Sirtuin 3 Activation by Honokiol Decreases Unilateral Ureteral Obstruction-Induced Renal Inflammation and Fibrosis via Regulation of Mitochondrial Dynamics and the Renal NF-κB-TGF-β1/Smad Signaling Pathway

Renal fibrosis is a common feature of all progressive chronic kidney diseases. Sirtuin 3 (SIRT3) is one of the mitochondrial sirtuins, and plays a role in the regulation of mitochondrial biogenesis, oxidative stress, fatty acid metabolism, and aging. Recently, honokiol (HKL), as a pharmaceutical SIRT3 activator, has been observed to have a protective effect against pressure overload-induced cardiac hypertrophy by increasing SIRT3 activity. In this study, we investigated whether HKL, as a SIRT3 activator, also has protective effects against unilateral ureteral obstruction (UUO)-induced renal tubulointerstitial fibrosis through SIRT3-dependent regulation of mitochondrial dynamics and the nuclear factor-kappa B (NF-kappa B)/transforming growth factor-beta 1 (TGF-beta 1)/Smad signaling pathway. We found that HKL decreased the UUO-induced increase in tubular injury and extracellular matrix (ECM) deposition in mice. HKL also decreased myofibroblast activation and proliferation in UUO kidneys and NRK-49F cells. Finally, we showed that HKL treatment decreased UUO-induced mitochondrial fission and promoted mitochondrial fusion through SIRT3-dependent effects. In conclusion, activation of SIRT3 via HKL treatment might have beneficial effects on UUO-induced renal fibrosis through SIRT3-dependent regulation of mitochondrial dynamics and the NF-kappa B/TGF-beta 1/Smad signaling pathway.