VEGF-mediated STAT3 activation inhibits retinal vascularization by down-regulating local erythropoietin expression.
Avascular, hypoxic retina has been postulated to be a source of angiogenic factors that cause aberrant angiogenesis and intravitreal neovascularization (IVNV) in retinopathy of prematurity. Vascular endothelial growth factor (VEGF) is an important factor involved. However, VEGF is also required for normal retinal vascular development, which raises concerns about inhibiting its activity to treat IVNV in retinopathy of prematurity. Therefore, understanding the effects that VEGF has on other factors in the development of avascular retina is important to prevent aberrant angiogenesis and IVNV. Here, we show that STAT3 was activated by increased retinal VEGF in the rat 50/10 oxygen-induced retinopathy model. Phospho-STAT3 colocalized with glutamine synthetase-labeled Müller cells. Inhibition of STAT3 reduced avascular retina and increased retinal erythropoietin (Epo) expression. Epo administered exogenously also reduced avascular retina in the model. In an in vitro study, hypoxia-induced VEGF inhibited Epo gene expression by STAT3 activation in rat Müller cells. The mechanism by which activated STAT3 regulated Epo was by inhibition of Epo promoter activity. Together, these findings show that increased retinal VEGF contributes to avascular retina by regulating retinal Epo expression through Janus kinase/STAT signaling. Our results suggest that rescuing Epo expression in the retina before the development of IVNV may promote normal developmental angiogenesis and, therefore, reduce the stimulus for later pathologic IVNV.
The John A. Moran Eye Center, The University of Utah, Salt Lake City, Utah.
Haibo
H
Wang
Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Grace
G
Byfield
The John A. Moran Eye Center, The University of Utah, Salt Lake City, Utah.
Yanchao
Y
Jiang
The John A. Moran Eye Center, The University of Utah, Salt Lake City, Utah.
George Wesley
GW
Smith
The John A. Moran Eye Center, The University of Utah, Salt Lake City, Utah.
Manabu
M
McCloskey
The John A. Moran Eye Center, The University of Utah, Salt Lake City, Utah. Electronic address: me.hartnett@hsc.utah.edu.
M Elizabeth
ME
Hartnett
D000818:Animals; D000831:Animals, Newborn; D053148:Caspase 3 / Q000378:metabolism; D015536:Down-Regulation; D004921:Erythropoietin / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D053612:Janus Kinases / Q000378:metabolism; D010100:Oxygen / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D015861:Retinal Neovascularization / Q000517:prevention & control*; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*
D050796:STAT3 Transcription Factor; D042461:Vascular Endothelial Growth Factor A; D004921:Erythropoietin; D053612:Janus Kinases; D053148:Caspase 3; D010100:Oxygen