NOX4 and pulmonary fibrosis: Previous studies demonstrated effective attenuation of bleomycin-induced lung fibrosis in rodents by airway delivery of siRNAs targeting IL-13 receptor α2 [25], NADPH oxidase-4 (NOX4) [26], plasminogen activator inhibitor-1 (PAI-1) [27], and the collagen-specific chaperon HSP47 [28].