Noninvasive Intratracheal Lipopolysaccharide Instillation in Mice

Summary

Here, we propose a protocol for intratracheal lipopolysaccharide (LPS) delivery via noninvasive oropharyngeal endotracheal intubation. This method minimizes the trauma of the surgical procedure for the animal and accurately delivers LPS to the trachea and then to the lungs.

Abstract

The acute lung injury (ALI) mouse model induced by lipopolysaccharide (LPS) or endotoxin is still among the most commonly used models in animal studies of acute lung injury or acute inflammation. The current most commonly used methods in acute lung injury mouse models are an intraperitoneal injection of LPS and tracheostomy for the tracheal infusion of LPS. However, the former method lacks lung targeting and damages other organs, and the latter method induces operative trauma, infection risk, and a low survival rate. Here, we recommend a noninvasive oropharyngeal endotracheal intubation method for LPS instillation in mice. In this method, LPS is noninvasively introduced into the trachea through the oropharyngeal cavity to be instilled into the lung with the help of an apparatus for endotracheal intubation. This method not only assures lung targeting but also avoids damage and the risk of death in the animals. We expect that this approach will become widely used in the field of acute lung injury.

Introduction

Acute lung injury (ALI) is a common clinical syndrome. Under a variety of pathogenic factors, the disruption of the physiological barrier of the lung epithelial cells and vascular endothelial cells leads to increased alveolar permeability, thereby causing decreased lung compliance, pulmonary edema, and severe hypoxemia¹. Acute respiratory distress syndrome (ARDS) is the most severe form of ALI. Uncontrolled inflammation and oxidative stress damage are considered to be the main causes of ALI and the more severe ARDS². When alveolar epithelial cells are directly injured due to trauma, the inflammatory response chain of alv....

Protocol

The animal experiment protocol was reviewed and approved by the Management Committee of Chengdu University of Traditional Chinese Medicine (Record No. 2021-11). Male C57/BL mice (20-25 g, 6-8 weeks old) were used for the present study. The mice were kept in an animal chamber and were free to drink and eat during the experiment.

1. Preparation

1. Ensure that the intubation platform consists of a base, a riser, a paper clip, two rubber bands, and some strings. Take a string, pass the string through the two holes at the top of the riser, and tie the two ends of the string, respectively, to the small protrusions at the....

Results

The proposed method for LPS instillation in mice was verified by evaluating the expression of the inflammatory cytokine TNF-α and the lung dry-wet weight ratio 12 h after LPS instillation. There were four groups in the experiment: blank control (without any treatment), surgical intubation¹⁶, intranasal^17,18, and noninvasive oropharyngeal intubation (n = 6). Compared with the blank control group, the serum T.......

Discussion

Initially, we looked inside the oral cavity to find the location of the trachea¹⁹. However, during this process, we discovered that the trachea of C57/BL mice is narrow, which makes it difficult to find the correct location by this method without the help of equipment such as an endoscope²⁰. Upon further exploration, we found that the light from the intubator lamp could penetrate the surface of the body, allowing the operator to determine the position of the cannula

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Lipopolysaccharide	MERK	L4130	LPS
Microliter Syringes	SHANGHAI GAOGE INDUSTRY AND TRADE CO., LTD	10028505008124	To deliver LPS
Mouse cannula	RWD Life Science	803-03008-00	Mouse cannula
Mouse intubation kit	RWD Life Science	903-03027-00	Including a base, a riser, a intubator, a surgical forceps and some strings
Pasteur pipette	Biosharp life science	BS-XG-03	To verify the success of intubation
Pentobarbital sodium	Beijing Chemical Co., China	20220918	To anesthetize mice