Abstract
Purpose: :
A comprehensive analysis of native A2PE–H2 (dihydro–N–retinylidene–N–retinylphosphatidylethanolamine) was conducted in order to examine its relationship to other retinal fluorophores and to ascertain the relevance of A2PE–H2 to A2E biosynthesis in vivo.
Methods: :
Native retinal fluorophores were extracted from ABCA4–/– mice and purified by HPLC. UV–visible absorbance, fluorescence and mass spectroscopy were utilized to examine spectral and structural homologies among these fluorophores. Purified A2PE–H2 was also used for intravitreal injections in wild–type mice to determine the role of A2PE–H2 in A2E biogenesis.
Results: :
Comparison of A2PE–H2 and A2E by derivative absorbance and fluorescence spectroscopy revealed striking similarities in the resonant features of these molecules strongly suggesting similar electronic structure. Additionally, collision–induced dissociation of A2PE–H2 produced daughter ions which were identical to those of authentic A2E and its daughter ions. Finally, intravitreal administration of A2PE–H2 to naive mice resulted in the formation of A2E over a 28–day period.
Conclusions: :
These data provide direct evidence which support a role for A2PE–H2 in A2E biosynthesis. The fluorescence properties of A2PE–H2 and other fluorophores characterized in this report have implications for early detection and diagnostic evaluation of human retinal diseases characterized by aberrant retinal autofluorescence.
Keywords: retinal degenerations: cell biology • retinoids/retinoid binding proteins • age-related macular degeneration