Carotenoid Uptake and Protection in Cultured RPE - Carotenoids: Physical, Chemical, and Biological Functions and Properties - page 309

15

Carotenoid Uptake and
Protection in Cultured RPE

Małgorzata Ró . anowska and Bartosz Ró . anowski

CONTENTS
15.1 Introduction ........................................................................................................................ 309
15.2 Potential Protective Role of Carotenoids in the Retina as Antioxidants ............................ 312
15.3 RPE as a Mediator of Specii c Uptake of Carotenoids into the Retina.............................. 313
15.3.1 RPE as the Blood-Retina Barrier.......................................................................... 314
15.3.2 Carotenoid Delivery to the RPE from Blood ........................................................ 314
15.3.2.1 Lipoprotein Receptors Expressed by the RPE...................................... 314
15.3.2.2 Metabolic Pathways in the RPE of Pro-Vitamin A Carotenoids .......... 315
15.3.2.3 Expression and Secretion of Lipoproteins by the RPE ........................ 318
15.3.2.4 Transporters Potentially Involved in Carotenoid Movement
in the Retina .......................................................................................... 320
15.4 Cultured RPE as a Model of Physiological RPE Functions ............................................... 323
15.4.1 Carotenoid Uptake, Accumulation, and Secretion in Cultured RPE Cells ........... 323
15.5 Carotenoid Protection in the RPE ...................................................................................... 326
15.5.1 Effects of Carotenoids on Oxidative Stress in Cultured RPE Cells ...................... 326
15.6 Pro-Oxidant Effects of Carotenoids ................................................................................... 328
15.7 Pro-Oxidant and Cytotoxic Properties of the Degradation Products of Carotenoids ........ 329
15.8 Pro-Oxidant and Cytotoxic Effects of Carotenoids and Their Degradation Products
in Cultured RPE Cells ........................................................................................................ 331
15.9 Effect of Binding to Proteins on Carotenoid Susceptibility to Degradation ...................... 332
15.10 Cooperation of Carotenoids with Other Antioxidants........................................................ 333
15.11 Bioactivities of Carotenoids other than Direct Antioxidants ............................................. 335
15.11.1 Modulation of Inl ammatory Pathways............................................................... 335
15.11.2 Remodeling of Extracellular Matrix ................................................................... 336
15.11.3 Modulation of Lipid Metabolism and Transport................................................. 336
15.11.4 Other Effects of Carotenoids............................................................................... 337
15.12 Summary ........................................................................................................................... 337
References ...................................................................................................................................... 338

15.1 INTRODUCTION
Carotenoids accumulating in the human body are obtained exclusively from our diet. Out of
almost 50 carotenoids present in a typical human diet, about 14 are absorbed into the blood
(Khachik et al., 1997), and only two of them—lutein and zeaxanthin (Figure 15.1)—accumulate
in the retina (Bernstein et al., 2001; Bone and Landrum, 1992; Bone et al., 1988, 1997; Davies
and Morland, 2004; Khachik et al., 1997, 2002). Lutein and zeaxanthin are particularly concen-
trated in photoreceptor axons and inner plexiform layer in the area including and surrounding

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