PS3, A Semisynthetic β-1,3-Glucan Sulfate, Diminishes Contact Hypersensitivity Responses Through Inhibition of L- and P-Selectin Functions

Heparanase Inhibitors in Cancer Progression: Recent Advances

BACKGROUND

An endo-β-glucuronidase enzyme, Heparanase (HPSE), degrades the side chains of polymeric heparan sulfate (HS), a glycosaminoglycan formed by alternate repetitive units of D-glucosamine and D-glucuronic acid/L-iduronic acid. HS is a major component of the extracellular matrix and basement membranes and has been implicated in processes of the tissue's integrity and functional state. The degradation of HS by HPSE enzyme leads to conditions like inflammation, angiogenesis, and metastasis. An elevated HPSE expression with a poor prognosis and its multiple roles in tumor growth and metastasis has attracted significant interest for its inhibition as a potential anti-neoplastic target.

METHODS

We reviewed the literature from journal publication websites and electronic databases such as Bentham, Science Direct, PubMed, Scopus, USFDA, etc., about HPSE, its structure, functions, and role in cancer.

RESULTS

The present review is focused on Heparanase inhibitors (HPIns) that have been isolated from natural resources or chemically synthesized as new therapeutics for metastatic tumors and chronic inflammatory diseases in recent years. The recent developments made in the HPSE structure and function are also discussed, which can lead to the future design of HPIns with more potency and specificity for the target.

CONCLUSION

HPIns can be a better target to be explored against various cancers.

Antitumor activity and structure-activity relationship of heparanase inhibitors: Recent advances

Heparanase (HPSE)-directed tumor progression plays a crucial role in mediating tumor-host crosstalk and priming the tumor microenvironment, leading to tumor growth, metastasis and chemo-resistance. HPSE-mediated breakdown of structural heparan sulfate (HS) networks in the extracellular matrix (ECM) and basement membranes (BM) directly facilitates tumor growth and metastasis. Lysosome HPSE also induces multi-drug resistance via enhanced autophagy. Therefore, HPSE inhibitors development has become an attractive topic to block tumor growth and metastasis or eliminate drug resistance. In this review, we summarize HPSE inhibitors applied experimentally and clinically according to interaction with the binding sites of HPSE and participation of growth factors. The antitumor activity and structure-activity relationship (SAR) are also emphasized.

Targeting Heparanase in Cancer: Inhibition by Synthetic, Chemically Modified, and Natural Compounds

Heparanase is an endoglycosidase involved in remodeling the extracellular matrix and thereby in regulating multiple cellular processes and biological activities. It cleaves heparan sulfate (HS) side chains of HS proteoglycans into smaller fragments and hence regulates tissue morphogenesis, differentiation, and homeostasis. Heparanase is overexpressed in various carcinomas, sarcomas, and hematological malignancies, and its upregulation correlates with increased tumor size, tumor angiogenesis, enhanced metastasis, and poor prognosis. In contrast, knockdown or inhibition of heparanase markedly attenuates tumor progression, further underscoring the potential of anti-heparanase therapy. Heparanase inhibitors were employed to interfere with tumor progression in preclinical studies, and selected heparin mimetics are being examined in clinical trials. However, despite tremendous efforts, the discovery of heparanase inhibitors with high clinical benefit and minimal adverse effects remains a therapeutic challenge. This review discusses the key roles of heparanase in cancer progression focusing on the status of natural, chemically modified, and synthetic heparanase inhibitors in various types of malignancies.

Heparin Mimetics: Their Therapeutic Potential

Heparin mimetics are synthetic and semi-synthetic compounds that are highly sulfated, structurally distinct analogues of glycosaminoglycans. These mimetics are often rationally designed to increase potency and binding selectivity towards specific proteins involved in disease manifestations. Some of the major therapeutic arenas towards which heparin mimetics are targeted include: coagulation and thrombosis, cancers, and inflammatory diseases. Although Fondaparinux, a rationally designed heparin mimetic, is now approved for prophylaxis and treatment of venous thromboembolism, the search for novel anticoagulant heparin mimetics with increased affinity and fewer side effects remains a subject of research. However, increasingly, research is focusing on the non-anticoagulant activities of these molecules. Heparin mimetics have potential as anti-cancer agents due to their ability to: (1) inhibit heparanase, an endoglycosidase which facilitates the spread of tumor cells; and (2) inhibit angiogenesis by binding to growth factors. The heparin mimetic, PI-88 is in clinical trials for post-surgical hepatocellular carcinoma and advanced melanoma. The anti-inflammatory properties of heparin mimetics have primarily been attributed to their ability to interact with: complement system proteins, selectins and chemokines; each of which function differently to facilitate inflammation. The efficacy of low/non-anticoagulant heparin mimetics in animal models of different inflammatory diseases has been demonstrated. These findings, plus clinical data that indicates heparin has anti-inflammatory activity, will raise the momentum for developing heparin mimetics as a new class of therapeutic agent for inflammatory diseases.

Regulation of Complement and Contact System Activation via C1 Inhibitor Potentiation and Factor XIIa Activity Modulation by Sulfated Glycans - Structure-Activity Relationships

The serpin C1 inhibitor (C1-INH) is the only regulator of classical complement activation as well as the major regulator of the contact system. Its importance is demonstrated by hereditary angioedema (HAE), a severe disease with potentially life-threatening attacks due to deficiency or dysfunction of C1-INH. C1-INH replacement is the therapy of choice in HAE. In addition, C1-INH showed to have beneficial effects in other diseases characterized by inappropriate complement and contact system activation. Due to some limitations of its clinical application, there is a need for improving the efficacy of therapeutically applied C1-INH or to enhance the activity of endogenous C1-INH. Given the known potentiating effect of heparin on C1-INH, sulfated glycans (SG) may be such candidates. The aim of this study was to characterize suitable SG by evaluating structure-activity relationships. For this, more than 40 structurally distinct SG were examined for their effects on C1-INH, C1s and FXIIa. The SG turned out to potentiate the C1s inhibition by C1-INH without any direct influence on C1s. Their potentiating activity proved to depend on their degree of sulfation, molecular mass as well as glycan structure. In contrast, the SG had no effect on the FXIIa inhibition by C1-INH, but structure-dependently modulated the activity of FXIIa. Among the tested SG, β-1,3-glucan sulfates with a Mr ≤ 10 000 were identified as most promising lead candidates for the development of a glycan-based C1-INH amplifier. In conclusion, the obtained information on structural characteristics of SG favoring C1-INH potentiation represent an useful elementary basis for the development of compounds improving the potency of C1-INH in diseases and clinical situations characterized by inappropriate activation of complement and contact system.

Short fungal fractions of β-1,3 glucans affect platelet activation

Platelets are capable of binding, aggregating, and internalizing microorganisms, which enhances the elimination of pathogens from the blood. The yeast Candida albicans is a pathobiont causing life-threatening invasive infections. Its cell wall contains β-1,3 glucans that are known to trigger a wide range of host cell activities and to circulate during infection. We studied the effect of β-1,3 glucan fractions (BGFs) consisting of diglucosides (Glc2), tetraglucosides (Glc4), and pentaglucosides (Glc5) on human platelets, their mechanisms of action, and their possible impact on host defenses. The effect of BGFs on the coagulation process was determined by measuring thrombin generation. Platelets pretreated with BGFs were analyzed in terms of activation, receptor expression, aggregation, and adhesion to neutrophils and to C. albicans The results show that BGFs affected the endogenous thrombin potential in a concentration-dependent manner. For platelet activation, BGFs at a low concentration (2 μmol/l) reduced ATP release and prevented the phosphorylation of protein kinase C. BGFs diminished the expression of P-selectin and the activation of αIIbβ3 BGFs decreased platelet aggregation and the interaction between thrombin-stimulated platelets and neutrophils, fibrinogen, and C. albicans GLc5 decreased ATP release and TGF-β1 production in response to TLR4 upregulation in thrombin-stimulated platelets, but TLR4 blockage abolished the effect of BGFs on platelets. This study provides evidence that fungal pentaglucosides modulate platelet activity mediated via TLR4 stimulation and reduce platelet-neutrophil interaction.

Recent advances in the discovery of heparanase inhibitors as anti-cancer agents

Heparanase, an only endo-β-d-glucuronidase capable of cleaving heparan sulfate (HS) side chains at specific sites, contributes to remodeling of the extracellular matrix (ECM) and releasing of HS-linked growth factors, cytokines and signaling proteins. In addition, heparanase also plays an indispensable role in tumor angiogenesis, invasion and metastasis, indicating that it is a promising target for the development of antitumor drugs. Recent progress leads to three classes of heparanase inhibitors, including active analogs of endogenous substance, synthetic small molecule compounds and natural products. In this review, following an outline on the heparanase structure and function, an overview of the advancement of heparanase inhibitors as novel and potent anti-cancer agents will be given, especially introducing various existing heparanase inhibitors, as well as their inhibitory activities and mechanisms of action.

Simple and rapid quality control of sulfated glycans by a fluorescence sensor assay--exemplarily developed for the sulfated polysaccharides from red algae Delesseria sanguinea

Sulfated polysaccharides (SP) from algae are of great interest due to their manifold biological activities. Obstacles to commercial (especially medical) application include considerable variability and complex chemical composition making the analysis and the quality control challenging. The aim of this study was to evaluate a simple microplate assay for screening the quality of SP. It is based on the fluorescence intensity (FI) increase of the sensor molecule Polymer-H by SP and was originally developed for direct quantification of SP. Exemplarily, 65 SP batches isolated from the red alga Delesseria sanguinea (D.s.-SP) and several other algae polysaccharides were investigated. Their FI increase in the Polymer-H assay was compared with other analytical parameters. By testing just one concentration of a D.s.-SP sample, quality deviations from the reference D.s.-SP and thus both batch-to-batch variability and stability can be detected. Further, structurally distinct SP showed to differ in their concentration-dependent FI profiles. By using corresponding reference compounds, the Polymer-H assay is therefore applicable as identification assay with high negative predictability. In conclusion, the Polymer-H assay showed to represent not only a simple method for quantification, but also for characterization identification and differentiation of SP of marine origin.

Testing of potential glycan-based heparanase inhibitors in a fluorescence activity assay using either bacterial heparinase II or human heparanase

Heparanase, an endo-β-glucuronidase cleaving heparan sulfate (HS) chains at cell surfaces and in the extracellular matrix (ECM), is involved in angiogenesis, tumor progression and metastasis as well as in inflammation and kidney dysfunction. Therefore, heparanase is considered a promising therapeutic target and diagnostic marker. Recently, we have developed a simple, rapid, fully automatable fluorimetric activity assay using the synthetic sulfated pentasaccharide fondaparinux as substrate and bacterial heparinase II (HEP-II) instead of human heparanase (hHEP). The aim of this study was to evaluate this assay for inhibitor testing as well as to check whether the assay principle is applicable to measure the activity and inhibition, respectively, of the actual target enzyme hHEP. Besides the known hHEP inhibitor suramin and the antiinflammatory and antimetastatic PS3, two series of β-1,3-glucan sulfates differing in their chain length and degree of sulfation, further semisynthetic sulfated glycans, and two sulfated polysaccharides isolated from algae were included to examine structure-activity relationships. The inhibitory activity of sulfated glycans showed to be greatly dependent on both their degree of sulfation and their basic glycan structure, but independent of their molecular size. The β-1,3-glucan sulfates were superior to suramin as well as to the other glycans with similar degree of sulfations. The most active inhibitor was found to be the β-1,3-glucan sulfate PS3 (IC₅₀=0.017 μM). By using hHEP instead of HEP-II comparable results were obtained. With an IC₅₀ being about 160 times lower than that of suramin, PS3 exhibited again the strongest inhibitory effects. Inhibition of hHEP may therefore contribute to the potent antiinflammatory and antimetastatic activities of PS3 in vivo. In conclusion, the fluorimetric hHEP activity assay proved to be a simple, fully automatable tool for testing potential inhibitors. In case of HS mimetic inhibitors, the assay variant with HEP-II may provide a fast and inexpensive option for initial screening purposes.

β-Glucans in the treatment and prevention of allergic diseases

β-glucans are a group of biologically active polysaccharides of natural origin with a proven pleiotropic immunomodulation effect. Their efficacy has been confirmed in the therapeutic treatment and prevention of various infectious diseases, secondary immune defects and also of oncologic disorders. Allergic diseases are one of the most frequent diseases and their prevalence continues to increase. They develop as a consequence of dysregulation of the immune system, especially when there is failure in the equilibrium of the response of TH1/TH2 lymphocytes towards TH2. New therapeutic approaches in the treatment of immunopathological conditions (e.g. allergic or oncologic) are directed to restoring the equilibrium among different T lymphocyte subpopulations. Based on in vitro experiments, and also on animal and human clinical studies, there is much evidence for the importance of β-glucans in the treatment and also prevention of allergic diseases; this opens new perspectives on the use of this widespread and popular group of natural substances.

Tunable heparan sulfate mimetics for modulating chemokine activity

Heparan sulfate (HS) glycosaminoglycans participate in critical biological processes by modulating the activity of a diverse set of protein binding partners. Such proteins include all known members of the chemokine superfamily, which are thought to guide the migration of immune cells through their interactions with HS. Here, we describe an expedient, divergent synthesis to prepare defined HS glycomimetics that recapitulate the overall structure and activity of HS glycosaminoglycans. Our approach uses a core disaccharide precursor to produce a variety of differentially sulfated glycopolymers. We demonstrate that a specific trisulfated mimetic antagonizes the chemotactic activity of the proinflammatory chemokine RANTES with potency similar to that of heparin, without inhibiting serine proteases in the blood coagulation cascade. Our work provides a general strategy for modulating chemokine activity and dissecting the pleiotropic functions of HS/heparin through the presentation of defined sulfation motifs within polymeric scaffolds.

Clinical presentation, pathogenesis, diagnosis, and treatment of epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a chronic mucocutaneous autoimmune skin blistering disease. The pathogenic relevance of autoantibodies targeting type VII collagen (COL7) has been well-documented. Therefore, EBA is a prototypical autoimmune disease with a well-characterized pathogenic relevance of autoantibody binding to the target antigen. EBA is a rare disease with an incidence of 0.2 new cases per million and per year. The current treatment of EBA relies on general immunosuppressive therapy, which does not lead to remission in all cases. Therefore, there is a high, so far unmet medical need for the development of novel therapeutic options. During the last 10 years, several novel in vitro and in vivo models of EBA have been established. These models demonstrated a critical role of the genetic background, T cells, and cytokines for mediating the loss of tolerance towards COL7. Neutrophils, complement activation, Fc gamma receptor engagement, cytokines, several molecules involved in cell signaling, release of reactive oxygen species, and matrix metalloproteinases are crucial for autoantibody-induced tissue injury in EBA. Based on this growing understanding of the diseases' pathogenesis, several potential novel therapeutic targets have emerged. In this review, the clinical presentation, pathogenesis, diagnosis, and current treatment options for EBA are discussed in detail.

Selectins and Associated Adhesion Proteins in Inflammatory disorders

Inflammation is defined as the normal response of living tissue to injury or infection. It is important to emphasize two components of this definition. First, that inflammation is a normal response and, as such, is expected to occur when tissue is damaged. Infact, if injured tissue does not exhibit signs of inflammation this would be considered abnormal and wounds and infections would never heal without inflammation. Secondly, inflammation occurs in living tissue, hence there is need for an adequate blood supply to the tissues in order to exhibit an inflammatory response. The inflammatory response may be triggered by mechanical injury, chemical toxins, and invasion by microorganisms, and hypersensitivity reactions. Three major events occur during the inflammatory response: the blood supply to the affected area is increased substantially, capillary permeability is increased, and leucocytes migrate from the capillary vessels into the surrounding interstitial spaces to the site of inflammation or injury. The inflammatory response represents a complex biological and biochemical process involving cells of the immune system and a plethora of biological mediators. Cell-to-cell communication molecules such as cytokines play an extremely important role in mediating the process of inflammation. Inflammation and platelet activation are critical phenomena in the setting of acute coronary syndromes. An extensive exposition of this complex phenomenon is beyond the scope of this article (Rankin 2004).

Absence of CCR4 exacerbates skin inflammation in an oxazolone-induced contact hypersensitivity model

Chemokine receptor CCR4 is expressed by Th2 cells and is involved in the recruitment of inflammatory cells into the skin. We studied the effects of CCR4 deficiency in the murine model of oxazolone-induced contact hypersensitivity in CCR4-/- and wild-type (WT) mice. The inflammatory response in the skin at 24  hours post-elicitation was stronger in CCR4-/- mice compared with WT, evidenced by increased ear swelling and inflammatory cell infiltration. In addition, the mRNA expression levels of several cytokines, chemokines, chemokine receptors, and selectins in the skin of CCR4-/- mice were significantly elevated compared with WT mice. Time kinetic experiments during the sensitization and elicitation phases revealed that the number of CD3+CD4+ cells in CCR4-/- mice remained high longer during the sensitization phase and increased more rapidly during the elicitation phase compared with WT mice. These data demonstrate that the absence of CCR4 results in enhanced secondary immune response during allergic skin inflammation.

Optimized and standardized isolation and structural characterization of anti-inflammatory sulfated polysaccharides from the red alga Delesseria sanguinea (Hudson) Lamouroux (Ceramiales, Delesseriaceae)

The red seaweed Delesseria sanguinea dominantly populates a large artificial reef in the southwestern Baltic Sea. It contains sulfated polysaccharides (SPs), which exhibit a pharmacological profile indicating anti-inflammatory and anti-skin aging potencies. To establish and optimize an extraction procedure for these SPs and to evaluate the influence of several parameters on their quality, 23 algae batches were harvested over the period of four years and extracted by different methods, resulting in 56 SP batches. Extraction with water at 85 degrees C proved to be superior and led to highly reproducible products with average yields of 11.6 +/- 3.9%, reaching 18% in spring. Their quality was independent of generation form and vitality of the algae. The SPs were identified as sulfated branched xylogalactans (degree of sulfation 0.50 +/- 0.08, mean M(r) 142000). The coextraction of floridean starch turned out to be the only parameter causing any seasonal variability. However, by using water, this concerns solely the yields of the isolated products. Compared to NaOH extracts, the antielastase activity of H(2)O extracted SPs was about twice as strong (IC(50) 0.204 +/- 0.024 microg/mL) and the batch to batch variability was much lower (CV 11.8 vs 28.6%). In conclusion, SPs from Delesseria sanguinea can be isolated in reproducibly high quality by using a specific extraction procedure. Thus, an important prerequisite for a potential economical utilization is fulfilled.

High-dose intravenous immunoglobulin (IVIG) therapy in autoimmune skin blistering diseases

Treatment of autoimmune bullous skin diseases can often be challenging and primarily consists of systemic corticosteroids and a variety of immunosuppressants. Current treatment strategies are effective in most cases but hampered by the side effects of long-term immunosuppressive treatment. Intravenous immunoglobulin (IVIG) is one potential promising therapy for patients with autoimmune bullous skin diseases, and evidence of its effectiveness and safety is increasing. A number of autoimmune bullous skin diseases have been identified in which IVIG treatment may be beneficial. However, experience with IVIG in patients with autoimmune skin blistering disease is limited, where it is recommended for patients not responding to conventional therapy. The mode of action of IVIG in autoimmune diseases, including bullous diseases is far from being completely understood. We here summarize the clinical evidence supporting the notion, that IVIG is a promising therapeutic agent for the treatment of patients with autoimmune bullous skin disease. In addition, we review the proposed modes of action. In the future, randomized controlled trials are necessary to better determine the efficacy and adverse effects of IVIG in the treatment of autoimmune bullous skin diseases. In addition, insights into IVIG's mode of action might enable us to develop novel therapeutics to overcome the current shortage of IVIG.

Proteoglycans on bone tumor development

Proteoglycans, extracellular matrix components, exert several activities on bone cells and seem crucial for maintaining an appropriate number of osteoblasts and osteoclasts. The overall data strengthen a pro-bone resorptive role for proteoglycans, through the control of osteoprotegerin availability and of receptor activator of NF-kappaB ligand bioactivity. In parallel, proteoglycans participate in the control of tumor development at different levels, including bone tumor development and bone metastases dissemination. This dual role makes them good candidates as regulatory molecules in the vicious cycle between tumor proliferation and bone resorption observed during tumor development in bone site. Knowledge of the biological roles of these molecules in cancer biology, tumor angiogenesis and metastasis has promoted the development of drugs targeting them.

Pharmacological profiles of animal- and nonanimal-derived sulfated polysaccharides--comparison of unfractionated heparin, the semisynthetic glucan sulfate PS3, and the sulfated polysaccharide fraction isolated from Delesseria sanguinea

Sulfated polysaccharides (SP) such as heparin are known to exhibit a wide range of biological activities, e.g., anticoagulant, anti-inflammatory, and antimetastastic effects. However, since the anticoagulant activity of heparin is dominating, its therapeutic use for other medical indications is limited due to an associated risk of bleeding. Further disadvantages of heparin are its animal origin, the shortage of resources, and its complex and variable composition. However, SP without these limitations may represent a substance class with good prospects for applications other than anticoagulation. In this study, the in vitro pharmacological profiles of two nonanimal-derived SP were investigated in comparison with unfractionated heparin. One is the natural SP fraction from the red algae Delesseria sanguinea (D.s.-SP). The other one is the chemically defined PS3, a semisynthetic β-1,3-glucan sulfate with proven in vivo anti-inflammatory and antimetastatic activities. All three polysaccharides were examined in vitro for their inhibitory effects on the coagulation and complement system, polymorphonuclear neutrophil elastase, hyaluronidase, matrix metalloproteinase-1, heparanase, and p-selectin-mediated cell adhesion. Compared with heparin, the nonanimal-derived polysaccharides have a four times weaker anticoagulant activity, but mostly exhibit stronger (1.4–224 times) effects on test systems investigating targets of inflammation or metastasis. According to their different structures, PS3 and D.s.-SP differ in their pharmacological profile with PS3 being the strongest inhibitor of heparanase and cell adhesion and D.s.-SP being the strongest inhibitor of hyaluronidase and complement activation. Considering both pharmacological profile and pharmaceutical quality parameters, PS3 represents a candidate for further development as an anti-inflammatory or antimetastatic drug whereas D.s.-SP might have perspectives for cosmetic applications.