γ干扰素与肿瘤坏死因子α对肠上皮屏障功能影响的实验研究

目的 观察炎症介质γ干扰素及TNF-α联合作用对肠上皮屏障功能的影响并探讨其分子机制.方法建立人肠上皮细胞株Caco-2单层细胞培养模型,分别在预处理的24孔板与6孔板中采用DMEM培养基培养.将2种培养板中细胞均按随机数字表法分为对照组(常规培养)、γ干扰素组(加入终浓度为10 ng/mL γ干扰素培养)、TNF-α组(加入终浓度为10 ng/mL TNF-α培养)、γ干扰素+TNF-α组(加入终浓度均为10 ng/mL的γ干扰素与TNF-α培养).24孔板细胞处理后0 h(即刻)及6、12、24、36、48 h,用电阻测定仪检测肠上皮细胞跨上皮电阻(TER);于48 h分别采用异硫氰酸荧光素-葡聚糖荧光示踪法与免疫荧光法,检测肠上皮细胞通透性及紧密连接咬合蛋白的分布与形态变化.6孔板细胞处理24 h时,用蛋白质印迹法检测咬合蛋白、磷酸化肌球蛋白轻链(pMLC)、肌球蛋白轻链激酶(MLCK)蛋白表达.对数据进行单因素方差分析与t检验.结果 (1)对照组各时相点肠上皮细胞TER无明显变化(F=0.86,P＞0.05);γ干扰素组与TNF-α组TER虽逐渐降低,但与处理后0 h比较差异均无统计学意义(F值分别为1.69、2.47,P值均大于0.05);γ干扰素+TNF-α组TER从24 h起显著低于处理后0 h(t=4.97,P＜0.05),并明显低于其余3组(F=11.54,P＜0.05).(2)γ干扰素+TNF-α组的肠上皮细胞通透性(1197±215)pmo1]显著高于对照组、γ干扰素组与TNF-α组(303±93)、(328±76)、(797±177)pmol,t值分别为4.8、5.0、6.9,P值均小于0.01].(3)24 h时各组咬合蛋白表达量无明显变化(F=0.26,P＞0.05).48 h时对照组咬合蛋白排列规则;γ干扰素组及TNF-α组咬合蛋白排列不规则;而γ干扰素+TNF-α组咬合蛋白排列不连续,发生明显重分布,胞质内分布增加.(4)γ干扰素+TNF-α组pMLC蛋白表达量(0.95±0.05)显著高于对照组、γ干扰素组与TNF-α组(0.57±0.12、0.56±0.07、0.59±0.10,F=17.97,P＜0.01),MLCK蛋白表达量(1.57±0.36)也显著高于其余3组(0.85±0.18、1.04±0.23、1.00±0.07,F=9.05,P＜0.05).结论γ干扰素与TNF-α联合作用通过增加MLCK及pMLC蛋白表达,引起肠上皮屏障功能损害.

Abstract：

Objective To investigate the effect of combination of interferon-gamma (IFN-γ) and tumor necrosis factor-alpha ( TNF-α ) on intestinal epithelial barrier function. Methods The Caco-2 monolayers were cultured in DMEM nutrient solution, and then they were inoculated in 24-well or 6-well plate with Transwell inserts. They were divided into control group ( ordinary treatment), IFN-γ group ( with addition of 10 ng/mL IFN-γ), TNF-α group (with addition of 10 ng/mL TNF-α), and IFN-γ plus TNF-α group (with addition of 10 ng/mL TNF-α and 10 ng/mL IFN-γ ). Monolayers inoculated in 24-well plate were collected for determination of transepithelial electrical resistance (TER) with an ohmmeter at post treatment hour (PTH) 0, 6, 12, 24, 36, and 48, the permeability of monolayers with fluorescein isothiocyahate-labeled dextran (FITC-dextran) tracer method at PTH 48, the distribution and morphological change of tight junction occludin with immunofluorescence assay at PTH 48. Monolayers inoculated in 6-well plate were collected for determination of protein expression of occludin, myosin light chain kinase (MLCK), and phosphorylated MLC (pMLC) with Western blot at PTH 24. Data were processed with one-way analysis of vaiiance and t test. Results ( 1 ) There was no obvious difference in TER in control group at each time point ( F = 0. 86, P ＞ 0.05 ). TER in IFN-γgroup and TNF-α group were gradually decreased during PTH 6-48,but showed no statistical difference as compared with that at PTH 0 ( with F value respectively 1.69, 2.47,P values all above 0.05 ). TER in IFN-γplus TNF-α group was significantly decreased from PTH 24 as compared with that at PTH0 ( t =4.97, P ＜0.05) and that in each of the other three groups ( F =11.54,P ＜ 0.05 ). (2) The permeability of monolayers in IFN-γplus TNF-α group ( 1197 ± 215 ) pmol] was significantly higher than that in control group, IFN-γ group, and TNF-α group ( 303 ± 93 ), ( 328 ± 76),(797 ± 177) pmol, with t value respectively 4.8, 5.0, 6.9, P values all below 0.01]. (3) There was no statistical difference in occludin expression at PTH 24 among four groups ( F = 0.26, P ＞ 0.05). The occludin in control group at PTH 48 was regular in arrangement, while that in IFN-γand TNF-α groups was irregular in arrangement. The arrangement of occludin in IFN-γ plus TNF-c group at PTH 48 was interrupted,with obvious redistribution in cytoplasm. (4) The protein expression of pMLC in IFN-γ plus TNF-α group (0.95 ±0.05) was significantly higher than that in control group, IFN-γ group, or TNF-α group (0.57 ±0.12, 0.56 ±0.07, 0.59 ±0. 10, respectively, F = 17.97, P ＜0.01). The protein expression of MLCK in IFN-γplus TNF-α group (1.57 ±0.36) was also significantly higher than that in control, IFN-γ, TNF-α groups (0.85 ± 0.18, 1.04 ± 0. 23, 1.00 ± 0.07, respectively, F = 9.05, P ＜ 0.05 ). Conclusions Combination of IFN-γand TNF-α can induce intestinal epithelial barrier dysfunction by up-regulating MLCK protein expression and promoting MLC phosphorylation.

An experimental study on intestinal epithelial barrier dysfunction induced by interferon-gamma and tumor necrosis factor-alpha

Objective To investigate the effect of combination of interferon-gamma (IFN-γ) and tumor necrosis factor-alpha ( TNF-α ) on intestinal epithelial barrier function. Methods The Caco-2 monolayers were cultured in DMEM nutrient solution, and then they were inoculated in 24-well or 6-well plate with Transwell inserts. They were divided into control group ( ordinary treatment), IFN-γ group ( with addition of 10 ng/mL IFN-γ), TNF-α group (with addition of 10 ng/mL TNF-α), and IFN-γ plus TNF-α group (with addition of 10 ng/mL TNF-α and 10 ng/mL IFN-γ ). Monolayers inoculated in 24-well plate were collected for determination of transepithelial electrical resistance (TER) with an ohmmeter at post treatment hour (PTH) 0, 6, 12, 24, 36, and 48, the permeability of monolayers with fluorescein isothiocyahate-labeled dextran (FITC-dextran) tracer method at PTH 48, the distribution and morphological change of tight junction occludin with immunofluorescence assay at PTH 48. Monolayers inoculated in 6-well plate were collected for determination of protein expression of occludin, myosin light chain kinase (MLCK), and phosphorylated MLC (pMLC) with Western blot at PTH 24. Data were processed with one-way analysis of vaiiance and t test. Results ( 1 ) There was no obvious difference in TER in control group at each time point ( F = 0. 86, P ＞ 0.05 ). TER in IFN-γgroup and TNF-α group were gradually decreased during PTH 6-48,but showed no statistical difference as compared with that at PTH 0 ( with F value respectively 1.69, 2.47,P values all above 0.05 ). TER in IFN-γplus TNF-α group was significantly decreased from PTH 24 as compared with that at PTH0 ( t =4.97, P ＜0.05) and that in each of the other three groups ( F =11.54,P ＜ 0.05 ). (2) The permeability of monolayers in IFN-γplus TNF-α group ( 1197 ± 215 ) pmol] was significantly higher than that in control group, IFN-γ group, and TNF-α group ( 303 ± 93 ), ( 328 ± 76),(797 ± 177) pmol, with t value respectively 4.8, 5.0, 6.9, P values all below 0.01]. (3) There was no statistical difference in occludin expression at PTH 24 among four groups ( F = 0.26, P ＞ 0.05). The occludin in control group at PTH 48 was regular in arrangement, while that in IFN-γand TNF-α groups was irregular in arrangement. The arrangement of occludin in IFN-γ plus TNF-c group at PTH 48 was interrupted,with obvious redistribution in cytoplasm. (4) The protein expression of pMLC in IFN-γ plus TNF-α group (0.95 ±0.05) was significantly higher than that in control group, IFN-γ group, or TNF-α group (0.57 ±0.12, 0.56 ±0.07, 0.59 ±0. 10, respectively, F = 17.97, P ＜0.01). The protein expression of MLCK in IFN-γplus TNF-α group (1.57 ±0.36) was also significantly higher than that in control, IFN-γ, TNF-α groups (0.85 ± 0.18, 1.04 ± 0. 23, 1.00 ± 0.07, respectively, F = 9.05, P ＜ 0.05 ). Conclusions Combination of IFN-γand TNF-α can induce intestinal epithelial barrier dysfunction by up-regulating MLCK protein expression and promoting MLC phosphorylation.