Trefoil peptide protection of intestinal epithelial barrier function: cooperative interaction with mucin glycoprotein.

Goblet cells secrete a combination of trefoil peptides and mucin glycoproteins to form a continuous gel on the mucosal surface. The functional effects of these products remain uncertain. Trefoil peptides and/or mucin glycoproteins were added to Transwell monolayers of the human colonic cancer-derived T84 cell line. Intact monolayers permitted penetration of < 4% of the inert marker [3H]mannitol at 4 hours. Exposure to the toxic lectin phytohemagglutinin (1 mg/mL), oleic acid (8 mmol/L) and taurocholic acid (12 mmol/L), or Clostridium difficile toxin A (0.7 microgram/mL) resulted in loss of barrier function with 36%, 62%, and 45% of [3H]mannitol penetration, respectively. Addition of recombinant human intestinal trefoil factor in physiological concentrations (1-5 micrograms/microL) resulted in attenuation of the damage to monolayer integrity by up to 52%. Protection was enhanced (up to 95%) by the copresence of human colonic mucin glycoproteins. Similar effects were observed when rat intestinal trefoil factor or human spasmolysin, another human trefoil peptide, were added alone or in the presence of human mucin glycoproteins. Conversely, mucin glycoproteins isolated from the rat colon or stomach facilitated protection when added with human spasmolysin or human intestinal trefoil factor. Trefoil peptides and mucin glycoproteins protect gastrointestinal mucosa from a variety of insults.