嗜酸乳杆菌对小鼠结肠炎的疗效及结肠黏膜转录因子表达的影响

Clinical effi cacy of Lactobacillus acidophilus against experimental murine colitis and its effects on the expression of STAT1,T-bet and GATA3

目的:观察嗜酸乳杆菌治疗DSS诱导小鼠实验性结肠炎的疗效以及对转录因子STAT1,T-bet及GATA3的影响,了解嗜酸乳杆菌的作用机制.方法:采用2.5%DSS诱导小鼠结肠炎模型,70只Balb/c小鼠随机分为7组:模型组、阴性对照组(菌粉保护剂组)、阳性对照组(美沙拉嗪组)、嗜酸乳杆菌低剂量组(1×109CFU/L)、中剂量组(1×1010CFU/L)、高剂量组(1×1011CFU/L)、正常组.用DAI评分和病理组织学积分检测各干预组疗效,RT-PCR法检测结肠组织中STAT1、T-bet、GATA3的表达水平,Western blot和免疫组织化学法检测结肠组织中T-bet的表达.结果:模型组小鼠DAI积分及组织病理学积分要明显高于正常组(均P<0.05),嗜酸乳杆菌低、中、高剂量组和美沙拉嗪干预后,小鼠DAI积分及组织病理学积分较模型组有明显下降(6.20±2.64,5.00±1.21,5.72±2.63,5.81±1.32vs7.81±1.02;4.25±2.05,2.56±1.81,2.20±1.12,3.10±2.60vs5.80±2.94,均P<0.05);嗜酸乳杆菌低、中、高剂量组及美沙拉嗪干预后转录因子在核酸水平较模型组STAT1、T-bet的表达降低(均P<0.05);GATA3的表达升高(均P<0.05),但仍低于正常组.而T-bet的蛋白和免疫组织化学表达都与mRNA有相同趋势,较模型组降低(0.27±0.04,0.23±0.02,0.18±0.04,0.27±0.11vs0.30±0.04;0.263±0.045,0.234±0.015,0.114±0.025,0.252±0.024vs0.322±0.064,均P<0.05).其中又以嗜酸乳杆菌高剂量组效果最佳.结论:嗜酸乳杆菌对实验性结肠炎小鼠有治疗作用,可抑制转录因子的表达,其部分作用机制可能为通过抑制STAT1、T-bet信号分子的激活来抑制Th1型免疫反应,减少对GATA3的抑制而发挥治疗作用.

AIM： To investigate the therapeutic efficacy of Lactobacillus acidophilus against experimental murine colitis and its effects on the expression of STAT1, T-bet and GATA3. METHODS： Experimental murine colitis was induced with 2.5% dextran sulfate sodium （DSS）. A total of 70 mice were randomly and equally divided into seven groups： model control group, negative control group, mesalamine group, low-dose Lactobacillus acidophilus group, mediumdose Lactobacillus acidophilus group, high-dose Lactobacillus acidophilus group and normal control group. The expression of STAT1, T-bet and GATA3 mRNAs in colonic mucosa was measured by reverse transcription-polymerase chain reaction （RT-PCR）. The expression of T-bet protein was measured by Western blot and immunohistochemistry （IHC）. Colonic tissue damage was assessed using histopathologic score. The body weight and disease activity index （DAI） of all rats were evaluated daily.RESULTS： Compared with the normal control group, the disease activity index and histopathologic scores were significantly increased （both P 〈 0.05） in the model control group. All doses of Lactobacillus acidophilus and mesalamine could significantly reduce disease activity index and histopathologic scores when compared to the model control group （6.20±2.64, 5.00±1.21, 5.72±2.63 and 5.81±1.32 vs 7.81±1.02; 4.25±2.05, 2.56±1.81, 2.20 ±1.12 and 3.10±2.60 vs 5.80±2.94; all P 〈0.05）. The expression levels of STAT1 and T-bet mRNAs in all Lactobacillus acidophilus groups （low-, medium- and high-dose） and mesalazine group were lower than that in the model control group （all P 〈 0.05）. Moreover, the expression levels of T-bet protein in all Lacto-bacillus acidophilus groups and mesalazine group were also significantly lower than that in the model control group （0.27±0.04, 0.23±0.02, 0.18± 0.04 and 0.27±0.11 vs 0.30±0.04; 0.263±0.045, 0.234±0.015, 0.114±0.025 and 0.252±0.024 vs 0.322±0.064; all P 〈 0.05）. Optimum effects were achieved in the high-dose Lactobacillus acidophilus group. CONCLUSION： Inhibition of transcriptional factors STAT1/T-bet activation maybe one mechanism contributing to the therapeutic effects of Lactobacillus acidophilus against ulcerative colitis.