circSHOC1-SLC25A3 promotes 2-naphthylamine-induced DNA damage in bronchial epithelial cells via activation of oxidative stress.

Smoking, a pivotal environmental risk factor, drives diseases including lung cancer through genetic and epigenetic alterations. While 2-Naphthylamine (2-NA), a tobacco-derived carcinogen, is established as a bladder carcinogen via DNA damage, its role in lung carcinogenesis remains mechanistically uncharacterized despite epidemiological associations. This study identifies bronchial epithelium as a direct target of 2-NA, demonstrating dose-dependent DNA damage in 16HBE cells (peak at 250 μM, 12 h; P < 0.05), accompanied by S-phase arrest, apoptosis, reduced proliferation, and reactive oxygen species (ROS) generation. 2-NA exposure upregulated the expression of circSHOC1, which is a circular RNA derived from the SHOC1 gene, in a dose-dependent manner. Functional assays revealed that circSHOC1 overexpression exacerbated 2-NA-induced DNA damage by enhancing ROS production and 8-hydroxy-2'-deoxyguanosine (8-OHdG) accumulation, whereas knockdown attenuated these effects. Mechanistically, circSHOC1 interacted with mitochondrial protein SLC25A3 (Solute Carrier Family 25 Member 3), a key oxidative stress regulator; SLC25A3 knockdown mitigated DNA damage (P < 0.01), and co-transfection experiments confirmed SLC25A3 as a critical mediator of circSHOC1-driven genotoxicity. Collectively, this work provides the first experimental evidence that 2-NA induces bronchial epithelial DNA damage via a circSHOC1-SLC25A3-ROS axis, supporting a novel mechanism for tobacco-associated lung carcinogenesis and highlighting 2-NA as a potential pulmonary carcinogen.