Fang Yao, Chen Hai, Hu Yi, Li Qian, Hu Zhiqiang, Ma Tengfei, Mao Xuhu
Department of Clinical Microbiology and Immunology of Southwest Hospital and the College of Medical Laboratory Science, Third Military Medical University, No. 30 Gaotanyan Street, Shapingba District, Chongqing, 400038, People's Republic of China.
PLA 161 Hospital, Wuhan, 430014, People's Republic of China.
BMC Microbiol. 2016 Nov 28;16(1):283. doi: 10.1186/s12866-016-0901-6.
Burkholderia pseudomallei (Bp) is the causative agent of melioidosis, a kind of tropical disease. Burkholderia thailandensis (Bt), with a high sequence similarity to Bp, is thought to be an avirulent organism. Since there are numerous similarities between Bp and Bt, their differences in pathogenesis of host response and related mechanism are still undermined. In recent years, microRNAs have been researched in many diseases, but seldom involved in bacterial infection, bacteria-host interaction or explaining the differences between virulent and avirulent species.
We found that Bp and Bt had similar phenotypes in terms of intracellular replication, dissemination (reflected by multinucleated giant cell formation), TNF-α release and apoptosis in RAW264.7 macrophages or TC-1 pulmonary cell but in different level. Especially, at the late infection phases (after 12 h post infection), Bp showed faster intracellular growth, stronger cytotoxicity, and higher TNF-α release. After microRNA array analysis, we found some microRNAs were significantly expressed in macrophages treated by Bp. miR-3473 was one of them specifically induced, but not significantly changed in Bt-treated macrophages. In addition, TargetScan suggested that miR-3473 possibly target TRAF3 (TNF receptor-associated factor 3), a well-known negative regulator of the NF-κB pathway, which was probably involved in the TNF-α induction and apoptosis in cells with Bp infection. In vivo, it was found that miR-3473 expression of total lungs cells from Bp-treated was higher than that from Bt-treated mice. And miR-3473 inhibitor was able to decrease the TNF-α release of mice and prolong the survival of mice with Bp infection.
In sum, miR-3473 plays an important role in the differential pathogenicity of Bp and Bt via miR-3473-TRAF3-TNF-α network, and regulates TNF-α release, cell apoptosis and animal survival after Bp treatment. In this study, we have found a specific microRNA is related to bacterial virulence and provide insight into the mechanism for host-bacteria interaction, which suggests that potential oligonucleotides should be applied against bacterial infection.
类鼻疽伯克霍尔德菌（Bp）是类鼻疽病的病原体，这是一种热带疾病。泰国伯克霍尔德菌（Bt）与Bp具有高度的序列相似性，被认为是一种无毒力的生物体。由于Bp和Bt之间存在许多相似之处，它们在宿主反应发病机制及相关机制上的差异仍未得到充分认识。近年来，微小RNA已在许多疾病中得到研究，但很少涉及细菌感染、细菌与宿主的相互作用或解释有毒力和无毒力物种之间的差异。
我们发现，在RAW264.7巨噬细胞或TC-1肺细胞中，Bp和Bt在细胞内复制、扩散（以多核巨细胞形成反映）、TNF-α释放和凋亡方面具有相似的表型，但程度不同。特别是在感染后期（感染后12小时后），Bp显示出更快的细胞内生长、更强的细胞毒性和更高的TNF-α释放。经过微小RNA芯片分析，我们发现一些微小RNA在Bp处理的巨噬细胞中显著表达。miR-3473是其中一种被特异性诱导的微小RNA，但在Bt处理的巨噬细胞中没有显著变化。此外，TargetScan表明miR-3473可能靶向TRAF3（TNF受体相关因子3），这是NF-κB通路中一种著名的负调节因子，可能参与了Bp感染细胞中TNF-α的诱导和凋亡。在体内，发现Bp处理的小鼠全肺细胞中miR-3473的表达高于Bt处理的小鼠。并且miR-3473抑制剂能够降低小鼠的TNF-α释放，并延长Bp感染小鼠的存活时间。
总之，miR-3473通过miR-3473-TRAF3-TNF-α网络在Bp和Bt的致病性差异中发挥重要作用，并在Bp处理后调节TNF-α释放、细胞凋亡和动物存活。在本研究中，我们发现了一种与细菌毒力相关的特异性微小RNA，并深入了解了宿主-细菌相互作用的机制，这表明潜在的寡核苷酸应被用于对抗细菌感染。
