Genotoxicity of tungsten carbide-cobalt (WC-Co) nanoparticles in vitro: mechanisms-of-action studies.

We showed previously that tungsten carbide-cobalt (WC-Co) nanoparticles (NP) can be used as a nanoparticulate positive control in some in vitro mammalian genotoxicity assays. Here, we investigate the mechanisms of action involved in WC-Co NP genotoxicity in L5178Y mouse lymphoma cells and primary human lymphocytes, in vitro. Data from the micronucleus assay coupled with centromere staining and from the chromosome-aberration assay show the involvement of both clastogenic and aneugenic events.

Tungsten carbide-cobalt as a nanoparticulate reference positive control in in vitro genotoxicity assays.

With the increasing human exposure to nanoparticles (NP), the evaluation of their genotoxic potential is of significant importance. However, relevance for NP of the routinely used in vitro genotoxicity assays is often questioned, and a nanoparticulate reference positive control would therefore constitute an important step to a better testing of NP, ensuring that test systems are really appropriate. In this study, we investigated the possibility of using tungsten carbide-cobalt (WC-Co) NP as reference positive control in in vitro genotoxicity assays, including 2 regulatory assays, the mouse lymphoma assay and the micronucleus assay, and in the Comet assay, recommended for the toxicological evaluation of nanomedicines by the French Agency of Human Health Products (Afssaps).

Genetic polymorphism of CYP4A11 and CYP4A22 genes and in silico insights from comparative 3D modelling in a French population.

The CYP4A subfamily is known to ω-hydroxylate the endogenous arachidonic acid into 20-hydroxyeicosatetranoic acid, which has renovascular and tubular functions. The aim of this work was to report a comprehensive investigation of the CYP4A11 and CYP4A22 genetic polymorphisms in a French population. Using PCR-SSCP and sequencing strategies, a total of 26 sequence variations were identified comprising 3 missense mutations for CYP4A11 (Ser404Phe, Phe434Ser and Arg505His) and 7 missense mutations for CYP4A22 (Arg126Trp, Gly130Ser, Asn152Tyr, Val185Phe, Cys231Arg, Leu428Pro and Leu509Phe).

Arachidonic acid ω-hydroxylase CYP4A11: inter-ethnic variations in the 8590T>C loss-of-function variant.

The human Cytochrome P450 4A11 (CYP4A11) is a major ω-hydroxylase involved in the regulation of blood pressure in the kidney through the conversion of arachidonic acid into 20-hydroxyeicosatetraenoic acid (20-HETE). Previous studies have reported a significant association between the 8590T>C genetic variant of CYP4A11 and hypertension. Interestingly, several population-based studies have reported ethnic differences in the prevalence of hypertension, with the highest prevalence in African populations.

Genetic polymorphisms of glycine N-acyltransferase (GLYAT) in a French Caucasian population.

In humans, the glycine N-acyltransferase enzyme (GLYAT) is thought to be important in the detoxification of endogenous and xenobiotic compounds which contain a carboxylic acid group, such as benzoic, isovaleric, or acetylsalicylic acids. The aim of this work was to report a comprehensive investigation of GLYAT genetic polymorphisms in DNA samples from 55 subjects of French Caucasian origin, using polymerase chain reaction-single-strand conformation polymorphism and sequencing strategies. Seven different polymorphisms of the GLYAT gene were identified, including two polymorphisms in the 5' flanking region of the gene (g.

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).

Evidence for a functional genetic polymorphism of the human thiosulfate sulfurtransferase (Rhodanese), a cyanide and H2S detoxification enzyme.

Rhodanese or thiosulfate sulfurtransferase (TST) is a mitochondrial matrix enzyme that plays roles in cyanide detoxification, the formation of iron-sulfur proteins and the modification of sulfur-containing enzymes. Transsulfuration reaction catalyzed by TST is also involved in H(2)S detoxification. To date, no polymorphism of the human TST gene had been reported.

Evidence for a functional genetic polymorphism of the human mercaptopyruvate sulfurtransferase (MPST), a cyanide detoxification enzyme.

Mercaptopyruvate sulfurtransferase (MPST) plays a central role in both cysteine degradation and cyanide detoxification. Moreover, deficiency in MPST activity has been suggested to be responsible for a rare inheritable disorder known as mercaptolactate-cysteine disulfiduria (MCDU). To date, no mutation of the human MPST gene has been reported.

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.

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.

Human CYP4F12 genetic polymorphism: identification and functional characterization of seven variant allozymes.

The human cytochrome CYP4F12 has been shown to be metabolically active toward inflammatory mediators and exogenous compounds such as antihistaminic drugs. We recently identified a genetic polymorphism within the promoter region, associated with a decreased level of enzyme expression. In the present study, we report the further identification of single nucleotide polymorphisms in the coding sequence of the CYP4F12 gene.

Functional characterization of genetic polymorphisms identified in the human cytochrome P450 4F12 (CYP4F12) promoter region.

The human cytochrome CYP4F12 has been shown to be active toward inflammatory mediators and exogenous compounds such as antihistaminic drugs. In the present study, we report the first investigation of polymorphisms in the human CYP4F12 gene. A screening for sequence variations in the 5'-flanking region was performed by a Polymerase Chain Reaction-Single Strand Conformational Polymorphism (PCR-SSCP) strategy, using DNA samples from 53 unrelated French individuals of Caucasian origin.

Genetic polymorphism of the human cytochrome CYP2A13 in a French population: implication in lung cancer susceptibility.

The human cytochrome CYP2A13, which is mainly expressed in the respiratory tract, has been shown to be highly efficient in vitro in the metabolism of tobacco-smoke carcinogens and procarcinogens such as 4-methylnitroso-1-(3-pyridyl)-1-butanone (NNK). In order to investigate the extent of CYP2A13 genetic polymorphism in a French Caucasian population of 102 individuals, a screening for sequence variations in the 5'-untranslated and protein encoding regions of its gene was performed using a polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) strategy. Six polymorphisms in the coding region were identified, including two rare missense mutations (C474G or Asp158Glu, G967T or Val323Leu) and one nonsense mutation (Arg101Stop).

First report of a genetic polymorphism of the cytochrome P450 3A43 (CYP3A43) gene: identification of a loss-of-function variant.

In the present study, we report the first investigation of polymorphisms in the human CYP3A43 gene. A screening for sequence variations in the 5'-flanking and protein coding regions of the CYP3A43 gene was performed by a Polymerase Chain Reaction - Single Strand Conformational Polymorphism (PCR-SSCP) strategy, using DNA samples from 48 unrelated French individuals. Three polymorphisms in the coding region were identified, comprising two nucleotide substitutions, one silent (c.

In vitro characterization of four novel non-functional variants of the thiopurine S-methyltransferase.

Human thiopurine S-methyltransferase (TPMT) is an enzyme responsible for the detoxification of widely used thiopurine drugs such as azathioprine (Aza). Its activity is inversely related to the risk of developing severe hematopoietic toxicity in certain patients treated with standard doses of thiopurines. DNA samples from four leucopenic patients treated with Aza were screened by PCR-SSCP analysis for mutations in the 10 exons of the TPMT gene.

Identification of a novel splice-site mutation in the CYP1A2 gene.

Aims: To identify the molecular basis for a low CYP1A2 metabolic status, as determined by a caffeine phenotyping test, in a 71-year-old, nonsmoking, Caucasian woman who presented with very high clozapine concentrations despite being administered a standard dose of the drug.

Methods: The nucleotide sequence of the 7 exons, exon-intron boundaries and 5'-flanking region of the CYP1A2 gene was analysed by direct sequencing.

Results: Only one heterozygous point mutation was identified in the donor splice site of intron 6 (3534G > A) of CYP1A2.

Sequence analysis, frequency and ethnic distribution of VNTR polymorphism in the 5'-untranslated region of the human prostacyclin synthase gene (CYP8A1).

The prostacyclin synthase enzyme (CYP8A1, EC 5.3.99.

Genetic polymorphism of the human cytochrome P450 CYP4B1: evidence for a non-functional allelic variant.

In the present study, we report the first systematic investigation of polymorphism in the human CYP4B1 gene. Using a strategy based on single-strand conformation polymorphism analysis of PCR products (PCR-SSCP), we analyzed the twelve exons of the gene, as well as their 5'- and 3'- proximal flanking sequences, in DNA samples from 190 French Caucasians. In addition to the wild-type CYP4B1* allele (CYP4B1*1), four variants, namely CYP4B1*2, *3, *4 and *5, were characterized.