Type IV secretion of Helicobacter pylori CagA into oral epithelial cells is prevented by the absence of CEACAM receptor expression

Background

Helicobacter pylori typically colonizes the human stomach, but it can occasionally be detected in the oral cavity of infected persons. Clinical outcome as a result of gastric colonization depends on presence of the pathogenicity island cagPAI that encodes a type-IV secretion system (T4SS) for translocation of the effector protein CagA and ADP-heptose. Upon injection into target cells, CagA is phosphorylated, which can be demonstrated by in vitro infection of the gastric epithelial cell line AGS, resulting in cell elongation. Here we investigated whether H. pylori can exert these responses during interaction with cells from the oral epithelium. To this purpose, three oral epithelial cell lines, HN, CAL-27 and BHY, were infected with various virulent wild-type H. pylori strains, and CagA delivery and ADP-heptose-mediated pro-inflammatory responses were monitored.

Results

All three oral cell lines were resistant to elongation upon infection, despite similar bacterial binding capabilities. Moreover, T4SS-dependent CagA injection was absent. Resistance to CagA delivery was shown to be due to absence of CEACAM expression in these cell lines, while these surface molecules have recently been recognized as H. pylori T4SS receptors. Lack of CEACAM expression in HN, CAL-27 and BHY cells was overcome by genetic introduction of either CEACAM1, CEACAM5, or CEACAM6, which in each of the cell lines was proven sufficient to facilitate CagA delivery and phosphorylation upon H. pylori infection to levels similar to those observed with the gastric AGS cells. Pro-inflammatory responses, as measured by interleukin-8 ELISA, were induced to high levels in each cell line and CEACAM-independent.

Conclusions

These results show that lack of CEACAM receptors on the surface of the oral epithelial cells was responsible for resistance to H. pylori CagA-dependent pathogenic activities, and confirms the important role for the T4SS-dependent interaction of these receptors with H. pylori in the gastric epithelium.

Endoscopic assessment of blood flow in duodenal ulcers

The importance of blood flow in duodenal ulcer healing is unclear. Endoscopic reflectance spectrophotometry measures the index of oxygen saturation (ISO2), which is significantly correlated with blood flow. In 97 consecutive patients who presented with duodenal ulcer bleeding, the difference in the index of oxygen saturation (delta ISO2: ulcer margin ISO2 minus adjacent mucosa ISO2) was determined during the initial endoscopic examination. Endoscopic examinations were repeated until the ulcers had healed (n = 86). Relative to the adjacent mucosa, 78% of the ulcer margins had increased blood flow (positive delta ISO2) and 22% had decreased blood flow (negative delta ISO2). Stepwise multi-linear regression analysis selected delta ISO2, ulcer size, and stigmata of recent hemorrhage as predictors of delayed healing. A significant negative linear correlation between delta ISO2 and ulcer healing time (r = -0.35, p < 0.001, n = 86) was demonstrated. The scatter in the data precludes prediction of ulcer healing based on delta ISO2 measurement in an individual patient. Multi-variate logistic regression analysis selected concurrent medical illness, duodenal deformity, frequent use of non-steroidal anti-inflammatory drugs, and stigmata of recent hemorrhage as factors significantly associated with delayed (longer than 5 weeks) ulcer healing. The results support the hypothesis that prognostic factors are identifiable at the time of ulcer diagnosis, even in patients who present with bleeding. Blood flow remains an equivocal factor that deserves to be re-studied taking multiple measurements around the ulcer and including a larger number of slow healers.

Reproducible demonstration of blood flow at duodenal ulcer margins by endoscopic reflectance spectrophotometry

Changes in gastrointestinal mucosal blood flow were evaluated by index of oxygen saturation (ISO2) and index of hemoglobin concentration (IHB) measured with a reflectance spectrophotometer. This report examined the reproducibility of endoscopic measurements of ISO2 and IHB. Study 1: The everted stomachs of three anesthetized rats provided hands-on instruction (one teacher and three learners). Six sets of readings were obtained endoscopically (the mean calculated to give the measurement) at each level of gastric mucosal perfusion when gastric blood flow was varied by withdrawing blood from the carotid artery. Study 2: Fourteen duodenal ulcer patients with ulcer bleeding were transfused and stabilized. Two endoscopists (one teacher and one learner) took turns to obtain endoscopic ISO2 and IHB measurements at the margin of the ulcer and at the adjacent normal appearing mucosa. delta ISO2 was calculated as the ulcer margin value minus adjacent mucosa value. In study 1, the correlation coefficients between the ISO2 measurements of the experienced and those of the other three observers were 0.99, 0.97, and 0.97, respectively. In study 2, the correlation coefficients between the ISO2 measurements obtained at the ulcer margin and at the adjacent normal mucosa, and delta ISO2 obtained by the experienced observer and one of the three learners were 0.94, 0.97, and 0.94, respectively. Relative to the adjacent area, 79% of the duodenal ulcers studied had increased (+delta ISO2), and 21% had decreased blood flow (-delta ISO2) at the ulcer margins. IHB measurements were less reproducible, particularly at the ulcer margin. The measurements of ISO2 and delta ISO2 were reproducible in the everted rat stomach and in duodenal ulcer patients.(ABSTRACT TRUNCATED AT 250 WORDS)