Bacterium can connect teeth and rheumatoid arthritis for some people
If you are genetically predisposed to rheumatoid arthritis and suffer from severe periodontitis, a specific bacterium in the mouth can increase the risk of developing rheumatoid arthritis. This is shown by a collaboration between biomedical basic research from Aarhus University and American researchers.
Years of basic research into periodontitis (inflammation of the gums and jaw bone) carried out at the Department of Biomedicine, Aarhus University (AU), has been an important prerequisite for the ground-breaking research result achieved in collaboration with American researchers. The results have now been published in the prestigious journal Science Translational Medicine.
Results indicate that a bacterium named Aggregatibacter actinomycetemcomitans (A.a.), which occurs in connection with a particularly aggressive form of periodontitis, has significance for the development of rheumatoid arthritis – assuming, however, that the patient is already genetically predisposed to the disease.
"But at the moment we cannot say anything about how significant this is," says Associate Professor Jesper Reinholdt from The Department of Biomedicine, Aarhus University.
"It is therefore important for me to emphasise that you cannot use our results as a basis for concluding that you get rheumatoid arthritis if you suffer from aggressive periodontitis".
Toxin from bacteria makes holes in the cells
Researchers from Aarhus have first and foremost been in charge of the scientific results, which relate to the bacterium A. a.'s ability to produce a toxin (leukotoxin) that promotes inflammation and which, at the same time, makes holes in – and kills – the cells (leukocytes) that normally have to protect us against microorganisms. Jesper Reinholdt – together with Associate Professor Knud Poulsen from The Department of Biomedicine, AU and others – is the person behind the development of a method for the manufacture of the leukotoxin in pure form, which is needed in order to understand the leukotoxin’s molecular mechanism of action. The role of the leukotoxin in cases of serious periodontitis in young people is thoroughly documented through research conducted by Professor Mogens Kilian (Department of Biomedicine, AU) and Professor Dorte Haubek (Department of Dentistry and Oral Health, AU).
Could have significance for other diseases as well as rheumatoid arthritis
The results from Aarhus have caught the attention of others, including arthritis researcher Filipe Andrade Gutierrez from John Hopkins University Medical School in Baltimore, USA.
Together with the other authors of the article, he has – independently of the Danish results – carried out research into the question of whether rheumatoid arthritis can be triggered by a genetically determined immune reaction against the body's own leukocytes caused by damage to the cell membrane of the leukocytes.
The results from Aarhus University led to the American researchers examining whether the effect of the toxin leukotoxin from the bacterium A. a. could have significance in the same way. This has now been confirmed, partly by patient examinations and partly by laboratory analysis with purified leukotoxin from The Department of Biomedicine, AU. In other words, it is possible to see a correlation between inflammation of the teeth and joints respectively, and a genetic predisposition for rheumatoid arthritis. But it is not possible to know the extent of this correlation.
The authors point out that the observed disease mechanisms may also apply to other diseases than rheumatoid arthritis. Not only the bacterium A. a., but also other bacteria which occasionally colonise people, are able to form lukotoxins that could be able to contribute to the development of autoimmune reactions.
Background for the results:
- Type of research: Basic research supplemented with studies of material from relevant patients.
- Partners: Rheumatologists/immunologists from Johns Hopkins University Medical School, Baltimore, USA.
- Financial support: Novo Nordisk Foundation, Aarhus University Research Foundation.
- The researchers involved do not have commercial interests.
- Read the abstract of the article “Aggregatibacter actinomycetemcomitans-induced hypercitrullination links periodontal infection to autoimmunity in rheumatoid arthritis”.
For more information, please contact:
Associate Professor Jesper Reinholdt
Department of Biomedicine, Aarhus University
Mobile: (+45) 3011 8468
jrei@biomed.au