PSMB1 and chronic obstructive pulmonary disease: This included decreased expression of PSMB1 and PSMC3 in healthy subjects (p = 0.028 and p = 0.028, respectively), and decreased expression of PSMB7 and PSMD13 in both healthy (p = 0.028 and p = 0.028, respectively) and COPD subjects (p = 0.028 and p = 0.046, respectively) after 30% CSE stimulation.