Inhaling menthol to fight Alzheimer’s disease?

The functioning of the brain depends on complex interactions between various types of nerve cells, immune cells, and neural stem cells. In this complex web of interactions, several studies have explored the immunomodulatory and neurological effects of odorants. Other previous works have also shown the existence of a correlation between the loss of the sense of smell and the appearance of the first symptoms in Alzheimer’s disease.

Researchers at the Center for Applied Medical Research (CIMA) of the University of Navarra (UNAV) in Spain have shown in animal models of Alzheimer’s disease that inhaling menthol improves their cognitive ability. With this study, they have discovered that this substance has properties capable of modulating the immune system and that, after sustained exposure over time, it can prevent the cognitive deterioration typical of this neurodegenerative disease. When analyzing its mechanism of action, they have observed that when smelling this aroma, the levels of a key protein in mediating the inflammatory response, interleukin-1-beta (IL-1 beta), were reduced. By inhibiting this protein with a drug approved for the treatment of some autoimmune diseases, they were also able to improve cognitive ability in these diseased mice.

This research highlights the potential of odors and immune modulators as therapeutic agents and opens the door to the development of therapies based on stimulating and training the olfactory system to prevent or alleviate the effects of Alzheimer’s and other diseases of the central nervous system.

“We have focused on the role that the olfactory system may have in the immune system and in the central nervous system and we have confirmed that menthol is an immunostimulant in animal models. But, surprisingly, we observed that exposure to this substance for six months prevented cognitive decline in the mice with Alzheimer’s disease and, what is more interesting, also improved the cognitive ability of healthy young mice”, says Dr. Juan José Lasarte, researcher at the CIMA Immunology and Immunotherapy Program and co-author of the study.

From left to right, members of the CIMA research team María Alfaro, María Espelosín, Mar Cuadrado, Flor Navarro, Ana García Osta, Paz Cartas-Cejudo, Noelia Casares, Enrique Santamaría (Navarrabiomed) and Juan José Lasarte. (Photo: TOP)

Another result noted by the researchers is that “blocking one type of immune cell, regulatory T cells, or Tregs, also improved the cognitive ability of the Alzheimer’s mouse and caused a clear benefit in the cognitive ability of healthy young mice,” he explains. Dr. Ana García-Osta, researcher at CIMA’s Program for Gene Therapy of Neurological Diseases and co-author of this study. “Both menthol exposure and Treg cell blockade caused a decrease in IL-1 beta, a protein that could be behind the cognitive decline observed in these models. The specific blockade of this protein with a drug that is used in the treatment of some autoimmune diseases, also achieved a beneficial effect on the cognitive capacity of healthy mice and mice with Alzheimer’s”.

“This study is an important step toward understanding the connection between the immune system, the central nervous system, and smell, as the results suggest that odors and immune modulators may play an important role in the prevention and treatment of Alzheimer’s.” and other diseases related to the central nervous system”, points out Dr. Noelia Casares, also a researcher at the Immunology and Immunotherapy Program and co-author of the study.

The study is titled “Improvement of cognitive function in wild-type and Alzheimer’s disease mouse models by the immunomodulatory properties of menthol inhalation or by depletion of T regulatory cells”. And it has been published in the academic journal Frontiers in Immunology. (Source: TOP)