Human platelet heparanase: purification, characterization and catalytic activity

Tissue factor-heparanase complex: intracellular nonhemostatic effects

Background

Heparanase, known to be involved in angiogenesis, cancer progression, and inflammation, was shown to form a complex with tissue factor (TF) via its procoagulant domain and to enhance the hemostatic system.

Objectives

To reveal a potential role of heparanase procoagulant domain in nonhemostatic effects.

Methods

Effects of peptides 16 and 16AC derived from the heparanase procoagulant domain, discovered by our group, were studied using the XTT proliferation assay, western blot analysis, and immunostaining in vitro and a mouse wound-healing model.

Results

Procoagulant peptides induced increased proliferation, release of heparanase, and upregulation of heparanase, TF, tissue factor pathway inhibitor (TFPI), and TFPI-2 in U87, T47D, and MCF-7 tumor cell lines and in endothelial cells. These results were reversed by a peptide derived from TFPI-2 that inhibited the heparanse procoagulant domain-TF complex. Thrombin had a similar effect on tumor cell proliferation and heparanase release, although the impact of thrombin on cell proliferation was mediated by the heparanase procoagulant domain. A mouse model of full-thickness skin incision exhibited higher levels of heparanase, TF, TFPI, and TFPI-2 in the healing skin, mainly in the blood vessel wall and lumen in animals injected with the procoagulant peptides compared to controls. The cells transfected to overexpress full-length TF or TF devoid of the cytoplasmic domain demonstrated that the procoagulant domain conveyed intracellular signaling via TF.

Conclusion

Heparanase procoagulant domain induces nonhemostatic effects via TF. The finding that TF serves as a receptor to heparanase supports the close direct relation between the hemostatic system and cancer progression.

Heparanase-A single protein with multiple enzymatic and nonenzymatic functions

Heparanase (Hpa1) is expressed by tumor cells and cells of the tumor microenvironment and functions extracellularly to remodel the extracellular matrix (ECM) and regulate the bioavailability of ECM-bound factors, augmenting, among other effects, gene transcription, autophagy, exosome formation, and heparan sulfate (HS) turnover. Much of the impact of heparanase on tumor progression is related to its function in mediating tumor-host crosstalk, priming the tumor microenvironment to better support tumor growth, metastasis, and chemoresistance. The enzyme appears to fulfill some normal functions associated, for example, with vesicular traffic, lysosomal-based secretion, autophagy, HS turnover, and gene transcription. It activates cells of the innate immune system, promotes the formation of exosomes and autophagosomes, and stimulates signal transduction pathways via enzymatic and nonenzymatic activities. These effects dynamically impact multiple regulatory pathways that together drive tumor growth, dissemination, and drug resistance as well as inflammatory responses. The emerging premise is that heparanase expressed by tumor cells, immune cells, endothelial cells, and other cells of the tumor microenvironment is a key regulator of the aggressive phenotype of cancer, an important contributor to the poor outcome of cancer patients and a valid target for therapy. So far, however, antiheparanase-based therapy has not been implemented in the clinic. Unlike heparanase, heparanase-2 (Hpa2), a close homolog of heparanase (Hpa1), does not undergo proteolytic processing and hence lacks intrinsic HS-degrading activity, the hallmark of heparanase. Hpa2 retains the capacity to bind heparin/HS and exhibits an even higher affinity towards HS than heparanase, thus competing for HS binding and inhibiting heparanase enzymatic activity. It appears that Hpa2 functions as a natural inhibitor of Hpa1 regulates the expression of selected genes that maintain tissue hemostasis and normal function, and plays a protective role against cancer and inflammation, together emphasizing the significance of maintaining a proper balance between Hpa1 and Hpa2.

Role of heparanase in ARDS through autophagy and exosome pathway (review)

Acute respiratory distress syndrome (ARDS) is the most common respiratory disease in ICU. Although there are many treatment and support methods, the mortality rate is still high. The main pathological feature of ARDS is the damage of pulmonary microvascular endothelium and alveolar epithelium caused by inflammatory reaction, which may lead to coagulation system disorder and pulmonary fibrosis. Heparanase (HPA) plays an significant role in inflammation, coagulation, fibrosis. It is reported that HPA degrades a large amount of HS in ARDS, leading to the damage of endothelial glycocalyx and inflammatory factors are released in large quantities. HPA can aggrandize the release of exosomes through syndecan-syntenin-Alix pathway, leading to a series of pathological reactions; at the same time, HPA can cause abnormal expression of autophagy. Therefore, we speculate that HPA promotes the occurrence and development of ARDS through exosomes and autophagy, which leads to a large amount of release of inflammatory factors, coagulation disorder and pulmonary fibrosis. This article mainly describes the mechanism of HPA on ARDS.

Investigating the Role of Heparanase in Breast Cancer Development Utilising the MMTV-PyMT Murine Model of Mammary Carcinoma

Breast cancer is the second most common human malignancy and is a major global health burden. Heparanase (HPSE) has been widely implicated in enhancing the development and progression of solid tumours, including breast cancer. In this study, the well-established spontaneous mammary tumour-developing MMTV-PyMT murine model was utilised to examine the role of HPSE in breast cancer establishment, progression, and metastasis. The use of HPSE-deficient MMTV-PyMT (MMTV-PyMTxHPSE^-/-) mice addressed the lack of genetic ablation models to investigate the role of HPSE in mammary tumours. It was demonstrated that even though HPSE regulated mammary tumour angiogenesis, mammary tumour progression and metastasis were HPSE-independent. Furthermore, there was no evidence of compensatory action by matrix metalloproteinases (MMPs) in response to the lack of HPSE expression in the mammary tumours. These findings suggest that HPSE may not play a significant role in the mammary tumour development of MMTV-PyMT animals. Collectively, these observations may have implications in the clinical setting of breast cancer and therapy using HPSE inhibitors.

4-O-Substituted Glucuronic Cyclophellitols are Selective Mechanism-Based Heparanase Inhibitors

Degradation of the extracellular matrix (ECM) supports tissue integrity and homeostasis, but is also a key factor in cancer metastasis. Heparanase (HPSE) is a mammalian ECM-remodeling enzyme with β-D-endo-glucuronidase activity overexpressed in several malignancies, and is thought to facilitate tumor growth and metastasis. By this virtue, HPSE is considered an attractive target for the development of cancer therapies, yet to date no HPSE inhibitors have progressed to the clinic. Here we report on the discovery of glucurono-configured cyclitol derivatives featuring simple substituents at the 4-O-position as irreversible HPSE inhibitors. We show that these compounds, unlike glucurono-cyclophellitol, are selective for HPSE over β-D-exo-glucuronidase (GUSB), also in platelet lysate. The observed selectivity is induced by steric and electrostatic interactions of the substituents at the 4-O-position. Crystallographic analysis supports this rationale for HPSE selectivity, and computer simulations provide insights in the conformational preferences and binding poses of the inhibitors, which we believe are good starting points for the future development of HPSE-targeting antimetastatic cancer drugs.

Heparin, Heparan Sulphate and Sepsis: Potential New Options for Treatment

Sepsis is a life-threatening hyperreaction to infection in which excessive inflammatory and immune responses cause damage to host tissues and organs. The glycosaminoglycan heparan sulphate (HS) is a major component of the cell surface glycocalyx. Cell surface HS modulates several of the mechanisms involved in sepsis such as pathogen interactions with the host cell and neutrophil recruitment and is a target for the pro-inflammatory enzyme heparanase. Heparin, a close structural relative of HS, is used in medicine as a powerful anticoagulant and antithrombotic. Many studies have shown that heparin can influence the course of sepsis-related processes as a result of its structural similarity to HS, including its strong negative charge. The anticoagulant activity of heparin, however, limits its potential in treatment of inflammatory conditions by introducing the risk of bleeding and other adverse side-effects. As the anticoagulant potency of heparin is largely determined by a single well-defined structural feature, it has been possible to develop heparin derivatives and mimetic compounds with reduced anticoagulant activity. Such heparin mimetics may have potential for use as therapeutic agents in the context of sepsis.

Design of an Ultralow Molecular Weight Heparin That Resists Heparanase Biodegradation

Heparanase, an endo-β-d-glucuronidase produced by a variety of cells and tissues, cleaves the glycosidic linkage between glucuronic acid (GlcA) and a 3-O- or 6-O-sulfated glucosamine, typified by the disaccharide -[GlcA-GlcNS3S6S]-, which is found within the antithrombin-binding domain of heparan sulfate or heparin. As such, all current forms of heparin are susceptible to degradation by heparanase with neutralization of anticoagulant properties. Here, we have designed a heparanase-resistant, ultralow molecular weight heparin as the structural analogue of fondaparinux that does not contain an internal GlcA residue but otherwise displays potent anticoagulant activity. This heparin oligosaccharide was synthesized following a chemoenzymatic scheme and displays nanomolar anti-FXa activity yet is resistant to heparanase digestion. Inhibition of thrombus formation was further demonstrated after subcutaneous administration of this compound in a murine model of venous thrombosis. Thrombus inhibition was comparable to that observed for enoxaparin with a similar effect on bleeding time.

Heparanase: A Novel Therapeutic Target for the Treatment of Atherosclerosis

Cardiovascular disease (CVD) is the leading cause of death and disability worldwide, and its management places a huge burden on healthcare systems through hospitalisation and treatment. Atherosclerosis is a chronic inflammatory disease of the arterial wall resulting in the formation of lipid-rich, fibrotic plaques under the subendothelium and is a key contributor to the development of CVD. As such, a detailed understanding of the mechanisms involved in the development of atherosclerosis is urgently required for more effective disease treatment and prevention strategies. Heparanase is the only mammalian enzyme known to cleave heparan sulfate of heparan sulfate proteoglycans, which is a key component of the extracellular matrix and basement membrane. By cleaving heparan sulfate, heparanase contributes to the regulation of numerous physiological and pathological processes such as wound healing, inflammation, tumour angiogenesis, and cell migration. Recent evidence suggests a multifactorial role for heparanase in atherosclerosis by promoting underlying inflammatory processes giving rise to plaque formation, as well as regulating lesion stability. This review provides an up-to-date overview of the role of heparanase in physiological and pathological processes with a focus on the emerging role of the enzyme in atherosclerosis.

Acute T-Cell-Driven Inflammation Requires the Endoglycosidase Heparanase-1 from Multiple Cell Types

It has been accepted for decades that T lymphocytes and metastasising tumour cells traverse basement membranes (BM) by deploying a battery of degradative enzymes, particularly proteases. However, since many redundant proteases can solubilise BM it has been difficult to prove that proteases aid cell migration, particularly in vivo. Recent studies also suggest that other mechanisms allow BM passage of cells. To resolve this issue we exploited heparanase-1 (HPSE-1), the only endoglycosidase in mammals that digests heparan sulfate (HS), a major constituent of BM. Initially we examined the effect of HPSE-1 deficiency on a well-characterised adoptive transfer model of T-cell-mediated inflammation. We found that total elimination of HPSE-1 from this system resulted in a drastic reduction in tissue injury and loss of target HS. Subsequent studies showed that the source of HPSE-1 in the transferred T cells was predominantly activated CD4⁺ T cells. Based on bone marrow chimeras, two cellular sources of HPSE-1 were identified in T cell recipients, one being haematopoiesis dependent and the other radiation resistant. Collectively our findings unequivocally demonstrate that an acute T-cell-initiated inflammatory response is HPSE-1 dependent and is reliant on HPSE-1 from at least three different cell types.

Computational design and experimental characterisation of a stable human heparanase variant

Heparanase is the only human enzyme known to hydrolyse heparin sulfate and is involved in many important physiological processes. However, it is also unregulated in many disease states, such as cancer, diabetes and Covid-19. It is thus an important drug target, yet the heterologous production of heparanase is challenging and only possible in mammalian or insect expression systems, which limits the ability of many laboratories to study it. Here we describe the computational redesign of heparanase to allow high yield expression in Escherchia coli. This mutated form of heparanase exhibits essentially identical kinetics, inhibition, structure and protein dynamics to the wild type protein, despite the presence of 26 mutations. This variant will facilitate wider study of this important enzyme and contributes to a growing body of literature that shows evolutionarily conserved and functionally neutral mutations can have significant effects on protein folding and expression.

A mutant heparanase that exhibits wild type structure and activity but can be heterologously produced in bacterial protein expression systems.

Serum heparanase levels and left atrial/left atrial appendage thrombus in patients with nonvalvular atrial fibrillation

INTRODUCTION

Data regarding the possible role of heparanase (HPA) in the occurrence of left atrial/left atrial appendage (LA/LAA) thrombus in patients with atrial fibrillation (AF) is lacking. The goal of the present study was to assess the association between plasma levels of HPA and LA/LAA thrombus in AF.

METHODS

A total of 687 patients with nonvalvular AF (NVAF) without anticoagulation therapy were included from January 2016 to June 2019. Serum HPA analysis was performed with a commercially available human ELISA kit. Logistic regression models were used to test for association.

RESULTS

Serum HPA levels were significantly higher in patients with LA/LAA thrombus than in those without LA/LAA thrombus (270.8 [193.4 ± 353.2] pg/mL vs 150.3 [125.2 ± 208.4] pg/mL; P < 0.001). In multivariate analysis, serum HPA remained a significantly independent predictor of LA/LAA thrombus (odds ratio 1.674, 95% confidence interval [CI] 1.339-2.289, P < 0.001). In the receiver operating characteristic (ROC) curve analysis, HPA showed a predictive value with an area under the curve (AUC) of 0.757 (95% CI 0.652-0.810, P < 0.001). The optimal cutoff level for HPA predicting LA/LAA thrombus was 210.7 pg/mL, with a sensitivity of 74.3% and a specificity of 64.8%.

CONCLUSION

An elevated HPA level was associated with the presence of LA/LAA thrombus in patients with AF. HPA might portend the risk for the prothrombotic state in AF patients.

Progestin type affects the increase of heparanase level and procoagulant activity mediated by the estrogen receptor

STUDY QUESTION

Does progestin have an effect on heparanase level and procoagulant activity?

SUMMARY ANSWER

Progestin increases the heparanase level and procoagulant activity via the estrogen receptor and the magnitude of the effect depends on the progestin type.

WHAT IS KNOWN ALREADY

Users of combined oral contraceptives (COCs) containing third- and fourth-generation progestins have a higher risk of venous thrombosis compared to those employing second-generation progestins. Heparanase protein is capable of degrading heparan sulfate (HS) chains and enhancing activation of the coagulation system. We have previously demonstrated that estrogen enhances the expression and procoagulant activity of heparanase.

STUDY DESIGN, SIZE, DURATION

Estrogen and progestin receptor positive breast carcinoma cell lines: EMT6, T47D and MCF-7 were compared to the MDA-231 breast carcinoma cell line devoid of these receptors. This observational study incorporated 45 users of third-generation COCs progestins, 21 users of fourth-generation COCs progestins and 28 individuals not using hormonal therapy and not pregnant per history.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Second-generation progestin-levonorgestrel, third-generation progestin-desogastrel (DSG), an estrogen receptor antagonist-ICI 182.780 and a progestin receptor antagonist-mifepristone, were added to cell lines. Heparanase level and procoagulant activity, HS levels, tissue factor (TF) activity and factor Xa levels were evaluated in the plasma of the study group.

MAIN RESULTS AND THE ROLE OF CHANCE

Levonorgestrel and DSG increased heparanase levels in the cells and medium. The effect of DSG was more prominent and additive to that of estrogen. The effect was inhibited by ICI 182.780. In the plasma of COC users, heparanase procoagulant activity, HS levels, TF activity and factor Xa levels were significantly higher compared to controls. In COC pills containing the same dose of estrogen, the procoagulant effect of drospirenone was significantly stronger than that of DSG and gestodene.

LIMITATIONS, REASONS FOR CAUTION

The limitations of the study include a small number of participants in each study group, although the results are statistically significant and evaluated by several different coagulation parameters.

WIDER IMPLICATIONS OF THE FINDINGS

The study demonstrates a new mechanism through which progestin affects coagulation system activation and shows that this effect is progestin type-dependent. Development of a progestin derivative with an attenuated effect on heparanase procoagulant activity may reduce thrombotic risk.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was sought for this study. Y.N. is named in a European patent application No. IL201200027 filed on 18 January 2012. Other authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Heparanase expression and activity are increased in platelets during clinical sepsis

BACKGROUND

Heparanase (HPSE) is the only known mammalian enzyme that can degrade heparan sulfate. Heparan sulfate proteoglycans are essential components of the glycocalyx, and maintain physiological barriers between the blood and endothelial cells. HPSE increases during sepsis, which contributes to injurious glyocalyx degradation, loss of endothelial barrier function, and mortality.

OBJECTIVES

As platelets are one of the most abundant cellular sources of HPSE, we sought to determine whether HPSE expression and activity increases in human platelets during clinical sepsis. We also examined associations between platelet HPSE expression and clinical outcomes.

PATIENTS/METHODS

Expression and activity of HPSE was determined in platelets isolated from septic patients (n = 59) and, for comparison, sex-matched healthy donors (n = 46) using complementary transcriptomic, proteomic, and functional enzymatic assays. Septic patients were followed for the primary outcome of mortality, and clinical data were captured prospectively for septic patients.

RESULTS

The mRNA expression of HPSE was significantly increased in platelets isolated from septic patients. Ribosomal footprint profiling, followed by [S35] methionine labeling assays, demonstrated that HPSE mRNA translation and HPSE protein synthesis were significantly upregulated in platelets during sepsis. While both the pro- and active forms of HPSE protein increased in platelets during sepsis, only the active form of HPSE protein significantly correlated with sepsis-associated mortality. Consistent with transcriptomic and proteomic upregulation, HPSE enzymatic activity was also increased in platelets during sepsis.

CONCLUSIONS

During clinical sepsis HPSE, translation, and enzymatic activity are increased in platelets. Increased expression of the active form of HPSE protein is associated with sepsis-associated mortality.

Effect of Heparanase and Heparan Sulfate Chains in Hemostasis

Heparanase, the only mammalian enzyme known to degrade heparan sulfate chains, affects the hemostatic system through several mechanisms. Along with the degrading effect, heparanase engenders release of syndecan-1 from the cell surface and directly enhances the activity of the blood coagulation initiator, tissue factor, in the coagulation system. Upregulation of tissue factor and release of tissue factor pathway inhibitor from the cell surface contribute to the prothrombotic effect. Tissue factor pathway inhibitor and the strongest physiological anticoagulant antithrombin are attached to the endothelial cell surface by heparan sulfate. Hence, degradation of heparan sulfate induces further release of these two natural anticoagulants from endothelial cells. Elevated heparanase procoagulant activity and heparan sulfate chain levels in plasma, demonstrated in cancer, pregnancy, oral contraceptive use, and aging, could suggest a potential mechanism for increased risk of thrombosis in these clinical settings. In contrast to the blood circulation, accumulation of heparan sulfate chains in transudate and exudate pleural effusions induces a local anticoagulant milieu. The anticoagulant effect of heparan sulfate chains in other closed spaces such as peritoneal or subdural cavities should be further investigated.

The expression of heparanase in term and preterm human placentas

PURPOSE

Heparanase is an endo-β-glucuronidase that cleaves side chains of heparan-sulfate proteoglycans, an integral constituent of the extra cellular matrix. The abundance of heparanase in placental trophoblast cells implies its role in the processes of placentation and trophoblast invasion. This study aims to explore the involvement of heparanase in parturition and preterm deliveries (PTD).

METHODS

Sixteen human placentas were collected following singleton spontaneous onset term vaginal deliveries (n = 6), spontaneous onset preterm vaginal deliveries (n = 7) and term elective cesarean sections (n = 3). Placentas were excluded in case of any maternal chronic illness, pregnancy or delivery complications apart from PTD. Placental tissue samples were dissected, homogenized and proteins were extracted. Additionally, cryosections were prepared from the placental tissues. Heparanase expression was evaluated utilizing western blot analysis and immunofluorescence staining using heparanase specific antibodies. Heparanase expression was compared between the study groups qualitatively and quantitatively.

RESULTS

Western blot analysis results demonstrated higher expression of both pro-heparanase and heparanase in PTD placentas compared to term vaginal placentas. Accordingly, immunofluorescence staining shows elevated heparanase expression in PTD placentas compared to term vaginal placentas (5.1 ± 0.92 vs. 1.2 ± 0.18, p < .005). Expression level of heparanase was higher in term cesarean section placentas as compared to term vaginal deliveries placentas, but did not reach statistical significance (1.8 ± 0.39 vs. 1.2 ± 0.18, p = .06).

CONCLUSION

This study demonstrates for the first time that preterm vaginal deliveries are associated with higher expression of heparanase in placental tissue. This may imply a direct effect of heparanase on preterm labor. Further studies should evaluate the functional role by which heparanase influence preterm delivery.

Diagnostic and Prognostic Biomarkers for Myocardial Infarction

The incidence of myocardial infarction (MI) increases every year worldwide. Better diagnostic and prognostic biomarkers for clinical applications are the consistent pursuit of MI research. In addition to electrocardiogram, echocardiography, coronary angiography, etc., circulating biomarkers are essential for the diagnosis, prognosis, and treatment effect monitoring of MI patients. In this review, we assessed both strength and weakness of MI circulating biomarkers including: (1) originated from damaged myocardial tissues including current golden standard cardiac troponin, (2) released from non-myocardial tissues due to MI-induced systems reactions, and (3) preexisted in blood circulation before the occurrence of MI event. We also summarized newly reported MI biomarkers. We proposed that the biomarkers preexisting in blood circulation before MI incidents should be emphasized in research and development for MI prevention in near future.

Neutralizing the pathological effects of extracellular histones with small polyanions

Extracellular histones in neutrophil extracellular traps (NETs) or in chromatin from injured tissues are highly pathological, particularly when liberated by DNases. We report the development of small polyanions (SPAs) (~0.9–1.4 kDa) that interact electrostatically with histones, neutralizing their pathological effects. In vitro, SPAs inhibited the cytotoxic, platelet-activating and erythrocyte-damaging effects of histones, mechanistic studies revealing that SPAs block disruption of lipid-bilayers by histones. In vivo, SPAs significantly inhibited sepsis, deep-vein thrombosis, and cardiac and tissue-flap models of ischemia-reperfusion injury (IRI), but appeared to differ in their capacity to neutralize NET-bound versus free histones. Analysis of sera from sepsis and cardiac IRI patients supported these differential findings. Further investigations revealed this effect was likely due to the ability of certain SPAs to displace histones from NETs, thus destabilising the structure. Finally, based on our work, a non-toxic SPA that inhibits both NET-bound and free histone mediated pathologies was identified for clinical development.

Histones, proteins that bind DNA, are toxic for pathogens outside cells but can also cause multi-organ damage as seen in sepsis. Here the authors develop small negatively charged molecules that can be used as histone antidotes, and show that they improve the phenotype in mouse models with histone-related pathologies.

Heparanase: Historical Aspects and Future Perspectives

Heparanase is an endo-β-glucuronidase that cleaves at a limited number of internal sites the glycosaminoglycan heparan sulfate (HS). Heparanase enzymatic activity was first reported in 1975 and by 1983 evidence was beginning to emerge that the enzyme was a facilitator of tumor metastasis by cleaving HS chains present in blood vessel basement membranes and, thereby, aiding the passage of tumor cells through blood vessel walls. Due to a range of technical difficulties, it took another 16 years before heparanase was cloned and characterized in 1999 and a further 14 years before the crystal structure of the enzyme was solved. Despite these substantial deficiencies, there was steady progress in our understanding of heparanase long before the enzyme was fully characterized. For example, it was found as early as 1984 that activated T cells upregulate heparanase expression, like metastatic tumor cells, and the enzyme aids the entry of T cells and other leukocytes into inflammatory sites. Furthermore, it was discovered in 1989 that heparanase releases pre-existing growth factors and cytokines associated with HS in the extracellular matrix (ECM), the liberated growth factors/cytokines enhancing angiogenesis and wound healing. There were also the first hints that heparanase may have functions other than enzymatic activity, in 1995 it being reported that under certain conditions the enzyme could act as a cell adhesion molecule. Also, in the same year PI-88 (Muparfostat), the first heparanase inhibitor to reach and successfully complete a Phase III clinical trial was patented.Nevertheless, the cloning of heparanase (also known as heparanase-1) in 1999 gave the field an enormous boost and some surprises. The biggest surprise was that there is only one heparanase encoding gene in the mammalian genome, despite earlier research, based on substrate specificity, suggesting that there are at least three different heparanases. This surprising conclusion has remained unchanged for the last 20 years. It also became evident that heparanase is a family 79 glycoside hydrolase that is initially produced as a pro-enzyme that needs to be processed by proteases to form an enzymatically active heterodimer. A related molecule, heparanase-2, was also discovered that is enzymatically inactive but, remarkably, recently has been shown to inhibit heparanase-1 activity as well as acting as a tumor suppressor that counteracts many of the pro-tumor properties of heparanase-1.The early claim that heparanase plays a key role in tumor metastasis, angiogenesis and inflammation has been confirmed by many studies over the last 20 years. In fact, heparanase expression is enhanced in all major cancer types, namely carcinomas, sarcomas, and hematological malignancies, and correlates with increased metastasis and poor prognosis. Also, there is mounting evidence that heparanase plays a central role in the induction of inflammation-associated cancers. The enzymatic activity of heparanase has also emerged in unexpected situations, such as in the spread of HS-binding viruses and in Type-1 diabetes where the destruction of intracellular HS in pancreatic insulin-producing beta cells precipitates diabetes. But the most extraordinary recent discoveries have been with the realization that heparanase can exert a range of biological activities that are independent of its enzymatic function, most notably activation of several signaling pathways and being a transcription factor that controls methylation of histone tails. Collectively, these data indicate that heparanase is a truly multifunctional protein that has the additional property of cleaving HS chains and releasing from ECM and cell surfaces hundreds of HS-binding proteins with a plethora of functional consequences. Clearly, there are many unique features of this intriguing molecule that still remain to be explored and are highlighted in this Chapter.

PI-88 and Related Heparan Sulfate Mimetics

The heparan sulfate mimetic PI-88 (muparfostat) is a complex mixture of sulfated oligosaccharides that was identified in the late 1990s as a potent inhibitor of heparanase. In preclinical animal models it was shown to block angiogenesis, metastasis and tumor growth, and subsequently became the first heparanase inhibitor to enter clinical trials for cancer. It progressed to Phase III trials but ultimately was not approved for use. Herein we summarize the preparation, physicochemical and biological properties of PI-88, and discuss preclinical/clinical and structure-activity relationship studies. In addition, we discuss the PI-88-inspired development of related HS mimetic heparanase inhibitors with improved properties, ultimately leading to the discovery of PG545 (pixatimod) which is currently in clinical trials.

Heparanase: Cloning, Function and Regulation

In 2019, we mark the 20th anniversary of the cloning of the human heparanase gene. Heparanase remains the only known enzyme to cleave heparan sulfate, which is an abundant component of the extracellular matrix. Thus, elucidating the mechanisms underlying heparanase expression and activity is critical to understanding its role in healthy and pathological settings. This chapter provides a historical account of the race to clone the human heparanase gene, describes the intracellular and extracellular function of the enzyme, and explores the various mechanisms regulating heparanase expression and activity at the gene, transcript, and protein level.

SULF1 suppresses Wnt3A-driven growth of bone metastatic prostate cancer in perlecan-modified 3D cancer-stroma-macrophage triculture models

Bone marrow stroma influences metastatic prostate cancer (PCa) progression, latency, and recurrence. At sites of PCa bone metastasis, cancer-associated fibroblasts and tumor-associated macrophages interact to establish a perlecan-rich desmoplastic stroma. As a heparan sulfate proteoglycan, perlecan (HSPG2) stores and stabilizes growth factors, including heparin-binding Wnt3A, a positive regulator of PCa cell growth. Because PCa cells alone do not induce CAF production of perlecan in the desmoplastic stroma, we sought to discover the sources of perlecan and its growth factor-releasing modifiers SULF1, SULF2, and heparanase in PCa cells and xenografts, bone marrow fibroblasts, and macrophages. SULF1, produced primarily by bone marrow fibroblasts, was the main glycosaminoglycanase present, a finding validated with primary tissue specimens of PCa metastases with desmoplastic bone stroma. Expression of both HSPG2 and SULF1 was concentrated in αSMA-rich stroma near PCa tumor nests, where infiltrating pro-tumor TAMs also were present. To decipher SULF1's role in the reactive bone stroma, we created a bone marrow biomimetic hydrogel incorporating perlecan, PCa cells, macrophages, and fibroblastic bone marrow stromal cells. Finding that M2-like macrophages increased levels of SULF1 and HSPG2 produced by fibroblasts, we examined SULF1 function in Wnt3A-mediated PCa tumoroid growth in tricultures. Comparing control or SULF1 knockout fibroblastic cells, we showed that SULF1 reduces Wnt3A-driven growth, cellularity, and cluster number of PCa cells in our 3D model. We conclude that SULF1 can suppress Wnt3A-driven growth signals in the desmoplastic stroma of PCa bone metastases, and SULF1 loss favors PCa progression, even in the presence of pro-tumorigenic TAMs.

Topical application of Heparanase-1 facilitates bone remodeling during the healing of bone defects in a mouse model

BACKGROUND

Although previous studies have suggested a stimulatory role of heparanase in physiological bone turnover, the potential therapeutic role of heparanase in bone healing has not been elucidated. The purpose of this study was to assess the effect of topical application of heparanase-1 on bone healing.

METHODS

Two different dosages of recombinant mouse heparanase-1 and vehicle control were prepared and delivered via an osmotic pump to provide continuous topical infusion of the therapeutic reagent in a mouse bone defect model at the distal femoral metaphysis. The bone healing progress was evaluated by micro-computed tomography and histological examination at 7, 14, and 21 days after the bone defect was created.

RESULTS

The peak of trabecular bone generation was achieved earlier than anticipated with the use of heparanase as measured by medullary bone volume fraction and trabecular number observed in micro-computed tomography, while the remodeling of trabecular bone to cortical bone was also achieved earlier than anticipated with the use of heparanase as measured by connectivity density. Histopathological observation revealed a higher frequency of the presence of cartilaginous tissue in the heparanase-treated groups. Both bone mineral density and cortical bone volume fraction showed the best healing outcome with low-dose heparanase, implying a biphasic effect of its mode of action.

CONCLUSION

These results indicated that with the appropriate dose of topical heparanase-1, the progress of bone healing could be accelerated in vivo.

Potential Mechanisms of Cancer-Related Hypercoagulability

The association between cancer and thrombosis has been known for over a century and a half. However, the mechanisms that underlie this correlation are not fully characterized. Hypercoagulability in cancer patients can be classified into two main categories: Type I and Type II. Type I occurs when the balance of endogenous heparin production and degradation is disturbed, with increased degradation of endogenous heparin by tumor-secreted heparanase. Type II hypercoagulability includes all the other etiologies, with factors related to the patient, the tumor, and/or the treatment. Patients with poor performance status are at higher risk of venous thromboembolism (VTE). Tumors can result in VTE through direct pressure on blood vessels, resulting in stasis. Several medications for cancer are correlated with a high risk of thrombosis. These include hormonal therapy (e.g., tamoxifen), chemotherapy (e.g., cisplatin, thalidomide and asparaginase), molecular targeted therapy (e.g., lenvatinib, osimertinib), and anti-angiogenesis monoclonal antibodies (e.g., bevacizumab and ramucirumab).

Forty Years of Basic and Translational Heparanase Research

This review summarizes key developments in the heparanase field obtained 20 years prior to cloning of the HPSE gene and nearly 20 years after its cloning. Of the numerous publications and review articles focusing on heparanase, we have selected those that best reflect the progression in the field as well as those we regard important accomplishments with preference to studies performed by scientists and groups that contributed to this book. Apart from a general 'introduction' and 'concluding remarks', the abstracts of these studies are presented essentially as published along the years. We apologize for not being objective and not being able to include some of the most relevant abstracts and references, due to space limitation. Heparanase research can be divided into two eras. The first, initiated around 1975, dealt with identifying the enzyme, establishing the relevant assay systems and investigating its biological activities and significance in cancer and other pathologies. Studies performed during the first area are briefly introduced in a layman style followed by the relevant abstracts presented chronologically, essentially as appears in PubMed. The second era started in 1999 when the heparanase gene was independently cloned by 4 research groups [1-4]. As expected, cloning of the heparanase gene boosted heparanase research by virtue of the readily available recombinant enzyme, molecular probes, and anti-heparanase antibodies. Studies performed during the second area are briefly introduced followed by selected abstracts of key findings, arranged according to specific topics.

An Overview of the Structure, Mechanism and Specificity of Human Heparanase

The retaining endo-β-D-glucuronidase Heparanase (HPSE) is the primary mammalian enzyme responsible for breakdown of the glycosaminoglycan heparan sulfate (HS). HPSE activity is essential for regulation and turnover of HS in the extracellular matrix, and its activity affects diverse processes such as inflammation, angiogenesis and cell migration. Aberrant heparanase activity is strongly linked to cancer metastasis, due to structural breakdown of extracellular HS networks and concomitant release of sequestered HS-binding growth factors. A full appreciation of HPSE activity in health and disease requires a structural understanding of the enzyme, and how it engages with its HS substrates. This chapter summarizes key findings from the recent crystal structures of human HPSE and its proenzyme. We present details regarding the 3-dimensional protein structure of HPSE and the molecular basis for its interaction with HS substrates of varying sulfation states. We also examine HPSE in a wider context against related β-D-glucuronidases from other species, highlighting the structural features that control exo/endo - glycosidase selectivity in this family of enzymes.

Heparan sulfate chains contribute to the anticoagulant milieu in malignant pleural effusion

Background

While malignant pleural effusion (MPE) is a common and significant cause of morbidity in patients with cancer, current treatment options are limited. Human heparanase, involved in angiogenesis and metastasis, cleaves heparan sulfate (HS) side chains on the cell surface.

Aims

To explore the coagulation milieu in MPE and infectious pleural effusion (IPE) focusing on the involvement of heparanase.

Methods

Samples of 30 patients with MPE and 44 patients with IPE were evaluated in comparison to those of 33 patients with transudate pleural effusions, using heparanase ELISA, heparanase procoagulant activity assay, thrombin and factor Xa chromogenic assays and thromboelastography. A cell proliferation assay was performed. EMT-6 breast cancer cells were injected to the pleural cavity of mice. A peptide inhibiting heparanase activity was administered subcutaneously.

Results

Levels of heparanase, factor Xa and thrombin were significantly higher in exudate than transudate. Thromboelastography detected almost no thrombus formation in the whole blood, mainly on MPE addition. This effect was completely reversed by bacterial heparinase. Direct measurement revealed high levels of HS chains in pleural effusions. Higher proliferation was observed in tumour cell lines incubated with exudate than with transudate and it was reduced when bacterial heparinase was added. The tumour size in the pleural cavity of mice treated with the heparanase inhibitor were significantly smaller compared with control (p=0.005).

Conclusions

HS chains released by heparanase form an anticoagulant milieu in MPE, preventing local thrombosis and enabling tumour cell proliferation. Inhibition of heparanase might provide a therapeutic option for patients with recurrent MPE.

The endothelial glycocalyx anchors von Willebrand factor fibers to the vascular endothelium

The dynamic change from a globular conformation to an elongated fiber determines the ability of von Willebrand factor (VWF) to trap platelets. Fiber formation is favored by the anchorage of VWF to the endothelial cell surface, and VWF-platelet aggregates on the endothelium contribute to inflammation, infection, and tumor progression. Although P-selectin and ανβ3-integrins may bind VWF, their precise role is unclear, and additional binding partners have been proposed. In the present study, we evaluated whether the endothelial glycocalyx anchors VWF fibers to the endothelium. Using microfluidic experiments, we showed that stabilization of the endothelial glycocalyx by chitosan oligosaccharides or overexpression of syndecan-1 (SDC-1) significantly supports the binding of VWF fibers to endothelial cells. Heparinase-mediated degradation or impaired synthesis of heparan sulfate (HS), a major component of the endothelial glycocalyx, reduces VWF fiber-dependent platelet recruitment. Molecular interaction studies using flow cytometry and live-cell fluorescence microscopy provided further evidence that VWF binds to HS linked to SDC-1. In a murine melanoma model, we found that protection of the endothelial glycocalyx through the silencing of heparanase increases the number of VWF fibers attached to the wall of tumor blood vessels. In conclusion, we identified HS chains as a relevant binding factor for VWF fibers at the endothelial cell surface in vitro and in vivo.

Heparanase is a predictive marker for high thrombus burden in patients with ST-segment elevation myocardial infarction

Objective: Heparanase (HPA) is an endo-β-D-glucuronidase capable of degrading heparin sulphate (HS) and heparin side chains. HPA plays a role in tumour growth, angiogenesis, cell invasion and in activation of the coagulation system. We aimed to investigate the relationship between HPA and thrombus burden (TB) in patients with ST-Segment Elevation Myocardial Infarction (STEMI). Methods: This prospective study enrolled 187 patients with STEMI who were treated with primary percutaneous coronary intervention (pPCI). Blood samples were taken to determine serum HPA levels prior to coronary angiography and heparin administration. Serum HPA analysis was performed with a commercially available Human Elisa kit. Results: Patients were divided into two groups: high TB (n:58) and low TB (n:129) group. Serum HPA levels were significantly higher in patients with high TB than low TB [250.1 (188.5-338.1) vs. 173.6 (134.3-219.8) pg/mL] (p < 0.001). Serum HPA levels were higher in patients with no-reflow phenomenon compared with others [(409.3 (375.6-512.5) pg/mL vs. 186.2 (144.2-247.4) pg/mL, p < 0.001]. In multiple logistic regression analysis HPA was a predictor of high TB. Conclusion: Elevated HPA level in patients with STEMI is related to high TB. Furthermore, increased HPA level may be associated with thrombotic complications such as no-reflow phenomenon in patients with STEMI.

The role of heparin, heparanase and heparan sulfates in hepcidin regulation

Hepcidin is considered the major regulator of systemic iron homeostasis in human and mice, and its expression in the liver is mainly regulated at a transcriptional level. Central to its regulation are the bone morphogenetic proteins, particularly BMP6, that are heparin binding proteins. Heparin was found to inhibit hepcidin expression and BMP6 activity in hepatic cell lines and in mice, suggesting that endogenous heparan sulfates are involved in the pathway of hepcidin expression. This was confirmed by the study of cells and mice overexpressing heparanase, the enzyme that hydrolyzes heparan sulfates, and by cellular models with altered heparan sulfates. The evidences supporting the role of heparan sulfate in hepcidin expression are summarized in this chapter and open the way for new understanding in hepcidin expression and its control in pathological condition.

Macrophage migration inhibitory factor antagonist (p425) ameliorates kidney histopathological and functional changes in diabetic rats

Introduction:

It is hypothesized that increased macrophage migration inhibitory factor (MIF) expression may contribute to diabetic nephropathy (DN) pathogenesis. The aim of the present study was to investigate the renal effects of MIF inhibition in a diabetic experimental model.

Methods:

Eighteen male Wistar rats (230 ± 20 g) were divided into three groups: 1) control, 2) diabetic (STZ, 50 mg/kg, dissolved in saline, ip), 3) diabetic + MIF antagonist (p425, 1 mg/kg per day, ip, on the 21th day, for 21 consecutive days). The treatment started since we founwd a significant increase in urine albumin excretion (UAE) rate in the diabetic rats in comparison with the control rats. The rats were kept individually in metabolic cages (8 AM-2 PM) and urine samples were collected in the 21 and 42th day. At the end, blood and tissue samples were collected for biochemical (BS, UPE, urine GAG, BUN, Cr, Na, and K) and histological analyses.

Results:

The results of this study showed that MIF antagonist (p425) significantly decreased urine protein and GAG excretion, urine protein/creatinine ratio, and serum BUN and Cr in the streptozotocin-induced DN in the rats. Pathological changes were significantly alleviated in the MIF antagonist (p425)-administered DN rats.

Conclusion:

Collectively, these data suggested that MIF antagonist (p425) was able to protect against functional and histopathological injury in the DN.

Is host heparanase required for the rapid spread of heparan sulfate binding viruses?

Vaccinia virus (VACV), like many other viruses, binds to cell surface heparan sulfate (HS) prior to infecting cells. Since HS is ubiquitously expressed extracellularly, it seemed likely that VACV-HS interaction may impede virus spread, with host heparanase, the only known mammalian endoglycosidase that can degrade HS, potentially overcoming this problem. In support of this hypothesis, we found that, compared to wild type, mice deficient in heparanase showed a 1-3 days delay in the spread of VACV to distant organs, such as ovaries, following intranasal inoculation, or to ovaries and spleen following intramuscular inoculation. These delays in spread occurred despite heparanase deficiency having no effect on VACV replication at inoculation sites. Subsequent in vitro studies revealed that heparanase treatment released VACV from HS expressing, but not HS deficient, infected cell monolayers. Collectively these data suggest that VACV relies on host heparanase to degrade HS in order to spread to distant sites.

Overexpression of heparanase in mice promoted megakaryopoiesis

Heparanase, an endo-glucuronidase that specifically cleaves heparan sulfate (HS), is upregulated in several pathological conditions. In this study, we aimed to find a correlation of heparanase expression and platelets production. In the transgenic mice overexpressing human heparanase (Hpa-tg), hematological analysis of blood samples revealed a significantly higher number of platelets in comparison with wild-type (Ctr) mice, while no significant difference was found in leukocytes and red blood cell number between the two groups. Total number of thiazole orange positive platelets was increased in Hpa-tg vs. Ctr blood, reflecting a higher rate of platelets production. Concomitantly, megakaryocytes from Hpa-tg mice produced more and shorter HS fragments that were shed into the medium. Further, thrombopoietin (TPO) level was elevated in the liver and plasma of Hpa-tg mice. Together, the data indicate that heparanase expression promoted megakaryopoiesis, which may be through upregulated expression of TPO and direct effect of released HS fragments expressed in the megakaryocytes.

The relationship between heparanase levels, thrombus burden and thromboembolism in patients receiving unfractionated heparin treatment for prosthetic valve thrombosis

INTRODUCTION

Procoagulant activity of heparanase has been recently described in several arterial and venous thrombotic disorders. In this study, we aimed to investigate the role of heparanase with regard to thrombus burden, thromboembolism, and treatment success with unfractionated heparin (UFH) in patients with prosthetic valve thrombosis (PVT).

METHODS

This study enrolled 79 PVT patients who received UFH for PVT and 82 controls. Plasma samples which were collected from patients both at baseline and after the UFH treatment and from controls at baseline only, were tested for heparanase levels by heparanase enzyme-linked immunosorbent assay.

RESULTS

The PVT group included 18 obstructive and 61 non-obstructive PVT patients who received UFH infusions for a median duration of 15 (7-20) days. The UFH treatment was successful in 37 (46.8%) patients. Baseline heparanase levels were significantly higher in the patient group than in the controls [0.29 (0.21-0.71) vs. 0.25 (0.17-0.33) ng/mL; p = 0.002]. Baseline heparanase levels were significantly higher in obstructive PVT patients. There was a significant increase in heparanase levels after UFH treatment. Post-UFH heparanase levels were higher in patients who experienced treatment failure compared to successfully treated group. Baseline and post-UFH heparanase levels were significantly higher in patients with a thrombus area ≥1 cm² and with a recent history of thromboembolism.

CONCLUSIONS

Increased heparanase levels may be one of the esoteric causes for PVT. UFH treatment may trigger an increase in heparanase levels which may affect the treatment success. Increased heparanase levels may be associated with high risk of thromboembolism and increased thrombus burden in PVT patients.

Cancer and Thrombosis-New Insights

Cancer patients have a pro-thrombotic state attributed to the ability of cancer cells to activate the coagulation system and interact with hemostatic cells, thus tilting the balance between pro- and anticoagulants. Mechanisms underlying the coagulation system activation involve tumor cells, endothelial cells, platelets, and white blood cells. Anti-cancer therapies, including anti-angiogenic drugs, significantly increase the risk of thrombosis during treatment. Along with the role of coagulation proteins in the hemostatic system, these proteins also serve as growth factors to the tumor. Heparanase is a pro-angiogenic and pro-metastatic protein. Our previous studies have demonstrated that it enhances tissue factor (TF) activity and is present at high levels in tumor cells and patients' blood. Strategies to attenuate heparanase effects by heparin mimetics or peptides interrupting the TF-heparanase interaction are good candidates to attenuate tumor growth and thrombotic manifestations.

Serum heparanase levels are associated with endothelial dysfunction in patients with obstructive sleep apnea

BACKGROUND AND AIM

Obstructive sleep apnea syndrome (OSAS) is well-known to be associated with high risk for cardiovascular (CV) diseases. Heparanase has been recently shown to be related to increased inflammation and vulnerability of the atherosclerotic plaques. Herein we aimed to investigate the relationships between OSAS, heparanase and endothelial dysfunction.

MATERIALS AND METHODS

A total of 120 patients with varying severity of OSAS and 31 controls without OSAS were enrolled. Flow-mediated dilatation (FMD) was measured as an indicator of endothelial dysfunction. Serum heparanase levels were measured with ELISA.

RESULTS

Serum heparanase levels increased in a stepwise fashion from controls to patients with more severe OSAS. When FMD was compared with controls and various degrees of severity of OSAS, a stepwise decrease in FMD was observed. Serum heparanase levels were found to be significantly associated with apnea hypopnea index (AHI) (r = .57, P < .001) and FMD (r= -.37, P < .001) in patients with OSAS. Serum heparanase levels were significantly associated with hemoglobin-A1c and body mass index in patients with OSAS. Serum heparanase and uric acid levels were independent predictors of FMD in linear regression analysis (R²  = .506, P < .001; P < .001 and P = .001 respectively).

CONCLUSIONS

Serum heparanase levels were significantly increased in patients with OSAS and associated with the severity of OSAS (AHI) and endothelial dysfunction (FMD). Increased heparanase activity in OSAS may be related to increased cardiovascular risk in patients with OSAS.

Peptides inhibiting heparanase procoagulant activity significantly reduce tumour growth and vascularisation in a mouse model

Heparanase is implicated in angiogenesis and tumour progression. We previously demonstrated that heparanase might also affect the haemostatic system in a non-enzymatic manner. It forms a complex and enhances the activity of the blood coagulation initiator tissue factor (TF). Peptides that we generated from TF pathway inhibitor (TFPI)-2, which inhibit heparanase procoagulant activity, were recently demonstrated to attenuate inflammation in a sepsis mouse model. The present study was designated to explore peptides effects on tumour growth and vascularisation. Cell lines of mouse melanoma (B16), mouse breast cancer (EMT-6), and human breast cancer (MDA-231) were injected subcutaneously to mice. Inhibitory peptides 5, 6 and 7 were injected subcutaneously in the area opposite to the tumour side. In the three tumour cell lines, peptides 5, 6 and 7 inhibited tumour growth and vascularisation in a dose-dependent manner, reaching a 2/3 reduction compared to control tumours (p<0.001). Additionally, a survival advantage (p<0.05) and reduced plasma thrombin-antithrombin complex (p<0.05) were observed in the treatment groups. Peptides delayed tumour relapse by six days and inhibited relapsed tumour size (p<0.001). In vitro, peptides did not inhibit tumour cell proliferation, migration or heparanase degradation of heparan sulfate chains, but significantly decreased tube formation. In conclusion, peptides inhibiting heparanase procoagulant activity significantly reduced tumour growth, vascularisation, and relapse. The procoagulant domain in heparanase protein may play a role in tumour growth, suggesting a new mechanism of coagulation system involvement in cancer.

Heparanase level and procoagulant activity are reduced in severe sepsis

BACKGROUND

During severe sepsis, levels and activity of all coagulation proteins are reduced. Heparanase is implicated in angiogenesis and tumor progression. We previously demonstrated that heparanase also affected the hemostatic system. It forms a complex and increases the activity of the blood coagulation initiator tissue factor.

AIM

To evaluate heparanase levels and procoagulant activity as predictors of sepsis severity.

MATERIALS AND METHODS

Twenty-one patients with non-trauma, non-surgical sepsis admitted to the intensive care unit and 35 controls were recruited. Plasma samples were drawn from the study participants on days 1 and 7 following admission.

RESULTS

Heparanase levels and procoagulant activity on day 1 were significantly reduced in patients compared to controls (P < .0001, P < .0001, respectively). Day 1 heparanase procoagulant activity ≥350 ng/mL yielded a negative predictive value for severe sepsis of 89%. Additionally, heparanase procoagulant activity on day 7 correlated with the change in the APACHE score between days 1 and 7 (r = .66, P = .007).

CONCLUSIONS

Heparanase procoagulant activity decreases during sepsis and returns to normal levels as soon as the patient recovers. Hence, it can be potentially used to predict the risk of severe sepsis. These findings need to be further explored in large-scale studies.

Thrombin is a selective inducer of heparanase release from platelets and granulocytes via protease-activated receptor-1

Heparanase, known to be involved in angiogenesis and metastasis, was shown to form a complex with tissue factor (TF) and to enhance the generation of factor Xa. Platelets and granulocytes contain abundant amounts of heparanase that may enhance the coagulation system upon discharge. It was the aim of this study to identify the inducer and pathway of heparanase release from these cells. Platelets and granulocytes were purified from pooled normal plasma and were incubated with ATP, ADP, epinephrine, collagen, ristocetin, arachidonic acid, serotonin, LPS and thrombin. Heparanase levels were assessed by ELISA, heparanase procoagulant activity assay and western blot analysis. The effects of selective protease-activated receptor (PAR)-1 and 2 inhibitors and PAR-1 and 4 activators were studied. An in-house synthesised inhibitory peptide to heparanase was used to evaluate platelet heparanase involvement in activation of the coagulation system. Heparanase was released from platelets only by thrombin induction while other inducers exerted no such effect. The heparanase level in a platelet was found to be 40 % higher than in a granulocyte. Heparanase released from platelets or granulocytes increased factor Xa generation by three-fold. PAR-1 activation via ERK intracellular pathway was found to induce heparanase release. In conclusion, heparanase is selectively released from platelets and granulocytes by thrombin interacting with PAR-1. Heparanase derived from platelets and granulocytes is involved in activation of the extrinsic coagulation pathway. The present study implies on a potential anticoagulant effect, in addition to anti-platelet effect, of the new clinically studied PAR-1 inhibitors.

JAK-2 V617F mutation increases heparanase procoagulant activity

Patients with polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF) are at increased risk of arterial and venous thrombosis. In patients with ET a positive correlation was observed between JAK-2 V617F mutation, that facilitates erythropoietin receptor signalling, and thrombotic events, although the mechanism involved is not clear. We previously demonstrated that heparanase protein forms a complex and enhances the activity of the blood coagulation initiator tissue factor (TF) which leads to increased factor Xa production and subsequent activation of the coagulation system. The present study was aimed to evaluate heparanase procoagulant activity in myeloproliferative neoplasms. Forty bone marrow biopsies of patients with ET, PV, PMF and chronic myelogenous leukaemia (CML) were immunostained to heparanase, TF and TF pathway inhibitor (TFPI). Erythropoietin receptor positive cell lines U87 human glioma and MCF-7 human breast carcinoma were studied. Heparanase and TFPI staining were more prominent in ET, PV and PMF compared to CML. The strongest staining was in JAK-2 positive ET biopsies. Heparanase level and procoagulant activity were higher in U87 cells transfected to over express JAK-2 V617F mutation compared to control and the effect was reversed using JAK-2 inhibitors (Ruxolitinib, VZ3) and hydroxyurea, although the latter drug did not inhibit JAK-2 phosphorylation. Erythropoietin increased while JAK-2 inhibitors decreased the heparanase level and procoagulant activity in U87 and MCF-7 parental cells. In conclusion, JAK-2 is involved in heparanase up-regulation via the erythropoietin receptor. The present findings may potentially point to a new mechanism of thrombosis in JAK-2 positive ET patients.

Venous thromboembolic events in lymphoma patients: Actual relationships between epidemiology, mechanisms, clinical profile and treatment

Venous thromboembolic events (VTE) are an underestimated health problem in patients with lymphoma. Many factors contribute to the pathogenesis of thromboembolism and the interplay between various mechanisms that provoke VTE is still poorly understood. The identification of parameters that are associated with an increased risk of VTE in lymphoma patients led to the creation of several risk-assessment models. The models that evaluate potential VTE risk in lymphoma patients in particular are quite limited, and have to be validated in larger study populations. Furthermore, the VTE prophylaxis in lymphoma patients is largely underused, despite the incidence of VTE. The lack of adequate guidelines for the prophylaxis and treatment of VTE in lymphoma patients, together with a cautious approach due to an increased risk of bleeding, demands great efforts to ensure the implementation of current knowledge in order to reduce the incidence and complications of VTE in lymphoma patients.

Heparan sulfate as a receptor for poxvirus infections and as a target for antiviral agents

To establish the importance of virus-heparan sulfate (HS) interactions in virus infectivity, the poxvirus vaccinia virus (VACV) was used, as it binds HS and has both enveloped virus (EV) and non-enveloped mature virus (MV) forms. Initial studies showed that heparin inhibited plaque formation by both MV-rich WR and EV-rich IHD-J strains of VACV, with the EV-rich strain also losing trademark 'comet'-shaped plaques. However, using GFP-tagged EV and MV forms of VACV, based on IC₅₀ values, heparin was 16-fold more effective at inhibiting the infectivity of the EV form compared to the MV form. Furthermore, 6-O and N-sulfation of the glucosamine residues of heparin was essential for inhibition of the infectivity of both VACV forms. Several low-molecular-weight HS mimetics were also shown to have substantial antiviral activity, with glycosidic linkages, chain length and monosaccharide backbone being important contributors towards anti-VACV activity. In fact, the d-mannose-based sulfated oligosaccharide mixture, PI-88 (Muparfostat), was four-fold more active than heparin at inhibiting MV infections. Paradoxically, despite heparin and HS mimetics being potent inhibitors of VACV infections, removal of HS from cell surfaces by enzymatic or genetic means resulted in only a modest reduction in infectivity. It is unlikely that this paradox can be explained by steric hindrance, due to the low molecular weight of the HS mimetics (~1-2.5 kDa), with a more likely explanation being that binding of heparin/HS mimetics to free VACV initiates an abortive viral infection. Based on this explanation, HS mimetics have considerable potential as antivirals against HS-binding viruses.

Involvement of the heparanase procoagulant domain in bleeding and wound healing

Essentials Heparanase forms a complex with tissue factor and enhances the generation of factor Xa. The present study was aimed to identify the procoagulant domain of heparanase. Procoagulant peptides significantly shortened bleeding time and enhanced wound healing. Tissue factor pathway inhibitor (TFPI)-2 derived peptides inhibited the procoagulant peptides.

SUMMARY

Background Heparanase, which is known to be involved in angiogenesis and metastasis, was shown to form a complex with tissue factor (TF) and to enhance the generation of activated factor X (FXa). Our study demonstrated that peptides derived from TF pathway inhibitor (TFPI)-2 impeded the procoagulant effect of heparanase, and attenuated inflammation, tumor growth, and vascularization. Aims To identify the procoagulant domain in the heparanase molecule, and to evaluate its effects in a model of wound healing that involves inflammation and angiogenesis. Methods Twenty-four potential peptides derived from heparanase were generated, and their effect was studied in an assay of FXa generation. Peptides 14 and 16, which showed the best procoagulant effect, were studied in a bleeding mouse model and in a wound-healing mouse model. Results Peptides 14 and 16 increased FXa levels by two-fold to three-fold, and, at high levels, caused consumption coagulopathy. The TFPI-2-derived peptides explored in our previous study were found to inhibit the procoagulant effect induced by peptides 14 and 16. In the bleeding model, time to clot formation was shortened by 50% when peptide 14 or peptide 16 was topically applied or injected subcutaneously. In the wound-healing model, the wound became more vascular, and its size was reduced to one-fifth as compared with controls, upon 1 week of exposure to peptide 14 or peptide 16 applied topically or injected subcutaneously. Conclusions The putative heparanase procoagulant domain was identified. Peptides derived from this domain significantly shortened bleeding time and enhanced wound healing.

Assessment of Heparanase-Mediated Angiogenesis Using Microvascular Endothelial Cells: Identification of λ-Carrageenan Derivative as a Potent Anti Angiogenic Agent

Heparanase is overexpressed by tumor cells and degrades the extracellular matrix proteoglycans through cleavage of heparan sulfates (HS), allowing pro-angiogenic factor release and thus playing a key role in tumor angiogenesis and metastasis. Here we propose new HS analogs as potent heparanase inhibitors: Heparin as a positive control, Dextran Sulfate, λ-Carrageenan, and modified forms of them obtained by depolymerization associated to glycol splitting (RD-GS). After heparanase activity assessment, 11 kDa RD-GS-λ-Carrageenan emerged as the most effective heparanase inhibitor with an IC₅₀ of 7.32 ng/mL compared to 10.7 ng/mL for the 16 kDa unfractionated heparin. The fractionated polysaccharides were then tested in a heparanase-rich medium-based in vitro model, mimicking tumor microenvironment, to determine their effect on microvascular endothelial cells (HSkMEC) angiogenesis. As a preliminary study, we identified that under hypoxic and nutrient poor conditions, MCF-7 cancer cells released much more mature heparanase in their supernatant than in normal conditions. Then a Matrigel^TM assay using HSkMEC cultured under hypoxic conditions in the presence (or not) of this heparanase-rich supernatant was realized. Adding heparanase-rich media strongly enhanced angiogenic network formation with a production of twice more pseudo-vessels than with the control. When sulfated polysaccharides were tested in this angiogenesis assay, RD-GS-λ-Carrageenan was identified as a promising anti-angiogenic agent.

Heparanase: a rainbow pharmacological target associated to multiple pathologies including rare diseases

In recent years, heparanase has attracted considerable attention as a promising target for innovative pharmacological applications. Heparanase is a multifaceted protein endowed with enzymatic activity, as an endo-β-D-glucuronidase, and nonenzymatic functions. It is responsible for the cleavage of heparan sulfate side chains of proteoglycans, resulting in structural alterations of the extracellular matrix. Heparanase appears to be involved in major human diseases, from the most studied tumors to chronic inflammation, diabetic nephropathy, bone osteolysis, thrombosis and atherosclerosis, in addition to more recent investigation in various rare diseases. The present review provides an overview on heparanase, its biological role, inhibitors and possible clinical applications, covering the latest findings in these areas.