Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumor necrosis factor (TNF) induced by bacterial lipopolysaccharide (LPS) was shown to have an important role in precipitation of septic shock and disseminated intravascular clotting (DIC). At the endothelial level TNF down-regulates thrombomodulin (thus preventing protein C formation) and inhibits the production of tissue plasminogen activator (t-PA), thus impairing anticoagulant mechanisms. On the other hand, TNF up-regulates the production of procoagulant factors such as t-PA inhibitor (PAI), tissue factor and platelet activating factor (PAF). These effects create an imbalance between procoagulant and anticoagulant mechanisms, in favor of the former. TNF also activates polymorphonuclears (PMNs), and increases their chemotaxis and adherence to endothelial surfaces by up-regulation of specific endothelial (ELAM-1) and PMN (CDw18) adherence proteins. The damage inflicted by activated PMN to the endothelial cell promotes tissue factor exposure and PAI release, with initiation of the characteristic explosive coagulation process of DIC, facilitated by the dissociation between pro- and anticoagulant mechanisms induced by TNF. These newly discovered mechanisms precipitating septic shock and DIC enable consideration of new treatments for this condition as anti-TNF antibodies or TNF inhibitors, anti-ELAM-1 antibodies anti-tissue factor antibodies, administration of activated factor C, etc. These therapeutic approaches may revolutionize the treatment of septic shock and DIC in the next decade.
 ...
PMID:Role of tumor necrosis factor in the pathogenesis of intravascular coagulopathy of sepsis: potential new therapeutic implications. 199 4

Endothelial cells form the luminal vascular surface and thus have a central role in the regulation of coagulation. One important way in which endothelial cells control the clotting system is by regulating the expression of binding sites for anticoagulant and procoagulant factors on the cell surface. In the quiescent state, endothelial cells maintain blood fluidity by promoting the activity of numerous anticoagulant pathways, including the protein C/protein S pathway. After activation, as can be brought about by cytokines, the balance of endothelial properties can be tipped to favor clot formation through coordinated induction of procoagulant and suppression of anticoagulant mechanisms. Tumor necrosis factor suppresses the endothelial anticoagulant cofactor thrombomodulin and induces expression of the procoagulant cofactor tissue factor. Working in concert, these changes can allow fibrin formation to proceed in an inflamed focus but maintain blood fluidity in the surrounding area of normal vasculature. Recent studies suggest that similar changes in endothelial coagulant properties can be induced by advanced glycosylation end products, proteins modified by glucose that accumulate in the vasculature at a rapid rate in diabetic subjects, indicating the potential relevance of these mechanisms in diabetic vascular disease.
 ...
PMID:Endothelium and regulation of coagulation. 206 Apr 25

Tumor necrosis factor (TNF), a mediator of the inflammatory response, induces tissue factor and decreases the expression of thrombomodulin (TM) on endothelial cells, thus shifting the hemostatic properties of the endothelium. To determine the mechanism of TM downregulation, bovine aortic endothelial cells in culture were treated with TNF (2 nmol/L) and the fate of TM followed. Both surface expressed TM (antigen and activity), and the total TM pool (measured by radioimmunoassay and activity in detergent extracts) dropped to less than or equal to 20% of control values within 12 hours of TNF treatment. TM was not found in an immunologically recognizable form in the supernatants of treated cultures. Chloroquine (greater than or equal to 100 mumol/L) was able to abrogate the TNF effect on the total TM pool but not the effect on surface-expressed TM activity. We conclude that TNF induces the internalization and subsequent degradation of the TM molecule. None of the components of the protein C anticoagulant pathway, either alone or in combination, prevented the TNF-dependent downregulation of TM antigen.
 ...
PMID:Tumor necrosis factor leads to the internalization and degradation of thrombomodulin from the surface of bovine aortic endothelial cells in culture. 253 43

Tumor necrosis factor/cachectin (TNF) is a mediator of the septic shock state, which can modulate hemostatic properties of the vessel wall. The interaction of TNF with endothelium is not cytotoxic, rather it is receptor mediated and results in a change in receptor expression on the endothelial cell surface, enabling endothelium to actively promote coagulation. Anticoagulant mechanisms, including the protein C/protein S system and fibrinolysis are suppressed, whereas the initiation and propagation of procoagulant activity is enhanced. This unidirectional shift in vessel wall coagulant activity favoring clot formation could contribute to the coagulopathy associated with sepsis and indicates a mechanism through which the coagulation system serves as an integral part of the host response.
 ...
PMID:Tumor necrosis factor/cachectin-induced modulation of endothelial cell hemostatic properties. 282

Tumor necrosis factor/cachectin (TNF) is a mediator of the septic state, which involves diffuse abnormalities of coagulation throughout the vasculature. Since previous studies have shown that endothelial cells can play an active role in coagulation, we wished to determine whether TNF could modulate endothelial cell hemostatic properties. Incubation of purified recombinant TNF with cultured endothelial cells resulted in a time- and dose-dependent acquisition of tissue factor procoagulant activity. Concomitant with enhanced procoagulant activity, TNF also suppressed endothelial cell cofactor activity for the anticoagulant protein C pathway; both thrombin-mediated protein C activation and formation of functional activated protein C-protein S complex on the cell surface were considerably attenuated. Comparable concentrations of TNF (half-maximal affect at approximately 50 pM) and incubation times (half-maximal affect by 4 h after addition to cultures) were required for each of these changes in endothelial cell coagulant properties. This unidirectional shift in cell surface hemostatic properties favoring promotion of clot formation indicates that, in addition to leukocyte procoagulants, endothelium can potentially be instrumental in the pathogenesis of the thrombotic state associated with inflammatory and malignant disorders.
 ...
PMID:Modulation of endothelial cell hemostatic properties by tumor necrosis factor. 375 96

Activated protein C (APC), a natural anticoagulant, is formed from protein C by the action of thrombin bound to thrombomodulin on the endothelial cell surface. APC regulates the coagulation system by inactivating the activated form of factors V and VIII in the presence of protein S. Tumor necrosis factor-alpha (TNF-alpha) plays critical roles in the development of disseminated intravascular coagulation, acute respiratory distress syndrome and shock in sepsis by inducing endothelial cell damage through activation of neutrophils. APC reduces the pulmonary endothelial cell injury and hypotension in rats administered endotoxin (ET) by inhibiting TNF-alpha production through inhibition of its transcription. Furthermore, APC reduces the ischemia/reperfusion-induced renal injury and the stress-induced gastric mucosal injury in rats. Inhibition by APC of the endothelial cell damage inhibited the decrease in the endothelial production of prostacyclin in vivo. These therapeutic effects could not be attributed to its anticoagulant effects, but to inhibition of TNF-alpha production. APC inhibits ET-induced TNF-alpha production in vitro in human monocytes by inhibiting activation of NFkappaB and AP-1 by inhibiting degradation of IkappaB and mitogen-activated protein kinase pathways, respectively. Recombinant APC was reported to reduce the mortality of patients with severe sepsis. These observations strongly suggest that APC might be involved not only in regulation of the coagulation system, but in regulation of inflammatory responses by preventing endothelial cell injury. Furthermore, APC reduced the spinal cord injury induced by compression-trauma or ischemia/reperfusion by inhibiting TNF-alpha production in rats, suggesting that APC may be a potential therapeutic agent for spinal cord injury in which only limited therapeutic measures are currently available.
 ...
PMID:Prevention of endothelial cell injury by activated protein C: the molecular mechanism(s) and therapeutic implications. 1532 May 13

Thrombomodulin has a central role in the regulation of coagulation through its ability to promote generation of the potent anticoagulant, activated protein C. Aurintricarboxylic acid (ATA) has been reported to inhibit platelet function by blocking von Willebrand factor binding to platelet glycoprotein Ib and to impede thrombosis development in vivo. In the present study, we demonstrated a novel antithrombotic effect of ATA. The surface thrombomodulin expression of endothelial cells and peripheral blood monocytes was upregulated by ATA in a dose-dependent and time-dependent manner. ATA also increased the mRNA level of endothelial thrombomodulin in a dose-dependent manner. Tumor necrosis factor (TNF)-alpha (50 ng/ml) or lipopolysaccharide (20 microg/ml) downregulated the expression of endothelial thrombomodulin. Blocking of nuclear factor-kappaB by parthenolide effectively inhibited the TNF-alpha-induced thrombomodulin downregulation of endothelial cells. ATA increased endothelial thrombomodulin expression that was downregulated by TNF-alpha or lipopolysaccharide, in a dose-dependent manner. The inhibition of small G proteins of the Rho family by the Clostridium difficile toxin B-1,0643 did not increase thrombomodulin expression of endothelial cells, and ATA did not activate Rac1 in endothelial cells. These findings provide, at least in part, a novel platelet-independent mechanism of ATA that may explain the demonstrated antithrombotic efficacy of ATA.
 ...
PMID:Aurintricarboxylic acid upregulates the thrombomodulin expression of endothelial cells and peripheral blood monocytes. 1868 31