Figure 2
Impact of TiO 2 -NPs on in vitro gut epithelia transport function and integrity. Transport functions of Caco-2 cells (A) or Caco-2/HT29-MTX coculture (B) exposed to 50 μg/mL TiO2-NPs for 48 h (TiO2-NP) or not exposed (Control). Paracellular transport is probed by FITC-Dextran 4 kDa (FD4) and 14C-sucrose (sucr.) fluxes; the activity of the P-gP is probed by 14C-vinblastin apical to basolateral (vin. A) or basolateral to apical (vin. B) fluxes. Papp is the permeability coefficient, calculated as Papp = dQ/(dt × A × C0) where dQ/dt is the amount of labelled compound transported per time unit; A is the surface of the transwell and C0 is the initial concentration in the donor compartment. Transepithelial resistance (TEER) of Caco-2 cells and Caco-2/HT29-MTX coculture exposed for 0 h, 6 h, 24 h or 48 h to 50 μg/mL of TiO2-NPs (C). Relative expression of genes encoding proteins involved in cell junction maintenance, measured in cells exposed to 50 μg/mL of TiO2-NPs for 6 h or 48 h (D). Immunstaining of the nucleus (DAPI) and ZO-1 (TJP1) protein distribution in Caco-2 cells either non exposed (Ctl) or exposed to 50 μg/mL TiO2-NPs for 48 h (E). Results are the average of three replicates ± standard deviation; they were considered statistically significant (*) when p < 0.05 (A-C). Statistical significance of qPCR data (D) was examined by randomization tests using REST2009 [37].