Antimonio e rischi per la salute umana: studio in vitro su adipociti e cellule epiteliali intestinali

Heavy metals are largely spread in the environment as a consequence of modern industrialisation. They can cause different chronic toxic effects, such as gastrointestinal and renal dysfunction, nervous system disorders, skin lesions, vascular damage, alterations to the immune system, congenital defects and cancer. In particular, antimony (Sb), a metalloid widely employed in industrial activities, especially as a catalyst in the manufacturing of polyethylene terephthalate (PET), a material largely used for food packaging, water bottles, toys and other household items, has attracted considerable interest in recent years. Humans are potentially exposed to Sb through oral, cutaneous, and inhalation routes. Trivalent Sb [Sb(III)] is the most toxic form in human tissues. Once absorbed into cells, Sb compounds can interact with different molecules, disrupting normal biochemical functions. Of particular concern is that, if subjected to stress conditions, like prolonged storage or exposure to high temperatures, Sb can migrate from the plastic materials into food or beverage in contact with, leading to important health concerns. In the present study, the effects of very low nanomolar concentrations of Sb(III) were evaluated in 3T3-L1 murine adipocytes and in Caco-2 human epithelial cells during the whole cell differentiation period, mimicking chronic human exposure. Exposure of 3T3-L1 adipocytes to Sb(III) induced lipid accumulation and induction of the master regulators of adipogenesis (C/EBP-β and PPAR-γ), demonstrating the obesogenic activity of this metal. Furthermore, Sb(III) promoted pre-adipocytes proliferation, increasing cells in G2/M phase of the cell cycle while reducing those in G0/G1 phase; this event is also correlated to reduced levels of the cell-cycle inhibitor p21. Moreover, this study demonstrates that Sb(III) can modulate the adipogenesis process through the interaction with the estrogen receptor, since Sb-induced PPAR-γ was reversed by the estrogen receptor antagonist ICI 182,780. Furthermore, Sb(III) exposure activated the pro-inflammatory NF-κB pathway and disrupted endoplasmic reticulum (ER) homeostasis by increasing reactive oxygen species (ROS) production and upregulating UPR (unfolded protein response) markers, such as XBP-1s, p-eIF2α, GRP78, and CHOP. On the other hand, Sb(III) exposure during cell differentiation affected intestinal epithelial barrier in the Caco-2 cells model, activating the pro-inflammatory NF-κB signaling pathway and apoptotic cell death, with modulation of Bcl-2, Bax and Caspase-3 protein levels. As in adipocytes, also in intestinal epithelial cells Sb(III) induced oxidative stress, by inducing an increase in intracellular ROS levels, and ER stress, as shown by main UPR markers levels. Additionally, Sb-induced ER stress activated SIRT1 signaling pathway. Treatment with the ER-stress specific inhibitor tauroursodeoxycholic acid (TUDCA) demonstrated the key role of ER stress in Sb-induced damage in Caco-2 cells. Finally, the beneficial effects of cyanidin-3-O-glucoside (C3G) against Sb-induced intestinal injury were evaluated: C3G protected Caco-2 cells against inflammation, apoptosis, and ER stress triggered by Sb(III) exposure during cell differentiation. In conclusion, this study, for the first time, supports the obesogenic and intestinal epithelial damaging effects of low concentrations of Sb(III), suggesting that it would be recommendable to limit Sb applications in industrial activities to minimise human health hazards.