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Review
. 2010 Dec 1;504(1):61-6.
doi: 10.1016/j.abb.2010.05.015. Epub 2010 May 28.

Location of macular xanthophylls in the most vulnerable regions of photoreceptor outer-segment membranes

Witold K Subczynski  1 , Anna Wisniewska, Justyna Widomska
Affiliations
Review

Location of macular xanthophylls in the most vulnerable regions of photoreceptor outer-segment membranes

Witold K Subczynski et al. Arch Biochem Biophys. .

Abstract

Lutein and zeaxanthin are two dietary carotenoids that compose the macular pigment of the primate retina. Another carotenoid, meso-zeaxanthin, is formed from lutein in the retina. A membrane location is one possible site where these dipolar, terminally dihydroxylated carotenoids, named macular xanthophylls, are accumulated in the nerve fibers and photoreceptor outer segments. Macular xanthophylls are oriented perpendicular to the membrane surface, which ensures their high solubility, stability, and significant effects on membrane properties. It was recently shown that they are selectively accumulated in membrane domains that contain unsaturated phospholipids, and thus are located in the most vulnerable regions of the membrane. This location is ideal if they are to act as lipid antioxidants, which is the most accepted mechanism through which lutein and zeaxanthin protect the retina from age-related macular degeneration. In this mini-review, we examine published data on carotenoid-membrane interactions and present our hypothesis that the specific orientation and location of macular xanthophylls maximize their protective action in membranes of the eye retina.

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Figures

Fig. 1
Fig. 1
(Mole ratio of carotenoids and total lipids in DSM)/(mole ratio of carotenoids and total lipids in DRM) indicated on the y-axis as (Carotenoid in DSM)/(Carotenoid in DRM) in domains isolated from membranes made of raft-forming mixture (equimolar ternary mixture of dioleoylphosphatidylcholine/sphingomyelin/cholesterol) with 1 mol% carotenoid added (see Ref. [90] for more detail) (A). (Mole ratio of xanthophylls and total lipids in DSM)/(mole ratio of xanthophylls and total lipids in DRM) indicated on the y-axis as (Xanthophyll in DSM)/(Xanthophyll in DRM) in domains isolated from the model of POS membranes (equimolar ternary mixture of 1-palmitoyl-2-docosahexaenoylphosphatidylcholine/distearoylphosphatidylcholine/cholesterol) with 1 mol% lutein or zeaxanthin added (see Ref. [89] for more detail) (B).
Fig. 2
Fig. 2
Schematic drawing of the distribution of xanthophyll molecules between the saturated raft domain and the unsaturated bulk domain in the membrane of the photoreceptor outer segment. In this illustration, the integral membrane protein, rhodopsin, which is located in the unsaturated membrane domain, is also included to show its co-localization with unsaturated lipids and xanthophylls. As was demonstrated by X-ray diffraction and linear dichroism (in thin membranes), xanthophyll molecules are inclined with respect to the bilayer normal [59]. This inclination decreases with membrane thickness [33] (see Ref. [99] for membrane thicknesses). The thickness of the POS membranes, which contain not only long-chain fatty acids such as DHA [82] but also very-long-chain fatty acids [100,101], should be significantly greater than those investigated in Refs. [33] and [59]. Therefore, we depict xanthophylls as perpendicular to the membrane surface.
Fig. 3
Fig. 3
Schematic drawing showing the localization of xanthophyll molecules in the cholesterol-rich raft domain and the cholesterol-poor bulk domain. Unfavorable interaction of rigid xanthophylls with cholesterol, which creates a free space in the membrane center, is indicated by the circle. When cholesterol is surrounded by phospholipids, such as in the cholesterol-pure domain, the created free space is filled by the flexible hydrocarbon chains of phospholipids.
See this image and copyright information in PMC

References

    1. Bone RA, Landrum JT, Tarsis SL. Preliminary identification of the human macular pigment. Vision Res. 1985;25:1531–1535. - PubMed
    1. Bone RA, Landrum JT, Fernandez L, Tarsis SL. Analysis of the macular pigment by HPLC: Retinal distribution and age study. Invest. Ophthalmol. Vis. Sci. 1988;29:843–849. - PubMed
    1. Landrum JT, Bone RA, Moore LL, Gomea CM. Analysis of zeaxanthin distribution within individual human retinas. Methods Enzymol. 1999;229:457–467. - PubMed
    1. Khachik F, Spangler CJ, Smith JC, Jr, Canfield LM, Steck A, Pfander H. Identification, quantification, and relative concentrations of carotenoids and their metabolites in human milk and serum. Anal. Chem. 1997;69:1873–1881. - PubMed
    1. Gale CR, Hall NF, Phillips DIW, Martyn CN. Lutein and zeaxanthin status and risk of age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 2003;44:2461–2465. - PubMed

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