How is gum disease linked to inflammation, heart disease, and cancer?

With gum disease or periodontitis, bacteria in plaque trigger an attack on the immune system. This triggers inflammation that over time erodes the soft tissues and bones that support the teeth.

According to the Centers for Disease Control and Prevention (CDC), nearly half of adults over 30 in the United States have periodontal disease.

Research suggests that it contributes to a variety of other conditions in which chronic inflammation plays a role. The long list includes arthritis, heart disease, diabetes, cancer, respiratory disease, and dementia.

However, the mechanism that links these conditions to periodontal disease has been unclear.

Experiments by researchers from the Faculty of Dentistry at the University of Toronto, Canada, have shown that gum disease trigger blood cells called neutrophils, which then overreact to infections elsewhere in the body.

The neutrophils, which are part of the body’s immune system, release signaling molecules called cytokines that make inflammation worse.

“It’s almost as if these white blood cells are in second gear when they should be in first gear,” says the study’s lead author, Prof. Michael Glogauer. “The [neutrophils] It is much more likely that cytokines will be released much faster, leading to negative results. ”

The results appear in the Journal of Dental Research.

When the researchers induced periodontal disease in mice, it led to proliferation of neutrophils in the animals’ bone marrow, suggesting a widespread or “systemic” immune response.

In contrast, mice with peritonitis – an infection of the peritoneum, the membrane that lines the abdomen – had increased levels of neutrophils in their blood near the site of infection.

However, mice that already had periodontitis when they developed peritonitis had significantly greater numbers of neutrophils at the site of infection.

After further investigation, the researchers found that neutrophils from animals with gum disease and peritonitis had molecular markers in their outer membranes that indicated they were “prepared” for inflammation.

However, in the mice with peritonitis but no gum disease, the neutrophils were not prepared in the same way.

To see if similar immune changes occur in people, the scientists asked healthy volunteers not to brush their teeth or floss for 3 weeks. This led to gingivitis, a mild form of gum disease.

When the scientists analyzed blood samples from the laboratory participants, they found neutrophils prepared to cause inflammation, just as in their previous animal studies.

After the volunteers brushed their teeth and flossed again, the neutrophils in their blood returned to their previous, less reactive state.

The authors conclude:

“Together, these results show that periodontal tissue inflammation has systemic effects that predispose to an increased innate immune response. This indicates that [neutrophils] can react synergistically to simultaneous and distant inflammation triggers and thus contribute to the interaction between them [periodontal disease] and other inflammatory diseases. ”

The researchers warn that their work had some limitations. In particular, they want to repeat their experiments on other models of periodontal disease, both mice and non-human primates.

In addition, it remains unclear whether inflammation from neutrophils prepared in this way contributes to poorer outcomes in inflammatory diseases such as heart disease.

According to one study, COVID-19 can be such a disease. In severe infections, an immune overreaction or “cytokine storm” can lead to vascular collapse, respiratory failure, and problems with other organs such as the kidneys.

“There is evidence that patients with periodontal disease are much more likely to have negative results with COVID-19,” says Prof. Glogauer. “Neutrophils are the cells that are at the greatest risk of causing cytokine storms. This is exactly the cell that we show in people with periodontal disease. ”

A new article in the magazine Medical hypotheses suggests that screening for periodontal disease could help identify people at high risk of developing severe COVID-19 infections.