Enhancement of Methacholine-Evoked Tracheal Contraction Induced by Bacterial Lipopolysaccharides Depends on Epithelium and Tumor Necrosis Factor

Abstract

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.

Forced expiration measurements in mouse models of obstructive and restrictive lung diseases

“…increased central airway resistance, R n ). In mice with ALI, the absence of MCh hyperresponsiveness in terms of R n is in line with the findings of Secher et al [ 24 ] in male C57BL/6 mice. However, this latter study contradicts the work of Card et al [ 25 ], in which it was reported that LPS-treated male C57BL/6 mice, and not female, exhibit an exaggerated MCh-evoked airway response.…”

Brazilian Green Propolis: Anti-Inflammatory Property by an Immunomodulatory Activity

“…One day before the first LPS application, the control, E10, and E11 treatment was started. This treatment continued for four days, and the sacrifice of the animals was performed 24 hours after the last application of LPS, when the bronchoalveolar lavage was performed as mentioned above [26]. …”

Tracheomalacia in bronchopulmonary dysplasia: Trachealis hyper‐relaxant responses to S‐nitrosoglutathione in a hyperoxic murine model

“…Segments from trachealis, main LB, and 2nd generation IPB were isolated and dissected free of connective tissue and cut into 1 to 2‐mm length segments (Figure A). A subgroup of IPB smooth muscle rings were gently denuded of lumen epithelium by fiber debridement under light microscopy as previously described . Segments were mounted on temperature‐controlled small vessel wire myographs (model 500A; Danish Myo Technology, Denmark) (Figure B) at 37°C, and gassed continuously with 21% O 2 , 5% CO 2 , and 74% N 2 (pH 7.35).…”