Parental exposure to TiO2 NPs promotes the multigenerational reproductive toxicity of Cd in Caenorhabditis elegans via bioaccumulation of Cd in germ cells

Abstract

Titanium dioxide nanoparticles (TiO₂ NPs) can modify the behavior and bioavailability of heavy metals in aquatic environments. However, the influence of TiO₂ NPs on the multigenerational impairments caused by heavy metals is largely unknown. This study revealed that parental exposure to TiO₂ NPs at a non-toxic concentration could increase the reproductive toxicity of Cd in both the Caenorhabditis elegans (C. elegans) parental generation and subsequent generations (F1, F2) cultured under pollutant-free conditions. TiO₂ NPs promoted the ingestion of Cd, and the lower pH environment in the gut accelerated the desorption of Cd from TiO₂ NPs, leading to enhanced Cd bioaccumulation, which was confirmed by the expression of metal responsive genes mtl-2, encoding metallothionein. Using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), an in situ imaging technology, we further found that Cd burden in the gonads and embryos was increased by concurrent exposure to TiO₂ NPs, indicating the potential transfer of Cd to the next generation through the germline. Our data provided new evidence that maternal exposure to TiO₂ NPs amplifies the multigenerational reproductive toxicity of Cd in C. elegans by promoting the accumulation of Cd in germ cells.