Identification with MRI of the pleura as a major site of the acute inflammatory effects induced by ovalbumin and endotoxin challenge in the airways of the rat

Abstract

Inflammatory effects in the rat lung have been investigated, non-invasively by MRI, at early time points (3 and 6 h) after ovalbumin (OA) or endotoxin (LPS) challenges. Six hours after challenge with OA, a strong, even inflammatory signal was present around the periphery of the lung in a region corresponding to the pleura. Histological analysis confirmed the presence of marked edema associated with the pleural cavity of OA-treated animals. Lower levels of pleural edema were observed in MRI and histological evaluation of LPS-treated animals and no abnormality was observed in actively sensitized and naïve, saline-treated groups. Diffuse edematous signals were detected in the lung 3 and 6 h after challenge with OA or LPS; the signal volumes were larger at both time points following OA instillation. Bronchoalveolar lavage (BAL) fluid analysis performed 6 h after challenge revealed increased levels of protein and greater cellular activation in OA- than in LPS-treated animals. Furthermore, increased levels of peribronchial edema were found by histology 6 h after OA. BAL fluid and histological assessments demonstrated that the inflammatory signals were due to edema and not mucus as no significant changes in BAL mucin concentrations or differences in goblet cells were identified between OA or LPS challenge and their respective vehicle groups. Our data show that MRI is able to detect, non-invasively, inflammatory signals in both the lung and the pleura in spontaneously breathing animals, highlighting its potential to study the consequences of pulmonary insults on both sites.

Electroporation-mediated Gene Transfer of the Na+,K+-ATPase Rescues Endotoxin-induced Lung Injury

“…During the course of these experiments, we noticed that, upon injury with LPS, the incidence of pleural effusions increased, as has been previously noted (11). At 2 and 3 days after LPS treatment, 3.4 6 2.1 and 3.3 6 1.2 ml of pleural effusion was collected from the mice, respectively.…”

In vivo monitoring of cystic fibrosis-like lung disease in mice by volumetric computed tomography

“…Thus, there is agreement that the usefulness of mCT for longitudinal in vivo studies is limited [19,33]. Other investigators employed magnetic resonance imaging (MRI) for visualisation of the pleura and gross pulmonary fluid in rat models of pulmonary inflammation [34,35]. However, the limited spatial resolution of MRI precludes its use for structural analysis of airways and lung parenchyma in small laboratory animals.…”

A View on Imaging in Drug Research and Development for Respiratory Diseases

“…A characteristic feature of lung inflammation is edema in the airways caused by an increase in the permeability of the microvasculature. MRI has been used to quantify edema in the lungs of spontaneously breathing mice (Blé et al, 2008;Conti et al, 2010) or rats (Beckmann et al, 2001a;Tigani et al, 2002;Quintana et al, 2006a) actively sensitized to and challenged with ovalbumin (OVA). The MRI signals after OVA challenge correlated significantly with a variety of inflammatory parameters determined in the BAL fluid recovered from the same animals.…”