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. MATERIAL AND 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). CONCLUSION: 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.
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. MATERIAL AND 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). CONCLUSION: 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.
Authors: Nicola J Mabjeesh; Dawn E Post; Margaret T Willard; Balveen Kaur; Erwin G Van Meir; Jonathan W Simons; Hua Zhong Journal: Cancer Res Date: 2002-05-01 Impact factor: 12.701
Authors: J B Hogenesch; W K Chan; V H Jackiw; R C Brown; Y Z Gu; M Pray-Grant; G H Perdew; C A Bradfield Journal: J Biol Chem Date: 1997-03-28 Impact factor: 5.157
Authors: K Gradin; J McGuire; R H Wenger; I Kvietikova; M L fhitelaw; R Toftgård; L Tora; M Gassmann; L Poellinger Journal: Mol Cell Biol Date: 1996-10 Impact factor: 4.272
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Authors: Kelvin K W Hui; Nicole Liadis; Jennifer Robertson; Anish Kanungo; Jeffrey T Henderson Journal: J Cell Mol Med Date: 2009-02-20 Impact factor: 5.310