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Cytochromes P450: Drug Metabolism and Bioactivation

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A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Biochemistry".

Deadline for manuscript submissions: closed (30 April 2018) | Viewed by 70577

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Special Issue Editors

Dr. Patrick M. Dansette

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Guest Editor

Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris Descartes, Sorbonne Paris Cité, 45 Rue des Saints-Pères, CEDEX 06, 75270 Paris, France
Interests: drug metabolism; cytochrome P450 structure and mechanism; biological reactive intermediates; thiophene-S-oxides; arene oxides; sulfenic acid; mechanism based inhibitors; ferrocifen; drug induced immunotoxicity.
Special Issues, Collections and Topics in MDPI journals

Dr. S. Cyrus Khojasteh

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Co-Guest Editor

Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., 1 DNA Way (MS 412a), South San Francisco, CA 94080, USA
Interests: bioactivation; drug metabolism; cytochrome P450; aldehyde oxidation; drug-induced liver toxicity

Dr. Donglu Zhang

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Co-Guest Editor

Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA
Interests: drug discovery; drug clearance pathways; enzyme inhibitors; P450 enzymes; high-resolution mass spectrometry; drug metabolites; site of metabolism; machine learning
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nearly seventy year ago, R.T. Williams and B.B. Brodie developed the concept of drug metabolism and the types of reactions and the mechanisms for the body to facilitate the excretion of a drug. Ten years later, Klingenberg and Garfinkel independently discovered the P450 protein, which was, five years later, demonstrated to be a cytochrome P450 by Omura and Sato. Later on, the prominent function of this enzyme and its role in drug metabolism was established. This resulted in a new chapter, and now more than 84,000 papers contain the concept of cytochrome P450. We now know this enzyme’s importance in clearance and potential toxicity, and, therefore, compounds do get tested for these reasons. This Special Issue focuses on “Cytochrome P450: Drug Metabolism and Bioactivation” and includes papers on: (1) its structures, (2) types and mechanisms of reaction, (3) pharmacogenomics, (4) bioactivation reactions and biological markers, (5) mechanism-based inactivation, (6) species differences, and (7) regulation.

We warmly welcome submissions, including original papers and reviews, on these widely-discussed topics.

Dr. Patrick M. Dansette
Guest Editor

Dr. S. Cyrus Khojasteh
Dr. Donglu Zhang
Co-Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

cytochrome P450
drug metabolism
bioactivation
pharmacogenomics
reactive intermediates
drug induced toxicity
reaction mechanisms

Published Papers (14 papers)

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Research

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13 pages, 7931 KiB

Open AccessArticle

Role of Arginine 117 in Substrate Recognition by Human Cytochrome P450 2J2

by Pierre Lafite, François André, Joan P. Graves, Darryl C. Zeldin, Patrick M. Dansette and Daniel Mansuy

Int. J. Mol. Sci. 2018, 19(7), 2066; https://doi.org/10.3390/ijms19072066 - 16 Jul 2018

Cited by 7 | Viewed by 3551

Abstract

The influence of Arginine 117 of human cytochrome P450 2J2 in the recognition of ebastine and a series of terfenadone derivatives was studied by site-directed mutagenesis. R117K, R117E, and R117L mutants were produced, and the behavior of these mutants in the hydroxylation of ebastine and terfenadone derivatives was compared to that of wild-type CYP2J2. The data clearly showed the importance of the formation of a hydrogen bond between R117 and the keto group of these substrates. The data were interpreted on the basis of 3D homology models of the mutants and of dynamic docking of the substrates in their active site. These modeling studies also suggested the existence of a R117-E222 salt bridge between helices B’ and F that would be important for maintaining the overall folding of CYP2J2. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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12 pages, 1142 KiB

Open AccessArticle

Effect of Nicotine on CYP2B1 Expression in a Glioma Animal Model and Analysis of CYP2B6 Expression in Pediatric Gliomas

by Sonia Nava-Salazar, Saúl Gómez-Manzo, Jaime Marcial-Quino, Alfonso Marhx-Bracho, Bryan V. Phillips-Farfán, Carlos Diaz-Avalos and America Vanoye-Carlo

Int. J. Mol. Sci. 2018, 19(6), 1790; https://doi.org/10.3390/ijms19061790 - 16 Jun 2018

Cited by 4 | Viewed by 3449

Abstract

Cyclophosphamide (CPA) is a pro-drug commonly used in the chemotherapeutic schemes for glioma treatment but has high toxicity and the side effects include brain damage and even death. Since CPA is activated mainly by CY2B6, over-expression of the enzyme in the tumor cells has been proposed to enhance CPA activation. In this study, we explored the induction of the Cyp2b1 (homologous to CYP2B6) by nicotine in an animal rat model with glioma. Gene expression and protein levels were analyzed by RT-PCR and Western blot. Nicotine treatment increased CYP2B1 protein levels in the healthy animals’ brain tissue. In the brain tissue of animals with glioma, the CYP2B1 showed a high expression, even before nicotine treatment. Nicotine did not increase significantly the CYP2B1 protein expression in the tumor, but increased its expression in the tumor vicinity, especially around blood vessels in the cortex. We also explored CY2B6 expression in glioma samples derived from pediatric patients. Tumor tissue showed a variable expression of the enzyme, which could depend on the tumor malignancy grade. Induction of the CYP2B6 in pediatric gliomas with lower expression of the enzyme, could be an alternative to improve the antitumoral effect of CPA treatment. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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14 pages, 2965 KiB

Open AccessArticle

Blooming of Unusual Cytochrome P450s by Tandem Duplication in the Pathogenic Fungus Conidiobolus coronatus

by Mathula Lancelot Ngwenya, Wanping Chen, Albert Kotze Basson, Jabulani Siyabonga Shandu, Jae-Hyuk Yu, David R. Nelson and Khajamohiddin Syed

Int. J. Mol. Sci. 2018, 19(6), 1711; https://doi.org/10.3390/ijms19061711 - 09 Jun 2018

Cited by 14 | Viewed by 4199

Abstract

While the Zygomycete fungus Conidiobolus coronatus primarily infects insects, it can be pathogenic to mammals as well, including humans. High variability in the treatment of this fungal infection with currently available drugs, including azole drugs is a very common phenomenon. Azoles bind to the cytochrome P450 monooxygenases (P450s/CYP) including CYP51, a sterol 14-α-demethylase, inhibiting the synthesis of cell membrane ergosterol and thus leading to the elimination of infecting fungi. Despite P450’s role as a drug target, to date, no information on C. coronatus P450s has been reported. Genome-wide data mining has revealed the presence of 142 P450s grouped into 12 families and 21 subfamilies in C. coronatus. Except for CYP51, the remaining 11 P450 families are new (CYP5854-CYP5864). Despite having a large number of P450s among entomopathogenic fungi, C. coronatus has the lowest number of P450 families, which suggests blooming P450s. Further analysis has revealed that 79% of the same family P450s is tandemly positioned, suggesting that P450 tandem duplication led to the blooming of P450s. The results of this study; i.e., unravelling the C. coronatus P450 content, will certainly help in designing experiments to understand P450s’ role in C. coronatus physiology, including a highly variable response to azole drugs with respect to P450s. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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14 pages, 1917 KiB

Open AccessArticle

Increased Phenacetin Oxidation upon the L382V Substitution in Cytochrome P450 1A2 is Associated with Altered Substrate Binding Orientation

by Qingbiao Huang and Grazyna D. Szklarz

Int. J. Mol. Sci. 2018, 19(6), 1580; https://doi.org/10.3390/ijms19061580 - 25 May 2018

Cited by 3 | Viewed by 3643

Abstract

Leucine382 of cytochrome P450 1A2 (CYP1A2) plays an important role in binding and O-dealkylation of phenacetin, with the L382V mutation increasing substrate oxidation (Huang and Szklarz, 2010, Drug Metab. Dispos. 38:1039–1045). This was attributed to altered substrate binding orientation, but no direct experimental evidence had been available. Therefore, in the current studies, we employed nuclear magnetic resonance (NMR) longitudinal (T₁) relaxation measurements to investigate phenacetin binding orientations within the active site of CYP1A2 wild type (WT) and mutants. Paramagnetic relaxation time (T_1P) for each proton of phenacetin was calculated from the T₁ value obtained from the enzymes in ferric and ferrous-CO state in the presence of phenacetin, and used to model the orientation of phenacetin in the active site. All aromatic protons of phenacetin were nearly equidistant from the heme iron (6.34–8.03 Å). In contrast, the distance between the proton of the –OCH₂– group, which is abstracted during phenacetin oxidation, and the heme iron, was much shorter in the L382V (5.93 Å) and L382V/N312L (5.96 Å) mutants compared to the N312L mutant (7.84 Å) and the wild type enzyme (6.55 Å), consistent with modeling results. These studies provide direct evidence for the molecular mechanism underlying increased oxidation of phenacetin upon the L382V mutation. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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13 pages, 5820 KiB

Open AccessArticle

Cytochrome P450 CYP6EV11 in Chironomus kiiensis Larvae Involved in Phenol Stress

by Qihui Zhang, Dong Chu, Lili Sun and Chuanwang Cao

Int. J. Mol. Sci. 2018, 19(4), 1119; https://doi.org/10.3390/ijms19041119 - 09 Apr 2018

Cited by 4 | Viewed by 3143

Abstract

Phenol is one of the organic pollutants which can cause water environment pollution. It is not only enriched in aquatic organisms but is also a serious threat to human health. Chironomus kiiensis is very sensitive to the contaminants in water and its cytochrome P450s are usually chosen as biomarkers for water pollution. To examine whether CYP6EV11 plays a role in the oxidative metabolism of phenol, we measured the silencing efficiency of CYP6EV11 and evaluated larval susceptibility to sublethal phenol levels by RNA interference (RNAi) technology. The results showed that the transcription of CYP6EV11 was found significantly up-regulated when the 4th instar C. kiiensis larvae were exposed to three doses of phenol. However, the transcriptional levels of CYP6EV11 were significantly suppressed by 92.7% in the 4th instar C. kiiensis larvae soaked in dsCYP6EV11 compared with those soaked in dsGFP for 6 h. The CYP6EV11 expression and mortality of the 4th instar C. kiiensis larvae with CYP6EV11 silencing were mostly decreased under phenol stress. Therefore, the CYP6EV11 gene may be used as a molecular biomarker for earlier warning and monitoring for water pollution. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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9 pages, 21879 KiB

Open AccessCommunication

Crystal Structure of CYP2B6 in Complex with an Efavirenz Analog

by Manish B. Shah, Qinghai Zhang and James R. Halpert

Int. J. Mol. Sci. 2018, 19(4), 1025; https://doi.org/10.3390/ijms19041025 - 29 Mar 2018

Cited by 6 | Viewed by 4541

Abstract

The over two dozen CYP2B structures of human, rabbit, and woodrat enzymes solved in the last decade have significantly enhanced our understanding of the structure-function relationships of drug metabolizing enzymes. More recently, an important role has emerged for halogen-π interactions in the CYP2B6 active site in substrate selectivity, explaining in part the preference for halogenated ligands as substrates. The mechanism by which such ligands interact with CYP2B enzymes involves conserved phenylalanine side chains, in particular F108, F115, or F297, in the active site, which form π bonds with halogens. To illustrate such halogen-π interactions using drugs that are major substrates of CYP2B6, we present here a crystal structure of CYP2B6 in complex with an analog of the widely used anti-HIV drug efavirenz, which contains a methyl group in place of the carbonyl oxygen. The chlorine of the efavirenz analog forms a π bond with the aromatic ring of F108, whereas the putative metabolism site on the distal end of the molecule is oriented towards the heme iron. The crystal structure showcases how CYP2B6 accommodates this important drug analog of considerable size in the active site by movement of various side chains without substantially increasing the active site volume. Furthermore, the CYP2B6-efavirenz analog complex provides a useful platform to investigate computationally as well as biophysically the effect of genetic polymorphisms on binding of the widely studied efavirenz. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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10 pages, 221 KiB

Open AccessArticle

Effects of Honokiol on CYP450 Activity and Transporter mRNA Expression in Type 2 Diabetic Rats

by Junjun Wang, Ting Zhai and Yong Chen

Int. J. Mol. Sci. 2018, 19(3), 815; https://doi.org/10.3390/ijms19030815 - 12 Mar 2018

Cited by 22 | Viewed by 3979

Abstract

This study was aimed to clarify the effect of honokiol (Hon) on the activity of Cytochrome P450 (CYP450) enzymes, and the level of mRNA expression of liver and kidney transporters in type 2 diabetic rats induced by high-fat diet and strepotozotocin. Rats were randomly divided into normal control (NC) group, diabetic control (DC) group and Hon groups (n = 6). The activities of hepatic CYP1A2, CYP2E1, CYP2C, CYP2B, CYP3A and CYP4A, and the mRNA expression levels of hepatic and renal transporters, were determined. Compared to the NC group, the activities of CYP1A2, CYP2E1, CYP4A and CYP2C in DC group were increased by 2.36-, 2.10-, 2.55- and 1.86-fold, respectively. The mRNA expression levels of hepatic Oat2, Oatp2b1 and Oatp1a5, and renal Oct1, Octn2, Oatp2b1 and Oatp1a5, were significantly down-regulated, while the mRNA expression levels of hepatic Octn2, Oatp3a1, Oatp1a1 and Mdr2, and renal Oat2, Mrp4 and Bcrp, were significantly upregulated. Compared to the DC group, Hon treatment significantly inhibited the activity of hepatic CYP2E1, CYP4A, 3A and CYP1A2 by 45.6%, 29.2%, 22.7% and 20.7% in Hon high dose group, respectively. Moreover, Hon treatment significantly inhibited the mRNA expression levels of renal Bcrp and Mrp4 by 2.63-fold and 1.54-fold, while significantly upregulated the mRNA expression levels of hepatic Oat2 and Oatp2b1 by 1.52-fold and 1.54-fold in Hon high dose group, respectively. The results suggested that under the diabetes condition, the changes of CYP450 activity and transporter expression inevitably interfere the normal transport, metabolism and efficacy of drugs. The present work firstly reported that Hon treatment ameliorated the abnormal change of hepatic CYP activity (including CYP2E1, CYP4A and CYP1A2) and the transporter mRNA expression (including hepatic Oat2 and Oatp2b1, renal Bcrp and Mrp4) in type 2 diabetic rats induced by high-fat diet and strepotozotocin, which are associated with the occurrence and development of diabetes. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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2059 KiB

Open AccessArticle

Buprofezin Is Metabolized by CYP353D1v2, a Cytochrome P450 Associated with Imidacloprid Resistance in Laodelphax striatellus

by Mohammed Esmail Abdalla Elzaki, Mohammad Asaduzzaman Miah and Zhaojun Han

Int. J. Mol. Sci. 2017, 18(12), 2564; https://doi.org/10.3390/ijms18122564 - 29 Nov 2017

Cited by 11 | Viewed by 5707

Abstract

CYP353D1v2 is a cytochrome P450 related to imidacloprid resistance in Laodelphax striatellus. This work was conducted to examine the ability of CYP353D1v2 to metabolize other insecticides. Carbon monoxide difference spectra analysis indicates that CYP353D1v2 was successfully expressed in insect cell Sf9. The catalytic activity of CYP353D1v2 relating to degrading buprofezin, chlorpyrifos, and deltamethrin was tested by measuring substrate depletion and analyzing the formation of metabolites. The results showed the nicotinamide–adenine dinucleotide phosphate (NADPH)-dependent depletion of buprofezin (eluting at 8.7 min) and parallel formation of an unknown metabolite (eluting 9.5 min). However, CYP353D1v2 is unable to metabolize deltamethrin and chlorpyrifos. The recombinant CYP353D1v2 protein efficiently catalyzed the model substrate p-nitroanisole with a maximum velocity of 9.24 nmol/min/mg of protein and a Michaelis constant of Km = 6.21 µM. In addition, imidacloprid was metabolized in vitro by the recombinant CYP353D1v2 microsomes (catalytic constant Kcat) 0.064 pmol/min/pmol P450, Km = 6.41 µM. The mass spectrum of UPLC-MS analysis shows that the metabolite was a product of buprofezin, which was buprofezin sulfone. This result provided direct evidence that L. striatellus cytochrome P450 CYP353D1v2 is capable of metabolizing imidacloprid and buprofezin. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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828 KiB

Open AccessCommunication

Inhibitory Effects of Trapping Agents of Sulfur Drug Reactive Intermediates against Major Human Cytochrome P450 Isoforms

by Jasleen K. Sodhi, Erlie Marie Delarosa, Jason S. Halladay, James P. Driscoll, Teresa Mulder, Patrick M. Dansette and S. Cyrus Khojasteh

Int. J. Mol. Sci. 2017, 18(7), 1553; https://doi.org/10.3390/ijms18071553 - 20 Jul 2017

Cited by 5 | Viewed by 5504

Abstract

In some cases, the formation of reactive species from the metabolism of xenobiotics has been linked to toxicity and therefore it is imperative to detect potential bioactivation for candidate drugs during drug discovery. Reactive species can covalently bind to trapping agents in in vitro incubations of compound with human liver microsomes (HLM) fortified with β-nicotinamide adenine dinucleotide phosphate (NADPH), resulting in a stable conjugate of trapping agent and reactive species, thereby facilitating analytical detection and providing evidence of short-lived reactive metabolites. Since reactive metabolites are typically generated by cytochrome P450 (CYP) oxidation, it is important to ensure high concentrations of trapping agents are not inhibiting the activities of CYP isoforms. Here we assessed the inhibitory properties of fourteen trapping agents against the major human CYP isoforms (CYP1A2, 2C9, 2C19, 2D6 and 3A). Based on our findings, eleven trapping agents displayed inhibition, three of which had IC₅₀ values less than 1 mM (2-mercaptoethanol, N-methylmaleimide and N-ethylmaleimide (NEM)). Three trapping agents (dimedone, N-acetyl-lysine and arsenite) did not inhibit CYP isoforms at concentrations tested. To illustrate effects of CYP inhibition by trapping agents on reactive intermediate trapping, an example drug (ticlopidine) and trapping agent (NEM) were chosen for further studies. For the same amount of ticlopidine (1 μM), increasing concentrations of the trapping agent NEM (0.007–40 mM) resulted in a bell-shaped response curve of NEM-trapped ticlopidine S-oxide (TSO-NEM), due to CYP inhibition by NEM. Thus, trapping studies should be designed to include several concentrations of trapping agent to ensure optimal trapping of reactive metabolites. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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Review

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16 pages, 259 KiB

Open AccessReview

Role of Cytochrome P450 Enzymes in the Metabolic Activation of Tyrosine Kinase Inhibitors

by Klarissa D. Jackson, Rebecca Durandis and Matthew J. Vergne

Int. J. Mol. Sci. 2018, 19(8), 2367; https://doi.org/10.3390/ijms19082367 - 11 Aug 2018

Cited by 36 | Viewed by 4860

Abstract

Tyrosine kinase inhibitors are a rapidly expanding class of molecular targeted therapies for the treatment of various types of cancer and other diseases. An increasing number of clinically important small molecule tyrosine kinase inhibitors have been shown to undergo cytochrome P450-mediated bioactivation to form chemically reactive, potentially toxic products. Metabolic activation of tyrosine kinase inhibitors is proposed to contribute to the development of serious adverse reactions, including idiosyncratic hepatotoxicity. This article will review recent findings and ongoing studies to elucidate the link between drug metabolism and tyrosine kinase inhibitor-associated hepatotoxicity. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

20 pages, 422 KiB

Open AccessReview

Regulation of CYP2J2 and EET Levels in Cardiac Disease and Diabetes

by Theresa Aliwarga, Eric A. Evangelista, Nona Sotoodehnia, Rozenn N. Lemaitre and Rheem A. Totah

Int. J. Mol. Sci. 2018, 19(7), 1916; https://doi.org/10.3390/ijms19071916 - 29 Jun 2018

Cited by 46 | Viewed by 6383

Abstract

Cytochrome P450 2J2 (CYP2J2) is a known arachidonic acid (AA) epoxygenase that mediates the formation of four bioactive regioisomers of cis-epoxyeicosatrienoic acids (EETs). Although its expression in the liver is low, CYP2J2 is mainly observed in extrahepatic tissues, including the small intestine, pancreas, lung, and heart. Changes in CYP2J2 levels or activity by xenobiotics, disease states, or polymorphisms are proposed to lead to various organ dysfunctions. Several studies have investigated the regulation of CYP2J2 and EET formation in various cell lines and have demonstrated that such regulation is tissue-dependent. In addition, studies linking CYP2J2 polymorphisms to the risk of developing cardiovascular disease (CVD) yielded contradictory results. This review will focus on the mechanisms of regulation of CYP2J2 by inducers, inhibitors, and oxidative stress modeling certain disease states in various cell lines and tissues. The implication of CYP2J2 expression, polymorphisms, activity and, as a result, EET levels in the pathophysiology of diabetes and CVD will also be discussed. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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25 pages, 1867 KiB

Open AccessReview

Mathematical Models in the Description of Pregnane X Receptor (PXR)-Regulated Cytochrome P450 Enzyme Induction

by Jurjen Duintjer Tebbens, Malek Azar, Elfriede Friedmann, Martin Lanzendörfer and Petr Pávek

Int. J. Mol. Sci. 2018, 19(6), 1785; https://doi.org/10.3390/ijms19061785 - 15 Jun 2018

Cited by 17 | Viewed by 5536

Abstract

The pregnane X receptor (PXR) is a drug/xenobiotic-activated transcription factor of crucial importance for major cytochrome P450 xenobiotic-metabolizing enzymes (CYP) expression and regulation in the liver and the intestine. One of the major target genes regulated by PXR is the cytochrome P450 enzyme (CYP3A4), which is the most important human drug-metabolizing enzyme. In addition, PXR is supposed to be involved both in basal and/or inducible expression of many other CYPs, such as CYP2B6, CYP2C8, 2C9 and 2C19, CYP3A5, CYP3A7, and CYP2A6. Interestingly, the dynamics of PXR-mediated target genes regulation has not been systematically studied and we have only a few mechanistic mathematical and biologically based models describing gene expression dynamics after PXR activation in cellular models. Furthermore, few indirect mathematical PKPD models for prediction of CYP3A metabolic activity in vivo have been built based on compartmental models with respect to drug–drug interactions or hormonal crosstalk. Importantly, several negative feedback loops have been described in PXR regulation. Although current mathematical models propose these adaptive mechanisms, a comprehensive mathematical model based on sufficient experimental data is still missing. In the current review, we summarize and compare these models and address some issues that should be considered for the improvement of PXR-mediated gene regulation modelling as well as for our better understanding of the quantitative and spatial dynamics of CYPs expression. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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16 pages, 235 KiB

Open AccessReview

The Role of Genetic Polymorphisms in Chronic Pain Patients

by Nebojsa Nick Knezevic, Tatiana Tverdohleb, Ivana Knezevic and Kenneth D. Candido

Int. J. Mol. Sci. 2018, 19(6), 1707; https://doi.org/10.3390/ijms19061707 - 08 Jun 2018

Cited by 23 | Viewed by 6696

Abstract

It is estimated that the total annual financial cost for pain management in the U.S. exceeds 100 billion dollars. However, when indirect costs are included, such as functional disability and reduction in working hours, the cost can reach more than 300 billion dollars. In chronic pain patients, the role of pharmacogenetics is determined by genetic effects on various pain types, as well as the genetic effect on drug safety and efficacy. In this review article, we discuss genetic polymorphisms present in different types of chronic pain, such as fibromyalgia, low back pain, migraine, painful peripheral diabetic neuropathy and trigeminal neuralgia. Furthermore, we discuss the role of CYP450 enzymes involved in metabolism of drugs, which have been used for treatment of chronic pain (amitriptyline, duloxetine, opioids, etc.). We also discuss how pharmacogenetics can be applied towards improving drug efficacy, shortening the time required to achieve therapeutic outcomes, reducing risks of side effects, and reducing medical costs and reliance upon polypharmacy. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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21 pages, 2503 KiB

Open AccessReview

Ligand Access Channels in Cytochrome P450 Enzymes: A Review

by Philippe Urban, Thomas Lautier, Denis Pompon and Gilles Truan

Int. J. Mol. Sci. 2018, 19(6), 1617; https://doi.org/10.3390/ijms19061617 - 30 May 2018

Cited by 56 | Viewed by 8368

Abstract

Quantitative structure-activity relationships may bring invaluable information on structural elements of both enzymes and substrates that, together, govern substrate specificity. Buried active sites in cytochrome P450 enzymes are connected to the solvent by a network of channels exiting at the distal surface of the protein. This review presents different in silico tools that were developed to uncover such channels in P450 crystal structures. It also lists some of the experimental evidence that actually suggest that these predicted channels might indeed play a critical role in modulating P450 functions. Amino acid residues at the entrance of the channels may participate to a first global ligand recognition of ligands by P450 enzymes before they reach the buried active site. Moreover, different P450 enzymes show different networks of predicted channels. The plasticity of P450 structures is also important to take into account when looking at how channels might play their role. Full article

(This article belongs to the Special Issue Cytochromes P450: Drug Metabolism and Bioactivation)

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