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. 2017 Sep 27;12(9):e0185474.
doi: 10.1371/journal.pone.0185474. eCollection 2017.

Early and late pulmonary effects of nebulized LPS in mice: An acute lung injury model

Natália de Souza Xavier Costa  1 , Gabriel Ribeiro Júnior  1 , Adair Aparecida Dos Santos Alemany  1 , Luciano Belotti  1 , Douglas Hidalgo Zati  1 , Marcela Frota Cavalcante  2 , Mariana Matera Veras  1 , Susan Ribeiro  3   4 , Esper Georges Kallás  3 , Paulo Hilário Nascimento Saldiva  1 , Marisa Dolhnikoff  1 , Luiz Fernando Ferraz da Silva  1
Affiliations

Early and late pulmonary effects of nebulized LPS in mice: An acute lung injury model

Natália de Souza Xavier Costa et al. PLoS One. .

Abstract

Background and objective: Acute respiratory distress syndrome (ARDS) has a high mortality rate of 35-46% depending on its severity. Animal models are crucial to better understand the pathophysiology of diseases, including ARDS. This study presents a feasible animal model of acute lung injury (ALI) using nebulized lipopolysaccharide (LPS) in a non-invasive approach, focusing on its short and long-term effects.

Methods: Mice received nebulized LPS or vehicle only (control group). Blood, BALF and lung tissue were collected 24 hours (LPS 24h) or 5 weeks (LPS 5w) after the nebulized LPS-induced lung injury. Inflammatory cytokines were assessed in the blood serum, BALF and lung tissue. Stereological analyses and remodeling changes were assessed by histology and immunohistochemistry at the specified time points.

Results: The LPS 24h group showed increased pro-inflammatory cytokine levels, intense cell influx, increased total septal volume, septal thickening and decreased surface density of the alveolar septa. The LPS 5w group showed persistent lung inflammation, septal thickening, increased total lung volume, accentuated collagen deposition, especially of collagen type I, and decreased MMP-2 protein expression.

Conclusion: We present a feasible, reproducible and non-invasive nebulized-LPS animal model that allows the assessment of both the acute and late phases of acute lung injury. The presence of lung remodeling with collagen deposition after 5 weeks makes it useful to study the pathophysiology, complications, and possible therapeutic intervention studies that aim to understand and reduce pulmonary fibrosis in the late phases of ALI.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Representative photomicrographs of lung tissue (H & E staining).
(A and B) Control group (10x and 20x, respectively): thin alveolar septa and no significant inflammation; (C and D) LPS 24h group (10x and 20x, respectively): intense presence of polymorphonuclear cells, alveolar thickening and focal areas of hemorrhage; (E and F) LPS 5w group (10x and 20x, respectively): alveolar thickening, persistent inflammatory cells and irregular alveolar enlargement.
Fig 2
Fig 2. Graphical representation of total cells and differential counts present in peripheral blood, BALF and lung tissue.
* p<0.05.
Fig 3
Fig 3. Graphical representation of quantitative results of IL-1beta, IL6 and TNF-alpha in the blood serum, BALF, protein and gene expression in lung tissue.
* p<0.05.
Fig 4
Fig 4. Graphical representation of total septal volume, septal thickness, septal surface density and alveolar space volume.
* p<0.05.
Fig 5
Fig 5. Representative photomicrographs of collagen in the lung tissue.
A and B–Control group 40x (Sirius Red staining and immunostained collagen type I, respectively); C and D–LPS 24h group 40x (Sirius Red staining and immunostained collagen type I, respectively); E and F–LPS 5w group 40x (Sirius Red staining and immunostained collagen type I, respectively).
Fig 6
Fig 6. Graphical representation of lung parenchyma total collagen, collagen type I and protein expression of MMP-2.
* p<0.05.
See this image and copyright information in PMC

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