An unexpected link between menthol and Alzheimer’s disease discovered in mice: ScienceAlert

A recent study reports something strange: When mice with Alzheimer’s disease inhaled menthol, their cognitive abilities improved. It appears the chemical compound may stop some of the brain damage commonly associated with the disease.

In particular, researchers noticed a reduction in the protein interleukin-1-beta (IL-1β), which helps regulate the body’s inflammatory response – a response that may offer natural protection but can be harmful when not used. is not properly controlled.

The team behind the study, published in April 2023, says it shows the potential of particular odors as therapies for Alzheimer’s disease. If we can determine which odors provoke which brain and immune system responses, we can harness them to improve health.

“We focused on the role of the olfactory system in the immune and central nervous systems and we confirmed that menthol is an immunostimulatory odor in animal models,” said immunologist Juan José Lasarte of the Center for Applied Medical Research ( CIMA) in Spain. the results have been published.

“But, surprisingly, we observed that short exposures to this substance for six months prevented cognitive decline in mice with Alzheimer’s disease and, most interestingly, also improved the cognitive ability of young healthy mouse.”

Having previously observed that inhaling menthol boosted the mice’s immune response, the team showed here that it could also improve the animals’ cognitive abilities, as observed in a series of hands-on laboratory tests.

In mice with Alzheimer’s disease, a six-month course of menthol was enough to prevent the deterioration of the mice’s cognitive abilities and memory. Additionally, it appears that menthol returned IL-1β protein to safe levels in the brain.

When researchers artificially reduced the number of regulatory T (Treg) cells – known to help control the immune system – some of the same effects were observed, paving the way for future treatments.

“Exposure to menthol and blocking Treg cells caused a decrease in IL-1β, a protein that could be behind the cognitive decline observed in these models,” said neuroscientist Ana Garcia-Osta of the CIMA.

“In addition, the specific blocking of this protein by a drug used in the treatment of certain autoimmune diseases also improved the cognitive ability of healthy mice and mice with Alzheimer’s disease.”

Scientists have already established many links between smells and our immune and nervous systems. These relationships are difficult to fully understand, but we know that our olfactory system can strongly influence the brain. Certain smells can trigger certain responses in the brain, leading to chemical reactions that affect memory, emotions, etc.

Indeed, diseases linked to the central nervous system – such as Alzheimer’s disease, Parkinson’s disease and schizophrenia – are often accompanied by a loss of smell. This new research adds promising data, but there is still much more to be done in humans and mice.

“This study is an important step towards understanding the link between the immune system, the central nervous system and the sense of smell,” said immunologist Noelia Casares from CIMA.

“The results suggest that odors and immune modulators could play an important role in the prevention and treatment of Alzheimer’s disease and other central nervous system-related diseases.”

The research was published in Frontiers in immunology.

An earlier version of this article was published in May 2023.