Caco-2 absorption

Correll MA, Broward-Partin SM, Hansen DK, Behlow HW, Lewis MM, Rose JQ, Thompson TN (2000) Achievement of higher throughput in the Caco-2 absorption screen using a simplified experimental design. AAPS PharmSci 2(4) abstract. 

In-vitro Microsomal Stability Screen Caco-2 Absorption Screen P450 Enzyme Inhibition Screen Rapid Rat" (CARRS) PO/PK Screen... 

Keywords ADME-Tox solubility Caco-2 absorption blood-brain barrier human intestinal absorption oral bioavailability plasma protein binding QSAR... 

Caco-2 cells and isolated small intestine are models of basic nutrition that contributed to the understanding of resveratrol absorption and bioavailability. While the Caco-2 absorption model is a well-defined cellular in vitro system based on a human colonic adenocarcinoma cell line, the isolated small intestine model is nearer to in vivo conditions and is also simpler to handle. It also avoids the methodological problems of in vivo perfusion models [Barthe et al., 1998, 1999]. 

Caco-2 absorption, 5,102 Cahn-Hilliard equations, 6, 240 CAMK group of kinases, 1,186,1%... 

Human intestinal absorption of 5 (01JPS749) and 6 (01MI30) was predicted by using five Abraham descriptors and CaCo-2 monolayer, respectively. The effect of hydrophobicity and molecular mass on the accumulation of 10 fluoroquinolones, including 5, by Staphylococcus aureus were evaluated (01MI14). 

In-vitro models can provide preliminary insights into some pharmacodynamic aspects. For example, cultured Caco 2 cell lines (derived from a human colorectal carcinoma) may be used to simulate intestinal absorption behaviour, while cultured hepatic cell lines are available for metabolic studies. However, a comprehensive understanding of the pharmacokinetic effects vfill require the use of in-vivo animal studies, where the drug levels in various tissues can be measured after different dosages and time intervals. Radioactively labelled drugs (carbon-14) may be used to facilitate detection. Animal model studies of human biopharmaceutical products may be compromised by immune responses that would not be expected when actually treating human subjects. 

Taylor, E.W., Giboons, J.A., and Baeck-man, R.A. Intestinal absorption screening of mixtures from combinatorial libraries in the Caco-2 model. Pharm. Res. 1997, 14, 572-577. 

Artursson P and Karlsson J. Correlation between oral drug absorption in humans and apparent drug permeability coefficients in human intestinal epithelial (Caco-2) cells. Biochem Biophys Res Commun 1991 175 880-5. 

LIU Y and HU m (2002) Absorption and metabolism of flavonoids in the caco-2 cell culture model and a perfused rat intestinal model. Drug Metab Dispos. 30 (4) 370-77. 

In culture, the human colon carcinoma cell hne Caco-2 spontaneously differentiates at confluency into polarized cells with enterocyte-like characteristics. The principle of this approach consists of following the passage of the compound of interest from the apical or lumen-like sides to the basolateral or lymph-hke sides of Caco-2 cells, thus following the absorption of the compound per se. One obhgate step for fat-soluble nutrients such as carotenoids to cross the intestinal barrier is their incorporation into CMs assembled in the enterocytes. Under normal cell culture conditions, Caco-2 cells are unable to form CMs. When supplemented with taurocholate and oleic acid, Caco-2 cells were reported to assemble and secrete CMs. ... 

In contrast to previous in vivo models, this in vitro model provides the possibility of dissociating experimentally two important processes of intestinal absorption cellular uptake and secretion. Under conditions mimicking the postprandial state (taurocholate/oleic acid supplementation), differentiated Caco-2 cells were able to (1) take up carotenoids at the apical sides and incorporate them into CMs and (2) secrete them at the basolateral sides associated with CM fractions. Using this approach, the extent of absorption of P-carotene through Caco-2 cell monolayers after 16 hr of incubation was 11.2%, a value falling within the in vivo range (9 to 22%). ° - Of the total amount of P-carotene secreted, 78% was associated with the two CM fractions and 10% with the VLDL fraction. ... 

This in vitro approach thus has a great potential for studying the intestinal absorption processes of carotenoids and other pigments. It is important to note the existence of several clones isolated from the parent Caco-2 cell line that can be used for studying... 

Caco-2 cells and ezetimibe, a potent inhibitor of chloresterol absorption in humans, it was reported that (1) carotenoid transport was inhibited by ezetimibe up to 50% and the extent of that inhibition diminished with increasing polarity of the carotenoid molecule, (2) the inhibitory effects of ezetimibe and the antibody against SR-BI on P-carotene transport were additive, and (3) ezetimibe may interact physically with cholesterol transporters as previously suggested - and also down-regulate the gene expression of three surface receptors, SR-BI, NPCILI, and ABCAl. 

The importance of drug ionization using cell-based methods such as Caco-2 in the in vitro prediction of in vivo absorption was discussed [45]. It was observed that when the apical pH used in Caco-2 studies was lowered from 7.4 to 6.0 a better correlation was obtained with in vivo data, demonstrating that careful selection of experimental conditions in vitro is crucial to produce a reUable model. Studies with Caco-2 monolayers also suggested that the ionic species might contribute considerably to overall drug transport [46]. 

When screening for absorption by passive membrane permeability, artificial membranes have the advantage of offering a highly reproducible and high-throughput system. Artificial membranes have been compared to Caco-2 cells and for passive... 

Absorption of angiotensin II antagonists in Ussing chambers, Caco-2, perfused jejunum loop and in vivo importance of drug ionization in the in vitro prediction of in vivo absorption. Eur. J. Pharm. Sci. 2000, 10, 215-224. 

Since experimental determination of intestinal absorption is quite demanding, Caco-2 cell monolayers have been successfully used to model passive drug absorption. Several models for the prediction of Caco-2 permeability using PSA were developed, including those of van de Waterbeemd et al. [5] and Palm et al. [22] who found that relationships between Caco-2 permeability and PSA is stronger than with Clog D, Krarup et al. [23] who used dynamic PSA calculated for water accessible molecular surface and Bergstrom et al. [24]. 

Recombinant CYP450s (also for safety assessment of drug-drug interactions) Permeability/absorption Caco-2 cells MDCK cells... 

The Roche investigators were able to relate their measured fluxes to human absorption values with a hyperbolic curve, much like that indicated in Caco-2... 

Caco-2 Models for Prediction of Human Intestinal Absorption (HIA)... 

Figure 7.64 Human intestinal absorption compared to Caco-2 permeabilities from several groups.

In conclusion, the double-sink su m-P, PAMPA in vitro GIT assay seems to predict human absorption as well as in vivo human permeability measurements (see Figs. 7.66a,b) and in vitro Caco-2 permeability measurements (see Figs. 7.60 and 7.63), but at a lower cost and higher speed. 

Artursson, R, Epithelial transport of drugs in cell culture. I A model for studying the passive diffusion of drugs over intestinal absorptive (Caco-2) cells, J. Pharm. Sci. 79, 476-482 (1990). 

Krishna, G. Chen, K.-J. Lin, C.-C. Nomeir, A. A., Permeability of lipophilic compounds in drug discovery using in-vitro human absorption model, Caco-2, Int. J. Pharm. 222, 77-89 (2001). 

Pontier, C. Pachot, J. Botham, R. Lefant, B. Amaud, R, HT29-MTX and Caco-2/TC7 monolayers as predictive models for human intestinal absorption Role of mucus layer, J. Pharm. Sci. 90, 1608-1619 (2001). 

Collett, A. Sims, E. Walker, D. He, Y.-L. Ayrton, J. Rowland, M. Warhurst, G., Comparison of HT29-18-C1 and Caco-2 cell lines as models for studying intestinal paracellular drug absorption, Pharm. Res. 13, 216-221 (1996). 

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