The effect of single and repeated ultraviolet radiation on the anterior segment of the rabbit eye

Abstract

Over the last two decades, depletion of stratospheric ozone has increased the flux of ultraviolet radiation (UVR) at the surface of the earth and the cumulative effect of UVR has become an important aspect of UV-induced eye damage. Epidemiological studies generally assess the chronic, low dose UVR exposure conditions while the laboratory animal experiments usually examine the acute response to high dose exposures. Thus, the study conditions are dissimilar and we are not free to assume that the two variant experimental settings necessarily trigger the same damage or repair mechanism. In order to correlate the results obtained from both experimental settings, laboratory studies of repeated UVR exposures under specific experimental design need to be conducted. The purpose of the present study was to focus on the comparison of the effects of single and repeated UVR-B exposures of the same overall doses on the metabolic profile of the anterior segment of the rabbit eye.

Rabbit eyes were exposed to single (312 nm, 3.12 J/cm2) or repeated (312 nm, 3 x 1.04 J/cm2) UVB irradiations and corneal, aqueous humour and lenticular samples were analysed by NMR spectroscopy. Special grouping patterns among the tissue samples and the relative percentage changes in particular metabolite concentrations were evaluated using advanced statistical methods (Principal component analysis, One-way ANOVA, Independent sample t-test).

The metabolic profiles of UVB irradiated and control samples were significantly different. Especially, alterations in the concentrations of antioxidants (ascorbate, GSH), compounds related to sugar metabolism (glucose, lactate), osmolytes (taurine, hypo-taurine, myoinositol, scylloinositol), choline-containing compounds (choline, phosphocholine) and amino acids were observed. A substantiall additivity of the repeated UVR-B exposures was revealed.

For the first time, a comparison of the effect of a single and repeated UVR exposure of the same overall dose on the metabolic profile of rabbit eye was conducted and described. This study reveals the cumulative effect of repeated UVB irradiation on the anterior segment of the rabbit eye and shows that even a 48 hours interval between subsequent UVR-B exposures is not sufficient for the healing process to restore normal metabolic status in the anterior segment of the rabbit eye.