Cytotoxic impacts of treated electroplating industrial effluent and the comparative effect of their metal components (Zn, Hg, and Zn+Hg) on Danio rerio gill (DrG) cell line

Abstract

Effluent produced during the electroplating process can contain high concentrations of heavy metals that can enter the environment and induce toxicity to aquatic organisms. Relatively high concentrations of zinc (Zn) and mercury (Hg) have been detected in treated electroplating industrial effluent (TEPIE), though the cytotoxic potential of these compounds has not been well assessed in fish gills. A novel cell line, Danio rerio gill (DrG), were exposed to TEPIE and concentrations of Zn, Hg, and Zn + Hg previously measured in treated effluent to evaluate the use of the DrG cell line following exposure to environmental pollutants. Several cytotoxic assays were employed to assess the effect of TEPIE, Zn, and Hg on this cell line. The percent cell viability was significantly reduced in a concentration-dependent manner following exposure to TEPIE, Zn, Hg, and Zn + Hg (p < 0.05) for 24 h, with additional morphological changes observed in exposure treatments relative to controls. Additionally, there was a significant induction of DNA damage detected in all exposure treatments determined through comet assay tail length. An increase in intracellular ROS generation was also observed in cells exposed to TEPIE, Zn, Hg, and Zn + Hg, corresponding to dose-dependent increases in apoptosis. Our study confirmed that TEPIE and the metals present in it induced cytotoxicity in the DrG cell line, demonstrating its usefulness as a model to explore relationships between pollutants and fish gills.