Abstract 26: Novel Role of Anticoagulant Heparan Sulfate in Antithrombin Anti-inflammatory Signaling

Abstract

Antithrombin (AT) therapy reduces morbidity/mortality in systemic inflammatory response syndromes, such as septic shock. These effects stem from the ability of AT to directly initiate cell signaling, which requires AT engagement with heparan sulfate proteoglycans. It is presently unclear if this process involves anticoagulant heparan sulfate (HS AT+ ), a specific motif with high affinity for AT that is produced by endothelial cells. If HS AT+ regulates anti-inflammatory signaling, then Hs3st1 -/- mice, which lack endothelial HS AT+ , should exhibit a proinflammatory state and should not benefit from AT treatment. We tested these hypotheses using a mouse model of lipopolysaccharide (LPS)-induced septic shock. Hemodynamics were monitored with a left ventricle pressure-volume catheter. Both Hs3st1 +/+ and Hs3st1 -/- mice die of cardiogenic shock. However, Hs3st1 -/- , compared to Hs3st1 +/+ , mice exhibited a much more rapid onset of death. Left ventricular gene expression profiles of mice with systemic LPS challenge showed enhanced expression of leukocyte recruitment genes (P-selectin, Cxcl10) in Hs3st1 -/- mice. Consistent with these data, LPS-treated Hs3st1 -/- mice, compared to Hs3st1 +/+ , exhibited enhanced leukocyte rolling flux within cremaster muscle venules. Thus, mice lacking HS AT+ exhibit a proinflammatory phenotype. AT treatment of Hs3st1 +/+ mice reduced both LPS-induced lethality and leukocyte-endothelial interactions. Conversely AT treatment of Hs3st1 -/- mice enhanced both LPS-induced lethality and leukocyte-endothelial interactions. Thus, AT failed to elicit anti-inflammatory effects in mice lacking HS AT+ . Our results indicate that endothelial HS AT+ is one component that mediates AT’s anti-inflammatory activity. These findings provide an initial step towards elucidating the role of HS AT+ and AT in a novel natural anti-inflammatory pathway of the blood vessel wall. This pathway is an ideal target for developing therapeutics to combat the devastating outcomes of septic shock.