Menthol is an organic compound naturally derived from peppermint and other variants of mint plants. Its introduction to tobacco in the 1920s and 1930s helped mitigate the roughness of cigarette smoke and the discomfort caused by nicotine.
A recently published study revealed that as mint-flavored vapes produce more toxic microparticles, they could damage the lungs more than any other flavor.
In April 2021, the United States Food and Drug Administration announced its intentions to prohibit menthol cigarettes. By February 2022, no fewer than 145 communities within the US had already put restrictions on the sale of menthol cigarettes and other flavored tobacco products.
Now, a new study, published in Frontiers in Immunology, found something strange: when Alzheimer’s mice were exposed to menthol, they display enhanced cognitive capabilities. The data suggest that the compound could halt some of the harm typically linked to Alzheimer’s in the brain.
The study, spearheaded by researchers at the Cima University of Navarra in Spain, showed that menthol inhalation in animal models of Alzheimer’s disease could enhance cognitive performance. Their observations demonstrated that intermittent short exposures to menthol have the potential to regulate the immune response and deter the cognitive decline that characterizes this form of neurodegenerative disease.
On probing the mechanism at play, the team noticed that the smell of menthol reduced the concentration of interleukin-1-beta (IL-1b), a protein pivotal to the inflammatory response. Intriguingly, using a drug designed to inhibit this protein, which is currently approved for treating certain autoimmune conditions, also led to improved cognitive function in the afflicted mice.
This research underscores the potential role of odors and immune modulators as medicinal agents. Furthermore, it paves the way for innovative therapies, including those that involve stimulating and exercising the olfactory system, to mitigate or prevent the impacts of Alzheimer’s and other central nervous system disorders.
The results of this study were published in the recent edition of Frontiers in Immunology.
The brain’s functional equilibrium relies on intricate interactions among various nerve cells, immune cells, and neural stem cells. Within this complex network, several investigations have focused on the impact of odorants on immunological and neurological processes. Previous studies have also shown a link between diminished olfactory senses and the onset of Alzheimer’s disease symptoms.
Principal author Dr. Juan José Lasarte says that they “have focused on the olfactory system’s role in the immune and central nervous systems, and we have confirmed that menthol is an immunostimulatory odor in animal models.
But, surprisingly, they found “that short exposures to this substance for six months prevented cognitive decline in the mice with Alzheimer’s and, what is most interesting, also improved the cognitive ability of healthy young mice.”
A noteworthy finding observed by the research team is that when the action of T regulatory cells—immunosuppressive immune cells—was inhibited, there was an improvement in the cognitive abilities of mice suffering from Alzheimer’s disease. Moreover, it led to noticeable benefits in the cognitive abilities of healthy young mice, according to co-author Dr. Ana García-Osta.
Both the exposure to menthol and the inhibition of Treg cells resulted in a reduction in IL-1b levels, a protein potentially responsible for the cognitive decline observed in these models. Remarkably, when this protein was specifically blocked with a medication used for certain autoimmune diseases, they noticed an enhancement in the cognitive capacities of both healthy and Alzheimer’s-afflicted mice.
This research marks a significant stride toward understanding the link between the immune system, the central nervous system, and the sense of smell. The findings indicate that odors and immune modulators could play a crucial role in the prevention and treatment of Alzheimer’s and other central nervous system-related disorders.
Image Credit: Getty