Antithrombin effects on endotoxin-induced microcirculatory disorders are mediated mainly by its interaction with microvascular endothelium

The future of intensive care: the study of the microcirculation will help to guide our therapies

The goal of hemodynamic resuscitation is to optimize the microcirculation of organs to meet their oxygen and metabolic needs. Clinicians are currently blind to what is happening in the microcirculation of organs, which prevents them from achieving an additional degree of individualization of the hemodynamic resuscitation at tissue level. Indeed, clinicians never know whether optimization of the microcirculation and tissue oxygenation is actually achieved after macrovascular hemodynamic optimization. The challenge for the future is to have noninvasive, easy-to-use equipment that allows reliable assessment and immediate quantitative analysis of the microcirculation at the bedside. There are different methods for assessing the microcirculation at the bedside; all have strengths and challenges. The use of automated analysis and the future possibility of introducing artificial intelligence into analysis software could eliminate observer bias and provide guidance on microvascular-targeted treatment options. In addition, to gain caregiver confidence and support for the need to monitor the microcirculation, it is necessary to demonstrate that incorporating microcirculation analysis into the reasoning guiding hemodynamic resuscitation prevents organ dysfunction and improves the outcome of critically ill patients.

Post-traumatic brain injury antithrombin III recovers Morris water maze cognitive performance, improving cued and spatial learning

BACKGROUND

Neuroinflammation and cerebral edema development following severe traumatic brain injury (TBI) affect subsequent cognitive recovery. Independent of its anticoagulant effects, antithrombin III (AT-III) has been shown to block neurovascular inflammation after severe TBI, reduce cerebral endothelial-leukocyte interactions, and decrease blood-brain barrier permeability. We hypothesized that AT-III administration after TBI would improve post-TBI cognitive recovery, specifically enhancing learning, and memory.

METHODS

Fifteen CD1 male mice were randomized to undergo severe TBI (controlled cortical impact [CCI]: velocity, 6 m/s; depth, 1 mm; diameter, 3 mm) or sham craniotomy and received either intravenous AT-III (250 IU/kg) or vehicle (VEH/saline) 15 minutes and 24 hours post-TBI. Animals underwent Morris water maze testing from 6 to 14 days postinjury consisting of cued learning trials (platform visible), spatial learning trials (platform invisible, spatial cues present), and probe (memory) trials (platform removed, spatial cues present). Intergroup differences were assessed by the Kruskal-Wallis test (p < 0.05).

RESULTS

Morris water maze testing demonstrated that cumulative cued learning (overall mean time in seconds to reach the platform on days 6-8) was worst in CCI-VEH animals (26.1 ± 2.4 seconds) compared with CCI-AT-III counterparts (20.3 ± 2.1 seconds, p < 0.01). Cumulative noncued spatial learning was also worst in the CCI-VEH group (23.4 ± 1.8 seconds) but improved with AT-III (17.6 ± 1.5 seconds, p < 0.01). In probe trials, AT-III failed to significantly improve memory ability. Animals that underwent sham craniotomy demonstrated preserved learning and memory compared with all CCI counterparts (p < 0.05).

CONCLUSION

Antithrombin III improves neurocognitive recovery weeks after TBI. This improvement is particularly related to improvement in learning but not memory function. Pharmacologic support of enhanced learning may support new skill acquisition or relearning to improve outcomes after TBI.

LEVEL OF EVIDENCE

Therapeutic/care management, level II.

Antithrombin III ameliorates post-traumatic brain injury cerebral leukocyte mobilization enhancing recovery of blood brain barrier integrity

BACKGROUND

Acute traumatic coagulopathy often accompanies traumatic brain injury (TBI) and may impair cognitive recovery. Antithrombin III (AT-III) reduces the hypercoagulability of TBI. Antithrombin III and heparinoids such as enoxaparin (ENX) demonstrate potent anti-inflammatory activity, reducing organ injury and modulating leukocyte (LEU) activation, independent of their anticoagulant effect. It is unknown what impact AT-III exerts on cerebral LEU activation and blood-brain barrier (BBB) permeability after TBI. We hypothesized that AT-III reduces live microcirculatory LEU-endothelial cell (EC) interactions and leakage at the BBB following TBI.

METHODS

CD1 mice (n = 71) underwent either severe TBI (controlled cortical impact (CCI), 6-m/s velocity, 1-mm depth, and 4-mm diameter) or sham craniotomy and then received either AT-III (250 IU/kg), ENX (1.5 mg/kg), or vehicle (saline) every 24 hours. Forty-eight hours post-TBI, cerebral intravital microscopy visualized in vivo penumbral microvascular LEU-EC interactions and microvascular leakage to assess BBB inflammation/permeability. Body weight loss and the Garcia neurological test (motor, sensory, reflex, balance) served as surrogates of clinical recovery.

RESULTS

Both AT-III and ENX similarly reduced in vivo penumbral LEU rolling and adhesion (p < 0.05). Antithrombin III also reduced live BBB leakage (p < 0.05). Antithrombin III animals demonstrated the least 48-hour body weight loss (8.4 ± 1%) versus controlled cortical impact and vehicle (11.4 ± 0.5%, p < 0.01). Garcia neurological test scores were similar among groups.

CONCLUSION

Antithrombin III reduces post-TBI penumbral LEU-EC interactions in the BBB leading to reduced neuromicrovascular permeability. Antithrombin III further reduced body weight loss compared with no therapy. Further study is needed to determine if these AT-III effects on neuroinflammation affect longer-term neurocognitive recovery after TBI.

The glycocalyx: a central regulator of vascular function

The endothelial glycocalyx is a specialized extracellular matrix that covers the apical side of vascular endothelial cells, projecting into the lumen of blood vessels. The composition of the glycocalyx has been studied in great detail, and it is known to be composed of a mixture of proteoglycans, glycosaminoglycans, and glycoproteins. Although this structure was once believed to be a passive physical barrier, it is now recognized as a multifunctional and dynamic structure that participates in many vascular processes, including but not limited to vascular permeability, inflammation, thrombosis, mechanotransduction, and cytokine signaling. Because of its participation in many physiological and pathophysiological states, comprehensive knowledge of the glycocalyx will aid future vascular biologists in their research. With that in mind, this review discusses the biochemical structure of the glycocalyx and its function in many vascular physiological processes. We also briefly review a more recent discovery in glycocalyx biology, the placental glycocalyx.

The compelling arguments for the need of microvascular investigation in COVID-19 critical patients

The burden of pandemic COVID-19 is growing worldwide, as the continuous increases of contagion. Only 10–15% of the entire infected population has the necessity of intensive care unit (ICU) treatments. But, this relatively low rate of patients has absorbed almost the whole availability of ICU during few days, becoming at least in Italy, an emergency for the national health system. In COVID-19 ICU patients massive aggression of lung with severe pulmonary failure, as well as kidney and liver injuries, heart, brain, bowel and spleen damages with lymph nodes necrosis and even cutaneous manifestations have been observed. Moreover, increased levels of cytokines so-called “cytokines storm (CS), and overt intravascular disseminated coagulation have been also reported. The hypercoagulation and CS would speculate about a microvascular dysfunction. Unfortunately, no specific observations have been performed on microcirculatory dysfunction in COVID-19 patients. Hence the presumed pathophysiological pathways and models about a microvascular involvement can be gathered by sepsis models studies. But despite this lack of evidence, the COVID-19 has emphasized the compelling need for microcirculation monitoring at the bedside in ICU patients.

Single Low Dose of Human Recombinant Antithrombin (ATryn) has no Impact on Endotoxin-Induced Disseminated Intravascular Coagulation: An Experimental Randomized Open Label Controlled Study

BACKGROUND

Antithrombin (AT) III physiological levels are decreased during septic shock and supplementation therapy could therefore be beneficial.

OBJECTIVE

We hypothesized that the use of recombinant human AT could reduce disseminated intravascular coagulation (DIC) occurrence.

METHODS

We conducted a randomized open label controlled experimental study. Ten female "Large White" pigs were challenged with i.v. infusion of Escherichia coli endotoxin. Two groups of 5 pigs were randomly assigned to receive either recombinant human AT 100 U/kg over 30 min (ATryn group) or 0.9% saline (control group). AT III levels, coagulation, hemostasis, inflammation parameters, hemodynamics, and microcirculatory parameters were measured over a 5-h period. Immediately after euthanasia, kidneys were withdrawn for histology evaluation. Statistical analysis was performed with nonparametric tests and Dunn's test for multiple comparisons.

RESULTS

AT III activity was significantly higher in the ATryn group than in the control group from 60% (213% [203-223] vs. 104% [98-115], P = 0.008, respectively) to 300 min (115% [95-124] vs. 79% [67-93], P = 0.03). Recombinant human AT supplementation had no impact on hemodynamics, microcirculatory parameters, and sequential changes of coagulation parameters (platelet count, fibrinogen level, thrombin-AT complexes, and von Willebrand factor). Interleukin 6 and tumor necrosis factor α values were statistically the same for both groups throughout the study. Percentage of thrombosed glomeruli and percentage of thrombosed capillary in glomerulus were not significantly different between both groups.

CONCLUSIONS

In our model of endotoxic shock, a single low dose of recombinant human AT did not prevent DIC occurrence, severity, inflammatory profile, or hemodynamic alterations.

Photonic monitoring of treatment during infection and sepsis: development of new detection strategies and potential clinical applications

Despite the strong decline in the infection-associated mortality since the development of the first antibiotics, infectious diseases are still a major cause of death in the world. With the rising number of antibiotic-resistant pathogens, the incidence of deaths caused by infections may increase strongly in the future. Survival rates in sepsis, which occurs when body response to infections becomes uncontrolled, are still very poor if an adequate therapy is not initiated immediately. Therefore, approaches to monitor the treatment efficacy are crucially needed to adapt therapeutic strategies according to the patient's response. An increasing number of photonic technologies are being considered for diagnostic purpose and monitoring of therapeutic response; however many of these strategies have not been introduced into clinical routine, yet. Here, we review photonic strategies to monitor response to treatment in patients with infectious disease, sepsis, and septic shock. We also include some selected approaches for the development of new drugs in animal models as well as new monitoring strategies which might be applicable to evaluate treatment response in humans in the future. Figure Label-free probing of blood properties using photonics.

To What Extent Are the Terminal Stages of Sepsis, Septic Shock, Systemic Inflammatory Response Syndrome, and Multiple Organ Dysfunction Syndrome Actually Driven by a Prion/Amyloid Form of Fibrin?

A well-established development of increasing disease severity leads from sepsis through systemic inflammatory response syndrome, septic shock, multiple organ dysfunction syndrome, and cellular and organismal death. Less commonly discussed are the equally well-established coagulopathies that accompany this. We argue that a lipopolysaccharide-initiated (often disseminated intravascular) coagulation is accompanied by a proteolysis of fibrinogen such that formed fibrin is both inflammatory and resistant to fibrinolysis. In particular, we argue that the form of fibrin generated is amyloid in nature because much of its normal α-helical content is transformed to β-sheets, as occurs with other proteins in established amyloidogenic and prion diseases. We hypothesize that these processes of amyloidogenic clotting and the attendant coagulopathies play a role in the passage along the aforementioned pathways to organismal death, and that their inhibition would be of significant therapeutic value, a claim for which there is considerable emerging evidence.

HS3ST1 genotype regulates antithrombin's inflammomodulatory tone and associates with atherosclerosis

The HS3ST1 gene controls endothelial cell production of HS^AT+ - a form of heparan sulfate containing a specific pentasaccharide motif that binds the anticoagulant protein antithrombin (AT). HS^AT+ has long been thought to act as an endogenous anticoagulant; however, coagulation was normal in Hs3st1^-/- mice that have greatly reduced HS^AT+ (HajMohammadi et al., 2003). This finding indicates that HS^AT+ is not essential for AT's anticoagulant activity. To determine if HS^AT+ is involved in AT's poorly understood inflammomodulatory activities, Hs3st1^-/- and Hs3st1^+/+ mice were subjected to a model of acute septic shock. Compared with Hs3st1^+/+ mice, Hs3st1^-/- mice were more susceptible to LPS-induced death due to an increased sensitivity to TNF. For Hs3st1^+/+ mice, AT treatment reduced LPS-lethality, reduced leukocyte firm adhesion to endothelial cells, and dilated isolated coronary arterioles. Conversely, for Hs3st1^-/- mice, AT induced the opposite effects. Thus, in the context of acute inflammation, HS^AT+ selectively mediates AT's anti-inflammatory activity; in the absence of HS^AT+, AT's pro-inflammatory effects predominate. To explore if the anti-inflammatory action of HS^AT+ also protects against a chronic vascular-inflammatory disease, atherosclerosis, we conducted a human candidate-gene association study on >2000 coronary catheterization patients. Bioinformatic analysis of the HS3ST1 gene identified an intronic SNP, rs16881446, in a putative transcriptional regulatory region. The rs16881446^G/G genotype independently associated with the severity of coronary artery disease and atherosclerotic cardiovascular events. In primary endothelial cells, the rs16881446^G allele associated with reduced HS3ST1 expression. Together with the mouse data, this leads us to conclude that the HS3ST1 gene is required for AT's anti-inflammatory activity that appears to protect against acute and chronic inflammatory disorders.

Hemodynamic coherence in sepsis

Microvascular alterations are a hallmark of sepsis and play a crucial role in its pathophysiology. Such alterations are the result of overwhelming inflammation, which negatively affects all the components of the microcirculation. As the severity of microvascular alterations is associated with organ dysfunction and mortality, several strategies have been tested for improving microcirculation. Nevertheless, they are mainly based on the conventional manipulation of systemic hemodynamics to increase the total flow to the organs and tissues. Other therapeutic interventions are still being investigated. In this review, we discuss the pathophysiology of septic microcirculatory dysfunction and its implications for possible treatments.

Microcirculatory dysfunction in sepsis: pathophysiology, clinical monitoring, and potential therapies

Abnormal microvascular perfusion, including decreased functional capillary density and increased blood flow heterogeneity, is observed in early stages of the systemic inflammatory response to infection and appears to have prognostic significance in human sepsis. It is known that improvements in systemic hemodynamics are weakly correlated with the correction of microcirculatory parameters, despite an appropriate treatment of macrohemodynamic abnormalities. Furthermore, conventional hemodynamic monitoring systems available in clinical practice fail to detect microcirculatory parameter changes and responses to treatments, as they do not evaluate intrinsic events that occur in the microcirculation. Fortunately, some bedside diagnostic methods and therapeutic options are specifically directed to the assessment and treatment of microcirculatory changes. In the present review we discuss fundamental aspects of septic microcirculatory abnormalities, including pathophysiology, clinical monitoring, and potential therapies.

Hemodynamic management of septic shock: is it time for "individualized goal-directed hemodynamic therapy" and for specifically targeting the microcirculation?

Septic shock is a life-threatening condition in both critically ill medical patients and surgical patients during the perioperative phase. In septic shock, specific alterations in global cardiovascular dynamics (i.e., the macrocirculation) and in the microcirculatory blood flow (i.e., the microcirculation) have been described. However, the presence and degree of microcirculatory failure are in part independent from systemic macrohemodynamic variables. Macrocirculatory and microcirculatory failure can independently induce organ dysfunction. We review current diagnostic and therapeutic approaches for the assessment and optimization of both the macrocirculation and the microcirculation in septic shock. There are various technologies for the determination of macrocirculatory hemodynamic variables. We discuss the data on early goal-directed therapy for the resuscitation of the macrocirculation. In addition, we describe the concept of "individualized goal-directed hemodynamic therapy." Technologies to assess the local microcirculation are also available. However, adequate resuscitation goals for the optimization of the microcirculation still need to be defined. At present, we are not ready to specifically monitor and target the microcirculation in clinical routine outside studies. In the future, concepts for an integrative approach for individualized hemodynamic management of the macrocirculation and in parallel the microcirculation might constitute a huge opportunity to define additional resuscitation end points in septic shock.

Analysis of the influence of antithrombin on microvascular thrombosis: anti-inflammation is crucial for anticoagulation

Purpose

Microvascular thrombosis during septic conditions is of essential clinical relevance, but the pathomechanisms are not yet completely understood. The purpose of this study was to study the distinguished differentiation of the interactions of inflammation and coagulation using antithrombin (AT), a mediator of anticoagulation and anti-inflammation.

Methods

Using a thrombosis model in a cremaster muscle preparation of male C57Bl/6J mice (n = 83), we quantitatively assessed microvascular thrombus formation by using intravital fluorescence microscopy. Experimental groups consisted of animals treated with AT or with tryptophan⁴⁹-blocked AT (TrypAT), which exerts only anticoagulant but no anti-inflammatory effects. To further see whether endothelial glycosaminoglycan (GAG) binding with consecutive prostacyclin (PGI₂) release is mandatory for the anticoagulant process of AT, animals were administered heparin or indomethacin either alone or in combination with AT.

Results

The antithrombotic capacity of AT significantly differs in the experimental groups in which anti-inflammation was antagonized. This is given by the significantly prolonged occlusion times (p < 0.05) and higher patency rates in case of application of AT alone; while all other groups in which the anti-inflammatory action of AT was blocked by TrypAT, heparin or indomethacin revealed thrombus kinetics comparable to controls.

Conclusions

The anti-inflammatory influence of AT is essentially linked to its anticoagulant effect in the microvascular system. Those specifications of the active profile of AT characterize the intimate interactions of the anticoagulant and anti-inflammatory pathways. This might be of relevance for AT as a therapeutic agent in critically diseased patients and the clinical understanding of microvascular thrombosis.

Endothelial barrier dysfunction in septic shock

The endothelium provides an essential and selective membrane barrier that regulates the movement of water, solutes, gases, macromolecules and the cellular elements of the blood from the tissue compartment in health and disease. Its structure and continuous function is essential for life for all vertebrate organisms. Recent evidence indicates that the endothelial surface does not have a passive role in systemic inflammatory states such as septic shock. In fact, endothelial cells are in dynamic equilibrium with a myriad of inflammatory mediators and elements of the innate immune and coagulation systems to orchestrate the host response in sepsis. The barrier function of the endothelial surface is almost uniformly impaired in septic shock, and it is likely that this contributes to adverse outcomes. In this review, we will highlight recent advances in the understanding of the signalling events that regulate endothelial function and molecular events that induce endothelial dysfunction in sepsis. Endothelial barrier repair strategies as a treatment for sepsis include modulation of C5a, high-mobility group box 1 and VEGF receptor 2; stimulation of angiopoietin-1, sphingosine 1 phosphate receptor 1 and Slit; and a number of other innovative approaches.

Contribution of protein Z and protein Z-dependent protease inhibitor in generalized Shwartzman reaction

OBJECTIVE

Sepsis, a leading cause of mortality in critically ill patients, is closely linked to the excessive activation of coagulation and inflammation. Protein Z, a cofactor for the protein Z-dependent protease inhibitor, enhances the inhibition of coagulation factor Xa, and protein Z-dependent protease inhibitor inhibits factor XIa in a protein Z-independent fashion. The functions of protein Z and protein Z-dependent protease inhibitor in the inflammatory and coagulant responses to septic illness have not been evaluated.

DESIGN

For induction of generalized Shwartzman reaction, dorsal skinfold chamber-equipped mice were challenged twice with lipopolysaccharide (0.05 mg/kg on day -1 and 5 mg/kg body weight 24 hr later). Time-matched control animals received equal volumes of saline.

SETTING

University research laboratory.

SUBJECTS, INTERVENTIONS, AND MEASUREMENTS

Using intravital fluorescence microscopy in protein Z-dependent protease inhibitor deficient (ZPI) and protein Z deficient (PZ) mice, as well as their wild-type littermates (ZPI, PZ), kinetics of light/dye-induced thrombus formation and microhemodynamics were assessed in randomly chosen venules. Plasma concentrations of chemokine (C-X-C motif) ligand 1, interleukin-6, and interleukin-10 were measured. Liver and lung were harvested for quantitative analysis of leukocytic tissue infiltration and thrombus formation.

MAIN RESULTS

After induction of generalized Shwartzman reaction, all mice showed significant impairment of microhemodynamics, including blood flow velocity, volumetric blood flow, and functional capillary density, as well as leukocytopenia and thrombocytopenia. Thrombus formation time was markedly prolonged after induction of generalized Shwartzman reaction in all mice, except of ZPI mice, which also had a significantly higher fraction of occluded vessels in liver sections. PZ mice developed the highest concentrations of interleukin-6 and interleukin-10 in response to generalized Shwartzman reaction and showed greater leukocytic tissue infiltration than their wild-type littermates.

CONCLUSIONS

In this murine model of generalized Shwartzman reaction, protein Z-dependent protease inhibitor deficiency enhanced the thrombotic response to vascular injury, whereas protein Z deficiency increased inflammatory response.

Pathophysiology of microcirculatory dysfunction and the pathogenesis of septic shock

Multiple experimental and human trials have shown that microcirculatory alterations are frequent in sepsis. In this review, we discuss the various mechanisms that are potentially involved in their development and the implications of these alterations. Endothelial dysfunction, impaired inter-cell communication, altered glycocalyx, adhesion and rolling of white blood cells and platelets, and altered red blood cell deformability are the main mechanisms involved in the development of these alterations. Microcirculatory alterations increase the diffusion distance for oxygen and, due to the heterogeneity of microcirculatory perfusion in sepsis, may promote development of areas of tissue hypoxia in close vicinity to well-oxygenated zones. The severity of microvascular alterations is associated with organ dysfunction and mortality. At this stage, therapies to specifically target the microcirculation are still being investigated.

The anti-inflammatory action of Bothrops jararaca snake antithrombin on acute inflammation induced by carrageenan in mice

OBJECTIVE AND DESIGN

Antithrombin is known as the most important natural coagulation inhibitor and has been shown to have anti-inflammatory properties. The present study aimed to investigate the effects of Bothrops jararaca antithrombin on acute inflammation induced by carrageenan in mice.

METHODS

We evaluated the anti-inflammatory activity of antithrombin on models of paw edema formation, cell migration and leukocyte-endothelium interaction in mice (Swiss; n = 5). Acute inflammation was induced by the administration of carrageenan (15 mg kg⁻¹).

RESULTS

Treatment with B. jararaca antithrombin (1 mg kg⁻¹) 1 h before or after carrageenan administration significantly inhibited paw edema formation, reduced cell influx to the peritoneal cavity due to reduction in the migration of polymorphonuclear cells, and attenuated leukocyte rolling in the microcirculation of the cremaster muscle.The effects of antithrombin on vascular and cellular events of inflammation were completely abolished by treatment with the cyclo-oxygenase inhibitor indomethacin (4 mg kg⁻¹), suggesting the involvement of prostacyclin in the mechanism of inflammation inhibition by B. jararaca antithrombin.

CONCLUSION

This work showed for the first time the anti-inflammatory properties of B. jararaca antithrombin on vascular and cellular events of inflammation. These findings suggest that antithrombin is effective in preventing paw edema formation, cell migration and leukocyte rolling induced by carrageenan in mice.

Anticoagulant activities of curcumin and its derivative

Curcumin, a polyphenol responsible for the yellow color of the curry spice turmeric, possesses antiinflammatory, antiproliferative and antiangiogenic activities. However, anticoagulant activities of curcumin have not been studied. Here, the anticoagulant properties of curcumin and its derivative (bisdemethoxycurcumin, BDMC) were determined by monitoring activated partial thromboplastin time (aPTT), prothrombin time (PT) as well as cell-based thrombin and activated factor X (FXa) generation activities. Data showed that curcumin and BDMC prolonged aPTT and PT significantly and inhibited thrombin and FXa activities. They inhibited the generation of thrombin or FXa. In accordance with these anticoagulant activities, curcumin and BDMC showed anticoagulant effect in vivo. Surprisingly, these anticoagulant effects of curcumin were better than those of BDMC indicating that methoxy group in curcumin positively regulated anticoagulant function of curcumin. Therefore, these results suggest that curcumin and BDMC possess antithrombotic activities and daily consumption of the curry spice turmeric might help maintain anticoagulant status.

Microcirculatory alterations: potential mechanisms and implications for therapy

Multiple experimental and human trials have shown that microcirculatory alterations are frequent in sepsis. In this review, we discuss the characteristics of these alterations, the various mechanisms potentially involved, and the implications for therapy. Sepsis-induced microvascular alterations are characterized by a decrease in capillary density with an increased number of stopped-flow and intermittent-flow capillaries, in close vicinity to well-perfused capillaries. Accordingly, the surface available for exchange is decreased but also is highly heterogeneous. Multiple mechanisms may contribute to these alterations, including endothelial dysfunction, impaired inter-cell communication, altered glycocalyx, adhesion and rolling of white blood cells and platelets, and altered red blood cell deformability. Given the heterogeneous nature of these alterations and the mechanisms potentially involved, classical hemodynamic interventions, such as fluids, red blood cell transfusions, vasopressors, and inotropic agents, have only a limited impact, and the microcirculatory changes often persist after resuscitation. Nevertheless, fluids seem to improve the microcirculation in the early phase of sepsis and dobutamine also can improve the microcirculation, although the magnitude of this effect varies considerably among patients. Finally, maintaining a sufficient perfusion pressure seems to positively influence the microcirculation; however, which mean arterial pressure levels should be targeted remains controversial. Some trials using vasodilating agents, especially nitroglycerin, showed promising initial results but they were challenged in other trials, so it is difficult to recommend the use of these agents in current practice. Other agents can markedly improve the microcirculation, including activated protein C and antithrombin, vitamin C, or steroids. In conclusion, microcirculatory alterations may play an important role in the development of sepsis-related organ dysfunction. At this stage, therapies to target microcirculation specifically are still being investigated.

Effect of recombinant interleukin-10 on some haematological and biochemical parameters in a rat endotoxaemic model

Recombinant interleukin-10 (rIL10) has been found to suppress the synthesis of tumour necrosis factor (TNF), interleukin-1 (IL-1), interleukin-6 (IL-6) and tissue factor and to improve survival from experimental sepsis. The aim of this study was to evaluate the protective effect of rIL-10 on lipopolysaccharide-(LPS-) induced haematological and biochemical disturbances in rats. In the present study, 40 rats were used and divided equally into four groups. Group 1 (control group, C) was treated with 0.9% saline. Group 2: LPS was injected intravenously (1.6 mg/100 g), Group 3 received rIL10 treatment (125 μg/kg) 2 min before 0.9% saline injection, Group 4 received rIL10 treatment 2 min before endotoxin treatment. When compared with the controls, platelet count, leukocyte count (with a marked neutrophilia and lymphopenia) and fibrinogen were decreased, while activated partial thromboplastin time (APTT) and prothrombin time (PT) were prolonged in the endotoxaemic rats. In addition, LPS caused statistically significant increases in plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities as well as creatinine, cholesterol and triglyceride concentrations, while it caused a statistically significant decrease in glucose, total protein and albumin levels as compared to the control group. On the other hand, rIL10 significantly suppressed disturbances in the haematological and biochemical parameters associated with endotoxaemia. As a result, rIL10 may be efficacious in preventing haematological disorders, tissue damage and changes in lipid, protein and carbohydrate metabolism in endotoxaemia.

ATIII attenuates endotoxemia induced healing impairment in the colon

BACKGROUND

Intra-abdominal infections are considered a contributing factor to the impairment of anastomotic healing in patients undergoing surgical procedures of digestive system. Antithrombin (ATIII) is known to improve the microcirculation in sepsis. We hypothesized that it may also positively influence the healing of the colon anastomoses under endotoxemia.

MATERIALS AND METHODS

Ninety Balb/c mice (n = 10 per group on day 2, 4, and 7) were randomly assigned to three groups: Control (N), Sepsis (S) (administration of lipopolysaccharides (LPS) dosed at 2 mg/kg bodyweight, 18 h before colon surgery), and Sepsis with ATIII therapy (SIII) (administration of LPS and ATIII). All the animals underwent colonic anastomoses. Immediately after their completion, microcirculatory parameters were measured, and both macroscopic and histological parameters were assessed on day 2, 4, and 7 postoperation. Additionally, immunohistology studies were performed for CD31, ssDNA, and iNOS, along with an examination for bacterial translocation to the mesenteric lymph nodes.

RESULTS

Compared with group S, the functional capillary network was denser in the control group N (P < 0.001) and group SIII (P < 0.01). Mean bursting pressures were significantly lower in group S compared with group N, on day 2, 4, and 7, and with group SIII on day 2 and 7. At the anastomosis, the inflammatory infiltrate in group S was denser compared with groups N (P < 0.001) and SIII (P < 0.01). Furthermore, the apoptotic rate was higher, and the vascular density was lower on day 7 in group S compared with groups SIII and N (P < 0.05). Bacterial translocation decreased over time (P < 0.05) with no significant differences between the groups.

CONCLUSION

ATIII improved the anastomotic microcirculatory parameters and anastomotic healing in mice with endotoxemia, though the improvement failed to achieve the levels of the control mice.

[Microcirculation of intensive care patients. From the physiology to the bedside]

The microcirculation is unique in its anatomy and physiology and is a self-contained organ system within the human body. It is the site where gas exchange and nutrient supply takes place, but it is also the site which experiences pathological alterations during various shock states and therefore compromises the oxygen supply to tissues and organs. Systemic inflammation for example leads amongst others to increased heterogeneous blood flow, formation of interstitial edema, altered viscosity, leukocyte activation, disturbances in the coagulation system, and to a breakdown of the endothelial barrier function. These alterations inevitably lead to limitations of the oxygen supply to tissues. Without interruption of these pathomechanisms, the dysfunction of the microcirculation will consequently result in organ dysfunction. In this review article a short description of the microcirculatory physiology, the interaction between the macrocirculation and the microcirculation, as well as microcirculatory alterations generated by a systemic inflammatory response will be given. Finally, various therapy options will be described, which, experimentally, can lead to an improvement in microcirculatory dysfunction.

Immunoglobulin M-enriched human intravenous immunoglobulins reduce leukocyte-endothelial cell interactions and attenuate microvascular perfusion failure in normotensive endotoxemia

Clinical studies indicate potential differences in the efficacy of immunoglobulin (Ig) preparations in patients with sepsis. A recent meta-analysis showed improved survival rates with IgM-enriched Igs. It was the objective of the present study to characterize microcirculatory actions of different clinically used Ig preparations in a rodent endotoxin model by intravital microscopy. Male Syrian golden hamsters 6 to 8 weeks old with a body weight of 60 to 80 g were investigated by intravital fluorescence microscopy. Endotoxemia was induced by administration of 2 mg/kg (i.v.) endotoxin (LPS, Escherichia coli). Two different Ig preparations containing IgM, IgA, and IgG (intravenous IgM group; n = 6; 5 mL Pentaglobin/kg body weight, i.v.) or exclusively IgG (intravenous IgG group; n = 5; 5 mL Flebogamma/kg body weight, i.v.) were applied 5 min before LPS. Saline-treated endotoxemic animals served as controls (control; n = 8). In controls, LPS induced massive leukocyte-endothelial cell interactions, pronounced microvascular leakage, a decrease of systemic platelet count, and distinct capillary perfusion failure (P < 0.05). Both intravenous IgM and IgG reduced venular leakage (P< 0.05) and ameliorated the decrease in platelet count (P < 0.05). Of interest, intravenous IgM was capable of significantly (P< 0.05) reducing leukocyte adhesion in venules. This was associated with normalization of capillary perfusion at 24 h of endotoxemia, whereas intravenous IgG could not prevent LPS-mediated microvascular perfusion failure. We demonstrate that IgM-enriched Igs are superior to IgG alone in attenuating LPS-induced leukocytic inflammation and microcirculatory dysfunction. Our findings can explain better efficacy of IgM-enriched Igs in patients with severe sepsis.

Efficacy of antithrombin in the prevention of microvascular thrombosis during endotoxemia: An intravital microscopic study

INTRODUCTION

The KyberSept trial in septic patients showed that antithrombin (AT) reduced 90-day mortality significantly in a subgroup of patients not receiving concomitant heparin for thrombosis prophylaxis. Microvascular thrombosis is a key pathophysiologic mechanism during sepsis, ischemia/reperfusion and disseminated intravascular coagulation (DIC). Therefore, this study investigated the antithrombotic property of AT as potential monotherapy in an experimental endotoxemia model in order to omit concomitant heparin.

MATERIALS AND METHODS

Using a light/dye injury model in the ear and the cremaster muscle preparation of mice, we quantitatively assessed microvascular thrombus formation in a total of 30 endotoxemic mice by means of intravital fluorescence microscopy. Before thrombus induction animals received a single i.v. bolus of AT (100 or 250 IU/kg), heparin (100 IU/kg) or saline (NaCl).

RESULTS

In NaCl-treated endotoxemic animals, light/dye exposure led to complete thrombotic occlusion in arterioles and venules within <450 s in the ear model. Heparin delayed thrombotic vessel occlusion by more than 50%. AT significantly prolonged times until thrombotic vessel occlusion in a dose-dependent manner and more effectively than heparin (p<0.05 vs. NaCl and heparin). This anti-coagulative effect of AT was especially pronounced in arterioles. Upon light/dye exposure to cremaster muscle preparations in endotoxemic mice AT also caused a 4-fold delay in microvascular thrombus growth with 827+/-77 s until complete thrombotic occlusion.

CONCLUSIONS

We could characterize for the first time AT-mediated antithrombotic activity during endotoxemia in two models of phototoxicity-induced microvascular thrombosis. Our results clearly demonstrate an additional AT mechanism of action that may be responsible for beneficial effects observed during endotoxemia and DIC. This AT profile may allow future high-dose AT application without giving heparin for thrombosis prophylaxis, an intriguing strategy that is to be tested under clinical conditions.

Microcirculatory disorders in sepsis and transplantation: therapy with natural coagulatory inhibitors antithrombin and activated protein C

PURPOSE OF REVIEW

Modern technologies allow visualization of microcirculatory disorders. This review describes how the coagulatory inhibitors antithrombin and activated protein C (APC) can improve microcirculation in sepsis and transplantation.

RECENT FINDINGS

The effects of antithrombin and APC on microcirculatory disorders in ischemia reperfusion and experimental sepsis have been reported recently. In addition, antithrombin has recently been clinically used to reduce graft pancreatitis after pancreas-kidney transplantation, and to improve kidney perfusion. It was demonstrated that septic capillary perfusion failure as well as leukocyte-endothelial cell interactions can be reversed by high-dose prophylactic antithrombin application. APC was also highly effective in this context. Thus, APC could improve microcirculatory blood flow in septic patients as recently measured by in-vivo orthogonal polarization spectral imaging techniques. For antithrombin, comparable measurements in humans are currently not available.

SUMMARY

Microcirculatory dysfunction plays a key role in the development of organ dysfunction in septic patients and after solid organ transplantation. The exogenous application of coagulatory inhibitors may provide a new important strategy for prevention and treatment of microcirculatory disorders. This mode of action may be the reason why coagulatory inhibitors could improve mortality in septic patients without directly influencing inflammatory mediator concentrations.

Single-shot antithrombin in human pancreas-kidney transplantation: reduction of reperfusion pancreatitis and prevention of graft thrombosis*

Reperfusion pancreatitis and graft thrombosis often induce early graft loss in simultaneous pancreas-kidney (SPK) transplantation. Antithrombin (AT) is a coagulatory inhibitor with pleiotropic activities that reduces experimental ischemia/reperfusion injury. This study retrospectively analyses prophylactic high-dose AT application in patients with first SPK. In an university transplantation center, 53 consecutive patients with SPK were studied without randomization. In one group, 3000 IU of AT was given intravenously before pancreatic reperfusion (AT, n = 24). Patients receiving standard therapy including postoperative AT supplementation (controls, n = 29) served as controls. Daily blood sampling was performed as a part of the clinical routine during four postoperative days. There were no differences in demographic and laboratory parameters [donor/recipient age, ischemia time, perfusion solution, body weight, mismatches] between both groups. Baseline creatinine values were lower in the control group versus AT group (P < 0.05). Coagulatory parameters and bleeding incidence were not influenced by AT, while incidence of graft thrombosis was reduced (control: 7/29; AT: 4/24; relative reduction of risk: -33%; P < 0.05). Single-shot AT application during SPK modulated serum lipase activity on postoperative days 2 and 3, and minimized risk for graft thromboses without increasing perioperative bleeding. This new concept should deserve testing in a prospective clinical trial.

Effects of antithrombin III on myeloperoxidase activity, superoxide dismutase activity, and malondialdehyde levels and histopathological findings after spinal cord injury in the rat

OBJECTIVE

Among the many possible mechanisms of the secondary spinal cord injury (SCI), microcirculatory disturbances as a result of activated leukocyte-induced endothelial cell injury is important because it is potentially treatable and reversible. Currently, clinically available pharmacological agents for treatment of acute SCI do not inhibit neutrophil activation. The effect of antithrombin III (AT-III) on neutrophil activation was studied in rats with SCI produced with an aneurysm clip on the T2-T7 segments.

METHODS

Forty rats were randomly allocated to four groups. Group I (10 rats) was killed to provide normal spinal cord tissue for testing. Group II (10 rats) underwent a six-segment laminectomy for the effects of total laminectomy to be determined. In Group III, 10 rats underwent a six-segment laminectomy and SCI was produced by extradural compression of the exposed cord. The same procedures were performed in 10 rats in Group IV, but they also received one (250 IU/kg) intraperitoneal injection of AT-III immediately after the injury and a second dose 24 hours later. The animals from Groups II through IV were killed 48 hours after the trauma. The effect of AT-III on the myeloperoxidase activity, superoxide dismutase activity, and malondialdehyde levels and histopathological findings were studied.

RESULTS

Myeloperoxidase activity, superoxide dismutase activity, and malondialdehyde levels were significantly lower and there was less histopathological damage in the AT-III treatment group than in the trauma group.

CONCLUSION

The results demonstrate that AT-III treatment may reduce secondary structural changes in damaged rat spinal cord tissue by inhibiting leukocyte activation.

Does Disseminated Intravascular Coagulation Lead to Multiple Organ Failure?

Microvascular dysfunction with its associated impaired regional oxygen transport and use is believed to be the final common pathway in the development of multiple organ failure. The precise mechanisms underlying this dysfunction, however, are uncertain. Activation of the coagulation system is a key feature in the pathogenesis of sepsis, but whether it is also the cause of multiple organ failure is unclear. This article discusses the evidence for and against a key role for disseminated intravascular coagulation in the pathogenesis of multiple organ failure.

Attenuation of leukocyte beta 2-integrin expression by antithrombin-III

Antithrombin-III exerts antiinflammatory effects via ligation of heparan sulfate proteoglycans. Here we show in vitro that recombinant human antithrombin-III attenuates CD11b/CD18 expression of activated neutrophils and monocytes in whole blood ex vivo. As leukocyte integrin expression is triggered by extracorporeal circulation, this observation may be of relevance for pharmacological treatment during cardiopulmonary bypass.

Effect of long-term and high-dose antithrombin supplementation on coagulation and fibrinolysis in patients with severe sepsis

OBJECTIVE

Sepsis is frequently associated with coagulatory activation, which may contribute to deteriorated organ function. Antithrombin is one important endogenous coagulation inhibitor that is therapeutically applied during sepsis. This study investigates the effect of 14-day antithrombin application on coagulatory variables.

DESIGN

Prospective study.

SETTING

Surgical intensive care unit of a university hospital.

PATIENTS

Forty patients with severe sepsis.

INTERVENTIONS

Patients with severe sepsis were randomly assigned to receive either conventional intensive care treatment (n = 20, controls) or antithrombin substitution that aimed at a plasma antithrombin activity > or =120% during a long-term (14-day) study period (n = 20, antithrombin). To allow comparative analysis of laboratory variables over time, all patients who did not survive the 14-day-period (five controls and six antithrombin patients) were prospectively excluded from the final evaluation. Their data were included in an intent-to-treat analysis.

MEASUREMENTS AND MAIN RESULTS

Antithrombin supplementation normalized global coagulation tests and increased prothrombin activity as well as fibrinogen concentration, reflecting less coagulation factor consumption (percent change from baseline in prothrombin activity, p <.01 vs. controls at days 9, 11-14 of antithrombin vs. controls [unpaired Student's t-test]; fibrinogen concentration, p <.01 vs. controls at days 10, 11, 13, and 14 of antithrombin). Simultaneously, antithrombin reduced contact system activation as indicated by increasing prekallikrein activities over time (% change, p <.01 vs. controls at days 6, 9-14) and increased protein C activities when compared with controls (% change, p <.01 vs. controls at days 10-14). Most changes occurred from day 7 to day 14 of antithrombin supplementation. Antithrombin did not influence C1 esterase inhibitor, plasminogen, alpha2 antiplasmin, or platelet counts (p >.01).

CONCLUSION

In this first study on long-term antithrombin therapy, antithrombin significantly reduced septic coagulatory response in patients with severe sepsis when given over 14 days.

Evolution of ischemic tissue injury in a random pattern flap: A new mouse model using intravital microscopy

BACKGROUND

Dissection of random pattern flaps may cause microcirculatory dysfunction and ischemia, which jeopardize wound healing due to impaired tissue viability. The aim of this study was to develop an in vivo model that enables continuous monitoring of the interplay between microcirculatory dysfunction, ischemia, and tissue injury by intravital microscopy.

MATERIALS AND METHODS

A laterally based random pattern skin flap (15 x 11 mm) including the panniculus carnosus was raised in the back of mice and fixed into a dorsal skinfold chamber (n = 10). Arteriolar blood flow, functional capillary density, number of apoptotic cells, and area of tissue necrosis were analyzed by intravital fluorescence microscopy in the proximal, middle, and distal part of the flap at day 1, 3, 5, and 7 after surgery. Chamber preparations without flap harvesting served as controls (n = 6).

RESULTS

At day 1, the distal part of the flap showed a decreased arteriolar blood flow (266 +/- 124 pl/s versus controls: 1418 +/- 351 pl/s; P < 0.05), which resulted in severe alteration of functional capillary density (43 +/- 11 cm/cm2 versus 270 +/- 7 cm/cm2; P < 0.001). The impaired microcirculation was associated with apoptotic cell death (277 +/- 50 cells/mm2 versus 50 +/- 5 cells/mm2; P < 0.05). Microcirculatory dysfunction persisted over 7 days, and, finally, resulted in 49 +/- 3% flap necrosis.

CONCLUSIONS

This new model enables repetitive and simultaneous in vivo microscopic evaluation of microvascular hypoperfusion, apoptosis, and tissue necrosis in a random pattern flap. By the use of gene-targeted mice, it bears great potential to analyze distinct mechanisms of flap failure. It further represents an ideal tool to study novel protective strategies, including induction of angiogenesis, heat shock proteins, and HIF-1alpha.

Inhibition of coagulation and inflammation by activated protein C or antithrombin reduces intestinal ischemia/reperfusion injury in rats

OBJECTIVE

To examine whether administration of activated protein C or antithrombin reduces local splanchnic derangement of coagulation and inflammation and attenuates intestinal dysfunction and injury following intestinal ischemia/reperfusion.

DESIGN

Randomized prospective animal study.

SETTING

University research institute.

SUBJECTS

Adult male Wistar rats, weighing 300-325 g (n = 72).

INTERVENTIONS

Rats were subjected to superior mesenteric artery occlusion consisting of 20 or 40 mins of ischemia and 3 hrs of reperfusion. A randomized intravenous administration of vehicle (0.9% NaCl), heparin, antithrombin, or activated protein C was performed during ischemia, 15 mins before reperfusion. Coagulation and fibrinolysis variables obtained from portal blood were correlated with mucosal fibrin deposition (determined by anti-rat fibrin antibody staining), intestinal function (glucose/water clearance), and intestinal injury (histologic evaluation by Park/Chiu score).

MEASUREMENTS AND MAIN RESULTS

Activated protein C- or antithrombin-treated animals demonstrated less ischemia/reperfusion-induced intestinal dysfunction and histologic changes compared with control animals, whereas intravenous administration of heparin only showed less histologic derangement. Activated protein C- or antithrombin-treated animals showed less thrombin generation, fibrin degradation products, and fibrin deposition compared with control animals, as confirmed by histologic examination, whereas heparin administration showed only a limited reduction of portal fibrin degradation product concentrations. Furthermore, activated protein C or antithrombin administration markedly inhibited the inflammatory response, as reflected by reduced interleukin-6 plasma concentrations to baseline values, whereas heparin had no effect.

CONCLUSIONS

Administration of activated protein C or antithrombin inhibited local and systemic derangement of coagulation and inflammation following intestinal ischemia/reperfusion, diminished mucosal fibrin deposition, and attenuated ischemia/reperfusion-induced intestinal injury. These observations suggest that activated protein C or antithrombin reduces ischemia/reperfusion-induced intestinal injury, both through their anticoagulant and anti-inflammatory effects.

Antithrombin III Diminishes Production of Oxygen Radical in Endotoxin-Infused Rat Lung

The interaction of antithrombin III (AT) with cell surface glycosaminoglycans is known to have an inhibitory effect on inflammatory processes. We evaluated the effect of AT on endotoxin-induced production of oxygen radical in the pulmonary circulation using a fluorescent imaging technique. Also measured was the myeloperoxidase content of the lung, which served as an index of neutrophil accumulation, and neutrophil F-actin levels. Four groups of rats were infused for 2 h with endotoxin at 4.5 mg/kg/h (Et group), physiological saline (CT group), 100 U/kg of AT + endotoxin (AT group), or 100 U/kg of low-heparin-affinity latent-AT + endotoxin (L-AT group), respectively. Production of oxygen radical, neutrophil accumulation, and neutrophil F-actin levels were all significantly higher in the ET and L-AT groups than in the CT or AT group. Moreover; the levels of myeloperoxidase within the lung were well correlated with levels of oxygen radical production, which was consistent with the electron microscopic finding that cerium was deposited almost exclusively around neutrophils. Thus, it appears that AT most likely reduces F-actin formation in neutrophil by binding to glycosaminoglycans (e.g., syndecan-4) on the neutrophil, thereby reducing neutrophil accumulation in the lung, which would in turn inhibit oxygen radical production in the lung.

Life-threatening thrombosis in mice with targeted Arg48-to-Cys mutation of the heparin-binding domain of antithrombin

Antithrombin (AT) inhibits thrombin and some other coagulation factors in a reaction that is dramatically accelerated by binding of a pentasaccharide sequence present in heparin/heparan-sulfate to a heparin-binding site on AT. Based on the involvement of R47 in the heparin/AT interaction and the frequent occurrence of R47 mutations in AT deficiency patients, targeted knock-in of the corresponding R48C substitution in AT in mice was performed to generate a murine model of spontaneous thrombosis. The mutation efficiently abolished the effect of heparin-like molecules on coagulation inhibition in vitro and in vivo. Mice homozygous for the mutation (AT(m/m) mice) developed spontaneous, life-threatening thrombosis, occurring as early as the day of birth. Only 60% of the AT(m/m) offspring reached weaning age, with further loss at different ages. Thrombotic events in adult homozygotes were most prominent in the heart, liver, and in ocular, placental, and penile vessels. In the neonate, spontaneous death invariably was associated with major thrombosis in the heart. This severe thrombotic phenotype underlines a critical function of the heparin-binding site of antithrombin and its interaction with heparin/heparan-sulfate moieties in health, reproduction, and survival, and represents an in vivo model for comparative analysis of heparin-derived and other antithrombotic molecules.

Antithrombin: a new look at the actions of a serine protease inhibitor

Antithrombin (AT) is a plasma-derived, single-chain glycoprotein with a molecular weight of 58 kDa. It is a serine protease inhibitor (serpin), sharing about 30% homology in amino acid sequence with other serpins. AT is a complex molecule with multiple biologically important properties. It is a potent anticoagulant that has been demonstrated to provide benefit in animal models and small cohorts of patients with coagulation disorders. AT also has remarkable anti-inflammatory properties, several of which result from its actions in the coagulation cascade. Activated coagulation proteases like activated factor X and thrombin contribute to inflammation; for instance, by the release of pro-inflammatory mediators. Inhibition of these proteases by AT prevents their specific interaction with cells and subsequent reactions. Anti-inflammatory properties of AT independent of coagulation involve direct interactions with cells leading to the release of, for instance, prostacyclin. Binding of AT to a recently identified cellular receptor, syndecan-4, leads to the interference with the intracellular signal induced by mediators like lipopolysaccharides and, thereby, to a down-modulation of the inflammatory response. AT has been shown to be effective in prospective and well-controlled small-scale studies of patients with inflammatory conditions, including sepsis. Although AT did not decrease overall patient mortality in a double-blind, placebo-controlled, phase III trial of patients with sepsis, it is important to note that AT improved the survival of individuals in this study not receiving heparin as a prophylactic regimen, which can be explained by the impaired interaction of AT with its cellular receptor in the presence of heparin, resulting in the reduction of the anti-inflammatory properties. Accordingly, the supplementation of AT without concomitant heparin may be beneficial in disorders with inflammatory characteristics, which has to be demonstrated in further clinical studies. Finally, recent results suggest that latent AT can induce apoptosis of endothelial cells by disrupting cell-matrix interactions. Further investigations will have to demonstrate whether latent and/or cleaved AT are physiological means to control angiogenesis. A potential prophylactic or therapeutic use as an anti-angiogenic and antitumor agent merits further exploration, including whether the growth of vessels in tumor tissues or close to tumors can be controlled by latent AT without affecting the formation of blood vessels during wound healing processes.

The anti-inflammatory actions of antithrombin--a review

Leukocyte-endothelial cell interaction and microvascular perfusion failure are characteristic deteriorations of the microcirculation in endotoxaemia and are known to play a crucial role in the development of septic multiple organ dysfunction. Recent studies have indicated that antithrombin III treatment is capable of significantly ameliorating these microcirculatory disorders. Endothelial cells have important anticoagulant systems, including the heparan sulfate-antithrombin system. Antithrombin III stimulates prostacyclin generation in endothelial cells by interacting with heparan sulfate of endothelial cells and inhibits cytokine and tissue factor production in endothelial cells and monocytes. Similar mechanisms may be involved in cellular actions of antithrombin III causing desensitization of chemoattractant receptors of leukocytes by activating the heparan sulfate proteoglycan, syndecan-4. Thus, antithrombin III might be among the useful agents for treating coagulation abnormalities associated with sepsis or other inflammation because it inhibits not only coagulation but also downregulation of anticoagulant activities of endothelial cells and affects leukocyte activation.