Abstract: 【Abstract】 Objective To evaluate the effect of isotretinoin on expression of acne-associated inflammatory genes induced by peptidoglycan in human SZ95 sebocytes, and to explore the molecular mechanism underlying the treatment of acne with isotretinoin. Methods Cultured SZ95 sebocytes were divided into 3 groups: control group receiving no treatment, peptidoglycan group treated with 20 mg/L peptidoglycan alone, and costimulation group treated with 20 mg/L peptidoglycan combined with 10-5 mol/L isotretinoin. After 3-hour treatment, real-time fluorescence-based quantitative PCR was performed to determine the mRNA expression of pro-inflammatory cytokines including interleukin （IL）-1α, IL-1β, IL-6, IL-8, tumor necrosis factor （TNF）-α, Toll-like receptor 2 （TLR2） and MyD88 （a downstream gene of TLR2） in SZ95 sebocytes in the above groups. After 24-hour treatment, enzyme-linked immunosorbent assay （ELISA） was performed to detect levels of IL-1α, IL-1β, IL-6, IL-8 and TNF-α in the cell culture supernatant in the above groups. After 48-hour treatment, Western blot analysis was conducted to determine the protein expression of TLR2 and MyD88. Statistical analysis was carried out with SPSS 23 software by one-way analysis of variance （ANOVA） for the comparison among the 3 groups, and by Bonferroni method for multiple comparisons. Results The mRNA and protein expression of pro-inflammatory cytokines including IL-1α, IL-1β, IL-6, IL-8 and TNF-α all significantly differed among the 3 groups （all P < 0.01）, and was significantly higher in the peptidoglycan group than in the control group and costimulation group （both P < 0.016 7）. The mRNA expression of MyD88 also significantly differed among the control group, peptidoglycan group and costimulation group （6.707 ± 0.950, 10.270 ± 0.477, 7.892 ± 0.900 respectively, F = 10.17, P < 0.01）, and was significantly higher in the peptidoglycan group than in the control group and costimulation group （t = 4.740, 3.298 respectively, both P < 0.016 7）. The mRNA and protein expression of TLR2 were markedly higher in the peptidoglycan group than in the control group, but did not differ between the peptidoglycan group and the costimulation group. Conclusion Isotretinoin can inhibit peptidoglycan-induced expression of inflammatory factors possibly associated with the occurrence of acne in human SZ95 sebocytes, likely by inhibiting the expression of MyD88, but not TLR2, in the innate immune response, which may be one of the mechanisms underlying the treatment of acne with isotretinoin.

Key words: Acne vulgaris, Isotretinoin, Molecular mechanisms of pharmacological action, Peptidoglycan, Cytokines, Toll-like receptor 2;Immunity, innate, Human sebocytes