Abstract: Yang Haiping*, Du Leilei, Zeng Rong, Duan Zhimin, Shen Yongnian, Hu Suquan, Liu Weida, Chen Qing, Li Min. *454th Hospital of PLA, Nanjing 210002, China Corresponding authors: Li Min, Email: drlimin@sina.cn; Chen Qing, Email: qngchen@hotmail.com 【Abstract】 Objective To investigate the effect of Candida albicans on the production of interleukin-6 by and activation of IκBα in an acute monocytic leukemia cell line THP-1. Methods THP-1 cells were classified into three groups to be stimulated by heat-killed C. albicans cells in concentrations of 105 and 106 colony-forming units （CFU）/ml and lipopolysaccharide （100 μg/L） in vitro respectively. Those remaining untreated served as the blank control group. After additional culture for different durations, real time reverse transcription PCR and enzyme-linked immunosorbent assay were performed to measure the mRNA and protein expression levels of interleukin-6 （IL-6） respectively, and Western blot was conducted to determine the levels of total and phosphorylated IκBα. Statistical analysis was carried out by t test. Results A significant increase was observed in the mRNA expression level （2-ΔΔCt） of IL-6 in THP-1 cells at 3 and 6 hours after starting treatment with C. albicans at 105 CFU/ml （6.48 ± 0.30 vs. 0.84 ± 0.16, 125.34 ± 1.47 vs. 1.22 ± 0.22, both P < 0.01）, and at 1, 3 and 6 hours after starting treatment with C. albicans at 106 CFU/ml （2.96 ± 0.35 vs. 1.03 ± 0.16, 8.57 ± 1.27 vs. 0.84 ± 0.16, 588.10 ± 2.31 vs. 1.22 ± 0.22, P < 0.05 or 0.01） compared with the blank control group, but no significant difference was noted between THP-1 cells at 1 hour after starting treatment with C. albicans at 105 CFU/ml and those remaining untreated （1.48 ± 0.06 vs. 1.03 ± 0.16, P > 0.05）. The protein expression level of IL-6 was （924.9 ± 30.13） ng/L in THP-1 cells at 24 hours after starting treatment with C. albicans at 106 CFU /ml, significantly different from that in the blank control group （P < 0.001）. There was a marked elevation in the level of phosphorylated IκBα protein, but an obvious reduction in the level of IκBα protein in THP-1 cells treated with C. albicans at 106 CFU/ml for 30 and 60 minutes. Conclusion Human THP-1 monocytes may play a role in innate immune responses against C. albicans through activation of nuclear factor-κB and production of IL-6.

Key words: Candida albicans, Leukemia, monocytic, acute, Interleukin-6, I-kappa B proteins, NF-kappa B