Spatiotemporal Mapping of Xenobiotic Disposition and Brain Metabolic Alterations after Cigarette Smoke Extract Exposure

Abstract Intratracheal instillation of cigarette smoke extract (CSE) provides a controlled model for investigating the biological effects of soluble smoke-derived constituents, yet the spatial fate of CSE-related xenobiotics and their metabolic consequences remain poorly defined. Here, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was used to map nicotine and its oxidative metabolite nicotine N-oxide in mouse organs and to characterize CSE-induced metabolic alterations in the brain. Nicotine rapidly entered the brain and preferentially localized to gray matter-enriched regions, including the thalamus, cortex, and caudoputamen, while showing relatively low signals in the corpus callosum and lateral ventricle-associated region. In contrast, nicotine N-oxide appeared later and became enriched in lateral ventricle- and corpus callosum-associated regions, revealing distinct spatiotemporal distributions of the parent compound and its oxidative metabolite. In orthotopic Lewis lung carcinoma tissues, nicotine signals were reduced whereas nicotine N-oxide signals were elevated relative to adjacent normal lung tissue, suggesting altered local disposition of these smoke-derived small molecules within the tumor microenvironment. Spatial metabolomics further showed that CSE induced marked brain metabolic disorders, including elevated AMP, ADP, ATP, and glutamate, reduced inosine, GMP, and tricarboxylic acid cycle intermediates, as well as glucose accumulation and glutamine depletion. These changes are consistent with perturbations in purine metabolism, oxidative energy metabolism, and carbon/nitrogen metabolism under CSE stress. Together, these findings suggest that CSE exposure induces spatially heterogeneous toxicological responses, characterized by differential tissue handling of nicotine and nicotine N-oxide, tumor microenvironment-associated differences in local disposition, and brain metabolic changes.