IGF-I induces vascular endothelial growth factor in human mesangial cells via a Src-dependent mechanism

G Gruden, S Araf, S Zonca, D Burt, S Thomas, L Gnudi, G Viberti

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    Abstract

    Background. Both insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor (VEGF) have been implicated in the pathogenesis of early renal dysfunction in diabetes. We investigated whether IGF-I affects VEGF gene expression and protein secretion in human mesangial cells. Furthermore, we studied the intracellular signaling pathway involved and the interaction of IGF-I with mechanical stretch, a known VEGF inducer. Methods. Human mesangial cells were exposed to IGF-I in the presence and in the absence of (1) anti-IGF-I type I receptor antibody (alphaIR3) (1 mug/mL), a monoclonal antibody blocking the IGF-I type I receptor; (2) wortmannin (600 nmol/L), a phosphatidylinositol 3-kinase (PI3K) inhibitor; (3) 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), a specific Src inhibitor (10 mumol/L); and (4) cyclic stretch (similar to10% elongation). Results. IGF-I induced a dose-dependent increase in VEGF protein levels (10(-11) mol/L, 5%; 10(-10) mol/L, 14%; 10(-9) mol/L, 46%; 10(-8) mol/L, 66%; 10(-7) mol/L, 68%; P <0.001). IGF-I-induced VEGF production rose by 6 hours with a peak at 12 hours, and declined by 24 hours (52%, 72%, and 34%, respectively; P <0.01 at 12 hours). A corresponding 50% increase in VEGF mRNA levels was seen at 6 hours (P <0.01). IGF-I-induced VEGF protein secretion was not affected by the addition of wortmannin (IGF-I, 76% vs. IGF-I + wortmannin, 79% increase over control; P = NS), but was abolished by αIR3 (IGF-I, 69% vs. IGF-I +αIR3, 0%; P <0.001) and significantly reduced by PP2 (IGF-I, 50% vs. IGF-I + PP2, 14%; P <0.01). Simultaneous exposure of human mesangial cells to both IGF-I and stretch failed to further increase VEGF production (IGF-I, 1.49 +/- 0.05; stretch, 1.76 +/- 0.05; and IGF-I + stretch, 1.83 +/- 0.11). Conclusion. IGF-I induces VEGF gene expression and protein secretion in human mesangial cells via a Src-dependent mechanism.
    Original languageEnglish
    Pages (from-to)1249 - 1255
    Number of pages7
    JournalKidney International
    Volume63
    Issue number4
    DOIs
    Publication statusPublished - 1 Apr 2003

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