Effects of COOH–Terminal Tripeptide –MSH11–13 on Corneal Epithelial Wound Healing: Role of Nitric Oxide

Abstract

Purpose: : It is known that α–melanocyte–stimulating hormone (α –MSH) may exert anti–inflammatory effects and facilitate reparative processes in different tissues. The effective message sequence of α –MSH resides in the COOH–terminal tripeptide α –MSH_11–13. This study was undertaken to investigate the effects of topical administration of the COOH–terminal tripeptide sequence of α–MSH (MSH_11–13, KPV) on corneal epithelial wound healing in rabbits and the possible role of nitric oxide (NO) in these effects.

Methods: : The whole corneal epithelium was denuded in both eyes by mechanical scraping. A group of animals was topically treated with KPV 1, 5 and 10 mg/ml (30 µl), two drops four times in a day for 4 days, starting immediately after debridment, while control animals received topical phosphate–buffered saline. In order to study the role of NO in corneal repair processes, the NO donor, sodium nitroprusside (SP, 10 mg/ml, 30 µl) was administered in both eyes of a group of animals, two drops four times in a day for 4 days. The effects of KPV or SP were challenged by a pre–treatment with the nitric oxide synthase inhibitor, Nω–nitro–L–arginine methyl ester (L–NAME, 10 mg/ml, 30 µl) 30 min prior the to KPV or SP instillation. The area of the corneal epithelial defect was stained with fluorescein, photographed, and then measured every 12 h by a computerized Autocad software.

Results: : The mean epithelial wound area and the mean percent of epithelial defect remaining at each follow–up were compared between the groups. The mean epithelial wound area and the mean percent epithelial defect remaining each time were significantly smaller in animals treated with KPV or SP in comparison to controls. Sixty hours later, 8 out of 8 (100%) corneas treated with KPV or SP were completely re–epithelized (p<0.05) while none of the corneas treated with placebo were re–epithelized. Pre–treatment with L–NAME inhibited the facilitating effect of KPV on corneal epithelial wound healing process and totally prevented the effect of SP.

Conclusions: : KPV may facilitate corneal epithelial wound healing in rabbits with a mechanism that seems to involve NO disposition in corneal tissue. However, it is not known whether this mechanism is likely to depend on a direct stimulating repairing activity shared by the entire molecule of α –MSH.

Keywords: wound healing • cornea: basic science • cornea: epithelium