Acute exposure to artificial sunlight induces the accumulation of eosinophils in rabbit conjunctival epithelium, in vivo

Abstract

Acute exposure of ocular and periocular tissues to natural or artificial light can induce inflammatory responses such as photokeratitis, anterior uveitis and conjunctivitis, attributed mainly to the UVB range of the spectrum. In this study, we have used a model of acute exposure of rabbit eyes to artificial sunlight, to study possible alterations in the architecture of corneal and conjunctival tissue as well as in the expression of selected genes related to the inflammatory response. We have also examined the effect of topical application of rupatadine, a dual H1 histamine receptor / platelet acti - vating factor receptor (PAFR) antagonist in the same system. Methods : New Zealand albino rabbits were immobilized opposite a 300W Osram Ultra-Vitalux ® light bulb with an emission radiation spectrum similar to that of normal sunlight at noon, and exposed for 30 min to an equiva - lent of 7,500 Jm -1 of UVB irradiation, in the range of the reported threshold for corneal damage. Corneal and conjunctival tissue samples were removed from exposed eyes at 2, 6 and 24 hours following the end of the exposure to the bulb light, and were subsequently processed for histochemical staining or RNA extraction. The gene expression of tumor necrosis factor (TNF), interleukin 6 (IL-6) and PAFR was monitored with conventional RT-PCR. Rupatadine fumarate, dissolved in DMSO, was applied topically in concen - trations similar to those routinely used in ocular preparations of other an - tihistamines, one hour before, immediately after, and one hour following exposure. Results : No specific alterations were detected, using standard eosin-hema - toxylin staining, in corneal tissue, as a result of acute exposure to artificial sunlight. In the conjunctiva however, a marked accumulation of eosi - nophils was noticed, as early as hour 2 post-exposure, which appears to be directed towards the upper part of the epithelial layer. This effect appears to subside by hour 24. No statistically significant changes were detected with respect to the gene expression examined, in either tissue. Rupatadine did not affect the eosinophil accumulation in the conjunctiva or the gene expression in either tissue. Conclusion : Acute exposure to artificial sunlight causes an accumulation of eosinophils in rabbit conjunctival epithelium, which was not prevented by the topical application of rupatadine, under the conditions used in this study.