Inducible nitric oxide synthase mediates hypoxia-induced hypoxia-inducible factor-1 alpha activation and vascular endothelial growth factor expression in oxygen-induced retinopathy.
OBJECTIVE
Previous studies provided evidence that many factors contribute to retinal angiogenesis, including inducible nitric oxide synthase (iNOS), hypoxia-inducible factor-1 alpha (HIF-1 alpha) and vascular endothelial growth factor (VEGF). But the role of nitric oxide generated by iNOS in the regulation of expression of hypoxia-inducible genes in retinopathy of prematurity remains unclear. So we sought to better define the molecular basis of this iNOS-dependent regulation.


METHODS
In this study, using immunohistochemistry, real-time PCR and Western blotting technologies, we investigated the changes of iNOS, HIF-1 alpha, VEGF and phosphatidylinositol 3-kinase/Akt (PI3K/Akt) expressions.


RESULTS
Hypoxia- induced overexpression of iNOS, HIF-1 alpha, VEGF, PI3K/Akt and phosphorylated PI3K/Akt was observed in the untreated retinopathy of the prematurity group. Administration of the selective iNOS inhibitor aminoguanidine hemisulfate markedly decreased the expression of these genes.


CONCLUSIONS
These results indicate that iNOS mediates HIF-1 alpha activation and VEGF expression in retinal angiogenesis and that the PI3K/Akt signaling pathway may play a role in this process.
He
Tao
T
Department of Ophthalmology, Renmin Hospital of Wuhan University, Wuhan, China.
Ai
Ming
M
Zhao
Xiao-Hui
XH
Xing
Yi-Qiao
YQ
D000818:Animals; D015153:Blotting, Western; D005260:Female; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007150:Immunohistochemistry; D007231:Infant, Newborn; D051379:Mice; D008810:Mice, Inbred C57BL; D018919:Neovascularization, Physiologic; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis; D010766:Phosphorylation; D011247:Pregnancy; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis; D012178:Retinopathy of Prematurity / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis*
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D042461:Vascular Endothelial Growth Factor A; D052247:Nitric Oxide Synthase Type II; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt