Molecular Mechanism Of Intestinal Insulin And Canonical Wnt/?-catenin Signaling Pathways In Regulating The Response To Nanopolystyrene At Predicted Environmental Concentration In C. Elegans

In the recent years,the potential toxicity of nanoplastic particles on organisms has received the great attentions.The predicted environmentally relevant concentrations of nanoplastic particles are in the range of 1 ? ?g/L.Nevertheless,the response of organisms to nanoplastic particles at environmentally relevant concentrations and the underlying mechanisms are still largely unclear.In C.elegans,insulin signaling is involved in the control of many important biological events,including the regulation of stress response.In organisms,canonical Wnt/?-catenin signaling is evolutionarily conserved with many important biological functions.This study aimed to employ a modified prolonged exposure assay system(from L1-larvae to adult day-1)to investigate the molecular mechanisms of insulin signaling and canonical Wnt/?-catenin signaling in regulating the response to nanopolystyrene at predicted environmental concentration in nematodes.Exposure to nanopolystyrene particles(1 ?g/ L)significantly decreased expressions of daf-2 encoding an insulin receptor,age-1 encoding a PI3 K,and akt-1 encoding an Akt/PKB,and increased expression of daf-16 encoding a FOXO transcriptional factor in insulin signaling pathway.Among these genes,mutation of daf-2,age-1,or akt-1 induced a resistance to toxicity of nanopolystyrene,whereas mutation of daf-16 induced a susceptibility to the toxicity of nanopolystyrene.The insulin signaling pathway acted in intestinal cells to regulate the response to nanopolystyrene.Moreover,sod-3 encoding a manganese superoxide dismutase,mtl-1 encoding a metallothionein,and gpd-2 encoding a glyceraldehyde-3-phosphate dehydrogenase were identified as downstream targeted genes for intestinal daf-16 in the regulation of response to nanopolystyrene.Exposure to nanopolystyrene particles(1 ?g/L)decreased the gsk-3 expression and increased the bar-1 and pop-1 expressions in canonical Wnt/?-catenin signaling pathway.Mutation of bar-1 or pop-1 induced a susceptibility to the toxicity of nanopolystyrene,whereas mutation of gsk-3 induced a resistance to the toxicity of nanopolystyrene.GSK-3 acted upstream of BAR-1 to regulate the response to nanopolystyrene.The canonical Wnt/?-catenin signaling pathway acted in intestinal cells to regulate the response to nanopolystyrene.We identified the FOXO transcriptional factor DAF-16 and peroxisomal protein PRX-5 as the downstream targets of intestinal BAR-1 and POP-1 in regulating the response to nanopolystyrene.During the control of response to nanopolystyrene,DAF-16 and PRX-5 functioned synergistically,suggesting that the intestinal canonical Wnt/?-catenin signaling mediates two different molecular signals to regulate the response to nanopolystyrene.Therefore,an intestinal signaling cascade of DAF-2-AGE-1-AKT-1-DAF-16-SOD-3/MTL-1/GPD-2 was raised in the insulin signaling pathway for nematodes in response to nanopolystyrene at predicted environmental concentration.An intestinal signaling cascade of GSK-3-BAR-1-POP-1-DAF-16/PRX-5 was raised in the canonical Wnt/?-catenin signaling pathway for nematodes in response to nanopolystyrene at predicted environmental concentration.Our results indicate the crucial function of intestinal insulin signaling and intestinal canonical Wnt/?-catenin signaling in modulating the response of nematodes to nanopolystyrene at predicted environmental concentration.