Time-of-flight secondary ion mass spectrometry to assess spatial distribution of A2E and its oxidized forms within lipofuscin granules isolated from human retinal pigment epithelium

• Published in: Analytical and bioanalytical chemistry 2016-10, Vol.408 (26), p.7521-7528
• Main Authors: Yakovleva, Marina A., Gulin, Alexander A., Feldman, Tatiana B., Bel’skich, Yuriy C., Arbukhanova, Patimat M., Astaf’ev, Artem A., Nadtochenko, Victor A., Borzenok, Sergey A., Ostrovsky, Mikhail A.
• Format: Article
• Language: English
• Subjects: Aged; Analytical Chemistry; Biochemistry; Cadavers; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Electrons; Epithelium; Fluorescence; Food Science; Granular materials; Granules; Health aspects; Humans; Laboratory Medicine; Lipids; Lipofuscin - chemistry; Macular degeneration; Mass spectrometry; Membranes; Methods; Middle Aged; Monitoring/Environmental Analysis; Oxidation; Oxidation-Reduction; Photodegradation; Photooxidation; Photoreceptors; Pigments; Proteins; Research Paper; Retina; Retinal Pigment Epithelium - chemistry; Retinal Pigment Epithelium - cytology; Retinoids - analysis; Scientific imaging; Secondary ion mass spectrometry; Spatial distribution; Spectrometry, Mass, Secondary Ion - methods; Time-of-flight mass spectrometry; Toxicity
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-016-9854-8

Lipofuscin granules accumulate in the cells of retinal pigment epithelium with age, particularly in patients with hereditary diseases. These granules are heterogeneous, being composed of mixtures of proteins and lipids, including more than 21 different fluorescent compounds. Bisretinoids and their photo-oxidation and photodegradation products represent the main source of lipofuscin fluorescence and exhibit phototoxic properties. This study used time-of-flight secondary ion mass spectrometry (ToF–SIMS) with in-depth probing to assess the depth distribution of N -retinylidene- N -retinylethanolamine (A2E) and its singly and doubly oxidized forms (A2E-ox and A2E-2ox, respectively) within lipofuscin granules and in their surface layer (lipid membrane). ToF–SIMS showed that A2E and its oxidized forms were uniformly distributed throughout lipofuscin granules but were not present at the membrane surface layer. This finding is important for understanding the process involved in the formation of lipofuscin granules and in their toxicity.