RNA干扰对活化的小鼠巨噬细胞肿瘤坏死因子α表达的影响

目的：观察靶向小鼠肿瘤坏死因子α（TNF-α）基因的小干扰RNA（siRNA）在体外对小鼠巨噬细胞系RAW264．7表达TNF-α的抑制作用。方法：采用化学法合成针对TNF-α mRNA不同位点设计的3条siRNA序列（siRNA1～3）和1条带有荧光标记的BLOCK—IT^TM荧光Oligo（修饰的荧光标记的dsRNA,siRNA4）通过脂质体包裹后将其分别转染至小鼠巨噬细胞系RAW264．7,同时设立1个无任何靶基因的siRNA作为阴性对照（siRNA4）。荧光显微镜下观察siRNA的转染效率;用实时荧光定量PCR和酶联免疫吸附实验（ELISA）法分别检测siRNA对TNF-α的mRNA和蛋白表达的抑制作用。结果：内毒素刺激后6h,巨噬细胞表达TNF-α mRNA和合成分泌的TNF-α量均增加,于9～12h达高峰。利用荧光标记的Oligo观察到siRNA转染效率达72％～80％。siRNA1～4转染巨噬细胞后,siRNA2、3可见内毒素刺激的TNF-α mRNA（0．158±0．030、0．114±0．028）和TNF-α蛋白表达（1355±348）pg／ml、（817±138）pg／m1]均明显少于未转染组TNF-α mRNA0．294±0．147,蛋白（2104±32）pg／ml,均P〈0．05],其中siRNA3的抑制率非常显著,达61．2％（P〈0．01）。阴性对照siRNA4对细胞基因及蛋白表达无影响。结论：内毒素可刺激小鼠巨噬细胞TNF-α的合成。化学合成siRNA转染小鼠巨噬细胞能有效抑制TNF-α mRNA及蛋白的表达。

Effects of RNA interference on expression of tumor necrosis factor-alpha in lipopolysaccharide-activated mouse macrophages

OBJECTIVE: To investigate the effects of siRNAs targeting mouse tumor necrosis factor (TNF)-alpha gene on the expression of TNF-alpha mRNA and protein in the LPS activated macrophages. METHODS: Mouse macrophages of the line RAW264.7 were cultured. Three siRNA sequences targeting different sites of mouse TNF-alpha gene (siRNA 1 - 3) and a fluorescein-labeled double-stranded RNA (dsRNA) oligomer (siRNA 4), as negative control, were designed and chemically synthesized. All siRNAs were transfected into the mouse macrophages. 0, 3, 6, 9, 12, 15, and 18 hours after the transfection samples of supernatant were collected. Inverse microscopy was used to observe the efficacy of transfection. Then the macrophages were co-incubated with LPS for 9 hours. Macrophages stimulated by LPS only and macrophages without transfection and LPS stimulation were used as controls. Then samples of supernatant were collected. TNF-alpha protein expression was detected by ELISA. Real time PCR was used to detect the TNF-alpha mRNA expression. RESULTS: The transfection rate was 72% - 80%. The TNF-alpha mRNA expression levels of the LPS + siRNA2 and LPS + siRNA3 groups were 0.158 +/- 0.031 and 0.114 +/- 0.028 respectively, both significantly lower than that of the LPS control group (0.294 +/- 0.147, P < 0.05 and P < 0.01 respectively), however, the TNF-alpha mRNA expression level of the LPS + siRNA1 and LPS + siRNA4 groups were not significantly different from that of the LPS control group. The TNF-alpha mRNA expression inhibition rates of the LPS + siRNA and LPS + siRNA3 groups were 46.0% and 61.2% respectively. The TNF-alpha protein expression levels of the LPS + siRNA2 and LPS + siRNA3 group were (1358 +/- 348) pg/ml and (817 +/- 138) pg/ml, both significantly lower than that of the LPS control group (2104 +/- 32) pg/ml, P < 0.05 and P < 0.01], and the TNF-alpha mRNA expression levels of the LPS + siRNA1 and LPS + siRNA4 groups were not significantly different from that of the LPS control group. CONCLUSION: LPS time-dependently increases the expression of TNF-alpha in macrophages. SiRNAs targeting TNF-alpha inhibit the expression levels of TNF-alpha mRNA and protein in macrophages treated with LPS.