ORIGINAL ABSTRACT

Environmental contaminants such as polystyrene nanoplastics (PSNPs, 1-1000 nm) and glyphosate pose significant environmental and public health risks. This study aimed to investigate the intestinal toxicity and molecular mechanisms induced by PSNPs and/or glyphosate. Mice were exposed to PSNPs (<100 nm), glyphosate, or a combination of both for 35 days via intragastric administration (PSNPs: 0.5 mg/d; glyphosate: 50 mg/kg-bw/day; PSNPs + glyphosate: 0.5 mg/d +50 mg/kg-bw/day). The control group received same volume of distilled water. Our findings revealed that exposure to PSNPs and/or glyphosate aggravated pathological alterations, including inflammatory cell infiltration, severe mitochondrial cristae fracture, and an approximately 50 % reduction in goblet cells in the intestine. Moreover, exposure to PSNPs and/or glyphosate caused a critical 75 % inhibition of FOXP3 and dissociation of tight junctions in the intestine (reflected by a 50 % decrease in Occludin, and a 20 %-50 % decrease in ZO-1). These changes were accompanied by significant alterations in beneficial gut microbiota, metabolic profiles, bile acid metabolism disorders, and a pronounced elevation in 3-β-deoxycholic acid, a metabolite tied to bile acid receptor signaling and barrier dysfunction. Although exposure to glyphosate led to the most significant upregulation of the pro-inflammatory factors TNF-α and the pro-apoptosis proteins Cleave-caspase-3, co-exposure did not exacerbate cell apoptosis in animal tissue experiments, which is contrasts with the cell-based findings. MODE-K (mouse intestinal epithelial) cells were treated with PSNPs (0.75 mg/mL) or glyphosate (0.5 mg/mL). In vitro experiments showed that PSNPs aggravated the disrupted Treg/Th17 immune-inflammatory balance, impaired intestinal barrier function (with a 50 % reduction in ZO-1 and Occludin), and increased cell apoptosis, caused by glyphosate. This study advances our understanding of the health risks posed by endocrine-disrupting chemical mixtures and provides critical insights into the molecular mechanisms of PSNP-glyphosate-induced intestinal toxicity. These findings lay the groundwork for future research aimed at mitigating the pathophysiological impacts of environmental pollutants.