白念珠菌对人急性单核细胞白血病细胞系产生肿瘤坏死因子α、活化信号分子p38MAPK 的影响

Effects of Candida albicans on the expression of tumor necrosis factor-α and activation of the intracellular signaling molecule p38MAPK in a human acute monocytic leukemia cell line THP-1

目的：探讨白念珠菌对人急性单核细胞白血病细胞系（THP-1细胞系）分泌肿瘤坏死因子α（TNF-α）和细胞内信号分子 p38丝裂原活化蛋白激酶（MAPK）激活的影响。方法实时荧光定量 PCR 分析105、106 CFU/ml 灭活白念珠菌及阳性刺激物脂多糖刺激 THP-1细胞1、3、6 h 后 TNF-α mRNA 表达水平变化。40μg/L 地塞米松预先与 THP-1细胞共培养30 min 后，再用106 CFU/ml 白念珠菌、脂多糖刺激6 h 后检测TNF-α mRNA 表达水平。酶联免疫吸附法检测白念珠菌刺激 THP-1细胞24 h 后 TNF-α分泌量。免疫印迹法分析白念珠菌体外作用 THP-1细胞30 min、1 h 后 p38MAPK 和磷酸化 p38MAPK 的水平。结果105 CFU/ml 白念珠菌、106 CFU/ml 白念珠菌、脂多糖刺激 THP-1细胞组以及空白对照组 TNF-α mRNA 表达水平差异有统计学意义（F =110.98，P 〈0.001）；白念珠菌刺激1、3、6 h 之间差异也有统计学意义（F =701.680，P 〈0.001），随培养时间延长，THP-1细胞 TNF-α mRNA 水平增高，呈时间依赖效应。106 CFU/ml 白念珠菌刺激 THP-1细胞后24 h，TNF-α蛋白水平（6385.70±533.99 ng/L）较空白对照组（147.10±0.53 ng/L）明显升高，差异有统计学意义（P 〈0.01）。106 CFU/ml 白念珠菌作用于 THP-1细胞30、60 min 后磷酸化 p38MAPK 蛋白水平也明显升高。40μg/L地塞米松预先与 THP-1细胞共培养30 min 后，再以106 CFU/ml 白念珠菌刺激6 h 后 TNF-α mRNA 表达水平（3.77±0.62）较未用地塞米松组（208.50±10.50）明显降低，地塞米松可阻断白念珠菌上调 TNF-α mRNA 水平。结论人 THP-1细胞体外与白念珠菌作用后激活信号分子 p38MAPK 并分泌 TNF-α，参与抗念珠菌感染固有免疫反应。

Objective To investigate the effects of Candida albicans on the expression of tumor necrosis factor-α（TNF-α）and activation of the intracellular signaling molecule p38 mitogen-activated protein kinase（p38MAPK）in a human acute monocytic leukemia cell line THP-1. Methods Some THP-1 cells were divided into several groups in vitro： two C. albicans groups treated with 105 CFU/ml and 106 CFU/ml heat-killed C. albicans respectively, a lipopolysaccharide （LPS）group treated with 100 μg/L LPS, a blank control group treated with RPMI 1640 medium, two dexamethasone-inhibited groups pretreated with 40 μg/L dexamethasone for 30 minutes followed by treatment with 106 CFU/ml heat-killed C. albicans and LPS respectively. After treatment for 1, 3 and 6 hours, real-time fluorescence-based quantitative PCR was performed to measure TNF-α mRNA expression in THP-1 cells in the above groups. Enzyme-linked immunosorbent assay（ELISA）was conducted to determine the level of TNF-α protein in the supernatant of THP-1 cells treated with 106 CFU/ml heat-killed C. albicans, 100 μg/L LPS or RPMI 1640 medium（blank control group）for 24 hours. Western blot was performed to measure the protein expression of p38MAPK and phosphorylated p38MAPK in THP-1 cells after treatment with 106 CFU/ml heat-killed C. albicans or RPMI 1640 medium （blank control group）for 30nbsp;and 60 minutes. Statistical analysis was carried out by using two-way analysis of variance, one-way analysis of variance and the least significant difference（LSD）-t test. Results Significant differences were observed in the mRNA expression level of TNF-α among the C. albicans groups, LPS group and blank control group （F = 110.98, P 〈 0.001）. The mRNA expression level of TNF-α in THP-1 cells increased over time in a time-dependent manner after C. albicans treatment, with significant differences among different time points （F = 701.680, P 〈 0.001）. Compared with the blank control group, both 106-CFU/ml C. albicans group and LPS group showed a significant increase in TNF-α protein expression （6385.70 ± 533.99 ng/L and 3212.06 ± 353.00 ng/L vs. 147.10 ± 0.53 ng/L, P 〈 0.001 and 0.005, respectively）. An obvious increase was observed in the expression level of phosphorylated p38MAPK protein, but no significant changes were noted in that of p38MAPK protein, in THP-1 cells treated with 106 CFU/ml C. albicans for 30 and 60 minutes compared with the blank control group. The mRNA expression level of TNF-α significantly decreased in dexamethasone-pretreated 106-CFU/ml C. albicans group and LPS group compared with those without dexamethasone pretreatment（3.77 ± 0.62 vs. 208.50 ± 10.50, 6.20 ± 1.93 vs. 161.35 ± 1.65, both P 〈 0.001）. Conclusions Heat-killed C. albicans can induce the activation of p38MAPK in and secretion of TNF-α by human THP-1 cells, which then participate in the innate immune response against C. albicans.