NOX4 and pulmonary fibrosis: Importantly, quercetin is also described as a potent inhibitor of NOX4 [122], which is found upregulated in fibroblast foci as well as the AECII of IPF lungs [47,48], and the full deficiency of Nox4 has been shown to protect mice against bleomycin-induced AECII apoptosis and lung fibrosis [123].