title: Sustained Wnt/β-catenin signaling rescues high glucose induction of transforming growth factor-β1-mediated renal fibrosis.
abstract: BACKGROUND
  Although diabetic nephropathy is attributable to transforming growth factor-β1 (TGF-β1) overproduction in glomer-ular mesangial cells, the biological role of Wnt/β-catenin signaling in controlling high glucose-induced TGF-β1 has not yet been elucidated.
  
  
  METHODS
  This study found that sustained Wnt/β-catenin signaling was required to protect glomerular mesangial cells from high glucose induction of TGF-β1-mediated fibrosis using in vitro and in vivo diabetic models.
  
  
  RESULTS
  High glucose down-regulated the Wnt signaling associated with increased TGF-β1 and fibronectin messenger RNA expression in glomerular mesangial cells. Restoring Wnt4, Wnt5a and cytosolic β-catenin levels by transfecting Wnt4, Wnt5a and stable β-catenin alleviated the stimulatory effect of high glucose on c-Jun mediated TGF-β1 fibrosis. Transfection of kinase-active glycogen synthase kinase-3β (GSK-3β) also abrogated high glucose promotion of nuclear c-Jun levels, TGF-β1 and fibronectin messenger RNA expression in mesangial cells. Pharmacological modulation of GSK-3ββ and ββ-catenin signaling by recombinant Wnt5a or GSK-3β inhibitor (BIO or LiCl) suppressed high glucose promotion of TGF-β1-mediated fibrosis. Exogenous BIO and SB216763 alleviated TGF-β1-mediated fibrogenic expression in the kidneys of diabetic rats. Immunohistochemistry showed that GSK-3β inhibitor significantly reversed the diabetic attenuation of TGF-β1 and c-Jun coinciding with fibronectin immunoreactivity within glomeruli. Immunofluorescence demonstrated that cells within the glomeruli restored β-catenin expression after BIO and SB216763 treatment in cells within diabetic glomeruli colocalized with fragmented nuclei by 4',6-diamidino-2-phenylindole staining.
  
  
  CONCLUSIONS
  Sustained Wnt signaling reduced c-Jun-dependent TGF-β1-mediated fibronectin accumulation in mesangial cells. These findings suggest that modulation of Wnt signaling is a viable alternative strategy to rescue the TGF-β1-mediated fibrotic signaling pathway in diabetic renal injury.
authors.affiliation: Division of Endocrinology and Metabolism, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors.forename: Cheng
authors.initials: C
authors.lastname: Ho
authors.forename: Pei-Hsien
authors.initials: PH
authors.lastname: Lee
authors.forename: Yung-Chien
authors.initials: YC
authors.lastname: Hsu
authors.forename: Feng-Sheng
authors.initials: FS
authors.lastname: Wang
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Huang
authors.forename: Chun-Liang
authors.initials: CL
authors.lastname: Lin
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D003921:Diabetes Mellitus, Experimental / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D005355:Fibrosis; D005947:Glucose / Q000008:administration & dosage*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; D007674:Kidney Diseases / Q000473:pathology*; D008297:Male; D051379:Mice; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000502:physiology*; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D053773:Transforming Growth Factor beta1; D051153:Wnt Proteins; D051176:beta Catenin; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D005947:Glucose