呼吸道合胞病毒感染上调Toll样受体7和3基因的早期表达

Upregulation of TLR7 and TLR3 gene expression in the lung early after respiratory syncytial virus infection of mice

摘要:

【目的】Toll样受体（Toll-like receptor，TLR）7和3是两个重要的模式识别受体，分别通过识别病毒的单股和双股RNA而活化细胞。呼吸道合胞病毒（RSV）能被TLR7和TLR3识别。在RSV感染致病的早期阶段，对肺中TLR7、TLR3的表达动力学和表达丰度进行研究，并探讨其表达与肺部炎症反应的关系。【方法】我们以活RSV滴鼻感染BALB/c鼠诱导急性肺炎，在RSV感染0，1，4，8，16和24h的不同时间点，用半定量RT-PCR方法检测鼠肺TLR7、TLR3的mRNA表达，用western blot法检测核转录因子NF-κB的蛋白表达，HE染色观察肺的病理学改变。【结果】我们发现，RSV感染早期能快速上调TLR7和TLR3的基因表达水平，与正常组相比，其升高有显著性差异，并与RSV感染之间存在时间依赖关系；TLR7的反应（RSV感染1h）早于TLR3（RSV感染4 h）。肺中NF-κB在RSV感染的4 h即可被活化。RSV介导的TLR7和TLR3早期转录反应与RSV肺炎的严重程度是平行的。【结论】TLR7和TLR3确实可通过识别病毒RNA参与RSV肺炎的发生和发展，表明感染的器官在识别病毒感染和激发前炎反应时，可能经由多个TLRs。这将对开发制剂用以调节治疗性TLR配体的活性具有重要意义。

Abstract:

[Objective] TLR7 and TLR3 (Toll-like receptor, TLR) are the two of important pattern recognition receptors (PRRs) that recognize the single-stranded (ss) RNA and double-stranded (ds) RNA of virus-origin leading to activation of cells, respectively. RSV (respiratory syncytial virus, RSV) could be recognized by both TLR7 and TLR3. The aim of this study was to investigate the kinetics and profile of lung TLR7 and TLR3 expression during the early phase of the pathogenesis of RSV infection, and to explore its correlation with pulmonary inflammatory response. [Methods] We intranasally inoculated BALB/c mice with live RSV to induce acute lung inflammation, and detected the lung expression of TLR7 and TLR3 mRNA by semiquantitative RT-PCR analysis at the indicated times on day 1 after RSV infection. We also measured the transcription factor nuclear factor-kappaB (NF-κB) protein expression with western blot assay in nuclear extracts. Lung tissue sections were stained with hematoxylin and eosin and examined under a light microscope to perform the histopathological examination. [Results] We found that RSV infection could rapidly upregulate the lung expression levels of both TLR7 and TLR3 gene in a time-dependent manner, furthermore, the response of TLR7 to RSV (1 h) was prior to that of TLR3 (4 h). The mice inoculated intranasally with RSV resulted in activation of NF-κB as soon as 4 h later in lung tissue. Moreover, RSV mediated early transcriptional responses of TLR7 and TLR3 were parallelling with the severe extent of RSV-induced pulmonary inflammation. [Conclusion] TLR7 and TLR3 were really involved in RSV-induced lung inflammation by detecting the viral RNA. This may allowed the infected organism to detect viral infections and initiate a proinflammatory response via multiple TLRs. This study may be useful in the development of tools to modulate the activities of therapeutic TLR ligands.