title: Paricalcitol protects against TGF-β1-induced fibrotic responses in hypoxia and stabilises HIF-α in renal epithelia.
abstract: Epithelial injury and tubulointerstitial fibrosis (TIF) within a hypoxic microenvironment are associated with progressive loss of renal function in chronic kidney disease [CKD]. Transforming growth factor beta-1 (TGF-β1) is an important mediator of renal fibrosis. Growing evidence suggests that Vitamin D [1,25-(OH)2D] and its analogues may have a renoprotective effect in CKD. Here we examined the protective effect of the vitamin D analogue paricalcitol [PC; 19-nor-1α,3β,25-trihydroxy-9,10-secoergosta-5(Z),7(E) 22(E)-triene] on the responses of human renal epithelial cells to TGF-β1. PC attenuated TGF-β1-induced Smad 2 phosphorylation and upregulation of the Notch ligand Jagged-1, α-smooth muscle actin and thrombospondin-1 and prevented the TGF-β1-mediated loss of E-Cadherin. To mimic the hypoxic milieu of CKD we cultured renal epithelial cells in hypoxia [1% O2] and observed similar attenuation by PC of TGF-β1-induced fibrotic responses. Furthermore, in cells cultured in normoxia [21% O2], PC induced an accumulation of hypoxia-inducible transcription factors (HIF) 1α and HIF-2α in a time and concentration [1 µM-2 µM] dependent manner. Here, PC-induced HIF stabilisation was dependent on activation of the PI-3Kinase pathway. This is the first study to demonstrate regulation of the HIF pathway by PC which may have importance in the mechanism underlying renoprotection by PC.
authors.affiliation: Diabetes Complications Research Centre, Conway Institute of Biomolecular and Biomedical Research, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: karenanolan@ucd.ie.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Nolan
authors.affiliation: Diabetes Complications Research Centre, Conway Institute of Biomolecular and Biomedical Research, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: eoin.brennan@ucd.ie.
authors.forename: Eoin P
authors.initials: EP
authors.lastname: Brennan
authors.affiliation: Systems Biology Ireland, Conway Institute of Biomolecular and Biomedical Research, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: carsten.scholz@ucd.ie.
authors.forename: Carsten C
authors.initials: CC
authors.lastname: Scholz
authors.affiliation: Diabetes Complications Research Centre, Conway Institute of Biomolecular and Biomedical Research, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: cliodhna.cullen@ucdconnect.ie.
authors.forename: Cliodhna
authors.initials: C
authors.lastname: Cullen
authors.affiliation: Diabetes Complications Research Centre, Conway Institute of Biomolecular and Biomedical Research, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: jackryan75@gmail.com.
authors.forename: Aidan
authors.initials: A
authors.lastname: Ryan
authors.affiliation: Conway Institute of Biomolecular and Biomedical Research, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: cormac.taylor@ucd.ie.
authors.forename: Cormac T
authors.initials: CT
authors.lastname: Taylor
authors.affiliation: Diabetes Complications Research Centre, Conway Institute of Biomolecular and Biomedical Research, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: catherine.godson@ucd.ie.
authors.forename: Catherine
authors.initials: C
authors.lastname: Godson
mesh_terms: D000199:Actins / Q000096:biosynthesis; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000096:biosynthesis; D015687:Cell Hypoxia; D002461:Cell Line, Transformed; D004847:Epithelial Cells / Q000187:drug effects* / Q000473:pathology; D004872:Ergocalciferols / Q000494:pharmacology*; D005355:Fibrosis; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis; D000072100:Jagged-1 Protein; D007668:Kidney / Q000187:drug effects* / Q000473:pathology*; D008565:Membrane Proteins / Q000096:biosynthesis; D009395:Nephritis, Interstitial / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D055550:Protein Stability; D034622:RNA Interference; D000072099:Serrate-Jagged Proteins; D051899:Smad2 Protein / Q000378:metabolism; D019700:Thrombospondin 1 / Q000096:biosynthesis; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D000199:Actins; D051792:Basic Helix-Loop-Helix Proteins; D015820:Cadherins; D002135:Calcium-Binding Proteins; D004872:Ergocalciferols; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D036341:Intercellular Signaling Peptides and Proteins; D000072100:Jagged-1 Protein; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D000072099:Serrate-Jagged Proteins; D051899:Smad2 Protein; D019700:Thrombospondin 1; D053773:Transforming Growth Factor beta1; D000099162:Endothelial PAS Domain-Containing Protein 1; C541116:ACTA2 protein, human; C497442:HIF1A protein, human; C000606273:JAG1 protein, human; C003564:1,25-dihydroxyergocalciferol; C084656:paricalcitol
keywords: Fibrosis; HIF; Hypoxia; Kidney; Paricalcitol; TGF-β1; Vitamin D