Adrenaline Attenuates the Acute Lung Injury After Intratracheal Lipopolysaccharide Instillation: an Experimental Study

Abstract

Endotoxin is a major cause of endotoxinemia, sepsis, and pneumonia due to gram-negative bacteria. Experimental endotoxin administration via the tracheal route has been extensively used to study the biological and pathophysiologic pathways of inflammation. In particular, experimental endotoxin instillation in the respiratory tree has allowed an extended research with regard to the local response of the lungs to the pathogenic stimulus. This study aims (a) to define early events in the inflammatory cascade and (b) to evaluate the efficacy of adrenaline to ameliorate the acute pulmonary inflammation in vivo after administration of intratracheal lipopolysaccharide (LPS) in an in vivo animal model. Two groups of animals were used for that purpose, a control group (single LPS administration) and a study group (subcutaneous adrenaline infusion following LPS administration). We found that mononuclear recruitment, along with an increased population of CD4⁺ T lymphocytes, is an early event during the course of LPS-challenged inflammation. In the study group, we determined that adrenaline mediated the lung inflammation in a statistically significant degree. By the use of immunohistochemistry, we identified (1) an increased population of CD4⁺ T lymphocytes in the inflammatory infiltrate, further endorsing the hypothesis that T-helper lymphocytes, along with macrophages, secrete cytokines which amplify the inflammatory response, and (2) an upregulation of ICAM-1 expression, suggesting an important role in the early pathogenesis of LPS-induced acute lung injury. Our study establishes that systemic adrenaline administration after LPS instillation may ameliorate the inflammatory lung response in vivo.