Interactions of Heparin and a Covalently Linked Antithrombin Heparin Complex with the Components of the Fibrinolytic Pathway.
Notice bibliographique
Résumé
Abstract Abstract 2211 Introduction: Unfractionated heparin (UFH) is used for the prophylaxis and treatment of thromboembolic diseases. UFH catalyzes inhibition by antithrombin (AT) of the serine proteases in the coagulation cascade. Additionally, UFH has been shown to interact with components of the fibrinolytic pathway in vitro. However UFH has several limitations which impact its utility as a therapeutic agent. Our lab has developed a novel covalent antithrombin-heparin complex (ATH) which inhibits most serine proteases of the coagulation pathway significantly faster when compared to non covalent mixtures of AT and UFH. However, the interactions of ATH with the components of the fibrinolytic pathway have not been studied before. Thus, the present study investigates possible serpin-heparin interactions of AT + UFH vs ATH within the fibrinolytic pathway. Methods: Discontinuous second order rate constant assays under pseudo-first order conditions were carried out to obtain second order rate constant (k2) values for the inhibition of plasmin by AT+UFH versus ATH. Briefly, at specific time intervals 20 nM plasmin was inhibited by 200 nM AT + 0–5000 nM UFH or by 200 nM ATH in the presence of 2.5 mM Ca2+. Reactions were neutralized by the simultaneous addition of a solution containing polybrene and plasmin substrate S-2366™ in buffer. Residual plasmin activity was measured and the final k2 values calculated. For experiments involving tPA, wells containing 40nM tPA and increasing concentrations of AT, UFH or ATH, at mole ratios ranging from 0 to 20:1, were incubated for 15 min. Reactions with tPA were neutralized by simultaneous addition of a solution containing either polybrene and tPA substrate, S-2288™ in buffer, (ATH and UFH) or only the substrate S-2288™ in buffer (AT). Enzyme activity was then determined by measuring rate of substrate cleavage (Vmax). Results: When plasmin was inhibited by AT in the absence of UFH, k2 values of 2.82×105 +/− 4.46×104 M−1 min−1 were observed. The k2 values increased with addition of successively higher concentrations of UFH up to a plateau with maximal k2 of 5.74×106 +/− 2.78×105 M−1 min−1 at a UFH concentration of 3000nM. For inhibition of plasmin by ATH, k2 values of 6.39 × 106 +/− 5.88 × 105 M−1 min−1 were observed. Inhibition of plasmin by ATH was not significantly different when compared to the highest k2 values obtained with UFH. (p=0.36) No statistically significant difference in tPA enzyme activity was observed when Vmax values for tPA alone were compared with those in the presence of AT, UFH or ATH. (p=0.932, p=0.085, p=0.31 respectively) Significance: The characteristic shape of the curve obtained from the k2vs. UFH plot suggests that the mechanism responsible for inhibition of plasmin by AT+UFH involves conformational activation of the serpin. The k2 values in this study for inhibition of plasmin by both AT+UFH and ATH were three orders of magnitude lower than k2 values for inhibition of thrombin or factor Xa. Furthermore these results suggest that tPA is not inhibited by AT + UFH or ATH, and is not influenced by the presence of UFH alone. Cumulatively, this indicates that the fibrinolytic pathway is minimally impacted by AT + UFH or ATH, allowing maximal antithrombotic potential to be achieved during anticoagulation. Overall, the favourable anticoagulant properties of ATH combined with the findings of this study strengthens the utility of the covalent conjugate over conventional UFH for the treatment of thromboembolic disorders. Disclosures: No relevant conflicts of interest to declare.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».