Angiotensin AT₁ receptor activation mediates high glucose‐induced epithelial–mesenchymal transition in renal proximal tubular cells

Abstract

SUMMARY1. Renal tubular epithelial cells can undergo epithelial to mesenchymal transition (EMT) under hyperglycaemic conditions, which is associated with renal interstitial fibrosis. Activation of the renin-angiotensin system (RAS) is involved in diabetic nephropathy. The present study investigated the positive role of angiotensin AT 1 receptors in high glucose-induced EMT in cultured tubular epithelial cells.2. A rat kidney proximal tubular epithelial cell line (NRK-52E) was used in the present study. Levels of EMT makers, namely E-cadherin and vimentin, were estimated using fluorescence immunocytochemistry, mRNA levels of angiotensinogen (AGT), angiotensin-converting enzyme (ACE) and AT 1 receptors were determined by real-time polymerase chain reaction, protein levels of E-cadherin, vimentin, fibronectin, matrix metallopeptidase (MMP)-9 and phosphorylated extracellular signal-regulated kinase (ERK) 1 ⁄ 2 were analysed by western blotting and the concentrations of angiotensin (Ang) II and transforming growth factor (TGF)-b1 in the culture medium were determined by enzyme immunoassay and ELISA.3. High glucose (30 mmol ⁄ L) induced EMT and increased the synthesis of fibronectin and MMP-9. Furthermore, high glucose increased AGT, ACE and AT 1 receptor mRNA levels, as well as AngII and TGF-b1 concentrations in the culture medium and ERK1 ⁄ 2 phosphorylation. Pretreatment of cells for 15 min with the AT 1 receptor antagonist losartan (10 )5 mol ⁄ L) attenuated high glucose-induced increases in TGF-b1 and ERK1⁄ 2 phosphorylation and reduced EMT, as well as the consequent synthesis of fibronectin and MMP-9. 4. The results of the present study suggest that the activated local RAS mediates high glucose-induced EMT. By activating AT 1 receptors and stimulating TGF-b1 synthesis, the elevated local RAS participates in high glucose-induced EMT and increased extracellular matrix secretion.

Overexpression of ACE2 produces antitumor effects via inhibition of angiogenesis and tumor cell invasion in vivo and in vitro

“…The RAS system increases expression of MMPs and modulates the balance between MMPs and tissue inhibitors of MMPs (TIMPs) in many heart and renal diseases (21)(22)(23)(24). Previous cancer studies have demonstrated that AngII augments the migration and invasion of choriocarcinoma cells through the AT1R and induces MMP-2 and MMP-9 expression in gastric cancer cells (25)(26)(27).…”

Fasudil Inhibits Epithelial-Myofibroblast Transdifferentiation of Human Renal Tubular Epithelial HK-2 Cells Induced by High Glucose

“…14) TGF-β 1 and CTGF have been found to be up-regulated in both experimental and human DN, and to be associated with EMT, 7,10,11,[15][16][17][18][19][20][21] supporting a key role for these signaling molecules. A previous study in diabetic rats showed that using fasudil as a treatment also decreased EMT.…”

“…Taken together, these data suggest that high glucose was able to induce EMT in HK-2 cells, consistent with previous studies. 17,38) The molecular mechanisms underlying EMT remain incompletely understood. Multiple intracellular signaling pathways are thought to be involved in EMT regulation, including TGF-β 1 /Smad, Wnt and p38 MAPK.…”

Angiotensin II stimulates fibronectin protein synthesis via a Gβγ/arachidonic acid-dependent pathway

“…Based on the data presented in this paper, we propose a role for the AT 2 receptor in the synthesis of fibronectin, in that the increased fibronectin response to ANG II was completely inhibited by the AT 2 receptor antagonist PD123319, while the AT 1 receptor antagonist losartan had no effect. Despite the fact that several studies have suggested that ANG II-induced fibronectin synthesis is mediated by AT 1 rather than AT 2 signaling, the interpretation relied on use of pharmacological concentrations of losartan that can compete at high concentrations for AT 2 receptor sites (38,41,51). Moreover, this is the first study to investigate the role of ANG AT 1 and AT 2 receptors in ANG II-induced fibronectin synthesis in cultured proximal tubular epithelial cells.…”