Secher T, Rodrigues Coelho F, Noulin N, Lino Dos Santos Franco A, Quesniaux V, Lignon J, Mitchell J, Moser R, Gomes E, Mirotti L, Tavares-de-Lima W, Ryffel B, Vargaftig B Boris, Russo M
Laboratory Molecular Immunology and Embryology, University of Orleans and CNRS, Orleans, France.
J Allergy (Cairo). 2012;2012:494085. doi: 10.1155/2012/494085. Epub 2012 Mar 11.
Inhaled bacterial lipopolysaccharides (LPSs) induce an acute tumour necrosis factor-alpha (TNF-α-) dependent inflammatory response in the murine airways mediated by Toll-like receptor 4 (TLR4) via the myeloid differentiation MyD88 adaptor protein pathway. However, the contractile response of the bronchial smooth muscle and the role of endogenous TNFα in this process have been elusive. We determined the in vivo respiratory pattern of C57BL/6 mice after intranasal LPS administration with or without the presence of increasing doses of methacholine (MCh). We found that LPS administration altered the basal and MCh-evoked respiratory pattern that peaked at 90 min and decreased thereafter in the next 48 h, reaching basal levels 7 days later. We investigated in controlled ex vivo condition the isometric contraction of isolated tracheal rings in response to MCh cholinergic stimulation. We observed that preincubation of the tracheal rings with LPS for 90 min enhanced the subsequent MCh-induced contractile response (hyperreactivity), which was prevented by prior neutralization of TNFα with a specific antibody. Furthermore, hyperreactivity induced by LPS depended on an intact epithelium, whereas hyperreactivity induced by TNFα was well maintained in the absence of epithelium. Finally, the enhanced contractile response to MCh induced by LPS when compared with control mice was not observed in tracheal rings from TLR4- or TNF- or TNF-receptor-deficient mice. We conclude that bacterial endotoxin-mediated hyperreactivity of isolated tracheal rings to MCh depends upon TLR4 integrity that signals the activation of epithelium, which release endogenous TNFα.
吸入性细菌脂多糖（LPS）可在小鼠气道中诱导一种急性的、依赖肿瘤坏死因子-α（TNF-α）的炎症反应，该反应由Toll样受体4（TLR4）通过髓样分化因子MyD88衔接蛋白途径介导。然而，支气管平滑肌的收缩反应以及内源性TNFα在此过程中的作用一直尚不明确。我们测定了鼻内给予LPS且存在或不存在递增剂量乙酰甲胆碱（MCh）时C57BL/6小鼠的体内呼吸模式。我们发现，给予LPS会改变基础呼吸模式以及MCh诱发的呼吸模式，该模式在90分钟时达到峰值，此后在接下来的48小时内下降，7天后恢复到基础水平。我们在可控的离体条件下研究了分离的气管环对MCh胆碱能刺激的等长收缩。我们观察到，气管环与LPS预孵育90分钟可增强随后MCh诱导的收缩反应（高反应性），而用特异性抗体预先中和TNFα可阻止这种反应。此外，LPS诱导的高反应性依赖于完整的上皮，而TNFα诱导的高反应性在无上皮时仍能很好地维持。最后，与对照小鼠相比，LPS诱导的对MCh的增强收缩反应在TLR4缺陷、TNF缺陷或TNF受体缺陷小鼠的气管环中未观察到。我们得出结论，细菌内毒素介导的分离气管环对MCh的高反应性取决于TLR4的完整性，TLR4发出信号激活上皮，上皮释放内源性TNFα。
