Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah.
Institute of Hypertension, Sun Yat-sen University School of Medicine, Guangzhou, China.
Am J Physiol Renal Physiol. 2020 May 1;318(5):F1122-F1135. doi: 10.1152/ajprenal.00606.2019. Epub 2020 Mar 16.
Emerging evidence has demonstrated that (pro)renin receptor (PRR)-mediated activation of intrarenal renin-angiotensin system (RAS) plays an essential role in renal handling of Na and water balance and blood pressure. The present study tested the possibility that the intrarenal RAS served as a molecular target for the protective action of ELABELA (ELA), a novel endogenous ligand of apelin receptor, in the distal nephron. By RNAscope and immunofluorescence, mRNA and protein expression of endogenous ELA was consistently localized to the collecting duct (CD). Apelin was also found in the medullary CDs as assessed by immunofluorescence. In cultured CD-derived M1 cells, exogenous ELA induced parallel decreases of full-length PRR (fPRR), soluble PRR (sPRR), and prorenin/renin protein expression as assessed by immunoblotting and medium sPRR and prorenin/renin levels by ELISA, all of which were reversed by 8-bromoadenosine 3',5'-cyclic monophosphate. Conversely, deletion of PRR in the CD or nephron in mice elevated and mRNA levels as well as urinary ELA and apelin excretion, supporting the antagonistic relationship between the two systems. Administration of exogenous ELA-32 infusion (1.5 mg·kg·day, minipump) to high salt (HS)-loaded Dahl salt-sensitive (SS) rats significantly lowered mean arterial pressure, systolic blood pressure, diastolic blood pressure, and albuminuria, accompanied with a reduction of urinary sPRR, angiotensin II, and prorenin/renin excretion. HS upregulated renal medullary protein expression of fPRR, sPRR, prorenin, and renin in Dahl SS rats, all of which were significantly blunted by exogenous ELA-32 infusion. Additionally, HS-induced upregulation of inflammatory cytokines (, , , , , , , and ), fibrosis markers (, , , , and ), and kidney injury markers (, , albuminuria, and urinary excretion) were markedly blocked by exogenous ELA infusion. Together, these results support the antagonistic interaction between ELA and intrarenal RAS in the distal nephron that appears to exert a major impact on blood pressure regulation.
越来越多的证据表明，（前）肾素受体（PRR）介导的肾内肾素-血管紧张素系统（RAS）激活在肾脏处理钠和水平衡及血压方面起着重要作用。本研究检测了内肾 RAS 作为 ELABELA（ELA）的分子靶点的可能性，ELABELA 是一种新型的 Apelin 受体内源性配体，在远端肾单位中发挥保护作用。通过 RNAscope 和免疫荧光，内源性 ELA 的 mRNA 和蛋白表达一致定位于集合管（CD）。通过免疫荧光评估，在髓质 CD 中也发现了 Apelin。在体外培养的 CD 衍生的 M1 细胞中，外源性 ELA 通过免疫印迹和 ELISA 评估诱导全长 PRR（fPRR）、可溶性 PRR（sPRR）和前肾素/肾素蛋白表达的平行减少，所有这些都被 8-溴腺苷 3'，5'-环单磷酸逆转。相反，在 CD 或小鼠肾单位中删除 PRR 会升高 和 mRNA 水平以及尿 ELA 和 Apelin 排泄，支持这两个系统之间的拮抗关系。向高盐（HS）负荷的 Dahl 盐敏感（SS）大鼠输注外源性 ELA-32（1.5mg·kg·day，迷你泵）可显著降低平均动脉压、收缩压、舒张压和白蛋白尿，同时降低尿 sPRR、血管紧张素 II 和前肾素/肾素排泄。HS 上调 Dahl SS 大鼠肾髓质蛋白表达 fPRR、sPRR、前肾素和肾素，外源性 ELA-32 输注显著减弱了这一表达。此外，HS 诱导的炎症细胞因子（、、、、、、、和）、纤维化标志物（、、、和）和肾损伤标志物（、、白蛋白尿和尿 排泄）的上调被外源性 ELA 输注显著阻断。总之，这些结果支持 ELA 和远端肾单位内肾 RAS 之间的拮抗相互作用，这似乎对血压调节有重大影响。
