ACTA1 and chronic obstructive pulmonary disease: Importantly, an immunofluorescent (IF) analysis further uncovered that the NOX4 and α-SMA proteins were colocalized in ASM cells of small airway as determined by a dual IF staining; more abundant NOX4 and α-SMA proteins were observed in COPD ASM cells than that in control lungs (Figures 6(a) and 6(b)).