BARD has been recognized to prevent kidney disease progression by acting as a potent Nrf2 activator [67]. In an experimental setting of nephropathy, BARD treatment attenuated acute kidney injury by ischemia [68]. Treatment with BARD analog, dh404, ameliorated functional and structural injury of glomeruli in STZ diabetic mice [69]. Moreover, BARD has shown beneficial effects in clinical settings [35,36], and is currently under Phase 3 clinical trials for CKD patients (stages 3–4) with type 2 diabetes mellitus [36]. It is noteworthy that our study provides novel evidence for the understanding of the mode of action of BARD: treatment with BARD elevated Smad7 levels in mesangial cells and suppressed TGF-β1/Smad signaling for ECM expression. Additionally, because lines of evidence suggest that BARD exerts inhibitory effects on inflammation, which is one of the core features of CKD [70], BARD-mediated Smad7 elevation might be involved in antiinflammatory effects. In fact, studies with Smad7 knockout mice demonstrated that Smad7 deletion aggravates renal inflammation that accompanies cytokine elevation and macrophage infiltration in animals with nephropathy [23,71]. Smad7 overexpression inhibited inflammatory cytokine production by suppressing NF-κB activity in a glomerulonephritis model [72]. Smad7 overexpression upregulated IκBα and inhibited NF-κB activity in mouse kidney [73]. These results suggest that renoprotective effects of BARD can be attributed to the Nrf2/Smad7-mediated antioxidant and anti-inflammatory effects. Taken together, these results suggest the Nrf2/Smad7 axis, which plays a critical role in TGF-β/Smad signaling, as a therapeutic target for the inhibition of renal fibrosis progression (Fig. 6). Additionally, we identified that BARD elevates Smad7 levels in glomerular mesangial cells, resulting in the suppression of TGF-β/Smad signaling and ECM expression.