Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P16104 (H2AX)
 3,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gammaH2AX focus assay, based on phosphorylation of the variant histone protein H2AX, was evaluated as a genotoxicity test in immortalised wild-type mouse embryonic fibroblasts (MEFs) treated for 4h with a panel of reference compounds routinely used in genotoxicity testing. The topoisomerase II poison etoposide (0.006-60 microg/ml), the alkylating agent methyl methanesulfonate (1.3-65 microg/ml) and the direct DNA-damaging agent bleomycin (0.1-10 microg/ml) all produced a positive concentration-response relationship. The non-genotoxic compounds ampicillin (0.035-3500 microg/ml) and sodium chloride (0.058-580 microg/ml) showed no such response with increased concentrations. The H2AX phosphorylation results were compared with the outcome of two standard in vitro genotoxicity tests, namely the micronucleus and comet assays. Compounds that produced measurable DNA damage in the focus assay generated micronuclei at comparable concentrations. In this study, the focus assay identified genotoxic agents with the same specificity as the comet assay. These results were substantiated when H2AX phosphorylation was analysed using flow cytometry in the murine cell line L5178Y, growing in suspension. The data were in concordance with the manual scoring focus assay. To further this investigation, the gammaH2AX flow cytometry was compared to the in vitro micronucleus flow cytometry and mouse lymphoma assay using the same cell population after MMS treatment. The median gammaH2AX value increased significantly above the control at all four MMS concentrations tested. The percentage of micronucleus events in the in vitro micronucleus flow test and the mutation frequency in the mouse lymphoma assay were also significantly increased at each MMS concentration. The current data indicate that H2AX phosphorylation could be used as a biomarker of genotoxicity, which could predict the outcome of in vitro mammalian cell genotoxicity assays.
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PMID:H2AX phosphorylation as a genotoxicity endpoint. 1962 53

The conventional in vitro assays for genotoxicity assessment of chemicals are characterised by a high false-positive rate, thus failing to correctly predict their in vivo genotoxic effects. This study aimed to identify the cellular mechanisms induced by the false-positive genotoxins quercetin, 8-Hydroxyquinoline and 17-beta oestradiol in comparison to true genotoxins and non-genotoxins, by combining in vitro phenotypic parameters with transcriptomics data from HepG2 cells. The effects of these compounds on the phosphorylation of H2AX, cell cycle distribution and whole genome gene expression following treatment for 12, 24 and 48 h were compared with the effects of true genotoxins [benzo[a]pyrene and aflatoxin B1] and non-genotoxins (2,3,7,8-tetrachlorodibenzodioxin, cyclosporin A and ampicillin C). Quercetin induced similar phenotypic effects as true genotoxins and to some extent similar gene expression alterations. Different gene expression changes were also observed, including the up-regulation of DNA repair-related genes. 8-Hydroxyquinoline and 17-beta oestradiol showed no similarities to the true genotoxins at both the phenotypic and the transcriptomic level. In a classification approach, classifiers were selected to discriminate between genotoxins and non-genotoxins. Subsequent analysis for the false-positive compounds showed quercetin to be predicted as genotoxic and 8-hydroxyquinoline and 17-beta oestradiol as non-genotoxic. Our results support that transcriptomics analysis of compound effects in HepG2 leads to similar results with phenotypic analysis and provides additional mechanistic information. Therefore, combined evaluation of gene expression alterations and relevant functional end points using HepG2 cells may contribute to the better understanding of modes-of-action of chemicals and the correct evaluation of their genotoxic properties.
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PMID:Comparison of phenotypic and transcriptomic effects of false-positive genotoxins, true genotoxins and non-genotoxins using HepG2 cells. 2163 81