Ma Chunyan, Li Yong, Li Min, Deng Guangcun, Wu Xiaoling, Zeng Jin, Hao Xiujing, Wang Xiaoping, Liu Jing, Cho William C S, Liu Xiaoming, Wang Yujiong
Key Laboratory of Ministry of Education for Conservation and Utilization of Special Biological Resources in the Western China and College of Life Science, Ningxia University, Yinchuan 750021, Ningxia, China.
Tuberculosis Hospital of Ningxia, Yinchuan 750021, Ningxia, China.
Mol Immunol. 2014 Nov;62(1):150-8. doi: 10.1016/j.molimm.2014.06.014. Epub 2014 Jul 2.
The emerging roles of microRNAs (miRNAs) in regulating immune responses have attracted increasing attention in recent years; and the alveolar macrophages (AMs) are the main targets of mycobacterial infection, which play a pivotal role in the pathogenesis of Mycobacterium tuberculosis infection. However, the immunoregulatory role of miRNAs in AMs has not been fully demonstrated. In this study, we find that miR-124 is up-regulated in the peripheral leukocytes of patients with pulmonary tuberculosis; furthermore, the expression miR-124 can be induced upon Mycobacterium bovis Bacillus Calmette-Guerin (BCG) infection in both RAW264.7 AM cells in vitro and murine AMs in vivo. Mechanistically, miR-124 is able to modulate toll-like receptor (TLR) signaling activity in RAW264.7 cells in response to BCG infection. In this regard, multiple components of TLR signaling cascade, including the TLR6, myeloid differentiation factor 88 (MyD88), TNFR-associated factor 6 and tumor necrosis factor-α are directly targeted by miR-124. In addition, both overexpression of TLR signaling adaptor MyD88 and BCG infection are able to augment miR-124 transcription, while MyD88 expression silenced by small interfering RNA dramatically suppresses miR-124 expression in AMs in vitro. Moreover, the abundance of miR-124 transcript in murine AMs of MyD88 deficient mice is significantly less than that of their wild-type or heterozygous littermates; and the BCG infection fails to induce miR-124 expression in the lung of MyD88 deficient mouse. These results indicate a negative regulatory role of miR-124 in fine-tuning inflammatory response in AMs upon mycobacterial infection, in part through a mechanism by directly targeting TLR signaling.
近年来，微小RNA（miRNA）在调节免疫反应中的新兴作用已引起越来越多的关注；肺泡巨噬细胞（AM）是分枝杆菌感染的主要靶点，在结核分枝杆菌感染的发病机制中起关键作用。然而，miRNA在AM中的免疫调节作用尚未得到充分证实。在本研究中，我们发现miR-124在肺结核患者外周血白细胞中上调；此外，在体外RAW264.7 AM细胞和体内小鼠AM中，牛分枝杆菌卡介苗（BCG）感染均可诱导miR-124表达。机制上，miR-124能够在RAW264.7细胞中响应BCG感染调节Toll样受体（TLR）信号活性。在这方面，miR-124直接靶向TLR信号级联的多个成分，包括TLR6、髓样分化因子88（MyD88）、肿瘤坏死因子受体相关因子6和肿瘤坏死因子-α。此外，TLR信号衔接蛋白MyD88的过表达和BCG感染均能增强miR-124转录，而小干扰RNA沉默MyD88表达则显著抑制体外AM中miR-124表达。此外，MyD88缺陷小鼠的小鼠AM中miR-124转录本的丰度明显低于其野生型或杂合子同窝小鼠；BCG感染未能在MyD88缺陷小鼠的肺中诱导miR-124表达。这些结果表明，miR-124在分枝杆菌感染时对AM中炎症反应的微调起负调节作用，部分是通过直接靶向TLR信号的机制实现的。
