Retinoids in lipofuscin granules from retinal pigment epithelium as biomarkers of the damaging effect of ionizing radiation.

Lipofuscin granules accumulate in the retinal pigment epithelium with age, especially in patients with visual diseases, including progressive age-related macular degeneration. Retinoids (bisretinoids and their oxidation products) are major sources of lipofuscin granule fluorescence. The aim of this work was to analyze the radiation-mediated oxidation of retinoids in lipofuscin granules obtained from the human cadaver eye retinal pigment epithelium. Fluorescent and chromatographic analyses of retinoids were performed before and after irradiation of lipofuscin granules with accelerated protons. The fluorescent properties of chloroform extracts from irradiated lipofuscin granules exhibited an increase in fluorescence intensity in the short-wavelength region of 555 nm. This change is associated with an increase in the quantity of retinoid oxidation cytotoxic products after accelerated proton exposure. The radiation-induced oxidation of retinoids caused a noticeable change in its fluorescent properties allows us to consider this phenomenon as a potential opportunity for non-invasively assessment of the degree of radiation exposure and its relative biological effect in humans. Thus, this research proposes a new strategy for assessing the extent of radiation exposure to humans, which evaluates the effects of ionizing radiation on human eye tissues. This approach is based on the principles of the modern non-invasive method of fundus autofluorescence used in ophthalmology for the diagnosis of the retina and retinal pigment epithelium degenerative diseases.