Tumor necrosis factor-alpha induces Cl- and K+ secretion in human distal colon driven by prostaglandin E2.
Increased levels of tumor necrosis factor-alpha (TNF-alpha) have been found in, for example, inflammatory bowel disease (IBD) and human immunodeficiency virus (HIV) infection. To investigate a possible contribution of TNF-alpha to the pathogenesis of diarrhea in these diseases, ion transport of human distal colon was studied in the Ussing chamber in vitro. Serosal addition of TNF-alpha increased short-circuit current (Isc) of partially stripped tissues in a dose-dependent manner. Maximum Isc increase of 1.8 +/- 0.2 mumol.h-1.cm-2 was reached after 60 +/- 9 min at 200 ng/ml TNF-alpha. Bidirectional tracer flux measurements revealed that TNF-alpha induced an increase in 36 Cl serosal-to-mucosal flux, a decrease in 36Cl- mucosal-to-serosal flux, and a slight increase in K+ secretion indicated by an increased secretory 86Rb net flux. In the highly differentiated colonic epithelial cell line HT-29/B6, TNF-alpha had no effect on Isc, suggesting a mediation step located in the subepithelium. This supposition was supported by measurements on totally stripped human tissues, since removal of subepithelial layers by total stripping reduced the TNF-alpha effect by 40%. Experiments with tetrodotoxin (10(-6)M) indicated that the TNF-alpha effect was not mediated by the enteric nervous system. The specific 5-lipoxygenase blocker ICI-230487 (5 x 10(-8)M) also had no effect on TNF-alpha action. In contrast, inhibition of cyclooxygenase by indomethacin (10(-6)M inhibited the effect of TNF-alpha. Radioimmunoassay of prostaglandin E2 (PGE2) in the serosal bathing solution revealed an increase in PGE2 production/release after addition of TNF-alpha, which paralleled the Isc response. We conclude that TNF-alpha changed Cl- and K+ transport toward secretion in human colon. This effect was mediated by PGE2 produced by subepithelial cells. Thus TNF-alpha could be a mediator of diarrhea during intestinal inflammation, e.g., in IBD and HIV infection.
Department of Gastroenterology, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Germany.
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H
Schmitz
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M
Fromm
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H
Bode
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P
Scholz
E O
EO
Riecken
J D
JD
Schulzke
D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003967:Diarrhea / Q000503:physiopathology; D015232:Dinoprostone / Q000502:physiology*; D015777:Eicosanoids / Q000502:physiology; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D002712:Chlorides; D016861:Cyclooxygenase Inhibitors; D015777:Eicosanoids; D014409:Tumor Necrosis Factor-alpha; D013779:Tetrodotoxin; D012964:Sodium; D015232:Dinoprostone; D012413:Rubidium; D011188:Potassium; D007213:Indomethacin