Role for Neutrophil Extracellular Traps (NETs) and Platelet Aggregation in Early Sepsis-induced Hepatic Dysfunction

Severe sepsis is associated with high morbidity and mortality rates. Inflammation and coagulation play pivotal roles in the pathogenesis of sepsis leading to multiple organ failure, especially in the liver. The aim of the present study was to assess the mechanism from sepsis to liver damage in a mouse model.

We created a sepsis model by injecting lipopolysaccharide (LPS) intraperitoneally in mice. At 0, 6, 12, and 24 h following intraperitoneal injection of LPS, mice were euthanised and analyzed. Primary antibodies against myeloperoxidase (MPO), hepatic sinusoidal endothelial cells (SE-1), and P-selectin (CD62p) were used. Expression and localization in neutrophil, sinusoidal endothelial, and platelet cells were assessed by immunohistochemistry.

Immunohistochemical analyses revealed a positive staining for MPO, most abundantly in neutrophil granulocytes, within the hepatic sinusoids immediately after injection. Neutrophil extracellular trap (NET)-like structures stained for MPO, indicating the presence of neutrophils undergoing NETosis, were confirmed at 6 h after LPS administration. SE-1 staining for liver sinusoidal endothelial cells was significantly reduced at 12 h post-LPS administration through sinusoidal endothelial injury or detachment. Furthermore, the presence of extravasated platelets was confirmed in the space of Disse at 24 h after LPS administration. Blood sample analyses showed that white blood cell counts and platelet counts decreased gradually, while MPO amounts increased until 12 h after LPS administration.

We conclude that NET formation and intravasated platelet aggregation are the first steps from sepsis to liver damage, and that extravasated platelet aggregation promoted by NET-facilitated detachment of sinusoidal endothelial cells is the origin of sepsis-induced liver dysfunction.