Xu Guangxian, Li Yuxing, Yang Jianmin, Zhou Xiangmei, Yin Xiaomin, Liu Meili, Zhao Deming
National Animal TSE Laboratory, College of Veterinary Medicine, China Agricultural University, Haidian District Yuanmingyuan Xi Lu 2, Beijing, 100094, China.
Mol Cell Biochem. 2007 Aug;302(1-2):1-7. doi: 10.1007/s11010-006-9395-0. Epub 2007 May 26.
The pathogenesis of tuberculosis-causing Mycobacterium bovis is largely due to its ability to enter and survive in alveolar macrophages. Its mechanism of entry, mediated by proteins encoded by mammalian cell entry (mce) genes, is important for its pathogenesis. Here we focussed on the role of the Mce4A protein in the pathogenesis of M. bovis in cattle. Cell livability decreased in a dosage-dependent manner when Mce4A proteins were used to stimulate alveolar macrophages, which suggested that the recombinant Mce4A protein significantly inhibited alveolar macrophage activity. To test whether Mce4A modulates the gene expression profile of alveolar macrophages, alveolar macrophages were stimulated by Mce4A protein and other proteins/ligands (such as MtbPPD, MbPPD, and BCG), followed by real-time RT-PCR assay for the mRNA expression level of TNF-alpha, iNOS, IL-6, and IL-12. The results showed that the expression of TNF-alpha, iNOS, and IL-6 in alveolar macrophages was up-regulated by stimulation with the recombinant Mce4A protein of M. bovis; in contrast, expression of IL-12 was unaffected. MbPPD and BCG up-regulated the mRNA expression of TNF-alpha, iNOS, IL-6, and IL-12 (P < 0.05), whereas MtbPPD stimulated the mRNA expression of TNF-alpha, IL-6, and IL-12 with no effect on iNOS. This study suggests that Mce4A proteins may induce the body's inflammation response to M. bovis and therefore may play an important role in the immune response.
导致结核病的牛分枝杆菌的发病机制很大程度上归因于其进入肺泡巨噬细胞并在其中存活的能力。其由哺乳动物细胞进入（mce）基因编码的蛋白质介导的进入机制对其发病机制很重要。在此，我们聚焦于Mce4A蛋白在牛分枝杆菌发病机制中的作用。当用Mce4A蛋白刺激肺泡巨噬细胞时，细胞活力以剂量依赖的方式下降，这表明重组Mce4A蛋白显著抑制肺泡巨噬细胞活性。为了测试Mce4A是否调节肺泡巨噬细胞的基因表达谱，用Mce4A蛋白和其他蛋白质/配体（如结核菌素纯蛋白衍生物、牛型结核菌素纯蛋白衍生物和卡介苗）刺激肺泡巨噬细胞，随后通过实时逆转录聚合酶链反应测定肿瘤坏死因子-α、诱导型一氧化氮合酶、白细胞介素-6和白细胞介素-12的mRNA表达水平。结果显示，牛分枝杆菌的重组Mce4A蛋白刺激后，肺泡巨噬细胞中肿瘤坏死因子-α、诱导型一氧化氮合酶和白细胞介素-6的表达上调；相反，白细胞介素-12的表达未受影响。牛型结核菌素纯蛋白衍生物和卡介苗上调了肿瘤坏死因子-α、诱导型一氧化氮合酶、白细胞介素-6和白细胞介素-12的mRNA表达（P<0.05），而结核菌素纯蛋白衍生物刺激了肿瘤坏死因子-α、白细胞介素-6和白细胞介素-12的mRNA表达，对诱导型一氧化氮合酶无影响。本研究表明，Mce4A蛋白可能诱导机体对牛分枝杆菌的炎症反应，因此可能在免疫反应中起重要作用。
