Sophocarpine Alleviates Renal Ischemia–Reperfusion Injury by Mitigating Oxidative Stress and Mitochondrial Dysfunction via the SIRT1/PGC-1α Axis

Background/Objectives: Renal ischemia–reperfusion injury (IRI) is a major cause of acute kidney injury and delayed graft function after kidney transplantation. Oxidative stress, mitochondrial dysfunction, and tubular epithelial cell apoptosis are central events in renal IRI. Sophocarpine (SOP), a quinolizidine alkaloid derived from Sophora species, has reported antioxidant and anti-apoptotic activities, but its effects in renal IRI remain unclear. This study investigated the role and function of SOP in renal IRI. Methods: A bilateral renal IRI mouse model and a hypoxia/reoxygenation (H/R) model in HK-2 human proximal tubular epithelial cells were used. Renal function, histological injury, apoptosis, reactive oxygen species, malondialdehyde, superoxide dismutase activity, glutathione, mitochondrial morphology, mitochondrial membrane potential, and mitochondrial dynamics-related proteins were evaluated. SIRT1 dependency was examined using Sirt1 small interfering RNA in HK-2 cells and EX527-mediated SIRT1 inhibition in mice. Results: SOP pretreatment reduced serum creatinine and blood urea nitrogen levels, attenuated tubular injury and apoptosis, decreased oxidative stress, and preserved mitochondrial morphology and function after renal IRI. Similar protective effects were observed in HK-2 cells exposed to H/R. SOP increased SIRT1 and PGC-1α expression, whereas Sirt1 knockdown or pharmacological SIRT1 inhibition weakened the antioxidant and mitochondrial protective effects of SOP. Conclusions: SOP attenuates renal IRI-associated oxidative stress and mitochondrial dysfunction, at least in part through the SIRT1/PGC-1α axis. These findings support further investigation of SOP as a candidate renoprotective compound for ischemic kidney injury.