School of Life Science, Central South University, Changsha, Hunan, China.
School of Life Science, Central South University, Changsha, Hunan, China.
Microbes Infect. 2020 Jan-Feb;22(1):31-39. doi: 10.1016/j.micinf.2019.07.002. Epub 2019 Jul 23.
Macrophages are major pathogen-killing cells. Mycobacteria can represent a serious threat to human health, in particular Mycobacterium tuberculosis and, less so, the opportunistic Mycobacterium avium. They can cause disseminated infections because of their capacity to survive and proliferate within macrophage phagolysosomes. Accumulating evidence indicates that the regulation of miRNA expression is implicated in the mechanisms of defense of macrophages against mycobacterial infections. Nevertheless, the precise contribution of miRNAs is largely unknown. The present study analyzes the expression profile of miRNAs during M. avium infection of macrophages by means of microarrays. We detected that the levels of 23 miRNAs were significantly changed ≥2.5-fold 24 h after M. avium infection. In particular, MiR-125a-5p was found to be highly expressed as part of the known immunological response of macrophages to bacterial or viral infections. MiR-125a-5p overexpression inhibited the expression of target signal transducers and activators of transcription 3 (STAT3) in THP-1 cells. Conversely, inhibitors of miR-125a-5p had the opposite effect. Silencing of STAT3 significantly enhanced the level of autophagy in both uninfected and M. avium-infected cells. Overexpression of miR-125a-5p significantly increased autophagy and decreased M. avium survival within THP-1 cells. Instead, co-transfection with miR-125a-5p mimic and a human STAT3 expressing construct reversed the effects: autophagy decreased and intracellular bactericidal survival was improved. Taken together, our findings indicate that miR-125a-5p participates in the regulation of innate host defenses by targeting STAT3 and enhancing autophagy levels. The results reported here contribute to a better understanding of host defense mechanisms against mycobacterial infections and offer some clues about their control.
巨噬细胞是主要的病原体杀伤细胞。分枝杆菌对人类健康构成严重威胁，特别是结核分枝杆菌，以及机会性分枝杆菌鸟分枝杆菌。它们能够在巨噬细胞吞噬溶酶体中存活和增殖，从而导致播散性感染。越来越多的证据表明，miRNA 表达的调节与巨噬细胞抵抗分枝杆菌感染的防御机制有关。然而，miRNAs 的确切作用在很大程度上尚不清楚。本研究通过微阵列分析了巨噬细胞感染鸟分枝杆菌时 miRNA 的表达谱。我们发现，在鸟分枝杆菌感染 24 小时后，有 23 种 miRNA 的水平发生了显著变化，变化倍数≥2.5 倍。特别是，miR-125a-5p 的表达水平升高，这是巨噬细胞对细菌或病毒感染的已知免疫反应的一部分。miR-125a-5p 的过表达抑制了 THP-1 细胞中转录信号转导和激活子 3（STAT3）的表达。相反，miR-125a-5p 抑制剂则产生相反的效果。在未感染和感染鸟分枝杆菌的细胞中，沉默 STAT3 显著增强了自噬水平。miR-125a-5p 的过表达显著增加了自噬，并减少了 THP-1 细胞内鸟分枝杆菌的存活。相反，miR-125a-5p 模拟物和人 STAT3 表达构建体的共转染逆转了这种效果：自噬减少，细胞内杀菌存活能力提高。总之，我们的研究结果表明，miR-125a-5p 通过靶向 STAT3 并增强自噬水平，参与了宿主固有防御的调节。本研究结果有助于更好地理解宿主对分枝杆菌感染的防御机制，并为其控制提供了一些线索。
