Pulmonary neuroendocrine cell-derived exosomes regulate iron homeostasis and oxidative stress in lung neurons.

Nicotine, the principal addictive component of cigarettes, is linked to cognitive decline and neurodegenerative alterations, likely through oxidative stress and impaired iron regulation in neurons. Yet, underlying molecular pathways remain unclear. This study examined the role of pulmonary neuroendocrine cells (PNECs) in smoke-induced neural changes. Using human pluripotent stem cells, we generated induced PNECs (iPNECs) to overcome culture limitations and performed mechanistic analyses. We found that nicotine exposure stimulates iPNECs to secrete exosomes enriched with serotransferrin, an iron-binding glycoprotein. Neurons internalizing these exosomes displayed elevated levels of transferrin receptor 1 (TFR1), divalent metal transporter 1, and duodenal cytochrome b, associated with ferritin accumulation, oxidative stress, and adenosine triphosphate depletion. Inhibition of TFR1 alleviated these effects. Furthermore, nicotine-triggered exosomes increased α-synuclein expression in neurons in a manner consistent with stress- and vulnerability-associated signatures observed in human lungs and nicotine-exposed mice, highlighting PNEC-derived exosomal signaling that may contribute to neuronal dysfunction.