Plasminogen kringle 5 inhibits alkali-burn-induced corneal neovascularization

PURPOSE: Plasminogen kringle 5 (K5) is a potent angiogenic inhibitor. The purpose of the present study was to evaluate the therapeutic effect of K5 on alkali-burn-induced corneal neovascularization (NV) and to investigate its mechanism of action. METHODS: Corneal NV was induced in rabbits by NaOH. The rabbits received eye drops containing K5 or vehicle alone, four times per day. Corneal NV and inflammation were monitored every other day with a slit lamp microscope, and the length of the vessels in the cornea and the area of NV were measured. Vascular endothelial growth factor (VEGF) was determined by immunohistochemical and Western blot analyses. The TUNEL assay was used to assess the apoptosis of endothelial cells. The effects of K5 on primary bovine aortic endothelial cells (BAECs) were determined by MTT assay, flow cytometry, transmission electron microscopy, and DNA fragmentation assay. RESULTS: Alkali-burn-induced progressive corneal NV and inflammation in the cornea. K5 delayed the onset of corneal NV (P < 0.05) and decreased NV areas (P < 0.05) in a dose-dependent manner. K5 treatment, after the formation of corneal NV, induced regression of newly formatted vessels in the cornea. K5 decreased the inflammatory index in the corneas at different time points after the alkali burn. Corneal VEGF levels were reduced by K5 treatment. K5 inhibits proliferation and induces apoptosis in BAECs. CONCLUSIONS: Topical application of K5 may have therapeutic potential for the chemical burn-induced corneal NV and inflammation. The inhibitory effect of K5 on corneal NV may be by downregulation of VEGF expression.