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In-vitro hepatotoxic factor in Helicobacter hepaticus, H. pylori and other Helicobacter species
1Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge 02139, USA.
Abstract:
Several inbred strains of mice in closed breeding colonies were found to have spiral-shaped bacteria associated with active, chronic hepatitis. A new species of Helicobacter, H. hepaticus, was isolated from the infected livers of some strains of mice. Other strains of mice were colonised with H. hepaticus in the caecum and colon, but not the liver. Filtersterilised supernatant fluid from five strains of H. hepaticus was tested in a mouse liver cell line (ATCC no. CCL 9.1) for cytotoxic activity. All strains produced a toxic factor causing morphological changes in the cells at dilutions up to 1 in 1000. Toxicity was observed after exposure to the supernatant fluid for 48-72 h. Other Helicobacter spp. that also produced the cytopathic effect (CPE) in the liver cell line were H. felis, H. acinonyx, H. pylori and one strain of H. mustelae. "Helicobacter rappini" and H. muridarum did not cause CPE in the liver cells. The soluble factor was stable at 4 degrees C for up to 3 months. It was also stable at 56 degrees C for 30 min, but was inactivated by boiling for 15 min. It was inactivated by incubation with trypsin. A partially purified preparation of the cytotoxin had a mol. wt of c. 100,000 and did not have urease activity. The cytotoxin produced by H. hepaticus did not cause vacuole formation in HeLa cells.
Insights
A newly identified bacterium, Helicobacter hepaticus, causes chronic hepatitis in mice. Its toxic factor induces cell damage in liver cell lines, indicating a potential mechanism for liver disease progression.
Area of Science:
- Hepatology
- Microbiology
- Toxicology
Background:
- Inbred mouse strains exhibit spiral-shaped bacteria linked to chronic hepatitis.
- Helicobacter hepaticus (H. hepaticus) was isolated from infected mouse livers.
Purpose of the Study:
- To investigate the cytotoxic activity of H. hepaticus in a mouse liver cell line.
- To characterize the toxic factor produced by H. hepaticus.
Main Methods:
- H. hepaticus supernatant fluid was tested on a mouse liver cell line (ATCC no. CCL 9.1).
- Cytotoxic activity and cytopathic effect (CPE) were assessed.
- The stability and properties of the toxic factor were analyzed.
Main Results:
- All tested H. hepaticus strains produced a toxic factor causing cell damage at dilutions up to 1:1000.
- The toxic factor induced morphological changes in liver cells after 48-72 hours.
- Other Helicobacter species like H. felis and H. pylori also caused CPE, while H. rappini and H. muridarum did not.
Conclusions:
- H. hepaticus produces a soluble, heat-stable cytotoxin that damages mouse liver cells.
- This cytotoxin may play a role in the pathogenesis of H. hepaticus-associated hepatitis in mice.