2型糖尿病患者TAFI、PAI-1、t-PA、F1+2与尿微量蛋白之间关系的研究

目的:探讨凝血酶激活的纤溶抑制物(TAFI)和纤溶酶原激活物抑制剂-1(PAI-1)在2型糖尿病患者中纤溶抑制的作用机制,并分析TAFI、PAI-1、组织型纤溶酶原激活剂(t-PA)、凝血酶原片段1+2(F1+2)等凝血、纤溶的指标与尿微量蛋白之间的关系。方法:64例2型糖尿病患者以尿蛋白排泄量分微量蛋白尿组(MAU)和正常蛋白尿组(NAU)组。TAFI、PAI-1、t-PA及F1+2等凝血纤溶指标测定用酶联免疫吸附双抗体夹心法(ELISH),并分析上述指标与尿微量蛋白、血压、血糖、血脂、功能参数之间的关系。结果:与对照组比较,血浆TAFI仅在MAU组显著性升高(P<0.05);血浆t-PA在T2DM的2组中增高均无显著性;而血浆PAI-1和F1+2在NAU和MAU组均显著性增高,差异有统计学意义(P<0.01)。但TAFI、PAI-1、t-PA、F1+2在2组之间无显著性差异。结论:2型糖尿病患者的纤溶功能降低主要是由于PAI-1的作用,随着蛋白尿的出现,其进一步的低纤溶状态则是由TAFI介导的,故TAFI和PAI-1在抑制纤溶系统功能上的作用是独立的。     

心房颤动患者血浆纤溶抑制系统的变化

目的:探讨心房颤动(房颤)患者血浆中纤溶抑制系统的变化.方法:将45例患者根据临床诊断分为3组:对照组(诊断为房性或室性期前收缩),特发性房颤组和房颤并发脑梗死组.3组患者年龄、TC和LDL差异无统计学意义(P>0.05),无其他临床并发症且未应用抗血栓治疗.取空腹外周血,用ELISA法检测血浆中凝血酶激活的纤溶酶抑制剂(TAFI)抗原、TAFI活性、纤溶酶-α2-抗纤溶酶复合物(PAP)和纤溶酶活化物抑制剂-1(PAI-1).结果:3组患者血浆中TAFI、TAFI活性、PAP和PAI-1差异无统计学意义(P>0.05).结论:房颤患者周围血中纤溶抑制系统指标变化不明显,心房局部纤溶抑制系统是否被激活及其在血栓形成中的意义需要进一步的研究.     

凝血酶激活的纤溶抑制物研究进展

血液凝固时,凝血酶激活的纤溶抑制物(TAFI)被凝血酶激活,裂解纤维蛋白C末端赖氨酸残基,下调纤溶系统,TAFI还参与炎症与创伤修复。动物实验中,抑制TAFI可以缩短血凝块溶解时间,增强溶栓药物的作用,开发特异性TAFI抑制物有可能成为血栓性疾病治疗的一类新的药物。     

慢性肝病患者血浆中凝血酶激活的纤溶系统检测的临床意义

目的:探讨慢性肝病患者血浆凝血酶激活的纤溶抑制物活性(TAFI:A)、纤溶酶原激活物抑制剂(PAI-1)及组织型纤溶酶原激活物(t-PA)水平变化的临床意义。方法:收集84例临床肝病患者的血液标本,同时选取52例体检健康者为对照组,TAFI:A测定采用发色底物法,PAI-1、t-PA含量测定采用ELISA法,并统计分析上述3项指标与不同类型慢性肝病间的相关性。结果:与对照组比较,病例组血浆TAFI:A水平均显著降低(P<0.05);血浆PAI-1水平显著增加(P<0.05);血浆t-PA水平亦显著增加(P<0.05,原发性胆汁性肝硬化除外)。结论:慢性肝损伤患者血浆TAFI:A水平降低,导致纤溶活性增加,是提示慢性肝病患者呈出血倾向的一项指标。     

急性冠脉综合征患者pentraxin-3与凝血酶活化的纤溶抑制物的变化

目的了解急性冠脉综合征(Acute Coronary Syndrome,ACS)患者炎性指标pentraxin-3与纤溶指标凝血酶活化的纤溶抑制物(Thrombin activatable finolysis inhibitor,TAFI)的变化。方法检测比较102例急性心肌梗死(AMI组)、81例不稳定心绞痛(UAP组)及23例健康体检者(对照组)的血浆pentraxin-3、TAFI水平。结果急性冠脉综合征患者血浆pentraxin-3、TAFI明显高于对照组,差异有统计学意义(P<0.01);AMI组血浆pentraxin-3及TAFI水平高于UAP组,差异有统计学意义(P<0.05)。pentraxin-3浓度与TAFI浓度呈正相关(r=0.17,P<0.05)。结论 pentraxin-3与TAFI共同在ACS的发生发展中起重要作用。     

TAFI与动脉粥样硬化性心脑血管疾病关系的研究进展

动脉粥样硬化（AS）是缺血性心脑血管疾病（如心绞痛、心肌梗死、脑卒中等）共同的病理生理基础,也是导致“罪犯”血管内血栓形成的原因.近几年的研究表明,AS的发生、发展与炎症、凝血-纤溶调节系统密切相关.凝血酶激活的纤溶抑制物（thrombin-activatable fibrinolysis inhibitor,TAFI）不仅作为凝血和纤溶的联系纽带发挥抑制纤溶的作用,同时作为一种急性反应蛋白参与炎症调节.近年来的研究显示TAFI在AS发生、发展中起重要作用.本文就TAFI的生物学作用、基因多态性以及与AS性心脑血管疾病关系作一综述。     

老年不稳定型心绞痛患者血浆凝血酶激活的纤溶抑制物的检测及其临床意义

目的探讨老年不稳定性心绞痛(UA)患者血浆凝血酶激活的纤溶抑制物(TAFI)的临床意义。方法采用ELISA法分别检测60例老年UA患者与30例正常对照组血浆TAFI的含量(TAFI:Ag)及活性(TAFIa:Ag)的变化情况,检测凝血-纤溶指标,结合病理资料进行相关性分析。结果老年UA患者治疗前TAFI:Ag和TAFIa:Ag及F1+2、D-D、Fib水平均明显高于治疗后和正常对照组(P<0.05),有效治疗2周后TAFIa:Ag降低,TAFI:Ag及F1+2、D-D、Fib基本恢复正常(P>0.05),治疗前血浆TAFI:Ag与F1+2、Fib呈正相关:血浆TAFIa:Ag与F1+2、Fib呈正相关。结论血浆TAFI含量和活性与老年UA发生发展密切相关,TAFI含量和活性的升高增加了老年UA的发病风险。     

细胞色素P450、凝血酶激活的纤溶抑制物在不稳定型心绞痛和急性心肌梗死中的表达

不稳定型心绞痛(UAP)与急性心肌梗死(AMI)临床表现有较多相似之处,其发病均建立在冠状动脉粥样硬化基础上,且均发生斑块破裂、血小板凝集、纤溶系统改变、细胞因子释放等病理变化.本研究探讨细胞色素P450( CYP450)、凝血酶激活的纤溶抑制物(TAFI)在两种疾病中的活性.     

2型糖尿病并大血管病变患者血浆纤溶酶原激活物抑制剂1及凝血酶激活的纤溶抑制物水平变化及意义

目的:探讨2型糖尿病(DM)并大血管病变患者血液中纤溶酶原激活物抑制剂1(PAI-1)、血浆组织型纤溶酶原激活物(t-PA)、D-二聚体(D-D)以及血浆凝血酶激活的纤溶抑制物(TAFI)水平的变化及临床意义。方法:分别应用ELISA及乳胶免疫分析测定DM患者血浆PAI-1、t-PA、TAFI、D-D活性;并与糖尿病无大血管并发症组和健康对照组比较。结果:DM组PAI-1、t-PA、D-D和TAFI含量分别为(48.36±7.92)ng/mL、(12.52±3.17)ng/mL、(0.75±0.58)mg/L和60.82%±14.71%,与健康对照组相比有显著差异(P<0.01);其中糖尿病大血管病变组PAI-1、t-PA及D-D水平与糖尿病无大血管病变组有显著差异(P<0.01)。结论:糖尿病患者血液中PAI-1、t-PA、D-D、TAFI水平与血管损伤和功能变化的进程有显著相关性,联合检测上述指标对糖尿病及其并发症的诊断、治疗和病情观察有重要的临床意义。     

黄芩苷对动脉粥样硬化大鼠凝血酶激活纤溶抑制物水平及血脂、凝血纤溶指标的影响

目的 观察黄芩苷对动脉粥样硬化(AS)模型大鼠的凝血酶激活纤溶抑制物(TAFI)水平及血脂、凝血纤溶指标的影响,探讨黄芩苷在干预AS进程中的机制.方法 40只健康雄性Wistar大鼠随机分为正常对照组、模型组、黄芩苷治疗组、辛伐他汀组,每组10只.正常对照组给予普通饲料喂养,其余3组在给予高脂饲料喂养的基础上行主动脉球囊损伤术,喂养4个月,以复制大鼠AS模型.用全自动生化仪测定血浆总胆固醇(TC)、三酰甘油(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C),用全自动血凝仪测定凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)、纤维蛋白原(Fib),发色底物法测定血浆TAFI的活性.结果 与正常对照组相比,其余各组大鼠的TC、TG、LDL-C、Fib和TAFI活性均明显升高 (P<0.01或P<0.05),PT、APTT明显缩短(P<0.01或P<0.05);实验结束时,与模型组相比,黄芩苷治疗组与辛伐他汀组的TC、TG、LDL-C、Fib和TAFI活性明显低于模型组(P<0.01或P<0.05),PT、APTT明显延长(P<0.01或P<0.05);与辛伐他汀组比较,黄芩苷治疗组TC、TG、LDL-C、Fib、PT、APTT改善程度稍低(P<0.05),而TAFI活性则无明显统计学差异(P>0.05).结论 黄芩苷可能通过降血脂、改善凝血纤溶系统平衡、下调TAFI水平等途径干预了AS的形成.     

Regulation of fibrinolysis by thrombin activatable fibrinolysis inhibitor, an unstable carboxypeptidase B that unites the pathways of coagulation and fibrinolysis

The coagulation and fibrinolytic systems safeguard the patency of the vasculature and surrounding tissue. Cross regulation of coagulation and fibrinolysis plays an important role in preserving a balanced hemostatic process. Identification of Thrombin Activatable Fibrinolysis Inhibitor (TAFI) as an inhibitor of fibrinolysis and one of the main intermediates between coagulation and fibrinolysis, greatly improved our understanding of cross regulation of coagulation and fibrinolysis. As TAFI is an enzyme that is activated by thrombin generated by the coagulation system, its activation is sensitive to the dynamics of the coagulation system. Defects in coagulation, such as in thrombosis or hemophilia, resonate in TAFI-mediated regulation of fibrinolysis and imply that clinical symptoms of coagulation defects are amplified by unbalanced fibrinolysis. Thrombomodulin promotes the generation of both antithrombotic activated protein C (APC) and prothrombotic (antifibrinolytic) activated TAFI, illustrating the paradoxical effects of thrombomodulin on the regulation of coagulation and fibrinolysis. This review will discuss the role of TAFI in the regulation of fibrinolysis and detail its regulation of activation and its potential therapeutic applications in thrombotic disease and bleeding disorders.     

Reduced activity of TAFI (thrombin-activatable fibrinolysis inhibitor) in acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) is a disease that is distinguished from other leukaemias by the high potential for early haemorrhagic death. Several processes are involved, such as disseminated intravascular coagulation and hyperfibrinolysis. Recently, TAFI (thrombin-activatable fibrinolysis inhibitor) was identified as a link between coagulation and fibrinolysis. TAFI can be activated by thrombin, and in its activated form potently attenuates fibrinolysis by removing C-terminal lysine and arginine residues that are important for the binding and activation of plasminogen. Activation of TAFI by the coagulation system results in a down-regulation of fibrinolytic activity and, thereby, prevents a rapid dissolution of the fibrin clot. To establish whether TAFI was involved in the severity of the bleeding complications in APL, the TAFI antigen and activity levels were determined in a group of 15 patients. The TAFI antigen concentration was normal, but the activity of TAFI was severely reduced in APL by approximately 60%. The reduction of TAFI activity was most probably caused by the action of plasmin on TAFI because in vitro experiments revealed that plasmin slightly reduced antigen levels but severely reduced TAFI activity. The acquired functional TAFI deficiency in APL may contribute to the severity of the haemorrhagic diathesis because of the impaired capacity of the coagulation system to protect the fibrin clot from fibrinolysis.     

Total thrombin-activatable fibrinolysis inhibitor (TAFI) antigen and pro-TAFI in patients with haemophilia A

Pro-thrombin-activatable fibrinolysis inhibitor (pro-TAFI), also known as TAFI, procarboxypeptidase U, or procarboxypeptidase B, is a relatively recently described plasma glycoprotein synthesized in the liver. It can be catalysed into its active form, TAFI (TAFIa, carboxypeptidase U or B) by a complex of thrombin/thrombomodulin. TAFI can potentially inhibit fibrinolysis by removing carboxyterminal lysine residues from partially degraded fibrin, decreasing plasminogen binding on the surface of fibrin, which thereby results in a decrease of the fibrinolytic activity. As TAFI represents a connection between coagulation and fibrinolysis, it can be expected that TAFI levels are altered in different thrombotic and haemorrhagic diseases, such as haemophilia A. Total TAFI antigen (including pro-TAFI, TAFI and the inactive form of TAFI [TAFIi]) and pro-TAFI were determined in 17 patients with haemophilia A. Thirteen healthy age-matched volunteers served as controls. No significant difference in levels of total TAFI antigen was observed between controls and patients with haemophilia, although it was slightly decreased in patients with haemophilia. Pro-TAFI was significantly reduced in haemophilia patients compared to controls (P=0.0113). TAFI antigen levels similar to controls have already been described in different clinical conditions, including haemophilia A. Decrease of pro-TAFI in haemophilia A can be an additional factor, together with decrease in thrombin generation, which induces impaired activation of pro-TAFI to TAFI, and could cause accelerated fibrinolysis. This supports the validity of usage of antifibrinolytics in the treatment of haemophilia A. In this paper we use new nomenclature for TAFI, and we believe that this recommended terminology for different forms of TAFI can simplify further standardization in TAFI investigation.     

Thrombin activatable fibrinolysis inhibitor (TAFI) and its importance in the regulation of fibrinolysis

Thrombin activatable fibrinolysis inhibitor (TAFI) also named procarboxypeptidase U (CPU), procarboxypeptidase R (CPR) and plasma procarboxypeptidase B (CPB) provides an important link between fibrinolysis and coagulation cascade. Activated TAFI (TAFIa) reduces a generation of plasmin because it cleaves off the carboxy-terminal lysine residues from partially degraded fibrin and thereby abrogates the fibrin cofactor function in the tPA-mediated catalysis of plasminogen to plasmin. TAFI is activated by thrombin-thrombomodulin complex. TAFI transformation to the activated TAFI (TAFIa) induced by thrombin supports the important role of coagulation cascade in regulation of fibrinolysis. This can be proved by a fact that the patients with a factor XI (FXI) deficiency are prone to bleeding from tissues with a high local fibrinolytic activity (urinary tract, nose, oral cavity, tonsils) that can be explained by a decreased thrombin-mediated TAFI activation. On the other hand the prothrombotic mutation of factor V (FV Leiden) associated with a resistance to activated protein C (APC-resistance) possess both mechanisms-an increased thrombin generation in coagulation cascade and a down regulation of fibrinolysis by a way of the thrombin-induced TAFI activation. For the future an inhibition of TAFI (e.g. by FXI inhibitors) offers the therapeutic possibilities to improve the decreased fibrinolysis and increase the efficiency of fibrinolytic therapy in thrombotic disorders. In bleeding disorders (hemophilia A, B) the drugs with a higher efficiency of TAFI for down regulation of an increased fibrinolysis could be used.     

Thrombin activatable fibrinolysis inhibitor and its relationship to fibrinolysis and inflammation during the acute and convalescent phase of ischemic stroke.

To investigate thrombin activatable fibrinolysis inhibitor (TAFI) in ischemic stroke and its relationship to fibrinolysis and inflammation, we investigated 32 patients with ischemic stroke during the acute phase and after 60 days. TAFI antigen levels, global markers of hemostasis (coagulation and fibrinolysis) and inflammatory markers were measured in plasma. TAFI antigen levels were significantly elevated at admission (128%; 109-151%) and at day 1 (129%; 109-152%) compared with day 60 (108%; 91-127%; both P < 0.01) and with healthy control individuals (99%; 76-122%; P < 0.05). In parallel, fibrinolysis assessed as the overall fibrinolysis potential (OFP), part of the overall hemostatic potential assay (OHP), was decreased at all time points compared with control individuals (P < 0.01 for all) and was found to be inversely related to TAFI (r = -0.40; P = 0.0008; n = 20). The OFP and the overall coagulation potential (another part of the OHP assay), and to a lesser degree TAFI, showed significant relationships to C-reactive protein and fibrinogen. In conclusion, elevated TAFI antigen levels may be a consequence of an acute phase reaction, and together with a depressed OFP suggest impaired fibrinolysis in patients with acute ischemic stroke. The OHP method may be useful as a complement to standard hemostatic variables in evaluating hemostasis in stroke patients.     

The in-vitro effect of fibrinogen, factor XIII and thrombin-activatable fibrinolysis inhibitor on clot formation and susceptibility to tissue plasminogen activator-induced fibrinolysis in hemodilution model

Patients suffering major traumatic or surgical bleeding are often exposed to hemodilution resulting in dilutional coagulopathy. The aim of this study was to evaluate in vitro the effects of fibrinogen, factor XIII and thrombin-activatable fibrinolysis inhibitor (TAFI) on clot formation and resistance to fibrinolysis in hemodilution conditions. Citrated whole blood from 36 healthy volunteers was diluted to 30 and 60% with lactated Ringer's solution. Blood samples were subsequently supplemented with fibrinogen, FXIII, TAFI or their combinations. Rotation thromboelastometry (ROTEM) in whole blood and thrombin generation in plasma were performed in the presence of CaCl? and tissue factor/EXTEM reagent, and fibrinolysis was induced by tissue plasminogen activator (tPA). Hemodilution was expressed by decrease of peak height in thrombin generation and α-angle and maximum clot firmness (MCF) in ROTEM. Fibrinogen, FXIII or TAFI did not correct the decrease in thrombin generation peak height. In ROTEM, spiking of diluted blood with fibrinogen stimulated clot propagation. In tPA-treated blood fibrinogen, FXIII and TAFI increased clot firmness and inhibited fibrinolysis. Stronger protection against fibrinolysis was achieved combining FXIII with TAFI. Hemodilution was associated with inhibition of thrombin generation; however, this effect was not sensitive to blood spiking with fibrinogen, FXIII and TAFI. In ROTEM, these hemostasis agents improved clot strength and decreased clot susceptibility to tPA in nondiluted and to more extent in diluted blood. The maximal protection against fibrinolysis was caused by TAFI. Combining FXIII with TAFI exerted synergistic inhibitory effect on fibrinolysis.     

Evaluation of the profibrinolytic properties of an anti-TAFI monoclonal antibody in a mouse thromboembolism model

The enhancement of fibrinolysis constitutes a promising approach to treat thrombotic diseases. Activated thrombin activatable fibrinolysis inhibitor (TAFIa) attenuates fibrinolysis and is an attractive target to develop profibrinolytic drugs. TAFI can be activated by thrombin, thrombin/thrombomodulin, or plasmin, but the in vivo physiologic TAFI activator(s) are unknown. Here, we generated and characterized MA-TCK26D6, a monoclonal antibody raised against human TAFI, and examined its profibrinolytic properties in vitro and in vivo. In vitro, MA-TCK26D6 showed a strong profibrinolytic effect caused by inhibition of the plasmin-mediated TAFI activation. In vivo, MA-TCK26D6 significantly decreased fibrin deposition in the lungs of thromboembolism-induced mice. Moreover, in the presence of MA-TCK26D6, plasmin-α(2)-antiplasmin complexes in plasma of thromboembolism-induced mice were significantly increased compared with a control antibody, indicative of an acceleration of fibrinolysis through MA-TCK26D6. In this study, we show that plasmin is an important TAFI activator that hampers in vitro clot lysis. Furthermore, this is the first report on an anti-TAFI monoclonal antibody that demonstrates a strong profibrinolytic effect in a mouse thromboembolism model.     

Thrombin-activatable fibrinolysis inhibitor deficiency in cirrhosis is not associated with increased plasma fibrinolysis.

BACKGROUND AND AIMS: The bleeding tendency of patients suffering from cirrhosis is in part ascribed to accelerated fibrinolysis. In this study, the role of the recently discovered inhibitor of fibrinolysis, thrombin-activatable fibrinolysis inhibitor (TAFI) in cirrhosis was examined. METHODS: In 64 patients with cirrhosis of varying severity, TAFI antigen levels were measured by enzyme-linked immunosorbent assay and compared with TAFI levels in control subjects. Furthermore, a plasma-based fibrinolysis assay was performed in the presence and absence of a specific inhibitor of activated TAFI. RESULTS: TAFI levels were decreased in cirrhosis. Mean TAFI levels were 66% in Child's A, 55% in Child's B, 47% in Child's C cirrhosis, and 26% in acute liver failure. Decreased TAFI antigen levels were highly correlated with antithrombin and alpha(2)-antiplasmin activity levels. Clot lysis times and clot lysis ratio (defined as ratio between clot lysis time in the absence and presence of a specific inhibitor of activated TAFI) of cirrhotics were not significantly different from healthy controls. CONCLUSIONS: Despite decreased levels of TAFI and other components of the fibrinolytic system, no evidence of increased plasma fibrinolytic potential in cirrhosis is observed using the plasma-based assay of this study. The reduction of antifibrinolytic factors in cirrhosis is compensated by the concomitant reduction in profibrinolytics.     

Identification of thrombin activatable fibrinolysis inhibitor (TAFI) in human platelets

Thrombin activatable fibrinolysis inhibitor (TAFI) is a carboxypeptidase B-like proenzyme that after activation down-regulates fibrinolysis. Platelets are known to contain antifibrinolytic factors that are secreted during platelet activation. Therefore, the presence of TAFI in platelets was analyzed. TAFI was identified in platelets in a concentration of about 50 ng/1 x 109 platelets and was secreted on platelet activation. Thrombin-mediated activation of platelet-derived TAFI resembled that of plasma-derived TAFI with respect to stimulation by thrombomodulin and spontaneous loss of activity at 37 degrees C. The different glycosylation of platelet-derived TAFI compared with plasma-derived TAFI suggests that platelet-derived TAFI is synthesized in the megakaryocyte. This suggestion was substantiated by the detection of mRNA in the megakaryocytic cell lines DAMI and CHRF, representing the intermediate and late stages of megakaryocyte development. These results establish the presence of TAFI in platelets and suggest a role for platelet-derived TAFI in the protection of the clot against fibrinolysis.     

Quantification of the effects of thrombin activatable fibrinolysis inhibitor and alpha2-antiplasmin on fibrinolysis in normal human plasma.

Two major proteins that inhibit fibrinolysis include thrombin activatable fibrinolysis inhibitor (TAFI) and alpha2-antiplasmin. Our goal was to quantify the contribution of TAFI and alpha2-antiplasmin to antifibrinolytic defenses with thrombelastography. Plasma activated with tissue factor/kaolin was subjected to fibrinolysis with tissue-type plasminogen activator (100 U/ml). Prior to activation, TAFI activity was inhibited with either potato carboxypeptidase inhibitor (25 microg/ml) or an anti-TAFI antibody, and alpha2-antiplasmin activity was inhibited with an anti-alpha2-antiplasmin antibody. Data were collected for 30 min, with the time of onset and rate of fibrinolysis determined. Compared with uninhibited samples, TAFI inhibition significantly (P < 0.05) decreased the time of onset of fibrinolysis by 70% and increased the rate of lysis by 70%. There was no difference between potato carboxypeptidase inhibitor and anti-TAFI antibody inhibition. Inhibition of alpha2-antiplasmin resulted in a significantly (P < 0.05) decreased time of onset (85%) and increased the rate of lysis (557%) compared with uninhibited samples. Inhibition of alpha2-antiplasmin activity resulted in a significantly (P < 0.05) greater fibrinolytic response than TAFI inhibition. In conclusion, utilization of standard inhibitors and thrombelastography permitted quantification of the effects of TAFI and alpha2-antiplasmin on fibrinolysis in plasma. Future investigation of diseases involving hypofibrinolysis (e.g. left ventricular assist devices) could be conducted using this assay system.