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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

The present protocol describes a lung injury model in mice using oleic acid to mimic acute respiratory distress syndrome (ARDS). This model increases the inflammatory mediators on edema and decreases lung compliance. Oleic acid is used in the salt form (oleate) since this physiological form avoids the risk of embolism.

Abstract

Acute respiratory distress syndrome (ARDS) is a significant threat to critically ill patients with a high fatality rate. Pollutant exposure, cigarette smoke, infectious agents, and fatty acids can induce ARDS. Animal models can mimic the complex pathomechanism of the ARDS. However, each of them has limitations. Notably, oleic acid (OA) is increased in critically ill patients with harmful effects on the lung. OA can induce lung injury by emboli, disrupting tissue, altering pH, and impairing edema clearance. OA-induced lung injury model resembles various features of ARDS with endothelial injury, increased alveolar permeability, inflammation, membrane hyaline formation, and cell death. Herein, induction of lung injury is described by injecting OA (in salt form) directly into the lung and intravenously in a mouse since it is the physiological form of OA at pH 7. Thus, the injection of OA in the salt form is a helpful animal model to study lung injury/ARDS without causing emboli or altering the pH, thereby getting close to what is happening in critically ill patients.

Introduction

Ashbaugh et al.1, in 1967, first described the acute respiratory distress syndrome (ARDS) and since then has been through multiple revisions. According to the Berlin definition, ARDS is a pulmonary inflammation that leads to an acute respiratory failure and hypoxemia (PaO2/FiO2 > 300 mm Hg) due to imbalance in the ventilation to perfusion ratio, diffuse bilateral alveolar damage (DAD) and infiltrate, increased lung weight, and edema2,3. The pulmonary parenchyma is a complex cellular environment compounded by epithelial, endothelial, and other cells. These cells....

Protocol

The procedures used in this study were approved by the Ethics Committee on the Use of Animals of the Oswaldo Cruz Foundation (CEUA licenses n°002-08, 36/10 and 054/2015). Male Swiss Webster mice weighing between 20-30 g, provided by the Institute of Science and Technology in Biomodels (ICTB) of the Oswaldo Cruz Foundation (FIOCRUZ), were used for the experiments. The animals were kept in ventilated isolators in the Pavilhão Ozório de Almeida's vivarium, and water and food were available ad libitum<.......

Representative Results

In an uninjured lung, alveolar fluid clearance occurs by the transport of ions through the intact alveolar epithelial layer. The osmotic gradient carries fluid from the alveoli into the pulmonary interstitium, where it is drained by lymphatic vessels or reabsorbed. Na/K-ATPase drives this transport11. OA is an inhibitor of Na/K-ATPase27 and sodium channel21, which may contribute to edema formation, as we have already suggested23

Discussion

Selecting the correct ARDS model is essential to carry out the preclinical studies, and the evaluator must consider all the possible variables, such as age, sex, administration methods, and others6. The chosen model must reproduce the disease based on risk factors such as sepsis, lipid embolism, ischemia-reperfusion of the pulmonary vasculature, and other clinical risks14. However, no animal model used for ARDS can recreate all the human syndrome's features. Multiple in.......

Acknowledgements

This research was funded by the Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (FIOCRUZ), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Grant 001, Programa de Biotecnologia da Universidade Federal Fluminense (UFF), Universidade Federal do Estado do Rio de Janeiro (UNIRIO), Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Figure 1 and Figure 2 are created with BioRender.com.

....

Materials

NameCompanyCatalog NumberComments
Anesthetic vaporizerSurgiVetmodel 100
Braided slik thread with needle number 5Shalon medicalN/A
Cabinet vivariumInsight Model EB273
CentrifugeEppendorf5430/5430R
CytofunnelThermoFisher11-025-48
Drontal puppyBayerN/A
Hank's balanced SaltsSigma-AldrichH4981
HeatpadtkreproduçãoTK-500
Hydrocloric AcidSigma-Aldrich30721
Insulin syringe UltrafineBD328322
Isoforine 1mL/mLCristáliaN/A
KetamineSyntecN/A
May-Grunwald-GiemsaSigma-Aldrich205435
Micro BCA Protein Assay KitThermoFisher23235
Microscope  PrimoStarCarl Zeiss
Mouse IL-1 beta duoSet ELISAR&D systemDY401
Mouse IL-6 duoSet ELISAR&D systemDY406
Mouse TNF-alpha duoSet ELISAR&D systemDY410
Neubauer chamber improved bright-lineGlobal optics
Oleic Acid (99%)Sigma-AldrichO1008
Osmium tetroxide solution (4%)Sigma-Aldrich75632
Peripheral Intravenous Catherter 20 GBD Angiocath388333
Prism 8 (graphic and statistic software)GraphpadN/A
Prostaglandin E2 ELISA Kit -MonoclonalCayman Chemical514010
Shandon Cytospin 3ThermoFisherN/A
Sodium hydroxideMerck1,06,49,81,000
SpectrophotometerMolecular DevicesSpectraMax ABS plus
Swiss webster miceICTB/FIOCRUZN/A
Syringe 1 mLBD990189
Tris-baseBio Rad161-0719Electrophoresis purity reagent
Türk's solutionSigma-Aldrich93770
XilazineSyntecN/A

References

  1. Ashbaugh, D. G., Bigelow, D. B., Petty, T. L., Levine, B. E. Acute respiratory distress in adults. Lancet. 2 (7511), 319-323 (1967).
  2. The ARDS Definition Task Force. Acute respiratory distress syndrome: The Berlin definition.

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