Effects of parasites on the gene expression of nitric oxide synthase and cytokine in macrophages

一氧化氮(NO)在小鼠巨噬细胞杀死包括寄生虫在内的感染性生物的能力中起着重要作用。诱导型一氧化氮合酶(INOS)负责巨噬细胞在细胞因子和/或脂多糖刺激下产生大量的NO。趋化因子是炎症反应的重要组成部分。红蜘蛛活体外抑制干扰素-γ和脂多糖刺激的巨噬细胞iNOS和JE、小鼠单核细胞趋化蛋白-1同源基因的表达以及亚硝酸盐的产生。排泄/分泌(ES)产物还以剂量依赖的方式抑制iNOS和JE mRNA的表达，减少亚硝酸盐的产生。然后，我们检测了PLerercoid预培养对巨噬细胞iNOS、趋化因子(IP-10、JE、KC)和肿瘤坏死因子-α基因表达的影响。用Northern杂交和放射自显影检测mRNA的表达，用磷光屏用分子图像分析仪检测mRNA的表达水平。内毒素刺激巨噬细胞3h可明显抑制巨噬细胞IP-10和JE基因的表达，抑制作用呈时间-效应关系。5种类固醇预先孵育也可抑制肿瘤坏死因子-αmRNA的表达。ES产物以预孵育时间依赖的方式预先孵育巨噬细胞，观察其对巨噬细胞诱导型一氧化氮合酶基因表达的上调作用。ES产物的这种抑制作用持续到ES产物去除后72h。根据这些结果，我们推测文昌鱼的ES产物可能在体内抑制巨噬细胞iNOS和趋化因子基因的表达，从而抑制宿主防御机制。

Nitric oxide (NO) is important in the ability of mouse macrophages to kill infectious organisms including parasites. An inducible form of NO synthase (iNOS) is responsible for high output generation of NO by macrophages after stimulation with cytokines and/or LPS.Chemoattactant peptides termed chemokine are important components of the inflammatory response. Alive plerocercoids of Spirometra erinaceieuropaei suppressed the mRNA expression of iNOS and JE, murine homologue of monocyte chemotactic protein-1, and nitrite production of macrophages stimulated with IFN-gamma and LPS in vitro. Excretory/secretory (ES) products from plerocercoids also suppressed the induced iNOS and JE mRNA and reduce nitrite production in a dose dependent manner.Then we examined that the effects of preculture with plerocercoids on iNOS, chemokines (IP-l0, JE, KC) and TNF-alpha gene expression in peritoneal macrophages. The expression of mRNA was detected by northern hybridization and autoradiography, and mRNA expression levels were read by molecular image analyser using a phosphorescence screen. The gene expression of IP-l0 and JE in macrophages stimulated with LPS for 3 h was apparently suppressed by 5 plerocercoids in a preincubation-time dependent manner. TNF-alpha mRNA expression was also suppressed by preincubation with 5 plerocercoids. The suuprressive effect of iNOS gene expression in macrophages stimulated with IFN-gamma and LPS for 24 h was also observed by preincubation of ES products in a preincubation-time dependent manner. This inhibitory effects of ES products continued until 72 h after removal of ES products. Judging from these results, we suppose that ES products from plerocercoids might suppress the iNOS and chemokine gene expression of macrophages in vivo, and suppress the host defense mechanism.