Conclusions
MTBI attenuates pneumonia-induced acute lung injury through the modulation of alveolar macrophage bactericidal capacity and M1 polarization in bacterial pneumonia model.
Methods
Mice (n = 104) were divided into control, MTBI, pneumonia, and MTBI + pneumonia groups. MTBI was induced by the weight-drop method. Pneumonia was induced by intratracheal injection with P. aeruginosa Xen5 strain. Animals were killed 24 h after bacterial challenging. Histological, cellular, and molecular indices of brain and lung injury were assessed using various methods.
Results
Mice in both the MTBI and pneumonia groups had more Fluoro-Jade C-positive neurons than did the controls ( P < 0.01), but mice in the MTBI + pneumonia group had fewer Fluoro-Jade C-positive cells than did the pneumonia group ( P < 0.01). The MTBI + pneumonia mice showed decreased bacterial load ( P < 0.05), reduced lung injury score and pulmonary permeability ( P < 0.01), less inflammatory cells, and lower levels of proinflammatory cytokines (TNF-α and IL-1β; P < 0.01) when compared with the pneumonia group. Molecular analysis indicated lower levels of phosphorylated nuclear factor-κB in the lung of MTBI + pneumonia mice compared with the pneumonia group ( P < 0.01). Furthermore, alveolar macrophages from MTBI mice exhibited enhanced bactericidal capacity compared with those from controls ( P < 0.01). Moreover, MTBI + pneumonia mice exhibited less CD86-positive M1 macrophages compared with the pneumonia group ( P < 0.01). Conclusions: MTBI attenuates pneumonia-induced acute lung injury through the modulation of alveolar macrophage bactericidal capacity and M1 polarization in bacterial pneumonia model.