Expression of receptors for plasminogen activators on endothelial cell surface depends on their origin

Summary.  Receptors for plasminogen activators present on endothelial cell (EC) surface regulate local plasmin activity. Plasmin generation by human ECs, derived from cerebral cortex, skin and lung, iliac artery, iliac vein, aorta and coronary artery, was studied. The respective ECs were treated with recombinant tissue plasminogen activator (rt-PA) or with recombinant urokinase-type plasminogen activator (ru-PA), washed, plasminogen added and the plasmin generated then assayed. The largest amounts of plasmin were generated by cerebral ECs, under baseline conditions or after exposure to rt-PA or ru-PA ( P  < 0.0001). Exposure to rt-PA also resulted in more plasmin generation than ru-PA in the cerebral ECs ( P  < 0.0001) but not in the other ECs. Heparin enhanced plasmin generation by both rt-PA and ru-PA. Specific antibody against annexin II, a t-PA receptor, blocked plasmin generation by rt-PA. Western blotting showed higher amounts of annexin II on the cell membrane in cerebral ECs. This suggests that expression of annexin II in ECs depends on their location, being greatest in cerebral ECs. In contrast, expression of u-PA receptor was the same for all ECs. This has implications for higher risk of intracranial bleeding during thrombolytic therapy, and for a role of t-PA in neurological development and function.     

Antibodies against dengue virus E protein peptide bind to human plasminogen and inhibit plasmin activity

Both mice and rabbits immunized with dengue virus E protein peptide spanning amino acids 100–119 (D4E) produced antibodies that reacted not only with the D4E peptide itself but also with human plasminogen, as shown by ELISA and Western blot. Sera from dengue virus-hyperimmunized mice and dengue patients also contained antibodies against D4E and plasminogen. Furthermore, such sera all contained plasmin inhibitory activity. Using affinity-purified anti-D4E antibodies and free D4E peptide for competitive inhibition, we demonstrated that the inhibition of plasmin activity was due to anti-D4E antibodies rather than other substances in the sera. Taken together, these results suggest dengue virus E protein amino acids 100–119 are a cross-reactive immunogenic region, and antibodies against this region may interfere with human fibrinolysis.     

Study of β‐casein denaturation by microparticle‐enhanced nephelometric immunoassay

Rabbit anti‐native bovine ß‐casein antiserum reacted with native ß‐casein and fragments f( 1–105/7) and f( 106–209) formed during ß‐casein proteolysis by plasmin. Agglutination of ß‐casein‐coated microparticles by anti‐native ß‐casein antiserum was weakly inhibited by ß‐casein f(1–105/7) and ß‐casein f( 106–209) (0·04 and 1·4%, respectively, compared with native ß‐casein). Immunoreactivity of these ß‐casein peptides in microparticle‐enhanced nephelometric immunoassay was more preserved in the whole ß‐casein than in its isolated fragments. The protein concentration producing 50% inhibition of the ß‐casein‐coated microparticle agglutination with anti‐native ß‐casein antiserum increased during ß‐casein denaturation. A microparticle‐enhanced nephelometric immunoassay, quantifying changes of this inhibiting protein concentration, permitted detection of alteration of the immunoreactivity of ß‐casein during its plasmin proteolysis and heat denaturation, providing an adequate test for the integrity of the whole molecule.     

颅脑肿瘤手术行急性等容血液稀释的临床研究

目的：研究急性等容血液稀释对颅脑肿瘤病人血流动力学、氧转运及凝血纤溶方面的影响,探讨该方法的安全性。方法：选择颅脑肿瘤手术病人12例,麻醉后从右颈内静脉放置Swan～Ganz导管,从桡动脉放血8ml/kg,同时等速从静脉输入等量的海脉素。分别测定血液稀释前后的血流动力学,氧转运及凝血纤溶方面的指标。结果：CO、SV、DO2显著增加(P＜0.05);PT延长(P＜0.05);PLT较血液稀释前减少,其余指标无明显改变。结论：急性等容血液稀释对颅脑肿瘤病人的血流动力学及凝血纤溶功能影响小,而氧供增加,是一安全有效的血液保护方法。     

Decreased Plasminogen Activator Inhibitor-1 Levels in Coronary Artery Aneurysmatic Patients

BACKGROUND: Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of arterial aneurysms through increased proteolysis of extracellular matrix proteins. Increased proteolysis due to elevated matrix degrading enzyme activity in the arterial wall may act as a susceptibility factor for the development of coronary aneurysms. Plasmin strongly stimulates pro-MMP enzyme conversion to the active form. Plasmin hyperactivity due to decreased plasminogen activator inhibitor-1 (PAI-1) may cause MMP over activity and coronary aneurysms. The aim of this study was to investigate the association between PAI-1 and presence of coronary aneurysms. METHODS: Twenty-three patients with aneurysmal coronary artery disease and stable angina were enrolled into study (Group 1). Twenty-two patients without coronary aneurysm were selected as a control group (Group 2). PAI-1 was measured in peripheral venous blood. RESULTS: The plasma PAI-1 level was lower in the coronary artery aneurysmatic patients compared to the control group (8.41 +/- 4.28 vs. 13.32 +/- 10.05 ng/ml, p = 0.037). Serum C-reactive protein (CRP) values were not significantly different between groups (3.83 +/- 1.08 vs. 4.01 +/- 1.35 mg/l, p >0.05). CONCLUSION: Increased matrix degrading enzyme activity can cause arterial wall destruction through increased proteolysis of extracellular matrix proteins. Unregulated plasmin hyperactivity due to decreased inhibition by PAI-1 may play an important role in coronary aneurysm formation.     

Interaction of spirochetes with the host fibrinolytic system and potential roles in pathogenesis

Abstract

The pathogenic spirochetes Borrelia burgdorferi, B. hermsii, B. recurrentis, Treponema denticola and Leptospira spp. are the etiologic agents of Lyme disease, relapsing fever, periodontitis and leptospirosis, respectively. Lyme borreliosis is a multi-systemic disorder and the most prevalent tick-borne disease in the northern hemisphere. Tick-borne relapsing fever is persistent in endemic areas worldwide, representing a significant burden in some African regions. Periodontal disease, a chronic inflammatory disorder that often leads to tooth loss, is caused by several potential pathogens found in the oral cavity including T. denticola. Leptospirosis is considered the most widespread zoonosis, and the predominant human disease in tropical, undeveloped regions. What these diseases have in common is that they are a significant burden to healthcare costs in the absence of prophylactic measures. This review addresses the interaction of these spirochetes with the fibrinolytic system, plasminogen (Plg) binding to the surface of bacteria and the generation of plasmin (Pla) on their surface. The consequences on host–pathogen interactions when the spirochetes are endowed with this proteolytic activity are discussed on the basis of the results reported in the literature. Spirochetes equipped with Pla activity have been shown to degrade extracellular matrix (ECM) components, in addition to digesting fibrin, facilitating bacterial invasion and dissemination. Pla generation triggers the induction of matrix metalloproteases (MMPs) in a cascade of events that enhances the proteolytic capacity of the spirochetes. These activities in concert with the interference exerted by the Plg/Pla on the complement system – helping the bacteria to evade the immune system – should illuminate our understanding of the mechanisms involved in host infection.     

Amiloride lowers blood pressure and attenuates urine plasminogen activation in patients with treatment–resistant hypertension

In conditions with albuminuria, plasminogen is aberrantly filtered across the glomerular barrier and activated along the tubular system to plasmin. In the collecting duct, plasmin activates epithelial sodium channels (ENaC) proteolytically. Hyperactivity of ENaC could link microalbuminuria/proteinuria to resistant hypertension. Amiloride, an ENaC inhibitor, inhibits urokinase–type plasminogen activator. We hypothesized that amiloride (1) reduces blood pressure (BP); (2) attenuates plasminogen–to–plasmin activation; and (3) inhibits urine urokinase–type plasminogen activator in patients with resistant hypertension and type 2 diabetes mellitus (T2DM).In an open–label, non–randomized, 8–week intervention study, a cohort (n = 80) of patients with resistant hypertension and T2DM were included. Amiloride (5 mg/d) was added to previous triple antihypertensive treatment (including a diuretic and an inhibitor of the renin–angiotensin–aldosterone system) and increased to 10 mg if BP control was not achieved at 4 weeks. Complete dataset for urine analysis was available in 60 patients. Systolic and diastolic BP measured by ambulatory BP monitoring and office monitoring were significantly reduced. Average daytime BP was reduced by 6.3/3.0 mm Hg. Seven of 80 cases (9%) discontinued amiloride due to hyperkalemia >5.5 mol/L, the most frequent adverse event. Urinary plasmin(ogen) and albumin excretions were significantly reduced after amiloride treatment (P < .0001). Urokinase activity was detectable in macroalbuminuric urine, with a tendency toward reduction in activity after amiloride treatment. Amiloride lowers BP, urine plasminogen excretion and activation, and albumin/creatinine ratio, and is a relevant add–on medication for the treatment of resistant hypertension in patients with T2DM and microalbuminuria.