Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, New York, USA; Renal Section, Northport Veterans Affairs Medical Center, Northport, New York, USA.
Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, New York, USA.
Kidney Int. 2022 Jul;102(1):58-77. doi: 10.1016/j.kint.2022.03.025. Epub 2022 Apr 26.
Thrombotic microangiopathy (TMA) in the kidney represents the most severe manifestation of kidney microvascular endothelial injury. Despite the source of the inciting event, the diverse clinical forms of kidney TMA share dysregulation of endothelial cell transcripts and complement activation. Here, we show that endothelial-specific knockdown of Krüppel-Like Factor 4 (Klf4), an anti-inflammatory and antithrombotic zinc-finger transcription factor, increases the susceptibility to glomerular endothelial injury and microangiopathy in two genetic murine models that included endothelial nitric oxide synthase knockout mice and aged mice (52 weeks), as well as in a pharmacologic model of TMA using Shiga-toxin 2. In all models, Klf4 mice exhibit increased pro-thrombotic and pro-inflammatory transcripts, as well as increased complement factors C3 and C5b-9 deposition and histologic features consistent with subacute TMA. Interestingly, complement activation in Klf4 mice was accompanied by reduced expression of a key KLF4 transcriptional target and membrane bound complement regulatory gene, Cd55. To assess a potential mechanism by which KLF4 might regulate CD55 expression, we performed in silico chromatin immunoprecipitation enrichment analysis of the CD55 promotor and found KLF4 binding sites upstream from the CD55 transcription start site. Using patient-derived kidney biopsy specimens, we found glomerular expression of KLF4 and CD55 was reduced in patients with TMA as compared to control biopsies of the unaffected pole of patient kidneys removed due to kidney cancer. Thus, our data support that endothelial Klf4 is necessary for maintenance of a quiescent glomerular endothelial phenotype and its loss increases susceptibility to complement activation and induction of prothrombotic and pro-inflammatory pathways.
肾脏的血栓性微血管病（TMA）代表了肾脏微血管内皮损伤的最严重表现。尽管激发事件的来源不同，但肾脏 TMA 的多种临床形式都存在内皮细胞转录物和补体激活的失调。在这里，我们表明，内皮特异性敲低 Krüppel-Like Factor 4（Klf4），一种抗炎和抗血栓形成的锌指转录因子，会增加两种遗传小鼠模型（包括内皮型一氧化氮合酶敲除小鼠和老年小鼠（52 周））以及使用志贺毒素 2 的 TMA 药理学模型中肾小球内皮损伤和微血管病的易感性。在所有模型中，Klf4 小鼠都表现出促血栓形成和促炎转录物增加，以及补体因子 C3 和 C5b-9 沉积增加和组织学特征与亚急性 TMA 一致。有趣的是，Klf4 小鼠中的补体激活伴随着关键 KLF4 转录靶标和膜结合补体调节基因 Cd55 的表达减少。为了评估 KLF4 可能调节 CD55 表达的潜在机制，我们对 CD55 启动子进行了计算机模拟染色质免疫沉淀富集分析，发现 KLF4 结合位点位于 CD55 转录起始位点的上游。使用患者来源的肾脏活检标本，我们发现与因肾癌切除的患者肾脏未受影响的对侧活检相比，TMA 患者的肾小球中 Klf4 和 CD55 的表达减少。因此，我们的数据支持内皮细胞 Klf4 对于维持静止的肾小球内皮表型是必需的，其缺失会增加对补体激活和诱导促血栓形成和促炎途径的易感性。
