Plasma markers of endothelial dysfunction in pulmonary hypertension.

STUDY OBJECTIVES: To evaluate and to correlate endothelial cell dysfunction, using recently available plasma markers, with the magnitude of pulmonary artery pressure in patients with severe pulmonary hypertension (PH). DESIGN: Selected plasma markers of endothelial cell dysfunction were studied: nitric oxide (NO), thrombomodulin, tissue factor pathway inhibitor, and soluble endothelium, leukocyte, and platelet selectins (sE-, sL-, sP-selectins, respectively). SETTING: Padova University Hospital and Department of Pathology and Pharmacology, Loyola University of Chicago, Chicago, IL. PATIENTS: Fifteen patients had severe PH (four men and 11 women; mean age, 49.7 +/- 2.9 years: seven patients had primary pulmonary hypertension [PPH] and eight patients had secondary pulmonary hypertension [SPH]), and 20 patients were healthy control subjects. MEASUREMENT AND RESULTS: In patients with PH, sP- and sE-selectins were elevated, whereas sL-selectin was lower in comparison with the selectin levels in control subjects. However, the differences between patients with PH and control subjects were significant only for sL-selectin (p < 0.0001) and sE-selectin (p < 0.03). The NO level was significantly lower in patients with PH compared with the NO level in control subjects (p < 0.01). No difference in tissue factor pathway inhibitor level was noted between control subjects and patients with PH. Only a weak correlation was found between thrombomodulin plasma levels and magnitude of systolic pulmonary artery pressure (r = -0.528, p < 0.05). CONCLUSIONS: Our data are in keeping with the evidence for significant endothelial cell dysfunction in patients with PH and the need for chronic anticoagulation believed to increase survival in these patients. In addition, these data seem to suggest a need for newer agents that are able to increase the antithrombotic endothelial function.

Plasma markers of endothelial dysfunction in chronic obstructive pulmonary disease.

We studied some endothelial cell activity plasma markers, nitric oxide (NO), thrombomodulin (TM), selectins (sP-, sE-, sL-selectin: platelet-P, endothelium-E, leukocyte-L), and tissue factor pathway inhibitor (TFPI) in 14 patients with chronic obstructive pulmonary disease (COPD), matched with 20 normal controls, to evaluate their endothelial cell dysfunction. Both NO (patients: 23.42 +/- 1.67 microg/mL: controls: 40.0 +/- 3.38 microg/mL) and TM levels (patients: 5.46 +/- 1.32 ng/mL; controls: 12.9 +/- 0.51 ng/mL) were significantly decreased in COPD (p < 0.001). sP-selectin levels (patients: 79.42 +/- 18.20 ng/mL, controls: 37.5 +/- 2.84 mg/mL) were significantly higher (p < 0.02), whereas sL-selectin levels (patients: 584.9 +/- 78.98 ng/mL, controls: 1,054.02 +/- 61.28 ng/mL) were significantly decreased in patients with COPD (p < 0.001). In contrast, no differences were seen in sE-selectin. Patients with COPD showed a significantly higher (p < 0.001) TFPI antigen plasma level (mean 112.28 +/- 6 .45 ng/mL; controls 77.68 +/- 0.28 ng/mL) than controls. Our data support the concept of some form of endothelial cell dysfunction, and coagulation abnormalities are present in patients with COPD. However, because the endothelium seems to produce a defense mechanism, the potential usefulness of an antithrombotic therapy in these patients needs further investigation.

Tissue factor pathway inhibitor release induced by defibrotide and heparins.

We evaluated the release of tissue factor pathway inhibitor (TFPI) induced by defibrotide (DF), a single-stranded, negatively charged polydeoxyribonucleotide extracted from mammalian organ. Ten normal volunteers were injected with an intravenous bolus of 400 mg DF and 2,000 IU unfractionated heparin (UFH). In addition, three volunteers were also injected with an intravenous bolus of 2,000 anti-Xa U of two low-molecular-weight heparins (LMWHs), enoxaparin and nadroparin. UFH caused a 4-fold increase in plasma TFPI at 5 minutes, with a decrease that was parallel to the heparin level measured by the anti-Xa assay. However, at 80 minutes, although the plasma anti-Xa activity of UFH was almost undetectable, the level of TFPI remained 2-fold baseline. DF induced an increase of TFPI that was 2-fold higher than the baseline level, with a steady state achieved between 5 and 20 minutes. At 40 minutes, the TFPI levels returned to basal level. This pattern was not coincident with the clearance of DF and at 40 minutes, the concentration of DF was still one third of the levels at 5 minutes (25.4 +/- 4.04 microg/mL). Both of the LMWHs induced a similar TFPI peak level at 5 minutes (1.5-fold increase) and at 40 minutes the TFPI levels returned to the initial levels. At 5 minutes, both LMWHs showed a higher plasma anti-Xa activity than UFH, which was detectable even at 80 minutes. The current study demonstrated that one of the mechanisms of the antithrombotic activity of DF is mediated via TFPI. Furthermore, the release of TFPI by heparin is mediated by non-antithrombin III binding fragments. Thus, polyanionic electrolytes are capable of releasing TFPI irrespective of their antithrombin III effect.

Tissue factor pathway inhibitor levels in patients with homocystinuria.

Thrombotic events are a well-recognized complication of homocystinuria. However, the mechanisms involved in the atherogenic and thrombotic effects of homocyst(e)ine remain incompletely understood. The objective of this study was to determine the role of endothelial cell activation/damage as indicated by levels of thrombomodulin, tissue factor and tissue factor pathway inhibitor, and factor VII activity in patients with homocystinuria. Six patients with homocystinuria, nonresponsive to pyridoxine, treated only with trimethylglycine (betaine) were injected with a bolus of 20 IU/kg body weight of unfractionated commercial heparin to induce the release of tissue factor pathway inhibitor from the vascular endothelium. Tissue factor, thrombomodulin, and factor VII activity were measured by enzyme-linked immunosorbent assay and clotting assay before heparin administration. Tissue factor pathway inhibitor antigen and activity were measured before and 5 minutes after the bolus of heparin. Levels of homocyst(e)ine were elevated (patients: 144.2+/-19.2 micromol/L; controls: 10.2+/-0.9 micromol/L); however, levels of thrombomodulin, tissue factor, and tissue factor pathway inhibitor antigen were not statistically different from the control group. In contrast, tissue factor pathway inhibitor activity showed a significantly increased level (patients: 2.09+/-0.34 U/L; controls: 1.14+/-0.20 U/L; p<0.05) that was correlated with homocyst(e)ine. Factor VII activity was significantly decreased (patients: 64.7+/-5.1%; controls: 91.4+/-4.7%; p<0.05) and inversely correlated with homocyst(e)ine. After heparin the patients released higher amounts of tissue factor pathway inhibitor antigen and activity compared with the control group; however, the difference was not statistically significant. Although not treated with antithrombotic drugs, none of the patients had any thromboembolic complications after starting betaine. In addition to betaine treatment, the enhanced factor pathway inhibitor antigen activity observed in this small series of patients suggests that factor pathway inhibitor antigen may play an additional, as yet unexplained, role in this genetic disorder.

Soluble plasma thrombomodulin levels in patients with chronic myeloproliferative disorder.

The plasma levels of soluble thrombomodulin (TM) were measured in 44 patients with chronic myeloproliferative disorder, 15 with polycythemia vera (PV), 29 with essential thrombocythemia (ET), and a group of 62 matched healthy controls. The younger patients had significantly lower TM levels (mean: 15.6 +/- 4.8 ng/mL) than the older patients (mean: 28.6 +/- 8.2 ng/mL, p < .001). Moreover, a significant negative correlation between platelet counts and plasma TM levels in healthy persons was noted (r = 0.317, p < .05). The only significant difference we found in plasma TM levels between patients and controls or among patients was between the young patients with ET (mean: 29.0 +/- 19.2 ng/mL) and young healthy controls (mean: 15.6 +/- 4.8 ng/mL). It is possible that younger ET patients with more active platelets are more susceptible to earlier vascular damage. The lack of any significant difference compared with the older patient population supports this hypothesis.

Endothelial cell-associated tissue factor pathway inhibitor (TFPI) antigen in severe nondiabetic obese patients: effect of hyperinsulinemia.

It has been suggested that the extrinsic coagulation system plays a crucial role in the initiation of blood coagulation in atherosclerotic disease and that TFPI, the inhibitor of the factor VIIa/tissue factor complex, bound to the endothelial cells, could prevent in vivo blood clotting. Because obesity has a role in the pathogenesis of atherosclerotic cardiovascular disease, we measured TFPI antigen plasma levels (ng/mL) by ELISA at baseline and 5 minutes after an IV bolus of 20 IU/kg body weight of unfractionated commercial mucous heparin in 12 obese patients with a mean body mass index (BMI) of 41.4 +/- 1.4 kg/m2 and 14 normal-weight control subjects (BMI 23.1 +/- 1.3 kg/m2). All subjects were submitted to an OGTT. The obese patients displayed a normal glucose tolerance. However, they had a different glucose-induced hyperinsulinemia (14.9 +/- 2.0 versus 7.8 +/- 0.8 mU/L, p < 0.01). Total serum cholesterol did not differ between controls and obese patients, whereas plasma triglycerides were higher in the latter group. Basal TFPI antigen plasma levels were similar in obese and controls (83.8 +/- 5.0 versus 77.7 +/- 3.5 ng/mL, p = N.S.). In contrast, after heparin a significantly lower rise in TFPI antigen plasma levels was observed in obese patients (511.2 +/- 43.4 ng/mL) (p < 0.003). Moreover, a significant inverse correlation was found between the heparin-stimulated TFPI antigen plasma levels and both BMI and basal plasma insulin concentrations. Thus, the link between insulin level and endothelial cell-associated TFPI could at least partially explain why obese patients are more prone to develop cardiovascular disorders.

Tissue factor pathway inhibitor (TFPI) antigen plasma level in patients with interstitial lung disease before and after heparin administration.

The extrinsic pathway is probably the predominant pathway in initiating blood coagulation in inflammatory lung diseases. Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor of factor VIIa/tissue factor in the presence of factor Xa. As it has been shown recently that TFPI plasma levels are increased under acute inflammatory conditions, we studied TFPI antigen plasma levels before and after injecting 20 IU/kg body weight of unfractionated heparin into 49 patients with different stages of sarcoidosis, into 9 with idiopathic pulmonary fibrosis, and into 15 normal controls. TFPI, before injecting heparin, was significantly increased in all sarcoidosis stages (stage I: 97.6 +/- 6.4 ng/mL; stage II: 116.2 +/- 11.9 ng/mL; stage III: 116.3 +/- 7.3 ng/mL) and in idiopathic pulmonary fibrosis (116.8 +/- 16.1 ng/mL), as compared to the control group (77.7 +/- 3.3 ng/mL). No correlation was found between the intensity of the activity of sarcoidosis, measured as BAL white cell count, and TFPI. Five minutes after heparin administration the rise in TFPI was lower, although not statistically significant, in all sarcoidosis stages than in controls. In contrast, idiopathic pulmonary fibrosis had a similar or even higher TFPI elevation than the control group. In sarcoidosis the elevated TFPI and the lower capacity by endothelial cells to release TFPI after heparin may represent a compensatory mechanism to prevent blood clotting and/or the endothelial cell dysfunction of the microvasculature in this condition. In contrast, the extensive mesenchymal cell proliferation present in idiopathic pulmonary fibrosis could explain our findings, as it has been shown that cultured human mesangial cells produce and release TFPI.

Tissue factor pathway inhibitor (TFPI) activity in uremic patients during hemodialysis.

We studied tissue factor pathway inhibitor (TFPI) activity during hemodialysis in 10 uremic patients who were not receiving anticoagulant for at least 120 minutes. TFPI activity before dialysis was normal (patients 107 +/- 5.8%, controls 104 +/- 4.5%). During extracorporeal circuit it rose progressively with a statistically significant difference, reaching a plateau between 60 and 120 minutes. Since thrombin induces a marked redistribution and release of TFPI from stimulated endothelial cells and platelets contain about 10% of TFPI activity that is secreted following activation it is possible that thrombin-induced release of TFPI by endothelium and platelets could account for the increased TFPI we found during hemodialysis. To investigate this possibility we measured during dialysis beta-thromboglobulin (beta-TG), thrombin-antithrombin complex (TAT) and prothrombin fragment 1.2 (F 1.2). The increased levels of beta-TG, TAT and F1.2 we noted during extracorporeal circuit are in keeping with this concept. One hundred eighty minutes after initiation of dialysis, by which time all patients were receiving heparin there was a further increase in TFPI (to more than 200% of baseline), due to the presence of the glycosaminoglycan. This was due the previously reported displacement by heparin of the major intravascular pool of TFPI, from endothelial cell surfaces.