title: C-peptide reverses TGF-beta1-induced changes in renal proximal tubular cells: implications for treatment of diabetic nephropathy.
abstract: The crucial pathology underlying progressive chronic kidney disease in diabetes is tubulointerstitial fibrosis. Central to this process is epithelial-mesenchymal transformation (EMT) of proximal tubular epithelial cells driven by maladaptive transforming growth factor-beta1 (TGF-beta1) signaling. Novel signaling roles for C-peptide have recently been discovered with evidence emerging that C-peptide may mitigate microvascular complications of diabetes. We studied the potential for C-peptide to interrupt injurious TGF-beta1 signaling pathways and thus block development of EMT in HK2 human kidney proximal tubular cells. Cells were incubated with TGF-beta1 either alone or with C-peptide in low or high glucose. Changes in cell morphology, TGF-beta1 receptor expression, vimentin, E-cadherin, and phosphorylated Smads were assessed. Luciferase reporters were used to assess Smad activity. The cytoskeleton was visualized by TRITC-phalloidin staining. The typical TGF-beta1-stimulated, EMT-associated morphological alterations of proximal tubular cells, including increased vimentin expression, decreased E-cadherin expression, and cytoskeletal rearrangements, were prevented by C-peptide treatment. C-peptide also blocked TGF-beta1-induced upregulation of expression of both type I and type II TGF-beta1 receptors and attenuated TGF-beta1-mediated Smad phosphorylation and Smad transcriptional activity. These effects of C-peptide were inhibited by pertussis toxin. The results demonstrate that C-peptide almost completely reversed the morphological changes in PT cells induced by TGF-beta1 and suggest a role or C-peptide as a renoprotective agent in diabetic nephropathy.
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester School of Medicine, Leicester, United Kingdom.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Hills
authors.forename: Nawal
authors.initials: N
authors.lastname: Al-Rasheed
authors.forename: Nouf
authors.initials: N
authors.lastname: Al-Rasheed
authors.forename: Gary B
authors.initials: GB
authors.lastname: Willars
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Brunskill
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002096:C-Peptide / Q000378:metabolism*; D015820:Cadherins / Q000378:metabolism; D002460:Cell Line; D003928:Diabetic Nephropathies / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000473:pathology; D008648:Mesoderm / Q000378:metabolism; D010641:Phenotype; D015398:Signal Transduction; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D015854:Up-Regulation; D014746:Vimentin / Q000378:metabolism
chemical_list: D015415:Biomarkers; D002096:C-Peptide; D015820:Cadherins; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; D014746:Vimentin