Geldanamycin treatment reduces neovascularization in a mouse model of retinopathy of prematurity.
BACKGROUND
The benzoquinoid antibiotic 17-allylaminogeldanamycin (17-AAG) inhibits the Ras/Raf/MEK and PI3-Kinase signaling pathways and down-regulates vascular endothelial factor expression. Here we use a mouse model of oxygen-induced retinopathy to investigate the effect of 17-AAG on retinal neovascularization and vascular recovery.


METHODS
C57BL/6 mice were exposed to 75% oxygen from postnatal day 7 (P7) to P12 and recovered in room air thereafter. Beginning with P12 mice were treated for 5 days by daily IP injection of 17-AAG (12.5 mg/kg body weight) micro dispersed in an emulsion of 4% Lipoid EPC, 5% sucrose, and 0.9% NaCl or Wortmannin (100 microg/kg body weight). On P17, the retinal vascular and avascular area, neovascular blood vessel tufts, and main vessel tortuosity were quantified after perfusion of the mice with FITC-Concanavalin A. The mRNA levels of VEGF, angiopoietin 1 and 2 were quantified by real-time RT-PCR.


RESULTS
After 17-AAG treatment, a reduction of the vascular area was measured from 37.8 +/- 5.2% to 30.8 +/- 5.7% (P = 0.005), and an increase of the avascular area from 10.8 +/- 5.6% to 20.3 +/- 6.6% (P = 0.001). No alteration of the vascular pattern, the number of blood vessel tufts and the main vessel tortuosity was achieved by treatment with the PI-3 kinase inhibitor Wortmannin. After treatment with 17-AAG, the numbers of tufts (127.9 33.2) were different from the controls (173.7 +/- 55.2, P = 0.035), but not the main vessel tortuosity. No significant change in VEGF and angiopoietin 1 mRNA expression could be achieved with either of the treatments. Wortmannin treatment also did not change the angiopoietin 2 mRNA level, whereas the level was reduced in 17-AAG treated mice retina from 436-fold (+/- 64) to 200-fold (+/-55) (P = 0.035).


CONCLUSIONS
An IP injection of 17-AAG is able to reduce angioproliferative retinopathy in a mouse model for oxygen-induced retinopathy. Our data indicate that the mechanism does not involve a direct or indirect reduction of the VEGF mRNA level, but acts downstream of the VEGF pathway. Thus, 17-AAG probably does not work by PI-3 kinase inhibition but via the Ras/Raf/MEK pathway. These data underline the potential utility of tyrosine kinase inhibitors in hypoxia induced neovascularization.
Kociok
Norbert
N
Department of Vitreoretinal Surgery, Center for Ophthalmology, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany. Norbert.Kociok@uni-koeln.de
Krohne
Tim U
TU
Poulaki
Vassiliki
V
Joussen
Antonia M
AM
D042683:Angiopoietin-1 / Q000235:genetics; D042702:Angiopoietin-2 / Q000235:genetics; D000818:Animals; D016227:Benzoquinones / Q000627:therapeutic use*; D004195:Disease Models, Animal; D005260:Female; D005451:Fluorescein Angiography; D006801:Humans; D007231:Infant, Newborn; D007274:Injections, Intraperitoneal; D047029:Lactams, Macrocyclic / Q000627:therapeutic use*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010100:Oxygen / Q000633:toxicity; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000378:metabolism; D015861:Retinal Neovascularization / Q000175:diagnosis / Q000188:drug therapy*; D012171:Retinal Vessels / Q000187:drug effects / Q000473:pathology; D012178:Retinopathy of Prematurity / Q000175:diagnosis / Q000188:drug therapy*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
D042683:Angiopoietin-1; D042702:Angiopoietin-2; C467628:Angpt1 protein, mouse; D016227:Benzoquinones; D047029:Lactams, Macrocyclic; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; C112765:tanespimycin; D017346:Protein Serine-Threonine Kinases; D010100:Oxygen