Genotypes of cytochrome P450 and clinical response to clomipramine in patients with major depression

The genetic cytochrome P450 polymorphism is reported in factors affecting the individual response to drugs. The interindividual variation at steady-state levels or also in elimination of drugs, finds an explanation in genetic differences in the metabolism. In particular, activities of the P450-IID6 isoenzyme are related to the sparteine/debrisoquine oxidation polymorphism. Phenotyping such a system has been proposed to analyse variability in the tricyclic antidepressant level. To analyse clinical relevance of a pharmacogenetic approach, we studied the cytochrome P450 CYP2D6 genotypes and the clinical responses to clomipramine in 21 hospitalised patients who met DSM-III-R criteria for major depression. Three patients were predicted as poor metabolizers. We suggested a limitation of clomipramine (CMI) hydroxylation in poor metaboliser (PM) patients which is balanced by a desmethylation. The clinical efficacy pattern does not differ in poor metaboliser and early metaboliser patients. Firstly, there is no significant differences in the evolution of scores on MADRS and specific retardation scale into the two groups. Secondly, outcome of side effects does not occur more frequently in PM patients. Clinical relevance of such an approach needs further study.

Influence of Acetaminophen Consumption on Perceived Exertion at the Lactate Concentration Threshold

The purpose of this investigation was to study effects of acetaminophen consumption on ratings of perceived exertion and estimated time limit responses at the lactate threshold. 98 young regional to national level athletes performed a graded exhausting exercise on an outdoor running track to estimate their maximal aerobic velocity and the velocity associated with their lactate concentration threshold. Urine (30 mL) was collected during this test and analysed for numerous substances. During urinary screening for doping substances, 9 acetaminophen consumers (9.2%) among the 98 included athletes were detected. These acetaminophen consumers have significantly lower perceived exertion at velocity corresponding to the lactate concentration threshold than nonconsumers (11.9 ± 2.1 vs 13.6 ± 2.1, respectively) although they were at the same relative exercise intensity. This result shows that acetaminophen consumption may have mediated the perceived exertion response at the lactate concentration threshold. This may then suggest that the pain induced by training load could be a factor in use of self-prescribed pain relievers. Such consumption must be taken into account by medical staff, trainers, or educators who have to give information on the use and adverse effects of this substance and to propose palliative methods to their athletes.

Prevention of isoniazid toxicity by NAT2 genotyping in Senegalese tuberculosis patients

Isoniazid (INH), recommended by WHO (World Health Organization) in the treatment of tuberculosis (TB), is metabolized primarily by the genetically polymorphic N-acetyltransferase 2 (NAT2) enzyme. The human population is divided into three different phenotypic groups according to acetylation rate: slow, intermediate, and fast acetylators. The objective of this study was to explore the relationship between NAT2 genotypes and the serum concentrations of INH. Blood samples from 96 patients with TB were taken for the analysis. NAT2 polymorphisms on coding region were examined by polymerase chain reaction (PCR) direct sequencing; the acetylation status was obtained by measuring isoniazid (INH) and its metabolite, acetylisoniazid (AcINH) in plasma was obtained by using the liquid chromatography coupled to mass spectrometry. TB patients were distributed into two groups of fast and slow acetylators according to the acetylation index calculated based on the plasma concentration of INH in the 3rd hour (T3) after an oral dose. Our PCR analysis identified several alleles, where NAT2*4, NAT2*5A, NAT2*6A, and NAT2*13A were the most important. The concentrations of INH varied between 1.10 mg/L and 13.10 mg/L at the 3rd hour and between 0.1 and 9.5 mg/L at the 6th hour. The use of the acetylating index I₃ allowed the classification of tested patients into two phenotypic groups: slow acetylators (44.3% of TB patients), and rapid acetylators (55.7%). Patient’s acetylation profile provides valuable information on their therapeutic, pharmacological, and toxicological responses.

Characterization of functional polymorphisms and glucocorticoid-responsive elements in the promoter of TDO2, a candidate gene for ethanol-induced behavioural disorders

AIMS

In response to acute ethanol consumption, tryptophan 2,3-dioxygenase (TDO) induces the kynurenine pathway (KP) through a glucocorticoid-mediated mechanism, which could lead to a dramatic accumulation of neurotoxic metabolites in association with serotonin depletion. As a result, interindividual variability in ethanol-induced behavioural disorders, such as black-outs and violent impulsive behaviours (BOVIBs) following binge drinking, could be partly explained by genetic polymorphisms affecting the KP. The aim of this study was to identify polymorphisms on the promoter of the TDO2 gene that could affect expression and/or activity of TDO through glucocorticoid induction.

METHODS

Polymorphisms were screened using a PCR-sequencing strategy applied to 31 alcohol-dependent patients and 49 unrelated healthy volunteers, and functionally analysed with bioinformatic prediction tools and gene reporter assays in HepG2 and A549 cell lines.

RESULTS

We identified 12 polymorphisms in the human TDO2 promoter region, 2 of them corresponding to previously unknown single-nucleotide polymorphisms (SNPs) and 3 of them located in putative glucocorticoid-responsive elements (GREs). Gene reporter assays using HepG2 and A549 cell lines confirmed the presence of several functional GREs in the promoter region of TDO2 and revealed that some of the identified polymorphisms affect the promoter activity under glucocorticoid receptor over-expression and dexamethasone exposure conditions.

CONCLUSIONS

Correlational studies in larger samples could help to determine whether these polymorphisms are responsible for variations of expression and/or activity of TDO, in particular under conditions where release of glucocorticoids is increased, such as acute ethanol intake. If confirmed, such results would be of major interest in explaining part of the interindividual variability observed in behavioural responses to acute ethanol consumption.

Drugs involved in drug-facilitated crimes: part I: alcohol, sedative-hypnotic drugs, gamma-hydroxybutyrate and ketamine. A review

SUMMARY

In recent years, there has been a notable increase in the number of reports of drug-facilitated crimes (DFCs). Usually, individuals report that they were robbed or assaulted while incapacitated by drugs. Most often, these cases have involved drugs that have the ability to produce an effect that leaves the victim in a semiconscious or unconscious state. It is reasonable to assume that the purpose of drug-induced incapacitation is probably largely unchanged with time. This covers the full range of property offences (particularly theft) and crimes against the person. What have changed are the drugs themselves: the number; type; their accessibility; effects and detection. The purpose of this review is to explore the different aspects related to the involvement and use of ethanol, sedative-hypnotics drugs, gamma-hydroxybutyrate (GHB) and ketamine in DFCs or offences, which may help people working in this field to expand their knowledge for better understanding of the nature of these crimes or offences.

Impact of tryptophan metabolism on the vulnerability to alcohol-related blackouts and violent impulsive behaviours

AIMS

We examined (1) the association of SLC6A4 genotypes and alcohol dependence (AD) in a sample of alcoholics; (2) the validity of lifetime occurrence of blacked-out violent impulsive behaviour (BOVIB) during binge drinking bouts as a criterion for subtyping AD patients and (3) a mechanistic hypothesis for BOVIB involving tryptophan-2,3-dioxygenase (TDO) activity.

METHODS

Three common polymorphisms of the SLC6A4 gene (5-HTTLPR, A/G SNP of LPR region and VNTR in intron 2) were genotyped. An oral tryptophan (Trp) load (OTL) was administered to a sample of patients seeking help for AD. BOVIB history and psychological status were screened by BOVIB-Q, depression (BDI), anxiety (BAI, STAI) and personality (TCI) questionnaires. During the 7 h following Trp load, serum kynurenine (Kyn) and Trp were monitored.

RESULTS

BOVIB+ patients showed significantly higher scores on depression, anxiety and character scales but no significant association was found between SLC6A4 polymorphisms and BOVIB. Patients with a history of BOVIB (BOVIB+ subgroup) differed from those exempt from such episodes (BOVIB- subgroup) for TDO activity response to OTL assessed by the Kyn:Trp ratio (P = 0.043) and the slope of concentration increase ratio (SCIR) of serum Kyn (P = 0.043).

CONCLUSIONS

Put together, these findings support the validity of the BOVIB criterion to differentiate a sub-group of vulnerable AD subjects and suggest that OTL may help to concurrently define a specific endophenotype.

Ethnic differences in the distribution ofCYP3A5gene polymorphisms

The genetic polymorphism affecting the CYP3A5 enzyme is responsible for interindividual and interethnic variability in the metabolism of CYP3A5 substrates. The full extent of the CYP3A5 genetic polymorphism was analysed in French Caucasian, Gabonese and Tunisian populations using a polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) strategy. In the three populations, eight, 17 and ten single nucleotide polymorphisms (SNPs), respectively, were identified, among which nine correspond to rare new mutations. Also identified were 16 alleles including eight new allelic variants. Significant differences were observed in the distribution of these alleles. Particularly, the frequency of the CYP3A5*3C null allele in French Caucasians (81.3%) and in Tunisians (80.0%) is higher than in the Gabonese population (12.5%) (p < 0.001). Considering the CYP3A5 genotypes of the tested individuals, only 10.4% of French Caucasians and 30.0% of Tunisians were identified as CYP3A5 expressors. In contrast, 90.0% of Gabonese subjects appear to express the CYP3A5 protein.

Indoleamine 2,3-dioxygenase activity of acute myeloid leukemia cells can be measured from patients' sera by HPLC and is inducible by IFN-gamma

The enzyme indoleamine 2,3-dioxygenase (IDO) converts tryptophan to kynurenine, blocking T-cell activation and inducing immunosuppression. In patients with acute myeloid leukemia (AML), the serum kynurenine/tryptophan ratio (Kyn/Trp) was raised, suggesting a higher IDO activity than in healthy people. Patients with higher Kyn/Trp ratios showed lower survival. IDO activity was also detected in AML cells after exposure to IFN-gammain vitro, suggesting that the higher Kyn/Trp ratio in serum of AML patients might have resulted from stimulated leukemic blast cells. Thus, in AML, the activity of IDO can be easily monitored, providing a tool for future clinical testing of IDO-blocking drugs.

Quantitative determination of glyphosate in human serum by 1H NMR spectroscopy

The determination and quantification of glyphosate in serum using (1)H NMR spectroscopy is reported. This method permitted serum samples to be analysed without derivatization or any other sample pre-treatment, using 3-trimethylsilyl 2,2',3,3'-tetradeuteropropionic acid (TSP-d(4)) as a qualitative and quantitative standard. Characterization of the herbicide N-(phosphonomethyl)glycine was performed by analysing chemical shifts and coupling constant patterns. Quantification was performed by relative integration of CH(2)-P protons to the TSP-d(4) resonance peak. The method was tested for repeatability (n=5) and yielded coefficients of variation of 1% and 3%, respectively: detection and quantification limits were also determined and were 0.03 and 0.1mmol/L, respectively. The method was applied to the quantification of glyphosate in a case of acute poisoning.

Prevalence of psychoactive substances in truck drivers in the Nord-Pas-de-Calais region (France)

A previous study conducted in 1995 showed that psychoactive drug use by workers was higher in safety/security workstations than in the rest of the labour force. In order to verify this finding, we conducted a new study in 2003-2004 in the Nord-Pas-de-Calais region, restricted to truck drivers. The aim of this study was to allow harmonizing the professional practice of the occupational physicians, proposing drug prevention and drug testing policies, validating the analytical methods and the guidelines in case of positive testing results. One thousand truck drivers were studied. Urines were tested for amphetamines, cannabinoids, cocaine, opiates, benzodiazepines, buprenorphine and methadone by immunoassay. Urine ethanol determinations were performed by an ADH method. Positive urines for drugs of abuse, methadone or buprenorphine were then tested by gas chromatography or liquid chromatography coupled to mass spectrometry. Out of the 1000 drivers, cannabinoids were detected in 85 cases, opiates in 41 cases, amphetamines in 3 cases and cocaine in only one case. Buprenorphine was detected in 18 cases, methadone in 5 cases and benzodiazepines in 4 cases. Urine ethanol was positive in 50 cases. We found only one case with 6-monoacetylmorphine. Other positive opiates were metabolites of antitussives. The relatively low number of benzodiazepine positive urines could be explained by the lack of sensitivity of the test we used. All these results confirm those of the previous study for cannabinoids and ethanol in safety/security workstations. Positive results for methadone and buprenorphine are eight times higher than in the general population. In conclusion, the authors think that it will be of a great interest to test urine of truck drivers for other classes of psychoactive drugs, using a liquid chromatography-mass spectrometry method.

Impact of an acute exposure to ethanol on the oxidative stress status in the hippocampus of prenatal restraint stress adolescent male rats

Prenatal restraint stress (PRS) in rats is associated with hippocampal dysfunctions and several behavioural and endocrine disorders related to this brain area. Recently, we have reported that the PRS modifies the hypothalamic-pituitary-adrenal (HPA) response to an ethanol challenge in adolescent animals. Since hippocampus is particularly sensitive to the deleterious effects of ethanol during adolescence, we investigated in this study the combined effects of PRS and ethanol administration on the oxidative status in the hippocampus of 28-day-old male rats. Thirty minutes after an intraperitoneal (i.p.) injection of ethanol (1.5 g/kg), the activities of several antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) but also non-enzymatic antioxidant (reduced glutathione) were assayed. Thiobarbituric acid reactive substances (TBARS) levels were also measured as a marker of lipid peroxidation. Ethanol enhanced superoxide dismutase activity in control rats but not in PRS rats. At basal level, catalase activity was lower in PRS rats than in control rats, indicating a potentially higher sensitivity to oxidative damages after this early stress. However, the hippocampal TBARS levels were not significantly affected by the ethanol administration, showing that an acute ethanol exposure does not induce oxidative damage in adolescent male rats. In conclusion, our data suggest that PRS affects both basal antioxidant status in the hippocampus and antioxidant response after an acute ethanol exposure. These findings extend previous works showing that PRS leads to hippocampal dysfunctions and raise the question of the potential increase of the hippocampal oxidative damage in PRS rats after repeated exposure to ethanol.

Molecular analysis of the CYP2F1 gene: identification of a frequent non-functional allelic variant

The CYP2F1 is a human cytochrome P450 that is selectively expressed in lung tissue and involved in the metabolism of various pneumotoxicants with potential carcinogenic effects. In the present study, we report the first systematic investigation of the genetic polymorphism of this enzyme. We analyzed the nucleotidic sequence of the CYP2F1 gene in DNA samples from 90 French Caucasians consisting in 44 patients with lung cancer and 46 control individuals, using single-strand conformation polymorphism analysis of PCR products (PCR-SSCP). We identified 24 novel mutations distributed in the promoter region of the gene, as well as in the coding regions and their flanking intronic sequences. In addition to the wild-type CYP2F1*1 allele, seven allelic variant, CYP2F1*2A, *2B, *3, *4, *5A, *5B and *6, were characterized. The most frequent allelic variant, CYP2F1*2A (25.6%), harbors a combination of 9 mutations, including 2 missense mutations (Asp218Asn and Gln266His) and a 1-bp insertion (c.14_15insC) that creates a premature stop codon in exon 2, probably leading to the synthesis of a severely truncated protein with no catalytic activity. The identification of around 7% of homozygotes for the frameshift mutation in our Caucasian population suggests the existence of an interindividual variation of the CYP2F1 activity and, consequently, the possibility of interindividual differences in the toxic response to some pneumotoxicants and in the susceptibility to certain chemically induced diseases. However, our preliminary results did not show any evidence that the CYP2F1 genetic polymorphism has implications in the pathogenesis of lung cancer.

Lipid-lowering drugs in the MPTP mouse model of Parkinson's disease: fenofibrate has a neuroprotective effect, whereas bezafibrate and HMG-CoA reductase inhibitors do not

We tested the ability of simvastatin, atorvastatin, fenofibrate and bezafibrate (two synthetic peroxisome proliferator-activated receptor-alpha (PPAR-alpha) agonists) to prevent dopaminergic cell death in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease. Tyrosine hydroxylase (TH) immunochemistry was performed 8 days after acute MPTP intoxication. When orally administered for the week prior to intoxication and a week thereafter, fenofibrate prevented the MPTP-induced dopaminergic cell loss in the substantia nigra pars compacta (SNpc) and attenuated the loss of tyrosine hydroxylase immunoreactivity in the striatum. The dosage of 1-methyl-4-phenyl pyridinium (MPP+) in the striatum by high-performance liquid chromatography indicated that fenofibrate did not affect MPTP metabolism. Bezafibrate had no effect and, strikingly, simvastatin and atorvastatin had a negative effect. We also demonstrated the presence of PPAR-alpha in the dopaminergic neurons of the murine substantia nigra. Our data suggest that PPAR-alpha activation by fenofibrate could have a neuroprotective effect in PD through inhibition of inflammation, oxidative stress and/or apoptosis.

Hair Analysis by LC-MS as Evidence of Nalbuphine Abuse by a Nurse

Individuals in any profession can succumb to chemical abuse. Among the healthcare profession, nurses represent a specific group because of their ease of access to drugs, particularly narcotics. Opioids, potentially highly addictive agents, are usually their drug of choice. Nalbuphine, a synthetic opioid analgesic, is prescribed for moderate-to-severe acute pain, for chronic pain syndromes, and in obstetrics to decrease the adverse respiratory effect of opioid epidural administration. The case of a nurse who was suspected of drug misuse after the disappearance of two nalbuphine ampules in an obstetrics service is described. Because of discrepancies in the results of her blood and urine samples, a sample of head hair was subsequently collected from the nurse. A hair analysis of nalbuphine by liquid chromatography-mass spectrometry has not been previously described. Following decontamination and grinding, hair was mixed with a Söerensen buffer, then subjected to ultrasonic treatment (1 h), and extracted with ethyl acetate. A quantitative analysis was performed with two channels (30 and 45 V), and it is based on a m/z 358 for nalbuphine and a m/z 330 for methylclonazepam as an internal standard. The method was linear from 0.020 to 12 ng/mg of hair (R(2) = 0.972), and the limit of detection and limit of quantitation are 0.020 ng/mg. Accuracy (CV), assessed at 0.4 and 1.6 ng/mg of hair, was 6.18% and 5.77%, respectively, for intraday assays and 4.5% and 10.9% for interday assays. Recovery efficiency at 1.6 ng/mg and 8 ng/mg of hair was 100% and 97.4%, respectively. The hair specimen from the nurse (6 cm) was cut into three equal lengths. Nalbuphine, venlafaxine, and nordiazepam were detected. The concentration of nalbuphine was similar in the three hair locks: 5.07, 7.06, and 5.70 ng/mg of hair. A hair analysis revealed the repeated intake of nalbuphine by the nurse. This person was treated for depression for several months with Effexor (venlafaxine) and Nordaz (nordiazepam) prior to the investigation. Hair appears to be a unique matrix to provide evidence for chronic drug exposure by establishing a historic record that is not possible by blood or urine analysis.

[Therapeutic failure: importance of genes?]

Drug management can be a difficult task in certain situations because of the variable response observed from one patient to another. Genetic factors affecting the pharmacokinetics and pharmacodynamics of drug reactions could explain the interindividual variability in drug response. Pharmacogenetic analysis provides insight into the molecular mechanisms involved in drug response, with the ultimate goal of achieving optimal drug efficacy and safety. Numerous polymorphisms have been described in genes encoding drug-metabolising enzymes, transporters, and receptors. For some drugs, the impact on drug bioavailability and effect has been elucidated. We review here the molecular basis of interindividual variation in drug response and the methods used to identify individual risk of drug failure or toxicity. Clinical applications, concerning enzymes metabolising drugs (cytochrome P4502D6, thiopurine S-methyltransferase and N-acetyltransferase) provide an illustrative demonstration of the usefulness of pharmacogenetic tests in improving patient management. Clinical validation of these tests and new technologies (real-time PCR, DNA chips) should, in the future promote pharmacogenetics in clinical practice and may be lead to more individualized drug therapy.

Factors associated with perceived exertion and estimated time limit at lactate threshold

The purpose was to identify the most predictive parameters for perceived exertion and estimated time limit responses at the velocity corresponding to the lactate concentration threshold. The former scale concerns the subject's current status (how hard he feels the exercise currently is) whereas the latter scale deals with a subjective prediction of how long the current exercise level can be maintained. Multiple regression equations were developed among physiological, psychological, nutritional, and individual parameters (subjects' characteristics and performances) as independent variables, and perceived exertion or estimated time limit as dependent variables. Independent variables were collected before or during an incremental running field test. 94 regional to national level athletes (47 endurance-trained runners, 11 sprinters, and 36 handball players) participated. Multiple stepwise regression showed that Rating of Perceived Exertion and Estimated Time Limit at the lactate threshold were mainly mediated by factors relative to the performance expressed in percentage of the maximal aerobic velocity. Secondary factors which contribute significantly as perceptual predictors were related to various classes of factors except for psychological factors.

Hypo-response of the hypothalamic-pituitary-adrenocortical axis after an ethanol challenge in prenatally stressed adolescent male rats

The period of adolescence and environmental factors, such as stress, are important in determining ethanol vulnerability in both humans and rats. Ethanol is a powerful activator of the hypothalamic-pituitary-adrenal (HPA) axis but attenuated responses of the HPA axis to ethanol have been described in populations with a high risk of ethanol abuse. In rats, prenatal stress leads to prolonged stress-induced corticosterone secretion and increases the vulnerability to drugs of abuse, such as amphetamine and nicotine in adulthood and 3,4-methylenedioxymethamphetamine in adolescent rats. The aim of the present study was to assess the impact of a prenatal stress on HPA axis responsiveness to a moderate dose of ethanol (1.5 g/kg i.p.) in adolescent male rats (28 days old). The parameters evaluated were plasma adrenocorticotropic hormone, plasma corticosterone and mRNA expression of HPA axis central markers (mineralocorticoid receptor, glucocorticoid receptor, corticotropin-releasing hormone and pro-opiomelanocortin). Contrary to prior expectations, our results demonstrate that prenatal stress blunts the HPA axis responsiveness to a moderate dose of ethanol in adolescent rats in spite of similar blood ethanol levels. These data suggest that prenatal stress may have the opposite effect on the response to stress depending on the attributes of the stressor stimulus. They thus raise questions about the possible impact of prenatal stress on the further development of ethanol vulnerability.

Analysis of Ingested Material and Urine by GC-MS and 1H NMR Spectroscopy: Poisoning of an Adult with Adulterated Soda

The purpose of this work is to characterize chemical compounds added to an ingested soda by (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy and by gas chromatography-mass spectrometry in the electron impact mode. A second point was to highlight possible metabolic disturbances by considering urinary profile. Without any pretreatment, dimethylphtalate, 2-butanone, and 2,2,4-trimethylpentanediol diisobutyrate were found in the adulterated soda. Quantitative analysis was performed by relative integration of peak areas. Huge quantities of 2,2,4-trimethylpentanediol diisobutyrate and dimethylphtalate were found in the oily layer. 2-Butanone, which is miscible in water, was found in the two phases as well as small quantities of dimethylphtalate. The urine sample was collected on hospital admission and was also analyzed by (1)H NMR spectroscopy. The major abnormal compound found was 1,2-propanediol. Other disturbances concerned endogenous metabolites such as 2-ketoglutaric acid, lactic acid, and betaine.

Identification by single-strand conformational polymorphism analysis of known and new mutations of the CYP3A5 gene in a French population

The cytochrome P450 3A5 (CYP3A5) has been shown to be highly involved in the metabolism of many therapeutic agents. To date, several polymorphisms affecting the CYP3A5 gene have been identified but few studies have shown a complete description of the variability of the CYP3A5 in the French population. Therefore, the extent of CYP3A5 genetic polymorphism was investigated in a French population of 114 patients. The screening of the coding region with their intron-exon boundaries and the proximal flanking regions was performed using a PCR-SSCP strategy. Eighteen polymorphisms were identified, including four new mutations. They correspond to -19 T>C upstream of the exon 1, 7360 T>C in intron 4, 12991 T>C in intron 5 and 29788 delG in exon 12. We also identified 13 alleles including six new alleles. As expected, the most frequent allelic variant is CYP3A5*3, with a frequency of 87% of all alleles. These data confirmed that CYP3A5 gene is highly polymorphic. Furthermore, it will be now interesting to evaluate the impact of this polymorphism on the pharmacokinetic parameters of different drugs.

Major Metabolites of Zolpidem: Expeditious Synthesis and Mass Spectra

An expeditious route to the two major metabolites of Zolpidem-and readily applicable to the synthesis of the drug-was established via a cyclization reaction between a 2-aminopyridine and a suitable alpha-bromoacetophenone. The structures of the target compounds were confirmed from a 2D (1)H-(15)N NMR correlation. Their mass spectra contribute to a reliable toxicological identification of the drug in the case of drug-facilitated crimes.

[Assessment of occupational exposure to ortho-toluidine using gas chromatography-mass spectrometry]

Ortho-toluidine is a carcinogen aromatic amine. It is in part eliminated as unchanged form and its urine determination allows biologic monitoriing of occupational exposure. We propose a new method simple and fast in gas chromatography mass spectrometry. In the Nord-Pas-de-Calais region, a company initiated destruction and depollution of an old industrialsite.The GS-MS method permits exposition evaluation of workers employed in demolition of a liquid SO2 plant polluted with ortho-toluidine. This plant has been stopped twenty years ago. These results are compared with results of workers without any exposure in the same company. A 5 mL urine sample spiked with internal standard (ortho-toluidine D9) is extracted with hexane. Derivatisation is achieved with anhydrous pentafluoropropionic acid during 30 min at 60 degrees C. Chromatographic separation is performed on a BPX5MS column (25 m x 0.25 mm, 0.25 microm; SGE). Initial column temperature (60 degrees C) is hold 3 min then is raised to 300 degrees C at 25 degrees C/min. Detection is performed with mass spectrometry with negative chemical ionisation with methane. Acquisition is performed in single ion monitoring. Identification ions are 233 ion (m/z) and 213 ion (m/z) with 233 (m/z) used for quantification. Linearity of the method is verified between 0.1 and 100 microg/L. The limit of detection is 0.02 micro/L. Repeatability and intermediate fidelity are satisfactory (CV < 9%). For unexposed workers, urinary concentrations of ortho-toluidine ranged between 0.17 microg/L and 2.46 microg/g creatinine. Urinary concentrations for exposed workers ranged between 26.14 and 462.00 microg/g creatinine and after new action of protection between 2.35 et 20.11 microg/g creatinine. This new GC-MS method is specific and sensitive and allows for urinary determination of ortho-toluidine. Results showed that this method is adapted for biomonitoring as much for unexposed workers to this aromatic amine as for exposed workers.

Evidence for a functional genetic polymorphism of the human retinoic acid–metabolizing enzyme CYP26A1, an enzyme that may be involved in spina bifida

BACKGROUND

CYP26A1, together with CYP26B1 and CYP26C1, are key enzymes of all-trans retinoic acid (RA) inactivation and their specific and restricted expression in developing embryos participate in the fine tuning RA levels. As RA is a critical regulator of gene expression during embryonic development, the imbalance between the synthesis and degradation of RA during embryogenesis could contribute to malformations and developmental defects.

METHODS

A PCR-single strand conformation polymorphism (PCR-SSCP) strategy was developed to screen for CYP26A1 sequence variations that could affect the enzyme expression and/or activity and applied to DNA samples from 80 unrelated Caucasians, comprising 40 French healthy volunteers and 40 Italian patients with spina bifida. The consequence of the 1-bp deletion identified in the coding sequence was investigated by an in vitro functional assay using COS-7 cells.

RESULTS

A total of 7 polymorphisms were identified, comprising 1 nucleotide deletion in the coding sequence (g.3116delT) that results in a frameshift and consequently in the creation of a premature stop codon. The g.3116delT mutation is of particular interest because it was identified in a patient with spina bifida and likely encodes a truncated protein with no enzymatic activity, as demonstrated by our preliminary in vitro data.

CONCLUSIONS

Despite the fact that our findings could not show any evidence that the CYP26A1 genetic polymorphism has implications in the pathogenesis of spina bifida, this work represents the first description of a functional genetic polymorphism affecting the coding sequence of the human CYP26A1 gene.

[Xenobiotic-metabolizing polymorphic enzymes. An opportunity for individualized drug treatment]

Interindividual variability in drug responses can complicate patient management. This variability is partly due to genetic factors that affect pharmacokinetic and pharmacodynamic behavior Pharmacogenetics is a discipline focusing on the molecular mechanisms underlying drug responses. Its overriding goal is to optimize drug treatments, in terms of both their efficacy and their safety. Polymorphisms of genes that encode drug-metabolizing enzymes, transporter molecules and receptors have a well-documented impact on the distribution and effects of many medications. This review examines the scope of pharmacogenetics, the molecular bases of interindividual variations in drug responses, and the methods used to assess the individual risk of drug failure or toxicity. Pharmacogenetic approaches have already entered the clinical arena, resulting in significant improvements in patient management. Clinical validation of new pharmacogenetic tests and the development of new efficient genotyping technologies should rapidly lead to patient-tailored therapy.

Grapefruit juice-nifedipine interaction: possible involvement of several mechanisms

OBJECTIVE

To develop a model based on mean residence time for better understanding the effect of grapefruit juice on the metabolism of nifedipine (NIF).

MATERIAL AND METHODS

Sixteen healthy volunteers from an urban population were included. For each trial, the subjects drank water, fresh grapefruit juice or bottled grapefruit juice. Thirty minutes later, the subjects took a 10 mg capsule of NIF, orally. Plasma concentration of NIF was measured and the kinetic parameters were calculated with a non-compartmental model.

RESULTS

Grapefruit juice increased the bioavailability of NIF, but did not significantly reduce the drug's metabolism as shown by the approximately constant metabolite to parent drug AUC ratio (P = 0.948). There was no significant increase in the amount of non-metabolized drug absorbed during first-pass: 0.12 and 0.16 (P = 0.470) without and with grapefruit juices respectively. There was an increase in the relative bioavailability (P = 0.039) and the apparent volume of distribution (Vdm) (P = 0.025) of dehydronifedipine with grapefruit co-administration. A second peak was also observed in the NIF plasma-concentration profile when the drug is co-administered with grapefruit juice. Therefore, the most likely explanation for the double peak phenomenon is a delay in gastric emptying (+32 min with grapefruit juice) caused by the pH of grapefruit juice.

CONCLUSION

This study shows that grapefruit juice interferes with the metabolism of NIF by inhibiting NIF metabolism and slowing down the rate of gastric emptying. This study also confirms that the metabolic inhibition is not a first pass effect, but is a secondary oxidative step.

Use of drugs of abuse in less than 30-year-old drivers killed in a road crash in France: a spectacular increase for cannabis, cocaine and amphetamines

A collaborative study was conducted in France in order to determine the prevalence of cannabinoids, opiates, cocaine metabolites and amphetamines in blood samples from drivers killed in road accidents in 2003 and 2004 and to compare these values with those of a previous study performed during the period 2000-2001 involving 900 drivers. Blood samples were provided from 2003 under 30-year-old drivers, killed in a traffic accident. Drugs of abuse were determined by gas chromatography-mass spectrometry using the same analytical procedures in all the 12 laboratories. The most frequently observed compounds were by far cannabinoids, that tested positive in 39.6% of the total number of samples. Delta9 tetrahydrocannabinol (THC), the most active of the principle constituents in marijuana (cannabis sativa), was detected in the blood of 28.9% drivers and was the single drug of abuse in 80.2% of the positive cases. It was associated with amphetamines in 7.4% and with opiates and cocaine in 1.9 and 4.8%, respectively. Amphetamines were present in 3.1% of the total number of samples, cocaine metabolites in 3.0% and opiates in 3.5%. When comparing these results with those of a previous study performed 3 years before, a significant increase is observed for THC (28.9% versus 16.9%), cocaine metabolites (3.0% versus 0.2%) and amphetamines (3.1% versus 1.4%). This study demonstrates the critical necessity of implementing in France as soon as possible systematical roadside testing for drugs of abuse.

Simultaneous determination of tryptophan and kynurenine in serum by HPLC with UV and fluorescence detection

Tryptophan metabolism is disturbed in mental depression, and the induction of indoleamine 2,3-dioxygenase increases kynurenine production. In order to determine this disturbance in patients with chronic hepatitis C and receiving interferon-based immunotherapy, a new and specific HPLC protocol was elaborated. For tryptophan, the assay was linear from 6.25 to 100 micromol L(-1), and the limits of detection (LOD) and quantitation (LOQ) for the method were 0.7 and 8.0 micromol L(-1). For kynurenine, the linearity of calibration was from 0.0625 to 6.25 micromol L(-1), with LOD and LOQ of 2 and 3 nmol L(-1). Reproducibility and repeatability were satisfactory. The method allowed study of human blood serum.

Functional analysis of CYP2D6.31 variant: Homology modeling suggests possible disruption of redox partner interaction by Arg440His substitution

Cytochrome P450 2D6 (CYP2D6) is an important human drug-metabolizing enzyme that exhibits a marked genetic polymorphism. Numerous CYP2D6 alleles have been characterized at a functional level, although the consequences for expression and/or catalytic activity of a substantial number of rare variants remain to be investigated. One such allele, CYP2D6*31, is characterized by mutations encoding three amino acid substitutions: Arg296Cys, Arg440His and Ser486Thr. The identification of this allele in an individual with an apparent in vivo poor metabolizer phenotype prompted us to analyze the functional consequence of these substitutions on enzyme activity using yeast as a heterologous expression system. We demonstrated that the Arg440His substitution, alone or in combination with Arg296Cys and/or Ser486Thr, altered the respective kinetic parameters [Km (microM) and kcat (min(-1))] of debrisoquine 4-hydroxylation (wild-type, 25; 0.92; variants, 43-68; 0.05-0.11) and dextromethorphan O-demethylation (wild-type, 1; 4.72; variants, 12-23; 0.64-1.43), such that their specificity constants (kcat/Km) were decreased by more than 95% compared to those observed with the wild-type enzyme. The rates of oxidation of rac-metoprolol at single substrate concentrations of 40 and 400 microM were also markedly decreased by approximately 90% with each CYP2D6 variant containing the Arg440His substitution. These in vitro data confirm that the CYP2D6*31 allele encodes an enzyme with a severely impaired but residual catalytic activity and, furthermore, that the Arg440His exchange alone is the inactivating mutation. A homology model of CYP2D6 based on the crystal structure of rabbit CYP2C5 locates Arg440 on the proximal surface of the protein. Docking the structure of the FMN domain of human cytochrome P450 reductase to the CYP2D6 model suggests that Arg440 is a key member of a cluster of basic amino acid residues important for reductase binding.

Brain ischemic preconditioning is abolished by antioxidant drugs but does not up-regulate superoxide dismutase and glutathion peroxidase

The present work examined the hypothesis that brain ischemic tolerance induced by ischemic preconditioning (IPC) is triggered by an initial oxidative stress and is associated with an increase in antioxidant enzyme activities as one end-effector of the neuroprotection. Wistar rats were preconditioned by a single 3-min occlusion of the middle cerebral artery. After a various duration of reperfusion (30 min, 24, 72 or 168 h), rats were subjected to a 60-min focal ischemia and sacrificed 24 h later. Cerebral infarcts were significantly reduced when performed during the 24- to 72-h time window after IPC. The pretreatment with the protein synthesis inhibitor, cycloheximide (1 mg/kg, i.p., 30 min prior to IPC), completely suppressed the neuroprotection. The free radical scavenger, dimethylthiourea (DMTU; 300 mg/kg, i.p., 30 min prior to IPC) and the antioxidant ebselen (10 mg/kg, oral cramming, 2 h before and 12 h after IPC) also abolished the IPC-induced protection of the brain. Nevertheless, IPC did not induce any delayed changes in antioxidant enzyme (superoxide dismutase, glutathion peroxidase) activities nor in the neuronal expression of Mn and Cu/Zn superoxide dismutase. These results indicate that an initial oxidative stress could be involved as a trigger of IPC, while antioxidant enzymes do not play a key role as end-effectors in such a neuroprotection.