MicroRNA biomarkers for chemical hazard screening identified by RNA deep sequencing analysis in mouse embryonic stem cells

Epigenetic alterations induced by genotoxic occupational and environmental human chemical carcinogens: An update of a systematic literature review

Epigenetic alterations, such as changes in DNA methylation, histones/chromatin structure, nucleosome positioning, and expression of non-coding RNAs, are recognized among key characteristics of carcinogens; they may occur independently or concomitantly with genotoxic effects. While data on genotoxicity are collected through standardized guideline tests, data collected on epigenetic effects is far less uniform. In 2016, we conducted a systematic review of published studies of genotoxic carcinogens that reported epigenetic endpoints to better understand the evidence for epigenetic alterations of human carcinogens, and the potential association with genotoxic endpoints. Since then, the number of studies of epigenetic effects of chemicals has nearly doubled. This review stands as an update on epigenetic alterations induced by occupational and environmental human carcinogens that were previously and recently classified as Group 1 by the International Agency for Research on Cancer. We found that the evidence of epigenetic effects remains uneven across agents. Studies of DNA methylation are most abundant, while reports concerning effects on non-coding RNA have increased over the past 5 years. By contrast, mechanistic toxicology studies of histone modifications and chromatin state alterations remain few. We found that most publications of epigenetic effects of carcinogens were studies in exposed humans or human cells. Studies in rodents represent the second most common species used for epigenetic studies in toxicology, in vivo exposures being the most predominant. Future studies should incorporate dose- and time-dependent study designs and also investigate the persistence of effects following cessation of exposure, considering the dynamic nature of most epigenetic alterations.

Spectroscopic Investigation of Increased Fluorescent Intensity of Fluorescent Dyes When Adsorbed onto Polystyrene Microparticles

Microplastics as environmental pollutants are increasingly a source of alarm. The characterization of microplastics will be necessary to discriminate microplastics from other types of particles. To discriminate specific microplastics, plastic-adsorbable fluorescent dyes are used, the stained microplastics are separated from the dye-microplastic mixture by filtration, and the type of fluorescent staining of the microplastics is analyzed by fluorescent microscopy. In this study, to realize the in situ analysis of fluorescent staining, i.e., to discriminate microplastics without any separation or filtration processes, we studied the change in the fluorescent properties after adsorption of the fluorescent dyes to the microplastic particle surfaces using a 3D excitation emission matrix fluorescence spectroscopy (the excitation wavelength-dependent emission spectrum). We used three fluorescent dyes: Fluorescein, Rhodamine 6G, and Methylene Blue, and polystyrene microparticles as our model microplastic. Fluorescein and Methylene Blue showed increases in the fluorescent intensity, while Rhodamine 6G showed negligible intensity changes. This is likely due to the degree of affinity of the dyes to the polystyrene particle surface, the structural stability of the dyes on the surface, and the changes in the environment around the dyes after the adsorption of each dye to the surface. We conclude that we have demonstrated the potential to look for appropriate fluorescent dyes using the method studied here to identify and estimate individual plastic materials.