IRON LOADING IN ALVEOLAR MACROPHAGES ALTERS ALVEOLAR TYPE II EPITHELIAL CELL FUNCTION IN COPD

Background: Continuous crosstalk between alveolar macrophages (AMs) and the alveolar epithelium is essential to maintaining alveolar health. While cellular iron loading in AMs has clearly been characterized in chronic obstructive pulmonary disease (COPD), little is known about whether these iron-loaded AMs contribute to alveolar epithelial cell (AEC) dysfunction and tissue damage in COPD pathophysiology.



Objectives/Hypothesis: This study aimed to show the effects of iron loading in AMs on alveolar type II epithelial cell (AEC2) cell function in an in vitro model of COPD using murine foetal liver-derived alveolar macrophages (FLAMs).



Materials and Methods: Iron loading in FLAMs was achieved by treatment with 26.5 ng/ml ferric ammonium citrate, 10 μM ferrous lactate, or 5% cigarette smoke extract for 24h. Treatments were washed away, and cells were allowed to secrete immunometabolic mediators into media for 6h. MLE-12 cells (an AEC2 cell line) were incubated with conditioned medium of FLAMs or cocultured with pre-treated FLAMs, spatially separated by trans-well inserts, for 24h. Changes in MLE-12 viability, function, and cellular iron metabolism were assessed by alamarBlue assay, immunoblotting, and RT-qPCR. Cellular iron contents were measured by graphite furnace absorption spectroscopy.



Results: Iron loading in FLAMs did not significantly affect MLE-12 viability, but altered MLE-12 cell identity markers as well as their function in vitro.



Conclusion: Dysregulated crosstalk between iron-loaded AMs and AEC2s may contribute to COPD pathophysiology by inducing AEC2 dysfunction and tissue damage.