Smad3-Targeted Therapy Protects against Cisplatin-Induced AKI by Attenuating Programmed Cell Death and Inflammation via a NOX4-Dependent Mechanism

Background: Transforming growth factor-β (TGF-β)/Smad signaling is the central mediator in renal fibrosis, yet its functional role in acute kidney injury (AKI) is not fully understood. Recent evidence showed that TGF-β/Smad3 may be involved in the pathogenesis of AKI, but its functional role and mechanism of action in cisplatin-induced AKI are unclear. Objectives: Demonstrating that Smad3 may play certain roles in cisplatin nephropathy due to its potential effect on programmed cell death and inflammation. Methods: Here, we established a cisplatin-induced AKI mouse model with Smad3 knockout mice and created stable in vitro models with Smad3 knockdown tubular epithelial cells. In addition, we tested the potential of Smad3-targeted therapy using 2 in vivo protocols – lentivirus-mediated Smad3 silencing in vivo and use of naringenin, a monomer used in traditional Chinese medicine and a natural inhibitor of Smad3. Results: Disruption of Smad3 attenuated cisplatin-induced kidney injury, inflammation, and NADPH oxidase 4-dependent oxidative stress. We found that Smad3-targeted therapy protected against loss of renal function and alleviated apoptosis, RIPK-mediated necroptosis, renal inflammation, and oxidative stress in cisplatin nephropathy. Conclusions: These findings show that Smad3 promotes cisplatin-induced AKI and Smad3-targeted therapy protects against this pathological process. These findings have substantial clinical relevance, as they suggest a therapeutic target for AKI.