While researchers and clinicians have long known about an association between two prevalent chronic inflammatory diseases, periodontal disease and rheumatoid arthritis, the microbiological mechanisms remain unclear.
Now researcher Jan Potempa, PhD, DSc, from the University of Louisville School of Dentistry Oral Health and Systemic Diseases Group, and an international team of scientists from the European Union's Gums and Joints project have uncovered how the bacterium responsible for periodontal disease, Porphyromonas gingivalis, worsens rheumatoid arthritis by leading to earlier onset, faster progression, and greater severity of the disease, including increased bone and cartilage destruction (PLOS Pathogens, September 12, 2013).
The scientists found that P. gingivalis produces a unique enzyme, peptidylarginine deiminase (PAD) which then enhances collagen-induced arthritis, a form of arthritis similar to rheumatoid arthritis produced in the lab. PAD changes residues of certain proteins into citrulline, and the body recognizes citullinated proteins as intruders, leading to an immune attack. In rheumatoid arthritis patients, the subsequent result is chronic inflammation responsible for bone and cartilage destruction within the joints.
Potempa and his team studied another oral bacterium, Prevotella intermedia, for the same effect, but learned it did not produce PAD and did not affect collagen-induced arthritis.
Taken together, the results suggest that bacterial PAD may constitute the mechanistic link between P. gingivalis periodontal infection and rheumatoid arthritis, but this ground-breaking conclusion will need to be verified with further research, he said. Potempa explained that he is hopeful these findings will shed new light on the treatment and prevention of rheumatoid arthritis.
Studies indicate that compared with the general population, people with periodontal disease have an increased prevalence of rheumatoid arthritis and, periodontal disease is at least two times more prevalent in rheumatoid arthritis patients. Other research has shown that a P. gingivalis infection in the mouth will precede rheumatoid arthritis, and the bacterium is the likely culprit for onset and continuation of the autoimmune inflammatory responses that occur in the disease.
