Effects of CuO nanoparticles on an in vitro model of intestinal barrier

The rapid growth in development and use of nanotechnological products increases the likelihood of human exposure to nanoparticles (NPs). Thus, this study aimed to investigate the effects of CuO NPs on the intestinal barrier using Caco-2 cells. CuO NPs were synthesized by sonochemistry and fully characterized by HRTEM, XRD, TCA and ICP-MS. Caco-2 cells were cultured on semi-permeable inserts and, after differentiation, treated for 24 h with CuO NPs (10 μg/ml, 50 μg/ml and 100 μg/ml) from the apical (Ap) or basolateral (Bl) side. To assess barrier integrity, the trans-epithelial electrical resistance (TEER) was measured after 1 h, 2 h and 24 h of treatment. After 24 h, medium was collected for interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor-α (TNF-α) determination. A significant (P < 0.05) TEER decrease was observed starting from the second hour of treatment after Ap exposure to the highest dose (100 μg/ml) of CuO NPs. Bl exposure to all doses was found to significantly (P < 0.05) decrease TEER starting from the first hour (50 and 100 μg/ml) or after 24 h of treatment (10 μg/ml). No significant release of the inflammatory mediator IL-6 and TNF-α was observed. On the contrary, a significant (P < 0.05) release of IL-8 was induced by Ap exposure to CuO NPs at 10 μg/ml and by Bl exposure to all CuO NP concentrations. Redox proteomic analysis of protein oxidative damage showed a dose-dependent oxidation of protein sulfhydryl groups only after Ap exposure to CuO-NPs. In contrast, neither Ap nor Bl exposure affected protein carbonylation.