Common bacterial cause of gum disease may drive rheumatoid arthritis

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Common bacterial cause of gum disease may drive rheumatoid arthritis

Investigators at Johns Hopkins found a new evidence that the bacteria causing chronic gum infections may also trigger the autoimmune inflammation thereby leading to rheumatoid arthritis (RA). It is a chronic form of arthritis linked to an overactive immune system. Although it prominantly affects joints, it can affect variety of body systems as well.

For decades, it has been known that people with RA are more susceptible to gum disease. The researchers identified, a common factor, Aggregatibacter actinomycetemcomitans, the bacteria responsible for periodontal disease and RA. Infection with this bacterium is supposed to  induce the production of proteins (citrullinated proteins) that activates the immune system and leads to a chain of reactions causing RA.

Earlier studies were focused on Porphyromonas gingivalis (with no signs of citrullinated proteins); however, researchers could not find association between P. Gingivalis and RA. Therefore, studies looking for other possible bacteria responsible for it were conducted. Later on, researchers found a pathogenesis similar to one observed in the joints with RA that was occurring in the gums of patients with periodontal disease. This common denominator is called hypercitrullination.

Citrullination is a regulatory process of proteins that naturally occur in all individuals.Unfortunately,  this process of proteins is overactive in RA patients which forms very high levels of anti-citrullinated protein antibodies and higher levels of antibodies, thereby caussing inflammation and attacking body‘s own tissues.

This finding raises the possibility that the bacterium A. actinomycetemcomitans is the only pathogen with ability to induce hypercitrullination in neutrophils, a white blood cell and part of the immune system. Neutrophils are the most abundant inflammatory cells found in the joints affected with RA and the gums with periodontal disease. They found that these bacteria can cause the citrullination damage by secreting a toxin, leukotoxin A (LtxA), that creates holes in the neutrophil immune cells.

However, study participants (>50%) with RA had no evidence of infection with A. Actinomycetemcomitans, but other bacteria in the gut, lung, or elsewhere can also induce hypercitrullination.

Source:

Johns Hopkins Medicine

Link to the source:

https://www.mdlinx.com/rheumatology/top-medical news/article/2016/12/16/1

Original title of article:

Researchers add to evidence that common bacterial cause of gum disease may drive rheumatoid arthritis

Johns Hopkins Medicine
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