Urotensin II Induces ER Stress and EMT and Increase Extracellular Matrix Production in Renal Tubular Epithelial Cell in Early Diabetic Mice

Abstract

Background/Aims: Urotensin II (UII) and its receptor are highly expressed in the kidney tissue of patients with diabetic nephropathy (DN). The aim of this study is to examine the roles of UII in the induction of endoplasmic reticulum stress (ER stress) and Epithelial-mesenchymal transition (EMT) in DN in vivo and in vitro. Methods: Kidney tissues were collected from patients with DN. C57BL/6 mice and mice with UII receptor knock out were injected with two consecutive doses of streptozotocin to induce diabetes and were sacrificed at 3^th week for in vivo study. HK-2 cells in vitro were cultured and treated with UII. Markers of ER stress and EMT, fibronectin and type IV collagen were detected by immunohistochemistry, real time PCR and western blot. Results: We found that the expressions of protein of UII, GRP78, CHOP, ALPHA-SMA, fibronectin and type IV collagen were upregulated while E-cadherin protein was downregulated as shown by immunohistochemistry or western blot analysis in kidney of diabetic mice in comparison to normal control; moreover expressions of GRP78, CHOP, ALPHA-SMA, fibronectin and type IV collagen were inhibited while E-caherin expression was enhanced in kidney in diabetic mice with UII receptor knock out in comparison to C57BL/6 diabetic mice. In HK-2 cells, UII induced upregulation of GRP78, CHOP, ALPHA-SMA, fibroblast-specifc protein 1(FSP-1), fibronectin and type collagen and downregulation of E-cadherin. UII receptor antagonist can block UII-induced ER stress and EMT; moreover, 4-PBA can inhibit the mRNA expression of ALPHA-SMA and FSP1 induced by UII in HK-2 cells. Conclusions: We are the first to verify UII induces ER stress and EMT and increase extracellular matrix production in renal tubular epithelial cell in early diabetic mice. Moreover, UII may induce renal tubular epithelial EMT via triggering ER stress pathway in vitro, which might be the new pathogenic pathway for the development of renal fibrosis in DN.

MiR‐4756 promotes albumin‐induced renal tubular epithelial cell epithelial‐to‐mesenchymal transition and endoplasmic reticulum stress via targeting Sestrin2

“…It has been demonstrated that ER stress can induce EMT regardless of the tissue of origin or malignant status of cells (Shah, Dupre, Siskind, & Beverly, ), and Scr‐dependent signaling may play a role (Moon, Kim, Nho, Jang, & Lee, ). Both Tang et al () and Pang et al () found that ER stress can induce EMT in HK‐2 cells. In this study, we found salubrinal, an inhibitor of ER stress, blocked miR‐4756‐induced EMT, which indicates that miR‐4756 regulates HK‐2 EMT partly through ER stress.…”

“…Recently, endoplasmic reticulum (ER) stress and the epithelial‐to‐mesenchymal transition (EMT) have been identified as key effects in tubulointerstitial fibrosis, thereby accelerating the progression of DKD (Maekawa & Inagi, ; Ravindran, Kuruvilla, Wilbur, & Munusamy, ). Several factors, including proteinuria, can trigger ER stress and EMT during the development of DKD (Allouch & Munusamy, ; Pang et al, ). Proteinuria is a key factor for promoting the progression of DKD.…”

Renal Urotensin II System Plays Roles in the Regulation of Blood Pressure in Dahl Salt-Resistant Rat

“…Genotype identification of UT gene knockout mice was performed by PCR according to our previous publications [6]. Lane 1 in Figure 6 (−/−) represents homozygotes of UT gene knockout (KO group) genotype; lanes 2 and 9 (+/−) represent heterozygotes of UT gene knockout; lane 10 (+/+) represents wild type (WT).…”

“…Amplification 756 bp means urotensin II receptor is knocked out and 63 bp means wild type; both 756 bp and 63 bp mean heterozygotes of UT gene knockout KO mouse as well as mRNA and protein expression of UT KO group, according to our previous publications [6]. …”

Endoplasmic reticulum stress and kidney dysfunction

“…Epithelial cells that are subjected to ER stress often lose epithelial features (for example E cadherin) and may acquire markers of mesenchymal (myofibroblastic) lineage such as vimentin, N‐cadherin, and α‐smooth muscle actin, in a process that recapitulates more or less the epithelial‐to‐mesenchymal transition observed in cancer. Incomplete EMT, also refereed as epithelial phenotypic changes (EPC), participates in the whole fibrotic process upon tissue injury in proportions that vary according to the model [Cuevas et al., ; Moon et al., ; Pang et al., ]. The specific contribution of these cells in fibrogenesis includes the production of extracellular matrix, and secretion of profibrotic mediators.…”