title: Autocrine effects of IGF-I-induced VEGF and IGFBP-3 secretion in retinal pigment epithelial cell line ARPE-19.
abstract: Hypoxia-induced physiological stress plays a central role in various neovascular diseases of the eye. Increased expression of hypoxia-inducible factor 1alpha (HIF-1alpha) and subsequent formation of HIF-1 dimers active at the vascular endothelial growth factor (VEGF) promoter lead to expression of this potent angiogenic factor in the retina, including retinal pigment epithelial (RPE) cells. We previously demonstrated that insulin-like growth factor I (IGF-I) stimulates VEGF and IGF binding protein (IGFBP)-3 secretion in RPE cells. In this study we examined IGF-I-induced HIF-1alpha expression, VEGF and IGFBP-3 secretion, and the autocrine actions of VEGF and IGFBP-3 on these processes in the spontaneously transformed RPE cell line ARPE-19. Cells were treated with CoCl(2), IGF-I, recombinant human (rh)IGFBP-3, and rhVEGF. Immunoblot analysis revealed IGF-I-induced upregulation of total HIF-1alpha protein, whereas luciferase reporter assays of HIF-1 transcriptional activity demonstrated accumulation of HIF-1alpha correlated with the formation of functional HIF-1 heterodimers. Western and ligand blot analyses of RPE cell conditioned medium confirmed that IGF-I stimulated VEGF and IGFBP-3 secretion. rhVEGF stimulated IGFBP-3 secretion in an IGF-I- and HIF-1alpha-independent manner, whereas rhIGFBP-3 attenuated IGF-I-induced VEGF secretion. These findings demonstrate the multifaceted autocrine regulation of IGF-I-induced VEGF secretion by IGFBP-3 secreted in response to both IGF-I and, to a lesser extent, VEGF. These results provide evidence for HIF-1-dependent and -independent mechanisms by which IGF-I regulates VEGF and IGFBP-3 secretion.
authors.affiliation: Dept. of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Slomiany
authors.forename: Steven A
authors.initials: SA
authors.lastname: Rosenzweig
mesh_terms: D019898:Autocrine Communication / Q000502:physiology*; D015153:Blotting, Western; D020256:Choroidal Neovascularization / Q000503:physiopathology; D003035:Cobalt / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis* / Q000187:drug effects / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D010857:Pigment Epithelium of Eye / Q000187:drug effects / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000187:drug effects / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000096:biosynthesis / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000187:drug effects / Q000494:pharmacology
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018972:Insulin-Like Growth Factor Binding Protein 3; D011994:Recombinant Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D003035:Cobalt; D007334:Insulin-Like Growth Factor I; C018021:cobaltous chloride