Department of Ophthalmology, The First Affiliated Hospital with Nanjing Medical University, Nanjing, China.
Key Laboratory of Targeted Intervention of Cardiovascular Disease and Collaborative Innovation Center for Cardiovascular Translational Medicine, Department of Pathophysiology, Nanjing Medical University, Nanjing, China.
Biochem Biophys Res Commun. 2019 Feb 12;509(3):633-640. doi: 10.1016/j.bbrc.2018.12.024. Epub 2018 Dec 13.
Diabetic retinopathy (DR) is one of the most devastating complications of diabetes mellitus. When exposed to high glucose (HG), retinal epithelial cells undergo profound alterations both morphologically and functionally in a well-conserved process known as epithelial-to-mesenchymal transition (EMT). The mechanism governing HG-induced EMT in retinal epithelial cells is not completely understood. Here we report that treatment with 25 mM glucose led to EMT in retinal pigmented epithelial cells (RPE) characterized by a simultaneous down-regulation of E-Cadherin (encoded by CDH1) and up-regulation of alpha smooth muscle actin (encoded by ACTA2). HG-induced EMT in RPEs was accompanied by augmented expression and enhanced nuclear enrichment of MKL1, a transcriptional modulator. In contrast, MKL1 knockdown by siRNA or inhibition by CCG-1423 abrogated HG-induced EMT in RPEs. Of interest, MKL1 mediated the transcriptional activation of LOX, a mesenchymal marker, in RPEs in response to HG stimulation. Mechanistically, MKL1 interacted with and was recruited by AP-1 to the proximal LOX promoter to promote LOX trans-activation likely through altering the chromatin structure. Finally, LOX depletion by siRNA or inhibition by aminopropionitrile in RPEs abolished HG-induced EMT. In conclusion, our data support a role for MKL1 in mediating HG-induced EMT in retinal epithelial cells via epigenetic activation of LOX transcription.
糖尿病性视网膜病变 (DR) 是糖尿病最具破坏性的并发症之一。在高葡萄糖 (HG) 暴露下，视网膜上皮细胞经历了深刻的形态和功能改变，这一过程在一个被很好地保守的过程中被称为上皮间质转化 (EMT)。然而，目前尚不完全清楚调控视网膜上皮细胞 HG 诱导 EMT 的机制。在这里，我们报告说，用 25mM 葡萄糖处理会导致视网膜色素上皮细胞 (RPE) 发生 EMT，其特征是 E-钙粘蛋白 (由 CDH1 编码) 的同时下调和α平滑肌肌动蛋白 (由 ACTA2 编码) 的上调。RPE 中 HG 诱导的 EMT 伴随着 MKL1 的表达增强和核富集，MKL1 是一种转录调节剂。相比之下，siRNA 敲低 MKL1 或 CCG-1423 抑制可消除 RPE 中的 HG 诱导的 EMT。有趣的是，MKL1 介导了 LOX（一种间充质标志物）在 RPE 中的转录激活，以响应 HG 刺激。在机制上，MKL1 与 AP-1 相互作用并被招募到近端 LOX 启动子，以促进 LOX 反式激活，可能通过改变染色质结构。最后，用 siRNA 敲低 LOX 或用氨基丙腈在 RPE 中抑制 LOX 可消除 HG 诱导的 EMT。总之，我们的数据支持 MKL1 通过表观遗传激活 LOX 转录来介导 HG 诱导的视网膜上皮细胞 EMT。
