Nrf2-Heme Oxygenase-1 Attenuates High-Glucose-Induced Epithelial-to-Mesenchymal Transition of Renal Tubule Cells by Inhibiting ROS-Mediated PI3K/Akt/GSK-3β Signaling

BACKGROUND: Epithelial-to-mesenchymal transition (EMT) is thought to play a significant role in the advancement to chronic kidney disease and contributes to the deposition of extracellular matrix proteins and renal fibrosis relating to diabetic nephropathy. METHOD: We studied the effect of Nrf2-HO-1 signaling on high-glucose- (HG-) induced EMT in normal human tubular epithelial cells, that is, HK2 cells. In short, we treated HK2 cells with HG and sulforaphane (SFN) as an Nrf2 activator. EMT was evaluated by the expression activity of the epithelial marker E-cadherin and mesenchymal markers such as vimentin and fibronectin. RESULTS: Exposure of HK2 cells to HG (60 mM) activated the expression of vimentin and fibronectin but decreased E-cadherin. Treatment of HK2 cells with SFN caused HG-induced attenuation in EMT markers with activated Nrf2-HO-1. We found that SFN decreased HG-induced production of reactive oxygen species (ROS), phosphorylation of PI3K/Akt at serine 473, and inhibitory phosphorylation of serine/threonine kinase glycogen synthase kinase-3β (GSK-3β) at serine 9. Subsequently, these signaling led to the downregulation of the Snail-1 transcriptional factor and the recovery of E-cadherin. CONCLUSION: The present study suggests that Nrf2-HO-1 signaling has an inhibitory role in the regulation of EMT through the modulation of ROS-mediated PI3K/Akt/GSK-3β activity, highlighting Nrf2-HO-1 and GSK-3β as potential therapeutic targets in diabetic nephropathy.