Microbial colonization of microplastics in wastewater accelerates the aging process associated with oxidative stress and the insulin/IGF1 signaling pathway

Abstract

Although polystyrene (PS)-induced toxicity in organisms has been documented, adverse effects on lifespan and molecular mechanisms underlying microbial colonization of PS remain elusive. Herein, physicochemical properties of biofilm-developed PS (B-PS) incubated in wastewater were altered compared with virgin PS (V-PS). Bacterial community adherence to the B-PS surface were also impacted. Acute exposure to V-PS (100 μg/L) and B-PS (10 μg/L) significantly altered the mean lifespan and lipofuscin accumulation of Caenorhabditis elegans, suggesting that B-PS exposure at environmentally relevant concentrations could more severely accelerate the aging process than V-PS. Generation of ROS, gst-4::GFP expression, and oxidative stress-related gene expression were significantly altered following B-PS exposure. Moreover, B-PS exposure increased the nucleus-cytoplasm translocation of DAF-16 and altered the expression of genes encoding the insulin/IGF1 signaling (IIS) pathway. Compared with wild-type nematodes, the daf-16 mutation markedly enhanced lipofuscin accumulation and reduced mean lifespan, whereas daf-2, age-1, pdk-1, and akt-1 mutants could recover lipofuscin accumulation and mean lifespan. Accordingly, B-PS exposure accelerated the aging process associated with oxidative stress and the IIS pathway, and the DAF-2-AGE-1-PDK-1-AKT-1-DAF-16 signaling cascade may play a critical role in regulating the lifespan of C. elegans. This study provides new insights into the potential risks associated with microbial colonization of microplastics.