RNA Sequencing reveals induction of specific renal inflammatory pathways in a rat model of malignant hypertension

In malignant hypertension, far more severe kidney injury occurs than in the “benign” form of the disease. The role of high blood pressure and the renin-angiotensin-aldosterone system are well recognized, but the development of malignant nephrosclerosis remains incompletely understood. Using the rat model of two-kidney, one-clip renovascular hypertension in which some but not all animals develop malignant nephrosclerosis, we performed an unbiased analysis of genes by RNA-sequencing to identify transcriptional changes in the kidney specific for malignant nephrosclerosis. Differential gene expression was assessed in three groups: malignant hypertension (MH), non-malignant hypertension (NMH) and normotensive, sham operated controls (sham). To distinguish MH from NMH, we considered two factors: weight loss and typical renovascular lesions. Mean blood pressure measured intraarterially was elevated to a similar degree in MH (220.0±6.5 mmHg) and NMH (192.0±6.4 mmHg) compared to controls (119.5±1.7 mmHg, p<0.05). 886 genes were exclusively regulated in MH only. Principal component analysis revealed a separated clustering of the three groups. The data pointed to an upregulation of many inflammatory mechanisms in MH including pathways, which did previously attract relatively little attention in the setting of hypertensive nephrosclerosis: Transcripts from all three complement activation pathways were upregulated in MH compared to NMH but not in NMH compared with controls; immunohistochemistry confirmed complement deposition in MH exclusively. The expression of chemokines attracting neutrophil granulocytes (CXCL6) as well as actual granulocyte infiltration were increased only in MH rats. The data suggest that these pathways may contribute to the most severe forms of hypertensive nephrosclerosis.在恶性高血压患者中，肾脏损伤的严重程度远高于该疾病的"良性"亚型。高血压与肾素-血管紧张素-醛固酮系统（renin-angiotensin-aldosterone system）的致病作用已得到广泛认可，但恶性肾硬化的发病机制仍未完全阐明。本研究采用两肾一夹型肾血管性高血压大鼠模型，该模型中仅有部分动物会出现恶性肾硬化。我们通过RNA测序（RNA-sequencing）对基因进行无偏分析，以鉴定出与恶性肾硬化特异性相关的肾脏转录组变化。我们对三组样本开展差异基因表达分析：恶性高血压组（malignant hypertension, MH）、非恶性高血压组（non-malignant hypertension, NMH）以及血压正常的假手术对照组（sham）。区分MH与NMH的依据为体重下降情况以及典型的肾血管病变特征。与对照组（119.5±1.7 mmHg）相比，MH组（220.0±6.5 mmHg）与NMH组（192.0±6.4 mmHg）的动脉内测平均血压均显著升高（p<0.05），且两组血压升高幅度相近。本研究共筛选出886个仅在MH组中受到调控的基因。主成分分析（principal component analysis）结果显示，三组样本呈现出明显的聚类分离。数据表明，MH组中多种炎症通路被显著激活，其中包括此前在高血压肾硬化研究中相对较少受到关注的通路：与NMH组相比，MH组的三条补体激活途径相关转录本均呈现上调，而NMH组与对照组相比则无此变化；免疫组织化学实验证实，补体沉积仅出现于MH组中。仅在MH组大鼠中，招募中性粒细胞的趋化因子（CXCL6）表达水平以及实际的粒细胞浸润程度均有所升高。本研究结果提示，上述通路可能参与了最为严重的高血压肾硬化病变进程。