Department of Ophthalmology, The Affiliated Hospital of Southwest Medical University, Luzhou, China.
Department of Rheumatology and Immunology, The Affiliated Hospital of Southwest Medical University, Luzhou, China.
Am J Physiol Endocrinol Metab. 2021 Mar 1;320(3):E598-E608. doi: 10.1152/ajpendo.00089.2020. Epub 2020 Dec 7.
Diabetic retinopathy (DR) is one of the serious complications that occurs in diabetic patients that frequently causes blindness. Long noncoding RNAs (lncRNAs) have been associated with DR pathology. This study aimed to determine the underlying mechanism of lncRNA maternally expressed gene 3 (MEG3) in association with DNA methyltransferase 1 (DNMT1) in the endothelial-mesenchymal transition (endMT) that occurs in DR. A rat model of DR was induced by streptozotocin (STZ) injection, and a high-glucose (HG)-induced cell model was established by exposing microvascular endothelial cells obtained from retina of rats to HG. Subsequently, MEG3 was overexpressed in rat and cell models to characterize its impact on endMT in DR and the involvement of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway. Furthermore, the methylation level of MEG3 promoter region was determined with the application of methylation-specific polymerase chain reaction, followed by chromatin immunoprecipitation assay for methyltransferase enrichment. Finally, we examined the regulation of DNMT1 on MEG3 methylation and endMT in the HG-induced cell model. The results obtained revealed downregulated MEG3 expression in DR rat and cell models. Overexpressed MEG3 was shown to suppress endMT in DR rat and cell models through the inhibition of the PI3K/Akt/mTOR signaling pathway. Notably, DNMT1 could promote MEG3 promoter methylation to inhibit MEG3 expression by recruiting methyltransferase, which activated the PI3K/Akt/mTOR signaling pathway to accelerate endMT in DR. These findings further highlighted the inhibitory effect of MEG3 on endMT in DR, thus presenting a novel therapeutic target candidate for DR treatment.
糖尿病视网膜病变（DR）是糖尿病患者常发生的严重并发症之一，常导致失明。长链非编码 RNA（lncRNA）与 DR 病理有关。本研究旨在确定 lncRNA 母系表达基因 3（MEG3）与 DNA 甲基转移酶 1（DNMT1）在 DR 中发生的内皮-间充质转化（endMT）中的潜在机制。通过链脲佐菌素（STZ）注射诱导 DR 大鼠模型，并通过将从小鼠视网膜获得的微血管内皮细胞暴露于高葡萄糖（HG）来建立 HG 诱导的细胞模型。随后，在大鼠和细胞模型中过表达 MEG3，以表征其对 DR 中 endMT 的影响以及磷脂酰肌醇 3-激酶（PI3K）/Akt/雷帕霉素哺乳动物靶蛋白（mTOR）信号通路的参与。此外，应用甲基化特异性聚合酶链反应测定 MEG3 启动子区域的甲基化水平，随后进行染色质免疫沉淀测定甲基转移酶富集。最后，我们研究了 DNMT1 对 HG 诱导的细胞模型中 MEG3 甲基化和 endMT 的调控作用。结果表明，DR 大鼠和细胞模型中 MEG3 表达下调。过表达的 MEG3 通过抑制 PI3K/Akt/mTOR 信号通路抑制 DR 大鼠和细胞模型中的 endMT。值得注意的是，DNMT1 可以通过募集甲基转移酶促进 MEG3 启动子甲基化，抑制 MEG3 表达，激活 PI3K/Akt/mTOR 信号通路，加速 DR 中的 endMT。这些发现进一步强调了 MEG3 对 DR 中 endMT 的抑制作用，因此为 DR 治疗提供了一个新的治疗靶点候选物。
