Glycogen synthase kinase-3β is required for epithelial-mesenchymal transition and barrier dysfunction in mouse podocytes under high glucose conditions

Abstract

Epithelial-mesenchymal transition (EMT) is important for diabetic nephropathy (DN). Podocytes are specialized epithelial cells, which form a major component of the glomerular filtration barrier. Podocyte damage has been suggested to be the primary mechanism behind the albuminuria associated with DN. The present study aimed to determine the function of glycogen synthase kinase (GSK)-3β in EMT and barrier dysfunction of mouse podocytes exposed to high glucose (HG) conditions. Matured and differentiated podocytes were treated with normal glucose (NG), HG or NG + mannitol. Podocytes were also transfected with a small interfering RNA (siRNA) against GSK-3β or a scrambled siRNA, or were treated with lithium chloride (LiCl), a GSK-3β inhibitor, under NG or HG conditions. The expression levels of the epithelial cell markers, nephrin and podocin, and the myofibroblast cell markers, α-smooth muscle actin (SMA) and fibronectin, in podocytes by western blot analysis and immunofluorescence staining, respectively. The monolayer barrier function was assessed by albumin inflow. The phosphorylation and activity levels of GSK-3β were also quantified. It was observed that HG promotes EMT in podocytes, due to the increased levels of podocin and nephrin expression and the reduced α-SMA and fibronectin expression levels. HG also induced barrier dysfunction and increased the expression level of total GSK-3β, Try216-phosphorylated-GSK-3β and the GSK-3β activity in podocytes. Transfection of GSK-3β siRNA or treatment with LiCl reversed the HG-induced EMT and barrier dysfunction in podocytes. In conclusion, the present study determined that GSK-3β is required for EMT and barrier dysfunction in podocytes under HG conditions; therefore, GSK-3β may be a novel target for the treatment of DN.

Glycogen synthase kinase 3β hyperactivity in urinary exfoliated cells predicts progression of diabetic kidney disease

“…This is congruous with another in vitro study, where GSK3b was found to mediate podocyte dedifferentiation and injury after exposure to high glucose medium. 47 On the contrary, Mariappan et al 48 claimed that the activation of GSK3b instead ameliorates diabetes-induced kidney injury. In their study, streptozotocininduced diabetic mice were treated with sodium nitroprusside, a nitric oxide donor that is able to activate GSK3b.…”

Molecular mechanisms involved in podocyte EMT and concomitant diabetic kidney diseases: an update

“…A recent study in 2016 proved the function of GSK-3β both in podocyte dysfunction and EMT, which emphasized the hallmarks podocytes lost when undergoing EMT. 20 …”

Serum and Glucocorticoid-Inducible Kinase 3/Nedd4-2 Signaling Pathway Participates in Podocyte Injury by Regulating the Stability of Nephrin

“…Nedd4-2 is a member of the E3 ubiquitin ligase that mediates substrate protein ubiquitination mediated degradation by transferring ubiquitin from its homologous to the E6-AP carboxyl terminus (HECT) domain to substrate proteins ( Abriel and Staub, 2005 ; Rotin and Kumar, 2009 ). GSK3β participates in podocyte damage by affecting podocyte actin skeleton destruction and short foot mutations ( Xu et al, 2014 ; Guo et al, 2016 ; Li et al, 2016 ). Previous reports have demonstrated that GSK3β regulates the nuclear transcription of nephrin through the transcriptional repressor Snail ( Matsui et al, 2007 ; Wan et al, 2016 ; Wang et al, 2017 ).…”