Fluorescently labeled methyl-beta-cyclodextrin enters intestinal epithelial Caco-2 cells by fluid-phase endocytosis

• Published in: PloS one 2014-01, Vol.9 (1), p.e84856-e84856
• Main Authors: Fenyvesi, Ferenc, Réti-Nagy, Katalin, Bacsó, Zsolt, Gutay-Tóth, Zsuzsanna, Malanga, Milo, Fenyvesi, Éva, Szente, Lajos, Váradi, Judit, Ujhelyi, Zoltán, Fehér, Pálma, Szabó, Gábor, Vecsernyés, Miklós, Bácskay, Ildikó
• Format: Article
• Language: English
• Subjects: Acetophenones - pharmacology; Benzopyrans - pharmacology; beta-Cyclodextrins - metabolism; Bioavailability; Biology; Biomarkers - metabolism; Biophysics; Caco-2 Cells; Cell Differentiation - drug effects; Cholesterol; Cyclodextrin; Cyclodextrins; Dendritic cells; Dextrins; Drugs; Endocytosis; Endocytosis - drug effects; Endosomes - drug effects; Endosomes - metabolism; Epithelial cells; Epithelial Cells - cytology; Epithelial Cells - drug effects; Fluorescence; Fluorescent Dyes - metabolism; Gas absorption; Gastrointestinal system; Gastrointestinal tract; Humans; Internalization; Intestine; Intestines - cytology; Laboratories; Medicine; Methyl-β-Cyclodextrin; Monomolecular films; Permeability; Permeability - drug effects; Permeability coefficient; Pharmaceutical industry; Pharmaceutical sciences; Protein Transport - drug effects; rab5 GTP-Binding Proteins - metabolism; Solubility
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0084856

Cyclodextrins are widely used excipients for increasing the bioavailability of poorly water-soluble drugs. Their effect on drug absorption in the gastrointestinal tract is explained by their solubility- and permeability-enhancement. The aims of this study were to investigate penetration properties of fluorescently labeled randomly methylated-beta-cyclodextrin (FITC-RAMEB) on Caco-2 cell layer and examine the cellular entry of cyclodextrins on intestinal cells. The permeability of FITC-RAMEB through Caco-2 monolayers was very limited. Using this compound in 0.05 mM concentration the permeability coefficient was 3.35±1.29×10(-8) cm/s and its permeability did not change in the presence of 5 mM randomly methylated-beta-cyclodextrin. Despite of the low permeability, cellular accumulation of FITC-RAMEB in cytoplasmic vesicles was significant and showed strong time and concentration dependence, similar to the characteristics of the macropinocytosis marker Lucifer Yellow. The internalization process was fully inhibited at 0°C and it was drastically reduced at 37°C applying rottlerin, an inhibitor of macropinocytosis. Notably, FITC-RAMEB colocalized with the early endosome organizer Rab5a. These results have revealed that FITC-RAMEB is able to enter intestinal epithelial cells by fluid-phase endocytosis from the apical side. This mechanism can be an additional process which helps to overcome the intestinal barrier and contributes to the bioavailability enhancement of cyclodextrins.