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Sulphation and secretion of the predominant secretory human colonic mucin MUC2 in ulcerative colitis
  1. B J-W Van Klinkena,
  2. J-W G Van der Wala,
  3. A W C Einerhandb,
  4. H A Büllerb,
  5. J Dekkerb
  1. aPediatric Gastroenterology and Nutrition, Department of Pediatrics, University of Amsterdam, Academic Medical Centre, Amsterdam, The Netherlands, bPediatric Gastroenterology and Nutrition, Department of Pediatrics, Sophia Children’s Hospital, Erasmus University, Rotterdam, The Netherlands
  1. Dr J Dekker, Pediatric Gastroenterology and Nutrition, Laboratory of Pediatrics, Rm Ee-1571b, Dr Molewaterplein 50, 3015 GE Rotterdam, The Netherlands.

Abstract

BACKGROUND Decreased synthesis of the predominant secretory human colonic mucin (MUC2) occurs during active ulcerative colitis.

AIMS To study possible alterations in mucin sulphation and mucin secretion, which could be the cause of decreased mucosal protection in ulcerative colitis.

METHODS Colonic biopsy specimens from patients with active ulcerative colitis, ulcerative colitis in remission, and controls were metabolically labelled with [35S]-amino acids or [35S]-sulphate, chase incubated and analysed by SDS-PAGE, followed by quantitation of mature [35S]-labelled MUC2. For quantitation of total MUC2, which includes non-radiolabelled and radiolabelled MUC2, dot blotting was performed, using a MUC2 monoclonal antibody.

RESULTS Between patient groups, no significant differences were found in [35S]-sulphate content of secreted MUC2 or in the secreted percentage of either [35S]-amino acid labelled MUC2 or total MUC2. During active ulcerative colitis, secretion of [35S]-sulphate labelled MUC2 was significantly increased twofold, whereas [35S]-sulphate incorporation into MUC2 was significantly reduced to half.

CONCLUSIONS During active ulcerative colitis, less MUC2 is secreted, because MUC2 synthesis is decreased while the secreted percentage of MUC2 is unaltered. Furthermore, sulphate content of secreted MUC2 is unaltered by a specific compensatory mechanism, because sulphated MUC2 is preferentially secreted while sulphate incorporation into MUC2 is reduced.

  • ulcerative colitis
  • mucin
  • MUC2
  • sulphation
  • secretion
  • Abbreviations

    UC
    ulcerative colitis
    EMEM
    Eagle’s minimum essential medium
    SDS-PAGE
    sodium dodecyl sulphate polyacrylamide gel electrophoresis
    PAS
    periodic acid/Schiff
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  • Abbreviations

    UC
    ulcerative colitis
    EMEM
    Eagle’s minimum essential medium
    SDS-PAGE
    sodium dodecyl sulphate polyacrylamide gel electrophoresis
    PAS
    periodic acid/Schiff
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