NOX4 and renal fibrosis: As shown in Figure 4, protein expression levels of the antioxidant enzymes, including catalase, superoxide dismutase 2 (SOD 2), and thioredoxin reductase 1 (TrxR1), a regulator of Nrf2 [34], were significantly suppressed, while Nox4, a member of the NADPH oxidase family, which is involved in the development of renal fibrosis [25,35], was significantly augmented in UUO kidneys.