Periodontal disease bacteria may kick-start Alzheimer's

October 4, 2018 by Jacqueline Carey, University of Illinois at Chicago
Drs. Keiko Watanabe and Vladimir Ilievski study periodontitis bacteria. (Photo: Chris Bevel. Credit: University of Illinois at Chicago

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, according to a new study from researchers at the University of Illinois at Chicago.

The findings, which are published in PLOS ONE, suggest that , a common but preventable gum infection, 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," said Dr. Keiko Watanabe, professor of periodontics at the UIC College of Dentistry and corresponding author on the study.

"This was a big surprise," Watanabe said. "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, the Watanabe and her colleagues—including Dr. Vladimir Ilievski, UIC research assistant professor and co-author on the paper—established chronic periodontitis, which is characterized by soft tissue damage and bone loss in the oral cavity, in 10 wild-type . 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 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 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 , but also that chronic infection leads to neural effects similar to Alzheimer's," Watanabe said.

The researchers say these findings are powerful in part because they used a wild-type mouse model; most model systems used to study Alzheimer's rely on transgenic mice, which have been genetically altered to more strongly express genes associated with the senile plaque and enable Alzheimer's development.

"Using a wild-type mouse model added strength to our study because these mice were not primed to develop the disease, and use of this model gives additional weight to our findings that periodontal may kick-start the development of the Alzheimer's," Watanabe said.

The researchers say that understanding causality and risk factors for the development of Alzheimer's is critical to the development of treatments, particularly when it comes to sporadic, or late-onset disease, which constitutes more than 95 percent of cases and has largely unknown causes and mechanisms.

While the findings are significant for the scientific community, Watanabe said there are lessons for everyone.

"Oral hygiene is an important predictor of disease, including diseases that happen outside the mouth," she said. "People can do so much for their personal health by taking oral health seriously."

Explore further: Researchers find potential link between gum disease and Alzheimer's

More information: Vladimir Ilievski et al. Chronic oral application of a periodontal pathogen results in brain inflammation, neurodegeneration and amyloid beta production in wild type mice, PLOS ONE (2018). DOI: 10.1371/journal.pone.0204941

Related Stories

Researchers find potential link between gum disease and Alzheimer's

October 4, 2013
(Medical Xpress)—Oral bacteria from poor dental hygiene have been linked to brain tissue degeneration, according to new evidence from an international team of researchers, including one at the University of Florida College ...

Researchers identify new potential biotherapy for Alzheimer's disease

August 29, 2018
Researchers at the University of Florida have discovered that a modified version of an important immune cell protein could be used to treat Alzheimer's disease. The study, which will be published August 29 in the Journal ...

Genes linking Alzheimer's and Down syndrome discovered

June 25, 2018
Scientists are a step closer to understanding which genes are responsible for early onset Alzheimer's disease in people with Down syndrome, thanks to a new study led by researchers at the Francis Crick Institute and UCL along ...

Good oral hygiene may help recovery after a heart attack

April 20, 2018
Good oral hygiene may help recovery after acute cardiovascular events such as heart attacks and aortic dissection, according to research presented today at Frontiers in CardioVascular Biology (FCVB) 2018, a European Society ...

Gut bacteria may play a role in Alzheimer's disease

February 10, 2017
New research from Lund University in Sweden has shown that intestinal bacteria can accelerate the development of Alzheimer's disease. According to the researchers behind the study, the results open up the door to new opportunities ...

How does alcohol influence the development of Alzheimer's disease?

June 4, 2018
Research from the University of Illinois at Chicago has found that some of the genes affected by alcohol and inflammation are also implicated in processes that clear amyloid beta—the protein that forms globs of plaques ...

Recommended for you

Researchers classify Alzheimer's patients in six subgroups

December 5, 2018
Researchers studying Alzheimer's disease have created an approach to classify patients with Alzheimer's disease, a finding that may open the door for personalized treatments.

Oral cancer prognostic signature identified

December 5, 2018
Researchers in Brazil have identified a correlation between oral cancer progression and the abundance of certain proteins present in tumor tissue and saliva. The discovery offers a parameter for predicting progression of ...

Neuroscientists pinpoint genes tied to dementia

December 3, 2018
A UCLA-led research team has identified genetic processes involved in the neurodegeneration that occurs in dementia—an important step on the path toward developing therapies that could slow or halt the course of the disease. ...

Detecting signs of neurodegeneration earlier and more accurately

November 30, 2018
Signs of neurodegenerative diseases, appearing years before the emergence of clinical manifestations, can be detected during the examination of medical samples by means of fluorescence microscopy by using new sensitive and ...

Never-before-seen DNA recombination in the brain linked to Alzheimer's disease

November 21, 2018
Scientists from Sanford Burnham Prebys Medical Discovery Institute (SBP) have identified gene recombination in neurons that produces thousands of new gene variants within Alzheimer's disease brains. The study, published today ...

New information on the pathological mechanisms of Alzheimer's disease

November 21, 2018
Researchers at the University of Helsinki have discovered a mechanism by which harmful tau protein aggregates are transmitted between neurons. Alongside amyloid plaques, tau aggregates in the brain are a significant factor ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.