Alzheimer’s disease is the most common form of dementia, and it is thought that both environment and genetics play a part in its development. Research suggests that pathogens may also contribute to the development of Alzheimer’s, but the pathways by which they enter the brain have, until recently, been unclear.
Now, a study from Australia has found that one bacterium, Chlamydia pneumoniae, enters the brain via the olfactory nerve from the nose leading to the development of amyloid beta plaques which are characteristic of Alzheimer’s.
The authors suggest that nose-picking damages the nasal mucosa, making it easier for the bacteria to reach the olfactory nerve and enter the brain.
Nose-picking is a habit that is generally seen as unpleasant, but harmless. However, research from Griffith University in Queensland, Australia, suggests that the activity might not be as risk-free as previously thought.
The research, published in Nature Scientific ReportsTrusted Source, shows that by damaging the nasal cavity in mice, bacteria can enter the brain through the olfactory nerve.
Once in the brain, certain bacteria stimulate the deposition of amyloid beta protein, potentially leading to the development of Alzheimer’s disease(AD).
Amyloid beta forms plaques that are thought to be responsible for many of the symptoms of AD, such as memory loss, language problems, and unpredictable behavior.
Currently, AD affects almost 6 million people in the United States, with the numbers set to reach 14 millionTrusted Source by 2060.
The olfactory nerve leads directly from the nasal cavity to the brain. Bacteria that enter the olfactory nerve can, therefore, bypass the blood-brain barrierTrusted Source that usually stops them from reaching the brain.
The study, carried out in mice, showed that Chlamydia pneumoniae, a bacterium that causes respiratory tract infections Trusted Source, such as pneumonia, used this route to gain access to the central nervous system.
Cells in the brain responded to the invasion by C. pneumoniae by depositing amyloid beta protein. Amyloid beta protein builds up into plaques which are a hallmark of Alzheimer’s disease.
Prof. James St John, head of the Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith University, Brisbane, was a supervising author of the study.