Targeting ferroptosis in renal tubular epithelial cells to improve outcomes of lupus nephritis

项目总结/摘要 狼疮性肾炎是系统性红斑狼疮最严重的终末器官表现之一。 免疫抑制，治疗这种疾病的基石，是复杂的许多不利影响。虽然 传统上被认为是肾小球疾病，高达80%的狼疮性肾炎患者存在肾小管损伤， 并且肾小管损伤是比肾小球损伤更好的进展到终末期肾病的预测因子。这 确定肾小管是狼疮性肾炎的治疗靶点。复杂的生物机制， 狼疮性肾炎中潜在的肾小管上皮细胞损伤在很大程度上仍不清楚。我们建议一 通过利用我们的关键新发现来实现这种机械的理解。 我们已经证明，铁积累在肾小管室的狼疮性肾炎，但没有 在肾小球中。肾脏中的大部分铁再循环是由近端肾小管上皮细胞进行的， 过量的铁引起铁凋亡--一种以高水平脂质为特征的炎症性细胞死亡 过氧化作用摘要铁蛋白沉积主要见于人类及鼠类狼疮性肾炎的肾小管节段 肾脏我们已经发现，酰基辅酶A合成酶长链家族成员4（ACSL 4）， 在狼疮性肾炎中，铁凋亡促进剂SLC 7A 11增加，而铁凋亡抑制剂SLC 7A 11减少。 此外，人狼疮肾炎血清诱导近端肾小管上皮细胞铁凋亡，这是因为 与炎症和损伤有关。一种新的铁凋亡抑制剂livestain-2阻断了这些结果。 这些数据使我们假设近端肾小管上皮细胞中的铁积累促进了 铁下垂，传播肾小管间质炎症和狼疮性肾炎的预后。我们的目标是测试 这一假设使用ACSL 4（Acsl 4PTEC-/-）和SCL 7A 11（Slc 7a 11 PTEC-/-）缺陷的同类小鼠，仅在它们的 近端肾小管上皮细胞（PTEC）。我们将首先研究Acsl 4PTEC-/-的抗性和Acsl 4PTEC-/-的易感性。 Slc 7a 11 PTEC-/-小鼠使用免疫复合物的诱导型和自发性小鼠模型致铁凋亡 肾小球肾炎，确定下游分子途径，阻止或导致铁凋亡，并遵循 肾损伤的后果。利用狼疮性肾炎患者和健康对照，我们将解剖铁下垂 全血清和免疫球蛋白耗尽的血清对近端肾小管上皮细胞的诱导能力以及测试 新型ACSL 4抑制剂。使用来自同一组患者和对照组的纯化细胞，我们将阻断已知的 SLC 7A 11的阻遏物，并评估铁下垂和肾小管病理学的结果。最后，我们将评估 在两种自发性狼疮性肾炎小鼠模型中， 肾损伤这些研究将确定狼疮近端肾小管上皮细胞损伤的新机制 肾炎和支持使用铁凋亡抑制剂作为一种新的辅助治疗，以减少对传统药物的依赖 免疫抑制剂

PROJECT SUMMARY/ABSTRACT Lupus nephritis is one of the most severe end-organ manifestations of systemic lupus erythematosus. Immunosuppression, the cornerstone for treating this disease, is complicated by many adverse effects. Although traditionally considered as a glomerular disease, up to 80% of lupus nephritis patients present with tubular injury, and tubular injury is a better predictor of progression to end stage kidney disease than glomerular injury. This identifies the renal tubules as a therapeutic target in lupus nephritis. The complex biological mechanisms that underlie tubular epithelial cell injury in lupus nephritis remain, for the most part, obscure. We propose to provide such a mechanistic understanding by leveraging our key novel findings. We have shown that iron accumulates in the tubular compartment of the lupus nephritis kidneys but not in the glomeruli. Most of the iron recycling in the kidney is performed by proximal tubular epithelial cells, and excess iron induces ferroptosis -- an inflammatory form of cell death characterized by high levels of lipid peroxidation. Ferroptosis is mostly observed in the tubular segments of human and murine lupus nephritis kidneys. We have found that the enzyme Acyl-CoA synthetase long-chain family member 4 (ACSL4), a ferroptosis promoter, was increased whereas SLC7A11, a ferroptosis inhibitor, was decreased in lupus nephritis. Additionally, human lupus nephritis serum induced ferroptosis in proximal tubular epithelial cells and this was associated with inflammation and injury. Liproxstain-2, a novel ferroptosis inhibitor, blocked these outcomes. These data led us to hypothesize that iron accumulation in proximal tubular epithelial cells promotes ferroptosis, propagates tubulointerstitial inflammation and worsens outcomes of lupus nephritis. We aim to test this hypothesis using congenic mice deficient for ACSL4 (Acsl4PTEC-/-) and SCL7A11 (Slc7a11PTEC-/-) only in their proximal tubular epithelial cells (PTEC). We will first investigate the resistance of Acsl4PTEC-/- and susceptibility of Slc7a11PTEC-/- mice to ferroptosis using an inducible and a spontaneous mouse model of immune complex glomerulonephritis, identify the downstream molecular pathways that block or lead to ferroptosis and follow the outcomes of kidney injury. Using lupus nephritis patients and healthy controls, we will dissect the ferroptosis inducing ability of whole and immunoglobin depleted serum on proximal tubular epithelial cells as well as test novel ACSL4 inhibitors. Using purified cells from the same cohort of patients and controls we will block known repressors of SLC7A11 and evaluate outcomes of ferroptosis and tubular pathology. Finally, we will evaluate the in vivo therapeutic efficacy of Liproxstain-2 in two spontaneous murine models of lupus nephritis with existing renal injury. These studies will identify novel mechanisms of proximal tubular epithelial cell injury in lupus nephritis and support use of ferroptosis inhibitors as a novel adjunct therapy to reduce dependency on traditional immunosuppressants.