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  • Polycyclic aromatic hydrocarbons PAHs are abundant environme

    2024-04-08

    Polycyclic aromatic hydrocarbons (PAHs) are abundant environmental contaminants that are produced by the incomplete combustion of organic matter, combustion engines, residential heating, marizomib receptor burning, and industrial activities (Gelboin, 1980; Phillips, 1999, Phillips, 2002). Some PAHs have been recognized as mutagenic, carcinogenic and teratogenic to humans (Ellard et al., 1991; Nebert, 1989). Benzo[a]pyrene (B[a]P) is the major carcinogenic PAH; its ability to induce lung tumor formation has been well documented, and it is currently listed by the International Agency for Research on Cancer (IARC) as a carcinogen to humans (IARC, 2012). The B[a]P mutagenic effects are mediated by the metabolites produced during the biotransformation of B[a]P by the cytochrome P450 1 family enzymes through the Aryl hydrocarbon Receptor (AhR) pathway (Schmidt and Bradfield, 1996; Fujii-Kuriyama and Mimura, 2005). AhR is a ligand-activated member of the Per-Arnt-Sim family of basic helix–loop–helix transcription factors. Inactivated AhR forms a cytoplasmic complex in association with a dimer of heat shock protein 90 and other scaffold proteins, such as p23 protein and immunophilin-like AhR interacting protein (AIP). It has also been reported that the AhR complex can interact with other cytosolic proteins, including kinome chaperone, Cdc37, and the non-receptor tyrosine kinase, Src (Park et al., 2007; Enan and Matsumura, 1996; Perdew, 1988; Ma and Whitlock, 1997; Sogawa and Fujii-Kuriyama, 1997; Kazlauskas et al., 1999). The binding of ligands to AhR induces the release of chaperone proteins and the translocation of the receptor into the nucleus, where it forms a heterodimer with the aryl hydrocarbon receptor nuclear translocator (ARNT). Following AhR/ARNT heterodimer formation, it binds to a cognate sequence (TNGCGTG) known as the xenobiotic response element (XRE) in the promoters of responsive genes and regulates its transcription. The regulated genes include cytochrome P450 1A1 (CYP1A1), 1A2 (CYP1A2) and 1B1 (CYP1B1) (Nebert et al., 2004; Hao and Whitelaw, 2013). At the end of the metabolic processing, B[a]P is activated to B[a]P-7,8-diol-9,10 epoxide (BPDE), which can form stable N2-B[a]PDE-deoxyguanosine (B[a]P-N2-dG) DNA adducts (Osborn and Crosby, 1987); these adducts are well known risk factors for lung cancer (Hecht, 2003; Rojas et al., 2004; Shimada and Fujii-Kuriyama, 2004; Alexandrov et al., 2010). Crosstalk between classical AhR and other cell signaling pathways may also occur as a consequence of AhR activation. There is evidence of AhR-dependent activation of mitogen activated protein kinases (MAPK). This activation of MAPK may produce changes in cellular processes, such as differentiation, proliferation, and apoptosis (Perez et al., 2008; Chramostová et al., 2004; Andrysík et al., 2006; Hoffer et al., 1996; Tan et al., 2002, Tan et al., 2004; Ding et al., 2009; Occhi et al., 2015). However, the potential participation of MAPK in the B[a]P biotransformation, the production of its metabolites, and the formation of B[a]P-N2-dG adducts have not been explored yet. It is known that toxic metabolites of B[a]P concentrate exclusively in bronchial epithelial cells (Rojas et al., 2004; Alexandrov et al., 2010), making the lung the major target of carcinogenic PAH. In spite of this, most studies on PAH have used hepatocytes or cancer-derived cell lines, which already have an impaired cell cycle regulation. For these reasons, in this work, we have investigated the participation of the ERK 1/2 kinases on AhR-dependant B[a]P bioactivation and the genotoxic damage caused by its metabolic product, BPDE, in a non-tumorigenic bronchial epithelial human cell line, BEAS-2B. We found that exposure of cells to B[a]P induced the activation of both Src and ERK 1/2 kinases and that the activity of these kinases promoted both the expression of CYP1A1 and the production of B[a]P-N2-dG adducts.