Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY, USA.
Division of Urology, Albany Medical College, Albany, NY, USA.
FASEB J. 2021 Jul;35(7):e21725. doi: 10.1096/fj.202002652RR.
Renal fibrosis leads to chronic kidney disease, which affects over 15% of the U.S. population. PAI-1 is highly upregulated in the tubulointerstitial compartment in several common nephropathies and PAI-1 global ablation affords protection from fibrogenesis in mice. The precise contribution of renal tubular PAI-1 induction to disease progression, however, is unknown and surprisingly, appears to be independent of uPA inhibition. Human renal epithelial (HK-2) cells engineered to stably overexpress PAI-1 underwent dedifferentiation (E-cadherin loss, gain of vimentin), G2/M growth arrest (increased p-Histone3, p21), and robust induction of fibronectin, collagen-1, and CCN2. These cells are also susceptible to apoptosis (elevated cleaved caspase-3, annexin-V positivity) compared to vector controls, demonstrating a previously unknown role for PAI-1 in tubular dysfunction. Persistent PAI-1 expression results in a loss of klotho expression, p53 upregulation, and increases in TGF-βRI/II levels and SMAD3 phosphorylation. Ectopic restoration of klotho in PAI-1-transductants attenuated fibrogenesis and reversed the proliferative defects, implicating PAI-1 in klotho loss in renal disease. Genetic suppression of p53 reversed the PA1-1-driven maladaptive repair, moreover, confirming a pathogenic role for p53 upregulation in this context and uncovering a novel role for PAI-1 in promoting renal p53 signaling. TGF-βRI inhibition also attenuated PAI-1-initiated epithelial dysfunction, independent of TGF-β1 ligand synthesis. Thus, PAI-1 promotes tubular dysfunction via klotho reduction, p53 upregulation, and activation of the TGF-βRI-SMAD3 axis. Since klotho is an upstream regulator of both PAI-1-mediated p53 induction and SMAD3 signaling, targeting tubular PAI-1 expression may provide a novel, multi-level approach to the therapy of CKD.
肾纤维化导致慢性肾病,影响了美国超过 15%的人口。PAI-1 在几种常见肾病的肾小管间质中高度上调,而 PAI-1 的全局缺失可防止小鼠的纤维化发生。然而,肾小管 PAI-1 诱导对疾病进展的确切贡献尚不清楚,令人惊讶的是,它似乎独立于 uPA 抑制。稳定过表达 PAI-1 的人肾小管上皮 (HK-2) 细胞经历去分化(E-钙粘蛋白丢失,波形蛋白获得)、G2/M 生长停滞(p-Histone3、p21 增加)和纤维连接蛋白、胶原-1 和 CCN2 的强烈诱导。与载体对照相比,这些细胞也容易发生凋亡(cleaved caspase-3 升高,annexin-V 阳性),表明 PAI-1 在肾小管功能障碍中具有以前未知的作用。持续的 PAI-1 表达导致 klotho 表达的丧失、p53 的上调以及 TGF-βRI/II 水平和 SMAD3 磷酸化的增加。在 PAI-1 转染细胞中外源恢复 klotho 减弱了纤维化并逆转了增殖缺陷,表明 PAI-1 在肾脏疾病中的 klotho 丧失中起作用。p53 的遗传抑制逆转了由 PA1-1 驱动的适应性修复,此外,证实了 p53 上调在这种情况下的致病作用,并揭示了 PAI-1 在促进肾脏 p53 信号中的新作用。TGF-βRI 抑制也减弱了 PAI-1 引发的上皮功能障碍,独立于 TGF-β1 配体合成。因此,PAI-1 通过 klotho 减少、p53 上调和激活 TGF-βRI-SMAD3 轴促进肾小管功能障碍。由于 klotho 是 PAI-1 介导的 p53 诱导和 SMAD3 信号的上游调节剂,靶向肾小管 PAI-1 表达可能为 CKD 的治疗提供一种新的、多层次的方法。