Lipoprotein-like particles and cholesteryl esters in human Bruch's membrane: initial characterization.

Published

Journal Article

PURPOSE: To isolate and characterize cholesteryl ester-containing, lipoprotein-like particles (LLPs) from normal aged human Bruch's membrane (BrM)/choroid (Ch). METHODS: From BrM/Ch of 20 eyes of 10 donors aged >60 years, LLPs were released by high-salt buffer, fractionated by density gradient ultracentrifugation, and characterized by determining cholesterol, triglyceride, and phospholipid concentration (by enzymatic colorimetry and fluorometry); cholesteryl ester composition (by electrospray ionization mass spectrometry, ESI/MS); and particle morphology (by negative stain electron microscopy). Apolipoprotein (apo) gene expression was determined with RT-PCR, Western blot analysis, and immunofluorescence of retinal-choroidal cryosections. In paraformaldehyde-preserved eyes (20 eyes of 20 donors), cholesteryl ester composition of BrM/Ch, cornea, and sclera was determined by ESI/MS. RESULTS: A pooled fraction of LLP released from BrM/Ch (concentrated total LLP, density [d] < 1.24 g/mL fraction) was fractionated into two peaks. A large Peak 1 (with plasma LDL-HDL density range), containing predominantly phospholipid and unesterified cholesterol, was morphologically heterogeneous. A small Peak 2 (with plasma VLDL density range), enriched with esterified cholesterol, contained approximately 100 nm diameter round electron-lucent particles. Both peaks contained apoB and apoA-I, RPE and retina contained apoA-I mRNA transcripts, and BrM and drusen contained apoA-I immunoreactivity. Peaks 1 and 2, native RPE, and fresh BrM/Ch were cholesteryl linoleate enriched and contained little cholesteryl docosahexaenoate. Preserved BrM/Ch was cholesteryl oleate-enriched, unlike sclera and cornea. CONCLUSIONS: BrM/Ch LLP do not resemble plasma lipoproteins in density profile, cholesterol distribution, or morphology. Peak 2 contains EC-rich LLP resembling BrM particles in situ. BrM/Ch cholesteryl esters respond to long-term storage differently than esters of plasma lipoprotein origin accumulated in other ocular tissues. Evidence of intraocular apoB and apoA-I expression supports an emerging hypothesis that the RPE assembles and secretes a large, possibly novel, lipoprotein particle.

Full Text

Duke Authors

Cited Authors

  • Li, C-M; Chung, BH; Presley, JB; Malek, G; Zhang, X; Dashti, N; Li, L; Chen, J; Bradley, K; Kruth, HS; Curcio, CA

Published Date

  • July 2005

Published In

Volume / Issue

  • 46 / 7

Start / End Page

  • 2576 - 2586

PubMed ID

  • 15980251

Pubmed Central ID

  • 15980251

Electronic International Standard Serial Number (EISSN)

  • 1552-5783

International Standard Serial Number (ISSN)

  • 0146-0404

Digital Object Identifier (DOI)

  • 10.1167/iovs.05-0034

Language

  • eng