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

Sorg H, Hoffmann JO, Hoffmann JN, Vollmar B - Intensive Care Med Exp (2015)

Bottom Line: Experimental groups consisted of animals treated with AT or with tryptophan(49)-blocked AT (TrypAT), which exerts only anticoagulant but no anti-inflammatory effects.The antithrombotic capacity of AT significantly differs in the experimental groups in which anti-inflammation was antagonized.The anti-inflammatory influence of AT is essentially linked to its anticoagulant effect in the microvascular system.

View Article: PubMed Central - PubMed

Affiliation: Institute for Experimental Surgery, University Medicine Rostock, Schillingallee 69a, 18057, Rostock, Germany, heiko.sorg@krupp-krankenhaus.de.

ABSTRACT

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

Methods: Using a thrombosis model in a cremaster muscle preparation of male C57Bl/6J mice (n = 83), we quantitatively assessed microvascular thrombus formation by using intravital fluorescence microscopy. Experimental groups consisted of animals treated with AT or with tryptophan(49)-blocked AT (TrypAT), which exerts only anticoagulant but no anti-inflammatory effects. To further see whether endothelial glycosaminoglycan (GAG) binding with consecutive prostacyclin (PGI2) release is mandatory for the anticoagulant process of AT, animals were administered heparin or indomethacin either alone or in combination with AT.

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

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

No MeSH data available.


Related in: MedlinePlus

Function of antithrombin. Schematic overview of the anticoagulant function of antithrombin (AT) and the mediation of anti-inflammation through glycosaminoglycan (GAG) binding at the endothelial cell (EC) with subsequent release of prostacyclin (PGI2). Until now, it was not clarified whether the antithrombotic potency of AT is exclusively based on its solitary anticoagulant capacity or if it might also depend on its anti-inflammatory mode of action. The data in the here-presented study indicates that the anti-inflammatory property of AT is a prerequisite for mediating adequate anticoagulation
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Fig5: Function of antithrombin. Schematic overview of the anticoagulant function of antithrombin (AT) and the mediation of anti-inflammation through glycosaminoglycan (GAG) binding at the endothelial cell (EC) with subsequent release of prostacyclin (PGI2). Until now, it was not clarified whether the antithrombotic potency of AT is exclusively based on its solitary anticoagulant capacity or if it might also depend on its anti-inflammatory mode of action. The data in the here-presented study indicates that the anti-inflammatory property of AT is a prerequisite for mediating adequate anticoagulation

Mentions: It is well known that AT is a pleiotropic inhibitor of the activated coagulation cascade and that binding of heparin to AT seems to be a prerequisite for enhanced anticoagulant effects [42]. Factor Xa-inhibition by AT deserves a unique heparin pentasaccharide sequence, whereas longer polysaccharide chain heparins are required to enhance the inhibition of thrombin by AT [43, 52, 53]. The observation that the combination of AT plus heparin in our study did not present a prolongation of thrombus formation challenges this view and might be explained as follows. On the endothelial surface, localized GAGs are also comprised of heparan sulfates and heparin-like structures, which exert the same effect on AT as heparin in the blood [42, 54]. These heparin-like binding sites are tenfold better developed in capillaries than in macro-vessels [55, 56], which might be the cause for the microcirculation being the preferential site of AT action. The counteraction of AT by heparin has so far only been described for the anti-inflammatory action, as heparin seems to diminish the vascular defense shield by keeping AT away from its cellular binding sites [42, 43]. While heparin and AT compete for these binding sites, exogenous administration of heparin might interfere not only with the anti-inflammatory but also in part with the anticoagulant activity of AT, as combined administration of heparin and AT was not able to achieve similar protection of thrombus formation as AT alone, which is displayed by the shorter CVO times. Furthermore, the heparin data is in line with previously published results by our own and other groups, showing that heparin in the applied dosage is not associated with changes in venular thrombus formation times [11, 55, 57–59]. However, at higher doses, heparin may also promote the activation of platelets and clot formation by interacting with platelet factor 4 [60, 61]. Our data reveals the essential importance of endothelial AT-GAG interactions for microvascular thrombosis. The competing situation between heparin and AT for endothelial GAGs is of crucial relevance, as AT is not able to trigger the release of PGI2 from the endothelium after the GAGs have been irreversibly blocked by heparin (Fig. 5).Fig. 5


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

Sorg H, Hoffmann JO, Hoffmann JN, Vollmar B - Intensive Care Med Exp (2015)

Function of antithrombin. Schematic overview of the anticoagulant function of antithrombin (AT) and the mediation of anti-inflammation through glycosaminoglycan (GAG) binding at the endothelial cell (EC) with subsequent release of prostacyclin (PGI2). Until now, it was not clarified whether the antithrombotic potency of AT is exclusively based on its solitary anticoagulant capacity or if it might also depend on its anti-inflammatory mode of action. The data in the here-presented study indicates that the anti-inflammatory property of AT is a prerequisite for mediating adequate anticoagulation
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495092&req=5

Fig5: Function of antithrombin. Schematic overview of the anticoagulant function of antithrombin (AT) and the mediation of anti-inflammation through glycosaminoglycan (GAG) binding at the endothelial cell (EC) with subsequent release of prostacyclin (PGI2). Until now, it was not clarified whether the antithrombotic potency of AT is exclusively based on its solitary anticoagulant capacity or if it might also depend on its anti-inflammatory mode of action. The data in the here-presented study indicates that the anti-inflammatory property of AT is a prerequisite for mediating adequate anticoagulation
Mentions: It is well known that AT is a pleiotropic inhibitor of the activated coagulation cascade and that binding of heparin to AT seems to be a prerequisite for enhanced anticoagulant effects [42]. Factor Xa-inhibition by AT deserves a unique heparin pentasaccharide sequence, whereas longer polysaccharide chain heparins are required to enhance the inhibition of thrombin by AT [43, 52, 53]. The observation that the combination of AT plus heparin in our study did not present a prolongation of thrombus formation challenges this view and might be explained as follows. On the endothelial surface, localized GAGs are also comprised of heparan sulfates and heparin-like structures, which exert the same effect on AT as heparin in the blood [42, 54]. These heparin-like binding sites are tenfold better developed in capillaries than in macro-vessels [55, 56], which might be the cause for the microcirculation being the preferential site of AT action. The counteraction of AT by heparin has so far only been described for the anti-inflammatory action, as heparin seems to diminish the vascular defense shield by keeping AT away from its cellular binding sites [42, 43]. While heparin and AT compete for these binding sites, exogenous administration of heparin might interfere not only with the anti-inflammatory but also in part with the anticoagulant activity of AT, as combined administration of heparin and AT was not able to achieve similar protection of thrombus formation as AT alone, which is displayed by the shorter CVO times. Furthermore, the heparin data is in line with previously published results by our own and other groups, showing that heparin in the applied dosage is not associated with changes in venular thrombus formation times [11, 55, 57–59]. However, at higher doses, heparin may also promote the activation of platelets and clot formation by interacting with platelet factor 4 [60, 61]. Our data reveals the essential importance of endothelial AT-GAG interactions for microvascular thrombosis. The competing situation between heparin and AT for endothelial GAGs is of crucial relevance, as AT is not able to trigger the release of PGI2 from the endothelium after the GAGs have been irreversibly blocked by heparin (Fig. 5).Fig. 5

Bottom Line: Experimental groups consisted of animals treated with AT or with tryptophan(49)-blocked AT (TrypAT), which exerts only anticoagulant but no anti-inflammatory effects.The antithrombotic capacity of AT significantly differs in the experimental groups in which anti-inflammation was antagonized.The anti-inflammatory influence of AT is essentially linked to its anticoagulant effect in the microvascular system.

View Article: PubMed Central - PubMed

Affiliation: Institute for Experimental Surgery, University Medicine Rostock, Schillingallee 69a, 18057, Rostock, Germany, heiko.sorg@krupp-krankenhaus.de.

ABSTRACT

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

Methods: Using a thrombosis model in a cremaster muscle preparation of male C57Bl/6J mice (n = 83), we quantitatively assessed microvascular thrombus formation by using intravital fluorescence microscopy. Experimental groups consisted of animals treated with AT or with tryptophan(49)-blocked AT (TrypAT), which exerts only anticoagulant but no anti-inflammatory effects. To further see whether endothelial glycosaminoglycan (GAG) binding with consecutive prostacyclin (PGI2) release is mandatory for the anticoagulant process of AT, animals were administered heparin or indomethacin either alone or in combination with AT.

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

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

No MeSH data available.


Related in: MedlinePlus