Coordinated expression of Ets-1, pERK1/2, and VEGF in retina of streptozotocin-induced diabetic rats.
OBJECTIVE
To investigate the role played by E26 transformation-specific-1 (Ets-1), a transcription factor, and extracellular signal-regulated kinase 1/2 (ERK1/2) in the expression of vascular endothelial growth factor (VEGF), and the interaction of Ets-1 and ERK1/2 in the retina of diabetic rats.


METHODS
Diabetes was induced in rats by an intraperitoneal injection of streptozotocin (STZ). To follow the time course in the expression of Ets-1, phosphorylated ERK1/2 (pERK1/2), and VEGF, rats were killed at 1, 2, 4, and 8 weeks after the injection of STZ, and total proteins were extracted from the isolated retinas. An adenovirus vector encoding dominant-negative Ets-1 and an inhibitor of PD98059 was injected intravitreally to investigate the effects of Ets-1 blockade and ERK1/2 inhibition on the expression of VEGF. Four weeks after the first intravitreal injection, total proteins and total RNA were extracted from the retinas for Western blot and Northern blot analyses.


RESULTS
The expression of Ets-1, pERK1/2, and VEGF in the retina increased in a time-dependent manner after STZ injection. The phosphorylation of ERK1/2 and protein level of VEGF were significantly reduced following intravitreal Ets-1. Inhibition of ERK1/2 phosphorylation resulted in a significant reduction in the expression of Ets-1 and the level of VEGF protein.


CONCLUSIONS
These results indicate that in the retina of STZ-induced diabetic rats: (1) the alterations of Ets-1, pERK1/2, and VEGF are approximately synchronized; (2) the phosphorylation of ERK1/2 is regulated by the expression of Ets-1; (3) the production of Ets-1 protein is dependent on the ERK1/2 pathway, and (4) the protein level of VEGF is regulated by both Ets-1 expression and ERK1/2 phosphorylation. We propose that VEGF, Ets-1, and ERK1 act synergistically in the development of diabetic retinopathy.
Du
Zhao-jiang
ZJ
Department of Ophthalmology, Xijing Hospital, the Fourth Military Medical University, Xi'an, China. tomdzj@163.com
Kamei
Motohiro
M
Suzuki
Mihoko
M
Tano
Yasuo
Y
Wang
Bai-ren
BR
Hui
Yan-nian
YN
D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D050784:Proto-Oncogene Protein c-ets-1 / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000378:metabolism*; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
C494043:Ets1 protein, rat; D050784:Proto-Oncogene Protein c-ets-1; D042461:Vascular Endothelial Growth Factor A; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3