Exposure of zebrafish (Danio rerio) to trans-2-hexenal induces oxidative stress and protein degeneration of the gill

Abstract

Trans-2-hexenal (T2H) has great commercial value for development as a biopesticide, but its toxicity risk to nontarget organisms is unknown. Here, the toxicity and underlying mechanism of T2H on zebrafish (Danio rerio) were investigated. The LC₅₀ (48 h) of T2H on zebrafish is 4.316 μg/mL, and the aldehyde group is essential to its toxicity. In 14-day chronic toxicity tests, 0.432 μg/mL T2H resulted in a higher mortality of zebrafish than the control group. Furthermore, the sensitivity of zebrafish to different administration methods was gill administration>oral administration>transdermal administration>intravenous injection. T2H induced significant cell death and ROS generation in zebrafish gill cells in a concentration-dependent manner. After treatment with 4.316 μg/mL T2H, the expression of oxidative stress-related genes (nrf2, gstp1, keap1b, sod1 and sod2) and the content of malondialdehyde (MDA) were up-regulated. Incubation with T2H caused an immediate denaturation of gill protein, which was aggravated with increasing dose of T2H. We also found that T2H at 21.225 mg/mL significantly reduced the in vitro activity of succinate dehydrogenase (SDH). Among the three amino acids tested, T2H was only found to react with methionine and glycine to form adducts, which may be the basis of the protein denaturation. This study confirmed that T2H could induce oxidative stress and protein denaturation in zebrafish gills, providing important information for risk assessment of T2H exposure.

Keywords: Adult zebrafish; Gill; Oxidative stress; Protein degeneration; Trans-2-hexenal.