Legumain is required for maintenance of normal kidney homeostasis. However, its role in acute kidney injury (AKI) is still unclear. Here, we induced AKI by bilateral ischemia-reperfusion injury (IRI) of renal arteries or folic acid in lgmn^WT and lgmn^KO mice. We assessed serum creatinine, blood urea nitrogen, histological indexes of tubular injury, and expression of KIM-1 and NGAL. Inflammatory infiltration was evaluated by immunohistological staining of CD3 and F4/80, and expression of TNF-α, CCL-2, IL-33, and IL-1α. Ferroptosis was evaluated by Acsl4, Cox-2, reactive oxygen species (ROS) indexes H₂DCFDA and DHE, MDA and glutathione peroxidase 4 (GPX4). We induced ferroptosis by hypoxia or erastin in primary mouse renal tubular epithelial cells (mRTECs). Cellular survival, Acsl4, Cox-2, LDH release, ROS, and MDA levels were measured. We analyzed the degradation of GPX4 through inhibition of proteasomes or autophagy. Lysosomal GPX4 was assessed to determine GPX4 degradation pathway. Immunoprecipitation (IP) was used to determine the interactions between legumain, GPX4, HSC70, and HSP90. For tentative treatment, RR-11a was administrated intraperitoneally to a mouse model of IRI-induced AKI. Our results showed that legumain deficiency attenuated acute tubular injury, inflammation, and ferroptosis in either IRI or folic acid-induced AKI model. Ferroptosis induced by hypoxia or erastin was dampened in lgmn^KO mRTECs compared with lgmn^WT control. Deficiency of legumain prevented chaperone-mediated autophagy of GPX4. Results of IP suggested interactions between legumain, HSC70, HSP90, and GPX4. Administration of RR-11a ameliorated ferroptosis and renal injury in the AKI model. Together, our data indicate that legumain promotes chaperone-mediated autophagy of GPX4 therefore facilitates tubular ferroptosis in AKI.

Legumain 是维持正常肾脏稳态所必需的。然而，其在急性肾损伤 (AKI) 中的作用仍不清楚。在这里，我们通过肾动脉的双侧缺血-再灌注损伤 (IRI) 或lgmn ^WT和lgmn ^KO小鼠的叶酸诱导 AKI 。我们评估了血清肌酐、血尿素氮、肾小管损伤的组织学指标以及 KIM-1 和 NGAL 的表达。通过 CD3 和 F4/80 的免疫组织学染色以及 TNF-α、CCL-2、IL-33 和 IL-1α 的表达来评估炎症浸润。通过 Acsl4、Cox-2、活性氧 (ROS) 指数 H ₂评估铁死亡DCFDA 和 DHE、MDA 和谷胱甘肽过氧化物酶 4 (GPX4)。我们在原代小鼠肾小管上皮细胞 (mRTECs) 中通过缺氧或erastin 诱导铁死亡。测量了细胞存活、Acsl4、Cox-2、LDH 释放、ROS 和 MDA 水平。我们通过抑制蛋白酶体或自噬分析了 GPX4 的降解。评估溶酶体 GPX4 以确定 GPX4 降解途径。免疫沉淀 (IP) 用于确定legumain、GPX4、HSC70 和 HSP90 之间的相互作用。对于试验性治疗，将 RR-11a 腹膜内给药于 IRI 诱导的 AKI 小鼠模型。我们的结果表明，在 IRI 或叶酸诱导的 AKI 模型中，legumain 缺乏减轻了急性肾小管损伤、炎症和铁死亡。lgmn ^KO抑制缺氧或依拉汀诱导的铁死亡mRTECs 与lgmn ^WT对照相比。缺乏legumain会阻止伴侣蛋白介导的GPX4自噬。IP 结果表明，legumain、HSC70、HSP90 和 GPX4 之间存在相互作用。RR-11a 的给药改善了 AKI 模型中的铁死亡和肾损伤。总之，我们的数据表明，legumain 促进了伴侣蛋白介导的 GPX4 自噬，因此促进了 AKI 中的管状铁死亡。