Mechanisms of neutrophil recruitment in septic lung injury

Sammanfattning: Sepsis is one of leading cause of death despite aggressive surgical intervention and antibiotic therapies. Excessive neutrophil recruitment is a major feature in early phase with immune system dysfunction at later phase. Lung is the most vulnerable, critical and sensitive organ during sepsis process. The aim of thesis was to prevent excessive neutrophil accumulation in lung parenchyma on one hand, and to reinforcement of immune system at later phase of sepsis on other hand. We hypothesized that CD44 may have a role in mediating pulmonary recruitment of neutrophils along with Rho GTPase subfamily in more than one way for enhancing neutrophil stiffness and migration. Peptides are new evolutionary compound with multifunctional effects, especially during infection and sepsis but potential therapeutic effect of them in polymicrobial sepsis remains elusive. Polymicrobial sepsis was induced by cecal ligation and puncture, purified monoclonal antibody against CD44, Rho kinase inhibitor (Y-27632) and Rac1 inhibitor (NSC23766). Specific TDPs, GKY20 and GKY25 were injected after procedure. Edema formation, bronchoalveolar accumulation of neutrophils, myeloperoxidase activity, and CXC chemokine in lung measured after CLP. We observed that sepsis triggered clear-cut lung damage characterized by edema formation, neutrophil infiltration, and increased levels of MIP-2 in the lung. We demonstrate that immunoneutralization with anti-CD44 reduce neutrophil activation and accumulation as well as edema formation and lung injury. Pretreatment with Y-27632 reduced the CLP-induced pulmonary injury and MPO activity as well as Mac-1 on neutrophils along with clear reduction in F-actin formation. Administration of NSC23766 markedly reduced CLP-triggered neutrophil infiltration, edema formation and tissue damage in the lung. Inhibition of Rac1 decreased CLP-induced neutrophil expression of Mac-1 and pulmonary formation of CXC chemokines. NSC23766 abolished the sepsis-evoked elevation of mRNA levels of CXC chemokines and TNF-α in alveolar macrophages. Moreover, TDPs maintain CD4 T-cells function in spleen by reducing T-cell apoptosis and clear reduction in sepsis-mediated T-regulatory production. TDPs abolished CLP- evoked HMGB1 and IL-6 production. Furthermore TDPs exerts clear cut bacterial clearance in the blood and spleen. Thus, this work show more details in neutrophil extravagation during sepsis. Our data may dig up the way for establishing more specific and effective treatments of sepsis.