Abstract: Xu Changchun, Du Leilei, Zeng Rong, Tong Jianbo, Liu Yuzhen, Duan Zhimin, Chen Xu, Xu Haoxiang, Gong Chunyan, Li Min Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Nanjing 210042, China Corresponding authors: Li Min, Email: drlimin@sina.cn; Gong Chunyan, Email: 13057687408@163.com 【Abstract】 Objective To determine the of interleukin-6（IL-6） in cystic lesions of patients with acne vulgaris, and to evaluate the in vitro effect of Propionibacterium acnes （P. acnes） on the production of IL-6 and activation of p38 mitogen-activated protein kinase （p38MAPK） in the human acute monocytic leukemia cell line THP-1. Methods Real-time fluorescence-based quantitative PCR was performed to determine the mRNA of IL-6 in cystic lesions of 6 patients with acne vulgaris, as well as in skin tissues of 6 healthy persons. Some cultured THP-1 cells were divided into 5 groups to be treated with 2 × 106 CFU/ml, 2 × 107 CFU/ml and 2 × 108 CFU/ml heat-killed P. acnes suspensions （P. acnes groups）, 100 μg/L lipopolysaccharide （LPS group） and RPMI 1640 medium （control group） respectively. After 1-, 3- and 6-hour treatment, real-time fluorescence-based quantitative PCR was conducted to determine the mRNA of IL-6 in the above groups. Enzyme-linked immunosorbent assay （ELISA） was performed to detect the level of IL-6 in the culture supernatant of cells in the 2 × 108-CFU/ml P. acnes group, LPS group and control group at 24 hours after the treatment. Western blot analysis was conducted to determine the protein of p38MAPK and phosphorylated p38MAPK in the 2 × 108-CFU/ml P. acnes group after 15-, 30- and 60-minute treatment, as well as in the LPS group after 30-minute treatment and in the control group. Some other THP-1 cells were divided into 3 groups: 2 × 108-CFU/ml P. acnes group treated with 2 × 108 CFU/ml P. acnes suspensions, SB203580 （an inhibitor of p38MAPK） group treated with 20 μmol/L SB203580 for 30 minutes followed by the treatment with 2 × 108 CFU/ml P. acnes suspensions, and control group treated with RPMI 1640 medium alone. After 6-hour treatment, the mRNA of IL-6 in the above 3 groups was measured by real-time fluorescence-based quantitative PCR. Results The mRNA of IL-6 was significantly higher in the cystic lesions of acne vulgaris than in the normal skin tissues （3.680 ± 0.790 vs. 1.155 ± 0.250, t = 3.047, P < 0.05）. Two-way analysis of variance showed that there were significant difference in the mRNA of IL-6 among the 2 × 106-CFU/ml, 2 × 107-CFU/ml and 2 × 108-CFU/ml P. acnes groups, LPS group and control group （F = 532.3, P < 0.001, v = 4）, and the mRNA of IL-6 significantly differed among different time points （F = 526.6, P < 0.001, v = 2）. There were also significant differences in the IL-6 level in the culture supernatant of cells among the 2 × 108-CFU/ml P. acnes group （［1 618.22 ± 32.23］ ng/L）, LPS group （［3 212.06 ± 353.00］ ng/L） and control group （［147.10 ± 0.53］ ng/L; v = 2, F = 102.35, P < 0.01）. After 15-, 30- and 60-minute treatment with 2 × 108 CFU/ml P. acnes suspensions, the protein of phosphorylated p38MAPK obviously increased. The mRNA of IL-6 in THP-1 cells was significantly lower in the SB203580 group than in the 2 × 108-CFU/ml P. acnes group （t = 15.91, P = 0.004）. Conclusions The mRNA of IL-6 evidently increases in the cystic lesions of patients with acne vulgaris. P. acnes can activate the signaling molecule p38MAPK in THP-1 cells, and promote the production of IL-6 by THP-1 cells.

Key words: Acne vulgaris, Propionibacterium acnes, Interleukin-6, Leukemia, monocytic, acute, p38 Mitogen-activated protein kinases