Abstract: Zhong Shaomin, Guo Jianmei, Tao Rong, Sun Nan, Wu Yan. Department of Dermatology, Peking University First Hospital, Beijing 100034, China Corresponding author: Wu Yan, Email: adelewu@medmail.com.cn 【Abstract】 Objective To investigate the effect of fusidic acid cream on inflammatory reaction caused by skin barrier damage. Methods Eight male SKH-1 hairless mice were included in this study. The back of each of these mice were equally divided into six regions measuring 1 cm × 2 cm in size, which were then assigned into six groups: blank control group remaining untreated, barrier-impaired group, barrier-impaired and fusidic acid-treated group, barrier-impaired and vehicle-treated group, barrier-unimpaired and fusidic acid-treated group, barrier-unimpaired and vehicle-treated group. Stratum corneum was removed by adhesive tape stripping to establish an animal model of acute skin barrier damage in the corresponding skin regions of these mice, and fusidic acid cream or vehicle was topically applied to the corresponding regions once. Twelve hours later, skin surface swab samples were collected from the back of these mice followed by bacterial culture and colony counting. Mice were then sacrificed, and skin tissue specimens were resected from these mice, and subjected to real-time fluorescence-based quantitative PCR for the measurement of the mRNA expressions of myeloid differentiation factor 88 （MyD88）, interleukin-1α （IL-1α）, IL-6, epidermal antibacterial peptides S100a8 and S100a9. Statistical analysis was carried out by repeated-measures analysis of variance （ANOVA） and least significant difference （LSD） test. Results The mRNA expressions of MyD88, IL-1α, IL-6, S100a8 and S100a9 were all significantly higher in the barrier-impaired group than in the blank control group （all P < 0.05）. Specifically, the mRNA expression level of MyD88 in the barrier-impaired group was 8 times that in the blank control group （8.3 ± 3.0 vs. 0.8 ± 0.4）. Compared with the barrier-impaired group, the barrier-impaired and fusidic acid-treated group showed a significant decrease in the mRNA expressions of IL-1α （2.8 ± 0.3 vs. 20.1 ± 10.0, F = 47.11, P < 0.01）, IL-6 （1.6 ± 2.3 vs. 9.4 ± 4.0, F = 16.18, P < 0.01）, S100a8 （1.5 ± 1.4 vs. 5.0 ± 1.6, F = 59.71, P < 0.05） and S100a9 （1.2 ± 0.7 vs. 3.4 ± 1.6, F = 21.94, P < 0.05）. Conlusions Fusidic acid cream could attenuate the inflammatory reaction caused by acute skin barrier damage, which might partly explain its action mechanism in the treatment of inflammatory skin diseases.

Key words: Fusidic acid, Skin barrier, Myeloid differentiation factor 88, Interleukins