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Role of protein tyrosine phosphorylation in rat corneal neovascularization
A Hayashi1, K S Popovich, H C Kim
1Wilmer Ophthalmological Institute, Johns Hopkins University, School of Medicine, Baltimore, MD 21287, USA.
Background:
Recent studies have suggested that tyrosine kinase pathways that are activated by angiogenic growth factors may play a role in corneal neovascularization.
Methods:
Corneal neovascularization was induced in rat corneas by chemical cauterization. At 6, 24, 48, 96, and 168 h after chemical cauterization the rat corneas without the corneal epithelium were prepared for gel electrophoresis. Total protein profiles of the corneal samples were examined by staining gels with Coomassie brilliant blue. Tyrosine-phosphorylated proteins, three angiogenic growth factors (basic fibroblast growth factor, vascular endothelial growth factor, and platelet-derived growth factor-B chain), and three intracellular signal proteins in the tyrosine kinase pathways (phospholipase C gamma, SHC, and mitogen-activated protein kinase) in the corneal samples were examined by western blot analysis. A topical treatment of genistein eye drop (5 mg/ml) was used for inhibition of corneal neovascularization after chemical cauterization in rats.
Results:
In total protein profiles, three bands in the corneal samples were increased after cauterization. Overall tyrosine-phosphorylated proteins and all three angiogenic growth factors increased with progression of corneal neovascularization. The tyrosine-phosphorylated forms of three intracellular signal proteins were also increased after cauterization. Treatment with topical genistein was effective in inhibiting corneal neovascularization in rats.
Conclusion:
Protein tyrosine phosphorylation was involved in inflammation-induced corneal neovascularization. Tyrosine kinase inhibitors may have utility as inhibitors of corneal neovascularization.