TNF and chronic obstructive pulmonary disease: Consistent with our findings in patients with COPD, DUOX1 was downregulated in 6-month-old SPC-TNF-α mice compared with WT counterparts, indicated by a trend towards decreased Duox1 mRNA expression (P = 0.09) (Figure 2A), and significantly decreased small airway DUOX1 protein levels (Figure 2, B and C).