Involvement of ferroptosis in COPD pathogenesis

Introduction: Programmed cell death (PCD) has been widely implicated in the pathogenesis of COPD. Iron dependent, non-apoptotic PCD has been recently proposed and is termed ferroptosis. Ferroptosis is attributed to lipid-oxidation caused by an iron-mediated Fenton reaction during hydroxyl radical generation. Accumulating evidence indicates increased iron storage in COPD lungs and animal lungs after cigarette smoke (CS) exposure. Enhanced ROS production in response to CS extract (CSE) exposure has been demonstrated in human bronchial epithelial cells (HBEC). We therefore hypothesized pathogenic involvement of CS-induced ferroptosis in lung epithelial cells during COPD. Method: Non heme iron expression in COPD lungs was detected by berlin blue staining. HBEC viability during CSE exposure was assessed by MTT assay. Cytotoxicity was evaluated by measuring released lactate dehydrogenase (LDH). Inhibitor of ferroptosis (Ferrostatin-1) and iron chelator deferoxamine (DFO) were used to inhibit ferroptosis. Glutathione peroxidase 4 (GPX4) siRNA transfection was performed to enhance lipid peroxidation. CM-H2DCFDA was used to evaluate intracellular ROS production. Result: Compared with normal lungs, enhanced Iron deposition in epithelial cells was detected in COPD lung. Ferritin expression levels were increased in CSE-treated HBEC and CS-exposed mouse lungs. Ferrostatin-1 and DFO ameliorated CSE-induced cell death in HBEC. Conversely, cell death was enhanced in the presence of excessive free iron and GPX4 knock down. Ferrostatin-1 also inhibited CSE-induced ROS production in HBEC. Conclusion: These findings suggest that CS-induced ferroptosis of HBEC is involved in COPD pathogenesis and can be a promising therapeutic target of COPD.