Cocaethylene metabolism and interaction with cocaine and ethanol: role of carboxylesterases

Mariani wine: What's really in it? Analysis of the most popular tonic drink of the 19th century after 100 years of storage

During the Belle Epoque, the use of cocaine, well known to the South American populations, spread among the European elite in the form of a tonic drink created from coca leaves macerated in Bordeaux wine, the Mariani wine. Nowadays, bottles in circulation are extremely rare but the investigations of a Parisian historian led him to the discovery of a bottle of wine that belonged to Angelo Mariani's estate at the end of the 19th century. Our laboratory was asked to analyse the contents of the bottle in order to search for the main active compounds and to estimate the state of preservation. The analysis of the centenarian product collected was aimed at identifying the alcohols and solvents by HS-GC/FID and HS-GC/MS after dilution in water, and the main alkaloids contained in all the samples by LC-HRMS screening and LC-MS/MS quantification. The Mariani wine presented an alcohol content of 15.7°. The screening and the subsequent dosage revealed the following substances: cocaine (86 ng/mL), benzoylecgonine (383 ng/mL), cocaethylene (17 ng/mL), ecgonine methyl ester (130 ng/mL), caffeine, cuscohygrine, cinnamoylcocaine and synephrine. The alkaloids found in the Mariani wine confirm the real presence of coca leaves in this drink. Their low concentrations may indicate drug instability. The presence of cocaethylene demonstrates that it can be formed without passing through the liver, which was supposed to be the site of production when cocaine and ethanol are present in the body at the same time. These appear to be the first report in the literature presenting the analysis of Mariani wine with the dosage of cocaine derivatives.

Transesterification of Indazole-3-carboxamide Synthetic Cannabinoids: Identification of Metabolite Biomarkers for Diagnosing Co-abuse of 5F-MDMB-PINACA and Alcohol

Concurrent use of alcohol with synthetic cannabinoids (SCs) has been widely recorded among drug abusers. The susceptibilities of three indazole-3-carboxamide type SCs with methyl ester moiety, 5F-MDMB-PINACA, 5F-MMB-PINACA, and MMB-FUBINACA, to transesterification in the presence of ethanol warranted further investigation in view of probable augmented toxicity. In vitro metabolite identification experiments were first performed using human liver microsomes (HLMs) to characterize the novel metabolites of the three parent SCs in the presence of ethanol. Formation of transesterified metabolite, hydrolyzed metabolite, and several oxidative metabolites in HLM in the presence of alcohol was further determined for each parent SC and the respective ethyl ester analog, 5F-EDMB-PINACA, 5F-EMB-PINACA, and EMB-FUBINACA, to quantitatively elucidate transesterification and hydrolysis activities. Our results suggested that all three SCs undergo carboxylesterase-mediated transesterification to their respective ethyl ester analog in the presence of ethanol, which was incubation time- and ethanol concentration-dependent. Each ethyl ester metabolite was sequentially and readily metabolized to novel oxidative metabolites with the intact ethyl ester moiety and the same hydrolyzed metabolite as derived from its parent SC. A smaller extent of transesterification was non-enzymatically driven. Notably, we proposed 5F-EDMB-PINACA oxidative defluorination metabolite as the biomarker for diagnosing the potential co-abuse of 5F-MDMB-PINACA and alcohol. Due to the comparable pharmacological activities between each SC and its ethyl ester metabolite, augmented toxicity associated with co-abuse of SCs and alcohol is probable and deserves further investigation.

Cocaine-Induced Time-Dependent Alterations in Cytochrome P450 and Liver Function

Cytochrome P450 is responsible for the metabolism of endogenous substrates, drugs and substances of abuse. The brain and nervous system regulate liver cytochrome P450 via neuroendocrine mechanisms, as shown in rodents. Cocaine exerts its addictive effects through the dopaminergic system, the functioning of which undergoes changes during its continuous use. Therefore, it can be hypothesized that the regulation of cytochrome P450 by cocaine may also alter during the addiction process, cessation and relapse. We analyzed preclinical studies on the mechanisms of the pharmacological action of cocaine, the role of the brain's dopaminergic system in the neuroendocrine regulation of cytochrome P450 and the in vitro and in vivo effects of cocaine on the cytochrome P450 expression/activity and hepatotoxicity. The results of passive cocaine administration indicate that cocaine affects liver cytochrome P450 enzymes (including those engaged in its own metabolism) via different mechanisms involving the expression of genes encoding cytochrome P450 enzymes and interaction with enzyme proteins. Thus, it may affect its own oxidative metabolism and the metabolism of endogenous substrates and other co-administered drugs and may lead to hepatotoxicity. Its effect depends on the specific cytochrome P450 enzyme affected, cocaine dosage, treatment duration and animal species. However, further complementary studies are needed to find out whether cocaine affects cytochrome P450 via the brain's dopaminergic system. The knowledge of cocaine's effect on cytochrome P450 function during the entire addiction process is still incomplete. There is a lack of information on the enzyme expression/activity in animals self-administering cocaine (addicted), in those withdrawn after cocaine self-administration, and during relapse in animals previously addicted; furthermore, there is no such information concerning humans. The subject of cytochrome P450 regulation by cocaine during the addiction process is an open issue, and addressing this topic may help in the treatment of drug abuse patients.

Cocaine: An Updated Overview on Chemistry, Detection, Biokinetics, and Pharmacotoxicological Aspects including Abuse Pattern

Cocaine is one of the most consumed stimulants throughout the world, as official sources report. It is a naturally occurring sympathomimetic tropane alkaloid derived from the leaves of Erythroxylon coca, which has been used by South American locals for millennia. Cocaine can usually be found in two forms, cocaine hydrochloride, a white powder, or ‘crack’ cocaine, the free base. While the first is commonly administered by insufflation (‘snorting’) or intravenously, the second is adapted for inhalation (smoking). Cocaine can exert local anaesthetic action by inhibiting voltage-gated sodium channels, thus halting electrical impulse propagation; cocaine also impacts neurotransmission by hindering monoamine reuptake, particularly dopamine, from the synaptic cleft. The excess of available dopamine for postsynaptic activation mediates the pleasurable effects reported by users and contributes to the addictive potential and toxic effects of the drug. Cocaine is metabolised (mostly hepatically) into two main metabolites, ecgonine methyl ester and benzoylecgonine. Other metabolites include, for example, norcocaine and cocaethylene, both displaying pharmacological action, and the last one constituting a biomarker for co-consumption of cocaine with alcohol. This review provides a brief overview of cocaine’s prevalence and patterns of use, its physical-chemical properties and methods for analysis, pharmacokinetics, pharmacodynamics, and multi-level toxicity.

Cocaethylene: When Cocaine and Alcohol Are Taken Together

Cocaine is taken frequently together with ethanol and this combination produces a psychoactive metabolite called cocaethylene which has similar properties to the parent drug and may be more cardiotoxic. Cocaethylene has a longer half-life than cocaine, so that people who combine cocaine and ethanol may experience a longer-lasting, as well as more intense, psychoactive effect. Cocaethylene is the only known instance where a new psychoactive substance is formed entirely within the body. Although known to science for decades, cocaethylene has not been extensively studied and even its metabolic pathways are not entirely elucidated. Like its parent drug, cocaethylene blocks the reuptake of dopamine and increases post-synaptic neuronal activity; the parent drug may also block reuptake of serotonin as well. Cocaethylene has been studied in animal models in terms of its pharmacology and its potential neurological effects. Since the combination of cocaine and alcohol is commonly used, it is important for clinicians to be aware of cocaethylene, its role in prolonging or intensifying cocaine intoxication, and how it may exacerbate cocaine-induced cardiovascular disorders. Most cardiac-related risk assessment tools do not ask about cocaine use, which can prevent clinicians from making optimal therapeutic choices. Greater awareness of cocaethylene is needed for clinicians, and those who use cocaine should also be aware of the potential for polysubstance use of cocaine and ethanol to produce a potentially potent and long-lasting psychoactive metabolite.

Human carboxylesterases and fluorescent probes to image their activity in live cells

Human carboxylesterases (CESs) are serine hydrolases that are responsible for the phase I metabolism of an assortment of ester, amide, thioester, carbonate, and carbamate containing drugs. CES activity is known to be influenced by a variety of factors including single nucleotide polymorphisms, alternative splicing, and drug-drug interactions. These different factors contribute to interindividual variability of CES activity which has been demonstrated to influence clinical outcomes among people treated with CES-substrate therapeutics. Detailed exploration of the factors that influence CES activity is emerging as an important area of research. The use of fluorescent probes with live cell imaging techniques can selectively visualize the real-time activity of CESs and have the potential to be useful tools to help reveal the impacts of CES activity variations on human health. This review summarizes the properties of the five known human CESs including factors reported to or that could potentially influence their activity before discussing the design aspects and use considerations of CES fluorescent probes in general in addition to highlighting several well-characterized probes.

A Genetically Modified Skin Graft for Treating Alcohol Use Disorder and/or Polysubstance Abuse With Cocaine

Alcohol use disorder (AUD) is one of the foremost public health problems. Alcohol is also frequently co-abused with cocaine. There is a huge unmet need for the treatment of AUD and/or cocaine co-abuse. We have developed and used a skin stem cell-based gene delivery platform and found that production of the glucagon-like peptide-1 (GLP1) from the grafted genetically modified skin reduced development and reinstatement of alcohol-induced drug-taking and seeking, voluntary oral alcohol consumption and alcohol-induced increase in dopamine (DA) levels in the nucleus accumbens (NAc). Moreover, we have developed a novel co-grafting procedure for both modified human butyrylcholinesterase (hBChE)- and GLP1-expressing cells. Skin grafts-derived hBChE and GLP1 reduced acquisition of drug-taking and toxicity induced by concurrent alcohol and cocaine injections. These results imply that gene delivery through skin transplants may add a new option to treat drug abuse and co-abuse.

The First Reported Case of a Synthetic Cannabinoid Ethyl Ester Detected in a Postmortem Blood Toxicological Analysis

Metabolites of synthetic cannabinoids (SCs) are widely used as markers for identifying SCs' intake. Polydrug use involving SCs and ethanol may generate new metabolites, namely SC ethyl esters, hereby shown for the first time as new blood markers of SC-alcohol concomitant abuse. We report a case involving both the presence of 5F-PB22 and ethanol and the detection of their transesterifcation product, namely 5F-PB22 ethyl ester, in a postmortem blood sample. This marker was found retrospectively in a preserved femoral blood analyzed via liquid chromatography-high-resolution mass spectrometry. A single-point calibration was used to estimate the concentration of 5F-PB22-Et in the sample, which found to be 0.4 μg/L. Retention time and fragment ions (within ±1 mmu extraction window) of 5F-PB22-Et in the sample gave a remarkable match with a synthetic reference material. To the best of our knowledge, this is the first case report of an SC ethyl ester in a biological sample to indicate SCs and ethanol co-consumption.

Alcohol and Cocaine Combined Substance Use on Adult Hypothalamic Neural Stem Cells and Neurogenesis

Many advancements have been made over the years looking at the individual and combined effects of drugs of abuse on the brain, with one key area of research focusing on the effects on neurogenesis. An integral part of fetal brain development and, later, maintenance in the adult brain, neurogenesis occurs in three main regions: subventricularzone of the lateral ventricles (SVZ), subgranularzone of the dentate gyrus (SGZ), and the tanycyte layer in the hypothalamus (TL). We will review current literature on combined drugs of abuse and their effect on adult neurogenesis. More specifically, this review will focus on the effect of combining cocaine and alcohol. Additionally, the tanycyte layer will be explored in more depth and probed to look at the neurogenic properties of tanycytes and their role in neurogenesis.

Stability of Cocaine Compounds in Biological Fluids During Post-Analytical Sample Storage

The objective of this study is to evaluate in vitro stability of cocaine compounds, cocaine (COC), benzoylecgonine (BE), ecgonine methyl ester (EME) and benzoylecgonine ethyl ester (EBE), in blood and urine, during post-analysis custody. Stability was evaluated by measuring percent recovery. Parameters evaluated were time of custody (1 year), storage temperature (-20°C and 4°C), influence of preservative (only for blood samples) and pH (only for urine samples). The impact of the temperature is very important in blood samples. At -20°C all compounds demonstrated to be stable, with recoveries higher than 80% after 1 year. In contrast, degradation was observed in the concentration for all four compounds when the samples were maintained at 4°C. In these same conditions, the influence of the preservative was also noticeable and a higher stability was found in samples preserved with NaF. COC and EBE had similar profiles, and both compounds disappeared after 30 days in samples without NaF and after 150 days in samples with NaF added. EME disappeared after 185 days and after 215 days in samples without and with preservative, respectively. BE recoveries, after 365 days of storage, were 68.5% (in samples with NaF) and 3.7% (in samples without NaF). In urine samples, the four compounds were stable in all the studied conditions except when samples were at pH 8 and stored at 4°C where the compounds disappeared (COC and EBE after 75 days of storage and EME after 15 days). The exception was BE, with a recovery of 23% after 1 year of storage. Of the temperatures evaluated, -20°C seems to be optimal for storage to maintain the stability of cocaine and metabolites in biological samples. This can be further enhanced by maintaining a pH of 4 in urine samples and adding a NaF preservative to blood.

Impact of polysubstance use on high-sensitivity cardiac troponin I over time in homeless and unstably housed women

INTRODUCTION

The use of controlled substances like cocaine increases the risk of cardiovascular disease (CVD) and myocardial infarction (MI). However, outside of alcohol and tobacco, substance use is not included in CVD risk assessment tools. We identified the effects of using multiple substances (nicotine/cotinine, cannabis, alcohol, cocaine, methamphetamine, heroin and other opioids) on cardiac injury measured by high-sensitivity troponin (hsTnI) in homeless and unstably housed women.

METHODS

We recruited 245 homeless and unstably housed women from shelters, free meal programs and street encampments. Participants completed six monthly study visits. Adjusting for traditional CVD risk factors, we examined longitudinal associations between substance use and hsTnI.

RESULTS

Median participant age was 53 years and 74 % were ethnic minority women. At baseline, 76 % of participants had hypertension, 31 % were HIV-positive, 8% had a history of a prior MI and 12 % of prior stroke. The most commonly used substances were cotinine/nicotine (80 %), cannabis (68 %) and cocaine (66 %). HsTnI exceeding the 99th percentile (14.7 ng/L) - a level high enough to signal possible MI - was observed in 14 participants during >1 study visit (6%). In adjusted analysis, cocaethylene and fentanyl were significantly associated with higher hsTnI levels.

CONCLUSIONS

Fentanyl use and the co-use of cocaine and alcohol are associated with myocardial injury, suggesting that the use of these substances may act as long-term cardiac insults. Whether risk counseling on these specific substances and/or including their use in CVD risk stratification would improve CVD outcomes in populations where substance use is high merits further investigation.

Cassie-Wenzel transition of a binary liquid mixture on a nanosculptured surface

The Cassie-Wenzel transition of a symmetric binary liquid mixture in contact with a nano-corrugated wall is studied. The corrugation consists of a periodic array of nanopits with square cross sections. The substrate potential is the sum over Lennard-Jones interactions, describing the pairwise interaction between the wall particles C and the fluid particles. The liquid is composed of two species of particles, A and B, which have the same size and equal A-A and B-B interactions. The liquid particles interact between each other also via A-B Lennard-Jones potentials. We have employed classical density functional theory to determine the equilibrium structure of binary liquid mixtures in contact with the nano-corrugated surface. Liquid intrusion into the pits is studied as a function of various system parameters such as the composition of the liquid, the strengths of various interparticle interactions, and the geometric parameters of the pits. The binary liquid mixture is taken to be at its mixed-liquid-vapor coexistence. For various sets of parameters the results obtained for the Cassie-Wenzel transition, as well as for the metastability of the two corresponding thermodynamic states, are compared with macroscopic predictions in order to check the range of validity of the macroscopic theories for systems exposed to nanoscopic confinements. Distinct from the macroscopic theory, it is found that the Cassie-Wenzel transition cannot be predicted based on the knowledge of a single parameter, such as the contact angle within the macroscopic theory.

Catalytic activities of cocaine hydrolases against the most toxic cocaine metabolite norcocaethylene

A majority of cocaine users also consume alcohol. The concurrent use of cocaine and alcohol produces the pharmacologically active metabolites cocaethylene and norcocaethylene, in addition to norcocaine. Both cocaethylene and norcocaethylene are more toxic than cocaine itself. Hence, a truly valuable cocaine-metabolizing enzyme for cocaine abuse/overdose treatment should be effective for the hydrolysis of not only cocaine, but also its metabolites norcocaine, cocaethylene, and norcocaethylene. However, there has been no report on enzymes capable of hydrolyzing norcocaethylene (the most toxic metabolite of cocaine). The catalytic efficiency parameters (kcat and KM) of human butyrylcholinesterase (BChE) and two mutants (known as cocaine hydrolases E14-3 and E12-7) against norcocaethylene have been characterized in the present study for the first time, and they are compared with those against cocaine. According to the obtained kinetic data, wild-type human BChE showed a similar catalytic efficiency against norcocaethylene (kcat = 9.5 min-1, KM = 11.7 μM, and kcat/KM = 8.12 × 105 M-1 min-1) to that against (-)-cocaine (kcat = 4.1 min-1, KM = 4.5 μM, and kcat/KM = 9.1 × 105 M-1 min-1). E14-3 and E12-7 showed an improved catalytic activity against norcocaethylene compared to wild-type BChE. E12-7 showed a 39-fold improved catalytic efficiency against norcocaethylene (kcat = 210 min-1, KM = 6.6 μM, and kcat/KM = 3.18 × 107 M-1 min-1). It has been demonstrated that E12-7 as an exogenous enzyme can efficiently metabolize norcocaethylene in rats.

Forensic Drug Profile: Cocaethylene

This article is intended as a brief review or primer about cocaethylene (CE), a pharmacologically active substance formed in the body when a person co-ingests ethanol and cocaine. Reference books widely used in forensic toxicology contain scant information about CE, even though this cocaine metabolite is commonly encountered in routine casework. CE and cocaine are equi-effective at blocking the reuptake of dopamine at receptor sites, thus reinforcing the stimulant effects of the neurotransmitter. In some animal species, the LD50 of CE was lower than for cocaine. CE is also considered more toxic to the heart and liver compared with the parent drug cocaine. The plasma elimination half-life of CE is ~2 h compared with ~1 h for cocaine. The concentrations of CE in blood after drinking alcohol and taking cocaine are difficult to predict and will depend on the timing of administration and the amounts of the two precursor drugs ingested. After an acute single dose of cocaine and ethanol, the concentration–time profile of CE runs on a lower level to that of cocaine, although CE is detectable in blood for several hours longer. A strong case can be made for adding together the concentrations of cocaine and CE in forensic blood samples when toxicological results are interpreted in relation to acute intoxication and the risk of an overdose death.

Risk of injury from alcohol, marijuana and other drug use among emergency department patients

BACKGROUND

Alcohol is known to be associated with injury, but little is known of combined use of alcohol and other drugs on injury; especially important for marijuana, given increasing legalization of use in the U.S. and Canada.

METHODS

Probability samples of patients 18 and older were interviewed in the emergency department at two sites in Vancouver and one in Victoria, BC (n=1191 injured and 1613 non-injured patients). Case-control and case-crossover analyses were used to analyze risk of injury, based on self-reported alcohol and drug use (marijuana, stimulants, depressants) prior to injury.

RESULTS

Risk of injury was significantly elevated (p<0.001) for alcohol use alone in both case-control (OR=2.72) and case-crossover analyses (OR=2.80) but not for any of the three drug classes. The interaction of alcohol with each class of drug was tested, and marginally significant only for marijuana in case-control analysis (OR=4.42; p=0.088). The interaction of alcohol and two or more drugs was also significant in case-control analysis (OR=03; p=0.035). The volume of alcohol consumed prior to injury was greater for those also using drugs during this time and positively associated with the number of drugs reported.

CONCLUSION

Given the potential issues involved with both case-control and case-crossover study designs, the inconsistent findings suggest caution in reaching any definite conclusion regarding whether there is extra risk related to combined use of alcohol and marijuana, and is an important area for future research.

The novel carboxylesterase 1 variant c.662A>G may decrease the bioactivation of oseltamivir in humans

Background

Human carboxylesterase 1 (CES1) is a serine esterase that hydrolyses various exogenous and endogenous compounds including oseltamivir, a prodrug used to treat influenza. A novel CES1 c.662A>G single nucleotide polymorphism (SNP) was predicted to decrease CES1 enzymatic activity in an in silico analysis. This study evaluated the effect of the c.662A>G SNP on the pharmacokinetics (PK) of oseltamivir in humans.

Methods

A single oral dose of oseltamivir at 75 mg was administered to 20 healthy subjects, 8 heterozygous c.662A>G carriers (c.662AG) and 12 non-carriers (c.662AA). The concentrations of oseltamivir and its active metabolite, oseltamivir carboxylate, were measured in plasma and urine using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The PK parameters were calculated using a noncompartmental method. The geometric mean ratios (GMR, c.662AG to c.662AA) of the PK parameters and their 90% confidence intervals (CI) were calculated.

Results

The systemic exposure to oseltamivir, as assessed by the AUC_0-48h of oseltamivir, was increased by 10% in c.662AG subjects, whereas the AUC_0-48h of oseltamivir carboxylate was 5% lower in c.662AG subjects. The GMR and 90% CI of the metabolic ratio (AUC_{0-48h, Oseltamivir carboxylate}/AUC_{0-48h, Oseltamivir}) was 0.87 (0.66–1.14). The amount of unchanged oseltamivir excreted in the urine was increased by 15% in subjects with the c.662AG genotype.

Conclusions

This result suggests that CES1 enzymatic activity may be decreased in these heterozygous allele carriers, although further studies are warranted to investigate the clinical implications of this genetic variation on CES1 substrate drugs.

Trial registration

ClinicalTtrials.gov NCT01902342

Effects of alcohol on human carboxylesterase drug metabolism

BACKGROUND AND OBJECTIVE

Human carboxylesterase-1 (CES1) and human carboxylesterase-2 (CES2) play an important role in metabolizing many medications. Alcohol is a known inhibitor of these enzymes but the relative effect on CES1 and CES2 is unknown. The aim of this study was to determine the impact of alcohol on the metabolism of specific probes for CES1 (oseltamivir) and CES2 (aspirin).

METHODS

The effect of alcohol on CES1- and CES2-mediated probe drug hydrolysis was determined in vitro using recombinant human carboxylesterase. To characterize the in vivo effects of alcohol, healthy volunteers received each probe drug alone and in combination with alcohol followed by blood sample collection and determination of oseltamivir, aspirin, and respective metabolite pharmacokinetics.

RESULTS

Alcohol significantly inhibited oseltamivir hydrolysis by CES1 in vitro but did not affect aspirin metabolism by CES2. Alcohol increased the oseltamivir area under the plasma concentration-time curve (AUC) from 0 to 6 h (AUC0 → 6 h) by 27% (range 11-46%, p = 0.011) and decreased the metabolite/oseltamivir AUC0 → 6 h ratio by 34% (range 25-41%, p < 0.001). Aspirin pharmacokinetics were not affected by alcohol.

CONCLUSIONS

Alcohol significantly inhibited the hydrolysis of oseltamivir by CES1 both in vitro and in humans, but did not affect the hydrolysis of aspirin to salicylic acid by CES2. These results suggest that alcohol's inhibition of CES1 could potentially result in clinically significant drug interactions with other CES1-substrate drugs, but it is unlikely to significantly affect CES2-substrate drug hydrolysis.

The usefulness of biomarkers of alcohol abuse in hair and serum carbohydrate-deficient transferrin: a case report

The detection of carbohydrate-deficient transferrin (CDT) in serum is widely accepted to identify chronic alcohol consumption over the previous two weeks, but minor ethanol metabolites detected in hair often complete the information obtained. In particular, ethylglucuronide and cocaethylene (a marker of simultaneous intake of cocaine and alcohol) allow correct interpretation of data obtained in forensic cases. We refer to a negative CDT value obtained from a serum sample collected during hospitalization of a man admitted for cardiac arrest who died about 14 h later. Clinical analysis performed on admission showed a high ethanol level and a positive urinary screening for cocaine. The toxicological analyses of post-mortem samples found cocaine metabolites in his urine and blood. The negative CDT level suggested the ethanol concentration at admission to be an acute episode. Cocaine and cocaethylene well above the cut-off suggested by the literature were found in hair analyzed for the entire length (about 1 cm). Ethylglucuronide detected on the same hair sample confirmed chronic abuse of ethanol in the previous month, at least. The present report suggests caution in the interpretation of biomarkers of alcohol abuse, encouraging the detection of more than one marker to avoid misinterpretation.

Efficient in vitro refolding and functional characterization of recombinant human liver carboxylesterase (CES1) expressed in E. coli

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Expression of recombinant human carboxylesterase I in E.coli is mainly insoluble.

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Refolding using a combination of 1% glycerol and 2 mM β-mercaptoethanol in Tris–HCl, pH 7.5 significantly improved solubility.

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Purified recombinant human CES1 is functionally active and stable.

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We provided efficient method to produce large amount and catalytically active CES1.

Human liver carboxylesterase 1 (CES1) plays a critical role in the hydrolysis of various ester- and amide-containing molecules, including active metabolites, drugs and prodrugs. However, it has been problematic to express recombinant CES1 in bacterial expression systems due to low solubility, with the CES1 protein being mainly expressed in inclusion bodies, accompanied by insufficient purity issues. In this study, we report an efficient in vitro method for refolding recombinant CES1 from inclusion bodies. A one-step purification with an immobilized-metal affinity column was utilized to purify His-tagged recombinant CES1. Conveniently, both denaturant and imidazole can be removed while the enzyme is refolded via buffer exchange, a dilution method. We show that the refolding of recombinant CES1 was successful in Tris–HCl at pH 7.5 containing a combination of 1% glycerol and 2 mM β-mercaptoethanol, whereas a mixture of other additives (trehalose, sorbitol and sucrose) and β-mercaptoethanol failed to recover a functional protein. His-tagged recombinant CES1 retains its biological activity after refolding and can be used directly without removing the fusion tag. Altogether, our results provide an alternative method for obtaining a substantial amount of functionally active protein, which is advantageous for further investigations such as structural and functional studies.

Stimulants and the lung : review of literature

Illicit stimulants, such as cocaine, amphetamine, and their derivatives (e.g., "ecstasy"), continue to exact heavy toll on health care in both developed and developing countries. The US Department of Health and Human Service reported over one million illicit drug-related emergency department visits in 2010, which was higher than any of the six previous years. Both inhaled and intravenous forms of these substances of abuse can result in a variety of acute and chronic injuries to practically every part of the respiratory tract, leading potentially to permanent morbidities as well as fatal consequences--including but not limited to nasal septum perforation, pulmonary hypertension, pneumothorax, pneumomediastinum, interstitial lung disease, alveolar hemorrhage, reactive airway disease, pulmonary edema, pulmonary granulomatosis, infections, foreign body aspiration, infections, bronchoconstriction, and thermal injuries. Stimulants are all rapidly absorbed substances that can also significantly alter the patient's systemic acid-base balance and central nervous system, thereby leading to further respiratory compromise. Mounting evidence in the past decade has demonstrated that adulterants coinhaled with these substances (e.g., levamisole) and the metabolites of these substances (e.g., cocaethylene) are associated with specific forms of systemic and respiratory complications as well. Recent studies have also demonstrated the effects of stimulants on autoimmune-mediated injuries of the respiratory tract, such as cocaine-induced midline destructive lesions. A persistent challenge to studies involving stimulant-associated respiratory toxidromes is the high prevalence of concomitant usage of various substances by drug abusers, including tobacco smoking. Now more than ever, health care providers must be familiar with the multitude of respiratory toxidromes as well as the diverse pathophysiology related to commonly abused stimulants to provide timely diagnosis and effective treatment.

The catalytic mechanism of carboxylesterases: a computational study

The catalytic mechanism of carboxylesterases (CEs, EC 3.1.1.1) is explored by computational means. CEs hydrolyze ester, amide, and carbamate bonds found in xenobiotics and endobiotics. They can also perform transesterification, a reaction important, for instance, in cholesterol homeostasis. The catalytic mechanisms with three different substrates (ester, thioester, and amide) have been established at the M06-2X/6-311++G**//B3LYP/6-31G* level of theory. It was found that the reactions proceed through a mechanism involving four steps instead of two as is generally proposed: (i) nucleophilic attack of serine to the substrate, forming the first tetrahedral intermediate, (ii) formation of the acyl-enzyme complex concomitant with the release of the alcohol product, (iii) nucleophilic attack of a water or alcohol molecule forming the second tetrahedral intermediate, and (iv) the release of the second product of the reaction. The results agree very well with the available experimental data and show that the hydrolytic and the transesterification reactions are competitive processes when the substrate is an ester. In all the other studied substrates (thioester or amide), the hydrolytic and transesterification process are less favorable and some of them might not even take place under in vivo conditions.

Kinetic characterization of human butyrylcholinesterase mutants for the hydrolysis of cocaethylene

It is known that the majority of cocaine users also consume alcohol. Alcohol can react with cocaine to produce a significantly more cytotoxic compound, cocaethylene. Hence a truly valuable cocaine-metabolizing enzyme as treatment for cocaine abuse/overdose should be efficient for not only cocaine itself, but also cocaethylene. The catalytic parameters (kcat and KM) of human BChE (butyrylcholinesterase) and two mutants (known as cocaine hydrolases E14-3 and E12-7) for cocaethylene are characterized in the present study, for the first time, in comparison with those for cocaine. On the basis of the obtained kinetic data, wild-type human BChE has a lower catalytic activity for cocaethylene (kcat=3.3 min(-1), KM=7.5 μM and kcat/KM=4.40 × 10(5) M(-1)·min(-1)) compared with its catalytic activity for (-)-cocaine. E14-3 and E12-7 have a considerably improved catalytic activity against cocaethylene compared with the wild-type BChE. E12-7 is identified as the most efficient enzyme for hydrolysing cocaethylene in addition to its high activity for (-)-cocaine. E12-7 has an 861-fold improved catalytic efficiency for cocaethylene (kcat=3600 min(-1), KM=9.5 μM and kcat/KM=3.79 × 10(8) M(-1)·min(-1)). It has been demonstrated that E12-7 as an exogenous enzyme can indeed rapidly metabolize cocaethylene in rats. Further kinetic modelling has suggested that E12-7 with an identical concentration as that of the endogenous BChE in human plasma can effectively eliminate (-)-cocaine, cocaethylene and norcocaine in simplified kinetic models of cocaine abuse and overdose associated with the concurrent use of cocaine and alcohol.

Mass loading and removal of select illicit drugs in two wastewater treatment plants in New York State and estimation of illicit drug usage in communities through wastewater analysis

Sewage epidemiology is a rapidly expanding field that can provide information on illicit drug usage in communities, based on the measured concentrations in samples from wastewater treatment plants (WWTPs). In this study, select illicit drugs (six drugs and eight metabolites) were determined on a daily basis for a week in wastewater, suspended particulate matter (SPM), and sludge from two WWTPs in the Albany area in New York State. The WWTP that served a larger population (∼100 000, with a flow rate of 83 300 m(3)/d) showed 3.2 (methadone) to 51 (3,4-methylenedioxyamphetamine; MDA) times higher mass flows of illicit drugs than did the WWTP that served a smaller population (∼15 000, with a flow rate of 6850 m(3)/d). The consumption rate of target illicit drugs in the communities served by the two WWTPs was estimated to range from 1.67 to 3510 mg/d/1000 people. Between the dissolved and particulate phases, the fraction of methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), amphetamine, and MDA sorbed to SPM ranged from 34.3% to 41.1% of the total mass in the waste stream. The removal efficiencies of illicit drugs from the two WWTPs ranged from 4% (norcocaine) to 99% (cocaine); however, methamphetamine, methadone, and EDDP showed a negative removal in WWTPs. The environmental emission of illicit drugs from WWTP discharges was calculated to range from 0.38 (MDEA) to 67.5 (EDDP) mg/d/1000 people. Other markers such as caffeine, paraxanthine, nicotine, and cotinine were found to predict the concentrations of select illicit drugs in raw wastewater (r(2) = 0.20-0.79; p ≤ 0.029).

Identification of alcohol-dependent clopidogrel metabolites using conventional liquid chromatography/triple quadrupole mass spectrometry

RATIONALE

Clopidogrel (CLO) is a prodrug used to prevent ischemic events in patients undergoing percutaneous coronary intervention or with myocardial infarction. A previous study found ethyl clopidogrel (ECLO) is formed by transesterification of CLO when incubated with alcohol in human liver microsomes. We hypothesize that ECLO will be subject to further metabolism and developed an assay to identify its metabolites.

METHODS

A liquid chromatography/triple quadrupole mass spectrometry (LC/MS/MS) method was developed to identify metabolites of ECLO. According to the predicted metabolic pathway of ECLO, precursor-product ion pairs were used to screen the possible metabolites of ECLO in human liver S9 fractions. Subsequently, the detected metabolites were characterized by the results of product ion scan.

RESULTS

In the presence of alcohol, CLO was tranesterified to ECLO, which was further oxidized to form ethylated 2-oxo-clopidogrel and several ethylated thiol metabolites including the ethylated form of the H4 active metabolite.

CONCLUSIONS

The ECLO formed by transesterification with alcohol is subject to metabolism by CYP450 enzymes producing ethylated forms of 2-oxo-clopidogrel and the active H4 thiol metabolite.

Pharmacokinetic drug interactions between drugs of abuse and antiretroviral medications: implications and management for clinical practice

Substance abuse and HIV/AIDS are two of the most serious, yet treatable diseases worldwide. Global access to HIV treatment continues to expand. In settings where both active illicit drug use and HIV treatment are concurrent, potentional problematic pharmacokinetic drug interactions may arise and complicate therapy. Clinical case series and carefully controlled pharmacokinetic interaction studies have been conducted between only a few drugs of abuse and approved antiretroviral therapies. Important pharmacokinetic drug interactions have been described for benzodiazepines, 3,4-methylenedioxymethamphetamine, methadone and buprenorphine; however, most have not been studied and few well-controlled studies have been conducted to adequately address the clinical implications of these interactions. The metabolism of drugs of abuse, description of the known interactions, and clinical implications and management of these interactions are reviewed. Certain interactions between drugs of abuse and antiretroviral therapies are known and others are likely based upon shared metabolic pathways. These may result in important clinical consequences. To optimize care, clinicians must be alert, knowledgeable about known and possible interactions and equipped to clinically manage the medical consequences. Moreover, there is considerable need for carefully controlled studies in this important and emerging area.

Alcohol and drug use as predictors of intentional injuries in two emergency departments in British Columbia

BACKGROUND

While a substantial literature exists demonstrating a strong association of alcohol and intentional injury, less is known about the association of intentional injury with recreational drug use, either alone, or in combination with alcohol.

OBJECTIVES

The risk of intentional injury due to alcohol and other drug use prior to injury is analyzed in a sample of emergency department (ED) patients.

METHODS

Logistic regression was used to examine the predictive value of alcohol and drug use on intentional versus non-intentional injury in a probability sample of ED patients in Vancouver, BC (n = 436).

RESULTS

Those reporting only alcohol use were close to four times more likely (OR = 3.73) to report an intentional injury, and those reporting alcohol combined with other drug(s) almost 18 times more likely (OR = 17.75) than those reporting no substance use. Those reporting both alcohol and drug use reported drinking significantly more alcohol (15.7 drinks) than those reporting alcohol use alone (5 drinks).

CONCLUSIONS

These data suggest that alcohol in combination with other drugs may be more strongly associated with intentional injury than alcohol alone.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

The strong association of alcohol combined with other drug use on injury may be due to the increased amount of alcohol consumed by those using both substances, and is an area requiring more research with larger samples of intentional injury patients.

Evaluation of in vitro metabolic systems for common drugs of abuse. 1. Cocaine

This study examined the efficacy of four common in vitro assay systems in producing metabolic profiles consistent with in vivo data for drugs of abuse. Cocaine (COC) was selected for this study because of its complex biotransformation pathways, diverse metabolic processes and because extensive Phase I and Phase II metabolomic examination of COC has not yet been reported by means of in vitro assay. COC metabolism was assessed with a series of common in vitro assay systems (human liver microsomes, cytosol and human liver S9 fraction and horseradish peroxidase) using liquid chromatography-tandem mass spectrometry with multiple reaction monitoring. Qualitative and quantitative differences in analyte production were noted among the various active Phase I and Phase II metabolic systems. Assay incubation time was found to be a determining factor in metabolic profile, specifically with primary versus secondary metabolite formation. Regioselective arene hydroxylation of COC was conclusively documented in human hepatic metabolic models, while peroxidase-based assay systems displayed less selectivity in oxidative aryl biotransformation. Results demonstrate the applicability of in vitro systems in studying COC metabolite production and the impact of assay selection and variation in method parameters on metabolite profiles for this important drug of abuse.

Identification of carboxylesterase-dependent dabigatran etexilate hydrolysis

Dabigatran etexilate (DABE) is an oral prodrug that is rapidly converted to the active thrombin inhibitor, dabigatran (DAB), by serine esterases. The aims of the present study were to investigate the in vitro kinetics and pathway of DABE hydrolysis by human carboxylesterase enzymes, and the effect of alcohol on these transformations. The kinetics of DABE hydrolysis in two human recombinant carboxylesterase enzymes (CES1 and CES2) and in human intestinal microsomes and human liver S9 fractions were determined. The effects of alcohol (a known CES1 inhibitor) on the formation of DABE metabolites in carboxylesterase enzymes and human liver S9 fractions were also examined. The inhibitory effect of bis(4-nitrophenyl) phosphate on the carboxylesterase-mediated metabolism of DABE and the effect of alcohol on the hydrolysis of a classic carboxylesterase substrate (cocaine) were studied to validate the in vitro model. The ethyl ester of DABE was hydrolyzed exclusively by CES1 to M1 (Km 24.9 ± 2.9 μM, Vmax 676 ± 26 pmol/min per milligram protein) and the carbamate ester of DABE was exclusively hydrolyzed by CES2 to M2 (Km 5.5 ± 0.8 μM; Vmax 71.1 ± 2.4 pmol/min per milligram protein). Sequential hydrolysis of DABE in human intestinal microsomes followed by hydrolysis in human liver S9 fractions resulted in complete conversion to DAB. These results suggest that after oral administration of DABE to humans, DABE is hydrolyzed by intestinal CES2 to the intermediate M2 metabolite followed by hydrolysis of M2 to DAB in the liver by CES1. Carboxylesterase-mediated hydrolysis of DABE was not inhibited by alcohol.

The role of human carboxylesterases in drug metabolism: have we overlooked their importance?

Carboxylesterases are a multigene family of mammalian enzymes widely distributed throughout the body that catalyze the hydrolysis of esters, amides, thioesters, and carbamates. In humans, two carboxylesterases, hCE1 and hCE2, are important mediators of drug metabolism. Both are expressed in the liver, but hCE1 greatly exceeds hCE2. In the intestine, only hCE2 is present and highly expressed. The most common drug substrates of these enzymes are ester prodrugs specifically designed to enhance oral bioavailability by hydrolysis to the active carboxylic acid after absorption from the gastrointestinal tract. Carboxylesterases also play an important role in the hydrolysis of some drugs to inactive metabolites. It has been widely believed that drugs undergoing hydrolysis by hCE1 and hCE2 are not subject to clinically significant alterations in their disposition, but evidence exists that genetic polymorphisms, drug-drug interactions, drug-disease interactions and other factors are important determinants of the variability in the therapeutic response to carboxylesterase-substrate drugs. The implications for drug therapy are far-reaching, as substrate drugs include numerous examples from widely prescribed therapeutic classes. Representative drugs include angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, antiplatelet drugs, statins, antivirals, and central nervous system agents. As research interest increases in the carboxylesterases, evidence is accumulating of their important role in drug metabolism and, therefore, the outcomes of pharmacotherapy.

LC/MS/MS evaluation of cocaine and its metabolites in different brain areas, peripheral organs and plasma in cocaine self-administering rats

BACKGROUND

We employed a cocaine intravenous self-administration model based on positive reinforcement of animals' instrumental reactions (i.e., lever pressing) rewarded by a dose of the drug. We also carried out simultaneous characterization of the pharmacokinetics of cocaine and its metabolites in rats during withdrawal; in this part of the experiments, we investigated the cocaine (2 mg/kg, iv)-induced changes in the distribution, rate constant, clearance and t₁/₂ of the parent drug and its metabolites in different structures of the brain and in peripheral tissues.

METHODS

By using liquid chromatography-tandem mass spectrometry (LC/MS/MS) we measured the levels of cocaine and its major metabolites.

RESULTS

Our results demonstrate differences in the levels of cocaine after cocaine self-administration in the rat, with the highest concentration seen in the striatum and the lowest in the cerebellum. Cocaine metabolites determined in the rat brain remained at very low levels (benzoylecgonine), irrespectively of the brain area, whereas the norcocaine concentration varied from 1.56 μg/g (the nucleus accumbens) to 2.73 μg/g (the striatum).

CONCLUSION

A tandem LC/MS/MS is a valid method for evaluation of brain and peripheral levels of cocaine and its metabolites. Our results demonstrate brain area-dependent differences in the levels of cocaine after its self-administration in the rat. There were also differences in pharmacokinetic parameters among the brain areas and peripheral tissues following a bolus iv injection of cocaine to rats withdrawn from cocaine; among brain structures the slowest metabolic rate was detected for the striatum.

Quantitative assessment of time dependent drug-use trends by the analysis of drugs and related metabolites in raw sewage

BACKGROUND

Accurate and timely information on the scale and dynamics of drug consumption is important for assessing the needs of law enforcement and public health services in a community.

AIMS

This paper presents a detailed examination of a comprehensive sewage-sampling campaign for the purposes of increasing an understanding of the dynamics of drug-flows in sewage streams, and developing new methodology by which this technique can support traditional drug-use surveys.

METHODS

A total of 104 sewage samples were collected from a treatment plant servicing approximately 500000 people and analysed for levels of methamphetamine, cocaine and cocaine metabolites. Careful examination of the kinetics of drug-flow profiles was then performed in order to identify trends or patterns of use within the community.

RESULTS

Results were validated against identical measurements of pharmaceutical reference compounds. Consumption profiles for cocaine and methamphetamine were found to differ in terms of frequency and timing of use. The majority of cocaine consumption occurs during the evening hours and 45% of consumption of this drug occurs in weekend periods. The flow of methamphetamine in the sewage system appears more evenly spread throughout the week.

CONCLUSIONS

This result is consistent with both an extended excretion half-life and a pattern of use that is more evenly balanced across all days of the week. Comprehensive investigation in to the scale and kinetics of drug flow in a sewage stream can therefore provide valuable information, not only in terms of the volume of drug consumed, but also in terms of identifying differing usage-patterns over daily and weekly time-scales.

Risk of injury from alcohol and drug use in the emergency department: a case-crossover study

INTRODUCTION AND AIMS

A substantial literature exists demonstrating the risk of injury from alcohol, but less is known about the association of alcohol in combination with other drugs and injury. This study examined the risk of injury associated with alcohol and drug use prior to the event.

DESIGN AND METHODS

Case-crossover analysis was used to estimate the relative risk (RR) of injury due to alcohol use alone, compared with alcohol in combination with other drug use in a sample of emergency department injured patients from two sites in Vancouver, British Columbia (n = 443). Alcohol and drug use in the 6 h prior to injury was compared with the patient's use of these substances during the same 6 h period the day prior and the week prior to injury.

RESULTS

Using multiple matching for the two control time periods, RR of injury was significantly related to both alcohol use (RR = 3.3) and to alcohol combined with drug use (RR = 3.0), but not to drug use alone. Effect modification was found only for age for alcohol combined with drug use, with a significant increase in injury risk (P = 0.087) for those over 30.

DISCUSSION AND CONCLUSION

While a similar elevated risk of injury was found for alcohol use alone and alcohol used with other drugs, the literature suggests that alcohol in combination with some drugs may be potentially more risky for injury occurrence. Findings suggest the need for future research on risk of injury for specific alcohol and drug combinations.

Effect of cocaine use on buprenorphine pharmacokinetics in humans

The effect of chronic cocaine use on buprenorphine pharmacokinetics was investigated to identify drug interactions and potential toxicities. In a retrospective analysis, pharmacokinetics were compared for 16 studies completed on subjects who were regular cocaine users and 74 studies on subjects who used cocaine only occasionally or not at all. All participants were stably maintained on buprenorphine/naloxone 16/4 mg daily. Participants who used cocaine regularly had lower buprenorphine exposure (AUC 34% lower; C(max) 27% lower and C(24) 37% lower; p <or= .001 for all comparisons). Regular cocaine users were younger (p = .0007), and used more heroin (p = .004) and cocaine (p < .0001). Regular cocaine use may result in lower buprenorphine plasma concentrations with potential for adverse clinical outcomes.

Oseltamivir treatment prevents the increased influenza virus disease severity and lethality occurring in chronic ethanol consuming mice

BACKGROUND

Chronic consumption of ethanol (EtOH) is well recognized to lead to defective innate and adaptive immune responses and increase the severity of pulmonary infections. Our own studies have demonstrated that chronic EtOH consumption decreases CD8 T-cell immunity to influenza virus infections (IAV) leading to severe infections and mortality. Interestingly, antiviral treatment of IAVs has been shown to be compromised in mice and humans that are immuno-deficient. It is known that EtOH can alter the pharmacokinetics of antivirals. Therefore, the effectiveness of influenza antiviral therapy during chronic ethanol consumption remains in question.

METHODS

BALB/c mice were placed on 18% (w/v) EtOH in their drinking water for 8 weeks. Chronic EtOH consuming and water controls were then treated with 10 mg/kg oseltamivir orally and infected intranasally with influenza virus 4 hours post-oseltamivir treatment. The mice were then treated with oseltamivir twice daily until day 7 postinfection. Influenza disease severity was measured by morbidity and mortality, pulmonary viral titers, and histology.

RESULTS

Chronic EtOH consuming mice infected with IAV and treated with oseltamivir have decreased morbidity and mortality, pulmonary viral titers, and pulmonary pathology compared to untreated EtOH mice.

CONCLUSIONS

Despite the severe immune defect seen in chronic EtOH mice as well as the potential for EtOH to inhibit the conversion of oseltamivir into an active form, treatment with oseltamivir reduces viral shedding as well as disease severity. These data suggest that the combination of a limited adaptive immune response plus the anti-IAV drug oseltamivir is sufficient to curb high mortality and mediate resolution of IAVs in mice chronically consuming ethanol.

The effect of ethanol on oral cocaine pharmacokinetics reveals an unrecognized class of ethanol-mediated drug interactions

Ethanol decreases the clearance of cocaine by inhibiting the hydrolysis of cocaine to benzoylecgonine and ecgonine methyl ester by carboxylesterases, and there is a large body of literature describing this interaction as it relates to the abuse of cocaine. In this study, we describe the effect of intravenous ethanol on the pharmacokinetics of cocaine after intravenous and oral administration in the dog. The intent is to determine the effect ethanol has on metabolic hydrolysis using cocaine metabolism as a surrogate marker of carboxylesterase activity. Five dogs were administered intravenous cocaine alone, intravenous cocaine after ethanol, oral cocaine alone, and oral cocaine after ethanol on separate study days. Cocaine, benzoylecgonine, and cocaethylene concentrations were determined by high-performance liquid chromatography. Cocaine had poor systemic bioavailability with an area under the plasma concentration-time curve that was approximately 4-fold higher after intravenous than after oral administration. The coadministration of ethanol and cocaine resulted in a 23% decrease in the clearance of intravenous cocaine and a 300% increase in the bioavailability of oral cocaine. Cocaine behaves as a high extraction drug, which undergoes first-pass metabolism in the intestines and liver that is profoundly inhibited by ethanol. We infer from these results that ethanol could inhibit the hydrolysis of other drug compounds subject to hydrolysis by carboxylesterases. Indeed, there are numerous commonly prescribed drugs with significant carboxylesterase-mediated metabolism such as enalapril, lovastatin, irinotecan, clopidogrel, prasugrel, methylphenidate, meperidine, and oseltamivir that may interact with ethanol. The clinical significance of the interaction of ethanol with specific drugs subject to carboxylesterase hydrolysis is not well recognized and has not been adequately studied.