Crucial role of intestinal barrier in the formation of transgenerational toxicity in quantum dot exposed nematodes Caenorhabditis elegans

Abstract

Previous studies have demonstrated that long-term exposure to quantum dots (QDs) causes adverse effects on organisms. However, the possible transgenerational toxicity of QDs and the underlying mechanisms are still largely unclear. In the present study, we employed Caenorhabditis elegans as an in vivo toxicity assessment assay system. With the aid of locomotion behavior and intestinal reactive oxygen species (ROS) production as endpoints, we found that exposure to CdTe QDs (2.5–20 mg L⁻¹) caused the formation of transgenerational toxicity in nematodes. In nematodes with the transgenerational toxicity of CdTe QDs, we observed that, besides the pharynx and intestine, CdTe QDs could also be accumulated in reproductive organs such as the gonad and embryos of the exposed animals. Moreover, ZnS coating could reduce the toxicity of CdTe QDs by maintaining the normal function of the intestinal barrier, suggesting the crucial role of the intestinal barrier against transgenerational toxicity of CdTe QDs. For the molecular mechanisms of the observed transgenerational toxicity of CdTe QDs, our results suggest that clk-1, isp-1, and daf-2 might positively regulate the formation of transgenerational toxicity in CdTe QD exposed nematodes. Mutation or intestine-specific RNAi of clk-1, isp-1, or daf-2 genes caused the formation of a resistant property of the nematodes to transgenerational toxicity of CdTe QDs, and prevented the translocation of CdTe QDs from the exposed nematodes to their progeny. Our data will provide insight to the transgenerational behavior of engineered nanomaterials and the possible underlying mechanisms in organisms.