Podocyte-derived vascular endothelial growth factor mediates the stimulation of alpha3(IV) collagen production by transforming growth factor-beta1 in mouse podocytes.
Podocyte-derived vascular endothelial growth factor (VEGF) is upregulated in diabetes and may contribute to albuminuria. Although believed to act upon the glomerular endothelium, VEGF may have pronounced effects on the podocyte itself. The functionality of this VEGF autocrine loop was investigated in conditionally immortalized mouse podocytes. Exogenous VEGF(164) increased the production of alpha3(IV) collagen, an integral component of the glomerular basement membrane (GBM); this effect was completely prevented by SU5416, a pan-VEGF receptor inhibitor. The VEGF inhibitor also partially prevented the stimulation of alpha3(IV) collagen by transforming growth factor (TGF)-beta1, establishing a novel role for endogenous VEGF. However, VEGF did not influence the production of another novel chain of collagen IV, alpha5(IV) collagen, and SU5416 failed to reverse the known inhibitory effect of TGF-beta1 on alpha5(IV) collagen production. Cultured mouse podocytes possess at least the VEGFR-1 receptor, confirmed by RT-PCR, immunoblotting, and immunocytochemistry. By these techniques, however, VEGFR-2 is absent. VEGF signaling proceeds via autophosphorylation of VEGFR-1 and activation of the phosphatidylinositol 3-kinase (PI3K) pathway. Thus, podocyte-derived VEGF operates in an autocrine loop, likely through VEGFR-1 and PI3K, to stimulate alpha3(IV) collagen production. The TGF-beta1-stimulated endogenous VEGF may have significant implications for podocyte dysfunction in diabetic glomerulopathy, manifesting as GBM thickening and altered macromolecular permeability.
Chen
Sheldon
S
Renal-Electrolyte and Hypertension Division, Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-4218, USA. chens@mail.med.upenn.edu.
Kasama
Yuki
Y
Lee
Joseph S
JS
Jim
Belinda
B
Marin
Maria
M
Ziyadeh
Fuad N
FN
D000818:Animals; D001324:Autoantigens / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D001483:Base Sequence; D002454:Cell Differentiation; D024141:Collagen Type IV / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D017931:DNA Primers; D004847:Epithelial Cells / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology* / Q000502:physiology; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000235:genetics / Q000502:physiology
D001324:Autoantigens; D024141:Collagen Type IV; D017931:DNA Primers; D011994:Recombinant Proteins; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; C057112:type IV collagen alpha3 chain; D040281:Vascular Endothelial Growth Factor Receptor-1