IgG plasma cells initiate changes in the protein C system in mouse ulcerative colitis through CD14+CD64+ macrophage activation

BACKGROUND

Inhibition of the protein C system (PCS) might be one of the mechanisms of ulcerative colitis (UC).

OBJECTIVES

The aim of the study was to explore the role of IgG plasma cells in changes in the PCS in UC.

MATERIAL AND METHODS

Dextran sulfate sodium (DSS) was chosen to induce mouse UC. Inflammation was assessed using hematoxylin & eosin (H&E) staining and immunofluorescence. The profiling of colonic plasma cells and macrophages from colitis mice was analyzed with flow cytometry. After stimulation of macrophages with IgG type immune complex (IgG-IC), western blot was used to determine tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) protein levels. After co-incubation of colonic mucosa microvascular endothelial cells (MVECs) with TNF-α or IL-6, mitogen-activated protein kinase (MAPK) expression was detected.

RESULTS

The DSS-colitis mice showed higher inflammatory indexes (p < 0.05 or p < 0.01), accompanied by greater infiltration of CD38+IgG+ plasma cells (p < 0.01), CD14+CD64+ macrophages (p < 0.01) and IgG-IC than healthy mice. Enhancement of TNF-α and IL-6 protein expression was demonstrated in this subset of macrophages when stimulated by IgG-IC (p < 0.01). After MVECs were incubated with TNF-α or IL-6, the expression of β-arrestin1, pP38 MAPK and pJNK MAPK exhibited an increase (p < 0.05 or p < 0.01), but downregulation of endothelial protein C receptor (EPCR) expression was observed (p < 0.05 or p < 0.01); this inhibition of EPCR expression was reversed by SB203580, SP600125 or U0126 (p < 0.05 or p < 0.01). In addition, changes in activated protein C (APC) presented results similar to those for EPCR expression (p < 0.05 or p < 0.01).

CONCLUSIONS

These results reveal that the PCS is inhibited during UC processing. There is a possibility that the interaction between IgG plasma cells and CD14+CD64+ macrophages, as well as further secretion of cytokines from CD14+CD64+ macrophages by the formation and stimulation of IgG-IC, subsequently influence MVECs through the β-arrestin-MAPK pathway. Enhancement of PCS activity may represent a novel approach for treating UC.

Research progress of acute coagulopathy of trauma-shock

Acute coagulopathy of trauma-shock (ACoTS) occurs in 25% of patients with severe trauma in the early phase, and the mortality of those patients is four-fold higher than patients without coagulopathy. The pathophysiology of this complicated phenomenon has been focused on in recent years. Tissue injury and hypoperfusion, activated protein C and Complements play important roles in the early phase after trauma. While the use of blood products, hypothermia, acidosis and inflammation are the main mechanism in late phase. Supplementing coagulation factors and platelets to improve ACoTS are inefficient. Only positive resuscitation from shock and improving tissue hypoperfusion have expected benefits.

Factor V Leiden: association with venous thromboembolism in pregnancy and screening issues

Disturbances of the natural balance between procoagulant and anticoagulant mechanisms can result in bleeding or thrombotic tendencies. Factor V, on activation by thrombin to factor Va, forms an essential component of the prothrombinase complex, in which it demonstrates its cofactor activity for factor Xa. Down-regulation of factor Va by activated protein C (APC) occurs through cleavage of specific peptide bonds in the heavy chain of the molecule. Factor V Leiden (FV Leiden) is a mutation of factor V that renders factor Va resistant to APC, due to loss of one of these cleavage sites. This mutation predisposes the patient to thrombosis. Prevalence of FV Leiden varies; however, heterozygosity for the FV Leiden mutation is recognised as the most common heritable thrombophilic defect in Caucasian populations. The association this inherited thrombophilia has with venous thromboembolism (VTE) is well established. Pregnancy is notably an acquired hypercoagulable state, due in part to physiological changes that occur in the coagulation system. This seems to have potential for interaction with FV Leiden to cause adverse experiences. A role has been suggested for FV Leiden in VTE events during pregnancy. At present only selected women are screened for FV Leiden. Pregnant women with a history of VTE or with a family history of the mutation are investigated. Whether or not the introduction of a routine screening plan for this mutation is justified remains a matter for debate.

Role of anhepatic time in endothelial-related coagulation in liver transplantation

BACKGROUND

Disturbances in coagulation homeostasis are common in patients undergoing orthotopic liver transplantation (OLT) and anhepatic period is one of the important factors related to the coagulation abnormalities. The endothelium can regulate hemostasisby producing substances such as thrombomodulin (TM). The primary aim was to evaluate the effect of an hepatic time on the thrombomodulin-protein C system in patients undergoing OLT.

METHODS

Fifty patients undergoing OLT were stratified in two groups: anhepatic time ≥ 60 min (N.=18) or anhepatic stage <60 min (N.=32). TM, protein C, activated protein C (APC) and (free) protein S plasma concentrations were measured by enzymelinked immunosorbent assays (ELISA) at the start of the surgery (To); immediately before the anhepatic period (A1); immediately before reperfusion (A2); 5 minutes; 15 minutes; 30 minutes after reperfusion of the graft (R1; R2; R3); at the end of operation (R4); the first day after operation (R5).

RESULTS

Blood loss and transfusion were significantly greater in patients whose anhepatic time ≥ 60 min during the operation. TM levels increased most in patients whose anhepatic time ≥ 60 min. Protein C levels remained low throughout the surgery and decreased significantly at other points compared with To (P<0.05). There were no differences in protein C levels between groups except R5. The ratio of circulating APC activity to protein C antigen (APC/PC) increased significantly during the surgery. APC/PC ratio in the neohepatic stage increased significantly in patients whose anhepatic time ≥ 60 min (P<0.05).

CONCLUSION

Patients with prolonged anhepatic time had greater changes in the thrombomodulin-protein C system.

Thrombomodulin in sepsis

Thrombomodulin has a pivotal role in the protein C system that is important in the pathogenesis of sepsis. In sepsis, endothelial cell expression of thrombomodulin is strongly downregulated, causing an impaired activation of protein C that is central in the modulation of coagulation activation and inflammatory processes. In addition, thrombomodulin itself has marked immunomodulatory effects, targeting neutrophil adhesion, complement activation and cytokine generation. Several preclinical studies in experimental sepsis models have shown that administration of soluble thrombomodulin is capable of improving the derangement of coagulation, ameliorates inflammatory responses and may restore organ dysfunction. Initial clinical studies in patients with disseminated intravascular coagulation, of whom a significant proportion were patients with sepsis, demonstrate a beneficial effect of recombinant soluble thrombomodulin on restoration of coagulation and improvement of organ failure.

Activated protein C modulates cardiac metabolism and augments autophagy in the ischemic heart

BACKGROUND

Modulation of energy substrate metabolism may constitute a novel therapeutic intervention against ischemia/reperfusion (I/R) injury. AMP-activated protein kinase (AMPK) has emerged as a key regulator of favorable metabolic signaling pathways in response to myocardial ischemia. Recently, we demonstrated that activated protein C (APC) is cardioprotective against ischemia/reperfusion (I/R) injury by augmenting AMPK signaling.

OBJECTIVES

The objective of this study was to determine whether the APC modulation of substrate metabolism contributes to its cardioprotective effect against I/R injury.

METHODS

An ex vivo working mouse heart perfusion system was used to characterize the effect of wild-type APC and its signaling-proficient mutant, APC-2Cys (which has dramatically reduced anticoagulant activity), on glucose transport in the ischemic heart.

RESULTS

Both APC and APC-2Cys (0.2 μg g(-1)) augment the ischemic stress-induced translocation of the glucose transporter (GLUT4) to the myocardial cell membrane, leading to increased glucose uptake and glucose oxidation in the ischemic heart (P < 0.05 vs. vehicle). Both APC derivatives increased the autophagic flux in the heart following I/R. The activity of APC-2Cys in modulating these metabolic pathways was significantly higher than APC during I/R (P < 0.05). Intriguingly, APC-2Cys, but not wild-type APC, attenuated the I/R-initiated fatty acid oxidation by 80% (P < 0.01 vs. vehicle).

CONCLUSIONS

APC exerts a cardioprotective effect against I/R injury by preferentially enhancing the oxidation of glucose over fatty acids as energy substrates in the ischemic heart. Given its significantly higher beneficial metabolic modulatory effect, APC-2Cys may be developed as a potential therapeutic drug for treating ischemic heart disease without risk of bleeding.

The effect of homocysteine on the clinical outcomes of ventilated patients with severe sepsis

BACKGROUND

There is considerable evidence that elevated plasma homocysteine levels are associated with a prothrombotic milieu, whereas activation of the coagulation cascade is an important component of the pathogenesis of sepsis. The protein C pathway has been reported to play a central role both in the propagation of sepsis and a hyperhomocysteinemia-induced hypercoagulable state. Our primary aim was to measure plasma homocysteine levels in mechanically ventilated patients with severe sepsis/septic shock and to assess the association of these levels with relevant clinical outcomes.

METHODS

The study cohort included 102 mechanically ventilated patients with severe sepsis or septic shock. Demographics, comorbidities, clinical data and severity scores were recorded. Plasma homocysteine, vitamin B12, folate, creatinine, and protein C levels were measured in all study subjects upon enrollment, and genotyping for the C677T and A1298C polymorphisisms of the methylenetetrahydrofolate reductase (MTHFR) gene and for factor V Leiden (FVL) mutations was performed as well. The primary outcomes were mortality at 28 and 90 days; secondary outcomes included the number of days without renal or cardiovascular failure and the ventilator-free days during the study period.

RESULTS

Homocysteine levels were not significantly associated with any primary or secondary outcomes in the multivariable analysis. In addition, a synergistic effect of homocysteine with protein C levels was not detected.

CONCLUSION

Our data suggest that plasma homocysteine levels may not inform the prognosis of mechanically ventilated patients with severe sepsis/septic shock.

Kinetics of cardiac muscle contraction and relaxation are linked and determined by properties of the cardiac sarcomere

The regulation of myocardial contraction and relaxation kinetics is currently incompletely understood. When the amplitude of contraction is increased via the Frank-Starling mechanism, the kinetics of the contraction slow down, but when the amplitude of contraction is increased with either an increase in heart rate or via β-adrenergic stimulation, the kinetics speed up. It is also unknown how physiological mechanisms affect the kinetics of contraction versus those of relaxation. We investigated contraction-relaxation coupling in isolated trabeculae from the mouse and rat and stimulated them to contract at various temperatures, frequencies, preloads, and in the absence and presence of β-adrenergic stimulation. In each muscle at least 16 different conditions were assessed, and the correlation coefficient of the speed of contraction and relaxation was very close (generally >0.98). Moreover, in all but one of the analyzed murine strains, the ratio of the minimum rate of the derivative of force development (dF/dt) over maximum dF/dt was not significantly different. Only in trabeculae isolated from myosin-binding protein-C mutant mice was this ratio significantly lower (0.61 ± 0.07 vs. 0.84 ± 0.02 in 11 other strains of mice). Within each strain, this ratio was unaffected by modulation of length, frequency, or β-adrenergic stimulation. Rat trabeculae showed identical results; the balance between kinetics of contraction and relaxation was generally constant (0.85 ± 0.04). Because of the great variety in underlying excitation-contraction coupling in the assessed strains, we concluded that contraction-relation coupling is a property residing in the cardiac sarcomere.

Laboratory tests for protein C deficiency

Hereditary protein C deficiency is a hypercoagulable state associated with an increased risk for venous thrombosis. The recommended initial test for protein C is an activity (functional) assay, which may be clotting time based or chromogenic. The advantages and disadvantages of the various testing options are presented. The causes of acquired protein C deficiency are much more common than hereditary deficiency. Therefore, this article describes the appropriate steps to take when protein C activity is low, to confirm or exclude a hereditary deficiency. The causes of falsely normal results are also described, including lupus anticoagulants and direct thrombin inhibitors.

Activated protein C action in inflammation

Activated protein C (APC) is a natural anticoagulant that plays an important role in coagulation homeostasis by inactivating the procoagulation factor Va and VIIIa. In addition to its anticoagulation functions, APC also has cytoprotective effects such as anti-inflammatory, anti-apoptotic, and endothelial barrier protection. Recently, a recombinant form of human APC (rhAPC or drotrecogin alfa activated; known commercially as 'Xigris') was approved by the US Federal Drug Administration for treatment of severe sepsis associated with a high risk of mortality. Sepsis, also known as systemic inflammatory response syndrome (SIRS) resulting from infection, is a serious medical condition in critical care patients. In sepsis, hyperactive and dysregulated inflammatory responses lead to secretion of pro- and anti-inflammatory cytokines, activation and migration of leucocytes, activation of coagulation, inhibition of fibrinolysis, and increased apoptosis. Although initial hypotheses focused on antithrombotic and profibrinolytic functions of APC in sepsis, other agents with more potent anticoagulation functions were not effective in treating severe sepsis. Furthermore, APC therapy is also associated with the risk of severe bleeding in treated patients. Therefore, the cytoprotective effects, rather than the anticoagulant effect of APC are postulated to be responsible for the therapeutic benefit of APC in the treatment of severe sepsis.

The protein C pathway in tissue inflammation and injury: pathogenic role and therapeutic implications

Inflammation and coagulation are closely linked interdependent processes. Under physiologic conditions, the tissue microcirculation functions in anticoagulant and anti-inflammatory fashions. However, when inflammation occurs, coagulation is also set in motion and actively participates in enhancing inflammation. Recently, novel and unexpected roles of hemostasis in the humoral and cellular components of innate immunity have been described. In particular, the protein C system, besides its well-recognized role in anticoagulation, plays a crucial role in inflammation. Indeed, the protein C system is now emerging as a novel participant in the pathogenesis of acute and chronic inflammatory diseases, such as sepsis, asthma, inflammatory bowel disease, atherosclerosis, and lung and heart inflammation, and may emerge as unexpected therapeutic targets for intervention.

Inflammation and coagulation

In the pathogenesis of sepsis, inflammation and coagulation play a pivotal role. Increasing evidence points to an extensive cross-talk between these two systems, whereby inflammation leads to activation of coagulation, and coagulation also considerably affects inflammatory activity. Molecular pathways that contribute to inflammation-induced activation of coagulation have been precisely identified. Pro-inflammatory cytokines and other mediators are capable of activating the coagulation system and down-regulating important physiologic anticoagulant pathways. Activation of the coagulation system and ensuing thrombin generation is dependent on expression of tissue factor and the simultaneous down-regulation of endothelial-bound anticoagulant mechanisms and endogenous fibrinolysis. Conversely, activated coagulation proteases may affect specific cellular receptors on inflammatory cells and endothelial cells and thereby modulate the inflammatory response.

Roles of inflammation and the activated protein C pathway in the brain edema associated with cerebral venous sinus thrombosis

BACKGROUND AND PURPOSE

Increased blood-brain barrier (BBB) permeability, brain edema, and hemorrhage are important consequences of cerebral venous sinus thrombosis (CVST). The objective of this study was to define the role of the protein C pathway in the BBB permeability and edema elicited by experimental CVST. The role of neutrophil recruitment was also evaluated.

METHODS

Edema, BBB permeability, leukocyte-endothelial cell adhesion (LECA) and inflammatory cytokine levels were monitored in a murine model of CVST. The role of activated protein C (APC) was assessed in wild type mice (WT) receiving APC neutralizing antibody and in endothelial protein C receptor overexpressing mice (EPCR-tg). Neutrophil involvement was evaluated using an anti-CD18 antibody (Ab) and antineutrophil serum.

RESULTS

Brain edema and increases in BBB permeability and LECA were noted 48 hours after CVST. APC immunoblockade exacerbated these responses, while EPCR-tg exhibited blunted responses, as did WT treated with either antineutrophil serum or the CD18 Ab.

CONCLUSIONS

The protein C pathway protects the brain against the deleterious microvascular responses to CVST, a response that appears to be linked to the recruitment of inflammatory cells.

The protein C pathway and pathologic processes

Alterations in expression of protein C (PC) pathway components have been identified in patients with active inflammatory disease states. While the PC pathway plays a pivotal role in regulating coagulation and fibrinolysis, activated PC (aPC) also exhibits cytoprotective properties. For example, PC-deficient mice challenged in septic/endotoxemic models exhibit phenotypes that include hypotension, disseminated intravascular coagulation, elevated inflammatory mediators, neutrophil adhesion to the microvascular endothelium, and loss of protective endothelial and epithelial cell barriers. Further, inflammatory bowel disease has been correlated with diminished endothelial PC receptor and thrombomodulin levels in the intestinal mucosa. Downregulated expression of the cofactor, protein S, as well as PC, is also associated with ischemic stroke. Studies to elucidate further the structural elements that differentiate the various functions of PC will serve to identify novel therapeutic approaches toward regulating these and other diseases.

Role of activated protein C and its receptor in inhibition of tumor metastasis

Engagement of endothelial protein C receptor (EPCR) by activated protein C (aPC) decreases expression of endothelial adhesion molecules implicated in tumor-endothelium interactions. We examined the role of the aPC/EPCR pathway on tumor migration and metastasis. In vitro, B16-F10 melanoma cells showed decreased adhesion to and transmigration through endothelium treated with recombinant human aPC (rhaPC). In murine B16-F10 metastasis models, transgenic EPCR overexpressing (Tie2-EPCR) mice exhibited marked reductions in liver (50%) and lung (92%) metastases compared with wild-type (WT) animals. Intravital imaging showed reduced B16-F10 entrapment within livers of Tie2-EPCR compared with WT mice. A similar reduction was observed in WT mice treated with rhaPC. Strikingly, rhaPC treatment resulted in a 44% reduction in lung metastases. This was associated with decreased lung P-selectin and TNF-alpha mRNA levels. These findings support an important role for the aPC/EPCR pathway in reducing metastasis via inhibition of tumor cell adhesion and transmigration.

The coagulation system and pulmonary endothelial function in acute lung injury

Acute lung injury (ALI) is a disease marked by diffuse endothelial injury and increased capillary permeability. The coagulation system is a major participant in ALI and activation of coagulation is both a consequence and contributor to ongoing lung injury. Increased coagulation and depressed fibrinolysis result in diffuse alveolar fibrin deposition which serves to amplify pulmonary inflammation. In addition, existing evidence demonstrates a direct role for different components of coagulation on vascular endothelial barrier function. In particular, the pro-coagulant protein thrombin disrupts the endothelial actin cytoskeleton resulting in increased endothelial leak. In contrast, the anti-coagulant activated protein C (APC) confers a barrier-protective actin configuration and enhances the vascular barrier in vitro and in vivo. However, recent studies suggest a complex landscape with receptor cross-talk, temporal heterogeneity and pro-coagulant/anti-coagulant protein interactions. In this article, the major signaling pathways governing endothelial permeability in lung injury are reviewed with a particular focus on the role that endothelial proteins, such as thrombin and APC, which play on the vascular barrier function.

[Abnormality in blood coagulation because of protein S-K196E mutation]

We recently identified protein S-K196E mutation as a genetic risk factor for venous thromboembolism in the Japanese population. The E allele frequency was found to be 0.009. Therefore, a substantial proportion of the Japanese population may be assumed to be carrying the E allele of protein S and is at risk of developing venous thromboembolism.

[Various effects of serine proteinases, activated protein C and duodenase, on mast cells]

Some serine proteinases of haemostasis can regulate blood clotting and inflammation acting at proteinase-activated receptors (PARs). It is known that the anticoagulant proteinase, activated protein C (APC), exhibits anti-inflammatory effects on endothelial cells and macrophages and this involves endothelial protein C receptor--EPCR and proteinase-activated receptor--PAR1. We have studied the effect of wide range of APC concentrations on functional activity of rat peritoneal mast cells (PMC), which secrete the proinflammatory mediators, under normal conditions and during acute inflammation in rats. APC was able to reduce beta-hexosaminidase release from PMC. APC at very low concentrations (0.2-2 nM) modulated the mediator secretion from PMC under normal conditions and also during acute inflammation in rats. APC abolished the proinflammatory activity of duodenase (80 nM), the proteinase from gastrointestinal tract and mast cells. Mast cells pretreated with cathepsin G (PAR1 antagonist) or duodenase abolished protective antiinflammatory effect of low concentrations of APC on PMC degranulation. Our data indicated that blockade of the mast cells proinflammatory mediator secretion by APC involved PAR1 activation.

[Changes in coagulation hemostasis in patients after coronary bypass surgery]

Changes in the coagulation link of hemostasis were studied in 37 patients who had undergone coronary bypass surgery using venous and arterial conduits and in 16 healthy individuals of the same age. The recordings of hemostasiograms were examined before and 14 days after surgery. Prior to coronary bypass surgery, the patients with ischemic heart disease were found to have coagulation hemostatic disorders as moderate hyperfibrinogenemia, fibrinolytic suppression, thrombinemia, and elevated D-dimer concentrations. Postoperatively, hypercoagulation substantially increased with suppressed fibrinolysis and decreased anticoagulants in the protein C system. In this connection, it is necessary to longer use anticoagulants in the postoperative period and to thoroughly monitor hemostasiogram recordings after their discontinuance.

Activated protein C via PAR1 receptor regulates survival of neurons under conditions of glutamate excitotoxicity

The effect of an anticoagulant and cytoprotector blood serine proteinase--activated protein C (APC)--on survival of cultured hippocampal and cortical neurons under conditions of glutamate-induced excitotoxicity has been studied. Low concentrations of APC (0.01-10 nM) did not cause neuron death, but in the narrow range of low concentrations APC twofold and stronger decreased cell death caused by glutamate toxicity. High concentrations of APC (>50 nM) induced the death of hippocampal neurons similarly to the toxic action of glutamate. The neuroprotective effect of APC on the neurons was mediated by type 1 proteinase-activated receptor (PAR1), because the inactivation of the enzyme with phenylmethylsulfonyl fluoride or PAR1 blockade by a PAR1 peptide antagonist ((Tyr1)-TRAP-7) prevented the protective effect of APC. Moreover, APC inhibited the proapoptotic effect of 10 nM thrombin on the neurons. Geldanamycin, a specific inhibitor of heat shock protein Hsp90, completely abolished the antiapoptotic effect of 0.1 nM APC on glutamate-induced cytotoxicity in the hippocampal neurons. Thus, APC at low concentrations, activating PAR1, prevents the death of hippocampal and cortical neurons under conditions of glutamate excitotoxicity.

Activated protein C modulates chemokine response and tissue injury in experimental sepsis

The protein C (PC) pathway plays an important role in vascular function, and acquired deficiency during sepsis is associated with increased mortality. We have explored the role of PC suppression in modulating early inflammatory events in a model of polymicrobial sepsis. We show that increased levels of organ damage and dysfunction are associated with decreased levels of endogenous PC. Notably, animals with low PC had correspondingly high levels of pulmonary iNOS expression, which correlated with chemokines KC/Gro and MIP2, previously shown to predict outcome in this model. Treatment with activated protein C (aPC) not only reduced the pathology score, leukocyte infiltration and markers of organ dysfunction, but also suppressed the induction of iNOS, and the chemokine response (including KC/Gro, MIP2, IP-10, RANTES, GCP-2 and lymphotactin), and increased apoA1. aPC treatment also suppressed the induction of VEGF, a marker recently suggested to play a pathophysiological role in sepsis. These data demonstrate a clear link between low protein C and degree of organ damage and dysfunction in sepsis, as well as the early reversal with aPC treatment. Moreover, our data show a direct role of aPC in broadly modulating monocyte and T-cell chemokines following systemic inflammatory response.

Differential regulation of matrix metalloproteinase 2 and matrix metalloproteinase 9 by activated protein C: relevance to inflammation in rheumatoid arthritis

OBJECTIVE

To investigate the in vitro effect of activated protein C (APC), a natural anticoagulant and novel antiinflammatory agent, on the regulation of the gelatinases matrix metalloproteinase 2 (MMP-2) and MMP-9.

METHODS

Synovial fibroblasts and peripheral blood monocytes isolated from patients with rheumatoid arthritis (RA) or osteoarthritis (OA) and Mono Mac6 cells were used in this study. After treatment, cells and culture supernatants were collected for zymography, enzyme-linked immunosorbent assay, reverse transcription-polymerase chain reaction, and Western blot analysis.

RESULTS

Fibroblasts and monocytes from RA patients produced substantially more MMP-9 than did those from OA patients; however, there was no difference in MMP-2 production. The addition of recombinant APC markedly reduced MMP-9 at the gene and protein levels. In contrast, APC up-regulated and activated MMP-2. Using a blocking antibody to the endothelial protein C receptor (EPCR), we showed that the inhibition of MMP-9 by APC was EPCR-dependent. Furthermore, APC directly suppressed the production of tumor necrosis factor (TNF) and the activation of NF-kappaB and MAP kinase p38, and inhibitors of NF-kappaB or p38 reduced the production of MMP-9, suggesting that APC inhibits MMP-9 by blocking TNF, NF-kappaB, and p38. Thus, APC acts on MMP-9 by binding to EPCRs on the cell surface and, subsequently, inhibiting the intracellular activation of the proinflammatory signaling molecules NF-kappaB and p38.

CONCLUSION

APC appears to be the first physiologic agent to inhibit the production of proinflammatory MMP-9, yet increase antiinflammatory MMP-2 activity. Our results provide the initial evidence that APC may be beneficial in the prevention of inflammation and joint destruction in RA.

[The role of PAR1 in the protective action of activated protein C in the non-immune mast cell activation]

Activated protein C (APC) regulates the functional activity of mast cells by reducing release of beta-hexosaminidase, the marker of mast cell degranulation. APC could modulate the cell secretion of both: the rest mast cells and the activated cells with degranulators, such as proteinase-activated receptor agonist peptide (PAR1-AP) and compound 48/80. PAR1 desensitization with thrombin abolishes the effect of low APC concentration (< or =1,5 nM) on beta-hexosaminidase release by mast cells. APC, inactivated with phenilmethylsulfonilftoride (PMSF), did non mimic the enzyme action on mast cells. The duodenal proteinase, duodenase, activates the peritoneal mast cell via PAR1. APC abolishes the proinflammatory action of duodenase and PAR1-AP by means of reducing release of mast cell mediators. Pretreatment of mast cell with L-NAME abolished these APC effects. Thus, APC-induced decrease of mediator release could be attributed to NO generation by mast cells. Our data indicate that PAR1 takes part in the mechanism of regulatory anti-inflammatory APC action.

Significance of endothelial dysfunction in the pathogenesis of early and delayed radiation enteropathy

This review summarizes the current state of knowledge regarding the role of endothelial dysfunction in the pathogenesis of early and delayed intestinal radiation toxicity and discusses various endothelial-oriented interventions aimed at reducing the risk of radiation enteropathy. Studies published in the biomedical literature during the past four decades and cited in PubMed, as well as clinical and laboratory data from our own research program are reviewed. The risk of injury to normal tissues limits the cancer cure rates that can be achieved with radiation therapy. During treatment of abdominal and pelvic tumors, the intestine is frequently a major dose-limiting factor. Microvascular injury is a prominent feature of both early (inflammatory), as well as delayed (fibroproliferative) radiation injuries in the intestine and in many other normal tissues. Evidence from our and other laboratories suggests that endothelial dysfunction, notably a deficiency of endothelial thrombomodulin, plays a key role in the pathogenesis of these radiation responses. Deficient levels of thrombomodulin cause loss of vascular thromboresistance, excessive activation of cellular thrombin receptors by thrombin, and insufficient activation of protein C, a plasma protein with anticoagulant, anti-inflammatory, and cytoprotective properties. These changes are presumed to be critically involved in many aspects of early intestinal radiation toxicity and may sustain the fibroproliferative processes that lead to delayed intestinal dysfunction, fibrosis, and clinical complications. In conclusion, injury of vascular endothelium is important in the pathogenesis of the intestinal radiation response. Endothelial-oriented interventions are appealing strategies to prevent or treat normal tissue toxicity associated with radiation treatment of cancer.

Bench-to-bedside review: the role of activated protein C in maintaining endothelial tight junction function and its relationship to organ injury

Activated protein C (APC) has emerged as a novel therapeutic agent for use in selected patients with severe sepsis, even though the mechanism of its benefit is not well established. APC has anticoagulant, anti-inflammatory, antiapoptotic, and profibrinolytic properties, but it is not clear through which of these mechanisms APC exerts its benefit in severe sepsis. Focus has recently turned to the role of APC in maintaining endothelial barrier function, and in vitro and in vivo studies have examined this relationship. This article critically reviews these studies, with a focus on potential mechanisms of action.

[The numerous properties of the anticoagulant protein C]

The systemic inflammation associated to the simultaneous activation of blood coagulation and the alterated blood fibrinolysis, leads to microvascular endothelial injury, acute organ dysfunction and possibly death. Activated Protein C, a natural, multifunctional protein, has demonstrated antithrombotic, anti-inflammatory, and profibrinolitic properties and may be an important modulator of the vicious cycle whereby inflammation initiates coagulation and coagulation amplifies inflammation. Protein C couples with its receptor, EPCR (endothelial-cell protein-C receptor), and the ligand-receptor complex then interact with thrombin-thrombomodulin on endothelial surface to produce activated protein C (APC). Once activated, protein C then interact with its cofactor, protein S, to catalyze the inactivation of factors Va and VIIILa, two important accelerators of the clotting cascade, reducing thrombin generation and microvascular thrombosis. In addiction to its anticoagulant activity APC promotes profibrinolytic activity through the inhibition of plasminogen activator inhibitor-1, which is upregulated during inflammation. Inhibition of thrombin generation by APC decreases inflammation by inhibiting platelet activation, neutrophil recruitment, and mast-cell degranulation. APC also shows direct antiinflammatory properties, including blocking of cytokines production by monocytes and blocking cell adhesion. Moreover, APC has antiapoptotic properties that may contribute to its efficacy. In conclusion, APC, besides its physiologic role in the coagulation cascade, plays a key role in the pathophysiology of systemic inflammation justifying its potential therapeutic role in sepsis and systemic inflammatory responses.

Up-regulation interleukin-6 and interleukin-8 by activated protein C in lipopolysaccharide-treated human umbilical vein endothelial cells

OBJECTIVE

To investigate the effect of activated protein C (APC) on inflammatory responses in human umbilical vein endothelial cells (HUVEC) stimulated with lipopolysaccharide (LPS).

METHODS

The second passage of collagenase digested HUVEC was divided into the following groups: serum free medium control group (SFM control), phosphate buffer solution control group (PBS control), LPS group with final concentration of 1 microg/ml (LPS group), APC group with final concentration of 7 microg/ml, Pre-APC group (APC pretreatment for 30 min prior to LPS challenge), and Post-APC group (APC administration 30 min after LPS challenge). Supernatant was harvested at 0, 4, 8, 12 and 24 h after LPS challenge. Interleukin-6 (IL-6) and Interleukin-8 (IL-8) levels were analyzed with ELISA. Cells were harvested at 24 h after LPS challenge, and total RNA was extracted. Messenger RNA levels for IL-6 and IL-8 were semi-quantitatively determined by RT-PCR.

RESULTS

Compared with control group, IL-6 and IL-8 levels steadily increased 4 to 24 h after LPS stimulation. APC treatment could increase LPS-induced IL-6 and IL-8 production. The mRNA levels of IL-6 and IL-8 exhibited a similar change.

CONCLUSION

APC can further increase the level of IL-6 and IL-8 induced by LPS. The effect of these elevated cytokines is still under investigation.

Activated protein C promotes breast cancer cell migration through interactions with EPCR and PAR-1

Activated protein C (APC) is a serine protease that regulates thrombin (IIa) production through inactivation of blood coagulation factors Va and VIIIa. APC also has non-hemostatic functions related to inflammation, proliferation, and apoptosis through various mechanisms. Using two breast cancer cell lines, MDA-MB-231 and MDA-MB-435, we investigated the role of APC in cell chemotaxis and invasion. Treatment of cells with increasing APC concentrations (1-50 microg/ml) increased invasion and chemotaxis in a concentration-dependent manner. Only the active form of APC increased invasion and chemotaxis of the MDA-MB-231 cells when compared to 3 inactive APC derivatives. Using a modified "checkerboard" analysis, APC was shown to only affect migration when plated with the cells; therefore, APC is not a chemoattractant. Blocking antibodies to endothelial protein C receptor (EPCR) and protease-activated receptor-1 (PAR-1) attenuated the effects of APC on chemotaxis in the MDA-MB-231 cells. Finally, treatment of the MDA-MB-231 cells with the proliferation inhibitor, Na butyrate, showed that APC did not increase migration by increasing cell number. Therefore, APC increases invasion and chemotaxis of cells by binding to the cell surface and activating specific signaling pathways through EPCR and PAR-1.

Management of Severe Sepsis in the Surgical Patient

Sepsis and septic shock are not uncommon conditions in the surgical intensive care unit. Sepsis is a generalized activation of the immune system in the presence of clinically suspected or culture-proven infection. Severe sepsis is sepsis with organ system dysfunction. Septic shock is sepsis with hypotension (systolic blood pressure <90 mm Hg) without other causes. Although the incidence of sepsis is increasing, the case fatality rate is falling. This improvement in outcome is in part due to bold initiatives like the Surviving Sepsis Campaign from the Institute for Health Care Improvement. In this article the authors present the epidemiology of severe sepsis and evidence-based campaigns for its treatment, with a focus on the surgical patient.

Upregulated but insufficient generation of activated protein C is associated with development of multiorgan failure in severe acute pancreatitis

INTRODUCTION

Disturbed protein C (PC) pathway homeostasis might contribute to the development of multiple organ failure (MOF) in acute pancreatitis (AP). We therefore evaluated circulating levels of PC and activated protein C (APC), evaluated monocyte deactivation in AP patients, and determined the relationship of these parameters to MOF.

PATIENTS AND METHODS

Thirty-one patients in the intensive care unit were categorized as cases (n = 13, severe AP with MOF) or controls (n = 18, severe AP without MOF). Blood samples were drawn every second day to determine the platelet count, the levels of APC, PC, and D-dimer, and the monocyte HLA-DR expression using flow cytometry. The APC/PC ratio was used to evaluate turnover of PC to APC.

RESULTS

During the initial two weeks of hospitalization, low PC levels (<70% of the adult mean) occurred in 92% of cases and 44% of controls (P = 0.008). The minimum APC level was lower in cases than in controls (median 85% versus 97%, P = 0.009). Using 87% as the cut-off value, 8/13 (62%) cases and 3/18 (17%) controls showed reduced APC levels (P = 0.021). A total of 92% of cases and 50% of controls had APC/PC ratios exceeding the upper normal limit (P = 0.013). Plasma samples drawn before MOF showed low PC levels and high APC/PC ratios. HLA-DR-positive monocytes correlated with PC levels (r = 0.38, P < 0.001) and APC levels (r = 0.27, P < 0.001), indicating that the PC pathway was associated with systemic inflammation-triggered immune suppression.

CONCLUSION

PC deficiency and decreased APC generation in severe AP probably contributed to a compromised anticoagulant and anti-inflammatory defence. The PC pathway defects were associated with the development of MOF. The data support feasibility of testing the use of APC or PC to improve the clinical outcome in AP.

Modulation of monocyte function by activated protein C, a natural anticoagulant

Activated protein C is the first effective biological therapy for the treatment of severe sepsis. Although activated protein C is well established as a physiological anticoagulant, emerging data suggest that it also exerts anti-inflammatory and antiapoptotic effects. In this study, we investigated the ability of activated protein C to modulate monocyte apoptosis, inflammation, phagocytosis, and adhesion. Using the immortalized human monocytic cell line THP-1, we demonstrated that activated protein C inhibited camptothecin-induced apoptosis in a dose-dependent manner. The antiapoptotic effect of activated protein C requires its serine protease domain and is dependent on the endothelial cell protein C receptor and protease-activated receptor-1. In primary blood monocytes from healthy individuals, activated protein C inhibited spontaneous apoptosis. With respect to inflammation, activated protein C inhibited the production of TNF, IL-1beta, IL-6, and IL-8 by LPS-stimulated THP-1 cells. Activated protein C did not influence the phagocytic internalization of Gram-negative and Gram-positive bioparticles by THP-1 cells or by primary blood monocytes. Activated protein C also did not affect the expression of adhesion molecules by LPS-stimulated blood monocytes nor the ability of monocytes to adhere to LPS-stimulated endothelial cells. We hypothesize that the protective effect of activated protein C in sepsis reflects, in part, its ability to prolong monocyte survival in a manner that selectively inhibits inflammatory cytokine production while maintaining phagocytosis and adherence capabilities, thereby promoting antimicrobial properties while limiting tissue damage.

The pivotal role of the endothelium in haemostasis and thrombosis

The endothelium plays a pivotal role in the regulation of the haemostatic balance. The function of endothelial cells exceeds far beyond providing a non-thrombogenic inner layer of the vascular wall which maintains the blood fluidity. In physiological circumstances endothelial cells carefully prevent thrombosis by different anticoagulant and antiplatelet mechanisms. Endothelial cells are involved in all major haemostatic pathways upon vascular injury and limit clot formation to the areas where haemostasis is needed to restore vascular integrity. Failure of this complex balance between pro- and anticoagulant systems because of genetic or acquired disturbances may result in bleeding or thrombosis. Endothelial heterogeneity assures adequate homeostasis in the different organs and parts of the vascular tree. The local environment induces heterogeneous endothelial cell phenotypes determined by local needs. This heterogeneity also explains the diverse pathological responses upon disturbed vascular integrity. Localised manifestation of thrombosis in spite of systemic procoagulant disturbances depends on vascular bed-specific properties. Endothelial dysfunction not only precedes atherogenesis but may also predispose to arterial thrombosis. The potential role of the endothelium in venous thrombosis with and without overt vessel wall injury is discussed. The vast majority of endothelial cells are located in the microvessels. Therefore, it is no surprise that endothelial cells play a key role in microcirculatory diseases such as thrombotic microangiopathies and diffuse intravascular coagulation. Microcirculatory endothelial cell activation is an important feature in all thrombotic microangiopathies. In diffuse intravascular coagulation, the endothelium is the interface between inflammation and inappropriate activation of the coagulation system.

Signal transduction induced by activated protein C: no role in protection against sepsis?

The anticoagulant activated protein C (APC) is historically known as a risk factor for venous thrombosis. However, after the positive results of the protein C worldwide evaluation in severe sepsis (PROWESS) trial, which showed that APC was the first drug that considerably reduced sepsis-related mortality, APC is considered a pleiotropic protein with both anticoagulant and anti-inflammatory properties. In addition, in vitro studies have suggested that APC-induced intracellular signal transduction is a potential mechanism by which APC might be protective against sepsis. Recently, however, the efficacy of APC in sepsis has been argued, and also the extent to which the signal transduction capacity of APC contributes to its pro-survival effects is debated. Here, we review the role of APC in the body natural defense against sepsis and discuss the mechanism by which APC might act at a cellular level.

Inflammation and the activated protein C anticoagulant pathway

After a coagulation stimulus, the blood clotting cascade amplifies largely unchecked until very high levels of thrombin are generated. Natural anticoagulant mechanisms (for example, the protein C anticoagulant pathway) are amplified to prevent excessive thrombin generation. Thrombin binds to thrombomodulin (TM) and this complex and then activates protein C approximately 1000 times faster than free thrombin. Protein C activation is enhanced approximately 20-fold further by the endothelial cell protein C receptor (EPCR). Activated protein C proteolytically inactivates factor Va (FVa) and FVIIIa, thereby blocking the amplification of the coagulation system, a process that is accelerated by protein S. TM not only accelerates protein C activation, but also decreases endothelial cell activation by blocking high-mobility group protein-B1 inflammatory functions and suppressing both nuclear factor-kappa B nuclear translocation and the mitogen-activated protein kinase pathways. The thrombin-TM complex also activates thrombin-activatable fibrinolysis inhibitor, a procarboxypeptidase that renders fibrin resistant to clot lysis and neutralizes vasoactive molecules such as complement C5a. Activated protein C has a variety of antiinflammatory activities. It suppresses inflammatory cytokine elevation in animal models of severe sepsis, inhibits leukocyte adhesion, decreases leukocyte chemotaxis, reduces endothelial cell apoptosis, helps maintain endothelial cell barrier function through activation of the sphingosine-1 phosphate receptor, and minimizes the decrease in blood pressure associated with severe sepsis. Most of these functions are dependent on binding to EPCR. Overall this pathway is critical to both regulation of the blood coagulation process, and control of the innate inflammatory response and some of its associated downstream pathologies.

FoxA2 involvement in suppression of protein C, an outcome predictor in experimental sepsis

Low levels of protein C (PC) predict outcome as early as 10 h after insult in a rat polymicrobial sepsis model and were associated with suppression of PC mRNA, upstream transcription factor FoxA2, and cofactor hepatocyte nuclear factor 6 (HNF6). Small interfering RNA suppression of FoxA2 in isolated hepatocytes demonstrated regulation of both its cofactor HNF6 and PC. Our data suggest that reduced FoxA2 may be important in the suppression of PC and resulting poor outcome in sepsis.

Soluble thrombomodulin is antithrombotic in the presence of neutralising antibodies to protein C and reduces circulating activated protein C levels in primates

We studied whether there was a relationship between the anticoagulant effects of recombinant human soluble thrombomodulin (rhsTM) and activation of protein C in a primate model of acute vascular graft thrombosis in 11 baboons (Papio species). Baboons were pretreated with 0.1, 1 and 5 mg/kg of rhsTM, with or without co-injection of a neutralising monoclonal antibody to protein C (HPC4) in the 1 mg/kg rhsTM group. Subsequently, thrombogenic polyester grafts were deployed for 3 h into chronic exteriorised arteriovenous shunts. Thrombus growth in the graft, plasma-activated protein C (APC) levels, coagulation and thrombosis markers were determined. In untreated baboons, baseline circulating APC levels more than doubled and graft thrombi propagated until reaching equilibrium in about 1 h. Treatment with rhsTM reduced thrombus propagation rates, prolonged the clotting and bleeding times, decreased thrombin-antithrombin complex, beta-thromboglobulin and fibrinopeptide A levels, and, surprisingly, also decreased systemic APC levels, in a dose-dependent manner. In the presence of HPC4 antibody to inhibit APC generation, the acute antithrombotic activity of rhsTM on graft thromboses was not attenuated for up to 80 min, but sustained thrombus accumulation was observed over a 180-min period. These findings suggest that, in contrast to the prevailing hypotheses, the primary antithrombotic activity of rhsTM is independent of protein C, at least in this primate model. Direct inhibition of thrombin's prothrombotic activity upon complex formation with rhsTM might explain the molecular mechanism of the observed antithrombotic effect.

Effects of recombinant human activated protein C in human models of endotoxin administration

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.