The expression of Fas ligand protein in ultraviolet-exposed rabbit corneas

Keratocytes undergo apoptosis during various pathologic conditions and after exposure to ultraviolet radiation (UVR). It was reported that the Fas/Fas ligand system is involved in modulating keratocyte apoptosis. The expression of Fas ligand (FasL) protein was studied in rabbit corneas after photokeratitis induced by different UV wavelengths.

Six New Zealand albino rabbit corneas were exposed to 280- and 310-nm UVR in 10-nm full wavebands at doses producing biomicroscopically significant keratitis (0.12 J/cm2 for 280 nm and 0.47 J/cm2 for 310 nm). Animals were killed 24 hours after exposure. Immunohistochemistry was performed to localize FasL protein in paraffin sections of rabbit corneas. Primary antibody was polyclonal goat anti-FasL IgG.

FasL protein was uniformly detected in epithelial and endothelial layers of all UVR-exposed and control, nonexposed corneas. The positive staining of keratocytes was confined to the anterior stroma of corneas that were exposed to 280-nm UVR. Corneas exposed to 310-nm UVR showed positively stained keratocytes throughout the entire thickness of the stroma.

These data strongly suggest that the Fas/FasL system may play an important role in apoptosis of corneal cells after UVR. The FasL expression in the corneal stroma was more extensive after exposures at 310-nm UVR than at 280-nm UVR.