The opportunistic pathogen Enterococcus faecalis resists phagosome acidification and autophagy to promote intracellular survival in macrophages
The opportunistic pathogen Enterococcus faecalis resists phagosome acidification and autophagy to promote intracellular survival in macrophages
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DOI：
10.1111/cmi.12556
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发表时间：
2016-06-01
影响因子：
3.4
通讯作者：
Shankar, Nathan
中科院分区：
文献类型：
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作者：
Zou, Jun;Shankar, Nathan
虽然据报道许多粪肠球菌菌株能够在巨噬细胞内存活较长时间，但所涉及的确切机制在很大程度上尚不清楚。在本研究中，我们发现巨噬细胞吞噬后，含有肠球菌的液泡抵抗酸化，而粪肠球菌则抵抗低pH值。通过透射电子显微镜对含有肠球菌的液泡进行超微结构检查，发现有一个单膜包膜，没有经典双膜自噬体的证据。 Western blot分析进一步证实粪肠球菌在感染过程中可以触发抑制LC3-II的产生。通过使用用RFP-LC3质粒转染并用GFP标记的粪肠球菌感染的细胞，我们还观察到在巨噬细胞感染期间粪肠球菌没有被递送到自噬体中。虽然这些观察结果表明自噬在消除细胞内粪肠球菌方面没有作用，但活性氧和一氧化氮的产生增加是这一过程的关键。刺激自噬可抑制体外巨噬细胞中粪肠球菌的细胞内存活，并减少体内粪肠球菌的负担。总之，这项研究的结果为粪肠球菌与宿主细胞的相互作用提供了新的见解，并可能为肠球菌感染的治疗提供新方法。
While many strains of Enterococcus faecalis have been reported to be capable of surviving within macrophages for extended periods, the exact mechanisms involved are largely unknown. In this study, we found that after phagocytosis by macrophages, enterococci-containing vacuoles resist acidification, and E. faecalis is resistant to low pH. Ultrastructural examination of the enterococci-containing vacuole by transmission electron microscopy revealed a single membrane envelope, with no evidence of the classical double-membraned autophagosomes. Western blot analysis further confirmed that E. faecalis could trigger inhibition of the production of LC3-II during infection. By employing cells transfected with RFP-LC3 plasmid and infected with GFP-labelled E. faecalis, we also observed that E. faecalis was not delivered into autophagosomes during macrophage infection. While these observations indicated no role for autophagy in elimination of intracellular E. faecalis, enhanced production of reactive oxygen species and nitric oxide were keys to this process. Stimulation of autophagy suppressed the intracellular survival of E. faecalis in macrophages in vitro and decreased the burden of E. faecalis in vivo. In summary, the results from this study offer new insights into the interaction of E. faecalis with host cells and may provide a new approach to treatment of enterococcal infections.