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Plasminogen is an abundant plasma protein that exists in various zymogenic forms. Plasmin, the proteolytically active form of plasminogen, is known for its essential role in fibrinolysis. To date, therapeutic targeting of the fibrinolytic system has been for 2 purposes: to promote plasmin generation for thromboembolic conditions or to stop plasmin to reduce bleeding. However, plasmin and plasminogen serve other important functions, some of which are unrelated to fibrin removal. Indeed, for >40 years, the antifibrinolytic agent tranexamic acid has been administered for its serendipitously discovered skin-whitening properties. Plasmin also plays an important role in the removal of misfolded/aggregated proteins and can trigger other enzymatic cascades, including complement. In addition, plasminogen, via binding to one of its dozen cell surface receptors, can modulate cell behavior and further influence immune and inflammatory processes. Plasminogen administration itself has been reported to improve thrombolysis and to accelerate wound repair. Although many of these more recent findings have been derived from in vitro or animal studies, the use of antifibrinolytic agents to reduce bleeding in humans has revealed additional clinically relevant consequences, particularly in relation to reducing infection risk that is independent of its hemostatic effects. The finding that many viruses harness the host plasminogen to aid infectivity has suggested that antifibrinolytic agents may have antiviral benefits. Here, we review the broadening role of the plasminogen-activating system in physiology and pathophysiology and how manipulation of this system may be harnessed for benefits unrelated to its conventional application in thrombosis and hemostasis., (© 2021 by The American Society of Hematology.)

The cornea is a relatively unique tissue in the body in that it possesses specific features such as a lack of blood vessels that contribute to its transparency. The cornea is supplied with soluble blood components such as albumin, globulin, and fibrinogen as well as with nutrients, oxygen, and bioactive substances by diffusion from aqueous humor and limbal vessels as well as a result of its exposure to tear fluid. The healthy cornea is largely devoid of cellular components of blood such as polymorphonuclear leukocytes, monocytes-macrophages, and platelets. The location of the cornea at the ocular surface renders it susceptible to external insults, and its avascular nature necessitates the operation of healing and defense mechanisms in a manner independent of a direct blood supply. The fibrinolytic system, which was first recognized for its role in the degradation of fibrin clots in the vasculature, has also been found to contribute to various biological processes outside of blood vessels. Fibrinolytic factors thus play an important role in biological defense of the cornea. In this review, we address the function of the fibrinolytic system in corneal defense including wound healing and the inflammatory response., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Competing Interests: The author has no conflict of interest to report.

Competing Interests: None.

Bradykinin mediated angioedema (BK-AE) can be associated either with C1Inhibitor deficiency (hereditary and acquired forms), either with normal C1Inh (hereditary form and drug induced AE as angiotensin converting enzyme inhibitors…). In case of high clinical suspicion of BK-AE, C1Inh exploration must be done at first: C1Inh function and antigenemy as well as C4 concentration. C1Inh deficiency is significant if the tests are below 50 % of the normal values and controlled a second time. In case of C1Inh deficiency, you have to identify hereditary from acquired forms. C1q and anti-C1Inh antibody tests are useful for acquired BK-AE. SERPING1 gene screening must be done if a hereditary angioedema is suspected, even if there is no family context (de novo mutation 15 %). If a hereditary BK-AE with normal C1Inh is suspected, F12 and PLG gene screening is suitable., (Copyright © 2018. Published by Elsevier Masson SAS.)

Plasmin is a proteolytic enzyme that is crucial in fibrinolysis. In oral tissues, the plasminogen system plays an essential role in physiological and pathological processes, which in addition to fibrinolysis include degradation of extracellular matrix, inflammation, immune response, angiogenesis, tissue remodeling, cell migration, and wound healing. Oral tissues reveal a change in the plasminogen system during pathological processes such as periodontitis, peri-implantitis, or pulpitis, as well as in response to mechanical load. The plasminogen system is also a key element in tissue regeneration. The number of studies investigating the plasminogen system in dentistry have grown continuously in recent years, highlighting its increasing relevance in dental medicine. In this review, we present the diverse functions of the plasminogen system in physiology and its importance for dental specialists in pathology and regeneration. We thus provide an overview of the current knowledge on the role of the plasminogen system in the different fields of dentistry, including endodontics, orthodontics, periodontics, and oral surgery., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Hyperfibrinolysis is a systemic condition occurring in various clinical disorders such as trauma, liver cirrhosis, and leukemia. Apart from increased bleeding tendency, the pathophysiological consequences of hyperfibrinolysis remain largely unknown. Our aim was to develop an experimental model of hyperfibrinolysis and to study its effects on the homeostasis of the blood-brain barrier (BBB). We induced a sustained hyperfibrinolytic state in mice by hydrodynamic transfection of a plasmid encoding for tissue-type plasminogen activator (tPA). As revealed by near-infrared fluorescence imaging, hyperfibrinolytic mice presented a significant increase in BBB permeability. Using a set of deletion variants of tPA and pharmacological approaches, we demonstrated that this effect was independent of N-methyl-D-aspartate receptor, low-density lipoprotein-related protein, protease-activated receptor-1, or matrix metalloproteinases. In contrast, we provide evidence that hyperfibrinolysis-induced BBB leakage is dependent on plasmin-mediated generation of bradykinin and subsequent activation of bradykinin B2 receptors. Accordingly, this effect was prevented by icatibant, a clinically available B2 receptor antagonist. In agreement with these preclinical data, bradykinin generation was also observed in humans in a context of acute pharmacological hyperfibrinolysis. Altogether, these results suggest that B2 receptor blockade may be a promising strategy to prevent the deleterious effects of hyperfibrinolysis on the homeostasis of the BBB., (© 2016 by The American Society of Hematology.)

Removal of dead cells in the absence of concomitant immune stimulation is essential for tissue homeostasis. We recently identified an injury-induced protein misfolding event that orchestrates the plasmin-dependent proteolytic degradation of necrotic cells. As impaired clearance of dead cells by the innate immune system predisposes to autoimmunity, we determined whether plasmin could influence endocytosis and immune cell stimulation by dendritic cells - a critical cell that links the innate and adaptive immune systems. We find that plasmin generated on the surface of necrotic cells enhances their phagocytic removal by human monocyte-derived dendritic cells. Plasmin also promoted phagocytosis of protease-resistant microparticles by diverse mouse dendritic cell sub-types both in vitro and in vivo. Together with an increased phagocytic capacity, plasmin-treated dendritic cells maintain an immature phenotype, exhibit reduced migration to lymph nodes, increase their expression/release of the immunosuppressive cytokine TGF-β, and lose their capacity to mount an allogeneic response. Collectively, our findings support a novel role for plasmin formed on dead cells and other phagocytic targets in maintaining tissue homeostasis by increasing the phagocytic function of dendritic cells while simultaneously decreasing their immunostimulatory capacity consistent with producing an immunosuppressive state.

The fibrinolytic system, known for its ability to regulate the activation of the zymogen plasminogen into active plasmin, has been primarily associated with the removal of fibrin and blood clots. Tissue-type plasminogen activator, the most well-recognized plasminogen activator, was harnessed for therapeutic benefit against thromboembolic disorders more than 30 years ago, whereas inhibition of this system has been proven effective for certain bleeding disorders. However, in recent years, new and unexpected functional roles for this system have been identified mostly in relation to the central nervous system that are both unrelated and independent of fibrin degradation and clot removal. Hence, it seems reasonable to ask whether agents used to modify components or activities of the fibrinolytic system have any clinical consequences unrelated to their intended use in hemostasis. This review will provide an overview of these new features of the fibrinolytic system and will also focus on prospective considerations in the use of fibrinolytic and antifibrinolytic agents., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aside from their role in hemostasis, coagulant and fibrinolytic proteases are important mediators of inflammation in diseases such as asthma, atherosclerosis, rheumatoid arthritis, and cancer. The blood circulating zymogens of these proteases enter damaged tissue as a consequence of vascular leak or rupture to become activated and contribute to extravascular coagulation or fibrinolysis. The coagulants, factor Xa (FXa), factor VIIa (FVIIa), tissue factor, and thrombin, also evoke cell-mediated actions on structural cells (e.g., fibroblasts and smooth muscle cells) or inflammatory cells (e.g., macrophages) via the proteolytic activation of protease-activated receptors (PARs). Plasmin, the principle enzymatic mediator of fibrinolysis, also forms toll-like receptor-4 (TLR-4) activating fibrin degradation products (FDPs) and can release latent-matrix bound growth factors such as transforming growth factor-β (TGF-β). Furthermore, the proteases that convert plasminogen into plasmin (e.g., urokinase plasminogen activator) evoke plasmin-independent proinflammatory actions involving coreceptor activation. Selectively targeting the receptor-mediated actions of hemostatic proteases is a strategy that may be used to treat inflammatory disease without the bleeding complications of conventional anticoagulant therapies. The mechanisms by which proteases of the coagulant and fibrinolytic systems contribute to extravascular inflammation in disease will be considered in this review.

Fibrinogen is cleaved by thrombin to fibrin, which provides the blood clot with its essential structural backbone. As an acute phase protein, the plasma levels of fibrinogen are increased in response to inflammatory conditions. In addition to fibrinogen levels, fibrin clot structure is altered by a number of factors. These include thrombin levels, treatment with common cardiovascular medications, such as aspirin, anticoagulants, statins and fibrates, as well as metabolic disease states such as diabetes mellitus and hyperhomocysteinaemia. In vitro studies of fibrin clot structure can provide information regarding fibre density, clot porosity, the mechanical strength of fibres and fibrinolysis. A change in fibrin clot structure, to a denser clot with smaller pores which is more resistant to lysis, is strongly associated with cardiovascular disease. This pathological change is present in patients with arterial as well as venous diseases, and is also found in a moderate form in relatives of patients with cardiovascular disease. Pharmacological therapies, aimed at both the treatment and prophylaxis of cardiovascular disease, appear to result in positive changes to the fibrin clot structure. As such, therapies aimed at 'normalising' fibrin clot structure may be of benefit in the prevention and treatment of cardiovascular disease.

Objective: Osteoporosis is a skeletal disorder characterized by low bone mass and increased bone fragility associated with aging, menopause, smoking, obesity, or diabetes. Persistent inflammation has been identified as an instigating factor in progressive bone loss. In addition to the role of fibrin in coagulation, inordinate fibrin deposition within a tissue matrix results in increased local inflammation. Given that fibrin accumulation is a hallmark of osteoporosis-related comorbidities, we undertook this study to test the hypothesis that persistent fibrin deposition causes inflammatory osteoporosis., Methods: Multiple imaging modalities, bone integrity metrics, and histologic analyses were employed to evaluate skeletal derangements in relation to fibrin deposition, circulating fibrinogen levels, and systemic markers of inflammation in mice that were plasminogen deficient and in plasminogen-deficient mice that were concomitantly either fibrinogen deficient or carrying a mutant form of fibrinogen lacking the αM β2 binding motif., Results: Mice generated with a genetic deficit in the key fibrinolytic protease, plasmin, uniformly developed severe osteoporosis. Furthermore, the development of osteoporosis was fibrin(ogen) dependent, and the derangements in the bone remodeling unit were mechanistically tied to fibrin(ogen)-mediated activation of osteoclasts via activation of the leukocyte integrin receptor αM β2 on monocytes and secondary stimulation of osteoblasts by RANKL. Notably, the genetic elimination of fibrin(ogen) or the expression of a mutant form of fibrinogen retaining clotting function but lacking the αM β2 binding motif prevented the degenerative skeletal phenotypes, resulting in normal local and systemic cytokine levels., Conclusion: Taken together, these data reveal for the first time that fibrin promotes inflammation-driven systemic osteoporosis, which suggests a novel association between hemostasis, inflammation, and bone biology., (Copyright © 2014 by the American College of Rheumatology.)

Great advances have been made in our understanding of the fibrinolytic system from the initial discovery of proteolysis of fibrin by plasmin to the multifaceted and complex role of the plasminogen-plasmin (P-P) system. We now know that the P-P system is composed of several serine proteases and their inhibitors (serpins). This system is involved in many physiological functions, including embryogenesis, cell migration, and wound healing. They also play an important role in the pathogenesis of many diseases, including atherosclerosis, obesity, cancer, and even autoimmune disorders, and neuronal degeneration. Knowledge of their role in cancer enables their use as a prognostic factor. Therapeutic use of various forms of proteases derived from this system has been employed as thrombolytic agents. In addition, small molecules designed to inhibit many of the components of the P-P system are now available for clinical trial, aimed at treatment of these various disorders. The history of such remarkable development of our knowledge on fibrinolysis is reviewed in this article., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

The α2-Antiplasmin (α2AP) protein is known as a principal physiological inhibitor of plasmin, but we previously demonstrated that it acts as a regulatory factor for cellular functions independent of plasmin. α2AP is highly expressed in the hippocampus, suggesting a potential role for α2AP in hippocampal neuronal functions. However, the role for α2AP was unclear. This study is the first to investigate the involvement of α2AP in the dendritic growth of hippocampal neurons. The expression of microtubule-associated protein 2, which contributes to neurite initiation and neuronal growth, was lower in the neurons from α2AP⁻/⁻ mice than in the neurons from α2AP⁺/⁺ mice. Exogenous treatment with α2AP enhanced the microtubule-associated protein 2 expression, dendritic growth and filopodia formation in the neurons. This study also elucidated the mechanism underlying the α2AP-induced dendritic growth. Aprotinin, another plasmin inhibitor, had little effect on the dendritic growth of neurons, and α2AP induced its expression in the neurons from plaminogen⁻/⁻ mice. The activation of p38 MAPK was involved in the α2AP-induced dendritic growth. Therefore, our findings suggest that α2AP induces dendritic growth in hippocampal neurons through p38 MAPK activation, independent of plasmin, providing new insights into the role of α2AP in the CNS., (© 2013 International Society for Neurochemistry.)

Lung and pleural injuries are characterized by inflammation, fibrinous transitional matrix deposition, and ultimate scarification. The accumulation of extravascular fibrin is due to concurrently increased local coagulation and decreased fibrinolysis, the latter mainly as a result of increased plasminogen activator inhibitor-1 (PAI-1) expression. Therapeutic targeting of disordered fibrin turnover has long been used for the treatment of pleural disease. Intrapleural fibrinolytic therapy has been found to be variably effective in clinical trials, which likely reflects empiric dosing that does not account for the wide variation in pleural fluid PAI-1 levels in individual patients. The incidence of empyema is increasing, providing a strong rationale to identify more effective, nonsurgical treatment to improve pleural drainage and patient outcomes. Therapeutics designed to resist inhibition by PAI-1 are in development for the treatment of pleural loculation and impaired drainage. The efficacy and safety of these strategies remains to be proven in clinical trial testing. Fibrinolytic therapy administered via the airway has also been proposed for the treatment of acute lung injury, but this approach has not been rigorously validated and is not part of routine clinical management at this time. Challenges to airway delivery of fibrinolysins relate to bioavailability, distribution, and dosing of the interventional agents., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

The network of fibrinolytic regulatory reactions is analyzed by means of a bipartite graph technique. Basic kinetic models relevant to the graphs describing the fibrinolytic regulatory system (FRS) with several degrees of resolution are derived. These models enable us to describe the phenomenon of threshold activation of fibrinolytic processes. The activation is accompanied by plasmin and urokinase blow-up generation. The areas in parametric space corresponding to threshold activation of FRS are established. It is shown that blow-up generation of plasmin may be caused by a supercritical perturbation of the values of dynamical variables (the active enzyme concentrations) as well as by the change of system parameters. An expression for the threshold activation value is suggested. Possible medical applications of the obtained results are discussed., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Inflammation and coagulation constitute two host defense systems with complementary roles in eliminating invading pathogens, limiting tissue damage, and restoring homeostasis. Extensive cross talk exists between these 2 systems, whereby inflammation leads to activation of coagulation, and coagulation considerably affects inflammatory activity. Infection leads to the production of proinflammatory cytokines that, in turn, stimulate the production of tissue factor. Activation of the coagulation system and ensuing thrombin generation are dependent on the expression of tissue factor. Conversely, activated coagulation proteases may affect specific receptors on inflammatory cells and endothelial cells and thereby modulate the inflammatory response. Activation of coagulation with the simultaneous down-regulation of endothelial-bound anticoagulant mechanisms and endogenous fibrinolysis characterizes the pathophysiology of sepsis. The mechanisms by which these highly complex and codependent defense strategies are linked together both in health and disease is the focus of this review., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Until recently, the role of the proteolytic system involving serine proteases in follicle rupture during ovulation in mammalian species has been a subject of controversy. We undertook the present study to examine whether proteases play a role in follicle rupture using the teleost medaka (Oryzias latipes) model. Various serine protease inhibitors, including a specific plasmin inhibitor, drastically reduced the rate of ovulation, as assessed by an in vitro ovulation assay, which was established for the fish. Biochemical, molecular biological, and immunological analyses demonstrated that plasminogen/plasmin was present in large follicles destined to ovulate. The active protease, plasmin, was detected in follicles approximately 3-7 h before the expected time of ovulation. Specific antibodies against the medaka plasmin light chain suppressed the ovulation rate of the follicles when antibodies were added to the medium during the period in which active plasmin was generated. This finding was an indication that a plasmin-like protease similar if not identical to plasmin plays a role in follicle rupture during ovulation in the medaka. Our data also indicate that this serine protease participates in the rupture for only a few hours prior to the activation of matrix metalloproteinase (Mmp)-mediated hydrolysis at ovulation. Based on our previous and current data, we propose a follicle rupture model involving two different proteolytic enzyme systems, serine protease and Mmp, in medaka ovulation. The current study is the first to provide evidence of the indispensable role of plasmin or a plasmin-like protease in the ovulation of a nonmammalian vertebrate species.

Angiogenesis is a process by which new blood vessels form from preexisting vasculature. This process includes differentiation of angioblasts into endothelial cells with the help of secreted angiogenic factors released from cells such as bone marrow (BM)-derived cells. The fibrinolytic factor plasmin, which is a serine protease, has been shown to promote endothelial cell migration either directly, by degrading matrix proteins such as fibrin, or indirectly, by converting matrix-bound angiogenic growth factors into a soluble form. Plasmin can also activate other pericellular proteases such as matrix metalloproteinases (MMPs). Recent studies indicate that plasmin can additionally alter cellular adhesion and migration. We showed that factors of the fibrinolytic pathway can recruit BM-derived hematopoietic cells into ischemic/hypoxic tissues by altering the activation status of MMPs. These BM-derived cells can function as accessory cells that promote angiogenesis by releasing angiogenic signals. This review will discuss recent data regarding the role of the fibrinolytic system in controlling myeloid cell-driven angiogenesis. We propose that plasmin/plasminogen may be a potential target not only for development of effective angiogenic therapeutic strategies for the treatment of cancer, but also for development of strategies to promote ischemic tissue regeneration.

Novel roles for the serine protease plasmin have been implicated recently in physiological and pathological processes. However, whether plasmin is involved in erythropoiesis is not known. In the present study, we studied the consequences of plasminogen deficiency on erythropoiesis in plasminogen-deficient (Plg knockout [KO]) mice. Erythroid differentiation was attenuated in male Plg KO mice and resulted in erythroblastic accumulation within the spleen and bone marrow, with increased apoptosis in the former, erythrocytosis, and splenomegaly, whereas similar erythropoietic defect was less prominent in female Plg KO mice. In addition, erythrocyte lifespan was shorter in both male and female Plg KO mice. Erythropoietin levels were compensatory increased in both male and female Plg KO mice, and resulted in a higher frequency of burst-forming units-erythroid within the spleen and bone marrow. Surprisingly, we found that male Plg KO mice, but not their female counterparts, exhibited normochromic normocytic anemia. The observed sex-linked erythropoietic defect was attributed to decreased serum testosterone levels in Plg KO mice as a consequence of impaired secretion of the pituitary luteinizing hormone (LH) under steady-state condition. Surgical castration causing testosterone deficiency and stimulating LH release attenuated erythroid differentiation and induced anemia in wild-type animals, but did not further decrease the hematocrit levels in Plg KO mice. In addition, complementation of LH using human choriogonadotropin, which increases testosterone production, improved the erythropoietic defect and anemia in Plg KO mice. The present results identify a novel role for plasmin in the hormonal regulation of postnatal erythropoiesis by the LH-testosterone axis., (Copyright © 2012 ISEH - Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.)

Background: The plasminogen-plasmin system affects tissue fibrosis, presumably by interacting with metalloproteinases (MMPs) and macrophage recruitment. This study tests the influence of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (tPa) on angiotensin II-mediated hypertensive kidney and heart injury., Method: Hypertension was induced by continuous angiotensin II (Ang II) infusion via osmotic mini-pumps over 4 weeks. The effects of Ang II infusion were determined in mice lacking PAI-1 (PAI-1), mice lacking tPa (tPa), and wild-type mice. Normotensive mice of the respective genotype served as controls. Blood pressure was recorded by continuous radiotelemetric intra-arterial measurements., Results: Ang II infusion significantly enhanced arterial blood pressure in all groups. However, the increase in blood pressure was more pronounced in the tPa group. Albuminuria was highest in hypertensive wild-type compared to the other Ang II-infused groups. Hypertensive PAI-1 mice exhibited less glomerulosclerosis, higher nephrin immunostaining, and lower renal interstitial collagen I deposition. Gelatin zymography revealed higher activity of MMP-2 in hypertensive PAI-1, whereas no differences were observed in macrophage infiltration. tPa deficiency did not alter kidney fibrosis, although hypertensive tPa revealed less renal expression of fibrotic genes, less macrophage infiltration, and reduced MMP-2 activity. On the other hand, hypertension-induced fibrosis as well as macrophage infiltration in the heart was profoundly enhanced in PAI-1 mice. Fibrin staining revealed perivascular exudations in the myocardium of hypertensive PAI-1 suggesting vascular leakage., Conclusion: These findings underscore the unexpectedly complex role of plasminogen activation for hypertensive target organ damage.

The influence of angiostatin K1-4.5--a fragment of the heavy chain of plasmin and a powerful inhibitor of angiogenesis--on kinetic parameters (k(Pg) and K(Pg)) of human Glu-plasminogen activation under the action of urokinase (uPA) not having affinity for fibrin and fibrin-specific tissue plasminogen activator (tPA) was investigated. Angiostatin does not affect the k(Pg) value, but increases the value K(Pg) urokinase plasminogen activation. A decrease in the k(Pg) value and an increase in the K(Pg) value were found for fibrin-stimulated plasminogen activation by tPA with increasing concentrations of angiostatin. The obtained results show that angiostatin is competitive inhibitor of the uPA activator activity, while it inhibits the activator activity of tPA by mixed type. Such an influence ofangiostatin on the kinetic constants ofthe urokinase plasminogen activation suggests that angiostatin dose dependent manner replaces plasminogen in the binary enzyme-substrate complex uPA-Pg. In case of fibrin-stimulated plasminogen activation by tPA, both zymogen and tPA are bound to fibrin with formation of the effective triple tPA-Pg-fibrin complex. Angiostatin replaces plasminogen both from the fibrin surface and from the enzyme-substrate tPA-Pg complex that leads to a decrease in k(Pg) and an increase in K(Pg) of plasminogen activation. Inhibition constants by angioststin (Ki) of plasminogen-activator activities of uPA and tPA determined by Dixon method were found to be 0.59 +/- 0.04 and 0.12 +/- 0.05 microM, respectively.

Background: Although increased levels of plasminogen activators have been found in psoriatic lesions, the role of plasmin converted from plasminogen by plasminogen activators in pathogenesis of psoriasis has not been investigated., Methodology/principal Findings: Here we examined the contribution of plasmin to amplification of inflammation in patients with psoriasis. We found that plasminogen was diminished, but that the amount and activity of its converted product plasmin were markedly increased in psoriasis. Moreover, annexin II, a receptor for plasmin was dramatically increased in both dermis and epidermis in psoriasis. Plasmin at sites of inflammation was pro-inflammatory, eliciting production of inflammatory factors, including CC chemokine ligand 20 (CCL20) and interleukin-23 (IL-23), that was mediated by the nuclear factor-kappaB (NF-κB) signaling pathway and that had an essential role in the recruitment and activation of pathogenic C-C chemokine receptor type 6 (CCR6)+ T cells. Moreover, intradermal injection of plasmin or plasmin together with recombinant monocyte/macrophage chemotactic protein-1 (MCP-1) resulted in induction of psoriasiform skin inflammation around the injection sites with several aspects of human psoriasis in mice., Conclusions/significance: Plasmin converted from plasminogen by plasminogen activators plays an essential role in amplification of psoriasiform skin inflammation in mice, and targeting plasmin receptor--annexin II--may harbor therapeutic potential for the treatment of human psoriasis.

Background: The aims of the present study were to confirm the consumption coagulopathy of disseminated intravascular coagulation with the fibrinolytic phenotype at an early phase of trauma and to test the hypothesis that thrombin-activatable fibrinolysis inhibitor, neutrophil elastase, and plasmin contribute to the increased fibrinolysis of this type of disseminated intravascular coagulation. Furthermore, we hypothesized that disseminated intravascular coagulation at an early phase of trauma progresses dependently to disseminated intravascular coagulation with a thorombotic phenotype from 3 to 5 days after injury., Methods: Fifty-seven trauma patients, including 30 patients with disseminated intravascular coagulation and 27 patients without disseminated intravascular coagulation, were studied prospectively. Levels of thrombin-activatable fibrinolysis inhibitor, tissue-type plasminogen activator plasminogen activator inhibitor-1 complex, plasmin alpha2 plasmin inhibitor complex, D-dimer, neutrophil elastase, and fibrin degradation product by neutrophil elastase were measured on days 1, 3, and 5 after trauma. The prothrombin time, fibrinogen, fibrin/fibrinogen degradation product, antithrombin, and lactate also were measured., Results: Independent of the lactate levels, disseminated intravascular coagulation patients showed a prolonged prothrombin time, lesser fibrinogen and antithrombin levels, and increased levels of fibrin/fibrinogen degradation product on day 1. Disseminated intravascular coagulation diagnosed on day 1 continued to late-phase disseminated intravascular coagulation on days 3 and 5 after trauma. Increased levels of tissue-type plasminogen activator plasminogen activator inhibitor-1 complex, plasmin alpha2 plasmin inhibitor complex, D-dimer, neutrophil elastase, and fibrin degradation product by neutrophil elastase but not thrombin-activatable fibrinolysis inhibitor were observed in the disseminated intravascular coagulation patients. No correlation was observed between plasmin alpha2 plasmin inhibitor complex and fibrin degradation product by neutrophil elastase in disseminated intravascular coagulation patients. Multiple regression analysis showed the disseminated intravascular coagulation score and the tissue-type plasminogen activator plasminogen activator inhibitor-1 complex levels on day 1 to correlate with the total volume of transfused blood. Patient prognosis deteriorated in accordance with the increasing disseminated intravascular coagulation severity., Conclusion: Disseminated intravascular coagulation at an early phase of trauma is associated with consumption coagulopathy and excessive fibrinolysis both by plasmin and neutrophil elastase independent of hypoperfusion and continues to disseminated intravascular coagulation at a late phase of trauma. Increased fibrinolysis requires more blood transfusions, contributing to a poor patient outcome., (Copyright © 2011 Mosby, Inc. All rights reserved.)

Background: Laparoscopic surgery has been incorporated into common surgical practice. The peritoneum is an organ with various biologic functions that may be affected in different ways by laparoscopic and open techniques. Clinically, these alterations may be important in issues such as peritoneal metastasis and adhesion formation., Methods: A literature search using the Pubmed and Cochrane databases identified articles focusing on the key issues of laparoscopy, peritoneum, inflammation, morphology, immunology, and fibrinolysis., Results: Laparoscopic surgery induces alterations in the peritoneal integrity and causes local acidosis, probably due to peritoneal hypoxia. The local immune system and inflammation are modulated by a pneumoperitoneum. Additionally, the peritoneal plasmin system is inhibited, leading to peritoneal hypofibrinolysis., Conclusion: Similar to open surgery, laparoscopic surgery affects both the integrity and biology of the peritoneum. These observations may have implications for various clinical conditions.

Cell activation by stressors is characterized by a sequence of detectable phenotypic cell changes. A given stimulus, depending on its strength, induces modifications in the activity of membrane phospholipid transporters and calpains, which lead to phosphatidylserine exposure, membrane blebbing and the release of microparticles (nanoscale membrane vesicles). This vesiculation could be considered as a warning signal that may be followed, if the stimulus is maintained, by cell detachment-induced apoptosis. In the present study, plasminogen incubated with adherent cells is converted into plasmin by constitutively expressed tPA (tissue-type plasminogen activator) or uPA (urokinase-type plasminogen activator). Plasmin formed on the cell membrane then induces a unique response characterized by membrane blebbing and vesiculation. Hitherto unknown for plasmin, these membrane changes are similar to those induced by thrombin on platelets. If plasmin formation persists, matrix proteins are then degraded, cells lose their attachments and enter the apoptotic process, characterized by DNA fragmentation and specific ultrastructural features. Since other proteolytic or inflammatory stimuli may evoke similar responses in different types of adherent cells, the proposed experimental procedure can be used to distinguish activated adherent cells from cells entering the apoptotic process. Such a distinction is crucial for evaluating the effects of mediators, inhibitors and potential therapeutic agents.

beta(2)-Glycoprotein-I (beta(2)gpI), an abundant plasma glycoprotein, functions as a regulator of thrombosis. Previously, we demonstrated that plasmin-clipped beta(2)gpI (cbeta(2)gpI) exerts an anti-angiogenic effect on human umbilical vein endothelial cells (HUVEC). The present study was focused on the molecular background responsible for this phenomenon. cbeta(2)gpI strongly reduced HUVEC growth and proliferation as evidenced by the MTT and BrdU assay and delayed cell cycle progression arresting HUVEC in the S-and G2/M-phase. Western blot analysis indicated that cbeta(2)gpI inhibited cyclin A, B and D1, and enhanced p21 and p27 expression. Activity of p38 was down-regulated independently from the cbeta(2)gpI incubation time. Phosphorylation of ERK1/2 was not changed early (30 and 60 min) but became enhanced later (90 min, 4h). JNK activity was reduced rapidly after cbeta(2)gpI treatment but compared to controls, increased thereafter. Annexin II blockade prevented growth inhibition and cell cycle delay evoked by cbeta(2)gpI. We assume that cbeta(2)gpI's effects on HUVEC growth is mediated via cyclin A, B and D1 suppression, up-regulation of p21 and p27 and coupled to modifications of the mitogen-activated protein (MAP) kinase signalling pathway. cbeta(2)gpI may represent a potential endogenous angiogenesis-targeted compound, opening the possibility of a novel tool to treat cancer., (2010 Elsevier Ireland Ltd. All rights reserved.)

In response to brain injury, microglia migrate and accumulate in the affected sites, which is an important step in the regulation of inflammation and neuronal degeneration/regeneration. In this study, we investigated the effect of urokinase-type plasminogen activator (uPA) on the BV-2 microglial cell migration. At resting state, BV-2 microglial cells secreted uPA and the release of uPA was increased by ATP, a chemoattractant released from injured neuron. The migration of BV-2 cell was significantly induced by uPA and inhibited by uPA inhibitors. In this condition, uPA increased the activity of matrix metalloproteinase (MMP-9) and the inhibition of MMP activity with pharmacological inhibitors against either uPA (amiloride) or MMP (phenanthrolene and SB-3CT) effectively prevented BV2 cell migration. Interestingly, the level of MMP-9 protein and mRNA in the cell were not changed by uPA. These results suggest that the increase of MMP-9 activity by uPA is regulated at the post-translational level, possibly via increased activation of the enzyme. Unlike the uPA inhibitor, plasmin inhibitor PAI-1 only partially inhibited uPA-induced cell migration and MMP-9 activation. The incubation of recombinant MMP-9 with uPA resulted in the activation of MMP-9. These results suggest that uPA plays a critical role in BV-2 microglial cell migration by activating pro-MMP-9, in part by its direct action on MMP-9 and also in part by the activation of plasminogen/plasmin cascade.

Previous studies have described remodelling of the extracellular substratum by matrix metalloproteinases (MMPs) in aortic valves. However, involvement of the fibrinolytic system has not yet been analysed. We hypothesized that plasminogen and plasminogen activator(s) are present in aortic valves and that plasminogen activation could induce the degradation of adhesive proteins and apoptosis of the valvular myofibroblasts. We employed ELISA, western blotting, fibrin-agar zymography, and immunochemistry to detect components of the plasminogen activation system, in samples of aortic valves and valvular myofibroblasts in primary culture. Using myofibroblast cultures, real-time measurement of plasminogen activation was performed in the absence and presence of inhibitors (amiloride, epsilon-aminocaproic acid, and an MMP inhibitor); the degradation of fibronectin was visualized on western blots; and the apoptotic process was assessed by detection of phosphatidylserine exposure (binding of FITC-annexin V) and DNA fragmentation (TUNEL and ELISA). We demonstrate that a time- and plasminogen concentration-dependent generation of plasmin occurs on the surface of cultured valvular myofibroblasts expressing both u-PA and t-PA. Only u-PA appears to activate plasminogen as t-PA is essentially found in complex with PAI-1. Plasmin-dependent degradation of pericellular proteins, such as fibronectin, leads to cell detachment and apoptosis. In conclusion, various proteins of the fibrinolytic system are synthesized in vitro by cultured myofibroblasts from aortic valves, leading to plasmin-dependent cell detachment-induced apoptosis, a biological process named anoikis. The presence of plasminogen in aortic valves suggests that this process may be operating in vivo and may participate in valvular tissue remodelling, as also suggested by the finding of apoptotic cells in valvular tissue. This is the first demonstration of the presence and potential role of enzymes of the fibrinolytic system in aortic valves., (Copyright (c) 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

The coagulation and fibrinolytic pathways regulate hemostasis and thrombosis, and an imbalance in these pathways may result in pathologic hemophilia or thrombosis. The plasminogen system is the primary proteolytic pathway for fibrinolysis, but also has important proteolytic functions in cell migration, extracellular matrix degradation, metalloproteinase activation, and hormone processing. Several studies have demonstrated plasmin cleavage and inactivation of several coagulation factors, suggesting plasmin may be not only be the primary fibrinolytic enzyme, but may have anticoagulant properties as well. The objective of this review is to examine both in vitro and in vivo evidence for plasmin inactivation of coagulation, and to consider whether plasmin may act as a physiological regulator of coagulation. While several studies have demonstrated strong evidence for plasmin cleavage and inactivation of coagulation factors FV, FVIII, FIX, and FX in vitro, in vivo evidence is lacking for a physiologic role for plasmin as an anticoagulant. However, inactivation of coagulation factors by plasmin may be useful as a localized anticoagulant therapy or as a combined thrombolytic and anticoagulant therapy.

Background: Plasmin role in transforming growth factor-beta (TGF-beta)-responsive gene regulation remains to be elucidated. Also, plasmin action on co-repressor Ski-related novel protein N (SnoN) and differential activation of matrix metalloproteinases (MMPs) are unknown. Thus, the role of plasmin on profibrogenic molecule expression, SnoN transcriptional kinetics and gelatinase activation was investigated., Methods: Hepatic stellate cells (HSC) were transduced with adenovirus-mediated human urokinase plasminogen activator (Ad-huPA) (4 x 10(9) viral particles/ml). Overexpression of urokinase plasminogen activator and therefore of plasmin, was blocked by tranexamic acid (TA) in transduced HSC. Gene expression was monitored by reverse transcriptase polymerase chain reaction. HSC-free supernatants were used to evaluate MMP-2 and MMP-9 by zymography. SnoN, TGF-beta and tissue inhibitor of metalloproteinase (TIMP)-1 were analysed by Western blot. Plasmin and SnoN expression kinetics were evaluated in bile duct-ligated (BDL) rats., Results: Plasmin overexpression in Ad-huPA-transduced HSC significantly decreased gene expression of profibrogenic molecules [alpha1(I)collagen 66%, TIMP-1 59%, alpha-smooth muscle actin 90% and TGF-beta 55%]. Interestingly, both SnoN gene and protein expression increased prominently. Plasmin inhibition by TA upregulated the profibrogenic genes, which respond to TGF-beta-intracellular signalling. In contrast, SnoN mRNA and protein dropped importantly. Plasmin-activated MMP-9 and MMP-2 in HSC supernatants. Taken together, these findings indicate that MMP-9 activation is totally plasmin dependent. SnoN levels significantly decreased in cholestatic-BDL rats (82%) as compared with control animals. Interestingly, hepatic plasmin levels dropped 46% in BDL rats as compared with control., Conclusion: Plasmin plays a key role in regulating TGF-beta-responding genes. In particular, regulation of TGF-beta-co-repressor (SnoN) is greatly affected, which suggests SnoN as a cardinal player in cholestasis-induced fibrogenesis.

In the pathogenesis of sepsis, inflammation and coagulation play a pivotal role. Increasing evidence points to an extensive cross-talk between these two systems, whereby inflammation leads to activation of coagulation, and coagulation also considerably affects inflammatory activity. Molecular pathways that contribute to inflammation-induced activation of coagulation have been precisely identified. Pro-inflammatory cytokines and other mediators are capable of activating the coagulation system and down-regulating important physiologic anticoagulant pathways. Activation of the coagulation system and ensuing thrombin generation is dependent on expression of tissue factor and the simultaneous down-regulation of endothelial-bound anticoagulant mechanisms and endogenous fibrinolysis. Conversely, activated coagulation proteases may affect specific cellular receptors on inflammatory cells and endothelial cells and thereby modulate the inflammatory response.

Aims: We investigated the causes of microvessel immaturity and destabilization in human atherosclerotic lesions., Methods and Results: Human atherosclerotic carotid plaques (n = 24) were classified as non-haemorrhagic (NH) or haemorrhagic (Hem), according to their macroscopic aspect and haemoglobin content. Plaque microvessel density and maturity were quantified by immunohistochemistry. Expression of angiogenic factors was studied by immunohistochemistry, in situ hybridization, and ELISA. Plaque-conditioned media were tested for plasmin and elastase activities and for their ability to degrade angiogenic factors and to induce smooth muscle cell migration. Microvessel density and leucocyte infiltration were increased in Hem compared with NH plaques. Plaque vasculature appeared vulnerable as indicated by the absence of alpha-actin-positive mural cells in most plaque vessels. Despite increased numbers of angiogenic factor-expressing microvessels and leucocytes in Hem plaques, lower levels of vascular endothelial growth factor, placental growth factor, and angiopoietin-1 were found in conditioned media from Hem plaques. However, NH and Hem plaques released similar levels of the vascular destabilizing factor, angiopoietin-2. Addition of recombinant angiogenic factors to plaque extracts showed that all factors but angiopoietin-2 were selectively degraded by plasmin and/or elastase released from Hem plaques. Furthermore, conditioned media from Hem plaques showed a reduced ability to induce smooth muscle cell migration., Conclusion: Our results provide evidence that immaturity of plaque vessels is associated with the degradation of angiogenic factors by haemorrhage-conveyed leucocytes and proteases.

Background: Alcoholism may result in severe neurological deficits and cognitive impairments. Many of the central effects of ethanol (EtOH) can be explained by upregulation of N-methyl-D-aspartate (NMDA) and downregulation of gamma-aminobutyric acid (GABA) A receptors (GABAA) in response to long-term EtOH consumption. Abrupt ethanol withdrawal (EW) may result in neuronal hyperexcitability leading to hallucinations, seizures, neurodegeneration, and sometimes death., Methods: Using a multidisciplinary approach in wild-type and genetically modified mice, we examined the contribution of the tissue plasminogen activator (tPA), plasminogen, and laminin to EW-induced cell death., Results: Here we show that EW-induced neurodegeneration is mediated by the tPA/plasmin system. During EW, tPA is upregulated in the hippocampus and converts plasminogen to plasmin, which in turn degrades an extracellular matrix component laminin, leading to caspase-3-dependent cell death. Consequently, mice in which the tPA or plasminogen genes have been deleted do not show EW-induced laminin degradation, mitochondrial dysfunction, and neurodegeneration. Finally, we demonstrated that disruption of the hippocampal laminin gamma-1 renders the mice resistant to neurotoxic effects of EW., Conclusions: Our data identify laminin gamma-1 as a novel target to combat neurodegeneration.

Opsonization by Abs represents a critical component of the host immune response against many pathogens. The mechanisms by which virulent microbes evade this protective response are not completely understood. In disease mediated by Francisella tularensis, Ab can effectively protect against infections with attenuated strains, for example, LVS, but not virulent strains such as SchuS4. Thus, it is likely that SchuS4 has mechanisms, which are not present in LVS, that allow evasion of opsonization by Ab, dampening the protective effects of these host molecules. Here we demonstrate that evasion of Ab-mediated opsonization and phagocytosis by the highly virulent SchuS4 is associated with its ability to bind the host serine protease plasmin. SchuS4, but not the closely related LVS, bound active plasmin. Plasmin bound SchuS4 degraded exogenous and opsonizing Abs, whereas LVS failed to do so. Furthermore, plasmin-mediated inhibition of Ab opsonization by SchuS4 also inhibited Ab-mediated uptake of this bacterium by macrophages. Ab-mediated uptake of uncoated and opsonized SchuS4 elicited a strong proinflammatory response in infected macrophages. However, plasmin-coated, opsonized SchuS4 poorly elicited production of these protective proinflammatory cytokines. This unique host-pathogen interplay is a novel immune evasion strategy utilized by virulent F. tularensis, and it provides one explanation for the ability of Ab to protect against attenuated, but not virulent, strains of F. tularensis. This mechanism may also represent a more common hereto unrecognized strategy by which virulent bacteria evade detection and clearance by Ig.

In this review we discuss the association of overall hypofibrinolysis and individual fibrinolytic protein levels with venous and arterial thrombosis. Decreased overall fibrinolytic potential and high plasma levels of thrombin-activatable fibrinolysis inhibitor have been consistently associated with risk of venous thrombosis, whereas little evidence exists for a role of plasminogen, alpha2-antiplasmin, tissue plasminogen activator, and plasminogen activator inhibitor 1. Overall fibrinolytic potential has been associated with arterial thrombosis in young individuals, but studies on the individual components gave conflicting results. These inconsistent results could be a consequence of nonfibrinolytic properties of fibrinolytic proteins, including roles in inflammation, vascular remodeling, atherosclerosis, and the metabolic syndrome. The nonfibrinolytic properties of these proteins may have opposing effects on development of arterial disease as compared with the lytic properties, which may explain opposite results in different studies with slightly different population characteristics. These properties may be more relevant in arterial than in venous thrombosis., (Copyright Thieme Medical Publishers.)

The physiological relevance of the activation of hepatocyte growth factor (Hgf) by the plasminogen (Plg) system of proteases and its contribution to tissue repair are largely undefined. Here, we investigated whether the defective liver repair in mice lacking Plg is due to impaired activation of Hgf. Loss of Plg in vivo suppressed Hgf activation and signaling through its Met tyrosine kinase receptor. Without Plg, hepatocytes were unresponsive to Hgf-induced proliferation and migration, with a more pronounced impairment in hepatocyte movement within the hepatic environment. Most notably, circumventing the defect in proteolytic activation of Hgf by the downstream expression of an activated Met receptor corrected the functional deficits and improved liver repair in Plg-deficient mice. These findings support a fibrinolysis-unrelated role for Plg in modulating cell proliferation and migration by activation of Hgf.

Plasmin, a major extracellular protease, activates platelets through PAR4 receptors. Plasmin-induced full aggregation is achieved at lower concentrations (0.1 U/mL) in murine platelets as compared to human platelets (1 U/mL). In COS7 cells expressing the murine PAR4 (mPAR4) receptor, 1 U/mL plasmin caused a higher intracellular calcium mobilization than in cells expressing the human PAR4 (hPAR4) receptor. This difference was reversed when the tethered ligand sequences of mPAR4 and hPAR4 were interchanged through site-directed mutagenesis. We further investigated whether PAR3 expressed in murine platelets serves as a co-receptor for PAR4 activation by plasmin. In COS7 cells, co-expressing mPAR3 and mPAR4, plamsin produced a smaller intracellular calcium mobilization compared to cells expressing mPAR4 alone, suggesting that PAR3 might inhibit plasmin-induced PAR4 stimulation. Consistent with these results, PAR3 null murine platelets also showed a greater plasmin-induced calcium mobilization and aggregation compared to wild-type murine platelets. In conclusion, murine platelets are more sensitive to activation by plasmin than human platelets due to differences in the primary sequence of PAR4. In contrast to thrombin-dependent activation of platelets, wherein PAR3 acts as a co-receptor, mPAR3 inhibits plasmin-induced PAR4 activation.

The airway remodeling that occurs in asthma is characterized by an excess of extracellular matrix deposition in the submucosa, hyperplasia/hypertrophy of smooth muscle, goblet cell metaplasia, and accumulation of fibroblasts/myofibroblasts. The urokinase-type plasminogen activator (uPA)/plasmin system participates in pericellular proteolysis and is capable of directly degrading matrix components, activating latent proteinases, and activating growth factors. In a mouse ovalbumin (OVA) asthma model, we increased plasminogen activator activity in the lung by administering exogenous uPA or by using mice genetically deficient in the uPA inhibitor plasminogen activator inhibitor-1 (PAI-1) to assess the role of this system in asthma pathogenesis. After intraperitoneal OVA sensitization, mice inhaled OVA plus uPA (500 IU/mouse) or saline by ultrasonic nebulization for 3 wk. When studied 24 h after the final exposure, the groups with upregulated plasmin activity had significantly reduced subepithelial fibrosis within the airway walls and had decreased airway hyperresponsiveness (AHR) to methacholine. Morphometric analysis showed that subepithelial wall thickening of the bronchi (subepithelial area ratio) was also reduced, as were collagen and alpha-smooth muscle actin. Upregulation of plasmin activity also increased the level of hepatocyte growth factor activity in bronchoalveolar lavage fluid, whereas the release of transforming growth factor-beta was decreased. The administration of uPA 1 wk after the last OVA inhalation also significantly reduced lung hydroxyproline content and AHR. These results show that enhancing uPA/plasmin activity lessens the airway remodeling in a murine asthma model.

It was shown that discovery by the author of the thrombin-plazmin system and establishment of its biological role consisting in maintenance of two fundamental opposite, internal and contradictory physiological processes--biological coagulation (cyto-histo-haemocoagulation) which is carried out by the thrombin subsystem and biological regeneration (cyto-histo-haemoregenerations) which is carried out by the plasmin subsystem, has given the chance to open the current mechanism of damage of structure and functions of human organs during DVS-syndrome. It has appeared that under intensification of biocoagulation, its damage is caused by the effect of thrombin which is present in all basic biological mediums--cytoplasm, interstitial connecting tissue and in blood and it causes primary direct coagulation (inherently degenerative) and secondary mediated coagulation (inherently dystrophic) damages, i.e. damage of human organs under intensification of biocoagulation has coagulation and hypotrophic (dystrophic) genesis. It gives the grounds to consider it not the DVS-syndrome but a coagulation dystrophy.

Components of the plasminogen-plasmin system participate in a wide variety of physiologic and pathologic processes, including tumor growth, invasion and metastasis, through their effect on angiogenesis and cell migration. These components are found in most tumors and their expression not only signifies their function but also carries a prognostic value. Their expression is in turn modulated by cytokines and growth factors, many of which are up-regulated in cancer. Though both tPA and uPA are expressed in tumor cells, uPA with its receptor (uPAR) is mostly involved in cellular functions, while tPA with its receptor Annexin II on endothelial surface, regulates intravascular fibrin deposition. Among the inhibitors of fibrinolysis, PAI-1 is a major player in the pathogenesis of many vascular diseases as well as in cancer. Therapeutic interventions, either using plasminogen activators or experimental inhibitor agents against PAI-1, have shown encouraging results in experimental tumors but not been verified clinically.

The principles of initiator and amplifications reactions of blood coagulation and fibrinolysis will be presented and discussed in relation to various regulatory pathways of haemostasis. In particular, cell surface-dependent activation and inhibition reactions are characteristics of multicomponent enzyme complexes that also allow the endogenous control of the haemostasis system. The understanding of these relationships in complications of haemostasis has lead to different strategies for the therapeutic intervention with pro- and anticoagulant substances.

Skeletal muscle regeneration is a highly synchronized process involving the activation of various cellular and molecular events, coordinating inflammation and regeneration processes which are crucial for the beneficial outcome of tissue remodeling. Fibrosis, a failure of tissue remodeling, is initiated with muscle regeneration; however, it is the result of an excessive inflammatory response, representing an imbalance between enhanced production and deposition and impaired degradation of extracellular matrix (ECM) components of the muscle. Therefore, factors influencing the relative degree of muscle fiber regeneration as compared to the amount of scar formation have a critical role in functional muscle remodeling. Herein we have focused on the role of urokinase-type plasminogen activator (uPA) and transforming growth factor beta 1 (TGF/1) in ECM degradation and reconstitution in muscles.

Drug addiction/dependence is defined as a chronically relapsing disorder that is characterized by compulsive drug taking, inability to limit intake, and intense drug cravings. The positive reinforcing/rewarding effects of drugs primarily depend on the mesocorticolimbic dopamine system innervating the nucleus accumbens while the craving for drugs is associated with activation of the prefrontal cortex. The chronic intake of drugs causes homeostatic molecular and functional changes in synapses, which may be critically associated with the development of drug dependence. Recent studies have demonstrated that various cytokines and proteinases are produced in the brain on treatment with drugs of abuse, and play a role in drug dependence. These endogenous modulators of drug dependence are classified into two groups, pro-addictive and anti-addictive factors. The former including basic fibroblast growth factor, brain-derived neurotrophic factor, tissue plasminogen activator, matrix metalloproteinase (MMP)-2 and MMP-9 act to potentiate the rewarding effects of drugs, while the latter such as tumor necrosis factor-alpha and glial cell line-derived neurotrophic factor reduce the reward. These findings suggest that an imbalance between pro-addictive and anti-addictive factors contributes to the development and relapse of drug dependence. Furthermore, targeting these endogenous modulators would provide new therapeutic approaches to the treatment of drug dependence.

Objectives: To determine if plasmin differentially augments platelet aggregation through variable efficiencies of IGF-IGFBP complex cleavage., Methods: We utilized ADP-triggered platelet aggregation assays to test the effects of IGF-I versus IGF-II in complex with IGFBP-2 or IGFBP-3 upon the efficiency of plasmin (a known IGFBP protease) as a pro-aggregatory stimulus. In vitro proteolysis assays were performed as controls., Results: We found that IGF-I complexes augmented platelet-mediated aggregation whereas IGF-II either had no effect (IGFBP-2) or inhibited platelet-mediated aggregation (IGFBP-3). In vitro proteolysis assays of IGFBP-2 and IGFBP-3 using plasmin revealed that three of the four aggregation findings were explained by the disparate efficiencies of IGFBP proteolysis associated with each IGF. Only IGF-II-IGFBP-2 complex resulted in a finding that could not be explained by the concept of differential regulation of plasmin's proteolysis efficiency by the two IGF ligands., Conclusions: Our findings demonstrate that the plasmin can differentially modulate platelet aggregation in response to intrinsic heterogeneities within the IGF axis.

The immature brains of newborns often respond differently from the brains of adults when exposed to similar insults. Previous studies have indicated that although hypoxia-ischemia (HI) induces persistent thrombosis in adult brains, it only modestly impairs blood perfusion in newborn brains. Here, we used the Vannucci model of HI encephalopathy to study age-related responses to cerebral HI in rat pups. We found that HI triggered fibrin deposition and impaired blood perfusion in both neonatal and adult brains. However, these effects were only transient in neonatal brains (<4 hours) and were accompanied by acute induction of both tissue-type and urinary-type plasminogen activators (tPA and uPA), which was not observed in adult brains subjected to the same insult. Interestingly, activation of the plasminogen system persisted up to 24 hours in neonatal brains, long after the clearance of fibrin-rich thrombi. Furthermore, astrocytes and macrophages outside blood vessels expressed tPA after HI, suggesting the possibility of tPA/plasmin-mediated cytotoxicity. Consistent with this hypothesis, injection of alpha2-antiplasmin into cerebral ventricles markedly ameliorated HI-induced damage to neurofilaments and white matter oligodendrocytes, providing a dose-response reduction of brain injury after 7 days of recovery. Conversely, ventricular injection of tPA increased HI-induced brain damage. Together, these results suggest that tPA/plasmin induction, which may contribute to acute fibrinolysis, is a critical component of extravascular proteolytic damage in immature brains, representing a new therapeutic target for the treatment of HI encephalopathy.