The Down-Regulation of Lactoferrin Expression Induced by Cigarette Smoke can Induce Ferroptosis in COPD.

Purpose: Lactoferrin (LTF) plays a crucial role in iron homeostasis, immune response, and inflammation. In the context of chronic obstructive pulmonary disease (COPD), LTF's expression is significantly influenced by environmental factors, particularly cigarette smoke. The pathological mechanism by which cigarette smoke regulates LTF and affects iron metabolism in COPD remains unclear. This study aims to clarify the mechanism therein.

Methods: In this study, cigarette smoke extract (CSE) was used to construct mouse and cell models of chronic obstructive pulmonary disease (COPD). Transcriptomic and proteomic tests were performed on the lung tissues of the mouse model of COPD to screen or measure the Hub gene. The interaction network prediction of LTF-related proteins was carried out using the STRING database. The Beas-2B cell model with LTF overexpression and interference was constructed by lentivirus transfection, and then the cell viability, cytotoxicity, lipid reactive oxygen species (ROS), iron ion deposition, and iron-related markers of bronchial epithelial cells after CSE exposure were detected. The morphological changes of mitochondria in bronchial epithelial cells were observed by transmission electron microscopy. The expression levels of ACSL4 and GPX4 proteins in bronchial epithelial cells were detected by Western blotting.

Results: The expression of LTF is down-regulated in both lung tissue of the COPD mouse model and bronchial epithelial cells, and it plays a key role in ferroptosis of CSE-induced bronchial epithelial cells. In the LTF-interfered bronchial epithelial cells treated with CSE, ferroptosis-related markers (such as ROS and MDA) were significantly increased, GSH was significantly decreased, mitochondrial volume was reduced, cristae were decreased, the expression of ACSL4 protein was increased, while the expression of GPX4 protein was decreased. Meanwhile, overexpression of LTF can reverse the ferroptosis status of bronchial epithelial cells treated with CSE.

Conclusion: Under CSE induction, the decrease in LTF expression level will lead to the accumulation of ferrous ions in bronchial epithelial cells and induce the occurrence of ferroptosis.