter H. J.; Oostenbrink, Chris; De Graaf, Chris; De Kruijf, Petra; Vermeulen, Nico P. E.; Gooijer, Cees; Commandeur, Jan N. M.; Van Der Zwan, Gert

    2005-01-01

    Enzyme structure and dynamics may play a main role in substrate binding and the subsequent steps in the CYP (cytochrome P450) catalytic cycle. In the present study, changes in the structure of human CYP2D6 upon binding of the substrate are studied using steady-state and time-resolved fluorescence methods, focusing not only on the emission of the tryptophan residues, but also on emission of the substrate. As a substrate, MAMC [7-methoxy-4-(aminomethyl)-coumarin] was selected, a compound exhibiting native fluorescence. As well as the wild-type, the W128F (Trp128→Phe) mutant of CYP2D6 was studied. After binding, a variety of energy transfer possibilities exist, and molecular dynamics simulations were performed to calculate distances and relative orientations of donors and acceptors. Energy transfer from Trp128 to haem appeared to be important; its emission was related to the shortest of the three average tryptophan fluorescence lifetimes observed for CYP2D6. MAMC to haem energy transfer was very efficient as well: when bound in the active site, the emission of MAMC was fully quenched. Steady-state anisotropy revealed that besides the MAMC in the active site, another 2.4% of MAMC was bound outside of the active site to wild-type CYP2D6. The tryptophan residues in CYP2D6 appeared to be less accessible for the external quenchers iodide and acrylamide in presence of MAMC, indicating a tightening of the enzyme structure upon substrate binding. However, the changes in the overall enzyme structure were not very large, since the emission characteristics of the enzyme were not very different in the presence of MAMC. PMID:16190863

  16. Application of a higher throughput approach to derive apparent Michaelis-Menten constants of isoform-selective p450-mediated biotransformation reactions in human hepatocytes.

    PubMed

    Li, Albert P; Schlicht, Kari E

    2014-01-01

    A higher throughput platform was developed for the determination of K(M) values for isoformselective P450 substrates in human hepatocytes via incubation of the hepatocytes with substrates in 384- well plates and metabolite quantification by RapidFire™ mass spectrometry. Isoform-selective P450 substrates were incubated at 8 concentrations in triplicate with cryopreserved human hepatocytes from 16 donors. The metabolic pathways examined were the CYP1A2-catalyzed tacrine 1-hydroxylation, CYP2B6-catalyzed bupropion hydroxylation, CYP2C8-catalyzed amodiaquine N-deethylation, CYP2C9- catalyzed diclofenac 4'-hydroxylation, CYP2D6-catalyzed dextromethorphan O-demethylation, and CYP3A4-catalyzed midazolam 1'-hydroxylation. Typical saturation enzyme kinetics was observed for all the pathways evaluated. Individual differences in the apparent V(max) and K(M) values were observed among the human hepatocytes from each of the 16 individual donors, with no statistically significant gender- or age-associated differences. A "composite" K(M) value was calculated for each of the pathways via normalizing the individual activities to their respective V(max) values to develop "relative activities" followed by Michaelis-Menten analysis of the mean relative activities of the 16 donors at each of the 8 substrate concentrations. The resulting "composite" K(M) values for the P450 substrates may be used to guide in vitro P450 inhibition and induction studies and kinetic modeling of in vivo drug-drug interaction.

  17. Characterizing the effect of cytochrome P450 (CYP) 2C8, CYP2C9, and CYP2D6 genetic polymorphisms on stereoselective N-demethylation of fluoxetine.

    PubMed

    Wang, Zhangting; Wang, Shengjia; Huang, Minmin; Hu, Haihong; Yu, Lushan; Zeng, Su

    2014-03-01

    Fluoxetine (FLX) is one of the most widely prescribed selective serotonin reuptake inhibitors. Although FLX is used as racemate in the clinic, the clinical pharmacokinetics of FLX and its N-demethylation metabolite norfluoxetine (NFLX) show obvious cytochrome P450 (CYP) polymorphism dependency and exhibit marked stereoselectivity. However, the kinetic profiles of CYP variants to FLX remain unclear. In the present study, some variants of human CYP2C8, CYP2C9, and CYP2D6 were first expressed in insect cells, and their catalytic roles with respect to FLX enantiomers were then investigated. CYP2C8.4 and CYP2C9.10 showed significantly lower activity and CYP2C8.3 showed significantly higher activity toward both R- and S-FLX compared with the wildtype, while CYP2C9.3, CYP2C9.13, and CYP2C9.16 showed significantly lower activity only toward R-FLX. Five CYP2C9 variants and CYP2D6.1 exhibited significantly stereoselective kinetic profiles prior to R-FLX, and CYP2C8.3 showed a slight stereoselectivity. Interestingly, obvious substrate inhibition was observed in the CYP2C9 wildtype and its three variants only in the case of R-FLX. Together, these findings suggest that CYP2C9 and CYP2D6 polymorphism may play an important role in the clearance of FLX and also in the stereoselective kinetic profiles of FLX enantiomers.

  18. Carbonated soft drinks alter hepatic cytochrome P450 isoform expression in Wistar rats.

    PubMed

    Alkhedaide, Adel; Soliman, Mohamed Mohamed; Ibrahim, Zein Shaban

    2016-11-01

    The aim of the current study was to examine the effects of chronic consumption of soft drinks (SDs) on hepatic oxidative stress and cytochrome P450 enzymes (CYPs) expression in the livers of Wistar rats. For 3 consecutive months, the rats had free access to three different soft drinks, Coca-Cola, Pepsi-Cola and 7-UP. The rats were subsequently compared with control group rats that had consumed water. Blood and hepatic tissue samples were assayed for the changes in antioxidants, liver function biomarkers and hepatic gene expression for different isoforms of hepatic CYP. The results indicated that SD consumption (SDC) decreased serum antioxidant levels and increased malondialdehyde secretion, and increased liver biomarkers (glutamate pyruvate transaminase and glutamate oxaloacetate). SD induced alterations in mRNA expression of hepatic antioxidants and cytochrome isoforms. The expression of peroxidase, catalase, CYP1A2, CYP3A2 and CYP2C11 in the liver were upregulated following SDC. By contrast, CYP2B1 was downregulated after 3 months of SDC in liver tissue samples. Thus, the present findings indicate that SDs induced oxidative stress in the liver of Wistar rats and for the first time, to the best of our knowledge, indicate that SDC disrupts hepatic CYP enzymes that may affect drug metabolism. Therefore, drug-dosing programs should be carefully designed to take these novel findings into consideration for the treatment of diseases.

  19. Carbonated soft drinks alter hepatic cytochrome P450 isoform expression in Wistar rats

    PubMed Central

    Alkhedaide, Adel; Soliman, Mohamed Mohamed; Ibrahim, Zein Shaban

    2016-01-01

    The aim of the current study was to examine the effects of chronic consumption of soft drinks (SDs) on hepatic oxidative stress and cytochrome P450 enzymes (CYPs) expression in the livers of Wistar rats. For 3 consecutive months, the rats had free access to three different soft drinks, Coca-Cola, Pepsi-Cola and 7-UP. The rats were subsequently compared with control group rats that had consumed water. Blood and hepatic tissue samples were assayed for the changes in antioxidants, liver function biomarkers and hepatic gene expression for different isoforms of hepatic CYP. The results indicated that SD consumption (SDC) decreased serum antioxidant levels and increased malondialdehyde secretion, and increased liver biomarkers (glutamate pyruvate transaminase and glutamate oxaloacetate). SD induced alterations in mRNA expression of hepatic antioxidants and cytochrome isoforms. The expression of peroxidase, catalase, CYP1A2, CYP3A2 and CYP2C11 in the liver were upregulated following SDC. By contrast, CYP2B1 was downregulated after 3 months of SDC in liver tissue samples. Thus, the present findings indicate that SDs induced oxidative stress in the liver of Wistar rats and for the first time, to the best of our knowledge, indicate that SDC disrupts hepatic CYP enzymes that may affect drug metabolism. Therefore, drug-dosing programs should be carefully designed to take these novel findings into consideration for the treatment of diseases. PMID:27882225

  20. Progression of cervical intraepithelial neoplasia to cervical cancer: interactions of cytochrome P450 CYP2D6 EM and glutathione s-transferase GSTM1 null genotypes and cigarette smoking.

    PubMed Central

    Warwick, A. P.; Redman, C. W.; Jones, P. W.; Fryer, A. A.; Gilford, J.; Alldersea, J.; Strange, R. C.

    1994-01-01

    The factors that determine progression of cervical intraepithelial neoplasia (CIN) to squamous cell carcinoma (SCC) are unknown. Cigarette smoking is an independent risk factor for cervical neoplasia, suggesting that polymorphism at detoxicating enzyme loci such as cytochrome P450 CYP2D6 and glutathione S-transferase GSTM1 may determine susceptibility to these cancers. We have studied the frequencies of genotypes at these loci in women suffering low-grade CIN, high-grade CIN and SCC. A non-cancer control group was provided by women with normal cervical histology suffering menorrhagia. Comparison of the frequency distributions of the CYP2D6 PM, HET and EM genotypes (G-->A transition at intron 3/exon 4 and base pair deletion in exon 5) revealed no significant differences between the menorrhagia and SCC groups. Frequency distributions in the menorrhagia group, however, were significantly different (P < 0.04) from those in the low- and high-grade CIN groups. Thus, the proportion of EM was significantly larger (P < 0.03) and of HET generally lower. We found that the frequency of GSTM1 null in the menorrhagia and case groups was not significantly different. Interactive effects of enzyme genotypes with cigarette smoking were studied by comparing the multinomial frequency distributions of CYP2D6 EM/GSTM1 null/smoking over mutually exclusive categories. These showed no significant differences between the menorrhagia group and SCC or low-grade CIN groups. The frequency distribution in high-grade CIN, however, was significantly different to that in the menorrhagia group and in both SCC and low-grade CIN groups. This study was identified, for the first time, an inherited characteristic in women with high-grade CIN who appear to be at reduced risk of SCC. Thus, women with CYP2D6 EM who smoke have increased susceptibility to high-grade CIN but are less likely to progress to SCC, possibly because they effectively detoxify an unidentified chemical involved in mediating disease

  1. A Unified Proteochemometric Model for Prediction of Inhibition of Cytochrome P450 Isoforms

    PubMed Central

    Lapins, Maris; Worachartcheewan, Apilak; Spjuth, Ola; Georgiev, Valentin; Prachayasittikul, Virapong; Nantasenamat, Chanin; Wikberg, Jarl E. S.

    2013-01-01

    A unified proteochemometric (PCM) model for the prediction of the ability of drug-like chemicals to inhibit five major drug metabolizing CYP isoforms (i.e. CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4) was created and made publicly available under the Bioclipse Decision Support open source system at www.cyp450model.org. In regards to the proteochemometric modeling we represented the chemical compounds by molecular signature descriptors and the CYP-isoforms by alignment-independent description of composition and transition of amino acid properties of their protein primary sequences. The entire training dataset contained 63 391 interactions and the best PCM model was obtained using signature descriptors of height 1, 2 and 3 and inducing the model with a support vector machine. The model showed excellent predictive ability with internal AUC = 0.923 and an external AUC = 0.940, as evaluated on a large external dataset. The advantage of PCM models is their extensibility making it possible to extend our model for new CYP isoforms and polymorphic CYP forms. A key benefit of PCM is that all proteins are confined in one single model, which makes it generally more stable and predictive as compared with single target models. The inclusion of the model in Bioclipse Decision Support makes it possible to make virtual instantaneous predictions (∼100 ms per prediction) while interactively drawing or modifying chemical structures in the Bioclipse chemical structure editor. PMID:23799117

  2. Cytochrome P450 Isoforms in the Metabolism of Decursin and Decursinol Angelate from Korean Angelica.

    PubMed

    Zhang, Jinhui; Li, Li; Tang, Suni; Hale, Thomas W; Xing, Chengguo; Jiang, Cheng; Lü, Junxuan

    2015-01-01

    We have shown that the in vitro hepatic microsomal metabolism of pyranocoumarin compound decursinol angelate (DA) to decursinol (DOH) exclusively requires cytochrome P450 (CYP) enzymes, whereas the conversion of its isomer decursin (D) to DOH can be mediated by CYP and esterase(s). To provide insight into specific isoforms involved, here we show with recombinant human CYP that 2C19 was the most active at metabolizing D and DA in vitro followed by 3A4. With carboxylesterases (CES), D was hydrolyzed by CES2 but not CES1, and DA was resistant to both CES1 and CES2. In human liver microsomal (HLM) preparation, the general CYP inhibitor 1-aminobenzotriazole (ABT) and respective competitive inhibitors for 2C19 and 3A4, (+)-N-3-benzylnirvanol (NBN) and ketoconazole substantially retarded the metabolism of DA and, to a lesser extent, of D. In healthy human subjects from a single-dose pharmacokinetic (PK) study, 2C19 extensive metabolizer genotype (2C19*17 allele) tended to have less plasma DA AUC0-48h and poor metabolizer genotype (2C19*2 allele) tended to have greater DA AUC0-48h. In mice given a single dose of D/DA, pretreatment with ABT boosted the plasma and prostate levels of D and DA by more than an order of magnitude. Taken together, our findings suggest that CYP isoforms 2C19 and 3A4 may play a crucial role in the first pass liver metabolism of DA and, to a lesser extent, that of D in humans. Pharmacogenetics with respect to CYP genotypes and interactions among CYP inhibitor drugs and D/DA should therefore be considered in designing future translation studies of DA and/or D.

  3. High-throughput screening of inhibitory effects of Bo-yang-hwan-o-tang on human cytochrome P450 isoforms in vitro using UPLC/MS/MS.

    PubMed

    Lee, Miran; Park, Jeonghyeon; Lim, Mi-sun; Seong, Sook Jin; Lee, Joomi; Seo, Jeong Ju; Park, Yong-Ki; Lee, Hae Won; Yoon, Young-Ran

    2012-01-01

    Bo-yang-hwan-o-tang (BHT) is an oriental herbal medicine for treating brain disorders such as cerebral ischemia. The objective of this study was to develop an economically feasible and time-saving high-throughput screening method to monitor the potential inhibitory effects of BHT on human cytochrome P450 (CYP) enzymes in vitro. Two cocktail sets were used for incubation of human liver microsomes: Cocktail A: 6 probe substrates for CYP1A2, CYP2A6, CYP2C8, CYP2C19, CYP2D6, CYP3A4; Cocktail B: 3 for CYP2B6, CYP2C9, CYP2E1. The concentrations of the substrate metabolites were simultaneously analyzed using UPLC/MS/MS. The BHT extract had almost negligible inhibitory effects on the nine human CYP isoforms tested, with the half-maximal inhibitory concentration value ranged from 3624.99 to 45412.44 μg/ml. The results suggest that BHT extract has no inhibitory effects on CYP isoforms within the clinically recommended dosage range. We conclude that BHT might be free of drug-herb interactions when co-administered with other medicines. However, more in vivo human studies are needed to confirm these results. The high-throughput screening method can be a useful tool for drug discovery and for understanding drug interactions.

  4. Guanfu base A, an antiarrhythmic alkaloid of Aconitum coreanum, Is a CYP2D6 inhibitor of human, monkey, and dog isoforms.

    PubMed

    Sun, Jianguo; Peng, Ying; Wu, Hui; Zhang, Xueyuan; Zhong, Yunxi; Xiao, Yanan; Zhang, Fengyi; Qi, Huanhuan; Shang, Lili; Zhu, Jianping; Sun, Yue; Liu, Ke; Liu, Jinghan; A, Jiye; Ho, Rodney J Y; Wang, Guangji

    2015-05-01

    Guanfu base A (GFA) is a novel heterocyclic antiarrhythmic drug isolated from Aconitum coreanum (Lèvl.) rapaics and is currently in a phase IV clinical trial in China. However, no study has investigated the influence of GFA on cytochrome P450 (P450) drug metabolism. We characterized the potency and specificity of GFA CYP2D inhibition based on dextromethorphan O-demethylation, a CYP2D6 probe substrate of activity in human, mouse, rat, dog, and monkey liver microsomes. In addition, (+)-bufuralol 1'-hydroxylation was used as a CYP2D6 probe for the recombinant form (rCYP2D6), 2D1 (rCYP2D1), and 2D2 (rCYP2D2) activities. Results show that GFA is a potent noncompetitive inhibitor of CYP2D6, with inhibition constant Ki = 1.20 ± 0.33 μM in human liver microsomes (HLMs) and Ki = 0.37 ± 0.16 μM for the human recombinant form (rCYP2D6). GFA is also a potent competitive inhibitor of CYP2D in monkey (Ki = 0.38 ± 0.12 μM) and dog (Ki = 2.4 ± 1.3 μM) microsomes. However, GFA has no inhibitory activity on mouse or rat CYP2Ds. GFA did not exhibit any inhibition activity on human recombinant CYP1A2, 2A6, 2C8, 2C19, 3A4, or 3A5, but showed slight inhibition of 2B6 and 2E1. Preincubation of HLMs and rCYP2D6 resulted in the inactivation of the enzyme, which was attenuated by GFA or quinidine. Beagle dogs treated intravenously with dextromethorphan (2 mg/ml) after pretreatment with GFA injection showed reduced CYP2D metabolic activity, with the Cmax of dextrorphan being one-third that of the saline-treated group and area under the plasma concentration-time curve half that of the saline-treated group. This study suggests that GFA is a specific CYP2D6 inhibitor that might play a role in CYP2D6 medicated drug-drug interaction.

  5. Two cytochrome P-450 isoforms catalysing O-de-ethylation of ethoxycoumarin and ethoxyresorufin in higher plants.

    PubMed Central

    Werck-Reichhart, D; Gabriac, B; Teutsch, H; Durst, F

    1990-01-01

    The O-dealkylating activities of 7-ethoxycoumarin O-de-ethylase (ECOD) and 7-ethoxyresorufin O-de-ethylase (EROD) have been fluorimetrically detected in microsomes prepared from manganese-induced Jerusalem artichoke tubers. Cytochrome P-450 dependence of the reactions was demonstrated by light-reversed CO inhibition, NADPH-dependence, NADH-NADPH synergism and by use of specific inhibitors: antibodies to NADPH-cytochrome P-450 reductase, mechanism-based inactivators and tetcyclasis. Apparent Km values of 161 microM for 7-ethoxycoumarin and 0.4 microM for 7-ethoxyresorufin were determined. O-De-ethylase activity was also detected in microsomes prepared from several other plant species, including wheat, maize, tulip, avocado and Vicia. ECOD and EROD were low or undetectable in uninduced plant tissues, and both activities were stimulated by wounding or by chemical inducers. Two distinct cytochrome P-450 isoforms are involved in ECOD and EROD activities since (1) they showed different distributions among plant species; (2) they showed contrasting inhibition and induction patterns; and (3) ECOD but not EROD activity was supported by cumene hydroperoxide. PMID:2241905

  6. Impact of Cytochrome P450 2D6 Function on the Chiral Blood Plasma Pharmacokinetics of 3,4-Methylenedioxymethamphetamine (MDMA) and Its Phase I and II Metabolites in Humans.

    PubMed

    Steuer, Andrea E; Schmidhauser, Corina; Tingelhoff, Eva H; Schmid, Yasmin; Rickli, Anna; Kraemer, Thomas; Liechti, Matthias E

    2016-01-01

    3,4-methylenedioxymethamphetamine (MDMA; ecstasy) metabolism is known to be stereoselective, with preference for S-stereoisomers. Its major metabolic step involves CYP2D6-catalyzed demethylenation to 3,4-dihydroxymethamphetamine (DHMA), followed by methylation and conjugation. Alterations in CYP2D6 genotype and/or phenotype have been associated with higher toxicity. Therefore, the impact of CYP2D6 function on the plasma pharmacokinetics of MDMA and its phase I and II metabolites was tested by comparing extensive metabolizers (EMs), intermediate metabolizers (IMs), and EMs that were pretreated with bupropion as a metabolic inhibitor in a controlled MDMA administration study. Blood plasma samples were collected from 16 healthy participants (13 EMs and three IMs) up to 24 h after MDMA administration in a double-blind, placebo-controlled, four-period, cross-over design, with subjects receiving 1 week placebo or bupropion pretreatment followed by a single placebo or MDMA (125 mg) dose. Bupropion pretreatment increased the maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from 0 to 24 h (AUC24) of R-MDMA (9% and 25%, respectively) and S-MDMA (16% and 38%, respectively). Bupropion reduced the Cmax and AUC24 of the CYP2D6-dependently formed metabolite stereoisomers of DHMA 3-sulfate, DHMA 4-sulfate, and 4-hydroxy-3-methoxymethamphetamine (HMMA sulfate and HMMA glucuronide) by approximately 40%. The changes that were observed in IMs were generally comparable to bupropion-pretreated EMs. Although changes in stereoselectivity based on CYP2D6 activity were observed, these likely have low clinical relevance. Bupropion and hydroxybupropion stereoisomer pharmacokinetics were unaltered by MDMA co-administration. The present data might aid further interpretations of toxicity based on CYP2D6-dependent MDMA metabolism.

  7. Impact of Cytochrome P450 2D6 Function on the Chiral Blood Plasma Pharmacokinetics of 3,4-Methylenedioxymethamphetamine (MDMA) and Its Phase I and II Metabolites in Humans

    PubMed Central

    Steuer, Andrea E.; Schmidhauser, Corina; Tingelhoff, Eva H.; Schmid, Yasmin; Rickli, Anna; Kraemer, Thomas; Liechti, Matthias E.

    2016-01-01

    3,4-methylenedioxymethamphetamine (MDMA; ecstasy) metabolism is known to be stereoselective, with preference for S-stereoisomers. Its major metabolic step involves CYP2D6-catalyzed demethylenation to 3,4-dihydroxymethamphetamine (DHMA), followed by methylation and conjugation. Alterations in CYP2D6 genotype and/or phenotype have been associated with higher toxicity. Therefore, the impact of CYP2D6 function on the plasma pharmacokinetics of MDMA and its phase I and II metabolites was tested by comparing extensive metabolizers (EMs), intermediate metabolizers (IMs), and EMs that were pretreated with bupropion as a metabolic inhibitor in a controlled MDMA administration study. Blood plasma samples were collected from 16 healthy participants (13 EMs and three IMs) up to 24 h after MDMA administration in a double-blind, placebo-controlled, four-period, cross-over design, with subjects receiving 1 week placebo or bupropion pretreatment followed by a single placebo or MDMA (125 mg) dose. Bupropion pretreatment increased the maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from 0 to 24 h (AUC24) of R-MDMA (9% and 25%, respectively) and S-MDMA (16% and 38%, respectively). Bupropion reduced the Cmax and AUC24 of the CYP2D6-dependently formed metabolite stereoisomers of DHMA 3-sulfate, DHMA 4-sulfate, and 4-hydroxy-3-methoxymethamphetamine (HMMA sulfate and HMMA glucuronide) by approximately 40%. The changes that were observed in IMs were generally comparable to bupropion-pretreated EMs. Although changes in stereoselectivity based on CYP2D6 activity were observed, these likely have low clinical relevance. Bupropion and hydroxybupropion stereoisomer pharmacokinetics were unaltered by MDMA co-administration. The present data might aid further interpretations of toxicity based on CYP2D6-dependent MDMA metabolism. PMID:26967321

  8. Distinct cytochrome P450 aromatase isoforms in the common carp (Cyprinus carpio): sexual dimorphism and onset of ontogenic expression.

    PubMed

    Barney, Megan L; Patil, Jawahar G; Gunasekera, Rasanthi M; Carter, Chris G

    2008-05-01

    Cytochrome P450 aromatase (CYP19) is a key enzyme in the steroidogenic pathway that catalyses the conversion of testosterone to estrogen, and therefore is thought to influence gonadal sex differentiation. In an effort to understand the role of this enzyme in ovarian differentiation, we isolated cDNA encoding the two distinct isoforms, ovarian and brain (termed cyp19a and cyp19b, respectively) of adult common carp, Cyprinus carpio. The cloned cDNA for cyp19a had an open reading frame (ORF) of 518 amino acid residues, in contrast to cyp19b with an ORF of 511 amino acids. Sequence and phylogenetic analysis showed that these CYP19 isoforms were orthologous with previously described cyp19a and cyp19b from other teleosts. Quantitative real-time PCR indicated that both isoforms are expressed in adult ovary and brain, with predominant expression of cyp19a in the ovary and cyp19b in the brain. The major aromatase expressing tissue was found to be the brain, with greatest cyp19b expression in the anterior quarter (telencephalon) in both sexes. The gonad showed sexually dimorphic expression of both genes and dimorphic expression of cyp19a was observed in the cerebellum and the liver. Ontogenic expression showed that only the ovarian aromatase transcript is inherited maternally, with lower expression observed through early larval development under warmer rearing conditions. The differential and overlapping expression suggests these two aromatase genes have different roles in reproductive physiology.

  9. Correlation of CpG Island Methylation of the Cytochrome P450 2E1/2D6 Genes with Liver Injury Induced by Anti-Tuberculosis Drugs: A Nested Case-Control Study

    PubMed Central

    Zhang, Jinling; Zhu, Xuebin; Li, Yuhong; Zhu, Lingyan; Li, Shiming; Zheng, Guoying; Ren, Qi; Xiao, Yonghong; Feng, Fumin

    2016-01-01

    This study investigated the role of CpG island methylation of the CYP2E1 and CYP2D6 genes in liver injury induced by anti-TB drugs from an epigenetic perspective in a Chinese cohort. A 1:1 matched nested case-control study design was applied. Pulmonary tuberculosis (TB) patients, who underwent standard anti-TB therapy and developed liver injury were defined as cases, while those who did not develop liver injury were defined as control. The two groups were matched in terms of sex, treatment regimen, and age. In 114 pairs of cases, CpG island methylation levels of the CYP2E1 and CYP2D6 genes in plasma cell-free DNA were found to be significantly correlated with the occurrence of anti-TB drug-induced liver injury (ADLI), with odds ratio (OR) values of 2.429 and 3.500, respectively (p < 0.01). Moreover, through multivariate logistic regression analysis, CpG island methylation of the CYP2E1 and CYP2D6 genes in plasma cell-free DNA were found to be significantly correlated with the occurrence of ADLI, with adjusted OR values of 4.390 (95% confidence interval (CI): 1.982–9.724) and 9.193 (95% CI: 3.624–25.888), respectively (p < 0.001). These results suggest that aberrantly elevated methylation of CpG islands of the CYP2E1 and CYP2D6 genes in plasma cell-free DNA may increase the risk of ADLI in Chinese TB patients. PMID:27490558

  10. Artificial neural network cascade identifies multi-P450 inhibitors in natural compounds

    PubMed Central

    Li, Zhangming; Li, Yan; Sun, Lu; Tang, Yun; Liu, Lanru

    2015-01-01

    Substantial evidence has shown that most exogenous substances are metabolized by multiple cytochrome P450 (P450) enzymes instead of by merely one P450 isoform. Thus, multi-P450 inhibition leads to greater drug-drug interaction risk than specific P450 inhibition. Herein, we innovatively established an artificial neural network cascade (NNC) model composed of 23 cascaded networks in a ladder-like framework to identify potential multi-P450 inhibitors among natural compounds by integrating 12 molecular descriptors into a P450 inhibition score (PIS). Experimental data reporting in vitro inhibition of five P450 isoforms (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) were obtained for 8,148 compounds from the Cytochrome P450 Inhibitors Database (CPID). The results indicate significant positive correlation between the PIS values and the number of inhibited P450 isoforms (Spearman’s ρ = 0.684, p < 0.0001). Thus, a higher PIS indicates a greater possibility for a chemical to inhibit the enzyme activity of at least three P450 isoforms. Ten-fold cross-validation of the NNC model suggested an accuracy of 78.7% for identifying whether a compound is a multi-P450 inhibitor or not. Using our NNC model, 22.2% of the approximately 160,000 natural compounds in TCM Database@Taiwan were identified as potential multi-P450 inhibitors. Furthermore, chemical similarity calculations suggested that the prevailing parent structures of natural multi-P450 inhibitors were alkaloids. Our findings show that dissection of chemical structure contributes to confident identification of natural multi-P450 inhibitors and provides a feasible method for virtually evaluating multi-P450 inhibition risk for a known structure. PMID:26719820

  11. Investigating the in vitro stereoselective metabolism of m-nisoldipine enantiomers: characterization of metabolites and cytochrome P450 isoforms involved.

    PubMed

    Sun, Yupeng; Jia, Peipei; Yuan, Lin; Liu, Yanyan; Zhang, Zhiyong; Du, Yumin; Zhang, Lantong

    2015-12-01

    m-Nisoldipine, as a novel 1,4-dihydropyridine calcium ion antagonist, was presented as a couple of enantiomers [(-), (+)-m-nisoldipine]. In this report, the in vitro metabolism of m-nisoldipine enantiomers was investigated in rat liver microsomes (RLM) by the combination of two liquid chromatography mass spectrometric techniques for the first time. The metabolites were separated and assayed by ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry and further identified by comparison of their mass and chromatographic behaviors with reference substances. A total of 18 metabolites of (-)-m-nisoldipine and 16 metabolites of (+)-m-nisoldipine were detected, respectively, which demonstrated that (+)-m-nisoldipine is more metabolically stable than (-)-m-nisoldipine. In addition, the identified metabolic pathways of m-nisoldipine enantiomers were involved in dehydrogenation, oxidation and ester hydrolysis. Afterwards, based on high-performance liquid chromatography coupled to triple quadrupole linear ion trap mass spectrometry, various selective cytochrome P450 (CYP) enzyme inhibitors were employed to evaluate CYP isoforms. The results indicated that the inhibitors of CYP1A1/2, CYP2B1/2, 2D and 2C11 had no obvious inhibitory effects, yet the inhibitor of CYP 3A had a significant inhibitory effect on metabolism of m-nisoldipine enantiomers. This showed that CYP 3A might primarily metabolize m-nisoldipine in RLM.

  12. Lack of association between schizophrenia and the CYP2D6 gene polymorphisms

    SciTech Connect

    Pirmohamed, M.; Wild, M.J.; Kitteringham, N.R.

    1996-04-09

    Approximately 5-10% of the Caucasian population lack the P450 isoform, CYP2D6. This polymorphism may be of importance in determining individual susceptibility to Parkinson`s disease. In this journal, Daniels et al. recently reported a negative association between the CYP2D6 gene locus and schizophrenia, a disease characterized by dopamine overactivity. It is important to exclude such an association because CYP2D6 is expressed in the brain and it is involved in dopamine catabolism. Between 1992 and 1993, we also performed a study similar to that, and reached the same conclusion. 7 refs., 1 tab.

  13. Metabolism of sesamin by cytochrome P450 in human liver microsomes.

    PubMed

    Yasuda, Kaori; Ikushiro, Shinichi; Kamakura, Masaki; Ohta, Miho; Sakaki, Toshiyuki

    2010-12-01

    Metabolism of sesamin by cytochrome P450 (P450) was examined using yeast expression system and human liver microsomes. Saccharomyces cerevisiae cells expressing each of human P450 isoforms (CYP1A1, 1A2, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, and 3A4) were cultivated with sesamin, and monocatechol metabolite was observed in most of P450s. Kinetic analysis using the microsomal fractions of the recombinant S. cerevisiae cells revealed that CYP2C19 had the largest k(cat)/K(m) value. Based on the kinetic data and average contents of the P450 isoforms in the human liver, the putative contribution of P450s for sesamin metabolism was large in the order of CYP2C9, 1A2, 2C19, and 2D6. A good correlation was observed between sesamin catecholization activity and CYP2C9-specific activity in in vitro studies using 10 individual human liver microsomes, strongly suggesting that CYP2C9 is the most important P450 isoform for sesamin catecholization in human liver. Inhibition studies using each anti-P450 isoform-specific antibody confirmed that CYP2C9 was the most important, and the secondary most important P450 was CYP1A2. We also examined the inhibitory effect of sesamin for P450 isoform-specific activities and found a mechanism-based inhibition of CYP2C9 by sesamin. In contrast, no mechanism-based inhibition by sesamin was observed in CYP1A2-specific activity. Our findings strongly suggest that further studies are needed to reveal the interaction between sesamin and therapeutic drugs mainly metabolized by CYP2C9.

  14. The impact of Cytochrome P450 CYP1A2, CYP2C9, CYP2C19 and CYP2D6 genes on suicide attempt and suicide risk-a European multicentre study on treatment-resistant major depressive disorder.

    PubMed

    Höfer, Peter; Schosser, Alexandra; Calati, Raffaella; Serretti, Alessandro; Massat, Isabelle; Kocabas, Neslihan Aygun; Konstantinidis, Anastasios; Linotte, Sylvie; Mendlewicz, Julien; Souery, Daniel; Zohar, Joseph; Juven-Wetzler, Alzbeta; Montgomery, Stuart; Kasper, Siegfried

    2013-08-01

    Recently published data have reported associations between cytochrome P450 metabolizer status and suicidality. The aim of our study was to investigate the role of genetic polymorphisms of the cytochrome P450 genes on suicide risk and/or a personal history of suicide attempts. Two hundred forty-three major depressive disorder patients were collected in the context of a European multicentre resistant depression study and treated with antidepressants at adequate doses for at least 4 weeks. Suicidality was assessed using the Mini International Neuropsychiatric Interview and the Hamilton Rating Scale for Depression (HAM-D). Treatment response was defined as HAM-D ≤ 17 and remission as HAM-D ≤ 7 after 4 weeks of treatment with antidepressants at adequate dose. Genotyping was performed for all relevant variations of the CYP1A2 gene (*1A, *1F, *1C, *1 J, *1 K), the CYP2C9 gene (*2, *3), the CYP2C19 gene (*2, *17) and the CYP2D6 gene (*3, *4, *5, *6, *9, *19, *XN). No association between both suicide risk and personal history of suicide attempts, and the above mentioned metabolic profiles were found after multiple testing corrections. In conclusion, the investigated cytochrome gene polymorphisms do not seem to be associated with suicide risk and/or a personal history of suicide attempts, though methodological and sample size limitations do not allow definitive conclusions.

  15. In vitro functional assessment of 22 newly identified CYP2D6 allelic variants in the Chinese population.

    PubMed

    Dai, Da-Peng; Geng, Pei-Wu; Wang, Shuang-Hu; Cai, Jie; Hu, Li-Ming; Nie, Jing-Jing; Hu, Ji-Hong; Hu, Guo-Xin; Cai, Jian-Ping

    2015-07-01

    Cytochrome P450 2D6 (CYP2D6) is one of the most widely investigated CYPs related to genetic polymorphisms and is responsible for one-quarter of the currently used clinical drugs. We previously detected 22 novel, non-synonymous, mutated sites in the Chinese population, but nothing is known about the functional effects of these mutations in terms of specific CYP2D6 substrates. In this study, wild-type CYP2D6, two common allelic variants and 22 newly reported CYP2D6 isoforms were transiently expressed in 293FT cells, and the enzymatic activities of these variants were systematically assessed using dextromethorphan and bufuralol as the probing substrates. Consequently, 19 and 21 allelic variants were found to exhibit significantly decreased enzymatic activities for dextromethorphan and bufuralol, respectively. Of 22 novel CYP2D6 variants, six allelic isoforms (CYP2D6.89, CYP2D6.92, CYP2D6.93, CYP2D6.96, E215K and R440C) exhibited absent or extremely reduced metabolic activities compared with those observed for the wild-type enzyme. Our in vitro functional data can be useful for CYP2D6 phenotype prediction and provide valuable information for the study of clinical impact of these newly found CYP2D6 variants in China.

  16. In vitro identification of human cytochrome P450 isoforms involved in the metabolism of Geissoschizine methyl ether, an active component of the traditional Japanese medicine Yokukansan.

    PubMed

    Matsumoto, Takashi; Kushida, Hirotaka; Maruyama, Takeshi; Nishimura, Hiroaki; Watanabe, Junko; Maemura, Kazuya; Kase, Yoshio

    2016-01-01

    1. Yokukansan (YKS) is a traditional Japanese medicine also called kampo, which has been used to treat neurosis, insomnia, and night crying and peevishness in children. Geissoschizine methyl ether (GM), a major indole alkaloid found in Uncaria hook, has been identified as a major active component of YKS with psychotropic effects. Recently, GM was reported to have a partial agonistic effect on serotonin 5-HT1A receptors. However, there is little published information on GM metabolism in humans, although several studies reported the blood kinetics of GM in rats and humans. In this study, we investigated the GM metabolic pathways and metabolizing enzymes in humans. 2. Using recombinant human cytochrome P450 (CYP) isoforms and polyclonal antibodies to CYP isoforms, we found that GM was metabolized into hydroxylated, dehydrogenated, hydroxylated+dehydrogenated, demethylated and water adduct forms by some CYP isoforms. 3. The relative activity factors in human liver microsomes were calculated to determine the relative contributions of individual CYP isoforms to GM metabolism in human liver microsomes (HLMs). We identified CYP3A4 as the CYP isoform primarily responsible for GM metabolism in human liver microsomes. 4. These findings provide an important basis for understanding the pharmacokinetics and pharmacodynamics of GM and YKS.

  17. Serum flecainide S/R ratio reflects the CYP2D6 genotype and changes in CYP2D6 activity.

    PubMed

    Doki, Kosuke; Sekiguchi, Yukio; Kuga, Keisuke; Aonuma, Kazutaka; Homma, Masato

    2015-08-01

    The aims of this study were to clarify whether the ratio of S- to R-flecainide (S/R ratio) in the serum flecainide concentration was associated with the stereoselectivity of flecainide metabolism, and to investigate the effects of the cytochrome P450 (CYP) 2D6 (CYP2D6) genotype and CYP2D6 inhibitor on the serum flecainide S/R ratio. In vitro studies using human liver microsomes and cDNA-expressed CYP isoforms suggested that variability in the serum flecainide S/R ratio was associated with the stereoselectivity of CYP2D6-mediated flecainide metabolism. We examined the serum flecainide S/R ratio in 143 patients with supraventricular tachyarrhythmia. The S/R ratio was significantly lower in intermediate metabolizers and poor metabolizers (IMs/PMs) than in extensive metabolizers (EMs) identified by the CYP2D6 genotype. The cut-off value for the S/R ratio to allow the discrimination between CYP2D6 EMs and IMs/PMs was 0.99. The S/R ratio in patients with co-administration of bepridil, a potent CYP2D6 inhibitor, was lower than 0.99, regardless of the CYP2D6 genotype status. Other factors, including age, sex, body weight, and renal function, did not affect the serum flecainide S/R ratio. This study suggests that the serum flecainide S/R ratio reflects the CYP2D6 genotype and changes in CYP2D6 activity on co-administration of a CYP2D6 inhibitor.

  18. Effect of CYP2D6 variants on venlafaxine metabolism in vitro.

    PubMed

    Zhan, Yun-Yun; Liang, Bing-Qing; Wang, Hao; Wang, Zhen-He; Weng, Qing-Hua; Dai, Da-Peng; Cai, Jian-Ping; Hu, Guo-Xin

    2016-01-01

    1. CYP2D6 is an important member of the cytochrome P450 (CYP450) enzyme superfamily, we recently identified 22 CYP2D6 alleles in the Han Chinese population. The aim of this study was to assess the catalytic activities of these allelic isoforms and their effects on the metabolism of venlafaxine in vitro. 2. The wild-type and 24 CYP2D6 variants were expressed in insect cells, and each variant was characterized using venlafaxine as the substrate. Reactions were performed at 37 °C with 5-500 μM substrate (three variants was adjusted to 1000 μM) for 50 min. By using high-performance liquid chromatography to detect the products, the kinetic parameters Km, Vmax, and intrinsic clearance (Vmax/Km) of O-desmethylvenlafaxine were determined. 3. Among the 22 CYP2D6 variants, the intrinsic clearance (Vmax/Km) values of all variants were significantly decreased (from 0.2% to 84.5%) compared with wild-type CYP2D6*1. In addition, the kinetic parameters of two CYP2D6 variants could not be detected because they have no detectable enzyme activity. 4. The comprehensive in vitro assessment of CYP2D6 variants provides significant insights into allele-specific activity towards venlafaxine in vivo.

  19. The participation of human hepatic P450 isoforms, flavin-containing monooxygenases and aldehyde oxidase in the biotransformation of the insecticide fenthion

    SciTech Connect

    Leoni, Claudia; Buratti, Franca M. Testai, Emanuela

    2008-12-01

    Although fenthion (FEN) is widely used as a broad spectrum insecticide on various crops in many countries, very scant data are available on its biotransformation in humans. In this study the in vitro human hepatic FEN biotransformation was characterized, identifying the relative contributions of cytochrome P450 (CYPs) and/or flavin-containing monooxygenase (FMOs) by using single c-DNA expressed human enzymes, human liver microsomes and cytosol and CYP/FMO-specific inhibitors. Two major metabolites, FEN-sulfoxide and FEN-oxon (FOX), are formed by some CYPs although at very different levels, depending on the relative CYP hepatic content. Formation of further oxidation products and the reduction of FEN-sulfoxide back to FEN by the cytosolic aldehyde oxidase enzyme were ruled out. Comparing intrinsic clearance values, FOX formation seemed to be favored and at low FEN concentrations CYP2B6 and 1A2 are mainly involved in its formation. At higher levels, a more widespread CYP involvement was evident, as in the case of FEN-sulfoxide, although a higher efficiency of CYP2C family was suggested. Hepatic FMOs were able to catalyze only sulfoxide formation, but at low FEN concentrations hepatic FEN sulfoxidation is predominantly P450-driven. Indeed, the contribution of the hepatic isoforms FMO{sub 3} and FMO{sub 5} was generally negligible, although at high FEN concentrations FMO's showed activities comparable to the active CYPs, accounting for up to 30% of total sulfoxidation. Recombinant FMO{sub 1} showed the highest efficiency with respect to CYPs and the other FMOs, but it is not expressed in the adult human liver. This suggests that FMO{sub 1}-catalysed sulfoxidation may represent the major extra-hepatic pathway of FEN biotransformation.

  20. Increased oxidative DNA damage and hepatocyte overexpression of specific cytochrome P450 isoforms in hepatitis of mice infected with Helicobacter hepaticus.

    PubMed Central

    Sipowicz, M. A.; Chomarat, P.; Diwan, B. A.; Anver, M. A.; Awasthi, Y. C.; Ward, J. M.; Rice, J. M.; Kasprzak, K. S.; Wild, C. P.; Anderson, L. M.

    1997-01-01

    A recently discovered bacterium, Helicobacter hepaticus, infects the intrahepatic bile canaliculi of mice, causing a severe chronic hepatitis culminating in liver cancer. Thus, it affords an animal model for study of bacteria-associated tumorigenesis including H. pylori-related gastric cancer. Reactive oxygen species are often postulated to contribute to this process. We now report that hepatitis of male mice infected with H. hepaticus show significant increases in the oxidatively damaged DNA deoxynucleoside 8-hydroxydeoxyguanosine, with the degree of damage increasing with progression of the disease. Perfusion of infected livers with nitro blue tetrazolium revealed that superoxide was produced in the cytoplasm of hepatocytes, especially in association with plasmacytic infiltrates near portal triads. Contrary to expectations, Kupffer cells, macrophages, and neutrophils were rarely involved. However, levels of cytochrome P450 (CYP) isoforms 1A2 and 2A5 in hepatocytes appeared to be greatly increased, as indicated by the number of cells positive in immunohistochemistry and the intensity of staining in many cells, concomitant with severe hepatitis. The CYP2A5 immunohistochemical staining co-localized with formazan deposits resulting from nitro blue tetrazolium reduction and occurred in nuclei as well as cytoplasm. These findings suggest that CYP2A5 contributes to the superoxide production and 8-hydroxydeoxyguanosine formation, although reactive oxygen species from an unknown source in the hepatocytes leading to CYP2A5 induction or coincidental occurrence of these events are also possibilities. Three glutathione S-transferase isoforms, mGSTP1-1 (pi), mGSTA1-1 (YaYa), and mGSTA4-4, also showed striking increases evidencing major oxidative stress in these livers. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 PMID:9327726

  1. Quantitative analysis of cytochrome P450 isoforms in human liver microsomes by the combination of proteomics and chemical probe-based assay.

    PubMed

    Liu, Xidong; Hu, Lianghai; Ge, Guangbo; Yang, Bo; Ning, Jing; Sun, Shixin; Yang, Ling; Pors, Klaus; Gu, Jingkai

    2014-08-01

    Cytochrome P450 (CYP) is one of the most important drug-metabolizing enzyme families, which participates in the biotransformation of many endogenous and exogenous compounds. Quantitative analysis of CYP expression levels is important when studying the efficacy of new drug molecules and assessing drug-drug interactions in drug development. At present, chemical probe-based assay is the most widely used approach for the evaluation of CYP activity although there are cross-reactions between the isoforms with high sequence homologies. Therefore, quantification of each isozyme is highly desired in regard to meeting the ever-increasing requirements for carrying out pharmacokinetics and personalized medicine in the academic, pharmaceutical, and clinical setting. Herein, an absolute quantification method was employed for the analysis of the seven isoforms CYP1A2, 2B6, 3A4, 3A5, 2C9, 2C19, and 2E1 using a proteome-derived approach in combination with stable isotope dilution assay. The average absolute amount measured from twelve human liver microsomes samples were 39.3, 4.3, 54.0, 4.6, 10.3, 3.0, and 9.3 (pmol/mg protein) for 1A2, 2B6, 3A4, 3A5, 2C9, 2C19, and 2E1, respectively. Importantly, the expression level of CYP3A4 showed high correlation (r = 0.943, p < 0.0001) with the functional activity, which was measured using bufalin-a highly selective chemical probe we have developed. The combination of MRM identification and analysis of the functional activity, as in the case of CYP3A4, provides a protocol which can be extended to other functional enzyme studies with wide application in pharmaceutical research.

  2. Porcine Hypothalamic Aromatase Cytochrome P450: Isoform Characterization, Sex-Dependent Activity, Regional Expression, and Regulation by Enzyme Inhibition in Neonatal Boars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Domestic pigs have three CYP19 genes encoding functional paralogues of the enzyme aromatase cytochrome P450 (P450arom) that are expressed in the gonads, placenta and pre-implantation blastocyst. All catalyze estrogen synthesis, but the “gonadal” type enzyme is unique in also synthesizing a nonaromat...

  3. In vitro characterization of the cytochrome P450 isoforms involved in the metabolism of 6-methoxy-2-napthylacetic acid, an active metabolite of the prodrug nabumetone.

    PubMed

    Matsumoto, Kaori; Nemoto, Eiichi; Hasegawa, Tetsuya; Akimoto, Masayuki; Sugibayashi, Kenji

    2011-01-01

    The cytochrome P450 (CYP) isoforms that catalyze the oxidation metabolism of 6-methoxy-2-napthylacetic acid (6-MNA), an active metabolite of nabumetone, were studied in rats and humans. Using an extractive reversed-phase HPLC assay with fluorescence detection, monophasic Michaelis-Menten kinetics was obtained for the formation of 6-hydroxy-2-naphthylacetic acid (6-HNA) in liver microsomes of rats and humans, and kinetic analysis showed that the K(m) and V(max) values for the formation of 6-HNA in humans and rats were 640.0 ± 30.9 and 722.9 ± 111.7 µM, and 1167.5 ± 33.0 and 1312.7 ± 73.8 pmol min⁻¹ mg protein⁻¹, respectively. The CYPs responsible for metabolism of 6-MNA in liver microsomes of rats and humans were identified using correlation study, recombinant CYP supersomes, and specific CYP inhibitors and antibodies. Recombinant human CYP2C9 exhibited appreciable catalytic activity with respect to 6-HNA formation from 6-MNA. Among 14 recombinant rat CYPs examined, CYP2C6, CYP2C11 and CYP1A2 were involved in the metabolism of 6-MNA. Sulfaphenazole (a selective inhibitor of CYP2C9) inhibited the formation of 6-HNA in pooled human microsomes by 89%, but failed to inhibit this reaction in rat liver microsomes. The treatment of pooled human liver microsomes with an antibody against CYP2C9 inhibited the formation of 6-HNA by about 80%. The antibody against CYP2C11 suppressed the activity by 20 to 30% in rat microsomes, whereas that of CYP1A2 microsomes did not show drastic inhibition. These findings suggest that CYP2C9 has the highest catalytic activity of 6-MNA metabolism in humans. In contrast, metabolism of 6-MNA is suggested to be mediated mainly by CYP2C6 and CYP2C11 in rats.

  4. Interaction of serum proteins with CYP isoforms in human liver microsomes: inhibitory effects of human and bovine albumin, alpha-globulins, alpha-1-acid glycoproteins and gamma-globulins on CYP2C19 and CYP2D6.

    PubMed

    Xu, Bang Qian; Ishii, Mikio; Ding, Li Rong; Fischer, Nancy E; Inaba, Tadanobu

    2003-03-14

    The effects of serum proteins on the in vitro hydroxylation pathways of mephenytoin (CYP2C19) and debrisoquine (CYP2D6) were studied to enhance the predictability of in vivo drug metabolism from in vitro assays. Both CYP substrates are known to be weakly bound to albumin and the applicability of the free drug hypothesis was further appraised. Since bovine serum albumin (BSA) is used widely in in vitro assays, a comparison between human and bovine proteins was made. Four major serum proteins were studied: albumin, alpha1-acid glycoprotein (AGP), alpha- and gamma-globulins. Human serum albumin (HSA) inhibited both CYP activities about 20% more than BSA. The addition of human alpha-globulins, but not the bovine protein, resulted in marked reduction of 86% and 41% in CYP2C19 and CYP2D6 activities, respectively. This reduction of activity was strikingly greater than the fraction bound (14 and 22%, respectively). The inhibition was of the competitive type and the Ki values of human alpha-globulins on CYP2C19 and CYP2D6 were found to be 0.45% (4.5 mg/ml) and 3.5% (35 mg/ml), respectively. The effect of both human and bovine gamma-globulins on CYP isoforms was negligible. The Ki values of human and bovine AGP for CYP2C19 were 1.84% (420 microM) and 0.93% (210 microM), respectively. For HSA, human alpha-globulins and human and bovine AGP, the strongly decreased CYP activities in vitro cannot be explained by the free drug hypothesis. A direct interaction of these serum proteins with CYP enzymes is postulated. Differential effects of bovine and human serum proteins and CYP specific inhibition were observed.

  5. CYP2D6 genotyping in natives and immigrants from the Emilia-Romagna Region (Italy).

    PubMed

    Riccardi, Laura N; Lanzellotto, Rossana; Luiselli, Donata; Ceccardi, Stefania; Falconi, Mirella; Bini, Carla; Pelotti, Susi

    2011-11-01

    Pharmacogenetic testing of drug metabolizing enzyme polymorphisms provides an important tool to improve prescribing decisions, avoiding therapeutic failure and adverse drug reactions. Cytochrome P450 2D6 isoform plays an important role in the metabolism of about 20%-25% of widely used clinical drugs. Interethnic differences in allele frequency distribution of the CYP2D6 gene are well established, but interethnic admixture, introducing variations in population ancestry and resulting in distinct levels of population structure, should be acknowledged in pharmacogenomic studies to avoid inappropriate extrapolation of CYP2D6 data. The aim of the present research was to characterize CYP2D6 polymorphism in a random sample of 122 natives and 175 immigrants from Africa, Asia, and South America living in the Emilia-Romagna region (Italy), considering the present scenario of immigration and back migration events, which is a source of admixture. The results are today consistent with the known interethnic genetic variation, but the observed significant divergence between natives and Africans or South-East Asians predicts that admixture will reshape the population structure and the native metabolic ratio curve requiring, for drug prescription and pharmacogenetics studies, an interdisciplinary approach applied in an appropriate biogeographical and anthropological frame.

  6. Short-term fasting alters cytochrome P450-mediated drug metabolism in humans.

    PubMed

    Lammers, Laureen A; Achterbergh, Roos; de Vries, Emmely M; van Nierop, F Samuel; Klümpen, Heinz-Josef; Soeters, Maarten R; Boelen, Anita; Romijn, Johannes A; Mathôt, Ron A A

    2015-06-01

    Experimental studies indicate that short-term fasting alters drug metabolism. However, the effects of short-term fasting on drug metabolism in humans need further investigation. Therefore, the aim of this study was to evaluate the effects of short-term fasting (36 h) on P450-mediated drug metabolism. In a randomized crossover study design, nine healthy subjects ingested a cocktail consisting of five P450-specific probe drugs [caffeine (CYP1A2), S-warfarin (CYP2C9), omeprazole (CYP2C19), metoprolol (CYP2D6), and midazolam (CYP3A4)] on two occasions (control study after an overnight fast and after 36 h of fasting). Blood samples were drawn for pharmacokinetic analysis using nonlinear mixed effects modeling. In addition, we studied in Wistar rats the effects of short-term fasting on hepatic mRNA expression of P450 isoforms corresponding with the five studied P450 enzymes in humans. In the healthy subjects, short-term fasting increased oral caffeine clearance by 20% (P = 0.03) and decreased oral S-warfarin clearance by 25% (P < 0.001). In rats, short-term fasting increased mRNA expression of the orthologs of human CYP1A2, CYP2C19, CYP2D6, and CYP3A4 (P < 0.05), and decreased the mRNA expression of the ortholog of CYP2C9 (P < 0.001) compared with the postabsorptive state. These results demonstrate that short-term fasting alters cytochrome P450-mediated drug metabolism in a nonuniform pattern. Therefore, short-term fasting is another factor affecting cytochrome P450-mediated drug metabolism in humans.

  7. Cytochromes P450

    PubMed Central

    Bak, Søren; Beisson, Fred; Bishop, Gerard; Hamberger, Björn; Höfer, René; Paquette, Suzanne; Werck-Reichhart, Danièle

    2011-01-01

    There are 244 cytochrome P450 genes (and 28 pseudogenes) in the Arabidopsis genome. P450s thus form one of the largest gene families in plants. Contrary to what was initially thought, this family diversification results in very limited functional redundancy and seems to mirror the complexity of plant metabolism. P450s sometimes share less than 20% identity and catalyze extremely diverse reactions leading to the precursors of structural macromolecules such as lignin, cutin, suberin and sporopollenin, or are involved in biosynthesis or catabolism of all hormone and signaling molecules, of pigments, odorants, flavors, antioxidants, allelochemicals and defense compounds, and in the metabolism of xenobiotics. The mechanisms of gene duplication and diversification are getting better understood and together with co-expression data provide leads to functional characterization. PMID:22303269

  8. Estrogen-Induced Cholestasis Leads to Repressed CYP2D6 Expression in CYP2D6-Humanized Mice.

    PubMed

    Pan, Xian; Jeong, Hyunyoung

    2015-07-01

    Cholestasis activates bile acid receptor farnesoid X receptor (FXR) and subsequently enhances hepatic expression of small heterodimer partner (SHP). We previously demonstrated that SHP represses the transactivation of cytochrome P450 2D6 (CYP2D6) promoter by hepatocyte nuclear factor (HNF) 4α. In this study, we investigated the effects of estrogen-induced cholestasis on CYP2D6 expression. Estrogen-induced cholestasis occurs in subjects receiving estrogen for contraception or hormone replacement, or in susceptible women during pregnancy. In CYP2D6-humanized transgenic (Tg-CYP2D6) mice, cholestasis triggered by administration of 17α-ethinylestradiol (EE2) at a high dose led to 2- to 3-fold decreases in CYP2D6 expression. This was accompanied by increased hepatic SHP expression and subsequent decreases in the recruitment of HNF4α to CYP2D6 promoter. Interestingly, estrogen-induced cholestasis also led to increased recruitment of estrogen receptor (ER) α, but not that of FXR, to Shp promoter, suggesting a predominant role of ERα in transcriptional regulation of SHP in estrogen-induced cholestasis. EE2 at a low dose (that does not cause cholestasis) also increased SHP (by ∼ 50%) and decreased CYP2D6 expression (by 1.5-fold) in Tg-CYP2D6 mice, the magnitude of differences being much smaller than that shown in EE2-induced cholestasis. Taken together, our data indicate that EE2-induced cholestasis increases SHP and represses CYP2D6 expression in Tg-CYP2D6 mice in part through ERα transactivation of Shp promoter.

  9. Utility of intersystem extrapolation factors in early reaction phenotyping and the quantitative extrapolation of human liver microsomal intrinsic clearance using recombinant cytochromes P450.

    PubMed

    Chen, Yuan; Liu, Liling; Nguyen, Khanh; Fretland, Adrian J

    2011-03-01

    Reaction phenotyping using recombinant human cytochromes P450 (P450) has great utility in early discovery. However, to fully realize the advantages of using recombinant expressed P450s, the extrapolation of data from recombinant systems to human liver microsomes (HLM) is required. In this study, intersystem extrapolation factors (ISEFs) were established for CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 using 11 probe substrates, based on substrate depletion and/or metabolite formation kinetics. The ISEF values for CYP2C9, CYP2D6, and CYP3A4 determined using multiple substrates were similar across substrates. When enzyme kinetics of metabolite formation for CYP1A2, 2C9, 2D6, and 3A4 were used, the ISEFs determined were generally within 2-fold of that determined on the basis of substrate depletion. Validation of ISEFs was conducted using 10 marketed drugs by comparing the extrapolated data with published data. The major isoforms responsible for the metabolism were identified, and the contribution of the predominant P450s was similar to that of previously reported data. In addition, phenotyping data from internal compounds, extrapolated using the rhP450-ISEF method, were comparable to those obtained using an HLM-based inhibition assay approach. Moreover, the intrinsic clearance (CL(int)) calculated from extrapolated rhP450 data correlated well with measured HLM CL(int). The ISEF method established in our laboratory provides a convenient tool in early reaction phenotyping for situations in which the HLM-based inhibition approach is limited by low turnover and/or unavailable metabolite formation. Furthermore, this method allows for quantitative extrapolation of HLM intrinsic clearance from rhP450 phenotyping data simultaneously to obtaining the participating metabolizing enzymes.

  10. Characterization of cytochrome P450 isoforms involved in sequential two-step bioactivation of diclofenac to reactive p-benzoquinone imines.

    PubMed

    den Braver, Michiel W; den Braver-Sewradj, Shalenie P; Vermeulen, Nico P E; Commandeur, Jan N M

    2016-06-24

    Idiosyncratic drug-induced lever injury (IDILI) is a rare but severe side effect of diclofenac (DF). Several mechanisms have been proposed as cause of DF-induced toxicity including the formation of protein-reactive diclofenac-1',4'-quinone imine (DF-1',4'-QI) and diclofenac-2,5-quinone imine (DF-2,5-QI). Formation of these p-benzoquinone imines result from two-step oxidative metabolism involving aromatic hydroxylation to 4'-hydroxydiclofenac and 5-hydroxydiclofenac followed by dehydrogenation to DF-1',4'-QI and DF-2,5-QI, respectively. Although the contribution of individual cytochrome P450s (CYPs) in aromatic hydroxylation of DF is well studied, the enzymes involved in the dehydrogenation reactions have been poorly characterized. The results of the present study show that both formation of 4'-hydroxydiclofenac and it subsequent bioactivation to DF-1',4'-QI is selectively catalyzed by CYP2C9. However, the two-step bioactivation to DF-2,5-QI appears to be catalyzed with highest activity by two different CYPs: 5-hydroxylation of DF is predominantly catalyzed by CYP3A4, whereas its subsequent bioactivation to DF-2,5-QI is catalyzed with 14-fold higher intrinsic clearance by CYP2C9. The fact that both CYPs involved in two-step bioactivation of DF show large interindividual variability may play a role in different susceptibility of patients to DF-induced IDILI. Furthermore, expression levels of these enzymes and protective enzymes might be important factors determining sensitivity of in vitro models for hepatotoxicity.

  11. Response to CYP2D6 substrate antidepressants is predicted by a CYP2D6 composite phenotype based on genotype and comedications with CYP2D6 inhibitors.

    PubMed

    Gressier, F; Verstuyft, C; Hardy, P; Becquemont, L; Corruble, E

    2015-01-01

    The cytochrome P450 2D6 (CYP2D6) is involved in the metabolism of most antidepressants. Comedication with a potent CYP2D6 inhibitor can convert patients with extensive metabolizer (EM) or ultra-rapid metabolizer (UM) genotypes into poor metabolizer (PM) phenotypes. Since comedication is frequent in depressed patients treated with antidepressants, we investigated the effect of the CYP2D6 composite phenotype on antidepressant efficacy, taking into account both the CYP2D6 genotype and comedication with CYP2D6 inhibitors. 87 Caucasian in patients with a major depressive episode were prospectively treated with flexible doses of antidepressant monotherapy as well as comedications and genotyped for the major CYP2D6 alleles (CYP2D6*3 rs35742686, *4 rs3892097, *5 del, *6 rs5030655, and *2xN). They were classified for CYP2D6 composite phenotype and assessed for antidepressant response after 4 weeks. In terms of genotypes (g), 6 subjects were UMg, 6 PMg, and 75 EMg. Ten patients were coprescribed a CYP2D6 inhibitor, resulting in the following composite phenotypes (cp): 5 UMcp, 16 PMcp, and 66 EMcp. Whereas none of the CYP2D6 genotypes were significantly associated with antidepressant response, UMcp had a lower antidepressant response than PMcp or EMcp (respectively: 39.0 ± 17.9, 50.0 ± 26.0, and 61.6 ± 23.4, p = 0.02). Despite small sample size, this study suggests that a CYP2D6 composite phenotype, taking into account both genotype and comedications with CYP2D6 inhibitors, could predict CYP2D6 substrate antidepressants response. Thus, to optimize antidepressant response, CYP2D6 genotype could be performed and comedications with CYP2D6 inhibitors should be avoided, when prescribing CYP2D6 substrate antidepressants.

  12. CYP2D6 variability in populations from Venezuela.

    PubMed

    Moreno, Nancy; Flores-Angulo, Carlos; Villegas, Cecilia; Mora, Yuselin

    2016-12-01

    CYP2D6 is an important cytochrome P450 enzyme that plays an important role in the metabolism of about 25% of currently prescribed drugs. The presence of polymorphisms in the CYP2D6 gene may modulate enzyme level and activity, thereby affecting individual responses to pharmacological treatments. The most prevalent diseases in the admixed population from Venezuela are cardiovascular and cancer, whereas viral, bacterial and parasitic diseases, particularly malaria, are prevalent in Amerindian populations; in the treatment of these diseases, several drugs that are metabolized by CYP2D6 are used. In this work, we reviewed the data on CYP2D6 variability and predicted metabolizer phenotypes, in healthy volunteers of two admixed and five Amerindian populations from Venezuela. The Venezuelan population is very heterogeneous as a result of the genetic admixture of three major ethnical components: Europeans, Africans and Amerindians. There are noticeable inter-regional and inter-population differences in the process of mixing of this population. Hitherto, there are few published studies in Venezuela on CYP2D6; therefore, it is necessary to increase research in this regard, in particular to develop studies with a larger sample size. There is a considerable amount of work remaining before CYP2D6 is integrated into clinical practice in Venezuela.

  13. Cytochrome P450 CYP3A in marsupials: cloning and characterisation of the second identified CYP3A subfamily member, isoform 3A78 from koala (Phascolarctos cinereus).

    PubMed

    El-Merhibi, Adaweyah; Ngo, Suong N T; Crittenden, Tamara A; Marchant, Ceilidh L; Stupans, Ieva; McKinnon, Ross A

    2011-11-01

    Cytochromes P450 (CYPs) are critically important in the oxidative metabolism of a diverse array of xenobiotics and endogenous substrates. Previously, we cloned and characterised the CYP2C, CYP4A, and CYP4B gene subfamilies from marsupials and demonstrated important species-differences in both activity and tissue expression of these CYP enzymes. Recently, we isolated the Eastern grey kangaroo CYP3A70. Here we have cloned and characterised the second identified member of marsupial CYP3A gene subfamily, CYP3A78 from the koala (Phascolarctos cinereus). In addition, we have examined the gender-differences in microsomal erythromycin N-demethylation activity (a CYP3A marker) and CYP3A protein expression across test marsupial species. Significant differences in hepatic erythromycin N-demethylation activity were observed between male and female koalas, with the activity detected in female koalas being 2.5-fold higher compared to that in male koalas (p<0.01). No gender-differences were observed in tammar wallaby or Eastern grey kangaroo. Immunoblot analysis utilising anti-human CYP3A4 antibody detected immunoreactive proteins in liver microsomes from all test male and female marsupials including the koala, tammar wallaby, and Eastern grey kangaroo, with no gender-differences detected across test marsupials. A 1610 bp koala hepatic CYP3A complete cDNA, designated CYP3A78, was cloned by reverse transcription-polymerase chain reaction approaches. It displays 64% nucleotide and 57% amino acid sequence identity to the Eastern grey kangaroo CYP3A70. The CYP3A78 cDNA encodes a protein of 515 amino acids, shares approximately 68% nucleotide and 56% amino acid sequence identity to human CYP3A4, and displays high sequence similarity to other published mammalian CYP3As from human, monkey, cow, pig, dog, rat, rabbit, mouse, hamster, and guinea pig. Collectively, this study provides primary molecular data regarding koala hepatic CYP3A78 gene and enables further functional analyses of CYP

  14. CYP2D6 and CYP2A6 biotransform dietary tyrosol into hydroxytyrosol.

    PubMed

    Rodríguez-Morató, Jose; Robledo, Patricia; Tanner, Julie-Anne; Boronat, Anna; Pérez-Mañá, Clara; Oliver Chen, C-Y; Tyndale, Rachel F; de la Torre, Rafael

    2017-02-15

    The dietary phenol tyrosol has been reported to be endogenously transformed into hydroxytyrosol, a potent antioxidant with multiple health benefits. In this work, we evaluated whether tyrosine hydroxylase (TH) and cytochrome P450s (CYPs) catalyzed this process. To assess TH involvement, Wistar rats were treated with α-methyl-L-tyrosine and tyrosol. Tyrosol was converted into hydroxytyrosol whilst α-methyl-L-tyrosine did not inhibit the biotransformation. The role of CYP was assessed in human liver microsomes (HLM) and tyrosol-to-hydroxytyrosol conversion was observed. Screening with selective enzymatic CYP inhibitors identified CYP2A6 as the major isoform involved in this process. Studies with baculosomes further demonstrated that CYP2D6 and CYP3A4 could transform tyrosol into hydroxytyrosol. Experiments using human genotyped livers showed an interindividual variability in hydroxytyrosol formation and supported findings that CYP2D6 and CYP2A6 mediated this reaction. The dietary health benefits of tyrosol-containing foods remain to be evaluated in light of CYP pharmacogenetics.

  15. Differential CYP 2D6 metabolism alters primaquine pharmacokinetics.

    PubMed

    Potter, Brittney M J; Xie, Lisa H; Vuong, Chau; Zhang, Jing; Zhang, Ping; Duan, Dehui; Luong, Thu-Lan T; Bandara Herath, H M T; Dhammika Nanayakkara, N P; Tekwani, Babu L; Walker, Larry A; Nolan, Christina K; Sciotti, Richard J; Zottig, Victor E; Smith, Philip L; Paris, Robert M; Read, Lisa T; Li, Qigui; Pybus, Brandon S; Sousa, Jason C; Reichard, Gregory A; Marcsisin, Sean R

    2015-04-01

    Primaquine (PQ) metabolism by the cytochrome P450 (CYP) 2D family of enzymes is required for antimalarial activity in both humans (2D6) and mice (2D). Human CYP 2D6 is highly polymorphic, and decreased CYP 2D6 enzyme activity has been linked to decreased PQ antimalarial activity. Despite the importance of CYP 2D metabolism in PQ efficacy, the exact role that these enzymes play in PQ metabolism and pharmacokinetics has not been extensively studied in vivo. In this study, a series of PQ pharmacokinetic experiments were conducted in mice with differential CYP 2D metabolism characteristics, including wild-type (WT), CYP 2D knockout (KO), and humanized CYP 2D6 (KO/knock-in [KO/KI]) mice. Plasma and liver pharmacokinetic profiles from a single PQ dose (20 mg/kg of body weight) differed significantly among the strains for PQ and carboxy-PQ. Additionally, due to the suspected role of phenolic metabolites in PQ efficacy, these were probed using reference standards. Levels of phenolic metabolites were highest in mice capable of metabolizing CYP 2D6 substrates (WT and KO/KI 2D6 mice). PQ phenolic metabolites were present in different quantities in the two strains, illustrating species-specific differences in PQ metabolism between the human and mouse enzymes. Taking the data together, this report furthers understanding of PQ pharmacokinetics in the context of differential CYP 2D metabolism and has important implications for PQ administration in humans with different levels of CYP 2D6 enzyme activity.

  16. The cytochrome p450 homepage.

    PubMed

    Nelson, David R

    2009-10-01

    The Cytochrome P450 Homepage is a universal resource for nomenclature and sequence information on cytochrome P450 ( CYP ) genes. The site has been in continuous operation since February 1995. Currently, naming information for 11,512 CYPs are available on the web pages. The P450 sequences are manually curated by David Nelson, and the nomenclature system conforms to an evolutionary scheme such that members of CYP families and subfamilies share common ancestors. The organisation and content of the Homepage are described.

  17. Metazoan cytochrome P450 evolution.

    PubMed

    Nelson, D R

    1998-11-01

    There are 37 cytochrome P450 families currently identified in animals. The concept of higher order groupings of P450 families called P450 CLANS is introduced. The mammalian CYP3 and CYP5 families belong to the same clan as insect CYP6 and CYP9. All mitochondrial P450s seem to belong to the same clan. Lack of mitochondrial P450s in C. elegans suggests that mitochondrial P450s probably arose from the mistargeting of a microsomal P450 after the coelomates diverged from acoelomates and pseudocoelomates. Different taxonomic groups appear to have recruited different ancestral P450s for expansion as they evolved, since each major taxon seems to have one large cluster of P450s. In insects, this cluster derives from the ancestor to the CYP4 family. Vertebrates and C. elegans may have used the same ancestor independently to generate the CYP1, 2, 17, and 21 families in vertebrates and a large distinctive clan with 45 genes in C. elegans.

  18. Inducible cytochrome P-450 from rat liver mitochondria

    SciTech Connect

    Raza, H.; Shayiq, F.M.; Avadhani, N.G.

    1987-05-01

    In the present study they have purified US -naphthoflavone (BNF, which induces isotypes similar to 3-MC) and PB induced mitochondrial isoforms. They have been able to purify two isoforms with molecular weights of 54 Kd and 52 Kd from BNF induced mitochondria. Only the 54 KD form, but not the 52 KD species reacts with the polyclonal antibody to microsomal P-450c, though, both show arylhydrocarbon hydroxylase activity in an in vitro system reconstituted with adrenodoxin and adrenodoxin-reductase. Fingerprint analyses, N-terminal sequencing and use of monoclonal antibody probes show that the two mitochondrial isoforms are different from the microsomal P-450c. Further, the 54 Kd mitochondrial isoform is not detected in control mitochondria indicating that it is truly an induced form. Similarly, a PB induced mitochondrial form which exhibits physical, immunochemical and enzymatic properties different from the microsomal P-450b has also been purified.

  19. Common CYP2D6 polymorphisms affecting alternative splicing and transcription: long-range haplotypes with two regulatory variants modulate CYP2D6 activity.

    PubMed

    Wang, Danxin; Poi, Ming J; Sun, Xiaochun; Gaedigk, Andrea; Leeder, J Steven; Sadee, Wolfgang

    2014-01-01

    Cytochrome P450 2D6 (CYP2D6) is involved in the metabolism of 25% of clinically used drugs. Genetic polymorphisms cause substantial variation in CYP2D6 activity and serve as biomarkers guiding drug therapy. However, genotype-phenotype relationships remain ambiguous except for poor metabolizers carrying null alleles, suggesting the presence of yet unknown genetic variants. Searching for regulatory CYP2D6 polymorphisms, we find that a SNP defining the CYP2D6*2 allele, rs16947 [R296C, 17-60% minor allele frequency (MAF)], previously thought to convey normal activity, alters exon 6 splicing, thereby reducing CYP2D6 expression at least 2-fold. In addition, two completely linked SNPs (rs5758550/rs133333, MAF 13-42%) increase CYP2D6 transcription more than 2-fold, located in a distant downstream enhancer region (>100 kb) that interacts with the CYP2D6 promoter. In high linkage disequilibrium (LD) with each other, rs16947 and the enhancer SNPs form haplotypes that affect CYP2D6 enzyme activity in vivo. In a pediatric cohort of 164 individuals, rs16947 alone (minor haplotype frequency 28%) was associated with reduced CYP2D6 metabolic activity (measured as dextromethorphan/metabolite ratios), whereas rs5758550/rs133333 alone (frequency 3%) resulted in increased CYP2D6 activity, while haplotypes containing both rs16947 and rs5758550/rs133333 were similar to the wild-type. Other alleles used in biomarker panels carrying these variants such as CYP2D6*41 require re-evaluation of independent effects on CYP2D6 activity. The occurrence of two regulatory variants of high frequency and in high LD, residing on a long haplotype, highlights the importance of gene architecture, likely shaped by evolutionary selection pressures, in determining activity of encoded proteins.

  20. Flexible and Scalable Full‐Length CYP2D6 Long Amplicon PacBio Sequencing

    PubMed Central

    Vossen, Rolf H.A.M.; Anvar, Seyed Yahya; Allard, William G.; Guchelaar, Henk‐Jan; White, Stefan J.; den Dunnen, Johan T.; Swen, Jesse J.; van der Straaten, Tahar

    2017-01-01

    ABSTRACT Cytochrome P450 2D6 (CYP2D6) is among the most important genes involved in drug metabolism. Specific variants are associated with changes in the enzyme's amount and activity. Multiple technologies exist to determine these variants, like the AmpliChip CYP450 test, Taqman qPCR, or Second‐Generation Sequencing, however, sequence homology between cytochrome P450 genes and pseudogene CYP2D7 impairs reliable CYP2D6 genotyping, and variant phasing cannot accurately be determined using these assays. To circumvent this, we sequenced CYP2D6 using the Pacific Biosciences RSII and obtained high‐quality, full‐length, phased CYP2D6 sequences, enabling accurate variant calling and haplotyping of the entire gene‐locus including exonic, intronic, and upstream and downstream regions. Unphased diplotypes (Roche AmpliChip CYP450 test) were confirmed for 24 of the 25 samples, including gene duplications. Cases with gene deletions required additional specific assays to resolve. In total, 61 unique variants were detected, including variants that had not previously been associated with specific haplotypes. To further aid genomic analysis using standard reference sequences, we have established an LOVD‐powered CYP2D6 gene‐variant database, and added all reference haplotypes and data reported here. We conclude that our CYP2D6 genotyping approach produces reliable CYP2D6 diplotypes and reveals information about additional variants, including phasing and copy‐number variation. PMID:28044414

  1. The Cytochrome P450 Homepage

    PubMed Central

    2009-01-01

    The Cytochrome P450 Homepage is a universal resource for nomenclature and sequence information on cytochrome P450 (CYP) genes. The site has been in continuous operation since February 1995. Currently, naming information for 11,512 CYPs are available on the web pages. The P450 sequences are manually curated by David Nelson, and the nomenclature system conforms to an evolutionary scheme such that members of CYP families and subfamilies share common ancestors. The organisation and content of the Homepage are described. PMID:19951895

  2. Frequency of undetected CYP2D6 hybrid genes in clinical samples: impact on phenotype prediction.

    PubMed

    Black, John Logan; Walker, Denise L; O'Kane, Dennis J; Harmandayan, Maria

    2012-01-01

    Cytochrome P450 2D6 (CYP2D6) is highly polymorphic. CYP2D6-2D7 hybrid genes can be present in samples containing CYP2D6*4 and CYP2D6*10 alleles. CYP2D7-2D6 hybrid genes can be present in samples with duplication signals and in samples with homozygous genotyping results. The frequency of hybrid genes in clinical samples is unknown. We evaluated 1390 samples for undetected hybrid genes by polymerase chain reaction (PCR) amplification, PCR fragment analysis, TaqMan copy number assays, DNA sequencing, and allele-specific primer extension assay. Of 508 CYP2D6*4-containing samples, 109 (21.5%) harbored CYP2D6*68 + *4-like, whereas 9 (1.8%) harbored CYP2D6*4N + *4-like. Of 209 CYP2D6*10-containing samples, 44 (21.1%) were found to have CYP2D6*36 + *10. Of 332 homozygous samples, 4 (1.2%) harbored a single CYP2D7-2D6 hybrid, and of 341 samples with duplication signals, 25 (7.3%) harbored an undetected CYP2D7-2D6 hybrid. Phenotype before and after accurate genotyping was predicted using a method in clinical use. The presence of hybrid genes had no effect on the phenotype prediction of CYP2D6*4- and CYP2D6*10-containing samples. Four of four (100%) homozygous samples containing a CYP2D7-2D6 gene had a change in predicted phenotype, and 23 of 25 (92%) samples with a duplication signal and a CYP2D7-2D6 gene had a change in predicted phenotype. Four novel genes were identified (CYP2D6*13A1 variants 1 and 2, CYP2D6*13G1, and CYP2D6*13G2), and two novel hybrid tandem structures consisting of CYP2D6*13B + *68×2 + *4-like and CYP2D6*13A1 variant 2 + *1×N were observed.

  3. Relationship between CYP 2D6 metabolic status and sexual dysfunction in paroxetine treatment.

    PubMed

    Zourková, Alexandra; Hadasová, Eva

    2002-01-01

    This article describes the incidence of sexual dysfunction in 30 patients subjected to long-term treatment by paroxetine in dependence on the P 450 CYP 2D6 isoenzyme metabolic status. Measured on the Arizona Sexual Experience Scale (ASEX; McGahuey, Delgado, & Gelenberg, 1999), the incidence of sexual dysfunction in patients converted to CYP 2D6 poor metabolizers was markedly higher compared with patients who had no history of such conversion, a difference that reached the level of statistical significance. Our article discusses the incidence of sexual dysfunction in connection with reduced CYP 2D6 capacity.

  4. MDMA, methamphetamine, and CYP2D6 pharmacogenetics: what is clinically relevant?

    PubMed Central

    de la Torre, Rafael; Yubero-Lahoz, Samanta; Pardo-Lozano, Ricardo; Farré, Magí

    2012-01-01

    In vitro human studies show that the metabolism of most amphetamine-like psychostimulants is regulated by the polymorphic cytochrome P450 isozyme CYP2D6. Two compounds, methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA), were selected as archetypes to discuss the translation and clinical significance of in vitro to in vivo findings. Both compounds were chosen based on their differential interaction with CYP2D6 and their high abuse prevalence in society. Methamphetamine behaves as both a weak substrate and competitive inhibitor of CYP2D6, while MDMA acts as a high affinity substrate and potent mechanism-based inhibitor (MBI) of the enzyme. The MBI behavior of MDMA on CYP2D6 implies that subjects, irrespective of their genotype/phenotype, are phenocopied to the poor metabolizer (PM) phenotype. The fraction of metabolic clearance regulated by CYP2D6 for both drugs is substantially lower than expected from in vitro studies. Other isoenzymes of cytochrome P450 and a relevant contribution of renal excretion play a part in their clearance. These facts tune down the potential contribution of CYP2D6 polymorphism in the clinical outcomes of both substances. Globally, the clinical relevance of CYP2D6 polymorphism is lower than that predicted by in vitro studies. PMID:23162568

  5. Understanding CYP2D6 and its role in tamoxifen metabolism.

    PubMed

    Smith, Edith Caroline

    2013-11-01

    The gene CYP2D6 has an extremely important role in drug metabolism. "Cytochrome P450, family 2, subfamily D, polypeptide 6" is the official name of CYP2D6. The gene is located at position 13.1 on the long (q) arm of chromosome 21 and encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases that are heavily involved in drug metabolism (Genetics Home Reference, 2013), and many drugs are activated into their biologically active compounds. Because of numerous polymorphisms, the gene also has significant person-to-person variability. To date, more than 80 distinct CYP2D6 alleles and specific types and frequencies have been associated with different ethnic groups. CYP2D6*4 is the most common variant allele in Caucasians and, in that population, has a frequency of about 25%. On the other hand, CYP2D6*10 is common in the Asian population (Stearns & Rae, 2008).

  6. CYP2D6 Genetic Polymorphisms and Phenotypes in Different Ethnicities of Malaysian Breast Cancer Patients.

    PubMed

    Chin, Fee Wai; Chan, Soon Choy; Abdul Rahman, Sabariah; Noor Akmal, Sharifah; Rosli, Rozita

    2016-01-01

    The cytochrome P450, family 2, subfamily D, polypeptide 6 (CYP2D6) is an enzyme that is predominantly involved in the metabolism of tamoxifen. Genetic polymorphisms of the CYP2D6 gene may contribute to inter-individual variability in tamoxifen metabolism, which leads to the differences in clinical response to tamoxifen among breast cancer patients. In Malaysia, the knowledge on CYP2D6 genetic polymorphisms as well as metabolizer status in Malaysian breast cancer patients remains unknown. Hence, this study aimed to comprehensively identify CYP2D6 genetic polymorphisms among 80 Malaysian breast cancer patients. The genetic polymorphisms of all the 9 exons of CYP2D6 gene were identified using high-resolution melting analysis and confirmed by DNA sequencing. Seven CYP2D6 alleles consisting of CYP2D6*1, CYP2D6*2, CYP2D6*4, CYP2D6*10, CYP2D6*39, CYP2D6*49, and CYP2D6*75 were identified in this study. Among these alleles, CYP2D6*10 is the most common allele in both Malaysian Malay (54.8%) and Chinese (71.4%) breast cancer patients, whereas CYP2D6*4 in Malaysian Indian (28.6%) breast cancer patients. In relation to CYP2D6 genotype, CYP2D6*10/*10 is more frequently observed in both Malaysian Malay (28.9%) and Chinese (57.1%) breast cancer patients, whereas CYP2D6*4/*10 is more frequently observed in Malaysian Indian (42.8%) breast cancer patients. In terms of CYP2D6 phenotype, 61.5% of Malaysian Malay breast cancer patients are predicted as extensive metabolizers in which they are most likely to respond well to tamoxifen therapy. However, 57.1% of Chinese as well as Indian breast cancer patients are predicted as intermediate metabolizers and they are less likely to gain optimal benefit from the tamoxifen therapy. This is the first report of CYP2D6 genetic polymorphisms and phenotypes in Malaysian breast cancer patients for different ethnicities. These data may aid clinicians in selecting an optimal drug therapy for Malaysian breast cancer patients, hence improve the

  7. Cytochrome p450nor, a novel class of mitochondrial cytochrome P450 involved in nitrate respiration in the fungus Fusarium oxysporum.

    PubMed

    Takaya, N; Suzuki, S; Kuwazaki, S; Shoun, H; Maruo, F; Yamaguchi, M; Takeo, K

    1999-12-15

    Fusarium oxysporum, an imperfect filamentous fungus performs nitrate respiration under limited oxygen. In the respiratory system, Cytochrome P450nor (P450nor) is thought to catalyze the last step; reduction of nitric oxide to nitrous oxide. We examined its intracellular localization using enzymatic, spectroscopic, and immunological analyses to show that P450nor is found in both the mitochondria and the cytosol. Translational fusions between the putative mitochondrial targeting signal on the amino terminus of P450nor and Escherichia coli beta-galactosidase resulted in significant beta-galactosidase activity in the mitochondrial fraction of nitrate-respiring cells, suggesting that one of the isoforms of P450nor (P450norA) is in anaerobic mitochondrion of F. oxysporum and acts as nitric oxide reductase. Furthermore, these findings suggest the involvement of P450nor in nitrate respiration in mitochondria.

  8. Assessment of 25 CYP2D6 alleles found in the Chinese population on propafenone metabolism in vitro.

    PubMed

    Su, Ying; Liang, Bing-Qing; Feng, Yan-Lin; Zhan, Yunyun; Gu, Ermin; Chen, Xinxin; Dai, Da-Peng; Hu, Guo-Xin; Cai, Jian-Ping

    2016-08-01

    Cytochrome P450 enzyme 2D6 (CYP2D6) is an important member of the cytochrome P450 enzyme superfamily, with more than 100 CYP2D6 allelic variants being previously reported. The aim of this study was to assess the catalytic characteristics of 25 alleles (CYP2D6.1 and 24 CYP2D6 variants) and their effects on the metabolism of propafenone in vitro. Twenty-five CYP2D6 alleles were expressing in 21 Spodoptera frugiperda (Sf) insect cells, and each variant was evaluated using propafenone as the substrate. Reactions were performed at 37 °C with 1-100 μmol/L propafenone for 30 min. After termination, the product 5-OH-propafenone was extracted and used for signal collection by ultra-performance liquid chromatography (UPLC). Compared with wild type CYP2D6.1, the intrinsic clearance (Vmax and Km) values of all variants were significantly altered. Three variants (CYP2D6.87, CYP2D6.90, CYP2D6.F219S) exhibited markedly increased intrinsic clearance values (129% to 165%), whereas 21 variants exhibited significantly decreased values (16% to 85%) due to increased Km and (or) decreased Vmax values. These results indicated that the majority of tested alleles had significantly altered catalytic activity towards propafenone hydroxylation in this expression system. Attention should be paid to subjects carrying these rare alleles when treated with propafenone.

  9. Cytochromes P450 in Nanodiscs

    PubMed Central

    Denisov, Ilia G.; Sligar, Stephen G.

    2010-01-01

    Nanodiscs have proven to be a versatile tool for the study all types of membrane proteins, including receptors, transporters, enzymes and viral antigens. The self-assembled Nanodisc system provides a robust and common means for rendering these targets soluble in aqueous media while providing a native like bilayer environment that maintains functional activity. This system has thus provided a means for studying the extensive collection of membrane bound cytochromes P450 with the same biochemical and biophysical tools that have been previously limited to use with the soluble P450s. These include a plethora of spectroscopic, kinetic and surface based methods. Significant improvements in homogeneity and stability of these preparations open new possibilities for detailed analysis of equilibrium and steady-state kinetic characteristics of catalytic mechanisms of human cytochromes P450 involved in xenobiotic metabolism and in steroid biosynthesis. The experimental methods developed for physico-chemical and functional studies of membrane cytochromes P450 incorporated in Nanodiscs allow for more detailed understanding of the scientific questions along the lines pioneered by Professor Klaus Ruckpaul and his array of colleagues and collaborators. PMID:20685623

  10. CYP2D6 variation, behaviour and psychopathology: implications for pharmacogenomics-guided clinical trials.

    PubMed

    Peñas-Lledó, Eva M; Llerena, Adrián

    2014-04-01

    Individual and population differences in polymorphic cytochrome P450 enzyme function have been known for decades. The biological significance of these differences has now been deciphered with regard to drug metabolism, action and toxicity as well as disposition of endogenous substrates, including neuroactive compounds. While the cytochrome P450 enzymes occur abundantly in the liver, they are expressed in most tissues of the body, albeit in varying amounts, including the brain. The latter location of cytochrome P450s is highly pertinent for susceptibility to neuropsychiatric diseases, not to mention local drug metabolism at the site of psychotropic drug action in the brain. In the current era of personality medicine with companion theranostics (i.e. the fusion of therapeutics with diagnostics), this article underscores that such versatile biological roles of cytochrome P450s offer multiple points of entry for personalized medicine and rational therapeutics. We focus our discussion on CYP2D6, one of the most intensively researched drug and endogenous compound metabolism pathways, with a view to relevance for, and optimization of, pharmacogenomic-guided clinical trials. Working on the premise that CYP2D6 is related to human behaviour and certain personality traits such as serotonin and dopamine system function, we further suggest that the motivation of healthy volunteers to participate in clinical trials may in part be influenced by an under- or over-representation of certain CYP2D6 metabolic groups.

  11. Inactivation of cytochrome P450 (P450) 3A4 but not P450 3A5 by OSI-930, a thiophene-containing anticancer drug.

    PubMed

    Lin, Hsia-lien; Zhang, Haoming; Medower, Christine; Hollenberg, Paul F; Johnson, William W

    2011-02-01

    An investigational anticancer agent that contains a thiophene moiety, 3-[(quinolin-4-ylmethyl)-amino]-N-[4-trifluoromethox)phenyl] thiophene-2-carboxamide (OSI-930), was tested to investigate its ability to modulate the activities of several cytochrome P450 enzymes. Results showed that OSI-930 inactivated purified, recombinant cytochrome P450 (P450) 3A4 in the reconstituted system in a mechanism-based manner. The inactivation was dependent on cytochrome b(5) and required NADPH. Catalase did not protect against the inactivation. No inactivation was observed in studies with human 2B6, 2D6, or 3A5 either in the presence or in the absence of b(5). The inactivation of 3A4 by OSI-930 was time- and concentration-dependent. The inactivation of the 7-benzyloxy-4-(trifluoromethyl)coumarin catalytic activity of 3A4 was characterized by a K(I) of 24 μM and a k(inact) of 0.04 min(-1). This K(I) is significantly greater than the clinical OSI-930 C(max) of 1.7 μM at the maximum tolerated dose, indicating that clinical drug interactions of OSI-930 via this pathway are not likely. Spectral analysis of the inactivated protein indicated that the decrease in the reduced CO spectrum at 450 nm was comparable to the amount of inactivation, thereby suggesting that the inactivation was primarily due to modification of the heme. High-pressure liquid chromatography (HPLC) analysis with detection at 400 nm showed a loss of heme comparable to the activity loss, but a modified heme was not detected. This result suggests either that the heme must have been modified enough so as not to be observed in a HPLC chromatograph or, possibly, that it was destroyed. The partition ratio for the inactivation of P450 3A4 was approximately 23, suggesting that this P450 3A4-mediated pathway occurs with approximately 4% frequency during the metabolism of OSI-930. Modeling studies on the binding of OSI-930 to the active site of the P450 3A4 indicated that OSI-930 would be oriented properly in the active site

  12. Variation in the inhibitory potency of terbinafine among genetic variants of CYP2D6.

    PubMed

    Akiyoshi, Takeshi; Ishiuchi, Miho; Imaoka, Ayuko; Ohtani, Hisakazu

    2015-08-01

    Cytochrome P450 2D6 (CYP2D6) is a highly polymorphic enzyme that is involved in the metabolism of many drugs. Terbinafine (TER) is a CYP2D6 inhibitor and causes persistent drug interactions in the clinical setting; however, its inhibitory mechanism and the differences in its inhibitory potency among genetic variants of CYP2D6 remain to be investigated. This study aimed to investigate the inhibitory mechanism of TER and the differences in its inhibitory potency among three CYP2D6 variants, CYP2D6.1, CYP2D6.2, and CYP2D6.10. In a competitive inhibition study, the metabolic activity of the CYP2D6 was assessed based on their demethylation of dextromethorphan in the presence or absence of TER, and the time-dependency of the inhibitory effects were examined by preincubating the enzymes with TER. TER had weaker inhibitory effects on CYP2D6.2 and CYP2D6.10 than on CYP2D6.1; i.e., TER exhibited Ki values (the concentration of inhibitor that results in half-maximal inhibition) of 0.0525, 0.355, and 1.85 μM for CYP2D6.1, CYP2D6.2, and CYP2D6.10, respectively. The inhibitory effects of TER were not time-dependent. Since TER's Ki value for CYP2D6.10 was 35.2-fold higher than its Ki value for CYP2D6.1, the CYP2D6 genotype of subjects should be taken into account when estimating the severity of drug interactions involving TER.

  13. Impact of CYP2D6 polymorphisms on clinical efficacy and tolerability of metoprolol tartrate.

    PubMed

    Hamadeh, I S; Langaee, T Y; Dwivedi, R; Garcia, S; Burkley, B M; Skaar, T C; Chapman, A B; Gums, J G; Turner, S T; Gong, Y; Cooper-DeHoff, R M; Johnson, J A

    2014-08-01

    Metoprolol is a selective β-1 adrenergic receptor blocker that undergoes extensive metabolism by the polymorphic enzyme cytochrome P450 2D6 (CYP2D6). Our objective was to investigate the influence of CYP2D6 polymorphisms on the efficacy and tolerability of metoprolol tartrate. Two hundred and eighty-one participants with uncomplicated hypertension received 50 mg of metoprolol twice daily followed by response-guided titration to 100 mg twice daily. Phenotypes were assigned based on results of CYP2D6 genotyping and copy number variation assays. Clinical response to metoprolol and adverse effect rates were analyzed in relation to CYP2D6 phenotypes using appropriate statistical tests. Heart rate response differed significantly by CYP2D6 phenotype (P < 0.0001), with poor and intermediate metabolizers showing greater reduction. However, blood pressure response and adverse effect rates were not significantly different by CYP2D6 phenotype. Other than a significant difference in heart rate response, CYP2D6 polymorphisms were not determinants of variability in metoprolol response or tolerability.

  14. Epitope spreading of the anti-CYP2D6 antibody response in patients with autoimmune hepatitis and in the CYP2D6 mouse model.

    PubMed

    Hintermann, Edith; Holdener, Martin; Bayer, Monika; Loges, Stephanie; Pfeilschifter, Josef M; Granier, Claude; Manns, Michael P; Christen, Urs

    2011-11-01

    Autoimmune hepatitis (AIH) is a serious chronic inflammatory disease of the liver with yet unknown etiology and largely uncertain immunopathology. The hallmark of type 2 AIH is the generation of liver kidney microsomal-1 (LKM-1) autoantibodies, which predominantly react to cytochrome P450 2D6 (CYP2D6). The identification of disease initiating factors has been hampered in the past, since antibody epitope mapping was mostly performed using serum samples collected late during disease resulting in the identification of immunodominant epitopes not necessarily representing those involved in disease initiation. In order to identify possible environmental triggers for AIH, we analyzed for the first time the spreading of the anti-CYP2D6 antibody response over a prolonged period of time in AIH patients and in the CYP2D6 mouse model, in which mice infected with Adenovirus-human CYP2D6 (Ad-h2D6) develop antibodies with a similar specificity than AIH patients. Epitope spreading was analyzed in six AIH-2-patients and in the CYP2D6 mouse model using SPOTs membranes containing peptides covering the entire CYP2D6 protein. Despite of a considerable variation, both mice and AIH patients largely focus their humoral immune response on an immunodominant epitope early after infection (mice) or diagnosis (patients). The CYP2D6 mouse model revealed that epitope spreading is initiated at the immunodominant epitope and later expands to neighboring and remote regions. Sequence homologies to human pathogens have been detected for all identified epitopes. Our study demonstrates that epitope spreading does indeed occur during the pathogenesis of AIH and supports the concept of molecular mimicry as a possible initiating mechanism for AIH.

  15. Effect of 22 CYP2D6 variants found in the Chinese population on tolterodine metabolism in vitro.

    PubMed

    Wang, Hao; Dai, Da-Peng; Sun, Peng; Xu, Li-Ping; Liang, Bing-Qing; Cai, Jian-Ping; Hu, Guo-Xin

    2017-02-25

    Cytochrome P450 2D6 (CYP2D6) is an important member of the cytochrome P450 enzyme superfamily. We recently identified 22 novel variants in the Chinese population using PCR and bidirectional sequencing methods. The aim of this study is to characterize the enzymatic activity of these variants and their effects on the metabolism of the antimuscarinic drug tolterodine in vitro. A baculovirus-mediated expression system was used to express wild-type CYP2D6 and 24 variants (CYP2D6*2, CYP2D6*10, and 22 novel CYP2D6 variants) at high levels. The insect microsomes expressing CYP2D6 proteins were incubated with 0.1-50 μM tolterodine at 37 °C for 30 min and the metabolites were analyzed by high-performance liquid chromatography-tandem mass spectrometry system. Of the 24 CYP2D6 variants tested, 2 variants (CYP2D6*92 and CYP2D6*96) were found to be catalytically inactive, 4 variants (CYP2D6*94, F164L, F219S and D336N) exhibited markedly increased intrinsic clearance values (Vmax/Km) compared with the wild-type (from 66.34 to 99.79%), whereas 4 variants (CYP2D6*10, *93, *95 and E215K) exhibited significantly decreased values (from 49.02 to 98.50%). This is the first report of all these rare alleles for tolterodine metabolism and these findings suggest that more attention should be paid to subjects carrying these infrequent CYP2D6 alleles when administering tolterodine in the clinic.

  16. CYP2D6 polymorphism: implications for antipsychotic drug response, schizophrenia and personality traits.

    PubMed

    Dorado, Pedro; Peñas-Lledó, Eva M; Llerena, Adrián

    2007-11-01

    The CYP2D6 gene is highly polymorphic, causing absent (poor metabolizers), decreased, normal or increased enzyme activity (extensive and ultrarapid metabolizers). The genetic polymorphism of the CYP2D6 influences plasma concentration of a wide variety of drugs metabolized in the liver by the cytochrome P450 (CYP) 2D6 enzyme, including antipsychotic drugs used for schizophrenia treatment. Additionally, CYP2D6 is involved in the metabolism of endogenous substrates in the brain, and reported to be located in regions such as the cortex, hippocampus and cerebellum, which are impaired in schizophrenia. Moreover, recently we have found that CYP2D6 poor metabolizers are under-represented in a case-control association study of schizophrenia. Furthermore, null CYP2D6 activity in healthy volunteers is associated with personality characteristics of social cognitive anxiety, which may bear some resemblance to milder forms of psychotic-like symptoms. In keeping with this, CYP2D6 may influence, not only variability to drug response, but also vulnerability to disease in schizophrenia patients.

  17. CYP2D6 polymorphisms and their influence on risperidone treatment

    PubMed Central

    Puangpetch, Apichaya; Vanwong, Natchaya; Nuntamool, Nopphadol; Hongkaew, Yaowaluck; Chamnanphon, Monpat; Sukasem, Chonlaphat

    2016-01-01

    Cytochrome P450 enzyme especially CYP2D6 plays a major role in biotransformation. The interindividual variations of treatment response and toxicity are influenced by the polymorphisms of this enzyme. This review emphasizes the effect of CYP2D6 polymorphisms in risperidone treatment in terms of basic knowledge, pharmacogenetics, effectiveness, adverse events, and clinical practice. Although the previous studies showed different results, the effective responses in risperidone treatment depend on the CYP2D6 polymorphisms. Several studies suggested that CYP2D6 polymorphisms were associated with plasma concentration of risperidone, 9-hydroxyrisperidone, and active moiety but did not impact on clinical outcomes. In addition, CYP2D6 poor metabolizer showed more serious adverse events such as weight gain and prolactin than other predicted phenotype groups. The knowledge of pharmacogenomics of CYP2D6 in risperidone treatment is increasing, and it can be used for the development of personalized medication in term of genetic-based dose recommendation. Moreover, the effects of many factors in risperidone treatment are still being investigated. Both the CYP2D6 genotyping and therapeutic drug monitoring are the important steps to complement the genetic-based risperidone treatment. PMID:27942231

  18. Cytochrome P450-activated prodrugs

    PubMed Central

    Ortiz de Montellano, Paul R

    2013-01-01

    A prodrug is a compound that has negligible, or lower, activity against a specified pharmacological target than one of its major metabolites. Prodrugs can be used to improve drug delivery or pharmacokinetics, to decrease toxicity, or to target the drug to specific cells or tissues. Ester and phosphate hydrolysis are widely used in prodrug design because of their simplicity, but such approaches are relatively ineffective for targeting drugs to specific sites. The activation of prodrugs by the cytochrome P450 system provides a highly versatile approach to prodrug design that is particularly adaptable for targeting drug activation to the liver, to tumors or to hypoxic tissues. PMID:23360144

  19. CYP2D6 Is Inducible by Endogenous and Exogenous Corticosteroids.

    PubMed

    Farooq, Muhammad; Kelly, Edward J; Unadkat, Jashvant D

    2016-05-01

    Although cytochrome P450 (CYP) 2D6 has been widely considered to be noninducible on the basis of human hepatocyte studies, in vivo data suggests that it is inducible by endo- and xenobiotics. Therefore, we investigated if the experimental conditions routinely used in human hepatocyte studies may be a confounding factor in the lack of in vitro induction of CYP2D6. Sandwich cultured human hepatocytes (SCHH) were preincubated with or without dexamethasone (100 nM) for 72 hours before incubation with 1μM endogenous (cortisol or corticosterone) or exogenous (dexamethasone or prednisolone) corticosteroids. At 72 hours, CYP2D6 mRNA, protein, and activity were quantified by real-time quantitative polymerase chain reaction, quantitative proteomics, and formation of dextrorphan from dextromethorphan, respectively. In the absence of supplemental dexamethasone, CYP2D6 activity, mRNA, and protein were significantly and robustly (>10-fold) induced by all four corticosteroids. However, this CYP2D6 induction was abolished in cells preincubated with supplemental dexamethasone. These data show, for the first time, that CYP2D6 is inducible in vitro but the routine presence of 100 nM dexamethasone in the culture medium masks this induction. Our cortisol data are in agreement with the clinical observation that CYP2D6 is inducible during the third trimester of pregnancy when the plasma concentrations of cortisol increase to ∼1μM. These findings, if confirmed in vivo, have implications for predicting CYP2D6-mediated drug-drug interactions and call for re-evaluation of regulatory guidelines on screening for CYP2D6 induction by xenobiotics. Our findings also suggest that cortisol may be a causative factor in the in vivo induction of CYP2D6 during pregnancy.

  20. Cytochrome P450 (CYP450) Tests

    MedlinePlus

    ... By Mayo Clinic Staff Your doctor may use cytochrome P450 (CYP450) tests to help determine how your body processes (metabolizes) a drug. The human body contains P450 enzymes to process medications. Because of inherited (genetic) traits ...

  1. Distribution of CYP2D6 alleles and phenotypes in the Brazilian population.

    PubMed

    Friedrich, Deise C; Genro, Júlia P; Sortica, Vinicius A; Suarez-Kurtz, Guilherme; de Moraes, Maria Elizabete; Pena, Sergio D J; dos Santos, Andrea K Ribeiro; Romano-Silva, Marco A; Hutz, Mara H

    2014-01-01

    The CYP2D6 enzyme is one of the most important members of the cytochrome P450 superfamily. This enzyme metabolizes approximately 25% of currently prescribed medications. The CYP2D6 gene presents a high allele heterogeneity that determines great inter-individual variation. The aim of this study was to evaluate the variability of CYP2D6 alleles, genotypes and predicted phenotypes in Brazilians. Eleven single nucleotide polymorphisms and CYP2D6 duplications/multiplications were genotyped by TaqMan assays in 1020 individuals from North, Northeast, South, and Southeast Brazil. Eighteen CYP2D6 alleles were identified in the Brazilian population. The CYP2D6*1 and CYP2D6*2 alleles were the most frequent and widely distributed in different geographical regions of Brazil. The highest number of CYPD6 alleles observed was six and the frequency of individuals with more than two copies ranged from 6.3% (in Southern Brazil) to 10.2% (Northern Brazil). The analysis of molecular variance showed that CYP2D6 is homogeneously distributed across different Brazilian regions and most of the differences can be attributed to inter-individual differences. The most frequent predicted metabolic status was EM (83.5%). Overall 2.5% and 3.7% of Brazilians were PMs and UMs respectively. Genomic ancestry proportions differ only in the prevalence of intermediate metabolizers. The IM predicted phenotype is associated with a higher proportion of African ancestry and a lower proportion of European ancestry in Brazilians. PM and UM classes did not vary among regions and/or ancestry proportions therefore unique CYP2D6 testing guidelines for Brazilians are possible and could potentially avoid ineffective or adverse events outcomes due to drug prescriptions.

  2. Distribution of CYP2D6 Alleles and Phenotypes in the Brazilian Population

    PubMed Central

    Sortica, Vinicius A.; Suarez-Kurtz, Guilherme; de Moraes, Maria Elizabete; Pena, Sergio D. J.; dos Santos, Ândrea K. Ribeiro; Romano-Silva, Marco A.; Hutz, Mara H.

    2014-01-01

    Abstract The CYP2D6 enzyme is one of the most important members of the cytochrome P450 superfamily. This enzyme metabolizes approximately 25% of currently prescribed medications. The CYP2D6 gene presents a high allele heterogeneity that determines great inter-individual variation. The aim of this study was to evaluate the variability of CYP2D6 alleles, genotypes and predicted phenotypes in Brazilians. Eleven single nucleotide polymorphisms and CYP2D6 duplications/multiplications were genotyped by TaqMan assays in 1020 individuals from North, Northeast, South, and Southeast Brazil. Eighteen CYP2D6 alleles were identified in the Brazilian population. The CYP2D6*1 and CYP2D6*2 alleles were the most frequent and widely distributed in different geographical regions of Brazil. The highest number of CYPD6 alleles observed was six and the frequency of individuals with more than two copies ranged from 6.3% (in Southern Brazil) to 10.2% (Northern Brazil). The analysis of molecular variance showed that CYP2D6 is homogeneously distributed across different Brazilian regions and most of the differences can be attributed to inter-individual differences. The most frequent predicted metabolic status was EM (83.5%). Overall 2.5% and 3.7% of Brazilians were PMs and UMs respectively. Genomic ancestry proportions differ only in the prevalence of intermediate metabolizers. The IM predicted phenotype is associated with a higher proportion of African ancestry and a lower proportion of European ancestry in Brazilians. PM and UM classes did not vary among regions and/or ancestry proportions therefore unique CYP2D6 testing guidelines for Brazilians are possible and could potentially avoid ineffective or adverse events outcomes due to drug prescriptions. PMID:25329392

  3. Reactive Intermediates in Cytochrome P450 Catalysis*

    PubMed Central

    Krest, Courtney M.; Onderko, Elizabeth L.; Yosca, Timothy H.; Calixto, Julio C.; Karp, Richard F.; Livada, Jovan; Rittle, Jonathan; Green, Michael T.

    2013-01-01

    Recently, we reported the spectroscopic and kinetic characterizations of cytochrome P450 compound I in CYP119A1, effectively closing the catalytic cycle of cytochrome P450-mediated hydroxylations. In this minireview, we focus on the developments that made this breakthrough possible. We examine the importance of enzyme purification in the quest for reactive intermediates and report the preparation of compound I in a second P450 (P450ST). In an effort to bring clarity to the field, we also examine the validity of controversial reports claiming the production of P450 compound I through the use of peroxynitrite and laser flash photolysis. PMID:23632017

  4. CYP2D6 allele distribution in Macedonians, Albanians and Romanies in the Republic of Macedonia

    PubMed Central

    Kuzmanovska, M; Dimishkovska, M; Maleva Kostovska, I; Noveski, P; Sukarova Stefanovska, E

    2015-01-01

    Abstract Cytochrome P450 2D6 (CYP2D6) is an enzyme of great importance for the metabolism of clinically used drugs. More than 100 variants of the CYP2D6 gene have been identified so far. The aim of this study was to investigate the allele distribution of CYP2D6 gene variants in 100 individuals of each of the Macedonian, Albanian and Romany population, by genotyping using long range polymerase chain reaction (PCR) and a multiplex single base extension method. The most frequent variants and almost equally distributed in the three groups were the fully functional alleles *1 and *2. The most common non functional allele in all groups was *4 that was found in 22.5% of the Albanians. The most common allele with decreased activity was *41 which was found in 23.0% of the Romany ethnic group, in 11.0% of the Macedonians and in 10.5% of the Albanians. Seven percent of the Albanians, 6.0% of the Romani and 4.0% of the Macedonians were poor metabolizers, while 5.0% of the Macedonians, 1.0% of Albanians and 1.0% of the Romanies were ultrarapid metabolizers. We concluded that the CYP2D6 gene locus is highly heterogeneous in these groups and that the prevalence of the CYP2D6 allele variants and genotypes in the Republic of Macedonia is in accordance with that of other European populations. PMID:27785397

  5. CYP2D6 allele distribution in Macedonians, Albanians and Romanies in the Republic of Macedonia.

    PubMed

    Kuzmanovska, M; Dimishkovska, M; Maleva Kostovska, I; Noveski, P; Sukarova Stefanovska, E; Plaseska-Karanfilska, D

    2015-12-01

    Cytochrome P450 2D6 (CYP2D6) is an enzyme of great importance for the metabolism of clinically used drugs. More than 100 variants of the CYP2D6 gene have been identified so far. The aim of this study was to investigate the allele distribution of CYP2D6 gene variants in 100 individuals of each of the Macedonian, Albanian and Romany population, by genotyping using long range polymerase chain reaction (PCR) and a multiplex single base extension method. The most frequent variants and almost equally distributed in the three groups were the fully functional alleles *1 and *2. The most common non functional allele in all groups was *4 that was found in 22.5% of the Albanians. The most common allele with decreased activity was *41 which was found in 23.0% of the Romany ethnic group, in 11.0% of the Macedonians and in 10.5% of the Albanians. Seven percent of the Albanians, 6.0% of the Romani and 4.0% of the Macedonians were poor metabolizers, while 5.0% of the Macedonians, 1.0% of Albanians and 1.0% of the Romanies were ultrarapid metabolizers. We concluded that the CYP2D6 gene locus is highly heterogeneous in these groups and that the prevalence of the CYP2D6 allele variants and genotypes in the Republic of Macedonia is in accordance with that of other European populations.

  6. CYP2D6 genotype and adjuvant tamoxifen: meta-analysis of heterogeneous study populations.

    PubMed

    Province, M A; Goetz, M P; Brauch, H; Flockhart, D A; Hebert, J M; Whaley, R; Suman, V J; Schroth, W; Winter, S; Zembutsu, H; Mushiroda, T; Newman, W G; Lee, M-T M; Ambrosone, C B; Beckmann, M W; Choi, J-Y; Dieudonné, A-S; Fasching, P A; Ferraldeschi, R; Gong, L; Haschke-Becher, E; Howell, A; Jordan, L B; Hamann, U; Kiyotani, K; Krippl, P; Lambrechts, D; Latif, A; Langsenlehner, U; Lorizio, W; Neven, P; Nguyen, A T; Park, B-W; Purdie, C A; Quinlan, P; Renner, W; Schmidt, M; Schwab, M; Shin, J-G; Stingl, J C; Wegman, P; Wingren, S; Wu, A H B; Ziv, E; Zirpoli, G; Thompson, A M; Jordan, V C; Nakamura, Y; Altman, R B; Ames, M M; Weinshilboum, R M; Eichelbaum, M; Ingle, J N; Klein, T E

    2014-02-01

    The International Tamoxifen Pharmacogenomics Consortium was established to address the controversy regarding cytochrome P450 2D6 (CYP2D6) status and clinical outcomes in tamoxifen therapy. We performed a meta-analysis on data from 4,973 tamoxifen-treated patients (12 globally distributed sites). Using strict eligibility requirements (postmenopausal women with estrogen receptor-positive breast cancer, receiving 20 mg/day tamoxifen for 5 years, criterion 1); CYP2D6 poor metabolizer status was associated with poorer invasive disease-free survival (IDFS: hazard ratio = 1.25; 95% confidence interval = 1.06, 1.47; P = 0.009). However, CYP2D6 status was not statistically significant when tamoxifen duration, menopausal status, and annual follow-up were not specified (criterion 2, n = 2,443; P = 0.25) or when no exclusions were applied (criterion 3, n = 4,935; P = 0.38). Although CYP2D6 is a strong predictor of IDFS using strict inclusion criteria, because the results are not robust to inclusion criteria (these were not defined a priori), prospective studies are necessary to fully establish the value of CYP2D6 genotyping in tamoxifen therapy.

  7. Cytochrome P450 gene polymorphism and cancer.

    PubMed

    Agundez, Jose A G

    2004-06-01

    Human cytochrome P450 (CYP) enzymes play a key role in the metabolism of drugs and environmental chemicals. Several CYP enzymes metabolically activate procarcinogens to genotoxic intermediates. Phenotyping analyses revealed an association between CYP enzyme activity and the risk to develop several forms of cancer. Research carried out in the last decade demonstrated that several CYP enzymes are polymorphic due to single nucleotide polymorphisms, gene duplications and deletions. As genotyping procedures became available for most human CYP, an impressive number of association studies on CYP polymorphisms and cancer risk were conducted. Here we review the findings obtained in these studies regarding CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2D6, CYP2E1, CYP3A4, CYP3A5, CYP3A7, CYP8A1 and CYP21 gene polymorphisms. Consistent evidences for association between CYP polymorphisms and lung, head and neck, and liver cancer were reported. Controversial findings suggest that colorectal and prostate cancers may be associated to CYP polymorphisms, whereas no evidences for a relevant association with breast or bladder cancers were reported. We summarize the available information related to the association of CYP polymorphisms with leukaemia, lymphomas and diverse types of cancer that were investigated only for some CYP genes, including brain, esophagus, stomach, pancreas, pituitary, cervical epithelium, melanoma, ovarian, kidney, anal and vulvar cancers. This review discusses on causes of heterogeneity in the proposed associations, controversial findings on cancer risk, and identifies topics that require further investigation. In addition, some recommendations on study design, in order to obtain more conclusive findings in further studies, are provided.

  8. Unusual Cytochrome P450 Enzymes and Reactions*

    PubMed Central

    Guengerich, F. Peter; Munro, Andrew W.

    2013-01-01

    Cytochrome P450 enzymes primarily catalyze mixed-function oxidation reactions, plus some reductions and rearrangements of oxygenated species, e.g. prostaglandins. Most of these reactions can be rationalized in a paradigm involving Compound I, a high-valent iron-oxygen complex (FeO3+), to explain seemingly unusual reactions, including ring couplings, ring expansion and contraction, and fusion of substrates. Most P450s interact with flavoenzymes or iron-sulfur proteins to receive electrons from NAD(P)H. In some cases, P450s are fused to protein partners. Other P450s catalyze non-redox isomerization reactions. A number of permutations on the P450 theme reveal the diversity of cytochrome P450 form and function. PMID:23632016

  9. Metabolism of methoxyphenamine in vitro by a CYP2D6 microsomal preparation.

    PubMed

    Coutts, R T; Bolaji, O O; Su, P; Baker, G B

    1994-01-01

    Metabolism of methoxyphenamine (MP) was conducted in vitro using commercially available microsomes prepared from human AHH-1 TK+/-cells in which CYP2D6 had been expressed. This study has confirmed the involvement of CYP2D6 in the metabolism of MP to O-desmethylmethoxyphenamine (ODMP) and 5-hydroxymethoxyphenamine (5HMP), but not to N-desmethylmethoxyphenamine. It has also revealed that CYP2D6 catalyzes the formation of another, hitherto unknown, ring-hydroxylated metabolite of MP, isomeric with 5HMP. The analytical procedure used to identify and quantify MP metabolites involved an acetylation procedure that had distinct advantages. MP and its basic and amphoteric metabolites were all converted to neutral products that were efficiently extracted into organic solvent. The acetylated products also had good chromatographic properties and provided mass spectra that were readily interpretable. MP metabolism studies were also conducted with CYP2D6 microsomes in the presence of quinidine and quinine. The former was the more potent inhibitor of CYP2D6-catalyzed oxidations of MP. Its inclusion resulted in complete inhibition of metabolism of MP to ODMP, 5HMP, and its novel isomer. This study shows that the in vitro use of human cytochrome P450 isozyme preparations in drug metabolism studies can aid in the identification of possible in vivo metabolites of these drugs in humans and can provide information on putative drug-drug interactions.

  10. Cytochrome P450s and molecular epidemiology

    NASA Astrophysics Data System (ADS)

    Gonzalez, Frank J.; Gelboin, Harry V.

    1993-03-01

    Cytochrome P450 (P450) represent a superfamily of heme-containing monooxygenases that are found throughout the animal and plant kingdoms and in many microorganisms. A number of these enzymes are involved in biosynthetic pathways of steroid synthesis but in mammals the vast majority of P450s function to metabolize foreign chemicals or xenobiotics. In the classical phase I reactions on the latter, a membrane-bound P450 will hydroxylate a compound, usually hydrophobic in nature, and the hydroxyl group will serve as a substrate for the various transferases or phase II enzymes that attach hydrophilic substituents such as glutathione, sulfate or glucuronic acid. Some chemicals, however, are metabolically-activated by P450s to electrophiles capable of reacting with cellular macromolecules. The cellular concentrations of the chemical and P450, reactivity of the active metabolite with nucleic acid and the repairability of the resultant adducts, in addition to the nature of the cell type, likely determines whether a chemical will be toxic and kill the cell or will transform the cell. Immunocorrelative and cDNA-directed expression have been used to define the substrate specificities of numerous human P450s. Levels of expression of different human P450 forms have been measured by both in vivo and in vitro methodologies leading to the realization that a large degree of interindividual differences occur in P450 expression. Reliable procedures for measuring P450 expression in healthy and diseased subjects will lead to prospective and case- cohort studies to determine whether interindividual differences in levels of P450 are associated with susceptibility or resistance to environmentally-based disease.

  11. Microsomal monooxygenase as a multienzyme system: the role of P450-P450 interactions

    PubMed Central

    Davydov, Dmitri R.

    2011-01-01

    Introduction There is increasing evidence of physical interactions (association) among cytochromes P450 in the membranes of the endoplasmic reticulum. Functional consequences of these interactions are often underestimated. Areas covered This article provides a comprehensive overview of available experimental material regarding P450-P450 interactions. Special emphasis is given to the interactions between different P450 species and to the functional consequences of homo- and heterooligomerization. Expert opinion Recent advances provide conclusive evidence for a substantial degree of P450 oligomerization in membranes. Interactions between different P450 species resulting in the formation of mixed oligomers with altered activity and substrate specificity have been demonstrated clearly. There are important indications that oligomerization of cytochromes P450 impedes electron flow to a fraction of the P450 population, which render some P450 species non-functional. Functional consequences of P450-P450 interactions make the integrated properties of the microsomal monooxygenase remarkably different from a simple summation of the properties of the individual P450 species. This complexity compromises the predictive power of the current in vitro models of drug metabolism and warrants an urgent need for development of new model systems that consider the interactions of multiple P450 species. PMID:21395496

  12. The Psychostimulant Khat (Catha edulis) Inhibits CYP2D6 Enzyme Activity in Humans.

    PubMed

    Bedada, Worku; de Andrés, Fernando; Engidawork, Ephrem; Pohanka, Anton; Beck, Olof; Bertilsson, Leif; Llerena, Adrián; Aklillu, Eleni

    2015-12-01

    The use of khat (Catha edulis) while on medication may alter treatment outcome. In particular, the influence of khat on the metabolic activities of drug-metabolizing enzymes is not known. We performed a comparative 1-way crossover study to evaluate the effect of khat on cytochrome P450 (CYP)2D6 and CYP3A4 enzyme activity. After 1 week of khat abstinence, baseline CYP2D6 and CYP3A4 metabolic activities were determined in 40 Ethiopian male volunteers using 30 mg dextromethorphan (DM) as a probe drug and then repeated after 1 week of daily use of 400 g fresh khat leaves. Urinary concentrations of cathinone and cathine were determined to monitor the subjects' compliance to the study protocol. Genotyping for CYP2D6*3 and CYP2D6*4 was done. Plasma DM, dextrorphan and 3-methoxymorphinan concentrations were quantified. CYP2D6 and CYP3A4 enzyme activities were assessed by comparing plasma log DM/dextrorphan and log DM/methoxymorphinan metabolic ratio (MR) respectively in the presence and absence of khat. Cytochrome 2D6 MR was significantly increased from baseline by concurrent khat use (paired t test, P = 0.003; geometric mean ratio, 1.38; 95% confidence interval [95% CI], 1.12-1.53). Moreover, the inhibition of CYP2D6 activity by khat was more pronounced in CYP2D6*1/*1 compared with CYP2D6*1/*4 genotypes (P = 0.01). A marginal inhibition of CYP3A4 activity in the presence of khat was observed (P = 0.24). The mean percentage increase of CYP2D6 and CYP3A4 MR from baseline by khat use was 46% (95% CI, 20-72) and 31% (95% CI, 8-54), respectively. This is the first report linking khat use with significant inhibition of CYP2D6 metabolic activity in humans.

  13. Cytochrome P450 CYP3A in marsupials: cloning and identification of the first CYP3A subfamily member, isoform 3A70 from Eastern gray kangaroo (Macropus giganteus).

    PubMed

    El-Merhibi, Adaweyah; Ngo, Suong N T; Marchant, Ceilidh L; Height, Tamara A; Stupans, Ieva; McKinnon, Ross A

    2012-09-15

    Australian marsupials are unique fauna that have evolved and adapted to unique environments and thus it is likely that their detoxification systems differ considerably from those of well-studied eutherian mammals. Knowledge of these processes in marsupials is therefore vital to understanding the consequences of exposure to xenobiotics. Cytochromes P450 (CYPs) are critically important in the oxidative metabolism of a diverse array of both xenobiotics and endogenous substrates. In this study we have cloned and characterized CYP3A70, the first identified member of the CYP3A gene subfamily from Eastern gray kangaroo (Macropus giganteus). A 1665 base pair kangaroo hepatic CYP3A complete cDNA, designated CYP3A70, was cloned by reverse transcription-polymerase chain reaction approaches, which encodes a protein of 506 amino acids. The CYP3A70 cDNA shares approximately 71% nucleotide and 65% amino acid sequence homology to human CYP3A4 and displays high sequence similarity to other published mammalian CYP3As from human, monkey, cow, pig, dog, rat, rabbit, mouse, hamster, and guinea pig. Transfection of the CYP3A70 cDNAs into 293T cells resulted in stable cell lines expressing a CYP3A immuno-reactive protein that was recognized by a goat anti-human CYP3A4 polyclonal antibody. The anti-human CYP3A4 antibody also detected immunoreactive proteins in liver microsomes from all test marsupials, including the kangaroo, koala, wallaby, and wombat, with multiple CYP3A immunoreactive bands observed in kangaroo and wallaby tissues. Relatively, very low CYP catalytic activity was detected for the kangaroo CYP3A70 cDNA-expressed proteins (19.6 relative luminescent units/μg protein), which may be due to low protein expression levels. Collectively, this study provides primary molecular data regarding the Eastern kangaroo hepatic CYP3A70 gene and enables further functional analyses of CYP3A enzymes in marsupials.

  14. Comparative modelling of cytochromes P450.

    PubMed

    Kirton, Stewart B; Baxter, Carol A; Sutcliffe, Michael J

    2002-03-31

    The superfamily of enzymes known as the cytochromes P450 (P450s) comprises a wide-ranging class of proteins with diverse functions. They are known, amongst other things, to be involved in the hormonal regulation of metabolism and reproduction, as well as having a major clinical significance through their association with diseases such as cancer, diabetes and hepatitis. Knowledge of the three-dimensional (3D) structure of a protein gives insight into its function. The 3D structures of P450s are therefore of considerable scientific interest. A number of high-resolution structures of P450s have been determined by X-ray crystallography and studies of these structures have provided valuable insights into the mechanism of these enzymes. Only one of these structures is mammalian and as yet there is no structural information on human P450s in the public domain. Until such a structure is solved it is necessary to employ alternative methods to gain structural insight into how human P450s perform their biological function. Here we report on the use of comparative modelling to predict the structure of human P450s based on knowledge of their amino acid sequences plus the 3D structures of other (not human) P450s. As an illustrative example of these techniques we have modelled the structure of P450 2C5 using five bacterial P450 structures as templates. We examine the importance of selecting suitable templates, obtaining a good amino acid sequence alignment, and evaluating the models generated. To improve the quality of the models an iterative cycle of sequence alignment, model building, and model evaluation is employed. The result is a model with excellent stereochemistry, good amino acid side chain environment properties, and a Calpha trace similar to the crystal structure.

  15. Inhibition of human cytochrome P450 enzymes by the natural hepatotoxin safrole.

    PubMed

    Ueng, Yune-Fang; Hsieh, Chih-Hang; Don, Ming-Jaw

    2005-05-01

    The hepatotoxin, safrole is a methylenedioxy phenyl compound, found in sassafras oil and certain other essential oils. Recombinant cytochrome P450 (CYP, P450) and human liver microsomes were studied to investigate the selective inhibitory effects of safrole on human P450 enzymes and the mechanisms of action. Using Escherichia coli-expressed human P450, our results demonstrated that safrole was a non-selective inhibitor of CYP1A2, CYP2A6, CYP2D6, CYP2E1, and CYP3A4 in the IC(50) order CYP2E1 < CYP1A2 < CYP2A6 < CYP3A4 < CYP2D6. Safrole strongly inhibited CYP1A2, CYP2A6, and CYP2E1 activities with IC(50) values less than 20 microM. Safrole caused competitive, non-competitive, and non-competitive inhibition of CYP1A2, CYP2A6 and CYP2E1 activities, respectively. The inhibitor constants were in the order CYP1A2 < CYP2E1 < CYP2A6. In human liver microsomes, 50 microM safrole strongly inhibited 7-ethoxyresorufin O-deethylation, coumarin hydroxylation, and chlorzoxazone hydroxylation activities. These results revealed that safrole was a potent inhibitor of human CYP1A2, CYP2A6, and CYP2E1. With relatively less potency, CYP2D6 and CYP3A4 were also inhibited.

  16. Cytochrome P450-mediated metabolism of triclosan attenuates its cytotoxicity in hepatic cells.

    PubMed

    Wu, Yuanfeng; Chitranshi, Priyanka; Loukotková, Lucie; Gamboa da Costa, Gonçalo; Beland, Frederick A; Zhang, Jie; Fang, Jia-Long

    2016-11-28

    Triclosan is a widely used broad-spectrum anti-bacterial agent. The objectives of this study were to identify which cytochrome P450 (CYP) isoforms metabolize triclosan and to examine the effects of CYP-mediated metabolism on triclosan-induced cytotoxicity. A panel of HepG2-derived cell lines was established, each of which overexpressed a single CYP isoform, including CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2A7, CYP2A13, CYP2B6, CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2D6, CYP2E1, CYP3A4, CYP3A5, CYP3A7, CYP4A11, and CYP4B1. The extent of triclosan metabolism by each CYP was assessed by reversed-phase high-performance liquid chromatography with online radiochemical detection. Seven isoforms were capable of metabolizing triclosan, with the order of activity being CYP1A2 > CYP2B6 > CYP2C19 > CYP2D6 ≈ CYP1B1 > CYP2C18 ≈ CYP1A1. The remaining 11 isoforms (CYP2A6, CYP2A7, CYP2A13, CYP2C8, CYP2C9, CYP2E1, CYP3A4, CYP3A5, CYP3A7, CYP4A11, and CYP4B1) had little or no activity toward triclosan. Three metabolites were detected: 2,4-dichlorophenol, 4-chlorocatechol, and 5'-hydroxytriclosan. Consistent with the in vitro screening data, triclosan was extensively metabolized in HepG2 cells overexpressing CYP1A2, CYP2B6, CYP2C19, CYP2D6, and CYP2C18, and these cells were much more resistant to triclosan-induced cytotoxicity compared to vector cells, suggesting that CYP-mediated metabolism of triclosan attenuated its cytotoxicity. In addition, 2,4-dichlorophenol and 4-chlorocatechol were less toxic than triclosan to HepG2/vector cells. Conjugation of triclosan, catalyzed by human glucuronosyltransferases (UGTs) and sulfotransferases (SULTs), also occurred in HepG2/CYP-overexpressing cells and primary human hepatocytes, with a greater extent of conjugation being associated with higher cell viability. Co-administration of triclosan with UGT or SULT inhibitors led to greater cytotoxicity in HepG2 cells and primary human hepatocytes, indicating that glucuronidation and

  17. Inhibition of human cytochrome P450 enzymes by Bacopa monnieri standardized extract and constituents.

    PubMed

    Ramasamy, Seetha; Kiew, Lik Voon; Chung, Lip Yong

    2014-02-24

    Bacopa monnieri and the constituents of this plant, especially bacosides, possess various neuropharmacological properties. Like drugs, some herbal extracts and the constituents of their extracts alter cytochrome P450 (CYP) enzymes, causing potential herb-drug interactions. The effects of Bacopa monnieri standardized extract and the bacosides from the extract on five major CYP isoforms in vitro were analyzed using a luminescent CYP recombinant human enzyme assay. B. monnieri extract exhibited non-competitive inhibition of CYP2C19 (IC50/Ki = 23.67/9.5 µg/mL), CYP2C9 (36.49/12.5 µg/mL), CYP1A2 (52.20/25.1 µg/mL); competitive inhibition of CYP3A4 (83.95/14.5 µg/mL) and weak inhibition of CYP2D6 (IC50 = 2061.50 µg/mL). However, the bacosides showed negligible inhibition of the same isoforms. B. monnieri, which is orally administered, has a higher concentration in the gut than the liver; therefore, this herb could exhibit stronger inhibition of intestinal CYPs than hepatic CYPs. At an estimated gut concentration of 600 µg/mL (based on a daily dosage of 300 mg/day), B. monnieri reduced the catalytic activities of CYP3A4, CYP2C9 and CYP2C19 to less than 10% compared to the total activity (without inhibitor = 100%). These findings suggest that B. monnieri extract could contribute to herb-drug interactions when orally co-administered with drugs metabolized by CYP1A2, CYP3A4, CYP2C9 and CYP2C19.

  18. Development of a PCR-based strategy for CYP2D6 genotyping including gene multiplication of worldwide potential use.

    PubMed

    Dorado, Pedro; Cáceres, Macarena; Pozo-Guisado, Eulalia; Wong, Ma-Li; Licinio, Julio; Llerena, Adrián

    2005-10-01

    There is growing consensus on the potential use of pharmacogenetics in clinical practice, and hopes have been expressed for application to the improvement of global health. However, two major challenges may lead to widening the "biotechnological gap" between the developing and the industrial world; first the unaffordability of some current technologies for poorer countries, and second the necessity of analyzing all described alleles for every clinical case due to the inability to predict the ethnic group of a given patient. Because of its role in the metabolism of a number of drugs, cytochrome P450 2D6 (CYP2D6) is an excellent candidate for use in the optimization of drug therapy. CYP2D6 is a highly polymorphic gene locus with more than 50 variant alleles, and subjects can be classified as poor metabolizers (PM), extensive metabolizers (EM), or ultrarapid metabolizers (UM) of a given CYP2D6 substrate. Several strategies and methods for CYP2D6 genotyping exist. Some, however, are expensive and laborious. The aim of this study was to design a PCR-based genotyping methodology to allow rapid, straightforward, and inexpensive identification of 90%-95% of CYP2D6 PM or UM genotypes for routine clinical use, independent of the individual's ethnic group. CYP2D6 is amplified in initial extra long PCRs (XL-PCRs), which subsequently undergo fragment-length polymorphism analysis for the determination of carriers of CYP2D6 allelic variants. The same XL-PCRs are also used for the determination of CYP2D6 multiplication and 2D6*5 allele (abolished activity). The application of this new strategy for the detection of CYP2D6 mutated alleles and multiplications to routine clinical analysis will enable the PM and UM phenotypes to be predicted and identified at a reasonable cost in a large number of individuals at most locations.

  19. Development of a PCR-based strategy for CYP2D6 genotyping including gene multiplication of worldwide potential use.

    PubMed

    Dorado, Pedro; Cáceres, Macarena C; Pozo-Guisado, Eulalia; Wong, Ma-Li; Licinio, Julio; Llerena, Adrian

    2005-10-01

    There is growing consensus on the potential use of pharmacogenetics in clinical practice, and hopes have been expressed for application to the improvement of global health. However, two major challenges may lead to widening the "biotechnological gap" between the developing and the industrial world;first the unaffordability of some current technologies for poorer countries, and second the necessity of analyzing all described alleles for every clinical case due to the inability to predict the ethnic group of a given patient. Because of its role in the metabolism of a number of drugs, cytochrome P450 2D6 (CYP2D6) is an excellent candidate for use in the optimization of drug therapy. CYP2D6 is a highly polymorphic gene locus with more than 50 variant alleles, and subjects can be classified as poor metabolizers (PM), extensive metabolizers (EM), or ultrarapid metabolizers (UM) of a given CYP2D6 substrate. Several strategies and methods for CYP2D6 genotyping exist. Some, however, are expensive and laborious. The aim of this study was to design a PCR-based genotyping methodology to allow rapid, straightforward, and inexpensive identification of 90%-95% of CYP2D6 PM or UM genotypes for routine clinical use, independent of the individual's ethnic group. CYP2D6 is amplified in initial extra long PCRs (XL-PCRs), which subsequently undergo fragment-length polymorphism analysis for the determination of carriers of CYP2D6 allelic variants. The same XL-PCRs are also used for the determination of CYP2D6 multiplication and 2D6*5 allele (abolished activity). The application of this new strategy for the detection of CYP2D6 mutated alleles and multiplications to routine clinical analysis will enable the PM and UM phenotypes to be predicted and identified at a reasonable cost in a large number of individuals at most locations.

  20. Challenges in CYP2D6 phenotype assignment from genotype data: a critical assessment and call for standardization.

    PubMed

    Hicks, J Kevin; Swen, Jesse J; Gaedigk, Andrea

    2014-02-01

    The cytochrome P450 2D6 (CYP2D6) enzyme contributes to the metabolism and/or bioactivation of approximately 25% of clinically used drugs. The CYP2D6 gene locus is highly polymorphic and complex, and variants within this gene locus affect CYP2D6 enzymatic function resulting in a wide range of metabolic activity from little to no activity to ultrarapid metabolism. For many of the drugs metabolized by CYP2D6, the variation in metabolic activity is one of the most important factors responsible for interindividual drug response. Therefore, determining an individual's CYP2D6 phenotype, or metabolic status, will help identify individuals that may benefit from a change in drug or drug dosage. Genotype analysis has become the method of choice to predict a person's metabolic status. Numerous reference laboratories now offer CYP2D6 genotyping; however, there can be substantial differences in the number of genetic variants interrogated as well as test interpretation. Furthermore, there is no standardized process of how a CYP2D6 genotype result is translated into a phenotype assignment. This review summarizes the complexity of CYP2D6 genotyping and highlights the major challenges for phenotype classification. We call for the implementation of a universally accepted system for CYP2D6 phenotype assignment to promote consistency of test interpretation among reference laboratories and medical institutions. We propose a system that utilizes the CYP2D6 activity score system to place individuals into a continuum of activity scores - rather than using the traditional poor, intermediate, extensive and ultra-rapid metabolizer categorizations - and directly translating activity scores into clinically actionable recommendations.

  1. Effect of cytochrome P450 enzyme polymorphisms on pharmacokinetics of venlafaxine.

    PubMed

    McAlpine, Donald E; Biernacka, Joanna M; Mrazek, David A; O'Kane, Dennis J; Stevens, Susanna R; Langman, Loralie J; Courson, Vicki L; Bhagia, Jyoti; Moyer, Thomas P

    2011-02-01

    This study examines the relationship between blood concentrations of venlafaxine and its active metabolite, O-desmethyl venlafaxine (ODV), and genetic variants of the cytochrome P450 enzymes CYP2D6 and CYP2C19 in human subjects. Trough blood concentrations were measured at steady state in patients treated with venlafaxine extended release in a clinical practice setting. CYP2D6 and CYP2C19 genotypes were converted to activity scores based on known activity levels of the two alleles comprising a genotype. After adjusting for drug dose and gender effects, higher CYP2D6 and CYP2C19 activity scores were significantly associated with lower venlafaxine concentrations (P < 0.001 for each). Only CYP2D6 was associated with the concentration of ODV (P < 0.001), in which genotypes with more active alleles were associated with higher ODV concentrations. The sum of venlafaxine plus ODV concentration showed the same pattern as venlafaxine concentrations with CYP2D6 and CYP2C19 genotypes with higher activity scores being associated with a lower venlafaxine plus ODV concentration (2D6 P = 0.01; 2C19 P < 0.001). Because allelic variants in both CYP2D6 and CYP2C19 influence the total concentration of the active compounds venlafaxine and ODV, both CYP2D6 and CYP2C19 genotypes should be considered when using pharmacogenomic information for venlafaxine dose alterations.

  2. Male specific expression of a cytochrome P450 (Cyp312a1) in Drosophila melanogaster.

    PubMed

    Kasai, Shinji; Tomita, Takashi

    2003-01-24

    Using cDNA array techniques, the transcriptional levels of Drosophila cytochrome P450 (P450) genes were compared between male and female flies. Of the 86 P450s, 15 isoforms were picked up and the levels of transcription were confirmed by the real time quantitative RT-PCR. Cyp315a1 and Cyp302a1, which had been reported as P450s involved in the ecdysteroid biosynthesis, were included in the 15 isoforms and expression of these P450s was 8.6- and 7.9-fold higher in females than in males, respectively. In addition, we confirmed that expression of Cyp312a1 was 82-fold higher in adult males than females. This gene expression was observed mostly in the abdomen and its transcription level gradually increased from pupal stage and peaked in the 5-day-old adult. Furthermore, the male specific expression of Cyp312a1 was universally observed in three Drosophila strains originated from the USA (Oregon R), China (Canton S), and Japan (HKJ), suggesting possible involvement of this P450 in significant endogenous catalytic reaction(s). This is the first report of a P450 enzyme being predominantly expressed in male Drosophila.

  3. Individualization of tamoxifen therapy: much more than just CYP2D6 genotyping.

    PubMed

    Binkhorst, Lisette; Mathijssen, Ron H J; Jager, Agnes; van Gelder, Teun

    2015-03-01

    Clinical response to tamoxifen varies widely among women treated with this drug for hormone receptor-positive breast cancer. The principal active metabolite - endoxifen - is generated through hepatic metabolism of tamoxifen, with key roles for cytochrome P450 (CYP) CYP2D6 and CYP3A. By influencing endoxifen formation, genetic variants of CYP2D6 may affect response to tamoxifen. After a decade of research, examining the effects of CYP2D6 genetic variants on tamoxifen efficacy, there is still no agreement on the clinical utility of CYP2D6 genotype as biomarker for the prediction of breast cancer outcome, because studies revealed conflicting results. However, tamoxifen metabolism is complex and involves several other drug-metabolizing enzymes. Genetic variants of other CYP enzymes, including CYP3A4 and CYP2C9/19, as well as co-medication interfering with the metabolic activity of CYP2D6 and CYP3A4 have been shown to affect endoxifen concentrations and may also contribute to the variability in response to tamoxifen. Phenotyping strategies can predict endoxifen exposure more accurately than CYP2D6 genotype, but do not take into account all factors influencing endoxifen exposure. Therapeutic drug monitoring (TDM) is likely to be the optimal strategy for individualization of tamoxifen treatment. According to a growing amount of literature, endoxifen concentration seems to be a predictor of clinical outcome. The relationship between endoxifen levels and breast cancer outcomes has to be replicated and confirmed and the value of TDM should be evaluated in prospective clinical trials. Caution is advised regarding the concomitant use of medications which could interact with tamoxifen, including inhibitors and inducers of CYP enzymes.

  4. Inhibitory effect of salvianolate on human cytochrome P450 3A4 in vitro involving a noncompetitive manner

    PubMed Central

    Qin, Chong-Zhen; Ren, Xian; Zhou, Hong-Hao; Mao, Xiao-Yuan; Liu, Zhao-Qian

    2015-01-01

    Salvianolic acid B (Sal B), which is purified from Danshen, is a popular herb extract. Sal B has anti-oxidative, anti-inflammatory, anti-hypoxic, anti-arteriosclerotic and anti-apoptotic properties. This substance can also ameliorate brain injury or neurodegenerative diseases. The listed drug Salvianolate, which contains a substantial amount of Sal B, has been used for the treatment of coronary heart disease. Our present work aimed to evaluate the inhibitory effect of salvianolate on seven cytochrome P450 isoforms (CYP450), namely, CYP1A2, CYP2A6, CYP2E1, CYP2C9, CYP2C19, CYP2D6 and CYP3A4, in human liver microsomes (HLMs) and recombinant enzymes through high-performance liquid chromatography (HPLC) assay. Salvianolate have a potent inhibitory effect on CYP3A4 activity with IC50 values of 1.438 (HLMs) and 3.582 (recombinant cDNA-expressed CYP3A4) mg/L, respectively. Salvianolate strongly dose, but not time-dependently decreased CYP3A4 activity in HLMs. The typical Lineweaver-Burk plots showed that Salvianolate inhibited CYP3A4 activity noncompetitively, with a Ki value of 2.27 mg/L in HLMs. Other CYP450 isoforms are not markedly affected by Salvianolate. These findings indicate that salvianolate may be involved in potential drug interactions when co-administrated with CYP3A4 substrates. PMID:26629047

  5. Inhibitory effect of salvianolate on human cytochrome P450 3A4 in vitro involving a noncompetitive manner.

    PubMed

    Qin, Chong-Zhen; Ren, Xian; Zhou, Hong-Hao; Mao, Xiao-Yuan; Liu, Zhao-Qian

    2015-01-01

    Salvianolic acid B (Sal B), which is purified from Danshen, is a popular herb extract. Sal B has anti-oxidative, anti-inflammatory, anti-hypoxic, anti-arteriosclerotic and anti-apoptotic properties. This substance can also ameliorate brain injury or neurodegenerative diseases. The listed drug Salvianolate, which contains a substantial amount of Sal B, has been used for the treatment of coronary heart disease. Our present work aimed to evaluate the inhibitory effect of salvianolate on seven cytochrome P450 isoforms (CYP450), namely, CYP1A2, CYP2A6, CYP2E1, CYP2C9, CYP2C19, CYP2D6 and CYP3A4, in human liver microsomes (HLMs) and recombinant enzymes through high-performance liquid chromatography (HPLC) assay. Salvianolate have a potent inhibitory effect on CYP3A4 activity with IC50 values of 1.438 (HLMs) and 3.582 (recombinant cDNA-expressed CYP3A4) mg/L, respectively. Salvianolate strongly dose, but not time-dependently decreased CYP3A4 activity in HLMs. The typical Lineweaver-Burk plots showed that Salvianolate inhibited CYP3A4 activity noncompetitively, with a Ki value of 2.27 mg/L in HLMs. Other CYP450 isoforms are not markedly affected by Salvianolate. These findings indicate that salvianolate may be involved in potential drug interactions when co-administrated with CYP3A4 substrates.

  6. The Role of Protein-Protein and Protein-Membrane Interactions on P450 Function

    PubMed Central

    Scott, Emily E.; Wolf, C. Roland; Otyepka, Michal; Humphreys, Sara C.; Reed, James R.; Henderson, Colin J.; McLaughlin, Lesley A.; Paloncýová, Markéta; Navrátilová, Veronika; Berka, Karel; Anzenbacher, Pavel; Dahal, Upendra P.; Barnaba, Carlo; Brozik, James A.; Jones, Jeffrey P.; Estrada, D. Fernando; Laurence, Jennifer S.; Park, Ji Won

    2016-01-01

    This symposium summary, sponsored by the ASPET, was held at Experimental Biology 2015 on March 29, 2015, in Boston, Massachusetts. The symposium focused on: 1) the interactions of cytochrome P450s (P450s) with their redox partners; and 2) the role of the lipid membrane in their orientation and stabilization. Two presentations discussed the interactions of P450s with NADPH-P450 reductase (CPR) and cytochrome b5. First, solution nuclear magnetic resonance was used to compare the protein interactions that facilitated either the hydroxylase or lyase activities of CYP17A1. The lyase interaction was stimulated by the presence of b5 and 17α-hydroxypregnenolone, whereas the hydroxylase reaction was predominant in the absence of b5. The role of b5 was also shown in vivo by selective hepatic knockout of b5 from mice expressing CYP3A4 and CYP2D6; the lack of b5 caused a decrease in the clearance of several substrates. The role of the membrane on P450 orientation was examined using computational methods, showing that the proximal region of the P450 molecule faced the aqueous phase. The distal region, containing the substrate-access channel, was associated with the membrane. The interaction of NADPH-P450 reductase (CPR) with the membrane was also described, showing the ability of CPR to “helicopter” above the membrane. Finally, the endoplasmic reticulum (ER) was shown to be heterogeneous, having ordered membrane regions containing cholesterol and more disordered regions. Interestingly, two closely related P450s, CYP1A1 and CYP1A2, resided in different regions of the ER. The structural characteristics of their localization were examined. These studies emphasize the importance of P450 protein organization to their function. PMID:26851242

  7. Regulation of cytochrome P450 (CYP) genes by nuclear receptors.

    PubMed Central

    Honkakoski, P; Negishi, M

    2000-01-01

    Members of the nuclear-receptor superfamily mediate crucial physiological functions by regulating the synthesis of their target genes. Nuclear receptors are usually activated by ligand binding. Cytochrome P450 (CYP) isoforms often catalyse both formation and degradation of these ligands. CYPs also metabolize many exogenous compounds, some of which may act as activators of nuclear receptors and disruptors of endocrine and cellular homoeostasis. This review summarizes recent findings that indicate that major classes of CYP genes are selectively regulated by certain ligand-activated nuclear receptors, thus creating tightly controlled networks. PMID:10749660

  8. CYP2D6 Genotype Dependent Oxycodone Metabolism in Postoperative Patients

    PubMed Central

    Stamer, Ulrike M.; Zhang, Lan; Book, Malte; Lehmann, Lutz E.; Stuber, Frank; Musshoff, Frank

    2013-01-01

    Background The impact of polymorphic cytochrome P450 CYP2D6 enzyme on oxycodone's metabolism and clinical efficacy is currently being discussed. However, there are only spare data from postoperative settings. The hypothesis of this study is that genotype dependent CYP2D6 activity influences plasma concentrations of oxycodone and its metabolites and impacts analgesic consumption. Methods Patients received oxycodone 0.05 mg/kg before emerging from anesthesia and patient-controlled analgesia (PCA) for the subsequent 48 postoperative hours. Blood samples were drawn at 30, 90 and 180 minutes after the initial oxycodone dose. Plasma concentrations of oxycodone and its metabolites oxymorphone, noroxycodone and noroxymorphone were analyzed by liquid chromatography-mass spectrometry with electrospray ionization. CYP2D6 genotyping was performed and 121 patients were allocated to the following genotype groups: PM (poor metabolizer: no functionally active CYP2D6 allele), HZ/IM (heterozygous subjects, intermediate metabolizers with decreased CYP2D6 activity), EM (extensive metabolizers, normal CYP2D6 activity) and UM (ultrarapid metabolizers, increased CYP2D6 activity). Primary endpoint was the genotype dependent metabolite ratio of plasma concentrations oxymorphone/oxycodone. Secondary endpoint was the genotype dependent analgesic consumption with calculation of equianalgesic doses compared to the standard non-CYP dependent opioid piritramide. Results Metabolism differed between CYP2D6 genotypes. Mean (95%-CI) oxymophone/oxycodone ratios were 0.10 (0.02/0.19), 0.13 (0.11/0.16), 0.18 (0.16/0.20) and 0.28 (0.07/0.49) in PM, HZ/IM, EM and UM, respectively (p = 0.005). Oxycodone consumption up to the 12th hour was highest in PM (p = 0.005), resulting in lowest equianalgesic doses of piritramide versus oxycodone for PM (1.6 (1.4/1.8); EM and UM 2.2 (2.1/2.3); p<0.001). Pain scores did not differ between genotypes. Conclusions In this postoperative setting, the number of

  9. Cytochrome p450 mRNA expression in the rodent brain: species-, sex-, and region-dependent differences.

    PubMed

    Stamou, Marianna; Wu, Xianai; Kania-Korwel, Izabela; Lehmler, Hans-Joachim; Lein, Pamela J

    2014-02-01

    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.

  10. Potent inhibition of cytochrome P450 2B6 by sibutramine in human liver microsomes.

    PubMed

    Bae, Soo Hyeon; Kwon, Min Jo; Choi, Eu Jin; Zheng, Yu Fen; Yoon, Kee Dong; Liu, Kwang-Hyeon; Bae, Soo Kyung

    2013-09-05

    The present study was performed to evaluate the potency and specificity of sibutramine as an inhibitor of the activities of nine human CYP isoforms in liver microsomes. Using a cocktail assay, the effects of sibutramine on specific marker reactions of the nine CYP isoforms were measured in human liver microsomes. Sibutramine showed potent inhibition of CYP2B6-mediated bupropion 6-hydroxylation with an IC50 value of 1.61μM and Ki value of 0.466μM in a competitive manner at microsomal protein concentrations of 0.25mg/ml; this was 3.49-fold more potent than the typical CYP2B6 inhibitor thio-TEPA (Ki=1.59μM). In addition, sibutramine slightly inhibited CYP2C19 activity (Ki=16.6μM, noncompetitive inhibition) and CYP2D6 activity (Ki=15.7μM, noncompetitive inhibition). These observations indicated 35.6- and 33.7-fold decreases in inhibition potency, respectively, compared with that of CYP2B6 by sibutramine. However, no inhibition of CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6, or CYP2E1 activities was observed. In addition, the CYP2B6 inhibitory potential of sibutramine was enhanced at a lower microsomal protein concentration of 0.05mg/ml. After 30min preincubation of human liver microsomes with sibutramine in the presence of NADPH, no shift in IC50 was observed in terms of inhibition of the activities of the nine CYPs, suggesting that sibutramine is not a time-dependent inactivator. These observations suggest that sibutramine is a selective and potent inhibitor of CYP2B6 in vitro, whereas inhibition of other CYPs is substantially lower. These in vitro data support the use of sibutramine as a well-known inhibitor of CYP2B6 for routine screening of P450 reversible inhibition when human liver microsomes are used as the enzyme source.

  11. National Prociency Testing Result of CYP2D6*10 Genotyping for Adjuvant Tamoxifen Therapy in China

    PubMed Central

    Lin, Guigao; Zhang, Kuo; Yi, Lang; Han, Yanxi; Xie, Jiehong; Li, Jinming

    2016-01-01

    Tamoxifen has been successfully used for treating breast cancer and preventing cancer recurrence. Cytochrome P450 2D6 (CYP2D6) plays a key role in the process of metabolizing tamoxifen to its active moiety, endoxifen. Patients with variants of the CYP2D6 gene may not receive the full benefit of tamoxifen treatment. The CYP2D6*10 variant (the most common variant in Asians) was analyzed to optimize the prescription of tamoxifen in China. To ensure referring clinicians have accurate information for genotype-guided tamoxifen treatment, the Chinese National Center for Clinical Laboratories (NCCL) organized a national proficiency testing (PT) to evaluate the performance of laboratories providing CYP2D6*10 genotyping. Ten genomic DNA samples with CYP2D6 wild-type or CYP2D6*10 variants were validated by PCR-sequencing and sent to 28 participant laboratories. The genotyping results and pharmacogenomic test reports were submitted and evaluated by NCCL experts. Additional information regarding the number of samples tested, the accreditation/certification status, and detecting technology was also requested. Thirty-one data sets were received, with a corresponding analytical sensitivity of 98.2% (548/558 challenges; 95% confidence interval: 96.7–99.1%) and an analytic specificity of 96.5% (675/682; 95% confidence interval: 97.9–99.5%). Overall, 25/28 participants correctly identified CYP2D6*10 status in 10 samples; however, two laboratories made serious genotyping errors. Most of the essential information was included in the 20 submitted CYP2D6*10 test reports. The majority of Chinese laboratories are reliable for detecting the CYP2D6*10 variant; however, several issues revealed in this study underline the importance of PT schemes in continued external assessment and provision of guidelines. PMID:27603206

  12. Pungent ginger components modulates human cytochrome P450 enzymes in vitro

    PubMed Central

    Li, Mian; Chen, Pei-zhan; Yue, Qing-xi; Li, Jing-quan; Chu, Rui-ai; Zhang, Wei; Wang, Hui

    2013-01-01

    Aim: Ginger rhizome is used worldwide as a spicy flavor agent. This study was designed to explore the potential effects of pungent ginger components, 6-, 8-, and 10-gingerol, on human cytochrome P450 (CYP450) enzymes that are responsible for the metabolism of many prescription drugs. Methods: The activities of human CYP2C9, CYP2C19, CYP2D6, and CYP3A4 were analyzed using Vivid P450 assay kits. The mRNA expression of CYP3A4 in human hepatocellular carcinoma cell line HepG2 was measured using quantitative real-time PCR assay. Results: All three gingerols potently inhibited CYP2C9 activity, exerted moderate inhibition on CYP2C19 and CYP3A4, and weak inhibion on CYP2D6. 8-Gingerol was the most potent in inhibition of P450 enzymes with IC50 values of 6.8, 12.5, 8.7, and 42.7 μmol/L for CYP2C9, CYP2C19, CYP3A4, and CYP2D6, respectively. By comparing the effects of gingerols on CYP3A4 with three different fluorescent substrate probes, it was demonstrated that the inhibition of gingerols on CYP3A4 had no substrate-dependence. In HepG2 cells, 8-gingerol and 10-gingerol inhibited, but 6-gingerol induced mRNA expression of CYP3A4. Conclusion: 6-, 8-, and 10-gingerol suppress human cytochrome P450 activity, while 8- and 10-gingerol inhibit CYP3A4 expression. The results may have an implication for the use of ginger or ginger products when combined with therapeutic drugs that are metabolized by cytochrome P450 enzymes. PMID:23770984

  13. Diversity and evolution of cytochrome P450 monooxygenases in Oomycetes.

    PubMed

    Sello, Mopeli Marshal; Jafta, Norventia; Nelson, David R; Chen, Wanping; Yu, Jae-Hyuk; Parvez, Mohammad; Kgosiemang, Ipeleng Kopano Rosinah; Monyaki, Richie; Raselemane, Seiso Caiphus; Qhanya, Lehlohonolo Benedict; Mthakathi, Ntsane Trevor; Sitheni Mashele, Samson; Syed, Khajamohiddin

    2015-07-01

    Cytochrome P450 monooxygenases (P450s) are heme-thiolate proteins whose role as drug targets against pathogens, as well as in valuable chemical production and bioremediation, has been explored. In this study we performed comprehensive comparative analysis of P450s in 13 newly explored oomycete pathogens. Three hundred and fifty-six P450s were found in oomycetes. These P450s were grouped into 15 P450 families and 84 P450 subfamilies. Among these, nine P450 families and 31 P450 subfamilies were newly found in oomycetes. Research revealed that oomycetes belonging to different orders contain distinct P450 families and subfamilies in their genomes. Evolutionary analysis and sequence homology data revealed P450 family blooms in oomycetes. Tandem arrangement of a large number of P450s belonging to the same family indicated that P450 family blooming is possibly due to its members' duplications. A unique combination of amino acid patterns was observed at EXXR and CXG motifs for the P450 families CYP5014, CYP5015 and CYP5017. A novel P450 fusion protein (CYP5619 family) with an N-terminal P450 domain fused to a heme peroxidase/dioxygenase domain was discovered in Saprolegnia declina. Oomycete P450 patterns suggested host influence in shaping their P450 content. This manuscript serves as reference for future P450 annotations in newly explored oomycetes.

  14. Diversity and evolution of cytochrome P450 monooxygenases in Oomycetes

    PubMed Central

    Sello, Mopeli Marshal; Jafta, Norventia; Nelson, David R; Chen, Wanping; Yu, Jae-Hyuk; Parvez, Mohammad; Kgosiemang, Ipeleng Kopano Rosinah; Monyaki, Richie; Raselemane, Seiso Caiphus; Qhanya, Lehlohonolo Benedict; Mthakathi, Ntsane Trevor; Sitheni Mashele, Samson; Syed, Khajamohiddin

    2015-01-01

    Cytochrome P450 monooxygenases (P450s) are heme-thiolate proteins whose role as drug targets against pathogens, as well as in valuable chemical production and bioremediation, has been explored. In this study we performed comprehensive comparative analysis of P450s in 13 newly explored oomycete pathogens. Three hundred and fifty-six P450s were found in oomycetes. These P450s were grouped into 15 P450 families and 84 P450 subfamilies. Among these, nine P450 families and 31 P450 subfamilies were newly found in oomycetes. Research revealed that oomycetes belonging to different orders contain distinct P450 families and subfamilies in their genomes. Evolutionary analysis and sequence homology data revealed P450 family blooms in oomycetes. Tandem arrangement of a large number of P450s belonging to the same family indicated that P450 family blooming is possibly due to its members’ duplications. A unique combination of amino acid patterns was observed at EXXR and CXG motifs for the P450 families CYP5014, CYP5015 and CYP5017. A novel P450 fusion protein (CYP5619 family) with an N-terminal P450 domain fused to a heme peroxidase/dioxygenase domain was discovered in Saprolegnia declina. Oomycete P450 patterns suggested host influence in shaping their P450 content. This manuscript serves as reference for future P450 annotations in newly explored oomycetes. PMID:26129850

  15. Aromatic hydroxylation of salicylic acid and aspirin by human cytochromes P450.

    PubMed

    Bojić, Mirza; Sedgeman, Carl A; Nagy, Leslie D; Guengerich, F Peter

    2015-06-20

    Aspirin (acetylsalicylic acid) is a well-known and widely-used analgesic. It is rapidly deacetylated to salicylic acid, which forms two hippuric acids-salicyluric acid and gentisuric acid-and two glucuronides. The oxidation of aspirin and salicylic acid has been reported with human liver microsomes, but data on individual cytochromes P450 involved in oxidation is lacking. In this study we monitored oxidation of these compounds by human liver microsomes and cytochrome P450 (P450) using UPLC with fluorescence detection. Microsomal oxidation of salicylic acid was much faster than aspirin. The two oxidation products were 2,5-dihydroxybenzoic acid (gentisic acid, documented by its UV and mass spectrum) and 2,3-dihydroxybenzoic acid. Formation of neither product was inhibited by desferrioxamine, suggesting a lack of contribution of oxygen radicals under these conditions. Although more liphophilic, aspirin was oxidized less efficiently, primarily to the 2,5-dihydroxy product. Recombinant human P450s 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4 all catalyzed the 5-hydroxylation of salicylic acid. Inhibitor studies with human liver microsomes indicated that all six of the previously mentioned P450s could contribute to both the 5- and 3-hydroxylation of salicylic acid and that P450s 2A6 and 2B6 have contributions to 5-hydroxylation. Inhibitor studies indicated that the major human P450 involved in both 3- and 5-hydroxylation of salicylic acid is P450 2E1.

  16. In silico study on the inhibitory interaction of drugs with wild-type CYP2D6.1 and the natural variant CYP2D6.17.

    PubMed

    Handa, Koichi; Nakagome, Izumi; Yamaotsu, Noriyuki; Gouda, Hiroaki; Hirono, Shuichi

    2014-01-01

    The natural variant of the cytochrome P450 enzyme CYP2D6.1, CYP2D6.17, is most common in African populations, has three amino acid substitutions (T107I, R296C, and S486T) compared to the wild-type, and is known to have a different ligand preference from CYP2D6.1. It is becoming increasingly important to understand differences in the metabolism of medicines in different ethnic groups in order to assess the relevance of clinical data from different countries. This study investigated differences in the inhibition profiles of drugs for CYP2D6 with respect to gene polymorphisms. Firstly, we used computer docking with six drugs to several CYP2D6.1 structures, sampled from the trajectory of MD simulations, and calculated MM-GB/SA scores representing binding free energies. We then used regression analysis to predict the potency with which drugs inhibited CYP2D6.1 based on MM-GB/SA scores. The pKi-values obtained were in good agreement with experimental values measured for the six drugs (r(2) = 0.81). We carried out the same analysis for CYP2D6.17 and the pKi-values calculated were also in good agreement with experimental values (r(2) = 0.92). Finally, we were able to successfully explain the different abilities of CYP2D6.1 and CYP2D6.17 to metabolize drugs in different ethnic groups with reference to their 3D-structures.

  17. Spaceflight Effects on Cytochrome P450 Content in Mouse Liver

    PubMed Central

    Moskaleva, Natalia; Moysa, Alexander; Novikova, Svetlana; Tikhonova, Olga; Zgoda, Victor; Archakov, Alexander

    2015-01-01

    Hard conditions of long-term manned spaceflight can affect functions of many biological systems including a system of drug metabolism. The cytochrome P450 (CYP) superfamily plays a key role in the drug metabolism. In this study we examined the hepatic content of some P450 isoforms in mice exposed to 30 days of space flight and microgravity. The CYP content was established by the mass-spectrometric method of selected reaction monitoring (SRM). Significant changes in the CYP2C29, CYP2E1 and CYP1A2 contents were detected in mice of the flight group compared to the ground control group. Within seven days after landing and corresponding recovery period changes in the content of CYP2C29 and CYP1A2 returned to the control level, while the CYP2E1 level remained elevated. The induction of enzyme observed in the mice in the conditions of the spaceflight could lead to an accelerated biotransformation and change in efficiency of pharmacological agents, metabolizing by corresponding CYP isoforms. Such possibility of an individual pharmacological response to medication during long-term spaceflights and early period of postflight adaptation should be taken into account in space medicine. PMID:26561010

  18. 2-Diethylaminoethyl-2,2-diphenylvalerate-HCl (SKF525A) revisited: comparative cytochrome P450 inhibition in human liver microsomes by SKF525A, its metabolites, and SKF-acid and SKF-alcohol.

    PubMed

    Franklin, Michael R; Hathaway, Laura B

    2008-12-01

    When incubated with human liver microsomes, 2-diethylaminoethyl-2,2-diphenylvalerate-HCl (SKF525A) undergoes cytochrome P450 (P450)-dependent oxidative N-deethylation to the secondary amine metabolite 2-ethylaminoethyl-2,2-diphenylvalerate (SKF8742). P450-selective inhibitors indicated CYP3As catalyzed this reaction, and the deethylation rate correlated best with the CYP3A activity across a range of human liver microsomes. SKF525A and its metabolite and primary amine analog all inhibited CYP2B6-, CYP2C9-, CYP2C19-, CYP2D6-, and CYP3A-selective reactions to varying degrees but had little effect on CYP1A2, CYP2A6, and CYP2E1 reactions. Only the inhibition of CYP3A showed major enhancement when the inhibitors were preincubated with NADPH-fortified microsomes, and the extent of metabolic intermediate (MI) complex formation approximated typical CYP3A content. Two "lost with time" SKF525A derivatives devoid of the ethylamine moiety, 2,2-diphenylpropylethanol (SKF-Alcohol) and 2,2-diphenylpropylacetic acid (SKF-Acid) did not form an MI complex and were identified as selective inhibitors of CYP2C9. Although without detectable metabolism, their CYP2C9 inhibition fitted best with a competitive mechanism. Thus, not all the human P450s are inhibited by SKF525A and related compounds, and the mechanisms contributing to those that are inhibited vary with the isoform. P450 MI-complex formation only seems to play a role with CYP3As.

  19. Nerval influences on liver cytochrome P450.

    PubMed

    Klinger, W; Karge, E; Danz, M; Krug, M

    1995-09-01

    In male young adult Wistar rats the influences of nucleus raphe electrocoagulation, spinal cord dissection (cordotomy between C7 and Th1), vagotomy and denervation of liver hilus by phenol on liver cytochrome P450-system (cytochrome P450 concentration, ethylmorphine N-demethylation and ethoxycoumarin O-deethylation activities, hexobarbitone sleeping time) were investigated. In general the influences were small or negligible when compared with sham operated controls, only after vagotomy the depressing effect of sham operation was abolished. In all cases sham operation had a depressing effect until up to five weeks after operation.

  20. Cytochromes P450 and species differences in xenobiotic metabolism and activation of carcinogen.

    PubMed Central

    Lewis, D F; Ioannides, C; Parke, D V

    1998-01-01

    The importance of cytochrome P450 isoforms to species differences in the metabolism of foreign compounds and activation of procarcinogens has been identified. The possible range of P450 isozymes in significant variations in toxicity exhibited by experimental rodent species may have a relevance to chemical risk assessment, especially as human P450s are likely to show changes in the way they metabolize xenobiotics. Consequently, in the safety evaluation of chemicals, we should be cautious in extrapolating results from experimental animal models to humans. This paper focuses on examples in which species differences in P450s lead to significant alterations in carcinogenic response, and includes a discussion of the current procedures for toxicity screening, with an emphasis on short-term tests. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:9755138

  1. Cytochrome P450 expression and activities in human tongue cells and their modulation by green tea extract

    SciTech Connect

    Yang, S.-P.; Raner, Gregory M. . E-mail: gmraner@uncg.edu

    2005-01-15

    The expression, inducibility, and activities of several cytochrome P450 (CYP) enzymes were investigated in a human tongue carcinoma cell model, CAL 27, and compared with the human liver model HepG2 cells. The modulation effects of green tea on various CYP isoforms in both cell lines were also examined. RT-PCR analysis of CAL 27 cells demonstrated constitutive expression of mRNA for CYPs 1A1, 1A2, 2C, 2E1, 2D6, and 4F3. The results were negative for CYP2A6, 2B6/7, 3A3/4, and 3A7. Both cell lines displayed identical expression and induction profiles for all of the isoforms examined in this study except 3A7 and 2B6/7, which were produced constitutively in HepG2 but not Cal-27 cells. CYP1A1 and 1A2 were both induced by treatment with {beta}-napthoflavone as indicated by RT-PCR and Western blotting, while CYP2C mRNA was upregulated by all-trans retinoic acid and farnesol. RT-PCR and Western blot analysis showed that the expressions of CYP1A1 and 1A2 were induced by green tea extract (GTE), which also caused an increase in mRNA for CYP2E1, CYP2D6, and CYP2C isoforms. The four tea catechins, EGC, EC, EGCG and ECG, applied to either HepG2 or Cal-27 cells at the concentration found in GTE failed to induce CYP1A1 or CYP1A2, as determined by RT-PCR. Of the isoforms that were apparently induced by GTE, only 7-ethoxycoumarin deethylase (ECOD) activity could be detected in CAL 27 or HepG2 cells. Interestingly, mRNA and protein for CYP1A1 and CYP1A2 were detected in both cell lines, and although protein and mRNA levels of CYP1A1 and CYP1A2 were increased by GTE, the observed ECOD activity in both cell lines was decreased.

  2. P450 AND METABOLISM IN TOXICOLOGY

    EPA Science Inventory

    The cytochromes P450 catalyze the initial phase of detoxification of many environmental chemicals, xenobiotic, drugs and the secondary metabolic product of plants. Plant secondary chemicals can be highly toxic, and they evolved in a coevolving plant - animal warfare - the plants ...

  3. Novel extrahepatic cytochrome P450s

    SciTech Connect

    Karlgren, Maria . E-mail: Maria.Karlgren@imm.ki.se; Miura, Shin-ichi; Ingelman-Sundberg, Magnus

    2005-09-01

    The cytochrome P450 enzymes are highly expressed in the liver and are involved in the metabolism of xenobiotics. Because of the initiatives associated with the Human Genome Project, a great progress has recently been seen in the identification and characterization of novel extrahepatic P450s, including CYP2S1, CYP2R1, CYP2U1 and CYP2W1. Like the hepatic enzymes, these P450s may play a role in the tissue-specific metabolism of foreign compounds, but they may also have important endogenous functions. CYP2S1 has been shown to metabolize all-trans retinoic acid and CYP2R1 is a major vitamin D 25-hydroxylase. Regarding their metabolism of xenobiotics, much remains to be established, but CYP2S1 metabolizes naphthalene and it is likely that these P450s are responsible for metabolic activation of several different kinds of xenobiotic chemicals and contribute to extrahepatic toxicity and carcinogenesis.

  4. Prediction of Cytochrome P450 Profiles of Environmental Chemicals with QSAR Models Built from Drug-like Molecules

    PubMed Central

    Sun, Hongmao; Veith, Henrike; Xia, Menghang; Austin, Christopher P.; Tice, Raymond R.; Huang, Ruili

    2012-01-01

    The human cytochrome P450 (CYP) enzyme family is involved in the biotransformation of many xenobiotics. As part of the U.S. Tox21 Phase I effort, we profiled the CYP activity of approximately three thousand compounds, primarily those of environmental concern, against human CYP1A2, CYP2C19, CYP2C9, CYP2D6, and CYP3A4 isoforms in a quantitative high throughput screening (qHTS) format. In order to evaluate the extent to which computational models built from a drug-like library screened in these five CYP assays under the same conditions can accurately predict the outcome of an environmental compound library, five support vector machines (SVM) models built from over 17,000 drug-like compounds were challenged to predict the CYP activities of the Tox21 compound collection. Although a large fraction of the test compounds fall outside of the applicability domain (AD) of the models, as measured by k-nearest neighbor (k-NN) similarities, the predictions were largely accurate for CYP1A2, CYP2C9, and CYP3A4 ioszymes with area under the receiver operator characteristic curves (AUC-ROC) ranging between 0.82 and 0.84. The lower predictive power of the CYP2C19 model (AUC-ROC = 0.76) is caused by experimental errors and that of the CYP2D6 model (AUC-ROC = 0.76) can be rescued by rebalancing the training data. Our results demonstrate that decomposing molecules into atom types enhanced the coverage of the AD and that computational models built from drug-like molecules can be used to predict the ability of non-drug like compounds to interact with these CYPs. PMID:23459712

  5. Impact of CYP2D6 Genetic Variation on the Response of the Cardiovascular Patient to Carvedilol and Metoprolol.

    PubMed

    Lymperopoulos, Anastasios; McCrink, Katie A; Brill, Ava

    2015-01-01

    Carvedilol and metoprolol are two of the most commonly prescribed β-blockers in cardiovascular medicine and primarily used in the treatment of hypertension and heart failure. Cytochrome P450 2D6 (CYP2D6) is the predominant metabolizing enzyme of these two drugs. Since the first description of a CYP2D6 sparteinedebrisoquine polymorphism in the mid-seventies, substantial genetic heterogeneity has been reported in the human CYP2D6 gene, with ~100 different polymorphisms identified to date. Some of these polymorphisms render the enzyme completely inactive while others do not modify its activity. Based on all the identified variants, four metabolizer phenotypes are nowadays used to characterize drug metabolism via CYP2D6 in humans: ultra-rapid metabolizer (UM); extensive metabolizer (EM); intermediate metabolizer (IM); and poor metabolizer (PM) phenotypes. As a consequence of these CYP2D6 metabolizer phenotypes, pharmacokinetics and bioavailability of carvedilol and metoprolol can range from therapeutically ineffective levels (in the UM patients) to excessive (overdose) and potentially toxic concentrations (in PM patients). This, in turn, can result in elevated risks for either treatment failure (in terms of blood pressure reduction of hypertensive patients and of improving survival and cardiovascular function of heart failure patients) or for adverse effects (e.g. hypotension and bradycardia). The present review will discuss the impact of these CYP2D6 genetic polymorphisms on the therapeutic responses of cardiovascular patients treated with either of these two β-blockers. In addition, the potential advantages and disadvantages of implementing CYP2D6 genetic testing in the clinic to guide/personalize therapy with these two drugs will be discussed.

  6. A Comparison of the In Vitro Inhibitory Effects of Thelephoric Acid and SKF-525A on Human Cytochrome P450 Activity.

    PubMed

    Song, Min; Do, Hyunhee; Kwon, Oh Kwang; Yang, Eun-Ju; Bae, Jong-Sup; Jeong, Tae Cheon; Song, Kyung-Sik; Lee, Sangkyu

    2014-02-01

    Thelephoric acid is an antioxidant produced by the hydrolysis of polyozellin, which is isolated from Polyozellus multiplex. In the present study, the inhibitory effects of polyozellin and thelephoric acid on 9 cytochrome P450 (CYP) family members (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) were examined in pooled human liver microsomes (HLMs) using a cocktail probe assay. Polyozellin exhibited weak inhibitory effects on the activities of all 9 CYPs examined, whereas thelephoric acid exhibited dose- and time-dependent inhibition of all 9 CYP isoforms (IC50 values, 3.2-33.7 μM). Dixon plots of CYP inhibition indicated that thelephoric acid was a competitive inhibitor of CYP1A2 and CYP3A4. In contrast, thelephoric acid was a noncompetitive inhibitor of CYP2D6. Our findings indicate that thelephoric acid may be a novel, non-specific CYP inhibitor, suggesting that it could replace SKF-525A in inhibitory studies designed to investigate the effects of CYP enzymes on the metabolism of given compounds.

  7. Evaluation of the likelihood of a selective CHK1 inhibitor (LY2603618) to inhibit CYP2D6 with desipramine as a probe substrate in cancer patients.

    PubMed

    Hynes, Scott M; Wickremsinhe, Enaksha; Zhang, Wei; Decker, Rodney; Ott, Jennifer; Chandler, Jason; Mitchell, Malcolm

    2015-01-01

    LY2603618 is a selective inhibitor of deoxyribonucleic acid damage checkpoint kinase 1 (CHK1) and has been in development for the enhancement of chemotherapeutic agents. The study described was to assess the potential interaction between LY2603618 and cytochrome P450 isoform 2D6 (CYP2D6) substrate desipramine in patients with cancer. Before clinical investigation, in silico simulations (using Simcyp®) were conducted. An open-label, two-period, fixed-sequence study was planned in 30 patients with advanced or metastatic cancers, in which a 50 mg oral dose of desipramine was administered alone and in combination with 275 mg of LY2603618 (i.v. infusion). An interim analysis was planned after 15 patients completed both periods. Ratios of geometric least squares means (LSMs) of primary pharmacokinetic (PK) parameters and 90% repeated confidence intervals (RCIs) between desipramine plus LY2603618 and desipramine alone were calculated. Lack of an interaction was declared if the 90% RCI fell between 0.8 and 1.25. The LSM ratios (90% RCI) for areas under the plasma concentration-time curve from time zero to tlast (AUC[0-tlast]) and to infinity (AUC[0-∞]) and maximum plasma concentration (Cmax) were 1.14 (1.04, 1.25), 1.09 (0.99, 1.21) and 1.16 (1.05, 1.29). In silico simulations were predictive of clinical results. Single doses of 275 mg LY2603618 administered with 50 mg desipramine were generally well tolerated. In conclusion, no clinically significant interaction was observed between LY2603618 and desipramine in patients with cancer. In silico predictions of clinical results demonstrated that mechanistic and physiologically based PK approaches may inform clinical study design in cancer patients.

  8. Cytochrome P450 structure, function and clinical significance: A review.

    PubMed

    Palrasu, Manikandan; Nagini, Siddavaram

    2017-01-25

    The cytochrome P450 (CYP) enzymes are membrane-bound hemoproteins that play a pivotal role in the detoxification of xenobiotics, cellular metabolism and homeostasis. Induction or inhibition of CYP enzymes is a major mechanism that underlies drug-drug interactions. CYP enzymes can be transcriptionally activated by various xenobiotics and endogenous substrates through receptor-dependent mechanisms. CYP enzyme inhibition is a principal mechanism for metabolism-based drug-drug interactions. Many chemotherapeutic drugs can cause drug interactions due to their ability to either inhibit or induce the CYP enzyme system. Predictions based on in silico analyses followed by validation have identified several microRNAs that regulate CYPs. Genetic polymorphisms and epigenetic changes in CYP genes may be responsible for inter-individual and inter-ethnic variations in disease susceptibility and the therapeutic efficacy of drugs. Knowledge about the substrates, inducers, inhibitors of CYP isoforms, and the polymorphisms of CYP enzymes may be used as an aid by clinicians to determine therapeutic strategy, and treatment doses for drugs that are metabolized by CYP gene products. The present review is a comprehensive compilation of cytochrome P450 structure, function, pharmacogenetics, and pharmacoepigenetics and clinical significance.

  9. CYP51--the omnipotent P450.

    PubMed

    Lepesheva, Galina I; Waterman, Michael R

    2004-02-27

    Sterol 14 alpha-demethylase (CYP51) is the single cytochrome P450 (CYP) required for sterol biosynthesis in different phyla, and it is the most widely distributed P450 gene family being found in all biological kingdoms. It catalyzes the first step following cyclization in sterol biosynthesis such as removal of the 14 alpha-methyl group from lanosterol in the cholesterol biosynthetic pathway, leading to formation of the initial substrate in steroid hormone biosynthesis. CYP51 from different phyla have low sequence similarity across kingdoms and contain only about 40 conserved amino acid residues in the whole family. An attempt to predict the possible role of these conserved residues is being made by a combination of the results of site-directed mutagenesis and information from the known crystal structure of sterol 14 alpha-demethylase from Mycobacterium tuberculosis.

  10. Generation and validation of rapid computational filters for cyp2d6 and cyp3a4.

    PubMed

    Ekins, Sean; Berbaum, Jennifer; Harrison, Richard K

    2003-09-01

    CYP2D6 and CYP3A4 represent two particularly important members of the cytochrome p450 enzyme family due to their involvement in the metabolism of many commercially available drugs. Avoiding potent inhibitory interactions with both of these enzymes is highly desirable in early drug discovery, long before entering clinical trials. Computational prediction of this liability as early as possible is desired. Using a commercially available data set of over 1750 molecules to train computer models that were generated with commercially available software enabled predictions of inhibition for CYP2D6 and CYP3A4, which were compared with empirical data. The results suggest that using a recursive partitioning (tree) technique with augmented atom descriptors enables a statistically significant rank ordering of test-set molecules (Spearman's rho of 0.61 and 0.48 for CYP2D6 and CYP3A4, respectively), which represents an increased rate of identifying the best compounds when compared with the random rate. This approach represents a valuable computational filter in early drug discovery to identify compounds that may have p450 inhibition liabilities prior to molecule synthesis. Such computational filters offer a new approach in which lead optimization in silico can occur with virtual molecules simultaneously tested against multiple enzymes implicated in drug-drug interactions, with a resultant cost savings from a decreased level of molecule synthesis and in vitro screening.

  11. CYP2J2 and CYP2C19 are the major enzymes responsible for metabolism of albendazole and fenbendazole in human liver microsomes and recombinant P450 assay systems.

    PubMed

    Wu, Zhexue; Lee, Doohyun; Joo, Jeongmin; Shin, Jung-Hoon; Kang, Wonku; Oh, Sangtaek; Lee, Do Yup; Lee, Su-Jun; Yea, Sung Su; Lee, Hye Suk; Lee, Taeho; Liu, Kwang-Hyeon

    2013-11-01

    Albendazole and fenbendazole are broad-spectrum anthelmintics that undergo extensive metabolism to form hydroxyl and sulfoxide metabolites. Although CYP3A and flavin-containing monooxygenase have been implicated in sulfoxide metabolite formation, the enzymes responsible for hydroxyl metabolite formation have not been identified. In this study, we used human liver microsomes and recombinant cytochrome P450s (P450s) to characterize the enzymes involved in the formation of hydroxyalbendazole and hydroxyfenbendazole from albendazole and fenbendazole, respectively. Of the 10 recombinant P450s, CYP2J2 and/or CYP2C19 was the predominant enzyme catalyzing the hydroxylation of albendazole and fenbendazole. Albendazole hydroxylation to hydroxyalbendazole is primarily mediated by CYP2J2 (0.34 μl/min/pmol P450, which is a rate 3.9- and 8.1-fold higher than the rates for CYP2C19 and CYP2E1, respectively), whereas CYP2C19 and CYP2J2 contributed to the formation of hydroxyfenbendazole from fenbendazole (2.68 and 1.94 μl/min/pmol P450 for CYP2C19 and CYP2J2, respectively, which are rates 11.7- and 8.4-fold higher than the rate for CYP2D6). Correlation analysis between the known P450 enzyme activities and the rate of hydroxyalbendazole and hydroxyfenbendazole formation in samples from 14 human liver microsomes showed that albendazole hydroxylation correlates with CYP2J2 activity and fenbendazole hydroxylation correlates with CYP2C19 and CYP2J2 activities. These findings were supported by a P450 isoform-selective inhibition study in human liver microsomes. In conclusion, our data for the first time suggest that albendazole hydroxylation is primarily catalyzed by CYP2J2, whereas fenbendazole hydroxylation is preferentially catalyzed by CYP2C19 and CYP2J2. The present data will be useful in understanding the pharmacokinetics and drug interactions of albendazole and fenbendazole in vivo.

  12. Inhibition of cytochrome p450 enzymes by enrofloxacin in the sea bass (Dicentrarchus labrax).

    PubMed

    Vaccaro, E; Giorgi, M; Longo, V; Mengozzi, G; Gervasi, P G

    2003-01-10

    Currently, there are no reports on the effects of enrofloxacin (EF), a fluoroquinolone antibiotic, on the cytochrome p450 enzymes in fish, although its use as antimicrobial agent in aquaculture has been put forward. Therefore, the in vivo and in vitro effects of EF on hepatic p450 enzymes of sea bass, a widespread food-producing fish, have been evaluated. Sea bass pretreated with a single dose of EF (3 mg/kg i.p.) or with three daily doses of EF (1 mg/kg i.p.) markedly depressed the microsomal N-demethylation of aminopyrine, erythromycin, the O-deethylation of 7-ethoxycoumarin, ethoxyresorufin and the 6beta-testosterone hydroxylase. In vitro experiments showed that EF at 10 microM inhibited the above-mentioned activities and, in particular, the erythromycin N-demethylase (ERND) and 6beta-testosterone-hydroxylase, likely dependant on a p450 3A isoform. When the nature of ERND inhibition by EF was specifically studied with sea bass liver microsomes, it was found that EF is a potent mechanism-based inhibitor, with K(i) of 3.7 microM and a K(inact) of 0.045 min(-1). An immunoblot analysis with anti p450 3A27 of trout showed that the p450 3A isoform, constitutively expressed in sea bass, is particularly susceptible to inactivation by EF. In vitro experiments with sea bass microsomes have also demonstrated that EF is oxidative deethylated by the p450 system to ciprofloxacin (CF) and that this compound maintains the ability to inactivate the p450 enzymes. The mechanism by which EF or CF inactivate the p450 enzymes has not been studied but an attack of p450 on the cyclopropan ring, present, both in EF and CF structure, with the formation of electrophilic intermediates (i.e. radicals) has been postulated. In conclusion, the EF seems to be a powerful inhibitor of p450s in the sea bass. Therefore, the clinical use of this antibiotic in aquaculture has to be considered with caution.

  13. Detection of human lung cytochromes P450 that are immunochemically related to cytochrome P450IIE1 and cytochrome P450IIIA.

    PubMed

    Wheeler, C W; Wrighton, S A; Guenthner, T M

    1992-07-07

    We have used monoclonal antibodies that were prepared against and specifically recognize human hepatic cytochromes P450 as probes for solid phase radioimmunoassay and Western immunoblotting to directly demonstrate the presence in human lung microsomes of cytochromes P450 immunochemically related to human liver cytochromes P450IIE1 (CYP2E1) and P450IIIA (CYP3A). The detected levels of these cytochromes are much lower than levels in human liver microsomes, but similar to the levels seen in microsomes from untreated baboon lung. Proteins immunochemically related to two other constitutive hepatic cytochromes P450, cytochrome P450IIC8 (CYP2C8) and cytochrome P450IIC9 (CYP2C9), were not detectable in lung microsomes.

  14. Simultaneous detection of single nucleotide polymorphisms and copy number variations in the CYP2D6 gene by multiplex polymerase chain reaction combined with capillary electrophoresis.

    PubMed

    Liao, Hsiao-Wei; Tsai, I-Lin; Chen, Guan-Yuan; Kuo, Chun-Ting; Wei, Ming-Feng; Hwang, Tzung-Jeng; Chen, Wei J; Shen, Li-Jiuan; Kuo, Ching-Hua

    2013-02-06

    CYP2D6 (cytochrome P450 2D6) is one of the most important enzymes involved in drug metabolism, and CYP2D6 gene variants may cause toxic effects of therapeutic drugs or treatment failure. In this research, a rapid and simple method for genotyping the most common mutant alleles in the Asian population (CYP2D6*1/*1, CYP2D6*1/*10, CYP2D6*10/*10, CYP2D6*1/*5, CYP2D6*5/*10, and CYP2D6*5/*5) was developed by allele-specific polymerase chain reaction (AS-PCR) combined with capillary electrophoresis (CE). We designed a second mismatch nucleotide next to the single nucleotide polymorphism (SNP) site in allele-specific primers to increase the difference in PCR amplification. Besides, we established simulation equations to predict the CYP2D6 genotypes by analyzing the DNA patterns in the CE chromatograms. The multiplex PCR combined with CE method was applied to test 50 patients, and all of the test results were compared with the DNA sequencing method, long-PCR method and real-time PCR method. The correlation of the analytical results between the proposed method and other methods were higher than 90%, and the proposed method is superior to other methods for being able to simultaneous detection of SNPs and copy number variations (CNV). Furthermore, we compared the plasma concentration of aripiprazole (a CYP2D6 substrate) and its major metabolites with the genotype of 25 patients. The results demonstrate the proposed genotyping method is effective for estimating the activity of the CYP2D6 enzyme and shows potential for application in personalized medicine. Similar approach can be applied to simultaneous detection of SNPs and CNVs of other genes.

  15. High-throughput mass spectrometric cytochrome P450 inhibition screening.

    PubMed

    Lim, Kheng B; Ozbal, Can C; Kassel, Daniel B

    2013-01-01

    We describe here a high-throughput assay to support rapid evaluation of drug discovery compounds for possible drug-drug interaction (DDI). Each compound is evaluated for its DDI potential by incubating over a range of eight concentrations and against a panel of six cytochrome P450 (CYP) enzymes: 1A2, 2C8, 2C9, 2C19, 2D6, and 3A4. The method utilizes automated liquid handling for sample preparation, and online solid-phase extraction/tandem mass spectrometry (SPE/MS/MS) for sample analyses. The system is capable of generating two 96-well assay plates in 30 min, and completes the data acquisition and analysis of both plates in about 30 min. Many laboratories that perform the CYP inhibition screening automate only part of the processes leaving a throughput bottleneck within the workflow. The protocols described in this chapter are aimed to streamline the entire process from assay to data acquisition and processing by incorporating automation and utilizing high-precision instrument to maximize throughput and minimize bottleneck.

  16. Pharmacogenetics and drug therapy in psychiatry--the role of the CYP2D6 polymorphism.

    PubMed

    Vandel, P; Talon, J M; Haffen, E; Sechter, D

    2007-01-01

    The importance of pharmacogenetics in medicine is growing with the identification of genetic variability by faster screening methods using automatic sequencers. A particularly interesting finding is that apart from environmental and psychological factors, drug response may be influenced by several biological factors as a result of genetic determinants leading to interindividual variability. Several mutations in genes coding for enzymes of the drug metabolizing system, as well as for neurotransmitter receptors or degrading enzymes and monoamine transport proteins, have been identified and investigated in psychiatry. But, despite the fact that some genetic polymorphisms of enzymes (mainly cytochrome P450 2D6) are well known, the application of pharmacogenetics as a therapeutic tool for improving patient care is rare. This review has three parts. In the first an overview is given of CYP450 characteristics and the genetic polymorphisms of interest to psychiatry. In the second the clinical implications of the CYP2D6 polymorphism are reviewed and in the third part other aspects on pharmacogenetic research in psychiatry are discussed. The aim of our review is to promote the application of pharmacogenetics in everyday clinical practice.

  17. Molecular evolutionary dynamics of cytochrome P450 monooxygenases across kingdoms: Special focus on mycobacterial P450s

    PubMed Central

    Parvez, Mohammad; Qhanya, Lehlohonolo Benedict; Mthakathi, Ntsane Trevor; Kgosiemang, Ipeleng Kopano Rosinah; Bamal, Hans Denis; Pagadala, Nataraj Sekhar; Xie, Ting; Yang, Haoran; Chen, Hengye; Theron, Chrispian William; Monyaki, Richie; Raselemane, Seiso Caiphus; Salewe, Vuyani; Mongale, Bogadi Lorato; Matowane, Retshedisitswe Godfrey; Abdalla, Sara Mohamed Hasaan; Booi, Wool Isaac; van Wyk, Mari; Olivier, Dedré; Boucher, Charlotte E.; Nelson, David R.; Tuszynski, Jack A.; Blackburn, Jonathan Michael; Yu, Jae-Hyuk; Mashele, Samson Sitheni; Chen, Wanping; Syed, Khajamohiddin

    2016-01-01

    Since the initial identification of cytochrome P450 monooxygenases (CYPs/P450s), great progress has been made in understanding their structure-function relationship, diversity and application in producing compounds beneficial to humans. However, the molecular evolution of P450s in terms of their dynamics both at protein and DNA levels and functional conservation across kingdoms still needs investigation. In this study, we analyzed 17 598 P450s belonging to 113 P450 families (bacteria −42; fungi −19; plant −28; animal −22; plant and animal −1 and common P450 family −1) and found highly conserved and rapidly evolving P450 families. Results suggested that bacterial P450s, particularly P450s belonging to mycobacteria, are highly conserved both at protein and DNA levels. Mycobacteria possess the highest P450 diversity percentage compared to other microbes and have a high coverage of P450s (≥1%) in their genomes, as found in fungi and plants. Phylogenetic and functional analyses revealed the functional conservation of P450s despite belonging to different biological kingdoms, suggesting the adherence of P450s to their innate function such as their involvement in either generation or oxidation of steroids and structurally related molecules, fatty acids and terpenoids. This study’s results offer new understanding of the dynamic structural nature of P450s. PMID:27616185

  18. Limitations of in silico predictability of specificity of co-immobilised cytochromes P450 and mimics in food-bioprocessing.

    PubMed

    Wiseman, Alan

    2003-04-01

    Cytochromes P450 (EC 1.14.14.1) are mixed function oxidases (oxygenases) that can catalyse redox bioconversions of food components. Also, efficacious removal of undesirable components can be achieved using solid-support immobilised enzyme (IME) of a selection from 2700 isoforms of cytochromes P450 (CYP). Cytochromes P450 co-immobilised with other enzymes, or protein receptors, may be used to confer a secondary order of regio- or stereo-specificity of chiral bioconversion: these can be predictable in silico by utilisation of QSARs (quantitative structure/activity relationships).

  19. Flower colour and cytochromes P450.

    PubMed

    Tanaka, Yoshikazu; Brugliera, Filippa

    2013-02-19

    Cytochromes P450 play important roles in biosynthesis of flavonoids and their coloured class of compounds, anthocyanins, both of which are major floral pigments. The number of hydroxyl groups on the B-ring of anthocyanidins (the chromophores and precursors of anthocyanins) impact the anthocyanin colour, the more the bluer. The hydroxylation pattern is determined by two cytochromes P450, flavonoid 3'-hydroxylase (F3'H) and flavonoid 3',5'-hydroxylase (F3'5'H) and thus they play a crucial role in the determination of flower colour. F3'H and F3'5'H mostly belong to CYP75B and CYP75A, respectively, except for the F3'5'Hs in Compositae that were derived from gene duplication of CYP75B and neofunctionalization. Roses and carnations lack blue/violet flower colours owing to the deficiency of F3'5'H and therefore lack the B-ring-trihydroxylated anthocyanins based upon delphinidin. Successful redirection of the anthocyanin biosynthesis pathway to delphinidin was achieved by expressing F3'5'H coding regions resulting in carnations and roses with novel blue hues that have been commercialized. Suppression of F3'5'H and F3'H in delphinidin-producing plants reduced the number of hydroxyl groups on the anthocyanidin B-ring resulting in the production of monohydroxylated anthocyanins based on pelargonidin with a shift in flower colour to orange/red. Pelargonidin biosynthesis is enhanced by additional expression of a dihydroflavonol 4-reductase that can use the monohydroxylated dihydrokaempferol (the pelargonidin precursor). Flavone synthase II (FNSII)-catalysing flavone biosynthesis from flavanones is also a P450 (CYP93B) and contributes to flower colour, because flavones act as co-pigments to anthocyanins and can cause blueing and darkening of colour. However, transgenic plants expression of a FNSII gene yielded paler flowers owing to a reduction of anthocyanins because flavanones are precursors of anthocyanins and flavones.

  20. P450monooxygenases (P450ome) of the model white rot fungus Phanerochaete chrysosporium

    PubMed Central

    Syed, Khajamohiddin; Yadav, Jagjit S

    2012-01-01

    Phanerochaete chrysosporium, the model white rot fungus, has been the focus of research for the past about four decades for understanding the mechanisms and processes of biodegradation of the natural aromatic polymer lignin and a broad range of environmental toxic chemicals. The ability to degrade this vast array of xenobiotic compounds was originally attributed to its lignin-degrading enzyme system (LDS), mainly the extracellular peroxidases. However, subsequent physiological, biochemical, and/or genetic studies by us and others identified the involvement of a peroxidase-independent oxidoreductase system, the cytochrome P450 monooxygenase system. The whole genome sequence revealed an extraordinarily large P450 contingent (P450ome) with an estimated 149 P450s in this organism. This review focuses on the current status of understanding on the P450 monooxygenase system of P. chrysosporium in terms of pre-genomic and post-genomic identification, structural and evolutionary analysis, transcriptional regulation, redox partners, and functional characterization for its biodegradative potential. Future research on this catalytically diverse oxidoreductase enzyme system and its major role as a newly emerged player in xenobiotic metabolism/degradation is discussed. PMID:22624627

  1. P450 enzymes of estrogen metabolism.

    PubMed

    Martucci, C P; Fishman, J

    1993-01-01

    Endogenous and exogenous estrogens undergo extensive oxidative metabolism by specific cytochrome P450 enzymes. Certain drugs and xenobiotics have been found to be potent inducers of estrogen hydroxylating enzymes with C-2 hydroxylase induction being greater than that of C-16 hydroxylase. Oxygenated estrogen metabolites have different biological activities, with C-2 metabolites having limited or no activity and C-4 and C-16 metabolites having similar potency to estradiol. Pathophysiological roles for some of the oxygenated estrogen metabolites have been proposed, e.g. 16 alpha-hydroxyestrone and 4-hydroxyestrone. These reactive estrogens are capable of damaging cellular proteins and DNA and may be carcinogenic in specific cells.

  2. UPLC-MS-MS method for simultaneous determination of caffeine, tolbutamide, metoprolol, and dapsone in rat plasma and its application to cytochrome P450 activity study in rats.

    PubMed

    Liu, Yan; Li, Xiang; Yang, Chunjuan; Tai, Sheng; Zhang, Xiangning; Liu, Gaofeng

    2013-01-01

    A specific ultra-performance liquid chromatography tandem mass spectrometry method has been described for the simultaneous determination of caffeine, tolbutamide, metoprolol and dapsone in rat plasma, which are the four probe drugs of the four cytochrome P450 (CYP450) isoforms CYP1A2, CYP2C9, CYP2D6 and CYP3A4. The chromatographic separation was achieved using a Waters Acquity UPLC BEH HILIC C(18) column (2.1 × 50 mm, 1.7 µm). The mobile phase consisted of acetonitrile and water (containing 0.1% formic acid) (15:85, v/v). The triple quadrupole mass spectrometric detection was operated by positive electrospray ionization. Phenacetin was chosen as internal standard. Plasma samples were extracted with dichloromethane-butanol (10:1, v/v). The recoveries ranged from 67.5% to 98.5%. The calibration curves in plasma were linear in the range of 2.5-1,000 ng/mL for caffeine and dapsone, 5-5,000 ng/mL for tolbutamide and 2.5-250 ng/mLfor metoprolol, with correlation coefficient (r(2)) of 0.9936, 0.9966, 0.9990 and 0.9998, respectively. The method was successfully applied to pharmacokinetic studies of the four probe drugs of the four CYP450 isoforms and used to evaluate the effects of breviscapine on the activities of CYP1A2, CYP2C9, CYP2D6 and CYP3A4 in rats.

  3. Cytochrome P450 expression in oesophageal cancer.

    PubMed Central

    Murray, G I; Shaw, D; Weaver, R J; McKay, J A; Ewen, S W; Melvin, W T; Burke, M D

    1994-01-01

    The cytochrome P450 superfamily of enzymes play a central part in the metabolism of carcinogens and anti-cancer drugs. The expression, cellular localisation, and distribution of different forms of P450 and the functionally associated enzymes epoxide hydrolase and glutathione S-transferases have been investigated in oesophageal cancer and non-neoplastic oesophageal tissue using immunohistochemistry. Expression of the different enzymes was confined to epithelial cells in both non-neoplastic samples and tumour samples except the CYP3A was also identified in mast cells and glutathione S-transferase pi was present in chronic inflammatory cells. CYP1A was present in a small percentage of non-neoplastic samples but both CYP2C and CYP3A were absent. Epoxide hydrolase was present in half of the non-neoplastic samples and the different classes of glutathione S-transferase were present in a low number of samples. In carcinomas CYP1A, CYP3A, epoxide hydrolase, and glutathione S-transferase pi were expressed in at least 60% of samples. The expression of glutathione S-transferases alpha and mu were significantly less in adenocarcinoma compared with squamous carcinoma. Images Figure 1 Figure 2 Figure 3 PMID:8200549

  4. Application of Mice Humanized for CYP2D6 to the Study of Tamoxifen Metabolism and Drug–Drug Interaction with Antidepressants

    PubMed Central

    MacLeod, A. Kenneth; McLaughlin, Lesley A.; Henderson, Colin J.

    2017-01-01

    Tamoxifen is an estrogen receptor antagonist used in the treatment of breast cancer. It is a prodrug that is converted by several cytochrome P450 enzymes to a primary metabolite, N-desmethyltamoxifen (NDT), which is then further modified by CYP2D6 to a pharmacologically potent secondary metabolite, 4-hydroxy-N-desmethyltamoxifen (endoxifen). Antidepressants (ADs), which are often coprescribed to patients receiving tamoxifen, are also metabolized by CYP2D6 and evidence suggests that a drug–drug interaction between these agents adversely affects the outcome of tamoxifen therapy by inhibiting endoxifen formation. We evaluated this potentially important drug–drug interaction in vivo in mice humanized for CYP2D6 (hCYP2D6). The rate of conversion of NDT to endoxifen by hCYP2D6 mouse liver microsomes (MLMs) in vitro was similar to that of the most active members of a panel of 13 individual human liver microsomes. Coincubation with quinidine, a CYP2D6 inhibitor, ablated endoxifen generation by hCYP2D6 MLMs. The NDT-hydroxylation activity of wild-type MLMs was 7.4 times higher than that of hCYP2D6, whereas MLMs from Cyp2d knockout animals were inactive. Hydroxylation of NDT correlated with that of bufuralol, a CYP2D6 probe substrate, in the human liver microsome panel. In vitro, ADs of the selective serotonin reuptake inhibitor class were, by an order of magnitude, more potent inhibitors of NDT hydroxylation by hCYP2D6 MLMs than were compounds of the tricyclic class. At a clinically relevant dose, paroxetine pretreatment inhibited the generation of endoxifen from NDT in hCYP2D6 mice in vivo. These data demonstrate the potential of ADs to affect endoxifen generation and, thereby, the outcome of tamoxifen therapy. PMID:27756789

  5. Molecular modeling of cytochrome P450 3A4

    NASA Astrophysics Data System (ADS)

    Szklarz, Grazyna D.; Halpert, James R.

    1997-05-01

    The three-dimensional structure of human cytochrome P450 3A4 was modeled based on crystallographic coordinates of four bacterial P450s: P450 BM-3, P450cam, P450terp, and P450eryF. The P450 3A4 sequence was aligned to those of the known proteins using a structure-based alignment of P450 BM-3, P450cam, P450terp, and P450eryF. The coordinates of the model were then calculated using a consensus strategy, and the final structure was optimized in the presence of water. The P450 3A4 model resembles P450 BM-3 the most, but the B' helix is similar to that of P450eryF, which leads to an enlarged active site when compared with P450 BM-3, P450cam, and P450terp. The 3A4 residues equivalent to known substrate contact residues of the bacterial proteins and key residues of rat P450 2B1 are located in the active site or the substrate access channel. Docking of progesterone into the P450 3A4 model demonstrated that the substrate bound in a 6β-orientation can interact with a number of active site residues, such as 114, 119, 301, 304, 305, 309, 370, 373, and 479, through hydrophobic interactions. The active site of the enzyme can also accommodate erythromycin, which, in addition to the residues listed for progesterone, also contacts residues 101, 104, 105, 214, 215, 217, 218, 374, and 478. The majority of 3A4 residues which interact with progesterone and/or erythromycin possess their equivalents in key residues of P450 2B enzymes, except for residues 297, 480 and 482, which do not contact either substrate in P450 3A4. The results from docking of progesterone and erythromycin into the enzyme model make it possible to pinpoint residues which may be important for 3A4 function and to target them for site-directed mutagenesis.

  6. Non-alcoholic fatty liver disease (NAFLD) potentiates autoimmune hepatitis in the CYP2D6 mouse model.

    PubMed

    Müller, Peter; Messmer, Marie; Bayer, Monika; Pfeilschifter, Josef M; Hintermann, Edith; Christen, Urs

    2016-05-01

    Non-alcoholic fatty liver disease (NAFLD) and its more severe development non-alcoholic steatohepatitis (NASH) are increasing worldwide. In particular NASH, which is characterized by an active hepatic inflammation, has often severe consequences including progressive fibrosis, cirrhosis, and eventually hepatocellular carcinoma (HCC). Here we investigated how metabolic liver injury is influencing the pathogenesis of autoimmune hepatitis (AIH). We used the CYP2D6 mouse model in which wild type C57BL/6 mice are infected with an Adenovirus expressing the major liver autoantigen cytochrome P450 2D6 (CYP2D6). Such mice display several features of human AIH, including interface hepatitis, formation of LKM-1 antibodies and CYP2D6-specific T cells, as well as hepatic fibrosis. NAFLD was induced with a high-fat diet (HFD). We found that pre-existing NAFLD potentiates the severity of AIH. Mice fed for 12 weeks with a HFD displayed increased cellular infiltration of the liver, enhanced hepatic fibrosis and elevated numbers of liver autoantigen-specific T cells. Our data suggest that a pre-existing metabolic liver injury constitutes an additional risk for the severity of an autoimmune condition of the liver, such as AIH.

  7. Oxidative metabolism of the bioactive and naturally occurring beta-carboline alkaloids, norharman and harman, by human cytochrome P450 enzymes.

    PubMed

    Herraiz, Tomás; Guillén, Hugo; Arán, Vicente J

    2008-11-01

    Norharman and harman are naturally occurring beta-carboline alkaloids exhibiting a wide range of biological, psychopharmacological, and toxicological actions. They occur in foods and tobacco smoke and also appear endogenously in humans. In this research, metabolic and kinetic studies with cytochrome P450 enzymes and human liver microsomes showed that beta-carbolines were efficiently oxidized to several ring-hydroxylated and N-oxidation products that were subsequently identified and quantified. 6-Hydroxy- beta-carboline (6-hydroxynorharman and 6-hydroxyharman) was a major metabolite efficiently produced (high kcat and low Km) by P450 1A2 and 1A1 and to a minor extent by P450 2D6, 2C19 and 2E1. 3-Hydroxy-beta-carboline (3-hydroxynorharman and 3-hydroxyharman), another major metabolite, was specifically produced by P450 1A2 and 1A1, whereas beta-carboline-N(2)-oxide (harman-2-oxide and norharman-2-oxide) was produced by P450 2E1. The same pattern of metabolism was confirmed for human liver microsomes. Oxidative metabolism for harman was slightly higher than norharman, but norharman showed lower Km values. The oxidation of beta-carbolines is a detoxication route performed mainly by P450 1A2 and 1A1, with the participation of P450 2D6, 2C19, and 2E1, as additional contributors. Then, individual variations in the levels and activity of these P450s may influence biotransformation of beta-carboline alkaloids and their ultimate biological effects. beta-Carbolines were previously reported as comutagens and/or inhibitors of mutagens activated by P450 1A enzymes such as heterocyclic amines and polycyclic hydrocarbons. Results in this work show that beta-carbolines are good ligands and substrates for P450 1A2/1A1, contributing to the explanation of some of their toxicological effects.

  8. Physical Studies of P450P450 Interactions: Predicting Quaternary Structures of P450 Complexes in Membranes from Their X-ray Crystal Structures

    PubMed Central

    Reed, James R.; Backes, Wayne L.

    2017-01-01

    Cytochrome P450 enzymes, which catalyze oxygenation reactions of both exogenous and endogenous chemicals, are membrane bound proteins that require interaction with their redox partners in order to function. Those responsible for drug and foreign compound metabolism are localized primarily in the endoplasmic reticulum of liver, lung, intestine, and other tissues. More recently, the potential for P450 enzymes to exist as supramolecular complexes has been shown by the demonstration of both homomeric and heteromeric complexes. The P450 units in these complexes are heterogeneous with respect to their distribution and function, and the interaction of different P450s can influence P450-specific metabolism. The goal of this review is to examine the evidence supporting the existence of physical complexes among P450 enzymes. Additionally, the review examines the crystal lattices of different P450 enzymes derived from X-ray diffraction data to make assumptions regarding possible quaternary structures in membranes and in turn, to predict how the quaternary structures could influence metabolism and explain the functional effects of specific P450P450 interactions. PMID:28194112

  9. Flower colour and cytochromes P450

    PubMed Central

    Tanaka, Yoshikazu; Brugliera, Filippa

    2013-01-01

    Cytochromes P450 play important roles in biosynthesis of flavonoids and their coloured class of compounds, anthocyanins, both of which are major floral pigments. The number of hydroxyl groups on the B-ring of anthocyanidins (the chromophores and precursors of anthocyanins) impact the anthocyanin colour, the more the bluer. The hydroxylation pattern is determined by two cytochromes P450, flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′,5′-hydroxylase (F3′5′H) and thus they play a crucial role in the determination of flower colour. F3′H and F3′5′H mostly belong to CYP75B and CYP75A, respectively, except for the F3′5′Hs in Compositae that were derived from gene duplication of CYP75B and neofunctionalization. Roses and carnations lack blue/violet flower colours owing to the deficiency of F3′5′H and therefore lack the B-ring-trihydroxylated anthocyanins based upon delphinidin. Successful redirection of the anthocyanin biosynthesis pathway to delphinidin was achieved by expressing F3′5′H coding regions resulting in carnations and roses with novel blue hues that have been commercialized. Suppression of F3′5′H and F3′H in delphinidin-producing plants reduced the number of hydroxyl groups on the anthocyanidin B-ring resulting in the production of monohydroxylated anthocyanins based on pelargonidin with a shift in flower colour to orange/red. Pelargonidin biosynthesis is enhanced by additional expression of a dihydroflavonol 4-reductase that can use the monohydroxylated dihydrokaempferol (the pelargonidin precursor). Flavone synthase II (FNSII)-catalysing flavone biosynthesis from flavanones is also a P450 (CYP93B) and contributes to flower colour, because flavones act as co-pigments to anthocyanins and can cause blueing and darkening of colour. However, transgenic plants expression of a FNSII gene yielded paler flowers owing to a reduction of anthocyanins because flavanones are precursors of anthocyanins and flavones. PMID:23297355

  10. In vitro inhibition and induction of human liver cytochrome p450 enzymes by milnacipran.

    PubMed

    Paris, Brandy L; Ogilvie, Brian W; Scheinkoenig, Julie A; Ndikum-Moffor, Florence; Gibson, Remi; Parkinson, Andrew

    2009-10-01

    Milnacipran (Savella) inhibits both norepinephrine and serotonin reuptake and is distinguished by a nearly 3-fold greater potency in inhibiting norepinephrine reuptake in vitro compared with serotonin. We evaluated the ability of milnacipran to inhibit and induce human cytochrome P450 enzymes in vitro. In human liver microsomes, milnacipran did not inhibit CYP1A2, 2B6, 2C8, 2C9, 2C19, or 2D6 (IC(50) >or= 100 microM); whereas, a comparator with dual reuptake properties [duloxetine (Cymbalta)] inhibited CYP2D6 (IC(50) = 7 microM) and CYP2B6 (IC(50) = 15 microM) with a relatively high potency. Milnacipran inhibited CYP3A4/5 in a substrate-dependent manner (i.e., midazolam 1'-hydroxylation IC(50) approximately 30 microM; testosterone 6beta-hydroxylation IC(50) approximately 100 microM); whereas, duloxetine inhibited both CYP3A4/5 activities with equal potency (IC(50) = 37 and 38 microM, respectively). Milnacipran produced no time-dependent inhibition (<10%) of P450 activity, whereas duloxetine produced time-dependent inhibition of CYP1A2, 2B6, 2C19, and 3A4/5. To evaluate P450 induction, freshly isolated human hepatocytes (n = 3) were cultured and treated once daily for 3 days with milnacipran (3, 10, and 30 microM), after which microsomal P450 activities were measured. Whereas positive controls (omeprazole, phenobarbital, and rifampin) caused anticipated P450 induction, milnacipran had minimal effect on CYP1A2, 2C8, 2C9, or 2C19 activity. The highest concentration of milnacipran (30 microM; >10 times plasma C(max)) produced 2.6- and 2.2-fold increases in CYP2B6 and CYP3A4/5 activity (making it 26 and 34% as effective as phenobarbital and rifampin, respectively). Given these results, milnacipran is not expected to cause clinically significant P450 inhibition or induction.

  11. Whole genome co-expression analysis of soybean cytochrome P450 genes identifies nodulation-specific P450 monooxygenases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cytochrome P450 monooxygenases (P450s) catalyze oxidation of various substrates using oxygen and NAD(P)H. Plant P450s are involved in the biosynthesis of primary and secondary metabolites performing diverse biological functions. The recent availability of soybean genome sequence allows us to ident...

  12. Molecular genetic analysis of the cytochrome P450-debrisoquine hydroxylase locus and association with cancer susceptibility.

    PubMed Central

    Smith, C A; Moss, J E; Gough, A C; Spurr, N K; Wolf, C R

    1992-01-01

    The cytochrome P450-dependent monooxygenases play a central role in the metabolism of chemical carcinogens. The action of these enzymes can lead to either carcinogen detoxication or activation. Differences in P450 expression in animal models give rise to large differences in susceptibility to chemical carcinogens, so genetic polymorphisms in P450 expression may be expected to be an important factor in individual human susceptibility to cancer. Of particular interest is the genetic polymorphism at the cytochrome P450-debrisoquine/sparteine hydroxylase locus (CYP2D6). Although this is a minor liver P450, its polymorphic expression is associated with the abnormal metabolism of at least 30 therapeutic drugs, including beta-blockers and tricyclic antidepressants. Conflicting reports have been made on the association of this polymorphism with cancer susceptibility. This disagreement may be attributable to limitations of the phenotyping assay used to identify affected individuals (poor metabolizers, PMs). In order to clarify these anomalies, we have developed a simple DNA-based assay with which we can identify the majority of PMs. The assay is centered around the primary gene defect responsible for the polymorphism, a G to A transition at the junction of intron 3/exon 4 which results in a frame-shift in the resultant mRNA. The frequency of this mutation is 70-80% in PMs. We have studied the frequency of mutated alleles in a control population and in a wide range of cancer patients. No association between this polymorphism and lung cancer susceptibility was observed; however, in other populations of cancer patients some very interesting shifts were found in the proportion of PMs and heterozygotes from that in the normal population. PMID:1486838

  13. Crystal Structure of Cindoxin, the P450cin Redox Partner

    PubMed Central

    2015-01-01

    The crystal structure of the flavin mononucleotide (FMN)-containing redox partner to P450cin, cindoxin (Cdx), has been determined to 1.3 Å resolution. The overall structure is similar to that of the FMN domain of human cytochrome P450 reductase. A Brownian dynamics–molecular dynamics docking method was used to produce a model of Cdx with its redox partner, P450cin. This Cdx–P450cin model highlights the potential importance of Cdx Tyr96 in bridging the FMN and heme cofactors as well P450cin Arg102 and Arg346. Each of the single-site Ala mutants exhibits ∼10% of the wild-type activity, thus demonstrating the importance of these residues for binding and/or electron transfer. In the well-studied P450cam system, redox partner binding stabilizes the open low-spin conformation of P450cam and greatly decreases the stability of the oxy complex. In sharp contrast, Cdx does not shift P450cin to a low-spin state, although the stability of oxy-P450cin is decreased 10-fold in the presence of Cdx. This indicates that Cdx may have a modest effect on the open–closed equilibrium in P450cin compared to that in P450cam. It has been postulated that part of the effector role of Pdx on P450cam is to promote a significant structural change that makes available a proton relay network involving Asp251 required for O2 activation. The structure around the corresponding Asp in P450cin, Asp241, provides a possible structural reason for why P450cin is less dependent on its redox partner for functionally important structural changes. PMID:24533927

  14. Characterization of benidipine and its enantiomers' metabolism by human liver cytochrome P450 enzymes.

    PubMed

    Yoon, Yune-Jung; Kim, Kwon-Bok; Kim, Hyunmi; Seo, Kyung-Ah; Kim, Ho-Sook; Cha, In-June; Kim, Eun-Young; Liu, Kwang-Hyeon; Shin, Jae-Gook

    2007-09-01

    Benidipine is a dihydropyridine calcium antagonist that has been used clinically as an antihypertensive and antianginal agent. It is used clinically as a racemate, containing the (-)-alpha and (+)-alpha isomers of benidipine. This study was performed to elucidate the metabolism of benidipine and its enantiomers in human liver microsomes (HLMs) and to characterize the cytochrome P450 (P450) enzymes that are involved in the metabolism of benidipine. Human liver microsomal incubation of benidipine in the presence of NADPH resulted in the formation of two metabolites, N-desbenzylbenidipine and dehydrobenidipine. The intrinsic clearance (CL(int)) of the formation of N-desbenzylbenidipine and dehydrobenidipine metabolites from (-)-alpha isomer was similar to those from the (+)-alpha isomer (1.9 +/- 0.1 versus 2.3 +/- 2.3 microl/min/pmol P450 and 0.5 +/- 0.2 versus 0.6 +/- 0.6 microl/min/pmol P450, respectively). Correlation analysis between the known P450 enzyme activities and the rate of the formation of benidipine metabolites in the 15 HLMs showed that benidipine metabolism is correlated with CYP3A activity. The P450 isoform-selective inhibition study in liver microsomes and the incubation study of cDNA-expressed enzymes also showed that theN-debenzylation and dehydrogenation of benidipine are mainly mediated by CYP3A4 and CYP3A5. The total CL(int) values of CYP3A4-mediated metabolite formation from (-)-alpha isomer were similar to those from (+)-alpha isomer (17.7 versus 14.4 microl/min/pmol P450, respectively). The total CL(int) values of CYP3A5-mediated metabolite formation from (-)-alpha isomer were also similar to those from (+)-alpha isomer (8.3 versus 11.0 microl/min/pmol P450, respectively). These findings suggest that CYP3A4 and CYP3A5 isoforms are major enzymes contributing to the disposition of benidipine, but stereoselective disposition of benidipine in vivo may be influenced not by stereoselective metabolism but by other factors.

  15. CHARACTERIZATION OF THE ALKANE-INDUCIBLE CYTOCHROME P450 (P450ALK) GENE FROM THE YEAST CANDIDA TROPICALIS: IDENTIFICATION OF A NEW P450 FAMILY

    EPA Science Inventory

    The P450alk gene, which is inducible by the assimilation of alkane in Candida tropicalis, was sequenced and characterized. Structural features described in promoter and terminator regions of Saccharomyces yeast genes are present in the P450alk gene and some particular structures ...

  16. Engineering Cytochrome P450 Biocatalysts for Biotechnology, Medicine, and Bioremediation

    PubMed Central

    Kumar, Santosh

    2009-01-01

    Importance of the field: Cytochrome P450 enzymes comprise a superfamily of heme monooxygenases that are of considerable interest for the: 1) synthesis of novel drugs and drug metabolites, 2) targeted cancer gene therapy, 3) biosensor design, and 4) bioremediation. However, their applications are limited because cytochrome P450, especially mammalian P450 enzymes, show a low turnover rate and stability, and require a complex source of electrons through cytochrome P450 reductase and NADPH. Areas covered in this review: In this review, we discuss the recent progress towards the use of P450 enzymes in a variety of above-mentioned applications. We also present alternate and cost-effective ways to perform P450-mediated reaction, especially using peroxides. Furthermore, we expand upon the current progress in P450 engineering approaches describing several recent examples that are utilized to enhance heterologous expression, stability, catalytic efficiency, and utilization of alternate oxidants. What the reader will gain: The review will provide a comprehensive knowledge in the design of P450 biocatalysts for potentially practical purposes. Finally, we provide a prospective on the future aspects of P450 engineering and its applications in biotechnology, medicine, and bioremediation. Take home message: Because of its wide applications, academic and pharmaceutical researchers, environmental scientists, and health care providers are expected to gain current knowledge and future prospects of the practical use of P450 biocatalysts. PMID:20064075

  17. Application of substrate depletion assay to evaluation of CYP isoforms responsible for stereoselective metabolism of carvedilol.

    PubMed

    Iwaki, Masahiro; Niwa, Toshiro; Bandoh, Saya; Itoh, Megumi; Hirose, Hitomi; Kawase, Atsushi; Komura, Hiroshi

    2016-12-01

    To evaluate the relative contribution of cytochrome P450 (CYP) isoforms responsible for carvedilol (CAR) oxidation, enantioselective metabolism of CAR was investigated in human liver microsomes (HLMs) and recombinant human CYPs by using the substrate depletion assay. CYP2D6 exhibited the highest contribution to the metabolism of R-CAR, followed by CYP3A4, CYP1A2, and CYP2C9, whereas the metabolism of the S-enantiomer was mainly mediated by CYP1A2, followed by CYP2D6 and CYP3A4. In HLMs, metabolism of R- and S-CAR was markedly inhibited by quinidine; R-CAR metabolism (57-61% decrease) was more inhibited than S-CAR metabolism (37-43% decrease), and furafylline and ketoconazole almost equally inhibited metabolism of both enantiomers by 25-32% and 30-50%, respectively. The absence of CYP2D6 in a mixture of five major recombinant CYP isoforms at the approximate ratio as in HLMs resulted in a 42% and 25% decrease in the metabolic activities for R- and S-CAR, respectively. Moreover, the absence of CYP1A2 in the mixture resulted in a 16% and 39% decrease in the metabolic activities for R- and S-CAR, respectively. Our results suggest the stereoselective metabolism of CAR is determined by not only the activity of CYP2D6 but also of CYP1A2 and CYP3A4.

  18. Inhibition of human P450 enzymes by natural extracts used in traditional medicine.

    PubMed

    Rodeiro, Idania; Donato, María T; Jimenez, Nuria; Garrido, Gabino; Molina-Torres, Jorge; Menendez, Roberto; Castell, José V; Gómez-Lechón, María J

    2009-02-01

    Different medicinal plants are widely used in Cuba and Mexico to treat several disorders. This paper reports in vitro inhibitory effects on the P450 system of herbal products commonly used by people in Cuba and Mexico in traditional medicine for decades. Experiments were conducted in human liver microsomes. The catalytic activities of CYP1A1/2, 2D6, and 3A4 were measured using specific probe substrates. The Heliopsis longipes extract exhibited a concentration-dependent inhibition of the three enzymes, and similar effects were produced by affinin (an alkamide isolated from the H. longipes extract) and two catalytically reduced alkamides. Mangifera indica L. and Thalassia testudinum extracts, two natural polyphenol-rich extracts, diminished CYP1A1/2 and 3A4 activities, but not the CYP2D6 activity. These results suggest that these herbs inhibit the major human P450 enzymes involved in drug metabolism and could induce potential herbal-drug interactions.

  19. Interaction of sanguinarine alkaloid, isolated from argemone oil, with hepatic cytochrome p450 in rats.

    PubMed

    Reddy, Naveen P; Das, Mukul

    2008-01-01

    ABSTRACT Prior studies have shown that argemone oil (AO), responsible for 'Epidemic dropsy', causes inhibition of catalytic activities of Cytochrome P450 (P450). In this study interaction of sanguinarine (SAN) alkaloid, isolated from AO, with rat hepatic P450 was investigated. Hepatic microsomes prepared from 3-methylcholantherene (3MC) treated rats when incubated with SAN (1-3 muM) resulted in a spectral peak at 385 nm and a trough at 415 nm, indicative of Type I binding. Incubation of SAN (50-200 muM) with hepatic microsomes prepared from phenobarbitone (PB) treated rats also showed a Type I spectra with a peak at 395 nm and a trough at 420 nm. Relative binding efficiency (DeltaA(max)/K(s)(app) factor) of SAN with P450 was found to be 1540 and 1030 absorbance units/nmol CYP/M for 3MC and PB induced microsomes, respectively. In a P450 spectral inhibition study SAN showed higher affinity towards 3MC eliciting inhibition at much lesser concentrations (0.25-5 muM) as compared to PB (100-300 muM). The IC50s of SAN with different catalytic markers of P450 isoforms, i.e. ethoxyresorufin-O-deethylase (EROD) for CYP1A1, was 2.8 muM and for methoxyresorufin-O-deethylase (MROD) for CYP1A2 was 2.2 muM in 3MC induced microsomes, while benzoyloxyresorufin-O-deethylase (BROD) for CYP 2B1/1A1 showed an IC50 of 50 muM but pentoxyresorufin-O-deethylase (PROD) for CYP2B1 showed no inhibition even at higher concentrations of SAN (> 60 muM) in PB-induced microsomes. These results indicate that higher affinity of SAN binding towards the CYP1A family may have a role in SAN toxicity.

  20. Plant activation of aromatic amines mediated by cytochromes P450 and flavin-containing monooxygenases.

    PubMed

    Chiapella, C; Radovan, R D; Moreno, J A; Casares, L; Barbé, J; Llagostera, M

    2000-10-31

    To know the mechanisms involved in the activation of promutagenic aromatic amines mediated by plants, we used Persea americana S117 system (S117) for the activation of 2-aminofluorene (2-AF) and m-phenylenediamine (m-PDA) in Ames assays. In these assays, the effect of the diphenylene iodonium (DPI), an inhibitor of flavin-containing monooxygenases (FMOs), of the 1-aminobenzotriazole (1-ABT), an inhibitor of cytochromes P450 (cyt-P450s) and of the methimazole, a high-affinity substrate for FMOs, was studied. The efficacy of both inhibitors and of the methimazole was verified to find that they did partially inhibit the mutagenesis of both aromatic amines, activated with rat liver S9. Similarly, both inhibitors and methimazole did produce a significant decrease in 2-AF and m-PDA mutagenesis, when the activation system was S117, indicating that, similar to what occurs in mammalian systems, plant FMOs and cyt-P450s can metabolize aromatic amines to mutagenic product(s). However, the affinity of both FMOs and cyt-P450s of plant for 2-AF and m-PDA was different. Data obtained indicate that the activities of plant FMOs must be the main enzymatic system of m-PDA activation while, in 2-AF activation, plant cyt-P450s have the most relevant activities. In addition, peroxidases of the S117 system must contribute to 2-AF activation and some isoforms of FMOs and/or cyt-P450s of the S117 system, uninhibited by the inhibitors used, must be the responsible for a partial activation of m-PDA.

  1. Molecular analysis and modeling of inactivation of human CYP2D6 by four mechanism based inactivators.

    PubMed

    Livezey, Mara; Nagy, Leslie D; Diffenderfer, Laura E; Arthur, Evan J; Hsi, David J; Holton, Jeffrey M; Furge, Laura Lowe

    2012-03-01

    Human cytochrome P450 2D6 (CYP2D6) is involved in metabolism of approximately 25% of pharmaceutical drugs. Inactivation of CYP2D6 can lead to adverse drug interactions. Four inactivators of CYP2D6 have previously been identified: 5-Fluoro-2-[4-[(2-phenyl-1H-imidazol-5-yl)methyl]-1-piperazinyl]pyrimidine(SCH66712), (1-[(2-ethyl- 4-methyl-1H-imidazol-5-yl)-methyl]-4-[4-(trifluoromethyl)-2-pyridinyl]piperazine(EMTPP), paroxetine, and 3,4- methylenedioxymethamphetamine (MDMA). All four contain planar, aromatic groups as well as basic nitrogens common to CYP2D6 substrates. SCH66712 and EMTPP also contain piperazine groups and substituted imidazole rings that are common in pharmaceutical agents, though neither of these compounds is clinically relevant. Paroxetine and MDMA contain methylenedioxyphenyls. SCH66712 and EMTPP are both known protein adductors while paroxetine and MDMA are probable heme modifiers. The current study shows that each inactivator displays Type I binding with Ks values that vary by 2-orders of magnitude with lower Ks values associated with greater inactivation. Comparison of KI, kinact, and partition ratio values shows SCH66712 is the most potent inactivator. Molecular modeling experiments using AutoDock identify Phe120 as a key interaction for all four inactivators with face-to-face and edge-to-face pi interactions apparent. Distance between the ligand and heme iron correlates with potency of inhibition. Ligand conformations were scored according to their binding energies as calculated by AutoDock and correlation was observed between molecular models and Ks values.

  2. MOLECULAR ANALYSIS AND MODELING OF INACTIVATION OF HUMAN CYP2D6 BY FOUR MECHANISM BASED INACTIVATORS

    PubMed Central

    Livezey, Mara; Nagy, Leslie D.; Diffenderfer, Laura E.; Arthur, Evan J.; Hsi, David J.; Holton, Jeffrey M.; Furge, Laura Lowe

    2014-01-01

    Human cytochrome P450 2D6 (CYP2D6) is involved in metabolism of approximately 25% of pharmaceutical drugs. Inactivation of CYP2D6 can lead to adverse drug interactions. Four inactivators of CYP2D6 have previously been identified: 5-Fluoro-2-[4-[(2-phenyl-1H-imidazol-5-yl)methyl]-1-piperazinyl]pyrimidine (SCH66712), (1-[(2-ethyl-4-methyl-1H(-EMTPP-imidazol-5-yl)-methyl]-4-[4-(trifluoromethyl)-2-pyridinyl]piperazine (EMTPP), paroxetine, and 3,4-methylenedioxymethamphetamine (MDMA). All four contain planar, aromatic groups as well as basic nitrogens common to CYP2D6 substrates. SCH66712 and EMTPP also contain piperazine groups and substituted imidazole rings that are common in pharmaceutical agents, though neither of these compounds is clinically relevant. Paroxetine and MDMA contain methylenedioxyphenyls. SCH66712 and EMTPP are both known protein adductors while paroxetine and MDMA are probable heme modifiers. The current study shows that each inactivator displays Type I binding with Ks values that vary by 2-orders of magnitude with lower Ks values associated with greater inactivation. Comparison of KI, kinact, and partition ratio values shows SCH66712 is the most potent inactivator. Molecular modeling experiments using AutoDock identify Phe120 as a key interaction for all four inactivators with face-to-face and edge-to-face pi interactions apparent. Distance between the ligand and heme iron correlates with potency of inhibition. Ligand conformations were scored according to their binding energies as calculated by AutoDock and correlation was observed between molecular models and Ks values. PMID:22372551

  3. In Vitro and in Vivo Inhibitory Effects of Glycyrrhetinic Acid in Mice and Human Cytochrome P450 3A4.

    PubMed

    Lv, Qiao-Li; Wang, Gui-Hua; Chen, Shu-Hui; Hu, Lei; Zhang, Xue; Ying, Guo; Qin, Chong-Zhen; Zhou, Hong-Hao

    2015-12-25

    Glycyrrhetinic acid (GA) has been used clinically in the treatment of patients with chronic hepatitis. This study evaluated the effect of GA on the activity of five P450(CYP450) cytochrome enzymes: CYP2A6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, in human liver microsomes (HLMs) and recombinant cDNA-expressed enzyme systems using a HPLC-MS/MS CYP-specific probe substrate assay. With midazolam as the probe substrate, GA greatly decreased CYP3A4 activity with IC50 values of 8.195 μM in HLMs and 7.498 μM in the recombinant cDNA-expressed CYP3A4 enzyme system, respectively. It significantly decreased CYP3A4 activity in a dose- but not time-dependent manner. Results from Lineweaver-Burk plots showed that GA could inhibit CYP3A4 activity competitively, with a Ki value of 1.57 μM in HLMs. Moreover, CYP2C9 and CYP2C19 could also be inhibited significantly by GA with IC50 of 42.89 and 40.26 μM in HLMs, respectively. Other CYP450 isoforms were not markedly affected by GA. The inhibition was also confirmed by an in vivo study of mice. In addition, it was observed that mRNA expressions of the Cyps2c and 3a family decreased significantly in the livers of mice treated with GA. In conclusion, this study indicates that GA may exert herb-drug interactions by competitively inhibiting CYP3A4.

  4. Variation in Human Cytochrome P-450 Drug-Metabolism Genes: A Gateway to the Understanding of Plasmodium vivax Relapses

    PubMed Central

    Silvino, Ana Carolina Rios; Costa, Gabriel Luiz; de Araújo, Flávia Carolina Faustino; Ascher, David Benjamin; Pires, Douglas Eduardo Valente; Fontes, Cor Jesus Fernandes; Carvalho, Luzia Helena; de Brito, Cristiana Ferreira Alves; Sousa, Tais Nobrega

    2016-01-01

    Although Plasmodium vivax relapses are classically associated with hypnozoite activation, it has been proposed that a proportion of these cases are due to primaquine (PQ) treatment failure caused by polymorphisms in cytochrome P-450 2D6 (CYP2D6). Here, we present evidence that CYP2D6 polymorphisms are implicated in PQ failure, which was reinforced by findings in genetically similar parasites, and may explain a number of vivax relapses. Using a computational approach, these polymorphisms were predicted to affect the activity of CYP2D6 through changes in the structural stability that could lead to disruption of the PQ-enzyme interactions. Furthermore, because PQ is co-administered with chloroquine (CQ), we investigated whether CQ-impaired metabolism by cytochrome P-450 2C8 (CYP2C8) could also contribute to vivax recurrences. Our results show that CYP2C8-mutated patients frequently relapsed early (<42 days) and had a higher proportion of genetically similar parasites, suggesting the possibility of recrudescence due to CQ therapeutic failure. These results highlight the importance of pharmacogenetic studies as a tool to monitor the efficacy of antimalarial therapy. PMID:27467145

  5. Impact of impurities on IC50 values of P450 inhibitors.

    PubMed

    Huang, Zeqi

    2011-08-01

    During early drug discovery, the synthetic pathways for test compounds are not well defined and impurities in the test compounds are inevitable. Compounds undergo serial screening tests at this stage to assess their biological activities and drug-like properties. Impurities in the test compounds can produce false positive results and therefore complicate the interpretation of data. P450 inhibition is one of the screens used in the early drug discovery process to assess the potential of drug-drug interactions caused by the inhibition of P450 enzymes. The impact of impurities on P450 inhibition has not been investigated. In this study, the impact of impurities on CYP2D6 IC(50) values was evaluated using model compounds. Cimetidine was chosen as the test compound. Quinidine, fluoxetine, fluvoxamine, and ibuprofen were chosen to represent impurities as they inhibit CYP2D6 to varying degrees. The IC(50) values of these model impurities for CYP2D6 were 0.11 µM, 0.98 µM, 13.4 µM, and >100 µM, respectively. Impurities with potent CYP2D6 inhibition, such as quinidine, can significantly decrease the apparent IC(50) value for the mixture. With the addition of only 2% quinidine to cimetidine (mol/mol), the apparent IC(50) value of cimetidine decreased from 98 µM to 4.4 µM. With the addition of 10% quinidine, the apparent IC(50) decreased to 1.04 µM. Such a significant decrease in apparent IC(50) values can produce a false alert and cause the inappropriate elimination of good compounds at an early stage. Impur6ities with low inhibitory potential, such as fluvoxamine and ibuprofen, did not cause a significant change in apparent IC(50) values. An impurity can have a similar effect on the IC(50) values for inhibition of other biological activities. The effect of an impurity on apparent IC(50) values can be predicted by using a simulation curve if the potency of the impurity is characterized.

  6. The Effects of Milk Thistle (Silybum marianum) on Human Cytochrome P450 Activity

    PubMed Central

    Kawaguchi-Suzuki, Marina; Frye, Reginald F.; Zhu, Hao-Jie; Brinda, Bryan J.; Chavin, Kenneth D.; Bernstein, Hilary J.

    2014-01-01

    Milk thistle (Silybum marianum) extracts are widely used as a complementary and alternative treatment of various hepatic conditions and a host of other diseases/disorders. The active constituents of milk thistle supplements are believed to be the flavonolignans contained within the extracts. In vitro studies have suggested that some milk thistle components may significantly inhibit specific cytochrome P450 (P450) enzymes. However, determining the potential for clinically significant drug interactions with milk thistle products has been complicated by inconsistencies between in vitro and in vivo study results. The aim of the present study was to determine the effect of a standardized milk thistle supplement on major P450 drug-metabolizing enzymes after a 14-day exposure period. CYP1A2, CYP2C9, CYP2D6, and CYP3A4/5 activities were measured by simultaneously administering the four probe drugs, caffeine, tolbutamide, dextromethorphan, and midazolam, to nine healthy volunteers before and after exposure to a standardized milk thistle extract given thrice daily for 14 days. The three most abundant falvonolignans found in plasma, following exposure to milk thistle extracts, were silybin A, silybin B, and isosilybin B. The concentrations of these three major constituents were individually measured in study subjects as potential perpetrators. The peak concentrations and areas under the time-concentration curves of the four probe drugs were determined with the milk thistle administration. Exposure to milk thistle extract produced no significant influence on CYP1A2, CYP2C9, CYP2D6, or CYP3A4/5 activities. PMID:25028567

  7. Effects of zedoary turmeric oil on P450 activities in rats with liver cirrhosis induced by thioacetamide.

    PubMed

    Cheng, Jing-Jing; Yang, Nai-Bin; Wu, Liang; Lin, Jia-Le; Dai, Ge-Xin; Zhu, Jia-Yin

    2014-01-01

    The aim of this study was to elucidate the effects of zedoary turmeric oil (ZTO) on P450 activities (CYP1A2, CYP2C9, CYP2C19, CYP2B6, CYP2D6 and CYP3A4) in rats with liver cirrhosis induced by thioacetamide (TAA). For the induction of liver cirrhosis, rats were given TAA in their drinking water at a concentration of 0.03% for consecutive 5 weeks and then 0.04% for the next consecutive 5 weeks throughout the establishment of cirrhosis. Then the cirrhotic rats were ip given saline, ZTO 100, 200 and 400 mg/kg, respectively, once daily for 2 weeks. When cirrhosis model was established at week 10, all rats of five groups were administered intragastrically with 15 mg/kg phenacetin, 0.6 mg/kg tolbutamide, 15 mg/kg omeprazole, 15 mg/kg bupropion, 15 mg/kg metoprolol, and 10 mg/kg midazolam. Blood samples were collected at a series of time-points and the concentrations of probe drugs in plasma were determined by HPLC-MS/MS. The degree of liver cirrhosis was assessed by HE staining. The serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) from the model group increased by approximately 4-fold, and a decreased level of albumin (Alb) was also observed, as compared to the control group (P < 0.05). However, ZTO was found to reverse those changes of serum levels observed in the model group, and the 200 mg/kg ZTO treatment group showed the most obvious reverse tendency with significantly decreased ALT, AST and increased Alb levels (P < 0.05). The results indicated that ZTO with the dose of 100 mg/kg could inhibit the activities of CYP450 isoforms CYP2C9 and CYP2D6 in vivo in cirrhotic rats induced by TAA, while ZTO with the dose of 400 mg/kg could induce the activity of CYP2C19 in vivo in cirrhotic rats induced by TAA. However, ZTO showed no influence on cirrhotic rat hepatic CYP1A2, CYP2B6 and CYP3A4 activity in vivo. This has certain guiding significance to clinical treatment.

  8. CYP1A2 and CYP2D6 Gene Polymorphisms in Schizophrenic Patients with Neuroleptic Drug-Induced Side Effects.

    PubMed

    Ivanova, S A; Filipenko, M L; Vyalova, N M; Voronina, E N; Pozhidaev, I V; Osmanova, D Z; Ivanov, M V; Fedorenko, O Yu; Semke, A V; Bokhan, N A

    2016-03-01

    Polymorphic variants of CYP1A2 and CYP2D6 genes of the cytochrome P450 system were studied in patients with schizophrenia with drug-induced motor disorders and hyperprolactinemia against the background of long-term neuroleptic therapy. We revealed an association of polymorphic variant C-163A CYP1A2*1F of CYP1A2 gene with tardive dyskinesia and association of polymorphic variant 1846G>A CY2D6*4 and genotype A/A of CYP2D6 gene (responsible for debrisoquin-4-hydroxylase synthesis) with limbotruncal tardive dyskinesia in patients with schizophrenia receiving neuroleptics for a long time.

  9. Cytochrome P450 1 family and cancers.

    PubMed

    Go, Ryeo-Eun; Hwang, Kyung-A; Choi, Kyung-Chul

    2015-03-01

    The aryl hydrocarbon receptor (AhR) is a ligand-activated transcriptional factor that dimerizes with aryl hydrocarbon receptor nuclear translocator (ARNT). This complex binds to xenobiotics response element (XREs), and then starts the expressions of downstream genes including cytochrome P450 (CYP) 1 family members: CYP1A1, CYP1A2 and CYP1B1. Role of CYP1 family is involved in the metabolism of endogenous hormones, xenobiotics and drug. The expression of CYP1 family is regulated by estradiol (E2) or xenobiotics in diverse cancers. In breast cancers expressing estrogen receptors (ERs), level of CYP1B1 is increased by E2 and reversed by an estrogen receptor antagonist, ICI 182,780 or 4-hydrotamoxifen, which indicates that the expression of CYP1 family in downstream region of AhR is regulated by an activation of ERα. In metabolic pathways, E2 is converted into 4-hydroxyestradiol by CYP1B1, which can be converted into mainly estradiol-3,4-quinone, a potential carcinogen, by peroxidase. Increased expression of CYP1 family indicates the possibility of carcinogenesis by exposure of xenobiotics in endometrial and ovarian cancers. Apart from roles of CYP1 family in relation with ER pathway, CYP1 family is over-expressed in ER independent cancers. CYP1A1 exhibits hydroxylase activity in oxidation of arachidonic acid, which has been transformed to 12(R)-hydrxyeicosatetraenoic (HETEs), a potent activator of AhR activity. On the basis of results, phytoestrogens and dexamethasone are provided as cancer therapy regulating the expression of CYP1 family. Thus, this review focuses on the role(s) of CYP1 family in ER-dependent or ER-independent cancers and the potential for cancer therapy to target CYP1 family in these cancers.

  10. Main contribution of the cytochrome P450 isoenzyme 1A2 (CYP1A2) to N-demethylation and 5-sulfoxidation of the phenothiazine neuroleptic chlorpromazine in human liver--A comparison with other phenothiazines.

    PubMed

    Wójcikowski, Jacek; Boksa, Jan; Daniel, Władysława A

    2010-10-15

    The aim of the present study was to identify cytochrome P450 (CYP) isoenzymes involved in the 5-sulfoxidation, mono-N-demethylation and di-N-demethylation of the aliphatic-type phenothiazine neuroleptic chlorpromazine in human liver. Experiments were performed in vitro using cDNA-expressed human CYP isoforms (Supersomes 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4), liver microsomes from different donors and CYP-selective inhibitors. The obtained results indicate that CYP1A2 is the only CYP isoform that catalyzes the mono-N-demethylation and di-N-demethylation of chlorpromazine (100%) and is the main isoform responsible for chlorpromazine 5-sulfoxidation (64%) at a therapeutic concentration of the drug (10 microM). CYP3A4 contributes to a lesser degree to chlorpromazine 5-sulfoxidation (34%). The role of CYP2B6, CYP2C19 and CYP2D6 in catalyzing of the latter reaction is negligible (0.1-2%). Similar results were obtained at a higher, non-therapeutic concentration of the drug (100 microM); however, the contribution of CYP1A2 to chlorpromazine mono-N-demethylation was noticeably lower (75%), mostly in favour of CYP2C19 and CYP3A4 (about 12% each). The obtained results indicate that the catalysis of chlorpromazine N-demethylation and 5-sulfoxidation in humans exhibits a stricter CYP1A2 preference compared to the previously tested phenothiazines (promazine, perazine, and thioridazine). Hence pharmacokinetic interactions involving chlorpromazine and CYP1A2 substrates and inhibitors are likely to occur. Considering strong dopaminergic D(2), noradrenergic alpha(1) and cholinergic M(1) receptor blocking properties of chlorpromazine and some of its metabolites, as well as their serious side effects, the obtained results may be of pharmacological and clinical importance.

  11. Update on allele nomenclature for human cytochromes P450 and the Human Cytochrome P450 Allele (CYP-allele) Nomenclature Database.

    PubMed

    Sim, Sarah C; Ingelman-Sundberg, Magnus

    2013-01-01

    Interindividual variability in xenobiotic metabolism and drug response is extensive and genetic factors play an important role in this variation. A majority of clinically used drugs are substrates for the cytochrome P450 (CYP) enzyme system and interindividual variability in expression and function of these enzymes is a major factor for explaining individual susceptibility for adverse drug reactions and drug response. Because of the existence of many polymorphic CYP genes, for many of which the number of allelic variants is continually increasing, a universal and official nomenclature system is important. Since 1999, all functionally relevant polymorphic CYP alleles are named and published on the Human Cytochrome P450 Allele (CYP-allele) Nomenclature Web site (http://www.cypalleles.ki.se). Currently, the database covers nomenclature of more than 660 alleles in a total of 30 genes that includes 29 CYPs as well as the cytochrome P450 oxidoreductase (POR) gene. On the CYP-allele Web site, each gene has its own Webpage, which lists the alleles with their nucleotide changes, their functional consequences, and links to publications identifying or characterizing the alleles. CYP2D6, CYP2C9, CYP2C19, and CYP3A4 are the most important CYPs in terms of drug metabolism, which is also reflected in their corresponding highest number of Webpage hits at the CYP-allele Web site.The main advantage of the CYP-allele database is that it offers a rapid online publication of CYP-alleles and their effects and provides an overview of peer-reviewed data to the scientific community. Here, we provide an update of the CYP-allele database and the associated nomenclature.

  12. Integrated in vitro analysis for the in vivo prediction of cytochrome P450-mediated drug-drug interactions.

    PubMed

    McGinnity, Dermot F; Waters, Nigel J; Tucker, James; Riley, Robert J

    2008-06-01

    Unbound IC(50) (IC(50,u)) values of 15 drugs were determined in eight recombinantly expressed human cytochromes P450 (P450s) and human hepatocytes, and the data were used to simulate clinical area under the plasma concentration-time curve changes (deltaAUC) on coadministration with prototypic CYP2D6 substrates. Significant differences in IC(50,u) values between enzyme sources were observed for quinidine (0.02 microM in recombinant CYP2D6 versus 0.5 microM in hepatocytes) and propafenone (0.02 versus 4.1 microM). The relative contribution of individual P450s toward the oxidative metabolism of clinical probes desipramine, imipramine, tolterodine, propranolol, and metoprolol was estimated via determinations of intrinsic clearance using recombinant P450s (rP450s). Simulated deltaAUC were compared with those observed in vivo via the ratios of unbound inhibitor concentration at the entrance to the liver to inhibition constants determined against rP450s ([I](in,u)/K(i)) and incorporating parallel substrate elimination pathways. For this dataset, there were 20% false negatives (observed deltaAUC >or= 2, predicted deltaAUC < 2), 77% correct predictions, and 3% false positives. Thus, the [I](in,u)/K(i) approach appears relatively successful at estimating the degree of clinical interactions and can be incorporated into drug discovery strategies. Using a Simcyp ADME (absorption, metabolism, distribution, elimination) simulator (Simcyp Ltd., Sheffield, UK), there were 3% false negatives, 94% correct simulations, and 3% false positives. False-negative predictions were rationalized as a result of mechanism-based inhibition, production of inhibitory metabolites, and/or hepatic uptake. Integrating inhibition and reaction phenotyping data from automated rP450 screens have shown applicability to predict the occurrence and degree of in vivo drug-drug interactions, and such data may identify the clinical consequences for candidate drugs as both "perpetrators" and "victims" of P450

  13. Epoxidation Activities of Human Cytochromes P450c17 and P450c21

    PubMed Central

    2015-01-01

    Some cytochrome P450 enzymes epoxidize unsaturated substrates, but this activity has not been described for the steroid hydroxylases. Physiologic steroid substrates, however, lack carbon–carbon double bonds in the parts of the pregnane molecules where steroidogenic hydroxylations occur. Limited data on the reactivity of steroidogenic P450s toward olefinic substrates exist, and the study of occult activities toward alternative substrates is a fundamental aspect of the growing field of combinatorial biosynthesis. We reasoned that human P450c17 (steroid 17-hydroxylase/17,20-lyase, CYP17A1), which 17- and 16α-hydroxylates progesterone, might catalyze the formation of the 16α,17-epoxide from 16,17-dehydroprogesterone (pregna-4,16-diene-3,20-dione). CYP17A1 catalyzed the novel 16α,17-epoxidation and the ordinarily minor 21-hydroxylation of 16,17-dehydroprogesterone in a 1:1 ratio. CYP17A1 mutation A105L, which has reduced progesterone 16α-hydroxylase activity, gave a 1:5 ratio of epoxide:21-hydroxylated products. In contrast, human P450c21 (steroid 21-hydroxylase, CYP21A2) converted 16,17-dehydroprogesterone to the 21-hydroxylated product and only a trace of epoxide. CYP21A2 mutation V359A, which has significant 16α-hydroxylase activity, likewise afforded the 21-hydroxylated product and slightly more epoxide. CYP17A1 wild-type and mutation A105L do not 21- or 16α-hydroxylate pregnenolone, but the enzymes 21-hydroxylated and 16α,17-epoxidized 16,17-dehydropregnenolone (pregna-5,16-diene-3β-ol-20-one) in 4:1 or 12:1 ratios, respectively. Catalase and superoxide dismutase did not prevent epoxide formation. The progesterone epoxide was not a time-dependent, irreversible CYP17A1 inhibitor. Our substrate modification studies have revealed occult epoxidase and 21-hydroxylase activities of CYP17A1, and the fraction of epoxide formed correlated with the 16α-hydroxylase activity of the enzymes. PMID:25386927

  14. Activity, Inhibition, and Induction of Cytochrome P450 2J2 in Adult Human Primary Cardiomyocytes

    PubMed Central

    Evangelista, Eric A.; Kaspera, Rüdiger; Mokadam, Nahush A.; Jones, J. P.

    2013-01-01

    Cytochrome P450 2J2 plays a significant role in the epoxidation of arachidonic acid to signaling molecules important in cardiovascular events. CYP2J2 also contributes to drug metabolism and is responsible for the intestinal clearance of ebastine. However, the interaction between arachidonic acid metabolism and drug metabolism in cardiac tissue, the main expression site of CYP2J2, has not been examined. Here we investigate an adult-derived human primary cardiac cell line as a suitable model to study metabolic drug interactions (inhibition and induction) of CYP2J2 in cardiac tissue. The primary human cardiomyocyte cell line demonstrated similar mRNA-expression profiles of P450 enzymes to adult human ventricular tissue. CYP2J2 was the dominant isozyme with minor contributions from CYP2D6 and CYP2E1. Both terfenadine and astemizole oxidation were observed in this cell line, whereas midazolam was not metabolized suggesting lack of CYP3A activity. Compared with recombinant CYP2J2, terfenadine was hydroxylated in cardiomyocytes at a similar Km value of 1.5 μM. The Vmax of terfenadine hydroxylation in recombinant enzyme was found to be 29.4 pmol/pmol P450 per minute and in the cells 6.0 pmol/pmol P450 per minute. CYP2J2 activity in the cell line was inhibited by danazol, astemizole, and ketoconazole in submicromolar range, but also by xenobiotics known to cause cardiac adverse effects. Of the 14 compounds tested for CYP2J2 induction, only rosiglitazone increased mRNA expression, by 1.8-fold. This cell model can be a useful in vitro model to investigate the role of CYP2J2-mediated drug metabolism, arachidonic acid metabolism, and their association to drug induced cardiotoxicity. PMID:24021950

  15. Human Recombinant Cytochrome P450 Enzymes Display Distinct Hydrogen Peroxide Generating Activities During Substrate Independent NADPH Oxidase Reactions

    PubMed Central

    Mishin, Vladimir; Heck, Diane E.; Laskin, Debra L.; Laskin, Jeffrey D.

    2014-01-01

    Microsomal enzymes generate H2O2 in the presence of NADPH. In this reaction, referred to as “oxidase” activity, H2O2 is generated directly or indirectly via the formation of superoxide anion. In the presence of redox active transition metals, H2O2 can form highly toxic hydroxyl radicals and, depending on the “oxidase” activity of individual cytochrome P450 isoenzymes, this can compromise cellular functioning and contribute to tissue injury. In the present studies, we compared the initial rates of H2O2 generating activity of microsomal preparations containing various human recombinant cytochromes P450s. In the absence of cytochrome P450s the human recombinant NADPH cytochrome P450 reductase (CPR) generated low, but detectable amounts of H2O2 (∼0.04 nmol H2O2/min/100 units of reductase). Significantly greater activity was detected in preparations containing individual cytochrome P450s coexpressed with CPR (from 6.0 nmol H2O2/min/nmol P450 to 0.2 nmol/min/nmol P450); CYP1A1 was the most active, followed by CYP2D6, CYP3A4, CYP2E1, CYP4A11, CYP1A2, and CYP2C subfamily enzymes. H2O2 generating activity of the cytochrome P450s was independent of the ratio of CYP/CPR. Thus, similar H2O2 generating activity was noted with the same cytochrome P450s (CYP3A4, CYP2E1, and CYP2C9) expressed at or near the ratio of CYP/CPR in human liver microsomes (5–7), and when CPR was present in excess (CYP/CPR = 0.2–0.3). Because CYP3A4/5/7 represent up to 40% of total cytochrome P450 in the liver, these data indicate that these enzymes are the major source of H2O2 in human liver microsomes. PMID:25061110

  16. Thiomers: Inhibition of cytochrome P450 activity.

    PubMed

    Iqbal, Javed; Sakloetsakun, Duangkamon; Bernkop-Schnürch, Andreas

    2011-08-01

    The aim of the present study was to investigate the potential of different thiolated polymers (thiomers) on the catalytic activity of CYP450s on one hand and to explore new inhibitors for CYP activity on the other hand. Several thiolated polymers including poly(acrylic acid)-cysteine (PAA-cysteine), chitosan-thioglycolic acid (chitosan-TGA), and thiolated PEG-g-PEI copolymer along with brij 35, myrj 52 and the well-established CYPP450 inhibitor verapamil were screened for their CYP3A4 and CYP2A6 inhibitory activity, and their IC(50) values were determined. Both enzyme inhibition assays were performed in 96-well microtiter plates. 7-Benzyloxy-4-(trifluoromethyl)-coumarin (BFC) and 7-hydroxycoumarin (7-HC) were used as fluorescent substrates in order to determine CYP3A4 and CYP2A6 catalytic activity, respectively. All investigated compounds inhibited CYP3A4 as well as CYP2A6 activity. All tested (thiolated) polymers were found to be more potent inhibitors of CYP3A4 than of CYP2A6 catalytic activity. Apart from verapamil that is a known CYP3A4 inhibitor, brij 35 and myrj 52 were explored as potent inhibitors of CYP3A4 and CYP2A6 catalytic activity. Among the tested polymers, the rank order for CYP3A4 inhibition was PAA-cysteine (100 kDa)>brij 35>thiolated PEG-g-PEI copolymer (16 kDa)>myrj 52>PAA (100 kDa)>PAA-cysteine (450 kDa)>verapamil>PAA (450 kDa)>chitosan-TGA (150 kDa)>chitosan (150 kDa). On the other hand, the rank order of CYP2A6 inhibition was brij 35>PAA-cysteine (100kDa)>chitosan-TGA (150 kDa)>PAA (100 kDa)>thiolated PEG-g-PEI copolymer (16 kDa)>PAA-cysteine (450 kDa)>chitosan (150 kDa)>verapamil>PAA (450 kDa)>myrj 52. Thus, this study suggests that (thiolated) polymers display a promising potential to inhibit cytochrome P450s activity and might turn out to be potentially valuable tools for improving the oral bioavailability of actively secreted compounds by avoiding intestinal metabolism.

  17. Radical intermediates in the catalytic oxidation of hydrocarbons by bacterial and human cytochrome P450 enzymes.

    PubMed

    Jiang, Yongying; He, Xiang; Ortiz de Montellano, Paul R

    2006-01-17

    Cytochromes P450cam and P450BM3 oxidize alpha- and beta-thujone into multiple products, including 7-hydroxy-alpha-(or beta-)thujone, 7,8-dehydro-alpha-(or beta-)thujone, 4-hydroxy-alpha-(or beta-)thujone, 2-hydroxy-alpha-(or beta-)thujone, 5-hydroxy-5-isopropyl-2-methyl-2-cyclohexen-1-one, 4,10-dehydrothujone, and carvacrol. Quantitative analysis of the 4-hydroxylated isomers and the ring-opened product indicates that the hydroxylation proceeds via a radical mechanism with a radical recombination rate ranging from 0.7 +/- 0.3 x 10(10) s(-1) to 12.5 +/- 3 x 10(10) s(-1) for the trapping of the carbon radical by the iron-bound hydroxyl radical equivalent. 7-[2H]-alpha-Thujone has been synthesized and used to amplify C-4 hydroxylation in situations where uninformative C-7 hydroxylation is the dominant reaction. The involvement of a carbon radical intermediate is confirmed by the observation of inversion of stereochemistry of the methyl-substituted C-4 carbon during the hydroxylation. With an L244A mutation that slightly increases the P450(cam) active-site volume, this inversion is observed in up to 40% of the C-4 hydroxylated products. The oxidation of alpha-thujone by human CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 occurs with up to 80% C-4 methyl inversion, in agreement with a dominant radical hydroxylation mechanism. Three minor desaturation products are produced, with at least one of them via a cationic pathway. The cation involved is proposed to form by electron abstraction from a radical intermediate. The absence of a solvent deuterium isotope effect on product distribution in the P450cam reaction precludes a significant role for the P450 ferric hydroperoxide intermediate in substrate hydroxylation. The results indicate that carbon hydroxylation is catalyzed exclusively by a P450 ferryl species via radical intermediates whose detailed properties are substrate- and enzyme-dependent.

  18. Electrochemistry of Canis familiaris cytochrome P450 2D15 with gold nanoparticles: An alternative to animal testing in drug discovery.

    PubMed

    Rua, Francesco; Sadeghi, Sheila J; Castrignanò, Silvia; Valetti, Francesca; Gilardi, Gianfranco

    2015-10-01

    This work reports for the first time the direct electron transfer of the Canis familiaris cytochrome P450 2D15 on glassy carbon electrodes to provide an analytical tool as an alternative to P450 animal testing in the drug discovery process. Cytochrome P450 2D15, that corresponds to the human homologue P450 2D6, was recombinantly expressed in Escherichia coli and entrapped on glassy carbon electrodes (GC) either with the cationic polymer polydiallyldimethylammonium chloride (PDDA) or in the presence of gold nanoparticles (AuNPs). Reversible electrochemical signals of P450 2D15 were observed with calculated midpoint potentials (E1/2) of −191 ± 5 and −233 ± 4 mV vs. Ag/AgCl for GC/PDDA/2D15 and GC/AuNPs/2D15, respectively. These experiments were then followed by the electro-catalytic activity of the immobilized enzyme in the presence of metoprolol. The latter drug is a beta-blocker used for the treatment of hypertension and is a specific marker of the human P450 2D6 activity. Electrocatalysis data showed that only in the presence of AuNps the expected α-hydroxy-metoprolol product was present as shown by HPLC. The successful immobilization of the electroactive C. familiaris cytochrome P450 2D15 on electrode surfaces addresses the ever increasing demand of developing alternative in vitromethods for amore detailed study of animal P450 enzymes' metabolism, reducing the number of animals sacrificed in preclinical tests.

  19. Inhibition of Cytochrome P450 by Propolis in Human Liver Microsomes

    PubMed Central

    Ryu, Chang Seon; Oh, Soo Jin; Oh, Jung Min; Lee, Ji-Yoon; Lee, Sang Yoon; Chae, Jung-woo; Kwon, Kwang-il; Kim, Sang Kyum

    2016-01-01

    Although propolis is one of the most popular functional foods for human health, there have been no comprehensive studies of herb-drug interactions through cytochrome P450 (CYP) inhibition. The purpose of this study was to determine the inhibitory effects of propolis on the activities of CYP1A2, 2A6, 2B6, 2C9, 2C19, 2D6, 2E1 and 3A4 using pooled human liver microsomes (HLMs). Propolis inhibited CYP1A2, CYP2E1 and CYP2C19 with an IC50 value of 6.9, 16.8, and 43.1 μg/mL, respectively, whereas CYP2A6, 2B6, 2C9, 2D6, and 3A4 were unaffected. Based on half-maximal inhibitory concentration shifts between microsomes incubated with and without nicotinamide adenine dinucleotide phosphate, propolis-induced CYP1A2, CYP2C19, and CYP2E1 inhibition was metabolism-independent. To evaluate the interaction potential between propolis and therapeutic drugs, the effects of propolis on metabolism of duloxetine, a serotonin-norepinephrine reuptake inhibitor, were determined in HLMs. CYP1A2 and CYP2D6 are involved in hydroxylation of duloxetine to 4-hydroxy duloxetine, the major metabolite, which was decreased following propolis addition in HLMs. These results raise the possibility of interactions between propolis and therapeutic drugs metabolized by CYP1A2. PMID:27437087

  20. In vitro inhibitory effect of 1-aminobenzotriazole on drug oxidations catalyzed by human cytochrome P450 enzymes: a comparison with SKF-525A and ketoconazole.

    PubMed

    Emoto, Chie; Murase, Shigeo; Sawada, Yasufusa; Jones, Barry C; Iwasaki, Kazuhide

    2003-01-01

    1-Aminobenzotriazole (ABT) is widely used as a non-specific inhibitor of animal cytochrome P450 (CYP). In the present study, the inhibitory effect of ABT was investigated on drug oxidations catalyzed by human CYP isoforms. This inhibitory effect was compared with that of SKF-525A, another non-specific inhibitor, and ketoconazole, a potent inhibitor of CYP3A. Bacurovirus-expressed recombinant human CYP isoforms were used as an enzyme source. The specific activities for human CYP isoforms are: phenacetin O-deethylation, for CYP1A2; diclofenac 4'-hydroxylation, for CYP2C9; S-mephenytoin 4'-hydroxylation, for CYP2C19; bufuralol 1'-hydroxylation, for CYP2D6; chlorzoxazone 6-hydroxylation, for CYP2E1; testosterone 6beta-hydroxylation, nifedipine oxidation, and midazolam 1'-hydroxylation, for CYP3A4. ABT inhibited both CYP1A2-dependent activity (Ki=330 microM) and CYP2E1-dependent activity (Ki=8.7 microM). In contrast, SKF-525A weakly inhibited CYP1A2-dependent activities (46% inhibition at 1200 microM) and CYP2E1-dependent activities (65% inhibition at 1000 microM). ABT exhibited the highest Ki value for CYP2C9-dependent diclofenac 4'-hydroxylation among those determined by this assay (Ki=3500 microM). Moreover, SKF-525A showed strong inhibition of CYP2D6-dependent bufuralol 1'-hydroxylation (Ki=0.043 microM). Ketoconazole inhibited all tested drug oxidations, however, its inhibitory effect on CYP1A2-dependent activities was very weak (50% inhibition at 120 microM). ABT, SKF-525A, and ketoconazole showed different selectivity and had a wide range of Ki values for the drug oxidations catalyzed by human CYP enzymes. Therefore, we conclude that inhibitory studies designed to predict the contribution of CYP enzymes to the metabolism of certain compounds should be performed using multiple CYP inhibitors, such as ABT, SKF-525A, and ketoconazole.

  1. The inhaled glucocorticoid fluticasone propionate efficiently inactivates cytochrome P450 3A5, a predominant lung P450 enzyme

    PubMed Central

    Murai, Takahiro; Reilly, Christopher R.; Ward, Robert M.; Yost, Garold S.

    2010-01-01

    Inhaled glucocorticoid (GC) therapy is a vital part of the management of chronic asthma. GCs are metabolized by members of the cytochrome P450 3A family in both liver and lung, but the enzymes are differentially expressed. Selective inhibition of one or more P450 3A enzymes could substantially modify target and systemic concentrations of GCs. In this study, we have evaluated the mechanism-based inactivation of P450 3A4, 3A5 and 3A7 enzymes by GCs. Among the five major inhaled GCs approved for clinical use in the United States, fluticasone propionate (FLT) was the most potent mechanism-based inactivator of P450 3A5, the predominant P450 enzyme in the lung. FLT inactivated P450 3A5 in a time- and concentration-dependent manner with KI, kinact and partition ratio of 16 μM, 0.027 min-1 and 3, respectively. In contrast, FLT minimally inactivated P450 3A4 and did not inactivate 3A7, even with a concentration of 100 μM. The inactivation of P450 3A5 by FLT was irreversible because dialysis did not restore enzyme activity. In addition, the exogenous nucleophilic scavenger GSH did not attenuate inactivation. The prosthetic heme of P450 3A5 was not modified by FLT. The loss of P450 3A5 activity in lung cells could substantially decrease the metabolism of FLT, which would increase the effective FLT concentration at its target site, the respiratory epithelium. Also, inactivation of lung P450 3A5 could increase the absorption of inhaled FLT, which could lead to high systemic concentrations and adverse effects, such as life-threatening adrenal crises or cataracts that have been documented in children receiving high doses of inhaled GCs. PMID:20707410

  2. A three-dimensional model of aromatase cytochrome P450.

    PubMed Central

    Graham-Lorence, S.; Amarneh, B.; White, R. E.; Peterson, J. A.; Simpson, E. R.

    1995-01-01

    P450 hemeproteins comprise a large gene superfamily that catalyzes monooxygenase reactions in the presence of a redox partner. Because the mammalian members are, without exception, membrane-bound proteins, they have resisted structure-function analysis by means of X-ray crystallographic methods. Among P450-catalyzed reactions, the aromatase reaction that catalyzes the conversion of C19 steroids to estrogens is one of the most complex and least understood. Thus, to better understand the reaction mechanism, we have constructed a three-dimensional model of P450arom not only to examine the active site and those residues potentially involved in catalysis, but to study other important structural features such as substrate recognition and redox-partner binding, which require examination of the entire molecule (excepting the putative membrane-spanning region). This model of P450arom was built based on a "core structure" identified from the structures of the soluble, bacterial P450s (P450cam, P450terp, and P450BM-P) rather than by molecular replacement, after which the less conserved elements and loops were added in a rational fashion. Minimization and dynamic simulations were used to optimize the model and the reasonableness of the structure was evaluated. From this model we have postulated a membrane-associated hydrophobic region of aliphatic and aromatic residues involved in substrate recognition, a redox-partner binding region that may be unique compared to other P450s, as well as residues involved in active site orientation of substrates and an inhibitor of P450arom, namely vorozole. We also have proposed a scheme for the reaction mechanism in which a "threonine switch" determines whether oxygen insertion into the substrate molecule involves an oxygen radical or a peroxide intermediate. PMID:7549871

  3. Role of Protein–Protein Interactions in Cytochrome P450-Mediated Drug Metabolism and Toxicity

    PubMed Central

    2015-01-01

    Through their unique oxidative chemistry, cytochrome P450 monooxygenases (CYPs) catalyze the elimination of most drugs and toxins from the human body. Protein–protein interactions play a critical role in this process. Historically, the study of CYP–protein interactions has focused on their electron transfer partners and allosteric mediators, cytochrome P450 reductase and cytochrome b5. However, CYPs can bind other proteins that also affect CYP function. Some examples include the progesterone receptor membrane component 1, damage resistance protein 1, human and bovine serum albumin, and intestinal fatty acid binding protein, in addition to other CYP isoforms. Furthermore, disruption of these interactions can lead to altered paths of metabolism and the production of toxic metabolites. In this review, we summarize the available evidence for CYP protein–protein interactions from the literature and offer a discussion of the potential impact of future studies aimed at characterizing noncanonical protein–protein interactions with CYP enzymes. PMID:25133307

  4. Role of protein-protein interactions in cytochrome P450-mediated drug metabolism and toxicity.

    PubMed

    Kandel, Sylvie E; Lampe, Jed N

    2014-09-15

    Through their unique oxidative chemistry, cytochrome P450 monooxygenases (CYPs) catalyze the elimination of most drugs and toxins from the human body. Protein-protein interactions play a critical role in this process. Historically, the study of CYP-protein interactions has focused on their electron transfer partners and allosteric mediators, cytochrome P450 reductase and cytochrome b5. However, CYPs can bind other proteins that also affect CYP function. Some examples include the progesterone receptor membrane component 1, damage resistance protein 1, human and bovine serum albumin, and intestinal fatty acid binding protein, in addition to other CYP isoforms. Furthermore, disruption of these interactions can lead to altered paths of metabolism and the production of toxic metabolites. In this review, we summarize the available evidence for CYP protein-protein interactions from the literature and offer a discussion of the potential impact of future studies aimed at characterizing noncanonical protein-protein interactions with CYP enzymes.

  5. Isolation of the alkane inducible cytochrome P450 (P450alk) gene from the yeast Candida tropicalis

    EPA Science Inventory

    The gene for the alkane-inducible cytochrome P450, P450alk, has been isolated from the yeast Candida tropicalis by immunoscreening a λgt11 library. Isolation of the gene has been identified on the basis of its inducibility and partial DNA sequence. Transcripts of this gene were i...

  6. Inhibition selectivity of grapefruit juice components on human cytochromes P450.

    PubMed

    Tassaneeyakul, W; Guo, L Q; Fukuda, K; Ohta, T; Yamazoe, Y

    2000-06-15

    Five compounds including furanocoumarin monomers (bergamottin, 6', 7'-dihydroxybergamottin (DHB)), furanocoumarin dimers (4-¿¿6-hydroxy-71-¿(1-hydroxy-1-methyl)ethyl-4-methyl-6-(7-oxo-7H- furo¿3,2-g1benzopyran-4-yl)-4-hexenyl]oxy]-3,7-dimethyl- 2-octenyl]oxy]-7H-furo[3,2-g]¿1benzopyran-7-one (GF-I-1) and 4-¿¿6-hydroxy-7¿¿4-methyl-1-(1-methylethenyl)-6-(7-oxo-7H-furo¿3, 2-g1benzopyran-4-yl)-4-hexenylŏxy-3, 7-dimethyl-2-octenylŏxy-7H-furo¿3,2-g1benzopyran-7-one (GF-I-4)), and a sesquiterpene nootkatone have been isolated from grapefruit juice and screened for their inhibitory effects toward human cytochrome P450 (P450) forms using selective substrate probes. Addition of ethyl acetate extract of grapefruit juice into an incubation mixture resulted in decreased activities of CYP3A4, CYP1A2, CYP2C9, and CYP2D6. All four furanocoumarins clearly inhibited CYP3A4-catalyzed nifedipine oxidation in concentration- and time-dependent manners, suggesting that these compounds are mechanism-based inhibitors of CYP3A4. Of the furanocoumarins investigated, furanocoumarin dimers, GF-I-1 and GF-I-4, were the most potent inhibitors of CYP3A4. Inhibitor concentration required for half-maximal rate of inactivation (K(I)) values for bergamottin, DHB, GF-I-1, and GF-I-4 were calculated, respectively, as 40.00, 5. 56, 0.31, and 0.13 microM, whereas similar values were observed on their inactivation rate constant at infinite concentration of inhibitor (k(inact), 0.05-0.08 min(-1)). Apparent selectivity toward CYP3A4 does occur with the furanocoumarin dimers. In contrast, bergamottin showed rather stronger inhibitory effect on CYP1A2, CYP2C9, CYP2C19, and CYP2D6 than on CYP3A4. DHB inhibited CYP3A4 and CYP1A2 activities at nearly equivalent potencies. Among P450 forms investigated, CYP2E1 was the least sensitive to the inhibitory effect of furanocoumarin components. A sesquiterpene nootkatone has no significant effect on P450 activities investigated except for CYP2A6 and CYP2C19

  7. The role of human hepatic cytochrome P450 isozymes in the metabolism of racemic 3,4-methylenedioxy-methamphetamine and its enantiomers.

    PubMed

    Meyer, Markus R; Peters, Frank T; Maurer, Hans H

    2008-11-01

    The entactogen, 3,4-methylenedioxy-methamphetamine (MDMA), is a chiral drug that is mainly metabolized by N-demethylation and demethylenation. The involvement of cytochrome P450 (P450) isozymes in these metabolic steps has been studied by inhibition assays with human liver microsomes and, in part, with heterologously expressed human P450 isozymes. However, a comprehensive study on the involvement of all relevant human P450s has not been published yet. In addition, the chirality of this drug was not considered in these in vitro studies. The aim of the present work was to study the contribution of human P450 isozymes in the N-demethylation and demethylenation of racemic MDMA and its single enantiomers. MDMA and its enantiomers were incubated using heterologously expressed human P450s, and the metabolites were quantified by gas chromatography-mass spectrometry after derivatization with S-heptafluorobutyrylprolyl chloride. The highest contribution for the N-demethylation as calculated from the enzyme kinetic data, were obtained for CYP2B6 (R,S-MDMA), CYP1A2 (R-MDMA), and CYP2B6 (S-MDMA). In the case of the demethylenation, the isozyme with the highest contribution to net clearance for R,S-MDMA, R-MDMA, and S-MDMA was CYP2D6. For the first time, marked enantioselectivity was observed for N-demethylation and demethylenation by CYP2C19 with a preference for the S-enantiomers. In addition, CYP2D6 showed preference for S-MDMA in the case of demethylenation. None of the other isozymes showed major preferences for certain enantiomers. In conclusion, therefore, the different pharmacokinetic properties of the MDMA enantiomers may be caused by enantioselective metabolism by CYP2C19 and CYP2D6.

  8. Purification of the pyrazole-inducible cytochrome P-450 isozyme

    SciTech Connect

    Palakodety, R.; Clejan, L.; Krikun, G.; Feierman, D.; Cederbaum, A.I.

    1987-05-01

    The alcohol dehydrogenase inhibitor, pyrazole, appears to induce a cytochrome P-450 isozyme with properties similar to the ethanol-inducible P-450. The pyrazole-inducible P-450 isozyme was purified from the liver microsomes of rats treated with pyrazole essentially by the procedure of Ryan et al and also by chromatofocussing. The final preparation appeared homogenous by SDS-PAGE with an apparent molecular weight of 52,000, had a specific content of 11 nmoles P-450 per mg protein, showed very high activity of low K/sub m/ dimethylnitrosamine demethylase and produced a type II binding spectrum with dimethylsulfoxide. The enzyme was also active with aniline and aminopyrine as substrates. Pyrazole itself served as an excellent substrate with 4-hydroxy pyrazole being the product. An antibody against the pyrazole-inducible P-450 raised in chickens recognized a protein with mol.wt of about 52,000 in control microsomes. This band was highly enriched in microsomes from rats treated with pyrazole, 4-methyl-pyrazole, ethanol or acetone, but not phenobarbital or 3-methylcholanthrene. In summary, the pyrazole-inducible P-450 has been purified and appears to be identical in its catalytic and immunological properties to the alcohol-inducible P-450.

  9. Conformational selectivity in cytochrome P450 redox partner interactions

    PubMed Central

    Hollingsworth, Scott A.; Batabyal, Dipanwita; Nguyen, Brian D.; Poulos, Thomas L.

    2016-01-01

    The heme iron of cytochromes P450 must be reduced to bind and activate molecular oxygen for substrate oxidation. Reducing equivalents are derived from a redox partner, which requires the formation of a protein–protein complex. A subject of increasing discussion is the role that redox partner binding plays, if any, in favoring significant structural changes in the P450s that are required for activity. Many P450s now have been shown to experience large open and closed motions. Several structural and spectral studies indicate that the well-studied P450cam adopts the open conformation when its redox partner, putidaredoxin (Pdx), binds, whereas recent NMR studies indicate that this view is incorrect. Given the relevance of this discrepancy to P450 chemistry, it is important to determine whether Pdx favors the open or closed form of P450cam. Here, we have used both computational and experimental isothermal titration calorimetry studies that unequivocally show Pdx favors binding to the open form of P450cam. Analyses of molecular-dynamic trajectories also provide insights into intermediate conformational states that could be relevant to catalysis. PMID:27439869

  10. Evolving P450pyr Monooxygenase for Regio- and Stereoselective Hydroxylations.

    PubMed

    Yang, Yi; Li, Zhi

    2015-01-01

    P450pyr monooxygenase from Sphingomonas sp. HXN-200 catalysed the regio- and stereoselective hydroxylation at a non-activated carbon atom, a useful but challenging reaction in classic chemistry, with unique substrate specificity for a number of alicyclic compounds. New P450pyr mutants were developed by directed evolution with improved catalytic performance, thus significantly extending the application of the P450pyr monooxygenase family in biohydroxylation to prepare useful and valuable chiral alcohols. Directed evolution of P450pyr created new enzymes with improved S-enantioselectivity or R-enantioselectivity for the hydroxylation of N-benzyl pyrrolidine, enhanced regioselectivity for the hydroxylation of N-benzyl pyrrolidinone, and increased enantioselectivity for the hydroxylation of N-benzyl piperidinone, respectively. Directed evolution of P450pyr generated also mutants with fully altered regioselectivity (from terminal to subterminal) and newly created excellent S-enantioselectivity for the biohydroxylation of n-octane and propylbenzene, respectively, providing new opportunities for the regio- and enantioselective alkane functionalization. New P450pyr mutants were engineered as the first catalyst for highly selective terminal hydroxylation of n-butanol to 1,4-butanediol. Several novel, accurate, sensitive, simple, and HTS assays based on colorimetric or MS detection for measuring the enantio- and/or regioselectivity of hydroxylation were developed and proven to be practical in directed evolution. The P450pyr X-ray structure was obtained and used to guide the evolution. In silico modelling and substrate docking provided some insight into the influence of several important amino acid mutations of the engineered P450pyr mutants on the altered or enhanced regio- and enantioselectivity as well as new substrate acceptance. The obtained information and knowledge is useful for further engineering of P450pyr for other hydroxylations and oxidations.

  11. Cytochrome P450-mediated changes in oxycodone pharmacokinetics/pharmacodynamics and their clinical implications.

    PubMed

    Söderberg Löfdal, Karin C; Andersson, Marine L; Gustafsson, Lars L

    2013-05-01

    In recent years the use of the opioid oxycodone has increased markedly and replacing morphine as the first-line choice of opioid in several countries. There are formulations for oral immediate, oral extended release and intravenous use. The bioavailability is higher than for morphine and less variable. Oxycodone is primarily metabolized in the liver by the cytochrome P450 (CYP) enzymes with CYP3A as the major metabolic pathway and CYP2D6 as the minor metabolic pathway to noroxycodone, oxymorphone and noroxymorphone. Oxycodone exerts its analgesic effect via the µ-opioid receptor. The metabolism of CYP2D6 substrates varies to a large degree between individuals as a result of allele functionality. Poor metabolizers (PM) have two non-functional alleles, extensive metabolizers (EM) are homozygous with two functional alleles or heterozygous with one functional allele and ultrarapid metabolizers (UM) have more than two functional alleles. There are pronounced interethnic differences in the allele distribution. On the basis of studies performed thus far, oxycodone concentrations in comparison with EM are similar in PM and reduced in UM. The pharmacokinetics in UM are insufficiently investigated. Simultaneous inhibition of both CYP3A and CYP2D6 results in increased oxycodone concentrations and such a combination should be avoided. A similar effect is to be expected with use of a CYP3A inhibitor in CYP2D6 PM. Concomitant use of enzyme inducers such as rifampicin, St John's wort and carbamazepine should be avoided because of the risk of subtherapeutic concentrations of oxycodone. When the dosage of morphine may result in unpredictable bioavailability, like in patients with severe hepatic cirrhosis, oxycodone might be beneficial because it has higher and less variability in bioavailability between patients than morphine.

  12. The cytochrome P450 genesis locus: the origin and evolution of animal cytochrome P450s

    PubMed Central

    Nelson, David R.; Goldstone, Jared V.; Stegeman, John J.

    2013-01-01

    The neighbourhoods of cytochrome P450 (CYP) genes in deuterostome genomes, as well as those of the cnidarians Nematostella vectensis and Acropora digitifera and the placozoan Trichoplax adhaerens were examined to find clues concerning the evolution of CYP genes in animals. CYP genes created by the 2R whole genome duplications in chordates have been identified. Both microsynteny and macrosynteny were used to identify genes that coexisted near CYP genes in the animal ancestor. We show that all 11 CYP clans began in a common gene environment. The evidence implies the existence of a single locus, which we term the ‘cytochrome P450 genesis locus’, where one progenitor CYP gene duplicated to create a tandem set of genes that were precursors of the 11 animal CYP clans: CYP Clans 2, 3, 4, 7, 19, 20, 26, 46, 51, 74 and mitochondrial. These early CYP genes existed side by side before the origin of cnidarians, possibly with a few additional genes interspersed. The Hox gene cluster, WNT genes, an NK gene cluster and at least one ARF gene were close neighbours to this original CYP locus. According to this evolutionary scenario, the CYP74 clan originated from animals and not from land plants nor from a common ancestor of plants and animals. The CYP7 and CYP19 families that are chordate-specific belong to CYP clans that seem to have originated in the CYP genesis locus as well, even though this requires many gene losses to explain their current distribution. The approach to uncovering the CYP genesis locus overcomes confounding effects because of gene conversion, sequence divergence, gene birth and death, and opens the way to understanding the biodiversity of CYP genes, families and subfamilies, which in animals has been obscured by more than 600 Myr of evolution. PMID:23297357

  13. CYP2D6 gene polymorphisms in Brazilian patients with breast cancer treated with adjuvant tamoxifen and its association with disease recurrence

    PubMed Central

    De Ameida Melo, Mariella; De Vasconcelos-Valença, Rodrigo José; Neto, Fidelis Manes; Borges, Rafael Soares; Costa-Silva, Danylo Rafhael; Da Conceição Barros-Oliveira, Maria; Borges, Umbelina Soares; Alencar, Airlane Pereira; Silva, Vladimir Costa; Da Silva, Benedito Borges

    2016-01-01

    At present, there is controversy regarding the efficacy of tamoxifen in breast cancer patients who are carriers of cytochrome P450 2D6 (CYP2D6) gene polymorphisms, in terms of recurrence and overall survival. Thus, the aim of the present study was to investigate the association of the CYP2D6 *4, *10 and *17 gene polymorphisms with breast cancer recurrence in a Brazilian population. The cohort comprised 40 receptor-positive breast cancer patients without recurrence and 40 with distant recurrence. A 3-ml sample of peripheral blood was collected from each patient to determine the presence of the *4, *10 and *17 single nucleotide polymorphisms of the CYP2D6 gene by quantitative polymerase chain reaction analysis. There was no statistically significant difference between the two groups regarding the polymorphism frequency (P=0.246). The results revealed that intermediate metabolizers occurred in 5% of patients without recurrence and in 15% of those with distant recurrence. Poor metabolizers occurred in only 1 patient (2.5%) per group, and there was no significant difference between the groups (P=0.789). The present study concluded that the CYP2D6 gene polymorphism in women with hormone-sensitive breast cancer treated with tamoxifen was not associated with disease recurrence. PMID:27882219

  14. An investigation of CYP2D6 genotype and response to metoprolol CR/XL during dose titration in patients with heart failure: a MERIT-HF substudy.

    PubMed

    Batty, J A; Hall, A S; White, H L; Wikstrand, J; de Boer, R A; van Veldhuisen, D J; van der Harst, P; Waagstein, F; Hjalmarson, Å; Kjekshus, J; Balmforth, A J

    2014-03-01

    To explore the pharmacogenetic effects of the cytochrome P450 (CYP)2D6 genotype in patients with systolic heart failure treated using controlled/extended-release (CR/XL) metoprolol, this study assessed the CYP2D6 locus for the nonfunctional *4 allele (1846G>A; rs3892097) in the Metoprolol CR/XL Randomised Intervention Trial in Congestive Heart Failure (MERIT-HF; n = 605). Participants were characterized as extensive, intermediate, or poor metabolizers (EMs, IMs, or PMs, respectively), based on the presence of the CYP2D6*4 allele (EM: *1*1, 60.4%; IM: *1*4, 35.8%; and PM: *4*4, 3.8%). Plasma metoprolol concentrations were 2.1-/4.6-fold greater in the IM/PM groups as compared with the EM group (P < 0.0001). Metoprolol induced significantly lower heart rates and diastolic blood pressures during early titration, indicating a CYP2D6*4 allele dose-response effect (P < 0.05). These effects were not observed at maximal dose, suggesting a saturable effect. Genotype did not adversely affect surrogate treatment efficacy. CYP2D6 genotype modulates metoprolol pharmacokinetics/pharmacodynamics during early titration; however, the MERIT-HF-defined titration schedule remains recommended for all patients, regardless of genotype.

  15. Development of GC-MS based cytochrome P450 assay for the investigation of multi-herb interaction.

    PubMed

    Oh, Hyun-A; Lee, Hyunbeom; Kim, Donghak; Jung, Byung Hwa

    2017-02-15

    As drug interactions with cytochrome P450 enzymes become increasingly important in the field of drug discovery, a high-throughput screening method for analysing the effects of a drug is needed. We have developed a simple and rapid simultaneous analytical method using a cocktail approach for measuring the activities of seven cytochrome P450 enzymes (CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4). Human liver microsomes were used as a source for the seven cytochrome P450 enzymes, and a gas chromatography-mass spectrometry (GC-MS) was used for analysing their activities. Kinetic studies and inhibition assays of CYP enzymes were performed using known substrates and inhibitors for validating and comparing the reaction rates and time-dependent activities between methods using each substrate versus a method using a cocktail solution. The optimized cocktail method was successfully applied to evaluate the effects of the decoction of Socheongryong-tang (SCRT) on cytochrome P450 enzymes. Our cocktail method provides a simultaneous high-throughput activity assay using GC-MS for the first time. This method is applicable for analysing the drug interactions of various plant-derived mixtures.

  16. Genetics Home Reference: cytochrome P450 oxidoreductase deficiency

    MedlinePlus

    ... hormones, which are needed for normal development and reproduction. The hormonal changes associated with cytochrome P450 oxidoreductase ... which are essential for normal sexual development and reproduction; corticosteroids, which are involved in the body's response ...

  17. Interactions among Cytochromes P450 in Microsomal Membranes

    PubMed Central

    Davydov, Dmitri R.; Davydova, Nadezhda Y.; Sineva, Elena V.; Halpert, James R.

    2015-01-01

    The body of evidence of physiologically relevant P450-P450 interactions in microsomal membranes continues to grow. Here we probe oligomerization of human CYP3A4, CYP3A5, and CYP2E1 in microsomal membranes. Using a technique based on luminescence resonance energy transfer, we demonstrate that all three proteins are subject to a concentration-dependent equilibrium between the monomeric and oligomeric states. We also observed the formation of mixed oligomers in CYP3A4/CYP3A5, CYP3A4/CYP2E1, and CYP3A5/CYP2E1 pairs and demonstrated that the association of either CYP3A4 or CYP3A5 with CYP2E1 causes activation of the latter enzyme. Earlier we hypothesized that the intersubunit interface in CYP3A4 oligomers is similar to that observed in the crystallographic dimers of some microsomal drug-metabolizing cytochromes P450 (Davydov, D. R., Davydova, N. Y., Sineva, E. V., Kufareva, I., and Halpert, J. R. (2013) Pivotal role of P450-P450 interactions in CYP3A4 allostery: the case of α-naphthoflavone. Biochem. J. 453, 219–230). Here we report the results of intermolecular cross-linking of CYP3A4 oligomers with thiol-reactive bifunctional reagents as well as the luminescence resonance energy transfer measurements of interprobe distances in the oligomers of labeled CYP3A4 single-cysteine mutants. The results provide compelling support for the physiological relevance of the dimer-specific peripheral ligand-binding site observed in certain CYP3A4 structures. According to our interpretation, these results reveal an important general mechanism that regulates the activity and substrate specificity of the cytochrome P450 ensemble through interactions between multiple P450 species. As a result of P450-P450 cross-talk, the catalytic properties of the cytochrome P450 ensemble cannot be predicted by simple summation of the properties of the individual P450 species. PMID:25533469

  18. Simultaneous determination of bupropion, metroprolol, midazolam, phenacetin, omeprazole and tolbutamide in rat plasma by UPLC-MS/MS and its application to cytochrome P450 activity study in rats.

    PubMed

    Ma, Jianshe; Wang, Shuanghu; Zhang, Meiling; Zhang, Qingwei; Zhou, Yunfang; Lin, Chongliang; Lin, Guanyang; Wang, Xianqin

    2015-08-01

    A specific ultra-performance liquid chromatography tandem mass spectrometry method is described for the simultaneous determination of bupropion, metroprolol, midazolam, phenacetin, omeprazole and tolbutamide in rat plasma with diazepam as internal standard, which are the six probe drugs of the six cytochrome P450 isoforms CYP2B6, CYP2D6, CYP3A4, CYP1A2, CYP2C19 and CYP2C9. Plasma samples were protein precipitated with acetonitrile. The chromatographic separation was achieved using a UPLC® BEH C18 column (2.1 × 100 mm, 1.7 µm). The mobile phase consisted of acetonitrile and water (containing 0.1% formic acid) with gradient elution. The triple quadrupole mass spectrometric detection was operated by multiple reaction monitoring in positive electrospray ionization. The precisions were <13%, and the accuracy ranged from 93.3 to 110.4%. The extraction efficiency was >90.5%, and the matrix effects ranged from 84.3 to 114.2%. The calibration curves in plasma were linear in the range of 2-2000 ng/mL, with correlation coefficient (r(2) ) >0.995. The method was successfully applied to pharmacokinetic studies of the six probe drugs of the six CYP450 isoforms and used to evaluate the effects of erlotinib on the activities of CYP2B6, CYP2D6, CYP3A4, CYP1A2, CYP2C19 and CYP2C9 in rats. Erlotinib may inhibit the activity of CYP2B6 and CYP3A4, and may induce CYP2C9 of rats.

  19. The contribution of atom accessibility to site of metabolism models for cytochromes P450.

    PubMed

    Rydberg, Patrik; Rostkowski, Michal; Gloriam, David E; Olsen, Lars

    2013-04-01

    Three different types of atom accessibility descriptors are investigated in relation to site of metabolism predictions. To enable the integration of local accessibility we have constructed 2DSASA, a method for the calculation of the atomic solvent accessible surface area that is independent of 3D coordinates. The method was implemented in the SMARTCyp site of metabolism prediction models and improved the results by up to 4 percentage points for nine cytochrome P450 isoforms. The final models are made available at http://www.farma.ku.dk/smartcyp.

  20. Special issue: Cytochrome P450 structure and function: introduction.

    PubMed

    Munro, Andrew W; Leys, David

    2012-05-01

    The 17th International Conference on Cytochrome P450 Biochemistry, Biophysics and Structure was held in Manchester, UK from 26-30 June 2011. This issue of FEBS J. contains review and primary research articles reflecting the breadth of science covered at this conference, and reflecting the impact of P450-related research in fields as diverse as steroid metabolism, plant biochemistry, structural biology and biotechnology.

  1. Enhanced expression of cytochrome P450 in stomach cancer.

    PubMed Central

    Murray, G. I.; Taylor, M. C.; Burke, M. D.; Melvin, W. T.

    1998-01-01

    The cytochromes P450 have a central role in the oxidative activation and detoxification of a wide range of xenobiotics, including many carcinogens and several anti-cancer drugs. Thus the cytochrome P450 enzyme system has important roles in both tumour development and influencing the response of tumours to chemotherapy. Stomach cancer is one of the commonest tumours of the alimentary tract and environmental factors, including dietary factors, have been implicated in the development of this tumour. This type of tumour has a poor prognosis and responds poorly to current therapies. In this study, the presence and cellular localization of several major forms of P450, CYP1A, CYP2E1 and CYP3A have been investigated in stomach cancer and compared with their expression in normal stomach. There was enhanced expression of CYP1A and CYP3A in stomach cancer with CYP1A present in 51% and CYP3A present in 28% of cases. In contrast, no P450 was identified in normal stomach. The presence of CYP1A and CYP3A in stomach cancer provides further evidence for the enhanced expression of specific forms of cytochrome P450 in tumours and may be important therapeutically for the development of anti-cancer drugs that are activated by these forms of P450. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:9569036

  2. IDSite: An accurate approach to predict P450-mediated drug metabolism

    PubMed Central

    Li, Jianing; Schneebeli, Severin T.; Bylund, Joseph; Farid, Ramy; Friesner, Richard A.

    2011-01-01

    Accurate prediction of drug metabolism is crucial for drug design. Since a large majority of drugs metabolism involves P450 enzymes, we herein describe a computational approach, IDSite, to predict P450-mediated drug metabolism. To model induced-fit effects, IDSite samples the conformational space with flexible docking in Glide followed by two refinement stages using the Protein Local Optimization Program (PLOP). Sites of metabolism (SOMs) are predicted according to a physical-based score that evaluates the potential of atoms to react with the catalytic iron center. As a preliminary test, we present in this paper the prediction of hydroxylation and O-dealkylation sites mediated by CYP2D6 using two different models: a physical-based simulation model, and a modification of this model in which a small number of parameters are fit to a training set. Without fitting any parameters to experimental data, the Physical IDSite scoring recovers 83% of the experimental observations for 56 compounds with a very low false positive rate. With only 4 fitted parameters, the Fitted IDSite was trained with the subset of 36 compounds and successfully applied to the other 20 compounds, recovering 94% of the experimental observations with high sensitivity and specificity for both sets. PMID:22247702

  3. Food Polyphenol Apigenin Inhibits the Cytochrome P450 Monoxygenase Branch of the Arachidonic Acid Cascade.

    PubMed

    Steuck, Maryvonne; Hellhake, Stefan; Schebb, Nils Helge

    2016-11-30

    The product of cytochrome P450 monooxygenase (P450) ω-hydroxylation of arachidonic acid (AA), 20- hydroxyeicosatetraenoic acid (HETE), is a potent vasoconstrictor. Utilizing microsomes as well as individual CYP4 isoforms we demonstrate here that flavonoids can block 20-HETE formation. Apigenin inhibits CYP4F2 with an IC50 value of 4.6 μM and 20-HETE formation in human liver and kidney microsomes at 2.4-9.8 μM. Interestingly, the structurally similar naringenin shows no relevant effect on the formation of 20-HETE. Based on these in vitro data, it is impossible to evaluate if a relevant blockade of 20-HETE formation can result in humans from intake of polyphenols with the diet. However, the potency of apigenin is comparable to those of P450 inhibitors such as ketoconazole. Moreover, an IC50 value in the micromolar range is also described for the inhibition of CYP-mediated drug metabolism leading to food-drug interactions. The modulation of the arachidonic acid cascade by food polyphenols therefore warrants further investigation.

  4. Size-dependent effects of nanoparticles on the activity of cytochrome P450 isoenzymes

    SciTech Connect

    Froehlich, Eleonore; Kueznik, Tatjana; Samberger, Claudia; Roblegg, Eva; Wrighton, Christopher

    2010-02-01

    Nanoparticles are known to be able to interfere with cellular metabolism and to cause cytotoxicity and moreover may interfere with specific cellular functions. Serious effects on the latter include changes in liver cell function. The cytochrome P450 system is expressed in many cells but is especially important in hepatocytes and hormone-producing cells. The interaction of polystyrene nanoparticles with the most important drug-metabolizing cytochrome P450 isoenzymes, CYP3A4, CYP2D6, CYP2C9 and CYP2A1 expressed individually in insect cells (BACULOSOMES) was studied by the cleavage of substrates coupled to a fluorescent dye. The data obtained for individual isoenzymes were compared to metabolism in microsomes isolated from normal liver and from the hepatoma cell line H4-II-E-C3. Small (20-60 nm) carboxyl polystyrene particles but not larger (200 nm) ones reached high intracellular concentrations in the vicinity of the endoplasmic reticulum. These small particles inhibited the enzymatic activity of CYP450 isoenzymes in BACULOSOMES and substrate cleavage in normal liver microsomes. They moreover increased the effect of known inhibitors of the cytochrome P450 system (cimetidine, phenobarbital and paclitaxel). Substrate cleavage by the hepatoma cell line H4-II-E-C3 in contrast was undetectable, making this cell line unsuitable for this type of study. Our results thus demonstrate that nanoparticles can inhibit the metabolism of xenobiotics by the CYP450 system in model systems in vitro. Such inhibition could also potentially occur in vivo and possibly cause adverse effects in persons receiving medication.

  5. CYP2D6 polymorphisms may predict occurrence of adverse effects to tamoxifen: a preliminary retrospective study

    PubMed Central

    Wickramage, Ishani; Tennekoon, Kamani Hemamala; Ariyaratne, Merenchi Arachchige Yasantha; Hewage, Asanka Sudeshini; Sundralingam, Tharmini

    2017-01-01

    Introduction and aims Tamoxifen is an adjuvant drug effective in treating hormone receptor – positive breast cancer. However, 30%–50% of patients relapse and many develop adverse effects, such as hot flashes and fatty liver. Allelic variations altering the activity of cytochrome P450-2D6 enzyme affect response to tamoxifen by modulating metabolism of tamoxifen into its pharmacologically active metabolite endoxifen. Although association between CYP2D6 polymorphisms and recurrence of breast cancer in patients on tamoxifen had been reported, little evidence exists on association between these polymorphisms and adverse effects to tamoxifen. This study explored the association between CYP2D6 polymorphisms and tamoxifen effects, hitherto not studied in Sri Lanka. Methods A retrospective preliminary study was carried out on 24 breast cancer patients on tamoxifen for minimally 3 months attending National Cancer Institute, Maharagama, Sri Lanka. They were not on CYP2D6-inhibiting drugs, chemotherapy or other endocrine therapy, and had no conditions that could occur as adverse effects to tamoxifen before starting the therapy. Their blood samples were collected, DNA was extracted and genotyped using SNaPshot Multiplex sequencing based single-nucleotide polymorphism (SNP) assay. Results SNP/allele frequencies detected: 1846G>A (confirmatory of *4 null allele)=8.3%; 2549delA (confirmatory of *3 null allele)=50%; 100C>T (suggestive of *10 reduced functional allele, in addition to other alleles)=0%; combination of 2988G>A, −1584C and 2850C>T (strongly suggestive of *41 or other reduced functional allele)=4.8%. Occurrence of heterozygous 2988G>A SNP with −1584C and 2850C>T was significantly higher among those with ultrasound-diagnosed fatty liver following the commencement of tamoxifen therapy (P=0.029). Adverse effects occurred at a significantly higher frequency among postmenopausal women (P=0.041). Three patients who developed recurrence of breast cancer had no

  6. The impact of experimental design on assessing mechanism-based inactivation of CYP2D6 by MDMA (Ecstasy).

    PubMed

    Van, Linh M; Heydari, Amir; Yang, Jiansong; Hargreaves, Judith; Rowland-Yeo, Karen; Lennard, Martin S; Tucker, Geoffrey T; Rostami-Hodjegan, Amin

    2006-11-01

    MDMA (3-4-methylenedioxymethamphetamine, commonly known as Ecstasy) is a potent mechanism-based inhibitor (MBI) of cytochrome P450 2D6 (CYP2D6), causing quasi-irreversible inhibition of the enzyme in vitro. An evaluation of the in vivo implications of this phenomenon depends on the accuracy of the estimates of the parameters that define the inhibition in vitro, namely k(inact) (the maximal inhibition rate) and KI (the inactivation constant). These values are determined in two steps, pre-incubation of the enzyme with the inhibitor (enzyme inactivation), followed by dilution and further incubation to measure residual enzyme activity with a probe substrate. The aim of this study was to assess the impact of different dilutions and probe substrate concentrations on the estimates of k(inact) and KI using recombinantly expressed CYP2D6. Enzyme activity was measured by the conversion of dextromethorphan (DEX) to dextrorphan (DOR). Dilution factors of 1.25, 2, 5, 10, 25 and 50 (DEX at 30 microM) gave mean (+/-SE) values of k(inact) (min-1) of 0.20+/-0.06, 0.21+/-0.05, 0.31+/-0.06, 0.37+/-0.11, 0.51+/-0.10 and 0.58+/-0.08, respectively, and KI (microM) values (after correction for non-specific microsomal binding) of 2.22+/-1.90, 2.80+/-1.34, 5.78+/-2.07, 6.36+/-2.93, 3.99+/-1.57 and 4.86+/-1.37, respectively. Accordingly, high (e.g. 50 fold) and low (e.g. 1.25 fold) dilutions were associated with statistically significant differences in kinetic values (p <0.05). Varying DEX concentration (10-100 microM) was not associated with significant changes in k(inact) and KI values when a five-fold dilution was used (with the exception of a lower KI at 10 microM DEX). High dilution was also shown to reduce non-specific microsomal binding of MDMA. The changes in the two kinetic parameters were dependent on the experimental procedure and shown to be unlikely to have a material influence on the maximum inhibition of CYP2D6 expected in vivo after typical recreational doses of MDMA (50

  7. Induction time course of cytochromes P450 by phenobarbital and 3-methylcholanthrene pretreatment in liver microsomes of Alligator mississippiensis.

    PubMed

    Ertl, R P; Stegeman, J J; Winston, G W

    1998-05-01

    Alligator mississippiensis has at least two classes of inducible hepatic microsomal cytochromes P450 (CYP): (1) those induced by 3-methylcholanthrene (3MC), and (2) those induced by phenobarbital (PB). The rates of induction by these xenobiotic compounds are significantly slower than those reported for mammals. Carbon monoxide binding, western blots, and enzymatic activity measurements indicated that at least 48-72 hr are required to reach full induction. A methoxy-, ethoxy-, pentoxy, and benzyloxyphenoxazone (resorufin) O-dealkylation (MROD, EROD, PROD, and BROD) profile was indicative of substrate selectivity typical of 3MC- and PB-induced P450s. MROD and BROD showed the greatest ability to discriminate between alligator hepatic microsomes induced by 3MC and PB, respectively. This is in contrast to mammals, in which EROD is a biomarker of polycyclic aromatic hydrocarbon exposure because of its ability to discriminate the induction of CYP 1A. In a similar manner, PROD is a highly preferred activity of CYP 2B in mammals; thus, it is used to indicate CYP 2B induction. The induction of P450 by PB is a general phenomenon in mammals and birds. To the best of our knowledge, this is the first report demonstrating PB induction of P450 activities typical of the mammalian CYP 2 family isoforms in alligator or any reptilian liver. The importance of this finding to the evolution of CYP 2 family regulation by PB is heightened by the fact that induction by this xenobiotic is not common to fish and other lower vertebrates (Ertl RP and Winston GW, Comp Biochem Physiol, in press). Although indicating the presence of CYP 1A- and CYP 2B-like isoforms in alligator, it remains to be established how closely related these alligator P450s are to mammalian isoforms.

  8. Cloning, Functional Expression, and Subcellular Localization of Multiple NADPH-Cytochrome P450 Reductases from Hybrid Poplar1

    PubMed Central

    Ro, Dae-Kyun; Ehlting, Jürgen; Douglas, Carl J.

    2002-01-01

    NADPH:cytochrome P450 reductase (CPR) provides reducing equivalents to diverse cytochrome P450 monooxygenases. We isolated cDNAs for three CPR genes (CPR1, CPR2, and CPR3) from hybrid poplar (Populus trichocarpa × Populus deltoides). Deduced CPR2 and CPR3 amino acid sequences were 91% identical, but encoded isoforms divergent from CPR1 (72% identity). CPR1 and CPR2 were co-expressed together with the P450 enzyme cinnamate-4-hydroxylase (C4H) in yeast (Saccharomyces cerevisiae). Microsomes isolated from strains expressing CPR1/C4H or CPR2/C4H enhanced C4H activities approximately 10-fold relative to the C4H-only control strain, and catalyzed NADPH-dependent cytochrome c reduction. The divergent CPR isoforms (CPR1 and CPR2/3) contained entirely different N-terminal sequences, which are conserved in other plant CPRs and are diagnostic for two distinct classes of CPRs within the angiosperms. C-terminal green fluorescent protein fusions to CPR1 and CPR2 were constructed and expressed in both yeast and Arabidopsis. The fusion proteins expressed in yeast retained the ability to support C4H activity and, thus, were catalytically active. Both CPR::green fluorescent protein fusion proteins were strictly localized to the endoplasmic reticulum in transgenic Arabidopsis. The lack of localization of either isoform to chloroplasts, where P450s are known to be present, suggests that an alternative P450 reduction system may be operative in this organelle. Transcripts for the three poplar CPR genes were present ubiquitously in all tissues examined, but CPR2 showed highest expression in young leaf tissue. PMID:12481067

  9. Optimization of the Bacterial Cytochrome P450 BM3 System for the Production of Human Drug Metabolites

    PubMed Central

    Di Nardo, Giovanna; Gilardi, Gianfranco

    2012-01-01

    Drug metabolism in human liver is a process involving many different enzymes. Among them, a number of cytochromes P450 isoforms catalyze the oxidation of most of the drugs commercially available. Each P450 isoform acts on more than one drug, and one drug may be oxidized by more than one enzyme. As a result, multiple products may be obtained from the same drug, and as the metabolites can be biologically active and may cause adverse drug reactions (ADRs), the metabolic profile of a new drug has to be known before this can be commercialized. Therefore, the metabolites of a certain drug must be identified, synthesized and tested for toxicity. Their synthesis must be in sufficient quantities to be used for metabolic tests. This review focuses on the progresses done in the field of the optimization of a bacterial self-sufficient and efficient cytochrome P450, P450 BM3 from Bacillus megaterium, used for the production of metabolites of human enzymes. The progress made in the improvement of its catalytic performance towards drugs, the substitution of the costly NADPH cofactor and its immobilization and scale-up of the process for industrial application are reported. PMID:23443101

  10. No association between schizophrenia and polymorphisms within the genes for debrisoquine 4-hydroxylase (CYP2D6) and the dopamine transporter (DAT)

    SciTech Connect

    Daniels, J.; Williams, J.; Asherson, P.; McGuffin, P.; Owen, M.

    1995-02-27

    It has been suggested that the cytochrome P450 mono-oxygenase, debrisoquine 4-hydroxylase, is involved in the catabolism and processing of neurotransmitters subsequent to their reuptake into target cells. It is also thought to be related to the dopamine transporter that acts to take released dopamine back up into presynaptic terminals. The present study used the association approach to test the hypothesis that mutations in the genes for debrisoquine 4-hydroxylase (CYP2D6) and the dopamine transporter (DAT) confer susceptibility to schizophrenia. There were no differences in allele or genotype frequencies between patients and controls in the mutations causing the poor metaboliser phenotype in CYP2D6. In addition there was no association found between schizophrenia and a 48 bp repeat within the 3{prime} untranslated region of DAT. 18 refs., 2 tabs.

  11. Inhibitory effects of kale ingestion on metabolism by cytochrome P450 enzymes in rats.

    PubMed

    Yamasaki, Izumi; Yamada, Masayoshi; Uotsu, Nobuo; Teramoto, Sachiyuki; Takayanagi, Risa; Yamada, Yasuhiko

    2012-01-01

    Kale (Brassica oleracea L. var acephala DC) is a leafy green vegetable belonging to the cabbage family (Brassicaceae) that contains a large amount of health-promoting phytochemicals. There are any reports about the effects of kale ingestion on the chemoprevention function and mechanism, but the interactions between kale and drugs have not been researched. We investigated the effects of kale intake on cytochrome P450 (CYP) metabolism by using cocktail probe drugs, including midazolam (for CYP3A4), caffeine (for CYP1A2), dextromethorphan (for CYP2D6), tolbutamide (for CYP2C9), omeprazole (for CYP2C19), and chlorzoxazone (for CYP2E1). Cocktail drugs were administered into rats treated with kale and cabbage (2000 mg/kg) for a week. The results showed that kale intake induced a significant increase in plasma levels and the AUC of midazolam, caffeine, and dextromethorphan. In addition, the plasma concentration and AUC of omeprazole tended to increase. Additionally, no almost differences in the mRNA expression levels of CYP enzymes in the liver were observed. In conclusion, kale ingestion was considered to have an inhibitory effect on the activities of CYP3A4, 1A2, 2D6, and 2C19 for a reason competitive inhibition than inhibitory changes in the mRNA expressions.

  12. Cytochrome P450 inhibition potential of new psychoactive substances of the tryptamine class.

    PubMed

    Dinger, Julia; Woods, Campbell; Brandt, Simon D; Meyer, Markus R; Maurer, Hans H

    2016-01-22

    New psychoactive substances (NPS) are not tested for their cytochrome P450 (CYP) inhibition potential before consumption. Therefore, this potential was explored for tryptamine-derived NPS (TDNPS) including alpha-methyl tryptamines (AMTs), dimethyl tryptamines (DMTs), diallyl tryptamines (DALTs), and diisopropyl tryptamines (DiPTs) using test substrates preferred by the Food and Drug Administration in a cocktail assay. All tested TDNPS with the exception of DMT inhibited CYP2D6 activity with IC50 values below 100μM. DALTs inhibited CYP2D6 activity similar to paroxetine and quinidine and CYP1A2 activity comparable to fluvoxamine. 5-Methoxy-N,N-diallyltryptamine reduced in vivo the caffeine metabolism in rats consistent with in vitro results. Five of the AMTs also inhibited CYP1A2 activity comparable to amiodarone. AMT and 6-F-AMT inhibited CYP2A6 activity in the range of the test inhibitor tranylcypromine. CYP2B6 activity was inhibited by 19 tryptamines, but weakly compared to efavirenz. CYP2C8 activity was inhibited by five of the tested TDNPS and three showed values comparable to trimethoprim and gemfibrozil. Six tryptamines inhibited CYP2C9 and seven CYP2C19 activities comparable to fluconazole and chloramphenicol, respectively. Nineteen compounds showed inhibition of CYP2E1 and 18 of CYP3A activity, respectively. These results showed that the CYP inhibition by TDNPS might be clinically relevant, but clinical studies are needed to explore this further.

  13. Comprehensive characterization of cytochrome P450 isozyme selectivity across chemical libraries.

    PubMed

    Veith, Henrike; Southall, Noel; Huang, Ruili; James, Tim; Fayne, Darren; Artemenko, Natalia; Shen, Min; Inglese, James; Austin, Christopher P; Lloyd, David G; Auld, Douglas S

    2009-11-01

    The cytochrome P450 (CYP) gene family catalyzes drug metabolism and bioactivation and is therefore relevant to drug development. We determined potency values for 17,143 compounds against five recombinant CYP isozymes (1A2, 2C9, 2C19, 2D6 and 3A4) using an in vitro bioluminescent assay. The compounds included libraries of US Food and Drug Administration (FDA)-approved drugs and screening libraries. We observed cross-library isozyme inhibition (30-78%) with important differences between libraries. Whereas only 7% of the typical screening library was inactive against all five isozymes, 33% of FDA-approved drugs were inactive, reflecting the optimized pharmacological properties of the latter. Our results suggest that low CYP 2C isozyme activity is a common property of drugs, whereas other isozymes, such as CYP 2D6, show little discrimination between drugs and unoptimized compounds found in screening libraries. We also identified chemical substructures that differentiated between the five isozymes. The pharmacological compendium described here should further the understanding of CYP isozymes.

  14. Identification of cytochrome p450 enzymes involved in the metabolism of 4'-methyl-alpha-pyrrolidinopropiophenone, a novel scheduled designer drug, in human liver microsomes.

    PubMed

    Springer, Dietmar; Paul, Liane D; Staack, Roland F; Kraemer, Thomas; Maurer, Hans H

    2003-08-01

    4'-Methyl-alpha-pyrrolidinopropiophenone (MPPP) is a new drug of abuse. It is believed to have an abuse potential similar to that of amphetamines. Previous studies with Wistar rats had shown that MPPP was metabolized mainly by hydroxylation in position 4' followed by dehydrogenation to the corresponding carboxylic acid. The aim of the study presented here was to identify the human hepatic cytochrome p450 (p450) enzymes involved in the biotransformation of MPPP to 4'-hydroxymethyl-pyrrolidinopropiophenone. Baculovirus-infected insect cell microsomes and human liver microsomes were used for this purpose. Only CYP2C19 and CYP2D6 catalyzed this hydroxylation. The apparent Km and Vmax values for the latter were 9.8 +/- 2.5 microM and 13.6 +/- 0.7 pmol/min/pmol p450, respectively. CYP2C19 was not saturable over the tested substrate range (2-1000 microM) and interestingly showed a biphasic kinetic profile with apparent Km,1 and Vmax,1 values of 47.2 +/- 12.5 microM and 8.1 +/- 1.4 pmol/min/pmol p450, respectively. Experiments with pooled human liver microsomes also revealed biphasic nonsaturable kinetics with apparent Km,1 and Vmax,1 values of 57.0 +/- 20.9 microM and 199.7 +/- 59.7 pmol/min/mg of protein for the high affinity enzyme, respectively. Incubation of 2 microM MPPP with 3 microM of the CYP2D6-specific inhibitor quinidine resulted in significant (p < 0.01) turnover inhibition (11.8 +/- 1.6% of control). Based on kinetic data corrected for the relative activity factors, CYP2D6 is the enzyme mainly responsible for MPPP hydroxylation, confirmed by CYP2D6 inhibition studies.

  15. Metoclopramide is metabolized by CYP2D6 and is a reversible inhibitor, but not inactivator, of CYP2D6.

    PubMed

    Livezey, Mara R; Briggs, Erran D; Bolles, Amanda K; Nagy, Leslie D; Fujiwara, Rina; Furge, Laura Lowe

    2014-04-01

    1. Metoclopramide is a widely used clinical drug in a variety of medical settings with rare acute dystonic events reported. The aim of this study was to assess a previous report of inactivation of CYP2D6 by metoclopramide, to determine the contribution of various CYPs to metoclopramide metabolism, and to identify the mono-oxygenated products of metoclopramide metabolism. 2. Metoclopramide interacted with CYP2D6 with Type I binding and a Ks value of 9.56 ± 1.09 µM. CYP2D6 was the major metabolizer of metoclopramide and the two major products were N-deethylation of the diethyl amine and N-hydroxylation on the phenyl ring amine. CYPs 1A2, 2C9, 2C19, and 3A4 also metabolized metoclopramide. 3. While reversible inhibition of CYP2D6 was noted, CYP2D6 inactivation by metoclopramide was not observed under conditions of varying concentration or varying time using Supersomes(TM) or pooled human liver microsomes. 4. The major metabolites of metoclopramide were N-hydroxylation and N-deethylation formed most efficiently by CYP2D6 but also formed by all CYPs examined. Also, while metoclopramide is metabolized primarily by CYP2D6, it is not a mechanism-based inactivator of CYP2D6 in vitro.

  16. Expression of cytochromes P450, conjugating enzymes and nuclear receptors in human hepatoma HepaRG cells.

    PubMed

    Aninat, Caroline; Piton, Amélie; Glaise, Denise; Le Charpentier, Typhen; Langouët, Sophie; Morel, Fabrice; Guguen-Guillouzo, Christiane; Guillouzo, André

    2006-01-01

    Most human hepatocyte cell lines lack a substantial set of liver-specific functions, especially major cytochrome P450 (P450)-related enzyme activities, making them unrepresentative of in vivo hepatocytes. We have used the HepaRG cells, derived from a human hepatocellular carcinoma, which exhibit a high differentiation pattern after 2 weeks at confluency to determine whether they could mimic human hepatocytes for drug metabolism and toxicity studies. We show that when passaged at low density, these cells reversed to an undifferentiated morphology, actively divided, and, after having reached confluency, formed typical hepatocyte-like colonies surrounded by biliary epithelial-like cells. By contrast, when seeded at high density, hepatocyte-like clusters retained their typical differentiated morphology. Transcripts of various nuclear receptors (aryl hydrocarbon receptor, pregnane X receptor, constitutive androstane receptor, peroxisome proliferator-activated receptor alpha), P450s (CYP1A2, 2C9, 2D6, 2E1, 3A4), phase 2 enzymes (UGT1A1, GSTA1, GSTA4, GSTM1), and other liver-specific functions were estimated by reverse transcriptase-quantitative polymerase chain reaction and were found to be expressed, for most of them, at comparable levels in both confluent differentiated and high-density differentiated HepaRG cells and in cultured primary human hepatocytes. For several transcripts, the levels were strongly increased in the presence of 2% dimethyl sulfoxide. Measurement of basal activities of several P450s and their response to prototypical inducers as well as analysis of metabolic profiles and cytotoxicity of several compounds confirmed the functional resemblance of HepaRG cells to primary cultured human hepatocytes. In conclusion, HepaRG cells constitute the first human hepatoma cell line expressing high levels of the major P450s involved in xenobiotic metabolism and represent a reliable surrogate to human hepatocytes for drug metabolism and toxicity studies.

  17. Sequential metabolism of sesamin by cytochrome P450 and UDP-glucuronosyltransferase in human liver.

    PubMed

    Yasuda, Kaori; Ikushiro, Shinichi; Kamakura, Masaki; Munetsuna, Eiji; Ohta, Miho; Sakaki, Toshiyuki

    2011-09-01

    Our previous study revealed that CYP2C9 played a central role in sesamin monocatecholization. In this study, we focused on the metabolism of sesamin monocatechol that was further converted into the dicatechol form by cytochrome P450 (P450) or the glucuronide by UDP-glucuronosyltransferase (UGT). Catecholization of sesamin monocatechol enhances its antioxidant activity, whereas glucuronidation strongly reduces its antioxidant activity. In human liver microsomes, the glucuronidation activity was much higher than the catecholization activity toward sesamin monocatechol. In contrast, in rat liver microsomes, catecholization is predominant over glucuronidation. In addition, rat liver produced two isomers of the glucuronide, whereas human liver produced only one glucuronide. These results suggest a significant species-based difference in the metabolism of sesamin between humans and rats. Kinetic studies using recombinant human UGT isoforms identified UGT2B7 as the most important UGT isoform for glucuronidation of sesamin monocatechol. In addition, a good correlation was observed between the glucuronidation activity and UGT2B7-specific activity in in vitro studies using 10 individual human liver microsomes. These results strongly suggest that UGT2B7 plays an important role in glucuronidation of sesamin monocatechol. Interindividual difference among the 10 human liver microsomes is approximately 2-fold. These results, together with our previous results on the metabolism of sesamin by human P450, suggest a small interindividual difference in sesamin metabolism. We observed the methylation activity toward sesamin monocatechol by catechol O-methyl transferase (COMT) in human liver cytosol. On the basis of these results, we concluded that CYP2C9, UGT2B7, and COMT played essential roles in the metabolism of sesamin in the human liver.

  18. Cytochrome P450-mediated metabolism of vitamin D

    PubMed Central

    Jones, Glenville; Prosser, David E.; Kaufmann, Martin

    2014-01-01

    The vitamin D signal transduction system involves a series of cytochrome P450-containing sterol hydroxylases to generate and degrade the active hormone, 1α,25-dihydroxyvitamin D3, which serves as a ligand for the vitamin D receptor-mediated transcriptional gene expression described in companion articles in this review series. This review updates our current knowledge of the specific anabolic cytochrome P450s involved in 25- and 1α-hydroxylation, as well as the catabolic cytochrome P450 involved in 24- and 23-hydroxylation steps, which are believed to initiate inactivation of the vitamin D molecule. We focus on the biochemical properties of these enzymes; key residues in their active sites derived from crystal structures and mutagenesis studies; the physiological roles of these enzymes as determined by animal knockout studies and human genetic diseases; and the regulation of these different cytochrome P450s by extracellular ions and peptide modulators. We highlight the importance of these cytochrome P450s in the pathogenesis of kidney disease, metabolic bone disease, and hyperproliferative diseases, such as psoriasis and cancer; as well as explore potential future developments in the field. PMID:23564710

  19. Homotropic cooperativity of monomeric cytochrome P450 3A4

    SciTech Connect

    Baas, Bradley J.; Denisov, Ilia G.; Sligar, Stephen G.

    2010-11-16

    Mechanistic studies of mammalian cytochrome P450s are often obscured by the phase heterogeneity of solubilized preparations of membrane enzymes. The various protein-protein aggregation states of microsomes, detergent solubilized cytochrome or a family of aqueous multimeric complexes can effect measured substrate binding events as well as subsequent steps in the reaction cycle. In addition, these P450 monooxygenases are normally found in a membrane environment and the bilayer composition and dynamics can also effect these catalytic steps. Here, we describe the structural and functional characterization of a homogeneous monomeric population of cytochrome P450 3A4 (CYP 3A4) in a soluble nanoscale membrane bilayer, or Nanodisc [Nano Lett. 2 (2002) 853]. Cytochrome P450 3A4:Nanodisc assemblies were formed and purified to yield a 1:1 ratio of CYP 3A4 to Nanodisc. Solution small angle X-ray scattering was used to structurally characterize this monomeric CYP 3A4 in the membrane bilayer. The purified CYP 3A4:Nanodiscs showed a heretofore undescribed high level of homotropic cooperativity in the binding of testosterone. Soluble CYP 3A4:Nanodisc retains its known function and shows prototypic hydroxylation of testosterone when driven by hydrogen peroxide. This represents the first functional characterization of a true monomeric preparation of cytochrome P450 monooxygenase in a phospholipid bilayer and elucidates new properties of the monomeric form.

  20. Immunohistochemical localization of cytochrome P450 aromatase in equine gonads.

    PubMed

    Almadhidi, J; Seralini, G E; Fresnel, J; Silberzahn, P; Gaillard, J L

    1995-06-01

    Estrogens are the major steroids produced by equine gonads. To identify the cells responsible for estrogen synthesis, an antiserum against purified equine testicular cytochrome P450 aromatase was produced in rabbits. The reactivity and specificity of the antiserum were assessed by ELISA, immunoblot analysis, and immunoneutralization studies. Immunofluorescence microscopy demonstrated that in the male gonad, cytochrome P450 aromatase (P450arom) was localized in the interstitial tissue, whereas, under the experimental conditions used, the Sertoli and germ cells did not show any specific staining. In the ovary, the granulosa cells of small follicles exhibited faint immunofluorescent staining for P450arom and the granulosa cells of large, viable more follicles showed a high degree of immunoreactivity. In the corpus luteum, all the luteinized cells showed immunoreactivity. No immunoreactivity was detected in other cells of small and large viable follicles. Immunolocalization of P450arom in the equine testicular Leydig cells and in ovarian granulosa and luteinized cells indicates that these cells have the ability to metabolize androgens to estrogens and possibly to catechol estrogens.

  1. Interaction potential of Trigonella foenum graceum through cytochrome P450 mediated inhibition

    PubMed Central

    Ahmmed, Sk Milan; Mukherjee, Pulok K.; Bahadur, Shiv; Kar, Amit; Mukherjee, Kakali; Karmakar, Sanmoy; Bandyopadhyay, Arun

    2015-01-01

    Objective: The seeds of Trigonella foenum-graecum (TFG) (family: Leguminosae) are widely consumed both as a spice in food and Traditional Medicine in India. The present study was undertaken to evaluate the inhibitory effect of standardized extract of TFG and its major constituent trigonelline (TG) on rat liver microsome (RLM) and cytochrome P450 (CYP450) drug metabolizing isozymes (CYP3A4 and CYP2D6), which may indicate the possibility of a probable unwanted interaction. Materials and Methods: Reverse phase-high performance liquid chromatography method was developed to standardize the hydroalcoholic seed extract with standard TG. The inhibitory potential of the extract and TG was evaluated on RLM and CYP isozymes using CYP450-carbon monoxide (CYP450-CO) complex assay and fluorescence assay, respectively. Results: The content of TG in TFG was found to be 3.38% (w/w). The CYP-CO complex assay showed 23.32% inhibition on RLM. Fluorescence study revealed that the extract and the biomarker had some inhibition on CYP450 isozymes e.g. CYP3A4 and CYP2D6 (IC50 values of the extract: 102.65 ± 2.63–142.23 ± 2.61 µg/ml and TG: 168.73 ± 4.03–180.90 ± 2.49 µg/ml) which was very less compared to positive controls ketoconazole and quinidine. Inhibition potential of TFG was little higher than TG but very less compared to positive controls. Conclusions: From the present study, we may conclude that the TFG or TG has very less potential to inhibit the CYP isozymes (CYP3A4, CYP2D6), so administration of this plant extract or its biomarker TG may be safe. PMID:26600643

  2. Metabolism of MPTP by cytochrome P4502D6 and the demonstration of 2D6 mRNA in human foetal and adult brain by in situ hybridization.

    PubMed

    Gilham, D E; Cairns, W; Paine, M J; Modi, S; Poulsom, R; Roberts, G C; Wolf, C R

    1997-01-01

    1. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a thermal breakdown product of synthetic 'street' heroin, is known to cause Parkinson's Disease-like symptoms in man. 2. The mechanism of action of this neurotoxin is thought to involve activation by the monoamine oxidase B system and subsequent toxicity by inhibition of neuronal mitochondrial respiration. The manifestation of toxicity will be a balance between the rate of activation of this compound versus its rate of inactivation through metabolism by enzymes such as the cytochrome P450-dependent monooxygenases. 3. In this report we demonstrate that MPTP N-demethylation, a detoxification pathway, is catalysed by cytochrome P450 CYP2D6 and up to 40% of the hepatic metabolism is mediated by this enzyme. 4. Perhaps more importantly we also demonstrate by in situ hybridization that CYP2D6 is localized in the pigmented neurons of the substantia nigra indicating that 2D6-mediated detoxification will occur in target cells. 5. These data present evidence that CYP2D6 will be a factor in susceptibility to MPTP neuronal toxicity and provide a biochemical rationale for the genetic observations linking a polymorphism at the CYP2D6 locus with susceptibility to Parkinson's.

  3. Design and synthesis of 6-fluoro-2-naphthyl derivatives as novel CCR3 antagonists with reduced CYP2D6 inhibition.

    PubMed

    Sato, Ippei; Morihira, Koichiro; Inami, Hiroshi; Kubota, Hirokazu; Morokata, Tatsuaki; Suzuki, Keiko; Iura, Yosuke; Nitta, Aiko; Imaoka, Takayuki; Takahashi, Toshiya; Takeuchi, Makoto; Ohta, Mitsuaki; Tsukamoto, Shin-Ichi

    2008-09-15

    In our previous study on discovering novel types of CCR3 antagonists, we found a fluoronaphthalene derivative (1) that exhibited potent CCR3 inhibitory activity with an IC(50) value of 20 nM. However, compound 1 also inhibited human cytochrome P450 2D6 (CYP2D6) with an IC(50) value of 400 nM. In order to reduce its CYP2D6 inhibitory activity, we performed further systematic structural modifications on 1. In particular, we focused on reducing the number of lipophilic moieties in the biphenyl part of 1, using ClogD(7.4) values as the reference index of lipophilicity. This research led to the identification of N-{(3-exo)-8-[(6-fluoro-2-naphthyl)methyl]-8-azabicyclo[3.2.1]oct-3-yl}-3-(piperidin-1-ylcarbonyl)isonicotinamide 1-oxide (30) which showed comparable CCR3 inhibitory activity (IC(50)=23 nM) with much reduced CYP2D6 inhibitory activity (IC(50)=29,000 nM) compared with 1.

  4. Technology evaluation: MetXia-P450, Oxford Biomedica.

    PubMed

    Hunt, S

    2001-12-01

    Oxford BioMedica is developing gene therapies for treating various forms of cancer. The therapies comprise the transfer of several anticancer genes at a time using a recombinant retrovirus approach based on the company's proprietary LTR Deleted Vector and Accelerated Vector Evolution technologies [238147]. MetXia-P450 is a gene therapy construct containing the cytochrome P450 gene CYP2B6, and is designed to be injected directly into tumors to convert them into 'drug factories'. This is achieved because CYP2B6 converts the inactive produg form cyclophosphamide into the active cytotoxic drug. MetXia-P450 is in phase I/II trials for breast cancer [339582].

  5. Repellents Inhibit P450 Enzymes in Stegomyia (Aedes) aegypti

    PubMed Central

    Jaramillo Ramirez, Gloria Isabel; Logan, James G.; Loza-Reyes, Elisa; Stashenko, Elena; Moores, Graham D.

    2012-01-01

    The primary defence against mosquitoes and other disease vectors is often the application of a repellent. Despite their common use, the mechanism(s) underlying the activity of repellents is not fully understood, with even the mode of action of DEET having been reported to be via different mechanisms; e.g. interference with olfactory receptor neurones or actively detected by olfactory receptor neurones on the antennae or maxillary palps. In this study, we discuss a novel mechanism for repellence, one of P450 inhibition. Thirteen essential oil extracts from Colombian plants were assayed for potency as P450 inhibitors, using a kinetic fluorometric assay, and for repellency using a modified World Health Organisation Pesticide Evaluations Scheme (WHOPES) arm-in cage assay with Stegomyia (Aedes) aegypti mosquitoes. Bootstrap analysis on the inhibition analysis revealed a significant correlation between P450-inhibition and repellent activity of the oils. PMID:23152795

  6. A Quantitative High-Throughput 96-well plate Fluorescence Assay for Mechanism-Based Inactivators of Cytochromes P450 Exemplified using CYP2B6

    PubMed Central

    Kenaan, Cesar; Zhang, Haoming; Hollenberg, Paul F.

    2010-01-01

    Mechanism-based inactivators such as bergamottin are useful chemical tools for identifying the roles of specific active-site amino acid residues in the reactions catalyzed by the cytochromes P450 (CYPs or P450s) that are responsible for the metabolism of a wide variety of drugs and endogenous substrates. In clinical settings mechanism-based inactivation of P450s involved in xenobiotic metabolism has the potential to lead to adverse drug-drug interactions and assays to identify and characterize drug candidates as P450 inactivators are important in drug discovery and development. Here we present a quantitative high-throughput protocol for investigating cytochrome P450 mechanism-based inactivators using the example of CYP2B6 and bergamottin to illustrate the finer points of this protocol. This protocol details the adaptation of a 7-ethoxytrifluoromethyl coumarin (7-EFC) O-deethylation fluorescence activity assay to a 96-well microtiter plate format and uses a plate-reader to detect the fluorescence of the product. Compared to previous methods, this protocol requires less P450 and takes significantly less time while greatly increasing throughput. The protocol as written takes approximately two hours to complete. The principles and procedures outlined in this protocol can be easily adapted to other inactivators, P450 isoforms, substrates and plate-readers. PMID:20885377

  7. Gender-specific induction of cytochrome P450s in nonylphenol-treated FVB/NJ mice.

    PubMed

    Hernandez, Juan P; Chapman, Laura M; Kretschmer, Xiomara C; Baldwin, William S

    2006-10-15

    Nonylphenol (NP) is a breakdown product of nonylphenol ethoxylates, which are used in a variety of industrial, agricultural, household cleaning, and beauty products. NP is one of the most commonly found toxicants in the United States and Europe and is considered a toxicant of concern because of its long half-life. NP is an environmental estrogen that also activates the pregnane X-receptor (PXR) and in turn induces P450s. No study to date has examined the gender-specific effects of NP on hepatic P450 expression. We provided NP at 0, 50 or 75 mg/kg/day for 7 days to male and female FVB/NJ mice and compared their P450 expression profiles. Q-PCR was performed on hepatic cDNA using primers to several CYP isoforms regulated by PXR or its relative, the constitutive androstane receptor (CAR). In female mice, NP induced Cyp2b10 and Cyp2b13, and downregulated the female-specific P450s, Cyp3a41 and Cyp3a44. In contrast, male mice treated with NP showed increased expression of Cyp2a4, Cyp2b9, and Cyp2b10. Western blots confirmed induction of Cyp2b subfamily members in both males and females. Consistent with the Q-PCR data, Western blots showed dose-dependent downregulation of Cyp3a only in females and induction of Cyp2a only in males. The overall increase in female-predominant P450s in males (Cyp2a4, 2b9) and the decrease in female-predominant P450s in females (Cyp3a41, 3a44) suggest that NP is in part feminizing the P450 profile in males and masculinizing the P450 profile in females. Testosterone hydroxylation was also altered in a gender-specific manner, as testosterone 16alpha-hydroxylase activity was only induced in NP-treated males. In contrast, NP-treated females demonstrated a greater propensity for metabolizing zoxazolamine probably due to greater Cyp2b induction in females. In conclusion, NP causes gender-specific P450 induction and therefore exposure to NP may cause distinct pharmacological and toxicological effects in males compared to females.

  8. Gender-specific induction of cytochrome P450s in nonylphenol-treated FVB/NJ mice

    SciTech Connect

    Hernandez, Juan P.; Chapman, Laura M.; Kretschmer, Xiomara C.; Baldwin, William S. . E-mail: wbaldwin@utep.edu

    2006-10-15

    Nonylphenol (NP) is a breakdown product of nonylphenol ethoxylates, which are used in a variety of industrial, agricultural, household cleaning, and beauty products. NP is one of the most commonly found toxicants in the United States and Europe and is considered a toxicant of concern because of its long half-life. NP is an environmental estrogen that also activates the pregnane X-receptor (PXR) and in turn induces P450s. No study to date has examined the gender-specific effects of NP on hepatic P450 expression. We provided NP at 0, 50 or 75 mg/kg/day for 7 days to male and female FVB/NJ mice and compared their P450 expression profiles. Q-PCR was performed on hepatic cDNA using primers to several CYP isoforms regulated by PXR or its relative, the constitutive androstane receptor (CAR). In female mice, NP induced Cyp2b10 and Cyp2b13, and downregulated the female-specific P450s, Cyp3a41 and Cyp3a44. In contrast, male mice treated with NP showed increased expression of Cyp2a4, Cyp2b9, and Cyp2b10. Western blots confirmed induction of Cyp2b subfamily members in both males and females. Consistent with the Q-PCR data, Western blots showed dose-dependent downregulation of Cyp3a only in females and induction of Cyp2a only in males. The overall increase in female-predominant P450s in males (Cyp2a4, 2b9) and the decrease in female-predominant P450s in females (Cyp3a41, 3a44) suggest that NP is in part feminizing the P450 profile in males and masculinizing the P450 profile in females. Testosterone hydroxylation was also altered in a gender-specific manner, as testosterone 16{alpha}-hydroxylase activity was only induced in NP-treated males. In contrast, NP-treated females demonstrated a greater propensity for metabolizing zoxazolamine probably due to greater Cyp2b induction in females. In conclusion, NP causes gender-specific P450 induction and therefore exposure to NP may cause distinct pharmacological and toxicological effects in males compared to females.

  9. Cytochrome P450 3A, NADPH cytochrome P450 reductase and cytochrome b5 in the upper airways in horse.

    PubMed

    Tydén, E; Olsén, L; Tallkvist, J; Tjälve, H; Larsson, P

    2008-08-01

    Gene and protein expression as well as catalytic activity of cytochrome P450 (CYP) 3A were studied in the nasal olfactory and respiratory mucosa and the tracheal mucosa of the horse. We also examined the activity of NADPH cytochrome P450 reductase (NADPH P450 reductase), the amount of cytochrome b(5) and the total CYP content in these tissues. Comparative values for the above were obtained using liver as a control. The CYP3A related catalytic activity in the tissues of the upper airways was considerably higher than in the liver. The CYP3A gene and protein expression, on the other hand, was higher in the liver than in the upper airway tissues. Thus, the pattern of CYP3A metabolic activity does not correlate with the CYP3A gene and protein expression. Our results showed that the activity of NADPH P450 reductase and the level of cytochrome b(5) in the relation to the gene and protein expression of CYP3A were higher in the tissues of the upper airways than in the liver. It is concluded that CYP3A related metabolism in horse is not solely dependent on the expression of the enzyme but also on adequate levels of NADPH P450 reductase and cytochrome b(5).

  10. Spectroscopic quantitation of cytochrome P-450 in human lung microsomes.

    PubMed

    Wheeler, C W; Guenthner, T M

    1990-01-01

    The cytochrome P-450 content of human lung microsomes was measured by difference spectroscopy of the carbon monoxide-complexed hemoprotein. These measurements were only possible after the microsome preparation had been subjected to centrifugation over a discontinuous sucrose gradient, to remove an opaque black contaminant. The specific concentration of total cytochrome P-450 in human lung microsomes is essentially identical to that of microsomes prepared under identical conditions from untreated baboon lungs, but is only 0.7% of the specific content found in lung microsomes from untreated rabbits. These measurements correspond well to the observed metabolic capacities of the various microsome samples.

  11. Genomewide annotation and comparative genomics of cytochrome P450 monooxygenases (P450s) in the polypore species Bjerkandera adusta, Ganoderma sp. and Phlebia brevispora.

    PubMed

    Syed, Khajamohiddin; Nelson, David R; Riley, Robert; Yadav, Jagjit S

    2013-01-01

    Genomewide annotation of cytochrome P450 monooxygenases (P450s) in three white-rot species of the fungal order Polyporales, namely Bjerkandera adusta, Ganoderma sp. and Phlebia brevispora, revealed a large contingent of P450 genes (P450ome) in their genomes. A total of 199 P450 genes in B. adusta and 209 P450 genes each in Ganoderma sp. and P. brevispora were identified. These P450omes were classified into families and subfamilies as follows: B. adusta (39 families, 86 subfamilies), Ganoderma sp. (41 families, 105 subfamilies) and P. brevispora (42 families, 111 subfamilies). Of note, the B. adusta genome lacked the CYP505 family (P450foxy), a group of P450-CPR fusion proteins. The three polypore species revealed differential enrichment of individual P450 families in their genomes. The largest CYP families in the three genomes were CYP5144 (67 P450s), CYP5359 (46 P450s) and CYP5344 (43 P450s) in B. adusta, Ganoderma sp. and P. brevispora, respectively. Our analyses showed that tandem gene duplications led to expansions in certain P450 families. An estimated 33% (72 P450s), 28% (55 P450s) and 23% (49 P450s) of P450ome genes were duplicated in P. brevispora, B. adusta and Ganoderma sp., respectively. Family-wise comparative analysis revealed that 22 CYP families are common across the three Polypore species. Comparative P450ome analysis with Ganoderma lucidum revealed the presence of 143 orthologs and 56 paralogs in Ganoderma sp. Multiple P450s were found near the characteristic biosynthetic genes for secondary metabolites, namely polyketide synthase (PKS), non-ribosomal peptide synthetase (NRPS), terpene cyclase and terpene synthase in the three genomes, suggesting a likely role of these P450s in secondary metabolism in these Polyporales. Overall, the three species had a richer P450 diversity both in terms of the P450 genes and P450 subfamilies as compared to the model white-rot and brown-rot polypore species Phanerochaete chrysosporium and Postia placenta.

  12. Polymorphisms in the Human Cytochrome P450 and Arylamine N-Acetyltransferase: Susceptibility to Head and Neck Cancers

    PubMed Central

    Khlifi, Rim; Messaoud, Olfa; Rebai, Ahmed; Hamza-Chaffai, Amel

    2013-01-01

    The occurrence of head and neck cancer (HNC) is associated with smoking and alcohol drinking. Tobacco smoking exposes smokers to a series of carcinogenic chemicals. Cytochrome P450 enzymes (CYP450s), such as CYP1A1, CYP1B1, and CYP2D6, usually metabolize carcinogens to their inactive derivatives, but they occasionally convert the chemicals to more potent carcinogens. In addition, via CYP450 (CYP2E1) oxidase, alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Furthermore, two N-acetyltransferase isozymes (NATs), NAT1 and NAT2, are polymorphic and catalyze both N-acetylation and O-acetylation of aromatic and heterocyclic amine carcinogens. Genetic polymorphisms are associated with a number of enzymes involved in the metabolism of carcinogens important in the induction of HNC. It has been suggested that such polymorphisms may be linked to cancer susceptibility. In this paper, we select four cytochrome P450 enzymes (CYP1A1, CYP1BA1, CYP2D6, and CYP2E1), and two N-acetyltransferase isozymes (NAT1 and NAT2) in order to summarize and analyze findings from the literature related to HNC risk by focusing on (i) the interaction between these genes and the environment, (ii) the impact of genetic defect on protein activity and/or expression, and (iii) the eventual involvement of race in such associations. PMID:24151610

  13. Carbon monoxide-bound red blood cells protect red blood cell transfusion-induced hepatic cytochrome P450 impairment in hemorrhagic-shock rats.

    PubMed

    Ogaki, Shigeru; Taguchi, Kazuaki; Watanabe, Hiroshi; Otagiri, Masaki; Maruyama, Toru

    2013-01-01

    Red blood cell (RBC) transfusions for massive hemorrhage induce systemic ischemic-reperfusion and influence the disposition and pharmacological activity of drugs as a result of a reduction in the level of expression and activity of cytochrome P450s (P450). It was reported that, when organ-preserving solutions are exposed to carbon monoxide (CO), the treatment was effective in suppressing the postreperfusion reduction in renal P450 levels in cases of kidney transplantation. Therefore, we hypothesized that transfusions with RBC that contain bound CO (CO-RBC) would protect the hepatic level of rat P450 during a massive hemorrhage, compared with plasma expanders and RBC resuscitation. To achieve this, we created 40% hemorrhagic-shock model rats, followed by resuscitation, with use of recombinant human serum albumin, RBCs, and CO-RBCs. At 1 hour after resuscitation, the expressions of hepatic P450 isoforms (1A2, 2C11, 2E1, and 3A2) were significantly decreased in the RBC resuscitation group, compared with the sham group. Such alterations in hepatic P450 significantly resulted in an increase in the plasma concentrations of substrate drugs (caffeine [1A2], tolbutamide [2C11], chlorzoxazone [2E1], and midazolam [3A2]) for each P450 isoform, and thus, the hypnotic action of midazolam could be significantly prolonged. Of interest, the reductions in hepatic P450 activity observed in the RBC group were significantly suppressed by CO-RBC resuscitation, and consequently, the pharmacokinetics of substrate drugs and the pharmacological action of midazolam remained at levels similar to those under sham conditions. These results indicate that CO-RBC resuscitation has considerable potential in terms of achieving safe and useful drug therapy during massive hemorrhages.

  14. The role of cytochrome P450s in polycyclic aromatic hydrocarbon carcinogenesis

    SciTech Connect

    Polzer, R.J.

    1993-01-01

    Metabolic activation of polycyclic aromatic hydrocarbons (PAH) to carcinogenic diol epoxides has been determined to be a critical step in tumor initiation by PAH. The key enzyme(s) involved in the metabolic activation are members of the cytochrome P450 superfamily. Two distinct isoforms of cytochrome P450 have been determined to be induced upon treatment of cells in culture with benzo(a)pyrene (B(a)P) by use of Immobilized Artificial Membrane Column High Performance Liquid Chromatography, Western blotting, Northern blotting, and in vitro metabolism studies. Cytochrome P4501A is involved in the metabolism of PAH in the human hepatoma cell line, HepG2; the human mammary carcinoma cell line, MCF-7; and the mouse hepatoma cell line; Hepa-1; whereas cytochrome P450EF is involved in this metabolism in both secondary hamster and mouse embryo cell cultures. Induction of cytochrome P450s by B(a)P generally leads to an increased metabolism of tritiated B(a)P, DMBA, and DB(a,1)P to water-soluble metabolities and to the formation of PAH-DNA adducts, suggesting that induction by B(a)P alters the metabolism of PAH to metabolic activation. DMBA induction of cytochrome P450s leads to various changes in metabolism and PAH-DNA binding and these changes were both cell and PAH specific. These results suggest that DMBA can shift metabolism of certain PAH towards metabolic activation in some cells, while in other cells DMBA or one of its metabolities can compete with other PAH for metabolic activation. UDP-glucuronosyl-transferase and epoxide hydrase do not have significant roles in detoxifying proximate or ultimate carcinogenic PAH metabolites, however, sulfotransferase and glutathione-S-transferase do detoxify proximate and ultimate carcinogenic metabolities in the HepG2 cell line. Finally, attempts to inhibit B(a)P metabolism and DNA-binding in intact cells in culture through conjugation of inhibitory cytochrome P4501A1 antibodies to insulin or folic acid were examined.

  15. Application of nanodisc technology for direct electrochemical investigation of plant cytochrome P450s and their NADPH P450 oxidoreductase

    PubMed Central

    Bavishi, Krutika; Laursen, Tomas; Martinez, Karen L.; Møller, Birger Lindberg; Della Pia, Eduardo Antonio

    2016-01-01

    Direct electrochemistry of cytochrome P450 containing systems has primarily focused on investigating enzymes from microbes and animals for bio-sensing applications. Plant P450s receive electrons from NADPH P450 oxidoreductase (POR) to orchestrate the bio-synthesis of a plethora of commercially valuable compounds. In this report, full length CYP79A1, CYP71E1 and POR of the dhurrin pathway in Sorghum bicolor were reconstituted individually in nanoscale lipid patches, “nanodiscs”, and directly immobilized on unmodified gold electrodes. Cyclic voltammograms of CYP79A1 and CYP71E1 revealed reversible redox peaks with average midpoint potentials of 80 ± 5 mV and 72 ± 5 mV vs. Ag/AgCl, respectively. POR yielded two pairs of redox peaks with midpoint potentials of 90 ± 5 mV and −300 ± 10 mV, respectively. The average heterogeneous electron transfer rate constant was calculated to be ~1.5 s−1. POR was electro-catalytically active while the P450s generated hydrogen peroxide (H2O2). These nanodisc-based investigations lay the prospects and guidelines for construction of a simplified platform to perform mediator-free, direct electrochemistry of non-engineered cytochromes P450 under native-like conditions. It is also a prelude for driving plant P450 systems electronically for simplified and cost-effective screening of potential substrates/inhibitors and fabrication of nano-bioreactors for synthesis of high value natural products. PMID:27386958

  16. High-sensitivity liquid chromatography-tandem mass spectrometry for the simultaneous determination of five drugs and their cytochrome P450-specific probe metabolites in human plasma.

    PubMed

    Oh, Kyung-Suk; Park, Su-Jin; Shinde, Dhananjay D; Shin, Jae-Gook; Kim, Dong-Hyun

    2012-05-01

    A sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method with electrospray ionization was developed for the simultaneous quantitation of five probe drugs and their metabolites in human plasma for assessing the in vivo activities of cytochrome P450 (CYP). CYP isoform specific substrates and their metabolites of CYP1A2 (caffeine), CYP2C9 (losartan), CYP2C19 (omeprazole), CYP2D6 (dextromethorphan) and CYP3A (midazolam) were all simultaneously analyzed using LC-MS/MS after administration of a mixture of five drugs (i.e., a "cocktail approach") to healthy volunteers. The assay uses propranolol as an internal standard; dual liquid extraction; a Xbridge MS C(18) (100 mm × 2.1mm, 3.5 μm) column; a gradient mobile phase of 0.1% formic acid/acetonitrile (7/3→3/7); mass spectrometric detection in positive ion mode. The method was validated from 5 to 500 ng/mL for caffeine and paraxanthine, 0.1-40 ng/mL for losartan and EXP3174, 0.05-20 ng/mL for omeprazole and 5-hydroxyomeprazole, 0.008-0.8 ng/mL for dextromethorphan and dextrorphan, 0.01-1.0 ng/mL for midazolam, and 0.04-4 ng/mL for 1'-hydroxymidazolam. The intra- and inter-day precision over the concentration ranges for all analytes were lower than 12.5% and 13.8% (relative standard deviation, %RSD), and accuracy was between 86.5% and 108.4% and between 87.0% and 107.0%, respectively. This highly sensitive and quantitative method allowed a pharmacokinetic study in subjects receiving doses 10-100 times lower than typical therapeutic doses.

  17. Evaluation of Mutual Drug-Drug Interaction within Geneva Cocktail for Cytochrome P450 Phenotyping using Innovative Dried Blood Sampling Method.

    PubMed

    Bosilkovska, Marija; Samer, Caroline; Déglon, Julien; Thomas, Aurélien; Walder, Bernhard; Desmeules, Jules; Daali, Youssef

    2016-09-01

    Cytochrome P450 (CYP) activity can be assessed using a 'cocktail' phenotyping approach. Recently, we have developed a cocktail (Geneva cocktail) which combines the use of low-dose probes with a low-invasiveness dried blood spots (DBS) sampling technique and a single analytical method for the phenotyping of six major CYP isoforms. We have previously demonstrated that modulation of CYP activity after pre-treatment with CYP inhibitors/inducer could be reliably predicted using Geneva cocktail. To further validate this cocktail, in this study, we have verified whether probe drugs contained in the latter cause mutual drug-drug interactions. In a randomized, four-way, Latin-square crossover study, 30 healthy volunteers received low-dose caffeine, flurbiprofen, omeprazole, dextromethorphan and midazolam (a previously validated combination with no mutual drug-drug interactions); fexofenadine alone; bupropion alone; or all seven drugs simultaneously (Geneva cocktail). Pharmacokinetic profiles of the probe drugs and their metabolites were determined in DBS samples using both conventional micropipette sampling and new microfluidic device allowing for self-sampling. The 90% confidence intervals for the geometric mean ratios of AUC metabolite/AUC probe for CYP probes administered alone or within Geneva cocktail fell within the 0.8-1.25 bioequivalence range indicating the absence of pharmacokinetic interaction. The same result was observed for the chosen phenotyping indices, that is metabolic ratios at 2 hr (CYP1A2, CYP3A) or 3 hr (CYP2B6, CYP2C9, CYP2C19, CYP2D6) post-cocktail administration. DBS sampling could successfully be performed using a new microfluidic device. In conclusion, Geneva cocktail combined with an innovative DBS sampling device can be used routinely as a test for simultaneous CYP phenotyping.

  18. In vitro metabolism of a novel antithrombotic compound, S002-333, and its enantiomers: quantitative cytochrome P450 phenotyping, metabolic profiling and enzyme kinetic studies.

    PubMed

    Saxena, Amrita; Jain, Girish K; Siddiqui, Hefazat H; Bhunia, Shom S; Saxena, Anil K; Gayen, Jiaur R

    2014-04-01

    1. S002-333, (2-(4'-methoxy-benzenesulfonyl)-2,3,4,9-tetrahydro-1H-pyrido (3,4-b) indole-3-carboxylic acid amide) is a novel potent antithrombotic molecule currently under development phase. It is the racemic mixture of two enantiomers, namely S004-1032 (R-form) and S007-1558 (S-form). 2. The contribution of five major isoenzymes, namely CYP2B6, 2C9, 2C19, 2D6 and 3A4 was quantified using recombinant P450s in the phase-I metabolism through relative activity factor approach. CYP2C19 was found to be the major contributor for S002-333 and S007-1558, while CYP3A4 showed greater involvement in S004-1032 metabolism. Chemical inhibition and immunoinhibition studies reconfirmed the results in human liver microsomes (HLM). 3. Four major phase-I metabolites of S002-333; M-1 and M-3 (oxidative), M-2 (O-demethylated) and M-4 (dehydrogenated) were characterized in HLM. These metabolites constituted 11.2, 11.3 and 21.5% of the parent in comparison with the net phase-I metabolism of 29.9, 31.4 and 38.3% of S002-333, S004-1032 and S007-1558, respectively. 4. Among CYP2C9, 2C19 and 3A4, the relative contribution of CYP2C9 was found to be maximum during M-1 through M-4 formation. Enzyme kinetic analysis for detected metabolites indicated that M-1 to M-3 followed classical hyperbolic kinetics, whereas M-4 showed evidence of autoactivation. In conclusion, the results suggest prominent role of CYP2C9, 2C19 and 3A4 isoforms for enantioselective disposition of S002-333 in vitro.

  19. P450 GENETIC VARIATION: IMPLICATIONS FOR ENVIRONMENTAL AND WORKPLACE EXPOSURE

    EPA Science Inventory

    The Cytochrome P450 array detoxifies many chemicals by catalyzing the conversion of mostly hydrophobic chemicals into more hydrophilic forms that can subsequently be excreted by the body. Human genetic variation in the genes for these enzymes produces wide variations in the abili...

  20. Cytochrome P450 arachidonic acid metabolism in bovine corneal epithelium

    SciTech Connect

    Masferrer, J.; Schwartzman, M.L.; Abraham, N.G.; Dunn, M.W.; McGiff, J.C.

    1986-03-01

    The presence of the cytochrom P450 system and its involvement in the metabolism of AA was studied in the corneal epithelium. This tissue contains cytochrome P450 as assessed directly by measurement of the carbon monoxide reduced spectrum (specific activity of 161 pmol/10 mg protein) and indirectly by measuring the activity of aryl hydrocarbon hydroxylase (AHH) - a cytochrome P450-dependent enzyme (11-39 pmol 3-OH benzopyrene/mg protein/10 min). When corneal epithelial microsomes were incubated with /sup 14/C-arachidonic acid, 30-50% of the total radioactivity was converted to two peaks, I and II. Further separation using high performance liquid chromatography has shown that each peak contains two metabolites, A,B and C,D. Metabolite formation was dependent on the addition of NADPH (1 mM) and inhibited by carbon monoxide and SKF-525A (100 ..mu..M) suggesting a cytochrome P450-dependent mechanism. Compound C (5-10 ..mu..M) inhibited the activity of corneal epithelial Na-K-ATPase by 30-60%, being 100-fold more potent than ouabain. Compound D (10-100 ng) induced a dose dependent relaxation of the rat caudal artery. Compound D also inhibited corneal Na-K-ATPase activity but less potently than compound C. These compounds may be important to transport processes of ocular epithelia and participate in the control of the ocular circulation and aqueous humor dynamics.

  1. Cytochromes P450 in the bioactivation of chemicals.

    PubMed

    Ioannides, Costas; Lewis, David F V

    2004-01-01

    The initial view that the cytochrome P450 enzyme system functions simply in the deactivation of xenobiotics is anachronistic on the face of mounting evidence that this system can also transform many innocuous chemicals to toxic products. However, not all xenobiotic-metabolising cytochrome P450 subfamilies show the same propensity in the bioactivation of chemicals. For example, the CYP2C, 2B and 2D subfamilies play virtually no role in the bioactivation of toxic and carcinogenic chemicals, whereas the CYP1A, 1B and 2E subfamilies are responsible for the bioactivation of the majority of xenobiotics. Electronic and molecular structural features of organic chemicals appear to predispose them to either bioactivation by one cytochrome P450 enzyme or deactivation by another. Consequently, the fate of a chemical in the body is largely dependent on the cytochrome P450 profile at the time of exposure. Any factor that modulates the enzymes involved in the metabolism of a certain chemical will also influence its toxicity and carcinogenicity. For example, many chemical carcinogens bioactivated by CYP1, on repeated administration, selectively induce this family, thus exacerbating their carcinogenicity. CYP1 induction potency by chemicals appears to be determined by a combination of their molecular shape and electron activation. The function of cytochromes P450 in the bioactivation of chemicals is currently being exploited to design systems that can be used clinically to facilitate the metabolic conversion of prodrugs to their biologically-active metabolites in cells that poorly express them, such as tumour cells, in the so-called gene-directed prodrug therapy.

  2. Expression of P450c17 in the human fetal nervous system.

    PubMed

    Schonemann, Marcus D; Muench, Marcus O; Tee, Meng Kian; Miller, Walter L; Mellon, Synthia H

    2012-05-01

    P450c17 catalyzes steroid 17α-hydroxylase and 17,20 lyase activities. P450c17 is expressed in human fetal and postnatal adrenals and gonads and in the developing mouse nervous system, but little is known about its expression in the human nervous system. We obtained portions of 9-, 10-, and 11-wk gestation human fetuses and delineated the pattern of expression of P450c17 in their peripheral nervous systems by immunocytochemistry using the P450c17 antiserum previously used to characterize P450c17 in the mouse brain. P450c17 was readily detected in the dorsal root ganglia (DRG) and spinal cord. Neural structures were identified with antisera to the cytoskeletal protein neural cell adhesion molecule; DRG were identified with antisera to the neuronal transcription factor BRN3A and neurotrophin receptor tropomyosin-receptor-kinase B. The identification of P450c17 was confirmed using commercial antisera directed against different domains of P450c17 and by using antisera immunodepleted with authentic human P450c17. We also found expression of the P450 cholesterol side-chain cleavage enzyme (P450scc) in the spinal cord and DRG. Expression of P450scc is limited to cell bodies; unlike P450c17, we never detected P450scc in fiber tracts. Catalysis by P450c17 requires electron donation from P450 oxidoreductase (POR). Dual-label immunohistochemistry detected P450c17 and POR colocalized in DRG bundles, but some fibers containing P450c17 lacked POR. These data suggest that neurosteroids synthesized via these two enzymes may act in the developing human nervous system. The expression of P450c17 in structures lacking POR means that P450c17 may not be steroidogenic in those locations, suggesting that P450c17 may have additional functions that do not require POR.

  3. A Physiologically Based Pharmacokinetic Model to Predict Disposition of CYP2D6 and CYP1A2 Metabolized Drugs in Pregnant Women

    PubMed Central

    Ke, Alice Ban; Nallani, Srikanth C.; Zhao, Ping; Rostami-Hodjegan, Amin; Isoherranen, Nina

    2013-01-01

    Conducting pharmacokinetic (PK) studies in pregnant women is challenging. Therefore, we asked if a physiologically based pharmacokinetic (PBPK) model could be used to evaluate different dosing regimens for pregnant women. We refined and verified our previously published pregnancy PBPK model by incorporating cytochrome P450 CYP1A2 suppression (based on caffeine PK) and CYP2D6 induction (based on metoprolol PK) into the model. This model accounts for gestational age–dependent changes in maternal physiology and hepatic CYP3A activity. For verification, the disposition of CYP1A2–metabolized drug theophylline (THEO) and CYP2D6–metabolized drugs paroxetine (PAR), dextromethorphan (DEX), and clonidine (CLO) during pregnancy was predicted. Our PBPK model successfully predicted THEO disposition during the third trimester (T3). Predicted mean postpartum to third trimester (PP:T3) ratios of THEO area under the curve (AUC), maximum plasma concentration, and minimum plasma concentration were 0.76, 0.95, and 0.66 versus observed values 0.75, 0.89, and 0.72, respectively. The predicted mean PAR steady-state plasma concentration (Css) ratio (PP:T3) was 7.1 versus the observed value 3.7. Predicted mean DEX urinary ratio (UR) (PP:T3) was 2.9 versus the observed value 1.9. Predicted mean CLO AUC ratio (PP:T3) was 2.2 versus the observed value 1.7. Sensitivity analysis suggested that a 100% induction of CYP2D6 during T3 was required to recover the observed PP:T3 ratios of PAR Css, DEX UR, and CLO AUC. Based on these data, it is prudent to conclude that the magnitude of hepatic CYP2D6 induction during T3 ranges from 100 to 200%. Our PBPK model can predict the disposition of CYP1A2, 2D6, and 3A drugs during pregnancy. PMID:23355638

  4. Cytochrome P450 Drug Metabolizing Enzymes in Roma Population Samples: Systematic Review of the Literature.

    PubMed

    Szalai, Renata; Hadzsiev, Kinga; Melegh, Bela

    2016-01-01

    The cytochrome P450 drug metabolizing enzymes are highly polymorphic and show inter-individual differences in variability in drug response, which varies widely also with ethnicity. This study aims to summarize the available data on genetic polymorphisms associated with cytochrome enzymes conducted on Roma populations. Our goal was to compare the frequency of the variant alleles, genotypes and predicted phenotypes with corresponding rates from other populations. We carried out a systematic review including the papers published on the pharmacogenetically relevant variants of cytochrome P450 genes related to Roma population. The study was performed using several articles, websites and databases, including PubMed, Ensembl, dbSNP, HapMap and 1000 Genomes Project. This review attempts to summarize and discuss our current knowledge about the frequency distribution of the ever investigated 20 allelic variants of 9 cytochrome genes (CYP1A2, CYP1B1, CYP2B6, CYP2C9, CYP2C19, CYP2C8, CYP2D6, CYP3A5, CYP4F2) in Roma DNA samples and compare them with other populations. Differences between Roma and Hungarian samples are reported for 7 variant genotypes. CYP2C9 *2/*3 and CYP2C19 *2/*2 genotypes showed more than 3-fold differences. Additional differences are displayed for allele frequency of 7 variants (rs762551, rs3745274, rs1058930, rs1065852, rs3892097, rs1057910 and rs4244285) in Roma population samples. The interethnic variability in clinically relevant genetic polymorphisms of drug metabolizing enzymes, which may explain distinct drug response, highlights the need to allow for the ancestry of participants in pharmacogenetic studies.

  5. Clinical drug-drug interaction assessment of ivacaftor as a potential inhibitor of cytochrome P450 and P-glycoprotein.

    PubMed

    Robertson, Sarah M; Luo, Xia; Dubey, Neeraj; Li, Chonghua; Chavan, Ajit B; Gilmartin, Geoffrey S; Higgins, Mark; Mahnke, Lisa

    2015-01-01

    Ivacaftor is approved in the USA for the treatment of cystic fibrosis (CF) in patients with a G551D-CFTR mutation or one of eight other CFTR mutations. A series of in vitro experiments conducted early in the development of ivacaftor indicated ivacaftor and metabolites may have the potential to inhibit cytochrome P450 (CYP) 2C8, CYP2C9, CYP3A, and CYP2D6, as well as P-glycoprotein (P-gp). Based on these results, a series of clinical drug-drug interaction (DDI) studies were conducted to evaluate the effect of ivacaftor on sensitive substrates of CYP2C8 (rosiglitazone), CYP3A (midazolam), CYP2D6 (desipramine), and P-gp (digoxin). In addition, a DDI study was conducted to evaluate the effect of ivacaftor on a combined oral contraceptive, as this is considered an important comedication in CF patients. The results indicate ivacaftor is a weak inhibitor of CYP3A and P-gp, but has no effect on CYP2C8 or CYP2D6. Ivacaftor caused non-clinically significant increases in ethinyl estradiol and norethisterone exposure. Based on these results, caution and appropriate monitoring are recommended when concomitant substrates of CYP2C9, CYP3A and/or P-gp are used during treatment with ivacaftor, particularly drugs with a narrow therapeutic index, such as warfarin.

  6. NADPH-Cytochrome P450 Oxidoreductase: Prototypic Member of the Diflavin Reductase Family

    PubMed Central

    Iyanagi, Takashi; Xia, Chuanwu; Kim, Jung-Ja P.

    2012-01-01

    NADPH-cytochrome P450 oxidoreductase (CYPOR) and nitric oxide synthase (NOS), two members of the diflavin oxidoreductase family, are multi-domain enzymes containing distinct FAD and FMN domains connected by a flexible hinge. FAD accepts a hydride ion from NADPH, and reduced FAD donates electrons to FMN, which in turn transfers electrons to the heme center of cytochrome P450 or NOS oxygenase domain. Structural analysis of CYPOR, the prototype of this enzyme family, has revealed the exact nature of the domain arrangement and the role of residues involved in cofactor binding. Recent structural and biophysical studies of CYPOR have shown that the two flavin domains undergo large domain movements during catalysis. NOS isoforms contain additional regulatory elements within the reductase domain that control electron transfer through Ca2+-dependent calmodulin (CaM) binding. The recent crystal structure of an iNOS Ca2+/CaM-FMN construct, containing the FMN domain in complex with Ca2+/CaM, provided structural information on the linkage between the reductase and oxgenase domains of NOS, making it possible to model the holo iNOS structure. This review summarizes recent advances in our understanding of the dynamics of domain movements during CYPOR catalysis and the role of the NOS diflavin reductase domain in the regulation of NOS isozyme activities. PMID:22982532

  7. Effects of Chinese, Japanese and Western tea on hepatic P450 enzyme activities in rats.

    PubMed

    Niwattisaiwong, N; Luo, X X; Coville, P F; Wanwimolruk, S

    2004-01-01

    Previous studies have reported that green tea effectively protects against cancers caused by various dietary carcinogens. As P450 enzymes are the major system responsible for the metabolism of many carcinogens, we hypothesise that tea consumption may alter the catalytic activities of P450 enzymes. We conducted this study to screen the effects of four different teas on the activities of P450 enzymes. Tea solutions (2.5%) were prepared by adding boiling water to tea leaves and filtering. Female Wistar rats were divided into five groups (n = 4 each); each had free access to tea solutions while the control group was supplied with water for 4 weeks. Animals were sacrificed and livers were removed for preparation of microsomes. Enzyme activities were determined by incubation of liver microsomes with the appropriate CYP substrate. The activity of CYP1A1 in livers from rats receiving Oolong (Chinese) tea (185 +/- 63 pmol/mg/min), Japanese green tea (197 +/- 22 pmol/mg/min) and Earl Grey tea (228 +/- 40 pmol/mg/min) was significantly higher (p < 0.05) than in the control group (94 +/- 34 pmol/mg/min), whereas no change was observed in the activity of CYP1A2 in any of tested animals. The hepatic activity of CYP2D6 was greater only in rats drinking Earl Grey tea compared to the controls (235 +/- 37 vs 161 +/- 41 pmol/mg/min, p < 0.05). There were also significant increases (p < 0.05) in the activity of CYP3A in livers of animals given Oolong tea (653 +/- 174 vs 382 +/- 114 pmol/mg/min) and Earl Grey tea (751 +/- 202 pmol/mg/min), while Jasmine and Japanese green tea had no significant effect. These results indicate that not all types of tea cause alterations in liver CYP enzymes as some elevated activities and some did not. Further studies are needed to determine whether there is a relationship between the effect of tea on CYP activities and anti-carcinogenesis.

  8. Steroid biotransformations in biphasic systems with Yarrowia lipolytica expressing human liver cytochrome P450 genes

    PubMed Central

    2012-01-01

    Background Yarrowia lipolytica efficiently metabolizes and assimilates hydrophobic compounds such as n-alkanes and fatty acids. Efficient substrate uptake is enabled by naturally secreted emulsifiers and a modified cell surface hydrophobicity and protrusions formed by this yeast. We were examining the potential of recombinant Y. lipolytica as a biocatalyst for the oxidation of hardly soluble hydrophobic steroids. Furthermore, two-liquid biphasic culture systems were evaluated to increase substrate availability. While cells, together with water soluble nutrients, are maintained in the aqueous phase, substrates and most of the products are contained in a second water-immiscible organic solvent phase. Results For the first time we have co-expressed the human cytochromes P450 2D6 and 3A4 genes in Y. lipolytica together with human cytochrome P450 reductase (hCPR) or Y. lipolytica cytochrome P450 reductase (YlCPR). These whole-cell biocatalysts were used for the conversion of poorly soluble steroids in biphasic systems. Employing a biphasic system with the organic solvent and Y. lipolytica carbon source ethyl oleate for the whole-cell bioconversion of progesterone, the initial specific hydroxylation rate in a 1.5 L stirred tank bioreactor was further increased 2-fold. Furthermore, the product formation was significantly prolonged as compared to the aqueous system. Co-expression of the human CPR gene led to a 4-10-fold higher specific activity, compared to the co-overexpression of the native Y. lipolytica CPR gene. Multicopy transformants showed a 50-70-fold increase of activity as compared to single copy strains. Conclusions Alkane-assimilating yeast Y. lipolytica, coupled with the described expression strategies, demonstrated its high potential for biotransformations of hydrophobic substrates in two-liquid biphasic systems. Especially organic solvents which can be efficiently taken up and/or metabolized by the cell might enable more efficient bioconversion as compared

  9. Role of cytochrome P450 in drug interactions

    PubMed Central

    Bibi, Zakia

    2008-01-01

    Drug-drug interactions have become an important issue in health care. It is now realized that many drug-drug interactions can be explained by alterations in the metabolic enzymes that are present in the liver and other extra-hepatic tissues. Many of the major pharmacokinetic interactions between drugs are due to hepatic cytochrome P450 (P450 or CYP) enzymes being affected by previous administration of other drugs. After coadministration, some drugs act as potent enzyme inducers, whereas others are inhibitors. However, reports of enzyme inhibition are very much more common. Understanding these mechanisms of enzyme inhibition or induction is extremely important in order to give appropriate multiple-drug therapies. In future, it may help to identify individuals at greatest risk of drug interactions and adverse events. PMID:18928560

  10. Stereoselective metabolism of donepezil and steady-state plasma concentrations of S-donepezil based on CYP2D6 polymorphisms in the therapeutic responses of Han Chinese patients with Alzheimer's disease.

    PubMed

    Lu, Jin; Wan, Lili; Zhong, Yuan; Yu, Qi; Han, Yonglong; Chen, Pengguo; Wang, Beiyun; Li, Wei; Miao, Ya; Guo, Cheng

    2015-11-01

    The therapeutic response rates of patients to donepezil vary from 20% to 60%, one of the reasons is their genetic differences in donepezil-metabolizing enzymes, which directly influence liver metabolism. However, the mechanism of donepezil metabolism and that of its enantiomers is unknown. This study evaluated CYP2D6 polymorphisms to elucidate the stereoselective metabolism of donepezil and to confirm the association between the steady-state plasma concentrations of the pharmaco-effective S-donepezil and the therapeutic responses of Han Chinese patients with Alzheimer's disease. The in vitro study of the stereoselective metabolism demonstrated that CYP2D6 is the predominant P450 enzyme that metabolizes donepezil and that different CYP2D6 alleles differentially affect donepezil enantiomers metabolism. A total of 77 Han Chinese patients with Alzheimer's disease were recruited to confirm these results, by measuring their steady-state plasma concentrations of S-donepezil. The related CYP2D6 genes were genotyped. Plasma concentrations of S-donepezil (based on CYP2D6 polymorphisms) were significantly associated with therapeutic responses. This finding suggests that plasma concentrations of S-donepezil influence therapeutic outcomes following treatment with donepezil in Han Chinese patients with Alzheimer's disease. Therefore, determining a patient's steady-state plasma concentration of S-donepezil in combination with their CYP2D6 genotype might be useful for clinically monitoring the therapeutic efficacy of donepezil.

  11. Immobilized Cytochrome P450 2C9 (CYP2C9): Applications for Metabolite Generation, Monitoring Protein-Protein Interactions, and Improving In-vivo Predictions Using Enhanced In-vitro Models

    NASA Astrophysics Data System (ADS)

    Wollenberg, Lance A.

    Cytochrome P450 (P450) enzymes are a family of oxoferroreductase enzymes containing a heme moiety and are well known to be involved in the metabolism of a wide variety of endogenous and xenobiotic materials. It is estimated that roughly 75% of all pharmaceutical compounds are metabolized by these enzymes. Traditional reconstituted in-vitro incubation studies using recombinant P450 enzymes are often used to predict in-vivo kinetic parameters of a drug early in development. However, in many cases, these reconstituted incubations are prone to aggregation which has been shown to affect the catalytic activity of an enzyme. Moreover, the presence of other isoforms of P450 enzymes present in a metabolic incubation, as is the case with microsomal systems, may affect the catalytic activity of an enzyme through isoform-specific protein-protein interactions. Both of these effects may result in inaccurate prediction of in-vivo drug metabolism using in-vitro experiments. Here we described the development of immobilized P450 constructs designed to elucidate the effects of aggregation and protein-protein interactions between P450 isoforms on catalytic activities. The long term objective of this project is to develop a system to control the oligomeric state of Cytochrome P450 enzymes to accurately elucidate discrepancies between in vitro reconstituted systems and actual in vivo drug metabolism for the precise prediction of metabolic activity. This approach will serve as a system to better draw correlations between in-vivo and in-vitro drug metabolism data. The central hypothesis is that Cytochrome P450 enzymes catalytic activity can be altered by protein-protein interactions occurring between Cytochrome P450 enzymes involved in drug metabolism, and is dependent on varying states of protein aggregation. This dissertation explains the details of the construction and characterization of a nanostructure device designed to control the state of aggregation of a P450 enzyme. Moreover

  12. Valence tautomerism in synthetic models of cytochrome P450

    PubMed Central

    Das, Pradip Kumar; Samanta, Subhra; McQuarters, Ashley B.; Lehnert, Nicolai

    2016-01-01

    CytP450s have a cysteine-bound heme cofactor that, in its as-isolated resting (oxidized) form, can be conclusively described as a ferric thiolate species. Unlike the native enzyme, most synthetic thiolate-bound ferric porphyrins are unstable in air unless the axial thiolate ligand is sterically protected. Spectroscopic investigations on a series of synthetic mimics of cytP450 indicate that a thiolate-bound ferric porphyrin coexists in organic solutions at room temperature (RT) with a thiyl-radical bound ferrous porphyrin, i.e., its valence tautomer. The ferric thiolate state is favored by greater enthalpy and is air stable. The ferrous thiyl state is favored by entropy, populates at RT, and degrades in air. These ground states can be reversibly interchanged at RT by the addition or removal of water to the apolar medium. It is concluded that hydrogen bonding and local electrostatics protect the resting oxidized cytP450 active site from degradation in air by stabilizing the ferric thiolate ground state in contrast to its synthetic analogs. PMID:27302948

  13. Human cytochromes P450 in health and disease

    PubMed Central

    Nebert, Daniel W.; Wikvall, Kjell; Miller, Walter L.

    2013-01-01

    There are 18 mammalian cytochrome P450 (CYP) families, which encode 57 genes in the human genome. CYP2, CYP3 and CYP4 families contain far more genes than the other 15 families; these three families are also the ones that are dramatically larger in rodent genomes. Most (if not all) genes in the CYP1, CYP2, CYP3 and CYP4 families encode enzymes involved in eicosanoid metabolism and are inducible by various environmental stimuli (i.e. diet, chemical inducers, drugs, pheromones, etc.), whereas the other 14 gene families often have only a single member, and are rarely if ever inducible or redundant. Although the CYP2 and CYP3 families can be regarded as largely redundant and promiscuous, mutations or other defects in one or more genes of the remaining 16 gene families are primarily the ones responsible for P450-specific diseases—confirming these genes are not superfluous or promiscuous but rather are more directly involved in critical life functions. P450-mediated diseases comprise those caused by: aberrant steroidogenesis; defects in fatty acid, cholesterol and bile acid pathways; vitamin D dysregulation and retinoid (as well as putative eicosanoid) dysregulation during fertilization, implantation, embryogenesis, foetogenesis and neonatal development. PMID:23297354

  14. Cytochrome P450-derived eicosanoids: the neglected pathway in cancer

    PubMed Central

    Kaipainen, Arja; Greene, Emily R.; Huang, Sui

    2010-01-01

    Endogenously produced lipid autacoids are locally acting small molecule mediators that play a central role in the regulation of inflammation and tissue homeostasis. A well-studied group of autacoids are the products of arachidonic acid metabolism, among which the prostaglandins and leukotrienes are the best known. They are generated by two pathways controlled by the enzyme systems cyclooxygenase and lipoxygenase, respectively. However, arachidonic acid is also substrate for a third enzymatic pathway, the cytochrome P450 (CYP) system. This third eicosanoid pathway consists of two main branches: ω-hydroxylases convert arachidonic acid to hydroxyeicosatetraenoic acids (HETEs) and epoxygenases convert it to epoxyeicosatrienoic acids (EETs). This third CYP pathway was originally studied in conjunction with inflammatory and cardiovascular disease. Arachidonic acid and its metabolites have recently stimulated great interest in cancer biology; but, unlike prostaglandins and leukotrienes the link between cytochome P450 metabolites and cancer has received little attention. In this review, the emerging role in cancer of cytochrome P450 metabolites, notably 20-HETE and EETs, are discussed. PMID:20941528

  15. Regulation of cytochrome P450 expression in Drosophila: Genomic insights

    PubMed Central

    Giraudo, Maeva; Unnithan, G. Chandran; Le Goff, Gaëlle; Feyereisen, René

    2009-01-01

    Genomic tools such as the availability of the Drosophila genome sequence, the relative ease of stable transformation, and DNA microarrays have made the fruit fly a powerful model in insecticide toxicology research. We have used transgenic promoter-GFP constructs to document the detailed pattern of induced Cyp6a2 gene expression in larval and adult Drosophila tissues. We also compared various insecticides and xenobiotics for their ability to induce this cytochrome P450 gene, and show that the pattern of Cyp6a2 inducibility is comparable to that of vertebrate CYP2B genes, and different from that of vertebrate CYP1A genes, suggesting a degree of evolutionary conservation for the “phenobarbital-type” induction mechanism. Our results are compared to the increasingly diverse reports on P450 induction that can be gleaned from whole genome or from “detox” microarray experiments in Drosophila. These suggest that only a third of the genomic repertoire of CYP genes is inducible by xenobiotics, and that there are distinct subsets of inducers / induced genes, suggesting multiple xenobiotic transduction mechanisms. A relationship between induction and resistance is not supported by expression data from the literature. The relative abundance of expression data now available is in contrast to the paucity of studies on functional expression of P450 enzymes, and this remains a challenge for our understanding of the toxicokinetic aspects of insecticide action. PMID:20582327

  16. Non-Michaelis-Menten kinetics in cytochrome P450-catalyzed reactions.

    PubMed

    Atkins, William M

    2005-01-01

    The cytochrome P450 monooxygenases (CYPs) are the dominant enzyme system responsible for xenobiotic detoxification and drug metabolism. Several CYP isoforms exhibit non-Michaelis-Menten, or "atypical," steady state kinetic patterns. The allosteric kinetics confound prediction of drug metabolism and drug-drug interactions, and they challenge the theoretical paradigms of allosterism. Both homotropic and heterotropic ligand effects are now widely documented. It is becoming apparent that multiple ligands can simultaneously bind within the active sites of individual CYPs, and the kinetic parameters change with ligand occupancy. In fact, the functional effect of any specific ligand as an activator or inhibitor can be substrate dependent. Divergent approaches, including kinetic modeling and X-ray crystallography, are providing new information about how multiple ligand binding yields complex CYP kinetics.

  17. Clinical Pharmacology of 3,4-Methylenedioxymethamphetamine (MDMA, “Ecstasy”): The Influence of Gender and Genetics (CYP2D6, COMT, 5-HTT)

    PubMed Central

    O’Mathúna, Brian; Torrens, Marta; Mustata, Cristina; Pérez-Mañá, Clara; Langohr, Klaus; Cuyàs, Elisabet; Carbó, Marcel·lí; de la Torre, Rafael

    2012-01-01

    The synthetic psychostimulant MDMA (±3,4-methylenedioxymethamphetamine, ecstasy) acts as an indirect serotonin, dopamine, and norepinephrine agonist and as a mechanism-based inhibitor of the cytochrome P-450 2D6 (CYP2D6). It has been suggested that women are more sensitive to MDMA effects than men but no clinical experimental studies have satisfactorily evaluated the factors contributing to such observations. There are no studies evaluating the influence of genetic polymorphism on the pharmacokinetics (CYP2D6; catechol-O-methyltransferase, COMT) and pharmacological effects of MDMA (serotonin transporter, 5-HTT; COMT). This clinical study was designed to evaluate the pharmacokinetics and physiological and subjective effects of MDMA considering gender and the genetic polymorphisms of CYP2D6, COMT, and 5-HTT. A total of 27 (12 women) healthy, recreational users of ecstasy were included (all extensive metabolizers for CYP2D6). A single oral weight-adjusted dose of MDMA was administered (1.4 mg/kg, range 75–100 mg) which was similar to recreational doses. None of the women were taking oral contraceptives and the experimental session was performed during the early follicular phase of their menstrual cycle. Principal findings show that subjects reached similar MDMA plasma concentrations, and experienced similar positive effects, irrespective of gender or CYP2D6 (not taking into consideration poor or ultra-rapid metabolizers) or COMT genotypes. However, HMMA plasma concentrations were linked to CYP2D6 genotype (higher with two functional alleles). Female subjects displayed more intense physiological (heart rate, and oral temperature) and negative effects (dizziness, sedation, depression, and psychotic symptoms). Genotypes of COMT val158met or 5-HTTLPR with high functionality (val/val or l/*) determined greater cardiovascular effects, and with low functionality (met/* or s/s) negative subjective effects (dizziness, anxiety, sedation). In conclusion, the contribution of

  18. Effect of age on hepatic cytochrome P450 of Ross 708 broiler chickens.

    PubMed

    Hu, S X

    2013-05-01

    Age has significant impact on hepatic cytochrome P450 (CYP450) systems in animals. Ross 708 broiler chicken is a breed of chicken with fast growth characteristics. Cytochrome P450 in the livers of Ross 708 broiler chicken of different ages has been investigated. The birds were raised under standard husbandry conditions. A certain number of chickens was randomly sampled weekly for liver collection from d 1 to 56 posthatch. The chicken body and liver weights were recorded. The chicken livers were processed for liver microsomes though a multiple-step procedure at low temperature. Total CYP450 content in chicken liver homogenates and liver microsomes was measured using a UV/visible spectroscopic method. The enzymatic activities of CYP450 in the chicken liver microsomes were determined through incubation of CYP450 isoform substrates followed by measurement of formation of their metabolites. The chicken showed an opposite age pattern in hepatic CYP450 content and activities compared with most mammals. The hepatic CYP450 content and activities of chicken at d 1 posthatch were higher than at other ages. The total hepatic CYP450 content in chickens at d 1 posthatch was more than twice the average hepatic value of the chickens at d 7 to 28. This high CYP450 fell quickly in the first week posthatch and slightly rose from d 28 to 56. Hepatic CYP450 activities of CYP1A, 3A, 2C, 2D, and 2H were much higher in the chicken at d 1 posthatch. The differences of these enzymatic activities between d 1 and other ages of chicken were CYP450 isoform dependent. This result suggests that embryonic development of chicken livers has a significant impact on the age profile of hepatic CYP450 content and activities of posthatch chickens.

  19. Chemical proteomic probes for profiling cytochrome P450 activities and drug interactions in vivo

    PubMed Central

    Wright, Aaron T.; Cravatt, Benjamin F.

    2007-01-01

    The cytochrome P450 (P450) superfamily metabolizes many endogenous signaling molecules and drugs. P450 enzymes are regulated by post-translational mechanisms in vivo, which hinders their functional characterization by conventional genomic or proteomic methods. Here, we describe a chemical proteomic strategy to profile P450 activities directly in living systems. Derivatization of a mechanism-based inhibitor with a “clickable” handle provided an activity-based probe that labels multiple P450s both in proteomic extracts and in vivo. This probe was used to record alterations in liver P450 activities triggered by chemical agents, including inducers of P450 expression and direct P450 inhibitors. The chemical proteomic strategy described herein thus offers a versatile method to monitor P450 activities and small molecule interactions in any biological system and, through doing so, should facilitate the functional characterization of this large and diverse enzyme class. PMID:17884636

  20. Applications of microbial cytochrome P450 enzymes in biotechnology and synthetic biology.

    PubMed

    Girvan, Hazel M; Munro, Andrew W

    2016-04-01

    Cytochrome P450 enzymes (P450s) are a superfamily of monooxygenase enzymes with enormous potential for synthetic biology applications. Across Nature, their substrate range is vast and exceeds that of other enzymes. The range of different chemical transformations performed by P450s is also substantial, and continues to expand through interrogation of the properties of novel P450s and by protein engineering studies. The ability of P450s to introduce oxygen atoms at specific positions on complex molecules makes these enzymes particularly valuable for applications in synthetic biology. This review focuses on the enzymatic properties and reaction mechanisms of P450 enzymes, and on recent studies that highlight their broad applications in the production of oxychemicals. For selected soluble bacterial P450s (notably the high-activity P450-cytochrome P450 reductase enzyme P450 BM3), variants with a multitude of diverse substrate selectivities have been generated both rationally and by random mutagenesis/directed evolution approaches. This highlights the robustness and malleability of the P450 fold, and the capacity of these biocatalysts to oxidise a wide range of chemical scaffolds. This article reviews recent research on the application of wild-type and engineered P450s in the production of important chemicals, including pharmaceuticals and drug metabolites, steroids and antibiotics. In addition, the properties of unusual members of the P450 superfamily that do not follow the canonical P450 catalytic pathway are described.

  1. Microsomal cytochrome P450 as a target for drug discovery and repurposing.

    PubMed

    El-Sherbeni, Ahmed A; El-Kadi, Ayman O S

    2017-02-01

    Cytochrome P450 (P450) enzymes are ancient electron-transfer-chain system of remarkable biological importance. Microsomal P450 enzymes are the P450 attached to endoplasmic reticulum, which, in humans, are critical for body's defenses against xenobiotics by mediating their metabolism, and cell signaling by mediating arachidonic acid (AA) transformation to several potent bioactive molecules. Only recently, modulating P450-mediated AA metabolism has risen as a promising new drug target. This review presents the therapeutic potential of finding effective, selective and safe treatments targeting P450-mediated AA metabolism, and the several approaches that have been used to find these treatments; among which, our focus was on modulators of P450 activities. We detailed the efforts done to develop new molecular entities designed to modulate P450, and the more recent efforts tried to employ our previous knowledge on drug metabolism to repurpose old drugs with the capacity to alter P450-mediated drug metabolism to target AA metabolism. Because of the long recognition of P450 role in xenobiotic metabolism, several clinically approved agents were identified to alter P450 activity. Repurposing old drugs as P450 modulators can facilitate bringing treatments targeting P450-mediated AA metabolism to clinical trials. However, the capacity of the modulation of P450-derived AA metabolites of clinically approved drugs has to be systematically investigated and validated for their new use in humans.

  2. Detection of an endogenous urinary biomarker associated with CYP2D6 activity using global metabolomics

    PubMed Central

    Tay-Sontheimer, Jessica; Shireman, Laura M; Beyer, Richard P; Senn, Taurence; Witten, Daniela; Pearce, Robin E; Gaedigk, Andrea; Fomban, Cletus L Gana; Lutz, Justin D; Isoherranen, Nina; Thummel, Kenneth E; Fiehn, Oliver; Leeder, J Steven; Lin, Yvonne S

    2015-01-01

    Aim We sought to discover endogenous urinary biomarkers of human CYP2D6 activity. Patients & methods Healthy pediatric subjects (n = 189) were phenotyped using dextromethorphan and randomized for candidate biomarker selection and validation. Global urinary metabolomics was performed using liquid chromatography quadrupole time-of-flight mass spectrometry. Candidate biomarkers were tested in adults receiving fluoxetine, a CYP2D6 inhibitor. Results A biomarker, M1 (m/z 444.3102) was correlated with CYP2D6 activity in both the pediatric training and validation sets. Poor metabolizers had undetectable levels of M1, whereas it was present in subjects with other phenotypes. In adult subjects, a 9.56-fold decrease in M1 abundance was observed during CYP2D6 inhibition. Conclusion Identification and validation of M1 may provide a noninvasive means of CYP2D6 phenotyping. PMID:25521354

  3. Insights on Cytochrome P450 Enzymes and Inhibitors Obtained Through QSAR Studies

    PubMed Central

    Sridhar, Jayalakshmi; Liu, Jiawang; Foroozesh, Maryam; Stevens, Cheryl L. Klein

    2013-01-01

    The cytochrome P450 (CYP) superfamily of heme enzymes play an important role in the metabolism of a large number of endogenous and exogenous compounds, including most of the drugs currently on the market. Inhibitors of CYP enzymes have important roles in the treatment of several disease conditions such as numerous cancers and fungal infections in addition to their critical role in drug-drug interactions. Structure activity relationships (SAR), and three-dimensional quantitative structure activity relationships (3D-QSAR) represent important tools in understanding the interactions of the inhibitors with the active sites of the CYP enzymes. A comprehensive account of the QSAR studies on the major human CYPs 1A1, 1A2, 1B1, 2A6, 2B6, 2C9, 2C19, 2D6, 2E1, 3A4 and a few other CYPs are detailed in this review which will provide us with an insight into the individual/common characteristics of the active sites of these enzymes and the enzyme-inhibitor interactions. PMID:22864238

  4. Polymorphic cytochrome P450 enzymes (CYPs) and their role in personalized therapy.

    PubMed

    Preissner, Sarah C; Hoffmann, Michael F; Preissner, Robert; Dunkel, Mathias; Gewiess, Andreas; Preissner, Saskia

    2013-01-01

    The cytochrome P450 (CYP) enzymes are major players in drug metabolism. More than 2,000 mutations have been described, and certain single nucleotide polymorphisms (SNPs) have been shown to have a large impact on CYP activity. Therefore, CYPs play an important role in inter-individual drug response and their genetic variability should be factored into personalized medicine. To identify the most relevant polymorphisms in human CYPs, a text mining approach was used. We investigated their frequencies in different ethnic groups, the number of drugs that are metabolized by each CYP, the impact of CYP SNPs, as well as CYP expression patterns in different tissues. The most important polymorphic CYPs were found to be 1A2, 2D6, 2C9 and 2C19. Thirty-four common allele variants in Caucasians led to altered enzyme activity. To compare the relevant Caucasian SNPs with those of other ethnicities a search in 1,000 individual genomes was undertaken. We found 199 non-synonymous SNPs with frequencies over one percent in the 1,000 genomes, many of them not described so far. With knowledge of frequent mutations and their impact on CYP activities, it may be possible to predict patient response to certain drugs, as well as adverse side effects. With improved availability of genotyping, our data may provide a resource for an understanding of the effects of specific SNPs in CYPs, enabling the selection of a more personalized treatment regimen.

  5. Interaction of isoflavonoids with human liver microsomal cytochromes P450: inhibition of CYP enzyme activities.

    PubMed

    Kopečná-Zapletalová, Michaela; Krasulová, Kristýna; Anzenbacher, Pavel; Hodek, Petr; Anzenbacherová, Eva

    2017-04-01

    1. The possibility of interaction of isoflavonoids with concomitantly taken drugs to determined isoflavonoids safety was studied. Inhibition of nine forms of cytochrome P450 (CYP3A4, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2C9, CYP2D6 and CYP2E1) by 12 isoflavonoids (daidzein, genistein, biochanin A, formononetin, glycitein, equol and six glucosides, daidzin, puerarin, genistin, sissotrin, ononin and glycitin) was studied systematically. 2. The most potent inhibitors were genistein and daidzein inhibiting noncompetitively the CYP2C9 with Ki of 35.95 ± 6.96 and 60.56 ± 3.53 μmol/l and CYP3A4 (inhibited by genistein with Ki of 23.25 ± 5.85 μmol/l also by a noncompetitive mechanism). Potent inhibition of CYP3A4 was observed also with biochanin A (Ki of 57.69 ± 2.36 μmol/l) and equol (Ki of 38.47 ± 2.32 μmol/l). 3. Genistein and daidzein inhibit noncompetitively CYP3A4 and CYP2C9. With plasma levels in micromolar range, a clinically important interaction with concomitantly taken drugs does not seem to be probable.

  6. The human genome project and novel aspects of cytochrome P450 research

    SciTech Connect

    Ingelman-Sundberg, Magnus . E-mail: maging@ki.se

    2005-09-01

    Currently, 57 active cytochrome P450 (CYP) genes and 58 pseudogenes are known to be present in the human genome. Among the genes discovered by initiatives in the human genome project are CYP2R1, CYP2W1, CYP2S1, CYP2U1 and CYP3A43, the latter apparently encoding a pseudoenzyme. The function, polymorphism and regulation of these genes are still to be discovered to a great extent. The polymorphism of drug metabolizing CYPs is extensive and influences the outcome of drug therapy causing lack of response or adverse drug reactions. The basis for the differences in the global distribution of the polymorphic variants is inactivating gene mutations and subsequent genetic drift. However, polymorphic alleles carrying multiple active gene copies also exist and are suggested in case of CYP2D6 to be caused by positive selection due to development of alkaloid resistance in North East Africa about 10,000-5000 BC. The knowledge about the CYP genes and their polymorphisms is of fundamental importance for effective drug therapy and for drug development as well as for understanding metabolic activation of carcinogens and other xenobiotics. Here, a short review of the current knowledge is given.

  7. Automated luminescence-based cytochrome P450 profiling using a simple, elegant robotic platform.

    PubMed

    Larson, Brad; Banks, Peter; Cali, James J; Sobol, Mary; Shultz, Sarah

    2011-02-01

    The determination of inhibitory effects that lead compounds have on cytochrome P450 (CYP) enzymes is an important part of today's drug discovery process. Assays can be performed early in the discovery process to predict adverse drug-drug interactions caused by CYP inhibition and to minimize the costs associated with terminating candidates in late stage development or worse, removing a drug from the market after launch. For early discovery work, testing substantial numbers of compounds is desirable, thus automated "mix and read" assays are beneficial. Here, we demonstrate the automation of the CYP profiling process using a simple, yet robust robotic platform. Compound titration, as well as transfer of compounds and assay components was performed by the same automated pipetting system. IC(50)s of small molecule drugs were determined using recombinant CYP enzymes, CYP3A4, -2C9, and -2D6 and luminogenic substrates specific to each. Compounds were profiled against all three enzymes on the same 384-well assay plate.

  8. Oxidative metabolism of flunarizine and cinnarizine by microsomes from B-lymphoblastoid cell lines expressing human cytochrome P450 enzymes.

    PubMed

    Kariya, S; Isozaki, S; Uchino, K; Suzuki, T; Narimatsu, S

    1996-11-01

    The oxidative metabolism of cinnarizine [(E)-1-(diphenylmethyl)-4-(3-phenyl-2-propyl)piperazine, CZ] and flunarizine [(E)-1-[bis(4-fluorophenyl)methyl]-4-(3-phenyl-2-propyl)piperazine, FZ] was examined in microsomes from lymphoblastoid cells that expressed human cytochrome P450 (CYP) enzymes. Among 10 kinds of CYP enzymes examined, only CYP2D6 catalyzed p-hydroxylation of the cinnamyl phenyl ring of CZ (C-2 formation) and FZ (F-2 formation), and only CYP2B6 exhibited activity for p-hydroxylation (C-4 formation) of the diphenylmethyl group of CZ at a substrate concentration of 50 microM. On the other hand, CYP2C9 together with CYP1A1, -1A2 and/or -2A6 mediated N-desalkylation at the 1- and 4-positions of the piperazine ring of the two drugs that formed C-1 and C-3 from CZ and F-1 and F-3 from FZ, respectively, whereas CYP2C8, -2C19, -2E1 or -3A4 did not show detectable activity for these reactions under the conditions used. We then examined kinetics for the oxidative metabolism of CZ and FZ using CYP2B6 and -2D6 that have considerable activities. CYP2D6 with Km values of 2 to 4 microM had intrinsic clearance values (Vmax/Km) of 0.31 and 0.14 ml/min/nmol CYP for C-2 and F-2 formation, respectively, while CYP2B6 with a Km value of 17 microM exhibited the clearance value of 0.10 ml/min/nmol CYP for C-4 formation. These results suggest that CYP2D6 mainly mediates p-hydroxylation of the cinnamyl phenyl rings of CZ and FZ, and CYP2B6 mediates that of the diphenylmethyl group of CZ.

  9. Cloning and expression of a member of a new cytochrome P-450 family: cytochrome P-450lin (CYP111) from Pseudomonas incognita.

    PubMed Central

    Ropp, J D; Gunsalus, I C; Sligar, S G

    1993-01-01

    Cytochrome P-450lin catalyzes the 8-methyl hydroxylation of linalool as the first committed step of its utilization by Pseudomonas incognita as the sole carbon source. By using a polymerase chain reaction-based cloning strategy, a 2.1-kb DNA fragment containing the cytochrome P-450lin gene (linC) was isolated. An open reading frame of 406 amino acids has been identified as that of P-450lin on the basis of amino acid sequence data from peptides of the native protein. Heterologous expression of functional holoprotein is exhibited by Escherichia coli transformed with pUC18 containing the subcloned linC gene under constitutive transcriptional control of the lac promoter. The G+C content of linC was found to be 55% overall and 58% in the third codon position. An optimized amino acid sequence alignment of P-450lin with cytochrome P-450cam shows that the two enzymes have only 25% identity. P-450lin was found to exhibit the expected conservation in the axial cysteine heme ligand-containing peptide and the threonine region postulated to form an O2-binding pocket (T. L. Poulos, B. C. Finzel, and A. J. Howard, J. Mol. Biol. 195:687-700, 1987). The low amino acid sequence identity between P-450lin and all other P-450 sequences has shown that P-450lin is the first member of the CYP111 P-450 gene family. PMID:8376348

  10. The Effect of CYP2D6 Drug-Drug Interactions on Hydrocodone Effectiveness

    PubMed Central

    Monte, Andrew A.; Heard, Kennon J.; Campbell, Jenny; Hamamura, D.; Weinshilboum, Richard M.; Vasiliou, Vasilis

    2014-01-01

    Objectives The hepatic cytochrome 2D6 (CYP2D6) is a saturable enzyme responsible for metabolism of approximately 25% of known pharmaceuticals. CYP interactions can alter the efficacy of prescribed medications. Hydrocodone is largely dependent on CYP2D6 metabolism for analgesia, ondansetron is inactivated by CYP2D6, and oxycodone analgesia is largely independent of CYP2D6. The objective was to determine if CYP2D6 medication co-ingestion decreases the effectiveness of hydrocodone. Methods This was a prospective observational study conducted in an academic U.S. emergency department (ED). Subjects were included if they had self-reported pain or nausea; and were excluded if they were unable to speak English, were less than 18 years of age, had liver or renal failure, or carried diagnoses of chronic pain or cyclic vomiting. Detailed drug ingestion histories for the preceding 48 hours prior to the ED visit were obtained. The patient's pain and nausea were quantified using a 100-millimeter visual analogue scale (VAS) at baseline prior to drug administration and following doses of hydrocodone, oxycodone, or ondansetron. We used a mixed model with random subject effect to determine the interaction between CYP2D6 drug ingestion and study drug effectiveness. Odds ratios (OR) were calculated to compare clinically significant VAS changes between CYP2D6 users and non-users. Results Two hundred fifty (49.8%) of the 502 subjects enrolled had taken at least one CYP2D6 substrate, inhibitor, or inducing pharmaceutical, supplement, or illicit drug in the 48 hours prior to ED presentation. CYP2D6-drug users were one third as likely to respond to hydrocodone (OR 0.33, 95% CI = 0.1 to 0.8), and more than three times as likely as non-users to respond to ondansetron (OR 3.4, 95% CI = 1.3 to 9.1). There was no significant difference in oxycodone effectiveness between CYP2D6 users and non-users (OR 0.53, 95% CI = 0.3 to 1.1). Conclusions CYP2D6 drug-drug interactions appear to change

  11. Coupled motions direct electrons along human microsomal P450 Chains.

    PubMed

    Pudney, Christopher R; Khara, Basile; Johannissen, Linus O; Scrutton, Nigel S

    2011-12-01

    Protein domain motion is often implicated in biological electron transfer, but the general significance of motion is not clear. Motion has been implicated in the transfer of electrons from human cytochrome P450 reductase (CPR) to all microsomal cytochrome P450s (CYPs). Our hypothesis is that tight coupling of motion with enzyme chemistry can signal "ready and waiting" states for electron transfer from CPR to downstream CYPs and support vectorial electron transfer across complex redox chains. We developed a novel approach to study the time-dependence of dynamical change during catalysis that reports on the changing conformational states of CPR. FRET was linked to stopped-flow studies of electron transfer in CPR that contains donor-acceptor fluorophores on the enzyme surface. Open and closed states of CPR were correlated with key steps in the catalytic cycle which demonstrated how redox chemistry and NADPH binding drive successive opening and closing of the enzyme. Specifically, we provide evidence that reduction of the flavin moieties in CPR induces CPR opening, whereas ligand binding induces CPR closing. A dynamic reaction cycle was created in which CPR optimizes internal electron transfer between flavin cofactors by adopting closed states and signals "ready and waiting" conformations to partner CYP enzymes by adopting more open states. This complex, temporal control of enzyme motion is used to catalyze directional electron transfer from NADPH→FAD→FMN→heme, thereby facilitating all microsomal P450-catalysed reactions. Motions critical to the broader biological functions of CPR are tightly coupled to enzyme chemistry in the human NADPH-CPR-CYP redox chain. That redox chemistry alone is sufficient to drive functionally necessary, large-scale conformational change is remarkable. Rather than relying on stochastic conformational sampling, our study highlights a need for tight coupling of motion to enzyme chemistry to give vectorial electron transfer along complex

  12. Cumene hydroperoxide effected hydroperoxidation by cytochrome P-450.

    PubMed

    Chen, C; Gurka, D P

    1985-04-01

    9-Methylfluorene was found to be oxygenated to 9-hydroperoxy-9-methylfluorene and 9-hydroxy-9-methylfluorene by cytochrome P-450 in the presence of cumene hydroperoxide. Molecular oxygen is required and carbon monoxide is inhibitory. The reaction is inhibited by SKF-525A and metyrapone. Metyrapone and cumene hydroperoxide also retard the conversion of 9-hydroperoxy-9-methylfluorene to 9-hydroxy-9-methylfluorene. The reaction is different from hydroperoxide-supported oxygenation, since the cumene hydroperoxide appears to act as an effector of the enzyme rather than oxygen donor. It is suggested that substrates with stable radicals can be dioxygenated in this manner.

  13. Cytochromes P450 for terpene functionalisation and metabolic engineering.

    PubMed

    Pateraki, Irini; Heskes, Allison Maree; Hamberger, Björn

    2015-01-01

    Plants have evolved the capacity to produce a striking array of specialised metabolites. Terpenoids are the oldest and most diverse class of such compounds and have attracted interest for industrial and pharmaceutical applications. The development of biotechnological alternatives for their production is the focus of intense research. Photosynthetic systems provide new strategies for autotrophic metabolic engineering. Focusing on cytochromes P450, involved in the functionalisation of the core terpene molecules, this review highlights the latest approaches in this field and looks towards recent discoveries that have the potential to shape the future of terpenoid bioengineering.

  14. Metabolic activation of the phenothiazine antipsychotics chlorpromazine and thioridazine to electrophilic iminoquinone species in human liver microsomes and recombinant P450s.

    PubMed

    Wen, Bo; Zhou, Mingyan

    2009-10-07

    The phenothiazine-derived antipsychotics, namely chlorpromazine and thioridazine, have been associated with very rare but severe incidences of hepatotoxicity in patients. While the mechanism of idiosyncratic hepatotoxicity remains unknown, it is possible that metabolic activation and subsequent covalently binding of reactive metabolites to cellular proteins play a causative role. Studies were initiated to determine whether chlorpromazine and thioridazine undergo cytochrome P450 (P450)-mediated bioactivation in human liver microsomes to electrophilic intermediates. LC/MS/MS analysis of incubations containing chlorpromazine or thioridazine in the presence of NADPH and glutathione (GSH) revealed the formation of GSH conjugates derived from the addition of the sulfydryl nucleophile to monohydroxy metabolites of chlorpromazine and thioridazine, respectively. Formation of reactive intermediates of chlorpromazine and thioridazine was primarily mediated by heterologously expressed recombinant CYP2D6, and to a less extent, CYP1A2. The 7-hydroxyl metabolites of chlorpromazine and thioridazine were also detected by tandem mass spectrometry. A tentative pathway states that after initial 7-hydroxylation, a bioactivation sequence involves P450-catalyzed oxidation of the phenothiazine core to an electrophilic quinone imine intermediate, which is subsequently attacked by glutathione yielding the sulfydryl conjugates. The results from the current investigation constitute the first report on the cytochrome P450-catalyzed bioactivation of the phenothiazine antipsychotics chlorpromazine and thioridazine.

  15. Quantitative Atlas of Cytochrome P450, UDP-Glucuronosyltransferase, and Transporter Proteins in Jejunum of Morbidly Obese Subjects.

    PubMed

    Miyauchi, Eisuke; Tachikawa, Masanori; Declèves, Xavier; Uchida, Yasuo; Bouillot, Jean-Luc; Poitou, Christine; Oppert, Jean-Michel; Mouly, Stéphane; Bergmann, Jean-François; Terasaki, Tetsuya; Scherrmann, Jean-Michel; Lloret-Linares, Célia

    2016-08-01

    Protein expression levels of drug-metabolizing enzymes and transporters in human jejunal tissues excised from morbidly obese subjects during gastric bypass surgery were evaluated using quantitative targeted absolute proteomics. Protein expression levels of 15 cytochrome P450 (CYP) enzymes, 10 UDP-glucuronosyltransferase (UGT) enzymes, and NADPH-P450 reductase (P450R) in microsomal fractions from 28 subjects and 49 transporters in plasma membrane fractions from 24 of the same subjects were determined using liquid chromatography-tandem mass spectrometry. Based on average values, UGT1A1, UGT2B15, UGT2B17, SGLT1, and GLUT2 exhibited high expression levels (over 10 fmol/μg protein), though UGT2B15 expression was detected at a high level in only one subject. CYP2C9, CYP2D6, CYP3A5, UGT1A6, P450R, ABCG2, GLUT5, PEPT1, MCT1, 4F2 cell-surface antigen heavy chain (4F2hc), LAT2, OSTα, and OSTβ showed intermediate levels (1-10 fmol/μg protein), and CYP1A1, CYP1A2, CYP1B1, CYP2C18, CYP2C19, CYP2J2, CYP3A7, CYP4A11, CYP51A1, UGT1A3, UGT1A4, UGT1A8, UGT2B4, ABCC1, ABCC4, ABCC5, ABCC6, ABCG8, TAUT, OATP2A1, OATP2B1, OATP3A1, OATP4A1, OCTN1, CNT2, PCFT, MCT4, GLUT4, and SLC22A18 showed low levels (less than 1 fmol/μg protein). The greatest interindividual difference (364-fold) was detected for UGT2B17. However, differences in expression levels of other quantified UGTs (except UGT2B15 and UGT2B17), CYPs (except CYP1A1 and CYP3A5), and P450R, and all quantified transporters, were within 10-fold. Expression levels of CYP1A2 and GLUT4 were significantly correlated with body-mass index. The levels of 4F2hc showed significant gender differences. Smokers showed increased levels of UGT1A1 and UGT1A3. These findings provide a basis for understanding the changes in molecular mechanisms of jejunal metabolism and transport, as well as their interindividual variability, in morbidly obese patients.

  16. Peganum harmala L. differentially modulates cytochrome P450 gene expression in human hepatoma HepG2 cells.

    PubMed

    El Gendy, Mohamed A M; El-Kadi, Ayman O S

    2009-12-01

    Peganum harmala L. (Zygophyllaceae) is a common plant in Middle East and it is still used traditionally to treat several diseases. The effect of P. harmala extract on the expression of different cytochrome P450's (CYP) involved in drug metabolism was examined in human HepG2 cells. Therefore, HepG2 cells were incubated with increasing concentrations of plant extract and the CYP gene expression was determined by real-time PCR. Our results showed that P. harmala extract significantly increased the expression of CYP1A2, 2C19, and 3A4 whereas; CYP 2B6, 2D6 and 2E1 was significantly decreased. We concluded that care should be taken when P. harmala is co-administered with other drugs.

  17. Ab initio dynamics of the cytochrome P450 hydroxylation reaction

    PubMed Central

    Elenewski, Justin E.; Hackett, John C

    2015-01-01

    The iron(IV)-oxo porphyrin π-cation radical known as Compound I is the primary oxidant within the cytochromes P450, allowing these enzymes to affect the substrate hydroxylation. In the course of this reaction, a hydrogen atom is abstracted from the substrate to generate hydroxyiron(IV) porphyrin and a substrate-centered radical. The hydroxy radical then rebounds from the iron to the substrate, yielding the hydroxylated product. While Compound I has succumbed to theoretical and spectroscopic characterization, the associated hydroxyiron species is elusive as a consequence of its very short lifetime, for which there are no quantitative estimates. To ascertain the physical mechanism underlying substrate hydroxylation and probe this timescale, ab initio molecular dynamics simulations and free energy calculations are performed for a model of Compound I catalysis. Semiclassical estimates based on these calculations reveal the hydrogen atom abstraction step to be extremely fast, kinetically comparable to enzymes such as carbonic anhydrase. Using an ensemble of ab initio simulations, the resultant hydroxyiron species is found to have a similarly short lifetime, ranging between 300 fs and 3600 fs, putatively depending on the enzyme active site architecture. The addition of tunneling corrections to these rates suggests a strong contribution from nuclear quantum effects, which should accelerate every step of substrate hydroxylation by an order of magnitude. These observations have strong implications for the detection of individual hydroxylation intermediates during P450 catalysis. PMID:25681906

  18. Cholesterol Ester Oxidation by Mycobacterial Cytochrome P450*

    PubMed Central

    Frank, Daniel J.; Madrona, Yarrow; Ortiz de Montellano, Paul R.

    2014-01-01

    Mycobacteria share a common cholesterol degradation pathway initiated by oxidation of the alkyl side chain by enzymes of cytochrome P450 (CYP) families 125 and 142. Structural and sequence comparisons of the two enzyme families revealed two insertions into the N-terminal region of the CYP125 family (residues 58–67 and 100–109 in the CYP125A1 sequence) that could potentially sterically block the oxidation of the longer cholesterol ester molecules. Catalytic assays revealed that only CYP142 enzymes are able to oxidize cholesteryl propionate, and although CYP125 enzymes could oxidize cholesteryl sulfate, they were much less efficient at doing so than the CYP142 enzymes. The crystal structure of CYP142A2 in complex with cholesteryl sulfate revealed a substrate tightly fit into a smaller active site than was previously observed for the complex of CYP125A1 with 4-cholesten-3-one. We propose that the larger CYP125 active site allows for multiple binding modes of cholesteryl sulfate, the majority of which trigger the P450 catalytic cycle, but in an uncoupled mode rather than one that oxidizes the sterol. In contrast, the more unhindered and compact CYP142 structure enables enzymes of this family to readily oxidize cholesteryl esters, thus providing an additional source of carbon for mycobacterial growth. PMID:25210044

  19. Zonation of hepatic cytochrome P-450 expression and regulation.

    PubMed Central

    Oinonen, T; Lindros, K O

    1998-01-01

    The CYP genes encode enzymes of the cytochrome P-450 superfamily. Cytochrome P-450 (CYP) enzymes are expressed mainly in the liver and are active in mono-oxygenation and hydroxylation of various xenobiotics, including drugs and alcohols, as well as that of endogenous compounds such as steroids, bile acids, prostaglandins, leukotrienes and biogenic amines. In the liver the CYP enzymes are constitutively expressed and commonly also induced by chemicals in a characteristic zonated pattern with high expression prevailing in the downstream perivenous region. In the present review we summarize recent studies, mainly based on rat liver, on the factors regulating this position-dependent expression and induction. Pituitary-dependent signals mediated by growth hormone and thyroid hormone seem to selectively down-regulate the upstream periportal expression of certain CYP forms. It is at present unknown to what extent other hormones that also affect total hepatic CYP activities, i.e. insulin, glucagon, glucocorticoids and gonadal hormones, act zone-specifically. The expression and induction of CYP enzymes in the perivenous region probably have important toxicological implications, since many CYP-activated chemicals cause cell injury primarily in this region of the liver. PMID:9405271

  20. Ab initio dynamics of the cytochrome P450 hydroxylation reaction

    SciTech Connect

    Elenewski, Justin E.; Hackett, John C

    2015-02-14

    The iron(IV)-oxo porphyrin π-cation radical known as Compound I is the primary oxidant within the cytochromes P450, allowing these enzymes to affect the substrate hydroxylation. In the course of this reaction, a hydrogen atom is abstracted from the substrate to generate hydroxyiron(IV) porphyrin and a substrate-centered radical. The hydroxy radical then rebounds from the iron to the substrate, yielding the hydroxylated product. While Compound I has succumbed to theoretical and spectroscopic characterization, the associated hydroxyiron species is elusive as a consequence of its very short lifetime, for which there are no quantitative estimates. To ascertain the physical mechanism underlying substrate hydroxylation and probe this timescale, ab initio molecular dynamics simulations and free energy calculations are performed for a model of Compound I catalysis. Semiclassical estimates based on these calculations reveal the hydrogen atom abstraction step to be extremely fast, kinetically comparable to enzymes such as carbonic anhydrase. Using an ensemble of ab initio simulations, the resultant hydroxyiron species is found to have a similarly short lifetime, ranging between 300 fs and 3600 fs, putatively depending on the enzyme active site architecture. The addition of tunneling corrections to these rates suggests a strong contribution from nuclear quantum effects, which should accelerate every step of substrate hydroxylation by an order of magnitude. These observations have strong implications for the detection of individual hydroxylation intermediates during P450 catalysis.

  1. Selective expression and induction of cytochrome P450PB and P450MC during the development of hereditary hepatitis and hepatoma of LEC rats.

    PubMed

    Sugiyama, T; Suzuki, K; Ookawara, T; Kurosawa, T; Taniguchi, N

    1989-11-01

    The Long-Evans rat with a cinnamon-like coat color (LEC rat) is a mutant strain displaying hereditary hepatitis with severe jaundice. The age related difference in microsomal dealkylation of pentoxyresorufin and ethoxyresorufin was examined. The enzyme activity levels of pentoxyresorufin O-depentylase in LEC rats were decreased to 25% of the levels in control [Long-Evans rats with an agouti coat color (LEA rats)]. In contrast, ethoxyresorufin O-deethylase exhibited a much less marked difference between the strains. In parallel with these strain differences in enzyme activities, a decrease in phenobarbital (PB) inducible P450 isozymes, mainly P450b and P450e, was observed by Western blot analysis. The level of P450PB in LEC rats was more markedly depressed than in the LEA strain. On the other hand, microsomes from uninduced LEC rat liver had more 3-methylcholanthrene (MC) inducible P450MC, mainly P450c and P450d, than microsomes from LEA rat liver and these isozymes in the LEC were markedly induced by 3-methylcholanthrene treatment. The great difference in cytochrome P450PB content of the liver microsomes between LEC and LEA rats and the maintained constitutive levels of hepatic cytochrome P450MC in the LEC rats suggest a possible role of these cytochrome isozymes in the onset of spontaneous hepatitis and hepatoma.

  2. A molecular model for the interaction between vorozole and other non-steroidal inhibitors and human cytochrome P450 19 (P450 aromatase).

    PubMed

    Koymans, L M; Moereels, H; Vanden Bossche, H

    1995-06-01

    In a previous study (Vanden Bossche et al., Breast Cancer Res. Treat. 30 (1994) 43) the interaction between (+)-S-vorozole and the I-helix of cytochrome P450 19 (P450 aromatase) has been reported. In the present study we extended the "I-helix model" by incorporating the C-terminus of P450 aromatase. The crystal structures of P450 101 (P450 cam), 102 (P450 BM-3) and 108 (P450 terp) reveal that the C-terminus is structurally conserved and forms part of their respective substrate binding pocket. Furthermore, the present study is extended to the interaction between P450 aromatase and its natural substrate androstenedione and the non-steroidal inhibitors (-)-R-vorozole, (-)-S-fadrozole, R-liarozole and (-)-R-aminoglutethimide. It is found that (+)-S-vorozole, (-)-S-fadrozole and R-liarozole bind in a comparable way to P450 aromatase and interact with both the I-helix (Glu302 and Asp309) and C-terminus (Ser478 and His480). The weak activity of (-)-R-aminoglutethimide might be attributed to a lack of interaction with the C-terminus.

  3. Understanding outliers on the usual dose-response curve: venlafaxine as a way to phenotype patients in terms of their CYP 2D6 status and why it matters.

    PubMed

    Preskorn, Sheldon H

    2010-01-01

    Venlafaxine is a model substrate for the drug metabolizing cytochrome P450 (CYP) enzyme 2D6. The desvenlafaxine/venlafaxine ratio, either after a single dose or at steady state, can be used to determine whether a patient is functionally (i.e., phenotypically) a CYP 2D6 extensive or poor metabolizer (EM or PM). In turn, CYP 2D6 EM and PM status is important in determining the efficacy of venlafaxine as an antidepressant. Based on a secondary analysis of four of the venlafaxine registration trials, venlafaxine was effective in patients who were CYP 2D6 EMs versus a parallel placebo-treated control group, whereas it was not effective in patients who were CYP 2D6 PMs. Thus, venlafaxine is a useful example of how drugs can be used to quantify differences in drug metabolizing capacity among patients and how such differences can in turn affect the efficacy of a drug (i.e., make a patient an outlier on the usual dose-response curve).

  4. CYP2D6 predicted metabolizer status and safety in adult patients with attention-deficit hyperactivity disorder participating in a large placebo-controlled atomoxetine maintenance of response clinical trial.

    PubMed

    Fijal, Bonnie A; Guo, Yingying; Li, Si G; Ahl, Jonna; Goto, Taro; Tanaka, Yoko; Nisenbaum, Laura K; Upadhyaya, Himanshu P

    2015-10-01

    Atomoxetine, which is indicated for treatment of attention-deficit hyperactivity disorder (ADHD), is predominantly metabolized by genetically polymorphic cytochrome P450 2D6 (CYP2D6). Based on identified CYP2D6 genotypes, individuals can be categorized into 4 phenotypic metabolizer groups as ultrarapid, extensive, intermediate, and poor. Previous studies have focused on observed differences between poor and extensive metabolizers, but it is not well understood whether the safety profile of intermediate metabolizers differs from that of ultrarapid and extensive metabolizers. This study compared safety and tolerability among the different CYP2D6 metabolizer groups in the 12-week open-label phase of an atomoxetine study in adult patients with ADHD. Genotyping identified 1039 patients as extensive/ultrarapid metabolizers, 780 patients as intermediate metabolizers, and 117 patients as poor metabolizers. Common (≥5% frequency) treatment-emergent adverse events did not significantly differ between extensive/ultrarapid and intermediate metabolizers (odds ratios were <2.0 or >0.5). Poor metabolizers had higher frequencies of dry mouth, erectile dysfunction, hyperhidrosis, insomnia, and urinary retention compared with the other metabolizer groups. There were no significant differences between extensive/ultrarapid and intermediate metabolizers in changes from baseline in vital signs. These results suggest that data from CYP2D6 intermediate and extensive/ultrarapid metabolizers can be combined when considering safety analyses related to atomoxetine.

  5. Metabolism of trimipramine in vitro by human CYP2D6 isozyme.

    PubMed

    Bolaji, O O; Coutts, R T; Baker, G B

    1993-10-01

    In vitro metabolism of the tricyclic antidepressant trimipramine using a commercial preparation of human CYP2D6 isozyme expressed in a human cell line is described. 2-Hydroxytrimipramine and a previously unreported metabolite, 2,10- or 2,11-dihydroxytrimipramine were isolated. Their structures were determined by gas chromatography/mass spectroscopy of underivatized and derivatized extracts. Acetylation of the new metabolite resulted in dehydration at C10 to give 10,11-dehydro-2-acetoxytrimipramine. No N-dealkylation of trimipramine was observed. Prior administration of quinidine produced a large reduction in the metabolic oxidation of trimipramine with CYP2D6 while prior administration of quinine had no effect. The use of this CYP2D6 isozyme preparation in vitro is of value in the identification of possible in vivo substrates for the human CYP2D6 isozyme.

  6. Promising Tools in Prostate Cancer Research: Selective Non-Steroidal Cytochrome P450 17A1 Inhibitors

    PubMed Central

    Bonomo, Silvia; Hansen, Cecilie H.; Petrunak, Elyse M.; Scott, Emily E.; Styrishave, Bjarne; Jørgensen, Flemming Steen; Olsen, Lars

    2016-01-01

    Cytochrome P450 17A1 (CYP17A1) is an important target in the treatment of prostate cancer because it produces androgens required for tumour growth. The FDA has approved only one CYP17A1 inhibitor, abiraterone, which contains a steroidal scaffold similar to the endogenous CYP17A1 substrates. Abiraterone is structurally similar to the substrates of other cytochrome P450 enzymes involved in steroidogenesis, and interference can pose a liability in terms of side effects. Using non-steroidal scaffolds is expected to enable the design of compounds that interact more selectively with CYP17A1. Therefore, we combined a structure-based virtual screening approach with density functional theory (DFT) calculations to suggest non-steroidal compounds selective for CYP17A1. In vitro assays demonstrated that two such compounds selectively inhibited CYP17A1 17α-hydroxylase and 17,20-lyase activities with IC50 values in the nanomolar range, without affinity for the major drug-metabolizing CYP2D6 and CYP3A4 enzymes and CYP21A2, with the latter result confirmed in human H295R cells. PMID:27406023

  7. Promising Tools in Prostate Cancer Research: Selective Non-Steroidal Cytochrome P450 17A1 Inhibitors

    NASA Astrophysics Data System (ADS)

    Bonomo, Silvia; Hansen, Cecilie H.; Petrunak, Elyse M.; Scott, Emily E.; Styrishave, Bjarne; Jørgensen, Flemming Steen; Olsen, Lars

    2016-07-01

    Cytochrome P450 17A1 (CYP17A1) is an important target in the treatment of prostate cancer because it produces androgens required for tumour growth. The FDA has approved only one CYP17A1 inhibitor, abiraterone, which contains a steroidal scaffold similar to the endogenous CYP17A1 substrates. Abiraterone is structurally similar to the substrates of other cytochrome P450 enzymes involved in steroidogenesis, and interference can pose a liability in terms of side effects. Using non-steroidal scaffolds is expected to enable the design of compounds that interact more selectively with CYP17A1. Therefore, we combined a structure-based virtual screening approach with density functional theory (DFT) calculations to suggest non-steroidal compounds selective for CYP17A1. In vitro assays demonstrated that two such compounds selectively inhibited CYP17A1 17α-hydroxylase and 17,20-lyase activities with IC50 values in the nanomolar range, without affinity for the major drug-metabolizing CYP2D6 and CYP3A4 enzymes and CYP21A2, with the latter result confirmed in human H295R cells.

  8. Hepatic Cytochrome P450 Activity, Abundance, and Expression Throughout Human Development

    PubMed Central

    Sadler, Natalie C.; Nandhikonda, Premchendar; Webb-Robertson, Bobbie-Jo; Ansong, Charles; Anderson, Lindsey N.; Smith, Jordan N.; Corley, Richard A.

    2016-01-01

    Cytochrome P450s are oxidative metabolic enzymes that play critical roles in the biotransformation of endogenous compounds and xenobiotics. The expression and activity of P450 enzymes varies considerably throughout human development; the deficit in our understanding of these dynamics limits our ability to predict environmental and pharmaceutical exposure effects. In an effort to develop a more comprehensive understanding of the ontogeny of P450 enzymes, we employed a multi-omic characterization of P450 transcript expression, protein abundance, and functional activity. Modified mechanism-based inhibitors of P450s were used as chemical probes for isolating active P450 proteoforms in human hepatic microsomes with developmental stages ranging from early gestation to late adult. High-resolution liquid chromatography–mass spectrometry was used to identify and quantify probe-labeled P450s, allowing for a functional profile of P450 ontogeny. Total protein abundance profiles and P450 rRNA was also measured, and our results reveal life-stage–dependent variability in P450 expression, abundance, and activity throughout human development and frequent discordant relationships between expression and activity. We have significantly expanded the knowledge of P450 ontogeny, particularly at the level of individual P450 activity. We anticipate that these results will be useful for enabling predictive therapeutic dosing, and for avoiding potentially adverse and harmful reactions during maturation from both therapeutic drugs and environmental xenobiotics. PMID:27084891

  9. Auto-interpreter for CYP2D6 SNaPshot genotyping.

    PubMed

    Ong, Sungmoon; Jeong, Hye-Eun; Lee, Sang Seop; Shon, Ji-Hong; Shin, Jae-Gook; Kim, Eun-Young

    2008-11-06

    CYP2D6 genotyping using SNaPshot method is a very useful tool clinically. However it's hard to interpret the obtained data as a genotype without training. Thus SNaPshot auto-interpreter for the genotype was designed to interpret obtained raw data to a genotype. The auto-interpreter showed good concordance with experts' reading. The validated auto-interpreter of CYP2D6 genotyping using SNaPshot can contribute to accelerating the clinical use.

  10. Combining in silico protein stability calculations with structure-function relationships to explore the effect of polymorphic variation on cytochrome P450 drug metabolism.

    PubMed

    Arendse, Lauren; Blundell, Tom L; Blackburn, Jonathan

    2013-09-01

    We carried out an in silico structural analysis of 348 non-synonymous single nucleotide polymorphisms, found across nine of the major human drug metabolising cytochrome P450 isoforms, to determine the effects of mutations on enzyme structure and function. Previous functional studies in our group have delineated regions of the cytochrome P450 structure important for substrate recognition, substrate and product access and egress from the active site and interaction with the cytochrome P450 reductase. Here we combine the information from those studies with new in silico calculations on the effect of mutations on protein stability and we compare our results to experimental data in order to establish the likely causes of altered drug metabolism observed for cytochrome P450 variants in functional assays to date, in the process creating a cytochrome P450 polymorphic variant map. Using the computational tool Site Directed Mutator we predicted destabilising mutations that result in altered enzyme function in vitro with a specificity of 83%. We found that 75% of all cytochrome P450 mutations that show altered activity in vitro are either predicted to be destabilising to protein structure or are found within regions predicted to be important for catalytic activity. Furthermore, we found that 70% of the mutations that showed similar activity to the wild-type enzyme in in vitro studies lie outside of functional regions important for catalytic activity and are predicted to have no effect on protein stability. Our resultant cytochrome P450 polymorphic variant map should therefore find utility in predicting the likely functional effect of uncharacterised variants on drug metabolism.

  11. Effect of CYP2D6 genetic polymorphism on the metabolism of citalopram in vitro.

    PubMed

    Hu, Xiao-Xia; Yuan, Ling-Jing; Fang, Ping; Mao, Yong-Hui; Zhan, Yun-Yun; Li, Xiang-Yu; Dai, Da-Peng; Cai, Jian-Ping; Hu, Guo-Xin

    2016-04-01

    Genetic polymorphisms of CYP2D6 significantly influence the efficacy and safety of some drugs, which might cause adverse effects and therapeutic failure. We aimed at investigating the role of CYP2D6 in the metabolism of citalopram and identifying the effect of 24 CYP2D6 allelic variants we found in Chinese Han population on the metabolism of citalopram in vitro. These CYP2D6 variants expressed by insect cells system were incubated with 10-1000 μM citalopram for 30 min at 37 °C and the reaction was terminated by cooling to -80 °C immediately. Citalopram and its metabolites were analyzed by high-performance liquid chromatography (HPLC). The intrinsic clearance (Vmax/Km) values of the variants toward citalopram metabolites were significantly altered, 38-129% for demethylcitalopram and 13-138% for citalopram N-oxide when compared with CYP2D6*1. Most of the tested rare alleles exhibited significantly decreased values due to increased Km and/or decreased Vmax values. We conclude that recombinant system could be used to investigate the enzymes involved in drug metabolism and these findings suggest that more attention should be paid to subjects carrying these CYP2D6 alleles when administering citalopram in the clinic.

  12. SNP genotyping using TaqMan technology: the CYP2D6*17 assay conundrum.

    PubMed

    Gaedigk, Andrea; Freeman, Natalie; Hartshorne, Toinette; Riffel, Amanda K; Irwin, David; Bishop, Jeffrey R; Stein, Mark A; Newcorn, Jeffrey H; Jaime, Lazara Karelia Montané; Cherner, Mariana; Leeder, J Steven

    2015-03-19

    CYP2D6 contributes to the metabolism of many clinically used drugs and is increasingly tested to individualize drug therapy. The CYP2D6 gene is challenging to genotype due to the highly complex nature of its gene locus. TaqMan technology is widely used in the clinical and research settings for genotype analysis due to assay reliability, low cost, and the availability of commercially available assays. The assay identifying 1023C>T (rs28371706) defining a reduced function (CYP2D6*17) and several nonfunctional alleles, produced a small number of unexpected diplotype calls in three independent sets of samples, i.e. calls suggested the presence of a CYP2D6*4 subvariant containing 1023C>T. Gene resequencing did not reveal any unknown SNPs in the primer or probe binding sites in any of the samples, but all affected samples featured a trio of SNPs on their CYP2D6*4 allele between one of the PCR primer and probe binding sites. While the phenomenon was ultimately overcome by an alternate assay utilizing a PCR primer excluding the SNP trio, the mechanism causing this phenomenon remains elusive. This rare and unexpected event underscores the importance of assay validation in samples representing a variety of genotypes, but also vigilance of assay performance in highly polymorphic genes such as CYP2D6.

  13. RRM1, TUBB3, TOP2A, CYP19A1, CYP2D6: Difference between mRNA and protein expression in predicting prognosis of breast cancer patients.

    PubMed

    Xu, Ying-Chun; Zhang, Feng-Chun; Li, Jun-Jian; Dai, Jia-Qi; Liu, Qiang; Tang, Lei; Ma, Yue; Xu, Qi; Lin, Xiao-Lin; Fan, Hong-Bin; Wang, Hong-Xia

    2015-10-01

    The study investigated the clinical significance of RRM1 (ribonucleoside reductase subunit M1), TUBB3 (tubulin-β-III), TOP2A (DNA topoisomerase II), CYP19A1 (cytochrome P450, family 19, subfamily A, polypeptide 1) and CYP2D6 (cytochrome P450, family 2, subfamily D, polypeptide 6) for the diagnosis and possible predictive roles in breast cancer. Tissue microarray detected the expression of RRM1, tubulin-β-III, Topo IIα, CYP19A1 and CYP2D6 protein in breast cancer tissue and tissue adjacent to tumors (TATs). In addition, a publically available tool, was used to assess the prognostic value of their gene expression in breast cancer (http://kmplot.com). Analysis for relapse-free survival (RFS), disease-free survival (DFS) and overall survival (OS) was performed. Cytoplasmic RRM1, tubulin-β-III, CYP19A1 and Topo IIα staining were significantly higher in breast cancer tissues compared with TATs (P<0.050). Significant correlation occurred between RRM1 expression with pathological classification (P=0.018), lymph node involvement (P=0.035) and ER status (P=0.003). Tubulin-β-III and CYP2D6 expression correlated significantly with tumor grade (P=0.021 for tubulin-β-III and P=0.029 for CYP2D6, respectively). Cox analysis showed that the protein expression of CYP2D6, CYP19A1, RRM1, Topo IIα or tubulin-β-III was not an independent prognostic factor. A significant association occurred between RFS and TUBB3, TOP2A, CYP19A1, and CYP2D6 mRNA expression. With CYP19A1 (P<0.001) and CYP2D6 (P<0.001), a high expression was associated with good clinical outcome. Conversely, a low expression of TUBB3 (P<0.001) and TOP2A (P<0.001) was associated with good clinical outcome. TUBB3 (P=0.0004) and TOP2A (P<0.001) were significant prognostic factors in predicting the patient OS. The expression of RRM1, tubulin-β-III, Topo IIα and CYP19A1 in tumor tissues was significantly higher than that in TATs. TUBB3, TOP2A, CYP19A1 and CYP2D6 gene expression, but not protein expression, was

  14. The Interaction of Microsomal Cytochrome P450 2B4 with its Redox Partners, Cytochrome P450 Reductase and Cytochrome b5

    PubMed Central

    Im, Sang-Choul; Waskell, Lucy

    2010-01-01

    1 Cytochrome P450 2B4 is a microsomal protein with a multi-step reaction cycle similar to that observed in the majority of other cytochromes P450. The cytochrome P450 2B4-substrate complex is reduced from the ferric to the ferrous form by cytochrome P450 reductase. After binding oxygen, the oxyferrous protein accepts a second electron which is provided by either cytochrome P450 reductase or cytochrome b5. In both instances, product formation occurs. When the second electron is donated by cytochrome b5, catalysis (product formation) is ∼ 10 to 100-fold faster than in the presence of cytochrome P450 reductase. This allows less time for side product formation (hydrogen peroxide and superoxide) and improves by ∼ 15% the coupling of NADPH consumption to product formation. Cytochrome b5 has also been shown to compete with cytochrome P450 reductase for a binding site on the proximal surface of cytochrome P450 2B4. These two different effects of cytochrome b5 on cytochrome P450 2B4 reactivity can explain how cytochrome b5 is able to stimulate, inhibit, or have no effect on cytochrome P450 2B4 activity. At low molar ratios (<1) of cytochrome b5 to cytochrome P450 reductase, the more rapid catalysis results in enhanced substrate metabolism. In contrast, at high molar ratios (>1) of cytochome b5 to cytochrome P450 reductase, cytochrome b5 inhibits activity by binding to the proximal surface of cytochrome P450 and preventing the reductase from reducing ferric cytochrome P450 to the ferrous protein, thereby aborting the catalytic reaction cycle. When the stimulatory and inhibitory effects of cytochrome b5 are equal, it will appear to have no effect on the enzymatic activity. It is hypothesized that cytochrome b5 stimulates catalysis by causing a conformational change in the active site, which allows the active oxidizing oxyferryl species of cytochrome P450 to be formed more rapidly than in the presence of reductase. PMID:21055385

  15. Cytochrome P450 Enzyme Metabolites in Lead Discovery and Development

    PubMed Central

    Kandel, Sylvie E.; Wienkers, Larry C.; Lampe, Jed N.

    2015-01-01

    The cytochrome P450 (CYP) enzymes are a versatile superfamily of heme-containing monooxygenases, perhaps best known for their role in the oxidation of xenobiotic compounds. However, due to their unique oxidative chemistry, CYPs are also important in natural product drug discovery and in the generation of active metabolites with unique therapeutic properties. New tools for the analysis and production of CYP metabolites, including microscale analytical technologies and combinatorial biosynthesis, are providing medicinal chemists with the opportunity to use CYPs as a novel platform for lead discovery and development. In this review, we will highlight some of the recent examples of drug leads identified from CYP metabolites and the exciting possibilities of using CYPs as catalysts for future drug discovery. PMID:25797999

  16. Enzyme kinetics of oxidative metabolism: cytochromes P450.

    PubMed

    Korzekwa, Ken

    2014-01-01

    The cytochrome P450 enzymes (CYPs) are the most important enzymes in the oxidative metabolism of hydrophobic drugs and other foreign compounds (xenobiotics). The versatility of these enzymes results in some unusual kinetic properties, stemming from the simultaneous interaction of multiple substrates with the CYP active site. Often, the CYPs display kinetics that deviate from standard hyperbolic saturation or inhibition kinetics. Non-Michaelis-Menten or "atypical" saturation kinetics include sigmoidal, biphasic, and substrate inhibition kinetics (see Chapter 3 ). Interactions between substrates include competitive inhibition, noncompetitive inhibition, mixed inhibition, partial inhibition, activation, and activation followed by inhibition (see Chapter 4 ). Models and equations that can result in these kinetic profiles will be presented and discussed.

  17. Personalized Cancer Therapy Considering Cytochrome P450 Variability.

    PubMed

    Preissner, Saskia; Simmaco, Maurizio; Gentile, Giovanna; Preissner, Robert

    2015-01-01

    The individual variability of pharmacokinetics is underestimated and few systematic studies exist in this field. In most cases, this leads to unwanted side effects or toxicity. In polychemotherapy, prodrugs (like ifosfamide), which have to be activated by cytochrome P450 enzymes (CYPs), play an important role. If patients are poor metabolizers for these drugs, the therapy will be ineffective. Furthermore, CYPs and transporters can be (over)expressed in target tissues, which is also not examined and considered in clinical routine. Here, we present a body map showing relevant enzymes in some organs and tissues. Finally, a typical case of a Caucasian chemotherapy patient with breast cancer is presented and discussed regarding a personalized cancer therapy considering the single nucleotide polymorphisms found via genotyping.

  18. Identification of small-molecule scaffolds for p450 inhibitors.

    PubMed

    von Kries, Jens P; Warrier, Thulasi; Podust, Larissa M

    2010-02-01

    Mycobacterium tuberculosis cytochrome P450 enzymes (CYP) attract ongoing interest for their pharmacological development potential, driving direct screening efforts against potential CYP targets with the ultimate goal of developing potent CYP-specific inhibitors and/or molecular probes to address M. tuberculosis biology. The property of CYP enzymes to shift the ferric heme Fe Soret band in response to ligand binding provides the basis for an experimental platform for high-throughput screening (HTS) of compound libraries to select chemotypes with high binding affinities to the target. Promising compounds can be evaluated in in vitro assays or in vivo disease models and further characterized by x-ray crystallography, leading to optimization strategies to assist drug design. Protocols are provided for compound library screening, analysis of inhibitory potential, and co-crystallization with the target CYP, as well as expression and purification of soluble CYP enzymes.

  19. Bacterial Cytochrome P450 System Catabolizing the Fusarium Toxin Deoxynivalenol

    PubMed Central

    Ito, Michihiro; Sato, Ikuo; Ishizaka, Masumi; Yoshida, Shin-ichiro; Koitabashi, Motoo; Yoshida, Shigenobu

    2013-01-01

    Deoxynivalenol (DON) is a natural toxin of fungi that cause Fusarium head blight disease of wheat and other small-grain cereals. DON accumulates in infected grains and promotes the spread of the infection on wheat, posing serious problems to grain production. The elucidation of DON-catabolic genes and enzymes in DON-degrading microbes will provide new approaches to decrease DON contamination. Here, we report a cytochrome P450 system capable of catabolizing DON in Sphingomonas sp. strain KSM1, a DON-utilizing bacterium newly isolated from lake water. The P450 gene ddnA was cloned through an activity-based screening of a KSM1 genomic library. The genes of its redox partner candidates (flavin adenine dinucleotide [FAD]-dependent ferredoxin reductase and mitochondrial-type [2Fe-2S] ferredoxin) were not found adjacent to ddnA; the redox partner candidates were further cloned separately based on conserved motifs. The DON-catabolic activity was reconstituted in vitro in an electron transfer chain comprising the three enzymes and NADH, with a catalytic efficiency (kcat/Km) of 6.4 mM−1 s−1. The reaction product was identified as 16-hydroxy-deoxynivalenol. A bioassay using wheat seedlings revealed that the hydroxylation dramatically reduced the toxicity of DON to wheat. The enzyme system showed similar catalytic efficiencies toward nivalenol and 3-acetyl deoxynivalenol, toxins that frequently cooccur with DON. These findings identify an enzyme system that catabolizes DON, leading to reduced phytotoxicity to wheat. PMID:23275503

  20. Genetic polymorphism of CYP2D6 in patients with systemic lupus erythematosus and systemic sclerosis.

    PubMed

    Barańska, Małgorzata; Rychlik-Sych, Mariola; Kaszuba, Andrzej; Dziankowska-Bartkowiak, Bożena; Skrętkowicz, Jadwiga; Waszczykowska, Elżbieta

    2016-01-20

    Human organism is constantly exposed to harmful exogenous factors (xenobiotics) including drugs and carcinogenic compounds that can induce development of a large number of diseases. The processes of biotransformation in the organism are multidirectional and xenobiotics can be transformed into active or inactive metabolites via the oxidative route. The knowledge of oxidation polymorphism in the course of systemic lupus erythematosus and systemic sclerosis may be helpful in choosing more efficient and safer therapy, particularly in the case of a disease involving various organs and treated with drugs belonging to diverse therapeutic groups. The aim of the study was to evaluate the CYP2D6 polymorphism in the SLE (systemic lupus erythematosus) and SSc (systemic sclerosis) patients and to investigate a possible correlation with disease susceptibility. The study was carried out in 296 patients: 65 patients with SLE, 81 patients with SSc, and 150 healthy volunteers. The CYP2D6 genotypes were analyzed by polymerase chain reaction fragment length polymorphism (PCR-RFLP) method. The relative risk of developing SSc, expressed by the odds ratio, was three-fold higher for persons with the CYP2D6*1/CYP2D6*4 genotype (OR = 2.9; statistically significant difference, p = 0.0002). A statistically significant correlation between the CYP2D6*4 allele prevalence and the risk for developing SSc was found (OR = 1.53; p = 0.047). No effect of the CYP2D6 gene mutations on the incidence of SLE was noted. The obtained results may suggest the influence of CYP2D6*4 gene variants alleles on increased incidence of systemic sclerosis.

  1. Relevance of cytochrome P450s in plants: also one of Ron Estabrook's research interests.

    PubMed

    Shet, Manjunath S

    2007-01-01

    I worked with Dr. Ronald Estabrook for nearly 10 years at The University of Texas Southwestern Medical Center in Dallas, Texas. In Ron's lab, when I joined I was initially involved in the isolation, purification, and characterization of cytochrome P450s and NADPH-P450(c) reductase(s) from plants, which was his new exploratory project at the time. We developed methods for the isolation, solubilization, and purification of P450s and NADPH-P450(c) reductase from plant tissue microsomes. We carried out number of in vitro experiments to study the involvement P450s and NADPH-P450(c) reductase in the biosynthesis of number of phytoalexins. We successfully isolated, purified, and cloned NADPH-P450(c) reductase from etiolated mung bean (Vigna radiate) seedlings. In addition, a series of studies were undertaken to show that purified mung bean NADPH-P450(c) reductase was able to catalyze P450-supported reactions for mammalian and bacterial P450s. My stay in Ron's lab was very educational and productive. He provided the necessary support and led the way through the maze in different research projects in the lab, which allowed me to understand the roles of P450s in humans, animals, plants, and microorganisms. He liked to teach and discover new things everyday in the lab. He is a great scientist, as well as loving and caring mentor.

  2. Monooxygenation of small hydrocarbons catalyzed by bacterial cytochrome p450s.

    PubMed

    Shoji, Osami; Watanabe, Yoshihito

    2015-01-01

    Cytochrome P450s (P450s) catalyze the NAD(P)H/O2-dependent monooxygenation of less reactive organic molecules under mild conditions. The catalytic activity of bacterial P450s is very high compared with P450s isolated from animals and plants, and the substrate specificity of bacterial P450s is also very high. Accordingly, their catalytic activities toward nonnative substrates are generally low especially toward small hydrocarbons. However, mutagenesis approaches have been very successful for engineering bacterial P450s for the hydroxylation of small hydrocarbons. On the other hand, "decoy" molecules, whose structures are very similar to natural substrates, can be used to trick the substrate recognition of bacterial P450s, allowing the P450s to catalyze oxidation reactions of nonnative substrates without any substitution of amino acid residues in the presence of decoy molecules. Thus, the hydroxylation of small hydrocarbons such as ethane, propane, butane and benzene can be catalyzed by P450BM3, a long-alkyl-chain hydroxylase, using substrate misrecognition of P450s induced by decoy molecules. Furthermore, a number of H2O2-dependent bacterial P450s can catalyze the peroxygenation of a variety of nonnative substrates through a simple substrate-misrecognition trick, in which catalytic activities and enantioselectivity are dependent on the structure of decoy molecules.

  3. Expression of cytochrome P450 genes in CD34+ hematopoietic stem and progenitor cells.

    PubMed

    Soucek, Pavel; Anzenbacher, Pavel; Skoumalová, Ivana; Dvorák, Michal

    2005-10-01

    Expression of major cytochrome P450 forms (P450) was followed in preparation of purified hematopoietic CD34+ stem and progenitor cells. Levels of transcripts as well as mature proteins were traced by quantitative real-time polymerase chain reaction and by Northern and Western blotting. P450 1B1 and P450 2E1 proteins and respective mRNAs were found in all cases. On the other hand, no expression of P450 3A4, P450 3A7, and P450 2C9 was found. The results showed that expression of various P450 enzymes starts at different stages of cell differentiation. Both P450 forms found are known to be connected with cancer cells and with activation of procarcinogens (P450 1B1, polycyclic aromatic hydrocarbons; P450 2E1, nitrosamines, and solvents). Hence, cells at the early stage of differentiation already may be influenced by interaction with xenobiotics. This fact should also be taken into consideration when hematopoietic cell transplant therapy is applied.

  4. Time-dependent inhibition of human drug metabolizing cytochromes P450 by tricyclic antidepressants

    PubMed Central

    Polasek, Thomas M; Miners, John O

    2008-01-01

    AIMS To investigate time-dependent inhibition (TDI) of human drug metabolizing CYP enzymes by tricyclic antidepressants (TCAs). METHODS CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A/CYP3A4 activities were investigated following co- and preincubation with TCAs using human liver microsomes (HLM) and human recombinant CYP proteins (expressed in Escherichia coli) as the enzyme sources. A two-step incubation method was employed to examine the in vitro mechanism-based inactivation (MBI) criteria. Potential metabolite–intermediate complex (MIC) formation was studied by spectral analysis. RESULTS TCAs generally exhibited significant TDI of recombinant CYP1A2, CYP2C19 and CYP2D6 (>10% positive inhibition differences between co- and preincubation conditions). TDI of recombinant CYP2C9 was minor (<10%), and was minor or absent in experiments utilizing recombinant CYP3A4 or HLM as the enzyme sources. Where observed, TDI of recombinant CYP occurred via alkylamine MIC formation, but evidence to support similar behaviour in HLM was limited. Indeed, only secondary amine TCAs reduced the apparent P450 content of HLM (3–6%) consistent with complexation. As a representative TCA, nortriptyline fulfilled the in vitro MBI criteria using recombinant CYP2C19 and CYP3A4 (KI and kinact values of 4 µm and 0.19 min−1, and 70 µm and 0.06 min−1), but not with the human liver microsomal enzymes. CONCLUSIONS TCAs appear to have minimal potential for MBI of human liver microsomal CYP enzymes involved in drug metabolism. HLM and recombinant CYP (expressed in E. coli) are not equivalent enzyme sources for evaluating the TDI associated with some drugs. WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT Much of the literature evidence for mechanism-based inactivation (MBI) of CYP by tricyclic antidepressants is limited to studies in rat liver microsomes. One report from this laboratory characterized MBI of human recombinant CYP2C8 by nortriptyline. WHAT THIS STUDY ADDS Tricyclic antidepressants form

  5. Cytochrome P450 3A Enzymes Catalyze the O6-Demethylation of Thebaine, a Key Step in Endogenous Mammalian Morphine Biosynthesis.

    PubMed

    Kramlinger, Valerie M; Alvarado Rojas, Mónica; Kanamori, Tatsuyuki; Guengerich, F Peter

    2015-08-14

    Morphine, first characterized in opium from the poppy Papaver somniferum, is one of the strongest known analgesics. Endogenous morphine has been identified in several mammalian cells and tissues. The synthetic pathway of morphine in the opium poppy has been elucidated. The presence of common intermediates in plants and mammals suggests that biosynthesis occurs through similar pathways (beginning with the amino acid L-tyrosine), and the pathway has been completely delineated in plants. Some of the enzymes in the mammalian pathway have been identified and characterized. Two of the latter steps in the morphine biosynthesis pathway are demethylation of thebaine at the O(3)- and the O(6)-positions, the latter of which has been difficult to demonstrate. The plant enzymes responsible for both the O(3)-demethylation and the O(6)-demethylation are members of the Fe(II)/α-ketoglutarate-dependent dioxygenase family. Previous studies showed that human cytochrome P450 (P450) 2D6 can catalyze thebaine O(3)-demethylation. We report that demethylation of thebaine at the O(6)-position is selectively catalyzed by human P450s 3A4 and 3A5, with the latter being more efficient, and rat P450 3A2. Our results do not support O(6)-demethylation of thebaine by an Fe(II)/α-ketoglutarate-dependent dioxygenase. In rat brain microsomes, O(6)-demethylation was inhibited by ketoconazole, but not sulfaphenazole, suggesting that P450 3A enzymes are responsible for this activity in the brain. An alternate pathway to morphine, oripavine O(6)-demethylation, was not detected. The major enzymatic steps in mammalian morphine synthesis have now been identified.

  6. Effects of 22 CYP2D6 Genetic Variations Newly Identified in Chinese Population on Olanzapine Metabolism in vitro.

    PubMed

    Zhou, Hong-Yu; Gu, Er-Min; Chen, Qiu-Lei; Zhan, Yun-Yun; Wang, Shuang-Hu; Liang, Bing-Qing; Dai, Da-Peng; Cai, Jian-Ping; Hu, Guo-Xin

    2016-01-01

    The objective of this study was to assess the catalytic activity of 22 novel CYP2D6 allelic variants (2D6*87-*98, R25Q, F164L, E215K, F219S, V327M, D336N, V342M, R344Q, R440C and R497C) to olanzapine in vitro. Their protein products expressed in Spodoptera frugiperda 21 (Sf21) insect cells were incubated with olanzapine 100-2,000 μmol/l for 30 min. The kinetic parameters of Km, Vmax and intrinsic clearance were determined by 2-hydroxymethylolanzapine, the metabolite of olanzapine mediated by CYP2D6, using ultra-performance liquid chromatography tandem mass spectrometry. Results showed that the kinetic parameters of 2 alleles, CYP2D6*92 and 2D6*96, could not be detected; 17 allelic variants, CYP2D6*87-*88, 2D6*90-*91, 2D6*93-*95, 2D6*97, R25Q, F164L, E215K, F219S, V327M, V342M, R344Q, R440C and R497C, significantly reduced the intrinsic clearance of olanzapine; 2 variants, CYP2D6*89 and 2D6*98, increased the intrinsic clearance of olanzapine; no difference was found in intrinsic clearance of D336N. Furthermore, 6 alleles, CYP2D6*87, 2D6*88, 2D6*91, 2D6*93, 2D6*97 and R497C, exhibited higher Km values in a range of 120.80-217.56% relative to wild-type CYP2D6*1. The research demonstrated the metabolic phenotype of the 22 novel CYP2D6 variants for olanzapine that were different from probe drugs we used previously and might provide beneficial information to the personalized medicine of olanzapine.

  7. tert-Butylphenylacetylene Is a Potent Mechanism-Based Inactivator of Cytochrome P450 2B4: Inhibition of Cytochrome P450 Catalysis by Steric Hindrance

    PubMed Central

    Zhang, Haoming; Lin, Hsia-lien; Walker, Vyvyca J.; Hamdane, Djemel

    2009-01-01

    We have demonstrated that 4-(tert-butyl)-phenylacetylene (tBPA) is a potent mechanism-based inactivator for cytochrome P450 2B4 (P450 2B4) in the reconstituted system. It inactivates P450 2B4 in a NADPH- and time-dependent manner with a KI of 0.44 μM and kinact of 0.12 min−1. The partition ratio was approximately zero, indicating that inactivation occurs without the reactive intermediate leaving the active site. Liquid chromatography-mass spectrometry analyses revealed that tBPA forms a protein adduct with a 1:1 stoichiometry. Peptide mapping of the tBPA-modified protein provides evidence that tBPA is covalently bound to Thr302. This is consistent with results of molecular modeling that show the terminal carbon of the acetylenic group is only 3.65 Å away from Thr302. To characterize the effect of covalent modification of Thr302, tBPA-modified P450 2B4 was purified to homogeneity from the reconstituted system. The Soret band of tBPA-modified protein is red-shifted by 5 to 422 nm compared with unmodified protein. Benzphetamine binding to the modified P450 2B4 causes no spin shift, indicating that substrate binding and/or the heme environment has been altered by covalently bound tBPA. Cytochrome P450 reductase reduces the unmodified and tBPA-modified P450s at approximately the same rate. However, addition of benzphetamine stimulates the rate of reduction of unmodified P450 2B4 by ∼20-fold but only marginally stimulates reduction of the tBPA-modified protein. This large discrepancy in the stimulation of the first electron transfer by benzphetamine strongly suggests that the impairment of P450 catalysis is due to inhibition of benzphetamine binding to the tBPA-modified P450 2B4. PMID:19720728

  8. In vitro cytochrome P450 inhibition potential of methylenedioxy-derived designer drugs studied with a two-cocktail approach.

    PubMed

    Dinger, Julia; Meyer, Markus R; Maurer, Hans H

    2016-02-01

    In vitro cytochrome P450 (CYP) inhibition assays are common approaches for testing the inhibition potential of drugs for predicting potential interactions. In contrast to marketed medicaments, drugs of abuse, particularly the so-called novel psychoactive substances, were not tested before distribution and consumption. Therefore, the inhibition potential of methylenedioxy-derived designer drugs (MDD) of different drug classes such as aminoindanes, amphetamines, benzofurans, cathinones, piperazines, pyrrolidinophenones, and tryptamines should be elucidated. The FDA-preferred test substrates, split in two cocktails, were incubated with pooled human liver microsomes and analysed after protein precipitation using LC-high-resolution-MS/MS. IC50 values were determined of MDD showing more than 50 % inhibition in the prescreening. Values were calculated by plotting the relative metabolite concentration formed over the logarithm of the inhibitor concentration. All MDD showed inhibition against CYP2D6 activity and most of them in the range of the clinically relevant CYP2D6 inhibitors quinidine and fluoxetine. In addition, the beta-keto compounds showed inhibition of the activity of CYP2B6, 5,6-MD-DALT of CYP1A2 and CYP3A, and MDAI of CYP2A6, all in the range of clinically relevant inhibitors. In summary, all MDD showed inhibition of the activity of CYP2D6, six of CYP1A2, three of CYP2A6, 13 of CYP2B6, two of CYP2C9, six of CYP2C19, one of CYP2E1, and six of CYP3A. These results showed that the CYP inhibition by MDD might be clinically relevant, but further studies are needed for final conclusions.

  9. In Silico Prediction of Cytochrome P450-Drug Interaction: QSARs for CYP3A4 and CYP2C9

    PubMed Central

    Nembri, Serena; Grisoni, Francesca; Consonni, Viviana; Todeschini, Roberto

    2016-01-01

    Cytochromes P450 (CYP) are the main actors in the oxidation of xenobiotics and play a crucial role in drug safety, persistence, bioactivation, and drug-drug/food-drug interaction. This work aims to develop Quantitative Structure-Activity Relationship (QSAR) models to predict the drug interaction with two of the most important CYP isoforms, namely 2C9 and 3A4. The presented models are calibrated on 9122 drug-like compounds, using three different modelling approaches and two types of molecular description (classical molecular descriptors and binary fingerprints). For each isoform, three classification models are presented, based on a different approach and with different advantages: (1) a very simple and interpretable classification tree; (2) a local (k-Nearest Neighbor) model based classical descriptors and; (3) a model based on a recently proposed local classifier (N-Nearest Neighbor) on binary fingerprints. The salient features of the work are (1) the thorough model validation and the applicability domain assessment; (2) the descriptor interpretation, which highlighted the crucial aspects of P450-drug interaction; and (3) the consensus aggregation of models, which largely increased the prediction accuracy. PMID:27294921

  10. Influence of CYP2D6 genotype on the disposition of the enantiomers of venlafaxine and its major metabolites in postmortem femoral blood.

    PubMed

    Kingbäck, Maria; Karlsson, Louise; Zackrisson, Anna-Lena; Carlsson, Björn; Josefsson, Martin; Bengtsson, Finn; Ahlner, Johan; Kugelberg, Fredrik C

    2012-01-10

    Venlafaxine (VEN) is an antidepressant drug mainly metabolized by the cytochrome P450 (CYP) enzyme CYP2D6 to the active metabolite O-desmethylvenlafaxine (ODV). VEN is also metabolized to N-desmetylvenlafaxine (NDV) via CYP3A4. ODV and NDV are further metabolized to N,O-didesmethylvenlafaxine (DDV). VEN is a racemic mixture of the S- and R-enantiomers and these have in vitro displayed different degrees of serotonin and noradrenaline reuptake inhibition. The aim of the study was to investigate if an enantioselective analysis of VEN and its metabolites, in combination with genotyping for CYP2D6, could assist in the interpretation of forensic toxicological results in cases with different causes of deaths. Concentrations of the enantiomers of VEN and metabolites were determined in femoral blood obtained from 56 autopsy cases with different causes of death. The drug analysis was done by liquid chromatography tandem mass spectrometry (LC/MS/MS) and the CYP2D6 genotyping by PCR and pyrosequencing. The mean (median) enantiomeric S/R ratios of VEN, ODV, NDV and DDV were 0.99 (0.91), 2.17 (0.93), 0.92 (0.86) and 1.08 (1.03), respectively. However, a substantial variation in the relationship between the S- and R-enantiomers of VEN and metabolites was evident (S/R ratios ranging from 0.23 to 17.6). In six cases, a low S/R VEN ratio (mean 0.5) was associated with a high S/R ODV ratio (mean 11.9). Genotyping showed that these individuals carried two inactive CYP2D6 genes indicating a poor metabolizer phenotype. From these data we conclude that enantioselective analysis of VEN and ODV can predict if a person is a poor metabolizer genotype/phenotype for CYP2D6. Knowledge of the relationship between the S- and R-enantiomers of this antidepressant drug and its active metabolite is also important since the enantiomers display different pharmacodynamic profiles.

  11. The diverse chemistry of cytochrome P450 17A1 (P450c17, CYP17A1)

    PubMed Central

    Yoshimoto, Francis K.; Auchus, Richard J.

    2014-01-01

    The steroid hydroxylation and carbon-carbon bond cleavage activities of cytochrome P450 17A1 (CYP17A1) are responsible for the production of glucocorticoids and androgens, respectively. The inhibition of androgen synthesis is an important strategy to treat androgen-dependent prostate cancer. We discuss the different enzymatic activities towards the various substrates of CYP17A1, demonstrating its promiscuity. Additionally, a novel interhelical interaction is proposed between the F-G loop and the B′-helix to explain the 16α-hydroxylase activity of human CYP17A1 with progesterone as the substrate. The techniques used by biochemists to study this important enzyme are also summarized. PMID:25482340

  12. The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.

    PubMed

    Parashar, Abhinav; Gade, Sudeep Kumar; Potnuru, Mahesh; Madhavan, Nandita; Manoj, Kelath Murali

    2014-01-01

    Cytochrome P450 (CYP) family of redox enzymes metabolize drugs and xenobiotics in liver microsomes. Isozyme CYP2C9 is reported to be inhibited by benzbromarone (BzBr) and this phenomenon was hitherto explained by classical active-site binding. Theoretically, it was impossible to envisage the experimentally derived sub-nM Ki for an inhibitor, when supra-nM enzyme and 10X KM substrate concentrations were employed. We set out to find a more plausible explanation for this highly intriguing "super-inhibition" phenomenon. In silico docking of various BzBr analogs with known crystal structure of CYP2C9 did not provide any evidence in support of active-site based inhibition hypothesis. Experiments tested the effects of BzBr and nine analogs on CYPs in reconstituted systems of lab-purified proteins, complex baculosomes & crude microsomal preparations. In certain setups, BzBr and its analogs could even enhance reactions, which cannot be explained by an active site hypothesis. Generally, it was seen that Ki became smaller by orders of magnitude, upon increasing the dilution order of BzBr analogs. Also, it was seen that BzBr could also inhibit other CYP isozymes like CYP3A4, CYP2D6 and CYP2E1. Further, amphipathic derivatives of vitamins C & E (scavengers of diffusible reactive oxygen species or DROS) effectively inhibited CYP2C9 reactions in different reaction setups. Therefore, the inhibition of CYP activity by BzBr analogs (which are also surface-active redox agents) is attributed to catalytic scavenging of DROS at phospholipid interface. The current work expands the scope of interpretations of inhibitions in redox enzymes and ushers in a new cellular biochemistry paradigm that small amounts of DROS may be obligatorily required in routine redox metabolism for constructive catalytic roles.

  13. An enlarged, adaptable active site in CYP164 family P450 enzymes, the sole P450 in Mycobacterium leprae.

    PubMed

    Agnew, Christopher R J; Warrilow, Andrew G S; Burton, Nicholas M; Lamb, David C; Kelly, Steven L; Brady, R Leo

    2012-01-01

    CYP164 family P450 enzymes are found in only a subset of mycobacteria and include CYP164A1, which is the sole P450 found in Mycobacterium leprae, the causative agent of leprosy. This has previously led to interest in this enzyme as a potential drug target. Here we describe the first crystal structure of a CYP164 enzyme, CYP164A2 from Mycobacterium smegmatis. CYP164A2 has a distinctive, enlarged hydrophobic active site that extends above the porphyrin ring toward the access channels. Unusually, we find that CYP164A2 can simultaneously bind two econazole molecules in different regions of the enlarged active site and is accompanied by the rearrangement and ordering of the BC loop. The primary location is through a classic interaction of the azole group with the porphyrin iron. The second econazole molecule is bound to a unique site and is linked to a tetracoordinated metal ion complexed to one of the heme carboxylates and to the side chains of His 105 and His 364. All of these features are preserved in the closely homologous M. leprae CYP164A1. The computational docking of azole compounds to a homology model of CYP164A1 suggests that these compounds will form effective inhibitors and is supported by the correlation of parallel docking with experimental binding studies of CYP164A2. The binding of econazole to CYP164A2 occurs primarily through the high-spin "open" conformation of the enzyme (K(d) [dissociation constant] of 0.1 μM), with binding to the low-spin "closed" form being significantly hindered (K(d) of 338 μM). These studies support previous suggestions that azole derivatives may provide an effective strategy to improve the treatment of leprosy.

  14. Phylogenetic analysis of Bacillus P450 monooxygenases and evaluation of their activity towards steroids.

    PubMed

    Furuya, Toshiki; Shibata, Daisuke; Kino, Kuniki

    2009-11-01

    Cytochrome P450 (P450) open reading frames (ORFs) identified in genome sequences of Bacillus species are potential resources for new oxidation biocatalysts. Phylogenetic analysis of 29 Bacillus P450 ORFs revealed that the P450s consist of a limited number of P450 families, CYP102, CYP106, CYP107, CYP109, CYP134, CYP152, and CYP197. Previously, we identified the catalytic activities of three P450s of Bacillus subtilis towards steroids by rapid substrate screening using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Here, we further applied this method to evaluate the activity of Bacillus cereus P450s towards steroids. Five P450 genes were cloned from B. cereus ATCC 10987 based on its genomic sequence and were expressed in Escherichia coli. These P450s were reacted with a mixture of 30 compounds that mainly included steroids, and the reaction mixtures were analyzed using FT-ICR/MS. We found that BCE_2659 (CYP106) catalyzed the monooxygenation of methyltestosterone, progesterone, 11-ketoprogesterone, medroxyprogesterone acetate, and chlormadinone acetate. BCE_2654 (CYP107) monooxygenated testosterone enanthate, and BCE_3250 (CYP109) monooxygenated testosterone and compactin. Based on the phylogenetic relationship and the known substrate specificities including ones identified in this study, we discuss the catalytic potential of Bacillus P450s towards steroids.

  15. Involvement of Cytochrome P450 in Pentachlorophenol Transformation in a White Rot Fungus Phanerochaete chrysosporium

    PubMed Central

    Ning, Daliang; Wang, Hui

    2012-01-01

    The occurrence of cytochrome P450 and P450-mediated pentachlorophenol oxidation in a white rot fungus Phanerochaete chrysosporium was demonstrated in this study. The carbon monoxide difference spectra indicated induction of P450 (103±13 pmol P450 per mg protein in the microsomal fraction) by pentachlorophenol. The pentachlorophenol oxidation by the microsomal P450 was NADPH-dependent at a rate of 19.0±1.2 pmol min−1 (mg protein)−1, which led to formation of tetrachlorohydroquinone and was significantly inhibited by piperonyl butoxide (a P450 inhibitor). Tetrachlorohydroquinone was also found in the cultures, while the extracellular ligninases which were reported to be involved in tetrachlorohydroquinone formation were undetectable. The formation of tetrachlorohydroquinone was not detectable in the cultures added with either piperonyl butoxide or cycloheximide (an inhibitor of de novo protein synthesis). These results revealed the pentachlorophenol oxidation by induced P450 in the fungus, and it should be the first time that P450-mediated pentachlorophenol oxidation was demonstrated in a microorganism. Furthermore, the addition of the P450 inhibitor to the cultures led to obvious increase of pentachlorophenol, suggesting that the relationship between P450 and pentachlorophenol methylation is worthy of further research. PMID:23029295

  16. Sequence analysis of ripening-related cytochrome P-450 cDNAs from avocado fruit.

    PubMed Central

    Bozak, K R; Yu, H; Sirevåg, R; Christoffersen, R E

    1990-01-01

    The ripening of avocado fruit is associated with the expression of a number of mRNAs concomitant with overt changes in texture and flavor. Two overlapping cDNAs for a mRNA that accumulates during ripening were identified. Sequence analysis of these two cDNAs revealed a polypeptide of 471 amino acids with characteristics of a typical P-450: an N-terminal hydrophobic membrane anchor, a conserved heme-binding domain in the C-terminal region, and patches of similarity to various P-450 family members. Further evidence that this polypeptide represents a cytochrome P-450 oxidase comes from the recent isolation and characterization of a cytochrome P-450 from ripe avocado mesocarp [O'Keefe, D. P. & Leto, K. J. (1989) Plant Physiol. 89, 1141-1149]. The N terminus of the predicted polypeptide in the cDNAs is identical to the N terminus of the purified avocado P-450. Gel blot analysis of RNA from fruit at various stages of ripening showed the accumulation of an 1800-nucleotide P-450 mRNA that hybridized to the P-450 cDNA. The P-450 protein predicted by the avocado cDNA sequence shares less than 40% positional identity with any known P-450 gene family. We propose therefore that it be placed in a separate family, P450LXXI, and that the corresponding gene from avocado be named cyp71A1. Images PMID:1692626

  17. Hepatic cytochrome P450 activity, abundance, and expression throughout human development

    SciTech Connect

    Sadler, Natalie C.; Nandhikonda, Premchendar; Webb-Robertson, Bobbie-Jo M.; Ansong, Charles; Anderson, Lindsey N.; Smith, Jordan N.; Corley, Richard A.; Wright, Aaron T.

    2016-07-01

    Cytochrome P450s are Phase I metabolic enzymes that play critical roles in the biotransformation of endogenous compounds and xenobiotics. The expression and activity of P450 enzymes can vary considerably throughout human development, especially when comparing fetal development to neonates, children, and adults. In an effort to develop a more comprehensive understanding of the ontogeny of P450 expression and activity we employed a multi-omic characterization of P450 transcript expression, protein abundance, and functional activity. To quantify the functional activity of individual P450s we employ activity-based protein profiling, which uses modified mechanism-based inhibitors of P450s as chemical probes, in tandem with proteomic analyses to quantify activity. Our results reveal life-stage-dependent variability in P450 expression, abundance, and activity throughout human development and frequent discordant relationships between expression and activity. The results were used to distribute P450s into three general classes based upon developmental stage of expression and activity. We have significantly expanded the knowledge of P450 ontogeny, particularly at the level of individual P450 activity. We anticipate that our ontogeny results will be useful for enabling predictive therapeutic dosing, and for avoiding potentially adverse and harmful reactions during maturation from both therapeutic drugs and environmental xenobiotics.

  18. Interpreting the CYP2D6 Results From the International Tamoxifen Pharmacogenetics Consortium

    PubMed Central

    Province, MA; Altman, RB; Klein, TE

    2014-01-01

    Meta-analysis of the entire analyzable cohort of 4,935 tamoxifen-treated breast cancer patients by the International Tamoxifen Pharmacogenetics Consortium (ITPC) (criterion 3) revealed no CYP2D6 effect on outcomes but strong heterogeneity across sites.1 However, a post hoc–defined subgroup (criterion 1: postmenopausal, estrogen receptor positive, receiving 20 mg/day tamoxifen for 5 years; n = 1,996) did find statistically significant effect of CYP2D6 on both invasive disease–free survival as well as breast cancer–free interval, with little site heterogeneity. How should we interpret these discrepant findings? PMID:25056393

  19. Expression and purification of orphan cytochrome P450 4X1 and oxidation of anandamide

    PubMed Central

    Stark, Katarina; Dostalek, Miroslav; Guengerich, F. Peter

    2016-01-01

    Summary Cytochrome P450 (P450) 4X1 is one of the so-called “orphan” P450s without assigned biological function. Codon-optimized P450 4X1 and a number of N-terminal modified sequences were expressed in Escherichia coli. Native P450 4X1 showed a characteristic P450 spectrum but low expression in E. coli DH5α cells (<100 nmol P450/L). The highest level of expression (300-450 nmol P450/L culture) was achieved with a bicistronic P450 4X1 construct (N-terminal MAKKTSSKGKL, change of E2A, amino acids 3-44 truncated). Anandamide (arachidonoyl ethanolamide) has emerged as an important signaling molecule in the neurovascular cascade. Recombinant P450 4X1 protein, co-expressed with human NADPH-P450 reductase in E. coli, was found to convert the natural endocannabinoid anandamide to a single monooxygenated product, 14,15-epoxyeicosatrienoic (EET) ethanolamide. A stable anandamide analog (CD-25) was also converted to a monooxygenated product. Arachidonic acid was oxidized more slowly to 14,15- and 8,9-EETs but only in the presence of cytochrome b5. Other fatty acids were investigated as putative substrates but showed only little or minor oxidation. Real-time PCR analysis demonstrated extrahepatic mRNA expression, including several human brain structures (cerebellum, amygdala, and basal ganglia), in addition to expression in human heart, liver, prostate, and breast. The highest mRNA expression levels were detected in amygdala and skin. The ability of P450 4X1 to generate anandamide derivatives and the mRNA distribution pattern suggest a potential role for P450 4X1 in anandamide signaling in the brain. PMID:18549450

  20. Identification of N-(hydroxymethyl) norcotinine as a major product of cytochrome P450 2A6, but not cytochrome P450 2A13-catalyzed cotinine metabolism.

    PubMed

    Brown, Kathryn M; von Weymarn, Linda B; Murphy, Sharon E

    2005-12-01

    Cotinine formation is the major pathway of nicotine metabolism in smokers, and the primary pathway of cotinine metabolism is trans-3'-hydroxylation. trans-3'-Hydroxycotinine and its glucuronide conjugate account for up to 50% of the nicotine metabolites excreted by smokers. Minor metabolites of cotinine excreted by smokers include norcotinine and cotinine N-oxide, each of which account for <5% of the nicotine dose. It has been reported that P450 2A6 is the catalyst of cotinine metabolism. However, we report here that the major product of P450 2A6-catalyzed cotinine metabolism is N-(hydroxymethyl)norcotinine, a previously unknown human metabolite of cotinine. N-(Hydroxymethyl)norcotinine was chemically synthesized, and its stability under the conditions of the enzyme reactions was confirmed. The products of P450 2A6-catalyzed [5-3H]cotinine metabolism were quantified by radioflow HPLC. The identification of N-(hydroxymethyl)norcotinine as the major metabolite was based on HPLC analysis on three unique systems and coelution with N-(hydroxymethyl)norcotinine standard. 5'-Hydroxycotinine and trans-3'-hydroxycotinine were minor products of P450 2A6-catalyzed cotinine metabolism, accounting for 14 and 8% of the total cotinine metabolites, respectively. N-(Hydroxymethyl)norcotinine was a product of cotinine metabolism by the extrahepatic P450, 2A13, but it was a minor one. The major product of P450 2A13-catalyzed cotinine metabolism was 5'-hydroxycotinine, which was formed at twice the rate of trans-3'-hydroxycotinine. The identification of all cotinine metabolites formed by both enzymes was confirmed by LC/MS/MS analysis. Kinetic parameters for cotinine metabolism were determined for P450 2A6 and P450 2A13. This work has confirmed that the major metabolite of cotinine in smokers, trans-3'-hydroxycotinine, is only a minor metabolite of P450 2A6-catalyzed cotinine metabolism.

  1. Investigations on the human hepatic cytochrome P450 isozymes involved in the metabolism of 3,4-methylenedioxy-amphetamine (MDA) and benzodioxolyl-butanamine (BDB) enantiomers.

    PubMed

    Meyer, Markus R; Peters, Frank T; Maurer, Hans H

    2009-10-08

    3,4-Methylenedioxy-amphetamine (MDA) and benzodioxolyl-butanamine (BDB) are chiral designer drugs distributed on the illicit drug market and they are also N-dealkyl metabolites of 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy, Adam), 3,4-methylenedioxyethylamphetamine (MDEA, Eve), and N-methyl-benzodioxolyl-butanamine (MBDB, Eden), respectively. MDA and BDB are mainly metabolized via demethylenation to the corresponding catecholamines. The aim of the present work was to elucidate the contribution of the relevant human P450s in the demethylenation of the MDA and BDB enantiomers. They were incubated using heterologously expressed human P450s and the corresponding metabolites dihydroxyamphetamine and 1,2-dihydroxy-4-[2-amino-butyl]benzene were determined. Highest contributions to the demethylenation as calculated from the enzyme kinetic data were obtained for CYP2D6 (MDA and BDB) and additionally CYP3A4 in the case of BDB at substrate concentrations corresponding to plasma concentrations of recreational users. A preferred transformation of the S-enantiomer could be observed for the CYP2D6- and CYP3A4-catalyzed reactions.

  2. First principles calculation of the activity of cytochrome P450

    NASA Astrophysics Data System (ADS)

    Segall, M. D.; Payne, M. C.; Ellis, S. W.; Tucker, G. T.; Boyes, R. N.

    1998-04-01

    The cytochrome P450 superfamily of enzymes is of enormous interest in the biological sciences due to the wide range of endogenous and xenobiotic compounds which it metabolises, including many drugs. We describe the use of first principles quantum mechanical modeling techniques, based on density functional theory, to determine the outcome of interactions between an enzyme and a number of compounds. Specifically, we calculate the spin state of an Fe3+ ion present in a haem moiety at the active site of these enzymes. The spin state of this ion indicates if the catalytic reaction will proceed. The computational results obtained compare favorably with experimental data. Only the principle components of the active site of the enzyme are included in the computational models, demonstrating that only a small fragment of the protein needs to be included in the models in order to accurately reproduce this aspect of the enzymes' function. These results open the way for further investigation of this superfamily of enzymes using the methods detailed in this paper.

  3. Cytochrome P450 ω-Hydroxylases in Inflammation and Cancer

    PubMed Central

    Johnson, Amanda L.; Edson, Katheryne Z.; Totah, Rheem A.; Rettie, Allan E.

    2015-01-01

    Cytochrome P450-dependent ω-hydroxylation is a prototypic metabolic reaction of CYP4 family members that is important for the elimination and bioactivation of not only therapeutic drugs, but also endogenous compounds, principally fatty acids. Eicosanoids, derived from arachidonic acid, are key substrates in the latter category. Human CYP4 enzymes, mainly CYP4A11, CYP4F2, and CYP4F3B, hydroxylate arachidonic acid at the omega position to form 20-HETE, which has important effects in tumor progression and on angiogenesis and blood pressure regulation in the vasculature and kidney. CYP4F3A in myeloid tissue catalyzes the ω-hydroxylation of leukotriene B4 to 20-hydroxy leukotriene B4, an inactivation process that is critical for the regulation of the inflammatory response. Here, we review the enzymology, tissue distribution, and substrate selectivity of human CYP4 ω-hydroxylases and their roles as catalysts for the formation and termination of the biological effects of key eicosanoid metabolites in inflammation and cancer progression. PMID:26233909

  4. Oxidation of Acenaphthene and Acenaphthylene by Human Cytochrome P450 Enzymes

    PubMed Central

    Shimada, Tsutomu; Takenaka, Shigeo; Murayama, Norie; Yamazaki, Hiroshi; Kim, Joo-Hwan; Kim, Donghak; Yoshimoto, Francis K.; Guengerich, F. Peter; Komori, Masayuki

    2016-01-01

    Acenaphthene and acenaphthylene, two known environmental polycyclic aromatic hydrocarbon (PAH) pollutants, were incubated at 50 µM concentrations in a standard reaction mixture with human P450s 2A6, 2A13, 1B1, 1A2, 2C9, and 3A4 and the oxidation products were determined using HPLC and LC-MS. HPLC analysis showed that P450 2A6 converted acenaphthene and acenaphthylene to several mono- and di-oxygenated products. LC-MS analysis of acenaphthene oxidation by P450s indicated the formation of 1-acenaphthenol as a major product, with turnover rates of 6.7, 4.5, and 3.6 nmol product formed/min/nmol P450 for P450 2A6, 2A13, and 1B1, respectively. Acenaphthylene oxidation by P450 2A6 showed the formation of 1,2-epoxyacenaphthene as a major product (4.4 nmol epoxide formed/min/nmol P450) and also several mono- and di-oxygenated products. P450 2A13, 1B1, 1A2, 2C9, and 3A4 formed 1,2-epoxyacenaphthene at rates of 0.18, 5.3 2.4, 0.16, and 3.8 nmol/min nmol P450, respectively. 1-Acenaphthenol, which induced Type I binding spectra with P450 2A13, was further oxidized by P450 2A13 but not P450 2A6. 1,2-Epoxyacenaphthene induced Type I binding spectra with P450 2A6 and 2A13 (Ks 1.8 and 0.16 µM, respectively) and was also oxidized to several oxidation products by these P450s. Molecular docking analysis suggested different orientations of acenaphthene, acenaphthylene, 1-acenaphthenol, and 1,2-epoxyacenaphthene in their interactions with P450 2A6 and 2A13. Neither these four PAHs induced umu gene expression in a Salmonella typhimurium NM tester strain. These results suggest, for the first time, that acenaphthene and acenaphthylene are oxidized by human P450s 2A6 and 2A13 and other P450s to form several mono- and di-oxygenated products. The results are of use in considering the biological and toxicological significance of these environmental PAHs in humans. PMID:25642975

  5. Cytochrome P450IA1 induction and localization in endothelium of vertebrate (teleost) heart.

    PubMed

    Stegeman, J J; Miller, M R; Hinton, D E

    1989-11-01

    Previous studies have shown that high levels of cytochrome P450 can occur in cardiac microsomes of vertebrates [Mol. Pharmacol. 21:517-526, (1982)]. Here we identify the dominant cardiac P450 in the marine fish scup as P450E, a teleost representative of P450IA1, and we describe its restricted cellular localization in the heart. Treatment of scup with beta-naphthoflavone produced an unusually strong (10-fold) induction of spectrally measured P450 in cardiac microsomes, with specific content reaching levels (0.5 nmol/mg) similar to those induced in scup liver. Microsomal ethoxyresorufin O-deethylase and aryl hydrocarbon hydroxylase activities, catalytic functions of scup P450E, were induced in parallel with P450 content. Similar induction was seen in both atrium and ventricle. Immunoblot analysis with monoclonal antibody 1-12-3, specific to scup P450E and other vertebrate P450IA1 proteins, showed that this hydrocarbon-inducible P450 is the dominant and possibly sole P450 form in heart microsomes of experimentally induced animals. Immunohistochemical analysis of scup heart sections (2-4-microns) with monoclonal antibody 1-12-3 revealed that P450E was detectable only in endothelial cells of the endocardium and of the coronary vasculature. A similar endothelial cell localization of the monoclonal antibody 1-12-3 epitope was observed in heart of rainbow trout, induced with beta-naphthoflavone, indicating a general nature for the endothelial localization of induced cardiac P450. Morphometric analysis showed that endothelium could constitute 8-9% of the volume of teleost heart, from which we calculate that P450IA1 could account for as much as 25% of the endothelial cell microsomal protein. Heart microsomes of untreated animals from contaminated environments also contained high levels of P450E, indicating that induction like that caused by beta-naphthoflavone could occur with chemicals in the environment. Strongly induced P450E (P450IA1) in endothelium could play a critical

  6. Active-site structure, binding and redox activity of the heme–thiolate enzyme CYP2D6 immobilized on coated Ag electrodes: a surface-enhanced resonance Raman scattering study

    PubMed Central

    Bonifacio, Alois; Millo, Diego; Keizers, Peter H. J.; Boegschoten, Roald; Commandeur, Jan N. M.; Vermeulen, Nico P. E.; Gooijer, Cees

    2007-01-01

    Surface-enhance resonance Raman scattering spectra of the heme–thiolate enzyme cytochrome P450 2D6 (CYP2D6) adsorbed on Ag electrodes coated with 11-mercaptoundecanoic acid (MUA) were obtained in various experimental conditions. An analysis of these spectra, and a comparison between them and the RR spectra of CYP2D6 in solution, indicated that the enzyme’s active site retained its nature of six-coordinated low-spin heme upon immobilization. Moreover, the spectral changes detected in the presence of dextromethorphan (a CYP2D6 substrate) and imidazole (an exogenous heme axial ligand) indicated that the immobilized enzyme also preserved its ability to reversibly bind a substrate and form a heme–imidazole complex. The reversibility of these processes could be easily verified by flowing alternately solutions of the various compounds and the buffer through a home-built spectroelectrochemical flow cell which contained a sample of immobilized protein, without the need to disassemble the cell between consecutive spectral data acquisitions. Despite immobilized CYP2D6 being effectively reduced by a sodium dithionite solution, electrochemical reduction via the Ag electrode was not able to completely reduce the enzyme, and led to its extensive inactivation. This behavior indicated that although the enzyme’s ability to exchange electrons is not altered by immobilization per se, MUA-coated electrodes are not suited to perform direct electrochemistry of CYP2D6. Electronic supplementary material The online version of this article (doi:10.1007/s00775-007-0303-1) contains supplementary material, which is available to authorized users. PMID:17899220

  7. Exploiting the versatility of human cytochrome P450 enzymes: the promise of blue roses from biotechnology.

    PubMed

    Gillam, E M; Guengerich, F P

    2001-12-01

    The cytochrome P450 (P450) enzymes involved in drug metabolism are among the most versatile biological catalysts known. A small number of discrete forms of human P450 are capable of catalyzing the monooxygenation of a practically unlimited variety of xenobiotic substrates, with each enzyme showing a more or less wide and overlapping substrate range. This versatility makes P450s ideally suited as starting materials for engineering designer catalysts for industrial applications. In the course of heterologous expression of P450s in bacteria, we observed the unexpected formation of blue pigments. Although this was initially assumed to be an artifact, subsequent work led to the discovery of a new function of P450s in intermediary metabolism and toxicology, new screens for protein engineering, and potential applications in the dye and horticulture industries.

  8. Ruthenium-containing P450 inhibitors for dual enzyme inhibition and DNA damage.

    PubMed

    Zamora, Ana; Denning, Catherine A; Heidary, David K; Wachter, Erin; Nease, Leona A; Ruiz, José; Glazer, Edith C

    2017-02-14

    Cytochrome P450s are key players in drug metabolism, and overexpression in tumors is associated with significant resistance to many medicinal agents. Consequently, inhibition of P450s could serve as a strategy to restore drug efficacy. However, the widespread expression of P450s throughout the human body and the critical roles they play in various biosynthetic pathways motivates the development of P450 inhibitors capable of controlled local administration. Ruthenium complexes containing P450 inhibitors as ligands were synthesized in order to develop pro-drugs that can be triggered to release the inhibitors in a spatially and temporally controlled fashion. Upon light activation the compounds release ligands that directly bind and inhibit P450 enzymes, while the ruthenium center is able to directly damage DNA.

  9. Controlling substrate specificity and product regio- and stereo-selectivities of P450 enzymes without mutagenesis.

    PubMed

    Polic, Vanja; Auclair, Karine

    2014-10-15

    P450 enzymes (P450s) are well known for their ability to oxidize unactivated CH bonds with high regio- and stereoselectivity. Hence, there is emerging interest in exploiting P450s as potential biocatalysts. Although bacterial P450s typically show higher activity than their mammalian counterparts, they tend to be more substrate selective. Most drug-metabolizing P450s on the other hand, display remarkable substrate promiscuity, yet product prediction remains challenging. Protein engineering is one established strategy to overcome these issues. A less explored, yet promising alternative involves substrate engineering. This review discusses the use of small molecules for controlling the substrate specificity and product selectivity of P450s. The focus is on two approaches, one taking advantage of non-covalent decoy molecules, and the other involving covalent substrate modifications.

  10. Targeting Steroidogenic Cytochromes P450 (CYPs) with 6-Substituted 1-Imidazolylmethylxanthones.

    PubMed

    Gobbi, Silvia; Hu, Qingzhong; Zimmer, Christina; Belluti, Federica; Rampa, Angela; Hartmann, Rolf W; Bisi, Alessandra

    2016-08-19

    Abnormally high corticosteroid levels are responsible for the onset of serious hormone-related diseases, and the inhibition of their biosynthesis by targeting cytochrome P450 (CYP) isoforms CYP11B1 and CYP11B2 has emerged as a promising strategy to restore healthy physiological levels of corticosteroids. With the aim of exploiting the xanthone scaffold as a privileged structure in medicinal chemistry and to further explore the chemical space of inhibitors of these CYPs, a small library of imidazolylmethylxanthones was designed based on the results of a previously described compound series. Assuming the capacity for an additional interaction with these enzymes, a properly selected substituent was introduced at position 6 of the xanthone core, maintaining the key imidazolylmethyl moiety at position 1. The 6-fluoro and 6-nitro derivatives [1-(1H-imidazol-1-yl)methyl-6-fluoro-9H-xanthen-9-one (1 a) and 1-(1H-imidazol-1-yl)methyl-6-nitro-9H-xanthen-9-one (1 d), respectively] proved to be active in the low nanomolar range, showing selectivity toward the related steroidogenic enzymes CYP19 and CYP17, even if the problem of selectivity between the two CYP11B isoforms remains unsolved. On the other hand, the 6-chloro derivative 1-(1H-imidazol-1-yl)methyl-6-chloro-9H-xanthen-9-one (1 b) was found to be a fairly potent and somewhat selective CYP19 inhibitor, confirming the versatility of the scaffold.

  11. Genomics of Dementia: APOE- and CYP2D6-Related Pharmacogenetics

    PubMed Central

    Cacabelos, Ramón; Martínez, Rocío; Fernández-Novoa, Lucía; Carril, Juan C.; Lombardi, Valter; Carrera, Iván; Corzo, Lola; Tellado, Iván; Leszek, Jerzy; McKay, Adam; Takeda, Masatoshi

    2012-01-01

    Dementia is a major problem of health in developed societies. Alzheimer's disease (AD), vascular dementia, and mixed dementia account for over 90% of the most prevalent forms of dementia. Both genetic and environmental factors are determinant for the phenotypic expression of dementia. AD is a complex disorder in which many different gene clusters may be involved. Most genes screened to date belong to different proteomic and metabolomic pathways potentially affecting AD pathogenesis. The ε4 variant of the APOE gene seems to be a major risk factor for both degenerative and vascular dementia. Metabolic factors, cerebrovascular disorders, and epigenetic phenomena also contribute to neurodegeneration. Five categories of genes are mainly involved in pharmacogenomics: genes associated with disease pathogenesis, genes associated with the mechanism of action of a particular drug, genes associated with phase I and phase II metabolic reactions, genes associated with transporters, and pleiotropic genes and/or genes associated with concomitant pathologies. The APOE and CYP2D6 genes have been extensively studied in AD. The therapeutic response to conventional drugs in patients with AD is genotype specific, with CYP2D6-PMs, CYP2D6-UMs, and APOE-4/4 carriers acting as the worst responders. APOE and CYP2D6 may cooperate, as pleiotropic genes, in the metabolism of drugs and hepatic function. The introduction of pharmacogenetic procedures into AD pharmacological treatment may help to optimize therapeutics. PMID:22482072

  12. Mangifera indica L. extract and mangiferin modulate cytochrome P450 and UDP-glucuronosyltransferase enzymes in primary cultures of human hepatocytes.

    PubMed

    Rodeiro, Idania; José Gómez-Lechón, M; Perez, Gabriela; Hernandez, Ivones; Herrera, José Alfredo; Delgado, Rene; Castell, José V; Teresa Donato, M

    2013-05-01

    The aqueous stem bark extract of Mangifera indica L. (MSBE) has been reported to have antioxidant, anti-inflammatory and analgesic properties. In previous studies, we showed that MSBE and mangiferin, its main component, lower the activity of some cytochrome P-450 (P450) enzymes in rat hepatocytes and human liver microsomes. In the present study, the effects of MSBE and mangiferin on several P450 enzymes and UDP-glucuronosyltransferases (UGTs) in human-cultured hepatocytes have been examined. After hepatocytes underwent a 48-h treatment with sub-cytotoxic concentrations of the products (50-250 µg/mL), a concentration-dependent decrease of the activity of the five P450 enzymes measured (CYP1A2, 2A6, 2C9, 2D6 and 3A4) was observed. For all the activities, a reduction of at least 50% at the highest concentration (250 µg/mL) was observed. In addition, UGT activities diminished. MSBE considerably reduced UGT1A9 activity (about 60% at 250 µg/mL) and lesser effects on the other UGTs. In contrast, 250 µg/mL mangiferin had greater effects on UGT1A1 and 2B7 than on UGT1A9 (about 55% vs. 35% reduction, respectively). Quantification of specific mRNAs revealed reduced CYP3A4 and 3A5 mRNAs content, and an increase in CYP1A1, CYP1A2, UGT1A1 and UGT1A9 mRNAs. No remarkable effects on the CYP2A6, 2B6, 2C9, 2C19, 2D6 and 2E1 levels were observed. Our results suggest that the activity and/or expression of major P450 and UGT enzymes is modulated by MSBE and that potential herb-drugs interactions could arise after a combined intake of this extract with conventional medicines. Therefore, the potential safety risks of this natural product derived by altering the ADMET properties of co-administered drugs should be examined.

  13. Clinical inhibition of CYP2D6-catalysed metabolism by the antianginal agent perhexiline

    PubMed Central

    Davies, Benjamin J L; Coller, Janet K; James, Heather M; Gillis, David; Somogyi, Andrew A; Horowitz, John D; Morris, Raymond G; Sallustio, Benedetta C

    2004-01-01

    Aims Perhexiline is an antianginal agent that displays both saturable and polymorphic metabolism via CYP2D6. The aim of this study was to determine whether perhexiline produces clinically significant inhibition of CYP2D6-catalysed metabolism in angina patients. Methods The effects of perhexiline on CYP2D6-catalysed metabolism were investigated by comparing urinary total dextrorphan/dextromethorphan metabolic ratios following a single dose of dextromethorphan (16.4 mg) in eight matched control patients not taking perhexiline and 24 patients taking perhexiline. All of the patients taking perhexiline had blood drawn for CYP2D6 genotyping as well as to measure plasma perhexiline and cis-OH-perhexiline concentrations. Results Median (range) dextrorphan/dextromethorphan metabolic ratios were significantly higher (P < 0.0001) in control patients, 271.1 (40.3–686.1), compared with perhexiline-treated patients, 5.0 (0.3–107.9). In the perhexiline-treated group 10/24 patients had metabolic ratios consistent with poor metabolizer phenotypes; however, none was a genotypic poor metabolizer. Interestingly, 89% of patients who had phenocopied to poor metabolizers had only one functional CYP2D6 gene. There was a significant negative linear correlation between the log of the dextrorphan/dextromethorphan metabolic ratio and plasma perhexiline concentrations (r2 = 0.69, P < 0.0001). Compared with patients with at least two functional CYP2D6 genes, those with one functional gene were on similar perhexiline dosage regimens but had significantly higher plasma perhexiline concentrations, 0.73 (0.21–1.00) vs. 0.36 (0.04–0.69) mg l−1 (P = 0.04), lower cis-OH-perhexiline/perhexiline ratios, 2.85 (0.35–6.10) vs. 6.51 (1.84–11.67) (P = 0.03), and lower dextrorphan/dextromethorphan metabolic ratios, 2.51 (0.33–39.56) vs. 11.80 (2.90–36.93) (P = 0.005). Conclusions Perhexiline significantly inhibits CYP2D6-catalysed metabolism in angina patients. The plasma cis

  14. CYP2D6 genotyping in patients on psychoactive drug therapy.

    PubMed

    Topić, E; Stefanović, M; Ivanisević, A M; Blazinić, F; Culav, J; Skocilić, Z

    2000-09-01

    The polymorphic isoenzyme CYP2D6 has a major role in the oxidative metabolism of many deal of psychoactive drugs. Its six mutant alleles (null alleles *3, *4, *5, *6, *7 and *8) encode for inactive enzyme molecules. A carrier of two mutant alleles is considered a poor metabolizer phenotype, while a carrier of only one damaged allele is considered an intermediate metabolizer phenotype. The aim of the study was to assess the prevalence of null alleles in a group of psychiatric patients suffering from depression (n=49) and schizophrenia (n=86) in comparison with healthy individuals (n=145) by the method of multiplex allele specific PCR. Only CYP2D6*3,*4 and *6 mutant alleles were found in the study subjects. No significant difference between the depression and control groups was found for allele prevalence, genotype or phenotype distribution (p>0.05). However, a significant difference was observed between schizophrenic patients and controls for allele frequency (p=0.002), genotype distribution (p=0.016), and phenotype prevalence (p=0.018). The odds ratio of 2.542 for 2D6*4 suggested a significant association between this allele and schizophrenia, significantly contributing to poor metabolizer phenotype (odds ratio=5.020). The relationship between CYP2D6 gene polymorphism and side effects in schizophrenic patients undergoing long-term psychoactive drug therapy was investigated. A significant difference was obtained for allele prevalence (p=0.002), genotype (p=0.029), and phenotype (p=0.002) distribution between patients without and with side effects. A relative risk of 2.626 and 5.333 for 2D6*4 and 2D6*6, respectively, and of 7.08 for poor metabolizer phenotype suggested a significant association between the hereditary susceptibility for a particular type of drug metabolism (defect alleles) and side effects. These preliminary results suggest that the CYP2D6 genotyping appears to be useful for predicting risks for side effects of psychoactive drugs in schizophrenic

  15. Engineering of daidzein 3’-hydroxylase P450 enzyme into catalytically self-sufficient cytochrome P450

    PubMed Central

    2012-01-01

    A cytochrome P450 (CYP) enzyme, 3’-daidzein hydroxylase, CYP105D7 (3’-DH), responsible for daidzein hydroxylation at the 3’-position, was recently reported. CYP105D7 (3’-DH) is a class I type of CYP that requires electrons provided through electron transfer proteins such as ferredoxin and ferredoxin reductase. Presently, we constructed an artificial CYP in order to develop a reaction host for the production of a hydroxylated product. Fusion-mediated construction with the reductase domain from self-sufficient CYP102D1 was done to increase electron transfer efficiency and coupling with the oxidative process. An artificial self-sufficient daidzein hydroxylase (3’-ASDH) displayed distinct spectral properties of both flavoprotein and CYP. The fusion enzyme catalyzed hydroxylation of daidzein more efficiently, with a kcat/Km value of 16.8 μM-1 min-1, which was about 24-fold higher than that of the 3’-DH-camA/B reconstituted enzyme. Finally, a recombinant Streptomyces avermitilis host for the expression of 3’-ASDH and production of the hydroxylated product was developed. The conversion that was attained (34.6%) was 5.2-fold higher than that of the wild-type. PMID:22697884

  16. Resveratrol stimulates cortisol biosynthesis by activating SIRT-dependent deacetylation of P450scc.

    PubMed

    Li, Donghui; Dammer, Eric B; Sewer, Marion B

    2012-07-01

    In the human adrenal cortex, cortisol is synthesized from cholesterol by members of the cytochrome P450 superfamily and hydroxysteroid dehydrogenases. Both the first and last steps of cortisol biosynthesis occur in mitochondria. Based on our previous findings that activation of ACTH signaling changes the ratio of nicotinamide adenine dinucleotide (NAD) phosphate to reduced NAD phosphate in adrenocortical cells, we hypothesized that pyridine nucleotide metabolism may regulate the activity of the mitochondrial NAD(+)-dependent sirtuin (SIRT) deacetylases. We show that resveratrol increases the protein expression and half-life of P450 side chain cleavage enzyme (P450scc). The effects of resveratrol on P450scc protein levels and acetylation status are dependent on SIRT3 and SIRT5 expression. Stable overexpression of SIRT3 abrogates the cellular content of acetylated P450scc, concomitant with an increase in P450scc protein expression and cortisol secretion. Mutation of K148 and K149 to alanine stabilizes the expression of P450scc and results in a 1.5-fold increase in pregnenolone biosynthesis. Finally, resveratrol also increases the protein expression of P450 11β, another mitochondrial enzyme required for cortisol biosynthesis. Collectively, this study identifies a role for NAD(+)-dependent SIRT deacetylase activity in regulating the expression of mitochondrial steroidogenic P450.

  17. Cytochrome P450IA mRNA expression in feral Hudson River tomcod

    SciTech Connect

    Kreamer, G.L.; Squibb, K.; Gioeli, D.; Garte, S.J.; Wirgin, I. )

    1991-06-01

    The authors sought to determine if levels of cytochrome P450IA gene expression are environmentally induced in feral populations of Hudson River tomcod, a cancer prone fish, and whether laboratory exposure of tomcod to artificially spiked and naturally contaminated Hudson sediments can elicit a significant response. Using Northern blot analysis, they found levels of P450IA mRNA in tomcod collected from two Hudson River sites higher than those in tomcod from a river in Maine. Depuration of environmentally induced Hudson tomcod P450IA mRNA was rapid, with an initial detectable decline in P450 gene expression by 8 hr and basal levels reached by 5 days. Intraperitoneal injection of {beta}-napthoflavone in depurated Hudson tomcod resulted in a 15-fold induction of P450 gene expression within 26 hr. Exposure of depurated Hudson tomcod to natural sediment spiked with two PAHs resulted in a 7-fold induction of P450 gene expression. Exposure of depurated tomcod to sediment from a contaminated Hudson site also resulted in a 7- to 15-fold induction of P450IA mRNA expression. Northern blot analysis revealed a second polymorphic cytochrome P450IA mRNA band in some tomcod which was also detected by Southern blot analysis. Induction of cytochrome P450IA mRNA in Atlantic tomcod may provide a sensitive biomarker of environmentally relevant concentrations of some pollutants in the Hudson and other northeastern tidal rivers.

  18. Pharmacophore modeling and in silico screening for new P450 19 (aromatase) inhibitors.

    PubMed

    Schuster, Daniela; Laggner, Christian; Steindl, Theodora M; Palusczak, Anja; Hartmann, Rolf W; Langer, Thierry

    2006-01-01

    Cytochrome P450 19 (P450 19, aromatase) constitutes a successful target for the treatment of breast cancer. This study analyzes chemical features common to P450 19 inhibitors to develop ligand-based, selective pharmacophore models for this enzyme. The HipHop and HypoRefine algorithms implemented in the Catalyst software package were employed to create both common feature and quantitative models. The common feature model for P450 19 includes two ring aromatic features in its core and two hydrogen bond acceptors at the ends. The models were used as database search queries to identify active compounds from the NCI database.

  19. Characterization of cytochrome P-450 2D1 activity in rat brain: high-affinity kinetics for dextromethorphan.

    PubMed

    Tyndale, R F; Li, Y; Li, N Y; Messina, E; Miksys, S; Sellers, E M

    1999-08-01

    We investigated the enzymatic function, stability, and regional distribution of rat brain cytochrome P-450 (CYP) 2D1 activity. CYP2D1 is the homolog of human CYP2D6, a genetically variable enzyme that activates or inactivates many clinical drugs acting on the central nervous system (e.g., antidepressants, monoamine oxidase inhibitors, serotonin uptake inhibitors, and neuroleptics), drugs of abuse (e.g., amphetamine and codeine), neurotoxins (e.g., 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 1,2,3, 4-tetrahydroquinoline), and endogenous neurochemicals (e.g., tryptamine). The CYP2D family has been identified in rodent, canine, and primate brain. Conversion of dextromethorphan to dextrorphan by rat brain membranes was assayed by HPLC and was dependent on NADPH, protein concentration, and incubation time. Significant loss of activity was observed in some homogenizing buffers and after freezing of whole tissues or membrane preparations. Dextromethorphan (0.5-640 microM) metabolism was mediated by high- and low-affinity enzyme systems; K(m1) was 2.7 +/- 2.6 and K(m2) was 757 +/- 156 microM (n = 3 rats, mean +/- S.E.). The enzyme activity was significantly (p <.01) and stereoselectively inhibited by CYP2D1 inhibitors quinine and quinidine (not by CYP2C or CYP3A inhibitors), and by anti-CYP2D6 peptide antiserum (not by anti-CYP2C, -CYP2B, or -CYP3A antibodies). The enzymatic activity demonstrated significant brain regional variation (n = 10 regions, p <.001). These data characterize CYP2D1-mediated dextromethorphan metabolism in rat brain and suggest that localized metabolism of other CYP2D1 substrates (drugs, neurotoxins, and possibly endogenous compounds) within the brain will occur. In humans, CYP2D6 is genetically polymorphic; the variable expression of brain CYP2D6 may result in interindividual differences in central drug and neurotoxin metabolism, possibly contributing to interindividual differences in drug effects and neurotoxicity.

  20. The role of renal proximal tubule P450 enzymes in chloroform-induced nephrotoxicity: Utility of renal specific P450 reductase knockout mouse models

    SciTech Connect

    Liu, Senyan; Yao, Yunyi; Lu, Shijun; Aldous, Kenneth; Ding, Xinxin; Mei, Changlin; Gu, Jun

    2013-10-01

    The kidney is a primary target for numerous toxic compounds. Cytochrome P450 enzymes (P450) are responsible for the metabolic activation of various chemical compounds, and in the kidney are predominantly expressed in proximal tubules. The aim of this study was to test the hypothesis that renal proximal tubular P450s are critical for nephrotoxicity caused by chemicals such as chloroform. We developed two new mouse models, one having proximal tubule-specific deletion of the cytochrome P450 reductase (Cpr) gene (the enzyme required for all microsomal P450 activities), designated proximal tubule-Cpr-null (PTCN), and the other having proximal tubule-specific rescue of CPR activity with the global suppression of CPR activity in all extra-proximal tubular tissues, designated extra-proximal tubule-Cpr-low (XPT-CL). The PTCN, XPT-CL, Cpr-low (CL), and wild-type (WT) mice were treated with a single oral dose of chloroform at 200 mg/kg. Blood, liver and kidney samples were obtained at 24 h after the treatment. Renal toxicity was assessed by measuring BUN and creatinine levels, and by pathological examination. The blood and tissue levels of chloroform were determined. The severity of toxicity was less in PTCN and CL mice, compared with that of WT and XPT-CL mice. There were no significant differences in chloroform levels in the blood, liver, or kidney, between PTCN and WT mice, or between XPT-CL and CL mice. These findings indicate that local P450-dependent activities play an important role in the nephrotoxicity induced by chloroform. Our results also demonstrate the usefulness of these novel mouse models for studies of chemical-induced kidney toxicity. - Highlights: • New mouse models were developed with varying P450 activities in the proximal tubule. • These mouse models were treated with chloroform, a nephrotoxicant. • Studies showed the importance of local P450s in chloroform-induced nephrotoxicity.

  1. Cytochrome P450-dependent metabolism of caffeine in Drosophila melanogaster.

    PubMed

    Coelho, Alexandra; Fraichard, Stephane; Le Goff, Gaëlle; Faure, Philippe; Artur, Yves; Ferveur, Jean-François; Heydel, Jean-Marie

    2015-01-01

    Caffeine (1, 3, 7-trimethylxanthine), an alkaloid produced by plants, has antioxidant and insecticide properties that can affect metabolism and cognition. In vertebrates, the metabolites derived from caffeine have been identified, and their functions have been characterized. However, the metabolites of caffeine in insects remain unknown. Thus, using radiolabelled caffeine, we have identified some of the primary caffeine metabolites produced in the body of Drosophila melanogaster males, including theobromine, paraxanthine and theophylline. In contrast to mammals, theobromine was the predominant metabolite (paraxanthine in humans; theophylline in monkeys; 1, 3, 7-trimethyluric acid in rodents). A transcriptomic screen of Drosophila flies exposed to caffeine revealed the coordinated variation of a large set of genes that encode xenobiotic-metabolizing proteins, including several cytochromes P450s (CYPs) that were highly overexpressed. Flies treated with metyrapone--an inhibitor of CYP enzymes--showed dramatically decreased caffeine metabolism, indicating that CYPs are involved in this process. Using interference RNA genetic silencing, we measured the metabolic and transcriptomic effect of three candidate CYPs. Silencing of CYP6d5 completely abolished theobromine synthesis, whereas CYP6a8 and CYP12d1 silencing induced different consequences on metabolism and gene expression. Therefore, we characterized several metabolic products and some enzymes potentially involved in the degradation of caffeine. In conclusion, this pioneer approach to caffeine metabolism in insects opens novel perspectives for the investigation of the physiological effects of caffeine metabolites. It also indicates that caffeine could be used as a biomarker to evaluate CYP phenotypes in Drosophila and other insects.

  2. Mechanistic Scrutiny Identifies a Kinetic Role for Cytochrome b5 Regulation of Human Cytochrome P450c17 (CYP17A1, P450 17A1)

    PubMed Central

    Simonov, Alexandr N.; Holien, Jessica K.; Yeung, Joyee Chun In; Nguyen, Ann D.; Corbin, C. Jo; Zheng, Jie; Kuznetsov, Vladimir L.; Auchus, Richard J.; Conley, Alan J.; Bond, Alan M.; Parker, Michael W.; Rodgers, Raymond J.; Martin, Lisandra L.

    2015-01-01

    Cytochrome P450c17 (P450 17A1, CYP17A1) is a critical enzyme in the synthesis of androgens and is now a target enzyme for the treatment of prostate cancer. Cytochrome P450c17 can exhibit either one or two physiological enzymatic activities differentially regulated by cytochrome b5. How this is achieved remains unknown. Here, comprehensive in silico, in vivo and in vitro analyses were undertaken. Fluorescence Resonance Energy Transfer analysis showed close interactions within living cells between cytochrome P450c17 and cytochrome b5. In silico modeling identified the sites of interaction and confirmed that E48 and E49 residues in cytochrome b5 are essential for activity. Quartz crystal microbalance studies identified specific protein-protein interactions in a lipid membrane. Voltammetric analysis revealed that the wild type cytochrome b5, but not a mutated, E48G/E49G cyt b5, altered the kinetics of electron transfer between the electrode and the P450c17. We conclude that cytochrome b5 can influence the electronic conductivity of cytochrome P450c17 via allosteric, protein-protein interactions. PMID:26587646

  3. CYP94A1, a plant cytochrome P450-catalyzing fatty acid omega-hydroxylase, is selectively induced by chemical stress in Vicia sativa seedlings.

    PubMed

    Benveniste, Irène; Bronner, Roberte; Wang, Yong; Compagnon, Vincent; Michler, Pierre; Schreiber, Lukas; Salaün, Jean-Pierre; Durst, Francis; Pinot, Franck

    2005-08-01

    CYP94A1 is a cytochrome P450 (P450) catalyzing fatty acid (FA) omega-hydroxylation in Vicia sativa seedlings. To study the physiological role of this FA monooxygenase, we report here on its regulation at the transcriptional level (Northern blot). Transcripts of CYP94A1, as those of two other P450-dependent FA hydroxylases (CYP94A2 and CYP94A3) from V. sativa, are barely detectable during the early development of the seedlings. CYP94A1 transcripts, in contrast to those of the two other isoforms, are rapidly (less than 20 min) and strongly (more than 100 times) enhanced after treatment by clofibrate, an hypolipidemic drug in animals and an antiauxin (p-chlorophenoxyisobutyric acid) in plants, by auxins (2,4-dichlorophenoxyacetic acid and indole-3-acetic acid), by an inactive auxin analog (2,3-dichlorophenoxyacetic acid), and also by salicylic acid. All these compounds activate CYP94A1 transcription only at high concentrations (50-500 microM range). In parallel, these high levels of clofibrate and auxins modify seedling growth and development. Therefore, the expression of CYP94A1 under these conditions and the concomitant morphological and cytological modifications would suggest the implication of this P450 in a process of plant defense against chemical injury.

  4. Human hepatic cytochrome P450-specific metabolism of the organophosphorus pesticides methyl parathion and diazinon.

    PubMed

    Ellison, Corie A; Tian, Yuan; Knaak, James B; Kostyniak, Paul J; Olson, James R

    2012-01-01

    Organophosphorus pesticides (OPs) are a public health concern due to their worldwide use and documented human exposures. Phosphorothioate OPs are metabolized by cytochrome P450s (P450s) through either a dearylation reaction to form an inactive metabolite, or through a desulfuration reaction to form an active oxon metabolite, which is a potent cholinesterase inhibitor. This study investigated the rate of desulfuration (activation) and dearylation (detoxification) of methyl parathion and diazinon in human liver microsomes. In addition, recombinant human P450s were used to determine the P450-specific kinetic parameters (K(m) and V(max)) for each compound for future use in refining human physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) models of OP exposure. The primary enzymes involved in bioactivation of methyl parathion were CYP2B6 (K(m) = 1.25 μM; V(max) = 9.78 nmol · min(-1) · nmol P450(-1)), CYP2C19 (K(m) = 1.03 μM; V(max) = 4.67 nmol · min(-1) · nmol P450(-1)), and CYP1A2 (K(m) = 1.96 μM; V(max) = 5.14 nmol · min(-1) · nmol P450(-1)), and the bioactivation of diazinon was mediated primarily by CYP1A1 (K(m) = 3.05 μM; V(max) = 2.35 nmol · min(-1) · nmol P450(-1)), CYP2C19 (K(m) = 7.74 μM; V(max) = 4.14 nmol · min(-1) · nmol P450(-1)), and CYP2B6 (K(m) = 14.83 μM; V(max) = 5.44 nmol · min(-1) · nmol P450(-1)). P450-mediated detoxification of methyl parathion only occurred to a limited extent with CYP1A2 (K(m) = 16.8 μM; V(max) = 1.38 nmol · min(-1) · nmol P450(-1)) and 3A4 (K(m) = 104 μM; V(max) = 5.15 nmol · min(-1) · nmol P450(-1)), whereas the major enzyme involved in diazinon detoxification was CYP2C19 (K(m) = 5.04 μM; V(max) = 5.58 nmol · min(-1) · nmol P450(-1)). The OP- and P450-specific kinetic values will be helpful for future use in refining human PBPK/PD models of OP exposure.

  5. Human Hepatic Cytochrome P450-Specific Metabolism of the Organophosphorus Pesticides Methyl Parathion and Diazinon

    PubMed Central

    Tian, Yuan; Knaak, James B.; Kostyniak, Paul J.; Olson, James R.

    2012-01-01

    Organophosphorus pesticides (OPs) are a public health concern due to their worldwide use and documented human exposures. Phosphorothioate OPs are metabolized by cytochrome P450s (P450s) through either a dearylation reaction to form an inactive metabolite, or through a desulfuration reaction to form an active oxon metabolite, which is a potent cholinesterase inhibitor. This study investigated the rate of desulfuration (activation) and dearylation (detoxification) of methyl parathion and diazinon in human liver microsomes. In addition, recombinant human P450s were used to determine the P450-specific kinetic parameters (Km and Vmax) for each compound for future use in refining human physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) models of OP exposure. The primary enzymes involved in bioactivation of methyl parathion were CYP2B6 (Km = 1.25 μM; Vmax = 9.78 nmol · min−1 · nmol P450−1), CYP2C19 (Km = 1.03 μM; Vmax = 4.67 nmol · min−1 · nmol P450−1), and CYP1A2 (Km = 1.96 μM; Vmax = 5.14 nmol · min−1 · nmol P450−1), and the bioactivation of diazinon was mediated primarily by CYP1A1 (Km = 3.05 μM; Vmax = 2.35 nmol · min−1 · nmol P450−1), CYP2C19 (Km = 7.74 μM; Vmax = 4.14 nmol · min−1 · nmol P450−1), and CYP2B6 (Km = 14.83 μM; Vmax = 5.44 nmol · min−1 · nmol P450−1). P450-mediated detoxification of methyl parathion only occurred to a limited extent with CYP1A2 (Km = 16.8 μM; Vmax = 1.38 nmol · min−1 · nmol P450−1) and 3A4 (Km = 104 μM; Vmax = 5.15 nmol · min−1 · nmol P450−1), whereas the major enzyme involved in diazinon detoxification was CYP2C19 (Km = 5.04 μM; Vmax = 5.58 nmol · min−1 · nmol P450−1). The OP- and P450-specific kinetic values will be helpful for future use in refining human PBPK/PD models of OP exposure. PMID:21969518

  6. Defective Cytochrome P450-Catalysed Drug Metabolism in Niemann-Pick Type C Disease

    PubMed Central

    Wassif, Christopher A.; Gray, James; Burkert, Kathryn R.; Smith, David A.; Morris, Lauren; Cologna, Stephanie M.; Peer, Cody J.; Sissung, Tristan M.; Uscatu, Constantin-Daniel; Figg, William D.; Pavan, William J.; Vite, Charles H.; Porter, Forbes D.; Platt, Frances M.

    2016-01-01

    Niemann-Pick type C (NPC) disease is a neurodegenerative lysosomal storage disease caused by mutations in either the NPC1 or NPC2 gene. NPC is characterised by storage of multiple lipids in the late endosomal/lysosomal compartment, resulting in cellular and organ system dysfunction. The underlying molecular mechanisms that lead to the range of clinical presentations in NPC are not fully understood. While evaluating potential small molecule therapies in Npc1-/- mice, we observed a consistent pattern of toxicity associated with drugs metabolised by the cytochrome P450 system, suggesting a potential drug metabolism defect in NPC1 disease. Investigation of the P450 system in the context of NPC1 dysfunction revealed significant changes in the gene expression of many P450 associated genes across the full lifespan of Npc1-/- mice, decreased activity of cytochrome P450 reductase, and a global decrease of multiple cytochrome P450 catalysed dealkylation reactions. In vivo drug metabolism studies using a prototypic P450 metabolised drug, midazolam, confirmed dysfunction in drug clearance in the Npc1-/- mouse. Expression of the Phase II enzyme uridinediphosphate-glucuronosyltransferase (UGT) was also significantly reduced in Npc1-/- mice. Interestingly, reduced activity within the P450 system was also observed in heterozygous Npc1+/- mice. The reduced activity of P450 enzymes may be the result of bile acid deficiency/imbalance in Npc1-/- mice, as bile acid treatment significantly rescued P450 enzyme activity in Npc1-/- mice and has the potential to be an adjunctive therapy for NPC disease patients. The dysfunction in the cytochrome P450 system were recapitulated in the NPC1 feline model. Additionally, we present the first evidence that there are alterations in the P450 system in NPC1 patients. PMID:27019000

  7. CYP2D6 poor metabolizer status might be associated with better response to risperidone treatment.

    PubMed

    Almoguera, Berta; Riveiro-Alvarez, Rosa; Lopez-Castroman, Jorge; Dorado, Pedro; Vaquero-Lorenzo, Concepción; Fernandez-Piqueras, José; Llerena, Adrián; Abad-Santos, Francisco; Baca-García, Enrique; Dal-Ré, Rafael; Ayuso, Carmen

    2013-11-01

    The variability in the antipsychotic response is, to some extent, genetically determined. Several studies have attempted to establish a role for genetic variation in genes coding pharmacokinetic and pharmacodynamic targets, but to date, no definite genetic predictive marker has been identified. We aimed to explore the putative role of 19 genetic variants and risperidone clinical improvement in 76 White schizophrenic inpatients, measured as change in Positiv