Effect of high population density environment on skin barrier function in mice
Introduction
To elucidate the influences of stress events on physiological conditions and homeostasis, various forms of stress such as footshock, forced swimming, immobilization and overcrowding stress have been examined. Previously immunological and psychoneuroimmunological studies revealed the influence of stress on delayed type hypersensitivity [1], antigen-specific cell-mediated immunity [2] and levels of cytokines [3], [4], [5]. On the other hand, the association of stressful stimuli with skin diseases such as psoriasis and atopic dermatitis has long been recognized [6], [7], [8], [9]. Furthermore, recent cutaneous biological reports have demonstrated that immobilization stress and/or overcrowding stress induced a decrease in lipogenesis in sebaceous glands [10] and a delay of skin barrier recovery [11]. These suggest that stressful events could influence cutaneous functions. Barrier function and water retention property are important cutaneous functions to maintain homeostasis. However, the relationship between stressful stimuli and these functions is unclear. Here, we have attempted to clarify the relationship between these functions and high population density environment which is a technique used extensively in the field of neurophysiology, neuropathology and neuropharmacology as a good model for psychosocial mental stress [12], [13], [14].
Section snippets
Animals and stress paradigm
BALB/c male mice (6 week old) were obtained from Nihon SLC (Shizuoka, Japan) and examinations performed after housing for 6 days. Mice were assigned to two groups. One group was maintained under high population density environment (40 mice/cage, cage size: 182×260×128 mm3) for 7 days, while the control group was maintained under five mice/cage condition. Diet and water were provided ad libitum and the consumption was measured through stress paradigm period. Mice were denuded with electric
Weight change
Body weight in the control group and the stress group increased until initiating stress process. For 3 days after starting stress, body weight in the stress group decreased dramatically, and continued decreasing until finishing stress, indicating significant differences (P<0.001) to the control group. Body weight in the stress group recovered gradually after stress; however, there was a significant difference (P<0.001) between both groups through experiment period (Fig. 2). While body weight in
Discussion
It has been demonstrated that stressful events influence on physiological conditions and homeostasis. In addition, the relationship between mental stress, and medical and psychiatric disorders are still to be addressed. On the other hand, skin is always exposed to chemical stress such as ultraviolet and environmental pollutant developing inflammation and pigmentation [21], and regulated by hormone levels reflecting emotional condition [22]. Clinically, the association of stressful stimuli with
Acknowledgements
The authors are grateful to Dr H. Matsuda for giving us good suggestions for this study.
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