Synergistic Effects of Resistive Breathing on Endotoxin-Induced Lung Injury in Mice

Abstract

Dimitrios Toumpanakis,1 Constantinos Glynos,1 Pinelopi Schoini,2 Vyronia Vassilakopoulou,1 Athanasia Chatzianastasiou,1 Maria Dettoraki,1 Eleftheria Mizi,1 Dionysios Tsoukalas,1 Fotis Perlikos,1 Christina Magkou,3 Andreas Papapetropoulos,4,5 Theodoros Vassilakopoulos1,6 1“Marianthi Simou” Applied Biomedical Research and Training Center, Medical School, National and Kapodistrian University of Athens, Evangelismos Hospital, Athens, Greece; 2 4th Respiratory Clinic, “Sotiria” General Hospital for Thoracic Diseases of Athens, Athens, Greece; 3Department of Pathology, Evangelismos Hospital, Athens, Greece; 4Biomedical Research Foundation of the Academy of Athens, Athens, Greece; 5Division of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece; 6Department of Physiology, Medical School, National and Kapodistrian University of Athens, Athens, GreeceCorrespondence: Dimitrios Toumpanakis, “Marianthi Simou” Applied Biomedical Research and Training Center, Medical School, National and Kapodistrian University of Athens, Evangelismos Hospital, 3rd Ploutarchou Street, 2nd Floor, Athens, 10675, Greece, Tel [phone], Email [email protected]: Resistive breathing (RB) is characterized by forceful contractions of the inspiratory muscles, mainly the diaphragm, resulting in large negative intrathoracic pressure and mechanical stress imposed on the lung. We have shown that RB induces lung injury in healthy animals. Whether RB exerts additional injurious effects when added to pulmonary or extrapulmonary lung injury is unknown. Our aim was to study the synergistic effect of RB on lipopolysaccharide (LPS)-induced lung injury.Methods: C57BL/6 mice inhaled an LPS aerosol (10mg/3mL) or received an intraperitoneal injection of LPS (10 mg/kg). Mice were then anaesthetized, the trachea was surgically exposed, and a nylon band of a specified length was sutured around the trachea, to provoke a reduction of the surface area at 50%. RB through tracheal banding was applied for 24 hours. Respiratory system mechanics were measured, BAL was performed, and lung sections were evaluated for histological features of lung injury.Results: LPS inhalation increased BAL cellularity, mainly neutrophils (p < 0.001 to ctr), total protein and IL-6 in BAL (p < 0.001 and p < 0.001, respectively) and increased the lung injury score (p = 0.001). Lung mechanics were not altered. Adding RB to inhaled LPS further increased BAL cellularity (p < 0.001 to LPS inh.), total protein (p = 0.016), lung injury score (p = 0.001) and increased TNFa levels in BAL (p = 0.011). Intraperitoneal LPS increased BAL cellularity, mainly macrophages (p < 0.001 to ctr.), total protein levels (p = 0.017), decreased static compliance (p = 0.004) and increased lung injury score (p < 0.001). Adding RB further increased histological features of lung injury (p = 0.022 to LPS ip).Conclusion: Resistive breathing exerts synergistic injurious effects when combined with inhalational LPS-induced lung injury, while the additive effect on extrapulmonary lung injury is less prominent.Keywords: endotoxin, resistive breathing, lung, inflammation, injury

Keywords

• endotoxin
• resistive breathing
• lung
• inflammation
• injury