Gut-Mediated Systemic Toxicity of Micro- and Nanoplastics: Nanoscale Biointerface Properties, Microbiota-Metabolite...

Microplastics and nanoplastics (MNPs) have been recognized as ubiquitous emerging global pollutants, which are extensively detectable in diverse environmental media and food matrices. Increasing evidence indicates that the intestine is a primary target of orally ingested MNPs and a critical initiating hub for systemic toxicity. Once ingested orally, MNPs can interact with the intestinal mucus layer and epithelial barrier, induce gut microbiota dysbiosis, remodel bile acid and short-chain fatty acid metabolism, and activate oxidative stress, inflammation, apoptosis, and immune imbalance. These gut-derived disturbances may subsequently propagate adverse signals to distal organs through the gut-liver, gut-brain, gut-kidney, gut-lung, gut-reproductive, and gut-mammary axes. Intestinal barrier dysfunction, endotoxin translocation, abnormal microbial metabolites, and microbiota-derived immune signals constitute common mediating pathways linking local intestinal injury to multi-organ toxicity. In addition, smaller particle size, surface oxidation, environmental aging, bio-corona/plastisphere formation, and co-exposure with other contaminants can further modulate the intensity and specificity of gut-organ axis disruption. Prior reviews are limited to separate analyses of single-organ toxicity or isolated gut-organ pathways. To fill this gap, this work synthesizes contemporary mechanistic and experimental evidence to establish a gut-initiated systemic toxicology framework for MNPs. We differentiate direct particle translocation from gut-derived indirect signaling, evaluate the varying robustness of supporting evidence for each gut-organ axis, and underscore nanoscale biointerface properties as key modulators of MNPs systemic toxic potency.