Long-term exposure to periodontal disease bacteria causes inflammation and degeneration of brain neurons in mice that is similar to the effects of Alzheimer’s disease in humans, US researchers have found.
A recent study by a team from the University of Illinois, Chicago—and published in PLOS ONE—suggests that periodontal disease may be an initiator of Alzheimer’s, which currently has no treatment or cure.
“Other studies have demonstrated a close association between periodontitis and cognitive impairment, but this is the first study to show that exposure to the periodontal bacteria results in the formation of senile plaques that accelerate the development of neuropathology found in Alzheimer’s patients,” Dr Keiko Watanabe, professor of periodontics at the UIC College of Dentistry, said.
“This was a big surprise. We did not expect that the periodontal pathogen would have this much influence on the brain, or that the effects would so thoroughly resemble Alzheimer’s disease.”
To study the impact of the bacteria on brain health, Dr Watanabe and her colleagues established chronic periodontitis in 10 wild-type mice. Another 10 mice served as the control group.
After 22 weeks of repeated oral application of the bacteria to the study group, the researchers studied the brain tissue of the mice and compared brain health.
The researchers found that the mice chronically exposed to the bacteria had significantly higher amounts of accumulated amyloid beta—a senile plaque found in the brain tissue of Alzheimer’s patients. The study group also had more brain inflammation and fewer intact neurons due to degeneration.
These findings were further supported by amyloid beta protein analysis, and RNA analysis that showed greater expression of genes associated with inflammation and degeneration in the study group.
DNA from the periodontal bacteria was also found in the brain tissue of mice in the study group, and a bacterial protein was observed inside their neurons.
“Our data not only demonstrate the movement of bacteria from the mouth to the brain, but also that chronic infection leads to neural effects similar to Alzheimer’s,” Dr Watanabe said.