Lutein transport by Caco-2 TC-7 cells occurs partly by a facilitated process involving the scavenger receptor class B type I (SR-BI).
The carotenoid lutein is thought to play a role in the human eye and to protect against age-related macular degeneration. Lutein transport in the human intestine has not been characterized. We examined lutein transport processes using Caco-2 TC-7 monolayers as a model for human intestinal epithelium. Purified lutein was mixed with phospholipids, lysophospholipids, cholesterol, mono-olein, oleic acid and taurocholate to obtain lutein-rich mixed micelles that mimicked those found under physiological conditions. The micelles were added to the apical side of Caco-2 TC-7 cell monolayers for 30 min or 3 h at 37 degrees C. Absorbed lutein, i.e. the sum of lutein recovered in the scraped cells and in the basolateral chamber, was quantified by HPLC. Transport rate was measured (i) as a function of time (from 15 to 60 min), (ii) as a function of micellar lutein concentration (from 1.5 to 15 microM), (iii) at 4 degrees C, (iv) in the basolateral to apical direction, (v) after trypsin pretreatment, (vi) in the presence of beta-carotene and/or lycopene, (vii) in the presence of increasing concentrations of antibody against SR-BI (scavenger receptor class B type 1) and (viii) in the presence of increasing concentrations of a chemical inhibitor of the selective transfer of lipids mediated by SR-BI, i.e. BLT1 (blocks lipid transport 1). The rate of transport of lutein as a function of time and as a function of concentration was saturable. It was significantly lower at 4 degrees C than at 37 degrees C (approx. 50%), in the basal to apical direction than in the opposite direction (approx. 85%), and after trypsin pretreatment (up to 45%). Co-incubation with beta-carotene, but not lycopene, decreased the lutein absorption rate (approx. 20%) significantly. Anti-SR-BI antibody and BLT1 significantly impaired the absorption rate (approx. 30% and 57% respectively). Overall, these results indicate that lutein absorption is, at least partly, protein-mediated and that some lutein is taken up through SR-BI.
Reboul
Emmanuelle
E
UMR 476 INSERM, Faculté de Médecine, 27 Bd Jean Moulin, 13385 Marseille Cedex 5, France.
Abou
Lydia
L
Mikail
Céline
C
Ghiringhelli
Odette
O
André
Marc
M
Portugal
Henri
H
Jourdheuil-Rahmani
Dominique
D
Amiot
Marie-Josèphe
MJ
Lairon
Denis
D
Borel
Patrick
P
D001667:Binding, Competitive; D001692:Biological Transport; D018955:CD36 Antigens; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism; D020895:Enterocytes / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D014975:Lutein / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B
D018955:CD36 Antigens; D002352:Carrier Proteins; D011971:Receptors, Immunologic; D051116:Receptors, Scavenger; C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B; D014975:Lutein