A recent study demonstrates that menthol inhalation enhances cognitive function in animal models of Alzheimer’s. Researchers discovered that inhaling menthol reduced interleukin-1-beta levels, a protein that induces inflammation. The findings imply that some inhaled substances may help treat Alzheimer’s.
Repetitive brief exposure to methanol can affect the immune system and stave off the cognitive deterioration that occurs in people with Alzheimer’s disease, according to a recent mouse study published in Frontiers in Immunology.
Researchers discovered that when mice sniffed this chemical, their levels of interleukin-1-beta reduced. This protein has a role in the inflammatory response.
Additionally, researchers improved cognitive function in the mice with Alzheimer’s-like symptoms by inhibiting this protein with a medication used to treat autoimmune diseases.
These results highlight the potential for scents and immune modulators to treat this neurodegenerative condition.
The discovery is intriguing because it demonstrates how we might influence the brain’s olfactory (smell) pathways. Furthermore, there is no need for the implanting deep brain stimulator electrode or a vagal nerve stimulator system. The research shows that by administering a disease-modifying medication through the nose, the mouse Alzheimer’s brain can be “accessed” and favorably impacted at the cellular level.
Why inhaling menthol might be beneficial
According to the study, immune cells called regulatory T cells (T-regs), which have immunosuppressive activity, play a crucial role in modulating cognitive performance in mice designed to acquire Alzheimer’s. Intriguingly, the effectiveness of menthol inhalation and T-reg blocking in reducing cognitive impairment was equal.
The specifics of their signaling could shed light on the underlying mechanisms since the researchers conclude that T-reg blocking and olfaction appear to be mediated by the same cytokines. It is well known that T-regs release the cytokine IL-17 in proinflammatory circumstances, which starts with the onset of cognitive and synaptic impairments in the early stages of Alzheimer’s. Interestingly, the researcher did not investigate IL-17 as a possible mechanistic relationship in the study.
The connection of the brain, smell, & immune system
Complex connections between different types of nerve cells, immune cells, and neural stem cells are essential for maintaining the brain’s functional equilibrium. Numerous research have examined the odors’ immunomodulatory and neurological effects in this intricate web of interactions. Previous studies have also demonstrated a connection between the loss of scent and the onset of Alzheimer’s initial symptoms.
Menthol reduces inflammation in the region of the brain linked with memory. It appears to have immunomodulatory effects in the prefrontal cortex, a memory-related area that malfunctions in Alzheimer’s patients.
Researchers also found that limiting the activity of T regulatory cells (a type of immune cell with immunosuppressive activity) also improved the cognitive capacity of mice with Alzheimer’s and even generated a clear benefit in the cognitive ability of young, healthy mice.
Both Treg cell blockage and menthol exposure resulted in a drop in IL-1, a protein that may be responsible for cognitive deterioration in mice. Furthermore, blocking this protein with a medicine used to treat some inflammatory diseases increased the cognitive capacity of both healthy and Alzheimer’s mice.
More specifically, menthol inhalation reduced the cytokine (inflammatory chemicals) quantity in this region in the mice Alzheimer’s model compared to the control group. The outcome was less brain inflammation. This result can be due to at least one of the ways through which the mice exposed to menthol displayed enhanced cognitive function.
The study demonstrates that inflammation is the driving force behind Alzheimer’s, and if medicines get developed to address this pathogenic component, Alzheimer’s progression may be postponed.
Are the conclusions applicable to humans?
We cannot predict how a human might be affected because this study only involved mice. Often, such research doesn’t correspond to a human. It is due to various genetic, anatomical, metabolic, and physiologic differences among the species.
Another drawback of the study is the lack of characterization of immune cells involved in the process alongside T-regs.
This area requires further research to help us understand how it might work in humans.
A Significant Advancement
One of the authors claims that this study is a significant advancement toward understanding the relationship between smell, the immune system, and the central nervous system. The findings suggest that odors and immune modulators may be crucial in preventing and treating Alzheimer’s and other central nervous system disorders.
References
- Casares, N., Alfaro, M., Cuadrado-Tejedor, M., Lasarte-Cia, A., Navarro, F., Vivas, I., Espelosin, M., Cartas-Cejudo, P., Fernández-Irigoyen, J., Santamaría, E. and García-Osta, A., 2023. 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. Frontiers in Immunology, 14, p.2143.
- Inhaling menthol improves cognitive function in Alzheimer’s disease. Cima Universidad de Navarra. https://cima.cun.es/en/news/news/cima-menthol-improves-cognitive-function-alzheimer. Published Online: 10th May, 2023. Accessed: 1st June, 2023.
- Could inhaling menthol help improve memory in Alzheimer’s disease? Medical News Today. https://www.medicalnewstoday.com/articles/could-inhaling-menthol-help-improve-memory-in-alzheimers-disease. Published Online: 19th May, 2023. Accessed: 1st June, 2023.
