Nanoplastic at environmentally relevant concentrations activates a germline mir-240-rab-5 signaling cascade to affect the secreted ligands associated with transgenerational toxicity induction in C. elegans

Abstract

Epigenetic regulation plays an important role in regulating the transgenerational toxicity of pollutants. However, the underlying mechanism of microRNAs (miRNAs) in regulating transgenerational nanoplastic toxicity remains largely unclear. We aimed to determine the miRNA-mediated mechanism for the induction of transgenerational nanoplastic toxicity. In Caenorhabditis elegans, although germline RNAi of both mir-240 and mir-36 suppressed polystyrene nanoparticle (PS-NP) toxicity, exposure to PS-NPs (1–100 μg L⁻¹) only increased mir-240 expression. A transgenerational increase in mir-240 expression was observed after PS-NP exposure at P0 generation (P0-G), and the germline RNAi of mir-240 suppressed transgenerational PS-NP toxicity. Among the predicted target genes of mir-240 in the germline, the exposure to PS-NPs (1–100 μg L⁻¹) decreased rab-5 and rab-6.2 expressions, whereas the germline RNAi of mir-240 only increased rab-5 expression in PS-NP exposed nematodes. A transgenerational decrease in rab-5 expression was detected after PS-NP exposure at P0-G, and the germline RNAi of rab-5 strengthened transgenerational PS-NP toxicity. Moreover, the resistance of mir-240(RNAi) to transgenerational PS-NP toxicity in inhibiting locomotion behavior and in reducing the brood size was inhibited by the germline RNAi of rab-5. Among the secreted ligands, the germline RNAi of rab-5 increased the expressions of genes encoding insulin peptides (ins-3, ins-39, and daf-28), FGF ligand (egl-17), and ephrin ligand (efn-3) in PS-NP exposed nematodes and their corresponding receptor genes (daf-2, egl-15, and vab-1) in the offspring of PS-NP exposed nematodes. Therefore, an increase in germline mir-240 mediated transgenerational PS-NP toxicity through insulin, FGF, and ephrin signals by affecting its target RAB-5. Our data demonstrated the important involvement of germline microRNA in mediating nanoplastic toxicity across multiple generations in organisms.