Non-Invasive Endotracheal Administration of Lipopolysaccharide to Induce Acute Lung Injury in Rodents

The scope of our research is to develop a clinically relevant, non-invasive model of acute lung injury to improve the clinical testing. Modern lung biology research integrates advanced lung models, nano carriers and aerosol technologies to optimize and study targeted drug delivery within physiologically relevant models. To begin, weigh each animal using a calibrated balance.

Prepare the lipopolysaccharide solution by diluting the lyophilized Escherichia coli lipopolysaccharide in sterile PBS to achieve the desired concentration. After anesthetizing the rat, check the depth of anesthesia and position the animal in a semi recumbent position with its incisors suspended on a solid supporting platform. Then open the mouth of the anesthetized animal.

Gently grasp the tongue using curved blunt ended forceps and retract it in an upward and lateral direction. Then carefully insert the laryngoscope, aligning it precisely for optimal visualization of the tracheal opening. Now, draw 100 microliters of lipopolysaccharide solution into a syringe and attach it to a 16 gauge rat endotracheal tube.

Administer the lipopolysaccharide solution near the tracheal opening. Immediately after installation, gently occlude the nostrils using blunt ended forceps for two to four seconds to promote aspiration of the solution into the lungs through the trachea. Then, carefully reposition the tongue to its normal anatomical orientation following lipopolysaccharide delivery.

Transfer the animal back to its cage and closely monitor for any signs of respiratory compromise or choking for at least one minute. After performing bronchoalveolar lavage and tracheotomy, gently infused two milliliters of cold PBS into the lungs and retrieve the fluid carefully. Centrifuge the collected lavage fluid at 5, 000 G for five minutes at four degrees Celsius.

Use the supernatant to detect inflammatory markers. Collect the lungs for histopathological examination, or homogenize them for myeloperoxidase activity. Compared to the control group, the group euthanized 24 hours after lipopolysaccharide installation, showed a significant increase in interleukin-1 beta levels, elevated myeloperoxidase activity and higher total protein content.

At 120 hours post lipopolysaccharide installation, interleukin-1 beta, myeloperoxidase activity and total protein levels had returned to near baseline values. Lung histopathology at 24 hours demonstrated disintegrated alveolar structure, swelling of the alveolar wall, hemolysis, and severe neutrophil infiltration. Lung architecture was restored at 120 hours post lipopolysaccharide installation.

Using non-invasive endotracheal pulmonary delivery, we created a self-limiting acute lung injury models for testing targeted therapeutics and studying lung repair. The key benefit of this method is it's precise non-traumatic delivery, which facilitates repeated dosing in the same animal and customization for a particular research objectives. Future acute lung injury research will focus on developing targeted therapies and understanding lung injury and repair mechanism.