Physical and Chemical Analysis of the Lipofuscin Granule of Bisretinoid Photodestruction Products From Retinal Pigment Epithelium Cells of the Eye

In this paper, the mechanisms of the formation of the bisretinoid oxidation products in lipofuscin granules (LGs) isolated from the retinal pigment epithelium cells of the human eye are studied. The physicochemical characteristics of the bisretinoid photooxidation products are described. The methods of IR spectroscopy, Raman spectroscopy, fluorescence spectroscopy, scanning confocal microscopy, time-of-flight mass spectrometry of secondary ions, and high-performance liquid chromatography are used for the study. The properties of the products of photooxidation and degradation of the fluorophore of LGs, including synthetic N-retinylidene-N-retinylethanolamine (A2E), are described in detail. It is shown that the products of oxidative degradation of LGs are similar to the products of photooxidation of the main bisretinoid of LGs: A2E. These data are important both for understanding the mechanisms of the formation of cytotoxic products in LGs and for establishing their chemical nature.