Location: Plant, Soil and Nutrition Research
Project Number: 8062-52000-003-005-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2018
End Date: Jul 31, 2020
Objective:
The proposed work will generate the first controlled model for quantitatively assessing epithelial-microbiota-nanoparticle interactions. The specific objectives are:
1. Identify GI function affected by bacterial and nanoparticle exposure. We will introduce individual strains of commensal or opportunistic bacteria (Lactobacillus rhamnosus GG, Bifidobacterium bifidum VPI 1124, Streptococcus salivarius strain SS2, and Enterococcus faecalis NCTC 775) into our in vitro GI tract model. We will identify how molecular (gene, protein expression), functional (nutrient absorption, enzyme activity), and structural (microvilli, tight junctions, mucus layer) epithelial characteristics and microbial viability and genotoxicity are affected by acute and chronic nanoparticle exposure. We will text AnO and MgO (+2 oxidation state), Fe2 O3 and Al2O3 (+3 oxidation state), and TiO2 and SiO2 (+4 oxidation state) nanoparticles at physiologically realistic doses, both digested and within a food matrix. We will analyze nanomaterials following microbe interactions to determine if and how they are detoxified by microorganisms.
2. Engineer a mock community of upper GI bacteria. We will create a mock community of upper GI bacteria composed of L. rhamnosus, B. bifidum, S. salivarius, and E. faecalis; incorporate that community into our GI tract in vitro model; and determine the effects of acute or chronic metal oxide nanoparticle exposure on microbial community dynamics and epithelial cell properties under both static and fluidic conditions.
3. Validate in vitro results with an in vivo animal model. We will use a broiler chicken model (Gallus gallus), which is an established and robust method for quantifying nutrient bioavailability and microbiome alterations (9-13), to validate in vitro results. We will screen for NP-GI function or NP-microbiome interactions with an in ovo model, which will direct in vivo adult studies on nutrient absorption and microbiome composition.
Approach:
Overall well-being is related to gut health and function. The gastrointestinal (GI) tract serves as a significant interface between the body and the external environment and has hundreds of square meters that are needed for nutrient absorption, but must also be defended from external threats. Microorganisms that form a largely symbiotic relationship with host cells colonize the GI tract and comprise the resident human microbiota(1). A healthy gut microbiome is critical to regulating metabolism, promoting immune function, and eliminating xenobiotics, and changes in the number or composition of microbes may lead to pathophysiologic conditions. The average American consumes 10-12 – 10-14 engineered nanoparticles per day (2-4), primarily as metal oxide nanoparticles used in processed foods and food packaging. The effects of nanoparticles on GI health and function are not well understood.
We have developed a cell culture model of the GI tract and a panel of functional assays for investigating nutrient absorption that includes digestion, a mucus layer, multiple physiologically relevant human cell types, and has been validated in vivo(5-7). Our data shows that dietary doses of pristine metal oxide nanoparticles decrease mineral, glucose, and lipid absorption. These decreases in absorption are due to nanoparticle-induced alterations in microvilli structure(8). The presence of a single species of beneficial bacteria in the cell culture model prevents changes in nutrient absorption following exposure to nanoparticles, and early results suggest that nanoparticle reactivity with biological components is related to metal oxidation state. Preliminary data with our animal model of nutrient absorption and microbiome composition shows that chick embryos exposed to metal oxide nanomaterials in ovo had a significant increase in cecum to body weight ratio at hatching. Furthermore, an analysis of the cecum contents showed a significant increase in beneficial bacteria in chicks fed metal oxide nanomaterials, suggesting a potential protective mechanism. To date, the relationship between metal oxide nanoparticle ingestion, gut microbial populations, and intestinal function has yet to be fully established. This constitutes the premise of our work, where the ultimate goal is to determine if and how ingested metal oxide nanoparticles alter microorganism populations and intestinal function. We seek to fill this knowledge gap by building on our previous findings showing that pristine metal oxide nanomaterials affect intestinal function in vitro and microbial populations in vivo. We will test the following hypotheses:
a) The microbiota can detoxify ingested metal oxide nanomaterials (RWHC).
b) High doses or chronic exposure to metal oxide nanomaterials can induce small intestinal dysbiosis, alter intestinal epithelial structure, and result in decreased barrier properties and nutrient absorption (BU).
