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Inhibition of plasminogen activation by polymerized ampicillin
A al-Roof Higazi1, M Hermoni, R Aziza
1Department of Clinical Biochemistry, Hadassah Hospital, Jerusalem, Israel.
Abstract:
The polymerized beta-lactam antibiotic ampicillin inhibits the proteolytic activity of human plasmin upon 125I-labeled fibrin clots. The inhibition is dose-dependent, with half-maximal inhibition occurring at 1.25 mM of the polymerized antibiotic. Polymerized ampicillin also inhibits binding of plasmin to fibrin, and 38% inhibition of binding occurs at 10 mM of the antibiotic. Furthermore, polymerized ampicillin inhibits the activation of plasminogen by either urokinase-like plasminogen activator (uPA) or tissue type-plasminogen activator (tPA). At 7.5 mM of polymerized ampicillin, the uPA-mediated plasminogen activation is suppressed by 94%, and half-maximal inhibition is obtained at 0.66 mM. The direct activity of uPA on the chromogenic substrate L-pyroglutamyl-glycyl-L-arginine p-nitroanilide hydrochloride (S-2444) is unaffected by polymerized ampicillin levels of up to 10 mM. The inhibitory effects of the polymerized antibiotic on the activation of plasminogen by both uPA and tPA is totally abolished in presence of fibrin. These interactions may serve as a novel model for ligands that enhance the clot-specificity of thrombolytic agents.
Insights
Polymerized ampicillin inhibits plasmin activity on fibrin clots and plasminogen activation by urokinase-like plasminogen activator (uPA) and tissue-type plasminogen activator (tPA). This antibiotic may offer a new strategy for targeted clot-specific thrombolytic therapy.
Area of Science:
- Biochemistry
- Pharmacology
- Thrombosis Research
Background:
- Human plasmin plays a critical role in fibrinolysis, breaking down blood clots.
- Plasminogen activators, such as urokinase-like plasminogen activator (uPA) and tissue-type plasminogen activator (tPA), initiate fibrinolysis by converting plasminogen to plasmin.
- Understanding agents that modulate fibrinolysis is crucial for developing effective antithrombotic therapies.
Purpose of the Study:
- To investigate the inhibitory effects of polymerized ampicillin on the proteolytic activity of human plasmin.
- To examine the impact of polymerized ampicillin on plasminogen activation mediated by uPA and tPA.
- To explore the potential of polymerized ampicillin as a novel therapeutic agent for modulating clot-specific thrombolysis.
Main Methods:
- Assessing the inhibition of plasmin's proteolytic activity on 125I-labeled fibrin clots by polymerized ampicillin.
- Quantifying the effect of polymerized ampicillin on the binding of plasmin to fibrin.
- Measuring the inhibition of plasminogen activation by uPA and tPA in the presence and absence of fibrin.
- Evaluating the direct enzymatic activity of uPA on a chromogenic substrate (S-2444) with varying concentrations of polymerized ampicillin.
Main Results:
- Polymerized ampicillin demonstrated dose-dependent inhibition of plasmin's proteolytic activity on fibrin clots, with half-maximal inhibition at 1.25 mM.
- The antibiotic inhibited plasmin binding to fibrin by 38% at 10 mM.
- Polymerized ampicillin significantly suppressed uPA-mediated plasminogen activation (94% inhibition at 7.5 mM, half-maximal inhibition at 0.66 mM) and tPA-mediated activation.
- Direct uPA enzymatic activity was unaffected by polymerized ampicillin up to 10 mM.
- The inhibitory effects on plasminogen activation by uPA and tPA were abolished in the presence of fibrin.
Conclusions:
- Polymerized ampicillin effectively inhibits plasmin activity and plasminogen activation.
- The presence of fibrin abolishes the inhibitory effects, suggesting a clot-specific mechanism.
- These findings propose a novel model where polymerized ampicillin could enhance the clot-specificity of thrombolytic agents.