Exposing the immune system to citrullinated bacterial proteins is seen as a trigger for rheumatoid arthritis (RA). The anti-citrullinated protein antibodies (ACPAs) seen in many RA patients, which serve as a diagnostic marker, may have their origin in periodontal disease, researchers said.
Traces of bacteria associated with periodontal disease have been found in samples collected from rheumatoid arthritis patients.
The research group wrote in Science Translational Medicine: “Our findings indicate that damage of the oral mucosal barrier mediated by [periodontal disease] results in repeated, spontaneous translocation of citrullinated oral bacteria to the blood, which trigger innate and adaptive immune responses in RA associated with systemic disease flares”.
Researchers conducted a series of studies in several patient cohorts. Their findings confirmed that oral bacterial components (especially from Streptococcus species) entered the circulation at higher rates in the RA patients with periodontal disease compared to those without. The researchers also determined that during RA clinical exacerbations, expression spiked for genes associated with inflammatory monocyte responses in synovial tissue, but only in the patients with periodontal disease. Tracing the connection between the two conditions could help develop therapies for rheumatoid arthritis, while the approach that led to the study could prove fruitful in other disease contexts, such as cancer.