Evaluation of<i>in vitro</i>metabolic systems for common drugs of abuse. 1. Cocaine

Schneider, Kevin J.; DeCaprio, Anthony P.

doi:10.3109/00498254.2013.795254

Cited by 3 publications

(1 citation statement)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Calculated descriptors for electrophilic mediators of adduct formation included those for the parent compound (cocaine), a hypothesized reactive intermediate (cocaine-3,4-epoxide), and the resultant stable metabolites reported from human data (3- and 4-hydroxycocaine) (Table ). − While variations in chemical potential and chemical hardness were minimal between parent, reactive intermediate, and stable metabolic products, the higher order parameter describing electrophilicity (ω) demonstrated an increase for the reactive epoxide as compared to the stable parent drug and metabolites. Stereoisomeric forms of cocaine-3,4-epoxide were found to have HOMO and LUMO energies that were quantitatively identical, demonstrating that stereochemistry of the epoxide does not modify electrophilicity (data not shown).…”

Section: Resultsmentioning

confidence: 99%

Covalent Thiol Adducts Arising from Reactive Intermediates of Cocaine Biotransformation

Schneider

DeCaprio

2013

Chem. Res. Toxicol.

Self Cite

View full text Add to dashboard Cite

Exposure to cocaine results in the depletion of hepatocellular glutathione and macromolecular protein binding in humans. Such cocaine-induced responses have generally been attributed to oxidative stress and reactive metabolites resulting from oxidative activation of the cocaine tropane nitrogen. However, little conclusive data exists on the mechanistic pathways leading to protein modification or the structure and specificity of cocaine-derived adduction products. We now report a previously uncharacterized route of cocaine bioactivation leading to the covalent adduction of biological thiols, including cysteine and glutathione. Incubation of cocaine with biological nucleophiles in an in vitro biotransformation system containing human liver microsomes identified a monooxygenase-mediated event leading to the oxidation of, and subsequent sulfhydryl addition to, the cocaine aryl moiety. Adduct structures were confirmed using ultra-high performance liquid chromatography coupled to high resolution, high mass accuracy mass spectrometry. Examination of assays containing transgenic bactosomes expressing single human cytochrome P450 isoforms determined the role of P450s 1A2, 2C19, and 2D6 in the oxidation process resulting in adduct formation. P450-catalyzed aryl epoxide formation and subsequent attack by free nucleophilic moieties is consistent with the resulting adduct structures, mechanisms of formation, and the empirical observation of multiple structural and stereo isomers. Analogous adduction mechanisms were maintained across all sulfhydryl-containing nucleophile models examined; N-acetylcysteine, glutathione, and a synthetic cysteine-containing hexapeptide. Predictive in silico calculations of molecular reactivity and electrophilicity/nucleophilicity were compared to the results of in vitro assay incubations in order to better understand the adduction process using the principles of hard and soft acid and base (HSAB) theory. This study elucidated a novel metabolic pathway that may be of particular significance to the clinical and forensic toxicology of cocaine and provides analytical tools and methods that can be applied to the determination of these conjugates in humans, opening a new area of research on cocaine biotransformation and toxicology.

show abstract

Section: Resultsmentioning

confidence: 99%

Covalent Thiol Adducts Arising from Reactive Intermediates of Cocaine Biotransformation

Schneider

DeCaprio

2013

Chem. Res. Toxicol.

Self Cite

View full text Add to dashboard Cite

show abstract

Investigating Drug Metabolism of New Psychoactive Substances Using Human Liver Preparations and Animal Studies

Meyer

Maurer

2016

Forensic Toxicology: Drug Use and Misuse

View full text Add to dashboard Cite

Knowing the chemical identity and properties of the main metabolites of a compound is of great importance for assessing pharmacokinetics, toxic risks, and for developing toxicological and doping control screening procedures. Unfortunately, such studies are usually not done with drugs of abuse or new psychoactive substances. As it is not possible to perform controlled studies on the in vivo metabolism of new psychoactive substance in humans for ethical reasons, in vitro approaches or in vivo animal experiments are the methods of choice. This chapter therefore summarizes in vitro and in vivo strategies on such metabolism studies for developing toxicological and doping control screening procedures.

show abstract

Covalent Protein Adduction by Drugs of Abuse

Schneider¹

View full text Add to dashboard Cite

Recreational abuse of the drugs cocaine, methamphetamine, and morphine continues to be prevalent in the United States of America and around the world. While numerous methods of detection exist for each drug, they are generally limited by the lifetime of the parent drug and its metabolites in the body. However, the covalent modification of endogenous proteins by these drugs of abuse may act as biomarkers of exposure and allow for extension of detection windows for these drugs beyond the lifetime of parent molecules or metabolites in the free fraction. Additionally, existence of covalently bound molecules arising from drug ingestion can offer insight into downstream toxicities associated with each of these drugs.This research investigated the metabolism of cocaine, methamphetamine, and morphine in common in vitro assay systems, specifically focusing on the generation of reactive intermediates and metabolites that have the potential to form covalent protein adducts. Results demonstrated the formation of covalent adduction products between biological cysteine thiols and reactive moieties on cocaine and morphine metabolites. Rigorous mass spectrometric analysis in conjunction with in vitro metabolic activation, pharmacogenetic reaction phenotyping, and computational modeling were utilized to characterize structures and mechanisms of formation for each resultant thiol adduction product. For cocaine, data collected demonstrated the formation of adduction products from a reactive arene epoxide intermediate, designating a novel metabolic pathway for cocaine. In the case of morphine, data expanded on known adduct-forming pathways using sensitive and selective analysis techniques, following the known reactive metabolite, morphinone, and a proposed novel metabolite, morphine quinone methide. Data collected in this study describe novel metabolic events for multiple important drugs of abuse, culminating v in detection methods and mechanistic descriptors useful to both medical and forensic investigators when examining the toxicology associated with cocaine, methamphetamine, and morphine.

show abstract

Evaluation ofin vitrometabolic systems for common drugs of abuse. 1. Cocaine

Cited by 3 publications

References 36 publications

Covalent Thiol Adducts Arising from Reactive Intermediates of Cocaine Biotransformation

Covalent Thiol Adducts Arising from Reactive Intermediates of Cocaine Biotransformation

Investigating Drug Metabolism of New Psychoactive Substances Using Human Liver Preparations and Animal Studies

Covalent Protein Adduction by Drugs of Abuse

Contact Info

Product

Resources

About