A new study shows that inhaling menthol improves cognitive functions in animal models of Alzheimer’s disease. Researchers found that inhaling menthol decreased levels of interleukin-1-beta, a protein that causes inflammation. Decreased levels of IL-1-beta have been linked to better cognitive function in healthy mice and mice with Alzheimer’s disease.
These results suggest that certain inhalants could contribute to the treatment of Alzheimer’s disease.
According to a recent study in mouse models, published in Frontiers in Immunology, repeated brief exposure to methanol can impact the immune system and prevent the cognitive decline that occurs in people with Alzheimer’s disease. The researchers found that when the mice smelled this substance, the level of interleukin-1-beta decreased. This protein is associated with the inflammatory response. In addition, by blocking this protein with a drug used to treat autoimmune diseases, the researchers were able to boost the cognitive abilities of mice with symptoms similar to those of Alzheimer’s disease.
These results illustrate the ability of odors and immune modulators to potentially treat this neurodegenerative disease.
This study is interesting in that it sheds light on the fact that, through the olfactory pathways. It is possible to modulate the brain. We can bring positive change to the brain through smell and smell alone.
Also, it does not require the implantation of a deep brain stimulation electrode or a vagal nerve stimulation system. The study demonstrates that it is possible not only to access the brain of rodents with Alzheimer’s disease, but also to positively affect it at the cellular level, in the form of a disease-modifying treatment, by the nasal passages.
Why can menthol inhalation help?
Loss of smell has previously been linked to cognitive impairment and biomarkers of Alzheimer’s disease in patients. The study identifies the clear role of regulatory T cells (T-regs), immune cells with immunosuppressive activity, in mediating cognitive function in mice modeled to develop Alzheimer’s disease. This is an important finding, which does not yet have a mechanistic explanation. Strikingly, menthol inhalation and T-reg blockade have comparable potency in alleviating cognitive impairment.
The link between brain health and smell
Menthol reduces inflammation in the part of the brain associated with memory. Menthol appears to have an immunomodulatory effect on the prefrontal cortex, an area related to memory input that is dysfunctional in patients with Alzheimer’s disease. Specifically, menthol inhalation reduced the cytokine (inflammatory chemical) load in this region in the rodent model with Alzheimer’s disease compared to the control group. The result ? A less inflamed brain. It is assumed that this effect is at least one of the mechanisms by which the mice (with Alzheimer’s disease) in the group exposed to menthol saw their cognitive functions improve.
Implications for Alzheimer’s disease research
Inflammation and Alzheimer’s disease are closely linked, and therapies such as menthol inhalation could be beneficial in treating this disease. The study reinforces the fact that Alzheimer’s disease is underpinned by inflammation and that if therapies can be designed to address this pathogenic component, the onset of Alzheimer’s disease can be delayed and its progress thwarted. Potentially, this therapy could be administered through an inhaled agent, menthol for example, which would be directly delivered to the limbic system of the brain, responsible for our emotions and our memory, via the olfactory nerves, since it There are neural connections between the olfactory and limbic systems.
Odors as therapeutic agents
There is a direct link between the nerves and olfactory pathways and the limbic system. The limbic system is associated with memory processing, emotional responses, fight or flight responses, aggression, and sexual response. It is also important to note that the connectivity between the limbic system and the olfactory system is at the origin of the intimate association between memory and smell.
The study did not use aromatherapy, but we already know that smells often stimulate memory. They can also evoke emotions, good or bad. In the latter case, they can confer a survival advantage: a toxic smell can cause us to run away or flee out of fear of exposure to a chemical or toxin, because the escape centers are activated by the only smell.
Do these conclusions apply to humans?
As this study was only conducted on animals, it is not possible to know how a human being would be affected. This is a rodent model. Often such studies do not apply to humans. There is a whole series of genetic, anatomical, metabolic and physiological differences between species that explain this phenomenon. Also, only menthol was tested as an olfactory stimulant in the study. Further research is needed