NFE2L2 and chronic obstructive pulmonary disease: Thiol based antioxidants, such as N-acetylcysteine, have had disappointing clinical effects, as they are probably inactivated in the lungs, so there is a need to study more effective antioxidants, such as mt-antioxidants, as mitochondria are major sources of ROS in COPD and activators of Nrf2, which should restore impaired endogenous antioxidants.