Details

Autor(en) / Beteiligte

• Platt, Daniel H

Titel

Molecular mechanisms of high glucose -induced vascular endothelial growth factor expression in retinal endothelial cells

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2004

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Studies in diabetic patients and in models of diabetes have shown a close association between pathologic vascular growth, over-expression of VEGF and oxidative stress. Studies of diabetic patients and high glucose treated cells have shown increased levels of tyrosine nitration, a marker of peroxynitrite formation. Excess formation of reactive oxygen/nitrogen species has been shown to activate two VEGF transcription factors HIF-1 and STAT3. These observations suggest that diabetes causes increases in VEGF expression due to the effects of high glucose in stimulating the formation of peroxynitrite, which leads to the activation of HIF-1 and/or STAT3 and increases in VEGF expression. This hypothesis was tested by experiments using primary cultures of retinal endothelial cells (BRE) treated with peroxynitrite or high glucose. Both treatments increased VEGF mRNA and protein levels. Further, pretreatment with the specific peroxynitrite decomposition catalyst FeTPPs blocked the increase in VEGF expression. To determine if HIF-1 and/or STAT3 play a role in the peroxynitrite-induced VEGF expression, studies were done to analyze the activation patterns of both transcription factors. These studies showed a rapid activation and nuclear translocation of STAT3, but not HIF-1α. Over-expression of dominant-negative STAT3 blocked the effects of either peroxynitrite or high glucose in increasing VEGF mRNA. Further, treatment with FeTPPS blocked the effects of high glucose in stimulating activation of STAT3. cSrc, has been shown to play a role in the activation of STAT3 as well as the induction of VEGF expression during tumor angiogenesis. To determine if cSrc plays a role in STAT3 regulated VEGF expression, BRE were transduced with an adenovirus over-expressing a constitutively active Src (vSrc). vSrc induced activation of STAT3 and increased VEGF expression. Further, FeTPPs blocked the effects of peroxynitrite and high glucose in stimulating activation of cSrc. Additionally, the Src inhibitor PP1 blocked the effects of peroxynitrite and high glucose in increasing VEGF mRNA and protein expression. This work is the first to show that (1) high glucose-induced peroxynitrite formation increases VEGF expression, (2) STAT3 activation by high glucose-induced peroxynitrite formation regulates VEGF expression and (3) cSrc activation by high glucose-induced peroxynitrite formation activates STAT3 and increases VEGF expression.