Hemostatic factors and the risk of myocardial infarction or sudden death in patients with angina pectoris. European Concerted Action on Thrombosis and Disabilities Angina Pectoris Study Group

BACKGROUND

Increased levels of certain hemostatic factors may play a part in the development of acute coronary syndromes and may be associated with an increased risk of coronary events in patients with angina pectoris.

METHODS

We conducted a prospective multicenter study of 3043 patients with angina pectoris who underwent coronary angiography and were followed for two years. Base-line measurements included the concentrations of selected hemostatic factors indicative of a thrombophilic state or endothelial injury. The results were analyzed in relation to the subsequent incidence of myocardial infarction or sudden coronary death.

RESULTS

After adjustment for the extent of coronary artery disease and other risk factors, an increased incidence of myocardial infarction or sudden death was associated with higher base-line concentrations of fibrinogen (mean +/- SD, 3.28 +/- 0.74 g per liter in patients who subsequently had coronary events, as compared with 3.00 +/- 0.71 g per liter in those who did not; P = 0.01), von Willebrand factor antigen (138 +/- 49 percent vs. 125 +/- 49 percent, P = 0.05), and tissue plasminogen activator (t-PA) antigen (11.9 +/- 4.7 ng per milliliter vs. 10.0 +/- 4.2 ng per milliliter, P = 0.02). The concentration of C-reactive protein was also directly correlated with the incidence of coronary events (P = 0.05), except when we adjusted for the fibrinogen concentration. In patients with high serum cholesterol levels, the risk of coronary events rose with increasing levels of fibrinogen and C-reactive protein, but the risk remained low even given high serum cholesterol levels in the presence of low fibrinogen concentrations.

CONCLUSIONS

In patients with angina pectoris, the levels of fibrinogen, von Willebrand factor antigen, and t-PA antigen are independent predictors of subsequent acute coronary syndromes. In addition, low fibrinogen concentrations characterize patients at low risk for coronary events despite increased serum cholesterol levels. Our data are consistent with a pathogenetic role of impaired fibrinolysis, endothelial-cell injury, and inflammatory activity in the progression of coronary artery disease.

Influence of fibrin network conformation and fibrin fiber diameter on fibrinolysis speed: dynamic and structural approaches by confocal microscopy

Abnormal fibrin architecture is thought to be a determinant factor of hypofibrinolysis. However, because of the lack of structural knowledge of the process of fibrin digestion, relationships between fibrin architecture and hypofibrinolysis remain controversial. To elucidate further structural and dynamic changes occurring during fibrinolysis, cross-linked plasma fibrin was labeled with colloidal gold particles, and fibrinolysis was followed by confocal microscopy. Morphological changes were characterized at fibrin network and fiber levels. The observation of a progressive disaggregation of the fibrin fibers emphasizes that fibrinolysis proceeds by transverse cutting rather than by progressive cleavage uniformly around the fiber. Plasma fibrin clots with a tight fibrin conformation made of thin fibers were dissolved at a slower rate than those with a loose fibrin conformation made of thicker (coarse) fibers, although the overall fibrin content remained constant. Unexpectedly, thin fibers were cleaved at a faster rate than thick ones. A dynamic study of FITC-recombinant tissue plasminogen activator distribution within the fibrin matrix during the course of fibrinolysis showed that the binding front was broader in coarse fibrin clots and moved more rapidly than that of fine plasma fibrin clots. These dynamic and structural approaches to fibrin digestion at the network and the fiber levels reveal aspects of the physical process of clot lysis. Furthermore, these results provide a clear explanation for the hypofibrinolysis related to a defective fibrin architecture as described in venous thromboembolism and in premature coronary artery disease.

Extracellular proteolysis in the adult murine brain

Plasminogen activators are important mediators of extracellular metabolism. In the nervous system, plasminogen activators are thought to be involved in the remodeling events required for cell migration during development and regeneration. We have now explored the expression of the plasminogen activator/plasmin system in the adult murine central nervous system. Tissue-type plasminogen activator is synthesized by neurons of most brain regions, while prominent tissue-type plasminogen activator-catalyzed proteolysis is restricted to discrete areas, in particular within the hippocampus and hypothalamus. Our observations indicate that tissue-type plasminogen activator-catalyzed proteolysis in neural tissues is not limited to ontogeny, but may also contribute to adult central nervous system physiology, for instance by influencing neuronal plasticity and synaptic reorganization. The identification of an extracellular proteolytic system active in the adult central nervous system may also help gain insights into the pathogeny of neurodegenerative disorders associated with extracellular protein deposition.

Involvement of the mural thrombus as a site of protease release and activation in human aortic aneurysms

Acquired abdominal aortic aneurysms are usually associated with a mural thrombus through which blood continues to flow. Some early data suggest that aneurysmal evolution correlates with the biological activity of the thrombus. Our hypothesis was therefore that the thrombus could adsorb blood components and store, release, and participate in the activation of proteases involved in aneurysmal evolution. For this purpose, we have explored both the metalloproteinase and fibrinolytic systems in the thrombus and the wall of human aneurysms. We have first investigated blood clot formation and lysis in vitro. Spontaneous clotting induces a release of promatrix metalloproteinase (pro-MMP)-9 into the serum that was fourfold higher than in paired control plasma (P < 0.001). Fibrinolysis progressively released more MMP-9 in a time-dependent manner (P < 0.01). After selective isolation, we demonstrated that polymorphonuclear leukocytes are the main source of MMP-9 release during clot formation. Protease content was then analyzed in 35 mural thrombi and walls of human abdominal aortic aneurysms sampled during surgical repair. In 15 aneurysms, the liquid phase at the interface between the thrombus and the wall was sampled separately. Both thrombus and wall contained MMP-2 and MMP-9 but the ratio MMP-9/MMP-2 was higher in the thrombus than in the wall. The liquid interface also contained active MMP-9. Immunohistochemistry of the thrombus confirmed these findings, showing the presence of polymorphonuclear leukocytes at the luminal pole of the thrombus, co-localizing with MMP-9 storage. In contrast, MMP-3 and MMP-7 were only present in the aneurysmal wall. Plasminogen was present in the mural thrombus but plasmin activity was present in both thrombus and wall. In the liquid interface, plasmin-alpha(2)-anti-plasmin complexes were detected demonstrating in vivo the activation of plasminogen. In contrast, u-PA and t-PA were detectable only in the wall, suggesting that plasminogen present in the thrombus could be activated by factors secreted by the arterial wall. This was demonstrated in vitro, in which co-incubation of thrombus and wall extracts generated plasmin in the presence of a fibrin matrix and activated MMPs. In conclusion, our study strongly suggests that the mural thrombus, by trapping polymorphonuclear leukocytes and adsorbing plasma components could act as a source of proteases in aneurysms that may play a critical role in enlargement and rupture.

Thrombin induction of plasminogen activator-inhibitor in cultured human endothelial cells

We have examined the effect of thrombin on the activity of plasminogen activator (PA) and plasminogen activator-inhibitor (PA-I) in medium conditioned by primary cultures of human umbilical vein endothelial cells. PA activity was measured by fibrinolytic and esterolytic assays, and total tissue-type PA (tPA) antigen by radioimmunoassay. Net PA-I activity was assayed by titration of human urokinase esterolytic activity. Incubation of confluent endothelial cell cultures with thrombin for 24 h caused a sixfold increase in PA-I activity. The effect of thrombin was half-maximal at approximately 0.4 U/ml (less than 4 nM), and required concomitant RNA and protein synthesis. The stimulation of PA-I activity required active alpha-thrombin and was not obtained with gamma-thrombin nor with thrombin catalytically inactivated with hirudin. Because of the excess of PA-I, PA activity was not measurable in either control or thrombin-treated cells. Thrombin did, however, increase medium concentration of tPA antigen by approximately fourfold. The thrombin-induced PA-I inhibited both tPA and urokinase, did not lose activity upon acidification, and was stable to sodium dodecyl sulfate and thiol reduction. We conclude that physiologic concentrations of thrombin increase both PA-I activity and tPA antigen in medium conditioned by human umbilical vein endothelial cells. Because there was always a several-fold increase in the net activity of free PA-I, these observations suggest that the net effect of thrombin is to decrease fibrinolytic activity in human endothelial cells. Thus, thrombin, in addition to its role in coagulation, may protect clots from premature lysis by increasing the amount of a specific fibrinolytic inhibitor.

Which Hemostatic Markers Add to the Predictive Value of Conventional Risk Factors for Coronary Heart Disease and Ischemic Stroke?

Background— Few studies have examined whether hemostatic markers contribute to risk of coronary disease and ischemic stroke independently of conventional risk factors. This study examines 11 hemostatic markers that reflect different aspects of the coagulation process to determine which have prognostic value after accounting for conventional risk factors.

Methods and Results— A total of 2398 men aged 49 to 65 years were examined in 1984 to 1988, and the majority gave a fasting blood sample for assay of lipids and hemostatic markers. Men were followed up for a median of 13 years, and cardiovascular disease (CVD) events were recorded. There were 486 CVD events in total, 353 with prospective coronary disease and 133 with prospective ischemic stroke. On univariable analysis, fibrinogen, low activated protein C ratio, D-dimer, tissue plasminogen activator (tPA), and plasminogen activator inhibitor-1 (PAI-1) were associated significantly with risk of CVD. On multivariable analyses with conventional risk factors forced into the proportional hazards model, fibrinogen, D-dimer, and PAI-1 were significantly associated with risk of CVD, whereas factor VIIc showed an inverse association ( P =0.001). In a model that contained the conventional risk factors, the hazard ratio for subsequent CVD in the top third of the distribution of predicted risk relative to the bottom third was 2.7 for subjects without preexisting CVD. This ratio increased to 3.7 for the model that also contained the 4 hemostatic factors.

Conclusions— Fibrinogen, D-dimer, PAI-1 activity, and factor VIIc each has potential to increase the prediction of coronary disease/ischemic stroke in middle-aged men, in addition to conventional risk factors.

Hemostatic factors as predictors of ischemic heart disease and stroke in the Edinburgh Artery Study

Plasma fibrinogen is a consistent predictor of ischemic heart disease (IHD) in prospective studies, but there are fewer data relating other hemostatic variables to IHD and also to stroke. We therefore studied the relationships of plasma fibrinogen, von Willebrand factor antigen, tissue plasminogen activator (TPA) antigen, factor VII, and fibrin D-dimer to incidence of IHD and stroke and determined whether any associations could be explained by conventional risk factors and baseline heart disease. In the Edinburgh Artery study, 1592 men and women aged 55 to 74 years, randomly sampled from the general population, were followed prospectively over 5 years to detect fatal and nonfatal IHD and stroke events. During the 5 years, 268 new vascular events were identified. Baseline plasma fibrinogen was independently related to risk of stroke in multivariate analysis that adjusted for cigarette smoking, LDL-cholesterol, systolic blood pressure, and preexisting IHD (relative risk [RR] 1.52, 95% confidence interval [CI] 1.17, 1.98). TPA antigen, and fibrin D-dimer were also independently associated with risk of stroke (RR 1.69,95% CI 1.22,2.35 and RR 1.96, 95% CI 1.12,3.41, respectively). Significant relationships were found between TPA antigen and myocardial infarction (P < or = .05). In older men and women, increased coagulation activity and disturbed fibrinolysis are predictors of future vascular events (both IHD and stroke).

Urokinase- and tissue-type plasminogen activators in keratinocytes during wound reepithelialization in vivo

Urokinase- and tissue-type plasminogen activators (u-PA and t-PA) were identified immunohistochemically during reepithelialization of mouse and human skin wounds, by means of polyclonal and monoclonal antibodies. In incised mouse skin wounds u-PA immunoreactivity was found in keratinocytes at the edge of the wound after 12 h, and at days 2 to 10 after wounding it was found in virtually all keratinocytes of the epithelial outgrowth that gradually covered the wound. At day 14, the epidermis appeared normal and no u-PA immunoreactivity was detected. t-PA immunoreactivity was found from day 5 to day 10 in some keratinocytes located superficially in the epidermal outgrowths near the edge of the mouse wounds. In 3- and 5-day old human skin wounds, u-PA immunoreactivity was found in keratinocytes in the epithelial outgrowths, whereas no t-PA immunoreactivity was detected. No u-PA and no t-PA immunoreactivity was found in normal mouse and human epidermis. The specificity of the staining was supported by a variety of controls, including absorption of the polyclonal antibodies with highly purified u-PA and t-PA preparations and zymographic analysis of extracts of wound tissue. The function of the plasminogen activators during reepithelialization is discussed and it is suggested that the keratinocytes use plasmin activated by u-PA for dissecting their way through the provisional matrix in the upper part of the granulation tissue.

Effects of physical conditioning on fibrinolytic variables and fibrinogen in young and old healthy adults

BACKGROUND

The effects of 6 months of intensive endurance exercise training on resting tissue-type plasminogen activator (t-PA) activity, plasminogen activator inhibitor type 1 (PAI-1) activity, t-PA antigen, and fibrinogen were studied in 10 young (24-30 years) and in 13 old male subjects (60-82 years).

METHODS AND RESULTS

After training, maximum oxygen consumption was increased in the young group by 18% (44.9 +/- 5.0 to 52.9 +/- 6.6 ml/kg/min, p less than 0.001), whereas it was increased in the old group by 22% (29.0 +/- 4.2 to 35.5 +/- 3.6 ml/kg/min, p less than 0.001). The young group had no significant changes in any of the measured variables, whereas the old group had a 39% increase in t-PA activity (0.82 +/- 0.47 to 1.14 +/- 0.42 IU/ml, p less than 0.03), a 141% increase in the percentage of t-PA in the active form (11.1 +/- 7.7 to 26.8 +/- 15.1%, p less than 0.01), a 58% decrease in PAI-1 activity (8.4 +/- 4.9 to 3.5 +/- 1.7 AU/ml, p less than 0.01), and a 13% decrease in fibrinogen (3.57 +/- 0.79 to 3.11 +/- 0.52 g/l, p less than 0.01).

CONCLUSIONS

We conclude that intensive exercise training enhances resting t-PA activity and reduces fibrinogen and PAI-1 activity in older men. These effects are potential mechanisms by which habitual physical activity might reduce the risk of cardiovascular disease.

Association of fibrinolytic parameters with early atherosclerosis. The ARIC Study. Atherosclerosis Risk in Communities Study

BACKGROUND

Thrombosis, provoked by a rupture of an atherosclerotic plaque, plays a crucial role in precipitating a coronary heart disease event. Its role at the early stage of atherosclerosis has, however, been unclear, but it has been hypothesized that thrombosis or defective fibrinolysis contributes to the progression of atherosclerotic lesions.

METHODS AND RESULTS

We studied the association of plasminogen activator inhibitor antigen (PAI-1), tissue-type plasminogen activator antigen (TPA), and D-dimer with early atherosclerosis in a cross-sectional case-control study involving 457 pairs chosen from the biracial cohort of the Atherosclerosis Risk in Communities (ARIC) Study. As examined by B-mode ultrasound, patients (cases) had intima-media thickness of carotid arteries above the 90th percentile and control subjects had thickness below the 75th percentile of the ARIC cohort. Persons with a history of heart disease, stroke, or claudication were excluded from the case-control selection. PAI-1, TPA, and D-dimer were higher in patients than in control subjects (P < or = .001, Wilcoxon signed rank statistic). In conditional logistic regression analyses, the odds ratios of carotid atherosclerosis were, for PAI-1, for example, 1.22, 1.54, and 1.60 in the second, third, and fourth quartiles compared with the first quartile (P < .0001, test of linear trend, adjusting for age, systolic blood pressure, total cholesterol, acetylsalicylic acid use, and time of blood draw). Corresponding tests for D-dimer and TPA also showed an increasing trend (P < .0001).

CONCLUSIONS

The findings support the hypothesis that thrombosis and fibrinolysis play a role at the early stage of the atherosclerotic process.

Vascular extracellular matrix remodeling in cerebral aneurysms

OBJECT

The occurrence of cerebral aneurysms has been linked to alterations in the extracellular matrix and to matrix-degrading proteases. The purpose of the present study was to determine whether active extracellular matrix remodeling occurs within cerebral aneurysms.

METHODS

Aneurysm tissue was collected from 23 patients (two of whom had a ruptured aneurysm and 21 of whom had an unruptured aneurysm) and compared with 11 control basilar arteries harvested at autopsy. Active proteinases capable of gelatin lysis were identified by performing in situ zymography in the presence and absence of a metalloproteinase inhibitor (ethylenediamine tetraacetic acid) and a serine proteinase inhibitor (phenylmethylsulfonyl fluoride). Immunohistochemical analysis was used to localize plasmin, tissue-type (t)-plasminogen activator (PA), urokinase-type (u)-PA, membranetype (MT1)-matrix metalloproteinase (MMP), MMP-2, MMP-9, and tenascin. Focal areas of gelatin lysis occurred in most cerebral aneurysm tissue samples (17 of 21), but rarely in control arteries (two of 11) (p = 0.002). Both serine proteinases and MMPs contributed to gelatin lysis; however, the MMPs were the predominant enzyme family. Plasmin (p = 0.04) and MT1-MMP (p = 0.04) were expressed in the aneurysm tissue but were unusual in control tissue. The MMP-2 was also expressed more commonly in aneurysm than in control tissue (p = 0.07). The MMP-9 and t-PA were expressed in both groups; however, different staining patterns were observed between aneurysm and control tissue. Tenascin staining was commonly present in both groups, whereas u-PA staining was rarely present.

CONCLUSIONS

Aneurysm tissue demonstrates increased proteolytic activity capable of lysing gelatin and increased expression of plasmin, MT1-MMP, and MMP-2 when compared with normal cerebral arteries. This activity may contribute to focal degradation of the vascular extracellular matrix and may be related to aneurysm formation and growth.

The clinical significance of epidermal growth factor receptor (EGF-R) in human breast cancer: a review on 5232 patients

EGF-R positivity was shown to be present in 2500 (48%) of 5232 breast tumors in 40 different series of patients. The mean of the percentages of EGF-R positivity in the individual series reported by these 40 different groups of investigators is 45% (range 14-91%). Overall there are generally no clear differences between results obtained by radioligand binding assays, immunological methods, autoradiography, and measurement of EGF-R transcripts although the mean percentage of EGF-R-positive tumors determined by immunological methods tends to be somewhat lower. Nearly all studies indicate a negative relationship between EGF-R and steroid receptor status (28 of 31 studies for ER, 12/19 for PR) showing that EGF-R positivity is twice as high in ER or PR- negative tumors compared to ER or PR- positive tumors (approximately 50-60% vs. 30%). With regard to other prognostic factors the majority of investigators (10/18) also reported a significant (positive) correlation with tumor grade, but only a minority found a significant relationship between EGF-R status and patient age (2/9), menopausal status (1/7), histological type (3/7), tumor size (2/17), nodal status (5-9/20), ploidy (1/7), or proliferation indices (3/9). No relationship was observed with tumor insulin-like growth factor I receptor, PRL receptor (PRL-R), and LHRH receptor (LHRH-R) status, but an inverse relationship between EGF-R and somatostatin receptor may be present. However, it has to be stressed that the series in which the relationship between EGF-R status and other prognostic factors were investigated, contained relatively few patients (mostly less than 100). Therefore, when larger groups of patients are investigated, more significant relationships may be observed, especially with respect to nodal status, tumor ploidy, and proliferation indices. In fact, we calculated the presence of EGF-R positivity overall in 35% of 253 aneuploid tumors vs. in only 15% of 114 diploid tumors (P less than 0.0001). In addition most studies observed a trend, if no significant correlation, between higher EGF-R levels in tumors with the highest percentages of S-phase or Ki-67 expression. With regard to relapse-free and overall survival, five of nine different groups of investigators showed significant prognostic value of EGF-R after short-term (1- to 4-yr) follow-up, indicating that patients with EGF-R-positive tumors have a poor prognosis. However, three of five groups with a maximal follow-up of at least 6 yr found only a tendency for any relationship between EGF-R status and long-term outcome.

Peritoneal fibrinolytic activity and intra-abdominal adhesions

The mechanisms leading to reduction of peritoneal fibrinolytic activity in conditions that are associated with the formation of intra-abdominal adhesions were studied. Tissue plasminogen activator was found, by antibody inhibition techniques, to be the activator of fibrinolysis in homogenates of control peritoneum (n = 6). Homogenates of control (n = 10) and inflamed peritoneum (n = 10) were analysed. Plasminogen activating activity was much lower in inflamed peritoneum (median 0.07 IU/cm2) than in control tissue (median 12.0 IU/cm2) (p less than 0.001). Levels of tissue plasminogen activator and alpha 2-antiplasmin were similar in both control and inflamed tissue. Plasminogen activator inhibitor-1, not detectable in control peritoneum, was present in inflamed tissue and might be the reason for the reduction in functional fibrinolytic activity.

Isolation and culture of human trabecular meshwork cells by extracellular matrix digestion

Like corneal endothelial cells, human trabecular meshwork cells are believed to be of neural crest origin, but demonstrate physiological properties and an antithrombogenic surface similar to vascular endothelial cells. One current method for isolating trabecular meshwork cells utilizes the motile nature of these cells to migrate away from a trabecular meshwork explant in culture to more distal regions of the culture dish. This 'outgrowth' technique is limited in practice by the relatively small number of cells that migrate per explant per unit time, thus hindering the ability to gather sufficient numbers of cells for comprehensive experimentation. For this reason, we have modified an extracellular matrix digestion technique in current use for the isolation of microvascular endothelial cells to isolate human trabecular meshwork cells. This procedure is both efficient and rapid for isolating large numbers of trabecular meshwork cells and results in the availability of trabecular meshwork cells in sufficient quantities for subsequent experimentation.

Cell-type-specific and site-specific N-glycosylation of type I and type II human tissue plasminogen activator

Tissue plasminogen activator (t-PA) is an important initiator of fibrinolysis. The t-PA polypeptide has four potential N-glycosylation sites of which three are occupied in type I (Asn-117, -184, and -448) and two in type II (Asn-117 and -448). In an effort to elucidate the factors controlling the expression of N-linked oligosaccharides on this polypeptide, we have used a combination of sequential exoglycosidase digestion, methylation analysis, and controlled acetolysis to determine the oligosaccharide structures at each of the N-glycosylation sites of type I and type II t-PA when isolated from a human colon fibroblast cell strain and from a Bowes melanoma cell line. Our results suggest the following: (i) type I and type II t-PA are N-glycosylated in an identical way at Asn-117 and Asn-448, when isolated from the same cell line; (ii) Asn-117 is predominantly associated with oligomannose-type structures in all cases; (iii) Asn-184 and Asn-448 are predominantly associated with complex-type structures when t-PA is isolated from fibroblast cells, but with both complex- and oligomannose-type structures when isolated from melanoma cells; (iv) fibroblast cell derived t-PA is associated with both neutral and sialylated oligosaccharides, while melanoma cell derived t-PA is also associated with sulfated oligosaccharides, which are located exclusively at Asn-448 of type II t-PA; (v) no complex-type structures occur in common between t-PA from the two cell lines. These results indicate that the t-PA glycoprotein is secreted by each cell line as a set of glycoforms, each glycoform being unique with respect to the nature and disposition of oligosaccharides on a common polypeptide. Further, the two cell lines express no glycoform in common, despite expressing the same t-PA polypeptide. The implications of these results for both the control of oligosaccharide processing in different cell lines and the genetic engineering of mammalian glycoproteins are discussed.

Plasminogen activator expression in human atherosclerotic lesions

The plasminogen activator (PA) system may participate in the pathogenesis of atherosclerosis by modulating the turnover of intimal fibrin and extracellular matrix deposits and by contributing to intimal cell migration. We present an analysis of tissue-type PA (tPA) and urokinase-type PA (uPA) expression at three levels: mRNA by in situ hybridization, antigen by immunohistochemistry, and enzymatic activity by histoenzymology and zymography. For PA colocalization with cellular or matrix components, we used double immunofluorescence labeling in conjunction with confocal microscopy. In normal arteries, tPA antigen and mRNA were detected in endothelial cells and smooth muscle cells (SMCs). In atherosclerotic arteries, tPA antigen and mRNA were increased in intimal SMCs and in macrophage-derived foam cells of fibro-fatty lesions. Part of the tPA was detected in the extracellular space and colocalized with fibrin deposits. uPA antigen and mRNA were detected in association with the intimal macrophages and SMCs. A particularly high uPA expression was noted on macrophages localized on the rims of the necrotic core. Moreover, using a novel histoenzymological assay as well as classic zymography, we revealed uPA-dependent lytic activity in the advanced lesions, whereas in normal arteries, only tPA-dependent activity was detected, mainly over the vasa vasorum. Also, strong tPA and uPA staining was detected in neomicrovessels of the plaques, suggesting that PAs may play a role in plaque angiogenesis. Our results suggest a local dynamic process of PA-dependent proteolysis in lesion areas that is associated with macrophages and SMCs. A better comprehension of these proteolytic mechanisms in advanced atherosclerotic plaques may provide the basis for therapeutic approaches for plaque stabilization.

Activation of coagulation and fibrinolysis during cardiothoracic operations

BACKGROUND

During open cardiac operations using cardiopulmonary bypass, there is activation of coagulation and fibrinolysis. We assessed the separate contributions of the surgical procedure itself and cardiopulmonary bypass to this, by studying sequential samples from patients undergoing routine open cardiac operations or thoracic operations without cardiopulmonary bypass.

METHODS

Activation of coagulation and the extent of fibrinolysis were measured from sequential samples obtained before the operation to 48 hours after the operation for 7 thoracic patients and 8 cardiac patients.

RESULTS

In the thoracic group operation length was shorter (p = 0.002), and there was no significant increase in thrombin-antithrombin III complexes or D-dimers until 24 hours postoperatively. In contrast, there was a highly significant increase in thrombin-antithrombin III complexes (p = 0.0043) and D-dimer levels (p = 0.009) during cardiopulmonary bypass. The increase in fibrinolytic activity was caused by an increase in tissue plasminogen activator (p = 0.013). At 48 hours postoperatively, the cardiac patients had a more hypercoagulable state than thoracic patients with significantly higher levels of thrombin-antithrombin III complexes (p = 0.041) and plasminogen activator inhibitor-1 activity (p = 0.0033).

CONCLUSIONS

This study suggests the major activation of coagulation and fibrinolysis seen during cardiac operations is caused by the use of cardiopulmonary bypass.

Two-dimensional manipulation of confluently cultured vascular endothelial cells using temperature-responsive poly(N-isopropylacrylamide)-grafted surfaces

Temperature-responsive hydration/dehydration changes in surface-grafted poly(N-isopropylacrylamide) (PIPAAm) were utilized for hydrophilic/hydrophobic surface property alterations in cell culture. In this report, we utilized PIPAAm-grafted surfaces to recover confluently-cultured vascular endothelial cells as coherent monolayers from this cell culture substrate and to transfer to new cell culture substrates. For this purpose, we used two different methods to recover and transfer cell monolayer cultures: (1) chitin membranes used as an apical side cell support during cultured cell transfer, allowing cell basal side reattachment to new culture substrates after transfer; and (2) a cell culture insert (porous PET) used as both a support as well as new substrate, allowing basal surfaces of cultured cells to be exposed to the medium after transfer. In both cases, all cells grown on PIPAAm-grafted surfaces detach completely with maintenance of basement membrane-like structure. Recovered cells attach to the second culture surfaces, covering more than 60% of the new substrate, and retain approximately 90% viability and their original function as judged from tissue-type plasminogen activator secretion. This technique could be utilized to prepare novel bioartificial organs as well as cell co-culture systems by multi-layering different cell types to mimic tissue structures for tissue engineering.

Fibrinolysis in human peritoneum during operation

BACKGROUND

A reduced local fibrinolysis seems to be an important mechanism in the formation of adhesions. Peritonitis may cause adhesions, and the aim of the present study was to determine peritoneal fibrinolytic capacity in inflamed and normal peritoneum.

METHODS

Biopsy specimens from normal and inflamed human peritoneum were taken at the beginning and end of operation. After extraction plasminogen activator activity (PAA) was determined by using a chromogenic substrate assay in the presence or absence of inhibitory antibodies against tissue-type plasminogen activator (t-PA), urokinase or plasminogen activator inhibitor-1.

RESULTS

t-PA exerted 95% of the PAA. PAA was significantly reduced (p < 0.01) during peritonitis (3.0 IU/micrograms protein; range, 0.3 to 4.2) compared with normal peritoneum (7.1 IU/micrograms protein; range, 0.6 to 18.1). A significant reduction (p < 0.05) in PAA occurred during operation both in normal peritoneum (3.8 IU/micrograms protein; range, 0.8 to 8.6) and in peritonitis (0.6 IU/micrograms protein; range, 0.16 to 2.1). Values are given as medians.

CONCLUSIONS

The main PAA in human peritoneum was t-PA. The activity was decreasing during operation and reduced in peritonitis. This reduction in PAA might be a local response to inflammation.

Approaches to the study of N-linked glycoproteins in human plasma using lectin affinity chromatography and nano-HPLC coupled to electrospray linear ion trap--Fourier transform mass spectrometry

In this publication, we will describe the combination of lectin affinity chromatography with nano high performance liquid chromatography (HPLC) coupled to a linear ion trap Fourier transform mass spectrometer (capillary LC-LTQ/FTMS) to characterize N-linked glycosylation structures in human plasma proteins. We used a well-characterized glycoprotein, tissue plasminogen activator (rt-PA), which is present at low levels in blood, as a standard to determine the dynamic range of this approach. N-linked glycopeptides derived from rt-PA could be characterized at a ratio of 1:200 in human plasma (rtPA: total plasma protein, w/w) by accurate mass measurement in the FTMS and fragmentation (MS(n)) in the linear ion trap. We demonstrated that this platform has the potential to characterize the general N-linked glycosylation structures of abundant glycoproteins present in human plasma without the requirement for antibody-based purification, or additional carbohydrate analytical protocols. This conclusion was supported by the determination of carbohydrate structures for three glycoproteins, IgG, haptoglobin, and alpha-1-acid glycoprotein, at their natural levels in a human plasma sample, but only after the lectin enrichment step.

Transforming growth factor-beta is a potent inhibitor of extracellular matrix degradation by cultured human mesangial cells

Accumulation of the glomerular extracellular matrix (ECM) is a pivotal event in the progression from acute glomerular injury to end-stage renal disease. Although enhanced ECM synthesis has been demonstrated to contribute to ECM accumulation, the role of decreased ECM degradation is largely unknown. It was previously shown that glomerular ECM degradation is mediated by a plasminogen activator (PA)/plasmin/matrix metalloproteinase 2 (MMP-2) cascade. However, little information is available regarding the factors that regulate the activity of this degradative cascade in normal or pathologic states. Transforming growth factor-beta1 (TGF-beta1) is shown here to be a potent inhibitor of ECM degradation by cultured human mesangial cells. Using human mesangial cells grown on thin films of 125I-labeled Matrigel, dose-dependent inhibition of ECM degradation in the presence of TGF-beta1 was observed, reaching >90% inhibition with 0.4 ng/ml TGF-beta1. Addition of anti-TGF-beta antibodies (4 microg/ml) in the absence of exogenous TGF-beta increased ECM degradation (1.8+/-0.2-fold versus controls, P<0.05). In contrast, platelet-derived growth factor, at concentrations up to 10 ng/ml, had no effect on ECM degradation. TGF-beta completely blocked the conversion of plasminogen to plasmin and markedly reduced the conversion of latent MMP-2 to active MMP-2. TGF-beta did not significantly alter the levels of tissue PA, total MMP-2, or tissue inhibitor of metalloproteinase-1, but did increase the levels of PA inhibitor- (1.8-fold, P<0.05), the major physiologic inhibitor of PA. These data document that TGF-beta is a potent inhibitor of ECM degradation by cultured human mesangial cells, and they suggest that decreased mesangial matrix degradation, caused by TGF-beta-mediated decreases in the activity of the PA/plasmin/MMP-2 cascade, may contribute to the glomerular matrix accumulation that occurs in progressive renal disease.

Mass spectrometric determination of disulfide linkages in recombinant therapeutic proteins using online LC-MS with electron-transfer dissociation

In the biotechnology industry, the generation of incorrectly folded recombinant proteins, either from an E.coli expression system or from an overexpressed CHO cell line (disulfide scrambling), is often a great concern as such incorrectly folded forms may not be completely removed in the final product. Thus, significant efforts have been devoted to map disulfide bonds to ensure drug quality. Similar to ECD, disulfide bond cleavages are preferred over peptide backbone fragmentation in ETD. Thus, an online LC-MS strategy combining collision-induced dissociation (CID-MS(2)), electron-transfer dissociation (ETD-MS(2)), and CID of an isolated product ion derived from ETD (MS(3)) has been used to characterize disulfide-linked peptides. Disulfide-linked peptide ions were identified by CID and ETD fragmentation, and the disulfide-dissociated (or partially dissociated) peptide ions were characterized in the subsequent MS(3) step. The online LC-MS approach is successfully demonstrated in the characterization of disulfide linkages of recombinant human growth hormone (Nutropin), a therapeutic monoclonal antibody, and tissue plasminogen activator (Activase). The characterization of disulfide-dissociated or partially dissociated peptide ions in the MS(3) step is important to assign the disulfide linkages, particularly, for intertwined disulfide bridges and the unexpected disulfide scrambling of tissue plasminogen activator. The disulfide-dissociated peptide ions are shown to be obtained either directly from the ETD fragmentation of the precursors (disulfide-linked peptide ions) or indirectly from the charge-reduced species in the ETD fragmentation of the precursors. The simultaneous observation of disulfide-linked and disulfide-dissociated peptide ions with high abundance not only provided facile interpretation with high confidence but also simplified the conventional approach for determination of disulfide linkages, which often requires two separate experiments (with and without chemical reduction). The online LC-MS with ETD methodology represents a powerful approach to aid in the characterization of the correct folding of therapeutic proteins.

Structural characterization of glycoprotein carbohydrate chains by using diagoxigenin-labeled lectins on blots

The carbohydrate structures of blotted glycoproteins can be analyzed by probing them with lectins. Here we describe a method where lectins conjugated with digoxigenin are used in combination with an anti-digoxigenin antibody AP conjugate as a very sensitive detection system for this type of analysis. The specificity of the lectins used, and the sensitivity of the detection system, provide valuable conclusions on the glycan structures. Only small amounts of glycoproteins are required for the analysis. The binding specificity of a set of lectins is demonstrated with various glycoproteins of defined carbohydrate structure. The application of these labeled lectins in combination with specific glycosidases for the characterization of the carbohydrate chains of recombinant tissue plasminogen activator and erythropoietin is presented.

Characterization of the tryptic map of recombinant DNA derived tissue plasminogen activator by high-performance liquid chromatography-electrospray ionization mass spectrometry

A detailed tryptic map is presented for recombinant human tissue plasminogen activator (rt-PA). Electrospray ionization mass spectrometry is utilized as an on-line HPLC detector for tryptic mapping of this glycoprotein. The additional dimension provided by mass spectrometry gives considerably more detail about the complex tryptic map and significantly enhances the high-resolution chromatographic separation by distinguishing by mass any coeluting components. Through this improvement, the proline isomers of a tryptic peptide were observed eluting over a broad range of retention times. The glycopeptides of rt-PA are observed as well as any corresponding nonglycosylated peptides. In addition, the carbohydrate heterogeneity is readily observed, allowing analysis of the carbohydrate composition. The characteristic diagonal patterns formed by glycopeptides in a contour plot of the data allow rapid recognition of the glycopeptides.