PERK-CHOP pathway molecules were up-regulated in CSE2W, CSE3W, and CSE4W groups, which may indicate that the PERK pathway exerts its effect in all stages of CSE-induced emphysema through ERS-associated apoptosis, and the out-of-sync of the peak may be related to the activation order of the pathway and the presence of feedback effect (Liao et al., 2016). Here, DDIT3 is linked to pulmonary emphysema.