The conformational switch from the factor X zymogen to protease state mediates exosite expression and prothrombinase assembly

Zymogens of the chymotrypsin-like serine protease family are converted to the protease state following insertion of a newly formed, highly conserved N terminus. This transition is accompanied by active site formation and ordering of several surface loops in the catalytic domain. Here we show that disruption of this transition in factor X through mutagenesis (FXa(I16L) and FXa(V17A)) not only alters active site function, but also significantly impairs Na(+) and factor Va binding. Active site binding was improved in the presence of high NaCl or with saturating amounts of factor Va membranes, suggesting that allosteric linkage exists between these sites. In line with this, irreversible stabilization of FXa(I16L) with Glu-Gly-Arg-chloromethyl ketone fully rescued FVa binding. Furthermore, the K(m) for prothrombin conversion with the factor Xa variants assembled into prothrombinase was unaltered, whereas the k(cat) was modestly reduced (3- to 4-fold). These findings show that intramolecular activation of factor X following the zymogen to protease transition not only drives catalytic site activation but also contributes to the formation of the Na(+) and factor Va binding sites. This structural plasticity of the catalytic domain plays a key role in the regulation of exosite expression and prothrombinase assembly.     

A computational modeling and molecular dynamics study of the Michaelis complex of human protein Z-dependent protease inhibitor (ZPI) and factor Xa (FXa)

Protein Z-dependent protease inhibitor (ZPI) and antithrombin III (AT3) are members of the serpin superfamily of protease inhibitors that inhibit factor Xa (FXa) and other proteases in the coagulation pathway. While experimental structural information is available for the interaction of AT3 with FXa, at present there is no structural data regarding the interaction of ZPI with FXa, and the precise role of this interaction in the blood coagulation pathway is poorly understood. In an effort to gain a structural understanding of this system, we have built a solvent equilibrated three-dimensional structural model of the Michaelis complex of human ZPI/FXa using homology modeling, protein–protein docking and molecular dynamics simulation methods. Preliminary analysis of interactions at the complex interface from our simulations suggests that the interactions of the reactive center loop (RCL) and the exosite surface of ZPI with FXa are similar to those observed from X-ray crystal structure-based simulations of AT3/FXa. However, detailed comparison of our modeled structure of ZPI/FXa with that of AT3/FXa points to differences in interaction specificity at the reactive center and in the stability of the inhibitory complex, due to the presence of a tyrosine residue at the P1 position in ZPI, instead of the P1 arginine residue in AT3. The modeled structure also shows specific structural differences between AT3 and ZPI in the heparin-binding and flexible N-terminal tail regions. Our structural model of ZPI/FXa is also compatible with available experimental information regarding the importance for the inhibitory action of certain basic residues in FXa. Figure Solvent equilibrated models for protein z-dependent protease inhibitor and its initial reactive complex with coagulation factor Xa (show here) are developed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. V.C. and C.J.L. contributed equally to this work. The solvent-equilibrated PDB structure of the ZPI/FXa will be made available upon request. Conflict of interest statement  The authors state that they have no conflict of interest.     

Porcine Model of Hemophilia A

Hemophilia A is a common X chromosome-linked genetic bleeding disorder caused by abnormalities in the coagulation factor VIII gene (F8). Hemophilia A patients suffer from a bleeding diathesis, such as life-threatening bleeding in the brain and harmful bleeding in joints and muscles. Because it could potentially be cured by gene therapy, subhuman animal models have been sought. Current mouse hemophilia A models generated by gene targeting of the F8 have difficulties to extrapolate human disease due to differences in the coagulation and immune systems between mice and humans. Here, we generated a porcine model of hemophilia A by nuclear transfer cloning from F8-targeted fibroblasts. The hemophilia A pigs showed a severe bleeding tendency upon birth, similar to human severe hemophiliacs, but in contrast to hemophilia A mice which rarely bleed under standard breed conditions. Infusion of human factor VIII was effective in stopping bleeding and reducing the bleeding frequency of a hemophilia A piglet but was blocked by the inhibitor against human factor VIII. These data suggest that the hemophilia A pig is a severe hemophilia A animal model for studying not only hemophilia A gene therapy but also the next generation recombinant coagulation factors, such as recombinant factor VIII variants with a slower clearance rate.     

Exploration of conformational transition in the aryl-binding site of human FXa using molecular dynamics simulations

Human coagulation Factor X (FX), a member of the vitamin K-dependent serine protease family, is a crucial component of the human coagulation cascade. Activated FX (FXa) participates in forming the prothrombinase complex on activated platelets to convert prothrombin to thrombin in coagulation reactions. In the current study, 30-ns MD simulations were performed on both the open and closed states of human FXa. Root mean squares (RMS) fluctuations showed that structural fluctuations concentrated on the loop regions of FXa, and the presence of a ligand in the closed system resulted in larger fluctuations of the gating residues. The open system had a gating distance from 9.23 to 11.33 ?, i.e., significantly larger than that of the closed system (4.69-6.35 ?), which allows diversified substrates of variable size to enter. Although the solvent accessible surface areas (SASA) of FXa remained the same in both systems, the open system generally had a larger total SASA or hydrophobic SASA (or both) for residues surrounding the S4 pocket. Additionally, more hydrogen bonds were formed in the closed state than in the open state of FXa, which is believed to play a significant role in maintaining the closed confirmation of the aryl-binding site. Based on the results of MD simulations, we propose that an induced-fit mechanism governs the functioning of human coagulation FX, which helps provide a better understanding of the interactions between FXa and its substrate, and the mechanism of the conformational changes involved in human coagulation.     

Gene Targeting of Tissue Factor, Factor X, and Factor VII in Mice: Their Involvement in Embryonic Development

Inactivation of specific genes in mammals by gene targeting has accelerated our ability to determine gene function. Nearly all genes involved in the blood coagulation system have been knocked out in mice. Tissue factor (TF) is the main initiator of the coagulation system and functions as a cell surface receptor for coagulation factor VII (FVII). Knockout studies have shown that TF deficiency results in lethality around embryonic day (E) 8.5-10.5. The results suggest a role for TF in embryonic blood vessel development and maintenance of vascular integrity in the yolk sac. In addition, TF may be involved in the maintenance of the placental labyrinth. Factor X (FX) deficiency causes partial embryonic lethality between E11.5-12.5.FX^–/– mice that were born died from fatal neonatal bleeding. In contrast, FVII deficiency is not embryonic lethal, but FVII^–/– neonates died from hemorrhage within the first days after birth. The various lethal phenotypes of deficiencies of the different coagulation factors suggest involvement in processes beyond hemostasis. Both TF/FVIIa and FXa can trigger intracellular signaling events in certain cell types. Signaling by coagulation proteases and protease activated receptors (PARs) may have important roles in embryonic development.     

Discovery of sulfonylalkylamides: A new class of orally active factor Xa inhibitors

Factor Xa (FXa) is a trypsin-like serine protease involved in the coagulation cascade and has received great interest as a potential target for the development of new antithrombotic agents. Most of amidine-type FXa inhibitors reported have been found to show extremely poor oral bioavailability. Compound 1 is one of the first reported non-amidine type FXa inhibitors. To discover novel and orally active FXa inhibitors, we investigated flexible linear linkers between the 6-chloronaphthalene ring and the 1-(pyridin-4-yl)piperidine moiety of 1 and found the orally active sulfonylalkylamide 2f with an FXa IC(50) of 0.05 microM, comparable with that of 1. Further modification to reduce the CYP3A4 inhibitory activity of 2f resulted in the potent, selective, and orally active 2-methylpyridine analogue 2s (FXa IC(50) of 0.061 microM), for which the liability of CYP3A4 inhibition was significantly weakened compared to 2f. Compound 2s also showed long lasting anticoagulant activity in cynomolgus monkeys.     

A bipartite autoinhibitory region within the B-domain suppresses function in factor V

Activation of blood coagulation factor V (FV) is a key reaction of hemostasis. FV circulates in plasma as an inactive procofactor, and proteolytic removal of a large central B-domain converts it to an active cofactor (FVa) for factor Xa (FXa). Here we show that two short evolutionary conserved segments of the B-domain, together termed the procofactor regulatory region, serve an essential autoinhibitory function. This newly identified motif consists of a basic (963-1008) and an acidic (1493-1537) region and defines the minimal sequence requirements to maintain FV as a procofactor. Our data suggest that dismantling this autoinhibitory region via deletion or proteolysis is the driving force to unveil a high affinity binding site(s) for FXa. These findings document an unexpected sequence-specific role for the B-domain by negatively regulating FV function and preventing activity of the procofactor. These new mechanistic insights point to new ways in which the FV procofactor to cofactor transition could be modulated to alter hemostasis.     

BPTI and N-terminal extended analogues generated by factor Xa cleavage and cathepsin C trimming of a fusion protein expressed in Escherichia coli

A recombinant gene for BPTI (bovine pancreatic trypsin inhibitor) is expressed in Escherichia coli using a MBP (maltose-binding protein) fusion vector. BPTI is fused through an FXa (blood coagulation factor Xa protease) target sequence (Ile-Glu-Gly-Arg) to the C-terminus of MBP. The MBP moiety of the hybrid protein enables purification in one step utilizing MBP's affinity to cross-linked amylose, and the FXa target sequence allows specific cleavage of the hybrid protein. Effective FXa cleavage is achieved by spacing the FXa target sequence and Arg-1 of the BPTI sequence with four residues (Met-Glu-Ala-Glu). The resulting N-terminal extended BPTI is readily converted to the wild-type sequence by trimming with cathepsin C exopeptidase, for the activity of which the spacing tetrapeptide is optimized. FXa cleavage is prohibited when the target sequence is placed next to Arg-1. In this construction, off-target cleavage at a somewhat homologous sequence (Val-Pro-Gly-Arg) results in five- or six-residue extended BPTI, indicating new details of the FXa specificity. The yield of highly purified recombinant BPTI is 3-6 mg/liter of culture, making the MBP-BPTI expression system convenient for the production of sufficient amounts of protein for NMR studies. 1H NMR is used to analyze the N-extended BPTI analogues.     

Characterization of a recombinant granzyme B derivative as a "restriction" protease

Blood coagulation factor Xa (FXa) and Thrombin are well-known serine proteases often used for processing of recombinant fusion proteins, but because they are purified from bovine blood or other animal sources, there is a risk of pathogenic contaminants in the preparation of the proteases. We report here the characterization of a recombinant serine protease produced in Escherichia coli, which can be used as a specific and efficient alternative to FXa and Thrombin as processing protease. This recombinant protease is derived from human granzyme B (GrB). The protease is found to be very stable in general, and it performs very well in the cleavage of several different fusion proteins tested and was even found superior to processing by FXa in two cases.     

Design,synthesis and biological activity of YM-60828 derivatives: potent and orally-bioavailable factor Xa inhibitors based on naphthoanilide and naphthalensulfonanilide templates

Factor Xa (FXa) is a serine protease which plays a pivotal role in the coagulation cascade. The inhibition of FXa has received great interest as a potential target for the development of new antithrombotic drug. Herein we describe a series of novel 7-amidino-2-naphthoanilide and 7-amidino-2-naphthalensulfonanilide derivatives which are potent FXa inhibitors. These scaffolds are rigid and are allowed to adopt an L-shape conformation which was estimated as the active conformation based on a docking study of YM-60828 with FXa. Optimization of the side chain at the central aniline nitrogen of 7-amidino-2-naphthoanilide has led to several potent and orally active FXa inhibitors. 5h (YM-169964), the best compound of these series, showed potent FXa inhibitory activity (IC(50)=3.9nM) and effectively prolonged prothrombin time by 9.6-fold ex vivo at an oral dose of 3mg/kg in squirrel monkeys.     

Thrombin-like serine protease,antiquorin from Euphorbia antiquorum latex induces platelet aggregation via PAR1-Akt/p38 signaling axis

Plant latex proteases (PLPs) are pharmacologically essential and are integral components of traditional medicine in the management of bleeding wounds. PLPs are known to promote blood coagulation and stop bleeding by interfering at various stages of hemostasis. There are a handful of scientific reports on thrombin-like enzymes characterized from plant latices. However, the role of plant latex thrombin-like enzymes in platelet aggregation is not well known. In the present study, we attempted to purify and characterize thrombin-like protease responsible for platelet aggregation. Among tested plant latices, Euphorbia genus latex protease fractions (LPFs) induced platelet aggregation. In Euphorbia genus, E. antiquorum LPF (EaLPF) strongly induced platelet aggregation and attenuated bleeding in mice. The purified thrombin-like serine protease, antiquorin (Aqn) is a glycoprotein with platelet aggregating activities that interfere in intrinsic and common pathways of blood coagulation cascade and alleviates bleeding and enhanced excision wound healing in mice. In continuation, the pharmacological inhibitor of PAR1 inhibited Aqn-induced phosphorylation of cPLA₂, Akt, and P38 in human platelets. Moreover, Aqn-induced platelet aggregation was inhibited by pharmacological inhibitors of PAR1, PI3K, and P38. These data indicate that PAR1-Akt/P38 signaling pathways are involved in Aqn-induced platelet aggregation. The findings of the present study may open up a new avenue for exploiting Aqn in the treatment of bleeding wounds.     

Role of the alpha-helix 163-170 in factor Xa catalytic activity

Factor Xa (FXa) is a key protease of the coagulation pathway whose activity is known to be in part modulated by binding to factor Va (FVa) and sodium ions. Previous investigations have established that solvent-exposed, charged residues of the FXa alpha-helix 163-170 (h163-170), Arg(165) and Lys(169), participate in its binding to FVa. In the present study we aimed to investigate the role of the other residues of h163-170 in the catalytic functions of the enzyme. FX derivatives were constructed in which point mutations were made or parts of h163-170 were substituted with the corresponding region of either FVIIa or FIXa. Purified FXa derivatives were compared with wild-type FXa. Kinetic studies in the absence of FVa revealed that, compared with wild-type FXa, key functional parameters (catalytic activity toward prothrombin and tripeptidyl substrates and non-enzymatic interaction of a probe with the S1 site) were diminished by mutations in the NH(2)-terminal portion of h163-170. The defective amidolytic activity of these FXa derivatives appears to result from their impaired interaction with Na(+) because using a higher Na(+) concentration partially restored normal catalytic parameters. Furthermore, kinetic measurements with tripeptidyl substrates or prothrombin indicated that assembly of these FXa derivatives with an excess of FVa in the prothrombinase complex improves their low catalytic efficiency. These data indicate that residues in the NH(2)-terminal portion of the FVa-binding h163-170 are energetically linked to the S1 site and Na(+)-binding site of the protease and that residues Val(163) and Ser(167) play a key role in this interaction.     

The C-terminal and beta-wing regions of ammodytoxin A, a neurotoxic phospholipase A2 from Vipera ammodytes ammodytes, are critical for binding to factor Xa and for anticoagulant effect

Ammodytoxin A (AtxA) from the venom of Vipera ammodytes ammodytes belongs to group IIA secreted phospholipase A2 (sPLA2), for which the major pathologic activity is presynaptic neurotoxicity. We show here that this toxin also affects hemostasis because it exhibits strong anticoagulant activity. AtxA binds directly to human coagulation factor Xa (FXa) with Kdapp of 32 nM, thus inhibiting the activity of the prothrombinase complex with an IC50 of 20 nM. To map the FXa-interaction site on AtxA, various mutants of AtxA produced by site-directed mutagenesis and expressed in Escherichia coli were tested in the study. In surface plasmon resonance (SPR) measurements, with FXa covalently attached to the sensor chip, we show that the FXa-binding site on AtxA includes several basic amino acid residues at the C-terminal and beta-wing regions of the molecule. Applying an in vitro biological test for inhibition of prothrombinase activity, we further demonstrate that the same residues are also very important for the anticoagulant activity of AtxA. We conclude that the anticoagulant site of AtxA is located in the C-terminal and beta-wing regions of this phospholipase A2. Synthetic peptides comprising residues of the deduced anticoagulant site of AtxA provide a basis to synthesize novel anticoagulant drugs.     

Thermodynamic linkage between the S1 site, the Na+ site, and the Ca2+ site in the protease domain of human coagulation factor xa. Studies on catalytic efficiency and inhibitor binding

The serine protease domain of factor Xa (FXa) contains a sodium as well as a calcium-binding site. Here, we investigated the functional significance of these two cation-binding sites and their thermodynamic links to the S1 site. Kinetic data reveal that Na(+) binds to the substrate bound FXa with K(d) approximately 39 mm in the absence and approximately 9.5 mm in the presence of Ca(2+). Sodium-bound FXa (sodium-Xa) has approximately 18-fold increased catalytic efficiency ( approximately 4.5-fold decrease in K(m) and approximately 4-fold increase in k(cat)) in hydrolyzing S-2222 (benzoyl-Ile-Glu-Gly-Arg-p-nitroanilide), and Ca(2+) further increases this k(cat) approximately 1.4-fold. Ca(2+) binds to the protease domain of substrate bound FXa with K(d) approximately 705 microm in the absence and approximately 175 microm in the presence of Na(+). Ca(2+) binding to the protease domain of FXa (Xa-calcium) has no effect on the K(m) but increases the k(cat) approximately 4-fold in hydrolyzing S-2222, and Na(+) further increases this k(cat) approximately 1.4-fold. In agreement with the K(m) data, sodium-Xa has approximately 5-fold increased affinity in its interaction with p-aminobenzamidine (S1 site probe) and approximately 4-fold increased rate in binding to the two-domain tissue factor pathway inhibitor; Ca(2+) (+/-Na(+)) has no effect on these interactions. Antithrombin binds to Xa-calcium with a approximately 4-fold faster rate, to sodium-Xa with a approximately 24-fold faster rate and to sodium-Xa-calcium with a approximately 28-fold faster rate. Thus, Ca(2+) and Na(+) together increase the catalytic efficiency of FXa approximately 28-fold. Na(+) enhances Ca(2+) binding, and Ca(2+) enhances Na(+) binding. Further, Na(+) enhances S1 site occupancy, and S1 site occupancy enhances Na(+) binding. Therefore, Na(+) site is thermodynamically linked to the S1 site as well as to the protease domain Ca(2+) site, whereas Ca(2+) site is only linked to the Na(+) site. The significance of these findings is that during physiologic coagulation, most of the FXa formed will exist as sodium-Xa-calcium, which has maximum biologic activity.     

Factor Xa: at the crossroads between coagulation and signaling in physiology and disease

Activated factor Xa (FXa) is traditionally known as an important player in the coagulation cascade responsible for thrombin generation. Long considered a passive bystander, it is now evident that FXa exerts direct effects on a wide variety of cell types via activation of its two main receptors, protease-activated receptor-1 (PAR-1) and PAR-2. Recent findings suggest that PAR-2 plays a crucial role in fibro-proliferative diseases such as fibrosis, tissue remodeling and cancer and point towards FXa as the important mediator coordinating the interface between coagulation and disease progression. Here, we provide an overview of the FXa signaling pathways that mediate its effects in pathophysiology and explore the potential therapeutic implications of targeting FXa; in terms of arresting disease progression, the modulation of FXa activity might be more important than the modulation of FVIIa or thrombin.     

Determinants of the specificity of protease-activated receptors 1 and 2 signaling by factor Xa and thrombin

Factor Xa (FXa) elicits intracellular signaling responses through the activation of protease-activated receptor 2 (PAR2) and possibly also through PAR1 in endothelial cells. In this study, we investigated FXa signaling in endothelial cells when the protease was either in free form or assembled into the prothrombinase complex. Furthermore, we prepared several wild-type and mutant PAR1 and PAR2 cleavage-reporter constructs in which their exodomains were fused to cDNA encoding for a soluble alkaline phosphatase (ALP). In the mutants, P2 residues were exchanged between PAR1 and PAR2 cleavage-reporter constructs and the hirudin-like binding site (HLBS) of PAR1 was inserted into the homologous site of PAR2. In non-transfected cells, FXa elicited a protective response which could be blocked by a specific anti-PAR2 but not by an anti-PAR1 antibody. A similar protective activity was observed for FXa in the prothrombinase complex. Further studies revealed that neither the Gla- nor EGF1-domain of FXa is required for its signaling activity, however, the N-terminus Arg-86 and Lys-87 of the EGF2-domain were essential. In the cleavage-reporter transfected cells, FXa cleaved the PAR2 construct effectively, however, replacing its P2-Gly with P2-Pro of PAR1 impaired its cleavage by FXa but improved it by thrombin. A PAR2 construct containing both P2-Pro and HLBS of PAR1 was poorly cleaved by FXa, but effectively by thrombin. A PAR1 construct containing P2 and P3 residues of PAR2 was poorly cleaved by thrombin but effectively by FXa. These results provide new insight into mechanisms through which coagulation proteases specifically interact with their target PAR receptors.     

The extended interactions and Gla domain of blood coagulation factor Xa

The serine protease factor Xa (FXa) is inhibited by ecotin with picomolar affinity. The structure of the tetrameric complex of ecotin variant M84R (M84R) with FXa has been determined to 2.8 A. Substrate directed induced fit of the binding interactions at the S2 and S4 pockets modulates the discrimination of the protease. Specifically, the Tyr at position 99 of FXa changes its conformation with respect to incoming ligand, changing the size of the S2 and S4 pockets. The role of residue 192 in substrate and inhibitor recognition is also examined. Gln 192 from FXa forms a hydrogen bond with the P2 carbonyl group of ecotin. This confirms previous biochemical and structural analyses on thrombin and activated protein C, which suggested that residue 192 may play a more general role in mediating the interactions between coagulation proteases and their inhibitors. The structure of ecotin M84R-FXa (M84R-FXa) also reveals the structure of the Gla domain in the presence of Mg(2+). The first 11 residues of the domain assume a novel conformation and likely represent an intermediate folding state of the domain.     

Proteolytic modulation of factor Xa–antithrombin complex enhances fibrinolysis in plasma

Our previous work showed that purified coagulation factor Xa (FXa) acquires fibrinolysis cofactor activity after plasmin-mediated cleavage. The predominant functional species is a non-covalent heterodimer of 33 and 13 kDa, termed Xa33/13, which has predicted newly exposed C-terminal lysines that are important for tissue plasminogen activator (tPA)-mediated plasminogen activation to plasmin. To provide evidence that this mechanism occurs in a physiological context, here we demonstrated the appearance of Xa33 in clotting plasma by western blot analysis. Since the normal fate of FXa is stable association with antithrombin (AT), an AT western blot was conducted, which revealed a band of ~ 13 kDa higher apparent molecular weight than AT that appeared concurrent to Xa33. Sequencing of purified proteins confirmed the generation of Xa13 covalently bound to AT and Xa33 (Xa33/13-AT) by cleavages at Lys–Met339 and Lys–Asp389. Ligand blots demonstrated ¹²⁵I-plasminogen binding to the Xa33 subunit of plasmin-generated Xa33/13-AT. Purified XaAT added to plasma that was induced to clot enhanced the rate of tPA-mediated fibrinolysis by ~ 16-fold. Similarly, purified plasminogen activation by tPA was enhanced by ~ 16-fold by XaAT. Plasmin cleaves XaAT and exposes plasminogen binding sites at least 10-fold faster than FXa. Here we demonstrate a novel function for AT, which accelerates the modulation of FXa into the fibrinolytic form, Xa33/13. The consequent exposure of C-terminal lysine binding sites essential for plasminogen activation enhances fibrinolysis. These results are consistent with a model where auxiliary cofactors link coagulation to fibrinolysis by priming the accelerating role of fibrin.     

高剂量生长抑素、奥美拉唑联合止血芳酸治疗急性上消化道出血合并凝血功能障碍患者的临床效果

目的:探讨高剂量生长抑素、奥美拉唑联合止血芳酸治疗急性上消化道出血合并凝血功能障碍患者的临床效果及安全性。方法:选择我院2014年1月~2017年12月收治的92例急性上消化出血合并凝血功能障碍的患者,并按随机数表法将其分为对照组和研究组。对照组予以常规剂量生长抑素、奥美拉唑联合止血芳酸治疗,研究组予以高剂量生长抑素治疗,其余奥美拉唑及止血芳酸用法同对照组。治疗后,比较两组的临床疗效、止血情况、住院时间,治疗前后血常规指标、凝血功能的变化及并发症的发生情况。结果:治疗后,研究组总有效率明显高于对照组[91.30%vs.74.42%](P0.05),而平均止血时间、再止血率及住院时间均明显短于对照组(P0.05);两组白细胞计数(WBC)、部分活化凝血酶原时间(APTT)及凝血酶原时间(PT)均较治疗前明显下降,血红蛋白(Hb)、红细胞计数(RBC)、红细胞压积(Hct)及血小板计数(PLT)均较治疗前明显上升,且研究组以上指标变化较对照组更明显(P0.05)。两组并发症的发生率比较差异均无统计学意义(P0.05)。结论:高剂量生长抑素、奥美拉唑联合止血芳酸治疗急性上消化道出血合并凝血功能障碍的效果明显优于常规剂量生长抑素、奥美拉唑联合止血芳酸治疗,其能够更有效缩短止血时间,避免再出血,且未增加药物不良反应,安全性高。