Research Article
Keiichi Hiramoto, Eisuke F
Abstract
Atopic dermatitis (AD) is known to be effected by mild or strong stress. However, the mechanism underlying this phenomenon is unclear. This study analyzed the mechanism(s) responsible for the influence of different levels of stress on AD. Specific pathogen-free (SPF) and conventional NC/Nga mice were used for the studies. Conventional mice, but not SPF mice, spontaneously develop dermal symptoms similar to that of patients with AD. Two types of stress, mild (20 m/min for 60 min) or strong (25 m/min for 90 min) exercise were applied using a treadmill four times per day. The symptoms of the conventional group were strongly exacerbated by strong exercise but ameliorated by mild exercise. The plasma concentration of β-endorphin was increased by mild exercise. The transepidermal water loss of strong exercise in the conventional mice was higher than that of the no-exercise conventional mouse group. The levels of collagen IV in conventional group were unchanged by mild exercise, but decreased by strong exercise. The level of matrix metalloproteinase-9 was suppressed by mild exercise in the conventional groups, and elevated further by strong exercise. In addition, the expression of the μ-opioid receptor was increased on the mast cell surface of the conventional mice that were subjected to mild exercise. These observations suggest that exercise-induced stress significantly affects the symptoms of AD concomitant with the levels of β-endorphin. This hormone might control the collagen IV degradation from mast cells, and thus affect the barrier function of the skin.