Benzo(a)anthracene\nTargeting SLC1A5 to Synergistically\nEnhance PAH Mixture Toxicity

Human exposure to polycyclic aromatic hydrocarbons (PAHs)\nas mutagenic\nand carcinogenic pollutants in the environment often occurs in the\nform of mixtures. Although the mixture effects of PAHs have been previously\nrecognized, the toxicological mechanisms to explain them still remain\nquite unclear. This study combined metabolomics and chemical proteomics\nmethods to comprehensively understand the mixture effects of a PAH\nmixture including benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF),\nbenzo(a)pyrene (BaP), and chrysene (CHR). Among them, BaA has shown\na strong synergistic effect with other PAHs. Interestingly, BaA alone\nis not a potent oxidative stress inducer in liver cells but dose-dependently\namplifies oxidative damage caused by the PAH mixture. Global metabolomics\nanalysis results revealed damage to the antioxidant glutathione synthesis,\nwhich was caused by the glutamine depletion caused by BaA in the mixture.\nSubsequently, the label-free chemical proteomics and cellular thermal\nshift analysis (CETSA) demonstrated that the PAH mixture altered the\nthermal shift of glutamine transporter SLC1A5. Furthermore, Western\nblotting and the isothermal titration calorimetry (ITC) interaction\nmeasurements showed nanomolar <i>K</i><sub>D</sub> values\nbetween BaA and SLC1A5. Overall, this study showed that BaA synergistically\ncontributed to PAH mixture induced oxidative damage by targeting SLC1A5\nto inhibit glutamate transport into cells, resulting in the inhibition\nof glutathione synthesis.