Support vector machine (SVM) based multiclass prediction with basic statistical analysis of plasminogen activators

Plasminogen (Pg), the precursor of the proteolytic and fibrinolytic enzyme of blood, is converted to the active enzyme plasmin (Pm) by different plasminogen activators (tissue plasminogen activators and urokinase), including the bacterial activators streptokinase and staphylokinase, which activate Pg to Pm and thus are used clinically for thrombolysis. The identification of Pg-activators is therefore an important step in understanding their functional mechanism and derives new therapies.

Expression of protease nexin-1 and plasminogen activators during follicular growth and the periovulatory period in cattle

Extracellular matrix remodeling occurs during ovarian follicular development, mediated by plasminogen activators (PAs) and PA inhibitors including protease nexin-1 (PN-1). In the present study we measured expression/activity of the PA system in bovine follicles at different stages of development by timed collection of ovaries during the first follicular wave and during the periovulatory period, and in follicles collected from an abattoir. The abundance of mRNA encoding PN-1, tissue-type PA (tPA), urokinase (uPA) and PA inhibitor-1 (PAI-1) were initially upregulated by human chorionic gonadotropin (hCG) in bovine preovulatory follicular wall homogenates. PN-1, PAI-1 and tPA mRNA expression then decreased near the expected time of ovulation, whereas uPA mRNA levels remained high. PN-1 concentration in follicular fluid (FF) decreased and reached the lowest level at the time of ovulation, whereas plasmin activity in FF increased significantly after hCG. Follicles collected from the abattoir were classified as non-atretic, early-atretic or atretic based on FF estradiol and progesterone content: PN-1 protein levels in FF were significantly higher in non-atretic than in atretic follicles, and plasmin activity was correspondingly higher in the atretic follicles. No changes in PN-1 levels in FF were observed during the growth of pre-deviation follicles early in a follicular wave. These results indicate that PN-1 may be involved in the process of atresia in non-ovulatory dominant follicles and the prevention of precocious proteolysis in periovulatory follicles.

Influence of temperature on the release of plasminogen activator.

Fibrinolysis is a basic defense mechanism of the organism designed to control the deposition of fibrin in the vascular system and elsewhere. Fibrinolytic activity was measured by the fibrin plate method for three groups of rats (N = 6) that were maintained at room temperature, 20-25 degrees C, 3 degrees C or 38 degrees C for 4 h before testing. Based on measurement of fibrinolytic activity, the level of plasminogen activator released from isolated aortic segments of rats maintained at room temperature (24-28 degrees C) differed significantly from that of the 38 degrees C group. The animals maintained at 3 degrees C did not release plasminogen activator, suggesting that the fibrinolytic response was impaired at low temperature.

Subconjunctival and topical application of recombinant tissue plasminogen activator in rabbits

To quantify fibrin degradation products after topical and subconjunctival administration of recombinant tissue plasminogen activator in rabbits. Methods: Fibrin formation was induced in the anterior chamber in 25 rabbits. Subsequently, five rabbits received an injection of r-TPA (positive control) in the anterior chamber, another 10 received a subconjunctival injection of r-TPA, and the remaining 10 received instillations of topical r-TPA. Afterwards, samples of aqueous humor were collected and semi-quantitative analysis of fibrin degradation products (FDP) was performed. Results: No statistical differences were noted between the treatment and control groups at any time point. Fibrin degradation products semi-quantification showed statistical improvement in the control group and the subconjunctival group. Conclusion: Fibrin degradation products were observed in the anterior chamber after subconjunctival administration of r-TPA. However, it was probably not sufficient to cause fibrin degradation. Topical r-TPA did not effectively absorb anterior chamber fibrin.

OmpL1 Is an Extracellular Matrix- and Plasminogen-Interacting Protein of Leptospira spp.

Leptospirosis is a zoonosis with multisystem involvement caused by pathogenic strains of the genus Leptospira. OmpL1 is an outer membrane protein of Leptospira spp. that is expressed during infection. In this work, we investigated novel features of this protein. We describe that OmpL1 is a novel leptospiral extracellular matrix (ECM)-binding protein and a plasminogen (PLG) receptor. The recombinant protein was expressed in Escherichia coli BL21(DE3) Star/pLysS as inclusion bodies, refolded, and purified by metal-chelating chromatography. The protein presented a typical beta-strand secondary structure, as evaluated by circular dichroism spectroscopy. The recombinant protein reacted with antibodies in serum samples from convalescent leptospirosis patients with a high specificity compared to serum samples from individuals with unrelated diseases. These data strengthen the usefulness of OmpL1 as a diagnostic marker of leptospirosis. The characterization of the immunogenicity of recombinant OmpL1 in inoculated BALB/c mice showed that the protein has the capacity to elicit humoral and cellular immune responses, as denoted by high antibody titers and the proliferation of lymphocytes. We demonstrate that OmpL1 has the ability to mediate attachment to laminin and plasma fibronectin, with KD (equilibrium dissociation constant) values of 2,099.93 +/- 871.03 nM and 1,239.23 +/- 506.85 nM, respectively. OmpL1 is also a PLG receptor, with a KD of 368.63 +/- 121.23 nM, capable of generating enzymatically active plasmin. This is the first report that shows and characterizes OmpL1 as an ECM-interacting and a PLG-binding protein of Leptospira spp. that may play a role in bacterial pathogenesis when expressed during infection.

Lsa30, a novel adhesin of Leptospira interrogans binds human plasminogen and the complement regulator C4bp

Pathogenic Leptospira is the etiological agent of leptospirosis, a life-threatening disease that affects populations worldwide. Surface proteins have the potential to promote several activities, including adhesion. This work aimed to study the leptospiral coding sequence (CDS) LIC11087, genome annotated as hypothetical outer membrane protein. The LIC11087 gene was cloned and expressed in Escherichia coil BL21 (DE3) strain by using the expression vector pAE. The recombinant protein tagged with N-terminal 6XHis was purified by metal-charged chromatography and characterized by circular dichroism (CD) spectroscopy. The recombinant protein has the ability to mediate attachment to the extracellular matrix (ECM) components, laminin and plasma fibronectin, and was named Lsa30 (Leptospiral surface adhesin of 30 kDa). Lsa30 binds to laminin and to plasma fibronectin in a dose-dependent and saturable manner, with dissociation equilibrium constants (K-D) of 292 +/- 24 nM and 157 +/- 35 nM, respectively. Moreover, the Lsa30 is a plasminogen (PLC) receptor, capable of generating plasmin, in the presence of activator. This protein may interfere with the complement cascade by interacting with C4bp regulator. The Lsa30 is probably a new surface protein of Leptospira as revealed by immunofluorescence assays with living organisms and the reactivity with antibodies present in serum samples of experimentally infected hamsters. Thus, Lsa30 is a novel versatile protein that may play a role in mediating adhesion and may help pathogenic Leptospira to overcome tissue barriers and to escape the immune system. (C) 2012 Elsevier Ltd. All rights reserved.

Calcium Binding to Leptospira Outer Membrane Antigen LipL32 Is Not Necessary for Its Interaction with Plasma Fibronectin, Collagen Type IV, and Plasminogen

LipL32 is the most abundant outer membrane protein from pathogenic Leptospira and has been shown to bind extracellular matrix (ECM) proteins as well as Ca2+. Recent crystal structures have been obtained for the protein in the apo-and Ca2+-bound forms. In this work, we produced three LipL32 mutants (D163-168A, Q67A, and S247A) and evaluated their ability to interact with Ca2+ and with ECM glycoproteins and human plasminogen. The D163-168A mutant modifies aspartate residues involved in Ca2+ binding, whereas the other two modify residues in a cavity on the other side of the protein structure. Loss of calcium binding in the D163-D168A mutant was confirmed using intrinsic tryptophan fluorescence, circular dichroism, and thermal denaturation whereas the Q67A and S247A mutants presented the same Ca2+ affinity as the wild-type protein. We then evaluated if Ca2+ binding to LipL32 would be crucial for its interaction with collagen type IV and plasma proteins fibronectin and plasminogen. Surprisingly, the wild-type protein and all three mutants, including the D163-168A variant, bound to these ECM proteins with very similar affinities, both in the presence and absence of Ca2+ ions. In conclusion, calcium binding to LipL32 may be important to stabilize the protein, but is not necessary to mediate interaction with host extracellular matrix proteins.

Interaction of leptospira elongation factor tu with plasminogen and complement factor h: a metabolic leptospiral protein with moonlighting activities

The elongation factor Tu (EF-Tu), an abundant bacterial protein involved in protein synthesis, has been shown to display moonlighting activities. Known to perform more than one function at different times or in different places, it is found in several subcellular locations in a single organism, and may serve as a virulence factor in a range of important human pathogens. Here we demonstrate that Leptospira EF-Tu is surface-exposed and performs additional roles as a cell-surface receptor for host plasma proteins. It binds plasminogen in a dose-dependent manner, and lysine residues are critical for this interaction. Bound plasminogen is converted to active plasmin, which, in turn, is able to cleave the natural substrates C3b and fibrinogen. Leptospira EF-Tu also acquires the complement regulator Factor H (FH). FH bound to immobilized EF-Tu displays cofactor activity, mediating C3b degradation by Factor I (FI). In this manner, EF-Tu may contribute to leptospiral tissue invasion and complement inactivation. To our knowledge, this is the first description of a leptospiral protein exhibiting moonlighting activities

Bifidobacterium - Human Host Interaction: Role of Human Plasminogen

Bifidobacterium is an important genus of the human gastrointestinal microbiota, affecting several host physiological features. Despite the numerous Bifidobacterium related health-promoting activities, there is still a dearth of information about the molecular mechanisms at the basis of the interaction between this microorganism and the host. Bacterial surface associated proteins may play an important role in this interaction because of their ability to intervene with host molecules, as recently reported for the host protein plasminogen. Plasminogen is the zymogen of the trypsin-like serine protease plasmin, an enzyme with a broad substrate specificity. Aim of this thesis is to deepen the knowledge about the interaction between Bifidobacterium and the human plasminogen system and its role in the Bifidobacterium-host interaction process. As a bifidobacterial model, B. animalis subsp. lactis BI07 has been used because of its large usage in dairy and pharmaceutical preparations. We started from the molecular characterization of the interaction between plasminogen and one bifidobacterial plasminogen receptor, DnaK, a cell wall protein showing high affinity for plasminogen, and went on with the study of the impact of intestinal environmental factors, such as bile salts and inflammation, on the plasminogen-mediated Bifidobacterium-host interaction. According to our in vitro findings, by enhancing the activation of the bifidobacterial bound plasminogen to plasmin, the host inflammatory response results in the decrease of the bifidobacterial adhesion to the host enterocytes, favouring bacterial migration to the luminal compartment. Conversely, in the absence of inflammation, plasminogen acts as a molecular bridge between host enterocytes and bifidobacteria, enhancing Bifidobacterium adhesion. Furthermore, adaptation to physiological concentrations of bile salts enhances the capability of this microorganism to interact with the host plasminogen system. The host plasminogen system thus represents an important and flexible tool used by bifidobacteria in the cross-talk with the host.

Management of submacular hemorrhage with intravitreal versus subretinal injection of recombinant tissue plasminogen activator

To compare the efficacy of pars plana vitrectomy (ppV) with intravitreal injection of recombinant tissue plasminogen activator (rtPA) and gas versus ppV with subretinal injection of rtPA and intravitreal injection of gas.

Differential release of plasminogen activator inhibitors (PAIs) during dual perfusion of human placenta: implications in preeclampsia

Plasminogen activator inhibitors (PAIs) play critical roles in regulating cellular invasion and fibrinolysis. An increase in the ratio of PAI-1/PAI-2 in placenta and maternal serum is suggested to result in excessive intervillous fibrin deposition and placental infarction in pregnancies complicated by preeclampsia (PE) and intrauterine growth restriction (IUGR). In the current study we used dual (maternal and fetal) perfusion of human term placentas to examine the release of PAIs to the intervillous space. ELISA revealed a significant time-dependent increase in total PAI-1 levels in maternal perfusate (MP) between 1 and 7h of perfusion. Conversely, PAI-2 levels decreased resulting in a 3-fold increase in the PAI-1/PAI-2 ratio in MP. Levels of PAI-1, but not PAI-2, in placental tissue extracts increased during perfusion. In perfusions carried out with xanthine and xanthine oxidase (X + XO), compounds used to generate reactive oxygen species (ROS), no time-dependent increase in total PAI-1 levels was observed. In addition, X + XO treatment promoted a 3-fold reduction in active PAI-1 levels in MP, indicating that ROS decrease PAI-1 release to MP. The finding of a time-dependent change in patterns of PAI expression and response to ROS indicates the utility of dual perfusion as a model to dissect mechanism(s) promoting aberrant fibrinolysis in pregnancies complicated by PE and IUGR.

Time- and dose-related regional fluxes of tissue-type plasminogen activator in anesthetized endotoxemic pigs

BACKGROUND: Acute endotoxinemia elicits an early fibrinolytic response. This study analyzes the effects of the dose and duration of endotoxin infusion on arterial levels of tissue-type plasminogen activator (tPA) and pulmonary, mesenteric and hepatic plasma tPA fluxes. METHODS: Pigs were randomized to receive an acute, high-dose (for 6 h, n=13, high ETX) or a prolonged, low-dose (for 18 h, n=18, low ETX) infusion of endotoxin or saline vehicle alone (for 18 h, n=14, control). All animals were fluid resuscitated to maintain a normodynamic circulation. Systemic and regional blood flows were measured and arterial, pulmonary arterial, portal and hepatic venous blood samples were analyzed to calculate regional net fluxes of tPA. Plasma tumor necrosis factor (TNF-alpha) levels were analyzed. RESULTS: Mesenteric tPA release and hepatic uptake increased maximally at 1.5 h in ETX groups related to dose. Maximal mesenteric tPA release [high ETX 612 (138-1185) microg/min/kg, low ETX 72 (32-94) microg/min/kg, median+/-interquartile range] and hepatic tPA uptake [high ETX -1549 (-1134 to -2194) microg/min/kg, low ETX -153 (-105 to -307) microg/min/kg] correlated to TNF-alpha levels. Regional tPA fluxes returned to baseline levels at 6 h in both ETX groups and also remained low during sustained low ETX. No changes were observed in control animals. CONCLUSIONS: Endotoxemia induces an early increase in mesenteric tPA release and hepatic tPA uptake related to the severity of endotoxemia. The time patterns of changes in mesenteric and hepatic tPA fluxes are similar in acute high-dose endotoxemia and sustained low-dose endotoxemia.