Vincent Haufroid

CYP3A5 and ABCB1 Polymorphisms and Tacrolimus Pharmacokinetics in Renal Transplant Candidates: Guidelines from an Experimental Study

Genetic polymorphisms in biotransformation enzyme CYP3A5 (6986G > A, CYP3A5*3; 14690A > G, CYP3A5*6) and drug transporter ABCB1 (1236C > T; 2677G > T/A; 3435C > T) are known to influence tacrolimus (Tac) dose requirements and trough blood levels in stable transplant patients. In a group of 19 volunteers selected with relevant genotypes among a list of 221 adult renal transplant candidates, we evaluated whether consideration of CYP3A5 and ABCB1 genetic polymorphisms could explain the interindividual variability in Tac pharmacokinetics after the first administration of a standard dose (0.1 mg/kg body weight twice a day). Lower area under the time versus blood concentration curves (AUC) or lower trough concentrations were observed among CYP3A5 expressors (n = 9) than among nonexpressors (n = 10) using two different analytical methods for Tac determination (liquid chromatography with tandem mass spectrometry (LC‐MS/MS) and immunoassay). The median AUC0−∞ was 2.6‐ and 2.1‐fold higher in nonexpressors for LC‐MS/MS and immunologic methods, respectively. No difference was observed in Tac pharmacokinetic parameters in relation to ABCB1 polymorphisms. In conclusion, our study confirms the very significant effect of CYP3A5 polymorphism early after the first administration of Tac. It also provides a strong argument for a doubling of the loading dose in patients early identified a priori on the transplantation list as possessing at least one CYP3A5*1 allele.

Interest of genotyping and phenotyping of drug-metabolizing enzymes for the interpretation of biological monitoring of exposure to styrene

In the field of occupational and/or environmental toxicology, the measurement of specific metabolites in urine may serve to assess exposure to the parent compounds (biological monitoring of exposure). Styrene is one of the chemicals for which biological monitoring programs have been validated and implemented in environmental and occupational medicine. However, inter-individual differences in the urinary excretion exist both for the main end-products (mandelic acid and phenylglyoxylic acid) and for its specific mercapturic acids (phenylhydroxyethylmercapturic acids, PHEMA). This limits to a certain extent the use of these metabolites for an accurate assessment of styrene exposure. In a group of 26 volunteers selected with relevant genotypes, and exposed to styrene vapours (50 mg/m3, 8 h) in an inhalation chamber, we evaluated whether genotyping or phenotyping relevant drug-metabolizing enzymes (CYP2E1, EPHX1, GSTM1, GSTT1 and GSTP1) may help to explain the observed inter-individual variability in the urinary metabolite excretion. Peripheral blood lymphocytes were used for genotyping and as reporter cells for the phenotyping of CYP2E1 and EPHX1. The GSTM1 genotype was clearly the most significant parameter explaining the variance in urinary PHEMA excretion (6-fold lower in GSTM1 null subjects; P < 0.0001) so that systematic GSTM1 genotyping should be recommended routinely for a correct interpretation of PHEMA urinary levels. Variant alleles CYP2E1*6 (7632T>A) and His113EPHX1 were associated with a significant reduction of, respectively, the expression (P = 0.047) and activity (P = 0.022) of the enzyme in peripheral blood lymphocytes. In combination with GSTM1 genotyping, the phenotyping approach also contributed to improve the interpretation of urinary results, as illustrated by the combined effect of CYP2E1 expression and GSTM1 allelic status that explained 77% of the variance in PHEMA excretion and allows the recommendation of mercapturates as specific and reliable biomarkers of exposure to styrene.

Confounders in the assessment of the renal effects associated with low-level urinary cadmium : an analysis in industrial workers

BackgroundAssociations of proteinuria with low-level urinary cadmium (Cd) are currently interpreted as the sign of renal dysfunction induced by Cd. Few studies have considered the possibility that these associations might be non causal and arise from confounding by factors influencing the renal excretion of Cd and proteins.MethodsWe examined 184 healthy male workers (mean age, 39.5 years) from a zinc smelter (n = 132) or a blanket factory (n = 52). We measured the concentrations of Cd in blood (B-Cd) and the urinary excretion of Cd (U-Cd), retinol-binding protein (RBP), protein HC and albumin. Associations between biomarkers of metal exposure and urinary proteins were assessed by simple and multiple regression analyses.ResultsThe medians (interquartile range) of B-Cd (μg/l) and U-Cd (μg/g creatinine) were 0.80 (0.45-1.16) and 0.70 (0.40-1.3) in smelter workers and 0.66 (0.47-0.87) and 0.55 (0.40-0.90) in blanket factory workers, respectively. Occupation had no influence on these values, which varied mainly with smoking habits. In univariate analysis, concentrations of RBP and protein HC in urine were significantly correlated with both U-Cd and B-Cd but these associations were substantially weakened by the adjustment for current smoking and the residual influence of diuresis after correction for urinary creatinine. Albumin in urine did not correlate with B-Cd but was consistently associated with U-Cd through a relationship, which was unaffected by smoking or diuresis. Further analyses showed that RBP and albumin in urine mutually distort their associations with U-Cd and that the relationship between RBP and Cd in urine was almost the replicate of that linking RBP to albuminConclusionsAssociations between proteinuria and low-level urinary Cd should be interpreted with caution as they appear to be largely driven by diuresis, current smoking and probably also the co-excretion of Cd with plasma proteins.

Serum pneumoproteins and biomarkers of exposure to urban air pollution: a cross-sectional comparison of policemen and foresters

Very few biomarkers are available for the non-invasive detection of effects of urban air pollution on the respiratory tract. The objective was to evaluate whether Clara cell protein (CC16) and surfactant-associated protein-A (SP-A), two pulmonary secretory proteins, were useful in the detection of effects of urban air pollutants on the pulmonary epithelium. These proteins were determined in the serum of 53 policemen working in Brussels, Belgium, and a control group of 59 foresters working in the countryside. Except for ozone (O3), annual concentrations of the main air pollutants (PM10, NO2, CO, SO2 and benzene) were significantly higher in Brussels than in the country. The proportion of smokers was lower in urban policemen compared with foresters, but they smoked on average a similar number of cigarettes per day as confirmed by their urinary excretion of cotinine. Muconic acid, a marker of benzene exposure, was significantly higher in urban policemen than in foresters, in both smokers and non-smokers. Multiple regression analysis showed that the type of work, smoking habits and time spent outdoors and in a car were significant determinants of benzene uptake. Tobacco smoking impaired lung function to a similar extent in urban policemen and foresters. The serum levels of SP-A were significantly increased in smokers but were not different between policemen and foresters. Serum CC16 was significantly reduced by tobacco smoking and slightly decreased in policemen compared with foresters. Interestingly, the reduction of serum CC16 was more pronounced in the subgroup of traffic compared with survey policemen, the latter being also less exposed to benzene. The results suggest that serum pneumoproteins and especially serum CC16 could be useful in the detection of chronic effects of urban air pollutants on the respiratory epithelium of populations particularly at risk.

Survival after a lethal dose of arsenic trioxide.

A case of a 27‐year‐old woman who ingested 9000 mg arsenic trioxide (As2O3) is reported. Classical symptoms of an acute arsenicum (As) poisoning such as gastrointestinal cramps, vomiting, diarrhea, ECG changes and disturbed liver function tests were observed. The absorption of the ingested As was minimalized by a continuous gastric irrigation with highly concentrated NaHCO3 andintestinal cleansing with NaHCO3 and polyethyleneglycol was performed. Forced diuresis, BAL (2,3‐dimercaptopropanol) and DMSA (meso‐2,3‐dimercaptosuccinic acid) were started and therapy to enhance the formation of methylated As derivatives, which are potentially less toxic and which can be excreted more easily, was then administered. The patient survived this massive dose of ingested inorganic As with only polyneuropathy one year later.

Cytochrome P4502E1 (CYP2E1) expression in peripheral blood lymphocytes: evaluation in hepatitis C and diabetes

ObjectiveCytochrome P4502E1 (CYP2E1) is expressed in human peripheral blood lymphocytes (PBLs), and previous reports have suggested the possibility of using this readily available tissue as a reporter of CYP2E1 status. To further explore the relevance of this approach we assessed CYP2E1 expression in PBLs in two contrasting conditions, chronic hepatitis C and insulin-dependent diabetes (IDD), illustrating an organ and a systemic disease, respectively.MethodsTotal RNA was isolated from extracted PBLs (hepatitis C patients + IDD) and by percutaneous needle biopsy (hepatitis C patients only). Gene expression for CYP2E1 was determined by real-time reverse-transcription polymerase chain reaction. Histological changes in liver tissue were assessed according to Ludwigs criteria.ResultsIn patients with chronic hepatitis C a clear relationship was found between CYP2E1 expression in the liver and the progression of hepatic disease (both lobular inflammation and fibrosis indices), and observed variations were consistent with the preferential distribution of CYP2E1 in the lobular zone. No effect of the liver disease was, however, found at the PBL level. A statistically significant increase in mean CYP2E1 expression level was observed in the lymphocytes from poorly controlled IDD subjects compared to controls.ConclusionsTaken together, our data indicate that the measurement of CYP2E1 expression in PBLs is not useful in liver diseases. However, in a systemic condition (IDD) this measurement can be proposed for monitoring the CYP2E1 induction in a relatively noninvasive manner. This tool should therefore be further validated in clinical field or experimental studies for CYP2E1 phenotyping purposes.

Lung epithelium injury biomarkers in workers exposed to sulphur dioxide in a non-ferrous smelter.

Serum Clara cell protein (CC16) and surfactant-associated protein D (SP-D) were measured in 161 workers exposed to sulphur dioxide (SO2) in a non-ferrous smelter. Seventy workers from a blanket manufacture served as referents. Exposure to SO2 and tobacco smoking were associated with a decrease of CC16 and an increase of SP-D in serum. Tobacco smoking and exposure SO2 interacted synergistically to decrease serum CC16 but not to increase serum SP-D. While further illustrating the potential of serum CC16 and SP-D, our study confirms that SO2 can cause airways damage at exposure levels below current occupational exposure limits.

Quantitative determination of 5-hydroxy-N-methylpyrrolidone in urine for biological monitoring of N-methylpyrrolidone exposure

The aim of this work was to validate a sensitive method for quantitative analysis of 5-hydroxy-N-methylpyrrolidone (5-HNMP) in urine. This compound has been recommended as a marker for biological monitoring of N-methylpyrrolidone (NMP) exposure. Different solvents and alternative methods of extraction including liquid-liquid extraction (LLE) on Chem Elut and solid-phase extraction (SPE) on Oasis HLB columns were tested. The most efficient extraction of 5-HNMP in urine was LLE with Chem Elut columns and dichloromethane as a solvent (consistently 22% of recovery). The urinary extracts were derivatized by bis(trimethylsilyl)trifluoroacetamide and analysed by gas chromatography-mass spectrometry (GC-MS) with tetradeutered 5-HNMP as an internal standard. The detection limit of this method is 0.017 mg/l urine with an intraassay precision of 1.6-2.6%. The proposed method of extraction is simple and reproducible. Four different m/z signal ratios of TMS-5-HNMP and tetralabelled TMS-5-HNMP have been validated and could be indifferently used in case of unexpected impurities from urine matrix.

Consistency of Biomarkers of Exposure to Inorganic Arsenic: Review of Recent Data

Publisher Summary Health impairments can be observed following undue absorption of inorganic arsenic (Asi), which mainly occurs through inhalation in occupational settings or ingestion in the general population. Assessment of exposure based on the determination of the external dose often lacks precision due to variations in chemical species involved, in concentrations or due to varying toxicokinetic parameters. Therefore, on the basis of As metabolism data, the following biomarkers of internal exposure are generally proposed: the urinary excretion of the element and its concentration in hair and nails. This chapter has as its main purpose the review of recent studies of the relationship between external and internal As doses to assess their consistency among investigators. To avoid difficulties from possibly poor analytical techniques only literature published during the last two decades is considered. Despite some encouraging reports, the value of As levels in hair and nails as indices of internal exposure appears limited and efforts are needed to develop a standardized procedure to solve the problem of external contamination of samples. The agreement on the relationship between airborne As concentration and urinary excretion appears better. The level of As urinary excretion (seafood excluded) as a function of As oral intake through drinking water in steady state conditions has been reported by several authors from different countries. Despite possible ethnic and environmental differences, reported results display a quite satisfactory consistency.