Factor Xa-inhibitor (DX-9065a) modulates the leukocyte-endothelial cell interaction in endotoxemic rat

The effect of plasma-derived activated protein C on leukocyte cell-death and vascular endothelial damage

INTRODUCTION

The role of leukocyte and its death in the progression in inflammation attracts attention nowadays. The purpose of this study is to examine the effects of activated protein C (APC) on leucocyte cell death and vascular endothelial damage in sepsis.

METHODS

Wistar rats were infused with lipopolysaccharide (8.0mg/kg) concomitantly with either a low dose (0.5mg/kg), a high dose (5.0mg/kg) of plasma-derived APC or albumin. One and 3hours after the injections, the mesenteric microcirculation was observed by intravital microscopy. The serum levels of nucleosome and High Mobility Group Box 1 (HMGB1) were measured in each group. In another series, cultured leukocyte cell-death in the medium supplemented with serum obtained from each group was examined in vitro.

RESULTS

Microcirculatory disturbance was significantly suppressed in both the high-dose and low-dose groups compared to the control group (P<0.01, 0.05, respectively). The bleeding area was significantly increased in the control and high-dose groups (P<0.05, 0.01, respectively). Serum levels of cell death markers such as nucleosome and HMGB1 were significantly decreased in the treatment groups (P<0.01), and the protective effect was more pronounced in high-dose group. Cell death suppression was most prominent in high-dose group and the formation of neutrophil extracellular traps (NETs) was significantly suppressed in the treatment groups.

CONCLUSION

Low-dose plasma-derived APC exerted protective effects on the microcirculation without increasing the risk of bleeding. The protective effect against leukocyte cell death and the suppressive effect on NETs formation of APC might be related to its beneficial effects.

Is the neutrophil a 'prima donna' in the procoagulant process during sepsis?

Activation of the coagulation system is a fundamental host defense mechanism. Microorganisms that have invaded the body are trapped and disposed of in clots. Monocytes/macrophages are widely accepted as the main players in the procoagulant process; however, recent evidence suggests that neutrophils also play important roles. Tissue factor, which initiates the extrinsic coagulation cascade, is reportedly expressed on the surface of neutrophils, as well as on microparticles derived from neutrophils. Neutrophil extracellular traps (NETs) are another source of tissue factor. The components of NETs, such as DNA, histones, and granule proteins, also provide procoagulant activities. For instance, DNA initiates the intrinsic pathway, histones are a strong generator of thrombin, and granule proteins such as neutrophil elastase, cathepsin G and myeloperoxidase contribute to the suppression of the anticoagulation systems. Although understanding of the mechanisms that are involved in coagulation/fibrinolysis in sepsis has gradually progressed, the impact of neutrophils on thrombogenicity during sepsis remains to be addressed. Since the importance of the connection between coagulation and inflammation is advocated nowadays, further research on neutrophils is required.

Effect of hemoperfusion using polymyxin B-immobilized fibers on acute lung injury in a rat sepsis model

Direct hemoperfusion using polymyxin B-immobilized column (PMX-DHP) is recognized as an effective treatment for septic shock. However, whether its efficacy is limited to cardiovascular dysfunction remains unknown. Therefore, we planned to examine the effects of PMX-DHP in an acute lung injury model. [Materials and methods] Rats were assigned to either PMX-DHP group or control group (n= 7 in each). A lung injury was created by the intratracheal instillation of LPS. In PMX-DHP group, an arteriovenous extracorporeal circuit using PMX column was applied for three hours. The same procedure using a dummy column was applied in control group. The lung microcirculation was observed, and adherent leukocytes, RBC velocity, and the arterial PaO2 were calculated. Pathological changes and the wet/dry weight ratio of the lungs were examined. [Results] Adherent leukocytes and platelets to the lung venules were recognized at 3 hours, and their numbers increased over time. Treatment with PMX-DHP significantly suppressed these events and helped maintenance of the blood flow and PaO2 levels. The lung edema and the histologic damages were also suppressed. [Conclusions] PMX-DHP improved the microcirculation by suppressing leukocyte and platelet adhesion. PMX-DHP had beneficial effects in a model for acute lung injury.

Rivaroxaban attenuates leukocyte adhesion in the microvasculature and thrombus formation in an experimental mouse model of type 2 diabetes mellitus

INTRODUCTION

Thrombosis is a major complication in diabetes mellitus. Since Factor Xa inhibitors are not only inhibit the coagulation system but also attenuate the leukocyte-endothelial interaction in acute inflammation models, the purpose of this study is to confirm the similar effects of rivaroxaban in a mouse model of type 2 diabetes mellitus.

MATERIALS AND METHODS

In the treatment groups, either 5 or 10mg/kg of rivaroxaban dissolved in DMSO was orally given to KK-A(y) mice for 7 weeks (n=6 in each group). KK-A(y) mice fed by chow containing DMSO without rivaroxaban for 7 weeks were served for the control group (n=6). Following clamping of the mesenteric vein for 20 minutes, intravital microscopic observation of the intestinal microcirculation and the measurement of bleeding time after the needle puncture were carried-out. In another series, the calculation for blood cell counts and the measurement of blood fluidity using micro channel array flow analyzer (MC-FAN) were performed.

RESULTS

The initial event in the microvasculature is the leukocyte adhesion on endothelium. Then, the leukocytes make clusters and the platelets are involved in. These leukocyte-platelet conjugates aggregate and form thrombus. The leukocyte adherence and the microthrombus formation was significantly suppressed with the treatment of 10 mg/kg of rivaroxaban compared to the control group (P<0.05). While, the bleeding time was significantly extended with the treatment with 10mg/kg of rivaroxaban (P<0.01). The blood fluidity was maintained best with the treatment of 10 mg/kg rivaroxaban.

CONCLUSIONS

Rivaroxaban attenuates the leukocyte-platelet-endothelial interaction, which leads to the attenuation of microthrombus formation in a mouse model of diabetes mellitus.

Combination of antithrombin and recombinant thrombomodulin attenuates leukocyte-endothelial interaction and suppresses the increase of intrinsic damage-associated molecular patterns in endotoxemic rats

INTRODUCTION

Both antithrombin (AT) and thrombomodulin are key players in physiological anticoagulant systems. Because the levels of both factors are known to decrease significantly during severe sepsis, we hypothesized that a combination therapy would be effective.

METHODS

A sepsis model was established using the intravenous infusion of lipopolysaccharide (LPS). A dose of 125 IU/kg of AT, 0.25 mg/kg of recombinant thrombomodulin, or a combination of both agents was injected immediately after LPS infusion (n = 7, each). Intravital observation of the mesenteric microcirculation was performed, and leukocyte adhesion and blood flow were calculated at 3 h after LPS infusion. Immediately after the observation, blood samples were obtained and coagulation markers, organ damage markers, the circulating levels of nucleosome and high-mobility group box 1 were measured.

RESULTS

Microscopic findings revealed the suppression of leukocyte adhesion and thrombus formation in the combination group. The number of adhesive leukocytes on the endothelium was significantly suppressed (P < 0.01), and the blood flow in venules was better maintained in the combination group compared with the placebo control (P < 0.01). The blood samples showed the suppressed activation in coagulation, no significant changes were observed in the organ damage markers in the treatment groups. The circulating levels of nucleosome and high-mobility group box 1 were both decreased significantly in the combination group compared with the placebo control (P < 0.01).

CONCLUSIONS

The coadministration of AT and recombinant thrombomodulin is effective for the suppression of leukocyte activation and cell death during sepsis.

Recombinant thrombomodulin improves the visceral microcirculation by attenuating the leukocyte-endothelial interaction in a rat LPS model

INTRODUCTION

Abnormalities in vascular endothelial function play an important role in the development of septic organ dysfunction. The aim of this study was to examine the effect of recombinant thrombomodulin (rTM) on leukocyte-endothelial interaction and subsequent malcirculation in endotoxemia.

MATERIALS AND METHODS

Wistar rats were administered with either low, medium or high dose of rTM (n=7 each) 2hours after lipopolysaccharide (LPS) infusion. Mesenteric microcirculation after the treatment was observed under the intravital microscopy. In another series (n=5 each), plasma levels of high-mobility group box 1 (HMGB1) levels were measured at 5hours after LPS infusion.

RESULTS

Microscopic findings revealed suppression in leukocyte adhesion, thrombus formation and endothelial damage with the treatment by rTM. However, high-dose rTM tended to increase the bleeding events. Thus, blood flow was better maintained with medium-dose rTM (P<0.05). The increase in HMGB1 level was significantly suppressed by medium and high-dose rTM (P<0.05, respectively).

CONCLUSIONS

rTM demonstrated a protective effect on microcirculation through the inhibition of leukocyte-endothelial interaction and suppression of HMGB1.

Tissue factor, blood coagulation, and beyond: an overview

Emerging evidence shows a broad spectrum of biological functions of tissue factor (TF). TF classical role in initiating the extrinsic blood coagulation and its direct thrombotic action in close relation to cardiovascular risks have long been established. TF overexpression/hypercoagulability often observed in many clinical conditions certainly expands its role in proinflammation, diabetes, obesity, cardiovascular diseases, angiogenesis, tumor metastasis, wound repairs, embryonic development, cell adhesion/migration, innate immunity, infection, pregnancy loss, and many others. This paper broadly covers seminal observations to discuss TF pathogenic roles in relation to diverse disease development or manifestation. Biochemically, extracellular TF signaling interfaced through protease-activated receptors (PARs) elicits cellular activation and inflammatory responses. TF diverse biological roles are associated with either coagulation-dependent or noncoagulation-mediated actions. Apparently, TF hypercoagulability refuels a coagulation-inflammation-thrombosis circuit in “autocrine” or “paracrine” fashions, which triggers a wide spectrum of pathophysiology. Accordingly, TF suppression, anticoagulation, PAR blockade, or general anti-inflammation offers an array of therapeutical benefits for easing diverse pathological conditions.

Factor Xa induces tissue factor expression in endothelial cells by P44/42 MAPK and NF-κB-dependent pathways

BACKGROUND

Tissue factor (TF) is an initiator of coagulation. The serine protease factor Xa (FXa) is the convergence point of the extrinsic and intrinsic components of the coagulation cascade. In addition to its hemostatic function, FXa elicits inflammatory responses in endothelial cells that may be important in surgical procedures in which inflammation is triggered. This study tested the hypothesis that FXa can up-regulate TF on vascular endothelial cells by a mitogen-activated protein kinase (MAPK)- and NF-κB-dependent pathway.

METHODS AND RESULTS

Incubation of cultured human umbilical vein endothelial cells (HUVECs) with FXa increased TF protein expression and activity in a dose-dependent manner. Pre-incubation of HUVECs with the serine protease inhibitor antithrombin, which targets not only thrombin but also FXa and FIXa, inhibited FXa-induced TF expression, but the selective thrombin inhibitor hirudin did not inhibit FXa-induced TF expression, ruling out a thrombin-mediated pathway. After 10 min incubation with HUVECs, FXa rapidly induced P44/42 MAPK activation (immunoblotting of phosphorylated P44/42 MAPK) with a peak at 30 min. The MEK 1/2 inhibitor PD98059 partially reduced FXa-induced TF expression and activity (3.82 ± 0.11 vs 6.54 ± 0.08 fmol/min/cm(2), P < 0.05). NF-κB was activated by FXa, confirmed by cytoplasmic IkBα degradation and increased NF-κB P65 nuclear translocation. Interruption of the NF-κB pathway by the IkBα phosphorylation inhibitor Bay 11-7802 abrogated FXa-induced TF protein expression and activity (1.93 ± 0.02 versus 6.54 ± 0.08 fmol/min/cm(2), P < 0.05). However, inhibition of PI3 kinase by LY 294002 did not attenuate FXa-induced TF protein expression and activity.

CONCLUSIONS

(1) FXa up-regulates TF protein expression and activity in HUVECs, (2) FXa-induced up-regulation of TF is independent of the thrombin-PAR1 pathway, and (3) the MAPK and NF-κB pathways, but not PI3 kinase pathway, are involved in FXa-induced TF expression on human umbilical endothelial cells. FXa may be a feed-forward alternative mechanism of activating TF expression and activity, thereby increasing a procoagulant state or inflammation. This mechanism may be important in the pro-inflammatory state initiated by cardiac surgical procedures.

Enoxaparin attenuates endothelial damage with less bleeding compared with unfractionated heparin in endotoxemic rats

Prophylactic use of anticoagulants during sepsis is strongly recommended for the prevention of venous thrombosis. Moreover, recent studies suggested the positive effects of anticoagulants to the inflammation. In this study, we planned to confirm the effects of heparins on protecting against endothelial damage in endotoxemia. In addition, we also examined the differences between unfractionated heparin (UFH) and enoxaparin. Wistar rats received 8.5 mg/kg (i.v.) LPS, followed by a bolus infusion of either 350 U/kg of UFH, 2.0 mg/kg of enoxaparin, or placebo. Microscopic observation of the mesenteric microcirculation and the measurement of the bleeding area after puncture with a microneedle were performed 3 h later (n = 6 in each group). In another series, blood samples were taken 3 h after the LPS injection, and blood cell counts, coagulation markers, and organ damage markers were measured (n = 6 in each). As a result, the leukocyte adherence to the endothelium was significantly reduced in both the UFH and enoxaparin groups, and thus, endothelial damage was attenuated in these groups. The bleeding area was markedly expanded in the UFH group compared with the other groups (P < 0.01 each). The decrease in white blood cells and platelet count was significantly suppressed in the enoxaparin group compared with the UFH group (P < 0.05 each). The fibrinogen level was maintained at significantly better levels, and the elevation of alanine aminotransferase was significantly suppressed in enoxaparin group (P < 0.05 each). In conclusion, both UFH and enoxaparin protect against endothelial damage by preventing leukocyte adhesion. However, UFH significantly increases the bleeding area, whereas enoxaparin does not increase bleeding, and thus, it can reduce organ damages in the endotoxemic rat.

Danaparoid sodium inhibits systemic inflammation and prevents endotoxin-induced acute lung injury in rats

Introduction

Systemic inflammatory mediators, including high mobility group box 1 (HMGB1), play an important role in the development of sepsis. Anticoagulants, such as danaparoid sodium (DA), may be able to inhibit sepsis-induced inflammation, but the mechanism of action is not well understood. We hypothesised that DA would act as an inhibitor of systemic inflammation and prevent endotoxin-induced acute lung injury in a rat model.

Methods

We used male Wistar rats. Animals in the intervention arm received a bolus of 50 U/kg of DA or saline injected into the tail vein after lipopolysaccharide (LPS) administration. We measured cytokine (tumour necrosis factor (TNF)α, interleukin (IL)-6 and IL-10) and HMGB1 levels in serum and lung tissue at regular intervals for 12 h following LPS injection. The mouse macrophage cell line RAW 264.7 was assessed following stimulation with LPS alone or concurrently with DA with identification of HMGB1 and other cytokines in the supernatant.

Results

Survival was significantly higher and lung histopathology significantly improved among the DA (50 U/kg) animals compared to the control rats. The serum and lung HMGB1 levels were lower over time among DA-treated animals. In the in vitro study, administration of DA was associated with decreased production of HMGB1. In the cell signalling studies, DA administration inhibited the phosphorylation of IκB.

Conclusion

DA decreases cytokine and HMGB1 levels during LPS-induced inflammation. As a result, DA ameliorated lung pathology and reduces mortality in endotoxin-induced systemic inflammation in a rat model. This effect may be mediated through the inhibition of cytokines and HMGB1.

Comparison of the protective effects of type III phosphodiesterase (PDE3) inhibitor (cilostazol) and acetylsalicylic acid on intestinal microcirculation after ischemia reperfusion injury in mice

Antiplatelet therapy has been proposed as the treatment of choice for ischemia/reperfusion injury. The aim of this study is to elucidate the difference in effect between cilostazol (CZ) and acetylsalicylic acid (ASA) on microcirculatory disturbance in ischemia/reperfusion injury. Either 10 mg/kg of CZ (n = 14) or 100 mg/kg of ASA (n = 14) was administered orally to mice. Thereafter, 20 min of intestinal ischemia, followed by 60-min reperfusion, was applied; then, the status of submucosal microcirculation was observed under intravital microscopy. The blood cell counts and organ damage markers were examined in the portal blood. Next, 5 mm of the ileum was excised and was then histologically examined. Platelet-leukocyte aggregates were often observed in the postcapillary venules, and this formation was significantly reduced by both CZ and ASA. The number of adherent leukocytes was significantly lesser in the CZ-treated mice than in the ASA-treated mice (P < 0.01). The leukocyte number, lactate dehydrogenase, and lactate levels were best maintained in the CZ-treated mice (P < 0.05). The villus height was best preserved in the CZ-treated mice. Cilostazol inhibited not only the platelet aggregation but also the leukocyte adhesion to the endothelium, thereby inducing organ protection.

Tissue factor upregulation drives a thrombosis-inflammation circuit in relation to cardiovascular complications

The extrinsic coagulation is recognized as an 'inducible' signalling cascade resulting from tissue factor (TF) upregulation by exposure to clotting zymogen FVII upon inflammation or tissue injury. Following the substantial initiation, an array of proteolytic activation generates mediating signals (active serine proteases: FVIIa, FXa and FIIa) that lead to hypercoagulation with fibrin overproduction manifesting thrombosis. In addition, TF upregulation plays a central role in driving a thrombosis-inflammation circuit. Coagulant mediators (FVIIa, FXa and FIIa) and endproduct (fibrin) are proinflammatory, eliciting tissue necrosis factor, interleukins, adhesion molecules and many other intracellular signals in different cell types. Such resulting inflammation could ensure 'fibrin' thrombosis via feedback upregulation of TF. Alternatively, the resulting inflammation triggers platelet/leukocyte/polymononuclear cell activation thus contributing to 'cellular' thrombosis. TF is very vulnerable to upregulation resulting in hypercoagulability and subsequent thrombosis and inflammation, either of which presents cardiovascular risks. The prevention and intervention of TF hypercoagulability are of importance in cardioprotection. Blockade of inflammation reception and its intracellular signalling prevents TF expression from upregulation. Natural (activated protein C, tissue factor pathway inhibitor, or antithrombin III) or pharmacological anticoagulants readily offset the extrinsic hypercoagulation mainly through FVIIa, FXa or FIIa inhibition. Therefore, anticoagulants turn off the thrombosis-inflammation circuit, offering not only antithrombotic but anti-inflammatory significance in the prevention of cardiovascular complications.

Tissue factor mediates inflammation

The role of tissue factor (TF) in inflammation is mediated by blood coagulation. TF initiates the extrinsic blood coagulation that proceeds as an extracellular signaling cascade by a series of active serine proteases: FVIIa, FXa, and thrombin (FIIa) for fibrin clot production in the presence of phospholipids and Ca2+. TF upregulation resulting from its enhanced exposure to clotting factor FVII/FVIIa often manifests not only hypercoagulable but also inflammatory state. Coagulant mediators (FVIIa, FXa, and FIIa) are proinflammatory, which are largely transmitted by protease-activated receptors (PAR) to elicit inflammation including the expression of tissue necrosis factor, interleukins, adhesion molecules (MCP-1, ICAM-1, VCAM-1, selectins, etc.), and growth factors (VEGF, PDGF, bFGF, etc.). In addition, fibrin, and its fragments are also able to promote inflammation. In the event of TF hypercoagulability accompanied by the elevations in clotting signals including fibrin overproduction, the inflammatory consequence could be enormous. Antagonism to coagulation-dependent inflammation includes (1) TF downregulation, (2) anti-coagulation, and (3) PAR blockade. TF downregulation and anti-coagulation prevent and limit the proceeding of coagulation cascade in the generation of proinflammatory coagulant signals, while PAR antagonists block the transmission of such signals. These approaches are of significance in interrupting the coagulation-inflammation cycle in contribution to not only anti-inflammation but also anti-thrombosis for cardioprotection.

Antithrombin ameliorates endotoxin-induced organ dysfunction more efficiently when combined with danaparoid sodium than with unfractionated heparin

OBJECTIVE

This study investigated the potential benefits of combination therapy using antithrombin (AT) with danaparoid sodium (DA) compared with the use of AT with unfractionated heparin (UFH) in the treatment of sepsis.

METHODS

Rats infused with lipopolysaccharide were treated with either DA alone, AT alone, AT plus DA, AT plus UFH, or human serum albumin as controls. AT (125 U/kg) was injected into the AT group immediately after lipopolysaccharide infusion. The AT/DA and AT/UFH groups received the same dose of AT in conjunction with either DA (400 U/kg) or UFH (400 U/kg). The status of the mesenteric microcirculation was examined by intra-vital microscopy and the laboratory indices of coagulation, inflammation, and organ dysfunction were measured.

RESULTS

The coagulation markers were improved following the administration of DA or UFH. The decreases in the WBC counts were significantly suppressed in the AT/DA group. The elevation of IL-6 decreased in the AT, DA, and AT/DA groups (all p<0.01) but not in the AT/UFH group. The prostaglandin I2 levels were significantly elevated only in the AT/DA group (p<0.05). The WBC adhesion was significantly suppressed in the DA, AT/UFH, and AT/DA groups (p<0.05), and the RBC velocity was best maintained in the AT/DA group with no associated increase in capillary hemorrhage. The elevation of ALT and BUN significantly improved only in the AT/DA group. ONCLUSION: Organ dysfunction can thus be alleviated by even moderate doses of AT replacement when co-administered with DA.

Antithrombotic agents in the treatment of severe sepsis

Sepsis, a systemic inflammatory syndrome, is a response to infection and when associated with multiple organ dysfunction is termed severe sepsis. It remains a leading cause of mortality in the critically ill. The response to the invading microorganisms may be considered as a balance between a pro-inflammatory and an anti-inflammatory reaction. While an inadequate pro-inflammatory reaction and a strong anti-inflammatory response could lead to overwhelming infection and the death of the patient, a strong and uncontrolled pro-inflammatory response, manifested by the release of pro-inflammatory mediators may lead to microvascular thrombosis and multiple organ failure. Endotoxin triggers sepsis via the release of various mediators such as tumour necrosis factor-alpha and interleukin-1 (IL-1). These cytokines activate the complement and coagulation systems, release adhesion molecules, prostaglandins, leukotrienes, reactive oxygen species and nitric oxide. Other mediators involved in the sepsis syndrome include IL-1, -6 and -8; arachidonic acid metabolites; platelet activating factor; histamine; bradykinin; angiotensin; complement components and vasoactive intestinal peptide. These pro-inflammatory responses are counteracted by IL-10. Most of the trials targeting the different mediators of the pro-inflammatory response have failed due to a lack of correct definition of sepsis. Understanding the exact pathophysiology of the disease will enable more advanced treatment options. Targeting the coagulation system with various anticoagulant agents including, activated protein C, and tissue factor pathway inhibitor (TFPI) is a rational approach. Many clinical trials have been conducted to evaluate these agents in severe sepsis. While trials on antithrombin and TFPI were not so successful, the double-blind, placebo-controlled, Phase III trial of recombinant human activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) was successful, creating a significant decrease in mortality when compared to the placebo group. A better understanding of the pathophysiologic mechanism of severe sepsis will provide better treatment options, and combination antithrombotic treatment may provide a multipronged approach for the treatment of severe sepsis.

Activated protein C improves the visceral microcirculation by attenuating the leukocyte-endothelial interaction in a rat lipopolysaccharide model

OBJECTIVE

Abnormalities in the vascular endothelial function play an important role in the development of septic organ dysfunction. The aim of the study was to examine the effect of recombinant human activated protein C on leukocyte-endothelial interaction in endotoxemia.

DESIGN

Experimental animal model of sepsis.

SETTING

University research laboratory.

SUBJECTS

Normal Wistar rats. Each animal was infused with 4.5 mg/kg lipopolysaccharide to simulate severe sepsis.

INTERVENTIONS

Rats were injected with endotoxin simultaneously with either a low or a high dose of recombinant human activated protein C (n = 7). One, 2, and 3 hrs after injection, mesenteric microcirculation was observed under intravital microscopy. In another series, tumor necrosis factor, interleukin-6, alanine transaminase, and blood urea nitrogen levels were evaluated (n = 5).

MEASUREMENTS AND MAIN RESULTS

The adhesive leukocyte count on the endothelium was significantly suppressed in both high-dose and low-dose groups (p < .01 and .05, respectively). The bleeding events decreased in the low-dose treatment group compared with both the control (p < .05) and high-dose group (p < .05). Microcirculatory flow as expressed by red blood cell velocity was maintained better in the low-dose group. Comparison of cytokine levels showed a significant decrease in the treatment groups. Organ damage markers were also suppressed in the treatment groups (p < .05)

CONCLUSIONS

Recombinant human activated protein C demonstrated a protective effect on microcirculation through the inhibition of leukocyte-endothelial interaction and suppression of inflammatory cytokine production.

Clinical and experimental experience with factor Xa inhibitors

Cardiovascular disease is the major cause of mortality in the industrial world today. We are constantly moving towards new and better ways of fighting this epidemic. Advances have been made in various fields such as patient education, imaging techniques, interventional cardiology, and novel therapeutic agents. In particular, antithrombotics are being studied with great interest and hope. Amid this class of agents, factor Xa inhibitors have already begun to show promising results in trials involving patients with acute coronary syndromes. Whereas DX-9065a is in late stage clinical trials, fondaparinux sodium is available for clinical use. Promising results have been obtained with fondaparinux sodium in patients with coronary artery disease in the PENTUA (Pentasaccharide in Unstable Angina) and PENTALYSE (Pentasaccharide as an Adjunct to Fibrinolysis in ST-Elevation Acute Myocardial Infarction) trials. Besides having a direct effect on the coagulation cascade, they have shown properties that indirectly influence the remodeling of plaques in the coronary circulation. Available evidence on factor Xa inhibitors does not ensure a remedy to acute coronary syndromes but it gives hope of improving current treatments and reducing the morbidity and mortality of cardiovascular disease. The efficacy and tolerability of fondaparinux sodium in the prevention and treatment of deep vein thrombosis (with or without pulmonary embolism) has been established in several large trials such as PENTATHLON (Pentasaccharide in Total Hip Replacement Surgery), PENTAMAKS (Pentasaccharide in Major Knee Surgery), EPHESUS (European Pentasaccharide Hip Elective Surgery), PENTHIFRA (Pentasaccharide in Hip-Fracture Surgery), and PENTHIFRA-Plus. Whereas fondaparinux sodium offers benefits over low molecular weight heparins and unfractionated heparin, the incidence of bleeding complications was greater with fondaparinux sodium than with unfractionated heparin. Treatment with factor VIIa can reverse the anticoagulant effect of fondaparinux sodium and this may be particularly important in patients who need to undergo emergency surgical procedures. Fondaparinux sodium has been recently approved for use, in conjunction with warfarin, in patients with symptomatic deep vein thrombosis or acute pulmonary embolism based on the results of two large trials conducted by the Matisse investigators. In conclusion, these observations strongly suggest the clinical potential of this class of agents in preventing arterial and venous thrombosis.

Antithrombin Modulates the Leukocyte???Endothelial Cell Interaction in the Staphylococcal Enterotoxin B-Challenged Mouse

BACKGROUND

The beneficial effects of antithrombin on endotoxemia are well known. The purpose of this study was to examine the effects of antithrombin in a supertoxin-induced sepsis.

METHODS

Mice were injected with staphylococcal enterotoxin B simultaneously with antithrombin. At 1 hour after injection, the mesenteric microcirculation was observed under intravital microscopy. In addition, humoral mediators were measured at the same time.

RESULTS

The number of rolling leukocytes on the endothelium was significantly reduced in the treated mice (p < 0.01). The decrease of white blood cell and platelet counts was significantly inhibited in the treated animals (p < 0.01 for both). A comparison of the intercellular adhesion molecule-1 (p < 0.05), soluble tumor necrosis factor-alpha receptor (p < 0.05), and interleukin-6 (p < 0.01) levels showed less increase in the treated mice.

CONCLUSION

Antithrombin showed a protective effects on the microcirculation of staphylococcal enterotoxin B-challenged mice by attenuating leukocyte-endothelial cell interaction. Suppression of adhesive molecule expression and cytokine production appears to play roles in this effect.