NOX4 and asthma: The TGF-β-induced activation of the reactive oxygen species (ROS)-generating enzyme, NADPH oxidase 4 (Nox4) that induces myofibroblast differentiation (157), is implicated in ASM proliferation and hypercontractility in asthma (158, 159), as well as in epithelial ciliary dysfunction in neutrophilic asthma.