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Effect of leukocyte proteinases on tissue factor pathway inhibitor
L C Petersen1, S E Bjørn, O Nordfang
1Novo Nordisk Research Institute, Denmark.
Abstract:
The effect of human neutrophil elastase and cathepsin G on recombinant tissue factor pathway inhibitor (TFPI) was investigated. A weak inhibition by TFPI of both elastase (Ki = 0.4 microM) and cathepsin G (Ki = 0.1 microM) was observed. Neutrophil elastase rapidly cleaved TFPI at the Thr87-Thr88 bond situated at the link between Kunitz domains I and II. Cleavage of TFPI by cathepsin G was also observed, but the reaction was much slower and resulted in a number of fragments. Proteolytic cleavage by both elastase and cathepsin G resulted in destruction of inhibitor function with respect to TFPI's inhibition of factor Xa. Cleavage by neutrophil elastase was capable of restoring factor Xa amidolytic activity after its initial inhibition by TFPI. Inhibition of cathepsin G by TFPI was strongly augmented by stoichiometric amounts of factor Xa. However, the augmentation was temporary, presumably due to concomitant cleavage of TFPI by cathepsin G. These observations may have implications for the putative effect of neutrophil leukocyte stimulation on the regulation of the tissue factor-mediated coagulation pathway. Conversely, formation of a factor Xa/TFPI complex may reduce or modulate the proteolytic potential of stimulated leukocytes by temporary inhibition of cathepsin G.
Insights
Human neutrophil elastase and cathepsin G degrade tissue factor pathway inhibitor (TFPI), destroying its anticoagulant function. This cleavage impacts coagulation regulation and leukocyte proteolytic activity.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Tissue factor pathway inhibitor (TFPI) is a key regulator of the extrinsic coagulation pathway.
- Neutrophil proteases, such as elastase and cathepsin G, are released during inflammation and can affect coagulation.
- The interaction between TFPI and neutrophil proteases is not fully understood.
Purpose of the Study:
- To investigate the effect of human neutrophil elastase and cathepsin G on recombinant TFPI.
- To determine how these proteases impact TFPI's inhibitory function and structure.
- To explore the implications for coagulation regulation during neutrophil activation.
Main Methods:
- Recombinant TFPI was incubated with purified human neutrophil elastase and cathepsin G.
- TFPI cleavage sites and fragmentation patterns were analyzed.
- TFPI's inhibition of factor Xa and cathepsin G's amidolytic activity were measured.
- The effect of factor Xa on TFPI-cathepsin G interaction was assessed.
Main Results:
- TFPI exhibited weak inhibition of both elastase (Ki = 0.4 microM) and cathepsin G (Ki = 0.1 microM).
- Neutrophil elastase rapidly cleaved TFPI at the Thr87-Thr88 bond, while cathepsin G caused slower, more extensive fragmentation.
- Proteolytic cleavage destroyed TFPI's ability to inhibit factor Xa and, in the case of elastase, restored factor Xa amidolytic activity.
- Factor Xa temporarily augmented TFPI's inhibition of cathepsin G, but this was transient due to TFPI cleavage.
Conclusions:
- Neutrophil elastase and cathepsin G degrade TFPI, compromising its anticoagulant function.
- These interactions suggest that neutrophil activation may alter the regulation of the tissue factor-mediated coagulation pathway.
- Formation of a factor Xa/TFPI complex might temporarily modulate leukocyte proteolytic activity by inhibiting cathepsin G.