Danielle Alberti Memorial Centre for Diabetic Complications, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia.
Am J Physiol Renal Physiol. 2010 Sep;299(3):F585-93. doi: 10.1152/ajprenal.00538.2009. Epub 2010 Jun 16.
Epithelial-to-mesenchymal transformation (EMT) of tubular cells into a myofibroblastic phenotype is an important mediator of renal scarring in chronic nephropathy. This study examines the role of the renin-angiotensin system (RAS) in this process. NRK-52E cells were exposed to angiotensin (ANG) II and ANG 1-7 in the presence or absence of inhibitors and agonists of RAS signaling. EMT was assessed at 3 days by expression of alpha-smooth muscle actin (alpha-SMA) and E-cadherin and the induction of a myofibroblastic phenotype. Expression of fibrogenic growth factors and matrix proteins was assessed by RT-PCR and immunofluorescence microscopy. To confirm findings in vivo, rats were also infused with ANG 1-7 (24 microg*kg(-1)*h(-1)) or saline via an osmotic minipump for 10 days, and renal fibrogenesis was then assessed. Treatment of NRK-52E cells with ANG II induced characteristic changes of EMT. Selective blockade of the AT(1) receptor or the AT(2) receptor failed to inhibit ANG II-induced EMT. However, blockade of the ANG 1-7 receptor, Mas-1, was able to prevent ANG II-dependent EMT. To confirm these findings, both ANG 1-7 and the selective Mas receptor agonist, AVE-0991, were able to induce NRK-52E cells in a dose-dependent manner. Exposing cells to recombinant ACE2 was also able to induce EMT. In addition, an infusion of ANG 1-7 induced the tubular expression of alpha-SMA and the expression of matrix proteins in the kidney. ANG II is a potent stimulus for EMT, but not through conventional pathways. This study points to the possible limitations of conventional RAS blockade, which not only fails to antagonize this pathway, but also may enhance it via augmenting the synthesis of ANG 1-7.
上皮-间充质转化（EMT）管状细胞成肌成纤维表型是慢性肾病肾瘢痕形成的重要介质。本研究探讨了肾素-血管紧张素系统（RAS）在这个过程中的作用。NRK-52E 细胞在存在或不存在 RAS 信号转导抑制剂和激动剂的情况下，暴露于血管紧张素（ANG）II 和 ANG 1-7 中。在第 3 天通过表达α-平滑肌肌动蛋白（α-SMA）和 E-钙粘蛋白和诱导肌成纤维表型来评估 EMT。通过 RT-PCR 和免疫荧光显微镜评估纤维发生生长因子和基质蛋白的表达。为了在体内证实发现，还通过渗透微型泵向大鼠输注 ANG 1-7（24μg*kg(-1)*h(-1)）或盐水 10 天，然后评估肾纤维化。用 ANG II 处理 NRK-52E 细胞诱导 EMT 的特征变化。选择性阻断 AT(1)受体或 AT(2)受体不能抑制 ANG II 诱导的 EMT。然而，阻断 ANG 1-7 受体，Mas-1，能够防止 ANG II 依赖性 EMT。为了证实这些发现，ANG 1-7 和选择性 Mas 受体激动剂 AVE-0991 都能够以剂量依赖性方式诱导 NRK-52E 细胞。暴露于重组 ACE2 的细胞也能够诱导 EMT。此外，ANG 1-7 的输注诱导肾小管中 α-SMA 的表达和肾脏中基质蛋白的表达。ANG II 是 EMT 的有效刺激物，但不是通过常规途径。这项研究指出了常规 RAS 阻断的可能局限性，它不仅不能拮抗这条途径，而且还可能通过增强 ANG 1-7 的合成来增强它。
