lncRNA MALAT1 mediated high glucose-induced HK-2 cell epithelial-to-mesenchymal transition and injury

Epithelial-to-mesenchymal transition (EMT) and injury of tubular cells play critical roles in the pathogenesis of diabetic nephropathy (DN). lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) has been shown to be involved in DN progression. However, whether MALAT1 induces EMT and injury in tubular cells is unclear. Here, we investigated the effects of MALAT1 on human proximal tubular cells (HK-2 cells) and the underlying mechanism. We performed qPCR to detect MALAT1, E-cadherin, alpha-smooth muscle actin (alpha-SMA), kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL). Additionally, we conducted Western blot analyses to measure E-cadherin, alpha-SMA, cyclin D1, c-Myc, and beta-catenin in HK-2 cells cultured with normal glucose and high glucose (HG) and in transfected cells or cells treated with LiCl and DKK-1. The beta-catenin localization was observed using immunofluorescence, and the protein levels of NGAL and KIM-1 were evaluated by ELISA. We found that HG-upregulated MALAT1 decreased E-cadherin and increased alpha-SMA, KIM-1, NGAL, cyclin D1, c-Myc, and beta-catenin in HK-2 cells. LiCl exposure increased the expression of alpha-SMA but decreased that of E-cadherin on the base of knocking down MALAT1, and decreased NGAL and KIM-1 expression. DKK-1 showed the opposite effects. Our results suggested that upregulated MALAT1 induced EMT in HG-treated HK-2 cells through activating the Wnt/beta-catenin pathway. However, MALAT1-mediated injury in HK-2 cells was not mediated by activation of the Wnt/beta-catenin pathway. Our results indicate that MALAT1 might serve as a novel therapeutic target for suppressing the progression of DN.