Helicobacter pylori alters exogenous antigen absorption and processing in a digestive tract epithelial cell line model

Abstract

To study the influence of Helicobacter pylori on epithelial barrier function, bacteria, bacterial sonicates, or broth culture supernatants were incubated for 24 h with HT29-19A intestinal cells grown as monolayers. Subsequently, the monolayers were mounted in Ussing chambers, and electrical resistance (R), fluxes of 22Na (JNa) and 14C-mannitol (JMan) (markers of the paracellular pathway), and fluxes of horseradish peroxidase (HRP) in total (J3H-HRP), intact (JHRPi), and degraded forms were measured. H. pylori did not induce any modification of the paracellular pathway (R = 148 +/- 10 versus 174 +/- 16 Omega. cm2; JNa = 4.16 +/- 0.44 versus 3.51 +/- 0.41 microEq/h. cm2; JMan = 0.081 +/- 0.01 versus 0.058 +/- 0.009 micromol/h. cm2), nor did it modify J3H-HRP (2,201 +/- 255 versus 2, 110 +/- 210 ng/h. cm2 for H. pylori-infected and control cells, respectively). However, in the presence of H. pylori, we observed a significant increase in JHRPi (520 +/- 146 versus 171 +/- 88 ng/h. cm2). This effect was not dependent of the cag status of the strain and was not reproduced by the sonicates or the culture supernatants. It was related to the presence of urease, since a urease-negative mutant of H. pylori did not induce this effect. Ammonia and bafilomycin A1, two agents known to increase the endolysosomal pH, reproduced the increase in JHRPi. In conclusion, H. pylori does not affect directly the integrity of intercellular junctions of epithelial cells in vitro, but it increases the passage of intact HRP, probably by inhibition of the intralysosomal degradation due to the release of ammonia. The increased transport of intact macromolecules may contribute to the induction and maintenance of gastric inflammation by H. pylori.

FIG. 1

Effect of infection of HT29-19A epithelial cell monolayers with H. pylori cagA(+) strains on epithelial barrier function in an Ussing chamber. (A) Parameters reflecting paracellular permeability. No significant difference between the H. pylori-treated and control cells was found, indicating that H. pylori does not alter the paracellular permeability of the epithelium. (B) Parameters reflecting the transcellular transport of HRP by transcytosis. ∗, Significantly different from control value (P < 0.04). Results are expressed (for units of measure, see Table 1) as means ± SE of control (n = 20) or H. pylori-infected (n = 20) cell monolayers.

FIG. 2

Effect of infection of HT29-19A epithelial cell monolayers with a cagA-positive, urease-positive, VacA-positive H. pylori strain on HRP transcytosis and processing. An increase in HRP transport in intact form, representing 10 and 25% of the total transport in control and H. pylori infection conditions, respectively, is observed. ▪, intact HRP; ▨, peptides; □, amino acids.

FIG. 3

Effect of a urease-negative mutant of H. pylori () on HRP transport and processing across HT29-19A epithelial cell monolayers (n = 12). □, control.