Renal ischemia-reperfusion (I/R) injury is closely associated with delayed graft function and poor long-term graft survival following transplantation. Various pathophysiologies can cause the deterioration of renal function; however, the immune system plays important roles in promoting and protecting renal tissues. Receptor activator of NFκB ligand (RANKL) is a member of the TNF superfamily and is produced by bone-forming osteoblasts; the receptor for RANKL is called RANK. In bone biology, RANKL-RANK signaling has been extensively studied, but its roles in the immune system are still obscure. We investigated the role of the RANK system in I/R injury of the kidney using an experimental mouse I/R model. The left renal pedicles of 10-week-old male mice were clamped for 60 min, and reperfusion and right nephrectomy were simultaneously performed. Separate groups were administered an anti-RANKL antibody and recombinant RANKL (rRANKL) 24 h prior to I/R. After reperfusion for a set period of time, the serum creatinine level was measured, and the left kidney was removed for histological examination and western blotting to evaluate the expression and localization of RANK-associated molecules and cytokines. The serum creatinine levels were significantly elevated after I/R injury. A time-dependent increase in RANKL was observed up to 24 h, whereas RANK was induced for 12 h after reperfusion. RANK was expressed in infiltrating inflammatory cells, which were positive for CD68, a marker of monocytes/macrophages. The pre-treatment with the anti-RANKL antibody significantly impaired renal function and increased the induction of inflammatory cytokines (TNFα and IL-6), Toll-like receptor (TLR4) and MyD88 (all p < .05) compared to the levels in the I/R group. However, rRANKL significantly improved renal function and decreased the levels of inflammatory cytokines (TNFα and IL-6), TLR4 and MyD88 (p < .05) compared to those in the I/R group. The present study is the first to evaluate the role of the RANK system in renal I/R injury. RANKL-RANK signaling affects macrophage function and results in the downregulation of TLR4 and reduction in TNFα and IL-6, leading to improved renal function following I/R injury.

肾缺血-再灌注（I / R）损伤与移植后移植物功能延迟和长期移植物长期存活率低下密切相关。各种病理生理可导致肾功能恶化；然而，免疫系统在促进和保护肾脏组织中起着重要作用。NFκB配体的受体激活剂（RANKL）是TNF超家族的成员，由成骨性成骨细胞产生。RANKL的受体称为RANK。在骨骼生物学中，已经广泛研究了RANKL-RANK信号传导，但是其在免疫系统中的作用仍然不清楚。我们使用实验性小鼠I / R模型研究了RANK系统在肾脏I / R损伤中的作用。将10周龄雄性小鼠的左肾蒂进行钳夹60分钟，并同时进行再灌注和右肾切除术。在I / R前24小时，分别给各个组施用抗RANKL抗体和重组RANKL（rRANKL）。再灌注一段时间后，测量血清肌酐水平，取出左肾进行组织学检查和蛋白质印迹，以评估RANK相关分子和细胞因子的表达和定位。I / R损伤后血清肌酐水平显着升高。观察到RANKL随时间的增加直至24小时，而RANK在再灌注后诱导12小时。RANK在浸润的炎性细胞中表达，其对单核细胞/巨噬细胞的标志物CD68呈阳性。用抗RANKL抗体进行的预处理明显损害了肾功能，并增加了炎症细胞因子（TNFα和IL-6）的诱导，p  <.05）与I / R组的水平相比。然而， 与I / R组相比，rRANKL显着改善了肾功能并降低了炎性细胞因子（TNFα和IL-6），TLR4和MyD88的水平（p <.05）。本研究是第一个评估RANK系统在肾I / R损伤中的作用的研究。RANKL-RANK信号传导影响巨噬细胞功能并导致TLR4的下调以及TNFα和IL-6的减少，从而导致I / R损伤后肾功能的改善。