Four cases of bleeding diathesis in children due to congenital plasminogen activator inhibitor-1 deficiency

Bleeding Disorders in Primary Fibrinolysis

Fibrinolysis is a complex enzymatic process aimed at dissolving blood clots to prevent vascular occlusions. The fibrinolytic system is composed of a number of cofactors that, by regulating fibrin degradation, maintain the hemostatic balance. A dysregulation of fibrinolysis is associated with various pathological processes that result, depending on the type of abnormality, in prothrombotic or hemorrhagic states. This narrative review is focused on the congenital and acquired disorders of primary fibrinolysis in both adults and children characterized by a hyperfibrinolytic state with a bleeding phenotype.

Thrombin and plasmin generation in patients with plasminogen or plasminogen activator inhibitor type 1 deficiency

INTRODUCTION

Deficiencies of plasminogen and plasminogen activator inhibitor type 1 (PAI-1) are rare disorders of fibrinolysis. Current laboratory assays for analysis of activity of plasminogen and PAI-1 do not provide an accurate correlation with clinical phenotype.

METHODS

The Nijmegen Hemostasis Assay (NHA) was used to simultaneously measure thrombin and plasmin generation in 5 patients with plasminogen deficiency (PLGD) and 10 patients with complete PAI-1 deficiency. Parameters analysed included: lag time ratio, thrombin peak time ratio, thrombin peak height, thrombin potential (AUC), fibrin lysis time, plasmin peak height and plasmin potential. Parameters were expressed as a percentage compared to a reference value of 53 healthy normal controls.

RESULTS

Patients with PLGD demonstrated a short lag time and thrombin peak time, with normal thrombin peak height but an increased AUC. Plasmin generation was able to be detected in only one (23% plasminogen activity) of the five PLGD patients. All ten PAI-1 deficient patients demonstrated a short lag and thrombin peak time, low thrombin peak height with normal AUC. Plasmin generation revealed an increased plasmin peak and plasmin potential; interestingly, there was a large variation between individual patients despite all patients having the same homozygous defect.

CONCLUSION

Patients with either PLGD or PAI-1 deficiency show distinct abnormalities in plasmin and thrombin generation in the NHA. The differences observed in the propagation phase of thrombin generation may be explained by plasmin generation. These results suggest that disorders of fibrinolysis also influence coagulation and a global assay measuring both activities may better correlate with clinical outcome.

Effects of epinephrine on angiogenesis-related gene expressions in cultured rat cardiomyocytes

Epinephrine is often used for the treatment of patients with heart failure, low cardiac output and cardiac arrest. It can acutely improve hemodynamic parameters; however, it does not seem to improve longer term clinical outcomes. Therefore, we hypothesized that epinephrine may induce unfavorable changes in gene expression of cardiomyocyte. Thus, we investigated effects of epinephrine exposure on the mediation or modulation of gene expression of cultured cardiomyocytes at a genome-wide scale. Our investigation revealed that exposure of cardiomyocytes to epinephrine in an in vitro environment can up-regulate the expression of angiopoietin-2 gene (+2.1 times), and down-regulate the gene expression of neuregulin 1 (−3.7 times), plasminogen activator inhibitor-1 (−2.4 times) and SPARC-related modular calcium-binding protein-2 (−4.5 times). These changes suggest that epinephrine exposure may induce inhibition of angiogenesis-related gene expressions in cultured rat cardiomyocytes. The precise clinical significance of these changes in gene expression, which was induced by epinephrine exposure, warrants further experimental and clinical investigations.

Application of long-acting VLHL PAI-1 during sutureless partial nephrectomy in mice reduces bleeding

PAI-1 prevents lysis of blood clot by inhibiting the urokinase and tPA induced conversion of plasminogen to plasmin. VLHL PAI-1 protein mutant was created to extend half-life over 700 hours. The objective of this paper was to test VLHL PAI-1 effects on bleeding during partial nephrectomy in mice. All animals had a left partial nephrectomy after intravenous infusion of saline or tPA. The animals were divided into four groups. Group 1 was infused with saline and kidney was exposed to saline too; Group 2 was infused with saline and kidney was exposed to PAI-1. Group 3 was infused with tPA and kidney was exposed to saline, while Group 4 was infused with tPA and kidney was exposed to PAI-1. Preweighed gauze containing PAI-1 or saline was then applied to the kidney for 30 minutes. The gauze was afterward weighed and blood loss was measured by subtracting the preweight of gauze from the final weight. We have observed a statistically significant (P ≤ 0.05) reduction of bleeding in PAI-1-treated group in comparison to saline and tPA-treated groups. Based on these results we propose that VLHL PAI-1 can be used therapeutically in limiting the flow of blood from renal wounds.

Functional stability of plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is the main inhibitor of plasminogen activators, such as tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA), and a major regulator of the fibrinolytic system. PAI-1 plays a pivotal role in acute thrombotic events such as deep vein thrombosis (DVT) and myocardial infarction (MI). The biological effects of PAI-1 extend far beyond thrombosis including its critical role in fibrotic disorders, atherosclerosis, renal and pulmonary fibrosis, type-2 diabetes, and cancer. The conversion of PAI-1 from the active to the latent conformation appears to be unique among serpins in that it occurs spontaneously at a relatively rapid rate. Latency transition is believed to represent a regulatory mechanism, reducing the risk of thrombosis from a prolonged antifibrinolytic action of PAI-1. Thus, relying solely on plasma concentrations of PAI-1 without assessing its function may be misleading in interpreting the role of PAI-1 in many complex diseases. Environmental conditions, interaction with other proteins, mutations, and glycosylation are the main factors that have a significant impact on the stability of the PAI-1 structure. This review provides an overview on the current knowledge on PAI-1 especially importance of PAI-1 level and stability and highlights the potential use of PAI-1 inhibitors for treating cardiovascular disease.

Clinical practice: the bleeding child. Part II: disorders of secondary hemostasis and fibrinolysis

Bleeding complications in children may be caused by disorders of secondary hemostasis or fibrinolysis. Characteristic features in medical history and physical examination, especially of hemophilia, are palpable deep hematomas, bleeding in joints and muscles, and recurrent bleedings. A detailed medical and family history combined with a thorough physical examination is essential to distinguish abnormal from normal bleeding and to decide whether it is necessary to perform diagnostic laboratory evaluation. Initial laboratory tests include prothrombin time and activated partial thromboplastin time. Knowledge of the classical coagulation cascade with its intrinsic, extrinsic, and common pathways, is useful to identify potential defects in the coagulation in order to decide which additional coagulation tests should be performed.

Low Molecular Weight Antagonists of Plasminogen Activator Inhibitor-1: Therapeutic Potential in Cardiovascular Disease

Plasminogen activator inhibitor-1 (PAI-1; SERPINE1) is the major physiologic regulator of the plasmin-based pericellular proteolytic cascade, a modulator of vascular smooth muscle cell (VSMC) migration and a causative factor in cardiovascular disease and restenosis, particularly in the context of increased vessel transforming growth factor- β1 (TGF-β1) levels. PAI-1 limits conversion of plasminogen to plasmin (and, thereby, fibrin degradation) by inhibiting its protease targets urokinase and tissue-type plasminogen activators (uPA, tPA). PAI-1 also has signaling functions and binds to the low density lipoprotein receptor-related protein 1 (LRP1) to regulate LRP1-dependent cell motility that, in turn, contributes to neointima formation. PAI-1/uPA/uPA receptor/LRPI/integrin complexes are endocytosed with subsequent uPAR/LRP1/integrin redistribution to the leading edge, initiating an "adhesion-detachment-readhesion" cycle to promote cell migration. PAI-1 also interacts with LRP1 in a uPA/uPAR-independent manner triggering Jak/Stat1 pathway activation to stimulate cell motility. PAI-1 itself is a substrate for extracellular proteases and exists in a "cleaved" form which, while unable to interact with uPA and tPA, retains LRP1-binding and migratory activity. These findings suggest that there are multiple mechanisms through which inhibition of PAI-1 may promote cardiovascular health. Several studies have focused on the design, synthesis and preclinical assessment of PAI-1 antagonists including monoclonal antibodies, peptides and low molecular weight (LMW) antagonists. This review discusses the translational impact of LMW PAI-1 antagonists on cardiovascular disease addressing PAI-1-initiated signaling, PAI-1 structure, the design and characteristics of PAI-1-targeting drugs, results of in vitro and in vivo studies, and their clinical implications.

Bruising and bleeding in infants and children - a practical approach

Bruising and bleeding are commonly seen in children and are usually associated with minor injury and trauma. However, in two groups of children the bruising may be more significant than expected: those with an underlying haemostatic abnormality, such as an inherited bleeding disorder, or those who have been subjected to non-accidental injury (NAI). Diagnosing inherited bleeding disorders in children is fraught with difficulty, from venous access to interpretation of results; the possibility of NAI should be borne in mind, even in those children with proven significant bleeding disorders when the severity of the injury and the history are non-compatible. We describe the investigation of the haemostatic system in children with bruising and/or bleeding with emphasis on the key haemostatic disorders that need to be excluded.

Massive subhyaloidal hemorrhage associated with severe PAI-1 deficiency

PURPOSE

To report an association between spontaneous subhyaloidal hemorrhage and severe plasminogen activator inhibitor-1 (PAI-1) deficiency.

METHODS

Case report.

RESULTS

A 29-year-old woman presented with sudden, painless visual loss to hand motion in her right eye. Ophthalmoscopy showed a massive subhyaloidal hemorrhage. The patients' medical history was negative for cardiovascular risk factors, trauma, infections or bleeding complications. Further investigation into possible causes revealed hyperfibrinolysis secondary to severe PAI-1 deficiency. The non-clearing subhyaloidal hemorrhage was successfully treated by pars plana vitrectomy, and her visual acuity improved to 20/20.

CONCLUSION

When ordering laboratory tests in patients with spontaneous subhyaloidal hemorrhage to rule out fibrinolytic disorders, severe PAI-1 deficiency should be considered in the differential diagnosis. Selective screening may be helpful in identifying ophthalmologic patients with hyperfibrinolysis, especially in young individuals with subhyaloidal hemorrhages in the absence of other recognized risk factors.

Haemostatic management of intraoral bleeding in patients with congenital deficiency of alpha2-plasmin inhibitor or plasminogen activator inhibitor-1

Haemostatic management of intraoral bleeding was investigated in patients with congenital alpha2-plasmin inhibitor (alpha2-PI) deficiency or congenital plasminogen activator inhibitor- 1 (PAI-1) deficiency. When extracting teeth from patients with congenital alpha2-PI deficiency, we advocate that 7.5-10 mg kg(-1) of tranexamic acid be administered orally every 6 h, starting 3 h before surgery and continuing for about 7 days. For the treatment of continuous bleeding, such as post-extraction bleeding, 20 mg kg(-1) of tranexamic acid should be administered intravenously, and after achieving local haemostasis 7.5 mg kg(-1) of tranexamic acid should be administered orally every 6 h for several days. In addition, when treating haematoma caused by labial or gingival laceration or buccal or mandibular contusion, haemostasis should be achieved by administering 7.5-10 mg kg(-1) of tranexamic acid every 6 h. Tranexamic acid can also be used for haemostatic management of intraoral bleeding in patients with congenital PAI-1 deficiency, but is less effective when compared with use in patients with congenital alpha2-PI deficiency. Continuous infusion of 1.5 mg kg(-1) h(-1) of tranexamic acid is necessary for impacted tooth extraction requiring gingival incision or removal of local bone.

Successful arthroscopic treatment of pigmented villonodular synovitis of the knee in a patient with congenital deficiency of plasminogen activator inhibitor-1 and recurrent haemarthrosis

We report the arthroscopic treatment of pigmented villonodular synovitis (PVNS) in a 13-year-old Japanese boy with congenital partial deficiency of plasminogen activator inhibitor-1 (PAI-1). He was admitted to our hospital with recurrent haemarthrosis of his right knee. Characteristic abnormalities of fibrinolysis included shortened euglobulin lysis time, low PAI-1 activity and low PAI-1 antigen levels. In addition, levels of "active PAI" in the plasma, which is a measure of total PAI bound to exogenous plasminogen activator, were very low. These parameters remained low after venous occlusion. The diagnosis of PVNS was established by synovial membrane biopsy, and arthroscopic synovectomy was performed with adjuvant administration of intravenous tranexamic acid. Subsequent bleeding episodes have been well controlled by oral administration of tranexamic acid on demand.