The endothelial cell protein C receptor aids in host defense against Escherichia coli sepsis

Abstract

The influence of the endothelial protein C receptor (EPCR) on the host response to Escherichia coli was studied. Animals were treated with 4 separate protocols for survival studies and analysis of physiologic and biochemical parameters: (1) monoclonal antibody (mAb) that blocks protein C/activated protein C binding to EPCR plus sublethal numbers of E coli (SLEC) (n = 4); (2) mAb to EPCR that does not block binding plus SLEC (n = 3); (3) SLEC alone (n = 4); and (4) blocking mAB alone (n = 1). Those animals receiving blocking mAb to EPCR plus sublethal E coli died 7 to 54 hours after challenge, whereas all animals treated with the other protocols were permanent survivors. Histopathologic studies of tissues from animals receiving blocking mAb plus SLEC removed at postmortem were compared with those animals receiving SLEC alone killed at T+24 hours. The animals receiving the blocking mAb exhibited consumption of fibrinogen, microvascular thrombosis with hemorrhage of both the adrenal and renal cortex, and an intense influx of neutrophils into the adrenal, renal, and hepatic microvasculature, whereas the tissues from animals receiving only sublethal E coli exhibited none of these abnormal histopathologic changes. Compared with the control animals, the animals receiving the blocking mAb exhibited significantly elevated serum glutamic pyruvic transaminase, anion gap, thrombin-antithrombin complex, IL-6, IL-8, and soluble thrombomodulin. The levels of circulating activated protein C varied too widely to allow a clear determination of whether the extent of protein C activation was altered in vivo by blocking protein C binding to EPCR. We conclude that protein C/activated protein C binding to EPCR contributes to the negative regulation of the coagulopathic and inflammatory response to E coli and that EPCR provides an additional critical step in the host defense against E coli.

The benefits of excess EPCR

“…They did, however, exhibit an eightfold increase in APC generation in response to infusion of thrombin and were partially resistant to a lethal dose of bacterial lipopolysaccharide. These findings confirm and extend the results of previous studies in which EPCR blocking antibodies were found to decrease protein C activation and increase susceptibility to bacterial sepsis in baboons [9,10]. Increased vulnerability to bacterial lipopolysaccharide also has been reported in EPCR-deficient mice [11], but until now no animal model was available to examine the consequences of EPCR overexpression.…”

Overexpressing endothelial cell protein C receptor alters the hemostatic balance and protects mice from endotoxin

“…As APC has been shown to increase survival in animal models of sepsis and EPCR has been implicated in the protection [6], we tested whether the Tie2-EPCR mice would be protected from the deleterious effects of LPS. The results clearly showed that the Tie2-EPCR mice were protected relative to wild type mice.…”

Lipid raft localization regulates the cleavage specificity of protease activated receptor 1 in endothelial cells

“…Activated protein C (APC) is a multifunctional plasma serine protease that exhibits anticoagulant, profibrinolytic, cytoprotective and anti-inflammatory activities [1][2][3][4][5][6][7][8][9]. Specific cofactors are required for the normal physiological function of APC in these diverse pathways.…”