Reproductive toxicities of dimethyl phthalates on Caenorhabditis elegans with alteration in responses over life stages

Phthalate esters (PAEs) raised serious concerns on their health risk due to their toxicities. However, toxicities of low-molecular-weight PAEs, for example, dimethyl phthalates (DMPs), remained poorly investigated. In the present study, the reproductive toxicities of dimethyl (o-)phthalate (DMOP), dimethyl (p-)phthalate (DMPP), and dimethyl (m-)phthalate (DMMP) were measured on Caenorhabditis elegans with mechanical exploration. Results showed that DMPP, DMOP, and DMMP commonly inhibited the total reproduction while stimulated lifespan, showing trade-off effects. In effects on gene expressions, DMPP, DMOP, and DMMP caused different regulations on the expressions of vab-1, ceh-18, and gsa-1 which are involved in oocyte growth, ovulation, and maturation. Meanwhile, they commonly downregulated those of rme-2 and rcy-4 that regulate germ cells and gonads and lipid metabolism in oocytes. Moreover, the effects on biochemicals that regulate reproductive processes showed alteration between stimulation and inhibition over life stages. In addition, effects at apical, biochemical, and molecular levels clearly showed the structure influences on the toxicities. Summing up, reproductive toxicities of DMPs depended on the exposure life stages and also the chemical structures.