Disruption of colonic barrier function and induction of mediator release by strains of Campylobacter jejuni that invade epithelial cells

Figure 1 Time course and dose-response of changes in transepithelial resistance after inoculation of T84 cells with three different strains of C jejuni. A: Strain 2801055 reduced resistance to baseline over 6 h in a time- and dose-dependent manner [data are mean ± SE, n = 3 for each bacterial concentration; P < 0.05 compared with controls (uninfected monolayers)]. Baseline resistance across the filter membrane was 100 Ω.cm²; B: Strain 12189 had no effect on resistance across the monolayer; C: Strain 2102011 had no effect on resistance across the monolayer.

Figure 2 Invasion of monolayers of HCA-7 cells determined by a gentamicin protection assay, corrected for the number of cells remaining per monolayer. C. jejuni strain 2801055 invaded the cells of the monolayer in a time-dependent manner, while strains 12189 and 2102011 showed no cellular invasion. Data are mean ± SE, n = 4. Analysis of variance showed that the total number of C. jejuni per monolayer was higher for those strains that abrogated transepithelial resistance compared to those that did not (P = 0.033), and that this increased with time (P = 0.02).

Figure 3 HCA-7 monolayer release of LDH, [³H] mannitol flux and release of IL8 and PGE2 after inoculation with different strains of C. jejuni. All data are mean ± SE at 4 h, (n = 4). A: Strain 2801055 showed a significantly higher LDH release after 4 h (^aP < 0.05) incubation compared to the other two strains, which were similar to control values; B: Strain 2801055 induced a significantly higher flux rate across the monolayer after 4 h (^aP < 0.05) incubation compared to the other two strains, which were similar to control values; C: Strain 2801055 showed a significantly higher IL8 release after 4 h (^aP < 0.05) incubation compared to the other two strains, which were similar to control values; D: Strain 2801055 showed a significantly higher PGE2 release after 4 h (^aP < 0.05) incubation compared to the other two strains, which were similar to control values.

Figure 4 Comparison of the effects of strains 12189 and 2801055 on transmission electron micrograph appearance of monolayers of HCA-7 cells. A: Following inoculation of strain 12189, 10⁷ bacteria/0.5 mL, on the apical side for 6 h, there was no disruption of monolayer integrity; B: There were normal tight junctions and normal apical microvilli; C: Close cell-to-cell contact is seen with occasional bacteria located in the pores of the filter membrane; D: Following inoculation of strain 12189, 10⁷ bacteria/0.5 mL, on the apical side for 6 h, monolayer integrity was compromised with disruption of tight junctions; E: Monolayers showed condensation of the plasma membrane with lifting and rounding of cells off the supporting membrane. C. jejuni are also seen beneath a cell which is lifting off the membrane; F: Changes are seen at higher power.

Figure 5 ΔSCC after stimulation with bradykinin (10^-6 mol/L) and carbachol (10^-4 mol/L) in monolayers inoculated with different strains of C. jejuni. Data are mean ± SE (n = 4) and are shown as percentage of control. A: Reduced chloride secretory response (represented by SCC) to bradykinin after 8 h inoculation with strain 2801055. ^aP < 0.05; B: Reduced chloride secretory response to carbachol after 8 h inoculation with strains 2801055 and 2102011. ^aP < 0.05.