Expression of interleukin-6 in cystic lesions of patients with acne vulgaris and in vitro effect of Propionibacterium acnes on the production of interleukin-6 by human THP-1 monocytes / 中华皮肤科杂志

ABSTRACT

Objective To determine the expression 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 expression 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 μμtg/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 expression 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 expression 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 groups2 × 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 expression of IL-6 in the above 3 groups was measured by real-time fluorescencebased quantitative PCR.Results The mRNA expression 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 expression 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 expression 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 expression of phosphorylated p38MAPK obviously increased.The mRNA expression 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 expression 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.