Bacteria that are responsible for causing gum infection could trigger inflammatory responses in people with rheumatoid arthritis, reports a recent study.

Researchers from Johns Hopkins Medicine have found that the bacteria Aggregatibacter actinomycetemcomitans that causes periodontal diseases could be contributing to RA, the autoimmune disease characterized by chronic inflammation of joints.

Gum Disease And Rheumatoid Arthritis

The study published in Science Translational Medicine notes that A. actinomycetemcomitans stimulates the citrullinated protein production in the body, which could be leading to a series of reactions that results in RA.

"This is like putting together the last few pieces of a complicated jigsaw puzzle that has been worked on for many years," said Felipe Andrade, the senior author of the study, in a press release.

The theory is nothing new as gum disease was associated with RA for quite a long time. The investigators suspected the bacteria Porphyromonas gingivalis to be responsible for causing both the ailments. However, no solid evidence has been found by far to establish the association.

The researcher and his team worked on other microbes that could be the common causative agent of both the diseases. On analysis, Andrade and team found A. actinomycetemcomitans in periodontal infection that exhibited a process called hypercitrullination which is seen in the joint inflammation in RA.

Process Of Hypercitrullination

While citrullination is a usual process that happens in the human body to regulate the functions of proteins, RA patients show hypercitrullination that results in the accumulation of high amounts of citrullinated proteins. As a result, the body creates antibodies against these proteins, attack the body's own tissue and result in inflammation.

The researchers found that A. actinomycetemcomitans is the only bacteria that causes hypercitrullination in neutrophils, a type of white blood cell that is rich in the enzyme peptidylarginine deiminase (PAD), which is essential for citrullination. It was noted that among other immune cells, neutrophils are the ones found abundant in gums and joints of RA patients as well as periodontal diseases.

A. actinomycetemcomitans fights the host defense by secreting leukotoxin A, a toxin that creates a hole on the neutrophils. This leads to the entry of high amounts of calcium into the immune cells. Since calcium is the compound that activates PAD to cause citrullination, the abundance of calcium induces hypercitrullination in the cells.

A. Actinomycetemcomitans And Rheumatoid Arthritis

When 196 blood samples of RA patients were analyzed, the investigators found that 92 of them had A. actinomycetemcomitans infection and 60 percent of patients with periodontal disease had A. actinomycetemcomitans infection.

However, the researchers cautioned that an in-depth study of the subject is necessary to come to any kind of conclusion.