title: Enzymatic degradation of A2E, a retinal pigment epithelial lipofuscin bisretinoid.
abstract: Some forms of blinding macular disease are associated with excessive accumulation of bisretinoid lipofuscin in retinal pigment epithelial (RPE) cells of the eye. This material is refractory to lysosomal enzyme degradation. In addition to gene and drug-based therapies, treatments that reverse the accumulation of bisretinoid would be beneficial. Thus, we have examined the feasibility of degrading the bisretinoids by delivery of exogenous enzyme. As proof of principle we report that horseradish peroxidase (HRP) can cleave the RPE bisretinoid A2E. In both cell-free and cell-based assays, A2E levels were decreased in the presence of HRP. HRP-associated cleavage products were detected by ultraperformance liquid chromatography (UPLC) coupled to electrospray ionization mass spectrometry, and the structures of the aldehyde-bearing cleavage products were elucidated by 18O-labeling and 1H NMR spectroscopy and by recording UV−vis absorbance spectra. These findings indicate that RPE bisretinoids such as A2E can be degraded by appropriate enzyme activities.
authors.affiliation: Department of Ophthalmology, Columbia University, 630 West 168th Street, New York, New York 10032, United States.
authors.forename: Yalin
authors.initials: Y
authors.lastname: Wu
authors.forename: Jilin
authors.initials: J
authors.lastname: Zhou
authors.forename: Nathan
authors.initials: N
authors.lastname: Fishkin
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.forename: Janet R
authors.initials: JR
authors.lastname: Sparrow
mesh_terms: D000328:Adult; D000447:Aldehydes / Q000737:chemistry; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002474:Cell-Free System; D002851:Chromatography, High Pressure Liquid; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D008062:Lipofuscin / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D011726:Pyridinium Compounds / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012176:Retinoids / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity
chemical_list: C112040:A2-E (N-retinylidene-N-retinylethanolamine); D000447:Aldehydes; D008062:Lipofuscin; D011726:Pyridinium Compounds; D012176:Retinoids; D006735:Horseradish Peroxidase