期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：16
页码：7275-7280
DOI：10.1073/pnas.0913112107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Fluorescent bisretinoids, such as A2E and all-trans-retinal dimer, form as a by-product of vitamin A cycling in retina and accumulate in retinal pigment epithelial (RPE) cells as lipofuscin pigments. These pigments are implicated in pathological mechanisms involved in several vision-threatening diseases including age-related macular degeneration. Efforts to understand damaging events initiated by these bisretinoids have revealed that photoexcitation of A2E by wavelengths in the visible spectrum leads to singlet oxygen production and photooxidation of A2E. Here we have employed liquid chromatography coupled to electrospray ionization mass spectrometry together with tandem mass spectrometry (MS/MS), to demonstrate that A2E also undergoes photooxidation-induced degradation and we have elucidated the structures of some of the aldehyde-bearing cleavage products. Studies in which A2E was incubated with a singlet oxygen generator yielded results consistent with a mechanism involving bisretinoid photocleavage at sites of singlet molecular oxygen addition. We provide evidence that one of the products released by A2E photodegradation is methylglyoxal, a low molecular weight reactive dicarbonyl with the capacity to form advanced glycation end products. Methylglyoxal is already known to be generated by carbohydrate and lipid oxidation; this is the first report of its production via bisretinoid photocleavage. It is significant that AGE-modified proteins are detected in deposits (drusen) that accumulate below RPE cells in vivo; drusen have been linked to age-related macular degeneration pathogenesis. Whereas various processes play a role in drusen formation, these findings are indicative of a contribution from lipofuscin photooxidation in RPE.
