title: Platelet-activating factor regulates chloride transport in colonic epithelial cell monolayers.
abstract: Platelet-activating factor (PAF) has been implicated in the pathogenesis of gastrointestinal diseases such as necrotizing enterocolitis, Crohn's disease, and ulcerative colitis. However, neither the physiologic role of PAF in the intestine, nor the mechanisms by which PAF participates in the pathogenesis of disease are well understood. The aim of the present study was to determine the direct effect of PAF on intestinal epithelial cell ion transport, and to delineate the mechanisms of regulation. Ion transport was evaluated by measuring short circuit current (I(sc)) in HT29-CL19A cell monolayers using Ussing chambers. PAF receptor polarity was assessed using domain-selective biotinylation followed by immunoprecipitation and streptavidin blotting of intact epithelial monolayers. PAF (1-200 microM) stimulated I(sc) that followed the direction of a Cl(-) gradient and was specifically inhibited by the Cl(-) channel blockers glybenclamide, 2,2' iminodibenzoic acid and 4,4' diisothiocyanostilbene-2, 2' disulfonic acid, but was unaffected by the inhibition of prostaglandin synthesis with indomethacin. Stimulated I(sc) was only detected after apical addition of PAF, correlating with the results of biotinylation experiments indicating an exclusive apical polarity of the PAF receptor. PAF receptor antagonists CV6209 and octylonium bromide abolished PAF-stimulated I(sc). Thus, mucosal acting PAF directly and specifically stimulates ion transport via activation of an apical Cl(-) channel in intestinal epithelial cell monolayers independent of prostaglandin biosynthesis.
authors.affiliation: Division of Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital East Building, Charlestown 02129, USA.
authors.forename: Erika C
authors.initials: EC
authors.lastname: Claud
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.forename: Yu
authors.initials: Y
authors.lastname: Xiao
authors.forename: Michael S
authors.initials: MS
authors.lastname: Caplan
authors.forename: Tamas
authors.initials: T
authors.lastname: Jilling
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D016764:Cell Polarity / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D019073:HT29 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology; D008564:Membrane Potentials / Q000502:physiology; D010972:Platelet Activating Factor / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011453:Prostaglandins / Q000096:biosynthesis; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled
chemical_list: D002712:Chlorides; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011453:Prostaglandins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D000242:Cyclic AMP