Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC.
Blood. 2018 Nov 1;132(18):1974-1984. doi: 10.1182/blood-2018-05-846592. Epub 2018 Aug 8.
Warfarin, acenocoumarol, phenprocoumon, and fluindione are commonly prescribed oral anticoagulants for the prevention and treatment of thromboembolic disorders. These anticoagulants function by impairing the biosynthesis of active vitamin K-dependent coagulation factors through the inhibition of vitamin K epoxide reductase (VKOR). Genetic variations in VKOR have been closely associated with the resistant phenotype of oral anticoagulation therapy. However, the relative efficacy of these anticoagulants, their mechanisms of action, and their resistance variations among naturally occurring VKOR mutations remain elusive. Here, we explored these questions using our recently established cell-based VKOR activity assay with the endogenous VKOR function ablated. Our results show that the efficacy of these anticoagulants on VKOR inactivation, from most to least, is: acenocoumarol > phenprocoumon > warfarin > fluindione. This is consistent with their effective clinical dosages for stable anticoagulation control. Cell-based functional studies of how each of the 27 naturally occurring VKOR mutations responds to these 4 oral anticoagulants indicate that phenprocoumon has the largest resistance variation (up to 199-fold), whereas the resistance of acenocoumarol varies the least (<14-fold). Cell-based kinetics studies show that fluindione appears to be a competitive inhibitor of VKOR, whereas warfarin is likely to be a mixed-type inhibitor of VKOR. The anticoagulation effect of these oral anticoagulants can be reversed by the administration of a high dose of vitamin K, apparently due to the existence of a different enzyme that can directly reduce vitamin K. These findings provide new insights into the selection of oral anticoagulants, their effective dosage management, and their mechanisms of anticoagulation.
华法林、醋硝香豆素、苯丙香豆素和氟茚二酮是常用于预防和治疗血栓栓塞性疾病的口服抗凝剂。这些抗凝剂通过抑制维生素 K 环氧化物还原酶（VKOR）来损害活性维生素 K 依赖性凝血因子的生物合成。VKOR 的遗传变异与口服抗凝治疗的耐药表型密切相关。然而，这些抗凝剂的相对疗效、作用机制以及自然发生的 VKOR 突变中的耐药性变化仍不清楚。在这里，我们使用我们最近建立的细胞基础 VKOR 活性测定法，该方法消除了内源性 VKOR 功能，探讨了这些问题。我们的结果表明，这些抗凝剂对 VKOR 失活的疗效从高到低依次为：醋硝香豆素>苯丙香豆素>华法林>氟茚二酮。这与它们用于稳定抗凝控制的有效临床剂量一致。对 27 种天然 VKOR 突变中的每一种如何对这 4 种口服抗凝剂产生反应的细胞功能研究表明，苯丙香豆素的耐药性变化最大（高达 199 倍），而醋硝香豆素的耐药性变化最小（<14 倍）。细胞动力学研究表明，氟茚二酮似乎是 VKOR 的竞争性抑制剂，而华法林可能是 VKOR 的混合型抑制剂。这些口服抗凝剂的抗凝作用可以通过给予高剂量的维生素 K 来逆转，这显然是由于存在一种可以直接还原维生素 K 的不同酶。这些发现为口服抗凝剂的选择、有效剂量管理及其抗凝机制提供了新的见解。
