Enhanced toxic effects of photoaged microplastics on the trophoblast cells

Microplastics (MPs) are emerging as a novel pollutant, raising significant concerns regarding their adverse effects on human health. Furthermore, MPs are susceptible to light-induced aging in the environment, which alters their physical characteristics and potentially alters their toxic effects. While previous studies have documented the retention of MPs in the placenta, the specific impacts of MPs, particularly aged MPs, on placental function remain poorly understood. In the current study, we utilized 1 µm polystyrene microplastics (PS-MPs), a widely used model for MPs, to evaluate the effects of photoaged MPs on the placenta. Following oral administration of PS-MPs beginning on embryonic day 3.5 (E3.5), we observed impaired fetal growth and damage to the placental labyrinth chorionic layer in the treated pregnant mice by embryonic day 13.5 (E13.5). The photoaged PS-MPs were generated by exposure to simulated lighting for 7 or 14 days, resulting in alterations to their physical properties. Notably, enhanced cytotoxicity in trophoblast cells was observed for photoaged PS-MPs compared to pristine PS-MPs. Mechanistically, the altered physical properties of PS-MPs, along with elevated lipid peroxidation, may contribute to the increased cytotoxicity of the photoaged MPs. Our findings provide new insights into the detrimental effects and underlying mechanisms of both MPs and, in particular, aged MPs on the placenta and embryonic development. These insights are crucial for assessing the risks posed by MPs to human pregnancy.