Phostine PST3.1a Targets MGAT5 and Inhibits Glioblastoma-Initiating Cell Invasiveness and Proliferation.

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor and accounts for a significant proportion of all primary brain tumors. Median survival after treatment is around 15 months. Remodeling of N-glycans by the N-acetylglucosamine glycosyltransferase (MGAT5) regulates tumoral development. Here, perturbation of MGAT5 enzymatic activity by the small-molecule inhibitor 3-hydroxy-4,5-bis-benzyloxy-6-benzyloxymethyl-2-phenyl2-oxo-2λ5-[1,2]oxaphosphinane (PST3.1a) restrains GBM growth. In cell-based assays, it is demonstrated that PST3.1a alters the ß1,6-GlcNAc N-glycans of GBM-initiating cells (GIC) by inhibiting MGAT5 enzymatic activity, resulting in the inhibition of TGFßR and FAK signaling associated with doublecortin (DCX) upregulation and increase oligodendrocyte lineage transcription factor 2 (OLIG2) expression. PST3.1a thus affects microtubule and microfilament integrity of GBM stem cells, leading to the inhibition of GIC proliferation, migration, invasiveness, and clonogenic capacities. Orthotopic graft models of GIC revealed that PST3.1a treatment leads to a drastic reduction of invasive and proliferative capacity and to an increase in overall survival relative to standard temozolomide therapy. Finally, bioinformatics analyses exposed that PST3.1a cytotoxic activity is positively correlated with the expression of genes of the epithelial-mesenchymal transition (EMT), while the expression of mitochondrial genes correlated negatively with cell sensitivity to the compound. These data demonstrate the relevance of targeting MGAT5, with a novel anti-invasive chemotherapy, to limit glioblastoma stem cell invasion. Mol Cancer Res; 15(10); 1376-87. ©2017 AACR.

Evidencing 98 secondary metabolites of Penicillium verrucosum using substrate isotopic labeling and high-resolution mass spectrometry.

Industrial applications of fungal compounds, coupled with the emergence of fungal threats to natural ecosystems and public health, have increased interest in filamentous fungi. Among all pathogenic fungi, Penicillium verrucosum is one of the most common mold-infecting stored cereals in temperate regions. However, it is estimated that 80% of fungal secondary metabolites remain unknown. To detect new P. verrucosum compounds, an untargeted metabolomic approach was applied to fungus grown on wheat grains labeled with stable isotopes: (i) natural grains (99% 12C); (ii) grains enriched with 97% of 13C; and (iii) grains enriched with 53% of 13C and 97% of 15N. Analyses performed by high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS) enabled the specific detection of fungal metabolites, and the unambiguous characterization of their chemical formulas. In this way, 98 secondary metabolites were detected and their chemical formulas were determined. Of these, only 18 identifications could be made based on databases, the literature and mass spectrometry fragmentation experiments, with the result that 80 were totally unknown. Molecular networks were generated to analyze these results, leading to the characterization by MSn experiments of a new fungisporin produced by P. verrucosum. More generally, this article provides precise mass spectrometric data about all these compounds for further studies of the Penicillium metabolome.

Lactococcus lactis is an Efficient Expression System for Mammalian Membrane Proteins Involved in Liver Detoxification, CYP3A4, and MGST1.

Despite the great importance of human membrane proteins involved in detoxification mechanisms, their wide use for biochemical approaches is still hampered by several technical difficulties considering eukaryotic protein expression in order to obtain the large amounts of protein required for functional and/or structural studies. Lactococcus lactis has emerged recently as an alternative heterologous expression system to Escherichia coli for proteins that are difficult to express. The aim of this work was to check its ability to express mammalian membrane proteins involved in liver detoxification, i.e., CYP3A4 and two isoforms of MGST1 (rat and human). Genes were cloned using two different strategies, i.e., classical or Gateway-compatible cloning, and we checked the possible influence of two affinity tags (6×-His-tag and Strep-tag II). Interestingly, all proteins could be successfully expressed in L. lactis at higher yields than those previously obtained for these proteins with classical expression systems (E. coli, Saccharomyces cerevisiae) or those of other eukaryotic membrane proteins expressed in L. lactis. In addition, rMGST1 was fairly active after expression in L. lactis. This study highlights L. lactis as an attractive system for efficient expression of mammalian detoxification membrane proteins at levels compatible with further functional and structural studies.

Safety and pharmacokinetics of the CIME combination of drugs and their metabolites after a single oral dosing in healthy volunteers.

This phase I, pilot clinical study was designed to evaluate the safety and the pharmacokinetic (PK) profiles of the CIME (Metabolic Identity Card) combination of ten drugs, with a view to its use as a phenotyping cocktail. Ten healthy Caucasian subjects were orally dosed with the CIME combination (caffeine-CYP1A2, repaglinide-CYP2C8, tolbutamide-CYP2C9, omeprazole-CYP2C19, dextromethorphan-CYP2D6, midazolam-CYP3A, acetaminophen-UGT1A1, 6&9 and 2B15, digoxin-P-gp, rosuvastatin-OATP1B1&3 and memantine-active renal transport). Blood was collected over 3 days and on day 7. CIME probes and relevant metabolites were assayed by LC-MS/MS and PK parameters were calculated. Main results were: (1) good safety with reversible mild or moderate adverse effects, (2) an analytical method able to quantify simultaneously the 10 probes and the major metabolites, (3) calculation of PK parameters for all probes in general agreed with published values, and (4) identification of the low CYP2D6 metabolizer. This pilot study showed that the CIME combination was well tolerated and that its pharmacokinetics could be accurately measured in healthy volunteers. This combination can now confidently be checked for sensitivity and specificity and for lack of interaction to be validated as a phenotyping cocktail.

Design optimisation for pharmacokinetic modeling of a cocktail of phenotyping drugs.

Our paper proposes a methodological strategy to select optimal sampling designs for phenotyping studies including a cocktail of drugs. A cocktail approach is of high interest to determine the simultaneous activity of enzymes responsible for drug metabolism and pharmacokinetics, therefore useful in anticipating drug-drug interactions and in personalized medicine. Phenotyping indexes, which are area under the concentration-time curves, can be derived from a few samples using nonlinear mixed effect models and maximum a posteriori estimation. Because of clinical constraints in phenotyping studies, the number of samples that can be collected in individuals is limited and the sampling times must be as flexible as possible. Therefore to optimize joint design for several drugs (i.e., to determine a compromise between informative times that best characterize each drug's kinetics), we proposed to use a compound optimality criterion based on the expected population Fisher information matrix in nonlinear mixed effect models. This criterion allows weighting different models, which might be useful to take into account the importance accorded to each target in a phenotyping test. We also computed windows around the optimal times based on recursive random sampling and Monte-Carlo simulation while maintaining a reasonable level of efficiency for parameter estimation. We illustrated this strategy for two drugs often included in phenotyping cocktails, midazolam (probe for CYP3A) and digoxin (P-glycoprotein), based on the data of a previous study, and were able to find a sparse and flexible design. The obtained design was evaluated by clinical trial simulations and shown to be efficient for the estimation of population and individual parameters.

Metabolic detoxification pathways for 5-methoxy-sterigmatocystin in primary tracheal epithelial cells.

1. The health effects of inhaled mycotoxins remain poorly documented despite their presence in bioaerosols. 5-methoxy-sterigmatocystin is produced in association with sterigmatocystin by some Aspergillus spp., sometimes in larger amounts than sterigmatocystin. Whereas sterigmatocystin can be metabolized through cytochromes P450 (CYP), UDP-glucuronosyltransferases and sulfotransferases in airway epithelial cells, little is known about 5-methoxy-sterigmatocystin. 2. The 5-methoxy-sterigmatocystin metabolites were analyzed using human recombinant CYP and porcine tracheal epithelial cell (PTEC) primary cultures at an air-liquid interface. The induction of xenobiotic-metabolizing enzymes was examined by real-time quantitative PCR for mRNA expression and 7-ethoxyresorufin O-deethylation activity. 3. CYP1A1 metabolized 5-methoxy-sterigmatocystin into hydroxy-nor-methoxy-sterigmatocystin, nor-methoxy-sterigmatocystin and dihydroxy-methoxy-sterigmatocystin. CYP1A2 led to monohydroxy-methoxy-sterigmatocystin. In PTEC, 5-methoxy-sterigmatocystin metabolism resulted into a glucuroconjugate of 5-methoxy-sterigmatocystin, a sulfoconjugate and a glucuroconjugate of monohydroxy-methoxy-sterigmatocystin. The exposure of PTEC for 24 h to 1 µM 5-methoxy-sterigmatocystin induced a significant increase in the mRNA levels of CYP1A1, without significant induction of the 7-ethoxyresorufin O-deethylation activity. 4. These data suggest that 5-methoxy-sterigmatocystin is mainly detoxified in airway cells through conjugation, as sterigmatocystin. However, while CYP produced a reactive metabolite of sterigmatocystin, no such metabolite was detected with 5-methoxy-sterigmatocystin. Nevertheless, 5-methoxy-sterigmatocystin increases the CYP1A1 mRNA levels. The long-term consequences remain unknown.

New untargeted metabolic profiling combining mass spectrometry and isotopic labeling: application on Aspergillus fumigatus grown on wheat.

Characterization of fungal secondary metabolomes has become a challenge due to the industrial applications of many of these molecules, and also due to the emergence of fungal threats to public health and natural ecosystems. Given that, the aim of the present study was to develop an untargeted method to analyze fungal secondary metabolomes by combining high-accuracy mass spectrometry and double isotopic labeling of fungal metabolomes. The strain NRRL 35693 of Aspergillus fumigatus , an important fungal pathogen, was grown on three wheat grain substrates: (1) naturally enriched grains (99% (12)C), (2) grains enriched 96.8% with (13)C, (3) grains enriched with 53.4% with (13)C and 96.8% with (15)N. Twenty-one secondary metabolites were unambiguously identified by high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS) analysis. AntiBase 2012 was used to confirm the identity of these metabolites. Additionally, on the basis of tandem mass spectrometry (MS(n)) experiments, it was possible to identify for the first time the formula and the structure of fumigaclavine D, a new member of the fumigaclavines family. Post biosynthesis degradation of tryptoquivaline F by methanol was also identified during HPLC-HRMS analysis by the detection of a carbon atom of nonfungal origin. The interest of this method lies not only on the unambiguous determination of the exact chemical formulas of fungal secondary metabolites but also on the easy discrimination of nonfungal products. Validation of the method was thus successfully achieved in this study, and it can now be applied to other fungal metabolomes, offering great possibilities for the discovery of new drugs or toxins.

Acebutolol and alprenolol metabolism predictions: comparative study of electrochemical and cytochrome P450-catalyzed reactions using liquid chromatography coupled to high-resolution mass spectrometry.

A comparative study of the electrochemical conversion and the biotransformation performed by the cytochrome P450 (CYP450) obtained by rat liver microsomes has been achieved to elucidate the oxidation mechanism of both acebutolol and alprenolol. For this purpose, a wide range of reactions such as N-dealkylation, O-dealkoxylation, aromatic hydroxylation, benzyl hydroxylation, alkyl hydroxylation, and aromatic hydroxylation have been examined in this study, and their mechanisms have been compared. Most of the results of the electrochemical oxidation have been found to be in accordance with those obtained by incubating acebutolol and alprenolol in the presence of CYP450, i.e., N-dealkylation, benzyl hydroxylation, and O-dealkoxylation reactions catalyzed by liver microsomes were found to be predicted by the electrochemical oxidation. The difficulty for the electrochemical process to mimic both aromatic and alkyl hydroxylation reactions has also been discussed, and the hypothesis for the absence of aromatic hydroxylated and alkyl hydroxylated products, respectively, for alprenolol and acebutolol, under the anodic oxidation has been supported by theoretical calculation. The present study highlights the potential and limitation of coupling of electrochemistry-liquid chromatography-high-resolution mass spectrometry for the study of phase I and phase II reactions of acebutolol and alprenolol.

Jewelry boxes contaminated by Aspergillus oryzae: an occupational health risk?

In 2009, 100,000 jewelry boxes, manufactured in China, were delivered to a jewelry manufacturer in Besançon, France. All the boxes were contaminated by mold. Because the workers refused to handle these jewelry boxes, the company contacted our laboratory to determine how to deal with the problem. Three choices were available: (1) decontaminate the boxes, (2) return the boxes to the Chinese manufacturer, or (3) destroy the entire shipment. Based on microscopic identification, the culture analysis was positive for A. oryzae. This could not be confirmed by molecular techniques because of the genetic proximity of A. oryzae and A. flavus. Because A. flavus can produce aflatoxins, we tested for them using mass spectrometry. Aflatoxins B1, B2, G1, G2, and M1 were not detected; however, given the specifics of this situation, we could not discard the possibility of the presence of other aflatoxins, such as P1, B3, GM2, and ethoxyaflatoxin B2. We concluded that the contamination by A. oryzae was probably due to food products. However, because of the possible presence of aflatoxins, occupational health risks could not be entirely ruled out. The decision was therefore taken to destroy all the jewelry boxes by incineration. To avoid a similar situation we propose: (1) to maintain conditions limiting mold contamination during production (not eating on the work site, efficient ventilation systems); (2) to desiccate the products before sending them; and (3) to closely control the levels of dampness during storage and transport.

Cytochrome P450-catalyzed degradation of nicotine: fundamental parameters determining hydroxylation by cytochrome P450 2A6 at the 5'-carbon or the n-methyl carbon.

The oxidation of (2'S)-nicotine in the active site of human cytochrome P450 2A6 has been subjected to a detailed analysis by theoretical quantum mechanical/molecular mechanical (QM/MM) calculations linked with a theoretical and experimental study of the associated isotope effects. The study has focused on seeking an explanation as to why oxidation at the 5'-carbon position (A) is favored over oxidation at the methyl carbon (CMe) position (B). It is deduced that the choice of hydrogen for abstraction is not determined by geometric features of the active site, but by the lower energy barrier associated with 5' oxidation. N-Demethylation leading to N-hydroxymethylnornicotine requires ca. 6.5 kcal/mol more energy to transfer a hydrogen atom than is required for oxidation on the carbon 5'. Neither protonation of the pyrrolidine nitrogen (N1') nor inclusion of a water molecule in the reaction process influences the balance between the two oxidation pathways. In both cases, the hydrogen transfer step is rate limiting. An analysis of the calculated kinetic isotope effects indicates that the presence of a (2)H in either the C5' or the CMepositions has a significant effect on the reaction kinetics. However, the experimental values of around 2.2-2.6 are considerably lower than those predicted by theoretical calculations (9.3 and 6.9 for C5' or the CMe positions, respectively, in the LS state of Cpd I), typical of the masking commonly found for CYP450 reactions. The fact that similar values are found for cotinine formation from both substrates, however, may indicate that the measured value is not that for H-abstraction but, rather, is a combined value for (2)H influence on electronic redistribution between iminium states of the pyrrolidine ring. This is the first time that oxidation at the C5' or the CMe positions has been directly compared and that isotope effects have been obtained for this reaction in a human cytochrome P450 reaction.

Can a cocktail designed for phenotyping pharmacokinetics and metabolism enzymes in human be used efficiently in rat?

We recently designed the CIME cocktail consisting of 10 drugs to assess the activity of the major human CYPs (CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A), a phase II enzyme (UGT1A1/6/9), two drug transporters (P-gp and OATP1B1) and a component of the renal function ( Videau et al. 2010 ). The present work aimed at studying the usefulness of the CIME cocktail in the rat.The CIME cocktail was given per os to three male and three female rats, or incubated with rat liver microsomes. Parent substrates and metabolites were quantified by LC-MS/MS in plasma, urine and hepatic microsomal media, and phenotyping index were subsequently calculated.The CIME cocktail could therefore be used in the rat to phenotype rapidly and simultaneously CYP3A1/2 with omeprazole/omeprazole-sulfone, midazolam/1'-hydroxymidazolam or 4-hydroxymidazolam and/or dextromethorphan/3-methoxymorphinan, CYP2C6/11 with tolbutamide/4-hydroxytolbutamide, CYP2D1/2 with omeprazole/5-hydroxyomeprazole or dextromethorphan/dextrorphan, and UGT1A6/7 with acetaminophen/acetaminophen-glucuronide. Our results confirmed also several known gender differences and brought new information on the urinary excretion of rosuvastatin. However, the major rat CYPs, CYP2C11 and CYP2C12, are not specifically assessed. An optimized version of the CIME cocktail should therefore be designed and would be of major importance to more largely phenotype DMPK enzymes in rats to study DMPK variability factors such as disease, age, or to exposure to inductors or inhibitors.

In vivo effects of zearalenone on the expression of proteins involved in the detoxification of rat xenobiotics.

Zearalenone (ZEN) is a lactone derivative of the resorcylic acid produced by various Fusarium species that are widely found in foods and animal feeds. ZEN exerts species-specific estrogenic effects, possibly because of the metabolism differences arising from reduction, hydroxylation, or glucuro-conjugation. The main objective of this study was to determine the levels of expression of rat proteins that are involved in the ZEN detoxification pathway upon acute ZEN treatment. This was achieved by monitoring the mRNA associated with 25 genes using RT-PCR upon ZEN uptake. These genes code for a variety of proteins that are involved in cellular detoxifying pathways, transporters, cytochromes P450 (CYPs), hydroxysteroid dehydrogenases, and transferases, and receptors that are involved in CYP expression or steroid metabolism. Liver samples from rats treated with ZEN were compared to untreated rats or animals treated with classical CYP inducers (phenobarbital, dexamethasone, ß-naphtoflavone, and clofibrate). Significant changes of mRNA expression were observed for the efflux transporter, P-glycoprotein, monooxygenases (CYP2C7, CYP2E1, CYP3A1, CYP3A2, and aromatase), steroid dehydrogenases, and Uridine diphospho-glucuronyl transferases (UGTs). Following a single ZEN treatment, the initial modifications in mRNA levels indicate a close association with microsomal enzyme activity of the CYP2B, CYP2C, and CYP3A protein families.

Contribution of uniformly 13C-enriched sterigmatocystin to the study of its pulmonary metabolism.

Mycotoxins are secondary metabolites of filamentous fungi which can cause a wide range of systemic effects. Human health effects of inhaled mycotoxins remain poorly documented, despite the large amounts present, associated with air-borne particles. Among these mycotoxins, sterigmatocystin is one of the most prevalent. Because its chemical structure is close to that of the aflatoxins, we studied its metabolism and its cellular consequences when in contact with the airway epithelium, using the mass spectral signature from the 10% (13)C uniformly enriched sterigmatocystin. The metabolism was studied in vitro, using recombinant cytochrome P450s enzymes, and in porcine tracheal epithelial cell (PTEC) primary cultures at an air-liquid interface. The metabolites were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry detection. Expressed enzymes and PTECs were exposed to uniformly (13)C-enriched sterigmatocystin to confirm the relationship between sterigmatocystin and its metabolites because this isotopic cluster shape is conserved for all metabolites and their product ions. Incubation of sterigmatocystin with recombinant cytochrome P450 1A1 led to the formation of three metabolites identified as monohydroxysterigmatocystin, dihydroxysterigmatocystin and one glutathione adduct, the latter after the formation of a transient intermediate. In the PTEC cultures, sterigmatocystin metabolism resulted in a glucuro-conjugate. Two other products were detected, a sulfo-conjugate and a glucuro-conjugate of hydroxysterigmatocystin upon cytochrome P450 1A1 induction. This is the first study to report sterigmatocystin metabolism in airway epithelium, and it suggests that, contrary to the aflatoxins, sterigmatocystin is mainly detoxified into its conjugates and is unable to produce significant amounts of reactive metabolites in respiratory cells, at least in pigs.

Metabolism of N-methyl-amide by cytochrome P450s: formation and characterization of highly stable carbinol-amide intermediate.

We report unambiguous proof of the stability of a carbinol intermediate in the case of P450 metabolism of an N-methylated natural cyclo-peptide, namely tentoxin. Under mild acidic or neutral conditions, the lifetime of carbinol-amide is long enough to be fully characterized. This metabolite has been characterized using specifically labeled (14) C-methyl tentoxin isotopomers, HPLC, HPLC-MS, MS-MS and NMR. Under stronger acidic conditions, the stability of this metabolite vanishes through deformylation. A theoretical mechanistic investigation reveals that the stability is governed by the accessibility of the nitrogen lone pair and its protonation state. For carbinol-amines, even in neutral conditions, the energy barrier for deformylation is low enough to allow rapid deformylation. Carbinol-amide behaves differently. Under neutral conditions, delocalization of the nitrogen lone pair increases the energy barrier of deformylation that is a slow process under such conditions. After protonation, we were able to optimize a deformylation transition that is lower in energy and thus accounts for the lower stability of carbinol-amides observed experimentally in acidic conditions. Finally, by considering the protocol usually used for extraction and analysis of this type of metabolite, carbinol-amide may thus be frequently ignored in drug metabolism pathways.

Metabolic detoxication pathways for sterigmatocystin in primary tracheal epithelial cells.

Human health effects of inhaled mycotoxins remain poorly documented, despite the large amounts present in bioaerosols. Among these mycotoxins, sterigmatocystin is one of the most prevalent. Our aim was to study the metabolism and cellular consequences of sterigmatocystin once it is in contact with the airway epithelium. Metabolites were analyzed first in vitro, using recombinant P450 1A1, 1A2, 2A6, 2A13, and 3A4 enzymes, and subsequently in porcine tracheal epithelial cell (PTEC) primary cultures at an air-liquid interface. Expressed enzymes and PTECs were exposed to sterigmatocystin, uniformly enriched with (13)C to confirm the relationship between sterigmatocystin and metabolites. Induction of the expression of xenobiotic-metabolizing enzymes upon sterigmatocystin exposure was examined by real-time quantitative real-time polymerase chain reaction. Incubation of 50 µM sterigmatocystin with recombinant P450 1A1 led to the formation of three metabolites: monohydroxy-sterigmatocystin (M1), dihydroxy-sterigmatocystin (M2), and one glutathione adduct (M3), the latter after the formation of a transient epoxide. Recombinant P450 1A2 also led to M1 and M3. P450 3A4 led to only M3. In PTEC, 1 µM sterigmatocystin metabolism resulted in a glucuro conjugate (M4) mainly excreted at the basal side of cells. If PTEC were treated with ß-naphthoflavone prior to sterigmatocystin incubation, two other products were detected, i.e., a sulfo conjugate (M5) and a glucoro conjugate (M6) of hydroxy-sterigmatocystin. Exposure of PTEC for 24 h to 1 µM sterigmatocystin induced an 18-fold increase in the mRNA levels of P450 1A1, without significantly induced 7-ethoxyresorufin O-deethylation activity. These data suggest that sterigmatocystin is mainly detoxified and is unable to produce significant amounts of reactive epoxide metabolites in respiratory cells. However, sterigmatocystin increases the P450 1A1 mRNA levels with unknown long-term consequences. These in vitro results obtained in the porcine pulmonary tract need to be confirmed in human epithelial cells.

Biochemical and analytical development of the CIME cocktail for drug fate assessment in humans.

Phenotyping based on drug metabolism activity appears to be informative regarding mechanism-based interactions during drug development. We report here the first steps of the development of the innovative CIME cocktail. This cocktail is designed not only for the major cytochrome P450, with caffeine, amodiaquine, tolbutamide, omeprazole, dextromethorphan and midazolam as substrates of CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A, respectively, but also phase II enzymes UGT 1A1/6/9 with acetaminophen, P-gp and OATP1B1 with digoxin and rosuvastatin, and renal function with memantine. An assay combining ultra-performance liquid chromatography using a 1.7 microm particle size column with tandem mass spectrometry (UPLC/MS/MS) was set up for the simultaneous quantification of the 20 substrates and metabolites after extraction from human plasma using solid-phase extraction. The method was validated in the spirit of the FDA guidelines. Mean accuracy ranged from 87.7 to 115%, the coefficient of variance (CV%) of intra- and inter-run from 1.7 to 16.4% and from 1.6 to 14.9%, respectively, and for the limit of quantification (LOQ) with ten lots of plasma, accuracy ranged from 84 to 115% and CV% precision was <16%. Short-term stability was evaluated in eluate (4 h, room temperature), plasma (24 h, room temperature), the autosampler (24 h, 4 degrees C) and in three freeze/thaw cycles in plasma. All except three analytes were stable under these conditions. For the three others a specific process can be followed. This robust, fast and sensitive assay in human plasma provides an analytical tool for ten-probe drugs of the CIME cocktail. Clinical samples will be assayed in the near future using this new assay method.

Development of a new HPLC method used for determination of zearalenone and its metabolites in broiler samples. Influence of zearalenone on the nutritional properties of broiler meat.

This paper presents the development, optimization and validation of a new HPLC method used for the separation and determination of zearalenone, ZON, and its metabolites in biological samples of Leghorn broiler. ZON and its metabolites can be separated with good resolution in 11 min, using a Hypersil Gold C18 column, a mobile phase mixture of 50 mM aqueous ammonium acetate:acetonitrile:methanol, 45:8:47 (v/v/v), flow rate 1 mL/min and column temperature 40 degrees C. Based on the results obtained by this method applied on biological samples one can conclude that liver is the site for zearalenone localization and detoxification. Influence of zearalenone on the nutritional properties of broiler meat (weight variation, gross chemical composition, fatty acids profile of the meat) was studied, also. Results obtained during 4 days of treatment with ZON showed minimal or no effects of the dietary zearalenone on broiler meat nutritional quality.

ABCC1, ABCC2 and ABCC3 are implicated in the transepithelial transport of the myco-estrogen zearalenone and its major metabolites.

The myco-estrogene zearalenone (ZEA) is a worldwide cereal contaminant, implicated in reproductive disorders in animals and humans. Intestinal cells constitute a first barrier to mycotoxins exposure, since they express membrane ABC transporters that may affect the bioavailability of food xenobiotics. In this study, we investigated the mechanisms involved in the transepithelial transfer of ZEA and its major metabolites alpha- and beta-zearalenols (ZOLs), first using human intestinal Caco-2 cells. When exposed to ZEA, alpha-ZOL or beta-ZOL either in the apical (AP) or basolateral (BL) compartment, cells showed asymmetry in the AP-BL and BL-AP transfer of mycotoxins. Metabolic inhibitors increased ZEA, alpha-ZOL and beta-ZOL intracellular accumulation. Caco-2 cells apically exposed to ZEA produced metabolites (ZOLs and glucuronides) whose distribution between AP, BL and intracellular compartments was significantly modified by ABCCs inhibitor MK571. ABCB1-, ABCC1-, ABCC2 and ABCC3-transfected cells were used for studies of intracellular accumulation of ZEA, alpha-ZOL and beta-ZOL with or without specific inhibitors, and for competitive studies using fluorescent substrates. The results showed that ZEA, alpha-ZOL and beta-ZOL were substrates for ABCC2. ABCC1 was also involved in ZEA and alpha-ZOL transport, whereas ABCC3 only interacted with beta-ZOL. These specific interactions suggest a role for ABCC1-3 transport proteins in zearalenone exposure and its resulting risk for human health.

In vitro cytochrome p450 formation of a mono-hydroxylated metabolite of zearalenone exhibiting estrogenic activities: possible occurrence of this metabolite in vivo.

The mycoestrogen zearalenone (ZEN), as well as its reduced metabolites, which belong to the endocrine disruptor bio-molecule family, are substrates for various enzymes involved in steroid metabolism. In addition to its reduction by the steroid dehydrogenase pathway, ZEN also interacts with hepatic detoxification enzymes, which convert it into hydroxylated metabolites (OH-ZEN). Due to their structures to that of estradiol, ZEN and its derived metabolites bind to the estrogen receptors and are involved in endocrinal perturbations and are possibly associated with estrogen-dependent cancers. The primary aim of this present study was to identify the enzymatic cytochrome P450 isoforms responsible for the formation of the most abundant OH-ZEN. We thus studied its in vitro formation using hepatic microsomes in a range of animal model systems including man. OH-ZEN was also recovered in liver and urine of rats treated orally with ZEN. Finally we compared the activity of ZEN and its active metabolites (alpha-ZAL and OH-ZEN) on estrogen receptors using HeLa ER-alpha and ER-beta reporter cell lines as reporters. OH-ZEN estrogenic activities were revealed to be limited and not as significant as those of ZEN or alpha-ZAL.

Intramolecular hydrogen bonding as a determinant of the inhibitory potency of N-unsubstituted imidazole derivatives towards mammalian hemoproteins.

Enzymes involved in the mammalian microsomal metabolism of drugs are, in numerous cases, inhibited by compounds bearing an imidazolyl scaffold. However, the inhibition potency is highly dependent upon the accessibility of the imidazolyl nitrogen lone pair. In order to highlight some structural parameters of inhibitors that control this phenomenon, a series of compounds containing a nitrogen unsubstituted imidazolyl moiety with varying degrees of nitrogen lone pair accessibility was tested on human and rat hepatic cytochromes P450 and microperoxidase 8, an enzymatically active peptide derived from cytochrome c. In each case, we have shown that the accessibility of the imidazole lone pair determined the extent of inhibition. Nitrogen accessibility was tuned not only by varying the steric hindrance in the vicinity of the imidazolyl ring but also by modifying its surrounding hydrogen bonding network. Compounds in which there exists intramolecular hydrogen bonding between the imidazole moiety and an H-bond acceptor, such as an appropriately positioned amide carbonyl group, demonstrated enhanced inhibitory effects. Conversely, imidazole moieties which are in proximity to H-bond donors, such as an amide NH group, displayed reduced potency. This trend was observed in cyclo-peptide derivatives in which the intramolecular H-bond network was adjusted through the modification of the stereochemistry of a dehydrohistidine residue. It was observed that (Z)-isomers weakly bind heme, whereas (E)-isomers demonstrated higher degrees of metal binding. Therefore, enzymatic inhibition of heme-containing proteins by compounds bearing a dehydrohistidine motif seems to be closely related to its stereochemistry and hydrogen binding propensity. At neutral pH, these differences in binding affinities can be confidently attributed to the ambident H-bond properties of imidazole nitrogen atoms. This structure-activity relationship may be of use for the design of novel imidazolyl compounds as new P450 inhibitors or drug candidates.