Intestinal uptake, translocation, biodistribution, and toxicity of ingested environmentally relevant micro-nanoplastics (MNPs) and the role of inflammation using advanced cellular and in vivo models

EXECUTIVE SUMMARY/ABSTRACT After decades of increasing production of and reliance upon plastic materials, six billion metric tons of plastic waste has been deposited in our environment. Through environmental, commercial, and municipal degradation processes all plastics are eventually fragmented into micro-nanometer scale plastic particles and

fibers known as micro-nanoplastics (MNPs). Consequently, MNPs have become a nearly ubiquitous contaminant of our environment and food web, to the extent that concentrations of MNPs in meat, dairy, seafood, and grains range from 10 to over 3,000 µg/mL. Yet little is known about the hazards of MNP ingestion

exposures. A major concern is the ability of ingested MNPs, demonstrated by a growing number of studies, to reach the circulation and breach biological barriers to enter virtually any tissue. They have been found in human blood (at up to 13 µg/mL), colectomy samples, and placenta, and a recent study in our lab showed that

MNPs ingested by pregnant rats reach the livers, hearts, lungs, kidneys, and brains of fetal pups within 24 hours. Yet the impacts of MNP ingestion on human health, including absorption, biodistribution, toxicity, and inflammation remain unclear, constituting major knowledge gaps that impede any science-based risk

assessment of this emerging contaminant. To address these knowledge gaps, the proposed project, comprising three interconnected aims, will assess toxicity, uptake, and biodistribution of environmentally relevant MNPs, and the roles of MNP properties and intestinal inflammation in each. In Aim 1 we will develop and fully characterize 5 environmentally relevant

gold core – plastic shell MNPs of three major plastic polymers (polyethylene, polyethylene terephthalate, and polystyrene). The pristine core-shell MNPs will be photo-aged to simulate decades of environmental exposures. The Au cores will enable accurate quantification of MNPs in cells and tissues, and intracellular

localization in Aims 2 and 3. In Aim 2 we will use a triculture small intestinal epithelium model and an “intestine- on-chip” (IOC) model with organoids from both healthy donors and donors with inflammatory bowel disease (IBD) coupled with simulated digestions to determine the role of iMNP physicochemical properties in iMNP

toxicity, inflammation, uptake, and translocation, and the role of inflammation in iMNP uptake and toxicity. Specific molecular inhibitors and siRNA silencing will also be used to determine the cellular mechanisms involved in MNP translocation. In Aim 3 we will assess in vivo MNP uptake, toxicity, biodistribution, and the role

of inflammation in each, in healthy and IBD-susceptible intestinal Hnf4a knockout mice. These studies will provide validation and translational assessment of in vitro approaches as well as detailed data on iMNP organ and tissue biodistribution. The data generated from these studies will allow health risk assessors and policymakers to assess the

potential risks of iMNP exposures and provide the basis for future mechanistic and epidemiological studies.