title: Hypoxia response and VEGF-A expression in human proximal tubular epithelial cells in stable and progressive renal disease.
abstract: Proteinuria, inflammation, chronic hypoxia, and rarefaction of peritubular capillaries contribute to the progression of renal disease by affecting proximal tubular epithelial cells (PTECs). To study the transcriptional response that separates patients with a stable course from those with a progressive course of disease, we isolated PTECs by laser capture microdissection from cryocut tissue sections of patients with proteinuric glomerulopathies (stable n=20, progressive n=11) with a median clinical follow-up of 26 months. Gene-expression profiling and a systems biology analysis identified activation of intracellular vascular endothelial growth factor (VEGF) signaling and hypoxia response pathways in progressive patients, which was associated with upregulation of hypoxia-inducible-factor (HIF)-1alpha and several HIF target genes, such as transferrin, transferrin-receptor, p21, and VEGF-receptor 1, but downregulation of VEGF-A. The inverse expression levels of HIF-1alpha and VEGF-A were significantly superior in predicting clinical outcome as compared with proteinuria, renal function, and degree of tubular atrophy and interstitial fibrosis at the time of biopsy. Interactome analysis showed the association of attenuated VEGF-A expression with the downregulation of genes that usually stimulate VEGF-A expression, such as epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1), and HIF-2alpha. In vitro experiments confirmed the positive regulatory effect of EGF and IGF-1 on VEGF-A transcription in human proximal tubular cells. Thus, in progressive but not in stable proteinuric kidney disease, human PTECs show an attenuated VEGF-A expression despite an activation of intracellular hypoxia response and VEGF signaling pathways, which might be due to a reduced expression of positive coregulators, such as EGF and IGF-1.
authors.affiliation: Department of Internal Medicine IV, Nephrology and Hypertension, Medical University Innsbruck, Innsbruck, Austria. michael.rudnicki@i-med.ac.at
authors.forename: Michael
authors.initials: M
authors.lastname: Rudnicki
authors.forename: Paul
authors.initials: P
authors.lastname: Perco
authors.forename: Julia
authors.initials: J
authors.lastname: Enrich
authors.forename: Susanne
authors.initials: S
authors.lastname: Eder
authors.forename: Dorothea
authors.initials: D
authors.lastname: Heininger
authors.forename: Andreas
authors.initials: A
authors.lastname: Bernthaler
authors.forename: Martin
authors.initials: M
authors.lastname: Wiesinger
authors.forename: Rita
authors.initials: R
authors.lastname: Sarközi
authors.forename: Susie-Jane
authors.initials: SJ
authors.lastname: Noppert
authors.forename: Herbert
authors.initials: H
authors.lastname: Schramek
authors.forename: Bernd
authors.initials: B
authors.lastname: Mayer
authors.forename: Rainer
authors.initials: R
authors.lastname: Oberbauer
authors.forename: Gert
authors.initials: G
authors.lastname: Mayer
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology*; D015331:Cohort Studies; D004815:Epidermal Growth Factor / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D007674:Kidney Diseases / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D007676:Kidney Failure, Chronic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D042282:Microdissection; D020411:Oligonucleotide Array Sequence Analysis; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics* / Q000378:metabolism; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004815:Epidermal Growth Factor; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007334:Insulin-Like Growth Factor I; D042461:Vascular Endothelial Growth Factor A; D054462:p21-Activated Kinases; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C467484:VEGFA protein, human