The para-phthalates and antimony used in the manufacture of PET induce in vitro adipocytes dysfunction and inflammation

The para-phthalates and antimony used in the manufacture of PET induce in vitro adipocytes dysfunction and inflammation Maria Sofia MOLONIA1, Antonio SPECIALE1, Federica Lina SALAMONE1, Giovanni TOSCANO1, Antonella SAIJA1, Francesco CIMINO1 1Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina - Italy Polyethylene terephthalate (PET) is a thermoplastic polymer broadly used for packaging foods and beverages. PET is produced by polymerizing ethylene glycol with terephthalic acid (TPA) or by transesterification with dimethyl terephthalate (DMT), using antimony trioxide as catalyst. Since application of PET has largely increased during the last decades, it has been subjected to many debates regarding environmental and health issues. In particular, the migration is an undesirable process where polymerization residues or stabilizers diffuse through the polymer matrix to the food. In fact, phthalates and antimony are usually present as a freely mobile and leachable phase so that they can be lost from plastic over time and then released into food and beverage during processing, storing, transportation, and preparation. Epidemiologic studies found that early phthalates exposure could induce significant neuro-developmental damage. Additionally, antimony and phthalates are suspected of causing endocrine-disrupting effects to humans and obesogenic activity. However, to date, very few information are reported in literature for para-phthalates, such as TPA, DMT and antimony. In this work we evaluated the in vitro effects of very low concentrations of para-phthalates (0,01 and 10 μM) and antimony (0.05 to 5 nM) exposing 3T3-L1 preadipocytes throughout all the 10 days of the differentiation process. The main markers involved in adipogenesis and inflammatory process were evaluated by means of Western blot and real-time PCR. The results obtained show that TPA, DMT and antimony exposure throughout the differentiation process led to an induction of adipogenesis in a dose dependent way, as shown by the increased lipid accumulation and the highest levels of the main modulators of the adipogenic process (PPARγ pathway), also at very low nanomolar range. Interestingly, PPAR-γ activation was reverted by the estrogen receptor antagonist ICI 182,780. Furthermore, exposure to the tested compounds was able to activate the inflammatory process, inducing NF-κB pathway. Additionally, antimony altered endoplasmic reticulum (ER) homeostasis inducing ROS increase, ER stress markers XBP-1s and pEIF2a and downstream genes, such as Grp78 and CHOP. These findings suggest, therefore, that para-phthalates and antimony exposure could shift adipocytes toward an unhealthy phenotype. Interestingly, these effects were observed at nanomolar concentrations, lower than migration limits regulated by European Union (Regulation No. 10/2011 migration limits for TPA, DMT and antimony), providing basis to minimise exposure as far as possible including the option to limit the use of these substances. References [1] Wang, Y. and Qian, H. Phthalates and Their Impacts on Human Health. Healthcare 2021, 9, 603. [2] Lai, Z.; He, M.; Lin, C.; Ouyang, W.; Liu, X., Interactions of antimony with biomolecules and its effects on human health. Ecotoxicology and environmental safety 2022, 233, 113317. [3] Mihucz, V.G.; Záray, G. Occurrence of antimony and phthalate esters in polyethylene terephthalate bottled drinking water. Appl. Spectrosc. Rev. 2016, 51, 183–209.