Published online Nov 20, 2016. doi: 10.5493/wjem.v6.i4.63
Peer-review started: July 1, 2016
First decision: September 5, 2016
Revised: September 19, 2016
Accepted: October 17, 2016
Article in press: October 19, 2016
Published online: November 20, 2016
To investigate the effect of two ways of lipofuscin production (lipid peroxidation and glycation) on lipofuscin fluorescence characteristics and phototoxicity and to compare them with the properties of natural lipofuscin.
Model lipofuscins were prepared on the basis of bovine photoreceptor outer segments (POS) with bisretinoid A2E addition. One set of samples was prepared from POS modified by lipid peroxidation, while another set from POS modified by glycation with fructose. Fluorescent properties and kinetics of photoinduced superoxide generation of model lipofuscins and human retinal pigment epithelium (RPE) lipofuscin were compared. The fluorescence spectra of samples were measured at 365 nm excitation wavelength and 380-650 emission wavelength.
The fluorescence spectra of model lipofuscins are almost the same as the spectrum of natural lipofuscin. Visible light irradiation of both model lipofuscins and natural lipofuscin isolated from RPE cells leads to decrease of a fluorescence maximum at 550 nm and to appearance of a distinct, new maximum at 445-460 nm. The rate of photogeneration of reactive oxygen forms by both model lipofuscins was almost the same and approximately two times less than that of RPE lipofuscin granules.
These data suggest that fluorescent characteristics and phototoxicity of lipofuscin granules depend only to an insignificant degree on the oxidative modification of POS proteins and lipids, and generally are defined by the bisretinoid fluorophores contained in them.
Core tip: The aim of this work is to investigate the influence of different ways of protein-lipid modification of photoreceptor outer segments (POS) on the spectral characteristics and toxicity of lipofuscin. Therefore, model lipofuscins were prepared by protein-lipid modification of POS with products of lipid peroxidation or glycation reaction and the subsequent addition of the fluorophore A2E. The type of photoreceptor modification has no effect on model lipofuscins phototoxicity.