Nagase H, Enjyoji K, Kamikubo Y, Kitazato K T, Kitazato K, Saito H, Kato H
Taiho Pharmaceutical Co., Ltd, Tokushima, Japan.
Thromb Haemost. 1997 Aug;78(2):864-70.
Depolymerized holothurian glycosaminoglycan (DHG) is a glycosaminoglycan extracted from the sea cucumber Stichopus japonicus Selenka. In previous studies, we demonstrated that DHG has antithrombotic and anticoagulant activities that are distinguishable from those of heparin and dermatan sulfate. In the present study, we examined the effect of DHG on the tissue factor pathway inhibitor (TFPI), which inhibits the initial reaction of the tissue factor (TF)-mediated coagulation pathway. We first examined the effect of DHG on factor Xa inhibition by TFPI and the inhibition of TF-factor VIIa by TFPI-factor Xa in in vitro experiments using human purified proteins. DHG increased the rate of factor Xa inhibition by TFPI, which was abolished either with a synthetic C-terminal peptide or with a synthetic K3 domain peptide of TFPI. In contrast, DHG reduced the rate of TF-factor VIIa inhibition by TFPI-factor Xa. Therefore, the effect of DHG on in vitro activity of TFPI appears to be contradictory. We then examined the effect of DHG on TFPI in cynomolgus monkeys and compared it with that of unfractionated heparin. DHG induced an increase in the circulating level of free-form TFPI in plasma about 20-fold when administered i.v. at 1 mg/kg. The prothrombin time (PT) in monkey plasma after DHG administration was longer than that estimated from the plasma concentrations of DHG. Therefore, free-form TFPI released by DHG seems to play an additive role in the anticoagulant mechanisms of DHG through the extrinsic pathway in vivo. From the results shown in the present work and in previous studies, we conclude that DHG shows anticoagulant activity at various stages of coagulation reactions, i.e., by inhibiting the initial reaction of the extrinsic pathway, by inhibiting the intrinsic Xase, and by inhibiting thrombin.
解聚海参糖胺聚糖（DHG）是一种从刺参中提取的糖胺聚糖。在先前的研究中，我们证明了DHG具有抗血栓和抗凝活性，这些活性与肝素和硫酸皮肤素的活性不同。在本研究中，我们研究了DHG对组织因子途径抑制剂（TFPI）的影响，TFPI可抑制组织因子（TF）介导的凝血途径的初始反应。我们首先在使用人纯化蛋白的体外实验中研究了DHG对TFPI抑制因子Xa以及TFPI-因子Xa抑制TF-因子VIIa的影响。DHG提高了TFPI抑制因子Xa的速率，而该速率可被TFPI的合成C末端肽或合成K3结构域肽消除。相反，DHG降低了TFPI-因子Xa抑制TF-因子VIIa的速率。因此，DHG对TFPI体外活性的影响似乎是矛盾的。然后，我们研究了DHG对食蟹猴TFPI的影响，并将其与普通肝素的影响进行了比较。当以1 mg/kg静脉注射时，DHG可使血浆中游离形式TFPI的循环水平增加约20倍。给予DHG后，猴血浆中的凝血酶原时间（PT）比根据DHG血浆浓度估算的时间更长。因此，DHG释放的游离形式TFPI似乎在体内通过外源性途径在DHG的抗凝机制中发挥累加作用。根据本研究和先前研究的结果，我们得出结论，DHG在凝血反应的各个阶段均显示抗凝活性，即通过抑制外源性途径的初始反应、抑制内源性X酶和抑制凝血酶来实现。
