Troglitazone ameliorates high glucose-induced EMT and dysfunction of SGLTs through PI3K/Akt, GSK-3β, Snail1, and β-catenin in renal proximal tubule cells.
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.
Lee
Yu Jin
YJ
Department of Veterinary Physiology, Biotherapy Human Resources Center (BK21), College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
Han
Ho Jae
HJ
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*
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