Influence of Polyethylene Glycol and Acetone on the in Vitro Biotransformation of Tamoxifen and Alprazolam by Human Liver Microsomes

Cotreau-Bibbo, M. M.; Moltke, Lisa L. von; Greenblatt, David J.

doi:10.1021/js9601849

Cited by 17 publications

(13 citation statements)

References 27 publications

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“…Alprazolam undergoes 4-hydroxylation primarily by CYP3A4 to 4-hydroxyalprazolam, while -hydroxyalprazolam is formed by CYP3A5 [610][611][612][613][614], with minor contribution from CYP2C9 and 2C19 (Fig. (67)).…”

Section: Alprazolammentioning

confidence: 99%

Substrates, Inducers, Inhibitors and Structure-Activity Relationships of Human Cytochrome P450 2C9 and Implications in Drug Development

Zhou¹,

Zhou²,

Liu³

et al. 2009

CMC

147

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Cytochrome P450 2C9 (CYP2C9) is one of the most abundant CYP enzymes in the human liver. CYP2C9 metabolizes more than 100 therapeutic drugs, including tolbutamide, glyburide, diclofenac, celecoxib, torasemide, phenytoin losartan, and S-warfarin). Some natural and herbal compounds are also metabolized by CYP2C9, probably leading to the formation of toxic metabolites. CYP2C9 also plays a role in the metabolism of several endogenous compounds such as steroids, melatonin, retinoids and arachidonic acid. Many CYP2C9 substrates are weak acids, but CYP2C9 also has the capacity to metabolise neutral, highly lipophilic compounds. A number of ligand-based and homology models of CYP2C9 have been reported and this has provided insights into the binding of ligands to the active site of CYP2C9. Data from the site-directed mutagenesis studies have revealed that a number of residues (e.g. Arg97, Phe110, Val113, Phe114, Arg144, Ser286, Asn289, Asp293 and Phe476) play an important role in ligand binding and determination of substrate specificity. The resolved crystal structures of CYP2C9 have confirmed the importance of these residues in substrate recognition and ligand orientation. CYP2C9 is activated by dapsone and its analogues and R-lansoprazole in a stereo-specific and substrate-dependent manner, probably through binding to the active site and inducing positive cooperativity. CYP2C9 is subject to induction by rifampin, phenobarbital, and dexamethasone, indicating the involvement of pregnane X receptor, constitutive androstane receptor and glucocorticoid receptor in the regulation of CYP2C9. A number of compounds have been found to inhibit CYP2C9 and this may provide an explanation for some clinically important drug interactions. Tienilic acid, suprofen and silybin are mechanism-based inhibitors of CYP2C9. Given the critical role of CYP2C9 in drug metabolism and the presence of polymorphisms, it is important to identify drug candidates as potential substrates, inducer or inhibitors of CYP2C9 in drug development and drug discovery scientists should develop drugs with minimal interactions with this enzyme. Further studies are warranted to explore the molecular determinants for ligand-CYP2C9 binding and the structure-activity relationships.

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Section: Alprazolammentioning

confidence: 99%

Substrates, Inducers, Inhibitors and Structure-Activity Relationships of Human Cytochrome P450 2C9 and Implications in Drug Development

Zhou¹,

Zhou²,

Liu³

et al. 2009

CMC

147

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“…Although numerous studies have demonstrated inhibitory effects of organic solvents on CYP activity, reported stimulatory effects are rare [61,67,68] . Unlike other solvents, acetone (2 -4% v/v) and acetonitrile (2 -4% v/v) stimulated tolbutamide hydroxylation by 75 -90% and 78 -87%, respectively [68] .…”

Section: Effect Of Organic Solvents On Cyp Activitymentioning

confidence: 99%

Studying cytochrome P450 kinetics in drug metabolism

Kramer

Tracy

2008

Expert Opinion on Drug Metabolism & Toxicology

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Background : Determination of cytochrome P450 enzyme-mediated kinetics in vitro can be useful for predicting drug dosing and clearance in humans. Expressed P450s, human liver microsomes, human hepatocytes (both fresh and cryopreserved), and human liver slices are used to estimate K m and V max values for determination of intrinsic clearance of the drug for scale-up to predict in vivo clearance. Objective : To describe the advantages and disadvantages of the various in vitro systems used to estimate kinetic parameters for disposition of drugs and the various kinetic profiles that can be observed. Methods : A review of the literature was conducted to evaluate the utility of the various in vitro preparations, the methods for determining kinetic parameters and the types of kinetic profiles that may be observed. Results/conclusions : The choice of in vitro system for determining kinetic parameters will depend on the objective of the studies, as each system has advantages and disadvantages. Kinetic parameter determinations must be carefully assessed to assure that the correct kinetic model is applied and the most accurate kinetic parameters are determined.

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“…For example, ethoxyresorufin and pentoxyresorufin are both hydrophobic substrates as the biomarkers for CYP1A1 and CYP2B1, dimethyl sulfoxide (DMSO), or ethanol/bovine serum albumin (BSA) were added to increase the solubility in rat liver microsomes (RLM) incubation system (Rutten et al, 1992). Various studies have reported the effects of common organic solvents on the in vitro P450-mediated metabolic activities in human liver microsomes (HLM), human hepatocytes, or cDNA-expressed human microsomes (Cotreau-Bibbo et al, 1996;Draper et al, 1997;Chauret et al, 1998;Hickman et al, 1998;Busby et al, 1999;Coller et al, 1999;Palamanda et al, 2000). RLM were quite commonly used during in vitro studies (Yao et al, 2008;Bae et al, 2009;Pelkonen et al, 2009;Deroussent et al, 2010); however, fewer systemic studies about the effects of organic solvents on the activities of rat P450 enzymes have been reported, and those tested in rats were limited to an old system in which the S9 and older marker substrates were used (Kawalek and Andrews, 1980).…”

Section: Introductionmentioning

confidence: 99%

Effect of Regular Organic Solvents on Cytochrome P450-Mediated Metabolic Activities in Rat Liver Microsomes: Fig. 1.

Li¹,

Han²,

Meng³

et al. 2010

Drug Metab Dispos

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ABSTRACT:The effects of regular organic solvents on the metabolic activities of various human cytochromes P450 (P450s) have been reported. However, very little is known about their influence on metabolic activities mediated by P450s in the rat liver microsomes (RLM). The purpose of this study was to investigate the effects of organic solvents such as methanol, acetonitrile, dimethyl sulfoxide (DMSO), acetone, and ethanol on CYP1A, CYP2C, CYP2D, CYP2E, and CYP3A-mediated metabolism using RLM. The results showed that the activities of most rat P450 enzymes appeared to be organic solvent-dependent, and the metabolism of the tested probes were remarkably reduced when the concentration of organic solvents was up to 5% v/v, whereas most organic solvents demonstrated no significant interference when the concentration was below 1%, with the exception of DMSO. In addition, organic solvents exhibited different inhibitory effects, for example, CYP2D and CYP2E showed a significant reduction of activities at lower concentrations of organic solvents. Hence, this phenomenon should be taken into consideration when designing in vitro metabolism studies of new chemical entities. Therefore, we recommend acetonitrile as the most suitable solvent for RLM incubations, and the content of organic solvent should be kept lower than 1% v/v. IntroductionCytochromes P450 (P450s) are the principal enzymes for the oxidation of drugs, environmental pollutants, and a large number of xenobiotics, which present in many mammalian organs such as lungs, kidneys, intestines, and livers. Organic solvents are routinely used to dissolve substrates or other chemicals in the microsomal incubations for drug metabolism, P450 inhibition, and induction studies. For example, ethoxyresorufin and pentoxyresorufin are both hydrophobic substrates as the biomarkers for CYP1A1 and CYP2B1, dimethyl sulfoxide (DMSO), or ethanol/bovine serum albumin (BSA) were added to increase the solubility in rat liver microsomes (RLM) incubation system (Rutten et al., 1992). Various studies have reported the effects of common organic solvents on the in vitro P450-mediated metabolic activities in human liver microsomes (HLM), human hepatocytes, or cDNA-expressed human microsomes (Cotreau-Bibbo et al., 1996;Draper et al., 1997;Chauret et al., 1998;Hickman et al., 1998;Busby et al., 1999;Coller et al., 1999;Palamanda et al., 2000). RLM were quite commonly used during in vitro studies (Yao et al., 2008;Bae et al., 2009;Pelkonen et al., 2009;Deroussent et al., 2010); however, fewer systemic studies about the effects of organic solvents on the activities of rat P450 enzymes have been reported, and those tested in rats were limited to an old system in which the S9 and older marker substrates were used (Kawalek and Andrews, 1980). A previous study (Martignoni et al., 2006) indicated that the species-specific P450 enzymes of CYP1A, CYP2C, CYP2D, and CYP3A showed appreciable interspecies differences in terms of catalytic activity between rats and humans. Hence, the sensitivity of the P450 en...

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Influence of Polyethylene Glycol and Acetone on the in Vitro Biotransformation of Tamoxifen and Alprazolam by Human Liver Microsomes

Cited by 17 publications

References 27 publications

Substrates, Inducers, Inhibitors and Structure-Activity Relationships of Human Cytochrome P450 2C9 and Implications in Drug Development

Substrates, Inducers, Inhibitors and Structure-Activity Relationships of Human Cytochrome P450 2C9 and Implications in Drug Development

Studying cytochrome P450 kinetics in drug metabolism

Effect of Regular Organic Solvents on Cytochrome P450-Mediated Metabolic Activities in Rat Liver Microsomes: Fig. 1.

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