The protective effect of URP20 on ocular Staphylococcus aureus and Escherichia coli infection in rats.

BACKGROUND: Infectious keratitis, a medical emergency with acute and rapid disease progression may lead to severe visual impairment and even blindness. Herein, an antimicrobial polypeptide from Crassostrea hongkongensis, named URP20, was evaluated for its therapeutic efficacy against keratitis caused by Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) infection in rats, respectively. METHODS: A needle was used to scratch the surface of the eyeballs of rats and infect them with S. aureus and E.coli to construct a keratitis model. The two models were treated by giving 100 μL 100 μM URP20 drops. Positive drugs for S. aureus and E. coli infection were cefazolin eye drops and tobramycin eye drops, respectively. For the curative effect, the formation of blood vessels in the fundus was observed by a slit lamp (the third day). At the end of the experiment, the condition of the injured eye was photographed by cobalt blue light using 5 μL of 1% sodium fluorescein. The pathological damage to corneal tissues was assessed using hematoxylin-eosin staining, and the expression level of vascular endothelial growth factor (VEGF) was detected by immunohistochemistry. RESULTS: URP20 alleviated the symptoms of corneal neovascularization as observed by slit lamp and cobalt blue lamp. The activity of S. aureus and E.coli is inhibited by URP20 to protect corneal epithelial cells and reduce corneal stromal bacterial invasion. It also prevented corneal thickening and inhibited neovascularization by reducing VEGF expression at the cornea. CONCLUSION: URP20 can effectively inhibit keratitis caused by E.coli as well as S. aureus in rats, as reflected by the inhibition of corneal neovascularization and the reduction in bacterial damage to the cornea.