PAI与细胞凋亡

纤溶酶原激活物(PA)系统是体内重要的蛋白溶解复合物系统,主要参与降解细胞外基质。纤溶酶原激活物抑制剂(PAI),主要有PAI-1、PAI-2,是纤溶酶原激活物t-PA和u-PA的有效抑制物。最近研究证明,PAI与细胞凋亡存在较密切的关系:PAI-1和PAI-2可抑制细胞凋亡的发生;细胞内PAI-2的裂解产物可作为细胞凋亡的标志等。     

rt-PA动脉溶栓联合血管内支架成形术对早期急性脑梗死患者纤溶系统和血清神经功能损伤指标的影响

摘要 目的：探讨重组人组织型纤溶酶原激活物（rt-PA）动脉溶栓联合血管内支架成形术治疗早期急性脑梗死（ACI）的疗效及对纤溶系统和血清神经功能损伤指标的影响。方法：选取我院2018年9月~2021年3月间接收的80例早期ACI患者。根据随机数字表法分为对照组38例（rt-PA动脉溶栓治疗）和研究组42例（rt-PA动脉溶栓联合血管内支架成形术治疗）。对比两组血管再通情况、纤溶系统和血清神经功能损伤指标变化、日常生活能力量表（ADL）及美国国立卫生研究院卒中量表（NIHSS）评分,观察两组预后情况。结果：研究组的血管完全再通率高于对照组（P<0.05）。研究组治疗后1 d、治疗后7 d、治疗后3个月NIHSS评分低于对照组,ADL评分高于对照组（P<0.05）。研究组治疗7 d后血管性假血友病因子（vWF）、血浆纤溶酶原激活物抑制剂-1（PAI-1）低于对照组,组织型纤溶酶原激活剂（tPA）高于对照组（P<0.05）。研究组治疗7 d后胶质纤维酸性蛋白（GFAP）、神经元特异性烯醇化酶（NSE）、S100β蛋白低于对照组（P<0.05）。研究组患者的再发脑梗死率、死亡率低于对照组（P<0.05）。结论：rt-PA动脉溶栓联合血管内支架成形术治疗早期ACI患者,可改善患者近远期疗效和预后,有效调节纤溶系统,减轻机体神经功能损伤,提高患者日常生活能力。     

微创介入治疗对急性脑梗死患者血清相关细胞因子及生活质量的影响

目的:探讨微创介入治疗对急性脑梗死患者血清相关细胞因子及生活质量的影响。方法:选择2014年10月-2016年4月我院收治的70例急性脑梗死患者作为研究对象,按照数字列表法随机分为观察组和对照组,各35例,对照组给予药物溶栓保守治疗及常规治疗,观察组在常规治疗基础上行脑血管球囊成形支架置入术,比较两组患者治疗前后血管内皮生长因子(VEGF)、神经营养因子(NTF)、神经生长因子(NGF)水平,并采用SF-36量表评价两组患者治疗前后生活质量。结果:1治疗后两组患者VEGF、NTF及NGF水平均显著高于治疗前,且观察组均显著高于对照组,比较差异均有统计学意义(均P0.05);2治疗后两组患者SF-36总分显著高于治疗前,且观察组显著高于对照组,比较差异有统计学意义(P0.05)。结论:采用微创介入治疗急性脑梗死患者,能够显著提高其血清相关细胞因子水平,并明显改善患者生活质量,值得临床推广。     

三七皂苷Rg1对tPA和PAI-1活性的调节作用

探讨三七皂苷Rg1对组织型纤溶酶原激活物(tPA)和纤溶酶原激活物抑制物(PAI-1)活性的调节作用。运用发色底物方法测定三七皂苷Rg1在体外和静脉注射对家兔血浆纤溶酶原激活物(tPA)和血浆或血小板释放的纤溶酶原激活物抑制物(PAI-1)水平的影响。结果表明,三七皂苷Rg1在体外呈浓度依赖性明显抑制血浆PAI-1活性,同时提高血浆tPA活性;30和60 mg/kg的三七皂苷Rg1静脉注射显著抑制血浆PAI-1活性,提高血浆tPA活性,同时降低凝血酶激活的血小板所释放的PAI-1水平。本实验提示三七皂苷Rg1能抑制PAI-1活性,同时升高tPA活性可能是其抗血栓作用的分子机制之一。     

阿托伐他汀强化降脂治疗急性脑梗死的疗效及对TNF-α、IL-10、IL-18、MMP-9水平的影响

目的:探讨阿托伐他汀强化降脂治疗急性脑梗死(ACI)的临床疗效,并分析其对肿瘤坏死因子-α(TNF-α)、白细胞介素-10(IL-10)、白细胞介素-18(IL-18)及基质金属蛋白酶-9(MMP-9)水平的影响。方法:选取2015年3月-2016年12月我院收治的82例ACI患者,采用随机数字表法随机分为强化组(n=41)与常规组(n=41)。在常规治疗的基础上,常规组患者给予20 mg/次的阿托伐他汀治疗,强化组患者给予40 mg/次的阿托伐他汀治疗,两组均连续治疗8w。治疗结束后对比两组患者的临床疗效,对比两组患者治疗前后总胆固醇(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)、组织型纤溶酶原激活物(t-PA)、血浆纤溶酶原激活物抑制剂-1(PAI-1)、血浆纤维蛋白原(FIB)、TNF-α、IL-10、IL-18、MMP-9水平。结果:强化组与常规组患者的总有效率分别为95.12%、80.49%,与常规组对比,强化组患者的临床总有效率明显升高(P0.05);两组患者治疗后的TC、TG、LDL-C、PAI-1、FIB、TNF-α、IL-18、MMP-9水平均较治疗前显著降低,HDL-C、t-PA、IL-10水平均显著升高(P0.05),且治疗后强化组患者的TC、TG、LDL-C、PAI-1、FIB、TNF-α、IL-18、MMP-9水平均低于常规组,HDL-C、t-PA、IL-10均高于常规组(P0.05)。结论:阿托伐他汀强化降脂治疗ACI疗效较好,能够显著改善患者血脂、纤溶系统及炎症因子相关指标水平,具有降脂、调节纤溶活性及抑制炎症的作用。     

急性脑梗死患者相关生化指标检测的临床意义

目的：探讨急性脑梗死（ACI）患者治疗前后Hcy、ET-1、hs-CRP、TXA2水平和凝血纤溶指标的变化及临床意义。方法：分别采用ELISA法、发色底物法、凝血酶法、放射免疫法和免疫透射比浊法对68例ACI患者治疗前后Hcy、ET-1、hs-CRP、TXA2和各凝血纤溶指标水平进行检测,并以30例正常健康人作为对照组。结果：①ACI患者治疗前血浆Hcy、ET-1和血清hs-CRP、TXA2含量高于对照组（P〈0.01）,经过治疗,含量均明显下降,其中血浆Hcy、ET-1恢复至正常水平,与对照组间比较差异无统计学意义（P〉0.05）②轻、中、重型组间血浆ET-1和血清hs-CRP、TXA2含量逐渐增加,组间差异有显著性（P〈0.01或0.05）,而中重型患者血浆Hcy含量明显高于轻型患者（P〈0.01）。③经过治疗,ACI患者血浆vWF、GMP-140、Fg和F1＋2含量较治疗前显著下降,而血浆PS活性、PC活性与AT水平较治疗前明显上升（P〈0.01）,其中血浆PS和PC活性与对照组间比较差异无统计学意义（P〉0.05）。④ACI患者血浆中tPA水平低于对照组,血浆PAI-1含量高于对照组（P〈0.01）。治疗后血浆tPA增加,与对照组间差异无统计学意义（P〉0.05）,PAI-1减少,但仍显著高于对照组（P〈0.05）。结论：检测急性脑梗死（ACI）患者Hcy、ET-1、hs-CRP、TXA2和凝血纤溶指标水平的变化对于指导用药、病情观察和预后评估均有重要的临床意义。     

双歧三联活菌肠溶胶囊联合早期肠内营养支持在大面积脑梗死中的应用

目的探讨双歧三联活菌肠溶胶囊联合早期肠内营养支持在大面积脑梗死中的应用。方法选取住院治疗大面积脑梗死患者96例,随机分为观察组和对照组各48例。两组患者予以控制颅内压、血压及血糖、抗血小板聚集、改善微循环及营养和保护脑细胞等基础治疗。对照组患者行肠内营养支持治疗,予以肠内营养液输注泵持续恒速缓慢输注,先500mL/d后逐渐增至1 500~2 000mL/d。观察组患者在对照组基础上加用双歧三联活菌肠溶胶囊630mg研磨水化后自鼻饲注入,3次/d,连用4周。观察两组患者治疗前和治疗4周后营养状况指标、GCS评分、粪便分泌型IgA(sIgA)和胃肠功能的变化,并评估其临床疗效。结果治疗4周后,两组患者血清总蛋白(TP)和白蛋白(ALB)指标明显下降(t=2.26、2.37、2.92、3.07,P0.05或P0.01),且观察组下降幅度低于对照组(t=2.23、2.21,P0.05);两组患者GCS评分明显上升(t=2.39、3.27,P0.05或P0.01),且观察组上升幅度更明显(t=2.19,P0.05);两组患者粪便sIgA水平明显上升(t=2.35、3.14,P0.05或P0.01),且观察组上升幅度更明显(t=2.18,P0.05);治疗期间,观察组治疗时胃肠功能情况优于对照组(χ2=5.44,P0.05);治疗4周后,在总有效率上观察组优于对照组(χ2=4.38,P0.05)。结论双歧三联活菌肠溶胶囊联合早期肠内营养支持用于大面积脑梗死临床疗效较确切,促进神经功能康复,推测其可能通过提高患者粪便sIgA水平,改善其胃肠功能,从而减缓其营养状况恶化,提高GCS评分,改善其预后。     

动脉瘤性蛛网膜下腔出血患者vWF、GMP-140及ADAMTS13的表达水平及临床意义

目的:探讨动脉瘤性蛛网膜下腔出血(aSAH)患者中血管性假血友病因子(v WF)、血小板膜糖蛋白-140(GMP-140)、血管性血友病因子裂解蛋白酶(ADAMTS13)的表达水平及临床意义。方法:选取2014年1月至2016年12月我院神经外科收治的83例aSAH患者,分为脑血管痉挛(CVS)组37例和无CVS组46例;迟发性脑缺血(DCI)组31例和非DCI组52例;根据不同动脉瘤直径分为5 mm组43例,5-10 mm组29例,10 mm组11例;预后良好组49例和预后不良组34例,检测aSAH患者血浆v WF、GMP-140、ADAMTS13水平,并分析各指标之间的相关性。结果:CVS组患者第4 d、10 d血浆v WF水平高于非CVS组,第1 d、4 d、10 d血浆GMP-140水平高于非CVS组,第1 d、10 d血浆ADAMTS13水平低于非CVS组,差异均有统计学意义(P0.05)。DCI组患者第1 d血浆v WF水平高于非DCI组,ADAMTS13水平低于非DCI组,第4 d血浆v WF、GMP-140水平高于非DCI组,差异均有统计学意义(P0.05)。10 mm组患者第1 d、4 d血浆v WF、GMP-140水平高于5 mm组和5-10 mm组,且5-10 mm组第4d的血浆v WF水平、第1 d的血浆,水平均高于5 mm组,差异有统计学意义(P0.05);10 mm组患者第1d的血浆ADAMTS13水平低于5 mm组和5-10 mm组,且5-10 mm组低于5 mm组,差异有统计学意义(P0.05)。预后良好组患者第4 d、10 d血浆v WF水平低于预后不良组,第1 d、4 d、10 d血浆GMP-140水平低于预后不良组,第1 d、4 d血浆ADAMTS13水平高于预后不良组,差异均有统计学意义(P0.05)。Pearson相关分析结果显示,第1 d、4 d血浆v WF与GMP-140呈正相关,与ADAMTS13呈负相关,GMP-140与ADAMTS13呈负相关(r=0.334、-0.426、-0.398、0.278、-0.311、-0.235,P0.05),第10 d血浆v WF、GMP-140、ADAMTS13之间无明显相关性(P0.05)。结论:v WF、GMP-140、ADAMTS13与CVS、DCI、动脉瘤直径以及预后密切相关,联合检测有助于综合评估aSAH患者病情,改善预后,值得临床推广。     

急性脑梗死患者相关生化指标检测的临床意义

目的:探讨急性脑梗死(ACI)患者治疗前后Hcy、ET-1、hs-CRP、TXA2水平和凝血纤溶指标的变化及临床意义。方法:分别采用ELISA法、发色底物法、凝血酶法、放射免疫法和免疫透射比浊法对68例ACI患者治疗前后Hcy、ET-1、hs-CRP、TXA2和各凝血纤溶指标水平进行检测,并以30例正常健康人作为对照组。结果:①ACI患者治疗前血浆Hcy、ET-1和血清hs-CRP、TXA2含量高于对照组(P<0.01),经过治疗,含量均明显下降,其中血浆Hcy、ET-1恢复至正常水平,与对照组间比较差异无统计学意义(P>0.05)②轻、中、重型组间血浆ET-1和血清hs-CRP、TXA2含量逐渐增加,组间差异有显著性(P<0.01或0.05),而中重型患者血浆Hcy含量明显高于轻型患者(P<0.01)。③经过治疗,ACI患者血浆vWF、GMP-140、Fg和F1+2含量较治疗前显著下降,而血浆PS活性、PC活性与AT水平较治疗前明显上升(P<0.01),其中血浆PS和PC活性与对照组间比较差异无统计学意义(P>0.05)。④ACI患者血浆中tPA水平低于对照组,血浆PAI-1含量高于对照组(P<0.01)。治疗后血浆tPA增加,与对照组间差异无统计学意义(P>0.05),PAI-1减少,但仍显著高于对照组(P<0.05)。结论:检测急性脑梗死(ACI)患者Hcy、ET-1、hs-CRP、TXA2和凝血纤溶指标水平的变化对于指导用药、病情观察和预后评估均有重要的临床意义。     

Ⅱ型糖尿病视网膜病变与纤溶系统的关系探讨

目的:探讨2型糖尿痛视网膜病变与纤溶系统的关系。方法:随机选取2型糖尿病视网膜痛变患者30例,无并发症患者30例,健康人30例,测定血浆纤溶酶原、纤溶酶原激活抑制物,纤溶酶原(PLG)、纤溶酶原激活抑制物(PAI-1)均采用发色底物法检测。结果:与对照组相比2型糖尿病患者血浆PLG、PAI-1水平升高(P＜0．05),糖尿病视网膜病变组升高更明显(P＜0．01)。结论:糖尿病患者血液存在低纤状态,当发生视网膜并发症者更为明显,检测2型糖尿病患者血浆PLG、PAI-1水平对糖尿痛视网膜病变的预防及治疗具有一定的临床意义。     

Enhancement by homocysteine of plasminogen activator inhibitor-1 gene expression and secretion from vascular endothelial and smooth muscle cells

In order to elucidate the relationship between homocysteine and the fibrinolytic system, we examined the effect of homocysteine on plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (tPA) gene expression and protein secretion in cultured human vascular endothelial and smooth muscle cells in vitro. PAI-1 mRNA and secreted protein levels were both enhanced by homocysteine in a dose dependent manner, with significant stimulation of PAI-1 secretion observed at concentrations greater than 0.5 mM homocysteine. In contrast, secretion and mRNA expression of tPA were not significantly altered by homocysteine stimulation. Secretion of TGFbeta (transforming growth factor beta) and TNFalpha (tumor necrosis factor alpha), possible regulators of PAI-1 expression and secretion, were not stimulated by treatment with 1.0 mM homocysteine. These results suggests that hyperhomocysteinemia-induced atherosclerosis and/or thrombosis may be caused by homocysteine-induced stimulation of PAI-1 gene expression and secretion in the vasculatures by a mechanism independent from paracrine-autocrine activity of TGFbeta and TNFalpha.     

Pathophysiological changes of gram-negative bacterial infection can be reproduced by a synthetic peptide mimicking loop L7 sequence of Haemophilus influenzae porin

Several in vivo models have been used to dissect the molecular mechanisms that contribute to activate the coagulation and fibrinolytic systems by bacteria and bacterial products but many aspects remain poorly understood. In this study we examined the in vivo effect of the synthetic peptide corresponding to loop L7 from Haemophilus influenzae type b (Hib) porin to evaluate its role on the coagulative/fibrinolytic cascade and the circulating markers of endothelial injury. Plasma was obtained from rats injected intravenously with loop L7, Hib porin or a scrambled peptide and tested for fragment 1+2 (F1+2), tissue-type plasminogen activator (tPA), plasminogen activator inhibitor type I (PAI-1) antigen, von Willebrand factor (vWF) and soluble E-selectin (sE-selectin). The coagulative/fibrinolytic cascade was impaired as shown by PAI-1 level increased. Concomitantly, E-selectin, a marker of endothelial injury, was also significantly elevated. In addition either loop L7 or Hib porin injection induced hyperglycaemia and inflammatory cytokine production. The data were correlated with hemodynamic functions. The results indicate that loop L7 plays an essential role in the pathophysiologic events observed during gram-negative infection. These findings may have implications for the development of alternative therapies to counteract excessive inflammatory responses during septic shock.     

Biological control of tissue plasminogen activator-mediated fibrinolysis

Fibrinolysis, the body's ability to degrade fibrin, is an integrated part of hemostasis. Overactivity in the fibrinolytic system causes bleeding and underactivity causes thrombosis. Tissue plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1), alpha 2-antiplasmin (alpha 2-AP) and plasminogen are definitely involved in fibrinolysis because: (1) these components can be assigned a fibrinolytic role in purified systems, i.e. in vitro, and (2) abnormal structural variants and abnormal levels of these components give rise to bleeding or to thrombosis. The biological control of tPA-mediated fibrinolysis is both cellular and humoral. The cellular regulation compasses synthesis of tPA and PAI-1 and release/uptake of these components. The humoral regulation involves: (1) the reaction between tPA and PAI-1; (2) the fibrin-stimulated plasminogen activation; (3) the reaction between plasmin and alpha 2-AP and (4) plasmin degradation of fibrin. The highly developed biological control of tPA-mediated fibrinolysis is indicative of its physiological importance.     

Tissue plasminogen activator and plasminogen activator inhibitor 1 contribute to sonic hedgehog-induced in vitro cerebral angiogenesis

The molecular mechanisms underlying cerebral angiogenesis have not been fully investigated. Using primary mouse brain endothelial cells (MBECs) and a capillary-like tube formation assay, we investigated whether the sonic hedgehog (Shh) signaling pathway is coupled with the plasminogen/plasmin system in mediating cerebral angiogenesis. We found that incubation of MBECs with recombinant human Shh (rhShh) substantially increased the tube formation in naïve MBECs. This was associated with increases in tissue plasminogen activator (tPA) activation and reduction of plasminogen activator inhibitor 1 (PAI-1). Blockage of the Shh pathway with cyclopamine abolished the induction of tube formation and the effect of rhShh on tPA and PAI-1. Addition of PAI-1 reduced rhShh-augmented tube formation. Genetic ablation of tPA in MBECs impaired tube formation and downregulated of vascular endothelial growth factor (VEGF) and angiopoietin 1 (Ang1). Addition of rhShh to tPA−/− MBECs only partially restored the tube formation and upregulated Ang1, but not VEGF, although rhShh increased VEGF and Ang1 expression on wild-type MBECs. Complete restoration of tube formation in tPA−/− MBECs was observed only when both exogenous Shh and tPA were added. The present study provides evidence that tPA and PAI-1 contribute to Shh-induced in vitro cerebral angiogenesis.     

Expression of plasminogen activator and plasminogen activator inhibitor mRNA in human fibroblasts grown on different substrates

mRNA levels for urokinase type plasminogen activator (uPA), tissue type plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator inhibitor-2 (PAI-2) were examined in human diploid (neonatal foreskin) fibroblasts grown in 200-ml microcarrier suspension culture. Four different substrates were used. These included gelatin-coated polystyrene plastic, DEAE-dextran, glass-coated polystyrene plastic and uncoated polystyrene plastic. Our previous studies have shown that culture fluids from diploid fibroblasts grown on DEAE-dextran contained higher levels of plasminogen-dependent fibrinolytic activity than culture fluids from the same cells grown on other substrates. The increased plasminogen activator activity was due largely to elevated amounts of tPA (In Vitro Cell. Develop. Biol. 22: 575–582, 1986). The present study shows that there is a corresponding elevation of tPA mRNA in diploid fibroblasts cultured on DEAE-dextran relative to the other substrates. There does not appear to be any difference in uPA mRNA or in mRNA for PAI-1 or PAI-2 produced by the same cells on the four substrates. These data suggest that the influence of the substrate on plasminogen activator production is mediated at the genetic level.     

Reciprocal regulation of tissue-type and urokinase-type plasminogen activators in the differentiation of murine preadipocyte line 3T3-L1 and the hormonal regulation of fibrinolytic factors in the mature adipocytes

Adipose tissue expresses a variety of genes including tumor necrosis factor alpha and type-1 plasminogen activator inhibitor (PAI-1); and these factors, produced by adipocytes, may be associated with the risk of coronary events in obesity. In this study, we characterized the production of fibrinolytic factors including tissue-type plasminogen activator (tPA), urokinase-type PA (uPA), and PAI-1 in the differentiation of preadipocytes, and examined the hormonal regulation of these fibrinolytic factors in mature adipocytes. Mouse 3T3-L1 preadipocytes were employed as a model of adipocytes. Adipocyte differentiation was induced by insulin, dexamethasone, and 3-isobutyl-1-methyl xanthine (IBMX). alpha-Glycerophosphate dehydrogenase (GPDH) activity and glucose transporter 4 (GLUT4) mRNA, indices for adipocyte maturation, were induced on Day 4, and gradually increased. GPDH activity reached its maximum level on Day 14. The level of tPA, a major PA in preadipocytes, dramatically decreased with differentiation. On the other hand, that of uPA reciprocally increased. PAI-1 production was also dramatically induced concomitant with differentiation. In mature adipocytes, uPA production was dominant (25 microg/ml/24 h vs. 0.8 microg/ml/24 h for tPA). Total PA activity in the mature adipocytes was reduced by insulin or dexamethasone, but not by glucagon. Insulin, IBMX, and dexamethasone significantly decreased both uPA and tPA production, and increased PAI-1 production. Glucagon had no effect on the production of these fibrinolytic factors. Our results reveal that uPA is one of the markers for the differentiation of 3T3-L1 cells and that insulin, IBMX, and dexamethasone are potent regulators of the fibrinolytic activity in differentiated 3T3-L1 cells, reciprocally affecting PA and PAI-1 levels in them.     

Fibrinolytic activity is not dependent upon exercise mode in post-myocardial infarction patients

In this study we investigated possible differences in fibrinolytic activity in cardiac patients while they performed treadmill and cycle ergometry. Thirteen post-myocardial infarction patients completed two maximal exercise tests on treadmill and cycle ergometers. Blood was collected before and after each exercise test and was analyzed for the fibrinolytic variables, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) activity, and lactate. Maximal oxygen uptake, heart rate, and ventilation were greater (P < 0.05) on the treadmill than during cycle ergometry, however, blood lactate was similar between modes. t-PA activity significantly increased with exercise (P < 0.05) and there was a trend toward a reduction in PAI-1 activity with exercise, but this did not reach statistical significance. The fibrinolytic responses to maximal exercise did not differ between the two modes of exercise studied. Therefore, exercise intensity, but not the mode of exercise, appeared to be the primary determinant of the fibrinolytic response to acute exercise in these patients. Accepted: 29 January 1998     

Rt-PA静脉溶栓治疗急性脑梗死的疗效及对血清IL-6，IL-17及VEGF水平的影响

目的:探讨重组组织纤溶酶原激活剂(Rt-PA)静脉溶栓治疗急性脑梗死的疗效及对血清白介素-6(IL-6)、IL-17及血管内皮生长因子(VEGF)水平的影响。方法:选择2014年8月至2016年8月我院接诊的86例急性脑梗死患者,通过随机数表法分为观察组(n=43)和对照组(n=43)。对照组给予常规治疗,观察组在对照组基础上进行Rt-PA静脉溶栓。比较两组的治疗效果、不良反应的发生情况、治疗前后美国国立卫生研究院卒中量表(NIHSS)评分、Barthel指数、血清IL-6、IL-17及VEGF水平的变化。结果:治疗14 d后,观察组NIHSS评分显著低于对照组,Barthel指数明显高于对照组(P0.05);观察组在治疗后1 d、3 d、7 d、14 d时血清IL-6、IL-17水平均显著低于对照组(P0.05),治疗后1 d、3 d、7 d时血清VEGF水平明显高于对照组,治疗后14 d时血清VEGF水平显著低于对照组(P0.05)。观察组治疗后总有效率显著高于对照组(P0.05)。结论:在急性脑梗死患者中早期采用Rt-PA治疗的效果显著,可有效促进神经功能恢复,且安全性高,可能与其降低血清IL-6、IL-17、VEGF水平有关。     

Role of residue Y99 in tissue plasminogen activator

The crystal structure of the fibrinolytic enzyme tissue plasminogen activator (tPA) shows that the bulky side chain of Y99 hinders access to the active site by partially occluding the S2 site and may be responsible for the low catalytic activity of tPA toward plasminogen. We have tested the role of Y99 by replacing it with Leu, the residue found in more proficient proteases like trypsin and thrombin. The Y99L replacement results in an increase in the k(cat)/Km for chromogenic substrates due to enhanced diffusion into the active site. The increase is modest (threefold) for substrates specific for tPA that carry Pro or Gly at P2, but reaches 80-fold for less specific substrates carrying Arg at P2. On the other hand, the Y99L mutation has no effect on the activity of tPA toward the natural substrate plasminogen, that carries Gly at P2, and reduces more than 10-fold the inhibition of tPA by plasminogen activator inhibitor-1 (PAI-1), that carries Ala at P2. We conclude that the steric hindrance provided by Y99 in the crystal structure affects mostly nonphysiological substrates with bulky residues at P2. In addition, residue Y99 plays an active role in the recognition of PAI-1, but not plasminogen. Mutations of Y99 could therefore afford a resistance to inhibition by PAI-1 without compromising the fibrinolytic potency of tPA, a result of potential therapeutic relevance.