Sun-induced changes in stratum corneum function are gender and dose dependent in a Chinese population

Abstract

Previous studies have demonstrated that UVB radiation changes the epidermal permeability barrier and stratum corneum (SC) hydration. It is well known that sun exposure causes erythema, sunburn and melanoma. However, whether daily sun exposure alters SC integrity and epidermal permeability barrier function is largely unknown, especially in Chinese subjects. In the present study, we assess the SC integrity, SC hydration and epidermal permeability barrier function following various doses of sun exposure. A total of 258 subjects (124 males and 134 females) aged 18-50 years were enrolled. A multifunctional skin physiology monitor (Courage & Khazaka MPA5) was used to measure SC hydration and transepidermal water loss (TEWL) on the forearms. In males, basal TEWL was higher with higher doses of sun exposure than with lower doses and control, whereas in females, basal TEWL was higher with lower doses of sun exposure than with higher doses and control. In the group with higher doses of sun exposure, TEWL in females was significantly lower than that in males. The barrier recovery was faster in females than in males in both control and lower-dose groups. In both males and females, barrier recovery was delayed with higher doses of sun exposure. In males, sun exposure did not alter SC hydration, while in females SC hydration was lower with lower doses of sun exposure as compared with control and higher doses of sun exposure. These results demonstrated that sun-induced changes in SC function and SC hydration vary with gender and the extent of sun exposure.

Fig. 1

TEWL baseline following various doses of sun exposure. Basal TEWLs were compared by one-way ANOVA, with Tukey's correction, which was used to determine significant differences. Significant differences are shown in the figure. The number of subjects in each group is detailed in table 1.

Fig. 2

Comparison of barrier recovery rates after different doses of sun exposure. The comparison of barrier recovery rates was analyzed by one-way ANOVA, with Tukey's correction. The number of subjects in each group is detailed in table 1, and significances are indicated in the figure.

Fig. 3

Changes in SC integrity with gender and the doses of sun exposure: percent increase in TEWL following D-squame applications in males (a) and females (b). The number of subjects in each group is detailed in table 1. One-way ANOVA with Tukey's correction was used to determine the significant difference, and the significances are indicated in the figure.

Fig. 4

Changes in SC hydration with gender. Comparison of SC hydration in the groups exposed to various doses of sunlight was made in males and females. One-way ANOVA with Tukey's correction was used to determine the significant differences. The number of subjects in each group is detailed in table 1. The significance is indicated in the figure. AU = Arbitrary unit.