白介素-17在沙眼衣原体呼吸道感染中的早期产生可提高局部白介素-6和巨噬细胞炎性蛋白-2的表达

Early production of interleukin-17 in airway upon Chlamydia trachomatis infection increases the local secretion of IL-6 and MIP-2

目的:探讨炎症性细胞因子白介素-17(interleukin-17,IL-17)在沙眼衣原体呼吸道感染中的早期产生与细胞分泌白介素-6(interleukin-6,IL-6)和巨噬细胞炎性蛋白-2(macrophage inflammatory protein2,MIP-2)之间的关系。方法:在体内,用沙眼衣原体小鼠肺炎株(MoPn)通过鼻腔感染小鼠,用免疫荧光法(immunofluoresent assay,IFA)检测衣原体在肺组织的生长;通过酶联免疫吸附测定法(enzyme-linked immunosorbent assay,ELISA)检测小鼠肺组织IL-17,IL-6和MIP-2的表达,未感染小鼠作为对照组;在体外,用重组鼠IL-17(recombinant murine IL-17,rmIL-17)预处理L929细胞24h,rmIL-17预处理并感染MoPn的细胞作为实验组,未用rmIL-17预处理但感染MoPn的细胞作为对照组,24h后收集上清液,利用ELISA检测IL-6和MIP-2的产生,细胞则通过IFA进行衣原体包涵体计数(inclusion-forming unit,IFU)。结果:体内实验表明,MoPn感染后第1天,肺组织有衣原体生长,感染后第8天达高峰,以常用对数(lg)计数每个肺组织的IFU为6.49±0.19。感染后第2天,IL-17在小鼠肺组织中的产生达峰值(83.0±35.8)ng/L,并很快下降。IL-6在感染后第3天达到峰值(3.98±0.04)μg/L,而MIP-2则在第8天出现高峰(2.19±0.71)μg/L。体外实验发现,分别用20,100和500μg/L不同剂量的rmIL-17预处理细胞后再感染衣原体MoPn24h,细胞上清液中IL-6含量分别为(531.65±24.40),(629.95±7.71)和(646.51±35.92)ng/L,与对照组(55.10±16.54)ng/L比较差异有统计学意义(P<0.01),细胞上清液中MIP-2含量分别为(107.21±28.40),(181.95±25.51)和(221.9±17.32)ng/L,与对照组(13.71±0.84)ng/L比较差异有统计学意义(P<0.05)。单独rmIL-17对细胞并无刺激作用,rmIL-17对感染细胞衣原体包涵体生长无直接抑制作用。结论:IL-17在衣原体呼吸道感染中早期出现,rmIL-17能诱导感染MoPn的L929细胞分泌IL-6和MIP-2。IL-17在衣原体呼吸道感染早期可能通过诱导IL-6和MIP-2的产生,在宿主抵御细胞内病原菌感染中发挥重要的作用。

Objective：To evaluate the early interleukin-17 （IL-17） production in airway upon Chlamydia trachomatis infection and its relationship with the secretion of interleukin-6 （IL-6） and macrophage inflammatory protein 2 （MIP-2） in local site.Methods：In vivo,a murine model of pneumonia induced by intranasal inoculation with Chlamydia trachomatis mouse pneumonitis （MoPn,now classified as a new species C.muridarum） was used for the study.Chlamydial growth in the lung was assessed by inoculating HeLa cell monolayer with lung homogenates followed by enzyme-linked immunosorbent assay （IFA）.IL-17,IL-6 and MIP-2 were measured by enzyme-linked immunosorbent assay （ELISA）.Mice without infection acted as the control group.In vitro,L929 cells were pretreated with recombinant murine IL-17 （rmIL-17） at a dose ranging from 20,100 to 500 μg/L for 24 h then infected with MoPn for 24 h.The supernatants were harvested and tested for IL-6 and MIP-2 concentration using ELISA.The cells were assayed for the number of inclusion-forming unit（IFU） by IFA.L929 cells without pretreatment with rmIL-17 but infected with MoPn was the control group.Results：The study showed that in vivo,Chlamydial growth in the lung was found on day 1 after infection,and reached its peak at day 8 （6.49±0.19,lg IFU/lung） with subsequent decline in quantity.IL-17 peaked at 48 h （83.0 ng/L±35.8 ng/L） while IL-6 peaked on day 3 [（3.98±0.04）μg/L],MIP-2 peaked on day 8[（2.19±0.71） μg/L].The study showed that in vitro,compared with control group[（55.10±16.54） ng/L for IL-6 production and （13.71±0.84） ng/L for MIP-2],L929 cells pretreated with rmIL-17 at the different concentrations of 20,100 and 500 μg/L for 24 h then infected with MoPn for 24 h,could significantly increase IL-6 （P 〈0.01） and MIP-2 secretion（P 〈0.05）.The productions of IL-6 in the supernatants were （531.65±24.40）,（629.95±7.71）,and（646.51±35.92） ng/L.Meanwhile,the productions of MIP-2 were （107.21±28.40）,（181.95±25.51）,and （221.90±17.32） ng/L,respectively.RmIL-17 alone had no effect on IL-6 and MIP-2 secretion,and no direct effect on growth of chlamydial inclusion body was demonstrated either.Conclusion：IL-17 was produced early in airway upon Chlamydia trachomatis,and rmIL-17could induce IL-6 and MIP-2 production in L929 cells after infection with MoPn.These suggest that an early IL-17 response may play an important role by inducing the secretion of IL-6 and MIP-2 in initiating host defense against infection with Chlamydia trachomatis in the airway.