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Absorption enhancement, structural changes in tight junctions and cytotoxicity caused by palmitoyl carnitine in Caco-2 and IEC-18 cells

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Author: Duizer, E. · Wulp, C. van der · Versantvoort, C.H.M. · Groten, J.P.
Type:article
Date:1998
Institution: Centraal Instituut voor Voedingsonderzoek TNO
Source:Journal of Pharmacology and Experimental Therapeutics, 1, 287, 395-402
Identifier: 234728
Keywords: Nutrition · Lactate dehydrogenase · Palmitoylcarnitine · Propidium iodide · Apical membrane · Cell membrane · Cell strain caco 2 · Cell viability · Controlled study · Drug absorption · Drug cytotoxicity · Drug transport · Electric resistance · Human · Human cell · Image processing · Intestine absorption · Macromolecule · Oral drug administration · Priority journal · Protein localization · Tight junction · Animals · Biological Transport · Caco-2 Cells · Cell Survival · Dose-Response Relationship, Drug · Egtazic Acid · Electric Impedance · Humans · Immunohistochemistry · Intestinal Absorption · Membrane Proteins · Octoxynol · Palmitoylcarnitine · Phosphoproteins · Rats · Tight Junctions

Abstract

Palmitoyl carnitine chloride (PCC) has been shown to be an effective enhancer of intestinal transport of hydrophilic molecules. The exact mechanism by which the epithelial barrier function is decreased is not clear. In an attempt to elucidate the mechanism of action of PCC, we studied the relationship among absorption enhancement, cell viability and tight junction protein localization in the human colonic Caco-2 cell line and the rat small intestinal cell line IEC-18. Filter-grown cells were exposed to 0 to 1 mM PCC for 30 min, and the efficacy of PCC treatment was determined by assessing the transepithelial electrical resistance and the apparent permeability for mannitol and PEG-4000. Membrane lysis and cytotoxicity were assessed by measurement of lactate dehydrogenase leakage and uptake of propidium iodide and neutral red. The immunolocalization of the tight junctional protein ZO-1 was quantified using CSLM and image-processing software. In both cell lines, PCC caused a dose-dependent decrease in transepithelial electrical resistance and a concomitant increase in the permeability for mannitol and PEG-4000. The transport enhancement was accompanied by an increase in apical membrane permeability and a reduction in cell viability. At higher PCC concentrations (≥ 0.4 mM), the distribution of the tight junctional protein ZO-1 was changed and cells were unable to recover viability. PCC is effective as an absorption enhancer for hydrophilic macromolecules. However, lytic effects on the cell membrane and reduced cell viability were concomitant with transport enhancement.