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This Article Full Text Full Text (PDF) All Versions of this Article: 294/5/G1191    most recent 00318.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Claud, E. C. Articles by Jilling, T. Search for Related Content PubMed PubMed Citation Articles by Claud, E. C. Articles by Jilling, T.

MUCOSAL BIOLOGY

Platelet-activating factor-induced chloride channel activation is associated with intracellular acidosis and apoptosis of intestinal epithelial cells

Departments of ¹Pediatrics, ³Neurobiology, Pharmacology, and Physiology, ⁴Medicine, and ⁵Pathology, University of Chicago, Chicago, Illinois; ²Department of Pediatrics, Evanston Northwestern Healthcare, Northwestern University, Evanston, Illinois

Submitted 16 July 2007 ; accepted in final form 11 March 2008

Platelet-activating factor (PAF) is a phospholipid inter- and intracellular mediator implicated in intestinal injury primarily via induction of an inflammatory cascade. We find that PAF also has direct pathological effects on intestinal epithelial cells (IEC). PAF induces Cl^– channel activation, which is associated with intracellular acidosis and apoptosis. Using the rat small IEC line IEC-6, electrophysiological experiments demonstrated that PAF induces Cl^– channel activation. This PAF-activated Cl^– current was inhibited by Ca²⁺ chelation and a calcium calmodulin kinase II inhibitor, suggesting PAF activation of a Ca²⁺-activated Cl^– channel. To determine the pathological consequences of Cl^– channel activation, microfluorimetry experiments were performed, which revealed PAF-induced intracellular acidosis, which is also inhibited by the Cl^– channel inhibitor 4,4'diisothiocyanostilbene-2,2'disulfonic acid and Ca²⁺ chelation. PAF-induced intracellular acidosis is associated with caspase 3 activation and DNA fragmentation. PAF-induced caspase activation was abolished in cells transfected with a pH compensatory Na/H exchanger construct to enhance H⁺ extruding ability and prevent intracellular acidosis. As ClC-3 is a known intestinal Cl^– channel dependent on both Ca²⁺ and calcium calmodulin kinase II phosphorylation, we generated ClC-3 knockdown cells using short hairpin RNA. PAF induced Cl^– current; acidosis and apoptosis were all significantly decreased in ClC-3 knockdown cells. Our data suggest a novel mechanism of PAF-induced injury by which PAF induces intracellular acidosis via activation of the Ca²⁺-dependent Cl^– channel ClC-3, resulting in apoptosis of IEC.

intestinal injury; intestinal barrier; ion transport; Ca²⁺-activated Cl^– channel