Department of Regenerative and Cancer Cell Biology Albany Medical Center, Albany, New York, USA.
Division of Nephrology and Hypertension, Vanderbilt Medical School, Nashville, Tennessee, USA.
FASEB J. 2019 Sep;33(9):9797-9810. doi: 10.1096/fj.201802489RR. Epub 2019 May 16.
Rac-GTPases are major regulators of cytoskeletal remodeling and their deregulation contributes to numerous pathologies. Whether or how Rac promotes tubulointerstitial fibrosis and chronic kidney disease (CKD) is currently unknown. We showed that the major profibrotic cytokine, TGF-β1 promoted rapid Rac1-GTP loading in human kidney 2 (HK-2) human renal epithelial cells. A Rac-specific chemical inhibitor, EHT 1864, blocked TGF-β1-induced fibrotic reprogramming in kidney epithelial cells and fibroblasts. Stable Rac1 depletion in HK-2 cells, moreover, eliminated TGF-β1-mediated non-SMAD pathway activation [, Src, epidermal growth factor receptor (EGFR), p53] and subsequent plasminogen activator inhibitor-1 (PAI-1), connective tissue growth factor, fibronectin, and p21 induction. Rac1 and p22 knockdown abrogated free radical generation by TGF-β1 in HK-2 cells, consistent with the role of Rac1 in NAPD(H). TGF-β1-induced renal epithelial cytostasis was also completely bypassed by Rac1, p22, p47, and PAI-1 silencing. Rac1b isoform expression was robustly induced in the fibrotic kidneys of mice and humans. Intraperitoneal administration of EHT 1864 in mice dramatically attenuated ureteral unilateral obstruction-driven EGFR, p53, Rac1b, yes-associated protein/transcriptional coactivator with PDZ-binding motif activation/expression, dedifferentiation, cell cycle arrest, and renal fibrogenesis evident in vehicle-treated obstructed kidneys. Thus, the Rac1-directed redox response is critical for TGF-β1-driven epithelial dysfunction orchestrated, in part, PAI-1 up-regulation. Rac pathway inhibition suppressed renal oxidative stress and maladaptive repair, identifying Rac as a novel therapeutic target against progressive CKD.-Patel, S., Tang, J., Overstreet, J. M., Anorga, S., Lian, F., Arnouk, A., Goldschmeding, R., Higgins, P. J., Samarakoon, R. Rac-GTPase promotes fibrotic TGF-β1 signaling and chronic kidney disease EGFR, p53, and Hippo/YAP/TAZ pathways.
Rac-GTPases 是细胞骨架重塑的主要调节剂，其失调导致许多病理学的发生。Rac 是否以及如何促进肾小管间质纤维化和慢性肾脏病 (CKD) 目前尚不清楚。我们发现主要的促纤维化细胞因子 TGF-β1 可促进人肾 2 (HK-2) 人肾小管上皮细胞中 Rac1-GTP 的快速加载。 Rac 特异性化学抑制剂 EHT 1864 阻断了 TGF-β1 诱导的肾上皮细胞和成纤维细胞的纤维化重编程。此外，HK-2 细胞中稳定的 Rac1 耗竭消除了 TGF-β1 介导的非 SMAD 途径激活 [Src、表皮生长因子受体 (EGFR)、p53] 和随后的纤溶酶原激活物抑制剂-1 (PAI-1)、结缔组织生长因子、纤维连接蛋白和 p21 的诱导。 Rac1 和 p22 的敲低消除了 TGF-β1 在 HK-2 细胞中产生的自由基，这与 Rac1 在 NAPD(H)中的作用一致。 TGF-β1 诱导的肾上皮细胞细胞停滞也被 Rac1、p22、p47 和 PAI-1 的沉默完全绕过。 Rac1b 同工型在纤维化小鼠和人类肾脏中表达明显增加。在小鼠中，腹腔内给予 EHT 1864 可显著减弱单侧输尿管梗阻驱动的 EGFR、p53、Rac1b、Yes 相关蛋白/转录共激活因子与 PDZ 结合基序的激活/表达、去分化、细胞周期停滞和肾纤维化，在对照梗阻肾脏中可见。因此，Rac1 介导的氧化还原反应对于 TGF-β1 驱动的上皮功能障碍至关重要，部分原因是 PAI-1 的上调。 Rac 通路抑制抑制了肾脏氧化应激和适应性修复，确定 Rac 为针对进行性 CKD 的新型治疗靶点。-帕特尔，S.、唐，J.、奥弗斯特里特，J.M.、安诺卡，S.、连，F.、阿努克，A.、戈尔德施米丁，R.、希金斯，P.J.、萨马拉科恩，R. Rac-GTPase 促进纤维化 TGF-β1 信号转导和慢性肾脏病 EGFR、p53 和 Hippo/YAP/TAZ 通路。
