Metal contamination, bioaccumulation, ROS generation, and epigenotoxicity influences on zebrafish exposed to river water polluted by mining activities

Highlights: • Surface water from Le'an river were polluted heavily with trace metals. • Cadmium was bioaccumulated in liver and gill of zebrafish. • Elevation of activities of ROS, GSH-Px, and CAT were observed. • Abnormalities in global and gene-specific methylation status occur. • Dysregulated expression of gadd, c-jun, bax, p53 and rad51 genes in liver and gill were observed. Epigenetic mechanisms are important for gene expression regulation, which is closely related to human health, and epigenetic effects of polluted water bodies have gained increasing research attention. Le'an River suffers from severe trace metal pollution owing to mining activities. In this study, zebrafish was used as a biological model to study pollution of Le'an River after seven consecutive days of exposure. The results showed that midstream and downstream sections of the river were seriously polluted by trace metals. The liver and gill of zebrafish were enriched with trace metals, and cadmium had the highest bioaccumulation factor. Trace metals caused oxidative stress in zebrafish cells, with increases in reactive oxygen species levels. Significant increase of global DNA methylation in liver of middle and downstream section were observed, with values from 125.67% to 165.45% compared with control. Changes in DNA methylation in the promoter region cause significant increase or decrease of the expression of repair genes and apoptosis genes in liver and gill. In summary, Le'an River water exhibited significant epigenetic effects, and it is necessary to consider epigenetic effects in the evaluation of pollution and health risks of river water.