Disturbances in the tissue plasminogen activator/plasminogen activator inhibitor (TPA/PAI) system in systemic lupus erythematosus

Molecular mechanisms underlying thrombosis in systemic lupus erythematosus - A Systematic review

Patients with systemic lupus erythematosus (SLE) face an approximately 30 % risk of thrombosis post-diagnosis. However, there remains significant knowledge gaps regarding causative mechanisms, and there is a lack of specific antithrombotic guidelines. This systematic review aims to examine the existing literature regarding the mechanisms contributing to thrombosis risk in SLE, focusing on five predefined procoagulant domains: autoantibodies (including antiphospholipid antibodies (aPL)), the complement system, platelets, the endothelium, and the coagulation system. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statements and searched in PubMed and Embase without time restrictions. Risk of bias assessment was performed using a pre-specified evaluation tool. Out of 3,747 initially identified publications, 30 studies were included, with 28 demonstrating robust methodological quality in the risk of bias assessment. The studies were experimental, involving blood samples from cross-sectional SLE cohorts, except one animal -and one case-control study. We identified six different thrombosis mechanisms of action. Most studies concentrated on autoantibodies, predominantly aPL. Shared mechanisms between aPL and other autoantibodies may account for the increased thrombosis risk in aPL-negative SLE patients. Significant knowledge gaps remain, particularly regarding the role of the complement system in SLE-related thrombosis. Also, most research relies on cross-sectional designs, emphasizing the need for prospective cohort studies to better assess clinical factors. Finally, comprehensive studies examining the interactions between multiple procoagulant factors and their link to thrombosis are lacking. Closing these gaps in future research could improve both preventive and personalized treatment strategies for thrombosis in SLE.

The association of urinary plasmin level with renal involvement and disease flare among systemic lupus erythematosus patients

Objectives

To explore the ability to use urinary level of plasmin as an indicator for renal affection and activity in systemic lupus erythematosus (SLE) patients.

Patients and methods

Between April 2020 and October 2020, urine samples from 50 SLE patients (2 males, 48 females; mean age: 35.5±8.1 years; range, 22 to 39 years) and 20 age- and sex-matched healthy controls (2 males, 18 females; mean age: 34.1±6.5 years; range, 27 to 38 years) were collected. The patients were divided into two groups according to the presence or absence of renal manifestations as those with renal disease (n=28) and those without renal disease (n=22). The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), renal activity (rSLEDAI), and Systemic Lupus International Collaborating Clinics Damage Index (SLICC-DI) scores were calculated. Renal biopsy was performed to patients with active lupus nephritis (LN). The activity index (AI) and Chronicity Index (CI) were scored.

Results

There was a highly statistically significant difference in the mean urinary plasmin levels between SLE cases and the control group (88.9±42.6 ng/mL vs. 21.3±26.8 ng/mL, respectively; p<0.001). A significant elevation was observed (p<0.05) in patients with LN (97.9±46.6 ng/mL) than without (42.7±12.7 ng/mL), particularly in patients with active renal involvement (82.9±26.6 ng/mL) than patients with inactive renal disease (63.2±15.5 ng/mL). There were significant positive correlations between the mean urinary plasmin levels and inflammatory markers, SLEDAI, and rSLEDAI scores.

Conclusion

Urinary level of plasmin is significantly elevated among SLE cases, particularly in those with active LN. The remarkable association between urinary plasmin level and various activity status implies that urinary plasmin can be used as a beneficial marker to monitor lupus nephritis flare.

Urinary pro-thrombotic, anti-thrombotic, and fibrinolytic molecules as biomarkers of lupus nephritis

Objective

This study evaluates the utility of urinary pro-thrombotic molecules such as tissue factor (TF), anti-thrombotic molecules such as tissue factor pathway inhibitor (TFPI), and fibrinolytic molecules such as plasmin and d-dimer as biomarkers of lupus nephritis (LN).

Methods

Urine samples from 113 biopsy-proven LN patients (89 active LN and 24 inactive LN), 45 chronic kidney disease patients, and 41 healthy controls were examined for d-dimer, plasmin, TF, and TFPI levels by ELISA. The area under the receiver operating characteristic curve (AUC) analysis, multivariate regression analysis, and Bayesian network analysis were performed to assess the diagnostic value of the assayed molecules in LN.

Results

Although urinary d-dimer, plasmin, TF, and TFPI were all elevated in active LN compared to all control groups, and correlated with rSLEDAI and SLICC RAS disease activity indices, urine plasmin emerged as the strongest independent predictor of eGFR and renal disease status, by multivariate regression analysis and Bayesian network analysis. Whereas urine plasmin discriminated active LN from inactive disease with an AUC of 0.84, the combination of urine plasmin and TFPI discriminated ALN from ILN with an AUC of 0.86, with both surpassing the specificity and positive predictive value of traditional markers such as anti-dsDNA and complement C3.

Conclusion

Both thrombogenic and thrombolytic cascades appear to be upregulated in lupus nephritis, with proteins from both cascades appearing in the urine. Of the coagulation cascade proteins surveyed, urine plasmin emerges as the strongest predictor of eGFR and clinical renal disease in patients with LN.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1959-y) contains supplementary material, which is available to authorized users.

FXII promotes proteolytic processing of the LRP1 ectodomain

BACKGROUND

Factor XII (FXII) is a serine protease that is involved in activation of the intrinsic blood coagulation, the kallikrein-kinin system and the complement cascade. Although the binding of FXII to the cell surface has been demonstrated, the consequence of this event for proteolytic processing of membrane-anchored proteins has never been described.

METHODS

The effect of FXII on the proteolytic processing of the low-density lipoprotein receptor-related protein 1 (LRP1) ectodomain was tested in human primary lung fibroblasts (hLF), alveolar macrophages (hAM) and in human precision cut lung slices (hPCLS). The identity of generated LRP1 fragments was confirmed by MALDI-TOF-MS. Activity of FXII and gelatinases was measured by S-2302 hydrolysis and zymography, respectively.

RESULTS

Here, we demonstrate a new function of FXII, namely its ability to process LRP1 extracellular domain. Incubation of hLF, hAM, or hPCLS with FXII resulted in the accumulation of LRP1 ectodomain fragments in conditioned media. This effect was independent of metalloproteases and required FXII proteolytic activity. Binding of FXII to hLF surface induced its conversion to FXIIa and protected FXIIa against inactivation by a broad spectrum of serine protease inhibitors. Preincubation of hLF with collagenase I impaired FXII activation and, in consequence, LRP1 cleavage. FXII-triggered LRP1 processing was associated with the accumulation of gelatinases (MMP-2 and MMP-9) in conditioned media.

CONCLUSIONS

FXII controls LRP1 levels and function at the plasma membrane by modulating processing of its ectodomain.

GENERAL SIGNIFICANCE

FXII-dependent proteolytic processing of LRP1 may exacerbate extracellular proteolysis and thus promote pathological tissue remodeling.

Changes to fibrinolysis in patients with systemic lupus erythematosus are associated with endothelial cell damage and inflammation, but not antiphospholipid antibodies

We investigated whether changes to fibrinolysis were associated with other manifestations of systemic lupus erythematosus (SLE), including antiphospholipid (APL) antibody status, endothelial damage, and inflammation. Ninety-four patients (36 SLE patients, 58 healthy controls) were recruited from Tasmania, Australia. Circulating levels of plasminogen, α2-antiplasmin, tissue-type plasminogen activator, plasminogen activator inhibitor-1, and thrombin-activatable fibrinolysis inhibitor (TAFI) were measured, as well as APL antibodies (including lupus anticoagulant, anticardiolipin, and antibeta-2 glycoprotein-1 antibodies), soluble E-selectin, and interleukin-6. Whereas there was a significant decrease in plasminogen (patient vs. control; median) (210 vs. 444 ng/ml; P < 0.0001) and increase in α2-antiplasmin (0.53 vs. 0.09 μg/ml; P = 0.0007), there was increased t-PA (0.65 vs. 0.40 ng/ml; P = 0.0001) and decreased TAFI (8.8 vs. 10.0 ng/ml; P = 0.002) in SLE patients compared to healthy controls. Plasminogen was significantly associated with α2-antiplasmin (rho = -0.563, P < 0.001); TAFI (rho = 0.410, P = 0.011); soluble E-selectin (rho = 0.531, P = 0.001); and interleukin-6 (rho = 0.489, P = 0.002) in SLE patients; however, APL antibody status was not associated with any of the markers measured. This study has demonstrated that fibrinolysis is significantly altered in patients with SLE compared to controls, and associated with endothelial cell damage and inflammation, but not APL antibody status.

Tissue factor pathway inhibitor and thrombin-activatable carboxypeptidase B for prediction of early atherosclerosis in gouty arthritis

BACKGROUND

Gouty arthritis (GA) is a chronic inflammatory arthritis in which both clinical and subclinical atherosclerosis are more frequent. The dynamic equilibrium between coagulation and fibrinolysis is impaired in inflammatory diseases. We determined TFPI and TAFI antigen levels in GA patients and evaluated their association with subclinical atherosclerosis.

METHODS

We included 45 GA patients (41 males, 4 females; mean age: 51.6years) and 25 asymptomatic hyperuricemic (AHU) subjects (19 males, 6 females; mean age: 48.1years). Cardiovascular risk factors were determined. TAFI and TFPI levels were determined by ELISA. B-mode ultrasonography was used to detect subclinical atherosclerosis.

RESULTS

Cardiovascular risk factors were similar in both groups. The carotid IMT was significantly higher in GA group than in AHU group (0.74±0.23mm vs. 0.61±0.13mm, p=0.009). TFPI level was significantly higher in GA group than in AHU group (86.2±48.9ng/mL vs. 25.8±21.4ng/mL, p<0.001); TAFI antigen was significantly higher in AHU group (22.6±3.6ng/mL vs. 25.7±5.3ng/mL, p=0.006) than in GA patients. Atherosclerotic plaque formation was more frequent in GA group (p=0.041). When GA patients with and without plaques were compared, the first group had significantly higher mean age (p=0.01) and TFPI level (p=0.028). TFPI level correlated with carotid IMT (r=0.302; p=0.028). Logistic regression analysis showed that age (OR: 1.236, 95%CI: 1.059-1.443, p=0.007) and TFPI (OR: 1.031, 95%CI: 1.008-1.054, p=0.008) were independent risk factors for the presence of plaques.

CONCLUSIONS

GA patients had more frequent subclinical atherosclerosis than subjects with AHU. Higher TFPI levels in GA patients -probably associated with enhanced endothelial damage- were related to subclinical atherosclerosis. Lower TAFI levels in GA pointed to impaired fibrinolysis.

[Polymorphism of the plasminogen activator inhibitor type 1 gene, plasminogen level and thrombosis in patients with antiphospholipid syndrome]

The frequency of venous and arterial thromboses and plasminogen level were investigated in 78 patients with antiphospholipid syndrome (APS), 35 of whom with systemic lupus erythematosus (SLE+APS) and 43 - with primary APS (PAPS). The levels and genotype of plasminogen activator inhibitor type 1 (PAI-1) were determined in 45 patients with APS, of whom 21 patients with SLE + APS and 24 patients with PAPS. A control group included 10 healthy individuals without autoimmune disease signs and thromboses on period of investigation and in past history. It was shown for the first time that for one third of 67 patients with APS and thromboses high positive levels of antiphospholipid antibodies (aPL) are associated with low plasminogen levels. The levels of PAI-1 antigen measured by ELIZA method, which detects active, latent and bound with plasminogen activator PAI-1, were opposed with frequency of thromboses in APS patients. Correlation between the high and increased levels of PAI-1 and high positive aPL levels was found for one third of 43 patients with APS and thrombosis. One of the possible mechanisms of this interconnection was considered. It was shown that arterial and, to a more extent, venous thromboses are associated with the 4G/5G polymorphism of PAI-1 gene and high plasma level of the inhibitor in 79% of APS patients. At the presence of the 4G allele patients with SLE+APS had higher PAI-1 levels than patients with PAPS. The obtained results show that measuring the levels of plasminogen and PAI-1 as well as the 4G/5G polymorphism of PAI-1 gene which is associated with thromboses may have the practical significance for identification of high risk of thrombosis in APS patients.

Pathogenetic potential of antiphospholipid antibodies

Antiphospholipid antibodies are autoantibodies that recognize phospholipid-binding proteins such as beta2 glycoprotein (beta2GP)-I, prothrombin or annexins. These antibodies have been associated with arterial or venous thrombotic events and pregnancy morbidity. The molecular mechanisms responsible for the pathogenetic potential of these antibodies include: resistance to activated protein C, acquired Factor XII deficiency resulting in suppression of intrinsic fibrinolytic activity, activation of endothelial cells through the nuclear factor kappaB pathway leading to tissue factor upregulation, adhesion molecule and cytokine expression and activation of platelets. Opposite effects, such as the potentiation of the inhibitory action of beta2GPI on the activation of Factor XI, make the dynamics of the interaction of these antibodies with the coagulation system rather complex. Many of the above functions can be mediated by signaling through molecules of the tumor necrosis factor receptor family, such as CD40, which is recognized by purified anti-beta2GPI antibodies.

Expression of TGFbeta1 and its signaling components by peripheral lymphocytes in systemic lupus erythematosus

Transforming growth factor beta1 (TGFbeta1) is an important immunosuppressive cytokine. Defects in its production by lymphocytes and the failure of TGFbeta1 to regulate immunological functions have been described in SLE. Expression of TGFbeta1 and the related signaling pathway was studied in the peripheral lymphocytes of SLE patients. The total plasma TGFbeta1 level in active and inactive SLE patients compared to healthy controls was also measured. TGFbeta1 and all downstream signaling elements were expressed in normal cells. However, in more than 50% of SLE patients the isolated T cell population showed no TGFbeta1 mRNA expression and at least one member of the TGFbeta1 pathway was also missing (TGFbeta-RI, Smad2 and Smad3) in more than half of the patients. Total plasma TGFbeta1 level was increased in both active and inactive SLE groups compared to normal controls (p< 0.05). These data raise questions about the availability of TGFbeta1 signaling in lymphocytes in SLE patients, however, the elevated total plasma TGFbeta1 level suggests that the failure of TGFbeta1 effects is not the consequence of low level of this cytokine in SLE.

Antiphospholipid antibodies: laboratory and pathogenetic aspects

Antiphospholipid antibodies (aPL) constitute a heterogeneous group of autoantibodies that share the ability to bind phospholipids (PL) alone, protein-PL complexes, or PL-binding proteins. They have been detected in isolation, in association with autoimmune diseases such as systemic lupus erythematosus (SLE), and during the course of different infections. aPL have been associated with an array of clinical manifestations in virtually every organ, although deep vein and arterial thrombosis as well as pregnancy morbidity are predominant. The co-occurrence of these clinical findings with aPL constitutes the so-called antiphospholipid syndrome (APS). aPL can be detected by immunological methods [e.g., anticardiolipin antibodies (aCL)] or by functional methods that exploit the effect of aPL on blood coagulation [lupus anticoagulant (LA)]. Since aPL are heterogeneous, numerous immunological and coagulation assays have been developed. These assays have not been fully standardized, and, therefore, problems such as high interlaboratory variation are relatively frequent. Recently, recommendations have been published regarding LA and aCL testing. Not all aPL are pathogenic. However, when they are not associated with infections, they have a role in the pathogenesis of APS. Clinical and experimental data have shown that aPL exert their pathogenic activity by interfering with the function of coagulation factors, such as thrombin and factors X, XI and XII, and with the function of anticoagulant proteins of the protein C system. In addition, aPL interaction with platelets and endothelial cells induces a pro-adhesive activated phenotype.

Antiphospholipid antibodies induce monocyte chemoattractant protein-1 in endothelial cells

The presence of antiphospholipid Ab is associated with increased risk of thrombosis. The monocyte-endothelial cell interaction has been suggested to play a key role at the site of vascular injury during thrombosis. Therefore, we tested the effect of anticardiolipin Abs (aCL) on the production of monocyte chemoattractant protein-1 (MCP-1) in HUVEC. We found that monoclonal aCL as well as IgG fractions from patients with antiphospholipid syndrome (APS-IgG) could induce the production of MCP-1 in HUVEC. The ability of IgG aCL to induce MCP-1 production could be abrogated by preabsorption with cardiolipin liposomes. Simultaneous addition of either monoclonal aCL or APS-IgG with IL-1beta resulted in synergistic increase in MCP-1 production, whereas the addition of control IgG lacking aCL activity did not alter IL-1beta-induced levels of MCP-1. MCP-1 mRNA expression was also up-regulated when HUVEC were incubated with either APS-IgG or monoclonal aCL, and down-regulated by the treatment of dexamethasone. In addition, we found that serum levels of MCP-1 in 76 systemic lupus erythematosus patients correlated well with the titers of IgG aCL. Collectively, these results indicate that aCL could promote endothelial cell-monocyte cross-talk by enhancing the endothelial production of MCP-1, thereby shifting the hemostatic balance toward the prothrombotic state of APS.

The 4G/5G polymorphism of the type 1 plasminogen activator inhibitor gene and thrombosis in patients with antiphospholipid syndrome

OBJECTIVE

To investigate the relationship between the 4G/5G polymorphism of the type 1 plasminogen activator inhibitor (PAI-1) gene and thrombotic manifestations in patients with antiphospholipid syndrome (APS).

METHODS

We studied a total of 247 patients included in the following 4 groups: 70 patients with primary APS, 104 patients with systemic lupus erythematosus (40 with antiphospholipid antibodies [aPL] and clinical [secondary] APS, 13 with aPL but without clinical APS, and 51 with neither detectable aPL nor a history of thrombosis), 14 asymptomatic individuals with aPL, and 59 patients with thrombosis but without known thrombosis risk factors. A control group of 100 healthy individuals was also analyzed. PAI-1 4G/5G polymorphism was determined by polymerase chain reaction and endonuclease digestion.

RESULTS

The allele frequency of 4G/5G in controls was 0.47/0.53. There were no differences in allele distribution among patient groups or between patients and controls. However, a higher frequency of the 4G allele was observed in APS patients with versus those without thrombosis (0.57 versus 0.39; P < 0.05) (odds ratio [OR] 2.83, 95% confidence interval [95% CI] 1.18-6.76). This higher frequency of the 4G allele was attributable to the higher frequency in patients with versus those without arterial thrombosis (0.64 versus 0.43; P < 0.01) (OR 5.96, 95% CI 1.67-21.32), while patients with venous thrombosis had an allele distribution similar to that of those without venous thrombosis (0.49 versus 0.50; P not significant). There was a trend toward higher PAI-1 antigen and activity levels in APS patients and controls with the 4G/4G genotype, but this did not reach statistical significance.

CONCLUSION

The presence of the 4G allele of the 4G/5G polymorphism of the PAI-1 gene may be an additional risk factor for the development of arterial thrombosis in APS.

The G20210A polymorphism in the 3'-untranslated region of the prothrombin gene in Mexican mestizo patients with primary antiphospholipid syndrome

In an effort to identify alleles associated with an increased risk of venous thrombosis in patients with primary antiphospholipid syndrome, we studied the G20210A polymorphism (the G-->A mutation at nucleotide position 20210) in the 3'-untranslated region of the prothrombin gene in a group of 14 patients with primary antiphospholipid syndrome. We did not find any patient with the mutated gene. Since the prothrombin mutation is more prevalent in white populations, this finding may be related with the genetic composition of the Mexican mestizos, in whom the white component is low. The polymorphism of the prothrombin gene in Mexican mestizo patients with antiphospholipid syndrome does not seem to be related to the thrombophilia observed in these patients.

Primary thrombophilia in Mexico: a prospective study

A group of 102 Mexican Mestizo patients with appropriate clinical features suggestive of primary thrombophilia was prospectively studied. Thirty-nine percent of them had activated protein C resistance, but only four patients displayed the factor V Leiden mutation. Five percent of the individuals were found to be protein C deficient, whereas 2% had protein S deficiency. No cases of abnormalities in antithrombin III, plasminogen, tissue-type plasminogen activator or plasminogen activator inhibitor were found. The low prevalence of the activated protein C resistance genotype, probably stemming from the genetic admixture of the Mexican Mestizo group is noteworthy.

Effects of human monoclonal anticardiolipin antibodies on platelet function and on tissue factor expression on monocytes

OBJECTIVE

To investigate the effect of human monoclonal anticardiolipin antibodies (aCL) on platelet interaction with the subendothelium under flow conditions and on tissue factor (TF) expression on normal monocytes.

METHODS

Three monoclonal IgM aCL (TM1B3, GR1D5, and EY2C9) and 2 affinity-purified IgM aCL were studied. Immunoglobulins were added to normal blood and perfused through chambers containing denuded vascular segments. Platelet interactions were morphometrically evaluated by determining the percentage of total surface covered by platelets (PCS) or by large aggregates of thrombi platelets (TP). Expression of TF on monocytes was measured after immunoglobulin incubation with normal mononuclear cells.

RESULTS

Significant increases in the total PCS and expression of TF were observed using all aCL. Increased levels of TP were induced by all aCL except EY2C9 (obtained from a patient without thrombosis). Previous incubations of these aCL with subendothelial surfaces did not increase platelet interaction.

CONCLUSION

The effects of aCL on platelet function may help to explain the pathophysiology of thrombosis in the antiphospholipid syndrome.

Decreased Production of TGF-β by Lymphocytes from Patients with Systemic Lupus Erythematosus

TGF-β has marked inhibitory effects on the immune system but also serves as a costimulatory factor in the development of T cells with down-regulatory activities. This cytokine is secreted as a latent complex and converted extracellularly to its active form. We have recently learned that anti-CD2 is a potent inducer of lymphocyte-derived TGF-β and that NK cells are the predominant source. The objective of this study was to compare levels of constitutive, anti-CD2-induced and cytokine-regulated TGF-β produced by blood lymphocytes from patients with systemic lupus erythematosus (SLE) in comparison with healthy controls. Using a highly sensitive and specific bioassay to assess TGF-β, we report that unstimulated PBL from SLE patients, especially the NK cell subset, produced decreased levels of active TGF-β. In response to anti-CD2, concentrations of active and total TGF-β were also decreased in SLE. After learning that IL-2 and TNF-α enhance lymphocyte production of active TGF-β, we found that the addition of these cytokines was unable to increase active TGF-β to normal concentrations. Although we observed that IL-10 inhibited the production of active TGF-β, antagonism of this cytokine was unable to completely correct the defect. In two SLE patients with B cell hyperactivity, spontaneous IgG production was almost abolished by the combination of TGF-β and IL-2. Therefore, decreased production of each of these cytokines in SLE could be important in the perpetuation of B cell hyperactivity.

Hypercoagulable state in patients with antiphospholipid syndrome is related to high induced tissue factor expression on monocytes and to low free protein s

Antiphospholipid antibodies (aPLs) are associated with thrombosis, but the mechanisms of this thrombotic tendency are unknown. We studied 56 patients 612 with systemic lupus erythematosus [SLE] and aPLs and previous thrombosis, 12 with SLE and aPLs but no thrombosis, 15 with SLE without aPLs or thrombosis, 11 with primary antiphospholipid syndrome with thrombosis, and 6 asymptomatic subjects with aPLs) to investigate the ability of aPLs to induce tissue factor (TF) expression on human normal monocytes. A double direct immunofluorescence technique (anti-CD14 and anti-TF) was used, and procoagulant activity in viable and disrupted cells was measured after plasma incubation for 6 hours at 37 degrees C with normal mononuclear cells. Hemostasis regulatory proteins, prothrombin fragment 1 + 2, and thrombin-antithrombin III complex levels were determined. Increased TF expression and procoagulant activity were observed using plasma samples from SLE patients with aPLs and thrombosis (P < .01) and from primary antiphospholipid syndrome patients (P < .01) but not from patients with SLE and aPLs but no thrombosis, patients with SLE without aPLs, or asymptomatic patients with aPLs. Purified aPL immunoglobulins from one primary antiphospholipid syndrome and two SLE patients added to normal plasma showed a significant increase in both TF expression and procoagulant activity (P < .05) compared with purified aPL from two SLE patients without thrombosis. The addition of nonspecific IgG from three SLE patients without aPLs and from three control subjects did not increase TF expression. Low free protein S was seen in eight patients. Increased TF expression and low free protein S correlated with thrombosis (P < .01) and with higher prothrombin fragment 1 + 2 and thrombin-antithrombin III values (P < .01). These observations may contribute to a further understanding of the thrombotic risk in aPL patients.

Antibodies to fibrin-bound tissue-type plasminogen activator in systemic lupus erythematosus are associated with Raynaud's phenomenon and thrombosis

Fibrinolysis triggered by t-PA bound to fibrin is one of the main antithrombotic mechanisms. Defects in the fibrinolytic system-decreased tissue-type plasminogen activator (t-PA) activity and elevated levels of plasminogen activator inhibitor (PAI-1), in patients with SLE have been associated with an increased tendency to thrombosis. In the present study, 43 patients with SLE fulfilling the ACR criteria for the disease, were studied for the presence of autoantibodies to fibrin-bound t-PA, i.e. the physiological active form of this plasminogen activator. A solution of 200 IU/ml of t-PA was incubated with solid-phase fibrin prepared as previously described (Anal Biochem 1986; 153; 201-210). Sera diluted 1:50 were incubated with fibrin-bound t-PA, the plates were then washed, and bound immunoglobulins were detected using a polyvalent peroxidase-labeled goat anti-human Ig. Plates coated with fibrin alone were used as controls. Sera were considered positive when A490/630 obtained with normal human sera in two independent test was greater than the mean plus 2 SD. Eleven of 43 (26%) SLE sera demonstrated antibody reactivity against fibrin-bound t-PA. Within the anti-t-PA positive group there was a higher proportion of SLE patients with severe Raynaud's phenomenon and thrombotic events when compared to the anti-t-PA negative group: 36% vs 6% and 18% vs 6% respectively. These results suggest that autoantibodies to fibrin-bound t-PA could play a role in the pathogenesis of vascular disease in some SLE patients.

Antiphospholipid antibodies (aPL) increase the potential monocyte procoagulant activity in patients with systemic lupus erythematosus

Lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) are frequently detected in sera from patients affected by systemic lupus erythematosus (SLE). However, the role of antiphospholipid antibodies (aPL) in thrombus formation has not been defined as yet. Twenty-two patients affected by SLE, all fulfilling the 1982 ARA revised criteria, and twenty healthy subjects were investigated for the presence of LA, aCL and other aPLs. Monocyte procoagulant activity-PCA (Tissue Factor production) was evaluated by one stage plasma recalcification time. In all patients the plasma levels of F1 + 2 and of plasminogen activator inhibitor (PAI) were also determined. Monocyte PCA was significantly higher in SLE patients with LA and/or aCL in comparison to SLE patients without LA and/or aCL (p < 0.01) and to controls (p < 0.05). However, no connection was observed between PCA expression by mononuclear cells and LA or aCL levels. No differences in F1 + 2 and PAI plasma levels were found between SLE patients with or without aPL and controls. In our SLE patients LA and/or aCL positivity appears strictly related to an increased monocyte activation that could play an important role in the occurrence of thrombotic events.

Stroke is an emergency

Stroke is an emergency. Ischemic stroke is similar to myocardial infarction in that the pathogenesis is loss of blood supply to the tissue, which can result in irreversible damage if blood flow is not restored quickly. Public education is needed to emphasize the warning signs of stroke. Patients should seek medical help immediately, using emergency transport systems. Therapy geared toward minimizing the damage from an acute stroke should be started without delay in the emergency room. This includes measures to protect brain tissue, support perfusion pressure, and minimize cerebral edema. Strategies for improving recovery should also begin immediately. All major medical centers need stroke teams and stroke units. Stroke prevention should be given high priority as a public health strategy. Risk factor management should be part of general health care and should begin in childhood, with emphasis on nutrition, exercise, weight control, and avoidance of tobacco. Health screening and early treatment of hypertension and hypercholesterolemia has decreased the incidence of stroke and heart disease, but these efforts need to be expanded to reach all segments of the population. Basic research has opened the door to new therapies aimed at re-establishing blood flow and limiting tissue damage. Clinical trials have already led to changes in stroke prevention, including studies of carotid endarterectomy and ticlopidine and warfarin therapy (for patients with atrial fibrillation). Trials in progress are testing the usefulness of ancrod, neuroprotective agents, antioxidant agents, anti-inflammatory agents, low-molecular-weight heparin, thrombolytic drugs, and angioplasty. Any delay starting therapy after an acute stroke will result in progressive, irreversible loss of brain tissue. Clinicians should remember that for a stroke patient, time is brain tissue.

Serum antibodies to distinct epitopes of the tissue-type plasminogen activator (t-PA) in patients with systemic lupus erythematosus

Defective fibrinolysis due to decreased tissue-type plasminogen activator (t-PA) activity is a well-established finding in patients with systemic lupus erythematosus (SLE). The possibility that this decrease in t-PA activity may be related to the presence of autoantibodies directed against t-PA, and the possible role of these autoantibodies in the pathophysiology of fibrinolysis in SLE, were investigated. Serum samples from 115 SLE patients and 63 normal volunteers were analyzed for the presence of such antibodies. The search for antibodies to t-PA was performed by means of several systems, allowing for the identification of epitopes presented in different conformational physical states of t-PA: free or associated to its inhibitor (PAI-1) in plasma, specifically bound to fibrin surface, or passively adsorbed to solid supports. Antibodies in variable amounts were detected by all systems used; however, t-PA activity was not inhibited by the IgG fraction of the positive sera in a fibrin-agar fibrinolysis system. Moreover, the demonstration of serum anti-t-PA antibodies was not associated with clinical or laboratory abnormalities related to vasoocclusive episodes. These results indicate that, as in the case of other autoantibodies, their detection in serum does not imply their direct participation in the pathophysiology of thrombosis in SLE.

Fibrinolysis and coagulation abnormalities in systemic lupus erythematosus. Relationship with Raynaud's phenomenon, disease activity, inflammatory indices, anticardiolipin antibodies and corticosteroid therapy

Endothelial cell damage in systemic lupus erythematosus (SLE) was evaluated by measuring fibrinolytic activity and von Willebrand factor levels. Tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor (PAI) activity, and von Willebrand factor antigen (vWF:Ag) and activity (vWF:RCof) were measured in 21 SLE patients (12 of whom were therapy free) and 22 controls. In addition, the relationship between such parameters and Raynaud's phenomenon, disease activity [according to personal criteria, Systemic Lupus Activity Measure (SLAM) and European Consensus Lupus Activity Measurement (ECLAM) scores] inflammatory indices [ESR, C-reactive protein (CRP), alpha 2-globulin], anticardiolipin antibodies and corticosteroid therapy was investigated. Lower levels of t-PA antigen (P = 0.003) and higher levels of vWF:Ag (P = 0.001) were found in SLE patients in comparison with controls. Moreover, t-PA antigen was lower (P = 0.02) in steroid-free patients in comparison with those taking steroids. No relationship was found between fibrinolysis and coagulation abnormalities and Raynaud's phenomenon, disease activity, inflammatory indices and anticardiolipin antibodies. Endothelial cell damage is probably a common feature in SLE patients; nevertheless, we were unable to clarify the nature of such abnormality. It is worth noting that low doses of steroids seem to be effective in improving endothelial cell function in SLE patients.