Tuesday May 16 7:05 PM ET
By Alka Agrawal
SEATTLE (Reuters Health) - Extreme stress appears to protect mice from developing a multiple sclerosis-like illness, researchers report. It appears that the increased secretion of the hormone corticosterone during stress may be responsible for the protective effect, according to Dr. Caroline Whitacre of Ohio State University in Columbus.
Whitacre presented the study findings here at the joint annual meeting of the American Association of Immunologists and the Clinical Immunology Society.
To produce a stressed-out mouse, the researchers confined the animals in a small space during a time when the mice are normally very active. The animals were stressed in this way for 5 days followed by 2 days of rest, and then were compared with normal "control" mice.
A multiple sclerosis-like illness was produced in the animals by injecting them with a protein that is found in the myelin sheath surrounding nerve cells. In multiple sclerosis (MS), the immune system attacks and destroys myelin, producing weakness, dizziness and blurry vision.
According to the study findings, if animals were stressed before they were given the protein, they did not develop the illness until 10 days after the stress was terminated. If the stress was extended to day 21 after immunization, the researchers found that this could provide long-lasting protection against disease--up to 100 days. A closer examination revealed that after stress, mice had less myelin loss and a reduction in immune system activity around nerve cells.
However, the investigators found that stressing the animals after they began to experience symptoms had no effect. "It's only effective prior to disease," Whitacre stated.
In looking at reasons for the finding, Whitacre's group found increased levels of corticosterone in stressed mice.
"It was very striking that the increase in corticosterone was only seen during the stress period," she said. In contrast, there were no elevations of the hormone in the control mice.
"Corticosterone does seem to be the hormone responsible for the suppression of disease," Whitacre concluded.
However, some evidence suggests that stress can actually promote a relapse in patients with multiple sclerosis. The authors note that the degree of stress may be the key. Mild stress enhances immune function, while chronic stress, as was the case with her group's experiments, may suppress disease.
More research is needed to determine the exact role of stress in the