Related Experiment Videos
Mucin exocytosis: a major target for Helicobacter pylori
I Micots1, C Augeron, C L Laboisse
1Laboratoire de Bactériologie-Enfants, Hôpital Pellegrin, Bordeaux, France.
Aims:
To determine whether Helicobacter pylori impairs the secretory function of mucous cells.
Methods:
The mucus secreting human cell line CL. 16E, maintained as confluent monolayers on nitrocellulose filters, was infected with H pylori strain CIP 101260. After three hours of incubation with H pylori the monolayers were washed and reincubated with fresh culture medium for various time periods (24, 48, or 72 hours) before evaluating both the morphology and function of mucous cells. For morphological studies, epithelial monolayers were fixed in situ and processed for both standard histochemistry on paraffin wax sections, and electron microscopy. To measure mucins secreted from cultured cells, the cells were metabolically labelled with 3H-glucosamine. Undegraded mucins were quantitated as the radioactive glycoproteins blocked at the stacker gel interface after sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the secretory glycoproteins.
Results:
Control cultures of CL. 16E cells grew on filters as homogeneous monolayers of polarised mucous cells secreting a visco-elastic gel of mucins at the apical surface. In infected monolayers H pylori was in close contact with the apical surface of mucous cells. Cell counts and histological evaluation of the monolayers did not reveal any significant deleterious effect of H pylori on the mucous cells. H pylori induced only a modest inhibition of baseline mucus secretion from CL. 16E cells, this inhibition being significant only at 24 hours. In contrast, the mucus secretory response to two agents that raise intracellular cAMP and calcium--forskolin and ionophore A23187--was strongly inhibited. The inhibitory effect of H pylori on the exocytotic response was not paralleled by an inhibition of glycoprotein synthesis.
Conclusion:
Considering the fact that the exocytotic response to a variety of secretagogues constitutes the primary line of defence of the gastric mucosa in an emergency, it is suggested that H pylori exerts its deleterious effects by weakening this important physiological defence.
Insights
Helicobacter pylori infection modestly inhibits baseline mucus secretion and significantly impairs the mucus secretory response in gastric mucous cells. This weakens a key defense mechanism of the gastric mucosa.
Area of Science:
- Gastroenterology
- Microbiology
- Cell Biology
Background:
- Helicobacter pylori is a common pathogen associated with various gastric diseases.
- Gastric mucous cells play a crucial role in protecting the stomach lining through mucus secretion.
- The impact of H. pylori on the secretory function of these cells requires further elucidation.
Purpose of the Study:
- To investigate the effect of Helicobacter pylori infection on the secretory function of human gastric mucous cells (CL. 16E).
- To assess whether H. pylori impairs the baseline and stimulated mucus secretion.
- To evaluate the impact on cellular morphology and glycoprotein synthesis.
Main Methods:
- Human gastric mucous cell line (CL. 16E) cultured on filters were infected with H. pylori.
- Morphological analysis using histochemistry and electron microscopy.
- Mucin secretion measured by 3H-glucosamine labeling and quantification of radioactive glycoproteins.
- Stimulated secretion assessed using forskolin and ionophore A23187.
Main Results:
- H. pylori adhered to the apical surface of mucous cells without causing significant morphological damage.
- A modest inhibition of baseline mucus secretion was observed, significant at 24 hours post-infection.
- The mucus secretory response to cAMP- and calcium-elevating agents (forskolin, A23187) was strongly inhibited.
- Inhibition of exocytosis was not accompanied by reduced glycoprotein synthesis.
Conclusions:
- Helicobacter pylori weakens the physiological defense of the gastric mucosa by impairing the exocytotic mucus secretion.
- The findings suggest a mechanism by which H. pylori compromises gastric mucosal integrity.
- Targeting this impaired secretory response could be a therapeutic strategy.