GPX4 and chronic obstructive pulmonary disease: Beyond the core SLC7A11/GPX4 axis and the context-dependent HO-1 pathway, Nrf2 regulates ferroptosis in COPD through several other interconnected mechanisms, including the Nrf2/PPARγ/ferritinophagy axis, the ROS/Nrf2/SIRT3/inducible nitric oxide synthase (iNOS) axis, and lipid metabolism [15,19,106,120].