Effect of high population density environment on skin barrier function in mice

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Abstract

Previous reports have demonstrated that stressful stimuli markedly influenced physiological conditions and homeostasis. In this study, we examined the influence of high population density environment on barrier function and water retention property of skin in mice. Overcrowding stress induced dramatic body weight reduction and significant increase in adrenal gland weight. Macroscopic skin appearance showed moderate exfoliation and slight wrinkle formation in the stress group. Moreover epidermis hyperplasia not concomitant with inflammatory reactions such as infiltration of immunocytes and vasodilation was observed in the skin from the stress group. Skin surface conductance in the stress group was significantly lower than in the control group. On the other hand, transepidermal water loss in the stress group increased significantly, compared to the control group. Moreover, transdermal penetration of indomethacin and nicotinic acid amide was enhanced significantly. These results suggest that overcrowding stress induced impairment of barrier function and water retention property. To elucidate the mechanism of overcrowding stress-induce dry skin, contents of ceramide and pyrrolidone carboxylic acid, which are the important compounds contributing to those functions were evaluated. Both of them in stratum corneum declined significantly in the stress group. Taken together, these results demonstrate that overcrowding stress induced dry skin, and that the impairment of barrier function and water retention property correlated with decrease in ceramide and pyrrolidone carboxylic acid.

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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