Acute Exposure of Rabbit Eyes to Artificial Light in Vivo: Effect on Corneal and Third Eyelid Conjunctival Histology and the Gene Expression of PAFR

Abstract

Purpose: To study the effect of acute exposure of rabbit eyes to artificial sunlight in vivo, on the integrity of corneal and conjunctival tissue as well as on the gene expression of the receptor for platelet activating factor (PAFR).

Methods: New Zealand albino rabbits were immobilized opposite a 300 W Osram Ultra-Vitalux® light bulb with an emission radiation spectrum similar to that of normal sunlight at noon, and exposed to ultraviolet B radiation in the range of the reported threshold for corneal damage. Corneal and third eyelid tissue samples were removed from exposed eyes at 2, 6 and 24 h following the end of the exposure to the bulb light and were subsequently processed for histochemical staining and RNA extraction. The gene expression of PAFR was detected with real time reverse transcription polymerase chain reaction.

Results: Some epithelial shedding was detected in the corneal tissue as a result of acute exposure to artificial sunlight. In the eyelid conjunctiva, a marked accumulation of eosinophils was noticed, as early as 2 h post-exposure, apparently directed toward the upper part of the epithelial layer. This effect appears to subside by hour 24. No statistically significant changes in gene expression were detected in the corneal tissue, whereas in the third eyelid, PAFR gene expression was significantly induced, most prominently at t = 2 and 6 h post-exposure.

Conclusion: Acute exposure of rabbit eyes to artificial sunlight induced a marked infiltration of eosinophils into the epithelial layer of the conjunctiva but no gross alterations in the cornea or the third eyelid. The gene expression of PAFR was upregulated, as an effect of light exposure, in the third eyelid but not in the cornea.

• Artificial sunlight
• conjunctiva
• cornea
• eosinophils
• gene expression
• rabbit