title: Troglitazone ameliorates high glucose-induced EMT and dysfunction of SGLTs through PI3K/Akt, GSK-3β, Snail1, and β-catenin in renal proximal tubule cells.
abstract: Peroxisome proliferator-activated receptor-γ (PPARγ) agonists ameliorate renal fibrotic lesions in diabetic nephropathy. However, the effects of the agonists on the epithelial-mesenchymal transition (EMT) linked to membrane transport dysfunction are unknown. The present study aimed to verify the effects of the PPARγ agonist troglitazone on high glucose (HG)-induced EMT in primary cultured renal proximal tubular epithelial cells (PTCs). HG (25 mM) as well as hydrogen peroxide (H(2)O(2)) and transforming growth factor-β1 (TGF-β1) decreased expression of epithelial cell marker E-cadherin and increased the expression of the mesenchymal markers vimentin and α-smooth muscle actin (α-SMA). HG, H(2)O(2), and TGF-β1 decreased Na(+)/H(+) exchangers (NHEs) or Na(+)-glucose cotransporters (SGLTs) and glucose uptake, showing membrane transport dysfunction. HG stimulated the production of cellular reactive oxygen species (ROS), and antioxidants blocked the HG-induced increase in phosphatidylinositol 3-kinase (PI3K)/Akt activation. Antioxidants and inhibitors of PI3K/Akt reversed HG-induced EMT protein expression. Inhibition of PI3K/Akt also blocked HG-induced glycogen synthase kinase-3β (GSK-3β) phosphorylation. HG and lithium chloride (GSK-3β inhibitor) blocked Snail1 and β-catenin activation. Moreover, transfection with Snail1 or β-catenin small interfering RNA (siRNA) reversed HG-induced EMT protein expression. Importantly, HG decreased PPARγ activation and troglitazone reversed HG-induced expression of PI3K/Akt, GSK-3β, Snail1, and β-catenin as well as EMT proteins. Finally, inhibitors of PI3K/Akt, Snail1/β-catenin siRNA, and troglitazone blocking the HG-induced EMT restored glucose uptake in PTCs. In conclusion, HG induces EMT through ROS, PI3K/Akt, GSK-3β, Snail, and β-catenin. Subsequently, HG-induced EMT may result in SGLT dysfunction that is restored by the PPARγ agonist troglitazone in primary cultured PTCs.
authors.affiliation: Department of Veterinary Physiology, Biotherapy Human Resources Center (BK21), College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
authors.forename: Yu Jin
authors.initials: YJ
authors.lastname: Lee
authors.forename: Ho Jae
authors.initials: HJ
authors.lastname: Han
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects* / Q000502:physiology; D005947:Glucose / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D008297:Male; D023421:Models, Animal; D047495:PPAR gamma / Q000819:agonists; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000071250:Snail Family Transcription Factors; D051247:Sodium-Glucose Transport Proteins / Q000502:physiology*; D045162:Thiazolidinediones / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism*; D000077288:Troglitazone; D014746:Vimentin / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D000199:Actins; D015820:Cadherins; D002839:Chromans; D047495:PPAR gamma; D017382:Reactive Oxygen Species; C000604407:SNAI1 protein, human; D000071250:Snail Family Transcription Factors; D051247:Sodium-Glucose Transport Proteins; D045162:Thiazolidinediones; D014157:Transcription Factors; D014746:Vimentin; D051176:beta Catenin; D019869:Phosphatidylinositol 3-Kinases; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D000077288:Troglitazone; D005947:Glucose