title: Differential regulation of Snail by hypoxia and hyperglycemia in human proximal tubule cells.
abstract: The centrality of the transcriptional regulator Snail in epithelial-to-mesenchymal transformation (EMT), known to occur in models of diabetic nephropathy, has not been established. Transforming growth factor beta-1 (TGFbeta1) is induced in diabetic nephropathy and induces both Snail and EMT. Hypoxia inducible factors (HIFs) are known to induce Snail, independent of TGFbeta1. Notch induction is integral to Snail induction and EMT in tumour cells, but its role in the kidney is unknown. The present study was undertaken to determine the upstream regulators of Snail in the kidney in high glucose and hypoxic conditions. HK-2 cells were cultured in normoxic, hypoxic, high glucose and combined hypoxic/high glucose conditions. The expression of HIF1alpha, NotchIC, Snail, Lysyl oxidase-like 2 (Loxl2), and Hairy and Enhancer Split-1 (Hes1) were measured. We found that hypoxia increased HIF1alpha expression; however, concurrent exposure to high glucose blunted this effect. A similar pattern was observed in Lox12 expression, suggesting that Loxl2 was downstream of HIF1alpha, which was confirmed using siRNA techniques. Snail was upregulated by hypoxia and high glucose and in combination the effect was additive, suggesting independent upstream activation pathways by the two stimuli. Hes1 was upregulated by high glucose and to a lesser extent by hypoxia, but the effect of the combined stimuli was no greater than that observed with high glucose alone. NotchIC was downregulated by both hypoxia and high glucose, and in combination the effect was additive. Therefore, this study suggests that hypoxia and high glucose induce Snail expression through distinct pathways, independent of Notch signalling.
authors.affiliation: Department of Medicine, Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, New South Wales, Australia.
authors.forename: Siska
authors.initials: S
authors.lastname: Sumual
authors.forename: Sonia
authors.initials: S
authors.lastname: Saad
authors.forename: Owen
authors.initials: O
authors.lastname: Tang
authors.forename: Rachel
authors.initials: R
authors.lastname: Yong
authors.forename: Stella
authors.initials: S
authors.lastname: McGinn
authors.forename: Xin-Ming
authors.initials: XM
authors.lastname: Chen
authors.forename: Carol A
authors.initials: CA
authors.lastname: Pollock
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D003928:Diabetic Nephropathies / Q000235:genetics / Q000378:metabolism*; D058750:Epithelial-Mesenchymal Transition; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000235:genetics / Q000378:metabolism*; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000071250:Snail Family Transcription Factors; D000072056:Transcription Factor HES-1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D000594:Amino Acid Oxidoreductases; D051792:Basic Helix-Loop-Helix Proteins; D018398:Homeodomain Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D051881:Receptor, Notch1; D000071250:Snail Family Transcription Factors; D000072056:Transcription Factor HES-1; D014157:Transcription Factors; C497442:HIF1A protein, human; C078493:HES1 protein, human; C119091:LOXL2 protein, human