HMOX1 and chronic obstructive pulmonary disease: In cells from both non-COPD and COPD donors, DE significantly increased HMOX1 mRNA expression (marker for oxidative stress response) both in presence (*p = 0.0104 for non-COPD and p = 0.0128 for COPD donors) or absence of NTHi exposure (*p = 0.0101 and **p = 0.0068, Fig. 2a).