Caco-2 monolayers

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). 

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]. 

Another relatively new lipophilicity scale proposed for use in ADME studies is based on MEKC [106]. A further variant is called BMC and uses mobile phases of Brij35 [polyoxyethylene(23)lauryl ether] [129]. Similarly, the retention factors of 16 P-blockers obtained with micellar chromatography with sodium dodecyl sulfate as micelle-forming agent correlates well with permeability coefficients in Caco-2 monolayers and apparent permeability coefficients in rat intestinal segments [130]. 

Artursson, P., Palm, K., Luthman, K. Caco-2 monolayers in experimental and theoretical predictions of drug transport. Adv. Drug. Ddiv. Rev. 2001, 46, 27-43. 

Tanaka, Y. Taki, Y. Sakane, T. Nadai, T. Sezaki, H. Yamashita, S., Characterization of drug transport through tight-junctional pathway in Caco-2 monolayer Comparison with isolated rat jejunum and colon, Pharm. Res. 12, 523-528 (1995). 

Lentz, K. A. Hayashi, J. Lucisano, L. J. Polli, J. E., Development of a more rapid, reduced serum culture system for Caco-2 monolayers and application to the biopharmaceutics classification system, Int. J. Pharm. 200, 41-51 (2000). 

Hidalgo, I. J. Kato, A. Borchardt, R. T., Binding of epidermal growth factor by human colon carcinoma cell (Caco-2) monolayers, Biochem. Biophys. Res. Commun. 160, 317-324 (1989). 

Using the side-by-side diffusion cell system, Hidalgo et al. (1992) quantified the transflux of testosterone in Caco-2 monolayers at 37°C as a function of the flow rate of the 02/C02 gas mixture (Table 13). They concluded that the kinetics were ABL-controlled and proceeded to calculate the ABL thickness on each side of the diffusion chambers using... 

Figure 6 Correlation of the fraction of dose absorbed with Caco-2 cell permeability obtained in four different laboratories ( , , A, and A). Qualitatively similar correlations were established in all four laboratories, but the data are not directly comparable due to quantitative differences in the permeability of the Caco-2 monolayers. (From Ref. 38 with kind permission from Elsevier Science-NL, Amsterdam.)...

O Sullivan SM, Woods JA, and O Brien NM. 2004. Use of Tween 40 and Tween 80 to deliver a mixture of phytochemicals to human colonic adenocarcinoma cell (CaCo-2) monolayers. British Journal of Nutrition 91(5) 757-764. 

Electron microscopic evaluation of infected Caco-2 monolayers grown on membranes, under conditions that induced cellular polarization, prompted the conclusion that the larvae occupy the cytoplasm of cells they invade (ManWarren et al., 1997). Apical and basal plasma membranes appeared to be preserved in infected cells (Fig. 6.3). These findings reproduced the observations of Wright (1979) in his examination of intestinal tissues from infected mice. In contrast, when Li et al. (1998) performed similar experiments in HT29 monolayers grown on plastic, they concluded... 

Fig. 6.3. Electron micrograph revealing the location of larvae in polarized Caco-2 monolayers grown on filter inserts (ManWarren etal., 1997). Apical microvilli provide evidence of epithelial cell polarization. Epithelial cell cytoplasm is evident above and below the larva. Bar = 2 pm. The position of the filter substrate is marked (F). Photomicrograph prepared by S. Pearce-Kelling and J. Ailing, Cornell University. 

Ungell, and P. Artursson. pH-dependent bi-directional transport of weak basic drugs across Caco-2 monolayers, submitted. 

Fig. 5.2. Two-step process for evaluation of intestinal drug absorption. The first step represents the prediction of intestinal permeability (e.g., over Caco-2 monolayers) from in-silico models or from physico-chemical...

The rat intestinal cell line IEC-18 has been evaluated as a model to study small intestinal epithelial permeability. This cell line forms very leaky monolayers with TER of 50 n cm2 and permeability to mannitol of 8 x 10-6 cm s 1. The IEC-18 model was proposed to be a better model than the Caco-2 monolayers for evaluating the small intestinal paracellular permeation of hydrophilic molecules. However, the leakier paracellular pathway is related to the poor differentiation level of the cells and an undeveloped paracellular barrier lacking peri-junctional actin-belt. In addition, due to the poor differentiation the cells have minute expression of transporters and are therefore not useful for studies of carrier-mediated transport [82, 84]... 

Another limitation of the Caco-2 monolayers is their colonic origin and tight paracellular pathway, which tend to lead to underestimations in permeability to paracellularly transported compounds [97]. This is likely to be correct for small compounds (MW < 150) - i.e., compounds smaller than normal drugs - but it remains to be seen to what extent the Caco-2 model gives false-negative predictions of the fraction absorbed for polar drugs of normal size in humans where para-... 

Tab. 5.1. List of marker compounds used to establish relationship between oral dose absorbed in humans (Fa) and apparent permeability coefficient in Caco-2 monolayers.

The paracellular pathway, between the epithelial cells, is both size- (MW, volume) and charge-dependent [60, 109, 110]. In general, compounds that are limited to paracellular transport are not efficiently absorbed due to the small available absorptive area and the restriction by tight junctions. The molecular weight cut-off seems to be around 400 g mol-1 and 300 g mol-1 for the small and large intestine respectively, and 300 g mol-1 for the Caco-2 cell monolayers [60], which shows the more colonic nature of the Caco-2 monolayer model. Compounds with a... 

Fig. 5.5. Example of using the Caco-2 monolayers to evaluate paracellular transport of an unknown compound. Two markers, mannitol and propranolol are added together with the unknown compound to the apical side and transport of each of the molecules is measured both in the absence and in the...

B., Frokjaer, S., Influence of oligopeptide transporter binding affinity upon uptake and transport of D-Asp(OBzl)-Ala and Asp(OBzl)-Sar in filter grown Caco-2 monolayers, Int. J. Pharm. 1997, 156, 219-228. 

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