Abstract
Diabetic cataract is a common complication of diabetes. The epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is a key event in the development of diabetic cataracts. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) has been reported to be highly expressed in different tissues of diabetic patients. This study is aimed at investigating the function and mechanism of MALAT1 in the regulation of EMT in human LECs under high glucose conditions. MALAT1, α-smooth muscle actin (α-SMA), fibronectin (FN), and nuclear factor erythroid-derived 2-like 2 (NRF2) were highly expressed in the LECs of diabetic cataract patients and in the human LECs under high glucose conditions; meanwhile, the decreased expressions of E-cadherin and zonula occludens 1 (ZO-1) were detected. Knockdown of MALAT1 could significantly reduce ROS, prevent EMT, arrest S phase cell cycle, and suppress the expression of total NRF2 and its nucleus translocation in LECs. Furthermore, after NRF2 was knocked down, total NRF2, α-SMA, and FN in cells, and NRF2, Notch intracellular domain (NICD), and Snail were decreased in the nucleus. Using bioinformatics methods, we predicted that MALAT1 and NRF2 shared the same microRNA-144-3p (miR-144-3p) combining site. Luciferase reporter coupled with qRT-PCR assays revealed that miR-144-3p was a target of MALAT1, which was confirmed to downregulate miR-144-3p in the LECs. In addition, after transfection of miR-144-3p mimics or inhibitor, western blot assay demonstrated that miR-144-3p negatively regulated the expression of total NRF2, α-SMA, and FN in cells, and NRF2, NICD, and Snail in the nucleus without affecting Kelch-like ECH-associated protein 1 (KEAP1). Finally, we confirmed that transfection of shMALAT1 inhibited NRF2 expression, and its mediated EMT could be rescued by miR-144-3p inhibitor; transfection of pcDNA3.1-MALAT1 promoted NRF2 expression, and its mediated EMT could be reversed by miR-144-3p inhibitor. In summary, we demonstrate that MALAT1 regulates miR-144-3p to facilitate EMT of LECs via the ROS/NRF2/Notch1/Snail pathway.
Highlights
Diabetes is a metabolic disease characterized by elevated blood glucose
In HLE-B3 cells, qRT-PCR and western blot analysis showed that the expressions of α-SMA and FN increased gradually and significantly with the concentration (25.5 mM and 35.5 mM) and duration of high glucose (24 h and 48 h) on both RNA and protein levels compared with the control group (5.5 mM); the expressions of epithelial cell markers E-cadherin and zonula occludens 1 (ZO-1) were significantly decreased (Figures 1(c)–1(g))
These results suggested the occurrence of epithelial-mesenchymal transition (EMT) in human lens epithelial cells (LECs) of diabetic cataracts
Summary
Complications of diabetes occur in all organ systems, such as diabetic nephropathy, diabetic neuropathy, diabetic retinopathy, and diabetic cataracts [1,2,3,4,5]. Diabetic patients suffer from cataracts earlier than nondiabetic patients [6], and cataract surgery on diabetic patients may lead to more complications, especially in hyperglycemia conditions [7]. It is helpful to explore the pathogenesis of diabetic cataracts in order to find the most effective way to prevent them. Posterior subcapsular cataracts occur because of abnormal cells and extracellular matrix under the lens posterior capsules in humans [10], and diabetic subcapsular cataracts in rats and mice are highly associated with the epithelial-mesenchymal transition (EMT) of lens epithelial
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