Adverse outcome pathways

Assessment on the adverse effects on different kinds of fish induced by methamphetamine during the natural attenuation process based on adverse outcome pathway

The adverse effects on model fish induced by methamphetamine (METH) have been revealed. However, the toxicity of METH on different kinds of non-model fish during the natural attenuation remained unclear. Hence, in this study, we for the first time established a static lab-scale aquatic ecosystem spiked with METH (initial levels at 25 μg/L) for 40 days to estimate its metabolism and toxicity in Chinese medaka, rosy bitterling, loach, and mosquito fish. The concentrations of METH in water and fish's brain were detected termly. The physiological functions, histopathology of brain, neurotransmitters contents, and expressions of associated genes of the four kinds of fish were determined at day 0, 20, and 40, respectively. The results indicated METH could be remarkably accumulated in fish brains with the distribution factor vs water (DFw) at 232.5-folds, and attenuated both in water and fish body during the exposure. METH caused physiological functions (i.e., swimming trajectories, locomotion distances, and feeding rates) disorders of the four kinds of fish, and stimulated surfacing behavior of loach. Tissue and macro/micromolecular biomarkers including histopathology, neurotransmitters (i.e., dopamine, serotonin, and norepinephrine), and mRNA, were similarly affected by METH. Mitogen-activated protein kinase (MAPKs) signaling pathway, P53-regulated apoptosis signaling pathway, N-methyl-d-aspartate-dopamine system, and mTOR signaling pathway of different kinds of fish were regulated by METH. Additionally, the impairments of the physiological and macromolecular indicators of fish could be alleviated as the natural attenuation of METH occurred. All the biomarkers, as well as the recovery effects during the exposure were integrated onto an adverse outcome pathway (AOP) framework. The key event was the micromolecular indicators (genes). The adverse outcomes at individual and population levels would result in the ecological consequences, implying the imperative to consider the natural attenuation process while assessing the environmental risk of METH.

Targets and mechanisms of chemically induced aneuploidy. Part 1 of the report of the 2017 IWGT workgroup on assessing the risk of aneugens for carcinogenesis and hereditary diseases

An aneuploidy workgroup was established as part of the 7th International Workshops on Genotoxicity Testing. The workgroup conducted a review of the scientific literature on the biological mechanisms of aneuploidy in mammalian cells and methods used to detect chemical aneugens. In addition, the current regulatory framework was discussed, with the objective to arrive at consensus statements on the ramifications of exposure to chemical aneugens for human health risk assessment. As part of these efforts, the workgroup explored the use of adverse outcome pathways (AOPs) to document mechanisms of chemically induced aneuploidy in mammalian somatic cells. The group worked on two molecular initiating events (MIEs), tubulin binding and binding to the catalytic domain of aurora kinase B, which result in several adverse outcomes, including aneuploidy. The workgroup agreed that the AOP framework provides a useful approach to link evidence for MIEs with aneuploidy on a cellular level. The evidence linking chemically induced aneuploidy with carcinogenicity and hereditary disease was also reviewed and is presented in two companion papers. In addition, the group came to the consensus that the current regulatory test batteries, while not ideal, are sufficient for the identification of aneugens and human risk assessment. While it is obvious that there are many different MIEs that could lead to the induction of aneuploidy, the most commonly observed mechanisms involving chemical aneugens are related to tubulin binding and, to a lesser extent, inhibition of mitotic kinases. The comprehensive review presented here should help with the identification and risk management of aneugenic agents.

Screening Strategies and Methods for Better Off-Target Liability Prediction and Identification of Small-Molecule Pharmaceuticals

Pharmaceutical discovery and development is a long and expensive process that, unfortunately, still results in a low success rate, with drug safety continuing to be a major impedance. Improved safety screening strategies and methods are needed to more effectively fill this critical gap. Recent advances in informatics are now making it possible to manage bigger data sets and integrate multiple sources of screening data in a manner that can potentially improve the selection of higher-quality drug candidates. Integrated screening paradigms have become the norm in Pharma, both in discovery screening and in the identification of off-target toxicity mechanisms during later-stage development. Furthermore, advances in computational methods are making in silico screens more relevant and suggest that they may represent a feasible option for augmenting the current screening paradigm. This paper outlines several fundamental methods of the current drug screening processes across Pharma and emerging techniques/technologies that promise to improve molecule selection. In addition, the authors discuss integrated screening strategies and provide examples of advanced screening paradigms.