IL-18对大鼠分泌性中耳炎中耳NF-κB及Th2/Th1平衡的影响

Effects of IL-18 on Nuclear Factor Kappar B and Th2/Th1 Immune Homeotasis in Rat Otitis Media with Effusion

目的探讨白细胞介素18(interleukin-18,IL-18)对分泌性中耳炎(otitis media with effusion,OME)大鼠中耳微环境中核转录因子(nuclear transcription factors kappa B,NF-κB)及T辅助细胞(T helper cell,T helper cell)Th2/Th1细胞免疫平衡的影响。方法 18只SD大鼠,随机分为OME模型组(A组)、IL-18干预组(B组)和正常对照组(C组)每组各6只(12耳)。A组和B组以卵清蛋白(ovalbumin,OVA)腹腔注射致敏后以OVA耳内激发制成OME模型,C组耳内激发以磷酸盐缓冲液(phosphate Buffered Saline,PBS)替代OVA。IL-18干预组大鼠,于OVA全身致敏及耳内激发的同时,在第1、2、7、8、15、16d给予重组大鼠IL-18 1μg加生理盐水0.2ml腹腔注射,对照组和OME模型组在相同时间点腹腔注射生理盐水0.2ml替代IL-18。采用HE染色切片观察各组大鼠中耳炎症细胞的变化,免疫组化染色检测中耳黏膜和骨髓腔中IL-4、IFN-γ、NF-κB p65的表达。结果 B组中耳Th1型细胞因子IFN-γ含量较A组明显增高(P﹥0.05),Th2型细胞因子IL-4含量较A组稍有增高(P﹥0.05),A组和B组IL-4含量均明显高于C组(P﹥0.05);Th2/Th1比值A与B组比较差异无统计学意义(P﹥0.05),但A组比值明显高于C组(P﹥0.05);NF-κB p65蛋白在中耳黏膜和骨髓腔中表达三组间存在显著差异(P﹥0.05),B组NF-κB p65阳性细胞比率明显多于A组(P﹥0.05),而A组明显多于C组(P﹥0.05)。IL-18干预后OME大鼠中耳微环境中编码炎症介质基因表达的转录因子NF-κB活性明显增强,Th细胞过度活化,细胞因子过度分泌,其中IFN-γ合成显著增高,而IL-4合成也出现一定程度的增高,虽然一定程度上纠正了OME大鼠中耳微环境中的Th2/Th1免疫偏移,但是中耳变应性炎症并未得到根本缓解。结论 IL-18对Th1和Th2细胞存在双向调节作用参与OME大鼠中耳变应性炎症反应:一方面,刺激Th1细胞活化;另一方面,持续维系Th2过度反应,其机制之一可能与IL-18增强了大鼠中耳组织中NF-κB的活性有关。

Objective To investigate the effects of IL-18 on NF-KB and Th2/Thl immune homeotasis in the middle ear of a rat model of OME. Methods Eighteen Sprague-Dawley （SD） rats were randomly divided into three groups： group A （OME model group, n=12 ears）; group B （IL-18 injection group, n=12 ears）; and group C （control group, n=12 ears）. The rat model of OME was established in groups A and B by sensitization with ovalbumin and later transtympanic challenging. IL-18 （0.2 ml, 1μg） and Saline （0.2 ml） were respectively injected in all groups on days 1, 2, 7, 8, 15 and 16. Morphologic changes of middle ear epithelial cells and inflammatory cells infiltration were evaluated under a microscope. The expression of IFN-~/ , IL-4, NF-KB p65 in temporal bone marrow and middle ear mucosa was evaluated by immunohistochemistry. Results The expression of IFN-＂/in group B was stronger than that in group A and C （both P 〈 O. 05）. As compared to group C, the expression of IL-4 in group A and group B was remarkably stronger （both P 〈 0.05）, while no significant difference was found between groups A and B （P〉 0. 05）. Additionally, there was no significant difference in the Th2/Thl （IL-4/IFN-γ）ratio between groups A group B （P 〉 0.05）. Furthermore, NF-KB p65 expression in temporal bone marrow and middle ear mucosa was different among the three groups, with the highest rate of expression in group B and the lowest in group C （P 〈 0. 05）. Conclusion IL-18 plays a dual effect role that increases both Thl cytokine IFN-γ and Th2 cytokine IL-4 production. The underlying mechanism may be explained by the fact that IL-18 promotes the activation of NF-KB in the allergic OME rat model.