• A comparison of transgenic rodent mutation and in vivo comet assay responses for 91 chemicals.

      Kirkland, David; Levy, Dan D; LeBaron, Matthew J; Aardema, Marilyn J; Beevers, Carol; Bhalli, Javed; Douglas, George R; Escobar, Patricia A; Farabaugh, Christopher S; Guerard, Melanie; et al. (2019-03-01)
      A database of 91 chemicals with published data from both transgenic rodent mutation (TGR) and rodent comet assays has been compiled. The objective was to compare the sensitivity of the two assays for detecting genotoxicity. Critical aspects of study design and results were tabulated for each dataset. There were fewer datasets from rats than mice, particularly for the TGR assay, and therefore, results from both species were combined for further analysis. TGR and comet responses were compared in liver and bone marrow (the most commonly studied tissues), and in stomach and colon evaluated either separately or in combination with other GI tract segments. Overall positive, negative, or equivocal test results were assessed for each chemical across the tissues examined in the TGR and comet assays using two approaches: 1) overall calls based on weight of evidence (WoE) and expert judgement, and 2) curation of the data based on a priori acceptability criteria prior to deriving final tissue specific calls. Since the database contains a high prevalence of positive results, overall agreement between the assays was determined using statistics adjusted for prevalence (using AC1 and PABAK). These coefficients showed fair or moderate to good agreement for liver and the GI tract (predominantly stomach and colon data) using WoE, reduced agreement for stomach and colon evaluated separately using data curation, and poor or no agreement for bone marrow using both the WoE and data curation approaches. Confidence in these results is higher for liver than for the other tissues, for which there were less data. Our analysis finds that comet and TGR generally identify the same compounds (mainly potent mutagens) as genotoxic in liver, stomach and colon, but not in bone marrow. However, the current database content precluded drawing assay concordance conclusions for weak mutagens and non-DNA reactive chemicals.
    • Corrigendum to "Identifying germ cell mutagens using OECD test guideline 488 (transgenic rodent somatic and germ cell Gene mutation assays) and integration with somatic cell testing." [Mutat. Res. 832-833 (2018) 7-18].

      Marchetti, Francesco; Aardema, Marilyn J; Beevers, Carol; van Benthem, Jan; Godschalk, Roger; Williams, Andrew; Yauk, Carole L; Young, Robert; Douglas, George R (2019-08-01)
    • Corrigendum to "Simulation of mouse and rat spermatogenesis to inform genotoxicity testing using OECD test guideline 488" [Mutat. Res. 832-833 (2018) 19-28].

      Marchetti, Francesco; Aardema, Marilyn J; Beevers, Carol; van Benthem, Jan; Douglas, George R; Godschalk, Roger; Yauk, Carole L; Young, Robert; Williams, Andrew (2019-08-01)
    • Identifying germ cell mutagens using OECD test guideline 488 (transgenic rodent somatic and germ cell gene mutation assays) and integration with somatic cell testing

      Marchetti, Francesco; Aardema, Marilyn J.; Beevers, Carol; van Benthem, Jan; Godschalk, Roger; Williams, Andrew; Yauk, Carole L.; Young, Robert; Douglas, George R. (2018-08)
    • In vivo genotoxicity testing strategies: Report from the 7th International workshop on genotoxicity testing (IWGT).

      Kirkland, David; Uno, Yoshifumi; Luijten, Mirjam; Beevers, Carol; van Benthem, Jan; Burlinson, Brian; Dertinger, Stephen; Douglas, George R; Hamada, Shuichi; Horibata, Katsuyoshi; et al. (2019-11-01)
    • Progress towards an OECD reporting framework for transcriptomics and metabolomics in regulatory toxicology.

      Harrill, Joshua A; Viant, Mark R; Yauk, Carole L; Sachana, Magdalini; Gant, Timothy W; Auerbach, Scott S; Beger, Richard D; Bouhifd, Mounir; O'Brien, Jason; Burgoon, Lyle; et al. (2021-07-29)
    • Simulation of mouse and rat spermatogenesis to inform genotoxicity testing using OECD test guideline 488.

      Marchetti, Francesco; Aardema, Marilyn; Beevers, Carol; van Benthem, Jan; Douglas, George R; Godschalk, Roger; Yauk, Carole L; Young, Robert; Williams, Andrew (2018-08)
      The Organisation for Economic Co-operation and Development Test Guideline (TG) 488 for the transgenic rodent (TGR) mutation assay recommends two sampling times for assessing germ cell mutagenicity following the required 28-day exposure period: 28 + > 49 days for mouse sperm and 28 + >70 days for rat sperm from the cauda epididymis, or three days (i.e., 28 + 3d) for germ cells from seminiferous tubules (hereafter, tubule germ cells) plus caudal sperm for mouse and rat. Although the latter protocol is commonly used for mutagenicity testing in somatic tissues, it has several shortcomings for germ cell testing because it provides limited exposure of the proliferating phase of spermatogenesis when mutations are fixed in the transgene. Indeed, analysis of sperm at 28 + 3d has generated negative results with established germ cell mutagens, while the analysis of tubule germ cells has generated both positive and either negative or equivocal results. The Germ Cell workgroup of the Genetic Toxicology Technical Committee of the Health and Environmental Sciences Institute modelled mouse and rat spermatogenesis to better define the exposure history of the cell population collected from seminiferous tubules. The modelling showed that mouse tubule germ cells at 28 + 3d receive, as a whole, 42% of the total exposure during the proliferating phase. This percentage increases to 99% at 28 + 28d and reaches 100% at 28 + 30d. In the rat, these percentages are 22% and 80% at 28 + 3d and 28 + 28d, reaching 100% at 28 + 44d. These results show that analysis of tubule germ cells at 28 + 28d may be an effective protocol for assessing germ cell mutagenicity in mice and rats using TG 488. Since TG 488 recommends the 28 + 28d protocol for slow dividing somatic tissues, this appears to be a better compromise than 28 + 3d when slow dividing somatic tissues or germ cells are the critical tissues of interest.
    • Transcriptional profiling reveals gene expression changes associated with inflammation and cell proliferation following short-term inhalation exposure to copper oxide nanoparticles.

      Costa, Pedro M; Gosens, Ilse; Williams, Andrew; Farcal, Lucian; Pantano, Daniele; Brown, David M; Stone, Vicki; Cassee, Flemming R; Halappanavar, Sabina; Fadeel, Bengt (2018-03)
      Our recent studies revealed a dose-dependent proinflammatory response to copper oxide nanoparticles (CuO NPs) in rats following short-term inhalation exposure for five consecutive days. Here transcriptomics approaches were applied using the same model to assess global gene expression in lung tissues obtained 1 day post-exposure and after a recovery period of 22 days from rats exposed to clean air or 6 hour equivalent doses of 3.3 mg m-3(low dose) and 13.2 mg m-3(high dose). Microarray analyses yielded about 1000 differentially expressed genes in the high-dose group and 200 in low-dose compared to the clean air control group, and less than 20 after the recovery period. Pathway analysis indicated cell proliferation/survival and inflammation as the main processes triggered by exposure to CuO NPs. We did not find significant perturbations of pathways related to oxidative stress. Upregulation of epithelial cell transforming protein 2 (Ect2), a known oncogene, was noted and ECT2 protein was upregulated in the lungs of exposed animals. Proliferation of alveolar epithelial cells was demonstrated based on Ki67 expression. The gene encoding monocyte chemoattractant protein 1 (or CCL2) was also upregulated and this was confirmed by immunohistochemistry. However, no aberrant DNA methylation of inflammation-associated genes was observed. In conclusion, we have found that inhalation of CuO NPs in rats causes upregulation of the oncoprotein ECT2 and the chemokine CCL2 and other proinflammatory markers as well as proliferation in bronchoalveolar epithelium after a short-term inhalation exposure. Thus, pathways known to be associated with neoplastic processes and inflammation were affected in this model.