Mechanisms of provitamin A (carotenoid) and vitamin A (retinol) transport into and out of intestinal Caco-2 cells

Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA.
The Journal of Lipid Research (Impact Factor: 4.42). 11/2007; 48(10):2283-94. DOI: 10.1194/jlr.M700263-JLR200
Source: PubMed


The purpose of this study was to compare the mechanisms of intestinal retinol (ROL) and carotenoid transport. When differentiated Caco-2 cells were incubated with ROL for varying times, cellular ROL plateaued within 2 h, whereas retinyl ester (RE) formation increased continuously. ROL and RE efflux into basolateral medium (BM) increased linearly with time, ROL in the nonlipoprotein fraction and REs in chylomicrons (CMs). In contrast to carotenoids, ROL uptake was proportional to ROL concentration (0.5-110 microM). ROL efflux into BM occurred via two processes: a) a saturable process at low concentrations (<10 microM) and b) a nonsaturable process at higher concentrations. When ROL-loaded cells were maintained on retinoid-free medium, free ROL, but not REs, was secreted into BM. Glyburide significantly reduced ROL efflux but not ROL uptake. Inhibition of ABCA1 protein expression by small interfering RNAs decreased ROL efflux but not carotenoid efflux. Scavenger receptor class B type I (SR-BI) inhibition did not affect ROL transport but decreased carotenoid uptake. The present data suggest that a) ROL enters intestinal cells by diffusion, b) ROL efflux is partly facilitated, probably by the basolateral transporter ABCA1, and c) newly synthesized REs, but not preformed esters, are incorporated into CM and secreted. In contrast to ROL transport, carotenoid uptake is mediated by the apical transporter SR-BI, and carotenoid efflux occurs exclusively via their secretion in CM.

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Available from: Alexandrine During,
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    • "Tr es r ecemment, il a et e montr e qu'ABCA1 etait impliqu e dans la s ecr etion ent erocytaire de vitamine E libre mais pas de vitamine A est erifi ee (Reboul et al., 2009). Il a par ailleurs et e suppos e qu'ABCA1 pourrait intervenir dans la s ecr etion de r etinol libre (During et Harrison, 2007). Il est parfois difficile de diff erencier les implications d'ABCA1 et d'ABCG1, un autre transporteur membranaire impliqu e quant a lui dans l'efflux de lipides vers les HDL. "

    OCL - Oleagineux Corps Gras Lipides 03/2011; 18(2):53-58. DOI:10.1051/ocl.2011.0369
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    • "Lin et al. (2007) reported a better uptake of lycopene into DU145 prostate cancer cells from FCS-compared to THF-supplemented media. Lipoproteins appear to play an important role in the cellular uptake of carotenoids (During and Harrison 2007; O'Sullivan et al. 2007). The involvement of the scavenger receptor class B type I (SR-BI) in carotenoid uptake has been demonstrated (van Bennekum et al. 2005; During and Harrison 2007). "
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    ABSTRACT: The present investigation aimed to compare fetal calf serum (FCS) and Tween 40 with the commonly employed tetrahydrofuran (THF) with respect to cytotoxicity, stability of the solubilized carotenoids, and uptake and accumulation of the xanthophylls astaxanthin (AX) and canthaxanthin (CX) in cultured human liver cells (HepG2). Incubation of HepG2 cells for 24 h with THF (≥1.25%) or FCS (≥11.25%) with or without AX (≥25 μmol/L) or CX (≥25 μmol/L) did not affect cell viability. Tween 40 (0.25-1.25% in medium) reduced cell viability by 75-99%. The stabilities of AX and CX in cell-free RPMI 1640 medium for ≤24 h were higher when delivered with THF instead of FCS. The dose- and time-dependent accumulations of AX and CX (1-10 μmol/L) in HepG2 cells were higher when carotenoids were delivered with FCS compared to THF. In conclusion, FCS and THF, but not Tween 40, were suitable solvent systems for the delivery of AX and CX to HepG2 cells. In our experiments FCS was superior with regard to the uptake and accumulation of both carotenoids.
    Cytotechnology 01/2011; 63(1):89-97. DOI:10.1007/s10616-010-9324-7 · 1.75 Impact Factor
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    • "However, the response measured in both hepatic cell lines indicate functional interaction between intestinal and liver cells in this co-culture model. It has previously been reported that transport and metabolism of retinoids in Caco-2 cells is facilitated by delivering them in mixed lipid micelles (During et al., 2002; Yonekura and Nagao, 2007); we did not however, observe any improvement in RBP4 secretion when retinoids were added to the intestinal cells in mixed lipid micelles, compared to delivery with a polysorbate emulsifier (Tween 40). It is possible that further optimization of the micellar preparation and/or lipid composition may improve the performance of the co-culture system by facilitating retinoid delivery and metabolism, and promoting CM formation and secretion from Caco-2 cells. "
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    ABSTRACT: Dietary retinoid bioavailability involves the interplay of the intestine (transport and metabolism) and the liver (secondary metabolism). To reproduce these processes in vitro, differentiated human intestinal Caco-2/TC7 cells were co-cultured with two hepatocyte cell lines. Murine 3A cells and the more highly differentiated human HepaRG hepatocytes were both shown to respond to beta-carotene (BC) and retinol (ROH) treatment by secreting Retinol Binding Protein 4 (RBP4). In co-culture experiments, Caco-2/TC7 were differentiated on filter inserts and transferred for the time of the experiment to culture wells containing confluent 3A or differentiated HepaRG cells. Functionality of the co-cultures was assayed using as endpoints the retinol-dependent secretion of RBP4 and the retinoic acid-dependent induction of CYP26A1 in hepatocytes. BC and ROH added to intestinal Caco-2/TC7 induced a reduction in intracellular RBP4 levels in the underlying hepatocytes and its secretion into the medium. HepaRG hepatocytes were also shown to up-regulate the expression of CYP26A1 mRNA in response to retinoid treatment. This in vitro model represents a useful tool to analyze the absorption and metabolism of retinoids and could be further developed to investigate other dietary compounds and molecules of pharmacological interest.
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