Cellular effects of Titanium Dioxide Nanoparticles in the intestine

Rolo, Dora; Pereira, Joana F.S.; Matos, Paulo; Gonçalves, Lídia; Bettencourt, Ana Francisca; Jordan, Peter; Silva, Maria João; Louro, Henriqueta

http://hdl.handle.net/10400.18/7843

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Authors

Bettencourt, Ana Francisca

Jordan, Peter

Silva, Maria João

Louro, Henriqueta

Abstract(s)

Introduction: The increased use of titanium dioxide nanoparticles (TiO2-NPs) as a food additive demands a thorough assessment of their potential risk for human health. Via oral exposure they may lead to adverse local or systemic outcomes, and few studies have focused on the cellular internalization mechanisms (endocytosis) of TiO2-NPs. The objective was to analyze the mechanisms by which TiO2-NPs (NM-102, NM-103 and NM-105, JRC repository) translocate by the intestinal epithelium layer, using monolayers of human intestinal cell lines (Caco-2 and HT29-MTX), as well as polarized Caco-2 cells, and co-cultures of both cells. Results: We evaluated cell differentiation by transepithelial resistance measurements and the translocation of TiO2-NPs tagged with alizarin through the intestinal barrier by confocal microscopy and we confirmed the internalization of the TiO2-NPs in both cell line models. Co-localization studies suggested that the smallest TiO2-NPs were internalized into EEA1-positive early-endosomes and accumulate in late endosomes (Rab7), with only a small fraction following the degradative pathway to the lysosome (LAMP1). This suggested that at least part of the TiO2-NPs could be redirected to the secretory pathway. Consistently, we detected fluorescence passing from the apical (AP) to the basolateral (BL) chamber, depending on the characteristics of cell model and TiO2-NPs tested. Conclusions: Small TiO2-NPs were endocytosed by Caco-2 cells, with an increase in particle diameter suggesting intracellular aggregation, whereas larger agglomerates deposited mainly extracellularly. Following endocytosis, TiO2 NPs were trafficked through different intracellular compartments including early and late endosomes/endo-lysosomes, with part being subjected to AP to BL transport.

Summary: TiO2-NPs may be translocated across the intestinal epithelium layer; This study contributes to a better mechanistic understanding of in vitro TiO2-NPs kinetics as well as their potential fate and effects on humans; It is expected that such an approach will reduce uncertainties in the hazard assessment of ingested TiO2-NPs for human health.