Sodium caprate as an enhancer of macromolecule permeation across tricellular tight junctions of intestinal cells.
Sodium caprate is a promising candidate for inducing drug absorption enhancement. The mechanism of that uptake-enhancing effect is not fully understood so far. We investigated how caprate acts in an established human intestinal cell line, HT-29/B6, on the transient opening of transcellular (across the cell membranes) and paracellular (across the tight junction) pathways. Sodium caprate (10 mm) caused a rapid and reversible decrease of transepithelial resistance which is based, as measured by two-path impedance spectroscopy, exclusively on resistance changes of the paracellular pathway. Measurements of paracellular marker fluxes revealed an increased permeability for fluorescein (330 Da) and FITC-dextran (4 and 10 kDa), indicating an opening of the paracellular barrier. Confocal microscopy revealed a marked reduction of tricellulin in tricellular tight junctions and of claudin-5 in bicellular tight junctions. This was not due to altered protein expression, as occludin, claudins or tricellulin were not significantly changed in Western blots. Visualization of the translocation site of the cell membrane-impermeable marker molecule sulpho-NHS-SS-biotin (607 Da) indicated the tricellular tight junction to be the predominant pathway. We suggest that caprate's known enhancing effect on intestinal drug uptake is based on increased permeability in tricellular cell contacts, mediated by reversible removal of tricellulin from the tricellular tight junction.
Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Freie Universität and Humboldt-Universität, 12200 Berlin, Germany.
Susanne M
SM
Krug
Maren
M
Amasheh
Isabel
I
Dittmann
Ilya
I
Christoffel
Michael
M
Fromm
Salah
S
Amasheh
D000199:Actins / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D003652:Decanoic Acids / Q000494:pharmacology*; D017097:Electric Impedance; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D019073:HT29 Cells; D006801:Humans; D007422:Intestines / Q000166:cytology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D046911:Macromolecular Substances / Q000378:metabolism*; D062725:Tight Junction Proteins / Q000378:metabolism; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D000199:Actins; D015415:Biomarkers; D003652:Decanoic Acids; D046911:Macromolecular Substances; D062725:Tight Junction Proteins; C031071:decanoic acid; D007770:L-Lactate Dehydrogenase