NOX4 and asthma: NOX4 protein expression in epithelial cells of tissue bronchial biopsy specimens was significantly increased in patients with neutrophilic asthma (29.5% ± 3.7%) compared with patients with nonneutrophilic asthma (18.5% ± 3.2%; P = .041) and with healthy control subjects (18.6% ± 2.9%; P = .032) (ANOVA, P = .040) (Figs 3A, 3C), and it was significantly correlated with sputum neutrophil count (r = 0.52; P =.042) but not with lung function.