Rheumatoid Arthritis Exacerbations Linked to Gum Disease

High levels of certain bacteria in the mouth have been linked to signs of immune activity that can affect joints in a small study.

Oral bacteria can enter the bloodstream and cause signs of immune activity associated with rheumatoid arthritis, supporting the idea that gum disease can contribute to joint pain.

The study is one of the first to show that the same antibodies that target the joints in rheumatoid arthritis also attack bacteria living on the gums, and reinforces recommendations that people with the disease should maintain good oral hygiene, Dana says. Orange from Rockefeller University in New York.

Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the body’s tissues. Past research has shown that people with the condition are more likely to develop gum disease, where the gums become inflamed and sometimes bleed, but it’s not clear why.

In the latest study, Orange and her colleagues followed five people with rheumatoid arthritis, two of whom also had gum disease, by asking them to give weekly blood samples for four years. These samples were tested for bacterial genetic material as well as several markers of immune system activity.

Unlike the three people without gum disease, those with the disease often showed traces of mouth bacteria genes such as streptococcus species, in their bloodstream, usually seen every few weeks.

It’s probably caused by episodes of bleeding gums, Orange says. “When the blood comes out, the bacteria go in.”

As the number of bacteria in the mouth peaked, there were also signs of activity of a type of immune cell called monocytes, which are known to be involved in the immune response against joints in arthritis.

Researchers have also sometimes found traces of bacteria that normally live on the skin in blood samples, but they were not accompanied by immune activity. This suggests that skin bacteria contaminated the sample when it was taken from the participant, Orange says. “We know [the immune system] does not ignore bacteria in the blood – they are usually removed very quickly.

In the second part of the study, single blood samples were analyzed from 73 people, about half of whom suffered from rheumatoid arthritis. One blood test for rheumatoid arthritis looks for antibodies that target a group of proteins with a chemical modification called citrullination. This change can occur with any protein, but some citrullinated proteins are found in high amounts in the joints of people with rheumatoid arthritis.

In the study, antibodies against citrulline proteins in those who had rheumatoid arthritis also worked against citrulline proteins produced by oral bacteria that enter the bloodstream. This suggests that oral bacteria enter the bloodstream, causing immune cells to produce antibodies against citrullinated proteins, which trigger an immune attack on the joints, Orange says.

Although the study was small, Paul Emery of the University of Leeds, UK, says taking participants’ blood every week improves the validity of the results. “This is the first to show a correlation between [markers of] exacerbations of rheumatoid arthritis and bacteria in the blood.

Immune activity caused by gum disease has been linked to a growing number of different diseases, from heart attacks to Alzheimer’s disease, although different mechanisms and bacteria may be involved. For example, in Alzheimer’s disease, mouth bacteria called Porphyromonas gingiva were involved in the state.