STAT3 and fibrosis: Similarly, in a rat UUO fibrosis model, Prx5 levels fall as fibrosis progresses, and in NRK49F fibroblasts, wild-type—but not enzymatically inactive—Prx5 overexpression blocks TGF-β–induced fibronectin and alpha–smooth muscle actin via inhibition of STAT3 (Signal Transducer and Activator of Transcription 3) phosphorylation without altering SMAD2/3 (Figure 4) [105].