PM2.5 induces ferroptosis in chronic obstructive pulmonary diseases via the GSK-3β/NRF2 pathway.

Background

Recent studies have shown that fine particulate matter (PM2.5) exposure is a key harmful risk factor for chronic obstructive pulmonary disease (COPD) and PM2.5-associated ferroptosis plays an important role during the process of airway oxidative stress. Our preliminary study revealed that PM2.5 reduces the expression of phosphorylated glycogen synthase kinase (GSK)-3β in airway epithelial cells, the overactivity of the GSK-3β/Nuclear Factor erythroid 2-Related Factor 2 (NRF2) pathway is related to ferroptosis. Accordingly, we explored whether PM2.5 could induce ferroptosis in airway epithelial cells and promote the development of COPD via the GSK-3β/NRF2 pathway.

Methods

The effect of GSK-3β/NRF2-mediated ferroptosis was assessed using an in vivo model of 20 μg/μl PM2.5-induced COPD by tracheal infusion and 50 μg/ml PM2.5-exposed airway epithelial cells in vitro. Then we performed qRT-PCR to detect mRNA expression; Western blotting, immunofluorescence and immunohistochemical staining to detect protein expression; flow cytometry and spectrophotometry to measure the levels of intracellular lipid peroxidation; small animal spirometry to examine the lung function in mouse, and hematoxylin and eosin (H&E) staining to measure the average alveolar septa in mouse lung sections.

Results

We found that PM2.5 decreased the ferroptosis marker mRNA expression of NRF2, SLC7A11 and GPX4, and also decreased the protein expression of p-GSK-3β, NRF2, SLC7A11 and FTH-1, increased the protein expression of NCOA4, then increased the level of lipid peroxidation and MDA in human airway epithelial cells. Further, PM2.5 reduced the expression of p-GSK-3β, NRF2, SLC7A11 and GPX4 in the lungs, subsequently induced lung injury and impaired lung function of mice. Treatment with ferroptosis inhibitors FER-1 and GSK-3β inhibitor TDZD-8 reversed this effect.

Conclusion

Our findings suggested that PM2.5 induced ferroptosis of airway epithelial cells, contributing to airway oxidative stress via the GSK-3β/NRF2 signaling pathway in vivo and in vitro, which could be a therapeutic target for PM2.5-induced COPD.