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Cytopathic effects of Helicobacter pylori on cultured mammalian cells
H Konishi1, M Ishibashi, M G Morshed
1Department of Microbiology, Yamaguchi University School of Medicine, Japan.
Abstract:
Cytopathic effects of broth-culture filtrates from eight clinical isolates and one reference strain of Helicobacter pylori on three cultured mammalian cell lines were investigated. All the strains, including NCTC 11637, produced cytotoxic factors that caused intracellular vacuolation on these cell lines. AGS and SflEp cells were more sensitive than HEp-2 cells. To examine the role of urease in the cytotoxic effect, a urease-negative mutant was produced. Filtrates from both wild-type and mutant strains produced similar vacuolation on SflEp cells in the absence of urea, suggesting that H. pylori produces a cytotoxic substance other than urease. In contrast, ammonia alone, or jack bean urease with urea, also induced rounding and detachment of SflEp cells, whereas ammonium salts induced the production of small vacuoles. The combination of the broth filtrate of the wild-type strain and urea induced vacuolation followed by rounding and detachment of SflEp cells. Evidence is presented that the latter changes are due to ammonia produced during incubation. Nevertheless, the amounts produced were less than that needed to induce cytopathic effects by itself. These results suggest that the cytotoxic substance induces intracellular vacuolation, and that the vacuolated cells are more susceptible to killing by ammonia. Thus both the cytotoxic substance and urease may contribute to the lethal cytotoxicity of H. pylori in vitro.
Insights
Helicobacter pylori produces cytotoxic factors causing cell vacuolation. Urease contributes to cell damage, with ammonia enhancing the cytotoxic effects of H. pylori.
Area of Science:
- Microbiology
- Cell Biology
Background:
- Helicobacter pylori is a significant human pathogen.
- Understanding its cytotoxic mechanisms is crucial for treating infections.
Purpose of the Study:
- To investigate the cytopathic effects of Helicobacter pylori on mammalian cell lines.
- To elucidate the roles of cytotoxic factors and urease in H. pylori-induced cell damage.
Main Methods:
- Broth-culture filtrates from H. pylori strains were applied to cultured mammalian cells (AGS, SflEp, HEp-2).
- A urease-negative mutant was generated to assess urease's contribution.
- Cells were observed for intracellular vacuolation, rounding, and detachment.
Main Results:
- All H. pylori strains produced cytotoxic factors causing intracellular vacuolation.
- AGS and SflEp cells were more sensitive than HEp-2 cells.
- A cytotoxic substance distinct from urease was identified, inducing vacuolation.
- Ammonia, produced via urease activity, exacerbated cell damage, leading to rounding and detachment.
Conclusions:
- H. pylori secretes a cytotoxic substance responsible for intracellular vacuolation.
- Urease activity, producing ammonia, contributes to cell death.
- Both the cytotoxic substance and urease play a role in the overall cytotoxicity of H. pylori in vitro.