A model of in vivo human venous thrombosis that confirms changes in the release of specific soluble cell adhesion molecules in experimental venous thrombogenesis

Polymorphonuclear phenotypical expression of CD18, at baseline and after in vitro activation, in several clinical disorders: Revision of our case series

BACKGROUND

In relation to the different and important roles of the beta2 integrins, we have revisited the expression of polymorphonuclear leukocyte CD18 in several clinical disorders, at baseline and after in vitro activation.

SUBJECTS

we have examined subjects with type 1 diabetes mellitus, vascular atherosclerotic disease, type 2 diabetes mellitus without and with macrovascular complications, chronic renal failure on conservative treatment, essential hypertension, deep venous thrombosis, acute ischemic stroke and subjects with venous leg ulcers.

METHODS

unfractioned leukocyte suspension was prepared according to the Mikita's method, while the leukocyte were separated into mononuclear and polymorphonuclear cells with a Ficoll-Hypaque medium. Using specific monoclonal antibody, the CD18 expression was evaluated with cytofluorimetric analysis, using FACScan (Becton Dickinson) be Cellquest software; the activation in vitro with PMA was effected according to modified Yasui and Masuda methods.

RESULTS

in type 1 diabetes mellitus, at baseline CD18 is under expressed in comparison with normal control, and not changes after PMA activation were observed; in subjects with vascular atherosclerotic disease, in type 2 diabetes mellitus CD18 is over expressed at baseline but does not vary after activation; in subjects with chronic renal failure, essential hypertension and in subjects with acute ischemic stroke the CD18 up-regulate at baseline compared to normal control, and it increases further after activation; in subjects with deep venous thrombosis the CD18 expression is not different from control group at baseline, but it increases after activation; finally, in subjects with venous leg ulcers the CD18 is normally expressed at baseline, and it does not change after PMA activation.

CONCLUSIONS

in the different clinical disorders, the trend of this integrin subunit provides some specific information, useful to select the best therapeutic strategy in clinical practice.

State-of-Art in the Age Determination of Venous Thromboembolism: A Systematic Review

Venous thromboembolism (VTE), consisting of deep vein thrombosis (DVT) and pulmonary embolism (PE), requires a forensic age determination to ascertain their causal relationship with recent events, such as trauma or medical treatment. The main objective of this systematic review is to identify the current state-of-the-art immunohistochemical methods for age determination of fatal VTE. A literature search was performed through different databases, according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Within the study, we have selected only cases represented by deceased patients for DVT and/or PTE in which thromboembolic material was collected during an autoptic examination and then subjected to a histological and an immunohistochemical investigation. Studies based on animal models were not included. We assessed bias risk. A database-based search produced a total of 19 articles. After excluding duplicate items from the selection, 14 articles were reviewed. Ten articles were excluded because they did not meet the inclusion criteria. The results have pointed out 4 studies that were included in the present analysis for a total of 157 samples of DVT and 171 PTE samples. These were analyzed using traditional histological and immunohistochemical techniques. The results must be interpreted with a critical eye because of their heterogeneity in terms of time, geography, and study design. The present review highlights the importance of associating specific immunohistochemical markers with a histological analysis for the timing of DVT/PTE fatal events. Further future experiences will hopefully endorse actual knowledge on the subject to increase the accuracy in the assessment of thrombus-embolus age.

Soluble endothelial cell molecules and circulating endothelial cells in patients with venous thromboembolism

: To evaluate the plasma levels of soluble endothelial cell molecules in patients with venous thromboembolism (VTE) out of the acute phase as compared with healthy individuals. We also investigated the possible associations of the soluble endothelial cell molecules among them, as well as with other clinical and laboratory data, including the numbers of circulating endothelial cells (CEC), circulating endothelial progenitor cells (CEP), and CEC expressing activation-related [cluster of differentiation (CD)54 and CD62E] and procoagulant (CD142) markers. In total, 15 patients with VTE and 20 normal individuals were studied. The CEC and CEP were quantified and characterized by flow cytometry. The soluble molecules studied included P-selectin, E-selectin, intercellular cell adhesion molecule 1, vascular cell adhesion molecule 1 and tissue factor (ELISA), and von Willebrand factor antigen (immunoturbidimetry). VTE patients had significantly higher levels of vascular cell adhesion molecule 1 and von Willebrand factor antigen and lower levels of soluble E-selectin than controls. They also showed significantly higher numbers of CEC, as of activated/procoagulant CEC and lower numbers of CEP, compared with controls. We did not find any correlation between the levels of soluble molecules and the numbers of endothelial cell in circulation, but there was with several clinical and laboratory data in VTE patients. Our results would suggest that in VTE patients, the endothelium remains activated and in some hypercoagulable state. The levels of soluble endothelial cell molecules did not seem to be directly related to the numbers of CEC and CEP neither reflected the number of activated CEC, which may be because of the different function that surface and soluble molecules may have.

Gram-Negative Pneumonia Alters Large-Vein Cell-Adhesion Molecule Profile and Potentiates Experimental Stasis Venous Thrombosis

BACKGROUND/AIMS

Pneumonia is a significant risk factor for the development of venous thrombosis (VT). Cell-adhesion molecules (CAMs) are linked to the pathogenesis of both pneumonia and VT. We hypothesized that remote infection would confer a prothrombogenic milieu via systemic elevation of CAMs.

METHODS

Lung injury was induced in wild-type (C57BL/6) mice by lung contusion or intratracheal inoculation with Klebsiella pneumoniae or saline controls. K. pneumoniae-treated mice and controls additionally underwent inferior vena cava (IVC) ligation to generate VT.

RESULTS

Lung-contusion mice demonstrated no increase in E-selectin or P-selectin whereas mice infected with K. pneumoniae demonstrated increased circulating P-selectin, ICAM-1, VCAM-1 and thrombin-antithrombin (TAT) complexes. Mice with pneumonia formed VT 3 times larger than controls, demonstrated significantly more upregulation of vein-wall and systemic CAMs, and formed erythrocyte-rich thrombi.

CONCLUSION

Elevated CAM expression was identified in mice with pneumonia, but not lung contusion, indicating that the type of inflammatory stimulus and the presence of infection drive the vein-wall response. Elevation of CAMs was associated with amplified VT and may represent an alternate mechanism by which to target the prevention of VT.

Polymorphonuclear Leukocyte Integrinsin Deep Venous Thrombosis

The polymorphonuclear leukocytes (PMN) have a role in the pathophysiology of deep venous thrombosis (DVT). We examined the phenotypical expression of PMN beta2-integrins (CD l l a, CDl l b, CD 11c) in a group of 19 subjects with leg DVT. PMN cells were incubated with fluorescent monoclonal antibodies against CD11a, CD11b, CD11c, and the evaluation was made by flow cytofluorimetry. The same integrins were determined after in vitro activation with 4-phorbol 12-myristate 13-acetate (PMA) and N-formylmethionyl-leucyl-phenylalanine (fMLP). In DVT subjects, at baseline, the phenotypical expression of CD11b was decreased and that of CD11c increased when compared with normal controls. In normal subjects PMN activation with PMA and fMLP led to a constant increase of all PMN adhesion molecules, while in DVT subjects the CDl l a did not show any change. These data might have therapeutical ap plications, especially with the aim of preventing post-thrombotic deterioration of vein function.

Soluble adhesion molecules as markers of native arteriovenous fistula thrombosis in children on uremia

Vascular access represents a lifeline for children undergoing hemodialysis. A failure of vascular access among patients receiving regular hemodialysis is associated with increased morbidity, mortality and costs. We assessed the possibility of using soluble adhesion molecules as reliable predictors of vascular access failure in children on hemodialysis. Moreover, we evaluated whether there is an association among the different studied adhesion molecules in hemodialysis patients with thrombosed and non-thrombosed arteriovenous fistula fistulas (AVFs). This study included 55 hemodialysis children, 36 with good access and 19 with access failure, and 20 healthy volunteers. Forty-four patients had native AVFs and 11 patients had tunneled permanent catheter (11with thrombosed and 33 with non-thrombosed AVFs). Serum-soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), soluble E-selectin (sE-selectin) and soluble P-selectin (sP-selectin) were measured using ELISA technique. A significant increase was found in the levels of sVCAM-1, sICAM-1, sE-selectin and sP-selectin versus controls and all hemodialysis patients, hemodialysis patients with good access and hemodialysis patients with access failure (P=0.001 for sVCAM-1 and sICAM-1 and P=0.0001 for sE-selectin and sP-selectin). A significant increase was found in the levels of sVCAM-1, sE-selectin and sP-selectin in both chronic hemodialysis patients with thrombosed and non-thrombosed native AVFs versus controls (P=0.0001 for all parameters). There was significant difference between both chronic hemodialysis patients with thrombosed and non-thrombosed native AVFs as regard to sVCAM-1 (54.64±30.82 versus 25.69±27.96ng/ml, P=0.04). Both sICAM-1 and sP-selectin were positively correlated with the erythropoietin (EPO) dose in hemodialysis children (r=0.31, P=0.04 and r=0.32, P=0.04, respectively). A significant positive association was found between E-selectin and sP-selectin in hemodialysis patients with thrombosed AVFs (r=0.83, P=0.04). There was a significant correlation between sVCAM-1 and EPO dose in thrombosed AVF group (r=0.84, P=0.01). The assessment of serum sVCAM-1 might be useful for the identification of the chronic hemodialysis patients at an increased risk for native AVFs thrombosis. The role of EPO in vascular access failure should be taken into consideration. The clinical relevance of these observations warrants further investigations.

Endogenous pro-thrombotic biomarkers from the arm and leg may not have the same value

Objective

Assessments of endogenous pro-thrombotic biomarkers are performed invariably on arm blood. However, the commonest site for thrombosis is in the leg. A leg blood sample may reflect local pro-thrombotic processes more accurately than systemic arm blood. The aim was to determine whether pro-thrombotic biomarkers from standard venous arm samples differed significantly from leg samples.

Method

Concurrent blood samples were taken from an ankle/lower calf varicose vein and an ante-cubital vein in 24 patients awaiting laser treatment as well as age approximated and sex matched healthy controls without venous disease. The following assays were performed: thrombin–antithrombin (ng/ml), antithrombin (%) activity, microparticles (nM), fibrinogen (mg/dl), prothrombin fragment 1.2 (F1.2) (pM) and P-selectin (ng/ml).

Results

Expressed as median (inter-quartile range). Significant arm/leg differences were observed in thrombin–antithrombin, antithrombin, prothrombin fragment 1.2 and P-selectin. The legs of patients had significantly reduced antithrombin activity and P-selectin concentrations compared to their arms (leg: 101 (90–108) versus arm: 112 (99–126), P = 0.001 and leg: 42 (26–52) versus 45 (27–52), P = 0.044, respectively). Control leg samples had significantly increased thrombin–antithrombin and P-selectin compared to control arm samples (leg: 2.1 (0.9–3.2) versus arm: 0.8 (0.5–1.7), P = 0.015 and leg: 36 (24–50) versus arm: 30 (23–41), P = 0.007, respectively). However, the control legs had significantly reduced F1.2 (leg: 265 (230–333) versus arm: 299 (236–361), P = 0.028). No significant arm/leg differences were detected in the microparticle or fibrinogen levels.

Conclusions

These findings indicate that venous arm blood is significantly different from venous leg blood in four out of six biomarkers studied. Recognition of local venous leg sampling as a site for investigation may unravel why the leg has a greater predisposition to thrombosis and lead the way towards an arm/leg differential test.

A human monoclonal antibody inhibiting partially factor VIII activity reduces thrombus growth in baboons

BACKGROUND

The inhibitory activity of an anti-factor VIII (FVIII) antibody can be modulated through glycosylation of the antigen binding site, as has recently been described. This offers the opportunity to develop an optimized anticoagulant agent targeting partial FVIII inhibition.

OBJECTIVES

We investigated in non-human primates the antithrombotic activity, pharmacokinetics,and pharmacodynamics of a human monoclonal antibody, Mab-LE2E9Q, inhibiting FVIII activity partially.

METHODS

The ability of Mab-LE2E9Q to prevent thrombosis was evaluated in baboons after administration of 1.25 and 5 mg kg(-1) antibody or saline as a single intravenous (i.v.) bolus. Thrombus development was recorded in expansion ('venous') and in Dacron ('arterial') thrombosis chambers incorporated in an extracorporeal arteriovenous shunt implanted between the femoral vessels 1 h, 24 h and 7 days after the administration of Mab-LE2E9Q.

RESULTS

Mab-LE2E9Q reduced thrombus growth to a similar extend 1 h, 1 day and 1 week after administration of the antibody. Ex vivo pharmacodynamic analysis indicated that the evaluation of the residual FVIII activity was strongly dependent on the type of FVIII assay and on the phospholipid concentration in the assay. No significant difference in bleedings was observed between animals treated with Mab-LE2E9Q or with saline.

CONCLUSIONS

Understanding the role of glycosylation in FVIII inhibition by a human monoclonal antibody allowed selection of an antibody inhibiting only moderately FVIII activity while significantly reducing thrombus development in a baboon extracorporeal model. As that antibody did not increase the bleeding tendency, it may represent a novel type of a long-acting antithrombotic agent with an optimal safety/efficacy profile.

Trombectomia com cateter de Fogarty no tratamento da tromboflebite jugular experimental em eqüinos

Trombose da veia jugular é problema freqüente na medicina eqüina, implicando muitas vezes em conseqüências fatais. O objetivo deste trabalho foi avaliar em eqüinos a aplicabilidade da trombectomia com cateter de Fogarty, técnica rotineiramente empregada pela medicina humana, no restabelecimento da perviedade vascular. Foram utilizados 10 eqüinos divididos em dois grupos de cinco animais, em que se induziu a trombose da veia jugular direita, através do acesso cirúrgico à veia e aplicação de sutura estenosante e injeção de glicose a 50%. No grupo controle avaliou-se a evolução da tromboflebite sem qualquer tipo de intervenção terapêutica. Os animais do grupo tratado foram submetidos à trombectomia com cateter de Fogarty. Foram avaliados os parâmetros clínicos gerais, regionais, ultra-sonográficos e angiográficos, nos momentos pré-indução (M-PRÉ), indução da trombose (MTI) e 10 dias de evolução da trombose (M10). A técnica empregada induziu a tromboflebite, que obstruiu completamente um segmento da veia jugular de todos os animais. Os animais do grupo controle mantiveram os trombos obstruindo totalmente o lume vascular até o final do período de avaliação, sendo que avaliações regionais mostraram principalmente o edema parotídeo e o ingurgitamento vascular, cranial à tromboflebite da veia jugular. O grupo tratado apresentou as veias jugulares pérvias ao final do experimento, confirmadas pelos exames ultra-sonográficos e angiográficos, com remissão total dos sinais clínicos. Concluiu-se que a técnica da trombectomia com cateter de Fogarty foi eficiente na desobstrução da veia jugular submetida à trombose experimental.

Acute effects of periodontal therapy on bio-markers of vascular health

AIM

We aimed to study the impact of periodontal therapy on several bio-markers related to vascular health.

MATERIAL AND METHODS

Fifty-five consecutive subjects (age range 30-64 years) having severe periodontitis received an intensive session of periodontal therapy under local anaesthesia and provided blood samples before and 1 and 7 and 30 days following therapy. High-sensitivity assays were utilized to quantify serum concentrations of inflammatory markers [interleukin (IL)-1beta, tumour necrosis factor-alpha], plasma haemostatic (D-dimer) and endothelial soluble markers [soluble E-selectin (s-Es) and von Willebrand factor antigen (r-WF:Ag)].

RESULTS

Periodontal therapy elicited a significant activation of the haemostatic system (38% and 68% mean increases of plasma D-dimer 1 and 7 days after therapy, respectively, p<0.001), together with moderate endothelial dysfunction (10% and 30% mean increases at 24 h in plasma soluble E-selectin, p<0.05 and von-Willebrand factor, p<0.01, respectively). D-Dimer and s-Es acute changes were significantly correlated with periodontal treatment time (p<0.05). Cigarette smoking status and body mass index strongly influenced the acute release of IL-1beta (p<0.05), D-dimer (p<0.01) and s-Es (p<0.01).

CONCLUSIONS

Periodontal therapy represents a novel and reliable non-drug-induced model to investigate in vivo the interplay between inflammation, coagulation and endothelial cell activation.

P-selectin and platelet-derived microparticles associated with monocyte activation markers in patients with pulmonary embolism

Platelet activation markers (platelet-derived microparticles and P-selectin on activated platelets), chemokines (monocyte chemotactic peptide and regulated on activation normally T-cell expressed and secreted), and soluble markers (sP-selectin, sE-selectin, sVCAM-1, and sCD14) were measured and compared in patients with pulmonary embolism (PE). These substances are thought to participate in the pathogenesis of PE. Levels of all of the platelet activation markers, chemokines, and soluble markers were higher in the patients with PE than in normal controls. Levels of platelet activation markers were also significantly increased postoperatively after total knee arthroplasty. Anti-platelet therapy significantly inhibited the elevation of platelet activation markers after total knee arthroplasty. These findings suggest that antiplatelet therapy may be useful for PE-related interaction of platelets, leukocytes, and endothelial cells.

The role of soluble cell adhesion molecules in patients with suspected deep vein thrombosis

Activation of the endothelium, platelets and leukocytes has been shown to play an important role in the aetiology of deep venous thrombosis (DVT) in in-vitro experiments, resulting in the release of soluble cell adhesion molecules (sCAMs). We therefore assessed the value of soluble intracellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble E-selectin and soluble P-selectin for the diagnostic process in 69 consecutive patients with suspected DVT. Final diagnosis was based on the results of Duplex sonography or ascending venography. Thirty-seven patients (53.6%) finally suffered from DVT. Mean levels of sVCAM-1 were 589 +/- 530 ng/ml for controls and 587 +/- 328 ng/ml for patients. Corresponding levels concerning sICAM-1 were 316 +/- 161 and 342 +/- 186 ng/ml, those concerning soluble E-selectin were 54 +/- 38 and 42 +/- 18 ng/ml, and those concerning soluble P-selectin were 94 +/- 37 and 99 +/- 36 ng/ml (all P > 0.05). There was no significant correlation of the thrombus extension (all P > 0.05) or the duration of symptoms with sCAMs (all P > 0.05). In conclusion, we detected no significant differences concerning the concentration of four major sCAMs between patients with DVT and controls, so their assessment does not add any useful information for the diagnostic process of DVT.

Failure of thrombus to resolve in urokinase-type plasminogen activator gene-knockout mice: rescue by normal bone marrow-derived cells

BACKGROUND

Monocytes may have an important role in the resolution of venous thrombosis. Increased expression of tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) is associated with an ingress of monocytes into the thrombus. This study was designed to evaluate the importance of these activators in thrombus resolution.

METHODS AND RESULTS

Inferior caval vein thrombosis was induced in cohorts of adult wild-type, uPA gene-knockout (uPA-/-), and tPA gene-knockout (tPA-/-) mice in a flow model. Thrombi were harvested from wild-type and uPA-/- mice (n=60 per group) between 1 and 60 days. Thrombi were also obtained from groups of wild-type and tPA-/- mice (n=24 per group) between 1 and 28 days. Thrombus size and macrophage content were measured by computer-assisted image analysis. Thrombus resolution was significantly impaired in the uPA-/- mice compared with wild-type controls (P<0.0001) but was unaffected in tPA-/- mice. Monocyte content in wild-type mice was highest at 14 days after thrombus induction and was approximately 4 times greater than in uPA-/- mice (P=0.0043). Thrombus size in uPA-/- mice transplanted with wild-type marrow (0.29+/-0.06 mm2) was significantly smaller than in uPA-/- mice given uPA-/- bone marrow (3.9+/-1.1 mm2) (P=0.0022). Donor bone marrow-derived cells expressing LacZ were present in the thrombus after transplantation.

CONCLUSIONS

The resolution of experimental venous thrombus is dependent on uPA but is unaffected by the absence of tPA. Absence of uPA is also associated with delayed monocyte recruitment into the thrombus. Transplanting wild-type bone marrow restores thrombus resolution in uPA-/- animals, suggesting an important role for bone marrow-derived cells in this process.

Antithrombotic effects of controlled inhibition of factor VIII with a partially inhibitory human monoclonal antibody in a murine vena cava thrombosis model

The human monoclonal antibody mAb-LE2E9 partially inactivates human factor VIII (FVIII), leaving approximately 10% residual activity. The antithrombotic efficacy of the antibody was evaluated in mouse models of inferior vena cava thrombosis. Thrombi were induced in wild-type mice given either the antibody or saline. No thrombi occurred in any of 8 mice treated with mAb-LE2E9, whereas 6 of 8 control mice developed thrombi (P =.007). Treatment with mAb-LE2E9 did not result in a severe bleeding phenotype: a tail-cutting experiment that resulted in death of C57BL/6 FVIII-deficient (FVIII(-/-)) mice did not cause hemorrhagic death in mice treated with mAb-LE2E9. To evaluate the antithrombotic effect of mAb-LE2E9 in presence of human FVIII, thrombus formation was induced in FVIII(-/-) mice reconstituted intravenously with recombinant human FVIII (rhFVIII) or rhFVIII preincubated with mAb-LE2E9. Only 1 of 9 mice produced a thrombus in the rhFVIII/antibody complex-treated group, compared with 7 of 9 in the control group (P =.015). FVIII(-/-) mice were also reconstituted with rhFVIII and then injected with either mAb-LE2E9 or saline. One of 14 mice in the group treated with the antibody developed a thrombus, compared with 10 of 14 in the control group (P =.001). The thrombi occurring in antibody-treated animals were smaller than in controls (P <.01). All animals survived, and there were no bleeding complications. Thus, the mAb-LE2E9 antibody inhibits thrombosis without causing an overt bleeding tendency.

Autologous thrombin for treatment of pseudoaneurysms

Femoral pseudoaneurysms arise in up to 2% of patients after femoral cannulation for cardiac catheterisation. We used autologous thrombin for percutaneous obliteration of pseudoaneurysms occurring after catheterisation. We prepared autologous thrombin isolates from blood of ten patients with femoral pseudoaneurysms, and injected this solution into the pseudoaneurysms with duplex imaging guidance. We then assayed thrombin activity. All pseudoaneurysms were successfully thrombosed without substantial complications, although three patients needed a repeat procedure within 24 h. We have shown that autologous thrombin-induced thrombosis of pseudoaneurysms is reliable, simple, safe, and cheaper than commercial bovine or human thrombin, and avoids risks of anaphylaxis and contamination with prions.

Autologous thrombin: a new embolization treatment for traumatic intrasplenic pseudoaneurysm

PURPOSE

To report the use of autologous thrombin for transcatheter embolization of a traumatic parenchymal splenic pseudoaneurysm.

CASE REPORT

A 15-year-old boy presented with a splenic parenchymal laceration after blunt abdominal trauma. The patient was managed conservatively but developed an intrasplenic pseudoaneurysm (grade III AAST scale) with subcapsular contrast extravasation after 3 weeks. Autologous thrombin was isolated from the patient's blood and subsequently delivered to the lesion by transcatheter superselective injection into the aneurysm neck. The patient was asymptomatic after the procedure. Nine months' follow-up demonstrated a normal spleen with completely homogenous parenchyma.

CONCLUSIONS

Autologous thrombin injection to induce thrombosis of intrasplenic pseudoaneurysm represents a new treatment option for traumatic abdominal organ injuries. Intrasac thrombosis can be safely induced to successfully restore the splenic parenchymal integrity without introduction of foreign material and associated risks of adverse reactions or infection that might accompany the use of commercial thrombin preparations.

Regulation of vascular bed-specific prothrombotic potential

Hemostasis is the result of interdependent and complex systemic and local endothelial pathways that govern vascular integrity and rheology. A striking feature of hypercoagulable conditions is the focal nature of the resultant thrombotic pathology. Such disorders in hemostasis may be associated with distinct vascular beds, thus implying that the relative combined contribution of individual regulatory pathways may be specific and/or unique to a particular locale in the vasculature. Systemic factors and platelets mediate the formation of fibrin deposition; however, it is the diverse interrelationships in the interaction of these systemic elements with the local endothelial components that dictate vascular bed-specific hemostatic regulation. Indeed, the local activation of coagulation cascades, rather than increases in systemic thrombotic potential, is what leads to fibrin formation in different vascular beds. Hence, the propensity for congenital or acquired disorders to result in local thrombotic pathology is based on the relative contribution of the various hemostatic regulatory pathways in individual vascular beds. The present review highlights the role of local endothelial regulation in the interaction between local and systemic elements that contribute to vascular bed-specific prothrombotic potential.

P-Selectin-dependent inhibition of thrombosis during venous stasis

Leukocyte adhesion, transendothelial migration, and stasis are important components in the pathogenesis of deep vein thrombosis. Anesthetized cats were treated with saline, a recombinant soluble form of P-selectin glycoprotein ligand-1 (rPSGL-Ig), or an E- and L-selectin antibody (EL-246) before exposure and occlusion of a jugular vein. After 2 or 6 hours of occlusion, jugular veins were perfused with buffer, fixed, and prepared for scanning electron microscopy. In cats receiving saline, 2 and 6 hours of occlusion produced moderate levels of leukocyte and platelet adhesion and endothelial cell injury. Treatment of cats with rPSGL-Ig or EL-246 had no apparent effect on the magnitude of cell adhesion and endothelial cell injury compared with no treatment. After 6 hours of occlusion, the presence of a mural thrombus in untreated veins was observed and confirmed by scanning electron microscopy. Pretreatment of cats with rPSGL-Ig completely (4.0 mg/kg) or partially (1.0 mg/kg) prevented the occurrence of thrombi in the jugular veins. The reduction in thrombosis by rPSGL-Ig treatment after 6 hours of venous stasis, in the absence of any effect on leukocyte-mediated endothelial cell injury, suggests an antithrombotic mechanism of action for this protein.