Muangsombut Veerachat, Withatanung Patoo, Srinon Varintip, Chantratita Narisara, Stevens Mark P, Blackwell Jenefer M, Korbsrisate Sunee
Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol UniversityBangkok, Thailand.
Microbiology Laboratory, Veterinary Diagnostic Center, Faculty of Veterinary Science, Mahidol UniversityNakhon Pathom, Thailand.
Front Cell Infect Microbiol. 2017 Aug 8;7:350. doi: 10.3389/fcimb.2017.00350. eCollection 2017.
Bacterial survival in macrophages can be affected by the natural resistance-associated macrophage protein 1 (Nramp1; also known as solute carrier family 11 member a1 or Slc11a1) which localizes to phagosome membranes and transports divalent cations, including iron. Little is known about the role of Nramp1 in infection, in particular whether this differs for pathogenic species like causing melioidosis or non-pathogenic species like . Here we show that transfected macrophages stably expressing wild-type Nramp1 (Nramp1) control the net replication of , but not . Control of was associated with increased cytokine responses, and could be abrogated by blocking NADPH oxidase-mediated production of reactive oxygen species but not by blocking generation of reactive nitrogen species. The inability of Nramp1 macrophages to control was associated with rapid escape of bacteria from phagosomes, as indicated by decreased co-localization with LAMP1 compared to . A mutant impaired in escape from phagosomes was controlled to a greater extent than the parent strain in Nramp1 macrophages, but was also attenuated in Nramp1 cells. Consistent with reduced escape from phagosomes, formed fewer multinucleated giant cells in Nramp1 macrophages at later time points compared to exhibited elevated transcription of virulence-associated genes of Type VI Secretion System cluster 1 (T6SS-1), the Bsa Type III Secretion System (T3SS-3) and the gene required for actin-based motility in Nramp1 macrophages. Nramp1 macrophages were found to contain decreased iron levels that may impact on expression of such genes. Our data show that is able to evade Nramp1- and NADPH oxidase-mediated killing in macrophages and that expression of virulence-associated genes by pathogenic is enhanced in macrophages expressing wild-type compared to non-functional Nramp1. has been proposed as surrogate for in the study of melioidosis however our study highlights important differences in the interaction of these bacteria with macrophages.
巨噬细胞中的细菌存活情况可能会受到天然抗性相关巨噬细胞蛋白1（Nramp1；也称为溶质载体家族11成员a1或Slc11a1）的影响，该蛋白定位于吞噬体膜并运输包括铁在内的二价阳离子。关于Nramp1在感染中的作用知之甚少，特别是对于引起类鼻疽的致病物种或其他非致病物种而言是否存在差异。在这里，我们表明稳定表达野生型Nramp1（Nramp1）的转染巨噬细胞能够控制某菌的净复制，但不能控制另一菌的净复制。对某菌的控制与细胞因子反应增强有关，并且可以通过阻断NADPH氧化酶介导的活性氧产生来消除，但不能通过阻断活性氮的产生来消除。Nramp1巨噬细胞无法控制另一菌与细菌从吞噬体的快速逃逸有关，与某菌相比，与溶酶体相关膜蛋白1（LAMP1）的共定位减少表明了这一点。与亲本菌株相比，在Nramp1巨噬细胞中，一种在从吞噬体逃逸方面受损的突变体在更大程度上受到控制，但在Nramp1细胞中也减弱了。与从吞噬体逃逸减少一致，与某菌相比，另一菌在后期时间点在Nramp1巨噬细胞中形成的多核巨细胞更少。另一菌在Nramp1巨噬细胞中表现出VI型分泌系统簇1（T6SS-1）、Bsa III型分泌系统（T3SS-3）的毒力相关基因以及基于肌动蛋白运动所需的某基因的转录升高。发现Nramp1巨噬细胞中的铁水平降低，这可能会影响此类基因的表达。我们的数据表明，某菌能够逃避Nramp1和NADPH氧化酶介导的巨噬细胞杀伤作用，并且与无功能的Nramp1相比，致病的另一菌在表达野生型的巨噬细胞中毒力相关基因的表达增强。在类鼻疽研究中，某菌已被提议作为另一菌的替代物，然而我们的研究突出了这些细菌与巨噬细胞相互作用中的重要差异。
