Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036690 (sepsis)
 59,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Increased endothelial cell (EC) permeability is central to the pathophysiology of inflammatory syndromes such as sepsis and acute lung injury (ALI). Activated protein C (APC), a serine protease critically involved in the regulation of coagulation and inflammatory processes, improves sepsis survival through an unknown mechanism. We hypothesized a direct effect of APC to both prevent increased EC permeability and to restore vascular integrity after edemagenic agonists. We measured changes in transendothelial electrical resistance (TER) and observed that APC produced concentration-dependent attenuation of TER reductions evoked by thrombin. We next explored known EC barrier-protective signaling pathways and observed dose-dependent APC-mediated increases in cortical myosin light chain (MLC) phosphorylation in concert with cortically distributed actin polymerization, findings highly suggestive of Rac GTPase involvement. We next determined that APC directly increases Rac1 activity, with inhibition of Rac1 activity significantly attenuating APC-mediated barrier protection to thrombin challenge. Finally, as these signaling events were similar to those evoked by the potent EC barrier-enhancing agonist, sphingosine 1-phosphate (S1P), we explored potential cross-talk between endothelial protein C receptor (EPCR) and S1P1, the receptors for APC and S1P, respectively. EPCR-blocking antibody (RCR-252) significantly attenuated both APC-mediated barrier protection and increased MLC phosphorylation. We next observed rapid, EPCR and PI 3-kinase-dependent, APC-mediated phosphorylation of S1P1 on threonine residues consistent with S1P1 receptor activation. Co-immunoprecipitation studies demonstrate an interaction between EPCR and S1P1 upon APC treatment. Targeted silencing of S1P1 expression using siRNA significantly reduced APC-mediated barrier protection against thrombin. These data suggest that novel EPCR ligation and S1P1 transactivation results in EC cytoskeletal rearrangement and barrier protection, components potentially critical to the improved survival of APC-treated patients with severe sepsis.
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PMID:Activated protein C mediates novel lung endothelial barrier enhancement: role of sphingosine 1-phosphate receptor transactivation. 1571 Jun 22

Prostacyclin (PGI(2)) has beneficial cytoprotective properties, is a potent inhibitor of platelet aggregation and has been reported to improve microcirculatory blood flow during sepsis. The formation of PGI(2) in response to proinflammatory cytokines is catalysed by the inducible cyclooxygenase (COX) isoform COX-2. Recombinant human activated protein C (rhAPC, drotrecogin alfa (activated)) was shown to have multiple biological activities in vitro and to promote resolution of organ dysfunction in septic patients. Whether rhAPC exerts its beneficial effects by modulating prostanoid generation is unknown up to now. It was therefore the aim of the study to examine the in vitro effect of rhAPC on COX-2-mRNA-expression and PGI(2) release from human umbilical vein endothelial cells (HUVEC). We found that rhAPC, at supra-therapeutical concentrations (500 ng/ml-20 microg/ml), upregulated the amount of COX-2-mRNA in HUVEC at t=3-9 h and caused a time- and dose-dependent release of 6-keto PGF(1 alpha), the stable hydrolysis product of prostacyclin. RhAPC further increased the stimulating effect of tumor necrosis factor-alpha (TNF-alpha) and thrombin on COX-2-mRNA-levels. Transcript levels of cyclooxygenase-1 (COX-1) and prostaglandin 12 synthase, however, were unaffected by the stimulation with rhAPC or thrombin. The upregulatory effect on COX2-mRNA levels was specific for rhAPC since the zymogen protein C in equimolar concentrations had no effect on COX-2-mRNA-levels or 6-keto PGF(1 alpha)-release. Western Blot analysis revealed an increase of COX-2-protein content in HUVEC after treatment with rhAPC. As shown by experiments using monoclonal antibodies against the thrombin receptor PAR-1 (mAb=ATAP2) and against the endothelial protein C receptor (EPCR; mAb=RCR-252), the effect of rhAPC on COX-2-mRNA upregulation was mediated by binding to the EPCR-receptor and signaling via PAR-1. These results demonstrate that induction of COX-2-expression is an important response of HUVEC to stimulation with rhAPC and may represent a new molecular mechanism, by which rhAPC promotes upregulation of prostanoid production in human endothelium.
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PMID:Recombinant human activated protein C upregulates cyclooxygenase-2 expression in endothelial cells via binding to endothelial cell protein C receptor and activation of protease-activated receptor-1. 1584 23

Previous studies have shown that blocking endothelial protein C receptor (EPCR)-protein C interaction results in about an 88% decrease in circulating activated protein C (APC) levels generated in response to thrombin infusion and exacerbates the response to Escherichia coli. To determine whether higher levels of EPCR expression on endothelial cells might further enhance the activation of protein C and protect the host during septicemia, we generated a transgenic mouse (Tie2-EPCR) line which placed the expression of EPCR under the control of the Tie2 promoter. The mice express abundant EPCR on endothelial cells not only on large vessels, but also on capillaries where EPCR is generally low. Tie2-EPCR mice show higher levels of circulating APC after thrombin infusion. Upon infusion with factor Xa and phospholipids, Tie2-EPCR mice generate more APC, less thrombin and are protected from fibrin/ogen deposition compared with wild type controls. The Tie2-EPCR animals also generate more APC upon lipopolysaccharide (LPS) challenge and have a survival advantage. These results reveal that overexpression of EPCR can protect animals against thrombotic or septic challenge.
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PMID:Overexpressing endothelial cell protein C receptor alters the hemostatic balance and protects mice from endotoxin. 1597 89

Protein C is a plasma protease that when activated plays a central role in modulating the function of the vascular endothelium and its interface with the innate immune system. A recombinant form of human activated protein C (APC), drotrecogin alfa (activated), has shown efficacy in a number of preclinical models of thrombosis and ischemia and reduces mortality in patients that have a high risk of dying from severe sepsis. Studies have begun to elucidate the mechanism for the multifunctional role of APC in modulating not only coagulation, but also inflammation and apoptotic processes. From gene profiling to pharmacology studies, drotrecogin alfa (activated) appears to directly modulate endothelial dysfunction by blocking cytokine signaling, functional cell adhesion expression, vascular permeability and preventing the induction of apoptosis. Moreover, APC, via endothelial protein C receptor/protease activated receptor-1 mediated mechanisms, also appears to directly modulate leukocyte migration and adhesion. The ability of APC to suppress pro-inflammatory pathways and enhance cellular survival suggests that APC has a role in the adaptive response at the vessel wall, in which it protects the wall from vascular insult and prolongs endothelial, cellular, and organ survival. The emerging data further suggest that APC effectively modulates the complex changes that occur during multi-system activation and dysfunction in sepsis.
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PMID:Activated protein C and sepsis. 1614 61

It has been hypothesized that the protein C pathway is a pivotal link between the inflammation and coagulation cascades. The demonstration that a survival benefit is associated with administration of drotrecogin alfa (activated) (recombinant human activated protein C [APC]) in severe sepsis patients has provided new insights into the protein C pathway. APC was originally identified based on its antithrombotic properties, which result from the inhibition of activated Factors V and VIII. In the early 1990s, any potential anti-inflammatory properties of APC were thought to relate primarily to its inhibition of thrombin generation. However, the mid-1990s saw the identification of the endothelial protein C receptor (EPCR), which has subsequently been shown to be neither endothelial specific nor protein C specific, but has a primary function as a cofactor for enhancing the generation of APC or behaving as an APC receptor. Thus, the potential biologic activities of APC can be classed into two categories related either to the limiting of thrombin generation or to cellular effects initiated by binding to the EPCR. Intracellular signaling initiated by binding of APC to its receptor appears to be mediated by interaction with an adjacent protease-activated receptor (PAR), or by indirect activation of the sphingosine 1-phosphate pathway. Based mostly on in vitro studies, binding of APC to its receptor on endothelial cells leads to a decrease in thrombin-induced endothelial permeability injury, while such binding on blood cells, epithelial cells, and neurons has been shown to inhibit chemotaxis, be anti-apoptotic, and be neuroprotective, respectively. In the Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) study, drotrecogin alfa (activated) was associated with improved cardiovascular function, respiratory function, and a prevention of hematologic dysfunction. This article discusses the way in which the interactions of APC may alter the microcirculation.
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PMID:New insights into the protein C pathway: potential implications for the biological activities of drotrecogin alfa (activated). 1616 74

Alterations in the generation of activated protein C (APC) as well as in the interactions of APC with the endothelial protein C receptor are present in severe sepsis and acute lung injury. Administration of recombinant human activated protein C (rhAPC) improves the survival of critically ill patients with sepsis, but the mechanisms by which rhAPC produces benefit are not well defined. Human models of systemic and pulmonary endotoxin exposure may provide important insights into the mechanisms of action of rhAPC in critical illness. In volunteers given systemic endotoxin, rhAPC had minimal effects on physiologic parameters, including blood pressure, markers of inflammation, and measures of sepsis-induced coagulopathy. In contrast, in the setting of pulmonary endotoxin exposure, rhAPC decreased neutrophil migration into the airspaces and also diminished neutrophil chemotaxis. Administration of rhAPC did not affect other parameters of neutrophil function, including kinase activation, production of proinflammatory cytokines, or apoptosis. Such results indicate that the effects of rhAPC in inhibiting the infiltration of neutrophils into the lungs and other inflammatory sites may contribute to its beneficial effects in sepsis.
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PMID:Effects of recombinant human activated protein C in human models of endotoxin administration. 1622 45

Fractalkine is a unique endothelial cell-derived chemokine that functions both as a chemoattractant and as an adhesion molecule. Recent findings suggest that fractalkine plays an important role in inflammatory diseases by modulating leucocyte endothelial cell interactions. A modulating effect on the immune system in severe sepsis has been suggested for recombinant human activated protein C (rhAPC). However, a little is known about the effect of rhAPC on the endothelial release of soluble fractalkine. The effect of rhAPC (50 ng/ml to 10 microg/ml) and protein C (in equimolar concentrations) on the synthesis of fraktalkine-mRNA and release of soluble protein in human umbilical vein endothelial cells (HUVEC) was determined by reverse transcription-polymerase chain reaction and by an enzyme-linked immunosorbent assay. rhAPC at supra-pharmacological concentrations (1-10 microg/ml) stimulated fractalkine-messenger RNA-gene transcription and release of soluble fractalkine in a time- and dose-dependent manner, whereas the zymogen protein C was ineffective. As shown by experiments using monoclonal antibodies against the thrombin receptor, protease-activated receptor-1 (PAR-1), PAR-2 and against the endothelial protein C receptor (EPCR), the effect of rhAPC on fractalkine upregulation was mediated by binding to the EPCR-receptor and signalling via PAR-1. These in vitro data demonstrate that induction of fractalkine release is an important response of HUVEC to stimulation with rhAPC and may lead to a better understanding of the molecular pathways involved in the mode of action of rhAPC. Further clinical trials are needed to confirm the in vivo relevance of these data.
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PMID:Recombinant human activated protein C upregulates the release of soluble fractalkine from human endothelial cells. 1668 44

The anticoagulant protein C system is a dual function cofactor-dependent system. On one hand, it is designed to regulate coagulation, maintain the fluidity of the vasculature and prevent thrombosis. On the other hand, the protein C pathway provides anti-inflammatory and cytoprotective activities. Protein C, a vitamin K-dependent serine protease zymogen that circulates in plasma, is converted by limited proteolysis to activated protein C (APC) by the thrombin-thrombomodulin-endothelial protein C receptor complex on endothelial surfaces. APC and the cofactors of the protein C pathway exert two major distinct types of activities, namely a well-studied anticoagulant activity and a more recently revealed cytoprotective activity due to direct effects on cells. Because of these pleiotropic properties, APC and the protein C pathway components have important roles in the body's host-defense system and provide opportunities for therapeutic treatment of complex and challenging medical disorders, including thrombosis, severe sepsis and stroke.
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PMID:Protein C anticoagulant activity in relation to anti-inflammatory and anti-apoptotic activities. 1672 Mar 21

In addition to an anticoagulant activity, activated protein C (APC) also exhibits anti-inflammatory and cytoprotective properties. These properties may contribute to the beneficial effect of APC in treating severe sepsis patients. A higher incidence of bleeding because of its anticoagulant function has been found to be a major drawback of APC as an effective anti-inflammatory drug. In this study, we have prepared a protein C variant in which an engineered disulfide bond between two beta-sheets stabilized the functionally critical Ca2+-binding 70-80 loop of the molecule. The 70-80 loop of this mutant no longer bound Ca2+, and the activation of the mutant by thrombin was enhanced 60-80-fold independently of thrombomodulin. The anticoagulant activity of the activated protein C mutant was nearly eliminated as determined by a plasma-based clotting assay. However, the endothelial protein C receptor- and protease-activated receptor-1-dependent protective signaling properties of the mutant were minimally altered as determined by staurosporine-induced endothelial cell apoptosis, thrombin-induced endothelial cell permeability, and tumor necrosis-alpha-mediated neutrophil adhesion and migration assays. These results suggest that the mutant lost its ability to interact with the procoagulant cofactors but not with the protective signaling molecules; thus this mutant provides an important tool for in vivo studies to examine the role of anticoagulant versus anti-inflammatory function of activated protein C.
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PMID:Engineering a disulfide bond to stabilize the calcium-binding loop of activated protein C eliminates its anticoagulant but not its protective signaling properties. 1725 99

Endothelial protein C receptor (EPCR) is primarily localized on the endothelial cells of large blood vessels and is very low or absent in the microvascular endothelium of most tissues. EPCR augments the thrombin/thrombomodulin-dependent activation of protein C by 5- to 20-fold. EPCR appears to be physiologically significant in the control of blood coagulation and inflammation and in the host response to gram-negative sepsis. Here, the authors report an 8-month-old boy, who had chronic liver disease due to undetermined cause. He had Staphylococcus aureus and Candida albicans sepsis and died due to gastrointestinal, lung, and peritoneal bleeding during follow-up. Serum soluble EPCR level of the patient was high (225 ng/mL) during sepsis. A homozygous 23-bp insertion of EPCR gene was demonstrated. This case indicates the importance the EPCR gene plaus in pediatric sepsis. Homozygous 23-bp insertion of the EPCR gene may be associated with a tendency to sepsis and poor outcome.
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PMID:Homozygous 23-bp insertion of endothelial protein c receptor gene in a child with fatal sepsis. 1745 90


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