Conclusion : Acute stress can be detrimental to the fight against infection, especially COVID-19, and increases the risk of death in mouse models.
This study is the first to show how specific regions of the brain control the body’s cellular immune response when acutely stressed and infected with COVID-19 or influenza. Specifically, he demonstrated that acute stress triggers neurons in the region known as the paraventricular hypothalamus to instantly trigger a large-scale migration of white blood cells (immune cells or leukocytes) from the lymph nodes to the blood and bone marrow. This decreases the immune response to viruses such as COVID-19 and influenza, making the body less resistant to fighting infection and putting it at increased risk of complications and death.
Why it matters: This fundamental discovery linking the brain to the immune system provides insight into how stress affects the body’s response to a virus and why some may be more susceptible to serious illnesses and worse outcomes.
How the research was conducted/results: First, the researchers examined groups of relaxed and stressed mouse models and analyzed their immune systems. Within minutes, the acutely stressed mice showed great changes in their immune systems compared to the group of relaxed mice. Specifically, stress induced a major migration of the body’s immune cells from one location to another. The investigators wanted to explain this phenomenon. Using sophisticated tools such as optogenetics and chemogenetics, researchers discovered that neurons in the paraventricular hypothalamus stimulate immune cells to migrate from the lymph nodes to the blood and bone marrow.
Next, the researchers went further to analyze how mice in the relaxed and stressed models compared when infected with influenza and COVID-19. They noticed that the mice in the relaxed group fared better than those in the stressed group; they fought the infection better and got rid of the virus more easily. The mice in the stressed group were sicker, had less immunity, and had a higher death rate from the virus. The researchers also explored how other regions of the brain related to motor function control different types of immune cells traveling from the bone marrow to the blood.
conclusion: Distinct brain regions shape the distribution and function of leukocytes throughout the body during acute stress in mice. The effect of stress on white blood cells and its negative impact on fighting a virus is important to better understand the results and find ways to improve immunity. If white blood cells continually enter the bloodstream, this could also have implications for cardiovascular health.
What this means for clinicians/patients: This study is an important example of how the brain controls inflammation and how it relates to a diminished immune response during acute stress. This work may prompt doctors to take a closer look at patients’ mental status, including sleep patterns and stress levels. This may prompt interventions not only to adopt a healthier, less stressful lifestyle, but also to help the body fight infections better and improve outcomes.
“This work tells us that stress has a major impact on our immune system and its ability to fight infection. It raises many questions about how socio-economic factors, lifestyle and the environments in which we live control how our body can defend itself against infection,” says Dr. Swirski. “In the future, we need to better understand the long-term effects of stress. It will be particularly important to explore how we can build resilience to stress and whether resilience can decrease the negative effects of stress on our immune system.
Mount Sinai Health System
Poller, WC, et al. (2022) Brain and fear motor circuits regulate leukocytes during acute stress. Nature. doi.org/10.1038/s41586-022-04890-z.