HMOX1 and chronic obstructive pulmonary disease: We also investigated the effects of different Nrf2 activators on NQO1 activity and expression of Nrf2 target genes (NQO1, HMOX1, SOD1 and TXNRD1) in COPD alveolar macrophages, focusing on the comparison of the electrophilic compound CDDO with the PPI inhibitors GSK7 and C4X_6665.