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Role of NF-kappaB-mediated interleukin-8 expression in intraocular neovascularization
A Yoshida1, S Yoshida, A K Khalil
1Department of Ophthalmology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Purpose:
To investigate the role of interleukin (IL)-8 in intraocular neovascularization and the mechanism of its production.
Methods:
Interleukin-8 was measured with enzyme-linked immunosorbent assays in vitreous and aqueous fluid obtained from patients with neovascular diseases. Localization of IL-8 was examined by immunohistochemistry. An in vitro angiogenesis assay was performed on collagen gels, by using bovine aortic endothelial cells to determine the effect of the vitreous fluid. In bovine retinal glial cells under hypoxia, NF-kappaB activation was evaluated by immunoblot analysis and by electrophoretic mobility shift assay, and IL-8 and vascular endothelial growth factor (VEGF) mRNA expression was determined by semiquantitative reverse transcription-polymerase chain reaction.
Results:
The concentration of IL-8 in vitreous fluid of patients with retinal neovascularization was significantly higher than that of patients without neovascular disease. Interleukin-8 immunostaining was detected in vascular endothelial cells and glial cells in the retinas with neovascularization. Vitreous fluid with high concentrations of IL-8 induced tubular morphogenesis in endothelial cells, and this effect was inhibited to a similar extent by neutralizing antibodies to IL-8 or to VEGF. In glial cells, in vitro, hypoxia induced NF-kappaB activation and increased IL-8 and VEGF mRNA. Furthermore, pyrrolidine dithiocarbamate, a specific inhibitor of NF-kappaB activation, prevented the induction of the IL-8 gene, but not that of the VEGF gene.
Conclusions:
These results suggest that IL-8 induced by hypoxia and mediated by NF-kappaB may contribute to the pathogenesis of intraocular neovascularization.