Post Doctoral Research Fellow Lundquist Institute for Biomedical Innovation Torrance, California, United States
Disclosure(s):
Noushin Lotfi: No financial relationships to disclose
Introduction/Rationale: Macrophages are a key component of pulmonary immunity and are highly responsive to environmental toxins, including nicotine. Autophagy is a vital stress-response pathway that inhibits inflammation mediated via macrophages. We hypothesize that nicotine disrupts macrophage autophagy, promoting inflammation and immune dysregulation in the lungs.
Methods: Using a standard electronic nicotine delivery system, young adult female C57BL/6 mice were exposed to 4.8% nicotine + humectants propylene glycol/vegetable glycerin (PG/VG), PG/VG alone, or to filtered air for 6 weeks. Autophagy markers were assessed by immunoblotting of lung samples, while qRT-PCR, ELISA, BALF flow cytometry, and IHC were used to quantify lung inflammation. We next employed an in vitro RAW 264.7 macrophage model as a mechanistic surrogate to test whether nicotine directly disrupts macrophages. RAW macrophages were exposed to nicotine and a vehicle. Autophagy flux was modulated with rapamycin or bafilomycin A1, and autophagy markers (LC3B, p62, Beclin-1) were quantified by Western blot.
Results: Nicotine impaired macrophage autophagic flux, evidenced by p62 accumulation, reduced Beclin-1, and increased LC3B-II levels, consistent with defective autophagy turnover. Rapamycin partially restored autophagy markers, whereas bafilomycin further exacerbated autophagy disruption. Nicotine-exposed mice exhibited a significant increase in alveolar macrophage populations. Lung qRT-PCR demonstrated significantly elevated IL-1β, IL-6, MCP-1, and GM-CSF, while BALF showed increased IL-17 and IL-23 levels. Additionally, nicotine-exposed lungs displayed increased iNOS and decreased Arginase-1 expression, consistent with pro-inflammatory macrophage polarization.
Conclusion: These findings identify nicotine as a mechanistic driver of macrophage accumulation, inflammatory polarization, and lung immune dysregulation, and suggest macrophage autophagy as a potential therapeutic target
