Pulmonary Neuroendocrine Cells-derived Exosomes Regulate Iron Homeostasis and Oxi-dative Stress in Lung Neuron Cells

Nicotine, a major component of cigarettes, is linked to neurodegeneration and cognitive impairment potentially through oxidative stress and iron dysregulation in brain cells. The specific pathways connecting nicotine exposure to these neurodegenerative processes, however, still re-quire further clarification. This study explores the role of pulmonary neuroendocrine cells (PNECs); airway epithelial sensory cells with unique innervations that link directly to the brain via the vagal nerves. We focused on how PNEC-derived exosomes affect sensory nerve communi-cation in the context of smoking. To overcome the challenges associated with culturing primary human PNECs, we developed induced PNECs (iPNECs) from human pluripotent stem cells (hPSCs), which allowed for high resolution and in-depth analyses. Our research demonstrates that nicotine exposure increases the release of iPNEC-derived exosomes, which are enriched with serotransferrin, an iron-binding glycoprotein. These exosomes are internalized by neuronal cells, initiating a series of biochemical responses. This includes the upregulation of transferrin receptor 1 (TFR1), divalent metal transporter 1 (DMT1), and divalent cation transporter YB (DCTYB), leading to higher intracellular ferritin levels, enhanced oxidative stress, and reduced ATP levels in neurons. Notably, both pharmacological and genetic inhibition of TFR1 mitigated the oxidative stress in neurons treated with iPNEC-derived exosomes, including those from mouse PNECs isolated using synaptophysin-based magnetic immunocapture. Moreover, we ob-served increased levels of synuclein (SNCA), a protein implicated in neurodegenerative diseases and dementia, in both human and mouse lung neurons exposed to smoke and nicotine. Neuro-behavioral assessments of nicotine-treated mice showed significant declines in cognitive and mo-tor functions. Collectively, these findings suggest that serotransferrin-rich PNEC-derived exo-somes can disrupt iron homeostasis and oxidative metabolism in neuronal cells exposed to nico-tine or cigarette smoke, potentially leading to neurological dysfunction.