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

Cytochrome P450 2J2 is required for the natural compound austocystin D to elicit cancer cell toxicity

Austocystin D is a natural compound that induces cytochrome P450 (CYP) monooxygenase-dependent DNA damage and growth inhibition in certain cancer cell lines. Cancer cells exhibiting higher sensitivity to austocystin D often display elevated CYP2J2 expression. However, the essentiality and the role of CYP2J2 for the cytotoxicity of this compound remain unclear. In this study, we demonstrate that CYP2J2 depletion alleviates austocystin D sensitivity and DNA damage induction, while CYP2J2 overexpression enhances them. Moreover, the investigation into genes involved in austocystin D cytotoxicity identified POR and PGRMC1, positive regulators for CYP activity, and KAT7, a histone acetyltransferase. Through genetic manipulation and analysis of multiomics data, we elucidated a role for KAT7 in CYP2J2 transcriptional regulation. These findings strongly suggest that CYP2J2 is crucial for austocystin D metabolism and its subsequent cytotoxic effects. The potential use of austocystin D as a therapeutic prodrug is underscored, particularly in cancers where elevated CYP2J2 expression serves as a biomarker.

CYP2C19 and CYP2J2 genotypes predict praziquantel plasma exposure among Ethiopian school-aged children

Metabolism of praziquantel (PZQ), a racemic mixture and the only drug approved to treat S. mansoni infection, is mediated by genetically polymorphic enzymes. Periodic school-based mass drug administration (MDA) with PZQ is the core intervention to control schistosomiasis. However data on the impact of pharmacogenetic variation, nutrition, and infection status on plasma PZQ exposure is scarce. We investigated genetic and non-genetic factors influencing PZQ plasma concentration and its metabolic ratios (trans-4-OH-PZQ/PZQ and cis-4-OH-PZQ/PZQ). Four hundred forty-six school children aged 7-15 years from four primary schools in southern Ethiopia who received albendazole and PZQ preventive chemotherapy through MDA campaign were enrolled. Genotyping for common functional variants of CYP3A4 (*1B), CYP3A5 (*3, *6), CYP2C19 (*2, *3, *17), CYP2C9 (*2, *3), and CYP2J2*7 was performed. Plasma concentrations of PZQ, trans-4-OH-PZQ, and cis-4-OH-PZQ were quantified using UPLCMS/MS. Carriers of CYP2C19 defective variant alleles (*2 and *3) had significantly higher mean PZQ plasma concentration than CYP2C19*1/*1 or *17 carriers (p = 0.005). CYP2C19*1/*1 and CYP2C19*17 carriers had higher trans-4-OH-PZQ/PZQ and cis-4-OH-PZQ/PZQ metabolic ratios compared with CYP2C19*2 or *3 carriers (p < 0.001). CYP2J2*7 carriers had lower mean PZQ plasma concentration (p = 0.05) and higher trans-4-OH-PZQ/PZQ and cis-4-OH-PZQ/PZQ metabolic ratios. Male participants had significantly higher PZQ concentration (p = 0.006) and lower metabolic ratios (p = 0.001) than females. There was no significant effect of stunting, wasting, S. mansoni or soil-transmitted helminth infections, CYP3A4, CYP3A5, or CYP2C9 genotypes on plasma PZQ or its metabolic ratios. In conclusion, sex, CYP2C19 and CYP2J2 genotypes significantly predict PZQ plasma exposure among Ethiopian children. The impact of CYP2C19 and CYP2J2 genotypes on praziquantel treatment outcomes requires further investigation.

Investigating the association between CYP2J2 inhibitors and QT prolongation: a literature review

Drug withdrawal post-marketing due to cardiotoxicity is a major concern for drug developers, regulatory agencies, and patients. One common mechanism of cardiotoxicity is through inhibition of cardiac ion channels, leading to prolongation of the QT interval and sometimes fatal arrythmias. Recently, oxylipin signaling compounds have been shown to bind to and alter ion channel function, and disruption in their cardiac levels may contribute to QT prolongation. Cytochrome P450 2J2 (CYP2J2) is the predominant CYP isoform expressed in cardiomyocytes, where it oxidizes arachidonic acid to cardioprotective epoxyeicosatrienoic acids (EETs). In addition to roles in vasodilation and angiogenesis, EETs bind to and activate various ion channels. CYP2J2 inhibition can lower EET levels and decrease their ability to preserve cardiac rhythm. In this review, we investigated the ability of known CYP inhibitors to cause QT prolongation using Certara's Drug Interaction Database. We discovered that among the multiple CYP isozymes, CYP2J2 inhibitors were more likely to also be QT-prolonging drugs (by approximately 2-fold). We explored potential binding interactions between these inhibitors and CYP2J2 using molecular docking and identified four amino acid residues (Phe61, Ala223, Asn231, and Leu402) predicted to interact with QT-prolonging drugs. The four residues are located near the opening of egress channel 2, highlighting the potential importance of this channel in CYP2J2 binding and inhibition. These findings suggest that if a drug inhibits CYP2J2 and interacts with one of these four residues, then it may have a higher risk of QT prolongation and more preclinical studies are warranted to assess cardiovascular safety.

Population pharmacokinetics of ivermectin after mass drug administration in lymphatic filariasis endemic communities of Tanzania

Ivermectin (IVM) is a drug of choice used with albendazole for mass drug administration (MDA) to halt transmission of lymphatic filariasis. We investigated IVM pharmacokinetic (PK) variability for its dose optimization during MDA. PK samples were collected at 0, 2, 4, and 6 h from individuals weighing greater than 15 kg (n = 468) receiving IVM (3-, 6-, 9-, or 12 mg) and ALB (400 mg) during an MDA campaign in Tanzania. Individual characteristics, including demographics, laboratory/clinical parameters, and pharmacogenetic variations were assessed. IVM plasma concentrations were quantified by liquid-chromatography tandem mass spectrometry and analyzed using population-(PopPK) modeling. A two-compartment model with transit absorption kinetics, and allometrically scaled oral clearance (CL/F) and central volume (Vc /F) was adapted. Fitting of the model to the data identified 48% higher bioavailability for the 3 mg dose compared to higher doses and identified a subpopulation with 97% higher mean transit time (MTT). The final estimates for CL/F, Vc /F, intercompartment clearance, peripheral volume, MTT, and absorption rate constant for a 70 kg person (on dose other than 3 mg) were 7.7 L/h, 147 L, 20.4 L/h, 207 L, 1.5 h, and 0.71/h, respectively. Monte-Carlo simulations indicated that weight-based dosing provides comparable exposure across weight bands, but height-based dosing with capping IVM dose at 12 mg for individuals with height greater than 160 cm underdoses those weighing greater than 70 kg. Variability in IVM PKs is partly explained by body weight and dose. The established PopPK model can be used for IVM dose optimization. Height-based pole dosing results in varying IVM exposure in different weight bands, hence using weighing scales for IVM dosing during MDA is recommended.

Untargeted metabolomics-assisted comparative cytochrome P450-dependent metabolism of fenbendazole in human and dog liver microsomes

Fenbendazole (FBZ), a benzimidazole carbamate anthelmintic, has attracted attention for its antitumor activity. This study examined the metabolic characteristics of FBZ in humans compared with those in dogs. The phase I metabolites were identified in liver microsomal incubates using liquid chromatography-mass spectrometry (MS)-based untargeted metabolomics approaches. Seven metabolites of FBZ were identified by principal component analysis and orthogonal partial least square-discriminant analysis based on the global ion variables of the FBZ incubation groups. The chemical structure of the FBZ metabolites was suggested by examining the MS/MS spectrum and isotope distribution pattern. Cytochrome P450 (CYP) 1A1, CYP2D6, and CYP2J2 were the major isozymes responsible for the FBZ metabolism. No differences in the types of metabolites produced by the two species were noted. Multivariate analysis of human and dog incubation groups showed that five metabolites were relatively abundant in humans and the other two were not. In summary, the phase I metabolic profile of FBZ and the comparative metabolism between humans and dogs were examined using an untargeted metabolomics approach. This study suggests a successful investigation of FBZ metabolism in humans for conducting safety assessments regarding drug repositioning.

Cardiomyocyte-specific CYP2J2 and its therapeutic implications

INTRODUCTION

Cytochrome P450s (CYPs) are a superfamily of monooxygenases with diverse biological roles. CYP2J2 is an isozyme highly expressed in the heart where it metabolizes endogenous substrates such as N-3/N-6 polyunsaturated fatty acids (PUFA) to produce lipid mediators involved in homeostasis and cardioprotective responses. Expanding our knowledge of the role CYP2J2 has within the heart is important for understanding its impact on cardiac health and disease.

AREAS COVERED

The objective of this review was to assess the state of knowledge regarding cardiac CYP2J2. A literature search was conducted using PubMed-MEDLINE (from 2022 and earlier) to evaluate relevant studies regarding CYP2J2 mediated cardioprotection, small molecule modulators, effects of CYP2J2 substrates toward biologically relevant effects and implications of CYP2J2 polymorphisms and sexual dimorphism in the heart.

EXPERT OPINION

Cardiac CYP2J2-mediated metabolism of endogenous and exogenous substrates have been shown to impact cardiac function. Identifying individual factors, like sex and age, that affect CYP2J2 require further elucidation to better understand CYP2J2's clinical relevance. Resolving the biological targets and activities of CYP2J2-derived PUFA metabolites will be necessary to safely target CYP2J2 and design novel analogues. Targeting CYP2J2 for therapeutic aims offers a potential novel approach to regulating cardiac homeostasis, drug metabolism and cardioprotection.

Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions

This is an overview of the metabolic reactions of drugs, natural products, physiological compounds, and other (general) chemicals catalyzed by flavin monooxygenase (FMO), monoamine oxidase (MAO), NAD(P)H quinone oxidoreductase (NQO), and molybdenum hydroxylase enzymes (aldehyde oxidase (AOX) and xanthine oxidoreductase (XOR)), including roles as substrates, inducers, and inhibitors of the enzymes. The metabolism and bioactivation of selected examples of each group (i.e., drugs, “general chemicals,” natural products, and physiological compounds) are discussed. We identified a higher fraction of bioactivation reactions for FMO enzymes compared to other enzymes, predominately involving drugs and general chemicals. With MAO enzymes, physiological compounds predominate as substrates, and some products lead to unwanted side effects or illness. AOX and XOR enzymes are molybdenum hydroxylases that catalyze the oxidation of various heteroaromatic rings and aldehydes and the reduction of a number of different functional groups. While neither of these two enzymes contributes substantially to the metabolism of currently marketed drugs, AOX has become a frequently encountered route of metabolism among drug discovery programs in the past 10–15 years. XOR has even less of a role in the metabolism of clinical drugs and preclinical drug candidates than AOX, likely due to narrower substrate specificity.

Atypical kinetics of cytochrome P450 2J2: Epoxidation of arachidonic acid and reversible inhibition by xenobiotic inhibitors

Extrahepatic CYP2J2 metabolism of arachidonic acid (AA) to bioactive regioisomeric epoxyeicosatrienoic acids (EETs) is implicated in both physiological and pathological conditions. Here, we aimed to characterize atypical substrate inhibition kinetics of this endogenous metabolic pathway and its reversible inhibition by xenobiotic inhibitors when AA is used as the physiologically-relevant substrate vis-à-vis conventional probe substrate astemizole (AST). As compared to typical Michaelis-Menten kinetics observed for AST, complete substrate inhibition was observed for CYP2J2 metabolism of AA to 14,15-EET whereby velocity of the reaction declined significantly at concentrations of AA above 20-30 µM with an estimated substrate inhibition constant (K_s) of 31 µM. In silico sequential docking of two AA substrates to orthosteric (OBS) and adjacent secondary binding sites (SBS) within a 3-dimensional homology model of CYP2J2 revealed favorable and comparable binding poses of glide-scores -3.1 and -3.8 respectively. Molecular dynamics (MD) simulations ascertained CYP2J2 conformational stability with dual AA substrate binding as time-dependent root mean squared deviation (RMSD) of protein Cα atoms and ligand heavy atoms stabilized to a plateau in all but one trajectory (n=6). The distance between heme-iron and ω6 (C14, C15) double bond of AA in OBS also increased from 7.5 ± 1.4 Å to 8.5 ± 1.8 Å when CYP2J2 was simulated with only AA in OBS versus the presence of AA in both OBS and SBS (p<0.001), supporting the observed in vitro substrate inhibition phenomenon. Poor correlation was observed between inhibitory constants (K_i) determined for a panel of nine competitive and mixed mode xenobiotic inhibitors against CYP2J2 metabolism of AA as compared to AST, whereby 4 out of 9 drugs had a greater than 5-fold difference between K_i values. Nonlinear Eadie-Hofstee plots illustrated that complete substrate inhibition of CYP2J2 by AA was not attenuated even at high concentrations of xenobiotic inhibitors which further corroborates that CYP2J2 may accommodate three or more ligands simultaneously. In light of the atypical kinetics, our results highlight the importance of using physiologically-relevant substrates in in vitro enzymatic inhibition assays for the characterization of xenobiotic-endobiotic interactions which is applicable to other complex endogenous metabolic pathways beyond CYP2J2 metabolism of AA to EETs. The accurate determination of K_i would further facilitate the association of xenobiotic-endobiotic interactions to observed therapeutic or toxic outcomes.

High-Fat Breakfast Increases Bioavailability of Albendazole Compared to Low-Fat Breakfast: Single-Dose Study in Healthy Subjects

Purpose: Albendazole is a benzimidazole carbamate drug with anthelmintic and antiprotozoal activity against intestinal and tissue parasites. It has been described that the administration with meals increases albendazole absorption. Our aim was to compare the systemic exposure in healthy volunteers of two albendazole formulations after a single oral dose under fed conditions and to evaluate the effect of breakfast composition on albendazole and albendazole sulfoxide bioavailability. Methods: 12 healthy volunteers were included in a 4-period, 4-sequence, crossover, open, randomized, bioequivalence clinical trial, including two stages to compare two formulations of albendazole. Single oral doses of 400 mg albendazole were administered under fed conditions (a low-fat breakfast in first stage and a high-fat breakfast in the second) separated by 7-day washout periods. Plasma albendazole and albendazole sulfoxide concentrations were measured by HPLC-MS/MS. Findings: Albendazole absorption was clearly influenced by the meal composition. A high-fat breakfast increased albendazole and albendazole sulfoxide area under the concentration-time curve (AUC) and maximum concentration (Cmax) by double, compared to a low-fat breakfast. The bioavailability of the two formulations was very similar, although the sample size was not sufficient to demonstrate bioequivalence because the intraindividual variability of albendazole was approximately 60%. Implications: The higher albendazole and albendazole sulfoxide levels when administered with a high-fat meal could be of importance in clinical practice. Since albendazole labeling recommends its administration with meals, it is necessary to insist on taking it with a fatty meal so that the effectiveness of albendazole is not compromised.

Molecular determinant of substrate binding and specificity of cytochrome P450 2J2

Cytochrome P450 2J2 (CYP2J2) is responsible for the epoxidation of endogenous arachidonic acid, and is involved in the metabolism of exogenous drugs. To date, no crystal structure of CYP2J2 is available, and the proposed structural basis for the substrate recognition and specificity in CYP2J2 varies with the structural models developed using different computational protocols. In this study, we developed a new structural model of CYP2J2, and explored its sensitivity to substrate binding by molecular dynamics simulations of the interactions with chemically similar fluorescent probes. Our results showed that the induced-fit binding of these probes led to the preferred active poses ready for the catalysis by CYP2J2. Divergent conformational dynamics of CYP2J2 due to the binding of each probe were observed. However, a stable hydrophobic clamp composed of residues I127, F310, A311, V380, and I487 was identified to restrict any substrate access to the active site of CYP2J2. Molecular docking of a series of compounds including amiodarone, astemizole, danazol, ebastine, ketoconazole, terfenadine, terfenadone, and arachidonic acid to CYP2J2 confirmed the role of those residues in determining substrate binding and specificity of CYP2J2. In addition to the flexibility of CYP2J2, the present work also identified other factors such as electrostatic potential in the vicinity of the active site, and substrate strain energy and property that have implications for the interpretation of CYP2J2 metabolism.

6,8-Diprenylorobol Induces Apoptosis in Human Hepatocellular Carcinoma Cells via Activation of FOXO3 and Inhibition of CYP2J2

6,8-Diprenylorobol is a phytochemical derived from the roots of Glycyrrhiza uralensis Fisch. 6,8-Diprenylorobol exhibits several biological activities, but the effects of 6,8-diprenylorobol on cancers have been hardly investigated. This study is aimed at elucidating the anticancer effect and working mechanism of 6,8-diprenylorobol in HepG2 and Huh-7, two kinds of human hepatocellular carcinoma (HCC) cell lines. WST-1, cell counting, and colony formation assays and morphological change analysis showed that 6,8-diprenylorobol treatment decreased the cell viability and proliferation rate. Cell cycle analysis indicated that 6,8-diprenylorobol treatment increased the population of the G1/0 stage. Annexin V/PI double staining and TUNEL analysis showed that 6,8-diprenylorobol treatment increased the apoptotic cell population and DNA fragmentation. Western blot analysis showed that 6,8-diprenylorobol treatment increased the expression of cleaved PARP1, cleaved caspase-3, FOXO3, Bax, Bim, p21, and p27 but decreased the expression of Bcl2 and BclXL. Interestingly, 6,8-diprenylorobol inhibited CYP2J2-mediated astemizole O-demethylation and ebastine hydroxylase activities with K_i values of 9.46 and 2.61 μM, respectively. CYP2J2 siRNA transfection enhanced the anticancer effect of 6,8-diprenylorobol in HepG2 and Huh-7 cells through the downregulation of CYP2J2 protein expression and upregulation of FOXO3. Taken together, this study proposes that 6,8-diprenylorobol treatment may be a useful therapeutic option against HCC by targeting CYP2J2 and FOXO3.

CYP2J2 Molecular Recognition: A New Axis for Therapeutic Design

Cytochrome P450 (CYP) epoxygenases are a special subset of heme-containing CYP enzymes capable of performing the epoxidation of polyunsaturated fatty acids (PUFA) and the metabolism of xenobiotics. This dual functionality positions epoxygenases along a metabolic crossroad. Therefore, structure-function studies are critical for understanding their role in bioactive oxy-lipid synthesis, drug-PUFA interactions, and for designing therapeutics that directly target the epoxygenases. To better exploit CYP epoxygenases as therapeutic targets, there is a need for improved understanding of epoxygenase structure-function. Of the characterized epoxygenases, human CYP2J2 stands out as a potential target because of its role in cardiovascular physiology. In this review, the early research on the discovery and activity of epoxygenases is contextualized to more recent advances in CYP epoxygenase enzymology with respect to PUFA and drug metabolism. Additionally, this review employs CYP2J2 epoxygenase as a model system to highlight both the seminal works and recent advances in epoxygenase enzymology. Herein we cover CYP2J2's interactions with PUFAs and xenobiotics, its tissue-specific physiological roles in diseased states, and its structural features that enable epoxygenase function. Additionally, the enumeration of research on CYP2J2 identifies the future needs for the molecular characterization of CYP2J2 to enable a new axis of therapeutic design.

Pulmonary Metabolism of Substrates for Key Drug-Metabolizing Enzymes by Human Alveolar Type II Cells, Human and Rat Lung Microsomes, and the Isolated Perfused Rat Lung Model

Significant pulmonary metabolism of inhaled drugs could have drug safety implications or influence pharmacological effectiveness. To study this in vitro, lung microsomes or S9 are often employed. Here, we have determined if rat and human lung microsomes are fit for purpose or whether it is better to use specific cells where drug-metabolizing enzymes are concentrated, such as alveolar type II (ATII) cells. Activities for major hepatic and pulmonary human drug-metabolizing enzymes are assessed and the data contextualized towards an in vivo setting using an ex vivo isolated perfused rat lung model. Very low rates of metabolism are observed in incubations with human ATII cells when compared to isolated hepatocytes and fewer of the substrates are found to be metabolized when compared to human lung microsomal incubations. Reactions selective for flavin-containing monooxygenases (FMOs), CYP1B1, CYP2C9, CYP2J2, and CYP3A4 all show significant rates in human lung microsomal incubations, but all activities are higher when rat lung microsomes are used. The work also demonstrates that a lung microsomal intrinsic clearance value towards the lower limit of detection for this parameter (3 µL/min/mg protein) results in a very low level of pulmonary metabolic clearance during the absorption period, for a drug dosed into the lung in vivo.

Fenbendazole induces apoptosis of porcine uterine luminal epithelial and trophoblast cells during early pregnancy

Fenbendazole, is an effective benzimidazole anthelmintic that prevents parasite infection in both human and veterinary health care. Although the well-known and effect of benzimidazole was recently shown to have a broad spectrum of biological abilities, such as anticancer and anti-inflammation activities, the mechanism of benzimidazole's antiproliferative effect via cell signaling pathways and its role in preimplantation has not been studied. Therefore, the purpose of this study was to determine the effects of fenbendazole on porcine trophectoderm and luminal epithelial cells. First, we investigated cell viability in response to a low dose of fenbendazole, which highly inhibited cell proliferation. In addition, we investigated apoptotic molecules in the mitochondria, imbalanced intracellular calcium homeostasis, and the expression of some genes involved in apoptosis to explain the decrease in proliferation. Finally, we examined the intracellular mechanisms of fenbendazole by measuring the extracellular signal-regulated kinase, PI3K/AKT, and c-Jun N-terminal kinase signaling proteins by western blot analysis. Our findings suggest that fenbendazole functions as an effective anti-proliferative molecule that induces critical apoptosis in the porcine trophectoderm and uterine luminal epithelial cells by disrupting the mitochondria membrane potential during early pregnancy.

Screening of ten cytochrome P450 enzyme activities with 12 probe substrates in human liver microsomes using cocktail incubation and liquid chromatography-tandem mass spectrometry

Testing for potential drug interactions of new chemical entities is essential when developing a novel drug. In this study, an assay was designed to evaluate drug interactions with 10 major human cytochrome P450 (P450) enzymes incubated in liver microsomes, involving 12 probe substrates with two cocktail incubation sets used in a single liquid chromatography-tandem mass spectrometry (LC-MS/MS) run. The P450 substrate composition in each cocktail set was optimized to minimize solvent effects and mutual drug interactions among substrates as follows: cocktail A was composed of phenacetin for CYP1A2, bupropion for CYP2B6, amodiaquine for CYP2C8, diclofenac for CYP2C9, S-mephenytoin for CYP2C19, and dextromethorphan for CYP2D6; cocktail B was composed of coumarin for CYP2A6, chlorzoxazone for CYP2E1, astemizole for CYP2J2, and midazolam, nifedipine, and testosterone for CYP3A. Multiple probe substrates were used for CYP3A owing to the multiple substrate-binding sites and substrate-dependent inhibition. After incubation in human liver microsomes, each incubation mixture was pooled and all probe metabolites were simultaneously analysed in a single LC-MS/MS run. Polarity switching was used to acquire the negative-ion mode for hydroxychlorzoxazone and positive-ion mode for the remaining analytes. The method was validated by comparing the inhibition data obtained from incubation of each individual probe substrate alone and with the substrate cocktails. The half-maximal inhibitory concentration values obtained from the cocktail and individual incubations were well correlated and in agreement with previously reported values. This new method will be useful in assessing the drug interaction potential of new chemical entities during new drug development.

Modulations of bovine hepatic microsomal metabolism of benzimidazoles by secondary plant metabolites

The study was aimed to estimate the effect of plant secondary metabolites present in ruminants diet and phytogenic feed additives on liver microsomal metabolism of albendazole and fenbendazole. The selected phytocompounds comprised of flavonoids (apigenin, quercetin) and saponins (hederagenin, medicagenic acid). The experiments were performed on liver microsomal fraction obtained from routinely slaughtered cows. The intensity of albendazole and fenbendazole metabolism in the presence of flavonoids and saponins was analyzed in equimolar concentration (100 μM). The obtained results revealed that both flavonoids and saponins intensify the metabolism of albendazole and fenbendazole in bovine microsomes. In the case of albendazole, apigenin and quercetin doubled the amount of degraded drug and the amount of produced albendazole sulfoxide. Additionally, both flavonoids increased the amount of produced albendazole sulfone. Saponins, hederagenin, and medicagenic acid intensified the degradation of albendazole (1.8-fold) and the production of albendazole sulfoxide (twofold). Medicagenic acid inhibited the production of albendazole sulfone. In the case of fenbendazole, the degradation of the drug and the production of oxfendazole were increased four and five times in the presence of saponins and flavonoids, respectively. The enhancement of benzimidazoles' metabolism caused by the studied plant metabolites could change pharmacokinetics and the efficacy of benzimidazoles' treatment in cattle.

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

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.

Progress in the pharmacological treatment of human cystic and alveolar echinococcosis: Compounds and therapeutic targets

Human cystic and alveolar echinococcosis are helmintic zoonotic diseases caused by infections with the larval stages of the cestode parasites Echinococcus granulosus and E. multilocularis, respectively. Both diseases are progressive and chronic, and often fatal if left unattended for E. multilocularis. As a treatment approach, chemotherapy against these orphan and neglected diseases has been available for more than 40 years. However, drug options were limited to the benzimidazoles albendazole and mebendazole, the only chemical compounds currently licensed for treatment in humans. To compensate this therapeutic shortfall, new treatment alternatives are urgently needed, including the identification, development, and assessment of novel compound classes and drug targets. Here is presented a thorough overview of the range of compounds that have been tested against E. granulosus and E. multilocularis in recent years, including in vitro and in vivo data on their mode of action, dosage, administration regimen, therapeutic outcomes, and associated clinical symptoms. Drugs covered included albendazole, mebendazole, and other members of the benzimidazole family and their derivatives, including improved formulations and combined therapies with other biocidal agents. Chemically synthetized molecules previously known to be effective against other infectious and non-infectious conditions such as anti-virals, antibiotics, anti-parasites, anti-mycotics, and anti-neoplastics are addressed. In view of their increasing relevance, natural occurring compounds derived from plant and fungal extracts are also discussed. Special attention has been paid to the recent application of genomic science on drug discovery and clinical medicine, particularly through the identification of small inhibitor molecules tackling key metabolic enzymes or signalling pathways.

Human cystic and alveolar echinococcosis (CE and AE), caused by the larval stages of the helminths Echinococcus granulosus and E. multilocularis, respectively, are progressive and chronic diseases affecting more than 1 million people worldwide. Both are considered orphan and neglected diseases by the World Health Organization. As a treatment approach, chemotherapy is limited to the use of benzimidazoles, drugs that stop parasite growth but do not kill the parasite. To compensate this therapeutic shortfall, new treatment alternatives are urgently needed. Here, we present the state-of-the-art regarding the alternative compounds and new formulations of benzimidazoles assayed against these diseases until now. Some of these new and modified compounds, either alone or in combination, could represent a step forward in the treatment of CE and AE. Unfortunately, few compounds have reached clinical trials stage in humans and, when assayed, the design of these studies has not allowed evidence-based conclusions. Thus, there is still an urgent need for defining new compounds or improved formulations of those already assayed, and also for a careful design of clinical protocols that could lead to the draw of a broad international consensus on the use of a defined drug, or a combination of drugs, for the effective treatment of CE and AE.

Formation of Both Heme and Apoprotein Adducts Contributes to the Mechanism-Based Inactivation of Human CYP2J2 by 17α-Ethynylestradiol

17α-Ethynylestradiol (EE), a major component of many oral contraceptives, affects the activities of a number of the human cytochrome P450 (P450) enzymes. Here, we characterized the effect of EE on CYP2J2, a major human P450 isoform that participates in metabolism of arachidonic acid. EE inactivated the hydroxyebastine carboxylation activity of CYP2J2 in a reconstituted system. The loss of activity is time and concentration dependent and requires NADPH. The K_I and k_inact values for the inactivation were 3.6 μM and 0.08 minute^-1, respectively. Inactivation of CYP2J2 by EE was due to formation of a heme adduct as well as an apoprotein adduct. Mass spectral analysis of CYP2J2 partially inactivated by EE showed two distinct protein masses in the deconvoluted spectrum that exhibited a mass difference of approximately 312 Da, which is equivalent to the sum of the mass of EE and one oxygen atom. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed a heme adduct with MH⁺ ion at m/z 875.5, corresponding to alkylation of an iron-depleted prosthetic heme by EE plus one oxygen atom. The reactive intermediate responsible for covalently modifying both the prosthetic heme and apoprotein was characterized by trapping with glutathione (GSH). LC-MS/MS analysis revealed two GSH conjugate isomers with MH⁺ ions at m/z 620, which were formed by reaction between GSH and EE with the oxygen being added to either the internal or terminal carbon of the ethynyl moiety. High-pressure liquid chromatography analysis revealed that three other major metabolites were formed during EE metabolism by CYP2J2.

Acetylshikonin is a novel non-selective cytochrome P450 inhibitor

Acetylshikonin is a biologically active compound with anti-cancer and anti-inflammatory activity, which is isolated from the roots of Lithospermum erythrorhizoma. An inhibitory effect of acetylshikonin against CYP2J2 activity was discovered recently. Based on this result, this study was expanded to evaluate the inhibitory effects of acetylshikonin against nine different cytochrome P450 (P450) isoforms in human liver microsomes (HLMs) using substrate cocktails incubation assay. Acetylshikonin showed a strong inhibitory effect against all P450s tested with IC₅₀ values of 1.4-4.0 μ m. Pre-incubation of acetylshikonin with HLMs and NADPH did not alter the inhibition potency, indicating that acetylshikonin is not a mechanism-based inhibitor. SKF-525A, a widely used non-specific P450 inhibitor, had no inhibitory activity against CYP1A2, 2A6, 2E1 and 2J2, while it showed an inhibitory effect against CYP2B6, CYP2C19 and 2D6 with IC₅₀ values of 2.5, 3.6 and 0.5 μ m, respectively. Our findings indicate that acetylshikonin may be a novel general P450 inhibitor, which could replace SKF-525A.

Heme Modification Contributes to the Mechanism-Based Inactivation of Human Cytochrome P450 2J2 by Two Terminal Acetylenic Compounds

The mechanism-based inactivation of human CYP2J2 by three terminal acetylenic compounds: N-(methylsulfonyl)-6-(2-propargyloxyphenyl)hexanamide (MS), 17-octadecynoic acid (OD), and danazol (DZ) was investigated. The loss of hydroxyebastine (OHEB) carboxylation activity in a reconstituted system was time- and concentration-dependent and required NADPH for MS and OD, but not DZ. The kinetic constants for the mechanism-based inactivation of OHEB carboxylation activity were: K_I of 6.1 μM and k_inact of 0.22 min^-1 for MS and K_I of 2.5 μM and k_inact of 0.05 min^-1 for OD. The partition ratios for MS and OD were ∼10 and ∼20, respectively. Inactivation of CYP2J2 by MS or OD resulted in a loss of the native heme spectrum and a similar decrease in the reduced CO difference spectrum. A heme adduct was observed in the MS-inactivated CYP2J2. The possible reactive metabolite which covalently modified the prosthetic heme was characterized by analysis of the glutathione conjugates formed by MS or OD following oxygenation of the ethynyl moiety. Liquid chromatography-mass spectrometry showed that inactivation by MS or OD did not lead to modification of apoprotein. Interaction of CYP2J2 with DZ produced a type II binding spectrum with a K_s of 2.8 μM and the IC₅₀ for loss of OHEB carboxylation activity was 0.18 μM. In conclusion, heme modification by MS and OD was responsible for the mechanism-based inactivation of CYP2J2. The results suggest that the ethynyl moiety of MS and OD faces the heme iron, whereas the isoxazole ring of DZ is preferentially oriented toward the heme iron of CYP2J2.

In vitro and in vivo cysticidal activity of extracts and isolated flavanone from the bark of Prunus serotina: A bio-guided study

Currently, neurocysticercosis treatment involves two drugs: albendazole and praziquantel; however, their efficacy is suboptimal and new cysticidal drugs are needed. The present paper reports the cysticidal activity of extracts of the bark from Prunus serotina against Taenia crassiceps cysts and the isolation and identification of the main components of the most active extract. Results showed that all extracts displayed in vitro cysticidal activity (EC₅₀=17.9-88.5μg/mL), being the methanolic the most active and selective. Also, methanolic extract exhibited in vivo efficacy at 300mg/kg which was similar to that obtained with albendazole. Bio-guided fractionation of methanolic extract led the isolation of 2,3-dihydro-5,7-dihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one (naringenin, NGN), 3,4,5-trimethoxybenzoic acid and 1,3,5-trimethoxybenzene. NGN exhibited in vitro activity, in a time-concentration-dependent manner (EC₅₀=89.3μM]. Furthermore, NGN at a dose of 376.1μmol/kg displayed similar in vivo efficacy than those obtained with albendazole at 188.4μmol/kg. NGN also caused a high level of damage in all parasite tissue in a similar manner than that observed with the methanolic extract. This study represents the first report of the cysticidal properties of the bark of P. serotina. NGN was identified as the main active compound of this specie and other studies are required to explore the potential of this flavanone as cysticidal agent.

LKY-047: First Selective Inhibitor of Cytochrome P450 2J2

Highly selective cytochrome P450 CYP2J2 (CYP2J2) inhibitors suitable for reaction phenotyping are currently not available. (7S)-(+)-(4-Nitro-phenyl)-acrylic acid, 8,8-dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (LKY-047), a decursin derivative, was synthesized, and its inhibitor potencies toward CYP2J2 as well as other cytochrome P450 (P450) enzymes in human liver microsomes (HLM) were evaluated. LKY-047 was demonstrated to be a strong competitive inhibitor of CYP2J2-mediated astemizole O-demethylase and terfenadine hydroxylase activity, with K_i values of 0.96 and 2.61 μM, respectively. It also acted as an uncompetitive inhibitor of CYP2J2-mediated ebastine hydroxylation with a K_i value of 3.61 μM. Preincubation of LKY-047 with HLMs and NADPH did not alter inhibition potency, indicating that it is not a mechanism-based inhibitor. LKY-047 was found to be a selective CYP2J2 inhibitor with no inhibitory effect on other human P450s, such as CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A (IC₅₀ > 50 μM). These in vitro data support the use of LKY-047 as a selective CYP2J2 inhibitor with potential application in the identification of P450 isoforms responsible for drug metabolism in reaction phenotyping assays.

Inhibition and inactivation of human CYP2J2: Implications in cardiac pathophysiology and opportunities in cancer therapy

Extrahepatic cytochrome P450 enzymes (CYP450) are pivotal in the metabolism of endogenous substrates and xenobiotics. CYP2J2 is a major cardiac CYP450 and primarily metabolizes polyunsaturated fatty acids such as arachidonic acid to cardioactive epoxyeicosatrienoic acids. Due to its role in endobiotic metabolism, CYP2J2 has been actively studied in recent years with the focus on its biological functions in cardiac pathophysiology. Additionally, CYP2J2 metabolizes a number of xenobiotics such as astemizole and terfenadine and is potently inhibited by danazol and telmisartan. Notably, CYP2J2 is found to be upregulated in multiple cancers. Hence a number of specific CYP2J2 inhibitors have been developed and their efficacy in inhibiting tumor progression has been actively studied. CYP2J2 inhibitor such as C26 (1-[4-(vinyl)phenyl]-4-[4-(diphenyl-hydroxymethyl)-piperidinyl]-butanone hydrochloride) caused marked reduction in tumor proliferation and migration as well as promoted apoptosis in cancer cells. In this review, we discuss the role of CYP2J2 in cardiac pathophysiology and cancer therapeutics. Additionally, we provide an update on the substrates, reversible inhibitors and irreversible inhibitors of CYP2J2. Finally, we discuss the current gaps and future directions in CYP2J2 research.

Identification of acetylshikonin as the novel CYP2J2 inhibitor with anti-cancer activity in HepG2 cells

BACKGROUND

Acetylshikonin is one of the biologically active compounds derived from the root of Lithospermum erythrorhizon, a medicinal plant with anti-cancer and anti-inflammation activity. Although there have been a few previous reports demonstrating that acetylshikonin exerts anti-cancer activity in vitro and in vivo, it is still not clear what is the exact molecular target protein of acetylshikonin in cancer cells.

PURPOSE

The purpose of this study is to evaluate the inhibitory effect of acetylshikonin against CYP2J2 enzyme which is predominantly expressed in human tumor tissues and carcinoma cell lines.

STUDY DESIGN

The inhibitory effect of acetylshikonin on the activities of CYP2J2-mediated metabolism were investigated using human liver microsomes (HLMs), and its cytotoxicity against human hepatoma HepG2 cells was also evaluated.

METHOD

Astemizole, a representative CYP2J2 probe substrate, was incubated in HLMs in the presence or absence of acetylshikonin. After incubation, the samples were analyzed by liquid chromatography and triple quadrupole mass spectrometry. The anti-cancer activity of acetylshikonin was evaluated on human hepatocellular carcinoma HepG2 cells. WST-1, cell counting, and colony formation assays were further adopted for the estimation of the growth rate of HepG2 cells treated with acetylshikonin.

RESULTS

Acetylshikonin inhibited CYP2J2-mediated astemizole O-demethylation activity (K_i = 2.1µM) in a noncompetitive manner. The noncompetitive inhibitory effect of acetylshikonin on CYP2J2 enzyme was also demonstrated using this 3D structure, which showed different binding location of astemizole and acetylshikonin in CYP2J2 model. It showed cytotoxic effects against human hepatoma HepG2 cells (IC₅₀ = 2μM). In addition, acetylshikonin treatment inhibited growth of human hepatocellular carcinoma HepG2 cells leading to apoptosis accompanied with p53, bax, and caspase3 activation as well as bcl2 down-regulation.

CONCLUSION

Taken together, our present study elucidates acetylshikonin displays the inhibitory effects against CYP2J2 in HLMs and anti-cancer activity in human hepatocellular carcinoma HepG2 cells.

Resolution of a disputed albendazole result in the UK Official Control System - time for more guidance?

Albendazole, one of the benzimidazole anthelmintics, is used in ruminants and has maximum residue limits in muscle, fat and other tissue owing to reported teratogenicity. Albendazole is extensively metabolised in domestic animals and humans with rapid conversion to a sulphoxide and subsequently sulphone and amino sulphone metabolites. Sulphoxide metabolites are responsible for the systemic biological activity of benzimidazole drugs. Herein we report a case of disputed results for albendazole in a consignment sampled at import in which the Official Analyst certified against the consignment for excess albendazole. A laboratory acting for the importer reported data below the MRL, including a finding of the parent drug which is not included in the residue definition. The Government Chemist has a statutory duty as a route of technical appeal in the UK Official Food Control system and the case was referred for referee analysis. We report our findings based on a LC-MS/MS method, which confirmed the official findings, did not reveal the presence of the parent drug but identified hot spots of albendazole marker residues in the consignment. We discuss the need for recommendations on official sampling at import and interpretation of results.