Titanium dioxide nanoparticle exposure alters metabolic homeostasis in a cell culture model of the intestinal epithelium and Drosophila melanogaster

Abstract

Nanosized titanium dioxide (TiO) is a common additive in food and cosmetic products. The goal of this study was to investigate if TiO nanoparticles affect intestinal epithelial tissues, normal intestinal function, or metabolic homeostasis using in vitro and in vivo methods. An in vitro model of intestinal epithelial tissue was created by seeding co-cultures of Caco-2 and HT29-MTX cells on a Transwell permeable support. These experiments were repeated with monolayers that had been cultured with the beneficial commensal bacteria Lactobacillus rhamnosus GG (L. rhamnosus). Glucose uptake and transport in the presence of TiO nanoparticles was assessed using fluorescent glucose analog 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG). When the cell monolayers were exposed to physiologically relevant doses of TiO, a statistically significant reduction in glucose transport was observed. These differences in glucose absorption were eliminated in the presence of beneficial bacteria. The decrease in glucose absorption was caused by damage to intestinal microvilli, which decreased the surface area available for absorption. Damage to microvilli was ameliorated in the presence of L. rhamnosus. Complimentary studies in Drosophila melanogaster showed that TiO ingestion resulted in decreased body size and glucose content. The results suggest that TiO nanoparticles alter glucose transport across the intestinal epithelium, and that TiO nanoparticle ingestion may have physiological consequences.

TiO2 Nanoparticles and Commensal Bacteria Alter Mucus Layer Thickness and Composition in a Gastrointestinal Tract Model

“…[7] Transmission electron microscopy analysis showed that TiO 2 NPs sizes were within manufacturer's range ( Table 1). [7,46] Briefly, primary sizes of TiO 2 were demonstrated to range between 20 and 40 nm, which was found to be consistent with manufacturer-reported values. The behavior of TiO 2 NPs in suspension was assessed through dynamic light scattering (DLS) using a Zetasizer Nano ZS90 (Malvern Panalytical, Ltd.).…”

“…[53,54] Previous studies with the identical TiO 2 particles, concentrations, and exposure times showed that exposure of L. rhamnosus to TiO 2 NPs did not result in a loss of bacterial viability. [46] Additionally, experiments performed with TiO 2 of different sizes (100% rutile 17 nm, and rutile/anatase mixture M [37 and 9 nm] and P25 [48 and 55 nm]) demonstrated that, independently of their size, NPs were toxic and resulted in a decrease of E. coli viability at concentrations above 10 ppm. [42,53] This bacteria toxicity in response to TiO 2 NPs could be a result of the adsorption of NPs to the bacterial surface due to a gap of surface charge, highly oxidative radicals inducing ROS, a potential penetration of smallest NPs or abundance of aggregates in NPs suspensions.…”

“…[43] Similarly, previous work has shown that TiO 2 NPs induce ROS in an in vitro intestinal model, and it is possible that any decrease observed in the thickness of the mucus following exposure to TiO 2 NPs is due to ROS. [7,46] There are difficulties in the evaluation of the effects of NPs on the gut in vivo due to differences in species and variability in mucus composition. Additional studies focusing on physicochemical properties of mucins and the microbiota will be needed to further look into and determine changes in mucus layer function caused by ROS.…”

“…TiO 2 NPs ranged from 332 ± 42 nm in water and 355 ± 70 nm in serum free DMEM which suggested the formation of aggregates in solution. [7,46] A tendency toward agglomeration was shown with the size of agglomerates increasing based on dispersant (polydispersity index [Pdi]: 0.34-0.49 in 18 MΩ water and 0.42-0.54 in DMEM). [7] The hydrodynamic diameter of digested TiO 2 NPs was 220.9 ± 44.8 nm in digested dispersants ( Table 1).…”

“…Bacterial Cultures: Caco-2/HT29-MTX and bacteria triculture methods have been described previously. [46] Lactobacillus rhamnosus GG:pMF440 and E. coli ATCC 11775, and E. coli 10798:pMF440 were inoculated and grown in brain heart infusion media (BHI, Becton, Dickinson, Sparks, MD) in glass tubes for 48 and 24 h, respectively. pMF440 is a broad host range plasmid containing the mCherry gene.…”