If you hurt the inside of your nose, bacteria can easily get into your blood and go directly to your brain.
Scientists investigated what happens when the usually harmless bacterium Chlamydia pneumoniae, which causes sinus problems, comes into contact with the nerve that connects the nose to the brain.
The mouse study revealed bacteria in the brain within 72 hours. Within a month, the mice developed clumps of a protein plaque associated with Alzheimer’s.
“We are the first,” adds lead author Professor James St. John, “to show that Chlamydia pneumoniae can travel directly up the nose and into the brain, where it can trigger pathologies that resemble Alzheimer’s disease.”
They add that this happened “in a mouse model, and the evidence is also potentially frightening for humans.”
Alzheimer’s disease affects more than 6 million people in the United States, with people over the age of 75 accounting for 73% of all Alzheimer’s patients.
Obesity, poor diet, isolation and lack of sleep are some of the lifestyle variables linked to Alzheimer’s disease, although the exact causes are unknown.
The Griffith University team placed Chlamydia pneumoniae in the olfactory canals of rodents.
This is the fastest route for an external intruder to reach the brain and the nose, since they are connected through the nasal passages.
Other harmful bacteria, including the deadly brain-eating amoeba, can also enter the body through this pathway and kill the host.
The studies were based on mice, as their olfactory systems are functionally and structurally similar to those of humans.
When a person becomes infected with Chlamydia pneumoniae, it often results in pneumonia, sore throats, ear infections, sinusitis, and other sinus-related conditions.
It can be passed from host to host through the air and spread via respiratory droplets.
The hairs and mucus in the nose act as a natural barrier, but the body also has certain built-in defenses against bacteria that enter the brain.
When someone picks their nose, they throw off some of their body’s natural defenses.
Study co-author and director of the university’s Center for Neurobiology and Stem Cell Research, Professor St. John, says:
“Picking your nose and pulling out your nose hairs is not a good idea.
“We don’t want to damage the inside of our nose and picking and plucking can do that.
“If you damage the lining of your nose, it can increase the amount of bacteria that can get into your brain.”
The results of the investigation were reported in Scientific Reports.
In the study, mice whose olfactory nerves were implanted with bacteria had infections in their brains within three days.
This means that the bacteria were able to pass through the “blood-brain barrier,” which is the last line of defense for the central nervous system’s immune system.
The infected mice also suffered damage to nerve pathways in their brains, which could affect their ability to think, as well as the first signs of Alzheimer’s within 28 days.
The same type of amyloid beta plaques were also found in the brains of mice.
The toxins in the brain are thought to be caused by the bacteria.
The development of this plaque is related to Alzheimer’s.
The clusters make it difficult for neurons and other parts of the cell to communicate with each other and do their jobs.
Scientists around the world have not been able to prove that these plaques are the main cause of the disease.
Over the summer, a critical 2006 University of Minnesota study linking plaques to Alzheimer’s was also retracted after the results were shown to be skewed.
However, the Griffith University team is optimistic that they have discovered a likely source for the genesis of the mysterious condition.
They may also have discovered that the nose’s natural defense systems are more important to the brain than previously thought.
According to Professor St John, his team “need to do this study in humans and confirm if the same pathway works in the same way.
“It is an investigation that has been proposed by many people, but has not yet been completed. What we do know is that these same bacteria are present in humans, but we haven’t figured out how they get there.”
The number of Americans with Alzheimer’s is expected to double by 2050, from 6 million to 13 million, according to the Alzheimer’s Association.
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