Prourokinase activation on the surface of human rhabdomyosarcoma cells: localization and inactivation of newly formed urokinase-type plasminogen activator by recombinant class 2 plasminogen activator inhibitor.

Recombinant class 2 plasminogen activator inhibitor (PAI-2) was used in an approach to probe the formation and location of enzymatically active urokinase-type plasminogen activator (u-PA) sites on the surface of cultured human rhabdomyosarcoma cells (RD cells). Activation of pro-u-PA on the cell surface and consequent binding of PAI-2 was dependent on the addition of native plasminogen to serum cultures of the cells. Inhibition of the enzyme activity of surface-bound u-PA by the added PAI-2 resulted in a 79% reduction in the capacity of the RD cells to generate cell surface-associated plasmin activity from bound plasminogen. Under these conditions, the PAI-2 probe was localized at focal adhesions of RD cells, where it colocalized with both extracellular u-PA and intracellular vinculin antigens in double immunofluorescence labeling. Specificity of the probe's interaction with cell surface-bound u-PA was confirmed by blocking with a monoclonal antibody to human u-PA, which could also inhibit the formation of bound plasmin activity. These results showed the assembly of the plasmin-generating system at focal adhesions and the accessibility of bound u-PA on which it depends to added PAI-2. Therefore, PAI-2 has the potential both to localize at sites of tumor expression of functionally active u-PA and simultaneously to inhibit cell surface plasminogen activation.     

Urokinase, tissue-type plasminogen activator and plasminogen activator inhibitor-1 expression in severely stenosed and occluded vein grafts with thrombosis.

Intimal hyperplasia and subsequent thrombotic occlusions limit the success of vascular reconstructive procedures. Plasminogen activation in situ may be an important factor affecting re-stenosis of the graft. Tissue specimens from eight patients with failing or failed infra-inguinal vein bypasses and three specimens from normal veins were harvested to study urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) by in situ hybridization and immunohistochemistry. The possible presence of thrombi was monitored by platelet and fibrin-specific stainings. In occluded grafts, platelet endothelial cell adhesion molecule (PECAM-1) antibody stained the thrombi but not the endothelial area, indicating the absence of endothelium. Platelet glycoprotein (GP) IIb/IIIa co-localized with PECAM-1 and, furthermore, GP IIb/IIIa staining was positive on the vein walls with thrombi and to some extent in the grafts without thrombi. PAI-1 and u-PA were uniformly upregulated in intimal thickening in grafts without thrombus. In organized thrombi, enhanced u-PA, t-PA and PAI-1 reactivity was detected in the ingrowing subendothelium. In non-occluded grafts with small thrombi, u-PA expression was enriched beneath microthrombi co-localizing with the graft wall injury, while PAI-1 was scattered in the (sub)endothelium. We conclude that fibrinolytic system is upregulated at sites of graft stenosis, and local proteolytic degradation of the graft wall associates with thrombus formation.     

慢性阻塞性肺疾病患者气道尿激酶型纤溶酶原激活物系统成分的高水平状态

目的研究慢性阻塞性肺疾病(COPD)患者气道局部尿激酶型纤溶酶原激活物(u-PA)系统状态及其病理生理意义。方法(1)诱导痰检测临床稳定期COPD患者(诱导痰COPD组)56例,平均年龄(51±11)岁,第一秒用力呼气容积占预计值百分比(FEV1占预计值%)为(53.5%±14.4)%,诱导痰健康对照组26名,平均年龄(46±9)岁,FEV1占预计值%为(85.1±1.0)%;采用酶联免疫吸附法测定诱导痰中u-PA、尿激酶型纤溶酶原激活物受体(u-PAR)、纤溶酶原激活物抑制剂1(PAI-1)和白细胞介素8(IL-8)、γ干扰素(IFN-γ)、肿瘤坏死因子α(TNF-α)、白细胞介素10(IL-10)水平;(2)肺组织病理COPD并肺大疱接受手术治疗患者(免疫组化COPD组)11例,平均年龄(53±7)岁,FEV1占预计值%为(58.3±6.6)%;非COPD因肺部局灶病变接受手术治疗患者(非免疫组化COPD对照组)10例(其中炎性假瘤3例、错构瘤5例、结核球2例),平均年龄(47±12)岁,FEV1占预计值%为(84.3±1.6)%。采用免疫组化检测u-PA、u-PAR、PAI-1在肺组织中的细胞表达。结果(1)诱导痰COPD组诱导痰中可溶性u-PAR、PAI-1和IL-8水平分别为(570±614)ng/L、(6162±9247)ng/L、(12370±17292)ng/L,与健康对照组[(97±74)ng/L、(574±731)ng/L、(1868±1905)ng/L]比较差异有统计学意义(t值分别为5.629、4.346、4.486,P均<0.01);(2)相关分析诱导痰COPD组诱导痰中可溶性u-PAR和PAI-1水平分别与IL-8呈正相关(r值分别为0.483、0.770,P均<0.01),可溶性PAI-1水平与患者FEV1占预计值%呈负相关(r=-0.272,P<0.05);(3)免疫组化免疫组化COPD组u-PAR表达[(49±16)%]见于肺泡上皮细胞、巨噬细胞、中性粒细胞以及淋巴细胞,而免疫组化非COPD对照组[(33±18)%]表达着色浅淡,主要见于肺泡上皮细胞,两组阳性表达率比较差异有统计学意义(t=2.213,P<0.05);免疫组化COPD组PAI-1表达[(61±16)%]见于成纤维细胞、巨噬细胞和中性粒细胞,而免疫组化非COPD组[(37±16)%]表达着色浅淡,主要见于成纤维细胞,两组阳性表达率比较差异有统计学意义(t=3.419P<0.05)。结论u-PA系统成分是COPD气道局部重要的炎性介质,其中PAI-1在COPD的组织重塑中可能具有重要作用。     

The release of plasminogen activators (t-PA and u-PA) and plasminogen activator inhibitor (PAI-1) after venous stasis.

The aim of the present study was to compare plasma levels of urokinase-type plasminogen activator (u-PA), before and after 20 min of venous stasis, with those of tissue-type plasminogen activator (t-PA), type 1 plasminogen activator inhibitor (PAI-1) and t-PA/PAI-1 complexes, to determine whether both plasminogen activators and their inhibitor respond similarly to the same stimulus. We studied 36 patients with recurrent venous thrombosis in whom no coagulation defects predisposing them to thrombosis had been detected (mean age 38.2 years, range 15-70 years). Twenty healthy individuals (mean age 34.3 years, range 20-60 years) served as a control group. t-PA, PAI-1 and u-PA activity and antigen, as well as the t-PA/PAI-1 complex antigen, were measured before and after venous stasis. Post-stasis fibrinolytic parameters were corrected for the haemoconcentration which occurred during the venous occlusion test. Pathologically high PAI-1 levels (antigen and activity) were found in four out of 36 patients who were excluded from study. Functional and antigenic u-PA increased significantly after venous stasis when analysed as the absolute differences between paired samples (P less than 0.01). This increase in u-PA did not correlate with changes in t-PA or PAI-1 (r = 0.28 and r = 0.36 respectively). This leads us to suggest that different mechanisms relating to clearance and/or release from diverse sources might be involved in elevations of u-PA in response to a local endothelial stimulus. We conclude that venous stasis might not be the elective choice when evaluating 'bad responders' predisposed to thrombosis.     

Hepatocyte growth factor stimulates expression of plasminogen activator inhibitor type 1 and tissue factor in HepG2 cells

HGF is a powerful mitogen for both rat and human hepatocytes, epithelial cells and endothelial cells in vitro, and is angiogenic in vivo. It has considerable homology with plasminogen and has been shown to upregulate urokinase-type plasminogen activator (u-PA) in endothelial cells as well as u-PA and its receptor in kidney epithelial cells. In this study, we report that human recombinant HGF stimulates expression of plasminogen activator inhibitor type 1 (PAI-1) and tissue factor (TF) in the human hepatoma cell line HepG2. PAI-1 antigen as determined by a specific enzyme-linked immunosorbent assay increased up to threefold in conditioned media of HepG2. This increase was dose dependent with maximum stimulation achieved with a concentration of 50 ng/mL of hepatocyte growth factor (HGF). PAI-1 antigen also increased up to fourfold in the extracellular matrix in HGF treated HepG2. The production of the PAI-1 binding protein vitronectin (Vn) was not affected by HGF. In contrast, TF activity in HepG2 treated with HGF increased up to twofold. As determined by Northern blotting, PAI-1 and TF-specific mRNA were increased significantly in the presence of HGF, whereas Vn mRNA was not affected. The increase in PAI-1 and TF mRNA was also seen when HepG2 were incubated with HGF in the presence of cycloheximide, thereby indicating that de novo protein synthesis is not required to mediate the effect. u-PA could be detected neither in unstimulated or HGF-stimulated HepG2 cells on the antigen level nor on the mRNA level. In conclusion, our data give evidence that HGF, in addition to its proliferative effect for different cell types, is also involved in the local regulation of fibrinolysis and coagulation. One could speculate that HGF might modulate processes requiring matrix degradation by increasing the expression of the protease u-PA in one cell type and by upregulating the expression of the serine protease inhibitor PAI-1 in a different cell type. Because u-PA has been shown to activate latent HGF to the active form, it could furthermore be speculated that by upregulating PAI-1, which in turn could inhibit u- PA, HGF might regulate its own activation.     

Differential effects of gonadotropin-releasing hormone I and II on the urokinase-type plasminogen activator/plasminogen activator inhibitor system in human decidual stromal cells in vitro

To date, the factors capable of regulating the coordinate expression of the urokinase-type plasminogen activator (uPA) and its endogenous inhibitor, plasminogen activator inhibitor (PAI-1), at the maternal-fetal interface remain poorly characterized. In these studies we examined the ability of the classical form of gonadotropin-releasing hormone (GnRH) I and the second, mammalian form of this hormone, GnRH II, to regulate uPA and PAI-1 mRNA and protein expression levels in cultures of stromal cells isolated from first trimester decidual tissues using quantitative competitive-PCR and ELISA, respectively. GnRH I and GnRH II increased uPA mRNA and protein expression levels in these primary cell cultures in a dose- and time-dependent manner. In contrast, GnRH I increased, whereas GnRH II decreased PAI-1 mRNA and protein expression levels in these cells. Cetrorelix, a GnRH receptor antagonist, inhibited the regulatory effects of GnRH I, but not GnRH II, on uPA and PAI-1 expression levels in these decidual stromal cell cultures. Taken together, these observations suggest that GnRH I and GnRH II differentially regulate the balance between uPA and PAI-1 expression levels in the human decidua, possibly via distinct receptor-mediated signaling pathways.     

Functions of the fibrinolytic system in human Ito cells and its control by basic fibroblast and platelet-derived growth factor

During liver fibrogenesis, hepatic stellate cells (HSC) proliferate and migrate under the influence of growth factors, including platelet-derived growth factor (PDGF) and basic-fibroblast growth factor (b-FGF). The plasminogen activation system regulates extracellular matrix (ECM) catabolism and cell movement. We evaluated the expression and biological functions of the plasminogen activation system in human HSC and its interaction with PDGF and b-FGF. Urokinase-plasminogen activator receptors (u-PAR) were measured by radioligand binding, cell cross-linking, immunoassay, and RNAse protection assay. u-PA and plasminogen activator inhibitors (PAIs) expression and activities were analyzed by zymography, immunoassay, and RNase protection assay. Cell migration and proliferation, studied in Boyden chambers and by microscopic counting, were evaluated after the addition of PDGF, b-FGF, and blockade with anti-u-PA, anti-u-PAR antibodies, and antisense oligodeoxynucleotides (aODN) against u-PAR mRNA. We have shown that HSC produce u-PAR, u-PA, and PAI-1. PDGF and b-FGF up-regulate u-PA and u-PAR, but not PAI-1, and exogenous addition of u-PA stimulates HSC proliferation, chemotaxis, and chemoinvasion. Inhibition of u-PA/u-PAR with antibodies against u-PA or u-PAR and with u-PAR aODN inhibit the proliferative, chemotactic, and chemoinvasive activity of PDGF and b-FGF. These findings indicate that u-PA and u-PAR are required for the mitogenic and chemoinvasive activity of PDGF and b-FGF on HSC.     

The effects of gonadotropin-releasing hormone (GnRH) I and GnRH II on the urokinase-type plasminogen activator/plasminogen activator inhibitor system in human extravillous cytotrophoblasts in vitro

The regulated expression of the urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor (PAI-1) is believed to modulate the invasive capacity of human trophoblastic cells in vitro and in vivo. To date, the factors capable of regulating the expression of uPA and PAI-1 in these cells remain poorly characterized. In these studies, we have examined the ability of the classical mammalian GnRH I and the second form of GnRH (GnRH II) to regulate uPA and PAI-1 mRNA and protein expression levels in primary cultures of human extravillous cytotrophoblasts using quantitative competitive PCR and ELISA, respectively. Both GnRH I and II increased uPA and concomitantly decreased PAI-1 mRNA and protein expression levels in our extravillous cytotrophoblast cultures in a dose- and time-dependent manner. Cetrorelix, a peptide GnRH antagonist specific for the GnRH I receptor, was capable of inhibiting the regulatory effects of GnRH I, but not GnRH II on uPA and PAI-1 expression levels in primary cell cultures. Taken together, these observations suggest that GnRH I and GnRH II may facilitate trophoblast invasion by increasing the ratio of uPA/PAI-1 expression via interactions with two distinct GnRH receptors.     

Tumor necrosis factor induces the production of urokinase-type plasminogen activator by human endothelial cells

Endothelial cells play an important role in the regulation of fibrinolysis by the production of several key regulatory proteins. The cytokines tumor necrosis factor (TNF), lymphotoxin, and interleukin-1 (IL-1), but not interleukin-6, increase the production of plasminogen activator inhibitor-1 (PAI-1) by endothelial cells, whereas they have no stimulatory effect on the production of tissue-type plasminogen activator (t-PA). Primary cultures of human endothelial cells release very little urokinase-type plasminogen activator (u-PA). We report here that TNF and lymphotoxin induce, in a concentration-dependent way, the production of both cellular and secreted u-PA antigen in primary and subcultured human endothelial cells. The TNF-induced increase was accompanied by a more than 10-fold increase in u-PA mRNA. Upon stimulation of early passage umbilical vein endothelial cells by TNF, u-PA was predominantly secreted at the basolateral side, whereas PAI activity and t-PA were found in more equal amounts at the apical and basolateral sides of the cell monolayers. TNF-stimulated u-PA secretion by subcultured human aorta endothelial cells showed only a marginal polarity. The u-PA antigen was present in a plasmin-activatable form (single chain u-PA) and in a nonactivatable form (probably u-PA: PAI-1 complex). During the induction of u-PA by TNF, the ratio between plasmin-activatable u-PA and total u-PA decreased markedly. This may indicate that TNF also increases the degree of u-PA activation. The parallel induction of the synthesis and secretion of both u-PA and PAI-1 by endothelial cells adds a new aspect to the alterations of the fibrinolytic system caused by inflammatory mediators. This aspect may be significant for the regulation of cell-associated and interstitial plasminogen activator activity.     

丁酸对人结肠癌细胞尿激酶型纤溶酶原激活剂及受体表达的影响

目的探讨丁酸对人结肠癌细胞尿激酶型纤溶酶原激活剂(u-PA)及其受体(u-PAR)表达的影响。方法将人传代结肠癌细胞株SW1116接种于不含或含不同浓度丁酸(2、3、4、7、10mmol／L)的培养基中，培养6、24、48、72h后，收集细胞用ELISA法测定胞质中u-PA和u-PAR的表达情况。结果随着培养基中丁酸浓度的增加和培养时间的延长，经丁酸处理的SW1116细胞表达的u-PA和u-PAR与对照组相比显著减少，当丁酸浓度≥4mmol／L和培养时问≥48h时，两者表达不再增加，反而呈逐步下降趋势。结论丁酸可抑制SW1116细胞u-PA和u-PAR表达。     

Antithrombotic regulation in human endothelial cells by fibrinolytic factors

Vascular endothelial cells (ECs) modulate the blood fibrinolytic system by secreting tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), and their inhibitor, type-1 plasminogen activator inhibitor (PAI-1). ECs also express t-PA receptors (t-PAR) and u-PA receptors (u-PAR) on their cell surfaces, assembling both enzymes to regulate the cellular fibrinolytic activity. In addition, ECs modulate these factors in response to several stimuli. Fibrin clots on ECs induce the up- and downregulation of t-PA and PAI-1 production, respectively, thus causing an effective lysis of the fibrin clot. Heat shock (43 degrees C) increases the expression of u-PA, t-PA, PAI-1, and u-PAR by which ECs become more fibrinolytic around the cells. Furthermore, because ECs possess t-PAR and u-PAR on their cell surfaces, the binding of t-PA and u-PA is a critical event, which affords ECs the localized and condensed fibrinolytic potential. Therefore, ECs play a central role in antithrombotic activity by regulating the levels of these fibrinolytic factors.     

Plasminogen activator inhibitor 2 and urokinase-type plasminogen activator in plasma and leucocytes in patients with severe sepsis

Proteins influencing plasminogen activation to plasmin, namely plasminogen activators tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) and their principal inhibitors, plasminogen activator inhibitor 1 (PAI-1) and PAI-2, were measured in the plasma, the polymorph and mononuclear cell fractions taken from patients with major sepsis who were entering a general intensive care unit. The purpose of this study was to elucidate the factors favouring the persistence of fibrin in the microvasculature and thus contributing to multiple organ failure. Levels of u-PA antigen in plasma rose in sepsis and u-PA activity, not detectable in normal plasma, appeared. Levels of u-PA antigen in the cell fractions fell concomitantly. t-PA antigen in plasma and in the mononuclear cell fraction rose in sepsis, but t-PA activity was not detectable. Plasma PAI-1 antigen levels were strikingly raised in sepsis, presumably accounting for the complete neutralization of t-PA activity. PAI-2 antigen, not normally detected in plasma, appeared in the plasma of some patients, whereas it disappeared from the cellular fractions. Appearance of PAI-2 in plasma was associated with non-survival of the patient. The observations indicate that all the agents involved in plasminogen activation are released into the plasma in major sepsis. The levels of PAI-1 reached were quantitatively sufficient to suppress all activity of the released t-PA, but the inhibitors did not prevent expression of u-PA activity in the circulation. Circulating active u-PA and PAI-2 in the plasma of patients with severe sepsis may represent material originating from leucocytes. Leucocyte release of these agents within fibrin deposits may influence the persistence of fibrin and thus the development of multiple organ failure.     

Interleukin (IL)-1beta regulation of IL-1beta and IL-1 receptor antagonist expression in cultured human endometrial stromal cells

The interleukin (IL)-1 system is a major regulator of local cellular interactions during embryonic implantation. Because IL-1beta and IL receptor antagonist (IL-1ra) are both expressed in human endometrium, we hypothesized that an appropriate ratio of IL-1beta to IL-1ra might favor the process of embryo implantation. Therefore, we investigated IL-1 regulation of the quantitative ratio of IL-1beta/IL-1ra messenger RNA (mRNA) expression in human endometrial stromal cells using quantitative competitive PCR, as well as intracellular protein expression after stromal cell solubilization. Confluent stromal cell cultures were stimulated with human IL-1beta (0-1000 IU/mL) for 24 h. After 24 h, total RNA was extracted, reverse transcribed, and coamplified by PCR with a defined amount of internal standard. The quantitative ratio was determined by the density of target to the internal standard. After culture with IL-1beta for 24 and 48 h, stromal cells were solubilized, and the intracellular protein levels of IL-1beta and IL-1ra were measured by enzyme-linked immunosorbent assay. The IL-1beta and IL-1ra mRNA were both up-regulated, and IL-1R tI mRNA was down-regulated, by IL-1beta in a dose-dependent manner. The quantitative ratio of IL-1beta to IL-1ra mRNA was constant with the presence of increasing concentrations of IL-1beta (1-1000 IU/mL). IL-1beta and IL-1ra protein was not detected in conditioned media of cultures before addition of IL-1beta. IL-1beta and IL-1ra protein levels increased with increasing amounts of IL-1beta after solubilization of stromal cells. The IL-1beta was detectable after 12 h of culture, in comparison with IL-1ra, which was detectable after 24 h of IL-1beta stimulation. These results suggest that IL-1 may play a crucial role in embryo-maternal interaction by regulating stromal cell expression of IL-1beta and IL-1ra, resulting in an appropriate ratio during the process of embryonic implantation.     

Bone matrix degradation by the plasminogen activation system. Possible mechanism of bone destruction in arthritis

The observed increase in urokinase-type plasminogen activator (u-PA) and its receptor (u-PAR) in synovial tissue of patients with rheumatoid arthritis (RA) suggests pathophysiological involvement of the plasminogen activation (PA) system in inflammatory joint disease. In the present study, we investigated the capacity of the PA system to degrade non-mineralized and mineralized bone-like matrix in vitro as a model for bone destruction. Transfected mouse LB6 cell lines, that expressed either human u-PA or u-PAR, were cultured separately and simultaneously on radiolabelled bone matrix in the presence of plasminogen. Osteoblast-like murine calvarial MC3T3-E1 cells were used to produce a well-characterized, highly organized bone-like matrix, that could be mineralized in the presence of beta-glycerol phosphate. Bone matrix degradation was followed by the release of radioactivity in the culture medium. u-PA-producing cells, in contrast to u-PAR- producing cells, degraded both non-mineralized and mineralized bone matrix. This effect could be inhibited by anti-u-PA antibodies, as well as by tranexamic acid and by aprotinin, indicating that the degrading activity is u-PA mediated and plasmin dependent. Co-cultivation of a small portion of u-PA-producing cells with u-PAR-expressing cells resulted in a marked increase in degradation activity. Reduction of this potentiating effect by suramin or the amino-terminal fragment of u- PA, both competitive inhibitors of u-PA receptor binding, shows that this synergistic effect is due to binding of u-PA to u-PAR. u-PAR must be cell associated, as binding of u-PA to a soluble u-PAR prevented this enhancement. The capability of the PA system to degrade bone matrix in vitro, and the previously demonstrated increased expression of u-PA and u-PAR in synovial tissue of patients with RA, further support a role for the PA system in the development of bone erosions.      

Involvement of plasminogen activator and plasminogen activator inhibitor type 1 in spermatogenesis, sperm capacitation, and fertilization

Increasing evidence suggests that local fibrinolysis generated by plasminogen activator (PA) and modulated by plasminogen activator inhibitor type 1 (PAI-1) is essential for mammalian spermatogenesis, sperm capacitation, and fertilization. Tissue-type PA (t-PA), urokinase-type PA (u-PA), and PAI-1 have been reported in the testes of various animals. Sertoli cells within the seminiferous epithelium are believed to play a central role in the control and maintenance of spermatogenesis by producing regulatory factors, including PA/PAI-1. Fertilization is a unique and exquisitely choreographed cellular interaction between male and female gametes, in which some basic biochemical mechanisms remain unresolved. A key issue is the molecular basis of sperm-egg recognition, binding, and penetration. Sperm capacitation and the acrosomal reaction appear to rely on local fibrinolysis generated by the PA/PAI-1 system. Ejaculated spermatozoa from various species carry u-PA activity. The u-PA receptor (uPAR) and the inhibitor PAI-1 have also been reported to bind on the sperm membrane surface. Thus, it is possible that uPAR and PAI-1 function in a counterbalanced and coordinated way on the surface of spermatozoa to regulate the u-PA binding capacity. This review summarizes evidence for the involvement of PA/PAI-1 system in spermatogenesis, sperm capacitation, and fertilization.     

Plasminogen activator in acute myeloid leukaemic marrows: u-PA in contrast to t-PA in normal marrow

Leukaemic and normal bone marrow samples were compared in terms of their content of the fibrinolytic agents, tissue plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) and their inhibitors, plasminogen activator inhibitors 1 and 2 (PAI-1 and PAI-2). Normal marrow contained t-PA as the principal plasminogen activator, whereas in leukaemic marrow samples u-PA was the predominant activator. Both normal and leukaemic marrows contained PAI-1 in similar amounts, but whereas normal marrow contained significant amounts of PAI-2 the leukaemic marrows contained very little. Plasminogen activators were present in uncomplexed, active forms and plasmin–α₂-antiplasmin complexes were generated locally more prominently in leukaemic marrows. u-PA associated with blast cells may contribute to the severe forms of haemorrhage sometimes occurring in myeloid types of leukaemia.     

DIFFERENCE IN EXPRESSION OF THE PLASMINOGEN ACTIVATION SYSTEM IN SYNOVIAL TISSUE OF PATIENTS WITH RHEUMATOID ARTHRITIS AND OSTEOARTHRITIS

Protcolytic joint destruction in inflammatory and non-inflammatoryarthropathy is believed to be mediated, at least in part, bythe plasminogen activation (PA) system. To further investigatepossible involvement of the PA system, we quantified immunoreactiveurokinase-type plasminogen activator (u-PA), tissue-type plasminogenactivator (t-PA), both plasminogen activator inhibitors (PAI-1and PAI-2) and u-PA-receptor (u-PAR) in synovial tissue extractsof 14 patients with rheumatoid arthritis (RA) and 12 with osteoarthritis(OA). u-PA, PAI-1, PAI-2 and u-PAR concentrations were significantlyhigher in RA than in OA patients. t-PA antigen levels were significantlylower in RA than in OA synovial tissue extracts. Immunohistochemistrywas performed to compare the distribution and staining intensityof these components in samples of RA and OA synovial tissue.Intense immunostaining of u-PA, u-PAR, PAI-1 and, to a lesserdegree, PAI-2 was observed predominantly in the synovial liningof RA patients. In OA patients, u-PA, PAI-1, PAI-2 and u-PARwere barely detectable. t-PA immunostaining was restricted tothe endothelial side of vascular walls in both groups. We concludethat the observed increase of u-PA, u-PAR and PAI expression,distributed mainly in the synovial lining area of proliferativeand invasively growing synovial tissue in RA patients, supportsa pathogenic role for the PA system in destructive arthritis.Depressed t-PA-mediated plasminogen activation might contributeto delayed intra-articular fibrin removal. KEY WORDS: Urokinase, Plasminogen activation, Immunohistochemistry, Rheumatoid arthritis, Osteoarthritis