title: Aberrant Buildup of All-Trans-Retinal Dimer, a Nonpyridinium Bisretinoid Lipofuscin Fluorophore, Contributes to the Degeneration of the Retinal Pigment Epithelium.
abstract: Nondegradable fluorophores that accumulate as deleterious lipofuscin of RPE are involved in pathological mechanisms leading to the degeneration of RPE in AMD. A2E, a major component of RPE lipofuscin, could cause damage to RPE cells. Nevertheless, all-trans-retinal dimer (atRAL dimer) was found to be much more abundant than that of A2E in eyes of Abca4-/-Rdh8-/- double-knockout (DKO) mice, a rodent model showing the typical characteristics of retinopathies in AMD patients. Our aim was to elucidate the effect and mechanism of atRAL dimer-induced RPE degeneration.
  
  
  
  Eyes harvested from C57BL/6J wild-type (WT) and Abca4-/-Rdh8-/- DKO mice were examined by HPLC. Cellular uptake, subcellular localization, 5-bromo-2-deoxyuridine (BrdU), Cdc25C, DNA strand breaks, mitochondrial membrane potential (ΔΨm), and cytochrome c were analyzed by fluorescence microscopy. Cellular toxicity was assayed by lactate dehydrogenase (LDH) assay and dead cell staining. Apoptosis and cell-cycle stages were detected by flow cytometry. Furthermore, in vitro and in vivo expression of proteins associated with cell cycle and apoptosis was measured by immunoblot assays.
  
  
  
  All-trans-retinal dimer clearly could damage RPE cell membrane and inhibit the proliferation of RPE cells as well as induce DNA damage and cell-cycle arrest at the G2/M phase via activating the ATM/ATR-Chk2-p53 signaling pathway. Moreover, this di-retinal adduct triggered mitochondrion-associated apoptosis in RPE cells. Evidence from the cell-based experiments was also corroborated by a remarkable abnormality in expression of proteins associated with cell cycle (Cyclin B1 and Cdc2) and apoptosis (p53, Bcl-2 and Bax) in the RPE of Abca4-/-Rdh8-/- DKO mice.
  
  
  
  These findings suggest that atRAL dimer that accumulates beyond a critical level, facilitates age-dependent RPE degeneration.
authors.affiliation: Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University, College of Medicine, Xiamen University, Xiamen, China 2College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Junli
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University, College of Medicine, Xiamen University, Xiamen, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liao
authors.affiliation: Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University, College of Medicine, Xiamen University, Xiamen, China.
authors.forename: Jingmeng
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Ophthalmology, Guangdong Academy of Medical Science, Guangdong General Hospital, Guangzhou, China.
authors.forename: Xinran
authors.initials: X
authors.lastname: Dong
authors.affiliation: Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University, College of Medicine, Xiamen University, Xiamen, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Gao
authors.affiliation: Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University, College of Medicine, Xiamen University, Xiamen, China.
authors.forename: Houjian
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Center of Analysis and Measurement, Zhejiang University, Hangzhou, China.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Wu
authors.affiliation: Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University, College of Medicine, Xiamen University, Xiamen, China.
authors.forename: Zuguo
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University, College of Medicine, Xiamen University, Xiamen, China.
authors.forename: Yalin
authors.initials: Y
authors.lastname: Wu
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004195:Disease Models, Animal; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D008062:Lipofuscin / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D012160:Retina / Q000378:metabolism / Q000473:pathology; D012162:Retinal Degeneration / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D055213:Retinal Pigment Epithelium / Q000378:metabolism* / Q000473:pathology; D012172:Retinaldehyde / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D008062:Lipofuscin; C525876:retinal dimer; D012172:Retinaldehyde