Noninvasive detection of endotoxin-induced mucus hypersecretion in rat lung by MRI

Abstract

Using magnetic resonance imaging (MRI), we detected a signal in the lungs of Brown Norway rats after intratracheal administration of endotoxin [lipopolysaccharide (LPS)]. The signal had two components: one, of diffuse appearance and higher intensity, was particularly prominent up to 48 h after LPS; the second, showing an irregular appearance and weaker intensity, was predominant later. Bronchoalveolar lavage fluid analysis indicated that generalized granulocytic (especially neutrophilic) inflammation was a major contributor to the signal at the early time points, with mucus being a major factor contributing at the later time points. The facts that animals can breathe freely during data acquisition and that neither respiration nor cardiac triggering is applied render this MRI approach attractive for the routine testing of anti-inflammatory drugs. In particular, the prospect of noninvasively detecting a sustained mucus hypersecretory phenotype in the lung brings an important new perspective to models of chronic obstructive pulmonary diseases in animals.

Characterization of cigarette smoke-induced inflammatory and mucus hypersecretory changes in rat lung and the role of CXCR2 ligands in mediating this effect

“…Samples were assayed by a mucin enzyme-linked lectin assay as previously described by Jackson and colleagues (2,11). Briefly, 96-well plates were coated with UEA-1 (Sigma) at 1.25 g/ml overnight, blocked for 1 h at 37°C, followed by the addition of purified human mucin standard (24 units/ml) and BAL fluid samples in duplicate, and incubated for 1 h at 37°C.…”

Bleomycin‐induced lung injury assessed noninvasively and in spontaneously breathing rats by proton MRI

“…As demonstrated earlier, (22) averaging over several respiratory cycles suppressed artifacts caused by movements of the chest and the heart without the necessity of triggering the data acquisition. This technique easily To detect changes in lung fluid volume that might arise from inflammatory processes (e.g., edema, mucus hypersecretion) (22,24) or from massive fibrosis-related tissue collapse, a gradient-echo sequence with the following parameters was applied: repetition time (TR) ϭ 5.6 msec; echo time (TE) ϭ 2.7 msec; flip angle of the excitation pulse ϭ ϳ15°; field-of-view ϭ 6 ϫ 6 cm 2 ; matrix size ϭ 256 ϫ 128; and slice thickness ϭ 1.5 mm. A single slice image was obtained by computing the 2D Fourier transform (2DFT) of the averaged signal from 45 individual image acquisitions and interpolating the data set to 256 ϫ 256 pixels.…”

“…A single slice image was obtained by computing the 2D Fourier transform (2DFT) of the averaged signal from 45 individual image acquisitions and interpolating the data set to 256 ϫ 256 pixels. An average of 45 individual image acquisitions has been shown earlier to be effective for suppressing cardiac and respiratory movement artifacts (22,24,25). There was an interval of 530 msec between individual image acquisitions, resulting in a total acquisition time of 59 seconds for a single slice.…”

“…A detailed description of the procedure to obtain BAL fluid and the analysis of the parameters of inflammation therein has been provided earlier (22,24). Briefly, after killing the animals with an overdose of pentothal, the lungs were lavaged three times with 4 mL of ethylene diamine tetraacetic acid ϩ phosphate buffered saline (solution A).…”

“…Mucus in BAL fluid was assessed from 1 mL of BAL fluid per animal, retrieved before lavage for cell count and differentiation. The sandwich enzyme-linked lectin assay as described earlier (Beckmann et al (24)) was used to determine the quantity of mucus by measuring the optical density of flat-bottomed Coastar plates coated with Ulex europaeus agglutinin-1 (Sigma) at a wavelength of 492 nm using a SpectraMax 250 plate reader (Molecular Devices, Surrey, UK).…”