iRhom2 Promotes Lupus Nephritis through ADAM17-Dependent TNF-a and EGFR Signaling

Lupus nephritis (LN) often results in progressive renal dysfunction. The inactive Rhomboid 2 (iRhom2) is a newly identified key regulator of A disintegrin and metalloprotease 17 (ADAM17), whose substrates, such as TNF-a and heparin-binding EGF (HB-EGF), have been implicated in the pathogenesis of chronic kidney disease. Here we demonstrate that deficiency of iRhom2 protects the lupus-prone Fcgr2b-/- mice from developing severe kidney damage without altering anti-double stranded (ds) DNA Ab production, by simultaneously blocking the HB-EGF/EGFR and the TNF-a signaling in the kidney tissues. Unbiased transcriptome profiling of kidneys and kidney macrophages revealed that TNF-a and HB-EGF/EGFR signaling pathways are highly upregulated in Fcgr2b-/- mice; alterations that were diminished in the absence of iRhom2. Pharmacological blockade of either TNF-a or EGFR signaling protected Fcgr2b-/- mice from severe renal damage. Finally, kidneys from LN patients showed increased iRhom2 and HB-EGF expression, with interstitial HB-EGF expression significantly associated with chronicity indices. Our data suggest that activation of iRhom2/ADAM17-dependent TNF-a and EGFR signaling plays a crucial role in mediating irreversible kidney damage in LN, thereby uncovering a novel target for selective and simultaneous dual inhibition of two major pathological pathways in the effector arm of the disease. Overall design: [1] Analysis of total kidney transcriptomes in Fcgr2b-/- mice, Rhbdf2-/- mice; Rhbdf2 -/- Fcgr2b-/- mice and the wildtype control. [2] Analysis of CD45+F4/80hiCD11b+Ly6G-Ly6C- kidney macrophages transcriptomes in Fcgr2b-/- mice, Rhbdf2-/- mice; Rhbdf2 -/- Fcgr2b-/- mice and the wildtype control.狼疮肾炎（Lupus nephritis, LN）常引发进行性肾功能不全。失活菱形蛋白2（inactive Rhomboid 2, iRhom2）是新近鉴定的解整合素金属蛋白酶17（A disintegrin and metalloprotease 17, ADAM17）关键调控因子，其底物包括肿瘤坏死因子α（Tumor Necrosis Factor-α, TNF-α）、肝素结合表皮生长因子（heparin-binding EGF, HB-EGF）等，已被证实参与慢性肾脏病的发病过程。本研究证实，iRhom2缺失可通过同时阻断肾脏组织内的HB-EGF/表皮生长因子受体（Epidermal Growth Factor Receptor, EGFR）与TNF-α信号通路，使狼疮易感的Fcγ受体2b敲除（Fcgr2b-/-）小鼠免于发生严重肾损伤，且不影响抗双链DNA（double stranded DNA, dsDNA）抗体的产生。对肾脏及肾脏巨噬细胞的无偏转录组分析显示，Fcgr2b-/-小鼠肾脏内TNF-α与HB-EGF/EGFR信号通路显著上调；而在iRhom2缺失的背景下，上述通路的异常激活得到显著缓解。单独采用药物阻断TNF-α或EGFR信号通路，同样可保护Fcgr2b-/-小鼠免受严重肾损伤。进一步分析发现，LN患者的肾脏组织中iRhom2与HB-EGF的表达水平升高，且间质HB-EGF的表达与慢性化指数显著相关。本研究数据表明，iRhom2/ADAM17依赖的TNF-α与EGFR信号通路激活，在介导LN不可逆肾损伤中发挥关键作用，从而为同时靶向抑制该疾病效应臂中的两大病理通路提供了全新的干预靶点。实验整体设计：[1] 对Fcgr2b-/-小鼠、Rhbdf2-/-小鼠、Rhbdf2-/-Fcgr2b-/-双敲除小鼠及野生型对照小鼠的全肾脏转录组进行分析；[2] 对Fcgr2b-/-小鼠、Rhbdf2-/-小鼠、Rhbdf2-/-Fcgr2b-/-双敲除小鼠及野生型对照小鼠的CD45+F4/80hiCD11b+Ly6G-Ly6C-肾脏巨噬细胞进行转录组分析。