Cell-surface heparan sulfate proteoglycan-mediated regulation of human neutrophil migration by the serpin antithrombin III

Antithrombin III Levels and Outcomes Among Patients With Trauma

Importance

Patients with trauma exhibit a complex balance of coagulopathy manifested by both bleeding and thrombosis. Antithrombin III is a plasma protein that functions as an important regulator of coagulation. Previous studies have found a high incidence of antithrombin III deficiency among patients with trauma.

Objective

To assess whether changes in antithrombin III activity are associated with thrombohemorrhagic complications among patients with trauma.

Design, Setting, and Participants

This cohort study was conducted from December 2, 2015, to March 24, 2017, at a level I trauma center. A total of 292 patients with trauma were followed up from their arrival through 6 days from admission. Data, including quantification of antithrombin III activity, were collected for these patients. Thromboprophylaxis strategy; hemorrhage, deep vein thrombosis (DVT), and pulmonary embolism screenings; and follow-up evaluations were conducted per institutional protocols. Data analyses were performed from September 28, 2023, to June 4, 2024.

Main Outcomes and Measures

The primary study outcome measurements were associations between antithrombin III levels and outcomes among patients with trauma, including ventilator-free days, hospital-free days, intensive care unit (ICU)-free days, hemorrhage, venous thromboembolic events, and mortality.

Results

The 292 patients had a mean (SD) age of 54.4 (19.0) years and included 211 men (72.2%). Patients with an antithrombin III deficiency had fewer mean (SD) ventilator-free days (27.8 [5.1] vs 29.6 [1.4]; P = .0003), hospital-free days (20.3 [8.2] vs 24.0 [5.7]; P = 1.37 × 10-6), and ICU-free days (25.7 [4.9] vs 27.7 [2.3]; P = 9.38 × 10-6) compared with patients without a deficiency. Antithrombin III deficiency was also associated with greater rates of progressive intracranial hemorrhage (21.1% [28 of 133] vs 6.3% [10 of 159]; P = .0003) and thrombocytopenia (24.8% [33 of 133] vs 5.0% [8 of 159]; P = 1.94 × 10-6). Although antithrombin III deficiency was not significantly associated with DVT, patients who developed a DVT had a more precipitous decrease in antithrombin III levels that were significantly lower than patients who did not develop a DVT.

Conclusions and Relevance

In this cohort study of patients with trauma, antithrombin III deficiency was associated with greater injury severity, increased hemorrhage, and increased mortality, as well as fewer ventilator-free, hospital-free, and ICU-free days. Although this was an associative study, these data suggest that antithrombin III levels may be useful in the risk assessment of patients with trauma.

Heparan sulfates and heparan sulfate proteoglycans in hematopoiesis

ABSTRACT

From signaling mediators in stem cells to markers of differentiation and lineage commitment to facilitators for the entry of viruses, such as HIV-1, cell surface heparan sulfate (HS) glycans with distinct modification patterns play important roles in hematopoietic biology. In this review, we provide an overview of the importance of HS and the proteoglycans (HSPGs) to which they are attached within the major cellular subtypes of the hematopoietic system. We summarize the roles of HSPGs, HS, and HS modifications within each main hematopoietic cell lineage of both myeloid and lymphoid arms. Lastly, we discuss the biological advances in the detection of HS modifications and their potential to further discriminate cell types within hematopoietic tissue.

Store-operated Ca2+ entry-sensitive glycolysis regulates neutrophil adhesion and phagocytosis in dairy cows with subclinical hypocalcemia

Hypocalcemia in dairy cows is associated with a decrease of neutrophil adhesion and phagocytosis, an effect driven partly by changes in the expression of store-operated Ca2+ entry (SOCE)-related molecules. It is well established in nonruminants that neutrophils obtain the energy required for immune function through glycolysis. Whether glycolysis plays a role in the acquisition of energy by neutrophils during hypocalcemia in dairy cows is unknown. To address this relationship, we performed a cohort study and then a clinical trial. Neutrophils were isolated at 2 d postcalving from lactating Holstein dairy cows (average 2.83 ± 0.42 lactations, n = 6) diagnosed as clinically healthy (CON) or with plasma concentrations of Ca2+ <2.0 mmol/L as a criterion for diagnosing subclinical hypocalcemia (HYP, average 2.83 ± 0.42 lactations, n = 6). In the first experiment, neutrophils were isolated from blood of CON and HYP cows and used to analyze aspects of adhesion and phagocytosis function through quantitative reverse-transcription PCR along with confocal laser scanning microscopy, mRNA expression of the glycolysis-related gene hexokinase 2 (HKII), and components of the SOCE moiety ORAI calcium release-activated calcium modulator 1 (ORAI1, ORAI2, ORAI3, stromal interaction molecule 1 [STIM1], and STIM2). Results showed that adhesion and phagocytosis function were reduced in HYP cows. The mRNA expression of adhesion-related syndecan-4 (SDC4), integrin β9 (ITGA9), and integrin β3 (ITGB3) and phagocytosis-related molecules complement component 1 R subcomponent (C1R), CD36, tubulinß1 (TUBB1) were significantly decreased in the HYP group. In the second experiment, to address how glycolysis affects neutrophil adhesion and phagocytosis, neutrophils isolated from CON and HYP cows were treated with 2 μM HKII inhibitor benserazide-d3 or 1 μM fructose-bisphosphatase 1 (FBP1) inhibitor MB05032 for 1 h. Results revealed that the HKII inhibitor benserazide-d3 reduced phagocytosis and the mRNA abundance of ITGA9, and CD36 in the HYP group. The FBP1 inhibitor MB05032 increased adhesion and phagocytosis and increased mRNA abundance of HKII, ITGA9, and CD36 in the HYP group. Finally, to investigate the mechanism whereby SOCE-sensitive glycolysis affects neutrophil adhesion and phagocytosis, isolated neutrophils were treated with 1 μM SOCE activator thapsigargin or 50 μM inhibitor 2-APB for 1 h. Results showed that thapsigargin increased mRNA abundance of HKII, ITGA9, and CD36, and increased adhesion and phagocytosis in the HYP group. In contrast, 2-APB decreased mRNA abundance of HKII and both adhesion and phagocytosis of neutrophils in the CON group. Overall, the data indicated that SOCE-sensitive intracellular Ca2+ levels affect glycolysis and help regulate adhesion and phagocytosis of neutrophils during hypocalcemia in dairy cows.

Disseminated intravascular coagulation and its immune mechanisms

Disseminated intravascular coagulation (DIC) is a syndrome triggered by infectious and noninfectious pathologies characterized by excessive generation of thrombin within the vasculature and widespread proteolytic conversion of fibrinogen. Despite diverse clinical manifestations ranging from thrombo-occlusive damage to bleeding diathesis, DIC etiology commonly involves excessive activation of blood coagulation and overlapping dysregulation of anticoagulants and fibrinolysis. Initiation of blood coagulation follows intravascular expression of tissue factor or activation of the contact pathway in response to pathogen-associated or host-derived, damage-associated molecular patterns. The process is further amplified through inflammatory and immunothrombotic mechanisms. Consumption of anticoagulants and disruption of endothelial homeostasis lower the regulatory control and disseminate microvascular thrombosis. Clinical DIC development in patients is associated with worsening morbidities and increased mortality, regardless of the underlying pathology; therefore, timely recognition of DIC is critical for reducing the pathologic burden. Due to the diversity of triggers and pathogenic mechanisms leading to DIC, diagnosis is based on algorithms that quantify hemostatic imbalance, thrombocytopenia, and fibrinogen conversion. Because current diagnosis primarily assesses overt consumptive coagulopathies, there is a critical need for better recognition of nonovert DIC and/or pre-DIC states. Therapeutic strategies for patients with DIC involve resolution of the eliciting triggers and supportive care for the hemostatic imbalance. Despite medical care, mortality in patients with DIC remains high, and new strategies, tailored to the underlying pathologic mechanisms, are needed.

Antithrombin and Its Role in Host Defense and Inflammation

Antithrombin (AT) is a natural anticoagulant that interacts with activated proteases of the coagulation system and with heparan sulfate proteoglycans (HSPG) on the surface of cells. The protein, which is synthesized in the liver, is also essential to confer the effects of therapeutic heparin. However, AT levels drop in systemic inflammatory diseases. The reason for this decline is consumption by the coagulation system but also by immunological processes. Aside from the primarily known anticoagulant effects, AT elicits distinct anti-inflammatory signaling responses. It binds to structures of the glycocalyx (syndecan-4) and further modulates the inflammatory response of endothelial cells and leukocytes by interacting with surface receptors. Additionally, AT exerts direct antimicrobial effects: depending on AT glycosylation it can bind to and perforate bacterial cell walls. Peptide fragments derived from proteolytic degradation of AT exert antibacterial properties. Despite these promising characteristics, therapeutic supplementation in inflammatory conditions has not proven to be effective in randomized control trials. Nevertheless, new insights provided by subgroup analyses and retrospective trials suggest that a recommendation be made to identify the patient population that would benefit most from AT substitution. Recent experiment findings place the role of various AT isoforms in the spotlight. This review provides an overview of new insights into a supposedly well-known molecule.

Predictive Utility of Antithrombin III in Acute Kidney Injury in Living-Donor Liver Transplantation: A Retrospective Observational Cohort Study

INTRODUCTION

This study was performed to determine the association between the serum level of antithrombin III (ATIII) level and the risk of acute kidney injury (AKI) in patients undergoing living-donor liver transplantation (LDLT).

PATIENTS AND METHODS

A total of 591 patients undergoing LDLT were retrospectively investigated and 14 patients were excluded because of a history of kidney dysfunction or missing data; 577 patients were finally enrolled in the study. The study population was divided into normal and low ATIII groups. Data on all laboratory variables, including ATIII, were collected on the day before surgery.

RESULTS

After LDLT, 143 patients developed AKI (24.8%). A lower ATIII was independently associated with postoperative AKI along with preoperative (diabetes mellitus) and intraoperative (mean heart rate, hourly urine output) factors. Based on the standard cutoff for normal ATIII (<70%), the probability of AKI was 2.8-fold higher in the low ATIII group than in the normal ATIII group. In addition, patients with low ATIII received blood transfusion products during the operation and underwent longer duration mechanical ventilation.

CONCLUSIONS

Preoperative ATIII measurement will help improve risk stratification for postoperative AKI development in patients undergoing LDLT.

Antithrombin attenuates the progression of hepatocellular carcinoma by regulating neutrophil/interleukin-8 signaling

AIM

Inflammation plays an important role in hepatocellular carcinoma (HCC) progression. Here, we examined whether antithrombin (AT) plays a role in attenuating HCC progression, via its anti-inflammatory effects.

METHODS

HCCs were developed in AT-insufficient (AT^+/- ) mice and wild-type (AT^+/+ ) mice treated with diethyl nitrosamine and carbon tetrachloride. AT was administered to AT^+/- mice. The development of HCC was compared between the three groups. In vitro study, migration assay was performed. The association of the prognosis of patients with HCC and plasma AT values was clinically examined.

RESULTS

AT suppressed the release of interleukin (IL)-8 from lipopolysaccharide (LPS)-stimulated human neutrophils in vitro. Huh-7 cells that were co-cultured with neutrophils and stimulated with LPS showed significantly enhanced migration; however, Huh-7 cells co-cultured with LPS/AT-stimulated neutrophils showed significantly decreased migration. Moreover, the addition of anti-IL-8 antibodies to LPS-stimulated Huh-7 cells co-cultured with neutrophils also suppressed migration. AT^+/- mice (AT plasma activity: 64%) promoted liver cancer, as compared with wild-type mice (AT plasma activity: 135%); AT administration attenuated liver cancer in AT^+/- mice. Patients with HCC with a preoperative AT level of ≥70% showed better outcomes after liver resection, as compared with those with an AT level of <70%. IL-8 expression and neutrophil infiltration in HCC tissues were negatively correlated with the AT level.

CONCLUSIONS

AT attenuates HCC progression by regulating neutrophil/IL-8 signaling.

Lactobacillus casei CRL 431 improves endothelial and platelet functionality in a pneumococcal infection model

Streptococcus pneumoniae is able to activate coagulation and induce platelet aggregation, both of which are typical responses to systemic inflammation. The interactions between inflammation and coagulation and between soluble adhesion molecules and endothelial cells are important in the pathogenesis of an unbalanced haemostatic system. Therefore, an exaggerated and/or insufficiently controlled haemostatic activity may appreciably contribute to the severity of the disease. The aim of the present study was to evaluate the effect of the oral administration of Lactobacillus casei CRL 431 on platelet and endothelial activation mechanisms in a respiratory pneumococcal infection model in mice. S. pneumoniae induced an increase in platelet counts and enhanced the expression of P-selectin in control group, with higher endothelial activation in lung shown by the increase in von Willebrand factor (vWF) and vascular cell adhesion molecule 1 (VCAM-1) expression. Also, infection induced a decrease in CXCR-4 leukocytes, increased expression in annexinV and cell death at the pulmonary level and decreased antithrombin levels in bronchoalveolar lavage. In contrast, L. casei mice restored platelet counts, favoured faster P-selectin expression, lower vWF levels and VCAM-1 expression than control group. Also, L. casei induced higher levels of annexinV expression and lower cell death in the lung. Moreover, it was able to modulate antithrombin levels within the normal range, which would indicate lower coagulation activation and a protective effect locally exerted by L. casei. In this work, the ability of L. casei to favourably modulate platelet and endothelial functionality during a pulmonary infection with S. pneumoniae was demonstrated. Our findings offer a promising perspective for the use of this probiotic strain in the prevention of thrombotic complications associated with pneumococcal pneumonia, especially in at-risk patients. In addition, the use of L. casei would provide novel alternatives for the prevention and treatment of thrombosis associated with various diseases.

Different Isoforms of the Neuronal Guidance Molecule Slit2 Directly Cause Chemoattraction or Chemorepulsion of Human Neutrophils

The movement of neutrophils between blood and tissues appears to be regulated by chemoattractants and chemorepellents. Compared with neutrophil chemoattractants, relatively little is known about neutrophil chemorepellents. Slit proteins are endogenously cleaved into a variety of N- and C-terminal fragments, and these fragments are neuronal chemorepellents and inhibit chemoattraction of many cell types, including neutrophils. In this report, we show that the ∼140-kDa N-terminal Slit2 fragment (Slit2-N) is a chemoattractant and the ∼110-kDa N-terminal Slit2 fragment (Slit2-S) is a chemorepellent for human neutrophils. The effects of both Slit2 fragments were blocked by Abs to the Slit2 receptor Roundabout homolog 1 or the Slit2 coreceptor Syndecan-4. Slit2-N did not appear to activate Ras but increased phosphatidylinositol 3,4,5-triphosphate levels. Slit2-N-induced chemoattraction was unaffected by Ras inhibitors, reversed by PI3K inhibitors, and blocked by Cdc42 and Rac inhibitors. In contrast, Slit2-S activated Ras but did not increase phosphatidylinositol 3,4,5-triphosphate levels. Slit2-S-induced chemorepulsion was blocked by Ras and Rac inhibitors, not affected by PI3K inhibitors, and reversed by Cdc42 inhibitors. Slit2-N, but not Slit2-S, increased neutrophil adhesion, myosin L chain 2 phosphorylation, and polarized actin formation and single pseudopods at the leading edge of cells. Slit2-S induced multiple pseudopods. These data suggest that Slit2 isoforms use similar receptors but different intracellular signaling pathways and have different effects on the cytoskeleton and pseudopods to induce neutrophil chemoattraction or chemorepulsion.

Antithrombin Insufficiency Promotes Susceptibility to Liver Tumorigenesis

BACKGROUND

Antithrombin (AT) is not only a major regulator of hemostasis, but it shows anti-inflammatory properties as well. We aimed to investigate whether AT-insufficient mice increase susceptibility to liver tumorigenesis.

METHODS

We induced the development of liver tumor in AT-insufficient (AT^+/-) mice and wild-type (AT^+/+) mice by treating them with diethylnitrosamine (DEN) and CCl₄. The development of liver tumors and liver inflammation were compared between these mouse groups. Following this, AT was administered to the AT-insufficient mice treated with DEN and CCl₄.

RESULTS

Tumor size and the number of DEN and CCl₄-induced liver tumors significantly increased in AT-insufficient mice compared with the wild-type mice. Serum transaminase levels, cell death, and the expression of cleaved caspase-3 in liver were increased in AT^+/-. Furthermore, hepatic neutrophil infiltrations and serum interleukin 6 and tumor necrosis factor-α levels were significantly elevated in AT-insufficient mice. The levels of 8-OHdG, oxidative DNA damage marker, in liver were significantly increased in AT-insufficient mice. Administration of AT led to a significant decrease in DEN- and CCl₄-induced liver injury and inflammation in AT-insufficient mice, compared with the wild-type group.

CONCLUSIONS

AT insufficiency led to increased susceptibility to liver tumorigenesis by increasing hepatic inflammation.

Endothelial cell surface limits coagulation without modulating the antithrombin potency

Antithrombin (AT) binds in vitro and in vivo to endothelial cells through various receptors, including heparan sulphate glycosaminoglycan (HSPG) that could modulate the AT activity. A thrombin generation assay (TGA) was set up at the surface of HUVEC and HMVEC evaluating their participation in the coagulation-anticoagulation processes. TGA induced by 0.5 pM Tissue Factor was performed in normal or AT-deficient plasma spiked with various amounts of recombinant or plasma-derived AT (0, 0.1, 0.5 and 1.0 U/ml). To evaluate the role of HSPG or cellular anticoagulant receptors, cells were treated or not with heparin, a mix of heparanase I, II and III, a neutralizing anti-Endothelial Protein C Receptor (EPCR) or with an anti-Tissue Factor Pathway Inhibitor (TFPI) antibody. The presence of the cells diminished the TG in normal plasma and maintained anticoagulation in AT-deficient plasma. Spiking the AT-deficient plasma with different doses of AT demonstrated that the cells did not amplify the anticoagulant activity of AT. The recombinant AT binds the cells with a higher avidity than the plasma-derived one but this did not affect its anticoagulant potency. Moreover both bindings are independent of the HSPG. The antithrombotic activity kept in absence of AT was not inhibited by blocking antibodies directed against EPCR or TFPI. Our data did not reveal a major co-factor activity for AT from endothelial cells that could have been mediated by HSPG. In contrast, it reveals the presence of alternative anti-coagulant system(s) in two venous cell types that maintain an antithrombotic activity.

Antithrombin III prevents progression of chronic kidney disease following experimental ischaemic-reperfusion injury

Acute kidney disease (AKI) leads to increased risk of progression to chronic kidney disease (CKD). Antithrombin III (ATIII) is a potent anticoagulant with anti-inflammatory properties, and we previously reported that insufficiencies of ATIII exacerbated renal ischaemia-reperfusion injury (IRI) in rats. In this study, we examined the characteristic of AKI-CKD transition in rats with two distinct AKI models. Based on our observation, left IRI plus right nephrectomy (NX-IRI) was used to determine whether ATIII had therapeutic effects in preventing CKD progression after AKI. It was observed that NX-IRI resulted in significant functional and histological damage at 5 weeks after NX-IRI compared with sham rats, which was mitigated by ATIII administration. Besides, we noticed that ATIII administration significantly reduced NX-IRI-induced interstitial fibrosis. Consistently, renal expression of collagen-1, α-smooth muscle actin and fibronectin were substantial diminished in ATIII-administered rats compared with un-treated NX-IRI rats. Furthermore, the beneficial effects of ATIII were accompanied with decreased M1-like macrophage recruitment and down-regulation of M1-like macrophage-dependent pro-inflammatory cytokines such as tumour necrosis factor α, inducible nitric oxide synthase and interleukin-1β, indicating that ATIII prevented AKI-CKD transition via inhibiting inflammation. Overall, ATIII shows potential as a therapeutic strategy for the prevention of CKD progression after AKI.

Antithrombin III Protects Against Contrast-Induced Nephropathy

We previously reported that insufficiency of antithrombin III (ATIII), the major anti-coagulation molecule in vivo, exacerbated renal ischemia-reperfusion injury in animal models and possibly humans. In the present study, we investigated the relationship between ATIII level and contrast induced nephropathy (CIN) in patients and examined therapeutic effect of ATIII on CIN in Sprague-Dawley rats. Patients with low ATIII activity presented a higher incidence of acute kidney injury (AKI) following coronary angiography. ATIII (500 μg/kg) was intravenously injected before or after the induction of AKI in rats. Our data demonstrated ATIII significantly attenuated the elevation of serum creatinine, blood urea nitrogen, and renal histological injury. The beneficial effects of ATIII were accompanied by diminished renal inflammatory response, oxidative stress, cell apoptosis and improved renal blood flow in rats. In conclusion, ATIII appears to attenuate CIN through inhibiting inflammation, oxidative stress, apoptosis and improving renal blood flow. ATIII administration may represent a promising strategy for the prevention and treatment of contrast-induced AKI.

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Patients with low ATIII activity presented a higher incidence of acute kidney injury following coronary angiography.

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ATIII supplementation attenuated renal injury in animal models of contrast induced nephropathy.

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ATIII exerted renoprotective effect by inhibiting inflammation, oxidative stress, apoptosis and improving renal blood flow.

Antithrombin III (ATIII), a potent anti-coagulation molecule in vivo, has been reported that it can exert reno-protective effects in ischemia-reperfusion model. Nevertheless, whether exogenous ATIII administration can protect against contrast induced nephropathy (CIN) in animal models remains unclear. This study revealed that ATIII administration has therapeutic effects against CIN in Sprague-Dawley Rats. Furthermore, the reno-protection conferred by ATIII might be mediated by inhibition of inflammation, oxidative stress, apoptosis and improving renal blood flow. ATIII supplementation represents a promising prophylactic and treatment strategies for contrast induced AKI.

Antithrombin III improved neutrophil extracellular traps in lung after the onset of endotoxemia

BACKGROUND

Coagulation and inflammation are closely linked during acute inflammatory conditions, such as sepsis. Antithrombin (AT) is an anticoagulant that also has anti-inflammatory activities. The effects of therapeutically administering AT III after the onset of endotoxemia or sepsis were not clear. Here, we studied the effects of administering AT III after inducing lethal endotoxemia in mice.

METHODS

Mice were injected intraperitoneally with lipopolysaccharide (LPS) to induce endotoxemia. AT III was administered 3 h later. We assessed survival and the severity of endotoxemia and quantified plasma cytokine levels and biochemical markers of liver and kidney function. In the lungs, we examined neutrophil accumulation, neutrophil extracellular traps, alveolar wall thickness, and chemokine (C-X-C motif) ligand 1 (cxcl-1), cxcl-2, and high mobility group box 1 expression.

RESULTS

Administering AT III reduced the severity and mortality of LPS-induced endotoxemia as indicated by 24-h survival of 84% of the mice that received LPS + AT III and only 53% of mice given LPS alone (P < 0.05). AT III treatment attenuated several changes induced in the lungs by endotoxemia including cxcl-2 mRNA expression, high mobility group box 1 protein expression, neutrophil accumulation, alveolar septal thickening, and neutrophil extracellular trap formation. AT III did not decrease plasma cytokine levels or plasma urea nitrogen levels that were upregulated as a result of LPS-induced endotoxemia.

CONCLUSIONS

Administration of AT III after the onset of endotoxemia improved outcomes in a mouse model. The attenuation of lung inflammation may have a large impact on mortality and morbidity. Because lung inflammation increases the likelihood of mortality from sepsis, AT III could be a useful agent in septic patients.

The nexus between systemic inflammation and disordered coagulation in sepsis

The innate immune system is designed as an early defense system that recognizes and clears potential microbial invaders. The coagulation system co-evolved with the innate immune system from a common ancestral cellular origin, and these two systems continue to exhibit a remarkable degree of integration in their signaling pathways and regulatory circuits following tissue injury and microbial invasion. Inflammatory mediators generate procoagulant signals and intravascular thrombosis activates multiple components of the innate immune system. The success of recombinant human activated protein C for the treatment of human septic shock is likely attributable to its combined effects as an endogenous anticoagulant and an anti-inflammatory molecule. Further advances in the management of severe infections may accrue with a better understanding of the integral link between coagulation and innate immunity.

Anticardiolipin antibodies in various diseases in Taiwan: a retrospective analysis

The goals of this study are to determine the frequency of anticardiolipinantibodies (ACA) in patients with various diseases and to evaluate the clinical significance of ACA in Taiwan. We collected 690 patients from ACA laboratory records. They were divided into eight groups in order to compare ACA percentages. Positive rates of ACA in different disease groups were below 20%, except for 38.2% in autoimmune diseases with vascular thrombosis. Compared with old stroke, the ACA positivity in young stroke was not significantly different (P 0.482). The positive percentage of lupus anticoagulant (LA) (2.86%) was lower than that of ACA (15.66%) in young stroke (P 0.015). Among patients with pregnancy loss or prematurity, the ACA positivity in lupus patients (44.44%) was higher than without lupus (9.76%; P 0.01). The prevalence of ACA is higher in patients with vascular thrombosis complicated by autoimmune diseases than with thrombosis alone in Taiwan. Young and old stroke do not differ in ACA positivity. Moreover, ACA is more prevalent than LA for young stroke related coagulation.The ACA positivity for pregnancy loss or prematurity is very low in Taiwan. In summary, this is the first report on the frequency of ACA and other coagulation factors in various diseases in Taiwan.

Antithrombin III/SerpinC1 insufficiency exacerbates renal ischemia/reperfusion injury

Antithrombin III, encoded by SerpinC1, is a major anti-coagulation molecule in vivo and has anti-inflammatory effects. We found that patients with low antithrombin III activities presented a higher risk of developing acute kidney injury after cardiac surgery. To study this further, we generated SerpinC1 heterozygous knockout rats and followed the development of acute kidney injury in a model of modest renal ischemia/reperfusion injury. Renal injury, assessed by serum creatinine and renal tubular injury scores after 24 h of reperfusion, was significantly exacerbated in SerpinC1(+/-) rats compared to wild-type littermates. Concomitantly, renal oxidative stress, tubular apoptosis, and macrophage infiltration following this injury were significantly aggravated in SerpinC1(+/-) rats. However, significant thrombosis was not found in the kidneys of any group of rats. Antithrombin III is reported to stimulate the production of prostaglandin I2, a known regulator of renal cortical blood flow, in addition to having anti-inflammatory effects and to protect against renal failure. Prostaglandin F1α, an assayable metabolite of prostaglandin I2, was increased in the kidneys of the wild-type rats at 3 h after reperfusion. The increase of prostaglandin F1α was significantly blunted in SerpinC1(+/-) rats, which preceded increased tubular injury and oxidative stress. Thus, our study found a novel role of SerpinC1 insufficiency in increasing the severity of renal ischemia/reperfusion injury.

Antimicrobial effects of helix D-derived peptides of human antithrombin III

Antithrombin III (ATIII) is a key antiproteinase involved in blood coagulation. Previous investigations have shown that ATIII is degraded by Staphylococcus aureus V8 protease, leading to release of heparin binding fragments derived from its D helix. As heparin binding and antimicrobial activity of peptides frequently overlap, we here set out to explore possible antibacterial effects of intact and degraded ATIII. In contrast to intact ATIII, the results showed that extensive degradation of the molecule yielded fragments with antimicrobial activity. Correspondingly, the heparin-binding, helix D-derived, peptide FFFAKLNCRLYRKANKSSKLV (FFF21) of human ATIII, was found to be antimicrobial against particularly the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Fluorescence microscopy and electron microscopy studies demonstrated that FFF21 binds to and permeabilizes bacterial membranes. Analogously, FFF21 was found to induce membrane leakage of model anionic liposomes. In vivo, FFF21 significantly reduced P. aeruginosa infection in mice. Additionally, FFF21 displayed anti-endotoxic effects in vitro. Taken together, our results suggest novel roles for ATIII-derived peptide fragments in host defense.

Engineering D-helix of antithrombin in alpha-1-proteinase inhibitor confers antiinflammatory properties on the chimeric serpin

Antithrombin (AT) is a heparin-binding serpin in plasma which regulates the proteolytic activity of procoagulant proteases of the clotting cascade. In addition to being an anticoagulant, AT also exhibits antiinflammatory activities when it binds to cell surface heparan sulfate proteoglycans (HSPGs) on the endothelium via its basic residues of D-helix to elicit intracellular signalling responses. By contrast to AT, α1-proteinase inhibitor (α1-PI) is a non-heparin-binding serpin that exhibits very slow reactivity with coagulation proteases and possesses no HSPG-dependent antiinflammatory properties. To determine whether the antiinflammatory signaling specificity of AT can be transferred to α1-PI, we replaced the D-helix of human α1-PI with the corresponding sequence of human AT and expressed the chimeric serpin α1-PI/D-helix) in a bacterial expression system. High molecular weight heparin bound to α1-PI/D-helix and accelerated the inhibition of thrombin by the serpin mutant by a template mechanism reminiscent of the cofactor effect of heparin on inhibition of thrombin by AT. Like AT, α1-PI/D-helix exhibited antiinflammatory properties in both cellular and animal models. Thus, α1-PI/D-helix inhibited the barrier-disruptive effect of proinflammatory cytokines and inhibited the activation of nuclear factor-κB transcription factor in lipopolysaccharide-stimulated endothelial cells by a concentration-dependent manner. Furthermore, the chimeric serpin reduced lipopolysaccharide-mediated lethality, elicited a vascular protective effect and inhibited infiltration of activated leukocytes to the peritoneal cavity of mice in an HMGB1-mediated inflammatory model. These results suggest that grafting the D-helix of AT to α1-PI confers antiinflammatory properties on the serpin and that the chimeric serpin may have therapeutic utility for treating inflammatory disorders.

Clinical syndromes associated with acquired antithrombin deficiency via microvascular leakage and the related risk of thrombosis

Antithrombin (AT) is a 65kDa glycoprotein belonging to a group of inhibitory factors known as serpins (serine protease inhibitors). It plays a critical role in the inhibition of coagulation and inflammation processes within the environment of the vascular endothelium. Inadequate levels of functional AT in plasma results in an increased risk of thrombotic events, both venous and arterial. AT deficiency can be inherited or acquired. Congenital AT deficiency is the most severe inherited thrombophilic condition with an odds ratio of 20 for the increased risk of venous thrombosis. Acquired AT deficiency occurs in a variety of physiologic and pathologic medical conditions with similar risks of increased thrombosis. In this article, we review clinical settings characterized by an acquired AT deficiency largely or partly subsequent to protein microvascular leakage. Other different mechanisms of AT depletion are implied in some clinical conditions together with endothelial loss, and, therefore, outlined. In addition, we provide a description of the current knowledge on the specific mechanisms underlying endothelial AT leakage and on the consequences of this protein decrease, specifically looking at thrombosis. We identify potential directions of research that might prove useful in patients with acquired AT deficiency.

Antithrombin attenuates vascular leakage via inhibiting neutrophil activation in acute lung injury

OBJECTIVE

To test the hypothesis that restoration of antithrombin plasma concentrations attenuates vascular leakage by inhibiting neutrophil activation through syndecan-4 receptor inhibition in an established ovine model of acute lung injury.

DESIGN

Randomized controlled laboratory experiment.

SETTING

University animal research facility.

SUBJECTS

Eighteen chronically instrumented sheep.

INTERVENTIONS

Following combined burn and smoke inhalation injury (40% of total body surface area, third-degree flame burn; 4 × 12 breaths of cold cotton smoke), chronically instrumented sheep were randomly assigned to receive an IV infusion of 6 IU/kg/hr recombinant human antithrombin III or normal saline (n = 6 each) during the 48-hour study period. In addition, six sham animals (not injured, continuous infusion of vehicle) were used to obtain reference values for histological and immunohistochemical analyses.

MEASUREMENTS AND MAIN RESULTS

Compared to control animals, recombinant human antithrombin III reduced the number of neutrophils per hour in the pulmonary lymph (p < 0.01 at 24 and 48 hr), alveolar neutrophil infiltration (p = 0.04), and pulmonary myeloperoxidase activity (p = 0.026). Flow cytometric analysis revealed a significant reduction of syndecan-4-positive neutrophils (p = 0.002 vs control at 24 hr). Treatment with recombinant human antithrombin III resulted in a reduction of pulmonary nitrosative stress (p = 0.002), airway obstruction (bronchi: p = 0.001, bronchioli: p = 0.013), parenchymal edema (p = 0.044), and lung bloodless wet-to-dry-weight ratio (p = 0.015). Clinically, recombinant human antithrombin III attenuated the increased pulmonary transvascular fluid flux (12-48 hr: p ≤ 0.001 vs control each) and the deteriorated pulmonary gas exchange (12-48 hr: p < 0.05 vs control each) without increasing the risk of bleeding.

CONCLUSIONS

The present study provides evidence for the interaction between antithrombin and neutrophils in vivo, its pathophysiological role in vascular leakage, and the therapeutic potential of recombinant human antithrombin III in a large animal model of acute lung injury.

The role of the vessel wall

The role of the vessel wall is complex and its effects are wide-ranging. The vessel wall, specifically the endothelial monolayer that lines the inner lumen, possesses the ability to influence various physiological states both locally and systemically by controlling vascular tone, basement membrane component synthesis, angiogenesis, haemostatic properties, and immunogenicity. This is an overview of the function and structure of the vessel wall and how disruption and dysfunction in any of these regulatory roles can lead to disease states.

Antithrombin is protective against myocardial ischemia and reperfusion injury

BACKGROUND

Antithrombin (AT) is a plasma serpin inhibitor that regulates the proteolytic activity of procoagulant proteases of the clotting cascade. In addition to its anticoagulant activity, AT also possesses potent anti-inflammatory properties.

OBJECTIVES

The objective of this study was to investigate the anti-inflammatory activity of wild-type AT (AT-WT) and a reactive centre loop mutant of AT (AT-RCL) which is not capable of inhibiting thrombin.

METHODS

The cardioprotective activities of AT-WT and AT-RCL were monitored in a mouse model of ischemia/reperfusion (I/R) injury in which the left anterior descending coronary artery was occluded and then released.

RESULTS

We demonstrate that AT markedly reduces myocardial infarct size by a mechanism that is independent of its anticoagulant activity. Thus, AT-RCL attenuated myocardial infarct size to the same extent as AT-WT in this acute injury model. Further studies revealed that AT binds to vascular heparan sulfate proteoglycans via its heparin-binding domain to exert its protective activity as evidenced by the therapeutic AT-binding pentasaccharide (fondaparinux) abrogating the cardioprotective activity of AT and a heparin-site mutant of AT exhibiting no cardioprotective property. We further demonstrate that AT up-regulates the production of prostacyclin in myocardial tissues and inhibits expression of pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 in vivo by attenuating ischemia/reperfusion-induced JNK and NF-κB signaling pathways.

CONCLUSIONS

The present results suggest that both AT and the non-anticoagulant AT-RCL, through their anti-inflammatory signaling effects, elicit potent cardioprotective responses. Thus, AT may have therapeutic potential for treating cardiac I/R injury.

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.

Antithrombin attenuates myocardial dysfunction and reverses systemic fluid accumulation following burn and smoke inhalation injury: a randomized, controlled, experimental study

Introduction

We hypothesized that maintaining physiological plasma levels of antithrombin attenuates myocardial dysfunction and inflammation as well as vascular leakage associated with burn and smoke inhalation injury. Therefore, the present prospective, randomized experiment was conducted using an established ovine model.

Methods

Following 40% of total body surface area, third degree flame burn and 4 × 12 breaths of cold cotton smoke, chronically instrumented sheep were randomly assigned to receive an intravenous infusion of 6 IU/kg/h recombinant human antithrombin (rhAT) or normal saline (control group; n = 6 each). In addition, six sheep were designated as sham animals (not injured, continuous infusion of vehicle). During the 48 h study period the animals were awake, mechanically ventilated and fluid resuscitated according to standard formulas.

Results

Compared to the sham group, myocardial contractility was severely impaired in control animals, as suggested by lower stroke volume and left ventricular stroke work indexes. As a compensatory mechanism, heart rate increased, thereby increasing myocardial oxygen consumption. In parallel, myocardial inflammation was induced via nitric oxide production, neutrophil accumulation (myeloperoxidase activity) and activation of the p38-mitogen-activated protein kinase pathway resulting in cytokine release (tumor necrosis factor-alpha, interleukin-6) in control vs. sham animals. rhAT-treatment significantly attenuated these inflammatory changes leading to a myocardial contractility and myocardial oxygen consumption comparable to sham animals. In control animals, systemic fluid accumulation progressively increased over time resulting in a cumulative positive fluid balance of about 4,000 ml at the end of the study period. Contrarily, in rhAT-treated animals there was only an initial fluid accumulation until 24 h that was reversed back to the level of sham animals during the second day.

Conclusions

Based on these findings, the supplementation of rhAT may represent a valuable therapeutic approach for cardiovascular dysfunction and inflammation after burn and smoke inhalation injury.

In vivo anti-HIV activity of the heparin-activated serine protease inhibitor antithrombin III encapsulated in lymph-targeting immunoliposomes

Endogenous serine protease inhibitors (serpins) are anti-inflammatory mediators with multiple biologic functions. Several serpins have been reported to modulate HIV pathogenesis, or exhibit potent anti-HIV activity in vitro, but the efficacy of serpins as therapeutic agents for HIV in vivo has not yet been demonstrated. In the present study, we show that heparin-activated antithrombin III (hep-ATIII), a member of the serpin family, significantly inhibits lentiviral replication in a non-human primate model. We further demonstrate greater than one log(10) reduction in plasma viremia in the nonhuman primate system by loading of hep-ATIII into anti-HLA-DR immunoliposomes, which target tissue reservoirs of viral replication. We also demonstrate the utility of hep-ATIIII as a potential salvage agent for HIV strains resistant to standard anti-retroviral treatment. Finally, we applied gene-expression arrays to analyze hep-ATIII-induced host cell interactomes and found that downstream of hep-ATIII, two independent gene networks were modulated by host factors prostaglandin synthetase-2, ERK1/2 and NFκB. Ultimately, understanding how serpins, such as hep-ATIII, regulate host responses during HIV infection may reveal new avenues for therapeutic intervention.

Antithrombin III injection via the portal vein suppresses liver damage

AIM: To investigate the effects of antithrombin III (AT III) injection via the portal vein in acute liver failure.

METHODS: Thirty rats were intraperitoneally challenged with lipopolysaccharide (LPS) and D-galactosamine (GalN) and divided into three groups: a control group; a group injected with AT III via the tail vein; and a group injected with AT III via the portal vein. AT III (50 U/kg body weight) was administrated 1 h after challenge with LPS and GalN. Serum levels of inflammatory cytokines and fibrin degradation products, hepatic fibrin deposition, and hepatic mRNA expression of hypoxia-related genes were analyzed.

RESULTS: Serum levels of alanine aminotransferase, tumor necrosis factor-α and interleukin-6 decreased significantly following portal vein AT III injection compared with tail vein injection, and control rats. Portal vein AT III injection reduced liver cell destruction and decreased hepatic fibrin deposition. This treatment also significantly reduced hepatic mRNA expression of lactate dehydrogenase and heme oxygenase-1.

CONCLUSION: A clinically acceptable dose of AT III injection into the portal vein suppressed liver damage, probably through its enhanced anticoagulant and anti-inflammatory activities.

Mechanistic overview of reactive species-induced degradation of the endothelial glycocalyx during hepatic ischemia/reperfusion injury

Endothelial cells are covered by a delicate meshwork of glycoproteins known as the glycocalyx. Under normophysiological conditions the glycocalyx plays an active role in maintaining vascular homeostasis by deterring primary and secondary hemostasis and leukocyte adhesion and by regulating vascular permeability and tone. During (micro)vascular oxidative and nitrosative stress, which prevails in numerous metabolic (diabetes), vascular (atherosclerosis, hypertension), and surgical (ischemia/reperfusion injury, trauma) disease states, the glycocalyx is oxidatively and nitrosatively modified and degraded, which culminates in an exacerbation of the underlying pathology. Consequently, glycocalyx degradation due to oxidative/nitrosative stress has far-reaching clinical implications. In this review the molecular mechanisms of reactive oxygen and nitrogen species-induced destruction of the endothelial glycocalyx are addressed in the context of hepatic ischemia/reperfusion injury as a model disease state. Specifically, the review focuses on (i) the mechanisms of glycocalyx degradation during hepatic ischemia/reperfusion, (ii) the molecular and cellular players involved in the degradation process, and (iii) its implications for hepatic pathophysiology. These topics are projected against a background of liver anatomy, glycocalyx function and structure, and the biology/biochemistry and the sources/targets of reactive oxygen and nitrogen species. The majority of the glycocalyx-related mechanisms elucidated for hepatic ischemia/reperfusion are extrapolatable to the other aforementioned disease states.

Effects of antithrombin III treatment in vascular injury model of mice

BACKGROUND

Balloon angioplasty has recently been adopted as an acceptable form of treatment for stenotic vessel lesions of congenital heart diseases. However, precise mechanisms of restenosis and thrombosis, which are the most common complications after these procedures, are unknown.

METHODS

We examined the effects of antithrombin III (ATIII) on inflammation, thrombus formation, and remodeling of vascular wall after guidewire-induced injury in the femoral artery of mice. ATIII or saline was administered as a bolus intravenous infusion before injury.

RESULTS

Seventy-two hours after injury, approximately half of the saline-treated vessels showed macroscopic thrombus formation. In contrast, no thrombi were seen in the arteries pretreated with ATIII. Significantly higher levels of inflammation were induced in the injured vessels than in the sham-operated controls, as determined by CD11b-positive cell density in the adventitial area. ATIII treatment resulted in marked reduction of inflammatory cell infiltration. Twenty-eight days after injury, similar levels of neointimal proliferation were found in the injured arteries in both groups.

CONCLUSIONS

Our results suggested that a high dose of ATIII may influence the sequelae of arterial injury by reducing mural thrombus formation and limiting the inflammatory reaction of the vessel wall without altering the process of vascular remodeling.

Laboratory tests for antithrombin deficiency

Hereditary antithrombin deficiency is a hypercoagulable state associated with an increased risk for venous thrombosis. The recommended initial test for antithrombin is an activity (functional) assay. The advantages and disadvantages of the various testing options are presented. The causes of acquired antithrombin deficiency are much more common than hereditary deficiency. Therefore, this article describes the appropriate steps to take when antithrombin activity is low, in order to confirm or exclude a hereditary deficiency. The causes of falsely normal results are also described, including direct thrombin inhibitors. Am. J. Hematol. 85:947-950, 2010. © 2010 Wiley-Liss, Inc.

Mutagenesis studies toward understanding the intracellular signaling mechanism of antithrombin

SUMMARY BACKGROUND

Recent studies have indicated that antithrombin (AT) possesses both anti-inflammatory and antiangiogenic properties.

OBJECTIVES

The purpose of this study was to investigate the mechanism of the intracellular signaling activities of AT using wild-type and mutant serpins that have reduced anticoagulant activities due to mutations in either the reactive center loop (RCL) or the heparin-binding site.

METHODS

Direct cellular effects of the AT derivatives were compared in the LPS-stimulated endothelial cells by employing permeability and neutrophil adhesion assays in the absence and presence of pertussis toxin (PTX) and siRNAs for either syndecan-4 or sphingosine 1-phosphate receptor 1 (S1P(1)). Furthermore, the roles of prostacyclin and nuclear factor (NF)-kappaB in modulating these effects were investigated.

RESULTS

Both wild-type and the RCL mutant, AT/Proth-2, exhibited similar potent barrier protective activities and inhibited the adhesion of neutrophils to endothelial cells via inhibition of the NF-kappaB pathway. Indomethacin abrogated both activities. The heparin-binding site mutants, AT-K114E and AT-K125E, did not exhibit any protective activity in either one of these assays, but a potent pro-apoptotic activity was observed for the AT-K114E in endothelial cells. Both PTX and siRNA for syndecan-4 inhibited the protective effect of AT, but the siRNA for S1P(1) was inconsequential.

CONCLUSIONS

The interaction of AT with syndecan-4 is required for its prostacyclin-dependent protective effect through a PTX-sensitive and non-S1P(1)-related G(i)-protein coupled receptor. The RCL mutant, AT/Proth-2, with a markedly reduced anticoagulant but normal protective signaling properties, may potentially be developed as a safer anti-inflammatory drug without increasing the risk of bleeding.

The inflammatory response to skeletal muscle injury: illuminating complexities

Injury of skeletal muscle, and especially mechanically induced damage such as contusion injury, frequently occurs in contact sports, as well as in accidental contact sports, such as hockey and squash. The large variations with regard to injury severity and affected muscle group, as well as non-specificity of reported symptoms, complicate research aimed at finding suitable treatments. Therefore, in order to increase the chances of finding a successful treatment, it is important to understand the underlying mechanisms inherent to this type of skeletal muscle injury and the cellular processes involved in muscle healing following a contusion injury. Arguably the most important of these processes is inflammation since it is a consistent and lasting response. The inflammatory response is dependent on two factors, namely the extent of actual physical damage and the degree of muscle vascularization at the time of injury. However, long-term anti-inflammatory treatment is not necessarily effective in promoting healing, as indicated by various studies on NSAID treatment. Because of the factors named earlier, human studies on the inflammatory response to contusion injury are limited, but several experimental animal models have been designed to study muscle damage and regeneration. The early recovery phase is characterized by the overlapping processes of inflammation and occurrence of secondary damage. Although neutrophil infiltration has been named as a contributor to the latter, no clear evidence exists to support this claim. Macrophages, although forming part of the inflammatory response, have been shown to have a role in recovery, rather than in exacerbating secondary damage. Several probable roles for this cell type in the second phase of recovery, involving resolution processes, have been identified and include the following: (i) phagocytosis to remove cellular debris; (ii) switching from a pro- to anti-inflammatory phenotype in regenerating muscle; (iii) preventing muscle cells from undergoing apoptosis; (iv) releasing factors to promote muscle precursor cell activation and growth; and (v) secretion of cytokines and growth factors to facilitate vascular and muscle fibre repair. These many different roles suggest that a single treatment with one specific target cell population (e.g. neutrophils, macrophages or satellite cells) may not be equally effective in all phases of the post-injury response. To find the optimal targeted, but time-course-dependent, treatments requires substantial further investigations. However, the techniques currently used to induce mechanical injury vary considerably in terms of invasiveness, tools used to induce injury, muscle group selected for injury and contractile status of the muscle, all of which have an influence on the immune and/or cytokine responses. This makes interpretation of the complex responses more difficult. After our review of the literature, we propose that a standardized non-invasive contusion injury is the ideal model for investigations into the immune responses to mechanical skeletal muscle injury. Despite its suitability as a model, the currently available literature with respect to the inflammatory response to injury using contusion models is largely inadequate. Therefore, it may be premature to investigate highly targeted therapies, which may ultimately prove more effective in decreasing athlete recovery time than current therapies that are either not phase-specific, or not administered in a phase-specific fashion.

Staphylococcus aureus beta-toxin induces lung injury through syndecan-1

In pneumonia caused by the bacterium Staphylococcus aureus, the intense inflammatory response that is triggered by this infection can lead to the development of lung injury. Little is known, however, about the impact of specific virulence factors on this inflammatory disorder, which causes both significant mortality and morbidity. In this study, we examined the role of beta-toxin, a neutral sphingomyelinase, in S. aureus-induced lung injury. Our results showed that the central features of lung injury--specifically, increased neutrophilic inflammation, vascular leakage of serum proteins into the lung tissue, and exudation of proteins into the airway--are significantly attenuated in mice infected intranasally with S. aureus deficient in beta-toxin compared with mice infected with S. aureus expressing beta-toxin. In addition, intranasal administration of beta-toxin evoked the characteristic features of lung injury in wild-type mice whereas neutropenic mice were protected from such injury. However, mutant beta-toxin mice deficient in sphingomyelinase activity failed to trigger features of lung injury. Ablation of sphingomyelinase activity also interfered with the ability of beta-toxin to stimulate ectodomain shedding of syndecan-1, a major heparan sulfate proteoglycan found in epithelial cells. Moreover, syndecan-1-null mice were significantly protected from beta-toxin-induced lung injury relative to wild-type mice. These data indicate that S. aureus beta-toxin is a critical virulence factor that induces neutrophil-mediated lung injury through both its sphingomyelinase activity and syndecan-1.

Effects of anticoagulant strategies on activation of inflammation and coagulation

Acute inflammatory events, such as those that occur in sepsis, lead to dysregulation of the coagulation cascade. The hemostatic imbalance in sepsis, characterized by the excessive activation of procoagulant pathways and the impairment of anticoagulant activity, leads to disseminated intravascular coagulation and results in microvascular thrombosis, tissue hypoperfusion and, ultimately, multiple organ failure and death. Furthermore, natural anti-inflammatory mechanisms of the endogenous anticoagulants are diminished by the impaired coagulation. Supportive strategies aiming at inhibiting activation of coagulation and inflammation by treatment with exogenous anticoagulants have been found to be beneficial in experimental and initial clinical studies. This review summarizes the available experimental and clinical data regarding the interaction between coagulation and inflammation, focusing on the two anticoagulants which are in clinical use, antithrombin and activated protein C. Identification of the different biological mechanisms of the two endogenous anticoagulants might help to determine target patient populations as well as to develop new anticoagulant analogs that differ in there respective effects in coagulation and inflammation.

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.

Role of Antithrombin and Factor XIII In Leukocyte-Independent Plasma Extravasation During Endotoxemia: An Intravital-Microscopic Study in the Rat

BACKGROUND

Platelet-endothelial interactions have been shown to be main mediators of leukocyte-independent endothelial damage. Besides altering platelet-endothelial interactions, both antithrombin and factor XIII reduce microvascular permeability in leukocyte-dependent experimental models. Thus, it was our aim to investigate the effects of antithrombin and factor XIII on microvascular permeability during leukocyte-independent endotoxemia.

MATERIAL AND METHODS

In male Wistar rats, venular wall shear rate, macromolecular efflux, and leukocyte-endothelial interaction were determined in mesenteric postcapillary venules using intravital microscopy at baseline, 60, and 120 min after the start of the experiment. Fucoidin and a continuous infusion of lipopolysaccharides were used to generate leukocyte-independent endotoxemia. The experiment was divided into two parts 1) an antithrombin study and 2) a factor XIII study.

RESULTS

No differences between groups in leukocyte rolling and venular wall shear rate could be observed in both parts of the experiment. Pretreatment with antithrombin reduced microvascular permeability significantly compared with control subjects (120 min: Fuco [untreated]: 0.14 +/- 0.03; Fuco/ETX [control]: 0.37 +/- 0.06; Fuco + ATIII/ETX: 0.15 +/- 0.02; P < 0.05). Factor XIII reduced microvascular permeability significantly after 60 min (Fuco [untreated]: 0.10 +/- 0.03; Fuco/ETX [control]: 0.36 +/- 0.07; Fuco + FXIII/ETX: 0.13 +/- 0.04; P < 0.05). This effect diminished after 120 min (Fuco [untreated]: 0.12 +/- 0.03; Fuco/ETX [control]: 0.5 +/- 0.08; Fuco + FXIII/ETX: 0.29 +/- 0.05; P < 0.05).

CONCLUSIONS

Antithrombin and factor XIII reduce leukocyte-independent microvascular permeability. Yet, factor XIII also shows a nonprotective effect on a long-term basis. These data emphasize the central role of platelets in leukocyte-independent endotoxemia.

Clinical review: molecular mechanisms underlying the role of antithrombin in sepsis

In disseminated intravascular coagulation (DIC) there is extensive crosstalk between activation of inflammation and coagulation. Endogenous anticoagulatory pathways are downregulated by inflammation, thus decreasing the natural anti-inflammatory mechanisms that these pathways possess. Supportive strategies aimed at inhibiting activation of coagulation and inflammation may theoretically be justified and have been found to be beneficial in experimental and initial clinical studies. This review assembles the available experimental and clinical data on biological mechanisms of antithrombin in inflammatory coagulation activation. Preclinical research has demonstrated partial interference of heparin – administered even at low doses – with the therapeutic effects of antithrombin, and has confirmed – at the level of cellular mechanisms – a regulatory role for antithrombin in DIC. Against this biological background, re-analyses of data from randomized controlled trials of antithrombin in sepsis suggest that antithrombin has the potential to be developed further as a therapeutic agent in the treatment of DIC. Even though there is a lack of studies employing satisfactory methodology, the results of investigations conducted thus far into the mechanisms of action of antithrombin allow one to infer that there is biological plausibility in the value of this agent. Final assessment of the drug's effectiveness, however, must await the availability of positive, prospective, randomized and placebo-controlled studies.

Heparan sulfate proteoglycan-dependent neutrophil chemotaxis toward PR-39 cathelicidin

Cathelicidins are mammalian proteins containing a C-terminal cationic antimicrobial domain. Porcine PR-39 cathelicidin affects leukocyte biology. Mechanisms of action may involve alteration of heparan sulfate proteoglycan-dependent functions in inflammatory cells. It was tested whether PR-39 affects human neutrophil migration and if such effects involve heparan sulphate proteoglycans. Neutrophils were from forearm venous blood of healthy donors. Migration was tested in modified Boyden chamber assays. Involvement of heparan sulfate proteoglycans was tested by their chemical modification and by the use of specific antibodies. PR-39 induced migration in neutrophils in a concentration dependent manner. Modification of heparan sulfate proteoglycans with sodium chlorate inhibited migration whereas chemotaxis toward the chemoattractant formyl-Met-Leu-Phe was not affected. Removal of heparan sulfates or chondroitin sulfates from the surface of neutrophils by heparinase or chondroitinase inhibited migration toward PR-39. In conclusion, antimicrobial PR-39 stimulates human neutrophil chemotaxis in a heparan sulfate proteoglycan-dependent manner. Involvment of syndecans is likely as both heparinase and chondroitinase were abrogating. Data suggest active participation of heparan sulfate proteoglycans of neutrophils in cathelicidin peptide-mediated regulation of the antimicrobial host defense.

Antithrombin reduces monocyte and neutrophil CD11b up regulation in addition to blocking platelet activation during extracorporeal circulation

BACKGROUND

Patients undergoing cardiac surgery requiring cardiopulmonary bypass develop a systemic inflammatory reaction. Antithrombin III (AT) has anticoagulant effects but also shows evidence of anti-inflammatory activity. The aim of this study was to examine whether exogenous AT could reduce white blood cell activation (CD11b up regulation or elastase release), in addition to inhibiting platelet (PLT) activation and fibrin generation, during simulated cardiopulmonary bypass (sCPB), undertaken in the absence of endothelium.

STUDY DESIGN AND METHODS

sCPB was carried out with minimally heparinized (2 U/mL) human blood for 90 minutes in controls and with supplementation by low-dose (1 U/mL) and high-dose (5 U/mL) AT.

RESULTS

High-dose AT blunted thrombin generation during sCPB (prothrombin fragment 1.2); both doses significantly inhibited thrombin activity (fibrinopeptide A). Complement activation (C3a and C5b-9) was unaffected by AT. High-dose AT inhibited PLT activation (P-selectin expression and P-selectin-dependent monocyte-PLT conjugate formation). AT supplementation at the higher dose significantly abrogated monocyte and neutrophil CD11b up regulation and neutrophil elastase release.

CONCLUSION

In addition to anticoagulant and anti-PLT effects, pharmacologic AT doses significantly blunted monocyte and neutrophil CD11b up regulation and neutrophil elastase release during sCPB, independent of endothelial effects. These data provide evidence for the direct anti-inflammatory activity of AT that has clinical relevance for CPB complications.

Effect of antithrombin III on neutrophil deformability

As the spherical diameter of pulmonary capillaries is smaller than that of neutrophils, increased neutrophil stiffness or conversely, decreased neutrophil deformability is a key step in the initial sequestration of neutrophils within the lungs during inflammatory processes. Antithrombin III (AT) is known to exert a therapeutic effect against disseminated intravascular coagulation, and accumulating evidence suggests that AT also has anti-inflammatory properties. The mechanisms of its anti-inflammatory effects remain unclear, but in a rat endotoxin model, AT apparently inhibited neutrophil sequestration in the lung. In the present in vitro study, therefore, we examined the effect of AT on the deformability of human neutrophils and correlated those findings with their F-actin content. Isolated human neutrophils were stimulated with formyl-Met-Leu-Phe (1 muM, 2 min) in the presence or absence of the alpha, beta, or low heparin-affinity isoforms of AT (1 IU/ml, 20 min), and deformability was evaluated using a filter assay system. Neutrophils were also stained with fluorescein isothiocyanate-phalloidin and subjected to a fluorescein-activated cell sorter scan to assess F-actin content. The results showed that pretreatment with any of the three AT isoforms similarly inhibited the decreased neutrophil deformability and increased F-actin content of stimulated cells. Notably, heparinase had no effect on deformability or F-actin content in the presence or absence of AT, which was somewhat unexpected, as heparin sulfate proteoglycans likely function as AT receptors. These findings suggested that AT inhibits the increase in neutrophil stiffness seen during inflammatory processes by inhibiting actin polymerization via a heparin-independent pathway.

Tissue Factor Pathway Inhibitor and Anitithrombin Trial Results

The endogenous plasma anticoagulant proteins tissue factor pathway inhibitor (TFPI) and antithrombin (AT) have both been extensively studied in large, multinational phase III clinical trials in patients with severe sepsis. The TFPI and AT trials failed to result in significant reductions in the 28-day, all-cause mortality rates in their respective study populations. However, there appear to be definable patient populations within each study that may have benefited from TFPI or AT. Drug-drug interactions and dosing issues were observed in both trials. The similarities and differences of each anticoagulant and the lessons learned from the recent phase III clinical trials are examined in this review.

Antithrombin Reduces Compression-Induced Spinal Cord Injury in Rats

Antithrombin (AT), a natural anticoagulant, has been shown to exert anti-inflammatory activity by promoting the endothelial production of prostaglandin I2 (PGI2), thereby reducing tissue injury. To examine whether AT prevents post-traumatic spinal cord injury (SCI), a pathologic condition in which activated neutrophils are critically involved, we tested the effect of AT on SCI induced by compression trauma in rats. Intravenous administration of AT, either before or after the induction of SCI, significantly reduced SCI-related motor disturbances in these animals. AT also significantly inhibited both intramedullary hemorrhage and the decrease in the number of motor neurons following SCI, and inhibited the accumulation of neutrophils in the damaged segment of the spinal cord by inhibiting the increase in transcription of tumor necrosis factor-alpha (TNF-alpha). AT significantly enhanced the increase in the tissue level of 6-keto-PGF1alpha, a stable metabolite of PGI2, at the injured segment of the cord. These therapeutic effects of AT may not depend on its anticoagulant effect. AT did not show any effects in animals pretreated with indomethacin, a potent inhibitor of prostaglandin synthesis, and iloprost, a stable PGI2 analog, produced effects similar to those of AT. Furthermore, intravenously administered AT accumulated selectively at the injured segment of the spinal cord, where thrombin generation might be increased. These findings suggest that AT may reduce the effects of compression trauma-induced SCI by inhibiting neutrophil activation as a consequence of the AT-mediated inhibition of TNF-alpha production. Such therapeutic effects of AT might be mediated by its promoting the endothelial release of PGI2. These findings strongly suggest AT as a potential agent for treating SCI in the clinical setting.

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.

Coagulation in Sepsis

Activation of the coagulation cascade during invasive infection can result in purpura fulminans, with rapid progression of tissue ischemia, or may manifest as abnormal clotting indices alone. Although severe derangements in coagulation are associated with organ dysfunction and increased mortality, the contribution of coagulopathy to the pathophysiology of sepsis remains incompletely understood. Over the past decade, investigators have evaluated several therapeutic anticoagulant strategies in sepsis, and manipulation of the coagulation system has emerged as a key concept in the current management of this disease. Clinical observations during treatment of septic patients with the endogenous anticoagulant activated protein C have stimulated additional study of interactions between endothelial injury, coagulation, and inflammation. This review describes clotting abnormalities during sepsis and discusses the clinical experience with therapeutic strategies intended to oppose excessive coagulation.

Syndecan-4-dependent migration of human eosinophils

BACKGROUND

Heparan sulphate proteoglycans (HSPGs) are important participants in cell surface signalling and critical in controlling cell behaviour. They modulate inflammatory cell maturation and activation, leucocyte rolling, adhesion to endothelium as well as extravasation and chemotaxis. Whether eosinophil's function is affected has not yet been reported.

OBJECTIVE

We investigated the effects of transgenic, recombinant anti-thrombin III and Kybernin P, an anti-thrombin III concentrate, as HSPG ligands on spontaneous and chemokine-triggered migration of normal eosinophils from human peripheral blood in modified Boyden chamber micropore filter assays.

METHODS

Eosinophils from human peripheral blood were purified using magnetic antibody cell sorting. The signalling mechanisms required for anti-thrombin-dependent migration were studied using signalling enzyme blockers. Expression of HSPG core protein mRNA was studied by PCR.

RESULTS

Pre-treatment of eosinophils with anti-thrombin III inhibited chemotaxis toward optimal concentrations of eotaxin or RANTES (regulated upon activation normal T cell expressed and activated). In the absence of the chemokines, direct exposure to gradients of anti-thrombin III stimulated eosinophil migration. The effects of anti-thrombin III were abolished by pre-treating cells with heparinase-1, chondroitinase, sodium chlorate and anti-syndecan-4 antibodies. Syndecan-4 gene expression in eosinophils was confirmed in PCR. In the presence of pentasaccharide, anti-thrombin III lost its effect on the cells. Functional responses were also abrogated by inhibition of protein kinase C, phosphatidylinositol 3-kinase and phosphodiesterase.

CONCLUSION

Data indicate that anti-thrombin III affects eosinophil motility via the effects of its heparin-binding site on cell surface syndecan-4. Ligation of syndecan-4 with anti-thrombin III induces eosinophil migration and deactivates motility toward chemokines. These observations suggest that syndecan-4-dependent signalling may control eosinophil locomotion.