Scientists have made an interesting discovery: when mice with Alzheimer's disease breathe in menthol, their memory and thinking seem to get better.
Menthol, which is found in things like mint, appears to help protect the brain from some of the damage Alzheimer's causes. In particular, researchers noticed that it reduces a protein called IL-1β. This protein normally helps the body fight off threats, but when it gets out of control, it can actually harm the brain. Menthol seems to bring this protein back to safe levels.
The team behind this study, which was published in April 2023, believes that specific smells, like menthol, could one day be used as treatments for Alzheimer's. They think that certain smells may trigger helpful responses in the brain and immune system, improving overall health.
"We’ve been looking at how the sense of smell interacts with both the immune system and the brain, and it turns out menthol can stimulate the immune system in mice," said Juan José Lasarte, one of the researchers. "The really surprising part is that just short-term exposure to menthol over six months prevented memory loss in the Alzheimer's mice, and it even improved memory in healthy, younger mice."
The study showed that when the Alzheimer's mice were exposed to menthol for six months, it stopped their memory from getting worse. The menthol also lowered the IL-1β protein back to normal levels.
The scientists also experimented with lowering the number of T regulatory cells, which normally help keep the immune system in check. This had a similar effect to menthol, suggesting a potential new avenue for treatments.
"Both exposing the mice to menthol and reducing the T regulatory cells lowered the amount of IL-1β, which might be responsible for the memory problems in these Alzheimer's models," said neuroscientist Ana Garcia-Osta.
Interestingly, they also found that using a drug to block IL-1β improved memory not only in Alzheimer's mice but also in healthy ones.
It's already known that our sense of smell is closely tied to our brain and immune system, but the way these systems interact is still not fully understood. Certain smells can cause changes in the brain that affect memory and emotions.
It's worth noting that diseases like Alzheimer's, Parkinson's, and schizophrenia often involve a loss of smell. While this study shows promise, more research is needed, particularly in humans.
"This is a key step toward understanding how the immune system, brain, and sense of smell are all connected," said immunologist Noelia Casares. "The results suggest that smells and immune system regulators could play an important role in preventing and treating Alzheimer's and other brain-related diseases."
The study was published in Frontiers in Immunology.