Cigarette smoke–induced epithelial cell ferroptosis promotes neutrophilic inflammation in patients with nasal polyps

Abstract

Background

Regulation of epithelial cell death has emerged as a key mechanism maintaining immune homeostasis in the airway. However, the mechanisms governing epithelial cell survival in nasal polyps (NPs) remain poorly understood.

Objective

We sought to investigate the ferroptosis of nasal epithelial cells and its implications in the pathogenesis of NPs.

Methods

The cell death, lipid peroxidation, and ferrous iron levels in nasal epithelial cells were determined by flow cytometry. Biomarkers and signaling pathways associated with ferroptosis were evaluated by quantitative RT-PCR, single-cell and bulk RNA sequencing, immunofluorescence staining, and Western blotting. Human nasal epithelial cells (HNECs) and human bronchial epithelial cells (16HBE) were stimulated with different agents. Mitochondrial ultrastructure in HNECs was visualized by transmission electron microscopy. Cytokine levels were quantified using ELISA. A cigarette smoke extract (CSE)-induced mouse model was established and treated with deferoxamine.

Results

Nasal epithelial cells from both eosinophilic and noneosinophilic NPs showed intensified lipid peroxidation and altered mitochondrial morphology, resembling the features of ferroptosis. Ferroptosis triggered CXCL8 production in 16HBE cells and HNECs through the activation of mitogen-activated protein kinase pathway. CSE exposure elevated ferrous iron levels by upregulating transferrin receptor 1, leading to ferroptosis and subsequent CXCL8 production in HNECs. Deferoxamine treatment inhibited nasal epithelial cell ferroptosis, CXCL8 levels, and neutrophil numbers in a CSE-induced mice model. Smoking burden was correlated with CXCL8 levels and neutrophil infiltration in patients with NPs. An analysis of 494,176 UK Biobank participants revealed smoking as a risk factor for NPs (odds ratio, 1.346; 95% CI, 1.245-1.456; P < .001).

Conclusions

Smoking-induced ferroptosis promotes CXCL8 production in nasal epithelial cells and thus potentially exacerbates neutrophilic inflammation in NPs.