title: Phosphatidylcholine passes through lateral tight junctions for paracellular transport to the apical side of the polarized intestinal tumor cell-line CaCo2.
abstract: Phosphatidylcholine (PC) is the most abundant phospholipid in intestinal mucus, indicative of a specific transport system across the mucosal epithelium to the intestinal lumen. To elucidate this transport mechanism, we employed a transwell tissue culture system with polarized CaCo2 cells. It was shown that PC could not substantially be internalized by the cells. However, after basal application of increasing PC concentrations, an apical transport of 47.1±6.3nmolh(-1)mMPC(-1) was observed. Equilibrium distribution studies with PC applied in equal concentrations to the basal and apical compartments showed a 1.5-fold accumulation on the expense of basal PC. Disruption of tight junctions (TJ) by acetaldehyde or PPARγ inhibitors or by treatment with siRNA to TJ proteins suppressed paracellular transport by at least 50%. Transport was specific for the choline containing the phospholipids PC, lysoPC and sphingomyelin. We showed that translocation is driven by an electrochemical gradient generated by apical accumulation of Cl(-) and HCO3(-) through CFTR. Pretreatment with siRNA to mucin 3 which anchors in the apical plasma membrane of mucosal cells inhibited the final step of luminal PC secretion. PC accumulates in intestinal mucus using a paracellular, apically directed transport route across TJs.
authors.affiliation: Department of Internal Medicine IV, University Clinics of Heidelberg, Heidelberg, Germany. Electronic address: wolfgang.stremmel@med.uni-heidelberg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Stremmel
authors.affiliation: Department of Internal Medicine IV, University Clinics of Heidelberg, Heidelberg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Staffer
authors.affiliation: Department of Internal Medicine IV, University Clinics of Heidelberg, Heidelberg, Germany.
authors.forename: Hongying
authors.initials: H
authors.lastname: Gan-Schreier
authors.affiliation: Department of Internal Medicine IV, University Clinics of Heidelberg, Heidelberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Wannhoff
authors.affiliation: Department of Physics, Kirchhoff Institute of Physics, Heidelberg, Germany.
authors.forename: Margund
authors.initials: M
authors.lastname: Bach
authors.affiliation: Department of Internal Medicine IV, University Clinics of Heidelberg, Heidelberg, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Gauss
mesh_terms: D018938:Caco-2 Cells; D002463:Cell Membrane Permeability / Q000235:genetics; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D007414:Intestinal Neoplasms / Q000378:metabolism* / Q000473:pathology; D055263:Mucin-3 / Q000037:antagonists & inhibitors / Q000235:genetics; D047495:PPAR gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D019108:Tight Junctions / Q000378:metabolism*; D046509:Tissue Culture Techniques
chemical_list: C505032:CFTR protein, human; D055263:Mucin-3; D047495:PPAR gamma; D010713:Phosphatidylcholines; D034741:RNA, Small Interfering; D019005:Cystic Fibrosis Transmembrane Conductance Regulator
keywords: CFTR; Mucins; Mucosal barrier; Mucus; Phosphatidylcholine; Tight junctions; Ulcerative colitis