title: Advanced glycation end product (AGE) accumulation on Bruch's membrane: links to age-related RPE dysfunction.
abstract: OBJECTIVE
  Advanced glycation end products (AGEs) accumulate during aging and have been observed in postmortem eyes within the retinal pigment epithelium (RPE), Bruch's membrane, and subcellular deposits (drusen). AGEs have been associated with age-related dysfunction of the RPE-in particular with development and progression to age-related macular degeneration (AMD). In the present study the impact of AGEs at the RPE-Bruch's membrane interface was evaluated, to establish how these modifications may contribute to age-related disease.
  
  
  METHODS
  AGEs on Bruch's membrane were evaluated using immunohistochemistry. A clinically relevant in vitro model of substrate AGE accumulation was established to mimic Bruch's membrane ageing. Responses of ARPE-19 growing on AGE-modified basement membrane (AGE-BM) for 1 month were investigated by using a microarray approach and validated by quantitative (q)RT-PCR. In addition to identified AGE-related mRNA alterations, lysosomal enzyme activity and lipofuscin accumulation were also studied in ARPE-19 grown on AGE-BM.
  
  
  RESULTS
  Autofluorescent and glycolaldehyde-derived AGEs were observed in clinical specimens on Bruch's membrane and choroidal extracellular matrix. In vitro analysis identified a range of dysregulated mRNAs in ARPE-19 exposed to AGE-BM. Altered ARPE-19 degradative enzyme mRNA expression was observed on exposure to AGE-BM. AGE-BM caused a significant reduction in cathepsin-D activity in ARPE-19 (P < 0.05) and an increase in lipofuscin accumulation (P < 0.01).
  
  
  CONCLUSIONS
  AGEs influence ARPE-19 mRNA expression profiles and may contribute to reduced lysosomal enzyme degradative capacity and enhanced accumulation of lipofuscin. Formation of AGEs on Bruch's membrane may have important consequences for age-related dysfunction of the RPE, perhaps leading to age-related outer retinal disease.
authors.affiliation: Centre for Vision and Vascular Science, School of Medicine, Dentistry and BioMedical Science, Queen's University, Northern Ireland, United Kingdom.
authors.forename: Josephine V
authors.initials: JV
authors.lastname: Glenn
authors.forename: Helen
authors.initials: H
authors.lastname: Mahaffy
authors.forename: Keqiang
authors.initials: K
authors.lastname: Wu
authors.forename: Gill
authors.initials: G
authors.lastname: Smith
authors.forename: Ryoji
authors.initials: R
authors.lastname: Nagai
authors.forename: David A C
authors.initials: DA
authors.lastname: Simpson
authors.forename: Michael E
authors.initials: ME
authors.lastname: Boulton
authors.forename: Alan W
authors.initials: AW
authors.lastname: Stitt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D016570:Bruch Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002402:Cathepsin D / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002829:Choroid / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D005453:Fluorescence; D017127:Glycation End Products, Advanced / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008062:Lipofuscin / Q000235:genetics / Q000378:metabolism*; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000378:metabolism; D012164:Retinal Diseases / Q000378:metabolism* / Q000473:pathology; D055213:Retinal Pigment Epithelium / Q000378:metabolism* / Q000648:ultrastructure; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
chemical_list: D017127:Glycation End Products, Advanced; D008062:Lipofuscin; D012333:RNA, Messenger; C533922:CTSD protein, human; D002402:Cathepsin D