TY - JOUR
T1 - Hypoxia inducible factor-1α is increased in ischemic retina
T2 - Temporal and spatial correlation with VEGF expression
AU - Ozaki, Hiroaki
AU - Yu, Aimee Y.
AU - Della, Neil
AU - Ozaki, Keiko
AU - Luna, Jose D.
AU - Yamada, Haruhiko
AU - Hackett, Sean F.
AU - Okamoto, Naoyuki
AU - Zack, Donald J.
AU - Semenza, Gregg L.
AU - Campochiaro, Peter A.
PY - 1999
Y1 - 1999
N2 - Purpose. Hypoxia inducible factor-1 (HIF-1) is a transcription factor composed of HIF-1α and HIF-1̄ subunits. HIF-1 transactivates multiple genes whose products play key roles in oxygen homeostasis, including vascular endothelial growth factor (VEGF). This study was designed to determine whether HIF-1 levels are increased in ischemic retina and whether there is a correlation with increased expression of VEGF. Methods. C57BL/6J mice were killed at time points that span retinal vascular development (P0 to adult), or on postnatal day (P) 7 they were placed in a 75% oxygen environment for 5 days and then removed to room air and killed after 0, 2, or 6, or 24 hours and 5 or 14 days. Eyes were frozen, and retinas were isolated and used for immunoblot analysis, or eyes were sectioned for immunohistochemical staining for HIF-1γ or HIF-1β, or for in situ hybridization for VEGF. Results. Immunoblots of retinal lysates showed low levels of HIF-1α at P0 that were markedly increased at P4, remained high throughout the period of retinal vascular development and then decreased to an intermediate level in adults. HIF-1β levels were relatively constant at all time points. In mice with oxygen-induced ischemic retinopathy, HIF-1α levels were increased in the retina. The peak of increase occurred at 2 hours, and levels returned to baseline by 24 hours. Immunohistochemistry showed increased staining for HIF- 1α throughout the hypoxic inner retina, but not in the normoxic outer retina. There was no modulation of HIF-1β levels. There was constitutive expression of VEGF mRNA in the inner nuclear layer that was increased 6 hours after the onset of hypoxia and remained elevated for several days. Conclusions. There are increased levels of HIF-1α in ischemic retina that show temporal and spatial correlation with increased expression of VEGF. These findings are consistent with the hypothesis that HIF-1 plays a role in upregulation of VEGF in ischemic retina.
AB - Purpose. Hypoxia inducible factor-1 (HIF-1) is a transcription factor composed of HIF-1α and HIF-1̄ subunits. HIF-1 transactivates multiple genes whose products play key roles in oxygen homeostasis, including vascular endothelial growth factor (VEGF). This study was designed to determine whether HIF-1 levels are increased in ischemic retina and whether there is a correlation with increased expression of VEGF. Methods. C57BL/6J mice were killed at time points that span retinal vascular development (P0 to adult), or on postnatal day (P) 7 they were placed in a 75% oxygen environment for 5 days and then removed to room air and killed after 0, 2, or 6, or 24 hours and 5 or 14 days. Eyes were frozen, and retinas were isolated and used for immunoblot analysis, or eyes were sectioned for immunohistochemical staining for HIF-1γ or HIF-1β, or for in situ hybridization for VEGF. Results. Immunoblots of retinal lysates showed low levels of HIF-1α at P0 that were markedly increased at P4, remained high throughout the period of retinal vascular development and then decreased to an intermediate level in adults. HIF-1β levels were relatively constant at all time points. In mice with oxygen-induced ischemic retinopathy, HIF-1α levels were increased in the retina. The peak of increase occurred at 2 hours, and levels returned to baseline by 24 hours. Immunohistochemistry showed increased staining for HIF- 1α throughout the hypoxic inner retina, but not in the normoxic outer retina. There was no modulation of HIF-1β levels. There was constitutive expression of VEGF mRNA in the inner nuclear layer that was increased 6 hours after the onset of hypoxia and remained elevated for several days. Conclusions. There are increased levels of HIF-1α in ischemic retina that show temporal and spatial correlation with increased expression of VEGF. These findings are consistent with the hypothesis that HIF-1 plays a role in upregulation of VEGF in ischemic retina.
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M3 - Article
C2 - 9888442
AN - SCOPUS:0032932138
SN - 0146-0404
VL - 40
SP - 182
EP - 189
JO - Investigative Ophthalmology and Visual Science
JF - Investigative Ophthalmology and Visual Science
IS - 1
ER -