The fibrinolysis inhibitor α2-antiplasmin restricts lymphatic remodelling and metastasis in a mouse model of cancer.

Remodelling of lymphatic vessels in tumours facilitates metastasis to lymph nodes. The growth factors VEGF-C and VEGF-D are well known inducers of lymphatic remodelling and metastasis in cancer. They are initially produced as full-length proteins requiring proteolytic processing in order to bind VEGF receptors with high affinity and thereby promote lymphatic remodelling. The fibrinolytic protease plasmin promotes processing of VEGF-C and VEGF-D in vitro, but its role in processing them in cancer was unknown. Here we explore plasmin's role in proteolytically activating VEGF-D in vivo, and promoting lymphatic remodelling and metastasis in cancer, by co-expressing the plasmin inhibitor α2-antiplasmin with VEGF-D in a mouse tumour model. We show that α2-antiplasmin restricts activation of VEGF-D, enlargement of intra-tumoural lymphatics and occurrence of lymph node metastasis. Our findings indicate that the fibrinolytic system influences lymphatic remodelling in tumours which is consistent with previous clinicopathological observations correlating fibrinolytic components with cancer metastasis.

α2-Antiplasmin: New Insights and Opportunities for Ischemic Stroke.

Thrombotic vascular occlusion is the leading cause of ischemic stroke. High blood levels of α2-antiplasmin (a2AP), an ultrafast, covalent inhibitor of plasmin, have been linked in humans to increased risk of ischemic stroke and failure of tissue plasminogen activator (tPA) therapy. Consistent with these observations, a2AP neutralizes the therapeutic benefit of tPA therapy in experimental stroke. In addition, a2AP has deleterious, dose-related effects on ischemic brain injury in the absence of therapy. Experimental therapeutic inactivation of a2AP markedly reduces microvascular thrombosis, ischemic brain injury, brain swelling, brain hemorrhage, and death after thromboembolic stroke. These data provide new insights into the critical importance of a2AP in the pathogenesis of ischemic brain injury and suggest that transiently inactivating a2AP may have therapeutic value in ischemic stroke.

[Progress in diagnosis and treatment for disseminated intravascular coagulation].

As the development of a hypercoagulable state in the setting of disseminated intravascular coagulation (DIC) induces localized infection, therapy for DIC should be evaluated according to the findings of examinations for both severe sepsis and DIC. DIC is classified into the following types: "bleeding type," "organ failure type," "asymptomatic type," and "complication type." The "bleeding type" and "organ failure type" are considered to reflect the "plasmin inhibitor (PI) deficiency type" and "antithrombin (AT) deficiency type," respectively. In order to improve the diagnosis of DIC, in particular limitations in global coagulation tests, the Japanese Society of Thrombosis and Hemostasis recently proposed tentative diagnostic criteria for DIC using hemostatic molecular markers and AT. The recommendations for treatment of DIC, especially the use of AT concentrates, recombinant activated protein C and thrombomodulin, vary among several guidelines for the management of DIC. These agents inhibit the effects of key proteases in activating coagulation and consequently exert an anti-inflammatory effect on DIC. Hence, it is necessary to extensively evaluate these agents in well-conducted clinical trials.

Alpha2-antiplasmin: potential therapeutic roles in fibrin survival and removal.

Alpha2-antiplasmin (alpha2AP) is the primary inhibitor of plasmin, a proteinase that digests fibrin, the main component of blood clots. Two forms of alpha2AP circulate in human plasma: a 464-residue protein with methionine as the amino-terminus (Met-alpha2AP) and an N-terminally-shortened 452-residue form with asparagine as the amino-terminus (Asn-alpha2AP). Human plasma alpha2AP concentration is 1 micro M and consists of approximately 30% Met-alpha2AP and approximately 70% Asn-alpha2AP. The major form (Asn-alpha2AP) is rapidly crosslinked to fibrin during blood clotting by activated coagulation factor XIII and as a consequence, fibrin becomes more resistant to fibrinolysis. It is apparent that alpha2AP is important in modulating the effectiveness and persistence of fibrin with respect to its susceptibility to digestion and removal by plasmin. Hence, the physiologic role of alpha2AP suggests that it may be a useful target for developing more effective treatment of thrombotic diseases. Research on alpha2AP appears to be moving in two main directions: (1) efforts to use variant forms of alpha2AP to reduce bleeding secondary to thrombolytic therapy while not slowing thrombolysis; and (2) efforts to use variant forms to diminish the activity of alpha2AP as a plasmin inhibitor so that fibrinolysis becomes enhanced. Methods to accomplish these two goals mostly involve manipulation of defined functional domains within the molecular structure of alpha2AP, or inhibition of a newly described novel plasma proteinase, termed antiplasmin-cleaving enzyme, that generates the more favorable form of alpha2AP, Asn-alpha2AP, for crosslinking to fibrin. The antiplasmin-cleaving enzyme has similarity in primary structure and catalytic properties to fibroblast activation protein/seprase. This review summarizes recent studies that may hold promise for modulating alpha2AP activity and its interactions with certain proteins as new therapeutic strategies for preventing and treating thrombotic disorders.

Primary intestinal and thoracic lymphangiectasia: a response to antiplasmin therapy.

Lymphangiectasia is a congenital or acquired disorder characterized by abnormal, dilated lymphatics with a variable age of presentation. We describe a case of lymphangiectasia with intestinal and pulmonary involvement in an adolescent female, who presented with many of the classic features including chylous pleural effusions, lymphopenia, hypogammaglobinemia, and a protein-losing enteropathy. She also presented with recurrent lower gastrointestinal bleeding, which is infrequently described. The patient did not improve with bowel rest and a low-fat medium-chain triglyceride diet and had little improvement with octreotide acetate therapy. However, she had a clinical response to antiplasmin therapy, trans-4-aminothylcyclohexamine carboxylic acid (tranexamic acid) in terms of serum albumin and gastrointestinal bleeding. She continues to have exacerbations of her condition, as well as persistent lymphopenia and chronic pleural effusions.

Role of plasminogen system components in focal cerebral ischemic infarction: a gene targeting and gene transfer study in mice.

BACKGROUND: The role of plasminogen system components in focal cerebral ischemic infarction (FCI) was studied in mice deficient in plasminogen (Plg-/-), in tissue or urokinase plasminogen activator (tPA-/- or uPA-/-), or in plasminogen activator inhibitor-1 or alpha2-antiplasmin (PAI-1(-/-) or alpha2-AP-/-). METHODS AND RESULTS: FCI was produced by ligation of the left middle cerebral artery and measured after 24 hours by planimetry of stained brain slices. In control (wild-type) mice, infarct size was 7.6+/-1.1 mm3 (mean+/-SEM), uPA-/- mice had similar infarcts (7.8+/-1.0 mm3, P=NS), tPA-/- mice smaller (2.6+/-0.80 mm3, P<0.0001), PAI-1(-/-) mice larger (16+/-0.52 mm3, P<0.0001), and Plg-/- mice larger (12+/-1.2 mm3, P=0.037) infarcts. alpha2-AP-/- mice had smaller infarcts (2. 2+/-1.1 mm3, P<0.0001 versus wild-type), which increased to 13+/-2.5 mm3 (P<0.005 versus alpha2-AP-/-) after intravenous injection of human alpha2-AP. Injection into alpha2-AP-/- mice of Fab fragments of affinospecific rabbit IgG against human alpha2-AP, after injection of 200 microg human alpha2-AP, reduced FCI from 11+/-1.5 to 5.1+/-1.1 mm3 (P=0.004). CONCLUSIONS: Plg system components affect FCI at 2 different levels: (1) reduction of tPA activity (tPA gene inactivation) reduces whereas its augmentation (PAI-1 gene inactivation) increases infarct size, and (2) reduction of Plg activity (Plg gene inactivation or alpha2-AP injection) increases whereas its augmentation (alpha2-AP gene inactivation or alpha2-AP neutralization) reduces infarct size. Inhibition of alpha2-AP may constitute a potential avenue to treatment of FCI.

Effect of heparin and antiplasmin on platelet level in dengue haemorrhagic fever.

A study was carried out to determine the effect of heparin and antiplasmin in dengue haemorrhagic fever. The results shows that heparin and synthetic antiplasmin therapy could accelerate the restoration of platelet level which might reflect amelioration of disseminated intravascular coagulation in dengue haemorrhagic fever.

The application of tissue adhesives in small bowel anastomoses.

One layer everted end-to-end anastomosis was performed on the small bowel of mongrel dogs. Cultures of Serratia marcescens were injected into the lumen. Twenty-four hours later the animals were reexplored, and peritoneal cultures were observed. In animals where Fibrin Seal (consisting of fibrinogen, cold insoluble globulin, factor XIII, platelet growth factor, antiplasmin, thrombin, and calcium chloride) was applied to the suture line, negative cultures were found except for two experiments in which dehiscence or contamination from the Serratia injection site occurred.