3.4. A pharmacological Nrf2 activator, BARD, elevates Smad7 andsuppresses TGF-β signalingSynthetic triterpenoid BARD is known to have antioxidant effects with potent Nrf2 inducing activity [47]. In MES-13 cells, we tested whether this pharmacological Nrf2 activator could affect Smad7/TGF-β signaling. First, we confirmed BARD-mediated Nrf2 activation in MES13 cells. Protein levels of Nrf2 were increased at each dose of BARD treatment (0.025, 0.05, and 0.1 μM for 24 h) (Fig. 4A). In addition, ARE activity increased by 4-fold following BARD incubation (0.1 μM for 24 h) without any significant cytotoxicity (Fig. 4B). As shown in Fig. 4C, levels of Smad7 was increased by treatment with BARD (0.1 μM), which is accompanied by the increase in the expression of Nrf2 and its target Nqo1, Ho-1, and Gclc proteins (Fig. 4C). In addition, the levels of Smurf1 and TβRI were significantly decreased by BARD treatment, similar to the result from the genetic activation model of Nrf2 (Fig. 4D). Likewise, we confirmed that the elevation of p-Smad2/p-Smad3 and fibrotic markers (fibronectin and α-Sma) by TGF-β was blocked by BARD treatment (Fig. 4E). Whereas, Smad7 level that was elevated by TGF-β1 incubation was not altered by BARD treatment. These results showed that a pharmacological Nrf2 activator, BARD, similar to genetic Nrf2 activation, suppressed TGF-β-mediated fibrotic signaling through Smad7 elevation in mesangial cells.