Stressed mice unable to fight illness: Study
It's long been thought that stress is harmful to your health, but a new study finds chronic stress may increase a person's risk of developing or accelerating a neurodegenerative disease like multiple sclerosis.
Researchers have demonstrated for the first time that inflammation brought on by stress leads to the worsening of the mouse equivalent of MS.
In studies, stressed mice produced a cytokine which is released during stress. That cytokine increased the severity of an MS-like illness in the mice.
The findings were presented Friday at the annual convention of the American Psychological Association.
In the study, scientists simulated stressful situations on mice infected with Theiler's murine encephalomyelitis (TMEV), an acute infection of the central nervous system which is followed by a chronic autoimmune disease similar to that seen in humans with MS.
Another group of mice was also infected but not exposed to stress.
Researchers found that the stressed mice produced a cytokine — interleukin-6 (IL-6) — which is released during stress and regulates the part of the immune system that fights infection. IL-6 increases the severity of the MS-like illness.
Stressed mice were unable to clear the virus from their systems and had higher levels of inflammation, while the non-stressed mice had lower levels of the virus in their bloodstreams and less inflammation, researchers found.
They also discovered that injecting an antibody into the brain that neutralizes IL-6 prior to the stressful episode prevented the stress-related worsening of the disease, said the authors.
Blocking IL-6 halts disease
By blocking the elevation of IL-6, the TMEV infection was weakened, which decreased symptoms such as motor impairment, inflammation in the brain and spinal cord and the viral level in the central nervous system, researchers found.
Based on these findings, Mary Meagher, the lead researcher, theorizes that the adverse effects of stress-induced IL-6 on TMEV infection create a pro-inflammatory environment that interrupts a person's immune response to infection.
Scientists believe that the effects of stress on people who are vulnerable to certain inflammatory diseases may be prevented or reversed by treatments aimed at blocking increases in this cytokine.
Recent evidence suggests that some potential interventions include certain anti-inflammatory drugs, exercise, antidepressants, omega-3 fatty acids and relaxation training.
However, researchers say human clinical trials are needed to determine what preventive approaches will work.