PDF(Pubmed)
Abstract：
Salmonella infection entails a cascade of attacks and defence measures. After breaching the intestinal epithelial barrier, Salmonella is phagocytosed by macrophages, where the bacteria encounter multiple stresses, to which it employs relevant countermeasures. Our study shows that, in Salmonella, the polyamine spermidine activates a stress response mechanism by regulating critical antioxidant genes. Salmonella Typhimurium mutants for spermidine transport and synthesis cannot mount an antioxidative response, resulting in high intracellular ROS levels. These mutants are also compromised in their ability to be phagocytosed by macrophages. Furthermore, it regulates a novel enzyme in Salmonella, Glutathionyl-spermidine synthetase (GspSA), which prevents the oxidation of proteins in E. coli. Moreover, the spermidine mutants and the GspSA mutant show significantly reduced survival in the presence of hydrogen peroxide in vitro and reduced organ burden in the mouse model of Salmonella infection. Conversely, in macrophages isolated from gp91phox-/- mice, we observed a rescue in the attenuated fold proliferation previously observed upon infection. We found that Salmonella upregulates polyamine biosynthesis in the host through its effectors from SPI-1 and SPI-2, which addresses the attenuated proliferation observed in spermidine transport mutants. Thus, inhibition of this pathway in the host abrogates the proliferation of Salmonella Typhimurium in macrophages. From a therapeutic perspective, inhibiting host polyamine biosynthesis using an FDA-approved chemopreventive drug, D, L-α-difluoromethylornithine (DFMO), reduces Salmonella colonisation and tissue damage in the mouse model of infection while enhancing the survival of infected mice. Therefore, our work provides a mechanistic insight into the critical role of spermidine in stress resistance of Salmonella. It also reveals a bacterial strategy in modulating host metabolism to promote their intracellular survival and shows the potential of DFMO to curb Salmonella infection.
摘要：
沙门氏菌感染需要一系列的攻击和防御措施。突破肠上皮屏障后，沙门氏菌被巨噬细胞吞噬，细菌遇到多重压力的地方，对此，它采取了相关的对策。我们的研究表明,在沙门氏菌中，多胺亚精胺通过调节关键的抗氧化基因激活应激反应机制。用于亚精胺运输和合成的鼠伤寒沙门氏菌突变体不能产生抗氧化反应，导致高的细胞内ROS水平。这些突变体被巨噬细胞吞噬的能力也受损。此外，它调节沙门氏菌中的一种新型酶，谷氨酰-亚精胺合成酶（GspSA），这可以防止大肠杆菌中蛋白质的氧化。此外，在沙门氏菌感染的小鼠模型中,亚精胺突变体和GspSA突变体在体外过氧化氢存在下显示出显著降低的存活率和降低的器官负担。相反，在从gp91phox-/-小鼠分离的巨噬细胞中，我们观察到先前在感染时观察到的减毒倍数增殖中的挽救。我们发现沙门氏菌通过其来自SPI-1和SPI-2的效应子上调宿主中多胺的生物合成，从而解决了亚精胺转运突变体中观察到的减毒增殖。因此，在宿主中抑制该途径可以消除鼠伤寒沙门氏菌在巨噬细胞中的增殖。从治疗的角度来看，使用FDA批准的化学预防药物抑制宿主多胺生物合成，D,L-α-二氟甲基鸟氨酸(DFMO),减少感染小鼠模型中的沙门氏菌定植和组织损伤，同时增强感染小鼠的存活率。因此,我们的工作提供了对亚精胺在沙门氏菌抗应激中的关键作用的机制见解。它还揭示了调节宿主代谢以促进其细胞内存活的细菌策略，并显示了DFMO抑制沙门氏菌感染的潜力。
