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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2004;24:1963.)
© 2004 American Heart Association, Inc.

Thrombosis

PI3K-Akt Pathway Suppresses Coagulation and Inflammation in Endotoxemic Mice

Gernot Schabbauer; Michael Tencati; Brian Pedersen; Rafal Pawlinski; Nigel Mackman

From the Department of Immunology, The Scripps Research Institute, La Jolla, Calif.

Correspondence to Dr Nigel Mackman, The Scripps Research Institute, Departments of Immunology and Cell Biology, 10550 North Torrey Pines Road, CVN-18, La Jolla, CA 92037. E-mail nmackman{at}scripps.edu

Objective— In endotoxemia, lipopolysaccharide (LPS) induces a systemic inflammatory response and intravascular coagulation. Monocytes orchestrate the innate immune response to LPS by expressing a variety of pro-inflammatory cytokines, such as tumor necrosis factor- (TNF-), and the procoagulant molecule, tissue factor (TF). In this study, we analyzed the role of the phosphoinositide 3-kinase (PI3K)-Akt pathway in the activation of coagulation and the innate immune response in a mouse model of endotoxemia.

Methods and Results— Wortmannin and LY294002 were used to inhibit the PI3K-Akt pathway. We found that wortmannin inhibited LPS-induced Akt phosphorylation in blood cells. Inhibition of the PI3K-Akt pathway significantly increased TF mRNA expression in blood cells, TF antigen, and thrombin–antithrombin III levels in the plasma, and fibrin deposition in the liver of endotoxemic mice. Inhibition of the PI3K-Akt pathway also strongly enhanced LPS-induced cytokine expression and the levels of soluble E-selectin in the plasma, suggesting enhanced activation of both monocytes and endothelial cells. Wortmannin treatment also increased the number of macrophages in the liver and kidney of endotoxemic mice. Finally, wortmannin and LY294002 dramatically reduced the survival time of endotoxemic mice.

Conclusions— These data suggest that the PI3K-Akt pathway suppresses LPS-induced inflammation and coagulation in endotoxemic mice.

In this study, we analyzed the role of the phosphoinositide 3-kinase (PI3K)-Akt pathway in a mouse model of endotoxemia. Inhibition of PI3K strongly enhanced LPS-induced coagulation and inflammation, which resulted in reduced survival of endotoxemic mice.

Key Words: blood coagulation • PI3 kinase • inflammation • endothelium • fibrin • thrombosis

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