Potential Mechanisms for a Proinflammatory Vascular Cytokine Response to Coagulation Activation

We have previously shown that an anticoagulant could attenuate inflammation in animal models of sepsis with disseminated intravascular coagulation (DIC) and that coagulation activation of human whole blood ex vivo results in a proinflammatory cytokine response. The current studies were performed to better understand mechanisms for the blood cell cytokine response and extend the investigation of such a response to endothelial cells as likely contributors to a vascular inflammatory response. Utilizing cell separation techniques, it was determined that the whole blood IL-8 response to coagulation activation or thrombin, specifically, was mediated by CD14+ monocytes. Moreover, thrombin was observed to stimulate both IL-8 and IL-6 production in cultured mononuclear cells. Analyses of the effects of coagulation activation and thrombin were extended to cultured human endothelial cells, and a similar cytokine response was observed. Thrombin catalytic activity appeared essential, since hirudin reduced thrombin-stimulated proinflammatory cytokine production in cultured monocytes and endothelial cells and prothrombin only weakly mimicked the thrombin response. The endothelial cell IL-8 and IL-6 response to thrombin could be mimicked by the thrombin receptor agonist peptide (TRAP), implicating a functional role of the classic thrombin receptor. Altogether, the results facilitate a better understanding of potential proinflammatory vascular responses to coagulation activation.